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MAY 2001  1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.protel.com Contents FEATURES   4  Global Hawk: America’s Advanced Unmanned Aircraft Giant new US unmanned aircraft flies America to Australia non-stop. And it’s undergoing trials in Australia right now – by Bob Young Vol.14, No.5; May 2001 Using Linux To Share An Internet Connection – Page 14. 94  Help Reform Electrical Legislation Want to do your own wiring or repair appliances . . . and remain legal? You can help change the legislation. PROJECTS TO BUILD 28  Powerful 12V Mini Stereo Amplifier It fits in a tiny instrument case yet can deliver up to 18W RMS per channel into 4Ω loudspeakers. Here’s how to build it – by John Clarke 38  Microcontroller-Based 4-Digit Counter Modules You can build either a 0-9999 up/down counter or a presettable down counter. And the kit costs just $39.95 – by Peter Crowcroft & Frank Crivelli 58  Two White-LED Torches To Build Throw away that antiquated light bulb and use LED arrays instead. They give a high-brightness white light and increased battery life – by John Clarke Powerful 12V Mini Stereo Amplifier – Page 28. 68  A Servo With Lots Of Grunt Looking for a servo with a lot of grunt? This “Jumbo Servo” uses a robust 12V motor/gearbox assembly to give you real muscle – by Ross Tester 87  PowerPak: A Multi-Voltage Power Supply Robust device provides a well-regulated, switchable 3V, 6V, 9V or 12V output from a car cigarette lighter or DC plugpack supply – by Peter Smith COMPUTERS 14  Using Linux To Share An Internet Connection; Pt.1 Don’t know what to do with that old computer? Here’s an idea: install Linux on it and use it as a gateway to provide shared Internet access (plus a firewall) for PCs and Macs on a small network – by Greg Swain 26  Computer Tips: Tweaking Windows With Tweak UI Make Windows work the way you want with this free utility – by Peter Smith SPECIAL COLUMNS 45  Serviceman’s Log To fix or scrap; that is the question – by the TV Serviceman 80  Vintage Radio The magnificent 7-banders from AWA – by Rodney Champness Microcontroller-Based 4-Digit Counter Module – Page 38. PowerPack Multi-Voltage Power Supply – Page 87. DEPARTMENTS   2  Publisher’s Letter   98  Ask Silicon Chip 11  Mailbag 100  Notes & Errata 21  Circuit Notebook 102  Market Centre 57  Subscriptions Form 104  Advertising Index 76  Products Showcase MAY 2001  1 PUBLISHER’S LETTER Australia’s economy is far healthier than most people think www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Peter Smith Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0408 34 6669 Regular Contributors Brendan Akhurst Louis Challis Rodney Champness Julian Edgar, Dip.T.(Sec.), B.Ed Jim Rowe, B.A., B.Sc, VK2ZLO 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. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Are you sick of hearing all the doom and gloom about Aus­tralia’s economy and the parlous state of the dollar? I certainly am, particularly since most of what is portrayed in the media just isn’t true. I am also sick of hearing that electronics manufacturing in this country is dead and buried. That just isn’t the case at all. It is true that the manufacture of consumer electronics equipment in this country is long since gone but that is true of virtually every Western country in the world. As far as most people are concerned, and this applies to the media as well, electronics manufacturing in this country must be absent because it is invisible. But electronics manufacturing is thriving in this country even though most of it is done by privately-owned companies, not the large publicly-listed corporations. And some large concerns are doing well too. For example, Bosch, Siemens, Alcatel and others still make vast quantities of equipment and a good deal of it goes for export. For our part, one of the frustrations is that we know some of the smaller companies and what they do but most of it is confidential and certainly not in the public domain. However, if you want to look for it, there is plenty of evidence of thriving electronics manufacturing. First, you have the booming electron­ics parts suppliers such as Dick Smith Electronics, Jaycar Elec­tronics, Altronics, Farnell Electronics, RadioSpares and so on. And virtually every semiconductor and passive component manufacturer and test equipment maker in the world has either a direct presence or is represented in Australia. Together, all these companies are responsible for vast quantities of electronic components and electronic equipment being imported into this country. Why? For local manufacture. After all, you don’t imagine that it is all being purchased by electronics hobbyists to put together SILICON CHIP projects, do you? And apart from SILICON CHIP, there are three electronics trade magazines and a number of associated titles also servicing the industry. Not bad, for an industry which is supposedly de­funct. And where do all these manufactured electronics products go? Quite a surprising quantity are exported. Only recently, one of the most prominent financial commen­tators, Robert Gottliebsen, writing in “The Australian” wrote about the recent change in our terms of trade and the increase in exports. The export category which has had the biggest turnaround is “elaborately transformed manufactures”. This is something that many bureaucrats and financial commentators thought would never happen. And guess what makes up a significant part of that “elaborately transformed stuff”? Yep, electronic equipment made in good old Australia. So next time some talking head on TV is declaiming about the Australian economy and the supposed reasons for the dollar’s decline, remember that he (or she) probably hasn’t a clue about what is really going on. In the overall scheme of things, Austra­lia is doing pretty well. We could be doing better but then again, it could be a whole lot worse. Electrical legislation And by the way, in an area where we could be doing better, reform of Electrical Legislation, please get those Letters of Will into us (see pages 9495). With your help, the regulations will be changed. Leo Simpson                                                                                        While stocks last                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   Training Online       We welcome Bankcard, Mastercard and VISA NO SURCHARGE! 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MGRM0501/7   GLOBAL HAWK Part 2 in our UAV series By Bob Young a giant unmanned aircraft As we went to press in mid-April, the RAAF air base in Edinburgh, South Australia, was anxiously awaiting the arrival of one of the most unusual aircraft flying today. Soaring in from a non-stop, record-breaking flight across the vast Pacific Ocean, the landing of RQ-4A Global Hawk was set to mark the coming-of-age of the autonomous unmanned air vehicle, the UAV. P owered with a jet engine and with the wing-span of a Boeing 737, this is no miniature radio controlled aircraft. It has a maximum range of more than 25,000km, which is more than most commercial jet airliners and it can fly at 50,000 feet. After years of promising beginnings, disappointments, frustration and cancelled programs with UAVs, the success of Global Hawk is finally beginning to transform the military capability of unmanned air vehicles. However, as dramatic as the first flight of an unmanned air vehicle across the Pacific may prove to be, this flight is not about-record breaking. It is about proving the tactical and strategic value of long range UAVs. Deployed in Australia as part of a US–Australia Cooperative Project Agreement, Global Hawk will take part 4  Silicon Chip in a number of joint projects between April and June 2001. During the Australian deployment, Global Hawk will form the nucleus of a complex four-way partnership between the RAAF, USAF, DSTO and Northrop Grumman. The Australian project director is Dr Jackie Craig and the US project director is Col. Wayne Johnson. Australian interest in Global Hawk is aimed at investigating the compatibility of Global Hawk with existing defence and coastal surveillance systems. The Australian deployment begins with the historic flight on 21st April. It will then encompass 12 operational sorties aimed at demonstrating the capabilities of the aircraft in missions such as airfield surveillance, targeting and most important of all from an Australian point of view, coastal watch! Finally, Global Hawk will participate in Exercise Tandem Thrust. It is going to be a busy time for the Global Hawk flight and support team. The Global Hawk story The story of Global Hawk began back in 1993 with the pioneering work of Teledyne Ryan Aeronautical (TRA) when they conceived and began to pursue the idea of a high-altitude, long endurance (HALE) UAV. In 1994, the US Defence Advanced Research Projects Agency (DARPA) issued a request for proposals (RFP) for a HALE UAV. This request was prompted by the glaring shortfalls in real-time, consistent reconnaissance data which became obvious during Operation Desert Storm. Launching, operating and retrieving Global Hawk requires the use of a huge variety of communications, both direct to ground control stations and via communications satellites. It’s almost as complex as a space launch (some would say even more so!). The RFP called for an aircraft capable of carrying a 1000kg payload for more than 40 hours at altitudes of up to 65,000 feet (20,000m). In the peculiar jargon of the US defence forces, (sadly becoming all too common here) the successful proposal would be known as Tier 2 Plus and would be one of several UAVs planned by the US Defence Airborne Reconnaissance Office (DARO). The first of these, Tier 1, the General Atomics Gnat 750, was already in service with the CIA, peeping into hot spots in Bosnia. In May 1995, a TRA- lead team including E-systems as the sensor package supplier, won the Tier 2 plus competition and set about developing what has since become the Global Hawk. Originally budgeted to cost US$10,000,000 for each aircraft, based on a quantity of 20 units, cuts to the quantities ordered resulted in the current price of US$15,300,000 per airframe on seven aircraft delivered to date. This is still not a bad figure by modern standards, considering the complexity of the final system. As with all aircraft, the Global Hawk took shape out of a complex array of competing requirements. All were aimed at meeting the principal objective of flying at 65,000 feet for 24 hours. This is after covering 1,600nm (3000km) to arrive at the target, and with sufficient reserves to fly the 1,600nm back home. Stealth was not considered a major design factor as it was thought that the 65,000 feet altitude would provide sufficient protection against most ground and subsonic air-launched weapons. However, the relatively large sensor payload with the complex requirements governing the positioning of the sensor apertures certainly was most important. In the end, the airframe developed into a 35m (116 feet) span wing with a stubby 13.5m (44 feet) long fuselage. The thin slightly swept wings (5.9° sweep angle measured at the 25% chord point), when combined with the fuselage fuel tanks, can accommodate 6.8t of fuel. When the wing tanks are fully laden with fuel (4000kg), the wings sag 0.3m at the tips. The wing is a lightweight structure constructed entirely of carbon-fibre-epoxy composites, with four shear spars and a high modulus composite skin. The laminar flow, super-critical wing has an area of 540 square feet and an aspect ratio of 25:1. Design lift/drag ratio (L/D) was 37 but flight-testing has shown that it is actually 33 to 34; still a very respectable figure, comparable to some modern sailplanes. Design changes to the wing section are under way to overcome this shortfall. The lift to drag ratio of an aircraft is a measure of the aerodynamic efficiency and any improvement in this ratio will result in increases in speed, range and/or loiter time. All of these factors are extremely important to Global Hawk so time and effort spent improving this area will be well rewarded. While the wing is composed of composite materials, cost factors dictated that the fuselage should be of conventional aluminium monocoque construction. The fuselage accounts for some 35% of the airframe weight. The main undercarriage is a standard Learjet 45 assembly and the nose gear is a two-position unit from a Canadair CF-5F. Here's Global Hawk’s notional “mission profile”. The first phase is getting it into the air and to its target. Second phase is the surveillance mission itself (which can last for 24 hours or more) while the final phase is the safe return and landing. MAY 2001  5 Some idea of the size and complexity of the Global Hawk can be gleaned from these drawings and – most spectacularly – from the detailed drawing overleaf. It needs a full-size airfield to operate from and remote control is not quite your hand-held radio control unit, as can be seen from the photos below! The unusual, high dihedral angle (50°) tailplane assembly was settled on as a compromise between a variety of factors which included ground clearance, weight, drag, and simplicity of engine exhaust ducting. The Rolls-Royce AE3007H turbofan engine was chosen for its excellent specific fuel consumption/thrust performance at altitude. It is also an engine with a “good heritage”, developed from a common core used in power plants for the C-130J (Hercules), Bell Boeing V-22 Osprey and a host of small commercial and business jets. The maximum operational altitude of the Global Hawk is limited by the engine developing surging at around 70,000 feet, therefore the service ceiling was set at 65,000 feet. The engine is programmed to perform a slow “roll back” to a lower throttle setting as maximum altitude is approached. The highest altitude achieved to date is 66,400 feet. In-flight operation Mixing manned aircraft with unmanned aircraft on international air routes has been one of the most pressing concerns for aircraft operators, as well as those entrusted with formulating the legislation and operating procedures. Interestingly enough, Australia, because of its long history with unmanned aircraft, in particular Jindivik and Aerosonde, has risen to the challenge of formulating operating procedures and has published draft legislation in the form of Civil Aviation Safety Regulation Part 101 (CASR Part 101). For those interested in more detail, www.casa.gov.au will provide all 6  Silicon Chip VEHICLE SPECIFICATIONS Fuselage   Width (ft) 4.8   Length (ft) 44.4 Wing   Area (sq ft) 540   Span (ft) 116.2   Aspect Ratio 25.0   1/4 Chord Sweep 5.9° V-Tail   Area (sq ft) (each) 42.8   Span (ft) (each) 11.4   Aspect Ratio 3.0   Dihedral Angle 50° Empty weight (lbs) 9,200 Fuel (lbs) 14,900 Take-off gross (lbs) 26,000 of the answers. Aeromodellers may also be interested in CASR 101 as this legislation also governs model aircraft as part of the broader UAV spectrum. As may be imagined, a considerable amount of effort has been expended on emergency procedures for Global Hawk, to cover the various contingencies that may arise. Broadly these are broken into four main categories: (a) Loss of the Command and Control link (C2). The aircraft is programmed to continue on course for 1.5 minutes before returning to base if no signal is pick-ed up. (b) Imminent or actual failure of a critical system. Return to base. (c) Engine flame-out. Global Hawk is programmed to search onboard memory for the nearest “friendly” alternative runway.    Restart by diving (wind-milling) is out of the question because the slow flying UAV cannot attain the required dive speed. Alternative restart options such as compressed air bottles and/or an auxiliary Global Hawk – System Performance Summary PROGRAM GOALS 14,000NMI 65,000 feet + 42 Hours 1 Loss in 200 Missions 1.5-50Mbps >50Mbps 1.0/0.3m resolution (WAS/Spot) 20-200km/10m range resolution EO NIRS 6.5/6.0 (Spot/WAS) IR NIRS 5.5/5.0 (Spot/WAS) 40,000 sq nm/day 1,900 spots targets/day <20 metre CEP CHARACTERISTICS PROJECTED PERFORMANCE Maximum Range 13,500NMI Maximum Altitude 65,000 feet Maximum Endurance 36 Hours Flight Critical Reliability 1 loss in 605 missions SATCOM Datalink 1.5, 8.67, 20, 30, 40, 47.9Mbps LOS Datalink 137Mbps SAR 1.0/0.3m resolution (WAS/Spot) MTI 20-200km/10m range resolution EO EO NIRS 6.5/6.0 (Spot/WAS) IR IR NIRS 5.5/5.0 (Spot/WAS) Wide Area Search 40,000 sq nm/day Target Coverage 1,900 spots targets/day Location Accuracy <20 metre CEP While not all of Global Hawk’s program goals have been met, they’ve come pretty close! Moves are currently under way to improve the maximum endurance to come close to the goal. power unit were ruled out on the grounds of weight, cost or complexity.     If there is no suitable alternative landing field within range, then Global Hawk is programmed to glide to one of several pre-determined optional points and “die”. As an interesting aside, an aircraft with an L/D ratio of 30 will glide almost 600km from an altitude of 65,000 feet. (d) Take-off and landing failures. Global Hawk has its own embedded reactive programming to cope with such emergencies. Take-off will be aborted if the aircraft deviates too far from the runway centreline or fails to reach V1 (decision speed).    On landing, an automatic goaround is initiated if the aircraft is not lined up with the runway correctly. There is no outside (landing) pilot associated with Global Hawk. All landings are carried out under auto-land protocol. Electronic systems Upon examining the on-board electronics of Global Hawk, it becomes immediately obvious why UAVs have taken so long to mature. From automatic take-off to auto land, the entire operation of any UAV relies completely on a host of complex electronic gadgets and support systems from the relatively simple air-data sensors to the staggeringly sophisticated array of GPS satellites. Much of the complex array of command and support equipment has only just matured in its own right and it has taken considerable effort Where Global Hawk goes, so does its Launch and Recovery unit (left) and the Main Mission Control unit (below). Transporting Global Hawk (and all its equipment) around the world takes about three Hercules Transport loads. to bring these elements together into a successful system. Global Hawk has a dual redundant flight control system (FCS) which is controlled by two onboard flight computers which receive constant input from the aircraft’s suite of navigation and air data sensors. This includes an inertial navigation system, inertial measurement unit and a GPS. The flight control computers are pre-programmed with a flight plan before departure. No flight commands are accepted by Global Hawk until after take-off. Once airborne, the flight is controlled and monitored by the launch and recovery element (LRE). The LRE is responsible for launch and recovery, mission planning and back-up control. The LRE is housed in a separate van to the MCE (Mission Control Element). The MCE is responsible for mission planning and control, sensor control, data links monitoring, imagery review and dissemination. These vans can be located almost anywhere in the world and do not need to be located in the same area as each other. The LRE communicates with Global Hawk via a line of sight (LOS) common data link (CDL) and then by Ku-band and UHF satcom. Once Global Hawk has settled into the climb and departure phase of the flight, the UAV navigates by GPS waypoints. There are several inbuilt default waypoints that are activated if necessary. Control is then handed over to the MCE for the actual task of completing the mission. Ku-band and CDL are mostly used for data transmission, including threat information and UAV status, while UHF is mostly used for command and control. As the UAV ascends and crosses controlled airspace, the LRE and MCE crews communicate with air traffic control via VHF/UHF radio. On one occasion a controller asked the duty crewman what was it like up there. To which the crewman stationed thousands of miles away on the ground stated simply “I don’t know – I am not up there!” Otherwise, the Global Hawk is treated the same as any other aircraft operating in controlled air space and possessing an IFF system. Monitoring Status Global Hawk carries a fault log computer that monitors and records any MAY 2001  7 8  Silicon Chip MAY 2001  9 Look at the detail available to military strategists in this EO (electro/optical) image taken in the Mojave Desert, California. Altitude was in excess of 62,000 feet and the slant range (ie, distance from aircraft to target) was 20.3km. Notice the “tiling” effect as the image is built up from multiple smaller images – so called “step stare”. problems detected during a mission. The results can be down-loaded for analysis after a mission. Real time monitoring is via discrete and continuous signal comparators. These provide preset upper and lower operational limits for every on-board system, ranging from engine pressures, temperatures and RPM, to hydraulic pressures, electrical voltage levels and airspeed. If any of the levels move outside the acceptable range, a red light comes on in the control centre and if the system is critical to the vehicle it will start flashing. At this point Global Hawk will call it a day and return home. Regardless of the complexity of the control and command electronics, it is the imaging electronics that really take one’s breath away. The quality of the images is stunning, from all three systems. These comprise an EO (electro/ optical), IR (infrared) and SAR/MTI (synthetic aperture radar/moving target indicator). These systems require extensive monitoring and account for the much larger size vans used by the MCE compared with the LRE. The SAR/MTI antenna is housed in a bulged fairing immediately behind the nosegear and provides real-time imagery of the ground in several formats. With a field of view of ±45° either side of the aircraft, the Raytheon X-band radar can cover up to 138,000 10  Silicon Chip This one is infrared imagery, again taken more than 61,000 feet above the Mojave Desert and more than 22km away from the target. One of the big advantages of IR imagery is that “cover of darkness”, so long relied upon by the world’s armed forces, has ceased to be a cover at all! IR relies on heat radiated from virtually everything! square kilometres per day in search mode from a range of 200km. In ground MTI (GMTI) mode the radar can search up to 15,000 square kilometres a minute, detecting any targets with a velocity of 4kt (7.5km/h) or more, from a range of 100km. With a 10m range resolution, the GMTI mode scans a 90° sector, and can be used to cover zones between 20km and 200km either side of the aircraft. Is it any wonder that the Australian Government should find Global Hawk very interesting in regard to coastal surveillance? The Raytheon supplied EO/IR system mounted in the chin of GH combines a Recon/Optical camera with a Raytheon IR sensor. The EO system uses a commercial 1024 x 1024 pixel Kodak CCD (charge-coupled device) while the IR sensor uses a 640 x 480 pixel 3-5µm indium antimonide detector derived from Raytheon’s common module forward-looking infrared (FLIR) system. Both EO and IR sensors are fed by a fixed focal-length reflecting telescope with a beam splitter. Neither of the systems has the 6,000-plus pixel width needed to provide the required 1m resolution in a single exposure so a “step-stare” system is used. The telescope scans continuously and a mirror back scans to freeze the image on the sensor. Thus the mirror returns to the same spot every 1/30th of a second, while the small patches are assembled to create a larger picture. To help keep the avionics warm at altitude and cool at lower levels, air temperature is carefully controlled in a pressurised section of the fuselage. Monitored autonomously by a Honey-well environmental control system built to Northrop Grumman specifications, the system uses the aircraft’s own fuel as a heat sink. Fuel is fed through tubing in the leading edge of the wing to the outboard tanks and gravity fed back to the centre fuselage tank. Two pumps feed the fuel to the engine and excess fuel, which is pumped around the equipment, goes to a fuel/air heat exchanger. At altitude, bleed air from the engine is used to warm the fuel which is then pumped around the compartment to warm it. All in all, Global Hawk is a very sophisticated aircraft and one that has already made its mark on aviation history. For more information, visit Northrop Grumman websites: www.northgrum.com or www.iss.northgrum.com Acknowledgement: We are grateful to Erroll Walker in the Canberra office of Northrop Grumman for his assistance in obtaining the images used in this feature. Like the Global Hawk, they flew half-way SC around the world! MAILBAG Safety switches are sensitive to control tones I am writing this letter of warning to your publication since any approach to bureaucratic “black holes” would be a waste of time. The best way is to alert people to such problems. This may not be a problem in towns but it is certainly related to rural areas. As a person from the milliamp side of the electrical/elec­tronic disciplines I have considered the compulsory installation of Safety Switches (core balance relays) as not unreasonable but over the years I have heard rumblings about their nuisance value. There was always reference to some appliances, such as refrigera­tors, causing nuisance tripping. However, people need to take heed of my problem that started about two years ago. As regular as clockwork, 6:30am in winter and 7:30pm in summer (I live in a daylight saving area), about three weekday mornings every week, the breaker would trip out. Switch back on and no problems. I had no timers set in my house. It did occur on other occasions but the worst time was going away for several days knowing most likely that my freezer would become a hot box. I thought that it might have been a large pump starting in the district but a check of neighbours turned up no similar problems. I did contact electricians but the general response was that it was an intermittent fault and they were not really interested in spending an inordinate time trying to tie down the fault in a narrow window. I tried all the usual fault-finding methods. First, check appliances for earth leakage both by direct check of resistance and a high impedance check for capacitive loading by looking for a time constant rise. Then I had the tedious effort of isolating one distribution circuit before isolating individual loads over time, bearing in mind the 2-5 minute window to observe the ef­ fect. Just when I thought I was getting somewhere, the other circuit goes off. It did cross my mind that the problem was possibly the breaker itself. No, these are made to Australian Standards and therefore they work or they die. How wrong I was. A chance meeting with a rural-based electrician, a chance comment and the gist of his response was “It’s your Safety Switch. Replace it. I have had several go that way. Even some new replacements have had the problem. It is a problem related to off-peak control tones. I know of several cases in the surround­ing district”. A new Safety Switch (not Clipsal) solved the problem. This suggests that there is either a deficiency in the Standard, failure to maintain standards or a design fault. How widespread this problem is I am not sure but it is a situation that is less than satisfactory. Perhaps the sensing circuit has some unwanted capacitance that, coupled with the sensing coil inductance, creates a paral­lel tuned circuit at or near the control tone’s frequency that pushes the sense output over the trip limit. A simple addition to the Standard, if it does not include such a requirement, would require the sensing circuit to be positively desensitised to the tones used for off-peak power control. If this requirement exists then the Standard is not being achieved. Either the Standard needs revision to include such a requirement or the standard needs to be enforced. Being cynical, at almost $100 a pop there is no incentive for manufacturers to strictly comply since the consumer has to get a replacement. The only problem with this attitude is it creates an attitude to safety devices that they are treated with scorn and derision by being just a nuisance. Brendan Falvey, Gundaroo. NSW. What about a valve amplifier? As a regular reader who has not missed reading one of your magazines I would like to comment as follows. I buy your magazine for enjoyment and interest. The two articles I always enjoy reading are the Serviceman and Vintage Radio. Yes, I have built some of your transistorised projects but I also like working with valve equipment, even if it is old tech­nology. No different to collecting and working on vintage cars; people do it for enjoyment. What’s wrong with restoring old radios and bringing them back to life, especially in today’s throwaway society? I remember the first time I read your statement that SILI­CON CHIP would not publish a valve amplifier design. To me the statement had a sense of arrogance. In other words, if people weren’t interested in the latest technology then don’t read SILICON CHIP. But what about the people who simply enjoy valve technology? I would be interested to know how many people would be interested in building a high quality valve amplifier just for fun and enjoyment. Michael Justin, via email. Help wanted on army receiver I am seeking details on a piece of disposals equipment. It is a 5-band WWV receiver made by Beckman, model No 905WWW. It was used by the Australian Army with a DSN number of 6625-66-012-7046. I suspect the vintage to be 1963. The device is rack-mounting and has miniature tubes with crystal-locking for each channel. Any help would be appreciated. Craig Cook, Melbourne, Vic. (03) 9890 2117 (AH) email: craigc<at>melbpc.org.au AM Stereo is still alive in Australia I was surprised to recently learn of one of Australia’s closely guarded secrets, that many commercial AM radio stations and probably one ABC MAY 2001  11 Mailbag – continued . . . station (4QR) broadcast in stereo. Those in Melbourne are Magic 693, Sport 927 (3UZ), 3AW 1278, 3MP 1377 (temporarily in mono) and 3AK 1116. There are undoubtedly others in the other states. The stations themselves do not publicise this fact, possi­bly because stereo AM receivers are not normally available (although decoders may be added to some existing radios). This is also strange because the additional cost of incorporating AM stereo features into an AM/FM stereo radio at the time of manu­facture would be minimal, one would expect. www.amstereoradio.com will provide information to anyone interested in following up this matter. There is also an active discussion/lobby group on http://www.egroups.com/group/ iaaas-amstereo Alex Brown, via email. Comment: we published an AM Stereo radio in September, October & November 1989. We had the impression that AM Stereo was dead, despite the fact the stations may still be using the gear. More on New Zealand’s electrical regulations Further to my previous letters, I spent almost the whole of March in New Zealand and I had a very informative and productive meeting with a senior official of the Energy Safety Service within the Ministry of Economic Development. Here is a brief summary of some of the things I discovered. (1). In a comparative study of international annual electrical fatality statistics done by the New Zealand Energy Safety Serv­ ice, Queensland consistently had the highest levels of electrical fatalities in Australia. Much more interestingly, Australia had higher levels of electrical fatalities than any other country studied, with the exception of Northern Ireland. This New Zealand study confirmed the results of a similar study done by the German government, so the results are corrobo­rated. The country with the lowest electrical fatalities (by a huge margin, varying from year to year between 0.5 and less than 0.1 deaths per million of population), is 12  Silicon Chip The Netherlands, and this is one of the many countries that allow householder DIY wiring). Australia has the second highest levels of annual elec­trical fatalities (varying between 2.5 and 4 deaths per million of population). Now Northern Ireland is an extremely turbulent society. Yet by the German and New Zealand comparative studies, Northern Ireland is the only country with higher levels of electrical fatalities than Australia! The Australian statistics reflect the gross irresponsibility of the great Aussie tradition of allowing powerful vested interest groups to “regulate” themselves. (2). Prior to 1992, it was illegal for any electrician in New Zealand to explain any technical aspect of electrical wiring to anyone who was not a trainee electrician, or not otherwise li­censed to do “electrical work”. This prohibition was seen as a serious impediment to the new electrical safety regime and was eliminated in the 1992 changes to the NZ electrical safety re­gime. (It appears there is no similar prohibition in the current Queensland legislation). (3). Anyone can assist an electrician to do electrical work in New Zealand, without the electrician having to look over that person’s shoulder. So for instance, after an electrician has agreed to supervise your work, you could bolt up the control panel and connect the house cables to it on your own and the electrician would just do a quick check on your work when it is finished. (4). Only completely new work and extensions, etc, are required to be inspected in New Zealand. You can replace and relocate wiring, power points, switches, etc, without notifying the au­thorities as long as cable lengths are not altered. The exception is wiring in metal conduit. New Zealanders are not allowed to work on systems run through the old metal conduit systems. Howev­er, they can remove all the metal conduit and then rewire the house with modern cable and components. (5). Interestingly, the overwhelming majority of additions to houses in New Zealand are done on an owner-builder basis, there­fore much of New Zealand DIY electrical work is the wiring asso­ ciated with such additions. Of course, entire houses are built by owner-builders in New Zealand and in these cases almost all the wiring is done by the owner. (6). Specially certified “inspectors” do all required inspec­tions, not ordinary electricians. The “inspectors” are liable for the quality of the inspection but not for the quality of the work. If and when the work appears to be particularly shoddy or unsafe the inspector can refuse to do the inspection. New Zealanders are advised by their Energy Safety Service to secure the services of an “inspector” before they begin their DIY electrical installation work. These “inspectors” are private operators, not government employees, and of course, the homeowner has to pay for the inspection service. These inspectors advise the homeowner on the technical aspects of the installation if they feel such advice is needed. (7). The senior NZ Energy Safety Service official I spoke to made it clear to me that homeowner DIY wiring will not change in New Zealand as a result of all the ongoing reviews, which are now largely concerned with the health and safety of electrical work­ers in industry. The attitude of the New Zealand authorities is that there is no danger whatsoever when DIY electrical work is done according to law. (8). The New Zealand Energy Safety Service has the attitude that old cables, switches, power points and other fittings need to be able to be replaced at low cost. They believe the sorts of dan­ gerous situations where people continue to use cable and fittings of questionable serviceability are dramatically reduced by allow­ing householders to replace these items themselves. (9). Before 1992, electrical engineers and associate engineers in NZ were authorized to do all “electrical work”. This has now changed for new graduates though all licenses current in 1992 continue. Recently graduated engineers and associate engineers can apply for electrical contractor licenses after fulfilling appropriate (minimal) training. In Australia, there is no way to avoid the four-year ap­prenticeship. Let’s face it, which electrical contracting busi­ ness would take on an adult trainee on adult wages when they can get a teenage apprentice at slave labour rates? So effectively, there is no practical path to an electrical contractor’s license for engineers and associate engineers in Australia. (10). When New Zealand decided to reassess its electrical safety regime they sent an official overseas to study the electrical safety regimes in other countries, including the United Kingdom and USA systems. In the National Competition Policy review of electrical safety in Australia, there is no requirement whatsoev­er to even look at “world’s best practice”. (11). In the United Kingdom, electrical licensing is relatively weak and electrical standards compliance is primarily enforced through insurance. The UK, which has long had householder DIY wiring, has annual electrical fatality levels below 1.0 per million of population. Compare that to the Australian figures! My extensive interactions with New Zealanders were such that I can wholeheartedly confirm the comments of I. Morrison in the January 2001 Mailbag. New Zealand really is a much kinder, fairer society that is much more protective of civil liberties than we are in Australia. So please, wake up Australia! Otto S. Hoolhorst, Brisbane, Queensland. Solar power not bogged in bureaucracy I write in response to the letter entitled ‘Solar power bogged in bureaucracy’ on page 33 of the December 2000 issue. The Sustainable Energy Industry Association (Aust) Ltd - SEIA (Aust) is working hard to improve the quality, safety