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FEBRUARY 1994 E V E R VI D A V kvali PRACTICAll

INCORPORATING ELECTRONICS MONTHLY FULLY S.O.R. £1.95

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GREEN WELD 4411 mkt , 40 CATALOGUE SUPPLEMENT

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VALVE SOUND 361041

THE No. 1 NDEPENDENT MAGAZINE for ELECTRONICS, TECHNOLOGY and COMPUTER PROJECTS COMMODORE MICRODRIVE SYSTEM mini storage AMSTRAD DMP4000 Enure printer assemblies includIng device for C64's 4 times faster than disc dnves. 10 limes faster printhead. platen. cables, stepper motors etc Everytlung bar the electron- than tapes Complete unit just £12 REF: MAG12P1 ics and case. Good stripper,. Clearance pnce rue LS REF: MAG5 or 2 SCHOOL STRIPPERS We have quite a few of the above for Eli REF: MAGI! units which are 'returns' as they are quite comprehensive units VIEWDATA SYSTEMS Brandnew units made by TANDATA they could be used for other protects etc Let us know hcw many you compete with 1200/75 built in modern, infra red remote controled need at just 50p a unrt (minimum 10) keyboard BT approved. Prestel compatible, Centronice pnnter port. MASSIVE HEADPHONES 16P These are ex %/Iry Atlantic You can have RGB odour and composite output (works with any TV) complete with power supply and fully cased Price is rust £20 REF: MAG20 Also WAREHOUSE CLEARANCE 8 pars for E2 REF: MAG2P8 sane customer returned units available at £10 each REF: MAG10 PROXIMITY SENSORS These are smut PCB's with what look PPC MODEM CARDS These are high spec plug in cards made FANTASTIC £20.00 REDUCTION like a source and sensor LED on one end and lots of components on for the Amstrad laptcp computers 2400 baud dal up unit complete the rest of the PCB. Complete with fly leads Pack of 5E3 REF: MAO: with leads Clearance pnce is £5 REF: MAG5P1 3P5 or 20 for £8 REF: MAGEIP4 INFRA RED REMOTE CONTROLLERS Onginaly madelor REFURBISHED PC BASE UNITS FIBRE OPTIC CABLE Made for Hewlett Packard soprettygood hi spec satellite equipment but perfect for all sorts of remote control stunt you can have any length you want (min5m) first 5m £7 REF: protects Our clearance pnce is just £2 REF: MAG2 COMPLETE WITH KEYBOARD MAG7 thereafter E1 a metre (ie 20 m E22) REF: MAG1 Max length 250m TOWERS INTERNATIONAL TRANSISTOR GUIDE. A very usefii book for finding equivalent transistors, leadouts, specs FRO M ONLY £29.00 SNOOPERS EAR? Onginall made to clip over the earpiece of etc. £20 REF: MA020P1 telephone to amplify the sound-it also works quite well on the cable running along the wall Price is ES REF: MAG5P7 SINCLAIR C6 MOTORS We have a few left without gearboxes AMSTRAD 1512 BASE UNITS These are 12v DC 3.300 rpm Fire', 114'OP shaft £25 REF: MAG25 DOS PACKS Microsoft version 33 or higher complete with al GUARANTEED manuals or price just £5 REF: MAG5P8 Worth it just for the very UNIVERSAL SPEED CONTROLLER KIT Designed by us comprehensive manual' 5 25' only for the above motor but suitable for any 12v motor up to 30A. PERFECT WORKING ORDER. DOS PACK M iCrOSOft version 5 Onginal software but no man uals Candele with PCB etc A heat sink may be required. £17 00 A LOW COST INTRODUCTION TO THE HOME COMPUTER MARKET REF: MAG17 hence only £3 REF: MAG3P8 5 25' only VIDEO SENDER UNIT. Transmitsboth audio and video signals FOREIGN DOS 3 3-German.Frenchttalian etc £2 a pack with from wilier a video camera. video recorder, TV or Computer etc to AMSTRAD 1512SD manual 5 25' only REF:MAG2P9 any standard TV set in a 100 range' (tune TV to a sparechannel) 12v MONO VGA MONITOR Made by Amstrad. refurbished £49 1512 BASE UNIT, 5.25" FLOPPY DRIVE AND DCop. PnceisE15 REF: MAG15 12v psu isE5extra REF: MAG5P2 REF: MAC449 ▪ CORDLESS MICROPHONE smai hand held unn with a KEYBOARD. ALL YOU NEED IS A MONITOR AND CT31644COLOURMONITOR Madelo work withtheCPC464 lime computer Standard RGB input sown work with othermachnes 500' range! 2 transmit power levels Reqs PP3 Si battery Tuneable POWER SUPPLY. WAS £49.00 to any FM receiver. Pnce is £15 REF: MA015P1 Refurbished £59 00 REF: MAG59 NO W ONLY £29.00 LOW COST WALKIE TALKIES Parrot battery operated units JUST A SMALL SELCTION of whatwe nave- to see more gel with a range of about 200. Ideal for garden use or as an educational REF: MA G29 our 1994 catalogue (42p stamp) or call in Mon-Sat 9-5 30 toy. Price is Ea a pair REF: MAC BM 2 x PP3 reqd HAND HELD TONE DIALLERS Ideal for the control of the 'MINATURE RADIO TRANSCEIVERS A pair of wallue AMSTRAD 1512DD Response 200 and 400 machnes £5 REF MAG5P9 talkies with a range of up to 2 Icilcmetres in open country Units 1512 BASE UNIT AND KEYBOARD AND TWO PIR DETECTOR Made by famous UK alarm man ufacturer these measure 22x52x155mm Complete with cases an d earpieces 2kPP3 are h spec, long range internal units 12v operation Slight marks on req'd £30.03 pair REF: MAG30. 5.25" 360K DRIVES. ALL YOU NEED IS A MONITOR case and unboxed (although brand new) E8 REF: MAG8P5 COMPOSITE VIDEO KIT. Converts composite video into AND POWER SUPPLY WAS E59.00 WINDUP SOLAR POWERED RADIO AM/FM radio com- separate H sync. V sync. and video 12v DC operation £8 00 NO W ONLY £39.00 plete with hand charger and sdar panel! £14 REF. MAG14P1 REF: MAG8P2. REF: MA G39 COMMODORE 64 Customer returns but ok for spares etc £12 LC13600 PRINTER ASSEMBLIES Made by Amstrad they are REF MAG12P2 Tested and working units are £69 00 REF. MAG69 entre mechanical pnnter assembles including pnnthead, stepper at £4 motors etc etc In fact everything bar the case and electronics. a good COMMODORE 64 TAPE DRIVES Customer returns shipper' £5 REF: MAG5P3 or 2 for £8 REF: MAG8P3 REF MAG4P9 Fullytested and working u ntsare E12 REF: MAG12P5 PHILIPS LASER 2MW helium neon tube Brand new ful spec SO/AR PCWEll PANELS COMPUTER TERMINALS complete with screen, keyboard £40 REF MAG40 Mains power supply kit E20 REF: MAG20P2 and RS232 input/output. Ex equipment Price is £27 REF - MAG27 Fully buit and tested unit £75 REF: RAG 75. MA INS CABLES These are 2 core standard black 2 metre mains SPEAKER WIRE Brown two core. 100 foot hank E2 3FT X 1FT 10WATT GLASS PANELS cables fitted with a 13A plug on one enct cable the other Ideal for REF MAG2P1 14.5v/700mA protects. low cost manufactudng etc Pack or 10forE3 REF MAG3P8 LED PACK of 100 standard red 5rtirn leds £5 REF MAG5P4 Padt of 100E20 REF MAG20P5 JUG KETTLE ELEMENTS good general purpose heatng NOW AVAILABLE BY MAIL ORDER SURFACE MOUNT STRIPPER Onginaly made as some element (about 2kw) ideal for allsorts of heatng prqects etc 2 forE3 form of hgh frequency amplifier (man chip is a TSA5511T 1 3GHE REF MAG3 £33.95 synthesiser ) but good stripper value, an excellent way to play with surface mount components E1 00 REF MAG1P1 UNIVERSAL PC POWER SUPPLY complete with fiyleads, CMS £IO0 SPECIAL PACKAGING CHARGE) switch. fan etc Two types available 150* at £15 REF MAG15P2 MIC R O WAVE TIME R Electronic Omerwith relay outputsutable TOP QUALITY AMORPHOUS SILICON CELLS HAVE ALM OST A to make enlarger tmer etc E4 REF W ^4P4 (23x23‘23mm) and 200w at £20 REF: MAG20P3 (23x23x23mm) TIMELESS UFESPAN WITH AN INFINITE NUMBER OF POSSIBLE OZONE FRIENDLY LATEX 250mlbottle of liquid abber, sets APPLICATIONS. SOME OF WHICH MAY BE CAR BATTERY PLUG 420? showing your age? pack of 10 with leads for E2 REF in 2 hours Ideal for mountng PCBS, fixing wires etc £2 each REF CHARGING, FOR USE ON BOATS OR CARAVANS, OR ANY MAG2P 11 PAAG2P2 WHERE A PORTABLE 12V SUPPLY IS REQUIRED. REF: RAGS& MOBILE CAR PHONE £5.99 Well aknostl complete in car •FIM TRANSM rTTERhoused in a standard working 13Aadaptedi phone excluding the box or electronics normaily hidden under seat. the bug runs directly off the mains so lasts forever! why pay E7007 or ALSO 1FT X 1FT GLASS SOLAR PANELS 12v 200mA Can be made to illuminate with 12v aiso has built in light sensor so mice is £26 REF, MAG26 Transmits to any FM radio. ONLY £15.00. REF: MAG15P3 dispiayoNy illuminates when dark Totally conanangi REF MAG6P6 •FM BUG KR New design with PCB embedded col for extra ALARM BEACONS Zenon strobe madeto mount on an extemai stability Transmits to any FM nacho Si battery req'd £5 REF bell box but could be used for caravans etc 12v operation Just MAG5P5 FREE SOFTWARE! connect up and it flashes regularly) £5 REF MAG5P11 'FM BUG BUILT AND TESTED supenor design to kit, as FIRE ALARM CONTROL PANEL Hogh quality metal cased supplied to detective agencies etc Si battery req'd £14 REF Brand new. UNUSED top quality Famous brand alarm panel 350x165x8Ornm Comes with electronics but no nforrna- MAG14 lic ensed software discs. Available in 5.25' D SD D or 5.25' ton £15 REF MAG15P4 TALKING COIN BOX STRIPPER ongnaly made to HD only. You buy the disk and it comes with free BRAND SUPER SIZE HEATSINK Superb quality aluminium heatank retail at £79 each, these units are designed to convert and ordinary NEW UNUSED SOFTWARE. We are actually selling you the 365 x 183 x 61mm, 15 fins enamble high heat dissipation No holes' phone into a payp hone The units we have generally have the locks floppy disc for your own "MEGA CHEAP" storage facilities, £9 99 REF MAG10P1P missing anti sometmesbrcken hnges Howeverthey can be adapted if you happen to get software that you wont/need/like as REMOTE CONTROL PCB These are receiver boards for for their ongmal pupose or used for something else?? Pnce isjusIE3 well you get a •MEGA BARGAIN' tol REF: MAG3P1 garage door opening systems You may have another use? £4 ea 0900 PKTIO £2.99 RIP : MAGSP7 PKT100 116.00 REp MAG16 REF MAG4P5 100 WATT MOSFET PAIR Same spec as 25K343 and HD PKT10 £3.99 NM MAG4P3 Pima° 121.00 REF: MAG2611 26J413(8A,140v.103w) 1 N channel and 1P channel. E3apair REF: LOPTX Line output transformers believed to be for Iv res colour monitors but useful for getting high voltages from low west £2 each MAG3P2 LARGER GIANTITY PRICES AVAILABLE ON APPLICATION REF: MAG2P12 bumper pack of 10 for £12 REF: MAG12P3. VELCRO 1 metre length of each side 20mm wide (quck way or Axing POE temporary lobs etc) £2 REF: MAG2P3 fttc‘fr WE BUY SURPLUS STOCK£££££££ MAGNETIC AGITATORS Cosistng of a cased mains motor TURN YOUR SURPLUS STOCK INTO CASH. with lead The motor has tWOMag nets fixed to a rotor that spin round IMMEDIATE SETTLEMENT. WE WILL ALSO QUOTE FOR inside There are also 2 plastic covered magnets supplied Made for COMPLETE FACTORY CLEARANCE. PORTABLE RADIATION DETECTOR remotely st mng liquictslyou may have a use?E3 each REF: MAG3P3 COMING SOON 2 for £5 REF: MAG5P8 1994 CATALOGUE. TOP QUALITY SPEAKERS Made for HI Fl televisions these are 10wall 4R Jap made 4' round with large shelded magnets Good PLEASE SEND 42P A4 SIZED SAE FOR YOUR FREE COPY quality general purpose speaker £2 each REF: MAG2P4 or 4 for E6 monartni GOODS ORDER L500 TRADE ORDERS FROM GOVEIUGADIT SCHOOLS REF: MAGISP2 UNIVERSETTES & LOCAL AUTHORITIES WELCOME ALL (PODS SUPPLIED SUIUECT TO £49.99 OUR CONDMONS OF SALE AND UNLESS OTHERWISE STATED GUARANTEED FOR IO TWEETERS 2' diameter good quality tweeter 140R (would be DAYS RIGHTS RESERVED TO CHANGE PRICES & SPF-CTFICATIONS wrnroor PRIOR A Hand held personal Gam ma and X good vnth the above speaker) 2 for £2 REF: MAG2P5 or 4 for £3 NOTICE ORDERS SURTECT TO STOGIE QUOTATIONS WILLINGLY GIVEN FOR QUANTI REF: MAG3P4 TIES HIGHER THAN race! STATU, Ray detector. This unit contains two AT KEYBOARDS Made by Apncot these q ualtly keyboards need Geiger Tubes, has a 4 digit LCD dis- just a small modificaton to run on any AT. they work perfectly but you SOME OF OUR PRODUCTS MAY BE UNLICENSABLE IN THE UK WE have to put up with 1 or 2 foreign keycaps' Pnce £6 REF. play with a Plezo speaker, giving an MAGEIP3 audio visual indication. The unit de- XT KEYBOARDS Mixed types sane retums, sane good, sane BULL ELECTRICAL foreign etc but all goal for sparest Pnce is £2 each REF: MAG2P8 250 PORTLAND ROAD HOVE SUSSEX tects high energy electromagnetic or 4 for £6 REF: MAG8P4 SW SOT PC CASES Again mixed types so you take a chance next one off quanta with an energy from 30KeV to MAIL ORDER TERMS: CASH PO OR CHEQUE thepteE12REF:MAG12 hvoidentcal onesforE2OREF: MAG20P4 over 1.2M eV and a measuring range component pack bargain 1 COO resistors 0.000 capacitors (all WITH ORDER PLUS t3.00 POST PLUS VAT. of 5-9999 UR/h or 10-99990 Nr/h. Sup- same value) £2 50 a pack REF: MAG2P7 PLEASE ALLOW 7 -19 DAYS FOR DE.LIVERY plied complete with handbook. 1994 CATALOGUE TELEPHONE ORDERS WID,CO ME I M O TEL: 42'3 303500 REF: MAG50 OUT SOON rg FAX: 02 ,3 32-TOT7 EVERYDAY WITH PRACTICAL ELECTRONICS INCORPORATING ELECTRONICS MONTHLY

The No. 1 Independent Magazine for Electronics, VOL. 23 No. 2 FEBRUARY 1994 Technology and Computer Projects

ISSN 0262 3617 PROJECTS. . TH EORY ... NEWS . . . COM MENT... POPULAR FEATURES Preftetx

W HISTLE CONTROLLED LIGHT-S WITCH by Bart Trepak 104 Replaces a standard light switch to provide touch or whistle control REVIVING THE VALVE SOUND by Jake Rothman 112 Complete technical details, including circuits, to rebuild the Quad II valve power amplifier INTRODUCTION TO MICROCONTROLLERS — TIMEOUT 128 by Peter Crowcroft A simple countdown timer that will get you involved with microcontrollers BATTERY TO MAINS INVERTER AND UNINTERRUPTABLE PO WER SUPPLY-3 by Mark Daniels 134 The U. P.S charger and control section of the unit M ULTI -PURPOSE AUDIO SYSTE M — 5 by Max Horsey 156 Balanced microphone preamplifier and power supply 5enex CIRCUIT SURGERY by Alan Winstanley 120 Your problems solved, circuit ideas • hints and tips INTERFACE by Robert Penfold 144 The page for computer enthusiasts CALCULATION CORNER — 2 by Steve Knight 146 Removing the fear from circuit design calculations SAFETY FIRST -3 by T. R. de Vaux Balbirnie 150 Electrical safety in the home and caravan TECHNIQUES —ACTUALLY DOING IT by Robert Penfold 164 Cutting large holes in panels A MATEUR RADIO by Tony Smith G4FAI 172 All the news and views from the world of amateur radio leatgrex EDITORIAL 103 INNOVATIONS 108 Everyday news from the world of electronics NE W TECHNOLOGY UPDATE by Ian Poole 110 Developments in superconductors EUROPEAN INTERNATIONAL AUDIO & VIDEO FAIR 122 by Barry Fox New developments and products from last years show FOX REPORT by Barry Fox 132 The BBCs 3D transmission experiments ELECTRONIC PRINCIPLES 133 A new software service for those studying electronics SHOPTALK with David Barrington 143 Component buying for EPE projects HO ME BASE by Terry Pinnell 154 Jottings of an electronics hobbyist ELECTRONICS VIDEOS 166 Our range of educational videos to complement your studies DIRECT BOOK SERVICE 167 A wide range of technical books available by mail order PRINTED CIRCUIT BOARD SERVICE 170 Wimborne Publishing Ltd 1994. Copyright in PCBs for EPE projects - some at half price! all drawings, photographs and articles published in EVERYDAY with PRACTICAL ELECTRONICS is ADVERTISER'S INDEX 176 fully protected, and reproduction or imitations in whole or in part are expressly forbidden. FREE GREEN WELD CATALOGUE SUPPLE MENT between pages 132 and 133 Our March '94 Issue will be published on Friday, Readers Service • Editorial and Advertisement Departments 103 4 February 1994, See page 91 for details.

Everyday with Practical Electronics, February, 1994 S9 Surplus always Th Surplus always wanted for cash! • wanted for cash' j THE ORIGINAL SURPLUS WONDERLAND! LOW COST PC SPECIALISTS - ALL EXPANDABLE - ALL PC COMPATIBLE 8088 XT - PC99 286 AT - PC286 386 AT - PC386

• 640k RAM expandable • 2 serial & 1 parallel • 2 meg RA M expanded • 2 serial & 1 parallel with standard SIM MS ports by slots ports • 12 Mhz Land mark speed • MS-DOS 4.01 • 20 Mhz with 32k cache. • MS-DOS 4.01 • 256k RAM - expandable • Factory burnt-in • 20 meg hard disk • Co-processor socket Expandable to 64k to 640k • Co-processor socket • Standard 84 key Enhanced 102 key • 1.2 meg 5-1/4" floppy • • 40 meg hard disk • Enhanced 102 keyboard • 4.7 Mhz speed keyboard keyboard • 1.2 meg 5-1/4" floppy • 1.4 meg 3-1/2" floppy • Kwik Disk Accelerator • 360k 5-1/4" floppy • 12" green screen gal iiiicekr y&bcaaci zn udpar with included • EGA driver on board • VGA card installed Software - FREE • 2 serial & 1 parallel ports • In good used condition BRAND NE W AND BOXED! BRAND NE W AND BOXED! • MS-DOS 4.01 Optional FITTED extras: 640K RAM £39. 12' CGA colour monitor with card £39. 2nd 5-1/4 360K floppy £29.95. 20 Only mbyte MFM hard drive £99. £249.00,, Onl y £425.00(, The Philips 9CM073 is suggested for the PC286 and the MONITORS CM8873 for the PC386. Either may use the SVGA MTS-9600 if a suitable card is installed. We can fit this at a cost of £49.00 •:-•,.:::•••,•• 14" Forefront Model PATS-9600 SVGA multisync with resolution of 1024 x 768.0.28 °nI (F) for the PC286 and £39.00 for the PC386. Y E99 .00 pitch. 'Text' switch for word processing etc. POWER SUPPLIES • Overscan switch included. Ideal for the PC- FLOPPY DISK DRIVES % 386 or PC-286 with SVGA card added. Also Power One SPL200-5200P 200 watt (250 w peak).Semi open 14 12 „ compatibe with BBC, Amiga, Atari (including 5/ " from £22.95 - 3/" from £21.95! frame giving +5v 35a, -5v 1.5a, +12v 4a (8a peak), -12v 1.5a, Massive purchases of standard 51/4' and 312' drives enables us the monochrome high resolution mode), Ar- +24v 4a (6a peak). All outputs fully regulated with over voltage to present prime product at industry beating low prices! All units chimedes etc. In good used condition (possible minor screen protection on the +5v output. AC input selectable for 110/240 (unless stated) are removed from often brand new equipment bums). 90 day guarantee. 15' x 14' x 12'. Only £159(E( and are fully tested, aligned and shipped to you with a 90 day vac. Dirns13' x 5' x 2.5. Fully guaranteed RFE. £85.00 (8) 14" Philips Model CM8873 VGA mull sync guarantee and operate from standard voltages and are of stand- Power One SPL130. 130 watts. Selectable for 12v (4A) or 24 v with 640 x 480 resolution. CGA. EGA or ard size. All are IBM-PC compatible (if 31,2' supported). (2A). 5v @ 20A. ± 12v 0 1.5A. Switch mode. New. £59.95(B) VGA, digital/analog, switch selectable. 3.5" Panasonic JU363/4 720K or equivalent £29.95(B) Astec AC-8151 40 watts. Switch mode. +5v U 2.5a. +12v @ Sound with volume control. There is also a 3.5" Mitsubishi MF355C-L. 1.4 Meg. Laptops only' 29.95(B) 2a. -12v 0 0.1a. 6-1/4' x 4' x 1-3/4".New £22.95(B) special 'Text' switch for word processing, 3.5" Mitsubishi MF355C-D. 1.4 Meg. Non laptop £29.95(B) Greendale 19ABOE 60 watts switch rnode.+5v U 6a,±12v @ spreadsheets and the like. Compatible with 5.25" EXTRA SPECIAL BRAND NEW Mitsubishi MF501B 1a, +15v la. RFE and fully tested.11 x 20 x5.5cms. £24.95(C) IBM PC's, Amiga, Atari (excluding the 360K. Absolutely standard fits most computers £22.95(B) Conver AC130. 130 watt hi-grade VDE spec.Switch mode.+5v monochrome high resolution mode), BBC, • Data cable included In price. 15a,-5v 0 la,±12v @ 6a.27 x 12.5 x 6.5crns.New. £49.95(C) Archimedes etc. Good used condition (possible minor screen Shugart 800/801 SS refurbished & tested £175.00(E) Boshert 13090.Switch mode.Ideal for drives & system. +5.0 6a, bums) 90 day guarantee. 15' x 14' x 12'. Only ...... £139(E) Shugart 851 double sided refurbished & tested £275.00(E) +12v 0 2.5a, -12v 0 0.5a, -5v 0 0.5a. £29.95(8) Philips 9CM073 similar (not identical) to above for EGA/CGA Mitsubishi M2894-63 double sided switchable Famell G6/40A. Switch mode. 5v U 40a.Encased £95.00(C) PC and compats. 640 x 350 resolution. With Text switch with hard or soft sectors- BRAND NEW £250.00(E) Famell G24/5S. As above but 24v 0 5a. £65.00(C) amber or green screen selection. 14' x 12' x 13-1/2' £99(E) Dual 8" drives with 2 mbyte capacity housed in a smart case KME 10" high definition colour monitors. Nice with built in power supply! Ideal as exterior drives! C499.00(F) BBC Model B APM Board tight 0.28' dot pitch for superb clarity and End of line purchase scoop! Brand new NEC D2246 8' 85 £100 CASH FOR THE modem styling. Operates from any 15.625 khz megabyte of hard disk storage! Full CPU control and industry sync RGB video source, with RGB analog and M OST NOVEL standard SMD interface. Ultra hi speed transfer and access time composite sync such as Atari, Com modore leaves the good old ST506 interface standing. In mint condition DE M ONSTR ATABLE Amiga, Acorn Archimedes & BBC. Measures and comes complete with manual On £299(Ei APPLICATION! only 13.5' x 12' x 11'. Also works as quality Tv wen our HUB Telebox. Good used condition. 90 day guarantee. Only. t125 (E) THE AMAZING TELEBOX! BBC Model B type computer on a board. A major purchase KME as above for PC EGA standard £145 (E) allows us io offer you the PROFESSIONAL version of the BBC Converts your colour monitor into a Brand new Centronic 14' monitor for IBM PC and compatibles computer at a parts only price. Used as a front end graphics QUALITY COLOUR TV!! at a lower than ever price! Completely CGA equivalent. Hi-res system on large networked systems the architecture of the BBC Mitsubishi 0.42 dot pitch giving 669 x 507 pixels. Big 28 Mhz board has so many similarities to the regular BBC model B that bandwidth. A super monitor in attractive style moulded case.Full TV SO UND we are sure that with a bit of experimentation and ingenuity many 90 day guarantee. Only £129 (E) & VIDE O useful applications will be found for this board!! It is supplied NEC CGA 12' IBM-PC compatible. High TUNER! complete with a connector panel which brings all the I/O to 'D' quality ex-equipment fully tested with a 90 The TELEBOX consists of an attractive fully cased mains and BNC type connectors - all you have to do is provide +5 and day guarantee. In an attractive two tone powered unit, containing all electronics ready to plug into a host t 12 v DC. The APM consists of a single PCB with most major ribbed grey plastic case measuring 15'L x of video monitors made by manufacturers such as ic's socketed. The ic's are too numerous to list but include a 13'W x 12'H. The front cosmetic bezel has MICROVITEC, ATARI, SANYO, SONY, COMMODORE, 6502, RAM and an SAA5050 teletext chip. Three 27128 been removed for •• EPROMS contain the custom operating system on which we reasons. Only cont ract ualr..69 (E) PHILIPS, TATUNG, AMSTRAD and many more. The composite video output will also plug directly into most video recorders, have no data, On application of DC power the system boots arid 20% 12" and 26" AV SPECIALS allowing reception of TV channels not normally receivable on provides diagnostic information on the video output. On board Superbly made UK manufacture. PIL all solid state colour monitors, complete with composite video & sound inputs. Attrac- most television receivers (TELEBOX MB). Push button controls DIP switches and jumpers select the ECONET address and tive teak style case. Perfect for Schools,Shops,Disco, Clubs. on the front panel allow reception of 8 fully tuneable 'off air' UHF enable the four extra EPROM sockets for user software. App.. In EXCELLENT little used condition with full 90 day guarantee. colour television or video channels. TELEBOX MB covers vir- dims: main board 13' x 10'. I/O board 14' x 3'. Supplied tested tually all television frequencies VHF and UHF including the with circuit diagram, data and competition entry form. 20"....£135 22"....£155 26...S185 (F) HYPERBAND as used by most cable TV operators. Composite CALL FOR PRICING ON NTSC VERSIONS! and RGB video outputs are located on the rear panel for direct O nly £29.95 or 2 for £53 (B) Su • erb Own 6 foot 40u connection to most makes of monitor. For complete compatibility SPECIAL INTEREST - even for monitors without sound - an integral 4 watt audio Trio 0-18 vdc bench PSI). 30 amps. New £ 470 amplifier and low level Hi Fl audio output are provided as Fujitsu M3041 600 LPM band printer £2950 standard. DEC LS/02 CPU board £ 150 Massive Reductions Telebox ST for composite video input monitors £32.95 hwa SBUF TV test transmitter Telebox STL as ST but with integral speaker £36.50 Rhode25-1000mhz. & Sc Complete rz with SBTF2 Modulator £6500 li f Virtually New, Ultra Smart! Talsbox MB as ST with Mulliband tuner VHF-UHF-Cable. Caicomp 1036 large drum 3 pen plotter£ 650 & hyperband For overseas PAL versions state Thurlby LA 160B logic analyser C 375 Less Than Half Price! 5.5 or 6mhz sound specification. £69.95 1.51cw 115v 60hz power source £ 950 I H Top quality 19' rack cabinets made in UK Telebox RGB for analogue RGB monitors (15khz) £69.95 Anton Pillar 400 Hz 3 phase frequency converter 75Kw POA by Optima Enclosures Ltd. Units feature Shipping code on all Teleboxes is (B) Newton Derby 400 Hz 70 Kw converter POA designer, smoked acrylic lockable front ROB Telebox also suitable for IBM muitisync monitors with RGB Nikon PL-2 Projection lens meter/scope£750 door, full height lockable half louvered back analog and composite sync. Overseas versions VHF & UHF call Sekonic SD 150H 18 channelHybrid recorder £2000 door and removable side panels. Fully ad- SECAM / NTSC not available. HP 7580A Al 8 pen high speed drum plotter £1850 justable internal fixing struts, ready Kenwood DA-3501 CD tester, laser pickup simulator £ 350 punched for any configuration of equipment mounting plus ready No Break Uninterruptable PSU's mounted integral 12 way 13 amp socket switched mains distribu- Brand new and boxed 230 volts uninterruptable power suppliesBRAND NEW PRINTERS lion strip make these racks some of the most versatile we have from Dens** Model MUK 0565-AUAF is 0.5 kva and MUD Microline 183. NLQ 17x17 dot matrix. Full width. £139 (D) ever sold. Racks may be stacked side by side and therefore 1085-AHBH is 1 kva. Both have sealed lead acid batteries. MUK Hyundai HDP-920. NLO 24.18 dot matrix full width. £149 (D) require only two side panels or stand singly. Overall dimensions are internal, MUD has them in a matching case. Times from Oume LetterPro 20 daisy. Oume 05-3 interface. £39.95 (D) are 77-1/2'H x 32-1/2'D x 22'W. Order as: interrupt are 5 and 15 minutes respectively. Complete with full Centronics 152-2 9 x 7 dot matrix. Full width. £149 (D) Rack 1 Complete with removable side panels £275.00 (G) operation manuals MUK £249 (F) MUD £525 (G) Centronics 159-4 9 x 7 dot matrix.Serial. 9-1/2" width £ 99 (D) Rack 2 Less side panels £145.00 (G) 1992 Winter Issue of Dispray News now available - send large S(1E - POCKED with bargain:I LONDON SHOP MAIL ORDER & OFFICES DISTEL (J The Original ALL ENQUIRIES :ONO. SSS :000 . : ."*. Open Mon-Sal 9-5.30 Open Mon-Fri 9.00-5.30 Free dial-up database! • • • • Thursday till 9 00pm 01,0 Dept EE. 32 Biggin Way, 1000's of items+info on line *-... !--.* I • • • 215 Whitehorse Lane. • • • • Upper Norwood, V21. V22 8, V22 bis •: 0110 6 : • • South Norwood. 081167914414 London SE19 3XF. London. SE25 081-679-1888 Fax- 081-679-1927 At pnces for UK Mainland. UK customers add 17.5% VAT to TOTAL order amount. Minimum order £10. PO orders Iran Government.Universities.Schools & Local Authonties _ct crToravorc weicome.minimum account order cal Carnage charges (A)E2.00. (A1)=C3.75.181=C3.50. (C)=01.50. (D)=E1130 (E)L-E14.03 (F)=E18.00 (G)=Call Scotland surcharge: call. L. Lit All goods suppied subject to our standard Conciticns of Sale and unless otherwise stated guaranteed for 90 days. All guarantees on a return to base Oasts Rights reserved to change picas & specifications without prior notice. Orders sutiecl to stock. Quotations willinpy given lot higher quantities than those stated. Bulk surplus always wanted lot cash.

90 Everyday with Practical Electronics, February, 1994 CCD TV CAMERA AUDIO/RF MONITOR Give an eye to your computer This project started life when the author wanted to monitor the if, or neighbourhood watch with output from a TV tuner with which he was starting to experiment. A this money-saving monitor. quick lash-up with a detector diode and a rather elderly amplifier was This monochrome closed-circuit only partially successful, due among other things to mains hum. A television camera was originally small self-contained battery operated amplifier, specifically designed designed as a low cost unit for to operate with a matching r.1 detector probe was therefore designed inputting live visual images into a and built. It seemed sensible at the same time to make the amplifier PC-compatible computer for so that it was suitable for monitoring audio signals directly, over a graphical and general amusement wide range of amplitudes. The resulting instrument is described next purposes. However, following a spate of crimes in the author's month. locality, its potential as a security camera was recognised and the circuit was expanded to also allow live and recorded image interfacing with a cheap monochrome TV receiver. SMART KEY IMMOBILISER The cost of the author's camera was kept low by using a lens from In the UK approximately 25 cars are stolen every fifteen minutes. an old 35mm camera, and by the use of an image sensor Living in an inner city area, you have a 1 in 10 chance of having your inexpensively purchased as a slightly sub-standard manufacturing car stolen Auto crime accounts for nearly 30 per cent of all test sample. nationwide crime. In this constructional article, the camera circuitry and its TV receiver With statistics like this, it makes sense to install some sort of car interface are described. A follow-up article will describe the alarm/immobiliser. PC-compatible computer interface, the 'Frame Grab', which allows The design described next month, is a coded "Smart Key" live images from the TV camera to be output to the computer, where it immobiliser, which features anti-scan circuitry, fuel pump cut-oft, can be displayed, modified, coloured, stored on disc, printed to paper, ignition cut-off and a facility which prevents hot wiring. or output back to the TV screen via the camera unit. Programming The design is suitable for cars, boats, lorries or vans, the only examples will be included. amendment required being a suitable voltage relay - i.e. 24V for The camera can be used on its own without a computer, and the lorries. Frame Grab can be used without the camera for other data gathering purposes. EVERYDAY_ L_ FREE WALL CHART WITH PRACTICAL Both our March and April issues will carry free wall charts covering ELECTRONICS just about every formulae you could possibly want for general electronics work. Next month's chart gives formulae for D.C. Electricity i.e. everything from Ohms Law to T and sections. It also MARCH '94 ISSUE ON SALE FRIDAY. covers the colour code and provides a capacitance conversion chart. FEBRUARY 4th 1994

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Everyday with Practical Electronics, Febrawy, 1994 BREADB OAR DS - CAPACIT ORS - SOLAR CELLS - HEATSHRINK - ETC SOLAR CELL 2 volt 150mA max, size 60 x 100mm 1 35 each 5 tor 6 • ••••• •• • •••••• ••••••• BNC SOCKETS 50 ohm single hole fixing 50p each 10 for £4 00

Z. = Z = Z = •"1- - -,- - -.-.. ..- - MERCURY TILT SWITCH BREADBOARD Standard on/off £1 00 each 173 X 65mm 840TP C5 25 each Z.'. --= = .7-•. Z.L": -= Z.-1- .f.: = = -7= - - - 4 Contact (Directional) £1 50 each TEXTOOL ZIF SOCKET ------PIEZO VIBRATION SENSOR 28 pin zero insertion socket £5 95 each with data sheet £1 00 each

--ELECTRONIC COMPONENTS 6 VOLT NI-CAD PACK 5AA NI-CADS, tan charge type £3 95 CAPACITOR 10.000 mfd 25 volt with fixing clip 60p each PROJECT BOXES A range of high quality boxes moulded in black high impact ABS EPROMS 27C256 - 30 27C512 - 25. Once program med but never used eprom easily drilled or punched to produce a professional looking end product Mounted on a plastic carrier, can easily be removed from the carrier or used with a TYPE W L H PRICE low insertion force socket T2 75 56 25 £0 77 27C256 £1 00 each 6 for £5 00 27C512 Cl 20 each 5 for £5 00 T4 111 57 22 £0.92 CRYSTAL OSCILLAT ORS Suitable low insertion force socket 28 pin 40p each 3 for El 00 MB1 79 61 40 £1.35 MULTITURN PRESETS 20m m RECT, 500R, 1K, 5K, 10K, 20K, 50K, 100K 'IMO 4.0 mhz ALL MB2 100 76 41 £1.47 40p each. 3 for C1 00 MB3 118 98 45 £1.71 7.5 mhz £1.50 each CAR CIGAR LIGHTER ADAPTER (DUAL SIZE) MB4 216 130 85 £5.19 12.0 mhz OR mounted on two metres of cable £2 00 each MB5 150 100 60 £2.35 18.432 mhz 4 FOR 10041b PIEZO SOUNDER MB6 220 150 64 £3.95 2KHz note, 3-12V d.c 40Ma. 45mm dia. x 26mm £1.76 each 33.33 mhz £5.00 MB 7 177 120 83 £3.42 VIBRATION SENSITIVE ALARM BOARD WITH PIEZO SOUNDER MB8 150 80 50 £2.22 Originally a bike alarm There is a short delay after activation then the piezo All sizes are in millimetres sounder operates for a preset period. £3.76 each MICRO SWITCH roller arm operation spdt 40p each or the above alarm board with custom designed case, fixing clip and keyswitch £9.95 MINIATURE TOGGLE SWITCHES INFRA-RED BREAK BEAM Transmitter and receiver p.c.b. with 2 lens assemblies 12V d.c supply. These are ex-installation units and are not guaranteed to be spdt 60p each spdt 3 position c/otf 70p each working £4.96 pair dpdt 70p each dpdt 3 position c/off 80p each RECHARGEABLE BATTERIES £7.64 each spdt biased 60p each spdt 3 position c/oft biased both ways 70p each AA (HP7) 600 mAH £1 02 each C (HP11) 1200 mAH £2.29 each dpdt 3 position c/off biased one way 80p each D (HP2) 1200 mAH £2 40 each PP3 8 4V 100 mAH £4.77 each MINIATURE PUSH TO MAKE SWITCH 50p each FLOURESCENT LIGHT INVERTOR. Drives an 8 watt tube directly from 6V d.c Data DIL RELAYS 5 volt dp/changeover 60p 10 for £5 00 supplied £4 50 each 12 volt Op/changeover 80p 10 for £6 00 RELAY 10 amp contacts sp/changeover 12 volt coil £1 20 each CAR HORN RELAY in metal can with fixing lug, *13' CONNECTORS s/pole on 10 amp contacts £1 00 each 6 for £5.00 £1.00 BARGAIN PACKS plug socket cover 20 AMP RELAY dp on 12 volt coil 9 pin 30p 30p 35p SUB-MINIATURE TO G GLE SWITCHES £1.50 each 4 for E5 00 15 pin 40p 40p 35p PC B Mounting REED RELAY 12 volt 50p each 10 for £4.00 B01 S P on 4 for £1 00 25 pin 50p 50p 40p 240 VOLT AC RELAY. 3-pole c/o 10 amp 602 DP on 3 for Cl 00 contacts El .50 each 4 for £5 00 B03 3 xDP 3 pos. centre off 13004 DIL SWITCHES 4-way S P on 3 for Cl 00 SEMICONDUCTORS - TRANSISTORS - ICS - DIODES - REGULATORS -ETC B005 DIL SWITCHES 8-way S P on 2 for £1 00 VOLTAGE REGULATORS B006 DIL SWITCHES 12-way 90' sp on 2 for £1.00 1 amp 7805/7812/7815 all 33p each 7905/7912/7915 all 39p each SPECIAL OFFER B007 12 a PP3 BATTERY SNAPS 2 amp 78505/785212 54p each PROJECT BOX B008 1 a CAPACITOR 1 FARAD 5.5 VOLT 20mm dia x 7mm high 100mA 78L05/78412/78L15 all 26p each. 79L05/79L12/79L15 all 29p each B009 INSTRUMENT KNOBS (0.25" SHAFT) High quality grey plastic knob, collet In while Adjustable LM3177 47p each. LM723 29p each, L200 £1.28 each fixing 15mm dia. 5 for Cl 00 Transistors TIP2955 70p each. TIP 3055 70p each high impact ABS 13010 as above but 29mm dia. 3 for £1 00 2N3053 29p each. 2513055 70p each. 2N4403 28p each. 2N3819 40p each 50 x 70 x 25mm 13011 4 a MAGNETIC EARPIECE 8 ohm with 3 5mm plug MICRO IC'S -Z80A CPU £1.20: Z80A PIO £1 .50: Z8OB S10-1 £4.00 60p each 10 for £5.00 13012 4 a 28-WAY TURNED PIN OIL SOCKET B013 15 a 12 VOLT WIRE-ENDED LAMPS O PT O DEVICES - LEDS - ETC 8014 8 a 2 PIN DIN PLUGS screw terminal connection 5mm rnd red/yellow/green/amber 10p each 12 for £1.00 any mix B015 2 x LIGHT DEPENDENT RESISTOR Less than 200 ohms in daylight, greater 5mm rnd high brightness red/green 20p each 6 for £1.00 any mix than 10 megohms in darkness 5mm rnd flashing red 60p each. yellow/green 70p each 0016 1 a KEYPAD 20-key in 5 x 4 matrix bubble type switch contacts 5mm rnd bi-colour 35p each, tri-colour 45p each 6017 2 a PIEZO BUZZERS approx 3 to 20 volt d c LED mounted in chrome bezel red, yellow or green 30p each. 4 for £1 B018 5 a 78M12 VOLTAGE REGULATORS positive 12V 500mA LED mounted in a black bezel red only 25p each. 5 for £1.00 13019 4 x TL082CP bi-fet op-amps PLASTIC BEZEL for 5mm rod leds 10 for 40p 13020 20 a ASSORTED LEDS lull spec various shapes and sizes High brightness bi-colour I.e.d.. rectangular, red/green, two leads 40p each 13021 3 a INFRA-RED DIODE TX/RX PAIRS made by Honeywellino info) 8022 4 a CONSTANT CURRENT LED 5mm round. red 2-18V d c or a c nominal TE MPER ATU RE PR OBE 14mA High quality probe made for the medical profession Consists of a resistive sensor 13023 50 x IN4148 diode mounted in a plastic covered probe with a 1 meter curled lead. Temp range - 40 to 13024 2 a INFRA-RED TRANSISTOR FPT5133 150•C. Resistance at: 150 °C 188.3 ohms: - 40 •C 336.5 kohm: 25 °C 10.0 kohm t 70 ohms 61025 5 a DIACS The original price of these probes was over £24.00. Full data supplied. OUR PRICE £3.76 B026 3 BDX33C 10 amp 100V npn transistor RESET TIMER PCB 8027 12 a 2N3702 Transistor Gives a timed relay closure following a momentary input Requires 12V d.c. supply SP c/o E1028 12 a 2N3904 Transistor relay output LED indication. 19 different time intervals from 25sec to 35min 20sec. £5.98 each 8029 12 a BC337 Transistor 13030 4 a LM317T Variable regulator mounted on a small heatsink UNIVERS AL BELL TIMER 13031 2 a MAN6610 2 digit 06 - 7 segment display Com anode. amber 10 or 20 minute bell cut off + ve or - ve trigger • timed relay contacts. £4.96 B032 3 x PHONO TO PHONO LEAD 63cm long ALAR M CONTR OL UNIT 13033 15 x RECTANGULAR RED LEDs 6 x 6 x 2mm stackable Single zone alarm control unit built into a domestic light switch box. Ideal for home. B034 1 a PHOTO SENSITIVE SCR mounted on a PCB, data sheet supplied caravan, boat, garage, shed etc. 13035 4 a IEC Panel Mounting Mains Plug Snap fix 8036 5 a ASSORTED PIEZO TRANSDUCERS Facilities: - Normally closed loop for pir sensors, door/window contacts etc. Normally 6037 5 LENGTHS OF HEATSHRINK SLEEVING 8mm dia. 400mm long open loop for pressure mats. 24-hour loop for personal attack button Visual indication 13038 25 a CERAMIC DISC CAPACITORS 0 1 mfd 63V that the system is operational. Automatic SIREN 8039 iSa MONOLITHIC CERAMIC CAPACITORS 0 1 mfd 63V, in a dil package entry/exit delay. Automatic system reset. 12 volt dc for external use 115db £13 95 8040 25 a ASSORTED ELECTROLYTIC CAPACITORS PCB mounting useful values Alarm output cmos logic level 8041 25 ASSORTED PRE-SET RESISTORS PRICE COMPLETE WITH FULL INSTRUCTIONS £8.95 13042 6 a 3.5mm LINE JACK SOCKETS (mono) B043 6 x 3.5mm JACK PLUG (mono) SUB-MINIATURE PASSIVE INFRA-RED SENSOR ONLY (7.95 13044 8 x 3.5mm CHASSIS SOCKET (mono) Brand new passive infra-red sensor, measures only B045 2 a TRIACS 800 volt 8 amp 33m m W x 24mmH x 29mmD Logic level output. Full data 13046 12 a BC213L Transistor and application notes supplied 8047 12 a MIN SLIDE SWITCH dpdt EX INSTALLATION SENSORS tested working. 13048 15 a MIN CERMET TRIMMER POTS (good range of values) Type 1 Measures 180 x 112 x 70mm with walk test led, relay output B049 1 a PCB WITH TWO LARGE LEDS 15mm square, one red and one green and tamper protection 12 volt dc supply required £8.50 each 13050 1 x 12V DC RELAY 4-poie do with plug in base Type 2 As above but a smaller unit 123 x 62 x 50m m £11.75 each 6051 4 a LM324 quad op-amps Type 3. Ceiling mounting passive, infra red sensor 360 ° detection. 12V d.c. supply relay 6052 4 x 555 Timer output. tamper circuit and pulse count option Data supplied. £15.70 each 13053 5 a 741 op-amp B054 25 IN4001 diode Please note There may be variations in the size DOOR/WINDO W CONTACTS B055 20 a IN4007 diode of the above passive infra red sensors depend- Surface or flush mounting, white 8056 1 a SLOTTED OPTO ing on stock at the time of ordering But the unit Cl 10 each 13057 1 x DAC08 Digital to analogue convertor with data will certainly be within the stated sizes. JUNCTION BOX B058 4 a OPTO ISOLATOR white 6 way 60p DUAL TECH SENSOR Microwave and passive 13060 3 C106D Thyristor infra-red combined Separate led indication for each function. Measures 120 x 75 x 8061 5 x 78M05 VOLTAGE REGULATORS positive 5 volt 500mA 50mm. 12 volt d.c. supply, Relay output. Tamper protection £29.95 each Please use order code when ordering the bargain packs

ALAR M CONTR OL PANEL ST3000 Please make cheques and postal orders payable to Mailtech. •Wire free alarm control panel, detectors communicate with the All prices include VAT panel by means of radio transmitters' Speech synthesis for pro- gramming and general operating guidance' Built in user pro- Please add 01 00 postage to all orders grammable telephone dialler Up to 32 transmitters can be be At the mo ment it is not possible to have a full telephone answering used' Programmable exit/entry and bell timers' Programmable service. But we will have the phone definitely manned on Tuesdays. user codes • Full installation data supplied, the only thing that has Wednesdays and Thursdays between 10am and 4pm. to be handwired is the output to the siren/bell unit (not supplied) These control panels cost over £300.00. Yours for only £59.95. Suitable PASSIVE INFRA SENSOR/TX £25.85 D e pt E E, M ailt e c h Battery operated, available in 8m range, 10m range or 25m range. P O B o x 1 6 L u dl o w UNIVERSAL TX S hr o p s hir e S Y 8 4 N A For connection of normally open or closed contacts e.g. door/window switches, pressure mats etc £17.63 Tel: 058 47447 5 EASY-PC, Schematic and PCB CAD

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Everyday with Practical Electronics, February, 1994 93 S O M E P O P U L A R B A R G AIN S

MOTORS - BATTERY 1-12V LCD 3Y. DIGIT PANEL METER, this is a multi range POWER SUPPLIES - SWITCH MODE 3 DIFFERENT MODEL MOTORS, ft Order Ref 35 voltmeter/ammeter using the AD converter chip 7106 (all 230V mains operated) SPIN TO START 3V DC MOTORS for model aircraft etc 5 to provide 5 ranges each of volts and amps Supplied ASTEC REF. B51052 with outputs + 12 .5A. - 12V for ft Order Ref 134 with full data sheet Special snip price of £12. Order Ref. IA. i- 5V 3A. by 05A. + 5V •02A unboxed on CASSETTE MOTOR 1 5-12V. powerful speed increases 12P19. pcb size 180 x 130m m. £5, Order Ref. 5P188. with voltage £1. Order Ref 224 12V-0-12V 6VA PCB MOUNTING MAINS TRANS- ASTEC REF. BM4 1004 with outputs + 5V 3'/,A, MINI CASSETTE MOTOR, 6-9V working, £1, Order Ref 944 FORMER, normal 230V primary and conventional open 12V 1 3A, -- 12V •2A £5, Order Ref 5P199. HIGH EFFICIENCY MOTOR for solar cell working £1, winding construction. VI, Order Ref 938 ASTEC No. 12530 12V 1A, 12V .1A, + 5V 3A. Order Ref 643 AMSTRAD 3" DISK DRIVE brand new Standard re- uncased on pcb size 160 x 100m m, £3, Order Ref. 12V MOTOR, ex BSR record player. Cl, Order Ref 687 placement or why not have an extra one? £20, Order 9V CASSETTE MOTOR, brushless £.50, Order Ref Ref 20P28 A3PS1T4 EC No. BM41001 110W 38V 2.5A. 25.1V 3A 1 5P14 THIS COULD SAVE YOU EXPENSIVE BATTERIES, an in part metal cased with instrument type main input 1i1OHP 12V DC MOTOR, Smiths, £4, Order Ref 4P22 car unit for operating 6V radio, cassette player. etc. socket & on/oft dp rocker switch size 354 x 118 x VeRP 12v MOTOR, Smiths. EC Order Ref 6P1 from car lighter socket. £2, Order Rel. 2P318. 84m m. £8.50, Order Ref 8 5P2 1/BHP 12v MOTOR. Smiths. £3, Order Ref 8P14 MEDICINE CUPBOARD ALARM, or it could be used to ASTEC MODEL No. BM135-3302 12V 4A, + 5A 1 i3HP MOTOR, SIncl.t.r C`e £5, Ord. , Ref 15PP. warn when any cupboard door is opened, built and 16A, 12V 0.5A totally encased in plated steel neatly cased, requires only a battery. £3, Order Ref. with mains input plug, mains output socket & MAINS MOTORS WITH GEARBOXES 3P155 double pole on/off switch size 400 x 130 x 65m m. 5RPM 60W. £5, Order Ref 5P54 FULLY ENCLOSED MAINS TRANSFORMER, on a 2M 3- £9.50, Order Ref. 9.5P4. 4ORPM 100W, £6, Order Ref. 6P21 core lead terminating with a 13A plug. Secondary rated 5ORPM 60W, ES, Order Ref. 5P168. at 6V 4A Brought out on a well insulated 2-core lead POWER SUPPLIES — LINEAR (all cased unless stated) 6ORPM 60W, £5, Order Ref. 5P171 terminating with insulated push on tags, El, Order Ref 11ORPM 60W. £5, Order Ref 5P172 3P152. Dino but 8A. £4, Order Ref. 4P69. 4-5V DC 150mA, VI, Order Ref. 104. 15ORPM 60W. Order Ref 5P169 DON'T LET IT OVERFLOW, be it bath sink, cellar, sump 5V DC psu with filtering & volt regulation. 20ORPM 60W, £5, Order Ref 5P216 or any other thing that could flood. This device will tell uncased, £4, Order Ref. 4P63 500W MOTOR with gearbox & variable speed selec- you when the water has risen to the pre-set level. Ad- 6V DC 700mA. £1, Order Ref 103 tor 10Orpm upwards. £5, Order Ref 5P220 justable over quite a useful range. Neatly cased for wall 6V DC 200mA output in 13A case, £2, Order Ref 1 REV PER 24 HRS 2W MOTOR, £1, Order Ref 89 mounting. ready to work when battery fitted. £3, Order 2P112. 6-12V DC for models with switch to vary voltage 1 REV PER 12 HRS 2W MOTOR. £1, Order Ref 90 Ref 3P156 1 REV PER 4 HRS 2W MOTOR, £2. Order Ref 2P239 DIGITAL MULTI TESTER MG3800, single switching and reverse polarity, £2, Order Ref 2P3. 1 REV PER HOUR 2W EXTRA SMALL MOTOR, 2 for £1, covers 30 ranges including 20A AC and DC. 10 MEG 9V DC 150mA. VI, Order Ref. 762. Order Ref 500 input impedence. LCD display Complete with lead. 9V DC 2.1A by Sinclair £3, Order Ref. 3P151. '/,RPM MINI MOTOR. £3, Order Ref. 3P64. Currently advertised by many dealers at nearly £40. our 9V DC 100mA. £1, Order Ref 733 12V DC 200mA output in 13A case. £2, Order Ref 1RPM MINI MOTOR, £2, Order Ref 2P328. price only £25, Order Ref 25P14 4RPM 2W MOTOR. £1, Order Ref. 446 ANALOGUE TESTER, input impedence 2K ohms per 2P114 15RPM 2W MOTOR, £2, Order Ref. 2P321. volt It has 14 ranges. AC volts 0-500 DC volts 0-500. DC 12V DC 500mA on 13A base. £2.50, Order Ref. 25RPM 2W MOTOR. £2, Order Ref 2P322. current 500 micro amps at 250 milliamp. resistance 20ORPM 2W MOTOR. £1, Order Ref. 175. 0-1meg-ohm. decibels 20 56dB. Fined diode protection. 2512V P41A filtered & regulated on pcb with relays & Piezo sounder. uncased. £3, Order Ref. 3P80. 25ORPM 2W MOTOR, £1, Order Ref. 750. overall size 90 x 60 x 30mm Complete with test prods, AMSTRAD 13-5V DC at 1.8A or 2V DC at 2A. £6, £7.50, Order Ref 7 5P8. MAINS MOTORS LCD CLOCK MODULE, 1 5V battery operated. fits nicely Order Ref. 6P23. v. STACK MOTOR with V." spindle. Et, Order Ref 85 into our 50p project box. Order Ref 876 Only £2, Order 24V DC at 200mA twice for stereo amplifiers, £2, MOTOR 1Y." STACK with good length spindle from Ref 2P307 Order Ref. 2P4. each side, £2, Order Ref. 2P55. SENTINEL COMPONENT BOARD, amongst hundreds 9-5V AC 600mA made for BT, E1.50. Order Ref MOTOR 1Y." STACK with 4" long spindle. £2, Order of other parts this has 15 ICs all plug in so don't need 1 5P7 Ref. 2P203 desoldering. Cost well over £100, yours for £4, Order 15V 500mA AC on 13A base, £2, ref. 2P281. MOTOR BY CROMPTON 061-IP but little soiled. £3, AC OUT 9-8V at 60mA & 15-3V at 150mA, Et, Order Ref 4P67 Order Ref 3P4 AMSTRAD KEYBOARD MODEL KB5, this is a most Ref 751 JAP MADE PRECISION MOTOR balanced rotor re- comprehensive keyboard having over 100 keys in- BT POWER SUPPLY UNIT 206AS, charges 12V versible, 150Orprn. £2, Order Ref 2P12 battery and cuts off output should voltage fall cluding of course full numerical and qwerty. Brand TAPE MOTOR BY EMI, 2 speed & reversible. £2, Order below pre-Set. £16, Order Ref 16P6. Ref 2P70 new still in maker's packing, £5, Order Ref. 5P202. SINCLAIR MICROVISION PSU. £5. Ref 5P148 Y.HP100ORPM, £8, Order Ref 8P7 SOLAR PANEL BARGAIN gives 3V at 200mA. £2, VERY POWERFUL MAINS MOTOR, with extra long Order Ref 2P324 LASERS & LASER BITS (2",") shafts extending out each side Makes it ideal ULTRA SONIC TRANSDUCERS, 2 metal cased units. 2MW LASER, Helium neon by Philips, full spec for a reversing arrangement for. as you know, shaded one transmits one receives Built to operate around £30, Order Ref 30P1. pole motors are not reversible. £3, Order Ref. 3P157. 40kHz, £1.50 the pair. Order Ref. 1 5P4 POWER SUPPLY for this in kit form with case is INSULATION TESTER WITH MULTIMETER. internally £15, Order Ref 15P16, or in larger case to house MOTORS — STEPPER generates voltages which enable you to read insula- MINI MOTOR BY PHILIPS, 12V-7-5 degree step. quite tube as well. £18, Order Ref 18P2 tion directly in megohms. The multimeter has four standard data supplied. only £1, Order Ref 910 THE LARGER UNIT, made up. tested and ready ranges. AC/DC volts. 3 ranges DC milliamps. 3 MEDIUM POWERED Jap made 1 5 degree step. £3, to use, complete with laser tube. £69, Order Ref ranges resistance and 5 amps. These instruments are Order Ref 3P162 69P1 ex-British Telecom but in very good condition, tested VERY POWERFUL MOTOR by American Philips 10- HEATING UNITS and guaranteed OK. yours for only £7.50 with leads, 14V 7 5 degree step, ES, Order Ref 5P81. LINEAR QUARTZ GLASS TUBES 360W, 2 in series carrying case £2 extra Order Ref 7 5P4. for mains £1, Order Ref. 907 MAINS ISOLATION TRANSFORMER stops you getting LOUDSPEAKERS 1000W SPIRAL ELEMENTS for repairing fires etc. "to earth" shocks. 230V in and 230V out. 150 watt 2" ROUND 50 OHM COIL Y.W, 2 for £1, Order Ref 908 3 for El, Order Ref 223 upright mounting. £7.50, Order Ref. 7.5P5 and a 250W 2Y." 8 OHM. 2 for £1, Order Ref 454 1000W PENCIL ELEMENTS, 2 for £1, Ref. 376. torroidal isolation. £10, Order Ref 10P97. 2Y." 35 OHM, 2 for Et Order Ref 514 1 .2KW MINI TANGENTIAL HEATER, ideal for un- 3/14 " 8 OHM, 2 for ft Order Ref 682 MINI MONO AMP, on pcb. Size 4" , 2" with front der desk etc. £5, Order Ref. 5P23. 6V," 4 OHM WITH TWEETER, £1, Order Ref. 895. panel holding volume control and with spare hole 2KW TANGENTIAL HEATER, £6, Order Ref 6P30. 6Y." 6 OHM. £1, Order Ref 896 for switch or tone control Output is 4W into 4 ohm 3KW TANGENTIAL HEATER, £8, Order Ref. 8P24 6Y." 8 OHM WITH TWEETER, £1, Order Rel. 897 speaker using 12V or 1W into 8 ohm using 9V. Brand 12' TUBULAR HEATER, slightly storage soiled. £6, 6" x 4'' 4 OHM. £1, Order Ref 242. new and perfect. only El each, Order Ref 495. 5" ir 5" 15 OHM, £1, Order Ref 906. EXPERIMENTING WITH VALVES don't spend a fortune Order Ref 6P31 5" a 3" 16 OHM, £1, Order Ref. 725 WATER-PROOF HEATING WIRE, 60 ohms per on a mains transformer, we can supply one with stan- r ii 4" 16 OHM. 2 for £1, Order Ref. 684 metre. 15M is right length for connecting to dard mains input and secs of 250V-0V-250V at 75mA 8" 15 OHM AUDAX, £1, Order Ref 504. mains, £5, Order Ref. 5P109. 9" 3 8 OHM 5", £1, Order Ref 138 and 6 3V at 3A, £5, Order Ref 5P167 0-1MA FULL VISION PANEL METER 2/34 " square. 3 4 OHM TWEETER. El, Order Ref. 433 The above prices include VAT but please add £3 scaled 0-100 but scale easily removed for re-writing. GOODMANS 10W 4 OHM, £2, Order Ref 2P27. towards our packing and carriage if your order is El each. Order Ref 756 HORN SPEAKER, 8 OHM, £3, Order Ref. 3P82 under £50. Send cheque or postal orders or quote PCB DRILLS, 12 assorted sizes between .75 and 20W 5. BY GOODMAN, £3, Order Ref. 3P145. credit card number. 20W 4" OHM TWEETER, fl.50, Order Ref 1 5P9. 1.5mm. Et the lot. Order Ref 128 AMSTRAD 8 " 15W 8 OHM with matching tweeter, £4, 12V AXIAL FAN, for only £1, ideal for equipment Order Ref 4P57 cooling, brand new made by West German company. CASED PAIR OF STEREO SPEAKERS BY BUSH, 4 Brushless so virtually everlasting. Supplied complete M & B ELECTRICAL ohm. £5 per pair. Order Ref 5P141 with a circuit diagram of transistor driver. £1, Order DOUBLE WOUND VOICE COIL, 25W ITT, with tweeter Ref. 918 SUPPLIES LTD and crossover. £7. Order Ref 7P12 PC OPERATING SYSTEMS, fully user documented BULKHEAD SPEAKER metal cased. £0, Order Ref and including software. MS-DOS 3.20, with 5" disk. £5, 1043 Order Ref 5P2076, MS-DOS 33 with 3'i," disk. £5, Pilgrim Works (Dept. E.E.) 25W 2 WAY CROSSOVER, 2 for VI, Order Ref 22 Order Ref. 5P208. or with 5" disk. £5, Order Ref 40W 3 WAY CROSSOVER, ft, Order Ref. 23. 5P208/5. MS-DOS 401 with 3'/," disk, £0, Order Ref Stairbridge Lane, 10P99 MONITORS AND BITS 45A DOUBLE POLE MAINS SWITCH. Mounted on a 6 x Bolney, PHILIPS 9 HIGH RESOLUTION MONITOR. £15, Order 3,, aluminium plate. beautifully finished in gold, with pilot light Top quality made by MEM, £2, Order Ref. Rd i 15P1 Sussex RH17 5PA METAL CASE for the above Philips monitor, £12, 2P316 Order Ref 12P3 SOLAR ENERGY EDUCATIONAL KIT. It shows how to make solar circuits and electrical circuits, how to in- Telephone: 0444 881965 PHILIPS 9" HIGH RESOLUTION TUBE, ref M24 306W. £12. Order Ref 12P7 crease voltage or current. to work a radio, calculator. 6" ELECTROSTATIC MONITOR TUBE, ref SE5J31. cassette player and to charge NiCad batteries. The kit (Also fax but phone first) comprises 8 solar cells, one solar motor, fan blades £10, Order Ref 10P104 Callers to 1 2 Boundary Road, MINI SCOPE TUBE face size, 2" a 2/14 ", electrostatic to fit motor and metal frame to hold it to complete 3V heater, 1KV, in 'cu metal shield, £0, Order Ref. a free-standing electric fan A really well written in- Hove, Sussex. 10P73 struction manual. £8, Order Ref 8P42B

94 • Everyday with Practical Electronics, February, 1994 "... there is no doubt that running under Windows puts it ahead of the field and makes it a visually attractive package." Electronics World + Wireless World July 1993 High Quality PCB and Schematic Design for Windows 3/3 1 and DOS

O Supports over 150 printers/plotters including 9 or C2-1.1t — 711'7• 24 pin dot-matrix, DeskJet, LaserJet, Postscript, and HPGL. Professional Edition imports GERBER files, and exports GERBER and NC-DRILL files. jr,3-)„v oird) O Up to 200,000 pads/track nodes depending on memory. Simple auto-router and schematic capture tools with SPICE compatible net-list output. O S1 O ILS 01/ I, •1.11 O S.II 0 ISA oit 0 0 0 0 0 0 O Low cost DOS version (reduced features) also CID D OCIO .11,41 Y !SIMI

available Ring for full details , FX-144.1

iii 1 1 1 .11

"Quickroute provides a comprehensive and effective introduction to PCB design which is a pleasure to use" Radio Com munication May 1993.

