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Jet engines for radio-control models SILICON CHIP JANUARY 1998 $5.50* NZ $6.50 INCL GST IC M A N Y D 'S A I L A R AUST E N I Z A G A M S C I N ELECTRO SERVICING - VINTAGE RADIO - COMPUTERS - SATELLITE TV - PROJECTS TO BUILD Safe 12V 4-channel PRINT POST APPROVED - PP255003/01272 LightShow BONUS AV-COMM SATELLITE TV CATALOG Pan controller for CCD cameras Build a one or two-lamp flasher At last! - model railway command control ISSN 1030-2662 01 9 771030 266001 January 1998  1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.jaycar.com.au Contents Vol.11, No.1; January 1998 FEATURES   4  Understanding Electric Lighting; Pt.3 We describe the development of fluorescent lamps and take a look at how they work – by Julian Edgar 14  Compasses: From Magnetite To Digital New electronic compasses offer digital readout and unprecedented accuracy PROJECTS TO BUILD Build Your Own 4-Channel Light Show – Page 18 18  Build Your Own 4-Channel Lightshow New low-voltage unit controls four lighting channels and features several chaser patterns plus music modulation – by Leo Simpson & Rick Walters 28  Command Control System For Model Railways At last! – a Command Control system for Aussie enthusiasts. This one is easy to build and can control up to 16 locomotives – by Barry Grieger 58  Pan Controller For CCD Video Cameras Low-cost panning circuit controls two servos and draws no current while the camera is stationary – by Branco Justic 64  Build A One Or Two-Lamp Flasher Command Control System For Model Railways – Page 28 Use it to draw attention to a sign or display, or to liven up a party. The simple circuit drives 12V 20W or 50W halogen lamps – by John Clarke SPECIAL COLUMNS 40  Serviceman’s Log A clear case of sabotage – by the TV Serviceman 49  Vintage Radio A simple regenerative receiver – by John Hill 70  Radio Control Jet engines in model aircraft – by Bob Young Pan Controller For CCD Video Cameras – Page 58 76  Computer Bits Norton Utilities V2: hard disc maintenance for PCs – by Jason Cole DEPARTMENTS   2  Publisher’s Letter 37  Order Form 38 Mailbag 45  Product Showcase 74  Circuit Notebook 82  Ask Silicon Chip 85  Notes & Errata 86 Market Centre 88  Advertising Index Build A One or Two-Lamp Flasher – Page 64 January 1998  1 PUBLISHER'S LETTER Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Brendon Sheridan Phone (03) 9720 9198 Mobile 0416 009 217 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Mike Sheriff, B.Sc, VK2YFK Ross Tester Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $54 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. ISSN 1030-2662 and maximum * Recommended price only. 2  Silicon Chip The millennium bug – a lot of fuss over nothing How many articles have you seen in the press over recent months about the “Millennium Bug”? Bit of a worry, isn’t it? Supposedly, if you believe the most lurid of the stories, when the time and date clocks over on January 1st, 2000, there will be all sorts of dire consequences: computers will crash, pensioners and other social welfare recipients won’t get their cheques, planes will fall out of the sky, trains will come to a halt, banks will close their doors because they won’t be able to take transactions and so on . . . Well, to my mind it’s a lot of piffle. Sure there is some old Cobol-based accountancy and other software which does present a problem because of the requirement for a 2-digit year date. Some credit cards which were issued with a 2001 expiry date have had to be recalled and reissued with a 1999 expiry date. And some computers with older BIOS do present a problem but by now they’re getting on for ten years or more so they are pretty well obsolete. The truth is that the vast majority of large organisations have had to face this problem years ago. For example, banks, finance and insurance companies have long been dealing with repayment and premium schedules which stretch well into the next century. How could banks have granted 10, 15, 20 or 25-year loan terms if they hadn’t done all their projections? Just walk into your local bank and see if they can’t give you a repayment schedule for the whole term of your mortgage. You can bet they can. Even large government bureaucracies such as the Taxation Office can be expected to have done all their homework years ago so don’t worry about them not being able to send out assessments in the year 2000 and beyond. Nor should you bank on the police department not being able to send out fines or security firms not being able to monitor premises with the advent of the millennium. Things will continue as normal. Nor can I imagine a scenario whereby airline or train scheduling or other crucial systems come to complete stop because of the date. Yes, some systems might fall over but wholesale chaos does not seem likely. A more realistic assessment is that if a company or organisation is using a computer system and software which is more than ten years old, then there might be a problem. But it is fairly easy to simulate this. All that you have to do is to change the date, reboot the computer system and run the suspect software. If it does not fall over, then you don’t have a problem. Or am I missing something more insidious here? I don’t think so. I think that some companies stand to make quite a lot of money from consultancy work and seminars on the so-called “millennium bug”. Good luck to them. But let’s hope that they don’t get rich at the expense of you, me and other taxpayers. Leo Simpson M croGram Computers PCI Plug & Play Printer Cards Universal Programmer Power 100 The POWER-100 Universal Programmer and tester with built-in power supply connects to the printer port and supports over 1500 devices with manufacturer approved algorithms. It has a 42-pin textool with all pins programmable, including GND, VCC, VHH, VOP, CLOCK Oscillator, QUICK PULL-UP, PROTECTION DRIVER etc. It supports most adapters and converters to program and test different devices such as PLCC, QFP, SOP, SIP, SIMM/SIPP, etc. It will program Flash E/EPROM, PLD, PAL, PEEL, GAL, MAPL, MAX, MACH, BIPOLAR & SERIAL PROM, MPU/MCU and more. Cat. No. 3346 Universal Programmer Power 100 $2099 Console Extenders Our console extender allows one keyboard, monitor and mouse to be operated at up to 80 metres from the computer. Available for AT and PS/2 computers. Cat. No. 11624 Cat. No. 11625 Console Extender for AT Computer Consle Extender for PS/2 Computer $299 $309 Available in either 1, or 2 port versions, these PCI bus PnP bi-directional parallel ports have an 83 byte FIFO buffer and are able to replace faulty motherboard printer ports as LPT 1/2. Support is provided for DOS, Win 95 and Win NT. A high performance PCI bus multimedia / video / graphic adapter featuring an ATI 264VT 64 bit accelerator chip with 135MHz 24 bit True Cat. No. 2618 1 Port Printer PCI PnP $174 Colour RAMDAC. Multimedia Cat. No. 2619 2 Port Printer PCI PnP $220 functions supported include a cable ready TV tuner for live on screen TV display, MPEG and AVI video, Plug & Play ISA Serial Card With a PnP Motherboard BIOS this card will auto still image & video capture . Cat. No. 3357 TV and Capture PCI Card $369 configure with any 8 byte I/O address from 100H to 3F8H as well as auto configure with IRQ 3, 4, 5, 6, 7, Video Conferencing Kit 9, 10, 11, 12 or 15. In legacy mode it is software A high performance PCI full-motion video/still image configurable from COM1 to 4 and IRQ3-15. Fitted with capture solution for video conferencing on the net! 16550 UART’s, connection is via a DB9F connector. The kit includes video capture card, CCD camera & Cat. No. 2635 Plug & Play ISA Serial Card $80 VDONet’s video conference software. Ideal for applications such as Video Mail, Video Conferencing Ultra DMA HDD IDE Controller Give your existing motherboard Ultra DMA support. or Full-Motion Video Capture to AVI file format. Video Conferencing Kit $449 This IDE controller for the PCI bus gives Ultra DMA Cat. No. 3356 performance to suitable hard drives and CD-ROM Blood Pressure Monitoring System drives. Up to 33.6Mb/s. DynaPulse is a clinical accuracy blood pressure & Cat. No. 2632 HDD Controller PCI Ultra DMA IDE $169 VGA to Video Converter Dual Exhaust Fans TV & Capture PCI Card pulse monitoring device that connects to your computer via a serial port. The actual blood pressure waveform is displayed and systolic, diastolic & mean arterial pressures are measured rather than calculated. A database of long term trends as a result of diet, exercise or hypertensive medication can be viewed. High quality at an affordable price, this external unit does not require software drivers & supports up to 1024 x 768 with true Cat. No. 16000 Blood Pressure Monitoring System $429 colour for both PAL & NTSC systems. Connect to SIMM RAM Tester IBM, Macintosh or NEC computers. The output can Quickly identify the size & configbe viewed on a monitor & TV simultaneously. uration of memory as well as Connections are composite video, S-VHS and Analog identifying true or fake parity. RGB (15kHz). The TV display can be frozen while This RAM tester incorporates a the presenter prepares the next screen. microprocessor and a program- Two products to keep your computer and your hard drive cool! Dissipate heat with dual exhaust fans attached to a plenum to exhaust hot air from inside the computer. Reduce the possibility of data loss due to your hard drive overheating with dual fans attached to a ventillated face $499 plate. It will effectively dissipate heat from the HDD & Cat. No. 3102 VGA to Video Converter - External significantly lower the internal temperatures. They do not PCI Video Capture Card require any permanent case alteration. The PCI Video Capture card is WIN 95 Plug and Cat. No. 8564 Hard Drive Cooling Fan $49 Play compatible for easy installation and setup. Cat. No. 8420 Exhaust Fan Dual $45 Utility software provides full screen (640 x 480) or any size window live video display. Connections on PCI Plug & Play Serial Cards the card are Composite Video-In (RCA PhonoPCI bus serial cards Plug), S-Video In and an 8 pole mini DIN connector. with PnP BIOS support providing baud rates up Cat. No. 3358 PCI Video Capture Card $179 to 921.6KB/s. Single & Video Overlay Unit dual port versions are Dual functions in one fitted with 16550 UART’s & 16 bit FIFO buffers. They can replace box. It’s a VGA to faulty onboard serial ports as COM1/2 and support video converter as well as providing a is provided for DOS, Win 95 & Win NT. Cat. No. 2616 1 Port RS232 16550 PCI PnP $174 video overlay funcCat. No. 2617 2 Port RS232 16550 PCI PnP $220 tion. It supports overAlso available for the PCI bus, is a combination two lay mode, VGA only port serial and single port bi-directional printer card. mode, external video only mode and Genlock mode. Cat. No. 2620 Serial/Parallel PCI PnP: 2S/1P $230 Cat. No. 3355 Video Overlay Unit $619 mable delay line to auto test & display information. SIMM size may be 64K to 16Mb in 30-pin format, or 1Mb to 32Mb in 72-pin format. The test speed can be adjusted from 40-120 ns with a resolution of 1ns. Cat. No.3174 RAM Tester $1499 Compact Keyboard with MCR Ideal POS keyboard with a fully integrated magnetic card reader stylishly recessed into the keyboard above the function keys. The keyboard has a full complement of 101 keys including 90 relegendable keys in a layout which only occupies an area of 400mm x 210mm. The MCR reads track 1 & 2 (ISO 7811 standard), while Track 3 is optional. Cat. No. 8300 E & OE Compact Keyboard with MCR All prices include sales tax $599 MICROGRAM 0198 Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 FreeFax 1 800 625 777 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 Pt.3: Fluorescent Lamps Electric Lighting Along with incandescent lamps, fluorescent lights are amongst the most widely used of lamps. Where diffuse, general lighting is required in commercial and industrial applications, fluorescent tubes rule supreme. By JULIAN EDGAR While we see just a white tube emitting visible light, the fluorescent lamp is in fact a low pressure mercury discharge lamp. It produces light when the fluorescent powder coating on the inside of the glass is activated by ultraviolet (UV) energy. Fluorescent lamp history In 1710, Englishman Sir Francis Hawksbee produced a glow discharge 4  Silicon Chip inside a glass tube from which air had been evacuated and mercury added. He called the glow “electric light” and claimed that his experiment had proved that electricity could produce light. This experiment took place more than a century before the first primitive incandescent light. It wasn’t until 1852 that Sir George Stokes discovered the basic principle of transforming ultraviolet radiation into vis­ ible light. Specifically, he found that quinine sulphate solution glowed when irradiated by ultraviolet energy. In the period between this discovery and the development in the 1930s of the fluorescent lamp, much work was done on low and high pressure electric discharges in both mercury and sodium vapour. However, all of these devices were relatively inefficient at producing visible radiation. A major breakthrough occurred in the 1920s when it was discovered that a mixture of mercury vapour and an inert gas was about 60% efficient in converting electrical input power in-to a single (253.7nm) wavelength of light. By 1935, a General Electric team led by GE Inman produced a prototype green fluorescent lamp with an efficacy of 60lm/W. This efficacy is far better than even current incandescent lamps can achieve and must have been the cause of quite some excitement at the time. As a result of their work, several important characteris­ tics of fluorescent lamp behaviour were identified. It was re­alised that the discharge process is best started by electrically heating oxide-coated filaments positioned at either end of the tube. This causes the filaments to emit electrons which disperse along the length of the tube. When a high voltage is subsequently applied, an electric discharge occurs through the inert gas, exciting the gas atoms which then emit ultraviolet light. Very high efficiency is obtained if the excited atoms are of mercury vapour, which produces a single wavelength of ultra­violet light at 253.7nm. To produce visible light, phosphors with a peak sensitivity at 253.7nm are applied to the inside of the tube. The reason that the phosphors must be on the inside is that 253.7nm ultraviolet light does not pass through ordinary glass. By April 1938, the fluorescent tube was ready for market. Initially, it was released in white plus six other colours. The ballast choke in a fluorescent lamp fitting con­sists of a large number of turns of enamelled copper wire on a laminated iron core. Its primary functions are to limit current and to provide sufficient open-circuit voltage to initiate igni­tion. The fluorescent lamp A fluorescent tube consists of a soda-lime glass tube that has been doped with iron oxide to control the amount of shortwave transmission. The most common tube diameters are 16mm, 25mm and 38mm, while the most common lamp lengths are 600mm, 1200mm and 1500mm. The most important factors affecting the light characteris­tics of a fluorescent lamp are the type and composition of the applied phosphors. Phos­phors commonly used include calcium ha­lophosphate (for white light), magnesium fluoro-germanate (red) and calcium tungstate (blue). Colour temperature, colour rendering and to a large extent luminous efficacy, are all affected by the phosphors. Standard phosphors give a lamp with good efficacy but poor colour render­ing. Tri-phosphor lamps use special fluorescent powders contain­ing certain rare earths that give radiation peaks at three well-defined wavelengths (in blue, green and red) that are equally distributed over the A capacitor is used to provide power-factor compensation. Fig.1: a simplified view of what goes on in a fluorescent lamp. The glass tube is coated inside with fluorescent pow­ders that glow when excited by the ultraviolet energy of the discharge (diagram from the Philips Lighting Manual). January 1998  5 The starter allows the filaments to be pre-heated, increasing their emission of electrons. visible spectrum. These lamps give very good colour rendering together with high efficacies. Finally, the latest lamps use socalled multi-phosphors, which employ a mix of phosphors chosen to cover the entire vis­ ible spectrum. These give the highest colour rendering of all the fluorescent lamp types. The filament windings located at either end of the tube can be of either coiled-coil or straight coil types. They are similar to incandescent lamp filaments but are coated with barium or strontium oxide to aid electron emission. Most fluorescent tubes use a starter to preheat the fila­ments with an electric current just prior to lamp ignition. However, “rapid-start” tubes have continuously heated filaments while “cold-start” (or “instant start”) tubes Fig.2: the energy consumption of a 36W fluorescent lamp in still air at an ambient temperature of 25°C. 10W of visible radiation is produced. 6  Silicon Chip use no preheating of the filaments at all. The latter types do not use a separate starter but often employ an auxiliary electrode or a conductive strip on the outside of the tube to facilitate ignition. The gas in a fluorescent tube consists of a mixture of saturated mercury vapour and an inert buffer gas, commonly argon or krypton. Under normal operating conditions, mercury is present in the tube in both liquid and vapour forms. Fig.1 shows a simplified view of what occurs within a fluorescent lamp. The biggest change in fluorescent lamp technology in recent years has been the release of compact fluorescent lamps. Designed as plug-in replacements for incandescent lamps, they combine high efficacy and good colour characteristics with a life expectancy which is typically eight times that of an incandescent lamp. Lamp performance Fig.2 shows the total energy consumption of a 26mm diamet­er, 36 watt (36W) fluorescent lamp operated in still air with an ambient temperature of 25°C. Of the 45W input power, there is just 10W of visible radiation. Infrared radiation, convection and conduction make up 25.8W, with the remaining 0.2 watts lost as UV radiation. The reason that the ambient temperature needed to be speci­ fied in the above example can be seen in Fig.3. The luminous flux of a typical fluorescent lamp is very dependent on temperature. It is at its greatest at about 25°C, falling by 40% as the temper­ ature drops to 0°C. So when you go out to the shed on cold winter nights and flick on the fluoros, it’s not just your imagination that it all looks dim and cold! As temperatures rise above 25°C, the output of the lamp again falls, being over 30% down at 70°C. Not only does the luminous flux of the lamp drop rapidly at higher temperatures but so does the luminous efficacy. However, the power dissipated by the lamp also decreases rapidly with increased temperatures, so the luminous efficacy falls off less rapidly than the luminous flux. Operating a fluorescent lamp on a high-frequency supply improves luminous efficacy by about 10%, a major incentive for employing high frequency electronic ballasts. Using a high fre­quency ballast has the added advantage of reducing lamp blacken­ ing, a problem that occurs at the ends of the lamp due to the deposition of dispersed emitter material lost from the filaments. Another cause of a decrease in luminous flux over the life of the lamp is that the fluorescent powders slowly become less effective. When a mix of powders has been used, discolouration can also occur. After 8000 hours, the luminous flux of a typical fluorescent lamp will be between 70% and 90% of its original value. After starting, a fluorescent lamp takes two to three minutes before its luminous flux reaches its maximum. However, the initial flux is about 60% of its final value and so this is not normally noticed. The reason for the delay is that the mer­cury vapour needs a short period before it reaches its working pressure. Lamp circuits Every fluorescent tube requires a “ballast” of some sort and its purpose is twofold, as we shall see. At first switch-on, it is necessary to apply a much higher than normal voltage to the lamp to assist ionisation and thus to get the lamp to ignite. However, once the gas has begun to con­duct, its resistance rapidly falls, resulting in a current flow that would spiral out of control unless checked. In fact, as with all gas discharge devices, it has a negative resistance; ie, as the current rises the voltage drop across the tube is reduced. Ultimately, unless something is done to prevent it, the current will rise to such a high value that the tube will be destroyed. It is therefore necessary to use a current limiting device, a “ballast” to prevent current runaway. This ballast can take the form of a resistor, an incandescent lamp, an iron-cored choke or an electronic control circuit. Although relatively simple, a resistive (or incandescent lamp) ballast wastes energy, which is dissipated as heat. In fact, the power lost in the resistor is comparable to the power taken by the lamp! Resistive ballasts are therefore rare and are employed only in some fluorescent lamps operated from a DC sup­ply. An iron-cored choke (inductor) is the most widely used ballast in AC applications. It consists of a single coil with a large number of turns of enam- Fig.3: the luminous flux of fluorescent lamps varies a great deal at different ambient temperatures (diagram from the Philips Lighting Manual). elled copper wire on a laminated iron core. In addition to limiting current, the ballast also: (1) provides sufficient open-circuit voltage to initiate igni­tion; (2) regulates the lamp current against power supply voltage changes; (3) permits electrode heating in preheat and rapid-start lamps. To understand how the ballast provides all these functions, it is necessary to consider the circuit of a normal fluorescent lamp fitting which is shown in Fig.4. Fig.4 shows that the fluorescent tube has a filament (heater) winding at each end and these are connected in series with the ballast choke via the starter. The starter consists of a bimetallic strip mounted within a small argon or neon-filled bulb. When the supply is switched on, the bimetallic strip is cool and its contacts are open. The applied voltage causes the gas in the starter to ionise, allowing a small current flow. This heats the bimetallic strip, causing it to bend enough to close the internal switch. Current can then flow through the ballast and the two filaments, which are heated and start to emit elec­trons. The starter cools and the bimetallic strip opens, inter­rupting the current through the filaments. Since the inductor is also in series with the starter, the sudden switchoff causes it to produce a brief high voltage spike which appears across the ends of the lamp, causing it to ignite. The voltage required to ignite the tube depends on its length and diameter, its age and the temperature. The longest tubes are hardest to start and all tubes are much harder to start at low ambient temperatures. The voltage required to start the tube can be as high as 800V; ie, much higher than the normal peak voltage of Fig.4: the circuit of a conventional fluorescent lamp with a glow switch starter. The starter enables current to flow through the filaments and it opens after a short delay, causing the ballast choke to produce a high voltage spike which ignites the tube. January 1998  7 leading to burnout of the ballast. The way to avoid this is to replace both the tube and the starter immediately they start to give trouble. Starter capacitor Inside the bulb of the starter is a pair of contacts with the movable contact actually being a bimetallic strip. Visible behind the glass bulb is the small capacitor which shunts the starter and helps suppress electromagnetic interference. the 240VAC mains waveform. As the starter and the tube get older, starting becomes progressively harder until eventually the tube will not start at all and will only flash spasmodically. If left in this condition, the starter’s contacts may eventually weld shut, In the circuit of Fig.4 you will notice a capacitor con­nected across the starter bulb. The value and voltage rating of this capacitor is critical to the starter’s operation. Typically, the capacitor has a value of about 0.006µF and will typically have a voltage rating of 3kV if it is a ceramic disc and around 1kV or more if it is a wound plastic type. Clearly, the capacitor needs a high voltage rating if it is to withstand the spike voltage produced by the inductor when the starter contacts open. Second, the capacitance is critical as well. If the capacitor is too small in value or open circuit, the starter’s contacts will arc badly and quickly burn out. The capacitor effectively controls the rate of rise of the inductor voltage and if it is too large, the voltage will rise too slowly and the tube will fail to ignite. But there is another important function of the capacitor and that is to help suppress the very considerable electromagnet­ic interference produced by the tube when it is conducting and also when the starter contacts open. This interference is radiat­ed over a very wide spectrum, including the UHF bands. It is strongest and most apparent in the AM and shortwave radio bands. Even with the capacitor present, the interference is strong and for that reason, fluorescent lights and other forms of gas dis­charge lighting cannot be used in applications where low EMI is necessary. Electronic starters which replace the bimetallic strip design with an integrated circuit are now available (see SILICON CHIP, August 1996) but the adoption of an entirely new electronic control system does away for the need for a separate starter entirely. In addition to this, electronic systems have other major advantages. These include: (1) improved lamp and system efficacy; (2) no flicker or stroboscopic effects; (3) increased lamp life; (4) excellent light regulation possibilities; (5) reduced heating; (6) no need for power-factor correction; and (7) no hum. Ballast power loss is significant. As shown in Fig.2, a 36W lamp using a conventional ballast has an actual power consumption of 45W, with the ballast dissipating around 9W (20%) of the power drawn. Even a low-loss ballast dissipates 6W, compared with around 4.5W from an electronic ballast. Note that some compact fluorescent lamps have the ballast built-in and so, for these lamps only, the power rating includes ballast losses. Power factor Electronic starters are now available to replace the glow switch starters in fluorescent lamps fittings. They have a number of advantages, including the ability to disconnect the power and protect the ballast if the tube cannot be started. 