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DECEMBER 1999  1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.denon.com.au Contents Vol.12, No.12; December 1999 FEATURES 4 JBL’s 21st Century Loudspeaker Technology How they developed ribbon wire and dual voice coils – by Louis Challis 10 Review: Denon AVC-A1D AV Surround Amplifier 5.1 channels plus Dolby Digital plus DTS plus THX plus . . . Hey, it’s got the lot! – by Leo Simpson 64 Internet Connection Sharing Using Hardware IP gateways are fast and easy to set up and don’t extra require software. You also get a bonus DHCP server and firewall – by Greg Swain 82 Electric Lighting; Pt.16 Microwave sulphur lamps – by Julian Edgar 92 Index To Volume 12 All the articles, projects and columns for 1999 PROJECTS TO BUILD 23 Build A Solar Panel Regulator It works on 12V and 24V systems and has an LCD to show the battery voltage or current – design by Alan Bonnard 12V/24V Solar Panel Regulator – Page 23. 32 The PC Powerhouse Connects to your PC’s power supply and gives fixed +12V, +9V, +6V and +5V rails – design by Barry Hubble 36 The Fortune Finder Metal Locator A simple, low-cost metal detector that works – by John Clarke 54 Speed Alarm For Cars, Pt.2 Second article has all the construction details – by John Clarke 70 Railpower Model Train Controller; Pt.3 Don’t need infrared remote control? Here’s how to modify the circuit for a hard-wired walk-around throttle – by John Clarke SPECIAL COLUMNS 18 Serviceman’s Log All the same, only different – by the TV Serviceman The PC Powerhouse – Page 32. 76 Vintage Radio The Astor KM that blew its power plug off! – by Rodney Champness DEPARTMENTS 2 28 30 53 80 Publisher’s Letter Product Showcase Circuit Notebook Subscriptions Form Electronics Showcase 88 90 94 96 Ask Silicon Chip Notes & Errata Market Centre Advertising Index The Fortune Finder Metal Locator – Page 36. DECEMBER 1999  1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Peter Smith Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0414 34 6669 Regular Contributors Brendan Akhurst Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young 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: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip High definition TV not wanted in Australia Hands up all those readers who want high definition tele­vision? How many of you are prepared to pay around $8000 for the privilege? And how many are prepared to pay $1000 or more for a set-top converter for the privilege of receiving broadcasts that previously required no decoder? I would guess that the numbers replying yes to the above questions might start out fairly high, until people realise how much it is going to cost. The more you read about what is pro­posed, and until recently there has been very little technical information available, the more you have to conclude that the high-definition digital TV broadcasts being promoted are going to be a financial disaster – pretty much like pay TV, I suppose. Philips Industries, one of the major suppliers of consumer equipment, recently put the cat among the pigeons by stating that the high definition TV option was just not going to be viable, mainly because no other countries have adopted it. Unless high definition sets are going to be made in really large quantities their prices will not drop – they will always be too expensive for the average family to afford. The simple fact of the matter is that the Australian TV market is only a drop in the bucket compared to the total international market, so such sets will always be very expensive, provided that manufacturers can be persuaded to make them in the first place. But even if high definition sets were eventually going to come down in price, there is probably little justification for the huge outlays that will be required by the TV broadcasters. Why? Because most people would not recognise a high definition TV picture if it jumped out and punched them in the face. Large numbers of people routinely put up with picture quality which is appallingly bad. They just don’t realise how good a standard PAL broadcast can be, especially on a late-model 68cm set as made by Sony, Panasonic or any other mainstream manufacturer. And when you turn around and feed the same set with a signal from a DVD player, the picture is even better, even though it is still using the PAL standard. That same picture quality will be available from the standard mode digital broadcasts. Why go better? The fact is that unless you use a larger (more than 90cm) and higher resolution screen, say in a projection setup, there simply will not be a visible benefit. And even if there will be, most older people will still not be able to see it because their eyesight is not good enough. Mind you, now that Philips have made a major demonstration of high-definition pictures versus standard mode pictures, the politicians appear to be coming around to that view. This is just as well. But even if we do decide to go for standard mode broad­casts and use the extra channels for interactive TV, data-casting or whatever, the whole proposal still seems unnecessary to me. As a pay-TV customer, I already have 30-plus channels of mostly unviewable programs; why would I want heaps more? And remember, the scheme involves a proposed end to normal analog TV broadcast­ing by 2008 in capital cities and by 2011 in regional areas. If you want to know more, the draft report of the Produc­tivity Commission on TV broadcasting is available on the Internet as a 1.3MB file at www. pc.gov.au Leo Simpson                                   
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†“ €€  †ˆ ‚  „ ‚      „     –„  ƒƒ      ŽŠ  ¡  ƒ £ŒŒ¤ ƒ ƒ   ƒ         †ˆ ‚  „ E & OE € All prices include sales tax MICROGRAM 1299 Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 FreeFax 1 800 625 777 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 JBL's 21st Century Speaker Technology From the time that the first successful sound systems were installed in cinemas in America, JBL Loudspeakers have been at the forefront of quality sound reproduction. As this article shows, they still are. . . I t is now almost 80 years since James B. Lansing formed a partnership with Ken Decker in Los Angeles to manufacture loudspeakers for those new-fangled radios that hobbyists and affluent Americans aspired to own. Jim’s timing was perfect. He just happened to be in the right place at the right time to apply his innovative ideas to solve what turned out to be the motion picture industry’s most pressing problems. In 1927, Warner Bros introduced talking pictures with “The Jazz Singer”, starring Al Jolson. “Talkies” were an immediate success. Although the Depression subsequently cast a long shadow over Hollywood (and the rest of the world), there was no stopping the demand for talking pictures or the cinemas in which they could be shown. But there were problems associated with the “talkies”, many of which initially proved to be quite intractable. The most complex of those problems revolved around the absence of loudspeakers with sufficient power output and quality to suit large cinemas which frequently exceeded 1000 seats. The Western Electric Company was one of the first firms to tackle this problem and they assigned a large team of engineers to the task. But 4  Silicon Chip Western Electric didn’t have the field to themselves and there were numerous private researchers working on the same problems. It was during this period that one of the most successful researchers was Jim Lansing. As a result, his speakers had a marked edge over virtually every other loudspeaker in the market place at that time. Jim Lansing’s most significant achievement was the development of a milling procedure for producing flat voice coil wires. The flat wire could be wound into a much stronger, more durable ribbon voice coil that had James B (Jim) Lansing died in 1949 but his legacy lives on through products bearing his initials. By LOUIS CHALLIS the added advantage of significantly higher power-handling and a more effective use of the space available in the voice coil air-gap. Without that development, there was no simple way to resolve the fundamental design problems associated with producing an effective compression driver. At the same time, Jim Lansing developed an effective phasing plug. The combination of flat wire, more efficient voice coils and the phasing plugs ensured that his compression drivers were the best that money could buy. These two fundamental developments are as important today as they were 70 years ago. Throughout the rest of the 1930s, Jim Lansing focused his efforts on the design of high-powered loudspeakers, better power amplifiers and the associated crossover networks and DC power supplies. His products were snapped up by the most prestigious cinemas and were sought after in the major motion picture sound studios. During World War II, Jim worked on submarine detection systems. It was only following the end of the war that, with much soul-searching, he decided to leave Altec Theatre Services in which he had been a director, to form his own company, James B Lansing Sound Incorporated. The adoption of the Lansing in the company name upset his former partners at Altec-Lan- sing, so he changed the name to JBL. In the few short years before his death in 1949, Jim developed his famous D130 15" loudspeaker with a 4" flat wire voice coil that revolutionised theatre sound and set the standard against which other low frequency drivers would be assessed for the next two decades. JBL continued after Jim Lansing’s death and about 30 years ago, it was acquired by Harman International. In the ensuing period, JBL has continued to produce more powerful loudspeakers without sacrificing that equally important parameter of ‘fidelity’. Twin voice coils Let’s briefly discuss the topic of power-handling capacity. When a loudspeaker is called on to deliver high outputs, the large cone excursions typically cause the voice coil (or portions of it) to move out of linear flux region of the air gap in which it operates. As the excursions become greater, the thermal dissipation simultaneously increases and with it the risk of voice coil burn out. Even if the voice coil doesn’t burn out, there is still the nasty problem of gross non-linear distortion as the voice coil’s travel moves into the non-linear region at the fringes of the magnetic path gap. To solve this problem, most loudspeaker manufacturers have tended to concentrate on building bigger and/or more efficient magnets, larger voice coils or even larger speaker Two amplifiers - one for the woofer and one for the tweeter Built-in active crossovers Low mass titanium diaphragm Low distortion BiRadial Horn Thermal protection shuts down ampifier on overload Die-cast heat-absorbing baffle Active cooling from alumium fins Computer-designed EON woofer cones Polypropylene enclosure Flattened voice coil wires give 22% more wire in the magnetic gap Patented “differential drive” (two voice coils). Neodymium magnets - ten times lighter than conventional magnets Toroidal power transfer for minimum weight. Cutaway diagram of a typical JBL “EON” system showing significant levels of innovative technology diaphragms. Each of those approaches imposes significant functional, weight-related and thermal disadvantages. JBL came to the conclusion that there had to be a better way, without incurring gross harmonic distortion and premature failure of the driver. An early (1954) dual coil drive from Wolff, taken from the patent documents at the time. CM is the magnet, A1 & A2 are two air gaps, C1 & C2 the two voice coils, P1 & P2 two steel plates and PP2 is the pole piece. In the 1950s, Wolff and Kritter both described a loudspeaker transducer which had two voice coils wound in opposite directions and spaced apart on the same voice coil former. Their patents described magnetic circuits using Alnico permanent magnets and adopted two magnetic air Another early patented dual coil drive, this time from Kritter, 1959. Identified components are 1, the magnet; 2 is the steel pole piece and 3 & 4 steel plates. 7 & 8 are the two voice coils, 14 the speaker cone and 15 the speaker housing. DECEMBER 1999  5 Cross-section of a loudspeaker with “conventional” outside magnet construction – except that this one has two voice coils. Note also the square cross-section coil wire. gaps at outer ends of a magnet, with one coil placed in each air gap. As it turned out, neither of these researchers ever constructed a commercial example of their ideas or proved that they were capable of producing a working solution. Other researchers who experimented with Wolff and Kritter’s concepts discovered to their chagrin that there were almost intractable problems to be resolved in the construction of a voice coil that could handle twice the input power and safely dissipate the associated heat. JBL subsequently decided that the concept had merit and a decade ago developed its Eon loudspeaker. This used a dual voice coil and a neodymium magnet nested in an aluminium heatsink. The Eon gave an extremely effective differential drive offering some remarkable features. The main attributes of the Eon loudspeaker are its ability to provide twice the power output compared with that provided by a conventional single voice coil design. At the same time, it achieves a weight reduction of between 75 and 80%. The researchers at JBL were initially concerned that under high drive conditions when maximum excursion occurs, either one coil or the other would leave the air gap, with possibly adverse effects on the other coil. In the presence of any asymmetry in the loudspeaker, a voice coil could be expected to literally jump out of the gap in the direction of the asymmetry. Even if everything was perfectly 6  Silicon Chip Again with two coils, the lower weight and better magnetic efficiency having the magnet on the inside of the coils provides a far lighter and more effective solution. balanced, there was still a risk for the voice coil to jump out of the gap. Once the voice coil is out of the gap, the amplifier loses control, power dissipation goes up and the distortion is really bad. In a conventional loudspeaker driver, this is addressed by providing progressive or non-linear stiffness in the suspension elements and spider. The problem with that is the risk of premature fatigue failure and a relatively short driver life. The Eon design adopted a smarter solution. Claimed to be the strongest and lightest 14-inch driver ever, this is JBL’s 600W DCD Driver 2254J “professional” speaker. Dynamic braking JBL have cunningly placed a third shorted coil midway between the two drive coils. This becomes what we might term a ‘dynamic brake’. As the voice coil excursions become greater and greater, the shorted coil moves into the active magnetic field of either the front or rear coil. When this occurs, the damping generated by the shorted coil effectively limits the motion and the speaker experiences a form of ‘soft clipping’. The net effect is a highly effective protection system. JBL discovered that there were some other unusual magnetic features displayed by its dual-coil Eon design. When they examined the distribution of flux density along the voice coil air gap, they discovered that it was decidedly irregular and asymmetrical. They were even more disturbed to discover that the flux density on the inside of the voice coil was substantially different to that on the outside of the voice coil, ie, on the opposite side. But while the individual gap fluxes were not symmetrical, the overall distribution turned out to be almost perfectly symmetrical and the flux distribution on the inside and the outside of the voice coil performed in almost the same way as a single voice coil design behaves. The most significant advantage of the dual voice coil design is that it inherently has no asymmetric bias at all. As a consequence, the second harmonic distortion is then primarily associated with the non-linearity of the suspension rather than being at- tributable to the magnetic field or flux modulation. Because the dual design has double the coil surface area and a slightly higher magnetic flux density, the force factor is more than doubled when compared with a conventional single-coil design. JBL experimented with two other versions of the dual-coil design - one with the magnet on the outside of the coil (typically using a ceramic or neodymium magnet) and the second version with the neodymium or Alnico magnet on the inside of the coil. As they discovered, the lower weight and better magnetic efficiency of the inner option provides a far lighter and more effective solution than the outer magnet option. Neodymium offers further benefits with the main advantage being that it has lower flux modulation, leading to harmonic modulation distortion 10dB lower than that with a ceramic magnet. Double-blind listening tests The first dynamic loudspeakers were developed a little over 80 years ago. While they might have had some similarity in appearance to the current generation, there is simply no comparison in sound quality. In the beginning, researchers relied solely on their ears to assess the improvements in audible fidelity. Since then, many objective test methods were developed to measure improvements in performance. Nevertheless, a The EON 10: one of JBL’s innovative and high performing “EON” speaker systems intended for professional and commercial applications. well trained and perceptive set of ears still constitutes the most critical test of any loudspeaker’s fidelity. JBL’s current product philosophy has been developed by Harman International’s new Vice-President of Engineering, Floyd E. Toole. His experience had convinced him that any successful organization in this field simply had to have appropriate state-of-the-art research and testing facilities. Accordingly, JBL built a new Acoustical Research Centre with more than 1000 cubic metres of speaker development laboratory, equipped with three anechoic and hemi-choic test facilities. JBL is now able to perform complex automated speaker tests that comple- By adding a shorted coil between the two driver coils a dynamic brake is formed. Normally the shorted coil is between the two voice coil gaps so it has little, if any, effect. On large cone excursions, the shorted coil moves more and more into one or other of the voice coil gaps to produce a braking effect. The effect is shown in the graph at right. ment its outstanding subjective test facility - they have the finest and best equipped listening room that I’ve yet seen. It is not generally appreciated just how critical are the loudspeakers’ positions in a listening room when you wish to compare the performance of two or more sets of speakers. If those assessments are to be valid, then each pair of speakers has to occupy exactly the same positions. Now that is no easy task, particularly if you want to conduct a “double-blind” test, with neither the subject nor the tester being aware of which pair of speakers is being listened to at any one time. Let’s face it, when you go to a hifi The green curve shows the displacement of a dual coil standard 10-inch woofer while the blue curve shows the same woofer with the shorted centre coil for braking. DECEMBER 1999  7 retailer’s listening room, such demanding requirements cannot be met. But JBL has done it. They have constructed an automated platform system to move multiple pairs of speakers back and forth behind a curtain for subjective blind testing. I was intrigued to observe how each pair of loudspeakers can be moved almost silently into position in less than two seconds. As a consequence, listeners are able to make comparisons without adverse interaction problems generated by the listening room walls, floor and ceiling. The critical spatial parameters remain constant and the subjective test assessments are both accurate and, more importantly, credible! Few consumers understand just how important a loudspeaker’s position becomes in determining the quality of the sound you hear in a typical living room. JBL’s research team has devoted an immense amount of effort to accurately quantify the critical parameters that need to be determined. Their ultimate aim was to develop a procedure through which they could optimise a monitor loudspeaker’s effective sound output in both the horizontal and vertical planes. Now there are relatively few situations in either a domestic living room or even in a commercial sound dubbing suite or studio where there is a single significant or ‘sweet’ listening position. In the home, variable seating positions are inevitable. And in most typical commercial dubbing suites, two to four people frequently sit in on a crucial mix-down. A frequently forgotten element is the reflected energy from walls and ceiling. Those components interact with the primary (or direct sound) energy to produce the integrated sound field that the listener hears. Around twenty years ago, most loudspeakers were designed solely on the basis of achieving a flat frequency response on axis. JBL’s research and development team decided that loudspeaker should be designed to provide an appropriately integrated sound field. They describe it as ‘the listening window’, encompassing an arc of 30° in the horizontal plane and 15° in the vertical plane. Their research led them to the conclusion that the loudspeaker that sounds most natural provides uniform energy within those limits, even though their measurements confirmed that there may well be small differences in frequency response and perceived sound uniformity at the outer extremes of the field. As a result of that work, all current JBL consumer and professional monitor speaker systems are designed to satisfy this performance goal, and frankly, as I have observed, they do so remarkably well. I was fortunate to be able to listen to some of JBL’s developmental multi-channel speakers in one of its new test suites in Los Angeles. Prior to my visit to JBL I had no view on the desirability of installing a multi-channel sound system in my home. After Floyd Toole demonstrated the attributes of one of JBL’s new multi-channel systems, I realised just how effective and impressive such a SC system can be. Acknowledgement: Thanks to Jands Electronics (distributors of JBL Professional Equipment) for their assistance in the preparation of this feature. MORE FROM SAVE YOUR EFI CAR! UP TO 60% ON EFI TECH SPECIAL Electronic Components Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication A valuable collection of the best EFI features from ZOOM magazine, with all the tricks of the trade – and tricks the trade doesn’t know! Plus loads of do-it-yourself information to save you real $$$$ as well . . . HERE ARE JUST SOME OF THE CONTENTS . . . www.futurlec.com large range fast delivery 8  Silicon Chip  Making Your EFI Car Go Harder  Building A Mixture Meter  D-I-Y Head Jobs  Fault Finding EFI Systems  $70 Boost Control For 23% More Grunt  All About Engine Management  Modifying Engine Management Systems  Water/Air Intercooling  How To Use A Multimeter  Wiring An Engine Transplant  And Much More including some Awesome Engines! 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Small matching transmitter kit:(K122) All at special prices. RX module $22. TX kit $8 ALCOHOL BREATH TESTER KIT: Ref: EA Oct. 96. Based on a high quality Japanese thick film alcohol gas sensor. The kit includes a PCB, all on board components and a meter movement: (K80) reduced from$40 to &25 MASTHEAD AMPLIFIER KIT SPECIAL The MAR-6 available separately $4. The amplifier gives good results with any two metal wires or strips acting for the antenna. It should even work with a coathanger! Basic kit with both the PCBs & all on-board parts (K03) $15 ...Basic Kit + 2 Weather-proof Plastic Boxes + plug-pack: $20 (ask for your free case with this item) K Ref EA Aug. 96. Kit Connects to your PC parallel port & samples over 0-2V & 0-20V <at> between1 per hour to 1per 100uS. Ideal to monitor battery charging etc. or used as a basic 5KHz oscilloscope! Our kit inc. all onboard components, PCB, box & software on 3.5 disk:(K90) $25 15A PLUS 12V/24V HI EFFICIENCY SOLAR REGULATOR KIT Our regulator suits up to 100W panels. Features precision voltage ref., Hi eff. saturating MOSFET, Shotky diode isolation, charge indicator and a current limiter so it can be used with car battery chargers, generators etc. Low cost due to the use of some unused recycled components. complete kit inc. case $29... See our bargain solar panels in this ad.. MUSIC BOX KIT: Ref: EA Oct. 96. This little kit is the electronic equivalent music box. With a range of tunes & is activated by light. Use it in a music box, a musical jewellery case, or toys. Req. 2 x AA batteries. Kit is supplied with PCB, all on-board components, a small speaker and battery holder. Kit is available in two different versions; *Xmas Songs + M3481 IC: (K78C) $11 *Various Songs + M3485 IC: (K78V) $11 * Additional (M3481 or M3485) $3.50 each UHF AUDIO / VIDEO TRANSMITTER KIT Kit includes all components needed...... PCB plus all on-board components, connectors, switch, metal case, telescopic antenna, twin RCA A/V lead, all that is needed to complete the full kit. 12Vdc <at>10mA operation. Ideal for transmitting audio and video around you suitable home.. Complete plugcack $5 Kit for just $28 VIDEO CAMERAS HOUSED CAMERAS CMOS DOME COLOUR $160 CMOS COLOUR IN A SWIVEL CASE $160 PCB CAMERAS B/W CCD CAMERAS $89 pinhole (60deg.), 92 deg,120 deg. add $10 for 150 deg. CCD COLOUR $190 SUGAR CUBE CAMERAS $70 ALL WITH A FREE VHF MODULATOR & SUITABLE PLUG PACK O O L XENON FLASH TUBES Removed from disposable cameras. Just add a AA cel. $3 Ea. or 4 for $10 STROBE KIT also available. - battery not included + uses above flash$6 CFL INVERTER KIT our very popular inverter. The improved design uses a larger transformer and a SG3525 switch Mode Chip.This very Efficient Driver kit can drive a number of CFL’s from 12vdc. & would be great for lighting the weekender or caravan.. SPECIAL 1 inverter & 3 CFLs: $45 $55 $70 $160 COMPLETE INTELLIGENT BATTERY / POWER MANAGEMENT SYSTEM For the home or car New Battery Monitor Kit:12v / 24v monitor with low voltage cutout, audible alarm before cutout. Designed to use minimal power & has a battery saving 12 led bar-graph indicator. Kit inc PCB, all onboard parts, label, 10A cutout MOSFET + suitable surplus case for $32.... For 50A MOSFET (IRFZ44) add $3. To complete your solar system we have 12-24V SOLAR REGULATOR KIT: 15A Kit inc all onboard parts & PCB. $25 SC_DEC_99 BATTERY CONDITION 12V 14.6 29.2 14.2 28.4 POSSIBLE WATER LOSS FULLY CHARGED WARM BATTERY 13.8 27.6 13.4 26.8 13.0 COOL BATTERY OFF ON SOUND WARNING LOW VOLT CUT OUT 24V 26 12.6 25.2 12.2 24.4 11.8 23.6 11.4 22.8 11.0 22.0 10.6 21.8 10.2 20.4 BATTERY MANAGEMENT SYSTEM $0.80...Module (no case) only $8 $25 5KHz OSCILLOSCOPE $25!!! **NEW PRODUCT** $10 Line lens+$0.80...X-hair lens ( + ) 35-140 LED INFRA-RED ILLUMINATOR KIT Comes on when it gets dark or can be controlled by alarm system. 20-30M range Kit inc. mount ing tray & universal swivel mount. 