Ns ms- POWERware, Dept EE, 14 Ley Lane, Marple Bridge, Stockport, SK6 5DD, UK. ;444 from Ring us on 061 449 7101 or write, for a full information pack. PO WERwan.

Software . Quickroute is available for Windows 3/3 1 in Professional (£99.00) and Standard (£59.00) editions. • Design and for DOS with reduced features (£39.00). All prices inclusive. Add £5 P+P outside UK £49

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Update and reskill at home or in your workplace training centre with these highly practical industrially approved short courses. There is no travelling so commence at any time on....

Electronic Testing & Fault Diagnosis Analogue Electronics Digital Electronics Fibre/Optoelectronics Programmable Logic Controllers

Courses are supplied with NOT training workbooks, audio cassette lecturettes, PCB's, instruments, tools, components and leads as necessary for each course. Continuous tutor support and BTEC certification is available as an option from NOT. Individual course certificates can be credited towards a BTEC Continuing Education Certificate which is at NV() level 4. For the latest information on courses and your options write or telephone: National College of Technology, NCT Ltd., PO Box 11 Wendover, Bucks. Tel: (0296) 624270

Everyday with Practical Electronics, February, 1994 95 OMNI ELECTRONICS 174 Dalkeith Road, Edinburgh EH16 5DX * 031 667 2611

The supplier to use if you're looking for:- A LIBRARY A WIDE RANGE OF *COMPONENTS AIMED AT THE * OF IBM-PC SOFT WARE ' * HOBBYIST 0 at your fingertips S H A R E W A R E is the T RY-BEF O RE•Y O U•B UY APPR O AC H TO SOF T W ARE: \ You pay a nominal charge for progra m distribution to cover disks, copying. carriage, etc O NLY IF YOU FIN D A PACKA GE USEFUL *COMPETITIVE VAT INCLUSIVE* ARE YOU THEN RE QUIRE D TO PAY A RE GISTRATION FEE (to the software author), which allo ws you to continue using it.

. PRICES . THIS CAN W ORK OUT CONSIDERABLY LESS EXPE NSIVE THAN BUYIN G SIMILAR , ,•-_), S OFT WARE IN THE CONVENTIONAL WAY. Electronics design on your PC *MAIL ORDER -generally by* - Now simple & AFFORDABLE! E N GIN EE RIN G - G R A P HIC S - B USINE SS - PC-T U T O RIALS RETURN OF POST 7 • C AL C UL ATIO N S • S CIE N CE - ED U C ATIO N ier Re-inventing the wheel/ Don't do ittt Quicky select software tailored to your needs from the many 1000's of packages available in the Public Do main, and as :Iii-• Shareware. We distribute IBM-PC compatible progra ms exclusively * FRIENDLY SERVICE* on carefully grouped sets of high quality disks i - which you time, and m oney. Ask for our latest catalogue! OPEN: C A D/C A M - P C B DE SIG N - CIR C UIT E M UL ATIO N & TEST - P C-E N GIN EE RIN G - R A DIO - C O M M'S Monday-Thursday 9.15 - 6.00 Profile Electronics (EPE) Friday 9.15-5.00 VISA "Getting the job done" 1166, - Saturday 9.30-5.00 100-102 Woodhouse Road, Leytonstone, London, 1E11 3NA. Tel: 081-470 2038 (24 hours) Mail order only

"B OFFINS SPE CIAL" - VARIABLE VOLTAGE UNIQUE OFFER Surplus Precision Medical Unit. internally in eocel• TRANSFOR MERS lent condition Designed primarily to eject a precise INPUT 220/240V AC 50/60 controllable amount of fluid front a medical syringe O UTPUT 0-260V (latter not supplied) Contains the following rernov 1 994.1 9 9S EDITION Price P&P able components Dual Micro Processor Boards and OUT NOW!! EPRO MS Escap Precision 12V DC Motor with 0 5KVA 25 amp max £31.90 £6.00 300 1 Gear Bp and optical encoder coupled to a (E44 53 Inc VAT) precision threaded drive mechanism Mains supply 1-1EnRys 1KVA 5 amp max £41.15 £7.00 with Be 1 5V Ni-Cad A A cells back up LC D AUDIO ELECTRODIC5 ((56 58 inc VAT) Digital read-out 17mm high with legends Audible yvernong CATALOGUE 2KVA 10 amp max £59.40 £8.50 These are sold to, the disnsantling of the exceptional (E79 78 inc VAT) quality components Regret no CorcultS available 3KVA 15 amp max £78.65 £8.50 Ridiculously low price rico° • E4.00 p&p ELECTRONICS FOR (f102 40 inc VAT) ((23.50 incl VAT). Ilmwo EVER Y PURPOSE! -al.-. 5KVA 25 amp max £139.15 12V D.C. GEARED MOTOR mum (Plus Carriage) 12V 0 C Reversible precision built Motor Output v‘Essql5t mom Buy direct horn the Importers Keenest prices in the country Weeds no load approx 12V• 26 rpm. 9V-20 rpm. 6V•12 win COMPREHENSIVE RANGE OF per Will work at lower voltages and still retain a waft TRANSFORMERS-LT-ISOLATION & AUTO reasonable torque Ideal for robotics etc Size L Dam 10- 2401 Apo trans'sr eithe used nit. Artercen soar and 4Ornm W 29 mm H 39ntrn Shah 3mm dia • 10mm mare kW Do ore" o' anse • • Ce Aid ate 1P immediate delivery IPni) Price £B.00 • 50P P&P (C10 00 inc VAT) foo - mon TORIN CENTRIFUGAL BLO WER man WIDE RANGE Of XENON FLA-WISES 230V AC. 2.800 RPM, 09 amp 130mm diameter im• mow Wrp• Phone your volumes pallor outlet 63 • 37mm. overall size 195 • 160 • swin ULTRA VIOLET BLACK LIGHT 150mm long Price E17.50 C2 50 p&p j(23 50 inc FLOURESCENT TUBES VAT) 94 Wee • DAYS A *US • CALLSRS C Aft 40 wan £l2 00 (callers only) ((14 10 inc VAT) SOLID STATE RELAY '19 7 amp n 240V AC when mounted on suitable Heat - 2ft 20 watt (7.44 - Cl 25 P&P ((10 21 inc VAT) tom • itc." a •IN 12in 8 wan C4.90 75p p&p ((6 52 inc VAT) sink Can be driven frornTTL or Computer output be 40114,411044.y SIDES 9in 6 watt (3 96 • 50p p&p (C5 24. VAT) tween 3 10V DC Size 24rnm s 17mm x 15nvn high fi'oo 6in 4 wan £3.96 • 5013e4e ((5 24 Inc VAT) Fixing centres 30mm (TO 3) Price £3.00 • 40P P&O l = B M 230V AC BALLAST KIT (C4 00inc vAr) coita ' For either 6in 91n or 12rn tubes £6.06 • f 1 40 GEARED MOTORS P&P (18 75. VAT) 71 RPM 20Ib inch torque reversable 115V AC in Open 6 400 WATT UV LAMP put including capacitor and transformer for 240V AC 01* (38 00 - C4 00 p&p IC49 35 Inc VAT/ operation Price inc VAT & p&p (27.73. days a i f 160 WATT SELF BALLASTED BLACK SOUD STATE ENT UNIT coo week - LIGHT MERCURY BULB Available with B C or E S fining Input 230,240V AC Output app . 150', CALLERS % Pnce Inc VAT & o&p £25.55 Producing 10mm spark Built -in 10 sec tiny, W ELCO ME \ Easily modified for 20 sec 30 sec to continuous 12V D.C. BILGE PUMPS Designed for boiler ignition Dozens of uses in the oua.1114,to\k\e't° 500 GPM 155 head 3 amp £19.96 field of physics and electronics eg supplying neon 1750 G PH 1511 head 9 amp C34 55 or argon tubes etc Price less case E8.50 (2 40 Also now available P&P (C12 81 inc VAT) NMS HeIRY'S 24V D C 1750 GPH 1511 head 5 env f3455 SAVE POUNDS !!! 404 Edgware Road, All designed to be used submerged Build your own forged bank note detector Can PRICES INCLUDE P&P & VAT detect counterfeits amongst a quantity of notes London W2 lED EPRO M ERASURE KIT Complete kit ol parts less case. 240V a c induct RETAIL • MAIL ORDER VERSION Build you own EPRO M ERASURE tor a fraction of the mg 6' iv black light tube, starter and holder a pair Components once of a made up unit ka of parts less case includes b1 -pin tube holders Total price including p&p & With price lists, special offers and purchase 12in 8 watt 2537 Angsi Tube Ballast unit pair of bo-pin VAT only £13.99. Telephone: 071-723 1008 leads neon indica. on oft switch. safety microswitch and vouchers. Send PO/Cheque £4.00 (UK) circuit C15.00 .C2 00 p&p ((19 98 inc VAT). M IC ROS WITCH 1.'6 00 (EC) £10.00 (Non EC) Callers £2.00. Security - Communications SUPER WV-LIGHT STROBE Kn. Rye 15 amp changeover lever rnicroswitch type S171 Designed for Disco. Theatrical use etc. Brand new pee 5 for f 7 05 inc VAT & p&p Telephone: 071-724 0323 Appro. 16 joules Adjustable speed C50 00- 13 00 p&p W ASHING MACHINE WATER PU MP Education, trade, quantity purchasers 1(62 28 Inc VAT) Brand new 240V AC fan cooled Can be used for a Audio and Test Instruments Case and reflector £24.00 • 13 00 p&P (C31 73 Inc VAT) variety of purposes Inlet rein outlet 1 on did Price Post or fax letterhead for FREE copy SAE tor further details includrng Hy•Light and in- includes p&p A VAT £1 1.20 each or 2 for £20.50 Telephone: 071-724 3564 dustrial Strobe Kits inclusive with trade/quantity price list (UK). Overseas prices as above. Trade/Quantity SERVICE TR ADIN G CO VISA Telephone: 071-258 1831 57 BRID G M A N RO A D, CHI S WIC K, LO N D O N W 4 5BB TEL 081-995 1560 FAX 081 -995 0549 Ample Fax: 071 724 0322 44, ACCOUNT CUSTO ME R$ MIN ORDER C10 ParkIng Space

96 • Everyday with Practical Electronics, February, 1994 Low cost data acquisition for IBM PCs & compatibles...

A unique range of low cost data acquisition products for IBM PCs and compatibles. Installed in seconds they simply plug directly into either the serial or parallel port. They are completely self contained, require no external power supply and take up no expansion slots. Each device comes with an easy to use software package (PicoScope, PicoLog or both). C, Pascal, and Basic drivers are supplied for those who want to develop their own software, as is a manual giving full details of the hardware and software. All software supplied on 3.5" disk. ADC -10 Up to 24kHz sampling rate from Software selectable single a 386/33MHz machine ADC-16 ended or differential inputs 0-5V Input range Resolution programmable BNC input connector allows between 8 and 16 bits + sign use of standard scope probes ±2.5V input range 30V overload protection 5V reference output Parallel port connection Connects to serial port Includes PicoScope software Includes PicoLog software Single Channel 8 bit ADC £49 8 Channel 16 bit + sign ADC £99 ADC-11 15K samples per second PicoScope 'Virtual instrument' software 0-2.5V Input range package for the ADC-10, ADC- Digital output 11 and ADC-12. D25 input connector 30V overload protection Storage oscilloscope with Parallel port connection trigger and timebase. Traces Includes both PicoScope and can be printed and saved. PicoLog software Mutt iple meters onscreen. Real Scope, voltmeter, time spectrum analysis. "11 Channel 10 bit ADC £75 spectrum analyser ADC-12 Up to 18k Hz sampling rate PicoLog Collect samples from 1 per ms to 0-5V Input range A NIY.11111.11111.• one per day. Scale samples BNC input connector allows linearly, by equation or by table use of standard scope probes look-up. Graphical (against 30V overload protection time or XY) and text reports can Parallel port connection be displayed, printed or Includes both PicoScope and exported. PicoLog software Advanced data Picolog is also available for the Single Channel 12 bit ADC £85 logging software ADC-10: call for details.

Typical application ADC-10 ADC-11 ADC-12 ADC-16 PICO BENEFITS Oscilloscope • • 30 day no quibble Voltmeter • • money back policy Spectrum analyser • Audio sampling • • Full 1 year guarantee Chart recorder emulation • 1 year's free software Temperature measurement • • • upgrades Pressure measurement • • • Chromatography • Free technical support Automotive monitoring • • Free user newsletter Medical research • • • Same day dispatch Education • • •

Pico Technology Ltd. Broadway House, 149 -151 St Neots Road, Hardwick, Cambridge. CB3 7QJ.

IVLS4 TEL: 0954-211716 FAX: 0954-211880 Phone or FAX for sales, ordering information, data sheets, technical support. All prices exclusive of VAT.

Everyday with Practical Electronics, February, 1994 97 SYSTEM 200 DEVICE PROGRAMMER PD/SHAREWARE FOR THE PC

SYSTEM: Programs 24, 28, 32 pin EPROMS, Let us share our EE-PROMS, FLASH and Emulators as knowledge with YOU! standard, quickly, reliably and at low cost. * * * * ELECTRONICS * * * * Expandable to cover virtually any Fro m Beginner to Teacher E01 ELECTRON electrical & electronic calculators res codes calcs & more program mable part including serial E2, E06 LSYSTEM universal digital logic simulator PALS, GALS, EPLD's and microcontrollers E07 PC-TECH electronics tutor + electro8 calculator from all manufacturers. E09 RESISTOR GUIDE easy program color code to value - value to code + Tutorial EIO AUTOSKEM schematics drawing program - 40 electric symbols many features OUR LOW PRICE £1.95 per DISK (STATE DISK SIZE) DESIGN: Not a plug in card but connects to the PC ALL ABOVE PRICE £5.95 INCLUSIVE serial or parallel port: it comes complete * * * * SATELLITES & ASTRONO MY * * * * with powerful yet easy to control software. SPACE OBSERVER & MISSIONS cable and manual. WEFAX Display weather pic. on screen WXRDR22 Weather Radar receiving program SUPPORT: UK design, manufacture and support. PCT214a General Purpose Satellite Tracking Marsobsv NASA Presskit Mars Observer Mission Same day dispatch, 12 month warranty. 1010 Satellite items plus USAT & Scanner Freq. Database 10 day money back guarantee. ORBIT23 Locate satellites in orbit USAT92B2 Satellite tracking program. With C)BASIC source. OUR LOW PRICE £1.95 per DISK (STATE DISK SIZE) ALL ABOVE PRICE £8.95 INCLUSIVE cN3csv. * * * * AMATEUR RADIO * * * * Fro m Novice to Experienced HA M H01 Enjoy Packet Radio without a INC - Dutch Program - Not for the be vner H03 Decode Morse code with a Sound Blaster and a microphone HO? Novice/TechiGeneral/Adv /Extra Ham Radio exams ASK FOR FREE H10 Amateur radio logbook program (w/BAS) > MACHINE: Morse Code training program in BASIC INFORMATION MORSE BAS: Learn Morse Code PACK OUR LOW PRICE £1.95 per DISK (STATE DISK SIZE) ALL ABOVE PACK £7.95 Hundreds of software disks to choose from: Phone or send now for FREE Disk Catalogue ISATE DISK SIZE)

GERMANY 089/4602071 (Software) Ltd, 1 Silvey Grove, NORWAY 0702-17890 MOP ELECTRONICS Ltd. Spondon, Derby DE21 7GH. EISA Unit 2, Park Road Centre, ITALY 02 92 10 3554 rf= Malmesbury, Wiltshire, SN16 OBX UK FRANCE (1)69.41.28.01 Tel: 0332 678713 El TEL. 0666 825146 FAX. 0666 825141 Also from VEROSPEED UK

WE HAVE THE WIDEST CHOICE OF USED CHASE 14E122000 INTERFACE - Measuring Receiver with mains network El 750 AITKEN BROS & Co OSCILLOSCOPES IN THE COUNTRY DAMN 10616 Cs C49/ wan True RIA5 AC/Current Lino I 1M 102 ANALOGUE M U I XIM EfER CONSTRUCTOR'S DATRON 1%5 Mnineter S , drgt ACIDCrarns IEEE £100 TEKTRONIX 7000 SERIES OSCILLOSCOPES 19 ranges Inc leads & batts Avadabie from £200. IESSIETT PH,OrARD S4904 WO Multrneter 5 ace PACK AC (0C,Ohns MOD AC volts. 0. 10-50-250-1KV PLUG-INS SOLD SEPERATELY. Containing; MUM PIA2534 AIM Functo PM 3' .-6- : clgt we CPS IFE MO pc volts 0-2.5-10-50-250- I KV -50aCtia 2235 [la Trace 100A4Kr DeOr Sart.% 2 x stripboard 64,05mm VARCON Nam Frecuenn Veter £125 DC cu rrent 0-5 m050m.500131-10A N155 5065 2 -1 Chancels 1001.414 Dua TB Delay Sweeo £700 NtARCONI Paul Precursor Meter 24310 104R1001.1it £1S0 'BRONX 475 Cum Trace 2CO.att Delav Sweet) ESSO MARCONI Universal Canter Timer 243750-12080 Es 73 Resistance 0- 10K-100K-10M 5 linear ICs - TEMPE( 465 Dual Trace 100mic Del, Sweet' £450 srARCON Unsersal Canter Trner 2438 X-52%lie £225 Dims. 135x89s4Ornm 555,TL081,7805,7812L M386 HP 1725A Cuero 275ake £S50 &AO( $TAR Jupitor SOO SnerSqln 0150.50562 (70 MAO p insACwarace2OCW:- FEEDBACK FG600 SnerS47o NII42-1004NI £60 8 74LS IC's - -AFC 605 Nal T race 601.114z Dea . ORAFO SPECIAL PRICE £13.50 SCUANCESOIANNINIt12901910ters LS00(x2) 04,10,14(12) 20,74 a'aLiPS R4217 Cuai Trace SOW Delay Sweep COO NP L15.99 P105 PIA5244 4 Trace 50AN Delay Sweep £350 m u m risalert EISOO 'ILEOUPMENT CS5 Dual Trace 501h4 Deav Sweet £200 £3CO ALT26 DIGITAL MULTIAIETER 10 CM OS ICs -ABU 535705 3 Chime 4CUIE DeLay Sweet £400 7 ranges inc 10A DC Inc leads & baits 4000(12)4001,4011 W) .CA041122 Dual Trace 4014112 £32S (350 4017(12)4040,4081,4093 ri(USu 5530 Dui Trace 55450 010 £907 3.5 digit 12mm LCD display AID 0311000.4311race £160 Kw £350 AC volts 0-500v 100 asst..25watt resistors 4rACHv223 Dial Trace 204.12 Delay Sum E300 £125 ENO DC volts. 0-20-200v . • HAIEC 203 6 Dal Trace 201.4 Ccmcorent Tester • ".,;. 3cr.L.r L • £1501 14 Electrolytic Capacitors DOUG) 06300 Dual Trace 2CUM £203 £1000 DC current. 0-10A £123 BICODTEST 34315 Care Test Set Normal pice owr.114.50 COULD 03.2508 Nal Trace 1 Slat ARNELL RSV TY5704.142 7CN 5A 305 109 (HO Resistance 0-2K-2M TEKTRONX 2430 Dum Trace 1 501frIt WM Rena E7250 ARNEO. 1160125 0-60V. 0- 2SA Wearer £t00 TEMPS 466 Nal Trace 1006110 CNN Wee Analogue Dims. 148x73x.32mm Special price One O WL PSU L3010-30V. 0-SA Newel Strace ARNE-U.830)20 0-30/.201, £250 SPECIAL PRICE £14.99 p 17414 Dial ',we 'omit ON, Sweep Anaiogue AINEU. B70;10 0- 30V. 104 MOO £9.99 FASO NP I20.99 Storage VARCOM1F27C0 Unwrsal LOR Anna Battery l•ror- £193 ties PAST SAisti lAST EMIRS 6605.3.0.1 VO rave Ouramellak meter V00.1163 Es 73 SOLDERING EQUIPMENT Noun PR5193 Pregrammatem e.r esber Assalon SMELL I4520 RF Paler Amp 1 5.5201/e 300ns* Generator 0-1164-34111L RACAL 810:14acrokat Wattmeter 1010-10035 £100 rice As nem £1500 190 VAM I Runt. Meter R180 P 3311A RuncD:41 Gel 01 le- 51.4e Six %To Es 25 WRCON 2019 Seknescen NAIR Sg Gen 80042.104011HZ £3003 _5uR Avm23 Az voltmeter Da 1Detz.500Att Elal uARCON 2018 Synthesized 41.1RIA *Gen BOK12-57CUR £930 WORN 3512 ilicrorrave Pregercy Counter 20$0-1800 £960 FARRELL ISOLATING TRANSFORMERS ANTEX DE-SOLDER PORTASOL £306 RACAL 9921 FreClUenCy Canter KHz GUS00. 240V 500 VA Lin-used MO I8W SOLDERING IRON PUMP GAS IRON RACAL/DANA 1991 Nanosecat Unreal Gaunter MOO isolating Transformers Un-Cased £30 FACAL 9302 6R IMIutmeter Tnien610100.1500 £450 SPECIAL PRICE £230 SPECIAL PRICE EL.99 SPECIAL PRICE £11.99 RACAL 9501A RF lalsoltrneter True RMS 1 Oen -1 500 NP19.99 NP13.99 NP 14.99 RACAL 9009 Aatanatic Mal Meter 10001 300 *Me NEW EQUIPMENT Dentat 12911 HP Put/Generator tyre 2148 VIO MAE OSCLLOSCOPE H141 003 Trne Tram 150550 NI-CAD 4 sr NICAD Order the .5016 PC736 RAse Gen PIC Ne.20Me DSO Owy Traria £147 BATTERY CHARGER AA BA TTERIES BATTERY CHARGER (RILEY 224 PromaranableOrentScurce DNS MAE MOLLOSCOPE IM604 0.M Trxe 6C4.11e Darr Sweeo £653 + PARNELL PSC520H SynAlIT-1.1 Sop Cen 100kirt-520110 CIN HNC OSCILLOSCOPE 111203- 7 Dual Tau Me LEACER LSC216 &WPM* Cen 0 1.3011124 15.1151/HE £O0 Tester £362 II t'' a 4 s AA NI-CADS NA.VrOng l&COPE 40051 Cusi Race 206610901SO:um £la3 TOGETHER Null UM %OWN beltstlystos Ni otter meals Nast* cpcic6coDes suppled von 2 sax h(Joiiii n a Coisken Ntsclartastrs11.17 =21 n-rn,r, ectsrloNIE1211, ts ILACKRA11111111111114 P&P al LIZ £51 O w IN Ma wr isatLVLE APOLLO 10 10(1Rtz Counter Tmer PanstPeradrTme mann etc £222 SPECIAL PRICE £5.99 SPECIAL PRICE £180 SPECIAL PRICE £.99 SPECTRA' ANALYSERS APOLLO 100 12010 las above men more rumens) £525 NPC6.99 NPL4.00 Per4 NPL10.99 ..,1•41T855543Ersug-r I DAHt E1100 IAETECe 100 FREQUENCY COUNTER 12010 £119 HP 141T est 8548 & 85528 5C006-12504.16 £1300 leFTEOR600 FREQUENCY COUNTER 60CIAtt £14.5 HP 140Tren 85541 8552A 50E041.1250W E1001 051503 1000 FREQUENCY COUNT-171 M . £199 HP 141T sees 85S6A 685528 2012-30ant SPIT% 500 FUNCTION cEN 01Hz-50041d Sine/S47o £119 PLEASE ADD £1.00 POSTAGE TO ORDER HP 140T wei8S53i. 8552A 160/4-1101.146 EXO VON COLOUR BAR GENERATOR PaI7VVItleC £229 IAARCCNI TF2370 10e-1 I Me £1300 64 aner Back Star equonent avanne £1500 K g CATALOGUE AVAILABLE £1.50 HP 182C with 85938 100e.15001ke OSCLLOSCCPE PROBES Settee xi sio 'P&P ES Ell VISA Used Equipment - Guaranteed. Manuals aupplied II poultrie. (refundable with order) This Is a VERY SMALL SAMPLE OF STOCK SAE or telephone for i ists Please check avatiability ordering CARRIAGE all units £16 VAT to be added to total of goods and carriage 35 HIGH BRIDGE, NEWCASTLE UPON TYNE NEI IEW Tel. 091 2329877 Fax 091 2619664 110S T E W A R T OF RE A DIN G VISA prig W Y KEH A N RO A D, REA DIN G, BER KE Rafl 1 PL SCHOOL & COLLEGE ORDERS WELCO ME (automatic account facility) TM: 0734 268041 Fax:0734 351696 , - , . 5 30on, MON FR .

98 . Everyday with Practical Electronics, February, 1994 WINTER 1993/94 QTRANSFORMERS from 111 I I1 jj a w y ff,g CATALOGUE

1.90 UK Distributor for Standard Toroidal Transformers • •107 types available from stock •Sizes from 15VA to 625VA •Dual 120v primaries allowing 110/120v or 220/240v operation cc;c...2 CI componentsrklt kits test equipment

STEEL DISHED c/3 awe. WASHER OUTER INSULATION

t--- 5

SECONDARY NEOPRENE WINDING WASHERS

INSULATION

PRIMARY CORE WINDING ENDCAPS

TYPE SERIES SEC RIIS TYPE SERIES SEC RMS l'AG° NO. VOLTS CURRENT VOLTS CURRENT • New 111;c.ere,;.,, 15VA 03010 6+6 1.25 225VA 63012 12+12 9.38 03011 9+9 083 „„ 63013 15+15 7.50 c., £10.00 03012 12+12 063 £21.v4 63014 18+18 6.25 '[.11 •••i.. 03013 15+15 050 63015 22+22 5.11 • New VAOSTRAP Kits 03014 18+18 0.42 63016 25425 4.50 03015 22+22 0.34 63017 30430 3.75 03016 25+25 0.30 63018 35+35 3.21 03017 30+30 025 63026 40440 2.81 30VA 13010 64 2.50 63025 45445 2.50 ,s, 13011 9+9 1 66 63033 50+50 2.25 £12.z I 13012 12.12 1.25 63028 110 2.04 The new enlarged 13013 15+15 1.00 63029 220 1.02 13014 18+18 083 63030 240 053 13315 22+22 0.68 300VA 73013 15+15 10 00 13016 25+25 0.60 73014 18+18 833 13017 30+30 0.50 £22.94 73015 22+22 Catalogue is out now! 6.82 50VA 23010 64 4.16 73016 25425 600 , 23011 9+9 2.77 73017 30430 5.00 £13.og 23012 12+12 2.08 73018 35+35 4.28 • New direct phone lines for prompt service 23013 15+15 1.66 73026 40+40 3.75 23014 18+18 1.38 73025 45445 3.33 23015 22+22 1.13 73033 50+50 3.00 ). 16 more pages 23018 25+25 1.00 73028 110 Z72 23017 30+30 0.83 73029 220 1 36 23028 110 0.45 73030 240 1 25 • fff's worth of discount vouchers 23029 220 0.22 500VA 63016 25+25 10.00 23030 240 0.20 „ 83017 ; 30+30 8.33 80VA 33010 64 6.66 £29.57 83018 ' 3545 7.14 >. 100's new products ,,,, 33011 9+9 4.44 83026 40+40 6.25 £15.44 33012 12+12 3.33 63025 45445 555 33013 15+15 2.66 83033 50+50 5.00 )- 240 pages, 26 sections, over 4000 products 33014 18+18 2.22 83042 55+55 4.54 33315 22+22 1.81 83028 , 110 454 33016 25+25 1.60 83029 ! 220 227 • New section of entertainment and accessories 33017 30+30 1.33 83030 240 208 including disco equipment, audio mixers, car 33028 110 0.72 625VA 93017 )3.3o 10 41 33029 220 0.36 ,„, 93018 35+35 8.92 amplifiers, crossovers, speakers and boosters 33030 240 0.33 £32.o4 93026 40+40 781 1206A 43010 64 10.00 93025 45+45 6.54 .., 43011 949 6.66 93033 50+50 6.25 • Complete range of Velleman kits now stocked £16...0 43012 12+12 5.00 93042 55+55 5.68 43013 15+15 4.00 93028 110 5.68 43014 18+18 3.33 93029 220 2.84 • The latest scanning receivers and accessories 43015 22+22 2.72 93030 240 260 43018 25+25 2.40 43017 30+30 2.00 13.8V DC POWER SUPPLY • New Ni-cad batteries and chargers 43018 35+35 1.71 TRANSFORMERS 43027 20+20 3.00 43028 110 1.09 8C267 500VA 18+ 1 BV £32.64 • New range of telephone equipment and accessories 43029 220 0.54 43030 240 0.50 9T845 575VA 16 1 V £38.06 160VA 53011 9.0 8.89 • Published December 1993 ,. 53012 12+12 6.66 £19.z 1 53013 15+15 5.33 1 53014 18+18 4.44 L III1 A M )1. Available from most large newsagents 53015 22+22 3.63 530113 25+25 3.20 Prices include VAT and carriage or direct from Cirkit 53017 30+30 266 53018 35435 2.28 „ 53026 40440 2.00 Quantity prices • Send for your 53028 110 1A5 53029 220 0.72 available on request copy today! 53030 240 0.66 C.A •11,9P 3°P Write, phone or fax for free Data Pack

Access Jaytee Electronic Services Cirkit 143 Reculver Road, Herne Bay, Kent CT6 6PL Telephone: (0227) 375254 Fax: 0227 365104 CCIRKITI DISTRIBUTION LTD Park Lane • Broxbourne • Hertfordshire • EN10 7NQ Telephone (0992) 448899 • Fax (0992) 471314

Everyday with Practical Electronics, February, 1994 91) 135 Hunter Street Burton - on - Trent All& 0 Allinclude Prices V.A.T. Staffs. DE14 2ST VISAse Add £2.00 per EL E C T R O N I c D Tel 0283 65435 Fax 46932 -TicEE140 order p &p SHOP OPEN 9-5 MON-FRI. CLOSED SAT --- OFFICIAL ORDERS WELCO ME

E.E. TREASURE HUNTER 12V EPRO M ERASER A safe low cost eraser for up to 4 EPRO MS at a time P.I. METAL DETECTOR KIT HIG HLIG HT in less than 20 minutes Operates from a 12V supply Magenta's highly DIGITAL CAPACITANCE (400mA) Used extensively for mobile work - up- developed & dating equipment in the field etc Also in educa- tional situations where mains supplies are not al- acclaimed design METER KIT 493 lowed Safety interlock prevents contact with UV Quartz crystal This has been one of Megenta s best ever controlled circuit kits It provides clear readings of KIT 790 £28.51 M OSFET coil drive. capacitance values from a few pF up to thousands of jiF It is ideal for beginners D C coupled as there is no contusion over the placing of EE TREASURE HUNTER amplification Detects the decimal point and it allows obscurely Our own widely acclaimed design This sensitive 10p coin at 20 cm marked components to be identified quickly and Pulse Induction metal detector picks up coins and Full kit includes easily Quartz controlled accuracy of 1%. large rings etc up to 20cm deep Negligible ground ef- fect ' means that the detector can even be used with PCB, handle, • KIT INC clear 5 digit display and high speed operation the head immersed in sea water .Easy to use, cir- case & make it a very useful instrument for production HEADPHONES cuit requires only a minimum of setting up as a search coil and testing departments The kit is now supplied Quartz crystal provides all of the critical timing Kit • EFFICIENT with a punched and printed front panel as well as includes search- head. handle, case. PCB and all the case, all components and top quality printed CMOS DESIGN PRICE cizrinfogreit circuit board When assembled it looks a really • POWERFUL COIL professional job For a limited time this kit is of- £39.95 £45.95 DRIVE fered at a new low price INSULATION TESTER A reliable and neat electronic tester which checks MOSFET VARIABLE BENCH POWER insulation resistance of wiring and appliances etc • DETECTS FERROUS AND at 500 Volts The unit is battery powered. simple NON-FERROUS METAL GOLD, SUPPLY 25V 25A and safe to operate Leakage resistance of up to SILVER, COPPER ETC Our own high performance design Variable Output 100 Megohms can be read easily A very popular college project • 190mm SEARCH COIL Voltage from 0 to 25V and Current limit from 0 to 2 5,4 Capable of powering almost anything Two panel KIT 444 £22.37 • NO 'GROUND EFFECT' meters indicate Voltage and Current Fully protected against short-circuits The variable Current limit con KIT 815 £45.95 trol makes this supply ideal for constant current 3 BAND SHORT WAVE RADIO charging of NICAD cells and batteries A Power Covers 1 6 to 30MHz in three bands using modern MOSFET handles the output for exceptional rugged- miniature plug-in coils Audio output is via a built- DIGITAL LCD THERMOSTAT ness and reliability Uses a toroidal mains transformer in loudspeaker Advanced stable design gives ex- A versatile thermostat using a thermistor probe and cellent stability, sensitivity and selectivity Simple having an I c d display. MIN/MAX memories, -10 KIT 769 £56 82 to build battery powered circuit Receives a vast to 110 degrees celstus, or can be set to read in number of stations at all times of the day Fahrenheit. Individually settable upper and lower switching temperatures allow close control, or alter- ULTRASONIC PeST SCARER KIT 718 £30.30 natively allow a wide 'dead band' to be set which can result in substantial energy savings when used Keep pets/pests away DIGITAL COMBINATION LOCK with domestic hot water systems Ideal for green- from newly sown areas, P U house ventilation or heating control, aquaria, home Digital lock with 12 key keypad Entering a four fruit, vegetable and flower O L brewing. etc Mains powered. 10A SPCO relay Out- W T digit code operates a 250V 16A relay A special put Punched and printed case beds, children's play areas, anti-tamper circuit permits the relay board to be E R mounted remotely Ideal car immobiliser, operates KIT 841 £29.95 patios etc. This project R A from 12V Drilled case brushed aluminium keypad produces intense pulses of Sr.. S KIT 840 £19.86 4 CHANNEL LIGHT CHASER ultrasound which deter -;,• ••0 A 1000W per channel chaser with Zero Volt Switch- visiting animals. ing, Hard Drive, and full inductive load capability I PEsT „ PORTABLE ULTRASONIC Built-in mic and sophisticated 'Beat Seeker circuit SCARER c - chase steps to music or auto when silent Variable PEsT SCARER A powerful 23kHz ultrasound generator in a com- speed and mic sensitivity control. I e d mimic on • KIT INCLUDES ALL pact hand- held case MOSFET output drives a spe- front panel Switchable for 3 or 4 channels P552 COMPONENTS, PCB & CASE • COMPLETELY cial sealed transducer with intense pulses via a spe- output socket Suits Rope Lights. Pin Spots, Disco. INAUDIBLE TO cial tuned transformer Sweeping frequency output and Display lighting • EFFICIENT 100V HUMANS is designed to give maximum output without any KIT 833 £32.13 TRANSDUCER OUTPUT special setting up • UP TO 4 METRES KIT 842 £22.56 • LOW CURRENT DRAIN RANGE SUPERHET LW MW RADIO At last an easy to build SUPERHET AM radio LIGHT RIDER DISCO LIGHTS kit Covers Long and Medium waves Built in KIT Ref .812 £14.81 A six channel light driver that scans from left to loudspeaker with 1 Watt output Excellent sen- right and back continuously Variable speed con- sitivity and selectivity provided by ceramic IF fil- trol Up to 500 watts per channel Housed in a ter Simple alignment and tuning without special IONISER plastic box for complete safety Built on a single equipment Supplied with pre-drilled transparent printed circuit board A highly efficient mains powered Negative Ion Generator that clears the air by front panel and dial, for interesting see-through KIT 560 £22.41 appearance neutralising excess positive ions Many claimed health benefits due to the ioniser KIT 835 £17.16 removing dust and pollen from the air and clearing smoke particles Costs virtually nothing to run and is completely safe in operation Uses five point emitters LIGHT RIDER KIT 707 £17.75 9-12V CHASER LIGHTS ACOUSTIC PROBE A low voltage DC powered end-to-end type chaser A very popular project which picks up vibrations by that can be set for any number of lights between means of a contact probe and passes them on to a BAT DETECTOR 3 and 16 The kit is supplied with 16 led s but pair of headphones or an amplifier Sounds from An excellent circuit which reduces ultrasound frequencies between 20 and 100 kHz by adding power transistors it is possible to drive engines, watches, and speech travelling through to the normal (human) audible range Operating rather like a radio receiver the circuit filament bulbs for a larger brighter display Very walls can be amplified and heard clearly Useful allows the listner to tune-in to the ultrasonic frequencies of interest Listening to Bats popular with car customisers and modellers Leds for mechanics, instrument engineers, and nosey is fascinating, and it is possible to identify various different types using this project can be randomly positioned and paired to give parkersl Other uses have been found in industry for vibration monitoring etc twinkling effects KIT 740 £19.98 KIT 814 £21 44 KIT 559 £15.58

HAM EG HM203-7 20 MHz EDUCATIONAL BOOKS & PACKS DC MOTOR/GEARBOXES DUAL TRACE OSCILLOSCOPE ADVENTURES WITH ELECTRONICS & COMPONENT TESTER The classic book by Tom Duncan used throughout Ideal for robots, buggies Western Europe s best selling oscilloscope It is RELI- schools. Very well illustrated ideal first book for age 10 and many other mechanical ABLE, HIGH PERFOR MANCE, & EASY TO USE. on No soldering Uses an S DEC breadboard projects Min plastic gearbox Sharp bright display on 8 x 10cm screen with internal Book &Co mponents £28.95. Book only £6.99 with 1 5-4 5V DC motor 6 graticule A special extra feature is the built-in com- ratios can be set up ponent tester which allows capacitors, resistors, transis- FUN WITH ELECTRONICS Small type MGS....£4.77 Large type MGL....f 5.58 tors, diodes and many other components to be checked An Usborne book, wonderfully illustrated in colour Com , The quality of this instrument is outstanding, and is sup- ponent pack allows 6 projects to be built and kept Sol- ported by a two year parts and labour warranty dering is necessary Age 12 on. or younger with adult If you are buying an oscilloscope - this is the one It help Book & Components £20.88. Book only £2.95 STEPPING MOTORS costs a fraction more than some other 20 MHz 'scopes For computer control via M D35'. - standard 48 but it is far far superior Supplied with test probes, mains 30 SOLDERLESS BREADBOARD PROJECTS standard 4 pole unipolar steps per rev £12.99 lead, and manual A more advanced book to follow the others No soldering drivers £362.00+ £63.35 VAT Includes FREE Circuits cover a wide range of interests M D38 - miniature 48 M D200 miniature 200 ( Cheques must be cleared) Next -day delivery Book & Components £30.69, Book only £2 95 steps per rev £9. 15 steps per rev £12.10

100 Evervday with Practical Electronics, February, 1994 M G_LN_TA EL E C T R O N I C S LT D EL E C T R O N I C S LT D Teach-In P93 Teach-In '93

MINI LAB KITS MICRO LAB KITS ALL COMPONENTS TO ASSEMBLE ALL COMPONENTS TO ASSEMBLE THE EPE MINI LAB. THE EPE MICRO LAB. Follow this exciting educational series as A 6502 Microprocessor trainer with many featured in EPE through 1993 features. Accompanied by an excellent set Full set of reprints £4.00 of tutorial articles and a manual. Components are supplied in packs to keep Repair/fault-finding help assured when you ordering simple. buy your kit from us.

A full MINI LAB consists of ML1, ML3, ML5, Full MICRO LAB kit including PC Board, ML6. These are available at a special EPROM, PAL, &Manual. combined price of £114.99 MIC 1 £149.95 or less the p.c.b. ML2, ML3, ML5, ML6 at £104.99 (Also available less PCB etc. if required). The transformer unit ML4 is also needed....£21.45 Full set of reprints £4.60

KIT ML1 MINI-LAB P.C.B. + all components inclusive of breadboard for Part 1 (Nov. '92) £49.95 BUILT& TESTED KIT ML2 All Components for Part 1 less p.c.b £39.95 KIT ML3 Power Supply components £19.95 Full MICRO LAB AS MIC1 (above) KIT ML4 Transformer unit £21.45 MIC1B £179.95 KIT ML5 L.E.D. Voltmeter, signal Professionally assembled, inspected, generator, audio amplifier and cleaned and tested. Full back-up service, 555 timer £33.95 spares, etc available. KIT ML6 Logic probe, display, radio tuner £17.95 (Note: batteries not included) All prices include V.A.T. Add £2.00 p&p. All prices include V.A.T. Add £2.00 p&p Tel: 0283 65435 Fax: 0283 46932 Tel: 0283 65435 Fax: 0283 46932

Everyday with Practical Electronics, February, 1994 ESR ELE CTR O NIC CO M P O NE N TS Station Road, CLI Ilercoats, Tyne & Wear NE30 4PQ Tel. 091 251 4363 Fax. 091 252 2296

RF CO N NE CT OR S 74LS Seoes 4000 Set les TRA NSIST ORS LINE AR ICs SOL DE RIN G IRO N S Anton Soldering Iron, C. Solder Plug 506 CO 93 741S00 C0.14 4000 CO 17 291613 £0 31 BC186 CO 33 13D534 £0.47 (.4311E CO 28 M 12 Watt £8.18 BNC So 1der Plug 756 £0 96 741501 CO 14 4001 £0.21 291 711 CO 26 BC204C CO 72 80535 £0.48 CA324 £023 C 15Watt CB 18 7 £0 68 741502 CO 14 4002 £0.17 291893 £0.29 BC2068 £0.72 60536 £0.65 CA555 £022 BNC Crimp Plug 501 1 G I 8Watt £8.41 741503 £0.14 4006 £O.32 29221 84 £028 BC207C CO 72 80646 £0.52 C6741 CE £0.18 BNC Crimp Plug 756 CO 68 CA747CE £0.39 CS 17Watt £8.31 Cl 08 741SO4 CO 14 4007 £0.17 2922194 £0.25 BC208 £0.72 80648 £0.52 BNC Solder Skt XS 25 Wan £8.41 4008 £0.31 2922224 £0.18 BC2094 CO 72 BD650 £0.53 CA3046 CO 37 NC Chess's Skt CO 80 741505 £0.14 014 Stand £2 97 4009 £0.19 292646 £080 BC212 CO 08 BD707 £0.42 CA3080 CO 72 P1259 5 2mm CO 68 741508 £0 14 35VVatt Gas Iron Ell 58 4010 E0 23 2929044 CO 25 8 21 1 CO 08 50807 £080 C43130 £0.98 P125911rnm £0 62 741509 ft) 14 CA3130E CO 98 Gascat Gas Iron £15 26 4011 £0.16 2929054 £0.23 6C21 218 £0 08 BDX32 £1.78 AND UHF socket £0 68 741.510 CO 14 C43140 CO 56 Low Cost 15 Watt Iron £3 93 4012 £0.16 292907 £0.20 BC213 CO 08 BDX33C £0.49 SOR UHF socket £0 45 7415107 £0 23 CA3240 £1 22 Desolder Pump f 3 00 4013 £0.21 292926 £0.16 BC213LC £0 08 130534C £0.50 F Plug RG58 CO 30 741S109 CO 21 ICL7621 £1 70 Antistatoc Pump £4 30 4014 £0.30 293053 £0.27 BC214 £0 08 BDX53C £0.47 CO 27 741911 CO 17 ICM7555 CO 43 22S WG 0 5Kg Solder £7 40 F Plug 906 £0.31 293054 CO 90 BC2141 CO 08 80554C £0.50 7415112 CO 21 4015 ICM7556 £0 96 18S WG 0 5Kg Solder £6 60 N Plug RG8 f 1 60 293055 £0 62 BC23713 CO 09 8E180 £0.31 741S113 CO 21 4016 CO 18 LM3014 CO 25 lrnm 3 yds Solder £0.62 N Socket 608 Cl 40 293440 £0.50 BC238C CO 09 84182 £0.31 741_5114 £0.21 4017 £0.27 LM3489 CO 31 Desolder Brad £0.87 BNC Crimp Pliers £15 50 293702 £0.09 BC239C Eti 10 BF185 £0.31 74LS12 £0 14 4018 £0.27 IF351N CO 36 293703 CO 10 8C251 £0 13 6E194 £0.19 PC B (71.111' 1011 NI 7415122 £0.31 4019 £0.19 1E353 £0.41 293704 £0.10 BC252 CO 13 BF195 £0.19 4020 £0.31 LM3589 £0.27 E67 38 7415123 CO 31 £13.10 BC261B CO 24 13E244 £0.35 UV EXPOSURE UNIT 4021 £0.31 293705 LM377 £2.57 7415125 CO 21 13C26213 CO 24 8E257 £0.33 PLASTIC DEVELOPING TRAY £1 35 4022 £0.32 293706 £0.10 1M3809 £1.12 7415126 £0.21 £1 44 13C2678 £0.30 0E259 £0.33 PHOTO RESIST AEROSOL SPRAY (100m1) £3 90 4023 £0 16 293771 1M381 £2.70 741513 £0.14 £0.10 8E337 £0.36 £2 45 4024 CO 21 293772 £1 .51 BC307 LM386 CO 48 FERRIC CHLORIDE CRYSTALS (0 5Kg) 7415132 £0.21 BC308 CO 10 0E355 £0.38 £0 72 4025 CO 15 293773 £1.79 LM387 £1 60 ETCH RESIST PEN 7415133 E0.18 CO 10 BF423 CO 13 4026 £0.59 293819 £0.40 BC327 M39241 CO 79 PCB POLISHING BLOCK Cl 84 €018 £0.19 7415136 293820 CO 66 BC328 CO 10 8E451 CO 28 4027 £0 18 M3939 STRIPBOARD 01 PITCH BREADBOARD 741S138 £0.24 293904 CO 10 BC337 £0.10 BF459 £0.29 £0.31 4028 £0.22 LM748C41 64mm x 25mm CO 27 81mm a 60mm £3 30 7415139 CO 25 293905 £0.10 BC338 £0 10 BF469 f0.36 LM1458 £0 26 4029 £0.36 64mm x 95narn CO 90 175rnm 5 42mm £3 74 741514 £0.25 293906 £0.10 BC414C £1) 13 BFX29 £0.29 £0 72 4030 £0.17 LM3900 64mm a 431rnm £3 22 175mm a 67mm £5.56 74E9145 £0.56 294036 £0.31 8C441 CO 40 BFX84 £0.31 LM39I 4 £2.70 4031 CO 70 95mrn 127mo, £1 50 2031nrn a 75mrn mcludes 7419147 £1.26 295296 £0.57 BC461 £0 40 BFX135 £0.32 LM3915 £2.70 4033 £0.56 95mrn x 95mm £1 .10 mounung plate & posts f 7 36 7415148 £0.70 295321 £0 57 BC463 CO 29 BEY50 £0.29 MC3340 £1.60 4034 Cl 24 95narn x 431mm £4.80 741S15 CO 14 296107 £0.60 BC478 CO 32 BEY51 £0.26 MC4558 £0.36 COPPER BOARD (G. Fibre/ 4035 £0.31 119mm a 454/nm £6 20 100mm a 160mm CO 90 741.5151 CO 25 Ad 26 £0.30 BC479 CO 32 13E 1152 £0.28 96531 Cl 56 4040 CO 29 110mm a 220mm £1 .34 AC127 £0.30 BC490 £0 24 85107 £021 9E5569 CO 36 7415153 £0.25 4041 £0.31 AC128 £0.28 BC516 £0.22 135170 £0.21 NE567N CO 47 PHOTO RESIST BOARD PHOTO RESIST BOARD 7415154 £0.70 4042 £0.22 AC187 £0.45 BC517 £0.20 BSW66 £1.35 585532 CO 80 IG. F,tore) (Paper) 741S155 CO 25 4043 £13.28 £0.20 BU126 £1.70 - - 74(9156 £036 AC188 £0.37 BC527 NE5534 CO 66 3 n4 £0 86 3 x 4 £0.67 4044 £035 ACY17 £3.84 8C528 CO 20 BU205 fl .82 4' a 6' £1 62 4 s6 £1.24 7415157 CO 25 TBA120S CO 90 4046 £0.31 601 49 C1 67 BC537 £13 20 8112086 £1 73 TE148105 CO 68 4 . 8' £2 09 4 eB £1 58 7415158 CO 25 4047 £0.25 ADI 61 £0.92 BC546C CO 08 5U3264 £1 .80 TBA820M £0 39 f 2 41 8- .10 £4 63 7415160 £0 32 4048 £0.31 50162 £0.92 BC547C CO 09 BU500 £2.32 7042030 El 35 741S161 CO 32 4049 £0.20 BC107 CO 14 BC548C CO 08 BU50871 £.76 11061 £0.35 C A PA CIT O R S S WITC HE S 7415162 CO 32 4050 £0.20 BCI 07E1 C0.15 BC549C £0 10 BU526 £2.24 71062 £0.42 Cer4m4 Mar , Chsc 1 OU & 133V 3arnp 250v fi 4rnrn 7415163 CO 32 4051 £0.36 8C550C CO 08 BU806 £1.36 71064 £0,46 BC108 £0.13 SPST Toggle CO 58 7419164 CO 26 4052 £025 BCI 084 CO 14 8 C5564 CO 08 BUX84 CO 78 T1071CP CO 32 1 OpF to 100nF SPOT Toggle CO 60 741S165 £0.48 4053 CO 25 BCI 08C £0.14 BC557C CO 08 iRF540 £1 .60 71072CP CO 34 1pF lnE E0.06 1n2.2n7 C0.07 CO 64 7415170 £0.30 4054 £0 56 BC109 CO 17 BC558C CO 08 IRF740 E1.63 71074CN £048 3n3 4n7 f 0.12. SPOT CO Tog 7415173 CO 24 4055 £0.34 8C109C CO 15 BC559C £0 08 MJI1015 £2A 1 TL081 £0.33 10n & 12n £0.07 DPDT Toggle CO 68 7415174 £0.24 4060 £0.31 BC114 £0.41 BC560B CO 09 MJ11016 £2.11 71082CP CO 34 Polystyrene 160V 5% 47pF to lOnF DPDT CO Toggle CO 76 7415175 £0.24 4063 £0.29 BC115 £0.41 BC637 £0.21 MJ2501 £1.60 71084CN CO 46 47p 2n2 C0.09 2n7 10n £0.12 DPOT CO Toggle 74LS190 CO 25 4066 £0.18 BC116 £0.41 BC638 £0.21 MJ300I ft 52 UA733 CO 64 (biased) Cl 20 £0 48 7415191 £0 24 4067 £1 91 BC118 £0.41 BC639 £0.21 MI 6340 £0.40 U192004 D CO N NE CT OR S DPDT CO Toggle 294142 Cl 04 7415192 £0.42 4068 CO 16 BC132 £0.36 BC640 £0.21 MJE350 £0.42 Plug Socket (based I way) Cl 20 MPS413 £0.12 29425E f 4 68 7415193 £0 24 4069 £0.20 BC134 £0.36 BCY70 £0.21 q Pr £0.29 £0.30 DPDT rnini slide CO 15 7415195 CO 24 4070 £0.17 BCI 35 £0.38 BCY71 £0.20 MPS442 £0.17 294266 f 2 61 29427E £8 82 15 Pln £0.39 £0.39 Rotary Wafer 1P-12 W 2P 6W 741St 96 CO 24 4071 CO 20 BC140 £0.25 BCY72 CO 20 MRF475 £7.28 29428E £6.12 15 Pin H D £0.81 £0.90 3P.4 W. 4P-3 W CO 78 741S197 CO 24 4072 £0.17 BC141 £0.27 60135 £0.20 TIP121 £0.35 2943 58 £5 31 23 Pin £0.40 £0.49 Key SwItch SPST £2.70 741S20 CO 16 4073 £0.17 BC142 CO 31 60136 CO 21 TIP122 £0.37 25 P,n £0.48 £0.50 50137 CO 22 TIP125 £0.37 ZN448E £7 92 Push to make CO 25 741521 CO 14 4075 CO 17 BC143 CO 34 9 Way plastrc COVel £0.30 CO 22 11P127 £0.37 Push to break CO 28 741522 £0 14 4076 £0.30 BC149 £0.21 BD13/3 EPR O M S & 15 Way plastic cover £0.33 £0 23 TIP132 £0 46 CO 63 7415221 £0.40 4077 £0.17 BC154 £0.36 BD139 23 Way plastic cover CO 36 Latchrng Push So, 901 40 CO 24 TIP137 £0.46 RA M S 7415240 CO 32 4081 £0.14 BC157 £0.12 25 Way plasm cover £0 36 8 CE1 Tact 6 a 6mm CO 25 £0.82 TIP142 £1 08 7415241 £0 32 4082 CO 17 BC159 C0.12 BD150C 2716 £4.46 SCI 60 £0.28 80165 CO 42 TIP147 £1 12 RESIST O RS 7415242 £0.32 4085 CO 28 2732 8C170 £016 80166 £0.35 TIP2955 £0.63 7415243 £0.32 4086 £0.26 27128-20 £369 0 25W 5% CF El 2 Series £0.60 100 PRESETS Enclosed Hon 4089 £0 55 BC170B £0.16 80187 £0 39 TIP29C £0.31 2764 25 £3.00 0 5W 5% CF El 2 Series £13.967100 or Vert 10OR *IMO 0 15W £0.15 741S24,1 CO 32 BC171 CO 11 BD201 CO 40 TI P3055 £0.63 27C64-25 £2 17 0 25W 1% MF E24 Senes ft .72 '100 PRESETS Skeleton Horz 7415245 £0 33 4093 £0.18 4094 CO 31 BC1718 £0.16 BD202 CO 40 TIP30C £0.31 21728.20 £3.15 POTS Log or Lin 47OR IMO 25mm or Vert 100R IMO 0 1W £0.11 7415247 CO 32 TIP31C £0.32 4095 CO 56 BC172 £0.13 BD203 £0.40 27C128-20 £3.31 de 0 25,0 shah £0.42 741S251 £0 21 £0.32 4097 £1 20 BC172B CO 13 130204 CO 40 TIP32C 27256-20 £315 7415257 CO 24 £0.72 PLEASE STATE VAL ME REQUIRED 4098 CO 31 BC177 £0.18 50222 CO 40 TIP33C 27C256 20 £3.55 7415258 CO 24 T114414 £0 36 4099 ED 38 BC178 £0.18 80225 EV 42 27C512 £3.69 741S26 f0.14 CO 38 TIP42C £0.38 C O MP UTER ACCESS ORIES DIO DE S 4502 CO 38 BC 179 £0.17 80232 27C010 £4.97 7415266 CO 14 TIP47 CO 48 4503 CO 31 BCI 82 £0.08 130237 £0 32 6116 ,10 El 53 Leads Zeno/ Duxges 2‘; 7 331. 741527 £l3 14 CO 32 TIP48 £0.62 £306 4508 CO 90 BCI 821 £0 08 BD238 6264 10 RS232 Lead Male 2510 Female 9 1399 741S273 £0 32 613240E1 £0.37 TIP50 CO 53 62256-10 £5.35 B2188400Mw £13 08 4510 £0.26 8C182113 £0 06 Null Modem Lead Female 25-Female 25 I 2 99 7415279 CO 25 B 02438 CO 50 VN1OKM £0.44 4164 15 El 78 PC Link Lead Female 9 to Female 9 12 99 E12585 1 3W CO 14 4511 £0 32 BC183 £0.08 741S30 CO 14 BD244A £0.53 VN664F £1 50 41256-10 £2.80 PC 1ink Lead Female 9 4. 25-Female 9 6, 25 14 50 4512 £0.32 8C1831 £008 194001 £0 .06 74LS32 CO 14 BC183LB £0 08 90246 C1 06 275300 CO 16 511000-8 £5.61 Parallel Printer Lead 2m £5.40 4514 CO 77 194002 CO 07 7413365 CO 21 BC184 £0 08 90441 CO 41 ZTX500 CO 16 514256-8 £5 61 RS232 Lead (all pins/ Male Male £3.75 4515 £0.98 1414033 CO 07 7415367 £O.I1 BC1841 CO 08 00442 CO 41 RS232 Lead (all pins) Female Male £3 80 4516 £0.31 BRID GE 741S368 £0.21 Centromcs 36 Way Lead Male Male CO 78 194004 £13 07 4518 £13 27 CO 14 TRIAC S TH YRIST O RS RE CTIFIE R S Gender Changers CO 07 741S37 4520 CO 26 194005 741S373 £0.32 Z0105DA £0 42 9 Way D Mn, Female to Female fl 81 4521 CO 62 PO10244 £0.19 9 Way D Mini Male to Male Cl 95 194006 CO 08 7415374 CO 32 TIC206D CO 65 £0 '3° W005 1 54 5011 4526 CO 40 TIC106D WO2 1 54 200V £0.20 25 Way D Min, Female to Female £2 48 194007 CO 08 7415375 £0.34 TIC2260 CO 73 £o.40 4527 CO 39 £0.66 BR32 3A 200V £0 36 25 Way D Min; Male to Male £2 48 195400 CO 09 7415377 £0 32 87408-6008 CO 84 TIC1160 4528 CO 40 CO 77 BR62 6A 200V £0.64 9 Way D Female to Female £2 33 7415378 CO 62 TIC236D £0.96 TIC 126D 195401 CO 09 4529 CO 44 1004 10A 4000 Cl .39 9 Way D Male to Male £2 48 741538 £0.19 DISC £0 20 195402 CO 09 4532 CO 32 25 Way D Female to Female £2 71 £0.25 DIL S O C KETS 7415390 4534 £2 48 V OLT A GE H A R D WARE 25 Way D Male to Male £2 71 195404 CO 11 7415393 £0.24 4536 Cl 00 RE GUI AT O RS T2 Box 75 x 56 x 25mm CO 82 8 Pin C007 Adaptors 195406 CO 11 74LS395 £0 26 4538 £0.37 9 Way Male to 25 Way Female £2 33 13 Box 75 a 51 . 25mm CO 82 14 Pro £0.11 195407 £0 14 741S399 CO 62 78105 £0 24 25 Way Male to 9 Way Female E2 71 4541 CO 33 T4 Boa 111 x 57 x 22mm £0 98 16 Pro £0.15 74(940 £0.14 4543 £0.46 78112 CO 24 25 Way D Male to 36 Way Centronic £3 88 195408 £0 15 M81 Box 79 x 61 x 4Ornrn Cl 44 18 Pin £0.15 741542 CO 25 4555 ECI 34 78115 CO 24 25 Way Null Modem Female Female £3 02 19914 £13 06 MB2 Box 100 x 76 x 41mm £1 56 20 Pin £0.18 741S47 £0 42 4556 £0.34 79105 CO 28 24 Pin £0.19 25 Way Null Modem Male to Female £3 02 19916 £0.06 MB3 Box 118 x 98 x 45mm €1 .82 741S51 £0.14 4560 £1.18 79112 CO 28 28 Pm EV 22 25 Way Null Modem Male to Male £3 02 '.rllSBonl'iO.100r600rr £2 50 1414148 £0.05 741S670 £0.69 4566 £1.96 79115 £0 28 40 P u £0 25 RS232 Surge Protector Male Female £6 32 741573 CO 17 4572 £0.25 7805 CO 28 RS232 Jumper Box Male to Female £3 02 BY133 C0.13 ELE CTR OLYTIC RA DIAL CA PA CIT O R S 741S74 £0.19 458.1 CO 24 7812 £0 28 RS232 Tester (7 LEDsi Male Female £6 59 0447 CO 28 CO 28 Data Switch Boxes 741575 £0.19 4585 £0.32 7815 0490 £0.07 160 254 1/31. 1000' 450. Sorrel SwItch boa - 2 Way SIB £9 20 741576 CO 25 4724 £0 70 7905 £0 38 oF £0 38 £0.07 SenalSwoich box - 3 Way A/B/C £13 16 0491 £0 10 74LS83 CO 31 40106 £0.31 7912 047 £0.05 CO 38 £0.06 £0.15 Seoal Swrtch box - 4 Way A/B/C/D £15 15 04202 CO 27 741585 £0.35 40109 £0.50 7915 10 £0.05 LM3I 7T CO 56 £0.05 £0.06 £0.18 Serail Switch box - Cross OW, £19 69 741S86 £0.20 40163 CO 46 22 86157 CO 10 1M723 £0.29 C0.05 £0.08 Parallel box - 2 Way A/B £11 84 741590 £0.23 40174 £0.34 47 85158 CO 10 1200CV El 16 10 £0.06 £0.05 £0.06 £0.08 £0.48 Parallel boa - 3 Way A/B/C, E17 11 741S92 £0.35 40175 £0.36 Parallel box - 4 Way A/B/C/D El 8 43 84159 CO 10 LM323K £2 70 22 f 0 05 £0.06 £0.09 741593 £0.25 40193 CO 60 Parallel box - Cross over £20 42 LM338K £5 52 47 £0.06 £0.06 £0.11 194149 CO 06 Disks - 3 S' DSO° Disks Pack of 10 CO 56 100 CO 06 £0.09 £0.11 04200 CO 10 EN A MELLE D £0 09 £0.12 £0.31 3 5- DSDD Doks Pack of 50 £17 95 OPT O DE VICE S 220 39' DSHD Disks Pack 0110 £6 45 C OPPE R 470 CO 15 CO 19 CO 57 £0.09 39' DSHD Disks Pack of 50 f 28 48 5mrn Red LED £0 22 £0.29 WIRE 1000 3 9' x 50 Orsk Storage Box £4 26 5mrn Green LED CO 10 £0 37 CO 57 2200 39 x 100 Disk Store.° Boa f 5 45 All 2oz Reels 5mrn Yellow LED £0 10 4700 £1 11 £0.10 14 SWG £0.63 5rnm Orange LED ELE CT R OLYTIC AXIAL CAPA CIT O R S 16 SWG £0.67 3rnm Red LED £0.08 ORDERING INFOR MATION 18 SWG £0.67 3mrn Green LED £0.12 uF 160 25V 63V 100V 450V 20 SWG CO 72 3rnm Yellow LED £013 047 £015 All prices exclude VAT. 22 SWG £076 3rnm Orange LED £0.13 1 0 £0.10 CO 10 CO 19 £022 Please add £1.25 carriage to all orders and VAT (17.5%) 24 SWG CO 80 5mm Flash,ng Red 170.50 22 £0.10 CO 10 u :7, £0.09 CO 10 CO 10 CO 34 26 SWG CO 89 5nam Flashing Green CO 54 4 7 No minimum order charge. £0 12 CO 12 CO 12 28 SWG CO 91 CO 36 5rvorn B Colour £0 09 CO 13 CO 17 Please send payment with your order. 30 SWG CO 93 5rnrn Tri Colour £0.48 11 £0 10 £0 11 CO 16 £0.20 PO/Cheques made payable to 32 SWG CO 93 5rnm Plastic Bezel £0 04 100 £0 .10 CO 13 CO 21 34 SWG £0.99 3mm Plastic Bezel £0 05 220 CO 13 CO 18 CO 42 ESR Electronic Components M A 36 SWG £1 .04 0 3" 7 Segment Display Red 470 £0 21 £0 24 £0.69 CO 40 Cl 05 Access & Visa cards accepted 38 SWG £1.10 common anode ft .14 1000 CO 33 2200 £0 .52 CO 64 40 SWG £1.22 common cathode £1.14 Offical orders from schools & colleges welcome 4700 £0.90 CALL IN OPEN: MON-FRI 8.30-5.00 SAT 10.00-5.00

Everyday with Practical Electronics, February, 1994 102 Editorial Offices: EVERYDAY EVERYDAY with PRACTICAL ELECTRONICS EDITORIAL, 6 CHURCH STREET, WIMBORNE, WITH PRACTLW DORSET BH21 1JH Phone: Wimborne (0202) 881749 Fax: (0202) 841692. DX: Wimborne 45314. See notes on Readers' Enquiries below - we regret that lengthy technical enquiries cannot be answered over the ELECTRONICS telephone. Due to the high cost we cannot reply to overseas readers queries by Fax. INCORPORATING ELECTRONICS MONTHLY Advertisement Offices: EVERYDAY with PRACTICAL ELECTRONICS ADVERTISEMENTS, HOLLAND WOOD HOUSE, CHURCH LANE, GREAT HOLLAND, ESSEX C013 OJS. VOL. 23 No. 2 FEBRUARY '94 Phone/Fax: (0255) 850596

50's TECHNOLOGY Editor: MIKE KEN WARD Secretary: PAM BRO WN The valve sound seems to be a major topic again, with valve amplifiers Deputy Editor: DAVID BARRINGTON and kits available and much commotion in the hi-fl press. There have also Business Manager: DAVID J. LEAVER been some published designs, most of which show little change from the Subscriptions: MARILYN GOLDBERG original designs of the 50's and 60's. A cottage industry has grown up Editorial: Wimborne (0202) 881749 around refurbishment of certain amplifiers and small fortunes are being Advertisement Manager: asked for some refurbished products. PETER J. MEW, Frinton (0255) 850596 To give you an insight into this fascinating area of activity Jake Roth- Advertisement Copy Controller: DEREK NEW, Wimborne (0202) 882299 man has produced a full article showing how to rebuild one of the best READERS' ENQUIRIES amplifiers of its time, the Quad II. The article gives all the neessary techni- We are unable to offer any advice on the cal details and should allow almost anyone to recreate the type of amplifier use, purchase, repair or modification of commercial equipment or the incorporation that is presently changing hands for several hundred pounds. or modification of designs published in the Jake is also working on a new valve amplifier design for us, one that will magazine. We regret that we cannot provide employ some of the knowledge gained over the last 30 years, rather than data or answer queries on articles or projects that are more than five years old. just a rehash of an original. If this area of audio interests you then watch Letters requiring a personal reply must this space! be accompanied by a stamped sea: addressed envelope or a self ad- dressed envelope and international 90's TECHNOLOGY reply coupons. Due to the high cost we At the other end of the technology scale we also present a project using a cannot reply to overseas readers queries by Fax. Motorola K series microcontroller. The application of Timeout is simple All reasonable precautions are taken to but we hope that the project will help readers to get involved with modern ensure that the advice and data given to microcontroller i.c.s. readers is reliable. We cannot however guarantee it and we cannot accept legal Once again this fast developing area of electronics is fascinating. It could responsibility for it. of course eventually lead to the demise of' many hobbyist projects. Perhaps COMPONENT SUPPLIES the time will come when one simple universal microcontroller board can be We do not supply electronic com- ponents or kits for building the projects used for virtually any application, then we might be reduced to publishing featured, these can be supplied by adver- programming hints and tips. 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Send card number and/or imprisonment can result from illegal and card expiry date with your name and ad- use. The laws vary from country to country; dress etc. overseas readers should check local laws.

