March 2000 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Possible uses for computer cases
Feature: Doing A Lazarus On An Old Computer by Greg Swain
Project: Ultra-LD 100W Stereo Amplifier; Pt.1 by Leo Simpson
Feature: Inside An Electronic Washing Machine by Julian Edgar
Review: Multisim - For Circuit Design & Simulation by Peter Smith
Project: Electronic Wind Vane With 16-LED Display by John Clarke
Serviceman's Log: Some jobs aren't worth the trouble by The TV Serviceman
Back Issues
Project: Glowplug Driver For Powered Models by Ross Tester
Product Showcase
Order Form
Project: The OzTrip Car Computer; Pt.1 by Robert Priestley
Project: Aura Interactor Amplifier by Leo Simpson
Vintage Radio: The Hellier Award; Pt.2 by Rodney Champness
Book Store
Market Centre
Outer Back Cover

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March 2000 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SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.emona.com.au Contents Vol.13, No.3; March 2000 FEATURES 4 Doing A Lazarus On An Old Computer There’s no need to chuck that old 286 or 386. Here’s how to turn it into a useful machine – by Greg Swain 24 Inside An Electronic Washing Machine There’s much more than the washing – by Julian Edgar 33 Review: Multisim – For Circuit Design & Simulation Forget about hardware prototyping. This simulation package lets you design and test virtual hardware on a computer screen – by Peter Smith Ultra-Low Distortion Amplifier Module – Page 16. PROJECTS TO BUILD 16 Build The Ultra-LD 100W Amplifier Module; Pt.1 This 100W class-AB amplifier module has ultra low distortion – by Leo Simpson 40 Electronic Wind Vane With 16-LED Display Novel design uses a Gray encoded disc – by John Clarke 72 Glowplug Driver For Powered Models Electronic Wind Vane With 16-LED Display – Page 40. Simple circuit lets you start model engines from a 12V car battery – by Ross Tester 86 The OzTrip Car Computer; Pt.1 Versatile design can also be used as a rally computer or as a boat fuel computer – by Robert Priestley 96 A Solution Waiting For A Problem Think up an application for the Aura Interactor amplifier and you could win a $200 gift voucher – by Leo Simpson SPECIAL COLUMNS 65 Serviceman’s Log Some jobs aren’t worth the trouble – by the TV Serviceman 101 Vintage Radio The Hellier Award; Pt.2 – by Rodney Champness Glowplug Driver For Powered Models – Page 72. DEPARTMENTS 2 Publisher’s Letter 85 Subscriptions Form 38 Circuit Notebook 105 Ask Silicon Chip 76 Mailbag 107 Notes & Errata 77 Electronics Showcase 110 Market Centre 78 Product Showcase 112 Advertising Index OzTrip Car Computer – Page 86. March 2000 1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Peter Smith Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0414 34 6669 Regular Contributors Brendan Akhurst Louis Challis Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2 Silicon Chip Possible uses for computer cases This month we return to a subject which we have discussed before: “Putting older computers to work”. Now that the year 2000 is with us a great number of older and notso-old computers have been pensioned off and are being thrown out and in many cases there is nothing wrong with them. I don’t know about you but this waste of functional hardware distresses me even though I am well aware of the reasons why older machines are discarded. Hence, we have a major article this month on resurrecting older machines. It starts on page 4. However, while this article may serve the purpose of putting some older machines to work there are still many that will not find a use in their present form. Not to be deterred, we can still see uses for this well-designed hardware. In particular I am thinking of the typical desktop computer case. Next month, we plan to present a stereo version of the Ultra-LD 100W amplifier module in a standard computer case. The two modules will be mounted on either side of a fan-cooled heatsink tunnel. The 80mm fan can doubtless come from the discarded power supply of the computer and so can some other bits and pieces such as the front panel power switch, the IEC power socket and cord and so on. The beauty of this approach is that it saves the expense of metalwork for the amplifier. These days integrated stereo amplifiers tend to be unviable as electronic projects because the metalwork is just so costly. This way, we avoid the expense and get a well-designed case with plenty of room inside it. If you can get an older “clam-shell” computer case, with push-catches on either side to open it, so much the better. Perhaps you are thinking that you (or your partner) does not want a beige coloured computer case in your hifi system. Well, being just a stereo power amplifier, it does not need to be on view. Or if you really wanted to, there is no reason why you could not spray it black. This approach could probably be applied to other projects as well. For example, perhaps a computer case would be entirely suitable for a public address or guitar amplifier. What about a transmitter for the amateur bands? Perhaps a mini-tower case would be even more useful for these applications. The plastic front panels of these computer cases are easily drilled to take switches, knobs and other hardware and you can obtain infill panels to close off the rectangular openings left by disk drives. In fact, the more I think about it, if you are a keen electronics hobbyist, you should ensure that you have some of these computers put by, “just in case you might need them!” Anyway, put on your thinking caps and think about how these old computers or their cases might be put to good use. We shouldn’t be sending them all to the tip. Leo Simpson M croGram Computers 19 Key Keypad - Serial Connection This handy, light weight keypad plugs into a standard serial port and a small TSR program captures the keystrokes and directs them to the keyboard buffer. The keypad has a DB9 female plug. Cat. 8741 19 Key Keypad - Serial Connection $109 External Case for CD USB Port Web-Based Training from $14.95 per month* New courses now available! Including Windows 98, Quicken 98, Lotus Notes, Internet Tools (Netscape) and more courses on TCP / IP. External Case ffor CD Parallel Port $139 CD ROM Parallel Port 40xSpeed & Case $359 VGA to Video Converter 2 Port USB PCMCIA Card Cat. 3102 VGA to Video Converter $379 Ultra DMA 66 HDD PCI IDE Controller 10Mbps Ethernet 5 Port Hub & LAN Card Break the 8.4Gb drive barrier and get a lot more speed. Our Ultra DMA66 IDE controller has two enhanced Ultra DMA 66 IDE ports, it supports up to 4 IDE devices & co-resides with existing motherboard IDE ports i.e. 8 IDE devices on one computer. Cat. 2809 HDD Cont PCI IDE Ultra DMA 66 $129 PCMCIA Card Drive for Desktop PC This high performance PCMCIA Drive provides two frontaccess sockets on the 3.5" front bay and is connected to the Interface Adapter by ribbon cable. The drive supports DOS & Windows 3.1x, Win95/NT 3.5x & 4 & OS/2 Warp 3.0/4.0. Cat. 6121 Cat. 6458 PCMCIA Card Drive for Desktop PC PCMCIA Card Drive & FDD $219 $399 Dual Exhaust Fans Cat. 8564 Cat. 8420 Hard Drive Cooling Fans Dual Exhaust Fans $49 $45 No USB Port on your Notebook PC? Just slide this PC Card into your notebook and, instantly, you can connect USB peripherals. Connect USB-based printers, modems, speakers, scanners, etc. NO complex installation, confusing plug-ins, or IRQs. PC Card enables any Notebook PC with Card Bus Slot to connect USB products. Cat. 2810 Two Port USB PCMCIA Card $195 Short Haul Modem - Line Driver Internal PCI Plug & Play 5 Port hub and LAN card does not require external power supply. One port can be used as an uplink port for easy expansion, or used for hub connectivity at the server. This Line Driver provides efficient asynchronous transmission & reception of serial data without requiring an external +12V DC power source. The unit drives data at speeds up to 19,200 bps over distances up to Cat. 11295 Ethernet Hub & LAN Card 5 Port UTP 10Mb $66 0.8 km using 24-gauge wire. The driver provides Blood Pressure Monitoring System 1500 VAC lightning surge protection & excellent DynaPulse is a clinical accuracy noise rejection through use of differential circuitry. blood pressure & pulse monitoring Cat. 10056 Short Haul Modem - Line Driver $85 device that connects to your computer via a serial port. It displays FireWire to PCI Host Adapter the actual blood pressure waveform Connect your digital video camera to your PC. Our on screen as a visual confirmation of Firewire card allows IEEE 1394 FireWire devices measurement accuracy. More to connect to your PC at speeds up to 400Mbps. importantly, systolic, diastolic, & mean arterial pressures are The card has 3 external & 1 internal 1394 ports to measured rather than calculated. The home version main- allow connections to hard drives, scanners, VCRs, HDTV, printers etc. Editing videos is simplified with tains data for up to six people. the bundled Ulead Video Studio DV SE software. Blood Pressure Monitoring System Cat. No. 16000 $369 Cat. 2621 Mouse Tablet Two products to keep your computer & hard drive cool! Dissipate heat with dual exhaust fans attached to a plenum to exhaust hot air from inside the computer. Reduce possibility of data loss due to HD overheating with dual fans attached to a ventillated face plate. It will effectively dissipate heat from the HD & significantly lower temperatures. Now over 300 courses on offer *Full details at www.tol.com.au High quality at an affordable price, This external case will this totally external unit does not support standard IDE Bus require software drivers, hence, CD-ROM drives and conno software clashes. Scan rates nects to a USB port. It up to 100Hz are supported for includes built-in power supply and support for 640x480 resolution, up to 85Hz Windows 98 and Windows 2000. for 800x600 resolution, and up to 75Hz for 1024x768 External Case for CD USB Port Cat. 6622 $199 resolution. Cat. 6319 Cat. 6493 A number of courses are “Microsoft Certified Professional - Approved Study Guides” The Mouse Tablet is an input device that allows you to choose between an easy-to-use, high resolution, trackball-free mouse or a precise stylus pen. Both pointing devices are implemented with cutting-edge electromagnetic technology, and have a resolution up to 4064 LPI. The 3button stylus pen provides pinpoint accuracy and writing, drawing & painting abilities. Bundled software includes PhotoImpact 4 SE & PenGuard. Cat. 8676 Mouse Tablet $189 FireWire to PCI Host Adapter $199 Windows Terminal This windows based terminal is suitable for both NT Terminal Server & Citrix Metaframe. It supports Microsoft's RDP & Citrix ICA3 protocols. Ports are DB25 parallel, two DB9 serial, two USB, VGA DB 15, PS/2 mouse & keyboard ports & audio in & out. Just add a monitor, keyboard & mouse. Windows Terminal Cat. 1214 $1299 Serial and TCP/IP Ethernet LAN terminals. Serial Terminal 460Kbps TCP/IP Ethernet LAN Terminal Cat. 1133 Cat. 1134 E & OE $489 $519 All prices include sales tax MICROGRAM 0300 Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 FreeFax 1 800 625 777 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 What do you do with old 286 and 386 computers? Most people “chuck ’em” but for just $15 you can buy a new 486 mother board, do a transplant and turn it into a useful machine. Here’s how to go about it. Doing a By GREG SWAIN Lazarus on an old computer S CROUNGING OLD PCs has never been easier. They’re thrown away during council cleanups, given to employees during company upgrades and available for a pittance at garage sales. Just think of the number of machines that were scrapped as insurance against the dreaded Y2K bug – it’s just a matter of being in the right place at the right time. One of our staff members was in the right place recently, when his local pharmacist threw out an old 386 machine complete with supporting software (DOS 6.22 and Windows 3.11). He wanted a second machine for use at home but didn’t want to spend much money, so 4 Silicon Chip he brought it in to see if the machine was worth upgrading. At first glance, the hardware all looked in pretty good nick, although it was a bit grotty. It had obviously been used next to a printer because both the keyboard and the monitor were stained black from toner. By contrast, it was reasonably clean inside the system case but we did notice lots of corrosion around the battery. That meant that the old 25MHz 386 motherboard was almost certainly defunct but it was no loss – a 386 motherboard is next to useless. It was time to take stock and a quick inventory – the price is right and there are lots of applications for a refurbished machine. For example, it could be used as a word processor, a printer server, a dedicated fax machine, or even as an Internet firewall. It could also be used for networking experiments or for testing applications that you’re not too sure about and don’t want to risk on your main machine. The $15 motherboards come fitted with a “UMC” brand 40MHz 486SX processor as standard but you can set the bus speed to 25MHz, 33MHz or 40MHz if you wish to use a different processor. In fact, the unit can cater for Intel, AMD and Cyrix processors up to DX2-80 and DX4-75/100 in the standard Socket-5 configuration. If you have an Intel DX2-66 processor, for example, you can easily swap the processor to extract a bit more performance. A DX4-100 would be even better! You set the bus speed and various other parameters to suit the processor by changing links on the motherboard, as set out 1 Apart from the motherboard, it all looked pretty good inside! This in the manual. Also on the board are six old PC was an ideal candidate for a motherboard transplant. expansion sockets (five 16-bit and one 8-bit), plus four 30-pin and one 72-pin revealed the following goodies: (1) a sturdy desktop SIMM (single in-line memory) sockets supporting up to case with working power supply; (2) a 120MB hard 32Mb of RAM. disk drive; (3) a 1.44MB floppy disk drive; (4) a 1.2MB There is also provision on the board for up to 512KB floppy disk drive (OK, you can chuck that); (5) a generic of cache RAM but no TAG or cache RAM is fitted. You video card; (6) a rather nice D-Link network card; and can’t expect that for $15 but if you’re lucky, you can use (7) an I/O (input/output) card with serial and parallel the TAG and cache RAM from your old motherboard. ports plus connectors for the disk drives. Of course, it will still run without cache RAM – it just As for the monitor and keyboard, they may have won’t be as fast. looked grotty but they worked perfectly when tested One drawback is that there is no provision for I/O with another computer. They were both good-quality on the motherboard; ie, no serial or parallel port conNEC units and were worth cleaning up. nectors and no connectors for disk drives. Again, this There was just one thing missing – a mouse but we isn’t a problem if you have an I/O expansion card. Most had one spare anyway. 286, 386 and early 486 computers came with separate And that’s all quite typical of most old computers I/O cards but if yours didn’t, you’ll have to scrounge that have been rescued from the tip. Most of the hardone from another old computer or pick one up at a flea ware, including the disk drives, is usually quite OK but market. there will often be problems with the motherboard. If In case you’re wondering, the motherboard comes it’s a 286 or 386, the motherboard isn’t worth keeping even if it still works OK. Usually, however, they will have been damaged by a leaking battery and the same goes for many 486 motherboards as well. Apart from that, most old computers generally need a good clean up. The keyboard is always dirty and sometimes the keys stick because it is full of dust and fluff. There is also often quite a lot of dust inside the system case and it seems that no-one ever cleans monitors. New motherboard So what was needed to turn our old 386 into a useful working computer? Simple – a good clean up and a motherboard transplant. The first part is easy and for the latter, we had just the unit in mind. If you want a low-cost motherboard, Oatley Electronics has a really good deal – a brand new 486 motherboard for just $15 or three for $30. But why would you want to do it? Well, why not? 2 $15 buys you this brand new 40MHz 486SX mother board (without the memory) from Oatley Electronics. It’s just the shot for transplanting into an old 286 or 386. A Pentium motherboard would be even better! March 2000 5 3 Step 1 was to attack the keyboard. Undoing four screws along the top rear gives access to the innards. 