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  Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication       
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  Contents Vol.12, No.5; May 1999 FEATURES 3 A Web Site That’s Out Of This World Take a look at www.terraserver.microsoft.com – by Ross Tester 8 Model Plane Flies The Atlantic It’s only a model but this Australian-designed aircraft has flown across the Atlantic – by Bob Young 72 SPECIAL OFFER: Low-Cost Internet Access No time limits, no download limits, no fine print – and no hassles 80 Getting Started With Linux; Pt.3 Configuring Linux as a file and printer sharer and as a router for shared Internet access – by Bob Dyball X-Y Table With Stepper Motor Control – Page 24. PROJECTS TO BUILD 16 The Line Dancer Robot This cute little robot is easy to build and makes a great school or fun project – by Andersson Nguyen 24 An X-Y Table With Stepper Motor Control; Pt.1 Use it to control a router or for automatically drilling PC boards – by Rick Walters & Ken Ferguson 37 Three Electric Fence Testers Check your electric fence without getting a nasty shock – by John Clarke 56 Heart Of LEDS Build it for Mother’s Day. It has a microcontroller which drives 30 LEDs in a matrix, arranged in the shape of a heart – by Les Grant 61 Build A Carbon Monoxide Alarm Easy-to-build unit has two warning levels, detects CO gas concentrations down to 200ppm – by John Clarke Three Electric Fence Testers – Page 37. Just For Mother’s Day: Heart Of LEDs – Page 56. SPECIAL COLUMNS 29 Serviceman’s Log Life’s tough without TimTams – by the TV Serviceman 86 Vintage Radio Restoring the butchered set – by Rodney Champness DEPARTMENTS 2 44 53 70 74 Publisher’s Letter Order Form Product Showcase Mailbag Circuit Notebook 90 93 94 96 Ask Silicon Chip Notes & Errata Market Centre Advertising Index Build A Carbon Monoxide Alarm – Page 61. MAY 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.) Robert Flynn Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 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: $59 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 and maximum * Recommended price only. 2  Silicon Chip GPS navigation in cars How many times have you been really frustrated as you drove down an unknown city street? While I know Sydney comparatively well, there have been times when I have been completely lost, in spite of the fact that I had an up-to-date street directory open on the seat beside me. One of the big problems, in Sydney at least, is that there just aren’t enough street signs and some of the signs on major highways are downright misleading. On some long streets in Sydney, you can travel for kilome­tres without seeing a sign which clearly identifies the street you’re actually on. And many a driver has been unwittingly forced to cross the Harbour Bridge, the Harbour Tunnel or has entered a tollway because of confusing signs. I am sure that this is partly because the bureaucrats who design the signs never actually travel on the roads where they are posted. But now there is a solution in the form of GPS navigation in cars. This has been available for a number of years in up-market BMWs and in recent months has been available as a no-cost option in Hyundai Sonatas. And it has just been released as an option in Holden Commodores. The system covers Sydney, Melbourne, Brisbane, Perth, Adelaide and Canberra, as well as major high­ways. It draws information from three local global positioning satellites, maps on CD-ROM and the vehicle’s speed and direction to guide you through a maze of city streets. Your car is actually depicted on an on-screen map, with all the streets identified. And the map moves as you drive along, which is a big advance over what happens when you are using a street directory – when you change the page you have to orientate yourself again. You can set up the system to give you voice prompts along the way to a particular location and it will give you plenty of warning of up-coming turns; with calm, measured suggestions in dulcet tones. This could be a real boon for me - some of the most heated arguments I’ve ever had with my wife concerned street directions. Why is that? What is it about driving along unknown streets that causes stress with your loved one? Mind you, even with GPS navigation in a car, I’m not sure that there would not still be the occasional uttered swear word. Let’s face it: city streets will still be city streets and the traffic will still be the same. On the other hand, the GPS navigation system in the Commo­dore is pretty pricey at $4495, considering that the Hyundai Sonata’s is at no extra cost and the cost of some handheld GPS receivers is now under $300. On the positive side, this technolo­gy can only get cheaper. In the meantime, I might have to continue to make do with the street directory. Either that or catch taxis! Leo Simpson www.terraserver.microsoft.com s ’ t a h t e t i s b e w A ! d l r o W s i h T f O t u O r s Teste s o R y B Recently we came across a web site that could be described as the world’s greatest site – in the true sense of the word great, that is. www.terraserver.microsoft.com is, without doubt, the world’s largest site and its contents could truly be described as “out of this world”. With more than 1.2TB of data, TerraServer contains more data than all the HTML pages on the web combined. Hang on a minute, what’s a TB? You’ve heard of megabytes (most web sites are less than 1MB). Next up the scale is the gigabyte (GB), or 1,000MB. A terabyte, TB, is 1,000,000MB or 1,000,000,000,000 bytes. That's equivalent to about a billion pages of text or four million books. Whew! What occupies this mind-boggling storage space? Thousands upon thousands of black and white photographs of the Earth, taken from one of two satellites over the past decade or so. One of those satellites is courtesy of the United States Geological Survey and the other is from the Russian Space Agency, Sovinformsputnik. The US satellite has concentrated mainly on the United States, while the Russians are responsible for most of the rest of the world. While most populated areas of the US are covered, the rest of the world is someMAY 1999  3 MAY 1999  3 You can point and click to anywhere on the world map shaded in green (we've enlarged the map of Australia to show the areas that aren't covered). The area under the map allows you to select a number of famous places. what less represented – and patchy. In Australia, Melbourne, Brisbane and Perth are all covered but for some reason, the centre of the Universe (Sydney, to those living in it) is not. Melbourne, Brisbane and Perth readers are probably saying “rightly so!” Enough frivolity: let’s get back to TerraServer. By a happy coincidence (?), tera not only means 1012, add another “r” and you have the Latin word for earth. The surface area of the Earth is about 500 square terametres (there’s that word again!), of which about 100 are dry land. Of that, only about four square terametres are populated, the rest being mountain, desert, ice capped, farmland and so on. The Soviets have so far managed to photograph about two square tera-metres, or about half of the populated area. While some of the information is getting a little dated (Melbourne, for example, was photographed in 1991), it is still a valuable source of information for a huge variety of people. The Soviet images, by the way, are called SPIN-2, a reference to that two square terabytes. Or you search for a city/area and see if it is covered. The two columns on the right show the images from the US (left) and Russian (right) satellites. Point and click on either to load the respective image. virtually seamless precision. Those 16 photos will give you a base resolution of 16m to the centimetre. Click on an area of the photograph and the next resolution will load, this time at 8 to the centimetre. The highest resolution depends on the source of the photos: the US satellite pics are at the incredible resolution of 1m per pixel. That’s enough to pick out individual cars on a roadway but not, as you might have seen in spy movies, read their number plates or view the driver. Incidentally, such resolution, in real time, is believed to be possible from many of the spy satellites now in use. Number plates with their 100mm high letters are said to be a doddle. Fairly believable reports state that today’s spy satellites are good enough to pick up the dateline on the front of a newspaper (usually about 12-14pt type) while less believable rumours state that the latest generation of spy satellites can actually read the news- How does it work? When you access the TerraServer web site, you are presented with a map of the world with photographed areas coloured green. Click on any of these areas and the photographs for that area begin to download. When we say photographs, we mean just that: up to 16 photographs are assembled on screen with 4  Silicon Chip Melbourne's CBD as loaded from TerraServer. This is the lowest resolution image but even this is more than adequate to easily spot major landmarks – Docklands, the Yarra and the MCG, for example. We've also chosen the lowest size – this could be increased to full screen with the buttons on the left side of the screen. This montage covers roughly Ascot Vale in the top left to Richmond bottom right. paper itself (usually 7 or 8pt type!) But we digress – again. The resolution from the Russian-sourced photos is not quite as good; they are at 1.56 metres per pixel. More importantly, though, if you want to view hi-res images from the Russian source, you have to pay for them. But we imagine that most people using the site will be more than happy viewing the on-screen images (free). Hey, look, there’s our house. . . Terabytes of storage To hold, access and download Terabytes of information you might expect a system that’s a bit more than an old AT with a big hard disc. And you’d be right! The TerraServer system runs on a Digital Alpha 8400 system with eight (yes, 8) 440MHz Digital Alpha processors and a massive ten gigabytes (10GB) of memory (yes, memory!). The machine is connected to seven dual-ported Ultra-SCSI host-bus adaptors, each of which interfaces with a disc drive cabinet containing 46 nine gigabyte drives. Quickly doing a bit of mental arithmetic, 7 x 46 is 322 drives, plus the couple in the Digital Alpha 8400 – means a system with 324 drives totalling 2.9TB of storage. Using a RAID (redundant array of independent discs) setup, the drives are configured to act as four logical drives of 595GB each. SQL Server Enterprise Edition stripes the database across the four logical volume. After taking the data-management overhead into account, the array has about 2.4TB of storage capacity. And if something goes wrong, there’s a tape back-up which can handle 5TB of data. The system runs on Microsoft NT Server V4.0 with SQL Server, already mentioned. Here is the Brisbane CBD and inner west, photographed from space courtesy of the Russian satellite. This covers an area from about The Gap top left through to Kangaroo Pt in the bottom right. The white lines in the centre of this pic are where the joins between frames (automatically done on download) were not quite seamless. Enlarging up one step we find the CBD coming more clearly into view, along with the bridges over the Brisbane River. Note the shadow cast by the Story Bridge (right side) – obviously an early morning photograph. The advert (top right) helps pay for the site so it’s free for you to browse. We’ve enlarged again but this time also selected the larger view. We're looking here at Brisbane City, with the Roma Street station and goods yard along with the Brisbane River bottom left. At this scale you can start to pick out vehicles on the bridge and rail wagons. Who pays for it all? Love ’em or loathe ’em, you have to take your hat off to the people at Microsoft for getting behind this project. While the site is also supported by on-screen adverts (not too intrusive, as you’ll see from the screen grabs), it would appear that Mr Gates and his team are the money behind it. Of course, this is also an excellent advertisement for Microsoft and its operating system: if it can handle the world’s largest website 24 hours a day, Enlarged yet again to the highest resolution, this time back on the eastern City with the Story Bridge/Kangaroo Point on the right. Note the grey patches middle and lower left – these are glitches in the system which can sometimes be removed by refreshing the screen. MAY 1999  5 By way of contrast, here is an image of the San Francisco Fisherman's Wharf area, taken from the USGS satellite. There’s not a huge amount to choose from in this screen image but remember you can download a hi-res image of any of the USGS files free of charge. The Russian SPIN-2 images are also available but you have to pay for them! such as this, we want to use a system typical of that which most readers would have (we were using a midrange 486 with a pretty good graphics card and a fast [56K] modem). One of these days we’ll give it a fly on a fast Pentium II machine with heaps more “grunt” just to see how it goes. Obtaining images seven days a week, think how easy your system will work. . . Naturally, accessing Microsoft’s MSN is only a click away from the site, too. Others supporting the venture are Compaq, Storageworks and Storagetek. Once loaded, you can also move in any direction from that photo to the next (we have difficulty not calling them maps, but they are real photos) by clicking on any of the eight green arrow buttons around the edge of the pic. Accessing images But wait, there’s more! We’ve described how easy it is to “point and click” to obtain any area on Earth. But there’s more than one way to skin a dead cat, so to speak. You can also type a place name into the system’s search engine and it will find ALL places on Earth with that name. (Bet you didn’t know that there are 16 Sydneys, did you?). If the location is on the database, alongside it will be one or two clickable filenames. One column lists the USGS images, the second the Russian images. If the name is present, clicking has the same effect as clicking a location on the world map. When it loads, the name of the location is shown above the photo image. In fact, the name may be much more localised than you asked for: we loaded Brisbane by clicking on it, zoomed in and found that the name had changed to Petrie Terrace. Sure enough, our image showed the Brisbane suburb of Petrie Terrace! You don’t have to search for just a location, either: a pull-down menu lets you specify a qualifier such as river, bay, airport and so on. There are also images of famous places to view (mainly US, of course), many in superb resolution. But where is the Sydney Opera House or the Coathanger? As you might expect, the site is continually evolving and will – hopefully – contain many more areas in the not-to-distant future. A couple of negative comments, though: downloading huge files (which is what you are doing) takes a significant amount of time. And the system is by no means perfect – we found several times that one frame out of 16 simply refused to load; or one, perhaps two frames were corrupted, with “holes” in them or areas not appearing. Sometimes, the seams between adjacent frames did not quite work and a thin white line appeared. And sometimes, frames simply refuse to load. In many cases, hitting the “refresh” tab cleared these problems, but not always. It is more than possible that some of the limitations in the system were at our end. But whenever we do reports 6  Silicon Chip The vast majority of web surfers would simply visit the site to view places of interest. But if you want to obtain hi-res images, you can. If they are from the USGS satellite you can download them free of charge. The Russian images, though, will cost you (they’re actually provided by an American supplier – good ol’ capitalism strikes again!). Details are provided on the web site. If you get the impression that we’re pretty impressed with www.terraserver.microsoft.com, you’re spot on. Not just because of its awesome size and power; not just because it’s a site which will interest everybody; not just because it’s a technological breakthrough; not just because of its ease-of-use and, to use a hackneyed term these days, “user friendliness”. We’re also mightily impressed that, even if the technology to do all this was available a decade or so ago (it wasn’t!), can you imagine the Russians allowing Americans access to what would be (then) a top-secret photo library and then make it available to the world? Let’s just hope the spirit of cooperation which has seen this site evolve can find its way into other areas of technology. SC Acknowledgement: Much of the technical information in this article first appeared in the US magazine, Popular Electronics, March 1999. Screen grabs courtesy of www.terraserver.microsoft.com    ††        —  ˜  ­ †­–†   „  ‰ †­   ™†­€        ˆ— ­ •Œš›­†•Œš­‰š  ƒ  „ ™  ­˜ œ‰†ž †­ˆˆŸ   š      ‡Œ„†­ *Full details at www.tol.com.au    
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’      €‚ƒ„„„  € ‡Ž ‡ Œ•„„ ­ E & OE All prices include sales tax MICROGRAM 0599 ƒ   „ 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 When most people think of radio controlled aircraft, they imagine small models that fly around a small field. But this Australian designed and manufactured aircraft has crossed the Atlantic and performed many other record feats. The idea of a robot aircraft flying at 40,000 feet and with a range of up to 7000km takes some getting used to, especially when you realise that commercial jet aircraft fly at the same height and have a similar range. Add in the fact that this radiocontrolled aircraft has a wing‑span of only three metres and weighs only 15kg and the feat is all the more incredible. In what must be one of the leastpublicised epics for some time, the North Atlantic was crossed by the Australian-designed Aerosonde robotic aircraft in August 1998. The Aerosonde was the first robotic aircraft to cross the North Atlantic Ocean and it was also the smallest aircraft ever to do so. 8  Silicon Chip As you might imagine, for a crossing of the Atlantic the aircraft is not under radio control for most of the flight. Instead, the Aerosonde employs an autopilot and GPS fixes to guide it most of the way. So notable has this aircraft become that it is now a joint development with the US military and its future uses could be quite widespread. The history‑making Aerosonde, nicknamed “Laima,” landed smoothly on a field at the Benbecula military range in the Outer Hebrides, Scotland, after a 27‑hour non‑stop flight from St Johns, Newfoundland, Canada. By BOB YOUNG Powered by a tiny one‑cylinder 20cc engine, the aircraft autonomously guided itself across the 3200km stretch of the North Atlantic while burning less than six litres of fuel! The Aerosonde rigorously maintained a flight path approved by aviation authorities and landed exactly as scheduled while collecting meteorological data throughout the flight. The tiny aircraft is packed with computers, a communications radio, a GPS satellite guidance system and meteorological instruments. This crossing followed extensive trials held in Australia, Canada and Asia over the previous year. It followed a path similar to that taken by the first Atlantic manned crossing by Alcock and Brown. Hard to believe, but as the tiny Aerosonde makes a low pass over an airfield it could be coming in to land after a flight of thousands of kilometres from who knows where. The flight was conducted by the University of Washington and US engineering company, The Insitu Group, using aircraft purchased by the University from co‑developer Environmental Systems and Services. “We’ve flown the same mission as a $10 million unmanned craft at a fraction of the cost,” said Professor Juris Vagners of the University of Washington Aeronautics and Astronautics department. The aircraft cost $US25,000. Aerosonde development has been underway since 1992. Phase I Aero-sondes were given their full operational trial by the Bureau of Meteorology in early 1998 and passed with flying colours. In addition, Aerosonde RA have conducted several missions in Australia, Taiwan, Canada and the United States, including flights of over 30 hours and at 16,000 feet. To date over 30 Phase I Aerosondes have been delivered. Their specifications are as shown in Table 1. Aerosonde is currently working on a Phase 2 version which will have a range up to 7000km, up to 5 days endurance and a ceiling of 40,000 feet. While Aerosonde resembles a model aircraft externally, this resemblance is purely superficial. True, some components are essentially model aircraft components, however the operationing systems are structured along traditional military lines. Take‑off and landings are arranged so that manual or automatic control can be engaged. Manual control is en- gaged when the pilot plugs his control box into the computer control console. Currently, all take‑offs and landings are done under manual control. The Aerosonde uses a gyroscopic autopilot and standard model aircraft servos but the details of these have not been released. The aircraft is a joint Australian/ American design and manufacture has commenced at Melbourne. Component manufacture is contracted to a number of Australian and interna- Table 1: Phase 1 Aerosonde Specifications Wingspan: .............. 3 metres Weight: ................... 15kg Engine:.................... 20cc petrol (Avgas) Performance:........... Cruise 20‑30m/s Range:..................... >3,000km, Endurance .............. >30 hours Height Range: ........ Surface to 16,000 feet Payload:................... 1‑2 kg Operation:................ Autonomous Navigation:.............. GPS Communication:...... UHF Radio, Satellite Observations:.......... Wind, Pressure, Height, Temperature, Moisture MAY 1999  9 tional groups. Following a series of engineering demonstrators built in 1992-94, the first Aerosonde suitable for field testing was flown in June 1995. In November, the Aerosonde Development Consortium took several examples to Melville Island north of Darwin for the Maritime Continent Thunderstorm Experiment. This was primarily for engineering trials, since at the time of deployment they had flown less than 50 hours Since then, Aerosondes have come a long way. They can be used for meteorological and environmental monitoring. For example, they are able to do some very useful work in monitoring sea breeze fronts, gust fronts and storms, working with Doppler radar. Winds and thermodynamic data measured during the more interesting missions, along with more details on the aircraft, are available on the MCTEX web page at www.aerosonde.com An interesting point is that the Aerosonde cannot determine wind by the standard wind‑triangle method whereby wind is calculated directly by differencing groundspeed and airspeed vectors. This is because while it has vector groundspeed from its GPS, it does not have a heading sensor. Hence true airspeed is known only as a scalar. It turns out that vector groundspeed and scalar airspeed provide sufficient information for wind‑finding if they are compared through the course of a turn, say through about a quarter of a circle. The algorithm is given in the Aerosonde RA publications. Aerosonde flight‑plan segments therefore include a specified interval for wind‑finding S‑turns. Wind-finding requires about 10 seconds manoeuvring (spatial resolution of about 200 metres). The following flight reports downloaded from the Aerosonde web site make interesting reading: “1996: 24 HOUR FLIGHT ‑ 21st November 1996 At about 5 in the afternoon of 21 November 1996, Aerosonde Morti‑ cia landed at Geelong, having flown around the local model‑aircraft field for 24 hours at about 300m altitude. It Fig.1: this is the flight track of the record‑breaking North Atlantic flight. This consisted of a series of way points for a route that went slightly south of a great circle (shortest distance) to the landing site at DERA Benbecula Range in the Outer Hebrides. The altitude was specified at 1680m, dropping to around 150m on approach to Benbecula. Before launch, complete flight simulations had been made using winds provided by the US NOAA/NCEP model to provide approximate times at each way point. 10  Silicon Chip some tall clover. Overall the performance was quite comparable to a good manual land‑ ing. Although the landing was done under autopilot, it was not quite au‑ tonomous; guidance onto the runway centreline was done visually from the ground station rather than being left to the onboard tracker. However the test produced good results in position measurement by differential GPS, so the next step to fully autonomous landing will be straightforward.” The Aerosonde is normally launched from a cradle atop a car roof rack. Takeoff is normally under manual control but can be be completely automatic, as can the landing on a remote field. had enough fuel on board for another 10 hours or so of flying. Meteorological data were reported throughout, in conditions ranging from fair at the start to blustery, with heavy showers as a cold front moved through early on the 21st. For us this was a milestone in not only basic performance, but also reliability and readiness for routine operations. Several more such flights will have to be successful before we feel con‑ fident but certainly the program is steadily developing towards reliable and repeatable operations.” “1997: AUTOMATIC TAKEOFF AND LANDING ‑ 22nd September 1997 On 22nd September 1997 an impor‑ tant step was taken toward automatic rather than manual control of takeoff and landing. In a one‑hour test at Trout Lake in Washington, Aerosonde Millionaire flew under autopilot con‑ tinuously from launch to touchdown. Figures show the landing as plotted on ground‑station displays. The aircraft touched down smoothly on the Trout Lake runway, made one small bounce and a large‑angle yaw, and then decelerated rapidly through All in all the Aerosonde project is a credit to the dreamers who dared to make it happen. What an audacious project: to send a single engine, miniature aircraft across one of the most hostile stretches of ocean in the world. Once again we see vividly demonstrated, that by standing on the shoulders of giants, we can see past the crowds who would otherwise limit our vision. Where will this all lead? The developers envisage a global robotic airline operating out of Australia with a distributed set of launch and recovery sites (“airports” if you like) and a global command site possibly located SC in Melbourne. Acknowledgement: Much of the material in this article courtesy of Aerosonde Robotic Aircraft Pty Ltd. For more information, visit their website, www.aerosonde.com.au MAY 1999  11 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: 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 Here’s A Great School or Club Project: The Line Dancer This cute little robot is quite single‑minded: it will follow a black line on a white surface and if it meets an obstruction it will come to a stop. And to add visual interest, it has a six‑LED “scanner” which flashes back and forth and a two‑LED flasher as well. Best of all, it uses simple electronics and readily available mechanical parts. By ANDERSSON NGUYEN 16  Silicon Chip P owered by four AA batteries, the Line Dancer is an ideal high school electronics or industrial arts project, giving experience in Perspex work, metal work, electronics soldering, construction and even printed circuit manufacture if desired. The Line Dancer is roughly cylindrical in shape and has three wheels, two at the back to drive it and a trailing castor at the front to allow it to go around corners. Above the drive system is the circular PC board carrying the electronics and above that again is the battery holder. The two driving wheels are individually driven by miniature motor/ gearbox assemblies. The collision avoidance system uses ultrasonic trans­ d ucers which are driven at 40kHz. Fig.1 shows the simplicity of the circuit driving the Line Dancer. The line sensing circuit works on the principle of reflected light. There are two motors, one for each rear wheel and each is controlled by its own light- sensing circuit. So let’s look at the right motor and its sensor circuit first. When its sensor, photodiode D14, is positioned over a white (light-reflecting) background, it picks up light from the high intensity LED7 and this causes D14 to conduct. Note that the photodiode (D14) is of a type used in IR remote controls but without the IR filters and it reacts to white light. As you can see, the pho- to-diode is reverse‑biased and in the absence of light, it is non-conducting. When it picks up light from LED7, it conducts and so the voltage at the base of Q3 drops to around 0.3V or less, which turns off Q3. Therefore the collector of Q3 and pin 8 of NAND gate IC4c is high. Assuming for a moment that the other input (pin 9) to IC4c is also high, pin 10 of IC4c will be low and this will cause transistor Q2 to conduct and drive the right motor. The circuitry for the left drive motor, involving LED8, photodiode D15 and transistors Q4 & Q5, together with NAND gate IC4b, works in exactly the same way. The sensors and their respective illuminating LEDs are mounted on either side of the robot and hence are on either side of the black line. Supposing that the robot is “on track”, that is the black line is essentially in the middle, then both sensors receive reflected light from the light background and so both motors are running and the Line Dancer crawls forward. Now, when the robot encounters a curve in the black track, or deviates to one side (as it will inevitably do, particularly on long stretches of straight track) as a result of unequal motor speeds, one of the LEDs will cut onto the track, reducing its reflection. The photodiode sensor then stops conducting, becomes effectively a high resistance and the associated transistor (Q3 or Q5) switches on. As a result, the input to its respective NAND gate becomes low and the motor drive transistor switches off and its motor stops. Since the opposite motor continues to move forward, the robot is forced to rotate to the opposite side, taking the turned‑off photodiode away from the black track whereby both motors can run again. When turning 90° around a curve, this process usually occurs several times, depending on the radius of curvature. On long straight stretches, the robot will tend to zigzag a little as a result of slightly unequal motor speeds. Collision avoidance The circuit responsible for obstacle detection revolves around an ultrasonic receiver/transmitter pair. The transmitter is driven by a 555 timer operating at around 40kHz. When the Line Dancer encounters an obstacle, the 40kHz signal from the ultrasonic transducer is reflected by the obstacle to the ultrasonic receiver. Its output signal is amplified by transistor Q1 which drives a diode pump circuit consisting of diodes D10 & D11 and capacitors C3 & C4. The resulting DC signal across C4 is fed to op amp IC2 which is connected as a Schmitt trigger. The Schmitt trigger’s switching thresholds are set by resistors R4 & R8 and so if the DC voltage at pin 2 is a few volts or more, the output at pin 6 will switch low, Front (above) and rear (right) views of the Line Dancer. Only the rear wheels are driven, their drive proportional to the amount of light reflected from the underneath surface. If one photodiode detects more light than its partner it says “Hey! I'm going off course” and applies more power to its motor, bringing the Line Dancer back onto the black line. MAY 1999  17 pulling low pins 6, 9, 12 & 13 of IC4, the NAND gate package. This disables gates IC4b & IC4c, stopping the drive to both motors. It also drives IC4d which is connected as an inverter and this pulls pin 13 of IC1 high, stopping it from operating. LED scanner IC1 is a 4017 decade counter wired as a 6‑LED scanner. Its clock signal is provided by IC4a, the remaining 2‑ input NAND gate, which is wired as a Schmitt trigger oscillator running at about 10Hz. It clocks IC1 which counts up to 10 in the normal way, with each of its 10 outputs going high in succession. LED1 and LED6 are wired directly to the “0” and “5” outputs respectively but LEDs 5, 4, 3 & 2 are each wired via a pair of diodes to two respective outputs of IC1. This results in the LED array flash- ing back and forth to give the “scanning” effect as IC1 counts from 0 to 9. Three diodes in the circuit remain to be mentioned. D12 and D13 serve to decrease voltage to the motors because they are nominally rated at 4.5V, while diode D9 is connected in series with the positive supply lead from the 6V battery pack. It provides protection against a wrongly wired battery. Two flashing LEDs complete the Fig.1: the motor drive system for this robot is simple. Provided photodiode D14 picks up reflected light from LED7, Q2 drives the right motor. The same applies to photodiode D15 and LED8 which control Q4 and the left motor. 