and reliability of renewable energy systems designed and installed as grid-connected and standalone power supply systems. In doing so, the Associa­tion works closely with Standards Australia and with the Austra­ lian Greenhouse Office (and state Energy Departments). Under the rebate scheme alluded to in the ‘Solar power bogged’ letter, applicants can receive a rebate ($5 per watt) off the cost of the photovoltaic modules in the system. This is approximately half the cost of the modules and they can save thousands of dollars on the overall cost of their system. It would be folly of any state energy department distributing these amounts of money not to ascertain the bona fides of the system; ie, they must make sure that the number of panels claimed has actually been installed. This, unfortunately has already lead to rorts of the rebate system – owners have been claiming rebates for panels which were not supplied or, if supplied, had been taken away after the event. They also need to have some confidence that the system will work – hence the requirement for a load analysis. If the system has been poorly designed and there is no match between the design load and the size of the battery bank, the PV array and the other balance of system components, the reputation of solar as a viable energy source may be harmed. The system must also be safe! Many people seem to think that extra low voltage DC systems are inherently safe. They are – to the extent that the current and voltage in the cable from the array to the battery bank and from the battery bank to the load will probably not kill anyone. However, incorrect cable sizing can lead to the cable overheating with the result of a possible fire started in the roof space of a house. The ‘dead short’ current of a battery will be in the order of thousands of amperes – shifters vapourise at these currents. There are significant safety issues and installation to the appropriate Australian Standards should give greater confidence that the system presents no danger. One wonders whether the author of the letter understands AS 4086.2, AS 4509 parts 1, 2 & 3, AS 3000, AS 2676.2, AS 1170.2, AS 2676 parts 1 & 2 and even AS 1768. The issue of earthing is also raised. Consider a perfectly legitimate MEN earthing system on the AC side of the inverter and an earth on the battery negative. If an earth fault occurs on the AC side, there may be a 240V potential difference between the two earth stakes. A person standing between the two earth stakes could receive a fatal shock! Clearly with only one earth stake the system is inherently safer from this point of view. Earthing is not a simple issue – in some conditions it may be better to earth and in others it may be better not to. The installers of the AC and DC systems must liaise to determine the most appropriate earthing scheme for the overall system. Consequently, it is in the interests of consumers, the state energy departments and the industry, to impose the perceived ‘bureaucratic’ requirements. The ‘invasion of privacy’ is only to the extent that the state energy authority needs to ascertain the design and in­stallation characteristics. The choice is simple – accept the rebate and the associated perception of an invasion of privacy or don’t accept the rebate. Thousands of home owners around the country are quite prepared to have their system audited so that they may receive this generous assistance. The writer may not be aware that there are considerable losses from a solar system. The specifications of a photovoltaic module stipulate the current, voltage and power ratings under standard test conditions (STC) – one of which is an internal cell temperature of 25°C. The output power of a cell is de-rated at 0.5 % per degree above 25°C. If the ambient temperature is 35°C, the internal cell temperature will be approximately 55°C. This means that the output power is reduced by 15%. On top of this, there are system losses – 85% typical inverter efficiency, 90% typical battery efficiency and up to 5% cable losses. This gives a total loss of 45% – which is quite realistic in many circumstances. The figure mentioned (50%) may be slightly conservative – but not by much. In any case, the outcome of under-sizing the photovoltaic array will most probably be no lights and no power to run the computer. Any trained system designer will consider all of these losses and work from the load backwards to determine the capacity of the battery bank and photovoltaic array, specifying cable size, balance of system components and array tilt and orientation angles to optimise the performance of the system. The writer clearly has a system which he is happy with. Others have taken advantage of the rebate scheme to obtain the same satisfaction. If any readers wish to take advantage of the rebate program they should contact their state energy department or the national office of SEIA (Aust) on (02) 6230 1562. Ray Prowse, Executive Officer, Standards, Training & Accreditation. email: Ray.Prowse<at>seia.com.au MAY 2001  13 Using Linux To Share An Internet Connection; Pt.1 Using a Linux-based PC is a great way to provide shared Internet access for Windows (and Mac) machines on a network. It’s easy to set up, you don’t need fancy hardware and you don’t have to spend big dollars on a Microsoft operating system. By GREG SWAIN Almost everyone with a few computers on a small-office or home-office (SOHO) network faces the same problem – how to give all machines simultaneous access to the Internet via a shared modem. Usually, the main requirement is to give everyone email access. However, you don’t want everyone dialling out to the Internet on separate lines – that’s expensive and ties up lines that should be kept open for voice connections. The answer is to use one machine as a “gateway” to the Internet and have the other machines connect via this gateway. That way, everyone on the network can share the Internet connec­tion via a common modem and phone line. If you have only a couple of computers on a home network, Microsoft’s ICS (Internet Connection Sharing) utility – included with Windows 98SE, Windows Me and The Linux KDE desktop presents a Windows-like interface that’s easy to use. Programs are launched by clicking the “K” button and by clicking the icons on the “K panel”. 14  Silicon Chip Windows 2000 – is the way to go. It’s a snack to set up and you only have to install it on the gateway (or host) machine. The “client” machines don’t require ICS and can run other operating systems such as Windows 95 and Windows NT. If you want to know more about ICS, take a look at the article on home networking in the December 2000 issue of SILICON CHIP. The Linux alternative Although ICS will work in an office situation, you’ll even­tually find yourself wishing for something a bit more “robust” than Windows 98SE or Windows Me. This is where Linux shines as an operating system – it exhibits a rock-like stability that rivals Windows NT/2000 but you save big dollars on the licence fee. A Linux box configured as an Internet gateway will run for weeks or even months on end, without the need for regular reboots – in fact, you often don’t have to reboot until there’s a power interruption! Try doing that on a Win98 or WinMe box and see how far you get! But Linux has a few other advantages as well. For starters, it costs next to nothing and is sometimes even included on the CD-ROMs stuck to computer magazines. In any case, $15-20 will get you a “newsagent’s special”, consisting of a book and a set of CD ROMs with one or more Linux distributions. What’s more, a Linux distribution includes an amazing range of utilities – including a web server, an FTP server, a DHCP server and a mail server – plus lots of applications. Want a free office suite? Linux distributions invariably include Sun Star Office and sometimes even Wordperfect 8.0. Which Linux distribution should you use for the job? Well, that’s a matter of personal preference. The procedure outlined here is based on the author’s experience with Red Hat 6.2 and Red Hat 7.0 but should also work Fig.1: the basic details for setting up a small network to share an Internet connection. TCP/IP is used as the networking protocol and each machine is given it’s own IP address. Both Windows and Mac boxes will work through the Linux gateway, as will any other Linux boxes connected to the network. without modification on Mandrake Linux (although it hasn’t been tested). Other distributions keep some of their configuration and script files in different locations to Red Hat Linux, so you may have to modify the procedure slightly. You’ll figure it out. Hardware requirements You don’t need fancy hardware for a Linux gateway but forget the guff about running later distributions of Linux on an old 386. A 486 can be used at a pinch and will run perfectly as a gateway once set up has been completed. However, if you want to run X Windows (the graphical interface that comes with Linux) at a fair clip, you really need a Pentium machine with at least 32MB of memory. What’s more, distributions like Linux Mandrake 7.2 are optimised for Pentium machines and won’t even install on a 486. By contrast, Red Hat Linux 7.0 will install on a 486 and this will function perfectly as a Linux gateway – it’s just that X Windows will run very slowly, so you will have to be patient when setting up the gateway. That won’t matter once setup is complete – in fact, you don’t even have to start X Windows for the gateway to function. Anyway, this is all really just a long-winded way of saying that you can scrounge the hardware for your Linux gateway. A Pentium 120 or 133 will do just fine but don’t be afraid to fire up an old 486 if that’s what you have on hand. Naturally, the machine will have to be fitted with a net­ work card and (preferably) an external modem, although these items can also be added after Linux has been installed. And depending on the installation, you’ll also need about 1GB of hard disk space, although 1.6-2GB gives a bit more elbow room. Just about any modem should work OK with Linux but steer clear of so-called “Winmodems” – these normally rely on Windows-based software to work properly and will cause you grief with Linux. The basic network Fig.1 shows the details for a simple home or office net­work. You don’t need much in the way of networking hardware – just a few network interface cards (one for each computer), a hub and some Cat.5 ethernet cables to connect it all together. For a home network, you probably won’t need anything faster than a 10Mb/s hub and a 4 or 5-port model should cost no more than about $60. However, if purchasing network cards, go for 10/100Mb/s models so that the network can later be easily upgraded. Buy a 100Mb/s hub if speed is a requirement (eg, if transferring large files across the network). As shown in Fig.1, TCP/IP is used as the networking proto­col (NetBEUI won’t work across the gateway), which MAY 2001  15 network to the Internet – after all, if your network can “see out”, it’s always possible for a hacker to “see in” unless precautions are taken. Internet serving is not the only “trick” that we can per­ form with our Linux box. Want to make it into a file and print server as well? We’ll show you how to do just that in future articles but for now, let’s concentrate on our Internet gateway. Network cards & modems You don’t need much in the way of hardware for a Linux gateway machine. This rebuilt 120MHz Pentium PC with 64MB of RAM and a 1.6GB hard disk drive works fine but you can use a 486 if you have to. means that each machine is issued with a unique IP address. We’ll show you how to set up the network parameters later in this article. Note that Fig.1 shows two Windows clients and a Mac client – yes, that’s right, you can add Mac clients or even Linux clients to the network and they will all access the Internet via the Linux gateway. That’s because all three systems communicate with the Internet using TCP/IP and it’s the networking protocol that’s important here, not the operating system. However, sharing a common networking protocol is not sufficient for Windows and Mac clients to share files and other resources. For that, you need additional software (eg, MACLAN) but that’s another story. Demand dialling & firewalling To make our gateway easy to use, we’re going to show you how configure the Linux box for demand dialling. This means that it will automatically dial out whenever a client machine requests Internet access. The link will then stay up while ever there is TCP/IP “traffic” through it and will automatically disconnect after a preset (idle) time when traffic ceases. Another thing we’re going to do is construct a basic fire­wall. A firewall makes good sense when you connect a Linux supports a wide range of PCI Plug’n’Play network cards, including those based on the RealTek RTL81398 chip (ne2k-pic driver). 16  Silicon Chip Before installing Linux, it’s a good idea to take a look at the “Ethernet Howto” (one of many Linux “howto” articles included on the disk with your distribution). This has a list of supported network interface cards (NICs) and their drivers. As it stands, Linux supports a wide range of network cards out of the box. In general, it should have no trouble with Plug’n’Play (PnP) PCI cards, particularly those based on SMC, Western Digital, Intel, Via, Digital and RealTek/ Winbond (ne2k-pci) chips. A lot of Netgear cards aren’t directly supported, however. Many older ISA-based cards are also supported by Linux, including those from SMC, D-Link and 3Com. These include the popular SMC Ultra, D-Link 250 and 3Com 3c509 cards. If you are using an ISA-based card, it will be necessary to manually configure the IRQ and I/O address settings using either on-board jumpers (try I/O = 0x340 and IRQ = 10) or a setup utility. You can download the setup utility from the manufacturer’s website if you don’t already have it. If you have an ISA PnP card, the best advice is to first turn off the PnP support using the setup utility, then manual­ly assign the I/O address and IRQ settings as before. Make a note of these settings – you’ll need to specify them in a configura­tion file later on. If you know nothing about I/O address and IRQ settings, buy a supported PCI network card. Of course, if you’re using a 486, then you’re stuck with an ISA card but that really shouldn’t cause problems. Propellers not needed Getting Linux up and running was once a job for propeller-heads but not any more. The latest distributions have graphical install interfaces which make the job easy. You don’t need to be a rocket scientist and if you’ve successfully installed Windows before, you should have no problems. Older ISA-based network cards like this 3Com 3c509 are also supported by Linux. The card’s IRQ and I/O memory range are usually assigned using a setup utility. Fig.2: a non-destructive partitioning program such as PartitionMagic can be used to shrink an existing Windows partition if you want a dual-boot Windows/Linux system. Back up any critical data first, though. Fig.3: choose the custom install option if you want a dual-boot system. It also let’s you install what you want. Linux also comes with a choice of X Windows interfaces – either KDE or Gnome. If you’re used to Windows, go for the KDE interface; it’s the one that’s most like Windows, although both interfaces do much the same job. You even get a taskbar and programs are launched in almost identical fashion to Windows. That said, don’t expect Linux to behave like Windows. It’s really quite different and there’s a bit of a learning curve if you want to become really familiar with it. However, you don’t have to be an expert to set up a gateway since most of the job involves editing a few simple configuration files using a text editor. Installing Linux No, we’re not going to give you a blow-by-blow account on installing Linux. That will all be set out in the book that comes with your distribution. We’ll confine ourselves to a few basic tips. First, be aware that it’s possible to set up a dual-boot Windows/ Linux system – usually by installing Windows first and then Linux. If you do this, the Linux boot manager, called LILO (for Linux Loader), will allow you to choose between the two operating systems during boot-up. Note that it will be necessary to use a non-destructive disk partitioning program, such as PartitionMagic (Fig.2), to shrink the existing Windows partition, to make room for the Linux installa­tion. Alternatively, you can use the FIPS partitioning program that comes with Linux to do the job, although its interface is not particularly user friendly. Don’t try to use the MS-DOS fdisk utility to resize parti­tions as it will destroy any existing data on the hard disk. Also, back up any critical files before attempting to resize partitions. Of course, you don’t have to worry about any of this if Linux is to be the only operating system. Booting directly from the Linux installation CD is by far the easiest way to start the installation process – assuming that your PC is capable of booting directly from CD-ROM. You will have to change the boot order in the system BIOS to do this. Alternatively, you can boot from Fig.4: Disk Druid is used during installation to create the Linux native and swap partitions. Fig.5: the Network Configuration window appears if a network card is detected during the installation process. The network can also be configured later on. a DOS floppy with CD-ROM support (eg, a Windows 98 Startup Disk) and start the installation process from there. MAY 2001  17 that isn’t detected (eg, a sound­card or a ZIP drive) can be added later on, usually with the aid of the relevant Linux “how-to”. Network configuration Fig.6: you can choose which packages to install here. The KDE desktop is the one that’s most like Windows but go for the Gnome desktop if you prefer it’s appearance. After that, it’s literally a matter of following the bounc­ ing ball by filling in the blanks in the dialog boxes and click­ing the appropriate options. During the install process, you will be asked to choose the installation type, either Workstation, Server System or Custom (Fig.3). Don’t choose the Server System option if you want a dual-boot system, as this will wipe out any existing partitions on the hard disk. Similarly, don’t choose the Workstation option if you want to dual-boot with Windows NT. If you do, LILO will overwrite NT’s boot loader in the master boot record (MBR) and NT will no longer boot. Check out the “Linux/ Windows NT Howto” if you want a dual-boot Linux/ Windows NT setup. The best bet is to choose the Custom install option, as this lets you install what you want. It also lets you choose where to write LILO – either to the MBR or to the first sector of the Linux partition. Normally, you would choose to write LILO to the MBR and this applies to both standalone and Linux/Win98 dual-boot systems – but not for a Linux/NT dual-boot system. Selecting the Custom install will also bring up “Disk Druid” (Fig.4), which lets you set the size of the Linux partition and the size of the “Linux Swap” partition. A swap size of 120MB is plenty for most installations. You should choose “Linux Native” for the main Linux partition and set the mount point to / (that’s a single forward slash). Be sure to elect to create a Linux boot floppy at the LILO Configuration window. You should also write down your user name and the passwords chosen for your root and user accounts, as set up under Account Configuration. It’s probably best not to select the “Use Graphical Login” option during X Configuration. Once the gateway has been set up, you don’t need to run X Windows for the system to function. And, of course, you can always start X Windows manually after login. Despite being non-Plug’n’Play, the latest versions of Linux do a great job when it comes to “probing” and identifying your hardware. This includes video cards, mice, disk drives, CD-ROM drives and modems. Any hardware 18  Silicon Chip If a network card is detected during installation, the network configuration dialog box will appear (Fig.5). If the card isn’t detected, the details can be added in after installation has been completed. As shown in Fig.1, we’ve named the Linux box “penguin” and given it a domain name of “antarctic.work” (don’t use an Internet domain name). We’re also using 192.168.0.0 as our network address and given the Linux gateway an IP of 192.168.0.1. Note that IP addresses ranging from 192.168.0.0 to 192.168.255.255 are re­served for “private” networks. Do not use an arbitrary address from outside this range – stick to the addresses shown here. Assuming that you’re following our scheme, your networking parameters should look like this: IP Address: 192.168.0.1 Netmask: 255.255.255.0 Network: 192.168.0.0 Broadcast: 192.168.0.255 Hostname: penguin Gateway: Primary DNS: IP as provided by your ISP Secondary DNS: IP as provided by your ISP Note that the gateway address should be left blank. That’s because the Linux box is itself the gateway, but we do have to hand out the gateway address details to the clients. The Domain Name Server (DNS) IP numbers are as specified by your Internet Service Provider (ISP). Don’t worry if you don’t have all the necessary Fig.7: you can test the network card in the Linux box by entering the command ifconfig eth0 at a terminal window. You should get a response like this. Fig.8: local and remote network connections can also be tested by pinging IP addresses (eg, ping 192.168.0.1). informa­tion; it can be added to or altered later on. Startin’ up and shuttin’ down When installation is complete, boot Linux, log on as root and enter your password. If you’re now staring at a DOS-like terminal prompt and you’re new to Linux, you’re probably wonder­ing “how the hell do I launch X Windows?” Answer: type “startx” and press <Enter>. Conversely, to shutdown from the terminal prompt (or console), type shutdown -h now and press <Enter> or shutdown -r now to reboot. If you are in X Windows, you have to log out first before shutting down. Assuming that you are using KDE, click the K button and click Logout. Testing the network card Fig.9: the linux.conf utility (K -> Red Hat -> System -> LinuxConf) can be used for setting up the networking details on the Linux box. It is especially useful if the network card wasn’t detected during installation. If you used a PCI card, the chances are that it was recog­nised during the Linux install process and that it’s already working. The Linux kernel refers to your network card as eth0, while a second network card (if present) will be designated as eth1. There’s a very simple way of finding out if a network card is working correctly. Just launch a terminal session by clicking the console icon on the K panel (or Gnome panel) and type: /sbin/ifconfig eth0 You should see a response like that shown in Fig.7. Another useful test is to try pinging the local IP address. To do this, type the following from the console: ping 192.168.0.1 If the card is working, you should get a response similar to that shown in Fig.8. Hit <Ctrl>-C to stop the pinging. If the card isn’t being recognised (eg, if it’s an ISA card), then you have to tell the kernel where to find it and which driver to load. This is done by entering its I/O address and IRQ settings into a configuration file, along with the name of the driver. The relevant file to edit is /etc/conf.modules in Red Hat 6.2 and /etc/modules.conf in Red Hat 7.0. You can use the Advanced Text Editor to edit this file – just click the pencil icon on the “K panel” (taskbar). For a 10MB NE2000 clone at I/O address 0x340 and IRQ10, it should look like this: alias parport_lowlevel parport_pc alias eth0 ne options eth0 io=0x340 irq=10 Create the conf.modules file if it isn’t already there. The first line configures the parallel port and should be left as is; the second line instructs Linux to use the “ne” driver for eth0; and the third line tells the driver where to find the card. You will have to change the driver designation and the I/O and IRQ numbers to suit your card. The driver name will be listed in the “Linux Ethernet Howto”, which also tells you how to con­figure conf.modules if you have two network cards (eg, for a cable connection). You should check out the “Home-Network-Mini-Howto” as well – this has some really good information. Be prepared to play around with the conf.modules file if necessary. For example, a 3Com 3c509 PnP ISA card that we tested refused to work if its IRQ and I/O address were specified in the options line – this despite the fact that we disabled the PnP feature and specified those parameters using the setup utility. Conversely, it worked quite happily with just “alias eth0 3c509” entered into conf.modules. After editing conf.modules, try ifconfig eth0 again. Pro­ vided there’s a driver for your card, it should work. Using linux.conf Experienced Linux gurus will sneer at this, so we’ll just whisper it – in Red Hat 6.2 & 7.0, you can also use the graphical configuration utility linux.conf to enter your network set­tings (and lots of other things as well). Linux.conf is launched by clicking K -> Red Hat -> System -> LinuxConf. You then click the “Basic Host Information” entry under “Networking” to bring up the configuration box shown in Fig.9. Basically, any entries you make here are reflected in the corresponding configuration files: ie, conf.modules, resolve.conf and hostname. It’s really just an alternative to editing the configuration files. By the way, Linux stores most of its configuration files in the /etc folder and in sub-folders under this folder. And yes, that is a forward slash, unlike DOS which uses back slashes to designate folder paths. Setting up the Windows boxes You now have to assign the TCP/IP, gateway and DNS address­es on the Windows boxes (1) TCP/IP: TCP/IP is installed by default on Windows 98 and Windows Me machines when the network card is installed but if it isn’t there, you will have to launch the MAY 2001  19 Fig.10: each Windows machine is given a unique IP address, while the Subnet Mask is always 255.255.255.0. Fig.11: the IP address of the Linux gateway (192.168.0.1) must be entered at the Gateway tab. Network configuration utility from Control Panel and add it yourself. After the customary Windows reboot, launch the Network configuration utility again and check that TCP/IP is bound to the network card. Next, double-click the TCP/IP entry for the network card to launch the TCP/IP Properties configuration box shown in Fig.10. Give the first machine an IP addresses of 192.168.0.2, the next 192.168.0.3 and so on. The subnet mask is the same for each machine; ie, 255.255.255.0. (2) Gateway Configuration: click the Gateway tab on each machine, enter the IP address of the Linux box (192.168.0.1) into the “New gateway” field and click “Add”. In each case, the dialog box should be the same as Fig.11. (3) DNS Configuration: click the DNS Configuration tab, click Enable DNS and enter the computer’s name into the Host field (Fig.12). Now add your ISP’s primary and secondary DNS IP numbers to the DNS server Search Order (don’t use the numbers shown). This is done so that when you try to access a non-local machine, the Windows box sends out a name-server lookup which triggers the Linux box to dial out. (4) Identification: each machine must be correctly identi­fied on the network. First, click the Identification tab and enter a unique name for each machine ; eg orange1, orange2, etc. In each case, the name should agree with the name entered into the Host field under the DNS tab (Fig.13). Now type in the name of the Workgroup. This can be anything you like (eg, Homenet) but must be the same on all machines. Testing the network You can now reboot all the Windows boxes and check that the network is functioning. You can do that by pinging each IP address in turn from your Linux box and then doing the same from the Windows boxes (do this from a DOS box). If you get return packets similar to those shown in Fig.8, then “whoppeeee” – your network is functioning. Remember to press <Ctrl>-C to stop pinging from the Linux box. 20  Silicon Chip Fig.12: the IP address of the gateway should be first in the DNS search list, followed by the ISP’s nameservers. Fig.13: each of the Windows machines must be given its own name and assigned to a workgroup, so that it can be identified on the network. Finally, use a text editor to create an “lmhosts” file. This file contains a list of all the IP addresses and names of the machines on the network. It will look like this: # lmhosts 192.168.0.1 192.168.0.2 192.168.0.3 192.168.0.4 penguin orange1 orange2 apple1 Save the file as lmhosts (ie, no extension) and place a copy into the Windows folder of each machine. Once that’s done, the lmhosts file will be used for resolving names on the local network (ie, for translating names into IP addresses), rather than forcing the machines to broadcast nameserver queries. Your network is now functioning and you can set up file and printer sharing on your Windows boxes in the usual manner . That’s all for this month. In Pt.2 next month, we’ll show you how to connect your Linux box to the Internet and SC configure it for demand dialling. 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. Metering circuit for Sine/Square Generator The Sine/Square Wave Generator described in the February 2000 issue has been quite a popular project but we have had requests for a metering circuit for it. Both this and a frequency readout were left out of the original design to keep the design simple and low in cost. In fact, since the square output has a fixed amplitude, there is no point in monitoring its amplitude since it will always be 5V peak-topeak, as set by the 5V supply and the CMOS circuitry. However, it would be worthwhile having a metering circuit for the sine­ wave output which is adjustable in level from 0-2V RMS. The accompanying passive circuit, involving two ger­ manium diodes and a 100µA meter, can accomplish this. The 100µA meter movement is connected inside a bridge cir­ cuit consisting of two germanium diodes and two 10kΩ resistors. The input impedance of the metering circuit will be quite high, above 20kΩ, and therefore not cause any loading problems on the output of the Sine/Square Wave Generator circuit. While we have specified OA91s on the circuit, virtually any germanium signal diodes can be used in this application. Trimpot VR1 is provided for calibration against a digital multi­meter. Calibration should be done at a low frequency (eg, 100Hz), to ensure that the DMM’s bandwidth does not prejudice the meas­urement. SILICON CHIP. resistors selected by switches S2 and S1a. This should be done using a close tolerance (1% or better) standard capaci­tor; eg, 0.1µF. Gregory Freeman, Mt Baxter, SA. ($30) Crystal timebase for capacitance meter This crystal oscillator replaces the 7555 timer as the 950kHz timebase in the Digital Capacitance Meter published in the May 1990 issue of SILICON CHIP. The new circuit has a transistor oscillator based on a 4.75MHz crystal and this is fed to a 74HC390 which is set up to divide by a factor of five, giving the wanted frequency of 950kHz. This is fed to pin 1 of IC5 in the original circuit. To take advantage of the lower drift and greater precision of the new timebase, the Capacitance Meter should be recal­ibrated by trimming the charge MicroZed Computers GENUINE STAMP PRODUCTS DANISH SOUND TECHNOLOGY FROM 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 0409 036 775 Fax (02) 6772 8987 http://www.microzed.com.au Most Credit Cards OK Please quote “SILICONCHIP” when you order. ***SEE OUR WEBSITE FOR SPECIALS MAY 2001  21 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.dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dicksmith.com.au COMPUTER TIPS: Tweaking The Windows Interface Like to fiddle? Get Tweak UI (it’s free)! Rid your desktop of many of those annoying Windows eccentricities and perform lots of other useful tweaks with this updated utility from Microsoft. Tweak UI is probably one of the most useful utilities available for Windows. It gives you control over a whole multitude of desktop (or “user interface”) related settings, most of which previously required registry hacks to get at. This month, we’ll show you how to download and install it, and take a quick peak at some of the most popular “tweaks” it provides. Tweak UI 1.33 runs on Windows 95/ 98/ Me/ NT4 and 2000. It is free 26  Silicon Chip to download from the Microsoft web site at: www.microsoft.com/ntworkstation/ downloads/powertoys/networking/ nttweakui.asp You will receive a single file named tweakui.exe from the download page. Navigate to wherever you saved the file and double-click on it to extract the installation files to a temporary folder. Four files are extracted, all beginning with “tweakui”. Right-click on the by PETER SMITH tweakui.inf file and select install from the context menu. During installation, which only takes a few seconds, the Tweak UI help window appears – simply close it to allow the installation to complete. Once installed, double-click on the Tweak UI icon in Control Panel to launch it. Available settings vary slightly according to the version of Windows you are running. I usually work with NT4, so my first stop is the Explorer tab to turn off the animated “Click here to begin” arrow that slides along the task bar every time NT boots. I also like to “tone down” the shortcut arrow that Windows automatically places on all my shortcut icons by selecting the Light arrow option. Next stop is the Paranoia tab to Get rid of the Internet Explorer logo Tweak UI Problems If you’re already familiar with Tweak UI, then read on. Early versions are reported to be a little “buggy”. If you have an older version, then uninstall it via Control Panel -> Add/Remove Programs, reboot and install the latest version as described on the facing page. To determine which version you have installed, launch Windows Explorer and find the tweakui.cpl file. Right-click on it and choose Properties. Now click on the Version tab – the latest version is currently 1.33.0.0. Windows Me and Windows 2000 users should avoid the Show Control Panel on Start Menu option on the IE tab. We haven’t tried it, but deselecting this box apparently renders the Control Panel completely inaccessible! If this happens to you, start the registry editor by clicking the Start button, choose Run, type regedit and click OK. Drill down to: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer Delete the “NoControlPanel” entry from the right pane, close Regedit and restart Windows. disable CD auto play. Also popular here are the various options to clean up “history” files at logon. These are especially useful if more than one person uses your computer. The Repair tab exposes some very useful fix-it functions. If you’ve ever seen the desktop lose its marbles (the Recycle Bin icon is switched with the Internet Explorer icon, for example), know that help is at hand here. Well, that’s just a small sample of what you can do with Tweak UI. Have fun! The Tweak UI window has lots of tabs that take you to the various settings. The Paranoia, Repair and Explorer boxes are shown here. Does your copy of Internet Explorer feature an annoying logo (or other branding) from the computer company or on-line service that supplied your computer or IE installation CD? Get rid of it! Note that this procedure only works for Internet Explorer 4 and 5 running on Windows 95/98/ Me/2000. Make sure IE is closed, then click on the Start button, choose Run and type in the following line exactly as it appears below: RUNDLL32.EXE IEDKCS32.DLL,Clear Now click on the OK button. That’s it! Save time on-line updating Windows 98 If you’ve had to reinstall Windows 98 more than a few times, you’re probably really tired of surfing to the Microsoft Windows Update site to reload all the operating system updates and bug fixes. Each update is automatically applied as soon as download completes, so you don’t get the chance to save it for the next installation. The good news is that you can now download most Windows 98 updates and save them for use whenever you need. Check out what’s available at: www.microsoft.com/windows98/ downloads/corporate.asp Settings fever If you find Tweak UI a little tame, then why not up the stakes and try something that allows you to modify literally hundreds of obscure Windows settings? We did, and we’re still regretting it (urr – just kidding!). An excellent freeware utility called X-Setup lets you do just that. It features an Explorer-style interface for easy navigation and “Wizard” mode that helps you find what you’re looking for without needing expert knowledge. It’s well worth a look – check it out at: www.xteq.com/products/xset MAY 2001  27 Getting lots of power from an amplifier when you only have 12V to play with Powerful, 12V Mini Stereo Amplifier by JOHN CLARKE Many commercial 12V amplifiers can’t deliver much power, despite sometimes amazing claims to the contrary. This little stereo amplifier can: up to 18W per channel into 4Ω speakers and with the added bonus of volume, bass and treble controls. I (wryly!) is when we see consumer t’s small and compact and can de- the output devices with a 12V supply liver quite a punch to your loud- is 6V in the positive direction and 6V “hifi” claiming 50W output or more – and they take six “C” cell batteries. speakers. Controls are simple, with in the negative direction. This equals bass and treble controls which can about 4.25V RMS (6/1.4142). Oh yeah? be used to brighten up your listening Power output equals the square of So how can this stereo amplifier pleasure and a volume control to set the RMS voltage divided by the load produce any more output power? you rocking. resistance (P=I2/R), so we get 4.25 x The trick is to use two