4 The key carrier plate was lifted clear after prising open several retaining clips using a flat-bladed screwdriver. fitted with a recent Award BIOS and supports LBA mode (logical block addressing) for hard disk drives. Put simply, this means that the BIOS can support modern large-capacity disk drives and is not just restricted to drives of up to 528MB. So if you’ve got a 1.6GB drive, for example, you won’t need a special device driver to access its full capacity. If you’re using a motherboard with a BIOS that doesn’t support LBA, you will need to obtain a special driver to translate the drive geometry. Perhaps the best known of these are Ontrack Computer System’s “Disk Manager DiskGo” (as used by Seagate) and Western Digital Corporation’s “Data Lifeguard”. If you want something better than a 486, see if you can “acquire” a discarded Pentium motherboard and processor. This will allow you to run Windows 95/98 at a fair clip provided you fit enough memory (ie, at least 16MB). OK, it was time to get to work and resurrect our old 386 machine. The first thing to do was to disassemble and clean that grotty keyboard. Undoing four self-tapping screws along the rear top edge allowed us to lift the front cover clear. This done, we removed the black plastic carrier plate, complete with all the keys, by gently prising open a number of retaining clips using a flat-bladed screwdriver. There were three small green indicator LEDs clipped into the top, righthand corner and these were removed and placed to one side. As expected, the keyboard was full of dust and this one also gave up numerous paper clips and metal staples. A soft brush got rid of the dust, while the key/carrier plate assembly was sprayed with “Nifty” (a household cleaner) and scrubbed clean in a tub of water using an old toothbrush. It came up looking like new, as did the top cover when we gave it the same treatment. The plastic base was cleaned by wiping it with a cloth sprayed with “Nifty”, taking care not to touch the plastic keyboard membranes or the circuit boards. Naturally, the key/carrier plate assembly must be thoroughly dried before the keyboard is reassembled. It’s not just sufficient to dry the outside of the assembly because a lot of water becomes trapped in the key guides. This water can be dislodged by repeatedly tapping the assembly on your hand, after which you can use a hairdryer on a low setting to complete the process. In our case, we also left the key assembly to dry overnight before carefully putting the keyboard back 7 It’s a good idea to write down the lead colour coding for the front panel LEDs and switches. This makes it easier to place the connectors on the new motherboard later on. 8 Out with the old – the two power supply plug connect ors were the last be released before the old motherboard was lifted clear of the chassis. Keyboard capers 6 Silicon Chip 5 Time to clean up – spraying the keys with “Nifty” and scrubbing them with an old toothbrush worked like magic. 6 A soft brush was used to remove the dust, paper clips and staples before the keyboard was reassembled. together. When we had finished, it looked as though it had just come out of the factory. By the way, there are lots of variations when it comes to keyboard assemblies. It’s really just a matter of using your common sense. The monitor also responded well to the “Nifty” treatment but again you have to be careful. Don’t allow fluid to find its way through the ventilation slots and onto the circuit boards. If you do, the monitor could very well expire the next time it’s turned on. Now for the motherboard transplant. If you have a working system, it’s a good idea to first fire it up and take a peek at the hard disk parameters in the system BIOS. Make a note of these because you will need to re-enter them later on. If the system is defunct, just ignore this step. Most hard disk drives have their parameters printed on the drive label although you may have to remove the drive to see them. If it doesn’t, it’s quite easy to obtain the parameters by visiting the manufacturer’s web site. Alternatively, the Award BIOS supplied with the Oatley motherboard has an IDE hard disk drive auto-detection utility which should make the job easy. Our next step was to remove the power cord, open up the system case and remove the expansion cards. We didn’t completely remove the I/O card, however. Instead, we left all the cables connected to it and sat it on top of the power supply. Next, we removed the two power connectors to the motherboard and the connectors for the front-panel leads. These leads ran to the front-panel indicator LEDs, to the Turbo and Reset switches and to the keyboard lock. It’s a good idea to write down the colour coding for these as you go, to save tracing them back to the front panel later on. Removing the motherboard now involved undoing two retaining screws at the rear and sliding it sideways until the plastic standoffs cleared the metal keyways in the chassis. It then lifted clear, after which we transferred the plastic standoffs to the appropriate locations on the new board. If you are undertaking the same exercise, you may find that there is a slight variation on this theme but it will be obvious what you have to do. Test fitting the new board into the case will quickly indicate which holes should be fitted with plastic standoffs and which should be reserved for the retaining screws (these go into tapped metal standoffs). 9 More cleaning – a soft brush and a vacuum cleaner were used to spring-clean the chassis. This makes it more pleas ant to work on and is good for long-term reliability. 10 The plastic standoffs must be removed from the old board and fitted to the new motherboard. In some cases, it may be easier to fit the standoffs to the chassis first. Removing the hardware March 2000 7 11 RAM for free – our four 1MB SIMMs came from an old 286 motherboard. It sure pays to keep this stuff because you never know when it’s going to come in handy. Looking For Drivers? Go Directly To The Web O NE THING THAT’S usually missing when you acquire an old computer are the original setup disks, containing the driver files, for various hardware items. This particularly applies to video cards, soundcards, network cards, CD-ROM drives, printers and modems. By itself, Windows 95/98 usually makes a pretty good fist of identifying your hardware and supplying the correct driver from the Windows CD-ROM. But that doesn’t always happen, in which case the answer is to download the appropriate driver from the manufacturer’s website. If you’re looking for driver files, here are a few websites for you to try: (1) www.windrivers.com (all sorts of links to drivers plus help for identifying unknown hardware such as motherboards, modems, video cards, sound cards and network cards). (2) www.winfiles.com (lots of links to manufacturers, driver updates, bug fixes and other goodies here). (3) www.geocities.com/SiliconValley/6708/index. html (lots more links for you to try). Having trouble identifying the manufacturer or model of some hardware? If it’s got an FCC (US Federal Communications Commission) ID number, you can search for it at www.fcc.gov/oet/fccid/ Finally, there’s also help for identifying unknown modems at www.56k.com/trouble/noname.shtml 12 In with the new – the new motherboard, complete with RAM, is installed by sliding the plastic standoffs into the keyways in the case. Don’t forget the retaining screws. Before throwing the old motherboard in the rubbish bin, take a good look at the type of memory (RAM) that’s fitted to it. If it uses 256KB, 1MB or 4MB 30-pin SIMMS or 1, 2, 4, 8 or 16MB 72-pin SIMMs, you’re in luck and the memory can be salvaged for the new board. We weren’t so lucky – our old 386 motherboard used DIL (dual in-line) memory which is worthless. Once the old motherboard is out, it’s a good idea to remove any dust from inside the case using a soft brush and a vacuum cleaner. While you’re at it, you should also brush away any dust that’s on the expansion cards. Usually, it will be more convenient to fit the memory to the new motherboard before installing it in the case. We had four 1MB 30-pin SIMMs, previously salvaged from another old machine, sitting in a drawer, so we fitted that (yes, it really pays to keep this stuff). OK, so 4MB of RAM isn’t much but it’s usually adequate (barely) for a machine running Windows 3.1x. If you don’t have any memory that’s suitable, try to scrounge some from another old machine. The aim is to spend as little money as possible because old computers are not worth spending big bucks on. If you do have to buy memory, you’ll find that the 72pin stuff is considerably cheaper than the older 30-pin stuff. Also, if you’re using the Oatley board, be sure to Want to identify a hardware item? Try www.windrivers.com or if it has an FCC ID number, search for it at the FCC website listed above. 15 We’re fastidious, so we removed the old 1.2MB floppy drive and brushed away the dust. OK, so 1.2MB drives are now useless but we didn’t have a blank to take its place. 8 Silicon Chip 13 All hooked up and ready for the expansion cards. Note the arrangement for the power supply connectors – their black leads go to the centre pins of the power socket. 14 We connected the disk activity indicator LED to a pair of terminals on the disk drive itself. Usually, however, you will find suitable terminals on the motherboard. check the memory configuration table in the manual. Note that the largest 72-pin SIMM that you can use by itself is 8MB. A 16MB 72-pin SIMM can be fitted but this must be matched with 4 x 4MB 30-pin SIMMs in the other memory slots (giving a total of 32MB). How much RAM should you use? That depends on the operating system and applications you intend running. If you intend running Windows 95/98, for example, then you should aim for a minimum of 16MB. On the other hand, 4-8MB should be enough for Windows 3.1x. be oriented with its positive lead to pin 1. If you don’t know what a particular connector is for, the easiest way to find out is to trace it back to the front panel. Note that the Oatley board doesn’t have terminals for the hard disk activity LED. We solved that minor problem by plugging the connector directly into the relevant terminals on the hard disk drive itself. At this stage, it’s a good idea to take a look at the power switch. Make sure that the spade connectors are pushed all the way home on the switch terminals and that they are all well-insulated. The Earth lead at the switch end should be securely fastened to the case metalwork and a multimeter should indicate a good connection between the metalwork and the earth pin of each IEC mains socket at the rear of the computer (ie, you should get a reading of zero ohms). Fitting the new board Once all the memory had been loaded, we slid the motherboard into the case, installed the retaining screws and plugged in the two power connectors. How do you know which way around the two power connectors go? Easy – black goes to black which means that the black leads on the connectors go to the middle of the socket. Depending on the case and the location of the power supply, it may sometimes be easier to install the power connectors before sliding the motherboard into position. This particularly applies if the power socket sits directly beneath the power supply when it is in position. It may also sometimes be easier to install the plastic standoffs in the case before fitting the motherboard. That way, the motherboard can simply be positioned over them and clipped into position. It’s up to you to choose the easiest method. Finally, we refitted the various expansion cards (ie, the video, network and I/O cards) and installed the front panel wiring connectors. These connectors are for the Turbo and Reset switches, the Turbo LED, the Speaker Connector and the Keylock & Power LED Connector. The locations of these are clearly shown in the manual and are also shown on the board itself (this also applies to most other motherboards). How do you know which way around the connectors go? The Turbo and Reset switches can go either way, while the Keylock & Power LED connector must be oriented so that the positive lead from the power LED goes to pin 1. Similarly, the Turbo LED connector must Booting up Before applying power, it’s a good idea to carefully check your work. In particular, we checked that the 16 Make sure that the expansion cards are properly seated before tightening the backplane connector screws. Also be sure to plug the 16-bit cards into the 16-bit slots. March 2000 9 Adding Another Hard Disk Drive And All That Guff O NE OF THE DRAWBACKS of old computers is that the hard disk drive is usually of quite limited capacity. Many 286 machines, for example, came with a 40MB drive, while 386s and early 486s usually have a hard disk drive ranging from just 80MB to 240MB. By contrast, DX2-66 486 machines often have a 500MB or better hard disk drive which will be adequate for many applications. If the disk drive isn’t up to the job, the answer is to swap it for something bigger or perhaps add a second drive. Once again, the trick is to scrounge something from a defunct machine. This shouldn’t be too difficult, particularly if you are building one good machine from several write-offs. Most hard disk drives that you will encounter are IDE (integrated disk electronics) types and these connect to the IDE port on the motherboard or I/O card via a 40-way cable. This cable is usually fitted with two connectors at one end so that you can connect two disk drives, one configured as a “master” and the other as a “slave”. The master or slave configuration is set using jumper links on the back of the drive. For example, if only one drive is connected to an I/O cable, it’s generally configured as a “master”. Note, however, that some drives must be set to a “single” configuration if used on their own. On other drives, the “master” and “single” jumper settings are the same. If two drives are connected to the same cable, one is configured as a “master” and the other as a “slave”. Note, however, that if the second drive is used on its own on another I/O cable (some motherboards have two IDE ports), then it must be set to the “single” drive (or master) configuration. Just to confuse matters, most hard disk drives also come with a pair of jumper pins labelled “CS”, or “Cable Select”. This configuration is used only with a special I/O (CS) cable which has the disk connectors clearly marked; eg, drive 1 and drive 2 or master and slave. If you use a CS cable, you just set both drives to “CS” before connecting them to the cable. You’re not restricted to just using hard disk drives on All hard disk drives come with three or more pairs of jumper pins, usually located between the I/O socket and the power socket. These let you configure the drive as a “master” or as a “slave”, where more than two drives are used on the same cable. 