BRANCO JUSTIC and PETER PHILLIPS NIGHT-VISION SCOPES WERE DE- veloped as military surveillance devices to permit viewing en­ emy activities and aiming weap­ ons al night without revealing the observer's presence. The sensitivities of their principal components, image tubes, have been improved with fiber-optic lenses, more gain stages and better pbotocathodes. in addi­ tion, miniature, solid-state, ex­ tra high-voltage power supplies have reduced their size, weight, and power needs. Two night-vision scopes are described in this article. One is passive, meaning that it will work in faint natural light, and the other is active, meaning that it requires supplemental infrared illumination. They in­ clude surplus first-generation imaging tubes. Although, they have been superseded by more advanced devices, they will, nev­ ertheless, provide adequate sen­ sitivity for most hobbyists and science experimenters. The active scope will permit police to observe suspected criminal activity at night and citizens to monitor their homes View a scene In near total darkness or property without being de­ tected. The scope will also per­ with a passive night-vision scope? mit hunting, nature study, marine navigation, and many or illuminate it with infrared other slight time applications. The active scope is suitable for for an active scope some of these activities, but the scene must be illuminated by an siles, and "smart" bombs. tive lens, positioned at the cath­ infrared source. Neither will Night-vision systems were con­ ode end of the tube, focuses the disturb the eyes' adaptation to sidered military secrets for image on the photocathode. It is darkness. many years. After they were de­ selected for its intended ap­ The first night vision scopes classified, they could be sold as plication—long-distance or were designed for use by for- military surplus and commer­ short-range viewing. The eye­ wavo observers, snipers, avi­ cial versions based on the tech­ piece at the anode is for viewing ators, and tank crews. Some nology were offered for police the enhanced image. If is a sim­ that were made as monoscopes surveillance and as nighttime ple lens that magnifies the im­ to mount on rifles looked like marine navigational aids at age on the screen. It can be the devices shown in Fig, 1: prices that often exceed $2000. removed and replaced by a tele­ others were made as bin­ Both of the night-vision vision camera, camcorder, or oculars. The most sensitive pas­ scopes described in this article film camera for transmitting or sive units are called starlight are based on military surplus recording the image. scopes. Night-vision goggles equipment that includes both The image tubes are the are lightweight binoculars for an image tube and optics. The hearts of the night-vision helicopter crews that mount on parts for the active unit cost scopes. Before you start build­ their helmets. $90, and parts for the active ing one (or both), you might Active night-vision scopes, unit cost 6220. want to learn, more about how such as she one shown in Fig, 2, they work. See the sidebar en­ depend on infrared illumina­ Night-vision scopes titled "Image Converter and In- tion from sources such as lasers Figure 3 illustrates a typical tensifier Tubes.'" for aiming artillery guided mis­ night-vision scope. The objec­ The only electronics needed in both projects described in this article is a high-voltage power supply capable of provid- ing a typical working voltage of 13.5 kilovolts. This efficient and compact regulated supply oper- ates satisfactorily from a 9-volt, alkaline battery. The current drain of both tubes described here is small, so that their power consumption is low. The compact power supply is built into a small plastic project case that is fastened directly to the surplus night-vision scope that contains the imaging tube. The Russian-made monocular