amplifiIt makes a great little amplifier for your 4.25 / 4, or about 4.5W. ers, one to push current one direcWalkman, persontion through the al CD or mini-disc speaker and the SPECIFICATIONS player, etc. And it other to push curPower output : see graphs can be operated from rent the opposite see graphs a 12V battery or good Distortion: direction. Tone controls: see graphs 12V power supply. When one amW h e t h e r y o u Frequency response: plifier drives the -3dB <at> 10Hz and 100kHz want an amplifier Sensitivity for full power output: 50mV RMS loudspeaker in for your car, boat, Signal to noise ratio: a positive volt-69dB with respect to full output power caravan or for some age direction, the (20Hz to 20kHz filter, -78dB A weighted) other 12V appli- second amplifier -46dB at 100Hz, -36dB at 1kHz and 10kHz cation, it is often Channel separation: drives the louddifficult to find a speaker in a negdesign which will ative voltage direction. produce very much power output. However, even this 4.5W is a theThis means that the voltage across oretical maximum and the output the loudspeaker is effectively double It is just an unfortunate fact of life that at 12V the very absolute maximum power is more likely to be closer to 3W that of a single amplifier driver. power that can be delivered into a 4Ω due to losses in the output devices of Now from the formula above, we can the amplifier. load is 4.5W. see that doubling the voltage swing efAs an aside, one of those little The reason for this is that the maxfectively quadruples the output power. imum voltage “swing” possible from mysteries of life which make us smile So if we use two typical amplifiers 28  Silicon Chip which on their own can only deliver 4.5W into 4Ω we can expect to obtain about 18W into the same load (but with a 14.4V supply). Again, there are a few limiting factors which mean we cannot get this theoretical maximum without a fair bit of distortion but this little amp delivers about 14-15W before it “hits the hump” and, if you’re prepared to put up with distortion, up to about 18W – a lot better than 4.5W, you would agree! (Having listened to many, many car stereos and ghetto blasters being driven into massive distortion, it’s not unreasonable to suggest that many users don’t care. As long as it’s LOUD!) You might have noticed that we call this a “12V” amplifier yet our tests were done using a 14.4V supply. The 12V is a “nominal” figure. This is quite legitimate because virtually all vehicles run with more than 12V DC when the motor is running. That extra couple of volts is also handy in giving us an extra few watts! and treble controls to the front of the amplifier to improve its versatility. Most components mount onto a single PC board. It’s just the right size for mounting in a small plastic instrument case so you can really dress up your project if you want to. The circuit The circuit for the stereo amplifier is shown in Fig.1. Only the left channel is shown, based on IC2, with the right channel (IC3) pin numbering shown in brackets. Both channels “share” IC1, each using two of its four op amps. Signal is applied to the left channel via the 10µF bipolar capacitor and 10kΩ log volume potentiometer, VR1. Output from the wiper of VR1 is AC-coupled to the non-inverting input of one of IC1’s op amps (pin 10) via a 0.22µF capacitor in series with a 1kΩ AUDIO PRECISION SCTHD-W THD+N(%) vs measured LEVEL(W) 10 30 APR 100 06:34:48 1 Special IC The 12V Stereo Amplifier uses a hybrid IC package which incorporates all the amplifier circuitry into the one unit. All we need to make it fully operational is to add a few extra components, connect up a speaker and input signal, apply power and we have a ready-built amplifier. It could be that simple – but we have added a volume control and bass 0.1 0.1 1 10 20 Here’s proof: with a 14.4V supply and a 4Ω load, the amplifier does indeed produce up to 18W, albeit with a fair bit of distortion. The horizontal scale is output power (in watts); the vertical is total harmonic distortion (THD). MAY 2001  29 Believe it or not, this photo of the inside of the amplifier is actually larger-than-life, so you can get a good idea of just how tiny it is! The photo also shows all the component locations in glorious living colour. stopper resistor. This resistor helps prevent RF pickup. The 100kΩ resistor connects to the half-supply rail, which biases op amp IC1a at mid-supply voltage. This sets up the op amp to provide symmetrical voltage swing about the mid voltage. The tone controls IC1a is connected as a unity gain buffer to provide a low impedance drive to the following tone control circuitry. The tone controls are based on op amp IC1b and potentiometers VR2 & VR3. These pots and their as30  Silicon Chip sociated resistors and capacitors form the feedback between the op amp’s inverting input and output. Each of the bass and treble stages can be considered separately since they are connected in parallel between the signal input following IC1a and the inverting input (pin 2) to IC2 which is a virtual ground. Operation of the bass control is as follows: with VR2 centred, the same value of resistance is connected between the input from IC1a and the inverting input to IC1b as is between IC1b’s output and inverting input. Thus the gain is set at -1 (the minus symbol doesn’t mean less than zero in this case, it means that the output is inverted with respect to the input). The .01µF capacitor has no effect since it is equally balanced across the potentiometer. However, if we move the wiper of VR2 fully toward the input side (toward the IC1a output), the resistance becomes unbalanced and there is a 22kΩ resistance between input and the inverting input to IC1b and 122kΩ (100kΩ + 22kΩ) between the inverting input and output. (We can ignore the other 22kΩ resistor in the wiper as its job is simply to isolate the two pots). Also the .01µF capacitor is across the 100kΩ resistance in the feedback between IC1b’s output and inverting input. Without the capacitor the gain would be -122kΩ/ 22kΩ or -5.5 at all frequencies. The .001µF capacitor and 100kΩ resistance forms a rolloff above 100Hz so that below this frequency the gain remains at -5.5 or 14.8dB but above 100Hz the gain reduces towards -1 as the frequency increases. Thus we have boost at and below 100Hz. When the wiper is brought to the IC1b output side, the resistive gain becomes 22kΩ/122kΩ or -0.18 or -14.8dB. The capacitor is now on the input side and provides less gain at frequencies below 100Hz but with gain increasing to -1 at frequencies above 100Hz. Thus we have bass cut. Various settings of VR2 between these two extremes will provide less boost or cut. The treble section works in a similar manner except that there is now a .0047µF capacitor in series with the input and output. This produces a high frequency boost or cut at 10kHz. The 10pF capacitor between IC1b’s inverting input and output provides high frequency rolloff, preventing instability. The amplifier(s) The High Power 12V Amplifier is based on IC2 (or IC3), a Philips TDA1519A car radio power amplifier module. This incorporates all the complexity found in much higher power amplifiers. It has output protection against short circuits, good supply ripple rejection, overheating protection, reverse polarity protection, overvolt-age shutdown and is protected against static discharge. The best part is that it is virtually indestructible within its limits. The TDA1519A contains the two power amplifiers. The first power amplifier is non-inverting with its input at pin 1 and output at pin 4. The second amplifier is inverting with its input at pin 9 while its output is at pin 6. When both these amplifiers are fed Fig. 1: not much to it, is there? The amplifier modules (one for each channel) do most of the work. Only the left channel is shown here as the right channel is identical. MAY 2001  31 Fig. 2: all the components, including the three potentiometers, mount on the one PC board, so once you’ve finished the PC board off you’re about 90% of the way to sitting back and listening to your handywork! The final wiring diagram is overleaf. the same signal, their outputs have amplified signals which are effectively “mirror images” of each other, or 180° out of phase. This is described as “bridge mode” operation. The pin 3 input is for decoupling of a half-supply rail internal to the amplifier module. Pin 7 is the positive supply input while pins 2 and 5 are the signal and power grounds. Pin 8 is a mute and standby input which selects the amplifier to be ac- tive or on when connected to the pin 7 supply. When pin 8 is open circuit, the amplifier is effectively turned off and the quiescent current drawn by the circuit is around 100µA. This input is best used to provide the on and off switching since pin 8 draws a low current and we can use a lowcost switch. If we were to switch the 12V supply on and off with a switch, then we would need a switch rated at 4A or more. Signal input to the amplifier is applied to both the non-inverting amplifier input and the inverting amplifier input via a 1µF coupling capacitor. Input impedance is 25kΩ for this bridged mode of operation and so the low frequency rolloff is at 6Hz. The series 10Ω resistor provides some protection against RF pickup which could otherwise be amplified by IC2. The 12V supply is decoupled by a 2200µF and 0.1µF capacitor for each amplifier IC. The outputs of IC2 and IC3 appear at pins 4 and 6 and are connected to Zobel networks comprising 10Ω resistors and 0.1µF capacitors. These help prevent instability in the power amplifiers. Construction The front panel components of the amplifier, taken from the rear. Note the green earth wire which solders to the shield, the three pots and back to the PC board. 32  Silicon Chip The 12V Stereo Amplifier is constructed on a PC board coded 01105011 and measuring 117 x 100mm. It is housed in a small plastic instrument case measuring 140 x 110 x 38mm. Begin by installing the wire links and the resistors on the PC board. Use the accompanying resistor colour code Parts List – 12V Amplifier Both the amplifier modules mount on the heatsink/rear panel but must be insulated from it. Note also the insulation on the wires which go through the rear panel to the speaker connectors. You don’t want a short here! table as a guide to selecting the correct value or use a digital multimeter to measure each one. Now insert the PC stakes for the three input terminals, the power inputs and for the switch. Capacitors can be inserted next –take care to correctly orient the electro-lytics with the polarity as shown. Diode D1 and IC1 are also polarised and inserted as shown. The amplifier ICs can be mounted by firstly bending the leads at 90° about 12mm away from the body of the package. These can be inserted into the PC board holes. Do not solder the amplifiers in position yet. The potentiometer shafts are first cut to length, suitable for the knobs used, their distance from the front panel and the type of box (if any) you will be mounting the amplifier in. Before you insert and solder the pots directly into the PC board holes, scrape away a small portion of the coating on the top of each potent-iometer. You will shortly need to solder an earth wire to the pots and it can be very hard to solder to the passivated metal surface. The heatsink We don’t use the rear panel of the case; instead, it is replaced by an integral panel/heatsink made from 1.5mm aluminium. Its dimensions are shown in Fig.5. Before folding the heatsink/panel, you will need to drill holes for the DC socket, the fuseholder, the loudspeaker terminals and mounting screws and for the RCA sockets. Holes are also required for the amplifier ICs. A shield is also required on the base of the case. This can be made from either insulated aluminium foil glued to the case, or from a piece of single- sided PC board. Drill holes to This straight-on view of the rear panel/heatsink gives you a good idea of where the various sockets and the fuseholder are located. By the way, you can connect just about anything from a Walkman or minidisc to a CD/DVD player or tuner into the input sockets. You could even plug an electric guitar in for practice! 1 PC board coded 01105011, 117 x 100mm 1 plastic instrument case, 140 x 110 x 38mm 1 piece of aluminium, 50 x 135 x 1.5mm 1 100 x 115mm single sided PC board or insulated aluminium foil (for shield – see text) 1 10kΩ dual-ganged 16mm log pot (VR1) 1 100kΩ dual-ganged 16mm linear pot (VR2) 1 50kΩ dual-ganged 16mm linear pot (VR3) 1 dual insulated RCA panel socket 1 4-way loudspeaker terminal strip 64 x 17mm 1 SPST rocker switch 1 M203 fuse holder 1 5A M203 fast blow fuse 1 DC power socket 2 TOP3 insulating washers 5 M3 x 6mm screws 6 M3 x 10mm screws 2 M3 x 15 Nylon screws 10 M3 nuts 2 M3 solder or crimp lugs 1 150mm length of 0.8mm tinned copper wire 1 230mm length of green hookup wire 1 80mm length of red hookup wire 1 100mm length of black hookup wire 1 100mm length of blue hookup wire Semiconductors 1 TL074 quad op amp (IC1) 2 TDA1519A or TDA1519C 12V stereo amplifiers (IC2,IC3) 1 IN5404 3A diode (D1) Capacitors 2 2200µF 25VW PC electrolytic 2 100µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 4 10µF bipolar electrolytic 2 1µF bipolar electrolytic 2 0.22µF MKT polyester 6 0.1µF MKT polyester 2 .01µF MKT polyester 4 .0047µF MKT polyester 2 10pF ceramic Resistors (0.25W 1%) 4 100kΩ 4 22kΩ 2 10kΩ 4 4.7kΩ  4 1kΩ 6 10Ω MAY 2001  33 Fig.3 (left): there’s very little wiring to do as most is taken care of by the PC board. Don’t leave the earth wire out (shown in green) or forget to solder to the pot bodies as your amplifier could be very sensitive to hum and noise. Fig.4 (above): here’s how to mount the power amplifier ICs to both the PC board and the rear panel/heatsink. Fig.5: use this diagram as a template to both cut and fold your rear panel/heatsink but drill the holes for the connectors and fuses first. accommodate the integral standoffs in the base of the case. You will require a securing screw and nut plus a solder lug to make contact with the aluminium foil. For a PC board shield you can simply solder a wire directly to the board. Fit insulation (eg, a sheet of self-adhesive plastic) to the top side to prevent con34  Silicon Chip tact with the amplifier PC board (if you use a PC board for the shield, simply fit it upside down). Drill holes in the front panel for the power switch and pot shafts using the front panel label as a guide to the hole positions. Attach the front panel label in position. Attach the components to the heat- sink making sure that the RCA sockets are insulated from the metal, and stand the loudspeaker terminals off the heatsink with an extra M3 nut. This will allow extra cooling area for the heatsink. Secure the heatsink to the amplifier PC board using the screws and nuts as shown in the amplifier mounting details in Fig.4. The insulating washers are made from TOP3 insulators which are cut to shape. Cut a notch in the side of the washers in the positions required for the securing screws. If you use a mica washer, use heatsink compound between the two mating surfaces of the heatsink and amplifier package. No compound is necessary for silicone washers. Place the shield into the base of the case and the PC board and heatsink into the case. Note which of the inner mounting bushes in the case foul any of the pigtails on the underside of the PC board and cut them off or grind them down. Place the front panel in position. and secure the PC board in place with the corner mounting screws. Wire up the amplifier PC board as shown. We used heatshrink tubing over the loudspeaker terminal wiring to prevent shorting to the case. Also don’t forget to connect the wire which connects to the DC socket, negative Here’s how the heatsink/rear panel looks when folded up and secured to the PC board. The screws which hold the power amps in place also hold the heatsink in place. Drill the holes for these and the input/output sockets before folding. terminal on the PC board, the three pots and the shield. Testing Full testing of the amplifier will require a 12V supply which can deliver This photo shows the scrap of thin aluminium we used to make the shield for the bottom of the plastic case – you could use a scrap of PC board if you wish. Insulate the alumininium with plastic sheet. The doodles are an optional extra. Resistor Colour Codes                             No. Value   4-Band Code (1%)  5-Band Code (1%) 4   100kΩ brown black yellow brown  brown black black orange brown 4   22kΩ red red orange brown  red red black red brown 2   10kΩ brown black orange brown  brown black black red brown 4   4.7kΩ yellow violet red brown  yellow violet black brown brown 4   1kΩ brown black red brown  brown black black brown brown 6   10Ω brown black black brown  brown black black gold up to 4A but a lower current supply can be used for initial testing. Most 12V SLA (sealed lead acid) batteries, even those rated lower than 4A, will deliver 4A for a short time. Also note that most “12V” car battery chargers deliver significantly more than 12V (they have to, to charge!) but more importantly do not include any filtering and so are unsuitable for use as a DC supply. Without a speaker connected at this stage, apply power and check that there is 12V between pins 2 and 7 of IC2 and IC3. This voltage should also be between pins 4 and 11 of IC1. Check for about 6V at pins 3 and 5 of IC1 and at pin 3 of IC2 and IC3. Further testing is done by listening: connect a speaker to the outputs and apply a signal to the input. Turn the volume pot to minimum and apply power. Check that the amplifier can be switched on and off at the power switch and that the amplifier does amplify – ie, the volume control works! Also check that the tone controls operate as expected. Note that if you are using a power supply to drive the amplifier, it may prevent the amplifier delivering full power during transients. If this hap- Capacitor Codes   Value    IEC code    EIA code       0.22uF 220n 224   0.1uF 100n 104   .01uF 10n 103   .0047uF 4n7 472   10pF 10p 10 MAY 2001  35 Figs.6 & 7 (right): Full-size artwork for the PC board and front panel. You can make your own PC board using this artwork (see how in March 2001 SILICON CHIP) or use it to check commercial boards. The front panel artwork can also be used as a drilling template. pens, the signal may go off as the muting voltage threshold is reached when the power supply level drops. This occurs at around 8.5V. Using a 12V battery should allow the amplifier to drive the loudspeakers to full power. The amplifier can be run from slightly higher voltage and will give even more power output if it is. Car electrical systems normally don’t run at 12V, at least healthy ones don’t – most run at 13.8V or even 14.4V when the motor is running. This amplifier is designed to handle that voltage. The absolute maximum voltage rating of the power amplifier ICs is 17.5V so make sure your supply cannot ever exceed this or you may do some permanent damage. Speakers You can use a huge variety of speakers with this little amplifier – in fact, just about anything you can lay your hands on! AUDIO PRECISION FREQRESP AMPL(dBr) vs FREQ(Hz) 20.000 26 APR 100 08:33:40 15.000 10.000 5.0000 0.0 -5.000 -10.00 -15.00 -20.00 20 100 1k 10k 20k This graph shows the tone control responses with full bass boost, full treble boost, full bass cut and no boost. Note the flat response when the controls are set flat. 36  Silicon Chip Even speakers rated at less than the 18W output power can be used, just as long as you don’t wind the wick up too far! The amplifier is designed to use 4Ω speakers and will deliver maximum power into 4Ω. Most car audio speakers are 4Ω for this reason. However, the amplifier will operate quite happily into 8Ω speakers but you will only get half the power output of 4Ω speakers. There is a common misconception that large speakers require more power to drive than small speakers. This is not usually the case – a larger speaker tends to be more efficient than a small one of similar ratings so all else being equal, will sound louder when driven by the same amplifier. 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All prices include GST McGraw Hill books are available from Dick Smith, Jaycar, Altronics, M 2001  37 Technical Books Melbourne and all good bookstores AY This article presents two simple, l     One will count up or down and user-defined ways from a preset the modules is the softw By Peter Crowcroft M odern electronics allows products – consumer, industrial and scientific – to be produced with more features in smaller packages at less cost than ever before. Not too long ago, the controller for an appliance such as a washing machine or microwave oven would have been a mechanical timer, or perhaps discrete components (switches, transistors and 4000 series logic, etc). However, all these things take precious space and are costly to produce. Often they’re difficult to update or reuse for different product models or revisions. Today, these problems are neatly and cheaply solved with microcon-trollers – single chip computers complete with IO pins, RAM, pProgram storage (ROM) and sometimes other useful features like ADCs, UARTS and PWM drivers. One simply arranges for relevant inputs (switches and sensors) and outputs (motor and solenoid drivers, LEDs and displays) to be connected to the microcontroller and then write some software to manage the lot. The space saving and cost effectiveness of these small wonders are reason enough to use them. But when you consider the flexibility they provide to adapt the control system to changes in the device or consumer demanded functionality they are indispensable. Changes are simple: you change the software (which can often be done in-circuit) and the same hardware will perform the new task. There are very few fields left in electronic engineering where microcontrollers have not made their mark. It is becoming more and more important to understand how micro-controllers work and how they are applied in designs – and how to develop and debug their software. Fortunately, there are many sources on the Internet open to the engineer and hobbyist alike that provide free tools, examples and designs. Microcontroller manufacturers have lots TECHNICAL SPECIFICATIONS – Up/Down Counter Supply voltage Operating modes Count range Count rate Inputs Output Display Physical size Connection 38  Silicon Chip 9-15V DC (<40mA <at> 12V) Count Up (default), Count Down, Count Disable, Overflow, Reset 0000 to 9999 or 0000 to 0001 (0000, 9999, 9998, ... 0001) Maximum count rate of 30 to 35 counts per second Reset, Count (negative edge triggered), Count down NPN Transistor,100mA <at> 30V 14mm red LED, 7-segment common anode 51mm x 63mm 10-pin SIL header pins, 0.1” of details in their datasheets and application notes, so that is a good place to start. The counter circuits The use of an ATMEL AVR microcontroller allows the circuit to be greatly simplified. A larger range of useful features can be provided than could be achieved with conventional logic circuits. If we wanted to make a simple counter with conventional logic, we would need some components to condition the input and output signals, a counter for each digit (say a 74LS192 BCD Decade Counter), and then we would need to drive a 7-segment LED display using a BCD to 7-segment driver (74LS47). Straight away we have eight ICs (two per digit). Then we’d need some “glue logic” to hang everything together. And we’d get a counter that can only count up. To fit this into a reasonable space we’d have to use a double-sided board with plated-through holes because of the large number of connections required between ICs. We might even need to go to surface mount components to reduce the size. It begins to get very expensive and complex, not to mention tedious (if not impossible) for the hobbyist to assemble. (Yes, some hobbyists work with surface mount components but they are very much the exception to the rule!) With the microcontroller solution low-cost, four-digit counter modules. d the other will count down in several  value. The main difference between ware in the microcontroller.     and Frank Crivelli. presented here, this complexity is reduced to one IC only and a handful of discrete components to condition the input and output signals, all on a small (cheap!) single-sided PC board. All the hardware complexity has van- ished into the software where finding and fixing errors is easy. As we shall see, we also get the ability to change and add more useful features and modes of operation easily. The Up/Down Counter has an overflow output, allowing multiple units to be “daisy-chained” together for greater counter range. The unit will count between 0000 and 9999, producing the overflow pulse when the count rolls over to 0000. MAY 2001  39   Table 1: Up/Down Counter Inputs and Outputs   Name Description  Reset Reset the current value of the counter to 0000.  Clock Increment (or decrement) the value of the counter. If the counter rolls over to 0000, an overflow pulse is generated. The clock input is debounced in software to prevent extraneous counts when mechanical switches are used. This is achieved by ensuring a high to low or low to high transition remains valid for more then 15ms. This means the maximum count rate is around 30 counts per second. The count is triggered on a high-to-low transition (falling edge)  Down Controls the direction of the counter. When unconnected, the counter will increment; when driven low (grounded) it will decrement.  Disable When grounded, the counter will not count even if the clock input is being pulsed.  Overflow This is an open collector output. When the count rolls over to 0000, it is pulled to ground by the circuit for approximately 25ms. This may be connected to the Clock input of the next module to create a counter with a larger range or used to drive a relay, indicator or other circuit. The Presettable Down Counter allows the user to program a starting count and select one of four different operating modes which determine what happens when the count reaches 0000. Circuit description The modules are almost identical; in fact the display driver, the power supply and the output are identical. The differences are confined to the inputs and their “meaning” to the microcontroller. Let’s start by looking at the identical parts of the modules. The counter modules are designed around an AT90S1200 AVR microcontroller from ATMEL (http://www. atmel.com). A detailed product data-sheet is available from this website. This particular device was chosen because it has an internal R/C oscillator, eliminating the need for an external crystal. This simplifies the circuit and further reduces component costs. The display unit is a 4-digit, common anode, multiplexed, 7-segment LED display. This means that the LEDs in a single digit share a common anode (positive) connection. The cathodes (negative) of the segments (a, b, … g & dp) are connected across the four digits, forming a matrix. Multiplexing results in fewer connections and less board space being devoted to the display and reduces the number of microcontroller outputs required to drive the display. One negative is that the drive signals become more complex but this is 40  Silicon Chip relatively simple to achieve in the microcontroller’s program. Bits 1 to 7 of the microcontroller’s Port B are connected via 270Ω current limiting resistors (R1-R7) to the shared segment pins. Four of the Port D bits are then connected to drive the four common anodes via Q1-Q4, the PNP transistors. Resistors R8-R11 (4.7kΩ) protect the transistors from excessive base current which otherwise could destroy them. To display the current count, the microcontroller cycles through each of the four digits one at a time, providing current to the anode of the digit by turning on the appropriate transistor (driving the base low). It then arranges for outputs connected to the segments it wishes to light to be driven low so that current can flow from the transistor, through the LEDs in the display and to ground via the microcontroller port. The segments it wishes to remain unlit are driven high. After approximately 1ms, the display is extinguished and another 1ms delay occurs, then the next digit is lit. This then continues for the remaining digits and the cycle starts again. Therefore it takes about 8ms to fully display the current count, which is much too fast for the human eye to discern, so to us it looks like a constant display. The software programmed into the microcontroller uses a timer that triggers an interrupt about every 1ms to achieve this. When the interrupt occurs the next display is set up or the current display is extinguished. This allows it to be monitoring the inputs without constantly worrying about handling the display, simplifying the design of the software. Transistor Q5, an NPN device, provides an active low open collector output for the overflow signal in the up/down counter version and the output signal in the presettable down counter version. The remaining bit (Bit 0) of Port B drives this transistor via R18, a 1kΩ resistor. Q5 is protected by Zener diode Z1 which will break down and conduct if the voltage across Q5 exceeds 33V, or it will conduct if a negative voltage is applied to the collector. This is need-   Table 2: Presettable Down Counter Inputs and Outputs   Name Description  Reset Reset the current value of the counter to the preset value.   Count Decrement the value of the counter. If the counter rolls over to 0000, the current operating mode determines the output pulse and new count value. For more information see “Using the Modules”. The count is triggered on the high to low transition. Software debouncing is optionally applied to the count signal using the Rate input. If it is enabled, it is identical to the Up/Down counter.  Rate Select if software debouncing is applied to the count input signal. If high (by default), debouncing is applied; if driven low (grounded), debouncing is not applied. This is useful if the count is derived from another logic circuit that doesn’t exhibit extraneous pulses like a switch can do. If debouncing is disabled, the count input can be clocked a lot faster. Note that this input is not debounced at all as it is meant to be set permanently.   Output This is an open collector output. When the count rolls over to 0000, the current operating mode determines what this output does. ed when driving inductive loads such as relays, as the back EMF generated by the collapsing magnetic field in the coil when the current is turned off can easily exceed the rating of the transistor and destroy it. Power for the circuit is provided by an external 9-15V DC power supply and is regulated by IC2, C4 and C5, resulting in a 5V supply. IC2 looks like another transistor but is a 78L05 low-current voltage regulator in a TO-92 case. This regulator needs about 2.2V of headroom (ie, voltage in minus voltage out) to ensure regulation. Diode D1 provides reverse bias protection in case the power supply is connected the wrong way around. As there is about 0.6V or so drop across this diode, you must ensure that the voltage supplied to the circuit doesn’t drop below about 8V (5V + 2.2V +0.6V ~ 8V) Now let’s look at the input circuits for the different modules. Up/Down counter The Up/Down counter has four inputs and one output. These are detailed in Table 1. The four inputs are all pulled high TECHNICAL SPECIFICATIONS – Presettable Down Counter Supply voltage 12VDC <at> 50mA Operating modes Count Stop, Output Hold Over-Count, Output Hold Auto-Reset, One-Shot Output Over-Count, One-Shot Output Count range 0000 to 9999 (10,000 max) Count speed Low (selectable) High 30 cps (15mS high, 15mS low) 30,000 cps (measured) Inputs Reset, Count, Rate Output NPN Transistor, 100mA <at> 30V Display 14mm red LED, 7-segment common anode Physical size 51mm x 63mm Connection 10 pin SIL header pins, 0.1” by the 1kΩ resistors and have a low pass filter formed by a 27kΩ resistor and .001µF capacitor to filter out high frequency noise from the line to reduce the chance of false triggers. This filter’s time constant is approximately 20µs and any pulses shorter then this won’t make it to the microcontroller. A 20µs time constant equates to a frequency of 50kHz. The inputs are also debounced in software with the level in the input needing to be constant for 15ms before it is recognised as a valid input. Presettable Down counter The Presettable Down counter is a little more complex. It has two push-button switches added to its inputs. These are used to program the preset value and operating mode. This module has three inputs and one output, as detailed in Table 2. Like the other module, the inputs are pulled high by 1KΩ resistors. The Count and Reset inputs have the same low pass filtering applied with the 27KΩ resistors and .001µF capacitors. The SET switch (SW2) is connected directly to Port D, Bit 4 with a 1kΩ pull-up resistor. There is no need for filtering on this input as the microcontroller will debounce it in software. The INC (SW1) switch is interesting as it is shared with the Count input. This is an example of making efficient use of the available inputs. This can be done because in set-up mode, no MAY 2001  41 4-Digit Up-Down Counter Parts List - Up-down 1  PC board, 51 x 63mm, code K129 1  20 pin IC socket 1  set male and female 10 pin right angled connectors 1  2-pin SIL header Semiconductors 1  AT90S1200-12PC preprogrammed microcontroller, (IC1) 1  78L05 5V regulator (IC2) 4  BC557 PNP transistors (Q1-4) 1  BC547 NPN transistor, (Q5) 1  1N4004 power diode (D1) 1  33V 1W zener diode (Z1) 1  LN5644R 4 digit, common anode LED display (DISP1-4) Capacitors 1 .001µF ceramic  (C1,2,3,6) 1 0.1µF monobloc  (C4) 1 10µF 25V electrolytic  (C5) Resistors (0.25W, 5%) 4 27kΩ (R13,15,17,20) 4 4.7kΩ (R8-11) 5 1kΩ (R12,14,16,18,19) 7 270Ω (R1-7) Parts List – Presettable 1  PC board, 51 x 63mm, code K54 1  20 pin IC socket 1  set male and female 10 pin right angled connectors 2  PC mount pushbutton switches (SW1, SW2) Here is the component overlay and and matching photograph of the 4-digit Up-Down Counter, reproduced same size so you can see exactly where all of the components go. Note the 270Ω resistor is mounted under the IC socket. counting in done. This also means that the INC button can be used to decrement the counter when it is running. Software The software listing for the microcontroller is not supplied, however this description is provided for those who are curious or want to have a go at creating their own. The first thing the code does is set up all the inputs and outputs and initialises all the internal states. It then sets the count to the default value (0000 or the preset depending on the module) and starts the internal timer. The timer is set to trigger an interrupt every 200µs (observant readers may notice I said 1ms earlier – I lied for simplicity). When the interrupt occurs, the handler routine updates various internal counters used for debouncing inputs, 4-Digit Presettable Down Counter Semiconductors 1  AT90S1200-12PC preprogrammed microcontroller (IC1) 1  78L05 5V regulator (IC2) 4  BC557 PNP transistors (Q1-4) 1  BC547 NPN transistor, (Q5) 1  1N4004 power diode (D1) 1  33V 1W zener diode (Z1) 1  LN5644R 4-digit, common anode LED display (DISP1-4) Capacitors 2 .001µF ceramic  (C1,2) 1 0.1µF monobloc  (C4) 1 10µF 25V electrolytic  (C3) Resistors (0.25W, 5%) 3 27kΩ (R13,15,18) 4 4.7kΩ (R8-11) 4 1kΩ (R12,14,16,17) 7 270Ω (R1-7) 42  Silicon Chip There’s not a lot of difference between the Presettable Down Counter and the Up/Down Counter above . . . but there are differences! Follow this component overlay and photo and you shouldn’t have any problems. Table 3: Presettable Down Counter Modes  Name Description   Mode A (Default) Count Stop, Output Hold. When the count reaches 0000, the output goes low and stays low. The counter stops counting. The counter must be reset to continue counting again and to reset the output. When reset the count is set to the preset value.   Mode B Over-Count, Output Hold. When the count reaches 0000, the output goes low and stays low. The count will wrap around to 9999 on the next count input and continue counting from there. The output will remain low until the module is reset.   Mode C Auto-Reset, One-Shot Output. When the count reaches 0000, the counter automatically resets itself to the preset value and the output pulses goes low until the next count pulse occurs.   Mode D Over-Count, One Shot Output.   