Everyday with Practical Electronics, February, 1994 103 Constructional Project WHISTLE CONTROLLED LIGHTSWITCHç BART TREPAK

A co mpact unit that can replace The answer is, in fact, the most natural of all remote control links — the human a standard light switch to provide voice. It has an almost unlimited number of possible channels and would, in fact control by whistling. It also be the ultimate remote control. "TV on, Channel two, Hifi off, Lights Dim" is the includes a touch s witch. stuff science fiction is made of. The problem in the real world is of course, noise immunity not to mention EMOTE control of various appliances S P E A KIN G O U T simply decoding the sounds. While you has enjoyed a great deal of The TV is perhaps not a good example of are saying "TV on" someone might be popularity in the past few years, R where a remote control is of paramount calling from the kitchen. "Do you want especially as the cost of adding such a importance as "getting up" may be the a cup of tea?" drowning out your com- facility to a product has decreased with the mand. falling cost of integrated circuits. This can only exercise many viewers get in an eve- Even decoding the sounds is not be seen in the proliferation of gadgets to be ning! The lightswitch on the other hand enough, as the receiver would also have to seen' around your armchair for controlling would perhaps be more useful as one often "understand" what was being said. You the television, video. hi-fl and, if you are a enters a room (such as a kitchen for ex- might be explaining to a friend that "We keen electronics enthusiast, the curtains, ample) carrying the shopping or a tray often have the TV on and the lights dim" the heating and any other gadgets which which makes it difficult to reach the switch to find that the system switches on the TV you can think of. to turn the lights on. In this case unfor- and dims the lights! Worse still, (or While these perform admirably they all tunately, it would be no easier to operate perhaps better still) you may be watching suffer from the same weakness; namely your remote control handset even if this Neighbours and a character in the they all need a transmitter. Not only does were to hand. programme says in the dialogue "switch one need two or three different transmitters But do we need all these handsets? Well if that TV want—..." and the TV goes to control the various appliances (although we intend to use some form of remote con- off, I off! nowadays it is possible to purchase one trol link we have to have some way of Voice recognition systems do exist but programmable transmitter to replace all producing the necessary signal and if more are based on microcomputers which apart the others) but by Murphy's Law the than one appliance or function is to be from being relatively expensive and too transmitter you need to change channels to controlled, we need to be able to generate a complex to fit into a standard lightswitch see your favourite TV programme is out of corresponding number of different signals. box at present, also require the user to reach on the coffee table at the far end of So if we want to do away with all these speak clearly into a microphone which is the room. Since you have to get up to get it transmitters, the only approach is to use a conveniently placed close to his lips. This anyway and the TV is nearer, you may as form of link which uses signals that we can would probably be more inconvenient well not have a remote control handset and generate without the need for additional than the handset we are trying to replace! perform the task manually. gadgets. O WIN G T H E W HIS TL E Fortunately, there is another way and one for which a special integrated circuit is available. The only problem (there has to be one) is that the user needs to be able to whistle, but even this problem has been solved by including a touch control al- though, in this case of course, the user will have to forgo the "remote control" feature. The moral is that if you want to communi- cate you have to learn the language! The whistle switch circuit described here is based on an i.c. of the type used in keyfinders except that instead of the circuit responding with a tune, this chip has an output transistor which switches on or off. It has been found to have quite a good noise immunity and works even when the TV is on.

104 Everyday with Practical Electronics, February, 1994 Cl 100 ,, p1 4002 820 63 65 6806 620 061 C 2 4k7 C3 MIN 4 7, LAMP 470p 200 W MAX TB1

CSR1 TIC 2060

TR1 2400 AC TR3 BC 548 MAINS BC 548

BC548 164148

VR2 > 611 262 680k

BC 548

Fig. 1. Complete circuit of the Whistle Controlled Light Switch.

The only time it seemed to switch the Apart from the amplifier, ICI also con- O.C. S U P PL Y lights on other than to a whistle was when tains an oscillator running at a frequency The problem of obtaining a d.c. power our small son screamed (he seemed to have determined by resistor R3. With the value supply for the circuit is solved in an un- just the right pitch). It was then, of course, shown, this is about 18kHz and in opera- usual way because being a two wire cir- a simple matter to whistle and switch the tion the internal logic switches the output cuit, there would normally be no voltage lights off again. on and off each time an input signal of across the switch when the light was on. Apart from its convenience (you could between one-tenth and one-fifteenth of the In this case the load current is made to now switch on the lights before you entered clock frequency (i.e. 1•2kHz and I.8kHz) is flow through the Zener diode DI (as well a room) and providing a talking point received over a period of 256 clock cycles. as the triac CSR1) and the resulting a.c. amongst your friends, this device also has This gives the circuit a fair margin of noise its serious uses. The advantages of such a immunity without requiring a whistle of light switch for the old or disabled per- exactly the correct frequency to operate the son or in situations such as kitchens or unit. workshops where the hands are otherwise The output transistor TR1 is used to COMPONENTS occupied are obvious. It also means that trigger the triac CSR1 and switch the lights the lightswitch need no longer be sited by directly, and since d.c. or continuous trig- Resistors the door which can save a lot of work gering is employed, the triac conducts con- R1, R2, R5 820 (3 off) chasing out walls if additional lights are to tinuously and no radio frequency inter- R3, R11 680k (2 off) See be provided in a room. All this and you ference is generated thus eliminating bulky R4, R7, R9 10k (3 off) WCIP don't even need a transmitter! chokes and suppressor capacitors. R6, R8, R10 1M8 (3 off) A110 6W 5% carbon film TALK CIR C UIT Page T O U C H CO NTR OL Potentio meters D ES C RIPTIO N The touch control circuit consists of VR1 4k7 enclosed carbon The complete circuit diagram for the transistor TR4, decade counter IC2 and preset, vertical Whistle Controlled Light Switch is shown associated components. This i.c. simply VR2 2M2 enclosed carbon in Fig. I. As shown, the device is a two wire divides the clock signal by ten and feeds it preset, vertical circuit which derives its power through the to the input of the whistle switch ICI which Capacitors load and can therefore be fitted in place of causes it to switch the lights on and off each Cl 100n polyester, 400V a conventional light switch without altering time it receives 256 cycles. Normally this C2 C6 47p radial elect. 16V any of the house wiring. circuit is inhibited because the CE input C3, C4, C8 470p ceramic This is a big plus over many designs for (pin 13) is held low by resistor R11. C5 10n ceramic the home constructor, which usually re- Although the i.c.s operate from a voltage C7 100n poly. layer quire the provision of a Neutral (N) wire of about 4 volts due to the action of the Semiconductors which is of course not normally available Zener diode DI, the whole circuit is at D1 4.7V 1.5W Zener diode at the switch box. The live and load con- some 240V a.c. with respect to N or Earth D2 1N4148 signal diode nections are shown as for a conventional since N and Earth are roughly at the same CSR1 TIC206D 400V 4A triac switch but in practice which of the two potential. This means that when the base TR1 to TR4 BC548 npn silicon terminals on the switch is connected to (b) of transistor TR4 is "earthed" via the transistor (4 off) live is not important except in the case small capacitor consisting of your hand, IC1 UM3763 whistle switch of the touch control circuit, IC2. If the the plastic front plate and the metal foil IC2 CD4017 CMOS decade touch control feature is not required, IC2 "touch" plate behind it, its emitter (e) is counter and its associated components may be left still at 240V a.c. This has the same ef- Miscellaneous out and the circuit connected either way fect as far as TR4 is concerned as if the MIC1 Electret microphone around. emitter was earthed and a 240V a.c. sig- insert The sound (whistle) is picked up by an nal was injected into the base via a small Printed circuit board available from electret microphone MIC I and fed to a two capacitor. (Note the metal "touch" plate is EPE PCB Service, code 860; single stage amplifier based on transistors TR2 inside a fully enclosed plastic switch blank- swttchbox blanking frontplate (see and TR3 with the preset VR I acting as ing panel, thus safely isolating the user). Shop Talk); 2-way, p.c.b. mounting, mains screw terminal block; aluminium a sensitivity control. At a pinch, a single Transistor TR4 thus switches on during foil, about 4cm square, insulating stage amplifier could have been used as ICI the positive half cycles of this a.c. signal sleeving; solder. contains a further amplifying stage but on and charges capacitor C7 taking the CE in- the basis that it is better to have too much put (pin 13) of IC2 to a logic 1 enabling the gain and then reduce it, than not enough in circuit. When the hand is removed, C7 dis- Approx cost the first place it was decided to use two charges via resistor RI 1 and disables IC2 guidance only £15 transistors — and hang the expense! again.

Everyday with Practical Electronics, February, 1994 105 TR2f ie r re- TR3 • Cl cs no % 1. 10 :110 C 3

R7 e 2c a o k " aL. R9 /..f- 2, 11146 D2 TR1 • 1 Fig. 2 P.C. B.

-4- • L master and PE component layout

10 -41 for the Whistle Controlled Light Switch. :SF+

voltage across this component is rectified tions. If a higher load is to be switched, a soldering low profile components such as by diode D2 and smoothed by capacitor SW Zener can be fitted, giving a maximum resistors and diodes first, paying par- C2. When the triac is off, a smaller cur- load current of 2A which is equivalent to ticular attention to component orientation rent is provided by the "lossless dropper" 500W. where this is important (i.e. with diodes, capacitor CI with resistor RI limiting dis- electrolytic capacitors etc). Make sure also charge current of Cl which could damage C O NSTR UCTIO N that components are pushed down onto the the triac when it is switched on. I his unit carries mains voltages and it board and not left standing on long leads Another way of obtaining a d.c. supply should NOT be constructed h an one which could touch adjacent components or would be to delay the triggering of the without some experience of building mains even the wall box with potentially dis- triac slightly at the beginning of each powered projects. Any reader who is not astrous consequences. half cycle and rectify the resultant volt- certain of being able to build it safely is The triac CSRI is mounted flat on the age across the triac but this method strongly advised to seek professional advice board as shown in Fig. 3. Note that the would generate radio frequency inter- and help. heatsink tab is internally connected to the ference (r.f.i.) which would require further Bearing in mind that the unit is at mains centre lead of the device and should there- components to suppress. The advantage potential, and to ensure safety, the use fore NOT be allowed to touch any other of this circuit is that there is no delay in of the ready made printed circuit board component on the board. The i.c.s should switching the triac and so no r.f.i. is (p.c.b.) is recommended. This board is be mounted in sockets and normal precau- generated. available from the EPE PCB Service, code tions observed as these are both static sen- On the down side however, the maximum 860. The p.c.b. topside component layout sitive devices. load current is limited by the maximum and full size underside copper foil master The electret microphone is mounted dissipation in diode DI. During the nega- pattern is shown in Fig. 2. "off the board" on short pieces of stiff tive half cycle this amounts to the load The circuit is best constructed on a wire, such as discarded component leads, current times the forward voltage drop in printed circuit board as there is not much so that it will be near the 2mm to 3mm DI (about 0.6V), while in the positive half space available in the wall box and the high dia. hole in the side of the plastic front cycle it is the load current times the Zener mains voltages that exist in some parts plate which will need to be drilled in the voltage. of the circuit could cause problems if appropriate place. Note the polarity of For a 1.7W 4.3V Zener the maximum tracks are inadvertantly connected. If the this component: the negative lead, which load current will be about 600mA which board layout shown is used these problems is the pad connected to the microphone represents a load of approximately 150W should not arise. body, should go to the hole nearest the which should be sufficient for most applica- Start construction by inserting and transistors on the p.c.b. If it is not obvious which pad this is, a multimeter set to the ohms range may be used. Make sure that the body of the microphone insert will not touch the metal wall box when the unit is mounted • by insulating it with a piece of insulating tape or heatshrink sleeving. When con- struction is complete, check your work carefully as unlike many battery powered projects, mistakes can result in the destruction of the whole p.c.b. T O U C H PA D The next step is to solder a short piece of stiff wire (again a discarded component lead will do) to the base of transistor TR4 (the pad marked "TP") on the copper side of the p.c.b. This will form the connection to the touch plate by simply touching the metal foil. A piece of aluminium foil about 4cm square should now be stuck to the in- side of the plastic front plate between the mounting holes. Clean off an area of the foil around the place where the wire from the p.c.b. will touch it with a piece of fine abrasive paper or wire wool and mount the p.c.b. onto the rear of the plastic front-panel plate using two self-tapping screws as shown in Fig. 4. It is strongly recommended that you use the front plate specified and not a standard type available from electrical sup- pliers as these are not as deep and can result in components touching the earthed metal box when the unit is mounted in the wall.

106 Everyday with Practical Electronics, February, 1994 P.C.B. DO NOT BEND LEADS (COMPONENT SIDE I Z HERE

P.C.B. I TRACK SIDE I Fig. 3. Mounting CSR1 on the p.c.b.

Fig 4 (right). Touch plate connection inside the plastic mounting plate. FRONTPLATE

TESTIN G switch (remembering to switch off the mains powerful Zener diode and a suitable supply first), although the presets VR I and heatsink to the triac although it may then Mains voltages are present on the p.c.b. VR2 may require re-adjustment to suit the be difficult to fit the unit in a wall box, let and the finished unit should be carefully new location. When you remove the exist- alone remove the heat from such a confined checked befOre wiring it in. Also, if possible, ing lightswitch, make sure that the you space effectively so a figure of 300W would do not attempt to test the unit without first know which wire is Live (usually the red be more reasonable, which should be mounting the p.c.b. in a temporary fully one). This can be checked by testing with a sufficient for most applications. enclosed plastic box, with holes drilled for neon mains tester screwdriver and it will be leads and access to the preset controls. the wire which lights the neon. if you are W HIS TLIN G IN Remember that the circuit operates at unsure, connect the unit one way and if the mains voltage and must not be connected to T HE DA R K touch circuit does not work simply reverse Earth. SWITCH THE MAINS OFF before Although the circuit was designed the connections. fitting or making any alterations to the primarily for ordinary tungsten lamps it is The maximum load for the circuit should circuit and use an insulated screwdriver also suitable for switching fluorescent NOT EXC'EED 150W as mentioned above. when adjusting the presets. Failure to ob- lights or other loads such as transformers Higher powers up to a maximum of 500W serve these precautions could at best result in provided, of course, that the maximum you having to purchase a new set of com- could be handled by fitting a more load is not exceeded. There is also no ponents and a circuit board, and at worst minimum load requirement to enable the 240V never purchasing anything again! LO A C. triac to latch as in the on state the triac is Connect the mains with the live as shown continuously triggered. It should however 200W and a 60W to 100W lamp to the terminal MAX be remembered that the unit will pass block on the unit (see Fig. 5). If you get about 10mA in the off state due to the the polarity of the mains wrong it will not current flowing in capacitor Cl so that very damage the unit but you will find that the low power loads such as neon lamps or touch circuit will not operate. mains relays many not switch off unless a Turn the "wipers - of the presets VR I power resistor is connected across the load. 0 and VR2 fully anticlockwise and switch on. Since the frequency to which the unit will A short whistle should turn the lamp on. respond is determined solely by resistor R3, Initially try whistling at various frequencies it should be possible to control a few lights to ascertain the correct pitch required. Pre- or appliances independently by selecting set VR I may now be adjusted until the different value resistors for R3, although required sensitix ity is obtained. this has not been tried. As each resistor To set preset VR2 (which controls the will enable the unit to respond to a range touchplate sensitivity), touch the centre of of frequencies, this will limit the number the plastic faceplate and turn VR2 clock- of such units (depending on the frequency wise until the light turns on. If you keep range of your whistle and how good an ear you hand on the switch, the light will you have) to perhaps three of four if there switch on and off continuously. If you find is to be no overlap in the frequencies. that the light does not come on, switch off In any event, you will now have the 1:±1 and check that the wire is touching the luxury of being able to command your aluminium under the p.c.b. and that the lights, stereo or whatever to switch on or polarity of the mains is correct. off without first looking for your remote If all is well, the unit may be mounted in Fig. 5. Wiring to the mains supply and handset but remember not to go around the wall box replacing the existing light the load your house whistling absent mindedly! NEW STYLE EPE BINDERS A totally new type of binder is now available to hold and protect 12 issues of Everyday with Practical Elec- tronics. This new ring binder uses a special system to allow the issues to be easily removed and reinserted without any damage. A nylon strip slips over each issue and this passes over the four rings, thus holding the magazine in place (see photo). The new binders are finished in hard wearing royal blue p.v.c. with the magazine logo in gold on the spine. We were hoping to keep the price the same as the \TAk1011 SV4”S4WW‘t4 previous binders but unfortunately the postage cost 4CA-0 BIO MET has defeated us as they are much heavier than the PROEM THE RHYTHM previous ones. The price is £4.95 plus £3.50 post and OF LIFE INITH THIS packing (for overseas readers the postage is £6.00 to PULSE RATE MONITOR everywhere except Australia and Papua New Guinea which costs £10.50). SIMPLE RADIO CONTROL S' Send your payment in L's serling to Everyday with Practical Electronics, 6 Church Street, Wimborne, Dor- RtCHARGEABLE HMI() l_fat set BH21 1JH. Tel: 0202 881749. Fax: 0202 841692.

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107 A roundup of the latest Everyday News from the Innovations world of electronics

FASTER iie Lraph Network Analyse Frequency Dow ErrseniatIon Window Help

Overdriven am with hi hl inductive load Harmonics In load current from averdrIvIn ?* Fourier SIMULATION • • S••• ; 154a: \oad curr5„nr-- ) Version three of SpiceAge for Windows is now available from Those Engineers Ltd. The new verson of this well known V\.-" \/,^^1 circuit simulation package gives an order of magnitude of gnat Hoge speed rise over SpiceAge 2. "\•,A N To support this, a new 32-channel logic analyser display is ;supply power \ available, more digital models are provided and input signal .... . bus structures are supported. The Zetex SPICE library of analogue semiconductor models is shipped with V3 and the CMOS 555 wired as on oscIllatur up to 32 channels of event driven analysis analogue side is further expanded by a brand new op.amp T ansient Tuansient ..... Nt#: model especially developed to exploit the linear extrapolation valley pragmas provided in SpiceAge's polynomal functions. Not only is this topology more accurate than many SPICE models but is faster to analyse. Level 3 (professional base level) costs £395. Extra levels available at £150 each. It is published and supported by Those — • pacitor c Engineers, specialists in circuit simulation software since 1982. Contact: Those Engineers Ltd, Dept EPE, 31 Birkbeck Road, London NW7 4BP. Tel. 081 906 0155, Fax. 081 906 0969. 4 Band Radio If you are still looking for some- RFSIDENTAL COURSE IN thing to spend your Christmas money on then a neat new radio from Roberts Radio might be of interest. IO-ELECTRO MAGNETICS The R309 compact radio packs in a Are powerlines safe, or do they cause cancer? Could exposure to those non-ionising fields lie behind wide range of features for just £17.99. unexplained disorders like ME, cot death, MS, and other newly-identified illnesses? Could electromagnetic The set is attractive, with a digital fields and radiation impair mental and sexual performance? 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For over 60 years, Roberts has been These residential courses offer a general introduction to bio-electromagnetics, embracing the principles, the name for stylish classic radios. practice, historical overview, and the most up-to-date scientific literature from molecular biochemistry to Now its expanding range of modcm epidemiology. No formal qualification in any particular scientific discipline is necessary. Practical hands-on lifestyle and world radios are rapidly experience of measuring electric and magnetic fields in the domestic or work environment at power etc gaining recognition. Roberts Radio Co Ltd, Dept EPE, frequencies will be provided. 127 Molesey Ave, West Moseley, For further information contact Coghill Research Laboratories (Medcross lid), Dept EPE, Ker Menez, Surrey KT8 2RL. Lower Race, Pontypool, Gwent NP4 SUF. Tel/Fax: 0495 763389. BEST YET CAT ALOG UE The press release that came in with Electrovalue's new catalogue reads: "This is beyond question, the best yet that Electrovalue have produced since they began business in 1965 supplying to the consumer market by mail order and to the trade, industry and educational bodies. Amongst well known quality product names, that of SIEMENS features prominently in this 140 page A4 catalogue." Electrovalue are one of those com- St Judes Rd, Englefield Green, panies that have quietly and effi- Egham, Surrey "IW20 OWB and at ciently supplied hobbyists, educa- 680 Bumage Lane, Burnagc, tion and industry with components Manchester M19 I NA. for nearly 30 years. Their product range includes a wide selection of pot cores, many of which are not readily available to hobbyists from Novel Dual Audio Op.Amp any other source. They also sup- ply a number of capacitors which New from Analog Devices, the SSM-2135 is a dual-channel are also difficult to find elsewhere, op.amp with a unique set of performance specifications for + 5V these include high voltage electrolytic single-supply audio applications, including ultra-low noise and types. Electrovalue have a nominal distortion, wide voltage output swing, and high current output. UK prepaid postage charge of only Computer and ditigal audio systems will particularly benefit from + VAT. the SSM-2135's ability to drive headphone loads (approximately Electrovalue Ltd mail order dcpt, 240) directly with ultra-low distortion and without the addition of is at Dept EPE, Unit 3, Central Trading Estate, Staines 1W18 4UX. higher voltage and/or negative supplies. Tel: 0784 442253, Fax: 0784 Analog Devices Ltd, Dept EPE, Station Ave, Walton-on-Thames, 460320. The catalogue costs £1.50 Surrey KT12 1PF. inclusive. They also have shops at 28

108 Everyday with Practical Electronics, February, 1994 r NI NI IN MINI M = IIII III NI NM IM NM NI Ili II

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Everyday with Practical Electronics, February, 1994 109 New Technology

Ian Poole investigates the latest research Update developments in super-conductive materials. UPER-CONDUCTORS were once just a For the effect to be put to any practi- problem of removing heat from the chip and O laboratory curiosity. Now they are cal use it needed to be able to operate preventing it from overheating is one of the beginning to be used, and they are just above the temperature of liquid nitrogen main factors limiting the size of individual starting to repay some of the enormous 77°K ( — 196*C). The situation remained chips. If this could be overcome by the use of amount of money invested into their static for a number of years. Then in the super-conductors then i.c. technology would development. 1980s reports appeared showing that some take a large step forward. They offer the promise of tremendous specialised ceramic materials became su- A number of companies are investigat- performance in many areas. However in per-conducting at higher temperatures. ing technologies which could make su- view of the very low temperatures needed, Initially the temperatures were not much per-conducting i.c.s a reality. Recently a their acceptance has been quite slow. The higher than those of the metal alloys. How- breakthrough was reported which appears results of many years of work are begin- ever soon after a ceramic was discovered to be a major step forwards. ning to pay dividends as they are nearing a which remained super-conducting up to a The super-conductors which are being state where they can be used in many more temperature of 120°K ( — 153°C). used for this type of application are the applications. ceramic oxides. One of the major problems has been in processing them so that they New Discoveries can be deposited onto the substrate and What are They? The main problem with the ceramics has withstand the temperatures and any further It is found that veo leAk substances been that they are very brittle and can processing. become super-conducting when they are break when they are flexed. As many One method previously used to over- cooled below a certain temperature. This applications for super-conductors are in come the problem was to adopt a two stage temperature, called the transition point electrical machines, any movement of the process. The first deposited the basic varies from one substance to another. The conductor can cause major problems, limit- material. A second process was then main problem with super-conductors at the ing the number of applications. needed to convert the basic material into a moment is that most of the ones which Now another group of super-conductors super-conductor. have been discovered require very low has come to light. At first sight they appear Now a single stage process has been temperatures — often only a few degrees to be just as unlikely to be super-conduc- adopted. The particular material chosen is above absolute zero. tors as ceramics. These new materials are one of the thalium family of ceramics and it Super-conductivity seems to defy the all organic. However in view of the number is ideal because its transition temperature is laws of nature because it allows electricity of organic compounds which can be made as high as 125°K ( — 148*C). to flow without any resistance. It puzzled the possibilities for a whole new family of However, at the temperatures of around researchers for some time. However, a super-conductors are very exciting. 800°C required for manufacture the theory developed in the late 1950s has been The first steps for these new compounds material decomposes and the thalium generally accepted. were made when it was discovered that a evaporates. To overcome this a new In a normal conductor the vibrations of number of organic compounds could be deposition process has been used. This the atoms causes the free electrons carrying made which actually conducted electricity. requires a temperature of just over 500°C. the current to be impeded. They can only Once this was done people wondered if Thus reducing some of the problems travel a short distance before they "collide" these compounds could be made to super- associated with manufacture. with an atom. This takes energy which has conduct. This was soon proved to be so, to be supplied by the external source, and it but the transition temperature for the first means that power is dissipated in the con- organic super-conductor was less than one Commercial Viability ductor. In theory at absolute zero when degree Kelvin. A nunthet of companies are actually using there is no energy in the lattice all the Since then many other organic super- these high temperature super-conductors in vibrations should stop and the material conductors have been discovered. In fact their electronic circuitry. Obviously one of should become a super-conductor. the rate at which these new compounds are the main problems to overcome is that of the To explain how a super-conductor works being discovered is quite staggering and it basic super-conductor material itself. above absolute zero another theory is re- gives great promise for the future. Whilst large amounts of development ef- quired. A theory was put forward stat- Temperature is still a problem as the fort has been expended in this area, this is ing that instead of impeding the flow of highest transition temperature yet dis- not the whole picture. Highly specialised electrons the crystal lattice behaves in a covered is 33°K. In view of the number of refrigerators are needed to maintain the different way. It allows the electrons to pair organic compounds it seems highly likely very low temperatures needed. Now solid with one another and then it does not im- that transition temperatures will rise quite state refrigerators can be used that occupy pede their flow. In this way the current can considerably before too long. a fraction of the space and require con- flow without any resistance. siderably less power than the older units. This development on its own now means Super-conducting that super-conducting electronic circuits How they were are a viable solution in some applications. I.C.s For example they are now being used Discovered Whilst the obvious uses for super-con- in some microwave applications where Super-conductRity as first noticed back ductors are in power transmission and high the non-existent resistance of the cir- in 1911. It was discovered that below 4°K power electrical machinery, they are also cuit enables filters with extremely sharp (i.e. — 269°C) mercury lost all its resistance. investigated with a view to being used in responses and low losses be made. Since then many other metals and alloys integrated circuits. Their use would bring These and many more applications are have been shown to exhibit the same effect. two advantages. The first is speed. The beginning to become viable. No doubt as The main problem has always been the second is that the super-conductors would more research is performed into these very low temperatures required. In fact until dissipate no power. strange and interesting materials their recently the highest recorded temperature Power dissipation is one of the main operating temperatures will rise. This will for a metal or alloy was 23°K ( — 250°C). problems for i.e. designers today. The bring them into very widespread use.

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Everyday with Practical Electronics, February, 1994 Constructional Project REVIVING THE VALVE SOUND JAKE ROTHMAN

in the depths of a wooden radiogram With a whiff of nostalgia and cabinet and the mains was supplied to it from the pre-amplifier, which had the power switch mounted on the volume cooking valves, Jake rebuilds a control. High tension (HT) and low tension (LT) filament supplies were then sent to the pair of Quad II po wer-a mps. pre-amp from the power-amp. All of this, including the audio, was ADE FAMOUS by the Acoustical that of most power-amplifiers today, un- conveyed in thick multi-core screened Mfg. Co. of Huntingdon Quad II fortunately preventing it being driven di- cables terminated in Painton Multi- Mvalve power-amplifiers have had a rectly by most CD players. con six-pin plugs. These connectors are loyal following for many years. They The distortion characteristics are very usually found to be totally oxidised and represent that 1950s British technology well specified, taking into account the are now unobtainable. For reference the typified by English Electric Locomotives subjective characteristics of the different pin-out of the original connector is shown and the Vulcan bomber. harmonics. At low levels, the distortion is in Fig. I The design was engineering led, the looks better than many modern amplifiers, being determined by function, rather than because it operates in Class-A, and R E S T O R A TIOAI by some pink bow-tied market-led desig- therefore has no crossover distortion. W O R K ner. Most of this technology is easy to Loudspeaker damping is quite low, which Most of the restoration work entails rehabilitate because of its simplicity, rug- may result in boomy bass with some reflex adapting the power-amps so that they can gedness and bolted-together construction. loudspeakers, but with some overdamped be used on their own, employing standard With the current valve revival, it is worth closed-box designs, it may give the impres- connectors, without having to use the rebuilding old Quads to enjoy their in- sion of extra bass. pre-amp. Most people prefer to use the herent beauty and sound quality, as well as Quad Ils without the Quad pre-amps, such for profit — as some hi-fl companies are T H E OLJA 0 as the Stereo 22 and the Mono II, because now doing. There have been some articles S Y S TE M their sound quality is below that offered by about Quads in the hi-fl press but these did Quad II Power Amplifiers were modern pre-amplifiers. not deal much with the electronic side. The originally designed to be used in The Quad 22 control unit also has a aim here is to give the missing technical conjunction with a Quad Pre-Amplifier, or lot of redundant features, such as com- data. Control Unit as they were then known. The plex scratch filtering, mono source switch- OIVL Y TH E BE S T power-amplifier was designed to be hidden ing and multiple record EQ standards. Many Quads have survived, and they appear to be the most common old valve Table 1: Quad II Specification amps around. The best sources for second- hand Quads are Loot and car-boot sales Power Output: 15W rm.s. from 20Hz to 20kHz in affluent (pre-recession!) areas. Market prices for a pair of unrebuilt, but Frequency Response: 20Hz to 20kHz 0.2dB operational Quads start at around £150. Distortion: Total third harmonic and higher order: <01% at 700Hz. Fully renovated they can fetch £350. Non-functioning chassis can be obtained Higher order alone: <003% at 700Hz. for around £45. Valve mismatching up to 25% not to cause total Production of the Quad II ran from 1953 distortion to exceed 0.18%. to 1970 and many thousands were made. Total distortion at 50Hz not to exceed 0-25%. It was replaced by the transistorised 303, introduced in 1968. A single Quad II was Sensitivity: 1 .4V rm.s. (+ 6dBu) for 15W r.m.s. output. not cheap; being 21 Guineas in the early Signal-to-Noise/ 1960s, which would be around £200 today (£400 for a stereo pair). Along with Leaks Hum Ratio: 80dB. and Radfords, the Quad us were among Output Impedance the best available at the time. The specifica- Matching: Output transformer secondaries in series, 150. tion of the Quad II is shown in Table I. It is interesting to compare Table I speci- Effective output impedance 1.5.0, giving a fication with modern amplifiers, and the damping factor of 10. In parallel, 812. only thing that's much worse, is the power Power consumption: 90W output, which will only satisfy those who listen at low volumes. The sensitivity is half

112 Everyday with Practical Electronics, February, 1994 CIR C UIT DE S C RIPTIO N

The basic circuit topology is standard for the time. consisting of a two- 70 valve phase-splitter (which provides anti-phase drive signals) a.c. coupled to a push-pull beam-tetrode output stage. A small amount of overall negative feedback is used to reduce distortion, flatten the frequency response and lower the output impedance. ALL DIMS IN mrn The full circuit diagram for the Quad II Power Amplifier, with the first stage consisting of a common-cathode voltage-amplifier built around an EF86 pentode valve, is shown in Fig. 2. The input impedance is set by 105 resistor RI which holds VI grid at ground potential. This gives an input impedance of 1.5M with 10pF capacitance. Resistor R5 is the anode load for VI and this is used to develop an inverted amplified output voltage to drive output valve V3 and the second 1 OS (LINKED TO CHASSIS driver valve V2. The signal to V2 is attenuated by resistors R7 and R8 and 2 INPUT (1/R) 3 HT this, in conjunction with negative feedback, results in an overall stage gain 4 CV LINKED TO PIN I of unity. Only inversion of the signal is required to drive the second output valve V4, since the necessary voltage amplification has been provided by t;}6v3 valve VI. IT The screen grid of the EF86 (pin 1) is held at 110V by resistor R2 in the LS 663 case of VI and R3 in the case of V2. Capacitor Cl is strapped across the OUTPUT HEATERS

screen grids on both valves, decoupling any signal voltage that may be MAINS (OLD j 15 present. Normally this capacitor would go to ground, but in this case, it is 52 employed to provide the same function for the second driver valve V2. 25 Since the signal voltages involved are anti-phase, they cancel out, saving HT OV one capacitor and simplifying the wiring. CV Cathode bias for VI and V2 (pin 3) is provided by the voltage drop across /P resistors R4 and RIO. Part of the amplifiers output is applied across RIO, 120 developing the negative feedback voltage in correct proportion in conjunc- I.— 51 tion with R II. Some of the negative feedback (NFB) is also applied to the 7 grid (pin 9) of V2 via R8, which also helps define the gain of V2 at unity. This negative feedback compensates for any change in the valves gain and ensures that reasonable symmetry is obtained. This form of phase splitter, sometimes called a "floating paraphase", is Fig. 1. Pinout details for the original six-pin Quad II not the best, because it can go out of balance. However, to change it to connector something better, such as a triode split-load phase-inverter followed by separate triode drivers, as pioneered by the Williamson amplifier; would Photo 1 & 2 New involve a lot of extra work for little improvement. mains input (opposite end to O UTP UT STA G E Fig. 1) "chassis The output stage is almost a standard push-pull, apart from one unique mounted plug" feature, there is local negative feedback from the output transformer to the and mains lead cathodes of the output valves, accomplished by a special winding. Bias- with new input ing for the output valves is derived from a shared cathode resistor (R12) ":socket (Canon dropping 25V. This holds the control grids of the output valves at — 25V XRL plug) '1 with respect to their cathode's. This resistor is bypassed by an electrolytic capacitor C5, to maximise stage gain. These two components are often totally destroyed when valve failure (with inter-electrode shorts) occurs. Resistor R12 is rated at 3W in the original design, but its actual dissipation is often above this. The renowned KT66 beam-tetrode valves were originally used for the output stage. These valves were specially developed by the the Marconi Osram Valve Co. (a subsidiary of the General Electric Co. Ltd.) for low- distortion audio amplifiers. The valve is now very rare and hence fairly expensive to replace, but an alternative is available — see later.

330V

3 V3 KT66

I C (INTERNALLY C2 7mA I Fe—, CONNECTED) 100n 7 26pA R5 3506 180 MAIN HT 340V • R7 1.72 R3 R6 C5 6806 2 1M +80k 22p 18011 OSK2 406 115V ; p CATHODE FEEDBACK .- 11. -176 7/ 0/R TRANSFORMER V2 EF86 16 R12 N SERIES , V1 EF86 C3 WINDING 100n 1801) SW FOR 1511 350V R9 12011 680k 146mA 2 7 5K3 INPUT 1.4 V RM.S.0 PIN? SKI V4 KT66 RB 5 PIN 2 PIN 2 2k 7 RI SCREEN SCREEN 1M5 TO OV 4 5 TO OS 1 I-6— CV 84 i- 68011 R10 R11 3306 loon 47011

Ef4311401 CV NF 8

Fig. 2 Complete circuit diagram for the Quad II Power Amplifier (Courtesty Quad)

Everyday with Practical Electronics, February, 1994 1 I 3 HT PIN 3 V3 PIN 3 V4 OUTPUT WIRING

1511

En

Vi CS+R12 V3 R11 PIN 8 PIN e PARALLEL

(18438$01

Fig. 4. Output transformer pinout details and typical dc. resistances of the windings. Bottom view of output transformer Check also for interwiring shorts, especially betweenY and P.

O UTP UT 100V line systems, such as some BBC monitor loudspeakers that contained in- TRA NSFOR MER tegral transformers. These amplifiers have The layout of the inductive components a high impedance output windings (43 ohm and valves on top of the chassis is shown in d.c. resistance) which means they are use- Fig. 3. The output transformer T1 is the less for hi-fl puposes. These units can be key to the design and if this component is identified by the presence of a black flying damaged it may not be worth overhaul- lead from the output transformer. This is ing the amplifier. Quad still supply output the other end of the feedback winding, Photo 3 "Spotted" anode on an EL34 transformers on the basis that when a suffi- which in the normal transformer, is con- valve, a result of excessive dissipation. cient number of orders have built up, they nected internally to Q terminal of the will get a batch made. The trade price is speaker winding. Drive to the output valves is via coupling in the region of £70 + VAT. This high For most modern four ohm to eight ohm capacitors C2 and C3 which block the 115V price is because the primary and secondary loudspeakers the secondaries are best wired present on the phase-splitter valve anodes. windings are specially split into sections in parallel, for higher impedance 10 ohm For this reason, they must have very high and interleaved with each other to mini- to 20 ohm speakers, such as the LS3/5A, leakage-resistance, or the output valves may mise capacitance. This also makes rewind- series connection is better. become biased fully-on, resulting in the ing virtually impossible, so it is essential OISSA SE MBL Y anodes becoming red-hot. to ascertain that the output transformer It is worth replacing the original paper is okay before buying a Quad II. To as- A N D RE B UIL DIN G capacitors with decent polycarbonate or sist with this, Fig. 4 shows the pinout and For a full-scale rebuilding (usually only polypropylene types of at least 400V rating. d.c. resistances of the transformer to al- necessary where the unit is suffering from Photo 3. illustrates the consequences of low checking with a pocket DMM (Digital crumbling insulation in the wiring loom) allowing a valve to overheat, the anode Multimeter). the unit is stripped down to its bare chassis melts! Some Quad Ils were designed to drive as shown in Photo 4 and Photo 5. The

87

177 025

75 57 100

I MAINS 47 L I SOCKET FUSE OUTPUT CHOKE HOLDER TRANSFORMER 70

T2 10 MAINS TRANSFORMER 120

MAINS SELECTOR

100

NAME PLATE 30

65

310

1•16. 11S

45

177 ALL DIMS IN mm

118428841

Fig. 3. Chassis dimensions and layout of the inductive components and valves on the topside.

1 1 4 Everyday with Practical Electronics, February, 1994 ORIGINAL MAINS CONNECTOR !POWER FROM PRE-AMP)

N FUSE HOLDER REAR VIE W OF L LNE SOCKET r 0 0 EARTH NO EARTH I HT

L

1-0 \ *0 COMMON SV Fig,. 5 Original mains wiring. 240V • L 0 240V

VOLTAGE 0 220V 220V 0 r 0 SELECTOR 6V3 200V 200V 0 LO MAINS TRANSFORMER MAINS TRANSFORMER CONNECTIONS Fig 6 New mains wiring to the Cannon connector

NAME PLATE (n436761 COMPONENTS

Resistors most effective way to remove the baked-on M AIN S WI RIN G R1 1M5 When installing the new mains connec- grime of 30 years is to use tissue paper R2 R3 1M (2 off) tor, it is a good idea to put it close to the and a nylon pan-scourer (for the difficult R4 680 See bits) with plenty of isopropyl alcohol. A mains transformer. In the original design R5, R6 180k (2 off) re-spray is quite difficult because the un- this was at the opposite end of the chassis. R7, R9 680k (2 off) usual gun metal colour cannot be obtained as shown in Fig. 5. R8 2k7 TALK A Cannon mains XLR connector (a R10 100 in most car shops. A good rub with T-Cut Page worked wonders on the original paint. professional broadcast standard) will fit in R11 470 the fuseholder hole, with only a little R12 180 5W 5% wirewound All the inductive components are held (e.g. HSA05 metal-clad) reaming. This is illustrated in Photo I. on with 4BA bolts, as is the output valve R13', R14 1k 1W metal-film (e.g. assembly. A small tag board is used to Photo. 2 shows the mains plug. Vishay FP1.) (2 off) hold the driver valves and most of the Some readers may prefer to use an 1EC R15 1k 5W 10% wirewound small passive components - see Photo 5 or Euro socket, possibly with integral fil- • Not needed for 1:T66 valves. and Photo 7. This can be removed by un- ter. The mains fuse, being 2A, can go in All resistors 0.5W 5, 2 or 1% metal-film eg doing the 6BA nuts near the B9A valve- the mains plug. The voltage selector can Vishay TR5 or RS except where stated also be removed, since all areas of the UK holders on top of the chassis. Capacitors Take care when removing the name plate are now 240V, although some readers in Cl 100n 150V axial screws (which also hold the smoothing Europe may need to use the 220V tapping. plastic-film e.g. RS Stk. capacitor) since the gold paint may have The chassis is effectively Earthed by the No.113 049 stuck to the metal and may flake off. metal body of the mains connector. The C2, C3 100n 400V axial Unfortunately. Quad no longer have any signal earth (pin E on the mains trans- plastic-film (2 off) e.g. RS spare name plates in stock. former) is connected to the mains earth via Stk. No.113 156 a one kilohm SW wirewound "ground lift" C4 15p to 47p > 385V can electrolytic e.g. Philips resistor (R15) to prevent "earth loops - 059 58479 (Photographs by The new mains input wiring is illustrated in David Tarlo.) C5 22p to 100p 40V axial Fig. 6. electrolytic e.g. Philips 123 17479 C6 47p to 220p > 385V can electrolytic e.g. Philips 059 58101

Valves V1, V2 EF86 pentode (2 off) V3, V4 EL34 beam tetrode (2 off) see text V5 GZ34 rectifier

Miscellaneous Ti Output transformer Quad No. 1003A T2 Mains transformer Quad No.1001 L1 Smoothing choke Quad Photo. 4. Topside view of the stripped-down metal chassis. No. 1002 Connectors: Mains XLR chassis plug AXR-LNE-32; Mains XLR free socket AXR-LNE-11; 5-pin female XLR chassis socket AXR -5-31; 5-pin male cable XLR plug AXR -5-31; pair of banana sockets for speaker connectors. Valve sockets . pair chassis B9A un- skirted: pair chassis octal. Mounting clips, to suit smoothing capacitors pair; silicone sleeving (1mm); 22 s.w.g. tinned copper wire; lacing cord; 0.5in. 4BA cheese head bolts, (12 off); M3 12mm countersunk bolts for XLRs (4 off); solid-core wire.

Approx cost guidance only £50 excluding lransforrnets Photo. 5 Underside view of the stripped-down metal chassis.

Everyday with Practical Electronics, February, 1994 115 P O WER SUPPL Y The power supply is a typical 1950s MAI NS TR AN SFOR MER design, using a pi-network inductor- FS1 capacitor filter and full-wave valve rectifier 2A +340V HT TO POWER as illustrated in Fig.7. It is a good idea to VA LVES VW Ti retain the valve rectifier because it applies L1 the HT gradually to the circuit as it warms CHOKE 3-101-1 up; reducing stresses to the capacitors and To 40AVSETO providing maximum valve life (because CANNON LIN E SP LITTER valves do not like HT applied before the SOCKE T TO PRE -AMP 3 V5 - ETC cathodes have warmed up). If solid-state 0232/34 or 5V46 40mA C4 MAX rectifiers were to be employed it would be 3 16 TO 47).1 C) 450V essential to provide a standby (HT) switch C6 TO HE ATERS AN D or slow turn-on circuit. METALWORK 6V3 71 EXTERN AL OUTPUT IPLAIN I LSO To prevent buzz caused by charging cur- CO M I R15 T ETCHED6 TO 47H ) rents, the wiring layout of the power supply 1k SW GROUND SCREEN 1( is important and the connections should LIFT INTE RNAL be "starred" (commoned) to the smooth- RES ISTOR CO NNECT ION 00 V ing capacitors as shown in Fig. 8a. The old square smoothing capacitor is often (EE431194 I dried-up and it can be replaced by modern types. It was found that two of the original holes could be used to mount a pair of Fig 7 Circuit diagram for the valve Power Supply. Note that the -ground-lift" circular capacitor clips (as recommended in resistor R15 is a 5W wirewound type. the parts list) with only the necessity to drill one extra hole under the name plate. Valve rectifiers have a maximum load TA G BO A R D There is no need to go to ridiculous capacitance they can tolerate, which is in For those wishing to undertake the least lengths like using precision Holco resistors, the order of 47µF for a GZ34. This means arduous and cheapest bit of renovation, the ordinary 1% 0.5W types will be fine. Note that capacitor C6 should not be increased place to start is the tag board, which is that these should be the industrial half-watt beyond this value. Capacitor C4 however, located under the driver valves. After 30 rated types which are at least 10mm x is after the choke, which limits the cur- years most high-value carbon composition 3.2mm. The Maplin 0.6W metal films rent surges, so this can be increased up to resistors have a tendency to drift up. Quad have the commercial rating, their industrial around 220µF if desired, to get lower hum. designed for a long life by using 1W resis- rating is only 0.25W, and their small size of The original rectifier valves used were the tors where "half-watters" would have been 6.5mm x 2.5mm makes them too delicate GZ32 and 5V4G. These can now be re- adequate, but it is still worthwhile replac- for valve tag-strip work. placed by the higher current and cheaper ing these with modern metal film types, A drawing of the tag board is shown in GZ34. which would be better than the originals. Fig. 9 and a completely rebuilt tag board is shown in Photo. 6. When replacing the components, it is best to cut them off first OR AN GE /BLUE BLACK /WHITE and remove the wires one at a time, to TO PIN V5 TO L I Ctl MAINS minimise stress on the tags (the com- TRANSFOR MER' MA IN SYSTE M OV ponents can be replaced, but if a tag falls TO R12/ C5 off it is much more difficult!) For those wishing to undertake a full rebuild of the TO PIN 4 ON TO 55 CATHODE tag board, the additional wiring is also OUTP UT VAL VES AND XLR SKI PIN 8 shown.

TO CHOKE INPUT TO CHOKE OUTPUT TAKEN FRO M PIN 8 Fig. 9 (below). Tag board component BETTER STARRED TO C4 + IF POSSIBLE layout, wiring and valve base mounting details.

1E14392 6j

OUTPUT TRANSFORMER BOLTS THROUGH HOLE TO TRANSFORMER a CAP CL IP Fig 8c (above). Old smoothing capacitor connections.

NAM E PL ATE EE431110G I

Fig 8a. Wiring to the smoothing capacitors.

OV CI- TO Dv SC REEN 1

INTER NAL PINS CON NECTION HE ATE R FOR COM 01 RECT IFIER PIN 2 V5 1/2" 6 BA BOLT 1 24 OVU MAINS I— LE-L-L tatr' ‹ PRIMARY 1 PIN 2 8b (left). '6PAXOLIN V4 220 V 0 It '6 BA NUTS Mains VA LVE- - '1 CT TO OV PIN 7 transformer HOLDER VI/ V2 200V 0 PIN 5 MECHAN ICAL CONSTRUCT ION Ulf TO XLR pinout details. BOLT ALLOWS FI XI NG SKT VALVE HOLDER MOUNT ING PIN I. TO CHASS IS WITH NUT 0 ON TOP EE 43930 I

116 Everyday with Practical Electronics, February, 1994 O UTP UT VAL VES Also 807s can be used if the pin-out is The original KT66 valves are now very checked. The American 6L6s will work if expensive because of their scarcity. These R12 is increased to 2700, but will give 25% can be replaced by EL34s with the benefit less output. Overall, EL34s are the best of a slight increase in output power. Since choice when cost is taken into account. EL34s are made by many manufacturers. BIA SIN G they are much cheaper and more readil) available. Resistor R12 sets the standing current through the output stage at around 65mA However, a modification has to be made, for each valve. The voltage across RI 2 is since the KT66s have their beam-forming around 25V, so this means that the dissipa- plates internally connected to the cathode. tion is around 3.2W. This is not the case with the "replacement" In most old Quads this resistor is worn- valve and pin I must be linked to pin 8 out from thermal cycling, so to improve (cathode). The wiring of the output valves reliability it was replaced with a metal-clad in shown in Fig. 10. type bolted to the side of the chassis. R12 Another worthwhile modification with is bypassed with an electrolytic capacitor EL34s, is to place lk IW (RI3,R14) resis- C5. I used a Philips solid-aluminium type tors in series with the screen grids. This which can't dry-out. modification reduces damage due to valve Two tags are provided on the base of failure, aids stability and reduces the dis- the choke to support these biasing com- sipation at the screen grid, giving longer ponents, they have no internal connection Photo. 6. Rebuilt tag board ready for life. to the choke itself. The wiring is shown in installation into the chassis. Quad Ils are relatively insensitive to Fig. II. R12 can be replaced by a metal- apart from the changes required for the valve mis-matching and tolerances because clad type if desired. minor modifications. If the loom needs to they were well designed, so there is no need The output stage circuit diagram using be remade, it is best to use (0.7mm2) to go to the expense of buying matched EL34s is shown in Fig. 12. An alternative solid-core wire for rigidity. Remember, valves. Cheap East European ones do the biasing arrangement is also shown, where the heaters are high-current (around 3.5A) job well and last about 80 per cent as long each valve has an individual cathode resis- and only 6.3V, so use reasonably thick as the most expensive types. Buying spe- tor. This is useful to allow tweaking in wire ( > Imm 2) for these to reduce voltage cially selected "hi-fl buff" valves provides cases of severe valve mis-matching. drops. Fig. 13 shows the details of the little sonic improvement, so do not be wiring loom. persuaded into paying more than about L O O M A completely rebuilt Quad with a new £ I 5 for a pair of output valves. the original wiring layout was retained wiring loom is shown in Photo. 7. To Some people have old EL37s and these because it gave excellent hum levels, so prevent confusion, use sensible colour can be used with slightly higher distortion. there was no point in changing it much, codes for the wiring, such as red for HT

r-ALTERNATiVE MOUNTING FOR R12 USING 1' E I METAL-CLAD RESISTOR

CAPS HELD DOWN WITH P-CLIPS 1130f1 HSAIO

TO EARTH ON IT ON TAG STRIP SMOOTHING CAPS TO CENTRE TAPI V / P-CLIP ON OUPUT TRANSFORMER

HT TO TAG BOARD V5 VALVE BASE

EEL3IPSG

Fig. 10. Wiring to the new EL34 valve bases. The capacitors Fig. 11. Biasing components wiring. Resistor R12 can be. C2 and C3 should be held in place by P-clips replaced with a metal-ciao' type (shown dotted) if desired

Photo. 7 Underside view of a completely rebuilt Quad showing new wiring loom, tag board and metal-clad resistor

Everyday with Practical Electronics, February, 1994 1 17 330V

R13 V3 EL34 I k

NOTE PINS 1St 7mA CONNECTED TOGETHER INPUT FROM VI MAIN HT 340V

SK 2

IN SERIES 3600 2W5 ,, FOR 150 R12 SPLIT 3600 2W5'

144mA SK3

10w 35V OUTPUT FROM 02

Fig 15 P1k14 Wiring to the 1W V4 EL34 new 5-pin "female" XLR socket. NFB (EE439601

Fig. 12 Output circuit diagram using pair of EL 34 valves.

and green or black for Earth. Putting a worthwhile making a five-pin XLR to small loop of wire at each tag prevents phono adaptor as shown in Photo 9. This is strain and allows the connection to be constructed by inserting a phono in-line remade if necessary. For the finishing socket into the rubber cable strain-relief touch, lace up the loom with nylon cord. bush. In this case only pins 1 and 2 are The basic technique of lacing is illustrated connected. in Fig. 14. and can be summed up as "twice round, loop through, then pull". INP U T SO C K ET A five-pin female XLR socket is used to replace the original six-pin connector, since it is an audio standard and very reliable. This socket carries the HT and LT as well as input and earth to enable a Quad 22 control unit or other valve ancillaries to be used. Fig. 15 shows the wiring associated with the socket, which is mounted in the same hole originally occupied by the six- pin socket. The old mains socket hole is blanked off as shown in Photo 8. Fig. 16 shows the pin- out of the XLR. (CE431146 P H O N O AD A P T O R Most hi-ti equipment uses the dreaded phono plug, so to provide a degree of Fig. 16. Thhout details for the XLR Fig 14. Basic technique for lacing up compatibility with other equipment, it is socket. the wiring loom.

Fig. 13. Original wiring loom for the Quad power amplifier If a new loom is made up use multi-coloured wires wherever possible, see Fig. 6 for new mains input wiring.

118 Everyday with Practical Electronics, February, 1994 Photo. 8. Blanking of the old mains input socket cutout.

The refurbished Quad II Power Amplifier

T E S TIN G inductance of the output transformer. First of all, the obligatory warning - THE About 5.75V peak-to-peak is needed at the HT VOLTAGE CAN KILL, it is worse than input to get the output to clip, giving an mains because it is d.c., which can cause overall voltage gain of 10. All these the victim to become locked solid, unable measurements were taken using the output to let go. The old valve adage of keeping secondaries in series. the other hand in the pocket while test- Slight ringing is evident on 10kHz ing is sensible, because it will prevent volt- squarewaves, although this is typical of ages being developed across the chest (cue most valve amplifiers, because of the Casualty theme tune and de-fib' trolley!). transformer electrical resonances. A Zobel A Quad in good fettle should give network can be wired across the output to around 55V peak-to-peak into a 15 ohm damp this out, but no sonic differences load resistor before clipping (using EL34s) could be heard. Suitable values were 470nF when fed with a I kHz sine wave. This in series with 22 ohm. In fact, the Quad II Photo. 9. Adding a 5-pin XLR to phono corresponds to about 25W r.m.s. At lower was optimised to drive the Quad Electro- socket. Only pins 1 and 2 are con- frequencies, such as 20Hz, the power static loudspeaker which has a capacitative nected. output is less, due to the finite primary impedance characteristic.