viewer shown in Fig. 1 is actu- ally one half of a binocular. It is FIG. I-A PASSIVE NIGI-IT-VISION MONOSCOPE made from half of a Rus- complete with an objective lens sian night-vision binocular with an irnage intensifier tube and all optics. and an eyepiece. This assembly includes a first-generation, sin- gle-stage image intensifier tube. The active night-vision scope shown in Fig. 2 contains a sin- gle-stage image converter tube. Instructions on how to make several different low-cost in- frared illumination sources are described in this article. Active military night-vision weapons aiming systems typ- ically include an infrared-emit- ting laser. It pinpoints the target for a heat-seeking weap- on or for aiming other kinds of guns or missiles while also act- ing as a non-visible searchlight for the observer (bombardier or FIG. 2-THIS ACTIVE NIGHT-VISION SCOPE requires an infrared illumination gunner) with an active scope. source but it works from the same power supply as the scope in Fig. 1. Various svstems have been built for use oiland, in the air, or on the sea at night. Infrared-sensing missiles and "smart" bombs actually "home" on the IR-illuminated target which has been identi- fied by the observer who directs the laser beam and watches it with the active scope. Needless to say, aiming and firing must be fast because enemy gunners with active scopes can aiso see the laser illumination and take evasive action or retaliate. Power supp%ydesign Figure 4 is the schematic for a high-voltage power supply that will power both night-vision scopes described here. It pro- duces about 13.5 kilovolts from a 9-volt battery. The tubes draw tube, a high-voltage power supply, and a battery. about 20 milliamperes so about FIG. &THIS HIGH-VOLTAGE POWER SUPPLY has an inverter around Q1 that supplies 150-volt pulses to the converter of SCRi and C2. The output of T2 is a 4.5 kilovolt pulse that is multiplied by the voltage-tripler network (right) to produce 13.5 kilovolts. 36 hours of useful life can be obtained from a 9-volt alkaline battery. The output voltage will remain essentially constant for battery voltages of 6 to 12 volts. The power supply has three sections: the inverter, the con- verter, and the voltage multi- plier. The inverter section, a ringing-choke oscillator, con- sists of TI, R1, Dl. and (31. Resistor R1 provides bias cur- rent for starting the oscillator, and it also supplies the feed- back to maintain oscillation. Diode Dl protects the base- emitterjunction of Ql when the base voltage swings negative. The oscillator operates at about 120 Hz, set principally by the transformer. The resulting A@ voltage at the primary of T1 is stepped up by the secondary turns. The secondary voltage, which is rectified by diode D2, charges C2 through the pri- marv (low-resistancel windingV of trransformer T2. ' primary winding of T2. When is applied to the three-stage .g When the voltage across C2 C2 is discharged, the lamps ex- Cockcroft-Walton or Greinacher g exceeds the breakdown voltage tinguish, SCRl turns off, and voltage-multiplier circuit con- a of the two series-connected the charge cycle starts again. sisting of D3 to D8 and $ neon lamps NE1 and NE2 During the discharge cycle of @3to C8. V) (about 150 volts) the lamps turn C2, a pulse with a peak-to-peak The multiplier triples the 4.5- ,Z on. This conduction triggers voltage of 4.5 kilovolts is pro- kilovolt input to provide the si SCR1, and C2 is quickly dis- duced at the secondary of trig- 13.5-kilovolt output with very charged through SCRl and the ger transformer T2. This pulse low current. The capacitors and 59 OUTPUT TO put is nearly constant for DC C9 input voltage from 6 to 12 volts, the operating frequency of the inverter1 oscillator increases with the DC input voltage. The 0 waveforms and frequencies FOR DETAILS shown on Fig. 4 were obtained with a %volt input.