10 Silicon Chip the IDE ports, by the way. For example, you can add an IDE CD-ROM or a ZIP drive if you wish but be sure to configure the drive as a “master” or “slave”, as appropriate. Having installed the new disk drive, don’t forget to enter its parameters (or run Auto Detect) in the BIOS setup so that the system will recognise it. After that, it will have to be partitioned and formatted (if this hasn’t already been done) before installing the operating system. A word of warning here – if you’re moving a disk drive across from an existing system and want to keep your data, be careful with Auto Detect. If you do use it, you may find that the machine won’t boot up or, if it’s a nonboot disk, you may no longer be able to access files or the files may appear to be corrupted. The reason for this is that Auto Detect doesn’t read any settings that may have been manually assigned to the drive in the previous installation. Instead, it retrieves the drive’s parameters from a ROM (read only memory) that’s incorporated into the drive itself. This means that Auto Detect will cause errors if any previously-assigned parameters differ from those stored in the ROM. Naturally, this doesn’t matter if you no longer need the data stored on the drive. If that is the case, you can just reformat the drive and carry on with the new settings. On the other hand, if you wish to keep the existing data, you will have to manually assign the required drive parameters if Auto-Detect causes problems. By the way, don’t try to fix any disk errors using a disk management utility such as ScanDisk if Auto-Detect is causing problems. If you do, you will almost certainly corrupt your data. Another factor to consider is that old 386/486 motherboards generally have BIOS limitations when it comes to recognising hard disk drives bigger than 528MB. Other more recent BIOSes can’t “see” past 4.3GB or 8.6GB. One way around this is to use BIOS translating software. In each case, you should visit the manufacturer’s website and download the software that’s right for your hard disk drive. It’s important to obtain and install the latest version of any BIOS translating software. That’s because older versions aren’t compatible with FAT32. With an older version, if you installed Windows 98 and later converted to FAT32, you would no longer be able to access the drive. Yes, there is a way of retrieving the situation but you don’t want to know about it. Another way around the problem, provided your motherboard has a spare PCI slot, is to purchase an IDE controller card with its own on-board BIOS. But hey, you’re starting to spend money on an obsolete machine and that’s not the idea here. Finally, remember that the operating system itself may have limitations when it comes to recognising large hard disk drives. In particular, the FAT16 partitions created by DOS, Windows 3.1x and Windows 95A are limited to 2.1GB so if you have a 4.3GB drive, for example, the trick is to split is into two 2.1GB partitions. Windows 95B, Windows 98 and the recently released Windows 2000 can all use FAT32 partitions and have no trouble recognising large disk drives. 17 Into the home straight – the top cover on this old PC slides on from the front . . . 20 The resurrected machine, all cleaned up and running Windows 3.11. Now where did we put that old CD-ROM drive that’s been lying around? 18 . . . and is secured using screws at the rear and along the sides. 19 The best bit! – one of our staff members nicked the EEPROMs from the old motherboard before we threw it in the bin. Best place for an old 386SX motherboard, really. power connectors were correct. Installing one of these the wrong way around is a sure-fire way of cooking the motherboard! Check also that the disk drive cables haven’t come loose and don’t forget to connect the monitor, keyboard and mouse before switching on. In our case, we had a fully working system as soon as we had configured the system BIOS. As usual, the BIOS Configuration Setup is entered by pressing the Delete key at the on-screen prompt while the system is booting up. You then select the Standard CMOS Setup option and enter the details for the hard disk drive (HDD). This can either be done manually or you can go back to the main menu and run the “IDE HDD Auto Detection” utility that’s included in the Award BIOS. You also have to set the time and date, select the types of floppy disk drives fitted and select the type of video card used (invariably EGA/VGA). The other setup utilities let you set some of the more advanced features but unless you’ve changed the processor, you can stick to the defaults. Of course, you can swap the floppy disk drives, select a different boot drive sequence or turn NumLock off if you want to. If you’ve swapped the processor then you will need to alter the BIOS setup to suit. This is clearly illustrated in the manual that comes with the Oatley motherboard. Once we’d saved the BIOS setup, the machine booted up into glorious DOS followed by Windows 3.11. But who wants to use Windows 3.11? Now if we can just add more RAM, upgrade to Windows 98, install a bigger hard disk drive, add a CD-ROM drive and . . . SC March 2000 11 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au Build the Ultra Amplifier Mod A 100W class-AB amplifier with very low distortion This new amplifier module is a refined version of our highly successful “Plastic Power” module described in April 1996. The new version is quieter and has much lower distortion, particularly at the higher frequencies. By LEO SIMPSON T HIS AMPLIFIER MODULE has been under development, on and off, since late 1998. It was in July and August 1998 that we featured the ultra-low distortion 15W class-A amplifier. Since then, that amplifier has become our benchmark. Its distortion is so low that we had to resort to new procedures to be able to measure it. Inevitably, soon after the 15W class-A amplifier had been published, we wondered about producing a high16 Silicon Chip er power version. As good as the 15W amplifier is, it is still only 15W and on many types of music, particularly opera and classical piano, it simply does not have enough power. So we thought a 100W version would be really good. However, we shrank back from the idea of producing a 100W per channel class-A amplifier. After all, the stereo version of the 15W class-A amplifier dissipates about 100 watts at all times. If we produced a 100W stereo version, it would dissipate around 600 to 700 watts at all times. In other words, it would make a good heater for small rooms. So we wondered whether, with the lessons we had learned in the development of the class-A amplifier, we could apply them to a class-AB amplifier and get similarly dramatic results. That was the hope anyway, as we set out in late 1998 to produce this new amplifier. That we are publishing the results only now is a reflection on how difficult the process has been. Is this new amplifier as good as the 15W class-A amplifier? Alas, no. As far as we can tell, using currently available semiconductors and circuit tech niques, it will never be possible to produce a class-AB amplifier as good as our 15W class-A module. However, all the development has produced an a-LD dule The final version differs slightly from this prototype module. It delivers 100W into 8Ω with very low distortion. amplifier that is a major improvement on the 125W Plastic Power module published in April 1996. This new module has much lower distortion at the higher frequencies from 5kHz to 20kHz and it is quieter although not dramatically so, since the Plastic Power module was very quiet anyway. Specifications The major performance parameters are listed in an accompanying panel but the graphs of Fig.1, Fig.2 & Fig.3 give a better picture. Fig.1 shows the frequency response at 1W into 8Ω. As you can see, it is about -0.3dB down at 20Hz and at the other end of the spectrum, about -0.5dB down at 20kHz. It would have been a relatively simple matter to make the response much flatter at the high end, say to 50kHz and beyond, AUDIO PRECISION FREQRESP AMPL(dBr) vs FREQ(Hz) 5.0000 26 JAN 100 08:27:56 4.0000 3.0000 2.0000 1.0000 0.0 -1.000 -2.000 -3.000 -4.000 -5.000 10 100 1k 10k 100k Fig.1: the frequency response at 1W into 8Ω. The response is virtually flat from 20Hz to 20kHz and tapers off above that to avoid EMI. March 2000 17 AUDIO PRECISION DIST-PWR THD+N(%) vs FREQ(Hz) 5 26 JAN 100 12:34:48 1 0.1 0.010 0.001 .0005 20 100 1k 10k 20k Fig.2: THD versus signal frequency at 100W into 8Ω, taken with a measurement bandwidth of 10Hz to 80kHz. AUDIO PRECISION SCTHD-W THD+N(%) vs measured LEVEL(W) 10 26 JAN 100 12:58:57 1 0.1 0.010 0.001 .0005 0.5 1 10 100 200 Fig.3: THD versus power at 1kHz into an 8Ω load, taken with a measurement bandwidth of 10Hz to 22kHz. as some commercial amplifiers do, but we regard that practice as undesirable. Not only is it likely to render the amplifier more suscep tible to EMI (electromagnetic interference) but it also means that it will amplify extraneous residual high frequency signals such as 38kHz from FM tuners and over-sampling artefacts from CD players. Amplifying these extraneous 18 Silicon Chip signals might not be a problem to the amplifier itself but they might then cause audible beats with the harmonic distortion products of the higher frequency audio signals. For example, a 38kHz FM multiplex signal (usually about 60dB down) could beat with the 32kHz second harmonic of a legitimate audio signal. The 6kHz beat would certainly be audible although it might be at a very low level. Most of the time such residual signals would not cause any audible problems but our philosophy is “Why ask for trouble?” and so we roll off the frequency response above 20kHz, as shown in Fig.1. The graphs of Fig.2 & Fig.3 tell the real performance story of this new amplifier. Fig.2 shows the harmonic distortion versus signal frequency at virtually full power, 100W into 8Ω. As may be seen, for all frequencies below 2kHz, the THD (total harmonic distortion & noise) is .002% or below. But from 2kHz to 20kHz, the distortion rises very gently, to .006%. These figures are taken with a measurement bandwidth of 10Hz to 80kHz. These are really excellent figures for any class-AB ampli fier and especially when compared to the vast majority of domestic hifi amplifiers which may be comfortably below, say, .005% distortion for the mid-frequencies but then rocket up to around 0.1% or more at 20kHz and full power. Even our popular Plastic Power module referred to earlier had a THD approaching .03% at 20kHz, so this new amplifier is up to five times better at high frequencies! Fig.3 shows the distortion versus power at 1kHz into an 8Ω load. This time the measurement is made with a bandwidth of 10Hz to 22kHz, to limit the noise content, and this shows the amplifier comfortably under .002% from 20W to 100W and rising gradually at the lower powers, solely due to the increased residual noise content. Finally, this amplifier is extremely quiet, at -117dB unweighted with respect to 100W and -123dB A-weighted under the same conditions. This is a great deal quieter than any CD player and much quieter than the vast majority of domestic hifi amplifiers, regardless of price. By the way, we have made no mention of power output into 4Ω loads and in fact, we do not recommend operation with 4Ω loads. This is not to say that the amplifier could not drive 4Ω loads but there are two specific reasons for not recommending it. First, the distortion will be approximately double that achieved for 8Ω loads and in this respect it won’t be much better than the Plastic Power module. Second, the output transistors are connected as current feedback pairs Fig.4: the circuit can be regarded as a conventional direct-coupled feedback amplifier with compound current feedback transistor triples in the output stage. The input and class-A driver stages are fed with regulated supply rails. and there is no intrinsic method of ensuring even current sharing between each transistor. This is not a problem with the lower currents delivered to 8Ω (or 6Ω) loads but could be a problem with 4Ω loads. A similar recommendation applied to our 15W class-A amplifier design. While it would certainly drive 4Ω loads, it would not do it in class-A mode and therefore the distortion would be considerably higher. In any case, the vast majority of hifi loudspeakers are 8Ω or 6Ω nominal. The module As can be seen from the photos, the amplifier module is assembled onto a PC board measuring 176 x 105mm. The four plastic output power transistors and three smaller power transistors are aligned along one edge to make it easy to attach them to a relatively large single-sided heatsink. The PC board has two on-board supply fuses and provision for temporary mounting of two 5W wirewound resistors which are used for setting the quiescent current. Circuit details The circuit of the amplifier module itself is shown in Fig.4 but that is not all there is to it. Fig.5 is the circuit of the power supply and that is one of the major factors in obtaining the performance of the amplifier. Compared with the Plastic Power module of April 1996, the major circuit differences of this new module are as follows: (1) Uses Motorola MJL3281A and MJL1302A output transistors which have improved linearity compared to the MJL21193/94 transistors. (2) Uses Motorola MJE15030 and MJE15031 driver transistors which have improved linearity, gain-bandwidth product and higher gain than the previously used MJE340/350 transistors. (3) Improved constant current source for the input differential pair and driver stages. (4) Use of current feedback output stages for improved linearity compared to conventional complementary symmetry emitter follower output stages. (5) Use of regulated power supply rails for the input and driver stages of the amplifier to obtain increased power supply rejection ratio (PSRR). March 2000 19 Parts List AMPLIFIER BOARD 1 PC board, code 01103001, 105mm x 176mm 4 2AG fuse clips 2 2AG 5A fuses 1 coil former, 24mm OD x 13.7mm ID x 12.8mm long, Philips 4322 021 30362 2 metres 0.8mm diameter enamelled copper wire 11 PC board pins 1 large single-sided fan heatsink (Altronics H-0526; Jaycar HH-8546 or equivalent) 2 TO-126 heatsinks, Altronics Cat. H-0504 or equivalent 4 TO-3P insulating washers (for output transistors – see text) 3 TO-126 insulating washers 4 3mm x 20mm screws 3 3mm x 15mm screws 7 3mm nuts 1 200Ω multi-turn trimpot Bourns 3296W series (VR1) Semiconductors 2 MJL1302A PNP power transistors (Q13, Q14) 2 MJL3281A NPN power transistors (Q15, Q16) 1 MJE15030 NPN driver transistor (Q11) 1 MJE15031 PNP driver transistor (Q12) 1 MJE340 NPN power transistor (Q10) 1 BF469 NPN transistor (Q8) 1 BF470 PNP transistor (Q9) 3 BC546 NPN transistors (Q5, Q6, Q7) 4 BC556 PNP transistors (Q1, Q2, Q3, Q4) 1 3.3V 0.5W zener diode (ZD1) Capacitors 2 1000µF 63VW electrolytic 2 100µF 63VW electrolytic 1 100µF 16VW electrolytic 1 2.2µF 25VW electrolytic 1 0.15µF 400VW MKC, Philips 2222 344 51154 or Wima MKC 4 In most other respects, the circuit of the new module is virtually identical in configuration (but not component 20 Silicon Chip 5 0.1µF 63V MKT polyester 1 .0012 63MKT polyester 1 100pF 100V ceramic Resistors (0.25W, 1%) 2 220Ω 5W (for current setting) 1 12kΩ 1W 1 1kΩ 1 8.2kΩ 1W 1 390Ω 1 6.8Ω 1W 1 330Ω 8 1.5Ω 1W 2 150Ω 2 18kΩ 3 120Ω 1 3.3kΩ 4 100Ω 1 1.2kΩ 2 47Ω POWER SUPPLY 1 160VA or 300VA toroidal transformer with 2 x 35V 2.25A secondaries and 2 x 50V 0.1A secondaries 1 DPDT 5A 250VAC switch (S1) 1 3AG fuseholder 1 3A 3AG fuse 1 PC board, code 01103002, 61 x 92mm 6 PC pins 2 2kΩ multi-turn trimpots Bourns 3296W series (VR2,VR3) Semiconductors 2 TIP33B NPN power transistors (Q17, Q18) 1 LM317 adjustable positive 3-terminal regulator (REG1) 1 LM337 adjustable negative 3-terminal regulator (REG2) 1 PA40 bridge rectifier (BR1) 1 BR610 bridge rectifier (BR2) 2 1N4004 silicon