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September 1995  1 GETTING INTO CAR MODS? GET INTO THIS BOOK! From the pages of Australia’s most dynamic electronics magazine, Silicon Chip, come 20 electronic projects you can build for your car. Not just circuits, but complete articles with complete instructions, including fitting. Even the novice constructor can do it! YES! Twenty great projects for cars, including: ✦ High Energy & Breakerless Ignition Systems ✦ Ultrasonic Alarm ✦ Digital Tachometer ✦ Coolant Level Alarm ✦ Flashing Alarm Light ✦ Talking Headlight Reminder ✦ UHF Remote Switch ✦ Thermostatic Switch For Electrically Operated Radiator Fans ✦ And much more! ✦ Bonus: there are eight quick circuit ideas too. All this for only $895 ORDER FROM: (+$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_____/_____ Name ___________________________Phone No (____)_____________ PLEASE PRINT Street _____________________________________________________ Suburb/town _______________________________ Postcode___________ 2  Silicon Chip Order today: phone, fax or mail . . . Simply phone (02) 9979 5644 & quote your credit card number; or fill in the coupon & fax it to (02) 9979 6503 (any time); or mail the coupon to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Vol.8, No.9; September 1995 Contents FEATURES 4 Automotive Ignition Timing; Pt.1 Firing the spark at the correct instant is critical for optimum engine performance. Here’s a rundown on the basics of ignition timing – by Julian Edgar 8 Review: Philips Brilliance 21A Autoscan Computer Monitor KEYPAD COMBINATION LOCK – PAGE 16 This new monitor from Philips features digital convergence control and has “Cyberscreen” technology to compensate for external magnetic fields – by Bob Flynn PROJECTS TO BUILD 16 Build A Keypad Combination Lock This unit is based on a dedicated IC and accepts codes up to 12 digits long. Use it to activate alarms or door strikes – by Jeff Monegal 22 The Incredible Vader Voice Disguise your voice to sound like Darth Vader or some other being from a far-off galaxy – by John Clarke 40 Railpower MkII: A Walk-Around Throttle For Model Railways; Pt.1 It’s based on a microprocessor and includes pulse power, pushbutton control, inertia, metering and overload protection – by Rick Walters 62 Notes On The Train Detector For Model Railways Using the detector without block switching – by Leo Simpson 68 Build A Jacob’s Ladder Display Watch as the spark seemingly defies gravity and climbs the “ladder” – by John Clarke 74 Audio Lab: A PC-Controlled Audio Test Instrument; Pt.2 Constructional details plus the calibration procedure – by Roger Kent RAILPOWER MK.2 WALK-AROUND THROTTLE FOR MODEL RAILWAYS – PAGE 40 SPECIAL COLUMNS 34 Serviceman’s Log What’s happened to service backup? – by the TV Serviceman 57 Computer Bits Running MemMaker and avoiding memory conflicts – by Greg Swain 84 Vintage Radio An interesting grid bias problem – by John Hill DEPARTMENTS 2 Publisher’s Letter 11 Mailbag 32 Circuit Notebook 67 Order Form 88 Bookshelf 92 Product Showcase 98 Ask Silicon Chip 102 Market Centre 104 Advertising Index 100 Notes And Errata RUNNING MEMMAKER AND AVOIDING MEMORY CONFLICTS – PAGE 57 September 1995  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. 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 Marque Crozman, VK2ZLZ Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Jim Lawler, MTETIA Philip Watson, MIREE, VK2ZPW Jim Yalden, VK2YGY 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: $49 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 Ignorance & hysteria often carry the day Anyone who follows the news and people’s reactions must often wonder whether Australians really are as keen on new tech­nology as we are made out to be. Often, the reaction is one of fear and loathing, or more precisely, hysteria and ignorance. These comments have been prompted by the recent action by parents with children at a preschool centre in Harbord, a Sydney beach-side suburb. The parents are reacting against the installa­tion of a cellular phone transmitter tower some 50 metres away from the centre. Predictably, all the local politicians have jumped on the bandwagon and are saying how bad all the “unknown” health risks are and so it goes on. In the middle of all this, Telstra is in a no-win situation. It has legally installed the transmitter site and complied with all the regulations. Now really, it is about time that such whingeing wimps ceased to get any publicity for their irrational fears and state­ments. And as for the pollies, they are being hypocritical as usual. You can bet that all politicians and council officials who have made supporting noises for this band of parents will have mobile phones and use them constantly. By doing so, they are subjecting themselves and all around them to much higher RF fields than would be present in the preschool yard. Do they really think there is a risk? I’ll bet they have never thought about it at all. Furthermore, you can bet that some or most of the parents who are so concerned about their little darlings’ health risks will have mobile phones as well. Do they refuse to use them in their car when their little darlings are strapped into the back seat? I think not. I’ll bet they use them while driving too, a more immediate risk to health. If any of these people really has a concern about the health risks of mobile phones, why do they continue to use them? The truth of the matter is that no-one likes these cellular phone transmitters because they are ugly. Telstra and the other mobile phone operators would be wise to do some design work to disguise them but apparently that has not occurred to them yet. So in the meantime, we get people whingeing about the health risks. It has to stop. If they honestly thought about the health risks, they would realise that their children are exposed to a far greater risk from running around in the Sun than from any exposure to a cellular phone transmitter. But I doubt that honest thought comes into the process at all. What we are dealing with is ignorance and hysteria and sadly, they often carry the day. 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 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 detector HEWLETT PACKARD HEWLETT PACKARD 3400A RMS Voltmeter 5328A Universal Counter • voltage range 1mV to 300V full scale 12 ranges • dB range -72dBm to +52dBm • frequency range 10Hz to 10MHz • responds to rms value of input signal • 5Hz to 600kHz • 5 ranges • 10V out • balanced output HEWLETT PACKARD 5340A Microwave Counter • allows frequency measurements to 500MHz • HPIB interface • 100ns time interval • T.I. averaging to 10 ps resolution • channel C <at> 50ohms • single input 10Hz - 18GHz • automatic amplitude discrimination • high sensitivity -35dBm • high AM & FM tolerance • exceptional reliability $1050 $79 $475 $695 $1950 BALLANTINE 6310A Test Oscillator BALLANTINE 3440A Millivoltmeter AWA F240 Distortion & Noise Meter ...................... $425 AWA G231 Low Distortion Oscillator ...................... $595 EATON 2075 Noise Gain Analyser ...................$6500(ex) EUROCARD 6 Slot Frames ........................................ $40 GR 1381 Random Noise Generator ........................ $295 HP 180/HP1810 Sampl CRO to 1GHz ................... $1350 HP 400EL AC Voltmeter .......................................... $195 HP 432A Power Meter C/W Head & Cable .............. $825 HP 652A Test Oscillator .......................................... $375 HP 1222A Oscilloscope DC-15MHz ........................ $410 HP 3406A Broadband Sampling Voltmeter ................................................................ $575 HP 5245L/5253/5255 Elect Counter ....................... $550 HP 5300/5302A Univ Counter to 50MHz ................ $195 HP 5326B Universal Timer/Counter/DVM ............... $295 HP 8005A Pulse Generator 20MHz 3 Channel ........ $350 HP 8405A Vector Voltmeter (with cal. cert.) ......... $1100 HP 8690B/8698/8699 400KHz-4GHz Sweep Osc ............................................................ $2450 MARCONI TF2300A FM/AM Mod Meter 500kHz-1000MHz ................................................... $450 MARCONI TF2500 AF Power/Volt Meter ................. $180 SD 6054B Microwave Freq Counter 20Hz-18GHz ......................................................... $2500 SD 6054C Microwave Freq Counter 1-18GHz ............................................................... $2000 TEKTRONIX 465 Scope DC-100MHz .................... $1190 TEKTRONIX 475 Scope DC-200MHz .................... $1550 TEKTRONIX 7904 Scope DC-500MHz .................. $2800 WAVETEK 143 Function Gen 20MHz ...................... $475 FLUKE 8840A Multimeter RACAL DANA 9500 Universal Timer/Counter • true RMS response to 30mV • frequency coverage 10kHz1.2GHz • measurement from 100µV to 300V • stable measurement • accuracy ±1% full scale to 150MHz • list price elsewhere over $5500 • 2Hz-1MHz frequency range • digital counter with 5 digit LED display • output impedance switch selectable • output terminals fuse protected $350 $795 HEWLETT PACKARD 1740A Oscilloscope RADIO COMMUNICATIONS TEST SETS: IFR500A ............................................................... $8250 IFR1500 .............................................................. $12000 MARCONI 2955A .................................................. $8500 SCHLUMBERGER 4040 ........................................ $7500 TEKTRONIX 475A Oscilloscope TEKTRONIX 7603 Oscilloscope (military) • frequency range to 100MHz • auto trigger • A & B input controls • resolution 0.1Hz to 1MHz • 9-digit LED display • IEEE • high stability timebase • C channel at 50 ohms • fully programmable 5½ digit multimeter • 0 to 1000V DC voltage • 0.005% basic accuracy • high reliability/self test • vacuum fluoro display • current list $1780 $695 $350 TEKTRONIX FG504/TM503 40MHz Function Generator TEKTRONIX CF/CD SERIES CFC250 Frequency Counter: $270 • DC-100MHz bandwidth • 2-channel display mode • trigger - main/delay sweep • coupling AC, DC, LF rej, HF rej $990 • 250MHz bandwidth • 2-channel display mode • trigger - main/delay sweep • coupling AC, DC, LF rej, HF rej • mil spec AN/USM 281-C • triggers to 100MHz • dual trace • dual timebase • large screen $1690 $650 The name that means quality CFG250 2MHz Function Generator $375 • 0.001Hz-40MHz • 3 basic waveforms • built-in attenuator • phase lock mode $1290 CDC250 Universal Counter: $405 NEW EQUIPMENT Affordable Laboratory Instruments PS305 Single Output Supply SSI-2360 60MHz Dual Trace Dual Timebase CRO • 60MHz dual trace, dual trigger • Vertical sens. 1mV/div. • Maximum sweep rate 5ns/div. • Built-in component tester • With delay sweep, single sweep • Two high quality probes $1110 + Tax Frequency Counter 1000MHz High Resolution Microprocessor Design CN3165 • 8 digit LED display • Gate time cont. variable • At least 7 digits/ second readout • Uses reciprocal techniques for low frequency resolution $330 + Tax Function Generator 2/5MHz High Stability FG1617 & FG 1627 • • • • • • Multiple waveforms 1Hz to 10MHz Counter Output 20V open VCF input Var sweep lin/log Pulse output TTL/CMOS FG1617 $340 + Tax FG1627 $390 + Tax PS303D Dual Output Supply • 0-30V & 0-3A • Four output meters • Independent or Tracking modes • Low ripple output $420 + Tax • PS305D Dual Output Supply 0-30V and 0-5A $470 + Tax PS303 Single Output Supply • 0-30V & 0-3A • Two output meters • Constant I/V $265 + Tax Audio Generator AG2601A • 10Hz-1MHz 5 bands • High frequency stability • Sine/Square output $245 + Tax • 0-30V & 0-5A $300 + Tax PS8112 Single Output Supply • 0-60V & 0-5A $490 + Tax Pattern Generator CPG1367A • Colour pattern to test PAL system TV circuit • Dot, cross hatch, vertical, horizontal, raster, colour $275 + Tax MACSERVICE PTY LTD Australia’s Largest Remarketer of Test & Measurement Equipment September 20 Fulton Street, Oakleigh Sth, Vic., 3167   Tel: (03) 9562 9500 Fax: (03) 9562 9590 1995  3 **Illustrations are representative only Pt.1: when to fire the sparkplug Automotive Ignition Timing Firing the spark at the right moment is critical when it comes to obtaining good power, emissions and economy from an engine. Here’s a rundown on the basics of ignition timing. By JULIAN EDGAR The advent of programmable engine management has meant that people outside major engine manufacturing companies are devising complete ignition advance angle maps for the first time. While the old points-and-weights system may have been modified from time to time, any changes made were always based on the starting point provided by the car’s manufacturer. However, when program­ mable engine management systems can have ignition advance curves of literally any shape programmed into them, a whole new approach needs to be taken. This month, we examine the factors which influence ignition timing and also look at the traditional spark timing mechanisms. Next month, we will examine the ignition control provided by fully programmable engine management systems and look at the timing maps devised for some specific engines. While it is obvious that more air and fuel is required at higher engine loads, the same clarity of understanding does not apply to the ignition timing requirements. However, considering the number of factors that affect ignition timing, this isn’t surprising. The requirement for adjustable ignition timing is based mainly on one factor – the finite time taken for the fuel/air charge to be ignited and burned. In practice, the period between the spark firing and the complete combustion of the fuel/air mix is very short – about two milliseconds (2ms) on average. However, while this burn time is small, it is The timing of the ignition sparks during an engine’s cycle must be continually adjusted in order to obtain correct combustion behaviour. This, in turn, is necessary for achieving peak power and obtaining low exhaust emissions. Over-advanced ignition timing can cause knocking (or detonation) in the engine. This can destroy the elec­trodes of the spark plugs (see above) and lead to major engine damage. 4  Silicon Chip TDC (TOP DEAD CENTRE) Z 90° Fig.1: when advanced ignition timing is used, the spark plug is fired before the piston reaches top dead centre (TDC). However, because the com­bustion takes a finite time, the cylinder pressure peaks after the piston has actually just passed TDC. (Bosch). still sufficiently long enough to have an impact on when the spark should occur for best performance. In practice, the ignition must be timed so that the peak pressure caused by the explosion occurs just after the piston has passed top dead centre (TDC), and so is on its way back down the cylinder bore. If ignition occurs too early, then the piston will be slowed in its upward movement. Conversely, if it occurs too late, then the piston will be well down the cylinder and so the work done on it will be reduced. The timing of the ignition is normally expressed in crank­shaft degrees before TDC. For example, if the spark is fired when the crankshaft is 15 degrees before TDC, then the spark timing is referred to as “15 degrees advanced”. The greater the ignition advance angle, the earlier the spark is fired while the piston is still heading upwards. Note that in some situations (for example, emissions control), it is beneficial to retard the timing so much that the spark is actually fired after the piston has passed TDC. PRESSURE IN COMBUSTION CHAMBER BAR CRANKSHAFT ANGLE TDC 90° 180° 270° 0° BDC 360° 40 A 20 Z 10 180° B 90° 0° 90° 180° BEFORE TDC AFTER TDC ADVANCE ANGLE Fig.2: combustion cham­ber pressure during the compression and power strokes of the engine. The “A” curve indicates the combined compression and combustion pressure, while “B” shows the compression pressure only. “Z” is the point of ignition. (Bosch). BAR COMBUSTION PRESSURE PISTON If the composition of the mixture was constant (and it isn’t), then the elapsed time between ignition and full combus­tion would remain about the same at all rpm. As a result, if the ignition advance angle was set to a fixed angle before TDC, the combustion process would be shifted further and further into the combustion stroke as the engine speed increased. This is because the piston moves faster at higher engine speeds and thus would be further down the bore by the time combustion actually occurred. To prevent this from happening, the ignition advance must be progressively increased as engine speed rises (ie, the plug must be fired earlier in the ignition cycle). The other major factor affecting the amount of advance required is the engine load. As cylinder pressures and the air/fuel ratio decline (ie, the mixture becomes richer), the speed of combustion increases, meaning that ignition should be retarded. Conversely, even more advance than that dictated solely by the engine speed is needed at low loads where lean mixtures are used. If only it were that simple! Not only does engine speed and load determine the best timing for the combustion of the mixture, but the following factors are also relevant: (1). the design and size of the combustion chamber; (2). the position of the ignition spark(s) in the chamber; (3). the fuel type; (4). the emissions levels required; (5). the engine coolant temperature; & (6). the safety margin required before knocking occurs. The latter point is of vital importance. Knocking occurs in an engine when the pressure and tem­perature rises very rapidly due to an over-advanced ignition timing (possibly exacerbated by glowing coke deposits in the cylinder head). Instead of the flame front propagating at about 34 me­tres/ second, it moves at about 10 times this pace, causing a metallic pinging noise to be emitted from the engine. The noise is of little importance; what is a cause for concern is the damage that this hammer-blow can do to the internal engine components. Broken pistons, smashed heads and shattered sparkplugs can all occur in a just a few seconds. This problem must be particularly 50 BEFORE TDC AFTER TDC 40 2 30 1 20 10 Zb 0 75° 50° Za Zc 3 25° 0° -25° -50° IGNITION ADVANCE ANGLE -75° Fig.3: if the spark occurs too early (at Zb), then combustion knock (line 2) will occur. Line 1 shows normal combustion be­haviour, the result of ignition at Za. A spark fired too late in the cycle at Zc will result in low combustion pressure as shown by line 3. (Bosch). NOX EMISSIONS SPARKPLUG 20 50° BEFORE TDC 16 40° 12 30° 8 20° 4 0 0.7 0.8 0.9 1.0 1.1 EXCESS AIR FACTOR 1.2 1.3 Fig.4: not only is power output affected by ignition timing but also exhaust emissions and fuel economy. The affect of timing on the emission of oxides of nitrogen with different air/ fuel ratios is shown here. (Bosch). guarded against in en­ gines using forced induction (ie, supercharging or turbocharging). In this type of engine, September 1995  5 MANUAL LINKAGE CAM SLOT CENTRIFUGAL FORCE RETARD ADVANCE NO ADVANCE AT IDLE CENTRIFUGAL FORCE CAM ROTATION CLOCKWISE FULL ADVANCE AT HIGH ENGINE SPEED Fig.5: early vehicles used a fully-manual advance/retard mechan­ism, in which the breaker plate was rotated by the driver by means of a dash-mounted lever. This type of system could provide good control but only if the driver was interested! the burn occurs very quickly and so knocking can easily occur. To counter this, the ignition advance angle is retarded during boost periods. Traditional mechanisms The first adjustable ignition timing mechanism was a fully-manual advance system. In this system, a dash-mounted (or steering wheel-mounted) lever was used to rotate the dis­tributor plate. By moving Fig.7: the centrifugal timing mechanism increases spark advance as the engine speed increases. This is achieved by the action of weights and springs attached to the breaker shaft. As the engine speed increases the weights swing out, causing the shaft to shift position. this lever back and forth, the points could be made to open earlier or later in the cycle. A lever scale allowed the driver to gauge the degree of adjustment. In practice, the timing was normally retarded for starting and then advanced for running. However, although this approach meant that the timing could be fully controlled (with a sensitive driver), its efficiency depended so much on the indi­vidual that it was BREAKER POINTS CAM ROTATION VACUUM DIAPHRAGM LEVER BREAKER PLATE ROTATION Fig.6: the mechanical spark timing system used until quite re­cently combines both vacuum and centrifugal advance mechanisms. At times of low load, the manifold vacuum is high and a vacuum diaphragm is used to advance the spark. Conversely, high engine loads result in low vacuum and a relatively retarded spark. 6  Silicon Chip soon abandoned. The next step saw the introduction of an ignition timing mechanism which was to last for the next 80-odd years. This system took into account both the engine speed and load using centrifugal advance and vacuum advance mechanisms. Centrifugal advance was used to change the ignition timing on the basis of the speed of the engine, via a series of spring-loaded weights attached to the breaker shaft within the distribu­ tor. As the engine speed increases the weights swing out, causing the shaft to shift position. In turn, this causes the points to open sooner. Conversely, when the engine slows, the spring-loaded weights retract, allowing the breaker shaft to shift back in the other direction and thus retard the spark. At the same time, the vacuum advance mechanism is used to adjust the spark timing to suit the engine load. Vacuum advance takes advantage of the fact that when the throttle is only just open, a low pressure (high vacuum) is created in the manifold after the throttle butterfly valve. As the throttle opening increases, the vacuum decreases (a MAP sensor in an EFI system makes use of this parameter to determine engine load). In vacuum advance ignition timing mechanisms, one side of a diaphragm is linked to the distributor plate by a rod, while the other side is linked pneumatically (ie, via a hose) to a source of manifold vacuum. At times of high vacuum (low load), the distrib- 40° ADVANCE ANGLE BEFORE TDC B 30° A 20° 10° 0° TORR MBAR 600 This photo shows the workings of a traditional distributor that used points and relied on centrifugal and vacuum advance mechanisms. Fig.8 (right) shows the final timing curve achieved by this type of system. The full-load advance curve (A) is achieved through the centrifugal action of the weights, while the partial load advance curve (B) additionally advances the timing when loads are light (and vacuum is therefore high). “Road load” means that the engine is only partially loaded, while “full load” means that the throttle is wide open. (Bosch). utor plate is turned so that the spark is advanced. Con­ versely, when the vacuum drops, the spark is retarded in response to the increased load. Although this primitive system work­ed well for many years, it did not take into account many of the factors required for optimum ignition timing. Consequently, the safety-margin to detonation (knocking) was generally left high, thereby limiting power and reducing efficiency. Electronic systems The use of electronic spark advance systems revolutionised ignition tim- VACUUM 400 500 ROAD LOAD 400 300 A2 300 200 200 100 0 A1 100 0 1000 ing. First, the traditional parameters of engine speed and load are now catered for by a detailed timing map stored in an EPROM (electrically programmable read-only memory). An electronic timing map is far more accurate than the timing parameters produced by the traditional mechanical systems and is far more reliable. Many modern cars also now have antiknock sensors and these allow the engine management computer to set the ignition timing for best performance while still maintaining safe operation. In addition, other factors which affect optimum timing can now be IGNITION ADVANCE LOA D FULL LOAD 2000 3000 4000 5000 REV/MIN taken into consideration. Typically, a modern com­puter-controlled engine management system accepts data from sensors which monitor engine speed, manifold vacuum, throttle position, engine temperature, air temperature and battery vol­ tage, and sets the ignition timing accordingly. Such systems also usually provide full fuel management as well, by controlling the fuel injectors. As a result, electronic engine management systems provide improved starting and idle speed control, better fuel economy, increased performance SC and lower engine emissions. IGNITION ADVANCE ED E SPE ENGIN Fig.9: electronic spark advance and engine management systems allow complex ignition maps which provide optimal timing for a large range of load and engine speed conditions. (Bosch). LOA D EED E SP ENGIN Fig.10: the traditional mechanical advance mechanism produces a map which is far simpler than that achieved by electronic means. As a result, the ignition timing is far from optimum in many operating conditions. (Bosch). September 1995  7 For CAD and desktop publishing Philips Brilliance 21A autoscan monitor Announced by Philips in late 1994, the Brilliance 21A is a radical new development in computer monitors. Not only are all its specifications such as convergence under digital control but it even compensates for variations in the Earth’s magnetic field. By BOB FLYNN Ever since this new range of monitors was released, they have been in short supply but after a very long wait, we finally received a sample unit to review. It was quite an experience. We have a number of large screen monitors in the SILICON CHIP offices but for sheer size, the Brilliance 21A monitor puts them in the shade. It’s not so much that it has a large screen but its cabinet is quite bulky and heavy. Its overall dimensions are 528 x 540 x 501mm (W x H x D). So you need a large desk for one of these monitors and you need two men to lift it safely since it weighs 37 kilograms. The Brilliance 21A has a 54cm, flat, black matrix, square CRT with a dot pitch of 0.28mm, currently the best that can be made. The screen is anti-reflection and antistatic treated. Maximum resolution is 1600 x 1280 pixels although that does not tell the whole story. While many monitors can be switched to 1600 x 1280, their resulting picture may not be useable. The Bril­liance 21A, on the other hand, has been electronically tweaked to obtain the very best picture that can be obtained from existing 0.28mm dot CRT technology. In fact, it could be said the picture quality is theoretically better than is possible. We’ll see why, later. As with all large screen monitors, 8  Silicon Chip the Brilliance is an autoscan model and will automatically cope with horizontal scan rates from 30-82kHz and vertical scan rates from 50-160Hz. Video input is RGB analog and typical sensitivity is 0.7V. Video band­width is 150MHz and input impedance 75 ohms. Three modes of sync are accepted: composite sync on the green line, separate com­ posite TTL sync (positive or negative) and separate TTL Horizon­tal and Vertical sync (positive or negative). The monitor also has the following features: (1) digital control of contrast and brightness over the full screen, the brightness uniformity being better than 90%; (2) digital control of convergence so that it is better than 0.2mm (typically 0.15mm) over the full screen; and (3) automatic cancelling of the earth’s magnetic field through a magnetic sensor and a proprietary cir­cuit that maintains a constant magnetic field inside the monitor. This ensures that distortions of the display caused by changes of the position of the monitor do not occur. Power management Naturally, this monitor has energy saving features and they are quite comprehensive. It is TCO 1992 Power Management/Energy Star Power Management compatible. This requires a VESA-DPMS compliant signal. With screen saver programs, the power consump­tion drops 10%. With computers with VESA Display Power Manage­ment, the power consumption drops from a maximum of 180W to 15W, after one hour without vertical and horizontal sync signals. When sync signals are restored, recovery to normal operation takes less than 3 seconds. After a further one hour without sync signals, the monitor switches to its lowest power state, consum­ing a maximum of 8W. Recovery time from this state is the same as the normal switch-on period. The power state in these reduced modes is shown on the LCD panel. Storage in the monitor’s memory of 21 different graphic resolution files, 12 factory preset and nine user generated, is possible. Software is supplied with the monitor that allows the user to adjust the image for the correct size and centring and generate a correction table for the control of convergence, brightness and colour uniformity, if the application is not covered by the default files. Black screen Apart from the size, the first thing that most people notice about this monitor is the “blackness” of the screen. It certainly has the blackest screen we have seen. Apart from this the 21A looks very much like any other digital monitor. At the bottom centre of the front is a yellow backlit liquid crystal display, flanked on either side by a group of four push­buttons. Further to the right of these are controls for brightness and contrast and the power switch. The buttons to the left of the display are Function, Adjust (+), Degauss and Adjust (-). The + and - buttons each you need to store your mode by pushing the channel select button to select one of the user file memories (13-21). Error messages If no connection can be made between the monitor and your computer, the LCD will display an error message such as “Missing H sync”, “Missing V sync” or “Missing H & V sync”, meaning that cables are improperly connected or the computer is not switched on. The messages “V out of range” or “H out of range” mean that the vertical or horizontal scan frequencies of your computer are outside the monitor’s 50-160Hz vertical or 30-82kHz horizontal scan rates. Five additional error messages may be displayed to indicate monitor faults. Geometry & convergence For our tests, the Brilliance 21A was connected to a 486DX and used with programs operatThe model 21A is the top model in the Philips Brilliance range of monitors. It has ing at various resolutions from digital control of all picture parameters and automatic compensation for variations 800 x 600 to 1280 x 1024 pixels. in external magnetic fields. For the two highest resolutions, the message “Mode not found” allow adjustment of the geometry and internal microprocessor. A two-posi- was displayed and so we went through colour temperature through a scale of tion slide switch selects either 75-ohm the procedure for creating user gener0-9, indicated on the LCD. The buttons input impedance or high impedance. ated files. The supplied soft­ware runs to the right of the display are Memory With only one monitor connected to from Windows and involves linking Select, Memory Store, Memory Recall your computer this switch should be selected channels to user tables. This and Input select. in the 75-ohm position. The high im- done, Geometry Adjust was carried Pressing the Function button ac- pedance position should only be used out. This entails adjusting the raster cesses the following 10 functions if two monitors are connected to your to screen centre and setting the vertise­q­u en­t ial­l y: Horizontal position, graphics card. cal and horizontal borders to a width Width, Vertical position, Height, ColAt switch-on the LCD panel displays depending on the resolution for which our temperature, Pincushion, Pincush- the message “Wait...start up”, followed the table was being made. ion balance, Trapezoidal, Trapez­oidal by “F/W Release..(No.)”