Fullscreen HTML5Med Res (??MB)HTML4

SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au Vol.9, No.3; March 1996 Contents DISCOVER HOW THESE IMPORTANT TEST INSTRUMENTS WORK – PAGE 12 FEATURES 4 Traction Control: The Latest In Car Technology Traction control offers important new advances in vehicle safety and dynamics and some manufacturers already have systems that work in conjunction with ABS. We take a look at how it works – by Julian Edgar 12 Cathode Ray Oscilloscopes, Pt.1 Learn how these important items of test equipment work! This first article in the series looks at analog oscilloscopes and describes how they operate – by Bryan Maher PROJECTS TO BUILD 22 Programmable Electronic Ignition System For Cars Program your own ignition advance curve with this simple system. It can be easily added to the “Silicon Chip” High Energy Ignition System – by Anthony Nixon 32 A Zener Diode Tester For Your DMM Plug this simple adapter into your DMM to directly read the values of zener diodes. It covers the range from 2.2V to 100V – by John Clarke 42 Automatic Level Control For PA Systems Keep the volume from your PA system at a constant level with this easy-to-build system and forget about riding the gain control – by John Clarke 60 A 20ms Delay For Surround Sound Decoders Add this to your surround sound decoder for more realistic rear channel sound. It uses just one IC and a handful of other parts – by John Clarke 84 Build A Simple Battery Tester For Around $5 The recipe is simple: take one green tester strip from a Mallory® battery pack, add a battery clip, a case, and a sprinkling of nuts and bolts – by John Clarke PROGRAMMABLE IGNITION SYSTEM FOR CARS – PAGE 22 ZENER DIODE TESTER PLUGS INTO YOUR DMM – PAGE 32 SPECIAL COLUMNS 48 Serviceman’s Log Sound reasons for confusion – by the TV Serviceman 54 Remote Control Multi-channel radio control transmitter; Pt.2 – by Bob Young 74 Computer Bits Electronic organisers & your PC – by Geoff Cohen 77 Satellite Watch The latest in satellite TV reception – by Garry Cratt 86 Vintage Radio A console with a difference – by John Hill AUTOMATIC LEVEL CONTROL FOR PA SYSTEMS – PAGE 42 DEPARTMENTS 2 Publisher’s Letter 3 Mailbag 40 Circuit Notebook 63 Order Form 64 Bookshelf 80 Product Showcase 92 Ask Silicon Chip 95 Market Centre 96 Advertising Index March 1996  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson Phone (02) 9979 5644 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young Photography Stuart Bryce SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $55 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Selling Telstra is the wrong move So Telstra is to be sold off. Regardless of the election outcome this month, it seems that the sell-off of Telstra is a certainty. Both the Labor and Liberal parties appear to be mesmerised by the huge amount of cash that Telstra will realise. The estimates range from 24 billion to around 40 billion. In the face of that sort of money and the need to reduce Government deficits, there does not appear to be much prospect of a careful analysis of the costs and benefits of such a sale. We’ve seen Qantas sold, the Commonwealth Bank sold and Telstra is likely to be next cab off the rank. The really bad aspect of selling off Telstra now is that telecommunications is one area of the economy guaranteed to have huge growth over the next 10 years or more. So if Telstra is worth a motsa today, it’s going to be worth a great deal more in years to come. But if the Government sells it off now, it won’t get the benefits of that growth; it won’t get the dividends and it won’t have the asset. Sure, it will get tax revenue on the profits but somehow I don’t think that will amount to anywhere near as much. Moreover, if Telstra is sold, you can bet that many of the factors which have prevented it from raising its charges or which force it to provide service in uneconomic sectors will no longer apply. Timed local calls (for everyone) are a certainty. After all, if Government controls still apply to an asset to be sold, that would reduce the asking price, wouldn’t it? You can also bet that a fully privatised Telstra would reduce its workforce even further and that will have undeniable costs to the Government budget. And let’s not forget the considerable benefits that flow to Australian industry because Telstra is such a large buyer in the marketplace. Would that continue after Telstra becomes controlled by an overseas company? Oh, I haven’t mentioned that, have I? If you are unhappy about Telstra being sold off but think it might be worthwhile because of good effects on the budget or maybe the environment, as envisaged in the Liberal Party policy, then think about overseas control. Qantas is now controlled by an overseas company; ie, British Airways. With $40 billion as the asking price for Telstra, it’s highly likely that an overseas corporation will be the major buyer. Do we really want to see that happen? Leo Simpson ISSN 1030-2662 WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 2  Silicon Chip MAILBAG Software piracy protection As you would no doubt be aware, software piracy is costing legiti­mate publishers millions, perhaps hundreds of millions, of dollars annually in lost earnings. I have devised a scheme for copy-protecting software which could help reduce this problem. My scheme is based on the concept of laser marking floppy discs with an encoding process so that software is usable only if installed from the original disks. Special user-installed hardware, such as a dongle, is not re­quired. I have applied for a patent and would like to offer licences with options for the Australian and foreign patent rights to interest­ed parties. Specially designed laser marking equipment is re­quired, so I would prefer to negotiate with a company with design expertise in that area. To the best of my knowledge, my scheme is novel, although I am aware of a system which involves laser marking CD ROMs. If anyone knows of a similar system which applies to floppy discs, I would greatly appreciate them informing me, either directly or via your magazine. H. Nacinovich, 63 Belmore St, Gulgong, NSW 2852. Outboard motor electronics I enjoy reading Silicon Chip every month and using any informa­ tion from it that interests me. I am writing to ask if it is possible for you to run a series of articles on outboard motor electronics, the same way as you do with car engines? M. Bougourd, Hamersley, WA. More tips on making PC boards In one of my recent letters to you I mentioned the article in April 1995 Silicon Chip p.7 on “photocopies for PC boards”. I have found that a much better method is to iron on the reverse photocopy but it must be removed while hot. This puts a nice print on the copper and if you sharpen a felt tip pen (water resistant ink) with a balsa knife, the tracing can be gone over accurately and quickly. My PCB was a lovely job. Forget the thinners. D. Schofield, Caloundra, Qld. Delay a tad longer than 20ms After seeing your Surround Sound Mixer & Decoder in Silicon Chip January 1996 it was just what I wanted, particularly when you mentioned that you would be describing a 20ms delay unit in the February issue. So I built the unit, waiting for the next issue of Silicon Chip: no appearance, Your Worship. I think that you should at least stick to your guns. I have been waiting now 3 weeks for this issue, now another four weeks before the next issue before I can finish it off. I am not at all happy with this situation, as it is not the first time this has happened. K. Lloyd, Sth Tweed Heads, NSW. Comment: as you will have noted, the 20ms Delay is in this issue . And another anniversary The 12th July, 1996 marks the 90th anniversary of the first overseas wireless message sent from Australia. The enclosed photograph (reproduced below) shows a cairn which marks the spot from where the messages were sent, near Point Lonsdale, at the southwest corner of Port Phillip Bay, Victoria. The cairn is on the footpath in Port Lonsdale Road, near Lawrence Road, but is not visible from the road because of the presence of a high hedge along the edge of the footpath. At Wahroonga, NSW (cnr Stuart and Cleveland Sts), there is an even more impressive and imaginative memorial marking the spot where early wireless transmissions took place. John Richardson, West Pymble, NSW. 70 years of electric trains Readers who recall Bryan Maher’s series of articles entitled “The Evolution of Electric Railways” from the first issue of “Silicon Chip”, until 1990, may be interested to know that 1st March, 1996 will be the 70th Anniversary of the first electric train in revenue service in Sydney. This was a very significant event of 70 years ago. What would Sydney be like if that first electric train had not entered service and without the technology that was developed for electric trains? (And would have Silicon Chip have had such a fine series of articles to kick the magazine off?) What is remarkable is that one of the cars from that first train has been preserved and is fully operation­ al. Some of the technology that was developed in the 1920s is still in use today – which is just as remarkable! So why let this event pass unnoticed? The Sydney Electric Train Society intends marking the event with the assistance of CityRail. P. Maljevac, Sydney Electric Train Society Inc., Broadway, NSW. The inscription on the bronze plaque reads: "FROM THIS SPOT ON TWELFTH JULY 1906 THE FIRST OVERSEAS WIRELESS MESSAGES FROM AUSTRALIA WERE SENT BY LORD NORTHCOTE, GOVERNOR GENERAL. SIR R TALBOT, GOVERNOR. HON A DEAKIN, PRIME MINISTER. HON A CHAPMAN, POSTMASTER-GENERAL. HON RA COUCHMAN, MP FOR CORIO. EQUIPMENT SUPPLIED AND OPERATED BY MARCONI WIRELESS PTY LTD" March 1996  3 The Volkswagen Golf VR6 has an engine power of 128kW channelled through the front wheels. It uses a traction control system where individual front wheels are braked. s ic m a n y D & y t afe S e l c i h e V n I ces Advan Traction Control Traction control was first used in heavy locomotives but is now applied to vehicles as diverse as heavy trucks and small front-wheel drive cars. Until recently, it was also used in Formula 1 racing as an aid to handling. By JULIAN EDGAR 4  Silicon Chip Why have traction control? The need for traction control is based on the idea that a driven wheel that is slipping excessive­ly is not providing the maximum possible power transfer to the road surface. However, completely preventing slip is not the aim; some slippage actually increases the tractive force obtainable. On dry road surfaces, the maximum accelerative force is available at slip rates of between 10% and 30%, while on loose sand and gravel the coefficient of accelerative force continues to increase with slip rate, with the Wheel speeds are sensed through the use of a toothed tone wheel and an inductive pick-up. The same sensors usually provide infor­mation for the anti-lock braking and the traction control sys­tems. maximum being achieved at a slip rate of more than 60%! Traction control systems usually work within the slip range of 2-20% and so will not provide adequate traction under all conditions. For this reason, most systems can be disabled with a dash-mounted switch. Wheel spin may occur on icy, muddy or gravel surfaces, where the coefficient of friction between the tyre and the road surface is low. It may be as a result of an increase in engine Electronic control of the throttle position is already carried out in some cars, using this geared motor. Integrating a traction control system which uses throttle control can therefore be carried out more easily in certain cars. torque being unable to be transmitted through the tyre to the road surface, as a result of too great a retardation through excessive engine braking, or as a result of large cornering and propulsive loads simultaneously being transferred to the wheels. Spinning drive wheels cause problems because they: (a) inhibit propulsion; (b) create handling instability because they can transmit little cornering force; and (c) lead to a high rate of wear on the tyres and drive mechanicals, especially when they pass onto a high friction surface and suddenly stop spinning. Control methods A number of approaches can be taken to limit wheel spin. The most obvious is that the engine torque output can be reduced by partially closing the throttle. This is easily done in cars using an electronical­ ly controlled throttle butterfly (“drive-by-wire”) but the reaction time using throttle control Fig.1: the layout of the Vehicle Dynamics Control system. In addition to the sensors required for ABS/ASR operation, sensors for vehicle yaw, lateral acceleration and steering angle are also used (photo: Bosch). March 1996  5 A combined anti-lock braking and traction control system for a commercial vehicle: (1) wheel speed sensors; (2) ABS/ASR elec­tronic control unit; (3) pressure control valve; and (4) solenoid valve. alone is slow. In diesel engines, the amount of injected fuel can be reduced to achieve torque reduction, while in turbocharged engines, boost pressure can be controlled. In petrol engines, the ignition system can be used to very quickly reduce the engine’s output. The spark advance angle can be altered or ignition pulses can be suppressed, causing a “miss”. However, an engine running with either excessive ignition retard or a deliberate misfire can produce excessive exhaust emissions and can have high exhaust gas temperatures. The latter is the case because the unburnt charge may ignite in the exhaust port! Simultaneous suppression of the fuel injector operation can be carried out to reduce these problems. The suppression of fuel injector signals will also cause a misfire and a consequent reduction in engine torque. Injector cutoff is often used on a rotating basis, 6  Silicon Chip with a cylinder shut off for a single cycle or “half” a cylinder shut off by the deactivation of a cylinder every other 720° cycle. This maintains engine smoothness and minimises crankshaft torsional stresses. The brakes can also be applied to the spinning wheel to slow it until its speed matches that of the non-driven wheels. By using this approach, the existing ABS (anti-lock braking system) hydraulic hardware can be utilised, with some hardware additions to cater for the extra traction control function. Truck traction control An example of a traction control system is the Bosch unit used on trucks and other heavy vehicles. It is integrated with the ABS system, making use of the ABS wheel speed sensors and hydraulic control unit. It uses a mix of engine intervention and brake application to control wheel spin. The Traction Control System (ASR in Bosch-speak) monitors the speed of the powered and unpowered wheels and recognises when a wheel is tending towards spinning. At this time, a dashboard light is illuminated, warning the driver of the presence of slippery conditions. The system controls the wheel speed of the powered wheels by two means: (1) Brake control – at speeds up to 30km/h, if a powered wheel is tending towards spinning it is braked and the speeds of the driven wheels synchronised. (2) Engine control – if both powered wheels are losing traction, the torque of the engine is reduced. At speeds above 30km/h, the spinning of either of the wheels is also prevented by a reduction in engine output. In addition to the braking and engine torque reduction approaches, trucks with air suspension on the leading or trailing axles can have the load on the powered axle briefly increased by up to 30%. This occurs when the traction control system relieves the non-powered Some Mercedes models use the sophisticated Vehicle Dynamics Con­trol, where any of the four individual wheels are braked to aid car stability during cornering. Sensors for yaw, steering angle and lateral acceleration are amongst those used. Above & right: the hydraulic control unit of a Bosch 2E ABS/ASR system. The electronic control unit (seen at right) uses hybrid circuits on a ceramic substrate and is combined with the hydraulic control unit. March 1996  7 Traction Control In Action WITHOUT TRACTION CONTROL WITH TRACTION CONTROL 1 4 2 5 3 6 This amazing sequence of photos showing the affect of the Vehicle Dynamics Control system, with the car cornering on a skid pan at high speed. Picture 1 shows the car understeering off line, mowing down the cones. By picture 2, the front outside tyre is giving off smoke as the car slides across the track in plough understeer. In Picture 3, it can be seen that the car is more than its own axle of its load by bleeding its air suspension bellows. Car traction control Powerful front wheel drive cars can have major wheel-spin problems, especially when accelerating from standstill. This is especially so because limited slip differentials are uncommon in FWD cars, because of the excessive torque reaction which would be felt through the steering wheel during differential lockup. The Volkswagen Golf VR6 uses a traction control system dubbed an Electronic 8  Silicon Chip width outside the appropriate cornering line. The righthand sequence (pictures 4-6) shows the same corner, same speed and same car – but with the VDC system operating. The amount of front wheel slip angle remains the same, as shown by the tyre smoke and amount of steering lock being used. But because the lefthand rear wheel is being braked, the car follows the chosen line. Differential Lock (EDS in German). The system uses only brake intervention to slow the spinning wheel. As with the truck system discussed above, EDS largely uses components already in place for ABS. The ECU continuously com­pares the speed of the front wheels, using appropriately placed sensors. If the difference in speed is greater than 110RPM, the slipping wheel is braked until it reaches approximately the speed of the non-slipping wheel. The system is activated until a road speed of 40km/h is reached, whereupon the effect of the system is gradually reduced. EDS also works in reverse gear, which may be desirable for those with very steep driveways! In very slippery conditions, the possibility exists that excessive brake temperatures may be realised – remember, this system doesn’t reduce the engine output. The electronic control unit continuously monitors the duration and frequency of EDS operation, with the probable temperature of the braking compon­ents calculated from these factors. When a preset level is reached, the EDS Fig.2: the VDC system controls understeer and oversteer by braking one of the wheels (photo: Bosch). system is disabled, although the ABS remains fully functioning. The system is very effective when one wheel is on a much more slippery surface than the other. In fact, with the left-hand wheels on dry tarmac and the right-hand wheels on a wet and icy road, a non-EDS Golf is able to transfer a drive force of 692 Newtons to the road, while an EDS-equipped car in identical circumstances can transfer 3112 Newtons – nearly 4.5 times as much. Interestingly, the VW EDS system can be retrofitted to recent ABS Volks­ wagens, with an additional valve block used on the hydraulic control unit and a new ECU used together with a redesigned wiring harness. Vehicle dynamics control This system, currently fitted to some Mercedes cars, is designed to prevent skidding during cornering. Unlike ABS and ASR, Vehicle Dynamics Control (VDC – I love all these acronyms!) can be activated even when the car is free-wheeling and when the driver is neither deliberately braking or accel- erating. Fig.1 shows a schematic of the system layout. While anti-lock brakes and traction control prevent longi­ tudinal wheel slippage, VDC attempts to prevent lateral slip, particularly when cornering. Both understeer (the front wheels laterally slipping and the nose of the car running wide) and oversteer (the rear wheels sliding sideways, with the tail of the car moving out of line) can be countered. If a car understeers when being cornered, the system cor­rects by braking the inner rear wheel, effectively rearwheel steering the car back into line. The controller can brake the chosen wheel almost to the point of locking and so the correcting effect can be very strong. Simultaneously with the braking of the single wheel, the speed of the car is slowed to a level appro­priate for the situation. This is achiev­ed by reducing the engine torque output by partially closing the throttle and/or by braking the other wheels. If oversteer is starting to occur, the system stabilises the car by braking the outer front wheel. Fig.2 shows the effect on vehicle stability of braking just one wheel. In addition to ABS and ASR components, the VDC requires sensors for yaw rate, lateral acceleration and steering angle. Furthermore, the controller needs information on whether the car is accelerating, free rolling or being braked. Longitudinal slip is derived from the wheel speed sensors, while a lateral accelerometer responds to the forces occurring in curves, with the analog sensor very sensitive in the range of ±1.4G. In addition, a yaw rate sensor is used to measure the speed at which the car rotates around its vertical axis. This device uses four pairs of piezo elements to excite a hollow steel cylin­der. The yaw is a measure of the shifting vibration nodes which occur within the cylinder. The ECU for the VDC system has a memory capacity of 48Kb – more than double that required for a combined ABS/ASR system. Next month we’ll discuss the traction control systems used on Formula SC 1 racing cars. March 1996  9 ALL REFURBISHED PRODUCTS CARRY MINIMUM 90-DAY WARRANTY ● COUNTRY/INTERSTATE: FREE CALL 1800 680680 ● ALL REFURBISHED PRODUCTS CARRY A MINIMUM 90-DAY WARRANTY ● CONTACT MA HEWLETT PACKARD 334A Distortion Analyser HEWLETT PACKARD 200CD Audio Oscillator • measures distortion 5Hz600kHz • harmonics up to 3MHz • auto nulling mode • high pass filter • high impedance AM • 5Hz to 600kHz • 5 ranges • 10V out • balanced output detector HEWLETT PACKARD 8614A UHF Sig. Gen. HEWLETT PACKARD 8640B Sig. Generator HEWLETT PACKARD 654A Test Oscillator • 0.5-1024MHz freq. range • int. audio osc. 20Hz-600kHz • 800-2400MHz freq. range • select. functions: CW, lev­elled • reverse power protection • internal phase lock/synch. output, sq. wave mod., ext. • +19 to -145 dBm output AM, FM & pulse mod. power range • output attenuation 0 to -127 • low SSB phase noise dBm • sig. gen. can be phase locked • digital frequency readout • 10Hz - 10MHz freq. range • +11dBm to -90dBm output level in 1dB steps • calibrated impedance 50Ω • + 75Ω unblanced; 135Ω, 150Ω + 600Ω balanced distortion <at> 1-10MHz > 34dB below fundamental $795 $79 $525 $3995 $695 HEWLETT PACKARD 3336B Synthesizer/ Level Generator HEWLETT PACKARD 3586B Selective Level Meter HEWLETT PACKARD 1740A Oscilloscope HEWLETT PACKARD 1710A Oscilloscope HEWLETT PACKARD 141T/8552/8555A Spectrum Analyser • variable • Frequency coverage 10Hz- • Frequency coverage 50Hz20.9MHz 32.5MHz • Precise frequency & spectral • Excellent measurement purity 1 Microhertz res up accuracy ±.2dB to 100kHz • Autoranging & automatic • Absolute amplitude accuracy calibration ±.05dB at 10kHz • SSB mode provides • Unique levelled sweep demodulation capability capabilities • HPIB programmable $1650 Austron 2010B Oscillator 1MHz........................... $400 AWA A215-2 Transmission Measuring Set .......... $175 AWA E221 Level Meter ........................................ $650 AWA F240 Distortion & Noise Meter ................... $375 AWA G231 Audio 10Hz-30KHz ............................ $495 AWA G250 Test Oscillator 10Hz-610kHz .............. $525 AWA G251 Level Oscillator 50Hz-2MHz .............. $600 BECKMAN L10A Megohmeter ........................... $1400 EATON 2075 Noise Gain Analyser ...................... $6500 ESI DB62 Decade Box ......................................... $350 EUROCARD 6 Slot Frames ..................................... $40 FLUKE 408B 6kV 20mA Power Supply................. $800 GR 1381 Random Noise Generators .................... $160 HP 204C Oscillator............................................... $225 HP 332A Distortion & Noise Meter ...................... $495 HP 353 Audio Attenuator...................................... $170 HP 400EL AC Voltmeter ....................................... $195 HP 403B AC Voltmeter......................................... $150 HP410C Multimeter ............................................. $295 HP 427A Voltmeter ................................................ $95 HP 432A Power Meter C/W Head & Cable ........... $825 HP 435A Power Meter.......................................... $495 HP 652A Test Oscillator ....................................... $375 HP 1200B Oscilloscope DC-500kHz..................... $425 HP 3400A RMS Voltmeter (1mV - 300V)............. $475 HP 3406A Broadband Sampling Voltmeter .......... $575 HP 3455A 61/2 Digit DVM ................................... $650 HP 3490A 51/2 Digit Digital Multimeter ............... $295 HP 3555B Transmission & Noise Meas. Set......... $325 HP 4204A Oscillator 10Hz-1MHz ......................... $350 HP 4260 LCR Bridge............................................ $295 HP 5245L/5253/5255 Electronic Counter ............ $550 HP 5300/5302A Universal Counter to 50MHz ...... $195 HP 5326B Universal Timer/Counter/DVM ............ $295 HP 5328A Universal Counter to 500MHz.............. $695 HP 5335A 200MHz Universal Counter ............... $4500 HP 6002 50V/10A Power Supply........................ $1495 HP 8005A Pulse Gen. 20MHz 3-Channel ............. $350 HP 8690B/8698/8699 400KHz-4GHz Sweep Osc ..................................................... $2450 HP 8690B/8707A/8706A 4GHz-18GHz Sweep Osc ..................................................... $1500 MARCONI TF2006 FM Sig. Gen. 1000MHz........... $800 MARCONI TF2300A FM/AM Mod Meter 500kHz-1000MHz ............................................ $450 MARCONI TF2500 AF Power/Volt Meter .............. $180 MOTOROLA Sinad Meter ..................................... $325 NORTHEAST 4002A Transmission Meas. Set ...... $600 RACAL DANA 9500 Universal Timer/Counter ...... $350 SD 6054B Freq. Counter 20Hz-18GHz ............... $2500 SD 6054C Microwave Freq Counter 1-18GHz .... $2000 SD 6152A 512MHz Counter/Timer....................... $350 TEKTRONIX CFC 100MHz Freq. Counter.............. $270 TEKTRONIX CDC 175MHz Univ. Counter.............. $405 TEKTRONIX FG504/TM503 40MHz Fun. Gen...... $1290 TEKTRONIX 067-0502-01 Scope Calibrator......... $550 TEKTRONIX 464 Storage Scope DC-100MHz..... $1400 TEKTRONIX 465 Oscilloscope DC-100MHz ....... $1190 TEKTRONIX 475 Oscilloscope DC-200MHz ....... $1550 TEKTRONIX 485 Oscilloscope DC-350MHz........ $2400 TEKTRONIX 602 XY Display ................................ $350 TEKTRONIX 7603NIIS Scope DC-65MHz ............ $650 TEKTRONIX 7904 Oscilloscope DC-500MHz ..... $2800 W&G SPM3 Selective Level Meter C/W; W&G PS3 Signal Generator 300Hz-612kHz (pr)........ $450 WAVETEK 143 Function Generator 20MHz .......... $475 WAVETEK 907 Signal Generator 7-11GHz.......... $1600 • DC-100MHz bandwidth • 2-channel display mode • trigger - main/delay sweep • coupling AC, DC, LF & HF rej $990 • HP 1741A var. persistence expansion to full screen model available $1325 $1250 $3995 BALLANTINE 323 AC Voltmeter BALLANTINE 6310A Test Oscillator BALLANTINE 3440A Millivoltmeter $1450 BALL EFRATOM M100 Rubidium Frequency • factory cal certs • perfect for ISO accreditation • GPS applications • ruggedised military design • • • • • • • • • • • • • bandwidth DC-150MHz • trigger source channel A, B or composite • delay timebase with single sweep • main intensify timebase persistence storage mainframe internal graticule eliminates parallax error IF section 10Hz minimum bandwidth log & linear sens. control absolute amplitude accuracy to ±1.6dB direct coax input to 18GHz high res. 100Hz bandwidth true RMS response including harmonics + crest factors 300µV to 300V full scale 1% basic accuracy freq. range 2Hz - 25MHz full field portability fast response without thermal lag $2950 • true RMS • • • • • 2Hz-1MHz freq. range • digital counter with 5 digit LED display • output impedance switch selectable • output terminals fuse protected $425 response to 30mV frequency coverage 10kHz-1.2GHz measurement from 100µV to 300V accuracy ±1% full scale to 150MHz list price elsewhere over $5500 $350 $795 NEW EQUIPMENT Affordable Laboratory Instruments The name that means quality PS305 Single Output Supply • • • • • • • • SSI-2360 60MHz Scope 60MHz dual trace, dual trigger Vertical sens. 1mV/div. Maximum sweep rate 5ns/div. Component tester Delay sweep, single sweep Two high quality probes $1110 + Tax • • • • PS8203 Digital Dual Supply 0-30V & 0-5A Load & line regulation <=0.01%+3mV Ind. & tracking modes Low ripple output Constant current voltage 2 x 3.5 dual purpose digital voltmeters • PS303D Dual Output Supply • 0-30V & 0-3A • • Four separate output meters • Independent or Tracking modes • Low ripple output $420 + Tax PS305D Dual Output Supply 0-30V and 0-5A $470 + Tax 0-30V & 0-5A $300 + Tax PS303 Single Output Supply PS8112 Single • 0-30V & 0-3A Output Supply • Two output meters • Constant I/V • 0-60V & 0-5A $490 + Tax $265 + Tax Audio Generator AG2601A Pattern Generator CPG1367A $640 + Tax PS8201 Digital Single Supply digital display • 0-30V & 0-5A • Load & line regulation • Constant current analog display <=0.01%+3mV • Constant voltage $320 + Tax • 10Hz-1MHz 5 bands • Colour pattern to test PAL • High frequency system TV circuit stability • Dot, cross hatch, vertical, • Sine/Square output horizontal, raster, colour $245 + Tax $275 + Tax ● ALL REFURBISHED PRODUCTS CARRY A MINIMUM 90-DAY WARRANTY ● CONTACT TEKTRONIX 100kHz to 1800MHz Spectrum Analyser System Consisting of: 7613 7L12 7A17 TR501 TM503 WAVETEK Signal Generator/Deviation Meter Model 3000-200 incorporates a complete 1 to 520MHz FM, AM and CW Signal Generator with an FM Deviation Meter in one convenient instrument. Storage Mainframe 1.8GHz Spectrum Analyser Plug-In Amplifier 1.8GHz Tracking Generator 3 Slot Mainframe $4250 Please phone or fax today for a full specification sheet incorporating all the system’s features. SPECIAL OFFER: DM501 MULTIMETER ONLY $100 EXTRA Frequency Range: 1-520MHz selectable in 1kHz steps; 1kHz resolution; frequency programmable via rear-panel connector. RF Output Level: +13dBm to -137dBm (1V to .03µV RMS); output level continuously adjustable in 10dB steps and with an 11dB vernier; impedance = 50 ohms. RF Output Protection: resettable RF circuit breaker; RF trip voltage = 5V RMS nominal; maximum reverse power = 50W. Spectral Purity: harmonic output > 30dB below fundamental from 10-520MHz; residual AM > 55dB below carrier in a 50Hz to 15kHz post-detection bandwidth; residual FM <200Hz in a 50Hz to 15kHz post-detection bandwidth (100Hz typical). Amplitude Modulation: internal 400Hz and 1kHz ±10%; external DC to 20kHz; range 0-90%; distortion 3% to 70% AM at 1kHz. Frequency Modulation: internal 400Hz and 1kHz (±10%); 50Hz to 25kHz; accuracy ±500Hz on x1 range, ±5kHz on x10 range; distortion 4% at 1kHz. FM Deviation Meter: frequency range 30-500MHz; input level range 10mV to 5V RMS; impedance 50 ohms; deviation range 0 to ±5kHz, 0 to ±50kHz $1250 IMPORTANT: GARAGE SALE! This is our first ever Garage Sale and represents an opportunity to purchase a whole range of “as traded” and imported stock that has been accumulated over years. Some equipment is tested, others “as is” . . . You’re sure to find a bit of everything mechanical, etc. INTERSTATE/COUNTRY BUYERS: Send or phone for lists . . . All interstate lists returned to us for this sale will be opened on 1st May 1996 and drawn from a hat. First opened letter gets whatever – it could not be fairer for people out of town. All successful customers will be notified. PRICES START FROM $1.00 LOCAL BUYERS: LOCAL SALE SUNDAY 5TH MAY 1996 – 9AM to 3PM. Located at warehouse 26 Fulton St, South Oakleigh. Phone for further details. 100MHz Tektronix 465M Oscilloscope 2-Channel, Delayed Timebase VERTICAL SYSTEM Bandwidth & Rise Time: DC to 100MHz (-3dB) and 3.5ns or less for DC coupling and -15°C to +55°C. Bandwidth Limit Mode: Bandwidth limited to 20MHz. Deflection Factor: 5mV/div to 5V/div in 10 steps (1-2-5 sequence). DC accuracy: ±2% 0-40°C; ±3% -15-0°C, 40-55°C. Uncalibrated, continuously variable between settings, and to at least 12.5V/div. Common-Mode Rejection Ratio: 25:1 to 10MHz; 10:1 from 10-50MHz, 6cm sinewave. (ADD Mode with Ch 2 inverted.) Display Modes: Ch 1, Ch 2 (normal or inverted), alternate, chopped (250kHz rate), added, X-Y. Input R and C: 1MΩ ±2%; approx 20pF. Max Input Voltage: DC or AC coupled ±250VDC + peak AC at 50kHz, derated above 50KHz. HORIZONTAL DEFLECTION Timebase A: 0.5s/div to 0.05µs/div in 22 steps (1-25 sequence). X10 mag extends fastest sweep rate to 5ns/div. Timebase B: 50ms/div to 0.05µs/div in 19 steps (1-2-5 sequence). X10 mag extends maximum sweep rate to 5ns/div. Horizontal Display Modes: A, A Intensified by B, B delayed by A, and mixed. CALIBRATED SWEEP DELAY Calibrated Delay Time: Continuous from 0.1µs to at least 5s after the start of the delaying A sweep. Differential Time Measurement Accuracy: for measurements of two or more major dial divisions: +15°C to +35°C 1% + 0.1% of full scale; 0°C to +55°C additional 1% allowed. TRIGGERING A & B A Trigger Modes: Normal Sweep is triggered by an internal vertical amplifier signal, external signal, or internal power line signal. A bright baseline is provided only in presence of trigger signal. Automatic: a bright baseline is displayed in the absence of input signals. Triggering is the same as normal-mode above 40Hz. Single (main timebase only): The sweep occurs once with the same triggering as normal. The capability to re-arm the sweep and illuminate the reset lamp is provided. The sweep activates when the next trigger is applied for rearming. A Trigger Holdoff: Increases A sweep holdoff time to at least 10X the TIME/DIV settings, except at 0.2s and 0.5s. Trigger View: View external and internal trigger signals; Ext X1, 100mV/div, Ext -: 10, 1V/div. Level and Slope: Internal, permits triggering at any point on the positive or negative slopes of the displayed waveform. External, permits continuously variable triggering on any level between +1.0V and -1.0V on either slope of the trigger signal. A Sources: Ch 1, Ch 2, NORM (all display modes triggered by the combined waveforms from Ch 1 and 2), LINE, EXT, EXT :-10. B Sources: B starts after delay time; Ch 1, Ch 2, NORM, EXT, EXT :-10. X-Y OPERATION Sensitivity: 5mV/div to 5V/div in 10 steps (1-2-5 sequence) through the vertical system. Continuously variable between steps and to at least 12.5V/div. MACSERVICE PTY LTD $900 Optional cover for CRT screen – $35 X Axis Bandwidth: DC to at least 4MHz; Y Axis Bandwidth: DC to 100MHz; X-Y Phase: Less than 3° from DC to 50kHz. DISPLAY CRT: 5-inch, rectangular tube; 8 x 10cm display; P31 phosphor. Graticule: Internal, non-parallax; illuminated. 8 x 10cm markings with horizontal and vertical centerlines further marked in 0.2cm increments. 