diodes (D1,D2) 2 33V 5W zener diodes (ZD2, ZD3) Capacitors 4 8000µF 63VW chassis mounting electrolytics 2 470µF 100VW electrolytics 2 100µF 63VW electrolytics Resistors 2 6.8kΩ 0.25W 2 180Ω 0.25W 2 47Ω 0.25W 6 15Ω 1W values) to the Plastic Power module. However, for the sake of complete ness, we will now give the full circuit description. In all, the circuit uses 16 transistors and one zener diode, plus those semiconductors used in the power supply. The input signal is coupled via a 2.2µF capacitor and 1kΩ resistor to the base of Q1 which together with Q2 makes up a differential pair. Q3 & Q4 act as a constant current tail to set the current through Q1 & Q2 and thereby makes the amplifier insensitive to variations in the power supply rails. Current mirror The collector loads of Q1 & Q2 are provided by current mirror transistors Q5 & Q6. Commonly used in operational amplifi er ICs, current mirrors provide increased gain and improved linearity in differential amplifier stages. In a conventional direct-coupled amplifier, the signal from the collector of Q1 would be connected directly to the base of the following class-A driver stage transistor. In our circuit though, the signal from the collector of Q1 connects to the base of Q7, part of a cascode stage comprising Q7 & Q8, with Q9 pro viding a constant current load to Q8. Q4 does double-duty, providing the base voltage reference for constant current sources Q3 & Q9. In fact, the operation of the Q3/Q4 current source is a lot more complicated than it appears to be at first sight but let’s just simplify matters by saying that it is an improvement on the constant current tail used in the Plastic Power module. A 3.3V zener diode, ZD1, provides the reference bias to the base of Q8. In effect, Q8 acts like an emitter follower and applies a constant voltage (+2.7V) to the collector of Q7 and this im proves its linearity. The output signal from the cascode appears at the collector of Q8. A 100pF capacitor from the collector of Q8 to the base of Q7 rolls off the open-loop gain of the amplifier to ensure a good margin of stability. The output signal from the cascode stage is coupled directly to the output stage, comprising driver transistors Q11 & Q12 and the four output transistors, Q13-Q16. Actually, it may look as though the collector of Q9 drives Q11 and that Q8 drives Q12, and indeed they do, but in reality, the signals to the bases of Q11 and Q12 are identical, apart from the DC voltage offset provided by Q10. Vbe multiplier Q10 is a “Vbe multiplier”. It can be thought of as a tem p eraturecompensated floating voltage source of about 1V. Q10 “multiplies” the voltage between its base and emitter, as set by trimpot VR1, by the ratio of the total resistance between its collector and emitter (330Ω + 390Ω + VR1) to the resistance between its base and emitter (390Ω + VR1). In a typical setting, if VR1 is 100Ω (note: VR1 is wired as a variable resistor), the voltage between collector and emitter will be: Vce = Vbe x 820/490 = (0.6 x 820)/490 = 1.004V In practice, VR1 is adjusted not to produce a particular voltage across Q10 but to set the quiescent current through the output stage transistors. By the way, because we’re using a different output stage in this new amplifier module, the Vbe multiplier is set up differently to that in the Plastic Module where it was set to produce about 2V instead of 1V. Because Q10 is mounted on the same heatsink as the driver and output transistors, its temperature is much the same as the output devices. This means that its base-emitter voltage drops as the temperature of the output devices rises and so it throttles back the quiescent current if the devices become very hot, and vice versa. Driver & output stages Q11 & Q12 are the driver stages and they, like the output transistors, operate in class-AB mode (ie, class B with a small quiescent current). Resistors of 100Ω are connected in series with the bases of these transistors as “stoppers” and they reduce any tendency of the output stages to oscillate supersonically. As already mentioned, the output stages are connected as compound current feedback transistors. These are a development from the current feedback pair (CFB) configuration used in our class-A amplifier. However, that circuit used just one output transistor coupled to each driver transistor, with the emitter of the driver transistor connected to the collector of the output transistor. This config- This view shows the prototype amplifier module with the two outboard wirewound resistors in place for setting the quiescent current. Note that the paralleled 1.5Ω resistors will be laid out side-by-side in the final version of the PC board. The RCA input socket was for testing purposes only. uration acts like a very linear power transistor with only one base-emitter junction rather than two, as in a Darlington-connected power transistor. In this circuit, we have two paralleled power transistors, Q13 & Q14, connected to NPN driver transistor Q11 and Q15 & Q16 are connected to PNP driver transistor Q12. The four paralleled 1.5Ω emitter resistors for each com pound CFB transistor are there to help to stabilise the quiescent current and they also slightly improve the frequency response of the output stage by adding local current feedback. As already noted though, there is no intrinsic means in the circuit for ensuring even current sharing between Q13 & Q14 and between Q15 & Q16. What current sharing there is will depend on the inherent matching (or lack of it) between the transistors. Note that we did try the effect of small emitter resistors for each of the power transistors but these had the effect of worsening the distortion performance. So we left them out. Note that the current and power ratings of the output transistors are such that even if the current sharing is quite poor, there should not be a problem. Negative feedback is applied from the output stage back to the base of Performance Output power �� 100 watts into 8Ω Frequency response �� -0.3dB down at 20Hz; -0.5dB at 20kHz (see Fig.1) Input sensitivity �� 1.8V RMS (for full power into 8Ω) Harmonic distortion �� <.006% from 20Hz to 20kHz, typically <.002% Signal-to-noise ratio �� 117dB unweighted (20Hz to 20kHz); 123dB A-weighted Damping factor �� >170 at 100Hz & 1kHz; >60 at 10kHz Stability �� Unconditional March 2000 21 Fig.5: the circuit of the power supply. There are two sets of supply rails. The unregulated ±52.5V rails feed the class-AB output stages and nothing else. The fully regulated ±55V rails feed the class-A driver and input stages of the amplifier. Q2 via an 18kΩ resistor. The amount of feedback and therefore the gain, is set by the ratio of the 18kΩ resistor to the 1.2kΩ resistor at the base of Q2. Thus the gain is 16. This means that an input signal of just over 1.8V RMS is required for full power and this is less than -1dB with respect to the 2V maximum signal from a CD player. Thus under music conditions, the full signal from a CD player should not overload this amplifier. This approach is deliberate because we intend presenting a pair of these modules as a stereo amplifier, driven directly by a CD player for optimum sound reproduction. The low frequency rolloff of the 22 Silicon Chip amplifier is partly set by the ratio of the 1.2kΩ resistor to the impedance of the associated 100µF capacitor. This has a -3dB point of about 1.3Hz. The 2.2µF input capacitor and 18kΩ base bias resistor feeding Q1 have a more important effect and have a -3dB point at about 4Hz. The two time-constants combined give an overall rolloff of -3dB at about 5Hz. At the high frequency end, the .0012µF capacitor and the 1kΩ resistor feeding the base of Q1 form a low pass filter which rolls off frequencies above 130kHz (-3dB). An output RLC filter comprising a 6.8µH choke, a 6.8Ω resistor and a 0.15µF capacitor couples the output signal of the amplifier to the loud- speaker. It isolates the amplifier from any large capacitive reactances in the load and thus ensures stability. It also helps attenuate EMI (electromagnetic interference) signals picked up by the loudspeaker leads and stops them being fed back to the early stages of the amplifier where they could cause RF breakthrough. The low pass filter at the input is also there to prevent RF signal breakthrough. Finally, before leaving the circuit description, we should note that the PC board itself is an integral part of the circuit and is a major factor in the overall performance. The board features star earthing, for minimum interaction between signal, supply and output currents. Note that the small signal components are clustered at the front of the board while all the heavy current stuff is mostly at the back and sides. Note also that the class-B current pulses from the two halves of the output stage are added symmetrically (adjacent to Q9) before being fed to the output RLC stage. The configuration of the output stage copper tracks is also very important because the magnetic fields associated with their asymmetrical currents are partially cancelled by the lead dress of the cables from the power supply. In fact, the arrangement of the power supply cabling to the module is quite crucial in obtain the low distortion figures, particularly at high frequencies. Power supply Fig.5 shows the circuit of the power supply. There are two sets of supply rails. The unregulated ±52.5V rails feed the class-AB output stages and nothing else. The fully regulated ±55V rails feed the class-A driver and input stages of the amplifier. Why have we gone to this trouble when just about every commercial domestic stereo amplifier uses unregulated supply rails for the whole power amplifier circuit? The reasons are twofold. First, when we designed the 15W class-A amplifier we found that we had to resort to fully regulated supply rails in order to get the residual hum to a reason ably low value. This was critical in the class-A amplifier be cause the constant high power supply current means a high ripple voltage which the amplifier circuit cannot fully reject. With a class-AB amplifier such as this, the quiescent load currents are quite low and therefore hum is not a problem but the very high asymmetrical signal currents (equivalent to half-wave rectified signal) are an even bigger problem because they cause a distorted signal voltage to be superimposed on the amplifier supply rails. By using a fully regulated supply, we avoid the possibility of these signals being fed back into the input stages. Furthermore, in a stereo version, the fully regulated supply also improves the separation between channels. Looking now at the circuit for the power supply, it is effectively split This power supply module provides the fully regulated ±55V rails for the class-A driver and input stages. The power transistors provide over-voltage protection to the regulators at switch-on. into two parts. The two 35V windings are connected together to drive bridge rectifier BR1 and the four 8000µF 63VW electroly t ic capacitors and this gives an unregulated supply of around ±52.5V (at no signal) to power the output stages of the amplifier. The 50V windings on the transformer drive the second bridge rectifier BR2 and this gives unregulated supplies of about ±72V and these are fed to the regulator circuits to provide ±55V to the input and class-A driver stages of the amplifier, as noted above. It’s not what it seems However, the regulator circuit is not quite what it seems. At first sight it may appear like a conventional 3-terminal regulator plus booster transistor arrangement, with the power transistor being slaved to the regulator. But that’s not how this circuit works. In fact, you will notice that we have used an NPN power transistor in conjunction with both regulators while you would expect a PNP transistor to be used with the negative regulator. So what is going on? Looking at the positive regulator for the moment, REG1 carries all the current, around 20mA for a mono version of this amplifier or 40mA for a stereo version. So there is no need for a booster transistor or even a heatsink. But the 3-terminal regulator cannot do the whole job. Its input voltage is about 72V and when the power is first applied to the circuit this would appear directly across the regulator, causing it to blow. Its maximum input-output differential is only 40V. This is where the power transistor comes into play. When the voltage across REG1 exceeds 33V, zener diode ZD2 will be biased on via the associated 47Ω resistor. This causes Q17 to turn on and it limits the voltage to around 35V or so. The current through Q17 is limited to around 6.5A peak by the three paralleled 15Ω resistors in the emitter circuit. This peak current is very brief and occurs only while the 100µF capacitor at the output of REG1 is charged up to around 40V. From there on, the LM317 takes over and Q17 switches off. The same process occurs for the negative regulator REG2 and the NPN transistor Q18 takes care of the charging current for its associated 220µF output capacitor. The power transformer for a mono version of this amplifier can have a rating of 160VA or more while a stereo version will require a 300VA unit. In the next article, we will discuss the power supply and the construction of a stereo version of the amplifier in detail. SC March 2000 23 INSIDE AN ELECTRONIC WASHING MACHINE: There’s much more than washing! These days there is barely a device plugged into mains power that isn’t chockablock full of electronics. There are PC boards inside TVs, VCRs, computers, clock radios, telephones, sound systems, washing machines… By Julian Edgar Washing machines?! Surely not! Yes, if you have bought a new washing machine in the last few years it will probably have a digital display and pushbuttons. But isn’t that just for the sake of cosmetics? Isn’t the control system inside as it always has been? The answer is a definite ‘no’. The old way In the good ol’ days, the “brain” of every automatic washing machine was its timer – an electro-mechanical Fig.1: a typical modern washing machine control system, where the electromechanical timer of previous models has been replaced by the electronic control system. 