35 LEDs $25. Extra 35 LED pack (3extra packs max) $14 per pack. 140 LED kit: $67 OR base Kit + 105 extra LEDs, 140 LEDs TOTAL!!! for just $50. Use with B/W cameras to see in the dark. USED AUSSIE MADE TRANSFORMER 240V PRIMARY (120+120),ES screen, Secondary....1X12V<at>1.1A...10V<at>5A...7 V<at> 5A... 12-0-12V<at>7.5A. 100 X 115 X 100mm. bargain at $15 NEW FULLY FEATURED ANSWERING MACHINES.Brand new in original box with manual, tape, plug pack and phone lead Call screening, up to 2.5 min. out going message, VOX recording, power fail protection, memo record, plays music before beep, digital volume control, programable security code, remote call break-through, room monitor, full remote features, save messages, AUSTEL appd. Bargain at $25 12V-13W $25 24V-10W $23 OVER CHARGED 1 / 3 LED (RGB) $3.50 / $7.00 12V- & 24V DC CFLs CHARGING $60 **LOOK AT THIS** NORMAL **NEW**NEW**NEW** CHRISTMAS SPECIAL FLASHING MOBILE ANTENNAS To suit most popular mobile phones. PELTIER EFFECT DEVICES. Could be used for cooling overclocked PC CPUs. All 40 X 40mm. 4A T 65deg. Qmax 42W $25 6A T 65deg. Qmax 60W $27.50 8A T 65deg. Qmax 75W $30 Comes with info to build cooler / heater plus data. Some used heatsinks avail. TWO MOTOR LASER LIGHTSHOW KIT Inc. motors, mirrors, reversing switch & all electronic components. Can be controlled by variable DC input. Lots of patterns, flowers, stars etc. $16 Laser module $8 LOW BATTERY NEW SUPER LOW PRICE + LASER AUTOMATIC LASER LIGHT SHOW KIT: MKIII. Automatically changes every 5 - 60 secs. Countless great displays from single to multiple flowers, collapsing circles, rotating single and multiple ellipses, stars, etc. Easy mirror alignment with “Allen Key”. Kit inc. PCB, all on board components, three small DC motors, mirrors, precision adjustable mirror mounts: (K115) + very bright 650nM laser (LM2) module. Kit with laser module $60 Kit + laser module + plug-pack + instument style case all at a special price of $75 IR LASER DIODE SECIAL 5mW 780nM (barley visible) Sharp LTO26 Requires 65mA. Diode plus focus lens (no housing) $18....constant current driver kit $10 LITHiUM-ION BATTERY PACK AUDIOVOX BTR600R 400mAh 7.2V These battery packs contain two rechargeable Lithium-Ion cells, with an amazing 400 mAh capacity in such a small cell (51mm X14mm). Ideal for use as R/C receiver batteries etc. $4ea KEY-CHAIN LASER POINTER in a presentation box. Quality metal housing + 3X LR44 /AG13 bats. FREE. Extra bats. 50c Ea. The Denon AVC-A1D has a host of operating features while still managing to look very clean and uncluttered. It provides all possible operating modes for home theatre systems. Denon's AVC-A1D surround sound amplifier When is an amplifier not simply an amplifier? Answer: when it is a surround sound amplifier made by Denon. This new model Denon is described as an A/V surround sound amplifier but that hardly begins to tell the story. Briefly, it has virtually every conceivable amplifier feature you could want in a Home Theatre surround sound system. By LEO SIMPSON These days one accepts that audio equipment for home theatre systems is going to be complex. After all, there are all the program sources which must be catered for, the minimum of five audio power amplifiers, the need to cope with Dolby Digital (AC-3), DTS (Digital Theatre System) and Dolby Pro-Logic sources plus DSP (Digital Signal Processing) to give surround 10  Silicon Chip sound effects like concert hall, rock stadium, jazz club and so on. This Denon product does all that and a whole lot more and it takes quite a lot of time to work out just how many functions and features it has. In fact, for a unit which has so many features, it is quite inscrutable at first sight. It looks more like a large conventional stereo FM/AM receiver than a surround sound amplifier, doesn't it? After all, it appears to have a long dial scale and a large knob on the right, just like a stereo receiver. Well, the knob is the master volume control but it is not a normal potentiometer and it is not motorised, as are many in systems with remote control. The other knob on the front panel is the input selector but it is not a normal switch and it can be rotated continuously back and forth, without stops. There is a large door in the control panel and it drops down smoothly to reveal 18 pushbuttons and two more knobs, for the bass and treble controls. And yes, the tone controls aren't normal pots either - they rotate continuously while the amount of boost or cut is displayed on the large vacuum fluorescent dot matrix display. So after tentatively trying out some of the controls or the multi-button remote you quickly realise that this is no ordinary surround amplifier. Then you take a look at the back panel and stagger back - just how many inputs and outputs can this unit handle? The number of inputs is increased because it handles video as well as audio - that's where the A/V designation comes from. But in addition it also handles optical digital signals from four sources such as DVD and CD players. As well, there are S-video sockets for six sources such as DVD and VCRs as well as outputs to two TV monitors and two VCRs. There is also an AC-3 Dolby Digital) input All told, there are no less than 77 RCA sockets, six optical fibres sockets and ten S-video sockets. And there are seven pairs of binding post terminals for the speakers: front, left, centre, and two sets of rear speakers. After doing this quick reconnaissance, the natural reaction is to retreat to the owner's manual and a cup of coffee for an hour or two's quiet reading. Well that's what you would normally do if you had the owner's manual; we didn't, as this was an early review sample. We did have some Denon publicity material and a brochure and fortunately, the brochure was pretty comprehensive. So what have Denon attempted to do in producing this very impressive looking piece of equipment? Not only does it incorporate very comprehensive input signal handling for analog sources but it also handles digital signals which can be connected to the RCA sockets via normal shielded cables or via optical fibre. And it is in the digital domain that Denon have really spent the money in developing 96kHz 24-bit digital-to-analog converters. In fact, there are no less than six of these D/A converters, one each for the five normal audio channels and one for the sub-woofer output. There is a major story just in the development of these chips but Denon have gone further and incorporated 32-bit DSP chips for the Dolby Digital and DTS decoders and for the THX and surround sound signal reproduction. Just so the system will not be outmoded in the future, the Denon AVCA1D also has provision for 6-channel and 8-channel audio sources. Did we forget video? We mentioned S-video sockets but not the RCA sockets for composite video or so-called "component" video (ie, Red, Green & Blue) for direct connection to a TV monitor or video projection system. AUDIO PRECISION FREQRESP AMPL(dBr) & AMPL(dBr) vs FREQ(Hz) 5.0000 04 NOV 99 09:13:14 5.000 4.0000 4.000 3.0000 3.000 2.0000 2.000 1.0000 1.000 0.0 0.0 -1.000 -1.00 -2.000 -2.00 -3.000 -3.00 -4.000 -4.00 -5.000 -5.00 10 100 1k 10k 100k 200k Fig.1: frequency response over the amplifier at a power level of 1 watt into an 8Ω load. This is taken in Direct mode which bypasses the tone controls. AUDIO PRECISION SCTHD-W THD+N(%) vs measured LEVEL(W) 10 05 NOV 99 08:47:48 1 0.1 0.010 0.001 .0005 0.1 1 10 100 300 Fig.2: total harmonic distortion versus power at a frequency of 1kHz with the two front channels driven. Maximum power is 180 watts at the onset of clipping (measured with a bandwidth of 20Hz to 30kHz). As you might expect, the remote control is pretty complex as well, with lots of buttons to control all the different sources. It is a learning remote so when you set up your home theatre system there will be no need to juggle four or five remotes. A feature we really liked is that the most often-used buttons, for things like volume up/down, play, stop and so on, glow in the dark. So you can see 'em before you press 'em and you don't have the concern about battery usage for back-lighting. But perhaps the best feature of the remote control, and the Denon amplifier itself for that matter, is the on-screen display. This is just like the DECEMBER 1999  11 AUDIO PRECISION SCTHD-HZ THD+N(%) vs FREQ(Hz) 5 05 NOV 99 09:10:06 1 0.1 0.010 0.001 .0005 20 100 1k 10k 20k Fig.3: total harmonic distortion versus frequency at a power level of 100 watts into 8Ω (measured with a bandwidth of 20Hz to 80kHz). This remote control is a learning type so it will replace most remotes required for a home theatre system. on-screen display (on the TV monitor) which is a feature of today's VCRs. In fact, the on-screen display is a necessity, so that you don't have to remember all the settings you have made. After all, the front panel display only shows the control settings you just touched, not those which were previously set. For example, when you change the bass or treble control, the amount of boost or cut is shown on the front panel display, eg +7dB, but as soon as you select some other function, the boost setting disappears. Nor can you tell the tone control setting by looking at the knobs because they don't have any markings. With the on-screen display you can call up all these settings without having to touch them. 12  Silicon Chip By the way, you can bypass the tone controls by selecting the Direct mode although we could not measure any significant difference in performance when this was in use. Before we delve into the innards of the big Denon, I must say that I find the gold finish on the front panel a most refreshing change from the universal black or charcoal on most hifi equipment. It looks more at home in the living room to my mind although the unit is available in black for those who prefer the sombre look. Since the AVC-A1D is such a large and bulky unit I knew it would be crammed to the top with circuitry but I was not quite prepared for just how much there is. Removing the case shows it has lots of boards for signal processing on the righthand side (looking from the front) of the chassis and the big power supply on the left. Down the centre is the five-amplifier module, mounted on a heatsink tunnel and cooled with two fans. The power supply consists of the large toroidal power transformer and two large filter capacitors and these supply the five power amplifiers. Elsewhere in the chassis are the supplies for all the signal processing circuitry. Guess how all the analog signal switching is done? Not with CMOS gates but with relays, lots of them. So whenever you change a signal source or mode selection you can hear the relays clicking in and out. We don't how many PC boards there are in the unit because you would have to disassemble it to count them all but as you can see from the internal photograph, there are quite a few. All the signal processing boards are double-sided and are covered in surface-mount components on one side while the power supply bypassing and larger components are on the other side. Perhaps the most interesting (and understandable) module for me was that for the five power amplifiers. Each of these amplifier uses just two large power transistors in the output stages. These must be very rugged devices indeed because each power amplifier is rated to deliver up to 390W into 2Ω loads with normal program signals. They are plastic-encapsulated devices with the case measuring about 20 x 40mm, much bigger than the 200W-rated plastic devices we are used to seeing. Since we did not have any access to circuits, it is not possible for us comment in any detail but the power amplifiers appear to be conventional class-AB designs, albeit relying on those very large output devices. Each channel is rated at 140 watts RMS into 8Ω loads, with the power rising to 190 watts under dynamic conditions (ie, program rather than continuous sine wave signals). The rating rises again to 310 watts into 4Ω loads (dynamic) and 390 watts into 2Ω, as mentioned above. Rated harmonic distortion is .05%, for signals from 20Hz to 20kHz. Bench-testing the big Denon presented a real challenge. For a start we don't have a big load box which will cope with five power amplifiers simultaneously. This meant that we had to content ourselves with just testing the front left and right channels in stereo mode. Nor did we have time for a a full suite of audio tests and so we had to be selective. However, the tests that we did perform showed that the Denon amplifier comfortably met all its specifications, as you would expect. Fig.1 shows the frequency response of the analog circuitry in Direct mode, at a level of 1 watt into 8Ω loads. As you can see it is about 0.5dB down at 10Hz and just over 1dB down at 70kHz. At 20kHz it is about 0.35dB down - more than adequately wide for a hifi amplifier. Fig.2 & Fig.3 illustrate the performance of the power amplifiers and these were measured in Direct and non-Direct modes with negligible differences in performance, with both channels driven simultaneously. Under this stereo condition, the amplifiers comfortably exceed their power ratings, giving about 180 watts before the onset of clipping. By the way, the little zig-zags in the curves are an artefact of the attenuator switching The rear view is pretty cluttered though with no less than 77 RCA sockets (count them), plus S-video sockets and optical fibre sockets. in the Audio Precision test gear and do not have any significance in the amplifier's performance. One aspect we did have trouble with was the effect of residual noise at the lower power outputs. As you can see from Fig.2, the harmonic distortion is 0.03% for a power output of 100mW but that does not represent distortion; it is noise. This can be reduced by driving the unit with a bigger input signal and winding the volume control back and this is what we did, driving the unit with a 2V signal and measuring (for this test) with a bandwidth of 30kHz. Lest we give the wrong impression, the overall noise levels from the Denon are very low. Set for a sensitivity of 2V input and 140W output into 8Ω, the signal-to-noise ratio was -108dB This is the power amplifier module which has five power amplifiers mounted on a heatsink tunnel cooled by two fans. Notice the very large power transistors; only two of these are used in each power amplifier. unweighted. But they've done some clever things with their volume control attenuation because it drops to around -120dB at low volume settings and rises to around -92dB at maximum sensitivity, ie, with the volume setting flat out. This latter condition would never apply in practice so the overall noise levels are very low and even more creditable when you consider the amount of circuitry in the signal path. Fig.3 shows the distortion versus frequency at a power output of 100 watts into 8Ω loads, with both front channels driven. As you can see, the distortion is below .05% at all times and below .03% for frequencies below 10kHz which is a pretty credible result for power amplifiers with only two power transistors in the output stages. During the high power testing, the fans cut in regularly but they are relatively quiet and they cut out quite soon when the power level is reduced. They would probably not operate at all during normal listening. In any case, if you were listening at high levels you certainly would not hear the fans. We could go on with a lot more measurement results but you have the overall picture - this is a very impressive machine with a huge range of features. How does it sound? Very clean, very quiet and with heaps of power; what more can we say? The only drawback is that prospective buyers will need to be wellheeled; the recommended retail price is $5680 and it is covered by a 2-year parts and labour warranty. For further information, contact the Australian distributors for Denon equipment, AWA Audio Products by phoning 1 800 642 922 or by email info<at>audioproducts.com.au SC DECEMBER 1999  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: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SERVICEMAN'S LOG All the same – only different It’s not often that one set of notes deals almost exclu­sively with the same make of set. However, that’s the case this month because I had quite a few Sony TV sets to fix. Even so, each model is still a separate device, with its own quirks and problems. It’s really been quite a month, with TV set repairs pre­dominating. Computer repairs tend to be confined to older ma­ chines – machines which their owners can’t bear to throw away. It is hard to overcome the perception that most electronic applianc­es have a life-span of around 10 years and computers only about three years. This is not because they are not well made or because the manufacturers have incorporated “built-in obsolescence”. Instead, it is dominated by the demand for more features and, of course, faster operation – all ultimately involving the latest technolo­gy. I am happy to oblige by fixing older devices, provided the customer is prepared to accept the non-availability or high cost of spare parts. As already stated, this month I dealt with quite a few Sony TV sets. These are normally very reliable sets and the number of repairs that came in simply reflects their popularity in the marketplace. Unfortunately, apart from the brandname, the only thing they had in common was the diffi- Fig.1: the microcontroller circuitry in the Sony KV-2064EC colour TV set. Disconnecting R068 restored all the set’s functions but it was the microcontroller (IC001) itself that had to be replaced. 18  Silicon Chip culty I had in analysing and solving the problems. The KV-2064EC The first Sony was a 1983 stereo TV set, model KV-2064EC (XE 3 chassis), with no picture. Mr Hardy had already previously taken it to the local service agent but had become annoyed about the 3-week backlog, a non-refundable quote fee of $35 upfront, and an estimate of $290. I didn’t have the heart to tell him that some companies charge twice that price and require even longer queues. Although there was no picture, the sound was quite OK which seemed to suggest a straightforward problem. I don’t normally service TV sets more than 10 years old but I thought that this would probably be a piece of cake. And I even had the origi­nal service manual! Unfortunately, my optimism was to be short-lived. With the set on the bench, it didn’t take long to confirm that all the voltage rails were spot on, that the EHT, focus and screen voltages were correct, and that the CRT filaments were at 6.3V and glowing – in short, all the main “life signs” were there. The only voltages that were wrong were the tube cathodes. These were high which indicated that they were being cut off by the video processing circuits. I thought I would take a quick short cut here although I don’t really recommend it to others, on the grounds that there is a fair risk of damaging other components. By momentarily shorting each cathode to chassis in turn, there should be an intense single colour raster on the screen. This will indicate whether there is full vertical and horizontal scanning and if the tube is working. If, for example, the vertical timebase has failed, many sets will blank off the raster to prevent screen burn. In this instance, all was OK, with three bright fully scanned coloured screens. and Q316 (BLK). The base of Q316 is shown on the circuit diagram as 0V but was in fact at 5V, thus switching it hard on. Tracing back further, I found this same 5V on pin 9 of the micro­ controller IC (IC001) but this point is also shown on the circuit diagram as 0V – see Fig.1. Disconnecting pin 9 made no difference but removing R068 (22kΩ) which goes from pin 9 to the 5V rail restored everything, with a perfect picture on the screen. The set even continued to work OK when pin 9 was resoldered but with R068 left disconnect­ed. So what is the purpose of R068 and what does it do? Well, I really don’t know; there is no block diagram or description of the IC. Furthermore, the circuit shows IC001 to be a CX519-004P but I found a CX523-110P fitted. Worse still, neither IC is now available as a spare part, which isn’t unusual for a 16-year old set. Fortunately, I found a CX519004P in a scrapped Sony KV-2764. When fitted, this IC held its pin 9 low even when R068 was reconnected. I have no idea what caused the problem, which is very frustrating – but at least I had another satisfied customer. Mrs Mulligan’s KV-F29SZ2 It was now time to get really technical and bring the big guns into play. Using a signal generator and a CRO, I soon estab­lished that the video was getting as far as the colour decoder, IC301 (UPC1365), but was going no further. I checked all the waveforms on all the pins, especially pins 19 and 23 where I measured the shape of the horizontal pulses. Apart from no output on pins 26, 27 & 28, out of the RGB matrix block (which was understandable), all was correct. The video could be seen as far as pin 6 on the video ampli­fier part of IC301. Next, I measured the DC voltages on this IC, concentrating on the luminance section, especially the bright­ ness, contrast, blanking (BLK) and beam current limiter (ABL) circuitry. I found that the voltage on pin 4 was only half the 8.5V shown on the circuit and neither the remote controller nor the set controls could correct it. I now followed the circuit back from pin 4 to transistors Q308 (ABL) Items Covered This Month • • • • • Sony KV-2064EC stereo TV set Sony KV-F29SZ2 TV set Sony KV-2585AS TV set Sharp SX-51F7 TV set Sony KV-S29SN1 TV set The next Sony lived by the sea in a lovely unit overlooking the beach. The only trouble was that the onshore breezes blew the salt atmosphere right into the back of Mrs Mulligan’s 1995 KV-F29SZ2 (G3F chassis) TV set. When I called, she complained that all she could receive was channel 2 and play back the video cassette recorder. The on-screen display showed that it was switching bands and searching, with lots of snow on the screen. I checked the antenna and the video leads and they were all OK. The VCR could receive all channels perfectly and from all of this, I guessed that it was either the tuner or the IF module. However, I would have to take it back to the workshop. When it finally ended up on the bench, I removed the IF module block and resoldered a number of suspected dry joints around the coils and filters. Unfortunately, this produced no miracle cures so I laid the set on its front to provide access to the “A” board and started making measurements. And this provided the first clue – the DECEMBER 1999  19 band-switching voltages to the tuner weren’t changing, even though the on-screen display said they were. (Sony uses an alphabetical code to identify various PC boards. An “A” usually indicates the main board, while smaller boards may be desig­ nated down to “V”.) I traced the relevant PC track back to the microprocessor. Everything was perfect on the underside of the “A” board but it was a different story on top. Although everything looked fine from a casual glance, a closer inspection revealed that the fine copper tracks disappeared beneath the green solder mask. By scraping away the mask in several places and testing with a continuity meter, I found breaks in two of the tracks and narrowed them down to within a few centimetres. Connecting links across these breaks fixed the problems and the set could now tune all the Band III and UHF stations. Finally, I wiped the boards and sprayed them with a fine mist of CRC 2-26 to try to prevent further corrosion. However, considering where the set is located, I fear it was a fruitless task. Almost certainly, the set will be a write-off in a few years. Picking up the pieces The third Sony had been all over the place before finally landing on my 20  Silicon Chip bench. I hate taking on jobs like this; inevitably, I have to fix the previous technicians’ faults before getting on to the real repair. This set, a KV-2585AS, has a GP1A chassis, designated SCC-F35A-A according to the label stuck on the CRT metalwork. However the service man­ual says the same model uses a chassis designated as SCC-D23L-A. It may appear that I am being pedantic but this set had spent the better part of a year in various workshops and many parts had been replaced – not necessarily with the right ones. The main question mark hung over IC601, in the switchmode power supply. An STRS6708 was fitted but my circuit said it should be an STRS5941. And just to confuse matters, another GP-1A set that came in had an STRS­5741. In this case, the set was dead and the main fuse was open, due to IC601 having gone short circuit between pins 1 and 2 (ie, between collector and emitter of the internal switching transistor). Unfortunately, these ICs aren’t cheap, costing around $30 each. The chassis itself was a mess; several parts were either unsoldered or missing and others were quite clearly the wrong types. Fortunately, it wasn’t difficult to identify the compon­ents that had been replaced, from the fresh soldered joints. As it turned out, there were over half a dozen incorrect parts fitted. I replaced these with the correct types and I also replaced the horizontal output transistor, Q802 (2SC4927), which had a short circuit. Finally, I was ready to fire the set up but as an addition­al precaution, I connected a 200W globe where the main fuse should be. The set came on with both sound and picture but before I could measure the main voltage rail there was a loud bang and it died again, the globe turning very bright. This exercise cost the horizontal output transistor (Q802), a 1.2Ω feed resistor (R340) and the switchmode IC (IC601). I replaced all these parts and I tried again, this time using a Variac to wind up the voltage, a 100W globe and a meter across test point TP91 (135V) to chassis. As a further precau­tion, the base and emitter leads of Q802 were shorted. The 100W globe lit without stress and the voltage levelled at 139V. As there is no control to adjust this, I felt that the 3% error was within the design limitation of the set. Feeling much more confident, I removed the base-emitter short from the horizontal output transistor and again wound up the Variac. Once again, the picture and sound were good and there appeared to be no problems, although the test point was still at 139V. It ran for over half an hour and then, just as my back was turned, there was another loud bang followed by silence. There was a smell of electrical burning and the same com­ ponents had died again. And although I hadn’t seen what happened, I suspected the horizontal output transformer, T851. Once again, I had a problem deciding which was the correct one for this set, as the one fitted (NX-M 1601 1-439423-32) didn’t match the circuit or the other GP-1A set on hand. Eventually, I chose an NX-1604 1-439-416-41 and fitted it, along with all the other parts. This time the set came on and remained stable. I left it on for days, keeping an eye on it, and it performed faultlessly. Tube failures Just recently, I have had two cases of picture tube fai­lure, both in modern sets. The first was a 1995 Sony KV-F29SZ2 G3F chassis. I was called to this set, with the customer com­ plaining that there was no blue and that the set was “burning”. When I arrived, the symptoms I saw were no green and a burnt 1.5kΩ resistor, R713. This didn’t surprise me as it fed the green cathode. However when I asked the customer about this, he replied “Ah, well – I’m colour blind!” I replaced the resistor and all was well. However, I knew there could be only one reason why it had burnt and that was because the tube (M68KZT­ 10X) had an intermittent heater-to-cathode short. I told him the bad news and suggested that he “whinge” to Sony about it because, realistically, he had blown $1700 odd in four years on this largescreen “deluxe” TV set. At the same time, I pointed out that the set was well and truly out of war­ranty and so that would probably be the end of the story. A month later I bumped into him in the street and asked about the outcome. As it turned out, Sony had instructed him to take it to one of their service agents and if it really was faulty, they would replace the tube – he would have to pay for the labour costs only. He is still in the process of having this done. All I can say is, good for him and good for Sony. The second set was even younger, a 51cm Sharp SX-51F7. This set was only about two years old and the owners were watching it when it went “boom” and died. I was expecting something spectacu­lar when I called and I was surprised when I couldn’t find any­thing visually wrong on the circuit boards. All that was happen­ ing was that the picture tube (ASIK­ PD12SX) was arcing internally within the gun assembly. Obviously, it was “down to air” which is just another way of saying that the tube had lost its vacuum. I checked the power supply rails and the EHT. The HT was spot on at 115V and the EHT did not exceed 25kV. If either of these rails had momentarily gone high, they might have caused a flashover inside the tube, creating a fracture in the glass. However, both rails were steady and as there was no visible damage to the tube, I could only presume that there was a problem with the frit seal or with a part of the tube which cannot be seen. I thought that this too would be the end of the story but Sharp said it would come to the party with a free tube if the owners paid for an Fig.2: a section of the V board circuitry in the Sony KV-S29SN1. IC02 is at the top, while plug/socket CN01 is at left. Pin 3 (video) on the socket goes to pin 8 of IC02, while pin 2 (ST TV) goes to Q03’s emitter via R13. Fuse PS01 is at middle left, in the 8V line to the collector of Q02. authorised service agent (not me) to fit the tube. So full marks for customer service to Sharp as well. The giant Sony As soon as I saw this next set in Mrs Marsden’s home, I knew it was destined for the workshop. It was a 5-year-old 73cm Sony set with a KVS29SN1 G1 chassis and with lots of features, such as picture-in-picture, teletext and stereo sound. The set had developed two separate faults, one being inter­mittent no picture and the other no horizontal or vertical sync in the main picture (although the picture-in-picture was locked perfectly). To make matters worse, at least from a service view­ point, the set is big and heavy and access to the main module chassis is rather difficult. So there I was, on a Monday morning in the workshop, con­templating which was worse – fixing this set or working out how the GST was going to ruin me. I settled on the easier of the two problems and took the back off the set but even with a photocopy of the service manual, it was difficult to know where to start. In the end, I began by confirming that the “no sync” prob­lem persisted even if I injected a composite video waveform from a colour bar generator into the AV socket. I then took a look at the circuit diagram of the “A” board and quickly counted at least 10 devices marked SYNC this or SYNC that – there is even a module marked A2 SYNC. Unfortunately, the block diagram was too small and too badly copied to read. The only thing was to start somewhere – anywhere – and track down a sync signal. After that, I should be able to trace the signal until it disappeared and then figure out what the problem was. Now unless the reader has access to a manual or circuit, this description will not be easy to follow. It is set out, as much as anything, to give some idea of the frustrating chase involved in tracking down this most elusive fault. So bear with me. I placed the set face down but at a slight angle so that, by using a small mirror, I could see part of the screen. I then unscrewed the main chassis, pulled it out by about 150mm and wedged it on the bottom of the cabinet. The whole thing was incredibly precarious and the neck of the tube could be knocked off at any moment. Next, I fired up the CRO and started DECEMBER 1999  21 at the output of one of the twin IF modules. This went to transistor Q1101, designated sync-detect, and then to plug CN1108 and micro­ controller board “M”. (Note: Sony uses the prefix CN to denote plug and socket assemblies). There was plenty of composite video signal on CN1108. Simi­larly, there was video signal on transistor Q1130, also designat­ ed sync-detect, which came from board B, plug CN301. I then noticed IC1101, marked sync-selection, and started measuring the inputs and outputs of six transistors, all marked “SYNC”. In the course of all this measuring, I encountered several dry joints and resoldered them, each time praying that this would fix the 22  Silicon Chip problem. It didn’t. To add to my woes, the picture was now displaying the second fault - ie, no picture – on a regular basis, thus disrupt­ing my efforts to track down the missing sync signal. Trying to follow the video often meant going to a module where the circuit is marked “SYNC IN” and “SYNC OUT” – the only problem is from which board’s perspective? There are also several plug/socket combinations where the plug was marked one thing and the socket something else. As I continued my somewhat random quest, I was also pulling out modules, soldering them, reinstalling them and where possi­ble, measuring any voltages. Gradually I was getting a feel for the thing – the intermittent picture appeared to be caused by the J board/B board connection, a rather clever plug and socket combination (CN308/2301 CN309/2302) that also acts as a hinge. This was either noisy due to dirty contacts or had dry joints. Anyway, I cleaned the contacts and resoldered all the joints around this assembly and that fixed the intermittent picture problem. Getting back to the sync problem, I eventually found that there was video coming out of IC1101 into pin 3 of CN1113 but no video was coming out of SYNC pin 2. This pin in turn connects to pin 3 of CN1107 (marked SYNC IN), after which the signal goes to sync module A2 CN4401 and then back to IC3501 on the A board, via Q3512 SYNC 3, etc. CN1113 is connected to CN01 of the Teletext “V” board and the circuit, on page 107 of the service manual, designates pin 2 as ST TV. I took the board out and did a routine dry joint check but could find nothing untoward at first glance. However, the circuit shows a 0.6A fuse (PS01) connected between an 8V rail (pin 6 of CN01) and the collector of 5V regu­lator transistor, Q02 (Fig.2). This transistor delivers a regulated 5V at its emitter and this rail feeds pin 10 of IC02. The PS01 fuse, by the way, is called a “circuit protector chip” and looks like a two-legged transistor with N15 marked on it. Anyway, as luck would have it, this fuse measured open circuit, meaning that there was no 5V on pin 10 of IC02 or on the collector of Q03 (SYNC-OUT). Replacing it restored the composite video and gave a perfect picture. Subsequently, I was talking to a Sony service centre a few days later. After concluding other business, I mentioned my saga and its victorious outcome only to be promptly informed that it was a well-known problem. However, my informant did admit that he didn’t know why it happened. In effect, this was a classic example of the effort which can be involved in tracing a fault in an unfamiliar chassis. The fault was simple enough in itself but the symptoms provided few clues and in the absence of someone who says “that’s a well known problem”, there is nothing for it but to do it the SC hard way. This handy solar panel regulator measures the voltage across your battery or the charging current and will disconnect the panel to stop overcharging. It works with 12V or 24V systems and has a 3.5-digit liquid crystal display. Design by ALAN BONNARD Solar panels are becoming ever more commonplace but the regulators can be pricey items indeed. You do need a regulator otherwise there is a real risk that a permanently connected solar panel will overcharge your battery and cause it to boil dry. This low cost regulator is especially attractive since it has the bonus of the LCD panel to show the voltage or current. There will no longer be any need to dig out your trusty multimet­er to check the state of the battery – it is on display all the time. There are two switches associated with the regulator. The slide switch selects 24V or 12V operation and will only need to be set when the unit is initially connected up. The toggle switch is used to select voltage or current readings on the LCD panel. It will read current up to 5A and voltage up to 30V. There is a 4-way insulated terminal block December DECEMBER 1999  23 1999  23 Whether you have a large or small solar panel, you will need a solar panel regulator to avoid overcharging your battery. This design works at 12V or 24V and includes an LCD to show voltage or current. The solar panel is from BP Solar – Model BP 280F, 80W, $795 rrp. Phone (02) 9454 5111. for the connec­tions to the battery and solar panel and all connections can be permanent, since the regulator’s operation is automatic. A relay disconnects the solar panel when the battery reach­es full charge and a LED comes on to indicate this condition. A series diode prevents the battery from discharging via the panel when the sun goes down. Circuit description Fig.1 shows the circuit diagram and it can be broken down into two parts. First, there is the voltage and current sensing portion which drives the 3.5-digit liquid crystal display (LCD). Second, there is a voltage comparator for controlling the relay which connects the solar panel to the battery bank. Let’s have a look at the voltage and current sensing func­tions for the LCD first. The LCD is driven by IC5, an ICL7106 digital voltmeter chip which is normally set to provide a maximum sensitivity of 2V or 200mV DC, depending on the resistors at pins 32, 35 & 36. In this circuit, the ICL7106 is set to a sensitivity of 1V by trimpot VR1. Ergo, the voltage monitoring circuit should feed no more than 1V to IC5. 