10% and 90% markings for rise time measurements. Graticule Illumination: variable. Beam Finder: Limits the display to within the graticule area and provides a visible display when pushed. Australia’s Largest Remarketer of Test & Measurement Equipment 20 Fulton Street, Oakleigh Sth, Vic, 3167. Tel: (03) 9562 9500; Fax: (03) 9562 9590 **All illustrations are representative only. Products listed are refurbished unless otherwise stated. Countr Interstate y & Call Free Ca ers 1800 680 ll 680 T MACSERVICE P/L FOR ALL YOUR FLUKE REQUIREMENTS ●   FREE CALL: 1800 680680 REFURBISHED PRODUCTS: MINIMUM 90-DAY WARRANTY ● CONTACT MACSERVICE FOR ALL YOUR FLUKE REQUIREMENTS ACSERVICE FOR ALL YOUR FLUKE REQUIREMENTS ●   FREE CALL 1800 680680 ● ALL In this short series, we will investigate those most useful electronic instruments, Cathode Ray Oscilloscopes. In this first part we will look at analog oscilloscopes and delve into their basic operation. By BRYAN MAHER T HE CATHODE RAY Oscilloscope, commonly referred to as a CRO or scope, is an extremely useful instrument for experimenters and designers, and for servicing. The purpose of any oscilloscope is to enable us to observe a light pattern in the shape of a graph of whatever electrical signal is applied to the instrument, as depicted in Fig.1. Many details of voltage waveforms can be inspected, such as peak values, rise and fall times, frequency, period, glitches, interferences, oscillation or instability. Also, we can trace signals through circuits for the source of gross distortion, if present, as shown in the photo next to Fig.1. The pure sinewave is the input voltage to an audio power amplifier which is faulty, while the distorted signal is the output of that amplifier resulting from severe crossover distortion. A CRO can be used with radio transmitters or receivers to display amplitude modulated (AM) signals and show clearly the modulation percentage and any over-modulation, if present. With suitable probes, current waveforms can be displayed. Also, we can display the magnetic properties of iron or ferrite materials, draw the B/H curve and illustrate hysteresis. In fact, the range of device parameters which can be measured and displayed on an oscilloscope is virtually unlimited. The heart of any oscilloscope is the 12  Silicon Chip cathode ray tube, sometimes called a CRT. A simplified cross section of an oscillo­scope tube is shown in Fig.2. The long glass vacuum tube has a screen at one end, the inside surface of which is coated with a fluorescent phosphor materi­ al. Also the inside surface of the glass side walls, near the screen, is coated with a conductive material called Aquadag which is connected to an external terminal. At the opposite (socket) end is a heater filament and a coated cathode which emits elec­trons. A high voltage DC source has its positive output connected to the aquadag coating near the screen while the negative termi­nal is connected to the cathode. Electrons emitted from the cathode are attracted and accel­erated to the front screen by the high positive voltage. The electrons arrive at the The Hitachi V223A is a modern dual-channel oscilloscope. This portable model, intended for field service as well as laboratory work, offers DC to 20MHz bandwidth, 1mV/div sensitivity and numerous "creature comforts". Above: most oscilloscopes can display two separate signals simul­taneously. In this off-screen photo, a dual input CRO is being used to signal trace through an amplifier under repair, to find the point at which the signal becomes distorted. By comparing the input (sinewave) signal with the signals found at different points along the circuit, the faulty section can be identified. Fig.1: by moving a spot of light on its front screen, a cathode ray oscilloscope (CRO) can draw a graph of any voltage signal applied to its vertical deflection plates. screen with sufficient energy to cause the sensitised material on the inside surface of the front screen glass to fluoresce, or to emit light, at point L. This material, or phosphor, consists of extremely fine grained compounds of specially select­ed light metals. Screen persistence Any point on the CRO screen will give off some light for a little time after the electron beam has moved away. The time taken for this lingering light to fade away to 1% of its initial value is called the persistence time. A typical value for screen persistence in the phosphors used in oscilloscopes is 250 microseconds. Imagine that the frequency of the vertical deflec­tion signal applied to the Y1-Y2 plates in Fig.2 is increased – so that the spot moves up and down the screen faster in less than 250 microseconds. The light spot will be moving faster than screen persistence time and so the spot will trace the whole vertical pathway before any one point can fade away. As a result, we will see a complete vertical line drawn on the screen. When the emitted light ceases al- Fig.2: simplified part diagram of a CRO tube, showing only the evacuated hard glass envelope; the heater and cathode at the lefthand end; the vertical deflection plates Y1, Y2; and the fluorescent phosphor screen at right. The heated cathode emits electrons. A conduc­tive coating called aquadag (AQD) is deposited on the inside surface of the tube near the righthand end. This is connected to the positive end of high voltage supply. March 1996  13 Fig.3: cutaway drawing of a simple CRO tube showing the heater h, cathode K, control grid G1, focus grid G2, accelerating grid G3, vertical deflection plates Y1 & Y2, and horizontal deflection plates X1 & X2. This example shows a 5kV acceleration potential between G3/ screen and cathode K. A1-A5 form the vertical deflection amplifier system, while A6-A10 make up the timebase gen­erator which provides the sawtooth horizontal sweep voltage. Oscilloscopes are such useful instruments that two or more are often used simultaneously on an electronic workbench, as in the scene above. The scope at the right is actually a spectrum analyser and is showing the harmonics of the waveform on the scope at left. 14  Silicon Chip tence time. Some of the common screen phosphors and their specific uses are listed in Table 1. Vertical deflection In Fig.2, a pair of metal plates, Y1 and Y2, are placed above and below the beam of electrons. If a voltage is applied between these plates, with Y1 more positive than Y2, then the resulting electric field will attract the electron beam upwards in the direction of Y1. Thus the electrons will strike the screen material at point M and cause light to be Fig.4: simplified horizontal sweep voltage which deflects the electron beam across emitted there. the CRO tube screen. The rising ramp voltage from time t1 to t3 sweeps the beam Similarly, if the potentials on forward from left to right of screen. During the short time t3 to t5 the beam is swept Y1 and Y2 are reversed, the elecback (retrace or flyback) from right to left of screen. In very simple systems the next tric field will deflect the electron forward sweep then commences. beam downwards, striking the screen material at point P, where most immediately after the elec­tron removed (ie, a long persistence time), light will be emitted. Y1 and Y2 are irradiation has been removed (ie, a we call that screen phosphorescent. called the vertical deflection plates. very short persistence time), we say If a very low frequency repetitive Phosphor numbers that the screen is fluorescent. voltage, which swings through both Conversely, in cases where light conpositive and negative values, is These days oscilloscope tube mantinues to be emitted for a considerable ufacturers can produce screens with applied between plates Y1 and Y2, time after the electron beam has been the electron beam will follow this almost any desired colour and persis- Table 1: Commonly Used Phosphor Numbers & Screen Properties Phosphor Number Screen Colour Persistence Time to 1% Uses and comments P1 Green 50ms Cathode Ray Oscilloscopes and RADAR P2 Yellow/Green 200us to 4% CRO tubes and RADAR P4 White Blue 150us Yellow 480us TV B/W Px tube. Blue component dominates the yellow component; giving daylight white. P5 Blue 52us High speed CRO, for off-screen photography P7 B/G/Y Blue 500us Yellow >3 sec. RADAR cascade screens. Blue image fades fast leaving lasting yellow record. P11 Blue 500us CRO off-screen photography P12 Orange 420ms RADAR receivers P14 (B+R)/Y Purple 200us Yellow 120ms RADAR two-layer cascade screens P15 UV/Violet/G (time to 10%) Violet 3us UV 0.05us Flying-Spot scanning TV camera tube. Fastest screen made P16 UV/Violet 0.12us (10%) Flying-Spot scanning TV camera tube. Fastest visible screen made P22 Blue/Green/Red Blue 5ms Green/Red 50ms Colour TV P28 Yellow/Green Yellow 7 sec RADAR P31 Green 250 microsec Preferred phosphor for Oscilloscopes. P33 Orange 8 seconds RADAR P34 B/G/Y 400 seconds RADAR long persistence March 1996  15 Fig.5: a sinewave signal (a) applied to the vertical input terminal of an oscilloscope deflects the beam (and the consequent spot of light on the screen) in a vertical direction in propor­tion to the voltage value of (a) at any time. At the same time, the electron beam is deflected horizontally by the ramp voltage (b) generated by the sweep system and applied to the horizontal deflection plates. The combined action of both voltages (a) and (b) draws a graph on the screen of voltage (a) as a function of time. changing Y1-Y2 field up and down. Observing the screen, we would see the light spot travel slowly up and down, following a straight line. Horizontal deflection When you draw a voltage waveform 16  Silicon Chip on paper, for instance a sinewave, you use a vertical scale of volts to represent the signal and a linear horizontal scale to represent time. To show the same waveform on the screen of the CRO, the spot of light is moved horizontally at constant speed (X input) and at the same time moved vertically, corresponding to the vertical input signal. Fig.3 depicts a cutaway view of a simple oscilloscope tube, with vertical deflection plates Y1 & Y2. In addition, there are a pair of horizontal deflection plates, X1 & X2, one each side of the electron beam. Any voltage waveform applied to these plates will deflect the electron beam sideways. For the electron beam to move horizontally at constant speed, the voltage applied to the horizontal deflection plates must increase in a straight line with respect to time. So a linear ramp voltage signal (or sawtooth) is applied to the horizon­tal plate. This waveform is shown in Fig.4. This horizontal deflection voltage must run from negative values, through zero, to positive values, to take the spot from far left to far right of screen. In Fig.4, this horizontal deflection voltage is at its most negative at time t1. Therefore, the spot of light will be at the left of the CRO screen. Below: in research laboratories, oscilloscopes are often dedicated to specific tasks. The scopes in this photo are permanently connected in a measurement setup. As the voltage rises towards zero, the light spot moves horizontally to the right, reaching centre screen at time t2. Continuing on, the trace reaches extreme right of screen at time t3. Now let us start again but this time with the vertical input signal applied to the Y1-Y2 plates. The light spot on the screen will trace out a graph of the vertical signal, as depicted in Fig.5, as its voltage values change with time. Notice that in Fig.5 we have arranged for the horizontal signal to start at time t1, just as the signal applied to the verti­cal plates passes through zero. This is called synchronisation, a topic we will go into a little later. This is an old 100mm CRO tube made by Cossor. The black aquadag conductive coating, extending from about the middle to near the screen end, can be seen on the inside of the glass envelope. These days, all but the cheapest CRO tubes have a rectangular screen. Flyback & blanking We have drawn the first trace on the screen, from time t1, through t2 to t3. Usually, to obtain a bright picture, we repeatedly redraw this trace many times, superimposed. To do this, the electron beam must return from the t3 position (at far right of screen) to the starting point at far left of screen as quickly as possible, so that it is ready to draw the trace over again, restarting at time t1. We cannot change the voltage of the horizontal deflection signal in Fig.4 from maximum positive to maximum negative instan­taneously (ie, it cannot be done in zero time). Therefore, in Fig.4, t3 (RHS of screen), t4 (mid screen) and t5 (LHS of screen) are not simultaneous. But they can occur in a very short interval of time. This fast return of the horizontal signal is called the “retrace” or “flyback” because the electron beam has to fly back to its initial starting position. To prevent a confusing trace being drawn on the screen by the spot of light flying back at high speed, the electron beam is turned off during retrace. This is called fly­back blanking. Vertical & horizontal stages The vertical amplifier is also shown in schematic form on Fig.3. There are five amplifier stages shown although typical scopes may have more or less amplifier stages. A1 accepts whatev­er input signal you want to view on your oscilloscope, reduced if too large by attenuator VR1. A3 provides a phase change action so that A4 and A5 can deliver a push-pull or complementary drive to the vertical deflection plates Y1 and Y2. The basic essentials of a timebase generator and X or hori­zontal sweep amplifiers are also shown in Fig.3. A6 is an oscil­lator which produces the linear ramp voltage signal. It is also referred to as a sawtooth waveform generator. CX indicates that capacitors can be switched in the A6 circuit to produce different rates of rise of voltage; ie, different amounts of time to get from t1 to t3. This is called changing the sweep rate. A9 provides a phase change for the drive to A10. Thus, A8 and A10 put out a complementary signal sufficient for the horizontal deflection plates X1 and X2 to deflect the electron beam across the full width of the CRO screen. Beam current In Fig.3, the CRO tube heater heats the cathode which emits copious quantities of electrons. The conductive coating (aquadag) and grid G3 are connected to the positive end of a high voltage supply, shown in this example as 5kV. The relatively positive G3 grid and screen end attract the electrons emitted from the cathode, K. The voltage applied to grid G1 is even more negative than that on the cathode. This allows G1 to control the quantity of electrons in the electron stream (the beam cur­ rent), by the voltage difference between G1 and the cathode. Yes, that stream of electrons is an electric current. Its value may be 20 microamps for some simple CRO tubes, or 50 milliamps or more in some high brightness top performance tubes. However, electron beam current does not obey Ohm’s Law. Instead, it is proportional to the square root of the acceleration voltage which causes it to flow! Hence, the G1-K potential decides the brightness of the trace on the CRO screen. G2 is called the focus grid. The mass of electrons is focused, by the potential difference between G2 and G3, into a stream, to arrive at the screen at a fine point. G3 is a hollow metal cylinder called the accelerating grid. Being more positive than the cathode, G3 attracts electrons away from the cathode. The electron stream passes straight through G3 without touching it and continues on to the screen. In this example of a simple CRO tube, G3 and the screen are at the same poten­ tial. In more complex tubes this is not so, as we shall see in a future article. Grounding of 5kV supply To prevent deceleration of the electrons, everything to the right of G3 must be either at the same potential as G3, or more positive. Because all deflection plates are part of the vertical (Y) or horizontal (X) amplifier circuits, their voltage levels are at amplifier potentials: usually no more than a few hundred volts above or below ground. The above two statements together imply that G3 and the CRO tube screen must be no more than a couple of hundred volts above ground, about the same potential as Y1, Y2 and X1, continued on page 83 March 1996  17 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Programmable Electronic Ignition System For Cars From time to time, many enthusiasts wish that they could vary the ignition advance curve or alter the dwell angle on the distributor of an old car or motorbike. This simple but sophisti­cated system will readily meet those needs. By ANTHONY NIXON This user programmable ignition system can be easily in­tegrated with the SILICON CHIP High Energy Ignition System (see May 1988), or readily adapted to suit other systems. Its main features are listed in Table 1. As shown in the photographs, the Ignition Programmer is built on a small PC board which carries a keypad. All data is entered via this keypad, so that 22  Silicon Chip new advance curves and dwell angles can be quickly programmed. To simplify the circuit and make construction easy, the unit is based on the versatile PIC16C84 microprocessor. The following parameters can be programmed into the system: • The revs (RPM) at which ignition advance begins; • The revs (RPM) for full advance; • • • • • • Maximum advance angle; Rev limit; Dwell angle; Vacuum advance; Number of cylinders; and A 2-digit security code. A useful feature of the system is that it allows two sets of data to be entered, either of which can be selected when the ignition is turned on. For example, the module can accommodate an engine which runs on both petrol and gas, as it allows the timing to be quickly changed for these different fuels to get the best performance. How it works The circuit (see Fig.1) is fairly simple, thanks to the PIC microprocessor (IC1). In operation, ignition timing information from the points Fig.1: the circuit is based on a PIC16C84 programmed microprocessor (IC1). This processes timing information from the points (or some other pick-up) and drives the High Energy Ignition System to switch the coil. Table 1: Main Feat ures • User programmable • Keypad data entry • Security coded (2 di gits) • Can store two sets of data • Tachometer drive ou tput • Points or other sens or input • Automatic coil curre • • nt switch nning off if motor not ru 7-segment LED di splay LED indicator for initial timing setup conditioning circuitry on the High Energy Igni­ tion module is fed into pin 1 (RA2) of IC1, while the ignition coil is controlled from pin 2 (RA3). This pin 2 output drives the coil via the “business-end” of the High-Energy Ignition System. The keypad used is a standard 12key unit with * and # symbols. Its rows connect to the RB3-RB6 outputs of the microprocessor, while its columns go to RB0-RB2. As it operates, the microprocessor alternately takes its RB3-RB6 outputs high and low. Thus, when a key is pressed, the logic level is sensed by one of the inputs RB0RB2 and the microprocessor takes the appro­priate action. For example, if key “3” is pressed, then RB3 of IC1 (pin 9) will be connected to RB2 (pin 8). Resistors R5-R7 (10kΩ) normally pull RB0-RB2 low. RA4 (pin 3) of IC1 is the vacuum advance input, while S1 is a micro­switch which is actuated by the vac­ uum advance motor (see photo). When the manifold vacuum is high, S1 is held open and RA4 is pulled high via R8 (10kΩ). Conversely, when the vacuum is low, S1 is closed and RA4 is pulled low so that the microproces­sor retards the timing. The 7-segment display is driven from IC2, a 74HC164 serial-to-parallel shift register. This receives serial information from pin 17 (RA0) of IC1 and is clocked from pin 18 (RA1). It displays such things as errors, programmable system variables and which set of data will be used. IC3, an MC34064 undervoltage sensing circuit, is used to ensure that the microprocessor resets reliably when the ignition is turned on. An 8MHz crystal, in conjunction with C6, C7 & R4, sets the microprocessor clock, while LED1 is driven from pin 13 (RB7) to provide points status indication (ie, it indicates whether the points are open or closed). The power supply uses a series diode (D1) for reverse polarity protection, a zener diode (ZD1) to clip any large spikes, and a 5V 3-terminal regulator (REG1). The latter provides a +5V supply rail for the ICs. Fig.2 shows how the Programmer Module interfaces with the SILICON CHIP High Energy Ignition System. As shown, the voltage across the points is filtered and fed to Q2’s base via D5 and a 10kΩ resistor. The signal at the collector has a 5V logic level and this is the “POINTS” input signal to the microprocessor on the programmer module. The “COIL” output from the programmer module is used to trigger IC1, the MC3334 ignition chip. IC1 in turn drives Q1 which is the coil switching transis­tor. Zener diodes D1-D4 protect Q1 from the high voltage spikes generated by the back EMF of the coil. Ignition timing In older engines, the centrifugal force generated by weights spinning in the distributor causes the engine March 1996  23 Fig.2: here’s how the Ignition Programmer module interfaces with the High Energy Ignition System. The coil output triggers the MC3334 ignition chip (IC1) and this in turn drives the coil switching transis­tor (Q1). timing to advance with increasing revs. Additionally, a vacuum advance mechanism increases the advance as the manifold vacuum rises. This either adds to or subtracts from the centrifugal advance, so that varying degrees of advance are obtained for different engine speeds and loads. Electronic advance In this system, the centrifugal advance is calculated according to engine RPM, while the vacuum advance is either on or off, as determined by the logic level on the vacuum advance input (RA4, pin 3) of the microprocessor. Because the advance is now determined electronically, the mechanical centrifugal advance mechanism in the distributor is clamped in the fully advanced position. To do this, the advance weight return springs are removed and the weights themselves are wired so they are held in the fully out position. In addition, the movable vacuum advance plate must be clamp­ ed so that it can’t move when the vacuum actuator is removed. In operation, the Ignition Programmer retards the ignition timing from its preset maximum value, to give the correct amount of advance to suit the operating conditions. As already mentioned, microswitch S1 is operated by the vacuum advance motor. It operates when the required vacuum is reached in the intake manifold (note: this system is also used on some production engines). 24  Silicon Chip Rev limiting is achieved by excessively retarding the igni­tion when the preset value is reached. All other variables are then ignored until the engine revolutions fall below this value. Microprocessor functions Instead of generating look-up tables for engine data, the program calculates a set of variables based on the data entered by the user and stores these in the PIC’s internal EEPROM. When the motor is sensed to be running, the microprocessor uses these variables to generate the timing of the output waveform. Some of the microprocessor’s ignition functions include monitoring the engine RPM, advance timing, dwell pulse width, maximum RPM, vacuum advance pulse width and number of cylinders. As all but the last of these are dynamic and constantly changing, the processor has to continuously recalculate new data. It is interesting to note that to create the various pulse widths and functions while the engine is running, the micropro­cessor only executes about 50 bytes of code and takes about 30µs to do it. Most of the program memory is taken up by the user interface, while the rest is used for data generation, the serial display and setup. When the ignition routine is first activated, the coil is turned on. If the motor is not started within 10 seconds, the coil will switch off and the system will enter MENU mode. This eliminates the possibility of any damage to the coil caused by leaving the ignition on, without the motor running. The coil will also be switched off if the motor stalls. In this case, the system will stay in the ignition routine and wait for the engine to be restarted or the power to be switched off. Construction The Ignition Programmer is easy to build, since all the parts except for microswitch S1 are installed on a PC board coded 05103961. Fig.3(a) shows the parts layout on the PC board. As always, check the PC board for open circuit or bridged tracks before you begin assembly. This done, fit the resistors, diodes and sockets for IC1 and IC2, then install the capacitors and other components. The LED display plugs into a wire-wrap socket (install this at full lead length), while the keypad plugs into an 8-pin header socket. Make sure that the LED display is correctly oriented when plugging it into its socket – it must be mounted with the decimal point(s) towards the bottom of the board. The 8MHz crystal can be mounted either way around but take care with the polarity of the ICs and LED1 – the anode lead of LED1 will be the longer of the two. It will be necessary to solder a wire to the +5V stake which is adjacent to pin 18 of IC1 before you fit the keypad. The keypad on the prototype was secured using machine screws and nuts (use nylon washers on the track Fig.3(a): install the parts on the PC board as shown here and take care if using a different keypad to that shown – see text. side of the board, to prevent shorts). Adjust the assembly so that the keypad is parallel to the PC board when it is plugged into its pin header socket. There’s just one wrinkle here – many keypads have their connections at the bottom instead of at the top. If you have this type of keypad, then it’s simply a matter of running a length of 8-way ribbon cable between the key­pad and the PC board. Note, however, that the pin connections to the keypad matrix will differ from keypad to keypad. The numbers Fig.3(b): this is the full-size etching pattern for the PC board. Check the board carefully for defects before installing any of the parts. in brackets on the circuit diagram (Fig.1) indicate the connections for a Jaycar keypad (Cat. SP-0770) – (ie, pin 2 of the keypad goes to pin 6 on the PC board, pin 7 goes to pin 8, etc). If you buy some other keypad (eg, the Altronics Cat. S-5381), then use the data supplied with the unit to determine the connections. Once the assembly is complete, check all your soldered joints carefully and check the polarity of D1. When you are satisfied that all is OK, connect 12V from a power supply or car battery to the terminals adjacent to the keyboard connector. Installation The exact installation will depend on your particular vehi­cle. If the unit is going in a car, the programmer could be mounted on the dashboard or centre console. Note that the microprocessor board should not be installed under the bonnet, as the components used are not rated for high temperatures. For a motorbike installation, the unit could be mount­ed in a weatherproof box on the handle­bars. Be sure to run all wiring in a professional manner, using proper automotive connectors to ensure reliability. Fig.4 shows how the unit is interfaced to the SILICON CHIP High Energy Ignition System. Note that it will be necessary Fig.4: this diagram shows how the Ignition Programmer is connected to the High Energy Ignition (HEI) module. Note that it is necessary to remove some parts from the HEI board if you are adapting an existing unit. March 1996  25 Make sure that all parts are correctly oriented when building the PC board and don’t forget the wire link next to crystal X1. to remove a number of parts from the centre of the board if you are adapting an existing ignition module. Fig.5 shows the mounting details for the microswitch S1. It is mounted on a rightangle bracket which is attached to the vacuum motor. The arm of the microswitch sits in a slot cut into the vacuum motor actuator and, in the absence of vacuum, is normally held Fig.5: the microswitch (S1) is mounted on the vacuum motor using a right-angle bracket. At low vacuum (ie, ignition off or at high engine loads), the microswitch arm is held down. Conversely, when the manifold vacuum is high (ie, at light engine loads), the microswitch arm is released. 26  Silicon Chip down. When vacuum is present, the actuator moves upwards and the microswitch arm releas­es. Be sure to connect the leads to the microswitch contacts exactly as shown (ie, the lead from pin 3 of the microprocessor goes to the contact marked “NO”). As mentioned previously, the advance plate in the distributor must be clamped at the maximum advance position (see photo). When the ignition is timed (using a timing light), the vacuum advance must be disabled. This is accomplished by removing and blocking the vacuum hose, so that it can have no effect on the vacuum switch. To time the ignition with the engine stopped, turn the crankshaft to the correct position, then rotate the distributor until the LED just turns on. This indicates that the points have just opened. The LED will be off when the microprocessor detects that the points are closed. Note that because the LED drive signal frequency is propor­tional to the engine RPM, this signal can be used to drive a suitable tachometer. Operation When the module is initially powered up, it will enter one of three states. These are as follows: (1). If there is no valid data in the EEPROM, the system will enter the MENU mode and the display will show “-”. This is what should be displayed at the initial power up. (2). If there is valid data but no security code has been pro­grammed, the system will begin its ignition routine and wait until the motor is started. The display will show the selected data channel. If the “9” key is pressed before the motor is started, the system will exit the ignition routine and enter the MENU mode to enable the user to make data changes. This option will not work after the motor has been started. (3). If there is valid data and a security code has been pro­grammed, the display will be blank and the system will not oper­ ate until the security code is entered. It will then show the selected data channel. If a mistake is made when entering the first digit, you can press the “#” key, then enter the digit again. This function does not work for the second digit, however. If it is entered incor­ rectly, the microprocessor shuts down until it is reset by turn­ing the power off and on again. MENU access using the “9” key is as detailed in (2) above. The keypad used in the prototype has its connecting pads at the top and plugs directly into the connector on the PC board. If you use a Jaycar or Altronics keypad with the pads at the bottom of the unit, the connections will have to be run using ribbon cable. Note, however, that the pin connections to the keypads will be different (see text). Keypad modes (1) Keypad Power-up Mode: if key 7 is pressed while powering up, the alternative channel is selected (other keys have no function). (2) Keypad Security Mode (after power is first applied and if data is valid): Key Function # Enter/exit code entry 0-9 Code entry (2 digits) * No function (3) Keypad Ignition Mode (ignition on, engine not running and data valid): Key Function 9 Enter menu mode Other No function When the system is initially turned on and no data has been entered into the internal EEPROM, the ignition won’t work. The system switches to MENU mode automatically and this is indicat­ed by the display coming on with only the centre segment lit. When in MENU mode, the keypad functions are as shown in the follow­ ing list: This close-up view shows how the microswitch arm is normally held down by the vacuum motor actuator. The common contact (COM) of the microswitch is connected to ground, while the NO contact goes to the PC board. March 1996  27 are shown. Data needs to be entered in the following manner, taking care to enter the digits properly and in the correct sequence: Variable Data Digits Allocated Start advance RPM 800 4 Finish advance RPM 2000 4 Advance angle 30° 2 Cylinders 2 2 Dwell angle 30° 2 Rev limit RPM 5000 2 Vacuum advance angle 10° 2 Security code 59 2 Because all timing in now controlled electronically, the advance plate inside the distributor must be securely clamped in the fully advanced position. In effect, the Ignition Programmer retards the timing from this preset maximum to give the correct value according to engine speed and load. Key 1 2 3 4 5 6 7 8 9 * 0 # Menu Mode Clear EEPROM Clear RAM data Read RAM data Write EEPROM data to RAM Enter new data to RAM Clear display No function Display data set selected at power-up (1 or 2) No function Create ignition data No function Exit to ignition A more detailed explanation of these various keypad functions is as fol­lows: • Key 1: Clears the user data stored in EEPROM. • Key 2: Clears the user data stored in RAM. • Key 3: Displays the data stored in RAM. Each data value entered has a letter assigned to it. A decimal point lights with the letters, to help differentiate between them and the numbers while they are being viewed. The data functions indicated by the let­ters are as follows: 28  Silicon Chip A. – RPM at start of advance b. – RPM at end of advance C. – Advance angle d. – Number of cylinders E. – Dwell angle F. – Rev limit G. – Vacuum advance angle H. – Security code To cycle through the data, press the “*” key. After the security code has been shown, the display wraps around to the RPM at start of advance again. To exit this display mode, press the “#” key. No other keys has any effect while reading data. A typical example display is as follows: A.0800, b.2000, C.30, d.02, E.30, F.50, G.10, H.59. Key Data Read 0-9 No function * Cycle to next data # Exit data read routine • Key 4: Gets the data from EEPROM and puts it into RAM. To view this data, press the “3” key and use the “*” key to cycle through the data, as explained above. Any data previously in RAM will be overwritten. • Key 5: Enters new data into RAM. Initially, an “A” will be dis­ played to indicate the first data entry. For simplicity, and as internal memory is limited, no further letter delimiters This data is entered exactly as follows: 0800 2000 30 02 30 50 10 59 There are a few things to note here: (1) No further letter delimiters after A are shown; (2) After entering the security code, “-” is displayed, indicat­ing the end of data entry; (3) There are leading zeros for the Start Advance RPM and for the Cylinder; (4) 50 is entered for the 5000 RPM limit; and (5) Make sure that you don’t forget the security code! If valid data is detected on power-up with a non-zero value in the security code, then this code must be entered when the system is to be used –eg, turn ignition on, press #, press 5, press 9 (code from data above). The ignition routine will now begin and the display will show the data set selected. If an incorrect code is entered, the ignition routine will not begin and no further response will be available from the keyboard. Turning the ignition off and then on again will allow the code to be re-entered. If you forget