24 Silicon Chip device powered by a tiny electric motor. The timer motor turned a series of gears that in turn moved cams to activate switches. The switches controlled the various functions – wash, spin and rinse, and so on. While there was some control over the length of each stage, generally the sequence and duration of each event was fixed. A pressure switch sensed the level of water within the bowl. A very sensitive device with a large diaphragm, the pressure switch connected to a chamber whose air pressure changed as the washbowl filled. The ‘water level’ control simply placed a variable mechanical preload on the switch. The temperature dial was also mechanical in action, controlling the position of a water mixing valve. Other controls included a power on/off switch, lid switch (preventing operation of the machine with the lid up) and an out-of-balance switch that stopped a spin cycle if the washbowl began to rock too badly. Mechanically, the washing machine consisted of a stainless or vitreous enamel coated steel perforated drum, an agitator (a finned device rising from the floor of the drum), an electric motor (either a universal or brushless induction design) and a gearbox. The main function of the latter was to convert the rotary motion of the motor shaft into the back-and-forth motion of the agitator. It also allowed the washbowl to spin at high speed, to remove excess water from the clothes. So that was then – how about now? Component Layout Many modern washing machines run to full microcontrollers, error messages, self diagnosis, timed starts and other sophisticated features! Fig.1 shows a block diagram of a current Simpson washing machine. The range of Simpson washing machines is designed and manufactured in Australia by the Email Washing Products Group. Kym Mahlo, Appliance Controls Design Engineer for washing machines, was kind enough to give us an extensive tour of both the R&D lab and the insides of his favourite Simpson models. Electro-mechanical machines are still the majority of Email’s manufacturing base (approximately 80% electromechanical, 20% fully electronic). However, even the electro-mechanical machines contain an electronic Agitation Controller which controls the agitation and spin processes. The electric motor used in the Simpson machines is a 1500 RPM, induction design manufactured inhouse. It is connected via belt and pulleys to a gearbox that slows its speed for agitation and also allows the agitator and the washbowl to be locked together for the high-speed spin cycle (ie, bypassing the gearbox). The motor can be run in either direction, depending on how the windings are energised. During agitation, the motor typically runs 0.8 seconds forward, 0.5 seconds off, 0.8 seconds reverse, 0.5 seconds off, 0.8 seconds forward, and so on. The agitator rotates at 100 RPM. However, the Simpson machines have 40 In this photo taken from directly underneath the washbowl, the induction motor is at the top, driving the different “agitator gearbox through a reduction belt drive. The brake motor profiles” stored in is at bottom right. the microcontroller memory, so The motor speed is varied through its this sequence and speed is variable. current supply being pulsed on and During a spin cycle, the washbowl is off. For example, when the required rotated at up to 800 RPM; woollens speed is a nominal 400 RPM, the are spun at 400 RPM and delicates power to the motor is switched off at 600 RPM. until the speed drops to 300 RPM. The speed of the motor is moni- This means that the actual speed of tored by a Hall Effect sensor, working the motor varies within a 100 RPM in conjunction with an 8-pole ring band. This approach to motor speed magnet mounted on the motor shaft. control is taken because it achieves (Right): A cutaway view of a Simpson model a few years old shows the general layout of parts. The motor and gearbox are at the base, with the perforated stainless steel washbowl above. Behind the control panel is the PC board for the con trol system. (Below): At the bottom left is the induction motor, with the gearbox to its right. The main shaft (supported on hefty roller bearings) rises vertically, ending inside the base of the agitator. The brake motor is just to the right of the gearbox. March 2000 25 (Right): The front side of the PC board in a first generation Simpson design. Directly below the PC board are (from far left) an inductor-type pressure sensor, the hot and cold water solenoids, and the motor run capacitor. (Below): The exposed side of the PC board is covered in a bright orange “conformal” coating, designed to repel water. Much of the PC board is at 240VAC potential. diverter valve is also used during the water save function, directing water into the laundry trough rather than into the waste water system. Incidentally, the diverter valve is a slow-acting device that relies on the melting of a wax pellet to move its internals. The hot and cold water valves are 240VAC solenoid actuated, controlled by Triacs. Directly switching the 240VAC is cheaper than taking other approaches. However, it does mean that you shouldn’t lift off the covers and go fishing around behind the washing machine control the lowest energy consumption. As with each of the panel with the power on . . . eight electronic control system outputs, Triacs are used The final output of the control system is the brake moto perform this motor switching function. tor, used to slow the washbowl at the end of the spinning The pump (out) and pump (in) are respectively used cycle. It consists of a small induction motor and gearbox, for emptying and filling the washbowl. The filling pump to which a stainless steel wire is attached. When switched is used only when the “water save” function is activated. on, the wire is gradually pulled out of the gearbox casing, This is where either the sudsy wash water or non sudsy causing a pawl to engage the brake band. deep rinse water is stored in a laundry trough and pumped The lid microswitch has two purposes: it goes open back into the machine for the next washing load. Normally, circuit when the lid is lifted, to stop the machine when mains water pressure is used to fill the washbowl. The the lid is raised; it also functions as an out-of-balance shut-off, being reset when the lid is opened. The cost-saving Fig.2: the various inputs and outputs effected by using the switch for to the microcontroller. Compared to both purposes is important: older models, virtually all functions again and again Kym Mahlo are now variable. stressed that even a saving of a few cents was vital in this very competitive market. Two of the input sensors can also be seen in Fig.1. As with old machines, the level of water within the washbowl is sensed by air pressure but instead of a switch, a Motorola solid state sensor is used. It has a 0-5V output and is calibrated over the range of 0-400mm of water. The use of an analog sensor rather than the old on/off switch allows the micro to sense the speed with which the washbowl is being filled, in addition to the 26 Silicon Chip The brake motor slows the washbowl at the end of the spinning cycle. It consists of a small induction motor and gearbox, to which a stainless steel wire is attached. When switched on, the wire is gradually pulled out of the gearbox casing, causing a pawl to engage the brake band. water level itself. In fact, another approach was used in the model prior to this machine. That design used a sensor whose inductance varied with pressure. The sensor was used to change the frequency of an oscillating circuit, with the frequency then being roughly proportional to the water level. Temperature sensing is carried out with an LM335 solid state sensor which is embedded in a mixing chamber through which the water passes before entering the bowl. The Microcontroller Two different micros have been used in the Simpson washing machines, an SGS Thomson ST9 or a Toshiba TMP870. Both of these controllers are designed for appliance appliFig.3: an excerpt from cations. Both have interrupt inputs, allowing part of the software logic. synchronisation of the microcontroller (and The software is written in so Triac operations) with the mains. These C and the microconcontrollers use an 8MHz external oscillator, troller program length have analog and digital inputs and digital varies from 5 to 30KB, outputs for driving the LEDs and Triacs via depending on the higher current buffers or transistors. “A micromachine in which the controller is a one chip solution” said Kym, control system is being “It’s the most appropriate technology at the used. lowest cost.” A large inductor is fitted to the PC board at the motor drive outputs, to protect the motor drive Triacs fail to switch off, resulting in a flood! It can be seen that against noise which could cause the micro to turn both the prevention of noise from disrupting the micro is very the forward and reverse Triacs on together. In fact in the important. A 5VA 5V power supply is used to supply the microconarea of EMC, Kym commented that it was the immunity of the washing machine control system from external troller, sensors and their signal conditioners and the LEDs. noise - rather than preventing the emission of EMI - that A buzzer is also mounted on the PC board, giving audible indication that the buttons have been pressed, signalling was the more important design requirement. Another potential disaster is where the water solenoids the end of the washing cycle, and also indicating errors. March 2000 27 A test bench system is used to debug the software. It consists of a modified washing machine control panel, EPROM emulator and PC. The potentiometer inputs for water level and motor speed can be seen, along with the toggle switch that simulates the operation of the lid microswitch. The LED display is able to indicate more than 16 codes, displaying cycle times, machine status (eg ‘SP’ - start/ pause) and error codes (eg ‘PU’ – drain hose blocked). All fault codes are stored in an EEPROM that – depending on which of the micros is being used – is either internal or external to the microcontroller. In addition to storing error codes, the EEPROM is also used to store the information for the user’s “favourite wash” program. This can be set by the user to provide their favourite cycle, load and water temp parameters. Another feature possible is delayed start, where the washing machine can be programmed to start its operation after up to 23 hours. Finally, the EEPROM is used to configure the control system to the washing machine model in which it is being used. Fig.2 shows the inputs and outputs to the microcontroller. The PC board tracks are entirely covered with a bright orange “conformal” coating which repels water. This is applied so that water cannot come in contact with the board, much of which is working at 240VAC potential. Part of the Email test sequence is to pour a bucket of water over the top of the working machine, a behaviour apparently not unknown in customers… In fact, in the R&D lab, a number of washing machines are set up to allow wet testing. Monitoring equipment displays factors such as the ‘on’ and ‘off’ time of the agitator, hot and cold water flows, and the temperature of the hot water, cold water or washbowl water. The software writing and debugging is carried out entirely in-house. 28 Silicon Chip Written in C, the microcontroller program length varies from 5 to 30KB, depending on the machine in which the control system is being used. Fig.3 is an excerpt from part of the software logic. Laying out the complete program in this way would require literally hundreds of pages, Kym suggested. For example, he made the point that the second box in Fig.3 (“Turn hot and cold on in a ratio according to temperature selection”) is a very simplistic representation. This process in fact uses the feedback from both the temperature and pressure sensors to modify the ‘on’ times of each of the solenoids to achieve the required water temperature. The monitoring gear measures and displays factors such as the ‘on’ and ‘off’ time of the agitator, hot and cold water flows and water temperatures. In order that the program can be debugged and the effect of software changes easily studied, a control system test bed is used. This consists of a microcontroller emulator working in conjunction with a PC. It is connected to a modified washing machine control panel that incorporates the normal LEDs, electronic control board and buttons. In addition, other LEDs have been fitted to indicate the status of each of the outputs. Potentiometers are used to simulate the input of water level and motor speed, while a toggle switch replaces the lid microswitch. So as you can see, electronics is making major inroads into all consumer goods – even the humble SC washing machine! A wet washing machine test area is set up in the Email R&D lab. It allows the testing of a wide variety of parameters, from washing efficacy to the temperature and flows of the water. And yes, there was a basket of washing just out of the shot! 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 Prototyping and testing complicated electronic circuits can be time consuming. This versatile package lets you throw away the hardware and design and test on a computer screen. REVIEWED BY PETER SMITH Multisim: for advanced circuit design & simulation O PEN ALMOST any piece of electronic equipment these days and chances are you’ll see just one or two ICs, often with hundreds of pins and only a handful of discrete components. Usually, the components are so small it’s difficult if not impossible to identify exactly what they are (resistor, capacitor, inductor, or what?). It’s easy to imagine the control and precision needed to assemble these miniature PC boards. What about the design of the ICs themselves though – how the heck do they design, prototype and test the circuits inside a 300-pin “mega-chip”? And how do they make sure the ICs will work in a real circuit before committing them to manufacture? Computer software, of course, is the big answer. Ingenious software developers have been able to create virtual development environments which allow the entire design and test phase to be carried out without a piece of hardware in sight. Bringing the design elements together in this way has less obvious advantages, too. For example, hardware engineers can work at a level of abstraction above the underlying logic elements, greatly increasing design speed. In this review, we look at Multisim V6 from Electronics Workbench, a collection of state-of-the-art circuit design and simulation tools. Multisim includes all the tools necessary to take a design from inception to finished project and as such, a detailed review would have to cover an enormous amount of ground. We cannot hope to do justice to all aspects of the product in this short review, so we’ve settled on describing some of the main features instead. Schematic capture Designs are drawn in a familiar Windows environment using the Schematic Capture module. As with all other schematic capture programs, Multisim has a database of the most commonly used components (more than 16,000 in the Power-Pro edition) that can be placed and wired immediately. However, Multisim’s database is perhaps unique in that every component has a simulation model attached to it (we look at simulation a little further on). If a part that you want isn’t in the database, Multisim includes a Symbol Editor that allows you to create your own, either from scratch or based on March 2000 33 Truscott’s • RESELLER FOR MAJOR KIT RETAILERS • PROTOTYPING EQUIPMENT • COMPLETE CB RADIO SUPPLY HOUSE • TV ANTENNA ON SPECIAL (DIGITAL READY) • LARGE RANGE OF ELECTRONIC COMPONENTS Professional Mail Order Service Truscott’s Come And See In ur New StoO re ELECTRONIC WORLD Pty Ltd ACN 069 935 397 Ph (03) 9723 3860 Fax (03) 9725 9443 27 The Mall, South Croydon, Vic 3136 (Melway Map 50 G7) email: truscott<at>acepia.net.au www.electronicworld.aus.as 34 Silicon Chip Fig.1: schematic entry and editing is a straightforward process. Fonts, colours and label positions can easily be changed for a more professional look. an existing component (or “symbol”). Wiring between components is a simple matter of clicking on the start and end points and Multisim makes the connection automatically. Manual control is possible too, of course. Once wires and components are placed, they can be moved by clicking and dragging. Multisim includes a multi-level undo feature but it performs more like an “undelete” than an “undo”. This means, for example, that deleted symbols and wires can be restored but operations like wire and component movement cannot be undone. Each node in the circuit is automatically assigned a unique node number during the wiring process. Using a feature called Virtual Wiring (“virtual” because no actual interconnections are shown), it is possible to connect nodes together by manually assigning the same node numbers. Typically, the supply rails in a circuit are connected in this way, resulting in less clutter and more readability. Readability is also one of the aims of Multisim’s subcircuit feature. A section or entire page of an existing circuit can be defined as a subcircuit and then used within another circuit. An optional add-on module expands the functionality of subcircuits even further, allowing them to be saved and edited just like any other schematic