When the count reaches 0000, the output goes low until the next count pulse occurs. The count will wrap around to 9999 and continue output pulse timing and the display timer routines. If any of these counters reach zero they need attention and are processed. For example, every 1ms the display routine is called to update the display. The main loop constantly monitors the inputs and sets up the debounce counters when they change. If a valid clock pulse is detected and the count isn’t disabled, a routine to either count up or down is called. The count is stored as four binary coded decimal (BCD) values, so constant conversion is not required in the display driver routine. This is updated by the count up or down routines and if the value changes to 0000, the overflow output of the counter is activated and a counter set up to turn it off in about 25ms. In the Presettable Down Counter, the output is determined by the current operating mode. The display update interrupt routine uses a BCD-to-7-segment conversion routine to map the 0-9 value of the digit being displayed to the correct output for driving the segments in the display. The Presettable Down Counter also has a set-up mode that is entered when a high-to-low transition is detected on the Set input. This allows the preset count value to be set one digit at a time and the mode to be selected. Construction Both kits include all components, a high quality PC board and a preprogram-med microcontroller. All you will need is a power supply and a clock source. Start construction by separating out all the components into values, using the parts list as a guide. I’d suggest a fine conical tip on your soldering iron, as there are some small, closely spaced pads especially for the transistors. The PC board is very good quality and has a solder mask so it isn’t too difficult to avoid solder bridges. Start by installing the resistors. Pay particular attention to R4 as it is situated under the socket for the microcontroller. You may want to leave it until last and ensure the socket fits over it before soldering it and the IC socket in. Next put in the capacitors, paying attention to C5 as it is polarised and laid over on its side. I’d suggest that you bend the leads at a right angle first and then insert it into the board and solder it, to avoid having the legs too short to bend over later. Install the two diodes next, ensuring that the cathode (striped) end matches the stripe on the PC board overlay. Now install the transistors and IC2. Don’t get these confused, there are four BC557s (Q1-Q4), one BC547 (Q5) and the 78L05 (IC2). Use the outline on the PC board as a guide for orientation. Q1-Q4 and IC2 are close together and close to the edge of the LED display so get them as low as possible and as straight as you can so they wont get in the way. Double check that you don’t have any solder bridges across the transistor pins as they are close together. If you’re building the Presettable Down Counter, install the two switch-es. They will fit with the pins coming out towards the display and the connector. Install the LED display; the decimal points go towards the microcontroller. Then install the 2-pin header for power (Up/Down Counter only) and the 10-pin 90° header for the inputs and outputs. The kit also includes a socket for this header; this doesn’t mount on the PC board but can be used to make connections to the completed module. Carefully install the microcontroller into its socket (noting its polarity) and assembly is finished. After checking your board, apply power and you should see 0000 displayed (this is the power-on default for both modules. If you short the two count pins (or press the Inc button on the Presettable Down Counter) the display should increment (or decrement). If it doesn’t work Poor soldering (dry joints) is the most common cause of problems. Check all your joints under a good light; they should all be smooth and shiny. Resolder any suspicious ones. Keep an eye out for solder bridges and for any pads that you may have forgotten to solder as well. Make sure that you inserted the diodes the correct way and that the microcontroller is also the correct way around and securely sitting in the socket. Also check the orientation of electrolytic capacitor C5. Make sure that you didn’t mix any of the transistors up and that they are in their correct places and the right way around – including the voltage regulator. Use a multimeter to check the supply voltage. Measure it from the cathode (stripe end) of D1 and 0V. It should be at least 8V or the 5V regulator will have difficulties and not operate correctly. The voltage from the output of the regulator should be MAY 2001  43 Table 4: Resistor Colour Codes   No. Value     3  27kΩ     4  4.7kΩ     4  1kΩ     7  270Ω 4-Band Code (5%) red violet orange gold yellow violet red gold brown black red gold red violet brown gold within a few tens of millivolts of 5V. If it’s much lower, then you probably have the regulator in back-to-front or something (such as a solder bridge or misplaced component) is causing too much current to be drawn from the regulator, shutting it down. If it’s much higher, check for a solder bridge across the regulator pads (or the regulator itself might be shot). Using the modules The counter module has three or four inputs and one output that are accessed via a 10-way header. The input lines are all active low, which means that grounding them performs their function. More correctly, each of the inputs is normally pulled high by the module circuitry and must be pulled low to become active. Each of the lines has a corresponding ground pin beside it, simplifying the connection to a switch. The input lines may be connected to simple ‘make’ contacts, switches, relays or even open collector outputs from other circuits. The module requires a 9 to 15V DC power supply and consumes between 20mA and 40mA, depending on the number being displayed. A small plugpack will easily supply enough power for several modules. Alternatively, the module could be battery powered. The Up/Down Counter is fairly straightforward. Just connect a switch to the count input and set the direction on the Down input and you’re ready to go. However, the Presettable Down Counter, is a little more complex. Connect the count input and output as needed, and then apply power to the unit. By default, it will display 0000. It will overflow to 9999 and continue counting down with clock inputs until it reaches 0000 again. This is Mode A and it is the default mode. A description of each of the modes is given in Table 3. The two pushbuttons marked, SET and INC are used to configure both the 44  Silicon Chip preset value and the operating mode. The preset value is entered one digit at a time starting at the thousands and then the Mode is selected. To enter the programming mode, press the SET button. The display will show the preset value for the thousands digit and the rest of the display shows a minus (-) sign. Use the INC button to select the required value then press the SET button to advance to the next digit. Continue setting each of the preset digit values unit the last one is set. The display will now show the current operating mode with the letters A, b, C or d. Use the INC button to select the desired mode and press the SET button to accept it. This will also exit programming mode and the counter is ready for use. Software flexibility To illustrate the power of using a microcontroller versus discrete logic circuit the following “user requested” modifications have been made to the Up/Down counter at no cost to the user since the change was very easy to do in software (note these changes are not included in the kit software – they are mentioned only to illustrate the ease of change). 1.  Count by five instead of by one. 2.  Show digits “upside down” so the PC board could be placed in a pre-designed box upside down. 3.  Only display digits on a “keypress” so that the kit could be more efficiently battery powered. These were done by simply changing the software. Try doing that with discrete logic circuits!!! Further information The following may be good starting points to find more information: • ATMEL (makers of the microcontroller used in this project) have a website at www.atmel.com There you will find data-sheets for all their micro-controllers with detailed information about using and programming them. •  DIY Electronics (the kit manufacturer for this project) have a website at http://kitsrus.com They also have an AVR Programmer kit (Kit 122) and BASCOM Basic Compiler which are useful for people wishing to experiment with AVR micro-controllers. Questions or comment about the PROGRAMMING THE DOWN COUNTER Two pushbutton switches, marked “SET” and “INC”, are used to preset the starting count and select the operating mode. Presetting the count value is done one digit at a time, starting with the thousands digit. Press the SET button to enter programming mode. The display shows the current preset value of the thousands digit and the rest of the display shows minus (–) signs. Use the INC button to set the value required. Press the SET button when done. The current preset hundreds digit is shown. Use the INC button to set the value required. Press the SET button when done. Repeat the above steps for the tens and units digits. After setting the units digit the display shows the current operating mode. The mode is indicated by the letters “A, b, C or d”. Use the INC button to set the operating mode then press SET to exit programming mode. The display will blank momentarily to indicate that programming mode has ended. The counter is now ready for use. As mentioned before the RESET input resets the counter to its preset value. It does not change the operating mode. If the counter loses power it will restart in Mode A with a preset value of “0000” (count = 10,000). Kit can be directed to Peter Crowcroft, peter<at>kitsrus.com, while technical questions may be directed to the kit’s designer, Frank Crivelli, frank<at> ozi-tronics.com Kit availability Copyright of the kit designs, the PC board patterns and the software (residing in the microcontroller) is retained by DIY Electronics (HK) Ltd. A kit of parts for either of these kits may be obtained from Jaycar Electronics stores, Jaycar mail order or via their online store at www.jaycar.com.au Both kits sell for $39.95. The 4-Digit Up/Down Counter is Cat No KD-6084, while the 4-Digit Presettable Down Counter is Cat No SC KD-6058. SERVICEMAN'S LOG To fix or scrap – that is the question Equipment suffering catastrophic damage is an unknown quantity. It can have umtpeen damaged components, some expensive or unavailable. The cost is unknown until the last one is found and by then, it’s often too late to go back on the job. Storm damaged TV receivers are a classic example of this problem. They are invariably dodgy; the extent and path of the damage is entirely random, is impossible to follow logically and it’s difficult to assess the best approach. So it was with dread that I responded to a call from Mr Philips about his 6-year old 68cm Sanyo stereo TV set, a C29PK81B-00 employing an AA1-A29 chassis, which was dead. There had been a severe storm the previous evening, with a lot of lightning but Mr Philips had been out during that time. When he returned and tried the set, it wasn’t working. I removed the back and found that the 4A fuse, F501, had blown. Though I knew it was futile, I replaced it and switched on. There were no signs of life. I them measured R508A, 3.9Ω 5W, and from there traced the circuit to the culprit, the chopper transistor, Q313 (2SC4429), which was short circuit. At this stage, it was time to take the set to the workshop and so I loaded the wagon and set off. I had to order a replacement transistor but, in the mean­time, I did a few checks with the ohmmeter in the primary part of the circuit, checking Q311, Q312, R320 and R321. All were OK. I felt fairly safe in replacing the chopper, Q313, when it arrived. I switched the set on and monitored the main B1 rail but was horrified to find it was at nearly 180V instead of 140V. I checked the optocoupler which was OK but Q353 wasn’t. Replac­ing it brought all six rails up to scratch. But the set was still dead, and even the standby LED wasn’t on. This was no great mystery as there was no 5V and, in turn, Q521 was open circuit and there was a dead short on the 5V rail. Replacing microprocessor IC701 and memory EPROM IC790 fixed that and at last I had a raster on the screen. But there was still no sound and no remote control. A new RC preamp module fixed the latter but a bizarre thing was now happening. On standby, I had 5V but with the set switched on this rose to nearly 10V. From where was it getting the extra 5V? To begin with, I felt sure there was something wrong with the supply via Q521, which is on the front control board, because there was 16V on the emitter of the 2SC2568. This was further complicated because, when I unplugged the board, the set wouldn’t start and the 5V was rock solid. Perhaps it was breaking down under load? This was possible but unlikely, especially with a new transistor fitted. Gut feeling So I put that on the back burner. My gut feeling was there was another power source that was breaking through onto the 5V rail via a faulty component – but only when the set was on. The problem was where; the MAY 2001  45 31 is less that 2V for a few seconds, the set should switch to standby. This is a fault I had with another similar model (CP29ST2T-00 using an AC2-A chassis), where R485 180Ω went high. This held the cathode of D486 high in the video output 210V supply, causing the set to shut down. That wasn’t the end 5V goes everywhere to all sorts of devic­es. Rather than trace and disconnect the 5V circuit everywhere it went – with the high probability of switching the set off in the process – I decided to disconnect each power rail until the 10V on the 5V rail changed. I started with the horizontal output stage, by shorting base to emitter of the line output transistor (Q432). This switches off all the horizontal transformer derived power rails, including a highly suspicious 5V rail from pin 8 of the horizontal output transformer (T471). However, in the event, this turned out to be a furphy; it made no difference and subsequently, it became clear that this circuit was not fitted to this model. (It is really only for Teletext sets). So back to the drawing board and the six rails off the chopper transformer, T311. Disconnecting one at a time, I found no less than three rails were able to affect this wretched 10V, which, I might add, was probably causing oodles of problems to the devices attached to it. After all, if a device is supposed to work at 5V, it is probably very unhappy at double that voltage. My only hope was that they could all just hang in until I solved the source of this higher voltage. I was as brief as I could be on each measurement with the set on and mentally 46  Silicon Chip apolo­gised to each component for the stress it was enduring. In the end, it was rails B2, 24V; B5, 15V; and B6, 12V; which caused the 5V to rise. The common denominator between these and the 5V rail seemed to be the protect rail – but this didn’t seem to be very logical; surely this circuit would at least have turned the set off. Another furphy; that wasn’t the answer. To cut down this somewhat elaborate tale, I found diodes D393, D362 and D363 to be in various stages of breakdown. Q792 and Q793 seemed to be OK but I replaced them anyway. That fixed this problem and the 5V was now steady in the STANDBY and ON modes. I must admit I really can’t quite see why this would raise the 5V rail so high, especially as there is never less than 33kΩ between them. I can only surmise that if the voltage is high on pin 31 (protect) of the microprocessor IC701, it will feed back out on the Vcc rail (pin 27). There is not much information about the protect rail cir­cuit. If pin Items Covered This Month •  Sanyo C29PK81B-00 68cm TV set (AA1-A29 chassis). •  JVC C-21T1AU 55cm TV set (KY chassis). •  Philips Matchline TV set (FL 1.2 AA chassis) Unfortunately and predictably, that wasn’t the end of my troubles with this set. And that brings me to the conflict that faces all technicians in deciding where to draw the line between a write-off and a viable business proposition. It is very hard to be a good technician and a good businessman at the same time. With so much effort having been poured into fixing this set this far, all I had was a raster. Would I be only one cheap component away from finally cracking the problem or would there be umpteen other components that would need replacement? I was already down the mine for a couple of hundred dollars for parts, not to mention labour – was I going to write this off? Who was going to pay for the work done so far? In practice, I often tend to muddle along on a wing and a prayer – the job is put on the back-burner and only brought out during quiet times. It is either eventually repaired and returned to the customer or cannibalised for parts (for more profit­able repairs) – or even fixed and sold. In this case, I decided to quit before things got complete­ly out of hand. Mr Philips and his insurance company were advised that his set was uneconomical to repair and he received a new one. I scored the wreck with a little cash to sweeten the deal. All things considered, it was the right decision and would seem to be the logical approach in all such cases where insurance is available. Much later I went back into it and checked transistors Q700 (Tuning), Q708 (Reset), Q182 (Sound IF), Q1709, D1705 and C1705 (a kind of spot wobble circuit?), all of which turned out to be faulty. When these were replaced, the set produced a good picture in the A/V mode with a VCR connected and a poor picture off air. The sound output ICs were both faulty (and hideously expensive!). The final hurdle to restoring full sound and a good picture off-air was the jungle IC (IC101). The circuit is extremely confusing as it is tied up with the multisystem switching and A2 stereo decoder. The main sound IF goes through IC181 (pin 14), Q182 (SIF multisystem filtering circuit), the jungle IC (IC101, pins 5 & 1) and then to the multiple sound processor IC1103 (pin 3). It then goes via Q857/858, with a sub-sound going from IC181 pin 6 to IC1103 pin 2 via Q183/184. The audio management control separates mono, stereo, A/V inputs and outputs, sound carrier and different decoder circuits – all controlled by the Philips I2C bus data lines from the CPU. With this set you can – if one really wants to – record a TV broadcast while playing back a tape from another VCR, with all the connections going through the set! There were a number of other confusing situations that occurred during the course of the repair but they were eventually all sorted out with the aid of the expensive service manual and instruction book. These included the child lock and censored program sites (private position) and the stereo separation settings which have to be done after the EPROM is replaced. All in all, an interesting but unprofitable venture into the Sanyo way of thinking. But at least I eventually scored a working set. A miserly customer Mrs Parker wanted to know how much it would cost to fine tune her TV receiver. I reasoned that if she had to ask, then she couldn’t afford it and so I was ready for the inevitable “that much!” I pointed out that it was the same charge as 10 years ago except for the GST. But, I suggested, if she felt that was too much, why not go back to the instruction book and do it herself? Somewhat taken aback, she hung up and I thought that was that. But it wasn’t. Three weeks later, she phoned again and wanted me to call. I asked her if she had been able to fine-tune the set herself? Well, she said, her friend is an electrical engineer and he managed to tune all the stations except channel 7, where there was no sound. “Well”, I said, “surely he could have tuned channel 7 as well”. “No”, she said and she wanted me to come around that afternoon and though she thought it was daylight robbery, she was prepared to pay my fee. Mrs Parker’s set was a 1991 55cm JVC C-21T1AU which employs a KY chassis and is a multisystem receiver. I connected the aerial directly to the TV set in case the VCR was affecting it and checked each channel. All were perfect except channel 7 VHF. I negotiated the on-screen menu system and adjusted the fine tuning which was able to improve the sound at the cost of the quality of the picture. I then tried auto-tuning the sta­tions. The set searched and found every station with perfect sound and picture – except channel 7. Next, I tried the colour system which was the same in Auto as in PAL. What I was really looking for was a switch to change the CCIR system, because the symptoms were very similar to some which can occur in the CCIR system, using 6.0MHz intercarri­er sound. I could see from the specification in the instruction booklet that this set could automatically detect 5.5MHz, 6.5MHz and 6.0MHz sound IF but couldn’t be overridden manually. The suggestion, therefore, was that interference was acting in such a way as to make the receiver believe that it was handling a 6MHz inter­carrier sound signal, rather than 5.5MHz. And why channel 7? Presumably because it was receiving the stron­gest interfering signal. It was just a theory, of course, but it was the best one I had. I told Mrs Parker I would have to do some research on this but she was totally unimpressed with the idea and started bleating about money costs. I was past caring by now. “Look”, I said, “do you want this fixed properly or not?” She admitted that it was important to her. I then asked her when the problem first started. She didn’t know this exactly but guessed that it was several months ago. I also confirmed that the aerial hadn’t been altered and neither had any new build­ings been constructed nearby. Everything was now pointing to one major suspect; interfer­ence from digital TV transmissions. Australia is the only country using digital transmissions on VHF as well as UHF and there are many sets which were never designed to work alongside broadband, high-level, digital chan­nels in the VHF band. A common symptom of digital co-channel interference is a white dot pattern on channel 9. I told Mrs Parker that I would be back and, as good as my word, I returned two days later armed with a few gizmos. Number one in my arMAY 2001  47 moury was a very expensive Polytron adjustable filter, model TFV-3K. Connecting this in the antenna system and adjusting the two trimmers restored the sound completely. The only trouble was that it was well out of Mrs Parker’s budget. Next, I tried some attenuators but they just added snow. Finally, I reconnected the VCR into the set, via RF and A/V leads, and made sure that it was able to receive all channels satisfactorily. The point here was that the VCR tuner is not bogged down with an AUTO function to select the sound IF; it is fixed permanently on 5.5MHz. I then explained and demonstrated the options available and suggested that using the VCR tuner was the cheapest and most convenient solution. Had I not demonstrated the filter to her, she would never have believed me. As it was, she begrudged paying me for my time and advice. Subsequently, I was talking over this problem with a col­league and he solved it in a different way altogether. He had a similar model JVC, which was also multisystem. He very cleverly modified the automatic system circuit so that when the set switched to system I (6.0MHz sound), the 5.5MHz ceramic filters were switched in instead of the 6.0MHz filters. This meant that the set was now permanently aligned for CCIR system B/G Australia (5.5MHz) and the sound was perfect. A crook Philips Mr Stephens wanted a service call on his Philips TV which had just gone “crack” and then the picture disappeared. However, he still had a picture and sound from his video, which was connected via the AV sockets. I enquired whether this had happened during a storm but apparently it hadn’t. He told me that it was a 1991 Philips Matchline Collection (36ML8906/00B), employing an FL 1.2 AA chassis, and cost about $8000 new 10 years ago! This set is very large, employing an 86cm screen tube and is extremely heavy and difficult to move. Despite this, I informed him that the difference between the cost of my taking the workshop to his set, which I had never seen before, or of him bringing it to me could be somewhat significant. That clinched 48  Silicon Chip it – his set was on my bench the very next morning. This digital set has all the bells and whistles and surprised me how technically advanced it was for 10 years old. I soon found that the second tuner in the set gave a good picture and stereo sound in the PIP mode (Picture in Picture) and could be swapped around so that the main screen gave the off air/ terrestrial broadcast picture. But the main tuner was not working properly. Intermittently, it would flash, drift off and give a snowy picture. Occasionally it even came good. The tuner IF module (1160) is a long metal can and cannot be removed without first using a very hot soldering iron to remove the earth lugs. Once out, I took the covers off and examined it. I was about to replace all the electros inside it and touch up a few dry joints when I noticed black soot markings around IC7507 (TDA3856). It was fairly clear that something drastic had happened to this IC. In fact, considering the black markings adjacent to its legs, it looked as though this IC had exploded – and yet it was still almost working. This IC is not available as a spare part and neither is the tuner. It is only available as an exchange repair. So it was duly packed up and sent off to Philips. My big mistake was not to have carefully written down all the details that were marked on the tuner (I think it was an FQ816MS KR11 21122). When the replacement tuner arrived (it looked like new), I again didn’t pay any attention to the part numbers, but was somewhat aggrieved that it was more than the quoted price. I soldered it in and switched the set on. Well, the new tuner didn’t seem to be any better than the old one so I tried to tune the stations in. Although I could do this, there was absolutely no sound at all! I read the manual and found that there is an Option Code procedure for tuners and perhaps this needed setting up. To do this, the service mode is engaged by shorting pins S23 and S24 together and selecting the Option Code 1 and 2 menus and assigning a number from the list according to the hardware options fitted in the set. You then add up all these options and punch in the numbers with the remote control and store it with the “pp” button on the remote control The original option code 1 was 154 for this set but I couldn’t deduce how to get this number. I tried a variety of numbers consistent with what I thought we had. Finally, I got extremely technical and worked out why no sound was coming out of the tuner – it was because there were three missing pins on the replacement tuner (pins 16, 17 & 25), pin 25 being the L + R/A signal to the stereo decoder (IC7200, TDA­8417). I sent the tuner back and received an FQ816ME/1 which had the right number of pins and the correct quoted price. This time, when fitted, the stations tuned in correctly and the sound was terrific. Option Code 1 was indeed 154, being the sum of 2 + 8 + 16 + 128: 2 = Front End FE816/ME 8 = PIP module fitted 16 = NTSC-M reception possible with FE816/ME 128 = Second front end for PIP fitted I assume FE means Front End but I have no idea what FQ means. Option code 2 remained at 4 for 100Hz highend box fitted (modules L and M). There are no less than six variations of tuner for this set. The correct part number for this particular model is 4822 210 10507 (Repair). Mr Stephens was happy to get his set back, but we are still puzzled as to what caused the problem in the SC first instance. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au Order Form/Tax Invoice Silicon Chip Publications Pty Ltd ABN 49 003 205 490 PRICE GUIDE- Subscriptions YOUR DETAILS (all subscription prices INCLUDE P&P and GST) Your Name________________________________________________________ (PLEASE PRINT) Organisation (if applicable)___________________________________________ Please state month to start. 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Folded: $A5.95 inc p&p within Australia; elsewhere $A10 inc p&p. *BOOKSHOP TITLES: Please refer to current issue of SILICON CHIP for currently available titles and prices as these may vary from month to month. SUBSCRIBERS QUALIFY FOR 10% DISCOUNT ON ALL SILICON CHIP PRODUCTS AND SERVICES* *except subscriptions/renewals and Internet access Item Price Qty Item Description P&P if extra Total Price Spec i SUB al Offer SCR IBE & COM PUTE GET R OM FO N Aust R FREE! IBUS ralia Only* Total $A TO PLACE YOUR ORDER Phone (02) 9979 5644 9am-5pm Mon-Fri Please have your credit card details ready OR Fax this form to (02) 9979 6503 with your credit card details 24 hours 7 days a week OR Mail this form, with your cheque/money order, to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy, NSW, Australia 2097 * Special offer applies while stocks last. 05-01 NOT 1 WHITE LED TORC TOR Both of these LED torches have considerably more light output than our original design in the December 2000 issue. They use more LEDs and they run from a single AA or D cell which will have a long life. They make very good torches for camping, walking at night or for emergency work on your car. Design by JOHN CLARKE T hese LED torches produce a beautiful even spread of white light which is quite different from that of conventional torches using Krypton bulbs. Conventional torches tend to produce a “hot spot” that can penetrate the darkness for some distance and they have a larger cone of much less intense illumination. Overall, they tend to have quite a narrow beam and you have to move the torch around a lot to adequately light up the area in front of you. By contrast, these LED torches have a much wider diffuse beam, giving a very even spread of light without a central hot spot. For most of the time, this more diffuse beam is much easier on the eyes and the colour of objects is much more natural. In fact, it is like carrying a source of daylight around. So these LED torches are ideal for bushwalking (at night!), even in very 58  Silicon Chip rough terrain, for illumination inside a tent or over a picnic table and as noted above, for emergency work on your car if, perish the thought, you break down at night. Constant brightness Another big advantage of these LED torches is their constant brightness, regardless of battery voltage. Conventional torches start out with high brightness when the batteries are fresh but they soon dull down as the cells discharge. By the time the cells are down to 1V, the light output is woeful. These LED torches have the same light output even if the cell voltage goes below 1V. And they can also run with Nicad and NiMH cells which give a nominal 1.2V. Conventional torches are hopeless with 1.2V cells, unless they have been specifically designed to run from rechargeables. Not only that, torch bulbs have a notoriously short life and they can fail at the most inopportune moments. In fact, any time a torch bulb fails is inconvenient, by definition. After all, if a torch bulb failed when it was convenient, you probably don’t need it. Once you change over to a LED torch, you will never need to change a LED – they last a life-time (well, practically). Two versions We are describing two versions of this LED torch, both of which use the same basic circuit. One version uses three white LEDs and runs from a single AA cell in a 2-cell torch. The second version uses six white LEDs and runs from one or two D cells and can fit in a 2-cell or 3-cell torch. These torches use far less current than a conventional Krypton bulb torch. A twin D-cell torch bulb nor- BUT 2 CHES TO BUILD! RCHES Features       mally pulls about 0.8A at 3V, dropping to around 0.7A at 2.4V. In power terms, this is 2.4W at 3V, dropping to 1.68W at 2.4V – this is why conventional torches are so dull when the cells aren’t fresh. By comparison, our D cell 6-LED version of the torch pulls only 480mA at 1.5V, rising to 650mA at 1V. This is less than one third of the power drain of the conventional torch. Again, in a conventional twin AA cell torch, the Krypton bulb pulls about 0.47A at 2.2V or just over 1W. Super soft white light Constant brightness over cell life Indefinite lamp life Extended cell life Ideal for use with Nicad & NiMH cells D cell version has brightness control Our single AA cell 3-LED torch pulls 210mA at 1.5V, rising to about 360mA at 1V. Again this is one third of the power drain of the equivalent conventional torch. Circuit details As with our original white LED torch described in the December 2000 issue, both these torches are based on a DC-DC converter. The DC-DC converter for the AA-cell torch is about the same size as an AA cell, while the converter for the D-cell torch is about the same size as a D cell. The larger D-cell converter includes a brightness control and can drive six white LEDs instead of three. Fig.1 shows the D-cell torch while Fig.2 shows the AA-cell version. Both use a Maxim MAX1676 high efficiency step-up DC-DC converter and an inductor to provide the power conversion. The Maxim MAX1676 was originally intended for use in mobile phones, as a single cell voltage booster, so it is ideal for this torch application. An “exploded” view of the “D” torch which has a DC-DC converter capable of driving six ultrabright white LEDs from a single C or D cell. The white cylinder insulates the PC board assembly from any metal fittings in the torch. MAY 2001  59 Top trace is the inductor waveform at pin 9 of IC1 for the A-cell version. Its frequency is 176kHz. The period when the voltage is low charges the inductor and the high level is when the charge is transferred to the output. The lower trace is the output voltage. It is 3.96V and has a 160mV of ripple. The block diagram of Fig.3 shows the internal schematic of the MAX1676 and the external components needed, including the key component – L1, a 22µH inductor. The internal Mosfets, Q1 & Q2, do all the high speed switching work. Circuit operation is as follows: current flows through inductor L1 and Mosfet Q1. When the current builds up to 1A, Q1 turns off and Q2 turns on. The charge in inductor L1 is then transferred via Q2 to capacitor C1 and the load. The voltage at Vout is fed back to the MAX1676 via a resistive divider comprising R5 & R6. The internal control circuit derives its power from the Vout terminal and so when power is first applied to the circuit, current flows through L1 and Q2 to power the control circuit. Q2 is a P-channel Mosfet which requires at least 1V at the power source in order to be closed and pass the voltage back to the control circuit. For lower voltages it is necessary to include an external Schottky diode in parallel with Q2 to allow current to flow to the control circuit. Once the circuit starts up, it is powered from the Vout supply and Q2 then performs its task of switching the charge from L1 to the load with minimal voltage loss and the diode is effectively out of circuit. 60  Silicon Chip As shown in Fig.1 & Fig.2, the two circuits are very similar. Let’s have a look at Fig.2, the AA cell version. It has a fixed resistive divider for the voltage feedback at pin 1. Inductor L1 must have very low DC resistance to ensure high efficiency of the circuit. As mentioned above, the inductor is charged until the current through it reaches 1A. The inductor must not saturate at 1A and also it must have a low enough resistance to ensure that the current actually rises to 1A. The step-up circuit will not operate if the 1A limit is not reached. Thus we have used an inductor which has a DC resistance of 0.2Ω. Standard commercially wound inductors with wire resistances of more than 0.5Ω will not let the circuit operate. The output supply rail is close to 4V, as set by the 100kΩ and 47kΩ divider resistors and it is bypassed with a 47µF tantalum capacitor. Each LED is powered separately using a 27Ω current limiting resistor to ensure equal current sharing. The nominal LED forward voltage is about 3.5V and so the calculated current through each LED is (4V 3.5V)/27Ω = 18.5mA. In practice, the LED current is slightly higher than this. By the way, the AA-cell version could be powered with a C cell, if built into a C-cell torch. D-cell version The D-cell version uses an inductor which has a lower resistance again than in the AA-cell version and it uses a larger core. The value of inductance is the same at 22µH but the lower resistance ensures higher efficiency for step-up conversion. This circuit can Top trace is the inductor waveform at pin 9 of IC1 for the D-cell version. The glitches are a reset that automatically occurs within the IC to ensure operation at low loads. Frequency of operation is 133kHz and the low output is when the inductor is charging. The energy is transferred to the load when the waveform is high. Lower trace is the output voltage at 4.07V with a 350mV ripple. Fig.1 (above left) and Fig.2 (above right) show the “D” cell and “AA” cell variants respectively. Both are based on the MAX1676 IC high-efficiency DC-DC converter, a chip originally designed for use in mobile phones. MAY 2001  61 Fig.3: inside the MAX1676 DC-DC converter. Its operation is fully described in the text. drive up to six white LEDs. There is also a trimpot, VR1, to adjust the output voltage so that the LED brightness can be varied from almost zero to maximum brilliance. A 200Ω resistor at pin 7, in conjunction with internal Mosfet Q3, provides damping for the inductor when it is released from charging. This damps oscillations and ringing which can otherwise cause electromagnetic interference (EMI). The Schottky diode D1 is not required if the circuit is powered with two D cells. Both circuits include reverse polarity protection, by virtue of diode D2, which conducts if the battery is inserted incorrectly. Diode D2 provides only short-term protection since the current flow will be high. You should check the battery polar- ity immediately if the torch is found not to work. Construction Construction of these LED torches will require patience, good eyesight, a magnifying glass and some experience with soldering. Why? Because we are using a surface-mount IC for IC1. The IC is soldered onto a u10MAX carrier PC board for the D-cell version (Fig.4). but solders directly to the PC board of the AA-cell version (Fig.5). Regardless of which version you build, soldering this IC in place will require a modified soldering bit which has been filed to a narrow screwdriver shape. The idea is to solder all five pins on each side of the IC at the one time. Before soldering in the IC, check the PC boards for any shorts or breaks in the tracks. Any problems in the surface mount area probably cannot be fixed unless there is only a small short between tracks which can be cleared with a sharp knife. The PC boards must be tinned (solder-plated) before use so that the IC can be soldered in without damaging the fine tracks. This should have already been done by the PC board manufacturer. One method of soldering in the IC by hand is to initially cover the underside of the IC pins with solder by wiping over them with a standard chisel-shaped soldering bit which is lightly coated with solder. Make sure that the solder does not bridge between the IC pins. If it does, clean the soldering tip and wipe the excess solder off the IC pins with the now cleaned tip. Check the IC with a magnifying Fig.4: the component overlay of the “D” cell version. Note the position of the “daughter board” containing the MAX1676 SMD (surface mount device) IC. These devices can be a little tricky to solder – the text of this article should help! The photo at right shows the complete board but it is rotated through 180° compared to the component overlay. 