24  Silicon Chip The circuit is set to monitor voltage or current. The bat­tery voltage is monitored using a divider network compris­ing resistors R3 and R4. These provide a division ratio of about 93:1 to reduce the voltage to around 130mV for a 12V battery or 260mV for a 24V battery. This divided down voltage is fed to op amp IC1b which is connected as a unity gain buffer to drive the input of IC5, the ICL7106. We will come back to IC5 in a moment. To monitor current, we use IC2, a MAX472 current sensing amplifier. The charging current from the solar panel array is fed via a .01Ω (10 milliohms) shunt resistor connected to the inputs of IC2 and it provides a current output which is proportional to the current being monitored. The output current is then fed to a 1kΩ resistor Main Features • • • • • Suitable for 12V and 24V systems. High efficiency. Voltage and current readout on 3.5-digit LCD. Automatic disconnection and reconnection of battery at set points. Suitable for currents up to 5A. and the result is a voltage which is proportional to the charging current: 100mV for every 1A of current flow through the sensing resistor. Thus for a charging current of 5A, we will have 500mV fed to IC5. The voltage and current signals are fed via switch S2a to IC5, the ICL7106. Since the voltage and current signals are referred to the 0V line in the circuit, the ICL7106 needs a negative supply rail if it is to function correctly. This is provided by IC4, an ICL7660 +5V to -5V converter. This is essen­tially a “charge pump”, which alternately switches two capacitors, C8 and C9, between the voltage rails to produce -5V at pin 5. IC5, the ICL7106, provides all the necessary internal cir­cuitry to carry out the conversion from the analog input at pin 31 to drive the liquid crystal display. Well, it drives all the relev­ant pins on the LCD except those for the decimal points and these vary, depending on whether voltage or current is being displayed. So to drive the decimal points we use two gates of a 4030 quad exclusive-OR gate package, IC6. This takes the backplane signal from IC5 and switches it to the appropriate decimal point connection on the LCD, depending on whether current or voltage has been selected by switch S2. Notice that the “test” output, pin 37 of IC5, is used Fig.1: op amp IC1a is set up as a comparator to monitor the battery voltage. If the voltage rises above 13.9V (for a 12V battery) the relay disconnects the solar panel. DECEMBER 1999  25 Parts List 1 PC board, 152 x 72mm 1 3.5-digit liquid crystal display 1 slide switch (S1) 1 DPDT toggle switch (S2) 1 6V SPST relay with 5A contacts 2 40-pin IC sockets 1 4-way PC terminal block 2 TO-220 heatsinks 1 20kΩ horizontal mount trimpot (VR1) Semiconductors 1 LM358 op amp (IC1) 1 MAX472 current sense op amp (IC2) 1 LM336Z 2.5V reference (IC3) 1 ICL7660 +5V to -5V converter (IC4) 1 ICL7106 3.5-digit LCD driver with A/D converter (IC5) 1 CD4030 exclusive-OR gate (IC6) 1 7805 5V regulator (REG1) 2 C9013 NPN transistors (Q1,Q2) 1 red LED (LED1) 1 U840 power diode (D1) 1 1N4004 diode (D2) Capacitors 1 100µF 50VW PC electrolytic 1 22µF 16VW PC electrolytic 3 10µF 16VW PC electrolytic 1 1µF MKT polyester 1 0.22µF MKT polyester 1 .047µF MKT polyester 1 .01µF MKT polyester 1 100pF ceramic Resistors (0.25W, 5%) 1 1MΩ 1 22kΩ 1 470kΩ 1 11kΩ 1 110kΩ 4 10kΩ 1 100kΩ 1 5.6kΩ 1 56kΩ 1 2.7kΩ 1 24kΩ 1 2.2kΩ 1 1kΩ 2W wirewound 1 1.2kΩ 4 1kΩ 1 470Ω 1 270Ω 2 100Ω 1 0.01Ω 1W as the ground supply connection for IC6. This is not a mistake as one of the functions of the test output is to serve as the ground supply connection for any decimal point switching circuit. Resistors R25 and R26 are included to pull pins 9 & 12 to 0V when they are not selected by switch pole S2b. Solar panel switching Op amp IC1a and transistors Q1 & Q2 control the relay switching of the solar panel. IC1a is connected as a comparator with IC3 providing a reference voltage to its non-inverting input, pin 3. Pin 2 then monitors the battery voltage via resis­tors R6, R7 & 26  Silicon Chip Fig.2: the parts layout for the PC board. The LCD mounts above the ICL7106 (IC5). Note that the 7805 regulator must be fitted with a heatsink. R8 for the 12V mode and R5, R7 & R8 for the 24V mode, as selected by slide switch S1. In the 12V mode, once the battery voltage rises above 13.9V, pin 1 of IC1a goes low and this turns off Q1 which turns on Q2 and the relay to disconnect the solar panel. LED1 is lit while ever the relay is energised and the panel is disconnected. The battery then discharges over a period of time to 13.1V whereupon pin 1 of IC1a goes high, Q1 turns on, and Q2 and the relay turn off to connect the solar panel again. For the 24V mode, the panel is dis- connected when the bat­tery voltage rises above 27.6V and reconnected when it falls to 25.9V. Another point to note about the circuit is that diode D1 is there to prevent the battery discharging via the solar panel when it is not delivering power (eg, after sunset or during heavy cloud cover). However, there is no protection for the circuit if the battery is connected the wrong way around. Construction All the components of the circuit, including the LCD panel, are mounted Resistor Colour Codes  No.   1   1   1   1   1   1   1   1   4   1   1   1   1   5   1   1   2   1 Value 1MΩ 470kΩ 110kΩ 100kΩ 56kΩ 24kΩ 22kΩ 11kΩ 10kΩ 5.6kΩ 2.7kΩ 2.2kΩ 1.2kΩ 1kΩ 470Ω 270Ω 100Ω 0.01Ω on a PC board measuring 152 x 72mm. The ICL7106 (IC5) and some of its associated components are mounted underneath the LCD panel to conserve board space. The component layout is shown in Fig.2. Insert and solder the links and resistors first, followed by the capacitors, diode D2, trimpot VR1 and the three transis­tors. Take care when mounting the LM336Z (IC3) because it looks like a TO-92 transistor – don’t get it mixed up with the transis­tors. Both the power diode (D1) and the 7805 3-terminal regulator require a heatsink although our prototype did not have a heatsink fitted to the regulator. A small U-shaped heatsink is adequate if 12V operation is all that is required but a somewhat larger U-shaped heatsink will be required to cope with 24V battery opera­tion. The four small ICs (IC1, IC2, IC3 & IC4) can be soldered directly into the PC board but IC5 and the LCD panel should be installed in sockets. For this reason, two 40-pin IC sockets are required. One of the 40-pin sockets must be cut in half and both halves installed to provide the socket for the LCD. Next, install the 4-way insulated terminal block, the relay, LED1 and the slide switch. Switch S2 is connected via a 6-way length of ribbon cable. Setup and testing Once all components are installed we are then ready to set up the regu- 4-Band Code (1%) brown black green brown yellow violet yellow brown brown brown yellow brown brown black yellow brown green blue orange brown red yellow orange brown red red orange brown brown brown orange brown brown black orange brown green blue red brown red violet red brown red red red brown brown red red brown brown black red brown yellow violet brown brown red violet brown brown brown black brown brown not applicable lator. The first step is to connect a variable DC power supply to the battery input connections. This should be set to around 12V. Now check that +5V is present at the output of REG1, at pin 8 of IC1 and IC4, at pin 1 of IC5 and pin 14 of IC6. You should also be able to measure +2.5V at the positive connec­ tion of IC3 (middle terminal). This is best measured at the junction of R9 & R10. On our prototype, we measured the 2.5V reference at 2.4864V (on a Tektronix 4.5-digit DMM). Now measure the supply voltage with your digital multimet­ er and adjust trimpot VR1 so that the LCD gives the same reading. Next, set the slide switch for 12V operation (slider away from relay) and slowly wind up the supply voltage. The relay should click and LED1 should light as the voltage rises above 13.9V. Now wind the supply slowly down and observe that the relay clicks again and LED1 goes out as the supply voltage goes below 13V. Note that the exact voltages are not crucial; anywhere between 13.7V and 14V is fine for the disconnection point, while the reconnection point should be around 13V. If the relay is not operating as it should, check the components around Q1 & Q2. You can also check whether pin 1 of IC1 switches low for supply voltages above 13.8V and low for voltages below 13V. If you are going to charge a 24V battery, set the slide switch for 24V operation (slider close to the relay) 5-Band Code (1%) brown black black yellow brown yellow violet black orange brown brown brown black orange brown brown black black orange brown green blue black red brown red yellow black red brown red red black red brown brown brown black red brown brown black black red brown green blue black brown brown red violet black brown brown red red black brown brown brown red black brown brown brown black black brown brown yellow violet black black brown red violet black black brown brown black black black brown not applicable Capacitor Codes  Value      1µF   1u0  105 0.22µF  220n  224 .047µF   47n  473 .01µF   10n  103 100pF  100p  101 IEC Code EIA Code and wind up the supply. The relay should click and LED1 should light as the voltage rises above 27.6V. Similarly, the relay should click again and LED1 should go out as the voltage drops below 25.9V. Once all is correct, connect your solar panel and the bat­ tery to the regulator. The current from the panel can then be monitored and the orientation can be optimised for maximum SC bat­tery charging. Where To Buy The Kit The design copyright for the Solar Regulator is owned by Futurlec who can supply the kit. The complete kit is available for $44 plus $5 packing and postage within Australia. Orders many be placed via the website at www.futurlec.com and payment may be made via Bankcard, Visa Card or Mastercard. Alternatively, orders may be sent with a credit card authorisation, cheque or postal money order to Futurlec, 24 William St, Paterson, NSW 2421. DECEMBER 1999  27 PRODUCT SHOWCASE Christmas Motif Lighting from DSE and Jaycar If you’ve always been a teensy bit envious of Chevy Chase’s home in Christmas Vacation, Dick Smith Electronics and Jaycar stores could be the place to head this festive season. Both are offering rages of Christmas motif lighting in various patterns and sizes, ranging from $19.90 for small patterns at Dick Smith Electronics up to $449 for a 184cmlong Santa Sleigh at Jaycar. The DSE models are for indoor use while the Jaycar displays are suitable for outdoor use as well. Alternatively, of course, you could build the microprocessor-controlled LED Christmas tree featured in the November issue of SILICON CHIP. Jaycar Electronics also have this kit in stock, selling for $49.95 (Cat. KC-5280). Flow, valve & position sensors A range of sensors of interest in organisations involved in gas and fluid handling have been announced by Melbourne company, ifm efector Pty Ltd. First is a pressure sensor with high, low and window alarm outputs. They cover the pressure range from 1 to 400 Bar, operate from 18 to 30V DC with outputs rated at 250mA. Programming is via push buttons. The centre photo is ifm efector’s new gas/liquid flow sensor, suitable for zone 1 hazardous areas. Made from 316Ti stainless steel and with integral ANSI B 16.5, 1-inch flanges, they operate to Eex 1a IIC T4 standards. Setting ranges are 3-300 Emona Y2K Cat Emona Instruments has a new 88-page Year 2000 catalog covering not the dreaded “bug” but instrumentation and equipment for electronics and electrical design, manufacturing, service and education. Many of the world’s leading test equipment manufacturers are represented including Tektronix (for whom Emona are a distributor), GW, Thurlby Thandar, Kikusui, Seaward, Escort, Nicolet, Stag and Weller. The catalog is free on request to (02) 9519 3999 or email testinst<at> emona.com.au cm/s (liquids) and 100-2000 cm/s (gases). The third photo is one of their new valve position sensors which easily fit to most standard valve actuators. There are various versions including standard versions and hazardous-area versions rated to IP67. For more information, contact ifm efector Pty Ltd, PO Box 4084, Auburn South, Vic 3122. Phone 1300 365 088; fax 1300 375 070. Precision Handheld Thermometers from Fluke Fluke Australia have released a new range of hand-held thermometers particularly suited to applications in the food and process manufacturing industries but also having electronics industry applications. There are 7 models in the new series ranging from the low-cost 50 II series (pictured) through to the 54 II which, along with the 53-II, features powerful logging capabilities and a PC interface. Accuracy is within 0.05% +0.3°C. 28  Silicon Chip All models can handle a much wider range of thermocouples than the previous 50 series. They are also splash and dust-resistant and each has a holster for protection. Included in the range is an infrared model which requires no physical contact with the item being measured. This is intended for applications where contact could be hazardous or the item is moving. A laser beam is incorporated to assist aim and accuracy is within 1°. There is a comprehensive range of accessories available. For further information contact Fluke Australia, 26/ 7 Anella Ave, Castle Hill NSW 2154. Phone (02) 8850 3300, fax (02) 8859 3300 or www. fluke.com Precision battery capacity meter Smart Fastchargers have a new PC-based battery capacity meter which can check battery capacity (at any discharge current) for applications where maximum capacity and a knowledge of the available discharge time are important. It can also be used to match individual cells in battery packs for optimum capacity. Connection to the PC is via any available serial port, which the software automatically detects. Operating range is from 1.2V to 48V 30mAh to 130Ah with adjustable end of discharge voltage from 0V to 48V ad discharge time range from 1 minute to 30 hours. It also calculates and displays optimum discharge voltage. The graphic display shows curves for capacity in mA.h and for discharge voltage. It also shows percentage of nominal capacity, energy in watt-hours, elapsed time, maximum discharge time and discharge current, plus end of discharge voltage. 60VA to 3KVA encased toroids The program also calculates and displays the optimum end of discharge voltage for each battery. The battery is discharged through a resistor – from 0.01Ω to 50kΩ, or an optional constant current sink from 5mA to 2000mA. The software runs on any PC with either DOS or Windows and a VGA display. For further information contact Smart Fastchargers – Phone 03 6492 1368, Fax 03 6492 1329, email smartfastchargers<at>bigpond.com Video microscope for industrial uses The new Chroma 7310 Video Microscope from Nilsen Technologies is ideally suited to electronics manufacture and general quality control applications. It’s a CCD-based camera which provides distortion-free images. An advantage of this approach is that multiple-viewing is possible, frames can be frozen and the image can be recorded to a VCR or PC fitted with a video capture card for archiving purposes. The magnification range is from 20x to 300x with a large depth-of-field, making a very versatile instrument. STEPDOWN TRANSFORMERS For more information contact Nilsen Technologies, 150 Oxford St, Collingwood, Vic 3066. Freephone 1800 623 350, freefax 1800 067 263. Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 New semis from REC REC Electronics have released three new semiconductors of interest to professionals and hobbyists alike. The new Zetek Schottky barrier diodes in miniature SOT323 and SOD-323 packages offer space savings of up to 60% over comparable SOT23 devices. Suitable for a wide range of detection, mixing and modulation tasks at UHF, they feature low forward voltage (410mV <at> 1mA max) and high breakdown voltage. Also released are new micropower low dropout linear regulators (300mV dropout) suitable for a range of portable equipment, with fixed outputs of 2.5V, 3.3V or 5V or adjustable between 1.22V and 20V. Finally, the Linear Technology A1, 600kHz boost switcher delivers 28V for TFT liquid crystal displays. For more information, contact REC Electronics, Locked Bag 29, PO Rydalmere NSW 2116. Phone (02) 9638 1888; fax (02) 9638 1798, or offices interstate and New Zealand. Meccano is back at DSE Hands up if you “cut your teeth” on Meccano? It’s the mechanical construction system that has enthralled children and adults alike for generations. Strips, girders, nuts, bolts, brackets, wheels, axles, gears and pulleys – they used to say if it could be made it could be made with Meccano. Now it’s back – at Dick Smith Electronics. With impeccable timing, given the Jolly Red Suited Chap is only days away, all DSE stores (including PowerHouse stores) have Meccano kits ranging from easy-to-build through to engineering level. All come with a motor to make things that actually “do things”. DECEMBER 1999  29 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. Reverse battery protection with low voltage drop It is often a good idea to incorporate a diode in series with the power leads to a circuit operating off an external battery. The diode will prevent damage in case of a reversed battery connection but it does have a drawback in that it will produce a voltage drop of typically around 0.7V in the case of an ordinary silicon diode or 0.4V in the case of a Schottky diode. This voltage drop is generally undesirable because it reduces both the voltage and power available to the circuit. The voltage drop can be reduced significantly by using an enhancement mode Mosfet transistor in place of a diode as shown in the accom­panying diagrams. This idea is based on the same principle as that of a “synchronous rectifier” as used in some switching inverters to improve These diagrams show how to use p-channel and n-channel Mosfets to provide reverse battery protection. efficiency. Initial operation depends on an internal diode in the Mosfet. Assuming that the battery connection is correct, the diode initially conducts, establishing a forward bias to the gate of the Mosfet. The Mosfet then turns on and transistor action takes over. Current now flows through the Mosfet itself rather than through the diode because of a smaller voltage drop across the Mosfet. In the case of a reversed battery connection, the diode is reverse biased and so is the gate of the Mosfet, so the Mosfet is thereby turned off, protecting the circuit from damage. The top circuit shows a version using a p-channel Mosfet in the positive power lead to a load. The bottom circuit is a ver­sion using an n-channel Mosfet in the negative power lead. Using this circuit I measured about 0.1V drop across the Mosfet at 2A load current and a 12V input. This compares with about 0.7V under the same conditions using an ordinary diode. This represents an 85% reduction in power dissipation in the Mosfet compared with that in the diode and a 10% increase in power available to a resistive load. Note that this circuit will not work in battery charging circuits. H. Nacinovich, Gulgong, NSW. ($30) Power-on muting for PC FM tuner This circuit shows the modifications required to provide a power-on reset. 30  Silicon Chip On some computers, the PC FM Tuner card (published June 1998) may produce noise while the machine is booting. The solu­tion to this is to provide a power-on reset to the 74LS273 octal D flipflop. The 74LS273 will then mute the 4053 multiplexer and no signal will be fed to the LM386 power amplifier. The power-on reset is provided by the 1kΩ resistor feeding pin 1 of IC1 from the +5V line and this is bypassed by the 100µF capacitor. When power is first applied, the 100µF capacitor will hold pin 1 low to reset the chip. The capacitor will then charge via the 1kΩ resistor and normal operation will then take place. The modification entails braking tracks on both sides of the PC board as shown on the accompa- Here’s how to modify the PC board. nying diagram and then connecting the 1kΩ resistor and 100µF capacitor as shown. The +5V connection to IC1 must then be made via a link from pin 14 of IC7. Note that if your PC FM tuner card does not experience the noise problem while booting, there is no need to do this modifi­cation. Mark Roberts, Hornsby, NSW. ($40) Truscott’s !RESELLER FOR MAJOR KIT RETAILERS !PROTOTYPING EQUIPMENT !COMPLETE CB RADIO SUPPLY HOUSE Backup battery for AC-powered cordless phones While the article on a backup battery for cordless phones in the October 1999 issue tried to cover all possibilities, inevitably it didn’t. Some cordless phones are powered by AC plugpacks such as 13.5V AC and 10VAC. If you have a 13.5VAC model there is no easy solution but if your cordless phone is powered from a 10VAC plugpack, the solution is shown in the accompanying circuit. The cordless phone itself will have an internal bridge rectifier so that it can be powered with AC or DC. Therefore we can use a modification of the October 1999 circuit whereby the 10VAC plugpack is connected to a bridge rectifier to keep the 12V SLA battery on trickle charge via the 100Ω resistor. The phone itself is then permanently powered from the unfiltered DC from the bridge rectifier (D1-D4) or from the battery during blackouts via diode D5. SILICON CHIP. !TV ANTENNA ON SPECIAL (DIGITAL READY) !LARGE RANGE OF ELECTRONIC COMPONENTS Professional Mail Order Service Truscott’s Come In And See O New Storeur ELECTRONIC WORLD Pty Ltd ACN 069 935 397 Ph (03) 9723 3860 Fax (03) 9725 9443 27 The Mall, South Croydon, Vic 3136 (Melway Map 50 G7) email: truscott<at>acepia.net.au www.electronicworld.aus.as R VA EAL $1 LUE AT +$5 2.9 5 ea O r bu P&P g y5 pos et themand tage free Order by phone or fax from SILICON CHIP - or use the handy order form in this issue DECEMBER 1999  31 Here's a way that anyone with a working computer can get a handy fixed rail power supply with several outputs. It's a little card to slot into your computer to give fixed +12V, +9V, +6V and +5V rails. You can use it to power equipment that would normally run from plugpacks or as an experimenter's power supply. PC POWERHOU Get four fixed rail supplies for minimum dollars Design by BARRY HUBBLE There are two good reasons to build this project. First, if you are plagued with the problem of having too many plugpacks to be fitted into a 240VAC power board, the PC Power Extender may enable to eliminate some or all of them. Second, perhaps you've often been working on a project and you want a power supply with a fixed output of 12V, 9V or whatever. Well, if you have a PC you already have a thumping big power supply builtin, so why not use it? Just getting back to those plugpacks for a moment, they really are a problem aren't they? You can't fit two plugpacks next to each other in any standard double power point or power-board and you often can't fit a standard power plug into a double power point if you already have a large plugpack running from it. They are just too big and bulky. Wouldn't it be good if you could get rid of them altogether? For example, if you have an external modem, a scanner and a printer all running from plugpacks, you might be able to run them all from your PC's built-in power supply. This is one of those ideas that is so 32  Silicon Chip obvious that you may well be thinking "Why didn't I think of that?" or "How come it's taken this long for someone to think of this?" Well, while we might contemplate our (collective) navels about why some ideas take such a long time to become obvious, let's not muck about. Let's just look at the circuit of Fig.1. As you can see, it takes power via a standard DC connector in an IBM-compatible comp u t e r. T h e +12V and +5V rails are connected via 1A fuses to standard 2.1mm sockets. At the same time, the +12V rail is also fed to two 3-terminal regulators which then provide a fixed +9V and +6V and their outputs also connect to 2.1mm sockets. Of course, you might want to vary it a bit. You might want an 8V output instead of 6V and this is easily fixed by fitting an 8V regulator instead of a 6V type. Or you might decide you want to two 9V outputs and this is easy: just fit two 9V regulators. Each regulator has an effective current limit of about 1A, so you get four fixed supply rails each with an output capability of about 1A. The circuit is so simple that there is really not much more to say. But perhaps you are worried about the extra load that might be placed on your computer's power supply. Can it handle it? Well, think of it this way. If your machine has a standard 200W or 250W power supply, you would not think twice about adding another hard disk drive, maybe another CD or DVD-ROM drive, a ZIP drive or whatever. Most computers have buckets of spare capacity, so the extra drain due to this small circuit is hardly worth thinking about. As well, PC power supplies are well designed and will normally shut down without damage if they are overloaded; normal operation being resumed after removal of the overload. A typical 200W computer power supply would have a capacity of 8A for the +12V rail and 20A for the +5V rail but how much of that your system uses is your guess. And whether the supply really can deliver a full 200W is probably doubtful but suffice to say that most computers still have oodles of spare power supply capacity. By having a power supply extender with four outputs of +12V, +9V, +6V and +5V, all at 1A capacity, we are unlikely to embarrass the vast majority of computer power supplies. After all, you are unlikely to use all output simultaneously at their full outputs a more likely scenario is that the PC Power Extender would only draw about 10W or less, depending on what you connect to it. By the way, computer power supplies also have -12V and -5V outputs but these have only a limited capacity and we do not recommend that you attempt to use these outputs as well. Leave them strictly alone. USE PC board mounting The PC board for this project is mounted in the computer with the aid of a PC mounting plate with integral Fig.1: using the existing +12V and +5V rails in your computer, this circuit uses two 3-terminal regulators to provide +9V and +6V. mounting brackets. You may have to salvage one from an obsolete card. If you can't obtain a PC mounting plate with these mounting brackets you may have to make up a couple of righthand brackets yourself; not an onerous task. Another part that you may be able to salvage would be a 4-pin PC-mounted power connector from a scrapped disk drive. Due to the mounting plate being screwed to the computer's chassis and therefore at mains Earth potential, all the jack output sockets MUST have the centre pin wired as the positive connection, to prevent the possibility of short circuiting an output. This may not conform to some of the devices you want to power. For example, powered multi-media speak- Fig.2: the component layout for the PC board. You will need to bolt down the regulators and their heatsinks to the board. Low profile heatsinks must be used. The additional holes alongside C1 & C2 are to accomodate physically larger capacitors if needed. DECEMBER 1999  33 The prototype PC Power Extender, looking towards the four output sockets. Note that these photos do not show the two 0.1µF capacitors that we have added to the input sides of the regulators. ers seem to have the centre pin as the negative connection. In such cases it will be necessary to reverse the leads on one end of the cable connecting the output to these devices. These leads must then be clearly labelled as being a reversed configuration. You could do this by using white heatshrink sleeving and a permanent marking pen to label the cable. While most devices these days are protected against reverse voltage, they are not necessarily protected against over-voltage and the outputs of the PC Power Extender must be clearly labelled. This problem was overcome with the prototype by having small printed labels, laminated them on both sides with an adhesive laminate to stiffen them. They were attached so they cover the outlets. By using an additional nut on each DC socket, the label can be mounted 34  Silicon Chip so that it may swivel freely to one side when a plug is inserted. Assembly You can begin construction by drilling the holes in the mounting plate, as shown in Fig.3. If necessary you will have to fabricate and attach two small `L' brackets to secure the blanking plate to the PC board. Install the four DC sockets with their output voltage labels. Next, mount the PC board so that its output pads are adjacent to their respective sockets. If you don't do this correctly, the PC board may be mounted too low and will liable to foul the bus expansion sockets on the motherboard. The two 3-terminal regulators and their heatsinks are bolted to the PC board. Mount all components on the PC board observing the polarity of the electrolytic capacitors. You can make the connections to the DC sockets Note: if this project is used to drive powered loudspeakers for a PC, you should first check that the ground of the signal line (ie, shield connection) is not connected to the positive supply for the speakers. While we have not encountered this situation, it is not suitable for the PC Powerhouse as it would cause a short circuit to occur across the 5V output. with tin-coated copper wire. In each case, the positive lead must go to the centre-pin of the socket. To make the connection from your computer's power supply to the PC board your will need to find a spare 4-pin disk drive power cable which will normally be dangling inside the machine. If there are no spares, you will have to install a disk drive power splitter cable. Before you make any connections, check the voltages at the pins of your disk drive connector. The yellow lead be +12V and the red lead +5V. The two black leads in the centre are the 0V returns. If you have a DC power supply which can deliver around 12V, it is a good idea to hook it up to the PC board and check the outputs of the two regulators. When installing the PC Power Extender board unit in your computer, it Fig.3: you will need to drill a PC card mounting bracket to take the four 2.1mm DC power sockets. Compare this to the photograph at left. The photo also shows small swivelling voltage labels which the author attached to the output socket mounting screws. Parts List is a good idea to mount it with a free slot on either side to help with heat dissipation. After installation and before putting the case back on, test the whole system to ensure the computer power supply isn't showing any signs of distress (strange whistles, groans, smells, or SMOKE!) and that your programs are SC operating normally. 