file. Completed schematics can be exported in variety of formats to suit all Fig.2: if a symbol is not in the database, it can be created from scratch or an existing symbol can be modified using the Symbol Editor. Fig.3: to access simulation model information, it’s just a matter of right-clicking on the component and choosing properties. Models can be created or imported from the model tab. Fig.4: using Model Makers to create a simulation model from the manufacturer’s data sheets. In this example, we have chosen to make a BJT (Bipolar Junction Transis tor) model. Model Makers supports many other model “classes”, including diodes, MOSFETs, SCRs, op amps, strip lines, waveguides, etc. major PCB layout software packages. However, the transition to PCB layout is much smoother when using the Electronics Workbench product – Ultiboard. This is because Ultiboard recognises information from Multisim like component footprints and minimum track widths (gleaned during simulation) without modification. Types of simulation As we mentioned earlier, simulation provides a means of examining circuit behaviour without having to physical- Fig.5: view from the drivers seat – the virtual oscilloscope. Fig.6: this spectrum analyser costs a lot less than its real world equivalent! ly construct it. Before we look at how a simulation is performed in Multisim, let’s touch briefly on the technologies involved. Multisim supports three different simulation technologies – SPICE, VHDL and Verilog. SPICE is an analog circuit simulator, the core (or kernel) of which has become an industry standard since its release to the public domain in 1972. A number of companies offer SPICE simulators that expand on the functionality and feature set of the original release. A notable example is XSPICE, which provides extensions for digital logic simulation. Multisim includes support for all of the most popular SPICE extensions. SPICE, by the way, is an acronym for Simulation Program with Integrated Circuit Emphasis! VHDL and Verilog are hardware description languages (HDLs) that are used to both document and design electronic systems. VHDL was born out of a US Defence Department contract and since its release in 1985, has been standardised by the IEEE (Institute of Electrical and Electronics Engineers). Verilog started life as a proprietary hardware modelling language and in 1990, it too was released to the public domain and standardised by the IEEE. VHDL and Verilog provide a means of designing and simulating complex digital logic, especially Complex Programmable Logic Devices (CPLDs) and Field Programmable Gate Arrays (FPGAs). Devices like our imaginary 300-pin “mega-chip” are designed using these languages. It is important to note that VHDL and Verilog are behavioural level languages. They describe what a circuit’s inputs and outputs are, what functions are performed in the middle and how long it all takes to happen. By contrast, when talking about digital logic, SPICE could be described as a transistor/gate level language. Multisim provides simulation engines for all three of these standards and what’s more, they can work together to co-simulate an entire mixed mode analog and digital circuit at the board level. This is a big advance, as separate simulators (often from different companies) were previously needed to simulate mixed mode circuits – and they rarely talked to one another! More about models We mentioned that all components in the database are associated with a simulation model. Simply put, these models “tell” the simulator how com- Fig.7: the logic analyser is another of Multisim’s virtual instruments. Setting up triggers couldn’t be simpler. Fig.8: signal sources are configured from their properties page. Here we set the amplitude and frequency of an AC voltage source. March 2000 35 Fig.9: in this screen shot, we have a virtual potentiometer (VR1) in circuit. The properties page shows that it is increased and decreased with the “a” and “A” keys, with each keystroke varying the value by 5%. ponents work. Multisim supports SPICE, VHDL, and Verilog models. In addition, where a ready-defined model isn’t available, Multisim provides a feature called Model Makers. This feature allows you to build an accurate simulation model (analog or digital) directly from the manufacturer’s data sheets. And if that’s not enough, circuits can be modelled at behavioural level using the C programming language – Multisim calls this Code Modelling. Whew! So, a simulator “knows” about com- ponents in a circuit by interpreting their respective models. But how do we “see” what the simulator is doing? Simulation in action To examine the operation of a prototype circuit we have constructed, we would apply appropriate stimulus to the input and view the results at the output. In a Multisim simulation, we do exactly the same thing, except that all our instruments are “virtual”. Multisim includes a whole host of virtual instruments that function Fig.10: the Bode plotter output from a high pass filter as displayed by the Analysis Grapher. With the aid of moveable cursors, we can see that the cutoff frequency is around 67Hz. Control over any of the available analyses and the way results are finally displayed is entirely customisable. 36 Silicon Chip just like their real-world counterparts. These include an oscilloscope, spectrum analyser, logic analyser, wattmeter, distortion analyser, network analyser, Bode plotter, function generator, word generator and of course a multimeter. Forget hunting for those missing test leads – simply drop your virtual instrument of choice onto the schematic and wire it in! Double-clicking on the instrument icon brings up its display and control panel, with mouse-activated knobs and switches. In addition to the function generator and word generator instruments, Multisim provides other means of applying stimulus to your circuits. A whole class of components called “sources” generate AC and DC currents and voltages, as well as clocks, pulses, one-shots, etc. Specialist AM and FM modulated sources for radio frequency design are also included. The parameters for each source (such as amplitude, frequency, etc) are individually controllable via their property pages. Well, this probably all sounds just too complex if you are a beginner to electronics. Connecting a logic analyser to a 2-chip counter circuit may seem like overkill but Multisim has the bases covered here, too. A class of components called “indicators” provides a voltmeter, ammeter, logic probe, hex display, lamp and bargraph, all of which operate like their real-world cousins. For example, the buzzer sounds the PC speaker and the hex display segments “light up” in line with their logic inputs. While simulating the high-power audio amplifier circuit published this month, I unexpectedly discovered that Multisim’s fuses actually go open-circuit when their rating is exceeded. As far as I know, Multisim doesn’t include sound effects or burning smells (I don’t miss them)! Virtual components With the circuit complete and instruments and sources connected and configured, it’s then just a matter of hitting the simulate switch to start the simulation running. One of the features I really like here is the ability to change component values in the circuit without even having to stop the simulation. This is achieved by temporarily substituting Fig.11: the Postprocessor can act on results from an analysis using a variety of mathematical operations. The results can then be displayed as a graph or table, or simply exported to Excel or Mathcad. any components you would like to vary with their “virtual” equivalents. Virtual components (resistors, capacitors and inductors) can be increased or decreased in value in real time by hitting certain keys on your keyboard – you decide which. Naturally, the property pages for virtual components allow setting things like initial value, percentage change with each keystroke, etc. Circuit analysis We’ve talked about how Multisim’s circuit simulator can display real-time results on virtual instruments but it is capable of far more. Using the SPICE simulation engine, many different types of analyses can be performed. These include DC operating point, transient, AC frequency sweep, Four ier analysis and noise and distortion, to name a few. The results from these analyses are automatically graphed and can be exported to other applications such as Excel or Mathcad. Analyses results can be handed to the Postprocessor module, which performs mathematical wizardry according to your requirements and plots the results on a chart or graph. Types of mathematical operations include arithmetic, trigonometric, exponential, logarithmic, complex, vector, etc. Programmable logic design As the name suggests, programmable logic devices (PLDs) are ICs containing many logic gates (or building blocks) which are connected at programming time to perform the desired functions. Our imaginary “mega-chip” could be one of these. In order to work efficiently with devices of this complexity, designers describe what they want in high level programming languages like VHDL and Verilog. Multisim provides a complete development environment for PLDs. Using the inbuilt editor, the engineer first enters a design using the VHDL or Verilog languages. The result is then passed to the simulator, which is used to examine and debug the design. Finally, an output file is generated for programming into the target PLD. Note that once a PLD design is complete, it can be simulated at the board level just like any other component in Multisim. The engineer would simply create a symbol for the PLD and import the VHDL/Verilog file. Unfortunately, a detailed look at PLD design is beyond the scope of this article. If you would like to know more about VHDL or Verilog, check out the EDA industries web page at www.eda.org Summary Fig.12: simulating and debugging VHDL code. This example was taken from one of the many Multisim sample designs. Multisim really is an outstanding package. It excels in the simulation department, with features that would make it attractive to both professionals and educators. Multisim is available in four editions, being Power Professional, Professional, Personal and Education – we reviewed the Power Professional edition. Not all features are available in all editions, and some tools, such as the Ultiboard PCB layout and the Programmable Logic Synthesis module must be purchased separately. For further information or to order, visit the Emona Instruments website at www.emona.com.au or phone (02) 9519 3933. Extensive information on the Multi sim package can also be obtained from the Electronics Workbench website at www.electronicsworkbench.com SC March 2000 37 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. Fig.1: this I-V curve tracer connects to the printer port of a PC and works in conjunction with a BASIC program. PC printer port controls I-V curve tracer When connected to the printer port of a PC, the circuit of Fig.1, taken from a Maxim application note, enables you to determine the current-voltage (I-V) characteristics of an active component or integrated circuit. A short BASIC program drives the port and displays the I-V characteristic as a graph on the PC’s video monitor. The result is a useful diagnostic tool for IC fault analysis. The 12-bit digital-to-analog con- Fig.2(a) shows the waveform generated across a Schottky diode while Fig.2(b) is from a more complex analog IC. 38 Silicon Chip Software operation During operation, the software drives the DAC to produce a current ramp and the ADC measures the resulting voltage across the DUT. This voltage waveform is displayed on the PC’s monitor at 640 x 480 resolution, as shown in the two examples in Fig.2(a) & Fig.2(b). Fig.2(a) is the waveform generated across a Schottky diode while Fig.2(b) is from a more complex analog IC. A 12-bit converter resolution is excessive with respect to this display resolution but 12 bits provides a margin for the use of higher resolution monitors and also for examining the response with a software “zoom.” The BASIC program, entitled “I-V Curve Tracer,” was written by Terry Millward, Maxim UK, and is available at Maxim’s website. The actual link to the file is http://pdfserv.maxim-ic. com/arpdf/software/ivcurve.txt Silicon Chip Binders REAL VALUE AT $ 12 +$5 ea.95 P&P Or buy 5a get th nd postag em e free  Each binder holds up to 14 issues  Heavy board covers with 2-tone green vinyl covering  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Just fill in & mail the handy order form below; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Yes! Please send me ________ SILICON CHIP binder(s) at $A12.95 each plus $5.00 p&p. Australia only – not available elsewhere. Enclosed is my cheque/money order for $__________ or please debit my  Bankcard  VisaCard  MasterCard Card No. Signature_________________________ Card expiry date_____/_____ Name ___________________________________________________ Street ___________________________________________________ Suburb/town _________________________ Postcode______________ SILICON CHIP PUBLICATIONS PO Box 139, Collaroy Beach, NSW 2097, Australia. Phone (02) 9979 5644 Fax: (02) 9979 6503. ✂ verter (DAC), IC4, is configured for bipolar outputs to ±2.048V. Op amp IC6a amplifies this signal with a gain of +2 and op amp IC7 converts the result to a current that passes through the device under test (DUT). This current ranges from ±40µA to ±40mA, according to the resistor value selected for RSENSE. For any combination of DUT and the selected range, the maximum current available equals (approximately) the output of IC6a (±4.096V max) divided by RSENSE. The current through the DUT produces a bipolar voltage that is sensed by the differential amplifier IC6b. To avoid the vari able-offset error that would otherwise occur with a change in switch position, this amplifier’s inverting-input signal is taken from the low impedance non-inverting input of IC7 rather than its inverting input. The penalty for this choice is the fixed input-offset error of IC7. The differential amplifier’s gain plus the offset supplied to it result in a maximum output swing (0V to 4.096V) compatible with the unipolar input range of the 12-bit analog-to-digital converter (ADC), IC3. IC3’s 3.3kΩ input resistor limits the input current in the event of an applied overvoltage. IC7 requires ±15V supply rails to provide sufficient voltage for its cur rent-source function. To supply all the other ICs, IC1 and IC2 regulate these rails to ±5V. March 2000 39 Our weathervane came from a commercial unit sold by a mail order company but you could also adapt one from a garden supply shop. The wind direction is indicated on the LED display unit pictured below, which has 16 LEDs arranged around a compass. Build an accurate wind vane with a 16-LED display How would you like to know the wind direction at any time, day or night? Build this electronic wind vane and its display to indicate the wind direction from any of 16 points on the compass. No longer do you have to go outside – just look at the LED display. By JOHN CLARKE 40 Silicon Chip Did you build the nifty wind speed indicator published in the March 1999 issue of SILICON CHIP? That design was based on a bicycle computer and was quite popular. In fact since then we have had quite a few requests for a companion electronic wind vane. And here it is. A common approach to building an electronic wind vane is to use a circular array of reed relays. The wind vane is attached to a disc and magnet and when it comes close to a reed relay, it actuates to drive a LED to indicate a particular wind direction. While that is a simple approach, it does have its limitations and it does become unwieldy if you want to indicate more than eight wind directions – you need