Elektor-2009-10.Pdf

www.elektor.com October 2009 AUS$ 13.90 - NZ$ 16.90 - SAR 99.95 £ 4.65

TThehe SSoundound of Silence 1100 noisenoise cancellingcancelling hheadphoneseadphones ttestedested Barometric Altimeter fforor mmountaineers,ountaineers, ddeltaelta ggliderlider & UULL ppilotsilots

✔ E-LABS INSIDE: PSoC kit with RF module – Portable solar chargers – Noise is not cool! ✔ LED touch panel for Arduino R43 ✔ Hearing treshold tester

UK0910_1_Cover-UK 10-2009.indd 1 10-09-2009 11:22:11 1

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0910_elektor_adv_UK.indd 2 10-09-2009 11:14:24 DEVELOPMENT TOOL J U ST THE WAY YOU LIKE IT Everything you’ve always wanted from a development tool Experience the ease of creating your own electronic devices! Thanks to many new features, you can start creating your own devices immediately. EasyPIC6 supports 8-, 14-, 18-, 20-, 28- and 40- pin PIC microcontrollers. The mikroICD (Hardware In-circuit Debugger) enables very efficient step by step debugging. Examples in C, BASIC and Pascal are provided with the board. Hardware In-Circuit Debugger High-Performance for step by step debugging at USB 2.0 On-Board hardware level Programmer Port Expander provides easy On-Board I/O expansion (2 additional 2x16 Serial LCD ports) using serial interface Display Full-featured and user-friendly Keypad enables development board for PIC easy and fast data microcontrollers entry

Find your distributor: mikroElektronika http://www.mikroe.com/en/distributors/ SOFTWARE AND HARDWARE SOLUTIONS FOR THE EMBEDDED WORLD

www.mikroe.com

0910_elektor_adv_UK.indd 3 10-09-2009 11:14:27 electronics & microcontrollers

Feedback is good! 14 Sound Sorcery At social gatherings the conversation often comes round to what you do for a living. Editor sounds a bit exotic and the question then turns to what skills are needed for the job. Many years ago, a (very) senior editor divulged that you should be something of a craftsman. The analogy is not a bad one: to be successful you need a little bit of talent, loads of practice and a touch of artistic ﬂ air. I have to admit that our magazine is not always a master- piece but I never doubt the level of commitment of our team. I always look forward to the end of the month when we sit down with some pride (and relief) to thumb through the latest edition hot off the press. However the analogy breaks down here — unlike the tailor, carpenter or sculptor we never get to see the customer’s face when they take ownership — or in our case read the magazine. Rarely do we get to know The science of acoustics holds many surprises: sound can be focused into if our choice of an article was a good one, if the writing style is good or beams, noise can be cancelled out by more noise, and sound waves can indeed what the overall impression be made to appear from nothing as if by magic. This article explains was. It is a shame because we are how the tricks are done. continually asking questions: How many projects or articles on funda- mentals should we run? Do our soft/hardware descriptions have enough depth? Are readers interested in projects that don’t include microcontrollers? Should the articles have a common layout or would it make a more attractive product if each article has a different layout? Raise that question at an editorial 20 Barometric Altimeter meeting and you are sure of a heated argument. It is interesting to see which work colleague takes which side in the debate. At the end of the day of course what we think is really not important, the customer is king! We really do value your feedback. Whether you found something to be really interesting or a total turn-off, we don’t mind criticism — in fact we encourage it! Maybe you would prefer to see the magazine concentrate on different subject areas or you dislike the direction the magazine is taking. Whatever the case, let us know, we look forward to your views at [email protected], or by post.

Jan Buiting In this project a piezoresistive transducer measures the atmospheric Editor pressure, enabling a PIC microcontroller to use the ISA model (with temperature compensation) to display your current height above sea level (ASL) on an LCD.

UK0910_4_5_Contents-UK 10-2009.i4 4 10-09-2009 11:22:53 Volume 35 October 2009 CONTENTS no. 394

projects 20 Barometric Altimeter 26 Touch LEDs for Arduino 36 Car Tilt Alarm 48 Hearing Threshold Tester 54 Pocket Preamp 58 Getting Started with Em- bedded C (part 3, ﬁ nal) 66 Mini Preampliﬁ er 48 Hearing Threshold Tester

Very few people realise how much portable music technology players like iPods and mp3 players can 14 Sound Sorcery affect our hearing. The hearing threshold tester presented here has been designed to check the state your ears are in. new sectionE-labs inside 43 Portable Solar Chargers 44 “Noise is not cool” 46 Review: PSoC kit with RF module

info & market 6 Colophon 8 News & New Products 32 High End Audio Ampliﬁ er Kits 58 The Sound of Silence 58 The Sound of Silence 80 Elektor SHOP 84 Coming Attractions

In this article we take a look at a number of noise cancelling headphones, designed to reduce background noise using anti-sound. infotainment How do these devices perform, 74 Hexadoku and what’s the price tag? 76 Retronics: Philbrick R2-W, the mother of all op amps)

UK0910_4_5_Contents-UK 10-2009.i5 5 10-09-2009 11:22:59 ELEKTOR ELECTRONICS WORLDWIDE

elektor international media Elektor International Media provides a multimedia and interactive platform for everyone interested in electronics. From professionals passionate about their work to enthusiasts with professional ambitions. From beginner to diehard, from student to lecturer. Information, education, inspiration and entertainment. Analogue and digital; practical and theoretical; software and hardware. English German Dutch French Chinese

Portugal Italian Spanish Swedish Finnish

Volume 35, Number 393, September 2009 ISSN 1757-0875 Elektor is also published in French, Spanish, American English, German and Editorial secretariat: Hedwig Hennekens ([email protected]) Dutch. Together with franchised editions the magazine is on circulation in more Elektor aims at inspiring people to master electronics at any personal level by than 50 countries. Graphic design / DTP: Giel Dols, Mart Schroijen presenting construction projects and spotting developments in electronics and information technology. International Editor: Managing Director / Publisher: Paul Snakkers Wisse Hettinga ([email protected]) Publishers: Elektor International Media, Regus Brentford, Marketing: Carlo van Nistelrooy Editor: Jan Buiting ([email protected]) 1000 Great West Road, Brentford TW8 9HH, England. Tel. (+44) 208 261 4509, fax: (+44) 208 261 4447 www.elektor.com International editorial staff: Harry Baggen, Thijs Beckers, Eduardo Corral, Ernst Krempelsauer, Jens Nickel, Clemens Valens. Subscriptions: Elektor International Media, The magazine is available from newsagents, bookshops and electronics retail Regus Brentford, 1000 Great West Road, Brentford TW8 9HH, England. outlets, or on subscription. Design staff: Antoine Authier (Head), Ton Giesberts, Tel. (+44) 208 261 4509, fax: (+44) 208 261 4447 Elektor is published 11 times a year with a double issue for July & August. Luc Lemmens, Daniel Rodrigues, Jan Visser, Christian Vossen Internet: www.elektor.com/subs

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colofon-UK 10-2009.indd 6 10-09-2009 11:25:47 Elektor PCB Service NEW! Your professional PCBs and Prototypes The advantages at a glance Elektor PCB Service is a new service from Elektor. You • The PCBs are professional quality. • No ﬁ lm charges or start-up charges. can have your designs converted into a professional- • There is no minimum order quantity or charge quality PCBs via the www.elektorpcbservice.com for this service. website. Elektor PCB Service is intended for prototype • Available to private and commercial customers. • We’ll ﬁ rst check if your project is producible. builders and designers who want to have their PCBs We’ll let you know within 4 hours! made to professional standards, and for users who • In order to supply two PCBs, we make three. If the third board is also good, you receive it want customised versions of Elektor PCBs. If you need as well – free of charge. a couple of ‘protos’ with fast turnaround or a batch of • You can use our online payment module to pay easily, quickly and securely with Visa or Master- 5 to 50 units, Card. we can meet

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Email: [email protected] Email: [email protected] publication is stored in a retrieval system of any nature. Patent protection may ex- Rates and terms are given on the Subscription Order Form. Internet: www.husonmedia.com ist in respect of circuits, devices, components etc. described in this magazine. The Advertising rates and terms available on request. Publisher does not accept responsibility for failing to identify such patent(s) or other Head Ofﬁ ce: Elektor International Media b.v. protection. The submission of designs or articles implies permission to the Publisher P.O. Box 11 NL-6114-ZG Susteren The Netherlands to alter the text and design, and to use the contents in other Elektor International Telephone: (+31) 46 4389444, Fax: (+31) 46 4370161 Copyright Notice Media publications and activities. The Publisher cannot guarantee to return any mate- The circuits described in this magazine are for domestic use only. All drawings, photo- rial submitted to them. Distribution: Seymour, 2 East Poultry Street, London EC1A, England graphs, printed circuit board layouts, programmed integrated circuits, disks, CD-ROMs, software carriers and article texts published in our books and magazines (other than Telephone:+44 207 429 4073 Disclaimer third-party advertisements) are copyright Elektor International Media b.v. and may Prices and descriptions of publication-related items subject to change. UK Advertising: Huson International Media, Cambridge House, not be reproduced or transmitted in any form or by any means, including photocopy- Errors and omissions excluded. Gogmore Lane, Chertsey, Surrey KT16 9AP, England. ing, scanning an recording, in whole or in part without prior written permission from Telephone: +44 1932 564999, Fax: +44 1932 564998 the Publisher. Such written permission must also be obtained before any part of this © Elektor International Media b.v. 2009 Printed in the Netherlands

10/2009 - elektor 7

ELEKcolofo UK09078n-UK 10-2 PCB009.i Servicesndd 7 s7.indSec1:7 Sec1:7 03-06-200910-09-2009 22:25:29 11:25:57 INFO & MARKET NEWS & NEW PRODUCTS

Actel offers free reference designs for LCD applications Actel Corp. is offering five ref- ﬁ tted with low-power Igloo FPGA to 7” and resolutions from erence designs, free of charge, with Flash Freeze technology and QVGA (320x240) to SVGA which are implemented using the features low static power with (800x480). You can also Igloo Video Demo Kit. The Igloo quick entry to and exit from Flash build your own customized Video Demo Kit was jointly devel- LCD adapter board. The oped by Actel, Attodyne, and IGLOO video demo board Avnet Memec. It is available from has an IGLOO device that Avnet Memec and can be ordered interfaces with several online or from any sales office. video/image sources, such The available reference designs as a digital visual interface target the following applications: (DVI) input and a CMOS DVI input to LCD, upscaling, photo Freeze mode. sensor interface. In addition, off- viewer, still and video cameras, Designers have a choice of sev- chip memory is provided for data and video MUXing. eral LCD adapter boards with buffer and storage. LCD panels of different sizes and The IGLOO Video Demo Kit con- resolutions. Two plug-and-play www.actel.com/products/solutions/ sists of two boards: a video demo display adapter board are avail- display/refdesign.aspx board and an LCD adapter board. able, and they can be ﬁ tted with The IGLOO video demo board is different LCDs, ranging from 5.5” (090569-IX)

A new name and new-generation products revitalize embedded software A change of name signals the ing systems in real time allows seamless, remote dynamic, fresh approach Cross- while they’re running, it non-intrusive testing and hairs Embedded is bringing to reduces downtime, helps monitoring of embedded revitalizing embedded software. increase efﬁ ciency, and systems even at large The company offers customers leads to greater proﬁ ts. distances. It’s also easy invaluable insight through precise Businesses will quickly to use and more depend- software solutions, with a new gen- find that Functional able and adaptable than eration of products that home-brew software test- deliver on that promise. ing solutions. The change of name from Functional Debug- Active DSP to Crosshairs ger v1.1 was officially Embedded reflects the launched at the Embed- company’s focus on opti- ded Systems Confer- mizing embedded systems ence (ESC) 2009 in for international markets. Boston. The company’s Leading Crosshair’s next Debugger v1.1 is reli- next new-generation product, the generation product lineup able and highly cost- powerful Interface Designer, will is the new Functional effective. It’s especially follow shortly. Debugger Version 1.1. valuable for organi- By enabling businesses zations with operat- www.CrosshairsEmbedded.com to debug, monitor and ing systems deployed optimize their operat- worldwide, since it (090569-XIII)

Paper-thin battery ETA scheduled for 2010 As researchers rush to develop targeting applications in music players. The commercial versions of printable such as smart credit researchers are aiming batteries with structured organic cards with battery-pow- at a price point under semiconductors on paper-thin, ered displays that can 10 cents per card. flexible substrates, a German display the card bal- The batteries are pro- team claims to be on track for a ance and other account duced using a screen 2010 product launch. Scientists at information. printing technique in the Fraunhofer Research Institution Fraunhofer’s batteries which a squeegee for Electronic Nano Systems col- use zinc anodes and presses the organic laborated on this project with col- manganese cathodes, semiconductor materials leagues at Chemnitz University of which react with each another to lifetime of the battery, making them through a screen onto a ﬂ exible Technology and Menippos GmbH produce electricity. These materi- suitable for short-term applica- substrate. In a process resembling (Chemnitz, Germany). They are als are gradually used up over the tions like greeting cards with built- lithography, templates are used to

8 elektor - 10/2009

090712-UK News 10-2009.indd 8 10-09-2009 11:26:32 create successive layers of battery and be less than 1 mm thick. The Fraunhofer researchers said their www.fraunhofer.de/en/press/ components, each about the thick- organic materials generate 1.5 V battery is already working in the research-news/2009/july/printable- ness of a human hair, until enough per cell, like conventional batter- lab, and their industrial partners batteries.jsp bulk has been achieved for a par- ies, and they are free of hazard- estimate that the ﬁ rst commercial ticular application. ous substances such as heavy met- models will be ready for beta test- (090569-X) Printable batteries for smart cards als used in conventional recharge- ing later this year. would weight less than 1 gram able and alkaline batteries.

KEF creates unique fl agship speakers In loudspeaker engineering as in ing and analysis of traditional as used in perfecting the design. everything else, true innovation well as experimental approaches While the technologies incorpo- sometimes requires rethinking a to loudspeaker design, they per- rated into the design are often very problem from fi rst principles. So fected a combination of technolo- complex, the focus has always when KEF set out to create the gies that generates an extraordi- been on simplicity. The drivers are Concept Blade, a unique not-for- narily pure sound. specifically designed to behave sale speaker system designed to Concept Blade is forged from these with zero break-up or resonance showcase their speaker technol- technologies. Its exceptional acous- over their frequency range, and ogy, the acoustic research depart- tic integrity derives from the fact the distinctive cabinet is carefully ment had complete freedom to that every element of the system engineered not to interfere with the explore radical new options, with has been conceived to perform as purity of their output. no preconceptions or aesthetic a single coherent unit with all parts restrictions, and no reliance on working in fl awless harmony. The www2.kef.com/us/conceptblade existing components. highest quality components and After three years of exhaustive test- advanced materials have been (090569-IV)

DC source-measure instruments compatible with ACS basic edition software Keithley Instruments, Inc. has vidual channels. a single test, allowing easier con- enhanced its popular ACS Basic The newly expan- ﬁ guration, test creation, and test Edition software, adding sup- ded source and execution – with no need to write port for a broader line of source- measure ranges code. measure (SMU) instrumentation. are especially The software now supports com- With the introduction of Version useful for tests on bining hardware from any of 1.1, ACS Basic Edition, a mem- evolving photovol- Keithley’s SMU families into a sin- ber of Keithley’s Automated Cha- taic panels/solar gle test, including Series 2600 and racterization Suite (ACS) family, cells and high 2600A System SourceMeter instru- can now support a far broader power electro- ments, Series 2400 SourceMeter range of DC voltage and current nics in research, instruments, the Model 4200-SCS test capabilities. It’s compatible failure analysis, Semiconductor Characterization with the company’s full SMU offe- and inspection System, and the Model 237 High- ring, the broadest array of choices applications. ACS Voltage SMU. in the industry. Depending on the Basic Edition now SMU selected, ACS Basic Edition also supports com- www.keithley.com/products/ supports sourcing and measuring bining different semiconductor/?mn=ACSBasicEdition up to 5A or 1100V DC on indi- SMU models into (090711-IX)

Orchid’s new 48V 1,400 watts brushless DC motor controller The new low cost brushless DC sible to develop high torque and as the brains of this brushless DC The ST7MC’s patented motor con- motor controller board from operating speeds when overall motor controller. The ST7MC’s fea- trol subsystem provides a highly Orchid Technologies Engineering product size and weight are appli- ture-rich complement of fl ash pro- cost-effective method to control and Consulting, Inc, packs enor- cation limited. gram store, static RAM, Eeprom, many different types of brushless mous power into a tiny electron- The new board combines cost- patented motor controller, timers, DC motors. Sensor and sensorless ics package. Designed to drive sensitive engineering with preci- analog-to-digital conversion cir- motors, 120- and 60-degree styles 48-Volt brushless DC motors up to sion power electronics to craft an cuitry, and robust processor reli- are all supported. 1400 watts, this miniature control- effi cient, high-performing, three- ability controls make the ST7MC ler may be the smallest in its class. phase power-output stage. Orchid a perfect fi t in the motor control www.orchid-tech.com Small physical sizes make it pos- selected an ST7MC microcontroller marketplace. (090712-I)

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090712-UK News 10-2009.indd 9 10-09-2009 11:26:35 INFO & MARKET NEWS & NEW PRODUCTS

True-Touch the HD Brilliance on hot new Samsung I8910 phone Samsung Electronics Company solution based on its fast response ing performance and lowering sys- Ltd. has selected the TrueTouch(TM) time, gesture support and charac- tem power in the new phone. solution from Cypress to imple- ter recognition capabilities that According to Samsung, Cypress’s ment the touchscreen in the new enable the I8910’s outstanding TrueTouch and MoBL dual-port solu- I8910 mobile phone. The I8910, multimedia player and fast inter- tions gave the company the ability also known as the OMNIAHD, lets net browsing. to go beyond the competition with users ‘Touch the HD Brilliance’ of In addition to the TrueTouch touch- new features and functions that the world’s ﬁ rst phone with 720P screen, the I8910 employs a customers are excited to use. high-definition video recording Cypress MoBL(R) dual-port as an and super vivid 3.7” AMOLED interconnect between the appli- www.cypress.com/go/TrueTouch display. cation and baseband processors, (090568-XI) Samsung selected the TrueTouch increasing multimedia and comput-

Antero Standard Development Kit for ARM7 The Antero Single Board Computer try Pack form factor. The IP module (SBC) family is the newest series version is compatible with Industry of products from Vesta Technol- Pack carrier boards. ogy. The Antero Development Kit The Antero SBC with its full devel- is optimised for embedded control opment environment is being applications and allows the SBC to offered now at a special introduc- be very conﬁ gurable, making it the tory rate. The SBC comes with soft- Swiss Army knife of SBC’s. Based ware tools, sample application pro- on the 32 bit ARM7 technology, grams and RTOS. Antero is ideal the SBC offers high performance for machine and industrial control, with low power consumption, and equipment monitoring, process small form factor. Antero features control, instrumentation and many a rich I/O set that includes CAN other applications. bus, USB, I2 C, SPI, multiple Serial, PWM, Quadrature and digital. www.vestatech.com Antero is constructed in the Indus- (090568-XII)

New microchip technology performs 1,000 chemical reactions at once

UCLA researchers have devel- duced on a chip, the research oped technology to perform more team pioneered a way to insti- than a thousand chemical reac- gate multiple reactions, thus tions at once on a stamp-size, offering a new method to quickly PC-controlled microchip, which screen which drug molecules could accelerate the identifi ca- may work most effectively with a tion of potential drug candidates targeted protein enzyme. In this for treating diseases like cancer. study, scientists produced a chip Their study appeared in the Aug. capable of conducting 1,024 21, 2009 edition of the journal reactions simultaneously, which, Lab on a Chip and is currently in a test system, ably identifi ed available online. potent inhibitors to the enzyme A team of UCLA chemists, biol- bovine carbonic anhydrase. ogists and engineers collabo- A thousand cycles of complex rated on the technology, which processes all took place on the is based on microfl uidics — the microchip device and were com- utilization of miniaturized devic- pleted in just a few hours. At es to automatically handle and the moment, the UCLA team is channel tiny amounts of liq- restricted to analyzing the reac- uids and chemicals invisible tion results off-line, but in future, to the eye. The chemical reac- they intend to automate this tions were performed using in aspect of the work as well. situ click chemistry, a technique to protein enzymes to either acti- spectrometry. (090711-I) often used to identify potential vate or inhibit an effect in a cell, While traditionally only a few drug molecules that bind tightly and were analyzed using mass chemical reactions could be pro-

10 elektor - 10/2009

090711-UK News 10-2009.indd 10 10-09-2009 11:27:39 Surface soldering the Propeller chip

Parallax Inc., has partnered with microcontroller on this convenient (090711-II) SchmartBoard to create an easy development platform, allowing Propeller prototyping system in the access to all 32 I/O pins of the form of a kit. multicore Propeller chip. The kit If you are new to surface solder- retails at $39.99 and includes sur- ing and don’t know where to start, face-mount and through-hole pack- the P8X32A-Q44 SchmartBoard age types for some components, kit is a perfect starting point. The offering a soldering choice and SchmartBoard technology makes challenge. surface mount soldering easy. Once completed, the board will www.Parallax.com host Parallax’s most powerful (search “SchmartBoard or “27150”)

SchmartBoard: cheapest ever development board for Microchip 8-bit PICs in SOIC case keep a number of development boards on hand and knowing Eight-bit PIC® microcontrollers they will work with any SOIC 8- in 8-, 14-, 18-, 20- and 28-pin bit PIC chip they use in the future. SOIC packages are all sup- Also, a distributor can now stock ported by the new PIC Develop- board to support over 100 PICs ment Board SchmartModule. A as opposed to a variety of differ- user simply hand solders a PIC® ent boards to support the many chip using SchmartBoard’s ‘EZ’ 8-bit PIC options. solder technology, adds a row of SchmartBoard will follow headers (included), and then con- this product up with an 8-bit ﬁ gures jumpers for the PIC type PIC board for chips in a QFP which was soldered onto the form factor, boards for 16-bit board. The 2” x 2.5” board has PICs and some development an onboard 5 V power regulator boards for other microcontroller and reset button. It also supports manufacturers. optional external clock options, The new PIC development board compatibility. If you use 8-bit PICs ICSP and RJ11 interfaces for is claimed to be the most ﬂ exible often, at $15, this inexpensive www.schmartboard.com programming. option on the market for PIC chip solution offers the opportunity to (090711-V)

Rapid prototyping of digital AV applications and ARM Cortex-M3 embedded systems Toshiba Electronics Europe (TEE) The MDK-ARM tools provide devel- and Keil have announced a developers with industry-standard com- opment kit that simpliﬁ es the design pilation tools and sophisticated of digital AV applications and debugging support. It features the other embedded systems based on Keil µVision Integrated Develop- Toshiba’s microcontrollers based ment Environment (IDE), debug- on the ARM Cortex™-M3 proc- ger and simulator, the ARM Com- essor. The new MCBTMPM330 pilation tools, and an RTX real- Starter Kit provides all of the hard- time kernel. Detailed startup code ware and software necessary for for the Toshiba microcontrollers, the rapid evaluation, prototyping Flash programming algorithms and testing of applications based for ULINK and extensive program on the Toshiba TMPM330Fx range examples all ensure that users can of devices. quickly begin developing their The new Starter Kit comprises the applications. MCBTMPM330 Evaluation Board, The MCBTMPM330 Starter Kit is a Keil™ ULINK-ME USB-JTAG available now and is the ﬁ rst in a adapter, an evaluation version of line of collaborative products from Keil’s Microcontroller Development As well as the microcontroller, the nectors for enabling developers to Toshiba and Keil. Kit (MDK-ARM), and a variety of evaluation board incorporates an debug and gather trace information example programs. All power for adjustable analogue voltage source from their applications. The board’s www.toshiba-components.com the evaluation board is provided for testing the TMPM330Fx inte- MCU pinout area provides easy www.arm.com by the host PC via the ULINK-ME. grated ADC, JTAG and ETM con- access to the device’s peripherals. (090711-IV)

10/2009 - elektor 11

090711-UK News 10-2009.indd 11 10-09-2009 11:27:47 INFO & MARKET NEWS & NEW PRODUCTS

Pololu Jrk USB motor controller with feedback Pololu announces the release of your own servos, and closed-loop the jrk line of USB motor control- speed control with frequency feed- lers: highly confi gurable, versatile back from a tachometer. The jrk devices that make it easy to add 21v3, the smaller of the two units open- or closed-loop control of currently available, has an operat- brushed DC motors to your coming range of 5-28 V and can deliver puter- or microcontroller-based 3 A continuous output (5 A peak). project. The jrk supports four inter- The jrk 12v12, the more powerful face modes — USB for PC-based of the two, has an operating range control, logic-level (TTL) serial for of 6-16 V and can deliver a con- use with embedded systems, ana- tinuous output of 12 A (30 A peak). such as control input, The unit price is $49.95 for the jrk log voltage for simple potentiome- Both devices can handle transients feedback, motor output, and current 21v3 (item #1392) and $99.95 for ters and joysticks, and RC pulse for of up to 40 V. draw make it easy to fi ne-tune set- the jrk 12v12 (item #1393). radio control systems — and can A free confi guration program (Win- tings such as PID constants, accel- All prices plus P&P. perform open-loop speed control, dows XP and Vista compatible) is eration, and current limit for closed-loop position control with available for calibrating your sys- your application. www.pololu.com analog voltage feedback to make tem. Real-time plots of variables (090711-VIII)

Sparkfun’s Holy Grail of new products

Sparkfun’s lively and fun approach hall-effect sensors, LEDs (RGBW), to DIY electronics is once again and the Blackberry Trackball. demonstrated by a ﬂ urry of new Check out the video! products released on the market, O-Clock, the AVR Oscilloscope a few of which are listed here — Clock is back in a new all SMD version. It turns your X-Y analogue oscilloscope into 1 of 30 display combinations. Solar cell is Sparkfun’s largest yet! It’s rated for 8 V open voltage and 650 mA short circuit. The TFT-LCD ScreenKey is a tactile switch combined with a 128x128 TFT-LCD display that can generate any text or graphics with up to 65,536 colour support. Why use just a button when you can display there’s much more to marvel at full colour images on one? Shield which extends all pins of everything on the main Arduino on their website. New Arduino Shields include the the Arduino out to 3.5 mm pitch board. Trackballer is a breakout board Arduino Mega (ATMega1280), screw terminals. Both sides of the for the Blackberry Trackball. The which now has its own prototyping shield are broken out to the side www.sparkfun.com board comes equipped with four shield and the WingShield Screw- of the Arduino, to allow access to (090711-VI)

better electronics from nanoelectronic transistors and a biological machine Lawrence Livermore National Lab- arsenal of membrane receptors, to ions and small molecules. oratory (LLNL) researchers have channels and pumps to control sig- The researchers incorporated lipid devised a versatile hybrid platform nal transduction that is unmatched bilayer membranes into silicon that uses lipid-coated nanowires to by even the most powerful comput- nanowire transistors by covering build prototype bionanoelectronic ers. For example, conversion of the nanowire with a continuous devices. Mingling biological com- sound waves into nerve impulses lipid bilayer shell that forms a bar- ponents in electronic circuits could is a very complicated process, yet rier between the nanowire surface enhance biosensing and diagnos- the human ear has no trouble per- and solution species. tic tools, advance neural prosthet- forming it. The team showed that by changing ics such as cochlear implants, and To create the bionanoelectronic the gate voltage of the device, they could even increase the effi ciency platform the LLNL team turned to can open and close the membrane of future computers. lipid membranes, which are ubiqui- pore electronically. While modern communication tous in biological cells. These mem- devices rely on electric fi elds and mation, biological systems are branes form a stable, self-healing, https://www.llnl.gov/ currents to carry the fl ow of infor- much more complex. They use an and virtually impenetrable barrier (090711-III)

12 elektor - 10/2009

090711-UK News 10-2009.indd 12 10-09-2009 11:27:52 125nA Supervisory circuits extend battery life Maxim Integrated Products intro- duces the MAX16056-MAX16059, ultra-low-power microprocessor supervisory circuits that monitor a single system supply voltage. These devices consume an industry-low 125 nA supply current to extend battery life in power-sensitive applications. Additionally, the devices feature capacitor-adjustable watchdog (MAX16056/MAX16058) and reset timeouts to maximize design ﬂ exibility. This conﬁ gura- bility makes it easy for designers to quickly change design parameters, and enables the supervisors to be used in unique power-saving schemes. To minimize system power consumption in battery-powered mere 125 nA, the operating sup- to 4.625 V. These devices assert tures immunity to power-supply applications, the MAX16056- ply current of these supervisory a reset signal whenever the Vcc transients. MAX16059 can be used to peri- circuits is much lower than the supply voltage drops below the odically wake up the processor to standby supply current of a typical reset threshold, manual reset complete its required duties, and microcontroller (> 1microamp). is pulled low, or the watchdog http://www. then turn off the processor when The MAX16056-MAX16059 can timer (MAX16056/MAX16058) maxim-ic.com/MAX16056 those functions are complete. At a monitor voltages from 1.575 V runs out. The reset function fea- (090711-VII)

10/2009 - elektor 13

090711-UK News 10-2009.indd 13 10-09-2009 11:27:55 TECHNOLOGY ACOUSTICS Sound Sorcery Sound projection, noise cancellation and wave ﬁ eld synthesis

By Jens Nickel (Elektor Germany Editorial)

Music, speech, noisy neighbours – sound is all around us. And yet the science of acoustics holds many surprises: sound can be focused into beams, noise can be cancelled out by more noise, and sound waves can be made to appear from nothing as if by magic. Here we explain how the tricks are done.