the code, the only way to gain access to the system is to start entering the 100 combinations one by one. Another example, this time with no security code, is shown below: Variable Data Digits Allocated Start advance RPM 650 4 Finish advance RPM 1500 4 Advance angle 12° 2 Cylinders 8 2 Dwell angle 0° 2 Rev limit RPM 4500 2 Vacuum advance angle 9° 2 Security code None 2 Example Programming Sequence A complete programming sequence (with no data entered) is as follows: Action Turn power on Press 5 Enter all data When finished Display A DATA - Reviewing Data Press 3 A ? DATA - Press * Press # Calculate & Store Data Press * if OK if error & delimiters finish reading display flashes ? if OK when finished if error ? A ? DATA - if OK if error if OK if error & delimiters finish reading Review EEPROM Press 4 Press 3 Press * Press # To program the second data set, first turn the power off and then turn it on again with key 7 pressed. The data is then programmed in and reviewed exactly as set out above. This data is entered exactly as follows: 0650 1500 12 08 00 45 09 00. As well as the previous items noted, if a zero dwell angle is entered, then a 1ms dwell angle will be set automatically. If any angle is calculated to be less than 1ms, then 1ms will be used. In addition, as the engine RPM increases, a point will be reached when the dwell width is theoretically less than 1ms. When the microprocessor detects this, it sets the minimum to 1ms. Important note: the dwell angle referred to above is the angle through which the points are open and not the angle through which they are closed, as is normally the case. The dwell angle from any input device has no effect on the system dwell setting. However, it is good practice to set the points normally, as speci­fied by the manufacturer. The microprocessor debounces the input, whether points or electronic sensors are used. • Key 6: Clears the display, so that it shows “-”. • Key 7: No function. • Key 8: Shows current data set selected (1 or 2). • Key 9: No function. • Key *: Calculates and stores, in EE­ PROM, new data that the system will use when the ignition routine is active. Valid data must have been enter­ed by the user. Care should be taken when choosing this data, as values which are too far away from standard may not work with the system. Memory constraints prohibit all but minor error checking of input data. If the number of cylinders is entered as zero then an error will occur in the calculations, as this will result in an inter­nal division by zero. Data entry can be aborted by pressing the “#” key. If this is done, no calculations can occur and there will be no data in RAM which can be read. Nor can it be stored in EEPROM. PARTS LIST 1 PC board, code 05103961, 76 x 70mm 1 12-key keypad (see text) 1 8MHz crystal (X1) 1 8-pin PC male connector (6mm pins) 1 8-pin PC female connector (6mm shroud) 1 14-pin wire wrap IC socket 1 18-pin IC socket (for IC1) 4 3mm x 20mm bolts 12 3mm hex nuts 4 3mm insulating washers 9 PC stakes Semiconductors 1 PIC16C84 programmed microprocessor (IC1) 1 74HC164 shift register (IC2) 1 MC34064 power-on reset (IC3) 1 78L05 regulator (REG1) 1 1N4002 diode (D1) 1 1N4745 16V 1W zener diode (ZD1) 1 LTS312 common anode 7-segment LED display (DS1) 1 red LED (LED1) Capacitors 1 100µF 25VW PC electrolytic 1 47µF 25VW PC electrolytic 3 0.1µF 100VW MKT polyester 2 18pF ceramic Resistors (0.25W, 1%) 6 10kΩ 9 1.5kΩ 1 2.2kΩ 1 22Ω Note: the programmed micro­ processor can be purchased for $27.00 including postage from Mr. A. Nixon, 20 Eramosa Road East, Somerville, Vic. 3912. Note that the display will flash while it is calculating the new variables, then turn off when finished. One major limitation of the system is that the total value of the advance, dwell and vacuum advance angles must not exceed the angle between cylinders. If this did happen, the microprocessor would still be in the middle of controlling the timing sequence from the previous trigger when the points opened again. This in turn would force new parameters to be calculated, which would over­write the old ones and cause erratic operation. In practice, this is not a problem March 1996  29 angle of 15°, the dwell angle results in a distributor angle of 30°, and the vacuum angle results in a distributor angle of 15°. This gives a total distributor angle of 60°, which is well over the 45° maximum. A more suitable set of parameters would be: Variable Start advance RPM Finish advance RPM Advance angle Cylinders Dwell angle Rev limit RPM Vacuum advance angle Security code The completed unit can be installed on the dashboard or centre console, or fitted into a weatherproof case and mounted on a motorbike. Do not mount the unit under the bonnet, as the parts are not rated for high temperatures. unless some “out of the ordinary” values are entered, especially for an 8-cylinder en­gine. The following example explains this more clearly: Variable Start advance RPM Finish advance RPM Advance angle Data 800 2000 30° Cylinders Dwell angle Rev limit RPM Vacuum advance angle Security code 8 30° 5000 30° 59 The cylinder angle for an 8-cylinder engine is 45°. From the above data, the advance angle results in a distributor Data 800 2000 12° 8 20° 5000 10° 59 The total distributor angle now becomes 31° and this repre­sents reasonable ignition timing for an 8-cylinder engine. • Key 0: No function. • Key #: This key terminates the data entry mode while entering data. Alternatively, it exits to the ignition routine if valid data is available while in MENU mode. If a keypress error occurs, then ? will be displayed. Key­press errors are: (1) Pressing key 3 with no RAM data; (2) Pressing key 4 with no EEPROM data; (3) Pressing key * with no data entered; (4) Pressing key # with no valid SC data. Fitting The Programmable Ignition System To A Motorbike I have tested this system on a 1948 Harley Davidson motor­cycle which originally only had a twist grip advance retard on the handle­bars.I also replaced the points with a Hall Effect transducer and thereafter had a fully programmable, maintenance-free ignition system. The major problem was how to run it off a 6V supply and this was overcome with a small switchmode supply. Another problem that I encountered was that the microprocessor behaved erratically while the engine was running. The solution involved removing the old copper-core plug leads and replacing them with suppressed ones. The program as it stands at the moment can only support distributors 30  Silicon Chip that have even spacing between cylinder angles – which covers most vehicles. However, engines that have irregular spacing (eg, Harley V Twins with two cylinders and a 45° angle) will fool the processor into retarding the timing for one of the cylinders. This is because the processor will calculate an ad­vance value for one cylinder but the calculated value for the other cylinder will be different because the two cylinders are not equally spaced at 180° around the crankshaft. In my case, a spe­ cial program was written to cater for this. If you want to eliminate the points, one option is to strip down the existing distributor and modify it for electronic operation. Alternatively, you can use a secondhand electronic unit from a wrecker if one is available. One advantage of keeping the points is that if the electronics decide to fail, the points can be connected directly to the coil and the ignition retarded (by rotating the distributor) to provide a limp-home mode. The next stage of development would be to eliminate the distributor completely and use the crank position as the timing reference. A crank sensor is certainly favourable when it comes to installing an electronic system but cost is another considera­tion – a “distributorless” ignition requires one dual output coil for every two cylinders and these would be fed by their own driver circuits, which in turn would be con­trolled by dedicated pins on the microprocessor. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Australian Defence Force – Navy Build this useful test accessory A zener diode tester for your DMM Plug this simple adaptor into your DMM and you can di­rectly read the values of zener diodes. It covers the range from about 2.2V right up to 100V. By JOHN CLARKE 32  Silicon Chip H OW MANY ZENER DIODES do you have stashed away which cannot be used simply because their value is unknown? In many cases, the type number will be missing (rubbed off) or will be very diffi­cult to read because the print is so small. And even if it can be read, the type number will not directly give you the value you anyway – instead, you have to look it up in a data book. This Zener Tester is the answer to this problem. It plugs directly into your DMM, so that you can directly read the break­down voltage of the zener being tested. The unit can measure all the common types from very low values of around 2.2V right up to 100V. It’s best for 400mW and 1W power devices, although it will also provide a reasonably accurate measurement for 3W zeners. Testing zener diodes Testing zener diodes has always been difficult. This is because the current needed to test a low-voltage zener is vastly different to that required for a higher voltage type. In the past, many zener testers tried to circumvent this problem by applying a constant 5mA and then reading off the value of breakdown voltage. Thus, for a 5V zener, the power dissipated would be 25mW and for a 30V zener, 150mW. While these values may appear OK, let’s see why the constant current idea does not work in practice. Fig.1 shows the typical zener characteristic. In the forward direction, the zener behaves as a diode and begins to conduct at about 0.7V. Conversely, in the reverse direction, there is very little current flow (as in a normal diode), until the “knee” is reached. At this point, the zener breaks down and the voltage remains essentially constant over a wide range of currents. Note the maximum power position (the power rating of the zener) and the 10% maximum power location. These two power limits set the operating range of the zener. If the current is taken below the 10% maximum power posi­tion, the zener voltage will drop markedly as it follows the knee in the curve. This means that if we read the zener voltage below the 10% position, the reading will be well under the correct zener voltage which can only be obtained Fig.1: the typical zener characteristic. In the reverse direction, there is very little current flow until the “knee” is reached, at which point the zener breaks down and the voltage remains virtually constant over a wide range of currents. at higher currents. Note: some zener diode types have a very sharp knee, which enables the diode to operate at very low currents Features • Tests 400mW and 1W zener diodes • • Test range from 2.2V to 100V • Connects to a multimeter for zener voltage reading • Battery powered Constant power testing at 200mW while maintain­ing its rated breakdown voltage. Fig.2 shows the curves for both 1W and 400mW zener diodes for voltages from 3-100V. The lower two traces show the 40mW (10% of 400mW) and the 100mW (10% of 1W) power curves, while the upper two traces show the maximum power curves for 400mW and 1W. To properly test 400mW and 1W diodes, we must have the zeners operate between the 100mW and 400mW curves. In this way, we will be above the 10% power point for both types and below their maximum limits. The trace (dotted) for a zener tester using a constant 5mA current shows Specifications Zener diode test power �������������������� 200mW Test power linearity �������������������������� within 10% of 200mW for zener diodes from 4V to 100V; less than 3.5% change for battery supply variation from 6-9V Battery current drain ������������������������ 35mA <at> 9V; 47mA <at> 6V Open circuit output voltage �������������� 112V nominal Overall efficiency ������������������������������ 63% Converter efficiency ������������������������� >90% March 1996  33 Fig.2: voltage vs. current curves for both 1W and 400mW zener diodes, for voltages from 3-100V. The lower two traces show the 40mW (10% of 400mW) and the 100mW (10% of 1W) power curves, while the upper two traces show the maximum power curves for 400mW and 1W. that while zeners from 20-80V fit between these limits, the maximum dissipation is exceeded for 400mW diodes above 80V. At the other end, the 10% limit prevents 1W diodes from giving accurate readings below 20V (for 400mW diodes, the limit is extended to below 8V). One way around this is to use a fixed resistor tester oper­ating from a 110V supply. This will enable all 400mW and 1W zener diodes to be 34  Silicon Chip tested down to about 3V. Note, however, that this type of tester will go close to the 400mW limit at about 66V. At the same time, the tester will also need to provide up to 1.42W of power to dissipate 40mW in a 3V zener. This repre­sents an efficiency of just 3%. While efficiency may not appear to be a problem, it does present a strain on a small 9V battery when it is called upon to deliver 160mA. The final trace shows the 200mW power curve and this fits neatly between the limits specified. The SILICON CHIP Zener Tester follows this curve closely. It always provides the same power to the zener diode, regardless of voltage. And, as a bonus, battery drain is much lower at 35mA. Block diagram The Zener Tester is based on a high voltage supply, pro­duced by stepping Fig.3: block diagram of the Zener Tester. It uses a converter to step up the voltage from a 9V battery so that high-voltage zeners can be tested. The error amplifier and pulse controller ensure that the power delivered to the zener diode remains constant. up from 9V using a converter – see Fig.3. This converter produces up to about 112V, so that high-voltage zeners can be tested. The current supplied to the converter is monitored by error amplifier IC1b which in turn drives a pulse controller (IC2). This maintains a constant current to the converter from the 9V battery. Since the battery voltage is also constant, the power delivered to the converter and thus to the zener is also constant. In practice, this means that the converter alters its cur­rent output depending on the zener voltage. At high zener voltag­es, the current is low and at low voltages, the current is high. A LED reference is used to provide a fixed voltage for the error amplifier, so that current can be maintained. Note that this reference is also compensated for input voltage, so that as the battery voltage falls, the reference voltage rises and allows more current flow through the converter. This maintains the constant power to the converter, regardless of variations in the supply voltage. A standard digital or analog mul- timeter is used to read the value of zener voltage. How it works The full circuit for the Zener Tester is shown in Fig.4. It consists of just a few low-cost components and a stepup trans­former. The step-up circuit uses the two windings of transformer T1 to produce up to 112V. Mosfet transistor (Q1) is used as a switch to charge the primary winding via the 9V supply. When Q1 is switched off, the charge is transferred to the secondary and delivered to a 0.1µF capacitor via diode D1. The advantage of using a 2:1 stepup transformer is that the voltage developed across Q1 is only half that developed across the secondary winding. This means that a 60V Mosfet can be used rather than a 200V type. Q1 is driven by an oscillator formed by 7555 timer IC2. This operates by successively charging and discharging a .0039µF capacitor via a 6.8kΩ timing resistor connected to the output (pin 3). When power is first applied, the .0039µF capacitor is dis­charged and the pin 3 output is high. The capacitor then charges to the threshold voltage at pin 6, at which point pin 3 goes low and the capacitor discharges to the lower threshold voltage at pin 2. Pin 3 then switches high again and so the process is repeated indefinitely while ever power is applied. The current through Q1 is monitored by measuring the vol­tage across the 1Ω source resistor. This voltage is filtered using a 120Ω resistor and a 0.1µF capacitor and applied to error amplifier IC1b. Its output (pin 7) directly drives the threshold pin (pin 5) of IC5. If the current is too high, IC1b pulls pin 5 of IC2 slight­ly lower, so that the pulse width duty cycle to Q1 Fig.4 (below): the circuit diagram of the Zener Tester. IC1b is the error amplifier and this controls the duty cycle of oscillator IC2. IC2 in turn drives Q1 which switches the primary of step-up transformer T1. The secondary output of T1 is then rectified via D1 and applied to the zener diode. March 1996  35 The PC board fits neatly into a standard plastic case, with room for the battery at one end. Take care to ensure that the test terminals are correctly wired. is reduced. This in turn reduces the current. Conversely, if the current is too low, IC1b pulls pin 5 of IC2 higher. This increases the duty cycle of the drive to Q1’s gate and thus increases the current. IC1b compares the average current value with a reference at its pin 5 (non-inverting) input. This reference is derived from the power supply and LED1 via IC1a. In operation, pin 2 of IC1a monitors a voltage dependant reference derived from a voltage divider (100kΩ & 560Ω) across the supply rails. This reference is fed to pin 2 via a 100kΩ resistor, while a 100kΩ feedback resistor gives the amplifier a gain of -1 for this signal path. Similarly, the 1.8V that appears across LED1 is divided using 100kΩ and 2.4kΩ resistors to give about 42mV at pin 3 of IC1a. IC1a then amplifies this signal by a factor of 2 (1 + 100kΩ/100kΩ) to give 84mV. To understand how this all works in practice, let’s assume that the power supply is at 9V. In this case, the voltage across the 560Ω resistor will be 50mV and so the output (pin 1) of IC1a will be at 84 - 50 = 34mV. However, if the power supply falls to 7.5V (for example), then the voltage across the 560Ω resistor will be 42mV. The pin Fig.5: this diagram shows the winding details for the stepup transformer (T1) – see text. Note that both windings are wound in the same direction. 36  Silicon Chip 1 output of IC1a will now be at 84 42mV = 42mV. Thus, as the supply voltage goes down, the reference vol­tage applied to pin 5 of IC1b goes up. This ensures that greater current is supplied at lower voltages, to maintain the constant power. As the accompanying specifications panel shows, this scheme works well, with the power varying by only 3.5% for bat­tery voltage ranging from 6-9V. Power supply Power for the circuit is derived from the 9V battery via switch S1. Note that the battery condition is indicated by the brightness of the LED. If LED1 is dim, then it is time to change the battery. The fact that the circuit will work down to below 6V means that battery life is quite good. Construction Construction of the SILICON CHIP Zener Tester is straight­forward, with most of the parts mounted on a PC board coded 04302961 (56 x 104mm). Begin construction by checking the PC board for shorted tracks or small breaks. In addition, the corners of the PC board will need filing out so that it will fit inside the case. The actual shape is shown on the copper side of the PC board. This done, install PC stakes at the Fig.6 (right): make sure that transformer T1 is correctly oriented when installing the parts on the PC board (ie, pin 1 to bottom left). Fig.7 (far right) shows the full-size PC pattern. external wiring points – see Fig.6. These are located at the positive (+) and negative (-) battery wiring points, at the positive and negative terminal connection positions, and at the switch (S1) and LED1 positions. Once these are in, in­stall the two wire links (next to IC1 and next to IC2). Next, install the resistors, followed by the diodes and ICs. Table 1 lists the resistor colour codes but it is also a good idea to check them using a digital multimeter. Make sure that the diodes and ICs are correctly oriented. The capacitors can now be installed, taking care to ensure that the 100µF electrolytic is oriented correctly. This done, install Mosfet Q1 on the board (metal tab towards IC2). LED1 is mounted on the end of its leads, so that it will later pro­trude through the front panel. Similarly, switch S1 is soldered on the top of its corresponding PC stakes. end on pin 6; (2) wind on 20 turns side-by-side in the direction shown and terminate the free end on pin 3; (4) wrap a layer of insulating tape around this winding. The secondary is wound on in similar fashion, starting at pin 5 and winding in the direction shown. Note that the 40 turns are wound on in two layers (20 turns in each), with a layer of insulating tape between them. Terminate the free end of the winding on pin 4. The transformer is now assembled by sliding the cores into each side of the former and then securing them Transformer winding Transformer T1 is wound using 0.25mm enamelled copper wire – see Fig.5. The primary is wound first, as follows: (1) remove the insulation from one end of the wire using a hot soldering iron tip and terminate this TABLE 1: RESISTOR COLOUR CODES ❏ No. ❏  1 ❏  1 ❏  4 ❏  1 ❏  1 ❏  2 ❏  1 ❏  1 ❏  1 ❏  1 Value 10MΩ 470kΩ 100kΩ 6.8kΩ 2.4kΩ 1kΩ 560Ω 120Ω 10Ω 1Ω 4-Band Code (1%) brown black blue brown yellow violet yellow brown brown black yellow brown blue grey red brown red yellow red brown brown black red brown green blue brown brown brown red brown brown brown black black brown brown black gold gold 5-Band Code (1%) brown black black green brown yellow violet black orange brown brown black black orange brown blue grey black brown brown red yellow black brown brown brown black black brown brown green blue black black brown brown red black black brown brown black black gold brown brown black black silver brown March 1996  37 + + - + Ζ + ENER TESTER POWER + Fig.8: this full-size artwork can be used as a drilling template for the front panel. The test leads are fitted with banana plugs (red for positive, black for negative), so that they can be plugged into standard multimeter terminals. The zener breakdown voltage is the read directly off the multimeter display. with the clips. This done, insert the transformer into the PC board, making sure that it is oriented correctly, and solder the pins. Final assembly A plastic case measuring 64 x 114 x 42mm is used to house the assembled PC board. This is fitted with a self-adhesive label measuring 55 x 103mm. Begin the final assembly by affixing the label to the front panel (lid), then drill out mounting holes for the LED bezel, switch S1 and the two banana plug terminals. You will also need to drill a hole in one end of the base to accept a small grommet. This done, mount the two test terminals (red for positive, black for negative) and fit the grommet and LED bezel in place. Next, fit the board inside the case (it 38  Silicon Chip sits on four inte­gral mounting pillars) and secure it using four small self-tapping screws. The lid can now be test fitted to check that the switch and LED line up correctly with the front panel. Adjust them for height as necessary, then solder the battery clip leads to their respective PC stakes. Finally, run short lengths of hookup wire from the PC board to the test terminals. Additional leads are then attached to the test terminals and brought out via the grommet fitted to one end of the case. Terminate these leads using banana plugs (red for positive, black for negative). This lets you plug the leads directly into a standard DMM or analog multimeter. Testing You are now ready to test the unit. Apply power and check that the LED lights. If is doesn’t, check that the LED is orient­ed correctly. Now measure the voltages on IC1 using a multi­meter. There should be about 9V DC across pins 4 & 8 and a similar voltage between pins 1 & 8 of IC2. If these voltage checks are correct, plug the output leads into your multimeter and press the Power button. Check that the meter reads 112V. If it doesn’t, switch off immediately and check for wiring errors. If everything is OK so far, connect a 1kΩ resistor across the test terminals and check the voltage again (press the Power button). This time, you should get a reading of about 14V across the resistor, which means that the resistor is dissipating about 200mW. If this reading is quite different, check that the voltage across LED1 is 1.7-1.8V and that about 42mV at present on pin 3 of IC1. Assuming a fresh battery, you should also get about 50mV across the 560Ω resistor. If the latter two reading are incor­ rect, check the associated voltage divider resistors. If all is working correctly, you are now ready to measure zener diodes. PARTS LIST 1 PC board, code 04302961, 104 x 56mm 1 plastic case, 64 x 114 x 42mm 1 front panel label, 55 x 103mm 1 pushbutton momentary contact switch (S1) 1 9V battery and battery clip 1 red banana socket 1 black banana socket 1 red banana plug 1 black banana plug 1 EFD20 transformer assembly (Philips 2 x 4312 020 4108 1 cores, 1 x 4322 021 3522 1 former, 2 x 4322 021 3515 1 clips) (T1) 1 2-metre length of 0.25mm enamelled copper wire 1 100mm length of red hook-up wire 1 100mm length of black hookup wire 1 30mm length of 0.8mm tinned copper wire 8 PC stakes 4 3mm screws 1 small grommet 1 3mm LED bezel Semiconductors 1 LM358 dual op amp (IC1) 1 7555, TLC555, LMC555CN CMOS timer (IC2) 1 MTP3055E or A version N-channel Mosfet (Q1) 1 3mm red LED (LED1) 1 1N4936 fast recovery diode (D1) 1 56V 3W zener diode (ZD1) Capacitors 1 100µF 16VW PC electrolytic 2 0.1µF MKT polyester 1 0.1µF 400VDC polyester 1 .0039µF MKT polyester Resistors (0.25W, 1%) 1 10MΩ 2 1kΩ 1 470kΩ 1 560Ω 4 100kΩ 1 120Ω 1 6.8kΩ 1 10Ω 1 2.4kΩ 1 1Ω SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ There’s just one important thing to watch out for here – be sure to connect the zener diode to the test terminals with the correct polarity; ie, cathode (banded end) to positive, anode to SC negative. Street ___________________________________________________________ March 1996  39 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Model railway level crossing control This circuit was used to control the boom gates for a model railway level crossing. It is based on light dependent resistors (LDRs). The LDRs are fitted between the rails and a “yard” light above illuminates them. As the train interrupts the light to the LDR beam, it operates the relay which then operates the gates long enough for a second LDR circuit to take over. The delay also takes care of any tendency for the booms to lift as the various wagons pass through the beam. Units 3 and 4 could be added for double track operation. Only one LDR circuit is shown and it essentially uses the 555 timer as a one-shot timer which is triggered by pin 2 being forced low; this occurs when the LDR is covered, raising its resistance. E. Scharenguivel, Cloverdale, WA. ($25) Binary counting demonstrator This circuit is used to demonstrate binary counting. IC1, a 555 timer, is wired in astable mode and clocks IC2, a 4024 7-stage binary counter. VR1 allows the speed of clocking to be varied. S1 is added to allow a count to 63 while in the early learning stage and then switched to allow a count to 127. S2 is the reset switch. The circuit can be run from a 9V rechargeable battery. E. Humphreys, Barrack Heights, NSW. ($25) Charge controller for a transceiver This circuit is based on one that originally appeared in “Amateur Radio”. It maintains the charge on a 12V battery which powers a transceiver. When the battery voltage drops below 12.5V, as set by VR1, op amp IC1 turns on Q1 and the relay. This connects the 14V trickle charger. The battery is trickle charged until it reaches 13.8V at which stage the relay is switched off. It remains in this state until the battery voltage drops below 12.5V, at which point 40  Silicon Chip the relay is again activated and the cycle is repeated. L. Toussaint, Shelley, WA. ($25) Precision timer uses cheap crystal This precision timer can be set for periods ranging from 15 minutes to 16 hours. ICI, an MM5369 oscillator/ divider, is accu­rately controlled by a commonly available 3.579545MHz TV colour burst crystal. The variable trimmer at pin 5 can be replaced with a fixed 6.8pF capacitor. The output at pin is 60Hz and this is fed to IC2, a 4040 binary counter configured to provide a count of 3374 via IC4. In effect, IC4 (a 4073 triple 3-input gate) sums the selected binary outputs of IC2 to 3374. At the 3374th count, pin 10 of IC4 goes high, resets IC2 via pin 11 and recommences the next counting cycle. This output also provides a clock input pulse to pin 10 of IC3, another 4040. The net effect is that an accurate clock input pulse of 56.233 seconds duration is provided to pin 10 of IC3. The decoded binary outputs of IC3, Q4-Q10, are then switched as required. Com­ mencing with pin 3/ Q4, a 15 minute delay (actually 449.83 sec­onds) is obtained as pin 3 transits from low to high. The .047µF capacitor and 100kΩ resistor at pin 11 of both 4040s provide an auto-reset function at switch-on. Pin 3 of IC2 pulses LED1 at approximately 0.5Hz intervals to indicate that the circuit is operational. Technically, the correct reset count through IC4 should be 3375 for an exact 15 minute delay at pin 3/Q4 of IC3. To achieve this, pin 9 of IC2 (providing the extra count of 1) would also have to be ANDed but this would require another AND gate IC. As it is, the circuit is accurate to better than 10 seconds in 16 hours. Note that a battery backup is desirable in areas of mains interruptions – each momentary glitch will otherwise cause the circuit to auto-reset. C. O’Donnell, Hoppers Crossing, Vic. ($40) Brake pedal alarm circuit This circuit was designed to sound a buzzer after about 30 seconds to let the driver of a car know that he has had his foot on the brake pedal for too long. The car was fitted with a manual transmission and the owner complained that his brake pads were wearing out too quickly. The reason was that he had his foot on the brakes for too long and thus the need for this timer. The +12V supply comes from the car’s brake switch. When the pedal is depressed, C1 charges via R1. After about 30 seconds, the voltage at the junction of C1 and R1 reaches approximately +10V. This causes ZD1 to con­ duct and bias Q1 on. This pulls down the base of Q2 and turns it on to apply 12V to the relay or a buzzer (in place of a relay). Thus, if the brake pedal is depressed continually for more than 30 seconds, a buzzer will sound or the relay will energise. R2 and D1 are used to discharge C1 quickly after each brake application. P. Howarth, Gunnedah, NSW. ($30) March 1996  41 Build a high-quality ALC for PA systems Designed specifically for PA systems, this high quality Automatic Level Control will maintain a constant output level over a wide range of input levels. It is ideal for setting the volume level in applications which are not monitored by a sound system operator. By JOHN CLARKE Maintaining a consistent volume level from a public address (PA) system is a constant problem requiring continuous adjustments. This is because as people speak, they continually move towards and away from the microphone or even sway from side to side. While this move­ment can 42  Silicon Chip be almost imperceptible, it can have a drastic effect on the volume level. Whenever there is a different person speaking or when music is played, there is again a volume change. These variations can be adjusted by the sound system operator who rides the volume control to maintain an audible level at all times. This can be satisfactory in most instances where there is an operator but for unattended sound systems, an automatic control is a great advan­tage. Again where there are remote loudspeakers driven by a sepa­ rate amplifier, adding an automatic volume control can ensure that the sound levels are consistent regardless of the source level. Ideally, an automatic level control should have as little effect on the sound quality as possible. To this end we have used low distortion and low noise components and have provided adjust­­ments for all the main paramet­ ers. In this way, the control opera­tion can be tailored to your requirements. For example, you may wish to use the unit as a compressor, where the dynamic range of the sound is restricted. This type of response is useful in areas which have high ambient noise. In this case the attack and decay times would be adjusted close to their fast response settings. The gain limit control is adjusted to set the threshold below which the output signal will drop off in level. If set to its lowest setting, the ALC will maintain a constant output for signals down to 2.5mV. This is a very low signal level and will probably be too sensitive for most applications. Adjustment of this control is usually made during listening tests so that the normal range of input signals are effectively amplified. The Automatic Level Control is housed in a small plastic case. A potentiometer is provided for the output level adjustment, while the gain limit, attack and decay controls are trimpots which can be accessed by a screwdriver through holes in the front panel. A power switch and indicator LED are also provided. On the rear panel are two RCA sockets for the input and output signals and a DC socket for the plugpack. Block diagram The general arrangement of the ALC circuit is shown in Fig.1. The input signal is amplified by 5.5 before being fed to IC2, a voltage controlled amplifier (VCA). IC2 is an Analog Devices SSM2018 VCA which features a 117dB dynamic range, .006% THD at 1kHz and unity gain, and a 140dB gain control range. In addition, it has the option to set the output amplifier in class A or AB modes. We opted for the class A mode since this provides excellent distortion characteristics. The AB mode improves noise performance by 3dB but distortion is 10 times higher. The change from one mode to the other is easily implemented by altering a resistor value. IC2 feeds the output level control VR5 and thence the output amplifier IC1b. It also feeds a precision fullwave rectifier. This rectifier monitors both the positive and negative signal excursions which are converted to a DC level by the following filter. The resulting output is applied to the VCA control input which adjusts the gain of this device so that the signal level is constant. The response of the filter will determine how quickly or slowly the gain of the VCA is controlled. Fig.1: the signal output from the VCO drives a precision full-wave rectifier to derive a control signal. This signal is then used to control the gain of the VCO, so that its output remains constant. A gain limit adjustment by way of VR4 and buffer amplifier IC3d prevents the control input from going below a certain preset voltage. This limits the overall gain of the VCA so that automat­ic level control is initiated from a preset minimum signal. Circuit description Fig.2 shows the complete ALC circuit. Input signals to amplifier IC1a are AC-coupled to pin 5. The 100kΩ feedback resis­tor and the 22kΩ resistor to ground set the gain to 5.5. Thus, a 1V input signal produces a 5.5V signal at pin 7. IC2 is the VCA, with the gain controlled by the voltage level at pin 11. The 18kΩ input resistors to pins 4 & 6 and between pins 3 & 14 set Features • • • • • • • Low noise and distortion Constant level over a 52dB input range Adjustable control level (gain limit control) Adjustable attack and decay times Output level control 12VAC plugpack powered Compact size the VCA gain to 1 when pin 11 is at ground. The 47pF capacitors at pins 5 & 8 and 3 & 14 are for compensation Performance Frequency response ��������������������-3dB at 40Hz and 20kHz (measured below compression limit) Signal-to-noise ratio ����������������������87dB with 22Hz to 22kHz filter and 89dB A-weighted at 100mV signal limiting; 74dB with 22Hz to 22kHz filter and 76dB A-weighted at 15mV limit­ing; with respect to 1V RMS output. Harmonic distortion at slowest attack and decay settings...............