8  Silicon Chip While the diagram of Fig.4 shows the most common fluores­cent lamp circuit as installed in most homes, the type installed in industrial and commercial installations typically has an addi­tional large capacitor connected directly across the 240VAC mains supply. The capacitor is included to provide power factor correc­tion. “Power factor” becomes a problem in any 50Hz mains circuit where the current waveform or phase is not identical with that of the 240VAC sine waveform. To explain further, in a resistive load connected across the 50HZ 240VAC mains supply, the current is exactly in phase with the voltage and it has the same shape; ie, a sinewave. In an inductive load, the current Are Fluorescent Lamps Mercury Hazards? If all this talk of the mercury vapour within a standard fluorescent tube makes you wonder about safety, you are not alone. Mercury – especially in the form of a vapour – is extreme­ly toxic. While the bulb remains unbroken there is little or no chance of ingesting the mercury. The problem comes, however, in the disposal of the used tube. While there is apparently little thought given to fluores­cent lamp disposal in Australia, a very different situation exists in the USA. There, the Environmental Protection Agency established in 1990 a Toxic Characteristics Leaching Procedure (TCLP) to assess the impact of substances that may be leached away from landfill dumps. Normal US-market fluorescent lamps generally fail the procedure! As a result of this and other pressures such as cost, fluorescent lamp producers have reduced the mercury content of lamps. In the US, the industry average for mercury in their standard 1.2 metre, 40 watt lamp has waveform still has a sinewave shape but it lags the voltage by up to a quarter of a cycle, ie, the phase lag can be up to 90 degrees. This presents a real problem because the power consumed by an inductive or ca­pacitive load is denoted by the following formula: P = VI.cos φ where phi is the phase angle between the voltage and current. Now the if the phase angle is 90 degrees, which will be the case in an ideal capacitor or inductor, then the value of cos phi will be zero. So in that case: P = VI.cos 90° = 0. In other words, while voltage is applied and current is flowing, the power being measured is zero! Now while the induc­tance in a fluorescent circuit is not perfect, there is still quite a lag between the voltage and current and so the power being measured (and paid for) by the customer is still quite low. This causes the energy authorities serious concerns because their distribution system still has to provide the current and take care of all the resistive losses between the generator and the been reduced from 48.2mg in 1985 to 22.8mg in 1994. However, lamps with 22.8 milligrams of mercury still do not pass the TCLP test! Philips has developed a new lamp which uses significantly less mercury. Mercury capsules are mounted in the lamp and are activated only after most lamp impurities are removed. The use of buffer gases further reduces mercury loss, meaning that less than 10mg of mercury is required to be used in their ALTO model lamps. In the US the green end-cap ALTO lamps have been available since 1995. It was expected that by the end of 1997 80 percent of all Philips fluorescent lamps sold in the US would feature low-mercury technology. The lamps feature the same life, colour rendering and efficacy as conventional fluorescent lamps. In Australia, as far as we can determine, fluorescent tubes also now have reduced mercury and the so-called buffer gases, argon and neon, have been increased. final (inductive) load. For this reason, commercial and industrial installations are generally required to have power factor correction capacitors installed in fluorescent light fittings. The term “power factor” comes from “cos φ” in the above equation. When the phase angle φ is zero, as for a resistive load, cos φ = 1. This is said to be a power factor of unity and is the ideal. To overcome the problem of lagging power factor, a capaci­tor is often placed across the mains supply to the lamp circuit. The capacitor draws current which “leads” the voltage waveform and so compensates for the “lagging” current drawn by the induc­tive portion of the circuit. This substantially improves the power factor, typically giving a ratio of 0.85, instead of around 0.7 for a fitting without power factor correction. Typically, a 4.2µF capacitor is fitted for a 36 or 40W lamp, and a 6.5µF capacitor for a 58W or 65W lamp. The capacitor also provides some smoothing of the current pulses drawn by the fluorescent tubes and thereby provides some reduction of the 50Hz harmonics which would otherwise be superimposed on the 240VAC mains supply. Mains control tones Typically though, correcting one problem causes another and so it is with power factor correction. The electricity supply authorities also superimpose control tones (typically around 1kHz) on the mains supply to switch hot water systems and control their distribution network. Unfortunately, power factor correc­ tion capacitors also cause the mains control tones to be reduced so in any large installation (ie, in factories and shops) a blocking inductor is connected in series with the lighting cir­cuits at the customer’s switchboard. This article has only covered the most common fluorescent lamp circuit using a glow switch starter. There are many other circuits, including rapid start, quick start and electronic ballasts which are beyond the scope of this article. Next month: high pressure mercury SC lamps SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. January 1998  9 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au Compasses: from magnetite to digital Compasses have not changed much since they were first invented. All compasses react to the Earth’s low level magnetic field and it is only now that electronic compasses are able to properly discriminate between the horizontal and vertical compon­ents of that field using technology developed by Precision Navi­gation, Inc. Compasses have helped guide people over the land and oceans for thousands of years. Historians date the first vehicle compass to 2634 BC, when a Chinese inventor suspended a piece of mag­netite from a thread to guide his chariot. The problem is, most compasses available today, whether mechanical or electronic, are not a great improvement upon the original. They still bounce over bumps, get thrown off course by magnetic interference and are adversely affected by factors such as vibration, tilt and acceleration. Only recently has technology been employed to improve on the original concept. The basic mechanical compass is still just a magnetised needle suspended on a jewelled bearing. The biggest innovation in mechanical compasses within the last few thousand years has been to envelop the magnetic needle in a viscous damping fluid. This allows the compass needle to settle more quickly after the com­pass 14  Silicon Chip has been moved and greatly reduces needle oscillation. Electronic magnetometers were developed decades ago but it wasn’t until the 1970s that there were any real production ver­sions of electronic compasses available to the general public. Most of these compasses were based upon flux-gate magnetometers, a technology first invented in the 1930s. All had mechanical gimbaling in order to eliminate errors due to tilt and were fairly limited for navigation. Most found application on sailboats. Designing a compass The most fundamental step in designing any compass is to have a device which reacts to the direction of the Earth’s low-level DC magnetic field. The mechanical compass magnetised needle has done this task fairly well for thousands of years. The elec­tronic compass, however, requires some sort of electrical trans­ducer to measure this low level field, which can then be trans­formed into a heading for display. A common approach used in the past combines a magnetised card which is optically encoded and a photodiode pair which can decode the position of this card. The magnetised card then acts as a normal mechanical compass and the optical electronics pro­vide input to a microprocessor which allows the heading informa­ t ion to be processed and displayed. Unfortunately, this approach has all the same weaknesses as any mechanical compass. To obtain a really improved compass, a different approach is required. Magnetic compass variables The Earth’s magnetic field is three-dimensional, having two horizontal components (X and Y axes) and one vertical component (Z axis). The closer you travel towards the Earth’s north or south magnetic poles, the Fig.1: block diagram of a digital compass based on the Precision Navigation variable permeability magnetometer. stronger becomes the Z component of the total magnetic field. For example, at the latitude of San Fran­cisco, the Z-component accounts for almost 70% of the Earth’s total magnetic vector. This creates a problem when a compass with fixed magnetome­ters for its X and Y axes is tilted. The relatively large Z component of the field gets mapped into the X-Y plane and is subsequently translated into a heading error. Depending upon the orientation of the compass and the latitude, this tilt error typically translates into two to five degrees of heading error for each degree of tilt from level. Tilt compensation There are three solutions to this problem. The first and most obvious is to ensure that the compass always remains level which is not always practical. The second is mechanical gimbaling of the magnetic sensors to ensure that they remain level when pitch and roll are present. The third method is electronic tilt compensation. This requires measurement of the Z component of the magnetic field via a third magnetometer and the measurement of pitch and roll of the system with some sort of tilt sensor. Tilt compensation is then taken care of mathematically via a microprocessor. In applications where the system remains level, fixed two-axis magnetic compasses are quite accurate and are less expensive than tilt-compensated systems. On rolling platforms requiring continuous accuracy, mechan­ical gimbal­ ing is the most common solution. A 2-axis magnetic sensor is attached to a pendulum (gimbal) which is encased in a viscous damping fluid to reduce oscillations. Typical pendulum designs accommodate tilts from ±20 de­grees up to ±45 degrees. Should the compass tilt beyond that range, the gimbaling is no longer effective and the accuracy is greatly reduced. This approach suffers from weaknesses such as gimbal lock, large size, fragility and the relative movement of the sensor with respect to the reference frame of the system. The third approach is a so-called “strapped down” solution. By using a triaxial magnetometer to measure the X, Y and Z axes of the magnetic field and including the input of the inclin­ ome­ter, errors generated by tilting the compass module are mathemat­ically corrected by the module’s microprocessor. The inclinome­ ter’s angular evaluation also can be displayed to the user or output to a host system. Dynamic environments Tilt-compensated magnetic compasses are vulnerable to vary­ing levels of vibration and acceleration. The limiting factor is not the magnetic sensors but the tilt-compensating mechanism, be it mechanical gimbaling or inclination sensors. Mechanically gimbaled compasses are the most susceptible to “sloshing” and slow response time on rolling or rumbling platforms. Liquid inclinometers are also compromised where there is rapid accelera­ tion. Varying the viscosity of the liquid can diminish this problem. For very dynamic platforms – military aircraft, for in­stance – accelerometers and gyroscopes, combined with magnetome­ ters provide the highest In applications where the system remains level, fixed two-axis magnetic compasses are quite accurate and can be catered for by Precision Navigation’s Vector-2X compass module, shown on the right. Where tilt compensation is required as well, the Precision TCM2 module on the left is available with ±20 de­grees, ±50 degrees and ±80 degrees of compensation. January 1998  15 Silicon Chip Binders REAL VALUE AT $12.95 PLUS P &P These binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. ★  Hold up to 14 issues ★  80mm internal width ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p Available only in Australia Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard  ❏  Visa   ❏ Mastercard Card No: ________________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ 16  Silicon Chip Made by Precision Navigation, Inc, this handheld digital compass has inbuilt tilt compensation up to ±15 degrees and many features that were undreamt of years ago. It can be referenced to true or magnetic north, has red and green lights to allow a fixed course to be maintained at night and can store up to 10 bearings and even multi-leg courses with a heading and time for each leg. It even alerts you to magnetic interference from nearby metallic objects, power lines, etc. reliability but at a substantially higher price. Magnetic distortion corrections All compasses can perform well in a controlled environment, where the ambient magnetic field consists solely of the Earth’s field. In most practical applications however, an electronic compass module will be mounted in a host system such as a vehi­cle, and this will contain large sources of magnetic fields such as steel chassis, transformer cores, electrical currents and permanent magnets in electric motors. This “hard iron” magnetism remains relatively stable over time and therefore can be measured and calibrated out of compass readings. Calibration typically involves rotating the vehicle through 360 degrees and storing several magnetic readings. Howev­ er, once the local magnetic fields which cause the distortion errors have been measured, the magnetic sensors must stay fixed in relative position to that local distortion field. This is a serious limitation of mechanically gimbaled com­passes. The sensors are mounted on the end of a pendulum and therefore change their relative position within the distortion field and this can degrade compass accuracies. Precision Navigations’s TCM2 module has fixed magnetometers that never move with respect to its host system, thus calibration data is valid through its full tilt range. This calibration data is stored in the device’s non-volatile EEPROM so that it is preserved during power-down. “Soft iron” magnetism is a more difficult local distortion which varies in strength and direction – ie, it can add or sub­tract to the Earth’s magnetic field within a vehicle or system. Only a few electronic compass modules can handle soft iron anoma­lies. and can be made quite small. Because they work inductively, they draw a fraction of the current of flux-gate sensors, typically 2-3mA instead of 40-60mA. Flux gate technology Magnetoresistive (MR) Flux gate sensors typically comprise a low-coercivity core surrounded by drive and sense coils. The core is saturated with an AC current in the drive coil, inducing an AC voltage in the sense coil which includes the drive frequency and its second and higher order harmonics. The presence of an external magnetic field will cause a shift of the core’s hysteresis loop, creating a second harmonic which can be correlated to the strength of the external magnetic field. Most flux gate magnetometers are biaxial; ie, they only sense the Earth’s horizontal (X and Y) magnetic field. Accurate sensing of the vertical (Z axis) magnetic field component is critical when a compass is electronically gimbaled. Some flux gate compass manufacturers do offer electronically gimbaled modules. These are typically coupled biaxial sensors with one redundant axis combined with a tilt sensor. Permalloy and other materials exhibit a variation of their ohmic resistance when subjected to varying external magnetic fields. Magnetoresistors are typically fabricated by depositing thin film or nickel-iron (NiFe) onto a silicon substrate as a standalone magnetoresistive bridge, or integrated with signal processing circuitry. A magnetic field rotates the internal magnetisation vector in the film and the varying angle of this vector with the current flow alters the resistance. MR sensors are relatively inexpensive to manufacture but like fluxgates, their analog output needs to be converted through A/D circuitry for many applications, which increases costs and complexity. Magneto-inductive Precision Navigation’s magnetoinductive sensors were pat­ented in 1989. Each single-axis sensing coil is wound on an elongated strip of high direct-current permeable magnetic materi­ al and is self-biasing. Each sensor provides an oscillation signal that varies in frequency when oriented at different angles with respect to the Earth’s magnetic field. A microprocessor can then receive sensor information in frequency form, which is converted into an orientation with respect to the Earth’s magnet­ic field. The frequency of the oscillating signal at the output of the sensing circuit varies substantially (eg, by about 100%) as the sensing coil is moving from a parallel to an antiparallel orientation, with respect to the Earth’s magnetic field. These substantial frequency differences mean that a very accurate digital readout of angle between the sensing coil orientation and magnetic North is obtained from the microprocessor. Due to the simplicity of design and materials, magneto-inductive sensors are very inexpensive to manufacture SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. Hall effect Hall effect sensors are at the low end of the sensitivity spectrum. They are fabricated with monolithic integrated circuit processes and are thus small and inexpensive. However, they are largely impractical for measuring the Earth’s field because they suffer from drift, instability and poor sensitivity. In the future, we can expect to see this technology in con­sumer products ranging from hand-held GPS receivers with built-in compassing to toys and mobile communications equipment. SMART ® FASTCHARGERS Brings you advanced technology at affordable prices Availability For further information on the Precision Navigation Vector-2X and TCM2 modules, contact Sphere Communications, PO Box 380, Darlinghurst, NSW 2010. Phone (02) 9344 9111; fax (02) 9349 5774. For information on the Precision Navigation Outback-ES digital compass, contact Sphere Communications or Av-Comm Pty Ltd, phone (02) 9949 7417 (see their 32-page catalog elsewhere in this issue). Acknowledgement: this article was adapted from an ar ticle entitled “Magnet­ ic Compass­ ing” by George Hsu of Precision Navigation originally published by Measurements & Control, SC September 1995. As featured in ‘Silicon Chip’ Jan. ’96 This REFLEX® charger charges single cells or battery packs from 1.2V to 13.2V and 110mAh to 7Ah. VERY FAST CHARGING. Standard batteries in maximum 1 hour, fast charge batteries in max. 15 minutes AVOID THE WELL KNOWN MEMORY EFFECT. NO NEED TO DISCHARGE. Just top up. This saves time and also extends the life of the batteries. SAVE MONEY. Restore most Nicads with memory effect to remaining capacity and rejuvenate many 0V worn-out Nicads EXTEND THE LIFE OF YOUR BATTERIES Recharge them up to 3000 times. DESIGNED AND MADE IN AUSTRALIA 12V-24V Converters, P. supplies and dedicated, fully automatic chargers for industrial applications are also available. For a FREE detailed technical description please Ph: (03) 6492 1368 or Fax: (03) 6492 1329 2567 Wilmot Rd, Devenport, TAS 7310 January 1998  17 Build your own LIGHTSHOW PART 1: By LEO SIMPSON & RICK WALTERS Whenever you go to hear your favourite band or disco, there is bound to be a light show. Now you can have your own, in your home, your car or virtually anywhere as this one runs on 12V AC or DC. 18  Silicon Chip T HIS IS NOT THE FIRST light show we have published. Our first was the highly successful DiscoLight published in the July & August 1988 issues of SILICON CHIP. Many thousands of Disco­Lights have been built over the years and they are standard equipment in many portable discos. They are still available as kits from Dick Smith Electronics and Altronics. This new Light Show has all the user features of the popu­lar DiscoLight but it operates from 12V DC or 12V AC and drives standard 20W or 50W halogen lamps. Like the DiscoLight, the Light Show drives four channels of coloured lights. It can be controlled directly from your stereo system’s loudspeakers or a portable CD player, or it can be trig­gered from live music picked up by an inbuilt microphone. It also has its own chaser functions so it can produce all sorts of light patterns on its own, with or without modulation by the music. Not only can the Light Show be used in your home but you could even use it in your car, caravan or recreational vehicle since it runs from a 12V battery, if you want. Think how it could boost the rating of your car in a “Sound Off” competition. What it does The Light Show divides the audio signal from your stereo system into four frequency bands to modulate the brightness of four halogen lamps. Each lamp shines through a coloured filter, to make an eye-catching display. You might use red for the lowest frequency band, then green, yellow and blue for the highest frequency band. When the music stops, the Light Show can be switched to provide its own light patterns: chaser, strobe and alternate patterns (we’ll describe these later). Let’s have a look at some of the features of the Light Show. On the rear panel is a two-way insulated terminal block for the 12V input and a fuseholder. Another five-way insulated termi­nal block is provided for connection of four 20W or 50W halogen lamps. There is also a set of four spring-loaded terminals so that you can connect the signals from both channels of your stereo amplifier (or portable CD player, Walkman or other program source). These are connected Main Features Operating features •  Four light channels controlled by four separate audio channels •  Forward, reverse and auto-reversing chaser patterns •  Simultaneous strobe on all four channels •  Alternate light mode •  Music modulation available on chaser, strobe and alternate modes •  Adjustable rate for chaser, strobe and alternate modes •  Inbuilt microphone for beat triggering or audio modulation of lights •  Direct inputs for beat triggering or audio modulation of lights •  Sensitivity control •  Internal presettable sensitivity levels for each channel •  Front panel LEDs mimic light display Electrical features •  Operates from 12V DC or 12V AC •  400W maximum lamp load •  100W maximum lamp load in each channel •  Fused supply to lamps in parallel with your loudspeakers and cause negligible loading of your amplifier’s outputs. On the front panel are two knobs, a power switch and a group of five toggle switches, three of which are 3-position types. There are also five LEDs, one to indicate it is ON while the other four LEDs show what’s happening in each of the four channels. Let’s look at the functions of the group of five toggle switches first. Right next to the SPEED knob is the INPUT switch and this selects either the internal electret microphone or an external source which will normally be your stereo amplifier outputs. If the Light Show is being used near a live band (or a loud amplifi­er) you can merely switch to microphone and eliminate the need for any cable connections. As you might expect, you can use the LEVEL knob to adjust the audio signal level for the best light display. In the centre of the five toggles is the DISPLAY switch. This 3-position switch is the key to the Light Show’s functions. In its top DISCO position, you get the basic Light Show function whereby the audio signal is split into four separate frequency bands (low bass, upper bass, mid-treble and upper treble) and each of these bands control their respective lights. The brightness of the lamps at any instant is directly proportional to the sound level in the respective audio frequency band. In the Modulate (MOD) position of the DISPLAY switch, the audio signal both modulates the lights and triggers the various modes selected by the adjacent PATTERN switch. Finally, the Unmodulated (UNMOD) setting of the DISPLAY switch allows the light display to be set by the PATTERN switch. The PATTERN switch gives three light displays: 4-light chaser, strobe and alternate. The Chaser mode is self explana­tory; the four lights chase each other in one direction or the other, as set by the adjacent DIRECTION switch. The speed at which the lights chase each other is set by the SPEED control knob. In the Strobe mode, all four lights flash on simultaneous­ly, at a rate set by the SPEED control. In the Alternate mode, two pairs of lights flash on and off alternately, again, at a rate set by the SPEED control. The DIRECTION switch controls the Chaser mode. You can have the lamps chase in one direction or the other or change direction automatically, every minute or so. Finally, the BEAT switch gives beat triggering from the music for the Chaser, Strobe and Alternate pattern modes. In the Oscillator setting of the BEAT switch, these functions are January 1998  19 Fig.1: the audio signal is split into four frequency bands, rectified and compared with a 50Hz ramp reference signal. The Mosfets are then switched either by the comparator outputs or by signals from the inbuilt pattern generator. con­trolled by the SPEED knob. The four LEDs on the front panel mimic the behaviour of the four light channels, so that even if you can’t see the lamps directly (say you are acting as disco operator), you can tell what they are doing by looking at the LEDs. The LEDs also come in handy during any troubleshooting which may have to be done and they also allow all the circuit functions to be tested without connecting the lamps. How it works The circuitry for the Light Show consists of three quad op amp ICs, five CMOS ICs, four power Mosfets, five LEDs, one 3-terminal regulator and 19 diodes. And that’s just the semis. Add in the resistors, capacitors, switches, pots and all the other hardware bits and it comes to quite a stack of components. Fig.1 shows the block diagram of the circuit. Switch S1 selects the audio signal, either from the internal microphone or from the loudspeaker terminals (which connect to your stereo). The audio signal is then fed to four filters which split it into four 20  Silicon Chip distinct frequency bands: Low Bass, Upper Bass, Mid Treble and Upper Treble. The Low Bass frequency band is provided by a 200Hz low pass filter – this means that only signal frequencies below 200Hz are allowed to pass. Then there is the Upper Bass band which passes a band of frequencies centred on about 440Hz. This is actually a narrow bandpass filter centred on 440Hz. The Mid Treble band is another bandpass filter, centred on 1kHz. Finally, the Upper Treble band is from 2kHz to 20kHz and is provided by a 2kHz high pass filter (ie, everything above 2kHz passes). Fig.2 shows the response of all the filter bands. As you can see, the whole audio band is not treated equally, in that some frequencies around 300Hz, 600-700Hz and 1.5kHz are somewhat attenuated but that does not matter in the overall scheme of things. The audio signal from each of the four filters is rectified and smoothed to provide a varying DC level, which is then fed to one of four comparators. The comparators compare the varying DC signal to a 50Hz ramp reference signal which is derived from the pulse generator and shaper. Fig.3 shows the interaction of the varying DC, from one of the audio filters and rectifiers, with the 50Hz ramp reference signal. Whenever the slowly varying DC signal is above the level of the 50Hz reference signal, the output of the comparator goes high to turn on the associated Mosfet. That’s the basic process of how the audio signal is filtered and rectified and then used to control the Mosfet switching time to vary the re­spective lamp’s brightness. But as you might have guessed, there’s a lot more to it than that, otherwise the circuit of the Light Show (which you’ve probably looked at and shuddered) would be a lot simpler. Now refer back to Fig.1. Instead of the four comparator outputs going directly to trigger the Mosfets they go via a block labelled as a 4-pole double throw switch (IC5). This switching IC selects either the signals from the four comparators or a pattern generator. Signals from the pattern generator drive the Mosfets and hence the lamps in the chaser, strobe or alternate modes. Well, that’s probably as far as we can go with block dia­grams in describing the basic operation of the Light Show. Now, we have to stop dithering about and get into the circuit descrip­tion proper. Circuit description Let’s start at the extreme top lefthand corner of circuit of Fig.4. Op amp IC1b provides gain for the electret microphone. The electret is powered via a network consisting of a 1kΩ resis­ tor and 100µF capacitor which provide decoupling from the main +10V supply while bias current is fed via the 4.7kΩ resistor. The electret’s signal is coupled by a .047µF capacitor to the non-inverting (+) input of IC1b which boosts the signal by about 31 times. The output of IC1b is coupled via a .047µF capacitor to the INPUT switch S1. Also connected to this switch is an input atten­uator consisting of two 10kΩ resistors, one for each speaker lead from your stereo amplifier. The 10kΩ resistors connect via a common 1.8kΩ resistor to ground. This networks mixes the two stereo channels together as well as attenuating them. After INPUT switch S1, the signal is fed to the LEVEL con­trol (VR5) and then to op amp IC1a (a stage identical to IC1b) which again provides a gain of 31 times. IC1a’s output is then fed to the four filter stages to provide the four frequency bands mentioned previously. IC2d and its associated components form the 2kHz high pass filter. This is a third order (three RC time-constants) filter which means that signals below 2kHz are rolled off at 18dB/oc­tave. IC2c and associated components form the 200Hz low pass filter and again this is a third order type. IC2a and IC2b and their associated components form twin-T filters. These are the 440Hz and 1kHz bandpass filters for the upper-bass and mid-treble frequency bands (as shown on Fig.1). The output of each filter is rectified with a diode pump consisting of two diodes, a 10µF coupling capacitor and a 1µF smoothing capacitor. The varying DC output from each filter stage is fed to a 50kΩ preset potentiometer (VR1-VR4). Thus the sen­ sitivity of each channel can be set to provide equal brightness of the lamps for typical music signals. Following the presets, the DC signals are fed to the non-inverting inputs of op amps IC3a, IC3b, IC3c & IC3d which are wired as comparators. These compare the varying DC AUDIO PRECISION SCFREQRE AMPL(dBr) & AMPL(dBr) vs FREQ(Hz) 15.000 13 NOV 97 13:57:55 15.00 10.000 10.00 5.0000 5.000 0.0 0.0 -5.000 -5.00 -10.00 -10.0 T -15.00 20 100 1k T T T 10k -15.0 20k Fig.2: this plot shows the response of the four filter bands which drive the Mosfets. As you can see, the whole audio band is not treated equally, in that some