The human sensory system has evolved over hundreds We will look at three of the simpler techniques for mak- of thousands of years of hunting and gathering. From ing a focused beam of sound. The easiest to understand the rustle of a predator to the music of a fl ute, sounds are is the refl ector method. Here the transducer is mounted continuously bombarding us from all sides, and humans backwards, pointing towards a spherical reflector. The have acquired the essential survival skill of determining sound waves emitted hit the refl ector and are sent back the direction from which a sound comes. in the desired direction (Figure 1). This creates a kind of So it seems like magic that it is possible to create a focused focus where sound waves arrive with equal delays: this beam of sound: music or speech made clearly audible if means that relative phase is preserved. We therefore have you stand at just the right point, but take a step to the constructive interference (see the text box for more about left or right and the sound disappears. Focused beams of interference). This method has not seen wide use, apart sound can be used, for example, to link visual advertising from in the ‘Sound Dome’ system by the American com- with an audio track that can only be heard by a person pany Brown Innovations [1]. standing directly in front of the relevant hoarding or display. Museums, art installations and other exhibitions are all already making use of ‘directed sound’. Phase, delays and transducer arrays So how does it work? Even an ordinary loudspeaker is A similar effect can be achieved by using a large number somewhat directional, but the beam is generally not nar- of individual transducers, all fed with the same signal and row enough for the applications mentioned above. This arranged in a spherical pattern (Figure 1). It is also possible is because the wavelength of sound waves in the audi- to use a fl at array of loudspeakers, as long as we ensure ble range is large compared to the size of the transducer, that each loudspeaker is fed with a suitably-delayed sig- which therefore behaves approximately as a point source. nal. The nearer a loudspeaker is to the middle of the array, If we want to focus the sound into a narrower beam, it is the greater the delay required in the signal that is fed to it necessary to make the transducer several metres across. relative to the signal fed to the loudspeakers at the edge

Figure 1. Reﬂ ector (left) and spherical loudspeaker array (centre): there is constructive interference at the focus. The same effect can be achieved with a planar array if the transducers are

driven with suitably phase- 090558 - 13 shifted signals.

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UK0910_14_19_090558-UK Sound.in14 14 10-09-2009 11:28:33 of the array. Usually a DSP device is used to generate the of the ultrasound: it is only required signals, with an independent D/A converter created along the length and amplifi er for each output transducer. An advantage of the emitted beam. The of this digital beamforming technique, in contrast to the situation can be visual- refl ector-based techniques, is that both the direction and ised as a string of ‘virtual the width of the beam can be adjusted without making loudspeakers’. Since the mechanical alterations to the system. The American com- ultrasound signals and pany Dakota Audio [2] makes loudspeaker arrays based the audible signal prop- on this technique, for use in advertising, exhibitions and agate with the same Figure 2. other applications. speed, there is strong This loudspeaker array by The technique also has an interesting application in con- constructive interfer- Dakota Audio is designed sumer electronics. The Japanese company Yamaha makes ence along the axis of for ceiling mounting. so-called digital sound projectors aimed at the home cin- the beam, and destruc- The circumference is about ema and surround sound market (Figure 3). Forty small tive interference at var- 90 cm. tweeters create several beams of sound in various direc- ious angles off the axis tions; the lower frequency components are handled by conventional mid-range and bass loudspeakers. An optional sub-woofer is also available [3]. The loudspeakers simultaneously generate a separate sound beam for each channel (front left and right, centre, rear left and right). The front and rear channels are emitted at preset angles to the left and right, to be refl ected from the walls of the room (see Figure 4). The rear channels then appear Figure 3. to be coming from behind the listener. The designers seem The Yamaha ‘Sound to have been very successful in their work: both the spe- Projector’ uses 40 tiny cialist press and customers have raved about the intensity tweeters to create of the surround effect, although it cannot match a care- a surround sound effect fully-set-up high-end traditional surround sound system without the need for consisting of fi ve separate loudspeakers. The sound pro- additional speakers jector system is aimed at customers with limited space or behind the listener. whose aesthetic sensibilities rule out installing a full surround-sound system. The YSP-1100 model, which has a 40-speaker array, can be bought on-line for a little over £/€ 500. There are cheaper models with smaller arrays, as well as rather dearer models with various extra features. Figure 4. Not to be outdone, Pioneer introduced its digital sound In sound projection projector PDSP-1 [4], a rather more complex device sport- systems a separate beam ing an astonishing 254 transducers and 254 digital ampli- is produced for each fi ers (Figure 5). The device came on the market in 2003 for channel (front left and around £15000, but is no longer available. Jürgen Timm of right, centre, and rear left Pioneer Germany says the “very expensive project” was and right). The beams are discontinued when British start-up ‘1 Limited’, on whose simultaneously generated development work the sound projector was based, fell by the transducer array. prey to “internal disputes”. (Graphic courtesy Pioneer)

Ultrasound as a carrier A third technique for generating a beam of sound uses ultrasonics. Since ultrasound can have a wavelength of just a few millimetres, it is relatively easy to construct one suf- ﬁ ciently large transducer (or a dense array of smaller transducers) which, rather than behaving as a point source, creates a plane wave (see text box). In order to generate frequencies in the audible range a technique called intermodulation is used, where two powerful ultrasonic waves of different frequencies are overlaid. The ultrasonic waves affect the properties of the air through which they travel in such a way that non-linear effects cause them to combine to produce a wave at a new frequency. Many readers will be familiar with the way that mixture products are generated when two radio frequency signals are combined in a non-linear circuit, and indeed the mathematics behind the Figure 5. two effects is the same [5]. If we simultaneously generate The Pioneer PDSP-1 digital an ultrasound signal at 40 kHz and another at 41 kHz, an sound projector sports 254 audible sound at the difference frequency of 1 kHz will transducers be produced; and in general it is possible to modulate the (and 254 digital ampliﬁ ers), ultrasound signals to create audible speech and music. but unfortunately is no The audible sound is not actually present at the source longer available.

10/2009 - elektor 15

UK0910_14_19_090558-UK Sound.in15 15 10-09-2009 11:28:34 TECHNOLOGY ACOUSTICS

of the beam. This kind of system can produce a beam that carries over a distance of more than ten metres, with an attenuation of 20 dB in signal level at an angle of 5 ° off- axis. Commercial products based on this principle, such as those made by Sennheiser [6] and the American companies Holotronics [7] and American Technology Corpora- tion (ATC) [8], consist of an ultrasound driver unit and an amplifi er with the necessary modulation electronics (see Figure 6 and Figure 7). Using these devices it is possible to ‘speak’ to a chosen person in a crowd. Figure 8 shows another interesting possibility. Although the focusing effect is astonishingly sharp, the method does suffer from a disadvantage: it is only practical to generate frequencies above about 300 Hz. In contrast to this, phased array techniques are limited only by the capa- Figure 6. bility of the individual transducers used, easily reaching The Sennheiser ‘AudioBeam’ 70 Hz or even lower. uses 150 piezoelectric Manufacturers are of course keen to point out the limi- transducers to generate tations of their competitors’ approaches. Phased array a directional ultrasound enthusiasts Dakota Audio characterise the reproduction of fi eld onto which the audio information is modulated. natural sounds using ultrasonic systems as screechy or like breaking glass. Meanwhile, Dr Joseph Pompei, founder of Holosonics, stresses that driver area is the only thing that matters when trying to produce a focused beam of sound. He claims that it can be proved mathematically that any additional phasing or masking can only have an adverse effect on beam quality. As well as the HSS ultrasound system ATC also makes the LRAD (long range acoustic device), shown in Figure 9. This loudspeaker system is capable of transmitting acoustic Figure 7. messages or warning sounds over long distances, includ- The ‘HSS’ system, made ing over open sea. The most powerful model can even by American company be used by a ship’s crew to ward off pirates: according to ATC. One panel, including ATC the sound pressure level can reach 152 dB, with levels electronics, costs around of up to 90 dB at a distance of 300 m. Various US military US$ 1400. organisations have already ordered LRAD devices, and so technical details are kept largely under wraps. Wikipedia claims that the system uses an array of tweeters driven in phase, giving a moderately narrow beam [9]. Wikipedia also has an entry on current research into so-called ‘sonic weapons’ [10], though of course publicly-available infor- Figure 8. mation is again rather thin on the ground. Hairdresser high-tech. In the ceiling there are Anti-sound panels that form part of the ‘Audio Spotlight’ system Now we turn to another counter-intuitive aspect of by American manufacturer acoustics. The effects of long-term exposure to noise from Holosonics. machinery or vehicles can range from discomfort to seri- The panels create an ous health problems. It is possible to reduce the noise ultrasound fi eld using level using passive damping, but an active technique is a vibrating metal-polymer also available: anti-sound, or active noise cancellation. hybrid fi lm. The technique uses the principle of destructive interference (see text box). It is easy to see that sound and anti- sound of the same frequency must have opposite phases, and the theory of this was worked out in the 1930s; the practice, however, has fallen somewhat behind and active noise cancellation is only really successful in certain special situations. Figure 9. If the source of unwanted noise acts (at least approxi- The LRAD (Long Range mately) as a point emitter, and remains fi xed in position, Acoustic Device) is the then things are relatively straightforward. A microphone circular object towards the is placed between the noise source and the area where top right of the picture. the noise is to be cancelled, arranged so as to pick up the The loudspeaker sound. Some simple electronics shifts the phase of the sig- arrangement creates sound nal and outputs the result to a loudspeaker, which creates at levels of up to 150 dB, the wanted anti-sound. enough even to ward A suitable circuit can be built fairly easily using analogue off pirates! components [11]. Alternatively it is possible to digitise the

16 elektor - 10/2009

UK0910_14_19_090558-UK Sound.in16 16 10-09-2009 11:28:36 noise signal, and use a DSP device to calculate the (digital) anti-sound signal, which is then converted back to analogue form and amplifi ed. There are also dedicated devices available [12] which additionally offer various fi l- tering functions. As sound travels at about 340 m/s in air, it is necessary to calculate the anti-sound signal quickly: a delay of 1 ms corresponds to a distance of 34 cm. The method described above is known as the ‘feedfor- Figure 10. ward’ technique, where the system attempts to cancel the Anti-sound headphones by sound before it reaches the target area. An alternative is Sennheiser. the ‘feedback’ technique, which works well in noise-cancel- The ‘NoiseGuard’ range ling headphones. Here a microphone is placed within each uses analogue circuitry, ear-cup of the headphones to measure the noise signal, which the manufacturer and an algorithm is used to calculate the anti-sound sig- claims has benefi ts in terms nal that should be added in to minimise the overall error of cost and speed. from the wanted signal. Headphones like this (Figure 10) are aimed not only at the consumer audio market but also at aircraft pilots and call centre workers. The environment noise-cancelling headphones can achieve an attenuation in which the system has to work is relatively friendly, in of 20 dB over the entire audio spectrum. There is a test of that the area over which cancellation must take place is various headphones with active noise cancellation else- very small, much smaller than the wavelength of the fre- where in this issue. quency components that are to be cancelled. This means that the sound pressure level is roughly constant over the whole of the inside of the headphone ear-cup. It is there- The road to peace fore perhaps more appropriate to think of the system as For the reasons we mentioned the techniques above are regulating the pressure inside the ear-cup to the desired particularly effective at combating noise from engines, fans value at any given instant rather than as creating an anti- and other machinery. The technical diffi culties increase sound. The principle is particularly effective at lower fre- considerably, however, if it is desired to suppress noise quencies, for example when cancelling the engine noise that is complex in nature over a wide area, especially if from a turbine helicopter. the sources of the noise are not stationary. Analysing the If we combine these active techniques with passive meas- entire sound fi eld in terms of the amplitude and direction ures that in practice work better at higher frequencies, of the noise sources requires a spherical array of closely-

Effects Interference Sound propagates through a medium, such as air, as a wavefront shape wave. The sound wave from a point source can be visu- that matches exactly alised as similar to the waves on the surface of the water that which would when a stone is thrown into a lake, although in the case be a produced by of the sound wave the motion of the particles involved in a single loudspea- the wave is parallel to the direction of propagation rather ker acting as a than perpendicular to it. When a trough in a sound wave point source. With from one source meets a peak in the wave from another a densely-packed source, the waves cancel each other out: this phenome- spherical arrange- non is called destructive interference. If two peaks meet ment of loudspea- one another, the result is constructive interference. kers it is possible to simulate the effect of sound sources at Plane waves any point outside A so-called ‘plane wave’ Grafik: Fraunhofer IDMT (or even inside) the is produced when several sphere. Using a circular array of loudspeakers it is possible to sources, all emitting the simulate closely the effect of a loudspeaker anywhere within same sound signal, are the plane of the circle. The distance between adjacent trans- arranged in a plane array. ducers in the circle should be less than half the wavelength of For clarity we show a one- the highest frequency component to be generated. dimensional arrangement here. A similar situation occurs when the diameter Sound ﬁ eld analysis of the transducer is much The position of a sound source can be determined from the larger than the wavelength signals picked up by microphones arranged in a grid. A com-

of the sound. 090558 - 11 plete sphere of microphones is needed in order to identify sources located anywhere in the surrounding space. The sig- Virtual sound sources nals picked up determine the sound ﬁ eld at all points within If the sources are arranged to emit signals with different pha- the sphere. ses, it is possible to create curved wavefronts. If the transdu- If all the sound sources to a good approximation lie in a sin- cers are driven with the right signals it is possible to create a gle plane, a circular microphone array is sufﬁ cient.

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UK0910_14_19_090558-UK Sound.in17 17 10-09-2009 11:28:40 TECHNOLOGY ACOUSTICS

the main circuit board of the system with a daughter card carrying the converters for 24 analogue input channels and 12 analogue output channels. The system was demonstrated working in prototype form Figure 11. at the CeBit exhibition in 2002, but now, some years later, The electronics in the the system is still undergoing extensive adjustments and Wuppertal anti-sound fi ne tuning. The demands on the system are enormous. system. The converter card The anti-sound signal must be matched to the incoming has 24 analogue inputs noise signal to within 1 dB of amplitude and to within 6 ° and twelve analogue in phase over the entire frequency range to achieve a noise outputs. (Photograph attenuation of 20 dB [14]. courtesy WaveScape Technologies GmbH). It’s a beautiful noise At the Fraunhofer Institute for Digital Media Technology packed microphones around the target area (see the text (IDMT) in Ilmenau, Germany, the concerns are rather box on sound fi eld analysis). different. Their aim is to reconstruct recorded sound Professor Detlef Krahé and his team at the Faculty of sources as faithfully as possible using wave fi eld synthesis Electrical Engineering of the University of Wuppertal (WFS) [15]. The German engineers have taken the theory, in Germany [13] has taken up this challenge. The long- which was developed in the 1980s at the Technical Uni- term aim of the research is to create an affordable, weath- versity of Delft in the Netherlands, and converted it into erproof system that can cancel street noise over the area a market-ready product [16]. A WFS system can be used of a balcony or patio. Since the vast majority of the rele- to play back ordinary audio material, such as a stereo or vant noise sources lie in a horizontal plane, the engineers surround-sound signal. A circular formation comprising a can represent them using a two-dimensional model. A large number of loudspeakers, all driven from a computer, circular array of microphones is used, placed roughly at can generate ‘virtual loudspeakers’ at any desired posi- ear height around the area where the noise is to be can- tion outside the physical array. Each source channel can be celled. As Krahé explains, a microphone is needed every assigned to a different virtual loudspeaker. Whereas a con- 35 cm (approx. 1 foot) in order to analyse frequencies up ventional system consisting of fi ve or seven physical loud- to 500 Hz adequately: this fi gure is derived using a spatial speakers set around a living room always involves a com- analogue of the Nyquist sampling theorem. In practice two promise to the quality of the sound stage, sound played microphones are used at each point so that both the sound through a WFS system has a very sharply defi ned aural pressure and its gradient can be measured. image. Also the so-called ‘sweet spot’ (the listening area Within the ring of microphones is a ring of loudspeak- where the effect is most striking) is considerably enlarged, ers that creates an anti-sound field matching the noise which increases the range of possible applications: for sound fi eld. The computation involved is ‘simply’ to cal- example, the ‘Linden Lichtspiele’ cinema in Ilmenau has culate a suitable transfer function for each combination been fi tted with a WFS system by Fraunhofer IDMT (see of one microphone and one loudspeaker. The calculation Figure 12). The auditorium is surrounded by loudspeak- must be done within the 2 ms that it takes for an incom- ers, arranged in panels each comprising eight mid-range ing sound wave to propagate from the microphone ring devices and eight tweeters. Each panel also contains the to the loudspeaker ring. According to Professor Krahé, amplification circuitry, and receives audio information with an array of 24 microphones and 12 loudspeakers the over an ADAT lightpipe. job is now within the capabilities of a single DSP device: As you might imagine, the computer power required to an older version of his system required a network of four generate all these audio signals is considerable. Accord- Texas Instruments TMS320C6713 processors, but the most ing to Dr Sandra Brix, an engineer at Fraunhofer IDMT, recent version runs on a single TMS320C6455. This latter a modern PC (with four quad-core processors) is enough device, clocked at 1 GHz, is capable of performing eight for a smaller system with twelve groups of eight channels. billion multiply-accumulate operations per second. To min- She adds that besides the audio rendering functions, the imise the propagation delay through the electronics, spe- computer also performs fi ltering and delay interpolation cial low-latency A/D and D/A converters are used. The A/D functions for rapidly-moving sources. The system can also converter selected is a successive approximation type, the add room refl ection and reverberation effects, for example ADS8364 from Texas Instruments, with a conversion time to simulate a concert hall. of 4 µs. D/A conversion is done by a Burr-Brown DAC7744, Conventional multi-track audio material does not really which has a conversion time of just 10 µs. Figure 11 shows challenge the WFS system. The system is most impressive

Figure 12. A wave ﬁ eld synthesis system in the ‘Linden Lichtspiele’ cinema in Ilmenau. The system has over 192 separate channels. (Photograph courtesy Fraunhofer IDMT/Ingo Herzog).

18 elektor - 10/2009

UK0910_14_19_090558-UK Sound.in18 18 10-09-2009 11:28:44 Advertisement when the position of an audio source is known along with the signal it is producing. The MPEG-4 compression standard supports ‘audio objects’, and the system can process up to 64 of these objects simultaneously in real time. Each can The new PicoScope 4000 Series be independently positioned anywhere inside or outside the area covered by the system. The positions can even be high-resolution oscilloscopes changed dynamically during a performance. The audio objects might be the individual instruments of an orchestra or extra sounds added into a mix by a DJ during a live performance. Assuming the style (and volume) of the music doesn’t put you off, you can experience the effect for yourself at the famous ‘Tresor’ club in Berlin, which is equipped with a WFS system made by Iosono GmbH [17], a spin-off company from Fraunhofer IDMT. The researchers are now working on a system aimed at the home user. The main problems to be tackled are the large number of loudspeakers required and the lack of a standardised distribution format. The fi rst problem may be solved with the introduction of new fl at loudspeakers. The second may be harder to overcome: the WFS system will only be able to be sold easily into home cinemas (and indeed, into full-scale commercial cinemas) when fi lms exist with suitably-coded audio material, for example to allow the sound of a helicopter to roar through an audi- Series 4000 PicoScope torium. However, such material will only be produced in reasonable quantities when there is enough compatible hardware in existence: a chicken-and-egg situation similar to the one experienced during the introduction of HDTV. The PicoScope 4224 and 4424 High Resolution Nevertheless, Sandra Brix is confi dent that there will be WFS systems in living rooms within fi ve to ten years. Oscilloscopes have true 12-bit resolution inputs (090558-I) with a vertical accuracy of 1%. This latest generation of PicoScopes features a deep memory Internet Links of 32 M samples. When combined with rapid [1] www.browninnovations.com/sound_domes.html trigger mode, this can capture up to 1000 trigger events at a rate of thousands of waveforms per [2] www.dakotaaudio.com second. [3] www.yamaha.com/yec/soundprojectors/ [4] www.pioneer.eu/eur/content/press/news_20021010_PDSP1. • PC-based - capture, view and use the acquired html waveform on your PC, right where you need it [5] http://en.wikipedia.org/wiki/Intermodulation • Software updates - free software updates for the life of the product [6] www.sennheiser.com/sennheiser/home_en.nsf/root/press_ar- chive_2_2001_110aes_2 • USB powered and connected - perfect for use in the field or the lab [7] www.holosonics.com • Programmable - supplied with drivers and example code [8] www.atcsd.com/site/ [9] http://en.wikipedia.org/wiki/Long_Range_Acoustic_Device [10] http://en.wikipedia.org/wiki/Sonic_weapon Resolution 12 bits (up to 16 bits with resolution enhancement) [11] http://www.headwize.com/projects/noise_prj.htm Bandwidth 20 MHz (for oscillscope and spectrum modes) [12] http://www.austriamicrosystems.com/eng/Products/Audio/ Buffer Size 32 M samples shared between active channels Active-Noise-Cancellation/AS3501 Sample Rate 80 MS/s maximum [13] http://www.uni-wuppertal.de/index-en.html Channels PicoScope 4224: 2 channels [14] http://deposit.ddb.de/cgi-bin/dokserv?idn=969174241&d PicoScope 4424: 4 channels ok_var=d1&dok_ext=pdf&fi lename=969174241.pdf (doc- toral thesis in German) Connection USB 2.0 [15] http://en.wikipedia.org/wiki/Wave_fi eld_synthesis Trigger Types Rising edge, falling edge, edge with hysteresis, [16] www.idmt.fraunhofer.de/eng/research_topics/wave_fi eld_ pulse width, runt pulse, drop out, windowed synthesis.htm [17] www.iosono-sound.com/ www.picotech.com/scope1036 01480 396395

10/2009 - elektor 19

UK0910_14_19_090558-UK Sound.in19 19 10-09-2009 11:28:59 PROJECTS TEST & MEASUREMENT BBarometricarometric AltimeterAltimeter

By C.V. Niras (India)

In this project a piezoresistive transducer measures the atmospheric pressure, enabling a PIC microcontroller to use the ISA model (with temperature compensation) to display your current height above sea level (ASL) on an LCD.

Whereas office managers typically calibrated to show your altitude above ture sensor type TC77-5.0. Freescale’s associate ‘height’ with promotion, the mean sea level (MSL) based on a MPXHZ6115A (Figures 1 and 2) is a career building and a desk on the top mathematical model called Interna- monolithic, signal conditioned, silicon floor, everyone else with a healthier tional Standard Atmosphere (ISA). The pressure sensor with an on-chip bipo- mind will be looking up towards the ISA model describes the troposphere lar op amp circuit and thin ﬁ lm resis- skies, down into chasms or valleys, or range with a linear temperature dis- tor networks to provide a high output for a safe place to land. tribution and although that’s unlikely signal and temperature compensation When mountaineering, climbing, to change with time, it does as a func- from –40°C to +125°C. para-sailing, hang-gliding or flying tion of temperature, with barometric ULs (ultralights), it’s plain essential pressure as an inherent dependency. A fluorosilicone gel isolates the die to know your ‘ASL’: height above sea Right, this project does take tempera- surface and wire bonds from the envi- level. ture deviation into account to compen- ronment, while allowing the pressure sate the altitude reading! signal to be transmitted to the silicon diaphragm. With a typical current con- Pressure — in theory sumption of 6 mA (at 5 V), it’s neces- Since barometric pressure is closely ISA rulez: the components… sary to keep the sensor in the off state approximated by the hydrostatic pres- For accurate and reliable ASL readings when not in use. sure caused by the weight of the air a temperature measurement device has Note that it requires about 20 ms to above you, your altitude on the planet to be included in the project. So let’s list warm up, i.e. before taking any read- above a reference level can be calcu- the crucial components: a PIC18F2423 ing. Maximum error is 1.5% over 0° to lated fairly easily and shown on a dis- microcontroller, an MPXHZ6115A pres- 85 °C, and the component provides the play. The altimeter described here is sure transducer and a digital tempera- transfer function

20 elektor - 10/2009

UK0910_20_24_080444-UK Altimeter20 20 10-09-2009 11:29:19 MMountaineers,ountaineers, ddeltaelta ggliderlider aandnd UULL ppilotsilots — tthishis oone’sne’s 4 U

Speciﬁ cation and features

• Altitude range: 0 to 11,000m A(M)SL • Compliant with ISA model, extended with temperature compensation • Barometer range: 15 kPa to 115 kPa • Resolution: 3 m. • Temperature range: –55 °C to +125 °C • Real Time Clock • Supply voltage: 6–15 VDC; • Current consumption - LCD backlight on: 18 mA; - LCD backlight off: 8 mA; - Standby: 20 µA • Menu controlled • Software: C for PIC

=× ×− VVout s (.0 009 P 0 . 095 ) of ±3 °C. A band-gap type tempera- For a column of air with base area A ture sensor, a 12-bit plus sign (13-bit) and height h, the formula can be writ- ±×× × [Eq. 1] (.)PE TF0 009 Vs Sigma-Delta ADC, an internal conver- ten as sion oscillator (approx. 30 kHz) and an hATk×=/ [Eq. 4] where P is the applied pressure, Vs is SPI-compatible serial input/output port the supply voltage, PE is the pressure — the works! error and TF the temperature factor. Comparing standard atmosphere The output from the pressure sensor is with actual conditions, k is still con- measured using the microcontroller’s … and the software stant and for a column of air with the internal ADC. Altitudes below 11,000 The ISA model is based on air pressure same base area A becomes a constant, m (33,000 ft) can be calculated using at sea level of 101.325 kPa and a tem- too, and the variations are in h and T. the barometric formula: perature of +15 °C. The temperature Using index s from he ISA model and r at 11,000 m is taken to be –56.5 °C, so for the real ambient air we can write −×0. 19026 temperature decreases 6.5 °C for every ((/)1PPref 288 . 15 hT//= hT [Eq. 5] h= 1,000 m, up to about 11,000 m. The rr ss 0. 0065 [Eq. 2] actual atmospheric temperature can or deviate considerably from this model, =× hhTTrssa(/) [Eq. 6] where Pref is the pressure at the base requiring a correction for altitude read- (i.e. at MSL), and h the altitude in ings to be applied. metres. The temperature correction can be cal- The software is written to calculate The TC77-5.0 temperature sensor from culated with help of Charles’s Law for and solve the above equations and you Microchip is a serially accessible dig- ideal gases. It states that the volume need not worry about it! C code munch- ital temperature sensor with a reso- of the gas is proportional to absolute ers delve into ﬁ le 080444-11.zip avail- lution of 0.0625 °C and a maximum temperature, or able free from the Elektor website! [1] accuracy of ± 1 °C within the +25 °C VT/ = k [Eq. 3] to +65 °C range. Temperature data is available as a 13-bit 2’s complement QNH setting format, and covers a range of –55°C to where V = volume of gas; T = abso- ‘QNH’ is a Q code rather than the lat- +125 °C. with a maximum accuracy lute temperature and k = constant. est PIC mnemonic. It is a pressure set-

10/2009 - elektor 21

UK0910_20_24_080444-UK Altimeter21 21 10-09-2009 11:29:23 PROJECTS TEST & MEASUREMENT

phere for the part between the MSL

Fluoro Silicone and ground level. It’s essentially iden- Gel Die Coat Stainless tical to ISA, but extends the altitude Die Steel Cap P1 coverage up to 80 km. Wire Bond Thermoplastic You can set the QNH in this altimeter MPX5100A MPXHZ6115A6U Case CASE 867-08 CASE 1317-04 Lead in two ways: either directly enter the Frame POSITIVE PRESSURE QNH using the menu screen, or enter (P1) the known altitude for your location. 1 Absolute Element Die Bond

1 Sealed Vacuum Reference 080444 - 13 Circuit description 123456 080444 - 12 At the heart of the circuit shown in Figure 2 sits a Microchip PIC18F2423 Figure 1. Internal structure of the MPXHZ6115A pressure nanowatt technology, fl ash microcon- Figure 2. Case shapes of the two pressure transducers that may transducer. (source: Freescale) be used on the Altimeter board. (source: Freescale) troller with 12-bit ADC. The device also sports 16 K code space, 768 bytes of RAM, 256 bytes of EEPROM and ting used by pilots, air traffi c control- an internal oscillator. Here a standard metric within the specifi ed excitation lers and weather beacons to enable 32.768 kHz watch crystal (X1) with two range and supplied from the ADC ref- altimeters to read altitude above MSL 15 pF load capacitors are the hardware erence terminal, it is not necessary to within a certain region. QNH is calcu- elements of the (otherwise invisible) use a precision reference voltage. The lated from the barometric pressure at real time clock. sensor is shut down and woken up ground level using ICAO STD atmos- Since the pressure sensor, IC4, is ratio- using MOSFET T2 on port line RA5.

IC1 LCD1 MCP1703T-5002E/CB PC1 +5V

6–15V 2x16

C1 C2 C3 C4

PC2 47u 100n 100n 47u VSS VDD VL RS R/W E D0 D1 D2 D3 D4 D5 D6 D7 LED-C LED+A 1 2 3 4 5 6 7 8 9 L- 10 11 12 13 14 L+ GND R9 T1 Vdd +5V FDV304P Vdd 100R

R1 R5 +5V C6 +5V 10k

1k C10 R7 100n R6 C5 47u 4k7

Vpp 1k 100n D1 - D4 = 4x TS4148 IC2 20 S1 S2 S3 S4

5 TC77-5.0 1 21 MCLR/Vpp RB0 VDD 1 13 22 CS RC2 RB1 3 14 23 D1 D2 D3 D4 SCK SCK RB2 4 15 24 SI/O SDI IC3 RB3 GND 16 25 R2 SDO RB4 2 26 100k PIC18F2423 RB5 3 27 +5V RA1 RB6/PGC 6 28 RA4 RB7/PGD 1 K1 2 17 2 +5V RC6/TX/CK AN0 3 18 7 AVDD RC7/RX/DT RA5 K2 4 5 Vpp 1 +5V VREF+ C11 C12 C13 9 4 2 OSC1 VREF- L1 D5 R3* 10n 100n 47u 3 T1OSO T1OSI 10uH 4

1% 8 TS4148 5k1 19 11 12 5 X1 IC4* T2 AGND VDD R8 ICSP C7* C8 C9 VOUT 750R NP0 NP0 NP0 C14 FDV304P GND 100p 15p 32.768kHz 15p R4 0R 330n +5V AGND AGND AGND 080444 - 11

Figure 3. Circuit diagram of the Barometric Altimeter. Note the difference between A(nalog)GND and digital ground.