1 PC board mounting bracket with rightangle lugs (see text) 1 PC board, 89 x 89mm, code 12112991 4 2.1mm rectangular panel mount DC sockets 2 M205 1A slow blow fuses 4 M205 PC-mount fuse clips 1 PC rightangle mount disk drive 4-pin power connector (Altronics Cat P-5671 or equivalent) 2 low profile TO220 heatsinks 2 'L' mounting brackets (see text) 12 2.5mm x 9mm screws 18 2.5mm nuts Capacitors 2 470uF 25VW electrolytic 2 0.1uF MKT polyester 2 .01uF MKT polyester Fig.4: actual size artwork for the PC board. Use this to check your board for defects before installing any of the components. Semiconductors 1 7809 9V regulator (REG1) 1 7806 6V regulator (REG2) Miscellaneous Hookup wire if required for power connector Disk drive power splitter cable if required DECEMBER 1999  35 easure – r t d e i r u ble! or b nce a f e u i g l r n a e i v p h x y c g or l e r n l i g a t c e n i r Sea e d p g r s n a o i eth rew ou go pr y e can be ally if you find som m i t t nex especia this metal locator Try out mbing. beachco arke l by John C S EARCHING FOR BURIED TREASURE is a popular pastime for many people. For some it's a dream. For others it's a full-time (and occasionally lucrative) occupation. Some comb the beaches for dropped coins and jewellery (have you ever noticed when you drop a coin at the beach how the sand seems to eat it immediately, even if you see exactly where it lands? That’s one of Murphy’s corollaries and is one of the reasons metal detectors were invented!) Others try the goldfields, hoping to “strike it rich” either from a nugget left undisturbed over the centuries, or perhaps overlooked in the tailings, or spoil, from earlier gold mining. Who knows, there could be another “Welcome Stranger” just waiting for you to claim it. (Let us know if you do!!!!) Types of detectors There are many types of metal detectors on the market today ranging 36  Silicon Chip from the simple and low-cost amateur variety up to the very complex professional units costing many hundreds, sometimes thousands, of dollars. While they’re all designed to perform the one function, to detect metal objects, they do this in different ways. Some are able to differentiate between non-magnetic metals (such as gold, silver and copper) and magnetic metals comprising iron. These are called discriminating metal detectors and are usually complex in their operation and of course are expensive. Professional treasure hunters usually use this type because it saves them lots of digging – to find nails, metal cans and ring-pulls from old aluminium cans! (Ring-pulls haven't been around for more than a decade but our experience is that every single one of them was discarded exactly where we wanted to seach . . .) Other metal detectors are simply designed to react in the presence of any metal. The metal locator described here is of this type. It simply gives an audible indication whenever it detects any type of metal. Whether you’ve found gold or garbage, well, that’s pure luck! It is very easy to use and gives a change in the audio frequency as the search head is swept across any metal. It is good for detecting small objects at a moderate depth and large objects at a greater depth. Pin-point accuracy is quite good and with a bit of practice you can locate an object to within a few centimeters very easily. How it works This detector uses the principle that the inductance of a coil changes when a piece of metal is brought near to it. The coil is a part of a free-running oscillator with its the coil inductance and added capacitance setting the operating frequency. The coil is located in the search head which is swept over the ground. When the coil encounters metal, the oscillator changes in frequency. This change is detected and converted to an audio signal which the operator can hear via an inbuilt speaker or headphones. Block diagram Fig.1 shows the general operating principle of the metal locator. There are two oscillators: the search oscillator and a second fixed oscillator. A comparator monitors both oscillator signals and when the search oscillator shifts its frequency, the comparator's output changes audibly. The fixed oscillator runs at nine times the frequency of the search oscillator and so a 1Hz change in the search oscillator will give a 9Hz change in the audible output, making it very sensitive. This can be regarded as a modified beat frequency oscillator (BFO) circuit except that instead of two oscillators being very close in frequency, one is nine times the other. How can this be? The secret lies in the comparator which is really a D-type flipflop. The output is buffered and amplified to drive a loudspeaker. In operation the search oscillator frequency is adjusted via coarse and fine tuning controls so that there is no sound, or a very low frequency growl, comming from the loudspeaker. When the search head is brought near metal, the frequency will rise rapidly. The circuit is shown in Fig.2. It comprises three low cost ICs, three transistors, a regulator and the search coil, along with several resistors and capacitors. The search oscillator is in a Colpits configuration with the coil in the collector of Q1. The .001µF capacitor between collector and emitter provides feedback. The oscillator frequency is set by the search coil inductance, the paralleled .001µF capacitors across the 1kΩ emitter resistor and the .001µF capacitor between collector and emitter. Small changes in the base voltage of Q1 change the collector capacitance which in turn alters the oscillation frequency. The oscillator must be stable (that is, with minimal drift) so that the frequency controls will not constant adjustment. To ensure this stability we have specified polystyrene capacitors for the oscillation setting components. Features * Audible metal detection * Loudspeaker or headphones * Course and fine controls * Volume control * Stable circuit * Battery operated * Low cost * Ground capacitance effect eliminated with shielding * Ideal for finding small objects near soil or sand surface Fig.1: block diagram of the metal detector. The text above explains the theory of operation. DECEMBER 1999  37 Fig.2: the circuit diagram. The signal at the collector is coupled via a 100pF capacitor to the gate of JFET Q2. Its gate is biassed at half supply using by two series connected 150kΩ resistors. The output at the source follows the gate signal and effectively buffers the oscillator signal from the next stage, an amplifier based on NAND gates IC1a and IC1b. These normally digital gates are operated in a linear mode by the 100kΩ feedback resistor between the output (pin 8) and the input (pins 12/13). The 10kΩ input resistor and 100kΩ feedback resistor set the gain at 10. The resultant signal is “squared up” by gates with the IC1c and IC1d which are connected as inverters. The output from IC1d is applied to the clock input of the D-flipflop, IC3b. The fixed oscillator is based on a 2MHz crystal and IC2a, a NAND gate with its two inputs tied together so that it becomes an inverter. The 1MΩ resistor between the output (pin 6) and the inputs (pins 4 & 5) sets the inverter as a high gain amplifier and provides drive to the crystal on the input side. The 4.7kΩ resistor driving the crys38  Silicon Chip tal and the 68pF loading capacitors form a low pass filter, preventing the crystal from oscillating at a spurious frequency. The output of IC2a (pin 6) drives another inverter, IC2b, which squares up the waveform. IC2c and ICd are connected in parallel and further buffer the signal and provide drive to the the clock input to of IC3a, a D-flipflop. The flipflop divides the 2MHz input by two to give 1MHz at the Q output. This is applied to the D input of comparator flipflop IC3b. Oscilloscope Traces Operation of this flipflop as a comparator is best described by the accompanying oscilloscope waveforms. The top trace in Fig.4 is the clock input from the search oscillator after it has been squared up by IC1c and IC1d as described earlier. The centre trace is the 1MHz signal from IC3a. Note that the search oscillator has been adjusted so that it is a precise sub-harmonic of the 1MHz oscillator. This means that the rising and falling edges of both waveforms will remain fixed relative to one another and so the rising edge of the top waveform which clocks IC3b will occur when the 1MHz waveform (the data input to IC3b) is either always high or always low. The Q output of IC3b is latched to the logic level on the D input on each rising edge of the clock input. Thus if the level on the D data input is always the same when the clock goes high we will have no change at the Q output. The waveforms in FIg.4show the fixed oscillator and the search oscillator signals and the resultant mixer output when the frequencies are in an exact 9-times multiple. The waveforms are in phase. At top is the search oscillator running at 111kHz. The middle trace is the 1MHz fixed oscillation frequency. Below it is the mixer output which remains low. This is because the positive edges of the search oscillator always find a low on the fixed oscillator and so the Q output of IC3b stays low. Now if the search oscillator changes in frequency (hey! you’ve found gold!) the clock signal to IC3b will not be in phase with the 1MHz input. We therefore have a slow drift between a Fig.3: the component overlay. Only the headphone socket is mounted off the board – even the speaker is glued in place using silicone sealant. Compare this layout to the photograph overleaf when assembling the board. high and a low voltage at the D input as the clock is sent high. The Q output thus goes high and low in response to the changing data pattern. The oscilloscope waveforms in Fig.5 show what happens when the search oscillator is slightly slower than the 111kHz in phase frequency. The positive edge of the search oscillator finds a low on the fixed oscillator first and then finds a high two cycles later. This is shown as the lower trace and has a frequency of about 32.5kHz (the beat between 1MHz and 107.5kHz). Output The output signal is fed to Q3, an emitter follower amplifier, via thevolume control potentiometer. This Fig.4: the top trace is the clock input from the search oscillator after it has been squared up. The centre trace is the 1MHz signal from IC3a. transistor drives the internal speaker or the headphones. Plugging in headphones automatically switches the internal speaker off. Power for the circuit is derived from a 6V battery comprising four AA cells. The audio amplifier is powered directly from the 6V rail but the rest of the circuit runs from a regulated 5V rail provided by REG1, an LM2940T-5. Fig.5: this shows what happens when the search oscillaor is slightly slower. The mixer output now shows a frequency of 27kHz. DECEMBER 1999  39 Two views of the disassembled case showing the PC board from above and below. In the photo above, note the way the speaker is glued to the board using silicone sealant. The battery case (left photo) needs to be of the “long skinny” variety to fit under the PC board. This is a low dropout regulator which will continue to regulate even if the battery voltage is close to 5V. Current consumption of the circuit is 15mA when the volume is turned fully down, rising to 25mA when there is a loud tone in from the loudspaeker. Much care has been taken to ensure that the various stages are isolated from each another. This prevents the search oscillator from being “pulled” by the fixed oscillator to lock onto a sub-harmonic. This would cause reduced sensitivity. The search oscillator is decoupled from the 5V supply via a 220Ω resistor and 47µF capacitor in parallel with a 0.1µF capacitor. The 0.1µF capacitor is there to compensate for the fact that the 47µF electrolytic capacitor is not as effective at high frequencies. IC1 is also decoupled with a 220Ω resistor and 47µF capacitor, while the fixed oscillator (IC2) is decoupled with a 10Ω resistor and 47µF and 0.1µF capacitors. Construction Most of the components for the Fortune Finder are mounted on a PC board 40  Silicon Chip coded 04303001 and measuring 132 x 87mm. It mounts in a plastic case 157 x 95 x 54mm and a label measuring 154 x 90mm is affixed to the lid. Begin construction by checking the PC board for shorts between tracks, breaks in tracks and hole sizes. Larger holes are required to mount the regulator (3mm hole using an M3 screw and nut), for the switch S1 lugs (1.5mm each) and the cutout required for the loudspeaker magnet to pass through (about 35mm). You can make the cutout for the loudspeaker using a series of small holes around the perimeter and then filing to shape. Some commercial PC boards may have this hole punched. Begin by inserting the resistors and links using tinned copper wire. The resistors can be selected using the colour code table and/or measuring each value with a digital multimeter. The capacitors are inserted next, taking care to orient the electrolytics with the shown polarity. The accompanying table shows the possible markings on the low value capacitor. Apart from the five .001µF capacitors which must be polystyrene types for stability, the low-value capac- itors can be either monolithic or ceramic types. Next, insert and solder the crystal and semiconductors (transistors, and crystalICs and regulator), making sure you insert the semiconductors with the correct orientation and position. The regulator is mounted lying down and secured with an M3 screw and nut. The leads are bent down 90° at the appropriate points, inserted through their holes and soldered into the PC board. Switch S1 mounts with the terminals inserted directly into through the PC board holes and soldered on the other side.. Cut the pot shafts to about 10mm long, suitable for the knobs used. Note that there are five pins used for each potentiometer with three pins for the terminals and two pins for securing and earthing each pot body. Immediately before inserting and soldering the pots, scrape the plating off the pot body alongside where the two pins will be located to make soldering these pins to the body easier. Each pot is mounted about 2mm above the PC board, with the PC stakes soldered to the terminals. Solder the scraped pot body to the PC pin along- The handle assembly prior to mounting the box. Note the rebates in the dowel for the saddle clamps. . . side. You will need a good, hot iron for this operation. The lid of the case requires drilling for the loudspeaker holes, the pot shafts and for the power switch. Use the front panel label (or a photocopy) as a guide to the locations of the holes. Attach the label after drilling and cut the holes in this with a sharp knife. Attach a 130mm length of hookup wire to one terminal of the loudspeaker and a 60mm length to the second terminal and insert the loudspeaker through the hole in the PC board. . . . and an “above” and “below” view showing how the box is fixed to the dowel. Secure the PC board to the lid of the case with the pot bushes and power switch. Turn the assembly over with the pot shafts resting on a table. Centre the loudspeaker and secure it to the rear of the PC board with some silicone sealant. Allow to cure. Drill holes in the case for the cord grip grommet at the front edge and for the headphone jack socket on the side. Search Coil Assembly Fig.4 shows the coil plate assembly. It consists of a baseplate, coil assembly, brackets for the handle and a cover plate. The coil assembly is attached to the baseplate with silicone sealant. The brackets are attached with wood glue (PVA) and with holes in the side suitable for the wooden or plastic dowel. A slot is cut in the plastic plate for the broomstick to pass through and attach to the angle brackets. The plate is then held in place with two 4G self-tapping screws into the brackets. The use of such small metal screws does not affect the metal locator operation. Fig.8: complete details of the various components of the Fortune Finder metal locator. We have specified a broom stick instead of dowel because broom sticks are usuall more durable timber than ordinary dowel. DECEMBER 1999  41 Parts List 1 PC board, code 04303001, 132 x 87mm 1 label, 154 x 90mm 1 plastic case, 157 x 95 x 54mm 1 57mm 8Ω loudspeaker 1 SPDT toggle switch, S1 1 4 x AA cell holder (2 x AA long x 2 x AA wide) 4 AA cells 1 2MHz parallel resonant crystal, X1 2 10kΩ 25mm log potentiometers, VR1,VR3 1 100kΩ 25mm linear potentiometer, VR2 1 stereo switched 6.35mm jack panel socket 3 knobs 1 small cord grip grommet 21 PC stakes 6 6g x 10mm self tapping screws 2 4g x 10mm self tapping screws 1 wood or plastic dowel 8mm diameter 40mm long 1 300mm x 300mm piece of aluminium foil 1 roll of insulating tape 1 20mm x 60mm x 1.5mm aluminium for battery holder bracket 1 plastic cable tie 1 container of silicone sealant (non-acid cure ­– eg, roof and gutter sealant) Hardware and wire 1 base of 3mm MDF, 170mm diameter or thicker lightweight timber 1 plastic plate 170mm inside diameter (size to suit base) 2 timber or plastic angle brackets (20 x 20 x 20mm minimum) 2 2m long 20-22mm diameter broom handles 2 dual mounting 20mm conduit plastic saddle clamps 3 90 degree 20mm pvc elbows (Clipsal 245/20 or equiv) 1 32m length of 0.4mm enamelled copper wire 1 1m length of 0.8mm tinned copper wire 1 2m length of single core shielded cable 2 M3 screws x 6mm 4 M3 screws x 10mm 6 M3 nuts 1 6g x 30mm wood screw The search coil is made using 0.4mm enamelled copper wire. It has 70 turns, wound to make a 140mm inside diameter circle. The accompanying panel shows how it is done. If you don’t have a 140mm diameter former to wind it on, the simplest way of winding the coil is to find a 215mm x 30mm length of wood or plastic. Wind 70 turns around this, slide the coil off the wood or plastic and then open this rectangle into a 140mm circle. Wind a layer of insulating tape tightly around this, with the two start and finish wiresleads exiting at the same point. Now cut aluminium foil into strips 20mm wide and wind these around the coil, starting at the wire exit point. Cover the start end with insulating tape for the first 20mm or so. Completely wrap the coil in the aluminium foil until it reaches the wire exit point and continue to cover the insulation-taped coil for the next 10mm. Make sure the finish end of this aluminium does not come in contact 42  Silicon Chip Semiconductors 2 74HC00 quad NAND gates (IC1,IC2) 1 74HC74 dual D-flipflop (IC3) 1 BC558 PNP transistor (Q1) 1 2N5484 N-channel JFET (Q2) 1 BC338 NPN transistor (Q3) 1 LM2940T-5 low dropout 5V regulator (REG1) Capacitors 4 47µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.22µF polyester or ceramic 4 0.1µF polyester or ceramic 5 .001µF (1000pF) polystyrene 1 100pF NP0 ceramic 2 68pF NP0 ceramic Resistors (0.25W 1%) 1 1MΩ 2 150kΩ 3 10kΩ 2 4.7kΩ 2 220Ω 1 10Ω with the start end or the coil will be shorted. Next, wind on 15 turns of 0.8mm tinned copper wire evenly spaced around the aluminium foil. This shorts to the aluminium foil, giving something to solder to (you cannot solder to aluminium foil). Solder one end (only) of this tinned copper wire to one end of the 70-turn coil underneath. You will need to remove some of the insulation from the enamelled copper wire. Fortunately, enamelled copper wire is normally coated with a heat stripping coating insulation which can be removed with a hot soldering iron. Capacitor Codes       Value   IEC EIA 0.22µF 220n 224 0.1µF 100n 104 .001µF   1n 102 100pF 100p 101 68pF   68p   68 1 100kΩ 2 1kΩ This “earthy” end of the coil connecting to the tinned copper wire can be terminated to the shield of the connecting cable. The shielded cable core attaches to the other end of the 70-turn coil. Insulate the terminations and the whole coil assembly in with another layer of insulation tape. Note that one end of the tinned copper wire coil you wound does not connect to anything. The coil assembly needs to be mounted onto a wooden baseplate using silicone sealant. We used some scrap western red cedar and routed a channel for the coil to sit into. Alternatively, you could use 3mm MDF but this would be more likely to suffer water damage. We used a plastic dinner plate as a cover for the coil/baseplate assembly. The baseplate is made to suit the diamater of the plastic plate – ours was about 170mm. The plate can be obtained from stores selling plastic dinnerware. The support stick and handle are made with broomstick timber (dowel) Winding The Search Head 1 Wind 70 turns of 0.4mm enamelled copper wire onto either a 140mm diameter former or a length of thin wood or plastic about 215mm long. Remove the coil from the former and pull it into a circular shape. Leave about 100mm of wire protruding and cover the complete coil with a layer of insulation tape. 2 Cut aluminium foil into strips 20mm wide and wind over insulation tape, overlapping each turn slightly. Cover the first 20mm or so with insulation tape to hold it in place. Continue winding the foil on right around the coil and onto the insulation tape but do not let the finish of the foil touch the start of the foil. and 20mm PVC conduit fittings. The stick may need to be filed down where it enters the conduit elbows and for the saddle clamps if it is the standard 22mm diameter. We painted the broomstick handle before assembly. The final 100mm length of handle is attached at a right angle to the main stick using a wood screw. Each elbow is locked to the stick with 6g self tapping screws. Saddle clamps secure the detector box to the handle with M3 screws and nuts. After the silicone sealant has cured (for both the search head assembly and where it holds the speaker onto the PC board), you can continue the wiring for the headphone jack socket and attach this to the side of the case. Attach the search head to the broom handlein place and wire the shielded The search coil assembly viewed from underneath . . . 3 Wind 15 tight turns of 0.8mm tinned copper wire directly over the aluminium foil. Solder one end (only) to one of the wires of the inner coil. Solder these to the shield wire of the shielded cable which goes to the detector electronics. Connect the inner conductor of the shielded cable to the other wire protruding from the inner coil. The remaining wire from the 15 turns is not connected. Cover the whole coil with a layer of overlapping turns of insulation tape. 4 Secure the coil assembly to the base with non-acidic silicone sealant. The base can be made from lightweight timber with a 150mm diameter groove routed into it, or can be a 3mm MDF sheet with the coil glued to the inside surface. When the silicone sealant has dried, give the whole base several coats of oil-based paint to make it as weatherproof as possible. . . . from above showing the handle mounting brackets . . . . . . and finally with the “dinner plate” cover in place. DECEMBER 1999  43 cable to the PC board via the cord grip grommet in the case. This cable should be wrapped around the main stem several times and tied in place with a cable tie. Note that any movement of the lead will alter the search head frequency. Place the pot knobs on and connect the AA battery pack to the 6V supply terminals on the PC board. (Some battery holders can be screwed directly to the base of the case but some will require a bracket to be made). Apply power – you should be greeted with an audio tone. If not, adjust the volume control fully clockwise and adjust the coarse knob until a sound is heard. Extreme left and right settings of the coarse control should prevent oscillator operation. Check the power supply using a multimeter. There should be 5V between the metal tab of REG1 and the output. This 5V should also be on pin 14 of IC3. Check the voltage between pin 14 of IC1 and earth or 0V, and also pin 14 of IC2 and 0V. These should be just a little less than 5V. Adjust the controls until the frequency becomes a very low growl or stops completely. You will find that there are several positions on the coarse control where the output tone reduces to a low frequency but there will be one position which gives the loudest tone. Use the dominant tone to begin with, although you may find another position is better for some types of ground or metal. Now bring the search head near a metal object and check that the frequency increases. Note that the fine control is logarithmic and will give very fine adjustment at the anticlockwise position and coarser adjustment toward the clockwise position. This means that the adjustment of the coarse control should be done with the fine control past its halfway anticlockwise position. When you bring the search head near the ground you may find that the frequency changes, requiring readjustment of the controls. There is also the possibility that this adjustment was made in a location where metal was located and so it is a good idea to sweep the ground and find a good compromise adjustment. While the search oscillator has been designed to be stable in frequency with minimal drift, it will be far more stable after about a 15-minute warm-up with the power switched on. Also it will work best if it is given the chance to stabilise in the environment in which it is to be used. So do not store it in some cool dungeon and then expect the search oscillator to be stable when it is brought out No.  1  1  1  1  1  1  1  1 Value 1MΩ 150kΩ 100kΩ 10kΩ 4.7kΩ 1kΩ 220Ω 10Ω 44  Silicon Chip into the midday heat. The metal locator can be used with headphones that are high impedance types, as used with hifi systems and personal stereos. These are typically 32 ohms. Using these will reduce current consumption from the batteries and enable the locator to be used in noisy environments. Also the sensitivity to metal detection will appear to be better due to the closer proximity of the sound to your ear and the your ability to concentrate on the Resistor Codes sound more effectively. You can experiment with the 4-Band Code (1%) 5-Band Code (1%) locator by burying various items brown black green brown brown black green yellow brown in dirt or sand to learn how the brown green yellow brown brown green black orange brown metal locator responds to various brown black yellow brown brown black black orange brown items at different depths. Typical brown black orange brown brown black black red brown detection depths are 40cm for a tin can, 10cm for a wedding ring and yellow violet red brown yellow violet black brown brown 14cm for a 10 cent coin. brown black red brown brown black black brown brown You are now ready to tackle red red brown brown red red black black brown the beaches and exploration brown black black brown brown black black gold brown SC goldfields. 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 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 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 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 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 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 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 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 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. Buy five and get them postage free. e & Get Subscrib count is D A 10% on ther Silic e O ll A n O is d n a h rc Chip Me $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia DECEMBER 1999  53 BUILDING THE Speed Alarm Last month, we gave the circuit details of our new compact Speed Alarm. This month, we show you how to build it and give the installation details. We also show you how to fit the speed sensor. Pt.2: By JOHN CLARKE Lack of space prevented us from describing the power supply circuit for the Speed Alarm last month, so we’ll give a brief rundown on how this works before moving on to the construction. You will need to refer back to Fig.1 on page 19 of the November issue to see the circuit details. As shown, a +12V rail is derived 54  Silicon Chip from the vehicle’s battery via the ignition switch. A 10Ω 1W resistor and 47µF capacitor decouple the supply, while 16V zener diode ZD1 protects the circuit from transient voltage spikes above 16V. The decoupled ignition supply voltage is fed to regulator REG1, which provides a +5V rail. This rail is then used to power all the circuitry with the exception of IC2 which is powered directly from the decoupled +12V rail. A second 47µF capacitor plus several 0.1µF capacitors are used to decouple the regula­tor’s output. OK, so much for the circuitry. Of course, most of the clever stuff takes place inside the PIC16F84 micro­ controller under software control. For a broad overview of how this software works, take a look at the accompanying panel. Construction Fortunately, you don’t have to understand how the software works to build this project. Instead, you just buy the ready-programmed PIC chip and “plug it in”. As mentioned earlier, all the parts 7-WAY SOCKET 8-WAY SOCKET BC328 7 x 150 BC328 BC328 2.2k 0.1 D3 D4 47F TO COIL (L1) 15pF 680 22k ZD1 XTAL 1 REG1 7805 # SOLDER XTAL BODY TO WIRE 1 680 1 15pF # 680 500k 2.2k IC2 LM358 VR1 Q2 0.1 Q3 IC1 PIC16F84 Q1 Q4 BC338 0.1 2.2k 1M 10 1W +12V VIA IGNITION SWITCH 2 x 47F 1k CHASSIS 7-WAY SOCKET 560 7-WAY PIN HEADER* 8-WAY PIN HEADER* 0.1 LED1 A K A K LED4 DISPLAY 3 DISPLAY 2 680 A K S3 LED3 MODE 680 S2 DOWN DISPLAY 1 D2 S4 CAL D1 LDR1 10k (except for the piezo alarm and the speed sensor) are installed on two small PC boards. These are coded 05310991 and 05310992 and are stacked together using pin headers and IC sockets. Before installing any of the parts, check both boards care­fully for etching defects. In particular, note that a hole is required just below DISPLAY3 on the display board (05310991). This must be large enough to accept a small screwdriver so that you can later adjust VR1 on the processor board. Fig.4 shows the assembly details. We suggest that you assemble the processor board (05310992) first. Begin by install­ing the seven wire links, then install the resistors, diodes D3 & D4 and zener diode ZD1. Make sure that all the diodes are orient­ed correctly and note that the seven 150Ω resistors are all mounted end on. Next solder in a socket for IC1 (but don’t install the IC just yet), then solder IC2 in place. Take care to ensure that pin 1 of IC2 is nearest to the lefthand side of the board. REG1 can now be installed with its metal tab flat against the board and with its leads bent at rightangles so that they pass through their respective mounting holes. Note that the hole in its metal tab must accurately align with the board mounting hole – see Fig.4. Next, install the capacitors in the locations shown. Watch the orientation of the electrolytic types and note the following points: (1) the two 47µF capacitors below REG1 have their leads bent at right­ angles, so that the capacitors lie horizontally over REG1’s leads (see photo); (2) the 47µF capacitor to the left of D3 & D4 has its leads bent at right­angles, so that it lies across these two diodes. The four transistors, crystal X1 and trimpot VR1 can now be installed. You 680 A K LED2 1k PIEZO BUZZER S1 UP 1k 7-WAY PIN HEADER* * PIN HEADERS MOUNTED ON UNDERSIDE OF PC BOARD Fig.4: install the parts on the two PC boards as shown here. Note particularly the orientation of the three pushbutton switches and switch S4. The terminals of S4 must be oriented as shown. should also fit PC stakes to the board at the external wiring points. Note that transistor Q4 is a BC338 while the others are BC328s, so don’t get them mixed up. The crystal lies flat against the PC board and is secured by soldering a short length of tinned copper wire between the end of its case and an adjacent PC pad (to the right of Q2). Finally, the single in-line sockets (two 7-way and one 8-way) can be fitted. These are made by cutting 