frequencies around 300Hz, 600-700Hz and 1.5kHz are somewhat attenuated but that does not matter in the overall scheme of things. Fig.3: these digital scope waveforms show how the varying DC signal from one of the audio filters and rectifiers (middle trace) interacts with the 50Hz ramp reference signal (top trace). Whenever the slowly varying DC signal is above the level of the 50Hz reference signal, the output of the comparator (bottom trace) goes high to turn on the associated Mosfet. Fig.4 (following page): the complete circuit diagram of the Light Show. IC2a, b, c & d are the four audio filters which are followed by rectifiers which feed trimpots VR1, VR2, VR3 and VR4 and then IC3a, b, c & d which are the comparators. IC5 is the display selector while IC4b, IC6 & IC7 make up the pattern generator. January 1998  21 22  Silicon Chip January 1998  23 Parts List 1 main PC board, code 01112971, 234mm x 160mm 1 front panel PC board, code 01112972, 120mm x 50mm 1 plastic case, 260mm x 180mm x 65mm, complete with metal panels; Jaycar HB-5974 or equivalent 4 20W or 50W halogen lamps (see text) 4 halogen lamp sockets 1 12V 5.25A enclosed halogen lamp transformer; Jaycar MP-3050 or equivalent (AC operation; see text) 3 SPDT toggle switches (S1,S5, S6) 1 SP3T toggle switch (S2); Jaycar ST-0558 or equivalent 2 DP3T toggle switches (S3,S4) 5 bezels for 5mm LEDs 2 16-pin IDC headers, Jaycar PI-6550 or equivalent 1 150mm-length 16-way ribbon cable to suit header 1 electret microphone 1 4-way speaker terminal panel 1 5-way terminal block 1 2-way terminal block 1 panel mount 3AG fuseholder 1 10A 3AG fuse 2 knobs to suit VR5 and VR6 5 16-pin IC sockets 5 14-pin IC sockets 2 3mm x 6mm bolt 3 3mm x 15mm bolt 5 3mm star/crinkle washer 5 3mm nut 2 6PK x 5mm screw 19 PC stakes Semiconductors 3 LM324 quad op amps (IC1IC3) 1 4093 quad NAND gate (IC4) 1 4019 4PDT switch (IC5) 1 4029 up/down counter (IC6) 1 4051 1-of-8 multiplexer (IC7) 1 4081 quad AND gate (IC8) for each frequency with the ramp reference signal from IC4d which is connected to the inverting input of each comparator. Pulse generator IC4d is one section of a 4093 quad 24  Silicon Chip 4 BUK456/A/B/H Mosfets (Q1Q4) 1 7805 5V regulator (REG1) 1 39V 5W zener diode (for AC operation) 18 1N914 small signal diodes (D1-D18) 1 1N4004 power diode (D19) 5 5mm red LEDs 1 400V 35A bridge rectifier BR1 (for AC operation) 4 50kΩ trimpots, horizontal PC mounting (VR1-VR4) 1 100kΩ log PC-mount potentiometer (VR5) 1 1MΩ linear PC-mount potentiometer (VR6) Capacitors 1 2200µF 25VW PC electrolytic 3 100µF 16VW PC electrolytic 7 10µF 16VW PC electrolytic 1 2.2µF 16VW PC electrolytic 4 1µF 16VW PC electrolytic 1 0.12µF MKT polyester 2 0.1µF MKT polyester 1 .068µF MKT polyester 1 .056µF MKT polyester 3 .047µF MKT polyester 3 .033µF MKT polyester 1 .022µF MKT polyester 2 .015µF MKT polyester 1 .0068µF MKT polyester 3 .0022µF MKT polyester Resistors (0.25W, 1%) 2 1MΩ 1 18kΩ 1 510kΩ 4 11kΩ 3 470kΩ 18 10kΩ 4 220kΩ 2 5.6kΩ 3 180kΩ 2 4.7kΩ 3 100kΩ 2 3.3kΩ 1 47kΩ 1 2.2kΩ 1 39kΩ 1 1.8kΩ 1 27kΩ 6 1kΩ 8 22kΩ 1 470Ω 1 68Ω 1W (AC operation) Miscellaneous Tinned copper wire, hookup wire NAND gate which is con­ nected to function as a pulse generator with a positive duration of about 1ms and a period of 20ms; ie, the pulse repetition rate or frequency is 50Hz. Each time the output of IC4d goes high, diode D18 charges the 0.1µF capacitor to +10V and this capacitor will discharge exponentially through the 10kΩ and 39kΩ resistors. This gives us the falling ramp waveform shown in Fig.3. As noted above, whenever the slowly varying input DC signal to a comparator is above the level of the 50Hz reference signal, the output of that comparator goes high to turn on the associated Mosfet. However, the comparator outputs do not change state (ie, go low or high) fast enough to drive the Mosfet gates directly. Instead, the four comparator outputs go via IC5 and then via the 4081 quad AND gate IC8. This is used as a buffer to speed up the rising and falling edges of the comparator outputs. Hence, comparator IC3a connects via IC5 to AND gate IC8d which drives Mosfet Q4. Each Mosfet gate is connected to the 0V line via a 10kΩ resistor. This ensures that the Mosfets are held off when the power to the driving circuitry is off. This is important because the 12V supply to the lamps and Mosfet drains is always connected and the power switch only switches the power to the 3-terminal regulator. Well that’s how the DISCO section works. Now let’s look at the other functions. In the DISCO mode the moving contact of switch S4b is con­nected to +10V. This holds pin 14 of IC5 and pins 8 & 9 of IC4c high. IC4c acts as an inverter and so pin 9 of IC5 will be low. Under these conditions, IC5 feeds the four comparator outputs through to the Mosfet gates. If DISPLAY switch S4 is in the MODulated or UNMODulated position, pin 14 of IC5 and pins 8 & 9 of IC4c are held low by the 10kΩ resistor. So inverter IC4c’s output and thus pin 9 of IC5, will be high. This disconnects the Mosfet gates from the comparator outputs and connects them to the other set of inputs on pins 2, 6, 4 and 15. These inputs are fed from the 1-of-8 multiplexer 4051, IC7. This has one input (pin 3) which can be connected to any one of its eight outputs, depending on the logic levels applied to pins 9, 10 and 11. Outputs 1-4 (pins 13,14,15,12) are connected to IC5 with output 1 connected to Q1 through IC8c and so forth. Output 5 (pin 1) is connected through diodes D9-D12 so if it is high IC7 stays high, pin 10 is now low and pin 11 is toggled by pin 6 of IC6. This means that pin 1 of IC7 will toggle high and low and it will turn all the Mosfets on and off via diodes D9-D12, IC5 and so on. This means that all lamps will turn on and off at full brightness in sym­pathy with the OSCILLATOR or BEAT signal. With S3 in the CHASER position, pin 9 of IC7 is low while pins 10 & 11 are toggled by pins 6 & 11 of IC6. To modulate or not Inside the Light Show: the four Mosfets grouped at the back of the PC board drive the halogen lamps. They do not need any heat­sinks and will normally run cold to the touch. the four inputs to IC5 will be high. Output 7 (pin 2) is connected through diodes D15 and D16 to inputs 1 and 2 of IC5 and output 8 (pin 4) is connected through diodes D13 and D14 to inputs 3 and 4. Chaser control Op amp IC1c is configured as a Schmitt trigger oscillator which produces a square wave and its frequency is adjusted by VR6, the SPEED control. Op amp IC1d is connected as a comparator which is fed from trimpot VR1 through a 10kΩ resistor. This is the signal from the 200Hz filter and it goes high whenever there is a bass beat to cause the output at pin 14 of IC1d to go high. Depending on the setting of the BEAT switch S5, the output of IC1c (SPEED oscillator) or IC1d (audio beat comparator) will be used to clock IC6, a 4029 4-bit counter. We’re only using two outputs, from pin 6 and pin 11. IC6 can be made to count up or down, which we refer to as FORWARD and REVERSE in this circuit. Pin 10 and the 3-position DIRECTION switch S2 controls this function. In the FORWARD set­ting of switch S2, pin 10 is pulled high while in the centre-off position, pin 10 is pulled low by the 10kΩ resistor and so IC6 runs in the REVERSE direction. In the AUTO position of S2, we use the square wave signal from Schmitt trigger oscillator IC4b. This changes its logic level roughly once a minute and this will cause the counter to reverse the chaser direction every minute. Pattern selection IC7 and the PATTERN switch S3 control the patterns dis­played by the lamps. Assume for the moment that the DISPLAY switch S4 is set to the UNMODulated position. This will pull pin 6 of IC7 low. This is the inhibit pin and when it is high all the outputs are low. By pulling pin 6 low, we enable the outputs, which means the output selected by the logic on pins 9, 10 and 11 will be connected to pin 3. We now vary the logic values on pins 9, 10 and 11, to obtain the three patterns selectable by switch S3. For example, with S3 set to the ALTERNATE position, pins 9 and 10 of IC7 are high and pin 11 is toggled by pin 6 of IC6. This will cause pins 2 and 4 to alternately go high and low. Pin 2 will turn Q1 and Q2 on through D15 and D16, pin 4 will turn Q3 and Q4 on via D13 and D14. This will alternately turn the pairs of lamps on. Strobe & chaser With S3 set to STROBE, pin 9 of All the foregoing descriptions had the DISPLAY switch S4 in the UNMOD-ulated position whereby the inhibit pin of IC7 was held low. In the MODulate setting of S4, pin 6 of IC7 is connect­ed through a 22kΩ resistor to the output of inverter IC4a. IC4a is connected to IC3d, the low pass filter comparator and therefore responds to the bass beat of the music. Now what happens is that the lamps respond in the pattern set by the display switch; ie, chaser, strobe or alternate but instead of flashing to full brightness, their brightness varies in sympathy with the loudness of the bass beat. Power supply As shown on the circuit, the input from a 12V DC power supply or battery is fed via a 10A fuse, direct to the lamps and to the power switch S6. So, as already noted, there will be voltage present at the drains of the Mosfets while ever 12V is present at the supply inputs. That is why it is important for the gates of the Mosfets to be normally tied low. Following switch S6, the supply is fed via diode D19 to a 3-terminal 5V regulator which is connected to provide +10V and +5V supply rails. The +5V rail is used as a convenient “half supply” reference to bias the op amps in the circuit; ie, IC1a, IC1b and IC2a, b, c & d. The other op amps are wired as oscilla­tors or comparators so they don’t need the same biasing. Both the +10V and +5V rails are bypass­ed with 10µF and 100µF capac­ itors respectively, to provide decoupl­ ing and bypassing of high frequency “hash”. That completes the circuit description. Next month we’ll present the constructional information for 12V AC and DC versions of the circuit plus SC a troubleshooting proce­dure. January 1998  25 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au Run your model railway with Command 28  Silicon Chip Part 1: How would you like to run as many as 16 locomotives on your layout, all at the same time? And would you like to be able to do it without masses of wiring in the layout and the need for separate speed controllers for each locomotive? You would? – then read on. Design by BARRY GRIEGER F While this photo shows just seven locomotives, the Protopower 16 Command Control system to be described in this series of articles can control up to 16 locomotives simultaneous­ly. OR MANY MODEL RAILWAY enthusiasts, the enjoyment comes from the variety of prototype operations that can be built into a layout, irrespective of home or a club. Some modellers enjoy mainline running of interstate freights and passenger trains. Others enjoy yard and industry switching, engine terminal service and branch line operation. Still others enjoy the make-up and splitting-up of trains at terminals. But the enjoyment can rapidly turn to frustration and disillusion when it comes to wiring a layout for operation of more than a single cab for train control. “Single cab” means single loco or single train in model railway jargon and if you want multiple locos you need “multiple cab” operation, with a separate controller for each locomotive. In addition, each locomotive can only run in a block section of the layout. Now block wiring for multiple cabs can become very compli­cated, especially if you want say, five or six locomotives oper­ating simultaneously. For 16 locomotives, the wiring would be extremely complex and it is doubtful if anyone would attempt it, even on a large club layout. Fortunately, there is an alternative approach that offers simple layout wiring while allowing you to run as many as 16 locomotives or trains independently and simultaneously. The solution is Command Control. OK, would you really want to be able to control 16 locomo­tives simultaneously? Well, why not? You want realistic opera­tion, don’t you? Consider, for example, if you had a large double loop of track which means that you can run trains in both directions at the same time. That double loop could have several stations and stops along the way and you could have, say, four separate trains running and stopping on the east (direction) track and the same number of trains on the west track. And you might have a few locomotives running on spur lines and a few working on shunting duties in marshalling yards. You can see how the number of loco­motives starts to climb, can’t you? Of course, this range of operation is nothing like as com­plex as a real full scale railway but even so, it would Control January 1998  29 require a huge amount of wiring, a lot of speed controllers and probably quite a few people to run it as well. With Command Control, the wiring is greatly simplified, you don’t need block sections and you only need one power supply. History of Command Control For too long, Command Control for model railways has been out of reach for the average Aussie modeller, for a number of reasons. In the early 1980s, Keith Gutierrez paved the way in North America with his “CTC-16” system. It is a digital propor­ tional command control system and was published in detail in “Model Railroader” magazine. A few years later, the next genera­ tion system, “CTC16e” was published. Since then, there have been other systems such as “Dyna­trol” by Power Systems Inc, “CTC-80” by Keeler Rail Specialties, “Zero 1” by Hornby and “PMP 112” by Pressed Metal Products. Unfortunately, not many of these systems were compatible and due to the physical size of the electronic components used, they were only suitable for HO and larger scale locomotives. As the benefits of command control are realistic prototype operation and easier layout wiring, the National Model Railroad Association of America in due course proposed a set of standards for Command Control. These standards were based upon the Lenz System of Europe and the concept of Digital Command Control was born. Today, DCC is gaining popularity due to the small size of the receivers (decoders) – so small, in fact, that they can be fitted into N-scale locos. This has recently motivated Keith Gutierrez to publish his “EasyDCC “ command control system in “Model Railroad­er”. So DCC has brought freedom for the modeller but at a price. The technology is brilliant but being based upon microprocessors and surface mount components it represents a field that many railway modellers don’t want to venture into. Over the next few months, we will publish a Command Control system. This will enable the average modeller or electronics hobbyist who has a collection of wide bodied locomotives like Athearn, Life-Like, Bachmann, Powerline and Lima, to build their 30  Silicon Chip Brief Specifications •  Can control up to 16 separate locomotives. •  Consists of four easy-to-build parts: Throttles, Command Station, Power Station(s) & Receiver/Decoders. •  Receiver/decoders fit inside locomotives (HO & larger scale). •  Provision for momentum (inertia), braking & constant brightness headlamps. own system, understand how it works, construct their own decoders and make any repairs themselves. What is Command Control? Command Control is quite different from any conventional model railway speed control. A conventional speed control or throttle varies the voltage and voltage polarity to the track and thereby varies the speed and direction of the locomotive. By contrast, Command Control maintains a constant voltage with fixed polarity across the track at all times. Superimposed on this constant track voltage is a serial data stream with blocks of 16 pulses, one pulse for each of the 16 locomotives which can be used on the system. These pulses have an amplitude of about 5V peakto-peak and so form a very “robust” data stream which will not be subject to interference from the commutator hash of typical model locomotives. The serial data is fed to every locomotive on the track. Each locomotive has its own decoder so that only it responds to the speed and direction commands of its particular handheld throttle control. The locomotive decoder drives its own pulse amplifier to drive the locomotive at the right speed, slow or fast, and in the right direction, forward or reverse. The serial data stream on the track is similar to, but not the same as, the serial data transmitted to radio-controlled model aircraft, cars and boats. In radio controlled models, the serial data stream is used to control servos and the speed of the engine in just one model. In this Command Control system for model railways, the track serial data stream is used to control the speed and direction of up to 16 model locomotives. (Editor’s note: for a good explanation of radio control principles, see the November & December 1997 issues of SILICON CHIP). Protopower 16 Protopower 16 is my version of the original CTC 16 command control system designed by Keith Gutierrez in January 1980. This system was made obsolete by the demise of the Signetics NE544N chip used in the decoders. Protopower uses a Plessey ZN409CE decoder which is still available. Fig.1 is a graphical representation of how the system works. Only one locomotive and one throttle is shown, to keep things simple. (1). The handheld throttle settings for speed and direction of the specific locomotive are fed to the command station. In this case we have shown throttle number 5. (2). The command station takes the speed and direction informa­tion from each throttle and in turn inserts it into one of the 16 channels in the serial data stream. (3). The command station checks all 16 throttle inputs approx­imately 100 times per second for speed and direction data and sends the resulting serial data stream to the power station. (4). The power station then combines this data stream with a constant 11.2V DC to form a composite voltage of about 16V DC. (5). A preprogrammed receiver/ decoder installed inside each locomotive receives this voltage, decodes the programmed channel from the serial data stream and then extracts the speed and direction data to power the electric motor in the locomotive according to the original throttle settings. (6). If more than one throttle is being used at the same time, then each preprogrammed decoder inside a locomotive will only react to its own channel. Other channels or locomotives won’t do anything. Therefore, it is possible to have two locomotives within centimetres of each other, each under separate control. This means that head-on and tailend collisions and other aberrations are quite possible! Fig.2a shows the special composite waveform present on the track at all times. Fig.2b shows how the pulse Fig.1: this is a graphical representation of a Command Control system for model railways. The speed and direction settings from each handheld throttle are feed to the command station which produces a serial data stream. The pulses of the data stream are superimposed on the constant voltage to the track and fed to all locomotives. Each locomotive has its own receiver/ decoder to drive it at the correct speed and direction. January 1998  31 Fig.2: this is a representation of the serial data stream super­imposed on the constant track voltage. It (a) consists of blocks of 16 pulses separated by a sync pulse pause. Depending on the width of each channel pulse, it may be decoded as a command to (b) stop the loco; (c) run at maximum reverse; or (d) run at maximum forward speed or any speed setting in between. must be installed inside each locomotive. If you have 16 locomotives, you will need 16 receiv­er/decoders. If you have more than 16 locomotives, you will still need one receiver/decoder for each loco and this means that more than one loco will be assigned to some channels. So if you have 50 locomotives and you want to be able to run them all (not simulta­neously, of course), you will need 50 receiver/ decoder PC boards. (2). Each locomotive will be labelled on the underside with its channel number. Two identical locomotives assigned to the same channel can be used for “double heading”. (3). The PC board is to be cut if necessary and joined with flexible wiring to enable the circuitry to be fitted into the restricted spaced inside the body shells of locomotives. (4). Constant brightness for locomotive headlights is standard. (5). Changing receiver channels is a simple matter. A locomotive assigned to one channel can be easily changed to any other chan­nel. (6). Each receiver has a maximum current rating of 1A DC. Critical parts width of a specif­i c channel determines the speed and direction. The Protopower 16 System consists of simple throttles, the command station, the power station and the receiver/decoders. (1). This is the brains of the system and incorporates a master digital oscillator, a triggered ramp generator, a pulse width modulator, digital switching of analog throttle data, multiple line driver outputs for connection to power stations/auxiliary power stations, and a throttle power supply. composite voltage and has a current rating of 5A. If each of your locomotives draws a maximum of 1A and you want to operate 16 locos, then you will need more power. Up to four more power stations can be added to the system. (2). These additional power stations are used to divide your layout into divisions (blocks). Each division is connected to its own power station and separated from other divisions by a gap in the rails. Since each power station is fed the same serial data signal from the command station, each division has an identical composite voltage signal on the rails. Each locomotive can cross the gap in the rails and continue to run without hesitation. As far as the receiver/decoder is concerned, it sees identical signals and it will behave as if there were no gap between divi­sions. Such blocks or divisions in a large layout have a number of uses, one of which is to enable short circuits or open circuits to be more easily pinpointed. Power Stations Receiver/decoders Throttles (1). Each throttle is wired directly to a specific channel (locomotive). (2). Simple throttles have only two parts – a directional switch and a potentiometer. (3). Each throttle needs four wires to connect it to the command station. (4). Throttles incorporating momentum (inertia) and braking can be easily built into the simple design. Command Station (1). The power station produces the 32  Silicon Chip (1). A receiver/decoder PC board While most of the circuitry involved in the Protopower 16 system uses standard readily available parts, each receiver/decoder has three critical parts and you may want to order them to ensure that you have a reasonable number on hand for your layout. The parts are as follows: (1). A 14-pin DIL Servo Control integrated circuit, ZN409CE, made by Plessey. These are available from Farnell Electronic Compon­ents, order code 407.574. Phone (02) 9645 8888. They are also available from RS Components, product code 304-813. Phone (02) 9737 9966. (2). A top-adjusted, sealed, single turn 1kΩ 0.5W cermet trimpot. These are available from Farnell, order code 107.617 or from RS Components, product code 187-955. (3). A .015µF or .018µF 5% NPO ceramic disc capacitor (.018µF preferred). These are available from Crusader Electronics (Sydney & Melbourne), order code C333C153J1G5CA for .015µF or C333C183J1G5CA for .018µF. Next month we will describe the circuit and construction details for SC the Command Station. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia January 1998  37 MAILBAG Internet a disaster for small business Each month I carry around the current issue of SILICON CHIP in my briefcase in order that I may read it from cover to cover during my meal breaks. This may take several weeks and I have a fairly strict order in which I read the articles. I usually turn to my own article first, for two reasons: one because like Isaac Asimov, I always enjoy reading what I write, and secondly to see what sort of job you guys have made of presenting it. I then read “The Serviceman”. I do not know why I like this column but I have been reading it for more years than I can remember and yet I have never serviced a TV in my life and intend never to service a TV in my life. So why do I enjoy this series so much? I think it is to do with the fact that it contains jolly good yarns and I love a good story. Anyway, next I turn to the front page and begin a systemat­ic reading of the rest of the magazine, which means the “Publish­er’s Letter” comes next. Now when I read this editorial in the September 1997 issue I nearly inhaled my toasted cheese and ham sandwich as a result of my gasp of incredulity. I could not believe my eyes, for here was a poorly thought through argument indeed! I need not remind you that in general small business in this country has taken a battering over the past decade, partly because it is continually being loaded down with an endless series of government interventions; ever escalating taxation and charges, increasingly restrictive legislation, and stop-start invest­ment and R&D policies – the list goes on. If this is not enough, we now have the spectre of GST looming over us, a tax that will turn all small business and professional people into an army of tax collectors, with the attendant hoards of tax investigators to look over the shoulders of this huge army. And yet here you are proposing that the Internet consumer and prospective customers of these business people should be exempt from all of 38  Silicon Chip these charges. As I see it, we will have an army of small business people staggering around with kitbags full of heavy duty impositions harassed on all flanks by ankle nipping nuisances, whilst their customers are free to scour the world for the cheapest source of supply, completely exempt from any form of government charge or intervention. Sadly this scenario is already taking shape in the hobby trade. Hobbyists are notoriously tightfisted with their money and techno-junkies to boot. The Internet is already a big deal in the R/C business and the R/C enthusiasts use it extensively for research, communications and last but not least, for sourcing of commercial products. These purchases already come in free of sales tax and duty if they are under $1000 (from memory) and what is more, they are delivered to the customer’s door. Whilst there is no proof yet of the detrimental effect of this trading on the small model shops, it is interesting to note that in the past few months eleven model shops in Sydney have closed their doors. Until there is a move to unload small business in this country and free them from the onerous impositions forced upon them by governments, both state and federal, it would be economic suicide to carry through your proposal. I believe that it would deal a crippling blow to small business in this country. In essence I agree with you but it cannot be done without an equal adjustment to the charges applied to small business and I believe that this will never happen. Contrary to prevailing opinion, I believe that the tariff is the only way in which the international economic playing field can be levelled. A well considered tariff system can adjust for the differences in social conditions prevailing in each country in such a manner that goods and services compete on quality rather than price. Besides this, the tariff is a true “user pays” tax. If you buy imports you pay the tax, if you buy local you do not. If we must collect taxes why not impose them in such a way that they have some benefit to the national economy instead of imposing a load. Charge the tariff and drop the sales tax is a much more sensible approach to my mind. So for the good of the country I hope your plea for the removal of duty and sales tax on the internet is ignored. Bob Young, Silvertone Electronics. 