. Each of these The next step is to Select Reference balance and Language. messages display for 1-2 seconds and Points. A green mark has to be moved The colour temperature function are then followed by the message to the top left of the screen and a secallows the choice of either a 9300° or “Test in progress”. This message is ond green mark moved to the bottom 6500° white. A third choice allows displayed for 2-3 seconds while the right of the screen. The program then the operator to set his own colour monitor does its self checks. If the creates the correction table for brighttemperature by the adjustment of the moni­ tor recognises the timing sup- ness and convergence of the operating red, green and blue mixture using the plied by your video card as one of its mode. The files so created should be + and - pushbuttons. default modes the LCD will show the saved to the hard disc so that the chanOn the rear of the monitor is a power resolution being used. If it does not, nel settings can be restored if re­quired input socket (the monitor can operate then the message “Mode not found” at a later date. from 90-132VAC and 180-264VAC, 47- will be displayed. Why do all this? Because the Philips 76Hz auto selected) and five BNC sockThis means that the current timing Brilliance 21A is capable of much ets for the signal connections. A 15-pin is not stored though the monitor is better convergence than typical comMini D-Sub socket for video input is working, with a proper screen display. puter monitors but it has to be done for also provided. A socket not normally You can elect to ignore the “Mode each and every screen resolution and found on monitors is 9-pin Mini D not found” message but if you do combination of horizontal and vertical to provide a serial interface between you will not be able to optimise the sync. With such a large screen and the computer and the monitor’s own convergence for your mode. Hence, fine dot pitch, picture imperfections September 1995  9 Fig.1: the schematic of the magnetic compensation cir­cuitry in the Philips Brilliance 21A monitor. It continuously compensates for any variations in external magnetic fields and ensures that optimum picture quality is maintained. that would go unnoticed on smaller monitors become critical, particu­larly at the higher screen resolutions. Magnetic field compensation All of the fine attention to detail in obtaining the best convergence, geo­ metry and uniformity of screen brightness are subject to a big hazard in the larger monitors. Simply rotating the monitor changes its orientation to the Earth’s magnetic field and thus the electronic beams scanning the picture are thrown off their optimised paths. This happens in all monitors but again, the larger the monitor, the worse the effect on the picture, especially as far as purity is concerned. Philips has been really clever here in introducing their innovative Cyber­screen Technology, a high fal­ utin’ name which embraces all the 21A’s digital control circuitry and, more par­ticularly, its magnetic field compensation. In essence, the 21A monitors the magnetic fields acting upon the monitor and then produces a compensating magnetic field so that the high convergence standard is constantly main­tained. The schematic of Fig.1 shows the general arrangement. A bridge of Hall Effect devices is used to monitor the magnetic fields and produce an offset voltage. This voltage is converted to 10  Silicon Chip a square wave by alternating current pulses fed to the inver­sion coil. The output square wave’s amplitude is proportional to the magnetic field strength. The square wave is AC coupled to the processing unit to remove the offset and amplified. The signal is then applied to the purity coils to correct the monitor’s conver­gence – a classic feedback circuit. The correction signal is also rectified to produce a DC voltage proportional to the magnetic field. This voltage is applied to the degauss circuit where any change in level triggers the degauss circuit. Hence, at any time, the Brilliance 21A may perform an automatic degauss which you see as a momentary picture distortion accompanied by the characteristic audible twitch from the degauss coils. The proof of the pudding While it is easy to be overwhelmed by the complexity of this monitor and its operating procedures, the proof is in the outstanding picture quality. The monitor was used mainly with a CAD program at a resolution of 1280 x 1024 pixels and the display showed excellent geometry, even brightness and good resolution. With my usual monitor (a 20-inch colour monitor with 0.31mm dot pitch), I need to zoom in frequently on large drawings, particu­larly when placing type; circles that appear round at the centre of the screen are not so when moved away from centre. This is not the case with the 21A. Type placement does not require the same level of zoom and circles are circles no matter where they are placed on the screen. As noted above, high resolution mode in one monitor is not the same as on another and this is where you really notice the picture quality of the Brilliance 21A –it is aptly named. A minor irritation is the delay that occurs when the reso­lution changes within a program. For example, if the program shells out to DOS, to perform a print command, then the monitor takes a noticeable time to find the correct resolution file and show a correctly scanned picture. This delay is longer than the switching time of the relays in a multi-sync monitor. As well as being ideal for desktop publishing and CAD pro­ grams, the Brilliance 21A would appear to be ideally suited to any program where colour accuracy is paramount such as in advertising production, textile and fashion design, and so on. At the time of writing, the Philips Brilliance 21A is priced at $5270 plus tax where applicable. Further information can be obtained from Philips Business Electronics, Technology Park, 3 Figtree Drive, Homebush, NSW 2140. Phone 1 800 658 086. SC MAILBAG Two project suggestions I would like to suggest two ideas for future projects. The first is a low pow­ er, say 5W maximum, general purpose stereo amplifier. I recently repaired a cheap 3-in-1 which was suffering from severe distortion from one channel. It turned out that the audio chip was (a) dead and (b) obsolete. I replaced the chip with the Mini Stereo Amplifier kit from the Dick Smith Funway series, as it was the only small stereo amplifier available. The LM380s are only good for around 2W flat out (if you don’t mind 10% distortion!) and can be unstable little mon­grels when they want to be. There must be a suitable stereo chip lurking in the data books somewhere that could be useful as a slightly higher power general purpose amplifier. The second is slightly more unusual – a replacement for the spark start system in a gas stove. I was visiting a relative recently who is badly affected by arthritis and found her strug­gling with matches to light the gas because the electric start system in the stove had given up the ghost. After whipping the back off the stove, the spark unit turned out to be a black box, about the size of an average sized jiffy box, with six wires, for the six jets and run from the 240VAC supply. Unfortunately, it was sealed in epoxy plastic which made repair impossible. This was the second unit that had failed and she did not want to bear the expense of another serv­ice call, for it to fail again. The length of the spark would not have to be too large, say 5mm, but it should have separate out­puts in case one of the outputs is shorted to earth accidentally. M. Allen, Artarmon, NSW. Comment: a suitable low cost amplifier is the LM1875T module featured in the December 1993 issue. While capable of 25W it can be derated to deliver 4W with a 20V supply rail. The best approach to reliable gas lighting (particularly with natural gas) is to dispense with the electronic spark units altogether and to use a gas lighter designed for the job. One such unit, branded “Red Head” is a modified cigarette lighter with a long nozzle. They sell quite cheaply, for just a few dollars. Disappointment with speaker review I am writing to express my disappointment of the quality of the review of the Jamo classic speakers by Leo Simpson in the July 1995 issue. It reads more like a paid advertorial and forum for personal opinion rather than a clear unbiased technical and subjective evaluation of the products. In particular, I object to his comments on bi-wiring. If Leo or “we” cannot see the point of bi-wiring I suggest you read “High Performance Loudspeakers”, by Martin Colloms (4th edition). He is considered a world authority on loudspeaker design and in his opinion the advantages of bi-wiring are quite clear, whether the crossover be at the amplifier end (preferred) or at the speakers. Briefly, it reduces currents in conductors that are common to HF and LF drivers and reduces the bandwidth each cir­cuit has to handle. Bi-amping is great but bi-wiring has definite advantages, albeit small, but isn’t true hifi all about small gains (pun not intended)? The Jamo Classic 4’s appear to use the M-T-M arrangement popular in designs by Joe D’Apolito who writes for “Speaker Builder” magazine and designs systems for major US and Scandinavian manufacturers. I have built his excellent Aria 5’s which are similar to the Jamo 4’s. I feel Leo missed an opportunity to comment on the properties of this configuration. Where are the frequency, phase and polar response plots, comments on imaging, comparisons with similarly priced units, etc? An earlier speaker review referred to oxygen-free cable as “a lot of rubbish” or some such comment. Rightly or wrongly, many stereophiles use OFC and I am sure they were insulted by such statements. As you should know, sound reproduction is part sci­ ence and part art with many grey areas, preferences and opinions and to be dogmatic about any aspect is only to show ignorance of the subject and thereby lose one’s credibility. On a more positive note, I have read SILICON CHIP since its inception and commend you on its quality, broad range of topics and excellent designs, many of which I have built. Electronics and audio have been my profession and hobby since 1948 and I can relate to the “Serviceman” and “Vintage Radio” segments. Please keep up the good work. R. W. Field, Bonnie Doon, Vic. Comment. We note that you have cited Martin Colloms as a “world authority” but the fact is that there is no technical justifica­tion for bi-wiring loudspeakers. The Theory of Super­ position clearly demonstrates that two signals or voltages do not interact in a passive network but add linearly. Bi-amping is a different matter but to gain the advantages of reduced inter­modulation in the amplifiers you need to use an electronic crossover and elim­inate the passive network. We are familiar with the so-called D’Apolito configuration but we are not sure that it was intended as a feature of the Jamo Classic 4’s. It would seem logical that if the D’Apolito configu­ ration is to work properly, the tweeter should be at or near ear level. With most small loudspeakers, the D’Apolito arrangement places the tweeter at a lower than optimum level. As far as we know, the central placement of a tweeter flanked by the other drivers above and below was pioneered not by Joe D’Apolito but by Richard Dunleavey with his Duntech speakers, designed and made in Australia. We do not remember making a comment on oxygen-free copper cables in a previous review but there is no justification for using OFC cables in any audio application. OFC cable was origi­nally developed by Hitachi as a solution to hydrogen embrittle­ment of conductors inside large alternators in power stations (alternators use a pressurised hydrogen atmosphere). As far as we know, OFC cables were first advocated by Japanese hifi enthu­ siasts who have a well-known taste for the esoteric. We have not seen one technical paper on the merits of OFC SC cables for hifi use. September 1995  11 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 12  Silicon Chip 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 September 1995  13 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 14  Silicon Chip 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 September 1995  15 Build a keypad combination lock This keypad combination lock can be used to arm/disarm a house or car alarm, or to activate a solenoid-operated door strike. It accepts codes up to 12 digits long and is easy to program. Design by JEFF MONEGAL Keypad combination locks are a great idea in security applications, since they are far more convenient to use than keys. What’s more, the code can be quickly and easily changed at the user’s whim to restrict people who previously had access or just to maintain security. By contrast, keys can be easily copied or lost, while locks are expensive and time-consuming to change. The Keypad Combination Lock described here can be used in a range of security applications. These include: (1) turning bur­glar alarms on and off; (2) activating solenoid-operated locking mechanisms in security doors and 16  Silicon Chip gates; (3) controlling ignition killers and fuel cutout systems in cars and boats; and (4) oper­ating power doors on garages. When used with a home burglar alarm, the keypad would typi­cally be mounted just inside the front door. Alternatively, the keypad could be mounted in a weatherproof case just outside the door. That way, you could reduce the entry and exit delays to a bare minimum or simply wire the alarm for instant triggering. Main features Unlike previous circuits, this unit is based on a dedicated kepad com- bination lock IC and this has greatly simplified the circuitry. Called the UA3730, this 18-pin CMOS device contains all the necessary logic circuitry to monitor the keypad matrix, plus the necessary output logic for latched and momentary opera­tion. In addition, the chip includes onboard memory which is used to store the code. Up to 12 numbers can be stored in memory (for 1012 possible combinations) but this will depend on the level of security required. Unlike previous systems, the code can be quickly changed (provided you have access to the PC board), since there are no wire links to solder in or DIP switch­es to set. In most cases, a simple 4-digit code will give you adequate security while retaining the benefits of a number that’s easy to remember. This number of digits provides odds of greater than 10,000 to one against someone guessing the correct code. Of course, you can use more than four digits for even greater secur­ity (although it’s never D6 1N4004 IN +12V C3 1000 D1 IC2 78L05 GND OUT C4 10 D3 I G R6 1k A R8 14 10k B 8 7 5 R3 1k 16 IC1 UA3730 11 10 17 B E C K R4 1k B 1 2 3 C2 10 D5 1N4004 SIREN E Q2 BD140 C R4 1k B ALARM ON/OFF E 18 4 B O 13 S MEMORY SET LK1 K A Q3 BC548 15 6 P  LED2 C E PLASTIC SIDE C PIEZO BUZZER C5 0.1 9 3x1N4148 D2 KEYPAD 1 1 2 3 2 4 5 6 3 7 8 9 4 * 0 # 5 6 7 E R7 4.7k Q1 BD140 C R1 12k R5 1k A C1 270pF LOCK SOLENOID D4 1N4004  LED1 K VIEWED FROM BELOW KEYPAD COMBINATION LOCK Fig.1: the circuit is based on IC1 which is a UA3730 keypad combination lock IC. This device scans the keypad and, when the correct code is entered, the Alarm On/Off output toggles and the Lock Solenoid output goes high for two seconds. The piezo buzzer echoes the key presses. a good idea to use your telephone number). The keypad used is a standard 3 x 4 unit as used in some telephone diallers. It includes the digits 0-9 plus “✳” and “#” keys. Only the digits (0-9) can be used as part of the code but you can use the same digit more than once. Three outputs are provided by the Keypad Combination Lock: (1) Lock Solenoid (momentary); (2) Alarm On/ Off (latched); and (3) Siren. The unit is easy to operate – all you have to do is enter the correct code and press the “#” key. A small piezo transducer “beeps” briefly (for 0.2s) each time a key is pressed. Because it can only register one key at a time, you can’t fool the unit by simultaneously pressing all the keys at once. In addition, the IC includes a time-out feature so that you only have one minute to complete the code entry after the first key is pressed. If you take longer than one minute, the IC resets and you have to start all over again. When the correct code is entered, the Door Lock output goes high for two seconds (to open the door) and lights a red indica­tor LED. By contrast, the Alarm On/Off output alternately toggles between high (+12V) and open circuit (O/C); ie, it changes state each time the correct code is entered. The Alarm On/Off output can be used for switching burglar alarms or other equipment on and off, either directly or via a relay. Wrong code If the wrong code is entered, the transducer beeps once but only on the first two attempts. After the third incorrect at­tempt, the Siren output goes low for 60 seconds to sound an external siren or trigger a central alarm system. During this period, the transducer beeps once every second and the circuit lights an orange indicator LED. The circuit subsequently automatically resets at the end of the 1-minute alarm period. Alternatively, the circuit can be reset at any time during the alarm period by entering the correct code. Note that the use of any output is entirely optional. You might elect to Features Of The Keypad Combination Lock • • • • Based on a dedicated combination lock IC. • • • LED indicators for Lock Solenoid and Siren outputs. • Programmed code can be maintained in the event of power failure using three dry cells to provide battery backup. Accepts codes up to 12 digits long for 1012 possible combina­tions. Code is stored by the IC and is programmed from the keypad. Three outputs: (1) Lock Solenoid (momentary); (2) Alarm On/Off (latched); and Siren (1-minute alarm). Siren output activated if three incorrect codes entered in sequence. Piezo buzzer echoes key press­es; beeps once every second for duration of Siren output. September 1995  17 +12V GND SIREN DOOR LOCK D6 0.1 LED2 Q2 D5 1k 1k 10uF LK1 S P PIEZO BUZZER Q3 IC1 UA3730 12k 270pF 10uF 1k Q1 D4 1000uF IC2 4.7k 1k 1k 1 D1 D2 D3 10k ALARM ON/OFF LED1 2 3 7 4 5 16 TO CORRESPONDING NUMBERS ON KEYPAD 7 6 5 4 3 2 1 TO CORRESPONDING NUMBERS ON PCB BACK OF KEYPAD Fig.2: install the parts on the PC board as shown in this layout diagram. The two LEDs can either be mounted on the PC board, or they can be installed along with the keypad on the front panel of a case or switch plate. use only the Lock Solenoid output, for example, and leave the Alarm On/Off and Siren outputs disconnected. Supply requirements Because it is a CMOS device, the UA3730 has a typical quiescent current of just 5µA. This makes it suitable for battery backup using dry cells, since these will last for the length of their shelf-life. In fact, battery backup 18  Silicon Chip Take particular care when wiring the keypad, as some of the leads of the 7-way cable from the PC board have to be crossed over as shown here. Just be sure to connect the wiring exactly as shown in Fig.2. for the IC is desir­able since the memory is volatile. This means that the programmed code is lost if the power is interrupted, with the unit reverting to its default code of 0#. The circuit itself is powered from a 12V DC source, with the current requirements dictated by the external load. A typical door lock solenoid will require a supply capable of delivering about 400mA but many applications will require only 100mA or less. Battery backup is not a feature of the original circuit but it can be easily added, as we shall see later on. Note that the suggested circuit using dry cells is only suitable for main­taining the programmed code in the IC until regular power is re­stored. Circuit details Refer now to Fig.1 for the circuit details. Apart from the IC and the keypad, there are just two transistors, a 3-terminal regulator, a piezo transducer and a few minor parts. R1 and C1 are the timing components for IC1’s on-board oscillator. In operation, IC1 scans the keyboard matrix and decodes the key presses. The internal logic of the IC then de­ cides whether or not the correct code has been entered and wheth­er or not it has been entered in the required 1-minute period. Pins 17, 16 & 15 are the device outputs. Normally, pin 17 of IC1 is high and so PNP transistor Q1 is off. However, each time the correct code is entered, pin 17 goes low for two seconds and so Q1 briefly turns on and supplies current to the door lock solenoid. It also supplies current to LED 1 via a 1kΩ limiting resistor. At the same time, pin 16 changes state. If it was high before the code was entered, it switches low and Q2 turns on. Conversely, if it was low, it switches high and Q2 turns off; ie, pin 16 behaves as a latching output. The third output, pin 15, is normally high but switches low for one minute if three incorrect codes are entered in a row. This lights LED 2 and also drives an external siren circuit via diode D5 and current limiting resistor R4. At the end of the 1-minute period, IC1 resets and pin 15 switches high again. Pin 14 is the piezo driver output. Each time a key is pressed, this output generates a 3kHz signal for 0.2s which drives Q3. Q3 in turn drives the piezo transducer (B1) with this 3kHz pulse signal. R7 is necessary to provide a DC current path for the transistor. In addition, pin 14 generates a 0.2s burst at 3kHz each time an incorrect code is entered. It also generates a 3kHz burst every second for a period of one minute if three incorrect codes are entered (ie, while pin 15 is low). Pin 13 is used to control the pro- This view shows the programming jumper in the store (S) position. It must be placed in the program (P) position when a new code is to be programmed into the UA3730 IC. gramming function of IC1. Normally, this pin is left floating but is grounded (by install­ing link LK1) to program in a new code. The programming link is then removed again after the new code has been entered. This task has been made easy by installing a pair of adjacent 2-way pin headers on the PC board. A jumper is then used to short out two of the pins in one position to provide the programming link. The other position is simply used to store the jumper when programming has been completed. The Lock Solenoid output of the circuit can be used to drive a 12V door strike such as the unit shown here (available from locksmiths). Power for the circuit comes from an external 12V supply (battery or DC plugpack) and is applied to 3-terminal regulator IC2 via reverse polarity protection diode D6. The 5V regulated output from IC2 is then applied to pin 9 of IC1. Ca­pacitors C3, C4 & C5 decouple the input and output terminals of the regulator respectively. Note that transistors Q1 & Q2 are powered directly from the +12V rail. Construction All the parts except the buzzer and the keypad are mounted on a PC board measuring 105 x 60mm. This board carries a screen printed overlay so that you can see at a glance where each part fits. Fig.2 shows the assembly details. No particular order need be followed when installing the parts on the PC board but take care to ensure that all polarised parts are correctly oriented. In particular, note that the two BD140 transistors are installed with their metal faces towards the LEDs. There are four wire links on the board. Install these at the locations shown and install the two 2-way pin headers at the LK1 position. Separate pin headers are also installed for the buzzer terminals. Resistors R2 and R3 are shown as 2.2kΩ types on the PC board screened overlay but we recommend that you reduce them to 1kΩ, in line with the circuit diagram. Depending on the application, the two LEDs can either be installed directly on the PC board, as shown in Fig.2, or con­nected to the board via flying leads. Make sure that the LEDs are correctly oriented – the anode lead is usually (but not always) the longer of the two. It is a good idea to check PARTS LIST 1 PC board, 105 x 60mm, copyright Oatley Electronics 1 keypad 1 12V piezo transducer 1 plastic cable tie 1 200mm-length 7-way ribbon cable 1 18-pin IC socket 3 2-way pin headers 1 jumper (for pin headers) 1 80mm-length of tinned copper wire (for links) Semiconductors 1 UA3730 CMOS electronic lock (IC1) 1 78L05 3-terminal regulator (IC2) 2 BD140 PNP transistors (Q1,Q2) 1 BC548 NPN transistor (Q3) 1 5mm red LED (LED1) 1 5mm orange (LED2) 3 1N4148 signal diodes (D1-D3) 3 1N4004 silicon diodes (D4-D6) Capacitors 1 1000µF 16VW electrolytic 2 10µF 16VW electrolytic 1 0.1µF monolithic 1 270pF ceramic Resistors 1 12kΩ 1 10kΩ 1 4.7kΩ 5 1kΩ WHERE TO BUY A KIT A kit of parts comprising the PC board, all on-board parts, the keypad and the piezo transducer is available from Oatley Electronics for $20 plus $4 p&p. A suitable plastic case (see photo) costs an extra $4. Contact Oatley Electron­ ics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985 or fax (02) 570 7910. Note: copyright the PC board associated with this design is retained by Oatley Electronics this point with your multimeter before the LEDs are installed. The red LED is used for LED 1 (alarm on/off), while the orange LED is used for LED 2 (ie, siren indication). The IC is best left until last. It is installed in an IC socket and must be oriented so that its pin 1 is adjacent to R1 (12kΩ). September 1995  19 Adding Battery Backup & Alarm On/Off Indication +12V R3 1k TO PIN16 IC1 E B Q2 BD140 C Programming 1k LED3 12V RELAY D9 1N4004  Fig.3: this diagram shows how to add LED indication and a relay to the Alarm On/Off output. If you don’t need the relay, just leave it (and D9) out. +12V D6 1N4004 IN C3 1000 IC2 78L05 GND 2x1N4004 D7 OUT C4 10 D8 C5 0.1 TO PIN9 IC1 4.5V Fig.4: here’s how to add battery backup to the circuit. Note that this circuit is only intended to maintain the code in the UA3730 IC in the event of a power failure. Once the board assembly is completed, it can be wired to the keypad via a 7-way ribbon cable. A cable length of 150mm should be sufficient for most applications. You will need to take extreme care when making the connections to the keypad, since some of the leads must be crossed over to reach their correct terminals. Just ignore the screened “1” on the PC board and connect the leads as shown in Fig.3. A plastic cable tie is used to anchor the keypad cable to the PC board, to stop the leads from coming adrift. Finally, the piezo transducer can be wired into circuit. Be sure to connect the red lead to the positive terminal. The Keypad Combi­nation Lock is now ready for testing. Testing All you have to do here is connect a 12V DC power supply to the unit and try it out. Wait a few seconds after switch on for the circuit to reset correctly – the piezo transducer will beep when all is ready. Now press 0# and check that LED 1 lights for two seconds and then goes out again. If it does, then all is 20  Silicon Chip If you strike problems, first check that the keypad is wired correctly, as it’s easy to make a mistake here. This done, check that all polarised parts are correctly oriented and that the correct part has been used at each location. well and you can check the other two outputs. To do this, use a multimeter (set to a low DC range) to monitor the Alarm On/Off output and check that this output tog­gles each time the correct code is entered. This done, check that the transducer beeps once every second and that LED 2 lights for a period of one minute when three incorrect codes are entered. Changing The Code The default code for the unit is “0” and this is entered by pressing “0” on the keypad and then pressing the “#” key. To change the code: (1) Place the jumper in the “P” (program) position of LK1. (2) Enter the desired code (up to 12 digits). (3) Press the “✳” key. (4) Transfer the jumper to the “S” (store) position of LK1 (this is necessary, otherwise the unit can be quickly reprogrammed from the keypad). To program the unit, first install the jumper between the two pin header terminals labelled “P” at the LK1 position (ie, between the two righthand terminals) – see Fig.2. Pin 13 of IC1 is now grounded. Now enter in the required code (up to 12 digits), press the “✳” key and transfer the jumper to the store (S) position. Your new code is now programmed into the lock. Check that the unit will recognise this code by keying it in and pressing the “#” key. Options (1) Alarm On/Off Indicator: Most burglar alarms sound a small buzzer during the exit and entry periods, so a LED indicator was considered unnecessary for the Alarm On/Off output. If you do need a LED indicator on this output, then it can be easily added as shown in Fig.3. Fig.3 also shows how this output could be used to drive a relay. Note that a diode must be connected across the relay coil to protect Q2 from voltage spikes when the relay turns off. (2) Battery Backup: A 4.5V battery pack (eg, three 1.5V dry cells) and a couple of 1N4004 diodes are all that are required to maintain the code programmed into IC1 if the power fails. Fig.4 shows how this is done. The circuit works like this: normally, the cathode of D7 is at 4.5V and so D8 will be reverse biased and no current flows from the batteries. However, if the power fails, D8 becomes for­ward biased and the backup batteries take over and supply IC1. D7 can be easily added to the existing PC board by substi­tuting it for the wire link immediately below the 1000µF capaci­tor (C3). Be sure to install it with its cathode lead to the right. D8 can be wired in series with the positive supply lead from the batteries and its cathode connected to D7’s cathode. (3) Door Sensor: Although not shown on the circuit of Fig.1, pin 12 is designated as the on/off sensor input. This pin is normally left floating but if YOU CAN AFFORD AN INTERNATIONAL SATELLITE TV SYSTEM SATELLITE ENTHUSIASTS STARTER KIT The two LED indicators can be affixed to the plastic case using epoxy resin, as shown here. Similarly, the keypad is attached by first drilling clearance holes for its four corner posts and then using epoxy resin to glue these corner posts to the inside of the case. it is shorted to the commoned anodes of D1-D3, the siren output goes low for one minute (ie, the effect is the same as if three incorrect codes are entered in sequence). Despite not being shown on the circuit, provision for this feature has been made on the PC board. All you have to do is wire the two unused pads to a normally open switch (eg, a reed switch or an under-carpet pressure mat), or even several switches wired in parallel. These switches could be used to detect other doors or windows being forced. YOUR OWN INTERNATIONAL SYSTEM FROM ONLY: FREE RECEPTION FROM Installation The exact method of installation will depend on the appli­cation but make sure that the electronic circuitry is secure so that the keypad cannot be circumvented. In most cases, the keypad can be mounted on a blank mains wall plate and this can be installed with the PC board behind it in a wall cavity. This means that the two indicator LEDs would also have to be mounted on the wall plate (eg, directly beneath the keypad) and connected to the PC board via flying leads. The LEDs can be secured using epoxy resin. Another option is to mount the keypad and circuitry in a plastic utility case and this method would be suitable for low-security applications. Power for the circuit can be derived either from a DC plug­ pack supply or from an existing alarm power supply, preferably with battery backup. Note that Mounting the circuit in a plastic case is OK if the alarm system has a battery for low-security applications. Alternatively, backup, then the optional batyou can mount the keypad on a blank mains tery backup circuit depicted in wall plate and hide the PC board close by in Fig.3 is unnecessary. SC the wall cavity. 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 September 1995  21 Disguise your voice to sound like Darth Vader from “Star Wars” or a Cylon from “Star Trek”. With the added menace of a new strange-sounding voice, you too can travel the galaxy for profit and entertainment. By JOHN CLARKE e c i o V r e d Va T HE DARTH VADER and Cylon characters have always had great appeal, probably because of their distinctive metallic voice styles. This simple project lets you imitate the dastardly Darth and other diabolical characters from the nether regions of the galaxy. All you do is switch it on, speak into a small electret microphone and adjust a single pot to get the effect you want. Now it’s quite possible that some people might not see the need for building such a handy space-war accessory as this. To others, the reasons will be self-evident – after all, why should you be forced to stick with your own everyday boring voice? As can be seen from the photos, 22  Silicon Chip the Vader Voice is housed in a small plastic case. The controls include an effects rate ad­justment (which varies the type of sound), a volume control to set the output level from the loudspeaker and an on/off switch. The loudspeaker is mounted inside the case while the microphone is located in a small film canister connected via a length of shielded cable. How it works Fig.1 shows the block diagram for the Vader Voice. The action starts on the lefthand side, where an electret microphone feeds signal to an op amp stage (IC1a) which has a gain of about 15. A chopper circuit (ie, CMOS switch IC2) then switches the signal on and off at a rate determined by oscillator stage IC3 and potentiometer VR1. The output from the chopper stage is fed to a 3kHz low-pass filter based on IC1b. This stage removes the residual signals produced by the switching action in IC2. Finally, IC4 feeds the processed signal to power amplifier stage IC4 via volume control VR2. Fig.2 illustrates how the circuit produces the sound ef­ fects. Waveform A is the audio signal from the microphone after passing through amplifier IC1a, while waveform B is the square wave output from the oscillator. Waveform C shows the audio signal after it has been “chopped” at the oscillator frequency. The bottom waveform at D shows the corresponding output from the low-pass filter (IC1b). Note that this waveform is quite different in appearance to the original waveform shown at A and it sounds correspondingly different too. Refer now to Fig.3 for the complete circuit. Apart from the microphone and loudspeaker, it uses four lowcost ICs plus a few resistors and capacitors. The electret microphone requires a bias in order to func­tion. This is supplied via a 10kΩ resistor which is decoupled from the supply rail via a 1kΩ resistor and 33µF capacitor. This decoupling arrangement is necessary to prevent supply line fluc­ tuations caused by the power amplifier stage from modulating the microphone and causing positive feedback. The signal from the electret microphone is fed via a .0033µF capacitor to pin 3 of op amp IC1a. This stage is con­nected as a non-inverting amplifier with a gain of about 15, as set by the 470kΩ feedback resistor and the 33kΩ resistor on pin 2 (ie, Gain = 1 + 470/33 = 15.2). IC1a is biased at half the supply voltage via two 220kΩ resistors and the associated 470kΩ resistor connected to pin 10. A 10µF electrolytic capacitor decouples the half-supply voltage, which is also used to bias pins 2 & 1 of IC2 and pin 5 of op amp IC1b. As a result of this bias arrangement, the output from IC1a swings above and below +4.5V. AMPLIFIER x15.5 MICROPHONE IC1a 3kHz LOW PASS FILTER IC1b CHOPPER IC2 A C POWER AMPLIFIER D VOLUME VR2 IC4 B EFFECT RATE VR1 LOUDSPEAKER OSCILLATOR IC3 Fig.1 (above): block diagram of the Vader Voice. The signal from the microphone is amplified in IC1a and “chopped” in IC2 at a rate set by oscillator IC3. The resulting signal is ten filtered in IC1b and fed to audio amplifier stage IC4. A B Fig.2 (right): this diagram shows the effect on the input waveform at various points in the circuit. Note that the output waveform (D) is quite different to the input waveform (A). The oscillator stage is formed by IC3 which is a 7555 CMOS timer. This stage generates a square wave output with a frequency in the range from 1.3kHz to 14kHz, depending on the setting of VR1. Let’s see how it works. At switch on, the 0.1µF timing capacitor is initially dis­ c harged and the output at pin 3 is high. The 0.1µF capacitor then charges via the 1kΩ resistor and VR1 until it reaches 2/ Vcc (ie, 2/ the supply voltage). 