14pin and 16-pin IC sockets into single in-line strips using a sharp knife or fine-toothed hacksaw. Clean up the rough edges with a file before installing them on the PC board. Display board Now for the display board. Begin by installing the eight links, diodes D1 & D2 and the resistors, then mount the three 7-segment LED displays with Capacitor Codes    Value IEC Code EIA Code 0.1µF 100n   104 15pF  15p   15 Resistor Colour Codes  No.   1   1   1   3   3   6   1   1 Value 1MΩ 22kΩ 10kΩ 2.2kΩ 1kΩ 680Ω 560Ω 10Ω 4-Band Code (1%) brown black green brown red red orange brown brown black orange brown red red red brown brown black red brown blue grey brown brown green blue brown brown brown black black brown 5-Band Code (1%) brown black black yellow brown red red black red brown brown black black red brown red red black brown brown brown black black brown brown blue grey black black brown green blue black black brown brown black black gold brown DECEMBER 1999  55 the pin headers are installed from the copper side of the board, with their leads protruding 1mm above the surface. You will need a fine tipped soldering iron to solder the pin header leads to the copper pads on the board. It is necessary to slide the plastic spacers along the leads to give sufficient room for soldering to take place. Final assembly The display board (above) plugs into the pin header sockets on the processor board (top), to make the electrical connections between the two. Note how the three red LEDs on the display board are bent towards the pushbutton switches, to illuminate them at night. their decimal points towards bottom right. Note that seven of the links go under the displays, which is why they’re shown dotted on Fig.4. Next, install switches S1-S3, taking care to ensure that the flat side of each switch faces the direction shown in Fig.4. Switch S4 must also be oriented correctly – it must be installed so that there is normally an open circuit between its lefthand and right­hand leads (you can check this using a DMM). In practice, it’s simply a matter of installing the switch with its terminals oriented as shown on Fig.4. LEDs 2-4 can now be fitted to the board and bent towards their respec56  Silicon Chip tive switches (so that they will illuminate the mounting holes for S1-S3), as shown in one of the photographs. The tops of these LEDs should be at the same height as the top faces of the dis­plays. The LDR can be installed now. It should be mounted so that it is 2mm above the displays, while LED1 should be 3mm above the displays. It doesn’t matter which way around you install the LDR but make sure that all the LEDs are oriented correctly. You can now complete the display board assembly by fitting PC stakes to the buzzer wiring points and by installing the pin headers. Note that Work can now begin on the plastic case. First, use a sharp chisel to remove the integral side pillars, then slide the pro­cessor PC board into the case and drill two mounting holes – one through REG1’s metal tab and the other immediately below the 0.1µF capacitor on the lefthand side. This done, use an oversize drill to countersink these holes on the rear of the case, to suit the specified M3 x 6mm CSK screws. Next, remove the processor board from the case and secure it to the display board as shown in Fig.5. Be sure to use a Nylon screw in the location indicated on Fig.5, to prevent shorts between the two boards. Check that the leads from the parts on the display board do not interfere with any of the parts on the processor board. Trim the leads on the display board if necessary, to avoid this. The front panel label can now be affixed to the panel and used as a template for drilling the various holes and making the display cutout. The holes for switches S1-S3 are made slightly oversize, to take 9.5mm inside diameter translucent rings. These allow the light from the switch LEDs to form a semicircular glowing arc around each switch at night. We made the translucent rings by cutting them from the dispenser nozzles supplied with the containers used in caulking guns. Three nozzles are required and are cut to make the rings which are 11.5mm outside diameter and 2mm thick. Alternatively, you can use the plastic moulding from a PAL line socket which has a 12mm outside diameter and a 10.5mm inside dia­meter. Ream the holes in the front panel so that the rings are a tight fit. They can be held in position by applying a smear of silicone sealant around the edges before they are inserted into the holes. If you don’t wish to use the rings, The unit all fits neatly inside a compact plastic case. Note the cardboard light shield around the 7-segment LED displays. then simply make the holes about 10mm in diameter. Some light will then escape around the switches at night to indicate their positions. The display cutout is made by first drilling a series of small holes around the inside perimeter, then knocking out the centre piece and filing to a smooth shape. The cutout should be made so that the red transparent Perspex or Acrylic window is a tight fit. This window can be further secured by applying several small dabs of super glue along the inside edges. You will also have to drill holes for the alarm LED, the LDR and the piezo alarm, plus a hole to provide probe access to the calibration switch. A hole is also required in the rear of the case to accept a rubber grommet for the external leads. Once all the holes have been drilled, the piezo transducer can be affixed to the inside of the front panel using super glue and its leads connected to the PC stakes on the display board (it can be connected either way around). Note that the PC stakes will need to be trimmed close to the board, so that they don’t foul the transducer when the front panel is attached to the case. Finally, we made a cardboard 2 x 1mm PLASTIC SPACERS 6mm SPACER M3 x 15mm SCREW M3 x 15mm NYLON SCREW DISPLAY BOARD REGULATOR TAB M3 NUT PROCESSOR BOARD 6mm TAPPED SPACER REAR OF CASE M3 x 6mm CSK SCREW Fig.5: this diagram shows how the two PC boards are stacked together. Be sure to use a nylon screw as indicated, to prevent shorts between the two boards. surround for the LED displays (see photo). This prevents the switch LED lighting from encroach­ ing onto the display window at night. In addition, you may wish to apply some black paint to the links running between the displays, so that they cannot be seen during daylight hours. Speed sensor The speed sensor is made by winding 500 turns of 0.18mm enamelled copper wire onto a plastic bobbin measuring 15mm OD x 8mm ID x 5mm. Use electrical tape to secure the turns and leave 10-20mm of lead length at each end. Once the coil has been wound, solder its leads to a suit­able length of shielded cable (one lead goes to the core and the other to the shield). Secure this lead to the side of the coil with some tape, then cover the coil with silicone sealant to waterproof it. We recommend that you use the non-acid cure sili­cone sealant (eg, a roof and gutter sealant). Finally, cover the coil with a short length of heatshrink tubing and shrink it into place using a hot-air gun. The sealant should now be left to dry for about eight hours. Testing It is best to check the supply rails before plugging in the PIC micro­ DECEMBER 1999  57 How The Software Works W E WON’T GO INTO a detailed analysis of the software here – it’s much too complicated for that. However, it can be broken down into a number of easy-to-understand sections, so we can at least give a broad overview of how the software works with the aid of a couple of flowcharts. Basically, there are two separate programs in the speed alarm software and these are called MAIN and INTER. Fig.6(a) shows the flow chart for the MAIN program. This operates when the processor is reset when power is first applied. It sets up the RB0 and RA4 ports as inputs and the RB1RB7 and RA0-RA3 ports as outputs. It then reads the values stored in memory for the last speed setting, display mode and calibration and places these in working memories. Next, the program looks for a pressed Mode, Down or Up switch (these are used to change the speedometer option and repeat alarm feature, as described previously). If one of these switches is pressed, it toggles to the alternative option. The new option is then written to memory for storage. The program now calculates a value called the “speed equival­ent”. This is a value based on the current speed alarm setting. It has a value of eight per 5km/h. For example, if the speed alarm value is 10km/h, then the speed equivalent value is 16. For 60km/h, the speed equivalent value is 96. Interrupts At this point, the program looks for a switch closure and allows interrupts to occur. An interrupt causes the system to jump to a different part of the program whenever it receives an appropriate (ie, interrupt) signal. In this case, we are using two interrupts: (1) an internal signal from a timer which occurs regularly every 353µs; and (2) an interrupt at the speed sensor input. As soon as it receives a signal from either of these sources, the MAIN program is inter­rupted and goes to the INTER program. This flowchart is shown in Fig.6(b). The INTER program does a lot of work. If the interrupt is from the RB0 input (ie, from the speed sensor), it increments the pulse counter. In this way, the pulse counter counts the speed sensor pulses applied to the RB0 input. Alternatively, if the interrupt is from the timer, the program multiplexes the display so that the next display is lit and the previous one is switched off. The 7-segment display 58  Silicon Chip values on the RB1-RB7 outputs are changed accordingly. Basically, this updates the display to show the relevant values, whether in speed alarm, speedometer or off mode. In addition, if the value in the display is below 10km/h, the two lefthand digits are blanked, so that only the righthand digit is shown. Similarly, for speeds below 100, the lefthand digit is blanked and the two righthand digits show the speed. An interrupt from the timer also increases the time period counter. This counter is incremented every 353µs and its value is compared with the calibration number value (assuming that the circuit isn’t in calibration mode). The pulse counter is then reset when the time period counter equals the calibration number. The value in the pulse counter just before it is reset indicates the speed. This value is used for the speedometer mode and for comparing the vehicle speed against the alarm speed setting. What happens is that the speed equivalent value is compared with the pulse count just before reset. If the pulse counter value is equal to or greater than the speed equivalent value, it triggers the alarm output. As described previously, the speed alarm will remain on until the pulse count value drops below the speed equivalent. However, if we were to simply switch off the alarm as soon as the pulse count value was just below the speed equivalent value, we could have a situation whereby the alarm continuously turns on and off as the vehicle travels at the alarm set speed. To counteract this, we add two to the pulse count value and then compare this to the speed equivalent. When this new pulse count value is less than the speed equivalent, the alarm goes off. This provides us with a speed hysteresis of 1.25km/h, where­by the vehicle speed must drop this much below the set alarm speed before the alarm switches off. This provides us with the low threshold setting. Alternatively, the high threshold setting adds two to the speed equivalent value so that the alarm will sound when the speed is 1.25km/h above the alarm set speed. The alarm then turns off when the vehicle’s speed drops back to the alarm set speed. Calibration Let’s now backtrack to the Calibration Mode decision box in the middle of Fig.6(b). If the answer here is ‘Yes’, we allow the pulse counter to continue counting speed pulses and compare its value with the speed equivalent value. Meanwhile, the time period counter is incrementing every 353µs. When the pulse counter equals the speed equivalent value, we read the value in the time period counter and use this as the new calibration number. Note that the calibration process does not change the number of speed pulses per km/h counted in the pulse counter, as this is fixed at 8 per 5km/h. Instead, the calibration process sets the time period over which the pulse counter counts the speed pulses. Switch closures Returning now to the MAIN program, after allowing for the interrupts, the program looks for a switch closure. If there are no switch closures, the program continues looking until a switch is closed. It then detects which switch was closed and acts according­ly. If it is the Cal switch, it clears both the pulse and period counters and sets flags so that the interrupt program will know that it is in the calibration mode. The display is also set to show “CAL”. When the calibration is finished, the display may sometimes show “Err”. This means that the time period counter has overranged before the pulse counter value reached the speed equivalent value. This error message indicates that the calibration was unsuccessful. Alternatively, if calibration is successful, the display will return to the speed alarm setting and the new calibration number will be stored in the onboard EEPROM. This calibration value can be anywhere from 1 to 65,536 although in practice, it will usually be somewhere in the range from 1200 to 6500. This corresponds to speed update times of 0.4 seconds and 2 seconds, respectively. If, on the other hand, the mode switch is pressed, the dis­play will be toggled to the next mode of operation which is then stored in memory. And if the up or down switch is pressed, the speed alarm value will be either increased or decreased accord­ingly, stored in memory and a new speed equivalent value calcu­lated. Note that there are many more details concerning the soft­ware operation that we haven’t mentioned here. Readers who are interested in all the programming details can obtain a full copy of the software (called SPEED.ASM) from our website (www.sili­conchip.com.au). MAIN PROGRAM FLOWCHART MAIN INTER PROGRAM FLOWCHART INTER INITIALISE PORTS RA4, RB0 INPUT RB0 INTERRUPT INPUT RA0-RA3, RB1-RB7 OUTPUT INTERRUPT SOURCE? RB0 INCREMENT PULSE COUNTER TRANSFER EEPROM STORAGE TO WORKING RAM TIMER SHOW CURRENT MODE DISPLAY SPEED ALARM, SPEEDOMETER OR OFF LEADING ZERO BLANKING MODE SET SPEEDOMETER ON OR OFF STORE IN EEPROM IS MODE OR UP SWITCH PRESSED? NO RETURN UP INCREMENT TIME PERIOD COUNTER SET REPEAT ALARM ON OR OFF STORE IN EEPROM YES CALIBRATION MODE NO CALCULATE SPEED EQUIVALENT OF 8 PER 5km/h COMPARE PULSE COUNTER WITH SPEED EQUIVALENT ALLOW INTERRUPTS NOT EQUAL SET END OF CALIBRATION FLAG NO IS A SWITCH CLOSED RETURN COMPARE CALIBRATION VALUE WITH TIME PERIOD COUNTER EQUAL PULSE COUNT USED FOR SPEEDOMETER RETURN YES EQUAL OR MORE CAL WHICH SWITCH ON UP OR DOWN LESS ALARM CLEAR PULSE COUNTER & PERIOD COUNTER SET CALIBRATION MODE WAIT UNTIL CALIBRATION FINISHED STORE TIME PERIOD COUNTER VALUE AS CALIBRATION VALUE MODE SELECT NEXT DISPLAY MODE: SPEED ALARM SPEEDOMETER OR OFF RECALCULATE SPEED EQUIVALENT VALUE OFF RETURN LESS INCREASE OR DECREASE SPEED ALARM VALUE COMPARE PULSE COUNT WITH SPEED EQUIVALENT ADD 2 TO PULSE COUNTER COMPARE WITH SPEED EQUIVALENT EQUAL OR MORE RETURN STORE NEW VALUES IN EEPROM WAIT FOR SWITCH TO OPEN Fig.6a (left) shows the flowchart for the MAIN program, while Fig.6b (above) is the flowchart for the INTER (interrupt) software. The INTER software processes the multiplexing of the displays, the timer update function and the speed pulses. DECEMBER 1999  59 Fig.7: here are the full-size artworks for the two PC boards. Check your boards carefully before installing any of the parts. controller (IC1). To do this, first connect suitable lengths of automotive hookup wire to the +12V and GND (chassis) inputs on the back of the processor board and apply power. Now use your multimeter to check for +5V on pins 4 & 14 of IC1’s socket. If this is correct, disconnect the pow­er and install IC1, taking care to ensure that it is oriented correctly. Now reapply power – the display should light and should show 60km/h. Check that this value can be increased and decreased using the Up and Down switch­es. Now press the Mode switch. The display should show 0 and if you press the switch again, it should show three dashes. Now press the Mode switch yet again and set the display to 0 using the Down switch. The alarm should sound and the alarm LED should light after about 1.6 seconds. The alarm should now sound every 10 seconds if the display is left on 0. Note that if you select the high threshold by pressing the Down switch at power up, the alarm will not sound at the “0” speed setting. Assuming that everything works OK, you can now test the display dimming feature by placing your finger over the LDR and adjusting VR1 until the display dims. If you have a sinewave generator, there are a few more tests that can be carried out. The generator should be 60  Silicon Chip set to provide a 300mV RMS sinewave output and this output should be floating rather than having the common grounded. Alternatively, the power supply should be floating. Attach the signal generator to the coil input terminals on the speed alarm and set the mode to speedometer. The reading should be close to 100km/h per 100Hz input. You can also test the calibration operation by pressing the Cal switch when in the speed alarm display mode (it will not work in the speedometer mode). Installation Be sure to use automotive cable and connectors when in­stalling the unit into a vehicle. The +12V supply is derived via the ignition switch and MAGNETS (4) ALUMINUIM BRACKET (ATTACH TO CHASSIS) 6mm BOLT & NUT DRIVESHAFT COIL CABLE TIE 10mm MAXIMUM GAP Fig.9: the mounting details for the speed sensor. You will probably require 4-6 magnets to obtain a satisfactory update time – see text. Fig.8: the full size front panel artwork. a suitable connection can usually be made at the fusebox. Be sure to choose the fused side of the supply rail, so that the existing fuse is in series. The ground connection can be made by connecting the lead to the chassis via a solder eyelet and a self-tapping screw. Fig.9 shows the mounting details for the speed sensor. As can be seen, the magnets are attached to the driveshaft, while the pickup coil is bolted to an aluminium bracket attached to the chassis. The sensor is then connected to its inputs on the back of the processor board via the attached shielded cable, after which the PC board assembly can be finally installed in the case. Note that the magnets must all be installed with the same polarity facing outwards (ie, the magnets must all have their north pole facing outwards, or they must all have their south pole facing outwards). This can be checked by attaching the magnets together in a stack. This will either give a N-S-N-S, etc stack or a S-N-S-N, etc stack (it doesn’t matter which). The trick is to mark the outside face of the top magnet and remove it from the stack. You then mark the outside face of the next magnet and so on, until all the magnets have been marked and removed. The magnets are then all positioned on the shaft with the marked sides facing outwards and If the small internal buzzer isn’t loud enough, you can substitute an external buzzer similar to the units shown here. is operating in the alarm speed mode. In addition, if there are insufficient pulses from the speed sensor (ie, if the speed is too low), the display will show “Err” to indicate that calibration could not be achieved. By the way, do not attempt to carry out the calibration procedure on your own – it’s all too easy to have an accident if you are distracted. Instead, take an assistant with you and instruct him/her to press the Cal button when the car is travell­ing at the set alarm speed. Check that the speed alarm operates correctly after the calibration procedure. If it does, you can now check the update time. To do this, set the alarm speed to a value that’s below the current vehicle speed, then press the Down switch again. The time it now takes for the alarm to sound (ie, after pressing the switch) is the update time and should be in the range from 0.4 to 2 seconds. If it is much longer than this, you can improve the update time by increasing the number of magnets on the driveshaft. Doubling the number of magnets will half the update time, for example. Conversely, if the update time is much shorter that 0.4 seconds, you can increase it by removing magnets. When the Speed Alarm is operating satisfactorily, you can secure the magnets to the drive shaft with silicone sealant. This will prevent them from sliding out from under the cable tie. Assuming that everything is working correctly, you can now give the unit a final calibration at 100km/h (speed limits per­mitting). This will give a more accurate result than the initial low-speed calibration. Speedometer comparisons The speed sensor coil must be waterproofed before mounting it under the vehicle – see text. temporarily secured with a long cable tie (or several short cable ties joined together). Calibration As mentioned before, the unit is virtually (but not com­pletely) self-calibrating. The first step is to set the Speed Alarm to a speed within the current speed limit (eg, 60km/h). You then drive at that speed as indicated on your car’s speedometer and briefly press the Cal button using a small probe. The Speed Alarm will then automatically calibrate itself so that it matches the vehicle’s speedometer reading. During the calibration period, which should be around 0.4-2 seconds, the display shows the letters “CAL”, after which the display reverts to its normal mode. Note that calibration can only take place when the unit By the way, you may notice that your vehicle’s speedometer is not very linear compared with the very linear speedometer of the Speed Alarm (within ±1 digit on the display). On the other hand, don’t expect the Speed Alarm to indicate speeds much below 15km/h. This is because the magnets need to rotate at a reason­ably fast rate before they induce voltage pulses of sufficient amplitude in the pickup coil for reliable processing by the following circuitry. Finally, if you want to measure very low speeds, use a small magnet-to-coil gap or try using stronger magnets. SC DECEMBER 1999  61 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 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 Sharing an Internet connection using an IP Gateway Want to share a single modem between several users for Internet access? You can either use a software proxy server to do the job or you can take the hardware route and use an IP gateway. Here’s a look at what IP gateways are, what they do and how they’re set up. By GREG SWAIN M ANY SMALL OFFICE networks use a single dedicated line to connect to the Internet for email and web browsing. This works fine as long as only one person (ie, the person with the modem) requires access but how do you share a single modem between all users on a network, so that they can connect individually (or simultane­ ously) as required? Perhaps the easiest answer for Windows 98 users is to obtain the latest version of this popular operating system, known as Windows 98 SE (second edition). Another approach is to use a software proxy server such as WinGate, as described in the Octob­ er 1999 issue. Basically, WinGate is installed on the PC with the modem 64  Silicon Chip which then acts as a “proxy” for the client machines on the network. With WinGate installed, each client machine behaves as if it had its own modem. When a user wants access, the proxy automatically initiates a dial-up session. As a bonus, WinGate also functions as a DHCP server and acts as basic firewall for the clients. DHCP stands for “Dynamic Host Configuration Protocol” and allows the WinGate server to automatically hand out unique addresses to client computers on a TCP/ IP network as they boot up. OK, let’s just back up a little bit and explain the jargon. TCP/IP is an acronym for “Transmission Control Protocol/Internet Protocol” and is the language of the Internet. It’s also used on many local area networks (LANs), both large and small. Each machine on a TCP/IP network is given a unique IP address consisting of four groups of numbers (between 1 and 255) separated by full points (eg, 192.168.1.10). A DHCP server saves the network administrator from having to manually assign an IP address to each machine on the network – something that can quickly become unwieldy when there are more than about 10 machines involved. IP gateway An alternative to proxy server software is the “IP gateway” (also called an “Internet access server”). This device can be thought of as a box that provides Internet access to multiple users on a network. Basically, all users connect via a common access point or “gate”. An IP gateway offers similar functions to a proxy server and has a few extra features of its own. It’s also a snack to set up and get going – you just plug it in, tweak a few software settings to configure it and it works. The two devices featured here are from MicroGram Computers and are fairly typical of the IP gateways that are now available. The larger of the two is called a “Dual Speed Gateway Hub” while the smaller unit is called a “Dual Port IP Gateway”. Despite their size disparity, the two units are really quite similar. Both function as IP gateways, as DHCP servers and as firewalls (to prevent “hackers” on the Internet from accessing your private LAN). They simply plug into the network and provide users with simultaneous Internet access via one or (optionally) two modem ports. In addition, the larger of the two units rolls an 8-port 10/100Mb dual-speed hub into the package. This means that if you are setting up an office network from scratch, you don’t have to purchase a separate hub. By contrast, the Dual Port IP Gateway plugs into an exist­ing ethernet network, either via a BNC connector or via an RJ-45 (UTP) connector. Indicator LEDs on the front panels of the two units indicate modem and network connections and port activity. In operation, the IP gateway runs in the background and is completely unobtrusive. When a client computer requires Internet access, the gateway automatically dials out and makes the connec­tion. Alternatively, if the connection is already open, the dial-up process is bypassed and new clients have immediate access (the IP gateways also works with ISDN and leased line connections, by the way). Note that, unlike a software proxy server, no dial-up monitor appears on the screen when you initiate a dial-up ses­sion. This means that there is no way for the user to force a disconnection at the end of a session, even if no other users on the network are using Internet resources. Instead, the IP gateway automatically disconnects at the end of the idle period, as specified during the setup procedure. Fig.3: the TCP/IP networking protocol must be installed for the IP gateway to work. This shows the entry for an SMC network adapter. Fig.4: select the “Obtain an IP address automatically” option here if you intend using DHCP. Alternatively, you can assign static IP addresses Fig.5: if you don’t intend using DHCP, you should enter a static IP address for the IP gateway as shown here. Just type in the address and click “Add”. Phone Line Dual-Speed Gateway Hub Phone Line Client PC Modem 1 Modem 2 Client PC Client PC Fig.1: the Dual Speed Gateway Hub combines an IP gateway, a DHCP server and an 8-port fast network hub into one unit. Two modems can be connected, the second dialling out automatically as traffic requirements dictate. Dual Port IP Gateway Existing Hub Phone Line Phone Line Client PC Modem 1 Modem 2 Client PC Client PC Fig.2: the Dual Port IP Gateway can also handle two modems but doesn’t include a hub. It is connected to an existing network as shown here. DHCP server As with software proxies, these IP gateways can also function as DHCP servers. And although they might not be as versatile as a software-based DECEMBER 1999  65 Fig.6: you load the Web Management utility by entering 192.168.1.1 in your web browser and typing “admin” in the password dialog box. Fig.7: this is the OnePage Setup screen. You have to enter in the details for your ISP plus your user ID and password. Fig.8: the Intranet Setting (IP Setting tab) lets you enable/disable the DHCP service, specify a starting address and specify the number of users. Fig.9: this dialog lets you block Internet access for up to five clients and/or block access to certain Internet services. Fig.10: the Virtual Servers dialog lets you redirect external Internet users to internal network functions (eg, to FTP and SMTP servers, as shown here). Fig.11: the basic Modem setup lets you choose the line type (dial-up, ISDN or leased line) and ISP authentication setting. A login script can also be used. DHCP server, they do have two advantages: (1) they are simple to setup; and (2) you only have to leave the IP gate­way itself powered up to keep the DHCP service operating. By contrast, a PC that’s running a DHCP service must be kept on all the time, otherwise the network goes down (unless there’s a backup DHCP server running). That said, there’s probably no good reason to run a DHCP service on a small network – unless you really don’t want to manually assign IP addresses. A common approach is to use both manually-assigned IP addresses and DHCP. The administrator assigns fixed IP ad­dresses to those computers that are permanently connected but uses DHCP to hand out addresses to any new machines that subsequently join the network or are often moved from one location to another. To do this, the administrator has to assign fixed IP addresses within a certain range and then exclude these addresses from the DHCP “scope”; ie, the range of addresses that can be handed out by the DHCP service. For example, the administrator could hand out IP addresses in the range from 192.168.1.2 to 192.168.1.99 and con­ figure the DHCP service to hand out addresses starting at 192.168.1.100. Note that addresses ranging from 192.168.0.0 to 192.168.255.255 are for use on private LANs and cannot normally be accessed via the Internet. and have the second modem automatically dial out to provide extra bandwidth during high traffic periods. The second modem then automatically disconnects when the traffic congestion eases. Alternatively, the second modem can be configured to pro­vide dial-in access only. This allows a user at a remote location to dial in and access network resources without affecting Inter­net access via modem 1. Two modem ports Fig.12: the Advanced modem tab lets you adjust the modem settings and set the disconnect “idle” period. 