22 elektor - 10/2009

UK0910_20_24_080444-UK Altimeter22 22 10-09-2009 11:29:24 The pressure sensor output is conversion, the result is available in the The PCB accommodates SSOP cased nected to the microcontroller’s ADC ADRESH:ADRESL register pair, and pressure sensors like the MPXH- channel 0 (AN0) via an RC low-pass it is right-aligned (i.e. first four bits Z6115A6U used in our prototype, as fi lter with cut-off frequency of about of ADRESH read as zeros). This 10- well as UP (Unibody Package) through- 650 Hz. The 750-Ω resistor (R8) allows bit result can be directly converted to hole devices like the MPX5100A. a low source impedance to be matched pressure by multiplying it with a con- The PCB was designed with two to the PIC’s on-chip ADC, thus mini- stant and adding the pressure offset. ground planes: one for the analogue mising the offset voltage at the ana- The ADC acquisition times for the PIC part of the circuit (comprising the sen- logue input [2][3]. The pressure sensor is supplied via an LC fi lter (L1, C11, C12 and C13) where D5 is a free-wheel diode. The LCD is wired to the PIC micro in 4-bit mode, requiring data to be sent twice using the upper nibble of PORTB, with the port also doing the key scanning and multiplexing. Supply power to the LCD arrives via MOSFET T1, which is controlled by port line RB1. Since the PIC has an SPI module, it is not too diffi cult to get it interfaced to the TC77-5.0 temperature sensor chip (IC2). The TC77-5.0 starts to send data when its CS input is pulled logic Low Figure 4. Top side component mounting plan (double-sided board). by port line RC2. Copper track layouts available free from www.elektor.com/080444. The PIC micro may be programmed in-circuit via ICSP connector K2. Push buttons S1–S4 are read in multiplex COMPONENTS LIST IC2 = TC77-5.0, SOT-23 (Farnell # fashion. 1292291) IC3 = PIC18F2423, SO-Wide, program- Components R3 and C7 are not Resistors med, Elektor Shop # 080444-41 (1%, SMD 0805) required with the supplied fi rmware, Ω IC4 = MPXHZ6115A6U or MPX5100A R1, R6 = 1k (Freescale), SSOP (see text) because the internal oscillator is being R2 = 100kΩ used. T1,T2 = FDV304P, SOT-23 (Farnell # R3 = not fi tted (see text) 9846123) If you do not wish to use the LCD back- R4 = 0Ω Ω light, R9 should be omitted. R5 = 10k Miscellaneous R7 = 4.7kΩ The rest of the circuit is no more than Ω K1 = 4-way SIL pinheader, right angled R8 = 750 solder pins, lead pitch 2.54mm (0.1’’) the expected low-dropout power sup- R9 = 100Ω ply (IC1) and an array of supply decou- K2 = 5-way SIL pinheader, right angled solder pins, lead pitch 2.54mm (0.1’’) pling caps at crucial locations (C1–C4, Capacitors L1 = 10µH ferrite inductor, SMD 1812 C5, C6, C11, C12, C13). C1,C10 = 47µF /35V radial electrolytic, (Farnell # 1174073) lead pitch 2.54mm (0.1’’) LCD1 = 2x16, alphanumeric, DEM16217 C2,C3,C5,C6,C12 = 100nF 50V ceramic, SYH-PY /V, e.g. Elektor Shop # Software X7R, SMD 0805 030451-72 C4,C13 = 10µF 16V radial electrolytic, PC1,PC2 = solder pin, 1mm diam. The program was written in C and lead pitch 2.54mm (0.1’’) S1–S4 = switch, tactile, SPNO compiled using Microchip’s C18 com- C7 = not fi tted (see text) X1 = 32.768kHz quartz crystal, cylindrical C8,C9 = 15pF ceramic, NP0, SMD 0805 case piler. The PIC can be programmed C11 = 10nF 50V ceramic, X7R, SMD 0805 using simple homebrew programmers 4 PCB supports, nylon, 12mm height, C14 = 330nF ceramic, X7R, SMD 0805 4.6mm diam. (Farnell # 1325986) like the MultiPIC Programmer [4] and PCB, ref. 080444-1 from ICProg. Be sure to disconnect the LCD Semiconductors www.thepcbshop.com D1–D5 = TS4148, SMD 0805 (Farnell # while ICSP-ing the PIC. 8150206) All is revealed in the C source code fi le IC1 = MCP1703T-5002E/CB, SOT-23, found in archive # 080444-11 supplied (Farnell # 1439519) for the project. Timer1 is initialised to 0x8000h, causing it to overfl ow every second. It continues operating in sleep mode (consuming a few microamps micro (i.e. the time required to charge sor, RC low-pass fi lter and the sensor’s only) so it’s unnecessary to use an CHOLD in the internal sample and hold decoupling capacitors), and the other external RTCC chip for timekeeping. circuit) is about 2.96 µs; this must also for the digital circuitry, i.e. the remain- The altitude is determined by using observed before taking readings. ing part of the circuit. Eq. [2] and is displayed along with the The PCB ground planes are intercon- atmospheric pressure. The fi rmware nected at a single point only by means uses 32-bit fl oating point arithmetic. Construction of zero-ohm resistor R4 (a wire link or The conversion starts when the ADGO A double-sided through-plated circuit a drop of solder is also an option). This bit is set, and is cleared after com- board was designed for the project — see bridge provides a single path for return pletion of the conversion. After con- Figure 4 and pdf fi le 08044-1 from [1]. currents. The only necessary trace

10/2009 - elektor 23

UK0910_20_24_080444-UK Altimeter23 23 10-09-2009 11:29:25 PROJECTS TEST & MEASUREMENT

Figure 5. Finished board with MPXHZ6115A SMD pressure sensor Figure 6. The Altimeter board and the LCD are connected by a mounted at far left of the board. 16-way SIL pinheader/socket combination.

that’s routed from the digital Acknowledgement to the analogue ground plane Send us photos of the readout The help of Prof. T. K. Mani, carries the sensor’s supply Principal College of Engineer- voltage and is intentionally at low-oxygen heights ing Cherthala, India, is gratefully routed underneath the bridge. acknowledged. This way we have two equal currents order and your mind at ease, apply fl owing in opposite directions causing power and check if the LCD contrast the resulting electromagnetic fi elds to is as desired. If not, adjust the val- cancel out. ues of resistors R5 and R6 until you’re Internet Links Assuming you’ve some experience in happy. soldering SMD parts whether refl ow- For construction standards, the pho- [1] www.elektor.com/080444 style or manually, the critical ones are tographs in Figures 5 and 6 show the [2] http://www.freescale.com/fi les/sensors/ the PIC and the pressure sensor. The levels to match or surpass by your doc/app_note/AN1646.pdf push buttons and the 16-way LCD con- efforts. [3] http://www.microchip.com/wwwproducts/ nector are mounted at the top side of (080444-I) Devices.aspx?dDocName=en026428 the board. [4] www.hamradio.in/circuits/feng.php Run a careful check on your soldering and component mounting before [5] http://wiki.motionbased.com/mb/ applying power for the fi rst time. All in Barometric_Altimeter

Practical use Initially the EEPROM is programmed with typical values of the calibra- The menu contains following items. tion constants, so apart from the time there’s nothing to set unless a Set Pressure: this screen is used to calibrate the pressure sensor. solid reference is available for your current altitude. Set Altitude: this is the fi rst method to set the pressure at MSL. The For the instrument to work correctly, a few calibration adjustments are known value of altitude is entered here. Based on the ambient tem- required. A menu system is provided. Using the four buttons (top to perature and pressure, the software will fi nd out the pressure at MSL bottom): and save it to memory. Menu / Cursor position Set QNH: directly enter the pressure for MSL based on QNH Up / Power On information. Down / Power Off Set Time: set / adjust time Esc / Save To change the value of the selected parameter(s), use the Up (increase) or Down key (decrease) to adjust the value. The underscoring you can easily set all calibration parameters correctly. cursor indicates the digit subject to changing, if necessary, by a short The second function of each key is accessed if the key is held down for press of the Menu key. To exit from the selected menu press Esc (S4). about one second. The altimeter is turned off by keeping the Down key pressed for more Enter the menu system by pressing and releasing the Menu button than one second. This is actually the power-down mode, and the RTC (S1). The fi rst menu item will be displayed on the LCD. To go to next will continue to keep the time. In this state the processor consumes menu, press Up (S2) or Down (S3). To enter the selected menu, press only minimum power (approx. 20 µA average for the whole circuit). the Menu key again. Switch on again with the Up key.

24 elektor - 10/2009

UK0910_20_24_080444-UK Altimeter24 24 10-09-2009 11:29:25 Microcontrollers The World’s Lowest Sleep Current MCUs: PIC® MCUs with nanoWatt XLP Technology Controllers Digital Signal Signal Digital Analog EEPROMs Serial

Microchip’s PIC® Microcontrollers with nanoWatt XLP GET THE MOST FROM YOUR BATTERY IN YOUR NEXT DESIGN! Technology offer the industry’s lowest currents for line 2nd Direct... Microchip sleep, where extreme low power applications spend up 1. View the Low Power Comparison to 99% of their time. demo 2. View free Webinars and Application t Extend Battery Life Notes – Sleep current down to 20 nA 3. Download the Low Power Tips ‘n Tricks – Brown-out Reset down to 45 nA 4. Order samples and development tools – Watchdog Timer down to 400 nA www.microchip.com/XLP – Real time clock down to 500 nA t Extreme Flexibility – 5 different low power modes to improve power & performance in your application – Many low-power supervisors, alarms, and wake-up sources t Expanded Peripheral Set – Integrated USB, LCD, RTCC & touch sensing – Eliminates costly external components Intelligent Electronics start with Microchip

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The Microchip name and logo, the Microchip logo and PIC are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. All other trademarks mentioned herein are property of their respective companies. © 2009, Microchip Technology Incorporated. All Rights Reserved. ME235Eng/08.09

0910_elektor_adv_UK.indd 25 10-09-2009 11:14:30 PROJECTS ARDUINO & MONOME Touch LEDs for Arduino A cheap 4x4 Monome shield

By Clemens Valens (Elektor France Editorial)

Most of the projects published in Elektor simply provide a solution to a problem or fulﬁ l a need. Even though their designers have often tried to propose an elegant circuit or design an attractive PCB, the aesthetic effect of the project itself, if there is one, usually takes second place. One exception is the Monome open source project, a USB luminous matrix keyboard that was designed to be good-looking. Here, it’s the application that seems to have been relegated to second place.

Let’s make it clear right from the start: only produced in small runs and their Main Speciﬁ cations the project shown here is not espe- prices are high (expect to pay €/£ 375 cially good-looking. It was inspired or $500 for a basic Monome) — espe-

• 4x4 Monome shield for Arduino by the Monome project [2], which is cially when you think that they are attractive. Even if the design of a genu- nothing more than simple USB keypads • Open source hardware ine Monome may not to your taste, it that don’t even work with MS Word! • 16 push buttons has to be admitted that the aesthetic aspect of the project is very important The aim of the project described here • 16 LEDs — you only have to visit the website to is to offer everyone the opportunity to • TLC5940NT LED controller see for yourself. produce their own Monome for a cost • 12-bit LED brightness control Exclusiveness seems to be one of the that is derisory compared with the project’s other goals. Monomes are price of a ‘real’ one. What’s more, our

26 elektor - 10/2009

UK0910_26_31_090527-UK Monome.in26 26 10-09-2009 11:30:38 Monome can be used for any other pur- pose, since the software, like the hardware, is open and you can modify everything. The brightness of each LED is 12-bit adjustable, thanks to the LED 16x driver, and we can dream up all manner of fi ne, luminous objects. USB ARDUINO PC But just what is a Monome exactly? A Monome is a rather special USB keypad. First of all, the keys, positioned 4x4 SHIELD on a grid (usually square, though not necessarily so), do not have predefi ned 090527 - 11 functions, and are all identical. In addition, each key is fi tted with an indicator that makes it light up. Figure 1. Block diagram of our Monome. Here, ‘Shield’ doesn’t mean screening, but indicates an extension card for Arduino.

The Monome communicates with a computer via USB. When we press or allows analogue values to be sent to OK, I want one! release a key, the Monome sends the the computer. co-ordinates of the key and its status. In fact, Monome is the name of the Once you’ve understood the concept The application running on the com- company that developed the keypad, of the Monome, it’s easy to build your puter that receives the co-ordinates which itself has names like 40h (8×8), own version. All you have to do is of the keys decides how to interpret two ﬁ fty six (16×16), one twenty eight assemble a lot of keyswitches around them. And the application also drives (16×8) or sixty four (8×8). So the name a small microcontroller, and the job is the Monome’s lights. So the Monome indicates the number of keys. 40h is done. This is when you realize that key- does not control its own lights — it’s the hexadecimal value for 64, and so switches with built-in indicators are a bit like a keypad and a display built the Monome described in this article not very cheap, and that you’ll need 16 into the same housing. is called 10h, as it is based on the 40h, just for a little 10h Monome. The ofﬁ - but only has 16 keys. cial Monomes use thermo-formed key- Even though a Monome is a USB keypads in transparent silicone. This type pad, it doesn’t operate like a standard For those people who like to know eve- of cheap keypad is unfortunately not keyboard and can’t be used to replace rything, Monome is a company that available to amateurs, who will have one. This is because of the commu- sees itself as minimalist. Its name to make do with standard illuminated nication protocol used by the Mon- refers to the monomial matrix, a square push-buttons at €/£ 3 each. That’s ome, which is incompatible with nor- matrix that only contains 1’s and 0’s, why the following project is interest- mal keyboards. And there are several with only a single 1 in any given row ing, because we’re going to explain different Monome protocols, which or column. The company is fairly envi- how to make your own illuminated makes thinks even more complicated. ronmentally-friendly, and its products push-buttons for less than €/£ 1! If you Some Monomes include an accelerom- are manufactured with minimum envi- are good at DIY and a shrewd buyer, eter and the communication protocol ronmental impact. it’s possible to build a 10h Monome

Programming the FTDI chip MProg gives you access to the parameters of the FTDI chip on the Arduino (or - Check the Use Fixed Serial Number other) board, and as you can see, there box are quite a few of them! If you’re not -Enter an 8-digit serial number starting careful, you risk disabling your USB in- with ‘a40h-’ — for example, a40h-001 terface, so don’t change any parameters if you don’t know what they’re for. -Save the conﬁ guration: File -> Save As… MProg can be a bit temperamental. Sometimes, it’s impossible to change - Click Device -> Program between editor and programmer modes. Everything hangs up for a couple of sec- It seems that opening or saving a ﬁ le onds, then the message Programmed should clear this blockage. The following Serial Number: a40h-001 ap- procedure seems to work quite well: pears. Your Arduino is now Monome -Run MProg compatible! -Connect the Arduino board - Click Tools -> Read and Parse

10/2009 - elektor 27

UK0910_26_31_090527-UK Monome.in27 27 10-09-2009 11:30:41 PROJECTS ARDUINO & MONOME

26 S1 S2 S3 S4 5V 21 17 AN5 VCC LD1 LD2 LD3 LD4 18 27 28 AN4 3V3 OUT0 19 19 1 AN3 DCPROG OUT1 S5 S6 S7 S8 20 2 AN2 OUT2 21 27 3 AN1 VPROG OUT3 23 22 24 VIN AN0 XLAT IC2 LD5 LD6 LD7 LD8 28 16 4 RESET XERR OUT4 5 S9 S10 S11 S12 OUT5 ARDUINO 6 9 18 OUT6 D7 GSCLK 7 1 10 23 OUT7 AREF D6/PWM BLANK 2 11 LD9 LD10 LD11 LD12 AGND D5/PWM 8 3 12 26 OUT8 S13 S14 S15 S16 D13 D4 SIN 9 4 13 17 OUT9 D12 D3/PWM SOUT 10 14 25 OUT10 D2 SCLK 11 15 OUT11 D1/TX 16 TLC5940NT LD13 LD14 LD15 LD16 D0/RX 12 8 OUT12 D8 20 13 7 IREF OUT13 D9/PWM 14 6 OUT14 D10/PWM R1 15 5 C1 OUT15 D11/PWM GND 3k3 GND1 GND2 22 24 25 100n

090527 - 12

Figure 2. Monome circuit diagram. The Arduino board is based on an ATmega8 or ATmega168, as the PWM function is not used.

for less than €/£ 35. What’s more, the controller pins. Broadly speaking, the project can be used for other things, as interface is divided into two parts, one it is just a simple display keypad. for the data transfer and the other for refreshing the LEDs. This interface can be optimised by combining certain sig- Let’s get down to business! nals, but this has not been done here. We are basing our design on an LED If you are thinking of experimenting Arduino board [3][4], which is inex- with this device, you may like to know pensive and easy to program, but you that it lets you adjust the maximum can use a different controller board if S current individually for each output, you prefer. The only thing that really a nice option that could cause you to matters is the USB interface, which waste a lot of time. If you can no longer absolutely has to be a variant of the 090527 - 13 get one or more LEDs to light up, or if FT232R chip from FTDI, otherwise the the brightness levels are no longer the communication software wouldn’t be Figure 3. How to construct a touch LED using an LED, a same, it could be that you have inad- able to detect your Monome. Because keyswitch, and a little bit of patience. vertently modiﬁ ed the parameters of our Monome uses Arduino, it one or more outputs. In this belongs to the family of Ardui- case, disconnect the power to nomes, which is no pointless reinitialize the device — just distinction, since it requires resetting isn’t enough. special software. R1 sets the maximum cur- You’ll ﬁ nd the block diagram of rent for all the outputs, you the project in Figure 1 and the can select this to increase or circuit in Figure 2. As you can reduce the brightness of the see, it’s quite simple, thanks Monome overall. to Arduino and the LED driver IC1. This IC contains 16 current sources for driving 16 LEDs. So, these keys? Each output is controlled by We’re going to construct the 12-bit PWM (pulse width mod- Monome keys using 10 mm ulation), offering 4,096 bright- LEDs and miniature push-but- ness levels per LED. This tons (Figures 3 and 4). The device has a slightly special idea is to use the LEDs to serial interface, not very well press the push-buttons. The explained in the data sheet, LEDs are large enough to hide but which only requires six Figure 4. Building the prototype. the push-buttons, and seen

28 elektor - 10/2009

UK0910_26_31_090527-UK Monome.in28 28 10-09-2009 11:30:42 from above, only the LEDs are visible. To obtain vertical-action keys, the LED COMPONENT LIST leadouts have to be bent in such a way as to obtain a sort of ‘shock-absorber’. Resistors Ω Then the push-button is slipped into R1 = 3.3k the shock-absorber and the LED + but- Capacitors ton assembly is fi tted to the board. C1 = 100nF Concerning the LEDs, before you start making the keys, check that all the Semiconductors D1–D16 = LED, 10mm diam. LEDS have the same brightness for IC1 = TLC5940NT a given current. It can vary from one LED to another, especially with cheap Miscellaneous ones. Don’t skip this step, since once S1–S16 = miniature pushbutton, the keys have been fi tted, it’s not easy 6x6 mm, e.g. Omron type B3W-1000 2 pcs 6-way SIL pinheader, 0.1” to remove them again. (2.54mm) lead pitch 2 pcs 8-way SIL pinheader, 0.1” (2.54mm) lead pitch Construction PCB # 090527-1 [1] Arduino board A PCB has been designed for this project [1], see Figure 5. In keeping with the ‘Open Source’ philosophy, you’ll find on the web page for this Figure 5. Component side of the PCB. project the complete Eagle fi le (circuit and PCB) which you can modify as you wish. Take care not to route any tracks beneath the push-buttons on the com- imum) and then starts all over again. have opted for automatic detection of ponent side, as the LED leadouts This loop lasts for around 40 seconds the Monome by interrogating the USB already pass through this space. or so. If you press on an LED, the peripherals; it’s not possible to do this Start by fi tting R1, C1, and IC1. Then brightness of this LED is reset and it manually, which is a bit of a pity. fi t the keys, starting with the ones in restarts its loop. In this way, you can In order to be recognized as a Mon- the centre of the grid. Fit the push- create some hypnotic sequences. The ome, the peripheral must have a serial buttons carefully horizontal, and try to fi rst reception of a Monome command number in the format a40h-xxx (xxx is keep a small space between the LED exits the demonstration mode. For the for you to choose). We adopted a40h- leadouts and the board to improve the moment, your circuit still isn’t a real 001. Refer to the box for details about vertical movement of the keys. This job Monome, so it is unable to receive programming the FTDI chip. requires a bit of patience and accuracy Monome commands — so let’s carry to end up with a satisfactory result. on getting it ready. Finish the wiring with the pin head- On the computer side... ers that have to be fi tted on the solder As explained above, the FTDI chip also To finish off our Monome, or rather side of the board. has to be programmed. You may not the operational testing, there are two know it, but this device is programma- more pieces of software to be installed ble thanks to a small EEPROM mem- on the computer (Figure 6). The fi rst Initial testing ory. FTDI provides the MProg tool for piece of software, Arduinome Serial [6], Two components have to be pro- doing this [5]. This is necessary in is used to translate the Monome com- grammed before the Monome will order to make our Monome work with munication protocol into MIDI (Musi- work: the microcontroller and, surprise, the driver on the computer. In their cal Instrument Digital Interface [7], a the USB interface! The microcontroller efforts to make it as simple as possible language dating from the 80’s, mainly is programmed like an Arduino, since to use a Monome, the driver’s writers used for synthesizers) or into OSC it is an Arduino, and this can be done from the Arduino environment [4], but if you prefer, you can fl ash the microcontroller directly with the HEX fi le. PC You’ll fi nd all the source codes and the HEX fi le at [1]. Arduinome Serial If you’ve programmed your circuit with 16x the software available in the article’s monome App. monome USB 40h prot. web page, your Monome now has a 10h demonstration mode that lets us see if (4 x 4) MIDI / ex. MAX/MSP the board is working properly. Restart OSC the circuit and watch the LEDs. You’ll see fi rst of all that all the LEDs light up briefly: flash! Then the program 090527 - 14 goes into a loop which progressively increases the LED brightness from zero Figure 6. Arduinome Serial translates the data sent by the Monome into MIDI or Open Sound Control (OSC). The translated messages up to a certain maximum (not the max- are sent to the Max/MSP application via the computer’s internal network.

10/2009 - elektor 29

UK0910_26_31_090527-UK Monome.in29 29 10-09-2009 11:30:43 PROJECTS ARDUINO & MONOME

(Open Sound Control [8], a language package from [1] and unzip it onto your that is more recent, more powerful, computer’s hard disk somewhere. and more ﬂ exible than MIDI). Ardui- nome Serial has to be used for Mono- mes based on Arduino or, to be more Final testing precise, Monomes that use the FT232R Connect the Monome to the computer chip for their USB interface. (For the via a USB cable and run Arduinome others, there is Monome Serial.) Serial. If all is well, the software will The second piece of software to install ﬁ nd the Monome and display the serial is Max/MSP [9] (also see inset). This number you’ve just programmed for it software is a powerful graphical pro- (Figure 7). There’s no need to mod- gramming environment for music, ify the parameters for our tests, the audio, and multimedia which is used default values will do. for developing multimedia patches. Now run Max/MSP and load the Mon- The part of the environment that runs ome_test.mxb patch, in the ‘Monome the patches (the runtime) is free, which base’ package (don’t take any notice lets you run them on any Mac- or Win- of the messages about matrixctrl). A

Max, Pure Data, jMax Max/MSP is one of the pieces of music software most used by professional and amateur mu- sicians alike; it lets you synthesize sounds, analyse, and record, as well as controlling MIDI instruments. Originally called Patcher, Max was invented and developed by Miller Puckette at IRCAM in the mid 80’s. The ﬁ rst commercial version was distributed by Opcode System in 1990, and Cycling ‘74 [9] has been looking after its development since 1999. In 1996, Miller Puckette, working at San Diego University, created a free version called Pure Data, while IRCAM has developed a free version jMax in Java with a graphical interface. There’s a substantial community of users and developers around Max/MSP, a collaboration that mainly consists of exchanging ‘patches’ and ‘external’ objects, and suggesting improvements to the Figure 7. Arduinome Serial detects the Monome automatically, software. [source Wikipedia] and the default parameters are good enough for testing.

Here’s what a PureData patch looks like for breaking down, modifying, and re-synthesising an audio signal using wavelets. The rectangles in the ‘program’ part are objects that contain sub-programs, the lines between the rectangles are the data ﬂ ows.

Other music programming languages, albeit without nice graphical interfaces, are, for example, Csound (www.csounds.com) and ChucK (http://chuck.cs.princeton.edu/).

Pure Data: http://puredata.info/ jMax: http://freesoftware.ircam.fr/rubrique.php3?id_rubrique=2

dows-compatible computer. So down- second window opens with two grids load and install just the Max/MSP in particular (Figure 8), one for the runtime. keys (‘keypads’) and the other for the LEDs (‘lights’). Click on the ‘/sys/pre- On the Monome website there are some ﬁ x/test’ button and check that Ardui- patches for Max/MSP that will enable nome Serial now displays ‘/test’ in the Figure 8. The Monome_test script for Max/MSP lets you check you to check your Monome is working Address Pattern Preﬁ x box. If so, the that a Monome is working properly. properly. Download the ‘Monome base’ two pieces of software are managing

30 elektor - 10/2009

UK0910_26_31_090527-UK Monome.in30 30 10-09-2009 11:30:44 to communicate with each other. let you do a test that’s a bit more fun. you to modify the quite simple Mon- Then, in the Monome_test window, Open the fi le and click the focus prefi x ome software to sort everything out, click the button next to the word ‘pair- button in the Monome_midi_64 win- as the options provided by Arduinome ing’, just below the ‘keypads’ grid, and dow to change the Arduinome Serial Serial aren’t enough. Now it’s over to select ‘press’. If you click somewhere in Address Pattern Prefi x to . If you... the ‘keypads’ grid, the corresponding you press an LED, you’ll hear a sound (090527-I) box in the ‘lights’ grid changes colour. and you’ll be able to play a tune. You Reboot the Monome. This is neces- can change the sound (the default is Internet Links sary because for some reason the piano) and the note values by clicking automatic detection of the Monome and moving the mouse around in the [1] www.elektor.com/090527 by Arduinome Serial makes the serial matrix. [2] www.monome.org link crash. Press the LEDs and you’ll [3] www.arduino.cc see the corresponding boxes in the You’ll probably have noticed that the ‘keypads’ grid light up. If you have boxes in the ‘keypads’ grid that light [4] www.elektor.com/080931 selected ‘press’, the LEDs will also up when you press the LEDs are some- [5] www.ftdichip.com/Resources/Utilities.htm light up. If you release an LED, it will where in the middle of the grid, and [6] www.sourceforge.net/project/show- go out. If you have selected ‘toggle’, the orientation is not the same as on fi les.php?group_id=235473&package_ the fi rst press lights the LED, pressing the Monome. This is due to the Mon- id=285957 a second time will extinguish it. You ome software, which doesn’t com- [7] www.midi.org/ can also use the mouse to click in the pletely follow the convention. Ardui- ‘lights’ grid to light up or extinguish nome Serial has a ‘Cable Orientation’ [8] www.opensoundcontrol.org/ the LEDs without pressing any keys. box that lets you choose between [9] www.cycling74.com If all this is working, you Monome is ‘up’, ‘down’, ‘left’, and ‘right’ — see [10] www.Monome.org/data/app/base operational (at last!) Figure 6. This box is used to orient the Monome with respect to its USB cable. So if you’re holding the Mon- Just to fi nish off... ome in your hand with the USB cable If your computer has a sound card, coming out downwards, you’ll need the Monome_midi_64.mxb patch will to choose the ‘down’ option. It’s up to

10/2009 - elektor 31

UK0910_26_31_090527-UK Monome.in31 31 10-09-2009 11:30:45 INFO & MARKET DIY VALVE AMPLIFIERS High-End Audio Amplifier Kits Build your own valve preamp and power ampliﬁ er

By Harry Baggen (Elektor Netherlands Editorial)

In the midst of all the surround-sound and multimedia hype, more and more people are discovering (or rediscovering) the value of a good audio system. This is an area where there is still plenty of room to build your own equipment, including amplifi ers and loudspeakers. To make things easier for DIY enthusiasts with limited experience, Amplimo offers high- quality construction kits for a valve preamplifi er and power amplifi er.

It appears that the interest in good audio reproduction has which are sold in kit form by Amplimo. In the audio world, declined dramatically in recent years. Flashy sound effects Menno van der Veen is primarily known as a specialist on seem to have won out over natural stereo reproduction, the subject of output transformers and valve amplifi ers. He and everyone is happy with the quality of their MP3 play- also conducts workshops and master classes on valve ampli- ers with their obligatory ear pods, most of which are mis- fi er design. A few years ago he developed a valve ampli- erable. What else can you expect when most people are fi er for DIY construction, which since then has established a easily satisfi ed? good reputation among hi-fi enthusiasts. There was also a version of this amplifi er as a pure power amplifi er, without Fortunately, we are again seeing a growing interest in high- a volume control or selectable inputs. Naturally, a power quality sound reproduction. Unfortunately, the downside is amplifi er of this sort needs a matching preamplifi er, and it that the necessary equipment is usually rather pricey, but the also appeared recently. This was suffi cient reason for us to upside is that you can do a lot yourself in this area. Espe- have a closer look at the combination of the MCML05 and cially in the high-end realm, people are more inclined to UL40S2P units. look for refi nement in the details than in complex circuitry, which encourages others to make their own modifi cations or even build (or copy) complete amplifi ers. However, not Complete kits everyone is able to do this. The kits for these two amplifi ers include all of the necessary parts, nicely sorted and packaged in several bags: PCBs, If you enjoy the idea of building your own high-quality components, connectors, screws, wires, and even cable ties amplifi er without and saving a pot of money at the same and safety labels. The valves (some of them selected) are time, you should certainly have a look at the preamplifi er packaged separately and numbered. Each kit also includes and power amplifi er kits described here. These are valve a machined enclosure with pre-fi tted threaded bushes and a amplifi er designs from the hand of Menno van der Veen,

32 elektor - 10/2009

UK0910_32_35_081035-UK Buizenver32 32 10-09-2009 11:35:14 separate front panel (plastic or metal). The detailed assembly instructions (around 65 pages for the preamplifi er and 40 pages for the power amplifi er) are located in a folder. The construction of each amplifi er is described step by step, and the approach is so clear that it’s practically impossible to go wrong. Of course, you do need to have some technical knowledge and know how to use a soldering iron. Each project begins with the assembly of the circuit boards. All of the components of a particular type are fi tted in each step, such the solder lugs, followed by the resistors, then the diodes, and so on. The instructions explain what these components look like, how to make sure that you get the polarity right, and the value marked on each component. For anyone who’s an old hand at electronics this is all a matter of course, but there’s many an audio enthusiast who knows little or nothing about electronics. Figure 1. After all the PCBs are assembled, the next task is the Interior view of the mechanical assembly, such as fi tting the circuit boards in MCML05 preamplifi er. The the enclosure and connecting the wiring. Here again the special MC transformers instructions are very detailed; every length of wire and can be seen at the piece of heat-shrink tubing is described and shown in a rear, next to the input drawing. connectors.