3 3 When it does, pin 3 switches low C D and the timing capacitor discharges via the 1kΩ resistor and VR1 until it reaches 1/3Vcc. This switches pin 3 high again and so the process is repeated indefinitely while ever power is applied. Fig.3 (below): the final circuit uses 7555 timer IC3 to drive CMOS switch IC2 and this stage in turn chops the audio waveform from IC1a. IC1b is the 3kHz low-pass filter stage and this drives IC4 via volume control VR2. S1 1k 33 10k 0.1 220k .0033 470k MIC 220k 8 3 10 16VW 33k 2 IC1a LM358 9V IC2 4066 1 .0068 14 2 13 470k 470k 1 7 10k .012 22k 10k .01 .001 10k 6 5 4 470k 7 IC1b VOLUME VR2 10k LOG RATE VR1 10k LIN +9V 4 1k 6 8 3 6 5 IC4 2 LM386 4 .047 100 16VW 8W 10  0.1 3 IC3 7555 2 100 16VW 0.18 1 VADER VOICE 0.1 September 1995  23 1 100uF 33k 470k 220k 220k IC2 4066 .01 .012 C ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ 9V BATTERY AND CLIP 1 .0033 .047 TABLE 2: CAPACITOR CODES 10uF IC1 LM358 0.1 IC3 7555 0.1 0.1 1 D .0068 470k A 470k B 1k 100uF S1 10k IEC Code 180n 100n 47n 12n 10n 6n8 3n3 1n0 EIA Code 184 104 473 123 103 682 332 102 10k 0.18 1 1k 22k 10k 470k 10  IC4 LM386 10k Value 0.18µF 0.1µF .047µF .012µF .01µF .0068µF .0033µF .001µF .001 33uF C the output each time the potentiometer was operated. Following VR2, the signal is coupled to pin 3 of IC4, an LM386 audio amplifier which is capable of driving an 8Ω loud­speaker at an output power of up to 1W. Its output appears at pin 5 and drives the loudspeaker via a 100µF capacitor which rolls off the response below about 200Hz. In addition, a Zobel network consisting of a .047µF capacitor and a 10Ω resistor is connected across the output of IC4 to prevent high frequency instability. Power for the circuit comes from a 9V battery and is ap­plied via on/off switch S1. A 100µF electrolytic capac­ itor provides supply line de­coup­ling, to minimise variations due to the peak currents through the LM386 audio amplifier. D VR2 A B SPEAKER VR1 MICROPHONE Fig.4: install the parts on the PC board and complete the wiring as shown in this diagram. Note that shielded cable is used for the connections to volume control VR2 and to the electret microphone. The square wave output at pin 3 of IC3 toggles CMOS analog switch IC2 on and off. When pin 3 of IC3 is high, the CMOS switch is closed. Conversely, when pin 3 is low, the CMOS switch is open. As a result, the signal from IC1a is gated at the oscilla­tor frequency before it is fed to IC1b. IC1b and its associated resistors and capacitors form the third order Construction low-pass filter. This rolls off the signal above 3kHz at 60dB per decade (ie, 20dB/octave). This means that at 30kHz the signal is attenuated by 60dB. The filtered signal appears at pin 7 of IC1b and is AC-coupled via a 0.18µF capacitor to volume control VR2. This AC coupling prevents DC from flowing in VR2, which would cause noise in A PC board coded 08310951 carries most of the parts for the prototype. This board was housed in a plastic case measuring 130 x 67 x 43mm, while a self-adhesive label was designed for the front panel. Fig.4 shows the wiring details. Start the PC board assembly by installing PC stakes at all external wiring points and at the S1 position. This done, install TABLE 1: RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 4 2 1 1 4 2 1 24  Silicon Chip Value 470kΩ 220kΩ 33kΩ 22kΩ 10kΩ 1kΩ 10Ω 4-Band Code (1%) yellow violet yellow brown red red yellow brown orange orange orange brown red red orange brown brown black orange brown brown black red brown brown black black brown 5-Band Code (1%) yellow violet black orange brown red red black orange brown orange orange black red brown red red black red brown brown black black red brown brown black black brown brown brown black black gold brown PARTS LIST 1 PC board, code 08310951, 82 x 62mm 1 plastic case, 130 x 67 x 43mm 1 front panel label, 62 x 212mm 2 knobs 1 SPDT toggle switch (S1) 1 57mm diameter 8-ohm loudspeaker 1 9V battery clip 1 9V battery 12 PC stakes 1 electret microphone insert 1 16mm 10kΩ linear pot (VR1) 1 16mm 10kΩ log pot (VR2) 1 800mm-length of shielded cable 1 80mm-length of twin speaker wire 1 200mm-length of hookup wire 1 20mm-length of 0.8mm tinned copper wire Semiconductors 1 LM358N dual op amp (IC1) 1 4066B quad analog switch (IC2) 1 7555 CMOS timer (IC3) 1 LM386N audio amplifier (IC4) The PC board was secured by clipping it into slots that run along either side of the case, while the loudspeaker was fastened to the lid using contact adhesive. Make sure that the battery clip is correctly wired to the board. the wire link adjacent to IC2, then install the resistors and capacitors. Tables 1 & 2 show the resistor and capacitors codes but it is also a good idea to check the resistor values using a multimeter, as some colours can be difficult to read. Take care to ensure that the four electrolytic capacitors are correctly oriented. In particular, note that the two 100µF capacitors are oriented in opposite directions. The three ICs can now be installed, again taking care to ensure that they are all correctly oriented. It is quite easy to identify pin 1 of an IC, as it is always adjacent to a dot or notch in one end of the IC’s body (see Fig.4). Be careful not to get the 8-pin ICs mixed up and don’t use a conventional 555 timer for IC3. It must be a CMOS 7555 type to ensure low battery drain. Switch S1 is mounted on top of the PC stakes, to give it sufficient height to later protrude through the front panel. When the PC board has been completed, it can be clipped into the case as shown in the photo. Next, affix the adhesive label to the lid of the case and use it as a template for drilling the holes. You will have to drill holes for the Volume and Effect pots, the Power switch and the loudspeaker grille. A small hole is also required in one end of the case for the microphone lead. Take care when mounting the two pots on the lid. VR1 (Ef­fects) is a 10kΩ linear type, while VR2 (Volume) is a 10kΩ log type. The loudspeaker is mount­ed using contact adhesive. Once everything is in position, the wiring can be completed as shown in Fig.4. Light-duty figure-8 cable is used Capacitors 2 100µF 16VW PC electrolytic 1 33µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.18µF MKT polyester 3 0.1µF MKT polyester 1 .047µF MKT polyester 1 .012µF MKT polyester 1 .01µF MKT polyester 1 .0068µF MKT polyester 1 .0033µF MKT polyester 1 .001µF MKT polyester Resistors (0.25W, 1%) 4 470kΩ 4 10kΩ 2 220kΩ 2 1kΩ 1 33kΩ 1 10Ω 1 22kΩ Miscellaneous Plastic 35mm film canister, epoxy resin, solder for the loudspeaker connections and for wiring the Effects pot, while shielded cable must be used for the Volume control wiring. The battery clip can also be wired in at this stage –be sure to connect the red lead to the positive terminal on the PC board. Shielded cable must also be used September 1995  25 Fig.5: this is the full-size etching pattern for the PC board. Check your board carefully before installing any parts. for the microphone lead. Use a length of about 600mm and feed it through the end of the case before soldering it to the PC board terminals. The micro­phone itself can be mounted in a plastic film canister or some other similar plastic container. In the prototype, the microphone was mounted through a hole drilled in the cap of the film canister and secured with a dab of epoxy. The lead passes through a second hole drilled in the bottom of the canister. Finally, the battery can be clipped into position and the lid attached. Testing To test the project, simply switch it on, wind the volume control up and speak into the microphone. You should immediately be rewarded with a metallic sounding voice. Adjust the Effects pot (VR1) until you obtain the sound you want. All you need now is a helmet, a black cloak, a breathing mask and a light stick to terrorise the galaxy, or just the immediate neighbourhood. If Darth doesn’t do his stuff, first check that each com­ ponent is in its correct location and that all polarised parts are correctly oriented. You should also carefully check the underside of the PC board for solder bridges or missed (or bad) solder connections. Next, check for +9V on pin 8 of IC1, pin 14 of IC2, pins 4 & 8 of IC3 and pin 6 of IC4. Pins 2 & 5 of IC1 should be at +4.5V, as should pins 1 & 2 of IC2. Check the relevant circuit components carefully if you do encounter any incorrect voltages. If all you get is your normal amplified voice, check that oscillator IC3 is working correctly. It should have an average voltage of 4.5V at pin 3, as measured on a multimeter. If you don’t get any sound at all, try bridging pins 2 & 1 on IC2. This will tell you whether or not CMOS switch IC2 is functioning, or whether the fault lies elsewhere in the circuit. SC ANOTHER GREAT DEAL FROM MACSERVICE 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 (1-2-5 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 time base 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. Optional cover for CRT screen – $35 through the vertical system. Continuously variable between steps and to at least 12.5V/div. 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% for rise time measurements. Australia’s Largest Remarketer of markings Graticule Illumination: variable. Beam Test & Measurement Equipment Finder: Limits the display to within the graticule area and provides a visible 9500; Fax: (03) 9562 9590 display when pushed. X-Y OPERATION Sensitivity: 5mV/div to 5V/div in 10 steps (1-2-5 sequence) MACSERVICE PTY LTD 20 Fulton Street, Oakleigh Sth, Vic., 3167. Tel: (03) 9562 **Illustrations are representative only. Products listed are refurbished unless otherwise stated. 26  Silicon Chip $900 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 September 1995  27 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 30  Silicon Chip 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 September 1995  31 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. +12V +8V 18k FROM COIL NEGATIVE Q1 BC337 33k 0.5W 10k .022 .01 10k B D1 1N4004 10k 2 C 8 IC1a 3 LM393 E 100k 10k +12V FROM IGNITION SWITCH 10 ZD1 16V 1W IN 100 16VW Rev limit indicator for rally cars For racing and rally vehicles, knowing precisely when to change gear can give you the edge in competition. While a tachometer will give a reliable indication of the engine revs, it is not always easy to read when there is a lot of action going on outside the wind­screen. This rev limit indicator will provide a warning light above a preset RPM. The light is located in a position which is in­ stantly noticed by the driver, so that the gear changing point can be indicated without looking at the tachome­ter. The circuit takes the RPM signal from the negative (switched) side of the ignition coil. This means that the circuit will operate from any type of ignition system whether driven by Car courtesy light monitor & extender This circuit monitors the on-time of your car’s interior light. If the car door is left ajar, the light will be switched off after a preset time. This prevents an “early-morning” flat battery due to the interior light(s) being left on all night because a door has not been shut properly. 32  Silicon Chip REG1 7808 GND 10k 1k 1 10k 100k 5 10 FILTER 2.2k 1M 6 7 IC1b 12V INDICATOR Q2 BD681 B E 4 REV LIMIT VR1 2k C LAMP DRIVER COMPARATOR INVERTER OUT 10 16VW PLASTIC SIDE B +8V E C VIEWED FROM BELOW E C B I GO points, Hall Effect sensor, reluctor or optical pick-up. The 33kΩ and 10kΩ resistors divide the voltage from the coil and high frequency spikes are suppressed with a .01µF capacitor. The signal is then AC-coupled to the base of transis­tor Q1, while diode D1 clamps negative swings of the input sign­al. The collector of Q1 will normally be high and will go low whenever the coil fires. Q1’s pulse output is inverted by IC1a, a comparator connected as an inverter. Pin 3, the non-inverting input, is referenced to about half the supply voltage using two 10kΩ resistors across the 8V rail. A small amount of positive feedback is applied to pin 3 using the 100kΩ resistor from pin 1. This increases the hysteresis to prevent high frequency oscilla­tion at the switching point. A 1kΩ resistor is used as a pullup between pin 1 and the +8V rail since these comparator outputs are open collector. A 10kΩ resistor and 10µF capacitor filter the signal from pin 1. The higher the engine RPM, the higher the filtered voltage which is fed to pin 5 of comparator IC1b. Here, the reference voltage for the inverting input (pin 6) is set by the 10kΩ resistor and trimpot VR1, which determines the rev limit. When the output of IC1b output goes high, at the rev limit, transistor Q2 is turned on to drive the indicator lamp. The circuit is powered via an 8V regulator which is pro­tected against voltage transients using a 10Ω resis­tor and 16V zener diode. Note that the lamp is powered directly from 12V rather than the 8V regulator output. VR1 is adjusted so that the lamp lights at the desired gear change point. SILICON CHIP In addition, an on-time extender has been incorporated into the circuit. This ensures that the interior light stays on for seven seconds after the door has been shut. When the car door is opened, S1 closes and capacitor C1 begins to charge via R4 (1MΩ). At the same time, pin 3 of IC1a is pulled low and so its output at pin 4 switches high. This in turn holds Mosfet Q1 on via D2, inverter IC1d and paralleled inverters IC1e & IC1f. Q1 in turn drives the courtesy lamp. If the door is left open, C1 continues charging and eventu­ally pin 1 of IC1a is pulled high. When this happens, pin 2 of IC1a switches low and Q1 and the courtesy lamp turn off (after approximately 70 seconds). IC1b, IC1c and their associated parts provide the on-time extension feature. When the R2 1k door is opened, +12V C3 pin 3 of IC1b is ZD1 100 also pulled low and COURTESY 9.6V 16VW R3 R4 LAMP so its output (pin 33k 1M IC1e Q1 4) switches high IC1a C1 D2 11 10 BUZ71A 40106 100 R6 and discharges C2. 1N4148 IC1d 14 16VW 220  9 2 8 1 When the door is IC1f subsequently shut, 13 7 12 R5 pin 4 of IC1b goes D3 100k 1N4148 low again and C2 C2 IC1b IC1c begins charging via 47 3 5 4 6 R5. R1 16VW D u r i n g C 2 ’s 470 charging period, Note that this circuit is designed for the input to IC1c is negative earth elec­trical systems, with D1 1N4148 low and so its pin 6 the door switches in the negative line. output is high. This It will have to be modified for positive DOOR S1 holds Q1 on via D3, earth vehicles, or for vehicles with the IC1d, IC1e & IC1f. full battery voltage is applied to the door switches in the positive line. When C2 charges, interior light. D1 and R1 isolate the The prototype was built on a small after about seven seconds, pin 6 of IC1c circuit from any other circuitry (eg, piece of veroboard. This was wrapped switches low again and Q1 turns off. a door ajar alarm), while R2, C3 and in insulation tape and installed in the A BUZ71A pow­er Mosfet is used ZD1 filter spikes from the vehicle’s roof lining, next to the interior light. as the switch to reduce heat dissipa- electrical system that might cause false D. Harvey, tion and to ensure that virtually the triggering or destroy the IC. Stanthorpe, Qld. $30 +5-15V 100 470k 6.8k TOUCH PLATE 0.1 470k 10k 2 IC1a 3 LM324 .0047 1 10k 6 5 IC1b 7 10 Q D1 1N4148 9 220k C2 1 10 4 IC1c 11 3.9k 47 33 Touch sensitive switch uses a single IC This simple circuit uses one quad op amp (IC1a-IC1d) and a few minor components to make an effective touch sensitive switch. As shown in the circuit, the non-inverting inputs of all the op amps are biased to half the supply voltage (ie, ½Vcc). At the same time, the DC bias at the inverting input of IC1c (pin 9) is considerably less than this figure. This bias is de- 12 IC1d 14 Q 10k D2 2.7k 8 13 1N4148 rived from the junction of the 3.9k and 2.7kΩ resistors and is applied to pin 9 of IC1c via a 10kΩ resistor and diode D1. IC1c is wired as a comparator. As a result, its pin 8 output is normally switched high and so pin 14 of comparator IC1d is normally low. When a finger is applied to the touch plate, the increased hash and hum is greatly amplified by op amp stages IC1 & IC2. These two inverting amplifier stages both function with a gain of 47. The amplified hum signal appears at pin 7 of IC1b and is rectified by D1 & D2 and filtered by C2. As a result, the voltage on pin 9 of IC1c now exceeds the bias on pin 10 and so pin 8 of IC1c switches low. This in turn means that pin 14 of IC1d switches high. This output can be used to turn on a transistor to drive a relay or sound a buzzer, or used directly to switch external circuitry. The resistors across D2 & C2 increase the settling rate and make for cleaner switching. The switching time is approximately 100µs. Bill Jolly, Tranmere, SA. ($30 September 1995  33 SERVICEMAN'S LOG What’s happened to service backup? I have a rather mixed bag this month, ranging from an el cheapo, downmarket TV set to an allsinging, all-dancing, state-of-the-art model with more bells and whistles than are ever likely to be used. Neither set was an easy exercise. The first story concerns a 34cm portable colour TV set made in China and marketed under the Vision brandname (model VIS-146R). It is not only a story of technical problems, although it has its share, but also one of woefully ineffective backup and support for imports from this part of Asia. More on that later. The technical problem, as described by the owner, was simply a form of frame collapse or, as he put it, “after the set’s been running for a while, a black band comes down from the top and up from the bottom.” Well, there’s nothing new about a complaint like that. And, while I had no data of any kind for this set – it was the first one I had seen – I didn’t imagine that it would a particularly difficult fault to fix. On the bench, the set behaved exactly as the owner had said. It performed normally for about 10 or 15 minutes then suddenly went into the fault condition. Fortunately, even without a circuit, the vertical system appeared to be fairly conventional and based on a 7-pin IC (IC205, a TA8403K). After taking some voltage measurements around this IC, in both the normal and fault conditions, and checking associated components, I concluded that the IC was faulty. Unfortunately, my regular spare parts supplier did not list this IC, so I approached another organisation who were supposed to be the agents for this set. And this was the first hurdle. When I identified the set and nominated the IC type number, I was promptly informed that that IC was not fitted in that set. 34  Silicon Chip And in vain did I emphasise that I had the set on the bench and the IC in my hand. “Aw no, it can’t be”, was the only re­sponse I could get. There followed quite an argument, which culminated in a grudging offer to investigate and ring me back. Of course they didn’t and I had to follow up with several more phone calls, only to be shoved around from technician to storeman and back again. The upshot was that, while tacitly admitting that I had correctly quoted the number in the set on my bench, they suggested a substitute unit, LA7830. And they quoted a price of something over $20. I said, “thank you very much; I’ll let you know”. And there was a very good reason why I didn’t immediately place an order. I was familiar with the LA7830 and I knew that my regular supplier stocked it. More importantly, he listed it at about half the quoted price. So the replacement IC was duly acquired and fitted. And that fixed the fault; the set came good immediately. I gave it a thorough workout for the next week or so (the owner had stressed that he was not in a hurry) and, in view of subsequent events, I was very glad I did. During the test week, however, it didn’t miss a beat, in spite of all the abuse I could heap upon it. And so it was duly collected by the owner. That was the last I heard of it for the next couple of months. Then the owner was on the phone with the bad news; the set had failed again with the same fault. He was quite reasonable about it – almost apologetic – but it was a bit of a shock to have the set bounce. I asked him to bring it in immediately. On the bench, the set did appear to be exhibiting the same fault – at least superficially. And it even fooled me at first. But it wasn’t exactly the same. I recalled that the original fault had been quite predictable in its onset; it would appear every time within 10 or 15 minutes of switch-on. Not so now. Sometimes the set would run perfectly for hours, then suddenly go into fault condition. At other times it was in fault condition at switch-on. My suspicions aroused, I made a check around the previous culprit, IC205. There were none of the voltage changes which had lead me to this component be­fore. But there was one change, not evident on the previous occasion. The supply rail to the IC was normally 25V but now, in fault condition, it dropped by about 3V. Another IC fault? Not very likely I felt, since the IC gave no sign of overheating. So was it a fault in the power supply, or somewhere along the line to the IC? That was probably the explanation but it was time to call a halt. I wasn’t prepared to go any further without some service data – a circuit diagram at the very least. A sorry tale And that brings me to hurdle number two – and a sorry tale it is. I approached the aforementioned agents and asked what they could provide. The best they could offer was a circuit diagram. I was prepared to settle for this and they promised to send one. When it didn’t arrived in a reasonable time, I rang them to see what the problem was. They made some vague excuses about a shortage but my impression was that they had forgotten all about it. They promised to chase it up but it still didn’t arrive and further phone calls over several weeks pro- duced further vague excuses. Finally, after some fairly straight talking on my part, a circuit arrived. But – you’ve guessed it – it was the wrong circuit. In fact, it was nothing like the set on the bench. It took several more phone calls (and related excuses) before the correct circuit turned up – for what it was worth. My guess is that it was about a 10th generation photocopy, made via a couple of pretty grotty copying machines along the way. It was almost completely unreadable with component values, type numbers, identification symbols, voltages (such as there were) IC pin numbers and any lettering all just blobs. The best I could do was try to relate actual component type numbers or values with the blobs on the circuit and see whether they seemed to match. In most cases, it was guess work more than anything. And that was all I had to work with. Granted, it was better than nothing, in the sense that I could at least follow the general circuit trend which all seemed fairly conventional. Well, that was something. Power supply checks So back to the fault. Following up the lowered 25V rail clue, I checked the main HT rail. With the set running normally, it sat at about 120V but in fault condition, this dropped to around 93V, although this figure varied somewhat. OK, so we had a main power supply fault. And this fitted in with another earlier observation. When the vertical deflection decreased, so did the horizontal scan (though less obviously) – something that suggested a common fault. The power supply appeared to be quite conventional and very similar to some used in Samsung sets. And it used the same common IC, an STR5404. Well, that was a small plus. I turned the set on and waited for the first sign of the fault. When it appeared, I began prodding around the board, hoping to get some kind of a lead. And I did; the board was extremely sensitive, particularly around the IC. In fact, the IC itself appeared to be the most sensitive. My next trick was to try a spot of freezer on the IC while the set was in fault condition, taking great care to keep the freezer off any other components. Result – an instant cure. And it worked every time. I carry this IC in stock and, with only five pins involved, it took only a few minutes to fit a new one. My self-confidence was shattered immediately at switch – there was absolutely no improvement. In fact, I soon established that I could cure the fault by spraying the new IC or any component on the board. I was back to square one. Well, not quite. All these observations added up to a strong suggestion of a dry joint or a hairline crack in a copper track. I pulled the board out again and went over the copper side with a magnifying glass. And in spite of a careful inspection, I could find nothing even vaguely like a faulty joint. But there had to be a fault in there somewhere, so I decided on a brute force approach – go right over the board and resolder every joint. Yes, I know, it takes time and may also dent one’s ego a little but it is often the most effective approach. And it certainly was in this case. It took me about 20 minutes to do the job – and I could have spent more time than that just prodding and pondering – and it cured the fault. And when all is said and done, that was the purpose of the exercise. Another intermittent Naturally, I gave the set a good workout over the next few days and nothing I could do would produce the fault. But it wasn’t the end of the story. During this procedure, I became aware of another fault – also intermittent – which the owner had apparently not September 1995  35 of that set or any of it brethren. In fact, another one turned up a few weeks later but I had to say “sorry, I can’t service it”. And I went on to explain the problems of obtaining data and other technical back­up. And unless those concerned can get their act together, I suspect other servicemen will be forced to adopt the same atti­tude. The snack Fig.1: the IF and stereo sound decoding circuitry in the Sony KV2764EC. IC102, which contains the FM detector, is at top left, with L111 between pins 9 & 10 and L105 and C124 between pins 7 & 8. noticed and which I hadn’t noticed either in the confusion associated with the original fault. Now that I could watch the screen in a more relaxed manner, I suddenly became aware that there was a loss of blue in the pic­ture from time to time. The effect could be somewhat subtle at times, depending on the overall colour content, but it was defi­nitely happening. This part of the circuit is quite conventional. Three drive transistors – red, blue and green – on the neck board feed the three picture tube cathodes and, in turn, are fed from the PAL decoder IC on the main board. My first reaction was to suspect the blue drive transistor. This is a common type, a BF422, and it was easy enough to replace it with one from stock. But no joy, the fault remained. Next, I checked the voltages, particularly the base voltag­ es, around all three transistors, first while the set was normal, then when the fault appeared. Under normal conditions the reading on all three bases was about 4V but, in the fault condition, 36  Silicon Chip this was something less the 2V on the blue base. The base of this transistor connects to a 2.8kΩ trimpot, used for colour balance adjustment, and from there to the main board and the PAL decoder blue output. However, there are two more components in the line: a small RF type choke and a 100Ω resistor. Tracing this line showed the low voltage at the connection to the main board but the correct voltage at the PAL decoder. By then retracing the line from the decoder, I found the correct voltage up to and beyond the 100Ω resistor but not beyond the choke. I checked the choke’s soldered joints very carefully but they appeared to be perfect. Nor could I find anything wrong with the choke when I pulled it out and tested it. As a result, I refitted the choke, this time taking particular care with the soldering. And that was it. It took me several days of constant monitor­ ing to be quite sure but the fault was fixed. And it has remained fixed for several months now. So I hope that is the last I shall see Well, after all that, a change of pace is called for. Here are some shorter stories; stories I have been holding back for some time, due to space problems. And the first one is something of a reversal of the usual theme. One of my common themes is the fault which looks like a snack but turns out to be a real stinker. In this case, it was a strange new fault which I thought would be a stinker but which turned to be much easier than I expected, if only by good luck. It concerns a Sony KV2764EC colour TV set (PE-3 chassis) and the owner complained that there was very little or no sound when operating the VCR, although there was plenty from the chan­nels on the TV set. It had started by being intermittent but was now permanent. The set was too heavy for the owner to carry it in by himself, so we brought it in together, placed it straight on the bench, and connected a VCR to it in the usual manner. In some perverse way, and in spite of my apprehension, I was actually looking forward to seeing this fault because it sounded like a challenge. When the owner first mentioned the trouble I had thought he may have connected the VCR incorrectly to the audio and video connections of the 21-pin (SCART) socket on the rear. Or perhaps he suffered from finger trouble and had pressed the wrong buttons on the TV set. But he turned out to be an intelligent bloke, in­trigued as much as I was by the fault. More importantly, he was fortunate enough to have two VCRs. So, when he first noticed the fault, he swapped them around but to no avail. Then he tried swapping the video RF output from Ch1 to Ch0 and retuning the TV set to it. Still no luck. Not only was the sound weak when playing tapes but also when selecting the stations on the VCR’s own tuner (sometimes called the EE mode). And, alter the fault again. I even tried changing the IC, a TDA2546A, but no joy. I noticed the freezer seemed to have more effect around the end near L111 and L105, where there also happened to be a 470pF styro capacitor C124. I pounced on this because this type of capacitor has a habit of changing its characteristics. I gently squeezed and moved C124 whilst the set was on and was rewarded by a momentary change in sound level. That was enough; I changed it for a new one and the sound was restored. I phoned Sony technical support on another matter and in the course of the conversation told them about this fault, only to find that this is a common one and the styro is now replaced by the higher grade gold version! I guess I should have phoned them first. Anyway, the customer was as delighted as I was and departed as happy as a sand-boy. But I have to thank lady luck. The super Mitsubishi as I soon discovered, the situation was no better with my VCR which used an RF output on UHF Ch37. Next I tried using the video-in/ audio-in connections via the SCART socket. Ah-ha, plenty of sound, so it must be some sort of RF/IF problem. But why on earth was it discriminating against VCRs? Didn’t this set like them or something? More realistically, what was the difference between an off-air TV station and a VCR? The shape of the sync pulses? No – it took a while but the penny finally dropped. All our TV chan­ nels transmit in stereo, using the German Zweiton or two-tone system. But a VCR always transmits in monaural sound, probably because it is too expensive to provide stereo modulation. So the set was discriminating between a stereo transmission and a monaural one and was muting the latter for some reason. I confirmed this to some extent with an RF signal generator but, not having a stereo generator, I tried attenuating a TV channel until the stereo light went out, which dropped the sound simulta­neously. But where was the fault? Was it in the tuner, IF, stereo decoder, or audio logic circuits? Fortunately, all these areas, except the last, are located on board “A”. I decided to start working from the decoder and move out from there. The two inter­carrier signals at 5.5MHz and 5.74MHz are fed into IC151 and IC152 where they are decoded. I began by measuring the voltages around these ICs and found them close to those shown on the circuit. But I was getting a gut feeling that I should concentrate on the 5.5MHz signal which is the usual monaural signal (L+R) rather than the 5.74MHz signal (2R), used for stereo only. This focused my suspicion to IC102 which contains the FM detector. I decided to hit the components in this area with the hot and cold treatment, on the off-chance of a clue. I was lucky – the freezer momentarily brought the sound up but it quickly disappeared and heating or freezing the components around the IC didn’t It wasn’t much later when I encountered a similar fault to this involving a Mitsubishi CT-2553EST, fitted with an E4-Z chas­sis (very similar to the AS2M chassis). This is one of the newer generation, all bells and whistles, super-deluxe models, boasting just about every feature you can think of, including a multi-standards facility (PAL, NTSC and SECAM). It’s is all very clever but I do wonder how often these features are used, or even understood, by the average person. Of course, it makes for a beaut sales pitch but it means a higher price tag and, more to the point, much greater complexity when trying to service the monster. And so it was in this case. A major problem in this set is access; trying to take measurements on the main board and the modules while the set is on is a very dodgy procedure. The leads are very tightly dressed in a wiring loom, preventing the board from being easily inverted, while the plug-in modules are just too close together for examination. And to unplug them is a major operation! Anyway, the complaint amounted to intermittent loss of luminance; ie, a ghostly, over-saturated, dark picture. It was clearly a job for the CRO and we started from pin 10, video out, of the VIF pack, IP1A1, on the main board, September 1995  37 Fig.2: a corroded track in the 12V supply line to transistor Q254 caused the original loss of sound in the Mitsubishi CT2553EST. Note that the 12V rail comes in on pin 3 of socket VC2 at lower right. PCB-MAIN. There was nothing wrong here, the CRO showing a very clean composite wave­form. OK, but which way next? What follows from here is a bewildering maze of video switching circuits but I managed to trace it, eventually, to PCB-Y/C-SW, via plug/socket VS3, thence through transistors Q2P1 and Q2P2, IC2P1 and Q2P3. From here, despite many blind alleys, I traced the signal to PCB-VC/RGB-CTI via plug/ socket YS1 and thence to the emitter of Q254, where the trail became cold, or rather distorted. The collector voltage of Q254, shown as 11.9V, was very low. This is derived from a 12V rail coming in on plug/socket VC2-3 and which was correct at that point. I was getting close. To cut a long story short, after much bad temper, due to the awkward access to this module, I traced the 12V copper track around the edge of the board. Near the top, it disappeared under that horrible brown glue which I have mentioned in these notes in the past and which the Japanese are so fond of using to anchor parts. Hasn’t anyone ever told them – or don’t they listen? I’m still finding this glue in near new sets. Anyway, as usual, the glue had hardened, changed colour (darkened) and corroded the copper track, changing it, effective­ly, into a high value resistor. I linked the break and 12V was restored, along with the luminance. It all sounds so simple but it meant taking the module out, measuring and working on it, and replacing it a number of times. This was a very slow and weari­some process . And that should have been the end of the story. Unfortunate­ly, after reinstallation at its home with its VCR, it bounced. Yes, you’ve guessed it; intermittent no sound, or rather very little sound, from the VCR. Unfortunately, I sensed that the owner wasn’t very happy. He didn’t say much; it was rather what he didn’t say that alerted me. It was obviously a different fault, for which I was not to blame, but it was too difficult to argue at that stage. Fig.3: the TU1A1 U/V TUNER and IP1A1 VIF-PACK are only available as a combined pair in the Mitsubishi CT2553EST. The VIF-PACK is prone to dry joints around the filters, coils and the SAW filter. 38  Silicon Chip I confirmed it was OK through the audio/video sockets and I was half-tempted just to supply suitable leads and leave it at that (no, not seriously)! But my reputation was at stake. Since I was – apparently – the one who had wrecked a beloved set, I had to be sure I “fixed it proper”! As with the Sony, I started at the decoder, located on the PCB-SOUND board, and went straight to IC3001, a TDA3803A. I have had a lot of trouble with the TDA3800G which was used widely on earlier models, especially JVC. But changing this made no dif­ ference and I moved to IC3000 and its associated circuitry. I examined this very carefully, particularly capacitor C3002, which plays a similar role to C124 in the Sony circuit. But everything checked out OK and wouldn’t succumb to the hot and cold treat­ment. The next major suspect was the previously mentioned VIF-PACK IP1A1. I have had a lot of trouble with this module over the years, including a variety of intermittent faults, mainly video, and everything from no picture to patterning, or snow on UHF only. And you cannot purchase a new module by itself. Instead, it is part of a (very expensive) matched pair consisting of Tuner TU1A1 and VIFPACK IP1A1. I unsoldered the module and examined it. Normally, it is very prone to dry joints everywhere but more so around the filters, coils and the SAW filter. But this set had already been worked over so I reinstalled it with the covers off. I switched the set on and tried freezing the ceramic filters, something that is not usually recommended as it can sometimes damage them. In this case it made no difference. I then tried a trick I learned from a colleague some time ago; running a moist finger over the circuit. (Don’t try this trick unless you’re very sure you know what you’re doing; par­ ticularly on a live chassis!) It was his extension of the tradi­tional bash and prod, wobble and twist, hot and cold techniques, often needed as a last resort to pinpoint a difficult fault – particularly one involving a change in a characteristic, rather than a clean cut failure. I had tried it a couple of times before without any luck. But this time it worked. I noticed a change in the sound level when touching around the 5.5MHz ceramic filters X3 & X4. The module was removed again and two new filters fitted. And that was it; sweet success – the sound level was back to normal. Apparently, one of the filters was faulty and off frequen­ cy. My finger on the board pattern was re-tuning it slightly. Once again I was lucky. And, hopefully, my reputation had SC been restored. Especially For Model Railway Enthusiasts Includes 14 projects for model railway layouts, including throttle controllers, sound simulators (diesel & steam) & a level crossing detector. Price: $7.95 plus $3 for postage. Order today by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or send cheque, money order or credit card details to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. September 1995  39 Rail p A Walk-A 40  Silicon Chip power MkII: Around Throttle For Model Rail­ways Want to build a walk-around throttle for your model railway? This completely new design offers all the features you could want, including pulse power, pushbutton control, track voltage metering, inertia (momentum) and full overload protec­tion. By RICK WALTERS September 1995  41 S MAIN FEATURE ­piece. tions on the hand nc fu l al ith w l • Walkaround contro eed operation. d reliable low sp an th oo sm r fo d regu• Pulse power r excellent spee fo F M -E ck ba or • Monitoring of mot n. d the latio as though it ha untts ac el od m entum) so hed off for sh • Inertia (mom ertia can be switc in n; ai tr al re a weight of dible ing. g visible and au in ud cl in n, tio ec • Full overlo. ad prot rs indicato g thrown into events train bein pr t; ou ck lo e rs op. • Forward/reve st comes to a st reverse until it fir or ultimate s current speed e pressed. te ca di in g; in er met wer buttons ar • Track voltattge hen Faster or Slo w g in se d ee sp THE RAILPOWER MKII incorporates all the features of our very popular Railpower design featured in April & May 1988. While the original Rail­ power is still a valid design, the MkII version has a lot of new features. In spite of the extra functions, the new design uses less parts and is easier to build. How can that be? Just read on. The outstanding feature of our previous Railpower design was the use of pulse power and simulated inertia, allowing the train to move off from rest at a very low speed and accelerate very gradually, which looks very realistic. Another big feature is the concept of a walk-around throt­tle. This has all the functions on a hand control and allows you to follow your train all around the layout. Nor do you need a long cable which will get tangled up as you move around. You can have a number of sockets around the layout and you can plug into whichever socket is handy. And when you unplug the hand control in order to move it to another socket, the train carries on at its exact same speed setting, without any disruption. Hand control The hand control of the Railpower MkII features a small meter and six pushbut­t ons. These are labelled Faster, Slower, Forward, Reverse, Iner­tia and Stop. The latter four buttons have LED indicators to show the selected functions. 