Cbelmer Valve Company for High Grade Audio Valves / Major Brands e.g. Nitillard, Brimar, Philips, GE (UK), GE (USA), etc A2900 GEC £12.00 GZ34 Mullard €10 E8OF Philips £10.00 0237 Mullard ECC8I /CV4024 Mullard £6.00 6CA7 EL34 GE IN ECC82/CV4003 Mullard £6.00 6L6GA Sylvania ET that brings the 1993-94 ECG% Mullard £6.00 6SN7GT Brimar E88CC Mullard £8.50 6V6GT Brimar EF86 1CV4085 Mullard f8.50 12AT7WC Sylvania E184 Mullard £6.00 6146B GE El 5 k I CATALOGUE E184 GE (USA) £5.00 6550A GE £10 c GZ32 Mullard £8.00 7581A GE £12 140 pages. A4, copiously illustrated, 0233 Mullard £8.00 bang up to date and with bonus C YC PREMIU M: Our own BRAND from selected worldwide Ivouchers, Send cheque/PO for £1.50. sources, processed in our special facility to provide low noise/hum/microphony Pre-Amp Valves and Power Valves burnt-in for improved stability and reliability. I that brings the PRE-A MP VALVES POWER VALVES - contd. ECC81,12AT7 £5.00 E84L 7I89A Ei I : ECC82 12AU7 £4.00 KT66 IN ECC83 12AX7 £5.00 KT88 fr. - I SERVICE ECC85 £4.00 KT88 (GOLD Q) ECC88 £5.00 6L6GC with choice of very wide ranges of famous-name quality EF136 £4.00 6L6WGC '5881 f;•4, electronic components and associated gear sent E81CC (GOLD PIN) £6.00 6V6GT ei . Ipromptly on receipt of your order. A service E82CC (GOLD PIN) £6.00 6I46B CC E83CC (GOLD PIN) £6.00 6336A €3C , E88CC (GOLD PIN) £7.00 6550A £11 , E8OF £9.00 RECTIFIERS I E83F £5.50 GZ33 that :lectro slue 6SL7GT £4.00 GZ34 5AR4 £5.00 6SN7GT £4.20 51_140 £5.00 POWER VALVES 5`13GT £3.20 Ihave been providing constructors with continuously 2A3 (OCTAL) or (4 PIN) £14.00 5Z4GT £3.50 Isince 1965. With thisCatalogue, you will find our service 211 £22.00 SOCKETS the best ever. Send for your copy NOW! 300B £50.50 B9A (PCB) £1.60 811A £9.50 B9A (CHASSIS) f1.60 . ELECTROVALUE LTD.. UNIT 3. CENTRAL TRADING ESTATE, STAINES. MIDDY TW18 4UX I 845 £29.90 OCTAL (CHASSIS) £1.75 I Tel: 0784 442253 Fat 0764 460320 i EL34/6CA7 £7.50 4 PIN (UX4) £3.00 1 ; enclose Cheque/PO/Credit Card No EL84'6BQ5 £4.00 4 PIN (for 211) f11.00 i . Value C1.50 for your 1993-94 Cataiog ue Add £1.00 per valve for matching if required. Plus Post iSa Packing £3.00 + VAT at I 7.5 % for UK Europe. ; Name I Send, Fax order with cheque or credit card details to: . Address 1 Chelmer Valve Co., 130 New London Road, Chelmsford. Essex CM2 ORt . i I Tel: (0245) 265865 Fax: (0245) 490064 I 7 L. P..st Code M I I

Everyday with Practical Electronics, February, 1994 119 Regular CIMIc cmcuir

ig %, AC P SURGERY i i .4 ALAN WINSTANLEY *

Circuit Surgery is the monthly column which tries to help readers to simplift those suspect circuits and pass on handy hints and tips. Ify ou have a particular problem in the field of hobby electronics then let Circuit Surgery shed some light! Or ify ou think you have a useful piece of advice which you'd like to share with your fellow constructors, then write in and I'll try to spread the word.

HIS is your column but as regular opposite magnetic polarities and become relevant part of the panel with a small Treaders know, space is often limited mutually attracted. Thus the contacts are magnet, such as a small horseshoe type — so although I try to reply personally, magnetised together to make a circuit. available from d.i.y. stores. This fools please accept that I can't answer every- Removing the external magnetic force any opportunists who hopefully would one individually. Circuit Surgery tries to permits the contacts to spring apart, not come equipped to de-activate the appeal to readers of all abilities and relies breaking the circuit. alarm! You could perhaps adapt the on your queries which I will try to principle to switch outdoor projects on include on these pages where possible. Low Power or off, when you would avoid problems Having munched my ration of mince Reed switches are only really suitable caused by exposing switches to weather. pies, it's down to business! for low power circuitry — certainly not The Waterproof Delay Switch published for mains voltages. Since the glass en- last month worked in this way. Reed On velopes are a little delicate, it's possible Firstly, thanks to Gavin Poulton of to buy specially encapsulated reed con- Dinosaur Roar Fulwood, near Preston who put me in a tacts which are designed for rugged use — An interesting letter came from Mr. jolly mood with this letter: such as in burglar alarm systems. These H.S. Lenton of Oldbury, West Mid- In last November's issue, Circuit Sur- can be sunk into door jambs where lands. who asked for a dinosaur roar gery described a simple room alarm they become tamperproof. A Hall Effect sound effects unit to entertain his young designed by Mike Tooley, using an I.d.r. switch is a solid-state, magnetically sensi- family. Drastic Park strikes again! Un- (light dependent resistor) as a sensor. I tive device which could be used as a fortunately it isn't that easy to create reckoned the I.d.r. might be tricky to set proximity sensor, instead (see Interface complex sounds using simple discrete up and disguise, so a better alternative last month. Ed.). circuitry. In the past I've dealt with might be to use a reed switch which can be I have also used reed switches as a chip manufacturers in Taiwan and Hong hidden under the carpet by the door. A form of "invisible" keypad on security Kong who specialise in integrated cir- small bar magnet can be "blu-tacked" to projects. They can be glued behind the cuits which can generate a variety of the bottom of the door. I really bemused surface of a plastic control panel so that sound effects, mainly for novelty use. my brother this way! nothing is visible from the outside — the Many of these devices are based on a Sounds like you've got your security panel can be suitably embellished with standard i.c. chip which is customised problems licked, Gavin — thanks for rub-down lettering. during manufacture by using a process writing in! The reed switch would also To activate the project, touch the called "masking". Thus a basic chip is solve the problem of reduced sensitivity programmed or masked to produce a during daylight hours, which Mike cured certain sound, which could be a digitised by adding a second compensating photo- version of a real event — an animal noise, conductive cell (LDR). Reed switches for instance. The customer (that's me) can themselves are readily available for use pay several hundred U.S. dollars for a in burglar alarm systems, and it's inter- Dissimilar Vol.. attract masking charge to have his own required esting to see how they work. Fig. 1 each other. closing Ow ...Itch effect etched onto a standard chip. shows a typical reed contact switch, of Alternatively, many standard sounds the sort which is encapsulated in a glass Spring metal contacts are available off the shelf. Otherwise the envelope. i.c. chip is specially fabricated onto a tiny They contain a set of springy metal p.c.b., protected by a blob of resin. All contacts which generally are normally that's then needed is a piezo sounder and apart. A magnetic field is then created a watch battery (plus an order for half a around the switch using, say, a bar million units), and you're away! magnet or a coil. This causes the con- It's much easier to reproduce a sound Glass envelope tacts to become in effect, two adjacent this way by copying the real thing, rather bar magnets separated by the contact than starting from scratch trying to gap. The "poles" of the magnet adopt Fig. 1. A glass encapsulated reed switch. emulate a complex noise. Video games

120 Everyday with Practical Electronics, February, 1994 often contain sampled effects and speech suggestion would be an ideal applica- should be a pnp Darlington transistor. (and images, for that matter, such as the tion for the 8211 Programmable Voltage For example, a TIP125 is a 5A type in a characters in the Mortal Konthat game Detector which we investigated in depth TO-220 package - or you could try a - or "Mortal Wombat" according to last month. Fig. 2 shows how an 8211 BDX34B (10 Amps). If you are involved my computer's Spellcheck!) because it is can be used to monitor the supply volt- with low power projects then a modest relatively easy to capture a sound or age elsewhere in a circuit. The load and type like a ZTX7 12 (500mA) might music track and then transfer this in the supply voltages weren't specified, but suffice. The rectifiers should be chosen digital form into the game cartridge chip. this circuit could easily be adapted to for their forward current rating. An Sampled sounds and images are now suit individual needs. B1 is the "main" 1N4001 is good for up to 1 A of course, finding their way onto games stored on battery - let's assume it's a 9V battery an 1N5401 could handle 3 amps average. compact disc, too. pack. R 1 and VR I monitor the potential Indeed our advanced Teach-In Micro of B1 and so a voltage appears at the Hysteresis Lab microprocessor trainer contains a threshold pin of ICI (pin 3). You could add some hysteresis by in- sound sampling and playback facility as This threshold voltage falls as the bat- cluding a IM resistor between pins 2 and part of its demonstration routine, which tery starts to age. Remember that the 3. This will produce a difference in the will digitise and store an audio signal. All i.e. has an internal 1.15V reference, and switching levels should your circuitry be of which begs the question, what does a when the voltage at pin 3 falls below particularly sensitive to supply rail "jit- real dinosaur roar sound like? How do 1.15V (8211 only - the 8212 works in ters". Don't forget to adjust VR1 to give you know? reverse), the output pin 4 goes low and just over 1•15V at the required battery sinks current. threshold voltage. Battery Back Up Fortunately the circuit does not add Mr. Andrew Judge of Tadworth. Sur- All Change any appreciable load to the batteries, rey contacted us following on with a When B1 is in a healthy state, it drives especially the all-important back-up B2. topic which was dealt with in Circuit the load directly through DI. When the The bipolar ICL821 I has a low quiescent Surgery quite a few issues ago that of voltage of BI falls to a point deter- current and the potential divider would "low battery" warning devices: mined by VR1, then ICI conducts which consume well under 50µA depending I need a circuit that automatically switches TR1 on. This pnp transistor on the battery voltage. The CMOS switches .from a first battery to a second saturates, connecting the higher voltage MAX8211 version is even better in this back-up battery when the first fills below of the back-up battery B2 to the load. respect, of course. Sources for these a certain (variable?) threshold. Ideally it The rectifier DI is then reverse biased parts were given last month. should be possible to change the first and ceases conduction, so B1 is effec- Incidentally, I prototyped and built without interrupting the supply and to tively disconnected. At this point the this circuit on my own Teach-In Mini know which supply is actually in use. Can I.e.d. D2 illuminates (the current-limited Lab which is equipped with both a fixed you help? sink of pin 3 is only a few milliamps) I 2V and variable 1.25-1 8V d.c. supply. Mr. Judge explained that his own to warn that the back-up battery is The 12V rail represented the back-up attempts had drawn a blank, mainly now operating. The I.e.d. could be a battery whilst the variable supply was because of the lack of a clean change- high-intensity type for a much brighter deemed the main battery, slowly running over, and also the back-up battery some- display. down. It seemed to work perfectly! times ran down before the first! Power Hopefully it should then be safe (I recently learned that some 800 Mini supply monitoring seems to be an area of enough to replace B1 without interrupt- Labs are now in use amongst readers - i.e. technology which is growing, be- ing the drive to the load. I placed a large see the Magenta Electronics advertise- cause there's an increasing demand for capacitor Cl across the load which helps ment in this issue for details of the Mini these "supervisory" circuits. Often they to smooth the transition, though it will Lab and Micro Lab kits.) are used in portable laptop computers, draw a minor leakage current from mobile phones, test equipment - even either battery. Note that both batteries Electronics Club rechargeable razors! must be commoned to OV as shown. The My very first Circuit Surgery resulted Certain families of logic run at 3V d.c. operation of the circuit will also be in a letter from Mr. H.F. Howard, Chair- -- when it's vital that close attention is defeated if you allow B2 to fall below the man of the British Amateur Electronics paid to the battery or power supply con- minimum voltage required across BI. Club, who says that the subject of fuse dition to prevent a mal-operation, and Possibly add another 8211 with an I.e.d. ratings and testing them has been a lively also the power supply may need to gen- to monitor B2! topic in the BAEC Newsletter, which erate a "clean" reset signal for starting There is room for experimentation and is published quarterly and circulated the logic properly in the first place. you can select the components TR1 and amongst its members. Incidentally one I reckoned though that Mr. Judge's R3 to suit your own application. TR1 idea I had regarding the simple fuse tester circuit was to use two adjacent metal "touch pads" (supplied by Maplin, Part. No. HYO1B) on the front of the plastic box. Simply bridge the pads with the suspect fuse. I used this idea in my Continuity Tester design (Everyday Elec- (ronics July 1985 for loyal readers!). If you would like further information about the BAEC, please refer to their advertisement in the "Classified" section at the end of this issue. If there are any other active Electronics Groups out there, especially in schools, Circuit Sur- gery will be delighted to hear from you. If you have any topical queries or comments, hints or tips, why not drop me a line and I will try to feature it in this column. Regrettably I can't guarantee to reply individually (but 1'11 try) though I read every letter. Please write to me c/o Circuit Surgery, 6 Church Street, Wimborne, Dorset, BH21 1JH. Happy New Year! Fig. 2. The automatic battery back-up circuit.

Everyday with Practical Electronics, February, 1994 121 Show Report EUROPEAN INTERNATIONAL AUDIO and VIDEO FAIR BARRY FOX

There has been a public Radio Show or Funkausstellung in Berlin since 1924. In 1970 the biennial show was renamed the International Audio and Video Fair and has become the European showcase jiff new electronics. Last year there were 740 exhibitors from 33 countries spread through some 30 large halts and pavilions.

AP RE you going to write your usual piece about the Berlin N e w TV Syste ms Funkausstellung calling itself an "international" show, but 1FA 1993 was the first Berlin Show for more than ten years at s il not living up to the name, someone asked me. I hope not, but I which high definition television (HDTV) was not being launched. expect so, was all I could say. There was virtually no mention of MAC anywhere, and the And yes. Some things never change. Although the Berlin Radio demonstration of HD-MAC was buried at the end of a small hall Show changed its name to the International Audio and Video Fair devoted to technical specialities. in 1970, the event still remains a resolutely German show. Grun- A sign proclaimed, "Post Olympic Improvements", including dig, for instance, held a large press conference to tell Europe how improved compatibility between HD-MAC transmission and D2- the company is "going on the offensive with new products and a MAC reception, with "reduction of motion judder etc." new organisation", but talked about its plans only in German. HD-MAC was sold on the promise of compatibility with D2- At least Grundig had some English language literature which is MAC. It is thus quaintly ironical that only now, after MAC and more than can be said of many others. Sharp and Swiss com- HD-MAC are dead, the developers admit that they needed to im- pany Swatch, for instance, held press conferences in German only, prove on the core issue of compatibility. with only German literature, despite Swatch's plans to launch its wristwatch pager in the UK next year. The PALplus group provided no translation either, leaving those Digital TV in the audience who rely on English (Brits, French, Spanish, The demise of MAC and HD-MAC has left the way clear Italian, Scandinavian etc) wondering what the German speakers for digital TV and HDTV. The HD-Divine consortium of Scan- were talking about, and leaving some of the German press strug- dinavian broadcasters and electronics companies has now signed a gling to understand the points being made by the UK broad- deal with Nokia of Finland. The HD-Divine group has developed casters. Joked Richard Ellis, of Granada TV, "It falls on me to add a digital HDTV system which will work over terrestrial, satellite or the international flavour to this meeting", So much of the good cable networks. Nokia will make the receivers. news message, that PA Lplus transmissions could stimulate sales of The target is to have demonstration receivers available for the widescreen sets, got lost. 1994 Winter Olympics in Lillehammer, Norway. Even before that,

The tented "village" at the Berlin Audio and Video Fail: Inside one of the many exhibition halls.

122 Everyday witlz Practical Electronics, February, 1994 terrestrial transmissions will be demonstrated at the International the profits go? As with all Japanese ventures in Europe, back to Broadcasting Convention to be held in Amsterdam in September Tokyo. 1994. D C C P ALplus There is a growing feeling in the trade that the only thing that How does this affect the chances of PALplus, people asked? It will pull Digital Compact Cassette (DCC) through to success is a doesn't, because digital transmissions can only be seen by people radical re-think on price. Says Henk Bodt, Head of Philips Con- who invest in new receivers or decoders. PALpus is compatible sumer Electronics Division: "DCC will always be more expensive. with existing PAL receivers; it gives letterbox pictures on existing It needs more silicon and more complicated heads. When will 4:3 PAL sets and higher quality widescreen pictures on 16:9 sets. the price differential between analogue and digital recorders give Despite the language barrier created by failure of the PALplus people sufficiently good reason to buy digital? We still think this is group to provide translation, two messages came clearly across. two years away. In the long run a price differential of between $75 One is that German broadcasters ARD (public) and ZDF and $100 is achievable." (commercial) are now prepared to start PALplus broadcasting, The DCC partners fear a price pull in 1995 will be too late. By provided that they can win the subsidy money recently promised then DCC will have missed the boat. Philips will very soon of- by the European Commission. So are satellite broadcasters Pro 7 fer part-exchange on old cassette decks. But this will not please and Premiere. dealers who will have to take back the old gear. In the UK the BBC has no official plans, but Channel 4 has Thomson (French owner of Ferguson) is supposedly a supporter already broadcast programmes in PALplus without telling anyone, of DCC, but is now rumoured to be backing Mini Disc. Thomson to see if there were any objections from viewers. So far there have held a press briefing with top man Alain Prestat but the invitation been none, because no-one has noticed any difference. The pic- list was carefully tailored to protect him from awkward questions, ture looks just like a conventional letter-box movie. The analogue like "why is Thomson not giving Philips the support it needs" and helper signal, buried in the top and bottom bars to help future "why did Thomson buy Ferguson if all it wanted to do was shut widescreen sets display a clear picture, is — as it should be — in- Ferguson's factories"? visible on existing 4:3 sets unless the picture brightness is turned up JVC is hedging bets, and will start manufacturing its own to absurd levels. record/playback Mini Disc portable this year and its own DCC The main sticking point now is on how the EC interprets its deck next year. JVC already presses Mini Discs, at its CD pressing funding promise. Those who claim a share of the EC subsidy plant in Japan. Hiroki Shimizu, General Manager of JVC's audio money must match it ECU for ECU, with their own money. division admits "Sales in Japan are still very small". Dr. Albert Ziemer, Chairman of the PALplus steering committee Says Shimizu "Mini Disc could be very good for dictation believes that the broadcasters may seek money from industry, recording or conference recording where you want fast access. It namely the TV set manufacturers. But the TV set manufacturers could also be good as a ROM carrier for games, where you do not must invest money in producing PALplus sets so will not want to need the full data capacity of a Sin. CD-ROM". give money to the broadcasters as well. BASF, is hedging bets too. The German company has invested It will cost the broadcaster just 370,000 DM (£150,000) to buy a heavily in the production of DCC tape, and is now getting very PALplus encoder. There is then nothing more to pay for using it to worried about slow sales of DCC hardware, and correspondingly transmit widescreen films. By buying decoders now, the broad- small demand for tape. Significantly BASF took a bow at Sony's casters get half their money back from the EC. This is why MD press conference, as a new supplier of MD blanks. ZDF undertook PAIplus "field trials" in November, and Pro 7 at At Panasonic's press conference, the company reaffirmed com- around the same time. mitment to DCC, but then cleared the room of journalists, and Philips has invested in the development of a PALplus chip set sent the remainder to sleep, by launching into an extraordinarily which will be ready in 1995. Nokia will use the Philips chip set, but boring description of the "virtual battery operation" of Technics is building a prototype receiver which relies on microcomputer amplifiers. DCC seemed very low on Panasonic's priority list. software processing to emulate the functions which the chips will Philips will not give numbers for DCC sales until after a year of perform when ready. So far there are only two prototype PALplus sales. "Until then they do not mean anything", says Henk Bodt. receivers, one from Nokia and one from Grundig, both using large cabinets of outboard electronics. Mini Disc The big news of the PALplus briefing was that the all-European "Mini Disc is well on the way to becoming a world standard", committee has now welcomed Sony on board. Until now the said a panel of top brass including Norio Ohga, Sony's President, PALplus committee has jealously guarded its secrets, and made Michael Schulhof, Head of Sony Music, Ron Sommer, head of them available for European companies only. But Sony is develop- Sony's operation in Europe plus Toshikazu Mitsuda. Executive ing its own PALplus chip set and although there is clearly dissen- Director of Sharp. sion inside the European committee, it has accepted that the only "In 1993 worldwide shipments of Mini Disc hardware have been way to get PALplus moving is to throw the technology open to 300,000 units, with 100,000 into Europe" they said. "Sony Japanese manufacturers as well as European companies. has produced 3 million discs, a million of them going to Although this will get PALplus moving, it also creates the risk Europe....hardware sales will reach 10 million by the end of 1995". that what began as an all-European initiative will end up as But Ohga ducked the question of how many of the players another example of Europe developing the technology, and Far "shipped" have actually been sold for cash to customers. Eastern manufacturers reaping the rewards. "The real future of tape is definitely a disc" said Sommer. Political highspot of the press conference was the protestation, Michael Schulhof then screened a lengthy selection of video by Ron Sommer, President and CEO of Sony in Europe, that Sony music clips. The projected pictures were predictably poor, and the is a European company. Yes it employs Europeans, but where do over-loud sound was riddled with distortion.

Philips DCC130 Digital Compact Cassette personal stereo

Everyday with Practical Electronics, February, 1994 123 Exclaimed Schulhof "You have just witnessed an amazing ex- answer from an engineer. "We were talking about future players, ample of the power of technology ... digital quality sound ... the that are modifed". optical disc experience". By then Philips had held its own press conference, like Panasonic In fact, as Sony then had to admit, what Schulhof thought was with no-one on hand to answer technical questions. John Hawkins "digital quality sound" and "the optical disc experience", was in failed to volunteer the promised clarification. He answered ques- fact the analogue sound you get from the Betacam SP video tape. tions with the clear confirmation that the FMV movie discs due this winter from Philips (with Paramount titles) will be on CD-I C OI/ Video CO format discs, not linear Video CDs. But then he got into a muddle Sega and Nintendo dominate the games market. The more over questions about Video CDs playing on audio players. advanced multimedia market is now shaking down to a straight All it needed, both at the Panasonic and Philips conferences, fight between CD-I, developed by Philips and supposedly backed was one engineer on hand to answer technical questions. Both by Panasonic, and 3DO, developed in California and most companies employ engineers who could have done the job. But definitely backed by Panasonic. CD-I is already on sale and 3D0 is the executives thought they could manage without them. They promised for sale this winter. couldn't. The two systems are wholly incompatible, although both players The facts of the matter, which the four largest electronics com- will play CD audio discs, CD + G discs that have simple graphics panies in the world seem incapable of drawing, is this: buried in the audio sub-codes, and Photo CDs. There will be at least two types of FMV CD. One will be a There is now a digital video compression standard, MPEG- I , CD-I/FMV disc which plays back on CD-I players, when for putting 74 minutes of Full Motion Video on a CD. Philips equipped with an FMV decoder. These discs will not play on will start selling a plug-in MPEG adaptor which lets a CD-I another player. player play CD-I/FMV discs. 3D0 promises a similar adaptor, for The other version will be a White Book linear Digital Video CD. 3D0/FMV discs. This will play on CD-I players with FMV adaptors, on personal Philips, Panasonic, Sony and JVC recently agreed a new "White computers with CD-ROM drives and FMV adaptors, and on a Book" standard for Video CD, or Digital Video CD. This is a CD new generation of Linear Video CD player which are designed to with MPEG FMV, but without the control codes which a CD-I work either with Red Book audio CDs or White Book Video CDs. player uses to provide full interactivity. Video CD is "linear" for- These discs may play on a 3D0 player, but no-one will know until mat, like a video tape. You play it and watch it from start to finish. 3D0 delivers a player with FMV label. Video CD follows the CD-ROM XA "Bridge" standard, like a Photo CD. This lets it play on a Personal Computer with CD- Flat screen TV ROM drive and FMV decoder, a CD-I player with FMV decoder, While most Japanese elctronics companies pin their faith for or a new generation of Video CD player which is broadly similar future flat screen TVs on liquid crystal technology, Matsushita has to an audio CD player but has a built-in FMV decoder. been developing a flat version of the traditional cathode ray tube, Because the Video CD is a ROM XA disc, it has a Yellow Book called Beam Matrix. data flag in the bit stream. This flag will (or should) mute all the Matsushita first showed a prototype BM screen at the Tsukuba outputs of a CD audio player, to prevent speaker damage. This Expo in Japan in 1985, and at Berlin showed a new TV set with kills the idea of making Video CDs play on a conventional audio 36cm BM screen, just 10cm thick. This Flat Vision set will go on CD player, of the type which has a digital output, connected to an sale in Japan next month under the Panasonic brand. add-on decoder. In a conventional cathode ray tube, an electron gun produces Nimbus has suggested that the problem can be solved, very an electron beam which is scanned across the screen surface by simply, by making the Video CD follow the Red Book i.e. not have magnetic coils. A BM tube is a sandwich of plates. A rear plate a data flag. But this would stop the Video CD playing on a CD-I player, or ROM drive, because both these are designed to treat any Red Book disc as a music disc. They will try and decode the FMV data as audio, and fail. Also the White Book now specifies control codes for VCR func- tions, like fast search and freeze frame. So the decoder must feed control signals back to the player drive. There is no input for these control signals on any existing CD audio player.

C onfusion Even before Berlin there was massive confusion over this scenario. And it all stems from the clumsy wording of a joint statement put out in late June by Philips, JVC, Sony and Matsushita (parent of Panasonic). This statement on the White Book promised playback of Video CDs on "modified CD players (with a digital data output) with an add-on Video-CD box". What they meant to say was that there will be a future gener- ation of CD audio players, built slightly differently to play either Red Book audio CDs or Yellow Book Video CDs, when connected by digital output to a Video decoder. But what people undestood them to say was that Video CDs will play on existing Red Book audio CD players which already have a digital audio output, con- nected to an external video decoder. Just as we thought everything would be clarified by statements at the giant Berlin International Audio and Video Fair, the same four companies put out another statement which made things even worse by repeating the error, this time without even the qualifying word "modified". "Video CD discs can be played on ... CD players (with a digital data output) with an add-on Video CD adaptor". Press briefings held in Berlin both by Panasonic and Philips merely compounded the confusion. After puffing 3D0 with video clips of promised software, a panel of top brass chaired by Panasonic's Managing Director in Europe, Yoshihide Tsujimoto answered questions. "Yes" they said "you can use CD-I discs on a 3D0 player". "Yes" they said again when asked to confirm that all four Panasonic executives really did think a CD-I disc would play on a 3D0 player. It won't, of course, unless 3D0 takes a CD-I licence, which would create a new format, 3D-I, and that seems pretty unlikely. All four Panasonic executives then collapsed into a heap of con- fusion when asked to explain how a CD audio player could play a The Virtual Vision "Sport glasses" are claimed to allow the Video CD with muting data flag. No-one present had any techni- wearer to view their favourite TV programme while carrying cal understanding of the issues involved. Two days later I got an out other work.

124 Everyday with Practical Electronics, February, 1994 carries strip cathodes which produce electrons. A perforated con- trol plate is electrostatically charged to focus these electrons into pencil beams. The beams then pass first through a modulating plate, which varies their strength, and then through horizontal and vertical deflection electrodes, which move the beams sideways and up and down. At the front of the sandwich there is a phosphor-coated screen plate, which is divided into 10,000 small rectangular sections. Each section is scanned by its own beam, so each section thus forms a small part of the picture. The trick is to get all the small parts of the picture to combine, and provide a full TV picture, without any seams or joins showing. Although Matushita has made BM technology work, people who want flat TV sets will have to pay for the priviledge. Flat Vision sets will cost 288,000 yen (nearly 1500). Matsushita is only making a thousand a month.

Voice Control With so much confusion over technical issues it was entirely predictable that the popular press would latched onto Philips' new easy-to-understand infra red remote control for TV sets and VCRs. It looks like a conventional unit but incorporates a micrphone and speech recognition circuitry. On purchase the owner switches to learning mode and speaks words into the microphone which correspond to a list of basic commands, like "On", "Ofr,"BBC-l", "ITV", "Play" and "Record". The words can be different from the commands, and in any language, for instance "Wake up" for "On" or "Shut up" for "Off- . The remote control has four memories, for four voices, so each member of a family can use the same control, but only one can talk to it at a time. Although mainly a gimmick, the remote could be very useful to people who are physically handicapped, for instance with arthritis. The Philips voice recognition remote control will accept up to four voices. Goggle Sox US company Virtual Vision of Redmond, Washington says it Power is also wasted in the set's de-gaussing coil. This is only will start selling its "Sport" TV spectacles in Europe by the end of occasionally used to remove residual magnetism from metalwork this year, for around £750. The aim is to let someone watch TV of the set, which would distort the electron beam in the picture while doing something else. tube and sour the picture colours. But the coil is powered even in The viewer wears a pair of dark spectacles, like large sunglasses, standby. which connect to a battery-powered belt pack. The pack feeds a Nokia of Finland has thought laterally and redesigned the in- video signal, from a TV tuner, VCR or camcorder, to a small fra-red sensor. A simple circuit, ahead of the transformer and de- colour I.c.d. screen which is mounted inside the top of the spec- gaussing coil, has only one function. It senses any incoming infra- tacles frame. A prism and lens reflects the image from the I.c.d. and red pulse and switches a semiconductor to allow power through to superimposes it on the wearer's natural field of vision. So the the mains coils. This sensor draws only 0.1W from the mains. So wearer sees a TV picture apparently hanging in space. Although power waste in standby mode is reduced by a factor of a hundred. the picture is clear, and its position can be adjusted, the effect is Says Dr Helmut Stein, Vice-President in charge of Research and likely to be fatiguing. Development at Nokia. "Multiply 10 watts by the number of TV sets in a country and you realise how much energy is being wasted Shocker as heat". In the UK there are around 20 million homes with at least one An innocent-looking little gadget, tucked away in a corner of the TV set, which equates to a standby power drain of 200 megawatts, exhibition hall, could prove very dangerous in the wrong hands. 20 hours a day. With Nokia's design this could be reduced to two The Z-Force Power Elektro Shocker looks like a battery- megawatts. powered shaver, but with two metal prongs on the front. These connect with circuitry inside which steps up the low voltage delivered by 9V radio batteries, to 80,000, 120,000 or 175,000 Po wer Loser volts. Squeezing a trigger delivers the high voltage through the Swiss company Swatch plans to launch is Beepup wristwatch electrodes in pulses lasting between 0.25 to 5 seconds, which pager in the UK, this year. Swatch is already selling Beepup in Los the German exhibitor assured will "go through clothing, even Angeles, Dallas and Atlanta, and in Switzerland, Italy and Ger- leather". many. The company needs to strike a deal with an existing paging Although the current flow is small, the shock effect of such high service, is talking with British Telecom, Mercury and Hutchison, voltages is debilitating, much worse than grasping the leads which but currently favours Hutchison. run from a car ingition coil to the sparking plugs. These usually Beepup looks like a rather large wristwatch and costs around carry only 25,000 volts but inflict a very unpleasant shock. £100 (plus the similar cost per year of subscribing to a paging Ostensibly intended for self-defence, the Elektro Shocker could service). It beeps when receiving a message, and displays up to equally well be used for offence. Dealers can buy them for a trade 15 digits on a small display, signifying a telephone number to be price of between 80 and 100 DM (under £40). called. Swatch says people can use it to stay in touch at all times, The Home Office says the device would be classed as a whatever they are doing, even surfing. "probibited weapon" under the Firearms Acts, and that anyone Beepup runs on expendible lithium button cells. When the pager trying to import them would risk prosecution. is left switched on, waiting for a signal, the battery goes flat within 18 days. Acknowledging the need to have a spare battery always Po wer Sever available, Swatch makes room for one in the wristwatch strap. But Perhaps the most important innovation at the Berlin IFA show the battery is secured in the waterproof shell by a plate and four was also the simplest, and most widely overlooked. very tiny screws. These can only be removed with a matching, All modern TV sets now have a remote control. The set sits, on precision screwdriver, for which there is no mount in the strap. So average, twenty hours a day, waiting for an infra-red pulse to bring the user must remember always to carry a matching screwdriver, it to life. While on standby the set consumes up to 10 watts of and hope not to lose or damage the tiny screws when removing mains power, which it wastes as heat. them every 18 days. The power is wasted in the primary coil of the mains transformer Anyone who has ever fiddled with precision screw fittings will which powers all the circuitry in the TV. Although this transformer know that this will be a vain hope. If any one thing in this world is is only delivering a small amount of power to the infra-red sensor certain, it is that small screws want nothing more from life than to when the set is in standby mode, all transformers are inefficient and leap off as soon as they are freed and get lost in a deep carpet, waste power when connected to the mains. patch of grass or dirt, or nearest drain.

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Everyday with Practical Electronics, February, 1994 127 Constructional Projec nmEour INTRODUCTION TO MICROCONTROLLERS PETER CROWCROFT

Timeout will count down fro m 60 seconds There is no copyright what-so-ever on the o r 9 0 seconds, bleep every ten seconds Printed Circuit artwork, program code or documentation. We encourage you to and every second of the final ten seconds, copy, learn from and add to the annotated but more importantly it will introduce you software code. The project is available in kit form but individual components includ- to the world of microcontrollers. ing the programmed K1 and the p.c.b. are available separately. QUIET revolution is taking place in ing down in price) and the instruction electronics today. It is almost as im- set is a bit strange. We will not dis- T'IME OLIT Aportant as the replacement of valves cuss them further here. (Small Controllers Timeout is a down-counter. The circuit by transistors and i.c.s in the 60's and 70's. from other manufacturers also suffer from for it is shown in Fig. I. It is preset to This is the rise of the microcontroller. Their the problem of high cost of tools for start from 60 or 90 seconds. Press any increasing power and versatility at steadily code development and programming, even button to wake it up. There is no off/on decreasing prices is now such that many of higher than the PIC series.) switch. Press B to start the countdown; the simplest logic i.c. circuits may now be The beauty of using the K I Motorola during count down pressing B will pause better designed using them. range of microcontrollers is that the full the count. Pressing it a second time will Microntrollers are a computer on a range of development tools needed by the restart the count down. Pressing A will single chip — a central processing unit plus amateur to develop applications are readily toggle the initial count setting between 60 memory, clock, input/output plus some available at low cost, say under £150. The and 90 seconds. sort of peripheral device (for example, a programs (called assemblers) to develop During the count down the buzzer will timer, AD/DA, communication ports.) code for the chips on a PC are freeware and beep every 10 seconds. It will beep every Nowadays these devices are to be found all are available from Motorola and its dis- second for the final 10 seconds and give a around us. To name a few applica- tributors. The hardware schematic for the long beep when zero is reached. If another tions; washing machines, microwave ovens, programmer is published in the Motorola count down is not started within a minute mobile phones, bar code readers, printers, Data Book and the software to use the the unit will power-down and turn off. video casette players, photocopiers and, programmer is also freeware. As described so far this counter could be most importantly, motor cars — engine A low-cost in-circuit simulator, which constructed using logic i.c.s. The com- fuel management, braking systems, active also acts as as programmer, is also avail- ponent count would be higher (especially suspension, multiplexed wiring, mirror and able with software and the chip comes in all the current limiting resistors on the window movement. various packages including the EPROM displays) and the area needed on a p.c.b. In all cases the application program in- version. A truly excellent manual Under- would be greater but it could be done. side the microcontroller is not accessible to standing Small Microcontrollers which in- However, using the microcontroller opens the hobbyist and therefore of little use. troduces the K series of microcontrollers up a versatility not possible with straight Even if it was the tools to develop pro- from basic principles is also available. logic components. grams for these devices are expensive — With this project we have tried to do two Suppose you wanted a counter to start typically over £500. Also learning the pro- things: at 68 seconds, beep every 8 seconds then gramming language has not been easy. Firstly, bring you face to face with a give a different beep for the last 4 seconds, It has generally been true that to learn to modern microcontroller, and show you then restart automatically to 68 seconds program a microntroller attendance at a that it is now possible for anyone to learn again. Try to do that using logic i.c.s! With technical college or some similar formal to program them. Timeout it is a simple matter of minor teaching institution has been required. To Secondly, to demonstrate how a changes to the software program. try to teach yourself the older devices such microcontroller can replace circuits built This single example should be sufficient as the 8748 or 8051 family from a data out of traditional logic i.c.s with simpler to demonstrate the enormous advantages book was not easy. and far more versatile circuits. that microcontrollers have to offer over straight logic TIMES HA VE We have attempted to make this article as easy as possible for beginners to under- CIR C UIT C HAIVGE O stand. We gave first drafts of it to computer This situation has changed in the last literate people who had no experience with D E S C RIPTIO N year or two. Microcontrollers and the tools microcontrollers and noted their questions The heart of the circuit is the K1 to develop them and program code for and areas of difficulty. We have added in- microcontroller and the software it con- them have now reached a level the amateur creased explanation in those areas. It is in- tains (Fig. I ICI). The other components can afford and understand. Two chips have tended that this be read together with the are the power supply, external pas- led the way. They are the PIC series from Technical Data manual for the Kl and the sive components for the oscillator and Microchip and the K series chips from "Understanding" book. I/O components to get information into Motorola. The unit is constructed on a single- and out of the microntroller. The K 1 The PLC chips have been out longer but sided printed circuit board. Software was is a low-end version of the Motorola the development tools to use them are developed in part using a Motorola 68HCO5 8-bit controller. Its I 6-pin d.i.p. is relatively expensive (though they are corn- 68HC705K I ICS (in-circuit simulator). the smallest pin package for any 8-bit

128 Everyday with Practical Electronics, February, 1994 55

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Fig. 1. Complete circuit diagram of Tirneout IC1 is the microcontroller microcontroller. We will not spend time describing it in depth here — please see the MC68HC705K1 Technical Data manual. The LM2936 (IC3) from National Semiconductor is an ultra-low quiescent current 5V regulator which is used to provide power to the circuit. There is no hardware off/on switch as the current drain from the battery, both when it is operating and when it is in STOP mode, is so low — approximately 25 micro-amps when the K I is in STOP mode and 19 milli-amps when it is running. The off/on switch is in software. The 15 bit multi-function timer inside the microcontroller is used to do the one second counting. The frequency of opera- tion is then 262,144Hz. The three pin oscil- lator using R2. R3 and Cl was chosen as the simplest option for the project. If more exact timing is required then a crystal oscil- lator can be used with appropriate software changes. The K I controls the display through port A. PA4 to PA7 present BCD code to IC2 which decodes it into seven segment rep- resentation. Pins PA3 and PA2 control TR I and TR2 respectively which determine which display is turned on. The two pushbutton switches, SI and S2, are connected to PAO and PA I. They use the programmable pulldown resistors built into the K I to eliminate the need for exter- nal pulldown resistors on each switch. Also these pins will bring the K1 out of the low power STOP mode. This facility eliminates the need for an off/on switch. S OFT WA RE D ES C RIPTIO N Print out the linteoutisi program con- tained on the floppy disk supplied with the kit. This is a combined listing of the software code, mnemonics used to write the code, a line number for reference and, most important, a lot of comments to explain what is happening. Also print out kidefist.

Everyday with Practical Electronics, February, 1994 129 This is the header file. Flowcharts to the code are shown in Fig. 2a, b and c. See the Learning Code section on the next TINE NTERRUPY page if you have not studied any assembly language code before. The software may be divided into six sections. These are summarized in the six flowcharts. They are: What happens when the battery is first connected to the circuit. What happens when a key is pressed and the unit is woken up. The MAIN loop where the most of the CL/AR CLEAR [Ti SET RE, A CLEAR TO, PREVIOUS REY NTERRUPT FLAG time is spent when Timeout is working. 'CIRRUS", A STATUS The DOBEEP subroutine. The DOKEYS subroutine. The TIMER interrupt routine. The microcontroller sits in a powered SET Rll SET KEY A SET TOE FLAG FLAG PR EVIO US down state drawing just a few micro-amps STATUS until either key is pressed. There is no off/on switch. The timer is based around the multi-function timer in the K1. The Real Time Interrupt (RTI) generates an TOF CKT DESPI-AT CLEAR CCV interrupt every second. The Timer Over- TOE PET -1 I COUNT flow (TOF) interrupt generates an interrupt every 7.8 milliseconds. RTI is used to decrement the count and stop the timer when zero is reached. It is YET also used to enter STOP mode when the counter has not been counting down for 60 seconds. TOF is used to scan the displays and check the pushbuttons. The register STOP COLATT CLEAR CLEAR TOFCNT counts the number of TOF DOWN TINE 0 VT PREVIOUS KEY COUNTER S STATUS interrupts. This register is equivalent to the most significant bits of the multifunction timer which are not accessible to the programmer except as sources of RTI SET KEY S COUNT - III/M OUT - STOP ) PREVIOUS COUNT - I interrupts. Bit 5 of this register is used to TIYO uT + sTAnAl blink the display twice a second if the timer is not counting down. If the timer is counting down then the display is scanned every TOF interrupt. The TOF interrupt checks the status of

(TEL .'S) the keys by detecting a rising edge on PAO and PA. It compares the current status of the keys to what they were last time the TOF interrupt was serviced. If the status is the same then there has not been 2b (above). a keypress. However, if a key is now The TIMER interrupt HIGH when it was previously LOW then a subroutine. keypress (the rising edge of a keystroke) will be recognised. Every time the hardware detects an inter- rupt the program counter is loaded with the address where the TIMER interrupt routine is located. This is $03F8. TIMER sets a keyflag in 'flags' (depending on which interrupt was generated — RTIFLG or TOFFLG). "Flags" is our own creation. Fig. 3. (left). Full size (We could have called it "Fred". It is just a p.c.b. layout and byte we created in RAM to store the 7 bits master for Timeout which we define it to contain. Then we give it a name we will remember.) It contains (EE4,020 information needed to run the program. When the program returns to the MAIN

•e 1.A • ae-"N. FolifF ait

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1 30 Everyday with Practical Electronics, February, 1994 loop from servicing the interrupt it im- mediately finds that a flag has been set and it branches to the subroutine indicated - either DOBEEP or DOKEYS. DOBEEP handles the timing beeps. The three types of timing beeps are: When the counter reaches zero. When the count is less than ten. Every multiple of ten seconds. DOKEYS checks if any key flags have been set. There are two functions for each key, one when the unit is counting down and the other when it is not. Key A (SI): If counting down stop count- ing and reset to default count down time. If not counting down toggle the default time. Key B (S2): If counting down pause. If not counting down, resume counting. Sixty seconds after the count down or being paused the K I goes to a powered down state. Do not confuse flags with interrupts. Some of the routines in TIMER could have been put in DOKEYS or DOBEEP. And, alternatively, some of the routines in DOKEYS or DOBEEP could have been put in the interrupt routine. The choice is determined by the programmer and where a particular routine is best suited. What is important here is that both methods have been demonstrated. It is difficult to remember binary bit patterns and hexadecimal addresses when you write code. It is far easier to remember mnemonic names for register addresses and bit positions. Using these names also makes the program easier to read. K !der consists entirely of EQUate directives. These associate a label with a binary number or address. Note that this is a Fig. 2c. The Initial Connection flowchart (left), the DOBEEP subroutine and the Wakeup flowchart (right). COMPONENTS

Resistors general purpose header file. Not all labels correct position on the p.c.b., especially the Al 4k7 defined are used in Timeout. You may use two i.c.s, electrolytic capacitors, and the R2 27k I K 1 def when you write your own K1 two displays. If you have an oscilloscope R3 9k1 I • YAW metal film ± 1% programs. check the oscillator. Also check that the R4 to R6 4k7 (3 off) Note that K 1 delasm is called by 5V/9V supply is going to the correct places. R7 100 All Y.W carbon film ± 5% except where timeout.asm using the $include directive stated. when timeout is assembled. L EA R NIN G CO M E See The main purpose of this project is to in- Capacitors C O NSTR UCTIO N troduce you to a microcontroller and how CI 100p ceramic SHOP The complete unit is housed on one small to program it. You will need the following C2 101.1 elect. 10V printed circuit board (p.c.b.) as shown in items to learn the programming code: C3 100n ceramic TALK Pogo Fig. 3. Commence construction by fitting Printout of timeoutist and kldellst the smallest components first and working The six flowcharts of Timeout Semiconductors up to the displays, i.c. sockets switches and Try to buy the K1 KICS kit from TR1 to Motorola or their distributors. This was an TR3 BC547 npn transistor (3 off) sounder. Take care when fitting the buzzer, IC1 68HC705K1 programmed C2, TR1, TR2, TR3 and the i.c.s, make introductory offer in 1993. It is excellent microncontroller see sure that they are correctly oriented. The value for money. It contains the Technical Shop Talk displays must have the decimal point in the Manual, an excellent book Understand- IC2 CD14511 seven segment bottom right hand corner. ing Small Microcontrollers specifically with display driver The microcontroller for this project is the reference to the K1, plus an in-circuit IC3 LM2936Z-5 5V regulator one time programmable version (OTP) of simulator and all the software to go with it. X1, X2 CM1 -5615 seven segment the 68HC705K1 which has been pro- If you cannot buy the KICS kit then buy display (2 off) grammed with the Timeout software. the K1 in-circuit simulator, K1 assembler to use on a PC and get a copy of the Miscellaneous There is no window in this chip and the WDI Miniature d.c. operated 5V program cannot be erased. An EPROM MC68HC705KI Technical Data manual. buzzer version can be used but this is more Try to buy the "Understanding" book. Si S2 p.c.b. mounting push switch expensive. Make sure you get an EPROM version single pole, push to make The p.c.b. can be mounted in place of of the K1. (2 off) the lid of a small plastic box. The display Try to buy another slightly more ad- 9V battery and battery clip; plastic box and switches (together with the other com- vanced book from Motorola, M68HCO5 approx 82mm x 53mm x 28mm; p.c.b. - ponents) are then displayed. The battery Microcontroller Applications Guide. This see Shop Talk: software on disc; 16-pin also has a lot of general discussion and d.i.l. socket (2 off). leads should be soldered to the back of the p.c.b. so that the battery is housed inside microcontroller explanation in it. the box. You will need a quiet space to work, Poor soldering is the most likely reason good light and a few uninterrupted hours. Approx cost that the circuit does not work. Check all We have found that the following guidance only £38 solder joints carefully under a good light. practical considerations apply to learning Next check that all components are in their microcontroller code:

Everyday with Practical Electronics, February, 1994 131 You are not going to learn everything in about the logic of what you are trying to small steps Then program a EPROM K I one or even ten sittings. You will soon do. Clear logical thinking in your early for final testing. find code fragments you do not under- programs will lead to simpler code in your Best, but most expensive to use, is the stand. Looking in the manual may not later work. full, real-time emulator. Get practice and help. However we can assure you that the Start to write and practice immediately. advice on all methods. answers to most things are, in fact, in the The simplest way to start is to write your book - it is just that they are cryptic or code on a PC, assemble it using an as- may not be "obvious". (This is why the sembler program available for free from FURTHER "Understanding" book is so good. Com- Motorola, program a EPROM K I, put it READING pare it with the Technical Manual on the into the target hardware and run it. Then There are a whole range of discussion of the Multifunction Timer, for when a mistake is found, erase the K I and microcontrollers available from Motorola example.) Make a list of your problems repeat the cycle. with increasing memory and different and then move on. There are software and hardware tools peripherals on them suited for different Try to get someone to help you. Note to help you in code development. We jobs. Do not be put off by the size of the that some programmers are most reluc- think that software simulators which run list. Only a few of them are suitable for the tant to share their knowledge with begin- as a program on a PC are probably a beginner. (The rest are for mass production ners. (They learnt their knowledge the waste of time and effort. They are tedious hard way and tend to be very jealous to use, can only . find gross errors and use.) The ones you need have a "7" in of it.) Our advice is to forget these cannot deal with the main functions of them. These are the microntrollers with people. Try to find someone who knows microcontroller which are timing and 1,0. EPROM - P3, C4, C8. where you are at and will anticipate your The in-circuit simulator like the K ICS As with the K I , the programming problems before you know them yourself. allows some debugging and is less tedious tools to use these devices are low cost There are many ways to do the same to use. Break your program down into and readily available compared to other thing in software. When milliseconds are small individual routines and use the microcontroller families. Each of these not important any way to get the job done simulator to verify their correct opera- device has a Manual. Technical Manual or is OK. However, at the same time think tion. Thus build up the total program in Data Book.

wearing a dimming filter over one eye will see the swirl appear in 3D. For Nuoptix to work with ordinary TV programmes, there must be relative P IC:03 C movement beween the camera, scene and actors. The camera can move in an arc or circle round the actors or track alongside them. Or it can pan and turn on its own axis. Alternatively the actors can keep moving backwards and for- by Barry Fox wards in front of the camera. Or the image can be manipulated by a digital New Dimension? camera is moving. So viewers without special effects system, as used for pop "Stunning 3D" promised the BBC for its spectacles may well have been left won- videos. week of "New Dimension" progammes dering why there was so much motion at the beginning of December. The BBC on the screen. Although the BBC's pro- Green and Purple was planning to celebrate thirty years of grammes were to be marked with a 3D The spectacles sold for the BBC week Doctor Who with two new episodes shot logo, viewers can still see similar effects if use a new idea which Beard has licensed in a way which gives an illusion of depth they wear the same spectacles to watch to Telecast International of Munich. In- to viewers who pay 99p for a pair of any programme in which there is motion. stead of making one eye lens clear and the coloured spectacles. The BBC also had Viewers can make their own spectacles other a neutral grey, one lens is a very 3D versions of several other programmes too, although with the BBC promising that light green and the other a dark purple. (including Children in Need, Blue Peter the Children in Need fund would get 25p This colouring, claims Beard in his patent, and Top of the Pops) lined up for trans- from every pair sold, it seems a pity to do is chosen to match the spectral emission mission using the same technology. so. characteristics of the phosphors used in a Most important, the BBC promised that By now the BBC's week will have come colour TV screen. viewers without the special spectacles and gone, and viewers will have had a These phosphors have emission peaks would see "a normal television picture". chance to judge the effect for themeselves. in the purple-blue, yellow-green and red- This promise brought back memories of Good or bad I will bet that a lot of orange regions, and the dark filter colour 1982, when TVS, the TV station then viewers were left wondering how the is tuned to block at these peaks. So the serving Southern England, promised full sytem worked. The publicity material put spectacles create a large difference in ap- colour TV in 30 from a new and highly out was vague, bordering on gibberish, so parent brightness between the two eyes secret process. The secret system turned the national press had little hope of ex- when looking at a TV screen, while creat- out to be yet another variation on the plaining it. ing less of a difference when the wearer age-old anaglyph theme, with left and looks round the room in ambient light. right eye images overlapping on screen Nuoptix and colour fringing to distiguish them. The system used is called Nuoptix. US Sports Viewers with the special spectacles, Although described as patented, it relies The system has already been used in the which put a red filter over one eye and a on the old and well-known optical US for sports matches, where there is blue filter over the other, got an illusion of phenonemon, called the Pulfrich effect. If naturally a lot of movement on screen. But depth and a degree of colour. But the both eyes see the same 2D view, but one as the depth effect reverses when the millions of other viewers who watched eye is given a dimmer image than the direction of motion reverses, with players the cowboy feature film Fort Ti; which other, moving objects will stand out a standing proud of the background one TVS broadcast at peak hours, saw little. This is because the brain takes moment and then receding behind it the drunken double images. They jammed longer to process the dimmer image and next, viewers may quickly lose interest. the switchboards of both TVS and thus registers different perspectives of a Programmes shot in a studio can be struc- the Independent Broadcasting Authority moving object for each eye. tured to keep the effect more constant. with complaints and all broadcasters The effect can be seen by putting a If you see some spectacles around, per- have been very wary of 3D ever since. neutral filter, like a sunglass lens, over haps being sold off cheaply, buy a pair and one eye only and watching TV. A par- try watching any programme that contains Moving Depth ticularly dramatic effect is seen if the a lot of motion. If you cannot buy the What the BBC did not say was that the aerial to the TV set is disconencted, so coloured spectacles, just knock one lens effect of depth would only be seen on that the screen displays only a swirling out of a pair of dark sunglasses and put moving objects, or in scenes where the mass of white snow "noise". Anyone them on when you watch TV.

132 Everyday with Practical Electronics, February, 1994 4 'CTRONICS PRINCIPE ES SO F1T WARE from E.P.T. Educational Software If you are looking for a means of improving your knowledge of the basics of electronics then this software is for you. Electronics Principles covers: * Insulators, Conductors, Resistance Half Wave Recaaer. * D.C. Circuits 01 1 'rm. bowl p D r••••••• bumed.

!spat U. impak. • 100V * Capacitance and Inductance Serie. Isolator = SO Load Register = 1002 DL Voltage drop its 4.7619V * A.C. Series Circuits Voltage drop DI = 60010 8 V8 \7 Peak voltage Load = 94.63S1V Peak Currest Load = 952.381.0 Cl. . 1000 0 * A.C. Parallel Circuits Voltage Ripple p-p • 19.047610 * Reactance and Impedance Example Inputs. Vie peak 100volte : Rs Soling :Q1 .d 100ohas , CI = 1000 0. Positive half cycles > 0.6volts cause the diode to conduct •nd current flo w lot. the lead. also charges Cl. Daring the negative half cycles the diode le rot-off. and CI discharges via IL. Until the next positive pulse * A.C. and D.C. Power arrives. The charge stored in CI cam be increeoed by making it larger. This * Frequency and Tuned Circuits td a Zriejr. the TI 1, volt... yin Ileitis the diode foruaril current. * Using Numbers Half Wave Rectifier screen

* Complex Numbers, Phase Angles Having reviewed a dozen, or more, educational * P.N. Junction Diode software packages designed to "teach" electronics, I * Transistors was more than a little sceptical when I first heard about Electronics Principles: there seemed to be * Operational Amplifiers little that could be done that has not been done * Logic Gates elsewhere. When I started to use the package my views changed. Indeed, I was so impressed with it * Digital Number Systems that I quickly came to the conclusion that Everyday * Combinational Logic with Practical Electronics readers should have an * Flip Flops opportunity to try the package out for themselves! * Counters and Shift Registers MIKE TOOLEY B.A. Dean of Faculty of Technology, * Memory Brooklands Technical College Over 200 menu driven screens with interactive graphics enabling a learning by doing approach to encourage experimentation. Electronics Principles requires a PC (or fully compatible system) running DOS with an 80286 or better processor and VGA (ideally colour) graphics. In addition you must have 4Mb of hard disk space, a high density (1.44Mb) floppy drive and at least 640K of RAM. We also recommend the use of a mouse with this program. The program is supplied on three 3.5 inch disks. Demonstration disk available send £2 (Overseas order Complete package send £3) — includes P& P Only £49.95 inc. VAT, plus £1 post and packing.

Distributed by Direct Book Service, 33 Gravel Hill, Merley, Wimborne, Dorset, BH21 1RW. (Mail Order Only). Direct Book Service is a division of Wimborne Publishing Ltd. publishers of Everyday with Practical Electronics. Tel: 0202 881749. Fax: 0202 841692. Visa and Mastercard orders accepted for the complete package — please give card number, card expiry date and cardholders address if different to the delivery address. Credit card orders NOT ACCEPTED for demonstration disks. OVERSEAS ORDERS: Add £2 postage for countries in the E.E.C. Overseas readers, outside the E.E.C. countries send £42.51 (price less VAT) plus £3 airmail postage (Total £45.51).

Everyday with Practical Electronics, February, 1994 133 Constructional Project BArrERY To MAINS INVERTER AND UNINTERRUPTABLE POWER SUPPLY MARK DANIELS Part Three

A 25 0 0/ to 60 0 0/ design with pulse inverter derived supply in the event of mains failure. There is normally a brief width modulation for voltage control delay between loss of power and the in- and an uninterruptable supply verter starting up and taking the load. In many applications, such as emergency add-on. It can also be built for 50 Hz lighting, this is perfectly acceptable, but some critical systems, such as computers, or 60 Hz operation. may not even tolerate a very short break, rendering this solution unsuitable. HE mains electricity supply, though the U.P.S. for applications such as video The obvious alternative to this is to run considerably more reliable than in its recording of broadcast material or for the inverter continuously, with the mains Tearly years, is not infallible and for more general use with lighting and power battery charger supplying the power for some critical applications, such as comput- circuits. the inverter in addition to charging the ing, needs occasional support from a accumulators. The block diagram, shown secondary power source. Traditionally Additional Specifications for U.P.S. in Fig. I, appears very simple, comprising mains back-up has been by petrol or diesel (See Part 1 for Inverter spec.) only a charger, battery and inverter. These generators which require a somewhat are the only essential components for a lengthy start-up period of several seconds, Type On Line functional system, but in practice a number by which time a computer will normally Mains Input Voltage 200 to 260 volts of other features are added for increased have suffered terminal amnesia. Max Input VA 625VA reliability and functionality. Any data not saved to disk prior to the Autonomy at full load 10 mins from It does offer a number of advantages power outage will be totally irrecoverable, internal battery over the change-over type, including a zero though that which was successfully saved Transfer Time Zero transfer time at mains failure as the bat- will normally be intact. A power failure U.P.S. Failure teries take over the load. The isolation of which occurs during a write to disk will Protection Relay bypass to the load from the mains and any transients completely trash the current file, and unless mains imposed on it by motors, ensures that it the program uses two separate files for suc- Recharge Time <12 Hours to 80% will be unaffected by these undesirable cessive writes, all data will be lost from the capacity conditions. disk as well as memory. Weight Including To preserve power (and sanity) an Unin- Battery 18kg approx. B A TTE R Y terruptable Power Supply (U.P.S.), which Design M.T.B.F. > 20,000 hours C HA R GIIV G derives its power from batteries, may be inserted between the national grid supply CIR C UITS and the computer equipment. With mains LJ.P.S. TYPE S The U.P.S. is intended to be used in electricity available the U.P.S. just sits there There are basically two types of U.P.S., conjunction with a sealed lead acid ac- charging its batteries, but the instant a the change-over variety and the on-line cumulator as its reserve source of electrical power cut occurs it draws on its reserve of version, each with features that make them energy. In a float charging application the energy stored in the accumulators and more viable for some applications than charger should maintain a constant poten- produces an independent mains voltage others. tial of 13.8 volts across the terminals of a supply. The change-over type uses a relay to nominal 12 volt accumulator, with less Obviously the energy stored in the ac- switch the load between the mains and an than 10mV of ripple. cumulators cannot keep the computer run- ning indefinitely, but will allow sufficient time for adequate back-ups of data to be made before shutting down, or to allow an STAND - BY auxiliary generator to be started and come BATTERY "on line". Short duration drop outs of a few seconds or minutes will be ridden over by the reserve energy with no user inter- vention and operations will carry on as normal. MAINS PROTECTED CHARGER INVERTER So far the use of a U.P.S. has been INPUT OUTPUT discussed only in connection with com- puters, this being by far the most popular application and one which requires only (fE440G short duration autonomy of the supply. Larger (external) storage batteries will lengthen the independent operation time of Fig 1. Block diagram of on-line U.P.S.