After this is fi nished, you can start the process of testing and adjusting the amplifi er. In each of the instruction manuals, special step-up transformers (also designed by Menno) to Menno van der Veen provides suitable explanations of the boost the weak MC signal by a factor of 10 before it goes design and design philosophy of the amplifi er. In the case to the input of the phono stage. of the preamplifi er, there is also an extensive discussion of how to use the input transformers with a moving-coil (MC) The power supply is built entirely using semiconductor cartridge. There are also various suggestions for modifi ca- devices and has a switch-on delay to ensure that the fi l- tions to the preamplifi er and the power amplifi er. ament voltage first builds up slowly over an interval of 15 seconds. After this, the high voltage is switched on and reaches it maximum value after around 30 seconds. The MCML05 preamplifi er design power supply board also hosts a headphone amplifi er built When developing the concept for the preamplifi er, Menno around a TL072 dual opamp. van der Veen was clearly more interested in sound quality Figure 2 shows the interior view of a fully assembled than technical perfection (i.e. minimal distortion). The sig- preamplifi er. nal path of the MCML05 is very simple and consists of a volume control and a balance control (both from Alps) followed by a buffer stage consisting of two triodes in a sort of UL40S2P power amplifi er design SRPP confi guration. Clearly a minimalist design, intended to In the preamplifi er, the circuitry is spread over fi ve PCBs, have minimum effect on the signal passing through. but in the power amplifi er it is all located on a single, rela- This preamplifi er is perfect for vinyl enthusiasts, since the tively large circuit board. The mechanical layout is tradi- MCML05 includes a two-stage MD preamplifi er with a pas- tional, with the valves and transformers fi tted on top of the sive RIAA compensation network (see Figure 1). To allow it enclosure (see Figure 3). For safety, they are covered by to be used with moving-coil (MC) cartridges, there are two a protective hood.

R22 R23 V-2 1k 1k V-1 1W 47 uF 100nF 47 uF 100nF 250V 200V 250V 200V C22 C23 C24 C25

B2 C13 C14 B3 C21 R13 1k2 ECC82 220 Fu 100nF C15 ECC81 R19 1k2 1uF 25 V 100V 200V

MD input 220 nF 2 R16* * MD OUTPUT R1 200V R17 470E 180k 0 E C16

12 nF C17 C18 100V C11 C12 C10* C19 C20 R21 Figure 2. R14 1k2 1M R18 27k R11* 1k2 47k 3,9 nF R15 R20 220k 220 Fu 100nF 220 pF 220 Fu 100nF Schematic diagram of the 25 V 100V 25 V 100V phono preamp. The RIAA R11 , C10 , R16 , R17 : see manual C.opyright 2004: Ir. bureau Vanderveen B.V compensation network is entirely passive.

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UK0910_32_35_081035-UK Buizenver33 33 10-09-2009 11:35:16 INFO & MARKET DIY VALVE AMPLIFIERS

Measured results Despite the fact that sound quality ultimately plays a greater role than technical specifi cations in the concept of these amplifi ers, as engineers we could not resist the desire to connect them to our Audio Precision System II analyser and have a look at the fi gures. Here we describe some of the results, with comments. The distortion of the preamplifi er and the power amplifi er is not especially low, but you can hardly expect low distortion from a valve amplifi er without negative feedback. Figure 6 shows the distortion spectrum of the power amplifi er at an output level of 1 watt into an 8 Ω load. Here the THD plus Figure 3. noise is approximately 0.4%. This is an acceptable value The UL40S2P power for an amplifi er design of this sort without negative feed- amplifi er with its protective cover removed. back. Some mains hum from the power rail can be seen at the bottom end. With our unit, the maximum output power was 23 W per channel into 4 Ω, with a distortion level of 3%. However, in this connection we should note that the Just like the preamplifi er, the power amplifi er has been kept mains voltage in the lab of our castle is on the low side, so strictly minimalist and does not employ any overall negative the fi gure will probably be higher in most home settings. feedback (see Figure 4). The circuit consists of a phase The bandwidth of the power amplifi er is decently large splitter built around a 6922 and a balanced output stage at around 85 kHz, with the lower 3-dB point well below with a pair of EL34s (6CA7s), which are connected to a 10 Hz. All of these results were measured in the ultralinear special toroidal Vanderveen output transformer. The power confi guration. transformer is also a toroidal type. The damping factor of the power amplifi er is only 5 (with The amplifi er can be wired in various confi gurations (triode, an 8-Ω load), which is fairly low. This is primarily due to ultralinear and pentode), which gives enthusiasts extensive the designer’s resolution not to use overall negative feed- opportunities for experimentation. back in the amplifi er. Although this is a noble aim that can The UL40S2P delivers approximately 30 W per channel in certainly benefi t the sound quality of the amplifi er, it can the pentode or ultralinear confi guration The output power also create diffi culties when driving loudspeakers because in the triode confi guration is half this value. they generally have very complex impedance characteris- The power amplifi er has a standby switch so the high volt- tics. In combination with the output transformer, the speaker age can be switched off while leaving the fi lament voltage impedance yields a curve such as that shown in Figure 7. on. This dramatically reduces the aging of the output valves In practice, this means that the frequency response of the and allows the amplifi er to be used immediately at any time speaker is affected by the impedance curve, which can without a long warm-up interval. lead to deviations of up to several decibels. The resulting sound image is entirely different from that of an amplifi er In addition to the various output stage confi gurations, with with a higher damping factor, but this ultimately has noth- this amplifi er you can experiment with other types of driver ing to do with ‘valve sound’. Consequently, it is advisable valves and output valves. There is an optional output trans- to use the UL40S2P with loudspeaker systems that have a former with windings made from silver wire, although this fl at impedance curve or loudspeakers equipped with imped- represents a considerable investment in comparison with ance correction networks. the overall price of the kit. The rated sensitivity of the preamplifi er is 220 mV for a 1- V output signal, which is the signal level necessary to drive the power amplifi er to its maximum output power. The distortion is 0.3% with an output level of 1 V and decreases to approximately 0.1% with the volume control set to an overall gain of 1. The accuracy of the phono stage is very precise. The deviation from the standard RIAA characteristic is less than 0.2 dB between 50 Hz and 10 kHz, and less than 0.7 dB over the range of 20 Hz to 20 kHz. The signal to noise ratio and hum from the line inputs of the preamplifi er are both at a nice level of –76 dB (lin.). The sensitivity of the MD input is 7.6 mV, while the sensitivity of the MC input is 720 µV (both for 1 V out). Especially for the MC input, it is best to choose an MC cartridge with a relatively high output voltage for use with the MCML05.

Listening results Figure 4. After a few days of playing with the various options, we Bottom view of the power listened to the combination of the two ampliﬁ ers along with ampliﬁ er. All of the a Sony SADC player and a set of B&W 803 speakers. The circuitry, including the spaciousness of the reproduced music was striking with this valve sockets, is located on combination. The overall sound image proved to be a good a single PCB. deal further away from the listener, being located more

34 elektor - 10/2009

UK0910_32_35_081035-UK Buizenver34 34 10-09-2009 11:35:19 V1 EL34

R4 47k INPUTS (5X) 470nF 2 630V R10 S0 C 1k 10k ALPS R1 R2 a 10k B1 B2 2k7 2k2 AMPLIMO

REC. OUT 50k VDV6040P 4pF 12 13 PB R7 R9 R R 1000 1 180k * 220k 10 150 16V 100V C L (R) CHANNEL R3 680 ' R11 C1 C1 180 VL V0

1000 C4 40V R5 R8 680 150k E R14 R15 R17 6N1P 220k 10 150 T1 S R18 b P Figure 5. 100k 10 B1 B3 Schematic diagram of R16 the power ampliﬁ er,

470nF 1k C3 630V which can be wired in R6 cnopyright Ir. buro Vandervee various conﬁ gurations febr. 1993 47k (triode, ultralinear or EL34 081035 - 12 V1 pentode) by making small modiﬁ cations.

behind the loudspeakers than with the transistor amplifi er +0 we normally use in this system. Remarkably, we found that -10 the treble reproduction had slightly more presence than -20 with the transistor amplifi er, which is the opposite of what -30 you would expect. This resulted in increased detailing in -40 the reproduction. -50 -60 d The bass reproduction remained controlled under all condi- B -70 r tions; apparently the low damping factor does not have any -80 A adverse effect in this regard. However, this can vary from -90 one loudspeaker to the next. At higher volume levels, the -100 transistor amplifi er delivered distinctly more pressure in the -110 bass region, but this difference may be due to the modest -120 output level of the Amplimo power amplifi er. -130 All in all, we can say that the MCML05 and UL40S2P form -140 Figure 6. -150 a combination that can give audio enthusiasts a whole lot 20 50 100 200 500 1k 2k 5k 10k 20k 50k 100k FFT distortion analysis at Hz 081035 - 13 of listening pleasure, in part due to the many confi guration 1 kHz with 1 W into 8 Ω. and tuning options.

Vanderveen MCML05 preamplifi er: Conclusion kit price € 1245 (approx. £ 1080). The design and construction of both of these amplifi ers are well conceived. We can recommend these kits without res- Vanderveen UL40S2P power amplifi er: ervation to serious audio enthusiasts who want to try a standard kit price € 1295 (approx. £ 1120). valve system. Menno van der Veen has devoted a lot of time not only to the technical development of these amplifi ers, but also to optimising their sound quality. This can be seen in the choice of components, the layouts of the circuit +15 boards, and the quality of the connecting cables. The kits +12

even include silver solder for the solder joints. +9 +6 Neither of the kits can be regarded as inexpensive, but this +3 will certainly not form a hindrance for serious audio enthu- +0 -3 d siasts – especially when you consider that a ready-made B -6 r valve combo (preamplifi er and fi nal amplifi er) of this quality -9 A costs at least twice as much. -12 (081035-I) -15 Figure 7. -18

-21 Frequency response of the

-24 power ampliﬁ er. The upper Additional information: -27 curve shows the frequency -30 response with the ampliﬁ er 10 20 50 100 200 500 1k 2k 5k 10k 20k 50k 100k www.amplimo.nl Hz 081035 - 14 connected to a real www.mennovanderveen.nl loudspeaker.

10/2009 - elektor 35

UK0910_32_35_081035-UK Buizenver35 35 10-09-2009 11:35:25 PROJECTS MICROCONTROLLERS Car Tilt Alarm Protect your alloy wheels By Mickael Bulet (France)

This project is aimed at all those who have fine alloy wheels on their car and are worried about finding it propped up on bricks. Whether you already have a car alarm or not, this project could be used in conjunction with that, or stand alone. This alarm has been designed to be adapted to your needs and is easy to use thanks to the built-in installation aid.

The car alarm described here detects together via the diodes changes in the tilt angle of the vehi- (D2–D9 and D12–D15) cle in which the alarm is installed. It and require only four is set off when the change in the angle inputs. They are multi- exceeds a threshold (adjustable) for too plexed using three outputs from long (5 seconds). Short of cutting the port C. power to it, the only way to stop the alarm is to put the car back to its initial Four other outputs from port C are used used for dis- angle. The change in angle to which to drive three LEDs and a relay, buff- playing parameters the alarm is sensitive can be adjusted ered by a ULN2803, powered from 12 V with the help of an EasyPIC4 from 0 to 25°. to avoid excessive loading on the 5 V board from Mikroelektronika [2]. rail. The ULN2803 works out cheaper and above all less cumbersome than The power for the alarm is taken from Hardware a solution using transistors. The LED the vehicle, either from a permanent + The alarm is built around a PIC16F877 driven by RC3 shows if the system is rail, or directly from the battery. Don’t microcontroller (Figure 1). A dual-axis armed, the other two LEDs are used by forget to include an in-line fuse to pro- accelerometer connected to the con- the installation aid for leveling. tect the circuit. A quick-blow 100 mA troller’s port-A analog input is used as fuse will be enough if the circuit a tilt angle detector. In a static situa- Pin PC7 is used as an input for arming doesn’t have its own siren, but if used tion, it will output a DC voltage on the the system. This input is opto-isolated as a stand-alone alarm, you’ll need to X and Y axes depending on the angle it and fi ltered by R7 and C7; R5 limits the allow for the extra current drawn by is at with respect to the horizontal. The current in the opto-isolator’s LED. In the siren. accelerometer is an ADXL322 [1] from this way, a permanent +12 V available The 5 V supply is perfectly standard, Analog Devices, pre-fi tted to a small in the passenger compartment can be with D1 protecting the regulator from board, as the device is tricky to solder used, and only one wire to the alarm is reverse current when the system is by hand. needed, instead of two wires if the 5 V shut down completely. rail were used, with a greater risk of The alarm is confi gured using jumpers interference too. on three 2×4-contact pinheaders and Software four switches connected to the con- The other PIC ports are not used. While The fi rmware was written in mikroBa- troller’s port B. The headers are OR-ed developing the program, port D was sic [2] and is small enough to be com-

In some countries, this type of sound nuisance is punishable under Disturbing the peace laws addressing disturbances of the peace at night. In a few coun- Alarms have a tendency to go off at random both day and night, with tries, car alarms with sirens are even prohibited. Consult your local no thought for the neighbours. legislation.

36 elektor - 10/2009

UK0910_36_41_080064-UK Alarme d'36 36 10-09-2009 11:36:07 Technical Speciﬁ cations

• trigger angle: 0–25° • operating time adjustable 0–165 s; • two activation modes: intermittent @ 0.5 Hz or continuous • built-in installation aid.

JP1 JP2 JP3 JP4 JP5 JP6 JP7 JP8 JP9 JP10 JP11 JP12 VDD +12V D2 D3 D4 D5 D6 D7 D8 D9 D12 D13 D14 D15

C6 D11 D10 K1 X=0 Y=0 NO +12V 100n NC R2 R3 RE1 COM

VDD 11 32

IC3 10 1k 1k K3

D2...D9, D12...D15 = 1N4148 VDD VDD 1 15 1 18 MCLR/VPP RC0/T1OSO/T1CKI IN1 OUT1 16 2 COM D 17 RC1/T1OSI/CCP2 IN2 OUT2 X 2 17 3 16 RA0/AN0 RC2/CCP1 IN3 OUT3 R4 Y 3 18 4 15 RA1/AN1 RC3/SCK/SCL IN4 OUT4 1k K2 4 23 5 14 RA2/AN2/VREF- RC4/SDI/SDA IN5 OUT5 LED 5 24 6 13 RA3/AN3/VREF+ RC5/SDO IN6 OUT6 ARM 6 25 7 12 RA4/T0CKI RC6/TX/CK IN7 OUT7 GND 7 26 8 11 RA5/AN4/SS RC7/RX/DT IN8 OUT8

IC1 GND 8 RE0/RD/AN5 9 K5 9 RE1/WR/AN6 ULN2803A VDD GND 10 R5 GND RE2/CS/AN7 R6 +12V

PIC16F877-20/P 4k7 33 19 330R RB0/INT RD0/PSP0 VDD 34 20 RB1 RD1/PSP1 +12V 35 21 RB2 RD2/PSP2 5 6 1 K6 S1 36 22 R7 RB3/PGM RD3/PSP3 C7 +12V 1 8 37 27 tol * 10 RB4 RD4/PSP4 IC4 +12V 2 7 38 28 10k pulse/cont RB5 RD5/PSP5 4N25 +12V 3 6 39 29 100n cal. RB6/PGC RD6/PSP6 4 2 4 5 40 30 RB7/PGD RD7/PSP7

VSS OSC1/CLKIN OSC2/CLKOUT VSS D1

12 13 14 31 1N4001 IC2

9 8 7 6 5 4 3 2 X1 R1 7805 1 2 VDD 8x 4k7 +12V C1 C2 C3 C4 8MHz C5 3 1 470u 100u 100n 15p 15p 25V 25V 080064 - 11

Figure 1. Alarm circuit diagram.

10/2009 - elektor 37

UK0910_36_41_080064-UK Alarme d'37 37 10-09-2009 11:36:09 PROJECTS MICROCONTROLLERS

piled using the demo version of the the alarm proper. The choice between High. Figure 2 shows the ﬂ ow diagram compiler. the two programs is made using switch of the program. The software consists of two sub-pro- S1 3-6 on the RB6 line. The installation In normal mode (alarm), the settings grams: the vehicle installation aid and aid is enabled when RB6 sees a logic on the headers are read at the start of the program. To read a header, the corresponding output of port C must be taken High and the hex-coded data is Normal mode False Installation aid input to port B. The other port C out- ? puts connected to the other headers True must remain low. By way of an exam- Read tilt angle ple, here’s how the alarm triggering Read tolerance angle time is read:

X = 0 False Read ON time ? Reading the units - RC0 to 1, RC1 and RC2 to 0 True - delay of a few milliseconds for the LED X lights values to stabilize System activated False - data read at port B ? - four MSBs suppressed True - data obtained stored in memory Y = 0 False ? 10-second delay Reading the tens True - RC1 to 1, RC0 and RC2 to 0 - delay Read tilt angle LED Y lights and store as reference - port B read - four MSBs suppressed

Calculate Trigger time = 10 × tens + units lower and upper angle limit observing tolerance This process makes it possible to read four headers using one 8-bit port: the Read current angle four MSBs as an Enable output for the headers and the four LSBs for reading the data. Masking via an AND will Tolerance False suppress the four MSBs from the read exceeded data. ? True After reading the operating parame- 5-second delay ters, the program waits in a loop for RC7 to be taken to 1 before going into ‘armed’ mode. Once armed, the ‘real’ Read current angle surveillance will only start after a 10- second delay — the time to get out of the vehicle and allow it to stabilize. Tolerance False exceeded The current angular position of the ? vehicle is then stored in memory and True the alarm trigger values are calculated. In this way, you can leave the vehicle Alarm in False at any angle, and when the alarm is continuous mode ? armed, the current value will be taken True as the reference for the calculations. Actuate relay 0.5 second The trigger thresholds (lower and Actuate relay upper) depend on jumpers JP9–JP12 for angles from 0 to 15° and switch Deactuate relay 0.5 second S1 1-8 which lets you add another 10°. ON time False Hence we get an adjustment range elapsed from 0 to 25°. ? True ON time False Now the program goes into a loop, from elapsed which the only way out is when one ? Deactuate relay of the two thresholds is exceeded, or True the system is put into standby mode. If

080064 -12 one of the two thresholds is exceeded for some reason, the software will wait 5 seconds before conﬁ rming the Figure 2. Software block diagram. threshold is still being exceeded. This

38 elektor - 10/2009

UK0910_36_41_080064-UK Alarme d'38 38 10-09-2009 11:36:12 precaution will avoid unwanted trig- Table 1. gering caused by a slight impact, a How to set the jumpers to obtain specifi c values. gust of wind, or a passing truck. Even in Formula 1, fi ve seconds is a bit short JP4, JP8, JP12 JP3, JP7, JP11 JP2, JP6, JP10 JP1, JP5, JP9 Value for lifting up the car, removing the four ––––0 wheels, and putting the car back into –––fi tted 1 its original position! ––fi tted – 2 If the second tilt check confi rms that the angle of the vehicle is out of limits, ––fi tted fi tted 3 the alarm goes off. –fi tted – – 4 There are two options for operating the –fi tted – fi tted 5 output relay (S1 2-7): continuous operation throughout the time programmed –fi tted fi tted – 6 by the jumpers, or intermittent oper- –fi tted fi tted fi tted 7 ation (0.5 Hz) for the programmed fi tted – – – 8 time. fi tted – – fi tted 9 Once an alarm cycle has been completed, the program goes back to the fi tted – fi tted – 10 fi rst tilt checking loop. If in the mean- fi tted – fi tted fi tted 11 time the car has returned to its original fi tted fi tted – – 12 position, the alarm will stop. Of course, the system can be put into fi tted fi tted – fi tted 13 standby at any time, even while the fi tted fi tted fi tted – 14 relay is operating. fi tted fi tted fi tted fi tted 15

Construction Table 2. Functions of the S1 switches. Switch Open Closed You can build this project in your usual S1 1-8 threshold +0° threshold +10° manner. Note that the accelerometer will S1 2-7 intermittent alarm continuous alarm need to be ﬁ xed in such a way that it S1 3-6 normal mode installation aid mode doesn’t vibrate while the car is mov- S1 4-5 – – ing. To achieve this, one pad has been

10/2009 - elektor 39

UK0910_36_41_080064-UK Alarme d'39 39 10-09-2009 11:36:12 PROJECTS MICROCONTROLLERS

Adjustments Setting the alarm time The alarm time is set by JP1–JP4 (‘units’ 0–15) and JP5–JP8 (‘tens’ Note that changes in the jumper or switch positions must be validated 0–15) from 0 to 165 s, i.e. 2 min 45 s, which seems to be more than by resetting the circuit, which means cutting the power for a few sec- enough, given that the alert is continued (after around 5 s) if the ve- onds, as there is no reset button. See Tables 1 and 2 for how to posi- hicle fails to return to its original position. When using this circuit in tion the jumpers and switches. conjunction with an existing alarm, select 1 s maximum. This is more than enough for it to be detected by a alarm. Setting the trigger threshold Setting the relay operating mode The trigger threshold is set by jumpers JP9–JP12 for angles from 0 Use S1 2-7 to select the relay operating mode: continuous or intermit- to 15° and switch S1 1-8 which lets you add another 10°. Hence the tent. This choice will be determined by the type of wiring and the siren threshold can be set between 0 and 25°, though it’s better not to go you are planning to use. For a siren with a modulated output, choose below 2°, as possible drifts in the accelerometer or PIC’s analog/digi- continuous mode. Use continuous mode when using this circuit in tal convertor voltages could result in unwanted triggering. conjunction with an existing alarm.

provided on one end of the accelerom- against vibration, which might break off externally, to save having a master eter (opposite the row of contacts) for the soldered connections and cause switch, and to protect against possible soldering a loop the end of a piece of false contacts. shorts) and a ground connection made stiff wire. This can then be connected Bolt the regulator IC2 onto the PCB. to the chassis or a grounding point on to the accelerometer board. the car. The two large ﬁ lter capacitors (C1 and C2) should be soldered as close as pos- Installation All wires should be at least AWG17 sible to the PCB, and if necessary held The alarm must be powered from a per- c.s.a. and should be run inside plas- in place with a big blob of hot-melt manent +12 V supply via an in-line car tic sleeving (you may be able to use glue. All this is intended to protect fuse (so that the device can be turned domestic 6.25 inch diameter flexi-

Connections A to boot/trunk contact This alarm was designed to be used either in conjunction with an existing system that already monitors the opening of the bonnet, the boot (trunk), breaking into the passenger compartment, or engine starting, or on its own, with the addition of a simply 12 V siren. from alarm or independent switch Wiring as an auxiliary to an existing alarm The unit will be armed either by a separate switch concealed in the passenger compartment, or by the main alarm itself. To achieve this, most alarms have a contact that makes when they are armed, for connecting a relay to cut the power to the fuel pump (immobilizer!) ground Our circuit’s input draws very little current, just for the opto-isolator LED. So it can be connected directly to the coil of this relay (the + side, of course!)

In order to set off the original alarm from our circuit, you’ll need to permanent +V connect the common of the unit’s relay to ground and the make (or from battery N/O) contact to a boot or bonnet microswitch. In this way, our circuit will simulate the opening of one or other of these elements by B grounding the monitoring contact.

Siren Standalone wiring Here, the alarm will have to be armed using a concealed switch. For the alarm signal, we’ll use a 12 V siren hidden within the engine com- activation partment. The +12 V will go to the relay common contact and the switch make (N/O) contact will be connected to the siren, then the siren to ground (there are enough ways on the connecting terminal block to make these bridges internally). We strongly recommend you do not use the car horn as the warning system by simply connecting it in parallel. If it is driven by a transis- ground tor in the car’s electronics unit, this will be destroyed at the ﬁ rst alarm. What’s more, any intruder won’t necessarily be expecting there to be a second siren.

permanent +V from battery 080064 - 14

40 elektor - 10/2009

UK0910_36_41_080064-UK Alarme d'40 40 10-09-2009 11:36:16 ble plastic conduit). Never allow any wire to be in contact with a metal X X metal bracket part (bodywork, engine components, etc.), in case one day you end up with a short (or even a ﬁ re!) caused by the insulation wearing through because of the vibration when the car is being screw to secure driven. bracket to vehicle Y Y The alarm can be ﬁ tted anywhere, as long as it can be fixed in a horizontal position (see Figure 3). Provide a warning LED on the dash if you want to see if the circuit is armed or not. To adjust the level, proceed as follows: screw to secure X bracket to case • Park the vehicle in a spot where it is level; Y • Cut the power to the alarm (remove the fuse from its holder); 080064 - 13 • Set switch S1 3-6 (installation aid) to ON; Figure 3. One option for mechanically mounting the alarm horizontally.

• Power the circuit back up again (reﬁ t the fuse); horizontal installation offers the best • Apply power to the alarm again, and performance in all situations; it’s ready for use! • Tilt the alarm very gently in both (080064-I) axes until the X and Y LEDs both • Tighten the fixing screws firmly, come on, indicating that it is hori- using shakeproof washers, Nylock ® Internet Links zontal. This adjustment is very sen- nuts, or thread locking compound to sitive and can be quite tricky to get avoid loosening over time caused by [1] www.analog.com/en/mems-and-sensors/ just right. It doesn’t matter if you vibration. imems-accelerometers/adxl322/products/ can’t manage it, as the alarm will product.html still work in relative mode, i.e. it will • Cut the power; [2] www.mikroe.com be triggered according to the cur- [3] www.elektor-usa.com/080064 rent angle of the car. But properly • Set S1 3-6 back to OFF;

S1 = 4-way DIP switch block 2-axis accelerometer module with ADXL322 COMPONENT LIST RE1 = relay, 12V coil, miniature, 2RT (Lextronic France # ADXL322) K1,K2,K5,K6 = 3-way SIL pinheader, lead Fuse and in-line fuseholder for vehicles Resistors pitch 2.54mm (0.1”) Standoffs, screws, case, etc. R1 = SIL array 8x 4.7kΩ Ω Support for on/off LED, color and diameter R2,R3,R4 = 1k to personal requirements R5 = 330Ω R6 = 4.7kΩ R7 = 10kΩ

Capacitors C1 = 470µF 25V axial electrolytic C2 = 100µF 25V axial electrolytic C3, C6 = 100nF C4, C5 = 15pF ceramic

Semiconductors IC1 = PIC16F877-20/P, programmed IC2 = 7805 IC3 = ULN2803A IC4 = 4N25 or equivalent D1 = 1N4001 D2–D9, D12–D15 = 1N4148 D10, D11 = LED, 3mm

Miscellaneous X1 = 8MHz quartz crystal, low proﬁ le JP1–JP4, JP5–JP8, JP9–JP12 : 8-way (2x4) DIL pinheader with jumpers

10/2009 - elektor 41

UK0910_36_41_080064-UK Alarme d'41 41 10-09-2009 11:36:16 Don’t just test it...... Analyse it! Special Offer prices for limited period or while stocks last! electronic design ltd The New Atlas ESR Plus, Model ESR70

This new model of the famousAtlas ESR offers all the great features of the ESR60 but with extended measurement range and audible alerts. £89.00 inc VAT Atlas ESR Plus Take out a free subscription to (£77.39+VAT) This is the ! Capacitance from 1uF to 22,000uF. ESR from 0.01 ohms to 40 ohms. E-weekly now Great for ESR and low resistance measurements (short tracing etc). Automatic controlled discharge. Do you want to stay up to date with electronics and Audible Alerts (for good ESR, poor computer technology? Always looking for useful hints, tips ESR, open circuit and more). NEW MODEL Gold plated croc clips. and interesting offers? Subscribe now to E-weekly, the free Elektor Newsletter. Atlas SCR - Model SCR100 Atlas IT - Model UTP05 Atlas ESR - Model ESR60 Your benefits: Connect Triacs or Thyristors any way round. Special Offer! Special Offer! The latest news on electronics in your own mailbox Auto part+pinout identification Identify network cabling type. Check gate 100uA to 100mA. Capacitance and ESR! each Friday Identify many fault types. Measures gate voltage drop. Capacitance 1uF to 22,000uF Tests sockets and cables. Free access to the News Archive on the Elektor website Regulated load test conditions ESR 0.01ohms to 20 ohms Complete with all this: Gold plated croc clips You’re authorized to post replies and new topics in our forum £75.00 inc VAT (£65.21+VAT)

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The famous Peak Atlas! Passive component analyser. Money Saving Pack: Save £20 Identify inductors, capacitors Now with premium probes. Includes the Atlas LCR, and resistors. Auto frequency Connect any way round to Atlas DCA and a premium selection. Removable probes. identify semiconductor type, padded carry case. pinout and lots of parameters. with extra spare battery. Transistors Darlingtons er! 1uH - 10H MOSFETs

Diodes Best 1pF - 10,000uF LEDs Sell 1Ohm-2M and more... £53.83 inc VAT £77.31 inc VAT £124.99 inc VAT (£46.81+VAT) (£67.23+VAT) (£108.69+VAT) Peak Electronic Design Ltd, West Road House, West Road, UK: Please add £2.00 p&p per order. Buxton, Derbyshire, SK17 6HF. Prices include UK VAT. Register today on www.elektor.com/newsletter tel. 01298 70012 www.peakelec.co.uk [email protected] See website for overseas prices.