Bmudhg the power supply All the electronic components of the power supply except the capacitors and diodes in the voltage tripler are mounted on a 11%6X %?&-inch printed-circuit board that will fit with a 9-volt BLACK GROUND rectangular battery inside a 2 x "MOUNT R1 VERTICALLY 3Y4 x l-inch plastic project case. FIG &PARTS PLACEMENT DIAGRAM for the high-voltage power supply. Weferto Fig. A foil pattern has been provided 4 for the layout of the voltage-tripler network that is connected to its output. here for those who want to make their own circuit boards. Refer to parts placement di- PARTS LIST agram Fig. 5. Insert SCRl so are ?&watt, 10% , PCB mounted; plastic that its metal heatsink faces R1, R2, R3-22 kiiohms sleeving; RTV silicone potting NE2.When inserting Capacitors compound; tinned copper wire, electrolytic Cl and di- C1-100 pF, 25 volts, aluminum 22 AWG; insulated hookup wire, odes Dl and D2, observe their electrolytic 22 AWG, solder, polarities. Mount resistor R% C2--0.47pF, 350 volts, polyester Note: The following items are vertically oh the circuit board. C3, C4, C5, C6, C7, C8-220 pF, 5 all kV breakdown, ceramic available from Oatley Elec- Solder components and trim Semiconductors tronics, P.O. Box 89, Oatley, excess lead lengths. Dl-1 N914 silicon signal diode Sydney, NSW, Australia 2223: Refer back to the schematic D2-1N4007, IOOOV, 1A silicon di- Phone 011 61 2 579 4985 (Time Fig. 4, and wire the leads of ca- ode (DO-41 case), Motorola or zones USA-East 7 PM to 2 AM, pacitors C3 to C8 and diodes D3 equiv. Central 6 PM to 1 AM, Mountain to D8 together mechanically to BY509--silicon diode, 10 kV, 3 mA, 5 PM to 12 AM, Pacific 4 PM to 11 form a rigid unit according to Philips or equiv, (rating must be PM), Fax 011 61 2 570 7910. Mas- the schematic. Keep all exposed greater than 6 kV, 2 mA) tercard and Visa accepted with lead lengths about '/&inch long. 2 N 221 9 A- N P N trans i st o r, telephone or fax orders, Inter- Then solder the network to- Motor013 or equiv. national bank drafts and gether as rapidly as possible to MCR106-6 (C106D)-SCR, 400 V, money orders accepted by avoid applying damaging exces- 4 A in a T-126 package, Motorola mail. Customers please in- sive heat to the capacitors and or equiv, clude phone and/or fax diodes. The cathodes of some Other components number. diodes are identified with a red NE1, NE2-neon tubes, miniature o Complete kit of passive dot on the cathode lead. T1-transformer, inverter, 3 kilohm night-vision scope and parts Figure 6 shows the completed CT, iron core, audio, miniature PC for the HV power supply- power supply with the tripler mount $220.00 network to the right of the T2-transformer, trigger type, 250 e Complete kit of active night- board. Battery B1 and switch V primary, 6 kV secondary vision scope and parts for WV Miscellaneous printed circuit power supply--$90.80 Sl, both off-board components, board; passive night-vision e Kit of parts for HV power are not shown. Solder one lead monoscope with imaging tube supply only-$24.00 from C3and one lead from C6 in and optics (see text); active night- 0 Kit of non-standard parts the tripler network to the termi- $ vision scope with converter tube (TI, T2, NE1, NE2, and C2)-. nal points on the circuit board, t as shown in Fig. 5. (The tripler Q (see text); plastic project box (see $8.00 I! text); 9-volt alkaline transistor Include $15.00 for shipping and will be potted in silicone after 6 battery, 9-volt transistor battery handling, $6.00 for air mail the system has been tested.) 5 clip with ; miniature toggle from Australia. NOTE: The image converter 0 Z tube in the active night-vision .-8 scope shown in Fig. 2 requires a diodes must be rated to with- The neon lamps regulate the positive ground. If you build stand at least 4.5 kilovolts. For output so that the voltage ap- this unit, reverse diodes D3 to E this reason, the capacitors are plied to the primary of T2 is con- D8 to convert the supply from allratedat5kilovolts,andthe stant at 150 volts, peak. one with a positive to a negative 60 diodes are high-voltage units. Although the power supply out- output with respect to ground. Meehaicd assembly. Drill a hole in the body of the plastic project case for mount- ing the miniature toggle switch S1. The location of the switch is not critical, but it should not interfere with the other compo- nents. In the passive night-vi- sion scope, it was positioned at the end of the case facing the eyepiece. Drill the hole in the case for mounting it to the passive scope body with a single screw. The hole for this screw, already drilled and tapped in the body of the scope, is located under the coupling bracket. Brill another hole Iarge enough to pass the power cable to the image tube. Its location will depend on the project you build. Mount switch SE in the sidewall of the case. Fasten the case to the passive network pott&in silicone is shown as t6; white patch at right. ' viewer with a screw. If you build the active viewer, cement the case to the scope body with ep- oxy, as shown in Fig. 2. Cut the supply lead from the scope about 6 inches long, and strip back about 1 inch of the jacket to expose the braid and the insulated central conductor. Twist the braid into a lead and insulate it with a length of plas- tic tubing. Insert the cable lead into the project box, solder the braid to the ground connection of the circuit board, and solder the inner conductor to the high- voltage terminal of the tripier network, as shown in Fig. 4. VeriQ that there are no short circuits in the construction of the tripler and that the leads are CUTAWAY VIEW OF SINGLE-STAGE image tube showing the position of its key parts. spaced by at least %-inch from each other. Wire toggle switch enough to permit lifting the cir- SB in series with the positive cuit board out of the case. Insert lead from the battery clip. Cut the battery and wiring in the the battery Ieads from the cir- case, but leave the tripler net- . cuit board so they are long work and circuit board outside temporarily.