18  Silicon Chip picture and they are connected directly across the +5.4V rail. Construction This is a real hands‑on project and you will need to make a lot of the parts yourself. For this reason, we have included quite a few diagrams and photographs showing how the Line Dancer is put together. Let’s begin with the PC board assembly. The component overlay for the PC board is shown in Fig.2. Check the board carefully for broken or shorted tracks and undrilled holes before you start inserting components. Mount the wire links, resistors and diodes first, followed by the capacitors and transistors. Next, mount the ICs, remembering the CMOS items (IC1,IC3) are static sensitive. Their positive and negative pins should be soldered first, followed by the others. Watch the orientation of the scanner LEDs. They are not all oriented the same way. LEDs 7 & 8 and photo-diodes D14 & D15 are mounted on the underside of the PC board with the tip of each LED/photodiode pair being 32mm from the underside of the PC board, as shown in cross‑sectional diagram, Fig.3. Now they are not likely to be supplied with sufficiently long leads to achieve this so you will need to extend them. You can do this for each LED and photodiode by connecting each lead via a 10Ω or similar low value resistor and this can be seen in the photos of the prototype. LED9 and LED10 are used to illuminate the top Perspex sheet in the robot assembly and should be installed later, along with the ultrasonic receiver and transmitter transducers. 100mm lengths of miniature hookup should be soldered to the PC board for the ultrasonic transducers, LEDs, motors and battery supply. Look, mum, a wheelie! Maybe the Line Dancer hasn't quite got enough power to stand on end – but if it could, this is what you would see. What you don't see in this pic are the sleeves shielding the two photodiodes – these have been removed for clarity. +5.4V at pin 16 of IC1, pin 7 of IC2, pins 4 & 8 of IC3, pin 14 of IC4 and at the emitters of Q2 and Q4. If you have an oscilloscope or frequency meter, connect it to pin 3 of IC3 and adjust trimpot VR1 to obtain a frequency of 40kHz. If these test instruments are not available, the circuit is adjusted for best operation by “feel”; ie, adjust trimpot VR1 so that the LED scanner stops when your hand is brought within about 50 or 60mm from the ultrasonic transducers. Trimpots VR2 & VR3 should be adjusted to have a resistance of about 45kΩ. Motor gearbox assembly The two motor and gearbox assemblies can be purchased ready‑ assembled from any Jaycar Electronics store (Cat. YG‑2725). These are a relatively cheap variety of gearbox but any other hobby motor/gearbox which runs on 3-4.5V will suffice. An appropriate speed reduction ratio should be selected. The Jaycar gearboxes have long Initial checks With the board complete, connect the ultrasonic transducers and angle them as shown in the photos. Connect a 6V battery pack or DC supply and check the voltages around the circuit. You should be able to measure Fig.2: the component overlay for the PC board. Note that LEDs7 & 8 and photodiodes D14 & D15 are connected to the board via 10Ω resistors in each leg. (See text). MAY 1999  19 These two photos, from front and back, show Line Dancer with the battery pack and acrylic plate "1" removed (left) and the acrylic plate "2" removed (above). These will assist both PC board assembly and final construction. shafts on both sides and these need to be cut to the required length. This is done by clamping the shafts in a vice. For each gearbox, one side is cut to within 2mm of the gearbox, the other cut to protrude 15mm. The two gearboxes must not be cut identically but instead as a mirror image of each other; ie, the lefthand gearbox should have its 15mm shaft on the lefthand side and the righthand gearbox should have its 15mm shaft on the righthand side. The wheels need to be cannibalised from a cheap toy such as a “World‑4‑ Kids” Cat. 373845 which has the same wheel shaft diameter as the gearbox. Removing the wheels takes considerable force and they can then be glued to the gearbox shafts with Araldite. To ensure that the shafts don’t slip within the wheels, they should have grooves cut in them. Ensure that both wheels are equidistant from their respective gearbox and leave them aside to set. You can’t! Plainly, the only approach is to build your own. In the prototype, this was made from two sliding door roller wheels, 20mm in diameter, available at hardware stores. Both are ball bearing type, one of which comes complete with a thread- ed shaft on one side with matching nut. The other simply has a through hole for a shaft. A wheel bracket can be made using sheet aluminium or a strip of brass (see Fig.4). The bracket was then attached to the first roller wheel and secured with the nut. The second roller wheel forms the actual front wheel and was secured to the bracket using a bolt, nut and some washers. The bracket is fixed to the swivel Front wheel castor A castor has to be made to serve as the robot’s front wheel. For those who don’t know what a castor is, it is a wheel which swivels on its base, typically used under bed ensembles, mobile cabinets and other furniture. The only problem is finding one small enough to suit the Line Dancer. 20  Silicon Chip Fig.3 : this diagram shows how the Line Dancer is a stacked assembly of three Acrylic or Perspex pieces which carry the motor/gearboxes, PC board, battery pack and so on. Here is the Line Dancer fully “opened up”, showing how the motors and ultrasonic transducers are attached to plate “3”. The holes in the plate are for the sensor photodiodes and LEDs to poke through. Note (above) the small tube shields slipped over the photodiodes (removed in right photo). bearing slightly off‑centre with a nut and screw through the hole in the bracket. The drawing of Fig.4 is only meant as an example and you may construct your castor in any manner which is suitable. Remember however, that if the wheel is not completely free to swivel, then operation may impaired. The dimensions of the three plates (pieces of Perspex or Acrylic) for the Line Dancer assembly are shown in Fig.5. They should be roughly cut out with a bandsaw or coping saw. The pieces can then be trimmed to size with a bench disc sander. Holes should be drilled where indicated. Deviations in the locations of holes will result in the parts not fitting together during assembly. The two elongated holes in Plate 1 are made by drilling two adjacent holes, then opening them out with a small file. Six untapped metal spacers, three 15mm long and three 20mm, were cut from hobby brass tubing using tube cutters. If you can’t get this tubing, you can always stack groups of 6mm untapped spacers to get the desired results, as these can be purchased cheaply in quantities of 100. You will need to use the spacers to stack the three Perspex plates as shown in Fig.3. The gearbox/motor/wheel assemblies are glued to the largest of the Perspex pieces (Plate 3) using contact adhesive. The front wheel is similarly attached, being extra careful not to get glue into the rotating components. The PC board is fixed to the secA piece of tubing 8mm long is fitted ond Perspex sheet (Plate 2) using over each of the photodiodes, which the 15mm spacers and 32mm screws are hanging down from the underside and nuts. This is then attached to of the PC board. The tubing helps to the third Perspex sheet, threading limit the effect of extraneous light. the photo-diodes and LEDs through The LEDs and photodiodes are then the holes. Nuts on the underside are bent to the appropriate angle with used to hold these pieces in place. respect to each other to optimise the The nut which is to go in between the two motors will require a steady hand and a pair of tweezers. The ultrasonic receiver and transmitter are glued at the front of Plate 3, on either side of the LED scanner. They are positioned at an angle of approximately 80° to each other, as shown in Fig.6. Glue LED19 & LED20 to Plate 1 in the elongated holes. The wires from the PC board can now be connected to these, along with the motors and ultrasonic transducers. A switch (S1) is mounted on Plate 1 and power connections to the battery holder are made via this switch. The battery holder Fig.4: the front castor was made using small is attached to Plate wheels from a sliding door roller set, available 2 with double‑sided from hardware stores. tape. MAY 1999  21 Fig.6: the ultrasonic transducers should be positioned at an angle of 80° to ensure that the collision avoidance system works. reflection of light into the sensors. Remember the basic rule of optics: Incident angle = Reflected angle. To further shield the photodiodes from ambient light, you need to fit a plastic skirt to the underside of the base plate of Perspex. This can be fashioned from a couple of pieces of 80mm diameter PVC pipe and then glued to the Perspex piece. Alternatively, you could use a 90mm PVC end cap, instead of making the skirt and the bottom Perspex piece. Note that the skirt should have about 5mm of clearance above the table top or working surface. Before operation, tidy up all your wiring. You will need to mark out a large circular or roughly rectangular track using plain black electrical insulating tape on a smooth, light surface, preferably a white floor or large table. The radius of curvature of the track should not be less than 30cm and rightangle turns are not negotiable. Troubleshooting Fig.5: use this diagram to cut and drill the three Acrylic or Perspex pieces for the robot. In this project, we have used the terms “Acrylic” and “Perspex” as though they are interchangeable. While different products, either can be used for the Line Dancer (as could some other plastics). 22  Silicon Chip All things being equal, the Line Dancer should function well. However, under certain circumstances it may not behave as it should. For example, if the Line Dancer is initially adjusted to operate in a relatively poorly lit room and then operated in a brightly lit room, it may well cut across the tracks and wander off into oblivion. Trimpots VR2 or VR3 should then be adjusted to compensate for the brighter lighting conditions. If you attempt to use the Line Dancer in sunlight, it will probably not work reliably. It’s really an indoor creature and it misbehaves in intense lighting. The use of modulated infrared LEDs and IR sensors, along the lines of the Infrared Sentry project published in last month’s Resistor Colour Codes      No.    Value     4-Band Code (1%)  1    1.5MΩ   brown green green brown  1    1MΩ   brown black green brown  1    47kΩ   yellow violet orange brown  1    33kΩ   orange orange orange brown  6    10kΩ   brown black orange brown  1  4.7kΩ   yellow violet red brown  3   1kΩ   brown black red brown  1    470Ω   yellow violet brown brown  5    270Ω   red violet brown brown  4    10Ω   brown black black brown Parts List 5-Band Code (1%) brown green black yellow brown brown black black yellow brown yellow violet black red brown orange orange black red brown brown black black red brown yellow violet black brown brown brown black black brown brown yellow violet black black brown red violet black black brown brown black black gold brown REMOVE THIS SECTOR OF PCB 1 Line Dancer PC board, code 11385991 1 SPDT miniature toggle switch 4 AA cells 1 4 AA‑cell holder 2 gearbox/motors, Jaycar YG‑2725 or equivalent 2 wheels from toy car to match gearboxes (World‑4‑Kids 373845) 1 miniature castor (see text and Fig.4) 3 20mm untapped spacers 3 15mm untapped spacers (see text) 6 3mm x 32mm screws 9 3mm nuts 1 piece light gauge aluminium or brass strip, 12mm x 50mm 1 clear Acrylic or Perspex sheet, 30 x 11cm 2 pieces plastic tubing, 10mm x 5mm ID Semiconductors 1 4017 counter (IC1) 1 CA3130 op amp (IC2) 1 555 timer (IC3) 1 4093 quad 2‑input NAND Schmitt trigger (IC4) 3 BC548 NPN transistors (Q1,Q3,Q5) 2 BD140 PNP transistors (Q2,Q4) 10 1N4148, 1N914 diodes (D1‑8,D10,11) 3 1N4004 diodes (D9,D12,D13) 6 yellow high brightness LEDs (LED1‑6) 4 1000mCd red LEDs (LED7‑10) 2 green flashing LEDs (LED11,12) 2 IR photodiodes (D14,D15)(Jaycar ZD‑1950 or equiv) 1 ultrasonic transmitter/receiver pair (Dick Smith Electronics L‑7055 or equivalent) Resistors (0.25W, 1%) 1 1.5MΩ 1 1MΩ 1 47kΩ 1 4.7kΩ 3 1kΩ 1 470Ω 1 20kΩ trimpot (VR1) 2 50kΩ trimpots (VR2,VR3) 1 33kΩ 5 270Ω 6 10kΩ 4 10Ω Capacitors 1 100µF PC electrolytic 1 4.7µF tantalum electrolytic 1 0.47µF MKT polyester or monolithic 1 0.1µF MKT polyester or monolithic 1 .001µF ceramic Miscellaneous Araldite adhesive, tinned copper wire, hookup wire, solder etc. Fig.7: actual size artwork for the PC board. issue, would have alleviated this problem but it would have made this circuit a lot more complicated. If the Line Dancer cuts across the track only at certain places, check the amount of light from other sources falling on those areas. Also check that the track curvature is not too sharp and check that both VR2 and VR3 are appropriately set. The use of one and a half tape track widths in some circumstances may help with “track cutting”. Check that the LEDs and photodiodes are within 7mm of the surface and that they are angled correctly. This is crucial to the operation and minor deviations will result in failure to follow the track. Track cutting can further be limited by the use of an additional diode in series with the negative lead to the motors, ie; in series with diodes D12 & D13. This reduces the motor voltage and speed, and the reduced momentum means that there is less likelihood of the Line Dancer running away from the black track. If you have trouble finding a light coloured surface on which to operate the Line Dancer, the use of white insulating tape on either side of the black track will SC make it work. MAY 1999  23 X‑Y TABLE WITH STEPPER MOTOR CONTROL From the number of enquiries we receive it is obvious that there is a great amount of interest in machine control. With this in mind, we have produced a practical demonstration X‑Y table project using stepper motor control. It could be expanded to control a variety of processes and machines. First of all, though, perhaps we should explain what an X-Y table is because many readers may not have come across such a device before. Casting your mind back to school days, you will recall that a graph has two axes, the “X” axis, which is the horizontal direction, and the “Y” axis – not surprisingly, the vertical direction. Within the confines of the graph, any point can be located from the origin by giving its coordinates in terms of plus or minus X units, and plus or minus Y units. The origin, or reference point, is normally called (0,0), meaning X=0 and Y=0. The same logic – no pun intended (or was it?) – can be applied to locate positions away from an origin for just about anything, as long as you know the units being used. Map co-ordinates are just one example. Suppose we want to locate a position on a solid (flat) object? Exactly the same system applies. And this is the basis for the X-Y table. We lock the object – a piece of paper for drawing on, a PC board to be drilled, a piece of metal to be engraved – in position, and by either moving the object with respect to a fixed point, or moving something else with respect to the fixed object, we can move a pen, a drill, an engraving head, you name it, to an exact spot by giving it the X-Y coordinates. In this case, we cheat a little and place our origin (0,0) in the bottom Have you been wondering how to use the stepper motor driver cards we featured in the latter stages of 1997? We had this project in mind then and though it has taken a while, it has finally come to fruition. This series of articles will show you how to assemble the hardware and software to drive an X‑Y table. PART 1: INTRODUCTION left hand corner, so all points on the object are positive numbers (it just makes life easier to do it that way). X-Y tables are commonly used in a huge variety of applications from industry through to medicine and virtually everything in between. Our X-Y table is reasonably small by industry standards but it will be capable of doing quite large and sophisticated jobs. In the months to come, it will be extended so that it can be used to plot and drill PC boards which have been laid out using Protel. For the moment though, let us now describe the basic X‑Y table with stepper motor drive. An IBM-style computer is used as the interface between the operator and the table. It doesn’t have to be the latest whizz‑bang Pentium. A 486 or even a 386 will work quite well as long as it has a VGA graphics card fitted. While the slower processors Mechanical Design & Construction by Ken Ferguson Electronics by Rick Walters 24  Silicon Chip To be fully described next month, here is the complete X-Y table with a blank piece of PC board mounted in its clamps. Construction should be well within the capabilities of most hobbyists with basic metalworking and welding skills. will take a little longer to run a task, the stepping speed of the motors will be the limiting factor. Most programs, although written in GW Basic, are supplied as an EXE as well as a BAS file. The BAS file will allow you to readily make any changes to the software that you may deem necessary. The computer controls the dual stepper motor driver card, featured in the September 1997 issue of SILICON CHIP. The +5V and +12V supplies for this card can be picked up from an internal disc drive power connector or from an external power supply. The stepper motors we have used are 12V 1.8° types which with the hardware used, make four steps for a table movement of one thousandth of an inch (.001"). In some respects this is too fine, as it takes a while to traverse from zero to maximum but with the limited availability of threaded rods, this proved to be the optimum choice. Although Australia is a metric country, Imperial measurements were chosen as most PC board components are still laid out on an Imperial grid (ie, 100ths and 10ths of an inch). The outline of the table measures 750mm x 700mm and the X and Y axes can each traverse 300mm. Software details We shall describe the software first before we go onto the mechanical side, as this will be your interface while operating the table. The control screen is shown in Fig.1. This is the only screen for XYTABLE.BAS or XYTABLE.EXE and shows the current X and Y position of the table, along with a menu across the bottom of the screen. “Arrow keys X‑Y direction” indicates that the four arrow keys on the keyboard are used to move the table in the X and Y directions. The right arrow and up arrow keys increase the X and Y position, while the left arrow and down arrow keys reduce it. The next menu entry is “I or M ‑ units”. These keys select either an Imperial or Metric screen display of the current X and Y position. The metric display (Fig.2) is just a mathematical conversion of the inch value. If the Metric display is selected, then the X and/or Y co‑ordinate is changed and the table will only move to the closest converted Imperial measurement. If, for example, we commanded the table to move to 25mm it would move to 25.018mm or .985 inches. The next lower imperial step is .984 inches and this converts to 24.994mm which is less than the 25 called up. “X‑Y to set” indicates that by pressing, for example, the X key on the keyboard, you will be asked for the new X position. This message is shown in Fig.3. The value can be entered as a number with a decimal point (ie, 3.2 or 3.186) or without the decimal point (ie, 3200 or 3186). On the metric display, entering 43 will be interpreted as 43mm. You are then asked if you wish to alter the Y position. You may enter a value or by pressing the ENTER key, you can bypass this entry. Similarly, pressing the Y key follows the same MAY 1999  25 sequence in the reverse order. If values larger than the preset maximum values are entered, the table will move to the maximum and then stop. The menu shows another keyboard function key as “S‑Stepinc”. Pressing this key allows you to select Manual or Automatic control of the stepping increment in units, tens or hundreds of thou (U, T or H). After a value is selected, the arrow keys will only step in that increment. Fig.4 shows the screen with the three feed increments after M (for manual) has been pressed. If the “X‑Y to set” mode is used, the program will switch to automatic stepping and leave the feed set to the last automatic stepping increment. The automatic mode always steps in the largest possible increment (hundreds), stepping down to tens and units (if necessary) as it homes to the selected coordinate. Stepping rate All the functional keys described so far are shown in the menu bar at the bottom of the screen. There is one additional key which is not identified on the menu and this is the R key. It is used initially to optimise the stepping Rate. When the R key is pressed, the current stepping delay is shown with an invitation to change it; a bigger delay will slow the rate and vice versa. This value can be tested while running the program by selecting X or Y values an inch larger or smaller than the current position then reducing the value until the motors begin to mis‑step, then increasing it until they run smoothly again. The motors can be stopped at any time by hitting the spacebar (or any key). They will always make one additional step before stopping, as the instruction to look for a keypress is at the beginning of the stepping subroutine. There are two other keys which you may find useful. The HOME key will rapidly move the table to X=0, Y=0 when it is pressed and the END key will move the table to the maximum limits. These limits, along with a few other parameters which will be explained later, are initially written to a disc file (XYPLOT.FIL) using a separate program (XYSETUP.BAS or XYSETUP.EXE). We will not go into the details of the stepper card in this article. If you need more information, refer to the September 1997 issue. The card is allocated an address between 1 and 8 via a jumper on it and this allows the computer to control several cards connected in parallel to the one printer port. The selected address of this card is also written to the disc file. This file allows you to run XYTABLE.EXE but alter the values it uses, as the compiled EXE program runs a great deal faster than the interpreted Basic. The other parameters saved to the file are the X and Y positions each time the program is exited, the motor stepping rate, the selected measurement units and the printer port used to drive the card. Figs. 1-4 (left): these X-Y table control screens are fully described in the text. The difference between the first and second screens is that the first is imperial and the second metric – even though Australia uses the metric system, most engineering specifications are given in imperial units. 26  Silicon Chip When using this interface card, it is important that the program is loaded and run before the 12V is applied to the cards. When power is applied to the card, the outputs of IC2 may be high or low. This is a random function but if the Q0 and Q1 outputs were both high, Q1 and Q4 as well as Q2 and Q3 would be turned on, causing at least one transistor to self‑destruct. The others could also be seriously damaged. Relay modification To overcome this problem, we have produced an add‑on circuit with some extra logic and a relay to switch the +12V supply to the output transistors only after the software has set all IC2's outputs low. The circuit for this modification is shown in Fig.5. At switch‑on, both flipflops are reset by the 1MΩ resistor and the 0.1µF capacitor connected to pins 14 and 15, which means that the Q outputs are low. Thus D1 and D2 will hold the base of Q1 low and the transistor will be turned off. When the software is run, it first sets all the IC2 outputs low then takes IC1‑Y6 low and high then IC1‑Y7 low and high. These outputs are normally high but again, at power‑up any one output could be low. This is why we toggle two outputs (to be sure, to be sure). As each flipflop is clocked the Q output will go high. The 1kΩ resistor will now pull the base of Q1 high, which will energise RLY1 which feeds the 12V supply to the output drivers. If you already have this card you could build the circuit up on a piece of perf board and mount it on the PC board in the vacant area adjacent to IC2. Maximum stepping rate The maximum motor stepping rate will vary, depending on several factors: the applied motor voltage, the motors themselves and the computer’s clock speed. We need to step the motors as fast as possible but there is a problem. If the maximum stepping speed was set to suit a 486, then if the program was run on a Pentium, it would step the motors so quickly that they would not be able to respond and would just sit there chattering. We found values around 190 worked well with a 386 using GW‑Ba- sic and 1950 when using the EXE file. Use these values as the starting point for faster computers. Don’t contemplate running the BASIC program for anything but testing your software modifications as it is FAR TOO SLOW to be useful. While XYTABLE is useful for manoeuvring the table and getting the feel for the system, it is not much use if you wish to move it through a sequence of positions over and over. To this end, we have produced another program called XYREAD.BAS. This is capable of reading a sequence of positions which you have tabulated and saved as a file. It has not been converted to an EXE file as you will obviously wish to modify it to add your particular requirements to it. We have made the table move to the X‑Y position it reads from the file then the computer will beep, waiting for a keypress. It will then move to the next set of co‑ordinates it reads and beep. The opening screen for this program is similar to that of Fig.1 except that instead of a menu across the bottom of the screen, you will be asked for the name of your file. To assist you we have included a Here is a close-up of one of the two stepper motors and drive mechanisms for the X-Y table. The stepper motors themselves are commonly available 12V, 1.8° types which with the hardware used, make four steps for a table movement of one thousandth of an inch. That’s pretty good accuracy by anyone’s standards! MAY 1999  27 file named XYTEST.MOV which has a sequence of X‑Y movements. The file structure is based on that used by NC drills but without tooling information. It consists of an X location followed by a Y location. If either location stays the same on the next step only the new value is printed. A brief extract of a typical file would look like this: X04125Y008 X045 X00825Y0065 X00975 Y039 As you can see, it consists of one X‑Y instruction per line. All dimensions are based on 99.999" being the maximum allowable value, although the decimal point is omitted. Thus X04125Y008 defines X at 4.125" and Y at 0.8". If the X value was to remain the same the next entry (on the next line) could be Y00775. Trailing zeros are omitted. Once the end of the file is reached the table is homed to 0,0. This is just a precaution in case XYPLOT.FIL is corrupted, as this file stores the last X and Y co‑ordinates before the program is exited. A file like this can easily be created with a text editor using non‑document or ASCII mode to save it. We have used the MOV suffix for our file but you may choose whatever you find logical. However, you should always add a suffix, as it helps to identify or Fig 5: this add-on circuit for the stepper motor controller will prevent damage if two outputs are high at the same time. It can be built on a scrap of perforated board or even blank PC board. group files (DIR *.MOV), especially if you don’t create a special subdirectory. The seven files, XYREAD.BAS, XYTEST.MOV, XYTABLE.BAS, XYTABLE.EXE, XYSETUP.BAS, XYSETUP. EXE and XYPLOT.FIL are available free from our web site, or on floppy disc (price is $7.00 including p&p from SILICON CHIP). If you don’t have a subdirectory called BAS on your hard disc, create one (from c:\ type MD BAS then press Enter). Copy the seven files to this directory, and either add C:\BAS; in your path statement or change to the BAS directory (CD \BAS) to run the programs. Naturally, if you edit the BAS programs you can change the file location in line 6030 to suit yourself. Next month, we will give details of construction for the X‑Y table. See SC you then. This photo shows three projects: (right) the power supply for stepper motor cards (December 1997), and left, the controller for two stepper motors (September 1997) mounted in a case, together with the single stepper controller (August 1997) which will give X, Y and Z control. Whoops! Have we let the cat out of the bag? OK, an X-Y-Z table is planned for a future issue! 