134 Everyday with Practical Electronics, February, 1994 Fig. 2 Simple regulated linear p.s.u. Fig. 3. Low loss linear regulator

The charger in an on-line U.P.S. has not the output voltage at the junction of RI A grand total of seven volts represents only to provide the charging current for the and R2 is compared by the op-amp with our minimum operating headroom for a stand-by batteries, it must also deliver the the stable reference voltage, Vref, across the simple linear supply of this type. With a power required by the inverter to drive Zener diode and the output is adjusted continuous operating current of 25 amps the connected load. This places very much until the two are identical. The voltage the power lost in the regulator could exceed greater demands on the charging circuit, is thus maintained, so long as the sup- 175 watts. Compare this with a switch requiring it to be virtually 100 per cent ply voltage does not fall below a certain mode supply offering an efficiency of 85 per reliable whilst operating under, at times, limiting value, at which point regulation cent, its total losses would be just 53 watts very arduous conditions. will be lost. Normally the input voltage to at 12 volts output. Unavoidable inefficiencies in the power the regulator must be several volts higher circuits of both the inverter and charger than the required output, the excess being A N AL TE RAIA TIVE will contribute to a significant operat- dropped by a pass transistor, TR 1 in this ing temperature rise, which for obvious example. LIN EA R reasons it is desirable to minimise. A In low current supplies this presents The main reason for the high unregu- significant reduction in these losses may be no problem as such, the mains trans- lated supply voltage is to allow the op-amp achieved through careful design of the former being selected to provide suffi- to drive the base of the output Darlington charger. There are a number of design cient "headroom" for satisfactory opera- up to three volts above the desired output possibilities which may achieve this and tion. However, this requires the output voltage. The collector of the output device these will be discussed below. transistor to dissipate the excess as heat does not need to be at this same high Since a constant charging potential is and, with high current supplies, there could voltage, as long as we drive the base of the required as outlined above, external regula- be a lot of it. first stage transistor with a sufficiently high tion must be employed to maintain a A typical high current, low voltage sup- voltage. The only places at which a high steady 13.8 volts. Regulation, however, ply may have three output transistors con- voltage needs to be present then is in the always implies energy losses and an at- nected as a Darlington (or super-alpha) low current stages, which should reduce tempt must be made to keep these losses as emitter follower configuration to provide dissipation significantly, raising overall small as possible. Switched mode control, sufficient current gain. Each transistor in efficiency by a considerable degree. where the unregulated supply is chopped the chain will drop a minimum of 0.7 volts, The basic circuit required to do this is with a switching transistor and then in- possibly one volt or more at high currents, shown in Fig. 3. Here the op-amp is driven tegrated by an output filter comprising requiring a minimum overhead of three from an auxiliary supply of nominally 24 chokes and capacitors, is the most efficient volts, but preferably more. volts d.c. enabling its output to rise to 22 method available to us and would appear The output of the op-amp driving the volts if required. A two stage Darlington on the list of likely candidates. transistors will normally only swing to output stage buffers the low current output Switching supplies, although very effi- within about two volts of the positive supply of the op-amp and takes its supply from cient and light weight, are notoriously rail and a further couple of volts must be a separate, unregulated and lower voltage difficult to design and set up, particularly allowed for ripple on the rectified and source of just 18 volts nominal, off load. when very high output currents are in- smoothed d.c. input from the transformer. Before looking at how this circuit works, volved, as here. Further, a high current switcher such as required for this applica- tion would normally entail rectification of the mains with the switching transistors operating at 340 volts. This makes the circuit undesirable for home construction. The alternative is our old friend the linear supply, along with its undesirable attributes of low efficiency and high weight. The weight can be significantly reduced by using a toroidal mains transformer, rather than a conventional laminated type. At first glance there appears to be little we can do about efficiency, since all linear regulators demand a higher input voltage than that required at the output. LINEA R PO WE R S U P PLIE S A basic linear design using a "discrete" operational amplifier (as opposed to a dedi- cated regulator i.c.) with feedback to control the output voltage is shown in Fig. 2. The op-amp is used in its non-inverting mode with negative feedback. A portion of

Everyday with Practical Electronics let us consider what the likely losses are volt. The transistor is ultimately driven dary windings. The relay coil is energised and compare them with the simple linear into saturation, dropping the smallest pos- by transistor 1R102 when SI (on the design described above. Under load the sible voltage. A base resistor RB limits the Inverter) is switched on (R103 is connected unregulated 18 volt supply is likely to drop, base current in this situation. to D2 cathode in the Inverter). Resistor possibly to 15 volts, hence we have just Obviously this will have even greater R104 is necessary to run the 12 volt relay 3 volts to drop across the pass transis- effect with multiple stage Darlingtons, coil from the 19.3 volt auxiliary supply. tor this time. The output stage power loss since this is where the larger voltages are When the Inverter is switched on, energis- will be just 75 watts in this case (3V x dropped in emitter follower mode, whilst ing the relay, T101 primary tap Orn (orange 25A), considerably less than a conventional the common emitter mode still allows the lead) is selected increasing the number of linear and not significantly more than the same small voltage as with a single primary winding turns in circuit and hence switch mode example. transistor. the primary to secondary turns ratio, reduc- At low output currents the circuit of ing the output voltage in proportion. Con- Fig. 3 works in the same manner as the CIR C UIT versely, when RLA is de-energised the pink basic regulator in Fig. 2, with the output tap (Pnk) is connected and the output volt- stage driven in emitter follower mode, D E S C RIPTIO N age increases. The reason for this will be- dropping up to one volt (for each transis- The full schematic for the battery charger come apparent later. tor) from its input to its output. However, is given in Fig. 4 A conventional 50Hz as the load increases the supply voltage to power transformer T101 (the component HIG H CU R RE NT the transistor collector will fall and will designations are 100 + or 200+ numbers In order to obtain the very high output ultimately reach the point where there is to distinguish them from those in the currents necessary for driving the Inverter insufficient voltage available for an emitter Inverter circuit), is employed to transform at full load without incurring severe cost follower to work. Once this occurs in the the 240 volt a.c. mains to suitable lower penalties in the transformer and rectifiers conventional linear regulator regulation is voltages and higher currents as required. two separate circuits are used for parts of lost as the transistor maintains this volt The supply to the transformer is filtered by the high current path. Significantly, two drop and its emitter sits at up to one volt the network comprising various chokes, separate 13.2 volt 22.5A secondary wind- below the collector voltage. capacitors and varistors, L101, L102, ings on the transformer allow this to be In the modified circuit, as this point CI01, C102 and VDR101 to VDR104, achieved in a simple manner. Each of the is reached the op-amp is able to take removing the majority of the spikes which 13.2 volt secondaries are double wound to advantage of its higher output voltage may be present on the mains. enable use of thinner winding wire. capability to drive TR1 base harder, for- A relay RLA, with a single change- Fusing, via FS102 and FS103, provides a cing it into common emitter mode where over contact RLA101, selects one of two degree of protection for the transformer the voltage dropped across the collector primary winding taps, thus determining the and rectifiers. Two separate encapsulated and emitter may fall to a small fraction of a voltages present across each of the secon- bridge rectifiers, BRIO2 and BRI03, ap- plied separately to each of the fused high current

FS102 secondaries, provide the 0101 154 raw d.c., being cheaper

Red 13V2 AC than four high current MAIN OUTPUT 1 Ye I stud devices. This, until FS101 51010 L101 the output of the rectifiers, a, N/O keeps the two circuits RLA101 13V2 AC MAIN OUTPUT 2 essentially separate. Parallel connection of 240V the rectified outputs is 50 Hz , 101 only possible by virtue 20V A C AUXILIARY OUTPUT of the series resistance N provided in each circuit by the two separate +26V matched secondary wind- UNREGULATED ings and their respec- tive fuses, which ensures 1 20V AC proper current sharing by INPUT the bridge rectifiers. With- +19V3(±512) out this, one of the rectifiers would pass sig-

100mA nificantly more current, AUXILIARY heating it up which would SUPPLY cause its resistance to drop and allow it to pass more current (so called "avalanche" effect) un- til eventually it was destroyed. This would

+1903 0 leave the surviving rec- DC tifier handling more cur- RLA TR 104 293055 TRIOS rent than it was designed GUV20 R105 for and it too would fail, 109T C 301 2k7 extremely rapidly! TR103 R107 BD 437 Smoothing is provided 22 by two large can 13V2 AC R108 6k8 INPUT 1 12V6 electrolytic capacitors R104 R106 TO C105, C106, this gives an 22 4709 13 V8 VR101 off-load unregulated volt- 1k 0106 220000 =1M age of approximately 17 C105 o Di 04,02 OUTPUT to 18 volts d.c. 220000 mo szyse A TR 102 S1b Cl 09 ani TO BC182L C5V6 k BATTERY VP 102 T E R R O R 7.5 1/ 1k 1352 AC °NE INPUT 2 (ifiViNiFR) R109 A M PLIFIE R 4k7 100 The supply for the error amplifier, IC101 is derived from an auxiliary 20 volt EfL40,6 secondary winding on the power transformer and is Fig. 4. Battery charger circuit for the U.P.S R103 is connected to 02 cathode in the Inverter circuit rectified and smoothed by

136 Everyday with Practical Electronics, February, 1994 a small encapsulated bridge rectifier BRIOI and capacitor CI03. A Zener diode D101 provides the voltage reference for a series COMPONENTS regulator constructed around a small power transistor TRIO!. D102, a 5mm blue led., CH AR GER provides indication of mains power. Resistors A second Zener diode D104, a 5.6 volt R101 1k R102 560 device, is used as the voltage reference R103 10k for the error amplifier. R105 limits the R104 22 1W metal film See Zener current to approximately 5mA and R105 2k7 IROV C107 suppresses Zener noise. The amplifier, R106 470k IC101, is a small power op.amp capable of R107 22 0.5W metal film TALK handling output currents of up to one amp R108 6k8 Page and dissipating one watt, this device actually R109 4k7 contains two such op.amps, only one of All 0.25W carbon ± 5% except where stated. which is used here. Capacitors The power op.amp is used in the non- C101, C102 0µ22 250V a.c. Class X mains rated polyester (2 off) inverting mode and has negative feedback C103 220i radial elect. 63V applied by the network of resistors and C104, C107 100n boxed polyester, 5mm pitch (2 off) C105, C106 22,000i (minimum) can elect. 25V (2 off)• preset potentiometers RI08, R109, VR101 C108 1 t polyester layer, lOmm pitch and VRI02, connected across the output of 'A single capacitor of 47,000µ (minimum) may be substitued if desired. the power stage. SI b, the spare pole of the Semiconductors on/off switch of the Inverter, selects the 0101 BZX88C2OV 20V 400mW Zener diode appropriate tapping point on the potential D102 5mm bright blue I.e.d. divider, providing regulation at 12.6 volts 0103 1N4001 lA 50V rectifier for running the inverter or 13.8 volts for D104 BZX88C5V6 5.6V 400mW Zener diode charging the battery. Resistor R106 ensures BR101 WO1 lA 100V encapsulated bridge rectifier that even during operation of SI feedback is BR102, BR103 KO1 25A 100V encapsulated bridge rectifier (2 off) always applied. Without this the output TR101, TR103 BD437 npn transistor (2 off) voltage could rise uncontrolled and cause TR102 BC182L npn transistor TR104 damage to connected circuits. 2N3055 npn transistor TR105 BUV20, npn transistor The error amplifier, as already indicated, IC101 L272 dual power op.amp is capable of handling a maximum output current of just one amp. To cater for the Miscellaneous VDR101,VDR102 expected currents of 25 to 30 amps consider- V275LA15 275V metal oxide varistor (2 off) VDR103, VDR104 V250LA15 250V metal oxide varistor (2 off) able buffering is required. This is provided VDR105 V33ZA5 20V metal oxide varistor (optional) by transistors TR 103 to TRIOS, connected T101 625VA Charger transformer, Jaytee 9E 284 in a Darlington configuration and normally L101, L102 4itH 3A axial choke (2 off), JPG Electronics operating as a unity gain emitter follower. FS101 10A 20mm fuse However, IC101 is capable of providing suf- FS102, FS103 15A 32mm fuse (2 off) ficient output voltage (by virtue of its higher FS104 400mA 20mm fuse supply voltage) to drive them into a quasi S101 miniature d.p.d.t. mains 10A rocker switch SK101 common emitter mode when the situation 6A I.E.C. panel mounting mains inlet connector SK102, SK103 2-way socket housing for p.c.b. locking connector (2 off) with demands. To prevent damage to the i.e. or terminals transistors when operating in this mode a SK104 3-way socket housing for p.c.b. locking connector with terminals base resistor R107 is provided to limit the PL101, PL102 p.c.b. plugs to match SK102, SK103 (2 off) maximum base current available. PL103 p.c.b. plug to match SK104 A capacitor, C108, connected across the TB101 2-way lOmm pitch (or 3-way 5mm) p.c.b. mounting screw terminal output removes noise and reduces any ten- connector dency towards instability. TB102 4-way 5mm pitch p.c.b. mounting screw terminal connector TB103 5-way 5mm pitch p.c.b. mounting screw terminal connector R LA s.p.s.t. p.c.b. mounting 8A "flat" relay, 12 volt coil F AIL-S A FE RLB 3.p.d.t. standard industrial round base power relay, 240 volt ac. Obviously there is a very real possibility coil, and socket that either the Inverter or the battery M101 90mm Mains 240V axial fan charger may eventually fail, although this B101, B102 6V, 10AH sealed lead acid acumulators (2 off) 32mm screwdriver release panel mount fuseholders (2 off); 20mm screwdriver release should not happen for a very long time, but panel mount fuseholder; 20mm p.c.b. mount fuseholder; heatsink for TR104, 2.9°C/W; it does depend very much on the quality heatsink for TR105, BR102, BR103, 0.5°C/W; 30mm p.c.b. pillars; small heatsinks for of construction. To cater for this even- TR101, TR103; connecting wire mains rated 0.75mm2, blue, brown and green and tuality a mains failsafe switching circuit is yellow, thin low voltage assorted colours, 2.5mm 2, red, yellow, blue and black, 6mm 2 employed. The schematic of this simple, black and red; heat shrink sleaving, various sizes; TO3 silicone isolating kits with but effective, circuit is provided in Fig. 5. bushes (2 sets off); cable ties; M3 panhead screws (12mm, 20mm, 30mm), plain Relay RLB is a three-pole changeover washers, spring washers and nuts; M3 solder tags (10 off). P.C.B. available from the relay and has its coil connected across the EPE PCB Service, order code 862. secondary of the Inverter transformer T1 (see Part One). Under normal operating ALAR M Resistors conditions, with mains present and the In- R201 470k verter running, RLB coil is energised con- R202 1k necting the load to the secondary of T1 via R203 10k contacts RLB I and RLB3. An auxiliary R204 4M7 contact RLB2 connects the cooling fan to R205 68k the mains whenever both the charger and All 0 25W carbon ± 5% Inverter are running to provide necessary Capacitors extra cooling capacity to the heatsink fitted C201 21,2 radial elect. 15V to the power transistor TR3 and rectifiers C202 4n7 boxed polyester, 5mm pitch BRIO2 and BRI03. Semiconductors If the output from the Inverter is lost, TR201 BC182L npn transistor for whatever reason (including switching it IC201 4011B quad two input NAND gate off via SI), RLB de-energises, the contacts Miscellaneous revert to their "at rest" positions as in the WD201 Piezo electric sounder p.c.b. mounting diagram and the load is connected directly to the mains after a very brief delay of less than 20 milliseconds. The only warning of Approx cost this is the neon LP1 extinguishing and a guidance only r140 excluding batteries change in tone of the U.P.S.

Everyday with Practical Electronics, February, 1994 I 3' A L A R M An optional audible alarm, shown schematically in Fig. 6, may be fitted to the U.P.S. on the charger p.c.b. 2408 The circuit is extremely simple and is UV' SIO1a based around a single CMOS integrated INVERTER circuit. Of the four NAND gates contained DERI VED in the chip, two, IC201 c and IC201d, INPUT PROTECTED are connected as a gated astable oscil- OUTPUT MAINS lator running at around 2kliz as set by INPUT timing components R205 and C202 (the actual frequency obtained will vary con-

siderably due to manufacturing tolerances 0 OV in the CMOS i.c.). Reducing the values ri°14L133' NEUTRAL 0 of either C202 or R205 will reduce the S101 b operating frequency and conversely raising their values will have the opposite effect. Et44104 WD20 I, a piezo-electric transducer, con- verts the alternating signal produced by the Fig. 5 Failsafe switching circuit oscillator into sound. A monostable, short period, timer is constructed from the two remaining +120 NAND gates IC20Ia and IC201 b in the same package to cut the alarm off after a pre-determined short delay of around ten seconds. Again, this period will vary from one i.c. to another, and may be increased by raising the values of C201 or R204 (or decreased by reducing either of these components values). The alarm is triggered when TR201 is turned off as the 19-3 volt supply rail drops to zero. Resistor R202 then takes pin 1 of IC201c IC201d 1C201a high and also supplies power to the 40118 40118 chip, enabling it and starting the timing sequence. A C.13. AS S E M BL Y The majority of the small charger and (E144110 I alarm components are assembled on a single-sided p.c.b., available from the EPE P.C.B. Service, code 862. The foil pattern Fig. 6. Mains failure alarm circuit and component overlay are shown in Fig. 7. The following order of assembly is sembly bolted to the p.c.b. with M3 x it and all associated components in the recommended: small passive components, 12mm set screws. Ensure that both the Alarm Components List may be omitted. socket for IC201, connectors and fixings make good electrical contact with fuseholder, large passive components, both the p.c.b. and the transistor case as M AIN AS S E M BL Y small semiconductors. IC101 should be this forms the collector connections. Spring All the case preparation details were soldered in place, with the minimum washers should be used under the nuts to given in part two last month, and the amount of heat. Do NOT use a socket as prevent them loosening from vibration. remaining parts may now be fitted to the this may reduce the reliability of the All thick tracks associated with heavy back panel in accordance with Fig. 8. completed unit as the contacts oxidise. current paths, i.e. those around TRIO4 and A metal finger grille should be fitted on Pre-form the leads of TR 102 and TRIO3 the mains voltage components, should be the outside of the back panel over the fan before bolting them to the p.c.b., with their heavily tinned to reduce track heating and M101 using the fan fixings. Ensure that the heatsinks, metal side down. TRIO4 should aid reliability. connections on the fan are oriented for ease be mounted on a heatsink using a silicone If the alarm function is required IC201 of connection at a later stage. gasket for thermal transfer and the as- may now be fitted in its socket. If not, The majority of components may be mounted using the pre-punched holes in the lower case panel (if the recommended case is used). Exercise care when bolt- ing down the toroidal power transformer T101, since over-tightening the mounting bolt can stress the winding insulation, causing breakdown and premature failure of the transformer. Also ensure that the bolt cannot contact the lid of the case as this will effect a shorted turn and cause subsequent overheating of the transformer. The simplest way to secure the batteries in placed whilst allowing easy removal, is to use self-adhesive Velcro. Stick a strip of the "loops" at either end of the underside of each battery and fasten a similar length of the "hooks" to each piece. Remove the protective backing and lower the battery into place, bonding will be instantaneous, so ensure correct positioning before con- tact is made. Drill the large heatsink to accept TRIOS • • and the two high current bridge rectifiers. De-burr all the transistor mounting holes on both sides of the heatsink to prevent damage to the transistor insulating corn-

138 Everyday with Practical Electronics, February, 1994 °.• °.•

9 L-ot L-ot 0 0 -0 - -- • • • JrN° 0 0 0 0 F n. F n. i-r° i-r° T 0103 0103 T 18101 18101 1 1 • • • • C10 C10 VC R101 R101 VC • • • • • • 014 014 L'02 L'02 0102 0102 103 102 D lIDO • VD O O ® ® IS IS • • C102 C102 0202 0202 11) 11) 11) 11) O O i TRIO4 i TRIO4 C20 C20 a a • • • • 0204 0204 RLA RLA T T 0202 0203 4 10 R10, R10, 0R 105 105 0R TCD107 TCD107 e R201 R201 • • TRIO2 TRIO2 RIO RIO TR201 TR201 C • • • • • P1102 P1102 P1103 0103 0103 20V 20V S 104 104 S LE D LE D

Fig. 7 PCB. component layout and copper foil master for the charger and alarm circuit. ponents. Fit a silicone gasket to TR105, crimp and then solder two uninsulated butt connectors to its pins (see Part Two last month) insulating them to within 5mm of their ends with heatshrink sleeving or insulating braid. Fit long top-hat insulating bushes in the heatsink to accept M3 X 30mm set screws and fasten the transistor down with the nuts on the same side of the heatsink as the transistor pins. Use a plain washer under both screw head and nut with a spring washer under the nut. Apply a thin film of heatsink compound to the mounting surface of each bridge rectifier before bolting to the heatsink with M4 hardware. The assembled and wired heatsink is ultimately mounted with the component mounting platform vertical as shown in Fig. 8. This allows more effective fan cooling of the assembly. L O W CU R R E N T WI RIN G All the low current wiring for the U.P.S. is shown in Fig. 9 and should be wired using 0.5mm wire. Refer to Fig. 10 for transistor pinouts as necessary. The majority of the low current wiring is straight forward and should not pose any problems. Sensible use of colour coding at this stage will ensure that if fault finding be- comes necessary it is a much simplified matter. The terminals for the small p.c.b. connectors should be crimped or soldered to the wires before inserting them into their respective plastic shells, ensuring that they latch firmly in place. The base connection to TRIOS is made via a solder tag which should be slipped over the butt connector already fitted to the transistor and sol- dered in place. A large soldering iron would be a definite advantage here, as the smaller irons will not be able to heat the connec- tion adequately. The collector connection is also made via a solder tag and is simply fitted to one • of the transistor mounting bolts between two washers, a spring washer and nut securely clamping it in place. Do not make the battery connections at this stage as these are made to the main battery leads, fitted later. R O WE R WI RIN G There are two types of power wiring involved in this project, both of which present their own kind of hazard. The danger of the 240 volt mains supply should be apparent to all constructors. The second is perhaps not so ob- vious: low voltage supplies operating at high currents. Great care should be taken not to short circuit the secondary of the power transformer as this may cause an arc, which will constitute a fire risk and also may cause

METAL SURFAC

B C E

TO126

(iti.41561 Fig. 8. Case layout showing the existing Inverter components (unlabelled) and additional U. PS. components. Fig 10. Transistor connections.

140 'Everyday with Practical Electronics, February, 1994 damage to eye sight if viewed for a prolonged period without adequate eye protection. The trans- CHARGER former and associated PC B 10103 HEATSINK wiring will also become S1 EXISTING very hot. Always discon- 0 WIRING io - -•43 nect the mains supply °TRIOS 0- before working on the unit, 131•11 1 E o whether on the mains side 111104 P1102 or the low voltage side. (Constructors should also P1103 read the Safety section in Part One). If the Inverter was built INSULATING as described in parts 1 and SLEEVING T B102 2 the wiring associated Lai. (2 18101 with TB2, L3, SKI and SK2 will need altering in accordance with Fig.I I of • this part. All wiring con- • nected to the mains or Inverter output should be VIOLET GREEN rated for mains operation and be capable of safely P11 carrying the full load cur- rent of 1.5 amps for the inverter. The mains wiring P12 to the charger transformer 1101 should be rated at 10 I NVERTER amps or more to al- PC B low fusing at 10 amps 8101 8102 to cope with the surge into the transformer at switch on. All connections should be adequately insu- lated, either with heat shrink sleeving or recep- tacle covers in the case of the push on terminals for PL101. The secondary leads of ItE4414.01 TIO1 are solid copper and quite thick, making them very difficult to work. To Fig 9. Signal wiring for the UP S

Layout and mounting of the U. PS. components; batteries and 77? 105 heatsink are on the left.

Everyday with Practical Electronics, February, 1994 141 --- I WHITE

ORANGE

OEtoSK1 &SK2

r— LtoSKI&SK2 O ON to SKI SK2

FS101

PL101

CHARGER P. C B.

HIGH 2.5mny, CURRENT WIRING 1 T810 3 I YELLOW BLUE

I F510 2 F5103 4% GREY

2 51no? 2 Srorn2

r 2.5moi 2.5rnm2 2. 5 mm 2 HEATS! NK a 0 C 0 OTR10:3) Mo m

L. Srnni 8R103 ALTERATIONS HIGH A L TO EXISTING VOLTAGE 2.5mm2 INVERTER WIRING WIRING

2.5mm'

2.5mm

Fig. 1 1 . High voltage and high current wiring for the U. PS.

simplify connections to the transformer mechanically sound. Use a proper crimp- apply mains, with a meter set to read extend the leads with 2-5mm2 flex, making ing tool for the job, these are inexpensive 25 volts d.c. connected across C105 or the joins with 30 amp connector blocks or and do a much better job than pliers. C106. A reading of 18 to 20 volts should solder and insulate with heat shrink sleev- Collect together the remaining wires be accepted as normal, though variations ing. The connections to the bridge rectifiers which need connecting to the same battery of two or three volts either side may be should be made with 0.25 inch insulated terminal and strip 60mm of insulation from obtained, depending on the mains volt- female receptacles, properly crimped or each. Align the insulation with the pre- age present. Check the output from the soldered to the leads. terminated lead and twist the strands regulator by connecting the meter across An eye crimp is used to facilitate the tightly around the exposed conductor of the disconnected battery leads and adjust connection to TRIOS emitter. After crimp- this lead. Repeat with the remaining leads VR102 to obtain exactly 13.8 volts. ing to the 6mm battery lead it should be before soldering the completed termination Re-connect the battery, replace the 5 slipped over the the butt connector already and insulating with heat shrink sleeving. amp fuses with 15 amp ones and fit RLB. fitted to the transistor and soldered in The lead connecting the two batteries in Ensure that the Inverter is switched off by place. Ensure that this joint and all other series is made up in the normal manner SI and switch the charger on, with the high current joints are properly made, since with 6mm 2 wire and crimp terminals. meter still connected across the battery. these are potential weak points which may Check that the battery voltage eventually later cause the unit to fail. S ETTIN G UP rises to 13.8 volts, this may take quite a The remainder of the wiring is carried A N D TESTIN G while if the battery is in a poor initial state out using the methods described above, Remove RLB from its socket and of charge. following the wiring diagram and using remove FS102 and FS103. Ensure that Disconnect the battery positive lead with the appropriate wire sizes indicated on the FS101 is fitted and rated at 10A. Switch the meter connected to the leads and switch drawing. off S101 and connect the mains supply. on the charger, the voltage should rapidly B A TTER Y Connect a multimeter to one of the 13.2 stabilise at 13.8 volts. Now switch on the volt windings of T101, set to read a.c. Inverter, the fan should start running and C O N NECTIO NS volts on a suitable scale (e.g. 25V) and the measured voltage should fall. Adjust There are several leads to be connected switch on, keeping hands well clear, the VR101 to obtain 12.6 volts. The battery to the battery terminals and this may pose meter should indicate 14 to 15 volts. may now be re-connected. problems. The method outlined below was Switch off before repeating the test on the Check the a.c. voltage across the high used successfully in the prototype and second winding. current secondaries of T101, with the should prove extremely reliable in opera- Check all wiring around the mains side Inverter switched on and then off. The tion over many years. of T101 if the measured voltages are sig- voltage should fall when the Inverter is Cut the 6mm 2 battery leads to length and nificantly different from those given. If switched on. If it does not check that RLA strip 50mm of insulation from the ends of the two voltages are not identical check is operating correctly. each. Twist the strands together and crimp secondary wiring. If the alarm is fitted it should operate a yellow insulated (6mm 2) 0-25 inch female Once the correct results are obtained for a few seconds every time that the receptacle to the very end of the wire, disconnect the battery, fit 5 amp fuses mains is switched off, or the unit un- ensuring that the joint is electrically and in FS102 and FS103 positions and re- plugged.

142 Everyday with Practical Electronics, February, 1994 L OA M TESTIN G Inverter or the charger switched off. Only with a 10 amp rating these appear only to when both are switched off will the supply be available in 32mm types. Operate the U.P.S with a 200 watt, or be interrupted. Errors around RLB are fairly likely larger, load connected and check all heat- since this is hand wired. Check it carefully sinks for excessive temperature rise. The against the wiring diagram and Fig. 5. large fan cooled heatsink fitted to the F A ULT FIN DIN G Only the specified components should be rectifiers and TRIOS will get quite warm The circuit, although moderately com- used for RLA and RLB since these both after a long period of running. The others plex, is fairly simple to diagnose. Many of have cadmium flashed silver oxide con- should remain quite cool. the relevant circuit voltages are marked on tacts. Other contact materials, as used in Check all high current connections for the diagram or noted in the text. cheaper relays will fail prematurely with signs of overheating, especially TRIOS If the measured voltage across either the high inductive currents being switched emitter connection since this is the most of the Zener diodes is around 0.6 volts, here, causing the contacts to be welded heavily stressed joint. instead of its marked voltage, then the together. With the case lid in place cooling of the device is incorrectly polarised and should main heatsink will be much more effec- be removed and refitted correctly. If fault finding does become necessary, a tive as this ducts the air more efficiently. No voltage across the reservoir systematic approach will pay dividends in In normal operation the unit should only capacitors C105 and C106 may indicate reduced time and increased success rates. be run with the case fully assembled, not ruptured or missing fuses. FS101 is most Follow the circuit through from input to only for cooling, but for safety as well. likely as this has to take a large surge at output with the schematic, Fig. 4, in front Note that the supply to the load should switch on and may fail prematurely. An of you, along with the relevant wiring and be maintained at all times with either the anti-surge fuse may be the solution, but layout diagrams.

containing the labelled software used in the chip and a copy of the Motorola Instruction Set for the microcontroller. The kit costs £37.80 plus £3 p&p inclusive SHOP 71Ff TA LK of VAT and is available from Greenweld Electronics, Dept EPE, 27 Park Road, Southampton, SO1 3TB. Phone: 0703 with David Barrington 236363; Fax: 0703236307.

250 W/600 W Battery to Mains W histle Controlled Light Switch Reviving The Valve Sound - Inverter Only two items called up in the "comps Quad II Power Amplifier Once again, we should like to stress that list" for the Whistle Controlled Light Switch It is difficult to point readers towards one anyone undertaking the task of building the prompted further comment. These concern direction for components for the Quad II Battery to Mains Inverter project should be the whistle switch i.c. and the switch plate, Power Amplifier rebuild project as the varia- skilled in construction work. Also, it is most which takes the p.c.b. and replaces the stan- tion in supplies of the "old" and "new" important that the "Safety Panel," pub- dard light switch. parts seem to vary, i.e. they may stock the lished in part one, be read before commen- The UM3763 whistle switch i.c. is a spe- valves but not the XLR sockets or specified cing any practical work. cial "custom" device and when we first capacitors. To this end, we include a list of This month we tackle the UPS. or published a design using this device over a possible contacts as supplied by the author. Uniterruptable Power Supply section and year ago we found that stocks rapidly dried Also in the components list stock codes some of the components need to be selected up. Further investigations at the time resulted for RS components have been included. Any very carefully. The 8A "flatpack" 12V relay, in the information that the chip was no bona-fide stockist will be able to order these with cadmium oxide flashed silver change- longer being manufactured and new sup- for you. over contacts, is the Maplin (11P 0702 plies would not be forthcoming. Obviously, the most important contact 554161), code HY20. The high power, However, the good news is that the desig- address is Quad themselves and they can round octal base, industrial standard relay is ner had purchased over 500 whistle switch be found at: Quad Electroacoustics Ltd, the 240V a.c. 10A 3-pole "double-throw" i.c.s and is offering these for sale to readers Dept EPE, Huntingdon, Cambs, PE18 (3PDT) type, with 11-pin base, also from the together with the switch plate. Incidently, it 7DB. Tel: 0480 52581. same source, codes JG64 and JG53. is recommended that the specified switch One specialist valve supplier with a very The 41.1H 3A choke was purchased from plate be used as the standard types are not good reputation and, who advertises in this JPG Electronics (1r 0264 211202). The considered deep enough and can result in magazine is the Chelmer Valve Company main heatsink is an RS device and was components touching the earthed metal wall NIP 0245 265865) and is certainly worth purchased through their mail order outlet, box. giving a call. Chelmer Valve Company, Electromail (VIP 0536 204555) order code The UM3763 i.c. and switch plate are Dept EPE, 130 New London Road, 401-958. available, Mall Order only, from B. Trepak, Chelmsford, Essex, CM2 ORG. Another Now for some further clarification on the Dept EPE, 20 The Avenue, London, VV13 advertiser who stocks the specified valves is two types of recommended toriodal trans- 8PH for the sum of £6.50, inclusive for the Cricklewood Electronics (ini 081 452 formers. The toriodals have been specially pair. Cheques or Postal Orders should be 0181). made up by Jaytee (11. 0227 375254)and made out to B. Trepak. Other usefull contacts are: Electro Sup- the 9E284 (600VA) has been designed to The two terminal microphone insert is an plies imp 061 477 9272 (sells surplus function as both the step-up transformer in Altai type and should be available from smoothing capacitors, valves and holders); the 600W Inverter and also as the charger most of our component advertisers. Alterna- Maplin Illp 0702 554161 (valve com- transformer in the UPS., with a 7E283 tive types may be offered by suppliers and ponents, but are expensive); ESD Electronics (300VA in the inverter section. these should work in this circuit but they Services 0279 626777 (good for caps, Obviously, it must be connected dif- have not been tried in the model. resistors and connectors); Colomor (Elec- ferently in each case, since in the inverter it is The small printed circuit board fits on the tronics) Ltd ir 081 743 0899 (cheap used as a step-up transformer, whilst in the specified switch plate and is available from valves); Electromail/RS ir 0536 201 234 charger it steps the mains input down. The the EPE PCB Service, code 860. (0.5W metal film resistors) and finally Falcon wiring diagrams in parts two and three Warning:This unit carries mains voltages Acoustics lip 0508 78272 (good selection should clarify this. and any reader who is not certain of being of valve publications). Also, constructors should refer to the data able to install it safely is strongly advised to sheet supplied by Jaytee with the trans- seek professional advice and help. Remem- Balance Stereo Microphone formers which gives full details of the wind- ber to switch off the household mains Preamplifier ings, including which are used as primary supply when replacing the light switch. We do not expect any component pur- and secondary in each case. It is advised that chasing problems to be encountered when the instructions are read carefully before Introduction to Microntrollers - shopping for parts for this month's audio connecting this transformer, it could save Timeout module in the Multi-Purpose Audio Sys- you a lot of time and trouble! For those readers taking their first steps tem. The Balanced Stereo Microphone The 7E283 300VA toriod cost £32.50 and into the world of microcontrollers, the Preamplifier is based on the relatively new the 9E284 625VA toriod cost £49, both in- package put together by Greenweld for the SSM2017 audio pre-amp i.c. and currently clusive of VAT and post/packing. Timeout project could not be better, (except only appears to be available from Maplin, The 19 inch rack-mounted case used in of course our "Micro Lab" board produced code CP89W. They also carry a reasonably the prototype is the Maplin XM70, some as part of our recent Teach-In '93 Series - priced range of XLR connectors. other rack cases do not appear to be deep but we are obviously biased). Before purchasing the metal screening enough (front to back) for all the parts to fit, The complete kit for the Timeout box you should check that the p.c.b. will fit check this out before buying, minimum in- project, with programmed 68H C705K1 inside, in some instances it did not. The one ternal dimensions must be 432mm x 120mm microcontroller plus all other components in the model is the Rapid box, code 30- x 293mm. including p.c.b. and plastic box, but 0305. The U.P.S. charger printed circuit board is excluding the battery, is available from The two small printed circuit boards are available from the EPE PCB Service, code Greenwald (VP. 0703 236363). The kit available from the EPE PCB Service, codes 862 (see page 171). also includes a PC compatible disc 858 (pre-amp) and 859 (power supply).

Everyday ivith Practical Electronics, February, 1994 143 INTER Robert Penfold

T HIS month we continue our discus - address lines (AO to Al2 or AO to A13) to Binary Counter 1 sion of EPROM programming with an almost instantly access the required address. Using a binary counter to drive the ad- in-depth look at programming the 27*** When I first experimented with EPROMs dress inputs is very convenient when check- series EPROMS using a computer based some years ago I found that a binary ing the contents of an EPROM and during system. Pinout details for the 2764 and counter (or "ripple" counter as they are programming. The basic course of events is 27128 were published in a previous Inter- often called) provided a simple but effective much the same in both cases. The counter is face article, but as this was several months means of driving the address inputs. This reset to zero, and then the first address is ago the relevant diagram is reproduced remains my preferred method of controlling read or programmed. Then the counter is again in Fig.1. the address bus. No matter how many incremented by one, and the next address address inputs the EPROM has, only two In Control is read or programmed. This sequence of control lines from the computer are required. events is continued until all the addresses Apart from the supply lines and VPP (the These are both outputs. have been checked or programmed. programming voltage), all the other pins of One output from the computer controls There are several CMOS binary counters the EPROMs must be controlled by the pro- the "reset" input of the counter, and this which look promising for use in the present grammer. For a computer based programmer is initially pulsed high to ensure that the application. In practice there is a problem the obvious solution is to have an add-on counter starts out at a known value (zero). with some of these counters in that they do parallel port which provides numerous input The other output drives the counter's "clock not give access to the output of every stage. and output lines. Each pin of the EPROM pulse" input. The count is incremented by Some of the longer dividers do not provide is then fed from an input or output line, as one each time a complete pulse (i.e. a set of appropriate. access to one or more of the early divider low - high - low transitions) is supplied to stages. There is an obvious disadvantage to this the clock input of the counter. A two chip counter made up from two approach in that it requires about two dozen There is clearly a drawback in this system or so input and output lines. In practice 4024BEs or 741-IC4024s connected in series in that it is rather cumbersome. There is probably the cheapest way of driving the the parallel port would probably have to is no instant way of randomly accessing 13 address inputs of a 2764, or the 14 provide more lines than this, since there addresses. However, you can access any address inputs of a 27128. The 4024BE is a would almost certainly be some inefficiency desired address simply by resetting the seven stage binary counter, so using two in the system. For example, you might have counter and supplying the appropriate num- in series provides up to 14 outputs. Fig.2 to commit an eight bit port as eight outputs, ber of clock pulses to the counter. To access shows the circuit for a 14-bit counter based even though there was only one input of the address 24987 for example, it would just be on two of these chips. Of course, when this EPROM left to control. a matter of resetting the counter, and then circuit is used with a 2764 the A13 output is It would probably be possible to control a using a software loop to produce 24987 not needed. However, this output can be left 2764 EPRO M from the 24 lines of an 8255 clock pulses. This is not very difficult from connected to pin 26 of the 2764 EPRO M parallel I/O board, but the 25 input/output the software point of view, and assuming a as this pin is not connected to anything terminals of a 27128 would seem to neces- fast programming language is used, it is internally. sitate a second 8255, or perhaps the addition possible to access any address quite rapidly. of a simple TL output port. Alternatively, In practice it is not often necessary for Control Inputs the interfacing can be rationalised in order an EPROM programmer to randomly access The general scheme of things so far is to to reduce the number of input/output lines addresses anyway. In the normal course of required. have the address lines controlled by two events the EPROM is first checked to see outputs of the computer port via a binary that all the memory stores are blank (set to counter, and VPP fed from a suitable stabi- Counting Up 1). This is just a matter of going through the lised supply (usually with a potential of 115 One advantage of controlling each ter- addresses one-by-one, in sequence, reading volts). The eight input/output lines are used minal of the EPROM from an individual each byte to ensure that a value of 255 is to write data to the EPROM when program- input/output line is that it is possible to returned. Then the EPROM is taken back to ming, and to read back data once the device access any address at any time. Simply set address 0, and each address is programmed has been programmed. Although it might at up the appropriate binary pattern on the with the new data, in sequence. first seem as though these lines could be

1 28 1 28 vPP C • 3 VCC VPP C • ) VCC 412 C 3 "FrCTA 412 C 3 1g71,1 47 C NC 47C 3 413 46 C 3 48 46 C 3 48 45 C 49 45 C 3 49 44 C 3 411 A4 C 3 Al 1 A3 C ZYE A3 C 33:51 2764 27128 A2 C 3 A10 A2 C 3 410 Al C 3tT A1C 3 a AO C 31/07 AO C 31/07 1/00 C 3 i/06 1/00 C 31/06 1/01C 31/05 i/01 C 31/05 1/02 C 31/04 1/02 31/04 VSS C )1/03 VSS C 31/03 14 15 14 15

Fig. 1. Pinout details of the 2764 and 27128 EPRO Ms. Fig. 2. (right). Using a 14 stage ripple counter to drive the EPRO M address bus.

144 .Everydav with Practical Electronics, February, 1994 driven from output lines, in practice it is essential to read data from the EPROM +5V 0 o Pin 28 (Vcc) during programming. As already pointed out, it is normal to 12.5V 0 Pin 1 (VPP) Supply check that an EPROM is blank before reprogramming it. It is also essential to PAO 0 o Pin 11 (1/00) check that programmed devices have been programmed correctly. Therefore, in prac- PA I o 0 Pin 12 (1/01) tice the input/output terminals must be fed PA2 0 13 Pin 13 (1/02) from eight lines that are capable of operat- PA3 0 o Pin 15 (1/03) ing as inputs and outputs. A port of an 8255 PA4 0 o Pin 16 (1/04) is capable of being switched to operate as an PAS o 0 Pin 17 (1/05) input type under software control, and is From 8255 To 2764 Or therefore perfectly suitable for this applica- Parallel Port PA6 0 O Pin 18 (1/06) 27128 EPROM tion. Other PIA chips (6522, 6821, etc.) also PA7 0 0 Pin 19 (1/07) seem to be capable of this bidirectional Clk operation. PBO 0 Binary AO To Al 3 Rst Counter This still leaves three terminals of the PB1 0 EPROM to contend with, and these are all inputs. Pin 20 is the chip enable ("CE") input, PB2 0 0 Pin 22 (r) and this must be taken low in order to make P83 0 o Pin 27 ( T.1) the EPROM active. With this pin taken high the EPROM is effectively switched off, and o Pin 20 (a) OV 0 it is not possible to read from or write to 0 Pin 14 (Gnd) the device. This input is needed when the EPROM is used as one of the chips in a Fig. 3. Suggested method of controlling an EPROM via an 8255 or similar PIA. multi-chip memory bank. It does not serve any obvious use when the EPROM is being amnesia for at least ten years. The pro- the need to find a reliable method of programmed. This input could be fed from gramming voltage is used to break down obtaining accurate software timing. Using a an output line of the computer, but there is the insulation in the EPROM, and alter the monostable is a safer approach, but it probably no disadvantage in simply wiring charges on certain capacitors so that their precludes the use of fast programming it to the 0 volt supply rail. bits are set to logic 0. techniques. Pin 22 is the output enable ("OE") ter- minal, which controls the tristate buffers Programming Voltage Basic Programmer at the data inputs/outputs. This terminal is An important point to note here is that A basic computer based EPROM pro- taken low to activate the tristate buffers, and the programming voltage must only be grammer could therefore consist of some- it must therefore be taken low when reading applied to each memory cell for 78.75ms or thing along the lines of Fig.3. Port A of from the EPROM. Obviously the tristate less. Applying the programming voltage for an 8255 is used to provide the eight buffers must be inactive during program- longer than this could result in the EPROM input/output lines which are used to write ming, which means that pin 22 should be being damaged. Pin 27 is pulsed low to data to the EPRO M and read from it. Two high when programming. When program- apply the programming voltage to the lines of Port B are used as outputs to ming a 2764 or 27128 pin 22 effectively eight memory cells at the currently selected control the address inputs via a binary becomes the read/write input (low to read - address. ripple counter, and two more outputs of high to write). If any bits of the data bus are set to 0, the Port B are used to drive the output enable Finally, the PGM input at pin 27 effec- appropriate memory cells will be altered to and PGM inputs. tively switches the programming voltage at suit. Another important point to note is that The chip enable input is simply connected pin 1 on and off. An EPROM is based on memory cells can only be altered from 1 to to the 0 volt supply rail. This enables the field effect transistors having charge storage 0, and not the other way round. If even one EPROM to be controlled via just eight capacitors at their inputs. Normally each bit is incorrectly set at 0, this can only be bidirectional lines and four outputs, which bit of memory is set at logic 1, and the corrected by erasing the EPROM and com- requires only half the capacity of an 8255. very high insulation resistances in the cir- pletely reprogramming it. Although the EPROM is shown as being cuit prevent the charge voltage from leak- PGM can be fed from any spare latching controlled via an 8255, the same method ing away and setting some bits to logic output line of a parallel port, or it can be applies equally well to ports based on the 0. This is actually a slight exaggeration, driven via a monostable having a suitable 6522, 6821, etc. since the charges will eventually change due pulse duration. A monostable provides a Next month we will continue on the to minute leakage currents, but a properly means of giving an output pulse of the same theme with a detailed discussion of the cared for EPROM should not suffer from precisely the required duration, and avoids programming cycle.

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Everyday vvith Practical Electronics, February, 1994 145 Special Series

• CALCULAnoN CORNER Ohm's Law and its applications (t- STEVE KNIGHT Part Two This series is designed to help you make your way, at your own pace, through the often imagined fears of mathe matics, as this is applied to electronic and electrical engineering matters.

NUMBER of formulae turn up in this month's offering. Don't 1=11+12+13= E E E be put off by this and don't just give time to memorising formulae. That is not the way to master things. The way A by the application of Ohm's law to these currents. ahead is to understand the principles from which such formulae are derived. Constant usage of the principles then fix thE'formulae If now the total equivalent resistance of the circuit is Re ohms, without conscious effort then the current passing through it would be I and the voltage across it would be E. Hence for this equivalent circuit I = E/Re and R E SIST O R S IA! SE RIE S from the above When resistors are connected in series, as in Fig. 2.1 the same E = E, E , E current passes through each of them and the applied e.m.f. divides -K W1 R2 R3 between them as a series of potential differences or voltage drops. Cancelling out the common e.m.f. E, gives us These are the important characteristics of a series circuit. The sum total of the individual p.d.'s must be equal to the ap- 1_1 + 1 + 1 plied e.m.f., therefore, from Fig 2.1 we can say 1ff

E= V1 +-V2 + V3 This arrangement (which applies to any number of resistances) always gives an equivalent resistance which is smaller than the Suppose now that the total equivalent resistance of the circuit is Re smallest individual resistance used in the arrangement. ohms. Then the current passing through Re would be I and the A simplification in calculation comes along when only two resis- voltage across it would be E. Applying Ohm's law to this equiva- tors are wired in parallel. For we then have lent circuit gives us E = I Re, hence from the above I 1 I _RI +RI !Re= Vi + V2 4- V3 =IRI +1R2+IR3 K = R7i x R2 Cancelling out the common current I, gives us Then R,=R1+R2+R3 R _RI x R2 Product e R I + R2 — In words, the total equivalent resistance of a series circuit is simply the sum of the individual resistances. This arrangement (which It is important to keep in mind that this holds good for only two applies to any number of resistors) gives the greatest possible total resistors. resistance. Armed now with all the forms of Ohm's law and the equiv- alent resistance of series and parallel combinations, the following R ESIS T O R S IN PA R ALL EL worked problems shouldn't give you any difficulties in understand- When resistors are connected in parallel, as in Fig. 2.2, the same ing how the calculations are made. voltage is present across each of them and the current divides be- I. Two resistors of 2.712 and 5.612 are wired in parallel across tween them. These are the important characteristics of a parallel a I.5V source. Find the equivalent resistance and the current circuit. From the figure we can see that the total circuit current I drawn from the source. must be equal to the sum of the currents flowing into the individual As there are two resistors here, we can use the product/sum rule resistors (this is actually Kirchhors law, of which more later), so to find R:

Va -oi

RI R2 R3 +11-E-11

Fig. 21. A series circuit where I Fig. 2.2. A parallel circuit where E Fig. 2.3. How does the current divide in flows through each resistance and volts is applied to each resistance and this circuit? E=V1+ V2 + V3. 1=1 1+12 +13.

146 .Everyday with Practical Electronics, February, 1994 A1. 3n3k I- VI .,- V2 I I

100 1211 1110

0.5A

+II- 11 - E

Fig 24. Here we to have to find the Fig. 2.5. What should R2 be so that the Fig. 2.6. Which is the best way of solving total resistance, the e.m.f. E and the total resistance is 1 .51

2-7 x 5-6- 15.12 - 0 , r) have in the formula for resistances in parallel is the sum of conduc- i‘c- 2.7 + 5-6 8-3 tances, that is The current drawn 1 _I 1+ 1 is the same as G, = G I + G2 + G3 1=E _ 1.821.5 = 0.82A or 820mA L - K1 inin Hence, the sum of the conductances gives us the total equivalent 2. How does the current divide between the two resistors of the conductance, Ge, which, being inverted, provides the equivalent previous problem? resistance. Here is an example: Well, looking at Fig. 2.3, each resistor has 1.5V across it, so the I I currents will be given by the application of Ohm's law once again: Let RI = 1512, then G I -_ -ry= 0.0667 S

RI 1- E - 1.5 =0-55A or 550mA Let R, = 7512, then G2 = 1= I = 0-0133 S

1, - E = 1.5 = 0-27A or 270mA Let R3= 15012, then G3 = AIN = rs!-O- = 0.0067 S

Adding these two branch currents as a check, we find that Then G, = GI + G2 + G3 = 0.0667 + 0-0133 + 0-0067= 0.0867 S 0-55 + 0-27A = 0-82A which agrees with the total circuit current found earlier. Hence R,= *= 11.5312 3. Three resistors, 10Q, 1212, and 18Q respectively are wired in series across a battery of e.m.f E volts. If a current of 0-5A DI VISIO N OF CU R RE NT (500mA) flows from the battery find (a) the total circuit resis- Looking back at Problem 2 above, we learned there a method of tance, (b) the e.m.f. of the battery, (c) the voltage across each finding the current in each branch of a parallel circuit. Only two resistor. resistors were involved, but the method can clearly be applied in The circuit is shown in Fig. 2.4. Get into the habit of sketching a exactly the same way for any number. circuit in this way; this avoids any confusion between the various We can illustrate an alternative method by thinking in terms of units, resistor numbering and so on. conductance: the branch with greatest conductance (the smallest (a)Re=R1+R2+ R3= 10 + 12 +18=400 resistance) will take the greatest share of the current, and con- versely. Once we have found the shares, the current can be readily (b) E.m.f. E = IR, = 0-5 x 40 = 20V split up into them. (c) The same current (0.5A) flows through each of the resistors, In Fig. 2.6 we have three resistors in parallel. The current flow- so we can say ing into this circuit divides inversely as the resistances but directly as the conductances. So if the resistances are 111, R2 and R3 respec- VI =IR! = 0.5 x 10=5V tively, the current divides among them in the ratio 1/R1, 1/R2 and V2= IR2=0.5 x 12=6V 1/R3, or as G I, G2 and G3. Hence we can say

V3=IR3=0.5x 18=9V : 12: 13 : : G 1 : G2 : G3 As a check on our working, the sum of the individual p.d.'s We will illustrate this method by an example. Of course, if you should equal the e.m.f. E: 5+ 6 + 9 = 20V which they do. are working out problems of this sort for yourself, use whichever method you feel happiest with. 4. What would you parallel with a 3.3k0 resistor to give you an equivalent resistance of 1-51(12? Fig. 2.5 shows the situation; 6. The resistors of Fig. 2.6 are respectively 8, 12 and 240. If the when we add R2 to the 3-3k0 resistor we should finish up with total current is 2A, find the current in each branch. a 1 -5k12 resistor. We know that a simple rearrangement of the The current is shared in the ratio of the conductances: parallel formula for two resistors we shall have I. 1 . 1 .. 3 : 2 : 1 I _ 1 _ 1 _RI 611-14"- ' • - 24-- Rix & Therefore the total number of shares is 6, and the current divides from which as follows: R2 = RI x Re_ product current in the 8S2 branch = 3 of 2 = IA RI Re difference

Going back to the problem, and treating R2 as the resistance we current in the 120 branch = of 2 = 0.67A need to find, we write current in the 2412 branch = I of 2= 0-33A R2 = 3.3 x l5_495 _ 6 3.3 - 1.5 2.751cf/ This method does save a bit of work; there is no need to find Notice here that we are working in terms of kilohms, so that the either the equivalent resistance or the applied voltage as we did in answer will be in kilohms. Don't complicate things by using the Problem 2. values in ohms in a case like this; this leads to large and awkward numbers where mistakes can be more easily made. INTER NAL RESISTA N C E The answer 2-75k12 is not a preferred resistor value but with When a cell or battery (or any other source of e.m.f. for that normal tolerances, a 2-7k12 would doubtless do the job. matter) supplies current to an external system, then a part of the e.m.f. generated is required to drive the current through the in- U SIN G CO N D U CTA N C ES ternal resistance of the source itself. This internal resistance is very We introduced conductance in Part 1 of this series and saw that small in a new or freshly charged battery but increases as the bat-

Conductance (G)- resistance I(R) Siemens (S) tery "runs down". Because of this, the voltage measured at the terminals of the source falls as the battery ages so that eventually This provides us with a very convenient method of finding the we either chuck it away or give it a recharge. equivalent resistance of a number of resistors in parallel and is From Fig. 2.7 we see that for an internal resistance r ohms and a suited to calculators with a reciprocal (1/x) key. What we really circuit current I amps, the voltage drop across r will be Ir volts and

Everyday with Practical Electronics, February, 1994 147 Fig. 27 How internal resistance affects Fig. 28 What is the equivalent resis- Fig. 29. A simple circuit with a curious the term mat p.d tance of this circuit? property.

hence the terminal p.d. will be the e.m.f. minus the internal drop. I. Find the equivalent resistance of 9, 18 and 360 in parallel. Or in symbols V = E - Ir. 2. In Fig. 2.9, what is the resistance between terminals A and B? If no current is drawn from the battery, there is no voltage drop If a 9V battery is connected to A and B, what will be the across r and the voltage at the terminals is equal to the e.m.f. voltage between C and D? With an external load connected, however, the greater the current 3. If N resistors, all of the same value R12. are wired in paral- drawn, the greater the internal voltage drop and the smaller the lel deduce that the equivalent terminal p.d. becomes. As we shall see in due course, internal resis- resistance is R/Nf2. tance is not simply restricted to batteries. 4. Six 1200 resistors are wired Here are a couple of examples so that you will be able to deal in parallel. What is the equiv- with internal resistance problems. Remember, it's just Ohm's law alent resistance? again. 5. How many !MD resistors 7. A cell has an e.m.f. of 1.5V and an internal resistance of 0.050. must be connected in parallel Find the terminal voltage when a load resistor of 40 is con- to give an equivalent resis- nected to the cell. tance of 200kfr Here we have E = 1.5V, r = 0.05Q. Then the total circuit 6. If the resistance ratio of two resistors wired in parallel is resistance (from Fig. 2.7) is 4 + 0.05= 4.050 and the circuit current will be 1:2, then the current ratio is 2:1. Is this a true statement? _ 1.5 I = E TT = 0.37A 7. The transistor shown in Fig. 2.10 draws a current of 2mA Hence the terminal p.d. will be from the 9V supply. What Fig. 210. What is the volt- V= E - Ir = 1.5- (0.37 x 0.05)V would a voltmeter connected age at the collector? as shown read? =1.5-0.0185 8. If a 300 resistor is connected =1.48V between terminals C and D in Fig. 2.9, what resistance will 8. When a battery is connected to an external resistance of 40 the be measured between A and B? Do you notice anything circuit current is 1.5A, and when it is connected to 90 it is "curious" about your answer? 0.75A. Find the e.m.f. and internal resistance of the battery. 9. A circuit has two resistors of 2012 and 300 connected in paral- We can use the formula E= l(R+r) here. With the 40 resistor lel. This group is then joined in series with a third resistor of connected we have E = l(R + r)= 1.5(4 + r), and with the 90 resis- 180. What is the equivalent resistance and what current flows tor connected we have E = 0.75(9+ r). Hence we have two equa- in each resistor when the circuit is connected to a 6V supply? tions and two unknown quantities. Since both of these equations 10. A cell has an e.m.f. of 1.45V and an internal resistance of are equal to E. their right-hand sides must also be equal, so we get 400milliohms (mf2). It supplies a current of 350mA to an 1.5(4 + r)= 0.75(9 + r) external circuit. Find (a) the terminal p.d. (b) the external resistance. and multiplying out 6 + 1.5r= 6.75 + 0.75r Last month's answers: I. The coulomb; 2. 1.58 x 10-19 C; 3. 180 secs; 4. 0.021S; 5. 8f2; 6. 11-75V, p.d.; 7. (a) 15 x I0-3 A (b) 256 x 10- Therefore 1.5r - 0.75r = 6.75 - 6 6V (c) 8.2 x 1061/ (d) 3.185S (e) 650 x 10 -6C; 8. I = VG, V=I/G, or 075r=075 G = I/V. Therefore r = IQ Next month: Work, enerp and poser.

Substituting this value for r back into either of the original equa- tions we find that E = 7.5V. E S E RIES-PA RALL EL CIR C UITS k ri PRACTICAL Circuits made up of series and parallel combinations of resistors do not often turn up in practical designs, but they do in some ELECTRONICS examination papers and we conclude this month's subject with methods of dealing with them. SUBSCRIPTION ORDER FOR M A combined arrangement of this type is shown in Fig. 2.8. The Annual subscription rates (1994): UK £22.00. total equivalent resistance Re of such circuits can be found by Overseas £28 (surface mail); £45.50 (airmail) progressively reducing all the parallel parts to a single equivalent, To: Everyday with Practical Electronics, then adding together any series parts remaining. You may have to 6 Church Street, Wimborne, Dorset BH21 1 JH do this a number of times, but the circuit can always be reduced to a single equivalent in the end. Though perhaps it is fair to say that Na me for some circuit, techniques beyond those we have studied here must be used! Address Turning to Fig. 2.8, to resolve this we first of all eliminate the parallel grc p of RI and R2. Using the product/sum rule, we find that 10f2 and I 5Q in parallel come to 60 (be sure and try this for yourself); this 6Q is now in series with R3 which is 120 making a total of 180, which itself is in parallel with R4. Again using the I enclose payment of £ (cheque/PO in C sterling only, payable product/sum rule, we find that 180 in parallel with 90 gives us 60. to Everyday with Practical Electronics) VISA Finally we have 60 in series with R5, 220, making a final equiv- Access or Visa No alent equal to 6 + 22 = 280. As an exercise, make a circuit sketch for each of the steps out- lined in the text above. Now here are last month's solutions and a further set of self- Signature Card Ex. Date assessment problems for this month. Please supply name and address of card -holder if different from the subscription address shown above Subscriptions can only start with the neat availsble issue. For back numbers see Editorial page 2/94

148 Everyday with Practical Electronics, February, 1994 S U RVEILL A N CE PIUWESSNEVAL 01J/turf KITS N o. 11 for Kits Whether your requirement for surveillance equipment is amateur, professional or you are just fascinated by this unique area of electronics SUMA DESIGNS has a kit to fit the bill. We have been designing electronic surveillance equipment for over 12 years and you can be sure that all our kits are very well tried, tested and proven and come complete with full instructions, circuit diagrams, assembly details and all high quality components including fibreglass PCB. Unless otherwise stated all transmitters are tuneable and can be received on an ordinary VHF FM radio. Genuine SUMA kits available only direct from Suma Designs. Beware inferior imitations!

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Ever rday with Practical Electronics, February, 1994 149 Special Series SAFETY FIRST! T.R. de VAUX-BALBIRNIE Part three

Staying alive with electrical equipment

HIS is the third article in a four-part short series sidered in some detail last month. Since the ground could concerned with household electrical safety. Over the be wet, such a shock could easily prove fatal. Tlast two months, we have discussed the danger of If the caravan became live with its structure earthed, a electric shock, the theory and some life-saving first-aid large current would flow from live to earth and complete procedures. This month and next, we shall look at some the circuit to neutral. This would blow a fuse immediately other dangers arising from the use of electricity — over- so isolating it from the supply. The following information heating and fire. covers the main practical points but readers requiring fur- ther guidance should seek specialist advice at a reputable H O O KE D O N CA R A V A N S caravan centre. However, following-on from last month, we shall first look at some safety aspects in the use of mains hook-up R O U N D—PIN S O C K ET S facilities in touring caravans. This may be helpful to some Mains hook-up supplies at caravan pitches terminate in readers. special 16A round-pin sockets providing live (L), neutral There will be no problem if the user is content to use (N) and earth (E) connections. For some reason, the live only a rechargeable (car-type) battery to provide an extra and neutral connections are the opposite way round com- low-voltage (12V) supply for lights, water pump, etc. This pared with a standard UK socket. Each has a fuse or is too low to present a shock hazard. However, although other over-current protection and groups of sockets are such a supply is adequate, there is often a wish to operate protected by an RCD (Residual Current Device). mains appliances and this has certain advantages, chief of Regulations state that there should be no more than 20m which is that electricity may be used more liberally. On (66h approximately) between a supply socket and any the other hand, mains hook-up installations can be dan- caravan intending to use it. Also, in the UK, no more than gerous if not correctly installed and maintained. one caravan may use the same outlet. A caravan amounts to a metal box which is normally A matching inlet plug fitted with a waterproof cover is isolated from the ground due to the insulating effect of the fitted on the side of the caravan (see photograph). This is rubber tyres. When hooking-up to the mains it will be linked to the supply using a line socket and a length of up necessary to Earth the caravan (see Fig. 1). If this is not to 25m (82ft approximately) of three-core flexible cable. carried out and the live (L) wire touched a metal part of This will have 2.5mm2 conductors providing a maximum the structure, then a person touching the caravan and loading of 16A which is more than adequate in practice. having some contact with the ground would receive an The Live, Neutral and Earth wires inside the caravan earth-loop shock. This type of electric shock was con- lead to a small consumer unit. This has a double-pole main switch, an RCD and a separate fuse for each circuit. A thick wire is securely attached to the caravan chas- sis and is connected to the earth pin on the plug. There will be a notice with standard wording attached near the main switch — this provides the user with information concerning safe use of the system. It is essential for the caravan installation and flexible lead to be tested at a caravan centre every three years — more if it is used often. Note that, when in use, the lead must be fully uncoiled from any reel on which it is stored to prevent any possibility EARTH WIRE BONDED TO CARAVAN STRUCTURE of overheating (see later). N MAINS AC We now go on to the main part of [E4.3124 I Fig. 1. The caravan body and chassis must be earthed this month's work — danger of over- heating and fire.

150 Everyday with Practical Electronics, February, 1994 FIRE! In the UK there are some 55,000 accidental fires each year killing 650 people and injuring a further 8,000. Many thousands of incidents are not reported because they cause only slight damage and minor injuries. A large propor- tion of fires are caused by electrical faults and mis- use of electrical equipment but almost all could have been avoided by exercising simple precautions. Every household should have a fire extinguisher — even a simple dry powder one is adequate for minor fires but, remember, never use a water-type extinguisher on an electrical fire. The electrical installation in a house does not remain in good condition for ever. Householders are advised to have it checked professionally every 15 years and certainly before moving into a house where there is evidence of amateurish additions to the system. One sign that re-wiring is necessary is the existence of round-pin sockets and old-fashioned surface-mounted light switches. Fixed-wiring jobs are best left to the profes- sionals unless you are certain that you know what you are doing. Amateurs installing mains wiring accounts for a Never use underrated cable. The overheating of the wire will high proportion of all fires since they often choose a cable melt the insulation and it may even burst into flames causing a major fire. having too low a current rating for the job. If you are unfortunate enough to have a fire at home, soldering iron or light bulb. In other situations, it is a follow this procedure. Note that further information may nuisance and wastes energy. Where the heat is produced in be obtained from your local Fire Brigade. a connecting wire, it is important that it is thick enough to Procedure in the event of fire carry the current safely so that there is no excessive rise in • Decide if you can safely tackle the fire yourself. Never temperature. use water or a water-type fire extinguisher on an Using wire of a thinner type than needed.— perhaps for electrical fire. an extension lead — is a common cause of fire. Suppose a • If you cannot deal with the fire yourself, get out of the piece of wire rated at 6A is used for an electric fire requir- room and close the door. This will delay the spread of ing 13A. The copper conductors would soon overheat, the fire. Ordinary doors are effective in containing fire until plastic insulation melt and begin to burn (see photograph). the Fire Brigade arrives. If there was combustible material nearby this could cause • Get everyone out of the house and dial 999 from a a major fire. neighbour's house or public telephone. Never go back If some copper strands are lost when the insulation is into the building. removed from the end of a piece of wire — probably to fit a plug — this can lead to local overheating when it is operat- B A SIC THE O R Y ing near to its maximum current capacity. This is because When an electric current flows through a wire, heat is the wire is made effectively thinner and the current-carry- produced. This effect is put to good use in an electric fire, ing capacity reduced.

Caravan site m ains "hook-up" 16A round-pin outlet socket Caravan consumer unit. This has a double-pole switch, an and matching caravan plug, with waterproof flap. RCD trip and a separate fuse for each circuit.