10th birthday congratulations Congratulations SILICON CHIP on your 10th anniversary. I have been a dedicated reader for the past few years and I have found the magazine to be very insightful, as electronics is the area of my interest. I have completed numerous kits that have been introduced by SILICON CHIP and I have an occasional laugh at the Serviceman’s Log. Your computer sections have helped me in the past to speed and soup up my computer. Also the advertise­ments from Dick Smith Electronics and Jaycar have saved me a bit of time. Once again, congratulations, for completing your tenth year. N. Gobsill, Ingleside, NSW. Mosfets vs. bipolar transistors in high power amplifiers As a user and repairer of high powered amplifiers I have been following your series of articles on the 500W amplifier with some interest. However, I would like to make some comments. The first concerns a comment in the first article that the authors of this article have a philosophy of not using mosfets in amplifier designs. I have a philosophy of not using bipolar amplifiers in my PA systems as I have found that firstly mosfet amplifiers tend to be more rugged and reliable as I have yet to have one fail under normal operating conditions. The only mosfet failures I have had were due to the output being short circuited. Secondly, in the event of failure, bipolar amplifiers almost always take the speakers out with them as bipolar transis­tors usually go short circuit when they fail. As good as a lot of speaker protection circuits are, they are all a compromise between being sufficiently slow so as to avoid nuisance tripping and being fast enough to stop your expensive drivers overheating and tearing themselves to shreds. In comparison, however, the normal failure for a mosfet is to go open circuit which usually means that by the time enough mosfets have failed to become noticeable, the worst you usually get is a distorted signal, a still intact speaker and not a whole lot of DC. One of the reasons given for avoiding mosfet design is that mosfet amplifiers “shut down” when pushed hard. This is something that I have never noticed, either at gigs (and I have had occa­sion to push my amplifiers and system hard) or when “thrash testing” amplifiers (full power into 4Ω for two hours for mosfet amplifiers, one hour for bipolar amplifiers) after servicing them. As an example, on an amplifier I recently repaired, an HH M900 which has a similar if not smaller heatsink size to the 500W amplifier, I measured 62V peak into 4Ω (approx 480W RMS) at the beginning of the thrash test. By the end of the two hours, I was still getting 62V which suggests to me that the so-called mosfet “sag” is a myth (possibly perpetuated by sales people of bipolar amplifiers), at least in any mosfet amplifiers I have used (HH, Perraux, ARX and Australian Moniter). However, my bottom line is that I would rather have an amplifier lose power than shut down completely, either permanent­ly or temporarily. Another comment I wish to make is regarding the cooling for the amplifier. The second article explains that the air is fan forced up the heatsink and through the vents on top. The problem with this design is that if two of these amplifiers are racked up together (very likely as they are mono units), then unless they are separated by a gap the top amplifier will obstruct the air­flow of the bottom amplifier. Finally, the statement that rock music has a limited dyna­mic range is not necessarily true, although I would agree that classical music is more likely to require a broader dynamic range. However, a lot of contemporary artists, such as Jethro Tull, Icehouse and Simple Minds are making increasingly more use of the extended dynamic range that modern technology has to offer. R. Freeman, Hornsby Heights, NSW. Comment: we agree that Mosfet amplifiers are rugged and we are a little surprised that you were unlucky enough to have had one fail under short circuit conditions. We expect that any well-designed amplifier should not fail under S/C conditions; the fuses should blow or the protection circuit should be activated but there should not be any device failures. EMC regulations add to business costs I read with interest your editorial in the November 1997 issue of SILICON CHIP regarding the new EMC standards. Being involved in the design of new products which fall within EMC framework, I can attest that the EMC regulations do indeed add enormously to the design complexity and cost of these products. With these costs you can include the capital expense of acquiring specialised equipment for EMC testing, if done in-house, or the possibility of even greater cost of testing if done outside. Also, the deadline of January 1999 for all products to comply, including those which were originally offered for sale prior to the regulations, can put a considerable burden on some manufacturers in achieving formal compliance of those existing products whether or not they meet the EMC limits. In some cases, existing products will have to be redesigned, re-tested and sub­ jected to formal (expensive) approval under one or more standards additional to the EMC standards. This may apply even though the products might not pose an inter- ference problem at all but merely that they might not meet the precise limits of the EMC standards, by however small an amount. The irony is that, while the standards and the procedure specified by the standards may indeed appear to be precise, the conditions of eventual use of any product are variable in their effects on EMI and the actual EMI levels are anything but precise or predictable in many instances. For large volume manufacturing companies, the increased cost of design effort, time and capital expenditure involved in product development might be absorbed into the product price, provided that the production volume is sufficiently high. Howev­er, this is not applicable to manufacturers of products with inherently small production runs or manufacturers of smaller production capacities, some of which might have been battling to stay in the black, even without the additional cost of meeting EMC compliance. Furthermore, the cost of testing, if carried out by an accredited laboratory, is incredibly high, from what I under­stand, more than enough to place such testing absolutely out of the question on economic grounds, I would think, for many small manufacturers. Curiously, the SMA, in their publication outlining the EMC framework recommend that manufacturers use an accredited laboratory rather than do their testing in house. I wonder, then, whether the effect of the EMC framework, even if not intentional­ly so, might be to drive some otherwise viable manufacturing businesses to the wall. I have read comments in technical magazines from represen­ t ative of small businesses, all of which have been highly con­cerned with the effect of the EMC framework on their manufactur­ing costs, and hence their viability. I don’t recall having seen comments from representatives of the really big manufacturing organisations. I would be interested to know what some of their views would be. H. Nacinovich, Gulgong, NSW. January 1998  39 SERVICEMAN'S LOG A clear case of sabotage As I have shown very often in these notes, servicing involves much more than merely finding and fixing faults. All too unwittingly, one can easily become involved in a domestic battle of wills; a situation which can call for the diplomacy of an ambassador. One tends to relax more on Saturday mornings, knowing that the weekend starts when I close the shop in a couple of hours and that I can leave my worries behind. This morning was particularly glorious; it was a beautiful day, I was relaxing with a cup of coffee which tasted really good, and I had only a couple of routine jobs to finish off. So I didn’t really notice Mr Roberts carry in his huge TV set – a Mitsubishi C6343 – all by himself. I must have been half asleep because you really can’t miss Mr Roberts; he is a giant of a man with muscles everywhere. His presence brought me back to earth with a bump. I booked the set in, noting that the complaint was that it was dead and that it was needed urgently. I went back to my coffee but somehow it didn’t taste quite the same. The lovely morning had been spoilt. There was nothing for it but to attack this huge TV set. I removed the back and checked the mains fuse – it was OK. I plugged it in and checked if the HT rail was OK – it wasn’t. Being fairly familiar with this model, I knew that the grey power switch gives a lot of trouble and decided to check it. This wasn’t really necessary as it had already been replaced but I checked it anyway. It was OK. The multimeter indicated that there was no AC input and I traced the fault back to the AC power lead, which was open cir­cuit. I noticed someone had wound some insulating tape along the first 7cm of the lead, next to the moulded mains plug. I cut off about 10cm and checked continuity – it was now OK. I fitted a new mains plug, plugged it to the power socket and switched on. The set burst into life and both picture and sound checked out OK. A case of sabotage Intrigued as to why the mains lead had failed, I removed the insulating tape. To my amazement, I realised immediately that the set had been sabotaged; the blue lead had been neatly cut and bent back. But why? Had someone set up a bodgie fault, designed to trap some unsuspecting serviceman – muggins in this case – into making an embarrassing diagnosis? Perish the thought. There was nothing for it but to confront Mr Roberts and find out what was going on. When the phone was answered, I in­formed the listener who I was and asked could I speak to Mr Roberts. A juvenile voice replied “I am Mr Roberts’ son, Roger, and I know all about the TV set. Have you fixed the lead OK?” “How do you know about that?” I asked. 40  Silicon Chip “Well, it’s like this. My dad watches TV all night and none of us can get any sleep, and we don’t dare tell him to turn it down or off. My HSC exams are due and I need all my sleep, so I cut the wire last night before he came in, intending to reconnect it first thing this morning. When I got up, the set had already gone.” “Well, you realise you will be up for the minimum service charge and the plug”. “Yes, yes, that will be all right but please, please, don’t tell Dad. Just write on the invoice that you repaired the power supply and don’t mention the cut lead.” Apparently, Mr Roberts senior was not a new age bloke and definitely would not understand the situation. I took pity on Roger and was suitably vague with the report’s repair details. Mr Roberts paid up without comment and left with the set under his arm – figuratively speaking, that is! And I hope Roger’s HSC exam went off well. Fig.1: Akai VS-303EA. The review guide (A) mounts on the review lever arm which is pivoted at (C). The pinch roller mounts on the play arm and this pivots on the top hole at below right. Akai video recorder My next story is about an Akai VS303EA video recorder. This is getting a bit long in the tooth now but, in its day, has proved to be a good and reliable performer. The owner carefully reiterated what “the boss” (his wife) had told him. He cheerfully confessed he knew nothing about it but the message was that there was a cassette stuck inside it and it wouldn’t eject or play. I checked it out and it behaved exactly as he said it would. I also discovered that it could still fast forward and rewind. Removing the covers and checking the controls, I noticed that the loading motor made no attempt to turn in either direc­tion. By disconnecting one lead and applying an external DC supply, I could make it eject the cassette. So the motor was OK but there was no drive to it. When the cassette ejected, I noticed that the tape hadn’t retracted fully back into it. I didn’t pay much attention to this at first, as the reel motor wasn’t being told that I was artifi­cially operating the loading motor. It was when I put the cassette back in that I noticed that the cue/review guide pin had not moved back into its correct position, although the loading guides were correct. Fig.1 will make this easier for the reader to follow. Fig.2: Akai VS-303EA. This mechanism is on the opposite side of deck to the parts shown in Fig.1. The play arm is shown dotted and is engaged by the pinch roller link. This in turn engages the cam plate and is moved by cams in the mode selector switch. The guide, indicated by arrow “A”, is mounted on the review lever arm (partly ob­ scured), which pivots on nut “C”. Well it should but it didn’t – pivot, that is. Instead, it had seized solid. A little lubrication and the arm soon came free and the tape now played and ejected OK. Unfortunately, the story didn’t end there. A day later, while soak testing it, it became erratic and intermittent in playing and ejecting. I returned it to the workbench and removed the covers again. After much erratic behaviour and red herrings, I eventually concluded that there was a problem involving the mode selector switch/ cam assembly and the pinch roller. In broad terms, the pinch roller wasn’t being moved far enough. This takes us back to Fig.1. The pinch roller is mounted on the larger plate – sometimes called the “play arm” – and this is shown with two circles at its larger end, at extreme right. The upper circle indicates a pivot point, while the lower circle indicates the point where the plate is engaged by a lever. This lever is part of the “pinch roller link”, on the other side of the deck, and is shown in Fig.2 (the play arm is shown dotted at the left of the diagram). This link in turn engages the cam plate; a triangular plate which pivots near its apex. The axle on which this pivots was also suspect but more of that in a moment. The cam plate engages cams in the mode selector switch. So the cam action is transferred, via the cam plate January 1998  41 and the pinch roller link, to the play arm carrying the pinch roller. So, why wasn’t the pinch roller moving through its full range. Basically, the problem was due to wear between the cam plate and the pinch roller link. I consulted Akai and learned that the pinch roller link has been modified, with extra metal reinforcement where it moved against the cam plate. Ordering and replacing this part helped considerably but still left something to be desired. The problem now involved the support for the axle which supported the cam plate. This was slightly loose, although this movement could be felt rather than seen. As far as I could ascer­tain, the axle and its associated support was fastened to the deck simply as a push-fit arrangement. I couldn’t do much with this other than treat it with Loc-Tite. It wasn’t the most elegant solution perhaps but should prove to be both adequate and economical. 42  Silicon Chip Anyway, that seemed to provide the final answer, the ma­chine functioning perfectly during a prolonged soak test. More to come But it wasn’t really the end of the story and, as it turned out, in more senses than one. There is one part of this story which I bypassed initially, for the sake of clarity. But it needs to be told. Not all the erratic behaviour I en­ coun­ tered after the initial simple lubricating exercise were due to the mechanical problems already described. And the reason wasn’t very clear initially, until I re­ alised that this model recorder can be fitted with two different types of ejector assembly. The first type is a conventional one, as shown in the service manual, and uses a 7-pin plug (P134/132). The second type (not mentioned anywhere) has a 9-pin plug to accommodate an optical slack tape sensor. This consists of an infrared LED sender and an optocoupler receiver, which creates a monitoring light path. And if the tape isn’t fully withdrawn into the cassette and clear of the infrared light path – or if any­thing else temporarily obstructs this path – it will prevent the system from playing or ejecting. At the time, neither this mechanism nor its function were obvious. Consequently, I wasted a lot of time following red herrings, especially considering the fault’s intermittent nature. But there it is; one to make a note of in your own records. The machine bounces Anyway, I was relieved when every­ thing was finally fixed and the machine returned to the owner. I thought no more of it until a few weeks later when he returned with it, complaining of exactly the same fault. After spending so much time and repairing three faults for the same symptom, I was shocked – not to mention embarrassed – to find that the machine had bounced. I checked it again in front of him and he was quite correct. I apologised and assured him that I would get back onto it straight away. Fortunately, he is a very pleasant, easy- going fellow and remained unfazed. I pushed aside the work I was doing and went straight onto the recall. Looking straight at the top of the ejector, I could­n’t see anything wrong with the optical slack sensor but the cassette was in the way. I removed it by disconnecting and power­ ing the loading motor from an external source, as before. With the cassette removed, I had a clear view of the in­frared diode sender and optocoupler receiver and could see imme­diately what had happened. A small sticky label belonging to the tape cassette had come away and become stuck over the receiver sensor, causing the same symptoms as before. I was quite relieved that it wasn’t due to any carelessness on my part and the owner accepted that it was just one of those one-in-a-million chances. So it all ended happily. stock of the kit. No matter; Bob just ordered the IC separately from another supplier. He had a resistor in stock and plenty of heatsink com­pound left over from previous kits. When it arrived, he fitted the IC and resistor just as he had done on dozens of previous occasions. However, when he switched the set on, absolutely nothing happened. He had subse­ quently spent hours investigating why and had run out of inspira­tion, before finally asking if I would take a look at it for him. As he had often done the same for me, I was happy to return the favour and in due course he dropped the set around, along with a list of all the things he had tried. The only problem with a list is, of course, the possibility of missing something some­where. I would have to recheck his list as well as add my own checklist. Measuring the set’s vital signs, I established that 330V was present on pin 3 of IC801 but there was only 40V at pin 5 instead of the 113V shown on the circuit. My checklist included T801, R803, Q833, IC601, Q500, T500, Q451, T501, Q504, D502, R511, C836 C808 and all stops along the way but I wasn’t getting anywhere either. As a precaution, Bob had ordered two STR50113 ICs and had tried them both to no effect. Fortunately, I had a scrapped set (broken tube) and was confident that it had worked correctly. This meant that I could check suspect components by substitution with the knowledge that they should work. At this stage, more in desperation than anything else, I decided to swap IC801 from my set into Bob’s. And would you believe it? – it worked perfectly and con­tinued to do so even after I replaced all the original parts. So why did Bob’s two brand new STR50113s not work in this set? It’s interesting to note that the part number specified in the circuit and the parts list is STR50113-M but the M isn’t marked on either the original or any of the substitute. The internal circuit of the IC (see Fig.3) is shown as consisting of two NPN transistors and one resistor but this may be only a simplistic block diagram. In the end, the only conclusion I could come to was that the two ICs Bob fitted were cheap clones that weren’t up to the job in the Panasonic circuit. Significantly, neither the A friend in need Bob is a colleague who works for an opposition service organisation and has been in the game for as long as I have - too long perhaps, or so it seems at times. Anyway, we help each other out on odd difficult problems. It’s good to be able to discuss and think through a problem, or maybe get a different perspective – a spot of lateral thinking and all that. So it was with a National TC2038 TV set with which he had been lumbered. This set uses an M14 chassis which has been highly reliable over the years, making it a good rental set. Most prob­lems are well known and understood and this one should have been the same. Its symptom was simply that it was dead and he had discov­ered that resistor R841 (4.7Ω, 7W) was open circuit and that the switchmode IC (IC801, STR50113) was short circuit. The usual reason why this switchmode IC fails is poor heat transference. Normally, one purchases this IC as part of a small kit that includes a new insulating washer and thermal grease. However, on this occasion, our mutual suppliers were temporarily out of LOUDSPEAKER SALE - Limited stocks Prices include sales tax Australian Audio Consultants PO Box 11 Stockport SA 5410 Phone or Fax 08 85 282 201 Fs Sens Qts Vas Size Vifa D25AG-35-06 $69.00 $45.00 850 89 Metal dome tweeter Vifa D19SD-05-08 $49.00 $34.00 1700 89.5 Shielded tweeter Vifa D26SG-05-06 $62.00 $49.00 1450 92 Shielded tweeter Dynaudio D21/2 $185.40 $99.00 1300 89 Dome tweeter SEAS ExcelT25-001 $194.00 $179.00 750 90 5mm soft dome tweeter. Scanspeak D2905/9300 $160.00 $90.00 600 90 28mm soft dome tweeter Vifa M11WG-09-08 $99.00 $79.00 68 0.46 4.3 125 woofer Vifa P13WH-00-08 $99.00 $75.00 60 0.33 10.0 140 woofer Vifa P17WJ-00-08 $99.00 $75.00 37 0.35 34.7 170 woofer Vifa P17SJ-00-08 $109.00 $75.00 41 0.35 33 170 shielded P17WJ Vifa M18WO-08-08 $145.00 $90.00 33 0.34 34 180 woofer Vifa M18WN-19-04 $149.00 $90.00 63 0.66 10 180 Car woofer Vifa M22WR-09-06 $195.00 $110.00 30 0.33 55 225 sub woofer Vifa M22WR-19-04 $195.00 $120.00 48 0.70 20 225 car sub woofer Vifa M22WR-29-04 DVC $210.00 $125.00 47 0.66 20 225 car sub woofer Vifa M26WR-09-08 $229.00 $135.00 26 0.32 130 271 sub woofer Vifa M26WR-19-04 $229.00 $150.00 44 0.69 53 271 car sub woofer Vifa M26WR-29-04 DVC $249.00 $159.00 40 0.67 53 271 car sub woofer Dynaudio 24W100 $399.00 $199.00 32 0.35 62 2 40 woofer Scanspeak D3806/8200 $181.00 $90.00 38mm soft dome midrange 1000-13500Hz Call for full specs. Many other drivers available at special prices. January 1998  43 Serviceman’s Log – continued suppli­ers nor anyone else have been able to come with another theory. The end of the weekend After a fairly lax weekend, I arrived on a Monday to find three jobs awaiting me. One was a large stereo Teac CT-M631S TV set which was described as “dead and burning”. Well, fortunately, the latter symptom had long since stopped but the acrid smell of burnt plastic was obvious. As soon as I removed the back, I expected the cause would be obvious and straightforward – for example, burnt horizontal output transformer insulation. I was surprised, therefore, to find that the AC power line input filter coil (L901) had burnt and taken fuse F901 with it. The adjacent 0.47µF capacitor across the AC mains (C901) was also badly melted. So had the coil shorted and melted the capacitor or vice versa? When I measured the capacitor it still read OK but I have had cases in the past where capacitors like this develop and clear their own shorts, blowing the fuses on a random basis. However, I don’t think that this was the case this time as the heating process must have lasted for quite some time. But that wasn’t the end of it. In the course of cleaning and resoldering the board, I noticed that the main electrolytic (C905, 220µF 400V) appeared to be loose. I unsoldered one leg and the whole capacitor came away in my hand. The other terminal had been corroded by the electrolyte. I replaced this along with C908 and Fig.3: National TC-2038. The circuit shows that IC801 (STR50113-M) consists of just two NPN transistors and a resistor. Note the suffix “M” which is not marked on either the original or any of the replacement units. C910 which can also cause the HT rail to fail. On reassembling and powering up, everything was now OK; the sound and picture were perfect. But it left a niggling thought in my mind as to what was the original fault and what caused what to fail in what order. The second set was an NEC N-3419 with a Daewoo C-43M chassis. The fault description on the job sheet stated that the picture height decreased after about half an hour, so I left it to run Silicon Chip Binders ★  Heavy board covers with 2-tone green vinyl covering ★  Each binder holds up to 14 issues ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p each (Australia only; not available elsewhere) 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. 44  Silicon Chip REAL VALUE AT $12.95 PLUS P &P while I dealt with the third set. This set was a Teac Televideo MV-1440 combination TV/VCR and it was dead. Removing the covers revealed a chassis which is quite difficult to work on, as access to the PC board is restricted by the short connecting leads to the video recorder beneath it. I measured the main HT rail, which should be at 112V, and there was nothing. Nor was there any voltage on the 12V secondary rail. Next, I checked the 320V rail to IC1501 (STK7348) and again there was nothing. I had to remove the chassis altogether to get the ohmmeter to finally confirm that the IC was short circuit and that R1501, an 8.2Ω 5W anti-surge resistor, had gone open cir­cuit. I replaced the IC (along with fresh heatsink compound) and replaced C1507 (2.2µF, 50V) and R1501 for good measure. I also found that D1506 was short circuit and replaced that as well. This restored both the 112V and 12V rails but the set was still dead. I quickly established that there was no voltage on the collector of Q1401, the horizontal output transistor, but it was there on R1407, the supply resistor. When I subsequently removed the horizontal output trans­ former (T1401), I found that its primary was open circuit due to a corroded lead to one leg. After mucking around with extra wire splints and microsurgery, I eventually managed to repair the coil and reassemble the set again. And that was the end of it. The set now worked fine and it must surely be bad luck to find so much wrong all at once. Shrunken picture In the meantime, the NEC TV set had been doing its thing and the picture had indeed shrunk from top and the bottom. I measured the main HT rail and found that it was 125V instead of 103V. Freezing IC Q801 (STR5412) caused the HT rail to drop and the height to increase. I replaced the IC, applying fresh heatsink compound in the process, and changed C806 (100µF). I also re­moved some brown goo from around IC 1502 (the 12V regulator) and reworked a few potential dry joints before trying it out. The set now worked perfectly and it was still going strong after a 3-hour SC soak test. PRODUCT SHOWCASE Jaycar opens in New Zealand Jaycar Electronics have opened their first retail store in New Zealand. It stocks the entire Jaycar range so that NZ enthu­siasts no longer have to make their orders across the Tasman. Located in Auckland, the store is managed by Jeff Wild who is widely experienced in electronics and previously managed the Jaycar Melbourne City store. Jaycar cordially invite new customers and old to come and check out their new store at 14A Gillies Avenue, Newmarket, Auckland. Phone 529 9916; fax 529 9917. A keen eye that never sleeps movement and change. Constant longterm use takes its toll on tape and moving parts of a VCR. Poor picture quality is a symptom of this wear and tear. Mitsubishi’s digital time-lapse video recorder avoids these problems because it doesn’t require changes of motors and heads and doesn’t use tape at all. Recordings are stored instead on a 2GB hard disc. This means maintenance costs are low and the clear, noiseless images with a high resolution of 720 x 240 pixels won’t deteriorate with long-term use. Accurate retrieval of any particular moment of a digital recording is easy and instantaneous. Users can search for partic­ ular recordings using the time, date or other criteria such as index alarms or comments recorded at random. Searching is made easy with “jog” and “shuttle” operation. With “jog”, pictures can be stepped field by field. Replay speed can be continuously varied from a stationary picture to speed search with the “shuttle” operation. The Mitsubishi time lapse video recorder has 10 modes of recording intervals, from recording a picture every 16 seconds to 25 pictures per Mitsubishi Electric has released a new digital time-lapse video recorder, the DX-TL100E. Time-lapse video recorders work using a series of snapshots to capture AUDIO 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 January 1998  45 Multimedia PAL/NTSC video encoder-decoder BBS Electronics Australia has released Harris Semiconduc­ tor’s first PAL/NTSC video encoder-decoder chipset. Available now, the PAL/NTSC chipset consists of the HMP8112 decoder and HMP8156 encoder. The new chipset will allow manufacturers to lower system costs for a range of new video functions on Personal Computers. These include VCR (video cassette recorder)-to-personal computer editing systems, PC video capture (TV tuners, frame grabbers), tele­ con­ ferencing systems, digital video disc players and digital VCRs. Because the chipset supports both the PAL (as used in Australia and England) and NTSC formats (mainly the US market), Australian manufacturers can design equipment that is compatible with virtually all standard video equipment throughout the world. The HMP8112 decoder IC contains a patented comb filter implementation for better luminance/ colour (Y/C) separation without loss of vertical detail; a patented sample rate converter that lets the decoder use any available clock instead of a second, and six modes of image compression rates. In single shot mode, about 135,000 pictures can be record­ed. An alarm signal switches the recorder into continuous record mode so that it doesn’t miss a second. All details of an incident, accident or disaster are recorded from the beginning of the event that triggered the alarm. The unit can record continuously for up to 600 hours (25 days). When it reaches its capacity, it overwrites the oldest informa­tion on the hard disc to keep continuity. For longer term archiv­al use, an optional DDS-2 Drive Unit is available for backing-up recordings onto Digital Audio Tape (DAT). The DX-TL100E can be used as a standalone digital recorder to replace conventional VHS monitoring systems or it can be con­trolled remotely via a computer using the PC interface. 