28  Silicon Chip SERVICEMAN'S LOG Life’s tough without TimTams I must be getting old because a couple of jobs really had me on the go this month. Fortunately, persistence won the day and I had a really good win over a recalcitrant VCR. If only I’d stocked up on TimTams . . . Panasonic are up to sneaky things – they seem to think that people cannot remember anything that’s older than 10 years and so now they are recycling their television model numbers (of course, in those days they were called National so it doesn’t really matter). This is extremely confusing for old codgers like myself who can still actually remember the original model. In this particu­lar case, it was a model TC1401. The original cost over $550 and was an extremely heavy, 14-inch, portable TV set with a white cabinet and rotary tuning (VHF only). By contrast, the beast on my bench, also a model TC1401, was a dual-speaker 34cm set with remote control and a black cabinet. It weighs just 12kg and is so light that the owner has to be careful they don’t lose their grip if they are carrying it in a heavy wind! The complaint with this one was “no memory” – I’m glad I am not the only thing that suffers from this fault from time to time! When the set was switched on, the only channel available was 1 and on opening the “Preset” menu all the channels were designated as “skipped”. They could be retuned in any con­figura­tion you wanted, with the correct TV channel numbers, but when the Preset button was pushed again all the information was lost. So the fault description at least was accurate and seeing as there is an IC (IC1104, MN12C25D) marked “MEM­ ORY”, the obvious thing to do was to replace it. I ordered in the chip, fitted it and switched on. Initially, this seemed to have fixed the problem because the set worked but then, after about five minutes or so, it failed again. Curses – it wasn’t going to be that easy. Next, I checked all the voltage rails, especially the 5V and 30V rails, but they were all OK. I even checked them for ripple using an oscilloscope but there was none. I also checked all the other voltage rails before going on to measure the voltages on all the pins of IC1104 and IC1102. There was nothing was untoward – not even a dry joint. By now thoroughly frustrated, I reordered another MN12C25D IC plus an MN151142TEA (IC1102), if only to make sure that it really wasn’t one of these chips. When they arrived, I couldn’t wait to fit them one at a time. IC1102 was a bit tricky as it is a 42-pin high-density chip but eventually they were fitted prop­erly and this time the symptoms were . . . exactly the same as before! This was definitely not the result I was looking for! What next? By now, I was totally perplexed by all this and was contem­ plating abandoning the repair. Maybe a cup of coffee would get the ol’ brain cells working again? Well, maybe it did Sets Covered This Month • • • • • Panasonic TC1401 TV set Teac CTM-143 TV set NEC FS-6325 TV set AWA CT-1447AM TV set Mitsubishi HS-338A VCR help be­cause I was closely examining the main board (rather hatefully) when I noticed that the small glass diodes fitted to it were completely different to the diodes fitted in modern TVs (like 1N4148). And as I quickly discovered from the circuit, that was because they were completely different. Surprisingly, they were germanium OA90s, a diode rarely seen these days except in the odd discriminator. Yet here was a fairly modern set using lots of them and – hey-ho – they were predominantly in and around the memory circuit I was working on. Well, this was all academic and of purely historical inter­est except, of course, one of the main reasons for the shift from germanium to silicon was reliability. Silicon diodes are much more reliable than their germanium counterparts and have better (read “less”) leakage. The only drawback with silicon is that it requires 0.6V to bias the junction, as opposed to 0.2V for ger­manium diodes. Well, I didn’t have any better ideas, so I began testing each diode in circuit on the x10 ohm range of my multimeter. The reverse leakage varied a lot between them but at least there was a difference between the forward and reverse directions until I got to D1129. This diode connects pin 5 of IC1104 to pin 20 of IC1102, the microprocessor. D1129 measured nearly open circuit in both directions and it just had to be the culprit. I rummaged around an old miscellaneous diode box and found an OA90 and fitted it. And that solved the problem – everything was now properly stored and remained that way even after the set was switched off. Without the benefit of a block diagram, I cannot tell the precise function of D1129 except to say it con­nects C2 with P32-C2 (I’m sure you are all the wiser for that bit of priceless information). I have to admit this repair was pretty fluky and I’m now off to buy MAY 1999  29 a lottery ticket. Maybe I’ll crack the jackpot? Unhappy customer Mr Burton wasn’t too happy about his Teac CTM-143 TV set. It still had the same fault as when I’d fixed it last time, or so he claimed. Well, he may have genuinely believed this but it was 1996 when I fixed it last and I don’t give 3-year warranties. And as it turned out, it wasn’t the same fault as last time. On this occasion, the set was intermittently not coming on and it appeared again to be a problem with the line drive stage in the 34cm Goldstar PC04A chassis. The previous fault allowed the set to start but it would then “go off” after a short period of time. This was caused by D402 in the 27V rail being open circuit. This allowed the driver stage power to start via D401 (18V) but because D402 was open circuit, the stage would then shut down. This time, the voltage on the collector of Q401 (KTC2230A) was 20V. Sometimes there was a kind of square wave on this col­lector, while at other 30  Silicon Chip times the waveform collapsed into a re­duced waveform with large negative spikes, which in turn produced a waveform on the secondary of T401. This was insufficient to turn on Q402 (KDS1555), the line output transistor. This was baf­fling because the square waveform on the base of Q401 seemed adequate to turn the stage on and, of course, it would have to be intermittent, just to complicate matters. To eliminate any traces of the problem I had addressed last time, I connected an external variable power supply to the junc­tion of C404 and T401 and pumped in 18-28V. It made no dif­ ference, thus eliminating the power supplies. The square waveform WF2 was correct at all times. I replaced Q401 and Q402 and the fault went away for one week but it was back again just after I had confidently given Mr Burton a quote for the fault. Next, I checked all the components in the collector circuit of Q401 and in the base circuit of Q402, to no avail. So what was I overlooking? Basically Q401 is biased and switched on by the square wave arriving via C401 (which had also tested OK) but the waveform became distorted on its collector. Why? It’s always the way; the simpler the circuit, the harder it is to find what’s wrong. The vital clue came when I monitored the waveforms with an oscilloscope. This showed that the amplitude of the waveform was much greater before R402 than after it. Certainly, the difference was much greater than I expected, considering that R402 is nomi­nally only 560Ω. When I removed R402 from the board and measured it, I found that it’s value was actually 750Ω, an increase of almost 50%. Replacing this resistor increased the waveform amplitude at the base of Q401 and the set now remained on. I soak tested it for a week and crossed my fingers when Mr Burton collected it. No TimTams It was a hot day and I was praying that Mrs Norris’ NEC FS-6325 TV set was going to be straightforward. I was running late because the previous job had taken far too long, due mainly to the client’s addiction to talking – she could talk the hind leg off a donkey! CURRENT MODEL YAMAHA LINEAR ROBOTIC ARMS AT 5% OF THEIR ORIGINAL COST , X-RAY MACHINES, HEART MONITORS, SATELLITE TV, TEST EQUIPMENT These are some of the items that may still be for sale at our Web Site. See our BARGAIN CORNER, TRADERS CORNER & FREE ADS FREE ADS should be E-mailed with “FREE ADS” in the subject window KITS OF THE MONTH COMPLETE INTELLIGENT BATTERY / POWER MANAGEMENT SYSTEM FOR THE HOME OR CAR COMING SOON New Battery Monitor Kit: 12v / 24v monitor with low voltage cut-out, audible alarm before cut-out. Designed to use minimal power & has a battery saving 12 led bar-graph indicator. Kit inc PCB, all onboard parts, label, 10A cut-out MOSFET + suitable surplus case . Introductory price of $32....For 50A MOSFET (IRFZ44) add $3. SWITCHING REGULATOR KIT: Designed to work with the above system charges battery to 13.4V / 26.8V and turn off <at>13.8V / 27.6V. Kit includes PCB + all on-board parts inc. a 50A MOSFET (space on PCB for more MOSFETS) Switching regulator $18. 29.2 28.4 FULLY CHARGED WARM BATTERY 13.8 27.6 13.4 26.8 COOL BATTERY 12.6 25.2 12.2 24.4 OVER CHARGED CHARGING NORMAL 24V 14.2 13.0 OFF 12V LIGHTING SPECIAL! INVERTER, BATTERY, CHARGER Ideal for weekenders camping or caravan, emergency lighting or a portable lantern NEW DESIGN H.P. CFL INVERTER KIT The new improved Very Efficient design uses a larger transformer & a SG3525 switch mode Chip. Can drive up to 11 X 10w CFL’s from 12vdc. Kit inc. 1 inverter & 1 CFL: $30 BATTERY: 12V / AHR, 150 X 65 X 93 mm TRICKLE CHARGER: Designed to trickle charge sealed lead acid batteries 12V 14.6 POSSIBLE WATER LOSS ON SOUND WARNING LOW VOLT CUT OUT 26 11.8 23.6 11.4 22.8 11.0 22.0 10.6 21.8 10.2 20.4 BATTERY MANAGEMENT SYSTEM BATTERY CONDITION LOW BATTERY COLOUR CCD 42X42mm CAMERAS with 1 of these lenses 3.6mm-92 deg./4.3mm -78 deg. 5.5mm60 deg. Special introductory Price of just $189 ** CCD CAMERA SPECIAL ** WITH A FREE UHF MODULATOR The best "value for money" CCD camera on the market! 0.1 lux, High IR response & hi-res. Better than most cheaper models. 32 X 32mm $99... With 1of these lenses pinhole (60deg.), 78 deg.; 92 deg.; 120 deg. or for (150 deg) add $10 MINI AUDIO MODULE - (Pre-built) This amp/pre-amp is Ideal for use with our cameras. 12Vdc, Hi sensitivity, 0.6W output operation includes electret mic. $10 4 CHANNEL VIDEO SWITCHER KIT This kit can switch manually or sequentially up to 4 audio/video sources. Other features inc. VCR relay output to switch STOP/REC, can be switched with PIR or alarm system inputs Add a security channel to your TV using a UHF modulator, watch TV & flick channels & see who’s at the door or what the Kids are doing. This unit can be switched automatically using the PIR units below. Kit +PCB+all on-bourd components inc. 18 relays. Less than Half price of most units $50. Optional VHF modulator / mixer $18 MINI PIR DETECTOR PCB MODULE (G66) Pre-built 30mmX34mm PIR module with an attached Freznel lens & cable with 4 pin connector Ideal for switching cameras, alarms etc. bargain at just: $18 POWERFUL IR ILLUMINATORS With strong universal swivel mount & 50X50X50mm housing:10 LED $10... 30 LED $20...80 LED $36 VCR CONTROLLER KIT: Ref: SC Sept 97. With our Trigger Kit, a ready made USED PIR Detector & Learning Remote Control you can trigger any domestic IR remote controlled VCR to record human activity within a 6m range with a 180deg. view. Starts VCR recording at the first movement & stops a few min. after the last movement. No connection needed to your existing VCR. This kit has Relay outputs, easy to interface with a VCR / Remote Control. PCB and all on board parts:$25. A suitable miniture used PIR Detector module:$16. Inverter kit with 1 CFL $22 Battery $25 Trickle Charger $6 One of each $58 Extra CFLs $12 Made in 98, worth $1800!! Made for a govt. contract that failed. Use it “as is” or “Pull it apart” to recover: SIX MINEBEA STEPPER MOTORS, 2x4 wire type 23LM-C355-38V 50x55mm, 3x4 wire type 17PM-H303-04V 37x 42mm, 1x4 wire type 17PM-M007-02, 42x33mm, PCB WITH SGS STEPPER DRIVER ICS. POWERFUL, COMPACT, SW.-M0DE P.S. WITH FAN: 240V input, output: 1+5V/8a, -12v/ 1.5a, +12v/1a, +32v/4a. NUMEROUS OTHER PARTS: Include 24 PIN PRINT HEAD, OPTICAL SCANNER, CPU, EPROM, matching BELTS & PULLEYS, two GEARED MOTOR ASSY’S with micro switches, MAINS FILTER etc. etc. UNBELIEVABLE PRICE: $36 < < BEST VALUE $1 CLOCK WITH CALENDER AND TIMER 12V DC 12Hr. clock for automotive / for our famous wiring kit with any order domestic/ timer use, large (13mm) Green PERSONAL POCKET ORGANISER LED display, AM-PM indicator, Date, Stores Phone Nos. etc. plus Memos, Month, 24Hr. Alarm, 59 Min. sleep timer, Calculator, Clock SPECIAL PRICE $8 back up batt. Xtal controlled 50Hz (20ms) clock can also be used for CRO calibration OATLEY ELECTRONICS MODE OFF 02- 95843563 &inverters. Can switch external load during Alarm/timer, 0.5A load directly, or 7 A 8 B 9 C x D RCM E DAY F T/SETG SHIFT 10A with extra MOSFET, Alarm piezo _ DEL 4 H 5 I 6 J : K M- L PM M N speaker provided. _ INS # M+ 1 O 2 PCB & all parts kit, S U P 3 Q R T _ = Suitable surplus + 0 V W % X Y Z SPACE ENTER CE/C used box, swivel N E W * * * N E W * * * N E W***NEW mount:$14,12A PELTIER CONTROLLER: This kit is a swmosfet: $4, Small mode design & correctly controls temp. of MM5382 Piezo speaker to peltiers to 10A (very efficient design) PCB suit $1extra, Data + onboard parts + new surplus case. $15 sheet for LSI IC H AV E Y O U M A S T E R E D P I C (MM5382): $0.80 PROGRAMING?...TRY OUR OPTO PACK 104 devices: various colours P R O F E S S I O N A L . P I C M I C R O & types. Top brands. Siemens etc. just $10 PROGRAMER KIT. VISIBLE LEDs...5mm...14X Yellow clear, Programs up to 39 Different 8, 18, 28, and 6X Red (clear) 24deg, 2X Yellow (clear) 40 pin types of PIC chip. Quick Easy 24deg, 16X Red (clear) 24deg,38X Green construction and uses serial programing ( c l e a r ) 2 4 d e g . V I S I B L E L E D s . . . method via your Pc’s parallel port and 3mm...14X Red diffused 70deg. 4X 3mm uses BOJAN DOBAJ’s software that or rect. Yel. diffused 70deg SPECIAL...1X works under Dos, Win3 & 95. Kit inc PCB 5mm IR,3X 3mm Clear Phototransistor, 3X plus all 5mm Phototransistor, 1X IR RX module. on-board 2X DIL rect. black PIN Photodiode. parts FOG MACHINES....... JUST ARRIVED but no PIC Professional quality fog machines. This chip Just:$25... unit would be the perfect 16F84 PIC chips $12 to our laser KEY-CHAIN LASER POINTER F R E E * * * F R E E * * * F R E E partner light shows, Ideal 650Nm High quality machinA s k f o r a f r e e t u n a b l e for discos, ed metal housing parties, fashion balanced mini VHF Astec parades LASER MODULE etc. brand Hi quality modulator A special price of $199 650Nm as used in the above pointer. (Lm2) with any camera order. PELTIER EFFECT DEVICES Make a solid state food cooler / warmer for NSW new laws may apply soon Connection Diagram supplied the car etc. with 2 heatsinks, a fan and one SHOP MINDER / IR FENCE of the following. Could be used for cooling IR transmitter & receiver kits (two separate overclocked PC CPUs. All 40 X 40mm. PCB’s), basic range is up to 20M but can PO Box 89 Oatley NSW 2223 4A T 65deg. Qmax 42W $25 be greatly increased by adding a lens. Ph ( 02 ) 9584 3563 Fax 9584 3561 6A T 65deg. Qmax 60W $27.50 Output to drive piezo buzzers or relays etc. orders by e-mail: oatley<at>world.net 8A T 65deg. Qmax 75W $30 2 PCB’s + all on-board parts: $17. 2 suitwww.oatleyelectronics.com Device comes with instructions to build able boxes + 2 swivel mounts: $6, Buzzer: major cards with ph. & fax orders, cooler / heater plus data. Some used $3, 12A relay: $3 (fits on PCB) Lens: $0.80 Post & Pack typically $6 surplus heatsinks avail. NEW SUPER LOW PRICE + LASER CIGARETTE LIGHTER PLUG & LEAD AUTOMATIC LASER LIGHT SHOW KIT: With LED indicator, Fuse and small internal PCB. MKIII. Automatically changes every 5 - 60 secs. Countless great displays from single Space for small projects like voltage regulators etc. to multiple flowers, collapsing circles, 10 for $4 or 100 for $30 rotating single and multiple ellipses, stars, CURLY CORD (two core) etc. Easy mirror alignment with “Allen With STD 2 pin MOLEX connecter & DC plug Key”. Kit inc. PCB, all on board comp10 for $2 or 100 for $12 onents, three small DC motors, mirrors, VOLTAGE REGULATORS (7812) 70c Ea. or 10 for $5 precision adjustable USED 27C256-20 EPROMS mounts: HUGE WEB SITE SALE mirror $1.20 Ea. or 10 for $8 (K115) + very FROM JUNE 4th. until JUNE 7th bright 650nM QUALITY DYNAMIC MIC INSERTS SHURE brand MC125 $2 Ea.- 4 for $10 MORE INFO ON OUR WEB PAGE laser (LM2) module. . 4 2. 34 Printer ribbon to suit $5, extra. Delivery to most Aust. cities $12, . box approx. 0.25 CM - 15Kg MORE INFO, LINKS AND PHOTOS IN BARGAIN CORNER ON OUR WEB SITE NEW MOSFET VERSION OF OUR 1/2/3 AXIS CNC(computer numerical control) SYSTEM. This system includes a new stepper motor driver kit (one kit required for each axis) designed to be used with software freely available on the Internet for use with home or professionally built a milling machine, lathe, engraver or cutter etc. with home & limit switches & a high degree of accuracy (can be better than .001”. We supply the kit inc. Pcb all onboard parts etc. plus Internet resources for shareware software & building or buying mechanical components. Around $40 per axis. Call for details. BUILD YOUR OWN COMPUTER CONTROLLED 2/3 AXIS CNC MILLING MACHINE / ENGRAVER OR PEN PLOTTER: Using the parts of the above printer, with the above stepper drivers and software and with the addition of about $10 worth of materials from your local hardware store you can build the machine of your choice. Plans/notes on floppy for an A3 plotter and a 2/3 axis mill:$9. PLANS/NOTES ON FLOPPY $9 $25 $18 $14 OATLEY ELECTRONICS BULK BUYS BRAND NEW GERMAN MADE DUAL PRINTER / SCANNER MECHANISM $59 **LOOK** LOOK** LOOK** NEW STEPPER MOTORS 30 oz./in. torque, 2.5 deg. 144 step, low voltage, compact 57 x 38mm: $14 COMPUTER CONTROLLED STEPPER MOTOR DRIVER KIT can drive larger motors, Has optoIsolation. Inc. Software & notes: $40 Or $50 with two Used 23 frame 200 step 1.8 Deg. motors!! CHECK OUR WEB SITE FOR DRIVERS KIT MADNESS SPECIALS 20A DC MOTOR SPEED CONTROL: $15.FM TRANSMITTER MKII: $15.1 CHANNEL UHF REMOTE CONTROL KIT: $35.2 CHANNEL UHF R E M O T E C O N T R O L K I T: $ 4 5 . . 8CHANNEL IR REMOTE CONTROL KIT: $30...LOGIC PROBE:$8...INFRA RED TESTER: with case $7STROBE KIT: $6...UV MONEY TESTER: $6 UNIDIRECTIONAL ELECTRET MICROPHONE: With tie-clip, plug and lead. Aplication notes supplied $4 SC-MAY-99 Serviceman’s Log – continued Anyway, if this next job was easy, I could still make it back to the workshop in time for a leisurely cup of coffee and a couple of “TimTams” before knocking off for the day. When I arrived, I quickly unscrewed the back and it was easy to see why the set was dead – F601, a 2A mains fuse, was as black as the ace of spades. I unplugged the degaussing coils and measured the resistance across the bridge rectifier – it was still nearly a complete short circuit. By following the path from the bridge rectifier, I soon established that IC601 (STR­ 41090) was short circuit and hopefully the cause was due to the obvious dry joints on C609, the main tuning capacitor. As luck would have it, I had a new STR41090 in the van. I quickly ran out, found it, shot back into the house and replaced it before you could say “Micky Finn”. I then switched the set on and prayed hard but nothing happened. It looked as though I was snookered. Suitably chastened, I turned the set off and measured the main HT voltage across C609. It was still 340V which told me that the circuit was stable DC wise but wasn’t starting up. I desperately looked around and saw a 1MΩ resistor (R607). Hoping that this was the critical startup bias resistor, I replaced it and switched on again. Much to my frustration, there was still no response – my TimTams were melting away as in a mirage. That was when I spotted that R610 had a little chip missing from its body. There was enough of it left to determine that it was once a 1Ω resistor. I measured Q601 (sandwiched between R610 and R607) to find that it was short circuit as well. I tore back out to the van, rummaged through the mess in the back, found the parts I needed (miracles do happen) and rushed back inside and fitted them. This time, the set fired up and the picture and sound 32  Silicon Chip were good. Thank you God, thank you. I quickly scribbled out the bill, put the back on the set, hopped in the van and shot back to the workshop. I went straight for the percolator the minute I got back. Great; there was still some coffee left but what – NO MORE TIM TAMS. Life lost all its meaning! Predictable trouble Mike Tester’s (the name is changed to protect the guilty) AWA CT-1447AM was always going to be trouble. You see, Mike always fancied himself as a technician and he also lived near the sea. This combination meant his set was always breaking down and he was the kind of guy who liked to have a go. Well, this time there was no picture but the sound was good and there was a raster with the on-screen display working OK. Anyway, it looked as though he had lost only the video between the IF detector and chrominance/luminance decoder IC. As he is a good friend of mine – despite his foibles – I tried to help him over the phone but I really didn’t have a clue as to the exact cause of the problem. Initially, I told him to check all the voltage rails, especially those feeding the signal circuits. This he dutifully did but everything measured fine, so I told him that the only course of action was to feed in a signal from a colour bar generator and trace it through with an oscilloscope. After a bit of coercion, he finally agreed and dropped the set off at my workshop. When I removed the back, I could see how rusty the whole set was from the salt air. I started by confirming everything he did by checking all the voltage rails. These all proved OK, so I hooked up the oscilloscope and followed the video from the video detector (pin 10 of IC101, MS51496P) through to Q1A0 TP12 (wave­form 1), thence to LC201 DL/BPF and finally to pin 18 of IC201 (M51412SP). After that the scent became very cold. I then spent an inordinate amount of time examining the contrast control circuits but got nowhere. By now I was beginning to think that the fault was somewhere in the beam limiting cir­cuit. I started at pin 8 of the flyback transformer and traced the circuit until I got to the two beam limiting test points designated PT1 and PT2. It was then that I noticed that R555 and R556 were badly corroded. I de­ soldered them and measured them to find that they were both nearly open circuit. Replacing them fixed the problem completely but I had to warn Mike to keep the set dry, otherwise it wouldn’t last very long. Unfortunately, he didn’t listen too well and within another three months the set was worse than before and he was forced to bin it. A Heath Robinson job Mrs Daniels, a widower living in a housing commission flat, was a very keen soap watcher and loved to record her serials every day on her beloved Mitsubishi HS-338A video. She first brought it in complaining of poor fast forward and rewind, which just turned out to be belts and tyres, but a month later it was back. This time, the complaint was “snowy pictures”. At the time, I felt sure it was just dirty heads but after cleaning them vigorously I came to the conclusion that the heads were worn out, especially as (with the same tapes, at least) I was getting almost clear pictures with Pause/Freeze Frame/Still. I removed the heads and checked them on my tester to find that they were indeed low – enough, I thought, to be causing the problem. When faced with the news, Mrs Daniels was very stoic, accepting that as it was in use every day, the heads were bound to wear out eventually. And although she could hardly afford new heads, she would find a way to come up with the money as it really was her main source of entertainment. I ordered in the new heads, fitted them and confidently switched the machine on. To my horror, I found that the problem was just as bad as before, although the picture was still OK when paused. It was obvious that I had misdiagnosed the fault. I got the CRO out and examined the FM envelope at TP-2A to find half of it missing. It was unlikely to be the new heads but it could be the head amplifier IC, the switching pulse or worse still, the toroidal transformer inside the drum itself. Using the second channel of the CRO, I quickly established that the switching pulse (FF or flipflop on pin 2 of IC201 M51473P) was exactly in phase with the FM envelope switching. From there, it didn’t take long to find that the toroidal trans­former primary measured 100kΩ between pins 1 and 2 of plug SB. I removed the entire drum assembly, then removed the drum motor and upper transformer to reveal the lower primary coils glued to the bottom with – yes, you’ve guessed it – the notorious brown glue. There was nothing that could be done to fix it as the coils were only accessible on the underside and the transformer was glued too tightly to the base. Unfortunately, the trade cost of a complete drum assembly was a prohibitive $416.18 (if indeed it was available), so I tried to obtain a junked machine from one of my colleagues in the trade. Two heads or three When I enquired, one young technician asked me whether it was the 3-head version (which it is) or the earlier 2-head HS337A. At first, I didn’t quite realise the significance of his question but he went on to suggest that I substitute the pause head and Fig.1: this diagram shows how the connections to the transformer windings inside the drum were modified. Fig.1(a) is the original circuit, while Fig.1(b) is the modified circuit. Fig.1(b) also shows how the leads to the heads were modified on the top of the drum. Fig.2: here’s how the connections to the head terminals on the top of the drum were modified. The pins were desoldered from the PC board at all points marked A and B and the two pins at A then connected to pins C using short lengths of insulated wire. This photograph shows the modified drum assembly. Amazingly, it worked and produced quite a good picture. its winding for the open circuit winding. At first I thought that this was an absurd idea, knowing the tolerances these heads are made to, but having had no success in obtaining a second­ hand drum assembly, I decided to at least give it a try. First, I completely reassembled the drum, refitting the old heads in the process. I then fitted two jumpers across the toroidal transformer primary windings, connecting the pause head on wind­ing (L1) in parallel with the open circuit winding (R). There was an added complication in that the open circuit winding (R) shared the centre tap with the good winding (L). I now had to guess which head was which on the upper drum, as they are not marked anywhere. The pause head is L1 and I reasoned that this would be mounted close to play head L, which would be diagonally opposite head R. I then unsol­dered head R, fitted two links to the pause head winding (L1) and tried it out. It made no difference, which meant that I probably had the L and R heads mixed up. Next, I assumed that the heads were arranged as shown in Fig.2, with the R head adjacent to the pause head (L1). I then rearranged the leads as shown so that the active heads were L and R but I still didn’t really expect it to work. However, I was thrilled to see that it actually did work and what’s more, the pictures were pretty good. Even more surprisingly, the pause mode wasn’t bad either. I then made a recording and played it back and the picture was still quite acceptable. Frankly, I was amazed that this had worked at all and I am full of praise for my friend. Obviously, it isn’t perfect but Mrs Daniels thought it was acceptable under the circumstances, especially as I didn’t charge her for the new heads and put them SC back into stock. MAY 1999  33 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 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 3 ELECTRIC FENCE TESTERS By JOHN CLARKE Do you need to test your electric fence to see if it is working? You could try the wet grass trick but then again you might get a shock. Why not build one of these three electric fence testers instead? MINI MIDI MAXI MAY 1999  37 I t’s all very well having a fancy electric fence installed to keep animals corralled but how do you know if it’s working properly? By the time you discover that the fence has a fault, you could be faced with a real roundup job. Of course, electric fences are not only used to keep ani­mals in a paddock but are often also used to keep animals away from a conventional fenceline. This particularly applies to horses. If the fence uses a large wire mesh, it’s all too easy for a horse to become entangled in the wire, panic and cause itself a serious injury. In fact, unless a trapped horse is released fairly quickly, it can die. One common way of testing an electric fence is to use the wet grass method. The technique is simple: all you have to do is take hold of a short length of wet grass and touch it against the fence. Because the wet grass is somewhat conductive, you’ll get a bit of a belt if the fence is working but the shock won’t be anywhere near as severe as if you touched the fence with your bare hands. The drawback with this method is that it’s a bit hit and miss. Because you’re (hopefully) only getting a “bit of a tingle” through the wet grass, you can’t tell how much “bite” the fence really has. That’s why some hardy souls choose the direct touch method but it’s not one that we recommend. If the fence is func­tioning properly, it will bite like a Northern Territory croco­dile. A far better way is to use one of the three electric fence testers described here. They will quickly indicate whether or not the fence is working and also indicate its effectiveness. For example, although the fence controller itself might be working correctly, there may be problems with the installation that make the fence ineffective. Common faults include poor conduction of the earth stakes, shorts between the high tension (HT) wires and ground, and breaks in the line. Shorts can be caused by long, wet grass brushing against the HT line and/or faulty insulators. Sometimes, the further away you get from the controller, the less effective the fence becomes. This commonly occurs if wet grass is loading down the controller’s output. It’s possible too for one section of the fence to go completely “dead”, due to a break in the line. For this reason, it’s a good idea to check all sections of the fence on a regular basis. Unfortunately, you can’t use a standard multimeter to test an electric fence. This is because the peak voltage on the fence can be as much as 10kV, with each pulse only lasting for 1ms or less. What’s more, the pulses only occur once every second or longer. So while there may be a significant amount of energy in each pulse, the multimeter does not integrate this into any mean­ingful reading. This is particularly true for digital multimeters which have a one or 2-second response time. These three fence testers can be used as more reliable aids for fence maintenance and, best of all, they do not induce an electric shock into the operator. Each contains a “light” which flashes to indicate fence pulse operation. Which one you use depends on what you want to do. We’ve called our three Electric Fence testers the “Mini”, the “Midi” and the “Maxi”. The first unit flashes a neon lamp each time it detects a pulse on the fence, while the second unit can measure the fence peak voltage (up to 10.8kV). The third unit is designed for permanent installation on the fence and flashes periodically if the fence is operating correctly. All three units are powered directly by the electric fence being tested. That way, there are no batteries to replace or leak if the unit has been left unused for some time. OK, let’s take a look at each of our fence testers in turn and find out how they work. WHY AN ELECTRIC FENCE TESTER? This project grew out of necessity: we needed a means of testing the output of the SILICON CHIP Electric Fence Controller, featured in last month's (April ’99) issue. We called for volunteers around the office to act as a tester using the old fingeron-the-fence-and-hope-itdoesn’t-hurt-too-much routine. But there were no takers! (Even Ross Tester refused to live up to his name . . .) So we looked at ways of testing the electric fence with38  Silicon Chip out getting a belt and found that there were several ways to do it – hence the three projects featured here. Incidentally, if all this talk about electric fences and controllers is foreign to you, it’s probably because you missed out on last month’s issue of SILICON CHIP. The high power electric fence controller shown here was described in detail in that issue. It’s easy to build, costs a fraction of commercial controllers . . . and back issues of the magazine are still available for $7.00 including P&P – a bargain in anyone’s language. “Mini” Electric Fence Tester Fig.1 shows the circuit of the Mini Electric Fence Tester. It is a low-cost unit that’s easily carried in a shirt pocket and can be quickly used to indicate whether or not a fence is work­ing. This is the simplest of the three units and uses just a neon indicator and three 330kΩ resistors. These parts are all mounted on a small PC board and there are two contacts, one at each end. In use, one contact (the finger pad) is held in the fingers and the other is touched onto the electric fence wire. If the fence is operating correctly, the neon indicator will briefly flash each time the HT wire is pulsed. The total resistance in series with the neon indicator (3 x 330kΩ) limits the current flowing from the fence and through your body to ground. In practice, this current is so low that the pulse will not be felt. Note that the light output from the neon indicator is quite low and you may need to shield it from sun­light so that it can be properly observed. By the way, this circuit is somewhat similar to the neon test screwdrivers that are sometimes used to test for mains voltages around power points and light switches. Do not, under any circumstances, use the Mini Electric Fence Tester to check for mains voltages. It’s not designed for this role. Conversely, do not use a test screwdriver to check the operation of an electric fence. This is because they are not rated for electric fence voltages and the resistance in series with the neon indicator may break down. Once damaged, the test screwdriver could present a serious electric shock risk if it is then used on the mains supply. Fig.1 (above): the mini electric fence tester is simply a neon lamp in series with enough resistance to stop you getting a belt! Building it Fig.2 : the PC board layout. Construction is simplicity itself! The hardest part will be soldering the wire loops. Fig.2a shows the assembly details for the PC board (code 11303994, 45 x 20mm). Install the parts as shown and make some wire loops at each end for the contacts. We used paper clip wire for the loops and soldered this directly to the copper pads. Alternatively, you could use small screws and nuts to Fig.2a : you hardly need a PC secure the wire in place. This latter board pattern as it is so simple method will ensure that the copper – but here it is anyway! pads don’t come adrift due to strain from the wire loops. Once the assembly is complete, the PC board can be wrapped in some clear heatshrink tubing, leaving the wire loops exposed. It’s not easy to see any components through the heatshrink but this photo gives an idea of construction. Parts List Mini Electric Fence Tester 1 PC board, code 11303994, 45 x 20mm 1 neon indicator, pigtail type 1 80mm length of 1mm diameter tinned copper wire or paper clip 3 330kΩ 1W resistors 1 45mm length of 25mm diameter clear heatshrink tubing MAY 1999  39 “Midi” Electric Fence Voltage Tester The Midi Electric Fence Voltage Tester is a slightly more elabo­rate instrument than the Mini Tester. It also uses a neon indica­tor but in this case the fence voltage can be read off a cal­ibrated scale after adjusting a single control knob. As shown in the photo, the unit is housed in a small plas­tic case and a small hole in the front panel allows the neon indicator light to be seen when it flashes. As before, the light output is quite low and you need to watch closely to see the flash. Fig.3 shows the circuit details. It’s really very simple and consists of a voltage divider and the neon indicator itself. In operation, the electric fence voltage is applied to a series string of 19 10kΩ resistors which in turn feed a 10kΩ potentiome­ter (VR1). The divided voltage is then tapped off from VR1’s wiper. Why use so many 10kΩ resistors? The answer is that they are necessary to provide a sufficient voltage rating for the divider, which could encounter fence voltages up to 10kV. Fig.3 (left): the midi electric fence tester is essentially a voltage divider across the fence high tension. The neon lamp glows when the fence voltage matches the scale voltage selected by the potentiometer. Fig.4a (above): the component layout on the PC board. Note the comments in the text about reversing the lead connections: you have been warned!!! 