42  Silicon Chip The Forward and Reverse buttons are interlocked. If the train is moving forward and the Reverse button is pressed, the Railpower will switch to Stop, the Stop LED will light and the train will slow to a stop. The controller will then switch to Reverse and the Reverse LED will be lit. A similar sequence occurs if the Forward button is pressed while the train is trav­elling in the reverse direction. This overcomes a drawback of the original design and all other controllers that we know of – if you mistakenly throw a train into reverse while it is moving at a reasonable speed, it will be derailed. The Stop button, when pressed, will bring the train to a realistic but reasonably rapid halt. The braking time is adjusted by the “brake” trimpot (VR2) on the main PC board. If you are shunting wagons, the inertia function can be a hindrance. Hence, it can be switched out, by pushing the Inertia button, if the train is stopped or running at a low speed. Once switched out, Inertia can be switched back in at any time. Railpower controller Apart from the hand control, the Railpower MkII consists of a plast i c case containing a PC board which has all the com­ ponents mount­ ed on it. There is no transformer as we have assumed that the typical model railway enthusiast already has a self-contained power supply which can be hooked up to the Railpower. We’ll talk more about this aspect when we discuss construction. The front panel of the Railpower is bare except for six LEDs. These echo the LEDs on the hand control and add two others, one for Power and the other to indicate Overload (short circuit). +5V 5 M1 500uA 450W 2 çç 3 10 10k METER ZERO VR1 5k 560 16 4.7k 15 4.7k 7 14 13 6x1N914 8 D3 0.1 D6 STOP S6 12 A B O0 IC1 74HC42 C O2 D O3 8 4 O1 1 K  2 3 4 LED1 RED K A K A  K A  A  LED4 ORANGE LED2 GREEN LED3 YELLOW gradually increases (assuming that the inertia setting is large) the meter reading will increase to reflect this. If the Faster or Slower button is pressed, the meter will momentarily indicate the previous selected speed setting and then move up or down to show the new setting. The new speed setting is only indicated while the buttons are actually being pressed. Micro-speak for modellers REVERSE S3 For many readers and railway modellers, this might be the first time you have come “face to face” 6 with a microprocessor. Never INERTIA FORW'D K D2 D4 A S5 S4 fear, it’s just a smarter IC than those you may have used before DECEL ACCEL but otherwise it’s just another S2 S1 1 black inscrutable chip. In essence, this Z8 micro is 8-PIN RAILPOWER MKII HAND CONTROL DIN PLUG only a bunch of counters and gates, crammed into an 18-pin Fig.1: the hand controller circuit is based on IC1, a 74HC42 BCD decoder. This chip is used to indicate four modes of operation (via LEDs1-4) with only two lines from IC package. The big advantage is the microprocessor. The meter indicates both the track voltage and the selected that we can control the logic in speed setting when the faster or slower buttons are being pressed. a manner which suits each par­ ticular application. While there On the PC board, there are four halt much more quickly and the time are only a few leads to and from the trimpot adjustments: for maximum it takes is set by the brake adjustment processor, inside the chip we can have speed, minimum speed, inertia and trimpot. the equivalent of 50 or 60 gates and brake. The maximum speed setting is perhaps five counters interconnected. Low-cost microprocessor usually set to give the maximum rated These might give an output on just voltage for the particular locomotive. one pin, should a certain sequence of The design brief for the Railpower Typically, this is 12V DC for HO scale events occur. MkII was that it had to be easier to models but it can be lower for other Just as we use standard ICs (hardbuild than the previous version, it scales such as N or Z. The minimum had to have more features and it had ware) and interconnect them to obtain speed setting is determined by the to have all pushbutton operation. the circuit functions we require, a simquality of the locomotive’s motor. Very To achieve this, we have designed a ilar design process is carried out when good models may start to move with completely new circuit which uses using a microprocessor. The difference less than 1V across the track while oth- a low-cost microprocessor, the Zilog in this case is that the design relies on a ers may need 4V or more before they Z86E08. Now don’t be scared off be- set of instructions (software) stored in start moving. By setting the minimum cause the circuit uses a microproces- the internal ROM (read only memory) speed just below the point where the of the micro. sor. Have a read of the section headed loco starts to move, more realistic and “Micro-speak for modellers” and be Thus, each time we use the microrespon­sive operation is obtained. processor in a different project, we reassured. The inertia setting controls the store a different sequence of instrucThe Z86E08 (Z8, for short) comes time the train takes to accelerate to in an 18-pin package and contains tions in its ROM. maximum speed. This adjustment Before we go further, we should 2Kb bytes of OTP (one time programranges from zero to four minutes. mable) memory. Two pins are for V+ explain the pin descrip­tions for the At the maximum setting, a loco may and ground and two pins are for the microprocessor (IC1). It has three take more than one scale mile before crystal, while the remaining 14 pins groups of pins, called ports in computit reaches its selected speed, just like are all available for control functions. er jargon. These are port 0, port 2 and a real train. port 3, abbreviated to P0, P2 and P3. Using the processor allows us to Inertia applies to deceleration as carry out complex tasks which would P0 has three I/O pins (input/output), well as acceleration so a train will take P2 has eight and P3 has three. otherwise require lots of conventional approximately the same time to come Thus, pin 15 which is labelled P20 circuitry. The best example of this is to a stop as it took to reach its selected the meter in the hand control. During is Port 2 line zero (computer people speed setting. normal running, it indicates the speed, start counting from zero, not one like On the other hand, if you push the normal mortals). We have assigned from zero to 100%, at which the train Stop button, the train will come to a is actually travelling. As the speed this pin to be the one that turns the D1 D5 September 1995  43 44  Silicon Chip 8-PIN DIN SOCKET 1 7 3 2 6 4 8 5 12 13 14 D C B A 10 680W .047 22k METER SPEED MAX VR5 5k 10k MIN VR4 5k MAX VR3 5k 16 8 O3 O2 O1 O0 4 3 2 1 K K   A  A A 470  12 12 13 5 6 15 16 22pF 22pF X1 10MHz +5V INH VEE VSS 6 8 7 OUT/IN 3 IC4 A 11 4051 B 10 C 9 +5V ZD1 3.9V 12VAC INPUT 74HC11 14 2 12 IC3a 13 1 BACK EMF 16 VDD 4.7k LED2 GREEN LED3 YELLOW 3 13 0 15 2 14 1  LED4 ORANGE K A K LED1 RED BRAKE VR2 5k PO1 PO2 X1 X2 P20 P21 9 P32 P31 8 180k 0.1 IC1 Z86E08 5 VCC 10 P33 GND 14 17 P22 18 P23 11 PO0 4 P27 P24 2 P25 3 P26 MODE INDICATION INERTIA VR1 5k 10k IC2 74HC42 D3 1N914 15 0.1 10k Q10 BC338 D2 1N914 D4-D7 4x1N5404 +5V E C 2200 C 10 5V 10k B E C B 0.1 +5V  BUZZER +5V 0.1 10k E Q6 BD649 C B C Q2 BD650 E 1k B Q12 BC328 470  C E LED5 GREEN 22 Q9 BC338 E Q5 BC338 C 1.8k B CURRENT MONITOR 10k 22k 10k 6 OUT  7 IC3b IN914 10k B REG1 7805 B GND IN +17V E C LED6 RED 560  4 3 5 8 470  D1 IC3c RAILPOWER MKII 2200 Q11 BC338 B 22k 10k 9 10 11 Q1 BC338 10k E B C B PLASTIC SIDE E C VIEWED FROM BELOW E B 1k Q8 C BD649 B C 0.1  10k MOTOR Q4 BD650 E E C E C Q7 BC338 B 2.2k A B 10k Q3 BC338 K I GO +17V power to the track on and off. We did not have to use this pin; we could have used any pin on P2, or for that matter, P0. We could not use P3 as the pins on this port connect to two comparators, which are used to convert the analog voltages from preset potentiome­ters VR1-VR4 to digital values, which can be used by the proces­sor. Enough on micros, let’s get back to the main story. Hand control circuit The hand control consists of six pushbuttons, four LEDs, one IC (integrated circuit) and a few resistors, diodes and capacitors mounted on a small PC board measuring 74 x 50mm. The hand control connects to the Railpower via a 9-core cable (one unused) and an 8pin DIN plug. The circuit is shown in Fig.1. Supply rails of 5V and 0V are fed via pins 5 and 1 on the DIN connector to IC1, a 74HC42 BCD (binary coded decimal) decoder. Four outputs from IC1 are used to drive the four LEDs. It was necessary to use the IC as there were insufficient outputs available on the micro­processor. By using the 74HC42, the microprocessor only needs two lines to control four LEDs. Again, due to limited processor outputs and only eight pins on the connector, the six pushbuttons are accessed by three lines. We do this by using diodes D1-D6 which are connected in a simple matrix, allowing each button to pull one or two lines to 0V. As each line, or pair of lines, is connected to ground, it signals to the microprocessor the function required. Main board The main PC board contains four ICs, a 7805 regulator, 12 transistors, five trimpots and a handful of small components, mounted on a PC board measuring 143.5 x 108mm. The circuit is shown in Fig.2. Note the eight lines of the DIN socket. These connect to the hand control circuit of Fig.1. The best way to explain the circuit Fig.2 (left): IC1, the microprocessor, controls all facets of circuit operation. As well as driving the H-bridge circuit (Q1-Q8), it reads the buttons in the hand control, the settings of the trimpots (VR1-VR4) via IC4, the backEMF and the load current. As well, it drives the mode indicator (IC2) and the meter. Q1 BC338 10k B +17V Q2 BD650 E 1k B C E Q4 BD650 C B 1k C C MOTOR E IC3, Q9 Q5 BC338 C 1.8k B E Q3 BC338 B 10k E 10k Q6 BD649 C B 10k Q8 C BD649 B E C Q7 BC338 B 2.2k E E 0.1  Fig.3: the H-bridge circuit. This controls the speed of the motor (depending on the pulse width), as well as its direction. For example, to make the motor go forward, Q8 is turned on continuously while Q2 is pulsed on and off. For reverse, Q6 is turned on continuously and Q4 is pulsed on and off. is to go through the microprocessor start-up sequence. When power is first applied, the Z86E08 microprocessor executes a series of steps. First, it sets pin 15 low; ie, to 0V. This pin applies power to the track when it is high (+5V). Pin 16 is taken high to set the train direction to forward (low for reverse). Pins 17 and 18 are both taken low, which via IC2, another 74HC42 BCD decoder, illuminates the Stop LED. The same lines go to IC1 in the hand control to illuminate its Stop LED. It then takes pins 12 and 13, which control the output of IC4, low. IC4, a 74C4051 8-input analog multiplexer, is simply a switch which can route any one of eight inputs to its output (pin 3). With pins 10 and 11 low, the wiper of the maximum speed trimpot, VR3, is connected via IC4’s output to pin 9 of IC1. The microprocessor converts the voltage on the wiper to a digital value which it stores. Pins 12 and 13 of IC1 are taken high and low in sequence and the voltages from trimpots VR1, VR2 & VR4 are subsequently read and stored. IC1 has now finished its “power on routine” and is ready to look at the hand control, to see if a button has been pressed. motor drive circuit which is known as an “H-bridge”. This consists of four Darlington transistors – Q2, Q4, Q6 & Q8 – and these are driven by buffer transistors Q1, Q3, Q5 & Q7. To explain this part of the circuit better, we have reproduced it in Fig.3. The H-bridge circuit does two things. First, it switches the power on and off to the motor. The rate of switching is 150Hz and the voltage fed to the motor is directly proportional to the width of the pulses. Second, the H-bridge allows the direction of the motor to be reversed, depending on which transistors are actually turned on. In this case, to make the motor go forward, Q8 is turned on continuously while Q2 is pulsed on and off. Q4 & Q7 are turned off. To make the motor go in reverse, Q2 & Q8 are turned off, Q6 is turned on continuously and Q4 is pulsed on and off. Transis­tors Q1 & Q3 ensure that the Darlington transistors Q2 & Q4 turn on hard (ie, saturate) so that their power dissipation H-bridge motor drive Before we discuss this operation, let’s look at the September 1995  45 Myths & Magic of Pulse Power Pulse power as used in the Railpower Mk I & MkII circuits is quite different to that used in some commercial train con­trollers. In the Railpower, the voltage is applied to the track in pulse form at 150Hz. At low speeds, the pulses are very short and high speeds, the pulses are much longer. This is very similar to the system used in switch-mode power supplies and is highly efficient. However, the reason we use this pulse power system is to get more reliable running. Because the peak voltage applied to the track is about 17 to 18V at all speed settings, it is much more effective at overcoming resistance due to dirty track, dirty motor brushes and commutators. The result is really good slow speed operation which means that your trains will look much more realistic. It’s magic. On the other hand, some modelling enthusiasts believe that pulse power can make motors run hot and can even burn them out. This is not true and there are a number of factors which ensure that pulse power does not damage model locomotive motors. First, virtually all motors used in model locomotives are permanent is minimal and small heat­sinks can suffice. More importantly, Q1 & Q3 per­form voltage translation of the 5V logic signals to Q2 & Q4 which have a supply voltage of +17V. Q5 & Q7 ensure that their respec­tive Darlingtons, Q6 & Q8, turn on fully. Having described how the H-bridge works, we can now see how it is controlled by the micro, IC1. As we stated previously, to select the forward direction, pin 16 of IC1 goes high, taking pins 1, 2 & 13 of AND gate IC3a high. IC3a is used simply as a non-inverting buffer, so its output at pin 12 is also high and thus Q7 & Q8 are turned on. The output of IC3a also turns on Q9 which pulls its collec­tor to 0V. This will turn Q5, and thus Q6, off. Pin 15 of IC1 is the pulse drive (150Hz) signal and this is fed via AND gate IC3c to turn on Q1 & Q2. Q9 also pulls pin 46  Silicon Chip magnet or series wound motors. In both types, the torque generated is proportional to the average current through the windings while the heating effect is proportional to the RMS value of the current. Now because we are using pulse power and the RMS voltage will be slightly higher than the average value, particularly at low speed settings, then it might be supposed that the motor’s winding would get hotter than if pure DC was applied. In practice though, two things come to the rescue. First, the motor’s inductance tends to reduce the current drain when the speed settings are low, due to the very narrow applied pulses. Second, because the narrow pulses are actually much more effec­tive in making the motor rotate and thus moving the locomotive forward, the motor then generates more back-EMF than it otherwise would with a low value of DC and thus the current is actually reduced. So in practice, the difference in motor dissipation between the unfiltered DC of most controllers and the pulsed DC of the Railpower is negligible. The big danger of motors burning out is if the motor stalls due to a bind- 5 of IC3b low, via diode D1, and this means that output pin 6 will be low, turning off Q3 & Q4. To reverse the motor, pin 16 of IC1 goes low, so pin 12 of IC3a is low, turning off Q7, Q8 & Q9. This allows Q5 & Q6 to turn on and the pulse signal from pin 15 of IC1 passes via IC3b to Q3 & Q4. Overload protection Note that the emitters of Q6 & Q8 are connected via a common 0.1Ω resistor to the 0V line. This resistor is used to monitor the current supplied to the track. If there is a short circuit across the track, the voltage across this resistor will increase. This voltage is applied to transistor Q11. If the voltage across the resistor rises above 0.6V, Q11 turns on, lighting LED 6 (overload indicator) and also turning on Q12, which drives the buzzer to give an audible indication of the short. ing gear system. This risk applies to any model train controller, not just the Railpower. Pulsed DC is also reputed to cause more motor noise than with pure DC. This tends to be true, partly because the Railpower allows the loco to run at a much lower speed than would be possi­ble with unfiltered or pure DC across the track. At these much lower speeds, the motor noise is more significant; at higher speeds, the motor noise is drowned out by gear noise and wheel/rail noise. Motor noise is also dependent on the quality of the gear systems and it can be amplified by locos of brass construction. Overall though, pulsed DC as used in the Railpower gives signifi­cantly better running, greater realism and more reliable opera­tion. However, coreless motors, such as those branded Portescap or Escap, should not be used with pulsed DC as they have very little inductance and generate very low back-EMF. These motors should only be used with pure DC train controllers. However, these motors are not generally used in model locomotives and so will rarely be encountered. Not only do we get a visible and audible indication of the short but the system goes further and shuts down the voltage on the track, so that no damage can occur. This happens in the following way. As pins 4 & 9 of IC3 are connected to Q11’s collector, they will also be pulled low when Q11 turns on. This will turn off the power to the motor, whether it is running forwards or is in reverse. As there is now no voltage applied to it, there can be no current flow through the resistor and consequently Q11 will turn off. Power will be re-applied and the whole sequence will repeat until the short circuit is removed. We have previously stated in the description that pin 15 of IC1 goes high to run the motor. Actually pin 15 goes high every 6.5 milliseconds, for a time dependent on the adjustment of VR4, the minimum speed setting. If the operator presses the Faster button on the controller, the pulses from pin 15 are longer, effectively putting a higher voltage on the track. Similarly if the Slower button is pressed, pin 15’s pulse output will become shorter, reducing the average track voltage. Speed regulator & back-EMF As a model train comes to a gradient, it will tend to slow down, the speed reduction being dependent upon the motor’s power and the slope. In severe situations, the train might even stop and this is not very realistic. Our circuit compensates for the extra load on the motor by increasing the voltage to the track so that the speed setting is maintained more or less constant. How is this done? By measuring the back-EMF of the motor and using it to control the micro, is the quick answer. All electric motors generate a “backEMF” which is the voltage which opposes current flow through the motor windings. If the motor speed is high, the back-EMF is high and current will be low. If the motor is stalled, the back-EMF will be close to zero and the current will be very high. So how do we measure the motor’s back-EMF while it is running? It turns out that this pulse power system makes it fairly easy and we measure the back-EMF in the periods when the voltage applied to the track is zero; ie, between each pulse on pin 15. We monitor the motor’s back-EMF by means of the 10kΩ resis­tors connected to either side of the motor. While one side of the motor is always close to 0V (depending on whether Q6 or Q8 is off), the opposite side will always have the track voltage ap­plied to it and thus one or other of the 10kΩ resistors will feed the voltage to the collector of Q10, then through D2 and the 180kΩ resistor to pin 8 of IC1. The capacitor on this pin filters this voltage. Now the trick is to make sure that the voltage fed back to IC1 is the backEMF and not the track voltage. This is done by turning on transistor Q10 via the pulse line, pin 15, of IC1. Thus, each time a pulse appears on the track, Q10 is turned on to short the anode of D2 to the 0V line. Hence, the signal applied via D2 to pin 8 is a sample of the motor-back PARTS LIST HAND CONTROL 1 PC board, code 09109952, 74 x 50mm 1 plastic case, (Jaycar HB-6032 or equivalent) 1 8 pin DIN plug (Jaycar PP0312 or equivalent) 1 500uA FSD edge reading meter (DSE Q-2110 or equivalent) 2 yellow PC mount momentary switches (Jaycar SP-0722 or equival­ent) 1 red PC mount momentary switches (Jaycar SP-0720 or equivalent) 1 black PC mount momentary switch (Jaycar SP-0721 or equivalent) 1 white PC mount momentary switch (Jaycar SP-0723 or equivalent) 1 green PC mount momentary switch (Jaycar SP-0724 or equivalent) 1 5kΩ horizontal trimpot (VR1) Semiconductors 1 74HC42 BCD decoder (IC1) 6 1N914 signal diodes (D1-D6) 1 3mm red LED (LED1) 1 3mm green LED (LED2) 1 3mm yellow LED (LED3) 1 3mm orange LED (LED4) Capacitors 1 10µF 50VW electrolytic 1 0.1µF monolithic Resistors (0.25W, 1%) 1 10kΩ 1 560Ω 2 4.7kΩ Miscellaneous 1 cable clamp, Jaycar HP-0718 or equivalent 1 12mm x 2.5mm countersunk screw 1 2.5mm nut 2 #8 x 10mm self tapping screws 1 8mm untapped spacer 2 5mm untapped spacers MAIN BOARD 1 PC board code 09109951, 143.5 x 108mm 1 plastic case, 140 x 110 x 35mm (Jaycar HB-5970 or equivalent) 1 8 pin chassis mounting DIN socket (Jaycar PS-0360 or equival­ent) 1 10MHz crystal 1 PC board mounting buzzer (Jaycar HB-3458 or equivalent) 2 TO-220 heatsinks 5 5kΩ horizontal trimpots (VR1VR5) 3 metres 9-way cable (Jaycar WB-1578 or equivalent) 4 PC stakes Semiconductors 1 Z86E08 programmed OTP microprocessor (IC1) 1 74HC42 BCD decoder (IC2) 1 74HC11 triple AND gate (IC3) 1 74HC4051 or 4051B analog multiplexer (IC4) 1 7805 +5V regulator (REG1) 2 BD650 PNP Darlington transistors (Q2,Q4) 2 BD649 NPN Darlington transistors (Q6,Q8) 7 BC338 NPN transistors (Q1,Q3,Q5,Q7,Q9-Q11) 1 BC328 PNP transistor (Q12) 1 3.9V 500mW zener diode (ZD1) 3 1N914, 1N4148 signal diodes (D1-D3) 4 1N5404 rectifier diodes (D4D7) 2 5mm red LEDs (LED1,6) 2 5mm green LEDs (LED2,5) 1 5mm yellow LED (LED3) 1 5mm orange LED (LED4) Capacitors 2 2200µF 25VW electrolytic 1 22µF 16VW electrolytic 2 10µF 50VW electrolytic 4 0.1µF monolithic 1 .047µF MKT polyester 2 22pF NPO ceramic Resistors (0.25W, 1%) 1 180kΩ 2 1kΩ 3 22kΩ 1 680Ω 12 10kΩ 1 560Ω 1 4.7kΩ 3 470Ω 1 2.2kΩ 1 0.1Ω 5W 1 1.8kΩ Miscellaneous Solder, hook-up wire, plastic cable ties. September 1995  47 Although the circuit of the Railpower MkII is quite complicated, the PC board is relatively simple and has very little wiring. EMF, not the track voltage. The voltage at pin 8 is filtered by the 0.1µF capacitor, so that commutator hash does not give false readings. This voltage at pin 8 is compared with the desired setting and if the value starts to drop, due to the train slowing or the load increasing, the microprocessor increases the track voltage, to keep the loco running at a constant speed. Maximum speed setting Previously, we discussed VR3, the maximum speed adjustment, and described how it is used to set the maximum track voltage, to suit the locomotives being used. We also discussed the meter which has two modes, one to indicate the actual track voltage and the other, to indicate the track voltage being set by the Faster and Slower buttons. The meter is driven directly from 48  Silicon Chip pin 4 of the microprocessor, via trimpot VR5. During the setup procedure, trimpot VR3 is used to set the maximum track voltage and then VR5 is used to set the meter’s pointer to full scale, to give a 100% reading. In the same proce­dure, trimpot VR4 is used to set the minimum track voltage and trimpot VR1, in the hand control, is used to set the meter to zero. In practice, it will be necessary to do the adjustments for the various trimpots more than once, before they are correct. A 10MHz crystal is used by the microprocessor and is con­ n ected between pins 6 & 7, along with two 22pF capacitors to ensure the crystal oscillates reliably. Power supply No power transformer is included in the circuit as it is assumed that mod- elling enthusiasts will already have a suitable controller power supply or a 12V battery charger. As presented, the circuit can deliver peak currents of about 6A, which corresponds to a maximum output of about 4A continuous. A 12V charger rated for at least 4A or a 12V power transformer with a rating of 60VA is recommended. Unfiltered DC from the external 12V battery charger or AC from an external 12V power transformer is applied to a bridge rectifier consisting of diodes D4-D7. These rectify the input and their output is filtered with two 2200µF capacitors to give unregulated DC of about +17V and this is the motor supply, ap­plied to the emitters of Q2 & Q3. The +17V rail is also applied to the 7805 5V regulator which supplies all the other circuitry in the Railpower. Next month, we will complete the description of the Rail­ power MkII, giving all the construction details and setting up proce­dure. SC 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 September 1995  49 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 50  Silicon Chip 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 September 1995  51 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 52  Silicon Chip 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 September 1995  53 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 54  Silicon Chip 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 September 1995  55 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 56  Silicon Chip COMPUTER BITS BY GREG SWAIN Running MemMaker & avoiding memory conf licts Having trouble with General Protection Faults in Wind­ows? Try running the MemMaker memory optimisation program. This will sometimes overcome the problem and your programs will run more efficiently too. I remember seeing a movie some time ago – a Western actual­ly – in which someone gets shot. “Who would want to shoot Bad Bart?”, queried a bystander after the bullets had stopped flying and everyone had crawled out from behind the bar. “Just about every­one who ever knew him”, came the reply. What’s this got to computers and memory? Well, in this case, the question is “Who’s encountered a General Protection Fault when running Windows?” Answer: “just about everyone who’s ever used it”. OK, so it’s a bad analogy but you get the general idea – General Protection Faults in Windows are not uncommon. There you are working away happily, running lots of applications, when all of sudden up comes an error message. Often, it will read someth­ing like this: Progman caused a General Protection Fault in module File­name at 0001:0296. Now isn’t that helpful? What this means in plain English is that your Windows application has written to a memory space that was already occupied, clobbering another module (or file) in the process. As a result, the system becomes unstable and the wisest course is usually to exit all applications and reboot Windows. Now there are lots of reasons why GP faults can occur, including incompatible terminate-and-stay-resident programs (TSRs) or device drivers in your CONFIG.SYS and AUTOEX­EC. BAT files. In that case, you can often troubleshoot the problem by removing these TSRs – just type “REM: in front of the appropriate entries. If that solves the problem, you can then proceed to replace the lines one by one until the problem reappears. When it does, you’ll know which one is causing the GP fault. Often, however, GP faults are caused by other memory man­agement problems. If you consistently get the same error message when a certain function is performed, then running Mem­Maker may overcome (or at least minimise) the problem. EXTENDED MEMORY 1024K FFFF UPPER MEMORY AREA 384K 640K A000 CONVENTIONAL MEMORY AREA 640K Computer memory Before we take a look at the Mem­ Maker program, let’s first briefly look at how memory is organised in a PC. Fig.1 shows the memory configuration of a typical computer. The first 640Kb is called “conventional” mem­ory and is used by all MS-DOS programs. Above that but below 1Mb is a 384Kb block called the “upper mem­ory area”. This block is normally reserved for use by hardware expansion cards, such as your display adapt­ er, and for shadowing video ROM and the ROM BIOS. Following the upper memory area, the area beyond 1Mb is known as “extended” memory. This memory HIGH MEMORY AREA 64K 0K 0000 Fig.1: the memory configuration in a PC. The first 640Kb is called “conventional” memory, while the area from 640Kb to 1024Kb (1Mb) is the “upper memory area”. The area beyond 1Mb is known as “extended” memory. requires the use of an extended memory manager such as HIMEM. SYS and this device driver is typically loaded as the first line in your CONFIG.SYS file. Finally, the first 64Kb of extended memory is known as the “high September 1995  57 drivers and programs. On the other hand, if you run a DOS-based program that does require expanded memory, you will have to replace the NOEMS switch with the RAM switch instead. This will allow EMM386.EXE to simulate expanded memory so that the program will run. For exam­ple, the command: DEVICE=C:\DOS\EMM386.EXE 512 RAM By typing mem /c/p at the DOS prompt, you can see which programs are loaded into conventional memory and which are loaded into upper memory. It will also tell you how much free conventional memory you have and whether or not MSDOS is resident in the high memory area. memory area” (HMA). Usually, MSDOS is set to run in the HMA, to free up conventional memory for use by other programs. To see how your computer currently organises memory, exit Windows and type mem /c/p at the DOS prompt. This will show you which programs are loaded into conventional memory and which are loaded into upper memory. It does this by displaying a detailed listing of the load order and size of these programs – see Fig.2. It will also tell you how much free memory you have, the largest executable program size and whether or not MS-DOS is resident in the high memory area. What MemMaker does Because the hardware expansion cards do not use up the entire upper memory area, it contains free areas of space and these are known as “upper memory blocks” (UMBs). When you run MemMak­er, it modifies your AUTOEXEC.BAT and CONFIG.SYS files so that some TSRs and device drivers are loaded into these UMBs instead of into conventional memory. As a result, conventional memory is freed and this can make a big difference to the way your programs run. 58  Silicon Chip If you’ve already run MemMaker and subsequently installed additional software, it can also help to avoid memory management conflicts be reallocating space in the upper memory blocks. By the way, in order to load programs into the upper memory blocks, you must use an expanded memory manager such as EMM386.EXE. Depending on the entry in your CONFIG. SYS file, this device driver can also use extended memory to simulate expanded memory for those DOS-based programs that require it. Typically, the first three lines of CONFIG.SYS will look like this: DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE NOEMS DOS=HIGH,UMB Note that it is necessary to load HIMEM.SYS before EMM386.EXE to gain access to the upper memory blocks. The NOEMS switch ensures that EMM386.EXE behaves as an upper memory manager only and prevents it from allocating extended memory (EMS) for use as expanded memory (XMS). Use this switch if your programs do not require expanded memory, as this frees an additional 64Kb of upper memory for running device will allocate 512Kb of your computer’s extended memory for use as expanded memory. Note that you should only allocate as much expanded memory as the program requires and this will usually be specified in the installation manual. If the command line that loads EMM386.EXE is missing, it can easily be added by editing the CONFIG.SYS file in an ASCII text editor. Alternatively, the MemMaker program will automatically install and configure EMM­386.EXE for you. Start-up disc Before running MemMaker, it’s vital that you create a start-up disc in case anything goes wrong. To do this, install an unformatted floppy disc in drive A and type: FORMAT A:/S. This done, copy your AUTOEXEC.BAT and CONFIG.SYS files (and preferably your SYSTEM.INI file in the Windows directory) to the floppy disc. That way, if anything goes wrong, you can boot from the start up disc and simply copy the original files over the top of the modified files on the hard disc. It’s also a good idea to disable any commands in your AU­TOEXEC.BAT and CONFIG.SYS files that start unnecessary device drivers and utility programs. This will help to free up conven­ tional memory by ensuring that such programs do not compete for space in upper memory. For example, if you only use a mouse when running Windows, then you can disable any mouse device drivers such as MOUSE. COM. To disable a command, simply open the file in an ASCII text editor (eg, DOS Edit or Notepad) and insert a REM statement at the beginning of the command line, eg: REM DEVICE =C:\DOS\MOUSE. This done, save the file and then reboot the computer. By disabling the command in this manner, rather than deleting the line, you can easily restore it later on if required. Running MemMaker MemMaker is supplied with MSDOS 6.0 and above and is straightforward to run – just quit all programs, go to the com­mand prompt (ie, C:>) and type Memmaker. All you have to do then is follow the on-screen prompts or the step-by-step proce­dure set out in the manual. Unless you are an experienced user, it’s best to choose Express Setup (as opposed to Custom Setup) when running MemMaker for the first time. You should also initially answer “No” to the prompt that asks you whether you use any programs that require expanded memory, unless you are sure that the reverse is true. If you choose No and subsequently find that some programs no longer run or display error messages (eg, “Expanded Memory Unavailable”), then its simply a matter of running Mem­Maker again and answering “Yes” to the same question. After you have finished running MemMaker, take a look at your CONFIG.SYS and AUTOEXEC.BAT files. In CONFIG.SYS, you will see that MemMaker has changed certain “device” commands to “devicehigh” and added switches to those “device­high” commands. Similarly, in AUTO­EXEC. BAT, you will find that Mem­Maker has added “lh” (loadhigh) to the beginning certain commands. These “devicehigh” and “lh” commands ensure that the corre­ sponding device drivers and TSRs are loaded into the upper memory area. Note, however, that HIMEM.SYS and EMM386.EXE