%st and checkout After rechecking your work 1 15/16 INCHES and verifying the polarities and I1- orientation of all components, FOIL PATTERN FOR POWER SUPPLY snap the battery to the battery circuit board. clip. The current drain on a 9- volt alkaline transistor battery about 13.5 kilovolts, and is ca- should be about 20 milliam- pable of giving you a startling peresin a correctcircuit. electric shock. While not nor- power supply circuit board with the volt- WARNING! The power supply mally life-threatening, it can age-tripler, diode-capacitor network described in this article pro- have a temporarily debilitating shown unpoRed at right. duces an output voltage of effect. Consequently, treat it with respect and always make on a DMM. The AC voltage at the sure switch S1 is off and the ca- base of Q1 was about 0.45 volt pacitors are discharged before RMS. handling the circuit board. When the scope is working When you switch on S1, a cor- properly, switch off the power ona discharge might appear and wait for the tube to dis- around the tripler network. charge completely. Insert the This is non-destructive, but tripler section carefully inside avoid electrical shock by keep- the case as shown at the right ing your hands away from that side of Fig. 7. Encapsulate it part of the circuit. with neutral-cure, room-tem- Alternatively, you can test the perature vulcanizing (RTVI sil- power supply by placing a wire icone potting compound to connected to the circuit's pievent high-voltage corona ground bus close to the high- and discharge, which increases voltage output lead. It should with relative humidity. The produce an arc as much as Y4- compound will also fasten the inch long. tripler network inside of the When the switch is off, con- case. nect the ground wire directly to the high-voltage output to dis- Viewing with the scope charge all the capacitors. Be- The lens of the surplus Rus- cause of the short-duty cycle sian passive night-vision scope discharge pulses, the illumina- specified in this article is tion of neon lamps NE1 and NE2 focused to infinity, making it will be visible only in darkness. useful for viewing images more If power supplies have been than a few meters away. By built and installed correctly, the loosening a small locking screw, screen of the image the lens can be adjusted. This tube should emit a green glow, will permit viewing objects more whether or not light is incident than 100 meters away under on the cathode. The green glow near starlight illumination. persists for a about a minute Imaging tubes will be after the power has been switch- damaged if they are exposed to ed off, indicating that sufficient bright light for long periods. voltage still exists between the Don't use either scope in sun- anode and cathode to form an light, or even in well lighted image. rooms. Always cover both ends If, after following the direc- of a night-vision scope with tions closely and checking your suitable lens caps when it is not workmanship, the scope still in use to keep the imaging tube doesn't work, check the volt- in darkness. The monocular ages at the base and collector of passive scope offered by the transistor Q1 with a digital volt- source given in the parts list meter. The values shown on the has a rubber lens cap that can schematic, Fig. 4, are DC values be snapped in place. It also has expected with a 9-volt power a focusing eyepiece. supply. Both of the night-vision Do not attempt to measure scopes will detect IR energy, so the high-voltage output directly they can verify the operation of unless you have a suitable high- stereo and TV remote controls. voltage probe on your meter. In a darkened room, point the The waveforms shown were also emitting face of the control at obtained with a 9-volt supply. If the scope. A pulsing green light you don't have an oscilloscope will be seen when any of the re- available, measure the AC volt- mote control's