62  Silicon Chip glass to be sure the IC pins are all tinned, without any shorts between the pins. Then place the IC onto the PC board and align the pin 1 indicator on the IC (a small dot on the body) with the pin 1 pad on the PC board. Straighten up the IC so it sits correctly on the IC pads. Now heat up the modified soldering iron tip (sharp screwdriver shape) which is untinned or cleaned of solder with a wet sponge. Apply the tip to the leads on one side of the IC to solder it in place. Check that it is still aligned onto the IC pads correctly. If not reheat the pins and align correctly. When one side has been soldered in place heat the remaining pins on the other side of the IC to the PC board. Now you will need to carefully inspect the IC soldering using a magnifying glass. Check for lifted pins on the IC and shorts between pins. Finally, use a multimeter to check that each pin is indeed connected to its respective track on the PC board. D-Cell version The D-cell version of the LED Torch can be assembled as shown in Fig.4. Insert the PC stakes with the long end going down into the PC board to give a similar pin height above and below the PC board. Install the u10MAX PC board onto the main board using short lengths of tinned copper wire passing through each PC board. Make sure that the u10MAX board is oriented correctly, with pin 1 lined up on both boards. Insert and solder all the resistors and capacitors, taking care with the tantalum and electrolytic types which must be oriented with the polarity shown. Now solder in the diodes and trim- Here’s the 6-LED array for the “D” cell version. The five 27Ω LED current limiting resistors all solder to a spacer. Parts List – D Cell Version 1 2 x D-Cell torch (Eveready E250K or similar) or a 3 x D-cell torch 1 PC board coded 11105011, 59 x 33mm (46 holes) 1 micro-DIP x 10-pin PC board coded u10MAX, 13 x 12mm (10 holes) (must be solder plated) 1 ferrite toroid, 19 x 10 x 5mm (L1) (Jaycar LO-1230) 1 200mm length of 1mm enamelled copper wire 1 60mm length of 0.8mm tinned copper wire 1 50mm length of red hookup wire 1 50mm length of green hookup wire 1 12mm OD steel or brass washer 1 16mm OD x 10mm ID steel or brass washer 2 3mm x 70mm steel or brass threaded rod 1 M3 tapped metal spacer 1 M3 crimp solder lug 1 M3 x 10mm screw 1 M3 star washer 1 100mm long cable tie 9 PC stakes 1 plastic translucent diffuser (cylinder 23mm ID x 17mm long) (ours was cut from a cover cap supplied with a “FRUITY FLAVORITS” 250mm drink container) 1 72 x 115mm piece of thin cardboard Semiconductors 6 5mm 5600mcd white LEDs (LED1-6) 1 MAX1676EUB step-up DC-DC converter (IC1) 1 BYV10-20 Schottky diode (D1) 1 IN5404 3A diode (D2) Capacitors 2 47µF tantalum capacitors 1 1µF PC electrolytic capacitor 3 0.1µF monolithic ceramic capacitors (code 104 or 100n) Resistors 1 100kΩ (brown black black orange brown or brown black yellow brown) 1 43kΩ (yellow orange black red brown or yellow orange orange brown) 1 200Ω (red black black black brown or red black brown brown) 6 27Ω (red violet black gold brown or red violet black brown) 1 50kΩ horizontal trimpot (VR1) pot VR1. Inductor L1 is wound using 4 turns of 1mm enamelled copper wire around the ferrite toroidal core. Bare the ends of the wire with some fine emery paper or a sharp knife, to remove the enamel insulation before soldering to the PC stakes. Inductor L1 is secured to the PC board using short lengths of tinned copper wire which wrap over the toroid in the two positions shown. Solder a 12mm washer to the PC stakes at the positive end of the PC board (lefthand side of Fig.4). A crimp-type solder lug is attached to the other end of the PC board. You need to pry open the crimp end with pliers and flatten it and then solder the flattened section to the PC pins on the top side of the board; the circular lug section then hangs beneath the PC board. Solder a short length of hookup wire between the “A” PC board pin and one of the eyelet PC stakes. LED Array All of the steps for assembling the LED array for the D-cell torch are shown in Fig.5. First, we have to make the LED array. The 6-LED array for this torch is made using a 16mm OD (outside dia-meter) washer which has five 1mm holes drilled evenly around it. Insert the K (cathode) lead, which is the shorter lead, of each LED into a hole and solder in place. Do this for five LEDs and each should have about 4mm lead length above the washer. Also the anode lead should be orientMAY 2001  63 Fig.5: step-by-step assembly of the D-cell version of the torch. Naturally, this assumes you have already completed the PC board! 64  Silicon Chip These three photos give a good idea of the mounting “hardware” associated with the D-cell PC board. In particular, note the opened-out crimp eyelet in the shots above and the washer in the shot at right; also the soldered joint between the threaded rod and D2. ed toward the centre of the washer. The sixth LED is placed in the centre of the washer with its cathode lead bent over to be soldered to the washer. Each anode lead is cut to about 5mm long and a 27Ω resistor soldered to it. The other ends of the resistors are soldered to a tapped spacer so that there is 25mm between the end of the spacer and the lower lip of the washer. The spacer should be mount-ed along the centre axis of the washer. The torch bulb holder is unscrewed from the reflector and the bulb, spring and contactor plate are removed. Drill a 3mm hole in the end for the screw. Remove the reflector cap and glass by squeezing the cap to an oval shape and then prising it off. Insert the LED assembly from the reflector end. Screw on the bulb holder and secure the LED assembly with an M3 x 10mm screw and star washer through the crimp lug on the PC board. Solder a wire from the GND PC terminal to the reflector switch flange. Two 70mm-long threaded rods are attached by soldering to the PC stakes on the positive end of the PC board and secured to the bulb holder with a plastic cable tie. This will provide a stiff mechanical assembly. Solder diode D2 between the GND PC stake under the PC board and the threaded rod as shown. The inside of the torch includes a spring as the negative contract for the cell. This spring is too stiff and may distort the PC board when it is assembled inside the torch. We recommend removing the spring and squashing it down so that the overall height is about half of its original. Squash the spring by bending the smaller diameter loops closer together with pliers. The PC board assembly will require a cardboard tube around it to prevent it from being caught within the torch as it is turned while the cap is screwed on. We made our tube with a piece of cardboard measuring 72 x 115mm. It was wrapped around to make a 30mm ID (inside diameter) cylinder x 72mm long. We glued the ends with PVA adhesive and used pegs to hold the joint in place while the glue dried. The LED array is surrounded with a cylinder of translucent plastic 23mm in diameter by 17mm long and it is retained between the reflector and front glass. This prevents star effects caused by the reflector focussing the light emitting from the sides of the LEDs. The plastic cylinder diffuses this light to substantially reduce the effect. Our cylinder was obtained from the cap cover of a “Fruity Flavorits” 250mm drink container. The whole assembly can now be inserted into the torch with the D cell inserted first, negative end down. Then place in the diffuser, the reflector glass and then press on the screw cap. Now screw the assembly in place.The torch should operate when switched on. You can remove the assembly to adjust VR1 for the brightness required. In most cases this would be at maximum (fully clockwise) but for some uses it may be helpful to turn it down. Testing If your torch does not work, firstly check that the cell has voltage across it. It should be at least 1.0V when measured with a multimeter. Clean the cell terminals to ensure good contact and check that the torch switch is operating correctly. Sometimes the switch contact is bent incorrectly so it does not make contact with the reflector switch flange. You can check that the washer for the LED array makes contact with the inside of the reflector. Other problems could be that the LEDs have been installed with reverse polarity or the components on the PC board have been incorrectly oriented or placed. Check that the leads on IC1 make contact with the PC board tracks. You can operate the torch using a power supply which produces about 1.2-1.5V, but make sure the polarity And here’s the final assembly, ready to be placed into the torch barrel – naked (left) and clothed (right)! MAY 2001  65 Fig.6 (top right) and the above photographs show the “AA” version PC board from both sides. Inset at right is an enlarged view of the MAX1676 IC – in this version it is soldered direct to the PC board. is correct. Check that the converter produces voltage at the “A” terminal. It should be adjustable from below 3V up to about 4.2V by varying VR1. AA-cell version First solder the surface-mount IC direct to the PC board (see “D” version for the method used). Next, insert the PC stakes with the long end going down into the PC board to give a similar pin height above and below the PC board. Insert and solder all the resistors. They are shown mounted vertically in the diagram but should sit parallel with the PC board. The capacitors go in next, taking care with the tantalum types which must be oriented with the correct polarity. Now solder in the two diodes and wire link. Inductor L1 is wound on a Xenon trigger transformer former. The original windings are removed from the trigger transformer; unwind the primary winding and then cut the Parts List – AA Cell Version 1 2-AA cell torch (Dorcy FrostBrite or equivalent) 1 PC board coded 11205011, 49 x 13mm (must be solder plated) 1 Xenon tube trigger transformer (L1) 1 900mm length of 0.4mm enamelled copper wire 1 10mm OD steel or brass washer 1 15mm OD x 10mm ID Neoprene “O” ring 1 50mm length of red hookup wire 1 50mm length of green hookup wire 6 PC stakes Semiconductors 3 5mm white LEDs (LED1-3) 1 MAX1676EUB step-up DC-DC converter (IC1) 1 BYV10-20 Schottky diode (D1) 1 IN4002 1A diode (D2) Capacitors 2 47µF tantalum capacitors 3 0.1µF monolithic ceramic capacitors (code 104 or 100n) Resistors (0.25W, 1%) 1 100kΩ (brown black black orange brown or brown black yellow brown) 1 47kΩ (yellow violet black red brown or yellow violet orange brown) 3 27Ω (red violet black black brown or red violet black brown) 66  Silicon Chip finer secondary wires with a knife. Unsolder the wires from the end leads and attach one end of the 0.4mm enamel copper wire to one end of the former, making sure the end is stripped of insulation before soldering. Wind on 45 turns and terminate the wire to the other end of the former. The inductor is mounted from the underside of the PC board. Solder a 10mm washer to the PC stakes at the positive end of the PC board. Solder a short length of hookup wire between the “A” PC board pin and one of the end PC stakes. LED array The 3-LED array is made within a torch bulb socket. The details are shown in Fig.7. First, remove the glass and filament from inside it. Wear goggles when doing this; crack the glass with pliers and scrape out the inside with a screwdriver. The solder at the end can be removed with some solder braid or by using a solder sucker. Cut the LED anode leads to 5mm in length and solder each one of these leads close to the bodies of a 27Ω resistor. The other end of the resistor is passed through the solder hole at the end of the bulb. The K (cathode) leads need to be cut to 5mm in length and soldered to the rim of the The reflector must be slightly modified to fit the three LEDs through, as shown here. bulb. The metal switch flange is also tack-soldered to the bulb. Now solder the resistor leads to the solder end of the bulb and cut the lead ends flush. The reflector will need to have cutouts made so that the LED array can be inserted into the reflector area. You can do this with a small round file. The PC board pins at the end of the board solder directly to the brass end cap on the bulb holder. This must be done quickly to avoid melting the plastic. We found that the internal spring contact did not give a reliable connection so we drilled a small hole in the side of the bulb holder just at the base of the spring and passed a wire through this and soldered it directly to the solder end of the bulb. The other end of the wire connects to the “A” PC stake. Insert the LED assembly into the reflector and secure the bulb holder in place with the wire soldered to the end of the bulb. Now attach a ground wire to the switch flange. The positive end of the PC board requires a 15mm diameter locator so that it will be centrally positioned inside the torch. We used a 15mm outside diameter “O” ring which was secured with some hot glue adhesive. Fig.7: here's how to assemble the “AA” version of the LED torch. These details suit the Dorcy FrostBrite torch but should be adaptable to most similarly switched and similar size torches. This circuit can also be powered by a single “C” cell in installed in a C-cell torch. This close-up of the “AA” torch reflector assembly shows the three-LED array and the way it pokes through the reflector. In this case, the LEDs are soldered into the old (filament) globe base. The corners of this end of the PC board will require filing down a little so that the “O” ring is not distorted out of shape when attached to the end of the PC board. Insert an AA cell (negative end first) and place the PC board and reflector assembly into the torch body. Secure with the reflector cap. The torch should now work. If it does not work, check that the cell has voltage across it. Again, it should be at least 1.0V when measured with a multimeter. Clean the cell terminals to ensure good contact and check that the torch switch is operating correctly. Sometimes the switch contact may be bent incorrectly so it does not make contact with the switch flange on the reflector. Other problems could be that the LEDs have been installed with reverse polarity or the components on the PC board have been incorrectly oriented or placed. Check that the leads on IC1 make contact with the PC board tracks. You can operate the torch using a power supply which produces about 1.2-1.5V, making sure the polarity is correct. Check that the converter produces voltage at the “A” terminal. SC It should be about 3.9V. Fig.8: PC board patterns for the “AA” version (above) and the “D” version (far right), with its SMD IC daughter board at immediate right. MAY 2001  67 Ein Servo Mit Most hobbyists would be familiar with the little servos used to control model planes, boats and cars. They’re fine if that’s all you want to control. But what if your application calls for a servo with industrial-strength muscle? That’s when you need our new, B-I-G, powerful, industrial-strength, Jumbo Servo. Y our typical model servo is capable of very fine adjustment over a range of about 90° or so. It measures about 40 x 20 x 35mm, weighs about 50g and has a torque somewhere around 5kg-cm (some a bit more, some a bit less). Our new “Jumbo” servo is also capable of very fine adjustment over a 90° range. It comes in at 180 x 110 x 110mm, weighs about 1300g and has a torque somewhere in the kg-m range (no, we couldn’t measure it!). Suffice to say it’s a tad more than “typical” model servos! Possible applications What on earth would you want that sort of muscle for? Here are just a few applications that we thought of – you can probably think of many more (in fact, right now there are readers throughout the South Pacific thinking “at last! Now I can…..”). •  Robotics – no longer are you limited to piddly little designs. Build a monster! •  Radio control of large (eg, 1/4-scale or even bigger) models – steering, brakes, etc which require some real power. •  Remote (as distinct from radio) control (ie “fly by wire”) in real boats, cars, etc – eg, the rudder, trim or even throttle control without the usual mechanical linkages. •  Rotator for a radio or TV antenna; even a satellite dish azimuth/elevation positioner. •  Remote gate or door controller. 68  Silicon Chip •  Heavy duty pan or tilt controller for a remote camera or camcorder – eg, unattended wildlife photography or surveillance work. • Remote (or even local) electronic control of valves or flow control devices, especially if they are in hazardous areas. •  Flue, vent or high hopper window openers/closers. • Remote winch or sail furling on a real yacht (you add the hardware!) •  Perhaps (obviously with additional electronics) even navigation control with feedback from a GPS unit (as published last month in SILICON CHIP). We’re sure we have merely scratched the surface of ideas for this one. It’s one of those projects that is a solution waiting for an application – and there are literally countless applications. Servo control The vast majority of servos sold today are designed to operate to a somewhat standard 1.0-2.0ms pulse width on a 20ms (+/-) frame rate. At centre, the pulse width should be 1.5ms. Increase the pulse width and the servo turns “forward”, proportionally all the way up to 2.0ms where it is at full forward. Similarly, decrease the pulse width and the servo turns “reverse”, with the servo in full reverse at 1.0ms. The frame rate, or time between pulses, is usually quoted as 20ms (or 50Hz) but this does not appear to be crucial. The pulse width, though, is – for obvious reasons. The Jumbo Servo also uses this 1.0-2.0ms/50Hz standard, so it is compatible with the vast majority of radio control equipment sold. Radio control units tend to use a standard colour coding in their output leads – red, yellow and black. Red and black are + and – power respectively, while the yellow is the pulse train (normally referenced to the black lead). For convenience, we often use red, brown and black wires in hobby radio control wiring because these are the first three colours in a rainbow cable – very handy because the three wires can be stripped off together. (In fact, in most rainbow cables you get two lots of black, brown, red wires – most rainbow cables have 15 or more conductors). Inside a “normal” servo is a tiny electric motor/gearbox, which is driven one way to send the servo actuator forward and the opposite way to go reverse. Outside our jumbo servo is a much larger electric motor/gearbox which works in exactly the same way. While we used a particular motor/gearbox combination in the prototype, you could choose from a huge range of motors and gearboxes, depending on the amount of grunt you need. The motor/gearbox we used is actually a powerful little German unit (aha! so that’s the association in the title!) from Oatley Electronics but others which you could use include a variety of automotive models – wind- Gerrunttt! screen wiper motors, auto headlight motors, electric antenna motors and so on). You can also obtain a variety of motors and gearboxes from hobby and electronics stores. Bear in mind, though, that a too-high gear ratio (say 100:1 or more) may result in a particular servo position being difficult to accurately or consistently reproduce. This is because of the latency of the motor/gearbox – the motor might make several turns before the geared output starts to turn. Of course, the higher the ratio, the more torque you’ll get from a given motor so it’s something of a tradeoff. In a lot of cases, this won’t matter. The prototype had also slightly lower than the normal 90° travel – it was about 85°. This is because of component tolerance spreads and could be corrected by closer component selection. However, this may or may not be important to you – some applications may only need half this travel, or even less, so less wouldn’t matter. Fly-by-wire If you don’t have (or don’t want) a radio-control unit with receiver, you won’t have a source of the 1.0-2.0ms/50Hz pulses required to control the servo. Fortunately, that’s easy to solve. You can quite simply synthesize such a pulse stream with just a few components. As we mentioned before, the frame or pulse rate (50Hz) is not particularly critical but the 1.0-2.0ms pulse width is. For those who want to use a wired controller for the servo, we show details of a small variable pulse generator which creates those 1.0-2.0ms pulses at about 50Hz. The pulse width is controlled by a pot; centre is off, full anti-clockwise is full reverse and full clockwise is full forward. This can be connected as far as you like (within reason!) from the servo unit itself. Mechanicals We show the details of our prototype in the drawings and photographs which accompany this article. Needless to say, there are many ways to skin a cat – and your servo mounting arrangements could obviously be very different if you use a different motor. The two basic requirements are: (a) some means of mounting the servo Article by Ross Tester actuator “arm” to the motor (gearbox) shaft, and (b) some means of connecting the positioning sensing, or feedback, pot­entiometer to the motor (gearbox) shaft. The photographs and drawings show how we accomplished this in the prototype – again, yours will depend on the motor/gearbox used. Our servo actuator arm was a 250 x 15mm strip of 10 gauge aluminium, bent over on itself but with a 10mm “bell” at the midpoint. A hole was drilled into this to accommodate a screw and locknut which in turn fastened on the gearbox shaft. Of course, holes were also drilled in the arm to allow the shaft to pass through (a fairly tight, or “friction” fit). One or two 3mm screw(s) and lockMAY 2001  69 The circuit of the servo controller section. The input can be from a radio control receiver or, as we explain later, a purpose-built oscillator. nut(s) prevented the two halves from “opening up”. This screw could also be a connection point for whatever the servo arm was actuating, if necessary. A shallow “U”-shaped bracket was made up to support the feedback pot and, for convenience, the servo controller electronics housed in a small zippy box. (The electronics can be mounted remotely if desired). The bracket was glued, not screwed, to the electronics box, again more for convenience than anything else. The pot shaft was connected to the motor shaft with a short length of heatshrink tubing, shrunk into position once the pot was mounted and the two shafts aligned. Circuit description There’s not a great deal to the circuit. It basically consists of two sections: the pulse detection, shaft position and driving circuitry based on the ZN409 70  Silicon Chip Servo Driver IC and the “H-bridge” motor driver (Q1-Q8). The circuit is in fact very similar to one contributed by Nicholas Baroni in “Circuit Notebook”, SILICON CHIP December 1997. The 50Hz pulse stream is fed into pin 14 of IC1. This chip has its own reference oscillator, producing 1.5mswide pulses every 20ms (ie, 50Hz). The incoming pulse stream is compared to this reference. Usually, a trimpot would be used to adjust the reference oscillator to account for variations in receiver outputs but in this case there is a pot, rather than a trimpot, and it is connected rather differently. The potentiomenter is now physically connected to the gearbox shaft and varies as the servo position varies. This gives the IC feedback, letting it know where the shaft is at that time. More on this shortly. Also, most ZN409 motor-driver circuits have the outputs from pin 5 and 9 – as you can see from the circuit, our outputs are pins 7 and 8. If the incoming receiver pulses are longer than the reference oscillator pulses, the pin 7 output is taken high and pin 8 output taken low. Conversely, if shorter, pin 7 goes low and pin 8 high. If the pulses are the same length, both pin 7 and pin 8 are high. As Q1 and Q2 are PNP devices, a logic “high” on their bases will turn them off and a “low” will turn them on. Therefore, unless the IC sends both pins 9 and 5 high, when Q1 is on Q2 must be off and vice versa. If the pulses are long and Q1 is off, Q3 and Q5 will also be off. At the same time the base of Q2 is taken low, turning it on. Q6, Q8 and Q4 are also turned on. Current can therefore flow from positive, through Q4, the motor, Q8 and back to negative. The PC board component overlay shows where everything fits. There are two additional 0.1µF capacitors not shown on this overlay; they are for motor noise supression and are wired directly between the motor terminals and the earthed motor, with leads as short as possible. The wiring on the right side of the PC board should be heavy duty, able to handle the heavy motor current. The wiring on the left is ideally made from ribbon cable. Close-up of the servo controller, removed from its case. Compare this to the PC board overlay above. Therefore, the motor will turn in one direction, turning the servo actuator arm attached to its shaft (or more correctly, its gearbox shaft). But remember that feedback pot we mentioned before? As its resistance varies, it changes the width of the pulses from the reference oscillator in IC1. At a certain point, the comparator will register that the reference pulses and the incoming receiver pulses are identical and send both pins 9 and 5 high. When this happens Q1 and Q2 are both turned off, in turn turning Q3 and Q6 off. Q5 and Q8 turn off when this happens, so current cannot pass to the negative supply and therefore the motor cannot turn. If the incoming pulses become shorter than the reference, the whole operation above reverses; the net result is that current can flow from positive to negative via Q7, the motor and Q5. But this current flow is in the oppo- site direction as far as the motor is concerned, therefore it turns the opposite way – that is, until equilibrium is once again reached, with the feedback pot fooling the comparator into believing that the pulse widths are equal. Power supplies The circuit requires two supplies, +12V (or the voltage at which your motor operates) and +5V. The 5V is usually supplied by the radio-control receiver (via the 3-wire cable which also supplies pulses); if you build the servo oscillator/controller unit there is also a 5V regulated supply built into that. Otherwise you may need to lash together a similar 7805 regulator circuit which can derive its input from the 12V DC source for the motor supply. While we are specifying 12V for the motor supply, there may be users Viewed from the underside, this pic shows the electronics of the Jumbo Servo with the case cover removed for clarity. Note the position feedback pot mounted on the bracket which also holds the case and PC board. MAY 2001  71 These two close-up shots show the servo controller arm and its method of mounting on the gearbox shaft. The position feedback potentiometer must be aligned with this shaft and connected to it – we found the easiest way was with heatshrink. who want to run higher voltage motor/ gearboxes. One advantage of this is that for the same torque, a higher voltage motor will normally draw less current. With the transistors specified, higher voltage motors are a possibility (eg, 24V truck wipers) but we must emphasise that these have not been tried. You may also need to supply heatsinking for the power transistors. Inertia and dead band The ZN409 has a built-in “deadband” which stops it trying to adjust the servo over too close a range. Without the deadband, the servo motor would continually “hunt” or chatter as it tried to correct its position. This is caused by the mechanical inertia of the motor/gearbox assembly. The circuit tells the motor to spin for so long then, when the circuit senses that it has reached the right point, motor current is cut off. But the motor cannot stop spinning immediately – it slows to a stop. This takes the servo slightly beyond where it should be. So the circuit tries to correct this and spins the motor back the other way – woops, too far, so it corrects this and... The dead band stops this happening. It won’t let the controller supply power to the motor if the servo is within a certain band or percentage of where it should be. The capacitor connected to pin 13 slightly extends the ZN409 normal deadband to take into account the longer inertia of the larger motors used in this servo. With the .022µF capacitor shown, the dead band is about 14% of the servo travel – fairly normal for a servo but if unacceptably large, you could reduce this capacitor somewhat. See what works for your application. 72  Silicon Chip The two 2.2MΩ resistors serve a related function, albeit inverse, in the “stick” of the radio control unit. They give the stick more control, without a lot of dead stick (ie, the amount the stick must be moved before there’s any reaction from the servo). If necessary, these resistors can be reduced but don’t go below about 560kΩ. Lastly, the two 22µF capacitors between these resistors really are connected “back-to-back” as shown, as the polarity across them can (and does!) reverse. Pulse source We’ve already mentioned that this controller is compatible with the vast Parts List – Jumbo Servo (Actuator) 1 PC board, 52 x 77mm, code K165 1 12V motor/gearbox assembly (see text) 1 14-pin DIL IC socket 8 PC stakes 3 lengths black-brown-red ribbon cable (to suit) 1 length 3-conductor ribbon cable (to suit) 2 lengths heavy-duty red hookup wire 2 lengths heavy-duty black hookup wire 1 aluminium bracket to hold feedback pot (see text) 1 aluminium servo actuator arm, captive to shaft (see text) 1 length heatshrink tubing to suit gearbox shaft & potentiometer Semiconductors 1 ZN409 servo controller IC (IC1) 2 C8550 PNP transistors (Q1, Q2) 2 BC639 NPN transistors (Q3, Q6) 2 MJE2955 PNP power transistors (Q4, Q7) 2 MJE3055 NPN power transistors (Q5, Q8) Capacitors 1 470µF 35VW electrolytic, radial type (C2) 2 22µF 25VW electrolytics, PC mounting (C3, C4) 1 2.2µF 25VW electrolytic, PC mounting (C9) 1 0.47µF polyester (C7) 3 0.1µF polyester or MKT (C1, C5, C6) 3 0.1µF ceramic (C10, C11*) 1 0.022µF polyester (C8) Resistors 2 2.2MΩ     2 100kΩ     2 10kΩ    1 12kΩ    1 5.6kΩ    1 1.2kΩ 8 470Ω      2 68W 1Ω 1 10kΩ linear potentiometer * solder between motor terminals and earthed motor case­ It’s not so much a Jumbo Servo Controller as a Jumbo Servo Controller Controller. It contains two oscillators whose pulse width is variable between one and two milliseconds; ie, perfect for “driving” the Jumbo Servo. majority of radio control receiver outputs, with their 1.5ms-wide output pulses (±0.5ms) on a 50Hz square wave. Connect the output of the radio control receiver to this circuit and you should find the combination works perfectly. However, if you don’t have an R/C receiver (or want to wire the controller direct) it’s very easy to build an oscillator which simulates this waveform. That’s what the other box in our photographs does. In fact, built into this box, with oodles of room to spare, are two such oscillators (obviously for controlling two Jumbo Servos). If you want to control more, you could arguably fit four or even six oscillators in the disposals box we used. This box was once a 110V power supply – not exactly usable in Oz or NZ, so we threw away the transformer (OK, we lied – it’s a great paper weight!). We did keep and use the small rectifier PC board, though – it provides some useful filtering and also protects against reverse polarity supply. This board also fits into the box – still with plenty of room. The oscillator is based on a 555 Inside the box looks like a dog’s breakfast (’cos it is!). The vertical PC board contains two oscillators (hence the two pots on the front) while the other PC board is a rectifier board retrieved from a 110V supply and “crammed in”. timer, running at around 50Hz. This circuit is a little different from most 555 timer circuits in that it is effectively “back to front”. Normally, pin 3 of a 555 is its output pin but we use pin 3 to charge and discharge the timing capacitor, taking the output pulses from what would normally be the discharge pin (pin 7). The 555 output can both source and sink current. When its output is low, C3 discharges through the IC and when high, it charges C3, with both the charge and discharge times dependent on the setting of VR1. Note, though, the large discrepancy in series resistors between the charge and discharge cycles: these set up the oscillator to provide the one-to-two millisecond-wide output pulses, taken from pin 7 . Construction Start, as always, by examining the PC board(s) to ensure it (they) is (are) free from defects. We’ll assemble the main PC board first. Mount and solder the lowest-profile, non-polarised components first –ie, the resistors and ceramic or polyester capacitors. Use the colour code in the table or check their value with a digital multimeter if you aren’t sure. Next solder in the electrolytic capacitors. The large electro near the power transistors is a little unusual these days – it is an axial type rather than a PC board mounting type. Detail of our servo arm. Exact size is not important – this size was chosen because it is easily made from a 250mm length of 20mm x 3mm strip aluminium, commonly available at hardware stores. MAY 2001  73 Here’s what the contents of the controller oscillator box reveal: the two oscillators (on one PC board) at left, while the board in the background is the one recovered from a 110V supply. It contains a bridge rectifier along with a nice big smoothing capacitor and a fuse, so it doesn’t matter which way around you connect power (low voltage AC, even!). The ICs at the back of the oscillators are 7805 regulators to give a 5V supply. If for some reason you cannot get an axial, a PC board type can be used but you’ll have to run one of its leads back along the body in order to lie it flat on the board. (Standing up it would be too high to fit in the case). Now solder in the small transistors, taking care that you don’t mix ’em up. All look much the same but they aren’t! Solder in the IC socket, making sure its notch goes the same way as shown on the PC board overlay. And finally, solder the four power transistors in place. Again, they are not all the same. They mount down close to, but not right on, the PC board – allow say 3mm space under them. Try to mount them all at exactly the same height – just because they look neater that way. Plug the IC into its socket, again ensuring the notch lines up with the notch on the socket. Apart from soldering on the various connecting wires, this PC board is now complete. Note that one resistor and the pot should be left over – the resistor solders direct to the pot terminals. In like manner to the controller board, solder the components to the smaller PC board (the oscillator board). If you are only going to control one servo, you only need to place one set of components (the board contains two identical halves for two oscillators in case you want to control two Jumbo 74  Silicon Chip Servos – eg, steering and brakes on a big model car). Connecting cables Most of the connecting cables can be trios (ie, 3 wires in one strip) peeled off a length of ribbon cable. Bearing in mind what we said above about blackbrown-red colours, remove suitable lengths of cable and connect as shown in the diagrams. Wires to the remote pot can also be a trio from ribbon cable – colours here aren’t at all important; use what you have the most of. Just remember to connect the right one to the right point on the PC board! Cables which connect to the motor and to the battery or power source should be considerably heavier than ribbon cable. For a motor which draws, say, 5A continuous, we would be inclined to use 10A cable to minimise voltage drop (I2R losses) – especially if the motor is mounted any distance away. You can buy “auto” cable rated at 20A or more which is even better. We would normally always use red and black cable for polarised (ie, power) connections – it minimises the chance of a mistake. Having said that, you may note from the photographs we used red and green for the motor because that’s what the motor was supplied with. Oh well, 50% right is better than 100% rong! You may also have noticed that we used a trio of black-brown-red ribbon cable to connect power to the oscillator board (it’s more than thick enough for this purpose). In this case, we simply chopped off the brown in the middle but kept to the red and black convention for power. In this demonstration prototype, too, we have used much thinner red and black cable for the power connection to the PC board than we would have preferred. It’s just that we had some of this on hand and the lolly shop was closed and… Firing it up You might find it easier to check it all out without the servo actuator arm The Servo Oscillator is based around an old friend, the 555 timer. This circuit also includes a regulated 5V supply for the servo driver chip on the other PC