cannot be loaded high. Now for the acid test – to find out AUTOEXEC.BAT Before MemMaker <at>ECHO OFF VERIFY OFF PATH C:\DOS;C:\WINDOWS;C:\ALDUS;C:\PM5;C:\UTIL; C:\DESKSCAN;C:\TSCSI; SET TEMP=C:\TEMP SET DIRCMD=/P/O PROMPT $P$G C:\DOS\MOUSE C:\DOS\MSCDEX.EXE /D:PANASON /L:R C:\DOS\DOSKEY VER WIN After MemMaker <at>ECHO OFF VERIFY OFF PATH C:\DOS;C:\WINDOWS;C:\ALDUS;C:\PM5;C:\UTIL; C:\DESKSCAN;C:\TSCSI; SET TEMP=C:\TEMP SET DIRCMD=/P/O PROMPT $P$G LH /L:3,56928 C:\DOS\MOUSE LH /L:3,27984 C:\DOS\MSCDEX.EXE /D:PANASON /L:R LH /L:2,6400 C:\DOS\DOSKEY VER WIN Fig.3 (above): a typical AUTOEXEC.BAT file before and after running MemMaker. MemMaker has added “LH” commands to the start of several lines, to ensure that these TSRs are loaded into the upper memory blocks. Fig.4 (right): devices are loaded into the upper memory blocks using the DEVICEHIGH command. Note, however, that HIMEM.SYS and EMM386.EXE cannot be loaded high. what effect MemMaker has had on your system, go to the command prompt and again type mem /c/p. You should see that many (if not all) of the available device drivers and TSRs are now loaded into upper memory instead of conventional memory. In addition, you should have a corre­ sponding increase in conventional memory. Fig.3 shows a typical AUTOEX­EC. BAT file before and after running MemMaker, while Fig.4 shows typical before and after CONFIG.SYS files. If you encounter problems after running MemMaker, you can easily undo the changes that have been made. To do this, you simply go to the command prompt (ie, C:\>) and type: Memmaker /undo. By then following the on-screen prompts, the program will restore the original AUTOEX­EC. BAT, CONFIG.SYS and SYSTEM.INI files, using backups that it made during CONFIG.SYS Before MemMaker DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE NOEMS X=C800-CBFF BUFFERS=30,0 FILES=60 DOS=HIGH,UMB LASTDRIVE=Z FCBS=4,0 DEVICE=C:\TSCSI\MA348.SYS DEVICE=C:\TSCSI\TSCSI.SYS DEVICE=C:\CDMKE.SYS /D:PANASON DEVICE=C:\DOS\SETVER.EXE DEVICE=C:\DESKSCAN\SJII.SYS BREAK=ON COUNTRY=61,,C:\DOS\COUNTRY.SYS SHELL=C:\DOS\COMMAND.COM C:\DOS\ /E:1024 /p STACKS=9,256 After MemMaker DEVICE=C:\DOS\HIMEM.SYS DEVICE=C:\DOS\EMM386.EXE NOEMS X=C800-CBFF BUFFERS=30,0 FILES=60 DOS=HIGH,UMB LASTDRIVE=Z FCBS=4,0 DEVICEHIGH /L:2,9568 =C:\TSCSI\MA348.SYS DEVICEHIGH /L:2,15488 =C:\TSCSI\TSCSI.SYS DEVICEHIGH /L:2,13472 =C:\CDMKE.SYS /D:PANASON DEVICEHIGH /L:2,12048 =C:\DOS\SETVER.EXE DEVICEHIGH /L:1,7040 =C:\DESKSCAN\SJII.SYS BREAK=ON COUNTRY=61,,C:\DOS\COUNTRY.SYS SHELL=C:\DOS\COMMAND.COM C:\DOS\ /E:1024 /p STACKS=9,256 September 1995  59 Fig.6: this detailed map shows the upper memory area from A000-FFFF. The gray areas are treated as ROM and are reserved for the video card (C000C7FF) and the ROM BIOS (F000-FFFF). The areas marked with “U” indicated used UMBs, while “F” indicates free UMBs. the optimisation process. Alternatively, if you suspect that the problem might be caused by one or more commands in AUTO­EX­EC.BAT or CONFIG.SYS, you can bypas some or all of the commands in these files (MS-DOS 6.0 and above). To bypass all the commands in these two files, press the F5 key when you see the text “Starting MS-DOS . . .” while the computer is booting up. Alternatively, to bypass individual commands, press the F8 key instead and follow the on-screen prompts to carry out or bypass each command in turn. The Memmaker.sts file That’s not necessarily the end of the memory optimisation process. Often, you can free up even more memory by changing the order of the command lines in your CONFIG.SYS and AUTOEXEC.BAT files. The reason for this is that as each driver is loaded in turn into the upper memory area, it uses the largest free remain­ing UMB. This means that if the smaller drivers are loaded first, the remaining UMBs might not be able to accommodate some of the larger drivers. In this case, these remaining large device drivers will be loaded into 60  Silicon Chip conventional memory rather than upper memory, despite the presence of “devicehigh” or “lh” commands. The trick is to reorganise your CONFIG.SYS and AUTOEXEC.BAT files so that the largest device drivers are loaded first. That way, it will be easier to fit the remaining drivers into the smaller UMBs that are left over. How do you know the sizes of your device drivers? Well, when you run MemMaker for the first time, it logs this informa­tion in a file called MEMMAKER.STS (in the C:\DOS directory). Open this file in an ASCII text editor (or better still print it out) and make a note of the MaxSize line for each command in the [SizeData] section – see Fig.5. It’s now simply a matter of editing the CONFIG.SYS and AUTOEXE­C.BAT files so that those command lines with larger Max­File values are positioned Command=C:\DOS\SETVER.EXE Line=11 FinalSize=864 MaxSize=12048 FinalUpperSizes=0 MaxUpperSizes=0 ProgramType=DEVICE Fig.5: a typical section from a MEMMAKER.STS file. The MaxSize value is the one to note. above those with smaller MaxFile values (make sure that HIMEM.SYS and EMM386.EXE are before any of these, however). Save each file in turn, then reboot your comput­er to check that the system starts properly and that there are no error messages during start-up. If all is well, run MemMaker again to optimise the system for the revised CONFIG.SYS and AUTOEX­EC. BAT files. By now typing mem /c/p at the command prompt again, you can quickly check how much more conventional memory has been freed. Note, however, that the above procedure is not always hassle free. Sometimes, for example, it is necessary to load the drivers for a particular device in a set order (where more than one driver is involved). If the order is incorrect, you will get an error message during boot-up, often to the effect that a particular driver is missing. In that case, it’s usually just a matter of moving the command line for the “missing” driver ahead of its companion driver. Fig.4 shows an example of this. If you look at this file, you will see that the line DEVICEHIGH /L:2,9568 =C:\TSCSI\MA348.SYS precedes the line DEVICEHIGH /L:2,15488 =C:\TSCSI\TSCSI.SYS even though the second line has the largest MaxSize value. That’s because it’s necessary to load MA348.SYS before TSCSI.SYS for this particular device (an external cartridge drive). Fine tuning Now take a look at the detailed memory map of Fig.6. One im­portant thing to realise here is that not all addresses in the upper memory area are available for loading device drivers and TSRs. For example, the area from A000-C800 is reserved as ROM for video card addresses, while the area from F000-FFFF is reserved for shadowing the ROM BIOS. Similarly, the area from E000-EFFF is also normally a reserved area. What this means is that these ranges are out of bounds for use as UMBs unless you specifically instruct EMM386. EXE to in­clude certain areas within them (ie, EMM386.EXE does not map over unused ROM). This is done using the I= switch. For example, if your computer has a VGA or EGA monitor, you can generally include the range of address from B000-B7FF and from E000-EFFF. In this case, the EMM386 entry in your CONFIG.SYS file would look something like this: Exploring the Memory with MSD 1. To see how memory is allocated in your machine, go to the DOS prompt and type MSD. The screen shown at left will appear. Click on Memory. DEVICE=C:\DOS\EMM386.EXE I=E000-EFFF I=B000-B7FF NOEMS If you subsequently find that your monitor doesn’t respond correctly or your computer hangs when you start Windows, delete the I=B000-B7FF entry. If you still have problems, delete the I=E000-EFFF statement On the other hand, it is also often necessary to specifi­cally exclude certain address ranges to prevent memory conflicts with hardware cards. If this is not done, a device driver can be loaded into the address normally occupied by the hardware card and this will prevent the card from being found. For example, let’s say that you have a hardware card (eg, a scanner card) at address C800. In this case, you might want to exclude the range from C800-CBFF and this is done using the X= switch, ie: 2. The resulting screen shows free (F) and used (U) UMBs, plus areas which are reserved as ROM. Click the down arrow to see the area below C000. 3. Clicking “Utilities” and then “Memory Block Display” brings up this screen. You can now examine the memory allocated to each driver by clicking on it (in this case, SMARTDRV.EXE). DEVICE=C:\DOS\EMM386.EXE I=E000-EFFF I=B000-B7FF NOEMS X=C800-CBFF Note that MemMaker will normally automatically exclude the address ranges occupied by hardware cards the first time you run it. If you subsequently install another hardware card and you strike problems, try changing the address setting on the card. Alternatively, you can work through the section entitled “You Installed A Hardware Device And Your Computer Stopped Working” in chapter 8 of the MS-DOS 6 manual. By the way, it’s also a good idea to edit the Emmexclude= entry in SYSTEM.INI, to prevent Windows from accessing this address range when running in Enhanced mode – ie, add the line Emmexclude=C800-CBFF to the [386Enh] section of SYSTEM.INI. In addition, some video cards use additional memory in the region from C400-C700. Although Windows automatically detects most of these cards and avoids this area, there are cases where you have to specifically exclude it using the Emmexclude entry. For example, to avoid the area from C400-C7FF (to prevent conflict with a video card) and from C800-CBFF to prevent conflict with another hardware card, the line would read: Emm­ex­clude=C400-CBFF. If you are still having trouble running Windows in enhanced mode (eg if the system frequently crashes), try starting Windows using the “/d:x” switch – ie, type win /d:x at the command prompt. This will prevent Windows from accessing any of the upper memory area and is equivalent to adding Emmexclude=A000-EFFF to SYSTEM.INI. If this solves the problem it means that there is a con­flict with some hardware card that Windows is unable to detect. To solve this problem, you need to identify which hardware card is causing the problem and then exclude its address with Emmexclude. To find out the address, check the address switches on the card or use the Micro­ soft Diagnostics program MSD.EXE . Try to limit the excluded the range to the specific card. If Windows is unable to find enough free UMBs for what are called “translation buffers” when it loads, it uses conventional memory instead. As a result, there will be less memory available to run non-Windows applications. Finally, if it’s all too hard, consider upgrading to Windows 95. With this system, the old DOS/Windows combination is gone and you don’t have to worry about tweak­ing AUTOEX­EC. BAT, CONFIG.SYS and SYSTEM.INI files. Is your computer up to Windows 95? Here we go again! SC September 1995  61 Further Notes On The Train Detector For Model Railways As soon as the June 1995 issue appeared on the streets, we received very favourable feedback to the Train Detector cir­cuit. But as often happens, one reader wanted to use it in a way we had not envisaged. In this short article, we feature his prob­lem and describe how to solve it. By LEO SIMPSON The reader’s problem is as follows and sets out an applica­tion where the block switching covered in the June 1995 article is not required. This application envisages the Train Detector being used in a one-off situation. Reader’s letter I am keen to build the Train Detector featured in the June 1995 issue and wish to use it with the Sound & Lights for Level Crossings, as featured in the April 1994 issue. My problem is that I don’t want to use the block switching system you describe for the Train Detector. I just want to use it to detect the train moving into the section which has the level crossing. I also don’t want to run wires all the way back to my train controller Fig.1: this diagram shows how to connect the Train Detector board to the Train Controller without using block switching. Note that the current for the isolated track section must flow through the two large detector diodes. ISOLATED RAIL COMMON RAIL RAIL 2 TRACK 1 +/- TRAIN CONTROLLER TRACK 2 0V AC SIGNAL RAIL 1 +12V 0V -12V OUTPUT GND 62  Silicon Chip (Infrared Remote Control, April & May 1992) because I have a large layout and I want to minimise the amount of extra wiring required. Therefore, instead of wiring back to the con­troller I just want to wire the Track Detector directly off the track where the level crossing is going to be. Now, if that doesn’t sound too confusing, how do I go about it? Finally, can I use the same power supply to run the Sound & Lights circuit as for the Train Detector? (K. A., Mona Vale, NSW). How it’s done It’s amazing, isn’t it? No matter how much thought we put into the presentation of these projects, someone always writes in to ask how to do something else that we hadn’t thought of doing. As it happens, this proposal does not present any real problems. First, you do need a section of the track to be isolated from the rest of the layout. One rail can be common to the rest of the layout and one section of rail must be isolated, as shown in the diagram of Fig.1. This shows one side of the controller wired to the common rail (rail 1) while the other side of the train controller goes to the 0V terminal on the Train Detector PC board. The rail 1 connection also connects to the track 1 termi­nal on the PC board (labelled “+/-” on the copper side of the board). The isolated rail (rail 2) goes to the track 2 terminal on the PC board, adjacent to the 0V terminal. Fig.1 shows how the train controller is connected to the isolated section of track but the reader wants to wire the Train Detector directly to the track, without wiring back to the con­troller. OK, Fig.2 shows how to do it. This shows a track with an isolated section. As before, the common rail is rail 1 while the isolated rail is rail 2. The corresponding rail connections to the COMMON RAIL SATELLITE SUPPLIES RAIL 1 TRACK 1 +/- AC SIGNAL RAIL 2 Aussat systems from under $850 ISOLATED RAIL SATELLITE RECEIVERS FROM .$280 +12V TRACK 2 0V -12V 0V OUTPUT GND LNB’s Ku FROM ..............................$229 LNB’s C FROM .................................$330 FEEDHORNS Ku BAND FROM ......$45 FEEDHORNS C.BAND FROM .........$95 DISHES 60m to 3.7m FROM ...........$130 Fig.2: this diagram shows how the Train Detector can be wired to an isolated section of track without the need for any connections to the Train Controller itself. Note that, as before, the current for the isolated track section must flow through the two detector diodes. Train Detector are the same as in Fig.1. Note that the DC and AC connections from the power supply to the Train Detector must still be as shown in Fig.3 on page 29 of the June 1995 issue. One small point to note with this proposal is that the voltage applied from the train controller to the isolated track section will be lower by 0.6V than the voltage supplied to the rest of the track. This is a consequence of the voltage drop across the current detector diodes, D1 & D2. This will lead to a small drop in speed as the loco enters the isolated track section and a slight pick-up in speed as the loco leaves the section but this is unlikely to lead to problems and may actually give an increase in realism. As far as the idea of using the Train Detector power supply for the Sound & Lights circuit is concerned, remember that the Train Detector has +12V, 0V & -12V supply lines while the Sound & Lights circuit needs only +12V and 0V lines. In that case, all you need do is to connect the +12V and 0V lines from the Train Detec­tor power supply to the Sound & Lights board. The output line from the Train Connector goes to the input of the Sound & Lights board. There is no need to connect the GND terminal on the Train Detector to the GND terminal on the Sound & Lights board since the circuit will be completed via the 0V connections. Do not make any connection from the -12V line to the Sound & Lights board. Especially For Model Railway Enthusiasts 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). Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or send a cheque, money order or credit card details to PO Box 139, Collaroy, NSW 2097. LOTS OF OTHER ITEMS FROM COAXIAL CABLE, DECODERS, ANGLE METERS, IN-LINE COAX AMPS, PAY-TV DECODER FOR JAPANESE, NTSC TO PAL TRANSCODERS, E-PAL DECODERS, PLUS MANY MORE For a free catalogue, fill in & mail or fax this coupon. ✍     Please send me a free catalog on your satellite systems. Name:____________________________ Street:____________________________ Suburb:_________________________ P/code________Phone_____________ L&M Satellite Supplies 33-35 Wickham Rd, Moorabin 3189 Ph (03) 9553 1763; Fax (03) 9532 2957 September 1995  63 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 64  Silicon Chip 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 September 1995  65 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 66  Silicon Chip ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) 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. TOTAL $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. 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No._______________   ❏ Gift subscription ☞ RATES (please tick one) Australia Australia with binder(s)* NZ & PNG (airmail) Overseas surface mail 2 years (24 issues) 1 year (12 issues) ❏ $A90 ❏ $A49 ❏ $A114 ❏ $A61 ❏ $A135 ❏ $A72 ❏ $A135 ❏ $A72 ❏ $A240 Overseas airmail ❏ $A120 *1 binder with 1-year subscription; 2 binders with 2-year subscription GIFT SUBSCRIPTION DETAILS Month to start__________________ Message_____________________ _____________________________ _____________________________ Gift for: Name_________________________ (PLEASE PRINT) YOUR DETAILS Your Name_________________________________________________ (PLEASE PRINT) Address___________________________________________________ Address______________________ _____________________________ State__________Postcode_______ ______________________________________Postcode___________ Daytime Phone No.____________________Total Price $A __________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ Master Card 9am-5pm Mon-Fri. Please have your credit card details ready ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail coupon to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia September 1995  67 Build a Jacob’s Ladder display & amaze your friends Ever since scientific showmen like Tesla and Edison were able to generate really high voltages, the Jacob’s Ladder display has been creating awe amongst laymen. In this article, we show how you can build your own Jacob’s Ladder using a low cost cir­cuit. By LEO SIMPSON & JOHN CLARKE Virtually any high voltage power supply which generates more than about 10kV (DC or AC) can be used to provide a Jacob’s Ladder display. The display consists of two vertical wires close spaced at the bottom and splayed apart to increase the gap as the spark rises. It is the paradoxical nature of the ladder discharge which intrigues most people. Who would believe that the spark would want to become longer and travel upward, seeming- ly defying gravi­ty? And surely the spark would take the shortest path rather than extend itself as it travels upward. In reality, the spark discharge is taking the easiest route from one electrode to the other. Initially, the discharge does take the shortest path which is at the bottom of the wires. But the Jacob’s Ladder display works because the continuous spark discharge gets hot and heats up the air around it. This heated ionised air rises, carrying Fig.1: the circuit uses 555 timer IC1 to pulse transistors Q1 & Q2 on and off. Q2 in turn drives a standard automotive ignition coil and this delivers high voltage pulses to the ladder. JACOB'S LADDER L1 IGNITION COIL F1 10A 12V the discharge with it until the gap is too wide to maintain the spark. The discharge then starts at the bottom again and works its way back up and the cycle contin­ues. Why is it called a Jacob’s Ladder? We don’t know who first came up with the name but it is an allusion to the Bible story of Jacob: “He dreamed that he saw a ladder standing on the earth, with its top reaching into heaven; a stairway for the angels of God to go up and come down” (Genesis, XXVIII;12). The high voltage supply is easy –either of the plasma bottle displays from the August or November 1988 issues of SILI­CON CHIP will do the trick but there is a better approach – adapt the low cost Electric Fence Controller from the July 1995 issue of SILICON CHIP. A kit for this design is avail­able from Dick Smith Electronics and from Jaycar Electronics and only requires a few simple modifications. D1 1N4004 10 470 16VW ZD4 16V 1W 1k 7 12k 4 IC1 555 6 2 B E C E B C 8 Q1 BC327 E 3 2.2k B Q2 MJ10012 100  C C 5W B 5 1 0.1 0.33 VIEWED FROM BELOW JACOB'S LADDER EHT DRIVER 68  Silicon Chip E ZD1 75V 5W ZD2 75V 5W ZD3 75V 5W HT GND PARTS LIST 1 PC board, code 11306951, 171 x 79mm 1 12V ignition coil (see text) 3 280 x 5mm cable ties 5 PC stakes 2 3AG PC mount fuse clips 1 10A 3AG fuse 2 5mm ID crimp eyelet terminals 1 TO-3 transistor insulating cap 2 3mm screws, nuts and star washers 1 red battery clip 1 black battery clip 1 ignition coil EHT connector 1 2-way terminal block 1 2m length of twin red/black automotive wire 1 60mm length of red heavy duty hook-up wire 1 60mm length of blue heavy duty hook-up wire 1 370mm length of 1.5mm copper wire 1 40mm length of 0.8mm tinned copper wire Semiconductors 1 555 timer (IC1) 1 BC327 PNP transistor (Q1) 1 MJ10012 500V NPN Darlington (Q2) 1 1N4004 1A diode (D1) 3 75V 5W zener diodes (ZD1ZD3) 1 16V 1W zener diode (ZD4) Capacitors 1 470µF 16VW PC electrolytic 1 0.33µF MKT polyester 1 0.1µF MKT polyester This photo is really a composite of two separate photographs which were combined using a computer. It shows how the spark climbs the ladder formed by the two vertical wires attached to the ignition coil. Note that the multiple discharge paths shown here are a result of the ¼-second exposure time used when taking the photo. In practice, fewer sparks are visible at any one time. Actually, using the Electric Fence Controller to generate the spark discharge provides a big advantage in that the result­ing Jacob’s Ladder is much more spectacular. Instead of having just one spark discharge which climbs up the wires, our version produces about 130 sparks second, so you have a whole series of sparks which appear to be climbing up the wires, as shown in the accompanying photo. The result is noisy and smelly, and all those sparks look quite nasty and dangerous – as indeed they are. How it works The Jacob’s Ladder is based on an automotive ignition coil. These can be purchased new from automotive retail­ ers but will be cheaper if purchased secondhand from motor wreckers. Select one which requires a ballast resistor. The circuit comprises a 555 timer IC, two transistors, the ignition coil Resistors (0.25W 1%) 1 12kΩ 1 100Ω 5W 1 2.2kΩ 1 10Ω 1 1kΩ and several resistors, capacitors and diodes – see Fig.1. The revised circuit pulls a lot more current than the Electric Fence Controller and generates lots of fat, juicy sparks instead of the deliberately restricted high voltage transients of the original circuit. IC1 is a 555 timer used to produce the short pulses. Note that we used a standard 555 timer here since it is more rugged than the CMOS (7555) version and less likely to be damaged by any high voltage transients which September 1995  69 The ignition coil is secured to the PC board using plastic cable ties, while a plastic cap is fitted to Darlington transistor Q2 to prevent unexpected shocks during testing. Note that you don’t have to buy a new coil – a secondhand coil obtained from a wrecker’s yard will do the job quite nicely. may be present on the PC board. IC1 is connected to oscillate at about 133Hz, as determined by the 0.33µF capacitor at pin 6 and the associated 12kΩ and 1kΩ resistors. The two resistors set the duty cycle of the pulse train delivered by pin 3 at essentially 14:13; ie, close to a square wave. When pin 3 is high, transistor Q1 is held off and no base current flows in Q2. When pin 3 goes low, Q1 is switched on due to the base current flow through the 2.2kΩ resistor and Q1 switches on Q2 via its 100Ω base resistor. The coil now begins to charge via fuse F1. The instant pin 3 goes high again, Q2 switch­es off and the coil develops a high voltage and generates a spark across the gap. Q2 is an MJ10012 Darlington power transistor, specifically designed as a coil driver in automotive ignition systems. It has a 500V collector-emitter rating so it can withstand the high voltages developed across the coil’s primary winding. Depending on the spark gap, the coil’s peak primary voltage will only be about 200V or so, but if the gap is very large or the coil is operated without any EHT output lead, the secondary voltage can be excessive and there can be a flashover inside the coil. Not only can this damage the coil but it can also produce a very high primary voltage points. This done, solder in all the low profile components such as the IC, diodes and resistors. Table 1 lists the resistor colour codes but it is also a good idea to check the resistor values using a digital multimeter before soldering them in position. Now solder in the capacitors, taking care to ensure that the 470µF electrolytic is oriented as shown. Take care to ensure that the semiconductors are correctly oriented as well. In par­ ticular, note that D1 (1N4004) faces in the opposite direction to the three zener diodes (ZD1-ZD3). Note that ZD4 is mounted under the PC board across the 470µF capacitor. Pin 1 of the IC is adjacent to a notch in one end of the plastic body. Transistor Q1 should be pushed down onto the board as far as it will easily go before soldering its leads. Q2 is secured directly to the board (ie, no insulating washer) using 3mm ma­chine screws and nuts. As well as securing Q2 in place, these mounting screws and nuts also connect Q2’s collector (ie, the case) to a track on the PC board. To ensure reliable connections, use star washers under the screw heads and solder the nuts to their surrounding copper pads. This done, fit an insulating cap to Q2 – this will prevent any nasty shocks during the testing procedure. The 100Ω 5W wirewound resistor is mounted about 6mm above the PC board, to avoid any possibility of charring – it does get hot. which may damage Q2. Accordingly, three 75V 5W zener diodes, ZD1 to ZD3, are connected in series across Q2 to limit the primary voltage devel­oped by the coil to about 225V, well within the transistor’s rating of 500V. Power supply Power for IC1 is provided by the battery via fuse F1, the 10Ω resistor and diode D1. A 470µF capacitor filters the supply to provide reliable triggering for the timer. Transient protec­tion is provided with ZD4, a 16V zener diode. A 0.1µF capacitor at pin 5 filters the trigger point voltage to ensure that the timer does not false trigger. Diode D1 offers reverse polarity protection for IC1, while the fuse protects the battery from supplying excessive current should a fault occur. Construction The circuit is constructed on a PC board coded 11306951 and measuring 171 x 79mm. This board, together with the ignition coil mounted on it, fits neatly inside a 230mm length of 90mm plastic stormwater pipe (available from plumbing supply outlets). Fig.2 shows the assembly details for the PC board. Begin the assembly by installing PC stakes at the five external wiring TABLE 1: RESISTOR COLOUR CODES ❏ No. Value 4-Band Code (1%) 5-Band Code (1%) ❏ 1 12kΩ brown red orange brown brown red black red brown ❏ 1 2.2kΩ red red red brown red red black brown brown ❏ 1 1kΩ brown black red brown brown black black brown brown ❏ 1 10Ω brown black black brown brown black black gold brown 70  Silicon Chip ▲ JACOB'S LADDER Fig.2 (left): install the parts on the PC board as shown in this wiring diagram, making sure that all polarised parts are correctly oriented. The EHT connection to the coil is made using a brass EHT ignition coil connector. Warning! TERMINAL BLOCK This Jacob’s Ladder display uses very high voltage which can give a nasty shock. Do not put your fingers near the display or coil while ever the power is applied. Fig.3 (below): check your PC board for defects by comparing it against this full-size etching pattern before installing any of the parts. CABLE TIE IGNITION COIL CABLE TIE CABLE TIE 10  100  5W Q1 IC1 555 F1 D1 1k 12k 12V BATTERY POSITIVE Q2 2.2k 0.1 1 0.33 ZD1-ZD3 470uF ZD4 12V BATTERY NEGATIVE September 1995  71 The fuse clips can now be installed. Note that these each have a little lug at one end to retain the fuse after it has been installed. These lugs must go to the outside ends, otherwise you will not be able to fit the fuse. The ignition coil is secured to the PC board using three cable ties (see photo), after which the leads can be run to its primary terminals. These leads should be terminated using 5mm eyelet connectors to allow for easy connection to the coil. Don’t just crimp the connectors to these leads – solder them as well to ensure long-term reliability. Finally, complete the construction by fitting the twinlead battery cable (red to positive, black to negative). The free ends of this cable are fitted with large (30A) battery clips the battery leads and carefully slide the assembly into its 90mm tubular plastic hous­ing. This done, feed the battery cable through the hole in its end cap, secure it using a cordgrip grommet and reconnect the leads to the PC board. The board assembly will be held in position when the end caps are fitted and, generally, this should be sufficient. Howev­er, if you wish the board to be held even more securely, wrap a small amount of foam rubber around the top of the coil so that the assembly is a tight fit within the tube. We made our Jacob’s Ladder spark gap with a 220mm length and a 150mm length of 1.5mm copper wire. The shorter length was soldered to an ignition connector which plugs into the coil EHT, while the longer wire was soldered to the GND terminal. We used a 2-way terminal block to separate the wires at the base of the ladder. If enamelled copper wire is used, scrape the insulation away along the inside edges to allow the spark to travel free­ly. Testing Before you apply power, you must provide a temporary spark gap for the ignition coil, otherwise it could be damaged, as noted above. The gap can be made quite simply with a paper clip. Extend the paper clip so that you have a hooked section at each end. Fit one hook into the EHT socket on the coil and make sure that it cannot fall out easily. This done, bend the other end of the clip so that it is close to (less than 5mm) but not touching the negative primary connection of the coil. Now for the smoke test. Immediately, there should be a continuous spark across the temporary spark gap. Do not attempt to touch any part of the coil while power is applied because it can give you a very nasty shock! If everything works OK, disconnect M FRO NEW N CHIP O SILIC No kinks A large coffee jar placed over the ladder will prevent high-voltage shocks, although it does tend to diminish the spectacle of the display. Note that the two wires should be as straight as possible without any kinks. Any slight kinks will mean that the sparks will not progress smoothly up the ladder but will tend to “stick” at the kinks. So keep the wires as straight as possible and splay them apart very slightly so that the gap at the top is no more than about 20mm. You can also place a large coffee jar over the complete assembly for safety’s sake (see photo) although this does tend to diminish the spectacle of SC the display. 