Everyday with Practical Electronics, February, 1994 151 Ideally, the heat should be free to leave the surface of a wire and be carried off into the air. Particular care must be taken when using a cassette-type extension lead of the type which winds into a plastic casing (see photograph). Sup- pose the wire is rated at 13A. This figure is quoted for use in free air. For this reason, when carrying a high current, the wire must be fully uncoiled. If it is partially wound into the cassette, the wire will not be able to rid itself of the heat so effectively, possibly overheat and cause a fire. Commercial extension leads are usually fitted with a thermal cut-out but this cannot be relied on. For a capacity of 13A when unwound, a typical rating is only 6A when wound in — figures such as these will be inscribed on the plastic case (see photograph) and must never be exceeded. There is some confusion because the general public cannot easily relate current (amps) with the more familiar wattage (power rating) of an appliance. This involves using a simple formula (see below). Readers who have been following the series will recognize it as the same one used in Part 1 to predict Electric shock current: A commercial extension lead showing the coiled (6A) rating and the fully unwound (13A) rating inscribed on the cable I = P/V housing. Where / is the current in amps, P the power of the Incidentally, all the following plug fuse values are avail- appliance (in watts) and V, the voltage of the supply. able: 1A, 2A, 3A, 5A, 7A, 10A and 13A. However, if By dividing power by voltage, the current if found. Sup- buying locally you will probably have to be content with a pose the extension lead above were to be used for a 2kW limited range. People often leave the 13A fuse in the (2000 watt) electric fire operating from 240V mains. Using plug because it was there when they bought it. This is the above formula: dangerous because it provides no safety in the event of / = P/V = 2000/240 = 8.33A. overload. This shows that it would be safe to operate the fire with A fuse is just a thin piece of wire — usually copper — the extension lead fully unwound but the wire would over- which is protected by a heatproof case. The fuse is meant heat if it were left wound on its cassette. On the other to be the weakest (that is, most easily melted) part of a hand, if a soldering iron of rating 15W on 240V mains circuit and will "blow" before there is any danger. A were to be used with the same extension lead, a similar standard UK plug fuse has a case made of high-rupture calculation shows that the current would be only 0.063A ceramic. This is strong enough to contain the flying pieces (63mA) and so safe to use with the wire fully wound on of red hot copper which are produced when a fuse blows the reel. violently. The thickness of the wire in the fuse is carefully selected BL O WIN G A F U S E so that any current up to its rated value can be accom- People frequently buy extension leads having a current modated but the wire will become hot, melt and break the rating only just sufficient for their immediate needs — prob- circuit very quickly in the event of an overload. Never ably because it is cheaper. If you buy one which is rated at bridge the fuse clips inside a plug with a piece of wire or 6A, it will be necessary to prevent someone using it with aluminium foil to make a temporary fuse. an appliance which requires a higher current. This would involve fitting a 5A fuse in the mains plug. This would C H O O SIN G blow straight away if the rating was exceeded. T H E C O R R E CT FU S E When a piece of equipment is purchased, the correct plug fuse value will be advised in the instructions. How- ever, this may not be known for appliances which have *tip been in the house for a number of years. The formula used previously may then be used to find the correct value. Note that the power rating is usually given on a metal plate or piece of tape located on the back or underside of the appliance. Example: A toaster is rated at 800W and is connected to the 240V mains supply. What is the correct value of fuse to 41PN use in the plug? 4 • Using: I = P/V = 800/240 = 3.3A. A 3A fuse would be unsuitable. The next easily-ob- tainable value is 7A which is satisfactory but a 5A fuse, if 416 , thN44 y available, would be an even better choice. 4 Example: A soldering iron is rated at 25W. This is con- v4,444 nected to the 240V supply mains. What is the correct value 4 of fuse to use in the plug? 0 , Using: I = P/V = 25/240 = 0.104A It is likely that a 3A fuse will be the lowest value which can be obtained locally but a 2A or 1A fuse would be better. Sometimes, where inductive loads such as motors are A selection of cartridge fuses from 1A to 134 involved, the theoretically "correct" fuse keeps blowing

152 Everyday with Practical Electronics, February, 1994 because of the current surge which occurs on switching on. If this happens, refer to the instructions or contact the manufacturer. Everyone should do a plug fuse check in their home. It is likely that you will find 13A fuses in many of the plugs where a lower value would be much better.

N E VE R REF U SE A fuse must never be replaced with one of a higher rating without competent advice. It has been known for a householder to replace a fuse in the main fusebox with a thick nail in an attempt to prevent it from blowing. Ob- viously, the nail will withstand an enormous current — hundreds of amps — and will no longer be the weakest part of the circuit. Some section of the wiring is now likely to overheat and cause a fire. In one sad tale, the wire ran close to a lead gas pipe which melted and released gas. The resulting explosion totally destroyed the house. A fuse does sometimes blow due to "old age" especially when being used near the limit of its rating. However, do not replace a fuse until you have investigated possible causes. If you cannot find the cause, replace the fuse once. If it blows again, seek professional advice. It often happens that people join together pieces of wire of differing thicknesses to make one long extension lead. This is asking for trouble. The combination can only handle the current of the thinnest wire. Twisted and taped joints are another cause of trouble. Where wires are joined together by twisting, the contact between the pieces of conductor will not be perfect and the joint is likely to have a higher resistance than the rest of the wire. This may lead to local overheating and possible fire. Also, a twisted joint is mechanically weak so, with an accidental pull, the bare conductors may be exposed and give rise to a risk of electric shock. Ideally, wire should not be joined at all but bought in

one length. However, if it has to be joined, a proper flex Using multiple adaptors, -piggy-back fashion"; on a single connector having cable clamps may be used. These con- outlet is asking for trouble and must be avoided. nectors are often of less than 13A rating so the plug fuse should be chosen to take account of this as well as the In the case of the headlamp, the current is: rating of the wire itself (whichever is the lower). Readers I = P/V = 48/12 = 4A who have not been following the series should note that But in the case of the 100W mains bulb, it is: further information was given about the safe use of flex I = PIV = 100/240 = 0.42A connectors and extension leads last month. This seems surprising. The car headlight has a lower power rating than the mains bulb yet more current flows M ULTIPLE A D A PT O R S in the circuit. In practice, this means that automotive People forget that the maximum current which can be wiring is generally fairly thick to carry the large currents supplied through a multiple adaptor is 13A total. Unfor- involved. When wiring-up car accessories it is essential to tunately, these do not generally have an internal fuse use proper auto-type wire of the appropriate rating. which would be a safety measure. Vehicle fires are often caused by amateurs using thin Suppose a double adaptor were used for a kettle requir- mains-type wire or light-duty "bell wire" to connect high- ing 13A and a fire needing 8A — a total of 21A. The fuse at powered accessories. Consider a pair of spotlights rated at the main fusebox will be appropriate for the whole ring- 200W total. The current in the feed wires will be: main — usually 30A. This will not blow but it is likely that I = PIV = 200/12 = 17A approximately the adaptor itself will overheat and possibly cause a fire. If mains-type wire of 3A rating were used, the result Multi-way adaptors are sometimes necessary and can be could be catastrophic. A similar cause of fire is plugging acceptable if used within their rating. Multiple adaptors a "power" appliance into the household lighting circuit. riding piggy-back on further adaptors to increase the num- This will be looked at in more detail next month. ber of outlets (see photograph) is asking for trouble. The For complete safety, all electrical appliances should be popular type of 4-way or 8-way distribution sockets are switched off at night and unplugged from the mains. This better but must, again, be used with caution — the total may have been easy years ago but it is more difficult today loading must not exceed 13A and less if the connecting in the world of video recorders and digital clocks. wire has a lower current rating than this. These sockets Unplugging these is impractical and they have been have an internal fuse which should be appropriate to the designed to be powered continuously. However, overheat- wire being used. ing will occur if the ventilation holes are covered up or the air flow restricted in some other way. Check how warm C U R RE NT SIT U ATIO N the case feels every so often and disconnect the appliance if Returning to the "Power Equation'', it can be seen that there is any sign of an abnormal rise in temperature. low voltage supplies require a larger current for a given That's all for this month. Next time we shall complete power compared with a high voltage. To illustrate this, the series by continuing with our discussion of fire. We compare the current passing through the connecting wires shall look particularly at the use of car batteries and ex- of a 12V 48W car headlight bulb and a 100W light bulb amine some other sources of danger — Direct and Indirect connected to the 240V mains. Burns and some Chemical Hazards.

Everyday with Practical Electronics, February, 1994 153 to each gate and see that the outputs at pins 3. 4. I 1 and 10 all go correspondingly low. Home Base Short Waves and Sea Waves Jottings of an electronics hobbyist-Terry Pinnell At the complex end of the scale. I reckon that 13 of the 145 projects took me more than a month to complete. Mind you, there's Car or Domestic? Not that it's a matter of no clear correlation with intricacy. For ex- Who Makes WhatP earth-shattering importance anyway; I'm ample, my house burglar alarm, built in my Where does all that solder and circuit not going to get arrested for mis-coding relatively novice period, probably took me board end up? Not to mention those count- anything! a couple of months (plus various enhance- less millions of components? It would be I also had some difficulty keeping the ments over subsequent years). Looking at interesting to see a really thorough survey number of projects allocated to Miscel- the circuit now it seems like it should be no of what we hobbyists actually construct. If laneous to a minimum. It helped to intro- more than a couple of week's work. there has been one, then I've missed it. duce a Toys/Novelties category, reserv- Apart from circuit design and the per- Of course, the construction mix has ing Miscellaneous for those projects that sonal learning curve, there's the issue of changed significantly over the years. wouldn't even fit in that. Judge for your- physical construction difficulty too. In that Nowadays, for example, there are self from the two lists out of the nine particular case, as I was using reed switches probably many more digital circuits getting types. in doors and windows, a major chunk of built than analogue, and I expect Incidentally, I did cheat a bit in coming the effort was the wiring. That was true computer-orientated projects in particular up with the 145; there was a handful of of some of my car alarms also; getting a feature strongly. But over the last decade projects that I'd somehow left out of the connection from A to B without disman- or so I wonder if the average constructor's binder, so those had to be added retrospec- tling the vehicle sometimes took an inor- output would be much different from the tively. Of these, a few were arguably not dinate length of time. Similarly, making sort of things I've turned out? I've been "projects" at all, but on balance I decided my sound-to-light unit in its tall, wooden, doing a little analysis of my own projects, to put them in. glass-fronted case proved to be more of a and the pie chart in Fig.1 boils it down. For instance, my cupboard light would challenge to my poor carpentry skills than I have my Finished Circuits Binder to come high in a bid for the title of Most any prowess in electronics. thank as the source of this data. I used to Trivial Project. It consists of a microswitch One genuinely complex design of which 1 find that, although a circuit seemed ob- and a few lengths of wire, supplying mains was proud was my twelve band short wave vious at the time I made it, I would soon voltage to an overhead bulb whenever radio. Mastering the mysteries of the su- completely forget how it worked, even after the door to the under-stairs cupboard is perheterodyne gave me great pleasure, and only a few weeks. So I started keeping opened. But as it was just about the first at the flick of a switch the radio still works written records, in the shape of a loose-leaf constructive thing I did after mastering the perfectly. Waves also featured centrally in binder. I'd scribble at least the bare details basic principles of electricity, I thought it another project of similar complexity, my of every finished project on A4 sheets, give deserved a place, on sentimental grounds if surf simulator. A bedside toggle brings the it a name — hopefully one I'd recall months nothing else. sound of crashing breakers, complete with or years later — punch some holes in it and the deeper roar of shingle and the constant, just file it alphabetically. The set now con- soporific background hiss. sists of three separate thick binders and Cutting Remarks Unlike a tape recording (which would contains some 145 different projects, split Top place for triviality surely goes to the have been a lot easier!) it has the merit of over nine broad categories. Polystyrene Cutter though. That is noth- being random — you don't know whether ing more than a couple of feet of resis- the next wave will be loud or soft, or tance wire, with hooks on either end. It's whether it wIl come in five seconds or What's in a NameP cheeky to call it a finished project, as it is thirty. Gradually it fades away, and there There are clearly lots of ways you can really an accessory to my heavy duty bat- are controls to vary the time taken as well classify circuits, depending on how your tery charger, without which it doesn't do a the overall volume. I recall one of the mind works and on what you want to do lot. But with the wire stretched tightly be- satisfying puzzles to solve was finding with the results. My nine categories are an tween a couple of nails or whatever, and a way to make the fade-out absolutely admittedly arbitrary choice, made recently the croc-clips of my charger supplying it smooth. Having gently soothed you to I hasten to add, not selected way back with an awesome 20 amps, it glows a nice sleep over 15 to 30 minutes, that final click and sustained throughout the years. Not red and cuts clean lines in any polystyrene from the loudspeaker — inaudible in every- that I didn't give it some thought before you draw through it. day circumstances — was just enough to homing in on this particular set. One of the OK, you're probably wondering why wake you up again! problems was that useful labels are often you'd need to cut poystyrene. To be honest not mutually exclusive. Is a burglar alarm I can't remember an enormous demand TOYS/NOVELTIES for the house best pigeon-holed in the myself. But I do recall that my Yoghurt Buzz bar Domestic or Alarm category? After all, any Maker needed a biscuit tin lined with the Electronic Safe project used indoors could logically be stuff, to serve as insulation to maintain a ElectroMagnetic Pulser (EMP) classified as Domestic. steady temperature, which is what prob- EMP (large) Similarly, is a gong used in a car alarm ably prompted the digression. EMP (small) best labelled Audio or Alarm or Car? What There are quite a few more candidates Light Rifle Metronome about a headlamp-operated garage light — for that Most Trivial award. For instance, Random Light Flasher Lighting 9 my simple attenuator consists of a four Siren Test/instruments 45 8% Domestic 15 inch length of soft wood, with six nails Train Controller 31% hammered into it, and five resistors strung Xmas Tree Flasher between them, giving four levels of at- Xmas Tree Fader Car 15 tenuation (by 10, 100, 1000 and 10,000). TOTAL: 12 10% Despite its simplicity it actually gets used occasionally too. MISCELLANEOUS Audio 8 Another simple but much-used Agitator 4% Capacitor Tester: BBC Micro "project" is my CMOS tester; just a tiny Computer light pen plastic case with a 14 pin i.c. holder wired Divider (for timer contest) Alarm 19 up to test the four gates of 4001 and 4011 Light Trigger Radio 14 13% chips, which I tend to use a lot. The two 10% Metal Detector (kit) pins of each gate (1/2, 5/6, 13/12 and 8/9) Mousetrap Toys/Novelties 12 Misc 10 are connected together and normally held Polystyrene Cutter 8% 7% at OV with a 12 megohm resistor. To test Yoghurt Maker Fig. 1. A decade or so of electronics whether they are working satisfactorily ZX81 Interface construction. you just apply a logic high signal in turn TOTAL: 10

I 54 .Everyday with Practical Electronics, February, 1994 HART AUDIO KITS-YOUR VALUE FOR M ONEY ROUTE TO ULTIMATE HI-Fl

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Hot Off the Press. the definitive electronics giving you guided hands-on experience of modern and audio book by the renowned John Linsley Hood. electronic techniques This 300 page book will give you an unparalleled In short HART is your 'friend in the trade' giving insight into the workings of all types of audio circuits. you, as a knowledgeable constructor, access to Learn how to read circuit diagrams and understand better equipment at lower prices than the man in amplifiers and how they are designed to give the best sound. The virtues and vices of passive and active the street. components are examined and there are separate You can buy the reprints and construction manual sections covering power supplies and the sources of for any kit to see how easy it is to build your own noise and hum. As one would expect from this writer equipment the HART way The FULL cost can be the history and derivation of audio amplifier circuitry Modern, ultimate sound systems are evolving credited against your subsequent kit purchase. have an entire chapter, as does test and measure- Our list will give you fuller details of all our Audio towards built-in preamplifiers within or near the ment equipment. Kits, components and special offers turntable unit. This keeps noise pickup and treble Copiously illustrated this book is incredible value for loss to a minimum. We now offer two units, both the amount of information it contains on the much AUDIO DESIGN 80 WATT POWER AMPLIFIER. having the sonically preferred shunt feedback neglected field of linear, as opposed to digital. elec- configuration to give an accurate and musical tronics. Indeed it must be destined to become the sound. and both having the ability to use both standard reference for all who work, or are inter- moving magnet and moving coil cartridges. ested in. this field Kit K1500 uses modern integrated circuits to SPECIAL OFFER. With each book purchased you may achieve outstanding sound quality at minimal cost. request a FREE extended index, written by the Author, exclusively from HART. The very low power requirements enable this unit to 0-7806-0868-4 £16.95 be operated from dry batteries and the kit comes Don't forget most of our kits have reprints of articles by with very detailed instructions making it ideal for the John Linsley Hood that you can purchase separately. beginner. K1500 Complete kit with all components, "THE ART OF SOLDERING", R. Brewster. printed circuit board, full instructions and fully This fantastic John Linsley Hood designed Absolutely essential reading for anyone who ever amplifier is the flagship of our range, and the ideal finished case £67.99 picks up a soldering iron. Written from knowledge powerhouse for your ultimate hifi system. This kit Instructions only £2.80 gained in a lifetime in the field, this is the first book is your way to get £K performance for a few tenths Kit K1450 is a fully discrete component implementa- ever solely devoted to this essential and neglected of the cost!. Featured on the front cover of tion of the shunt feedback concept and used with the skill for all electronic enthusiasts Covers everything 'Electronics Today International' this complete right cartridge offers the discerning user the ul- from the correct choice of soldering iron and solder stereo power amplifier offers World Class perfor- timate in sound quality from vinyl disks. Can be to the correct procedures to follow with many illustra- tions and practical exercises mance allied to the famous HART quality and ease fitted inside our 1400 Preamp, used externally or as 0-85935-324-3 £3.95 of construction. John Linsley Hood's com ments on a standalone unit It has a higher power require- seeing a complete unit were enthusiastic.- "The ment and needs to be powered from our 1400 Series "AUDIO", F.A. Wilson, 320 pages. 178 x 111 Publ external view is that of a thoroughly professional preamplifier or its own dedicated power supply. 1985. piece of audio gear, neat elegant and functional. K1450 Complete Discrete Component RIAA Phono BP111 "AUDIO" by F.A. Wilson £3.95 This impression is greatly reinforced by the Preamp £109.58 "AN INTRODUCTION TO LOUDSPEAKERS 8, ENCLOSURE DESIGN", V. Capel, 160 pages. 178 x internal appearance, which is redolent of quality, Factory Assembled and Tested £159 58 both in components and in layout." Options K1565 Matching Audio Grade Power Supply with 111. Publ. 1988. BP256 £2.95 include a stereo LED power meter and a versatile potted toroidal transformer and limited shift passive front end giving switched inputs using earthing system £79.42 "LOUDSPEAKERS FOR MUSICIANS", V. Capel, 176 ALPS precision, low-noise volume and balance Factory Assembled and Tested £118.42 pages 178 x 111 Publ 1991 controls. A new relay switched front end option U1115 Power Interconnect Cable £7.29 BP297 £3.95 also gives a tape input and output facility so that "HO W TO USE OSCILLOSCOPES & OTHER TEST for use with tuners, tape and CD players, or EQUIPMENT", R.A. Penfold, 112 pages. 178 x 111. indeed any other 'flat' inputs the power amplifier SPECIAL OFFER Publ. 1989 may be used on its own, without the need for any PRECISION Triple Purpose TEST BP267 £3.50 external signal handling stages. 'Slave' and Classics from the "Golden Age" 'monobloc' versions without the passive input CASSETTE TC1DD. "THE WILLIAMSON AMPLIFIER", D.T.N. Williamson. stage and power meter are also available. All Are you sure your tape recorder is set up to give its In April 1947, Williamson's power amplifier, using ex- versions fit within our standard 420 x 260 x 75m m best? Our latest triple purpose test cassette checks cellent-quality push/pull output valves, a special out- case to match our 400 Series Tuner range. ALL six the three most important tape parameters without put transformer, and a highly filtered power supply. power supply rails are fully stabilised. and the test equipment Ideal when fitting new heads became an overnight success. The author takes the complete power supply, using a toroidal trans- A professional quality, digitally mastered test tape reader deep into his design considerations, offering former, is contained within a heavy gauge at a price anyone can afford practical advice on how to build the units plus con- aluminium chassis/heatsink fitted with IEC mains Test Cassette TC1DD Our price only £10 99 cise instructions on setting up the new amp. A cult input and output sockets. All the circuitry is on classic. professional grade printed circuit boards with DISK-COUNT Classical CD's. 1947. Reprinted 1990.40 Pages. roller tinned finish and green solder resist on the 0-9624-1918-4 £4.95 Top quality, Full Digital (DOD) Compact Disks of the component 'dent side, the power amplifiers LOUDSPEAKERS: THE WHY AND HOW OF GOOD great classical favourites. Like everyone else we feature an advanced double sided layout for REPRODUCTION, G.A. Briggs. didn't like the idea of paying silly prices for CD's maximum performance. All wiring in this kit is pre- This easy-to-read classic, last revised in 1949, intro- After a long search we have now located a source of terminated, ready for instant use! duces the reader to concepts such as impedance, top quality classical recordings at prices that make RLH11 Reprints of latest articles £1.80 phons and decibels, frequency response, response K 1100CM HART Construction Manual £5.50 you suspect the quality - until you try them! Send for curves, volume and watts, resonance and vibration. our list of titles. cabinets and baffles, horns. room acoustics, tran- LINSLEY HOOD 1400 SERIES sients, crossovers, negative feedback, Doppler and ULTRA HIGH-QUALITY PREA MP CD Roms phase effects, and much more. A provocative survey Joining our magnificent 80 Watt power amplifier of the right questions about sound reproduction. Like music CDs these have been overpriced for now is the most advanced preamplifier ever of- 1949, Reprinted 1990. 88 Pages. 215 x 140. some time but with the low pr ices of CD Rom drives fered on the kit, or indeed made-up marketplace. 0-9624-1913-3 £ 6 .95 the multimedia revolution is with us now. Send Facilities include separate tape signal selection for our list of titles. Most popular up to now have COMPUTER TITLES to enable you to listen to one program me while been "Too Many Typefonts - with 514 TrueType fonts "A CONCISE ADVANCED USERS GUIDE TO MS recording another, up to 7 inputs, cross record- along with 393 ATM and lots of others. "Shareware DOS", N. Kantaris. 144 pages 198 x 130. Publ. 1992. ing facilities. class A headphone amplifier, can- Overload" with over 6100 programs extending to BP264 £3.95 cellable 3-level tone controls and many other use- 550MB and "Kodak Photo CD Access -. The first two "A CONCISE USERS GUIDE TO MS DOS 5", N. Kan- ful functions, all selected by high quality relays. are only £12.95, the Kodak only £24. tans, 144 pages. 198 x 130. Publ. 1992. For full details see our list. BP318 £4.95 Send or 'phone for your copy of our List (50p) of these and many other Kits 8 Components. Enquiries from Overseas "MAKING MS DOS WORK FOR YOU", N. Kantaris customers are equally welcome, but PLEASE send 2 IRCs if you want a list sent surface post, or 5 for Airmail P R.M. Oliver, 160 pages 198 x 130. Publ. 1993 Ordering is easy Just write or telephone your requirements to sample the friendly and efficient HART BP319 £4.95 service Payment by cheque, cash or credit card A telephoned order with your credit card number will get your order on its way to you THAT DAY "A CONCISE USERS GUIDE TO WINDO WS 3.1", N. cuil Please add part cost of carriage and insurance as follows -INLAND Orders up to C20 - £I.50, Kantaris, 160 pages. 198 x 130. Publ, 1992. Orders over C20 - £3.50. Express Courier, next working day £10. BP325 £4 95 tOVERSEAS - Please see the ordering information with our lists. Q U ALITY 24 hr .SALES LINE ALL PRICES INCLUDE A U DIO KITS (0691) 652894 UK/EC VAT

E6lp o .

0 54 4SI Z'': 155 Everyday with Practical Electronics, February, 1994 Constructional Project MULTI-PURPOSE AUDIO SrsrEm Part 5-BALANCED STEREO MICROPHONE PREAMPLIFIER

MAX HORSEY P.C.B. Design PHILIP CLAYTON

If you want to set up a ho me recording syste m, mix sound videos, run a disco or a small band then these modules are for you! All m odules will operate alone, but are co mpatible with each other.

BAL A N CE D microphone pre-amp is Alternatively a dual rail I 5V (i.e. + I 5V, the other for an "out of phase" signal. This essential for high quality work since OV, - 15V) supply is suitable and a mains may sound complicated, but it makes little Amost higher priced microphones are driven power supply is included in this difference to the cost of the microphone of the balanced (explained later) variety. article. since the two ends of the microphone coil are The pre-amp described here is designed to out of phase anyway. Providing neither end electronically unbalance the signal and B AL A NCE D of the microphone coil is connected to the raise it to "line level"; in other words make A U DIO SYSTE M S screen or "ground", the microphone will be it suitable for any mixer or power amplifier "balanced". Most higher price microphones input which is designed for tape recorders. The term -balanced input" or "balanced microphone" may be a mystery to provide an output from each end of the coil. CD players, tuners etc. It may be connected plus a screen or ground connection. to the Mixer described in Part I of this many readers, but most higher priced The clever part of this arrangement is that series and includes a I 5V d.c. output which microphones are "balanced", and so a few general words about balancing may be both signal wires will pick up the same may be used to power the Six-Channel helpful. Many people will have experienced interference. A balanced input amplifier is Stereo Mixer. mains hum or other unwanted "noise" designed to respond only to the difference The preamplifier is based on a new i.c. picked up by long microphone leads. The between the two input signals and reject type SSM2017. This i.c. boasts very low problem occurs because microphone common signals. Hence the wanted audio noise, wide bandwidth and low cost, and is signal is amplified, but the interference available in an 8-pin d.i.l. package. It is signals are at a very low level, typically around I mV or less, and the slightest which is the same on both wires (i.e. in particularly suitable for use as a balanced magnetic interference from nearby mains phase) is rejected. microphone amplifier, although it can be cables or other equipment induces used with unbalanced microphones as well. electrical "noise— into the microphone B A SIC P O WER lead. Mains hum is very difficult to filter A RRAAIGE ME NT out since it is very close in frequency to R EQ UIRE ME NTS The pin connections for the SSM-2017 bass sounds which are generally required. low-noise audio preamplifier i.c. are shown The i.c. is designed for use on a dual rail Fig. 1(a) illustrates the problem. in Fig. 2. Note that the reference terminal supply, and since it only requires 22mA per Clearly, screening the microphone lead (pin 5) is connected to ground (OV) in this rail, two PP3 9V batteries may be used. will help reduce interference, but a far better application. This is useful if the amplifier is to be solution - in addition to screening - is to use A simplified arrangement showing the operated out of doors. a pair of signal wires, one for the signal, and principle of operation is shown in Fig. 3.

(a) UNBALANCED MICROPHONE

MICROPHONE V+ SIGNAL + NOISE NON-INVERTING Rgl Rg 2 INPUT GROUND (SCREEN I INVERTING INPUT POSITIVE SUPPLY GAIN SET 1+v I (b) BALANCED MICROPHONE RESISTOR NON -INVERTING OUTPUT INPUT MICROPHONE INVERTING SIGNAL + NOISE INPUT NEGATIVE I-VI REFERENCE r i ) OUT OF PHASE SIGNAL + NOISE t CASE v - GROUND (SCREEN)

Fig. 1. Unwanted noise on balanced and Fig. 2 Circuit and pinout connections for the SSM-201 7/ow-noise unbalanced microphones. preamplifier ic.

156 Everyday with Practical Electronics, February, 1994 The capacitor removes any very high fre- quencies which may appear at the input, and the two 6.8 kilohm resistors provide +68V d.c. bias to keep the d.c. input voltages to IN -PHASE within an acceptable range. INPUT TYPES OF MICROP HO NES The circuit (Fig. 5) is capable of working with any type of microphone but it ma)

be helpful to discuss the differing types MICROPHONE OUT OF PHASE at this stage since some components can INPUT be omitted if - for example - dynanth microphones are the only type to be used.

Balanced or unbalanced microphones may be used, but the circuit is designed for higher quality balanced microphones. The Fig 4. Phantom powered microphone CIICUlt diagram. two most common types of balanced or unbalanced microphones are Dynamic and For example, with a gain set resistor Capacitor (e.g. Electret) microphones. S ETTING THE GAIN value of 330 ohms, the voltage gain is 31.3 Returning to Fig. 3, pins 1 and 8 of the (= 30dB). A resistor value of 32 ohms i.e. are for the connection of a gain set Dynamic microphones work like tiny produces a voltage gain of 314 ( = 50dB). generators, generating an electrical sig- resistor. The gain of the circuit is deter- If the gain set resistor is removed, the nal whenever they receive a sound. They mined by the formula: gain will be unity (0 dB). IOW are robust, easy to use and can cost as Voltage Gain - + If the resistor value is reduced to zero, little as £5 or more than £100. More AG the gain will be infinite. expensive microphones offer a wider flat- where RG is the value of the gain The maximum gain permitted is 3500, ter frequency response (essential for hi-fl set resistor. and this should be more than sufficient recordings) improved noise immunity etc. for most microphones. The printed circuit Dynamic microphones do not require a The following table provides some typi- board has provision for a preset resistor to power supply. cal values: set the gain in each channel. Voltage Gain dB Rg(Q) The prototype was designed so that Capacitor (condenser) microphones do adjustment could be made with a not generate a signal, and do therefore 1 0 open screwdriver through holes in the front require a power supply. The higher 3.2 10 4700 panel. Alternatively the user could fit price types require a supply from the 10 20 1100 ordinary potentiometers (rotary or slider) preamplifier circuit. This is often known as 31.3 30 330 if frequent changing of gain is required. a phantom power supply. and Fig. 4 shows 100 40 100 The bandwidth (i.e. range of audio how a d.c. supply of 48V is connected to 314 50 32 frequencies which are amplified by the the microphone without requiring extra 1000 60 10 amounts quoted above) is greater than the cables. The Zener diodes prevent damage • caused by high voltages, produced when the microphone is plugged in or unplugged. A phantom power supply may seem a lot of trouble, but the highest quality (and most expensive!) microphones are generally capacitor types.

Ekciret microphones are similar to normal capacitor microphones but they are generally less expensive. In fact the cheapest electret inserts (i.e. microphones without the normal case) may cost less than fl. They require a power supply either from the circuit, or from a 1.5V battery which is often housed inside the microphone case. An electret microphone with its own in- ternal battery should be connected to the amplifier in the same way as a dynamic microphone i.e. it does not require a phan- Completed tom power supply. pre-amplifier showing front panel layout and lettering

+ V IN-PHASE INPUT

OUTPUT MICROPHONE MICROPHONE

OUT OF PHASE INPUT

OV SCREEN/GROUND

Fig. 3. Simplified circuit showing principle of operation.

Everyday with Practical Electronics, February, 1994 157 human audio range. For example with a any high frequency noise at the inputs and delivering well over 10mA, plus 10mA for voltage gain of 1000, the bandwidth is capacitors CIO. CI I, C21 and C22 remove an I e ci.. i.e. a total ()foyer 20mA. 200k Hz. noise on the supply lines. The gain set resistor is VR I. This could S ELECTING A CIRC UIT be a fixed resistor if you know in advance the gain required, or it could be a preset TRA NSFOR MER The maximum current required by the D ES C RIPTIO N (a space is available on the p.c.b.) or it power supply circuit is less than about The complete circuit diagram for the could be an external potentiometer control. 190mA from one winding and 60mA from Stereo Balanced Microphone Preamplifier Resistor R6 ensures that the total resis- the other. A 6VA (i.e. 3VA per coil) is shown in Fig. 5. The two stereo halves tance cannot fall be low 3.9 ohms, other- require the same circuit, and so only the left wise the gain would be too high. transformer will therefore be sufficient hand side will be described. since each I 5V winding can deliver 200mA. Most of the components at the input O UTP UT A I 2VA transformer will offer a higher safety margin, but in practice this is stage are required for the phantom power The output from the ICI is delivered via unnecessary unless several other devices operating mode. If phantom powering is capacitors C8 and C9. These allow the a.c. are to be powered. not required significant savings can be audio signal to flow, but prevent the flow of Another alternative worth considering is made as described later under "Omitting d.c. which may be present. Two capacitors a toroidal transformer. These produce less Phantom Power". are used in parallel so that top quality magnetic interference, but at a higher cost. Resistor RI couples the 48V phantom polylayer types can be used. (These are not The smallest type readily available is rated power supply to the junction between R2 yet available in values of 2.2µF). at I 5VA with two 15V secondaries. and R3. Capacitors Cl and C2 ensure that Resistor R7 prevents any damage to the It performed well in tests, but is much electrical noise on the supply is removed. i.e. if its output is accidentally shorted to more expensive than a standard 6VA type. R2 and R3 feed the 48V supply equally to ground. The value of R7 is too low to affect The standard 6VA transformer was there- both balanced microphone lines. This the output signal. assumes that the microphone used is fore chosen for the prototype on grounds designed for a + 48V supply on both the P O WER SUPPLIES of cost and size. In tests it performed very well, even with the Stereo Mixer (as des- in-phase and out-of-phase lines; most The preamplifier printed circuit board cribed in Part I) also connected to the capacitor microphones are of this type. (p.c.b.) (excluding the 48V supply) could be + I 5V supply. Capacitors C3 and C4 allow the al- powered by two PP3 batteries, or two sets ternating in-phase audio signal from the of cells arranged as shown in Fig. 6. This microphone to flow to pin 3 of ICI. C5 and would be an effective supply assuming that C6 do the same for the out-of-phase signal. phantom power is not required. It is impor- However these capacitors block the flow of tant to remember to switch the circuit off POSITIVE d.c., therefore preventing the 48V supply when not in use - two PP3 batteries will be from reaching the i.c. All the electrolytic drained in less than 24 hours of continuous PP3 By BATTERY capacitors in the circuit are bridged with use. OR L ,12V BATTERY PACK small 100nF capacitors since these are A mains power supply provides a more much better at conducting high frequency reliable alternative, and the circuit shown OV signals. in Fig. 7 provides a + I 5V, OV. - 15V sup- The input pins 3 and 2 of ICI need to ply in addition to a 48V supply all derived 9.11 PP3 BY BATTERY be referenced to OV and this is achieved by from a single mains transformer. OR 12V BATTERY PACK resistors R4 and R5. These ensure that the The current required by the balanced average signal received by ICI is OV. Hence amplifier is about 22mA per channel. NEGATIVE the output signal from pin 6 will "wobble" When testing, an extra 10mA was allowed, equally above and below OV. plus 10mA for the I.e.d. indicators. In other Zener diodes DI to D4 ensure that the words a total of 42mA per channel. i.c, will not be damaged by high voltage The phantom power supply is at about Fig. 6. Using two sets of PP3 bat- spikes which could pass through C3 or C5 48V, and typically 2mA is required by teries or battery packs to power the when the capacitor microphone is plugged an "average" capacitor microphone. The preamplifier p.c.b. (excluding the 48V in or unplugged. Capacitor C 7 removes phantom power circuit is capable of supply).

+40V C3 47 IN-PHASE 0 0+ SUPPLY INPUT 0 01 R1 R2 L i ii i C8 100 6kb 1p R6 CI. 02 3(19 0 p I RT LEFT C • C 7 SSNI -20' 0 LEFT OUTPUT MICROPHONE R3 3 C 1 220p I 5k B C6 C9 NMI 47p Ou1 03 1p ego C2 04 001 OUT OF PHASE 0 INPUT ALL 26NE S C10 1 11 C11 124 0.5W SCR EEN /GROUND 0.....•••• °P1T l22op 00V SUPPLY 0 V . 4 SCREE NJ GROUND C/. ..• 07 Cl' C002 1 I 1 . C22224 1.7.e IN-PHASE 0 T T INPUT C19

R13 C13 012 MID 119 70 015 RI' 309 Op 1 IC2 33 RIGHT VR2 0 SalCIS SSM -2017 RIGHT OUTPUT Cul MICROPHONE r4E1T 0 7 220p,00 ' C20 RE 2 1}.1 100 Db

OUT OF PHASE° 6311'°6 INPUT 0 1 SUPPLY 015 ALL ZENERS T + 48V 12 V 0.5W P O WER SUPPL Y SIC CIRC UIT 15V A.C. PEG 1 The circuit diagram for the power supply 1 AMP BRIDGE is shown in Fig. 7. The 240V a.c. mains RECTIFIER IN +15V is fed via a double-pole switch SI to the 240V mains transformer. The neon is connected A.C. MAINS before the switch to indicate when the unit is connected to the mains — whether or YELLOW not SI is switched on. Three I.e.d.s are :Zs 05

employed to indicate the state of the three 00 1 power supply outputs. The transformer provides a I 5V. OV, I 5V 06 GREEN a.c. supply. This is used to drive both the IC AN'r METAL regulated + I 5V. OV, — I 5V and the 48V OF CASE outputs. The bridge rectifier REC1 converts the -15V 781 5 7915 CAPACITORS FROM CI TO C9 30V a.c across the secondary winding of ARE 250 OR MORE

8351,14 ARE METAL FILM 1% IC3 +48V IA OUT 52 C9 £ 01 ADJUST COMPONENTS CON 0 Ul COD -.I 220re C11 PG R 5 wow 1200 82 61,8 PO WER SUPPLY U" k IF,D2 Resistors • C13 R1, R2 1k (2 off) ImMIN 1 y • R3 3k 1% metal film C10 A D3 2200 a 4- Al 07 • R4 82 1% metal film RED Cl? • R5 6k8 220m Pr+---• 3 All 0 25W 5% carbon, except where LOUSY OUT IN 3k stated 01. PIN-OUTS OF REGULATOR OV • • Capacitors D1-04.1N4001 CAPACITORS FROM C9 ARE ALL 630 Cl . C2 1000p radial elect. 25V (2 off) C3, C4 C5, C6 100n disc ceramic Fig. 7. Circuit diagram fora m ains powered dual-supply and a 48V supply. (4 off) C7, C8 10p radial elect. 25V the transformer to a d.c. supply, and the more positive than the lower end and (2 off) centre tapping of the transformer provides current will now flow through diode D4. •C9, •C10, the OV output. Capacitors Cl and C2 Whenever the voltage on one side of a C11, •C1 2 220p radial elect. 63V smooth the d.c. and increase the average capacitor changes, there will be a cor- (4 off) voltage to about 42V from plus to minus, in responding change on the other side. Since • C13 10 radial elect 63V other words 21V above OV, and —21V the right hand side of CIO is now at + I 5V, 'C14 10p radial elect. 63V below OV. The positive regulator ICI main- as the lower end of the transformer secon- Semiconductors tains an accurate + I 5V output, while the dary becomes positive again, the right hand 01 to •D4 1N4001 50V 1A rect. negative regulator IC2 produces — I 5V. side of CIO is boosted to + 30V. Current diode (4 off) Capacitors C3 and C5 remove electrical flows through diode D3 causing the voltage D5 5mm yellow led. noise and enhance stability for the positive across C12 to rise to about 30V. By, similar D6 5mm green led. supply: C4 and C6 do the same for the reasoning the voltage across CI I will also 'D7 5mm red led. negative supply. Note that the way they are rise to 30V. giving a combined voltage IC1 7815 +15V 1A voltage drawn implies that they should be con- across CI I and Cl2 of 60V. Capacitor C13 regulator nected close to their respective i.c.s for provides additional smoothing and the IC2 7915 — 15V 1A voltage maximum effect. regulator steady 60V supply is fed to IC3 input. •IC3 TL783C adjustable high Capacitors C7 and C8 provide additional Integrated circuit IC3 is a high voltage voltage ( + 1.25V to smoothing and I.e.d.s D5 and D6 indicate regulator (type TL783C) which can be pro- + 125V) regulator correct operation of the respective positive grammed to supply any voltage from 1.25V REC1 W005 50V 1.5A bridge and negative outputs. Resistors RI and R2 to 125V, given a suitable input voltage. rectifier limit the current through the I.e.d.s to a In this arrangement the output voltage is safe level. given by: Miscellaneous Output voltage = 1.25 x (1 + R3/R4) Ti 6VA mains transformer P HA NTO M PO WER Using a value of 3 kilohm for R3 and 82 with twin 15V 3VA per The obvious way to produce a 48V d.c. winding secondaries ohms for R4, the output voltage is 46.9V. LP1 Mains panel mounting output is to use a separate mains trans- If a different voltage is required for the neon former. However it is possible to step up an phantom supply, simply change the value FS1, FS2 Panel mounting a.c. output by a cunning arrangement of R3 to produce the desired result. fuseholder and of capacitors and diodes, and this was Capacitor C14 ensures that a smooth 500mA fuse the method chosen. The array formed by supply is produced and I.e.d. D7 indicates (2 off each) capacitors C9 to Cl2 and diodes DI to D4 correct functioning of the phantom supply. Si Mains rated double-pole form a diode/capacitor pump, raising the toggle switch a.c. supply of 15V to about 60V. •S2 On/Off slide switch O MITTING (optional) It is vital that the OV supply is derived Printed circuit board available from from the centre tap of the transformer for P HA NTO M PO WER the EPE PCB Service, code 859; self- all power supply outputs. In other words, If phantom power supply is not required. adhesive p.c.b. mounting plastic stand- the d.c. outputs of + I5V, — I 5V and the following components can be ()mined off pillar (2 off); 3-core mains cable; + 48V are all measured with respect to the from: I.e.d. clip (3 off); small cable ties; mul- same OV output from the centre tapping of MAIN P.C.B.: Left Channel: tistrand connecting wire; solder tag: the transformer. R I -R3, Cl-C6. DI ,D4. solder etc.. The "lower" end of the mains trans- Note: Components marked with an as- A wire link must be inserted in place of terisk (•) may be omitted if phantom former secondary winding is connected to C3 and C5. power is not required. both capacitor C9 and CIO. When this end , Right Channel: is positive, current appears to flow through R8-RIO, C12-C17, D5-D8. C9 and CIO, and hence through diodes DI A wire link must be inserted in place of Approx cost and D3, causing C 1 1 and Cl2 to charge up. C14 and C16. guidance only £22 As the a.c. output reverses the centre POWER SUPPLY PCB tapping of the transformer will become R3-R5, C9-C14, IC3, DI-D4, D7, S2.

Everyday with Practical Electronics, February, 1994 159 C O NSTR UCTIO N - The two presets (if used) may be fitted as C O NSTR UCTIO N- MICR OP HO NE shown. If fixed resistors are used, they may be mounted vertically in the two pairs of P O WER SUPPL Y P REA MPLIFIER holes indicated by an X in Fig. 10. If ex- All components for the power supply The printed circuit board (p.c.b.) top- ternal potentiometers are preferred, solder except the mains transformer, fuses and side component layout and full size under- wires (or terminal pins) into the two pairs "phantom supply - switch S2 (if fitted), are side copper foil master pattern for the Mic. of holes indicated, and connect the other mounted on a separate p.c.b. This board is Preamplifier is shown in Fig. 8. This board ends of the wires to the pots.. keeping the available from the EPE PCB Service. code is available from the EPE PCB Service, wires as short as possible to avoid inter- 859. code 858. ference. Note that the pots. arc not nor- The power supply p.c.b. is constructed in The stereo pre-amp p.c.b. is quite com- mal volume controls because they cannot much the same way. taking care to fit the pact, and having fitted the i.e. sockets, it reduce the output to zero. diodes and bridge rectifier the correct way will be advantageous to begin with the Finally solder in terminal pins for all round, and the electrolytic capacitors as smallest components and work up in size. the external connections and insert the i.c.s before. The regulator i.c.s should be fitted Take care to fit the eight Zener diodes the into their sockets, ensuring that the notches with care, noting that each has a different correct way round with their light coloured line up correctly. pin layout. bands (which indicate the cathode (k)) aligned as shown in Fig. 8.

The electrolytic capacitors must also be LEFT MIC fitted with the correct polarity: note that OUT OF PHASE.* the negative side is indicated on each capacitor body and the positive side has IN PHASE the longer lead. The I µF (and smaller) GROUND GROUND capacitors are not polarised and may be LEFT OUTPUT fitted either way round. GROUND RIGHT MIC OUT OF PHASE RIGHT OUTPUT

IN PHASE

GROUND BALANCED STEREO PRE-A MP Resistors •R1, 'R8 100 (2 off) 'R2, •R3, •R9, • R10 6k8 (4 off) POWER SUPPLY R4, R5, R11, R12 10k (4 off) See R6, R13 309 (2 off) R7, R14 33 (2 off) M OP All 0.6W 1% metal film TALK Page Potentio meters VR1, VR2 100 horizontal Cermet preset (2 off)

Capacitors 'Cl, 'C3, 'C5, *C12, *C14, *C16 47µ radial elect. 63V (6 off) •C2, 'C4, *C 6, C10, •C13, *C15, "C17, C21 100n disc ceramic d141-3 W .31W LIOLNSS I (8 off)

C7, C18 220p ceramic (2 off) Fig. 8. Printed circuit board component layout and full SIZe. p.c.b. foil pattern C8, C9, C19, C20 1ppolylayer (4 off) C11, C22 220p radial elect. 25V (2 off)

Semiconductors • D1 to • D8 12V 0-5W Zener diode (8 off) IC1, IC2 SSM2017 audio preamplifier (2 off)

Miscellaneous Printed circuit board available from the EPE PCB Service, code 858 (pre- amp); metal screening box, size 75mm x 55m x 25mm; console case (with metal sloping front panel), size 190mm x 100mm x 72/33mm; 8-pin d.j.!. socket (2 off); output socket, phono (2 off); input socket, XLR -audio (2 off) - see text; terminal pins; twin screened cable; multistrand connecting wire; solder etc. Note; Components marked with an asterisk (•) may be omitted if phantom power is not required, but note that two wire links must be inserted as described in the text.

Approx cost guidance only £24 plus case The preamplifier removed from the screening box showing the cable entry cut out.

1 6(1 • Everyday with Practical Electronics, February, 1994 The I.e.d.s D5 and D6 are likely to be mounted on the front of the case, and will BLUE AYELLOW need to be connected via leads and terminal TO T1 pins. Note that the I.e.d.s share a common 'Cl

OV pin. There is provision on the p.c.b. for C3 fg- " 'RI If I 05a D7 series resistor (R5). However, if switch CO YELLOW

S2 is fitted to enable the phantom power + C5 -1- +15v C7( ) (:)C supply to be switched off, it is more con- 0 V venient to connect the led. series resistor ra, -15 v R5 between S2 and the led. as shown in c4L c° 111, R 2 GREEN06k the photograph. 111.•

INTER WIRING 07 a RED The external wiring to and from the A J off-board components may be carried out + 0 T • AL. temporarily for testing, or permanently. in + 46 V IC3 which case the transformer etc. will need to • * CONNECTION NOT NEEDED be fitted into the case. The two ends of IF S2 IS FITTED the transformer secondary should be con- nected to the p.c.b. via fuses as shown in Fig. 13. The a.c. mains supply leads should ONLY FIT R5 HERE IF YOU DO NOT REQUIRE 52 be connected as shown having established exactly where the transformer and other main components will be located - or better still - fixing these items before completing the wiring. Remember the im- portance of neat wiring both for safety, and to reduce the risk of int aference. TESTING THE P O WER SUPPL Y DUE TO THE PRESENCE OF MAINS VOLTAGES, CARE MUST BE TAKEN WHEN TESTING THE POWER SUPPLY. The power supply should he tested using a roltnwter, hefiwe connecting it to tlw pre- amp. Connect a voltmeter to the OV and + I 5V output pins. Switch on the supply and check for a correct reading. If the read- ing is not correct, switch off immediately Fig. 9. Power supply p.c.b. component layout and full size copper foil pattern. and check for faults. If all is well, check the - I 5V supply. and the + 48V outputs.

ALTERNATIVE POTS PRESETS VR1 & VP? ALTERNATIVE TORIODAL TRANSFORMER

SHAFT YELLO W TO OV UPWARDS ON PCB BLUE GREY TO F S2 Ti RED TRANSFORMER TO PSI

OUT OF PHASE_ — B

IN PHASE 4.-- 11 • —•--e. GROUND ORANGE TO 2405 GROUND 4/-+-k/i 110—.--0.- LEFT OUTPUT ORANGE MAINS

.11- -kk• GROUND

OUT OF PHASE *0—,-,-1 9 111—..--••• RIGHT OUTPUT

IN PHASE 240V AC

GROUND 71 STANDARD TRANSFORMER

-15V OS 415V

ALL ZENER DIODES. DI TO DR ARE - ANODE 05 , e CATHODE TOWARDS THE BOTTOM YELLO W

CATHODE

MICROPHONE CONNECTIONS 06 GREEN GROUND VIE WED FROM FRONT IPLUGI SIDE

OUT OF PHASE 07 XLR RED

CONNECTION NOT NEEDED IF 52 IS FITTED IN PHASE ONLY FIT R5 HERE IF YOU OUT OF PHASE DO NOT REQUIRE 52 05- 07

FL 11,- JACK n - -\ • CH.-- IN PHASE # Fig. 11. Interwifing details for the GROUND power supply and alternative transformer SHORT Fig. 10. Interwiring and microphone connec- LONG wiring. tion details for the pre-amp board

Everyday with Practical Electronics, February, 1994 161 similar, but if compared with the signal from the generator, it should be out of phase. Repeat the same tests with the right- hand channel. It may be helpful for testing, or for use when balanced microphones are not avail- able, to make provision for the use of unbalanced microphones. This may be accomplished by connecting the inverting input (leading to pin 2) to OV. The microphone signal must then be connected to the non-inverting input, and the microphone screen to OV. FA ULT FINDING llopefillly. one or other Of not both!) of the stereo halves of the circuit will work. If not, check the power supply connections and diodes. Measure the voltage across pins 7 and 4 of each i.c. You should obtain a reading of about 30V. The voltage across pins 7 and 5. (and 5 and 4) should be about I 5V. Check that the four electrolytic capacitors are fitted the correct way round. If using balanced microphones check that the signal is passing through your plug and socket arrangement successfully. The Completed preamplifier showing wiring to front panel le.ds and on/off switch. The pin numbers are often marked on the XLR position of the ':screening box" is also shown. sockets to avoid confusion if they are viewed from the wrong direction. If the power supply is not work- Testing may be accomplished using ing correctly, switch off immediately in a signal generator and oscilloscope (if case components particularly electrolytic available) or by simply connecting a THE CA SE capacitors - are the wrong way round. microphone and listening to the output via Assuming that the pre-amp p.c.b. is to be Having checked this. ascertain that the an amplifier/speaker, or headphones. If a housed in the same case as the power sup- voltage across Cl and C2 is about 2IV (it signal generator is used, ensure that the ply. it is wise, if not essential to house it may be up to. say 10 per cent more. signal is attenuated (turned to a low in a separate inner metal case to provide depending upon the regulation offered by output) or the circuit will be overloaded. screening - see photos and Fig. 12. The the transformer). The reading across resulting in distortion. metal case should be linked to OV (ground). capacitor CI3 should he about 60V. Switch on the power supply. and apply a When fitting the p.c.b. into the case, ensure signal to the non-inverting input (pin 3) of. that no parts of the circuit are touching the TESTING THE say the left-hand channel, not forgetting metal - even if painted. to link the OV (ground) terminal to the If presets are used, try to install the p.c.b. P RE-A MP so that the presets may be adjusted via Having established that the power sup- input signal ground. Connect the output to the oscilloscope, again, not forgetting small holes drilled in the inner case which ply unit is providing the correct voltages. also line up with similar holes drilled in the it can be linked to the pre-amp p.c.b. the OV side. A suitable wave trace should be observed. Adjust the presets or poten- front panel. The prototype was constructed Reasonably long wires should be used since in this way and case layout and front panel the pre-amp will be housed in a metal tiometers if necessary. Now apply the input signal to the invert- layout can be seen in the photographs. The "screening— case lilted inside the main ing input (pin 2). The wave trace will look interwiring between boards and off-board case. components is shown in Fig. 13. The input sockets will normally be XLR types designed for balanced microphones. Alternatively. "stereo" jacks are sometimes used. The stereo output should be via a POWER SUPPLY PC B pair of phono sockets, or a single stereo 06 D5 jack socket. (or both for flexibility!). The outer case specified is identical to the case which housed the I W amplifier and tone control i.e. a smaller version of the SLOT FOR CABLES 480 PHAN TOM Stereo Mixer case. All the parts will fit into POWER this case, but care is required with the layout. The transformer employed was the 42 smallest 6VA type; however the larger 06 0 0 0 I 2VA will just fit (if screwed to the back of the case rather than the base), and the I 5VA toroidal type will fit reasonably easily. 07 Note that the transformer is fitted as far

05 away from the sensitive inputs as possible. The pre-amp p.c.b. is mounted inside a SCREWS HOLDING BASE TO LID metal box which provides complete screen- OR LEAD JOINED TO ing. This may not be essential, but there METAL BOX B HENCE LONG TO FRONT PANEL is little point in constructing a very high quality amplifier and then spoiling its per- formance with induced hum. Begin by drilling holes in the plastic body of the main case for the mains cable, neon, switch SI, two fuseholders, two phono

TOP sockets, optional power output socket, and REAR OF FRONT PANEL XLR (or jack) input sockets. The use of masking tape to help with marking, and to provide a non-skid surface when drilling is Fig 12 Wiring to components mounted on the rear of the front panel. a great advantage.

I 62 Everyday with Practical Electronics, February, 1994 WIRE LINK REAR OF 240v MAINS POWER OUTPUT

FS I F S 2

POWER SUPPLY PC B REAR OF MAINS +48V (UPSIDE DOWN I PHONO OUTPUTS CABLE

LEFT RI BHT OV TO PRE-AMP., • L E D 06 TRANSFORMER PC B WHITE RED OV TI

SL E D 05 +15 EARTH

OV

TWIN SCREENED CABLE

TWIN SCREENED CABLE LEFT OUT OF PHASE

IN PHASE GND \\ SCREEN LEFT 'I GROUND OUTPUTS WIRELINK INPUTS GNO W SCREEN RIGHT OUT OF PHASE (OUTER LAYER I RIGHT •••• WIN PHASE

TWIN SCREENED ',GROUND CABLE 1 +15V -1-413V i Soy -15 1 WIRELINK

XLIt'S VIE WED FROM REAR TO POWER SUPPLY P.C.B.

(EP.1.116

Fig. 13. Intent/1ring between boards. Completed pre-amp showing input and output socket A front panel layout guide as shown in positions. the photographs. Make two copies of the panel, one as a template for drilling and the other as a front panel cover. If possible. the front panel cover can be.inverted so that the markings are in white on a black back- ground. Drill all the holes required in the metal and drill two M2 front panel. The slide switch (S2) may be holes straight through awkward, since a rectangular hole is re- both the front panel and quired: a round toggle switch will do just as metal case lid. The temporary well. Do not forget the M2 holes required bolts may now be undone, and to mount the small metal inner case which M2 nuts and bolts used to fix the houses the pre-amp. metal box lid against the front panel. This method will ensure that the sets of M ETAL INNER CA SE gain adjust holes are in perfect alignment Before v‘orking on the metal box, check The M2 bolts should be countersunk to the p.c.b. will tit inside. Prepare the small leave a smooth surface on the top of the metal box by cutting a grove in one side as front panel. shown in photographs to allow the cables Note that when in place, the gain adjust to enter the box. Alternatively a cable entry holes are central in the front panel, but the hole could be drilled; however this makes small metal box is off centre — allowing the final connections more difficult since more space for the transformer. When the the wires first have to be threaded through front panel is placed on the plastic box Finally the front panel may be finished this hole. base, the metal box will fit neatly inside. by covering the copy card with book Three or four small (M2) holes should be covering material, then making holes for drilled in the pre-amp p.c.b., and in the FINAL WIRING the I.e.d.s and gain adjust openings by small metal box base so that M2 nuts and Link the XLR sockets with the pre- means of a cork borer. A craft knife may be bolts may be used to fasten the pre-amp in amp p.c.b. using twin screened cable for used to make the rectangular hole for place. Ensure that the p.c.b. is well clear of each channel. The convention is screen switch S2. Position the front cover over the the base by using insulated "spacers" such for ground (OV), red for out-of-phase, the panel, pierce the corners to allow the front as grommets. M3 nylon nuts etc. Also, other colour (e.g. white) for in-phase. The panel screws to enter and screw, gently, make sure that the p.c.b. is sufficiently clear output signal is linked via one length of into place of the screws which fasten the lid of the twin screened cable using the convention small box. screen for ground, red for right, other FINAL TESTING Having fixed the p.c.b. to the base of the colour for left. The power supply connec- Noss for the tinal test! Connect the metal box, mark and drill two holes in the tions should be completed, noting that a output of the Balanced Microphone lid so that a screwdriver may be inserted to single OV connection is sufficient. Preamplifier to a power amplifier, switch turn the presets. Now fix the metal box lid Carefully lift the small metal box base on and check for hum or other noises. If a firmly against the metal front panel so that so that it fits against its lid which is at- dynamic microphone is used, ensure that the all the preset gain control holes are in line. tached to the front panel. Once in place phantom power supply is switched off, Nuts and bolts may be temporarily placed use the self-tapping screws provided with Connect the microphone(s) and check that through these holes to achieve this. the box to fix the base into the lid. Check the system works correctly and that the Move the p.c.b.s to a safe distance to again that these screws do not touch the gain can be adjusted by means of the gain avoid contamination with metal filings, p.c.b. presets.

Everyday with Practical Electronics, February, 1994 163 FRA ME-UP Probably the best "Abrafile" for making cut-outs is the framed variety. This is basically just a junior hacksaw frame, but it has a rather "taller" frame than a normal junior hacksaw. It looks Techniques rather like a cross between a junior hacksaw and a coping saw. This tool actually comes complete with a normal 6 inch hacksaw blade, but it is the other blade supplied with the frame that is of ACTUALLY 20 NO more interest. This is a tension file blade, which is basically just a 6 inch long "Abrafile" which fits into the - by Robert Penfold frame in exactly the same way as an ome months ago the topic of large The characteristic which makes ordinary hacksaw blade. Scut-outs in cases and panels was "Abrafiles" so useful for making There is an obvious disadvantage to a covered in Techniques. This is a subject cut-outs is their relative coarseness. An framed file in that it cannot reach into which might not be expected to bring ordinary "needle" file can be used to the middle of large panels. However, much of a response from readers, but it make cut-outs, but progress is very the high access frame supplied with the did result in several letters offering use- slow even when working on relatively file has a reach of about 90 millimetres, ful suggestions. soft materials such as aluminium and which is adequate for all but the largest We are always interested in readers plastics. of projects. The main advantage of reactions to practically anything related These files are made primarily for having the frame is that it enables to the magazine, and my thanks are due smoothing purposes, and not for much more force to be used, which to those who wrote in on this occa- making long cuts. It is for this reason means that large cut-outs can be com- sion. I will always endeavour to try out that I generally suggest making a ring pleted very quickly. I also find that I can any useful tips and, where appropriate, of small holes first, and then using a make cuts with a greater degree of pass them on to others via this feature. "needle" file to join the holes. A large precision when using the framed ver- I think it is worth making the point half-round file can then be used to tidy sion of an "Abrafile". though, that no matter how good a things up. This may seem to be a The file is only about 1-5 millimetres method of doing something might be, roundabout way of doing things, but it in diameter. This means it can be used it is of little interest to others if it re- is far quicker than producing the to produce quite intricate cut-outs, al- quires access to expensive equipment cut-out using only the "needle" file. though it is less good in this respect or materials that are only available to "Abrafiles" are designed for general than a fretsaw. The .frame also provides those in some trade or other. cutting and filing purposes, and will far less reach than a fretsaw. on the cut through aluminium and most plas- other hand, the "Abrafile" has a big FLEXIBLE FRIEND tics at a reasonable speed. They can be advantage in that it is not necessary to Most of the letters on the subject used to cut in any direction at any time, stop every thirty seconds to replace a of cut-outs mentioned "Abrafiles". I broken blade! and can therefore be used to cut quite used these a great deal some years complex shapes. They can also be used ROTARY FILES ago, but have found them impossible in the middle of large panels without There is another variation on the to obtain locally in recent years. How- any difficulty. "Abrafiles" are available ever, they are still available, and if they "Abrafile" theme in the form of rotary in three diameters (1/8, 3/16, and 1/4 files. These are short round files which prove to be unobtainable locally they inch), but it is only the smallest size are supplied in packs of five. The pack are available direct from mail order which is of use in the current context. tool suppliers. contains files of five different diameters Packs of five "mouse-tail", files are ranging from 1/8 inch to 1/4 inch. "Abrafiles" look very much like or- also available. These are basically just a They are all double-ended, and are dinary round "needle" files, but they scaled-down version of the normal designed for use in power drills. have the unusual attribute of being type, having a diameter of about 1-5 For those who prefer to avoid the bendable. The idea is that these files millimetres. They are well suited to exertion of producing large cut-outs can be bent into shapes that enable small cut-outs, particularly where intri- them to reach the awkward parts that by hand, these rotary files would seem cate shapes are required. As only a very other files cannot reach. This is no to offer an ideal solution. This type of limited amount of pressure can be tool is best suited to a drill that is doubt very useful for model makers applied using such thin files, they cut and many other users, but I cannot mounted in a proper stand. It is then relatively slowly, and are less than ideal not too difficult to make cut-outs honestly say that I have ever found for large cut-outs. They are not recom- with reasonable precision, but I have this flexibility to be a useful property mended for use with steel or any very always found progress to be very when building electronic projects. hard materials. slow using any form of rotary file. These "Abrafiles" do not seem to be an exception, and they are better suited to their primary purpose of deburring and enlarging. When used 44. for these purposes a handheld drill is perfectly satisfactory provided you proceed carefully. A useful point to remember is that it is generally easier to have a panel clamped in a vertical position when working on it using something like an "Abrafile" or fretsaw. It is more com- fortable and therefore less tiring work- ing on a panel that is positioned verti- cally. Also, you can orientate every- thing so that you are not casting a shadow over the workpiece, making it easier to see what you are doing. The end result is usually a more precise Various types of Abrafile and a "tank cutter". cut-out and a lot less backache.