46  Silicon Chip spe­cific clock frequency; and digital phase-locked-loops (PLLs) for steadier images in PC-based home video editing equipment. The HMP8112 decoder accepts both analog video formats: CVBS (composite video blanking and synchronization) and S-video (separate luminance and chrominance). Compatible sources include cameras, VCRs and professional video equipment. The HMP8156 video encoder performs the op- The DX-100TLE time lapse video recorder has a recommended retail price of $6987 including sales tax. For further information, contact Mitsu­ bishi Electric, 348 Victoria Rd, Rydal­ mere 2116. Phone (02) 9684 7777; fax (02) 9898 0484. New loudspeakers from Morel Morel have released several new tweeters and woofers. The Solin range of four tweeters is specifically aimed at manufactur­ers and all have 28mm fabric domes. Two of these are of the miniature type, being only 54mm square. All are available in shielded versions. The new MDT 37 (DMS 37 - shielded version) is a hand-treated 28mm fabric dome tweeter with minor horn loading. It features a smooth response within ±2dB from 1.8kHz to 18kHz, a posite function to the HMP8112. It accepts inputs in three formats: YcbCr, 16/24-bit RGB, and Bt.656. YcbCr is the output format used by MPEG decoders in set-top boxes. Bt.656 is a high-end professional digital videotape standard, and RGB is the common format for PC multimedia cards. For further information, contact BBS Electronics, 24/5-7 Anella Avenue, Castle Hill, NSW 2154. Phone (02) 9894 5244; fax (02) 9894 5266. sensitivity of 93dB and 200W power handling (1kW transient), making this an impressive high frequency driver. A new family of woofers is also available, types MW-115S (118mm), MW-144 (142mm), MW-168 (160mm) and MW-265 (222mm). All feature Hexatech voice coils with power hand­ling of 150W and transient power handling of 1kW. The use of double neodymium magnets provides magnetic shielding. The final new driver is the MDM55, a 54mm soft dome mid­range unit with a frequency response from 500Hz to 6.5kHz and 200W power handling. Measuring only 87mm square, the unit matches the miniature range of tweeters that Morel produce. Elsewhere in this issue, Australian Audio Consultants are advertising a once only sale of loudspeaker drivers. They advise that stocks are very limited. Further information is available from the sole Australian distributor, Australian Audio Consultants, PO Box 11, Stockport, SA 5410. Phone/ fax (08) 8528 2201. Updated NATA directory The 1997-98 directory from NATA, which is Australia’s na­tional laboratory accreditation system, lists and describes nearly 2500 NATA-accredited Australian and international labora­ tories which can assist companies in meeting the increasing demand for quality standards compliance. Laboratories covered in the new directory include those examining and analysing products, materials and equipment in such areas as acoustic and vibration measurement, chemical testing, electrical testing and inspection, heat and temperature measurement, construction materials testing, engineering materials testing, medical and biological testing, non-destructive testing, metrology (measurement and calibration), optics and radiometry, wool test­ing and forensic testing. Four separate indexes guide users to laboratories best suited to their needs and each testing facility listed has a separate entry including details of tests and services covered by NATA accreditation, location and contact details and availability to provide testing services. Large loop antenna for testing luminaires The Laplace RF300 is a complete three-axis antenna with a switching unit to select each loop in turn. The RF300 fully complies with EMC tests on luminaires as called for by European product specific standard EN55015 (section 7.s) and annex B. The calibrated frequency range is from 9kHz to The A4 format publication is available for $140 (less for standing orders). For further information, contact NATA, 7 Leeds St, Rhodes, NSW 2138. Phone (02) 9736 8222; fax (02) 9743 5311. 30MHz and each antenna is supplied complete with antenna factor data, enabling the device to be used with any EMC receiver or spectrum analyser capable of antenna factor compensation. For further information, contact Nilsen Technologies, 150 Oxford Street, Collingwood, Vic 3066. Phone (03) 9419 9999; fax (03) 9416 1312; freecall 1-800-623-350; freefax 1-800-067-263. Rail-to-rail dual & quad op amps Analog Devices Inc has announced new dual and quad opera­tional amplifiers that offer rail-to-rail output January 1998  47 Yokogawa 8-channel digital scope The Yokogawa DL708 digital scope incorporates a large 26.5cm TFT colour liquid crystal display which has a wide viewing angle. It uses modular plug-in inputs which include high-speed types, isolated high-speed versions, temperature and logic mod­ules. Sampling speed is up to 10Ms/s, resolution is 16bit and the instrument has a long memory, up to 16M word, making it able to measure slow changing inputs such as temperature right through to high speed MHz signals and sporadic one-shot events. The DL708 provides a wide range of waveform capture and analysis functions including an extensive choice of trigger functions and storage options, automatic computations of min/max values, RMS, frequency, risetime and other time axis parameters. FFT analysis is also supported. Extra marker cursors enable the user to zoom in on part of a waveform to increase reading and logging resolution. The built-in printer records data on 112mm wide thermal paper and can be used for real time recording for a time axis of less than 500ms/ range while maintaining very low power consumption. Designed to operate at single supply voltages from 2.7-12V, the OP281 (dual) and OP481 (quad) draw 4µA (maximum per amplifier). This function makes the new op amps well-suited for applications where long-term battery life is essential. Designers can create micropower reference voltage genera­tors, window comparators, low-side current monitors, low voltage half and full-wave rectifiers, battery operated headset amplifi­ ers, and many other circuits using the OP281 and OP481. This makes them useful for use in security systems, medical instru­ments, safety monitoring, gas detection and tele­ phone headset applications. Whereas other low-supply-current amplifiers often take a relatively long time to recover from a saturation condition, the OP281 and OP481 recover in 50µs when the supply voltage is 3V 48  Silicon Chip div. A floppy disc drive saves instrument setups and waveform data in MS-DOS format, allowing data to be viewed off-line on a PC. Data can also be saved in ASCII if using soft­ware such as MS Excel. Image files are also supported so that waveforms can be read into word processors. RS-232C and GPIB interfaces allow the DL708 to be controlled by a PC. and in 100µs when the supply voltage is as high as 10V. This is an important advantage when using the OP281 or OP481 as a comparator or when their outputs are driven to the rails. Each amplifier features 100kHz bandwidth, low offset voltage (1.5mV) and outputs that will sink or source current. For further information, contact Hartec, 205A Middleborough Road, Box Hill, Vic 3128. Phone 1-800-335623. Surface-mount film capacitors Self-healing film capacitors in stacked-film technology are now available from Siemens as space-saving SMDs. The new chips can be reflow soldered. The dielectric is polyethy­ lene naphthalate (PEN) film, which is more heat-resistant than conven­tional polyethylene tere­phthalate (PET). These non-encapsulated SMD An optional internal hard disc drive can be used for real time recording with an ultra long memory up to 128M word with 1-channel use. Also optional is a SCSI interface for connection to an external device such as hard drive, Zip drive or MO disc. For more information, contact Yokogawa Australia Pty Ltd on (02) 9805 0699 or fax (02) 9888 1844. stacked-film capacitors are a good substitute for lead­e d c a p­­a c i t o r s based on PET film. They come with capacitance values ranging from .015µF to 2.2µF, at voltage ratings between 63V and 400V, in EIA standard sizes 1812 to 6050. For applications at high frequencies there are also non-encapsulated SMD staked-film capacitors based on polyphenyl sulphide film (PPS) in the same range of sizes. For further information contact Advanced Information Pro­ d ucts, Siemens Ltd. Phone (03) 9420 7716; fax (03) 9420 7275. VINTAGE RADIO By JOHN HILL A simple regenerative receiver Building simple regenerative receivers is a lot of fun and, best of all, it won’t break the bank. Here’s how to build a simple 1-transistor radio receiver. I can still remember the excitement caused by my first one valve regenerative receiver, which was built when I was a lad. It seemed to perform nearly as well as the 5-valve Radiola in the lounge room, the only difference being that my little radio would only drive headphones, not a loudspeaker. Of course, such a statement is strongly biased by youthful memories of something that had been homebuilt with loving care. Naturally, a 1-valve regenerative receiver could not compete with a 5-valve superhet – although it seemed to at the time! One station that was often received at night was 2NZ. To hear “this is 2NZ northern New South Wales” through the head­phones was nothing short of amazing when one lived in Bendigo. That little regenerative set could really drag in those distant stations. Regeneration or “reaction” is a form of positive feedback whereby some of the amplified radio frequency (RF) energy is fed back in phase to the tuning coil, boosting signal strength and improving selectivity. Another way of looking at this is to visualise the signal being fed back as acting to overcome the natural losses – mainly resistive – in the tuned circuit. It was a technique commonly used in early receiver designs before the superhet era. Unfortunately, too much regeneration causes distortion and the possibility of the set bursting into oscillation. Regeneration gave a simple receiver such as a 1-valver a tremendous lift in performance. In fact, when connected to a good aerial and earth, a 1-valve regenerative outfit is nothing short of amazing. One gets so much from so few parts. Even today, I still enjoy building and listening to simple 1 and 2-valve regenerative sets and I know that I’m not alone in this regard; many other vintage radio enthusiasts do likewise. It seems as though little boys never really grow up. A 1-transistor design The original Trans-1 as built by David Waldron. The receiver was built into an aluminium chassis and went through several experimental stages before this unit was produced. David, a young collector friend, is also a keen devotee of regenerative receivers and has built numerous sets employing this simple circuitry. He has built several AC-powered short-wave sets with plug-in coils and they really are good performers. With careful regeneration control manipulation, even single sideband transmissions can be received reasonably well. The latest regenerative set which David has built is a departure from normal and uses a single high gain transistor and a ferrite rod aerial. This month’s story is about David’s one-transistor regenerative receiver – the “Trans-1”. The circuit shown is as supplied and there have been no alterations to it at all. The set went through several January 1998  49 develop­mental stages before reaching finality and involved quite a few hours of trial and error experimentation. The main problem encountered with Trans-1 was with the regeneration control. It would operate reasonably well at the low-frequency end of the dial but was a bit touchy and difficult to control at the high-frequency end. The addition of a few resistors at strategic places in the regeneration circuit smoothed over this problem and the reaction control is as good as one could hope for in a receiver of this type. Regeneration is controlled by a 5kΩ linear potentiometer. This was used in preference to the small variable capacitor often used in this type of receiver. Perhaps the most remarkable aspect of this little 1-transistor radio is the fact that it performs every bit as good as a 2-valver. In fact, it outperforms my “Junk Box 2” with its two type 30 triodes (detector plus a transformer-coupled stage of audio). One reason for Trans-1’s better performance is the higher gain available from a transistor, even a simple low-cost device like the BC549 which David used. A type 30 (1H4G) triode valve has a theoretical gain (µ) of 9.3 (less in practice) whereas the BC549 has a minimum hfe of 200. On this basis, it’s not hard to see why the Trans-1 performs so well. As set up in the regenerative receiver circuit (see Fig.1), the BC549 draws 2.5mA from a 9V battery. Using the 2-valver as a comparison again, the filaments draw 120mA at 2V, while the plates consume about 2mA from the 45V “B” battery. Trans-1 can be used with either The author’s Trans-1 was built into an existing timber cabinet that had previously housed other projects. The switches are for on/off and for selecting between the 5 and 10-turn taps for the transistor base connection. Fig.1: the circuit diagram for the Trans-1. Transistor Q1 acts as a detector and amplifier stage, while VR1 sets the amount of regeneration. This rear view of the author’s partially completed unit shows all the major components in place. Note the two tag strips for mounting the minor components. 50  Silicon Chip This is what the unit looks like with all the minor parts in­stalled. A slightly larger cabinet would have made construction easier. An output transformer must be used if low impedance headphones are to be used. Shown here is the M1100 audio line output trans­former from Dick Smith Electronics. This end view shows the M1100 output transformer that’s used to drive a pair of 8-ohm headphones. The 9V battery is attached to the top of the transformer using double-sided masking tape. high-impedance headphones or can drive 8-ohm stereo headphones via an output transformer. The latter method is by far the better alternative when it comes to comfort and fidelity. A Dick Smith M1100 transformer or equiv­alent works reasonably well as an output transformer. Practical details David built his receiver on an aluminium chassis, whereas I built mine into an existing wooden box which had housed a few past projects. It doesn’t matter how you build Trans-1; the result will be much the same. However, one advantage of David’s metal chassis construc­tion is that it eliminates hand capacitance effects. The bakelite front panel on my set doesn’t do this and hand capacitance can be noticeable when the receiver is tuned to weak stations which require maximum regeneration. But it’s not much of a problem really. The choice of components is not critical and if a construc­tor doesn’t want to use a ferrite rod aerial, then he can do his own thing and wind a coil on a cardboard former. However, if a ferrite rod is not used, the coil winding information will differ considerably from that specified in the circuit. What’s more, the small 350pF tuning capacitor shown on the circuit may have insuf­ ficient capacitance range if used with an air-cored coil. In the latter case, a 400-500pF tuning capacitor should be used if the whole of the broadcast band is to be covered. It is interesting to note how few turns there are on the reaction coil, although the number can vary depending on where the transistor base The ferrite rod antenna is easy to wind. The author used a length of fibre tubing on which to wind the coils. Rubber grommets hold the unit together and allow it to be mounted on right-angle brackets secured to the baseboard. The wire diameter is 0.4mm, the rod diameter is 10mm and the reaction coil can be placed 2-3cm away from the tuning coil (the exact location isn’t critical). You can convert 8-ohm stereo headphones to 16-ohm mono by using the tip and ring connections only. This effectively connects the two 8-ohm earpieces in series but note that the they now operate in antiphase. connection is placed on the tuning coil. If the 10 or 15-turn taps are used, there will be sufficient regen­eration. If the 5-turn tap is used there may not be enough regen­eration at the low frequency end of the dial. Increasing the value of the 100Ω resistor or decreasing the 3.9kΩ resistor will increase the regeneration response. As the coil tap positions have a significant effect on the set’s selectivity A rotary switch is used to select the desired antenna tap and is mounted on the rear panel. January 1998  51 This photo shows one of David Waldron’s mains-operated regenerative short­ wave receivers. It drives a loudspeaker and is a good performer. EVATCO HOLIDAY READING Valve Amplifiers Theory & practice of valve amplifier design; 374pgs Mullard Circuits for Audio Amplifiers Circuits and plans for audio amplifiers; 136pgs $59.95 P&P $6 $26.95 P&P $6 Principles of Power $69.95 P&P $8 Guide to valve power amplifier design; 221pgs Build Your Own Valve Amplifier $42.95 P&P $6 Construction projects for valve amps; 251 pgs Principles of Electron Tubes $59.95 P&P $7 Learn the basics of how valves work; 398pgs TUBES Matching included EL34 Svetlana $24.00 6L6GC Svetlana $30.00 EL34WXT Sovtek $24.00 6L6GC Sovtek $14.00 E34L Tesla $24.00 6550C Svetlana $48.00 12AX7 Sovtek $10.00 5881 Sovtek $19.00 SSAE for CATALOGUE ELECTRONIC VALVE AND TUBE COMPANY PO Box 381 Chadstone Centre Vic 3148 Tel/Fax: (03) 9571 1160 Mobile: 0411 856 171 Email: evatco<at>mira.net 52  Silicon Chip and regeneration response, there may be some need to experiment in this regard. It’s all to do with the recep­tion conditions the set has to work in. In some cases, a wave-trap may be used to advantage to block out a strong local sta­tion. There is one aspect of Trans-1 that needs to be brought to the attention of would-be constructors and that is the capacitor that couples the radio frequency signal to the base of the tran­sistor. In the circuit diagram this capacitor is shown to have a value of 1µF or larger. This is important because a value less than 1µF has an adverse effect on tonal quality and will result in a thin, raspy, unpleasant sound. A small electrolytic will work OK in this position. Switchable taps My set differs from David’s in that I prefer switchable taps to wandering leads and alligator clips. On the back panel of my receiver there is a 3-position switch in the aerial circuit which connects the aerial to either tap 2, 5 or 15, the latter being used for short aerials. On the front panel, a 2-position switch connects the base of the tran­sistor, via the 1µF capacitor, to either tap 5 or 10. Construc­tors can do their own thing regarding tap connections. Building the Trans-1 is relatively straightforward and does not require detailed constructional information. The circuit diagram, a few hints, and the accompanying photographs should be suffi­cient. In conclusion, the good aspects of Trans-1 are as follows: it is easy and relatively cheap to build; it can be built using mostly over-the-counter parts; it works well on local stations without an aerial or earth; it is neat and compact; and it oper­ates from a single 9V battery. The only unfavourable aspect is that sound fidelity is not quite as good as that from a similar valve receiver, particularly when receiving distant transmissions at maximum regeneration. Although Trans-1 is based on modern components, the regeneration circuit on which it is based dates back to the early days of radio. It’s just a SC new version of an old idea. 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 Bookshop Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1997 (4th edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 383 pages, in hard cover at $55.00. Guide to TV & Video Technology By Eugene Trundle. First pub­lished 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $75.00. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $55.00. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $69.00. Power Electronics Handbook Components, Circuits & Applica­tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Surface Mount Technology By Rudolph Strauss. First pub­lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Radio Frequency Transistors Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $95.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First published 1989. 6th edition. This just has to be the best refer­ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semi­-custom electronics & data communications. 63 chapters, soft cover at $125.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order  ❏ Bankcard  ❏ Visa Card  ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Prices valid until 31st January, 1998 tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $55.00. Understanding Telephone Electronics By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. This is a very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $49.95. Video Scrambling & Descrambling For Satellite & Cable TV By Rudolf F. Graf & William Sheets. NOW IN STOCK First pub­lished 1987. This is an easy-to-understand book for those who want to scramble and unscramble video signals for their own use or just want to learn about the techniques involved. It begins with the basic techniques, then details the theory of video encryption and decryption. It also provides schematics and details for several encoder and decoder projects, has a chapter of relevant semiconductor data sheets, covers three relevant US patents on the subject of scrambling and concludes with a chapter of technical data. 246 pages, in soft cover at $50.00. ✓ Title o o o o o o o o o o Price Guide to Satellite TV $55.00 Servicing Personal Computers $90.00 Video Scrambling & Descrambling $50.00 The Ar t Of Linear Electronics $70.00 Digital Audio & Compact Disc Technology $90.00 Radio Frequency Transistors $95.00 Guide to TV & Video Technology $55.00 Electronic Engineer's Reference Book $160.00 Audio Electronics $75.00 Understanding Telephone Electronics $55.00 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ add $10.00 per book; elsewhere add $15 per book. TOTAL $A January 1998  57 Design by BRANCO JUSTIC* Two servos are used to provide tilt and pan motion to this small CCD video camera. Now you can remotely control a camera while you watch the video monitor. PAN 58  Silicon Chip your BY Do you have a video security system involving a minia­ture CCD camera? How would you like to be able to remotely pan it from side to side and up and down while you watch the video monitor? This circuit uses two servos to do the job and draws no current at all while the camera is stationary. More and more people are finding uses for tiny CCD video cameras. They’re not just being used in routine security applica­ tions but they are being used around the home for watching young children, especially around swimming pools, in hospitals and so on. But most of these cameras would be fixed installations, so the view on the screen is always of the same room or whatever. Now it is possible to remotely pan the camera while you watch the monitor. In practice, the CCD camera is mounted as shown in our photos. These show a typical miniature CCD camera mount­ed in a small plastic case which is attached to a servo disc (ie; a round flange attached to the servo shaft). This first servo is then mounted on an angle bracket which is attached to a second servo disc. The first servo pans the camera up and down while the second servo pans it from side to side. Servo driver The servo control circuit is mounted in a plastic utility case with two knobs and a central button. Each knob controls a servo while the central button is labelled “Execute”. This is not a form of punishment but merely means that nothing happens to the servos unless the button is pressed. This has the effect of minimising servo wear and tear but more importantly, if the button is not pressed, the circuit is completely dead and so the battery (if battery power is used) is conserved. This approach to servo drive is quite novel but is practi­cal in this application. After all, you don’t want the servos drawing current while the camera remains pointed in a fixed direction. It might be left in this condition for hours or days at a time, so it makes sense to power the circuit only while the camera is actually being moved. You could use the servo control circuit in one of two ways. First, you might rotate the pots to set a new camera position and then push the “execute” button. The camera will then move to the new position and stop. Second, you might hold the “execute” button down while you twiddle the pots so that the camera moves exactly in sympathy with rotation of the pots. An ideal method would be to use a joystick potentiometer set from a Parts List 1 plastic utility case, 130 x 67 x 42mm 1 PC board, 46 x 60mm 2 servos 2 servo discs 1 9V, 10V or 12V DC plugpack 1 momentary contact pushbutton switch (S1) 2 100kΩ potentiometers (VR1, VR2) Semiconductors 1 74C14, 40106 hex Schmitt trigger (IC1) 1 TIP41C NPN power transistor (Q1) 3 BC548 NPN transistors (Q2, Q3,Q4) 1 6.2V 400mW zener diode (ZD1) 3 1N4148, 1N914 silicon diodes (D1,D2,D3) Capacitors 3 10µF 16VW PC electrolytic 2 .012µF MKT or greencap polyester 2 .01µF MKT or greencap polyester Resistors 2 1MΩ 2 68kΩ 4 10kΩ 3 2.2kΩ 2 1kΩ radio control transmitter but at the time of writing we had not been able to access a suitable joystick at a reason­ able price. Circuit description Fig.1 shows the circuit of the servo controller. It uses just one 74C14 CMOS hex Schmitt trigger inverter, CCD video camera REMOTE CONTROL January 1998  59 Fig.1: the circuit consists of two one-shot (monostable) pulse generators driven by oscillator IC1b. Most of the circuit is shut down until pushbutton S1 is pressed. The circuit and servos consume no power when not in use. a few diodes and transistors and not much else. There are two separate servo pulse generators, the first involving IC1c & IC1d and the second involving IC1e & IC1f. These are both driven by IC1b which is a free-running oscillator. Before we get too far ahead of ourselves though, let’s have a look at how the circuit starts itself. When power is first applied to the circuit, nothing hap­pens as far as the two servo outputs are concerned and the various Schmitt triggers do nothing. The output of the 5V regula­tor, comprising transistors Q1 & Q2, is also close to zero. Everything depends on IC1a and its output is close to zero This prototype board differs somewhat from the final version which has a screened parts overlay and solder masking. 