40  Silicon Chip Housed in a small utility box, the midi electric fence tester is ideal for occasional testing. The probe is as used in a multimeter. VR1’s wiper applies the divided voltage to the neon indica­tor via two 2.2kΩ resistors, while the common side of the circuit is connected to the ground stake on the electric fence. A neon indicator will light when the voltage across it reaches about 90V and so we use this characteristic to calibrate the potentiometer (VR1). If the wiper is wound fully towards the 10kΩ resistors, then the divider ratio is such that the neon will flash when there is 1.8kV on the electric fence. Conversely, as VR1 is wound towards ground, the division ratio increases and so the input voltage from the fence needs to be higher than 1.8kV in order to light the neon indicator. Let’s say, for example, that VR1 is set to its mid-posi­ tion. In that case, the fence voltage needs to be at least 3.6kV to make the indicator flash. One small complication with this circuit is that it will not produce reliable results unless the body of the potentiometer is well grounded. If this isn’t done, the neon indicator conducts the fast rise-time fence voltage into the air and hence shows a small flash, even if the pot is wound fully down. Although the pot body is grounded on the board via a PC stake (and ultimately to the fence ground), the inductance of the ground lead is enough to cause problems with fast rise-time voltages. For this reason, we have specified a metal knob for the pot so that it can also be grounded via your body. In practice, this means that measurements must be made with your hand holding the metal knob, to 99% of the assembly work in this project is soldering resistors! Fortunately, most are the same value. prevent false readings from occurring. When using the tester, the pot is initially wound fully clockwise and gradually backed off until the neon indicator just begins to flash. The fence voltage can then be read directly off the scale. Note that the overall resistance of this tester is 200kΩ, so it shouldn’t load down the fence voltage to any measurable de­gree. leads. These holes should be fitted with small rubber grommets. The pot shaft can now be trimmed to suit the knob, after which the PC board assembly can be mounted on the lid and secured using the pot nut. When fitting the knob, rotate the pot shaft fully clockwise, then tighten the grub-screw with the pointer towards the 10.8kV position. This done, feed the external leads through the grommets and solder them to the PC board. These leads should have good insula­tion to prevent any voltage breakdown between them. Use a green or black alligator clip for the earth wire connection and a red insulated probe for the fence terminal. This will prevent any confusion when you are making the connections to the electric fence. Warning! – if you reverse the connections to this tester, the body of the pot and hence the knob will be at the fence voltage. If the fence is working correctly, this means that you will get a nasty belt as soon as you touch the knob. Get the connections the right way around and you won’t have any problems. Building it Fig.4a shows the assembly details for this fence tester. It’s built on a PC board coded 11303993 and measuring 77 x 47mm. Start the assembly by soldering in all the resistors, then in­ stall PC stakes at the fence and ground inputs, at the three pot terminal positions and at the ground position for the pot’s body. The potentiometer can now be installed by soldering its terminals to the PC stakes and by soldering its body directly to the adjacent ground stake. You will need to scrape away some of the plating from the pot body near the PC stake, using a file or sharp knife, so that it can be soldered easily. The neon indicator has its leads bent at right angles before being soldered into posi­tion. It can be secured to the board with a dob of silicone sealant. The next step is to attach the front panel label to the lid of the case and drill the holes for the pot shaft and for viewing the neon indicator. You will also need to drill two small holes in the sides of the case for the external Figs 4b & 4c: the front panel and PC board artwork, reproduced same size for those who wish to make their own. Parts List Midi Electric Fence Tester 1 plastic case, 82 x 54 x 30mm 1 PC board coded 11303993, 77 x 47mm 1 front panel, 80 x 52mm 1 neon indicator, pigtail type 2 small rubber grommets 6 PC stakes 1 10kΩ 16mm pot. (VR1) 1 black or green aligator clip 1 red instrument probe 1 metal knob 1 1m length of blue or black 250VAC rated wire 1 1m length of red 250VAC rated wire 19 10kΩ 0.5W 1% metal film resistors 2 2.2kΩ 0.5W 1% metal film resistors MAY 1999  41 “Maxi” Electric Fence Voltage Tester Unlike the other two testers, the Maxi Electric Fence Tester uses a high-brightness xenon flash tube although the circuit is only slightly more complicated than before. It uses an internal capacitor to store up some charge from each fence pulse and when this reaches a critical level, the xenon tube emits a bright flash. This cycle is then repeated, with the tube flashing at regular intervals if the fence is operating correctly. As shown in the photos, the unit is housed in a clear plas­tic case and is designed to be permanently attached to the fence. Fig.5: the maxi electric fence tester has a somewhat similar circuit to the midi model but in this case fires a bright Xenon flash tube, the frequency depending on the voltage on the fence. 42  Silicon Chip The maxi fence controller, housed in a see-through and weatherproof plastic case. The Xenon flash tube is clearly visible through the case so this can be left permanently connected to the fence. We used the small plastic clips on the top of the case and cable ties to secure this tester to a suitable fence post. Fig.5 shows the circuit details. It uses a string of 18 820Ω resistors to provide current limiting and these drive a bridge rectifier consisting of diodes D1-D4. The output of the bridge in turn is connected to the xenon tube and to a parallel 0.47µF 630V polyester capacitor. The trigger pulse for the xenon tube is derived by connecting its trigger (T) terminal to a point higher up the resistor string. In operation, each fence pulse charges the capacitor by 10-40V, depending on the pulse amplitude. When the voltage across the capacitor reaches 200-300V, the xenon tube is ready to fire. It then fires when the next fence pulse takes the trigger input sufficiently high. When the xenon tube fires, the 0.47µF capacitor quickly discharges. The capacitor now recharges on each successive elec­tric fence pulse until the breakover voltage of the xenon tube is reached again. The flash rate depends on the fence voltage. The circuit draws about 0.5mJ per pulse from the electric fence which does not affect normal operation. This is why the circuit can be left perma- nently connected to the fence. Building it A PC board coded 11303992 and measuring 77 x 47mm accommo­dates all the parts – see Fig.6a. Begin by installing PC stakes at the two external wiring positions, then fit the resistors and diodes. Make sure the diodes (D1D4) are all correctly oriented. The capacitor is installed on the copper side of the PC board. Bend its leads at right angles so that the body of the capacitor can lie flat against the board before soldering it into position (see photo). This is necessary to allow the PC board assembly to fit into the specified case. The leads of the xenon tube must also be bent at right angles before mounting it on the board. Use needle-nose pliers to hold the leads adjacent to the glass body before bending them – if you don’t do this, you could crack the glass tube. This done, solder the tube into position and don’t forget the trigger lead. You will need to drill two holes in the sides of the case for the external leads. Fit these holes with rubber Front (above) and rear (right) views of the completed PC board. Note that the 0.47µF discharge capacitor attaches to the copper side of the board. grommets, then pass the leads through and solder them to their respective PC stakes on the PC board. It’s a good idea to use a red lead for the HT connection to the fence and a blue or green lead for the fence ground connection. As with the previous design, these leads should have good insulation, to prevent any high-voltage leakage between them. The PC board is designed to clip into the case against the integral side pillars. If necessary, you can lightly file the sides of the PC board so that it is a neat fit. Because it will be exposed to the weather, it’s necessary to seal the wire entry holes and the case lid using silicone sealant. Before doing this, however, it’s a good idea to test the circuit to make sure it works correctly. That way, if you do have a fault, you can easily remove the board from the case and check for missed or bad solder joints, or incorrect component place­ment. Finally, you will have to figure out some way to mount this unit. This may involve fashioning a suitable clamp or you can do what we did and fit a couple of small plastic clips so that the unit can be tied to a convenient fence post using tie-wire. The HT lead can be attached to the electric fence using a suitable electric fence joiner, while the ground lead can be attached directly to a ground SC stake. Figs 6a & b: follow the PC board overlay (left) and you should have no problems assembling the board. The full-size PC board pattern above can be used to etch your own board or to check commercial boards before assembly. Parts List Maxi Electric Fence Tester 1 clear plastic plastic case, 82 x 54 x 30mm 1 PC board, code 11303992, 77 x 47mm 1 straight 32mm-long xenon flashtube 2 fence clips 2 PC stakes 1 1m length of green or blue 250VAC rated wire 1 1m length of red 250VAC rated wire 2 electric fence wire joiners 4 1N4936 1A fast diodes (D1-D4) 1 0.47µF 630V polyester capacitor 1 220kΩ 0.5W 1% metal film resistor 18 820Ω 0.5W 1% metal film resistors MAY 1999  43 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 44  Silicon Chip 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 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 PRODUCT SHOWCASE 1800W/230V Inverter With Pure Sinewave Output If you’ve ever needed to run sensitive test equipment, computers, audio or video equipment from an inverter, you would know the problems most inverters cause. That’s because most inverters have at best a modified sinewave output, meaning harmonics, distortion and interference. A new 1800W inverter available through Bainbridge Technologies solves that problem because it has true sinewave output, enabling devices connected to it to run at their full rating. Motors, for example, start easier and run cooler and quieter. Measuring 391 x 279 x 115 (mm) and weighing 7.5kg, the Statpower Prosine 1800 is no lightweight – but then again, with 1800W output, you wouldn’t expect it to be. It features short circuit protection, under/ over voltage shutdown, over temperature shutdown, overload shutdown and AC backfeed protection. Battery polarity is clearly marked but if you do manage to connect the battery with reverse polarity battery an internal fuse will blow and service will be required. Total harmonic distortion (THD) is claimed to be typically 1% while efficiency is claimed to range from 84% at 200W out up to 90% at 1kW out, dropping marginally at full output. The output must be derated above ambient temperatures of 35°C (dropping to 900W at 60°C). The 5-second surge rating is 2900W. Connection is via a pair of large bolt terminals and power output is via a standard 240V AC mains socket (a hard-wired version is also available). An LCD panel displays the DC input voltage and current while a bargraph shows the AC output in watts. The same panel will also display a range of fault conditions. With a current drain of 170A or more at full output, a heavy duty battery is required. Statpower specify a range of deep cycle batteries such as those used in marine, recreational vehicle and golf cart applications. Standard automotive batteries are not recommended, except in emergencies. In use We must admit we had a problem when we fired up the Statpower Prosine 1800. Not so much with the inverter operation – that was fine. We have the ’scope pattern to prove it: you couldn’t want a much better sinewave (ignore the digital scope artefacts on the waveform). And look at those measurements: as close to 50Hz as possible and the voltage just a tad over spec at 231.6V. That was with a load of about 200W. No, our problem was with our battery. Against the specific warning about using a car battery, we used. . . a car battery. None of us at SILICON CHIP is fortunate enough to own a golf cart or a fork lift so we couldn’t purloin a big battery. We tried to get away with a littlie: it tried hard but couldn’t handle the load. When we tried to draw significantly more power, the inverter did exactly the right thing and shut down. The LCD display told us why – under voltage). We tried using some monstrous leads (400A-ish) but it was the battery that was letting us down. Still, the results we did achieve lead us to believe that the Statpower Prosine 1800 would deliver the goods if used correctly. Curiosity got the better of us and we had a good look inside – and were impressed! It’s very well constructed and looks as though some very serious design work indeed has gone into this inverter! That’s not surprising, because Statpower makes a large range of similar equipment. Incidentally, if you’re looking for a smaller inverter, Bainbridge Technologies have available a much smaller (and lower cost) 150W inverter intended for domestic appliances and small hand tools (see pic below). For further information contact Bainbridge Technologies, 77 Shore St, Cleveland, Qld. Tel (07) 3821 3333. Fax (07) 3821 3977. MAY 1999  53 Redback PA Amps from Altronics High Quality A/V Cable Range Altronics has released a new range The output is AGC limited to of Redback Phase 4 Public Address prevent dangerously high voltages Amplifiers. Available in either mixer appearing at the output when lightly From DSE or booster format the Phase 4 incorporates thermally cued on demand cooling coupled with a custom-designed heatsink tunnel ensuring the amplifier runs cool under all conditions. Power outputs of 125 + 250W for the mixer amps and 125, 250 and 500W for the booster amps ALL in a 2RU chassis. loaded. Distortion is typically less than 0.2% at 1kHz full power full load, while LED monitors show output level, input presence, overload, AGC and power. The Redback Phase 4 Amplifiers are Australian designed and manufactured and are covered by a 2 year warranty. For further information contact Altronic Distributors on 08 9328 2199. Oxley Amateur Field Day One of the premier events for amateur radio operators and electronics enthusiasts of the mid-north and north coasts of NSW, the Oxley Amateur Field Day, is again being held at Port Macquarie on the Queen’s Birthday weekend, June 12&13. This annual event is very pop-ular with exhibits and demonstrations from a number of suppliers of equipment, the usual “bring and buy” flea market and various fox hunt events. The Field Day will be held at the Sea Scout Hall, Buller St, Port Macquarie from 1-4pm Saturday and the main day, 9am-4pm Sunday For further information contact David, VK2AYD on (02) 6585 2647 or email davpil<at>midcoast.com.au In response to the increasing popularity of Home Theatre systems and the re-emergence of separate hifi components, Dick Smith Electronics have introduced two new ranges of high quality cables. The “Harmony” and higher spec “Harmony Gold” ranges have more than 40 cables including audio, video and optical, in a variety of lengths and connectors. They range in price from $12.95 for the Harmony 2-metre RCA/ RCA lead up to $49.95 for the 5-metre Harmony Gold 3xRCA/3xRCA lead. The optical cables are suitable for the latest technology consumer products such as DVD players, digital video cameras, mini disc players and amplifiers with Dolby Digital and Dolby ProLogic. All cables are available from Dick Smith Electronics stores throughout Australia or via mail order. Two VGA Screens From One Computer There are many applications where computer images need to be displayed to a wider audience than one monitor will allow. Education is the most obvious but demonstrations, retailing, computer presentations, point-of-sale and even computer video/games/ entertainment can all benefit from a second screen. Questronix have released a small VGA splitter, the VGS2, which does exactly that: 1 VGA input in, 2 out. Perhaps even more importantly, the second screen can be up to 65 metres away from the source using “HQ” 54  Silicon Chip cables. The system works with VGA, SVGA and XGA signals. It also has the ability, via an optional remote switch assembly, to send the remote screen black while the local screen remains active. This is very handy in education where a teacher or trainer wants the students’ attention. Or it can be used to load programs or sensitive information without that being viewed on the remote screen. Priced at $169 (inc tax) and includ- ing a 12V plugpack supply and one VGA computer lead, the VGS2 is available direct from Questronix, PO Box 548, Hornsby NSW 2076. Tel (02) 9477 3681, Fax (02) 9477 3569. Mo r e info r m atio n is a l s o available from their website, www.questronix.com.au/~questav You’ve Heard of Caller ID; Now There’s Talking Caller ID! Jackson Industries, one of the major suppliers of telephone and communication accessories to retailers in Australia, has introduced a Talking Caller ID unit to the Australian market. The Model TC509 ID unit connects to the telephone line in the same way as conventional caller ID units but instead of displaying the calling number, announces it after the first “ring”. This patented technology, developed in the US, will be available in Australia from June this year. Recommended retail price is $59.95. The unit stores the last 10 calls for review and will announce the number, time and date of each incoming call for later review. In future months other models will be released which feature both incoming caller ID announcement and number display. Intusoft Offers Free Books Intusoft has announced that they are giving away free copies of their popular Power Specialist’s App Note Book on their company website. In addition, Intusoft has initiated a “SPICE Model of the Month” posting on their website. The book, an information-packed handbook for power supply designers, contains over 35 technical articles on power supply design and power electronics modeling. The book is available for immediate down-load from the Intusoft website, both in its entirety (in pdf format), or in individual articles at: http: //www.intusoft.com/psbook.htm The individual articles are also available in the Adobe Acrobat “pdf” format. Intusoft’s web site also features a new posting of a “SPICE Model Library of the Month”. Each month, a new SPICE model library will be available free. The “SPICE Model of the Month” can be found at: http://www.intusoft. com/models.htm The company offers other free SPICE models at: http://www.intusoft. com/models.htm#freemodels SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Use these REFLEX® chargers for all your Nicads and NIMH batteries: Power tools  Torches  Radio equip.  Mobile phones  Video cameras  Field test instruments  RC models incl. indoor flight  Laptops  Photographic equip.  Toys  Others  Rugged, compact and very portable. Designed for maximum battery capacity and longest battery life. For further information, contact Jackson Industries, PO Box 6388 BHBC, Baulkham Hills, NSW 2153. Phone (02) 9899 8833; Fax (02) 9899 8378; email chris<at>ji.com.au Nepcon ’99 for Melbourne The electronics equipment and component show, Nepcon 99, will be held in Melbourne’s Exhibition and Convention Centre from 25-27 May. The Australian debut of Nepcon in Sydney was hailed by exhibitors and visitors alike as a benchmark for the electronics industry’s direction into the next millennium. This year, Nepcon will feature the latest local and international electronics products including: design and manufacturing equipment, PCB fabrication and assembly components, test and measurement equipment, EMI/ RFI products, satellite and microwave technology, defence equipment, electronic design tools, racks, enclosures and components. Another first at Nepcon ’99 will be an informative specialised conference featuring national and international guest speakers who will present tutorials and workshops. The focus and theme of the conference is ‘Education’ and a comprehensive speaker and workshop program has been organised. For further information on Nepcon ’99 contact Reed Exhibitions Companies on (02) 9422 2518. SC AVOIDS THE WELL KNOWN MEMORY EFFECT. SAVES MONEY & TIME: Restore most Nicads with memory effect to capacity. Recover batteries with very low remaining voltage. CHARGES VERY FAST plus ELIMINATES THE NEED TO DISCHARGE: charge standard batteries in minimum 3 min., max. 1 to 4 hrs, depending on mA/h rating. Partially empty batteries are just topped up. Batteries always remain cool; this increases the total battery life and also the battery’s reliability. DESIGNED AND MADE IN AUSTRALIA For a FREE, detailed technical description please Ph (03) 6492 1368; Fax (03) 6492 1329; or email smartfastchargers<at>bigpond.com 2567 Wilmot Rd., Devonport, TAS 7310 PCB POWER TRANSFORMERS 1VA to 25VA Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 MAY 1999  55 Tell someone you love them! a e v a H art e H Now is the month of May-ing, when merry lads are play-ing, Fa-la-la-la and as everyone knows, it will soon be Mother’s Day. So we have produced a project for Mother’s Day and for any other day that you want to tell someone you love ’em. It is the Heart of LEDs. Build it now and you’ll be in that special someone’s “good books”. by LES GRANT* 56  Silicon Chip B ACK IN NOVEMBER 1998 we published the “Christmas Star”. It turned out to be very popular and just the ornament for the top of the Christmas tree. We’re taking the same basic idea and indeed the same circuit to produce a version for Mother’s Day: the Heart of LEDs. Now you can have something different to give to that special Mum or Grandmother. Or you may be able to redeem yourself if you forgot St Valentines Day! Either way, the Heart of LEDs will certainly last a lot longer than the traditional bunch of flowers! O r, i f y o u don’t want to give your heart away, you can actually wear it “on your sleeve” or better still, on your lapel. This is readily done if the Heart of LEDs is powered from four AA cells and these could be installed in a 4‑cell holder which you keep in your pocket. The Heart of LEDs is a modestly sized PC board with an array of 30 LEDs arranged in two concentric heart‑shaped patterns, ie, one heart inside the other. Driven by a single IC microcontroller, it flashes the LEDs in a seemingly endless sequence of patterns. For those who don’t like microcontroller projects, just pretend the micro is a dedicated LED driver IC that happens to have been designed to control 30 LEDs in the shape of a Heart (what a stroke of luck!). And it won’t be declared obsolete just after publication like a purposedesigned IC might be! As the design is derived from the Christmas Star, those readers who saw that article will notice that the schematic is very similar. In fact, you might think it is identical but the row connections to the microcontroller are different. The major differences between the Heart and the Star are in the shape of the PC board, the physical layout of the LEDs and the software. Why use a Microcontroller? Using a PC parallel port to control external devices is a popular approach these days but imagine the response when you present your Mum with a flashing Heart attached to an umbilical cable running into the next room! No, self‑contained is better. The answer is to use a small micro- Heart of my heart: give this to your Mum on Mother’s Day or wear it on your lapel when you’re out and about. This board has the 8‑pin socket for an optional EEPROM but this can be left out. controller. They are cheap and easy to use. And if the software doesn’t work first time (when does it?), you simply change the program and re‑program the micro. As this project demonstrates, by changing the software you can make a circuit which originally did one job do something quite different. Now we’re not going to go into the ins and outs of the circuit because that was done in the November 1998 issue of SILICON CHIP. We’ll just mention that the microcontroller is the Atmel AT89C2051 and is a version of the 8051 family. Here it is used to drive 30 LEDs which are connected in an X‑Y matrix; ie, the LEDs are interconnected in 6 rows and 5 columns. The appropriate combination of LEDs in a column is switched on for a short time (about 2ms) and the process is repeated for each column, taking just 10ms for a full cycle. Provided the multiplexing is done quickly enough, the persistence of vision “fills in the gaps” and we see all combinations of LEDs without any flicker. The power supply uses a 7805 3‑terminal regulator with 0.1µF bypass capacitors at its input and output. Diode D1 provides reverse polarity power protection. The maximum current drawn by the Heart is about 140mA with all LEDs on but less than about 50mA for most patterns. It is powered by a 9V DC plugpack. Do not use a 12V DC plugpack as the higher output voltage will cause excessive heat in the 3‑terminal regulator. The software As with the Christmas Star, the basic source code for the Heart will be available free (you can download it from www.grantronics.com.au). An extended version that uses an optional 24C16 EEPROM for storage may also eventually become available. The software is written in C language using the low cost Dunfield Development Systems Micro/C compiler. There is nothing particularly smart or tricky about the software – it was written to be easy to understand and to encourage use of small micros. Consequently, there are no interrupt routines and no use of the MAY 1999  57 Fig.1: the microcontroller (IC1) drives the 30 LEDs in a 5 x 6 matrix, with 5 columns and 6 rows. The EEPROM is optional, to store extra patterns in the future. It can be left out. counter/timers, the UART or the comparator though Micro/C can make use of these resources. The software is table driven. This means that the display patterns and sequences are determined by data stored in a table (an array of bytes). There is a simple interpreter that scans through the table to perform the specified operations. The defined byte values are listed in Table 1. Note that the software for the Heart is a little smarter than for the Christmas Star – so it can do more Table 1: Software Table Byte value or range 01 to 30 (0x01 to 0x1e) 33 to 62 (0x21 to 0x3e) 64 (0x40) 65 to 79 (0x41 to 0x4f) 128 (0x80) 129 to 191 (0x81 to 0xbf) 253 (0xfd) 254 (0xfe) 255 (0xff) 58  Silicon Chip Operation Turn on LED 1 to 30 Turn off LED 1 to 30 (LED number = byte ‑ 32) Go back to byte after loop start Loop start, count = byte ‑ 64 Delay (use last delay count), each count = 10ms Delay, count = byte ‑ 128, each count = 10ms All LEDs on All LEDs off End of table complex pattern sequences. Note also that there are still quite a few undefined values so future expansion is possible. Putting it together Assembly of the PC board is quite straightforward. You will need a soldering iron with a fine tip, preferably temperature‑controlled to about 320°C. The first step is to carefully check for shorts between tracks and broken tracks. Fit the smallest parts first, the wire links, followed by the resistors and diodes. Next, fit the crystal (or resonator) and the IC socket for the micro. Then install the transistors, capacitors and LEDs. Pay particular attention to the orientation of the LEDs – they all point the same way but they don’t work when installed backwards! Finally, install the 3‑terminal regulator and the 2.1mm DC power socket. Don’t insert the micro into its socket just yet. Do another close visual inspection, looking for solder bridges especially on the transistor pads. Then apply power and check for the presence of 5V between pin 20 (+) and pin 10 of the socket for IC1. If all is OK, remove the power, plug in the micro (make sure it’s the right way around) and apply power again. The micro then generates quite a range of patterns with the LEDs which then repeat after a while. Running it from batteries Earlier, we mentioned the possibility of running the circuit directly from four AA cells; ie, 6V. To do this, you would need to omit the 7805 regulator and connect a link from D1 to C5. This will give a supply rail of close to +5.4V. Note that the diode must be present because the maximum supply for the microcontroller is 6V. The hole near LED2 may be used to hang the Heart. If you hard‑wire the power supply, you may be able to use this hole as a strain relief and hang the Heart on the power wires. Finally, the appearance of the Heart may be enhanced by placing a piece of red cellophane over the front. Fig.2: the component overlay. Make sure that you insert all the LEDs correctly. The cathode or flat side is oriented away from the DC socket in all cases. Don’t insert the micro until you’ve done a voltage check on the board (see text). – it is so easy to change the behaviour by changing the software. And what about the optional 24C16 EEPROM? Well, an enhanced version of the Heart would read its data from the EEPROM for much longer sequences. To check out the latest version of Fault finding If the 5V DC is not present, check the applied power polarity. The centre pin of the 2.1mm DC socket (SK1) must be positive. Check that D1 is correctly fitted, and check the tracks from SK1 via diode D1 and the 7805 to IC1 for breaks or shorts. If one LED does not work, it may be inserted backwards or it may be shorted by a solder bridge between its pads. If one group of adjacent LEDs does not work, check the circuitry and soldering around the appropriate column drive transistor. If several individual LEDs do not work, check the corresponding row drive circuitry. Remember, faulty components are rare but soldering faults are common. The future The Heart is still evolving. That is part of the attraction of using a micro the software, log in at http://www. grantronics.com.au If you don’t have Internet access, send a stamped ($1) self‑addressed envelope with an IBM format 3.5‑inch disc to Grant-ronics and you will be sent the current software files. Parts List 1 Heart‑shaped PC board, code 08205991 1 2.1mm DC connector (SK1) 1 crystal or ceramic resonator, approx 12MHz (X1) 1 20‑pin IC socket 1 9V DC 150mA plugpack or 4 AA cells and 1 4 AA cell holder Semiconductors 1 AT89C2051 programmed microprocessor (IC1) # – See next page 1 7805 5V regulator (REG1) 30 red LEDs (LED1‑LED30) 5 BC557 PNP transistors (Q1‑Q5) 1 1N4002 power diode (D1) 1 1N4148, 1N914 silicon diode (D2) Resistors 5 2.2kΩ 6 120Ω (code: red red red brown or red red black brown brown) (code: brown red brown brown or brown red brown black brown) Capacitors 1 10µF 16VW electrolytic 3 0.1µF monolithic or MKT polyester 2 27pF ceramic (code: 104 or 100n) (code: 27 or 27p) MAY 1999  59 Included more for interest than anything else, this “accidental” photo clearly shows the multiplexing of the LEDs as they are being scanned in a linear motion. No, LEDs do not light up in stripes! Acknowledgement: I would like to thank the people at BEC Manufacturing who rushed the prototype boards through in time for publication. SC * Les Grant is the Engineering Director at Grantronics Pty Ltd, electronics design engineers. Grantronics are the Australian distributors for Dunfield Development Systems low priced software development tools. See the advertisement in the Market Centre. Fig.3 actual size artwork for the PC board. #Where to buy the kit Jaycar Electronics stores will have the complete kit available for $29.95. Alternatively, Grantronics Pty Ltd can supply the programmed microprocessors for $10 plus $5 for packing and postage. Send remittances to Grantronics Pty Ltd, PO Box 275, Wentworthville, NSW 2145. Phone (02) 9896 7150. When you need mains power and there's no power outlet available, look to Bainbridge Technologies. Look at the superb 1800W "Pure Sine Wave" inverter - because it's sine wave you'll have no trouble with delicate test equipment, computers, communications equipment, tools... anything. Don't need 1800W? Bainbridge Technologies have you covered – with 150W output, the 150i 12V to 240V inverter is ideal for consumer equipment including TVs and VCRs. There's a Bainbridge Technologies inverter to suit YOUR requirements. Call today for more details! 