board. The component overlay for one of the oscillators and 5V supplies. One is needed for each servo. At right are two such circuits on one PC board. in place, or at least not yet captive (ie, loosen the grub screw!). The arm has this annoying habit of getting caught in other things while flailing back on forth when spread out on the bench. Connect the feedback pot to the main PC board (remember that resistor across it!) and set it to roughly its midpoint. Apply power. You’ll probably find that nothing happens. That’s good, because without input pulses, the servo doesn’t know where it should be. Disconnect from power. Now’s the time to align the pot to the shaft – as we said, we used heatshrink for simplicity and ease; you might have other ideas. Now you’ll need either an R/C receiver with servo output or the oscillator. Connect either up to the “receiver” terminals on the PC board, observing the polarity of the power leads and the position of the signal lead (it goes to the centre). Apply power to the servo and oscillator (or turn on your R/C receiver and transmitter). Turning the pot (or moving the transmitter joystick) one way should make the servo turn one way, the opposite way should make it go back the other direction. If so, all you have to do is secure the Parts List – Servo Controller Oscillator (1 unit) 1 PC Board, 40 x 63mm, code K166 1 recovered PC board with components (see text) 1 8-pin DIL IC socket 8 PC stakes 2 lengths black-brown-red ribbon cable (to suit) 1 length 3-conductor ribbon cable (to suit) servo arm to the appropriate place on the gearbox shaft, mount the electronics in the appropriate boxes, run any necessary cables – and you’re done! If it doesn’t work There’s a snaffu somewhere, eh? Eliminate the radio control side by plugging in a standard servo (eg, from a model plane, car, etc) to the radio control receiver and make sure it works as intended. If you’ve built the oscillator, it can be plugged into a standard servo and checked. If everything works, there’s something wrong on the PC board – a component back to front or misplaced, a solder bridge or dry joint – or maybe you have simply forgotten to connect something to something else (the motor, maybe?) The board is quite simple, so if a check and double check finds nothing wrong, start checking voltages, for example: • power (from the R/C receiver or oscillator) at pin 10 of IC1 and also the emitters of both Q1 and Q2. • power (the same voltage as the battery) between the sources of Q5/Q7 and Q6/Q8. If you have access to an oscilloscope, Resistor Colour Codes                                       Value     2.2MΩ  100kΩ  12kΩ  10kΩ  5.6kΩ   1.2kΩ   470Ω   68Ω 4-Band Code (1%)  5-Band Code (1%) red red green brown  red red black yellow brown brown black yellow brown  brown black black orange brown brown red orange brown  brown red black red brown brown black orange brown  brown black black red brown green blue red brown  green blue black brown brown brown red red brown  brown red black brown brown yellow violet brown brown  yellow violet black black brown blue grey black brown  blue grey black black gold Semiconductors 1 7805 3-terminal regulator (IC1) 1 555 timer IC (IC2) 1 1N4004 power diode (D1) 2 1N4148 signal diodes (D2, D3) Capacitors 1 1000µF 35VW electrolytic, PC mounting (C1) 1 10µF 16VW electrolytic, PC mounting (C2) 2 .047µF polyester or MKT (C3, C4) Resistors (0.25W, 1%) 1 1MΩ    2 10kΩ 1 20kΩ linear potentiometer, PC board mounting you might check that there is indeed a 50Hz (ish) squarewave coming into pin 14 of IC1 and that pins 7 and 8 go high and low as they should. Wheredyageddit? Various kits are available from Oatley Electronics, who hold the copyright on the PC board patterns. They have the servo kit (all electronics, PC board and a case) for $35.00; a dual oscillator/controller kit (electronics, PC board and case) for $14.00; a power supply (including the 110V supply suitable for ratting) for $24 and, most importantly, they have the German Motor/Gearbox for $20.00 each. Contact Oatley Electronics on (02) 9584 3563, fax (02) 9584 3561 or via www.oatleyelectronics.com SC Capacitor Codes       Value    IEC code    EIA code   0.47uF 470n 474   0.1uF 100n 104   .047uF 47n 471   .022uF 22n 221 MAY 2001  75 PRODUCT SHOWCASE Aussie “AUDIOBUS” manufacturer takes on the world MASS Technologies’ founder, Hans Groothius, was so disappointed with his “top of the range” speaker system that he set out to design his own. His prototype, using active electronic crossovers, was immediately snapped up by a laser-disc fan to replace his own almost-new speakers. Active speaker systems are not new but have been relatively restricted to the echelons of high-grade profes- sional recording studios and ‘high-end’ consumers. The great expense traditionally associated with active crossover technology has been mostly due to their large number of interconnections and wiring. MASS has developed a method to drastically reduce this throughout its entire speaker range. Now Groothius has started demonstrating his company’s Australian-developed “AUDIOBUS” technology to audio manufacturers in the northern hemisphere. Having been demonstrated twice at the Consumer Electronics Show in Las Vegas, by MASS itself, and with Peerless/Danish Sound Technology, he believes his speakers will find a ready market where quality of sound reproduction is the ultimate goal. The quality of sound reproduction and power handling even in the first model outperformed most conventional passive and active systems many times their price and size, and MASS’ key technology has been further developed and miniaturised with a view to eventually chipping it. MASS Technologies Pty Ltd, was established four years ago in Perth. The company is now 76  Silicon Chip Contact: MASS Technologies Phone: (08) 9434 4030 Fax (08) 9434 9423 Website: www.mass.com.au Li-Ion Pulse Charger Dissipates No Heat Linear Technology Corporation has released the LTC1730, a complete Li-Ion pulse charger that dissipates virtually no heat while charging a 1-cell Li-Ion battery. Current limiting occurs inside the plug-pack adapter, allowing the charger IC to be built inside the portable device. This eliminates the need for an external MOSFET and blocking diode. Applications include PDAs, palmtop computers, portable GPS devices and cell phones that operate with a 1-cell Li-Ion bat­tery. The LTC1730 features end-of-charge detection and a programmable timer for maximum Slim-line loudspeakers from Jamo Jamo’s extreme X8 loudspeakers represent a big step forward in styling, away from the conventional black (boring) look to one that is tall and slim with a hammered gun-metal grey finish with silver fronts. There are two full range models, the X850 and X870. The X850 has a 8-inch woofer and a power rating of 200 watts while the X870 has a 10-inch woofer rated at up 280 watts and offer a frequency response down to 32Hz. If you want to go the whole hog with a home theatre setup, Jamo have released an add-on pack consisting of a 100W shielded centre speaker (X8CEN), a pair of 100W rear speakers the Australasian distributor for Vifa and Scan-speak drivers from Danish Sound Technology, working to re-establish these high quality drivers in the local market (X830) and a 200W active subwoofer (X8SUB) with a 12-inch long-throw driver. The X870 retail at $2395 a pair and the X850 at $1695 a pair. The addon surround sound package sells for $2695. Alterna­tively, you can purchase the components separately: X8CEN for $595, X830 $795 a pair and X8SUB for $1495. Contact: QualiFi Phone: 1 800 242 426 Website: www.jamospeakers.com capacity charging. Users can set the desired charge time with the addition of a capacitor. Contact: REC Electronics Phone: (02) 9741 0122 Fax (02) 9741 0133 Website: www.rec.com.au End of an era for Dick Smith Electronics. . . Since 1980, Dick Smith Electronics headquarters – and that giant Aussie flag – have been a landmark at North Ryde in Sydney. Then, the company had 17 stores and 275 employees. Today, with over 200 outlets throughout Australia and New Zealand and more than 2500 employees, the company has significantly outgrown the North Ryde site – despite two major building expansions and the splitting of the warehouse into three facilities around Sydney. Between now and June, Dick Smith Electronics will relocate to a new, purpose built complex in Chullora, about 13km away. It has 8000 square metres of office space and 10,100 square metres of warehouse, with room for even more expansion if needed. And that giant flag? “It’s going too,” Contact: Dick Smith Electronics 2 Davidson St, Chullora NSW Phone: (02) 9642 9100 Fax: (02) 9642 9111 Website: www.dse.com.au . . . and Jaycar move headquarters, too Not to be outdone by their competition, Jaycar Electronics have also decided that their Rhodes headquarters have become too small and have moved into a 6900 square metre, newly refurbished head office and warehouse in Silverwater. The new complex has been designed from the ground up to give new levels of service to customers and, of course, to Quality and management standards help lines Businesses and consumers can now find out whether Austra­lian and international standards are being met via two new help lines provided by Quality Assurance Services (QAS). The first is the quality management help line which answers questions on ISO 9001:2000, the key quality standard used worldwide. The ISO help line number is 1 900 920 727. Call costs for the ISO 9000:2000 help line are $5.50 per minute, with higher charges applying for mobile and public telephones. The second help line offers information on management sys­ tems including quality, environmental, food safety and occupa­tional health and safety. Bookings for advice can be made on 1800 815 438. An hourly charge of $175 applies to bookings made for IMS help line assistance. Contact: Quality Assurance Services (QAS) Website: www.qas.com.au TOROIDAL POWER said Jeff Grover, Dick Smith Electronics’ Managing Director. “A new flag pole, the same size as the one at North Ryde, will be erected at Chullora.” The new complex also includes a retail store, necessitating the closure of the old Chullora store. But the new one is easy to find – it’s adjacent to the Centenary Drive overpass, just off the Hume Highway. Just look for that flag! Jaycar’s internal operation. Contact: Jaycar Electronics 100 Silverwater Rd, Silverwater NSW Phone: (02) 9741 8555 Fax: (02) 9741 8500 Website: www.jaycar.com.au 16-Channel Colour Multiplexer Jaycar electronics has released a 16channel colour video surveillance multiplexer. It has 16 camera inputs and a host of useful features. Each camera can be given a 6-digit name such as ‘foyer, carpark, stairs, etc’ and this name is superimposed on the camera image to be displayed or recorded. The images can be displayed sequentially as a full screen image or in a number of display modes including TRANSFORMERS Manufactured in Australia Comprehensive data available Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 4, 7, 10, 13 & 16 simultaneous camera images. Each camera input channel has a corresponding alarm input and the multiplexer can be programmed to give priority to ‘alarmed’ cameras and display them more often than ‘unalarmed’ cameras. Two video output signals are provided, one for ‘live’ camera images and the other for output to a video recorder. The multiplexer will automatically detect the loss of video signal and indicate the lost channel by flashing the corresponding indicator on the from panel display. Alarm output may be used to control a VCR for ‘Event-Only’ recording. Audible Video Loss and Alarm buzzers can alert the user to intrusion and/ or interference with camera video or power supply wiring. The system can also display the date & time on the monitor and recorder output images. The Multiplexer is available through all Jaycar stores (see new head office SC details above left). NEW! HC-5 hi-res Vid eo Distribution Amplifier DVS5 Video & Audio Distribution Amplifier Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. For broadcast, audiovisual and film industries. Wide bandwidth, high output and unconditional stability with hum-cancelling circuitry, front-panel video gain and cable eq adjustments. 240V AC, 120V AC or 24V DC 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 MAY 2001  77 REFERENCE GREAT BOOKS FOR AUDIO POWER AMP DESIGN HANDBOOK INDUSTRIAL BRUSHLESS SERVOMOTORS By Douglas Self. 2nd Edition Published 2000 85 $ By Peter Moreton. Publ. 2000 From one of the world’s most respected audio authorities. The new 2nd edition is even more comprehensive, includes sections on load-invariant power amps, distortion residuals, diagnosis of amplifier problems, and much more. 368 pages in paperback. VIDEO SCRAMBLING AND DESCRAMBLING for If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! Encoding/decoding systems (analog and digital systems), encryption, even schematics and details of several encoder and decoder circuits for experimentation. Intended for both the hobbyist and the professional. 290 pages in paperback. NEW 2nd TCP/IP EXPLAINED 99 AUDIO ELECTRONICS Satellite & Cable TV by Graf & Sheets Edition 1998 $ By John Linsley Hood. First published 1995. Second edition 1999. 65 $ This book is for anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover. By Philip Miller. Published 1997. $ 99 By Tim Williams. First published 1991  (reprinted 1997). $ LOCAL AREA NETWORKS: An Introduction to the Technology 65   Includes grounding, printed circuit design and layout, the characteristics of practical active and passive components, cables, linear ICs, logic circuits and their interfaces, power supplies, electromagnetic compatibility, safety and thermal management. 302 pages, in paperback. ELECTRIC MOTORS AND DRIVES By John E. McNamara. 2nd edition 1996. EMC FOR PRODUCT DESIGNERS By Austin Hughes. Second edition published 1993 (reprinted 1997). 69 $ For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. ESSENTIAL LINUX By Tim Williams. First pub­­lished 1992. 2nd edition 1996. $ 99 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. 78  Silicon Chip 85 $ THE CIRCUIT DESIGNER’S COMPANION Assumes no prior knowledge of TCP/IP, only a basic understanding of LAN access protocols, explaining all the elements and alternatives. Combines study questions with reference material. Examples of network designs and implementations are given. 518 pages, in paperback. Want to become more familiar with local area networks (LANs) without facing the challenge of a 400-page text? . Gives familiarity with the concepts involved and provides a start for reading more detailed texts. 191 pages, in paperback. Designed as a guide for professionals and a module text for electrical and mechanical engineering students. A step-by-step approach covering construction, how they work, how the motor behaves and how it is rated and selected. It may only be a small book but it has outstanding content! 186 pages in hardback. 65 $ By Steve Heath. Published 1997. $ 85 Provides all the information and software that is necessary for a PC user to install and use the freeware Linux operating system. It details, setp-by-step, how to obtain and configure the operating system and utilities. It also explains all of the key commands. The text is generously illustrated with screen shots and examples that show how the commands work. Includes a CD-ROM containing Linux version 1.3 and including all the interim updates, basic utilities and compilers with their associated documentation. 257 pages, in paperback. BOOKSHOP WANT TO SAVE 10%? SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! ENQUIRING MINDS! (To subscribe, see page 57) ALL PRICES INCLUDE GST UNDERSTANDING TELEPHONE ELECTRONICS SETTING UP A WEB SERVER By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. $ 59 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. 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 to date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback. $ 59 SILICON CHIP'S ELECTRONICS TEST BENCH First published 2000 A collection of the “most asked for” Test Equipment projects and features from the pages of Australia’s “most asked for” electronics magazine. Exceptional value at $10.95 O R D E R H E R E P&P  AUDIO POWER AMPLIFIER DESIGN...............................$85.00  INDUSTRIAL BRUSHLESS SERVO MOTORS..................$99.00  VIDEO SCRAMBLING/DESCRAMBLING..........................$65.00  TCP/IP EXPLAINED.........................................................$99.00  LOCAL AREA NETWORKS...............................................$69.00  SETTING UP A WEB SERVER..........................................$69.00  THE CIRCUIT DESIGNER’S COMPANION........................$65.00  ELECTRIC MOTORS AND DRIVES...................................$65.00  UNDERSTANDING TELEPHONE ELECTRONICS.................$59.00  AUDIO ELECTRONICS.....................................................$85.00  GUIDE TO TV & VIDEO TECHNOLOGY............................$59.00  EMC FOR PRODUCT DESIGNERS...................................$99.00  DIGITAL ELECTRONICS ..................................................$65.00  ESSENTIAL LINUX..........................................................$85.00  SILICON CHIP TEST BENCH............................................$10.95  SILICON CHIP COMPUTER OMNIBUS............................$10.95               ORDER TOTAL: $...................... Orders over $100 P&P free in Australia. AUST: Add $A5.50 per book NZ: Add $A10 per book, $A15 elsewhere By Simon Collin. Published 1997. $ 69 Covers all major platforms, software, links and web techniques. It details each step required to choose, install and configure the hardware and software elements, create an effective site and promote it successfully. 273 pages, in paperback DIGITAL ELECTRONICS – A PRACTICAL APPROACH By Richard Monk. Published 1998. With this book you can learn the principles and practice of digital electronics without leaving your desk, through the popular simulation applications, EASY-PC Pro XM and Pulsar. Alternatively, if you want to discover the applications through a thoroughly practical exploration of digital electronics, this is the book for you. A free floppy disk is included, featuring limited function versions of EASY-PC Professional XM and Pulsar. 249 pages, in paperback. 65 $ SILICON CHIP'S COMPUTER OMNIBUS First published 1999 Hints, tips, Upgrades and Fixes for your computer from articles published in SILICON CHIP in recent years. Covers DOS, Windows 3.1, 95, 98 and NT. A must for the computer user. $10.95 INC GST TAX INVOICE Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ___________________________________ Postcode_______________ Daytime Phone No. (______) __________________________________ STD Email___________________<at>_________________________________  Cheque/Money Order enclosed OR    Charge my credit card   –    Bankcard   Visa Card   MasterCard No: Signature______________________Card expiry date PLUS P&P (if applic): $........................... TOTAL$ AU.............................. POST TO: SILICON CHIP Publications, PO Box 139, Collaroy NSW, Australia 2097. OR CALL (02) 9979 5644 & quote your credit card details; or FAX TO (02) 9979 6503 2001  79 ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. M ALLAY PRICES INCLUDE GST VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The magnificent 7-banders from AWA If ever there was a particular range that stood out in the AWA stable it was the 7-band radios of the 1940s and early 1950s. There were quite a few different models produced and they came in three cabinet formats – table, console and radiogram. They were powered by batteries (2V, 135V and sometimes a bias battery) or via a vibrator (6V) or from 240VAC. Prior to WWII, people were becoming quite keen on shortwave radio listening. People loved to hear Bradman making a century at Lords and shortwave radio was the only way to hear the tests in England. There was a proliferation of shortwave transmitting stations and the signals were definitely better than in the early 30s. Gone also were the difficult to handle sets of the early 30s, which didn’t have very good performance at the best of times, particularly on shortwave. Radio receiving principles had become mature by the late 1930s. The This is an early example of a 7-band AWA mains-powered set. The tuning knob is on the side of the cabinet. 80  Silicon Chip superheterodyne receiving principle using purpose-designed converter valves, such as the 6A7 and later types, overcame most of the problems experienced with the autodyne converter system. There were also quite a few good radio frequency (RF) pentodes such as the 6D6 and its successors. These valves in particular made the task of designing a set capable of good RF performance so much easier than it had been in the past. Also, the problems with detectors and audio stages had been solved several years beforehand with the advent of good, indirectly heated valves. Service information on the first 7-banders appeared in the 1940/41 Australian Official Radio Service (AORS) Manual. It is strange that the first ones appeared during the war when domestic radio production was severely restricted. Probably they had been designed before the war and were already in production when war was declared. By the time the 7-banders came onto the market octal valves had largely replaced the pre-octal valves, even though many of them were the same valves with a different base. So what was it that caused these sets to really stand out from the crowd? First, they had attractive but conservative timber cabi­nets, not tizzy like some other manufacturers’ products. The cabinets were well made and strong. And there was a choice of table sets, consoles and, ultimately, radiograms, all of which looked the part. Second, they were quite sensitive, having a tuned RF stage. Although RF stages had always been desirable in receivers intend­ed for long-range reception, they were not always included due to the extra cost. Where This restored AWA 617T table set has very conservative styling. Note the complex tuning dial. multi-band operation was required, the extra cost was considerable. These sets would certainly not have been cheap. Third, they covered all frequencies from 540 kilohertz (kHz) to 22.3 megahertz (MHz). This feature was uncommon on other brands. This meant that these sets were in demand as monitoring receivers for the HF communications were used by rural fire brigades. A variety of frequencies were used – eg, during the 1960s, frequencies ranging from 2160kHz to 3158kHz were employed by the Emergency Fire Services of South Australia. Other states may have used slightly different frequencies, with Victoria using a frequency as high as 3848kHz for fire front use. A few years earlier higher frequencies were used – around the six megahertz area. People in the outback could also listen to various Flying Doctor radio stations which used frequencies from 1600kHz to around 8830kHz. In addition, they could eavesdrop on other HF radio networks. European migrants bought these sets too, so that they could hear broadcasts from home in their own language. I am led to believe that the remote opal mining town of Coober Pedy in out­back South Australia had a large number of these sets. They really needed a receiver much better than the norm. The nearest AM broadcast stations (540kHz to 1600kHz) were many hundreds of kilometres away and the shortwave radio stations that migrants listened to were thousands of kilometres away. Sets such as these also caused many people (like me) to become interested in amateur radio, as I could hear amateurs on the various radio bands. Amateurs in the 40s, 50s and 60s operat­ed on AM or Morse code, and the voice transmissions were easily picked up This is the rear view of the restored model 617T table set shown at the top of the page. It features extensive shielding of the valves and IF stages. MAY 2001  81 on these radios. In fact, some of these receivers were still being used in this way into the late 1980s. Band-spread tuning Finally, the four highest frequency bands had the deluxe feature of bandspread tuning which made picking up remote sta­tions so much easier. Conventional dual-wave receivers tuned from 6MHz to 18MHz in one go, a total of 12MHz, whereas the biggest frequency sweep with the seven banders is 6.1MHz on the third band which tunes from 3.6MHz to 9.7MHz. On the highest frequency band, the tuning range is 17.7MHz to 22.3MHz, a sweep of just 4.7MHz. The dial tuning mechanism has a reasonable reduction drive and a large tuning knob. So it is a good receiver to tune, even on the highest frequency band. All in all, they were (and are) a pleasing set to use. Common characteristics This unrestored 617C console model will be an impressive set when the cabinet is refinished. AWA had a real winner and cashed in on the desires of lis­teners in the 1940s and 1950s. While the AC models were probably much more popular than the battery and vibrator models, the latter would have been keenly sought in remote locations. And while the battery and vibrator models may have been a little less sensitive, the opportunity to put up a larger antenna in remote areas would have more than compensated. All models had about the same tuning range, although the exact coverage on each band did vary a little. Cabinet styles varied over the time that this marque was produced, as can be seen from the photos. I even saw one table model in an antique shop with a leather covering over the timber. Alignment difficulties This is the rear view of the unrestored 617C console. Note the 12-inch electrodynamic speaker and its associated transformer. 82  Silicon Chip The dial mechanism is a bit of a monster, with the dial being attached to the cabinet. The band-change mech­anism is connected directly to the switch but the band indicator is on the dial scale and is connected via a cord and spring mechanism to the band-switch. AWA recognised the difficulty of aligning the tuned cir­cuits in the sets with the dial scale floating around and devised a method of aligning them with the dial scale removed. A pointer is positioned over the edge of the dial MAY 2001  83 The AWA 7-banders were deluxe sets with band-spread tuning and an RF stage. Some models even had push-pull 6V6GTs in the audio output stage. This is the front view of an unrestored 805GZ radiogram chassis. Note the rather elaborate tuning dial. drum which has a scale from 0-180° around one half of the periphery. The alignment details describe how to set the dial drum at a particular degree mark and then adjust a designated coil, etc. The alignment details are not in the AORS manuals, with the exception of volume six (1947) which has sufficient data so that the job can be done on all models. There are 19 adjustments in the aerial, RF and oscillator circuits. This is not an alignment task to be undertaken lightly unless you have the instruments and knowledge to do it all. It is a laborious task too. The intermediate frequency (IF) is 455kHz. Because of the RF stage, image problems are not severe, even on the higher frequencies. Battery and vibrator models The battery and vibrator models were basically the same. In a number of instances, the only difference was 84  Silicon Chip whether a vibrator power supply or a battery cable was plugged into the set. The first models had a valve line-up as follows: 1D5G RF; 1C7G converter; 1D5G IF; 1K7G detector and first audio; 1H4G audio driver and 1J6G class-B push-pull audio output. The 1J6G is capable of giving 2W of audio out so even as a battery set it was capable of impressive performance. In the table models, a 7-inch speaker was used which would have been quite effective. However, the 12-inch speaker in the console models, which had a decent baffle, would have been even more impressive. On batteries, the receivers used a 2V wet cell for the valve filaments and three series-connected 45V batteries which gave 135V. Bias was obtained for individual stages by tapping a 9V bias battery in the earliest sets. Some later units only required a 4.5V bias battery. One or two models were vibrator only and due to the way that the filaments were arranged in series across the 6V battery, it was possible to do away with the bias battery altogether. Most battery/vibrator models were 6-valve sets and used the 1J6G as the audio output. A few sets used the more conventional 1940s arrangement and had a 1M5G RF, 1C7G converter, 1M5G IF and 1K7G detector and first audio, followed by a 1L5G audio output. Certainly, this would not have had as much audio sting as the 1J6G but the current drain would have been less and the audio would have still been quite adequate. The AC models The RF sections of the AC models are virtually identical, with only small variations. The audio stages are different, depending on whether the particular set was a table, console or radiogram model. The table units were 6-valve sets using a 6U7G RF, 6J8GA converter, 6U7G IF, 6G8G detector and first audio and 6V6G audio output. Console models used the above valve line-up but I am not sure if in some instances they had a push-pull pair of 6V6G valves in the audio output. The radiograms certainly did use a more elaborate audio circuit. A typical valve complement was a 6SQ7GT as the detector and first audio, followed by 6SJ7G phase splitter and push-pull 6V6G valves in the audio output. Some models had a tuning-eye indicator (6U5/6G5) which was mounted behind a hole in the dial back-plate. The table and console models have the chassis mounted hori­ zontally, in the conventional manner. The dial scale (point­ er) moves horizontally across the dial, with station and frequency markings at right angles to the scale, as is also convention­al. Mechanically, the radiogram chassis dial mechanism is mounted in the same way as the table and console models. However, because the chassis is mounted so that one end of it is towards the user (as if mounted vertically), the scale “appears” to move vertically. Because of the way the chassis is mounted, the dial markings are printed in the same plane as the scale so that they can be read. Technical details While there is an oscillator coil and suitable adjustments for each frequency range, the same does not happen with the aerial and RF coils. If every range had a core and a trimmer for each coil, there would be six adjustments. For seven bands that would be 42 adjustments. As there are only 19 adjustments, you can assume that some compromises have been made. The complexity of the receiver in this area can be seen in the circuit accompanying this article. There were compromises in the design and some tuned cir­cuits are not tuned for optimum performance. However, any tuning inadequacy is compensated for by brute force amplification, with six valves instead of the normal five. It’s not a method I par­ticularly like but it works. As mentioned earlier, it is a complex job aligning the tuned circuits so I’d suggest leaving them alone unless you really know what you are doing. Someone that you know may be able to assist by aligning the set for you if you feel it is necessary. On the other hand, the IF stage is quite conventional and can easily be aligned. In my 617T, I found that the audio output had noticeable distortion. To overcome this, I modified the audio output stage slightly. On the speaker, I earthed the bare wire from the voice coil to the frame. The negative lead of C56 was lifted off earth and a wire connected to it and run to the insulated wire on the voice coil. A small connector was placed near the speaker plug. This improved the audio quality noticeably. It can always be put back to standard if need be. It seems to me to have been a mistake that some form of negative feedback had not been incorporated in such a quality receiver. Technical restoration The components in these receivers appear to remain in good order after many years of use. Although the AWA black “moulded mud” paper capacitors are considered unreliable, I’ve found them to be fairly reliable if there are no cracks in the moulding. I still replace any critical ones such as AGC bypasses, the audio interstage coupling capacitor, the output valve plate capacitor to earth and RF bypasses on the HT line. The main area where you hope to avoid replacing com­ ponents is around the coil and band-switch assembly. If you do, fine needle-nose pliers will be essential. The electrolytics should also be check­ed, although a surprising numb­er of these are still in good order in my experience. The valves should be checked by replacement if possible. Only rarely do I need to replace valves, averaging around one valve per radio restored. Summary The AWA 7-banders were a significant series of battery, vibrator and AC receivers. They were designed to give the best performance possible over a wide tuning range. They looked good, performed well and were easy to operate. They filled an important niche in the market and some of these sets are in use even today rather than just on display as ornaments. They are not particularly common as not everyone could afford one, as they would have been at the top end of the market. However, because of the calibre of the sets, it is likely that ELECTRONIC VALVE & TUBE COMPANY The Electronic Valve & Tube Company (EVATCO) stocks a large range of valves for vintage radio, amateur radio, industrial and small transmitting use. Major current brands such as SOV-TEK and SVETLANA are always stocked and we can supply some rare NOS (New - Old stock) brands such as Mullard, Telefunken, RCA and Philips. Hard to get high-voltage electrolytic capacitors and valve sockets are also available together with a wide range of books covering valve specifications, design and/or modification of valve audio amplifiers. PO Box 487 Drysdale, Victoria 3222. Tel: (03) 5257 2297; Fax: (03) 5257 1773 Mob: 0417 143 167; email: evatco<at>mira.net New premises at: 76 Bluff Road, St Leonards, Vic 3223 Truscott’s êRESELLER FOR MAJOR KIT RETAILERS êPROTOTYPING EQUIPMENT êCOMPLETE CB RADIO SUPPLY HOUSE êTV ANTENNA ON SPECIAL (DIGITAL READY) êLARGE RANGE OF ELECTRONIC COMPONENTS Professional Mail Order Service Truscott’s Amidon Stockist ELECTRONIC WORLD Pty Ltd ACN 069 935 397 Ph (03) 9723 3860 Fax (03) 9725 9443 27 The Mall, South Croydon, Vic 3136 (Melway Map 50 G7) email: truscott<at>acepia.net.au www.electronicworld.aus.as MAY 2001  85 P.C.B. Makers ! If you need: •  P.C.B. High Speed Drill •  3M Scotchmark Laser Labels •  P.C.B. Material – Negative or Positive acting •  Light Box – Single or Double Sided – Large or Small •  Etch Tank – Bubble •  Electronic Components and Equipment for TAFEs, Colleges and Schools •  Prompt and Economical Delivery •  FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE We now stock Hawera Carbide Tool Bits KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422  FAX (03) 9499 2381 ALL MAJOR CREDIT CARDS ACCEPTED 86  Silicon Chip This under chassis view of an 805GZ radiogram clearly shows the band-switch details. Note the modification with the old speaker field coil (bottom of chassis). a greater percentage of the production run has survived com­pared to more common receivers. They are not an easy set to service or to align. A complete service would have been quite expensive. The audio quality could have been improved with a slight modification to provide negative feedback. And although I am critical of the lack of tuned circuit adjustments, this does not seem to compromise the operation. AWA deemed that these sets had their day and didn’t produce any new models after 1950. However, the 617T appears to have been produced up until at least 1952. In 1953, AWA produced a scaled down version in the 1548MA. This is a 5-band 6-valve (including tuning eye) receiver. It has the same tuning range as the earlier receivers but has no RF stage. Also, it has the noisy 6BE6 converter so I believe it would not be anywhere near as good as the earlier sets. Hotpoint-Bandmaster also sold these sets, rebadged with their name. Overall, there were around 45 separate models with either AWA or Hotpoint-Bandmaster name badges. These are a very collectible series of receivers. My 617T is permanently on display. It is also used as our entertainment receiver on broadcast SC and shortwave bands. A safe, convenient multi-voltage supply for cars POWERPACK At last: a handy little project that will safely power just about any portable device from the lighter socket in your car. It can provide preset voltages of 3V, 6V, 6V. 9V & 12V. You can also use it to provide a well-regulated output from low-cost DC plugpacks. By PETER SMITH P owering electronic equipment of the alternator to respond instanta- transients, occur when the ignition from a vehicle’s electrical sys- neously to load changes. The response switch is turned off while current tem can be a risky business, time of an alternator is bound by the is flowing in inductive loads (windscreen wipers, alterespecially if the equipment nator field coil, etc.) wasn’t originally designed PowerPack Feature These are negative for in-car use. s  3/6/9/12V switcha in direction, with Large positive and negble output at 1A maxim um a similar energy to ative voltage transients  Operates from ca r cigarette lighter sock the positive swing occur regularly during et or DC plugpack  Protects sensitive devices from voltage tra of load dump tran“normal” operation of nsients  Automatic low batte sients. vehicle electrical systems. ry cut-out prevents ba ttery damage  Easy to read volta Switching spikes The alternator is unge selection from inductive loads doubtedly the main cullike windscreen wipprit. Load dump traners and power winsients, which occur when dows generate even heavy loads are switched higher voltages, as much as 200V off, can cause the alternator’s output to forces of mechanical inertia and the swing to as much as 100V for several long time constant of the excitation positive and negative. winding. milliseconds. These transients have much lower Other nasties, called field decay energy in comparison to load dumps This effect is caused by the inability MAY 2001  87 Opened-out view of the supply, immediately before final assembly. The hardest part is probably drilling the holes for the LEDs and cutting the slot for the switch – these must be done very accurately . However, National Semiconductor (and other companies) have developed versions specifically for the automotive market, and we’ve based this project around one of them – the LM2941 low dropout adjustable regulator. The LM2941 provides “out of the box” protection against line transients and reverse battery connection, as well all the familiar regulator features such as thermal and overload protection. How it does its stuff and field decay transients. Automotive regulator We’ve all seen those switchable plastic “regulators” that are either built into a cigarette-lighter plug or are housed in a small plastic case which plugs into the lighter. Believe it or not, some of the cheaper ones we’ve seen simply contain a resistive divider! They take a stab in the dark at the likely output current and assume “near enough is good enough”. It ain’t! Would you really trust your $200 personal CD player to one of these devices? Even the better ones with some form of regulation can’t cut the mustard. Standard linear 3-terminal regulators such as the 78XX series do not provide adequate protection in this environment. As you can see from the circuit diagram of Fig.1, there’s really not a lot to the PowerPack. Input voltage is applied to either CON1, the car input, or CON2, the plugpack input. Diode D1 provides reverse polarity protection on the plugpack input. A Schottky-type diode is used here to minimise forward voltage losses. Although REG1 incorporates reverse polarity protection, we’ve included D1 on the plugpack input Fig.1: the heart of the PowerPack is an LM2941 automotive regulator (REG1). We have combined it with a comparator to shut off the circuit for input voltages below 11.5V, to avoid excessive discharge of the car’s battery. 