<.015% at 1kHz, 10kHz and 20kHz for .......................................................18mV to 1V input levels ALC input range ����������������������������2.5mV to 1V Attack time ������������������������������������1ms to 150ms Decay time ������������������������������������20dB/second to 6dB/second Maximum input before clipping �����1.35V RMS Output level �����������������������������������0-1V RMS March 1996  43 Fig.2: the circuit is based on an Analog Devices SSM2018 VCA (IC2). Op amps IC3a & IC3b, together with diodes D1 and D2, form the precision full-wave rectifier. Its output appears at pin 1 of IC3b and is applied to pin 11 of IC2 via D3 and VR1. and rolloff at high frequencies. Op amps IC3a & IC3b, together with diodes D1, D2 and asso­ ciated resistors, form a precision full wave rectifier. When the input signal goes positive, the output of IC3a goes low and the gain set by the 20kΩ input and feedback resistors is -1. This signal is seen at the anode of D2 and is coupled to the inverting input of IC3b via the 10kΩ resistor. The gain for IC3b is set by the 10kΩ and 180kΩ resistors at -18. The overall gain for the input signal is therefore -1 x -18 = +18. Note, however, that there is an extra path for the input signal via the 20kΩ resistor at pin 2 of IC3b. This signal gives a negative signal at the output of IC3b with a gain of -9. Adding the two gains gives us +9. For negative signals, the output of 44  Silicon Chip IC3a is clamped due to the conduction of diode D1. The signal then passes via the 20kΩ resistor connecting to pin 2 of IC3b. IC3b inverts the signal and provides a gain of -9. Since the input signal is negative, the signal at pin 1 of IC3b is positive. The full-wave rectified signal is fed via D3 and VR1 to two back-to-back 100µF capacitors. Diode D3 allows the 100µF capaci­tors to be charged up via VR1 but they are only discharged using VR2 and a 470kΩ resistor. This allows separate control over attack and decay times of the voltage applied to pin 11 of IC2. Trimpot VR3 sets the ALC threshold and it is buffered by IC3c which then offsets the inverting inputs of IC3a and IC3b. VR3 is set so that the signal output at pin 14 of IC2 is at 1V under high signal conditions. Op amp IC3d and VR4 set the gain limit. Basically, VR4 is set so that the voltage at pin 11 of IC2 cannot go below the level clamped by D4 and the output of IC3d. Naturally, pin 11 of IC2 can go above this clamp voltage since D4 is then reverse biased. After it has varied the gain of the input signal, the output of IC2 is AC-coupled to the output level control, VR5. This is buffered by unity gain buffer IC1b. Its output is AC-coupled to the external amplifier via a 10µF bipolar electro­ lytic capacitor and a 100Ω resistor. Power for the circuit is derived from a 12V AC plugpack. This is fed via S1 to D5, D6 and two 470µF capacitors to provide positive and negative supply rails. These are then fed to two 3-terminal regulators (REG1 & REG2) to provide balanced ±12V supply rails. Construction The automatic level control is built PARTS LIST 1 PC board, code 01303961, 98 x 98mm 1 plastic case, 111 x 45 x 140mm, Arista UB14 1 12VAC 300mA plugpack 1 self-adhesive front panel label, 95 x 33mm 1 self-adhesive rear panel label, 95 x 33mm 1 SPDT toggle switch (S1) 1 1MΩ miniature vertical trimpot (VR2) 1 50kΩ miniature vertical trimpot (VR1) 1 22kΩ miniature vertical trimpot (VR4) 1 5kΩ multiturn top adjust trimpot, Bourns 3296 (VR3) 1 20kΩ log pot. (VR5) 1 15mm knob 2 panel mount RCA sockets 1 insulated panel mount DC socket 1 400mm length of hook-up wire 1 100mm length of shielded cable 1 60mm length of tinned copper wire 9 PC stakes Semiconductors 1 LM833 dual op amp (IC1) 1 SSM2018TN VCA (IC2) (available from HarTec Ltd) 1 LF347 quad op amp (IC3) 1 7812 +12V regulator (REG1) 1 7912 -12V regulator (REG2) 4 1N4148, 1N914 signal diodes (D1-D4) 2 1N4004 1A diodes (D5,D6) 1 3mm red LED (LED1) Fig.3: install the parts on the PC board as shown here. Make sure that all polarised parts are correctly oriented and take care to ensure that REG1 and REG2 are not transposed, as they are different devices. on a PC board coded 01303961 and measuring 98 x 98mm. It is housed in an Arista UB14 plastic case measuring 111 x 45 x 140mm. Two selfadhesive labels, each measuring 95 x 33mm, are fitted to the front and rear panels. The PC board layout and wiring diagram is shown in Fig.3. Start your assembly by checking the PC board against the published pattern. Repair any broken tracks or shorts that may be evident. This done, insert the ICs, diodes, resistors and links in the locations shown. Take care with the orientation of the ICs, noting that IC2 is oriented differently to the other two. The accompany­ing resistor colour code chart should be used in selecting each resistor value. Alternatively, use a digital multi­meter to meas­ure them. The diodes must be oriented with the polarity shown – the banded end is the cathode (K). Nine PC stakes are required for external connections to the PC board. When these are in, install the capaci- Capacitors 2 470µF 16VW PC electrolytic 2 100µF 16VW PC electrolytic 3 10µF 25VW PC electrolytic 1 10µF bipolar electrolytic 1 3.3µF bipolar electrolytic 5 0.47µF MKT polyester 1 270pF ceramic 1 68pF ceramic 2 47pF ceramic 1 10pF ceramic Resistors (0.25W 1%) 1 470kΩ 3 20kΩ 1 180kΩ 2 18kΩ 3 100kΩ 1 10kΩ 1 24kΩ 1 4.7kΩ 4 22kΩ 1 100Ω March 1996  45 Fig.4: full-size etching pattern for the PC board. 46  Silicon Chip tors taking care to orient the electrolytics with the polarity shown. The regulators are next and they are oriented with their metal tabs away from the 470µF capacitors. Insert the 7812 into the location nearest D5. Take care to insert each of the trimpots into its correct position. The LED is mounted at full lead length and bent over at right angles so that it goes into its matching front panel hole. It would be a good idea to sleeve one or both of the LED leads to prevent them from shorting together. When complete, the PC board can be secured inside the case by mounting it on the integral standoffs, using the self-tapping screws provided. Affix the adhesive labels to the front and rear panels and drill out the holes for the output level pot, the power switch and the rear panel components. Drill 3-4mm holes for the limit, attack and decay trimpots. A 3mm hole is required for the LED. Secure these components to the front and rear panels, attach the knob and slide the panels into the case. Affix the rubber feet to the base of the case. You can now do the remaining wiring inside the case. Use short lengths of shielded cable for TRIMPOT CODES Value 1MΩ 50kΩ 22kΩ 5kΩ The rear panel carries RCA sockets for the input and output connections, plus a DC power socket. Code 105 504 223 502 the input and output connec­tions as shown in Fig.3. Adjustment & voltage checks Check your work before applying power. Using a multimeter, check that pin 8 of IC1, pin 2 of IC2 and pin 4 of IC3 have +12V present. Similarly, check that pin 4 of IC1, pins 16 & 10 of IC2, and pin 11 of IC3 are at -12V. If the LED does not light, it is probably connected the wrong way around. Trimpot VR3 can only be set by applying a signal to the input. You can use a signal generator set to about 500mV and 1kHz or use a signal such as that from a CD player, tape deck or the audio output from a video player. Connect your multimeter to the output terminals and adjust it to read AC volts. Turn VR4 (the gain limit trimpot) fully anticlockwise and adjust VR3 for a 1VAC reading. Now the ALC is ready for testing on a signal. You can hook the unit up to the line output of the PA system or signal source as mentioned above and the output to the input of a power ampli­fier. Set the output level and adjust the gain limit so that with no signal there is no evidence of noise. Now you can experiment with the attack and decay controls for the type of compression or automatic level SC control required. AUTOMATIC LEVEL CONTROL OUTPUT + MIN GAIN LIMIT MAX + 12VAC IN DECAY ATTACK POWER + + + + LOW HIGH SLOW FAST SLOW FAST + OUT + + IN Fig.5: these full-size artworks can be used as drilling templates for the front and rear panels. RESISTOR COLOUR CODES ❏ No. ❏  1 ❏  1 ❏  3 ❏  1 ❏  4 ❏  3 ❏  2 ❏  1 ❏  1 ❏  1 Value 470kΩ 180kΩ 100kΩ 24kΩ 22kΩ 20kΩ 18kΩ 10kΩ 4.7kΩ 100Ω 4-Band Code (1%) yellow violet yellow brown brown grey yellow brown brown black yellow brown red yellow orange brown red red orange brown red black orange brown brown grey orange brown brown black orange brown yellow violet red brown brown black brown brown 5-Band Code (1%) yellow violet black orange brown brown grey black orange brown brown black black orange brown red yellow black red brown red red black red brown red black black red brown brown grey black red brown brown black black red brown yellow violet black brown brown brown black black black brown March 1996  47 SERVICEMAN'S LOG Sound reasons for confusion Yes, audio problems are the order this month. And before you sniff disdainfully, let me assure you that audio problems in TV sets “ain’t what they used to be”. Like everything else, they’ve gone high-tech. The first story is about an NEC colour TV set, a model N-4830 using a C500 chassis and made by Daewoo. The fault was straightforward enough; it was completely dead. More than that, the reason was obvious, at least to anyone who had seen it be­fore. This set has an inherent weakness. The power supply uses a 10-pin IC switching regulator (I801), a type STK-73410II. This IC overheats and fails, taking a lot of components with it. And that is what had happened in this case. But there is more to the fault than that. It appears that the failure is not the fault of the IC itself. Rather it is in the associated circuitry and the makers have issued a modification instruction to cover this. Attention to this is most important because if I801 is simply replaced, the set will back again in a few months with exactly the same fault. The modifications are quite extensive and I don’t propose to set them out here. Quite apart from the space needed, I under­ stand that since I did this job, further modifications have been issued which I have yet to receive. My original modification sheet came from NEC Spares, 23-25 Coombes Drive, Penrith, NSW 2750 – phone (047) 21 7655. It would be wise to contact them for the latest information. Suffice it to say, for the purpose of this story, that I carried out all the modifications prescribed at that time, re­placed the IC, then switched on with my fingers crossed. And, initially, all seemed well. There was no smoke, 48  Silicon Chip fire or confusion and the picture tube warmed up normally and presented a first class picture. There was only one thing wrong; there was no sound. In the good old days, audio faults were relatively rare and, when they did occur, they were usually quite easily found and fixed. It’s not quite the same these days, at least on some of the more elaborate sets such as this one. Signal tracing I commenced searching with an audio probe attached to a test amplifier, starting where the audio comes out of the IF module, at pin 9 (AUDIO OUT). Well, there was audio there all right, which was encouraging. All I had to do now was trace it through to the output stage and speaker. And that, as they say in the classics, was the hard part. The audio path is a real aroundthe-world-for-sixpence arrangement. From pin 9 it goes to pin 7 of I701 (on a separate page), comes out of I701 on pin 5, goes back to the IF module on pin 8 (ATT IN), comes out again on pin 10 (ATT OUT), and is finally fed to the audio output stage, I602. Tracing all this out on the circuit – with much turning of pages – was an exercise in itself. Then I had to relate this to the set itself, which involved a similar order of complexity. But laborious though it was, it paid off. Audio was being applied to pin 7 of I701 but there nothing coming out on pin 5. At this stage, I hadn’t paid a great deal of attention to the role of I701 but now I needed to know. It wasn’t hard to work out. This set Fig.1: the terminal connections for the IF module in the NEC N4830. Audio comes out on pin 9, goes back in on pin 8, and comes out on pin 10 to be fed to I602 (the power output IC). features audio and video input sockets (J202, J703) on the rear of the chassis, which allow external video and audio signals (eg, from video recorders and cameras) to be fed directly to the appropriate parts of the set. This avoids the losses involved in modulating a carrier, feeding it through the front end, then demodulating it to recover the original signals. And I701 is a switching module which feeds the audio and video sections of the set from either the front end or from the external audio/video inputs. Why no audio? So why wasn’t audio coming out of I701? In an effort to clarify the situation, I fed an audio signal into the audio input socket, J702, and, lo and behold, the signal went straight through to the speaker. What’s more, this situation remained, regardless of the switching signal instruction to pin 11. In short, the audio signal path through I701 was jammed in the external position. The most likely possibility was that the IC itself was faulty. The only other one was that power supply or switching voltages to it were at fault but I tended to rule this out on the grounds that the video switching function was normal. Nevertheless, I went through the motions. The IC is powered from the 12V rail at pin 6 and this was quickly cleared. The switching voltage is applied at pin 11 and this was turning on or off according to instructions from the control unit. That didn’t really surprise me. After all, the device was switching the video signal, so it should have been switching the audio signal as well. More to the point, it pointed the finger fairly and squarely at the IC. So I pulled it out, fitted a new one, and that was it. And as is often the case, it all seemed so simple and obvious once I’d found it. Why did the IC fail the way it did? Who knows? It could have been a simple random failure which just happened to occur at this time, or it could have been a byproduct of the power supply failure. But it’s worth keeping in mind. The set involved was a Philips type 02CR035, model 20CT6750/75Z, using a CTO-S chassis. It is a 48cm set, about 10 years old, with remote control and options built in for Teletext. More about the type number and options later. I didn’t deal directly with the customer – a hazard in itself, as it turned out – but with a colleague who was short of time and needed some help. The complaint was intermittent loss of picture, with a bright raster. He had tried to find it but the intermittent nature had made it difficult. He suspected a dry joint and nomi­ nated “the board on the left” as his prime suspect. The board on the left was the VST decoder board and I had my reservations about this diagnosis. It seemed unlikely that a fault here would produce the symptoms described and my experi­ence with this board is that Another sound failure My next story is also about a sound failure but that is the only similarity. By comparison, the previous fault was not unduly difficult to find, whereas this fault was one of the most frus­ trating I have encountered for a long time. And the irony was that it didn’t even start out as a sound problem. Fig.2: the audio from the IF module in the NEC N4830 is fed to pin 7 of I701 and comes out on pin 5. Note the external audio/video jacks, J702 and J703. March 1996  49 Fig.3: the relevant sound circuitry in the Philips 02CR034/35. Audio comes out of IC7664 (left) at pin 8 and goes to board 1070 via plug 3M12. It is subsequently applied to pin 7 of IC7681 via plug 2M12. it is remarkably free from dry joint problems. As it turned out, all this speculation was wasted. When I switched the set on, the fault appeared immediately – a brilliant white raster with no picture and no sound. And, as it turned out, this condition was permanent. I immediately suspected a voltage error around the picture tube; most likely a loss of cathode voltage, which is effectively the bias between the cathode and G1. And since the raster was white, rather than coloured, it suggested a fault common to all three guns. The cathodes are coupled to the RGB drive transistor collectors, so this voltage supply was the prime suspect. And so it proved to be. The collectors are fed from a 180V rail but there was no 180V. It didn’t take much tracking to find out why. A 4.7Ω resistor, R3583, in the power supply was open circuit. Apparently it had been intermittent but had finally failed completely. I fitted a new resistor and we had our 180V and a first class picture. So far so good but there was still no sound. I wasn’t particularly worried about this, as I imagined a spot of audio signal tracing, as described earlier, would quickly solve the problem. Before doing this, however, I went over the motherboard, checking it for 50  Silicon Chip dry joints. In particular, I checked the horizon­tal output transformer connections and remade several which look­ed suspicious. Having done this, I came back to the sound problem. And, in order to follow what happened next, it is necessary to describe the relevant part of the circuit – see Fig.3. The section shown is from the motherboard. The audio comes out on pin 8 of the demodulator module (IC7664 – left) and goes via plug 3M12 to an auxiliary board designated 1070 (Tone Con­trol/Headphone Panel). It is then supposed to come back to pin 7 of IC7681, the power output IC, via plug 2M12. I say “supposed” because it didn’t. Using the audio signal tracer, I detected audio at 3M12 but there was nothing at 2M12. Fun & games So the fault was on board 1070 which, as its name implies, provides remote control of the volume, treble, and bass levels. And this was where the fun and games started. I didn’t have a manual for the 02CR035; the closest I had was one for an 02CR034 which I believed used essentially the same circuit. And it did, at least for the main circuit, and I had used it to track down the original power supply fault. But board 1070 was another matter. There was a general similarity in that the same IC, a TDA1524 (IC7001), was used for the level control functions. However, there were significant differences between my circuit and the board in this set, which used additional circuitry and components. This didn’t worry me unduly at first. I confirmed that audio was coming into the board (connection 4C6) and to pin 15 of the IC but there was nothing at the IC’s output (pin 11). Next, I checked the supply voltage to the IC (pin 9) and all the asso­ciated components. I could find nothing wrong and that put suspi­cion squarely on the IC itself. I ordered one and fitted it but no joy; everything was just as before. I was getting worried now. The IC and everything around it tested OK, yet I couldn’t get any audio through it. I needed to delve into things at greater depth and, clearly, I needed an updated circuit. Fortunately, I found a colleague with a CR035 manual but my complacency was short lived. Although this circuit accounted for some of the additional circuitry, it still wasn’t complete. Apparently the set on the bench was a different version again! Service department My next stop was the Philips service department. I set out the circuit problem in some detail and was assured that a manual was available –price $84. I did a mental double take on that; it was high, even by current standards. Still, I needed it, and could need it again. I placed an order. The manual duly arrived and I turned eagerly to the 1070 circuit. Imagine my frustration when I realised that it was no different from the one my colleague had loaned me. I went back to the Philips service department – they were just as puzzled as I was and could find no record of a circuit which fitted the de­tails I described. Granted, after 10 years, the trail would be cold. However, they agreed to take the manual back and credit me and, at the time of writing, the search is still on. In the meantime, the silly situation remained; I could find nothing wrong with the IC or its associated circuit but it would not process the signal. I sought the assistance of various col­ leagues but without any real success. Some had experienced a similar failure but it had been traced to a faulty IC. And they, too, had sought an updated circuit without success. In desperation I finally decided to trace out the extra circuitry on the 1070 board in the hope that it might provide a clue. And it did. The extra components were connected to pins 1 and 17 of the IC. There was a 10µF electrolytic capacitor (C2010) to chassis; a 6.8kΩ resistor (R3010) to plug 1C3; and a 100Ω resistor (R3000) to a single additional plug, C7. Hot trails & smelly rats This plug connection went to a yellow lead which ran to the VST board, 1220, via pin 1 of a 3-pin plug and a mating connector on that board, mark­ed V17. And this was where I began to smell a rat. Pin 1 on the VST board went straight to chassis which, even with the limited knowledge I had gleaned of the circuit, didn’t seem to make sense. Hot on the trail, I disconnected the yellow lead, most conveniently at the 1070 board end, whereupon I had sound – lots of it and quite uncontrollable. That was both gratifying and confusing but it clearly indicated that there was something amiss with that part of the circuit. And there was something else I noted at that time. In both the manuals, the board pattern showed V17 as a 7-pin arrangement, whereas the set actually used a 3-pin combination, as already mentioned. But, with all the other differences, I didn’t attach much importance to it. I also noted that the yellow lead was anchored at the corner of the VST board and that it was pulled quite tight Fig.4: the circuitry for board 1070 in the Philips 02CR035, as shown in the manual. The actual board used in the faulty set con­tained extra circuitry and components. Audio goes into the IC on pin 15 and comes out on pin 11. March 1996  51 Serviceman’s Log ­– continued The result was music to my ears and this time it was com­pletely controllable. But it was not without some mixed feelings. Predominant, of course, was the relief at having solved the problem. On the other hand, I muttered some rude words about those responsible for the debacle in the first place. Mental abuse against the anchor tie to reach V17. Again, I thought little of it. But another observation proved more productive. Apparently, this board was designed to permit retrofitting of Teletext cir­cuitry and there were several unused connectors on the board. And one of these, V19, was a 52  Silicon Chip 3-pin type, sited close to and at right angles to V17. Way ahead of me? I’ll bet you are! I pulled the plug off V17 and fitted it to V19, noting in the process that the yellow lead was no longer strained against its anchor point. Then I switched on, for the umpteenth time. My colleague copped some of this mental abuse as well but that wasn’t really fair. Most of it was directed at whoever the bright spark was who put two identical plugs almost side by side on the same board. It was a disaster waiting to happen. With the benefit of hindsight, it was easy to work out how it had happened. My colleague had told me that he had suspected dry joints on the VST board, which meant that he must have re­moved the board for an inspection and work over. And in putting it back in place . . . Talk about Murphy’s law. And I don’t mean the fictitious leprechaun-like character who lurks in the corner of the work­shop, wrecking everything we try to do. I mean the real Murphy. More correctly Lieutenant Murphy of the US armed forces (I’m not sure which branch). As I understand it, Lieutenant Murphy was in charge of a series of tests involving acceleration and impact effects on military equipment, using a rocket propelled sled. In one such test, in which the equipment was tested to destruction, the measurements which were supposed to be record­ed during the run and impact were lost. The reason turned to be – wait for it – that two intercon­necting leads, fitted with identical plug and socket connections, had been transposed. I’ve no doubt Lieutenant Murphy muttered some rude words of his own but, for the record, he offered the classic statement “if anything can go wrong, it will go wrong.” I couldn’t agree more. But, again with the benefit of hindsight, I suppose I should have woken up sooner, knowing that the board had been removed and replaced. I wonder if anyone else out there has been caught SC like that? SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au REMOTE CONTROL BY BOB YOUNG Multi-channel radio control transmitter; Pt 2 This month, after a long hiatus, we continue the de­scription of the Mk.22 transmitter by presenting details of the encoder module. This is a great deal more flexible than was envisaged in the June 1995 issue and is still based on discrete ICs rather than a microprocessor. Here it is at last! What can I offer in my defence for the long delay? Nothing much except that the size and complexity of this project has grown alarmingly and has necessitated calling in additional help in order to get it finished. I am indebted to Dean Herbert (Microherb Electronics) for the design of the basic encoder module presented here. Once again, I set out to design one construction of the basic 8-channel transmitter. This transmitter is intended as a companion to the Silver­tone Mk.22 AM receiver published in the December 1994 & February, March & April 1995 issues of SILICON CHIP. However, it will also act as a replacement for almost any AM PPM transmitter currently on the market. While most transmitters on the As can be imagined, this transmitter did not fall out of a tree but came as a result of months of gruelling proto­ typing and missed deadlines. thing and instead ended up with something completely different; the best transmitter that Silvertone has ever produced. The complete transmitter consists of four PC boards: RF module (AM), basic 8-channel encoder, an expansion PC board with an additional 16 channels, and a configu­ration module. In the next few articles, we will be dealing with the design and 54  Silicon Chip market have a moulded plas­tic case, the new Silvertone Mk.22 has a more rugged powder-coated aluminium case measuring 170 x 140 x 47mm which is quite compact. Apart from being more robust, the metal case is a desir­able feature as it reduces the possibility of interference (third-order intermodulat­ion) from other transmitters close by. Packed into the case is a glittering array of features. Most are routine, common to all modern R/C systems but some are completely unique. As noted previously, it is expandable from 8 to 24 channels and has capabilities for channel alloca­tion, servo reversing, gain control, dual rate, servo travel length adjustment, pseudo endpoint adjustment and mixing on every channel. Also included are four programmable on-board mixers (two inverting and two non-inverting), two programmable on-board toggle switch control modules, fully programmable front panel switches and controls, and an expansion port for a configuration module of which there are four at the moment: F3B, Helicopter, Aerobatics and the very exciting and completely unique formation flying module. These modules plug into the configuration port (mix expand) and configure the transmitter into a task-oriented unit. Finally, as a topping for this culinary delight, we add a dash of exclusive Silvertone relish: frequency interlock and mixed mode dual control (buddy box). As can be imagined, this transmitter did not fall out of a tree but came as a result of months of gruelling proto­ typing and missed deadlines. By far the most difficult task was keeping the system user friendly. A great deal of work has been done on the development of the input networks to each channel and much care devoted to maintaining a completely identical board layout so that mastering one channel results in the mastery of all chan­nels. For example, there is only one type of front panel switch – a SPDT toggle fitted with a 3-pin socket. Thus, any switch may become a retract switch, dual rate switch, mix in-out switch etc, depending on which set of header pins it is connected to. The mix select switch only calls for a 2-pin socket, so any pair on a 3-pin socket will suffice. The sockets on the switches provide an added advantage in that the action of the switch (UP-ON) may be quickly and easily reversed (DOWN-ON). In other words, the front panel switches are fully program­ mable. Alternatively, the switches may be replaced by shorting links on the header pins for permanently installed features. Thus, for example, coupled Aileron/Rudder (CAR) may be installed perma­nently with a shorting link or set up to operate in the switch in/out mode from the front panel. On the other hand, Flap/Eleva­ tor auto compensation is more usually installed as a permanent feature and thus a simple shorting link on the header pins will suffice. Likewise, any channel may be programmed either to be pro­ portional or switched and there are two toggle switch modules onboard for this purpose. The major compromise in the system came about as a result of reducing the number of potentiometers to be adjusted and the number of shorting link combinations available. This was achieved by making the gain control pot programmable and is probably the most clever feature in the user interface. Thus, we ended up with only a single potentiometer to adjust for each channel, which in turn may be the servo travel volume adjust (ATV), endpoint ad­justment, dual rate set pot, mix ratio set pot or whatever, depending upon how the channel is programmed. As a result of this simplification, certain combinations tend to compromise the action of this pot. A good example is the simplification that took place in the dual rate programming. Originally the NORMAL/DUAL RATE programming pins TB1, TB3 etc consisted of six pins arranged in two rows of three; a very cumbersome programming arrangement with many combinations. Now the way we achieve 120% servo travel is to remove the 33kΩ input resistor from circuit, in the GAIN VARY setting. Thus, the NORMAL range is 1-2ms and with the 33kΩ resistor removed, 0.9-1.1ms. By placing the 33kΩ input resistor on the control pot side of TB1, it was possible to reduce the programming to a simple 3-pin plug which allowed the use of an SPST switch for remote operation. The trade-off is that the dual rate pot will actually increase instead of decreasing the servo travel as it approaches full clockwise rotation. This comes about because VR1 effectively shorts out R2 as it approaches the clockwise termi­nal. Thus, when setting the dual rate throw, starting from full clockwise rotation will give 120% servo travel. As the pot is rotated anticlockwise, this will drop back to 100% then on down to 20%. All of this will be explained in detail in future issue. Whilst this action is a little unusual, it is still dual rate even if it does go higher than normal throw. It is only tra- encoder circuit. Circuit operation The basic encoder follows the design philosophy pioneered in the early 1970s which culminated in the Signet­ ics NE5044. It uses a multiplexed ramp generator IC3b to generate standard pulse position modulation (PPM) – see Fig.1. Neutral for all 24 channels is set by a single pot, VR2, associated with IC1b. This feature represents a significant cost saving in transmitters with more than four channels. IC4 is the 8-channel multiplexer, a 4051. In a full system, there are three of these which will allow 24 channels, via the expansion PC board. IC4 samples each control input sequentially until all inputs are examined and then there is a pause (sync pause) before the process begins again. The rate at which Packed into the case is a glittering array of features. Most are routine, common to all modern R/C systems but some are completely unique. dition that states that dual rate must go down from the normal control throw. Another good example of this sort of compromise is the situation that arises when programming for dual rate combined with coupled channel mixing; CAR, for example. In this case, the Aileron gain set pot becomes primarily the dual rate set pot and the mix ratio adjustment is set on the auxiliary mix pot which is part of the four on-board mixers. This feature was a particularly difficult one to achieve, for in the beginning I could not switch the mix ratio with the dual rate switch. By utilising the spare pins on the MIX EXPAND port, I found the programming combination I required. This called for the pins on the MIX EXPAND port to be double-sided and we will cover this point in detail in the fol­lowing articles. Now we have full mixing with dual rate on the mix ratio. Actually, I’ve got a little ahead of myself in talking about these circuit details but they are really operational features so it was hard to avoid. Let’s now get down to the nitty gritty of the this sampling takes place is called the FRAME RATE and is typically 16-24ms in the 8-channel system. The eight identical input stages each contain a 3-pin plug (TB2, TB4, etc), to which the control stick pots are connected. These provide the channel allocation and servo reversing features. The second set of 3-pin plugs (TB1, TB3, etc) are used to select NORMAL or GAIN VARY modes, depending on how the asso­ciated shorting link is plugged in to short between the centre and one outside pin. Setting the shorting link on the NORMAL pair gives a fixed 1-2ms pulse width variation. Setting the Fig.1 (next page): the circuit uses an 8-input multiplexer (IC4) which is switched by counter IC5. IC4 samples all eight inputs in sequence and this creates a staircase waveform at the output of IC3a. the two comparators (IC1a & IC1b) then transform this into the pulse position modulation (PPM). March 1996  55 56  Silicon Chip March 1996  57 each individu­al channel or input in the encoder. Thus, the output of IC3a will be DC but stepped up and down (ie, a staircase), according to the settings on each of the eight inputs. This output is fed