66  Silicon Chip One interesting feature of these two units is that they both have two modem ports. Why two? The answer is that you can connect two modems Connecting the hardware If you’re setting up a network from scratch, the Dual Speed Gateway Hub is probably the way to go. Fig.1 shows a typical installation. Each PC is fitted with a network interface card (NIC) and is connected to a port on the hub via a Cat.5 cable. The eight ports on the hub are auto-negotiating which means that they run at either 10Mb/s or 100Mb/s, depending on your network cards. The eighth port can also be switched to uplink mode (via an adjacent switch), so that additional hubs can be cascaded as the network grows. By the way, hubs are cascaded by connecting the uplink port on one hub to a normal port on the second hub and so on. Hubs that don’t have uplink ports are cascaded by connecting two of their regular ports together via a crossover cable. Installing TCP/IP After connecting the hardware, the next step is to install the TCP/ IP networking protocol on the client machines. If you’re using Windows 95/98, double-click the Network icon in Control Panel to bring up the dialog box shown in Fig.3. If you don’t see a TCP/IP entry for the network adapter, click “Add” double-click “Protocol”, click “Microsoft”, select “TCP/IP” from the list of network protocols and click OK. Follow the on-screen prompts to complete the installation, then go back to the Network dialog box. You should now see a TCP/IP entry for your network adapter (Fig.3 shows the entry for an SMC EZ Card). Double-click this entry to bring up the TCP/IP Properties dialog box, click the IP Address tab and, assuming that you wish to use the DHCP service provided by the IP gateway, select “Obtain an IP address automatically” (Fig.4). And that’s all you have to do to get a working TCP/IP net­work, since the DHCP service on the IP gateway is enabled by default. You can ignore the Gateway and DNS settings, since the system configures these automatically. Alternatively, if you are using another DHCP service, you will have to specify the IP address for the gateway yourself. You do that by clicking the Gateway tab, entering the address 192.168.1.1 in the space provided and clicking “Add” – see Fig.5. This is the default address for the IP gateway and must not conflict with any other assigned IP address on the network. You will also have to manually assign the gateway address if you don’t intend to run a DHCP service. In addition, you will have to assign a unique IP address to each machine on the network but note that they must all use a Subnet Mask of 255.255.255.0. Configuring the gateway There are four ways to configure the IP gateway: (1) via a web browser (Web Management); (2) via the bundled GateKeeper software; (3) via a terminal program (eg, HyperTerminal); and (4) via Telnet. Most people will use Web Management since you don’t have to This view shows the rear panel of the Dual Speed Gateway Hub. The switch next to UTP port 8 allows this port to be switched to uplink mode, while the switch next to the modem 2 port can be used to select configuration mode. This last setting is used only for configuring the gateway via a terminal program. install any software, although you do get a cleaner interface and a couple of extra options using Gate­Keeper. Basically, you need to configure the gateway with all the information it requires to connect and log in to your ISP. Howev­er, there are lots of other options that can be configured, including restricting access to certain services and restricting all access by certain users. The Web Management utility is started by launching your web browser and typing 192.168.1.1 (ie, the gateway IP address) in the address window. When you press “Enter”, the Network Password dialog window will open (see Fig.6). By default, you can leave the User Name field blank and fill in the password “admin” before clicking OK to enter Web Management. Fig.7 shows the opening “OnePage Setup” dialog box. This page has all the settings that most users will need. The Modem 1 dial-out setting is enabled by default and you have to choose the ISP Name (in most cases, “Standard PPP”) and enter the ISP’s phone number, the DNS IP address, and your user ID and password. This information is all provided by your ISP. The Gateway IP Address and Subnet Mask are set to 192.168.1.1 and 255.255.255.0 by default but you can change these if necessary. You can also open and configure a number of other dialog boxes under the Advanced menu. For example, the Intra­net Setting dialog box has three tabs labelled “IP Setting”, “Filter” and “Virtual Server”. The first tab lets you enable or disable the DHCP service. You can also specify the starting IP address for the DHCP service (192.168.1.100 is the default) and the maximum number of users. However, there’s no way of specifying the “lease” period (ie the period for which an individual PC is assigned an IP address), which is apparently preset to six days. Assuming that you stick to the defaults, this means that the first address handed out by the DHCP service will be 192.168.1.100, the second 191.168.1.101, the third 192.168.1.102 and so on up to 192.168.1.149. Clicking the Filter tab brings up the dialog box shown in Fig.9. Here, you can prevent certain users from accessing the Internet via the gateway and/ or prevent access to certain servic­es. Up to five users can be locked out but in Fig.9, only the machine on 192.168.1.10 has been blocked from Internet access. Note that the machines to be excluded should be assigned static IP addresses for this to work correctly. They should not be part of the DHCP The Dual Port IP Gateway has both RJ-45 and BNC sockets for connecting to a network. DECEMBER 1999  67 Using The Alternative GateKeeper Software Fig.13: to use an IP gateway, all Internet applications must be set to connect via a LAN instead of via a modem. This is the setting for IE4. Fig.14: this is the connection setup for Outlook Express. service, since individual machines can be assigned a different IP address if their “lease” period on a previous address expires. The Filtered Private Ports entry lets you disable up to five Internet services by specifying their port numbers. As an example, entering 80 and 21 in the Port 1 and Port 2 windows will disable web browsing and FTP access, respectively. You might do this if you want to restrict users on the network to email access only and prevent them from web browsing or tying up the system while they download large files from FTP sites. Note that the port numbers given above are default values. The port number for your web service in particular will be dif­ferent if you use a proxy server at your ISP. 68  Silicon Chip The alternative Gate­ Keeper software supplied with these units duplicates the functions of the Web Management utility but has a cleaner interface and includes a couple of additional options (eg, there’s a firmware upgrade option, for updating the IP gateways with the latest code). The software is supplied on floppy disk and is installed by double-clicking the setup.exe file. The GateKeeper utility is then launched via the Windows Start menu in Fig.15: the OnePage setup dialog from GateKeeper. the usual manner. Fig.10 shows the dialog box that pops up when you click the Virtual Server tab. Normally, external Internet users cannot access your network because the IP gateway functions as a fire­wall. The Virtual Server dialog box lets you bypass this firewall to give external users access to selected services on your net­work; eg, an FTP server, a web server or a mail server. Note that, for this to work, you must have a fixed IP address which is allocated by your ISP (yes, it costs money). The Modem 1 and Modem 2 dialog boxes are pretty much self-explanatory. When you click on these, you will find that the settings are already there since these are part of the OnePage Setup – see Fig.11. You can also set up a logon script if that is required by your ISP. The Advanced tab lets you choose the modem type and the idle disconnect period (Fig.12). It also lets you specify whether to enable or disable a second modem and the traffic level at which the second modem automatically dials out. There’s also a dial-in dialog for Modem 2 that lets you specify a user ID and password for up to three users and enable or disable the call­back function. The last two buttons in the Advanced menu are labelled “Device Admin.” and “Status Monitor”. The “Device Admin.” dialog box lets you reset the device, revert to the factory defaults and change the password, while the “Status Monitor” shows a list of client computers on the network that have been given IP addresses by the DHCP service. Configuring your browser There’s no great magic involved in configuring your web browser or any other Internet application to work with an IP gateway. Basically, you set up your web browser in exactly the same manner as for a direct dial-up connection but with one important difference – you must configure it to connect via the LAN instead of via a modem. Fig.13 shows the setting for Internet Explorer 4 while Fig.14 shows the setting for Outlook Express. Apart from that, everything works as normal as far as each user is concerned. In short, these devices are fast to set up and provide a hassle-free way to configure a network and share an Internet connection. Where to buy them The Dual Speed IP Gateway Hub (Cat. 10108) and the Dual Port IP Gateway (Cat. 10112) are available from MicroGram Comput­ers and retail for $699 and $449 respectively (including sales tax). You can contact Micro­Gram Computers at Unit 1, 14 Bon Mace Close, Berkeley Vale, NSW 2261. Phone (02) 4389 8444; fax (02) 4389 8388; web site www.mgram.com.au; SC email sales<at>mgram.com.au NOW: PAY-BY-THE-MINUTE Internet access Why pay for HOU when you RS only n MINUTES? eed 4 STILL with no download limits! ❏ 4 STILL with your own free email address! ❏ 4 STILL with your own free website space ❏ 4 STILL with no fine print or hidden extras to pay for! ❏ BUT NOW WITH JUST ONE LOW-COST PLAN. YOU PAY JUST 2.7c PER MINUTE! (YOU SIMPLY CHOOSE YOUR INITIAL PERIOD, 1 MONTH OR 3, $10 PER MONTH MINIMUM CHARGE WITH 5 FREE HOURS PER MONTH APPLIES) Yes! SILICON CHIP’s famous Internet Service is now EVEN BETTER value. From December 1, all new and renewing Internet Service Subscribers can take advantage of our simpler, single rate! It’s time to get connected with SILICON CHIP! IT'S AS EASY AS A-B-C TO GET CONNECTED! (a) Fill in this form and either post it or fax it to SILICON CHIP – (02) 9979 6503; or (b) Call SILICON CHIP on (02) 9979 5644; 9am-4pm Mon-Fri and we'll guide you through it! (We’ll even call you back to save your phone bill!) (c) WE WILL THEN FAX YOU OR POST YOU your password and EASY setup details. Date of Application: ________________ YOUR DETAILS Name ___________________________ Company Name (if applicable) ____________________ ACN: ________ Address _________________________________________________________________­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­ ­­Postcode ________ Postal address (if different to above) _________________________________________ Postcode ________ Phone No. ( ) ______________________________Fax No. ( )_______________________________ Current email address (if applicable): ________________________ Signature:__________________________ Your PC Operating System: ❏ Windows NT ❏ Windows 95/98 ❏ Windows 3.1 ❏ Mac ❏ Linux SERVICE TYPE One month minimum. If you prepay for three months you avoid paying the setup fee of $10.00 ❏ One Month ($10.00 + $10.00 SETUP FEE) Three Months (NO SETUP FEE): $30.00 (5 hours included then 2.7 cents per minute) (15 hours included then 2.7 cents per minute) Note: charges are made on a calendar month basis. When do you wish to start:  straight away  beginning of next month Choose your email address (user name of 2-8 letters), eg, yourname<at>silchip.com.au First Choice:__________________Second Choice:___________________Third Choice:___________________ Choose your Dial-In Location (also known as POP - Point of Presence) from this list: ❏ Sydney (inc outer metro) ❏ Newcastle ❏ Wollongong ❏ Gosford, Windsor, Wiseman's Ferry ❏ Penrith, Mulgoa, Camden ❏ Campbelltown ❏ Melbourne (inc outer metro) ❏ Geelong ❏ Ballarat ❏ Bendigo ❏ Shepparton ❏ Cranbourne, Mornington ❏ Healesville, Emerald, Pakenham ❏ Gisborne, Romsey, Kilmore, Kinglake ❏ Lara, Balliang, Bacchus Marsh ❏ Canberra ❏ Adelaide ❏ Perth ❏ Hobart ❏ Brisbane (inc outer metro) ❏ Gold Coast ❏ Sunshine Coast ❏ Towoomba ❏ Townsville ❏ Cairns (Note: Some locations within these areas may be community or STD calls. Please check with your telephone service provider if in any doubt) Initial charges (Credit card charged ONLY after password & setup information have been forwarded): Monthly/3-monthly plan charge: $________ Plus setup fee: $10.00 (if applicable) $ _______ = Total: $ __________ PAYMENT DETAILS: CREDIT CARD ONLY! ❏ Bankcard ❏ VisaCard ❏ Mastercard Card No:     Card expiry date ____ /____ Cardholder Name (if different from above) ___________________________________ Modifying the circuit for a hard-wired “walk-around” throttle. PART 3: By JOHN CLARKE & LEO SIMPSON BUILD THE RAILPOWER As promised in part 2, here is the walk-around throttle version of the Railpower speed control for model railways. It uses four switches to control speed, forward/reverse, inertia and braking. W ELL, WHAT IS a walkaround throttle control any way? It is a little hand-held control that you can plug in on several places on your layout. It means that you don’t have to be tied down to one place on your layout. 70  Silicon Chip For example, for shunting manoeuvres you might want to be very close to the locomotive as you marshall up a train. At other times, you might want to be close to the straight, so you can see your train barreling down towards you. Or perhaps you have a turntable and you want to watch the locomotive closely as it comes on and off. Whatever the reason, you want to be able to plug the hand control into one of a number of sockets around the layout to closely observe and control your trains. You want to be able to plug it in, set the train speed and direction and then unplug, go to the new location and plug in again, all without the locomotive faltering in any way – it should just maintain the settings, as if you had not touched the controls. Of course, you have most of the advantages of a walk-around throttle with the infrared remote control version published in the previous two chapters. But perhaps there are parts of your layout which will not let you use the IR remote control – perhaps they don’t have a line-of-sight back to the control unit. Possibly, you don’t want the remote control version because it uses batteries and yes, the AAA-cells will need to be replaced from time to time. OK, so you want the walk-around throttle; here it is. It consists of a small plastic case with three toggle switches and a pushbutton. Note that there is no provision for the auxiliary switching although that could be done if need be. We leave those details to you. Of the three toggle switches, two are spring-loaded 3-position types with the centre-position being OFF (ie, centre-OFF). These are used as the up/down speed control and the Direction control (forward/reverse). The Speed switch is pushed to the right to make the speed increase (UP); push it the other way and the speed setting decreases (DOWN). The Direction switch is used in the same way: push it to the right to select Forward operation and to the left to select Reverse. Mind you, the Lockout feature of the circuit still works so that the locomotive must be virtually stopped before you can change the direction of operation. The remaining toggle switch is the inertia ON/OFF control. The pushbutton is a momentary push-on type. Pressing it once brings the STOP function into play. Pressing it again will release the STOP function and allow the locomotive to resume its previous speed setting. Alternatively, pushing the speed Inside the modified Railpower. The infrared receiver components have been replaced by a hard-wired connection terminated in an 8-pin DIN plug on the rear panel. The modification is quite simple. switch UP or DOWN will achieve the same result. The hand-held control is wired via a length of 8-way cable to an 8-pin DIN plug. Inside the Railpower itself, IC1, IC2, Q1, three resistors and a capacitor are omitted and a 14-pin socket is installed in place of IC2, to allow the circuit connections from the handheld control to be made via a 14-pin header plug. The circuit of the walk-around control is shown in Fig.1. What we have done is to reproduce the top lefthand corner of the of the Railpower circuit which previously involved IC1, the infrared receiver and IC2, the 8-channel decoder. Eight control lines run away from IC2 in the original Railpower circuit and we now control six of those lines (omitting the two for the Auxiliary outputs) via the hand-held control and the 14-pin socket. The circuit also involves the +5V rail at pin 14 and the 0V line at pin 1. The forward/reverse switch, S1, operates by pulling pin 3 or pin 8 A close-up view of the modified section of the PC board with the header connector shown in detail above. DECEMBER 1999  71 Parts List 1 plastic case 83 x 54 x 31mm 1 label, 80 x 50mm (see Fig.5) 2 centre-off spring return momentary SPDT toggle switches (S1,S4) 1 SPDT toggle switch (S3) 1 miniature pushbutton switch (S2) 1 8-pin DIN line plug 1 8-pin DIN panel socket 1 1.5m length of Cat 5 8-way stranded cable (cut to 1100mm and 400mm) 1 150mm length of 0.8mm tinned copper wire 1 small cord grip grommet 4 10kΩ 0.25W 1% resistors 1 22µF 16VW PC electrolytic capacitor 1 14-pin IDC header plug 1 14-pin IC socket 2 M3 screws and nuts pin high (ie, to +5V) when selected. The lines from these pins drive the bases of transistors Q10 or Q11, respectively. Pushbutton STOP switch S2 operates by pulling pin 7 high. When S2 is released, the 10kΩ resistor pulls pin 7 low again. The 22µF capacitor provides debouncing for the switch contacts. The inertia switch S3 pulls pin 9 high when it is set to OFF. When S3 is set to ON, pin 9 is pulled low via the associated 10kΩ resistor. Finally, Speed switch S4 operates by pulling either pin 5 or pin 6 high (+5V) for speed DOWN or speed UP. When released, the switch springs back to its centre-OFF position and the two 10kΩ resistors pull pins 5 & 6 low. Fig.1: compare this modified section of the circuit with the infrared circuit shown last month. Fig.5) as a template for drilling the holes. When the holes are drilled, attach the label to the lid and cut the holes out with a sharp utility knife. Fit the switches and then you are ready to start wiring. The wiring details for the handheld control and lead to the 8-pin DIN plug are shown in Fig.2. We used Cat 5 8-way stranded cable to wire up the switches. It consists of four twisted pairs. Pass one end of the 8-way cable through the hole prepared for the cordgrip grommet and strip back the outer plastic sheath by about 50mm before wiring to the switches. We used the colours as shown and note that there will be one wire spare (orange/white). You will need a common connection to the centre terminal of S1, S4 & S3 and one side of S2. This can be made using tinned copper wire. The 8-way cable is captured with a cordgrip grommet in the end of the case and the free end is cut to 1100mm long (or longer if you want but you will need more cable). The end is then stripped and terminated into the 8-pin DIN line plug. Do not forget to slide the plastic boot of the plug onto the lead before connecting the wires. Construction The walk-around throttle is housed in a standard plastic case measuring 83 x 54 x 31mm. The first step in construction involves drilling holes for the switches in the lid of the case and a hole for the cordgrip grommet in the end of the case. You can use a photocopy of the front panel label (see 72  Silicon Chip Fig.2: the wiring of the hand-held controller box and the DIN plug. The length of cable between the two can be as long as necessary (ours was 1.1m long). The inside of the handheld controller is shown in the photo at right. Fig.3: part of the PC board component layout from last month, with the components in red to be deleted from the hard-wired “walk around” version. The IC socket, though, is an addition. The Railpower itself requires a number of alterations from the wiring layout (Fig.6) depicted in last month’s issue. First, you will need to drill and ream out a hole for the 8-pin DIN panel socket at the rear panel. Secure this with screws and nuts. When assembling the PC board for the Railpower, leave out IC1, Q1, IC2, and the components associated with pins 2 & 13 of IC2. A 14-pin IC socket is installed in place of IC2. We have shown the relevant corner of the PC board with the omitted components dotted, in Fig.3. A 400mm length of 8-way cable needs to be made up with the 14-pin header at one end and the 8-pin DIN socket (on the rear panel) at the other end. The details of this are shown in Fig.4. Four 10kΩ resistors are connected between pin 1 and pins 5, 6, 7 & 9. A 22µF capacitor is connected between pins 1 and 7, with the positive lead going to pin 7. Fig.5: same size artwork for the front panel of the hand controller in the “walk around” Railpower. Testing Having finished assembly of your Railpower, do all the initial checks as described in last month’s article. Then plug in the handheld control. Check that the Inertia switch turns the associated LED on the Railpower panel either on or off and that the stop LED turns on or off with alternate pressings of the pushbutton. The speed up and speed down selections should alter the meter reading up or down. The track LED should gradually light up as the speed is increased and be of a different colour depending on the forward or reverse setting. It may come up very slowly in brightness because of the inertia set- ting. You can switch the inertia out for a faster response to the track voltage. Note also that the forward or reverse functions can only be made when the reverse lockout LED is off. You should be able to remove the plug from the socket at the rear of the Railpower unit without affecting the train’s motion. The only exception is that the inertia control will always return to the ON setting with the plug disconnected. If you want additional 8-pin DIN sockets around your layout, these can be wired in daisy-chain fashion using the Cat 5 cable. Fig.4: the DIN socket to header pin wiring which goes inside the RAILPOWER case. This cable should be about 400mm long. DECEMBER 1999  73 Installing a speed control knob Inevitably, someone always wants a variation to a design after we have published it and the Railpower is no different in this respect. No sooner had the October issue hit the streets than a reader wrote in to say that he wanted a walk-around throttle with a speed control knob instead of the UP and DOWN buttons. Could we please publish the details? Well, it is stretching the friendship but since other readers will probably want to do the same, we are publishing brief details here. We should point out right now that there are a few more modifications involved to the 74  Silicon Chip Railpower itself. Fortunately, the handheld control can still be wired up using 8-way Cat 5 cable. Note that while we have produced a prototype handheld walk-around controller as described in Figs.1 to 4, we have not produced a version with a speed control knob. In other words, we have not tested the following modifications. Fig.6 shows the relevant circuit modifications to the Railpower circuit. As before, IC1, IC2 and Q1 are omitted and a 14-pin socket installed in place of IC2. In addition, diodes D1, D3 & D4, transistors Q2 & Q3 and five resistors are left out. These omitted components are shown in red on the diagram of Fig.6. The 10kΩ speed potentiometer which is installed in the handheld control is wired via pins 11, 12 & 13 of the 14-pin header. Pin 13 of the header goes to pin 7 of IC3a and pin 11 of the header goes to the cathode of diode D2. The wiper of the 10kΩ potentiometer goes to pin 12 of the header and this, in turn, connects to C1 and thence to pin 5 of IC4b via a 1kΩ resistor. Two cuts must be made to the tracks of the PC board and again, these are shown on the diagram of Fig.6. First, the track between the cathode of D2 and pin 5 of IC5a must be cut and so must the track between pin 5 of IC5a and capacitor C1. These two cuts leave pin 5 of IC5a not connected to anything. A section of the PC board layout (Fig.7) shows where the cuts are to be made. The tracks can be cut with a sharp, heavy-duty knife (such as a “Stanley” knife) or they can be cut using a small drill bit. In either case, ensure the tracks are completely severed and no swarf shorts out adjacent tracks. (If in doubt, check with a multimeter). You will also need to place three long links between the cut tracks and the appropriate tracks near the IC header socket. Use fine insulated wire (single lengths cut from rainbow cable are ideal) and solder them to the back (copper side) of the PC board where shown. In wiring up this version of the walk-around handheld control, you can follow broadly the same procedure as described above and the testing procedure will be similar as well. However, there will be one difference in operating the Railpower and that involves the STOP function. In the 4-switch version described earlier, if you operate the STOP button to bring the locomotive to a halt or slow it down, you only need to push the Speed switch momentarily up or down to release the STOP function and allow the train to resume its previous speed setting. However, in this Speed knob version, that circuit feature has been disabled, because diodes D1 and D2 have been removed (there being no Speed switch to forward bias them). So to release the STOP function, the STOP button must be pressed again and this toggles flipflop IC6a to achieve that function. The Speed knob can then SC be used to vary the speed of the locomotive. Please note: there are two errors in the PC board component overlay on page 82 of last month’s issue. IC5 is identified as a 4052; it should be a 4053 (the circuit diagram in the October issue is correct. Also, IC8 (the IC closest to the 2000µF capacitors) is identified as IC3. IC3 (top right corner) is itself correctly identified. Fortunately both IC3 and IC8 are LM324 quad op amps. Figs.6 (opposite) and 7 (above): these modifications will allow the use of a 10kΩ potentiometer as a speed controller instead of push-button control. Again, the relevant sections only of both the circuit diagram and the component overlay are shown. Additional components are deleted in this version and you will also need to modify the circuit board as shown above with two tracks to be cut and three links to be inserted (the green, blue and purple wires). These should be soldered underneath the PC board (ie, on the copper side). DECEMBER 1999  75 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The Astor KM that blew its power plug off! Manufactured in the late 1940s, the Astor KM was a popular 4-valve mantle radio with some interesting design features. I was recently given the job of overhauling one of these sets which had developed an unusual fault. It all started when the lady who owned this particular set rang me to say “that the power plug had blown off the lead”. Apparently, the old Astor had been going well prior to that happening and she wanted the plug replaced and the set checked for faults. Now this sounded really interesting and I was really begin­ning to wonder whose leg was being pulled. And so I suggested that she bring the set to my workshop me so I could see what had happened. Sure enough, the lady eventually turned up with the set in a bag. I went to lift it out by putting my hand under the back of the top of the set and it was obvious that the cabinet was bro­ken. I said “the cabinet’s broken” and the lady said “you’ve broken the cabinet”. Wow, what have I got myself into Because of its compact size, the Astor KM was popular as a kitchen set. This particular unit included a number of manufacturing defects which were fixed when the set was overhauled. 