88  Silicon Chip Zener diode ZD1 forms a simple shunt regulator, powering IC1 with +5V, while the series LED5 gives a “power on” indication without additional current drain on the input. Diode D2 has been included solely to protect the pin 2 input of IC1 when insertion of the plugpack jack causes pin 2 to be pulled high via the 51kΩ resistor. Construction In order to squeeze everything into an easy-to-carry case, we’ve resorted to a rather unconventional mounting method for the PowerPack’s PC board. It simply sits atop the integral slots in the diecast case and is held in place by the lid and four acrylic feet. As the first step, check that the blank PC board rests snugly on top of the integral guides on all four sides 51k to protect the input filter capacitor tery was completely discharged, due as well. After all, you don’t want it to the PowerPack being inadvertently spewing its insides all over the PC left on indefinitely, it could damage board just because you accidentally the battery. got the supply connections wrong. In normal operation, IC1’s outA bi-directional transient suppresput (pin 1) is close to 0V, holding sor, TVS1, clamps all transients to the regulator in the ON state. If the less than ±150V, protecting the input voltage on pin 2 falls below that on capacitor somewhat and extending pin 3, the output at pin 1 swings to the inbuilt protection in the regulator +5V, switching the regulator off. The to well over ±1100V. switching, or “threshold”, point is set by the ratio of the resistors connected On the output side, a 220µF capacto pin 3. The 360kΩ resistor from pin itor provides the required filtering. 1 to pin 3 provides a small amount Unlike most other linear regulators, of hysteresis to prevent the output the ESR (equivalent series resistance) oscillating about the threshold point. of the LM2941 output capacitor is critical for stable regulator operation. Inserting a plug in the plugpack input (CON2) disconnects one end The output voltage is programmed of the 51kΩ resistor from the 0V line, by the ratio of the two resistors conforcing pin 2 of IC1 high and effectivenected to the ADJ pin (see “Getting ly disabling the cut-out circuit. This other output voltages” on page 93). allows use of 6V and 9V DC plugpacks Slide switch S1 allows selection of on the lower voltage selections. four different values for the top leg of the voltage divider, providing outputs of 3V, 6V, 9V and 12V. LEDs1 - LED4 give indication of the PLUGPACK selected voltage range. We’ve used INPUT a different value current limiting CON2 resistor with each of the LEDs so S1 as to keep the brightness roughPOWER ly equal at each setting. REG1 is a “low dropCON1 TVS1 out” regulator, meaning _ + 0.1mF in this case that we only D1 need about 0.5V (at 1A 100k load) more at the input 10k 1.8k D2 10mF than the output to mainF1 + tain regulation. For lower 22k current levels, the drop360k 100k LED1 1000mF out voltage is even less. 1 IC1 For example. with a load LM393 of 100mA, only 12.1V is 8.2k required on the car input A 12V K (CON1) to provide 12V at 680W + LED2 1 the output. 2 470W 3 9V Note that about 12.5V 4 5 S2 LED3 3.6k would be required on the 1k 110W plugpack input for the 270W 6V 1.3k same result, allowing for + LED4 56W the voltage drop across D1 68W and some ripple. 3V 470W 220W 220mF REG1 100mF 5.6k ZD1 1N 4148 + ACRYLIC FEET MOUNTED ON SOLDER SIDE (SEE TEXT) CABLE TIE CASE GROMMET _+ _+ OUTPUT IC1, an LM393 voltage comparator IC, forms the heart of the low battery cut-out circuit. It has been included to prevent discharge of the car’s battery below about 11.5V. If the battery was discharged below this level, there is a fair chance it will not be able to start the motor. And ultimately, if the bat- CON3 _ TO CIG LIGHTER PLUG Low battery cut-out LED5 Fig.2: use this diagram and the photo above as a guide when installing the components onto the PC board. Note the special comments in the text about mounting the 5-terminal regulator. MAY 2001  89 Parts List – PowerPack 1 PC board coded 11305011, 108mm x 59mm 1 115mm x 65mm x 30mm (LxWxH) diecast metal case (Jaycar Cat HB5036) 1 DPDT PC-mount miniature toggle switch (S1) (Jaycar Cat ST-0565) 1 DP4T miniature slide switch (S2) (Altronics Cat S-2040) 1 2.5mm PC-mount DC jack socket (CON1) (Altronics Cat P-0621) 2 2-way 5mm pitch miniature PC-mount terminal blocks (CON2, CON3) 2 M205 PC-mount fuse clips 1 M205 2A slow-blow fuse 1 Plugpack extension cable (DSE Cat M-9601) OR 1 Plugpack cable and 8 adaptor plugs (DSE Cat M-9603) 1 Cigarette lighter plug 4 Clear acrylic feet (DSE Cat H-1740) 1 3/16" x 5/16" rubber grommet (“Zenith” brand, from hardware stores) 1 2m medium duty 3.5A figure-8 cable 1 M3 x 6mm cheese head screw, nut and star washer Semiconductors 1 LM2941CT low dropout voltage regulator (REG1) (DSE Cat Z-6620) 1 LM393 dual comparator (IC1) 1 1N5822 3A 40V Schottky diode (D1) (Altronics Cat Z-0042) 1 1N4148 small signal diode (D2) 1 1.5KE33CA Transient Voltage Suppressor (TVS1) (Farnell Cat 166-492 or 752-307) 1 1N751A 5.1V 0.5W Zener diode (ZD1) (Altronics Cat Z-0314) 5 5mm high brightness red LEDs (LED1-5) (Jaycar Cat ZD-1793) Capacitors 1 1000µF 50VW PC electrolytic 1 220µF 25VW PC electrolytic 1 100µF 25VW PC electrolytic 1 10µF 25VW PC electrolytic 1 0.1µF 100V MKT polyester (Code 104 or 100n) Resistors (0.25W, 1%) 1 360kΩ 1 160kΩ 1 8.2kΩ 1 3.6kΩ 1 270Ω 1 220Ω 2 100kΩ 1 1.8kΩ 1 110Ω 1 51kΩ 1 1.3kΩ 1 68Ω 1 22kΩ 1 680Ω 2 56Ω 1 10kΩ 2 470Ω Miscellaneous 5cm 22AWG (0.71mm) tinned copper wire Cardboard for insulator Non-acidic silicone sealant of the case. Note that the copper side faces up, so the switch and LEDs will protrude through the bottom (which becomes the top!). If the board falls into the case on any side, it is undersized; compare it with the dimensions of the PC board pattern shown in Fig.7. Referring to the board overlay diagram in Fig.2, begin construction by installing the three wire links and all resistors. You will notice from the photographs that some resistors are mounted vertically instead of horizontally. These are identified on the overlay diagram by a circle (the body) and line. Next, install diodes D1, D2 and ZD1 90  Silicon Chip and the transient suppressor TVS1, taking care with their orientation. The three connectors CON1- CON3 should be mounted next, followed by toggle switch S1, slide switch S2 and the fuse clips for F1. Be sure that these components are seated squarely against the PC board before soldering. Note that the cable entry side of CON1 faces the adjacent 10µF capacitor. The five capacitors can be installed next. All the electrolytic types are polarised, so check their orientation carefully. The 1000µF capacitor is mounted horizontally, so bend its legs over at 90° (at about 3mm from the body) and align it as shown on the overlay diagram before soldering. To complete the first part of the assembly, install IC1, aligning pin 1 as shown on the overlay diagram. Now set the board aside for a moment and reach for your trusty drill! Pass the silver cheese, please Altogether, 10 or more holes need to be drilled in the case sides, ends and bottom. All holes should be marked with a sharp centre punch before drilling. For good results, start with a small drill size for the initial hole, then drill with several intermediate sizes before finishing with the indicated size. The easiest way to get everything in the right spot is to photocopy the drilling template (Fig.3) and label (Fig.6), cut the pieces out and tape to the indicated face of the case. The rounded edges of the case make exact alignment of the templates difficult – patience, patience! Centre punch each “hole” directly through the template, remove the template and drill. Make sure that the surface around the internal side of the regulator mounting hole is smooth and free from rough edges after drilling. If necessary, de-burr the hole. The slot for the slide switch (S2) can be made by drilling a series of holes inside the marked outline, then filing out with a fine jeweller’s file. Test-fit the PC board as you go to make sure that the switch is going to line up with your handiwork. Did we mention there is a tricky bit, involving a rabbit, hat and stick? Would you believe a blind screw? Our challenge was to devise a method of mounting the LM2941 regulator The regulator (right side of board) is shown here soldered in place – but DON’T DO IT LIKE THIS JUST YET!! The regulator is bolted to the case, the PC board is slipped over it THEN it is soldered. SWITCH (S1) THIS END REG1 Æ3 ACCESS HOLE Æ8 S1 HOLE SWITCH (S1) THIS END Æ6 Æ8 Fig.4: this diagram and the photo above shows how the 5-terminal regulator has its legs bent and how it is secured inside the case (see text). GROMMET HOLE DC SOCKET HOLE Fig.3: use these diagrams as a guide when drilling the diecast case. Note that the access hole does not line up with the regulator mounting screw (see text). (REG1) in such a confined space. As the PC board mounts “upside-down” in the case, there is no access to the regulator to screw it down once the board is installed. To solve this problem, we placed a screwdriver access hole on the opposite side of the case. Note that this hole is not directly in line with the regulator hole, as one of the LEDs effectively blocks that path. Begin by bending the regulator leads into shape so that it will assume a position like that shown in Fig.5. when inserted in the PC board. This photo, taken before the front panel was applied, shows the “plugpack” input socket and power switch on the top of the box. To reduce the possibility of the leads breaking off, don’t bend them right at the body of the regulator; allow a couple of mm space from the body. Take your time with this step, as radical bends that need to be undone might mean a replacement LM2941... Temporarily screw the regulator to the case as shown in Fig.4 (head of screw goes inside, nut and washer outside), and gently slide the PC board into position, making sure that all five regulator leads enter their correct PC board holes. Adjust the bends in the leads if necessary so that the board rests against the integral guides without applying any pressure at all to the regulator leads. There should also be approximately even spacing between all edges of the PC board and the sides of the case. Once you are happy with the position, solder REG1 in place. From now on, you’ll need a small Philips head screwdriver with a strongly magnetic tip in order to insert and remove the regulator mounting screw though the access hole on the opposite side of the case. Remove the screw now and remove the board from the case. OK, we’re almost there. Insert all the LEDs into the PC board, but don’t solder them or trim the leads just yet. Note the flat (cathode) side on the LED body is aligned as shown in the overlay diagram of Fig.2. Now slip the board back into place in the case and manipulate the LED leads protruding through the back of the PC board so as to place each LED in its hole in the bottom of the case. Adjust each LED so that its tip is flush with the case surface – easily achieved if the case itself is sitting on a flat surface – then solder in place. At this point, you should trim all component leads so that they are no more that 2mm above the surface of the PC board. This is very important, Fig.5: this chart shows the predicted maximum output current at the four selected output voltages, for variations in the input voltage. MAY 2001  91 The PC board really is a snug fit in the case – in fact, the odds are that you will have to file a little off commercial boards to make them fit. You can clearly see the acrylic stick-on feet in this picture. as leads much longer than this will short out on the lid of the case when we put the whole shebang together. Remove the board once more and glue the 1000µF capacitor to the PC board using non-acidic silicone sealant. Now is a good time to check that you’ve inserted the 2A fuse, too. Pre-flight checks It’s a good idea to perform some basic function tests at this point. At a minimum, you will need a digital multimeter and a 12V DC plugpack or similar power source. Before applying power, check for short circuits between the positive (+) and negative (-) terminals of both CON1 and CON2. With no load connected to the output, apply power and check that the “power” LED illuminates. If it doesn’t, check the orientation of D1, ZD1 and LED5. Next, connect your meter across CON3 and measure the output voltages for all four positions of the slide switch. Assuming you have sufficient input voltage, all measurements should be Resistor Colour Codes     Value    4-Band Code (1%)   5-Band Code (1%)     360kΩ orange blue yellow brown orange blue black orange brown     160kΩ brown blue yellow brown brown blue black orange brown     100kΩ brown black yellow brown brown black black orange brown     51kΩ green brown orange brown green brown black red brown     22kΩ red red orange brown red red black red brown     10kΩ brown black orange brown brown black black red brown     8.2kΩ grey red red brown grey red black brown brown     3.6kΩ orange blue red brown orange blue black brown brown     1.8kΩ brown grey red brown brown grey black brown brown     1.3kΩ brown orange red brown brown orange black brown gold   680Ω blue grey brown brown blue grey black black brown     470Ω yellow violet brown brown yellow violet black black brown     270Ω red violet brown brown red violet black black brown     220Ω red red brown brown red red black black brown     110Ω brown brown brown brown brown brown black black brown     68Ω blue grey black brown blue grey black gold gold     56Ω green blue black brown green blue black gold gold   92  Silicon Chip Fig.6: actual size front panel artwork. It goes on the underside of the case which then becomes the top. Use a photocopy of this as a template when drilling the underside of the case. within 0.1V of the advertised value. For example, when the “6V” position is selected, the output should be between 5.9V and 6.1V. If all voltages are incorrect, suspect a problem with the 1kΩ resistor or the associated connection to pin 1 of the regulator. If some voltages are OK but others are not, check that you have the correct resistor values in the feedback circuit associated with the problem voltage; refer to the circuit and overlay diagrams here. If you have a variable power supply, you can also check that the low battery cut-out circuit works. Starting from above 12V, slowly decrease the input voltage. At around 11.5V, REG1 should be switched off by IC1, disconnecting the output. Now increase the voltage slowly. At around 12.2V, REG1 should be switched on again. We won’t do any testing with a load connected just yet. Let’s continue on with the construction... Construction (episode 2) Fit the rubber grommet to the case. Some trimming with a sharp knife Getting other output voltages Setting the output voltage on the LM2941 is a fairly simple matter. Referring to Fig.8, you can see that all we need to do is set the ratio of R1 to R2 according to a simple formula. The PowerPack uses a fixed 1kΩ resistance for R1 and a switchable resistance for R2, selected via switch S2. For example, suppose we would like to produce 4.5V instead of 3V at the bottom-most switch position. We already know R1 (1kΩ), so we calculate R2 by massaging the formula in Fig.8 a little, so that: R2 = 1kΩ x (4.5/1.275 - 1) = 2.529kΩ 2.529kΩ is obviously not a “standard” resistor value, so we select two standard values (to be placed in series) that are the closest to the calculated value, namely 2.4kΩ and 130Ω. To check what the output voltage will be for our selected values: VOUT = 1.275 x (1kΩ + 2.4kΩ + 130Ω/1kΩ) = 4.50075V (Close enough!) The 2.4kΩ and 130Ω resistors are then installed in place of the 1.3kΩ and 56Ω resistors to get 4.5V at the bottom-most switch position. For more detailed information on the LM2941, you can download the data sheet from the National Semiconductor web site at http://www.natsemi.com If you’ve read the datasheet already and want to know how the PowerPack can provide a 3V (or 4.5V, for that matter) output when the data sheet specifies 5V as the minimum voltage, we’ll have to own up – we’ve made some assumptions about the internal workings of the regulator. We recommend keeping the input voltage (measured at the IN pin) above about 6V, and to be conservative with output loading at these low output voltages. Fig.7: the PC board must have the exact dimensions of the pattern shown here in order to be a snug fit into the specified diecast case. will be required to get a neat fit. Next, we’ll prepare and install the two cables. For the output side, we’ve used a plugpack extension cable for the job, as it already has a moulded connector on the end ready to accept all the various plugpack connector tips. The other end of this cable probably has crimped connections; cut these off and pass the end through the grommet and strip and tin it. For the car connection side, simply solder one end of the length of figure-8 cable to the cigarette lighter plug (wire with the white trace goes to the tip), and pass the other end through the same grommet and strip and tin. Hook up the cables to their respective terminal blocks (CON1 and CON3), connecting the wires with the white traces to the positive (+) sides. Secure a cable tie around both cables at the point they exit the grommet (inside the case) to provide strain relief. Apply a thin smear of heatsink compound to the back of the regulator as well as to the area that it will contact in the case. The metal tab of the regulator is connected to ground, so we don’t need to isolate it from the Fig.8: R1 and R2 are used to set the output voltage of the regulator according to the formula shown here. case. This significantly improves heat transfer and makes it much easier to get the board in and out of the case. Slip the assembly into the case, complete with attached cables. You may need to adjust the cable position and length in the case so as to avoid fouling the LEDs and slide switch, etc. Check that the board is correctly seated on the guides and then screw the regulator to the case. Turn the nut on the outside rather than the screwdriver so as to tighten up the works without applying a twisting force to the regulator package. If you wish, you can cut or file the screw flush with the nut for a neater appearance. Ta-Da! The last step is to secure the board inside the case. To do this, stick four acrylic feet onto the PC board (copper side) in positions roughly as shown in blue outline on Fig.2. We had to cut down one foot with a sharp utility knife so that it didn’t sit over the top of component leads. Next, cut out a piece of cardboard (a manilla folder is ideal stock) to fit neatly inside the inner ridge of the case lid. The lid should be an almost “perfect” fit on the case, meaning that it shouldn’t sit proud of the case by any appreciable amount. Don’t install the seal that is supplied with the case. Screw down the lid and proceed to the testing phase! When you’re sure that your Power-Pack is working properly, remove the lid and apply a daub of non-acidic silicone sealant to each corner of the PC board, right at the edge – in effect “gluing” the PC board to the case. This does make it a little harder to remove the board in future, but it is a necessary evil – it prevents the PC board from moving whenever the switch is toggled or the DC plug is inserted. Without this, the regulator leads and solder joints would take all the strain. SC MAY 2001  93 Want to do your own home wiring? Repair appliances? Replace a power point or light fitting? YOU can help make it happen! Ever since the subject was first raised in SILICON CHIP, readers have been asking how we in Australia could convince our politicians to change the rules which currently make it illegal for most people to even remove the screws in a light fitting or power point so they can paint under it! Here’s your opportunity to help change the rules so that anyone who feels competent can legally do their own electrical wiring, just as they have done for years in New Zealand and many other countries. We need to abolish the “closed shop” that state governments around Australia are presently maintaining through restrictive state legislation. Photocopy the “Statement of Will” form, insert the name of your state in each of the spaces provided, and circulate it among your friends, family and workplace colleagues. Ask each signatory to circulate additional copies among their friends and family, etc. If you have sufficient commitment to the cause, obtain signatures in public places, such as shopping areas, entries to train stations, etc. This is, after all, an issue of democracy that concerns not only electrical and electronic engineers, technical officers, technicians and hobbyists, but all householders. We must aim for a maximum number of signatories if we are to be successful. Send the completed forms to SILICON CHIP and we will forward them to the relevant state Ministers, along with copies of published correspondence, editorials, etc. The Ministers will be informed that their response, or a report that they apparently decided not to respond, will be published in SILICON CHIP! While in some ways similar to a petition, it must be our aim that it is not treated as a petition. If you have access to the Internet, go to http://www.rag.org.au/rag/petqld.htm and study the onerous requirements that must, by law, be observed in order to produce a petition that a state parliament will accept. Then click on Creative Petitioning at the bottom of the page to learn how easily parliaments can disregard petitions. Our state parliaments have refused to accept petitions that had many tens of thousands of signatures on them, simply because the form of the petition was not exactly correct. If you don’t have access to the Internet, suffice to say that conventional petitions to our state and federal parliaments are largely a waste of time. In addition to circulating the “Statement of Will” form, write an individual “MY WILL” letter, similar to the one below, to your local state member of parliament and encourage others to do the same. Don’t forget to date the letter and provide your name and address so the parliamentarian can confirm that you are a constituent. 94  Silicon Chip Dear Sir (or Dear Madam), I know that it is my duty to keep you informed of MY WILL on any matter that comes before Parliament, or that should come before Parliament. IT IS MY WILL that you take immediate action to end the “closed shop” that electricians enjoy in relation to “electrical work”, and that you promote the replacement of current electricity related legislation with legislation that is essentially equivalent to the New Zealand Electricity Act and Regulation, which allows householders to do their own “electrical work”, including appliance repairs and the installation of fixed wiring. Yours Faithfully, (signed) Above all, don’t enter into written argument with a politician. Politicians are masters in the art of avoiding what they don’t want to face up to, and become experts in manipulating words to their own benefit. Should your parliamentary member try to sidestep (and they are extremely adept at doing so) taking positive political action on your behalf (ie, they rattle on about what his/her party is or is not doing instead of agreeing to act in accordance with your WILL), you simply write back and state: Dear Sir (or Dear Madam), Further to my letter of (insert date of your original letter) and your reply of (insert date of their inadequate or fob-off reply), and in accordance with my lawful obligation to keep you informed of MY WILL, I again inform you that IT IS MY WILL that you take immediate action to end the “closed shop” that electricians enjoy in relation to “electrical work”, and that you promote the replacement of current electricity related legislation with legislation that is essentially equivalent to the New Zealand Electricity Act and Regulation, which allows householders to do their own “electrical work”, including appliance repairs and the installation of fixed wiring. Yours faithfully, (signed) If you have access to the internet, go to http://www.rag.org. au/ rag/mywillet.htm and learn about the background and potential power of the “MY WILL” letter. For each “MY WILL” letter you send to your parliamentary member, send a copy to SILICON CHIP so we can monitor the level of involvement in the campaign for reform. If your local parliamentarian shows interest in the issue, provide them with copies of relevant SILICON CHIP published correspondence and editorials, etc, or ask them to contact SILICON CHIP directly. Come on SILICON CHIP readers, you asked us to help you with this one – if you don’t want more and more restrictions, get those signatures rolling in! Statement of Will: Reform of Electrical Legislation The primary responsibility of parliamentary representatives and governments is to do the will of the people. Electors must make their will known to their parliamentary representatives and governments. We, the undersigned, hereby assert that it is our will that the government of *________________________ acknowledge that current electrical safety legislation unjustifiably discriminates against ordinary householders as well as electrical and electronic engineers, technical officers, and technicians and that the effect of its enactment has been, and continues to be, to protect a monopoly for licensed electricians. We also hereby assert that it is our will that the government of *___________________________________ acknowledge that the potential dangers of “electrical work” are grossly exaggerated by the state electrical licensing boards and that the New Zealand electrical fatalities and accidents statistics belie these claims of dangers. We further assert that it is our will that the government of *__________________________________________ repeal, in a timely manner, all current electrical safety legislation to replace it with legislation that is essentially equivalent to the New Zealand Electricity Act and Regulation, which allows ordinary householders to do their own “electrical work”, including appliance repairs and the installation of fixed wiring. * (insert state or territory)     Name           Address    Signature 1. ........................................................................ .......................................................................................................................................... ............................................................. 2. ........................................................................ .......................................................................................................................................... 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MAY 2001  95 Silicon Chip Back Issues April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. 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. 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. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. 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. 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. 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 Variable Power Supply; Solar Panel Switching Regulator; 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 – How They Work. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2. 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 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 Disk Drive Formats & Options. November 1991: 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. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. 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. 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 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Valve Substitution In Vintage Radios. 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. 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. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies. 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 Disk Drives. July 1994: Build A 4-Bay Bow-Tie UHF TV Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; 6V SLA Battery Charger; Electronic Engine Management, Pt.10. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple Electronic Die; A Low-Cost Dual Power Supply. 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 Care & Feeding Of Nicad Battery Packs (Getting The Most From Nicad Batteries). 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. November 1990: Connecting 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; A 6-Metre Amateur Transmitter. December 1990: 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. \January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine (Simple Poker Machine); Build A Two-Tone Alarm Module; The Dangers of Servicing Microwave Ovens. August 1992: Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting 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. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Engine Management, Pt.6. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; 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 Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper (For Resurrecting Nicad Batteries); 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. 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. 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. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); How To Plot Patterns Direct to PC Boards. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. December 1994: 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. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. 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. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Windows-Based Logic Analyser. 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. March 1991: 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. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. April 1991: Steam Sound Simulator For Model Railroads; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; A Look At Satellites & Their Orbits. 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. ORDER FORM Please send thethe following back issues: Please send following back issues:      ____________________________________________________________ Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 96  Silicon Chip 10% OF F SUBSCR TO IB OR IF Y ERS OU 10 OR M BUY ORE Note: prices include postage & packing Australia ....................... $A7.70 (incl. GST) Overseas (airmail) ............................ $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. Email: silchip<at>siliconchip.com.au 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. May 1995: 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. 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. 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 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. 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. 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. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. September 1999: Automatic Addressing On TCP/IP Networks; Autonomouse The Robot, Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5; Peltier-Powered Can Cooler. October 1999: Sharing A Modem For Internet & Email Access (WinGate); Build The Railpower Model Train Controller, Pt.1; Semiconductor Curve Tracer; Autonomouse The Robot, Pt.2; XYZ Table With Stepper Motor Control, Pt.6; Introducing Home Theatre. November 1999: Electric Lighting, Pt.15; Setting Up An Email Server; Speed Alarm For Cars, Pt.1; Multi-Colour LED Christmas Tree; Build An Intercom Station Expander; Foldback Loudspeaker System For Musicians; Railpower Model Train Controller, Pt.2. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; How To Identify IDE Hard Disk Drive Parameters. December 1997: 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. December 1999: Internet Connection Sharing Using Hardware; Electric Lighting, Pt.16; Build A Solar Panel Regulator; The PC Powerhouse (gives fixed +12V, +9V, +6V & +5V rails); The Fortune Finder Metal Locator; Speed Alarm For Cars, Pt.2; Railpower Model Train Controller, Pt.3; Index To Volume 12. 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. 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. January 2000: Spring Reverberation Module; An Audio-Video Test Generator; Build The Picman Programmable Robot; A Parallel Port Interface Card; Off-Hook Indicator For Telephone Lines; B&W Nautilus 801 Monitor Loudspeakers (Review). February 1998: Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. February 2000: Multi-Sector Sprinkler Controller; A Digital Voltmeter For Your Car; An Ultrasonic Parking Radar; Build A Safety Switch Checker; Build A Sine/Square Wave Oscillator; Marantz SR-18 Home Theatre Receiver (Review); The “Hot Chip” Starter Kit (Review). April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Adjustable Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator; Build A Laser Light Show; Understanding Electric Lighting; Pt.6. March 2000: Doing A Lazarus On An Old Computer; Ultra Low Distortion 100W Amplifier Module, Pt.1; Electronic Wind Vane With 16-LED Display; Glowplug Driver For Powered Models; The OzTrip Car Computer, Pt.1; Multisim Circuit Design & Simulation Package (Review). October 1995: 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. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­ verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Digital Speedometer & Fuel Gauge For Cars, Pt.2. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; 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. 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. 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. 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 Electric 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 Solving 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); Build The Opus One Loudspeaker System; Simple I/O Card With Automatic Data Logging; Build A Beat Triggered Strobe; A 15-Watt Per Channel Class-A Stereo Amplifier. July 1996: 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. September 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A Waa-Waa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. August 1996: Introduction to IGBTs; Electronic Starter For Fluores­ cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. October 1998: Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled StressO-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Cathode Ray Oscilloscopes, Pt.5. November 1998: The Christmas Star (Microprocessor-Controlled Christmas Decoration); A Turbo Timer For Cars; Build A Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Setting Up A LAN Using TCP/IP; Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. 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-Channel 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. 