a lot of reed relays and a lot of cabling from the wind vane itself to the LED display panel. With that in mind, we set out to produce a design which would indicate wind direction from 16 points of the compass and which would use a modest amount of electronics to eliminate the need for a thick multi-way cable. By the way, when we say 16 points of the compass, it means that the accuracy with which you can measure the wind direction is within 22.5°. In other words you Fig.1: the basic scheme for the Electronic Windvane. Depending on the position of the Gray encoded disc, the IR detectors pick up light from the IR LEDs and this information is decoded by IC1 and fed to the display. will be able to distinguish between a Nor-Easterly and a Nor-Nor-Easterly and so on. The Electronic Windvane comes in two parts, one to house the wind vane detector circuitry and the second to house the display circuitry. The readout on the display comprises 16 LEDs to display the directions N, S, E, W, NE, NW, SE and SW and the intermediate points NNE, NNW, ENE, WNW, SSE, SSW, ESE & WSW. Infrared LEDs and diodes Fig.1 shows the general arrangement of the circuitry involved. The detector comprises four infrared LEDs and four in frared detector diodes. They are aligned in two rows, with LED1 shining on IRD1, LED2 shining on IRD2, etc, with a translucent encoding disk located in between them. The disk is made of PC board material and comprises four concentric rings, one for each diode and detector pair. The rings have sections of copper to block the light transmission and sections of translucent board to allow the light to pass. Depending on whether or not light is shining on them, the four infrared diode outputs have two possible states (0 or 1) to provide us with 16 combinations corresponding to the 16 Fig.2: the complete circuit diagram for the Electronic Windvane. The position of the Gray encoded disc depends on the direction of the wind and this in turn determines which of the IR detectors (IRD1-4) picks up light from its companion LED. IC1 decodes the detector outputs and drives the direction indicator LEDs. March 2000 41 Fig.3: this diagram shows how the major parts are assembled inside the plastic case. The Gray encoded disc (board 3) sits between the IR LEDs on board 2 and the IR detectors on board 4. an incorrect direction reading as we move from one code to another with each change in direction. The 4-bit outputs from the detector diodes are applied to the 4-16 decoder. This is a binary decoder which does not decode in the Gray sequence but it is simple enough to rearrange the decoder outputs so that the correct directions are obtained on the LED display. Circuit description compass points. The ring pattern on the disc is shown in the PC patterns of Fig.7, toward the end of this article. Gray code The ring encoding on the disc is such that only one of the detector outputs changes state for any single change in direction. The 16 possible codes are shown in Table 1, together with the equivalent decimal value. Note that the numbers do not count in a standard sequence from 0 to 15 but are jumbled. By studying the table you will see that only one digit in the 4-bit code changes between each successive number. This type of encoding is called a Gray code (after Elisha Gray) and it ensures that we will not obtain Fig.2 shows the complete circuit and as you can see, there is not much to it. The four infrared LEDs (IRLED1IRLED4) are connected in series and powered from the 12V supply via a 1.8kΩ resistor. This allows about 2-3mA of current through the LEDs. The IRLEDs shine on to their respective infrared detector diodes (IRD1-IRD4) which are reverse biased between the positive supply and ground via 10kΩ resistors. When an IRD does not receive any light, its anode voltage is pulled low via its respective 10kΩ resistor. When light shines on the IRD, reverse current flows, from cathode to anode, and the voltage at the anode goes high. The four anode outputs connect to the A, B, C & D inputs of IC1, the 4514 decoder. The most significant bit is the D input and the least significant bit is the A input. The 16 outputs drive the display LEDs but only one is lit at a time. If the A, B, C & D inputs are all low, then the “0” output at pin 11 goes high to drive the North LED (LED1). Similarly, if only the A input is high, the “1” output goes high and drives the NNE LED. Current through Table 1: The Gray Codes Decimal B inary Decimal B inary 0 0000 12 1100 1 0001 13 1 1 01 3 0 0 11 15 1 1 11 2 0010 14 1110 6 0110 10 1010 7 0 1 11 11 1011 5 0 101 9 1001 4 0100 8 1000 Table 1 above shows the 16 codes that are encoded onto the disc, while the photo at left shows the corresponding ring pattern on the board. Note that only one digit in the 4-bit code changes between each successive number. 42 Silicon Chip Fig.4: install the parts on boards 2 and 4 as shown here, making sure that the IR LEDs and detectors are correctly oriented. It’s a good idea to used PC stakes at the external wiring points, as this will make the wiring easier. the powered LED is limited by the common 2.2kΩ resistor. Power for the circuit is derived from a 12V DC plugpack and diode (D1) prevents damage to the circuit if it is connected the wrong way around. The 47Ω resistor and zener diode ZD1 limit the voltage to 15V. The 100µF capacitor decouples the supply. Construction While the circuit is simple, the construction is more com plicated. There are four PC boards and two cases involved. The display board, board 1, coded 04103001, can be mounted in a plastic case or as we did, in a circular wooden enclosure 131mm in diameter. It could be salvaged from an old barometer or turned up if you have a wood lathe. Alternatively, you can purchase one from the supplier mentioned in this article. It includes provision for a glass or Perspex window in front of the display. Boards 2, 3 & 4, coded 04103002, 04103003 & 04103004 are for the position detector circuitry and are housed in a weatherproof plastic case measuring 115 x 90 x 55mm. You can start work on the PC boards by checking for shorts or breaks in the copper tracks. The Gray encoding PC These are the completed position detector circuit boards, ready for assembly into the case. Note the metal bushes which have been soldered to boards 3 and 4 (just visible from the top). March 2000 43 board (code 04103003, board 3) will need to be cut into a circular shape. The corners will also need to be removed from board 2 (code 04103002) to allow access to the retaining screws which ultimate ly hold the PC assembly in the case (see Fig.3, which shows the mechanical assembly of the PC boards). The corner holes for the three other boards should be 3mm in diameter while the centre hole in board 2 should provide clearance for a 6mm rod. The centre holes in boards 3 & 4 (04103003 and 04103004) should be reamed out to provide an interference fit for brass bushes which fit over the 6mm (or 1/4-inch) rod. Four brass bushes with grub screws will be required. These can be obtained from plastic knobs. OK. So you get four of these knobs, remove their grub screws and then squeeze them in a vise to crack the plastic housing. Remove the bushes and re-insert the grub screws so you do not lose them. Ream out the holes in boards 3 & 4 so that the bushes are an interference fit. The bushes are then pressed into the copper side of the PC boards and soldered into place. Do not press the bush for Board 3 in too far otherwise you will not be able to tighten the grub screw. You will need a rod 150mm long to suit the bushes and this may be 6mm or 1/4-inch in diameter. Test fit the rod in the bushes in the board and ensure that all run freely and true (without wobble). That done, you can assemble the electronic components onto each board. The component overlays are shown in Fig.4 & Fig.5. Start by soldering in the PC stakes which are located at all the wiring points, then install the links and resistors. Table 2 shows the colour codes. Make sure you install diode D1, zener ZD1 and the 100µF capacitor the correct way around. Similarly, when inserting IC1, be sure to orient Fig.5: the main display board carries the 16 direction indicator LEDs and the decoder IC. Make sure that these parts are all oriented correctly. Table 2: Resistor Colour Codes      No. 4 1 1 1 44 Silicon Chip Value 10kΩ 2.2kΩ 1.8kΩ 47Ω 4-Band Code (1%) brown black orange brown red red red brown brown grey red brown yellow violet black brown 5-Band Code (1%) brown black black red brown red red black brown brown brown grey black brown brown yellow violet black gold brown The wooden display housing is drilled to accept the LEDs, using the label as a template. This shows the rear view but note that the unit should be drilled from the front. it correctly before soldering in place. The infrared LEDs (IRD1-IRD4) are coloured smokey blue and are inserted into board 2 (code 04103002). Note that the anode lead is the longer one and these LEDs must be inserted with the correct polarity. Solder them so that the height from the top of the LED above the PC board is 14mm. The infrared detector diodes (IRD1IRD4) have clear lenses and are inserted into board 4 (code 04103003) with a height of 14mm above the board surface. Do not insert the 3mm red LEDs for the display PC board just yet. You are now ready to assemble the three wind detector boards as shown in Fig.3. Insert the rod into the bush of board 4 and fit another bush onto the rod to stop it from moving through the board. These two bushes become the lower thrust bearing for the wind vane. Now place board 3 onto the rod together with another bush and a washer. Secure board 2 in position using the 25mm and 6mm spacers and 3mm screws. Make sure that the IRLEDs and IR detector diodes are lined up directly opposite each other., then tighten the grub screw for board 3 so that it is positioned centrally between the infrared LEDs and diodes. Set the upper bush with a little clearance between it, the washer and top board so that the rod can spin freely. A drop of oil on the lower bushes will allow a freer movement. Attach The display board is mounted on the back of the housing using 6mm spacers and 10mm-long wood screws. A cable clamp is used to anchor the leads. the lower PC board to the base of the case with 3mm screws or self-tapping screws. The lid of the case can be drilled in the centre to accept a threaded bush from a rotary switch or potentiometer. The 6mm rod should fit neatly through this threaded bush. Also drill out the hole in the side of the box for the cable entry and grommet or cable gland. The lid of the case should have the supplied gasket fitted into the grooving, so that it will be weatherproof. Display housing The diagrams showing how the display board is housed in a plastic case or circular wooden enclosure are shown in Fig.6. If you are installing it in the plastic case, you can tack solder the LEDs on one lead only with the top of the LED being 27mm above the PC board. Then insert the board on 12mm long standoffs and secure with screws into the base of the case. Attach the label to the lid of the case and drill out the holes for the 16 LEDs. Note that although we have marked one LED as the North LED, this is arbitrary. Any LED can be chosen as the North LED and so the label can be oriented in any way to suit the case you have. Place the lid on the case and check that the LEDs are just protruding through the label. You may need to readjust the LED height before finally The front panel label is glued to an aluminium disc and the holes then drilled around its circumference so that is fits over the indicator LEDs. If you wish, the label can be protected using an acrylic or glass faceplate. March 2000 45 Fig.6: these two diagrams show how the display board is mounted in a plastic case (top) or in a wooden case (above). If using the wooden case, the LEDs are first mounted on the PC board, then the board is mounted in position and the LEDs pushed through the holes in the case before soldering. soldering all the leads in place. The wooden enclosure can be drill ed for the 16 LEDs in the front face using the label as a guide. Push the LEDs through the holes and secure the PC board to the case using 6mm The 6mm metal rod passes through a 6mm threaded bush which is attached to the case lid. This bush can be obtained from a rotary switch or a potentiometer. 46 Silicon Chip standoffs and wood screws as shown. Solder the LEDs in position. This done, remove the PC board and attach the label to the face of the enclosure. Again it does not matter which orientation you choose for the North LED. You can place a circular acrylic or glass face in position over the label if required. Wire up the boards as shown using 6 or 8-way cable. This cable must be long enough to extend from the position detector circuitry to the display board. Initially, the wiring will prob ably be only temporary since you will need to install the weather vane on a mast and the display case inside your home. We envisage that the wiring between the two would be passed through the wall and up to the mast. Attach the wires for the 12V DC plugpack supply to a DC line socket and connect up the supply. You should be immediately greeted with one LED alight. If you rotate the rod on the position detector, the LEDs should each light up in sequence. If the LED order is jumbled, then you possibly have the wiring to the A, B, C & D terminals mixed up. If the North position appears to have a greater range of movement before the adjacent LEDs light, you can reduce the value of the 1.8kΩ resistor for the IRLEDs. This will produce more light from the LEDs to reduce the shadow effect caused by the transition from dark to light as the coding on the Gray disc changes from copper to translucent PC board material. Increasing the current through the IRLEDs will reduce the range of movement that the rod moves with the North LED alight. Note also that the circuit is de signed to operate in the dark; ie, with the circuit in its box. If you test the as sembly in daylight or artificial light, the detectors will not work properly. Weather vane We adapted our weather vane from This is what the unit looks like before the bottom of the case is attached and the weathervane fitted. The skirt of the plastic hose fitting covers the threaded bush (to keep water from running down the shaft) but sits slightly proud of the case so that the shaft can turn. Note the plastic sleeve over the shaft. a commercial unit made of plastic and supplied by the mail order firm Magnamail. We just used the plastic arrow without the clip-on bird (well, it was an eagle instead of a proper rooster!). We also used a plastic snapon tap hose fitting which prevents water running down the rod and into the box via the top bush. Both the tap fitting and plastic wind vane were internally sleeved with Nylex plastic tubing which made them a friction fit onto the metal rod. Calibration Use a compass to find North. Set the rod on the position detector so that Parts List 1 PC board, code 04103001, 89 x 81mm 1 PC board, code 04103002, 89 x 81mm 1 PC board, code 04103003, 69 x 69mm 1 PC board, code 04103004, 89 x 81mm 1 weatherproof plastic box, 115 x 90 x 55mm 1 circular wooden display case, 131mm diameter (see panel) 4 6mm untapped spacers 5 10mm long wood screws 1 cable clamp (see text) OR 1 plastic case, 115 x 90 x 40mm 4 12mm untapped spacers 4 M3 x 20mm screws 1 6mm ID rubber grommet 1 display label, 71mm diameter 1 12VDC plugpack 1 DC line socket 1 150mm long 6mm or 1/4" metal rod 4 plastic knobs with 6mm brass bushes and grub screws 4 25mm tapped brass spacers 4 6mm untapped brass spacers 8 M3 10mm screws 4 M3 6mm self-taping screws to mount PC board in case 1 6mm brass washer 1 6mm threaded bush (from rotary switch or potentiometer) 16 PC stakes 1 120mm length of 0.8mm diameter tinned copper wire 1 length of 6-way or 8-way cable (for windvane sensor to display) 1 6mm ID rubber grommet or cable gland 1 100µF 16VW PC electrolytic capacitor Semiconductors 1 4514 CMOS 4-16 decoder (IC1) 16 3mm red LEDs (LED1-LED16) 4 5mm infrared LEDs (IRLED1IRLED4) 4 5mm diameter infrared detector diodes (IRD1-IRD4) 1 1N4004 1A diode (D1) 1 15V 1W zener diode (ZD1) Resistors (1%, 0.25W) 4 10kΩ 1 1.8kΩ 1 2.2kΩ 1 47Ω Miscellaneous Solder, weathervane, mast, plastic hose fitting, plastic sleeving, etc. March 2000 47 Fig.7: here are the full-size artworks for the four PC boards and for the front panel artwork. The boards should all be correctly drilled and the corners trimmed as shown before installing any parts. the North LED is alight and is in the middle of its angular travel between where the NNE or NNW LEDs light. Now point the weather vane towards North, make sure that it is not loose and you’re done. We fitted the underside of the wind vane case with a flange intended for a shower curtain rod. This makes it easy to mount on SC top of a wooden dowel or metal pipe. Where To Buy The Wooden Display Case The circular wooden display case can be purchased from Mr Rod Chambers, PO Box 18, Moonbi 2353. Send cheque or money order to the value of $15 plus $5 p&p. 48 Silicon Chip SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. 