to pin 2 of comparator IC1a where it is compared with the ramp generator (IC3b) at pin 3. The output of the comparator is a series of narrow pulses whose timing, rela­tive to each other, is a function of the DC input and the ramp; so the higher the DC input, the longer the time between successive pulses. Thus, the output of the comparator is a block of eight pulses which have times between them proportional to the gain settings on the inputs. This is known as pulse position modula­ tion (PPM). Synchronising This scope photo shows how the encoder produces PPM (pulse position modulation) from the eight multiplexed input channels. The upper trace is the staircase waveform at pin 1 of IC3a (following the multiplexer) while the locked pulse waveform is from pin 7 of IC1b. The long positive pulse the sync pause. shorting link on the GAIN VARY pair provides 20-120% servo travel controllable from VR1, VR3 etc. The shorting links on TB1, TB3, etc may be each replaced with an SPDT switch which allows remote programming from the front panel. VR1, VR3, etc are gain controls and can perform multiple functions depending on how the terminal blocks TB1, TB3, etc are set up (programmed). Thus, they can provide the dual rate adjust, servo gain (ATV) and mix ratio. Mixing expansion port TB10 is the mixing expansion port and this is normally fitted with a shorting plug for the main 8-channel input leads. This is removed when the configuration module is plugged into this port. The pins for this port are double-sided and they also act as pick-up points for the mixers involved with IC6. We’ll come to those later. TB11 is the 24-channel expansion port. TB12, TB13 and TB14 are the channel number select connectors and select 8, 16 and 24 channels respectively. For example, if TB13 is shorted, then 16-channel operation is selected. The main board comes with a short­ing bar on TB12 (on the PC tracks) which must be cut if you intend to install more than eight channels. Likewise, 58  Silicon Chip R25 must be removed for more than eight channels. These connectors may be hard wired or fitted with header pins if you intend to swap backwards and forwards from 8 to 16 or 24 channels. These pins could even be wired to a 3-position switch on the front panel which would allow front panel selection of 8, 16 or 24 channels. As pointed out previously, the flexibility of this system is virtually unlimited. TB7 is the power input connector and it also carries the modulation to the RF module. Let’s start our analysis with IC5, a 4024 counter which continually feeds a series of binary numbers to the A, B & C pins of IC4. Thus, IC4 sequentially switches each of its eight inputs through to R20, the input resistor for IC3a which is a DC ampli­fier. Because IC4 is an addressable analog switch, any resistance in series with its inputs (ie, R3, R6, R9, R12, R26, etc) must be considered to be in series with R20. This total resistance will therefore determine the gain of each individual input. From this simple fact derives the magic of the Mk.22 encoder. The ratio of this total resistance (including R20) and IC3a’s feedback resis­tor R18 will determine the servo travel (GAIN) for The 8-pulse block is synchronised by the sync pause generator, IC3c, an op amp functioning as a one-shot. Each time Q4 of IC5 goes high, it charges C9 via diode D2 and R16 and the resultant high pulse from IC3a resets IC5 via R21. So IC5 starts again and switches the first of the eight inputs through to IC3a and the sequence continues. The length of the sync pause is controlled by the RC time constant of R15 & C9, which set it at 8ms. This is a very important point, particularly in 16 and 24-channel transmitters, as it gives the minimum frame (repetition) rate and thus helps to minimise servo slow down. This can arise in some servos if the servo pulse stretcher cannot cope with the long repetition rates used in the high level transmitters. The alternative system found in some transmitters is to use a fixed frame rate which must be long enough to encompass the maximum width control pulse (2ms) plus the sync pause (8ms). Thus, a 24-channel transmitter of this type would use a fixed frame rate of [(24 x 2) + 8]ms = 56ms. By contrast, the Mk.22 uses a swinging frame rate which varies between [(24 x 1) + 8]ms = 32ms to 56ms, depending upon where each of the control pots is set. In high level transmit­ters, it is a good idea to leave all unused channels set at 1ms to speed up the repetition rate. In the 8-channel transmitter, we use a frame rate which will vary from 1624ms. The form of frame rate generation used in the Mk.22 also has another advantage when changing from 8, 16 or 24 channels. As the sync pause is tacked onto the last pulse, the frame rate increase is adjusted automatically to suit the number of channels in use. For people who are concerned about achieving the minimum frame rate (maximum data refresh rate), the sync pause may be set lower but be aware that there is no standard for the sync pause in commercial receivers. Some will operate comfortably on 4-5ms but others will fly out of sync even at 6 or 7ms. From past experience, I have found 8ms to be a fairly safe time constant. As the Mk.22 Tx is intended as a replacement for all commercial transmitters, we have been a little conservative here. Unfortunately, the picture of the circuit operation present­ed so far is a lot more complex in reality. IC2a, a D-type flip­flop, is actually the controller of everything. And to further confuse things, it is not even used like a conventional D-type. Instead, it is used as an RS flipflop which is “set” by the pulse output from IC1a and “reset” by IC1b, another comparator. Neutral comparator IC1b is the neutral comparator and is set by VR2. The vol­tage from VR2 is compared with the same ramp generator signal from IC3b and this produces a similar series of narrow pulses with a 1.5ms spacing between them. So each time IC2a is set by IC1a, it is reset by IC1b a little later. IC2a not only clocks counter IC5 but it also drives the ramp generator, IC3b, which is actually an RC integrator; it “integrates” the output of IC2a and so we have a sawtooth wave­form which is locked to IC2a, to the counter and to everything else. So how do the pulses from IC3a actually get to the modula­tion output on plug TB7? The answer is that they don’t. The pulses generated by IC1b, since they are locked to everything else, actually become the modulation. Comparator IC1b drives transistor Q1 and thence D-type flipflop IC2b which functions as a monostable multi­vibrator. Its Q output will go high when ever it is clocked by comparator 2 (IC1b) and stay high for a period set by the RC network of R11 & C5 which drives the reset pin. R52 and D3 speed up the recovery time and eliminate variations in the modulation pulse length due to variations in the width of the control channels. The nominal length of the modulation pulse is set at 350µs. IC3d is the pulse shaper, an op amp integrator used to adjust the rise and fall time of the modulation pulse to the RF modulator, an important point when we come to the RF module. A correctly set modulation pulse will result in a bandwidth of around ±10kHz. IC3 is a TLC 2274, specified to provide near rail-to-rail switch­ing for the RF modulator. R55 and C4 also help to reduce the modulation rise and fall times to reduce RF harmonics. Whilst in theory C6 should provide symmetry on both leading and trailing edges, in practice we found C6 controls the leading edge slope and R55 and C4 control the trailing edge slope. YOU CAN AFFORD AN INTERNATIONAL SATELLITE TV SYSTEM SATELLITE ENTHUSIASTS STARTER KIT Mixers Op amp IC6 provides four mixers with gain set by VR8, VR10, VR12 & VR15, respectively. The two small modules at bottom right – TB17, 20 and TB21, 24 – are toggle switch control modules. TB27 and TB28 (middle left) are mixer select programming pins. These mixers are connected to the main circuit by small patch cords to the appropriate pins on the mix expand port, TB10. Another very important feature of the circuit is the voltage reference rails provided by R22, R23, R58 & R61 which are 1% resis­tors. These accurate voltage references are derived from REG1, an LP2950 low drop-out 5V regulator This regulator allows reliable operation down to 5V or less on the transmitter battery. These accurate reference rails allow servo reversing on all channels by simply reversing the control pot polarity. In the Mk.22 encoder, this is done by reversing the 3-pin socket associated with each control pot. This function could be achieved with switches but it would mean the loss of channel allocation. Channel allocation in the Mk.22 is achieved by simply connecting any pot to any channel. Channel allocation is a vitally important feature when we come to the F3B module for example, where two channels are required for ailerons and another two for flaps; using only one stick axis for each pair of channels. So there we have it, a basic no frills 8-channel encoder with expansion to SC 24 channels if required. YOUR OWN INTERNATIONAL SYSTEM FROM ONLY: FREE RECEPTION FROM Asiasat II, Gorizont, Palapa, Panamsat, Intelsat HERE'S WHAT YOU GET: ● ● ● ● ● ● 400 channel dual input receiver preprogrammed for all viewable satellites 1.8m solid ground mount dish 20°K LNBF 25m coaxial cable easy set up instructions regular customer newsletters BEWARE OF IMITATORS Direct Importer: AV-COMM PTY. LTD. PO BOX 225, Balgowlah NSW 2093 Tel: (02) 9949 7417 / 9948 2667 Fax: (02) 9949 7095 VISIT OUR INTERNET SITE http://www.avcomm.com.au YES GARRY, please send me more information on international band satellite systems. Name: __________________________________ Address: ________________________________ ____________________P'code: __________ Phone: (_______) ________________________ ACN 002 174 478 March 1996  59 Build this 20ms delay board to add to your surround sound unit or use it to enhance musical instruments. It uses the latest digital conversion and memory storage techniques to pro­vide quality sound. Only one integrated circuit is required, plus a handful of passive components. By JOHN CLARKE A 20ms Delay For Surround Sound Decoders I F YOU HAVE BUILT a low cost surround sound decoder, you won’t be getting the best sound effect unless it has a delay for the rear channel. Now you can fix this drawback by adding our 20ms delay board. A typical lounge room with a surround sound setup will have the front, left, right and centre channel loudspeakers located well in front of the lounge and adjacent to the TV set. The rear loudspeakers will be directly behind the listener. Because of this, the sound from the rear will arrive at the listeners ears before that from the front loudspeakers. When this occurs, the sound from the surround loudspeakers will tend to dominate the perceived direction of the sound field. However, if a delay is added to the rear channel, its sound will arrive later than from the front and so the sound field will be correctly perceived by the 60  Silicon Chip ear. The normal delay time required is 20ms and this will cater for most lounge rooms. For public address use, it is also sometimes an advantage to add a delay to the sound fed to the loudspeakers at the rear of a hall compared to those at the front. For listeners at the rear of the hall, the sound from the loudspeakers near to them will normally arrive before the sound from the loudspeakers at the front. The result will be an echo that can cause considerable difficulty in under­standing the person speaking. By adding a delay to the rear speakers, Performance Delay 20ms (fixed) Gain Unity Frequency Response -1dB at 10Hz, -3dB at 7kHz Maximum Input 1.2V RMS Input Impedance 20kΩ Output Impedance 1kΩ Harmonic Distortion 0.3% at 1kHz and 300mV RMS (see graph) Signal To Noise Ratio With respect to 1V RMS: 97dB unweighted (20Hz-20kHz); 101dB A-weighted Fig.1: the M65830 IC converts in the incoming signal to digital form, stores it in memory, reads it out again and converts it back to an analog signal. The delay is a function of the size of the internal RAM and the clock speed, as set by the oscillator. this echo effect can be considerably reduced. A 20ms delay represents the time that it takes sound to travel 6.7 metres. Several delay units could be connected in series to increase the delay if necessary or, better still, you can alter the circuit components to obtain a 40ms delay. The circuit is based on the Mitsu­ bishi M65830P digital delay IC. This works by first converting the incoming analog signal to a digital format which is then clocked into memory. This digital signal is then clocked out at the end of the delay period and converted back to analog form. In addition, the M65830P contains AUDIO PRECISION THD-FRQ THD+N(%) vs FREQ(Hz) 5 21 DEC 95 13:16:35 1 0.1 0.010 10 100 1k 5k Fig.2: this graph plots the harmonic distortion for the 20ms Delay Circuit. The ripple evident in the curve is an artefact of the A-D (analog-to-digital) and D-A processes but is not audible. several op amps so that input and output filters can be added to the circuit without using addi­tional ICs. Circuit details The circuit is shown in Fig.1. The input signal is coupled to an inverting op amp input at pin 23 via a low pass filter comprising C1, C2, R1, R2 and R3. This rolls off signals above about 8.5kHz to prevent high frequencies affecting the following digital conversion which can cause spurious effects in the out­put. Capacitor C6 and resistor R7 control the rate of delta modulation which is the type of analog to digital conversion used in IC1. Similarly, C5 controls the digital to analog conversion output signal appearing at pin 15. This output is applied to a 7kHz filter comprising resistors R4, R5 and R6 and capacitors C4 and C5. The output of the filter op amp at pin 13 is AC-coupled via a 10µF capacitor. The circuit can be powered from a DC rail from 9-25V, although we have shown +12V as the supply input on Fig.1. Three-terminal regulator REG1 provides +5V to the IC’s Vcc and Vdd pins (1 & 24). Options Some readers may have an application which requires a longer delay time than 20ms or may desire a frequency March 1996  61 18kΩ; C1 & C3 should be 560pF and C2 & C4, 150pF. Note that using 15kHz filters will lead to a slight increase in residual noise and distortion. The harmonic distortion char­ ac­ter­­istic for the 20ms circuit, with 7kHz filters, is shown in Fig.2. Construction Fig.3: follow this parts layout when building the PC board. An IC socket is optional. Fig.4: this is the full-size artwork for the PC board. Check the etched board carefully before installing the parts. response above 7kHz. If you want a 40ms delay, the crystal must be 1MHz (instead of 2MHz), C5 & C6 should be .022µF and R7 should be 82Ω. To obtain a frequency response to 15kHz, the following components should be changed: R1, R2, R4 & R5 should be 39kΩ; R3 & R6 should be All of the delay circuit components are assembled onto a PC board coded 01401961 which measures 63 x 60mm. It is designed to fit horizontally into a plastic case measuring 130 x 67 x 32mm. This case is optional – we envisage many constructors will install the board into existing equipment (presumably the same case as the surround sound decoder). The component overlay is shown in Fig.3. Begin construction by checking the PC board for shorted or broken tracks. Repair any faults before assembling the compon­ents. Start with the PC stakes for all the input and output terminals. Next, the links can be installed, followed by the resistors. Use the accompanying table to assist you in selecting the correct colour code. Once the resistors are in, the IC and the capacitors can be installed. Make sure that the IC and the electrolytic capacitors are correctly oriented. Finally, install the 3-terminal regulator. It is oriented so that its tab faces the adjacent 10µF capacitor. Testing To test the unit, apply power to the DC input and check with your multimeter that the regulator output is close to +5V. PARTS LIST 1 PC board coded 01401961, 63 x 60mm 1 plastic case 130 x 67 x 32mm (optional) 1 2MHz crystal (X1) 6 PC stakes 1 50mm length of 0.8mm tinned copper wire Semiconductors 1 M65830P delay (IC1) 1 7805T 5V 3-terminal regulator (REG1) Capacitors 1 100mF 16VW PC electrolytic 1 47µF 16VW PC electrolytic 4 10µF 16VW PC electrolytic 3 0.1µF MKT polyester 2 .068µF MKT polyester 1 .0027µF MKT polyester 1 .0022µF MKT polyester 1 680pF ceramic 1 560pF ceramic 2 100pF ceramic Resistors (0.25W, 1%) 1 1MΩ 2 10kΩ 1 100kΩ 1 30Ω 4 22kΩ If you have access to an audio signal generator, you can use it to check the circuit operation. Note that the gain of the circuit from input to output is unity. A dual trace oscilloscope can be used to verify the delay between input and output. At 25Hz, the two signals should be 180° apart, while at 50Hz they will appear in-phase again. Final testing can be made after installation in your equip­ment. Note that the delay unit will only handle signals up to 1.2V RMS. For higher level signals, an input attenuator will SC be required. RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ 62  Silicon Chip No. 1 1 4 2 1 Value 1MΩ 100kΩ 22kΩ 10kΩ 30Ω 4-Band Code (1%) brown black green brown brown black yellow brown red red orange brown brown black orange brown orange black black brown 5-Band Code (1%) brown black black yellow brown brown black black orange brown red red black red brown brown black black red brown orange black black gold brown ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. GST)**  $A159  $A83 New Zealand (airmail)  $A145  $A77 Overseas surface mail  $A160  $A85  $A250 Overseas airmail  $A125 **1 binder with 1-year subscription; 2 binders with 2-year subscription YOUR DETAILS Your Name_________________________________________________ GIFT SUBSCRIPTION DETAILS Month to start__________________ Message_____________________ _____________________________ _____________________________ Gift for: Name_________________________ (PLEASE PRINT) Address______________________ _____________________________ (PLEASE PRINT) Address___________________________________________________ State__________Postcode_______ ______________________________________Postcode_____________ Daytime Phone No.____________________Total Price $A __________ Signature  Cheque/Money Order  Bankcard  Visa Card  Master Card ______________________________ Card No. Card expiry date________/________ Phone (02) 9979 5644 9am-5pm Mon-Fri. Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia March 1996  63 BOOKSHELF Satellite TV installation & repair Ku-Band Satellite TV; Theory Installation & Repair, by Frank Baylin. 4th edition published 1991 by Baylin Publications. Soft covers, 420 pages, 275 x 215mm, ISBN 0-917893-14-X. Price $59.00. This book is devoted to all aspects of the transmission and reception of signals in the 10.95 to 14.50GHz region of the electromagnetic spectrum. It is a very difficult book to review as there is so much information packed into its 400 odd pages. The volume is divided into nine chapters which range from the basics of satellite communication to scrambling technologies and erecting your own antenna. In the first chapter we are introduced to uplink and down­ link paths, worldwide frequency allocations and understanding satellite footprint maps. One of the paragraphs gives details of “station keeping”. This refers to the need for a satellite in geostationary orbit (35,786km above Earth) to have its thrusters fired every 3-4 weeks to maintain its E/W location and every 60-90 days to keep it on the equatorial plane. Chapter two covers all you need to know about antennas, including mounts, actuators, feedhorns, low noise block downcon­verters (LNBs), satellite receivers, modulators, TV receivers, monitors and audio reception. Much of this is useful background information, although the average reader wishing to acquire a satellite receiver system will probably purchase a package with a guarantee of performance for the location in which it will be used. A US study on judging picture quality concluded that a S/N ratio of 33dB gave passable results; 40dB was good and 45dB rated as excellent. These figures have been confirmed in subsequent studies and give potential owners an idea of the quality of the reception they can anticipate at their particular location. Chapter three covers the design and testing of Ku-band systems. Things that we do not normally consider, such as rain, atmospheric attenuation, ambient temperature and antenna size all play an important role when the signal from PC-based instrumentation & control PC-based Instrumentation and Control by M. Tooley. Pub­lished 1995 by Butterworth-Heinemann Australia. Soft covers, 388 pages 235 x 155mm, ISBN 0-7506-2093-5. Price $55.00 In the introduction to this book, the author states that it is aimed primarily at “the professional control and instrumenta­tion specialists. It does not assume any previous knowledge of microprocessors or microcomputer systems.” He also claims that his aim is to provide sufficient information to solve problems in the shortest time and without recourse to any other 64  Silicon Chip texts. For this reason there is a large amount of information in this book which will be readily available, and probably quite familiar, to the majority of PC owners. The first chapter charts the history of the IBM PC and compatibles, beginning with the 8088 processor and working through to the 80486. Maths co-processors, DMA (direct memory access) controllers, interval timers and interrupt controllers are only some of the programmable devices which are then de­tailed. The chapter continues with a discussion on RAM and ROM (random access and read only mem­ ory), BIOS (basic input output services) and concludes with details of power supplies, video standards and floppy and hard discs for PCs. Chapter two covers PC expansion systems in some depth. It begins by listing the PC bus connections, then detailing the requirements for bus expansion cards. A number of cards which are suitable for use with the PC, along with their specifications, are then detailed. The chapter concludes with information on Eurocard (160 x 100mm) modules which suit the satellite is usually less than 10-17 watts/m2. Chapters four and five detail the selection of equipment for, and the installation of, Ku band receivers. For ideal loca­tions with relatively strong signals, a small antenna is all that is required but for difficult sites a 3m dish is necessary and this must be well anchored to support it against high wind gusts. The sixth chapter covers the retrofitting of C band sys­tems to receive Ku band signals. In Australia, all channels are transmitted in the Ku band but a number of C band signals from overseas can be received (see SILICON CHIP, July 1995, page 40). Chapter seven explains the methods used in multiple receiv­ er and distribution systems. These could be required in hotels, etc where perhaps one or two satellite TV channels, as well as the local TV stations and perhaps several VCR channels would be made available to guests. This means that the satellite signals have to be down-converted to VHF so that they can be distributed over the existing installation and received by commercial TV receivers. Chapter eight is titled “Worldwide Ku band satellite tele­vision” in which just over one page is devoted to Australia, New Zealand and New Guinea. It gives details of the three Aussat satellites and their the STE bus. These cards plug into a backplane and normally contain a processor, memory and assorted peripheral chips. One of those described is also fitted with a hard disc controller and a multimode graphics controller. The next chapter covers the PC operating system’s internal and external commands, copying discs, files and their structure and the use of Debug. It concludes with a couple of pages devoted to Windows 3.10 and Windows NT. All this information will be readily available to the PC owner in the DOS and Windows manuals. Chapter four is titled “programming” and gives process control channel allocations. The last chapter is devoted to troubleshooting and repair. These 20 pages give an indication of the problems that can arise, from the movement of a dish, the damage to a buried feed cable by a keen gardener, to the routine electronic failures that have become familiar to the industry. Subtle faults are discussed, like “solar outages”, when the sun lines up directly along the antenna bore­sight (the direction along the principal axis) during the equinoxes and causes loss of, or very weak, signal reception. These can only be learned about by reading or word of mouth. The chances of finding a fault of this nature intuitively must be zero. The book concludes with a series of appendices covering things like antenna gain and beamwidth, noise temperature, anten­ na geometry, satellite footprints throughout the world, a glos­sary of terms and a listing of satellite channels. This book has a wealth of information on satellite TV and while the information is specialised and some not applicable to this country, it will prove an invaluable reference for anybody desiring to learn more about this fascinating subject. Our copy came from AvComm Pty Ltd, PO Box 225, Bal­ gow­ lah, 2093. Phone (02) 9949 7417. (R.J.W.) engineers an insight into the features they should ensure are available in programming languages which they may propose to use. For example IF ..ELSE ..END IF, DO WHILE ..LOOP, and WHILE ...WEND are often likely to be used in process control applications. Tooley then explains the steps involved in software development, which should normally be a top-down process, moving from the general to the specific. Flow chart symbols are introduced and several flow chart examples are shown. Explanations of control structures, pseudo-code (a mixture of English and the programming language being used) and program loops are examined in some detail. The chapter concludes with several pages stressing the importance of ade­quately documenting all software and gives several examples. Chapters five, six and seven cover programming in Assem­bler, Basic and C respectively. None is a step by step introduc­tion but more a background for each and by reading all three chapters a beginner would have some appreciation of the great differences between these languages. The IEEE-488 bus – also known as the HPIB (Hewlett Packard Instrumentation Bus) or the GPIB (General Purpose Instrumentation Bus) – is explained in chapter eight. This bus provides the means of interconnecting a microcomputer with a vast range of test and measuring instruments. In the past, only the more expensive in­struments were fitted with this bus but thanks to the development of low cost IEEE-488 chips it is becoming commonplace, even on cheaper equipment. This setup allows automated measurements to be made under the control of a computer. Interface cards are available for the PC, the one discussed being the MetraByte MBC-488. This plugs directly into the IBM bus and has an IEEE 24pin connector as its output. It can be con­trolled from the PC using any high level language. Interfacing the computer to the outside world is the sub­ject covered in the next chapter. Input devices are discussed first. Some simple digital devices can be readily connected through the parallel or serial ports, but any analog device will need an interface card with an A-D (analog to digital) converter. A-D cards for the PC are readily available, usually with multiple inputs, which enable a num­ber of different transducers to be monitored simultaneously. Some of the different types of sensors are explained, in­cluding position, liquid level, optical, temperature and pressure sensors. The author then details methods of adapting these and other devices to interface to the computer. He also covers areas where optical isolation may be required (eg, for monitoring mains voltages) and describes how this is achieved. Once the data is processed by the computer, the results need to be displayed somehow. It may be inconvenient or impossi­ble to use the screen of March 1996  65 Bookshelf: PC-Based Instrumentation & Control – continued the computer and usually the requirement will be for an alarm or relay to be actuated. Methods of inter­facing to LEDs, relays, lamps, audible alarms and motors are shown. Software Packages are the subject of chapter 10. The author details the criteria in selecting a software package, such as ease of use, flexibility, performance and functionality. He then describes three commercial packages: Asyst, Asystant and Dadisp­II. He goes on to detail two of the most popular tool kits, Norton Utilities and PC Tools. These both contain essential routines which are missing from DOS. Chapter 11 discusses the differing approaches which can be taken to solve a problem, depending on the complexity of the task. Simpler measurements might only require the addition of one extra card (perhaps a 16 channel A-D converter) to a standard PC. On the other hand, a system requiring a greater variety of measurements might re­quire several expansion cards in an external card frame, while a very large system might consist of several external pieces of instrumentation linked to the PC via the IEEE-488 bus. The chapter continues by describing the steps involved in analysing an application. These include the performance of the system, I/O devices, displays and operator inputs, storage devic­es, communications and future expansion. It concludes with the solutions to four applications: meas­urement of the stability of a VCO (voltage controlled oscillator); testing crystal filters; development and testing of a speech synthesiser; and, finally, strain measurement and processing on an aircraft undercarriage. “Reliability and Faultfinding” is the title of chapter 12. Reliability comes from good quality control procedures during the manufacture and installation of any system. The process control specialist should ensure that the quality is built in right from the beginning. Methods for monitoring performance, such as hard­ware watchdog timers and software diagnostics are expounded, along with a brief discussion on the POST (power on self-test) routines of the PC. A list is given of the necessary test equipment, which comprises a multimeter, logic probe, logic pulser and, perhaps, an oscilloscope. The last few pages of this chapter explain the methods of using these tools in fault finding procedures. Chapter 13 is titled “System Configuration” and covers device drivers, RAM drives, memory managers, printer.sys and autoexec.bat. The chapter concludes with autoexec.bat and config.sys listings for seven different computer systems. Appendices A-F cover a glossary of terms, SI units, multiples, decimal-binary-hex-ASCII tables, a bibliography and finally a list of suppliers of PC boards and PC based expansion boards. To sum up, the book certainly fulfils the author’s claim that there is no need to refer to other texts. However, since the first edition of the book in 1991, many more people now have a computer and there are probably very few instrumentation en­gineers who would not be familiar with a personal computer. Nevertheless the convenience of having all the information to­gether and the reasonable price makes this book a worthwhile investment. (R.J.W.) 20 Electronic Projects For Cars $8.9s5 plu $3 p&p Yes! Please send me ___ copies of 20 Electronic Projects For Cars Enclosed is my cheque/money order for $­________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­________________________ Card expiry date_____/______ Order by phoning (02) 979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail the coupon to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 66  Silicon Chip Name _______________________Phone No (_____)____________ Street PLEASE PRINT _________________________________________________ Suburb/town _____________________________ Postcode_________ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd Silicon Chip October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; Using The NE602 In Home-Brew Converter Circuits. BACK ISSUES November 1990: How To Connect Two TV Sets To One VCR; A Really Snazzy Egg Timer; Low-Cost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Simple 6-Metre Amateur Transmitter. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. Tips For Your VCR; Speed­ing Up Your PC; Phone Patch For Radio Amateurs; Active Antenna Kit; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Index to Volume 2. January 1990: High Quality Sine/Square Oscillator; Service March 1990: 6/12V Charger For Sealed Lead-Acid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception; How To Find Vintage Receivers From The 1920s. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Fitting A Fax Card To A Computer. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape – A Game Of Skill; Wiper Pulser For Rear Windows; A 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. August 1991: Build A Digital Tachometer; Masthead Amplifier ORDER FORM Please send me a back issue for: ❏ July 1989 ❏ September 1989 ❏ January 1990 ❏ February 1990 ❏ July 1990 ❏ August 1990 ❏ December 1990 ❏ January 1991 ❏ May 1991 ❏ June 1991 ❏ October 1991 ❏ November 1991 ❏ April 1992 ❏ May 1992 ❏ September 1992 ❏ October 1992 ❏ April 1993 ❏ May 1993 ❏ September 1993 ❏ October 1993 ❏ February 1994 ❏ March 1994 ❏ July 1994 ❏ August 1994 ❏ December 1994 ❏ January 1995 ❏ May 1995 ❏ June 1995 ❏ October 1995 ❏ November 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ September 1988 October 1989 March 1990 September 1990 February 1991 July 1991 December 1991 June 1992 January 1993 June 1993 November 1993 April 1994 September 1994 February 1995 July 1995 December 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ April 1989 November 1989 April 1990 October 1990 March 1991 August 1991 January 1992 July 1992 February 1993 July 1993 December 1993 May 1994 October 1994 March 1995 August 1995 January 1996 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ May 1989 December 1989 June 1990 November 1990 April 1991 September 1991 March 1992 August 1992 March 1993 August 1993 January 1994 June 1994 November 1994 April 1995 September 1995 February 1996 Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ____________________________ Card expiry date_____ /______ Name _______________________________ Phone No (___) ____________ PLEASE PRINT Street ________________________________________________________ Suburb/town ________________________________ Postcode ___________ 72  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. ✂ Card No. For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Step-By-Step Vintage Radio Repairs. September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & Ultralights, Pt.1; The Basics Of A/D & D/A Conversion; Windows 3 Swapfiles, Program Groups & Icons. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Alti­meter For Gliders & Ultralights, Pt.2; Getting To Know The Windows PIF Editor. November 1991: Colour TV Pattern Generator, Pt.1; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Solid-State Laser Pointer; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty Stereo Amplifier, Pt.1; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Direct­ories; Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Low-Cost Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; Infrared Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Multi-Station Headset Intercom, Pt.2. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; Dummy Load Box For Large Audio Amplifiers; Troubleshooting Vintage Radio Receivers. September 1992: Multi-Sector Home Burglar Alarm; Heavy-Duty 5A Drill speed Controller (see errata Nov. 1992); General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads; Build A Relative Field Strength Meter. October 1992: 2kW 24VDC To 240VAC Sine­wave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Build A Regulated Lead-Acid Battery Charger. January 1993: Peerless PSK60/2 2-Way Hifi Loudspeakers; Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; MAL-4 Micro­controller Board, Pt.3; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.5. March 1993: Build A Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Low-Cost Audio Mixer for Camcorders;A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Build An Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Step-Up Voltage Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Remote Volume Control For Hifi Systems, Pt.1; Alphanumeric LCD Demonstration Board; The Micro­soft Windows Sound System. June 1993: Build An AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Remote Volume Control For Hifi Systems, Pt.2. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Programming The Motorola 68HC705C8 – Lesson 1; Antenna Tuners – Why They Are Useful. Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Cruise Control – How It Works; Remote Control System for Models, Pt.1; Index to Vol.7. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; A Microprocessor-Based Sidereal Clock; The Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Preamplifier; The Latest Trends In Car Sound; Pt.1. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1; Programming The Motorola 68HC705C8 – Lesson 2. November 1993: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Electronic Engine Management, Pt.2; Experiments For Games Cards. December 1993: Remote Controller For Garage Doors; Low-Voltage LED Stroboscope; Low-Cost 25W Amplifier Module; Build A 1-Chip Melody Generator; Electronic Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Electronic Engine Management, Pt.4. February 1994: 90-Second Message Recorder; Compact & Efficient 12-240VAC 200W Inverter; Single Chip 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Electronic Engine Management, Pt.5; Airbags – How They Work. March 1994: Intelligent IR Remote Controller; Build A 50W Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Electronic Engine Management, Pt.6. April 1994: Remote Control Extender For VCRs; Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Low-Noise Universal Stereo Preamplifier; Build A Digital Water Tank Gauge; Electronic Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Two Simple Servo Driver Circuits; Electronic Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; An 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; A PC-Based Nicad Battery Monitor; Electronic Engine Management, Pt.9 July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Build a Nicad Zapper; Simple Crystal Checker; Electronic Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Aircraft Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Electronic Engine Management, Pt.12. October 1994: Dolby Surround Sound – How It Works; Dual Rail Variable Power Supply (±1.25V to ±15V); Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuv­enator; A Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, March 1995: 50W/Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. April 1995: Build An FM Radio Trainer, Pt.1; Photographic Timer For Darkrooms; Balanced Microphone Preamplifier & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. May 1995: Introduction To Satellite TV; What To Do When the Battery On Your Mother­board Goes Flat; Mains Music Transmitter & Receiver; Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Low Cost Transistor & Mosfet Tester For DMMs; 16-Channel Decoder For Radio Remote Control. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; A 1W Audio Amplifier Trainer; Low-Cost Video Security System; A Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1995: Low-Power Electric Fence Controller; How To Run Two Trains On A Single Track (Plus Level Crossing Lights & Sound Effects); Setting Up A Satellite TV Ground Station; Build A Door Minder; Adding RAM To A Computer. August 1995: Vifa JV-60 2-Way Bass Reflex Loudspeaker System; A Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; The Audio Lab PC Controlled Test Instrument, Pt.1; The Mighty-Mite Powered Loudspeaker; An Easy Way To Identify IDE Hard Disc Drive Parameters. September 1995: A Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walk-Around Throttle For Model Railways, Pt.1; Build A Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2; Automotive Ignition Timing, Pt.1. October 1995: Build A Compact Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walk-Around Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1; Automotive Ignition Timing, Pt.2. November 1995: LANsmart – A LAN For Home Or A Small Office; Mixture Display For Fuel Injected Cars; CB Transverter For The 80M Amateur Band, Pt.1; Low Cost PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. December 1995: Engine Immobiliser For Cars; Five Band Equaliser For Musicians; CB Transverter For The 80M Amateur Band, Pt.2; Build A Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; RAM Doubler Reviewed; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Build a Magnetic Card Reader & Display; Rain Brain Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Build A Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; The Fluke 98 Automotive ScopeMeter. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, Aug­ust 1989, May 1990, February 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear­sheets) at $7.00 per article (includes. p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. March 1996  73 COMPUTER BITS BYhttp://www.pcug.org.au/~gcohen GEOFF COHEN Electronic organisers & your PC Like many other computer people, I have an electronic organiser (a Sharp ZQ-5200) which I use constantly. As well as storing phone numbers and memos, I also use it to store details of the work I do for clients. A major reason I like organisers is that, being inherently lazy, I hated having to manually write stuff down three times – once in a pocket diary I carried around, then into a desk diary, and then by typing it out in a word processing program, to final­ly get it into the PC. As soon as I found out about organisers, I rushed out and got one. I then spent the next week learning how to actually use it. Anyhow, enough of the history lesson. Suffice it to say that if you write lots of text when you are away from the home/office, and don’t want to lug something around that won’t fit in your pocket, an organiser is the way to go. I am about to upgrade mine to a 74  Silicon Chip Fig.1: Text Exported Directly From The Organiser 19951215,”21:30",”hh:mm”,”21:30",”ARRIVE AT CARAVAN.”,”N” 19951226,”hh:mm”,”hh:mm”,”hh:mm”,”TODAY SMOKE DETS POLAROID CLIPON, “N” 19951226,”18:30",”hh:mm”,”18:30",”YES MINISTER”,”N” 19960102,”hh:mm”,”hh:mm”,”hh:mm”,”MAKE ERROR RECOVERY MENU OP­TION.”,”N” 19960103,”13:00",”16:35",”hh:mm”,”SILICON CHIP:START ARTICLE ON ORGANISERS”,”N” 19960104,”10:00",”12:20",”hh:mm”,”SILICON CHIP:LAST PART OF ARTICLE.”,”N” 19960108,”hh:mm”,”hh:mm”,”hh:mm”,”TAX DUE”,”N” 19960108,”20:00",”hh:mm”,”20:00",”FRONTLINE”,”Y” newer model with 256Kb of RAM and a much bigger screen (40 characters/ line instead of 16). Alas, I have not been organised enough to get one yet. Transferring data to a PC An essential extra for my organiser is its PC Link cable/adaptor, which allows data to be transferred to the PC (or vice versa). You can also export data from the organiser’s PC software to other programs, although this is not very elegant without extra software. With that proviso, I like the Sharp software – it is simple to install and use. For anyone who is considering the purchase of an organiser, and intends using it for “serious stuff”, I recommend the PC Link as an essential item. I have had two organisers. The first stopped working when it got dropped in the drink – fishing and organising don’t go together too well. If I hadn’t backed up the data before I went fishing, I would have been forced to spend hours retyping 60K of text, all retrieved from my own (fallible) memory. With the backup copy on my PC and the Link cable, it took only a few domain, so feel free to give it to anyone who wants a copy. I hope you find this combination of organiser and utility program as useful as I have. If any Clipper programmers want a copy of the source code, this is available from me either by email (no charge) or from my snail mail address ($10) at the end of the column. More on ZIP drives The Missing Link V.2 is a Windows-based organiser-to-PC linking program. minutes to restore the data to the new organiser. Data modes There are two modes of transferring data from the organiser to your PC: (1) the BACKUP menu option which does a complete backup to a named file (I use this option once a month); and (2) the GET applications menu option (I use this one daily). The latter copies the data to an emulator program on your PC and allows you to both view and, by using the advanced menu option, export this data to other programs. Unfortunately, the standard output format is not really suited to a word processing program, as you can see from the sample “comma delimited “ text shown Fig.1. What we really want to do is to extract the SILICON CHIP text, strip out the unwanted stuff, and convert it to The DOS version of ZIP works well. It only takes around 26Kb of RAM for its device driver and is compatible enough that Norton Disk Doctor (Version 8) runs quite happily on the ZIP drive, although it is a little slower than on a “real” hard disc. The more I use mine, the more uses I think of for it. I have tried it on DOS, Windows 3.11 and Windows 95 and apart from some glitches caused by not plugging in the connectors properly, I haven’t found any problems so far. On the basis of my own experience, it’s a good word pro­cessing compatible text. For those of you who don’t want to write a “C” or “BASIC” program, I have a little Clipper database pro­gram (ZQ.exe) to extract any desired text, for a specified date range. As you can see from the Fig.2: Output From ZQ.Exe resultant output (Fig.2), the Conversion Program program has extracted the de03/01/96 13:00 - 16:35 - Time 03:35 (Hrs:Min) sired text for the dates wanted SILICON CHIP: START ARTICLE ON ORGANISERS and has added the times up as well (I did say I was lazy). 04/01/96 10:00 - 12:20 - Time 02:20 (Hrs:Min) This program will be availSILICON CHIP: LAST PART OF ARTICLE. able either from me via email (no charge) or snail mail ($10 Total Time = 05:55 (includes disc) and is public Above and left: information transfer is a 2-way street. Data can be extracted from the pocket organiser for use in PC programs, or PC data can be sent to the organiser. This eliminates timeconsuming re-keying of information and avoids possible errors. March 1996  75 JAG 1Gb DRIVE Average seek time: 12ms Sustained transfer rate: 6.73Mb/s maximum; 5.51Mb/s avereage; 3.53Mb/s minimim Burst transfer rate: 10Mb/s Buffer size: 256Kb read/write Capacity: 1070Mb and 540Mb (PC formatted capacity) MTBF: 250,000 hours Service life: 5 years Disc drop height: 3ft Disc estimated shelf life in case: 10 years Operating system compatibility: DOS, Windows, Mac OS, OS/2 and Windows ‘95 Interface: fast SCSI-II idea to use the connector’s attach­ment screws rather than just relying on push-fitting the connectors. Currently, I have the ZIP drive connected to an old Windows 3.1 system, and it is available as a network drive from my main Windows 95 system. Jaz 1Gb removable drive This new drive from Iomega is similar in principle to the ZIP drive. But instead of a measly 100Mb(!), it is a full 1Gb removable hard disc and is said to be as fast as a “real” hard disc. I understand that it is due to be released in early 1996 and should cost around $800, with each 1Gb removable disc costing around $150. For the more technically minded, the specifications I down­loaded from their Internet site are shown in the panel at left. I can’t wait to get one to play with. If they work as well as the Zip drive, they should sell like hot cakes. Windows 95 The Windows 95 32-bit protected mode drivers are now avail­ able. I downloaded mine from the Iomega web site at www.iomega.com. In November 1995, the file was called Win95.exe (76Kb) and the full address was: www.iomega.com/users/filearea/ win95.exe. This file is a self extracting Zip file, so put it in a temporary directory and run it, then follow the installation instructions in the file WIN95INS.RTF. The version I was using had an error in the documentation for the parallel port installa­ tion procedure. When selecting the appropriate hardware from the control panel, select “other devices” and then “have disk”; not “SCSI” and then “have disk”, as the documentation instructs. The installation and operation NEXT MONTH In next month's column, I intend giving details on making your own home page on the Internet, with a primer on HTML (Hyper Text Markup Language). If you want a sneak preview, have a look at my new home page at: http://www. pcug.org.au/~gcohen I will also include all software from my SILICON CHIP columns at this address.You can currently obtain the Diskinfo software from it, as well as the Organiser-related files from this issue. worked fine, apart from this minor glitch, and the Win 95 plug and play loads the ZIP driver only if it is connected, without any nasty error messages if it isn’t. If you have any trouble getting the Windows 95 driver file (I have noticed the web site gets a tad busy at times), email me and I will send you a copy. Alternatively, I can send you a copy via snail mail for the normal $10 (includes disk, postage & han­dling). For snail mail copies of the software mentioned in this article, send $10 (cheque or money order) to Geoff Cohen, PO Box 136, Kippax, ACT SC 2615. POSTSCRIPT: AT LAST I'M ORGANISED! I finally managed to (dare I say it!) get organised enough to buy my new organiser, a Sharp 6600. With 256k of RAM and a 40 character screen instead of 16 characters, this is a big improvement over the old 5200. The only problem I had was converting the data from the 5200 to the 6600. The main catch was that the PC Link program uses the older term for the "memo" function, calling it "note". They could also do a little work on the on-line help files to make them easier for a novice user. After all, when you become experienced with the software you don't need the help files! (I always try out my software on a complete beginner. It's really amazing that something which is completely obvious to me means absolutely nothing to someone who hasn't been eating and sleeping the software for the last few weeks/months). The new 6600 organiser needs different link soft76  Silicon Chip ware, although the same cable can be used. I am using the Australian organiser link package "Missing Link", version 2, and have found it a good program. As it is Windows-based it is much better than the old Organiser Link II software which I was forced to use with the 5200. One nice feature of the new package is its script files, which allow me to completely automate routine functions, such as backing up and exporting files to other programs. With the aid of a conversion routine and some help from Gary at Creative Binary Engineering's organiser technical support program, I even managed to convert my old 5200 data to the new 6600 format. Gary emailed me a copy of their template files, which make conversion quite easy. I have included these on my Internet home page and, of course, they are also available from Gary at Creative Binary Engineering (03 9523 8057). SATELLITE WATCH The planned launch of Indonesia’s Palapa C1 satellite on February 15 will mark another milestone in the development of satellite communications in the Pacific Rim. The PALAPA C1 satellite will replace the ageing Palapa B2P satellite at 113° east longitude. The new bird will bring a host of signals from Indonesia, Malaysia, and the Philippines to satellite enthusiasts in Australia and New Zealand. • APSTAR 1R – 88° E LONGITUDE: Due to be launched in March, this satellite has a footprint that will provide massive signals across Australia. Although boresighted off the eastern coast of Africa, the signals will cover most of Asia, Russia and even some parts of Europe. Unfortunately for viewers in New Zealand, the satellite is below the visible horizon. • STATSIONAR 3 – 85° E longitude: Signals from “TVI” network can be seen from 1400 AEST on IF 1270MHz. This is an Indian network, often broadcasting in English. The signal polarisation is right-hand circular. • ASIASAT 2 – 100.5° E longitude: Commissioning is now complete on this spacecraft, and two signals can be seen. RTPi Portugal operate their PAL television service on IF 1165MHz, vertical polarisation. They will add a Portuguese radio service in coming months. Star TV commenced operations of the “V” music channel in analog, before changing to vidicrypt late in January. There are many more broadcasters soon to be loaded onto this satellite. Unfortunately, due to interference from a nearby Gorizont satellite, Asiasat has had to de-commission up to six transponders, causing additional delay to some operators. • PALAPA C1 – 113° E longitude: By the time this article goes to press, spacecraft commissioning should be well underway. The satellite was successfully launched from Cape Canaveral in the United States on Feb 15. Australia’s Compiled by GARRY CRATT* This screen shot does not do justice to the quality of signals received from the new Asiasat 2 satellite. Shown is a soccer match courtesy of RTPi Portugal. The apparent "venetian blind" effect is not interference as might be expected; it is in fact an out-offocus fence behind the player! ATVI (international arm of the ABC) will have a much larger potential audience, both in Asia and in outback Australia. It is expected the transition from the old B2P satellite to this new bird will be transparent to satellite viewers across the region, as the new satellite will take up the same orbital location. • INTELSAT 511 – 180° E longitude C band: The two main transponders of interest are RFO Tahiti and Worldnet. The Worldnet transponder (1175MHz IF) is shared by Deutsche Welle and the American C-SPAN network. As the satellite is in an inclined orbit, tracking equipment is required. • GORIZONT 41 – 130° E longitude: Formerly known as Rimsat G1 until “repossession” by the Russian Space Agency, this satellite still carries RAJ TV, a Tamil language channel from India. • GORIZONT 42 – 142.5° E longitude: Another “repossession” spacecraft, formerly known as Rimsat G2, this satellite carries ATN from India and EM TV from New Guinea. It is rumoured that the EM TV signal will move to Intelsat 701 (180° E) mid year. • OPTUS B3 – 156 E° longitude: Narrowcast operator “TV Oceania” has announced an end to their Japanese language service. Due to cease operations at the end of March, TVO will concentrate on their other business activities. They quote a downturn in subscriptions, primarily due to NHK free-to-air broadcasting on Panamsat’s PAS-2 satellite at 169° E. • OPTUS B1 – 160° E longitude, C band: This satellite is almost fully loaded with 5 interchange channels, 5 B-MAC channels, 3 E-PAL channels, and other omnicast and narrowcast services. No new reports from this bird. • PANAMSAT PAS-2 – 169 E longitude, C band: Two B-MAC operators, ESPN and Discovery Channel, have ad­vised they will change format to GI Digicypher II early in 1996, to take advantage of reduced uplink costs. CNN, CNBC Asia, NHK Japan and several interchange channels are still SC operating in analog. *Garry Cratt is Managing Director of Av-Comm Pty Ltd, suppliers of satellite TV reception systems. March 1996  77 NICS O R T 2223 LEC 7910 y, NSW EY E OATLBox 89, Oa8t5leFax (02) 5s7a0 C a rd MANY OF THE PRICES LISTED APPLY DURING APRIL AND MAY ONLY Vi PO 49 fax ) 579 e r C a rd , 2 0 ( ne & rs: choice for a special price. Choose motors from e o t n s h o a p h P M17 / M18 / M35. $44. , M ith rde d o w r a d d c e You can also purchase this kit with the B a n k x accepte most mix 0. Orders stepper motor pack described above: $65. e r 1 o m $ f A ) l i P Kit without motors is also available: $32. & & ma r i P a ( . s order 4-$10; NZ world.net FLUORESCENT TAPE $ <at> High quality Mitsubishi brand all weather Aust. IL: oatley 50mm wide red reflective tape with self A by EM adhesive backing: 3 metres for $5. MISCELLANEOUS ITEMS LED BRAKE LIGHT INDICATOR: make a 600mm long high intensity line display, includes 60 high intensity LEDs plus two PCBs plus 10 resistors: $20 (K14). AC MOTOR: 1RPM geared 24V-5W synchronous motor plus a 0.1 to 1RPM driver kit to vary speed; works from 12V DC: $12 (K38 + M30). TOMINON SYMMETRICAL LENS: 230mm focal length - f1:4.5, approximately 100mm diameter an 100mm long: $25 (O14). SPRING REVERB: 30cm long with three springs: $30 (A10). MICROSONIC MICRO RECORD PLAYER: includes amplifier: $4 (A11). MOTOR DRIVEN POTENTIOMETER: dual 20k with PCB: $9. ANGLED TELEPHONE STANDS: Angled, smoky perspex: 4 for $10 (G47). LARGE METER MOVEMENTS: moving iron, 150 x 150mm square face, with mounting hardware: $10. New ARLEC brand 24VDC-500mA approved plugpacks: $9. One FARAD 5.5V capacitors: $3. SPECIALS – POLLING FAX LINE Poll our 579 3955 fax number for new items and some very limited quantity specials. ALCOHOL TESTER KIT Based on a high quality Japanese thick film alcohol sensor. The kit includes a PCB, all on board components and a meter movement: $30. The circuitry includes a latching alarm output that can be used to drive a buzzer, siren etc. We should also have other gas sensors available for this kit. WIND POWER GENERATOR KIT In late April we will have available a low cost kit that employs a low cost electric motor, as used in car radiator cooling systems, to serve as a wind powered electricity generator. Construction drawings for an 800mm 2 blade propeller are supplied. The combination puts out up to 30W of power in high winds. Electronic kit price should be approximately $30. Price of a used suitable motor (available from car wreckers) should be under $40. We will have a limited quantity available for $35. LED FLASHER KIT 3V operated 3 pin IC that can flash 1 or two 2 high intensity LEDs. Very bright and efficient. IC plus 2 high intensity LEDs plus small PCB: $1.30. SIMPLE MUSIC KIT 3V operated 3-pin ICs that play a single tune. Two ICs that play different tunes plus a speaker plus a small PCB: $2.50. CD MECHANISMS AND CD HEADS Used CD mechanisms that have a small motor with geared worm drive assy. Popular with model railway enthusiasts: $5. Also new CD heads that include a laser diode, lenses etc: $3. STEPPER MOTOR PACK Buy a pack of 7 of our stepper motors and save 50%!! Includes 2XM17, 2XM18, 2XM35 and 1 used motor. Six new motors and one used motor for a total of: $36. COMPUTER CONTROLLED STEPPER MOTOR DRIVER KIT This kit will drive two 4, 5, 6 or 8-wire stepper motors from an IBM computer parallel port. The motors require a separate power supply (not included). A detailed manual on the computer control of motors plus circuit diagrams and descriptions are provided. Software is also supplied, on a 3.5" disk. NEW SOFTWARE WILL DRIVE UP TO 4 MOTORS (2 kits required), with LINEAR INTERPOLATION ACROSS FOUR AXES. PCB: 153 x 45mm. Great low cost educational kit. We provide the PCB and all on-board components kit, manual, disk with software, plus two stepper motors of your 78  Silicon Chip UHF REMOTE VOLUME CONTROL SPECIAL As published in EA Dec 95-Jan 96. We supply two UHF transmitters, plus a complete receiver kit, including the case and the motorised volume control potentiometer: $60. PC CONTROLLED PROGRAMMABLE POWER SWITCH MODULE This module is a four channel programmable on/off timer switch for high power relays. The timer software application is included with the module. Using this software the operator can program the on/off status of four independent devices in a period of a week within a resolution of 10 minutes. The module can be controlled through the Centronics or RS232 port. The computer is opto isolated from the unit. Although the high power relays included are designed for 240V operation, they have not been approved by the electrical authorities for attachment to the mains. Main module: 146 x 53 x 40mm. Display panel: 146 x 15mm. We supply: two fully assembled and tested PCBs (main plus control panel), four relays (each with 3 x 10A / 240V AC relay contacts), and software on 3.5" disk. We do not supply a casing or front panels: $92. (Cat G20) STOP THAT DOG BARK Troubles with barking dogs?? Muffle the mongrels and restore your sanity with the WOOFER STOPPER MK2, as published in the Feb 96 edition of Silicon Chip. A high power ultrasonic sweep generator which can be triggered by a barking dog. We supply a kit which includes a PCB and all the on-board components: all the resistors, capacitors, semiconductors, trimpotentiometers, heatsinks, and the transformer. We will also include the electret microphone. Note that our kit is supplied with a solder masked and silk screened PCB, and a pre-wound transformer!: $39. Single Motorola piezo horn speakers to suit (one is good, but up to four can be used): $14. Approved 12VDC-1A plugpack to suit: $14. UHF REMOTE CONTROL FOR THE DE-BARKER OF ANNOYING DOGS Operate your Woofer Stopper remotely from anywhere in your house, even your bedside. Allows you to remotely trigger your Woofer Stopper at any time. Nothing beats a randomly timed “human touch”. We supply one single channel UHF transmitter, one suitable UHF receiver and very simple interfacing instructions: $28. Based on the single channel transmitter and a slightly modified version of the 2 channel receiver, as published in the Feb 96 edition of Silicon Chip. Note that the article features 3 low cost remote controls: 1 ch UHF with central locking, 1-2 ch UHF, and an 8 ch IR remote. MOTOR DRIVEN VOLUME CONTROL/POT New high quality motor driven potentiometer, intended for use in commercial stereo sound systems. Includes clutch, so can also be manually adjusted. Standard 1/4" shaft, stereo (dual 20k pots) with 5V/20mA motor: $12 (Cat A13). MINI HIGH VOLTAGE POWER SUPPLY Miniature potted EHT power supply (17 x 27 x 56mm) that was originally designed to power small He-Ne Laser tubes. Produces a potent 10mm spark when powered from 8-12V / 500mA DC source. Great for experimentation, small portable Jacobs Ladder displays, and cattle prods. Use on humans is dangerous and illegal. A unit constructed for this purpose would be would be considered an offensive weapon. Inverter only: $25. CCD CAMERA SPECIAL Very small PCB CCD camera including auto iris lens: 0.1 Lux, 320K pixels, IR responsive; overall dimensions: 38 x 38 x 25mm. We will include a free VHF modulator kit with every camera purchase. Enables the viewing of the picture on any standard TV on a VHF Channel. Each camera is supplied with instructions and a 6 IR LED illuminator kit. $170. CCD CAMERA - TIME LAPSE VCR RECORDING SYSTEM This kit plus ready made PIR detector module and “learning remote control” combination can trigger any domestic IR remote controlled VCR to RECORD human activity within a 6M range and with an 180 deg angle of view! Starts VCR recording at first movement and ceases recording a few minutes after the last movement has stopped: just like commercial CCD/TIME LAPSE RECORDING systems costing thousands of dollars!! CCD camera not supplied. No connection is required to your existing domestic VCR as the system employs an “IR learning remote control”: $90 for an PIR detector module, plus control kit, plus a suitable “lR learning remote” control and instructions: $65 when purchased in conjunction with our CCD camera. Previous CCD camera purchasers may claim the reduced price with proof of purchase. SOUND FOR CCD CAMERAS/UNIVERSAL AMPLIFIER (To be published, EA). Uses an LM386 audio amplifier IC and a BC548 pre-amp. Signals picked up from an electret microphone are amplified and drives a speaker. Intended for use for listening to sound in the location of a CCD camera installation, but this kit could be used as a simple utility amplifier. Very high audio gain (adjustable) makes this unit suitable for use with directional parabolic reflectors etc. PCB: 63 x 37mm: $10. (K64) LOW COST IR ILLUMINATOR Illuminates night viewers or CCD cameras using 42 of our 880nm/30mW/12 degrees IR LEDs. Power output (and power consumption) is variable, using a trimpotentiometer. Operates from 10 to 15V and consumes from 5mA up to 0.6A (at maximum power). The LEDs are arranged into 6 strings of 7 series LEDs with each string controlled by an adjustable constant current source. PCB: 83 x 52mm: $40 (K36). MASTHEAD AMPLIFIER SPECIAL High performance low noise masthead amplifier covers VHF - FM UHF and is based on a MAR-6 IC. Includes two PCBs, all on-board components. For a limited time we will also include a suitable plugpack to power the amplifier from mains for a total price of: $25. VISIBLE LASER DIODE KIT A 5mW/660nM visible laser diode plus a collimating lens, plus a housing, plus an APC driver kit (Sept 94 EA). UNBELIEVABLE PRICE: $40. Suitable case and battery holder to make pointer as in EA Nov 95 $5 extra. SOLID STATE “PELTIER EFFECT” DEVICES We have reduced the price of our peltiers! These can be used to make a solid state thermoelectric cooler/heater. Basic information supplied. 12V-4.4A PELTIER: $25. We can also provide two thermal cut-out switches and a 12V DC fan to suit the above, for an additional price of $10. PLASMA EFFECTS SPECIAL Ref: EA Jan. 1994. This kit will produce a fascinating colourful changing high voltage discharge in a standard domestic light bulb. Light up any old fluorescent tube or any other gas filled bulb. Fascinating! The EHT circuit is powered from a 12V to 15V supply and draws a low 0.7A. Output is about 10kV AC peak. PCB: 130 x 32mm. PCB and all the on-board components (flyback transformer included) and the instructions: $28 (K16). Note: we do not supply any bulbs or casing. Hint: connect the AC output to one of the pins on a fluorescent tube or a non-functional but gassed laser tube for fascinating results! The SPECIAL???: We will supply a non-functional laser tube for an additional $5 but only when purchased with the above plasma kit: TOTAL PRICE: $33. 400 x 128 LCD DISPLAY MODULE - HITACHI These are silver grey Hitachi LM215 dot matrix displays. They are installed in an attractive housing. Housing dimensions: 340 x 125 x 30mm. Weight: 1.3kg. Effective display size is 65 x 235mm. Basic data for the display is provided. Driver ICs are fitted but require an external controller. New, unused units. $25 ea. (Cat D02) 3 for $60. VISIBLE LASER DIODE MODULE SPECIAL Industrial quality 5mW/670nM laser diode modules. Consists of a visible laser diode, diode housing, driver circuit, and collimation lens all factory assembled in one small module. APC control circuit assures. Features an automatic power control circuit (APC) driver, so brightness varies little with changes in supply voltage or temperature. Requires 3 to 5V to operate. Overall dimensions: 12mm diameter by 43mm long. Assembled into an anodised aluminium casing. This module has a superior collimating optic. Divergence angle is less than 1 milliradian. Spot size is typically 20mm in diameter at 30 metres: $65 (Cat L10). This unit may also be available with a 635nm laser diode fitted. dimensions: 25 x 43mm. Construction is easy and no coil winding is necessary as the coil is pre-assembled in a shielded metal can. The solder masked and screened PCB also makes for easy construction. The kit includes a PCB and all the on-board components, an electret microphone, and a 9V battery clip: $12 ea. or 3 for $33 (K11). CYCLE/VEHICLE COMPUTERS BRAND NEW SOLAR POWERED MODEL! Intended for bicycles, but with some ingenuity these could be adapted to any moving vehicle that has a rotating wheel. Could also be used with an old bicycle wheel to make a distance measuring wheel. Top of the range model. Weather and shock resistant. Functions: speedometer, average speed, maximum speed, tripmeter, odometer, auto trip timer, scan, freeze frame memory, clock. Programmable to allow operation with almost any wheel diameter. Uses a small spoke-mounted magnet, with a Hall effect switch fixed to the forks which detects each time the magnet passes. The Hall effect switch is linked to the small main unit mounted on the handlebars via a cable. Readout at main unit is via an LCD display. Main unit can be unclipped from the handlebar mounting to prevent it being stolen, and weighs only 30g. Maximum speed reading: 160km/h. Maximum odometer reading: 9999km. Maximum tripmeter reading: 999.9km. Dimensions of main unit: 64 x 50 x 19mm: $32 (Cat G16). FM TX MK 3 This kit has the most range of our kits (to around 200m). Uses a pre-wound RF coil. The design limits the deviation, so the volume control on the receiver will have to be set higher than normal. 6V operation only, at approx 20mA. PCB: 46 x 33mm: $18 (K33). PASSIVE TUBE - SUPPLY SPECIAL Russian passive tube plus supply combination at an unbelievable SPECIAL REDUCED PRICE: $70 for the pair! Ring or fax for more information. 27MHZ RECEIVERS Brand new military grade 27MHz single channel telemetry receivers. Enclosed in waterproof die cast metal boxes, telescopic antenna supplied. 270 x 145 x 65mm 2.8KG. Two separate PCBs: receiver PCB has audio output; signal filter/squelch PCB is used to detect various tones. Circuit provided: $20. BATTERY CHARGER WITH MECHANICAL TIMER A simple kit which is based on a commercial twelve-hour mechanical timer switch which sets the battery charging period from 0 to 12 hours. Employs a power transistor and five additional components. It can easily be “hard wired”. Information that shows how to select the charging current is included. We supply the information, a circuit and the wiring diagram, a hobby box with an aluminium cover that doubles up as a heatsink, a timer switch with knob, a power transistor and a few other small components to give you a wide selection of charge current. You will also need a DC supply with an output voltage which is greater by about 2V than the highest battery voltage you intend to charge. As an example, a cheap standard car battery charger could be used as the power source to charge any chargeable battery with a voltage range of 0 to 15V. Or you could use it in your car. No current is drawn at the end of the charging period: $15. SIREN USING SPEAKER Uses the same siren driver circuit as in the “Protect anything alarm kit”. 