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; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Glider Operations. April 2000: A Digital Tachometer For Your Car; RoomGuard – A LowCost Intruder Alarm; Build A Hot wire Cutter; The OzTrip Car Computer, Pt.2; Build A Temperature Logger; Atmel’s ICE 200 In-Circuit Emulator; How To Run A 3-Phase Induction Motor From 240VAC. May 2000: Ultra-LD Stereo Amplifier, Pt.2; Build A LED Dice (With PIC Microcontroller); Low-Cost AT Keyboard Translator (Converts IBM Scan-Codes To ASCII); 50A Motor Speed Controller For Models; What’s Inside A Furby. June 2000: Automatic Rain Gauge With Digital Readout; Parallel Port VHF FM Receiver; Li’l Powerhouse Switchmode Power Supply (1.23V to 40V) Pt.1; CD Compressor For Cars Or The Home. July 2000: A Moving Message Display; Compact Fluorescent Lamp Driver; El-Cheapo Musicians’ Lead Tester; Li’l Powerhouse Switchmode Power Supply (1.23V to 40V) Pt.2; Say Bye-Bye To Your 12V Car Battery. August 2000: Build A Theremin For Really Eeerie Sounds; Come In Spinner (writes messages in “thin-air”); Loudspeaker Protector & Fan Controller For The Ultra-LD Stereo Amplifier; Proximity Switch For 240VAC Lamps; Structured Cabling For Computer Networks. September 2000: Build A Swimming Pool Alarm; An 8-Channel PC Relay Board; Fuel Mixture Display For Cars, Pt.1; Protoboards – The Easy Way Into Electronics, Pt.1; Cybug The Solar Fly; Network Troubleshooting With Fluke’s NetTool. October 2000: Guitar Jammer For Practice & Jam Sessions; Booze Buster Breath Tester; A Wand-Mounted Inspection Camera); Installing A Free-Air Subwoofer In Your Car; Fuel Mixture Display For Cars, Pt.2; Protoboards – The Easy Way Into Electronics, Pt.2. November 2000: Santa & Rudolf Chrissie Display; 2-Channel Guitar Preamplifier, Pt.1; Message Bank & Missed Call Alert; Electronic Thermostat; Protoboards – The Easy Way Into Electronics, Pt.3. January 1999: High-Voltage Megohm Tester; Getting Started With BASIC Stamp; LED Bargraph Ammeter For Cars; Keypad Engine Immobiliser; Improving AM Radio Reception, Pt.3; Electric Lighting, Pt.10 December 2000: Home Networking For Shared Internet Access; Build A Bright-White LED Torch; 2-Channel Guitar Preamplifier, Pt.2 (Digital Reverb); Driving An LCD From The Parallel Port; Build A morse Clock; Protoboards – The Easy Way Into Electronics, Pt.4; Index To Vol.13. February 1999: Installing A Computer Network; Making Front Panels For Your Projects; Low Distortion Audio Signal Generator, Pt.1; Command Control Decoder For Model Railways; Build A Digital Capacitance Meter; Build A Remote Control Tester; Electric Lighting, Pt.11. January 2001: LP Resurrection – Transferring LPs & Tapes To CD; The LP Doctor – Clean Up Clicks & Pops, Pt.1; Arbitrary Waveform Generator; 2-Channel Guitar Preamplifier, Pt.3; PIC Programmer & TestBed; Wireless Networking. 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 Compressor; Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12. February 2001: How To Observe Meteors Using Junked Gear; An Easy Way To Make PC Boards; L’il Pulser Train Controller; Midi-Mate – A MIDI Interface For PCs; Build The Bass Blazer; 2-Metre Elevated Groundplane Antenna; The LP Doctor – Clean Up Clicks & Pops, Pt.2. 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. April 1999: Getting Started With Linux; Pt.2; High-Power Electric Fence Controller; Bass Cube Subwoofer; Programmable Thermostat/ Thermometer; Build An Infrared Sentry; Rev Limiter For Cars; Electric Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft. March 2001: Driving Your Phone From A PC; Making Photo Resist PC Boards At Home; Big-Digit 12/24 Hour Clock; Parallel Port PIC Programmer & Checkerboard; Protoboards – The Easy Way Into Electronics, Pt.5; More MIDI – A Simple MIDI Expansion Box. April 1997: 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 1999: The Line Dancer Robot; An X-Y Table With Stepper Motor Control, Pt.1; Three Electric Fence Testers; Heart Of LEDs; Build A Carbon Monoxide Alarm; Getting Started With Linux; Pt.3. May 1997: 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 1999: FM Radio Tuner Card For PCs; X-Y Table With Stepper Motor Control, Pt.2; Programmable Ignition Timing Module For Cars, Pt.1; Hard Disk Drive Upgrades Without Reinstalling Software; What Is A Groundplane Antenna?; Getting Started With Linux; Pt.4. April 2001: A GPS Module For Your PC; Dr Video – An Easy-To-Build Video Stabiliser; A Tremolo Unit For Musicians; Minimitter FM Stereo Transmitter; Intelligent Nicad Battery Charger; Computer Tips – Tweaking Internet Connection Sharing. June 1997: 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; Cathode Ray Oscilloscopes, Pt.10. July 1999: Build The Dog Silencer; A 10µH to 19.99mH Inductance Meter; Build An Audio-Video Transmitter; Programmable Ignition Timing Module For Cars, Pt.2; XYZ Table With Stepper Motor Control, Pt.3; The Hexapod Robot. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers. August 1999: Remote Modem Controller; Daytime Running Lights For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting, Pt.14; DOS & Windows Utilities For Reversing Protel PC Board Files. December 1996: Active Filter Cleans Up Your CW Reception; A Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source; Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Con­trolled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; The Alert-A-Phone Loud Sounding Telephone Alarm; Build A Control Panel For Multiple Smoke Alarms, Pt.2. PLEASE NOTE: November 1987 to March 1989, June 1989, August 1989, December 1989, May 1990, February 1991, June 1991, August 1991, February 1992, July 1992, September 1992, November 1992, December 1992, May 1993, February 1996 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 $7.70 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 disk for $11 including p&p, or can be downloaded free from our web site: www.siliconchip.com.au MAY 2001  97 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. High-temperature electrolytics for switchmode supplies I wish to replace a number of electrolytic capacitors in the power supply of an old fax machine. Beside the value of each capacitor is a temperature figure of 105°C, however all the ones available at retailers are marked with 85°C. I assume this must be related to either a shift in capaci­tive value with temperature or simply the operating temperature the capacitor is rated to withstand. Could you please clarify this, and if 105°C replacements are necessary, possibly advise where I might be able to source the parts. (T. D., via email). •  The inside of fax machines can get quite hot and ventilation is usually very poor so 105°C capacitors are a necessity. If you use 85°C caps they won’t have a long life. We also assume that the power supply is a switchmode type which probably means that the capacitors need to operate at very high frequencies. This means that need to have a low ESR (equivalent series resistance) other­wise their operation 5.1 Dolby Decoder wanted Have you thought of publishing a 5.1 Dolby digital decoder box that allowed uses to take advantage of their existing two channels via a preamp or integrated amp, while offering the extra three channel outputs to a second multi-channel amp? It would be a handy add-on for people who did not want to buy an expensive multi-channel integrated system. With the popularity of digital recording, it would be great to build a DA/AD converter that enabled the home user to record/play via SPDIF, optical and analog inputs and out98  Silicon Chip will be prejudiced. Low ESR 105°C rated capacitors are readily available from the following: Jaycar Electronics (www.jaycar.com.au) or Altronics in Perth (www.altronics.com.au). Driver transistors get hot in amplifier I have built six Plastic Power amplifier modules (April 1996) and find that the pre-driver transistors Q6 and Q8 (BF470 and BF469) get extremely hot under normal running conditions. There is 13.5mA running through them. The text quotes 13mA. The rail voltages are 59.8V due to a slightly higher mains voltage here in Victoria. The supplied heatsinks seem to be woefully inadequate. Even though it would be difficult to include these transistors on the main heatsink, they deserve much more serious attention in the heatsink department than they have received so far. This seems to be a common problem with most of the kit amps that I have built. Is this normal or is there is anything else that I could do (other than the obvious increase in heatsinking and possible addition of fan cooling) to puts. Some of us have high quality analog preamps that do not have the facilities to connect components via SPDIF/Optical. The unit could be designed around a 1U rack mount box. (J. H., Keswick, SA). •  We won’t be doing another Dolby decoder, for three rea­ sons. First, existing Dolby decoder equipment is now cheaper than a do-it-yourself project would be. Second, there is no readily available chipset. Third, standard consumer gear has inbuilt microcontrollers and fancy displays that would be extremely difficult for us to duplicate. And fourth, the Dolby licence fee is now over $30,000 – that puts it well out of our league! reduce the temperature without af­ fecting performance. The amplifiers work beautifully and I am very happy with their performance; just concerned about heat. (E. A., via email). •  These transistors do get very warm as they are dissipating about 700750mW. However, they are rated for 1.8W with a mounting base temperature of 114°C. This assumes a certain amount of heatsinking via the board. You can certainly use bigger flag heatsinks but paradoxically, because of the better transfer to the bigger heatsink, they may seem even hotter. We would expect the transistors to be running at no more than about 60°C (ie, uncomfortable to hold). This is hot but should not be a problem. We have not had any reports of failures. Door minder circuit wanted Have you ever had a door minder circuit in one of the magazines? I heard that you had but I can’t seem to find it on the website. (R. P., via email). •  We have published a number of Door Minder projects over the years. The first was in February 1988 and used an electret to sense the pressure change when opening the door. The second was in July 1995 and it used the same method. We also did light beam relay projects in December 1991 and July 1993. We can provide back issues (or photostat copies where back issues are not available) for $7.70 each, including postage. High power light dimmer causes flicker I have built the High Power Light Dimmer featured in the August 1994 issue and it seems to be working fine except for the following strange happening. When it is first switched on (ie, cold) it starts at full brilliance and then after about half a minute, it dims down to the level of the potentio­meter setting with an intermediate level of flicker. I have thoroughly checked and double checked and cannot find any reason for this strange behaviour. I regret having to trouble you with this one because as a rule every project I construct usually works flawlessly the first time which speaks volumes for the quality of SILICON CHIP’S projects and the at­tendant attention to detail. (R. M., via email). •  The flickering and slow action upon powering up could be due to insufficient drive to the Triac or Triac driver. Try reducing the value of resistance feeding pin 1 of IC3. Use 560Ω or 470Ω instead. Similarly, with the Triac drive, reduce the 390Ω and 470Ω resistors from pin 6 of IC3 to the A2 terminal of TR1 to 270Ω and 330Ω respectively. Railpower minimum speed problem Matching a Crane ignition to the HEI I just recently put together your High Energy Ignition pro­ject (June 1998). I also tried to install the Hall effect sensor to the dizzy to replace the points but was unable obtain the “chopper plate” as Bosch does not do them anymore. So I purchased a complete Crane Fireball Ignition system. It was simple to install and works very well. The only problem is that when I connected the output of this ignition model (which uses an optical sensor in the dizzy) to the HEI kit it does not work. The Crane unit says that it is compatible with HEIs and gives a ‘points type’ output. This output actually switches negative and the HEI kit needs a positive I have just built the Railpower from the October and Novem­ber 1999 issues of SILICON CHIP. It works as expected but I have a problem setting the minimum output voltage. When I rotate VR2 fully anticlockwise, the voltage on the track jumps up to 15V and you can’t get the voltage down. Even using the speed (-). After a lot of investigation I found that if you turn VR2 clockwise a quarter of a turn and use the speed (-) the voltage will start to drop but I can’t get the minimum speed setting without the meter scale off (0V on the track and 40 on the meter scale). Can you suggest what is wrong? (S. S., via email). •  We think you are winding the minimum speed trimpot (VR2) too far anticlockwise. Another way to adjust VR2 is to firstly set it at about mid setting. Then with the speed (-) button pressed, slowly adjust VR2 until the loco is just about to move. This procedure is as described on page 88 of the November 1999 issue. components are in the right place. I am using a Jaycar 12V power pack but get no sound. One thing I am concerned about is that the ICs don’t seem to clip together very well and are loose. Should these be soldered to the board? (L. C., via email). •  The loose ICs should be corrected by either soldering them in place or using better sockets. If you have a power supply capable of 9-12VDC, try the Theremin operation with this or use a 9V battery. This will check whether the plugpack you are using is working. Other tests would include checking the various power sup­plies around the circuit with respect to ground. Check for about 6V at pin 6 of IC3 and pin 8 of IC2. IC1 does not have a power supply pin (as it is a collection of transistors) but the various pins should have voltages on them. The drains of Q1-Q3 should be at about 5V. Theremin has loose IC sockets I have for a long time been dissatisfied with the jerk which occurs when I switch on my 1500W router. Recently, it became necessary to replace the switch which went open-circuit and I looked upon it as a chance to install a soft-start device to eliminate the jerk. Obviously, the soft-start unit has to be electrically after the switch which I just completed building the Theremin from the August 2000 issue of SILICON CHIP and was wondering if you could help me with a little troubleshooting advice. The kit is fully assembled and I have checked that all Soft-start circuit for a router input. What can be done to fix this? (P. W., via email). •  The Crane system presumably requires some sort of power to be applied to a LED within the optical sensor via a resistor from the 12V supply. Have you connected this up correctly and does the opto sensor output also go high and low as the distributor ro­tates when connected to the HEI? If the coil fires correctly but the timing is out because it gives a low signal at the trigger point instead of a high signal, you could investigate moving the sensor within the dis­ tributor so it does give a high-going signal at the correct firing point. We published diagrams for connection of optical pickups to the HEI in the “Circuit Notebook” pages of August 1998 and October 2000. means it has to be installed inside the router where there are serious physical space limitations. The nameplate current is 6.7A which is only marginally more than the 5A rating of your “Heavy Duty Drill Speed Controller” published in the September 1992 issue of SILICON CHIP. However, the only available high current Triac I could obtain was the BTA41 specified therein. But then I came up against a blank wall insofar as I could not obtain any thermal resistance information on this Triac. I am wondering whether you were able to obtain this information when the your drill speed controller was designed as your heatsinking seems quite moderate. I must add that the location within the router will mean that the Triac will be fan-cooled by quite a fair air blast. I have passed 6.6A of DC through the Triac and measured a 1.17V drop across it. This amounts to 7.72W dissipated and it rapidly becomes too hot to touch. The available heatsink space is a black-anodised plate 51 x 81mm. I have not yet mounted the Triac on the plate but I will undertake further thermal testing when I have done that. Your comments would be appreciated. (R. B., via email). •  You have just established the basic rule of thumb that dissipation in Triacs is a little over 1W per amp of MAY 2001  99 Curing thumps in subwoofer amplifier I have recently built the Plastic Power amplifier module from the April 1996 issue and an active crossover for subwoofers and have coupled them together to make quite a powerful mono subwoofer system. The problem I am ex­periencing is speaker “turn-on thumps”. I noticed Jaycar stocked a kit called a “Universal Loudspeaker Protector” (Cat. KC-5220) which eliminates turn-on thumps and so I bought the kit. I was wondering if you could tell me which wiring diagram I should be following in the instruction guide so as to achieve the result I’m after. I am not sure how to go about hooking up the unit to a mono mains amplifier current. You need a bigger heatsink. The Drill Speed Controller of Septem­ ber 1992 is not suitable because it will not let your router run at full speed (about 80% at no load) and nor will it give a soft start. You need our 10A Speed Control published in November 1997. This will let power tools run at full speed (as well as being variable over a wide range) and will also give a current-limited start which stops the kick from routers, circular saws etc. We can supply the November 1997 issue for $7.70 including postage. Excessive hash from the sine/square generator I recently bought and built the Sine/Square Generator de­scribed in the February 2000 issue. I followed the layouts and instructions to the such as mine. (L. B., via email). •  The loudspeaker protector you have was described in the April 1997 issue of SILICON CHIP and should be assembled as per Fig.5 on page 58 of the same issue. Its power requirements can be obtained from the power amplifier positive supply rail. Connect the protector PC board power connections to the GND and positive supply of the power amplifier. Note that the supply resistor RY should be 220Ω 5W. Since your amplifier is a mono unit, you need only use one side of the relay. Connect the amplifier output to the Amplifier 1 output connection on the PC board. The GND goes to amplifier GND and the Speaker 1 output on the PC board is for the speaker connection. letter but the final result was pretty well unusable for my requirements of testing aspects of my home-built stereo system. There was appalling audible hash and at some frequency set­tings really messy waveforms were produced. Inspection with a CRO showed that the output from the TL071 was dirtier than the input! This was traced to the -5V rail which had nearly 1V p-p hash on it. This was cured with a 47µF capacitor across the 0.1µF which is clearly inadequate on its own. The +5V rail has a 100µF by­pass; why not the -5V rail? This mod basically turned the unit into a usable one, although further reduction of very high frequency hash requires some shielded cabling – which again should really be included in the kit. (M. S., via email). •  The oscilloscope waveforms from WARNING! Fig.3 to Fig.8 in the Febru­ary 2000 issue show that the output from our prototype is rela­ tively clean from hash. Perchance you have a low-spec 79L05 regulator. Having said that, we agree that there could be im­provements made by using shielded cable for the level and range controls and from the output to prevent pickup from the switching circuitry. This would make the circuit more suited to critical audio applications. Combiner needed for two UHF antennas I have recently moved to an area where television is all in the UHF region. I need two antennas pointing in different direc­tions. Is there a preferred method of joining the output from these two? Commercial joiners seem to be UHF + VHF not UHF + UHF. (T. S., via email). •  You need a splitter/combiner. Normally used as a splitter, if you use it the other way, you can combine two signals into one, instead of splitting one signal into two. Get it? When you go to purchase your splitter, ensure that it can also be used as a combiner, eg, Altronics Cat L-1310 2-way. Notes and Errata 12/24 Hour Giant Clock, March 2001: The 10µF capacitor on the overlay adjacent to ZD1 should be a 100µF as shown on the cir­ cuit. Also the LDR should be a Jaycar RD-3480 not RD-3485. The description for easy daylight saving setting is incor­rect. Changing to daylight saving requires the hour switch to be pressed once to set it to the next hour. Returning to standard time requires the hour switch to be pressed until the previous hour is SC selected. 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. 100  Silicon Chip MAY 2001  101 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______________ 102  Silicon Chip FOR SALE EXTRA High 600 + H-Line Modules – Domes – Covert in PIR Case with SONY Super HAD CCD & SONY Chipset from $122 * Mini Cameras from $61 COLOUR from $85 * TIME LAPSE 24 hour VCRs from $599 National Service Centers * Multinational Manufacturer ! * VCR Controller use a std home VCR for Surveillance Event Recording Wireless IR Control only $39 * QUAD 1024 H-Pixels from $175 * COLOUR QUAD only ! $389 * DOME VIDEO CAMERAS from $53 ! COLOUR from $77 ! BULLET from $97 TWO YEAR WARRANTY * DIY PLUG-IN 20 m AV Cables from $20 * DOME 480 Line 0.05 Lux SONY CCD & ChipSet from $81 * COLOUR DSP DOME: 400 Line from $139 * 600 + Line from $164 * COLOUR DSP PIN in PIR CASE from $152 * MINI CAMS from $67 * DSP COLOUR from $133 * PC W98/W2000 REMOTE VIEW, PAGING, WEB-CAM, DVR System High 768 x 576 Resolution from $219 * MULTIPLEXER 4 Ch from $633 * 4 Ch / 8 Ch Switchers only $79 / $99 ! COLOUR Bullet Cameras from $122 * Digital PC 4 Ch Video Recorder System from $159 * BLEMISH FREE & LOW BLEMISH CCDs * UP TO 5 YEARS WARRANTY * OVERNIGHT DELIVERY * www.allthings.com.au Go to www.questronix.com.au for Video Equipment, Information, Techo Links & Monthly Specials. TELEPHONE EXCHANGE SIMULATOR: test equipment without the cost of telephone lines. Melb 9806 0110. http://www.alphalink.com.au/~zenere COVERT VIDEO Extra High 600 + H-Line Resolution SONY Super HAD CCD & SONY ChipSet PCB Pinhole Modules tiny sub-Matchbox size * Wireless Video & Audio TRANSMITTERS from $77 * Pinhole PCB Modules from $67. Easily concealed in: Mobile Phone Case, Clock, VCR Cassette, Toys, Teddy Bear (Nanny-Cam), Smoke Detector, Ornament, Cap, Cigarette Pack, etc. www.allthings.com.au ROLA AUSTRALIA PH/FAX (08) 8270 3175   WEB SITE WWW.BETTANET.NET.AU/GTD WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/Ecowatch phone: (03) 5968 4863; fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com SEE-in-the-DARK Camera with in-built IR LEDs in Water Resistant Case for disturbance-free Baby - Bird - Animal observation from $147 * NEW Wireless Version available NOW ! * www.allthings.com.au UNIVERSAL DEVICE PROGRAMMER: Low cost, high performance, 48-pin, works in DOS or Windows inc NT/2000. $1320. Universal EPROM programmer $429. Also adaptors, (E) EPROM, PIC, 8051 programmers, EPROM simulator and eraser. Dunfield 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: $198 each. Demo disk available. ImageCraft C Compilers: 32-bit Windows IDE and compiler. For AVR, 68HC11, 68HC12. $396. Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x, 89Sxx in both DIP and PLCC44 and some AVR’s, most 8-pin EEPROMS. Includes socket for serial ISP cable. $220, $11 p&p. SOIC adaptors: 20 pin $99, 14 pin $93.50, 8 pin $88. Full details on web site. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. (02) 9896 7150 or http://www.grantronics.com.au TRANSMITTERS, broadcast, 88100.8 FM stereo. Suit NZ, Unlicensed low-power radio stations, aerials, decks, P.C. Robo D.J., CD ROMs. Since 1920’s. Write/Ph Electronic Services, 0064 Model Flight Control Modules CHECK OUR WEBSITE FOR DETAILS ON KITS AND COMPONENTS •  TRANSMITTER KITS AND MODULES •  AUDIO MODULES •  COMPUTER INTERFACE KITS •  RADIO STATION AUDIO SOFTWARE NEW: Our MP3-CD player in short form for $169 inc GST. Includes the following: processor board, front panel display and tactile keypad; just add a case, cables, 12V power supply and a CD-ROM drive. Play CDs and up to 2600 MP3’s from a CDR. Great for car or home. 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, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au PDC 01 SERIAL INTERFACE $182.60 PDC 10 GPS INTERFACE MODULE $367.00 PDC 20 ALTITUDE HOLD MODULE $459.80 PDC25 SPEED HOLD MODULE $459.80 PDC 400 ALTIMETER AIR-DATA SENSOR $367.40 PDC 450 AIRSPEED-AIR DATA SENSOR $367.00 PDC1200 VIDEO OVERLAY (PAL-D) $644.60 TRACKER GPS TELEMETRY SOFTWARE $182.60 PDC 3200 AUTOPILOT AND GROUNDSTATION: PRICE ON APPLICATION (PRICE DEPENDS ON CONFIGURATION). (ALL PRICES INCLUDE GST) Silvertone Electronics, PO Box 580, Riverwood 2210. Phone/Fax (02) 9533 3517. www.silvertone.com.au Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Silverwater in Sydney. A genuine interest in electronics is a necessity. Phone 02 9741 8555 for current vacancies. 43847-177, PO Box 15-146, Wellington, New Zealand. HOME CCTV Mono / Colour PAKS only ! $119 / $151 Full DIY Plug-In to TV / VCR 20 metre Cable, Plug Pack & Camera www.allthings.com.au DIY CCTV PAKS 4 Cameras & Switcher .................$354 as above COLOUR ......................$466 4 Cams, Switcher/Monitor ...........$495 4 Cams & QUAD .........................$478 4 COLOUR & QUAD ....................$752 Time-Lapse 24 hr VCR only $599 with CCTV Systems ! MORE at: www.allthings.com.au Fully Plug-In DIY Paks with Cables & Power Supplies * PC W98/W2000 Digital Motion/Sound detection & activat­ ed Video/Audio Recording systems. RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production. Tel (02) 9738 0330; Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio 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. FREE – RADIOLA 656TA VALVE RADIO for restoration, inlaid veneer cabinet, collect in Killara, Sydney. Reply to freeradiola<at>hotmail.com PCBs MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Elec­tronics Pty Ltd. sesame<at>internetezy.com.au; http:// members.tripod.com/~sesame_elec Video Amplifiers, Stabilisers, TBCs, Converters, Mixers, etc. QUESTRONIX (02) 9477 3596. VALVES: Bought and for sale. All types. New and used. Also available R/C packs. continued next page MAY 2001  103 DON’T MISS THE ’BUS Advertising Index Aust. Video Systems..................101 Av-Comm Pty Ltd.........................95 Allthings Sales & Services..102,103 Do you feel left behind by the latest advances in com­puter technology? Don’t miss the bus: get the ’bus! Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. Dick Smith Electronics........... 22-25 Evatco..........................................85 Grantronics................................103 Harbuch Electronics....................77 Instant PCBs..............................103 Price: $12.50 (incl. GST) Order now by using the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. Special subscription offer available only while stocks last. Silicon Chip Binders   Each binder holds up to 14 issues   Heavy board covers with 2-tone green vinyl covering     SILICON CHIP logo printed in gold-coloured lettering on spine & cover REAL VALUE AT $12.95 PLUS P & P NEVILLE WALKER KIT ASSEMBLY & REPAIR: · Australia wide service · Small production runs · Specialist “one-off” applications Phone Neville Walker (07) 3857 2752 Email flashdog<at>optusnet.com.au Microgram Computers..........3,OBC MicroZed Computers...................21 Printed Electronics.................... 103 Protel.........................................IFC Questronix...................................77 RF Probes...................................21 Rola Australia............................103 WANTED Silicon Chip Back Issues....... 96-97 OWNER’S HANDBOOK service man­ ual for Conway Masteranger 639 multimeter. (02) 49 500680. Silicon Chip Binders..................103 PERSON WITH EXPERIENCE / APTITUDE able to fault find & repair PCBs – without diagrams. GENEROUS PKG NEG. Tel John<at>AER (03) 9482 4958 0415 305 470. 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 104  Silicon Chip McGraw Hill.................................37 Oatley Electronics......................IBC Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. KIT ASSEMBLY Kalex............................................86 Mass Electronics....................21,77 Price: $A12.95 plus $A5.50 p&p each (Australia only; not available elsewhere). Buy five and get them postage free. N.O.S. Ideal for valve radio restoration. 02 4751 5620. Jaycar ................................... 49-56 Silicon Chip Bookshop........... 78-79 SC Computer Omnibus.............103 Silicon Chip Subscriptions...........57 Silvertone Electronics................103 Smart Fastchargers.....................86 Solar Flair/Ecowatch..................104 Truscotts Electronic World...........85 _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: •  RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. BARGAIN OF THE MONTH * * N E W * * N E W * * N E W * * FUTABA 2 CHANNEL RADIO CONTROL This item is new in Its original box. VIDEO SYNC. STABILISERS 2ER A high-tech, lowpriced 2-channel radio This two-stick, digital proportional AM system is ideal for robotics, R/C cars, boats and planes etc. Features include fine trims that are easily accessible on the front panel, Short sticks that allow for full range of movement and Servo Reversing. Includes two S3003 servos, a R122JE receiver, battery holder, power switch and other accessaries. All for just $100 Various forms of copy protection are used on video tapes & DVDs, the problem is that the changes to the normal signal is that it may cause playback problems like the jitters. This device removes the copy protection by stripping and reinserting the sync. pulse & thus cleaning the picture. It has been suggested to us that these units could be used to copy commercial videos and DVDs but we do not condone any breach of copyright. This item comes as a ready built PCB with a new recycled metal case to suit. Just...$29 $29 20 x 2 LCD BACKLIT CHARACTER VIDEO CAMERAS The output of these cameras below is std DISPLAY: video & can be plugged into the "VIDEO IN" socket of any Australian std VCR, video monitor or TV, or via an RF Modulator to an Ant. Input. The B/W cameras are Infra Red responsive & can be used in total darkness with IR MICRO SWITCHES Illumination. 3 mini micro switch assembly Made by Optrex model #DMC2059 (this MONOCHROME CCD VIDEO CAMERA on a 600mm cable with a small model is not listed on the Optrex web site, B&W Camera built on a PCB with auto iris. plug. 3 assembut data is available for similar 20 x 2 (0.1 lux). Can be focused sharply down to blies for $5 displays). Each character measures a few mm(useful for people SOLENOID: #1 approximately 6mm x 8mm, display area This solenoid pushes a small shaft 122mm w x 30mm h. PCB dimensions with visual impair(diameter 4mm) a distance of 2mm. Coil 151mm wide x 56mm high. Uses standard ment). Spec.: Power req.: 10V to resistance is 60 Hitachi chipset (HD44780) mounted on a 12V <at> approx. ohms. Operates PCB with LED backlight & dual row 16 pin 50mA.CCD: 1/3", from 12V DC. header: (DL8) $11 ea or 3 for $27 30grams: with 60° $89, with 92° lens: Body is 29mm 12 BUTTON KEYPAD: long, 22mm diameter: (MA1) SUGAR CUBE CMOS B/W CAMERA: Matrix style with a 7 pin (Reviewed EA Sept. 1999) This (16 x 16 x SOLENOID: #2 connector. The buttons 15mm) black & white video camera This solenoid punches a small 1.5mm are metal and this whole includes a pinhole lens with a field of view diameter hole in a piece of cardboard or keypad appears to be of 56 x 42 degrees. Resolution is 240 TV paper. It was probably used to punch holes very rugged. Looks lines (288 x 352 pixels), 1/3" CMOS Image in phonecards. Coil resistance very similar to keySensor, 2:1 interlace with a shutter speed is 7ohms. Operates from pads used in public of 1/60 to 1/60,000. Other features include 12V DC. Body measures telephones. Overall dimensions are 70mm auto exposure control, backlight 34mm long, 40mm diawide by 79mm high. Each button compensation, auto gain control. Has an meter: (MA2) (MA1) + measures 10mm square. This keypad AGC disable pin which can be tied low for (MA2) $2.20 pair would be very suitable for security outdoor use. It operates from 5V DC and or 3 pairs for $5 a p p l i c a t i o n s d u e t o i t ' s r u g g e d only draws 10mA: (CAM2) $70 (NEW) MULTI FUNCTION BATTERY construction: (GKP1) $3.50 ea or 3 for $9 8 CHANNEL PC CONTROLLED RELAY CHARGER / DISCHARGER: 12V AUTOMOTIVE RELAY: INTERFACE KIT: Ref: Silicon Chip Sept New in original box with instructions. This Has 30A SPDT 2000. Operates eight relays from a PC unit was designed to charge NI-CD & NI- Contacts with parallel port. Kit inc. PCB & all on-board MH mobile phone batteries of 4.8V, 6.0V 73ohm relay parts inc. eight relays (2 higher current) and 7.2V. Operates from 12-24V DC input. coil. These are with indicating LED's & DB25 connector. Features include processor control & multi the standard Also some simple software stage charge indicator. By changing the size and normally on disk. written in Basic value of one resistor it can charge higher retail for around to operate the kit: voltages, although a higher voltage $7 each: (RL3) $3 each (K164) $40 plugpack is required for 9.4V or higher. A suitable DB25 Includes cigarette lighter lead, 12V / 1A DC (NEW) LABTEC PLUGPACK: male to DB25 plugpack & instructions for modifications Output is 15V DC female data for higher voltages. The unit has battery <at> 1A. Has a UK cable is also charging terminals but the user will have to plug that needs available for make their own adaptor to interface to a changing to an this kit: (K164C) $8 battery. The plugpack supplied alone is Australian plug: worth around $30 retail. Weight is 0.9kg. (ZA0055) $12 HIGH QUALITY STEREO $29 15V DC / 1A Plugpack for charging GEARED AC MOTOR: HEADPHONES: Clarion brand (model # batteries 9.4V or Brand new small mains operated geared PRO-97V), super responsive The higher: (ZA0055) motor. These are very strong and made for speakers use 40mm Samarium-Cobalt rotating microwave turntables. Operates magnets The 1.8m cord uses high purity from 240VAC 50/60Hz and consumes 3W. OFC Litz wire. They are Brand new and in Output speed is 5/6RPM. Generates a a presentation case. A 3.5 / 6.3mm These were rejected high voltage when due to a production probturned. Measures lem with some of them 50mm dia. x 17mm $6 If you ask high. Output shaft dia. (easy to fix with a pair of when ordering you is 7mm: (MAC2) $4 ea. or 4 for $12 pliers) Satisfaction guaranwill receive a free 6-pack of batteries. teed! A big loss for the (BRAND NEW) 486 MOTHERBOARD manufacturer, but a GERMAN PRINTERS with 40Mhz CPU. Motherboards complete great gain for the They are all sold out but we still have with 40Mhz UMC CPU, standard AT hobbyist. (PRO97V) $15 stocks of some of the stepper motors as Keyboard interface, 4x16 bit ISA slots, 1x8 used in the printers the largest of these are bit ISA, no Level2 cache. $18 ea and the smaller ones are $15 ea. (USED) AUSTRALIAN IEC LEAD: Accepts 1 x 72pin or 4 x Has 3 pin Australian Join our Bargain Corner Mailing List 30pin ram. Manual mains plug & IEC plug We’ll send updates on latest to Bargain supplied , the CMOS on other end. Has Corner & Test Equipment. To join send a battery may need approximately 1 metre blank email to: bargaincorner-subscribe replacing: (GMB1) long lead: (PL2) $2 each $15 or 3 for $30 <at>oatley electronics. com DC MOTOR WITH FEEDBACK: 12 to 24V starts at 3V. Coil resistance is 13ohms. Body measures 58mm long, 40mm diameter, shaft diameter 4mm, pulley on shaft diameter 8.5mm. The feedback section uses a hall effect sensor with a magnet on the end of the motor shaft. An output via a BA14741F op-amp and an open collector transistor gives a pulse for each revolution so the speed could be accurately maintained. The motor can be used independent of the feedback section: (M44) $7 each of 3 for $17 (USED) SAMSUNG TELEPHONE: Why pay a few dollars rental each month for your telephone? These used (ExOlympics) Samsung telephones will appear in "as new" condition after a couple of minutes cleaning. They feature Recall, Redial-Pause and On Hook keys. A light flashes when the telephone rings and it can be wall mounted by 2 screws (Screws are not provided), the plastic part that secures the handset will have to be reversed so to hold the handset in the vertical position. Has an adjustable 3 position switch for the Speaker volume and an adjustable 3 position switch for the Ringer volume. A line lead is NOT provided: (ZA0201) $14 each or 3 for $33 AUSTRALIAN MADE BARGAIN NEW.... EVAPORATIVE WATER COOLERS Features inc. economic running. safe 6VDC operation (Plugpack supplied), internal stainless steel reservoir, Can be used with commercially delivered water bottles or with a large soft-drink bottle...$35 (Bottle not supplied) SOLAR PANELS: Quality SIEMENS brand Polycrystalline cells. Open circuit voltage 5.7V, Short circuit current 0.22A, Peak power 1W <at> 100mW per square cm. 4 panels req. to charge 12V batteries. 160 x 55 x 5mm. Terminated with a 25cm long figure eight cable. $10 ea. or 4 for $36. 12V / 7AH SEALED LEAD ACID BATTERY BARGAIN: Now is the time to pick up a real bargain, 2.6kg, 150 x 65 x 92mm: (PB6) $25 We have more used test equipment. we need to clear some to make way for the next lot. Check out our web site Great bargains at a fraction of the new cost. If it’s not on our web site... ring us. www.oatleyelectronics.com Orders: Ph ( 02 ) 9584 3563, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89 Oatley NSW 2223 AY 2001  105 major cards with ph. & fax orders, Post & Pack typically $7 Prices subject to change without notice ACN 068 740 081 M ABN18068 740 081 SC_MAY_01