keys are pressed. age at the test points shown on A TV remote control can also Fig. 4. serve as a temporary IR il- The reading on most digital luminator. voltmeters will be RMS values, but they will give you a valid in- IR light source dication if there is a signal. The A better IR source can be AC voltage at the cathode of D2 made by covering a flashlight (to ground) of the prototype with an IR filter. You can pur- measured about 45 volts RMS Continued on page 73 with the component values shown in Fig. 12. The circuit FUNCTlON GENERATORS can only lock to input signals continued from page 50 within this frequency range. - Figures 13 and 14 are sche- matics for several practical fre- quency multiplier circuits. The circuit in Fig. 13 serves as a multiply by 100 frequency mul- tiplierlprescaler that can nature represents the forward change 1 Hz to 150 Hz input sig- voltage drop. The vertical part of nals into 150 Hz to 15 kHz out- the signature represents the for- put signals. ward current, and the horizon- The circuit in Fig. 14 is a sim- tal part represents the reverse ple frequency synthesizer. It is voltage drop. fed with a precise (crystal-de- In the waveform for the Zener rived) 1-kHz input signal, and diode in Fig. 9-d, the forward its output is a whole-number current is a function of the for- multiple (in the range x 1 to ward voltage. But when the re- x 9) of this signal. The verse voltage equals the PN CD4017B is organized as a pro- junction breakdown voltage, re- grammable divide-by-N counter verse current increases rapidly, in this application. A single producing a vertical line in the CD4017B can be replaced by a lower left quadrant of the series of programmable decade screen. This line is the break- counters to form a wide-range over point or Zener voltage, and (10 Hz to 1 MHz) synthesizer. n it is established by the knee in the signature. The signature technique can be applied to test and explain the operation of all electronic components. It is simple to use, I NIGHT VISION SCOPES 1 it can speed troubleshooting, 1 continued from Dacle 62 1 and it works well on unpowered circuit boards. Even electronic service centers operating under chase a suitable IR filter at most tight budget constraints can af- retail camera stores, or you can ford this method. stack four or five layers of com- It is worth noting that two pletely exposed, developed film functionally identical ICs which negatives between the incan- seem to be operating normally descent lamp and flashlight can have different pin sig- lens. This film can be obtained natures because of differences as scrap from local photo de- in chip fabrication. You might veloping shops. Cut four or five encounter this when testing disks from this exposed film to functionally identical IC's from fit inside the plastic or glass different manufacturers. Dif- lens cap of your flashlight. ferent signatures do not neces- A complete kit of parts to sarily indicate a device fault. build both of the scopes de- With experience in the careful scribed in this article can be ob- interpretation of signatures, tained from the source given in signature analysis can help you the parts list. If you elect to buy to identify defective compo- a surplus image tube to make a nents quickly--even those with night-vision scope from marginal problems. Defective scratch, purchase or obtain a ICs (open-circuited or short-cir- "fast" camera lens and a magni- cuited) can be isolated rapidly fying glass for use as an eye- by persons with little or no expe- piece. You can then assemble all rience doing this. a of these parts in a suitable met- al or plastic tube. The power FIG. 9-NORMALIZED CURRENT VS. supply described here will VOLTAGE SIGNATURES for electronic power most imaging tubes, re- components: resistor (a), or ca- gardless of their size or country pacitor (b), silicon signal diode (c), light- of origin. n emitting diode (4,and (e).