164 • Everyday with Practical Electronics, February, 1994 "Abrafiles" and tank cutters are available from Axminster Power Tool 40673 BF988 Centre, Chard Street, Axminster, (Base View) (Top View) Devon, EX13 5DZ (Tel. 0297 33656). Gate 2

TANKED-UP Drain—\ , // —Gate 2 Most constructors make large round cut-outs (for something like a moving Gate 1 Drain coil panel meter) using a fretsaw, "needle" file, etc. Most of the quick ways of making round holes are not Source--- / Gate 1 applicable to holes of about 40 mil- Source limetres or more in diameter. Even if you can find a chassis punch of the required size, it is likely to be extremely expensive, and it will only make a hole Fig. 1. Connections for the 40673 and BF988. of one size. The next time you need to (just a few r.p.m. in fact). They should not in the current catalogue. However, cut a large diameter hole it might be be used in a brace, and not in any the new Electrovalue catalogue does necessary to buy yet another chassis form of power drill, or even in a heavy include a similar device, the BF988. punch. duty hand-drill. The workpiece must Like the 3SK88, this is a surface There is a tool which seems to be very securely clamped in place, and mount device. On the face of it there solve the problem of producing large the cutting should be done very slowly are problems in using it in place of a diameter holes, and it is called a "tank and carefully. It takes so little time to 40673, which has four normal leadout cutter". I presume that its intended cut holes using this device that rushing wires. purpose is making inlet and outlet things is completely pointless anyway. In reality there is no difficulty in fit- holes in water tanks, etc. It is a The hole produced is nothing like as ting a 3SK88 or a BF988 into a printed delightfully simple idea, and it is based neat as one made using a chassis circuit layout designed for a 40673 or on a twist drill of about 6 millimetres or punch. The cut is not actually that similar device. As can be seen from the so in diameter. There is an L-shaped rough either, but it does require some pinout diagrams for these components cross piece which has the cutting blade deburring. Therefore, it is a good idea (Fig.1), they have what is basically the at one end. This is adjustable, and to cut a hole that is about one mil- same pinout arrangement. enables holes from (typically) about 25 limetre too small, to allow for some The flat tags of the BF988 can be to 100 millimetres in diameter to be cut. slight enlargement when it is deburred. carefully bent through right angles so In order to make a hole you first set One of the cheaper tank cutters that the device can be fitted straight the blade for the right diameter. Then a is more than adequate for cutting onto a printed circuit board designed centre punch is used to make an inden- through thin sheet aluminium. These for the 40673. There should be no need tation in the panel at the centre of the cost around £7, which has to be to enlarge the holes in the circuit board required cut-out. Next the drill part of considered a real bargain considering since the tags are less than one mil- the cutter is used to drill right through the ease with which holes can be limetre across. Anyone feeling adven- the panel so that the cutting blade can made, and the wide range of sizes that turous could try surface mounting the be brought down onto the panel. You can be accommodated. Using one of BF988 upside-down on the underside then just carry on drilling, except the these tools puts quite a lot of strain on of the board. drill now just acts as a spindle to keep the workpiece, so it is probably best The BF988 seems to work well as a the cutting blade on the correct circle. not to try one on a plastic case unless substitute for the 40673, etc. in short It is the blade which actually does you proceed extremely carefully and wave receivers, but I have not tried it the cutting. Working on an 18 s.w.g. gently. beyond 30MHz. Having tried a number aluminium panel it literally takes no of different dual-gate MOSFETs over more than a few seconds to make M OSFETs the years, I find the consistency of a hole of about 50 millimetres in The subject of dual-gate MOSFETs these devices rather surprising. Chang- diameter. and their virtual non-availability was ing from one type to another seems to discussed in an Actually Doing It IMPORTANT POINTS produce no significant change in article some time ago. Two or three performance, which is not the case Although cutting large holes using a readers pointed out that the 3SK88 with bipolar r.f. transistors. Swapping tank cutter is very easy, there are a few was still available from Maplin. Un- one of these for a different but important points to bear in mind. First fortunately, although it was in the supposedly similar device often gives and foremost, these tools are only in- Maplin catalogue at that time, it was either a marked loss of performance, or tended for operation at very low speeds definitely no longer available, and it is gross instability.

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Everyday with Practical Electronics, February, 1994 165 VIDEOS ON ELECTRONICS A range of videos designed to provide instruction on electronics theory. Each video gives a sound introduction and ground- ing in a specialised area of the subject. The tapes make learning both easier and more enjoyable than pure textbook or magazine study. They should prove particularly useful in schools, colleges, training departments and electronics clubs as well as to general hobbyists and those following distance learning courses etc. VT201 to VT206 is a basic electronics course and is designed to Now for the digital series of six videos. This series is designed be used as a complete series, if required. to provide a good grounding in computer technology. VT201 54 minutes. Part one; D.C. Circuits. This video is an absolute VT301 56 minutes. Digital One begins with the basics as you learn about must for the beginner. Series circuits, parallel circuits. Ohms law, how to seven of the most common gates which are used in almost every digital use the digital multimeter and much more. Order Code vr2o1 circuit, plus Binary notation. Order Code VT301 V1202 62 minutes. Part two; A.C. Circuits. This is your next step in understanding the basics of electronics. You will learn about how coils, VT302 55 minutes. Digital Two will further enhance your knowledge of transformers, capacitors, etc are used in common circuits. digital basics. You will learn about Octal and Hexadecimal notation groups, flip-flops, counters, etc. Order Code VT302 Order Code VT202 V203 57 minutes. Part three; Semiconductors. Gives you an exciting VT303 56 minutes. Digital Three is your next step in obtaining a solid look into the world of semiconductors. With basic semiconductor theory. understanding of the basic circuits found in todays digital design. Gets Plus 15 different semiconductor devices explained. Order Code VT203 into multiplexers, registers, display devices, etc. Order Code VT303 VT204 56 minutes. Part four; Power Supplies. Guides you step by step VT304 57 minutes. Digital Four shows you how the computer is able to through different sections of a power supply. Order Code VT204 communicate with the real world. You will learn about digital to analogue VF205 57 minutes. Part five; Amplifiers. Shows you how amplifiers work and analogue to digital converter circuits. Order Code VT304 as you have never seen them before. Class A. class B, class C. op.amps. VF305 56 minutes. Digital Five introduces you to the technology used in etc. Order Code VT205 many of todays memory devices. You will learn all about ROM devices VT206 56 minutes. Part six; Oscillators. Oscillators are found in both and then proceed into PROM. EPROM, EEPROM, SRAM, DRAM. and linear and digital circuits. Gives a good basic background in oscillator MBM devices. Order Code VT305 circuits. Order Code V206 VT306 56 minutes. Digital Six gives you a thorough understanding in the By the time you have completed V206 you have completed the basic basics of the central processing unit and the input/output circuits used to electronics course and should have a good understanding of the opera- tion of basic circuit elements. make the system work Order Code V1306

By now you should have a good understanding of computer technology and VCR MAINTENANCE what makes computers work This series is also invaluable to the computer vno2 84 minutes: Introduction to VCR Repair. Warning, not for the technician to understand the basics and thus aid troubleshooting. beginner. Through the use of block diagrams this video will take you through the various circuits found in the VHS system. You will follow Each video uses a mixture of animated current flow in circuits plus the signal from the input to the audio/video heads then from the text, plus cartoon instruction etc., and a very full commentary to get heads back to the output. Order Code v1102 the points across. The tapes are imported by us and originate from VT103 35 minutes: A step-by-step easy to follow procedure for profes- sionally cleaning the tape path and replacing many of the belts in VCR Educational Products Co, an American supplier. most VHS VCR's. The viewer will also become familiar with the various parts found in the tape path. Order Code vrlo3 (All videos are to the UK PAL standard on VHS tapes)

ORDERING: Add El p&p per order for UK orders. OVERSEAS ORDERS: Add £2 postage for countries in the EEC. Overseas orders outside the EEC countries send £24.44 per tape (price less VAT) plus £3 per tape airmail postage (or £3 per order surface mail postage). All payments in £ sterling only (send cheque or money order drawn on a UK bank Visa and Mastercard orders accepted — pleae give card number, card expiry date and cardholders address if different to the delivery address. Send your order to: Direct Book Service, 33 Gravel Hill, Merley, Wimborne, Dorset BH21 1RW (Mail Order Only) Direct Book Service is a division of Wimbome Publishing Ltd., publishers of Everyday with Practical Electronics. Tel: 0202 881749. Roc 0202 841692 £29195 IPHOTOTRANSISTOR, each inc. VAT

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Everyday with Practical Electronics, February, 1994 DIRECT Special Everyday Electronics Books 1 ELECTRONICS TEACH-IN No 3- EXPLORING Building with Vero; Project Development for GCSE: Get- ELECTRONICS (published by Everyday Electronics) ting your Protect Working; Guide to Printed Circuit Boards; O wen Bishop Choosing and Using Test Equipment - The Multimetec Another EE value for money publication aimed at students The Oscilloscope, PS Us. Logic Probes. Digital Fre- of electronics The course is designed to explain the work- quency Meters. Signal Generators, etc; Data - Circuit BOOK ings of electronic components and circuits by involving Symbols: Component Codes, Resistors. Identifying Com- the reader in experimenting with them The book does not ponents, Capacitors. Actually Doing It Understand- contain masses of theory or formulae but straightforward ing the Circuit Diagram. Component Codes. Mounting explanations and circuits to build and experiment with circuit boards and controls. Understanding Capacitors; Exploring Electronics contains more than 25 useful Projects - Lie Detector, Personal Stereo Amplifier, Digi- projects. assumes no previous knowledge of electronics tal Experimentsr's Unit; Quizmaster: Siren Effects Unit; SERVICE UV Exposure Unit; Low , cost Capacitance Meter; Personal and is split into 28 easily digestible sections 88 pages (A4 size) Lan all £2 45 Radio. The books listed have been 88 pages (A4 sae) germigwrgringi £2.95 ELECTRONICS TEACH-IN No.4 selected by Everyday with INTRODUCING DIGITAL ELECTRONICS (published ELECTRONICS TEACH-IN No.6 by Everyday Electronics) DESIGN YOUR OWN CIRCUITS Practical Electronics editorial Michael J. Cockcroft (Published by Everyday with Practical Electronics) Although this book is primarily a City & Guilds Introduc- Mike Tooley BA. staff as being of special in- tory level course (726/301), approximately 80% of the in- This book is designed for the beginner and experienced formation forms a very basic introduction to electronics in reader alike, and aims to dispell some of the mystique as- terest to everyone involved general, it therefore provides an excellent introductory text sociated with the design of electronic circuits. It shows how for beginners and a course and reference book for GCSE even the relative newcomer to electronics can, with the right in electronics and computing. students approach. design and realise quite complex circuits. Full details on registering for C&G assessment, details of Fourteen individual pc .b modules are described which, They are supplied by mail order assessment centres, components required and information with various detailed modifications, should allow anyone on the course in general are given to design and construct a very wide range of different The City & Guilds introduction to module 726/301 projects. Nine "hands-on" complete DIY projects have direct to your door. Full order- reads "A candidate who satisfactorily completes this also been included so readers can follow the think- module will have a competence to identify basic com- ing behind design, assembly, construction, testing and ing details are given on the last ponents and digital integrated circuits and connect them evaluation, together with suggested mods' to meet together to form simple working circuits and logic units' individual needs. The practical projects have each been book page. For another selec- This provides an excellent introduction to the book designed to stand on their own as complete items of 112 pages (A4 size) alnalliEn illa £2.95 equipment. PC B.s for all the modules arid projects are tion of books see next month's available by mail order b ook ELECTRONICS TEACH-IN No.5 GUIDE The subjects covered in each chapter of the b k are: issue. TO BUILDING ELECTRONIC PROJECTS Introduction and Power Supplies. Small Signal Amplifiers; Published by EVERYDAY ELECTRONICS Power Amplifiers. Oscillators; Logic Circuits; Timers; Due to the demand from students, teachers and hobbyists Radio; Power Control; Optoelectronics we have put together a range of articles from past issues of The nine complete constructional projects are . Ver- ELECTRONIC PROJECTS- BOOK 1 Everyday Electronics that will assist those involved with satile Bench Power Supply; Stmple Intercom, Bench Published by Everyday Electronics in association the construction of electronic projects Amplifier/Signal Tracer; Waveform Generator: Electronic with Magenta Electronics. The book contains the complete Project Development Die; Pulse Generator; Radio Receiver, Disco Lights Con- Contains twenty of the best projects from previous issues for GCSE series troller. Optical Communications Link. of EE each backed with a kit of components The protects Contents: Features - First Steps in Project Building, 136 pages p rnal nrink fil £3.45 are Seashell Sea Synthesiser, EE Treasure Hunter, Mini Strobe, Digital Capacitance Meter, Three Channel Sound to Light, BBC 16K Sideways Ram. Simple Short Wave Radio, Insulation Tester. Stepper Motor interface, Eprom Eraser, 200MHz Digital Frequency Meter, Infra Red Alarm. st sack „ ELECTRONICS EE Equaliser Ioniser, Bat Detector, Acoustic Probe, Mains IC-RECTA ataCT Tester and Fuse Finder. Light Rider - (Lapel Badge, Disco 01 \163 72. Terl,lc ETLEECATRoCHNI: Lights, Chaser Light). Musical Doorbell, Function Generator. ITEMCNI-1 GUIDE TO BUILDINGpNr Tilt Alarm, 10W Audio Amplifier. EE Buccaneer Induction Balance Metal Detector. BBC Midi Interface, Variable Bench EXPLoRiN a. Power Supply. Pet Scarer. Audio Si nal Generator ;''•11, .11VOA r 1.. C11111 .1 . 128 pages (A4 size) Islet llelãl £2.45

. ELECTRONICS TEACH-IN 873 89 w dorclifts INTRODUCING MICROPROCESSORS Mike Tooley BA (published by Everyday • 8.u,rex no pre,ous Electronics) -u sç ta2 Mat A complete course that can lead successful readers to the award of a City and Guilds Certificate in Introductory :••citn, • niir' D rai n corairtsixeY we.' Pots'''. Microprocessors (726/303) The book contains every- Ar,R CPrct, flru l rug er cvrtvnt Oat thing you need to know including full details on register- ing for assessment, etc Starting with basic terminology, City and Gtaids • integrated circuits, logic families and numbering systems Cortmione Course • the text builds in stages, with revision and assessments built in, up to programming, languages, flow charts, etc The course is ideal for the newcomer to the subject 80 pages (A4 size) relf111111211111SillatLia £2.45 Co mputers and Co mputing

HO W TO CHOOSE A SMALL BUSINESS AN INTRODUCTION TO 613000 ASSE MBLY book has also been designed to be circular. which means CO MPUTER SYSTE M LANGUAGE that you don't have to start at the beginning and go to D. Weale R. A. & J. W. Penfold the end. This book is for anyone intending to buy an IBM com- Obtain a vast increase in running speed by writing pro- The book explains: How to write customised batch patible computer system, whether it is their first system or grams for 6800 based micros such as the Commodore files which allow you to display what you want on your a replacement There are sections on hardware, applica- Amiga. Atari ST range or Apple Macintosh range etc in screen, and in the form and order you want it, instead of tion and systems programs and how to actually make your assembly language It is not as difficult as one might think being forced to use the DOS prompt on a blank screen. choice as well as sections on the law, ergonomics and a and this book covers the fundamentals How to design and set up a fast interachve and profes- glossary of common terms 112 pages = N W £2.95 sional looking menu system, so that you or anyone The text contains many useful tips and some warnings else can run utility applications or commercial software (which could save much effort and expense) THE ART OF PROGRA M MING THE 2X SPECTRU M packages easily. How the ANSI.SYS display and key- /14 pages Lagazuggaa £4.95 M. James, B.Sc.. M.B.C.S. board commands can be used to position the cursor It is one thing to have learnt how to use all the Spectrum's on any part of the screen, change the intensity of the commands and functions, but a very different one to be displayed characters or change their colour. How the UNDERSTANDING PC SPECIFICATIONS able to combine them into programs that do exactly what Edit screen editor or the Edlin line editor can be used R. A. Penfold you want them to This is just what this book is all about - to enter ESCape (ANSI.SYS) commands into simple If you require a microcomputer for business applications. teaching you the art of effective programming with your ASCII files to allow control of both your screen display or a high quality home computer, an IBM PC or compatible Spectrum and your printer. How to control the operation of the is often the obvious choice They are competitively priced, 144 pages ISZEZMIEUILLUE £2.50 two main types of printers in use today. Epson com- and are backed up by an enormous range of applications patible dot matrix and HP compatible laser printers. programs, hardware add-ons, etc The main difficulty for A CONCISE INTRODUCTION TO MS-DOS How to use several useful routines, such as moving and the uninitiated is deciding on the specification that will N. Kantaris finding files, protecting files from accidental erasure. a best suit his or her needs PCs range from simple systems This guide is written with the non-expert, busy person in simplified backup process, a screen saver, and a disc of limited capabilities up to complex systems that can mind and, as such, it has an underlying structure based on cataloguing system. happily run applications that would have been considered -what you need to know first, appears first" Nonetheless, The Debug program and how it can be used to create, beyond the abilities of a microcomputer not so long ago ft the guide is also designed to be circular, which means that see and change the contents of any file, including those would be very easy to choose a PC system that is inade- you don't have to start at the beginning and go to the end of programs written in assembler code. This includes quate to run your applications efficiently, or one which The more experienced user can start from any section how to find your way around the names and tasks goes beyond your needs and consequently represents poor The guide covers versions 30, 3 1 and 3 2 of both PC- of the CPU registers and the meaning of some simple value for money DOS and MS-DOS as implemented by IBM and other assembler mnemonics. manufacturers of -compatible" microcomputers, including This book explains PC specifications in detail. and the 182 pages W I: MTV £4.95 subjects covered include the following Differences the AMSTRAD PC's It covers both floppy disc-based between types of PC (XT. AT, 80386, etc), Maths systems and hard disc-based systems co-processors, Input devices (keyboards, mice, and 64 pages W EIV EZUSI U M £2.95 AN INTRODUCTION TO CP/M digitisers). Memory, including both expanded (EMS) and R. A. Penfold extended RAM RAM disks and disk caches, Floppy disk M AKING MS-DOS WORK In order to run and use programs operating under CP/M drive formats and compatibility: Hard disk drives (includ- FOR YOU it is not essential to have an understanding of the ing interleave factors and access times). Display adaptors, N. Kantanis 8. P. R. M. Oliver system, but a reasonable knowledge of the subject can including all standard PC types (CGA, Hercules, Super certainly be of immense help when minor problems VGA. etc), Contains everything you need to know if you This book was written with the busy person in mind and, occur, and also in fully exploiting the possible potential can't tell your EMS from your EGA! as such, it has an underlying structure based on -what of the system This book tells the story! 104 pages D EIMI EU M ati £3.96 you need to know first, appears first Nonetheless, the 84 pages rial = alia n £2.95

Everyday with Practical Electronics, February, 1994 167 A udio and Music Project Building

ACOUSTIC FEEDBACK - HO W AN INTRODUCTION TO LOUDSPEAKERS AND HO W TO GET YOUR ELECTRONIC PROJECTS TO AVOID IT ENCLOSURE DESIGN W ORKING Feedback is the bane of all public address systems While V. Capel R A Penfold feedback cannot be completely eliminated, many things can This book explores the various features. good points and We have all built projects only to find that they did not be done to reduce it to a level at which it is no longer a snags of speaker designs It examines the whys and work correctly or at all. when first switched on The aim problem wherefores so that the reader can understand the of this book is to help the reader overcome just these Much of the trouble is often the hall itself, not the equip- principles involved and so make an informed choice of problems by indicating how and where to start looking for ment, but there is a simple and practical way of greatly design, or even design loudspeaker enclosures for him or many of the common faults that can occur when building improving acoustics Some microphones are prone to feed- herself. Crossover units are also explained, the various up projects back while others are not Certain loudspeaker systems are types, how they work, the distortions they produce and 96 pages s rIel 'Aide BP11I £2.95 much better than others, and the way the units are positioned how to avoid them. Finally there is a step-by-step can produce or reduce feedback All these matters are fully description of the construction of the Kapellmerster HO W TO DESIGN AND MAKE YOUR OWN P.C.B.s explored as well as electronic aids such as equalizers, fre- loudspeaker enclosure. R. A. Penfold quency-shifters and notch filters 148 pages M EDZI M E MEAMI £2.95 Deals with the simple methods of copying printed cir- The special requirements of live group concerts are con- cuit board designs from magazines and books and covers sidered, and also the related problem of instability that is all aspects of simple p c b construction including photo- sometimes encountered with large set-ups We even take a CO MPUTERS AND MUSIC- AN INTRODUCTION graphic methods and designing your own pc b s look at some unsuccessful attempts to cure feedback so as to R. A. Penfold 80 pages • rder code BP1. 1 £2.50 save readers wasted time and effort duplicating them Computers are playing an increasingly important part in Also included is the circuit and layout of an inexpensive the world of music. and the days when computerised but highly successful twin-notch filter, and how to operate it music was strictly for the fanatical few are long gone 92 pages paugu m iga gg £3.95 If you are more used to the black and white keys of a How to qet Your synth keyboard than the OWERTY keyboard of a computer, Electronic Projects PRACTICAL MIDI HANDBOOK you may be understandably confused by the jargon and Working R. A. Penfold terminology bandied about by computer buffs But fear The Musical Instrument Digital Interface (MIDI) is sur- not, setting up and using a computer-based music making rounded by a great deal of misunderstanding, and many of system is not as difficult as you might think the user manuals that accompany MIDI equipment are quite This book will help you learn the basics of computing, incomprehensible to the reader running applications programs, wiring up a MIDI sys- The Practical MIDI Handbook is armed primarily at tem and using the system to good effect, in fact just musicians. enthusiasts and technicians who want to exploit about everything you need to know about hardware and the vast capabilities of MIDI, but who have no previous the programs, with no previous knowledge of computing knowledge of electronics or computing The majority of the needed or assumed This book will help you to choose the book is devoted to an explanation of what MIDI can do and right components for a system to suit your personal needs, how to exploit it to the full, with practical advice on and equip you to exploit that system fully connecting up a MIDI system and getting it to work. as well 174 pages o ximmem ag sga £8.95 as deciphering the technical information in those manuals 128 pages Elmiz ma sai £6.95 A BEGINNERS GUIDE TO MODERN ELECTRONIC ELECTRONIC PROJECTS FOR GUITAR CO MPONENTS R. A. Penfold R. A. Penfold PREA MPLIFIER AND FILTER CIRCUITS This book contains a collection of guitar effects and some The purpose of this book is to provide practical information R. A. Penfold general purpose effects units, many of which are suitable for to help the reader sort out the bewildering array of com- This book provides circuits and background information for a beginners to project building An introductory chapter gives ponents currently on offer An advanced knowledge of the range of preamplifiers, plus tone controls. filters, mixers, etc. guidance on construction theory of electronics is not needed, and this book is not The use of modern low noise operational amplifiers and a Each project has an introduction, an explanation of how intended to be a course in electronic theory The main aim specialist high performance audio preamplifier lc results in it works, a circuit diagram, complete instructions on strip- is to explain the differences between components of the circuits that have excellent performance, but which are still board layout and assembly, as well as notes on setting up same basic type (e g carbon, carbon film, metal film, and quite simple All the circuits featured can be built at quite low and using the units Contents include Guitar tuner, Guitar wire-wound resistors) so that the right component for a cost (lust a few pounds in most cases) preamplifier. Guitar headphone amplifier; Soft distortion unit; given application can be selected A wide range of com- The preamplifier circuits featured include - Microphone Compressor; Envelope waa we& Phaser; Dual tracking ef- ponents are included, with the emphasis firmly on those preamplifiers (low impendance, high impedance and crys- fects unit, Noise gate/expander, Treble booster, Dynamic components that are used a great deal in projects for the tal) Magnetic cartridge pick-up preamplifiers with R.I A A treble booster; Envelope modifier, Tremelo unit, DI box home constructor equalisation Crystal/ceramic pick -up preamplifier Guitar /10 pages ram =ad lig £8.95 166 pages reriraNTKIM:1119:14 £3.95 pick-up preamplifier Tape head preamplifier (for use with compact cassette systems) BEGINNER'S GUIDE TO BUILDING ELECTRONIC Other circuits include.- Audio limiter to prevent overload- HIGH PO WER AUDIO AMPLIFIER CONSTRUCTION PROJECTS ing of power amplifiers Passive tone controls Active tone R. A. penfold R. A. Penfold controls PA filters (highpass and lowpass) Scratch and Practical constructional details of how to build a number of Shows the complete beginner how to tackle the practi rumble filters Loudness filter Audio mixers Volume and audio power amplifiers ranging from about 50 to 300/400 cal side of electronics, so that he or she can confidently balance controls watts r m s. Includes MOSFET and bipolar transistor designs build the electronic projects that are regularly featured in .92 pages Lig nigun u o m £3.95 96 pages uni z m u nii £3.95 magazines and books. Also include examples in the form of simple projects 112 pages INESEEffr elA £1.95

ELECTRONICS SIMPLIFIED CRYSTAL SET Theory and Reference CONSTRUCTION F. A. Wilson. C.G.I.A.. C.Eng., F.I.E.E., F.I.E.R.E., F.B.I.M. Especially written for those who wish to participate in ELECTRONIC HOBBYISTS HANDBOOK of us do not wish to afford the cost of large reference the intricacies of electronics more through practical con- P A Penfold books which explain many concepts in fair detail Here is struction than by theoretical study It is designed for all Provides an inexpensive single source of easily lo- an answer, an inexpensive reference guide which ex - ages upwards from the day one can read intelligently and cated information that the amateur electronics en- plains briefly (but we hope, well) many of the underly- handle simple tools thusiast is likely to need for the day-to-day pursuance of ing electronics features of pratical devices, most of 80 pages ft .75 this fascinating hobby Covers common component which, to a certain extent, control our lives. colour codes Details the characteristics and pinouts of This book is in effect more than just a dictionary of GUIDE TO BUILDING ELECTRONIC PROJECTS many popular seimiconductor devices, including various practical electronics terms, it goes a stage further in also Published by Everyday Electronics types of logic ICs, operational amplifiers, transistors, getting down to fundamentals Accordingly the number See the first page of books ELECTRONICS TEACH-IN FETs, unijunctions, diodes, rectifiers. SCRs, diacs, m- of terms may be limited but the explanations of the many No 5 for full details acs, regulators and SMDs, etc. Illustrates many useful which are included are designed to leave the reader more types of circuits, such as timers and oscillators, audio competent and satisfied - and this is without the use of ELECTRONICS PROJECT BOOK amplifiers and filters, as well as including a separate complicated mathematics which often on first reading Published by Everyday Electronics in association section on power supplies Also contains a multitude of can even be confusing with Magenta Electronics. other useful data For those who also wish to get right down to the See the first page of books for full details 88 pages plit/0118702:1*-Mtli £4.95 root of the matter, there is a second volume entitled A Reference Guide to Basic Electronics Terms ( BP286), FRO M ATO MS TO AMPERES each of the books referring to its companion as neces- F. A. Wilson sary Explains in crystal clear terms the absolute fundamentals A reference guide for practically everybody concerned behind electricity and electronics Really helps you to with electronics discover and understand the subject. perhaps for the first 432 pages pirfsr mtri:12,141 £5.95 time ever Have you ever Wondered about the true link between NE WNES ELECTRONICS POCKET BOOK electricity and magnetism? Felt you could never under- E A. Parr stand the work of Einstein, Newton, Boltzmann, Planck Newnes Electronics Pocket Book has been in print for and other early scientists? Just accepted that an electron over twenty years and has covered the development of is like a little black ball? Got mixed up with em f and electronics from valve to semiconductor technology and pd ? Thought the idea of holes in semiconductors is a from transistors to LSI integrated circuits and micro- bit much? processors To keep up to date with the rapidly chang- Then help is at hand with this inexpensive book, in as ing world of electronics, continuous revision has been simple a way as possible and without too much complex necessary This new Fifth Edition takes account of recent Testing and mathematics and formulae changes and includes material suggested by readers of 244 pages = 1111111111 £3.60 previous editions New descriptions of op amp applica- tions and the design of digital circuits have been added, Test Gear ELECTRONICS - A "MADE SIMPLE" BOOK along with a totally new chapter on computing, plus G. H. Olsen other revisions throughout This book provides excellent background reading for our 315 pages (hard cover) rtarrarenrintql £12.95 Introducing Digital Electronics Teach-/n Book and will HO W TO USE OSCILLOSCOPES AND OTHER be of interest to everyone studying electronics The sub- ELECTRONIC MODULES AND SYSTE MS FOR TEST EQUIP MENT ject is simply explained and well illustrated and the book BEGINNERS R. A. Penfold assumes only a very basic knowledge of electricity O wen Bishop This book explains the basic function of an oscilloscope. 330 pages = n u n £6.95 This book describes over 60 modular electronic circuits - gives a detailed explanation of all the standard controls, how they work, how to build them, and how to use them and provides advice on buying A separate chapter deals The modules may be wired together to make hundreds of with using an oscilloscope for fault finding on linear A REFERENCE GUIDE TO PRACTICAL different electronic systems, both analogue and digital To and logic circuits plenty of example waveforms help to ELECTRONICS TER MS show the reader how to begin building systems from mod- illustrate the control functions and the effects of various F. A. Wilson ules, a selection of over 25 electronic systems are described fault conditions The function and use of various other Electronic devices surround us on all sides and their in detail, covering such widely differing applications as pieces of test equipment are also covered, including numbers are increasing without mercy Ours is the timing, home security measurement audio (including a signal generators, logic probes, logic pulsars, and crystal problem therefore in keeping up with this relentless simple radio receiver), games and remote control calibrators expansion unfortunately we cannot know it all and most 200 pages £3.95 104 pages RIZEIZIM MI Mal £3.50

168 Everyday with Practical Electronics, February, 1994 Circuits and Design

ELECTRONIC CIRCUITS FOR THE CO MPUTER amplifiers and filters; triggers and voltage comparators, gates and electronic switching; bargraphs, mixers: phase PRACTICAL ELECTRONIC FILTERS CONTROL OF ROBOTS Robert Penfold shifters, current mirrors, hold circuits, etc. O wen Bishop Over 150 circuits are provided, which it is hoped will be This book deals with the subject in a non-mathematical Robots and robotics offer one of the most interesting areas useful to all those involved in circuit design and applica- way. It reviews the main types of filter, explaining in simple for the electronics hobbyist to experiment in Today the terms how each type works and how it is used. mechanical side of robots is not too difficult, as there tion, be they professionals, students or hobbyists. 182 pages unu m Mala atal £4.95 The book also presents a dozen filter-based projects with are robotics kit and a wide range of mechanical com- applications in and around the home or in the constructor's ponents available. The micro controller is not too much of workshop These include a number of audio projects such a problem either, since the software need not be terribly CIRCUIT SOURCE BOOK 2 as a rythm sequencer and a multi-voiced electronic organ. complex and many inexpensive home computers are well Concluding the book is a practical step-by-step guide to suited to the task. R. A. Penfold This book will help you to create and experiment with designing simple filters for a wide range of purposes, with The main stumbling block for most would-be robot your own electronic designs by combining and using circuit diagrams and worked examples builders is the electronics to interface the computer to the the various standard "building blocks" circuits provided 192 pages 117111111017234tial £4.95 motors, and the sensors which provide feedback from the robot to the computer. The purpose of this book is to Where applicable, advice on how to alter the circuit explain and provide some relatively simple electronic parameters is provided The circuits covered are mainly concerned with signal ELECTRONIC ALAR M CIRCUITS MANUAL circuits which bridge this gap. generation, power supplies, and digital electronics. R. M. Marston 92 pages Temporarily out of print The topics covered in this book include: 555 oscillators, One hundred and forty useful alarm circuits, of a variety of sinewave oscillators; function generators; CMOS oscil- types, are shown in this volume The operating principle of ELECTRONIC PO WER SUPPLY HANDBOOK lators; voltage controlled oscillators; radio frequency oscil- each one is explained in concise but comprehensive terms, Ian R. Sinclair lators; 555 monostables; CMOS monostables; TTL monos- and brief construction notes are given where necessary. This book covers the often neglected topic of electronic tables; precision long timers; power supply and regulator Aimed at the practical design engineer, technician and power supplies All types of supplies that are used for elec- circuits; negative supply generators and voltage boosters, experimenter, as well as the electronics student and tronics purposes are covered in detail, starting with cells and digital dividers, decoders, etc; counters and display drivers; amateur. batteries and extending by way of rectified supplies and linear stabilisers to modern switch-mode systems, IC switch- D/A and A/D converters; opto- isolators, flip/flops, noise 124 pages 111 =1111 =11 0 £13.95 mode regulators, DC-DC converters and inverters generators, tone decoders, etc. The devices, their operating principles and typical cir- Over 170 circuits are provided, which it is hoped will be ELECTRONIC CIRCUITS FOR THE CO MPUTER cuits are all dealt with in detail. The action of rectifiers useful to all those involved in circuit design and applica- CONTROL OF MODEL RAIL WAYS and the reservoir capacitor is emphasised, and the subject tion, be they professionals, students or hobbyists. R. A. Penfold of stabilisation is covered. The book includes some useful 192 pages IEDES EME RW EEli £4.95 The projects consist of various types of interface and con- trollers, including a high quality pulse type, as well as cir- formulae for assessing the likely hum level of a conven- HO W TO USE OP-A MPS cuits for train position sensing, signal and electric points tional rectifier reservoir supply. 136 pages E =BEE M ZU £7.95 E. A. Parr control etc. This book has been written as a designer's guide covering The use of computers does not have to be restricted to many operational amplifiers, serving both as a source book massive layouts Something as simple as an oval track with 50 SIMPLE LED CIRCUITS of circuits and a reference book for design calculations. a single siding can be given a new dimension by adding R. N. Soar The approach has been made as non-mathematical as pos- computer control and much fun can be had from these Contains 50 interesting and useful circuits and applica- sible. relatively simple set ups tions, covering many different branches of electronics, 160 pages 01,1 1-0,1i: 8 P88 £2.95 88 pages ammEmn u m £2.95 using one of the most inexpensive and freely available components - the light-emitting diode (LED). Also in- MICRO INTERFACING CIRCUITS - BOOK 1 DIGITAL LOGIC GATES AND FLIP-FLOPS cludes circuits for the 707 common anode display. MICRO INTERFACING CIRCUITS - BOOK 2 Ian R. Sinclair 64 pages code BP4 £1.95 R. A. Penfold This book, intended for enthusiasts, students and tech- Both books include practical circuits together with details nicians, seeks to establish a firm foundation in digital BOOK 250 more I.e.d circuits relYINITTIfft7K1U010 £1 .95 of the circuit operation and useful background informa- electronics by treating the topics of gates and flip-flops tion. Any special constructional points are covered but thoroughly and from the beginning CIRCUIT SOURCE BOOK 1 pc.b. layouts and other detailed constructional informa- Topics such as Boolean algebra and Karnaugh mapping A. Penfold tion are not included. are explained, demonstrated and used extensively, and Written to help you create and experiment with your Book 1 is mainly concerned with getting signals in and more attention is paid to the subject of synchronous own electronic designs by combining and using the out of the computer; Book 2 deals primarily with circuits counters than to the simple but less important ripple various standard "building block" circuits provided. Where for practical applications counters applicable, advice on how to alter the circuit parameters is BOOK 1 112 pages del code I 0 £2.75 No background other than a basic knowledge of elec- given. BOOK 2 112 pages Order code BP131 £2.75 tronics is assumed, and the more theoretical topics are The circuits covered in this book are mainly concerned explained from the beginning, as also are many working with analogue signal processing and include: Audio practices The book concludes with an explanation of amplifiers (op.amp and bipolar transistors); audio power microprocessor techniques as applied to digital logic. amplifiers; d.c. amplifiers; highpass, lowness. bandpass 200 pages D m alm m usiga £.95 and notch filters; tone controls; voltage controlled DIRE CT Radio, TV, Satellite B O O K S E R VIC E PROJECTS FOR RADIO AMATEURS AN INTRODUCTION TO AMATEUR CO M MUNICATIONS SATELLITES AND S.W.L.S. O R D E RIN G DET AIL S R. A. Penfold A. Pickford Communications and broadcast satellites are normally This book describes a number of electronic circuits, most Please state the title and order code of which are quite simple, which can be used to enhance inaccessible to individuals unless they are actively in- the performance of most short wave radio systems. volved in their technicalities by working for organisations clearly, print your name and address and The circuits covered include:- An aerial tuning unit; A such as British Telecom, the various space agencies or add the required postage to the total simple active aerial, An add-on b.f.o for portable sets; A military bodies even those who possess a satellite televi- order. wavetrap for combat signals on spurious responses; An sion receiver system do not participate in the technical audio notch filter; A parametric equaliser; C.W and S.S.B. aspects of these highly technological systems. Add £1 to your total order for post- There are a large number of amateur communications audio filters; Simple noise limiters; A speech processor; A age and packing (overseas readers satellites in orbit around the world, traversing the globe volume expander add £2 for countries in Europe, or add Other useful circuits include a crystal oscillator, and continuously and they can be tracked and their sig• nals received with relatively inexpensive equipment. This £5 for all countries outside Europe, RTTY/C.W. tone decoder, and a RTTY serial to parallel converter A full range of interesting and usefull circuits for equipment can be connected to a home computer such as surface mail postage) and send a PO, short wave enthusiasts the BBC Micro or IBM compatible PCs, for the decoding of cheque, international money order, 92 pages 10171fITTMTTI:hicbq £3.95 received signals. This book describes several currently available systems, (£ sterling only) made payable to AN INTRODUCTION TO AMATEUR RADIO their connection to an appropriate computer and how they Direct Book Service or credit card can be operated with suitable software I. D. Poole details (including the card expiry date). Amateur radio is a unique and fascinating hobby which 102 pages u'iii,i lu BP2 0 £3.96 has attracted thousands of people since it began at the turn Visa or Mastercard (Access) - minimum AERIAL PROJECTS of the century credit card order is £5 - quoting your This book gives the newcomer a comprehensive and R. A. Penfold The subject of aerials is vast but in this book the author name and address, the order code easy to understand guide through the subject so that the and quantities required to DIRECT reader can gain the most from the hobby It then remains has considered practical aerial designs, including active. an essential reference volume to be used time and again. loop and ferrite aerials which give good performances and BOOK SERVICE, 33 GRAVEL HILL, Topics covered include the basic aspects of the hobby, are relatively simple and inexpensive to build. The com- WIMBORNE, DORSET BH21 1RW such as operating procedures. jargon and setting up a plex theory and mathematics of aerial design have been station Technical topics covered include propagation, avoided. (mail order only). receivers, transmitters and aerials etc Also included are constructional details of a number of Although books are normally sent aerial accessories including a pre-selector, attenuator, fil- 150 pages £3.50 within seven days of receipt of your order, ters and tuning unit. please allow a maximum of 28 days for SIMPLE SHORT WAVE RECEIVER CONSTRUCTION 96 pages L6111112111181LIZEI £2.50 R. A. Penfold delivery. Overseas readers allow extra Short wave radio is a fascinating hobby, but one that INTERNATIONAL RADIO STATIONS GUIDE P. Shore time for surface mail post. seems to be regarded by many as an expensive pastime Please check price and availability (see these days. In fact it is possible to pursue this hobby for a Provides the casual listener, amateur radio DXer and the minimal monetary outlay if you are prepared to undertake a professional radio monitor with an essential reference latest issue of Everyday with Practical bit of d.i.y.. and the receivers described in this book can all work designed to guide him or her around the ever more Electronics) before ordering from old lists. complex radio bands. This new edition has been com- be built at low cost All the sets are easy to construct, full Note - our postage charge is the pletely revised and rewritten and incorporates much more wiring diagrams etc are provided. and they are suitable same for one book or one hundred for complete beginners. The receivers only require simple information which is divided into the following sections: aerials, and do not need any complex alignment or other Listening to Short Wave Radio; Choosing a Short books! difficult setting up procedures. Wave Radio Receiver; How to Use the IRSG; Abbrevia- The topics covered in this book include, The broad- tions; Country Codes; Worldwide Short Wave Radio Sta- MORE BOOKS NEXT MONTH cast bands and their characteristics: The amateur bands tions; European. Middle Eastern and African Long Wave Radio Stations; European, Near and Middle Eastern and and their characteristics The propagation of radio signals: Direct Book Service is a division of Simple aerials; Making an earth connection. Short wave African Medium Wave Radio Stations. Canadian Medium Wimbome Publishing Ltd Wave Radio Stations: USA Medium Wave Radio Stations, crystal set, Simple t.r.f. receivers: Single sideband recep- Broadcasts in English; Programmes for DXers and Short tion; Direct conversion receiver Tel: 0202 881749 Wave Listeners: UK FM Radio Stations; Time Differences Contains everything you need to know in order to get From GMT; Wavelength/Frequency Conversion. started in this absorbing hobby Fax: 0202 841692 226 pages MO M M EU M M EI £6.95 88 pages )1111'1 /-1,(11 . BP 5 £3.95 169 Everyday with Practical Electronics, February, 1994 BABAN I BOOKS We now supply all the books published by Bernard Babani (Publish- would like to be able to purchase all the books from us and thus keep ing) Ltd. We have always supplied a selected list of Babani books and the postage charge to an absolute minimum (Cl for UK p&p no you will find many of them described on the previous pages or in next matter how many books you buy). We are pleased to be able to months issue of Everyday with Practical Electronics (the books with a respond; with the aid of Michael Babani (M 0.) we are now able to BP prefix to the order code are Babani books). meet all your requirements for their books. If it's Baton, and in print we Many readers have asked us to also supply various other Babani can supply it. Babani presently list over 180 different technical titles books, which have a reputation for value for money. Our customers tell those not described in detail on the previous Direct Book Service pages us they appreciate our speedy service and low postage charge and they or in next months issue are listed below . Code Title Price Code Title Price Code Title Price BP28 Resistor Selection Handbook £0.60 BP193 LOGO for Beginners £2 95 BP283 A Concise Introduction to SmartWare II £4.95 BP37 50 Projects using Relays, SCRs and BP196 BASIC & LOGO in Parallel £2.95 BP284 Programming in QuickBASIC £4,95 TRIACs £2.95 BP197 An Introduction to the Amstrad PC's £5.95 BP287 A Reference Guide to Practical Electronics BP39 50 (FET) Field Effect Transistor Protects £2.95 BP198 An Introduction to Antenna Theory £2.95 Terms £5.95 BP44 IC 555 Projects £2.95 BP230 A Concise Introduction to GEM £2.95 BP288 A Concise Introduction to Windows 3.0 £3,95 BP48 Electronic Projects for Beginners £1.95 BP243 BBC BASIC86 on the Amstrad PC's and BP291 A Concise Introduction to Ventura £3.95 BP49 Popular Electronic Projects £2.50 IBM Compatibles Book 1 Language £3.95 BP292 Public Address Loudspeaker Systems £3.95 BP56 Electronic Security Devices £2.50 BP244 BBC BASIC86 on the Amstrad PC's and BP293 An Introduction to Radio Wave BP74 Electronic Music Projects £2.95 IBM Compatibles Book 2 Graphics Propagation £3 95 BP76 Power Supply Projects £2.50 and Disk Files £3.95 BP294 A Concise Introduction to Microsoft BP78 Practical Computer Experiments £1.75 BP245 Digital Audio Projects £2.95 Works 0 0.P BP84 Digital IC Projects £1.95 BP246 Musical Applications of the Atari ST's £5.95 BP298 A Concise Introduction to the Mac System BP90 Audio Projects £2.50 BP247 More Advanced MIDI Projects £2.95 & Finder f 3 95 BP94 Electronic Protects for Cars and Boats £1 .95 BP249 More Advanced Test Equipment BP302 A Concise Users Guide to Lotus 1-2-3 BP95 Model Railway Projects £2 95 Construction £3.50 Release 3 1 £3 95 BP97 IC Projects for Beginners £1 .95 BP250 Programming in FORTRAN 77 £4.95 BP303 Understanding PC Software £4.95 BP122 Audio Amplifier Construction £2.95 BP251 Computer Hobbyists Handbook £5.95 BP306 A Concise Introduction to AmiPro 3 £4.95 BP125 25 Simple Amateur Band Aerials £1 .95 BP258 Learning to Program in C £4.95 BP307 A Concise Introduction to QuarkXPress £4.95 BP126 BASIC & PASCAL in Parallel £1.50 BP259 A Concise Introduction to UNIX £2.95 BP311 An Introduction to Scanners and Scanning £4.95 BP132 25 Simple SW Broadcast Band Aerials £1.95 BP260 A Concise Introduction to OS/2 £2.95 BP312 An Introduction to Microwaves £3.95 BPI 36 25 Simple Indoor and Window Aerials £1 75 BP261 A Concise Introduction to Lotus 1-2-3 BP313 A Concise Introduction to Sage £395 BP137 BASIC & FORTRAN in Parallel £1.95 (Revised Edition) £3.95 BP314 A Concise Introduction to Quattro Pro £4.95 BP138 BASIC & FORTH in Parallel ft 95 BP262 A Concise Introduction to Wordperfect BP315 An Introduction to the Electromagnetic BP144 Further Practical Electronics Calculations (Revised Edition) f 3.95 Wave £4.95 & Formulae £4.95 BP264 A Concise Advanced Users Guide to BP322 Circuits Source Book 2 £4.95 BP145 25 Simple Tropical and MW Band Aerials £1.75 MS-DOS £3.95 BP324 The Art of Soldering £3.95 BP148 Computer Terminology Explained El.95 BP269 An Introduction to Desktop Publishing 0.0.P. BP328 Sage Explained £5.95 BP171 Easy Add-on Projects for Amstrad CPC 464 , BP270 A Concise Introduction to Symphony £3.95 BP329 Electronic Music Learning Project £5.95 664,6128 and MSX Computers £2.95 BP272 Interfacing PC's & Compatibles £3.95 BP330 A Concise user's Guide to Lotus 1-2-3 BP182 MIDI Projects £2 95 BP273 Practical Electronic Sensors £4.95 Release 24 £4.95 BP187 A Practical Reference Guide to Word BP274 A Concise Introduction to SuperCal5 O.O.P. BP331 A Beginners Guide to MIDI £4.95 Processing on the Amstrad PCW8256 BP276 Short Wave Superhat Receiver BP334 Magic Electronics Projects £4 95 and PCW8512 £5.95 Construction £2.95 BP336 A Concise Users Guide to Lotus 1-2-3 BP190 More Advanced Electronic Security BP279 A Concise Introduction to Excel £3.95 Release 3.4 £5.95 Projects £2.95 BP280 Getting the Most From Your PC's Hard BP339 A Concise Introduction to WordPerfect 5 2 BP192 More Advanced Power Supply Projects £2.95 Disc £3.95 for Windows £595

IF NO PRICE IS SHO WN THE BOOK IS OUT OF PRINT (0.0.P.) SEE PREVIOUS PAGE FOR FULL ORDERING DETAILS

PROJECT TITLE Order Code Cost

Light Sentinel: Main Board APR 89 632 £9.20 4-Channel Auto-Fader Interface 642 £6.80 PrintedPCB circuit boards for certainSERVICE EPE constructional projects are available from Electronic Spirit Level AUG 89 649 £3.85 the PCB Service, see list. These are fabricated in glass fibre, and are fully drilled Distance Recorder 651 £5.23 and roller tinned. All prices include VAT and postage and packing. Add £1 per board for airmail outside of Europe. Remittances should be sent to The PCB Music on Hold OCT 89 646 £3.85 Service, Everyday with Practical Electronics, 6 Church Street, Wim- Power Supplies - 25V 700mA 656 £4.35 borne. Dorset BH21 1JH. Cheques should be crossed and made payable to EE Seismograph - Control board only 658 £4.08 Everyday with Practical Electronics ( Payment in sterling only). Wash Pro NOV 89 643 £3.83 NOTE: While 95% of our boards are now held in stock and are dispatched Logo/lego & Sepctrum Interface 664 £5.60 within seven days of receipt of order, please allow a maximum of 28 days for delivery -overseas readers allow extra if ordered by surface mail. Biofeedback Signal Generator JAN 90 666 £4.08 Back numbers or potostats of articles are available if required -seethe Editorial Quick Cap Tester FEB 90 668 £3.92 page for details. Superhet Receiver/Tuner/Amp MAR 90 Please check price and availability in the latest issue. 679/680 £4.22 Boards can only be supplied on a payment with order basis. Stereo Noise Generator APR'90 681 £4.24 All p.c.b.s on THIS page only reduced to Amstrad Speech Synthesiser MAY'90 689 £4.68 The Tester JUL'90 696 £4.15 Mains Appliance Remote Control AUG'90 Mains ON/OFF Decoder 697 £4.55 1/2 PRICE Hand Tally: Main Bd and Display Bd SE P'90 699,700 £10.95 Ghost Waker OCT'90 703 £4.32 Frequency Meter 704 £5.25 (Just send half the price Sh01477, while stocks last) Freq. Meter/Tachometer NOV 90 705 £3.98 PCBS ON OPPOSITE PAGE PRICES AS SHOWN Microcontroller Light Sequencer DEC'90 708/709 £10.90 Spatial Power Display JAN 91 PROJECT TITLE Order Code Cost 714 £5.33 Amstrad PCW Sound Generator 715 £5.03 Video Guard Alarm FEB'87 556 £3.80 Pocket Tone Dialler MAR 91 729 £4.36 Multi-Chan Remote Light Dim JUNE 88 Simple Basic Alarm 731 £4.50 Relay/Decoder 601 £4.86 Humidity Tester APR 91 Power Supply 603 £3.00 716 £4.97 Model Train Controller (double-sided) 736 £9.75 Tea Tune Thermostat AUG'88 609 £3.00 Suntan Timer 610 £3.07 Digital LCD Thermostat MAY 91 -Control Board Car Alarm 615 £3.12 740 £4.05 - Power Relay Board 741 £3.76 Eprom Eraser OCT 88 620 £4.07 Control and Power Relay Boards together £5.00 Doorbell Delay N O V 88 616 £3.56 Digilogue Car Tachometer JUN 91 744 £5.63 Sound-to-Light Interface M AR 89 637 £6.24 Modular Disco Lights-Simple Chaser 745 £5.00 Midi Pedal 639 £7.00 Sweeper Module 746 £5.17 Midi Merge 640 £3.00 Automatic Light Control - PSU Board 747 £4.88 Audio Lead Tester 641 £5.77 Logic Board 748 £5.17

1 70 Everyday with Practical Electronics. February. 1994 PROJECT TITLE Order Code Cost PROJECT TITLE Order Code Cost

Modular Disco Lights - Masterlink J Ul Y .91 752 £6.36 Electronic Snooker Scoreboard JUNE 93 832 £9.17 Ultrasonic Proximity Meter Mind Machine Mk11 JUIY 93 Display Unit (753) & Sensor Unit (754) 753/754 £7.06 - Computer Interface 833 £6.39 Mod. Disco Lights - Pattern Gen AUG 91 760 £6.79 Xenon Strobe 834 £5.84 Portable PEST Scarer 764 £3.77 Electronic Gong 835 £7.50 Micro Lab - p.c.b., EPRO M. PAL and booklet MICRO £35.00 Capacitance Meter SF P 91 751 £5.17 Modular Disco Lights - Dimmer Interface 765 £8.17 Bike Odometer (pair of boards) AUG 93 836/7 £7.00 Amstrad PCW A to D Converter(double sided) 838 £9.85 Mod. Disco Lights (U T 91 Experimental Electronic Pipe Descaler 839 £5.50 VU Sound Module (Double-sided) 767 £8.68 UV Exposure Unit 768 £4.63 Sound Activated Camera Trigger SEP 93 840 £5.34 PC-Scope Interface - Main Board 769 £6.95 L.E.D. Sandglass OCT 93 Expansion Plug (Double-sided) 770 £5.96 Main and Display boards 841/2 £7.30 Kettle Alert 843 £5.19 Mod. Disco Lights NOV 91 Linear Power Supply (double-sided) 844 £9.77 Superchaser (Double-sided) 771 £6.91 Multi-Purpose Audio System Supersweep (Double-sided) 772 £8.26 Six Channel Stereo Mixer 845 £11.98 Bicycle Alarm 773 £5.01 Darts Scorer 774 £.90 Multi-Purpose Audio System IM MO Microphone Pre-Amp module 846 £4.88 Knockerbox DEC 91 775 £5.35 RIAA Pre-Amp module 847 £5.11 Signal Generator - Main Board 776 £7.46 20 Metre Receiver 848 £6.63 PSU 777 £4.73 Multi-Purpose Audio System Dl C 93 Mind Machine - Main Board 778 £7.00 Tone Control and 1W Stereo Amplifier 849 £6.09 Auto Nightlight 779 £5.03 Tone Control 850 £5.12 Mind Machine - Programmer Board .1/1N 92 780 £.39 1W Stereo Amplifier 851 £4.88 Transistor Checker 781 £4.63 Three-Way Christmas Tree Lights Flasher 853 £5.65 Stepping Motor Driver/Interface 782 £10.39 Auto Alarm 854 £5.49 Micro-Sense Alarm 783 £5.42 250W/600W Battery to Mains Inverter 855 £13.92 f Telesound F F B 92 784 £4.66 Multi-Purpose Audio System .1AN 94 Programmable Timer 785 £4.63 10W+ 10W Stereo Power Amplifier Auto Garage Light MAR 92 786 £6.10 Amplifier 852a £5.65 Versatile BBC Computer Interface 787 £11.59 Power Supply 852b £5.49 Economy Seven Timer 788 £5.20 Pond Heater Thermostat 856 £5.77 Timer/NiCad Capacity Checker 857 £6.30 Sonic Continuity Tester APR 92 789 £4.79 Telephone Ringer 790 £5.46 Multi-Purpose Audio System F I B 94 858 £5.30 Experimental Weighing Scale MAY 92 792 £5.17 Balanced Microphone Preamplifier Balanced Microphone Power Suppy 859 £5.14 12V Drill Charger/PSU (both boards) 793 £5.31 Whistle Controlled Light Switch 860 £5.19 Digital Servo Interface JUNE 92 791 £4.73 Battery To Mains Inverter - U.P.S. charger board 862 £7.38 Tie Pulsar 794 £5.19 CCD Reverb Unit 795 £6.39 Switch-Mode Power Supply 796 £7.01 UV Exposure Timer JUIY 92 797 £5.33 1 Cricket Game 798 £6.77 (Lick Prom 799 £5.61 EPE PRINTED CIRCUIT Gas Alarm AUG 92 800 £5.47 Dual Metronome 801 £6.74 BOARD SERVICE Ultrasonic Tape Measure SIP 92 802 £6.06 Quicktest 803 £4.82 j Order Code Project Quantity Price

Extended Range Capacitance Meter OCT 92 804 £5.63 Traffic Lights System 806 £5.04

Mini Lab NOV 92 MINI LAB £14.95 CO EPE Altimet (Altimeter) 807 £6.30 I Name Personal Stereo Amplifier 808 £6.47 01 I O I Universal Infra-Red Remote Control OF C 92 8$17/811R £6.56 Combination Switch 812 £5.68 I Address 0 Christmas Lights Colour Spectrum 813 £5.97

TV/UHF Aerial Amp (double-sided) .lAN 93 814 £7.23 'V• I Continuously Variable Balanced Power Supply 815 £5.65 =I I Emergency Lighting Unit 816 £6.77 D r- Biomet Pulse Monitor FEB 93 Ch Sensor 817 £6.30 Display 818 £6.30 r-• I I enclose payment of £ (cheque/PO in sterling only to m I Biomet Pulse Monitor MAR'93 -ADC Interface (double-sided) 819 £7.11 Everyday with Practical Electronics) rA I m Car Electric Window Enhancer 821 £5.00 Access (MasterCard) or Visa No. Simplify Atari STFM Interface 822 £5.55 Minimum order for credit cards £5 Personal Stereo Amp. Add-On 823 £3.90 Electronic Fire APR 93 820 £4.84 Mind Machine MKII - Signal Generator 824 £5.57 WSA Ventilation Fan Timer 825 £4.70 Universal Data Logger 826 £5.88

Mind Machine Mk11- Magic Lights M AY 93 827 £6.58 Superhet Radio Control Receiver 828 £5.93 Guitar Preamp and Distrortion Unit 829 £5.46 Linear Clock - Timing Board 830 £8.00 Signature Card Ex. Date Display Board 831 £7.00 Universal Alarm Module 9070 £.00 Please supply name and addess of card-holder if different from the address shown L.

171 Everyday with Practical Electronics, February, 1994 REPORTING VAAL- -1 Tony Smith G4FAI

M ORE AMATEUR SATELLITES and lectures on all aspects of amateur ITU RESTRUCTURING An Anane launch vehicle from Kourou, satellite activity, provides an information The International Telecommunication in French Guiana, carried seven satellites service to members and offers advice and Union, the international legislative body into orbit on September 26th, including a general assistance to newcomers to this which, among many other things, lays number of OSCAR amateur communica- specialised field of amateur radio. down the rules for amateur radio, tions satellites. AMSAT nets, providing the latest infor- has been re-organised into three sec- Kitsat Oscar 25 (K0-25) is a 50kg mation and news on space activities are tors. Of most interest to amateurs satellite built by the Korean Advanced held on the amateur bands as follows: is the Radiocommunications Sector, Institute of Space Technology, and its Sundays, 1015hrs, on 3.780MHz; and the work of which will be con- mission is to take CCD pictures, process 1930hrs on 144.280MHz, in most parts ducted through World and Regional numerical information, measure radiation, of the UK. Mondays and Wednesdays, Radiocommunication Conferences and and receive and forward messages. Its 1900hrs, on 3.780 MHz. (All times local). Radiocommunications Assemblies to be uplink is 145.870/145.980MHz, and its held every two years. downlink is 435.175/436.500MHz. GETTING STARTED The previous World Administrative ltamsat Oscar 26 (10-26) is a 12kg To work through, or hear, an amateur Radio Conferences, which occupied satellite built by AMSAT-ITALY and is satellite you need to know when it will much of the time and effort of national intended to store and forward amateur be in a suitable position to transmit and radio societies in trying to influence radio messages. Its uplink frequencies receive radio signals to and from your par- their national delegations whenever are 145-875/145'900/145.925MHz and ticular location. This can be calculated by amateur radio was under consideration, 145.950MHz; with downlink on means of an "Oscalator" and an orbital will no longer be held. 435.867MHz (primary) and 435.822MHz prediction calendar, both obtainable from The new constitution, as from July 1, (secondary). AMSAT-UK, or can be calculated by com- 1994, continues to provide for par- Amrad Oscar 27 (A027) is a secon- puter using one of the AMSAT programs. ticipation in the work of the ITU by dary amateur communications payload While most satellites have either uplinks recognised international organisations carried on Eyesat-1, a 12.5kg commercial or downlinks in the 2m band, many such as the International Amateur Radio microsat built by Interferometrics Inc. of beginners start with the Russian RS Union, but they must now be prepared Vienna, Virginia. The amateur equipment 12 satellite, which has an uplink of for ITU conferences on a regular two- on this satellite was constructed by 21.210 - 21.250MHz, and a downlink of year basis instead of sporadically as members of AMRAD, a technically orien- 29.410 MHz - 29.450MHz with a beacon previously. tated organisation of radio amateurs in the on 29.408MHz. The first WRC was held in Novem- Virginia suburbs of Washington D.C., to This makes satellite operation possible ber 1993. Its only business was to meet the needs of amateurs for a platform for any amateur who has an h.f. amateur develop recommended agendas for the to conduct digital satellite communica- station plus a separate h.f. receiver, or for WRCs to be held in 1995 and 1997. tions experiments. Uplink - 145.850MHz, listeners who have receivers capable of An ITU Voluntary Group of Experts downlink - 436.800MHz. covering the amateur h.f. bands. Existing (VG E) is developing recommendations A further satellite is PoSat-1, awaiting a antennas will probably be quite suitable for simplification of the Radio Regula- decision from Portugal on whether the for transmitting, and a simple 10m dipole tions to be considered at a future amateur package on this 50kg com- will be suitable for receiving. There is no conference, probably in 1995. (1ARU mercial satellite will be activated, in need for any special "know-how", which News). which case it will become PoSat Oscar- can be acquired later if you get "hooked" 28 (P0-28). Built by Surrey Satellite on satellite operation. If your receiver is WINTER BROADCASTS GUIDE Technology Ltd (SSTL) of the Univer- a bit "deaf" around 30MHz, then AM - The International Short Wave League's sity of Surrey, for LNET1 (Portugal), SAT-UK can supply a suitable 28-30MHz Guide to English Language Short Wave its mission is to receive and trans- preamplifier to improve its performance in Broadcasts to Europe, Winter 1993/94, mit earth images, determine its position this band. is now available. Once again it provides using GPS, make radiation measure- If you are busy with other things in your invaluable assistance for SWLs with its ments, and receive and forward mes- shack, you can leave your receiver per- round-the-clock format and station in- sages. Uplink - 145.925/145.975MHz, manently on the beacon frequency and formation, including country, frequencies downlink - 435.250MHz (primary) and once every 104 minutes, when it is on a and programme information. 435.275MHz (secondary). Information suitable orbit, you will hear RS 12 come The introduction to this issue reminds from W5Y1Report. up. CW (Morse) signals should be heard us that during the present phase of the in the lower part of the band while SSB sunspot cycle the higher frequencies are INTERNATIONAL EFFORT (single sideband) speech signals will be less reliable. Accordingly, international There are now so many amateur radio heard in the the upper part. broadcasters are battling for space on satellites in orbit it would be confusing to the lower frequencies, sometimes caus- attempt to list them, but most are the result INFOR MATION PACK ing co-channel interference and making of the work of AMSAT, the Radio Amateur An information pack about AMSAT- reception difficult. Satellite Corporation, and associated or- UK and amateur radio satellites can be It also comments on the increase in the ganisations around the world. obtained by sending a 9x6inch self-ad- number of stations using AM compatible In this country, AMSAT-UK co- dressed envelope with a 29p stamp to SSB transmissions, which reduce the ordinates amateur satellite activities, raises AMSAT-UK, 94 Herongate Road, London "splatter" associated with normal AM funds, and engages in the design and E12 5EQ. An introductory booklet, Satel- broadcasts. To receive them clearly a building of apparatus for OSCAR lites for Beginners is also available, price receiver with SSB capability is to be launches. It publishes a bimonthly journal, £1.65, postpaid. preferred, although an AM-only radio Oscar News, which contains up-to-date For a limited period, new members join- can usually provide acceptable reception information on all aspects of satellite ing AMSAT-UK will receive on request a of these transmissions. operation, including listed orbits and free copy of an IBM computer tracking The Guide, which costs £1 .30 (stamps general advice; and has a number of useful program on 5.25inch disk. This program acceptable) or 2xIRCs, postpaid, can be publications and computer programs can also be supplied on 3.5inch disk if the obtained from ISWL, 10 Clyde Crescent, for both beginners and experienced member supplies his/her own formatted Wharton, Winsford, Cheshire CW7 3LA. operators. disk at the time of joining. An application Why not ask for information about the It has an annual Colloquium at the form for membership is supplied in the League at the same time if you don't University of Surrey with demonstrations information pack. already know about them?