Characteristics • Two 500 W DC drive motors ElektorWheelie • Two 12 V lead-acid AGM batteries, 9 Ah • Two sixteen-inch wheels with pneumatic tyres • H-bridge PWM motor control up to 25 A Elektor’s DIY self-balancing vehicle • Automatic power off on dismount • Maximum speed approx. 11 mph (18 km/h) Demo video on • Range approximately 5 miles (8 km) Everyone agrees; the internal combustion • Weight approximately 35 kg engine is coming to the end of its life cycle. .com/wheelie www.elektor The kit comprises two 500-watt DC drive However you don’t need to go to the expense motors, two 12-V lead-acid AGM batteries, of a Prius or Tesla to experience the future of two 16-inch ABS wheels, casing, control lever transportation devices. If you would prefer something and assembled and tested control board with more personal (and don’t mind turning a few heads) sensor board ﬁ tted on top. why not build the astonishing ElektorWheelie? Art.# 090248-71 • £1380.00 • € 1599.00 • US $2275.00*

First take two electric motors, two rechargeable batteries * Incl. VAT, excl. shipping costs. and two sensors, now add two microcontrollers and the ElektorWheelie is ready to transport you Elektor in style to your destination. Regus Brentford 1000 Great West Road Brentford TW8 9HH United Kingdom Tel. +44 20 8261 4509

Further information and ordering at www.elektor.com/wheelie

42 elektor - 10/2009

0910_elektor_adv_UK.indd 42 10-09-2009 11:14:34 Portable solar battery chargers

By Thijs Beckers (Elektor Netherlands Editorial) For the solar panel test, which was published in the July 2009 issue, we also asked for a number of smaller solar panels. These small panels are invariably intended to be used as battery chargers when on the road. However, at that time they had to give way to the large number of more interesting and bigger panels. We nevertheless were still keen to take a closer look at these mini panels. Elektor Lab worker designer Ton Giesberts carried out an evaluation of these panels. The charging current was measured using the supplied batteries. When no batteries were supplied we used our own. Here are the results!

The Ansmann Energy Solar Charger does not supply any voltage unless the batteries are connected. The charging current can easily reach 92 mA, charging two cells at the same time. This does require suffi cient sunlight of course (which is also true for the other chargers). The charger is fi tted with an indicator LED, a clip which functions both as a belt clip as well as a stand for fi xed mounting and a USB connection for charging devices using a USB cable. The latter is also possible when there is no light on the panel. With a set of fully charged batteries the charger can therefore also be used for charging a USB device that is suitable for this. Various adaptor plugs for mobile phones and USB are supplied. Two 1300 mAh NiMH-batteries are also supplied, which can be charged simultaneously.

The (unbranded) ES904 supplies and open circuit voltage of 6.1 V. The measured charging current amounts to about 93 mA. The charger is suitable for three AA batteries. Also supplied are an adaptor cable with a multiplug, two clips for attaching to a belt and a stand for optimal positioning when placed in a ﬁ xed location. The battery holder is separate from the charger.

The PowerFilm AA Foldable Solar Charger does not supply any voltage when no batteries are connected. The charging current amounts to a respectable 440 mA, which can be used to charge two or four AA cells. Two indicator LEDs are built in. Unfortunately there are no adapter plugs and no USB connection option.

Compared to the other panels the SolarDuo from SolarFocus was somewhat less sensitive to its orientation towards the sun. The measured charging current was 293 mA (420 mA according to the speciﬁ cations). The charger does not supply any voltage when no batteries are connected; it is provided with an indicator LED and a USB connection and comes with a variety of adaptor plugs and a cable. It is suitable for two AA cells, which are also supplied in the form of two 2300 mAh NiMH batteries.

The SolarFocus SolarUno supplied a charging current of only 160 mA (the speciﬁ cation is 420 mA). This charger does not supply an output voltage either when there are no batteries in the holder and therefore cannot be used as a standalone power supply. The charger is ﬁ tted with an indicator LED, a belt clip and a USB connection. The latter can also charge USB devices from the batteries without (sun) light. The charger can charge one or two AAA cells simultaneously. Two 700 mAh AAA NiMH batteries are supplied. Unfortunately there are no adaptor cable or plugs to be found anywhere in the packaging.

The tests were carried out on a very sunny day, outdoors, at Elektor House in Limbricht, the Netherlands. It is of course very conceivable that the chargers will perform differently when you take them on your sun-seeking holiday or on a trip to the Antarctic. The big- gest difference however is still the total surface area of the solar cells. In this respect: the bigger, the better. (090605-I) E-LABS INSIDE

elektor - 10/2009 43

UK0910_43_090605-UK Labcenter-so43 43 10-09-2009 11:38:16 “Noise is not cool”

By Ton Giesberts (Elektor Labs)

For the last few years we haven’t worried too much about noise in need to compromise on any part of the circuit — at most the total audio any more. In the past, and we mean the pre-CD era, the noise cost will be more of a determinant of the fi nal design. An example from a cassette player, record player or an FM radio was something of the latter is the MC amplifi er from March 1992. Here a dual PNP we had to learn to live with. You had HiFi and all was well. Now that transistor was used for the input stage (lower LF noise than a NPN nearly everything is digital, even the picture and sound on the TV, version) to obtain as low an input noise as was possible. We now it appears that noise for most audio designs is no longer a problem. use an ordinary opamp for that (for example the TL071). To avoid Is noise out of fashion? any other compromises, the small capacitors that were used for the correction network were not standard polyester devices but In other areas of electronics noise will continue to be a design con- expensive ‘styrofl ex’ types with polystyrene as the dielectric. For sideration. Take the accurate conversion of a sensor signal which the larger values ‘MKP’ types with a polypropylene dielectric were still requires analogue amplifi cation, conversion and fi ltering, be- used. The larger value polystyrene capacitors were also made by fore it can be digitised. Siemens, but production has been stopped since. With microphone signals, hum, noise and other interference signals are the criteria that will receive the most attention in studi- Or take the symmetrical microphone amplifi er from November os or live performances. Once the recording is in a digital format 1997. For optimal quality the phantom voltage has to be free of the greatest problems are overcome. The problem of noise is then ripple and the amplifi er has to have low noise. At the heart of the moved to sample frequency, the number of bits, digital operations circuit was a symmetrical audio amplifi er in an 8-pin DIP package and mixing. from Analog Devices (there are now pin-compatible successors With the arrival of the CD and the digital age the problems have such as the SSM2019 and INA217). With 1 nV/√Hz input noise (at become more complex and are harder to understand. For exam- 1000×) this is diffi cult to equal with a discrete design taking up ple, take the perennial discussion as to whether an LP sounds more the same amount of space. In the meantime even better versions faithful than a CD. The specifi cations of the noise in an analogue have appeared. In the datasheet for the SSM2019 you can fi nd a system are more informative to most people than the specifi ca- nice application where the noise of the microphone amplifi er is cal- tions of a digital linear phase fi lter. The noise of the latter is gener- culated based on the individual noise sources: source impedance ally so low that most people will have diffi culty comprehending it. of the microphone, current noise and voltage noise of the inputs. The dynamic range of most modern codecs is greater than that of The infl uence of the current noise is frequently overlooked, be- human hearing. Reproducing the sound pressure of a Saturn rocket cause it is not often found in the datasheets. Because the individual at take-off (about 195 dB) is not required in our living room. noise sources are not correlated they cannot be simply summed together but you need to take the square root of the sum of the You would think that the boundary of what is necessary and useful squares. If you would like to know more about different types of has now been reached. In Elektor magazine, audio circuits have ac- noise we can recommend the article by Hameg at www.hameg. quired a different position in recent years. The world of electronics com: “What is noise?”. these days revolves around microprocessors, FPGAs and so forth. With the exception of the revival of the LP and of valve amplifi ers The real work there seems to be little merit to be had from the familiar discrete From the well-known formula for noise √(4kTBR) — Boltzmann’s stereo power- and pre-amplifi ers from the good old days. Surround constant, temperature in Kelvin, bandwidth and the resistance — sound systems cost almost nothing nowadays and have more bells the noise of a resistor can be calculated. You can use this, for ex- and whistles than you could ever need. In addition, most people ample, to determine how low the noise of an opamp needs to be so are happy listening through cheap headphones (at levels that are that the effect on the signal processing is minimal compared to the much too loud) to the heavily compromised MP3 fi les. impedance of the network around the opamp. And the other way But nevertheless there appears to be a revival of the ordinary ster- around as well, of course. Once we have selected a certain applica- eo and so the story of noise reappears. tion for an opamp then we can calculate the equivalent resistance of, for example, the feedback network so that it contributes to the Noise of the oldies.. noise as little as possible. The noise voltage is normally expressed The vintage Elektor projects where a special effort was made to at a bandwidth of 1 Hz. At T = 290 K noise is then equal to control the noise were mainly high end MD and MC amplifi ers for record players. We also published discrete radio receivers where √(4×1.38×10-23×290×1×R) = 127×10-12×√R (per √Hz). the noise characteristics are very important. But here too there are changes happening. Recently we published a small FM receiver So a resistance of 10 kΩ theoretically produces a noise voltage (Mini FM receiver, January 2009) where the entire receiver is inte- of nearly 13 nV/√Hz. If we take the entire audio bandwidth then grated into a single IC. With RF designs it is sometimes diffi cult to the total noise voltage becomes 1.8 µV! Depending on the output justify a discrete design, certainly since everything can be made current capability of an opamp and the signal level, the resistor

E-LABS INSIDE so small now. The advantage of a discrete design is that there is no values in a design cannot be smaller than a certain value. Whether

44 elektor - 10/2009

UK0910_44_45_090560-UK Labcenter44 44 10-09-2009 11:39:05 The inﬂ uence of current noise is frequently forgotten and is often not even shown in the datasheet.

an expensive low-noise opamp 18VL C1 will make a difference is then C7 C12 47M C14 D1 ...D4 = 5V6 / 0W5 easily calculated. Other speci- 1000 100n R1 R5 100p M 25V C9 63V ﬁ cations can be more impor- 10k 3071 R3 C2 R7 120p tant, such as bandwidth, slew D1 12 IC1 S1a R11 6k81 1M 10k0 3 rate or distortion. We can also 20k0 D2 1 7 L RG1 quickly calculate the effect of C6 R10

7 6 2 R9 SSM2017 20k0

a resistor or network on the 100 1 4n7 8 IC2a D3 RG2 3 L signal-to-noise ratio of a cir- R4 R8 2 4 R12 R14 5 S1b C4 cuit: the noise of a resistor at 34 D4 6k81 10k0

10k R13

R2 R6 1k 221k a temperature of 290 K and a 1M C10 10k 3071 C3 bandwidth of 20 kHz is then C8 C13 C15 12 1M 6 18 nV×√R. 47M 100p 1000M 25V 100n 7 63V IC2b P1a If we wanted to design a micro- 5 48V 22V 18VL phone ampliﬁ er with a signal- R35 R36 10k

7 7 3 to-noise ratio of 100 dB (with S3 C5 100 100 IC2 = OP275 R15 C11 D5 D6 respect to 2 mV, B = 20 kHz), IC4 = OP275 100n R37 Re1 221k the total input noise would 1M 10k

have to be less than 20 nV. This C22 2x 1N4148 D13 Re1 = C35 C36 V23042-A2005-B101 corresponds to the noise of a 100n

resistor of 1.2 Ω. In practice 47M 47M 63V 63V 18VR 20 dB less of signal-to-noise C18 C24 C29 47M C31 ratio will be more realistic (re- D7 ...D10 = 5V6 / 0W5 1000 100n R18 R22 100p M 25V C26 sistance of 120 Ω). The source 63V 10k 3071 R20 C19 R24 impedance of the microphone 120p D7 12 IC3 is often the limiting factor. S2a R28 6k81 1M 10k0 3 20k0 (090560-I) D8 1 7 R RG1 C23 R27

7 6 2 R26 SSM2017 20k0

100 1 4n7 8 IC4a D9 RG2 3 R R21 R25 2 4 R29 R31 5 S2b C21 34 D10 6k81 10k0

10k R30

R19 R23 1k 221k 1M C27 10k 3071 C20 C25 C30 C32 45 1M 6 47M 100p 1000M 25V 100n 7 63V IC4b P1b 5 18VR 10k 6 R32 C28 D11 D12

1M 221k

2x 1N4148

Ton Giesberts studied Electrotechnical Engineering at Heerlen Poly- technic in the Netherlands and has worked in the Elektor Labs since 1987. As a designer and a technical editor Ton’s mainstay is the analogue project area. Ton’s help is also called for occasionally when there’s a niggling problem to solve with an RF circuit …

10/2009 - elektor 45

UK0910_44_45_090560-UK Labcenter45 45 10-09-2009 11:39:06 Review: PSoC kit with RF module

By Luc Lemmens (Elektor Labs) In addition there is the MultiFunction Expansion Card which — as the name suggests —– implements multiple functions. It contains This kit, made by Cypress, has been designed so that users can easily a CapSense slide controller (7 positions), a CapSense proximity become familiar with the fl exibility and ‘mixed signal’ capabilities sensor, a thermistor, a light sensor, a 3-colour LED and a miniature of their Programmable System-on-chip (PSoC) devices. On the ac- loudspeaker. This board does also have a connector with I2C inter- companying CD, in addition to face and unused I/O lines. There the development and program- are plenty of options for exper- ming software, are a suffi cient imenting with the various sen- number of ready-to-go exam- sors and actuators. ples so that you can quickly And fi nally, the development kit discover all the things that you contains two boards which are can do with these processors. intended as the battery power These contain programmable supplies for the last two boards analogue and digital blocks mentioned. that you can use to read sensors (such as thermistors, LDRs, This all invites you to get started etc.) and can drive actuators with experimenting right away, (such as LEDs, relays). In addi- but in practice it’s not that easy. tion there are the usual serial Firstly, the installation of the interfaces such as SPI and I2C. software, drivers and examples The PSoC designer integrat- is rather vague. Absolutely irri- ed development environment tating is the number of times (IDE) gives the user the option you have to click OK while you of developing both code-lev- have no other option, windows el (chip dependent) as well as which obscure other windows, graphical (chip independent) to put it briefl y: this could have applications. The Cypress 2.4 been done better. But this is not GHz CyFi technology offers the the end of the grief. If you think option of easily adding energy- that after the installation you effi cient, wireless connections can immediately start with the to embedded designs. supplied examples you’re mis- taken. The manual every now The kit contains everything and then skips essential steps, to get started right away. or indicates the wrong direc- OTo begin with, it contains a tory where certain fi les should programmer that can program be found. When starting the all the processors in the kit. programming software for the This also functions as a bridge fi rst time, the progress window between other boards in the shows only one line, so that es- kit and a PC, via a USB-I2C in- sential messages are outside terface. The kit also contains a the fi eld of view (such as which low-power CyFi transceiver and type of PSoC you should have when this is combined with a De ‘Cypress CY3271 PSoC® FirstTouch™ Starter Kit with CyFi™ selected). PSoC it can operate as a hub in low-power RF’ is available from several distributors for around But once you have overcome all a wireless CyFi network. 100 euros / 80 pounds / US$ 125 (ex. taxes). these problems you will quick- A second board, the so-called ly become enthusiastic about RF Expansion Card, contains a these parts. These are fantas- PSoC and a CyFi transceiver and it can also be a node in a CyFi wire- tic processors and in combination with the CyFi technology offer less network. It can be used to measure temperatures using the countless possibilities for experimenting and to develop your own thermistor mounted on the board. Using a connector, this board applications! can also be attached to other systems and allow them to be wire- lessly connected. A second connector makes an I2C interface and a couple of unused I/O lines from the processors available, which www.cypress.com/cyfi

E-LABS INSIDE can be used to connect your own prototypes.

46 elektor - 10/2009

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0910_elektor_adv_UK.indd 47 10-09-2009 11:14:41 PROJECTS AUDIO Hearing Threshold Tester for PC How good are your ears? By Jan Breemer (The Netherlands)

These days nearly everybody has a portable music player (iPod, mp3 player, etc.). But very few people realise how much these devices can affect our hearing. The hearing threshold tester presented here has been designed to check the state your ears are in.

The hardware and software presented The system produces pure tones at as well as the number of spot frequen- here is meant to be used to easily test various frequencies (generated by the cies in between. The frequency scale your hearing. It is possible to determine PC or laptop) and with various ampli- is logarithmic. your hearing threshold and you can tudes (determined by the attenuator perform an A-B-X test [1] to see what box); an LED is used to indicate that a differences there are in sound quality tone is being played and that you can Calibration between, for example, an MP3 fi le and use the push buttons to tell whether To make somewhat accurate measure- a WAV fi le. With future enhancements you heard the sound or not. In this ments you need to carry out two cal- of the software (which you could eas- way you can fi nd out what the quiet- ibrations. The first is to find out the ily write yourself) you can carry out a est sound is that you can just about relationship between the digital values number of other tests and gain a bet- hear. The results are shown in a graph sent to the sound card and the voltage ter understanding how your ears work and the whole process can be stored of its output signal. The second is to and what you can and cannot hear. in a log fi le. determine the sensitivity of the head- The procedure for measuring your hear- In the program you can specify the phones used. ing threshold is actually very simple: lowest and highest test frequencies There is an automatic procedure for the

The circuit described here is for educational use only as it gives only gives rough results. If you suspect that you have any hearing problems you should always consult your GP and/or an audiology specialist.

48 elektor - 10/2009

UK0910_48_52_090351-UK Hearing-t48 48 10-09-2009 11:40:27 About your hearing (the Sone is a somewhat older, non-logarithmic unit). For example, to When measuring sounds and how our ears react to them, two of the perceive a loudness of 40 Phon at 1 kHz you need a sound pressure most important factors are the Sound Pressure Level (SPL) and the of 40 dB. However, at 20 Hz you would need more than 90 dB to per- Loudness. SPL is an objective physical quantity that that indicates what ceive the same loudness. acoustic power density is associated with certain sounds. It is usually When hearing problems are diagnosed, a lot of attention is paid to

Pressure Intensity SPL Speed (m/s) Notes (Pascal) (W/m2) (dB) 200 5 x 10-1 100 140 riﬂ e shot at 1 m, above the threshold of pain 20 5 x 10-2 1 120 possible hearing damage during brief exposure 2 5 x 10-3 10-2 100 electric drill at 1 m distance 2 x 10-1 5 x 10-4 10-4 80 motorway at 10 m distance 2 x 10-2 5 x 10-5 10-6 60 TV at 1 m distance 2 x 10-3 5 x 10-6 10-8 40 normal conversation at 1 m distance 2 x 10-4 5 x 10-7 10-10 20 a quiet room 2 x 10-5 5 x 10-8 10-12 0 human hearing threshold

given in dB where 0 dB corresponds to a sound pressure of 20 micro- the hearing threshold. An increase at certain frequencies is an indica- Pascal. This is just about the quietest sound that can be perceived by tion of some measure of hearing loss. Audiologists will pay particular 2 human hearing at 2–4 kHz. (1 Pascal = 1 Newton/m ). attention to hearing loss within the frequency band that is important The relationship between the SPL and the actual sound pressure in for the understanding of speech, since that has the most far-reach- Pascal is exponential. There is also another factor involved, which is ing social consequences. The frequency range for this is about 200 to the speed at which the air particles move due to the differences in 8000 Hz. pressure. The acoustic power density is the product of this pressure and this speed. The speed is directly proportional to the actual sound pressure, because the relationship between them, the acoustic imped- 120 ance, is constant for air at atmospheric pressure. Sound pressure, 110

speed and SPL are always given as RMS values. 100 100 The table shows how the units relate to each other. 90

80 Loudness is a subjective measure of the sound intensity, which de- 80 pends very much on the frequency of the sound. The relationship be- 70

tween the SPL and the loudness as a function of frequency for human 60 hearing is given by the Fletcher-Munson graphs (see Figure). These 60 SPL (dB) SPL 50 graphs have been compiled using measurements on a very large 40 number of test subjects. These graphs show that when the frequency 40 moves away from 1 kHz the subjective perception deviates signiﬁ cant- 30 ly. The sensitivity deteriorates quickly at lower frequencies, and even 20 20 more so at lower sound levels. 10 The bottom line of the Fletcher-Munson curves corresponds to the 0 hearing threshold. This is the lowest sound level that can just be heard in extremely quiet surroundings. The wavy lines show the sound pres- 20 100 10005000 10000 f (Hz) sure (SPL) required to obtain a certain loudness in Phons or Sones 090351 - 56

fi rst. The microprocessor in the atten- - When only the sensitivity in dB/mW actual attenuation is carried out by a uator box has an on-board A/D con- is available, you will have to trust that PGA2311 made by Texas Instruments. verter that can be used to measure the frequency response of the head- This is driven by a Freescale microproc- the input signal. The software has a phones is fairly fl at. When you use this essor of the same type as described in calibration procedure that determines value you will also need the imped- the SpYder project in Elektor March the relation between the digital values ance of the headphones (for the calcu- 2007. An FT232 chip is used to inter- and the output voltage. During this lations, see [2]). When you use fi gures face the circuit with the PC. The sup- procedure the sound card produces a in dB/V the impedance isn’t required. ply is taken from the USB connection. 3 kHz tone at a certain amplitude for As an aside: an attenuator unit was 1 s. The peak-to-peak value is meas- used in this circuit because it has ured by the A/D converter. With this How does it work? more fl exibility and a greater range. value the program works out how to In this design the tones are produced Also, when you’re carrying out A-B-X make the sound card generate a sig- by the sound hardware inside the PC tests with music samples it becomes nal of 1 VRMS. or laptop. Two further requirements impractical to control the volume accu- The calibration for the sensitivity of are a pair of headphones and a quiet rately, especially if you want to intro- the headphones is more complicated. room. The attenuator box is the only duce differences to the left/right chan- There are a few ways of doing this: item that you have to build yourself for nels. And controlling all those different - The program has the facility to use this project. sound cards directly via their drivers the details from the frequency response The attenuator unit is a straight- wouldn’t be practical either. in dB/V for the calibration. forward circuit (see Figure 1). The

10/2009 - elektor 49

UK0910_48_52_090351-UK Hearing-t49 49 10-09-2009 11:40:30 PROJECTS AUDIO

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SK PRE C8 C9 C10 93-C46BSM 1 6 CS PE 100n 100n 100n 5 090351 - 11

Figure 1. In the circuit diagram we recognise a few ‘old favourites’: the processor from the SpYder kit, an FT232 USB to serial converter and the PGA2311 that was previously used in the April 2004 High End Preamp.

Circuit Diagram +21.5 dB). take a maximum of 100 mA from the At the centre of the circuit is the micro- IC2 takes care of the USB communica- USB connection. controller, which is responsible for con- tions. This is a USB to serial converter. The push button signals are fed to trolling IC3, the communications with Using a suitable driver, the PC program the microcontroller via fi lters (R11 to the PC/laptop via IC2, driving the LEDs can communicate with the attenuator R13/C8 to C10). R15 to R17 are used and monitoring the push buttons. The as if it was on a serial port. The VID, as pull-ups. original audio signal is fed to an ana- PID and USB confi guration are stored The negative supply voltage required logue input of the microprocessor via in a small EEPROM chip, IC1. R1 and by IC3 is generated by IC4. A number C11 (necessary for the calibration). The R2 provide the correct impedance for of decoupling capacitors have also DC offset of this input is kept at half the USB signal connection. R3 is a pull- been added. L1 C1, C6 and C13 form a the 3.3 V supply voltage by resistors up that signals to the USB host what fi lter to keep interference outside and/ R9 and R10/R25. Series resistor R14 type of USB device is connected (here or inside. D1 shows when the supply prevents the IC input from being over- it is version 2.0, full speed). R4 and R5 voltage is present, while D2 lights up driven when the input signal exceeds are pull-ups for the bi-directional data when communications with the PC 3.3 Vpp. connection to the EEPROM. take place. At the right of the controller we fi nd The LEDs in the switch box are driven The construction isn’t very difficult. the audio signal attenuator, IC3. It by three MOSFETs, T1 to T3. The exact Most of the components used are has a range from -95.5 dB to +31.5 dB, type isn’t that important. The current through-hole types. Start with the in steps of 0.5 dB. The input sig- through the LEDs is determined by R18 smallest components, in this case the nal has already been attenuated by to R20. Try to use LEDs with a higher SMD ICs and fi nish with the largest. 10 dB (by R21 to R24), so the effective effi ciency and increase the values of The trickiest will be IC2. A good tech- range starts at -105 dB (and ends at the resistors accordingly. We can only nique is to place a blob of solder on the

50 elektor - 10/2009

UK0910_48_52_090351-UK Hearing-t50 50 10-09-2009 11:40:30 solder pads, solder the IC and remove any excess solder using a desoldering braid. The PCB layout (which can be downloaded from [3]) has been designed such that all components are on one side. This makes it easy to mount the board into a box. If you are absolutely certain that the distance between your PC or laptop and the quiet room will never need more than 5 m of USB cable, you can mount the LEDs and push buttons into the same box. In Figure 2. The attenuator unit. From left to right: the yellow LED indicates when communication with the PC takes place, that case the RJ45 connector is no the green LED shows when the supply voltage is present. Next to that is the USB connector, the RJ45 connector for the push button box, longer needed. If you need more than the signal input and fi nally the connector for the headphones. 5 m you’ll have to mount the LEDs and push buttons into a separate box, which is then connected to the attenu- channel, bass boost, echo or reverb Unfortunately, good-quality closed ator box using Cat5 cable and an RJ45- effects, etc. The volume should be headphones are mainly made for the 8 plug. As with the headphone cable, at its maximum setting. Turn off any professional market and have a price this cable can be several tens of metres other programs that (may) use the tag to match. Low impedance head- long without any problems. sound card. phones (<300 Ohm) aren’t preferred The ideal headphone is a closed one for this project. Software and hardware that fi ts completely over your ears. Apart from the serial communications, the fi rmware for the HCS09 microcontroller also takes care of the LEDs and the scanning of the push buttons. The programming of the controller is made easy when you use the USB SpYder stick and its development software [4]. The PC software, which can be downloaded from [3], does not have to be installed. Extract the fi les onto your computer and place them in a suitable folder, such as C:\Program Files\Hear- ingTest\. You do need to have the Visual Basic 6 Run-time environment installed (can be downloaded from [5]). The hearing threshold tester makes use of a virtual COM port via USB. To make this work, you’ll need to have a driver installed on the PC for a virtual USB COM port. The driver found at [6] has been fully tested by the author and works well. In theory any sound card should be suitable. Connect the attenuator unit to the line output or the headphone socket. Don’t use an output meant to drive loudspeakers. You should also turn off any special effect on the sound card. This means no (pseudo) multi- Figure 3. The program displays a main window (‘System’) and a number of sub-windows depending on the type of test.

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UK0910_48_52_090351-UK Hearing-t51 51 10-09-2009 11:40:31 PROJECTS AUDIO

Enhancements

90 Enhancements for this program seem to present themselves naturally. In the 80 ﬁ rst instance you can determine the 70 hearing threshold as a function of frequency. This is the most important cri- 60 terion if you are looking for hearing loss

50 as a result of nights out in the disco or the use of portable music players. This 40 hardware offers many more possibili-

30 ties though. With additions to the software you 20 can investigate masking effects, for

10 example: - Pure harmonics; what percentage 0 harmonic distortion can you detect?

–10 - Nearby frequencies; how weak should 20 40 60 100200 400 600 1000 2000 4000 6000 10000 a tone that is close to another be before 090351 - 55 you can no longer hear it? - Distant frequencies; how soft does a tone with a clearly different frequency Figure 4. The result gives a clear overview of the hearing threshold. The blue line is the normal hearing threshold for young, healthy have to be before it can no longer be ears, measured in a perfectly quiet room. heard? - Noise; how loud should a tone be for Operation it to be heard above white noise? The noise can also be narrowband, cover- We’ll start with a hearing threshold the same tone at the same loudness. ing an octave or less. The tone can be test. Connect the attenuator unit to the The left and right LEDs indicate that inside or outside the noise band. All PC with a USB cable and connect the you should press one of the appropri- these tests can be carried out on one audio input to the line-out of the sound ate buttons. The left button is used to or two ears. card (see Figure 2). If all is well, the tell the system that you heard the tone. computer will fi nd a USB Serial Port. If you didn’t hear the tone you should The hardware can also be used to carry Take a look via the Device Manager (in press the right button. The same tone out A-B-X tests on, for example, music WinXP: Start -> Control Panel -> Sys- will then be played again, but louder samples. You could write a program tem -> Hardware tab -> Device Man- if you didn’t hear the previous one, or that could add a certain amount of ager) which COM port number has softer if you did hear it. Once the differ- distortion to music samples and then been assigned to the unit. Now start ence in loudness has become less than test to see how much distortion can be the program (TestYourEars.exe) and the setting in ‘Margin’, the same pro- noticed with which type of music. select your required language (see Fig- cedure will be followed with the next The interface details can be found on ure 3). From the main window, enter higher frequency. the author’s website [2]. The PCB art- the correct COM port number and tick In this way the system interactively work files (Eagle format, including the box if you’d like to see the attenu- determines the lowest level at which schematic) and the component list for ation panel in the future. Usually this you can hear a frequency and then this project may be found at [3]. isn’t required. Indicate whether you moves on to the next frequency. The (090351-I) want to use a single, fi xed number for results are shown immediately on a the calibration of the headphones, or graph on the screen. Internet Links if you have a calibration fi le. Next let Once the test has completed the red [1] http://en.wikipedia.org/wiki/ABX_test the program calibrate a 1VRMS signal. LED fl ashes quickly and the results can In the box ‘Calibrate 1 Vrms’ you can be inspected on the screen. The green [2] http://www.breem.nl/TyE see the peak value required to output a line represents the lowest level that [3] www.elektor.com/090351 1 VRMS from the sound card. You should could still be heard and the red line is expect a fi gure somewhere between the highest level that could no longer [4] www.elektor.com/shop, search for ‘spyder’ about 10000 and 32000. be heard. or ‘060296-91’ Now choose the hearing threshold test. The results can be saved as a bitmap [5] http://support.microsoft.com/kb/290887 If needed, change any settings in the or as a comma-separated-variables [6] http://www.ftdichip.com/Drivers/VCP.htm hearing threshold window and click on text-fi le. In the ‘Display’ section you Begin to start the test. Next, take the can change a few things regarding the switch box to an extremely quiet area graph. A white background is usually (a large wardrobe full of clothes works much better when you want to print well) and put on the headphones. The the graph. ‘Show Threshold’ displays (middle) red LED lights up whenever a the standard hearing threshold for tone is reproduced via the headphones. people. ‘Show Calibration’ displays the If you weren’t sure if you heard it, or calibration curve for the headphones, were disturbed by another noise, you if it’s used. can press the middle button to repeat

52 elektor - 10/2009

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10/2009 - elektor 53

0910_elektor_adv_UK.indd 53 10-09-2009 11:14:44 PROJECTS MINI PROJECT Pocket Preamp Part 2: a simple preampliﬁ er with tone control

By Ton Giesberts (Elektor Labs)

The PWM power stage discussed in the previous instalment (June 2009) can be used perfectly well on its own. But a matching preampliﬁ er with power supply would complete this ampliﬁ er nicely. That is why this month’s Mini Project presents the sequel: the Pocket Preamp.