60  Silicon Chip CARBON MONOXIDE ALARM By JOHN CLARKE Exposure to carbon monoxide (CO) gas produces an insidi­ous form of poisoning which at best can give the victim a head­ache and at worst can result in death. This CO Gas Monitor warns you of rising CO levels and emits a loud tone when the concentra­tion reaches a preset threshold. Features • • • • • • • • • Sensitive detection of CO gas (<200ppm) Uses rugged and reliable semiconductor sensor Sensitivity adjustment Precautionary CO level visual alarm Main higher CO level visual and auditory alarm Main alarm reset on continuous tone alarm Automatic purging of sensor 7-minute CO sensing time every ten minutes 2-minute sensor heat purging time MAY 1999  61 D ON’T BE TOO COMPLACENT here is that people often associate diz- on the dashboard of your vehicle or mounted towards the rear of a van or about the risks of CO poison- ziness and nausea with “car sickness” ing in your car, particularly if or “motion sickness”. However, it’s station-wagon. you drive an old “bomb”. Admittedly, quite possible that what is described While presented as a standalone there’s not much risk in a modern car as “car sickness” is really a good dose unit and perfectly practical as deof carbon monoxide. or if the vehicle is well maintained. scribed, even this small case might On older cars, however, there’s a Table 1 shows the effects of various look out of place in a today’s modern very real danger if the seal around the levels of CO concen­tration. As you cars – that’s if you can find a suitable rear door or bootlid has deteriorated can see, even small concentrations mounting position at all. suffi­ciently to allow exhaust gases to spell real danger. That’s because A more practical arrangement seep into the cabin. carbon monoxide has over 200 times might be to mount the PC board If the bootlid or rear door no longer more affinity with the haemoglobin without the case under the dashboard, in your blood than oxygen. It literally seal properly, ex­haust gases can be with the CO sensor, front panel LEDs stops the blood supply from carrying and switches mounted somewhere sucked into the rear of the vehicle oxygen and if enough haemoglobin is more suitable. as you drive along. Rust holes are affected, the brain suffers from oxygen another problem. Another idea would be to mount the starvation. Opening a window doesn’t ease the project, complete in its case in, say, In severe cases, a blood transfusion the boot, again with the CO sensor, situation; in fact it can often turn a bad situation deadly by altering LEDs and switches brought airflow within the vehicle. to a small plate mounted Table 1: Effects of CO Gas Poisoning and Symptoms You could be driving along on or under the dashboard. seemingly unaffected while Regardless of where it’s CO Gas      Symptoms your rear seat passengers cop installed, this unit is very Concentration a bad dose of carbon monsensitive to the presence of 50ppm Exposure for a few hours normally oxide (CO) poisoning with CO gas. Just driving along results in no symptoms possible fatal consequences. in heavy bumper-to-bumpThe other big danger is er traffic with the window 100ppm Exposure for a few hours results in from a poorly main­tained exopen or the airconditioner a slight headache in the forehead haust system. If there’s a hole set to “fresh-air” is enough 500ppm Exposure for one hour results in a anywhere in the system, it’s to trigger the unit, for exheadache with increas­ing severerity possible that exhaust gases ample. over time could seep past any defecSo far, we’ve only talked tive seals and into the cabin. about using this alarm in 1000ppm Exposure for 20-30 minutes results The answer here is obvious a motor vehicle. With a in a headache, dizzi­ness and nausea; – make sure that the exhaust suitable 12V supply, the possible death within 2 hours system is regularly inspected unit could also find use in 4000ppm Exposure results in possible death and correctly main­tained. a service workshop or anywithin 30 minutes Driving in bumpwhere else where exposure er-to-bumper traffic can also to CO gas is a risk. is the only way to save the victim expose you to excessive concentraThe unit is very easy to use and has from death. tions of CO gas. Because there are just two switches and four indicator By the way, it’s estimated that a LEDs on the front panel. The functions so many cars so close together, it’s heavy cigarette smoker will have of the Power and Reset switches are inevitable that there will be some about 5% of his/her available hae- self-explanatory, as is the function exposure to exhaust gases. moglobin tied up by CO at any given of the Reset switch. The other three This applies particularly if you drive with the window open or with time. The symptoms for CO poisoning LEDs are designated “Heat”, “Alarm” begin to occur when this percentage and “Warning”. your interior air fan or airconditionreaches about 10%, while the onset ing set to “fresh air”. Setting the fan The Heat LED indicates a heat or airconditioner to “recirculate” is of death occurs at about 20%. purging cycle for the gas sensor, while These figures suggest that a smoker the Alarm LED lights (and an internal the answer here, especially if you are is far more susceptible to CO poi- piezo alarm sounds) when a critical stopped at traffic lights. soning than a non-smoker, simply CO level is reached. Finally, the WarnHow do you know when you’re be­cause they are starting out from a ing LED flashes to give a preliminary being exposed to excessive CO levels? Well, you might not know until it’s 5% higher base. warning that the CO concentration is too late. That’s because CO is utterly on the rise. CO monitor colourless and odorless but nonetheThe CO sensor itself protrudes from Because CO gas is impossible for the rear panel of the case. This is a less quite deadly. First symptoms, from quite small the individual to detect, we set out to low-cost semiconductor unit made design an effective yet easy-to-build concentrations of CO gas, are headby Nemoto. It contains a heating aches, nausea and dizziness, while CO monitor. The end result is the element and a semiconductor senexposure to higher levels quickly self-contained unit described here. sor surrounded by a catalytic layer. It is housed in a small plastic in- These parts are contained in a 19mm causes unconsciousness and death. er cylindrical case with six An interesting point to consider strument case which can be placed diamet­ 62  Silicon Chip Self-contained in a plastic case and plugging into a car cigarette lighter socket, the CO Alarm can be moved from vehicle to vehicle. Alternatively, it could be “built in”, with or without the case. ° pins protruding from the base and with a double gauze wire mesh over the element. The double layer of wire mesh is there to prevent an explo­sion if the sensor is exposed to dangerous concentrations of inflammable gas. In operation, the sensor is heated to a temperature of 130-170°C and when CO gas becomes trapped on the catalytic layer, electrons are transferred to the semiconductor element. This markedly reduces the effective resistance of the semiconductor element to reveal the presence of the gas. When the gas dissi­ pates, the resistance of the semiconductor layer returns to normal. Over time, other gases such as hydrogen, petrol vapours and alcohol vapours are ab- sorbed onto the catalytic surface and cause contamination. To prevent false readings, these are periodically burnt off by raising the temperature of the heating element to around 450°C. By the way, in case you’re wondering, this unit is really only suitable for detecting carbon monoxide. It is fairly insen­sitive to hydrocarbon vapours (although it can detect very high concentrations), which means that it is unsuitable for detecting petrol fumes. Block diagram Fig.1 shows the block diagram of the CO Alarm. The circuit is powered from a 12V supply (eg, via the cigarette lighter socket) and this is regulated to give a +5.5V rail using REG1. This rail then supplies the heater and the semiconductor element in the CO sensor, along with the rest of the circuit. The sensor heater element must be driven correctly to suc­ cessfully purge any contaminating gases on the semiconductor element. The specifications state that the CO sensor be heated to 450°C for 1-3 minutes, while the CO sensing time should be 6-10 minutes. These times are set by the Timer circuit, with LED2 switching on during the heat purging period. In this case, the Timer circuit heats the sensor element for two minutes when power is first applied and repeats this 2-minute heating (purge) cycle every 10 minutes after that. Fig. 1: operation of the CO Alarm is easily understood when you break it down into circuit elements, as shown in this block diagram. MAY 1999  63 Fig.2: the circuit might seem a little complicated at first glance but it’s quite simple. It uses just three ICs, six transistors, a 3-terminal regulator and a handful of other parts plus, of course, the carbon monoxide sensor. During each 2-minute heating period and for one minute afterwards, the signal output from the CO sensor is grounded via Q3 in the Output Control section of the circuit. This is done to prevent false readings. At the end of each 3-minute period, Q3 turns off and so the signal from the CO sensor is fed to the following comparator stages. There are two comparator stages here – a “latching com­ parator” based on IC1a and a “warning comparator” based on IC1c. Basically, the warning comparator monitors the CO sensor output during the 7-minute sensing period. If the CO 64  Silicon Chip level reach­es a moderate level during this time, it enables a Flasher cir­cuit (IC1d). This in turn drives LED4, which flashes on and off to provide a preliminary warning. If the CO level subsequently rises past a critical point, the latching comparator (IC1a) lights LED3 via transistor Q4. It also activates a tone generator circuit based on IC1b and this then drives the piezo alarm via Q5 and Q6. Note that the piezo driver is modulated by the flasher so that the sound occurs in short bursts rather than continuously. The latching comparator now remains in this state until it is reset. This takes place automatically at the end of the first minute of the sensing period. If the CO level is still high after the reset, the comparator immediately returns to the latched-on state. Conversely, if the output from the CO sensor is below the comparator threshold at the time of reset (ie, the CO level has dropped), the comparator output switches low and turns off the alarm. Alternatively, the circuit can be reset manually at any time, so that the CO level can be retested. If CO is present, the output from the CO sensor will nor­mally only go low when heat purging starts again at the end of the 10-minute cycle. Provided it had already been triggered during the latter part of the sensing period, the piezo alarm will continue to sound into the purging period but the tone will change from pulsed to continuous. This continuous tone indicates that the manual reset can be used to silence the alarm. The circuit OK, so much for the basic theory of operation. To find out how it all works in practice, take a look now at the full circuit diagram (Fig.2). It might seem a little complicated at first glance but it’s really quite simple. It uses just three ICs, six transistors, a 3-terminal regulator and a handful of other parts – plus, of course, the CO sensor. The +12V rail from the car’s battery comes in via switch S1 and is applied directly to the input of REG1, an LM317T adjust­able regulator. Zener diode ZD1 protects the regulator from vol­tage transients, while the 100µF capacitor provides supply decou­pling. In operation, REG1 produces 1.25V between the adjust (ADJ) and output (OUT) terminals. The 120Ω resistor between these terminals sets the current between them to 10.4mA and this cur­rent flows Fig.3: use this component layout in conjunction with the photo overleaf to help with construction. to ground through trimpot VR1. Setting VR1 to 408Ω gives 4.25V between ADJ and ground, which means that the applied, its output at pin 3 is high and period is 0.693 x 150kΩ x 220µF. This output of REG1 will be at 4.25 + 1.25V the 220µF capacitor charges towards gives figures of 38.12s and 22.87s = 5.5V. In practice, VR1 is simply ad- the positive supply rail (Vcc) via the respec­tively, for a total period of just justed for the correct output voltage. 100kΩ and 150kΩ resistors. When the over one minute (60.99s). A second 100µF capacitor decou- voltage at pin 6 subsequently reaches In turn, pin 3 of IC2 clocks IC3, a ples the regulator output, while LED1 2/3Vcc, pin 7 switches low, as does 4017 decade (divide-by-10) counter. provides power indication. The 470Ω pin 3, and the capacitor discharges This counter has 10 independent resistor in series with LED1 limits the via the 150kΩ resistor until it reaches outputs which se­quentially go high 1/ Vcc. At this point, pin 7 goes open current through it to about 7mA. on receipt of a clock signal from IC1. 3 IC2, a 555 timer wired in astable circuit again, pin 3 goes high and the When power is first applied, IC3 is capacitor charges once more to 2/3Vcc. mode, forms the heart of the clock reset via the 10µF capacitor on pin circuit. Its timing components are This cycle repeats indefinitely while 15 (this capacitor briefly pulls pin ever power is applied. connected to pins 2 & 6 and consist 15 high) and so its “0” output at pin The charging period for the 220µF 3 is high. As a result, transistor Q1 is of a 220µF capacitor and the 150kΩ capacitor is simply 0.693 x (100kΩ + turned on via D6 and the associated and 100kΩ resistors. It operates as 150kΩ) x 220µF, while the discharge 4.7kΩ base resistor. Q1, in turn, drives follows: initially, when power is first MAY 1999  65 This photograph of the completed project, looking from front to back, gives you a good idea of how large the project is. It will also help with component placement during assembly. the base of Q2 which also turns on and con­nects pin 6 of the CO sensor to ground to apply the full 5.5V rail across the heating coil element. Q2 also turns on LED2 to indicate that the heater is operating. At the same time, transistor Q3 turns on via diodes D6 and D8. This transistor shunts the output of the CO sensor to ground via a 10kΩ resistor, to prevent the following comparator stages from detecting any false signals. When IC2 subsequently clocks the “1” output (pin 2) of IC3 high (after one minute), transistors Q1-Q3 all remain on due to the forward bias now provided via diode D7. At the end of the second minute, the “2” output (pin 4) of IC3 switches high and forward bias to Q3 is supplied via D9. Conversely, D8 is reverse biased and so Q1 & Q2 switch off to end the heating (purge) cycle after two minutes. Note, however, that a residual current still flows through the heater coil to ground via the parallel 180Ω and 3.9kΩ resis­tors on pin 6 of the sensor. The effective voltage across the heating coil is now only 0.8V and so the temperature quickly drops towards the desired 130-170°C operating range for CO sens­ing. 66  Silicon Chip Q3 remains on during this time, to short the sensor output to prevent false readings while the temperature stabilises. At the end of the third minute, IC3’s “2” output goes low, transis­ tor Q3 turns off and the signal from the sensor is now fed to comparators IC1a & IC1c via a 10kΩ resistor. Diode D1 isolates the comparator inputs. Warning comparator IC1c, part of an LM324 quad op amp, is the warning com­parator. Its pin 13 inverting input is biased to 1.28V by a voltage divider consisting of 33kΩ and 10kΩ resistors and this sets the comparator threshold. The output from the CO sensor appears at pins 5 & 7, while trimpot VR2 sets the sensitivity. Normally, when CO concentrations are low, the output from the sensor is less than the comparator theshold voltage (1.28V). As a result, pin 14 of IC1c is low and D5 pulls pin 9 of IC1d low to prevent this flasher oscillator from operating. Conversely, if the CO sensor output rises above 1.28V (ie, if excessive CO is detected), the voltage on pin 12 of IC1c will be greater than the voltage on pin 13. When this happens, pin 14 of IC1c switches high and reverse biases D5, thereby allowing the flasher oscillator based on IC1d to operate. IC1d is also part of the LM324 quad op amp package and is wired as a 0.5Hz oscillator. Its period of oscillation is set by the 100kΩ feedback resistor between pins 8 & 9 and by the asso­ ciated 10µF timing capacitor. The two 10kΩ resistors on pin 10 nominally bias the non-inverting input to half supply (1/2 Vcc), while the 10kΩ feedback resistor between pin 8 and pin 10 provides hysteresis. This feedback resistor provides upper and lower threshold voltages of +3.67V and +1.83V respectively. The circuit works as follows. When no CO gas is present, pin 9 of IC1d is held low and so the output at pin 8 is high and PNP transistor Q7 is off. However, if CO gas is detected, D5 becomes reverse biased as described previously and so the 10µF capacitor on pin 9 of IC1d charges via the 100kΩ feedback resis­tor until it reaches the upper threshold voltage (ie, 3.67V). At this point, pin 8 switches low and so Q7 turns on and lights LED 4 via a 470Ω resistor. The 10µF capacitor now discharges via the 100kΩ feedback resistor into pin 8 until it reaches the lower threshold voltage (1.83V). When it reaches this point, pin 8 goes high again, Q7 turns off and the 10µF capacitor again starts charging towards the upper threshold voltage. This cycle continues indefinitely and so LED4 flashes at a 0.5Hz rate while ever CO gas is present. Latching comparator IC1a is the latching comparator. Its pin 1 output switches high when the sensor output reaches half supply (ie, 2.25V), as set by the two 10kΩ bias resistors on pin 2. This high output in turn pulls pin 3 high via D2 and a series 10kΩ resistor and so the comparator output is latched high, even if the sensor output immediately drops below 2.25V. This turns on Q4 which in turn lights LED3 (alarm). Note that when pin 3 of IC1a is latched high, D1 is reverse biased. This ensures that the high on pin 3 has no affect on the sensor output. As soon as pin 1 of IC1a switches high, D3 is also reverse biased and so IC1b starts oscillating. This “tone generator” stage works in exactly the same way as the oscillator based on IC1d, except that the timing components on its pin 6 input are much smaller in value. As a result, IC1b oscillates at about 3kHz. IC1b drives Q5 & Q6 which together function as a push-pull output stage. In turn, these drive the piezo alarm to provide the audible alarm. Note, however, that the 3kHz alarm tone is not continuous but is modulated by IC1d. That’s because each time the output of IC1d switches low, it also pulls pin 6 of IC1b low via D4 and a series 4.7kΩ resistor and thus disables the tone genera­tor. IC1d oscillates at a 0.5Hz rate, which means that the tone generator stage (IC1b) operates in 1-second bursts. The latching comparator can be reset at any time by press­ing the Reset switch S2. This momentarily pulls pin 3 of IC1a low via a 1µF capacitor. If the voltage from the CO sensor is below the latching comparator threshold, then the comparator output stays low and the circuit reverts to the monitoring status. If not, it will go high again immediately after the reset and re­trigger the alarm. Alternatively, if the Reset button isn’t pressed, the latching comparator is automatically reset when the “4” output (pin 10) of IC3 goes high and switches on transistor Q8. This occurs one minute into the sensing period (ie, at the end of the fourth minute). As for a manual reset, the alarm is immediately retriggered if the sensor output is still above IC1a’s threshold voltage; otherwise it resumes its monitoring role. If the alarm immediately retriggers after the automatic reset, it will con- tinue to sound until IC3’s “4” output switches high again 10 minutes later. This means that the alarm will even continue to sound during the next heat purging period (unless, of course, the reset button is pressed). When the heat purging process starts, however, Q3 turns on and so pin 14 of IC14 goes low. As a result, oscillator IC1d is disabled which means that it no longer drives LED 4 (via Q7) or modulates the audible alarm. Therefore, the audible alarm switches from pulsed to continuous tone when the heat purging cycle begins. Pressing the Reset switch will now turn the alarm off, since the sensor output is effectively grounded by Q3 and can no longer retrigger the latching comparator. Note that the heat purging process does not start until six minutes after the automatic reset has taken place. That’s because IC3 is a decade counter and it takes a further six minutes for outputs “5-9” (not shown on the circuit) and then “0” to go high in turn. Construction Building the CO Alarm is easy since virtually all the parts are mounted on a single PC board coded 05303991 (117 x 102mm). Fig.3 shows the assembly details. Before installing any of the parts, carefully check your PC board for etching defects by comparing it with the published pattern. In particular, check for shorted or broken tracks and undrilled holes. Begin the assembly by installing the three wire links, then install PC stakes at the external wiring points. You will need 10 PC stakes in all – four for the CO sensor leads, two for the power supply connections, two for switch S2 and two for the piezo alarm. Once the PC stakes are in, you can install all the resis­tors. Table 2 shows the resistor colour codes but it’s also a good idea to check them using a digital multimeter, just to make sure. The three ICs can then be installed, followed by the diodes and the zener diode. Make sure that these semiconductor parts are correctly oriented. Now for the transistors. Be careful here, because there are three different types used and they all look the same. In partic­ular, be careful not to confuse the BC327 and BC337 types (one is a PNP transistor, the other an Parts List 1 Nemoto NAP-11A semiconductor type CO gas detector 1 PC board, code 05303991, 117 x 102mm 1 front panel label, 133 x 27mm 1 small instrument case, 110 x 140 x 35mm (see text) 1 automotive lighter plug 1 piezo transducer 1 SPDT toggle switch (S1) 1 momentary contact switch (S2) 1 1m length red/black figure-8 wire 1 60mm length 0.8mm tinned copper wire 1 80mm length yellow hookup wire 1 80mm length blue hookup wire 1 160mm length red hookup wire 1 cordgrip grommet 10 PC stakes 4 5mm LED bezels Table 3: Capacitor 2 3mm screws and nuts Codes 4 small self-tapping screws to [sb]Value IEC EIA secure PC board [sb]0.1uF 104 100n [sb].015 153 15n Semiconductors 1 LM324 quad op amp (IC1) 1 555 timer (IC2) 1 4017 divide-by-ten decoder (IC3) 1 LM317T adjustable regulator (REG1) 2 BC547 NPN transistors (Q1,Q8) 4 BC337 NPN transistors (Q2-Q5) 2 BC327 PNP transistors (Q6,Q7) 1 16V 1W zener diode (ZD1) 9 1N914, 1N4148 switching diodes (D1-D9) 4 5mm red LEDs (LED1-LED4) Capacitors 1 220µF 16VW PC electrolytic 2 100µF 16VW PC electrolytic 4 10µF 16VW PC electrolytic 1 1µF 16VW PC electrolytic 2 0.1µF MKT polyester 1 .015µF MKT polyester Resistors (0.25W, 1%) 1 330kΩ 1 220kΩ 1 150kΩ 3 100kΩ 1 33kΩ 19 10kΩ 2 4.7kΩ 1 3.9kΩ 1 2.2kΩ 2 1kΩ 5 470Ω 1 330Ω 1 180Ω 1 120Ω 1 10Ω 1 500Ω horizontal trimpot (VR1) 1 5kΩ horizontal trimpot (VR2) Miscellaneous Solder, etc MAY 1999  67 Table 2: Resistor Colour Codes                   No. 1 1 1 3 1 18 2 1 1 2 5 1 1 1 1 Value 330kΩ 220kΩ 150kΩ 100kΩ 33kΩ 10kΩ 4.7kΩ 3.9kΩ 2.2kΩ 1kΩ 470Ω 330Ω 180Ω 120Ω 10Ω 4-Band Code (1%) orange orange yellow brown red red yellow brown brown green yellow brown brown black yellow brown orange orange orange brown brown black orange brown yellow violet red brown orange white red brown red red red brown brown black red brown yellow violet brown brown orange orange brown brown brown grey brown brown brown red brown brown brown black black brown 5-Band Code (1%) orange orange black orange brown red red black orange brown brown green black orange brown brown black black orange brown orange orange black red brown brown black black red brown yellow violet black brown brown orange white black brown brown red red black brown brown brown black black brown brown yellow violet black black brown orange orange black black brown brown grey black black brown brown red black black brown brown black black gold brown NPN type). Note that Q8 needs to be bent over flat on the PC board to allow room for the Reset switch. Next, install the capacitors and note that the electrolytic types must be oriented correctly. Table 3 shows the value codes for the MKT polyester types. Regulator REG1 has its leads bent at right angles so that it can be mounted with its metal face flat against the PC board. Bend the leads as shown in the photo, so that they mate with the board mounting holes, then secure the regulator to the board using a screw and nut before soldering the leads. A separate heatsink isn’t required for REG1 – its metal tab allows sufficient cooling. The board assembly can now be completed by installing VR1, VR2 and the four LEDs. Mount the LEDs with a 20mm lead length so that they can later be bent over and pushed through the bezels fitted to the front panel. Make sure that the LEDs are correctly oriented – the anode lead is the longer of the two. In particular, note that LED4 is oriented differently to LEDs 1-3. Case And here is the final assembly, looking from the rear. The round grey object on the bottom left is the CO sensor, which could be mounted external to the case. 68  Silicon Chip As previously discussed, the prototype CO Alarm was housed in a low-profile instrument case measuring 110 x 140 x 35mm. Whether or not you use this case is up to you and your particular method of mounting. If you do, you will Table 3: Capacitor Codes   Value 0.1µF .015µF IEC 104 153 EIA 100n 15n have to drill four holes in the front panel to take the switches, plus four more to accept LED mounting bezels. Another two holes are drilled in the rear panel for the cordgrip grommet and CO sensor. First, the front panel. The best way to go about this job is to attach the label and then use this as a guide for drilling the holes. Alternatively, you can use the full-size artwork published with this article as a drilling template. Take care with the holes in the rear panel – both the sensor and the cordgrip grommet (for the 12V supply leads) should be a tight fit. The best way to make the sensor hole is to first drill a small pilot hole and then carefully enlarge it to size using a tapered reamer. The other hole should be carefully pro­filed to suit the shape of the cordgrip grommet. The PC board can now be installed in the case and secured using four self-tapping screws. These go into the integral stand­offs in the base of the case. This done, mount the switches on the front panel, then slide the panel into its slot at the front of the case and push the indicator LEDs through their matching bevels. All that remains now is to complete the wiring as shown in Fig.3. Use automotive cable for the supply leads and make sure these are firmly secured to the rear panel using the cordgrip grommet. The CO sensor can be wired using light-duty hookup wire, while switch S2’s contacts solder directly to the PC stakes adjacent to Q8. We mounted the piezo transducer on the lid of the case using hook and Fig. 4: use this same-size PC board pattern to make your own board or to check a commercial board for etching/drilling defects before commencing assembly. loop fasteners but a dab of super glue would also work. Finally, attach a cigarette lighter plug to the 12V supply lead. Testing You’re now ready for the smoke test. Rotate VR1 fully anti­clockwise, apply power to the circuit and measure the voltage on the output (centre) lead of REG1. Adjust VR1 for a reading of 5.5VDC and check that both LED1 and LED2 are now alight, indicat­ing that power is present and that the heating cycle has begun. If LED2 fails to light, try switching the power off and then on again, to activate the power-on reset for IC3. If that fails, check the 5.5V rail on pin 4 of IC1, pin 8 of IC2 and pin 16 of IC3. Assuming that all is well, wait for two minutes and check that the Heat LED (LED2) extinguishes. If you want to check operation of the sensor, place it near the exhaust pipe outlet of a running engine. Both the CO warning LED and the main alarm should be activated after a short time. Switch the power off and on again if you want to initiate the heat purging sequence immediately. This will also stop the main alarm if it has latched on. Installation The CO alarm is installed inside the vehicle and can be placed on the dashboard. Note that if you are already using the lighter socket for some other purpose, you can obtain a double lighter socket from automotive retailers or from Jaycar. VR2, the sensitivity control, should initially be set to mid-position and this should suit most applications. If you want greater sensitivity, adjust VR2 anticlockwise. Conversely, to decrease the sensitivity (eg, if the unit generates lots of nuisance alarms), adjust This same-size front panel artwork can be copied and used directly and/or used as a VR2 clockwise from its drilling template for the front panel. Artworks for panels and PC boards are also mid-position. SC available on the SILICON CHIP website, www.siliconchip.com.au MAY 1999  69 MAILBAG Replacing the loading block in an Akai VP170 I noticed a story about the replacement of a broken loading block in an Akai VP170 in “Serviceman’s Log” for the January 1999 issue. I would like to share with you a quicker method for re­placing the loading block: (1) remove the front panel from the unit; (2) remove screws right and left to remove upper plate, allowing access to the cradle; (3) unclip and remove the cradle; (4) turn the loading motor spindle in a forward direction until the arm loading block is in the 45° position. (5) unclip and remove the arm loading block, replace the faulty part and reassemble. With a little practice, this procedure will take about five minutes. T. Cairney, Mt. Gravatt, Qld. Modifications to Anemometer Thank you for producing a brilliant project in the wind speed meter in the March 1999 issue. I have constructed it and it works very well. There were some modifications I have made which may be of interest to your readers. Living in a small town in North Queensland has some disadvantages. When I asked the local bike shop about secondhand alloy wheel hubs they looked at me with a blank stare and said no! You can only buy them new and attached to the rest of the wheel at a cost of about $150. Strike one wheel hub as a bearing assembly. A rummage around in the junk bin uncovered a failed video head assembly with upper and lower drum complete. This has to be the best thing to use as it is entirely made of alloy and stain­less steel. After removing the drive magnet and circuit board, the heads and attached PC board and the inner rotary transformer, it was clear it would work perfectly. By attaching the lower half to a piece of poly cutting board and attaching the arm assembly to the upper head assembly, the thing spun quite freely. 