76  Silicon Chip here, I thought! I looked at the cabinet and could see dirt in one of the cracks which meant that it couldn’t have been done in the last few moments. She acknowledged this and when I showed her that there were a number of cracks both new and old she changed her mind and said it must have been done by the painters! I said that I could repair the cabinet. It just goes to show that some people are quite happy to lay the blame for a problem on someone else. So if you are re­storing a set for another person, make sure you know exactly what they want. It’s also a good idea for them to show you the set and to inspect it together if possible. Having overcome that little problem, the lady showed me the power plug and yes, it had literally blown off the twin-flex power lead. And it wasn’t hard to see why - the power lead was the original rubber-covered twin-flex and the rubber had perished badly and the two leads had shorted and then melted and blown apart (see photo). That such a melt-down occurred indicates to me that the mains fuse in the meter box may be much greater than 15A, con­sisting perhaps of several strands of 15A fuse wire (a dangerous practice). Don’t laugh – I’ve seen up to seven strands in a fuse­holder! Anyway, getting back to the Astor, there were several spots where the power lead had perished and where bare wire was show­ing. One spot had been taped up but for safety’s sake the entire lead should have been replaced years ago. Judging from the liber­al coating of grease over the chassis, this set is used in the kitchen so just The set is easy to work on, with all parts under the chassis readily accessible. Note the wooden dial pulley at top right and the rightangle worm gear drive for the tuning. how close the owner has been to electrocution over the years is anybody’s guess. The cooking grease did protect the chassis from going rusty though. The Astor KM These little sets came out in the late 1940s and were quite popular. They are only a 4-valve set but are reflexed, with the IF stage also acting as the first audio stage. Although the performance is not quite to 5-valve standard it is better than from a normal 4-valve set. If you want more information on re­ flexing, I suggest you read the article by John Hill and myself in the February 1996 issue of SILICON CHIP. Despite the fact that they are relatively small and use octal valves, these sets provide good chassis access. What’s more, the chassis can be tipped on one end or even placed upside down without any likelihood of damage to other parts. Having got the chassis out of the cabinet, the only damage I could find was that one of the pulleys in the dial-drive system had broken. Astor, along with some other manufacturers, used small turned wooden pulleys. I also noticed that the 5Y3GT recti­fier had been replaced by a 5AS4. The 5AS4 is much bigger physi­cally, has a much higher rated rectified current (as required for valve TV sets) and a higher heater current (3A compared to the 2A for the 5Y3GT). It had been in there a long time and there was no sign (smell) of overheating, so the power transformer was obviously not being run to its maximum capability. Despite this, I decided to replace the 5AS4 with a 5Y3GT, in the interests of long-term reliability. In fact, a later check with a contact thermometer showed that the transformer ran around 5° cooler with the correct rectifier fitted. However, before doing anything, the power lead had to be replaced (to ensure my personal safety as much as anything else). That done, the set was carefully checked for shorts using a high voltage insulation tester (several of these have been described in SILICON CHIP, the latest in January 1999). In particular, the power transformer mains winding was tested for leakage or shorts between it and the chassis. Fortunately, testing at 500V and 1000V showed no discernible leakage. I also like to test the transformer by applying power for half an hour or so with all valves removed to see whether it heats up to any extent, as this can indicate shorted turns. It tested 100%. A few of the rubber insulated wires in the set wiring were also perished and were replaced. This is a common problem in sets that used rubber-covered hook-up wire. As I normally do, I removed all the critical paper capaci­tors and replaced them with polyester or ceramic types. In par­ t icular, I replace all audio coupling and AGC bypass capacitors before applying power to the set’s amplifying stages. Often, just by doing that, the set will operate - perhaps not at its peak performance but enough to show that the restoration work will be successful. In this case, I decided to go one step further and replace all the leaky paper capacitors. Note however that it’s possible for a capacitor to be leaky but not cause any trouble in the set. For example, cathode bypass capacitors can be quite leaky but will cause no problems as they are usually in parallel with low-value resistors. Further checks revealed a couple of resistors that had gone high so they were also replaced. After that, DECEMBER 1999  77 Despite its age, the old Astor was in pretty good nick. The set used four valves in a reflex circuit, with the IF stage also acting as the first audio stage. It worked well, although the performance is not quite up to 5-valve standards. it was down to the serious business of getting the set running at peak performance. Alignment In this case, the set performed quite well without any attention to the alignment. In fact, some restorers leave the alignment well alone but I always prefer to go over it and make any necessary adjustments to ensure peak performance. In prac­tice, alignment is a straightforward procedure once the tech­niques are understood and will be dealt with in detail in a future article. I start by aligning the IF stages with the tuning gang closed. First, the signal generator is set to produce a strong signal on the expected IF of 455kHz and this signal is applied to the aerial terminal and adjusted until the receiver responds. Note that the converter stage is acting purely as a poor-quality IF amplifier at this stage. Once the IF amplifier responds, the signal level is reduced so that it is audible without significant noise with the volume turned up high. In most cases, the frequency will be close to 455kHz but variations of 1078  Silicon Chip 20kHz from the nominated frequency are usually unimportant. The slugs or screws in the top and bottom (and sometimes on the sides) of the IF cans are then adjusted for peak audio output. These adjustments can either be done by ear (ie, by (listening for maximum audio output) or by putting a sensitive AC millivoltmeter across the speaker terminals and reading the peak audio level. There are usually only four slugs to adjust for best performance. In this set, I found that the slug that tuned the IF wind­ing feeding the diode detector was all the way in but the stage hadn’t been peaked. It was close but just wouldn’t quite get there. This problem was solved by connecting a 3-30pF trimmer capacitor across the winding and adjusted it for maximum output. It peaked quite satisfactorily at about 18pF. Often, if the slug appears to be getting close to a peak but can’t quite get there, it’s an indication that the IF trans­former is faulty. I’ll go into that situation another time. In this case, the 18pF of additional capacitance allowed the detec­ tor tuned circuit to be peaked quite nicely but why it needed the additional capacitance is a bit of a mystery. The Astor’s performance improved considerably after the IF adjustments, so the exercise was well worthwhile. The aerial and oscillator coils were very close to optimum adjustment. However, a couple of turns of fine wire had to be removed from the “wire-type” oscillator trimmer to get the cor­rect tuning range. The aerial coil has no adjustment for the low frequency end of the broadcast band and only required a very minor tweak on the trimmer at around 1400kHz. By the way, any aerial coil adjustments should be carried out with the intended aerial connected to the aerial socket of the receiver (not the signal generator). That’s because the different characteristics of the signal generator could cause the aerial alignment to be incorrect in some cases. The signal from the generator is coupled in by wrapping its lead around the aerial lead and then increasing the output until there is enough signal pickup for the alignment to be carried out. It’s important to pick a spot on the dial away from any station otherwise, it will interfere with the alignment work. By this stage, the old Astor was performing really well. No valves needed replacing except for the rectifier, as explained earlier. However, dial lamps usually do need replacing and this set was no exception, requiring two 6V 0.3A MES lamps. Dial drive The dial drive mechanisms on some Astors leave a lot to be desired and this set initially looked like falling into that category. In this case, the set used the tried and proven rightangle worm gear drive from the tuning shaft to the gang. Fortunately, the fibre gear hadn’t been damaged (like so many are) but of the four pulleys in the dial system, only two were free to move and one of these had been broken (probably during the fall that cracked the cabinet). The other two pulleys couldn’t move at all as they were held tight by the mounting screws, which meant that the dial cord could only slide over them. And although the dial cord probably lasted a long time, it would last even longer if the pulleys turned. I decided to dismantle the two immoveable pulleys from their mounts and see if I there was any way that I could make them rotate freely. Once I had dismantled one of them, it became obvious that the star shakeproof washer had been put on in the wrong sequence and when the assembly was tightened up the pulley was squeezed against the mount and the star washer. No wonder the pulley couldn’t move. Installing the star washer under the head of the screw instead of between the nut and the pulley left enough room for the pulley to rotate freely and so both assemblies were modified accordingly. I suspect that this was an error that was made at the factory and it has subsequently escaped detection by various service personnel. The broken wooden dial-drive pulley initially looked like being a real problem. However, during discussions with the set’s owner, the idea that a wood turner may be able to make up a suitable pulley was floated. As it turned out, the lady knew a wood turner and the manufactured part, along with a new dial cord, did the job quite nicely. Tidying up Although the set was now working properly, there was still quite a bit of tidying up to do. First, the original speaker cloth was in a mess and had to be replaced. I fitted some darkbrown open-weave cloth that I had, gluing this to the front of the speaker frame with a thin smear of contact adhesive. Once the adhesive had dried, the cloth was trimmed around the edges of the speaker frame to give a neat finish. The on-off switch/volume control knob also needed atten­ tion. This control had been replaced at some stage but either the correct style either wasn’t available at the time or the repairer could­n’t be bothered obtaining the correct part, as the switch in the replacement unit is a push-pull type. The problem with the push-pull unit is that the original slide-on knob comes off in your hand after the control has been operated a few times. In this case, the repairer had overcome that problem by fitting a differ­ent knob. Unfortunately, the tuning knob was missing and it looked as though I would have to fit a couple of knobs that were roughly the right size but which certainly wouldn’t match the set. But as luck would have it, a friend The rubber insulation on the power cord had perished so badly that the wires shorted together and melted, detaching the power plug. Just how close the set’s owner had come to electrocution is anyone’s guess. had a couple of knobs that are similar to the originals and these are the ones that were finally fitted. They certainly look a lot better on this set than any of the knobs that I had in my junkbox. Finally, although the details of the cabinet repairs have been left until last, they were in fact done early in the piece. Sets with broken cabinets are not often viable to repair but in this case there were no missing pieces and the job was quite straightforward. First, the cabinet was given a good clean in warm, soapy water and then thoroughly rinsed, making sure all the cracks were as clean as possible. Most of these cracks were at one end of the cabinet. Where possible, each crack was sprung open, the gap filled with Araldite® and the crack allowed to close again. Any excess glue was removed after drying with a sharp blade. Of course, some of the cracks couldn’t be sprung open with­out the risk of wrecking the cabinet but these are hardly notice­able. The glue on the larger cracks did a good job and the cabi­net repair was quite successful. Performance The Astor KM was a popular 4-valve reflex set, its small size making it ideal for use as a kitchen set or second set. It doesn’t boast super sensitivity but it works and works well even in country areas. Like most Astor sets, it has a rather complex negative feedback tone/ loudness control. Its effectiveness is questionable in such a small set but similar tone control networks were very effective in some of the larger Astor sets. The set is also easy to work on and is apparently very reliable. Radio Corporation deservedly had a little SC winner in this little receiver. P.C.B. Makers ! • • • • • • • • • If you need: P.C.B. High Speed Drill P.C.B. Guillotine P.C.B. Material – Negative or Positive acting Light Box – Single or Double Sided – Large or Small Etch Tank – Bubble or Circulating – Large or Small U.V. Sensitive film for Negatives Electronic Components and Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE Prompt and Economical Delivery KALEX 40 Wallis Ave E. 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Vamtest Pty Ltd trading as Microgram Computers A.C.N. 003 062 100 Web site: Email: * Multiple Operating Systems in One System *Move data between home & office *Secure Data: Tray can be removed & locked in a Safe Ultra DMA 66 Hotp Swa All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only www.mgram.com.au info<at>mgram.com.au Check our web site Unit 1, 14 Bon Mace Close Berkeley Vale NSW 2261 Phone: (02) 4389 8444 Fax: (02) 4389 8388 Do you want YOUR product or service showcased to Australasia's most important electronics marketplace? CALL ME: RICK WINKLER on (02) 9979 5644 and let me explain how cost effective the SILICON CHIP ELECTRONICS SHOWCASE can be for YOU! UNIVERSAL WIRELESS DEVELOPMENT SYSTEM Linx RF modules from Clarke & Severn Electronics offer a simple, efficient and cost-effective method of making a product wireless. Want to know more? Contact CLARKE & SEVERN ELECTRONICS PO Box 1, Hornsby NSW 1630 Ph (02) 9482 1944 Fx 9482 1309 email: sales<at>clarke.com.au www.clarke.com.au Pt.16: Microwave Sulphur Lamps Electric Lighting Microwave sulphur lamps are a relatively new innovation in the lighting industry and the concept is quite simple: use a magnetron to excite sulphur to produce a high luminous output. The lamps are commercially available and are suitable for hollow light guide applications. By JULIAN EDGAR T HE MICROWAVE SULPHUR lamp was invented in 1990 by US scientist Michael Ury, at the end of a 4-year research period. Subsequently, in 1992, Fusion Lighting Inc, Maryland (USA) obtained all rights for the development of the light source, making it available commercially as the Fusion Light Drive 1000. 82  Silicon iliconCChip hip These sulphur lamps frequently use hollow light guides to distribute and transport the light, with 3M’s Light Pipe being a popular choice. We’ll talk more about light guides later on in this article. Lamp development The sulphur lamp bulb consists of a 35mm quartz sphere filled with a few milligrams of yellow sulphur powder and an inert gas (such as argon) which is weakly ionised using microwaves. When it is ionised, the argon heats the sulphur into a gaseous state, thereby forming diatomic sulphur molecules or “dimers”. These dimers emit a broad continuum of energy as they drop back to lower energy states. The light radiation that is produced is almost entirely within the visible spectrum, with very little undesirable ultraviolet or infrared radiation. The microwaves are generated by two magnetrons operating at a frequency of 2.45GHz. As it is irradiated, the lamp bulb is spun at 3400 rpm (apparently to stabilise the plasma’s position within the bulb), with two fans providing forced air FACING PAGE: microwave sulphur lamps are used in conjunction with long sections of 3M Light Pipe at the Volvo Bus Manufacturing Plant in Boras, Sweden. The system provides high output, significantly reduces energy costs and is said to be ideal for use where maintenance is difficult or hazardous. Fusion Lighting’s microwave sulphur lamp (below) has a tiny bulb compared with a 1000W metal halide lamp as seen at right. Not shown in this view is the extensive ancillary equipment needed to drive it! cooling. Fig.1 shows a schematic diagram of the lamp while Fig.2 is a more detailed view of the Fusion Light Drive 1000. Note that the sulphur bulb is installed in the optical centre of a reflector system, to direct the light output. Prior to the development of this lamp, sulphur had not been used because it quickly corrodes the electrodes used in conventional bulbs. However, while experimenting with a variety of substances, Ury and colleague James Dolan decided to replace the mercury used in UV lamps with sulphur and then subject the bulb to microwaves. They picked the correct magnetron and rotational speed for the bulb on the first try and Ury is quoted as saying “if we [hadn’t got] everything together like that, we might have missed it.” The first lamps were rated at 3.5kW and had a light output of 450,000 lumens. By contrast, the Light Drive 1000 sulphur lamp which was subsequently made commercially available is rated at 1kW and has a light output of 135,000 lumens. Together with the auxiliary system, this lamp requires a power input of 1.425kW which means that it has an efficacy of about 95 lumens/watt of the total lamp power. Lower power lamps that use radio frequencies (RF) instead of microwaves are also currently under development. An RF-driven sulphur lamp that produces up to 15,000 lumens with an RF input of only 100 watts has been demonstrated – a luminous efficacy of approximately 140 lumens per RF watt. As with the microwave-excited versions, these lamps still need to be rotated but their lower power operation allows the forced-air cooling to be eliminated. Lamp operation One of the most interesting characteristics of the microwave sulphur lamp is that its spectral output is remarkably similar to sunlight. This Fig.1: this diagram shows how the microwave sulphur lamp works. Microwaves generated by a magnetron are used to irradiate a quartz sphere containing argon and a small quantity of sulphur. The ionised argon heats the sulphur into a gaseous state, forming diatomic sulphur molecules which emit light. DECEMBER 1999  83 can under conventional high intensity gas discharge illumination. Warm-up time With the exception of fluorescent lamps, the warm-up time of the sulphur lamp is notably shorter than for other gas discharge lamps. A sulphur lamp reaches 80% of its final luminous flux within 20 seconds and the lamp can be restarted approximately 5 minutes after a power cut. By using a computer-controlled electronic power supply, the sulphur lamp can be dimmed to 20% of its maximum luminous flux, at which point its power consumption will have dropped by 60%. And unlike high intensity discharge lamps such as the metal halide design, the colour temperature of the sulphur lamp varies relatively little during the dimming process, dropping by only approximately 500K. The life of the lamp itself is expected to be at least 60,000 hours – in fact, Fusion Lighting suggest that the bulb itself may never wear out. However, the life of the magnetrons is much shorter, being about 15-20,000 hours. To overcome this problem, Fusion Lighting recently released a new Light­Drive 1000 with an electronic mag­ netron power supply and two spare magnetron kits. The new power supply is claimed to have increased each magnetron’s service life to at least 20,000 hours, meaning that with the spare magnetrons, a service life of at least 60,000 hours for the complete lamp is achievable. Lamp applications Fig.2: the Fusion LightDrive 1000 is a commercially available lamp using microwave sulphur technology. It uses two magnetrons to irradiate the sulphur bulb plus two fans to keep everything cool. The output from the lamp is coupled to a light pipe. means that objects viewed under the light of a microwave sulphur lamp have practically the same appearance as when viewed under sunlight. Fig.3 shows the spectrum of the sulphur lamp compared with the sensitivity of the eye and the spectral output of the Sun. The colour temperature of the LightDrive 1000 lamp is 5700K and the colour reproduction index is Ra 79. By the way, the amount of UV radiation emitted by the lamp is lower than for sunlight. In fact, for wavelengths less than 380nm, it comprises only 84  Silicon Chip 0.14% of the total light output. A similar situation occurs for infrared radiation, which makes up less than 8% of the total output for wavelengths higher than 780nm. The low UV radiation figure means that materials exposed to the light will age at a slower rate than if they were exposed to sunlight. What’s more, the heat load will be more favourable than for sunlight due to the reduced amount of infrared radiation. These two properties mean that plastics can be used more widely under sulphur lamp illumination than they The sulphur lamp’s very high luminous intensity and near point-source construction makes it very suitable for hollow light guide applications. One of the first uses of the sulphur lamp has been in a demonstration lighting system installed at the Smith­ sonian Institute’s National Air and Space Museum in Washington DC, USA. This system was installed in August 1994 and uses three 27-metre long (266mm diameter) hollow light guides, located three metres from the ceiling and 18 metres from the gallery floor. A single 455,000 lumen sulphur lamp illuminates each light guide, with about 222,000 lumens passed into the light guide itself. The hollow light guides have an efficiency of 55% and the light is Silicon Chip Binders REAL VALUE AT $12.95 PLUS P&P Fig.3: how 3M’s light-pipe system works. The light from the lamp is reflected by the prismatic film lining the inside walls as it travels down the tube, with some of the light escaping through a fine pattern of holes along the way. Fig.4: the spectral output of the sulphur lamp closely coincides with the spectral output of sunlight. This means that objects viewed under a sulphur lamp and under sunlight have practically the same appearance. These binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf.  Hold up to 14 issues  80mm internal width  SILICON CHIP logo printed in gold-coloured lettering on spine & cover extracted from them through a fine pattern of holes in the “micro-replicated” prismatic film material lining the inside surfaces. The density of the holes varies over the length of the tubes to create the desired light distribution pattern. After passing through the holes, the light is efficiently reflected downwards by a secondary micro-replicated prismatic film located on the underside of the guide. This results in uniform, efficient illumination far beneath the guide itself. The Smithsonian system is used to light 1150 square metres and replaced 94 high-intensity discharge lamps. It delivers around 350 lux at viewer level, a figure that’s about four times higher than the original light level – all this for less than half the cost of a conventional lighting upgrade. The US Department of Energy is a financial backer of the development of the sulphur lamp and also has its own installation. In this case, a single 85-metre long hollow light guide equipped with two sulphur lamps has been used to illuminate a plaza. This installation replaced a system that used 280 high-intensity mercury discharge luminaires, resulting in a measured energy reduction of 65% and saving the DOE US$8000 annually in direct energy costs. Reduced maintenance costs are said to save an additional US$1500 per year. At the same time, the new system provides light levels that are approximately four times higher than from the old mercury discharge system. Other installations of sulphur lamp light guides have been made in European subway stations, the Hill Air Force Base in the US, at a Volvo bus and truck assembly plant in Sweden, and at an indoor karting track at Westerholt in Germany. Finally, sulphur lights are being investigated by the motion picture industry due to the light’s daylight colour and high SC intensity. Footnote: as this was written, it appears that Fusion Lighting has withdrawn its current sulphur lamp from sale, pending the introduction of a new design. Price: $A12.95 plus $A5 p&p. Available only in Australia. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard ❏ Visa   ❏ Mastercard Card No: _________________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ DECEMBER 1999  85 TECHNICAL LOOK: TEN NEW NEW! TCP/IP EXPLAINED By Philip Miller. Published 1997. $ 90 This concise and practical book offers readers an in-depth understanding of the Internet Protocol suite. It assumes no prior knowledge of TCP/IP, only a basic understanding of LAN access protocols, explaining all the elements and alternatives. It leads the reader through the Internet protocols, combining study questions with reference material. Examples of network designs and implementations are given. 518 pages, in paperback, at $90.00. LOCAL AREA NETWORKS: An Introduction to the Technology NEW! SETTING UP A WEB SERVER A complete reference for anyone setting up a web server. Covers all major platforms, software, links and web techniques. It details each step required to choose, install and configure the hardware and software elements, create an effective site and promote it successfully. The book covers the main web server software applications, how they differ, and which work best in each environment. 273 pages, in paperback, at $65.00. NEW! 65 By Tim Williams. First published 1991 (reprinted 1997). By PK McBride & Nat McBride. Published 1999. $ O R D E R H E R E 29 95                 If you want to create web pages for your business or your own home site, but don't know where to start . . . or if you have some experience of Web page design and now need to master all aspects of HTML form then “HTML4.0 Made Simple” is for you. it uses a combination of tutorial approach, carefully focussed examples and quick reference guides. 198 pages, in paperback, at $29.95. TCP/IP EXPLAINED.............................................$90.00 LOCAL AREA NETWORKS..................................$65.00 HTML 4.0 MADE SIMPLE...................................$29.95 SETTING UP A WEB SERVER.............................$65.00 THE CIRCUIT DESIGNER’S COMPANION...........$59.95 ELECTRIC MOTORS AND DRIVES......................$59.95 UNDERSTANDING TELEPHONE ELECTRONICS....$55.00 AUDIO ELECTRONICS........................................$79.00 GUIDE TO TV & VIDEO TECHNOLOGY...............$55.00 EMC FOR PRODUCT DESIGNERS.......................$95.00 THE ART OF LINEAR ELECTRONICS..................$80.00 INTERNET HOME PAGES MADE SIMPLE...........$24.95 DIGITAL ELECTRONICS .....................................$59.95 ESSENTIAL LINUX..............................................$85.00               ORDER TOTAL: $............. 86  Silicon Chip Includes grounding, printed circuit design and layout, the characteristics of practical active and passive components, cables, linear ICs, logic circuits and their interfaces, power supplies, electromagnetic compatibility, safety and thermal management. Aimed at the practising designer who needs straightforward, easy-to-follow advice. 302 pages, in paperback, at $59.95. $ HTML 4.0 MADE SIMPLE $ 65 $ THE CIRCUIT DESIGNER’S COMPANION NEW! By John E. McNamara. 2nd edition 1996. Intended for those who want to become more familiar with local area networks (LANs) without facing the challenge of a 400-page text. The goals of the book are to give prospective LAN users or purchasers familiarity with the concepts involved and to provide a head start for reading more detailed texts. 191 pages, in paperback, at $65.00. NEW! By Simon Collin. Published 1997. 59 95 ELECTRIC MOTORS AND DRIVES NEW! By Austin Hughes. Second edition published 1993 (reprinted 1997). This book is for non-specialist users of electric motors and drives. The author explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction motors (mains and inverter-fed), stepping motors, synchronous motors (mains and converter-fed) and reluctance motors. 339 pages, in paperback, at $59.95. 59 95 $ Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ___________________________________ Postcode_______________ Daytime Phone No. (______) __________________________________ STD  Cheque/Money Order enclosed OR  Charge my credit card –  Bankcard  Visa Card  MasterCard Signature_________________________ Card expiry date______/______ PLUS P&P (if applic): $.............. TOTAL$ AU.................... ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. BOOKSHOP WANT TO SAVE 10%? SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL PURCHASES! TITLES AVAILABLE! UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. $ 55 (To subscribe, see page 53) A very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $55.00. AUDIO ELECTRONICS   GUIDE TO TV & VIDEO TECHNOLOGY $ By John Linsley Hood. First published 1993. NEW SECOND EDITION 1998. 80 All you need to get started. Create and design your own Internet home pages that include both text and graphics, using this practical, easy to follow, jargon free guide. This edition has been enhanced and updated and now covers HTML 4.0. 182 pages, in paperback, at $24.95. 79 $ Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback, at $55.00. 55 EMC FOR PRODUCT DESIGNERS NEW! P&P Add $A5.00 per book – Orders over $100 P&P free in Australia. NZ: Add $A10 per book, $A15 elsewhere 24 95 $ DIGITAL ELECTRONICS – A PRACTICAL APPROACH By Richard Monk. Published 1998. $ 59 95 With this book you can learn the principles and practice of digital electronics without leaving your desk, through the popular simulation applications, EASY-PC Pro XM and Pulsar. Alternatively, if you want to discover the applications through a thoroughly practical exploration of digital electronics, this is the book for you. A free floppy disk is included, featuring limited function versions of EASY-PC Professional XM and Pulsar. 249 pages, in paperback, at $59.95. ESSENTIAL LINUX By Steve Heath. Published 1997. By Tim Williams. First pub­­lished 1992. Second edition 1996. Widely regarded as the standard text on EMC, this book provides all the information necessary to meet the requirements of the EMC Directive. It includes chapters on standards, measurement techniques and design principles, including layout and grounding, digital and analog circuit design, filtering and shielding and interference sources. The four appendices give a design checklist and include useful tables, data and formulae. 299 pages, in soft cover at $95.00. NEW! By Lilian Hobbs. First published 1996. Second edition 1999. By Eugene Trundle. First pub­­lished 1988. Second edition 1996. $ This practical handbook from one of the world’s most prolific audio designers has been updated and amended to make it the leading practical source of information for those interested in linear electronics and its applications, particularly in the world of audio design. 348 pages, in paperback, at $80.00. DESIGNING INTERNET HOME PAGES MADE SIMPLE By John Linsley Hood. First published 1995. Second edition 1999. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover at $79.00. THE ART OF LINEAR ELECTRONICS NEW! 95 $ Provides all the information and software that is necessary for a PC user to install and use the freeware Linux operating system. It details, setp-by-step, how to obtain and configure the operating system and utilities. It also explains all of the key commands. The text is generously illustrated with screen shots and examples that show how the commands work. Includes a CD-ROM containing Linux version 1.3 and including all the interim updates, basic utilities and compilers with their associated documentation. 257 pages, in paperback, at $85.00. 