In the June 2009 instalment of this (see Figure 1). This is the best place series of articles we described a small Main Specifi cations to prevent the tone control stage from PWM amplifi er. What is missing from being overdriven. The first amplifier this are tone and volume controls. Since • 3-band tone control stage (IC1a) is non-inverting and has most people are spoilt these days with • Symmetrical supply a gain of 4 times as calculated from surround sound systems equipped • Compact with an equalizer as an absolute mini- • Connector layout matched to R3 / R2+1 mum, we made this preamp with a 3- associated boards way tone control, instead of the more At a supply voltage of ±9 V, a signal of customary bass/treble control. more than 1 V (i.e. a little over 1.2 Veff) can be processed without distortion, A control range of 12 dB means that, when the tone controls are in their Tone control because of the relatively limited power centre positions. It will be obvious The tone control has an adjustment of the output stage, there is an immi- that when either the high or the low range of ±12 dB for the low and high nent danger of overdriving it, particu- tone control is at its maximum value, frequencies and ±9 dB for the mid larly for the low and middle frequen- the maximum permissible input signal frequencies. The latter is more than cies. After all, an increase of 12 dB is a lot smaller at only 300 mV (for the enough, because our ears are more implies an increase in power by a fac- applicable frequencies, of course). At sensitive to mid-range frequencies. tor of 16! this point the output of the tone control The circuit will also remain reasonably is just below the point of being over- straightforward with these values. If driven (but it will already overdrive the these adjustment ranges are too small The circuit power amp, so take care!). then there is very likely something The volume control (P1) is connected The operation of the tone controller is wrong with the loudspeakers. directly tot the input of the preamplifi er not all diffi cult to understand. The part

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UK0910_54_57_080278-UK Miniproje54 54 10-09-2009 11:40:55 around IC1b is an inverting ampliﬁ er with three feedback circuits connected C1 C2 in parallel for the tone control. Resis- tor R12 ensures that the output cannot 68p 180n R3 R4 P2 R5 swing to the power supply rail in the 10k 2k2 2k2 10k lin. event of contact bounce by the wiper C8 of P2. Incidentally, R1 functions in a 2 R6 68p R12 similar way for volume control P1. C8 P1 1 15k IC1A 1M and C1 suppress RF (high frequency) 3 interference. R1 R2 6 10k R13 R9 7 log. IC1B 100R 3k3 P2 is the bass control. C2 determines 220k 5 4k7 the frequency range that will be con- C7 C4 trolled. Simply put, at higher frequen- IC1=NE5532 cies, C2 effectively shorts out P2. The R7 6n8 P3 27n R8 +9V 1k5 1k5 amplification is then determined by C9 10k lin. the ratio of R5 and R4. The ratios of P2 R10 R11 100n 8 C3 to R4 and R5 determine the minimum 1k 0 IC1 1k and maximum control range respec- C10 4 4n7 tively. The maximum gain for exam- 100n C5 P4 C6 ple is -9V 27n 10k lin. 27n 080278 - 11 (P2+R5) / R4

and amounts to about 5.5 times (15 dB, DC). R6 is necessary so that the other Figure 1. The preampliﬁ er is quite straightforward for a volume control with triple-band tone control. frequencies can be adjusted with P3 and P4. C7 primarily determines from which frequency the high tone control is required. The easiest solution is a gest advantage of this is the simplic- operates. C5 and C6 ensure that the circuit that inverts the positive power ity; only two external capacitors are tone control has a steeper response. supply. required. A small disadvantage is that Components R9 and C4 have the same the output voltage is not regulated. functions for the mid frequency control We selected a DC/DC converter from The unloaded output voltage is equal as R6 and C7 for the low and high con- Maxim, the ICL7662 (see Figure 2). to the input voltage, but negative. As trols. C3 has the same function as C2, This IC works as a charge pump and the output current increases the out- but ﬁ lters the high frequencies much can operate with voltages up to 20 V. put voltage will reduce however. To later. Together with C4 it sets the Pin-wise and functionally the IC is increase the stability of the output range of the mid control. In the end, compatible with the more common voltage two ICs are connected in par- the control ranges of the mid and high ICL7660, which can operate up to 10 V allel. If you load a single IC powered at adjustments are not only determined (the ‘A’ version can handle voltages up 9 V with a resistance of 100 Ω, the out- by, for example, the ratio of P3 to R7 to 12 V). These parts can also be used put voltage drops to about –4.6 V. With and R8, but the other components in here without any problems. The big- two ICs in parallel this drops to only the feedback circuit also play a role. That is why the ratios between P3 and P4 to R7/R8 and R10/R11 are greater than would be expected from the

actual control ranges. C9 C11 9V C5

R1 8 10u 100n The low tone control has quite a wide L1 63V 0

7 V+ 1 OSC TEST 100n 4 100k 8 R3 2 bandwidth, because we assume that 10uH CAP+ IC2 7 R C3 5 C10 C12

DIS 1k VOUT small loudspeakers will be used. If this R2 9V C1 IC1 ICL7662CPA 6 3 10u 63V 4 6 10u 100n tone control is going to be used with 9V 9V THR OUT CAP- LV L2 63V 100k R4 GND 100n a larger ampliﬁ er and ditto speakers 2 TLC555 3 1mH

TR 1k C7 C8 a larger value for C2 may result in a C2 CV 1 5 4u7 4u7 better sound. Output resistor R13 pre- 100p 63V 63V vents problems in the event an exces- C6 sive capacitive load is connected. 8

7 V+ 1 OSC TEST 100n 2 CAP+ IC3 C4 5 VOUT Power supply ICL7662CPA 10u 63V 4 6 CAP- LV GND

The power supply is symmetrical. This 3 way we can avoid relatively large cou- 080278 - 12 pling capacitors and their detrimental effects on sound quality. The disadvantage is that a negative supply voltage Figure 2. A voltage converter is used to convert a single power supply voltage into a symmetrical power supply.

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Resistors Capacitors COMPONENT LIST R1 = 220kΩ (lead pitch 5mm / 0.2”) Preampliﬁ er board R2 = 3.3kΩ C1,C8 = 68pF ceramic R3 = 10kΩ C2 = 180nF polyester / MKT R4,R5 = 2.2kΩ C3 = 4.7nF polyester / MKT R6 = 15kΩ C4,C5,C6 = 27nF polyester / MKT R7,R8 = 1.5kΩ C7 = 6.8nF polyester / MKT R9 = 4.7kΩ C9,C10 = 100nF polyester / MKT R10,R11 = 1kΩ R12 = 1MΩ Semiconductors R13 = 100Ω IC1 = NE5532 (DIP-8) P1 = 10kΩ potentiometer, logarithmic P2,P3,P4 = 10kΩ potentiometer, linear Miscellaneous PCB, # 080278-1, from www.thepcbshop.com

–6.3 V. With your preampliﬁ er as a load which results in a much smaller resist- amount of the switching frequency of the output voltage drops only 0.35 V ance loss for this coil. The inductor we the power ampliﬁ er can be seen. (the NE5532 draws about 7.5 mA). You used for L2 has a rated series resist- could also use other opamps that have ance of 12 Ω. L1 and L2 are standard a lower current consumption, but their axial noise suppression chokes, which Test results quality is often inferior; the NE5532 is are fitted upright here. The latter is The most interesting test results for an excellent audio opamp. also true for the four resistors in the the tone controller are of course the In our prototype we initially connected circuit; this saves space. individual frequency response curves four ICs in parallel, but with three or for the tone adjustments. Figure 3 four not much more is gained. There We won't dwell on the circuit around shows the maximum, minimum and was however a strange the 555. It is the standard neutral positions (the positions of the effect: the rip- astable configura- bass and treble controls remain ple in tion. IC1 drives the clock

the output was found to vary slowly between a minimum and a maximum value. This was caused by the asynchronous oper- inputs ation of the internal oscillators. In addi- of the two unchanged). tion, the frequency of this power supply converters, each In the neutral position a ripple was 10 kHz so it could become via a 1 kΩ resistor, to pre- slight attenuation of less than 1 dB audible. That’s why the ICs are driven vent potential problems at power-on at 20 kHz can be seen. This is mainly with an external clock furnished by a (risk of latch-up). The ripple across caused by RF suppression capacitors 555 IC. The frequency of the 555 is set the ﬁ lter capacitors C7 and C8, which C1 and C8. At 20 Hz the variation in to 40 kHz, so that the ripple at 20 kHz are connected in parallel for a lower gain is ±14 dB (±12 dB at 40 Hz) and is just outside the audible range. An series resistance, is almost completely at 20 kHz it is about ±12 dB. advantage is that the inductor in the removed by output ﬁ lter L2/C10/C12. output filter can be much smaller, On an oscilloscope only a very small The distortion with an input signal

COMPONENT LIST Resistors Inductors Power supply board R1,R2 = 100kΩ L1 = 10µH axial (vertical mounting) R3,R4 = 1kΩ L2 = 1mH axial (vertical mounting)

Capacitors Semiconductors C1,C5,C6,C11,C12 = 100nF ceramic, lead IC1 = TLC555 (DIP-8) pitch 5mm (0.2”) IC2,IC3 = ICL7662CPA+ (DIP-8) (Maxim C2 = 100pF, lead pitch 5mm (0.2”) IC) C3,C4,C9,C10 = 10µF 63V radial electrolytic, lead pitch 2.5mm (0.1”) Miscellaneous C7,C8 = 4.7µF 63V radial electrolytic, lead pitch 5mm (0.2”)

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UK0910_54_57_080278-UK Miniproje56 56 10-09-2009 11:40:56 of 0.5 V is less than 0.005 % (1 kHz, Construction of the three boards 22 kHz bandwidth, volume control to Kit set maximum, tone controls to neutral). The connections for the three boards As indicated in the parts list, you can The current consumption of the entire have been placed in the same posi- order the bare printed circuit boards circuit is 56 mA at 9 V, 12 mA up on the tions as much as possible. The output for this project from www.thepcbshop. Ω PWM amplifi er by itself. With an 8 of the preamplifi er is in the same cor- com. However, a complete kit set is also loudspeaker and the amplifier over- ner as the input to the power ampli- offered in the Elektor web shop, which driven slightly, the current consump- fi er. The power supply connections of comprises the printed circuit boards and tion peaks at about 162 mA. This really the preamplifi er are in the same place all necessary parts, see www.elektor. is too much for a 9 V battery. With mul- as the power supply outputs of the com/080278. tiple channels we therefore recommend power supply board. The 9-V input that you use an AC power adapter. of the power supply board is looped directly to the two connections for the During the tests we didn’t actually power amplifi er. The position of these use potentiometers for the tone con- corresponds to the power supply controls, but instead went for rotary nections of the power amplifier. On switches and resistors. This is the power amplifi er, next to the power because the interest is mainly in the supply connections, there are also performance at the neutral positions the connections for the power supply and at the upper and lower limits. So, switch (S1). This is only for the power

+15

+12

+10

d +2 B r +0

A -3

-5

-7

-9

-11

-13

-15 20 50 100 200 500 1k 2k 5k 10k 20k Hz 080278 - 13

Figure 3. The curves show the effects of the different maximum settings of the tone control.

each potentiometer is reduced to two ampliﬁ er. It is better to insert a switch resistors and a rotary switch. The tol- in series with the input to the power erance of pots is usually quite large; supply board. You can then short out ±20 % is typical, and inevitably has the connections for S1. an effect on the frequency ranges and maximum and minimum gains. Mounting holes were deliberately not With multiple channels the individ- included on all three of the boards so ual deviations can result in audible that everything is as compact as poss- differences. If you have the opportu- ible. For a reliable mounting option you nity to check whether the individual could consider a couple of plastic sup- channels of stereo potentiometers are ports with slots. The boards can then matched then it is certainly recom- be mounted one above the other. The mended that you do this. With more best order is the power supply board at than two channels, the use of rotary the bottom, the tone control above that switches with multiple poles may be and the power ampliﬁ er at the top. considered, but this is an expensive (080278-1) solution.

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A performance test of 10 noise cancelling headphones The Sound of Silence

By Harry Baggen (Elektor Netherlands Editorial) Background noise can be very irritating while you are listening to music. Fortunately we can get round this these days by using headphones that reduce background noise using anti-sound. In this article we’ll take a look at a number of these so-called noise cancelling headphones.

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10 10 passive active passive 20 20

30 30 Figure 1. residual noise residual noise Diagram (a) shows the 40 40 effect of the passive attenuation [dB] attenuation [dB] suppression caused by the 50 50 earcups of the headphones. 20 200 2k 20k 20 200 2k 20k When an active NC frequency [Hz] frequency [Hz] 045124 - 14 045124 - 15 system is added the lower abfrequencies are suppressed as well (b).

They’re becoming more and more common: people on the street, bus, train and plane wearing headphones or earphones, enjoying their favourite music. Unfortunately, the ‘enjoyment’ has to be taken with a pinch of salt. If it’s not the lack of quality of the headphones, then the background noise will introduce a measure of interference. Listening to music can be particularly relaxing when you’re travelling for hours on the train or plane. But in these situations there will be a continuous rumble in the background, caused by the wheels on the rails or the jet engines of the plane. Fortunately we can do something about this with the noise Figure 2. help of so-called antisound, so you can relax in (artifi cially Removing noise: anti-noise generated) peaceful surroundings and enjoy your music. The interference is sum of both waves 045124 - 12 measured, its phase inverted and mixed with Theory the original signal. There are two ways in which unwanted sounds can be reduced. The fi rst is really very simple: sealed headphones that have earcups covering the whole of the ears will pas- sively reduce the noise. This type of ear-protection is used Audio In widely within the construction industry. However, they’re usually not very comfortable. Furthermore, such passive A/D Digital processing system converter systems predominately suppress middle and high frequen- System cies, whereas train and plane noise is generally in the controller lower frequency band (Figure 1a). B In the second method electronics gives us a helping hand. The background noise is picked up using a microphone, DSP (Digital Signal Processor) amplifi ed, shifted 180° out of phase and fi nally mixed Digital with the music signal. In this way the interference signal is equalizer removed. Any changes in the background noise are imme- B diately picked up and effectively suppressed. In Figure 2 DNC software engine you can see the principles involved. A – B û C C Such an active system lends itself particularly well to the A suppression of noise with lower frequencies. When this is combined with passive suppression it results in good sup- A/D D/A converter converter pression across the whole audio spectrum (Figure 1b). A C

Microphone Headphone Practice amplifier amplifier Such noise cancelling headphones are made by many A C

manufacturers. There are special types designed to be used Detection Figure 3. by e.g. pilots, but these days there are also many head- microphone Driver unit In a digital NC system

phones available for general music playback on the bus, 081085 - 11 a DSP removes the train, plane, or even at home. It is the last category that background noise. we’ve explored in this article. Noise cancelling headphones for general consumer use can be roughly divided into three groups. There are purely passive types, where the mechanical construction of the earcups or earbuds provides a reduction of background noise. Examples of this are the SE420 and SE530 made by Shure. These are in-ear types, where the

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earbud is pushed into the ear canal. Despite its passive sound quality of these headphones. The price range is from construction there is a good amount of suppression. about £35 (€40) to £350 (€400), which leaves something With active noise cancelling (from now on abbreviated for everybody. Most samples were supplied with a set of to NC in this article) headphones we can differentiate accessories, such as a travel case, cables and converter between analogue and digital types. With analogue types plugs, and in one case it included a charger for the built-in the inverted signal that’s mixed with the original audio sig- rechargeable batteries. nal is generated by a microphone in conjunction with a Since it would be very diffi cult to directly measure the effec- small audio amplifi er. This is the system that can be found tiveness of these NC headphones (mainly due to the differ- in most NC headphones. The results can be quite good, ent types in our test set, like in-ear and sealed types), we but are dependent on the technical design of the control decided to use subjective judgments for the effectiveness system. of the noise suppression and the sound quality. With digital types (generally the more expensive ones) a The noise suppression is tested in several realistic environ- DSP is used to intelligently remove interfering sounds. With ments, such as traffi c noise, a server room with air condi- these the microphone signal and the audio input are fi rst tioning, and in a noisy offi ce. In other words, in places that digitised before being fed to a DSP, which compares them most of us experience on a regular basis. and performs some calculations on them. The resulting dig- We also noted how comfortable they are to wear, which ital signal is then converted back into analogue and fed isn’t an insignifi cant point when they’re worn for hours on to the earcups via an amplifi er. An example of this can be end. seen in Figure 3, which Sony uses in its more expensive On the basis of these criteria you should be able to pick models. In the most recent versions the composition of the your favourite, depending on what’s most important to background noise is analysed and the result is used by you. the DSP to choose a fi lter pattern that is most effective at Some other criteria that could affect your choice: How removing the noise. much are you prepared to pay for such NC headphones? How often would you use them and how important is the sound quality? Effective? For this article we’ve asked virtually all well-known manu- The ratings given to the products are on a scale of 10. facturers of headphones to supply us with several samples Prices approximate and subject to trade discounts. so we could get an impression of the effectiveness of the Products tested may not be available in all countries. built-in suppression electronics and, of course, the eventual

Audio Technica ATH-ANC7 and a solid bass response. With the NC system turned on, there is a slight noise noticeable from one earcup, but this These on-ear headphones are ﬁ nished to a high stand- all but disappears when music is played. When the NC ard. They come with a strong travel case, plane adapter system is turned off the response becomes a bit ﬂ atter. and a 6.3 mm in-line adapter. All plugs and adapters are The active NC system suppresses low-frequency noises gold-plated. The power is supplied by an AAA battery, very well, and voices are barely noticeable in the which should last about 30 hours according to the manual. background. Plus point: The headphones also work when the battery is empty, although they sound a bit quieter. Sound quality: 7 Noise suppression: 8 Comfort level: 6 Retail price: approx. £175 (€200)

Bose QuietComfort 3 These are well-designed on-ear headphones. The earpads are a bit smaller than those of the AT, but they’re very soft and hardly press on the ears. This makes the comfort level very good. A wide range of accessories is included, such as a plane adapter and 6.3 mm in-line adapter, an extension cable (nearly all plugs are gold-plated), a charge adapter for the two special batteries with several types of mains plug for world-wide use, and a sturdy travel case. The QuietComfort 3 can only work with the NC system turned on, so always make sure that you take a spare, fully charged battery with you (a spare battery is included in the The earcups are fairly small, so they rest on the ears. They box of accessories). The noise generated by the electronics don’t exert that much pressure, so the comfort level with is barely noticeable. longer use is reasonable. The Bose has a very good sound quality with a well-deﬁ ned The sound quality of these AT headphones is quite good, mid-range, but a slightly limited top range and a very pow- with a balanced mid-range and high frequency response, erful bass, which could have been a bit quieter, although

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UK0910_58_64_090577-UK Headphone60 60 10-09-2009 11:41:46 sure on the ears, which results in less acoustic isolation.

Sound quality: 7 Noise suppression: 6 Comfort level: 7 Retail price: approx. £175 (€200)

JVC HA-NCX77 These in-ear headphones have earbuds with an angled section onto which the rubber end-plugs ﬁ t, making it easier to put them into the ear canal. The electronics have been put inside a separate little box, which also contains the energy source (one AAA battery). This box also has a volume control, an on/off switch for the NC system and a monitor switch to temporarily turn off the music when you suddenly you get used to this after listening for a while. want to talk to somebody. Everything can be stored in an The noise suppression is very good and particularly effec- accompanying case. tive at lower frequencies. Voices come through a bit The sound quality of these earbuds is quite disappointing stronger than with the AT, but apart from that, all noise is when compared with the on-ear types. The sound appears suppressed very well. quite tight and there is only a limited bass response. We should point out that with earbuds the sound quality Sound quality: 8 Noise suppression: 8 Comfort level: 7 Retail price: approx. £350 (€400)

JVC HA-NC250 These relatively small and lightweight on-ear headphones also come with a travel case, connection cable, and several gold-plated in-line adapters. The HA-NC250 needs a single AAA battery and also functions with the NC system turned off. The earcups are not very big and therefore rest on the ears. They exert very little pressure on the ears, so are hardly noticeable. When you move your head the earcups stay in place very well. The HA-NC250 has an agreeable and somewhat neutral response with a good defi nition in the mid and high ranges. The bass response is perhaps not as powerful as depends very much on how they’re placed in the ears and with some other models, but still fi ts in well with the rest of how well they fi t, and this is something that can be differ- the frequency response. ent for different people. The noise suppression of the HA-NCX77 is only moder- ate. This is also affected by how well the earbuds fi t, and this too depends very much on the individual. This is also the reason why no scores have been given for the comfort level of earbuds. Some people don’t have any problems with earbuds, whereas others can’t seem to stand having them in their ears.

Sound quality: 5 Noise suppression: 4 Comfort level: not assessed Retail price: approx. £70 (€80)

Philips SHN2500

The cheapest set of earbuds with an active NC system in this test is the SHN2500. This time there is no carry-case, The noise suppression system works best at lower frequen- but you do get two in-line adapters. The earbuds have the cies and functions quiet well. Voices are quite noticeable, same shape and dimensions as most normal earbuds. As but that is also due to the small earcups and the light pres- far as we can tell, the microphone has been placed at

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The NC system manages to remove a fairly large amount of low-frequency noise from the signal, on top of the reduction caused by the acoustic isolation of the earbuds. This is quite a performance from a system costing £85!

Sound quality: 6.5 Noise suppression: 6 Comfort level: not assessed Retail price: approx. £85 (€100)

Sennheiser PXC 300 the back. The NC electronics have been put in a simple external case, which also contains an AAA battery for the These are light-weight on-ear headphones that can be power. A slide-switch is used to turn the NC system on or folded into a fairly small package. A carry case, plane off. With the NC system on there is some quiet background adapter and 6.3 mm in-line adapter are all included. The noise, although it isn’t disturbing. NC electronics are housed inside a tubular box that is pow- After choosing the right size of silicone end-plugs the ear- ered by 2 AAA batteries. This box can be clipped onto a buds fi tted quite well in the tester’s ears despite the straight shirt or suit. The headphones also work when the NC sys- shape, and also closed off the ear canal very well. The tem has been turned off. sound quality is quite acceptable, especially at this price. The PXC300 fi ts well on the ears and exerts little pres- The mid-range seemed somewhat limited, which is some- sure. Thanks to its light weight the earpads stay in place thing that many cheap in-ear headphones suffer from. during head movements. Some noise can be heard when The noise suppression manages to reduce some of the low- the NC system is turned on (the NoiseGard Advance sys- frequency noise, but most of the suppression is a result of tem by Sennheiser). Music reproduction is clear with a lit- the acoustic isolation caused by the earbuds themselves. tle too much emphasis on the mid and high ranges. This But this is certainly not a bad thing. makes the bass response seem a bit fl at, but it is still well defi ned. Sound quality: 6 Noise suppression: 5 Comfort level: not assessed Retail price: approx. £35 (€40)

Philips SHN7500 These deluxe in-ear headphones made by Philips have earbuds that are somewhat more ergonomically shaped. The microphones on this model are found on the sides. The SHN7500 comes with a storage case, several adapters and of course three different sizes of silicone end-plugs (just like all other in-ear models in this test). The NC system has also been put in an external box here, and works off an AAA battery. It has a switch for the noise suppression system and a linear volume control. The travel of the latter is very short, making it difﬁ cult to ﬁ nd the right volume level. The cabling runs partially along a strap that’s mounted to the box, so you can wear the box from your neck and there The noise suppression performs reasonably well. Although won’t be any other trailing cables. low-frequency noises are suppressed by the NoiseGard After picking the right size of silicone end-plugs the system, voices still come through due to the small (and SHN7500 produces a surprisingly good sound that comes somewhat loose) earcups. close to that from some larger on-ear headphones. A fairly The separate box housing the electronics isn’t really con- balanced response and a strong bass response result in an venient, but it does have the advantage that it keeps the enjoyable listening experience. headphones themselves very light.

Sound quality: 6 Noise suppression: 6 Comfort level: 8 Retail price: approx. £175 (€200)

Sennheiser PXC 450 These are large, sturdy on-ear headphones ﬁ nished to a high standard, which use the digital NoiseGard 2 system

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UK0910_58_64_090577-UK Headphone62 62 10-09-2009 11:42:06 by Sennheiser. This luxurious system comes with a sturdy earcups press somewhat hard against your head, and carry case, plane adapter and 6.3 mm in-line adapter. All therefore aren’t that comfortable if you wear the head- plugs have been gold-plated. The PXC 450 needs a single phones for a long time. AAA battery. The noise generated by the NC system is min- The sound reproduction of this top-model is very balanced, imal. On the headphones are an on/off switch, a volume with a tight and deep bass response, but it all sounds a bit control with two push buttons and a talk-switch for when too ﬂ at to really make the music come alive. you need to talk to someone for a moment. There is also a The (digital) NC system is extremely effective and manages bypass switch for when you want to use the headphones to strongly suppress background noise, even at higher fre- without the NC electronics. quencies up to 1 kHz. Most of the other types have to rely The large earcups completely cover the ears and form a on the passive suppression caused by the earcups at this good seal. According to Sennheiser they can even be used frequency. as passive ear protectors when the cable is removed. The Sound quality: 8 Noise suppression: 9 Comfort level: 7 Retail price: approx. £300 (€350)

Shure SE530 The SE530 is the only passive NC headphone in this test. Shure doesn’t actually use the term NC, but calls them ‘Sound Isolating Earphones’. It was interesting to see how these passive headphones compare with the active versions. The SE530 is the most expensive type from the SE series and is delivered in a deluxe case, which contains the earbuds (it almost sounds disrespectful at this price), a storage case, connecting cable with an in-line volume control, sev-

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UK0910_58_64_090577-UK Headphone63 63 10-09-2009 11:42:17 INFO & MARKET NC HEADPHONES REVIEW

An automatic setup system analyses the background noise and uses the results to select the optimum frequency band for the suppression of noise. There is a button on the ear- cup that can be used to start this test again at any time. The earcups are just a little bit too small to cover the ears completely, but with a bit of wriggling it could just be done. The headphones felt quite comfortable and hardly pressed against the head. The sound quality of the MDR-NC500D is excellent. The reproduction is very balanced and gives a spacious feel. The quality of the bass response was only bettered by the Sennheiser PXC 450, but according to our ears, these are eral in-line adapters, eight sets of end-plugs and a special overall the best sounding headphones in this test. cleaning tool. The way these earbuds are worn differs from The noise suppression system is very intelligent and fi gures all the other types. The connecting cable points upwards, out the best noise suppression to use in various situations, and this initially takes some getting used to. particularly with lower frequencies. Higher frequencies are It takes some time to pick out those end-plugs that fi t, since suppressed somewhat less, possibly because the earpads a large number of them are included, but it is very impor- aren’t pressing that hard against the ears. tant that you select the ones that fi t well in your ears and hence seal them as well as possible. Sound quality: 9 Once you’ve succeeded, the SE530 produces a very good, Noise suppression: 9 neutral sound, which no other headphones in this test come Comfort level: 8 close to. Voices sound as if they’re next to you, the high fre- Retail price: approx. £350 (€400) quency response is clear and very detailed, and the bass response is deep and powerful, without being overpower- ing. We couldn’t give it full marks (i.e. 10/10), otherwise that wouldn’t leave room for improvement. As for the noise suppression, the SE530 doesn’t score very high. Just like the other in-ear headphones, it provides rea- Conclusions sonable suppression of the mid and high range, but for a good suppression of the lower frequencies an active system After listening to a number of these special NC headphones really is essential. we can certainly conclude that most of them are effective, albeit at a cost. Nearly all of the headphones tested here Sound quality: 9 cost £175 (€200) or more, due to the extra electronics. Noise suppression: 4 However, if you travel a lot by public transport or by air Comfort level: not assessed and want to enjoy your favourite music with the minimum Retail price: approx. £435 (€500) of disturbance, it would be worthwhile to acquire some NC headphones. When using these headphones the sound quality is just as important as the level of noise suppression. What’s the point in having an effective noise cancelling system if the Sony MDR-NC500D sound quality is abysmal? The comfort level plays a role This highest priced on-ear-model made by Sony is made too. We’ve also made an assessment on this, but it is some- from magnesium and aluminium and uses a Li-ion battery thing that is best judged by yourself before you buy a pair for power. The well-designed headphones are delivered of headphones. with a strong case, universal charger, connecting cables The on-ear types appeared to give the best results in this and several (gold-plated) plugs. There is even a separate test, partially because their construction provides them with battery holder that can be used when the internal battery better acoustic isolation. Usually they also sound better runs out. This is just as well, since the headphones cannot than their in-ear compatriots, but it should be pointed out be used without the NC system. that three of the four in-ear types tested here are signifi - The MDR-NC500D uses a DSP for the noise suppression. cantly cheaper than the others. And the winner is... The best headphones appear to be the Sony MDR-NC500D. This is the only one that offers both an excellent sound quality and a very effective NC system. As far as the noise suppression is concerned, the Sennheiser PXC 450 was similar, but we weren’t quite as impressed by its tonal qualities. In the category ‘Best price/quality ratio’ the Philips SHN7500 comes out ahead. It offers reasonable sound quality and quite effective noise suppression, as long as you don’t mind wearing earbuds in your ears. At a cost of £85 (€100) Philips has placed a good product in the market.