70  Silicon Chip To waterproof the whole lot I used a lid from a spray can. It fits snugly over the head assembly without touching the sides. The bottom of the lid needed to be trimmed to size but once fitted no water will come up. A little silastic was applied to stop water entering holes in the head assembly. Where the shaft protruded from the poly board again I used a lid from a spray can and applied silastic underneath. Your article said that 10 metres of cable from the computer to the sensor was OK. I have mine working with about 20 metres of cable and haven’t experienced any problems. I also used a differ­ent computer; mine came from Oatley Electronics. It seemed a better choice as it gives more readings; ie, average wind speed and maximum wind speed. Colin Leonelli, Ingham, Qld. HTML files are a pest I read your Publisher’s Letter regarding email in the February 1999 edition with great interest. Yes, indeed, there are a lot of people out there who make it difficult for us to read the email they send. The one you forgot to mention is the person whose message is in HTML format littered with formatting commands that make it almost impossible to find the text in the middle of it. But sometimes the boot is on the other foot, especially with the way people answer their email. You tell us how the answer to a message may not be immediately available (“it might not get answered for a week or two”) but is the sender advised that there may be a delay? Most people just hold onto the message until it can be answered but give no indication whether it was received or lost in transit. Back in the “Good Old Days”, there were a lot of practices which were designed to keep the wheels of communication oiled and rolling smooth­ly. One of these was to always post out a note that “Your message has been received at this office” as soon as possi­ble after the message arrived when it looked as though an answer could not be given right away. Of course this meant the sending of two replies and this practice ceased at about the same time that people stopped mail­ ing out a receipt for payments by mail, when the cost of a stamp was considered more valuable than customer relations. But in these days of email, when the cost of sending a reply is no more than the time to write it, perhaps it is time to revive the practice. G. Mayman, Dover Gardens, SA (via email). Comment: good point. We are now answering most email within a day or two but where there will be a longer delay we are giving immediate ac‑ knowledgement. High voltage diodes get hot In the “Serviceman’s Log” story on a Masuda T092 in the April 1999 issue, you refer to the amazing heat from a 1000V FR607 rectifier, used to replace a 600V FR605. The reason is that the higher the voltage, the thicker the “intrinsic” layer in a high-voltage rectifier, and the slower the recovery time. Listings in a Diodes Incorporated catalog suggest that at the lower voltages in the FR60X family, this will be 150ns, rising to 250ns at 600V and 500ns at 800V (this particular company apparently does not make the 1000V FR607, which might be slower still). In other words, things can get bad rather quickly as the top voltage of a particular process is approached. A horizontal circuit is (in part) a switching supply and a slower recovery time means more heat. For example, an ordinary 6A 600V rectifier put into the circuit would probably short circuit instantly and take several other components with it. Note that switching-recovery dissipation is in part a function of voltage and frequency, not current alone, so paralleling diodes does not necessarily cut the heat per diode in half. Since the original diode blew out, it is possible it did not have a high enough voltage rating. So using a higher voltage part may well not have been a mistake. But extra heat would not be surprising; the recovery time may well be three times as long as with the original diode. There are other diode processes, such as “FRED”, that offer faster recovery times at high currents and voltages. The DigiKey catalog lists some Ixys devices at 8-12A and 35ns at 600V and 50ns at 1000V. (These families are faster than the FR60X but within a given family, the highest voltage ones still recover more slowly.) Of course, these are newer parts and come only in TO-220 and TO-247 packages (which have a large metal tab or pad at the potential of one of the leads) and not the cylindrical package, so depending on board layout, it might or might not be safe to use them. Paul Schick, Madison, WI, USA. Alternator speed & frequency With reference to the letter from Mr K. Russell of Willas­ton, SA, in the March 1999 issue concerning alternator speed and frequency, I would like to provide the following information. I am no expert in the Vestas system but it is my under­standing that the Vestas wind turbines are induction alternators (asynchronous machines). An induction alternator is basically an induction motor that is driven above its synchronous speed. The power output curve of an induction machine reaches a maximum for rotational power out (ie, motor mode) at a speed approximately 1-5% below its synchronous speed. At around 1-5% above synchronous speed, the electrical output (ie, generator mode) will be a maximum. Based on the information provided in your article, the Vestas machines are 4-pole machines which provides a synchronous speed of 1500rpm with Australia’s 50Hz system. The operating range is 1500-1560 RPM which is 0-4% above synchronous speed. As a related issue, induction machines require an input of reactive power to produce an electrical output and cannot there­fore provide nett reactive power to the electrical network, as can the synchronous machines that are employed in most large power stations. Any electrical machine can be used as a generator by driving the shaft that is normally driven in motor mode. In the case of an induction motor used in isolation from the electricity grid, an alternative source of reactive power is required. This is often provided by means of capacitors, similar to those used by electricity distribution companies to provide for system voltage control. A final point concerning Mr Russell’s comments about your graphs. Mr Russell has assumed that there is a linear relation­ship between wind speed, generator rotational speed and power output. This is not the case and in fact the power available from the wind varies in proportion to the cube of the wind speed. Therefore the graphs will not “superimpose” unless the vertical scales are changed to reflect this non-linear relationship bet­ween the quantities. Andrew Russack, Highgate, SA. More on AC alternators In response to your correspondents’ letters in the March 1999 issue, regarding AC alternators’ speed and their relation­ship to generated frequency, I take this opportunity to clarify the differences between synchronous and asynchronous generators. A standard synchronous alternator’s rotor has fixed magnetic poles that are “locked” into synchronism with the supply frequen­cy. It would appear that the “alternators” mentioned in the Wind Power article in the January 1999 issue are not of the synchro­nous type but are “induction generators”. These are no more than AC induction motors whose rotors run at a speed in excess of synchronous speed (the speed governed by the frequency of the supply grid). A standard induction motor’s rotor normally runs at a few percent less than synchronous speed (the speed difference known as slip) to enable the rotor windings to cut the stator’s field and produce the required rotor current needed to produce torque. In doing so, a motor consumes electrical energy from the supply. If the same rotor has its speed increased to synchronous speed (by some external mechanical means), the energy flow stops since the rotor windings no longer cut the stator field at “zero slip”. It follows then that if the rotor speed is increased further, a “negative slip” condition exists and the energy flow is reversed. The machine now generates back into the grid system (the mechanical energy is being converted to electrical energy). Thus the critical speed/frequency/ poles relationship does not apply. The beauty of the induction generator is that it does not require initial synchronising to the grid; it is merely a matter of running up to a speed slightly greater than synchronous speed and closing the supply circuit switch. There is, however, one main drawback in that the supply must normally (but not necessar­ily) be available for the machine to close on to, since an induc­tion generator usually derives its field from the running grid. Todd’s Corner Power Station in Tasmania’s central highlands operates in this manner. T. Ives, Penguin, Tasmania. Bass cube rear panel should not be glued I have read the article on the Bass Cube in the April 1999 issue and congratulate you on what appears to be an excellent project for the home audio market. However, I have one question which I can not answer. The article appears to say that the only access to service the driver is glued into the box (last paragraph on page 43). Looking at the photographs the driver appears to be mounted inside the box. I have been in the audio industry for many years, servicing all types of amps and speakers, including re-coning brands of speakers such as Altec Lansing, JBL, Electro-Voice, Klipsch, Cerwin Vega, Wharfdale, etc. I have never seen a box where it is virtually impossible to remove the speaker for service (well, almost never – some Bose units have the speakers glued into the box with hot melt glue!). Your article states that the manufacturer may not honour the speaker warranty if the wires are soldered to the speaker (strange!) but if the speaker can not be removed from the box, I continued on page 77 MAY 1999  71 NOW EVEN BETTER! Even 72  Silicon Chip LOWER cost Internet access 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! (c) WE WILL THEN FAX YOU OR POST YOU your password and EASY setup details. 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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: $ __________ August MAY 1999  73 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. Add bass harmony to a guitar This circuit was developed for use with a guitar although other instruments or sound sources could be used. The circuit divides the input frequency and produces an output that consists of the original input signal plus sub-harmonics at one and two octaves below. In essence, the input signal is amplified by op amps IC1a and IC1b and the resulting clipped signal is used to clock IC7, a 4024 7-stage binary counter. Subharmonic outputs are then taken from the Q1 and Q2 outputs of IC7 and fed via pots VR1 and VR2 to a mixer stage employing IC2a, followed 74  Silicon Chip by a low-pass filter stage comprising IC2b. The composite filtered sub-harmonic signal is then fed to a 3080 trans­con­ductance amplifier which automatically controls the gain according to the signal amplitude at the input. Note that the input signal is also fed to IC5, a 741 op amp which feeds a rectifier consisting of diodes D1 and D2, together with two 1µF capacitors. This rectifier feeds the control input on the 3080. The signal from the 3080 is buffered by IC4 and then mixed with the input signal in IC6. The bypass switch S1 allows the effect to be switched in and out. Setting up requires a little trial and error to find the correct setting for VR3 which sets the voltage gain. Start by setting it midway and then adjust it so that the low bass notes are not clipped or sound distorted but are sufficiently loud. The circuit runs on a single 9V battery and draws around 5mA. S. Williamson, Hamilton, NZ. ($40) Add remote control to an old VCR Yes, it is possible to add infrared remote control to any old VCR which has a two-wire remote control. To do it, you need to use this simple circuit together with the 8-channel IR remote control described in the February 1996 issue of SILICON CHIP. No modification is required to the VCR itself. As described in the February 1996 article, the IR receiver circuit has eight outputs, A to H. The first six are momentary, while the other two are latched outputs. Table 1 (under the circuit) shows the functions provided by a selection of VCR models, together with the resistance values needed to select each function. On the circuit, resistors R1 to R8 must be chosen from this table to suit the type of VCR. The switching is done using each gate of a 4066 analog switch (IC1 & IC2). Fortu­ nately, the nominal 90Ω on-resistance of these gates is low enough not to be a problem for the VCR models shown. Outputs A, B, C, D and F directly drive the control inputs of IC1 and IC2b respectively. Output E (used for the record function) drives switch IC2a via an RC delay circuit. This means line E has to stay high for about two seconds before IC2a will switch on. This ensures that the Record mode cannot be acciden­tally activated. The latched outputs G and H have been used to control the Channel Up and Channel Down VCR functions but these needed a little modification to make them useful. Exclusive-OR gates IC3a and IC3b are configured as edge-detectors to provide a short positive-going pulse in response to each press of the correspond­ing button on the transmitter. Each pulse momentarily closes the corresponding CMOS switch (IC2c or IC2d) to activate Ch.Up or Ch.Dn. Note that some early VCRs did not have remote channel-changing ability. Power for the circuit comes from the IR receiver PC board (from the emitter of Q2), giving a nominal supply rail of 5.6V. Chris Dunn, Nowra, NSW. ($50) MAY 1999  75 Silicon Chip Binders Circuit Notebook – continued REAL VALUE AT $12.95 PLUS P&P These binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 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 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_______ 76  Silicon Chip Low frequency RF preamplifier This low frequency RF preamplifier circuit is designed to be connected between a long wire antenna and a low frequency receiver. It was designed for listening to low frequency airport beacons and amateur radio low frequency signals. There is only one control to adjust and that is vari­able capacitor C1 which provides a series resonant circuit with the antenna at the required frequency. Simpler metering circuit for capacitance meter The Capacitance Meter published in the February 1999 of SILICON CHIP can be simplified with the release of a new LCD panel meter from Altron­ ics in Perth. This new panel meter has the advantage that it can share a com- When listening for amateur radio signals, usually Morse code, 181.4kHz New Zealand or 176.5kHz Tasmania, the antenna needs to be a few hundred metres long and about half a metre above the ground, facing end-on to the incoming signal. Q1 and Q2 can be regarded as a cascode stage with the output being taken from the collector of Q2. Further gain is provided by Q3 which is then buffered by the emitter follower stage, Q4. R. Milne, Moonah, Tasmania. ($25) mon ground with the circuit it is measuring. This means that the level-shifting op amp (IC3) in the original ca­ pacitance meter circuit can be dispensed with. The simplified circuit is shown here and can be wired up on the original PC board. The new Altronics panel meter retails for $25 (Cat Q-0570). SILICON CHIP Circuit Ideas Wanted Do you have a good circuit idea. If so, why not sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We pay up to $60 for a good circuit but don’t make it too big please. Send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, 2097. Mailbag: continued from page 71 guess it doesn’t matter how you connect the wires. Forgive me if I have missed something in the arti­ cle. I understand that the box has to be airtight but if I haven’t, some form of rebate or front mounting of the driver is a more practical idea if it develops a fault. Brad Sheargold, Collaroy, NSW. Comment: You are right. The rear panel should not be glued into place although some form of sealant should be applied before it is screwed down. PIC programmer feedback I have some feedback regarding the PIC programmer described in the March 1999 issue. I don’t know if anyone else has had any problems with theirs but when running the sample program that I obtained from the Oatley website, two LEDs were cycled instead of one. This was puzzling until I realised that the carry bit from the STATUS register was carrying over, so to speak, at the “rlf” command. Execution of the command “bcf STATUS,7” clears bit 7 of the STATUS register prior to rotating the bits left and apparent­ly fixes the problem. Also, when starting the NOPPP program, the message, “Hard­ware not found” occurs although the programmer appears to func­ tion perfectly. Has anyone else had this message? Is it a soft­ ware or hardware fault? Some feedback would be appreciated. Some tutorial articles examining the functions of the PIC16F84 and simple example code would be of great value to many of your readers. Kerry Helman (via email). Converting LCD calculators to 7-segment display Can anyone advise me how the output of LCD calculators can be converted to run 7-segment LED displays? Obviously a separate power supply and LED display would be required and I am prepared to locate in a separate enclosure. Any assistance that your readers may be able to give would be much appreciated. B. Allardice, Cunnamulla, Qld. MAY 1999  77 Silicon Chip Back Issues December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple Elec‑ tronic Die; A Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: A Low-Cost 3-Digit Counter Module; Build A Simple Shortwave Converter For The 2-Metre Band; The Bose Lifestyle Music System (Review); The Care & Feeding Of Nicad Battery Packs (Getting The Most From Nicad Batteries). March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Rail‑ ways; How To Install Multiple TV Outlets, Pt.1. June 1991: A Corner Reflector Antenna For UHF TV; Build A 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Trou‑ bleshooting Vintage Radio Receivers; The MIDI Interface Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cock‑ roach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanu‑ meric LCD Demonstration Board; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Build A Windows-Based Logic Analyser. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Win‑ dows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled Cockroach. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. ORDER FORM Please send me the following back issues: _____________________________________________________________________ _______________________________________________________________________________________________________________ _______________________________________________________________________________________________________________ Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ Note: all prices include post & packing Australia ....................................................... $A7 NZ & PNG (airmail) ...................................... $A8 Overseas (airmail) ...................................... $A10 Street ______________________________________________________ Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Suburb/town _______________________________ Postcode ___________ Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. PLEASE PRINT 78  Silicon Chip ✂ Card No. December 1993: Remote Controller For Garage Doors; Build A LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags In Cars – A Look At How They Work. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Pre‑ amplifier; Digital Water Tank Gauge; Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Elec‑ tronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Build A Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Dis‑ charger (See May 1993); How To Plot Patterns Direct to PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote Control System for Models, Pt.1; Index to Vol.7. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Trans‑ verter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. December 1997: A Heart Transplant For An Aging Computer; Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. March 1996: Programmable Electronic Ignition System; Zener Diode Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Audio Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. February 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Demonstration Board For Liquid Crystal Displays; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. May 1996: Upgrading The CPU In Your PC; High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluores­cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscil‑ loscopes, Pt.4. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­g rammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: Adding A Parallel Port To Your Computer; 8-Chan‑ nel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Pre­amp­lifier. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; Remote Control System For Models, Pt.2. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (For Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark­ rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Cathode Ray Oscilloscopes, Pt.7. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. November 1997: Heavy Duty 10A 240VAC Motor Speed Control‑ ler; Easy-To-Use Cable & Wiring Tester; Build A Musical Door‑ bell; Relocating Your CD-ROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. December 1996: CD Recorders –­ The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. May 1995: What To Do When the Battery On Your PC’s Mother­ board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. April 1997: Avoiding Win95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. May 1997: Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. September 1995: Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Keypad Combination Lock; The Vader Voice; Jacob’s Ladder Display; Audio Lab PC-Controlled Test Instrument, Pt.2. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How Holden’s Electronic Control Unit works, Pt.1. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home; How Holden’s Electronic Control Unit Works, Pt.2. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­ verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget; Win95, MSDOS.SYS & The Registry. April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Ad‑ justable Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator; Build A Laser Light Show; Understanding Electric Lighting; Pt.6; Jet Engines In Model Aircraft. May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. June 1998: Troubleshooting Your PC, Pt.2; Understanding Elec‑ tric Lighting, Pt.7; Universal High Energy Ignition System; The Roadies’ Friend Cable Tester; Universal Stepper Motor Controller; Command Control For Model Railways, Pt.5. July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem And Sorting Out Any Problems); Build A Heat Controller; 15-Watt Class-A Audio Amplifier Module; Simple Charger For 6V & 12V SLA Batteries; Automatic Semiconductor Analyser; Understanding Electric Lighting, Pt.8. August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory To Your PC); Build The Opus One Loudspeaker System; Simple I/O Card With Automatic Data Logging; Build A Beat Trig‑ gered Strobe; A 15-Watt Per Channel Class-A Stereo Amplifier. September 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A WaaWaa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. October 1998: CPU Upgrades & Overclocking; Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Con‑ ditions; Adding An External Battery Pack To Your Flashgun. November 1998: Silicon Chip On The World Wide Web; The Christmas Star (Microprocessor-Controlled Christmas Decora‑ tion); A Turbo Timer For Cars; Build Your Own Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltme‑ ter, Pt.2; Beyond The Basic Network (Setting Up A LAN Using TCP/IP); Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. December 1998: Protect Your Car With The Engine Immobiliser Mk.2; Thermocouple Adaptor For DMMs; A Regulated 12V DC Plugpack; Build Your Own Poker Machine, Pt.2; GM’s Advanced Technology Vehicles; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Glider Operations. January 1999: The Y2K Bug & A Few Other Worries; High-Voltage Megohm Tester; Getting Going With BASIC Stamp; LED Bargraph Ammeter For Cars; Keypad Engine Immobiliser; Improving AM Radio Reception, Pt.3; Electric Lighting, Pt.10 February 1999: Installing A Computer Network (Network Types, Hubs, Switches & Routers); Making Front Panels For Your Pro‑ jects; Low Distortion Audio Signal Generator, Pt.1; Command Control Decoder For Model Railways; Build A Digital Capacitance Meter; Remote Control Tester; Electric Lighting, Pt.11. March 1999: Getting Started With Linux; Pt.1; Build A Digital Anemometer; 3-Channel Current Monitor With Data Logging; Simple DIY PIC Programmer; Easy-To-Build Audio Compres‑ sor; Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12. April 1999: Getting Started With Linux; Pt.2; High-Power Electric Fence Controller; Bass Cube Subwoofer; Programmable Ther‑ mostat/Thermometer; Build An Infrared Sentry; Rev Limiter For Cars; Electric Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, December 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992, December 1992 and March 1998 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc for $10 including p&p, or can be downloaded free from our web site: www.siliconchip.com.au MAY 1999  79 Getting started with Linux; Pt.3 This month we’ll show you how to put Linux to work. In particular, we’ll look at configuring Linux as a file and printer server to a Windows network and describe how to use Linux as a router, so that several people can share an Internet connection. By BOB DYBALL For many people, the word “LAN” or even “computer” evokes fear and trepidation at the expenses that will be incurred. Fortunately, Linux can provide a low-cost solution to many networking requirements, especially when it comes to shared Internet access. As we learnt last month, by running Linux, there’s still some life that can be squeezed out of many old 486s and slower Pentium machines. For example, if you have 2, 3, 10 or even 20 people who would like Internet access (eg, for email), a humble 486 running Linux and a single Internet feed are about all you need to get going. Be warned though that Linux isn’t for everyone and takes some time to learn. If you really need to keep your existing system running (eg, in a production or office environment), don’t go messing with things too much. Instead, set up a small test network and work up to the grand plan slowly. Also, because of the differences between one version of Linux and another (eg., kernel 2.03.6 to 2.2.1) and between the different “distributions” (eg, Red Hat versus Caldera), it will be necessary to generalise here on occasions. Fortunately, most of the differences are quite minor, some simply involving a different installation directory or different standard settings, Fig.1: this screen shot is from a Windows 98 system, look-ing across a network at shared resources on a Windows 95 machine named “Lister”. 80  Silicon Chip The worst case scenario for a new Linux user might be the need to recompile the kernel – something that wouldn’t be too much fun early on unless you’re the adventurous type. OK, let’s take a look at how to set up a Linux installation to function as a file and printer server. The wrong and the right way to share printers The moment you have less printers than PCs, you’ll run into a familiar problem – how do you allow those people without printers to print documents without interrupting those with printers. Faced with this problem, some people don’t even consider a LAN or if they do, think that a printer switch box is the cheaper way to go. If you’ve just bought a printer switch box, you probably won’t like reading this. But think about it – if you allow $40 or so for the switch box and then add the cost of the cables to Fig.2: this screen shot is from the same Windows 98 system. It’s looking at the same machine as before but now running Linux, with file and printer sharing courtesy of Samba. connect the PCs, you’re not going to get much change from $100. In fact, depending on the number of PCs you have, it could cost you a lot more. Another drawback is that printer cables are limited in length to a couple of metres, unless you buy special (and expensive) long cables or a line buffer. After that, cable capacitance can cause signal degradation and reliability problems. What’s more, a man­ual printer switch is a real source of frustration. It’s all too easy to forget about the switch, which means that your job often won’t print because the wrong computer or printer is selected. There is a better, easier and cheaper way of doing things – network the computers. All you need for a two-PC LAN are a couple of cheap network cards at $25-$40 each, a length of coaxial cable, two T-pieces and a couple of 50Ω terminators. Make sure you use 50Ω cable, because leftover 75Ω TV coax won’t work. Also, it’s a good idea to buy “combo” network cards, which have connectors for both 10Base-2 (coax) and 10Base-T cable. By including the 10Base-T option, you can easily expand the network later on by adding a hub and changing over to Cat.5 cable – without the added cost of new network cards. Of course, a hub will add to the cost but a 10Base-T (star) network is more reliable than a 10Base-2 network once you have three or more PCs. A cable break only affects one computer on a 10-Base-T network, while all computers on a 10Base-2 network are affected. For a simple two or three-PC network though, coaxial cable is the cheapest way to go and reliability won’t be a problem. Depending on the cards you buy, you can network three PCs for less than $120-$150. Once you have a network up and running, you can easily share resources such as printers and CD-ROM drives without any hassles. And you can easily transfer files between computers and that’s something you can’t do via a printer switch box. Why a dedicated server? To avoid disrupting others on a network, you need to set up a dedicated server. Often, this needn’t be anything more than an old 486 with 8MB of RAM. This type of machine would run rather slowly under Windows 95 but would give quite good performance Fig.3: The Samba Configuration File # The main Samba configuration file - for sharing within a Workgroup #======================= Global Settings ===================================== [global] # workgroup = NT-Domain-Name or Workgroup-Name workgroup = WORKGROUP # server string is the equivalent of the NT Description field server string = Red Hat Linux 5.2 Samba Server # This option is important for security. It allows you to restrict # connections to machines which are on your local network. The # following example restricts access to two C class networks and # the “loopback” interface. For more examples of the syntax see # the smb.conf man page hosts allow = 192.168.1. 