20 Electronic Projects For Cars On sale now at selected newsagents Or order your copy from Silicon Chip. Price: $8.95 (plus $3 for postage). Order by phoning (02) 979 5644 & quoting your credit card number; or fax the details to (02) 979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 72  Silicon Chip 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.avcomm.com.au September 1995  73 Design by ROGER KENT* Audio Lab: a PC-controlled audio test instrument; Pt.2 In this second article on Audio Lab, we include all the circuit and wiring diagrams and give a rundown on the software. The calibration procedure includes 10 multi-turn pots and the software guides you through the full procedure. In last month’s article, the operation of Audio Lab and the functions of the various PC boards were described. Two more PC boards remain to be mentioned. The power supply board is fed by an external AC plugpack capable of delivering 1A. The 25-pin 74  Silicon Chip D connector for the serial port is also mounted on this board, together with the reset switch which is mounted on the rear of the case. There is also an optional board for fault-finding on the Boot board. This consists of eight LEDs with limiting resistors and plugs into port P1 on the Boot board. How this is used will be described later in the construction details but before we move on to that topic we will discuss some of the system software. System software On power up, machine code software is dumped from the PC to Audio Lab via the serial port. To show the code has been successfully loaded, the LEDs on Audio Lab flash and a verifica­tion message is displayed on the PC. The opening menu screen is then accessed and the various +5V CONN 5 TO A-D PCB D0 8 D1 7 D2 6 D3 5 D4 4 28 20 1 D0 A0 D1 A1 D2 A2 D3 12 14 15 D6 D7 11 11 8 12 13 15 16 17 18 19 D0 C3 0.1 OE 22 A14 27 D1 A13 A13 26 A12 2 D2 D3 9 10 IC6d D5 D7 14 C6 0.1 8 D6 IC4 D7 20 CE RAM 1 A14 26 A13 2 A12 RD WR 11 12 13 15 16 17 18 19 22 27 +5V CE 20 12 14 C4 0.1 C8 0.1 D5 24 A9 25 A8 A9 24 A8 25 D6 D4 23 A11 21 A10 A11 23 A10 21 D4 A13 +5V C18 1 D3 4 A6 3 A7 IC3 EPROM +5V C1 0.1 D1 D2 6 A4 5 A5 6 A4 5 A5 4 A6 3 A7 D0 8 A2 7 A3 8 A2 7 A3 IC2 A3 D4 74HC573 A4 16 3 17 D5 A5 2 18 D6 A6 1 19 D7 A7 D5 10 A0 9 A1 10 A0 9 A1 13 C17 0.1 1 A15 5 A14 4 14 IC6c 13 7 74HC00 IC6a 11 J4 3 A000 2 1 3 A000 2 IC6b C000 6 A000 40 C14 10 9 C000 30 39 38 37 36 35 34 33 32 21 22 23 24 25 26 27 28 ALE P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 P0.6 P0.7 P2.0 P2.1 P2.2 P2.3 P2.4 P2.5 P2.6 P2.7 16 P3.6 +5V IC1 80C31 18 X1 11.059MHz P3.0 P3.1 10 11 19 P3.6 P3.5 P3.4 P3.4 14 13 P3.3 12 P3.2 P3.7 P3.5 RESET R1 1k P3.7 31 20 17 P3.3 P3.2 CONN 3 TO A-D PCB 15 +5V C15 33pF CONN 1 TO PSU PCB RST C16 33pF C9 10 2 +5V 16 10 RST OUT 7 IN 8 0V 3 IC7 ADM232 IN 7805 OUT C7 0.1 GND C2 1 TANT 5 +5V C5 1 TANT C13 1 TANT AUDIO LAB BOOT PCB C12 10 6 2 3 C10 10 7 3 C11 10 15 4 1 J1 4 REG3 +DC 1 1 9 16 IC5 74HC257 10 11 5 13 2 14 6 15 8 I G0 Fig.1: The boot board circuit contains the 80C31 micro­processor, the EPROM, RAM and the RS-232 interface chip. measurement options can be select­ ed. The “Lab” screen consists of five main sections: a scope display which graphs the selected input, a display of the Audio Lab front panel which shows which Range, Mode and Mon- itor func­tions have been selected, two digital readouts showing the output frequency of the sinewave generator September 1995  75 +5V +5V 20 19 R12 10k VREF 4 D0 D2 INT 16 D2 15 D3 D3 D4 ZD1 CZM242 2.5V WR D6 CONN 3 FROM BOOT PCB C11 1 C4 0.1 3 R14 10k C7 O.1 C6 0.1 C1 0.1 R13 330 D2 1N914 +5V R10 100k RD 2 CE 8 1 10 C8 0.1 5 7 12 D6 11 D7 D7 C13 0.1 -5V C10 33pF 14 D4 13 D5 D5 C12 1 VIN 6 18 D0 17 D1 D1 9 IC7 ADC0804 C9 100pF R5 1k R11 10k Q1 2N3904 C B IC3 4093 2 14 1 3 5 IC3b 1 4 E D1 1N914 3 2 6 7 IC6a C5 100pF R5 20k +5V 16 LIN GAIN R8 VR3 20k 20k +5V 20 2 19 D0 IC5 DL0 18 3 74HC574 D1 DL1 17 4 D2 DL2 16 5 D3 DL3 15 6 D4 DL4 14 7 D5 DL5 13 8 DL6 D6 9 DL7 12 D7 OE CK 10 11 1 CONN 2 PSU PCB +5V 0V -5V P3.5 P3.6 P3.7 A000 7 V IN +5V YY 0V 12 C000 5 P3.7 4 11 R2 10k 2 5 C3 220 6 IC1 AD736JN 1 8 IC2a 3 TL072 R3 10k 8 1 4 -5V C E B VIEWED FROM BELOW IC6b C000 +5V 2 C2 10 R6 20k D-SINE 6 7 3 4 -5V +5V R4 20k VREF SINE OUT -5V IC6c +5V 74HC32 14 P3.6 13 7 R1 10k R7 10k RMS CAL VR2 20k +5V DL7 SINE OUT 7 IC2b 12 1 -5V DL6 A000 P3.4 DL3 DL5 5 C14 0.1 DL4 P3.3 P3.3 6 8 DL1 6 13 LIN NULL VR2 20k R9 3 68k IC4 4052 4 DL2 P3.4 CONN 4 FROM BOOT PCB P3.2 CONN 1 TO FRONT PCB DL0 10 9 11 -5V P3.2 AUDIO LAB A-D CONVERTER 76  Silicon Chip coloured green toggle between two options, and items coloured light blue signify that a selection of values is available. For example, on the “Lab” screen the options on the menu bar are: “—”, Input, Mike, Sine, Rms, Lin, *FREQ, *COMP, *SWEEP, Scroll and EXIT. To select an option, move the mouse Fig.2 (above): the A-D converter board is based on an ADC0804 8-bit A-D converter and also features the AD736 true-RMS converter. Fig.3 (right): the front panel board carries all the analog input circui­ try and CMOS switches which are controlled by the 80C31 proces­sor. 12 LEDs are used to indicate the various measurement modes. ▲ and the input voltage of the selected input, and finally, the Menu select bar at the bottom of the screen. All the screens use the same method to select the different options. Any red item on the Menu bar has another screen or further options available when that function is selected by clicking the left mouse button. Items 16 CONN 1 DL0 DL0 10 A DL1 R19 5.1k 1x 14 DL2 DL3 9 DL1 DL4 B 0x XX 500  R27 91k IC3 4052 DL7 7 R28 820k -5V SINE IN C10 0.1 V OUT +5V DC SINE IN DL6 R43 10k B IC2a TL072 1 -5V RMS LED7  R42 DL7 10k B C Q1 2N3904 E  VOUT C4 0.1 C1 0.1 R3 COARSE VR10 20k 680  5 IC2b C7 1 IC4a 16 11 A 4 IN/OUT 1 DL3 10 B 6 IN/OUT 2 DL4 9 C 5 IN/OUT 5 IC7 4051 15 2 IN/OUT 1 IN/OUT 0 IN/OUT 7 DL0 DL1 8 COMP LED12  A RANGE2 LED4  14 13 K   330   RANGE10 LED1 LED5 R45 8.2k SINE LED11 MIC LED8 R37 330  RANGE5 LED2 16 IC6 4052  x10 LED4 15 14 12 2x 1x 0x IN/OUT x A B OUT/IN 10 9 13 7 R46 8.2k ELECTRET +5V S1 +5V C2 1 C3 33pF 3 R2 100k 2 K B C E VIEWED FROM BELOW 8 IC1a TL072 5 R8 20k C6 1 1 MIC GAIN VR8 20k DL0 DL1 A 8 C13 10 MICROPHONE 8 OUT/IN DL2 11 A DL3 10 B DL4 9 C x1  6 IN/OUT R18 20k  x0.1 LED6 4 IN/OUT 3 DL4 R36 7 IN/OUT 7 3 -5V DL3 DL2 1 2 1 4 R40 330 R22 200k -5V 200k C8 0.1 4 R5 680  1.5pF R17 -5V R24 20k SINE ADJ VR1 20k 2 C5 47 C9 DL2 +5V 0 IN/OUT R11 10k 7 IC1b R23 20k 7 8 R4 10k 4 R6 8.2k IN914 LIN LED10 13 R12 10k SINE OUTPUT 6 5 +5V C12 0.1 0V C11 0.1 -5V R15 680 S2b FINE VR9 1k R7 8.2k R39 330  D1 R14 8.2k S2a LOW R38 330  +5V 14 1 IN/OUT R34 200k +5V COMPONENT A B 4 R10 8.2k Q2 2N3904 R35 100k VR4 500  6 HIGH 3 C E R44 200W LOW R16 100k R13 270k HIGH 2  7 R25 43k VR3 5k COMP CAL VR2 20k R9 10k IC4b TL072 IC5 4051 8 R41 330  FREQ LED9 6 R33 100k R26 820k -5V 4y IN/OUT 1 1y IN/OUT 5 +5V 8 15 2 IN/OUT 4 2 3y IN/OUT 2y IN/OUT -5V 5 R30 10k -5V AC 3 Y OUT/IN 0V R29 820k OFFSET VR7 5k D2 1N914 16 R32 100k R31 10k D3 1N914 R20 680 VR6 R21 12 560  DL5 DL6 +5V VR5 5k R1 680 AUDIO LAB FRONT PCB September 1995  77 mouse clicked then the screen reverts back to the previous setting. “OPTS” always has this function from any screen. Similarly, if “Mike” or “Sine” is selected then the mike input or the sine output is monitored and displayed. “Scroll” is light blue and toggles between “Plot” and “Scroll” which are two different modes on the “Scope” display. DB25 TO COM 2 CONN 4 TO BOOT PCB RESET OUT IN 0V +DC S1 RESET 2x1N4004 D2 IN 9-10VAC 1A D1 C1 3300 25VW REG1 7805 GND Measuring components OUT 1 TANT +5V 0V F1 1A 7805 7905 -5V C2 3300 25VW GND IN I GO GIO CONN 1 TO A-D PCB 1 TANT REG2 7905 OUT AUDIO LAB POWER SUPPLY Fig.4: the power supply is fed from a 9V AC plugpack and uses two halfwave rectifiers together with 3-terminal regulators to pro­duce the ±5V rails. until the desired selection is highlighted in yellow. Press the left mouse button and the selection is made. If “Input” has been selected, then the first item on the menu bar changes to “Range” and the monitor input is switched to the input terminals. The range is shown on the LEDs and also on the video screen. If RANGE is now selected, the menu bar changes to enable the range of the input voltage required to be selected; ie, 250mV, 500mV up to 100V. If “OPTS” is highlighted and the If “*COMP” is selected, the component measuring facility is loaded. To use this, the setting of the High/Low range switch must be entered and if the switch is changed at any time, the setting must be re-entered, otherwise the calculations will be meaningless. As described in last month’s article, a two-component potential divider with one of the components being accurately known (P/Res) is used to measure resistance, capacitance and inductance. The software defaults to measure resistance with P/Res at 100kΩ and frequency of 1kHz. The scope screen and Volts display indicate the voltage with respect to zero (Vx) at the junction of the potential divider. If the range switch is in the High position, then three values of P/Res are available: 1kΩ, 10kΩ and 100kΩ. By switching between these values, resistances from 200Ω to 10MΩ can be meas­ured and displayed, as well as impedance. For a pure resistance, the displayed resistance and impedance will remain the same irrespective of the frequency applied to the potential divider. If the resistor under test is not “pure”, (most wirewound resis­ tors have significant inductance, for example), then the im­ pedance will vary with frequency. Low value inductances The A-D board plugs into the Boot board as shown in this photograph, with the interconnections made via two 8-way pin connectors (CONN3 and CONN5). The A-D board is then secured in position using Nylon spacers and machine screws and nuts. 78  Silicon Chip Low value inductances can have significant resistance which causes misleading results when they are being measured. If LOW range is selected when measuring inductance, another option is available on the menu bar, namely S.res. When selected, this measures the impedance of low value inductors at 10Hz. The series resistance is measured, displayed, and then can be used when calculating the inductance. The X1 and X5 toggles on the menu bar increase the resolu­tion of the potential divider when measuring high value impedanc­ es with the range switch set high, or low value impedances with the range switch set low. 1 C3 J1 1 1 IC5 74HC257 IC4 RAM IC3 EPROM C15 C4 CONN5 1 J4 IC6 74HC00 CONN4 IC1 80C31 C14 CONN3 IC7 ADM232 C6 C9 C10 C11 C12 RST C5 REG3 OUT IN OV +DC 1 X1 C16 CONN2 1 2 3 C15 1 C13 1 2 3 1 IC2 74HC573 As the measurements taken by Audio Lab are obtained by an 8-bit analog to digital conversion, the data has a maximum reso­ lution of 255 steps. Also, because the equations used to calculate impedance are non-linear, the accuracy of the reading is a func­ tion of where in the range the measurements are taken. The “Scale%” display gives an indication of this accuracy. This is not an absolute indication of the accuracy of the system but is calculated by computing the value of the impedance of the device under test at the next quantised step and displaying it as a percentage of the actual reading. This enables a choice to be made as to which combination of P/Res and frequency to use to obtain the highest accuracy. The last selection on the menu bar is “*SWEEP”. This also appears on the “LAB” screen and its function is identical. Being coloured red, this takes us to another screen where frequency sweeps are performed. If entry to the Sweep screen is from the Component measure screen, then the selected active input is Component. If entry is from the LAB screen, then which ever input was enabled is active. The LEDs show which input is selected and this is also shown on the PC display. “G.Col” scrolls through the different colours of the graph plot. “Print” prints the graph to the printer. Toggle “.Xlin.” and “.Xlog.” selects either linear frequency sweep from the pre-selected start frequency with a selected frequency incre­ment, or a full log frequency sweep from 10Hz to 20kHz. To save a project, click on *SAVE and to load or delete a previously saved project, select *FILES. All the parameters associated with a given project are saved to disc, along with the sweep data, and if these parameters are not identical to the current parameters when loading a file, a warning of “Parameter Change” is given. This stops files that have been created and saved with different ranges, inputs, etc from creating misleading plots when multiple graphs are displayed simultaneously. However, this can be overridden if required. “* SETUP ” takes us to the last C2 C16 R1 Accuracy & resolution C1 C7 C8 CONN1 Fig.5: the component overlay for the boot board. Note that the crystal and 3-terminal regulator must lay flat on the board. screen which is used to select printer options and the start and increment frequencies for the linear frequency sweep mode. A printer choice of HP Deskjet+, Epson 9-pin or Epson 24-pin emulation in either draft, final, landscape or portrait is available. If HP is chosen, resolutions of 300, 150, 100 or 75DPI can also be selected which give different size printouts. At any time, a screen dump can be taken by pressing F10. This gives a different printout to the Print selected from the Sweep screen which only This view shows how the two RCA input sockets (DC & AC) are connected to the front panel board using short lengths of tinned copper wire. Note in particular how the two earth lugs are connect to the earth pattern on the board. September 1995  79 C6 C10 1 R14 ZD1 CONN3 VREF C13 CONN2 C12 -5V 0V +5V R15 C11 Boot board Fig.6: the component overlay for the A-D board. Care must be taken with the interboard connectors. It must be assembled onto the boot board before the interboard connectors are soldered in place. To keep the stray capacitance to a minimum, when assembled, all the boards should be cleaned using a proprietary flux clean­ing spray. The power supply board should be assembled first, taking note of component polarities and ensuring the correct positioning of the 3-terminal regulators. Do not fit the 25-pin D connec­tor yet. It is also important to observe the orientation of the connectors CONN1 and CONN4, making sure the pins face to the outside of the board. Connectors CONN2 and CONN5 are not used in this project. Assemble the socket for the AC plugpack into the hole on the back panel and connect it to the “AC in” connections on the PC board. Solder two wires into the holes marked “RST”, and connect them to the reset switch MIC S1 R6 R10 CONN1 S1 R46 R45 VR1 C12 1 R11 R12 R13 VR3 R14 R15 VR4 R16 1 C9 R17 IC3 4052 C2 C5 IC2 TL072 0V C1 R2 VR8 R1 C3 1 C8 VR2 C4 R9 VR9,10 R3 IC1 TL072 SINE OUT R5 R7 R8 R4 1 XX C11 A COMPONENT B 80  Silicon Chip D3 R30 D2 1 R31 R32 R33 R34 R35 LEDS ON OTHER SIDE OF PCB LED4 LED1 LED2 LED3 LED6 LED7 Q1 DC LED5 1 C10 AC S2 1 VR7 R20 R21 R22 R23 R24 C7 R44 C13 R25 R26 R27 R28 R29 C6 0V IC6 4052 Fig.7: the component overlay for the front panel board. Note that the LEDs, sockets and binding post terminals must line up with the front panel. IC5 4051 All the PC boards are double sided, with plated-through holes, screened component overlays and solder masks so construc­tion is quite straight forward. However, it is advisable to follow the sequence of assembly to ensure the correct align­ment of the boards, especially the Front PC board. All resistors are 1% with 4-band codes. It is a good idea to check each resistor’s value with a digital multimeter before it is soldered into place. IC4 TL072 Construction R19 R18 VR6 VR5 prints the currently active graph along with the setup data. This board should be assembled, using sockets for all the ICs. Take care not to overheat the crystal or ceramic capaci­tors. The 8-way socket strips are CONN3 and CONN2 while the 9-way strip is CONN5. CONN4 is not used. There are two links on the Boot board to select the running mode of the processor. On J1, link 2 and 3 to enable the run from RAM function, and on J4, link 2 and 3 to select the polarity of address A000H. Before inserting any ICs, connect the 6-way cable from the power board to the Boot board. Power up and check that +5V is present between pins 40 and 20 on the microprocessor socket. Switch off and insert all the integrated circuits, observing correct orientation. Do not mount the boot PC board into the case at this stage. If you are using the Test PC kit, the Boot and power supply boards can now be tested. After assembling the R42 R43 Q2 D1 LED9 R41 R38 R13 R39 LED10 R40 1 D2 D-SINE IC6 74HC32 IC7 ADC0804 R12 C9 D1 1 R37 C8 IC4 4052 IC7 4051 IC5 74HC574 R36 C14 R6 C7 1 R11 C4 CONN5 VR3 R8 1 1 VR2 R3 C2 after it has been assembled into the back panel. Apply power and check the +5V and -5V rails on CONN1 and check for about +12V to +15V between +V and 0V on CONN4. If all is correct, then mount the D connector onto the back panel and solder the power supply board into place. Assemble the 3-way and 6-way interconnecting cables, ob­serving the correct orientation of the connections. The way to be sure this is correct is to place the connectors flat, so that both ends are facing away from each other and the location guides on both connectors are facing up. Then wire the connectors to­gether with no twists in the cable. Q1 R5 IC3 4093 ICI AD736 R1 R2 C5 R7 CONN1 R4 1 R9 R10 C3 VR1 IC2 TL072 C1 YY LED8 LED11 LED12 The front panel board is secured using two sets of nuts on the binding post terminals. Be sure to orient the three potentiometers as shown here and note that the metal bodies of the pots are all earthed back to the PC board using tinned copper wire. test PC board plug the board into the bus connectors on the Boot PC. The eight interconnecting pins go to port P1 on CPU pins 1-8, which is CONN2, and the 5V supply connects to pin 40 on the 80C3 which is the top pin above CONN5. Apply power and the LED connected to pin 1 should flash. Press the reset switch and the LED should stop, either on or off, and when the reset switch is released the flashing should restart. If all is well, the CPU, EPROM, reset and decoding circuitry are functioning correctly. Power down and connect Audio Lab to the serial port on your the PC, using a standard 25-way maleto-female cable. On the Calibrate/test disc is a program called LABTEST.BAT. Power on Audio Lab and the same LED will flash. Now type LABTEST from A: drive. A small 8031 machine code program called “Test.bin” is now being dumped to the RAM at 9600 baud and the LED will flash faster. After installation, the LEDs will flash in order from P1.0 to P1.7 and an acknowledgment of cor- rect data transfer will be shown on the PC. The RAM and Serial interface have now been tested and the Boot PC is functioning correctly. If any of these tests fail, check all components and the power cables to the boards. A-to-D board Assemble this board as normal but do not insert the IC sock­ets for IC5, IC7 or the PC board interconnecting strips. Connect the 3-way power cable and disconnect the 6-way cable from the Boot PC board. When powered up, check for +5V between pins 16 and 8 on IC4 and -5V between pins 7 and 8 on IC4. Turn the power off and disconnect the 3-way power cable. Gently insert the ends from the plastic holder on the PC interconnecting strips into the two 8-way PC interconnecting sockets, CONN3 and CONN5 on the Boot PC, making sure they are seated all the way down. Note that the 8-way connector for CONN5 should start at the second pin down, leaving the top pin, marked +5, empty. Carefully position the A-to-D board and the pins into CONN3 and CONN5 C3 TO S1 RST OUT IN 0V +DC C4 -5V 0V +5V CONN1 CONN4 C1 C2 D2 REG1 D1 REG2 F1 DB25 AC IN Fig.8: the component overlay for the power supply board. This carries the 25-pin D socket which mounts to the rear panel. (on the A-to-D board). Place the nylon spacers between the two boards in the holes marked A and C and screw together, with the nuts on the reverse of the Boot board. Now solder the interboard connectors in place and also solder the nuts to the underside of the Boot board. The boards can now be disassembled and the remaining IC sockets soldered in place and the ICs inserted. The Boot board can now be screwed into the case. Carefully line up the A-to-D and Boot boards and bolt them together as before and connect the cables from the power supply to both boards. Front board assembly The interconnection between the A-to-D and Front boards is made via a 16-way cable which is provided ready assembled and tested. Assemble the Front PC board but do not insert the LEDs. The switch is mounted on the component side with the mounting nut on the copper side and links made between the holes adjacent to the relevant connector and the switch. The DC and AC RCA connectors should be fixed in place with the solder lug connectors facing down and slightly bent out to ease connecting to the Front board later. Assemble all the components on the front panel, using only one nut on the two binding post terminals, and noting the orien­tation of the three front mounting pots, as shown in the above photo. Insert, but do not solder, the 12 LEDs on the copper side of the board, noting their polarity and colour which is marked on the PC overlay. Do not push them too far into the board. The Front PC is now offered up to the front panel and held in place with the September 1995  81 The power supply board (bottom, left) is mounted on the DB25 connector and is wired to the A-D and Boot boards via 3-way and 6-way cable assemblies. A 16-way cable connects the A-D board to the Front-Panel board. remaining nuts on the two binding posts. The nuts should not be tightened but should just secure the board while allowing some movement and the switch should line up with the HIGH/LOW hole. The LEDs will now line up with the holes in the front panel and can be gently pushed through the clearance holes until they are flush and poking through the panel. Slightly tighten the nuts on the binding posts and carefully solder the LEDs in place. The front board can now be removed and the ICs inserted. Reassemble the front board to the front panel and wire the pots, connectors and the ELEC switch as per the circuit diagram and component overlay on the PC board, using screened cable for the Mike connection. Connect the two earth connectors on the DC and AC 82  Silicon Chip input connectors together and link to the 0V terminal on the PC board. Link the centre connectors of the RCA sockets to their respective points marked on the board and tighten the nuts on the two binding posts. They can be soldered to the board later when the system has been tested and proved to be functional. Calibration There are a total of 10 multi-turn Kit Availability Audio Lab is designed by R.S.K. Electronics Pty Ltd who hold the copyrights and sell the complete kit. Pricing details are shown in the advertisement elsewhere in this issue. pots in the Audio Lab but the calibration is made simple by means of the software. First, insert the Test/ calibrate disk into the A: drive. Type install and a direc­ tory called C:\ ALAB will be created and the software copied into this directory. Change directory to ALAB and type SETUP. This software steps through all the procedures involved in calibra­tion, with a full graphic interface showing which pots to adjust and the reason for the calibration. After calibration is complete, exit from the program and insert the disc marked ALAB into the A: drive and type INSTALL. The full suite of software will now be copied into C:\ALAB. To run the software simply type ALAB from the C:\ALAB directory. Once you have mastered the simple menu system you will be able to flip from screen to screen. You should find Audio Lab an invaluable addition to your test equipment. SC 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 September 1995  83 VINTAGE RADIO By JOHN HILL An interesting grid bias problem One of the more interesting aspects of vintage radio is repairing non-functioning receivers. As far as I’m concerned, getting them working again is the most satisfying part of this hobby. As a person having neither an electrical or electronics trade background, I have never been properly trained to do radio repairs. I have developed my own repair techniques from reading books, asking others and doing my own investigations. As a re­sult, there is a lot I have yet to learn and learning new things helps to maintain my interest in vintage radio. Having a limited background makes one easy prey to any new fault that comes along and these tricky problems always remind me of how inexperienced I really am. But perseverance usually wins and the fault is eventually found and rectified. Solving such faults is very satisfying. A recent repair to a mid-1950s 4-valve Radiola produced one of these mystery faults and it proved to be quite elusive. Allow me to explain. A real wreck This particular receiver was one of the worst wrecks I have seen for a long time. It had obviously been stored for many years in a workshed, judging by the number of multicoloured paint splats that were on it. Why people have to flick their paint brushes at old radios I will never know! The little Radiola was filthy and mouse infested. When the set was removed from its plastic bag there remained about a tablespoon full of The Radiola was a common mid-1950s 4-valve receiver. Considering its filthy condition when found, it scrubbed up fairly well. 84  Silicon Chip mouse droppings and other miscellaneous items such as partly eaten pumpkin seeds, small bones and other debris. I hate working on sets like these! After a thorough clean up, the usual checkout routine revealed that one of the oscillator coil windings was open cir­ cuit and the rectifier valve had almost no emission. As there were plenty of 6X4s in the valve box, the weak rectifier wasn’t a problem but it did arouse a suspicion that there was something else wrong with the receiver to reduce the valve’s emission to such a low level. Other problems with the old Radiola were: (1) all the original paper capacitors were still in place; (2) the speaker grille cloth was a filthy, tattered mess; and (3) the dial cord was made up of four different sections of string. As the knots in the dial cord would not go around the pulleys, dial movement was restricted to about one quarter of its total length of travel. The things that some people put up with! An examination of the oscillator coil revealed that one of its leads had broken off. If the truth be known, the wire had most likely been chewed through by a furry little rodent. Repairing the oscillator coil was relatively simple as the broken lead protruded from the sealing compound by about two millimetres which allowed a new lead-out wire to be attached. After reinstalling the repaired oscillator coil, the set was ready for a test run, even though the paper capacitors had not been replaced at this stage. The little Radiola fired up straight away and seemed to be in good tune, pulling in a number of stations while using only its built-in aerial. Regardless of the fact that the set was performing well, the paper capacitors RESURRECTION RADIO VALVE EQUIPMENT SPECIALISTS VINTAGE RADIO • Circuits • Valves • All parts The oscillator coil (centre right) needed repairing because of a broken lead-out wire. The volume control (left) also required attention as it was noisy. • Books Fully restored radios for sale ALL TYPES AND BRANDS OF AUDIO VALVES IN STOCK Send SSAE for Catalogue Visit our Showroom at 242 Chapel Street (PO Box 2029) PRAHRAN, VIC 3181 Tel: (03) 9510 4486; Fax (03) 9529 5639 Silicon Chip Binders Replacing the electrolytic and paper capacitors had little effect on performance. However, leaving them in service is only asking for trouble later on. were replaced with modern polyester types, which seemed to make little difference. Then the rot set in! Distorted sound After the receiver had been working for a few minutes, the sound gradually became more and more distorted. What’s more, as the sound distorted, the high tension dropped from around 200V to 175V. Leaving the set to cool off for a while produced a similar result. It worked perfectly for a few minutes, then the distor­ t ion slowly crept back. So what appeared at first to be a simple and straightforward repair had now developed into one of those mystery faults. I suspected a faulty output valve and so a good secondhand 6BV7 was substituted for the valve that came with the receiver. I might add, at this stage, that both of these valves tested “GOOD” when checked in a valve tester. The result was the same – the set was OK for a few minutes, then went into a slow downhill slide until the sound became quite distorted. It was time to start thinking! Distortion is usually associated with the audio end of a receiver (but not always) and is often caused by a lack of grid bias. With this thought in mind, the back bias circuit that provides the bias voltage to the output valve was checked. The 100Ω bias resistor seemed OK and nothing could be seen that looked remotely suspect. The grid bias on the 6BV7 output valve should be somewhere around -4V, taking into account the plate voltage at which the valve was operating. These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a dis­tinctive 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. September 1995  85 increase the bias voltage to -4V and it did! But the problem remained – the recep­tion was perfect for a few minutes and then went into a slow decline just as before. An interesting discovery When testing the faulty valves, only one produced a flicker in the shorts indicator neon. Testing a valve in a valve tester is only half a test. The other half is to give it a thorough work-out in a working receiver. It was at this stage that I made an interesting discovery. I replaced the original output valve in its socket while the set was still operating. The bias voltage immediately went back to -4V, stayed there for a short period, and then started dropping again. I repeated the operation with the other valve after it had cooled and the same thing happened. The fault was in the valve – both valves, in fact! They worked OK when cold but not after they had become hot! Out came all of the 6BV7s I had in stock. I selected a new valve and fitted it to the output socket with vastly different results. The bias voltage settled on -4V and stayed there! It was too good an opportunity to miss out on and all the 6BV7s were checked in the receiver. Out of the 13 valves tested, six of them had the diminishing grid bias characteristic. So, in one hit, my 13 “good” 6BV7 valves were reduced to almost half that number. The valve tester These are the faulty 6BV7 valves. Although they all tested “GOOD” in the valve tester, they had a problem that deprived the control grid of its negative bias. They worked OK when cold but not when they became hot. It seemed an appropriate time to check out the actual bias voltage. Grid bias voltages are best checked with a digital voltmet­ er as these instruments have a very high input impedance, which has little or no affect on the function of the receiver. A cheap analog 2,000Ω/V meter can seriously affect both the voltage reading and the operation of the receiver under test. The receiver was set up with two voltmeters, one to measure the high tension voltage and the other the bias voltage. The bias reading was -3V and 86  Silicon Chip after this reading had peaked, it went into reverse and dropped slowly until it almost reached zero. And as the bias voltage dropped, so too did the high tension voltage, due to the output valve passing increasingly more current. Dis­tortion did not become apparent until the bias voltage decreased to about -1V. Perhaps the bias resistor was faulty? Maybe its value decreased as it warm­ ed up? Not having a 100Ω resistor on hand I used a 130Ω resistor as a replacement instead. Hopefully it would It’s time for the valve tester to enter our story. I set it up to recheck all the valves that had failed in the re­ceiver, even though they had previously checked out OK in the valve tester. Of the six faulty valves, only one could manage to produce a flicker in the tester’s shorts indicator neon. This short was on pin number eight which is the control grid. It would appear that these valves have a problem when they reach full operating temperature. It is worth noting that the four new valves were all OK. Only the second­ hand units produced the diminishing grid bias characteristic, even though most of them had emission levels comparable to new valves. So there’s something new to ponder over! Is the 6BV7 a more troublesome valve compared to other output valves? And what is the mechanism of the fault anyway? Initially, the most likely possibility seemed to be that the valves were gassy. And a fellow enthusiast suggested that this could be aggravated by a grid There’s nothing very exciting about a 4-valve Radiola, as it was a very basic radio receiver. Note the built-in aerial mounted above the chassis. The valve line up is as follows: 6BE6, 6AU6, 6BV7 (output) and 6X4 (rectifier). resistor that had “gone high”, as they frequently did in those days. However, these ideas had to be discounted. All resistors are routinely checked during restoration and any found to be out of tolerance are replaced. Also, I took the opportunity to try these valves in another set and they behaved identically. That seemed to further confirm that the fault was in the valves rather than in any associated circuits. And the gas theory seemed to be ruled out by the fact that there was no violet glow in the valves, which is characteristic of this condition. Another idea which was considered was a fault known as “silver migration”. It occurred in valves with silver plated pins, the silver “migrating” across the glass, particularly between pins with a high voltage between them. This idea was also thrown out. For one thing, the warm-up delay didn’t seem to fit but, more importantly, the pins were not silver plated. Finally, the most likely explanation would seem to be a condition known as grid emission. Apparently, this can occur when the grid becomes coated with cathode material, generally due to the heater being overrun for long periods. So, perhaps that is the answer. But the question remains as to whether this type of valve is prone to this problem. An unusual valve Incidentally, for those unfamiliar with the 6BV7, it is a little unusual in that it is a duo-diode output pentode. As far as I’m concerned, it is the only one of its kind and I also suspect that it is a locally designed and manufactured valve, as it doesn’t seem to be mentioned in overseas valve lists. Actually, a duo-diode output valve is a logical type to use in a 4-valve VINTAGE RADIO SWAP MEET 22nd October 1995 Glenroy Tech School Hall Melbourne Admission: $3 Enquiries: (054) 49 3207 radio. If a receiver is to have automatic gain control and diode detection, then there have to be diodes some­where, so why not have them in the output valve? Another mid-1950s 4-valve setup was to use valves of the duo-diode RF pentode type (6N8, 6AR7) as an IF amplifier detector and pass the resulting audio signal to a standard output valve such as a 6M5 or 6AQ5. Looking back on the Radiola repair, perhaps the most annoy­ing aspect was the fact that the fault was accurately diagnosed quite early as being a suspect output valve. It was ironic (read rotten luck) that the substitute valve used to check out this theory happened to have exactly the same fault! Anyway, learning new things helps to maintain my interest in vintage radio. It is unusual faults like the one just de­scribed and their remedies that make vintage radio repairs both interesting and challenging. When I finally learn all there is to know about valve radio servicing, then all the fun will have gone out of it for me. However, as that time seems a long way off, I’m sure that vintage radio will continue to hold my interest for many years to come. SC September 1995  87 BOOKSHELF Servicing Personal Computers Servicing Personal Computers, by Michael Tooley, B. A. Pub­lished 1994 by Newnes, distributed by ButterworthHeinemann Australia. Hard covers, 387 pages, 240 x 170mm, ISBN 0-750-61757-8. Price $68.95. In this age of personal computers (or PCs as they have become known), many users, while not necessarily wanting to repair their own, will be keen to have a better understanding of the “innards” of their computer. This book will certainly en­lighten them. The first of the eight chapters in this book begins with an introduction to microprocessors, detailing the different modules that make up a typical computer. It then goes on to discuss the evolution of the home computer, beginning with the release of the 4004, a 4-bit processor, by Intel in 1971. Subsequent proces­sors of note are then listed, through to the Intel 80486 and Motorola 68030. A couple of pages are then devoted to a discourse on pro­gramming, mentioning both assembly and high-level languages. RAM (Random Access Memory) is then covered in some detail, after which brief details are given of keyboards, serial I/O (input/output), RS232 interfaces, raster scan displays and final­ly SCSI (Small Computer Systems Interface) controllers. The second chapter covers the selection of a suitable work­shop site and the consideration that should be given to work­ benches, storage, lighting, 88  Silicon Chip security and safety. A list of the basic tools required for competent service is given along with an extended list, although I believe that every workshop should consider the extended list to be the minimum. Tooley then gives a list of the minimum test equipment which would be required to set up a workshop with adequate facil­ities, then an extended list which would add many dollars to the cost. A short discussion follows on the methods of using multi­meters, oscilloscopes, logic probes, logic pulsers and logic analysers. Chapter three covers general fault diagnosis at three lev­els: basic, intermediate and advanced. Basic level skills are defined as being able to locate blown fuses, faulty cables or failed hard disc drives. Intermediate skills would allow the technician to locate intermittent connectors, faulty discrete components or a failed processor. Those possessing advanced skills would be able to locate intermittent problems, temperature faults and bus conflicts. The balance of the chapter is devot- ed to fault finding techniques for the CPU (Central Processing Unit), video circuits and RS-232 interface. Chapter four introduces the reader to tape and disc drives. Some of this material is rather antiquated (tape recorders using Kansas City recording standards) but if one is to make a living servicing computers, this know­ledge could be useful. The evolution of floppy discs is traced from the 8-inch though the 5.25inch to the current 3.5-inch types. As well, technical informa­tion is listed for a number of popular drives. The author then gives a description of the original IBM 8-inch format, which is still the basis for formatting current floppy discs. Details of several floppy disc controllers are included as well as methods of fault diagnosis for floppy disc drives. The balance of this chapter is devoted to hard disc drives, including formatting, partitioning and the use of the DOS FDISK program. Chapter five is devoted to printers, which, being mechani­ cal devices, require routine maintenance to keep them operating at peak performance. The author introduces dot matrix printers and explains how the print head actually prints a character, then lists the sensing mechanisms needed to keep track of the head position. A two-page table of dot matrix printer faults and repair procedures follows. A few lines are then devoted to the operation of laser printers and details of the self-test procedures which should be carried out to determine the cause of any failure. Routine main­ tenance and a one-page fault finding guide complete this chapter. “Displays” is the title for chapter six, which surprisingly only covers raster scan displays. A raster scan is one that uses a cathode ray tube and deflection coils to move the electron beam across the face of the tube, as distinct 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 Street ___________________________________________________________ 