All of the headphones covered should be available, or can be ordered, from audio/video stores as well as online retailers. (090577-I)

64 elektor - 10/2009

UK0910_58_64_090577-UK Headphone64 64 10-09-2009 11:42:22 0910_elektor_adv_UK.indd 65 10-09-2009 11:14:45 projects readers’ circuits Mini Preamplifier Easy to operate thanks to AVR micro & LCD

By Paul van der Vleuten (Belgium)

This small pre-amp has both a good sound quality and a simple and flexible control interface thanks to the use of an ATmega8 microcontroller. Two digital potentiometers are used to control the volume, and a two-line backlit LCD displays the volume and input source settings.

After listening to an expensive audio fier (apart from a good sound quality), trol that precedes such an amplifier. In system a few times the author wanted were a robust protection against a DC other words: a preamp. And this has to to buy a pair of Dynaudio loudspeakers. offset at the outputs and absolutely no be compact as well, of course! However, they were quite expensive clicks or pops should be heard when So what’s the most important com- at the time. Thinking of the expression it was turned on or off. In the end the ponent in a preamp — obviously the “the best things come to those who author choose an LM4780 made by potentiometer! But what type should wait”, the author eventually managed National Semiconductor in combination be used, a normal one or some exotic, to buy them at a discounted price. But with an NTE7100 (µPC1237) protec- expensive version? The latter was a pair of speakers on their own doesn’t tion IC. The latter provides a switch- rejected due to the abovementioned make a good audio system; at the very on delay, the detection of any DC offset criteria and an ordinary potentiometer least you’ll need a good amplifier as at the output and it also turns off the would not satisfy the quality require- well. Unfortunately, the budget was speakers when the mains voltage is ments. After some research it was (almost) spent. present at the transformer side. Along decided to use a digital potentiometer, That left the DIY route. First the power with the protection circuits inside the the AD5290 made by Analog Devices. amplifier had to be built. Since the LM4780, this pair makes a well-pro- This device has 256 steps, which is suf- lady of the house wanted everything tected power amplifier that can be ficient for a volume control. And a THD as compact as possible, it would have built in a very compact form. of only 0.006% isn’t bad either. Fine, but to be based on an integrated power But this isn’t what this article is about. it’s the symmetrical supply voltage of amplifier. The most important criteria In it we’ll concentrate how to select ±4.5 to ±15 V that makes this device that had to be met by the power ampli- the input source and the volume con- attractive as allows the AD5290 to be

66 elektor - 10/2009 easily added to opamp circuits using Controlling this potentiometer is quite • Input selection using relays. symmetrical power supplies. The dig- straightforward with the help of an • Volume control using a rotary ital potentiometer is controlled via a AVR micro and Bascom. The author encoder. 3-wire SPI. When a byte is clocked in chose an ATmega8 as the microcon- • Display the name of the input (MSB first), the ‘wiper’ of the AD5290 is troller. And since we’re working with source on the LCD. set to the corresponding position. The a microcontroller we may as well add • Select the names for the input AD5290 used here is a 100 kΩ type. some bells and whistles, such as: source from a predefined list. With this value no switching clicks could be heard.

LCD1 +5V IC3 JP1 7805 LC DISPLAY 2 x 16

C6 C5 A VSS VCC VO RS R/W E DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 K

100n 100n 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

TR1 22R 10k 4 6 MUTE VCC VCC 18 23 +5V ON/OFF AVCC PCO(ADC0) SETUP 20 24 AREF PC1(ADC1) 25 PC2(ADC2) 29 26 PC6(RESET) PC3(ADC3) 19 27 ADC6 PC4(ADC4/SDA) D2 D4 D3 D1 22 28 ADC7 PC5(ADC5/SCL) IC1 SV4 30 2 PDO(RXD) PD4(T0/XCK) 31 9 PD1(TXD) PD5(T1) 32 10 PD2(INT0) PD6(AIN0) 1 11 PD3(INT1) PD7(AIN1)

INPUT4 INPUT3 INPUT2 INPUT1

ATMEGA8-AU ENCODER 7 12 J1 J2 J3 J4 PB6(XTAL1/TOSC1) PB0(ICP1) A 13 090241PB1(OC1A)- 11 14 PB2(SS/OC1B) B PB3(MOSI/OC2) 15 8 16 +5V PB7(XTAL2/TOSC2) PB4(MISO) LED1 LED2 LED3 LED4 21 17 AGND PB5(SCK) GND GND 1 2 3 5 3 4 R6 5 6

7 8 1k5 9 10

+12V +5V IC2 K1 PS710B-1A 5 ++V LM317 SV2 IRIN ++V 6 4 R2 +5V adj. IRVS +5V SLAVE12V+ SLAVE5V+

120R SLAVE0 SLAVE5V-0 R5 IRGND R3 TR2

C3 C1 1k

1k2 1 2 0V 100n 100n 10k 00 1 2 Q1 00

0V C4 C2 BS170 100n 100n L1

100u - -V 6 4 - -V 0V 7912 K2 5 IC4 -12V PS710B-1A 090241 - 11

Figure 1. The controller board contains the ATmega8, the display, all controls and the voltage regulators.

10/2009 - elektor 67 projects readers’ circuits

+12V +12V R21 +12V L1 LED-COMM-A C13 5k2 L-1 C22 47u SV1 K1.B R1 D1 220u K1.A A 47k C21 G-1 351 LED1 R2 220u L2 A 1N4148 Q1 ANALOG 1 POWER 47u -12V 47k K1.C C14 R-1 JP3-1 BS170 JP2-2 +12V C15 L-2 D7 K2.B R3

JP2-1 D2 K2.A 47k G-2 D6 JP2-3 351 LED2 R4 A 3x 1N4148 Q2 ANALOG 2 D5 BAT85 47k SV2 C16 K2.C R-2 BS170

JP3-2 +12V C17 L-3

K3.B R5

D3 K3.A 47k G-3 JP3-3 351 LED3 R6 A 1N4148 Q3 ANALOG 3 47k

+12V +12V K3.C C18 R-3 5 6 8 7 5 6 8 7 BS170 9 9 CS CS SD1 SD1

C1 CLK C3 CLK SDO SDO VDD VDD C19 U$1 U$2 +12V L-4 100n 4 AD5290 100n 4 AD5290 A 100k A 100k K4.B R7 C2 GND C4 GND D4 K4.A 47k 100n 3 100n 3 G-4 VSS A VSS A

B W B W * 2 10 1 2 10 1 351 LED4 R8 A -12V -12V 1N4148 Q4 ANALOG 4 +12V 47k C11 K4.C C20 A R-4 BS170 A 100n R18 0R JP5* JPDAC* 5 4 2

R22 R16 +3V3

6 RXSEL1 100R 0R IC5 RXSEL0 3 3 6 R19 O-L OPA604 7 1 7 R14 R12 IC1.A IC1.B 100R 1 2 5

OP-L A C12 470k O-G 3 100n A OP-G -12V 1 IC2.A R9 R10 A 2

+12V 1M 1M 6 C10 R20 O-R 7 IC2.B 100R 5 OP-R A 100n R17 A +12V 0R 5 4 2 C5 C7 R23 R15 6 100R 0R IC4 3 100n 4 4 100n OPA604 7 A IC1 IC2 A IC1, IC2 = OPA2604 R13 R11 1 C6 8 8 C8

A C9 470k 100n 100n

100n A -12V 090241 - 12 -12V

Figure 2. On the analogue board you’ll find all analogue inputs and outputs, the digital potentiometers and a number of buffer stages.

• The facility to adjust the volume • And last but not least, the facility to lators and slave outputs. 2. The ana- slightly for each input, compen- turn everything on and off by press- logue board with four input relays, two sating for any differences in input ing the volume control for 3 sec- AD5290-100Ks and all the opamps. levels. onds. That way there is no need to • Remote control using an RC5 com- add an on/off switch to the (small) Controller section patible remote control. The preamp front panel. If we look at the circuit diagram for the reacts to address 16 for HIFI. controller section (Figure 1), we’ll see • A mute function that works by an ATmega8 at the heart of the circuit. briefly pressing the volume control Two-part circuit This employs an internal RC oscillator (encoder knob with a built-in push The circuit consists of two parts: 1. The as the clock. Make sure that this is set button). controller board with an ATmega8, a to 8 MHz in the fuse-bit settings. 2x16 LCD display, the encoder control, At the top is the LCD display that is the input selectors, the voltage regu- driven in 4-bit mode by pins PC0 to

68 elektor - 10/2009 PC5. Preset TR1 is used to adjust the encoder you should make sure that it contrast of the LCD (positive volt- is connected according to the example ps age contrast). R1 is the current lim- circuit given with Bascom (this is found iting resistor for the backlight LEDs in the Help file under ‘encoder’). • Display lighting: For standard (note that the value of this resistor is When the circuit is switched on, port green backlights the voltage drop across dependent on the type of LCD used). PB0 puts a BS170 (Q1) into conduction. the LEDs is about 4 V. For white back- The input selection happens via push This then pulls the cathode of the LCD lights this is significantly lower at about buttons INPUT1 to 4. These pull PD0 to backlight to ground, as well as the 3.2 V. Refer to the datasheet to find the PD3 to ground respectively. The inter- cathodes of the two NEC PS710B-1A exact voltage and adapt the value of R1 nal pull-up resistors of the ATmega8 solid-state relays. In this way the sym- accordingly. have been activated in the code so metrical supply is turned on for the • LED drivers: If you prefer to use these pins are normally high. analogue board. LEDs that require a larger current you’ll In order to save on the number of I/O In the circuit there are also several find that connections have been made pins, the Setup button is connected to slave connections for both 12 V as available for this on the analogue Input buttons 1 and 3 via two diodes. well as 5 V (note that for the 5 V the board. In this case they’re driven by a When the Setup button is pressed it ground connection is switched!). BS170, along with the associated relay results in both PD1 and PD3 being These connections are used by the (max. 500 mA). pulled low. This condition signals to author to drive relays, which turn on the code that it should jump to the a power amplifier and an optional A/D • Take care that the AD5290 100K Setup label (If Pind.1 = 0 And Pind.3 converter. digi-pots get the correct supply voltages. = 0 Then Goto Setup). A standard IR receiver takes care of They are extremely sensitive to this! It will The same principle is used for the the reception of infrared signals. It be catastrophic if one side of the sym- MUTEONOFF push button. The name is connected to pins IRIN, IRVS and metrical supply isn’t connected! MUTEONOFF refers to the fact that IRGND. The IR data goes to PB5 of the • If you make IC4 and IC5 amplify, this button has two functions: a short ATmega. remember that you may have to add press = mute, a press for more than The voltage regulators for the sym- a small capacitor across the feedback 3 s = on/off. metrical supply are also on this board. loop to prevent oscillations. We now come to pins PD4 to PD7. They consist of an LM317 and a 7912. • You should also bear in mind that not These drive the input relays via BS170 With the use of preset TR2 the +12 V all types of opamp remain stable MOSFETs. Four LEDs (LED 1 to 4) line can be adjusted, making the sup- when configured as voltage followers give a visual indication of the input ply exactly symmetrical. There is also (such as the well-known OPA627). In selected. The value of the current lim- a separate 5 V regulator for the con- that case you will need to add a com- iting resistor (R6) is dependent on the troller and the LCD. If there is a jumper pensation capacitor, or you could make type of LED used. When selecting the across JP1 the voltage for the 7805 will the opamp amplify the signal a little bit. resistor you have to make sure that be derived from the LM317. In that the maximum source current of the case there will be a voltage drop of 7 V • Programming: The ATmega8 has a ATmega8 (20 mA) isn’t exceeded. A across the 7805 and this would have fairly large number of fuse-bits. If you’re value of 1k5 works well with low-cur- to dissipate a lot of heat. A good heat- not fully familiar with these, it would be rent LEDs taking 2 mA. sink is therefore a must. It is also pos- a good idea to program the chip first in Several pins from Port B are used to sible to connect the 7805 to a separate a separate programmer with a TQFP32 create the control signals for the two 9 V supply via pin 2 of JP1. This supply adapter and only then solder it onto the digital potentiometers on the analogue would have to be on at all times, other- board. board. These are Data out (PB1), Clock wise the preamp couldn’t be turned on • If you do want to program the AT- (PB2) and chip selects CS1 & CS2 (PB3 or off via the remote control. Should, for mega8 on-board, remember that the and PB4). It would have been possible some reason or other, the supply fail IR receiver and the connections to the to use only one chip select signal since then all settings will be saved in the analogue board use the same pins as the AD5290s can be daisy-chained and internal NVRAM of the ATmega (Bas- the ISP, so should not yet be connected. the data could be sent as 16 bits. How- com: ERAM). • From the Bascom source code can be ever, it was decided to keep them sep- As you can see, there are many options seen that the code for the mute com- arate as that would make it possible to for the power supply. The two NEC mand from the remote control is set add a balance control to the software PS710B-1A relays aren’t strictly neces- to 5 instead of the usual 13. This was (at this point in time it hasn’t been sary (they can be left out and replaced done because the author’s universal re- added yet). by a wire link across pins 4 and 6), but mote control didn’t have a mute function The ISP connector also connects to then the 12 V slave function will no in hifi mode. To get round this, the but- port B, but this shouldn’t require any longer be available. ton for input-5 was redefined as a mute further explanation. Connectors SV4 For the power supply a small mains button. and SV2 carry all connections between transformer with a secondary of the two boards. 2x12 V/7 VA is sufficient, along with a • Compiling the program yourself From the circuit diagram can be seen bridge rectifier and a few electrolytic has the advantage that you can customi- that the rotary encoder is connected capacitors. se the names of the inputs to your own to PB6 and PB7. The author used a liking. This also applies to the sensitivity SW-ROT-02 made by Voti, which has The source code is, as mentioned of the rotary encoder in relation to the a built-in push button that is used earlier, written in Bascom and can volume. here for the MUTEONOFF function. If be freely downloaded from the Ele- you decide to use a different type of ktor website as file # 090241-11.zip.

10/2009 - elektor 69 projects readers’ circuits

added to prevent drift. There are no decoupling capacitors anywhere in the signal path. In the prototype wire links have been used for C13 to C20, but these can be replaced by capacitors if you do not need DC coupling (this also depends on the output configuration of the connected audio equipment). The selected input signal also goes to buffers IC1b and IC2b. The output signal of these opamps can be used to drive a headphone amplifier or to pass the audio signals to another room. These outputs could also be used as a Record Out, but this function will rarely be used these days. The 100 Ω resistors (R19 and R20, as well as R22 and R23) are compensation resistors for longer cables. They also protect the opamps against momentary shorts on the outputs. IC4 and IC5 buffer and amplify the output signals from the digital potentiometers, from where it goes to the power amplifier. There are a number of resis- Figure 3. An example of an A/D board with a CS8416, which provides three digital inputs. tors (R15/R17/R13, R16/R18/R14) in the circuit that can be used to make the opamps amplify the signal, but in the original configuration this option It’s extensively documented by the four stereo inputs along with the relays wasn’t used (wire links for R15 to R18, author, which should make the code used to select them. At the centre are R13 and R14 are left out). The total volt- easy to follow. The code is too big for it the two digital potentiometers made age gain of the preamp is then 0 dB, to be compiled with the freeware ver- by Analog Devices. which is a good value for use with sion of Bascom, but this shouldn’t be IC1a and IC2a are both configured as modern audio signal sources. a problem considering the low cost of voltage followers and are used to buffer The types of opamp used are OPA604 a licence. the chosen input before it goes to the and OPA2604 (since the author had input of the de digital potentiometer. some available), which provide good Analogue section The input impedance of all inputs is quality audio signals. It is of course Everything needed to process the set to 47 kΩ with the help of a number of possible to use other (pin-compatible) audio signals can be found on the ana- resistors connected directly to the inputs (R1 types. All inputs work at line levels. If logue board. At the right of the circuit to R8). R9 and R10 on the non-invert- you want to connect a record player diagram (Figure 2) you can see the ing inputs of IC1a and IC2a have been you’ll need an extra phono preamp, but that should be fairly obvious.

Analogue and digital inputs a Since the author regularly thinks of modifications and enhancements for his designs, he has added a number of headers and jumpers to the circuit to permit various configurations and expansion options. The settings are as b follows: Input 1 is always an analogue input and can’t be changed. If you require 4 analogue inputs you should use the following jumper settings: c JPIN2-1, JPIN2-2, JPIN2-3 = short pins 1&2 JPIN3-1, JPIN3-2, JPIN3-3 = short pins 1&2 If you also want a digital input you Figure 4. Several examples of the display output: a. set the name of an input b. preset the volume for an input can add a DAC board and connect its c. show the volume level. outputs to input 4 (connector JPDAC).

70 elektor - 10/2009 You’ll then have three analogue inputs JPIN3-3. When input 3 is selected, front panel for the buttons, display and and one digital input available. RXSEL0 = 0 and RXSEL1 = 1. And IR receiver. But this can be taken one stage fur- when input 4 is selected, only K4 turns The board with the analogue circuit ther. With a CS8416 digital audio inter- on and RXSEL0 = 1, RXSEL1 = 1. In is mounted at the back of the case, so face receiver it is possible to set it to that case input RXP3 of the CS8416 is that the phono sockets poke through hardware mode and use the RXSEL0 selected. Bear in mind that analogue holes in the back. You can use rib- and RXSEL1 pins to drive the internal inputs 2, 3 and 4 are no longer availa- bon cable for the wiring between the S/PDIF input multiplexer. In this way ble in this configuration, since they’ve boards, since no audio signals are car- you can select one of the four digital been ‘replaced’ by the digital inputs of ried across them. inputs (RXP0 to RXP3). (Refer to the the CS8416 in Figure 3.

Figure 5. A quick look at the prototype. At the back on the right is a small D/A converter made by AMB (Y1 DAC, see www.amb.org).

example of such a circuit in Figure 3.) In the middle of the case there should If we now move the jumpers on JPIN2- Practical construction be room to mount a mains power sup- 1, JPIN2-2 and JPIN2-3 such that pins The author has designed PCBs for both ply, which could easily fit on an experi- 2&3 are connected, the switch signal circuits, which can be downloaded menter’s board. Do make sure that you for input 2 will be connected via D6 to from the Elektor website (Eagle format, keep a sufficient isolation clearance relay 4. This means that when input 2 file # 090241-1.zip). The construction between the primary and secondary is selected it will drive both relay 2 as of the preamp is quite straightforward, sides! well as relay 4. The audio output of the and the photos of the prototype can (090241-I) DAC will then be connected to IC1a be used as guidelines. The enclosure and IC2a via K4 and K2 ensures that for the circuit can be fairly small. The the RXSEL1 pin of the CS8416 is pulled controller board is mounted behind the low via JPIN2-3. The result: RXSEL0 = front panel, where the rotary encoder, 1, RXSEL1 = 0 and the respective dig- the setup switch, the four input selec- ital input in Figure 3 is selected. The tion buttons and the display are. You same applies to JPIN3-1, JPIN3-2 and will need to make suitable holes in the

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The instructions for this puzzle are straightforward. number of clues are given in the puzzle and these determine the start situation. In the diagram composed of 16 × 16 boxes, enter numbers All correct entries received for each month’s puzzle go into a such that all hexadecimal numbers 0 through F (that’s 0-9 and draw for a main prize and three lesser prizes. All you need to A-F) occur once only in each row, once in each column and in do is send us the numbers in the grey boxes. The puzzle is also each of the 4x4 boxes (marked by the thicker black lines). A available as a free download from the Elektor website

SOLVE HEXADOKU AND WIN! PARTICIPATE! Correct solutions received from the entire Elektor readership Please send your solution (the numbers in the grey boxes) by email to: automatically enter a prize draw for an [email protected] - Subject: hexadoku 10-2009 (please copy exactly). E-blocks Note: new email address as of this month! Include with your solution: full name and street address. Starter Kit Alternatively, by fax or post to: Elektor Hexadoku Professional Regus Brentford - 1000 Great West Road - Brentford TW8 9HH United Kingdom - Fax (+44) 208 2614447 worth £300 The closing date is 1 November 2009. and three Elektor SHOP PRIZE WINNERS Vouchers worth The solution of the July/August 2009 Hexamurai is: BCE56. £40.00 each. The E-blocks Starter Kit Professional goes to: We believe these prizes Arwin J.Vosselman (Netherlands). should encourage An Elektor SHOP voucher worth £40.00 goes to: all our readers to participate! Dominik Johe (Germany), Gareth Hayes (United Kingdom) The competition is not open to employees of Elektor International Media, en Michel-Hugues Michel (France). its business partners and/or associated publishing houses. Congratulations everybody!

ED2753C1A68F0B49 F5CA80E794B31D26 39482FB65D10EA7C B01 6A94DEC27F538 8C7EB634F901A25D 130 BE275DA4698CF D4AF9C8025 7E631B 5692D1FA38 CB7E0 4 7FE40A53B2 6CD98192C1AE83460BDF57 ABD9146273 E85CF0DA6374BC5F298E01 6285FE9C10DA47B3847B0F25E1AD3C69 013C78DB4F5926EAE0F56D19C73824AB 4A5DC 7098132BF6E5D4AB278FE1 C09 36 28F13BAE6794C0D5182FE956D073BAC4 9E604 528CBFD31A7690E43CF25B A17 D8 C7B36D1F0EA58492B C37D10A698 4F5 2E 674D9B0153AE8FC25670A9E34 1BDCAFE38527690 920E3A84DCF751B628 4ED 7CF0 3A958617BDFE24C AC1B5F2794860ED3F9 1 A 25B4C 7862B D09 A4E531F F358CE D612B0A974B3DC0681F5E237 941 C60AB8D 2ED71038FACB946532 B 8 1CFA7ED095 A28 4F6C1B3 C96 0F57A8D34B2E1DF C 9 7 308A654FC3B0DE19872 1BFADC4E652 973 80A4E 69D5B2F1C8047B3956DEA 5834629B70E 1DC FA105 74E263B9816EDA2C740F5 4FE687AD391 C20 5BED6 1FA7984C3B025 752CB419E608FA3D958B624CE0713FDA BA8103C24F5DE6974C2 358 10DAFB6E97 0D93E6F52B7A184C7A0 FEB 3D9265841C 8079AD53C16F4B2E8BE 419 0536D7A2CF E6C548B0A7923D1F2FA7CED8B1940653 34AF21ECB8D56709563924BFAC0 ED7 81 D1B2796F0E43C5A8C01D36A7582F49EB B3CA9DF26750E1 48 D4F503861EA27CB9 1E72BC5A4389FD60 689071E4FDBC53A2 37B840CE251D9AF6 F14EA52B7936C80D A95CD7610FE82B34 02D68F93CB4A157E

74 elektor - 10/2009

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10/2009 - elektor 75

0910_elektor_adv_UK.indd 75 10-09-2009 11:14:53 INFOTAINMENT RETRONICS

Philbrick K2-W, the mother of all op amps

GAP/R vintage K2-W, K2-X and K2-P op amps. (Author’s collection) Embree Electronics C/50 op amp (opened up for curiosity), GAP/R ‘Computor’ tube and GAP/R ‘Airpax’ A-175 DC-to-AC chopper. (Author’s collection)

By Jan Didden Julie at Columbia University con- commercial use as well. The fi rst differential pair and causes a (The Netherlands) sulted for the George A Philbrick device was the K2-W shown in differential output signal at the Researches company (GAP/R), Figure 1. To this day the circuit anodes. The second pair buffers One popular belief among the to develop the electronic mod- confi guration is the basis of many this signal with cathode-follow- all-transistor generation of elec- ule for a bombing simulator high-gain, balanced-input circuits ers and provides a single-ended tronics enthusiasts is that opera- which GAP/R was developing including the balanced differen- output. Later circuits improved tional amplifi ers (op amps) came for the US Armed Forces. It was tial stage, cathode-coupled with on this with, for instance, a real after engineers learned to put Philbrick who saw the commer- a large cathode resistor acting current source to bias the input many transistors on a chip car- cial potential, and from 1952 as a current source. A differen- pair (which came to be known as rier. In fact, op amps are much GAP/R offered its op amps for tial-input signal unbalances the a ‘long-tailed pair’) and differ- older. ential outputs, see Figure 2. For As with many technologies, the amusement only, if you compare development of op amps was this to the circuit in Figure 3 of initially strongly driven by mili- an NE5532 op amp, the pedi- tary requirements. World War 2 gree is clear. saw developments in largely mechanical contraptions for The K2-W used bipolar sup- mathematical problems like plies of ±300 V. The output aiming anti-aircraft guns and could swing about ±50V peak, calculating the optimum point to and in this spec at least mod- release bombs over enemy tar- ern op amps are a big step gets. Functionally, the devices backwards! Other specs were consisted mostly of amplifiers, not so hot. The bandwidth was integrators and differentiators; about 100 kHz with a 2 µs rise very complex instruments com- time, and an open-loop gain

prising, for instance, gear wheels of 15,000. Rout was specifi ed as with logarithmically-arranged about 1 kOhms. cogs. These were phased out gradually and replaced with But the specs itself were of lesser electronic function blocks called importance compared to the operational amplifi ers: amplifi er concept behind these units. K2- blocks that could be confi gured W’s were built as plug-in units to perform an operation: ampli- that could be configured for fi cation, summing, differentiation a specifi c function by the user: and integration to name just the real operational amplifi ers! They simplest ones. The fi rst op amp were generally not supposed to type circuit design published be used open-loop, but with a was probably by Lovell and Par- feedback circuit to obtain the kinson of Bell Labs for the M9 desired transfer function. Just anti-aircraft gun director built by like today’s op amps, several dif- Western Electric. Later on, Loebe Fig 1. GAP/R K2-W opamp schematic diagram. You could easily build this yourself. ferent versions were developed

76 elektor - 10/2009

UK0910_76_77_090276_UK_Retronics76 76 10-09-2009 11:44:45 that had slightly different specs Semiconductor, wrote Philbrick’s for different tradeoffs in the fi nal very fi rst application note num- product: after the K2-W came the bered ‘R1’. Bob’s stories about K2-X, K2-XA and the K2-P. The his early years at GAP/R can be K2-XA had double the speed, found at [3]. double the bandwidth, double Capt. Clarence L Johnson, an the output swing and double the engineer with the US Air Force gain of the K2-W. These op amps and Professor at the Depart- all shared the same base socket ment of Mathematics at the Air connections and could be freely Force Institute of Technology, interchanged, similar to today’s wrote “Analog Computer Tech- ‘universal’ op amp pinouts. The niques”, published in 1956. This tubes used in the Philbrick units book gives a fascinating insight were dual triodes of the 12AX7, into the use of op amps to actu- 12AU7 12AT7 (ECC83, ECC82, ally ‘simulate’ (as it was called) ECC81) family. There were also electromechanical problems, as some specialised plug-in units well as their use in complex con- like mechanical choppers that stellations of electromechanical could take the place of the fi rst servos and electronic op amps. double triode to make the unit Figure 2. Tube-based ‘long tailed pair’. Figure 4 shows a simple cir- into a DC amplifier. Philbrick cuit to generate a logarithmic also selected tubes for tighter function. specs and these were stamped with the company name and While the military prompted the the indication ‘Computor Tube’. developments of tube op amps, GAP/R consequently used ‘com- they could also be relied on to putor’ in these days, not ‘compu- keep using them for a long, long ter’. A wealth of information on time. The Nike anti-aircraft mis- these and other Philbrick prod- sile system used tube op amps ucts may be found at Joe Sou- and wasn’t scrapped from NATO sa’s site [2]. inventory until the late 1990s. I found some NOS K2-W’s gath- With the success of these op ering dust at a military depot/ amps, competitors tried to jump repair unit that fi nally got rid of the bandwagon, of course. One their stock in 2003. outfi t, Embree Electronics Corp. offered the C/50/BP, very similar We often see the monolithic to the Philbrick units, except that opamp as a revolution in elec- mechanically it was different, and tronics. But with the concept of it could be opened up for repair operational amplifiers firmly if necessary. Philbrick’s units rooted in vacuum tube technol- could not; apparently they had Figure 3. Internal schematic of the industry standard NE5532 monolithic opamp. ogy on the one hand, and the enough trust in their products to rapid development of the tran- believe that repair would not be sistor and the integrated circuit necessary over the lifetime of the on the other, monolithic op amps unit, or maybe the price was low were just the next logical step in enough (for the military) to treat a technological evolution, and it as a consumable rather than a perhaps less than a conceptual repairable item. Another similar- breakthrough. ity to modern IC op amps. (090276-I)

GAP/R took the concept one step further and developed a sort of Internet Links universal unit that would take up [1] www.philbrickarchive.org/ to three op amp plug-ins plus an k3_series_components.htm additional tube, the K3. This unit [2] www.philbrickarchive.org/ offered a higher level of integra- [3] www.national.com/rap/ tion and was actually called an ‘analog computor’, see [1]. Author email: With the development of the [email protected] op amp, application notes and books on how to use them started Further Reading to appear as well. One early Analog Computer Techniques, GAP/R engineer, Bob Pease who Clarence L Johnson, until recently worked at National Figure 4. Using op amps to obtain the logarithmic of an input signal. McGraw-Hill, 1956

Retronics is a monthly column covering vintage electronics including legendary Elektor designs. Contributions, suggestions and requests are welcomed; please send an email to [email protected]

10/2009 - elektor 77

UK0910_76_77_090276_UK_Retronics77 77 10-09-2009 11:44:52 ELEKTORSHOWCASE To book your showcase space contact Huson International Media Tel. 0044 (0) 1932 564999 Fax 0044 (0) 1932 564998

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78 elektor - 10/2009

0910_elektor_adv_UK.indd 78 10-09-2009 11:14:55 products and services directory

ROBOT ELECTRONICS USB INSTRUMENTS www.elektor.com http://www.robot-electronics.co.uk http://www.usb-instruments.com Advanced Sensors and Electronics for Robotics USB Instruments specialises • Ultrasonic Range Finders in PC based instrumentation • Compass modules products and software such • Infra-Red Thermal sensors as Oscilloscopes, Data MQP ELECTRONICS • Motor Controllers Loggers, Logic Analaysers www.mqp.com • Vision Systems which interface to your PC via USB. • Low cost USB Bus Analysers • Wireless Telemetry Links • High, Full or Low speed captures • Embedded Controllers • Graphical analysis and filtering VIRTINS TECHNOLOGY • Automatic speed detection www.virtins.com • Bus powered from high speed PC PC and Pocket PC based virtual instrument such • Capture buttons and feature connector ROBOTIQ as sound card real time • Optional analysis classes http://www.robotiq.co.uk oscilloscope, spectrum Build your own Robot! analyzer, signal generator, Fun for the whole family! multimeter, sound meter, • MeccanoTM Compatible distortion analyzer, LCR meter. RFID COMPONENTS • Computer Control Free to download and try. http/www.apdanglia.org.uk • Radio Control For DIY, OEM's & Experimenters • Tank Treads • EM4100 Cards .99 p (Prices inc vat) • Hydraulics CANDO – CAN BUS ANALYSER • Keyfobs £1.09 Internet Technical Bookshop, http://www.cananalyser.co.uk • R/W Keyfobs £1.65 1-3 Fairlands House, North Street, Carshalton, • USB to CAN bus interface • RFID Coils £2.95 Surrey SM5 2HW • USB powered • RFID PCB email: [email protected] Tel: 020 8669 0769 • FREE CAN bus analyser S/W with RS232 port • Receive, transmit & log. • RFID IC’s EM4095 - U2270B CAN messages • microRFID module (similar to Core ID12) • ISO11898 & CAN • Free Reader download - Technical pages 2.0a/2.0b compliant Order online 24 hrs - Tel: 01244 520684 www.elektor.com • Rugged IP67 version available

SHOWCASE YOUR COMPANY HERE Elektor Electronics has a feature to help • For just £242 + VAT (£22 per issue for image - e.g. a product shot, a screen shot customers promote their business, eleven issues) Elektor will publish your from your site, a company logo - your Showcase - a permanent feature of the company name, website address and a choice magazine where you will be able to showcase 30-word description your products and services. • For £363 + VAT for the year (£33 per Places are limited and spaces will go on issue for eleven issues) we will publish a strictly first come, first served basis. the above plus run a 3cm deep full colour So-please fax back your order today!