60  Silicon Chip be­cause its input is held high due to the 1MΩ resistor and 10µF capacitor at pin 13. When pushbutton S1 is pressed, pin 13 of IC1a is pulled low and the 10µF capacitor is charged via the 2.2kΩ resistor, R2. Pin 12 of IC1a goes high and this does two things. First, it feeds a bias current to the base of Q2 via a 2.2kΩ resistor, R3. This develops 6.2V across zener diode ZD1 and allows Q2 and Q1 to work as a 5V regulator to provide power to the two servos and to transistors Q3 & Q4. At the same time, pin 12 of IC1a reverse-biases diode D1 and this allows IC1b to operate as a free-running oscillator, with its frequency set by the .01µF capacitor and 1MΩ resistor at its pin 1. It produces a square wave at about 60Hz. Now let’s look at the servo pulse generator involving IC1c & IC1d. This really operates as a one-shot to produce a single positive pulse with a duration set by the 100kΩ potenti-ometer VR1. Let’s look at what happens, in slow motion. First, each time the output of IC1b goes high, it pulls the input of IC1c, pin 11, high. This causes pin 10 to go low and this low signal is fed via the .012µF capacitor to pin 9 Fig.2: these scope waveforms show the servo signals from the emitters of Q3 & Q4. The pulse widths are varied by the poten­tiometers VR1 & VR2. of IC1d. Pin 8 of IC1d then goes high and stays high until the capacitor at pin 9 is charged via VR1 and the series 68kΩ resistor. This causes pin 9 to be pulled high to the point where pin 8 must go low. The result is a +12V pulse at pin 8 with a duration of between 1ms and 2ms (nominal), depending on the setting of VR1. This pulse is fed to Q3 which acts as a voltage level translator and buffer, changing the +12V pulse at pin 8 to a pulse with a nominal amplitude of +5V which is compatible with the servos. Exactly the same process happens with the other one-shot pulse generator comprising IC1e & IC1f. Each time the oscillator output of IC1b, pin 2, goes high, a positive pulse appears at pin 6 of IC1f and this is fed via transistor Q4 to the second servo. So both pulse wavetrains are synchronised to each other, as can be seen from the two scope waveforms shown in Fig.2. However, this whole process only lasts about 10 seconds which is more than enough for each servo to come to rest and stabilise at its new setting. After that time, the 10µF capacitor at pin 13 of IC1a will have discharged sufficiently via the shunt 1MΩ resistor to pull pin 13 high. This causes pin 12 to go low and this shuts down the 5V regulator and disables the oscillator involving IC1b via diode D1. Thus, the +5V rail to the servos and the servo pulse signals are killed and so the servos are stuck at their last position. In this condition the circuit draws negligible current. Note that as long as you hold Fig.3 (left): the wiring diagram for the dual servo controller. If you do not wish to use the power-saving feature, the pushbutton switch could be replaced by a wire link. Resistor Colour Codes ❏ ❏ ❏ ❏ ❏ ❏ No. 2 2 4 3 2 Value 1MΩ 68kΩ 10kΩ 2.2kΩ 1kΩ 4-Band Code (1%) brown black green brown blue grey orange brown brown black orange brown red red red brown brown black red brown 5-Band Code (1%) brown black black yellow brown blue grey black red brown brown black black red brown red red black brown brown brown black black brown brown January 1998  61 The PC board is mounted on the lid of the case and connected to the Pan and Tilt potentiometers via flying leads. Power comes from a DC plugpack supply. pushbutton S1 down the cir­cuit will continue to work but it will stop about 10 seconds after the button is released. If you want to have the circuit permanently powered, S1 could be a toggle switch or it could be linked across. Note: readers wanting a detailed description of the opera­tion of servo encoder and decoder circuitry should refer to the Radio Control articles by Bob Young in the November & December 1997 issues of SILICON CHIP. Construction All the components of the circuit, with the exception of the two potenti­ ometers and the pushbutton switch, are mounted on a small PC board measuring 46 x 60mm. The component layout is shown in Fig.3. Assembly is quite straightforward. Insert the PC pins first, followed by the resistors and diodes. Then insert the capacitors and the transistors. The CMOS IC should go in last. Note: there are positions on the supplied PC board labelled D4 and D5 but these diodes are not required for the circuit to work. The finished PC board is mounted in a plastic utility case and connected to the two potentiometers and push­ Where To Buy The Kit All the parts for this kit are available from Oatley Elec­tronics who own the design copyright. Their address is PO Box 89, Oatley, NSW 2223. Phone (02) 9584 3563; fax (02) 9584 3561. The prices are as follows: Complete kit for dual servo controller................................................$19.00 Servo kits.................................................................................$15.00 each DC plugpack......................................................................................$10.00 Pinhole or standard CCD video camera............................................$89.00 Camera box plus universal swivel bracket...........................................$4.00 62  Silicon Chip button switch via flying leads. When you have finished assembly, carefully check all your work against the circuit of Fig.1 and the wiring diagram of Fig.3. If everything is OK, apply +12V to the supply input and check voltages around the circuit. You should find +12V at pin 14 of IC1 and at the collectors of Q1 & Q2. No voltage should be present at the col­lectors of Q3 & Q5. Furthermore, pins 2, 3, 5, 9, 11 & 13 of IC1 should be high (ie, close to 12V) while pins 1, 4, 6, 8, 10 & 12 should be low (ie, close to 0V). When the pushbutton is pressed, pin 13 should go low, pin 12 will go high and the other pins of the IC will be at a voltage somewhere between high and low. The emitter of Q1 should be at +5V. The circuit will then revert to its original quiescent condition after about 10 seconds. Now connect your two servos, press the button again and you should be able to move both servos with their respective poten­tiometers. Having verified that the circuit works, you are ready to set up your camera and starting panning to your heart’s content. *Branco Justic is the Managing Director of Oatley Electronics. SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. NORBITON SYSTEMS NS_PC101 card for XT/AT/PCs allows access to 48 I/O lines. There are 5 groups (0 to 4) available on a de-facto industrial standard 50-way ribbon cable used in STEbus and VMEbus 19" rack mount control systems. The board uses 2 x 8255 ICs. Multiple boards can be used if more I/O lines are required. NS_LED PCB gives visual access to five groups (0 to 4) of the NS_PC1OX. There is a total of 40 status LEDs. The board offers a 25-way “D” type female socket. The lines are driven by 74244 ICs & configured as a parallel printer port. This socket gives access to printer port kits, eg, stepper motors, LCDs, direct digital synthesis. NS_16_8 PCB is a system conditioning card with 16 optically isolated inputs set-up for either 12V or 24V operation. The board provides 8 single pole, double throw relays with 10 Amp contact rating. For brochure write to: Reply Paid 68 KITS & CARDS NS_DC_DC is a step down converter with an input range 11 to 35V DC and an output of 5 volts DC at 5 Amps, with an output ripple of approx 150mV. There is an IN/OUT 50-way connector isolating the 5V and 12V+ &12V- rails of the PC power supply. This segregates PC’s power when working on prototypes. NSDC_DC1 module used with NS_DC_DC & NSDC_DC4 converters is a 5V to 12V(+/-) step- up converter. The board utilises 743 switch mode IC with 2 x 12V regulators, with output ripple of approx 200mV. NS_UTIL1 prototyping board has 1580 bread board holes access to any 3 groups (0 to 4) on the 50-way cable pinout. Power is available from the 50-way cable format 5 volts at 2 Amps & 12V+ 12V- at 1 Amp. There is provision for array resistors with either a ground or positive common connection. SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. NORBITON SYSTEMS PO Box 687 Rockingham WA 6968 January 1998  63 By JOHN CLARKE Build a one or two-lamp flasher This simple circuit lets you flash one halogen lamp at about twice a second to simulate a low frequency strobe or you can flash a pair of halogen lights alternately at rates from once a second to once every three seconds or so. You can use the flasher circuit to draw attention to a sign or wall display or simply just to liven up the atmosphere at a party. 64  Silicon Chip Flashing lights are a good way of attracting peoples’ attention. They are used to good effect on many advertising displays and at shows, particularly car & boat stands where the very latest high tech items are to be seen. Flashing lights are also often used at parties and the best example of this is the Light Show presented elsewhere in this issue. If your budget doesn’t run to a full-blown light show this project could give you at least some of the visual effect. The circuit is quite simple and provides for two varia­ tions. In its simplest strobe form it uses just one 555 timer IC and one Mosfet. In its two-lamp form it uses the 555, a 4013 time to cool and the effect would be merely a flicker in the lamp bright­ ness rather than flashing on and off. Hence the strobe effect is not like that from an Xenon flash tube which can be driven at very fast rates to give the effect of stopped or jerky motion of moving objects. Circuit description Fig.1 shows the strobe version of the circuit, IC1 is a standard 555 timer which is connected to operate as an astable oscillator. Initially, when power is first applied, the 47µF capacitor at pins 2 and 6 is discharged and pin 3 is high. It is charged via diode D2 and the 10kΩ connecting to the positive supply. When the capacitor voltage reaches 2/3rds Fig.1: the single lamp version of the circuit uses a 555 timer to drive a Mosfet which the supply, as detected by pin 6, flashes the lamp. Diode D2 ensures that the flash duration is fixed at about half a pin 7 goes low to discharge the second while the flash repetition rate is varied by VR1. 47µF capacitor via potentiometer VR1 and the series 10kΩ resistor. flipflop IC and two Mosfets. It can run At the same time as pin 7 goes low, Main Features from 12V DC or 12V AC. so does pin 3. The strobe version simply flashes When the 47µF capacitor is disone lamp on and off with a fixed lamp charged to 1/3rd the supply voltage, •  Strobe (one lamp) or flasher (two lamp) operation on time of about 0.5s and a variable off as detected at pin 2, pin 7 goes open duration from 0.5s to about 3.5s. The circuit and pin 3 goes high again. •  Adjustable flash rate flasher version switches each lamp Thus the capacitor charges again. on at between 1s and 4s as set by the Its voltage swings between 1/3rd and •  Operates from 12VAC or 2/ rds the supply while the voltage variable rate control. The flash rate 3 12VDC supply is limited in practical terms by the at pin 3 switches high and low at the thermal inertia of the halogen lamp’s same rate. •  Drives 20W or 50W halogen filament. If we were to flash the lamp Diode D2 is included between pin 7 lights too fast the filament would not have and 2 & 6 so that the capacitor charge Fig.2: the two-lamp version of the circuit adds a flipflop and another Mosfet to drive the second lamp. The flipflop is used to ensure that each lamp is on for precisely half the time. January 1998  65 Fig.3: component layout for the single lamp version. Note that one IC and one Mosfet position is vacant. rate is fixed and not dependent on the adjust­ment of VR1. This makes the duration of each flash constant while the time interval between flashes is adjustable. The pulse waveform at pin 3 of IC1 drives the gate of Mosfet Q1 via a 10Ω resistor. The Mosfet then drives the halogen lamp. Flasher circuit Fig.2 shows the flasher version of the circuit. Instead of driving a Mosfet, pin 3 of IC1 drives one half of a 4013 dual D-type flipflop. So each time pin 3 of IC1 goes high, it causes the Q and Q-bar outputs of IC2 to change state; ie, change from low to high or from high to low. The Q and Q-bar outputs of the flipflop then drive the gates of Mosfets Q1 and Q2 via 10Ω resistors. Each Mosfet then drives its own halogen lamp. So far, so good but some readers will ask why we bothered to use the flipflop in order to drive two Mosfets for alternately flashing the lamps. Why not just drive the second Mosfet from the drain of the first Mosfet? That would work but it wouldn’t look good, particularly if the flash rate was slow, say, once every three seconds. What you would find is that one lamp would be on for half a second, as set by D2, the 10kΩ resistor and the 47µF timing Resistor Colour Codes ❏ No. ❏  2 ❏  1 ❏  1 ❏  1 66  Silicon Chip Value 10kΩ 2.2kΩ 22Ω 10Ω 4-Band Code (1%) brown black orange brown red red red brown red red black brown brown black black brown 5-Band Code (1%) brown black black red brown red red black brown brown red red black gold brown brown black black gold brown Fig.4: component layout for the twolamp version. Note that a heatsink must be fitted to the bridge rectifier if 50W lamps are used. capacitor. But the other lamp would then be on for three seconds before the circuit flicked back to the first lamp. That would mean that one lamp would be on for most of the time and so the display would not look good. With the flipflop in circuit each lamp would be on for precisely the same amount of time, regardless of how the flashing rate potentiometer was set. DC or AC Both Fig.1 and Fig.2 show the supply input to the circuit via a bridge rectifier and that means that the circuit can run on 12V DC or 12V AC. A secondary benefit of the bridge rectifier is that if you are using a 12V DC battery or power supply, you can’t accidentally damage the circuit by connecting the supply the wrong way around. When you are using a 12V AC sup- Fig.5: actual size artwork for the PC board. Check the board carefully before installing any of the parts. ply, diode D1 isolates the rectified but unfiltered lamp supply from the supply for the ICs which is filtered by a 100µF capacitor and protected from voltage transients with a 16V zener diode, ZD1. The 0.68µF capacitor across the unfiltered DC supply prev­ents voltJanuary 1998  67 age overshoot when the Mosfets turn off. LED1 indicates when power is switched on via switch S1. Construction To make connecting the lamps easy, use the wired lamp bases. Trying to solder wires to the pins of the lamps is not really satisfactory. Parts List 1 PC board, code 16301981, 105 x 60mm 2 2-way PC mount terminal strips 1 DPDT miniature slider switch (S1) 1 12V 50W or 20W halogen lamp 1 base to suit halogen lamp (Jaycar Sl-2735 or equivalent) 1 mini heatsink, 20 x 20 x 10mm (Altronics H-0630 or equivalent) 1 mini U-shaped heatsink, 28 x 25 x 34mm (Altronics H-0625 or equivalent; for bridge rectifier) 2 3mm screws and nuts 1 100kΩ linear pot (VR1) 1 knob for VR1 1 3AG in-line fuse holder 1 3AG 6A fuse 1 5mm red LED (LED1) 3 PC stakes 1 60mm length of 0.8mm tinned copper wire Semiconductors 1 555 timer (IC1) 1 PW04 10A 400V bridge rectifier (BR1) 1 1N4004 1A 400V diode (D1) 1 1N914, 1N4148 signal diode (D2) 68  Silicon Chip 1 16V 1W zener diode (ZD1) 1 MTP3055E 12A 60V avalanche protected Mosfet (Q1) Capacitors 1 100µF 16VW PC electrolytic 1 47µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.68µF 250VDC MKT polyester 1 0.1µF MKT polyester Resistors (0.25W, 1%) 2 10kΩ 1 22Ω 1 2.2kΩ 1 10Ω Extra Parts required for flasher circuit 1 12V 50W or 20W halogen lamp 1 base to suit halogen lamp (Jaycar Sl-2735 or equivalent) 1 2-way PC mounting terminal strip 1 mini heatsink, 20 x 20 x 10mm (Altronics H-0630 or equivalent) 1 3mm screw and nut 1 MTP3055E 12A 60V avalanche protected Mosfet (Q2) 1 4013 dual D flipflop (IC2) 1 10Ω 0.25W 1% resistor (R1) Both versions of the circuit can be built on a PC board coded 16301981 and measuring 105 x 60mm. Fig.3 shows the compon­ent layout for the single lamp (strobe) version. Note that the positions for IC2 and Q2 are vacant and there are three links to be inserted. Fig.4 shows the component layout for the two-lamp version and this has both ICs present. Note that we have specified an in-line fuse for both versions. All components apart from the in-line fuse and lamps mount on the PC board. Follow the appropriate component layout diagram to build either the strobe or flasher. Start by installing and soldering in all the resistors using the accompanying colour code table as an aid in finding the values. Then insert and solder the PC stakes located at the three locations for VR1’s terminals. When the ICs are inserted, make sure they are oriented with pin 1 in the position shown. Diodes D1 and D2 and ZD1 mount with their cathode stripes closest to the slide switch S1. Make sure that the three electrolytic capacitors are ori­ented with the polarity shown. S1 is installed by inserting the switch pins into the PC board and soldering in place. If the pins are difficult to insert, crimp them with pliers first or use tinned copper wire through the switch pins which then insert into the PC board. LED1 mounts onto the PC board with the orientation shown. The potentiometer VR1 mounts with the terminals soldered to the tops of three PC stakes. The Mosfets are mounted with small heatsinks bolted to their tabs. Most important, a U-shaped heatsink must be bolted to the bridge rectifier if you are building the two-lamp version with 50W lamps. With two 50W lamps being driven, the bridge rectifier passes over 4A and dissipates over 6W so it is not surprising that it becomes a little red in the face if a heatsink is not fitted. On the other hand, if you are using 20W lamps, the heat­sink should not be necessary. The lamp and power supply con- SUNSHINE DEVICE PROGRAMMERS Power 100 Universal Programmer 48-pin Textool Socket para I/F ............$1371 Hep 101 Value for Money 8MB E(E)PROM - 1 slave socket ...................$283 Hep 808 High Speed 8MB E(E)PROM programmer 1 master 8 slave sockets .. $790 Jet 08 Production Series E(E)PROM Programmer Stand alone or PC (para) .$1590 PEP01 Portable 8MB E(E)PROM series Programmer, Parallel Port ....................$295 EML2M EPROM Emulator ....................$480 Picker 20 Stand Alone IC Dram CMOS Portable Tester ......................................$199 RU20IT 16 Piece UV EPROM Eraser with timer .............................................$187 Plus converters, adapters & eproms. Contact us for other spe­cialised development tools or data acquisition, industrial elec­tronics, computer and electronic parts and service. Available from: D.G.E. Systems; Nucleus Computer; Stewart Electronics; TECS; X-ON. SUNSHINE ELECTRONICS 9b Morton Ave, Carnegie, Vic, 3163 TEL: (03) 9569 1388 FAX: (03) 9569 1540 Email: nucleus<at>ozemail.com.au Floppy Index This photo shows the board assembled for a two-lamp version of the circuit and with the bridge rectifier fitted with a heatsink. This is necessary if 50W lamps are used. nections to the board are made via PC-mounting insulated terminal blocks. These enable connections to be made easily with a small screwdriver. Connect up the lamp or lamps with the wired base connectors to the output terminals and apply power. Note that you will need a 12V battery or a DC power supply which can deliver about 2A for two 20W lamps and 4.2A for two 50W lamps. For AC operation the halogen lamp transformer from Jaycar (Cat MP-3050) would be suitable. This transformer includes a wired in mains lead and plug, making it safe from the mains voltage. If the lamps fail to flash, check your board for faults including shorts between tracks and breaks. Also check that all the components are in their correct place with correct orienta­tion. The DC supply to IC1 and IC2 should be about 11V between pins 1 and 8 of IC1 and pins 14 and 7 for IC2. You can add colour to the flasher by placing a layer of tinted Cellophane over the halogen lamps but it should not touch the lens or lamp reflectors, as they become quite hot. If you want to alter the flash rate from the presently available range with VR1, change the 47µF capacitor to a smaller value for faster rates and to a SC larger value for slower flashes. Now you can search through all the articles ever published in SILICON CHIP. Whether it is a feature article, a project, a circuit notebook item, an article by one of our regular contributors or a major product review, it does not matter; they are all there, for you to browse through. The index comes as an ASCII file on a 3.5-inch or 5.25-inch floppy disc to suit IBM compatible computers. Also included is a handy file viewer with a search utility. Price: $7.00 plus $3 p&p. Send your order to SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bank­ card, Visacard and Mastercard). January 1998  69 RADIO CONTROL BY BOB YOUNG Jet engines in model aircraft This is the first in a series of articles covering the technical aspects of jet engines for model aircraft. In this coming series we will look at engine theory, engine management systems and fuel theory. For too long, modellers in general have been locked out of modelling modern jet aircraft due to the lack of a suitable power plant. Today however, we stand at the dawn of a new and tremen­dously exciting era in R/C modelling with the recent introduction of the pure turbine engine. In my opinion, the jet engine will do for R/C modelling what proportional control did back in the early 1960s. In the 1960s, we made do with reeds which did the job re­ markably well and it would have been difficult for a bystander in those days to tell the difference between a well-flown reed system and a proportional system. However, this was more to do with the skill of the pilot than an attribute of the R/C system. Reeds really were the sort of system that only the truly dedicat­ed modeller could warm to. There is an exact parallel today with the ducted fan model and pure turbine. The ducted fan model has been developed to a remarkably high This beautifully finished model of an F-20 Tigershark was built by Brett Davies. It is powered by an OS91 engined fitted with a Ramtec fan. It is 1.82 metres long and weighs just on 6kg. 70  Silicon Chip level and performs exceptionally well in the correct hands. But at no time can you ever forget that you are watching a model powered by a piston engine. In fact it is abso­lutely impossible to forget that fact for the simple reason that a ducted fan sounds like it is powered by the controlled fury of one thousand caged banshees. After eight hours of sharing the pits with this incredible din, one’s ears are begging for mercy. Again, the ducted fan system is the sort of system that only an absolutely dedicated modeller could develop a liking for. Turbine engines How delightful it is then to hear the soft pop of a turbine igniting and the gentle whine, or more correctly, whooshing of the turbine as the pilot runs it up prior to takeoff. And the differences do not end there. In flight the turbine pushes the model effortlessly and quietly (75dB) with that characteristic rumble that jets develop at a distance. Most jet model pilots only run their engines at about 60% power as the thrust on some model turbines is absolutely staggering. The overall effect is to produce a flight with a rock solid, very smooth and realistic sounding characteristic. In contrast the ducted fan model in flight is constantly screeching out a reminder that inside this machine is a very large reciprocating racing engine, worked up to the nth degree and being pushed to its limit at all times. Whilst there is little difference in the measured speed of both systems (at the moment, that is), the turbine engine produces an infinitely superior result. By now you may have noticed, I am hooked on the turbine powered model, especially now that kerosene is replacing propane gas. There is of course one proviso in all of this and that is the cost. The turbine at the moment is ferociously expensive ($5000-$10,000) and my bank manager was decidedly guarded in his response to my request for a loan of that magnitude, especially for an item that may disappear in a mushroom cloud at any moment! Be that as it may, progress will follow rapidly now that the initial breakthrough has been made and prices will fall as more manufacturers enter the field and volumes and production techniques improve accordingly. One other drawback will also succumb to the relentless march of progress and that is the question of fuel consumption. Turbines are notoriously thirsty and a typical fuel load current­ly is around 1.5 - 2kg for a 15-minute flight. So how do these wonderful gadgets work and why has it taken so long for the turbine to finally make its appearance on the model scene? This Mirage was built from a Jet Hobbies Hanger kit. It is powered by a Golden West Models FD-3/67LS turbine and controlled by a Silvertone transmitter. It has a wing span of 1.09m, length of 1.56m and a weight of 5kg. It carries 1.75kg of kerosene. Brief history In the “Aeromodeller” annual published in 1954 there appeared the most wonderful article on turbine-powered jets. The author, Mr W. Ball, claimed he had flown turbine-powered deltas in England as early as 1947 and gave details of some of his early flights. The lead photo in the article (p87) showed the author proudly posing beside a very modern looking delta model with his ground based transmitter at his side. Page 88 showed a cutaway drawing of a turbine engine featuring a 3-stage axial compressor with annular combustion chamber and a single stage turbine. The figures quoted are interesting and we will come back to these shortly – length 28 inches (711.2mm), diameter 6.5 inches (165mm), weight 3lb (1.36kg), static thrust 10.8lb at 26,000 rpm. The article went on to give scanty details of high speed flight (100 mph) with rudder and trimmable wing tips combined with 3-speed motor control. Sadly, in common with a lot of preco­ cious inventors, he suffered a terrible loss in the form of floods which swept away his entire workshop (and all evidence of his experiments). Nowadays they usually have a fire in the work­shop, a visit from the oil companies, the CIA or even the “men Chris Mounkley built this Star Jet which is powered by a JPX-260 turbine. Note the maze of wiring in cockpit. in black”. Thus at the time of writing he was only flying a ducted fan delta which could be adapted to take a turbine “if required”. Did it exist? So did this motor ever exist and did those models fly? Interestingly enough, I never forgot those articles for they had stirred my imagination and that of my friends and despite an intense search we could never find any evidence of those models being flown with turbines. Ever hopeful, I even asked David Boddington about this article on his recent visit to Australia but he could never find any evidence either. Today the consensus is that the whole thing was a fabulous hoax. Upon re-reading that article for this column, I even discovered one of the photos of the delta in “flight” was upside down. But we were young and we lapped it up for it articulated the dream. And anyway, who could ever January 1998  71 Kevin Dodds of Tingalpa, Qld built this semi-scale A-10 “wart hog”. Powered by a JPX-T-240 turbine, the model weighs 7kg empty and 8.5kg fuelled. Maximum engine speed is 122,000 rpm! system for its safe operation. Finally however, somewhere around the late 1980s, model turbines began to make their appearance on flying fields. Kurt Schreckling is credited with being the first person to construct very small, lightweight turbines using amateur means. To date there is no evidence to suggest that an axial flow turbine could run successfully at model sizes even today and all successful engines so far have used centrifugal compressors. This results in a shorter, more rotund engine than the axial flow engine but still of practical size. Kurt Schreck-ling’s motor was 235mm long, 110mm in diameter, 1.14kg in weight and produced around 30 Newtons of thrust (about 8lb) at approximately 100,000 rpm. At this thrust these engines will push models along at more than 320km/h. Compare this data to that of the Ball engine. Did those motors exist? I genuinely doubt it, especially when you consider that ceramic bearings give the best results at the RPM encountered in these engines. Having suggested that turbine engines would make a good series for SILICON CHIP, Leo Simpson sent me off to Leeton (the premier jet gathering in Australia) to gather first-hand data for the series to follow. So let us look now at what I found there. Leeton 1997 This is a closer view of the A-10 engine installation. The amount of plumbing in these models is amazing. doubt such an eminent authority as “Aeromodeller” magazine? The dream took a very long time to become a reality however and proved to be a fearsome task, taking even longer than the model helicopter to master. The engineering and metallurgy are quite demanding and the major difficulty facing the manufacturers of these engines is in matching components in one engine. Quite often motors will not run successfully until all components are correctly matched and that is 72  Silicon Chip with components manufactured with modern machine tools. RPM can be down, tailpipe temperatures up and in the worst case, the turbine can drip out onto the tarmac if local hot spots develop. An even distribution of temperature inside the engine was one of the major difficul­ties and can still cause problems. We will examine these points in detail in coming articles. More importantly, the successful engine relied upon a very sophisticated electronic engine management The Leeton Jet fly-in, hosted by the Leeton (NSW) Model Aircraft Club, is the longest running jet event in Australia and attracts fliers from all over Australia. Due to the increasing popularity of jet aircraft there are now many such events being staged in other localities and as a result numbers were down at Leeton this year. But Leeton was the first and is still consid­ered by many as the premier event. Certainly there was no lack of enthusiasm and the standard of models present staggered me – from electric ducted fans to swing-wing F111s fitted with turbines, they were all there. Fliers from as far afield as WA and Queensland were present in numbers and the sky was never clear of these daring young men and their flying machines. Basically the models are now divided into two classes, the older ducted fan system and the newer turbine engines. As the name suggests, a Starting a turbine Whilst starting a ducted fan model is a fairly laid back affair, starting a turbine takes on a more serious air. Compressed air is used to spin the compressor up to speed prior to ignition. This usually comes from a blower or compressed air bottles, while a helper stands by with a fire extinguisher. The propane gas used as fuel in the early turbines