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). ✂ from LCD and other newer solid state displays. Tooley starts by explaining the require­ments for a video monitor and the reasons why a normal TV set is unsatisfactory. This is followed up with a block diagram of a monochrome monitor. He continues with details of the colour shadow mask tube and the procedure for making colour adjustments. The chapter concludes with two pages of display faults and their cures. Chapter seven covers servicing of 68000 based microcomput­ers. Computers that use this chip include the Apple Macintosh, the Sinclair QL, the Atari ST and the Commodore Amiga. The sec­tion devoted to each of these products includes a block diagram of the computer, a memory map and details of upgrades or modifi­cations recommended by the respective manufacturers. The final chapter is about servicing the IBM and compatible PCs. It starts with a brief description of the original IBM XT and works through to the PS/2 80. While the chapter mainly covers IBM machines, the Amstrad PC1640 block diagram and other details are included. Details and pin connections of the 8087 maths co-processor, the 8273A DMA (Direct Memory Access) controller and the 8253 (PIT) programmable interval timer, as well as several other im­portant chips, are given, along with a Qbasic program to test whether a co-processor is fitted to the PC board. The memory terminology for PCs is explained as well as the function of the CMOS RAM and the BIOS (Basic Input Output System) ROM. The chapter continues with a description of the evolution of the PC bus and concludes with details of the video modes and colours available with each mode. A reference section of some 40 pages concludes this book, containing information on commonly used symbols, RAM data, char­acter sets, power on self test and seven other useful summaries. To conclude, a very interesting book which covers all as­pects of PCs, from basics to quite advanced fault finding. Our copy came from Butterworth-Heinemann Australia, PO Box 5577, West Chatswood, NSW 2067. Copies can be obtained from SILICON CHIP. The ordering details are shown in the SILICON CHIP Bookshop advertisement in this issue. SC September 1995  89 NICS O R T 2223 LEC PC CONTROLLED PROGRAMMABLE POWER SWITCH MODULE This module is a four channel programmable W 0 S 1 N 9 , driver for high power relays. It can be used in 7 y le 70 any application which requires algorithm control 9, Oat Fax (02) 5 rd 8 a x C o for high power switching. This module can work Visa PO B 579 4985 as a programmable power on/off switch to limit fax a rd , ) & C 2 0 e ( r unauthorised access to equipment where the n e e o t n s h : o s a p r h P access to use or change parameters is critical. , M ith rde d o w r a d d c e This module can also be used as a universal B a n k x accepte most mix 0. Orders timer. The timer software application is ine r 1 o m $ f A ) cluded with the module. Using this software l i P a & & m r the operator can program the on/off status (ai s. P t r Z e e N n d . r ; of four independent devices in a period of o rld $10 o w 4 $ <at> a week within an accuracy of 10 minutes. . tley a Aust o : The module can be controlled through L I A M the Centronics or RS232 port. The computer is opto by E isolated from the unit, to ensure no damage can occur to the computer. Although the relays included are designed for 240V operation, they have not been approved by the electrical LEARNING - UNIVERSAL REMOTE CONTROL authorities for attachment to the mains. Power consumption These Learning IR Remote Controls can be used to replace is 7W. Main module: 146 x 53 x 40mm. Display panel: 146 up to eight dedicated IR Remote Controls: $45 x 15mm. We supply: two fully assembled and tested PCBs (main plus control panel), four relays (each with 3 x 10A / NEW CATALOGUE AT OUR WEB SITE 240V AC relay contacts), and software on 3.5" disk. We do We have combined efforts with DIY ELECTRONICS (a Hong not supply a casing or front panels. Kong based company) in producing a WEB SITE on the $92 (Cat G20) INTERNET. At this site you can view and download a text version of both of our latest catalogues and other up to date 3.5 DIGIT LCD PANEL METER information. Email orders can also be placed through here. 200mV full scale input sensitivity, “1999” count, 9 to 12V The combined effort means that you get offered an extensive <at> 1mA operation, decimal point selectable (with jumper range of over 200 high quality, good value kits, and many wire), 13mm figure height, auto polarity indicator, overrange more interesting components and items. The range of kits indication, 100Mohm input resistance, 0.5% accuracy, 2 to offered includes simple to more advanced kits, and they cover 3 readings per second. With bezel and faceplate. Dimensions: a very wide field of applications: educational, experimental, 68 x 44mm. Use in instrumentation projects. EPROM, microprocessor, computer, remote control, high $27 (Cat D01) voltage, gas and diode lasers, night vision etc. We’ll leave it to you to do the exploring at: CCD CAMERA-VCR SECURITY SYSTEM http://www.hk.super.net/~diykit This kit plus ready made PIR detector module and “learning You can also request us to send you a copy of our FREE remote control” combination can trigger any domestic IR catalogue with your next order. remote controlled VCR to RECORD human activity within a 6M range and with an 180 deg. angle of view!. Starts HELIUM-NEON LASER BARGAIN VCR recording at first movement and ceases recording Helium neon 633nM red laser heads (ie tubes sealed in a few minutes after the last movement has stopped; just a tubular metal case with an inbuilt ballast resistor) that like commercial CCD-VIDEO RECORDING systems costing were removed from equipment that is less than 5 years thousands of dollars!! CCD camera not supplied. No conold. These are suitable for light shows. Output power is in nection is required to your existing domestic VCR as the the range of 2.5-7.5mW. Heads are grouped according to system employs an “IR learning remote control”: $90 for output power range. Dimensions of the head are 380mm an PIR detector module, plus control kit, plus a suitable long and 45mm diameter. Weight: 0.6kg. A special high “lR learning remote” control and instructions: $65 when voltage supply is required to operate these heads. With purchased in conjunction with our CCD camera. Previous each tube we will include our 12V universal laser power CCD camera purchasers may claim the reduced price with supply kit MkIV (our new transformers don’t fail). Warning: proof of purchase. involves high voltage operation at a very dangerous energy level. SUPER SPECIAL: FLUORESCENT LIGHTING SPECIAL $80 for a 2.5-4.0mW tube and supply. (Cat L01) A 12V-350V DC-DC converter (with larger MOSFETS) plus a $130 for a 4.0-6.5mW tube and supply. (Cat L02) dimmable mains operated HF ballast. This pair will operate a This combination will require a source of 12V <at> at least 32-40W fluorescent tube from a 12V battery: very efficient. 2.0A. A 12V gel battery or car battery is suitable, or if 240V See June 95 EA: $36 for the kit plus the ballast. operation is required our Wang computer power supply (cat number P01) is ideal. Our SPECIAL PRICE for the Wang power STEREO SPEAKER SETS supply when purchased with matching laser head/inverter A total of four speakers to suit the making of two 2-way kit is an additional $10. speakers (stereo). The bass-midrange speakers are of good quality, European made, with cloth surround, as used in LASER WARNINGS: upmarket stereo televisions, rectangular, 80 x 200mm. The 1. Do not stare into laser beams; eye damage will result. tweeters are good quality cone types, square, 85 x 85mm. 2. Laser tubes use high voltage at dangerous energy levels; Two woofers and two tweeters: $16. be aware of the dangers. 3. Some lasers may require licensing. NEW: PHOTOGRAPHIC KITS SLAVE FLASH: very small, very simple, very effective. ARGON-ION HEADS Triggers remote flashes from camera’s own flash to fill in Used Argon-Ion heads with 30-100mW output in the blueshadows. Does not false trigger and it is very sensitive. Can green spectrum. Head only supplied. Needs 3Vac <at> 15A even be used in large rooms. PCB and components kit: $7. for the filament and approx 100Vdc <at> 10A into the driver SOUND ACTIVATED FLASH: adapted from ETI Project circuitry that is built into the head. We provide a circuit for a 514. Adjustable sensitivity & delay enable the creation suitable power supply the main cost of which is for the large of some fascinating photographs. Has LED indicator that transformer required: $170 from the mentioned supplier. makes setting up much easier. PCB, components, plus Basic information on power supply provided. Dimensions: microphone: $13. 35 x 16 x 16cm. Weight: 5.9kg. 1 year guarantee on head. Price graded according to hours on the hour meter. SINGLE CHANNEL UHF WITH CENTRAL LOCKING Argon heads only, 4-8 thousand hours: $350 (Cat L04) Our single channel UHF receiver kit has been updated to Argon heads only, 8-13 thousand hours: $250 (Cat L05) provide provision for central locking!! Key chain Tx has SAW resonator locked, see SC Dec 92. Compact receiver GEIGER COUNTER AND GEIGER TUBES has prebuilt UHF receiver module, and has provision for two These ready made Geiger counters detect dangerous Beta and extra relays for vehicle central locking function. Kit comes Gamma rays, with energy levels between 30keV and 1.2MeV. with two relays. $36. Additional relays for central locking $3 Audible counts output, also a red LED flashes. Geiger tube ea. Single ch transmitter kit $18. unplugs from main unit. To measure and record the value of nuclear radiation level the operator may employ a PC which is MASTHEAD AMPLIFIER SPECIAL connected to the detector through the RS232 interface. This High performance low noise masthead amplifier covers gives a readout, after every 8 counts, of the time between each VHF-FM UHF and is based on a MAR-6 IC. Includes two count. Main unit is 70 x 52 x 35 mm. Geiger tube housing PCBs, all on-board components. For a limited time we will unit is 135mm long and is 20mm diameter. Power from 12 also include a suitable plugpack to power the amplifier from to 14V AC or DC. mains for a total price of: $75 (Cat G17) $25 EY OATL E 90  Silicon Chip CCD CAMERA Very small PCB CCD Camera including auto iris lens: 0.1Lux, 320K pixels, IR responsive, has 6 IR LEDs on PCB. Slightly bigger than a box of matches!: $180 VISIBLE LASER DIODE KIT A 5mW/670nM 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. 12V-2.5 WATT SOLAR PANEL KITS These US made amorphous glass solar panels only need terminating and weather proofing. We provide clips and backing glass. Very easy to complete. Dimensions: 305 x 228mm, Vo-c: 18-20V, Is-c: 250mA. SPECIAL REDUCED PRICE: $20 ea. or 4 for $60 A very efficient switching regulator kit is available: Suits 12-24V batteries, 0.1-16A panels, $27. Also available is a simple and efficient shunt regulator kit, $5. 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 either of the above, for an additional price of $10. BATTERY CHARGER Simple kit which is based on a commercial 12 hour mechanical timer switch which sets the battery charging period from 0 to 12 hrs. Timer clock mechanism is wound-up and started by turning the knob to the desired time setting. Linear dial with 2 hrs timing per 45 degrees of rotation, eg, 270 deg. rotation for 12 hr. setting. The contacts on the timer are used to switch on a simple constant current source. Employs a power transistor and 5 additional components. Can easily be “hard wired”. We supply a circuit, a wiring diagram, and tables showing how to select the charging current: changing one resistor value. Ideal for most rechargeable batteries. As an example most gel cells can be charged at a current which is equal to the battery capacity rating divided by 5-10. Therefore if you have a discharged gel cell that has 5Ah capacity and are using a charge current of 0.5A, the timer should be set for about 10 hours: Or 5hrs. <at> 500mA. This circuit is suitable for up to approximately 5A, but additional heatsinking would be required at currents greater than 2A. Parts and instructions only are supplied in this kit. Includes a T-03 mini fin heatsink, timer switch, power transistor and a few other small components to give you a limited 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 need 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 0-15V: $12 (K72) 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. 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 choice for a special price. Choose motors from M17/M18/M35. $44 (K21) Kit without motors is also available: $32 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. 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) 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) VHF MODULATOR FOR B/W CAMERAS (To be published, EA) Simple modulator which can be adjusted to operate between about channels 7 and 11 in the VHF TV band. This is designed for use in conjunction with monochrome CCD cameras to give adequate results with a cheap TV. The incoming video simply directly modulates the VHF oscillator. This allows operation with a TV without the necessity of connecting up wires, if not desired, by simply placing the modulator within about 50cm from the TV antenna. Suits PAL and NTSC systems. PCB: 63 x 37mm: $12 (K63) 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 1 to 2 CHANNEL UHF REMOTE CONTROL (To be published, SC) A single channel 304MHz UHF remote control with over 1/2 million code combinations, which also makes provision for a second channel expansion. The low cost design has a 2A relay contact output. The 1ch transmitter (K41) can be used to control one channel of the receiver. To access the second channel when another transmitter is purchased, the other transmitter is coded differently. Alternatively, the 3ch transmitter kit (K40) as used with the 4ch receiver kit is compatible with this receiver and allows access to both channels from the one transmitter. Note that the receiver uses two separate decoder ICs. This receiver operates from 10 to 15Vdc. Range is up to about 40m. 1ch Rx kit: $22 (K26) Expansion components (to convert the receiver to 2 channel operation; extra decoder IC and relay): $6 ONE CHANNEL UHF TRANSMITTER AX5326 encoder. Transmit frequency adjustable by trimcap. Centred around 304MHz. Powered from 12V lighter battery. LED flashes when transmitting. Size of transmitter case: 67 x 30 x 13 mm. This kit is trickier to assemble than the 3ch UHF transmitter: $11 (K41) THREE CHANNEL UHF TRANSMITTER The same basic circuit as the 1ch transmitter. Two buttons, allows up to 3 channel operation. Easier to assemble than the 1ch transmitter and has slightly greater range. Size of transmitter case: 54 x 36 x 15mm: $18 (K40) ULTRASONIC RADAR Ref: EA Oct 94. This unit is designed to sound a buzzer and/or operate a relay when there is an object at a preset distance (or less) away. The distance is adjustable from 200mm to around 2.5 metres. Intended as a parking aid in a car or truck, also may be used as an aid for the sight impaired, warning device when someone approaches a danger zone, door entry sensor. PCB: 92 x 52mm. PCB, all on-board components kit plus ultrasonic transducers (relay included): $22 (K25) Optional: buzzer $3, plastic box $4. SIREN USING SPEAKER Uses the same siren driver circuit as in the “Protect anything alarm kit”, kit number K18. 4" cone/8 ohm speaker is included. Generates a really irritating sound at a sound pressure level of 95dB <at> 1m. Based around a 40106 hex Schmitt trigger inverter IC. One oscillator modulates at 1Hz another oscillator, 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 (K71) PLASMA BALL Ref: EA Jan 94. This kit will produce a fascinating colourful changing high voltage discharge in a standard domestic light bulb. 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) We do not supply the standard light bulb or any casing. The prototype supply was housed in a large coffee jar, with the lamp mounted on the lid. Hint: connect the AC output to one of the pins on a fluorescent tube or a non-functional but gassed laser tube. Large non-functional laser tube or tube head: $10 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) TOMINON HIGH POWER LENS These 230mm (1:4.5) lens have never been used. They contain six coated glass lenses, symmetric, housed in a black aluminium case. Scale range is from 1:10 through to 1:1 to 10:1. Weight: 1.6kg. Applications include high quality image projection at macro scales, and portrait photography in large formats: $45 (Cat O14) PROJECTION LENS Brand new, precision angled projection lens. Overall size is 210 x 136mm. Weight: 1.3kg. High-impact lexan housing with focal length adjustment lever. When disassembled, this lens assembly yields three 4" diameter lenses (concave, convex-concave, convex-convex). Limited quantity: $35 (Cat O15) INTENSIFIED NIGHT VIEWER KIT Reference article: Silicon Chip Sept 94. See in the dark! Make your own 3 stage first generation night scope that will produce good vision in starlight illumination! Uses 3 of the above fibre optic tubes bonded together. These tubes have superior gain and resolution to Russian viewers. 25mm size tube only weighs 390g. 40mm size tube only weighs 1.1kg. We supply a three stage fibre optically coupled image intensifier tube, EHT power supply kit which operates from 6 to 12V, and sufficient plastics to make a monocular scope. The three tubes are already bonded together: $270 for the 25mm version (Cat N04) $300 for the 40mm version (Cat N05) We can also supply a quality Peak brand 10x “plalupe” for use as an eyepiece which suits all the above 25 and 40mm windowed tubes well: $18 35mm camera lenses or either of the Russian objective lenses detailed under “Optical” suit these tubes quite well. IR “TANK” TUBE/SUPPLY KIT These components can be the basis of a very responsive infra red night viewer; the exact construction of which we leave up to you. The new IR tube is as used in older style military tank viewers. The tube employed is probably the most sensitive IR responsive tube we have ever supplied. Responds well even to 940nm LED illumination. The resultant viewer requires IR illumination, as without this it will otherwise only “see” a little bit better than the naked eye. Single tube, first generation. Screen diameter: 18mm. Tube length 95mm. Diameter: 55mm. Weight: 100g. Tube can be operated up to about 15kV. Our miniature night viewer power supply (kit number K52) is supplied with its instructions included. Only very basic ideas for construction of viewer is provided. Tube and the power supply kit only: $80 (Cat N06) RUSSIAN SCOPE KIT Our hybrid Russian/Oatley kit design makes this the pick of the Russian scopes in this price range! We supply a fully assembled Russian compact scope housing containing the intensifier tube, adjustable eyepiece and objective lens. Housing is made from aluminium. The objective lens is fixed in focus, but it is adjustable after loosening a grub screw. We also include the night viewer power supply kit (kit number K52) and a small (84 x 55 x 32mm) jiffy box to house the supply in. The box must be attached by you to the scope housing. Operates from a 9V battery. This scope has a useful visible gain but is difficult to IR illuminate satisfactorily. Length of scope is 155mm: $290 (Cat N07) LASER POINTER A complete brand new 5mW/670nM pointer in a compact plastic case (75 x 42 x 18mm) with a key chain. Features an automatic power control circuit (APC) which is similar to our kit number K35 & our laser diode module’s circuit. Battery life: 10 hours of operation. Powered by two 1.5V N type batteries (included). This item may require licensing: $80 (Cat L08) MAGNETIC CARD READER Commercial cased unit that will read some information from most plastic cards, needs 8 to 12V DC supply such as a plugpack. Draws about 400mA. Power input socket is 2.5mm DC power type. Weight: 850g. 220 x 160 x 45mm: $70 (Cat G05) 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 MODULES 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. 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 and consumes approx 50mA. Note: 5V must not be exceeded and there must be no ripple on the power supply, or the module may be instantly destroyed. These items may require licensing. We have two types: 1. Overall dimensions: 11mm diameter by 40mm long. Driver board is heatshrinked onto the laser housing assembly. Collimating lens is the same as used in the above laser pointer, and our visible laser diode kit: $55 (Cat L09) 2. 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 1milliradian. 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. FLUORESCENT LIGHT HIGH FREQUENCY BALLASTS European made, new, “slim line” cased, high frequency (HF) electronic ballasts. They feature flicker free starting, extended tube life, improved efficiency, no visual flicker during operation (as high frequency operation), reduced chance of strobing with rotating machinery, generate no audible noise and generate much reduced radio frequency interference compared to conventional ballasts. The design of these appears to be similar to the one published in the October 1994 issue of Silicon Chip magazine, in that a high frequency sine wave is used, although these are much more complex. Some models include a dimming option which requires either an external 100K potentiometer or a 0-10V DC source. Some models require the use of a separate filter choke (with dimensions of 16 x 4 x 3.2cm); this is supplied where required. We have a limited stock of these and are offering them at fraction of the cost of the parts used in them! Type A: 1 x 16W tube, not dimmable, no filter, 44 x 4 x 3.5cm: $20 Type B: 1 x 16W tube, dimmable, filter used, 43 x 4 x 3cm: $26 Type C: 1 x 18W tube, not dimmable, no filter, 28 x 4 x 3cm: $20 Type D: 2 x 32W or 36W tubes, dimmable, no filter, 43 x 4 x 3cm: $26 Type E: 2 x 32W tubes, not dimmable, no filter, 44 x 4 x 3.5cm: $22 Type F: 1 x 32W or 36W tube, not dimmable, no filter, 34 x 4 x 3cm: $20 Type G: 1 x 36W tube, not dimmable, filter used, 28 x 4 x 3cm: $20 Type H: 1 x 32W or 36W tube, dimmable, filter used, 44 x 4 x 3.5cm: $20 (Cat G09, specify type). 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. 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. Max speed reading: 160km/h. Max odometer reading: 9999km. Maximum tripmeter reading: 999.9km. Dimensions of main unit: 64 x 50 x 19mm: $32 (Cat G16) September 1995  91 PRODUCT SHOWCASE Protek 505 digital multimeter has dual display This Protek 505 digital multimeter has a large dual digital display plus bar graph, true RMS readings, memory storage and 4000 count resolution. As well, it will measure temperature, frequency, capacitance and inductance. While all multimeters will perform voltage, current, resistance and diode tests, there are not many which can also measure temperature, frequency, capacitance, inductance, logic levels and dBm values. You can also measure time period for stop watch or alarm functions and store measured values in up to nine memory locations. The Protek 505 also includes a signal generator with three output frequencies (2048, 4096 and 8192Hz square wave). Naturally it is autoranging and this can be overridden if required. The Liquid Crystal Display (LCD) has a dual digital readout and bar graph plus numerous annunciators. This dual readout allows two measurements to be displayed and measured at once. For example, when measuring AUDIO TRANSFORMERS Manufactured in Australia Comprehensive data available Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 476-5854 Fx (02) 476-3231 92  Silicon Chip frequency, the display will show the reading in Hz on the main display and the value of AC volts on the secondary scale. When the time display is selected, this is shown on the secondary scale with the measured value of volts, current, temperature or resistance on the main digits. There is no skimping on the size of the display either. The main and secondary display digits are 19mm and 9mm high respectively while the bar graph displays from 0 to 40 with 21 active segments. The word "active" is used because the display appears to have 37 segments, however, 16 of these are doubled up so that they are "lit" together. Knowing this is important for attempting to read the bargraph value. The bargraph is useful for seeing the trend of value changes which can be too fast for the digital display to update. The display can be backlit for use in dark locations. Most of the functions available can be manipulated to provide maximum, minimum, average and relative readings. These are accessed using the menu key. Once this key has been pressed though, there is no way out; you are stuck with selecting either Max, Min, Avg, Rel or Keep On unless power is switched off. We would prefer to have an Out selection which restores the meter to provide normal readings. The relative (Rel) display is useful when there is a fixed offset in the measurement. This can be subtracted so that only the change is displayed. Relative readings can also be displayed as a percentage change from the reference value. A hold feature freezes the display at any time so that no further changes in the reading take place. Readings can also be placed in memory for a more permanent storage. There are 9 memories available, labelled 1-9. The "0" memory location is innactive and cannot be used for storage. It can be recalled but it only shows 0000. The handbook indicates that this memory location is not useable, however, they also claim that there are 10 memory locations! The memory locations are not erased when the meter turns off in the auto power off mode. To prevent the meter from switching off after 30 minutes of inactivity, a "keep on " facility is available which disables the automatic power off. Naturally, the meter can be turned on and off at will using a separate push button switch. The handbook recommends switching off manually rather than waiting for the automatic power Optical light sources & power meter Tektronix has introduced a new line of handheld optical test products that include the TOP130, TOP140 and TOP150 optical light sources, the TOP200 power meter and the TOP300 visual fault finder. The TOP130 emits at 850/1300nm and is suitable for testing multimode cable used in LANs and WANs; the TOP140 laser source emits at 1310nm and the TOP150 laser source emits at 1550nm. Models TOP140 and TOP150 are used for testing single mode cables in Telco and CATV networks. All the light sources feature a off feature. This would be a good idea since battery life is only about 60 hours with a carbon zinc battery. Fortunately, a low battery warning indicator is included so that you will know when to replace it and a separate battery compartment is provided allowing easy access. Diode readings display the foreward voltage measured between anode and cathode on the secondary display. The main display shows either SHrt (short), OPEn or Good. These are supposed to tell you whether the diode is operating correctly. We found that good Schottky and high speed diodes universal connector interface for easy upgrade and cleaning. Battery life is claimed to be over 100 hours with standard alkaline batteries. A companion product to Tektronix optical light sources is the TOP200 optical power meter. It is a lowcost, palm-size unit that makes the basic optical power measurements in either dB or dBm, calibrated at 850nm, 1300nm and 1550nm. This power meter provides 0.01dB resolution and allows the user to store reference values for each wavelength independently. For further information, contact Tektronix Australia Pty Ltd, 80 Waterloo Road, North Ryde, NSW 2113. Phone (02) 887 7066. gave a "short" indication because their forward voltage was below 0.5V. The diode test provides up to 4V and so LEDs can be tested. The LED will light up and an open indication will be given because the forward voltage of the LED is greater than 1V. Some discretion must therefore be used when interpreting the short and open indications. Temperature sensing must be done using a "K" type thermocouple, which is available as an accessory. The probe can measure temperature from -20 to 1200 degrees C which is then shown on the main display. The secondary September 1995  93 Video magnifier uses CCD camera This 1/2" colour CCD high resolution video camera/microscope provides 10x, 20x and 40x magnification with greater than 450 lines horizontal resolution. The SVC-228 offers advantages over magnifying glasses and other optical inspection devices. Several or groups of people can simultaneously observe the image for discussion; images may be recorded on a VCR or by using an interface card stored, in a personal computer for documentation, manipulation, measurement or printout. The SVC-228 comprises a main unit which houses the power supply and interface circuitry and connects via a 2 metre cable to the camera head. Optional lenses provide a choice of magnification. Also available is an adjustable stand with lamps display shows the Fahrenheit value. With no probe connected, the readout will show ambient temperature and is useful for finding out why you feel cold (we reviewed this meter in winter!). While the meter can read inductance it is restricted values above 10mH which is a relatively large value in practice. Most inductances used in RF and switchmode supplies are much smaller than this. Note also that if the Q is less than 10 or the coil resistance is greater than 100W, then inaccuracies will result. Capacitance measurement range is better, at up to 100µF with a 0.01µF resolution. This means that you can measure 10nF and larger up to 99µF. Audio Lab for illumination. Applications include assembly and inspection of mechanical parts, components, surface mount devices, printed circuit boards, contacts, connectors, measurement, quality control and verification. For further information contact Allthings Sales & Services, PO Box 25, Northlands, WA 6021. Phone (09) 349 9413 or fax (09) 344 5905. We would have preferred to be able to measure much smaller values than 10nF (.01µF). The frequency meter mode can be used for measurement from 1Hz up to 9999MHz with 4 digit resolution. The input signal for the frequency mode is a minimum of 1.5V RMS (4.24V p-p). This is find for CMOS and TTL circuits but most analog and RF circuits will need a preamp/buffer for meaningful measurements. Incidentally, the meter incorporates a logic level range which indicates a logic Hi and logic Lo on the main display. The in-between voltage where the logic is indeterminate is indicated by a "....". Logic voltage is set for TTL levels and so it is suitable for High R.S.K. Electronics Pty. Ltd. Complete Audio Lab kit with PCBs, 1% resistors, PTH screened PCBs, IC sockets, boot Eprom, screen printed case, 8K RAM, 8031 processor and all ICs. Includes calibration and Audio Lab V5.1 software 10 VAC 1A plugpack plus socket $18. 2-Metre serial cable $9. $330 inc. tax. Processor test kit $15. Freight $9. Fully assembled & calibrated complete with plugpack (1-year warranty) $450 5 Ludwig Place, Duncraig, Perth WA 6023 94  Silicon Chip Phone (09) 448 3787 Speed CMOS as well. Three output frequencies are available from the meter. These are at 8192, 4096 and 2048Hz with a 4V p-p minimum output. The source impedance is 1.5kW so that it can drive logic circuitry. Interestingly enough, the signal swings between -0.7V and +3.3V. The is indicates that the internal signal generator must be AC coupled with a diode clamp to prevent the negative excursion going beyond one diode drop. Timer counting is available for up to 10 hours with a count rate of one second. You can count up from zero to 9Hr 59min 59sec and the alarm will sound one second after this maximum count has been reached. The counter is presettable to any time within this range. Counting down is also possible. In this case, however, the alarm sounds one second after 0.00.00 has been reached. AC voltage measurement is true RMS. This means that the correct reading is obtained for waveforms other than pure sine waves. On a normal meter without true RMS readings, the display is calibrated to give a correct RMS reading only for sine waves. With true RMS, the reading is essentially correct for other types of waves. For example, the additional error in reading compared to the sine wave for square and triangle waves is 0.2% and 0.3% respectively. For crest factors up to 2, the additional error is 0.5%. For accuracy details see the latter part of this review. Also on the AC voltage range is displayed a dBm reading on the secondary display. A reading of 0dBm means that the voltage is 0.7746V. This corresponds to 1mW into a 600W load and all dBm values displayed are referenced to this level. Continuity measurements are available with or without a tone. With tone selected the meter will register an OPEn condition above 100W and will show a short otherwise. Without the tone selected, the meter only shows the value in ohms. Accuracy The Protek 505 has ±0.3% +2 digits accuracy for the 400mV DC range. For the 4V to 1000V ranges, the accuracy is ±0.5% +2 digits. AC voltage accuracy is ±1% +3 digits for the 400mVAC range from 50Hz to 1kHz. The 4VAC to 750VAC ranges are ±1.5% +5 digits accuracy from 50Hz to 100Hz for the 4VAC range and up to 500Hz for the remaining ranges. Resistance accuracy is ±0.5% +2 digits up to 400kW and 1% +2 digits for ranges above this. DC current accuracy is ±1% +2 digits and AC current is ±1.5% +3 digits from 50Hz to 100Hz. This rises to ±3% +5 digits from 100Hz to 1kHz. Frequency accuracy is ±0.01% ±2 digits. Temperature accuracy is ±3% +5 digits from -20 to 10 degrees C. It is ±3% +3 digits from 10 to 350 degrees C. Capacitance accuracy is ±3% +5 digits and inductance accuracy is the same for values up to 20H. The meter is fully protected from over voltage and over current using fuses and a PTC thermistor. A spare 0.5A fuse is included inside the case, however, there is no spare 20A fast blow type included. The meter is supplied in a vinyl case which also holds the probe leads and handbook. The probes have two screwon aligator clips for the probe tips which are a worthwhile inclusion. In short, the Protek 505 is a lot of meter for the money. With true RMS measurement, dual display, bar graph and a host of measurement functions, it will be a popular unit. It is priced at $229 including tax and is available from Altronics in Perth or from their dealers Australia wide. Phone 1 800 999 007. Fast response oxygen probe Novatech Controls have developed a fast responding oxygen sensing probe for flue gas, furnace and kiln applications. The development program was in response to market demands from within Australia and overseas. The zirconia sensor has a response time in the millisecond region but is extended by the time taken to introduce the gas sample from the process to the sensor. This total speed of response time can be critical, particularly in automatic combustion trim systems. The Novatech development, which was the result of extensive wind tunnel testing, provides users with a probe which will respond to changes in the oxygen level of the sample within four seconds. It has an optional 10 micron particulate filter for flues with fly ash or other material which can block up sensing ports. The benefit to users of fast responding flue gas oxygen sensing probes is improved trim control of combustion air/fuel ratio. This means savings in fuel. In some critical cases where process measurement lag cannot be tolerated, automatic control may be implemented where it was not previously possible. Novatech oxygen probes use advanced zirconia cell technology developed by the CSIRO Division of Materials Science and Technology. For further information, contact Novatech Controls (Aust) Pty Ltd, 429 Graham St, Port Melbourne, Vic 3207. Phone (03) 9645 2377 or fax (03) 9646 3027. KITS-R-US 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: FMTX5 built and tested, enclosed in a quality case with plugpack, DIN input •connector for audioa complete 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. Professional 19" Rack Mount PC Case: $999. •• 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. Pattern generator for TV & computer monitors Obiat Pty Ltd has introduced the Black Star 1410 video monitor tester, a microprocessor controlled instrument for aligning and testing computer and TV monitors and video projectors. The comprehensive range of line and frame frequencies, together with the variety of rear panel outputs, ensure compatibility with the majority of computer monitors. The Black Star 1410 produces a wide range of test patterns which includes a testcard, raster, vertical and horizontal lines, colour bars, checkerboard, dots and a focus function. The selected pattern, system, sync. polarity and line/frame frequencies are shown on the unit's liquid crystal display. It is suitable for CGA, MDA, PGA, VGA, SVGA and 8514A/ XGA computer displays in addition to TV monitors. Factory-programmed versions of the 1410 are also available. For more information, contact Obiat Pty Ltd, 129 Queen Street, Beaconsfield, NSW 2014. Phone (02) 698 4111 or fax (02) 699 9170. September 1995  95 Silicon Chip Supply For Burglar Alarms; Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; Using The NE602 In Home-Brew Converter Circuits. BACK ISSUES September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; LED Message Board, 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; All About Electrolytic Cap­acitors. 