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10/2009 - elektor 79

0910_elektor_adv_UK.indd 79 10-09-2009 11:15:00 SHOP BOOKS, CD-ROMS, DVDS, KITS & MODULES Going Strong

New! A world of electronics Home electric power Your own Eco-Electrical from a single shop! Home Power System This book provides the semi-technical, power-conscious homeowner a place to begin in the quest for home electric power. Both the essential principles and detailed information on how to build or maintain a home electric system off the utility grid are NEW! presented in an easy-going style. This booklet will help you to safeguard or develop your own home electricity supply. It contains step-by-step calculations, practical details, examples, electric system problems with emedies and much more.

96 pages • ISBN 978-0-905705-82-8 £16.50• US $26.00

Limited Period Offer for Subscribers!

£4 DISCOUNT Bring your microcontroller to life www.elektor.com/october FullyArtiﬁ elaborated cial electronics Intelligence projects 309 Circuits Look into the electronics of eco-power This book contains 23 special and exciting Theartificial present intelligence tenth edition machine-lear of the popularning Practical Eco-Electrical Home Power Electronics ‘30xprojects, Circuits’ for microcontroller series of books and once PC. again Learn This book “opens the hood” and looks into the electronics of eco-power. Explained from circuit dia- containshow to set a up comprehensive a neural network variety in a micro-of cir- grams of commercially-available products are the electronics of affordable eco-electrical power cuits,controller, sub-circuits, and how tips to andmake tricks the andnetwork de-

Books components such as solar chargers, battery inverters, and off-line chargers. Not only are circuits signself-learning. ideas for Or electronics. discover how Among changing many a analysed in detail, design modifi cations are presented, and basic design principles applied so that otherfi tness inspiring function resultstopics, in the a totallyfollowing diffe cat- rent you can do your own improvements and achieve high performance at low cost. The effects of vari- egoriesbe ha vior. are Several well artifipresented cial intelligence in this book: tech- ous kinds of loads on the power distribution lines reveal potential problems and insights. Included testniques & measurement;are discussed: expert RF (radio); system, neuralcom- are power circuits useful to homesteaders, such as LED and fl uorescentlamp drivers, optimal wind putersnetwork, and subsumption, peripherals; emerging audio & behav-video; converters, and improved system-level architecture for eco-power. The book ends with an alterna- hobbyior, genetic and modelling;algorithm, cellular microcontrollers; auto mata. tive solar power technique based on thermal instead of photovoltaic conversion, using thermoelec- homeroulette & brains garden; etc. etcetera. tric modules, and storing energy in a tank instead of batteries. 432256 pages • ISBN 978-0-905705-69-9978-0-905705-77-4 192 pages • ISBN 978-0-905705-83-5 • £24.90 • US $39.90 £19.95£32.00 • US $39.95$46.00

Prices and item descriptions subject to change. E. & O.E

80 elektor - 10/2009

ELEK UK0910 shop.indd 80 12-08-2009 16:50:01 Bestseller!

Learn by doing Learn more about C# programming and .NET See the light on Solid State Lighting C Programming C# 2008 and DVD LED Toolbox for Embedded Microcontrollers .NET programming This DVD-ROM contains carefully-sorted comprehensive technical documentation If you would like to learn the C Program- for Electronic Engineers about and around LEDs. For standard ming language to program microcon- This book is aimed at Engineers and models, and for a selection of LED mod- trollers, then this book is for you. No pro- Scientists who want to learn about the ules, this Toolbox gathers together data gramming experience is necessary! You’ll .NET environment and C# programming sheets from all the manufacturers, ap pli- start learning to program from the very or who have an interest in interfacing cation notes, design guides, white papers fi rst chapter with simple programs and hardware to a PC. The book covers the and so on. It offers several hundred dri- slowly build from there. Initially, you pro- Visual Studio 2008 development environ- vers for powering and controlling LEDs in gram on the PC only, so no need for de- ment, the .NET framework and C# pro- different configurations, along with dicated hardware. This book uses only free gramming language from data types and ready-to-use modules (power supply or open source software and sample pro- program fl ow to more advanced concepts units, DMX controllers, dimmers, etc.). In grams and exercises can be downloaded including object oriented programming. It addition to optical systems, light detec- from the Internet. continues with program debugging, fi le tors, hardware, etc., this DVD also ad- 324 pages • ISBN 978-0-905705-80-4 handling, databases, internet communi- dresses the main shortcoming of power £32.50 • US $52.00 cation and plotting before moving to hard- LEDs: heating. Of course, this DVD con- ware interfacing using serial and parallel tains several Elektor articles (more than ports and the USB port. It includes a hard- 100) on the subject of LEDs. ware design for a simple oscilloscope using a parallel port and interfa cing to ISBN 978-90-5381-245-7 • £28.50 • US $54.00 analogue and digital I/O using the USB port. This book is complete with many program examples, self assessment exercises and references to supporting videos.

240 pages • ISBN 978-0-905705-81-1 £29.50 • US $44.50 Bestseller! More information on the Creative solutions for all areas of electronics Elektor Website: 310 Circuits All articles published in 2008 310 Circuits, tips and design ideas in one www.elektor.com DVD Elektor 2008 book form a treasure trove for every area This DVD-ROM contains all editorial arti- Elektor of electronics: audio and video, hobby cles published in Volume 2008 of the Regus Brentford and modelling, RF techniques, home and English, Spanish, Dutch, French and Ger-

garden, test and measurement, microcon- 1000 Great West Road man editions of Elektor magazine. Using CD/DVD-ROMs trollers, computer hardware and software, Brentford Adobe Reader, articles are presented in power supplies and chargers – plus of TW8 9HH the same layout as originally found in course everything else that does not seem United Kingdom the magazine. The DVD is packed with to belong in any of these categories. 310 features including a powerful search en- Tel.: +44 20 8261 4509 Circuits contains many complete solutions gine and the possibility to edit PCB layouts Fax: +44 20 8261 4447 as well as useful starting points for your with a graphics program, or printing hard own projects. Email: [email protected] copy at printer resolution.

544 pages • ISBN 978-0-905705-78-1 ISBN 978-90-5381-235-8 • £17.50 • US $35.00 £29.90 • US $45.00

10/2009 - elektor 81

ELEK UK0910 shop.indd 81 12-08-2009 16:50:12 SHOP BOOKS, CD-ROMS, DVDS, KITS & MODULES

Incl. searchable i-TRIXX archive OBD Analyser NG The 32-bit Machine DVD i-TRIXX (September 2009) (April 2009) Freeware Collection 2009 This DVD contains 100 nifty freeware The compact OBD2 Analyser in the June With this attractively priced starter kit you applications, tools and utilities for the Win- 2007 issue was an enormous success – get everything you need for your ﬁ rst hands- dows PC. And as a free extra, it contains not surprising for an affordable handheld on experiments with the new R32C/ the full and searchable (!) i-TRIXX archive, onboard diagnostics device with automa- 111 32-bit microcontroller. The power sup- CD/DVD-ROMs with all the editions up until week 8 of tic protocol recognition and error codes ply is drawn from your computer via the 2009 from i-TRIXX, the e-magazine pub- explained in plain language. Now enhan- USB connection, which simplifies things lished by Elektor. Do you feel the need for ced with a graphical display, Cortex M3 rather nicely. The starter kit consists of an a decent and reliable antivirus program? processor and an Open Source user inter- R32C carrier board (a microcontroller A bandwidth monitor which keeps track of face, the next generation of Elektor’s stan- module equipped with the R32C/111 chip) your current up and download rate? An dalone analyser sets new standards for a and a software CD-ROM containing application for recording, editing and con- DIY OBD2 project. The key advantage of the necessary development tools. As with verting video to any conceivable format? this OBD2 Analyser NG is that it’s self- the earlier R8C/13 ‘Tom Thumb’ project in Anonymous surfing from any internet contained and can plug into any OBD Elektor Electronics (November 2005 access point from a USB stick? Checking, diagnostic port. through March 2006), the R32C carrier optimizing and cleaning up your com- board is an in-house-development of Glyn, puter? Keeping track of your privacy? You Kit of parts including DXM Module, PCB an authorised distributor for Renesas in can expect that and much more in the SMD-preﬁ tted, case, mounting materials Germany. i-TRIXX Freeware Collection 2009. and cable R32C/111 Starterkit (32-bit-Controller- Art.# 090451-71 • £84.00 • US $135.00 ISBN 978-90-5381-244-0 • £27.50 • US $39.50 board & CD-ROM)

Art.# 080928-91 • £27.00 • US $42.50

Bestseller! Completely updated Elektor’s Components Experimenting Automotive CAN controller Database 5 with the MSP430 (April 2009) (May 2009) The program package consists of eight Since cars contain an ever increasing databanks covering ICs, germanium and All the big electronics manufacturers su- amount of electronics, students learning silicon transistors, FETs, diodes, thyristors, pply microcontrollers offering a wide ran- about motor vehicle technology also need Kits & Modules triacs and optocouplers. A further eleven ge of functions. Texas Instruments supplies to know more about electronics and mi- applications cover the calculation of, for ex- handy USB evaluation sticks with related crocontrollers. In collaboration with the ample, LED series droppers, zener diode software for its low-cost MSP430 contro- Timloto o.s. Foundation in the Nether- series resistors, voltage regulators and llers. Unfortunately the I/O facilities are lands, Elektor designed a special control- AMVs. A colour band decoder is included somewhat limited. These can be substan- ler PCB, which will be used in schools in for determining resistor and inductor val- tially enhanced with the help of the Elektor several countries for teaching students ues. ECD 4 gives instant access to data on MSP430 board. about automotive technologies. But it can more than 69,000 components. All data- also be used for other applications, of bank applications are fully interactive, al- PCB, populated and tested course. The heart of this board is an Atmel lowing the user to add, edit and complete Art.# 080558-91 • £35.00 • US $55.00 AT90CAN32 with a fast RISC core. component data. This CD-ROM is a must- have for all electronics enthusiasts. TI eZ430-F2013 Evaluation Kit Kit of parts, incl. PCB with SMDs preﬁ tted

ISBN 978-90-5381-159-7 • £24.90 • US $39.50 Art.# 080558-91 • £24.50 • US $35.00 Art.# 080671-91 • £52.00 • US $79.00

Prices and item descriptions subject to change. E. & O.E

82 elektor - 10/2009

ELEK UK0910 shop.indd 82 12-08-2009 16:50:21 October 2009 (No. 394) £ US $ + + + Product Shortlist October: See www.elektor.com + + + September 2009 (No. 393) R32C Application Board Bestsellers 310 Circuits 080082-71 ....Kit of parts including Application Board with 1 ISBN 978-0-905705-78-1 ...... £29.90 .....US $45.00 SMD parts preﬁ tted, plus all other components ...... see www.elektor.com 080928-91 ....R32C Starterkit: Processor board populated and tested, C# 2008 and .NET programming Toolchain on CD ...... 27.00 ...... 42.50 2 ISBN 978-0-905705-81-1 ...... £29.50 .....US $44.50 OBD Analyser NG 090451-71 ....Kit of parts including DXM Module, PCB SMD-preﬁ tted, Elektor Personal Organizer 2010

case, mounting materials and cable ...... 84.00 ...... 135.00 Books 3 ISBN 978-90-5381-247-1 ...... £24.90 .....US $41.90 Battery Monitor 030451-72 ....LC display ...... 11.00 ...... 15.00 C Programming for Embedded Microcontrollers 080824-1 ...... Printed circuit board ...... 12.90 ...... 18.75 4 ISBN 978-0-905705-80-4 ...... £32.50 .....US $52.00 080824-41 ....Programmed controller LPC2103 ...... 16.50 ...... 24.00 July/August 2009 (No. 391/392) Artiﬁ cial Intelligence Books 5 ISBN 978-0-905705-77-4 ...... £32.00 .....US $46.00

Product Shortlist Product Luxeon Logic 081159-41 ....Programmed controller ATtiny25 ...... 6.40 ...... 10.50 Programmable Nokia RTTTL Player DVD LED Toolbox CD-ROMs 1 ISBN 978-90-5381-245-7 ...... £28.50 .....US $54.00 090243-41 ....Programmed Attiny13 ...... 6.40 ...... 10.50 Breadboard/Perfboard Combo ECD 5 080937-1 ...... Printed circuit board ...... 25.50 ...... 42.00 2 ISBN 978-90-5381-159-7 ...... £24.90 .....US $39.50 Annoy-a-Tron 090084-41 ....Programmed controller ATtiny13 ...... 6.40 ...... 10.50 DVD Elektor 1990 through 1999 Fan Speed Controller 3 ISBN 978-0-905705-76-7 ...... £69.00 .....US $99.00 070579-41 ....Programmed controller ATtiny13 ...... 7.70 ...... 12.60 Floating Message DVD Elektor 2008 080441-41 ....Programmed controller PIC16F616 ...... 6.40 ...... 10.50 Kits & Modules 4 ISBN 978-90-5381-235-8 ...... £17.50 .....US $35.00 Pulse Clock Driver with DCF Synchronisation 090035-41 ....Programmed PIC16F648A...... 7.70 ...... 12.60 DVD i-TRIXX Freeware Collection Frequency and Time Reference with ATtiny2313 CD/DVD-ROMs 5 ISBN 978-90-5381-244-0 ...... £27.50 .....US $39.50 080754-41 ....Programmed ATtiny2313, 20 MHz conﬁ guration ...... 7.70 ...... 12.60 PIC Detects Rotation Direction MSP430: PCB, populated and tested 081164-41 ....Programmed PIC12F509A...... 6.40 ...... 10.50 1 Art. # 080558-91 ...... £35.00 .....US $55.00 Simple Temperature Measurement and Control 090204-41 ....Programmed controller ATmega48 ...... 7.70 ...... 12.60 USB Radio Terminal Two-button Digital Lock 2 Art. # 071125-71 ...... £7.20 .....US $11.50 090127-41 ....Programmed ATtiny2313 ...... 7.70 ...... 12.60 MSP430: TI eZ430-F2013 Evaluation Kit Full-colour Night-ﬂ ight Illumination 3 080060-41 ....Programmed controller PIC12F675 ...... 6.40 ...... 10.50 Art. # 080558-92 ...... £24.50 .....US $35.00 Chill Out Loud 080700-41 ....Programmed controller PIC12F629 ...... 6.40 ...... 10.50 ElektorWheelie 4 Art. # 090248-71 ...... £1380.00 .US $2275.00 USB Radio Terminal 071125-71 ....868 MHz assembled and tested module ...... 7.30 ...... 11.90

080068-91 ....Assembled and tested R8C Board with USB ...... 55.00 ...... 82.50 Kits & Modules The 32-bit Machine 5 Art. # 080928-91 ...... £27.00 .....US $42.50 Digital Sweep and Sinewave Generator 080577-41 ....Programmed ATmega48-20PV ...... 6.40 ...... 10.50 June 2009 (No. 390) Campsite AC Monitor Order quickly and securely through 060316-1 ...... Printed circuit board ...... 21.50 ...... 30.00 ATM18 = RFID Savvy www.elektor.com/shop 080910-91 ....PCB, partly populated PCB populated with all SMDs ...... 16.50 ...... 26.00 May 2009 (No. 389) or use the Order Form near the end Experimenting with the MSP430 080558-91 ....PCB, populated and tested ...... 35.00 ...... 55.00 of the magazine! 080558-92 ....TI eZ430-F2013 Evaluation Kit ...... 24.50 ...... 35.00 RGB LED Driver 080178-41 ....Programmed controller ...... 8.90 ...... 13.75 Elektor April 2009 (No. 388) Regus Brentford 1000 Great West Road The 32-bit Machine Brentford TW8 9HH • United Kingdom 080928-91 ....R32C/111 Starterkit Tel. +44 20 8261 4509 (32-bit-Controllerboard & CD-ROM) ...... 27.00 ...... 42.50 Fax +44 20 8261 4447 Email: [email protected]

10/2009 - elektor 83

ELEK UK0910 shop.indd 83 12-08-2009 16:50:30 INFO & MARKET COMING ATTRACTIONS NEXT MONTH IN ELEKTOR

Blue LEDs fi ght winter blues During the wintertime many people suffer from tiredness and a general lack of energy. The effect is caused by lack of sunlight, among others. Recent studies indicate that these negative effects can be largely prevented by a controlled, daily dose of blue light. Our winter blues fi ghter circuit contains no fewer than 84 LEDs capable of emitting a considerable amount of blue light. Half an hour’s exposure on a daily basis should be suffi cient to make you feel better and fi tter. The circuit contains a PWM system for the brightness control, as well as a programmable timer with a range of 4 to 30 minutes, not forgetting a display showing the remaining ‘on’ time.

Soldering station with measurement function This project shows that it’s still economical to retro-ﬁ t a simple temperature control to a common 30-watt solder iron. The core of the circuit is a PIC18F4520 microcontroller employing pulsewidth modulation to regulate the energy supply to the solder iron. Settings are shown on a two-line LC display. An additional feature of the circuit is its two measurement inputs allowing two direct voltages to be measured (0–10 V and 0–40 V) and of course displayed. These channels employ the PIC’s internal A/D converters.

R32C webserver As promised in the September 2009 issue we’ll present a small module for the R32C experimenter’s board that’s sure to extend the CPU’s communicative skills considerably. We’re talking about an Ethernet network module comprising a hard-wired TCP/IP chip with a 10/100 Mbit/s interface, a network connector with a transformer and status LEDs. The project enables a webserver or another Internet application to be implemented without bothering about details like the TCP/IP protocol.

Article titles and magazine contents subject to change, please check ‘Magazine’ on www.elektor.com The November 2009 issue comes on sale on Thursday, October 22, 2009 (UK distribution only). UK mainland subscribers will receive the issue between October 17 and 20, 2009. ww.elektor.com www.elektor.com www.elektor.com www.elektor.com www.elektor. Elektor on the web All magazine articles back to volume 2000 are available online in pdf format. The article summary and parts list (if applicable) can be instantly viewed to help you positively identify an article. Article related items are also shown, including software downloads, circuit boards, programmed ICs and corrections and updates if applicable. Complete magazine issues may also be downloaded. In the Elektor Shop you’ll ﬁ nd all other products sold by the publishers, like CD-ROMs, kits and books. A powerful search function allows you to search for items and references across the entire website.

Also on the Elektor website: • Electronics news and Elektor announcements • Readers Forum • PCB, software and e-magazine downloads • Surveys and polls • FAQ, Author Guidelines and Contact

84 elektor - 10/2009

preview-UK 10-2009.indd 84 10-09-2009 11:45:19

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SubscriptionOrder Form10-2009 Order Form10-2009 EL10 Email EL10 Tel. Address +Post code Name shown heresupersedethoseinpreviousissues.E.&O.E. without priornotification.Pricesanditemdescriptions therighttochangeprices The publishersreserve Prices anditemdescriptionssubjecttochange. e. Eal Email Tel. Address +Post code Name Description Free ElektorCatalogue2009 DVD LED Toolbox C# 2008and.NET 310 Circuits Elektor Personal Organizer 2010 Home Power System Your own Eco-Electrical Home Power System Practical Eco-Electrical for Electronic Engineers 2GB MP3player andreceive afree to Elektor Yes, Iamtakingoutanannualsubscription I would like: Seereverse for rates andconditions. thelast12months. toElektorduring Offer subjecttoavailability. * Offer available whohave toSubscribers notheldasubscription + exclusive accesstowww.elektor-plus.com) (11 issuesplustheElektor Volume 2009CD-ROM Subscription-Plus Standard Subscription(11issues) rc ah t. oa OrderCode Total Qty. Priceeach ae Signature Date – Signature Date – programming

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All orders, except for subscriptions (for which see below), must be sent BY POST or FAX to our Brentford address using the Order Form overleaf. Online ordering: www.elektor.com/shop Readers in the USA and Canada should send orders, except for subscriptions (for which see below), to the USA address given on the order form. Please apply to Elektor US for applicable P&P charges. Please allow 4-6 weeks for delivery. Orders placed on our Brentford office must include P&P charges (Priority or Standard) as follows: Europe: £6.00 (Standard) or £7.00 (Prio rity) Outside Europe: £9.00 (Standard) or £11.00 (Priority)

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Delivery Although every effort will be made to dispatch your order within 2-3 weeks from receipt of your instructions, we can not guarantee this time scale for all orders. Returns Faulty goods or goods sent in error may be returned for replacement or refund, but not before obtaining our consent. All goods returned should be packed securely in a padded bag or box, enclosing a covering letter stating the dispatch note number. If the goods are returned because of a mistake on our part, we will refund the return postage. Damaged goods Claims for damaged goods must be received at our Brentford office within 10-days (UK); 14-days (Europe) or 21-days (all other countries). Cancelled orders All cancelled orders will be subject to a 10% handling charge with a minimum charge of £5.00. Patents Patent protection may exist in respect of circuits, devices, components, and so on, described in our books and magazines. Elektor does not accept responsibility or liability for failing to identify such patent or other protection. Copyright All drawings, photographs, articles, printed circuit boards, programmed integrated circuits, diskettes and software carriers published in our books and magazines (other than in third-party advertisements) are copyright and may not be reproduced or transmitted in any form or by any means, including photocopying and recording, in whole or in part, without the prior permission of Elektor in writing. Such written permission must also be obtained before any part of these publications is stored in a retrieval system of any nature. Notwithstanding the above, printed-circuit boards may be produced for private and personal use without prior permission. Limitation of liability Elektor shall not be liable in contract, tort, or otherwise, for any loss or damage suffered by the purchaser whatsoever or howsoever arising out of, or in connexion with, the supply of goods or services by Elektor other than to supply goods as described or, at the option of Elektor, to refund the purchaser any money paid in respect of the goods. Law Any question relating to the supply of goods and services by Elektor shall be determined in all respects by the laws of England. January 2009

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Please note that new subscriptions take about four weeks from HOW TO PAY receipt of order to become effective. Cancelled subscriptions will be subject to a charge of 25% (twenty-five per cent) of the full subscription price or £7.50, Bank transfer into account no. 40209520 held by Elektor Electronics. whichever is the higher, plus the cost of any issues already with ABN-AMRO Bank, London. IBAN: GB35 ABNA 4050 3040 2095 20. dispatched. Subsciptions cannot be cancelled after they have BIC: ABNAGB2L. Currency: sterling (UKP). Please ensure your full name run for six months or more. and address gets communicated to us. Cheque sent by post, made payable to Elektor Electronics. We can only accept sterling cheques and bank drafts from UK-resident customers or subscribers. We regret that no cheques can be accepted from customers or subscribers in any other country. Giro transfer into account no. 34-152-3801, held by Elektor Electronics. Please do not send giro transfer/deposit forms directly to us, but instead use the National Giro postage paid envelope and send it to your National Giro Centre. Credit card VISA and MasterCard can be processed by mail, email, web, fax and telephone. Online ordering through our website is SSL- protected for your security. January 2009

ELEK UK09010 Orderform.indd 2 12-08-2009 16:45:41 Visit China with Elektor combine electronics and culture

Elektor’s next Study Trip to China is planned for 7-16 November 2009. And you can join us! Programme: Check your diary today and visit the Elektor website for more detailed information. – A visit to the China Electronics Fair in Shanghai – Shopping in electronics department stores – Company visits – Conference about doing business in China – Culture: The Great Wall, The Temple of Heaven, The Forbidden City, Tiananmen square and The Shanghai TV tower – A cycling tour through Beijing

Further information at www.elektor.com/china

INDEX OF ADVERTISERS

Antex Electronics Ltd ...... www.antex.co.uk...... 13 Microchip ...... www.microchip.com/8bit ...... 25

APD, Showcase ...... www.apdanglia.org.uk...... 79 MikroElektronika...... www.mikroe.com ...... 3

Avit Research, Showcase...... www.avitresearch.co.uk ...... 78 MQP Electronics, Showcase...... www.mqp.com ...... 79

Beijing Draco Electronics Ltd ...... www.ezpcb.com ...... 53 Netronics, Showcase ...... www.cananalyser.co.uk...... 79

Bitscope Designs ...... www.bitscope.com ...... 2 Newbury Electronics ...... www.newburyelectronics.co.uk...... 75

Black Robotics, Showcase...... www.blackrobotics.com ...... 78 Nurve Networks ...... www.xgamestation.com ...... 75

ByVac, Showcase ...... www.byvac.com ...... 78 Parallax ...... www.parallax.com...... 31

Decibit Co. Ltd, Showcase ...... www.decibit.com ...... 78 PCBCORE ...... www.pcbcore.com ...... 53

Designer Systems, Showcase ...... www.designersystems.co.uk...... 78 Peak Electronic Design...... www.peakelec.co.uk ...... 42

EasyDAQ, Showcase ...... www.easydaq.biz ...... 78 Pico...... www.picotech.com/scope1036...... 19

Easysync, Showcase ...... www.easysync.co.uk...... 78 Quasar Electronics...... www.quasarelectronics.com ...... 47

Elnec, Showcase ...... www.elnec.com ...... 78 Robot Electronics, Showcase...... www.robot-electronics.co.uk...... 79

Eurocircuits ...... www.eurocircuits.com ...... 75 Robotiq, Showcase ...... www.robotiq.co.uk ...... 79

First Technology Transfer Ltd, Showcase . . www.ftt.co.uk ...... 78 Showcase ...... 78, 79

FlexiPanel Ltd, Showcase...... www.flexipanel.com ...... 78 Schaeffer AG ...... www.schaeffer-ag.de ...... 53

Future Technology Devices, Showcase. . . . www.ftdichip.com...... 78 USB Instruments, Showcase ...... www.usb-instruments.com ...... 79

Good Will Instruments ...... www.gwinstek.com...... 65 Virtins Technology, Showcase ...... www.virtins.com ...... 79

Hameg, Showcase...... www.hameg.com ...... 78

HexWax Ltd, Showcase ...... www.hexwax.com ...... 78 Advertising space for the issue 19 November 2009 may be reserved not later than 20 October 2009 Labcenter...... www.labcenter.com...... 88 with Huson International Media - Cambridge House - Gogmore Lane - Lcdmod Kit, Showcase ...... www.lcdmodkit.com ...... 78 Chertsey, Surrey KT16 9AP - England - Telephone 01932 564 999 - Fax 01932 564 998 - e-mail: [email protected] to whom all London Electronics College, Showcase . . . www.lec.org.uk...... 78 correspondence, copy instructions and artwork should be addressed.

0910_elektor_adv_UK.indd 87 10-09-2009 11:15:02 GO FASTER WITH PROTEUS PCB DESIGN The latest version of the Proteus Design Suite harnesses the power of your computer’s graphics card to provide lightning fast performance. Together with unique transparency options it’s now easier than ever to navigate and understand large, multi-layer boards.

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0910_elektor_adv_UK.indd 88 10-09-2009 11:15:03