does present some element of risk and caution is the order of the day. The more modern turbines are gradually changing across to liquid fuels and this is where the future lies. Once started, the turbine settles down to be just like other motors, with throttle control providing a complete range of thrust from idle to full power at will. In flight, the turbine-powered model presents a glorious sight and sound. The dream has finally become a reality and whilst Ball may have taken some poetic licence in his presentation of the facts, he provided the spur for SC it to finally become a reality. SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏  3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________  Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ “ducted fan” is a system whereby a reciprocating engine, usually a very highly developed racing motor, is used to drive a fan inside a close fitting, carefully designed duct. The ducted fan is still the predominant system and these were present in great numbers at Leeton. Turbines were not as well represented but there were at least six or seven in attendance. A striking feature of the models at Leeton was the amazing internal complex­ ity. There were tubes, pipes and cables in vast numbers. It has taken a long time from Charlie Peake’s .15 powered, catapult-launch­ ed “Screaming Mimi” delta in the early 1960s to the .91 powered missiles of today but the ducted fan system has finally come of age. Capable of speeds in excess of 320km/h, these models are impressive performers indeed. Usually fitted with retractable under­ carriages, these models can take off with­out the assistance of the catapults that were used in the early days of ducted fans. Several examples of ducted fan models are shown in the accompanying photos and externally there is nothing to suggest any difference between the turbine and the ducted fan models. It is not until the motor is started that the real difference is apparent. January 1998  73 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Programmable multispark CDI Using this simple circuit, the Multispark Capacitor Dis­ charge Ignition published in the September 1997 issue of SILICON CHIP can be operated in conjunction with the Programmable Electronic Ignition described in the March 1996. Q1 inverts the square wave signal from the points, Hall Effect or reluctor section of the CDI at diode D12 and feeds it to the points input to the Programmer board. The coil output signal from the Programmer is inverted by Q2 before it is applied to the 10kΩ base resistors for transistors Q4 and Q5 on the CDI board. Q1 and Q2 and the four resistors can be mounted on a small piece of Veroboard. To make the board connections, discon­nect the cathode of D12 and connect it to Q1. SILICON CHIP. Versatile laser beam door minder Now that solid state lasers and laser pointers are avail­ able, a laser door minder is a worthwhile proposition. The cir­cuit is based on an MEL12 phototransistor (Q1) and a 555 timer IC (IC1). Q1 detects the laser beam and conducts during normal standby. The base of Q1 need not be connected and should be clipped off the transistor. Trimpot VR1 is used to adjust the sensitivity of Q1 and should be varied according to the ambient light. When a person or object breaks the laser beam, Q1 switches off and Q2 is switched which then activates the relay. The re­lay’s sole purpose is to enable the 555 timer which is connected in standard monostable mode and drives a buzzer. The buzzer sounds for a time set by the 100µF capacitor and trimpot VR2. (Editor’s note: a number of variations of this circuit are possible. For example, the relay could be used to drive 12/24V courtesy lamp extender for cars 74  Silicon Chip the buzzer directly and the 555 could be omitted). Alternatively, Q2 could drive the buzzer directly, provided a diode was connected across the buzzer with its cathode to the collector of Q1). A. Nguyen, Bankstown, NSW. ($20) This courtesy lamp delay circuit is suitable for 12V or 24V systems and is inherently short circuit protected. Assuming S1 is closed initially, C1 has no charge and the lamp glows to full brilliance. Opening S1 activates the circuit with the lamp dimming slightly due to the voltage drop of about 0.9V. C1 supplies base drive to Q2 and turns on Q2, Q3 and Q4. As C1 slowly charges, the voltage drop across Q4 rises, gradually dimming the lamp until a threshold set by R2 & R3 turns the lamp off completely. G. LaRooy, Christchurch, NZ. ($25) This solid state LED oscilloscope uses an LM3914 display driver and a 4017 decade counter to drive a 100-LED array. Solid state LED oscilloscope This 100 LED array will give a rudimentary waveform display for frequencies set by the timebase generated by the oscillator formed with IC3c & IC3d. The oscillator drives a 4017 decade counter which provides the column drive to the LED grid. The analog signal is fed to an LM3914 dot/bar display driver which then drives the rows of the LED grid. The timebase for the column driver can be synchronised via IC3b or left in free-running mode, depending on the setting of switch S1. P. Melmoth, Wyalong, NSW. ($30) January 1998  75 COMPUTER BITS BY JASON COLE Norton Utilities Version 2: hard disc maintenance for your PC When it comes to taking care of a hard disc drive, Symantec’s Norton Utilities does the job and more. This month, we take a look at the Disk Doctor utility in Norton Utilities Version 2 for Windows 95. Version 2 of the Norton Utilities is “OSR 2 Aware”. This means that if you are running Windows 95 OSR 2 with a 32-bit FAT (file allocation table), then this version of Norton Utilities is fully compatible. Before Version 2, a small box would appear each time you started Speed Disk, warning that data could possibly be lost if you went ahead. And if you did take the risk and go ahead, Speed Disk would not optimise the swapfile. Norton Utilities Version 2 over- comes that problem. And, of course, Version 2 is backwards compatible with Windows 95 OSR 1. Useful utilities Essentially, Norton Utilities V2 is a collection of useful utilities for maintaining your hard disc. These utilities include Image, Norton Disk Doctor, Norton System Doctor, Space Wizard, Speed Disk and UnErase Wizard, to name just a few that are avail­able. All are useful and, over the next few Fig.1: this is the dialog box that appears when you boot Norton Disk Doctor. You can choose which disc(s) to diagnose and whether or not to automatically fix any errors that are detected. 76  Silicon Chip months, we shall take a closer look at some of them, beginning this month with the Disk Doctor which allows you to check your hard disc drive for errors and to fix any problems that are detected. Maintaining data As we all know, the most important thing you can do with your hard disc drive is to maintain the data in an orderly and reliable format. To do this, we use two programs from Norton Utilities package: Disk Doctor and Speed Disk. Disk Doctor is a versatile little program in itself and checks the hard disc for errors, including file allocation errors and hard platter errors. To run Norton Disk Doctor, you simply click Start, Programs, Norton Utilities and Norton Disk Doctor. Disk Doctor will now load and a box similar to Fig.1 will appear. After that, you simply select the drive(s) to be tested. I find it best if you don’t automatically fix errors. If you select the automatic fix and there is a problem, you may not be able to see what file was damaged. It could be a rather important file that you could still use but once Disk Doctor has altered it, you may not be able to use it again. If Disk Doctor does find a file that contains errors, stop the program and copy the file to another directory and test it to see if it still works. This goes for all files from text docu­ments to C++ programs. There are more options to play with and clicking on the Options button in the first window will let you change them. Fig.2: clicking the Options button at Fig.1 brings up this dialog box which has four sections to choose from. These sections let you set Norton Disk Doctor up the way you want it. When you click the Options button, a new window will appear – see Fig.2. There are four sections to choose from here: Gener­al, Appearance, Surface Test and Advanced. In the General section, you can choose to have Disk Doctor run on start-up. This is a nice option but can be a waste of time in many cases (I generally prefer to check my drive once a week). You also have the option of being prompted for repairs or ignor­ ing any errors. The Custom Repair Options box (Fig.3) lets you choose how problems are to be repaired – either “Auto-Repair”, “Ask Me First” or “Skip Repairs”. Surface test The Appearance section sets how the program will look and even sound. That’s right, you can play music while fixing the drive (an interesting option although I never use it). The Surface Test section is used to determine how the sur­face test is organised. A full surface test can take quite a long time on large hard disc drives, so surface testing is not done often. When you do run it, you can choose several options such as the number of “passes” it does; eg, will it test the drive once, 999 times or continuously. Continuous testing would usually Fig.3: this repair options dialog box lets you specify how problems are to be repaired – either “Auto-Repair”, “Ask Me First” or “Skip Repairs”. only be carried out to test a particular hard disc drive’s reliabili­ty, as it keeps working the drive non-stop. There are two types of testing: (1) a “Thorough” test; and (2) a “Normal” test. The Normal test will do everything except a surface test. A Thorough test, on the other hand, includes sur­ face testing and takes much longer to perform. This is because, depending on which option you choose, it may test every block on the hard disc drive. The surface test options are straightforward. You can either choose to perform a surface test on the entire disc or just the areas used by files. Note however that if there is a bad block on the drive, you may miss it by not testing the entire drive. The last Option in this section is what I like to call the “show me where I am map”. This means that a “map” will appear and show you what is happening. It doesn’t really do much but it gives you something to look at and helps translate the progress percentage into something a bit more readable. The last section is the Advanced Tip Of The Month If you have a Windows 95 keyboard, it is quite often quick­er to use the keyboard to open a program than it is to use the mouse. A Windows 95 keyboard has 104 keys instead of the standard 101 keys. If you look closely at the three extra keys, you will find that two carry the Windows logo. By using these keys in conjunction with certain characters, you can quickly achieve the following: (1) Windows Key + E opens Explorer; (2) Windows Key + F opens Find; (3) Windows Key + M minimises all open windows; and (4) Windows Key + R opens the Run window. These shortcuts are predefined in Windows 95 and you do not need a special driver to run a Windows 95 keyboard. January 1998  77 Fig.4 (left): Norton Disk Doctor gives a progress report as it diagnoses each disc. Here, the partition table, boot record, file structure and directory structure have all passed testing and the surface test has progressed 5%. The compressed disk indicates an error because disc compression is not used on this particular computer, which means that Disk Doctor cannot test for compression. Fig.5: after testing is complete, you should see a report similar to that shown here (provided everything is in order that is). area. In this area, you can skip certain tests that may be incompatible with Norton Disk Doctor. For example, if you use a third party drive compression utility, Disk Doctor may not be able to test it correctly. In this case, you would select the “Skip Compression Testing” option before continuing. This is important because Disk Doctor may try to fix what it thinks is an error and thus cause problems. This is one reason why it’s usually best to use the disc compression utility that is shipped with Windows 95. Finally, you can set the “Background Operation” so that it will start after a predefined period and display an alarm by emitting an error beep and/or flashing the Taskbar. When all 78  Silicon Chip Fig.6: clicking the Details button at Fig.5 brings up this dialog box. This shows all the relevant drive characteristics and totals and will also show what errors (if any) were encountered. the Options have been set, click OK to save your settings. Testing Now we come across the actual test. Simply click the Diag­nose button (Fig.1) and Disk Doctor will now test the selected drives (see Fig.4). As you can see from this example, the com­ pressed disc test indicates an error. This is because I am not using any compression and therefore Disk Doctor cannot test for compression. After testing, you should hopefully see a report similar to that shown in Fig.5 (ie, no problems). If you want to know more, just click the Details button. This will bring up a dialog box similar to that shown in Fig.6. This shows all the relevant drive character- istics and totals and will show what errors (if any) were encountered. If you like, you can even print out the results for your records or perhaps for insurance purposes. And that is pretty much all there is to running Norton Disk Doctor. If an error does occur, then think about what to do next. Disk Doctor will give you some options but in the end it is up to you to choose what to do. If it is just a file allocation error, then you can fix it and save the lost clusters to files. However, I do recommend that you always use a recovery disk. Just before Disk Doctor performs a repair job, it prompts for a disc to save the current setup. This way, you can easily go back to where you were if things go horribly wrong. SC CCD CAMERA WITH BONUS!!!!!!!!!!! The best "value for money" CCD camera on the market! Tiny CCD camera, 0.1 lux,IR responsive, high resolution. It has a metal lens housing and glass lenses, & performs better than many cheaper models. . WITH YOUR CHOICE OF ONE OF THE FOLLOWING LENS Pinhole (60deg.), 78 deg.; 92 deg.; 120 deg.; $89 or $99 with a 150 deg. . THE BONUS??? IF YOU PURCHASE THE CAMERA YOU CAN BUY UP TO ONE OF EACH OF THE FOLLOWING ITEMS AT THE REDUCED PRICE SHOWN. . CASE AND SWIVEL A small plastic case suitable for enclosing the CCD camera, plus a very strong multi angle and position adjustable universal joint swivel bracket plus screws: $6 - $4 . UHF A-V MODULATOR Professional tuneable UHF A/V modulator with built in Antenna booster and a test pattern generator: As used in VCR’s. With each unit we also supply parts for a 5V regulator $16-$12 . UHF A-V TRANSMITTER Metal enclosed with telescopic antenna, A/V leads supplied: $30 - $20 . AUDIO PREAMPLIFIER Small kit which includes a microphone. Gives Line level output for use with the above Modulator or transmitter: $8 - $5 . AUDIO POWER AMPLIFIER KIT A small LM386 based power amplifier kit that can directly drive a speaker, needs the above Preamplifier: $9 - $6 . TIME LAPSE RECORDING INTERFACE New kit, now has relay contact outputs! Can be directly connected to a VCR or via a learning remote control: $30 - $20 PIR MOVEMENT DETECTOR module to suit,very small: $15 - $10 . LED IR ILLUMINATORS KITS 10 LED: $14 - $10, 30 LED: $30 -$20 . HIGH RESOLUTION MONITOR Brand new 240V 30cm enclosed computer monitor + a video conversion kit. Gives better resolution than TV’s!! Avail. early Feb. Limited but good qty. BARGAIN PRICE. $50 /$70 SOLAR REGULATOR Ref: EA Nov/Dec 94 (intelligent battery charger). Efficiently charge 12-24V batteries from solar panels, but can also be used with simple car battery chargers to prevent over-charging. We now offer a 7.5A or 15A kit: $26 / $29 . LASER ENGINE Brand new complete laser engine as used in laser printers. Includes a Polygon scanner motor with Xtal controlled driver PCB, 5mW/780nM laser diode in collimated housing mirrors, lenses etc. Info on how to make the motor and laser operational included. Bargain at $35 .. CCD IMAGE SENSOR High quality "Thomson" brand 2/3" CCD image sensor, type TH7863, with full data but no, usable response from 400 to 1100nm, 12000 dynamic range, 2/3" optics compatible format: $35...........(IC aplication notes may be available soon) (. NICAD BATTERY SPECIAL New 1.2V-400mAhr cells wired in packs of 6, each pack has a thermal cut out switch, each cell is 16X45X5mm, as used in mobile phones, 5 packs (30batteries) for: $10 NETWORK 2 COMPUTERS FOR $50!! New Windows/95 compatible (DEC (DE101) etherworks LC/TP) DIGITAL brand Ethernet computer cards with software and booklet in original box. Cards include boot ROM so one of the computers does not even require a hard disc. We don’t supply the commonly available cable which can also be made up with RJ45 connectors and two twisted wire pairs: Diagram included. Limited quantity: $50 for a pair. . MAGNIFIERS / LOUPES Four magnifiers, as reviewed in the Silicon Chip May 96 edition. Small jewellers eyepiece with a plastic lens: $3. Twin lens Loupes: 50mm $8, 75mm $12, 110mm $15. SPECIAL: Buy the set of four magnifiers for a total price of $25. . COMPUTER POWER SUPPLY New PCB assembly only, 45X108X 200mm, 120/230V AC IN, +5V-6A / 12V1A / -12V-1A / -5V-1A OUT. Circuit provided, RU approval. Modern design. Not for the in-experienced! Be quick: $16 Ea. or 4 for $56 . 12V/7Ah GEL BATTERY BARGAIN Fresh stock standard battery plus one GEL/LEAD-ACID BATTERY CHARGER for:$30 . NEW!!! COMPUTER CONTROLLED STEPPER MOTOR KIT New improved kit that can drive larger motors and has optoisolation between the circuit and the computer. DB25 connector provided on PCB. Needs a standard cable for connection to a PC, and a power supply for the motor drive section. PCB and all on board components kit plus software and notes: $39 or $49 with two used 1.8deg. motors !!! . CGA COLOUR MONITOR New 12V DC-1A 6" colour monitor, ready for enclosing, no box, just the tube and driver PCB’s: $65 . DC MOTOR SPEED CONTROL EXPERIMENTERS PACK One 20A motor speed controller kit (similar to SC - Jun.97-$18) plus two small new 12VDC motors (40mm dia., 40mm length) plus one used car windscreen wiper motor (which have internal gear reduction) for: $32 . NEW SEMICONDUCTOR BARGAINS 2SK2175 - MOSFETS 15A, TO220, 60V, 30W: 10 for $15, CA3140 - MOSFET input op amp : 5 for $5, TL494 switchmode power supply IC : 5 for $5, NE555 - timer IC : 10 for $5, ICL7106 LCD display driver : $5, ICL7107 - LED display driver : $5, IRFZ44 MOSFETS 60V,0.028ohm on resistance,50A: 10 for $30 C8050 and C8550 transistors: 20 for $5, CMOS IC’S 4001/ 11/ 13/ 16/ 17/ 20/ 24/ 28/ 40/ 46/ 60/ 66/ 69/ 93 Any mixture 10 for $8 . GREEN DIODE LASER HEADS Green 532nM output heads. Very bright output at the peak response of a human eye, much brighter than equal powered blue Argon lasers. These employ an IR laser diode pumping a Yag rod, the output of which is applied to a frequency doubling crystal. Require an adjustable constant current source: 10mW head $1400, 20mW head $2020 Suitable constant current source kit plus supply plus fan: Approx $35. A LICENCE WOULD BE REQUIRED FOR THIS PRODUCT. . UNIDIRECTIONAL ELECTRET MICROPHONE New quality product with clip, 3M lead, 2.5mm plug: $4 Make a stage quality wireless microphone by combining it with our FMTX MK2 trans-mitter kit: $16 for the kit plus the microphone . DOG SILENCER We have a new improved high power swept ultrasonic generator kit that can drive up to 4 piezo tweeters. Works on dogs and most animals. PCB and all on-board components and horn piezo tweeter: $33, extra tweeters $7 ea. Suitable 13.8V-1A DC plugpack $10. VISIBLE LASER DIODE MODULE KIT This 5mW/650nM kit has the same circuit as our "visible laser diode kit" but has a much smaller PCB. Overall dimensions of the module are 15mm X 40mm long: $26 12V DC LIGHTING SPECIAL A very efficient and properly driven fluorescent white light source! The tubes last because the filaments are heated! Consists of an inverter kit capable of driving up to three 11W Compact Fluorescent lamps (CFL’s). One kit plus AUTOMATIC LASER LIGHT SHOW KIT one 11W CFL$25. extra CFL $11Ea. A laser display that changes every 5 60 seconds, and the time is manually LEARNING UHF REMOTE CONTROL adjustable. There are countless possible First time ever!! This small ready made interesting displays which vary key-chain transmitter that can learn up from single to multiple flowers, to 4 channels from almost any (Not code collapsing circles, rotating single and hopping) UHF remote control multiple ellipses,stars, etc. PCB, all on in the range of 280-460mHz! No track board components, three small DC cutting or DIP switches. Tuning indicator motors& mirrors : $77 Combine it with LED provided: $39 above module kit for a total of $89!! . . 650nM LASER MODULE New module, fitted with a 650nM laser CALLER ID See the phone No. of your incoming diode! Very small, 35mm long, 10mm calls displayed on a LCD screen when diameter, 3 to 4.5V operation: $45 the phone rings. Has 90 call memory . and a dialler: $55. Also avail- able is a SUPER BRIGHT BLUE LEDS BY FAR THE BRIGHTEST BLUE EVER complete phone with caller ID: $99 OFFERED, super bright at 400mCd: . 650nM VISIBLE LASER POINTER KIT $1.50 ea or 10 for $10...5mm LEDS AT Complete laser pointer that works from SUPER PRICES 1Cd red: 10 for $4 ; 3-4V DC. Includes 650nm/5mW laser 300mCd green: $1.10 ea. or 10 for $7 ; diode, new handheld case 125 x 39 x 3Cd red: $1.10 ea. or 10 for $7 ; 3Cd 25mm, adjustable collimator lens PCB yellow also available in 3mm: 10 for $9 ; Super bright...FLASHING LEDs: $1.50 battery holder: $28 ea. or 10 for $10...(Make white light by . mixing the output of red green and blue) 650nM LASER POINTER SPECIAL Light weight (2XAAA) pen sized pointer (small torch!) with 5mW/650nM laser diode, 140mm . MORE KITS long, 18mm diameter: $50 Geiger counter:$40,...Breath tester: . $40,... Music box: $11,... Ding dong NICAD CHARGER & DISCHARGER High quality assembled switch-mode doorbell: $3.50, Siren using a 10cm 7.2V Nicad Charger and Discharger speaker: $14,... Electric fence using PCB assembly only. Requires an used car coil: $25,... Ultrasonic car unregulated input of 13.7V DC <at> alarm: $35,... 1ch UHF Central locking, 900mA. Appears to use voltage drop 1Tx and 1Rx: $35,... 4 door car Central detection to end charge, also a timer to locking: $60,... 2 Channel UHF Remote end the charge. We supply a thermistor Control, 1Tx + 1Rx: $45. for temperature sensing. For . fast-charging 7.2V AA nicads. Basic LCD CHARACTER DISPLAYS information provided, Incredible pricing: Back in stock! Standard 4 line X 32 char.displays using NEC D7227G IC’s.: $9 ea or 3 for $21. $18 . . HELIUM NEON LASER BARGAINS Large 2-3mW He-Ne laser head plus a AUDIO LASER SCANNER KIT compact potted US made laser power Generate fascinating patterns that supply. The head plugs into the supply, depend on the sound or music being picked up by an electret microphone. Kit and two wires are connected to 240V mains. Needs 3-6V/5mA DC to includes PCB, all components microenable: $100, Also 5mW tubes plus a phone, 2 motors and 2 mirrors: $44 . 12V inverter kit: $80 NEED AN OVER POWERED SUPPLY . FOR THE STEPPER DRIVER PC POCKET SAMPLER KIT Ref EA Aug ’96. Data logger/sampler, KITS???....USED POWER SUPPLIES connects to PC parallel port, samples Partially enclosed, employ a "C" core over a 0-2V or 0-20V range at intervals transformer with shield. Primary taps: 100-200-220-240V, secondaries: 24Vof one/hour to one/100uS. Monitor battery charging, make a 5kHz scope 8.5A , 9.5V-1.5A, 9.5V-4A, 5KG, mains etc! Kit includes on-board components, filter, switch, 4 fuseholders, 3 bridge PCB, plastic box and software (3.5" rectifiers, and filter capacitors: $15, . disk): (K90) $25 GIANT LED MESSAGE DISPLAY . 12 large 5x7 LED dot matrices (38 X 52 STEPPER MOTOR DRIVER KITS Kit includes a large used 1.8deg. (200 mm), very bright, in metal housing, 240 step / rev) motor and used SAA1042A Vac power, 3 wire control lead, no info: IC. Can be driven by external or an $40, on-board clock; has a variable frequency . clock generator. External switches (not provided) or logic levels from a NICKEL METAL HYDRIDE (NiMh) computer etc determine CW or CCW RE-CHARGEABLE 1.2V CELLS,similar rotation, half or full step operation, to NiCads but higher capacity, removed operation enable/disable,clock speed. from recent equipment, guaranteed, PCB and all on-board components: $18 48mm X 16mm diam.: 8 for $4, 115VAC for kit with 1 motor, $28 for kit with 2 . "MUFFIN" FANS NEW motors. 50/60Hz, 0.20A, shaded pole motor, . metal, plastic blade, 40mm thick: $4. SWITCH MODE POWER SUPPLY Compact (50 x 360 x 380mm), in a . perforated metal case, 240V AC in, 12V DIGITAL BAR CODE WANDS New USA made wands with a curly cord DC/2A and 5VDC/5A out: $17 terminated with a 5pin DIN plug. . converts bar codes to a digital pulses as 27 MHz TRANSMITTERS New tested PCB assembly. Xtal locked it is swept across the bar code. uses a on 26.995 MHz., designed for Sapphire tip, spot size is 0.19mm. Open transmitting digital information. Power collector output TTL/CMOS compatible varies from 100mW to a few watts: needs to be powered from 5V. $45 3-12V DC operation. Should not be connected to an antenna as licencing Our ads will alternate monthly beetween Silicon Chip and Electronics Australia may be required: $7 Ea. or 4 for $20 FREE CATALOGUE WITH ORDERS!!!!! . MASTHEAD AMPLIFIER KIT Our famous MAR-6 based masthead amplifier. 2-section PCB (so power PO Box 89 Oatley NSW 2223 supply section can be indoors and components kit $15. Suitable plugpack: Ph ( 02 ) 9584 3563 Fax 9584 3561 $6 Weather-proof box:$2.50. Box for orders by e-mail: oatley<at>world.net power supply: $2.50 Rabbit-ears http://www.ozemail.com.au/~oatley antenna: $7 (MAR-6 available major cards with ph. & fax orders, separately) Post & Pack typically $6 OATLEY ELECTRONICS June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV. Silicon Chip Back Issues September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. 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. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Operating an R/C Transmitter; Index to Vol. 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. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. 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; The Snowy Mountains Hydro Scheme. 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. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band; the Bose Lifestyle Music System; The Care & Feeding Of Battery Packs; How To Make Dynamark Labels. 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: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; MIDI Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. 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 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. 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. June 1990: Multi-Sector Home Burglar Alarm; Build A LowNoise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. 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. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. ORDER FORM Please send me the following back issues: _____________________________________________________________________ _______________________________________________________________________________________________________________ ______________________________________________________________________________________________________________ Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 80  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A8 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. ✂ Card No. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; A Windows-Based Logic Analyser. 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. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. 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 Pre­amp­ lifier;The Latest Trends In Car Sound; Pt.1. September 1996: VGA Oscilloscope, Pt.3; Infrared Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­grammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; Infrared Stereo Headphone Link, Pt.2; Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. 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. November 1996: Adding An Extra 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. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark­rooms; 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: What To Do When the Battery On Your PC’s Mother­ board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. October 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. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. November 1993: Jumbo Digital Clock; 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. 