4" cone / 8 ohm speaker is included. Generates a very loud and irritating sound that is useful to far greater distances than expensive piezo screamers. Has penetrating high and low frequency components and the sound is similar to a Police siren. Output has frequency components between 500Hz and 4KHz. Current consumption is about 0.5A at 12V. PCB: 46 x 40mm. As a bonus, we include all the extra PCBs as used in the “Protect anything alarm kit”: $12. FM TRANSMITTER KIT - MKII Ref: SC Oct 93. This low cost FM transmitter features preemphasis, high audio sensitivity (easily picks up normal conversation in a large room), a range of around 100 metres, and excellent frequency stability. Specifications: tuning range: 88-108MHz; supply voltage 6-12V; current consumption <at> 9V: 3.5mA; pre-emphasis: 75uS; frequency response: 40Hz to greater than 15KHz; S/N ratio: greater than 60dB; sensitivity for full deviation: 20mV; frequency stability with extreme antenna movements: 0.03%; PCB MOTOR SPEED CONTROLLER PCB Simple circuit controls small DC powered motors which take up to around 2 amps. Uses variable duty cycle oscillator controlled by trimpot. Duty cycle is adjustable from almost 0 - 100%. Oscillator switches P222 MOSFET. PCB: 46 x 28mm. $11 (K67). For larger power motors use a BUZ11A MOSFET: $3. ELECTROCARDIOGRAM PCB + DISK The software disk and a silk screened and solder masked PCB (PCB size: 105 x 53mm) for the ECG kit published in EA July 95. No further components supplied: $10 (K47). DC MOTORS We have good stocks of the following high quality DC motors. These should suit many industrial, hobby, robotics and other applications. Types: Type M9: 12V. I no load = 0.52A <at> 15800 RPM at 12V. Weight: 150g. Main body is 36mm diameter. 67mm long: $7 (Cat M9). Type M14: made for slot cars. 4 to 8V. I no load = 0.84A at 6V. At max. efficiency I = 5.7A <at> 7500 RPM. Weight: 220g. Main body diameter is 30mm. 57mm long: $7 (Cat M14). MAGNETS: HIGH POWER RARE EARTH MAGNETS Very strong. You will not be able to separate two of these by pulling them apart directly away from each other. Zinc coated. CYLINDRICAL 7 x 3 mm: $2 (Cat G37) CYLINDRICAL 10 x 3 mm: $4 (Cat G38) TOROIDAL 50mm outer, 35mm inner, 5mm thick: $9.50 (Cat G39) CRYSTAL OSCILLATOR MODULES Small hermetically sealed, crystal oscillator modules. Used in computers. Operate from 5V and draw about 30mA. TTL logic level clock output. Available in 4MHz, 4.032MHz, 5.0688MHz, 20MHz, 20.2752MHz, 24.74MHz, 40MHz, and 50MHz.: $7 ea. (Cat G45) 5 for $25. XENON FLASH BOARDS Flash units with small (2cm long) xenon tube, as used in disposable cameras. Power from one AA 1.5V battery. Approx 7 joules energy: $3 (Cat G48). INDUCTIVE PICKUP KIT Ref: EA Oct 95. Kit includes coil pre-wound. Use receiver in conjunction with a transmit loop of wire which is plugged in in place of where a speaker is normally used. This wire loop is run around the perimeter of the room / house you wish to use the induction loop in. We do not supply the transmit loop wire. Also excellent for tracing AC magnetic fields. PCB: 61 x 32mm. Kit contains PCB and all on board components: $10 (K55). SLAVE FLASH TRIGGER Very simple, but very effective design using only a few components. Based on an ETI design. This kit activates a second flash unit when the master, or camera mounted, flash unit is activated. This is useful to fill in shadows and improve the evenness of the lighting. It works by picking up the bright flash with a phototransistor and triggering an SCR. The SCR is used as a switch across the flash contacts. This circuit does not false trigger even in strongly lit rooms, but is sensitive enough to operate almost anywhere within even a quite large room. Of course, by making more of these and fitting them to more slave flash units even better lighting and more shadow reduction is obtained. PCB: 21 x 21mm: $7 (K60). SOUND ACTIVATED FLASH TRIGGER Based on ETI project 514. Triggers a flash gun using an SCR, when sound level received by an electret microphone exceeds a certain level. This sound level is adjustable. The delay between the sound being received and operation of the flash is adjustable between 5 and 200 milliseconds. A red LED lights up every time the sound is loud enough to trigger the flash. This is handy when setting the unit up to suit the scene, without waiting for the flash unit to recharge or flatten its batteries in the process. This kit allows you take interesting pictures such as a light bulb breaking. PCB: 62 x 40mm: $14 (K61). OPTO PHOTO INTERRUPTER (SLOTTED): an IR LED and an phototransistor in a slotted PCB mounting assembly. The phototransistor responds to visible and IR light. The discrete components are easy to separate from the clip together assembly. Great for IR experiments: $2 ea. or 10 for $15. IR PHOTODIODE: similar to BPW50. Used in IR remote control receivers. Peak response is at 940nm. Use with 940nm LEDs: $1.50 ea. or 10 for $10. VISIBLE PHOTODIODE: this is the same diode element as used in our IR photodiode but with clear encapsulation, so it responds better to visible and IR spectrum: $1.50 ea. or 10 for $10. LDRs: large, 12mm diameter, <20ohm very bright conditions, >20Mohm very dark conditions: $1. LEDs BRIGHTNESS RATING: Normal, Bright, Superbright, Ultrabright. BLUE: 5mm, 20mA max, 3.0V typical forward voltage drop. $2.50 RED SUPERBRIGHT: 5mm, 0.6 to 1.0 Cd, 30mA max, forward voltage 1.7V, 12 degrees view angle, clear encapsulation: 10 for $4 or 100 for $30. BRIGHT: 5mm. Colours available: red, green, orange, yellow. Encapsulation colour is the same as the emitted colour. 30mA max.: 10 for $2 or 100 for $14. BRIGHT NARROW ANGLE: 5mm, clear encapsulation, 30mA. Colours available: yellow, green: 10 for $2.50 or 100 for $20. TWO COLOUR: 5mm, milky encapsulation, 3 pins, red plus green, yellow by switching both on: $0.60. ULTRABRIGHT YELLOW: Make a LED torch!: $2.50. PACK OF 2mm LEDs: 10 each of the following colours: red, green, amber. We include 30 1.0K ohm resistors for use as current limiting. Great for model train layouts using HO gauge rails: $10. IR LEDs: 800nm. Motorola type SFOE1025. Output 1mW <at> 48mA. Forward voltage 1.7V. Suitable for use with a focussing lens. At verge of IR and visible, so has some visible output. Illuminates Russian and second generation viewers: $2. HIGH POWER IR LEDs: 880nm/30mW output <at> 100mA. Forward voltage: 1.5V. The best 880nm LEDs available. Excellent for IR illumination of most night viewers and CCD cameras. We use these LEDs in our IR illuminator kit K36. Emits only a negligible visible output. Both wide angle (60 degrees) and narrow angle (12 degrees) versions of these LEDs are available. Specify type required: 10 for $9 or 100 for $80. IR LEDs: 940nm. Commonly used in IR remote control transmitters. Good for IR viewers with a deeper IR response. No visible output. 16mW output. 100mA max. Forward voltage is 1.5V: 10 for $5. 18V AC <at> 0.83A PLUGPACKS Also include a diecast box (100 x 50 x 25mm): Ferguson brand. Australian made and approved plugpacks. Output lead goes to diecast box with a few components inside. Holes drilled in box where LED and 2 RF connectors are secured: $8 (Cat P05). CASED TRANSFORMERS 230Vac to 11.7Vac <at> 300mA. New Italian transformers in small plastic case with separate input and output leads, each is over 2m long. European mains plug fitted; just cut it off and fit the local plug. This would be called a plugpack if it sat on the powerpoint: $6 (Cat P06). FREE CATALOGUE WITH YOUR ORDER Ask us to send you a copy of our FREE catalogue with your next order. Different items and kits with illustrations and ordering information. And don’t forget our website at: http://www.hk.super.net/~diykit March 1996  79 PRODUCT SHOWCASE New TDK video cassette tape Kenwood's latest dual cassette deck Kenwood's latest double cassette deck, the KX-W8070S features Dolby S, along with B and C noise reduction systems, double Auto Reverse, three motors and auto bias with fine adjust. Double cassette decks offer a number of advantages over single-well decks, such as tape-to-tape dubbing and extended play, offering a potential of three hours of music. The Dolby S noise reduction system offers up to 23dB of noise reduction and increased high-frequency headroom with less noise modulation. The KX-W8070S also features the HX-PRO Headroom Extension system that effectively allows more high frequency energy to be stored on the tape without saturation. This is achieved by varying the level of bias with the signal to be recorded, maintaining the signal within a certain threshold. The end result is significantly improved mid and high range headroom with lower distortion. Kenwood also employ their CCRS (Computer Controlled CD Recording System) that automatically scans the contents of CDs and adjusts the recording level to assure optimum results both in normal and high speed. The KX-W8070S also features Kenwood's DPSS search and Index Scan that enables quick access to specific tracks. The KX-W8070S is covered by a two year parts and labour warranty, has a recommended retail price of $799 and is available at selected Kenwood dealers. For further information on Kenwood products phone (02) 746 1888. Versatile infrared headphones The Infratronic IR-1800RC and IR-2000SRC infrared cordless stereo headphones allow the freedom of untethered high quality listening. They may be used with virtually any audio source: TV, VCRs, hifi, audio/ video systems and computer games. Automatic level control allows these units to be driven directly from the line level outputs of most CD players, cassette decks, receivers, video disc players, computers and video cassette recorders. Both headsets have a 20Hz to 80  Silicon Chip In support of recent digital VCR and camcorder hardware advancements, TDK have released a new digital video tape, the DVC60 which allows up to 60 minutes of recording/playback (in standard mode). Unlike VHS VCRs where the video head rotates 25 revolutions per second, in digital VCRs the head rotates about five times that speed, placing much greater demands on the tape, particularly in still frame modes. For this reason, TDK's DVC60 utilises a specially developed coating. Other features include an advanced back-coating for smooth tape travel and a highly stable cassette mechanism with a reel lock mechanism to prevent tape slippage. For further information on TDK's DVC, phone (02) 437 5100. 20kHz frequency response, 50 milliwatts audio output, up to 7 metre operating range and are each powered by two AAA rechargeable batteries. The headsets weigh just 180 grams, have a personal volume control and feature automatic battery recharging when placed on the transmitter stand. Additional headsets may be used and are available separately. Both sets are supplied with an AC/DC adaptor, 3.5mm to 6.3mm plug, stereo to mono jack and stereo jack. For more information, contact Allthings Sales & Services, PO Box 25, Northlands, WA 6021. Phone (09) 349 9413; fax (09) 344 5905. AUDIO MODULES broadcast quality Low-cost single-phase chassis-mounting filters Schaffner has launched a new series of single-phase chassis-mounting filers for a wide range of applications. Known as the FN 2000 series, the filters have a very compact form factor, achieved through the use of high performance magnetic and capacitive components, which makes them ideal for applications where space is at a premium. Excellent stop-band attenuation and current-carrying capabilities mean that the filters are particularly suitable for electrically noisy equipment, such as motor drives and switchmode power supplies. Tektronix extends its InstaVu family of DSOs Tektronix has announced a new family of lower-priced InstaVu acquisition oscilloscopes. The new TDS700A series and TDS500B series of digital storage oscilloscopes (DSOs) have Tektronix' proprietary InstaVu signal acquisition technology which lets users capture up to 400,000 wfm/s (waveforms per second), making these new digital scopes as fast as the world's fastest analog scopes. The new TDS700A series includes the TDS784A, TDS744A and TDS724A. It features colour displays, bandwidths up to 1GHz, sample rates up to 1GS/s and acquisition rates up to 400,000 wfm/s. The new TDS500B series includes the four-channel TDS540B and two-channel TDS520B. Both scopes feature 500MHz bandwidth, up to 2GS/s sampling rate, Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 476-5854 Fx (02) 476-3231 The FN 2000 filter series comprises 72 standard versions, covering current ranges from 1 to 30A, each of which is available in medical (B type) or safety (A type) configurations. Furthermore, the internal design is modular which enables Schaffner to produce custom versions of the filters. Each filter is contained within a chassis-mounting metal housing with a choice of fast-on, wire or screw feed-through connectors. The filters are all designed for operation at up to 250VAC and can handle supply frequencies from DC to 400Hz. All multistage filters in the FN 2000 series can be supplied with the capacitors connected to the load side, in order to present the best impedance mis- match between equipment and filter. The top of the range FN 2080 has high inductance and capacitance values, and employs independent differential mode, rather than common mode chokes to ensure excellent differential and common mode attenuation across a broad band of frequencies. A free 16-page design guide and short form catalogs on the new FN 2000 series filters are available from Westinghouse Industrial Products, Locked Bag 66, South Melbourne, Vic 3205. Phone (03) 9676 8888; fax (03) 9676 8702. monochrome displays and up to 100,000 wfm/s acquisition rate. Tektronix' InstaVu acquisition technology is designed to quickly pinpoint and capture unpredictable, rapidly changing signals, infrequent glitches, metastable behaviors and time jitter, that may never be detected by conventional analog or digital scopes or specialised triggering. InstaVu technology combines high-speed acquisition memory with highspeed display rasterisation to increase acquisition performance and ensure instantaneous live display of all signal changes. For design and debug applications, InstaVu technology cuts debug time from hours to seconds. Note: the Tektronix 784A was first reviewed in the March 1995 issue of SILICON CHIP. For further information, contact Tektronix at 80 Waterloo Rd, North Ryde, NSW 2113. March 1996  81 Wide screen TV from Mitsubishi Mitsubishi Electric's first wide screen colour television, the DIVA Wide model, is now available. As well as giving TV viewers a cinema-like picture, the DIVA Wide incorporates AI Fuzzy Logic circuitry for superb picture quality, and Auto Turn to allow the viewer to adjust the viewing angle of their TV.It also has Pro Logic Sound and four extension speakers. Six other digital surround sound modes are provided: Pro Logic Phantom, Theatre, Concert Hall, Stadium, Disco and Pseudo Stereo. The matching stand has a centre channel speaker and a built-in woofer as well as space to accommodate a VCR or laser disc player. The Mitsubishi wide screen TV also features eight picture modes so viewers can manipulate the 4:3 broadcast to fit the screen, as best suits the program. A feature called "picture-out-picture" (POP) makes the DIVA Wide different to its competitors. Using POP, the 16:9 screen can be broken down into a 4:3 82  Silicon Chip screen with three boxes in the remaining screen area. Viewers can then watch the main screen plus three other broadcast sources (from other TV channels, audio visual or laser disc). They can then alternate between sources, choosing which one appears on the main screen. The extra pictures appear next to the main one, not within it as is the case with picture-in-picture. With two TV tuners, the Mitsubishi set has both picture-in-picture and picture-out-picture. The full list of picture modes is: cinema (scroll up/down); cinema caption (scroll up/down); panorama 1 (stretches the left/right edge to fill screen); panorama 2 (compresses top/ bottom to fill screen); 16:9 full; 14:9 (leaves narrow black bands at each edge of screen); 4:3 normal; auto view (automatically selects appropriate screen size). Recommended retail price of the new Mitsubishi set is $6,999. For more information, contact Mitsubishi Electric Australia, 348 Victoria Road, Rydalmere, NSW 2116. Phone (02) 684 7777. DIGI ISDN Personal Computer card Sealcorp has announced the Australian release of the Digi PC IMAC ISDN card. The new PC card for ISDN connections is claimed to quadruple the speed of Internet access and provide much improved bandwidth on LAN/ WAN connections. The integrated terminal adaptor/network interface card installs in any ISA PC and connects directly to an ISDN line. ISDN connections are available in just one quarter of a second through the new Digi card, compared to 30-90 seconds for a modem over the public switched telephone network. A word processing file, for example, can be completely downloaded in the same time it takes a modem to make a connection. The new ISDN cards are manufactured by Digi International in North America and are fully Austel approved for Australian use. Recommended retail prices start at $1,952 excluding sales tax. They are supplied with a five year guarantee. For more information, contact Sealcorp, PO Box 670, Lane Cove, NSW 2066. Phone (02) 418 9099; fax (02) 418 9313. Function generators from Yokogawa Traditionally, high-performance function generators have been difficult to operate, involving the manipulation of many front panel keys. A new generation of 2-channel, compact function generators from Yokogawa, which feature a large LCD display and touch screen, has addressed this difficulty. The FG200/FG300 series function generators offer 2 channels in a compact, lightweight package and feature sweep and modulation capabilities. The new generators provide sine and square outputs up to +/-10V over a frequency range of 1uHz to 15MHz, and triangle, pulse and arbitrary (on the FG300) outputs from 1uHz to 200kHz. Frequency resolution is 1uHz or a maximum nine digits. Operation of the FG200/FG300 series has been simplified by virtue of the large LCD touch screen. The setup and display or arbitrary sweep patterns and simple arbitrary waveforms can be defined by entering points within the scaled ranges on the X and Y axes, and can be generated using linear, step or spline interpolations between the points. Alternatively, the data may be loaded in ASCII format via the internal floppy disc drive. This interface may also be used to load waveforms created with Yokogawa AG series waveform generators or captured with the company's digital oscilloscopes. Sweeps may be made in frequency, KITS-R-US Cathode Ray Oscilloscopes – from page 17 X2. But for good luminescent efficiency, thousands of volts acceleration voltage is necessary to produce bright sharp traces on the CRO screen. In this example, we have shown 5kV, which is relatively standard for a CRO. Therefore, in oscilloscopes using the simple CRO tubes shown, the high voltage supply is grounded (or nearly so) at the CRO screen end. Consequently, the heater, cathode, control grid G1 and focus grid G2 are all at high negative voltages with respect to ground. As a consequence, lethal voltages exist on the heater, cathode, grid and other wiring and terminals inside an oscilloscope. Next month we will dig further into how analog oscilloscopes are designed to reproduce high frequencies, up to 1000MHz (1GHz) and how the trace on the screen can be so bright, sharp, clear, calibrated and accurate. Acknowledgements Thanks to Philips Scientific & Industrial and to Tektronix Australia for data and illustrations; also to Ian Hartshorn, Jack Sandell, Professor David Curtis, Ian Marx and Dennis Cobley. References "ABCs of Oscilloscopes" – Philips/Fluke USA "Solid State Physical Electronics" – Van der Ziel A; Prentice Hall NJ, USA. "Basic Television" – McGraw-Hill NY, USA. Tektronix Aust. Application Notes. SC phase, amplitude, offset voltage or duty cycle, in linear, log linear step, log step or arbitrary sweep patterns. The sweep parameters may be controlled by an external analog or digital signal. Output amplitude and duty cycle are continuously variable and by linking multiple generators together, three or more channels of phase synchronised signals may be obtained, with even the sweep synchronised if required. For further information, contact Yokogawa Australia, 25-27 Paul St North, North Ryde, NSW 2113. Phone SC (02) 888 1844. PO Box 314 Blackwood SA 5051 Ph 018 806794 TRANSMITTER KITS $49: a simple to build 2.5 watt free running CD level input, FM band runs from 12-24VDC. •• FMTX1 FMTX2B $49: the best transmitter on the market, FM-Band XTAL locked on 100MHz. CD level input 3 stage design, very stable up to 30mW RF output. $49: a universal digital stereo encoder for use on either of our transmitters. XTAL locked. •• FMTX2A FMTX5 $99: both FMTX2A & FMTX2B on one PCB. FMTX10 $599: a complete FMTX5 built and tested, enclosed in a quality case with plugpack, DIN input •connector for audio and a 1/2mtr internal antenna, also available in 1U rack mount with balanced cannon input sockets, dual VU meter and BNC RF $1299. Ideal for cable FM or broadcast transmission over distances of up to 300 mtrs, i.e. drive-in theatres, sports arenas, football grounds up to 50mW RF out. FMTX10B $2599: same as rack mount version but also includes dual SCA coder with 67 & 92kHz subcarriers. • AUDIO Audio Power Amp: this has been the most popular kit of all time with some 24,000 PCBs being •soldDIGI-125 since 1987. Easy to build, small in size, high power, clever design, uses KISS principle. Manufacturing rights available with full technical support and PCB CAD artwork available to companies for a small royalty. 200 Watt Kit $29, PCB only $4.95. AEM 35 Watt Single Chip Audio Power Amp $19.95: this is an ideal amp for the beginner to construct; uses an LM1875 chip and a few parts on a 1 inch square PCB. Low Distortion Balanced Line Audio Oscillator Kit $69: designed to pump out line up tone around studio complexes at 400Hz or any other audio frequency you wish to us. Maximum output +21dBm. MONO Audio DA Amp Kit, 15 splits: $69. Universal BALUN Balanced Line Converter Kit $69: converts what you have to what you want, unbalanced to balanced or vice versa. Adjustable gain. Stereo. • • •• COMPUTERS I/O Card for PCs Kit $169: originally published in Silicon Chip, this is a real low cost way to interface •to Max the outside world from your PC, 7 relays, 8 TTL inputs, ADC & DAC, stepper motor drive/open collector 1 amp outputs. Sample software in basic supplied on disk. PC 8255 24 Line I/O Card Kit $69, PCB $39: described in ETI, this board is easy to construct with •onlyIBM3 chips and a double sided plated through hole PCB. Any of the 24 lines can be used as an input or output. Good value. 19" Rack Mount PC Case: $999. •• Professional All-In-One 486SLC-33 CPU Board $799: includes dual serial, games, printer floppy & IDE hard disk drive interface, up to 4Mb RAM 1/2 size card. PC104 486SLC CPU Board with 2Mb RAM included: 2 serial, printer, floppy & IDE hard disk $999; VGA •PC104 card $399. KIT WARRANTY – CHECK THIS OUT!!! If your kit does not work, provided good workmanship has been applied in assembly and all original parts have been correctly assembled, we will repair your kit FREE if returned within 14 days of purchase. Your only cost is postage both ways. Now, that’s a WARRANTY! KITS-R-US sell the entire range of designs by Graham Dicker. The designer has not extended his agreement with the previous distributor, PC Computers, in Adelaide. All products can be purchased with Visa/Bankcard by phone and shipped overnight via Australia EXPRESS POST for $6.80 per order. You can speak to the designer Mon-Fri direct from 6-7pm or place orders 24 hours a day on: PH 018 80 6794; FAX 08 270 3175. March 1996  83 To do a worthwhile check on a dry cell battery, you need to load it while you take a voltage measurement. The load can be a suitable resistor but there is a better way – use the green test strip which comes with Mallory Duracell “Copper TopTM” batter­ies. Build a simple battery tester for around $5 By JOHN CLARKE Most people have seen those green tester strips which are supplied with 9V and 1.5V battery packs. While you might think they are a marketing gimmick, they provide a far better means of determining the battery or cell condition than a simple multimet­er voltage measurement since they give a load test. In fact, they provide a more or less constant current load which presents a ideal battery test. But if you use these testers often, you will probably agree that they are fiddly to use. Of course, the battery manufacturer cannot be expected to produce a perfect tester for what amounts to a free addition to the battery pack. However, what they have supplied is a very good basis for making your own battery tester. All you need is a standard battery holder or clip lead suitable for the tester, short lengths of wire, a few screws, 84  Silicon Chip nuts, solder lugs and star washers, a bracket and a small plastic case. For 9V batteries, you have the choice of using a battery clip or the more expensive holder. The accompanying photos and diagrams show how we made a 9V tester. The same principle can be applied to single cell testers. The main thing to watch is that the tester strip is held away from any electrical or heat conductive surface. This means that it must be suspended in air to prevent the tester giving false results. Building it Fig.1 shows the assembly details. Begin the assembly by drilling and filing out the lid to accommodate the tester display and the battery clips. This done, drill small holes in the + and – contacts of the tester strip and line the strip up with the cutout in the PARTS LIST 1 battery tester strip 1 plastic case, 83 x 53 x 30mm 1 battery clip or holder and wire 1 bracket to support clip 1 3mm countersunk screw and nut 3 3mm x 10mm screws 4 3mm nuts 2 3mm flat washers 2 3mm star washers 2 solder lugs PVA glue lid. Mark out where these connector holes are and drill these holes in the lid. The tester strip can now be fastened to the lid – see Fig.1. Use star washers on the conduc­tive side and flat washers on the display side of the tester strip to ensure reliable contacts and Finally, the free end of the tester strip is held in place on the lid with a small dab of epoxy adhesive. Results Fig.1: here are the assembly details for the simple battery tester. Be sure to solder the wires to the lugs before bolting the assembly together and use star washers on the conduc­tive side of the tester strip, to ensure reliable contacts. We connected the 9V tester to a DC power supply in order to find out how the visible indications coincided with voltage and load conditions. For a start, the load current is about 100mA. Under this condition, a battery delivering more than about 8V shows as “good” and lights up all three segments of the display. Batteries delivering between 7V and 8V light up two seg­ments and are obviously marginal, according to the tester. Bat­teries delivering less than 7V will only light up one segment or none at all and, according to the tester, should be replaced. Whether you do replace a 9V battery delivering less than 7V is up to you. In some applications, 7V will be adequate; some applications will draw a lot less current than 100mA and so the battery will deliver correspondingly more voltage. For a single cell tester, the “good” indication comes on for battery volt­ ages greater than 1.25V, while the load current varies between 200mA at SC 1.25V to about 240mA at 1.5V. Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a dis­ tinctive 2-tone green vinyl & will look great on your bookshelf. The “free” end of tester is secured to the lid using a dab of epoxy adhesive. Note the mounting technique for the battery clip. solder wires to the lugs before fitting the screws. We used a piece of clear plastic to cover and protect the tester strip from damage. You could also use the origi- nal plastic cover found with the battery pack and glue this to the underside of the lid. The battery clip is held in place under the lid using a suitable bracket, countersunk screw and nut. Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. March 1996  85 VINTAGE RADIO By JOHN HILL A console with a difference This month, we will take a close look at an unusual console style radio receiver – a 1948 model 4-valve Peter Pan. Although it is a very modest little radio, its style and con­struction is far from normal. This radio is the only console I have ever encountered that does not have a timber cabinet. As such, there is little doubt that it was aimed at the budget end of the market. Any “normal” console would have had at least five valves, a timber cabinet and maybe shortwave reception as well. The cabinet is a mixture of materials. The main portion is sheet aluminium which is attached to a thick plywood base. The aluminium is reinforced inside with a few brackets, to which other items are bolted. Even so, the light gauge aluminium is far from rigid and flexes quite readily. The front of the cabinet is covered with vinyl and it has a textured surface which looks quite pleasing. There is a large speaker opening in the centre of the vinyl area and it is edged with a brown plastic trim. Instead of the usual grille cloth, there is a basket-weave wicker type material made from some natural fibre. These wicker grilles were common on early postwar Peter A full front-on view of the Peter Pan 4-valve console receiver. This particular cabinet is unusual in that it is not made of timber. The only wood used in its construction is the thick plywood base. 86  Silicon Chip Pan radios and some Astors and other makes also used them. The top section of the cabinet consists of a large bakelite moulding which contains the dial and control knobs, while the bottom consists of a wide strip of thick sheet plastic to act as a kick board. All things considered, it is a fairly cheap outfit from top to bottom. However, one should not be too critical. Here is a radio receiver which is nearly half a century old, yet it still looked neat and tidy on the outside –apart from a liberal coating of dust and grime. This is something that cannot be said for most timber cabinet receivers of similar vintage. Timber cabinets can look rather shabby after 50 years, with the lacquer becoming chipped and crazed. Cleaning it up As found, the little Peter Pan was decidedly grubby. Apart from the expected dust and grime, it had also taken several drink spills down its front. Fortunately, vinyl is a very durable material and it allowed all this muck to be scrubbed off. In fact, the exterior of the cabinet cleaned up really well, to near new condition. The final comment about the Peter Pan’s unusual cabinet relates to its peculiar shape. In plan view, it is triangular (obtuse isosceles), with the long side being the back of the receiver. The cabinet is very narrow and although the chassis is mounted low, the set has very poor stability and could be easily knocked over. When cleaning the empty cabinet, care had to be taken to ensure that the wind did not blow it over and damage the bakelite top. On the credit side, however, the little Peter Pan doesn’t take up much space for a console radio and it would fit into a room just about anywhere. somewhat better than one would normally expect from a 6-inch speaker. The speaker also produces quite good bass for its size. Chassis details This close-up view shows the wicker speaker grille. The basket weave speaker grille was popular during the late 1940s and was used by a number of manufacturers. The speaker opening is much larger than the speaker used. The bottom edge of cabinet consists of a wide plastic strip which serves as a kick board and carpet sweeper deflector. Note the textured surface of the vinyl covering. When flat against a wall, the front of the receiver protrudes into the room no more than about 18cm. Although the mini-console really is a weird shape, it is never­theless a practical one as far as space saving goes. Rola loudspeaker 1948 was a time of change in radio manufacturing and a new receiver at that time could have had either an electrodynamic loudspeaker or a per­mag loudspeaker. Electrodynamic speak­ers were used by some manufacturers up until 1950. The Peter Pan was fitted with a smallish 6-inch (150mm) Rola permag loudspeaker, although it is not the usual Rola loudspeaker of that era. This particular Rola has a larger housing at the back than most (maybe a bigger magnet?) and it has a larger than usual output transformer fitted to it. The five wires connecting the speaker to the receiver are for the output transformer primary, negative feedback from the secondary, and what seems to be a fairly unnecessary earth lead. When combined with the excellent baffling of the cabinet, the overall volume and tonal performance is The unusual construction of this mini-console receiver continues throughout the set and that includes the chassis, which can only be described as an upside down installation. The chassis is positioned at the bottom of the cabinet so as to lower the set’s centre of gravity and is mounted valves down and circuit wiring up. It is not as though the chassis has been simply inverted, however – the folded sides of the chassis go towards the valves. Why this is so is a bit of a mystery. The chassis set up could have easily been arranged in a conventional manner, whereby the circuit wiring and the valve sockets would not be subjected to dust accumulation. Because the chassis wiring is all exposed on top, there are no servicing conveniences like a speaker plug and socket, dial light wiring plugs and sockets, or even an aerial terminal. These wires are all soldered straight into the circuit and must be disconnected if the chassis is to be removed. Of course, all these wires (eight in all) should be care­fully marked before disconnecting them. It is unwise to rely on memory when so many connections are involved. Swapping some of the speaker connections could produce positive feedback and a loud howl in the speaker, for example. Other disconnections include the remote mechanical linkages from the control knobs on top of the cabinet to the tuning ca­pacitor and volume control potentiometer on the chassis below. All things considered, it is not the most convenient of sets to service, although most repairs can be done without having to remove the chassis once the dust has been removed from the wir­ing. Flexible drive As a matter of interest, the volume control knob is coupled to the potentiometer by a long brass rod. So too is the tuning control, except that in this case, the control knob is not posi­ tioned directly above its