85 $ NEW! POST 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 D DECEMBER ecember 1999  87 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. No attack or delay I have recently built the Guitar Limiter as described in the October 1998 issue of SILICON CHIP but the attack and delay functions don’t have any effect at all. The board seems to be in order. I had noticed that the component overlay diagram on page 70 has the capacitor next to a 22kΩ resistor not marked. The circuit diagram shows it to be a 1µF electrolytic. Am I correct on that? (D. F., Salisbury, SA). • The unlabelled electrolytic capacitor on the overlay diagram is 1µF. The only reason that the attack and decay controls would not operate, apart from misplaced components, is that the gain limit control is set too high or the output level is set incorrectly. Make sure that the output level trimpot, VR3, is set as per the instructions on page 73 under “Testing”. Hybrid bridge voice circuit I have a son with a severe hearing problem. Has SILICON CHIP ever described a suitable balanced amplifier Wiring up the Waa Waa pedal I recently bought a Waa Waa Effects kit, as described in the September 1998 issue of SILICON CHIP. As I have little experience in electronics I ran into a few snags. How do you wire the slider pot, the pedal and the SPDT slider switch to the circuit? The power supply is 12V but is it possible to run it off a 9V battery? Could I possibly have run it from a DC plugpack and a battery as well, to make it more versatile? (S. W., via email) • The slider potentiometer is wired with the two end connec­ tions to the terminals marked on 88  Silicon Chip for use in such an application; ie, adapted to amplifying incoming voice without affecting the outgoing voice? He is using some wheelbarrow size gear put together by his brother from disposals rack-mounted equipment and finds it very helpful but it’s certainly not portable! This must surely be a widespread problem. I would be grateful for any suggestions that occur to you. (G. B., O’Connor, ACT). • We don’t have a balanced amplifier for phones but you might like to have a look at the Hands-Free Telephone circuit published in the September 1988 issue. It used a special Motorola IC with an inbuilt hybrid circuit. We can supply a photocopy of the article for $7 including postage. Circuit for humidity control Is there a circuit diagram available for a humidity control or where could I find one? (J. D., Mathoura, NSW). • We published a 3-function weather station, incorporating barometer, temperature & humidity, in the April 1993 issue. It used a Philips humidity the PC board overlay as “To VR1”. One lug goes to one terminal and the other lug to the other terminal. The wiper of the slider pot goes to the terminal marked “To VR1 Wiper” on the PC board overlay diagram. If you subse­quently find that the Waa Waa effect operates backwards then swap the wires to the “to VR1” terminals. If you’re not sure which pot terminal is the wiper, it can be found by checking the resistance between the terminals. The two end terminals will not change in resistance as the pot slider is moved from one end to the other. Both the spare terminals are the wiper connection. The slider switch is mounted sensor. We can supply the April 1993 issue for $7, including postage. Rev limiter for race circuit car I have just purchased the Rev Limiter Kit and Ignition Switcher (described in April 1999) to install in my mid 70s 4-cylinder car. It is a dedicated circuit racing car with a 1.6 litre full race engine (carburettors). So this project is abso­lutely ideal for the car. But I was wondering if it was possible to modify the Rev Limiter to momentarily operate at a set RPM via an additional switch. What I need is to be able to hold the engine at say 4500 RPM (using the Rev Limiter to do so) whilst waiting for the green start light. When the lights go green and therefore the race starts, the engine would be held at the 4500 RPM (or whatever) to enable a perfect start. When the car gets going and has good traction, I would then release this button and the engine would then be able to spin out fully to the set Rev limit. Would this be possible and what modifications are needed? (Paul, via email). on the PC board with the common terminal in the centre. Note that the switch can be a SPDT (single pole double throw) type. If you want to wire the switch to a panel, then simply wire it to the board, maintaining the same connections. The pedal is connected to the PC board with a stereo jack plug and three-core wire such as a balanced microphone lead. This has two cores and a shield. The shield can be the 0V supply connection. You need to use a stereo socket on the pedal so that the three wires can be connected. The circuit can be operated from either a 9V battery or a DC plugpack without any further modifications. • It is certainly feasible to modify the Rev Limiter to pro­vide a preset limit. You could arrange to have the limit output switchable between pin 1 and pin 7 of IC2 to achieve this effect. However, while it is feasible we are not sure it would be suit­able for racing starts. The problem is that the rev limit severe­ly cuts back the power and also puts unburnt fuel into the ex­ haust system which might also cause a problem if you are really tromping on the accelerator. Upgrading the plastic power amplifier I recently built an amplifier based on the 125W/175W ampli­fier module published in the April 1996 issue of your magazine. I’m very happy with the sound quality but I would like an increase in power output without necessary jumping to the 500W module published in the August, September & October 1997 issues. My idea is to increase the size of the PC board (lengthwise) and add additional wiring, etc to accommodate an extra pair of output transistors. My questions are: (1). Would adding an extra pair of output transistors allow me to deliver more power to the load (8Ω) and keep within the distor­tion figures quoted (as per the April 1996 module)? (2). Would I have to do any modifications to the driver or input stages to cope with the additional loading? My power supply consists of a 500VA toroidal transformer and six (15,000µF 80VW) capacitors. The resulting supply rails are about ±63V. I have also changed the 100µF and 0.1µF capacitors (on the circuit board) from 63V rating to 100V. Also of note, I’m running the output transistors at the moment at about 30mA each of quiescent current and the main heatsink remains very cool and the heat­sinks on the BF470 (Q6) and BF469 (Q8) are lukewarm at best. Even after running the amplifier at a reasonable volume for an hour or so, both heat­sinks remain relatively cool. (B. F., via email). • If you are only going to drive 8Ω speakers, there is little point in adding the extra transistors. Your beefed up power supply will probably mean that the amplifier will deliver about 150W/channel and this can be easily handled by the existing transis­tors. However, if you wanted to drive Repairing a faulty NAD amplifier I have acquired an old NAD 3020 integrated stereo amplifier which I would like to use. However I find that the output to the speakers is very distorted and fuzzy even at very low levels. As this amplifier is so old, it is uneconomical to send it to a serviceman and I would like to troubleshoot and repair the amplifier myself. I am a former Telecom technician (retired) and have been an electronics hobbyist for many years but have no experience what­soever in the art of “audio troubleshooting”. Can you recommend a source of knowledge in this area that I could study and/ or per­haps offer some tips which 4Ω loads, you would defi­nitely need the extra transistors. There would then be some slight degradation of the distortion figures compared with those published. Mind you, the increase in power output from a nominal 125W to 150W is only 0.8dB which is inaudible on normal program mate­rial. On balance, we would leave the amplifier as is. Generating video crosshairs I came across your articles on the Colour TV Pattern Genera­tor in the June & July 1997 issues of SILICON CHIP while looking for a requirement I have. I wish to make use of some of those relatively cheap colour CCD miniature cameras for targeting objects in a range of applications. What I need is a device to generate a crosshair pattern superimposed on the camera video that can be retrofitted inside standard video monitors to allow them to be used as fairly accurate sights. Could the Pattern Generator be configured to perform this function easily with some slight modification to facilitate gen-locking, etc? (K. F., via email). • The generator could be adapted for your application since the checker­ board pattern could be modified to provide the crosshair pattern. The project was designed to allow con- may help me to achieve my goal of restoring the sound of this excellent old amplifier? My investi­gations so far indicate the problem to be in the power stage of the unit. (A. L., via email). • We understand that AWA Distribution handle NAD products so you might be able to get a circuit diagram from them. Failing that, we would give the amplifier a close inspection to find any overheated or otherwise faulty components. Then check the base-emitter voltage of every transistor in the circuit. They should all lie in the range from 0.6 to 0.75V. Any that don’t fall in this range are probably faulty or have an associated faulty component. We can’t suggest a suitable reference book. structors to modify the pattern in Basic on a computer and then reprogram the EPROM. The information supplied in the TV pattern generator articles should be sufficient to allow you to generate your own code for the crosshair. However the unit would be too large to be housed in a cam­era. The alternative would be to program a micro­controller to produce the patterns. While the TV pattern generator used an EPROM to store all pixels and sync signals in a sequential fash­ion, the microcontroller could be more economical on memory space by having the internal timer decide when to output a pulse. The crosshair pattern and sync signals are rather basic and so the coding would be only short. The PIC16F84 may be a good contender for this application. Software for developing it is freely available from the http:// www.microchip.com site. We published a simple programmer for it in the March 1999 issue of SILICON CHIP. Frequency accuracy of audio generator I was wondering if the digital readout on the Audio Signal Generator (featured in February & March 1999) was accurate or would I need a frequency counter for loudspeaker testing? (S. B., via email). DECEMBER 1999  89 Connecting the high energy ignition system I’ve just finished constructing the Universal High Energy Ignition (June 1998) to put into my 1979 Toyota Corolla but I am having a little difficulty with the connections. I have tested the unit and adjusted the current limit adjustment as described in the text. The transistor is correctly mounted and is not shorting out on the case. In the text, it describes connecting the wires as follows: one to the coil negative, +12V from the ignition, earth to the case and then to the chassis, tacho to the tacho (I already have the electronic tacho fitted) and points to the points. The coil is a standard type with an external ballast resis­ tor, connected to a single points-type distributor incorporating a condenser and noise resistor. This is where I am having troubles. All is connected as above, but the car won’t start. Now do I have to remove the existing wire that goes from the coil negative to the • For general purpose testing the frequency accuracy is good enough. If you had a signal source of known accuracy and you were willing to tweak the timing components associated with IC11 (the 555), you could get the accuracy to better than 1%. Car stereo project wanted I am currently doing a pre-apprenticeship in electrical and we points and use the kit connections instead? If so, and I have tried this, the car doesn’t start! I have also tried it without the tacho connected but that made no difference. Can you please assist me? (T. G., via email). • The existing negative lead from the points should be discon­nected from the points. The points wire is then connected to the High Energy Ignition (HEI) input and the output from the HEI goes to the coil negative. In other words, the wire from the points in the distributor is used to trigger the HEI system and the HEI output now does the switching job for the coil primary that used to be done by the points. Probably the problem you are having is that the second set of components for the points 2 circuit is in circuit. If you are only using one set of points, remove diode D2 and the 47Ω 5W resistor next to this diode. The tachometer connection can be made to the tachometer output on the HEI or left in its original position if this oper­ates it correctly. are allowed to build a project of our own choice. I was won­dering if you could suggest a project design for a 300-400W RMS car stereo amplifier? (Justin, via email). • We have not published any 300 to 400W car stereo systems as a DIY project would be more expensive than a built-up unit such as those stocked by Jaycar. However, we have published a 600W inverter for car sound systems in October & November 1996 (Jaycar kit) and a 350W amplifier module in the August 1996 issue (Al­tronics kit). We can supply back issues at $7 each including postage. Video-audio transmitter causes picture roll I recently purchased a video-audio transmitter kit, as described in the July 1999 issue, from Jaycar Electronics. I have a picture coming through onto my monitor but unfortunately it rolls all the time. Can you suggest a cure? (J. B., via email). • The rolling suggests that the sync level is too low for the monitor to lock and maintain a steady picture. This could be due to the levels on VR1 and VR2 not being set correctly. It is recommended that both VR1 and VR2 be initially set fully clock­wise so that the maximum signal level is applied to the modula­tor. The picture may be a little washed out (excessively bright) but the locking problem should be cured. Then wind VR1 back for best contrast without rolling. Then set VR2 for best contrast if necessary. If the picture cannot be made to lock with full clockwise settings for VR1 and VR2, then it is possible that the 470µF capacitors have been inserted incorrectly. Alternatively, one of them could be faulty. Notes & Errata LED Christmas Tree, November 1999: three 0.1µF monolithic capacitors are required, not two as specified in the parts list. One of these (C6) is not identified on the PC board component diagram but is adjacent to pin 1 of the microcontroller. Also the PC board overlay shows two 15pF capacitors but these should be 27pF as shown on the circuit and parts list. 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. 90  Silicon Chip DON’T UTER COMP MISS OMNIBUS THE ’BUS! www.siliconchip.com.au SILICON CHIP’S 132 Pages $ 95 * 9 ISBN 0 95852291 X 9780958522910 09 9 780958 522910 IN LINCLUDES FEA U TUR X E A collection of computer features from the pages of SILICON CHIP magazine Hints o Tips o Upgrades o Fixes Covers DOS, Windows 3.1, 95, 98, NT o RT Do you feel a little “left behind” by the latest advances and developments in computer hardware and software? Don’t miss the bus: get the ’bus! THIS IS IT: The computer reference you’ve been asking for! SILICON CHIP's Computer Omnibus is a valuable compendium of the most-requested computer hardware and software features from recent issues of SILICON CHIP magazine - all in one handy volume. Here's just a sample of the contents: Troubleshooting your PC: what to do when things go wrong NO Choosing, installing and taming computer networks AVA W Upgrading and overclocking CPUs DIRE ILABLE C Hard disk drive upgrades, tune-ups and tips SILIC T FROM Windows 3.1, 95, 98 and NT tips and tricks ON just $ CHIP The Y2K Bug - and how to swat it 125O* INC All about Linux GST & P& P And much more!!! ORDER NOW: Use the handy order form in this issue or call (02) 9979 5644, 9-5 Mon-Fri with your credit card details. * Price includes GST 09 Index to Volume 12: January-December 1999 Features 01/99 4 The Y2K Bug & A Few Other Worries 01/99 40 4.8MW – Blowing In The Wind 01/99 73 Electric Lighting; Pt.10 01/99 86 How To Listen to Community AM Radio 02/99 4 Installing A Computer Network 02/99 18 Traction Control Systems 02/99 34 Making Front Panels For Your Projects 02/99 80 Electric Lighting; Pt.11 03/99 4 Dead Computer? Don’t Throw It – Rat It! 03/99 7 Getting Started With Linux Pt.1 03/99 82 Electric Lighting; Pt.12 04/99 4 Autopilots For Radio-Controlled Model Aircraft 04/99 10 Getting Started With Linux Pt.2 04/99 71 Electric Lighting; Pt.13 05/99 3 A Web Site That’s Out Of This World 05/99 8 Model Plane Flies The Atlantic 05/99 80 Getting Started With Linux Pt.3 06/99 4 Hard Disk Upgrades Without Reinstalling Software 06/99 12 Your Valuable Magnetic Tapes Are Dying 06/99 66 What Is A Groundplane Antenna? 06/99 77 HomeFree: Diamond’s Wireless Network 06/99 86 Getting Started With Linux Pt.4 07/99 4 Tiny, Tiny Spy Planes 07/99 10 Sydney’s Superstorm 07/99 80 CLIO: PC-Driven Loudspeaker Testing 08/99 4 Cleaning The Smokestacks – Hazelwood Power Station 08/99 78 Making Negatives From Positives – Reversing Protel PCB Files 08/99 82 Electric Lighting; Pt.14 09/99 4 Automatic Addressing On TCP/ IP Networks 09/99 9 BreezeNet: Wireless Networking Without The Hassles 10/99 4 Sharing A Modem For Internet & Email Access 10/99 37 Introducing Home Theatre 10/99 79 JBL’s TC1000 Programmable Remote Control 11/99 4 USB: Hassle-Free Connections To Your PC 11/99 39 Electric Lighting, Pt.15 11/99 56 Setting Up An Email Server 12/99 4 JBL’s 21st Century Loudspeaker Technology 12/99 10 Review: Denon AVC-A1D AV 92  Silicon Chip Surround Amplifier 12/99 64 Internet Connection Sharing Using Hardware 12/99 82 Electric Lighting, Pt.16 Serviceman’s Log 01/99 68 Philips Matchline 33CE7538/42R; Akai VP170 Video Machine; Akai CT1406A; JVC C-14K1AU; Sony VTX100M TV Stereo Tuner; Sony PD-1704S SVGA Multiscan Computer Monitor 02/99 56 NEC FS6325; Toshiba 289X9M; Teac Televideo MV1440; Philips 28GR671 G111-S 03/99 19 Mintron MTV-3001CB CCD Colour Camera; Sony KVF29SZ2 (G3F chassis); Sony KV-G21S1; NEC FS-6391 Stereo TV; VHG-105 VCR 04/99 18 Sony KVF29S; Sharp CX4814; Sharp VC-H865X; Masuda T1092; Bell & Howell VS-IC 05/99 29 Panasonic TC1401; Teac CTM-143; NEC FS-6325; AWA CT-1447AM; Mitsubishi HS338A VCR 06/99 28 Sanyo TLS-1000P Time-Lapse Video Recorder; Sharp V1 Stereo A-V System; Sanyo C14ZA25 TV 07/99 42 Samsung CB230Z; Philips 21CT8873/75Z (KR5187R) 08/99 74 NEC FS6330; Telefunken SDX290H 09/99 30 Toshiba ER-562ETA Microwave Oven; Akai CT2105A TV; Mitsubishi HS-M54(A) VCR; Panasonic NV-HD100 VCR; Akai CT-2868 TV 10/99 20 Toshiba 2529SH TV; JVC 775AU TV; JVC CX-60ME TV; Hitachi C33-P900 TV; Mac LC630 Computer 11/99 26 Loewe Studio 70 (110C91 Chassis); Sharp VC-A200X VCR; Pye Radio/Cassette/CD Player; Teac CT-M144 TV 12/99 18 Sony TVs: KV-2064EC (XE3 Chassis), KV-F29SZ2 (G3F), KV-2585AS (GP-1A), KVF29SZ2 (G3F), KV-S29SN1 (G1); Sharp SX-51F7 Computer Features 01/99 4 The Y2K Bug & A Few Other Worries 02/99 4 Installing A Computer Network 03/99 4 Dead Computer? Don't Throw It – Rat It! 03/99 7 Getting Started With Linux Pt.1 04/99 10 Getting Started With Linux Pt.2 05/99 80 Getting Started With Linux Pt.3 06/99 4 Hard Disk Upgrades Without Reinstalling Software 06/99 77 HomeFree: Diamond’s Wireless Network 06/99 86 Getting Started With Linux Pt.4 09/99 4 Automatic Addressing On TCP/ IP Networks 09/99 9 BreezeNet: Wireless Networking Without The Hassles 10/99 4 Sharing A Modem For Internet & Email Access 11/99 4 USB: Hassle-Free Connections To Your PC 11/99 56 Setting Up An Email Server 12/99 64 Internet Connection Sharing Using Hardware Radio Control 01/99 80 Model R/C Helicopters; Pt.1 02/99 60 Model R/C Helicopters; Pt.2 03/99 53 Model R/C Helicopters; Pt.3 04/99 4 Autopilots For Radio-Controlled Model Aircraft 05/99 8 Model Plane Flies The Atlantic 07/99 4 Tiny, Tiny Spy Planes Vintage Radio 01/99 88 Improving AM Broadcast Reception; Pt.3 02/99 87 The Classic Atwater Kent Model 32 03/99 78 The Radiolette Model 31/32 04/99 76 Wow! My First Vintage Radio 05/99 86 Restoring The Butchered Set 06/99 74 Restoring An AWA B15 Mantle Radio 07/99 68 A Mainland Chinese Radio Receiver From The 1960s 08/99 42 A Killer – The Set From Hell (4-Valve Operatic TRF) 09/99 53 Vintage Hifi Stereo AM Radio 10/99 76 Jim Birtchness & His Radios 11/99 68 The Case Of The Disappearing TV Sets 12/99 76 The Astor KM That Blew Its Power Plug Off! Circuit Notebook 01/99 30 9V Battery Checker 01/99 30 Timed Audible Alarm 01/99 31 Balanced Input & Bridging Module 01/99 31 PC Stake Crimper 01/99 31 Low Current Shunt Regulator Projects to Build 04/99 80 A Rev Limiter For Cars 05/99 16 The Line Dancer Robot 05/99 24 XYZ Table With Stepper Motor Control; Pt.1 05/99 37 Three Electric Fence Testers 05/99 56 Heart of LEDs 05/99 61 Carbon Monoxide Alarm 06/99 18 FM Radio Tuner Card For PCs 06/99 38 XYZ Table With Stepper Motor Control; Pt.2 06/99 56 Programmable Ignition Timing Module For Cars; Pt.1 06/99 82 Make Your Burglar Alarm System More Versatile 07/99 18 Build The Dog Silencer 07/99 26 Inductance Meter 07/99 36 Audio-Video Transmitter 07/99 60 Programmable Ignition Timing Module For Cars; Pt.2 07/99 72 XYZ Table With Stepper Motor Control; Pt.3 07/99 84 The Hexapod Robot 08/99 16 Remote Modem Controller 08/99 26 Daytime Running Lights For Cars 08/99 35 Build A PC Monitor Checker 08/99 54 Switching Temperature Controller 08/99 60 XYZ Table With Stepper Motor Control; Pt.4 09/99 18 Autonomouse The Robot; Pt.1 09/99 35 Voice Direct Speech Recognition Module 09/99 63 Digital Electrolytic Capacitance Meter 09/99 72 XYZ Table With Stepper Motor Control; Pt.5 09/99 86 A Peltier-Powered Can Cooler 10/99 16 Backup Battery For Cordless Phones 10/99 24 Build The Railpower; Pt.1 10/99 54 Semiconductor Curve Tracer 10/99 64 Autonomouse The Robot; Pt.2 10/99 82 XYZ Table With Stepper Motor Control; Pt.6 11/99 16 A Speed Alarm For Cars; Pt.1 11/99 31 Multi-Colour LED Xmas Tree 11/99 62 Intercom Station Expander 11/99 72 Foldback Loudspeaker System For Musicians 11/99 80 Build The Railpower; Pt.2 12/99 23 Build A Solar Panel Regulator 12/99 32 The PC Powerhouse 12/99 36 Fortune Finder Metal Locator 12/99 54 A Speed Alarm For Cars; Pt.2 12/99 70 Build The Railpower; Pt.3 02/99 76 24V Output For Trickle Charger 02/99 76 Timed Audible Alarm 02/99 77 Temperature Controlled Fan For Power Amplifiers 02/99 77 Bedside Lamp/Tape Recorder Timer 03/99 42 Optical Pickup For 5-Digit Tachometer 03/99 42 PC-Controlled LED Matrix Display 03/99 44 12V Charge Indicator 03/99 44 Solid State Relay Circuit 03/99 44 Simple Alarm Circuit 03/99 44 Using The LED Ammeter on 24V 04/99 46 You Have Mail In Your Letterbox 04/99 46 Relax Your Brain With Just Two LEDs 04/99 47 Random LED Flasher 04/99 47 9V Battery Monitor 04/99 47 Simple Tester Checks Transistors & Continuity 05/99 74 Add Bass Harmony To A Guitar 05/99 74 Add Remote Control To An Old VCR 05/99 76 Low Frequency RF Preamp 05/99 76 Simple Metering Circuit For Capacitance Meter 06/99 64 Logic Probe With 7-Segment Display 06/99 64 Bistable Motor Switch 06/99 65 PC-Controlled Function Generator 06/99 65 Extra Reversing Light For Older Cars 07/99 58 DTMF Decoder & 1Hz Timebase 07/99 58 Auto Nicad Charger With Float 07/99 59 Rev Limiter Modification For Points Distributors 07/99 59 Mains-Powered Remote Control Tester 08/99 70 3-Digit Frequency Counter 08/99 70 Burglar Alarm For Continuous Security 08/99 71 One Chip Audio Preamplifier 09/99 58 Dry Cell Battery Checking 09/99 58 Foolproof Audio Compressor 09/99 59 Surveillance Lights With Buzzer 10/99 74 Audio Distribution Amplifier 10/99 74 Automotive Fuse Monitor 10/99 75 SLA Battery Charger 10/99 75 18W Fluorescent Light Inverter Uses Ferrite Rod 11/99 22 Refinements To The PC Monitor Checker 11/99 23 Simple Christmas Light Tester 11/99 23 Simple Lights-On Warning 11/99 23 Negative Line Switching For Daytime Lights For Cars 12/99 30 Reverse Battery Protection With Low Voltage Drop 12/99 30 Power-On Muting For PC FM Tuner 12/99 31 Backup Battery For AC-Powered Cordless Phones 01/99 92 Vintage Radio, Dec 1998 02/99 93 Turbo Timer, November 1998 03/99 92 Command Control Decoder, May 1998 04/99 93 LED Fun, March 1999 05/99 93 Audio Signal Generator, February & March 1999 05/99 93 Electric Fence, April 1999 05/99 93 Multi-Spark CDI, Sept 1997 05/99 93 LED Ammeter, January 1999 05/99 93 Capacitance Meter, Feb 1999 05/99 93 Bass Cube Subwoofer, April 1999 06/99 93 Capacitance Meter, Feb 1999 06/99 93 Command Control Encoder, February 1998 07/99 93 Sustain Unit For Electric Guitars, March 1998 08/99 93 Line Dancer, May 1999 08/99 93 Train Controller, April 1997 08/99 93 FM Radio Tuner, June 1999 09/99 93 Burglar Alarm, June 1999 09/99 93 A-V Transmitter, July 1999 09/99 93 Daytime Lights For Cars, August 1999 09/99 93 Line Dancer, May 1999 10/99 93 Voice Direct, September 1999 10/99 93 Autonomouse, Sept 1999 10/99 93 Surveillance Lights, Circuit Notebook, September 1999 10/99 93 Switching Temperature Controller, August 1999 11/99 93 Daytime Running Lights, August 1999 11/99 93 PC Monitor Checker, August 1999 12/99 90 LED Christmas Tree, November 1999 01/99 18 High Voltage Megohm Tester 01/99 32 Getting Going With BASIC Stamp 01/99 54 A LED Bargraph Ammeter For Your Car 01/99 62 Keypad Engine Immobiliser 02/99 24 Low Distortion Audio Signal Generator; Pt.1 02/99 40 Command Control Decoder For Model Railways 02/99 66 Digital Capacitance Meter 02/99 73 Remote Control Tester 02/99 84 LEDs Have Fun 03/99 14 Build A Digital Anemometer 03/99 24 3-Channel Current Monitor With Data Logging 03/99 34 Simple DIY PIC Programmer 03/99 56 Audio Compressor 03/99 62 Low Distortion Audio Signal Generator; Pt.2 04/99 24 High-Power Electric Fence Controller 04/99 38 The Bass Cube Subwoofer 04/99 54 Programmable Thermostat/ Thermometer 04/99 66 Build An Infrared Sentry Notes & Errata 01/99 92 Old PC Power Supply, December 1998 01/99 92 Thermocouple Adaptor For DMMs, December 1998 DECEMBER 1999  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FRWEEBE YES! Place your classified advertisement in SILICON CHIP Market Centre and your advert will also appear FREE in the Classifieds-on-the-Web page of the SILICON CHIP website, www.siliconchip.com.au And if you include an email address or your website URL in you classified advert, the links will be LIVE in your classified-on-the-web! S! D E I F I S C LAS EXCLUSIVE TO SILICON CHIP! CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12 words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) 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) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­ ________________________ Card expiry date______/______ Name _____________________________________________________ Street _____________________________________________________ Suburb/town _________________________ Postcode______________ 94  Silicon Chip FOR SALE ELECTRONIC/MECHANICAL DESIGN AND CONSTRUCTION: we offer a complete design service for electronic and mechanical devices. Most work is done in house and you deal directly with the designers. No job is too small and can be to prototype or “turn key” stage, in one offs or for future production. Simply send us an email at vladimir<at>u030.aone.net.au with your questions or requirements and we will get back to you. U.P.S. 240 VAC input 240 VAC 5kVA output. Keeps appliances running after mains shutdown. $2500 o.n.o. B/C only. Phone (03) 5859 1099. WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. $420.00 complete plus sales tax if appli­ cable. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/Ecowatch ph: (03) 5968 4863 fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. RAIN BRAIN AND DIGI-TEMP KITS: 8 station sprinkler controllers, 60 channel temp monitor uses DS1820s over 500 metres. Has PC Data logging. Mantis Micro Products, http://www.home.aone.net.au/mantismp TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. Melbourne 9806 0110. MOTOROLA 68HC11EVBU EVALUATION BOARD, manuals, 2 spare 68HC711E9 $250. New 16 x 2 LCD with LED backlight, surplus from previous project $15 each. Andrew (03) 9873 7919; and_wink<at>yahoo.com.au FREE 4 Ch Automatic Event-Only VCR Controller visit www.allthings. com.au for details * VIDEO Transmitters from $142 * 120 mW IR LEDS * FREE DIGITAL PC VIDEO RECORDER - TIME LAPSE - MOTION DETECTION Software with 4 Ch Capture Card * PIR DETECTOR with concealed PINHOLE Mono or DSP COLOUR Camera, Microphone & Timer/Controller for VCR - Lights - etc from $139 * BULLET 480 Line 0.05 lux SONY CCD or DSP COLOUR from $132 * QUADS 4 Pix 1 screen from $256 HI-RES better than SUPER-VHS Quality * Modules 32 x 32 from $76 COLOUR DSP Pinhole from $155 with Tiny On-Board MICROPHONE * MINI CAMERAS 36 x 36 from $85 - SONY CCD $102 - COLOUR DSP $162 * DOME from $88 - SONY CCD $107 - COLOUR DSP $164 * Video BALUNS from $7 * DIY PAKS: 4 Cameras, Switcher & Supply from $499 - with 12" Monitor from $582 with MUX for FULL SCREEN / RESOLUTION RECORDING from $1209 * 4 COLOUR CAMERAS, SWITCHER & POWER SUPPLY from $807 - with COLOUR QUAD 4 Pix 1 Screen from $1211 * With MUX $2028 * COLOUR QUADS from $512 * COLOUR DUPLEX MUX from $1329 * 14" MONITORS from $203 - with Inbuilt 4 Ch SWITCHER from $236 * SEE-in-the-DARK CAMERAS & INFRARED 50 x 120 mW LED ILLUMINATOR Kits from $19 * ANCILLARY EQUIPMENT * DISCOUNTS * Ask for our Catalogue & New Enquiry Offer * www.allthings.com.au * T 08 9349 9413. 1/3 PRICE Heat Shrink Tubing from 20 cents 2 : 1 Shrink CSA UL 125C GP 600 Volt www.allthings.com.au KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com CHEAP 200MHz TEKTRONIX SCOPE THS-730A, “NEW” in box, factory warranty, $5899. Phone 0412 566100. C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $155.00 each. Macro Cross Assemblers and Disassemblers Need prototype PC boards? We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5F to 180F. Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Rhodes in Sydney. A genuine interest in electronics is a necessity. Phone 02 9743 5222 for current vacancies. KITS-R-US PO Box 314 Blackwood S.A. Ph/fax 08 8270 3175 FMTX2A Universal Stereo Coder $49 FMTX2B 30mW Xtal Locked 100MHz Transmitter $49 FMTX1 1-3 Watt Free Running Transmitter $49 FMX1 200mW Full Broadcast Transmitter, built & tested $499 FM220 10-18 Watt FM BGY133 Philips Linear $499 FM1525 25 Watt Discrete Linear FM Band $499 FM2100 110 Watt Discrete Linear FM Band $699 FM3000 300 Watt Discrete Linear FM Band $1499 Philips 828E/A VHF Receiver Boards (6 metres) $9 AWA 721 VHF Receiver Boards (2 metres) $9 AWA 721 VHF transmitter boards 1 watt (2 metres) $19 Philips 323 UHF transmitter boards 500mW (70cm) $19 AEM 35 Watt Little Brick Audio Power Amp $15 Digi-125 200W RMS Audio Power Amp $39 CA Clipper Compiler, new in box $49 6dBd Gain Colinear FM Band Antenna $999 Roll Smart-1 FM Station Audio Processor $999 Free catalog on disk of discounted surplus components Same day shipping, credit cards OK, circuits supplied. SPECIAL STEAM BOAT KITS $14 PRINTED CIRCUIT BOARDS for all magazine projects, then go to http:// www.cia.com.au/rcsradio RCS Radio – Bexley (+61 2) 9587 3491. AV-COMM P/L, 198 Condamine St, Balgowlah, NSW 2093. Tel: 02 9949 7417 or 9948 2667. Fax: 9949 7095; www.avcomm.com.au for above CPUs + 6800/01/03/05, 6502 and 68HC12 for $78. Debug monitors: $78 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 Simulator (fast, now incl. 80C320): $78. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $199, $37 tax, $10 p&p. SOIC adaptors: 20-pin $90, 14-pin $85, 8-pin $80. Credit cards accepted. GRAN­TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; Fax (02) 9631 1236; or Internet: http://www.grantronics.com.au NEW ROLA POTTED ISOCORE TRANS­FORMERS: 40 types suitable valve equipment. Stamped self-addressed envelope for list. The Hill Homestead, Bingara, NSW 2404. SOLAR PANELS: 120 watt $995.00, 80 watt $650.00, 60 watt $510.00, 40 watt $395.00 (all with 25 year guarantee). UNBREAKABLE PANELS: 64 watt $550.00, 42 watt $420.00, 32 watt $340.00, 11 watt $190.00, 5 watt $120.00, 1.25 watt $80.00. WIND GENERATORS: 400 watt $950.00. INVERTERS: sinewave inverters, invert- Silvertone’s RC Receiver Still the best little performer available! Still only $129.50 AM or $149.50 FM. May be used with most ppm transmitters. This and many other radio control products available from: Silvertone Electronics, PO Box 580, Riverwood 2210. Phone/Fax (02) 9533 3517. www.silvertone.com.au er/chargers, mod. Sinewave inverters, call with requirements. AUST­RALIA WIDE DELIVERY (Free on orders over $500.00). TASMAN ENERGY: (03) 6362 3050 Fax (03) 6362 3054. PC-CONTROLS: Receiver 144148MHz (PLL), DS2401 ID-Reader, Temperature Recorder (DS1615), AF Generators, Temperature measurement, I/O cards, Data Logging, ActiveX. Ph/Fax (02) 9482 1565. http://www. ar.com.au/~softmark KIT ASSEMBLY ANY KITS assembled/repaired: professional, speedy service. Phone Nev­ille Walker (07) 3857 2752. DECEMBER 1999  95 14 Model Railway Projects Shop soiled but HALF PRICE! Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) This book will not be reprinted Yes! Please send me _____ copies of 14 Model Railway Projects at the special price of $A3.95 + $A3 p&p (p&p outside Aust. & NZ $A6). 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). HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. Email: tpeters<at>pip.elm.mq.edu.au 96  Silicon Chip Advertising Index Acetronics....................................81 Altronics................................. 62-63 Av-Comm Pty Ltd.........................95 AWA Audio Products.................IFC Clarke & Severn Electronics........81 Coffs Harbour Electronics............80 Computronics Corporation..........80 Convoy International................OBC Dick Smith Electronics........... 14-17 EMC Technologies.......................80 Futurlec.........................................8 Harbuch Electronics....................29 Instant PCBs................................95 Jaycar .............................. 45-52,95 Kalex............................................79 Kits-R-Us.....................................95 Microgram Computers.......3,IBC,81 MicroZed Computers...................80 Oatley Electronics..........................9 Pinfold Health Services...............80 Printed Electronics...................... 95 Questronix...................................81 Resurrection Radio......................61 Robotic Education Products........80 RobotOz......................................81 Rocom Electronics.......................81 R.T.N............................................80 SC Binders..................................31 SC Computer Omnibus...............91 SC EFI Tech Special..................IBC Silicon Chip Bookshop........... 86-87 SC Internet Service.....................69 Silicon Chip Subscriptions...........53 Silvertone Electronics..................95 Solar Flair/Ecowatch....................94 Speakerworks..............................80 Telelink Communications.............81 Truscott’s Electronic World...........30 Vass Electronics..........................80 Willis Communications................80 Zoom EFI Special........................11 _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730.                                   
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