172 Everyday with Practical Electronics, February, 1994 400 watt IBM L-shaped p.s.u., 100 off phono plugs £2.95' 115-240V Input, Outputs + 5V 50 off mixed terminal 45A, + 12V 13A, - 5V 0-5A, blocks £2.50' 12V1A £24.95 25 off buzzers & sounders £3.50' Everex network cards + software 25 off mixed relays £4.95' and manual £29.95 50 off mixed switches £7.50' RANSMITTERS Electret condensor mics 250 off i.c. sockets £3.95' AT ST. A fully comprehensive, easy to £1 ea 10 for £5* 1000 off Ceramic caps £7.50' follow guide to building short range 4 f 5%" to 3W' floppy convertor 5 off 3V Lithium memory 4 'VI c, 111,5;y 0 heads £1.50 ea• back-up batteries £2.00* micro transmitters. Packed with useful 360K 5%" customer returned 100 off 2200µF 25V caps • £6.00* information and circuits. disk drives 2 for £5 100 off 4-7pF 25V caps ..•• £2.50' * How to build micro surveillance /lie/ PS 9-pin High Density VGA 3Ib mixed component leads £2.50' pack £4.95 devices. 10A 250V IEC leads £1.50' Jumbo component pack £10 * Radio micS. Spectrum 128K + 2 p.s.u Crystal oscillators 9V 2-1A £4.95 10/12 MHz £1 ea * Tracking and signaling 1c4-• SIC p.s.u. 240V Input; 5V 6A 5V DPCO OIL. relay 60p ea • transmitters. Output, (converts to 12V 3A, 5V SPCO S.I.L. reed * Only £3.95 inc p&p details supplied) £5.95 relay 40p ea Temperature probes, with 12V Piezoelectric (Some 01 the Circuits included can not be used legally in the UK data £3.95' Sounders 50p ea Universal Timer (10 min. D.I.L. Switches 3/4/6 and MICRO FM TRANSMITTER. Easy to build, 1 mile range, very delay and 20 min. cut-off 12 -way 35p ea small including mic. Pick up on any FM radio. £6.95 functions) £3.95' UM1233 video modulators .... £2' TRACKING FM. Transmits a constant pulse tone that can be Dictaphone cassette mech £2.00' 3-5mm lack plugs 10 for £1' 35mm Camera returns, with 16A BT surge arrestors 10 for £5' used for direction finding, tracking cars or animals etc. £8.50 auto flash, wind on, etc. 100 off Zener diodes, mixed ... £2' CRYSTAL RADIO. Simple introduction to radio and electronics. 21-piece mini screwdriver £6 ea, 2 for £10 Includes easy instructions, ferrite rod, tuner etc. £5.75 16 Character x 2-line dot set £3.95' matrix display + data f4.95' Universal test lead kit £3.95' AM RADIO. Tuner and power amp that make a tiny AM radio. 40 Character x 1-line dot 10 crocodile clip leads £3.50' Will drive a small pair of headphones. Simple to make and matrix display f4.95" fun to use. £8.50 Car Dashboard Display (shows Q U ANTITY DIS C O U NTS AVAILABLE lights, indicators, doors, PLEASE RIN G INFRA RED REMOTE CONTROL. Simple but effective remote on picture of car) f4.95' We also buy all forms of electronic control of relay switch up to 10 metres. Ideal for car alarms, components, p s us disk drives etc 4-digit clock display f2.50' Lists to below address light switches etc. Includes 240V relay. £10.50 4-digit I.c.d. with 7211 ALL PRICES INCL U DE V.A. T. driver £3.50' PLEA SE AD D f2 00 p&p EX CEPT MUSIC KITS PREA MPS PO WER AMPS 17-digit v.f. display £2.95' ITE MS MA RKE D* W HIC H ARE 50P Giant 2 digit v.f. display £2.95 SAE FOR BULK BU YIN G LIS T Full range of on board units for guitars etc.-active tone 12V stepper motors, 48 steps PAY ME NT WI TH OR DE R TO controls/boosters, wah wah and other effects kits- send for list. per rev., 7-3° step angle.. £3.95' Dept EE, COIVIPELE C, Prices include P&P. Mail order only. 250 off mixed electrolytic 14 Constable Road, Make cheques and postal orders payable to: caps £4.95' St. Ives, Huntingdon, 250 off polyester caps £4.95' Ca mbs PE17 6EQ 1000 off mixed resistors J C GILD f4.95" Tel/Fax: 0480 300819 3 Bainbrigge Road, Headingley, Leeds LS6 3AD.

Inverter toroidal transformers 225VA 10 5-0 10 5V DC-DC converter Reliability model. V12P5. 12V ELECTRONIC DESIGNERS TOOLKITS purnary 0 260 285V secondary £29.95 .n by 200mA out, 300V mow to output isolation LEDs 3mrn or 5mm red or green op each. yellow with data £4.95 each or pack ol 10 £39.50 SHAREWARE FROM ONLY £2.49 A DISC lip each High intensity red green or yellow Hour counter used 7 digit 240V a c 50HY £1.45 5rnno 30p each Q WERTY keyboard 58 key good quality switches Cable Ties 1p each. C5.95 peg 1000 E49.50 peg new £5.00 10 000 Ai roes 582903•C large stepprog motor 14V Small stepping motor 4 . phase 12V 7 S siep 7 5' step 27 ohm. 68mm deo body 6 3mrn 50 ohms C8.96 shaft £8.96 or (200.00 for a box of 30 SAA1027 stepping motor driver chip£4.95 Polyester capacitors box type. 22 5rern lead pitch m-vVi• 0 9pF 250Vdc 18p each. 14p 100 h 9p 10004 High quality photo resist copper 1pF250Vd c 20peach 16p 100 -g• .10p 1000 • clad epoxy glass boards 2 2pF 250V d c 3Dp each. 20p 100. .15p 1000 - Dimensions single-sided double-sided 3 30F 100V d c 30p each. 20p100 ..15p1000 • 3,4 inches 4x8 inches CO 95 £1 07 10F 50V bipolar electrolytic axial leads 15p each. £2 40 £2.68 7.5p 1000 • 6x12 inches £5 37 0 220F 250V polyester axial leads 15p each 1 i T. • 1202 rnches £10 66 100 • 7•Sp each . . Philips 123 series solid aluminium axial leads Filt- er20. C- CI Analysis, DCCAD PCB Design, and Utes RECH AR GE ABLE BATTERIES 33pF 10V & 2 2pF 40V 40p each, 25p 100 • AA (FIP7) 500mAH £0.99 Previously sold Si over £100.00, now you can try these pro esslonal aids for only £19.95 Philips 108 series 220F 63V aural AA 700mAH These fully featured packages otter easy to use facilities for beginner and expen alike. Design 30p each. 15p 1000 • C 2AH porth solder lags Butterworth, Chebyshev. Ellipiical. Bessel filters at the touch of a key. CCICAP analyses Multilayer AV% ceramic capacitors. all 5mm £t£431.969°5 D 4AH with solder tags pach 100V 100pF. 150pF. 220pF, 10,000pF circuits with R.C.I, and FETs. BJTs. op-amps DCCAD designs schematics and Pca layouts 1 /2AA with solder tags £1 . 55 (10n) 10p each. Sp 100 •. 3.5p 1000 • for double sided boards. Utils minimise logic circuits and provide electronic calculators. AAA IHP16) 180mAH £1.75 500pF compression trim mer 60p El.- 8 360k discs all the above or £l9 95 E2.-Filters and Circuit analysis 4 360K discs £9.95, AS 500mAH with solder lags£1 55 40p F 370V a c motor start capacitor ldralectrol type E3 Electrical and Electronic calci.ators and Oils oriN E4 95, Please state size when ordering C IFIP1 1 1 8AH £2.20 containing no p c b sl C5.95 or C49.50 for 10 Charges relate solely to admin. See our FREE CATALOGUE for registration details (HP2 1 2A11 £2 60 Welwyn W23 9W 120 ohm 35p each. 20p 100 • PP3 8 4V 110ynAH £4 95 680 ohm 2W metal film resistor Sub C with solder tags £2 50 . .. 4p 100 • 2p 1000 • 1/3 AA with tags (Philips CTV) £1 95 Solid cartron resistors, only low inductance, ideal S&N Enterprises Tel: 0252 510486 Standard charger. charges 4 AA cells in 5 hours tn. r I circuits. 27ohrn 2W. 68ohm 2W 25p each or 4Cs or Ds in 12 to 14 hours • 1aPP3 g 1. 2 3 15p each 100 • Mail Order:- 5 Polden Close, Farnborough, Hants GU14 9HN or 4 cells may be charged at a trrne) £5.95 we have a range of 0 25W, 0 5W. 1W and 2W High power charger, as above but charges the solid carbon resistors please send SAE for lost Cs and Ds on 5 hours. AAs. Cs and Ds most be Inteligent 4 digit alphanumeric 15'7 dot 0 145 - / charged In twos or lours £10.95 red LED display. 12 pin 06 inch wide package. Siemens type OLR1414 E2.50 each. £2.0030. SPECIAL OFFERS PLEASE CHE CK data sheets £1.00 FOR AVAILABILITY AMD 27256 -3 EPROMS £2.00 each, C1.26100 • SECURITY EQUIPMENT F cells 32dm u 87nirro £3.95 DIL switch 3PCO 12 pen (FRG 50C-3-023140p F cell with solder tags. 1 25 £4 30 each. 40p 100 - 42m m x1Brrirn da 1 2V £1.45 Disk Drove Boxes for a 5 25 disk drive. with room COMPLETE SYSTEM Stick of 4171mrn x 16mm dra with red tor a power supply. light •grey plastic 67nun • and black leads 4 8V £5 95 268mm or 247mm C7.95 or £49.50 tor 10 Co mplete range of security parts to protect your 1 4 c(1 112bac trceirty)941nrit x 25mm Ora Handheld Ultrasonic remote control £3.95 • £3.50 house and property. Passive infra-red sensors CV24841gas relay 3Ornm 10mrn de with 1 1 Computer grade capacitors with screw terminals 3 wire terminals, will also work as a neon ultra-sonic move ment detectors, control panels, 38000pF 20V £2.50; 87000pF 10V £1.95; light 20p each E7.50 per 100 1 68000pF 15V £2.95: 10000pF 16V £1.50. 523 12V battery for car alarms or lighters cable, etc etc supplied with instructions. 58000p F 60V £4.95 75p each. E50 100 • 7-segment common anode led display 1 12mrn£0.45 All products advertised are new and LM2931AT 5 0 low drop out 5V unused unless otherwise stated 1 QUALITY AUDIO MODULES regulator 70220 package £0.85 7812 and 7912 12V 1A regulators £20.00 per 100 Wide range of CMOS TTL 74HC 74F Linear LM337K 103 case variable regulator £1.60 Transistors kits, rechargeable batteries I Power amplifiers from 10-125 W, mixer units, 100 • £.10 each capacitors, tools etc always in stock GaAs F E.T. low leakage current 58873 £12.95 g pre-a mplifiers etc. Build your own disco units, guitar each. £9.95 10 •. E7.96 100 • Please add £.95 towards P&P 135250 p channel MOSFET 45p VAT included in all prices I amps, public address syste ms etc., etc. BC559 transistor £3.95 per 100 741505 Hex inverter £10.00 per 100 Used 8748 Mrcrocontroller £3.50 JPG ELECTRONICS S1952 UHF Lomrong amplofier LC 16 surface 276-278 Chatsworth Road FREE LITERATURE TODAY mounting package with data sheet £ .95 A M 27S02 £1 .25 each 90p 100 • Chesterfield S40 2BH CD4037UB 10p 100 • Eip 1000 • Sinclair light gun termonated with a lack plug and Access Visa Orders: AUI'ONA LTD TEL 0844 346326 PP3 clip owes a signal when pointed at 50Ht (0246) 211202 flickering Irght. with output waveform chan £3.95 I 51 POPPY ROAD, PRINCES RISBORCHIGH, BUCKS. HP279DB I Callers welco me

Everyday with Practical Electronics, February, 1994 173 EVERYDAY CLASSIFIE D Everyday with Practical Electronics reaches twice as many UK readers as any other independent WITH PRACT1 monthly hobby electronics magazine, our audited sales figures prove it. We have been the leading independent monthly magazine in this market for ELECT' ONICS the last nine years If you want your advertisements to be seen by the largest readership at the most economical price our classified and semi-display pages offer the best value. The prepaid rate for semi-display space is £8 ( + VAT) per single column centimetre (minimum 2.5cm). The prepaid rate for classified adverts is 30p ( -i VAT) per word (minimum 12 words). All cheques, postal orders, etc., to be made payable to Everyday with Practical Electronics. VAT must be added. Advertise- ments, together with remittance, should be sent to Advertisements, Everyday with Practical Electronics, Holland Wood House, Church Lane, Great Holland, Essex C013 OJS. Phone/Fax (0255) 850596. For rates and information on display and classified advertising please contact our Advertisement Manager, Peter Mew as above.

PC TECHNICAL SHAREWARE Personal kttack klarms Mould suet hi,, to we the best range of 10. cost it.chni. al and Miscellaneous scientific public domain & sluirevrare for IBNI Pt in the I. A? HUGE RANGE includes. PACKET. FAX. RX TX control. Electronic, 130dB £11.50 PCB design, Circuit and ANTENNA sutras. QS° logPng. Gas powered, 110dB £5.00 PROTOTYPE PRINTED CIRCUIT BOARDS CAD ELECTRONIC& MECH engineenng. SCIENTIFIC:MATH S one offs and quantities, for details send s.a.e. STATS, MEDICAL PROGRA MMING, SOURCE CODE. DATA Childs Tag Alarm £38.50 EDUCATIONAL WINDOWS. BUSINESS and lots more to B. M. Ansbro, 38 Poynings Drive, Sussex Packing and postage 50p. Send today for list Wnte phonc or Fax lodak for kour Free 124 page pnnted catalogue BN3 8GR, or phone Brighton 883871. of Electronic and Radio component bargains. Thr Public Domain Software Librart G.C.S.E. ELECTRONICS KITS, at pocket Secure Assignments Ltd, 2 Cedar Lodge Drive, inicombe House, Beacom Road . money prices. S.A.E. for FREE catalogue. (ion borough, Sumer TAO Wolverton, MILTON KEYNES, MK125ES SIR-KIT Electronics, 70 Oxford Road, Clacton, Trl 002 M3298, Far 0892 66 -4-i Tel: (0908) 319245 C015 3TE. TO CLEAR. Hundreds of resistors, capacitors, RCS VARIABLE VOLTAGE D.C. BENCH POWER SUPPLY SURVEILLANCE KITS semiconductors, i.c. sockets, plastics boxes etc. I to 24 mite up to 'It amp 1 to 20 von up to t amp 1 to 16 'colts uP , ' . c MICRO TRANSMITTER, tuneable 70-115MHz. 500M amps d c Fully stabilised Iron panel meters tor alstam ....pc. a, c Retail value over £100. Only £19.95. Joe range. 40mm x 20mm including microphone. 3-12V. Kit rent readings Overload orotecbo , Fylly varrabN E 4 C inc. f 5.95. Assembled £9.95. Order Code KT1. Karajos, 42 West Parade, Peterborough, PE3 Operates trom xi./ VAT TELEPHONE TRANSMITTER. 30mm x 10mm, powered 6BD. 240V cc from line, transmits both sides of conversation, 500M range. Compact unrt a Tiall 11 i_ • Post and 88-130MHz. Kit f 7.95, Assembled f 12.95. Order Code KT3. DIY PLANS, catalogue of over 20 plans plus In insurance f 4 Size 9 ir 51, i 3 WATT TRANSMITTER. 80-110MHz. 12-15V. adjustable books and manuals including portable gener- NEW MODEL. Up to 38.oits ,1. ti b amps 10 amps peak Full, ..m.c.l, input sensitivity, varicap controlled. several nodes range. Kit Twin panel meters Sae 14,4 a 11 a Cron tel one VAT Carr f 6 £15.95, Assembled £25.95. Order Code KT4. ators, wind generators, inverters, electric bike, RADIO COMPONENT SPECIALISTS All prices include p&p welding generators, solar and water projects. Credit card orders telephone 021 486 3092 Send 2 x 1st class stamps. Jemmett Engineering, 337 WHITEHORSE ROAD, CROYDON Send 2a1 xi class stamps to, Catalogue Cheques.'P 0 s payable to = SURREY, U.K. Tel 081.6841665 C.E.C. 8 Hallam Gardens, Pinner, Middlesex HAS 4PR. Est Large SAE Delivery 7days Callers welcome Closed Wednesday (Dept. EPE), 515A Bristol Road. MINIATURE TRANSM ITTER. Long range, Birmingha m B29 6AU tuneable to FM radio, sensitive microphone, 20x28mm, detailed instructions. SPRING OF- CIRCUIT DESIGN ENGINEER Trans mitter & Receiver Modules FER: £7.95 assembled; kit £4.50. Cheques/PO's: If you want to make extra money in your 418MHz FM Transmitter and Receiver Excel Products, (EPE2), Unit 14, Sunningdale, modules DTI Approved. Legal 8 Licence spare time and you are very experienced Exempt Typical 50m range in-building, Bishop's Stortford, Herts CM23 2PA. in wireless home security alarm systems 200m range outside Low power, 5Kbps MULTI-PURPOSE TEST CASSETTE; real and have knowledge of mass production data rate ideal for home automation, time individually mastered. Tests Dolby level, security, car alarm, paging systems, process, please write ASAP to - robotics, elderly person/child alarm. azimuth, replay frequency response (30Hz- MIKE HILL nurse call. PC "wireless - networks. 15kHz), Dolby B/C tracking, speed. (120µs and P.O. BOX 98777 Complete with data, FULL application 70Its eq. available). Supplied with instructions notes and FREE Evaluation PCBs. Transmitter T.S.T. £39.50 per pair inclusive VAT PAP eft. and specifications. f20/tape; post free U.K. HONG KONG Datalogue 1E1 001 details other radio/remote control kits/modules (outside U.K. add f2.50/tape) cheques/postal Please enclose Cheque/PO with order (Sorry no Credit Cards) orders payable to: Ian Harrison, 7 Mill Hill, BTEC ELECTRONICS Please allow 14 days for delivery. (Mail Order only) Repton, Derby DE65 6GO. (0283) 702875. TECHNICIAN nikam electronics ltd West End Gardens Falrford Glos GL7 4JB HUNDREDS OF UNUSUAL ITEMS CHEAP! Tel/Fax: 0285 713862 Send 95p (coins/stamps) for interesting samples FULL-TIME TRAINING and list. Grimsby Electronics, Lambert Road, THOSE ELIGIBLE CAN APPLY FORE T GRANT SUPPORT THE BRITISH AMATEUR Grimsby. AN EQUAL OPPORTUNITIES PROGRAMME WANTED: Software V6.0 for Sunshine EPROM ELECTRONICS CLUB Programmer EW-904 (not EW-904 BN). D. 0.N.C., 0.N.D. and H.N.C. exists to help electronics enthusiasts by Reeves, 021-354 6264. Next course com mences personal contact and through a quarterly Newsletter Monday 10th January 1994 Thls 2/12 cm space in For membership details. FULL PROSPECTUS FROM write to the Secretary Everyday with Mr. J. F. Davies, 70 Ash Road, LONDON ELECTRONICS COLLEGE Practical Electronics Cuddington, Northwich, Would ONLY cost you (Dept EPE) 20 PENY WERN ROAD Cheshire CW8 2PB. EARLS COURT. LONDON SW5 9SU Space donated by Everyday with Practical VAT TEL: 071-373 8721 Electronics £20

NE W MARKET TRANSFOR MERS LTD EVERYDAY L Name Mail Order Transformer Specialists WITHip menc e Toroidal and Laminated Transformers, 3VA to 1 kVA EL CTRONICS Address Fast delivery .Competitive prices Quality guaranteed SUBSCRIPTION ORDER FOR M Phone: Michael Dornan on 0638 662989 for Immediate Quote Annual subscription rates I enclose payment of £ (1994): (cheque/PO in sterling only, payable to UK £22.00. Overseas £28 MAIL ORDER Everyday with Practical Electronics). Alternatively Extensive range of over 40,000 items includ- (surface mail). £45.50 (airmail) send Access or Visa number and card expiry date. ing - Electronic components. tools, computer hardrsoftware and office equip ment. all at very To: competitive prices Please send two first class Everyday with Practical Electronics, Signature sta mps with specific require ments for relevant 6 Church Street, Wimborne, Please supply name and address of card-holder if different price lists to - from the subscription address shown above Subscrip- 117 1 Dorset BH21 1J H = LB International, 76 Knighton Road, tions can only start with the next available issue. Leicester LE2 3HJ. Tel: 0202 881 749 Fax 0202 841692 For back numbers seethe Editorial page I M2/94

174 Everyday with Practical Electronics, February, 1994 VIM 4 f.a SERVICE MANUALS Cooke International SUPPLIER OF QUALITY USED TEST INSTRU MENTS We have what is probably the largest ANALYSERS. BRIDGES, CALIBRATORS, VOLTMETERS. GENERATORS. range of Service Information available OSCILLOSCOPES. POWER METERS, ETC. ALWAYS AVAILABLE ORIGINAL SERVICE MANUALS FOR SALE anywhere. COPY SERVICE ALSO AVAILABLE EXPORT, TRADE AND U.K. ENQUIRIES WELCOME From the Earliest Valve Wireless to SEND S.A.E. FOR LISTS OF EQUIPMENT AND MANUALS ALL PRICES EXCLUDE VAT AND CARRIAGE the Latest Video Recorders. DISCOUNT FOR BULK ORDERS SHIPPING ARRANGED Colour Televisions, Test Gear, Audio, REPAIRS & CALIBRATION UNDERTAKEN OPEN MONDAY TO FRIDAY 9AM-5PM Computers, Amateur Radio in fact Unit Four, Fordingbridge Site, Main Road, Bandiam, Bognor Regis, West Sussex, P022 OEB practically anything. Tel ( + 44) 0243 545111/2 Fax ( + 44) 0243 542457 HIGH END EQUIPMENT PURCHASED Originals or Photostats as available. '\ "Also available. Our FREE catalogue SHERVVOOD ELECTRONICS 9 Lower Birch wood, So mercotes, Derbyshire 0E55 4N G detailing Hundreds of Technical Books £1 Special Packs - choose 1 pack FREE for every 10 purchased and Repair Guides available. SP I 15 x 5mm Red Leds SP36 25 x 10uF/25V radial elect caps SP2 15 x 5rnm Green Leds SP37 20 100uF/40V radial elect caps SP3 12 x 5rnrn Yellow Leds SP39 12 x 470uF/16V radial elect caps Spa 150 3mm Red Leds SP42 200 x Mixed 0 25W C.Film resistors SP7 121 3mrn Green Leds SP47 5 o Min push button switches Send 2 x 1st class stamps for your copy SP8 10 x 3mm Yellow Leds SP102 20 a 8 pin OIL sockets SPIO 100 x 1N4148 diodes SP103 15 x 14 pin DIL sockets TODAY. SPI 30 x 1144001 diodes SP104 15 x 16 pin OIL sockets SP12 30 x 1144002 diodes SP112 6 o Cmos 4093 SP18 20 x BC182 transistors SP125 10 0 1000uF/16V rad. elect caps SP20 20 x BC184 transistors SP130 100 x Mixed 0.5W C Film resistors Mauritron Technical Services (EPE), SP23 20 x BC549 transistors SP133 20 x 1144004 diodeS SP25 5 5 555 timers SP134 15 x 1144007 diodes SP26 5 x 741 Op-amps SP135 6 a Mmn. slide switches 47A High Street, SP28 6 x Cnios 4011 SP137 4 a W005 bridge rectifiers SP29 4 x Cmos 4013 SP138 20 x 2.2uF/50V radial elect caps Chinnor, RESISTOR PACKS - 0 25W C Filer £2 75 Catalogue available £1 or FREE r Oxfordshire, VISA RP3 5 each value - total 365 RP7 10 each value - total 730 £4 15 with first order over £5 RPIO 1000 popular values 05 60 -li OX9 4DJ. Cheques or P.0 to NO VAT No m add CI P&P to all ordars Tel: 0844 351694. Fax: 0844 352554. S HER W OOD ELECTR ONICS i

CO MPONENTS WE CAN SUPPLY A VAST RANGE OF SPARES to, Many makes of N. Video. Computer & Audio Equipment WRITE For TV * Video (End sue please) Or PHONE FOR A 'PRICE & AVAILABILITY' CAMBRIDGE COMPUTER SCIENCE LIMITED Audio * Computer on your requirements. 0452 526883 Borland C + + 2.0 for DOS & Windows complete with mouse £45.00 LCD modules 16 char by 1. £4.00, 20 char by 2. £6.00, 40 char by 1 £6.00 910E0 SPARES COMPUTER SPARES 3.5" 720K Diskette Drives £25.00 each We can supply Pinch Rollers. Idlers. Belt PHILIPS MONITORS SPECIAL OFFER Used hard disk drives, 112MByte £110, 70MByte £75, 40MByte £45. Kits Heads many other Service 8 BM7513 Sery Manual £3 49 Sinclair. Atari 20MByte £29.10MByte £14, Limited quantities. phone before Ordering Specific parts for over 160 makes CM8833 Sery Manual £7 84 Commodore CHIPS Used PC memory/I0 card AST six pack with 384k RAM f15.00 each CM8833 Line 0/P Tx £24 94 T11 -SATELLITE 40054 ROM t 2, 111 69 CM9073 0/0 Switch £8 63 Used IBM PC hard disk controller, 8 bit MFM £5.00 each AUDIO SPARES TMS4S32NL4 DRAM CO 99 CM11342 Line OrP Tx £28 51 Used Tseng labs, multi I/O + mono video card for PCs £10.00 each Switches. Transformers. Semiconduc- 2X8302 ULA (OL) £e49 Used Compaq Enhanced Colour Graphics Card £5.00 each tors etc etc Large range available. AMSTRAD ZX8401ULA (Spec I £5.44 CPC.464 User Manual Ert) 95 CO25913 DMA (ST) £32.99 'Lucky Dip PC cards, untested, no warranty, various types E 1 .00 each EQUIPMENT MANUALS PCW 9512 Sets Manual £14 99 5 25 - Disk Drives,1 .2MByte Slimline PC £19.00 each Large selection ol Manufacturers Keyboard CPU (ST) £23.50 AY38912 £7 06 Service & User information available. PC713V (STE.PSUI £2.89 5.25" Disk Drives, 80 Tk, DSDD £19.00 each SED9420CAC £14 93 Original manuals supplied if possible PC900V/H IL3 (ST) 5.25" Disk Drives. 80 11, DSDD Used. No Wty £7.00 each Most Amslrad pans available 6569 VIC (C/34) £l9 95 SEMICONDUCTORS (The £7.00 drives are sold on a strictly "as is" basis) FLYBACK TRANSFORMERS 8565 VIC IC64C) C18.85 We can supply thousands of different DIGITAL 1/1320 £29 05 MB81416-12 DRAM iC16) £4 49 5.25" Disks, DSDD, 48tpi, boxes of 10 £2.00 box Custom & Industry Standard devices. Digital multimeter, 14 ranges, inc. leads & manual £9.00 each IBM 6512 (State type) £49 93 Further savings for 15 -1 84508A E1 50 TDA4601 C3 25 We can supply over 300 types of quantities Please enquire Apricot Disk drive PSU 5V a 2.5A, 12V 2A E10.00 each £4 99 UC38134 . £8.95 L 0 PTa Please enquire with COMMODORE 5V 6A PSU £4.00 each LM733Cfil £2 43 4646522 £6 99 into taken trom part C64/64CSery Manual £14 99 5V i. 10A PSU MA813049H £5 17 UPC1378H. £2 62 We only show a small sample C64C User Manual £4 49 Disk Drive Data lead BBC micro to Disk Drive(s) Single 2.00 Dual £4.00C5.00 each P8255A £2 85 UPC1397C E4 34 08 99 STK414111 tfl 79 2SK301R f 1 85 of our range Batteries. Leads. 906114-01 PL A i064i Disk Drive Power lead BBC Micro to Disk Drive(s) Single 2.00 Dual £4.00 each C44 ic TA7280P £6 88 27C256-200 £2 98 ribbons also stocked 83728 (A3000 68000 CPUs 8MHz £2.50 each 8086 CPU chips Order by Post or Phone VISA ACCESS Z E E Z80A CPU, CTC, PIO £1.20eacht DMA C2.00-, £4.50 all 4 DELTA 8 SWITCH accepted with pleasure M AR APET (EEB) 74LS TTL, pick and mix. buy 10 or more for C0.12 each Minimum POP charge is El 25 Please the 1 HOR N BE A M ME WS add extra 50p it ordering a Manual or LOPT s Types available: '00 '02 '04 08 10 11 '12 13 14 15 20 21 '26 27 30 32 33 37 .411 items subject to emlaboltly elm GL O U CESTER GL2 OUE 38 42 74 83 85 86 96 107 '109 '122 '125 '132 '136 '138 139 '145 '151 '153 Pm-es can change Without notice 157 '158 '160 '162'163'164 '165 '174 '191 '193 240253 257 260 298 353 365 '366'373 '385 '390399 '670 '682 27128 EPROMS (Ex equipment) £1.20 each £5.00. 5 27128 EPROMS £2.50 each 27C256 EPROMS (Ex Equipment) £1.40 each 27256 EPROMS £2.60 each INFOTECH & STREE = 27C256-25 EPROMS £3.50 each 27C512 EPROMS (Ex Equipment) £1.40 each 76 Church St, Larkhall, Lanarks, ML9 1HE 256K DRAM (Ex Equipment) £0 40 each 1MBit-10 DRAM (Ex Equipment)1.40 each £ Phone (0698) 883334/888343 or Fax (0698) 884825 6116 2K Byte SRAM £1 . 10 each 6264-12 8K Byte SRAM £3 80 each 62256-10 32K Byte SRAM £5.00 each Remember Not only do we have every sheet ever produced. but we also have 65256 32K Byte ramseach £4.00 8K Byte NV ram chips C3.00 each or E10.00 four 16 18& 20 pin dil low proflleiC sockets 0.3" wide £0.40/10; £3.00 100 The World's Largest Collection of 22 & 24 pin dil low profile IC sockets 0.4 wide £0.40/10; £3.00. 100 24, 28, 32,40 & 48 pin dil low profile IC sockets 0.6" Wide £0.40/ 10; £3.00/100 Circuit tester, finds faults in TTL & CMOS logic circuits, inc leac ., £6.00 each SERVICE MANUALS & CIRCUITS Metal project boxes drilled & painted but unused 28 x 32 5 x Scm £4.00 each Eurocard Racks. £10.00 each We are now successfully running a Library Service which allows you to borrow any Smoke detectors... £4.00 each Used computer cards many useful components (large ones socketed , manual you want for as long as you want, and when you need another manual, just return Wini controller (WD HOC chi I..... £1.00 each the one you have, plus a £3.95 exchange fee and tell us what you want next. CPU card (8088, Z80 & EPMs)... . £3.00 each Keyboards. full Owerty, number pad and LCD £8.00 each Desktop computer case with 200W mains PSU (used) £19.00 each Borrow any Service Manual for £3.95 Used IBM PC Cases with PSU. £30.00 each Prices inclucie neweuiro ss amen regardless of its size or normal cost Add 1q$1134A°ef Ati?callf OcVss rAit2nOsr'Alr,orilecrigTsig jIregr. Dept EE, 374 Milton Road, Ca mbridge CB4 1SU The cost of this service is a yearly subscription fee of only £59.95. Join now & get a free Tel: 0223 424602, 0831 430496 or 0831 430552 Mail order only) .1 Data Ref Guide'.

I 7 5 Everyday with Practical Electronics, February, 1994 'M AKE YOUR INTERESTS PAY! Millions of quality co mponents Over the past 100 years more than 10 million Students throughout the world have found at lowest ever prices! it worth their while! An ICS home-study course can help you get a better lob, make more money and have more fun out of life , ICS has over 100 years experience in home-studs courses and is the largest correspOndenCe school in the world You learn at your ow, Plus Tools, Watches, Fancy Goods, Toys. paCe when and where you want under the guidance of expert personal tutors Find ow how we can help YOU. Post or phone today for FM INFORMATION on the course of you! Mail order UK only. choice. [Tick one box only!) .N.. = = I. MI N MI •• IBM = BU M = MI MI m m m m m MI l• All inclusive prices - VICIe0 & .II Electronics i---,I-I • HTV,i-Fi Servicing I L NO VAT to add on. • • Basic Electronic r-- 1 Refrigeration 6 Send 43p stamped self addressed label or • Engineering lCity IL Guilds) L--, Air Conditioning E I Electrical Engineering 0 Car Mechanics E I envelope for catalogue/clearance list. I Electrical Contracting/ r-- 1 Computer installation I-1 Programming E At least 2,100 offers to amaze you I GCSE/GCE /Sal Over 40 examination subjects to choose from P.! I Brian J Reed I Name Address 6 Oueens mead Avenue, East Ewell

1,1 I el natiOnlliCorrespondence Schools Dept ECS 24 Epso m, Surrey KT17 3E0 ' 314 H,on Street Sutton. Surrey SM1 1PR or 041.221 7373 (24 hours) I IN N = m m m m m m MI Eli Ell MI MI = In ink Tel: 081-393 9055

N. R. BAR D WELL LTD (EPE)

200 Signal diodes 1N4148 CI 00 200 Printed circuit board 20mm fuse ADVERTISERS INDEX 75 Rectifier Diodes 1N4001 CI 00 clips .C1.00 50 Rectifier Diodes 1N4007 £1 00 200 Asstd. disc ceramic capacitors C1.00 AITKEN BROS. & CO 98 58 Rectifier Diodes I N 5401 £1.00 80 Meld. Capacitors int to lin ..£1.00 100 Asstd. Zeners Cl 00 80 Asstd electrolytic capacitors .C1.00 ANNEX SOFTWARE 145 10 NE555 Timer ICs Cl 00 80 1UF 16V Radial electrolytics C1.00 AUTONA 173 30 BC478 Trans,stom Cl 00 80 4 7UF 16V Radial electrolytics moo a EIFY51 Transistors £1.00 75 4 7UF 63V Radial electrolytics £1.00 N. R. BARD WELL 176 20 2N3904 Transistors £1.00 80 10UF 16V Radial electrolytics ..C100 R. BARTLETT 145 30 MPSA42 Transistors £1.00 50 IOUF SOV Radial electrolytics .£1.00 30 5mm red I.e d.s £1.00 40 22UF 25V Radial electrolytics £1.00 B.K. ELECTRONICS Cover (iii) 25 Asstd. high brightness Ieds Cl OD 60 33UF 16V Radial electrolytics .C1.00 24 Miniature red I.e.d.s 3mm die £1 00 80 100UF 10V Radial eletrolytics _CLOD BRIAN J. REED 176 50 Axial I.e.da (Diode package) wide 50 220UF 16V Radial electrolytics _O M BULL ELECTRICAL Cover (ii) angle I.e.d.s £1.00 60 470UF 10V Radial electrolytics ..C1.00 12 Asstd seven segment displays £1.00 40 1000UF 10V Anal electrolytics . £40 CAMBRIDGE COMP. SCIENCE 175 30 Asstd. IF transformers £.00 12 1000UF 25V Axial electronics . £1.00 CHATWIN GUITARS (JCG) 173 48 Asstd. C011 formers £1.00 I 1 Farad 5.5V memory back op 100 Asstd. RE chokes (inductors) £1.00 capacitor £1.00 CHELMER VALVE CO 119 30 Asstd. connectors edge-MI-MI etc C1.00 100 4N7 Mini Axial capacitors 10 4P 3W mBB min rotary switches £1.00 1 10 waft Stereo amplifier. 4 controls CIRKIT DISTRIBUTION 99 20 I inch Glass reed switches ci 00 plus data £2 95 COMPELEC 173 20 Magnetic ear pips plus lead 8 plug C1.00 20 Min SP/C0 slide switches. £1.00 Prices include VAT postage f1 25 Stamp or Lists COOKE INTERNATIONAL 175 30 Asstd S r.l sockets up to 40 pin .£1.00 20 24-way turned pin IC sockets E1.00 288 Abbeydale Road Sheffield S7 1FL CRICKLEWOOD ELECTRONICS 165 16 40 pin di I wire wrap IC sockets El 00 CR SUPPLY COMPANY 176 2 ORP12 light dependant res.stors Cl 00 Phone (0742) 552886 Fax (0742) 500689 DISPLAY ELECTRONICS 90 ELECTROVALUE 119 ESR ELECTRONIC COMPONENTS 102 Carbon Film resistors 1WV 5% E24 series 0.51 R to 10M0 1 p 100 off per value 75p even hundreds per value totalling 1000 £6 00p EUROCOM INTERNATIONAL 109 Metal Film resistors 'AlN 1OR to 1 MO 5% Et 2 series - 2p. 1% E24 series 3p HART ELECTRONIC KITS 155 Mixed metal, carbon film resistors 14W E24 series 1RO to 10M0 115p 1 watt mixed metal/Carbon Film 5% El 2 series 4R7 to 10 Megohms 5p HENRYS AUDIO ELECTRONICS 96 Linear Carbon pre-sets 100m W and 54W 100R to 4M7 E6 series 7p ICS 176 Miniature polyster capacitors 260V working for vertical mounting 015. 022, 033 04 7 068.4p. 0.1 - 5p. 0.12, 0.15, 0.22 - 6p. 0.47 - 8p. 0.68 - 8p. 1.0 - 12p INFOTECH & STREE 175 Mylar (polyester) capacitors 100V working E12 series vertical mounting JAYTEE ELECTRONIC SERVICES 99 1000p to 8200p - 3p 01 to .068 - 4p 01 - 5p 0 12, 0 1 5, 0.22 - 6p. 0.47/50V - 8p Submin ceramic plate capacitors 100V wkg vertical mountings. E12 series JPG ELECTRONICS 173 2% 1.8pf to 47pf - 3p. 2% 56pf to 330pf - 4p. 10% 390p-4700p 4p MAGENTA ELECTRONICS 100/101 Disc/plate ceramics 50V El 2 series 1 PO to 1000P. E6 Series 1500P to 47000P . . 2p Polystyrene capacitors 63V working El 2 series long axial wires MAILTECH 92 10pf to 820pf • 5p. 1000pf to 10.000pf - 69. 12,000pf 7p MAPLIN ELECTRONICS Cover (iv) 741 Op Amp - 20p. 555 Timer - 20p. LM3900 80p cmos 4001 - 20p. 4011 - 22p. 4017 - 40p. 4069UB unbuffered 20p MARAPET 175 ALU MINIU M ELECTROLYTICS (Mfds/Volts) MAURITRON 175 1/ 50. 2 2/50, 4.7/50. 10/25. 10/50 5p 22/16. 22/25. 22/50. 33/16, 47/16, 47/25, 47/50 6p M&B ELECTRICAL SUPPLIES 94 100/16. 100/25 7p; 100/50 12p M&B ELECTRONICS 109 220/16 8p; 220/25. 220/5010p; 470/16. 470/25 lip MOP ELECTRONICS 98 1000/25 25p; 1000/35, 2200/25 35p; 4700/25 70p Submin. tantalum bead electrolyics (Mfda/Volts) NATIONAL COLLEGE OF TECHNOLOGY 95 0.1/35, 0.22/35, 0.47/35, 1.0/35, 3.3/16. 4.7/16 14p NUMBER ONE SYSTEMS 93 2.2/35.4.7/25.4.7/35. 6.8/16 15p; 10/16. 22/6 20p 33/10.47/6. 22/16 30p; 47/10 35p; 47/16 60p; 47/35 80p OMNI ELECTRONICS 96 VOLTAGE REGULATORS PCL SOFTWARE 98 1A + or - 5V. By. 12V, 15V, 18V & 24V - 55p. 100mA. 5.8, 12. 15. V -i-- 30p DIODES (ply/amps) PICO TECHNOLOGY 97 75/25mA 1N4148 2p. 800/1A 1 N4006 4%p. 400/3A 1N5404 14p. 115/15mA 0A91 .. 8p POWERWARE 95 100/1A 1N4002 3%p. 1000/1A 1N4007 5p. 60/1.5A Si Ml 5p 100/1A bridge 400/1A 1N4004 4p. 1250/1A BY 127 10p. 30/150mA 0A47 gold bonded 18p PROFILE ELECTRONICS 96 Zener diodes E24 series 3V3 to 33V 400m W - 89. 1 watt 12p ROLINE SYSTEMS 126/127 Battery snaps for PP3 - 6p for PP9 12p SEETRAX CAE 91 LED's 3mm. & 5mm. Red. Green. Yellow - 10p. Grommets 3P-im 2p 5mm 2p Red flashing L.E.D.'s require 9-12V supply only .. 50p SERVICE TRADING CO. 96 Mains indicator neons with 220k resistor 10p SHERWOOD ELECTRONICS 175 20mm fuses 100mA to 5A. 0. blow 6p.A/surge 10p. Holders, chassis. mounting 6p High speed pc drill 0.8, 1.0, 1.3, 1.5, 2.0mm - 40p. Machines 12V dc £15 00 S&N ENTERPRISES 173 HELPING HANDS 6 ball joints and 2 croc clips to hold awkward jobs 13.50 STEWART OF READING 98 AA/H P7 Mead rechargeable cells 90p each. Universal charger unit f 6 50 AA/HP7 zinc/carbon batteries in packs of 4 . 11 10 per pack SUMA DESIGNS 149 Glass reed switches with single pole make contacts - 8p. Magnets . 15p TSIEN (UK) 111 0.1 Shipboard 2%" x 1" 9 rows 25 holes - 25p. 31. x 214" 24 rows 37 holes 70p Jack plugs 2.5 & 3.5m - 14p; Sockets Panel Mtg. 2.5 & 3.5m 10p Ear pieces 2.5 & 3 5mm, dynamic - 20p; 3.5mm crystal f 1 .50 ADVERTISE MENT MANAGER: Multi cored solder. 22G - 8p yard. 186 - 14p yard. TRANSISTORS PETER J MEW BC107/8/9 - 12p. BC547/8/9 - 8p. BC557/8/9 - 8p. BC182, 182L, BC183, 183L. ADVERTISE MENT OFFICES: BC184, 184L, BC212, 212L - 10p. BC327, 337, 337L - 12p. BC727, 737 - 12p. BD135/6/7/8/9 - 25p. BCY70 - 18p. EVERYDAY with PRACTICAL ELECTRONICS, BFY50/51/52 - 20p. BFX88 - 15p, 2N3055 - 55p. TIP31, 32 - 30p, TIP41, 42 - 40p BU208A - f 1 50, 8E195.197 - 12p ADVERTISEMENTS, Ionisers with seven year guarantee, list price £16.95 £12.50 HOLLAND WOOD HOUSE, CHURCH LANE, All prices are inclusive of VAT. Postage 30p (tree over f 5) Stamp for list. THE CR SUPPLY CO GREAT HOLLAND, ESSEX C013 OJS. 127 Chesterfield Rd., Sheffield S8 ORN Phone/Fax: (0255) 850596 Tel: 0742 557771 Return posting For Editorial address and phone numbers see page 103.

Published on approximately the first Friday of each month by Wimborne Publishing Ltd.. 6 Church Street. Wimborne. Dor,ei 1.111 2 I Ii)). Printed in Lngland ti) Benham & to. Ltd. Colchester. Essex. Distributed by Seymour. Windsor House. 1270 London Road. Norbury. London SW Hi 4DH. Sole Agents for Australia and New Zealand Gordon & Gotch (Asia) Ltd.. South Africa Central News Agency Ltd. Subscriptions INLAND £22 and OVERSEAS £28 1f45.50 airmail) payable to "Everyday with Practical Electronics" Subs Dept. 6 Church Street. Wimbome. Dorset BH2I DEL EVERYDAY with PRACTICAL ELECTRONICS is sold subject to the following conditions, namely that it shall not, without the written consent of the Publishers first having been given. be knt. resold, hired out or otherwise disposed of by way of Trade at more than the recommended selling price shown on the cover, and that it shall not be knt. resold, hired out or otherwise disposed of in a mutilated condition or in any unauthorised cover by way of Trade or affixed to or as part of any publication or advertising, literary or pictonal matter whatsoever. PO WER AM PLIFIE R MO D ULES-T U R NT A BLE S-DIM ME R S- • 11 • • - - • • • • 1 • • LO U D SPE A KE R S-19 INC H STERE O RA C K AM PLIFIE RS SERVICE • LARGE (A4)S.A E., SO STA MPE D FOR CATALOGUE

OMP MOS-FET POWER AMPLIFIERS THOUSANDS PURCHASED ; u r.),1114.,... SUPPLIED READY BUILT AND TESTED. HIGH PO WER TWO CHANNEL 19 INCH RACK BY PROFESSIONAL USERS These modules now enjoy • worldwide reputation lor quality. reliability and performance al e tealishc price. Four models are available to suit the needs of the professional and hobby market Is. Industry. Leisure. Instrumental and 111-F1 etc. When comparing prices. NOTE that all models include toroidal power supply. integral heal sink. glass ',bre P C.O. and drive circuits to power a compatible Vu meter All models are open and short circuit proof THOUSANDS OF MODULES PURCHASED BY PROFESSIONAL USERS

O MP/MF 100 Mos-Fet Output power 110 watts R.M.S. into 4 ohms, frequency response 1Hz - 100KHz -3d6. Damping Factor 300, Slew Rate 45V(uS, T.H.D. typical 0.002 %, Input Sensitivity 500mV, S.N.R. -110 dB. Size 300 x 123 x 60m m. PRICE £40.85 - £3.50 P&P

OMP/MF 200 Mos-Fet Output power 200 watts R.M.S. into 4 ohms, frequency response 1Hz - 100KHz TH E RE N O W N E D MXF SE RIES OF PO WE R AM PLIFIE RS -3d13, Damping Factor 300. Slew Rate 50V/uS, FOUR MODELS:- MXF200 (100W - 100W) MXF400 (200W + 200W) T.H.D. typical 0.001 %, Input Sensitivity 500mV. S.N.R. MXF600 (300W • 300W) MXF900 (450W + 450W) -110 dB. Size 300 x 155 x 100m m. ALL POWER RATINGS R.M.S. INTO 4 OHMS, BOTH CHANNELS DRIVEN PRICE £64.35 - £4.00 P&P FEATURES: *Independent power supplies with two toroidal transformers * Twin LED, Vu meters * Level controls * Illuminated onroff switch * nil connectors * Standard 775mV inputs * Open and short circuit OMP/MF 300 Mos-Fet Output power 300 watts proof * Latest Mos-Fets for stress free power delivery into virtually any load * High slew rate * Very low R.M.S. Into 4 ohms, frequency response 1Hz - 100KHz distortion * Aluminium cases * MXF600 & MXF900 tan cooled with D.C. loudspeaker and thermal protection. -3dB, Damping Factor 300, Slew Rate 60V/uS, USED THE WORLD OVER IN CLUBS, PUBS, CINEMAS, DISCOS ETC. T.H.D. typical 0.001 %. Input Sensitivity 500mV. S.N.R. -110 dB. Size 330 x 175 x 100m m. SIZES:- MXF200 W19" all3' (2U):11311" MXF400 W1 9"x115','" (3U)xD12" PRICE £81.75 - £5.00 P&P MXF600 W1 9"x115'," (3U):11313" MXF900 W1 Iii"x145'," (3U)x1314 4 ." O MP/MF 450 Mos-Fet Output power 450 watts PRICES:- MXF200 £175.00 M XF400 £233.85 R.M.S. into 4 ohms, frequency response 1Hz - 100KHz M XF600 £329.00 M XF900 £449.1 5 -3dB. Damping Factor 300. Slew Rate 75V/uS, SPECIALIST CARRIER DEL. £12.50 EACH T.H.D. typical 0.001 %. Input Sensitivity 500mV. S.N.R. -11 dB. Fan Cooled, D.C. Loudspeaker Protection, 2 :iiiriDF C•IT,3/47 4--7 T• V i V iT• WITI T•Ut•T:1-12:671-4-17 Second Anti-Thu mp Delay. Size 385 x 210 x 105m m. PRICE £132.85 • £5.00 P&P

OMP/MF 1000 Moe-Fat Output power 1000 watts R.M.S. into 2 ohms, 725 watts R.M.S. into 4 ohms, frequency response 1Hz - 100KHz -3dB, Damping Factor 300, Slew Rate 75V/uS. T.H.D. typical 0.002°0. Input Sensitivity 500mV. S.N.R. -110 dB. Fan Advanced 3-Way Stereo Active Cross-Over, housed in a 19 - 1U case. Each channel has three level controls: Cooled. D.C. Loudspeaker Protection, 2 Second bass. mid 8 top. The removable front fascia allows access to the programmable DIL switches to adjust the cross-over frequency: Bass-Mid 250/500/800Hz, Mid-Top 1.8/3/5KHz. all at 24dB per octave. Bass invert switches Anti-Thu mp Delay. Size 422 x 300 x 125m m. on each bass channel. Nominal 775mV inpuffoutput. Fully compatible with OMP rack amplifier and modules. PRICE £259.00 - £12.00 P&P Price £117.44 - £5.00 P&P NOTE MOS-FET MODULES ARE AVAILABLE IN TWO VERSIONS, STANDARD INPUT SENS 500mV, BAND WIDTH 100101x. r41-4i11:1 •17 1-FT T:r.-TillifF rririT.T3 * ECHO & SOUND EFFECTS* PEC (PROFESSIONAL EQUIP COMPATIBLE) - INPUT SUNS STEREO DISCO MIXER with 2 x 7 band 7 75mV. BAND WIDTH 501042. ORDER STANDARD OR PEG. L& R graphic equalisers with bar graph LED Vu meters MANY OUTSTANDING LOUDSPEAKER LARGE SELECTION OF SPECIALIST LOU DSPEA KERS FEATURES:- including Echo with repeat & AVAILABLE, INCLU DIN G CABIN ET FITTIN GS, SPEAKER speed control, DJ Mic with talk-over GRILLES, CR OSS-OVERS AN D HIG H PO WER, HIG H switch, 6 Channels with individual faders plus cross fade, Cue Headphone Monitor. 8 FRE QUEN CY BULLETS AN D HORNS, LAR GE (A4) S.A.E. Sound Effects. Useful combination of the (60p STA MPE D) FOR CO MPLETE LIST. following inputs:- 3 turntables (rnag), 3 mics, 5 Line for CD, Tape, Video etc. Mc Kenzie and Fane Loudspeakers are also available.

Price £144.99 + £5.00 P&P SIZE: 482 x 240 x 120 m m rqT TUT T M W M-I FIIIII4:1‘41;N Aielizisisi Aixi

J1,1, 0111 11 re% iel:Ix1 171 ALL EMINENCE UNITS 8 OHMS IMPEDANCE 8" 100 WATT R.M.S. ME8-100 GEN. PURPOSE. LEAD GUITAR. EXCELLENT MID. DISCO Join the Pies* revolution: The low dynamic mass (no voice coil) of a Plezo tweeter produces an improved transient response with a lower distortion level than ordinary dynamic hveeters. As a crossover is not required RES. FREQ. 72Hz. FREQ. RESP. TO 4KHz, SENS 97dB, PRICE £32.71 £2.00 P&P 10" 100 WATT R.M.S. MET 0-100 GUITAR, VOCAL. KEYBOARD, DISCO, EXCELLENT MID. these units can be added to existing speaker systems of up to 100 wags (more it two are put in series. FREE EXPLANATORY LEAFLETS ARE SUPPLIED WITH EACH TWEETER. RES. FREO. 71Hz. FREQ. RESP, TO 7KHz. SENS97dB. PRICE £33.74 - £2.50 P&P 10" 200 WATT R.M.S. ME10-200 GUITAR. KEYB'D. DISCO, VOCAL, EXCELLENT HIGH POWER MID. TYPE 'A' (KSN1036A) 3- round with protective wire mesh. Ideal for RES. FRED. 65Hz. FREO. RESP. TO 3.5KHz, SENS 99dB. PRICE £43.47 • £2.50 P&P bookshelf and medium sized speakers. Price £4.90 50p P&P. 12" 100 WATT R.M.S. ME12-100LE GEN. PURPOSE, LEAD GUITAR. DISCO, STAGE MONITOR. TYPE '13' (KSN1005A) 3Y0 - super horn for general purpose speakers, RES.FREO. 49Hz, FRED. RESP. TO 6101z, SENS 100dB. PRICE £35.64 • £3.50 P&P disco and P.A. systems etc. Price £5.99 • 50p P&P. 12" 100 WATT R.M.S. ME12-100LT (TWIN CONE) WIDE RESPONSE, P.A., VOCAL, STAGE MONITOR. ABS. FRED 42Hz, FRED. RESP. TO 10KHz, SENS 98dB. PRICE £36.67 • £3.50 P&P TYPE 'C' (KSN1016A) 2-x5 - wide dispersion horn for quality Hi-Fi sys- tems and quality discos eft. Price £6.99 50p P&P. 12" 200 WATT R.M.S. ME12-200 GEN. PURPOSE, GUITAR, DISCO, VOCAL. EXCELLENT MID. RES. FRED. 58Hz, FRED. RESP. TO 6KHz, SENS 9846. PRICE £48.71 • £3.50 P&P TYPE '0' (KSN1025A) 2-x6 - wide dispersion horn. Upper frequency 12" 300 WATT R.M.S MEI 2-300GP HIGH POWER BASS. LEAD GUITAR, KEYBOARD, DISCO ETC. response retained extending down to mid-range (2KHz). Suitable for high RES. FRED. 47Hz, FREO. RESP, TO 5KHz. SENS 103dB. PRICE £70.19 • £3.50 P&P quality Hi-Fi systems and quality discos. Price £9.99 • 50p P&P. 15" 200 WATT R.M.S. MET 5-200 GEN. PURPOSE BASS, INCLUDING BASS GUITAR. TYPE 'E' (KSN1038A)3 9." horn tweeter with attractive silver finish trim. RES. FREO. 46Hz. FRED. RESP. TO 5KHz, SENS 99dB. PRICE £50.72 • £4.00 P&P Suitable for Hi-Fi monitor systems etc. Price £5.99 • 50p P&P. 15" 300 WATT R.M.S. ME1 5-300 HIGH POWER BASS, INCLUDING BASS GUITAR. RES. FREO. 39Hz, FREO. RESP. TO 3KHz, SENS 103dB. PRICE £73.34 £4.001411 LEVEL CONTROL Combines, on a recessed mounting plate. level control and cabinet input jack socket. 85x85mm. Price £4.10 • 50p P&P. EARBENDERS:- HI-Fl, STUDIO, IN-CAR, ET ALL EARBENDER UNITS 8 OHMS (Except E138-50 EB10-50 which are dual Impedance tapped a 4EB ohm) BASS, SINGLE CONE, HIGH COMPLIANCE, ROLLED SURROUND ci,. 8" 50watt E1113-50 DUAL IMPEDENCE, TAPPED 4/8 OHM BASS, HI-Fl, IN-CAR. RES. FREO. 40Hz, FRED. RESP. TO 7KHz SENS 97dB. PRICE £8.90 - £.00 PAP A new range of quality loudspeakers, designed to take advantage of the latest 10" SOWATT EB10-50 DUAL IMPEDENCE, TAPPED 4/8 OHM BASS, HI-Fl, IN-CAR. speaker technology and enclosure designs Both models utilize studio quality RES. FREO. 40Hz, FREO. RESP. TO 5KHz, SENS. 99dB. PRICE £13.65 £2.50 P&P 12" cast aluminium loudspeakers with factory fitted grilles, wide dispersion 10" 100 WATT E111 0-100 BASS, HI-Fl, STUDIO. constant directivity horns. extruded aluminium corner protection and steel RES. FRED. 35Hz, FREO. RESP. TO 3KHz, SENS 96dB. PRICE £30.39 £3.50 P&P ball corners. complimented with heavy duty black covering The enclosures 12" 100 WATT eel 2-100 BASS, STUDIO, HI-Fl, EXCELLENT DISCO. are fitted as standard with top hats for optional loudspeaker stands RES. FRED. 26Hz, FREO. RESP. TO 3 KHz, SENS 93dB. PRICE £42.12 £3.50 P&P FULL RANGE TWIN CONE, HIGH COMPLIANCE, ROLLED SURROUND POWER RATINGS QUOTED IN WATTS RMS FOR EACH CABINET 60WATT EB5-60TC (TWIN CONE) HI-Fl, MULTI-ARRAY DISCO ETC. FREQUENCY RESPONSE FULL RANGE 45Hz - 20KHz RES. FREO. 63Hz, FRED. RESP. TO 20KHz, SENS 92dB. PRICE £9.99 £1.50 P&P ibl FC 12-100 WATTS (100dB) PRICE el 59.00 PER PAIR era" 60WATT 61116-60TC (TWIN CONE) HI-Fl, MULTI-ARRAY DISCO ETC fbi FC 12-200 WATTS (100dB) PRICE £175.00 PER PAIR RES. FRED. 38Hz, FRED. RESP. TO 20KHz, SENS 94413. PRICE £10.99 1.50 PEP SPECIALIST CARRIER DEL. £12.50 PER PAIR 8" 60WATT EB8-6OTC (TWIN CONE) HI-Fl, MILTI-ARRAY DISCO ETC. RES. FREO. 40Hz, FREO. RESP. TO 181(Hz, SENS 89dB. PRICE £12.99 £1.50 P&P OPTIONAL STANDS PRICE PER PAIR £49.00 10" 60WATT EB10-60TC (TWIN CONE) HI-Fl, MULTI ARRAY DISCO ETC Delivery £6.00 per pair RES. FREO. 35Hz, FRED. RESP. TO 12KHz, SENS 98dB. PRICE £16.49 • £2.00 PEP THREE SUPERB R1r4T TAITTTrYT•Tsli-iTTITTT4 marril5Wrir"" CAR STEREO BOOSTER AMPLIFIERS 150 WATTS (75 • 75) Stereo. 150W PROVEN TRANSMITTER DESIGNS INCLUDING GLASS FIBRE Bridged Mono PRINTED CIRCUIT BOARD AND HIGH QUALITY COMPONENTS /11/11 I 1 250 WATTS (125 • 125) Stereo. 250W COMPLETE WITH CIRCUIT AND INSTRUCTIONS Bridged Mono 3W TRANSMITTER B0.108MHz VARICAP CONTROLLED PROFESSIONAL 400 WATTS (200 • 2001 Stereo. 400W PERFORMANCE, RANGE UP TO 3 MILES. SIZE 38 x 123mm. SUPPLY 120 c: 0.5ALIP. Bridged Mono PRICE C14.85 C1.00 P&P ALL POWERS INTO 4 OHMS FM MICRO TRANSMITTER 100-108MHz, VARICAP TUNED. COMPLETE WITH Features: VERY SENS FET MIC. RANGE 100-300m. SIZE 56 46mrn. SUPPLY 9V BATTERY. * Stereo. bridgable mono * Choice of PRICE C8.80 Cf.00 P&P PHOTO, 3W PM TRANSMITTER high & low level inputs * L & R level PRICES: 1 50W £4 9.99 250 W £99.9 9 controls * Remote on-off * Speaker 8 400 W £109.95 PAP £2.00 EACH thermal protection. B.K. ELE CT R O NIC S IE 3n NU% CH,ARGES ,D1.117,, EMEERGET2,22,,,"T. 'rat, POLFCTETt. U NIT SI & 5 CO MET WA Y, SO UT HE N D-O N-SE A, PRICES INCLUSIVE OF V.A.T. SALES COUNTER. VISA AND ES SE X. SS2 ET R. ACCESS ACCEPTED BY POST, PHONE OR FAX. Tel.: 07 02- 52 75 7 2 Fax.: 07 02- 42 0243 FULL COLOUR GUIDE TO ELECTRONIC PRODUCTS

BS 5750 Part 2 1987 Level B: duality Assurance RS12750

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Southern Africa customers please contact Maplin (South Africa) Telephone (024) 51-5124