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 (Uses Pressure Sensing); Adding RAM To A Computer. December 1993: Remote Controller For Garage Doors; LED Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags – How They Work. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo 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; Passive Rebroadcasting For TV Signals. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Build A Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. September 1995: Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. March 1996: Programmable Electronic Ignition System; Zener Diode Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. April 1996: Cheap Battery Refills For Mobile Telephones; 125W 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; Build A 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. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Cruise Control – How It Works; Remote Control System for Models, Pt.1; Index to Vol.7. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluores­cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. December 1996: CD Recorders ­– The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. January 1997: How To Network Your PC; Using An Auto­ transformer To Save Light Bulbs; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (for Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. February 1997: Computer Problems: Sorting Out What’s At Fault; Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Audible Continuity Tester; Cathode Ray Oscilloscopes, Pt.7. April 1997: Avoiding Windows 95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; Installing A PC-Compatible Floppy Drive In An Amiga 500; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. May 1997: Windows 95 – The Hardware Required; Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How Holden’s Electronic Control Unit works, Pt.1. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home; How Holden’s Electronic Control Unit Works, Pt.2. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget; Win95, MSDOS.SYS & The Registry. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; The Flickering Flame Stage Prop; 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; Regulated Supply For Darkroom Lamps; Build A Musical Doorbell; Relocating Your CDROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1997: A Heart Transplant For An Aging Computer; Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc for $10 including p&p. January 1998  81 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. Stereo compressor wanted I have purchased the Gain Controlled Microphone Preamp with a similar purpose to its original intention. I have four differ­ent audio sources, namely two laser players, one video and a CD player. These are used in a Karaoke situation via a switch box so at any one time source A, B, C or D is used. Unfortunately, the audio is much louder from some discs so the main amplifier has to be continuously re-adjusted. I want to modify the above unit for this purpose and I would appreciate your advice as to the best method. (R. C., Rosebery, NSW). •  A circuit to suit your purposes was published in Circuit Notebook in January 1996. It used the same Vogad gain controlled IC. Also a better high quality unit was published in March Melt-down in a battery charger I have built the 10A battery charger from the June 1996 issue of SILICON CHIP. However, I have had problem of overheating to the point where it now seems I will have to replace the toroi­dal power transformer – all of its insulation has had a melt-down and the 4A mains fuse has blown. The heatsink baseplate has also melted the supports of the outer case. The MTP75N05 N-channel Mosfet (Q4) also has burnt out and shorted out onto the heatsink (the second time). This all seems to happen when the charger is on or near its highest charging rate. The charger does seem to work well unless it is running for too long on high charge. I am thinking of adding a separate heatsink for Q4, a better ventilated 82  Silicon Chip 1996 although it too was mono and you would need to double-up the circuit for a stereo version. It used an Analog Devices SSM2018 IC available from Farnell Electronic Components. Phone (02) 9645 8888. Reversing the speed controller I am very interested in building the heavy duty 10A 240VAC speed controller described in the November 1997 issue but I would like to add in the facility for reversing the motor. Can this be done with extra switching or whatever? (M. N., Surry Hills, NSW). •  Unfortunately, no can do. Regardless of the supply polarity fed to a series-wound motor (or a shunt-wound motor for that matter), whether it is AC, DC positive or DC negative, the motor will always run in the same direction. The only practical way case and possibly a 300VA toroidal transformer instead of 160VA. What do you think? (K. B., Seacliff Park, SA). •  One problem we have had with this kit is that the kit sup­pliers have supplied a thin aluminium baseplate for the charger instead of the 3mm baseplate you can see in the photograph on page 81 of the June issue. This will obviously affect the heat dissipation. Your power transformer should not get nearly as hot as you have described. Is it possible that the bridge rectifier is faulty? You also mention a 4A mains fuse. The fuse specified is a 2A slow-blow type. A separate heatsink for Q4 and better ventilation would definitely help if you expect to have the high charge rate for long periods. If you go to a 300VA transformer you will need a larger size case and you really shouldn’t need to do this. to reverse the motor is to swap the connections to the field wind­ ings. With the field reversed, the motor will run in the other direction. So unless you are willing to modify the wiring inside the housing of the motor, it cannot be reversed. This is a source of confusion to many enthusiasts but the only type of motor which can be reversed simply by changing the polarity of the supply is the permanent magnet motor. These are widely used in battery operated power tools and that is why such tools are commonly reversible – it is easy to do. Permanent magnet motors are also widely used in cars, model locomotives and model cars and again, these are applications requiring reversible motors. Checking the FM transmitter I have had the FM Stereo Transmitter (described in the October 1988 issue of SILICON CHIP) given to me as a present and it has been assembled as a kit. The trouble is, it doesn’t work. I’ve taken it to a repair place who tell me that it is all assem­bled correctly and they’ve even checked some of the chip outputs but they can’t make it work. For example, on the repair sheet they’ve indicated that the multiplex and pilot tones are present, the modulation present but there is not oscillator output. Help! Where do I go from here? (M. N., Bankstown, NSW). •  If the various outputs are stated to be present on the chip, it seems likely that the person concerned had an oscilloscope to make the checks. We’re betting that he then put his scope probe on the oscillator pins, saw nothing on the scope screen and concluded that the circuit wasn’t working and then gave up. There are two problems with using a scope to measure the oscillator output of the BA1404 FM stereo transmitter IC and they apply to any Protection diodes for stepper driver I am interested in building the manually controlled stepper driver described in the June 1997 issue of SILICON CHIP. However, I am concerned that perhaps the drive transistors may be blown by back-EMF spikes from the steppers. Why haven’t you specified protection diodes across each motor as would be normal practice? (C. N., Baulkham Hills, NSW). •  The simple answer is that we didn’t fit protection diodes because they are not necessary in this case. The scope waveform of Fig.1 shows that the collectors of Q2 and Q3 swing between ground and 5V as you would expect, seeing Q2’s emitter is at 5V and Q3’s emitter is at 0V. On the negative to positive transition of the waveform there is an overshoot to 15.3V before Q2 turns on. Similarly on the positive to negative transition there is a 7V overshoot. The VCEO rating of the BC548 and BC558 is 30V (ie, with the base open circuit), while with the base connected to the emitter through a resistor it is even higher. Thus our 15V spike is well within the transistor ratings. Looking at the waveform again you might wonder why the negative transient is not the same amplitude as the positive one. It is actually clipped by transistor Q3 acting as a 7V zener diode when its collector goes more negative than its base. The reason we only have such small spikes is that the motor windings are always energised with one end at the supply voltage and the other at 0V. In addition, the circuit was designed as a low power driver for a tiny stepper motor which would not draw much current, as evidenced by REG1 which will only supply 100mA maximum. The scope waveform of Fig.2 shows the effect of diodes across the transistors; they virtually eliminate the FM oscillator. First, you need an oscilloscope with a bandwidth of at least 100MHz, since the FM band is 88-108MHz. Second, if you put a scope probe on the oscillator pins, even a 10:1 probe, the capacitance of the probe is almost certain to kill the oscillation. It probably won’t kill the Fig.1: the waveform on the collectors of transistors Q2 and Q3. Fig.2: adding diodes across the transistors virtually eliminates the spikes. spikes. We used 1N4004s for this shot as the motor is only running at around 10 steps a second. So you can fit them if you wish. chip but it will stop the oscillation. The way to check whether oscillation is present is either to use an active probe, a sniffer loop or at least use a 10kΩ resistor on the tip of the 10:1 probe to stop its capacitance from loading the circuit. But you probably don’t need to do any scope checks at all. Our bet is that the person who built the kit for you ne­glected to do the short alignment procedure involving adjustment of the slugs in coils L1 & L2, as described in the article. If this is not done, the chances are that any transmission will not be received by a nearby FM radio. January 1998  83 Power rating of speed controller I have just built the Heavy Duty Speed Controller described in the November 1997 issue and it works very well with a variety of power tools. However, since you mentioned a 10A rating, I thought I would test it with a 2400W radiator. It works with that as well but the case becomes quite hot, so much so that I think the interior of the case would be stinking hot. The question is then: “Is it really suitable for a 10A load?” (B. R., Milperra, NSW). •  The answer is no. As we stated in the article, the con­troller is suitable for power tools rated up to 10A; ie, the nameplate rating of the tool should be no more than 10A. But perhaps misleadingly, we also had a features panel in the article which stated that it “can power appliances rated up to 2400W” so we see where you got the idea for testing it with a 2400W radia­tor. The reason why the speed controller is not suitable for a constant load of 10A is merely insufficient heat­ sinking; the circuit itself is capable but as you have found, it Big power supplies can cause problems I have constructed a pair of the 125W amplifier modules featured in the April 1996 edition, as the basis for a stereo power amplifier. For the power supplies, I am using two 500VA transformers with 24,000µF of filtering for each DC rail. Following construction and visual inspection, the modules were powered up for testing and quiescent current setting. The full chassis assembly as yet is incomplete and I haven’t tried out the modules with an input signal. On testing, all voltages on both boards measured very close to the nominated values and the voltage at the outputs measured +2mV and +24mV for each unit respectively. Although both voltages fall within the specified ±50mV, is the difference likely to have any implications for 84  Silicon Chip gets a little red in the face. In stating that the circuit is suitable for power tools with nameplate ratings up to 10A, the assumption is that the power tool is not being used constantly at full load. In fact, most power tools used constantly at the nameplate rating would quickly burn out. However, a 10A power tool such as circular saw or router will draw heavy current when starting and when actually cutting; at other times its current drain may only be 1A or so as it spins at full speed. Even power tools that might be used more or less constant­ly, such as routers or sanders, will rarely pull high currents all the time – their motors are generally not built for it, especially not the brushes and commutators. So the speed controller is suitable for power tools rated up to 10A. If you want to use with a load which pulls 10A contin­uously, it will need a bigger case with much better heatsinking for the bridge rectifier, the IGBT and the fast recovery diode. You might also think about fitting a 15A cartridge fuse as well, because the specified 10A fuse will be running too close to its limit. the overall performance as a stereo amplifier? Secondly, transistors Q6 and Q8 get quite hot very quickly, even at idle. Is this expected? (P. H., Rochedale South, Qld). •  We note that you have used a very large power supply and we wonder if the supply voltages are higher than specified. Normal­ ly, we would not expect that Q6 & Q8 would become hot. The solu­tion is to use a large flag heatsink on both devices or perhaps to substitute MJE340/350s. The different output offset voltages will have no measur­able or audible effect on the performance of the modules. Query on IGBTs I have a query regarding your Heavy Duty Motor Speed Con­trol circuit in the November 1997 edition of SILICON CHIP. The circuit specifies a BUP213 which the text says is an IGBT – Insulated Gate Bipolar Transistor. I have two problems with this component. The name insulated gate simply does not seem to apply to a bipolar transistor – a transistor does not have a gate it has a base. Also, when you think about it, if a component has an insulated gate, then it is not longer a BJT but a FET. Therefore, it should be called an IGFET not a IGBT. My second problem is that I cannot find a supplier of this component anywhere in Melbourne. I wonder if you could please let me know if there is a supplier for both this component and the high speed diode that is specified in the text. (A. M., Bayswa­ter, Vic). •  As far as the term IGBT is concerned, there is no mistake. The device is exactly what the letters suggest, a combination of a bipolar transistor with an insulated gate instead of a low impedance base. IGBTs have been around for at least a decade. We first used them in the 2kW sinewave inverter featured in the October 1992 to February 1993 issues. We published a general article entitled “An introduction to IGBTs” in the August 1996 issue. We can supply back issues at $7 including postage. We do not know of a supplier in Melbourne for these devices although it is available, along with the fast recovery diode, from Farnell Electronic Components. Phone (02) 9645 8888. Kitsets for the project are available from Dick Smith Electronics and Jaycar Electronics. Derating a PA amplifier The 175W PA Amplifier described in the March 1997 issue is no doubt a very useful device for open air venues, such as surf carnivals. However, brute force is not always required. Lower powered units for small zones in clubs, etc may not need to exceed 35-50 watts. Therefore my query is, if I delete Q13 and Q15, theoreti­cally dropping the output to 75W or thereabouts, what can I drop the rail voltages to in order to realise 50W or so, and still maintain good stability, retaining the 100V line transformer, at a lower power rating? Stability is the only thing that concerns me, as everything else should be fine. (P. M., Maitland, NSW). •  You can reduce the power of this module by removing a pair of output transistors as you suggest and then reducing the supply rails to about ±34V. However, we are inclined to think that using this module to deliver only 50W is a bit of a waste. Have you considered the 50W LM3876 module described in the March 1994 issue? It is cheaper and has short circuit protection. You would be advised to add the reverse biased diodes between the output and the supply rails, as in the 175W module. Amateur band receiver needs alignment I have made up a 3-band amateur receiver (SILICON CHIP, September 1996) and I am having problems. As supplied, my kit is slightly different from the published design. While the circuit specifies a number of 150pF capacitors, the PC board component layout has 68pF capacitors. Also for the F14 balun (T1), the copper wire supplied was not right because I could not get the right turns and had to go to a smaller gauge. Now, when I tune VR2 across the bands I only get one amateur station and one shortwave station all over the bands. Can you please tell me where I am going wrong? (W. S., Christchurch, NZ). •  We note that the PC board in your kit has changed capacitors compared with our article but unless you are unable to set the trimmer capacitors to give the precise oscillator frequencies, these changes are not important. You do not say whether you have been able to correctly align the receiver as outlined in the article. You will also need a fairly good antenna if you are to receive a reasonable number of stations. Have you put up an antenna, as suggested in our article? Is rectifier buzz a problem? I am preparing to build a compact, high performance ampli­fier for studio headphones, which I intend to use as the “heart” of a no-compromise listening system to be packed into a suitcase. It is to be housed in a small metal enclosure and powered from a 16V 1A AC plugpack. This arrangement appeals to me most of all possibilities and I can derive the two different split-rails that are required for the device’s operation “internally”, including rectification, filtering, stabilisation, decoupling, etc. It means, however, that the transformer will be connected to the rest of the power supply circuitry by about 2m of cable. Conventional wisdom implies a danger of “rectifier noise” radiation which could affect the performance of the device, as well as other electronics in the vicinity. How serious is this danger, for the given voltage and cur­rent? What kind of filter could I use and where, to safeguard against this? Would some sort of shielding on the plug­ pack lead be worth considering? And finally, would you suggest a larger case containing a transformer to be a better option – from the noise viewpoint alone? The amplifier will have an active tone control stage which I believe is especially prone to hum pickup. (A. K., Douglas, Qld. •  Conventional wisdom is right as far as rectifier noise is concerned. It is almost impossible to adequately suppress recti­fier noise radiated by a cable and it is even more difficult if the device you are using does not earth the core of the transformer. Having said that, the only way to gauge the serious­ ness of the problem is to give your proposed arrangement a try. It may be quite satisfactory. If not, you will need to resort to a more conventional power supply arrangement. Notes & Errata Stepper Motor Driver With Onboard Buffer, December 1997: the overlay diagram on page 64 shows a .01µF capacitor connected to pins 1 and 4 of IC2. This should be a .001µF as shown in the circuit and parts list. 240VAC 10A Motor Speed Controller, November 1997: while this controller is suitable for power tools with nameplate ratings up to 10A, it is not suitable for appliances such as 2400W radiators which draw 10A continuously. We have also been advised that the mica washers supplied in some early kits have been prone to flashover to the case. To avoid this, we suggest that a minimum of two mica washers be used for both the fast recovery diode and the IGBT. Better still, we suggest that SIL-PAD heatsink washers, a composite of silicone rubber and fibreglass be used, as these have a considerably higher voltage rating. The SIL-PAD 400 (.007) has a breakdown rating of 3.5kV AC. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. January 1998  85 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly on a separate sheet of paper, fill out the form below & 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. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my Signature­­­­­­­­­­­­__________________________  Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 86  Silicon Chip C COMPILERS: Ever ything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086 or 8096: $140.00 each. Macro Cross Assemblers for these CPUs + 6800/01/03/05 and 6502: $140 for the set. Debug monitors: $70 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 or 80C320 Simulator (fast): $70. Disassemblers for 12 CPUs only $75. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, the 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. Price: $189 + $10 p&p. 20pin SOIC adaptor only $70. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph/Fax (02) 9631 1236 or Internet: http://www.grantronics.com.au OSCILLOSCOPE TEKTRONIX 7403N 60MHz four channel plus delayed time base VGC. $550. Contact John, phone/ fax (07) 3269 6647. RTN Parallax Australia distributor. Parallax Basic Stamp modules BS1IC, BS2-IC and BS1 chipsets all ex stock. Carrier boards for the above also stocked. PicBus and StampBus modules also avail­able. Guaranteed best pricing and technical back up. Email: nollet<at> mail.enternet.com.au Http://people.enternet.com.au/~nollet Ph/fax (03) 9338 3306 MicroZed have 4-gang mini EPROM ERASER $80 + ST. You find 24 volt DC 100mA. HOMEMADE GENERATORS: how to instructions. Eight pages free text and colour photos on the Internet at: http://www.onekw.co.nz/ VIDEO CAMERAS & EQUIPMENT MONO MODULES ONLY $59! COLOUR MODULES ONLY $239! TOP QUALITY CAMERAS & MODULES 1 YEAR WARRANTY. 400 line 0.05 lux 32 x 32 MODULE with SONY SENSOR & CHIPSET ONLY $99! COLOUR MODULE (see pix CDI “Circuit & Design Ideas” page EA Dec) ONLY $239! COLOUR 450 TVL MODULES/ CAMERAS ONLY $369/$419! Opt/ Acc: 14 Lenses 2.1-12mm, MicroFine Focus, Infra Red Cut, Pass & Polarising Filters & 48-210 LED Infra Red Illuminators from $39. Range includes 380-570 Line Resolution, 0.2-0.05 lux IR sensitive, 50+dB S/N Ratio, TOP QUALITY 1/4" & 1/3" CCD Sensors with up to 437,664 Elements from SONY, SHARP & SAM-SUNG, 28mm x 28mm PCBs, up Digital Signal Processing Colour. Discreet 36mm SQUARE Cameras ONLY $99! (see pix p51 EA Oct) DOME CEILING Cam­ eras ONLY $99! (see pix CDI page) WIRELESS VIDEO-AUDIO Transmit­ter & Receiver Module/PCB PAIR ONLY $59! We stock: Monitors, Switchers, Quads, CCTV-TV Antenna Interface Modules, Outdoor Camera Housings, MULTI-RECORD PROCESSORS use one VCR to Record/ Playback up to NINE FULL-FRAME FULL-RESOLUTION images, Auto Iris Japanese Lenses ONLY $89! Use twisted pair cable for video Baluns ONLY $15! Before you buy Ask for our ILLUSTRATED CATALOGUE/PRICE LIST with Application Notes. Allthings Sales & Services 08 9349 9413 Fax 08 9344 5905. MicroZed have PIC 16C672 8 pin 6 I/O in limited qty Quartz window too. PCBs MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics (02) 9554 9760. sesame<at>nettrade.com.au PIC COMPILERS and programmers (the best ones) are available from Micro­­Zed. ELECTRONIC ENGINEERING SOLUTIONS: No matter what problem what industry we will find you a solution that meets your needs. Specialising in schematic & PCB design, custom Windows based software, embedded control, Windows/PC based test equipment, turnkey solutions. Fast turn around with competitive rates. DAM- MicroZed Computers BASIC STAMPS & PIC Tools 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. UE PTY LTD, 46 Whitby Road, Kings Langley NSW 2147. Phone (02) 9624 2802. Fax (02) 9624 2651 or E-mail alovell<at>ibm.net RTN Elab Digital products distributor. Basic Stamp add-on pro­ ducts. EDE-300, 8 I/O extra via just 1 pin from any Stamp or micro. EDE-700, Serial LCD interface IC via 1 pin display text on LCD modules ranging from 1*8 to 2*40 in size. EDE-1200, stepper motor controller IC, stand-alone or under host control. Email: nollet<at>mail.enternet.com.au Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals, with SUPPORT PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 014 036775 Fax (02 6772 8987 http://www.microzed.com.au/~microzed Credit cards OK. Send two 45c stamps for info Http://people.enternet.com.au/~nollet Ph/Fax (03) 9338 3306. A HOT SPOT FOR CHEAP PCB SUPPLIES, raw stock, drills etc plus quality manufactured boards is located at http://www.accsoft.com.au/~acetronics or phone 02 9743 9235. DONTRONICS can be found at: http://www.dontronics.com PARALLAX PIC programmers, professional and hobby versions (the best ones) are available from Microzed. SILICON CHIP FLOPPY INDEX WITH FILE VIEWER Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. Price $7.00 each + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 9979 5644 & quote your credit card number; or fax the details to (02) 9979 6503. Please specify 3.5-inch or 5.25-inch disc. January 1998  87 14 Model Railway Projects Shop soiled but HALF PRICE! Advertising Index Altronics................................. 26-27 Australian Audio Consultants.......43 Av-Comm Pty Ltd.........................17 Dick Smith Electronics........... 10-13 Harbuch Electronics....................47 Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. Instant PCBs................................87 SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) Microgram Computers...................3 This book will not be reprinted Jaycar ..................IFC, 33-36,53-56 Rola Australia..............................87 MicroZed Computers...................87 Norbiton Systems........................63 Yes! Please send me _____ copies of 14 Model Railway Projects at the special price of $A3.95 + $A3 p&p (p&p outside Aust. & NZ $A6). Enclosed is my cheque/money order for $­A__________ or please debit my Oatley Electronics........................79 Premier Batteries.........................63 ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Printed Electronics.......................87 Card No. Project Engraving Supplies..........63 Signature­­­­­­­­­­­­___________________________  Card expiry date______/______ Resurrection Radio......................52 Name Street ______________________________________________________ PLEASE PRINT ______________________________________________________ Suburb/town_________________________________ Postcode_________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). Scan Audio....................................9 Silicon Chip Bookshop.................57 Silicon Chip Binders/Wallcht....OBC Silicon Chip Software..................73 Smart Fastchargers.....................17 Sunshine Electronics...................69 Silicon Chip Binders ★  Heavy board covers with 2-tone green vinyl covering ★  Each binder holds up to 14 issues ★ SILICON CHIP logo printed in goldcoloured lettering on spine & cover Price: $21.95 plus $5 p&p each (Aust. only) 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. 88  Silicon Chip REAL VALUE AT $12.95 PLUS P &P Zoom Magazine.........................IBC _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: •  RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. •  Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. R AUSTRALIA’S BEST AUTO TECH MAGAZINE It’s a great mag... but could you be disappointed? If you’re looking for a magazine just filled with lots of beautiful cars, you could be disappointed. Sure, ZOOM has plenty of outstanding pictorials of superb cars, but it’s much more than that. If you’re looking for a magazine just filled with “how to” features, you could be disappointed. Sure, ZOOM has probably more “how to” features than any other car magazine, but it’s much more than that. If you’re looking for a magazine just filled with technical descriptions in layman’s language, you could be disappointed. Sure, ZOOM tells it in language you can understand . . . but it’s much more than that. If you’re looking for a magazine just filled with no-punches-pulled product comparisons, you could be disappointed . Sure, ZOOM has Australia’s best car-related comparisons . . . but it’s much more than that If you’re looking for a magazine just filled with car sound that you can afford, you could be disappointed. Sure, ZOOM has car hifi that will make your hair stand on end for low $$$$ . . . but it’s much more than that. If you’re looking for a magazine just filled with great products, ideas and sources for bits and pieces you’d only dreamed about, you could be disappointed. Sure, ZOOM has all these . . . but it’s much more than that. But if you’re looking for one magazine that has all this and much, much more crammed between the covers every issue, there is no way you’re going to be disappointed with ZOOM. Look for the June/July 1998 issue in your newsagent From the publishers of “SILICON CHIP”