counterpart below. To overcome this problem, a flexible drive is used to iron out the March 1996  87 The moulded bakelite top houses the dial and control knobs. Note that the dial is marked mainly for Victorian and Tasmanian sta­tions, although 2AY, 2WG, 2CO and 5RM also get a mention. misalignment – a simple yet effective method of overcoming an awkward arrange­ment. There was a problem with the two mounting brackets that hold the chassis in place. These brackets had been fitted too close together on the baseboard and their bolt holes would not line up with those in the chassis. This misfit had been solved at the factory by forcing the brackets to line up, thereby severely loosening the wood screws which held the brackets to the base­board. Completely 88  Silicon Chip repositioning the brackets fixed that particu­lar problem. Chassis repairs The receiver itself was an easy repair, as it was in work­ing order to start with. It appeared to be fairly original, with the exception of two 8µF electrolytic capacitors. These had replaced one of the original chassis-mounted 16µF units at some time in the not so distant past. As these capacitors were quite serviceable, they were left in place. The same could not be said for the other electrolytics, however. These were all originals and, as they all had leakage problems, were replaced with modern equivalents. One interesting aspect of the electro­ lytics was the fact that all four of them were high-voltage chassis-mounted types. The 16µF 525V pair were used in the high-tension filter but the 24µF 350V pair were used for quite low voltage applications; eg; as a cathode bypass capacitor on the output valve, as shown in one of the photos. Perhaps these high voltage units were the only ones avail­able at the time? In 1948, the demand for radio parts could have exceeded the supply and set manufacturers may have been forced to improvise at times and use whatever components they could find that would do the job. Well, that’s one explanation! The Peter Pan’s chassis used 10 paper capacitors and all of these were originals. They were all replaced without even a second thought. It was interesting to note that when checked later with an ohmmeter, more than Below: the chassis is mounted upside down inside the cabinet. As a result, the components were all covered in a thick blanket of dust and fluff, with only the larger components showing through. There was a resident redback too! ELECTRONIC VALVE & TUBE COMPANY VALVE SPECIALS! NEW SHIPMENT Sovtek 6V6GT 5AR4/GZ34 5Y3GT 6CA7 (Fat) 6L6GC 12AX7WA/7025 12AX7WB Others 655OB (Svetlana) KT88 (China) $10.00 $22.00 $12.00 $24.00 $10.00 $9.00 $12.00 EL84/6BQ5 EL34G (Slim) 5881 5881WXT (Based) 6550WA 6922 12AX7WXT $10.00 $20.00 $18.00 $23.00 $40.00 $18.00 $14.00 $48.00 $48.00 E34L (Tesla) EL34 (Telsa) $28.00 $23.00 Matching at $1 per valve Prices valid until 31.3.96 This view shows the Rola permag speaker used in the set, togeth­er with its attached output transformer. Both the magnet housing and the transformer are larger than normal for a 4-valve radio and no doubt contribute to the receiver’s remarkably good bass response. Send SSAE for our catalogue listing valves for audio, radio and industrial use. Also specialist valve books of all types. PO Box 381, Chadstone Centre, Vic. 3148 Tel/Fax (03) 9571 1160 or Mobile 018 557 380 Registered office: 10 Berrima Ave, East Malvern. Silicon Chip Binders Buy subsc a & get a ription discou nt on the binder Everything back and ready to go – it’s not a tidy arrangement by any means. Note the vertical rods at each end of the chassis. These connect to the tuning and volume controls on top. half of them showed some degree of leakage. If a paper capacitor leaks under a 3V test, what is it going to do with a couple of hundred volts across it? Although replacing all paper capacitors is probably unne­cessary, it is worth the effort for peace of mind, if nothing else. Let’s face it – old capacitors can be very troublesome! The interesting aspect of the capacitor changeover was the noticeably better performance. Prior to working on the chassis, it was a “1-station radio”, receiving only the strong local station with no aerial connected. After the capacitor job, it became a 5-station set and that was without any alignment – just the new capacitors. Alignment As far as alignment was concerned, there was very little to do. The IF (intermediate frequency) transformers were virtually spot on and the aerial trimmer needed only a slight tweak to These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a dis­ tinctive 2-tone green vinyl & will look great on your bookshelf. Price: $A11.95 plus $3 p&p each (NZ $8 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. March 1996  89 The major components (valves, IF transformers, power trans­former, tuning gang, etc) are mounted on the bottom of the chassis. The valve line up is: 6J8, 6B8, 6V6 and 5Y3. The four chassis-mounted electrolytics are all high voltage types. bring it in line. Even then, one could barely notice any difference. The little Peter Pan was a good set to work on as it had not pre­viously been tinkered with. It was at this alignment stage that some gremlins in the 6V6 output valve decided to do some arc welding and a series of sparks and flashes occurred from within. A replacement 6V6 re­ moved both the gremlins and their arc welder. A valve tester had previously passed the faulty valve as being OK. Maybe it didn’t like working upside down? The restoration was nearing completion and there were only a few jobs left to do – tighten the speaker mounts and polish the cabinet. The speaker mounting involves four short pillars and all of them were loose. Unfortunately, they could only be tightened by turning the screw heads on the other side of the speaker baffle – not a big job but a bit tedious considering the number of nuts that had to be undone in order to remove the baffle. It was a classic case of spending 10 minutes in order to do what should have been a 30-second job. Cabinet refurbishment A flexible drive shaft wass used to compensate for the misalign­ment between the tuning capacitor shaft and its matching control knob at the top of the set. 90  Silicon Chip The cabinet refurbishment consist­ ed of a cut and polish for the bakelite top and the “Armorall®” treatment for the vinyl. At this stage, the set was ready to go back together. There were no problems with the assembly and everything went back according to plan, with the chassis fitting the reposi­tioned mounting brackets as it should have done in the first place. A test run for a couple of hours indicated that all was OK inside and the little Peter Pan performed very well. It sounded remarkably good for a small 4-valver driving a moderately-sized speaker. There is no doubt about it: Radio Most of the electrolytic capacitors in the set required replace­ment. The 63V unit shown here (top of photo) was used to replace the original 24µF 350V original below. Corporation knew how to make top-performing 4-valve receivers. While many of their pro­ducts were aimed at the bottom end of the price scale, they were always value for money and performed as good or better than other comparably priced SC products. electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semicustom electronics & data communications. 63 chapters, in hard cover at $120.00. Silicon Chip Bookshop Radio Frequency Transistors Newnes Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Guide to TV & Video Technology By Eugene Trundle. First pub­lish-­ ed 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $49.95. Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Digital Audio & Compact Disc Technology Electronics Engineer’s Reference Book Hard cove Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM Power Electronics Handbook Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order r Edited by F. F. Mazda. version now available First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $85.00. Surface Mount Technology By Rudolph Strauss. First pub­ lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $52.95.   Title  Newnes Guide to Satellite TV  Guide to TV & Video Technology  Servicing Personal Computers  The Art Of Linear Electronics  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Electronic Engineer's Reference Book  Radio Frequency Transistors  Surface Mount Technology  Audio Electronics Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ & PNG add $10.00 per book, elsewhere add $15 per book. TOTAL $A Price $55.95 $39.95 $59.95 $49.95 $55.95 $59.95 $120.00 $85.00 $99.00 $52.95 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Motor control with current limiter I am currently in the process of designing a current limit­er and stall motor protection device for 12V DC motors. I have read through numerous electronics magazines and circuit designs references but have been unable to find a suitable design. I am hoping you can help me in some way. These are some of the speci­fications a design would have to meet: limit stall current to 3-4A; operating voltage range between 11-14.5V DC; supply voltage 11-15V DC; reverse polarity protection and use discrete components. The device will hopefully prevent a motor gearbox which is running at a speed of 20-30 RPM from stalling at high cur­rents. The motor is currently stalling at about 6-8 amps with a load. This, however, reduces the life of the motor considerably over time and it becomes hot when stalled for long periods. The motor stalls in both directions as it drives a gear, which in turn drives a shuttle nut on a 100mm long thread. This process is repeated numerous Power transformer runs too hot I have just built the SLA Battery Charger described in the August 1992 issue of SILICON CHIP. After evaluation, may I make the following observations? The M2165 transformer specified seems to be overrated because when run at the 3A charge rate for more than one hour it becomes very hot and I feel it could even­tually burn out. This transformer may be intermittently rated for 3-4 amps (60VA) but should more realistically be rated for 30-40VA continuously. The DSE M2000 transformer rated at 18 volt 6 amps used in the original version (March 1990) I think is still overrated at 6 amps but ideally will run coolly at 8 92  Silicon Chip times. (E. M., W. Norlane, Vic). While we have not produced a designed for this purpose, we can suggest a circuit which will do the job. It is a switchmode circuit with foldback current protection, important if you want to limit dissipation in the regulating devices when the overload occurs. The circuit appears on page 15 of the August 1992 issue of SILICON CHIP and is a simplification of our Railpower train controller which appeared in the April 1988 issue. • Automatic watering control I wish to use a Hardie Irrigation water valve for automatic watering of a small flower bed, which is in easy reach of a 240VAC power point. I’d like your opinion of my proposed plan. I would use a 240VAC timer and possibly a plugpack or transformer to suit the valve which has the markings 50Hz 8VA 24V. Hoping you can enlighten me on this project. (R. S., Loxton, SA) • Your irrigation water valve can be controlled by a 240VAC timer and powamps. Radiated heat from within charger cases will ultimately affect the voltage operating parameters of the UC­3906 IC. (M. F., Christchurch, NZ). • One of the dilemmas we face in publishing projects of this nature is that the quality of components such as transformers can vary, from supplier to supplier and also as the years pass by. Our original prototype transformer handled the job quite comfort­ably but it may well be that the one supplied to you does get quite red in the face. We opted for the M2165 transformer in the second version because the M2000 supplied a little more voltage than was necessary and consequently caused higher power dissipation in the series pass transistor (Q1). ered from a 24V 1A plugpack. Such a plugpack is available from Altronics in Perth (Cat. No. M9129) for $19.25 plus p&p. Altronics’ telephone number is 1800 999 007. Low cost high voltage transistor wanted Could a lower cost alternative to the Darlington transistor MJ10012 be made by using a 2N3055 driven by a BC639? With the MJ10012 listed at $14.50 in the Jaycar catalog, it is tempting to seek an alternative. Maybe you could feature the design considerations in making a Darlington in the Circuit Notebook chapter of your magazine. (B. P., Port Macquarie, NSW). • The MJ10012 is a high voltage Darl­ ington transistor espe­cially designed to take the high voltages generated in the primary winding of car igni­tion systems. These usually generate in excess of 250V each time the transistor switches off. Although there is a plastic equivalent to the MJ10012, it is not currently available in Australia, as far as we know. The 2N3055 would be blown up immediately power was applied if used in conjunction with an ignition coil. Bridging power amplifiers I have a few questions regarding the 50W Amplifier project from your February 1995 issue. Can you join two 50W amplifiers together to produce a 100W amplifier? Is there any relatively simple way of getting more power out of the 50W amplifier? How do you work out PMPO values for speakers? (J. B., Lower Hutt, NZ). • It is possible to combine two 50W amplifiers together to provide a 100W amplifier. Normally, you need an additional bridge circuit so that the phase of the signal to one amplifier can be re­versed. We published details of such a circuit on page 95 of our February 1988 issue. However, it is possible to do this more simply with 50W stereo Keep plumbers tape for plumbing I am writing regards the construction of the 20W fluoro inverter designed by Otto Priboj in the February 1991 issue of SILICON CHIP. My first kit took quite a bit of nutting out when it came to the transformer windings. I completed and still use this light, even after six months. I have had no problems with its operation. Since then I have purchased another kit and I am having all sorts of problems. I also bought enough components to make eight other lights. The same problem keeps surfacing. The light works for a few minutes then a buzzing noise appears, low tone at first, rapidly increasing to a high pitched buzzing then the light shuts off never to go again. I then module you refer to and we shall publish the details in a future issue. There is no relatively simple way of getting more power out of the 50W amplifier module as it stands. Our design runs the device to almost its maximum ratings. PMPO values for loudspeakers and amplifiers are largely imaginary as far as we can see. Typically, the PMPO (Peak Music Power Output) values are at least ten times the realistic RMS rating and some small music systems as sold in department stores have PMPO ratings which are as much as 20 times higher than their continuous (RMS) ratings. In this way, a system with a small stereo power chip rated at 6 watts RMS per channel can easily end up with a PMPO rating of 120 watts! In simple terms, such ratings are lies. Multiple remote control extender I recently completed construction of the April 1994 Remote Control Extender project and it works as expected, although the range isn’t what I had hoped for. In the construction article it says to expect a range of about a metre which is around what I am getting. Such a range wouldn’t be a problem if I was only inter­ested in controlling a VCR as the IR LED could be attached to the sensor on the front of the video. change the transistors; they go for a short time and then the same thing happens again. I think that my problem lies in the transformer winding though I cannot see that I am doing anything different to the first kit, except I am using plumbers’ tape for insulating the windings. On my second kit the light was in use for a good hour or so with no problems then the next time it was turned on it blew within thirty seconds. Please help. We only have a solar power source and I need to solve this problem for much needed light. (M. O., Bairnsdale, Vic). • Plumbers tape? You must be kidding. As outlined in the article, the winding of the transformer for this project is quite critical, particularly setting the air gap. If you don’t do it as described, you can’t expect reliable operation My problem is that I wish to control four different components comprising a VCR, television, CD player and stereo receiver. However, because of their physical sep­ar­a­tion and the directional nature of the IR beam produced by the LED arrangement, only one component at a time can be controlled by the extender unit – even if the LED is mounted in­trusive­ly in front of the stack of components What I want to know is if it is possible to upgrade the output of the system to significantly increase the range to about three metres, with the LED be mounted unobtrusively and able to cover enough area to operate all four components. I have already tried exchanging the 100mA LED for a 220mA one but the range does not seem to have increased by any measurable amount. Another option I have considered is to connect several other LEDs in parallel, either to increase the range, or as a last resort, tape one LED to each of the four components. Another possible solution would be to buy a “universal” remote control unit and, after disassembling it, connect the output LED and lens system of the remote control to the extender output circuit in place of the ordinary IR LED. That may be a little more expensive but a typical remote control has a much greater range than one metre and a much wider angle of operation. If it is at all possible, how can I do it? A reasonable extra cost in doing so, doesn’t unduly concern me because I was quoted $380 for the equivalent commercial product by a hifi store. (D. B., Homebush, NSW). • You should be able to connect two IR LEDs in series plus a couple of others in parallel with an extra resistor. Each LED can activate one of your four individual components. Train controller has too much inertia I have recently built the train controller described on page 76 of your “14 Model Railway Projects” book. Two features do not perform as described: (1). Throttle control: when reducing speed of running train, deceleration is very slow. Braking and inertia to start are OK but when turning down VR1, the voltage at Q1 stays at about + 10V almost indefinitely. I disconnected the 4700uF capacitor and it slows. I reduced this capacitor to 470uF and it works but then inertia start and brake are instant. (2). The overload LED does not light up on short circuit – it appears that overload protection works as Q2 does not get hot and voltage drops. I would appreciate your comments or suggestions or perhaps appropriate test procedure. (C. C., Swan Reach, Vic). • The response time for throttle reduction can be made about the same as for start-up by omitting diode D5. For LED1 to glow more prominently when the circuit is in current limiting mode, it needs to be a high brightness type. FM stereo transmitter alignment problem After much deliberating, I finally decided to build the “FM Stereo Transmitter” kit. I built the kit with no dramas (it’s very simple!). However, I cannot get it to work. I have checked around the BA1404 chip with a DVM and a CRO with the following results: +1.58V on the supply pins; 38kHz on pins 5 & 6; “hash” on pin 14 (with no audio input); there is 19kHz on pin 13 and 1.5V DC on pin 12; pin 7 (RF out) is sitting at 1.58V and DC only; pin 10 is at +1.58V and also DC only; and pin 9 is at about +0.8V, DC only. Obviously the modulation oscillator isn’t running but I can’t see why. I have checked for track faults and obviously March 1996  93 Oils ain’t oils when it comes to transistors I have built the 40W inverter from your February 1992 issue. Like a number of your designs I have made, it worked first go and gave magnificent service for a long time. Now it has devel­ oped a fault where it runs for months then suddenly blows either one or both MTP3055Es apart. This is always on start up, usually without load. I fitted a pilot light and this stopped the problem for a while but it has gradu­ ally got worse. Inverters are the most unreliable piece of equip­ment I have had to contend with. I had thought at last I had found one that I could rely on. I hope that you can help me, as shorted capacitors. I have double checked component locations and orientation. I have replace the BA1404 chip. Any ideas? (J. A., Giralang, ACT). • We think it unlikely that the modulation oscillator is not running. In our experience, the problem is more likely to be incorrect alignment. In general, unless you have a scope with a response to at least 100MHz and 10:1 probes, you are unlikely to see any evidence of RF output in the circuit. If you don’t use 10:1 probes the circuit loading is likely to stop the circuit working at all. We suggest you carefully go through the alignment procedure again. This project has proved very reliable and many thousands have been built since its publication eight years ago. No mods necessary for low ohms adaptor One of my Christmas presents was a digital multimeter and this prompted me to look over the various DMM plugin accessories which I have acquired over the years. One accessory still need­ed was a low ohms adaptor so I spent some time investigating the unit I built from the design published in the February 1988 issue of SILICON CHIP. I have never had much confidence in this device because the readings were not consistent across the ranges or were not in accordance with expectations from other evidence. 94  Silicon Chip at the moment I am running a 3kVA generator to have a shave. I consider this a bit of an overkill. Have I got a botchy lot of MTP3055E Mos­ fets? Are these problems just a part of using this inverter or can you suggest a way to overcome these problems? (R. B., Hey­field, Vic). • We hate to say it, but not all MTP­ 3055Es are born equal. Our experience suggests that those brand­ed with the Motorola batwing symbol are the best and some of the others are definitely dodgy. We have also found other transistors, originated by Motorola but second-sourced by others, are not as good. For example, if you are building high power audio amplifiers with MJE340s and 350s, the Motorola ones are the best. The others work, but not as well. I noticed an unstable reading on the high ranges. On examination with an oscilloscope, I found that there was about 7mV of noise at the output of the op amp but replacing it did not cure the problem. The noise was being generated in the BC559 and replacement with a BC558 (because I didn’t have another BC559) brought the noise level down to about 1mV. It seemed to me that, with the very low resistances to be measured, the resistance of the internal connections would have a significant effect. I separated the wires sourcing the current to Rx from the wires sampling the resultant voltage developed across it by running four wires to the terminals, a pair for each function. Thus, any voltage drop in the supply lines is not reflected in the measured voltage. It was necessary to cut the appropriate tracks on the PC board. Setting the test currents to 1mA and 10mA was very critical and it did not seem to retain the settings reliably, so I put resis­tors in series and in parallel with the 1kΩ and 100Ω multiturn pots. This gives a much smoother adjustment and seems to hold the set value better. Because the residual noise seemed to be worse on the x100 range than the x1000 range I used 10mA on the three higher ranges and reduce the gain of the op amp to 10 for x100. The spare switch pole enabled me to add a 1kΩ resistor in parallel with the feedback resistor. Incidentally, I found that the 10kΩ resistor was actually 9.9kΩ, giving the required gain of 100 directly without the need to subtract the input signal. A resistor closer to 10kΩ could be parallelled with 1MΩ to achieve this value. I changed this part of the circuit also to avoid the polarity reversal on the upper ranges. There was a degree of non-linearity on the upper ranges due to the lack of a negative supply line for the op amp. This was overcome by adding a couple of diodes in series with the negative battery lead and applying the result­ant -1.4V to pin 4. Once the 1mA and 10mA levels are set, final calibration is best achieved by using a resistor of between 0.1Ω and 0.2Ω and adjusting the offset until the reading on the x1000 range is as near as possible to 10 times the reading on the x100 range. The shortest possible piece of 1.5mm copper wire clamped firmly through the holes in the terminals should then give a reading of between 0.2 and 0.4mV on the x100 range and between 2 and 4mV on the x1000 range. This is about 3mΩ and is almost entirely contact resistance. A 24cm length of 0.66mm wire measured about 14mΩ which is consistent with a value of 12mΩ calculat­ed from wire tables. The unit is now accurate to within a couple of milliohms and testing over the last few days has shown completely consist­ent results. As you suggested in your original article, measure­ment of low resistances is a rather neglected area. I have re­cently been dabbling in speaker design and I am sure that this unit will be very useful. (A. M., North Turramurra, NSW). • We are glad that you have finally made your Low Ohms Adaptor work but apart from replacing a noisy transistor, we don’t think any of your modifications are really necessary. In particular, the CA3140 op amp was specified precisely because it can operate from a single supply and the addition of diodes will reduce the life of the battery because of their voltage drop. As the battery voltage drops we would also expect the diodes to introduce their own non-linearity into the circuit. Operating some of the ranges at 10mA instead of 1mA will also reduce battery life. We agree that the current adjustment is critical but we did specify multiturn pots to make the task straightforward. SC MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE KITS KITS KITS: Electronic kits for enthusiasts of all ages and abilities. Top quality. Large range. Free catalog and price list available. Call Ozitronics, 24 Ballandry Crescent, Greensborough 3088. Tel/Fax: (03) 9434 3806 email: ozitronics<at>c031. aone.net.au START WITH A MICROZED KIT then when your "test the market", small run project hits the big league MicroZed can help you with alternative schemes and quantities ex stock at the right pricing. CHEAP MICROCONTROLLER SYSTEM: 8MHz 280. Program via printer port. No EPROM or EPROM programmer needed. 32K RAM battery backed. 128 digital I/O. 32 analog inputs. Can run stand alone. Professional software with pulldown menus, text editor, simulator, compiler, dumper, reader and extensive help. Min XT/AT & EGA/VGA. Price includes circuit and all software (components extra, cost approx $65). Send $49.95 to N. Moxham, 23 Arizona Tce, Glenalta SA 5052. SATELLITE DISHES: international reception of Intelsat, Panamsat, Gori­ zont,Rimsat. Warehouse Sale – 4.6m dish & pole $1499; LNB $50; Feed $75. All accessories available. Videosat, 2/28 Salisbury Rd, Hornsby. Phone (02) 482 3100 8.30-5.00 M-F. MEMORY * DRIVES * MODEMS SPECIAL! (Incl Tax) 1Mbx9 – 70ns Simm $60 1Mbx9 – 80ns Simm $45 SIMMS (Parity/No Parity) 4MB 30 PIN-70 $175 $179 4MB 72 PIN-70 $177 $145 8MB 72 PIN-70 $347 $288 16MB 72 PIN-70 $695 $572 32MB 72 PIN-70 $1389 $1210 EDO SIMMS 8MB (2Mbx32)-60ns $369 16MB (2Mbx32)-60ns $683 MAC 8MB P’BOOK $470 VIDEO MEMORY 256KX16 70ns (SOJ) $24 256KX16 70ns (ZIP) $58 LASER PRINTER MEMORY HP 2MB UPGRADE $156 CO-PROCESSORS 80387SX/DX to 40MHz $90 COMPAQ 8MB CONTURA AERO $445 TOSHIBA PORTEGE/SATELLITE 8MB / 16MB $554 / $1105 DRIVES SEAGATE 850MB EIDE 11ms 3yr $318 1080MB EIDE 10.5ms 3yr $360 1080MB SCSI 9ms 5yr $484 MODEMS (Includes Sales Tax) 14,400 BANKSIA 5yr W $283 14,400 SPIRIT 2yr W $203 28,800 BANKSIA V.FC $321 28,800 SPIRIT V.34/V.FC $410 Phone for other products not listed A REAL BARGAIN: Riston type copper clad laminate. Develop cold, no toxic fumes, easy to use. Excellent results. Single sided 610x304 $34; 305 x 304 $17.50; 152 x 305 $9.95; 152 x 152 $6.50. Double-sided also available. 2 litre developer mix, worth $2.50, free this month. Add sales tax if applicable. Delivery $6.00. Money back guarantee. Ph (02) 743 9235. Fax (02) 644 2862. DonTronics HAS MICROCHIP PIC GEAR: Programmers from $20 to $225, PICBASIC: 64 $50, 57 $40, 84 $40, EEPROM: 93LC56 $5, 24LC16B $8, 24LC65 $16, CPU: 84/04/P $12, 57/04/P $12, 64/04/P $17. Serial and parallel I/F kits and lots of other stuff. VISA-MC-BC. Ask for free Promo Disk. ftp://laby­r inth.net.au/home/donmck/ public-html/index.htm. 29 Ellesmere Crescent, Tulla­marine 3043. (03) 9338 6286. Fax (03) 9338 2935. MicroZed HAVE GOOD stock of 12-bit A/D serial I/O chips for Stamp applications. These have two inputs or single differential input configurable by software. C COMPILERS: Dunfield compilers are now even better value. Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC16, 8051/2, 8080/85, 8086 or 8096: $140.00 each. Macro Cross Assemblers for these CPUs + 68000/01/03/05 amd 6502: $140 for the set. Debug monitors: $70 for 6 CPUs. All compilers, XASMs and monitors: $400. 8051/52 or 80C320 simulator (fast): $70. Demo disk: FREE. PELHAM Suite 6, 2 Hillcrest Rd, Pennant Hills, 2120. Ph: (02) 9980 6988 Fax: (02) 9980 6991 MICROCRAFT PRESENTS: Dunfield (DDS) products are now available exstock at a new low price; please ask for our catalogue. Micro C, the affordable “C” compiler for embedded applications. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $139.95 each + $3 p&h • Now on special is the SDK, a package of ALL the DDS “C” compilers for $399 + $6 p&h • EMILY52 is a PC based 8051/52 high speed simulator $69.95 + $3 p&h • DDS demo disks $7 + $3 p&h • VHS VIDEO from the USA (PAL) “CNC X-Y-Z using RCS RADIO PTY LTD RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 Scott Edwards Electronics BASIC Stamp I and II NEW Micro 68HC11 F1 boards and now 80535 (up spec 8051) both boards with BASIC, FORTH, ASM, Small C 80535 board has 8052AH INTEL BASIC installed 24 I/O expansion board now in stock for both boards EX TAX PRICING AS AT JANUARY ‘96 Sales Tax 22%, O/Night Delivery $8. Ring For Latest Prices. Credit Cards Welcome. We Also Buy And Trade-In Memory. All prices +$5 p&p. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph/Fax (02) 631 1236 or Internet: lgrant<at>mpx.com.au Versa Tech TICkit – a 21 I/O PIC based controller Accessories for Stamp and second source for Stamp 1 Recently developed accessories now available MicroZed Computers To order or enquire: PO Box 634, ARMIDALE 2350. (296 Cook’s Rd) Ph (067) 722 777  Fax (067) 728 987 Mobile (014) 036 775 Credit Cards OK Get your project on the way in hours, not months. Send two 45c stamps for information package March 1996  95 Advertising Index CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 979 6503. Altronics ....................................IFC Av-Comm.....................................59 Car Projects Book....................OBC Defence Force Recruiting............31 Dick Smith Electronics........... 18-21 Electronic Valve & Tube Co..........89 _____________ _____________ _____________ _____________ _____________ Harbuch Electronics....................81 Instant PCBs................................95 _____________ _____________ _____________ _____________ _____________ Jaycar .........................................53 Kits-R-US.....................................83 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Macservice............................ 10-11 MicroZed Computers...................95 Oatley Electronics.................. 78-79 Pelham........................................95 Railway Projects Book...............IBC _____________ _____________ _____________ _____________ _____________ RCS Radio ..................................95 Rod Irving Electronics .......... 67-71 Silicon Chip Back Issues....... 72-73 ❏ Bankcard   ❏ Visa Card   ❏ Master Card Silicon Chip Bookshop.................91 Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my Silicon Chip Software..................39 _________________________________ PC Boards Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Printed circuit boards for SILICON CHIP projects are made by: Name ______________________________________________________ • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ car alter­nators” (uses car alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Device programming EPROMs/PALs etc from $1.50 • Fixed price electronic design and PCB layout • Credit cards accepted • All goods sent certified mail • Call Bob for more de­tails. MICROCRAFT, PO Box 514, Concord NSW 2137. Phone (02) 744 5440 or fax (02) 744 9280. EDUCATIONAL ELECTRONIC KITS: Easy to build. Guaranteed to work. Good quality. Latest technology. Cheap. Good selection. LESSON PLANS FOR TEACH­ERS. Send $2 stamp for catalogue and price list. Log onto our bulletin board for full details. DIY Elect­ron­ics, 22 96  Silicon Chip McGregor St, Numurkah 3636. Ph/Fax (058) 62 1915. E-Mail: laurie.c<at>cnl.com .au BBS (058) 62 3303 COMPLETE WORKSHOP PROGRAM: suit IBM compatible 386 or better computer. Handles: Stock Control, Sales, Service Records, Debits, Credits, Faults, Service Manuals and Phone Directory. Full price $399.00. For demo disk, phone or fax your details to (045) 71 1640. Jack Albers Electronics & Software Development. NEW SPRINKLER CONTROLLER KITS: RAIN BRAIN version uses ‘C8 and switch mode supply. Features galore!! Contact Mantis Micro Pro­ducts, • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. 38 Garnet St, Niddrie 3042. Phone/fax (03) 337 1917. 68HC705 DEVELOPMENT SYSTEM: Oztechnics, PO Box 38, Illawong, NSW 2234. Phone (02) 541 0310, fax (02) 541 0734. Email: info<at>oztechnics.­com.au WWW: http://www.hutch.com.­au./~ozt­ ech/index.htm. SERVICE & REPAIRS PATRA ELECTRONICS: assembly and repairs of all kits. Repairs of electronic equipment. Call Peter on (02) 718 1202 or 015 215957. Especially For Model Railway Enthusiasts Order Direct From SILICON CHIP Order today by phoning (02) 9979 5644 & quoting your credit card number; or fill in the form below & fax it to (02) 9979 6503; or mail the form to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. This book has 14 model railway projects for you to build, including pulse power throttle controllers, a level crossing detector with matching lights & sound effects, & diesel sound & steam sound simulators. If you are a model railway enthusiast, then this collection of projects from SILICON CHIP is a must. Price: $7.95 plus $3 p&p Yes! Please send me _______ copies of 14 Model Railway Projects Enclosed is my cheque/money order for $­_________ or please debit my  Bankcard    Visa Card    Master Card Card No. Signature­­­­­­­­­­­­_________________________ Card expiry date_____/_____ Name _________________________Phone No (____)_____________ PLEASE PRINT Street ___________________________________________________ Suburb/town __________________________ Postcode____________