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 (Records Up To Four Separate Messages); UHF Remote Switch; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Index to Volume 2. 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. January 1990: High Quality Sine/Square Oscillator; Service 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. 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. 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. 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. 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. 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 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. 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. 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. 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. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2. 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. September 1990: Remote Control Extender For VCRs; Power July 1991: Battery Discharge Pacer For Electric Vehicles; 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 ❏ March 1992 ❏ April 1992 ❏ August 1992 ❏ September 1992 ❏ March 1993 ❏ April 1993 ❏ August 1993 ❏ September 1993 ❏ January 1994 ❏ February 1994 ❏ June 1994 ❏ July 1994 ❏ November 1994 ❏ December 1994 ❏ April 1995 ❏ May 1995 ❏ September 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ September 1988 October 1989 March 1990 September 1990 February 1991 July 1991 December 1991 May 1992 October 1992 May 1993 October 1993 March 1994 August 1994 January 1995 June 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ April 1989 November 1989 April 1990 October 1990 March 1991 August 1991 January 1992 June 1992 January 1993 June 1993 November 1993 April 1994 September 1994 February 1995 July 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ May 1989 December 1989 June 1990 November 1990 April 1991 September 1991 February 1992 July 1992 February 1993 July 1993 December 1993 May 1994 October 1994 March 1995 August 1995 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 ___________ 96  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) 979 5644 & quote your credit card details or fax the details to (02) 979 6503. ✂ Card No. 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. Alarm-Triggered Security Camera; Low-Cost Audio Mixer for Camcorders;A 24-Hour Sidereal Clock For Astronomers. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Step-By-Step Vintage Radio Repairs. 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. 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; Automatic Controller For Car Headlights; Experiments For Your Games Card; Restoring An AWA Radiolette. February 1992: Compact Digital Voice Recorder; 50-Watt/ Channel Stereo Power Amplifier; 12VDC/240VAC 40-Watt Inverter; Adjustable 0-45V 8A Power Supply, Pt.2; Designing A Speed Controller For Electric Models. 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; Electronics Workbench For Home Or Laboratory. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; Dummy Load Box For Large Audio Amplifiers; Internal Combustion Engines For Model Aircraft; 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; Electronically 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 Simple Projects For Model Railroads; A Low Fuel Indicator For Cars; Audio Level/VU Meter With LED Readout; Build An Electronic Cockroach; MAL-4 Microcontroller Board, Pt.3; 2kW 24VDC To 240VAC Sine­ wave Inverter, Pt.5. March 1993: Build A Solar Charger For 12V Batteries; 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: Windows-Based Digital Logic Analyser, Pt.1; 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: Build a Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Windows Based Digital Logic Analyser; Pt.2; Quiz Game Adjudicator; Programming The Motorola 68HC705C8 Micro­controller – Lesson 1; Antenna Tuners – Why They Are Useful. 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. 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; Servicing An R/C Transmitter, Pt.1. 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 Micro­controller – Lesson 2; Servicing An R/C Transmitter, Pt.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 For Beginners; Electronic Engine Management, Pt.4. 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, 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. January 1995: Build A 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; Pt1. 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; Pt2; Remote Control System For Models, Pt.2. March 1995: 50W/Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras & Night Viewers; 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. 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. May 1995: Introduction To Satellite TV; CMOS Memory Settings – What To Do When the Battery On Your Mother­ board Goes Flat; Mains Music Transmitter & Receiver; Guitar Headphone Amplifier For Practice Sessions; Build An FM Radio Trainer, Pt.2; Low Cost Transistor & Mosfet Tester For DMMs; 16-Channel Decoder For Radio Remote Control. 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. 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. 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. 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 Reliable Door Minder; Adding RAM To Your Computer; Philips’ CDI-210 Interactive CD Player. 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. 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. 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 PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, Aug­ust 1989, May 1990, 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. July 1994: SmallTalk – a Tiny Voice Digitiser For The PC; Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; September 1995  97 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. Controller for G-scale electric loco I am writing to you regarding building a speed control for a G scale electric train. I have a 7W solar panel connected to a bank of ten nicad batteries from which I would like to run the train. The whole system has to be in DC current (input and output) and every control I've seen is a combination of AC/DC which does not operate satisfactorily. The control also needs to have a forward/reverse switch. Do you have a suitable circuit? (G. O., Carine, WA). • Our most successful train controller, a walk-around throttle design published in April & May 1988, could be run from a supply rail of between 17 and 20V DC. Using ten nicad cells, you would be starting with a supply rail of 12V which is not really sufficient for this design. If you wish to use only 12V, the most effective design would be the simple DC speed control published in our February 1993 issue. Both the articles referred to have been reprinted in our "14 Model Railway Projects" book which is available from us at $7.95 plus $3 for postage. By the way, if you are using a 12V solar panel to charge your 10 Nicad LED temperature gauge for a motorcycle I need some information on making a LED readout temperature gauge for an Enduro motorcycle. I have the temperature sender. Does anyone make kits? The LEDs need to be approx 40mm long. Also, Id like some information on a LED tacho 0-14000rpm firing at once every 360 degrees (single cylinder 2-stroke) and twice very 360 degrees (twin cylinder 2-stroke). (P. S., Parap, NT). • A suitable circuit for a temperature gauge LED readout was 98  Silicon Chip batteries, it is unlikely that they will ever be fully charged and hence their effective service life is likely to be very short. To properly charge a 10-cell Nicad battery pack, you need a charging voltage of more than 18V. We plan to publish a fast charger for Nicads, running from a 12V car battery, in the coming October 1995 issue. Reducing current drain of Door Minder Your Door-Minder project in the July edition is a very novel idea. However, I estimate the current draw of this circuit to be around 8 to 10mA and not really suitable for batteries. Besides, why do you use hard to get (expensive) IGFET transistors (BS 170)? Can they be substituted by enhancement-mode Mosfets (25K679N) or perhaps J-FETs (MPF-102) etc? Is it feasible to make the following modifications to lower consumption: (1) deletion of the 7808 regulator; (2) use of a 5V reference diode for the bias-voltages for IC1; (3) switching off the power rail to IC3 when not used via transistor. Could it be modified to work with sliding-doors and how? (M. S., Edgewater, WA). • Your estimate of current drain is published in the February 1994 issue of Silicon Chip on page 45. It was for reading the output from an oxygen sensor but a temperature sensor could also be used if a 4.7kW resistor is connected between the 12V supply and input at pin 5. A LED Digital Tachometer was published in the August 1991 issue of Silicon Chip. For the single cylinder two stroke, use 180kW for Rx while the twin two stroke will require 82kW for Rx. Calibration using the 50Hz signal for the single cylinder engine is for a reading of 3000 RPM; for the twin, use 1500 RPM. about right and is really too much for a battery operated device. That is why we specified a 12V plugpack. While you could modify the circuit along the lines you suggest, the greatest economy would be obtained by substituting a TL062 for the TL072 and shutting down the LM386 when no signal is present. However, the latter modification would require more circuitry. Charger for deep cycle batteries I have a question regarding deep cycle batteries. I have an 85 amphour deep cycle battery that is used to power an electric outboard motor. How should these type of batteries be charged, and how can I tell when it's fully charged? Can I use the SLA battery charger published in the August 1992 issue? If so, where can I obtain a kit of parts? (C. W., Middle Park, Qld). • Your deep cycle battery could be charged with the SLA battery charger although at its maximum setting it would take many hours to charge a flat 85 amp-hour battery. As far as we know, kits for this project are no longer available but you can purchase the PC board from RCS Radio Pty Ltd, phone (02) 587 3491. We hope to publish a higher capacity charger for conventional lead acid batteries, sometime in the next three or four months. Fun with the weather beacon radio I recently bought a Dick Smith kit to make your LF weather beacon AM radio, as featured in the September 1994 issue. Wiring the components once assembled into the case was a bit fiddly, especially wiring the leads to the RF and Volume pots. However, it all came together in the end, including my own modification of a headphone socket that mutes the speaker when using headphones. The radio worked first try but at first I was disappointed in its performance. However, it is 50 years since I last used a TRF set, and now I have got the "feel" of it, I have had quite surprising results. My best reception so far is "WON", the Non-Directional Beacon at Wonthaggi, just over 110km away on the coast just south-east of Port Phillip Bay. I also receive Melbourne Radio Coastal Shipping station at excellent strength, on 500 and 430kHz, located 90km away. The only problem I have is a continual background of programmes from the two ABC stations on 621 and 774kHz, regardless of the setting of the tuning control. The stations are 18 to 20km away. I can minimise the babble by rotating the radio so that the ferrite rod is "end-on" to the stations but the background babble is still there. Despite this, I can receive eight NDBs which is good going for a TRF set with no external antenna. I did try coupling a long wire antenna to the set but the BC breakthrough rendered it useless. I would be interested to know if the original set, used in Penrith, suffered from broadcast band breakthrough, or am I just unlucky in being close to the Melbourne stations? (J. S., Glenroy, Vic). • You should not suffer from broadcast station breakthrough as you have found. One point to watch is to keep the wires from the ferrite rod to the PC board as short as possible and together. This will minimise direct pickup on the antenna wires. The ferrite rod must also not be too close to the PC board or to any surrounding metalwork. You may be able to improve the performance of your set by using a larger ferrite antenna. Source for solid state vibrators In the August 1995 issue, a reader asked about obtaining vibrators or the use of a solid state replacement. Replacement vibrators are obtainable through the many vintage radio restorers in NSW and Victoria, such as "Resurrection Radio" of 242 Chapel Street, Prahran, Victoria 3151, phone (03) 9510 4486, and come in a variety of voltages and, in their latest parts list were listed at $35. At that price the solid state device looks very attractive, unless you are a stickler for authenticity, but maybe Command control for model railways Over the years, I have followed with interest the various model railroad projects you have published. I have purchased a copy of "14 Model Railway Projects" and found it useful. Have you considered some projects based on the Digital Command Control system being adopted by the NMRA in the US? Public domain plans are available for standalone and computer controlled systems. I am very interested in moving to this form of control but lack the expertise to transform the basic circuits into an operating design, although I am capable of building the kits from the resulting plans. I don't know how much interest someone will find a way to fit the device into the case of an old vibrator to maintain the look of originality. (B. W., Caulfield North, Vic). Diagram for Audiosonic cassette recorder Do you, or any of your readers, know where I might be able to obtain the schematic diagram for the Audiosonic AM/FM stereo radio dual cassette recorder, which has item code 715 790, and art number WKC9558E? The stereo is virtually all black in colour, and would be about 5-7 years old. Does anybody know where I can get the book entitled Microprocessor Data Handbook 3rd Edition, which is published by Micro Tech? Jaycar Electronics did sell this item but have since run out. (P. Fullagar, 6 Highfield St, Mayfield, NSW 2304). Digital display for AM/FM radio I have bough a GE Superadio which is supposed to be very good at receiving medium wave broadcasts. It has medium wave and FM reception. Unfortunately, it is an analog model. It has no VU meter or anything else. I want to have a VU meter and digital readout installed in it, either LED or LCD. As there does not seem to be any there would be in such projects but I am convinced it is a very practical system, particularly for new layouts. I would also like to see some notes on how your previous projects, such as the train detector in the June 1995 issue, would operate with a command control system. (G. S., Esperance, WA). • We are aware of these developments but are concerned that the receivers to be installed in locos would require surface mount components which would be a big obstacle for most model railway enthusiasts. The overall cost could be a problem too, apart from the considerable development cost for such a project.The detector published in the June 1995 issue should work with command control systems, without any modifications. room on the radio for such additions, I suppose that it will have to be installed in a "zippy" box with wiring leading to the radio. Is such a project possible? (J. G., Runaway Bay, Qld). • Quite a lot of circuitry is required to add a digital readout to any conventional radio, particularly if it covers the AM broadcast and FM bands. In both cases the circuitry must measure the local oscillator in the radio and then subtract the intermediate frequency to find the station frequency. We have not published a suitable circuit and would hazard a guess that if we did, the resulting kit could easily cost $150 or more. Nor is there any guarantee that your radio would have internal access to the local oscillators - they may be buried inside a large integrated circuit and thus the job may not be feasible at all. LCD capacitance meter jitter I have put together a capacitance meter as described in the January 1991 issue. All ranges operate correctly except for the pF range. Here I experience an instability of the last digit. It remains steady for two or three updates and then it changes. The difference can be as high as 8pF. I am convinced that the synchronous coupling between the free running IC1 September 1995  99 Headphone amplifier for PA system After reviewing your recent articles on the 50W Stereo Amplifier (Feb-Apr 1995) and looking at my version of the 120W PA Amplifier (Nov. 1988 to Jan. 1989), which has four microphone inputs and a line output for a tape recorder or power amplifier, I would like to add a headphone amplifier. This would function in the same way as it does in your 50W Stereo Amplifier, having normally the audio signal feeding the output socket for the line output, but when the headphone jack (mono) is inserted, the signal is diverted to the headphone amplifier. Can the circuitry used in the 50W Stereo Amplifier for the headphone and the bistable IC2 is at fault. There may have been others who have experienced the same trouble and have been able to rectify the malfunction. I would also like to ask for a concise explanation, maybe from one of your readers, on how do the "LCD A/D converters-display drivers" activate the correct segments when they are bundled up in groups, ie agd, bc and ef respectively. (K. B., Forestville, NSW). • Jitter in the last digit of the display could be attributed to the changes in amplifier be used for this project? What alterations will have to be done? And lastly, what are the power supply requirements for the headphone amplifier? Please note the headphone amplifier will only need to be mono, not stereo. (R. T., Mundubbera, Qld). • The headphone amplifier to the 50W Stereo Amplifier should work without problems. If you need to increase the gain you can do so by reducing the 10kW resistor connected to pin 6 (2) of IC3a. The required supply voltage is ±15V DC. This can be derived in the same way as the existing low voltage supply rails in the 120W PA amplifier; ie, via 680W 5W dropping resistors and 15V 3-terminal regulators. output levels of IC1 and IC2 occurring at different times. These can affect the power supply rails which can slightly alter the timing sequence and thus the capacitance reading. The PC board design should be carefully checked for correct ground track layout so that current loops are not formed. The board pattern for the original design using LED displays can be seen in the May 1990 issue, where star point earthing was used. This design did not have problems with jitter on the pF range. Each segment of an LCD is driven SILICON CHIP FLOPPY INDEX WITH FILE VIEWER 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. Price $7.00 each + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 9979 5644 & quote your credit card number; or fax the details to (02) 9979 6503. Please specify 3.5-inch or 5.25-inch disc. 100  Silicon Chip entirely separately. They are not bundled together as in a multiplexed display. A "lit" or visible segment occurs when the signal applied to it is 180 degrees out of phase to the backplane. When the applied signal is in phase with the backplane, the segment is off. How to design an electromagnet Could you please give me a simple formula to calculate the ampere-turns necessary for a home-made electromagnet or solenoid for various battery-operated gadgets? For example, I wish to make an electromagnet or solenoid to operate a camera which requires 250 gram pressure on the trigger to operate. Hope this is in your field. (D. H., Mosman, NSW). • Unfortunately. we cannot help you directly since the design involves not just the ampere-turns produced by the coil, but also the details of the magnetic circuit as well. This involves the type of steel and design of the laminations, the design of the plunger and its return spring, if required. The driving circuit must also be taken into account because many solenoids are designed to be energised momentarily; if energised continuously they will quickly overheat and burn out. Your camera solenoid application is one requiring considerable power and would also need to be a momentary design otherwise it would be physically quite large. Having noted all of the above, why not try winding several hundred turns of fine gauge wire onto a bobbin which is a close fit over a 1/4-inch bol? Energised with a 6V lantern battery, this should provide quite a reasonable degree of thrust. At the very least it will provide a starting point. Notes & Errata Fuel Injector Monitor, August 1995: the specified LM358 op amp has been found to be non-linear in the circuit at low and high injector duty cycles. The problem is corrected by substituting an RCA CA 3260E op amp which has CMOS outputs. This op amp is a drop-in replacement but a change to the integration RC network at pin 3 is desirable. Change the 4.7kW resistor to 47kW and the 220µF capacitor to 10µF. SC SILICON CHIP BOOK SHOP Newnes Guide to Satellite TV 336 pages, in paperback at $49.95. 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. Servicing Personal Computers By Michael Tooley. First pub­ lished 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. 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. Optoelectronics: An Introduction By J. C. A. Chaimowicz. First published 1989, reprinted 1992. This particular field is about to explode and it is most important for engineers and technicians to bring themselves up to date. The subject is comprehensively covered, starting with optics and then moving into all aspects of fibre optic communications. 361 pages, in paperback at $55.95. Digital Audio & Compact Disc Technology 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 format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. Power Electronics Handbook 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. Surface Mount Technology By Rudolph Strauss. First pub­ lish-ed 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. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First pub­ lished 1989. 6th edition 1994. This just has to be the best reference book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order ❏ 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. semicustom electronics & data communications. 63 chapters, in paperback at $140.00. Radio Frequency Transistors Principles & Practical Appli­ cations. By Norm Dye & Helge Granberg. Published 1993. This timely 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 techniques, impedance matching & CAD. 235 pages, in hard cover at $85.00. Newnes Guide to TV & Video Technology By Eugene Trundle. First pub­ lish-ed 1988, reprinted 1990, 1992. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 432 pages, in paperback, at $39.95.  Title Price  Newnes Guide to Satellite TV  Servicing Personal Computers  The Art Of Linear Electronics  Optoelectronics: An Introduction  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Surface Mount Technology  Electronic Engineer's Reference Book  Radio Frequency Transistors  Newnes Guide to TV & Video Technology $55.95 $59.95 $49.95 $55.95 $55.95 $59.95 $99.00 $140.00 $85.00 $39.95 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 September 1995  101 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES FOR SALE 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. INVERTERS 12V-230VAC 90% EFFICIENCY. Modified Sine Wave. Compact 55 x 160 x 98mm. Light 800gm. Standby 50mA/0.6W. 100 Watt Continuous $99. 200 Watt $149. A.S.S. (09) 349 9413, fax (09) 344 5905. _____________ _____________ _____________ _____________ _____________ INFRA-RED CORDLESS RECHARG­ EABLE STEREO HEADPHONES. 20Hz-20kHz. Lightweight. $69. A.S.S. (09) 349 9413, fax (09) 344 5905. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ MicroZed have in stock NewMicro 68HC11 board, resident FORTH, with alternative BASIC, Small C, and Assembler, supplied. TINY 2/3 MATCHBOX SIZE VIDEO CAMERA MODULES $169. RF MODULATOR $30. Patch these into your TV Antenna System Display and/or Record on all TVs & VCRs. VERY FLEXIBLE & PRACTICAL VIDEO SUR­VEILLANCE PACKAGE only $199. Camera 400+ TVL, 35 x 35 x 25mm incl Lens, Auto Iris, Infra-Red & Low Light Sensitive. IR LEDs 50mW pkt/30 $15 SEE IN TOTAL DARKNESS. A.S.S. (09) 349 9413, fax (09) 344 5905. ADD AN IBM KEYBOARD DECODER (EA, Dec. 90) to your project. 8 left. PCB, Programmed 8749 & Disk $20. 15 Romloader 256K upgrade PCBs left. PCB, EPROM, 9346 EEPROM, 74HC­4053, Labels & Disk $25. P&P $5. Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Card No. ✂ ❏ Bankcard   ❏ Visa Card   ❏ Master Card Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 102  Silicon Chip 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 Tantau Australia, PO Box 1232, Lane Cove 2066. AH (02) 878 4715. D.I.Y. PACKAGED CCTV SYSTEMS. $699. 10" Monitor 4 Ch Switcher, Camera, 20M Cable & Stand PLUG-IN & GO! Features Two-Way Inter­com, Alarm I/Ps, VCR I/O, 400 TVL 0.2 Lux Low Light & IR Sensi­tive Camera. A.S.S. (09) 349 9413, fax (09) 344 5905. CLOSED CIRCUIT VIDEO EQUIPMENT. Mono & Colour Cameras incl. Lens from $249. 32 x 32 x 15mm CONCEALED PINHOLE Modules from $239. 4 & 8 Ch Quad & Freeze Screen Splitters & Switchers from $239. Combination Modulator/Antenna Boosters to Display/Record Video on TV/VCR. Video Microscopes 10X to 1000X. Discounts 10% - 37.5%. A.S.S. (09) 349 9413, fax (09) 344 5905. 68HC705 Development System: Editor, assembler, In Circuit Simula­tor and Programmer board. Oztechnics, PO Box 38, Illawong, NSW 2234. Phone (02) 541 0310. Fax (02) 541 0734. email:OZTEC<at>OZE­MAIL.COM.AU. MicroZed have PIC Source book gives code for Stamp routines to use in your own PIC programs. $70 plus $8 courier delivery. SWAPMEET: Glenroy 22 Oct. Sites 25/26. Vintage, amateur compon­ents, valves. Catalogue SAE T. Mitchell, 68 Rowan Street, Bendigo 3550. 486 DX4 100MHz AMD CPU on a VLB motherboard with 256 cache. $475 plus 5% S/H. Prices are in Canadian dollars. Other items are available. Please write for details. Send Money Orders to Renato Zannese, 615 Roding Street, Downsview, Ontario, Canada M3M 2A6. ftp://rasi.lr.ttu.ee/pub/sis/prod/microchip/3rd-Party/Don.McKen­z ie/ is the Internet address for my promo disk, or send a $2 coin. PIC84PGM $20, PIC16C84 (EEPROM) $15, Basic Stamps $65, lots more. Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. Ph (03) 9338 6286, 019 93 9799. FULLY APPROVED 12V DC 1 AMP “PLUGPACKS”. Buy direct from import­ er. $10 + sales tax. Many other models available. Call Av-Comm Pty Ltd (02) 9949 7414/9948 2667 or fax (02) 9949 7095. MEMORY & DRIVES EX. TAX PRICES AT JULY, 1995 SIMM (all 70ns) Parity/No Parity 1Mb 30-pin $64/58 4Mb 30-pin $250/215 2Mb 72-pin $151/135 4Mb 72-pin $250/232 8Mb 72-pin $515/452 16Mb 72-pin $850/765 32Mb 72-pin $1530/1700 MAC 8Mb P’BOOK CO-PROCESSORS 387S/DX to 40 $450 $90 LASER PRINTER HP with 2Mb $200 COMPAQ CONTURA 8Mb $544 Parallax Basic Stamp DRAM DIP 1Mb x 1 70ns DIP $9.00 256 x 4 70ns DIP $8.10 256 x 16 70ns DIP $55.00 IBM PS.2 THINKPAD L40/N33 8Mb 4Mb $590 $300 TOSHIBA 3100SX 2100/50 4Mb 8Mb $275 $590 SUN SPARC ELC 16Mb SPARC 10/20 64Mb $850 $3872 DRIVES – SEAGATE 545Mb 14ms 3yr wty $280 850Mb 11ms 3yr wty $355 1052Mb 9ms 5yr wty $535 Sales tax 21%. Overnight delivery. Credit cards welcome. Ring for latest prices. We buy & trade RAM. PELHAM Tel: (02) 980 6988 Fax: (02) 980 6991 Shop 6, 2 Hillcrest Rd, Pennant Hills, 2120. AUSTRALIAN AUDIO CONSULTANTS HAVE RELOCATED TO NEWLY DESIGNED PREMISES We can supply all your driver needs, direct from the manufacturer. Dynaudio, Vifa, Scanspeak, Morel, etc. Full Consulting Service available. We specialise in creating custom designs for the hobbyist or manufacturer. Home Theatre Specialists. For further details contact: Australian Audio Consultants, PO Box 11, Stockport, SA 5410. Phone or fax (085) 28 2201. MicroZed have Electric Piston, MUSCLE wires, project books and kits. Electric motorless motion. AIRBAND HAND-HELD TRANSCEIVER, AIR-960. Fully DOTC approved. 118-136MHz, thumbwheel frequency control. C/W, 12V 500mA NICAD pack, trickle charger, carry case, antenna, belt clip. 1 year warranty. Buy direct from importer, $520 + tax if applicable. Call Av-Comm Pty Ltd (02) 9949 7417/9948 2667 or fax (02) 9949 7095. PROTEL EASYTRAX Ver 2.04 PCB CAD software. $195. Phone 018 133 620 bh. LOGIC ANALYSER HP1651B 32-channel including pods and manuals. $3500 ono (02) 858 4790. MicroZed have large range accessories for Stamp and PIC applica­tions. BS1-IC Resident BASIC interpreter, 8 I/O, Minimum extra hardware needed for most jobs. Send 4 x 45c postage stamps for information package and prices for all products. MicroZed Computers PO Box 634 (296 Cook’s Rd), ARMIDALE 2350 V (067) 722 777 F (067) 728 987 Credit cards accepted. FBASIC TICkit Has 21 I/O From VersaTech PIC16C57 <at> 20MHz, on a 65mm square board, has on-board interpreter, 16 GP I/O, plus 5 I/O for IRQ, IRQ ack RTC/Counter 12C buss, handles SRAM and LCD too! Stores program in 8K EEPROM. Send 4 x 45c postage stamps for information. MicroZed Computers PO Box 634 (296 Cook’s Rd), ARMIDALE 2350 V (067) 722 777 F (067) 728 987 Credit cards accepted. Latest available is DS1620 temp measuring kit. LASERS: argon 30-100mW air-cooled, single line blue/green and 240 volt power supply. 100mW pumped diode green 532nm laser head size 75 x 50 x 35mm. LASER DYNAMICS (03) 9532 1981, fax (03) 9555 7449. COMPLETE WORKSHOP PROGRAM: suit IBM compatible 386 or better computer. Handles: Stock Control, Customer Records, Debits, Credits, Faults, Manuals and Phone Directory. For demo disk, ring Jack Albers Electronics & Software Development on (045) 71 1640. CHEAP HEATSHRINK TUBING: Australian made, red, black, blue, white, clear, 2.4mm/$1.10pm, 3.2/$1.30, 4.8/$1.70, 6.4/$2.10, 9.5/$2.30, 12.7/$2.70, 19/$3.70, 25.4/$5.10. P&P September 1995  103 Microprocessor For Digital Effects Unit Microprocessor For Stereo Preamplifier Advertising Index Now available: the 68HC705-C8P pre-programmed micro­pro­cessor IC for the Digital Effects Unit described in the Feb­ruary 1995 issue. Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Pub­lica­ tions, PO Box 139, Collaroy, NSW 2097. Phone (02) 9979 5644; Fax (02) 9979 6503. Available now: the 68HC705-C8P pre-programmed micro­pro­cessor for the Remote Controlled Stereo Preamplifier (Sept.-Oct. 1993). Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Pub­ lications, PO Box 139, Collaroy, NSW 2097. Phone (02) 9979 5644; Fax (02) 9979 6503. Altronics ........................... 64-66,83 C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC16, 8051/52, 8080/85, 8086 or 8096: $150.00 each. Macro Cross Assemblers for these CPUs + 6800/01/03/05 and 6502: $150 for the set. Debug monitors: $75 for 6 CPUs. All compilers, XASMs and monitors: $450. 8051/52 or 80C320 simulator (fast): $75. Demo disk: FREE. All prices + $5 postage. GRANTRONICS PTY LTD, PO Box 275, Wentworth­ville 2145. Ph/Fax (02) 631 1236. NEW SPRINKLER CONTROLLER KITS: RAIN BRAIN version uses ‘C8 104  Silicon Chip Avico Electronics.........................93 Car Projects Book......................IFC Dick Smith Electronics........... 12-15 Harbuch Electronics....................92 Instant PCBs..............................104 $3.00 up to 10 metres. Free data sheet. DOMCOR DISTRIBUTORS, 67 King Road, Beechboro, WA 6063. MICROCRAFT PRESENTS: Dunfield (DDS) products are now available in Australia. Micro C, the affordable “C” compiler for embedded applications. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $149.95 each + $3 p&h • Now on special is the SDK, a package of ALL the DDS “C” compilers for $410 + $6 p&h (save $139) • 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 car alter­nators” (uses alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Device programming EPROMs/PALs etc from $1.50 (inc label). We use and recommend the HILO ALL-07 Universal Programmer • Fixed price PCB layout & photoplots. We use and recommend PROTEL For Windows EDA tools • Credit cards accepted • Call Bob for more de­tails. MICROCRAFT, PO Box 514, Concord, NSW 2137. Phone (02) 744 5440 or Fax (02) 744 9280. Av-Comm................................21,73 Jaycar ................................... 49-56 Kits-R-US.....................................95 L & M Satellite Supplies...............63 and switch mode supply. Features galore!! Contact Mantis Micro Pro­ducts, 38 Garnet St, Niddrie 3042. Phone/fax (03) 337 1917. PROGRAMMER/EDITOR SOFTWARE for new Lattice EEPROM 7ns Generic Digital Switch ICs. Just connect to PC parallel port! Use to reconfigure circuits without rewiring! Send SSAE, phone or poll fax. Advanced R & D Solutions, 12 Copeland Road, Lethbridge Park 2770. Ph/Fax (02) 628 1223. Macservice...............................3,26 MicroZed Computers.................103 Oatley Electronics.................. 90-91 Pelham......................................103 Railway Projects Book.............OBC RCS Radio ................................102 Resurrection Radio......................85 SATELLITE DISHES: international reception of Intelsat, Panamsat, Gorizont, 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. Rod Irving Electronics .......... 27-31 UNUSUAL BOOKS: Electronic Devices, Fireworks, Locksmithing, Radar Invisibility, Surveillance, Self-Protection, Unusual Chem­ istry and more. For a complete catalog, send 95 cents in stamps to Vector Press, Dept S, PO Box 434, Brighton, SA 5048. Silicon Chip Software..................89 SATELLITE EQUIPMENT: we sell quality products at prices you can afford. Dishes from $140. Ku LNB voltage switching with built-in feedhorn from $150. C band LNB 23 deg from $140. Receivers; eg, Pace 919 low threshold is $420. We stock Gardiner, Drake, Pace, Chaparrel, KTI, plus many more. A catalogue is available. Contact Satellite Professionals on phone or fax (03) 803 0215. R.S.K. Electronics........................94 Silicon Chip Back Issues....... 96-97 Silicon Chip Bookshop...............101 Silicon Chip Walchart................IBC _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. • HT Electronics, Shop 4, 8 Roberts Rd, Hackham West, SA 5163. Phone (08) 326 5567.