127. # if you want to automatically load your printer list rather # than setting them up individually then you’ll need this printcap name = /etc/printcap load printers = yes # this tells Samba to use a separate log file for each machine # that connects log file = /var/log/samba/log.%m # Put a capping on the size of the log files (in Kb). max log size = 50 # Security mode. Most people will want user level security. See # security_level.txt for details. security = user # Most people will find that this option gives better performance. # See speed.txt and the manual pages for details socket options = TCP_NODELAY # Cause this host to announce itself to local subnets here remote announce = 192.168.1.255 # Browser Control Options: # set local master to no if you don’t want Samba to become a master # browser on your network. Otherwise the normal election rules apply local master = no # OS Level determines the precedence of this server in master browser # elections. The default value should be reasonable os level = 33 # DNS Proxy - tells Samba whether or not to try to resolve NetBIOS names dns proxy = no #============================ Share Definitions ============================== [a] comment = floppy drive under Linux path = /mnt/floppy public = yes writable = yes printable = no [c] comment = Win 95 C: drive via Linux path = /fatc public = yes writable = yes printable = no [d] comment = CDROM under Linux path = /mnt/cdrom public = yes writable = no printable = no [linux] comment = All of Linux - Not a good idea to do this!! path = / public = yes writable = yes printable = no [bjc4300] comment = Canon BJC4300 printer under Linux public = yes writable = no printable = yes MAY 1999  81 Fig.4: Alternative Samba Configuration File # The main Samba configuration file - for sharing within an NT-Domain #======================= Global Settings ===================================== [global] # workgroup = NT-Domain-Name or Workgroup-Name workgroup = REDDWARF # server string is the equivalent of the NT Description field server string = Red Hat Linux 5.2 Samba Server # This option is important for security. It allows you to restrict # connections to machines which are on your local network. The # following example restricts access to two C class networks and # the “loopback” interface. For more examples of the syntax see # the smb.conf man page hosts allow = 192.168.1. 127. # this tells Samba to use a separate log file for each machine # that connects log file = /var/log/samba/log.%m # Put a capping on the size of the log files (in Kb). max log size = 50 # Security mode. Most people will want user level security. See # security_level.txt for details. security = server # Use password server option only with security = server password server = REDDWARF # Most people will find that this option gives better performance. # See speed.txt and the manual pages for details socket options = TCP_NODELAY # Cause this host to announce itself to local subnets here remote announce = 192.168.1.255 # Browser Control Options: # set local master to no if you don’t want Samba to become a master # browser on your network. Otherwise the normal election rules apply local master = yes # OS Level determines the precedence of this server in master browser # elections. The default value should be reasonable os level = 33 # Domain Master specifies Samba to be the Domain Master Browser. This # allows Samba to collate browse lists between subnets. Don’t use this # if you already have a Windows NT domain controller doing this job domain master = yes # Preferred Master causes Samba to force a local browser election on startup # and gives it a slightly higher chance of winning the election preferred master = yes # Enable this if you want Samba to be a domain logon server for # Windows95 workstations. domain logons = yes # Where to store roving profiles (only for Win95 and WinNT) # %L substitutes for this servers netbios name, %U is username # You must uncomment the [Profiles] share below logon path = \\%L\Profiles\%U # DNS Proxy - tells Samba whether or not to try to resolve NetBIOS names # via DNS nslookups. The built-in default for versions 1.9.17 is yes, # this has been changed in version 1.9.18 to no. dns proxy = no #============================ Share Definitions ============================== … etc running Linux and “Samba”. With a little more work, a modest Linux PC could also be used to validate users on a network, all for a fraction of the cost of a Windows NT system – both in terms of software and hardware. For those familiar with workgroups as opposed to “domains” on a network, a Windows NT server can hold usernames and passwords. This allows you to centrally control access to file shares, printers and other devices. Another advantage of this scheme is that users need not worry about using the same PC from day to day, as their “profiles” (or settings) can travel with them as they log onto other PCs on the network. The log-on process 82  Silicon Chip under Linux with Samba (or Windows NT) saves you from having to set passwords right across a peer-to-peer network, which is very useful if more than a few people use the system. Samba has become a popular addition to most Linux distributions and is usually available as an option that can be installed with the rest of Linux. Both the popular Red Hat 5.2 and Caldera Open Linux 1.3 packages have Samba added to their installation programs. If you haven’t installed Samba or if your version of Linux doesn’t provide this, Samba is available as a compressed archive for download, or as an RPM file. RPM stands for “Red Hat Package Manager”, a handy format that packages the file and installation instructions to Linux. Samba has another part to it called “Samba Client”, which works in reverse. If there is a file share or printer share on a Windows network, then Samba Client can provide access to these from a Linux workstation. Setting up Samba Fig.3 shows the Samba configuration file (smb.conf) which is found in the /etc directory. From this, you should have no trouble when it comes to setting up share definitions. This much-simplified file is based on the standard Samba smb.conf file and is not designed with high security in mind. It’s probably best to start with a simple smb.conf file like this and work from there, as there are many options. Note that the original sample smb.conf file includes comments to show you where to add in username/ password access. If you want to have your Linux/ Samba server “look” more like a Windows NT server and use “Domain” logons instead, then you might change your smb.conf file to something more like Fig.4. At the same time, you’ll need to make a couple of changes to the configuration of your Windows 95/98 computers. These changes are both made using the Network applet found in Control Panel. Double-click the Network icon, then click Client for Microsoft Networks, then click Properties. For workgroup or “peer to peer” networking, make sure that the “Log onto Windows NT domain” option is unchecked – see Fig.5. Now click OK, then click the tab marked “Access Control”. For work­ group networking, you would normally select “Share-level access control” (see Fig.6), relying on each printer or file share across the network to have its own individual security though passwords, or not as the case may be. Alternatively, if using a domain log on, a single password log on to the Linux server (in the guise of a Windows NT domain server, again courtesy of Samba) will verify your access to file or printer shares across the network. With this system, there is only one password to remember, not one for every different machine across the network that has a resource you might wish to use. A Windows 95/98 PC set for do- Fig.5: for workgroup or “peer to peer” networking, make sure that the “Log onto Windows NT domain” option is unchecked. Controllers” or BDCs and take over if the PDC fails. A similar arrangement could also be set up using Linux servers running Samba, although that is beyond the scope of this article. So in summary, rather than have dozens of different passwords across a network, or none at all because it’s too cumbersome, consider running Samba in its domain setup rather than as a simple workgroup system. If you’ve only a few users to set up, you might do this manually using adduser. Note that Red Hat Linux has a slightly different adduser utility compared to other distributions, so check its use by using the command man adduser. Although it’s possible to edit the name/password file, it’s not good practice since file locks are placed on the file (/etc/passwd) during editing that might prevent others logging on. Note that passwords are visible in the /etc/passwd file but are encrypted. Another useful command is pass‑ wd, used to set a particular user’s password. Again, typing man passwd will give more information on this command. For more information on users and administration in general, either check the FAQ area of the website covering your distribution or see the Linux Doc­umentation Project at sunsite.unc.edu in the /pub/Linux/ docs/LDP directory. Setting up Linux as an Internet gateway or “router” Fig.6: for work­group networking, you would normally select “Share-level access control”, relying on each printer or file share across the network to have its own individual security though passwords. main log ons and user level access is set up as shown in Fig.7 and Fig.8. In this case, check the box “Log onto Windows NT domain” and enter in the domain name of the server you wish to log on to. Click OK, then click “User-level access control” and again enter the domain name. On large networks, one normally finds a Windows NT server set up as a “Primary Domain Controller” (or PDC). Such networks also usually include one or more NT machines running as backups. These are called, funnily enough, “Backup Domain Another common network problem is where multiple users require Inter­ net access but you only have one phone line available. So how do you go about solving this problem without installing extra phone lines and buying extra modems? A router is the answer and no, it need not break the bank. By installing a router, individuals on the network can access the Internet via a single modem attached to one computer – in this case, your Linux server. In fact, a router will even allow multiple users to access the Inter­net (all using the same ISP account) at the same time via this single connection, although things can get rather slow if more than a few people are logged on. By installing a router package, an old 486 running Linux can easily serve up to 10 or 20 people. Obviously, if everyone is a heavy user of the net, you need to provide the router with a decent Internet feed to keep things running smoothly. A household or a small business can usually get away with sharing one modem between several people (since not everyone’s going to be browsing at the same time), while a large business might need a 64k or 128k ISDN feed. In simple terms, you can think of a router as behaving like a mail sorter and postman. Incoming and outgoing envelopes, known as “packets” on the LAN, are “routed” to their correct destinations, depending on where they’re coming from and where they’re meant to go. Fig.7: here’s how to set up a Windows 95/98 PC for domain name log ons. Use the same domain name for all PCs on the network. Fig.8: after setting up the domain name (see Fig.7), click the Access Control tab, click “User-level access control” and again enter the domain name. MAY 1999  83 Fig.9(a): setting up the DNS configur­ation in the TCP/IP Properties dialog box. In this case, the Domain name is reddwarf.home (this is the same for all PCs on the network), while the Host name is starbug. The DNS Server Search Order numbers are those provided by your ISP. Fig.9(b): after setting the DNS Config­uration, click the Gateway tab and enter in the IP address for the Gateway/Router machine (ie, the Linux machine) in the window below “New gateway” and click Add. The address will then be shown in the “Installed gateways” window. Linux makes an ideal router, a fact attested to by the many Internet Service Providers (ISPs) who now use Linux, along with the increasing numbers of businesses, schools and even home users. There are three main things to consider when setting up your system: (1) Linux must have its Kernel set up for IP forwarding (some distributions do not have this as standard and will have to be recompiled with this option enabled; (2) Linux needs to have an Internet dialler set up, so that it can connect to the ISP account; and (3) The other “client” computers on the LAN must be set up to make use of the new “gateway” or “router”; ie, they must direct Internet traffic through the router PC instead of directly via a modem. We’ll assume here that you have IP forwarding enabled, since it is present by default in most, if not all, of the latest versions across various distributions. These include Red Hat 5.2, Caldera Open Linux 1.3 and Slackware 2.0.36. You might still have the option of disabling this feature during installation, so be careful not to choose the wrong options. When it comes to an Internet dialler for Linux, there are lots of choices. You’ll find there are diallers that provide only SLIP, while other diallers provide PPP. On your Linux distribution CD-ROM, you should find a useful guide to PPP access under / doc/FAQ/html/PPP-FAQ.html. If you don’t have a browser up and running, refer to the text version at /doc/FAQ/ txt/PPP-FAQ instead. As with the Windows 95/98 diallers, some Linux diallers have what’s known as “dial on demand”. This means that they automatically dial your ISP when ever a program function requires an Internet connection (eg, when checking for email). After a given period of inactivity, these will hang up the line automatically. If you are fortunate enough to have a permanent connection, the system should be set up to automatically redial if the line drops out for some reason (this is done to maintain the connection). For more information on dial on demand (diald), including examples, check the “how to” files on the distribution CD-ROM. These are usually found in /doc/HOWTO/ mini/diald (note: under Linux this, like most things, is case sensitive). If you want a quick and simple way to view these files, do the following: • type mount /mnt/cdrom to allow access to the CD (umount /mnt/cdrom releases it). • type mc to run Midnight Commander, for easy access to Linux. Once Midnight Commander is 84  Silicon Chip running, use F3 to view a file or F4 to edit (there’s also a range of other useful functions). You don’t have to be a Unix/Linux command whiz here, as Midnight Commander is quite easy to use (it’s certainly easier for the first time user than trying to figure out what to type at the command line). In addition to the information on diallers, you’ll also find information on firewalls and networking in general. Choose the dialler that suits you best and don’t worry too much about changing from one dialler to another. The actual diallers are usually just a “shell script” (rather like a super-batch file, for those used to DOS). Simple or even quite complex tasks that might otherwise be repetitive can easily be automated using “shell scripts”. Home users or casual users might prefer to dial up manually. This prevents the system from automatically reconnecting if the line drops out and someone has forgotten to turn off an email package that requests an email check at 10-minute intervals overnight. Local calls might be cheap but they can soon add up. IP addressing Finally, you need to ensure that the clients (ie, the other machines on the LAN) are set up to use the router as a gateway. Note that you don’t have to use “real” IP addresses for the clients. Instead, it’s best to use “non-routable” IP addresses (so that your LAN is invisible to other computers on the Internet) and let the router handle the rest. If you have a permanent connection, your ISP will usually assign you one IP address and this is given to the router. Alternatively, for dial up connections, the IP address is assigned automatically to the dialler, so you don’t have to bother about it. We talked about IP addressing in “Beyond the Basic Network – Setting up a LAN using TCP/IP” (see SILICON CHIP, November 1998). In particular, we mentioned that the Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of non-routable IP addresses for “private Internets” (ie, Intranets). These address blocks are as follows: 10.0.0.0     to 10.255.255.255 172.16.0.0   to 172.31.255.255 192.168.0.0 to 192.168.255.255 if you were running a single Windows 95/98 dial up. Lmhosts Fig.10(a): in most cases, you will have to select “Disable WINS Resolution” in this dialog box, as WINS (Windows Internet Naming Service) is generally only used on large networks. For small networks, you can use lmhosts. Fig.10(b): next, click the IP Address tab, check “Specify IP Address” and enter in the IP address for that computer (192.168.1.40 in this case), along with the Subnet Mask (use 255.255.255.0 for all machines). For this and further details on IP addressing, point your web browser to http://ucnet.canberra.edu.au/RFC/ rfc/rfc1918.html The IP address 127.0.0.1 is a special address that’s refers to some other program on the PC itself – in this case, the router. What you have to do now is assign an IP address for each of the machines on the network. For example, let’s use 192.168.1.1 for the Linux machine with the gateway/router, 192.168.1.40 for the first client computer on the network, 192.168.1.80 for a second client, and so on. Don’t use 192.168.1.255 or similar .255 addresses, and don’t use .0 addresses, as they have a special meaning in a network like this. You also have to enter in a Domain name and a Host name on each PC and you do that via the DNS Configuration tab of the TCP/IP Properties dialog box as shown in Fig.9(a). In this case, the Domain name is reddwarf. home (this is the same for all PCs on the network), while the Host name is starbug (a different Host name is used for each PC). This done, click the Gateway tab, enter in the IP address for the Gateway/Router machine (at New gateway) and click Add (Fig.9(b)). You also select Disable WINS Resolution (see Fig.10(a)), after which you click the IP Address tab and enter in the IP address for that computer (192.168.1.40), along with the Subnet Mask (use 255.255.255.0 in all cases) – see Fig.10(b). On the client computers, you would normally set the Primary and Secondary DNS to the addresses given to you by your ISP. Leave the gateway IP address blank on the gateway/router itself (since it is one) and configure the DNS settings on the router to reflect those your ISP would tell you to use Fig.11: Example LMHOSTS File #IP Address # 192.168.1.1 192.168.1.40 192.168.1.80 Fig.12: Example Linux hosts File 127.0.0.1 192.168.1.1 192.168.1.40 192.168.1.80 localhost.localdomain lister.reddwarf.home starbug.reddwarf.home holly.reddwarf.home localhost lister starbug holly Machine name lister starbug holly In order for the machines to “find” each other on the network, you now need to create a simple text file called LMHOSTS (ie, no extension) and copy it to the C:\WINDOWS directory of each Windows 95/98 machine. This lists the IP address of each machine on the network and its (Host) name. Fig.11 shows the LMHOSTS file you would use for the example given above (the lines starting with “#” are comments and don’t do anything). Note that a reboot is necessary after adding (or altering) an LMHOSTS file. You also need to add a similar file to the /etc directory of your Linux machine. In this case, the file is called hosts (not LMHOSTS) and you must list the IP address, the Domain name and the Host name of each computer – see Fig.12. You must also include the IP address for the localhost (this isn’t necessary for Windows 95/98/NT as localhost is automatically defined as 127.0.0.1). You may be wondering about the Domain name ending in .home rather than .com or .com.au. Well, you can use almost anything you like here since it only has to be recognised by your local network. What’s more, using the .home extension means that your private domain cannot be “seen” by the Internet, just as the Internet cannot access the non-routable IP addresses listed above. Should any reference to these domain names or IP addresses appear out in the outside world on the Inter­net, they would be ignored. If you have more than about 20 computers, editing all the LMHOSTS files becomes a nuisance when you want to add extra machines to the network. There are a few shortcuts but when you reach that stage, it’s best to consider using either WINS (Windows Internet Naming Service), DHCP (Dynamic Host Configuration Protocol), or a DNS (Domain Naming System). In Pt.4, we’ll talk about Linux fire­ walls and security issues. We also plan to discuss what DNS, WINS, DHCP and hosts or LMHOSTS actually do (probably in a separate article). And so that Windows users do not feel unloved, we’ll describe how these relate to Windows 95, Windows 98 SC and Windows NT as well. MAY 1999  85 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG Restoring the butchered set Restoring a vintage radio that someone else has had a go at can be a difficult job. Sometimes the fault will be quite subtle but all too often, the previous restorer will have made a complete mess of things. It’s not unusual to come across a set that has been really butchered. When you see such a set, it makes you think that the person who did the work on it should be granted the striped apron award and then hung, drawn and quartered. Often, these sets are obtained for what appears to be a reasonable price and the seller often says that there isn’t much wrong with the radio. Sometimes however, the seller has tried to get the set going but has finished up with a mess that’s bigger than when the work was started. This is a case where a little knowledge can be dangerous. Caution is needed in restoring sets that haven’t been “got at” and an enormous amount of caution is needed where as set has obviously This view shows the wiring around the 6M5 valve socket of the Little Nipper radio that I was given to service. Before removing any parts, it’s a good idea to make a drawing of the connections so that it can be easily reassembled later on. 86  Silicon Chip been “got at” and “butchered” into the bargain. In some cases, the restorer has been very careful with the work but has been unsuccessful because they didn’t understand how the circuit worked. In other cases, everything has been done correctly and the lack of success is due to a faulty new part. Yes, that happens occasionally and people with considerable experience get caught as well. A snap diagnosis When I built my first radio in 1954 (a “Marconi” 1-valve kit), I couldn’t get it to work. I then took the typical but totally useless approach of a novice and pulled it to pieces and rebuilt it – more than once, actually – and it still didn’t go! It must be the 3V4 valve, I reckoned, so I sent it back to the supplier and they sent me another one and the set then worked. For once, the diagnosis of “it must be the valve” was correct but it often isn’t. I had no test gear, virtually no radio knowledge and no hope of finding out what was wrong. My so-called diagnosis was nothing more than a lucky guess. Of course, once the set was operating, I became the local radio expert – at least, in my opinion. I was soon brought back to earth. A cousin and I tried to get his 1-valve (1D8GT) radio going a little later on and we had no success with it at all. Like mine, I wondered some years later if we had inadvertently put HT voltage on the filament of the valves! We’ll never know. In circumstances like this, it is better to get some advice from a restorer more experienced than you are. When we lack the experience of years in the trade, it’s easy to overlook things that Fig.1: the circuit of a late-model HMV “Little Nipper”. Substituting incorrect component values can really upset the performance of a circuit like this. a more knowledgeable person would detect quickly. For example, I got bogged down trying to get my VHF amateur radio station going on the 144-148MHz band soon after I got my licence. I literally didn’t have a clue and so a friend and I bundled all our amateur radio gear into the car and travelled 100km to the nearest VHF amateur radio operator. He helped both of us get the equipment going, explained to us what he was doing and encouraged us in various ways. We never looked back from that time onwards. And so it is with new restorers. A little help at the right time and you’ll really start to have a satisfying time restoring your radio gems. The things people do What people manage to do to the sets they are restoring could fill a book. My first story concerns a friend’s brother-in-law. He acquired a 6V vibrator mantle set which he asked my friend about and was told that it was a battery operated set. Obviously, this advice didn’t sink into the “smart-alec” brother-in-law’s head, as he promptly removed the 50A battery clips and substituted a 3-pin mains plug. He then plugged the set into the 240V mains supply. There are no prizes for guessing what happened next. All the valves now have no filaments, while the fate of the vibrator is unknown As for the rest of the set, heaven knows what damage has been done. A perfectly good set was instantly turned into junk and it’s now a very doubtful proposition for restoration. This same scenario often occurs when 32V sets are bought or sold to the local secondhand/antiques shop. Unfortunately, 32V sets look like their 240V AC cousins and usually have 3-pin plugs on their power cords. Plugged into 240V, things light up brilliantly for a fraction of a second until the fuses in the set blow – that is, if they haven’t been replaced with a 2-inch nail (the original 300A slowblow fuse). Remarkably, many 32V sets survive such harsh treatment but be aware that all may not be well in such a set. Then there are the sets that someone has actually got into and “serviced”. These are the real worry and before even switching them on, it’s advisable to obtain a circuit diagram from the Historical Radio Society of Looking for an old valve? or a new valve? BUYING - SELLING - TRADING Australasia's biggest selection Also valve audio & guitar amp. books SSAE DL size for CATALOGUE ELECTRONIC VALVE & TUBE COMPANY PO Box 381 Chadstone Centre VIC 3148 Tel: (03) 9571 1160 Fax: (03) 9505 6209 Mob: 0411 856 171 email: evatco<at>mira.net MAY 1999  87 Fixing the butchered set – continued Australia or the New Zealand Vintage Radio Society. Alternatively, you may know a fellow enthusiast who can supply a copy. If in doubt, trace the circuit out to determine whether it is as it should be. If not, a rewiring job lies ahead before the set can be turned on. Sometimes, the exact circuit diagram will be difficult to obtain. If this happens, select a circuit that’s similar (eg, for a slightly different model) and use this as a starting point for the restoration. Naturally, different valves require slightly different operating conditions and the Miniwatt Technical Data book can help you here. The Little Nipper I once had a late model Little Nipper HMV radio to service. These sets are quite reliable and, as shown in Fig.1, the circuit is quite straightforward . This particular set suffered from instability in the IF amplifier. In this circuit, the AGC bypass/ filter capacitor (C9) not only filters the AGC line but also acts as part of a neutralising circuit with C8 (this just goes to show that pentodes, as well as triodes, can benefit from neutralising in RF circuits). I found that the restorer had installed the wrong value for C9 (about 10 times the correct value). This in turn upset the neutralisation and caused the instability. As soon as the correct value was installed for C9, the set performed quite nicely. In another case, the restorer re- t Shop soiled bu ! HALF PRICE placed the diode detector RF filter capacitor (C15) with another capacitor that he thought was of the same value. Apparently, it wasn’t easy to read the value on the original and not having a circuit to refer to, he used a .01µF capacitor when the correct value was 100pF. As a result, the set was very “bassy” and had little audio gain. Once again, changing the capacitor fixed the problem. Capacitor values are not usually critical except in tuned circuits. Gross deviations from the correct values can create problems but one step up or down from the nominal value is rarely a problem. Note also that some of the nominal values that have been used for years through force of habit are not necessarily the optimum values. On the other hand, resistors tend to be more critical and so the correct values should be used in that part of that particular set’s circuit. By following the general component values, as shown in Fig.1, the performance should be quite reasonable. The worst sets The worst sets to get back into operation are those where the restorer has decided to replace things “willy-nilly”, in an effort to get the set going. In some cases, all the paper capacitors are taken out and then a new batch is put back in. Unfortunately, many people forget to draw diagrams of where things come from and often end up fitting the new parts in the wrong places. The result is a unique circuit that doesn’t work. I make it a policy to replace one component at a time so that I don’t forget where it came from. And if I have large component such as a valve socket to replace, I draw a diagram on a piece of paper that shows all the connections, so that I know what goes where. Sets that have been abused in various ways are not good choices for first-time restorers to cut their teeth on. Experienced restorers are not keen on them either and for good reason – they can be more trouble than they’re worth. If you do have a set that falls into this category it’s best to seek advice from an experienced vintage radio restorer. That way, you won’t spend a lot of time on a set that’s not worth restoring or that’s beyond your capabilities. Manufacturing faults Finally, note that some sets had faults built into them right from when they were manufactured. If you can detect the errors made (and they may not be easy to find), you may well be able to say “it goes better than new”. I’ve encountered a few stinkers like that over the years and they generally become first class sets once the problems have been ironed out. Of course, the faults are usually very subtle and take some hunting down. That said, restoring a vintage radio set that someone else has given up on is a very satisfying experience. SC Have fun. 14 Model Railway Projects THE PROJECTS: LED Flasher; Railpower Walkaround Throttle; SteamSound Simulator; Diesel Sound Generator; Fluorescent Light Simulator; IR Remote Controlled Throttle; Track Tester; Single Chip Sound Recorder; Three Simple Projects (Train Controller, Traffic Lights Simulator & Points Controller); Level Crossing Detector; Sound & Lights For Level Crossings; Diesel Sound Simulator. 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. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 88  Silicon Chip ELECTRONICS SHOWCASE LASER DIODE MODULE NORMALLLY $289 These very bright 5mW/650nM modules employ a simple 3V driver circuit: Data supplied on use with higher voltages.PCB & diode are not fixed to the lens assembly, adjustable focus. LOWEST PRICES EVER: $8 Ea. $8!! AM LASER COMMUNICATIONS KIT: Ref:EA July 97. Communicate high quality audio on a LASER BEAM. Basic kit includes two PCBs (TX & RX), all the on-board components, an electret microphone, a speaker, a photodiode. with above laser: (K73V) $35 LASER CROSS HAIR LENS industrial & alignment applications. 80c Ea NEW SUPER LOW PRICE LASER AUTOMATIC LASER LIGHT SHOW KIT: MKIII. Automatically changes every 5 - 60 secs. Countless displays from single to multiple flowers, collapsing circles, rotating single & multi ovals, stars, etc. Easy mirror adjust. Kit inc. PCB, all on board parts, 3 motors, mirrors, adjust. mirror mounts +above laser module. $55 NEW ELECTRIC FENCE: $34 Ref SC Apr, May.This hi-power short form kit inc. PRE WOUND TRANSFORMERS (T1 & T2), capacitor, silk screened PCB, + all on-board components. KEY-CHAIN LASER POINTER in a presentation box. Quality machined metal housing + 3X LR44/AG13 bat. FREE. Extra batteries 50c Ea. $10 oatleyelectronics.com SPECIAL OFFER: ONLY $249 EMONA INSTRUMENTS NSW (02) Phone 9519 3933 Fax 9550 1378 VIC (03) 9889 0427 9889 0715 QLD (07) WA (08) 3367 1744 9361 4200 3367 1497 9361 4300 MicroZed Computers BASIC Stamps Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 014 036775 Fax (02) 6772 8987 http://www.microzed.com.au Most Credit Cards OK 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. NEW FROM QUESTRONIX DVS5 Video & Audio Distribution Amplifier DVS5 Video & Audio Distribution Amplifier VGS2 Graphics Splitter Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. VGS2 Graphics Splitter High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email - questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC's, Converters, etc. QUESTRONIX All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only EMC Technologies' internationally recognised Electromagnetic Compatibility (EMC) test facilities are fully accredited for emissions, immunity and safety standards. EMC Technologies Melbourne: (03) 9335 3333 Sydney: (02) 9899 4599 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. Class A amplifier in monoblock form Could you please outline the modifications which would be necessary to run the Class-A amplifier as two monoblocks, each using their own dedicated power supply? To keep the convenience of one volume control, I would retain the separate amplifier and power-supply box design shown in your article. However, I would love to see you publish a control unit worthy of this amplifier! In such an event, would the monoblock setup enable each module to be housed in the same casing as its respective power supply, (ie, two self-contained units) or would it be best kept as is? In addition, I have two 20-0-20V 160VA toroidal transform­ers which I intend to use. Will I need to add some windings to the secondaries, or would the slightly lower voltage not Trigger problem in multi-spark CDI While building the Multi-Spark CDI described in the Septem­ ber 1997 issue, I came across the following faults: (1) if both points circuits are fitted to the board but only one is used, the circuit will not fire because the other points circuit will hold the input of Q4 high via diode D12 or D13; (2) in the circuit shown to trigger a standard tacho (page 30), Q1 should be a BC327 PNP transistor, not a BC337 as shown. Although I have the tacho circuit firing, it will not move the tacho at all. Can you offer any suggestions? Would a resistor in series with the transformer winding help? (R. J., El Arish, Qld). • The points trigger circuit included the option for using two sets of points. If you are only using one 90  Silicon Chip be significant? Just following on from that, I was thinking of building a pair of horn speakers and was wondering how the Class-A amplifier would play at the extremely low power levels (milli­watts) that horns require (due to their highly efficient nature). Many horn buffs recommend using low power Class-A triode amplifiers, claiming that some transistor amplifiers sound bad through horns, as they have difficulty playing cleanly at very low levels. Their reasoning is that the transistors perform best while driving the high currents they are designed for, rather than at a level which they describe as being “barely turned on/ hardly working”. Would the use of the high power Motorola MJL21193/4s suffer the problem described above? Or would this be the case with any transistor amplifier (Class-A or otherwise)? In addition, would the distortion levels at such a low power level increase to set of points, then the second set of components (D13 and the 47Ω resistor) should not be included on the PC board. This option was mentioned in the parts list but perhaps was not made clear enough in the construction section of the article and overlay diagram. Thanks for pointing out that transistor Q1 in the impulse tachometer circuit should be labelled a BC327 and not BC337 as shown. Impulse tachometers can sometimes be difficult to drive when the original ignition system has been altered. This is because the tacho­ meter may have been designed to detect the primary resonance of the ignition coil or it requires a slower or faster rise time from the coil. We suggest that you experiment with the value of ca­pacitance between the collector and emitter of transistor Q2. This will alter the rise time of the pulse. the point of becoming intrusive? (P. S., Mt Colah, NSW). • No component changes should be necessary to run class-A monoblocks although you will need two separate power supplies, as you have noted. Make sure that the volume control wiring is well shielded so that it does not pick up any hum from the power supply. We are giving serious thought to a control unit although it is far too early to say when a design might appear. The Class-A amplifier will perform superbly at low levels, simply due to the fact that it is class-A. As you can read in the article, we estimate that low level distortion is probably less than .0002%. This is vastly less than the typical distortion in a horn loudspeaker. The real merit of a horn loudspeaker is its efficiency not high fidelity. Triode amplifiers are generally low-fi designs. For best quality from a valve design you need to use an ultra-linear push-pull design and even that will not go anywhere near the quality of our Class-A design. SLA batteries need full charge I was interested to read your article in the October 1998 issue regarding the use of SLA batteries for electronic flash guns. Have you ever run a similar article for camcorders? If not, let me tell you my story. I have a Sony CCDF555E, bought in December 1992. It has a power consumption of 6.9W (in record mode), according to the owner’s handbook. Last year the three NiCd batteries which I bought in 1992 gave up the ghost, so I bought a 6V 4A.h SLA battery. I pulled the insides out of one of the NiCd battery packs to enable con­nection to the camcorder and tried to run it from the SLA bat­tery. This battery was only able to run the camcorder for about five minutes before the “low battery” indicator lit up. Several recharges using a charger designed for the battery failed to im- prove the available recording time. Testing with a multimeter after charging showed a voltage of 6.7V and on failure to run the camera, about 6.2V. The wording on the battery indicated that up to 7.3V could be available. This didn’t worry me since the mains adaptor supplied with the camcorder was rated at 7.2V. Would a battery setup using a 12V SLA battery be feasible, or would the zener or other regulator use up too much of the battery’s capacity to be worthwhile? In regards to a “proper” battery for the camcorder, I subsequently bought a 6V NiMH bat­tery which has given very poor service and has been returned to the maker for inspection and testing. None of the batteries which I have used with this camera have lived up to the performance I would have expected of them. Perhaps the camera is faulty and should be checked. The best performance was 60 minutes recording with a 2.2A.h NiCd about six months after I bought it, and using a discharger/charger to recharge it. (I. S., Castle Hill, NSW). • 6.7V does not constitute a full charge for a 6V SLA battery. Full charge should be around 2.4V or more per cell, or around 7.2 to 7.3V. Your charger is clearly not doing the job. Perhaps you should build our Multi-Purpose Battery Charger, as described in the February 1998 issue. Using a 12V battery and some sort of switchmode step-down circuit is a possibility but if your 6V battery is properly charged it should do the job. Fast clock for model railways I am a model railroader as well as a scale model builder and I looked at all your projects for model railways but the one thing that is lacking is a fast clock. This would enable running nights to be done to fast time instead of real time; eg, 12:1 fast time or 2 real hours = 24 scale hours. (R. S., Morphett Vale, SA). • We published a project along these lines in the December 1996 issue of SILICON CHIP. Gong circuit wanted Can you please help me with a circuit to produce a gong type sound Query on phone battery charging Having accepted the recent $10/ month fee digital mobile network promotion to upgrade my ancient analog phone, I opted for Telstra’s Motorola deal. My prime consideration in my choice of Motorola was the rather more reasonable $39.95 for an extra nickel metal-hydride battery. After familiarising myself with and customising the great number of menu options on the keypad, I fashioned a simple 100Ω 0.25W resistor battery holder discharger since the manual recom­ mended that discharge method; the manual also recommends a weekly complete discharge. I thought that NiMh cells had no memory effect, obviating the necessity for complete discharging. A second annoyance was the prohibition on allowing the battery to be connected to the charger for longer than 24 hours. Where’s this so-called smart chip technology? (similar to the start of Rank movies) each time a pushbutton is operated? It would need a variable frequency con­trol and would be connected to an amplifier and speaker system. (R. M., Mount Duneed, Vic). • While we have not published a circuit which meets your exact requirements, we did publish a Tom-Tom circuit in the May 1989 issue and this could be adapted to your application. Problem with sound level meter I have a problem with the Sound Level Meter as described in December 1996. I performed the calibration as per instructions with the following results: LED1 is lit, all ICs have close to either +9V or -9V (as appropriate) on their supply pins, the reference is -2.47V and pin 3 of IC4b has -18mV on it. Using the pink noise source on the 0dB setting, VR2 was adjusted to 1.002V. Using the same source on 60dB setting, VR1 could only be adjusted down to a reading of 713mV, not 400mV as required. Any assis- I thought I could plug the thing in and forget about it. Could you please give me the lowdown on NiMh cells? The customer service people at Motoro­la advised me not to use a 100Ω resistor discharge system since the higher capacity cells might reverse polarise the low capacity cells. (W. T., Oak Flats, NSW). • One of our staff members has the same phone. As far as we can tell, you can just leave the phone on standby and it will turn itself off when fully discharged. Similarly, it only takes a few hours to charge and it cuts off when the battery is fully charged. Why would you leave it on for more than 24 hours and why worry about having another battery pack, unless you need to be contactable 24 hours a day? Nickel metal-hydride cells apparently have greatly reduced memory effect compared to NiCd cells. We would be wary about discharging the battery pack using a 100Ω resistor unless you ensure that you do not discharge below 1V/cell. tance would be most appreciated. (N. P., Seven Hills, NSW). • There are several reasons why you cannot obtain the required 400mV from the output of IC3b when calibrating the instrument. First, the output from your pink noise source may not be 60dB down when this selection is made. Check the values of resistance around attenuator switch S2 to ensure that this is correct. Second, the output from the pink noise source may be exces­sively high due to an incorrect amount of amplification in either IC1a or IC1b. Check the resistor components around the feedback inputs for these amplifiers. Third, on the Sound Level Meter, there may be an incorrect value of resistance used for VR1 or the feedback components around IC3b may be incorrect. Fourth, check the gain of IC1a which should be x69 or meas­ure its feedback resistor values at pin 2. Fifth, check all resistor values used around IC2, IC3a and IC4a. Finally, wind VR1 fully anticlockwise first, to obtain the maximum gain from IC3b. MAY 1999  91 Interference to garage door opener I recently built and fitted the garage door opener from your April 1998 issue. It works well with the exception of two faults. I decided to use a power supply instead of a 12V battery. As of yet I haven’t fitted the remote. The problems I’m having are, firstly, if a light or an electrical tool such as a power saw is used, the door will open or close. For some reason the circuit is picking up an electrical signal which in turn operates the door. The second problem is that when the door is closing it will not stop when the limit is tripped (this only happens inter­mittently). The one micro­switch is used for open or close. I have a second garage door with a B&D door opener and two remotes. This should provide a voltage lower than the requisite 400mV during calibration. Drift in digital voltmeter I have built the Car Digital Voltmeter as described in the June 1993 issue of SILICON CHIP and have experienced drift with the readout. I recently check­ed the construction and can’t find anything noticeably wrong. If I let the meter stabilise overnight and then re-calibrate it I find that the unit still drifts high. Can you suggest a fix for this problem? The 7805 heatsink runs hotter than I expected even though you make mention of this in the construction details. (T. W., via email). • There are two components most likely to cause a temperature drift: trimpot VR1 and transistor Q1. Try changing these. Acoustic feedback in hearing aids I wish to monitor the high frequency oscillation generated by behindthe-ear hearing aids. This whistling sound can sometimes be heard by others but not by the user. I bought the Sound Level Meter kit described 92  Silicon Chip I thought that maybe I could change the code on one remote and reroute the received message through to the SILICON CHIP door opener. What do you think? The transmitter main IC is labelled B&D NSW serial TX 035966 and when this is peeled back its number is CD4067BL RCA 132. It also has an MC14624B and a CA555CE. The receiver has a CD4067BE RCA 749 and several other ICs. I tried some time ago to get some information on the circuit but was unsuccessful. Any light that you may be able to shed on this project would be appreciated. (A. K., Belmont, Vic). • You now know why we chose a battery, apart from ensuring that the garage door opener works during blackouts. Running the micro­switch leads in twin shielded microphone cable and earthing the in the December 1996 issue but I am hopeless with a soldering iron. A local electronics workshop quoted about $60 to assemble the kit but I do not know if it would meet my requirements. I would appreciate any advice. (P. M., Darwin, NT). • We doubt whether this circuit will be able to discriminate between any feedback whistle and the general background noise. Any circuit to monitor acoustic feedback would need to be sensi­tive to the particular frequencies of the resulting whistle and be able to reject noise or any other sounds picked up by the hearing aid. While such a circuit is feasible, we have not de­scribed anything which would be suitable for your purpose. LED ammeter green LED always on I have a problem with the LED ammeter described in the January 1999 issue of SILICON CHIP. Everything is fine with the circuit apart from the extreme RHS green LED being continuously on after power up. No amount of adjusting VR2 can change this. I have replaced IC1 but it made no difference. I also noted that the 10µF electrolytic capacitor’s positive electrode is connected to D1 in the overlay diagram but is connected to pin 4 of screen to the negative (ground) of the PC board should cure the first problem. Looping the DC power leads a few times through a powdered iron ring (Jaycar LO-1244 or LO-1246) may also reduce mains interference. The only reason we can suggest that the microswitch fails to work when the door in closing is that it is intermittently not being actuated. Without any mechanical details it is hard to be specific. The fact that it never misses in the up direction tends to indicate that the PC board is functioning OK. The feasibility of using your B&D remote to operate the SILICON CHIP design depends on the compatibility of the codes of the MC14624 and the A5885 decoders. You could give it a try but we are not hopeful that it would work. IC1 in the schematic. I oriented the capacitor this way but still no difference was evident. (N. P., via email). • The 10µF capacitor should have its negative electrode con­nected to pin 4. The circuit diagram is wrong. Thanks for bring­ing this to our attention. As far as LED1 is concerned, when pin 5 of IC2 is at 0V, LED1 should be off. Adjust VR2 to get 0V at pin 5 of IC2. You can check this with your multimeter. Also check that -5V is present at pin 4 of IC1. CDI system for an outboard motor I am interested in the Multi-Spark Capacitor Discharge Ignition described in the September 1997 issue. Could you please advise the suitability of this unit for an old Chrysler 85 bhp 3-cylinder outboard motor. This motor previously had a Magnapower ignition installed. If OK, what value should capacitor C3 be? You give values for 4, 6 & 8-cylinder motors. (W. B., via email). • The Multi-Spark Capacitor Discharge Ignition system is suitable for an outboard motor provided that there is a suitable trigger signal from either points, reluctor, or Hall effect unit. Many outboard motors use a magneto which then fires an electronic module. A second coil charges the discharge capacitor to a high voltage before triggering. It may be possible to fire the unit using the reluctor input from the magneto. However, we have not tried this. A suit­able capacitor for C3 should be 0.15µF. UHF remote control for car alarm In your August 1990 issue, you featured a transmitter which I bought from Dick Smith Electronics as a kit. I selected a code to work with my “commercial” car alarm. It works fine except that the range is a bit low (despite tweaking it on a spectrum analys­er). I haven’t seen the circuit for your 2-channel UHF transmit­ter (also avail from Dick Smith Electronics) but can you tell me: (1) Does it transmit on the same frequency? (2) Does it use the same encoder chip? (3) Does it have a greater range? (4) Will it therefore work (1-channel of course) with your old UHF remote control receiver kit? (O. W., via email). • The 2-channel transmitter transmits at 304MHz but does not use the same encoder. We expect that it has a similar range to the earlier design but cannot state whether it could be made to work with your car alarm. Enhancing the class-A amplifier I have a few questions regarding the 15 watt class-A ampli­fier project. I wish to provide extra inputs for CD, tuner, stereo VCR and tape in/ out sockets. The plan is to use gold RCA input sockets on the back panel. These would be selected via two Notes & Errata Low Distortion Audio Signal Generator, February & March 1999: on the circuit diagram on page 28 of the February issue, trimpot VR4 is incorrectly labelled as 100kΩ rather than 10kΩ. Also on the circuit there should be shown a 10kΩ resistor in between the 20kΩ resistor connecting to the 330µF capacitors at the output of IC1b and the pin 2 inverting input of IC4b. The PC board includes this resistor and this is shown on the overlay diagram, on page 63 of the March issue, as the third 10kΩ resis­tor below diode D2. The overlay diagram also has transposed the anode and cathodes (A & K) labelling for LED1 & LED2. The package outline orientation is correct. The polarity shown on the circuit is also correct. Electric Fence Controller, April 1999: the supply leads to the battery, as shown on the wiring diagram on page 28 (Fig.7) are reversed. In addition, the transformer bobbins for T1 & T2 may differ from those used in our prototype. The difference will be that the five rows of pins on each bobbin may be spaced wider than allowed for on rotary switches mounted toward the back of the case and con­trolled by an extension shaft to keep the wiring for the inputs as short as possible. If I take this approach are the performance figures likely to be degraded? All other construction details would be as per the article. One final question: was the rack the PC board. You can either bend the pins on the bobbin inward so that they will fit into the original holes or new holes can be drilled at the wider spacing. The larger bobbins mean that the transformers will be easier to wind and there will be more room to insert the ferrite cores. A revised PC board has been produced to provide for both bobbin types. Multi-Spark CDI, September 1997: transistor Q1 in the impulse tachometer circuit on page 30 should be labelled a BC327 and not BC337 as shown. LED Ammeter, January 1999: the circuit diagram on page 55 has an error. The 10µF capacitor associated with IC1a should have its negative electrode connected to pin 4. Capacitance Meter, February 1999: the wiring diagram on page 70 has a number of errors. The 100µF capacitor associated with D1 & D2 is unmarked and is shown with reverse polarity. Also VR3 & VR4 are swapped, although their values are the same. Bass Cube Subwoofer, April 1999: the rear panel should be screwed into place but not glued, although some sort of sealant should be used to avoid leaks. case used in the prototype a commercially available unit or was it built from scratch to incorporate the two heatsinks? (J. W., Five Dock, NSW). • Provided your input switching is well-shielded, it should not degrade the amplifier’s performance. Our case was an obsolete rack case to which we SC attached the heatsinks. 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. MAY 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 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 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, the 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 TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. $190. MAGNETIC CARD READER, SC January 1996. Holds up to 8 cards. Use as a door lock. $65. Melbourne 9806 0110. PC CONTROLS: AF Generators, I/O Cards, Temperature Measurement, Data Logging. Plus ActiveX. SOFTMARK, phone/fax 02 9482 1565 http:// www.ar.com.au/~softmark THE LOGIC ANALYSER KIT will stay at $750 ($800 - NZ). Ph 02 9878 4715. peter.baxter<at>tantau.com.au www.tantau.com.au 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 SINGLE-CABLE-SOLUTIONS 5 mm dia for Video, Audio & Power Supply from 40 Cents / metre ! NEW 16 mm BOARD & 25 mm PINHOLE LENSES Full-Screen “Head & Shoulders” or “Cash Drawer” shots <at> 3.5 metres ! BUNDLED DIY PAKS: FOUR Cameras, Switcher & Power Supply from $506 ! With 14 Inch Monitor from $636 ! With MULTIPLEXER for FULL-FRAME FULL-RESOLUTION RECORDING from $1196 ! FOUR COLOUR CAMERAS, SWITCHER & POWER SUPPLY from $873 ! WITH COLOUR QUAD 4 Pix 1 Screen from $1271 ! With MULTIPLEXER $2099 ! JAPANESE CS LENSES from $51 ! HIGH RESOLUTION QUADS 720 x 576 (Better than SUPER-VHS Quality) Time & Date from $313 ! COLOUR QUADS from $503 ! COLOUR DUPLEX MULTIPLEXERS from $1329 ! 14 Inch MONITORS from $218 ! With Inbuilt 4 Ch SWITCHER from $256 ! SEE-in-the-DARK with our Combination CAMERA INFRARED ILLUMINATOR Kit from $170 ! PCB MODULES from $78 ! PREMIUM SONY CCD & CHIPSET 480 + Line x 0.05 Lux 32 x 32 PCB MODULES from $91 ! CAMERAS: Mini from $88 ! Dome from $91 ! COLOUR DIGITAL SIGNAL PROCESSING CAMERAS & MODULES: 400 + Line from $180 ! DOME from $185 ! 480 + Line DOME with SONY CCD from $246 ! 600 + Line from $346 ! PREMIUM High Resolution 600 + Line (Better than SUPER-VHS Quality) High Sensitivity 0.2 Lux (with Slow Scan) COLOUR CAMERAS from $455 ! 30 + Lenses 2.1 to 16 mm INCLUDING JAPANESE VARIABLE FOCAL LENGTH. 50 LED DIY Infra Red Kits only $19 ! Quads 4 Pix 1 Screen from $280 ! ALSO: Outdoor Housings, Brackets, Dummy Cams, CCTV-TV/ VCR Interface Modules, Motorised Pan Units etc. 400 page CCTV BOOK $95 or FREE ! DISCOUNTS: Based on ORDER VALUE, BUYING HISTORY, for CASH/CHEQUE & NZ BUYERS ! BEFORE YOU BUY Ask about our New Enquiry Offer & visit our Web Site at www.allthings.com.au Allthings Sales & Services. Ph 08 9349 9413 Fax 08 9344 5905. 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 SOLAR PANELS: manufacturers surplus. Siemens polycrystaline cells on a plastic frame 55mm by 160mm. 1 Watt, 5.7V, 0.22A. CALL FOR DATA SHEET. Priced from $5 to $10 each depending on quantity. Dealer enquiries welcome. (02) 6628 2000. Silvertone’s RC Receiver Still the best little performer available! 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. SOLAR PANELS: buy by mail and save! 75 watt from $590.00, unbreakable s/steel 64 watt $555.00. Largest manufactured: 120 watt $995.00, flexible 32 watt $475.00. All other sizes available, top brands, lowest prices. INVERTERS: budget inverters from $110.00 (12V 140W). High quality pure sine wave inverters from $390.00. Call with your requirements. WIND GENERATORS: wide variety available, call with requirements. TASMAN ENERGY Free call 1800 226626 ELECTRONICS FOR BEGINNERS COURSES including DC & AC principles and operational amplifiers. Enquiries: 02 9130 7988. 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 76.5° to 180°. AV-COMM P/L, 198 Condamine St, Balgowlah, NSW 2093. Tel: 02 9949 7417 or 9948 2667. Fax: 9949 7095; www.avcomm.com.au Still only $129.50 AM or $149.50 FM. May be used with most ppm transmit‑ ters. 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 WORKBOOK FOR SALE: “Electronics for Beginners Stage 1, DC Electrical Principles” Phone 02 9130 7988. Win $500USD cash dontronics.com SPEAKERWORKS: specialist in speaker repairs and parts. DIY refoam kits: 31/2", 4", 5", 6", 7", 8", 9", 10", 11", 12" and 15" $39.95. Includes shims, dustcaps and adhesive. Largest inventory of cones, surrounds, gaskets, spiders, dustcaps, grilles, foam and cloth and 4,700 custom voice coils. Phone 02 9420 8121, Fax 9420 8131. 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, MAY 1999  95 Silicon Chip Binders Keep your copies safe, secure and always available with SILICON CHIP binders: they’re cheap insurance! REAL VALUE AT $12.95 PLUS P &P  Heavy board covers with 2-tone green vinyl covering Advertising Index Altronics................................. 34-36 Av-Comm Pty Ltd.........................95 Bainbridge Technologies..............60 Computronics Corporation..........89  Each binder holds up to 14 issues so that you can include catalogs Dick Smith Electronics........... 12-15  SILICON CHIP logo printed in goldcoloured lettering on spine & cover EMC Technologies.......................89 Emona Instruments.....................89 Price: $12.95 plus $5 p&p each (available Aust. only) Evatco..........................................87 Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Harbuch Electronics....................55 Instant PCBs................................95 Jaycar ................................... 45-52 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. A NEW address for Acetronics http://www.acetronics.com.au On-line PCB quotes, free software, DIY PCB supplies plus many other items & services. 02 9743 9235. RTN Australia Parallax distributor: Basic Stamps BS1, BS2, BS2-SX all ex stock. Chipsets also available for high volume applications. SX development tools and chips also available. New super BS1/2 development board Oz made now available. Custom I/O extender chips for the Basic Stamps. Serial Led driver kits, a/d kits, temperature kits, etc. FerretTronics servo and stepper motor chips. TiePie HandyScope HS2, Dos and Win software included. Ph/Fax (03) 9338 3306. Email: nollet<at>mail.enternet.com.au Http://people.enternet.com.au/~nollet PCBS MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics (02) 9554 9760 sesame<at>internetezy.com.au; http:// members.tripod.com/~sesame_elec 1A LASER DIODE DRIVER, 3W head laser power monitor, IR laser diode with housing, greatly reduced price, e-mail lmatthee<at>perthpcug.org.au for details and pictures. PRINTED CIRCUIT BOARDS for all magazine projects, then goto http:// www.cia.com.au/rcsradio RCS Radio – Bexley (+61 2) 9587 3491. KIT ASSEMBLY ANY KITS assembled/calibrated: professional, speedy service. Phone Nev­ille Walker (07) 3857 2752. Kits-R-Us.....................................95 Microgram Computers..............7,89 MicroZed Computers...................89 Nucleus Computer Services........89 Oatley Electronics...................31,89 Printed Electronics................. 89,95 Questronix...................................89 RobotOz......................................89 Silicon Chip Back Issues....... 78-79 Silicon Chip Binders/Wallcht....OBC Silicon Chip Bookshop...............IBC Silicon Chip Model Railway Book.88 Silicon Chip Subscriptions...........44 Silvertone Electronics..................95 Smart Fastchargers.....................55 Solar Flair/Ecowatch....................95 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 Zoom EFI Special......................IFC _____________________________ 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. Silicon Chip Bookshop SUBSCRIBE AND GET 10% OFF SEE PAGE 44 EMC For Product Designers* 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. Understanding Telephone Electronics* By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. This is 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. Guide To Satellite TV* Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1997 (4th edition). This is a practical guide on the installation and servicing of satellite television equipment, including antenna installation and alignment. The cover­age of the subject is extensive, without excessive theory or mathematics. 383 pages, in hard cover at $60.00. Audio Electronics* 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 equip‑ ment. 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. Digital Audio & Compact Disc Technology* Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. This is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $90.00. The Art of Linear Electronics* By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $80.00. Servicing Personal Computers* By Michael Tooley. First pub­ lished 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $90.00. Guide to TV & Video Technology* By Eugene Trundle. First pub­­lished 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback, at $55.00. Title Price  EMC For Product Designers $95.00  Understanding Telephone Electroni cs $55.00 Guide to Satell ite TV $60.00 Daytime Phone No._______________________Total Price $A _________   Audio Electroni cs $79.00  Cheque/Money Order  Bankcard  Visa Card  MasterCard  Digital Audio & Compact Di sc Technology $90.00  The Art Of Linear Electroni cs $80.00  Servi cing Personal Computers $90.00  Guide to TV & Vi deo Technology $55.00 Your Name__________________________________________________ PLEASE PRINT Address_____________________________________________________ ______________________________________Postcode_____________ Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Postage: add $5.00 per book. Orders over $100 are post free within Austral ia. NZ add $10.00 per book; el sewhere add $15 per book. TOTAL $A *All titles subject to availability. Prices valid until 30th May, 1999