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Please feel free to visit the advertiser’s website: www.altronics.com.au SERVICEMAN'S LOG Some jobs aren’t worth the trouble Some jobs really aren’t worth the trouble, particularly if the equipment is old or if the fault is intermittent. The trouble is, my persistent nature often stops me from giving up on jobs that have become uneconomic. I thought that fixing Mr Hilda’s JVC HR-D750EA VCR would be relatively simple. His story was that he went away on holidays and switched it off when he left but when he came back, it wouldn’t switch on straight away. Instead, he could only get it to work intermittently. Finally, it wouldn’t start at all, giving only a “squeak” and then nothing. I quizzed him further and established that he was trying to get it to start by switching it off and on using the power point switch on the wall. He wasn’t using the remote control or the power switch on the front of the VCR for this job. To me, this all suggested that one or more electrolytic capacitors had gone leaky in this now 10-year-old VCR, especially the start-up capacitor (which ever one it was) in the switchmode power supply. In this machine, the main section of the power supply con sists of a separate module in a metal cage, in the far righthand corner of the chassis. The rest of the power supply is on the main circuit board and consists mostly of IC regulators. My initial attention was drawn to a regulator in the cage, which was fairly easy to remove due to good access to the printed side of the board. The first thing I did was scrape off the liberal quantities of corrosive brown goo that had been applied to both sides of the board. The component side proved to be a bit of a nightmare as the parts were packed tightly between various metal screens and heatsinks. That done, I examined the service manual which is marked “switing regurator”. Anyway, there were two electrolytic capacitors on the primary side of the switchmode transformer (T1) that looked like the suspects I was seeking. These were C14 1µF 50V and C13 180µF 16V. I could see that all the electrolytics had been replaced some years previously but these two were now well and truly dried out due to their proximity to the heatsinks. I fitted two new EXR 105°C capacitors, substituting a 220µF unit for the 180µF capaci tor and also increasing the working voltage of both values. The new capacitors were smaller than the originals so this was straightforward. By the way, the EXR range of electrolytic capacitors is specially designed for high-frequency switchmode power supplies. They have very low impedance and low leakage, typically around 4µA, which should give extra long life. The equivalent (effective) series resistance, or ESR, of an electrolytic capacitor defines its performance and life; the lower it is, the better the capacitor. An Australian engineer, Sets Covered This Month Fig.1: part of the switchmode power supply circuitry in the JVC HR-D750EA VCR. There were several problems that prevented the supply from starting. • JVC HR-D750EA VCR • National TC1407 portable TV set • National NV-H70A VCR • Mitsubishi CT2584AS stereo TV set March 2000 65 Serviceman’s Log – continued Bob Parker, has designed an ESR meter kit (available from Dick Smith Electronics, Cat.K-7204) to measure this. Having just bought and built one of these, I was itching to give it a go. The two capacitors I had taken out both measured high impedance, the 180µF unit reading 44Ω and the 1µF unit not reading at all. I had fitted an additional buzzer circuit, designed 66 Silicon Chip by Mark Stevenson, that gives an audible sound if the capacitor is OK (ie, below 1Ω) and a slight noise if it is less than 10Ω. While I was at it, I measured all the remaining electrolytics in-circuit with the ESR meter and the buzzer indicated that they were OK, with two or three giving the lesser noise, (ie, possibly borderline). I then resoldered any suspicious joints before putting it all back together and switching it on, confident that it would work. To my surprise, nothing happened. However, I was still convinced it was really an electrolytic capacitor that was at fault, so I replaced the three units that had given a doubtful reading on the ESR meter. That didn’t fix it either. Finally, I took the advice of a colleague who always maintained that it was quicker and more reliable to just change the lot at one go. I did this, replacing all 11 of them, and bombed out again! Next, I checked the high value resistors R2, R3, R4, R7, R8 but still no joy. I then checked the secondary output rails for shorts and was finally rewarded by finding that D25, a 39V zener, was short circuit. But this still did not fix the fault. To make matters worse, I then introduced a red herring by unplugging the power supply from the VCR (in case the load was too much). This time the power supply finally fired up and I had voltages on all the rails. However, when I plugged it back into the VCR, it died again and so I checked for shorts on the main VCR rails. Again, nothing was found – this sorry tale was just too frustrating but worse was to come. I reconnected the two plugs while the power supply was on – fairly risky, I know, but I was desperate – and the whole video burst into life! I checked all the functions and apart from lines across the screen in playback mode, everything worked fine, including the power on/off on the set. But when I switched it off at the power point and then back on, it was dead again! By now I was feeling considerably older – I think my own electrolytics were past their use-by date! The only thing left I hadn’t tried was IC1 (STR1006), which I really doubted could be the problem – but naturally it was. It only has three transistors, one zener and three resistors but it was the culprit. My theory is that the two original electrolytics failed, causing the output voltages to rise. And this in turn destroyed D25 and, presumably, the zener diode in IC1. But I still wasn’t out of the woods – I still had the lines on playback, although they slowly weakened, the longer the set was on. From experience these are also usually caused by faulty electrolytic capacitors, this time on the 5V and 12V rails feed ing the head amplifier. As a result, I checked C802 to C807 with the ESR meter and they all checked OK. The ESR meter makes it so much quicker, as they can be checked in-circuit and the meter was proving to be very accurate. It was then that I remembered a previous repair I had done on a JVC HR-D400EA with the same fault. After a long saga, the fault had been traced to the underside of a small soldered metal shield on the main video board. This shield conceals a patch of brown goo which holds a 1kΩ resistor between pins 1 and 32 of IC102 (pin 3 being +5V Vcc and pin 1 9V Vss (PB12V) for the MS6967RS 1H delay). As before, removing the goo and corrosion also removed the final problem. However, my persistence with this job had been a little uneconomic and I really should have drawn the line sooner. I was, however, very impressed with the ESR meter and can recommend it to you – good one, Bob! National TV set My next story involves a complete change of scene. The local motel brought in a National portable TV set, complaining of horizontal white lines across the picture but only on Channel 7. I wasn’t all that keen about repairing such an old (1984) chassis – a TC1407 (M12H) – but was intrigued by the symptoms. Initially, I suspected the CATV (cable antenna television system) antenna used in the motel but when I connected my own antenna to the set, the same fault occurred. When I tuned to Channel 7 there were bright white horizontal retrace lines about two thirds the way down the screen from the top. Because it was only on Channel 7, I reasoned that this was because this is the only channel transmitting Teletext during the vertical flyback interval. The motel owner, while appreciating that the set was over 15 years old, was prepared to pay up to $100 to get it fixed. Apart from its current problem, the set produced a good picture and had been very reliable. Well, how difficult could it be to find a vertical blanking fault? Surely this would be an easy $100, I foolish- ly told myself. In fact, I still had an original service manual for this set, although the circuit diagram is a bit of a mess and difficult to follow. I discounted the AGC and IF stages and concentrated my efforts on the blanking circuit between IC401 (the vertical output IC, AN5521), IC601 (the chroma decoder IC, AN5625) and IC301 (the video output IC, AN5615). By using an oscilloscope, I thought that it wouldn’t take long too find out where the blanking pulses disappeared. My assumption was that it was probably a leaky electrolytic capacitor somewhere that was causing the problem. I started at pin 6 of the vertical output IC (IC401) and measured waveform 20, which is a 28V peakto-peak vertical pulse (the DC value being 0.3V). This turned out to be spot on. This pulse then goes through C416 and R424 where it joins the horizon tal blanking pulse from pin 2 of the horizontal output transform er via R553, C650, R678, R642 and D601. The horizontal waveform (waveform 37) started out at 30V peakto-peak on pin 2 and is reduced to about 9V on the anode of D601 but no information on the waveform at this point is supplied in the service manual. However, the 5ms vertical pulse, embedded between the horizontal pulses, was clearly visible. Because I was expecting something dramatic, I was rather perplexed to find that this waveform reached pin 18 of IC601 and pin 11 of IC301 quite correctly. This waveform (24) shows the horizontal pulse as 6.2V p-p, which was spot on at a DC voltage of 1.2V. The vertical pulse was still there too, so where was the obvious fault? In my notes of previous repairs, I had recorded that a TC1408 (M12C) had displayed the same symptoms due to a faulty AN5615 (IC301). I now felt sure this must also be the culprit here so I changed IC301, then IC601 and then IC401 – all without result. Clutching at straws, I then replaced C414, C416, C420 and C650. This made no difference either, so I measured the resistors and diodes in circuit and all read OK. By now I was really frustrated – by rights, I should have fixed this supposedly simple fault and moved onto another job. Unfortunately, I still didn’t have a clue but I was determined that it wasn’t going to beat me. My next theory was that perhaps it was the width of the vertical pulse that was the significant factor. An hour later I abandoned this idea in a bad temper, even though I could vary the number of retrace lines by carefully adjusting the vertical hold. March 2000 67 Serviceman’s Log – continued Fig.2: this circuit section for the National NV-G30 proved to an effective substitute for a National NV-H70A. In particular, it allowed me to identify transistors Q6005 and Q6006, both of which had been “cooked”. I even changed IC501, the jungle IC (AN5435) but the retrace lines were still visible on Channel 7. In the past, I have had similar symptoms due to poor smoothing of the 198V rail to the RGB outputs so I replaced C556 (10µF 250V). When that didn’t work, I checked the screen volts but I was getting nowhere fast. I had obviously overlooked something but I couldn’t think what it was. All I could do now was go back over what I had done and recheck my work. A previous fault I had encountered with another set with no colour had turned out to be a leaky diode (D602) which had distorted the horizontal pulses to the burst gate. I remembered that, at the time, I couldn’t measure this in-circuit to determine its leakage. Therefore, I felt it would be a good idea to measure D402, D601 and D602 out of circuit with the ohmmeter on the 100kΩ range. And it was when I measured D601 that I found the answer – there was significant reverse leakage. Replacing it with a 1N4148 fixed the fault and the vertical pulse on its cathode was double what it was previously. I richly deserved the $100 I charged 68 Silicon Chip for this job but when will I ever learn? National NV-H70A VCR Mr Peterson’s ageing National NVH70A VCR came into the workshop with the complaint that a tape was stuck inside. He neglected to mention that the set was otherwise dead but on removing the covers the cause was fairly obvious. F1102, a 2A fuse, was open circuit on the UNREG 18V rail that also supplies several other rails: 12V, 7.2V, 6V and 5V. Replacing the fuse restored all functions and I could do whatever I wanted with the tape. Next, the phone rang and I had to deal with an enquiry that took some time. Suddenly, towards the end of the conversation, I began to smell burning. I wound up the call as fast as I could and started sniffing around for the source. And when there is a lot of electrical gear spread out and all switched on, it can be hard to trace the source of a smell. Fortunately it didn’t take long to trace this one; it was coming from Mr Peterson’s VCR! Although it had been doing all its tricks minutes earlier, the tape was now firmly stuck inside and wouldn’t budge. Sniffing carefully, I traced the smell to two transistors on the right hand side of the motherboard. These had become so hot that they had un soldered themselves and fallen out of the PC board so that they were now resting on the bottom of the cabinet (the PC board is horizontal, with the wiring pattern on the top and the components underneath). Pretty neat trick, I thought – at least I wouldn’t have to unsolder them. But that was the easy part. After scooping them up, I was faced with the problem of identifying them; they had been carbonised and I didn’t have a circuit diagram. My approach was to find a similar National Panasonic cir c uit – one with the same microprocessor chip set used on the main CBA (Circuit Board Assembly VEP03309). That way, I would have a good chance of identifying the transistors used. The best substitute circuit I could find was for the NV-G30 model. The clue was IC6001, an MN15342VEB, which is used in both units. And the transistors in this part of the NV-G30 circuit, Q6005 and Q6006, turned out to be 2SB790s, which are general-purpose PNP transistors. Before replacing these, I checked the circuit board for burn marks. The two transistors are controlled by the microprocessor, with Q6006 switching a regulated +12V rail via the Record Safety Switch and Q6005 driven by pin 43 D-REC (Delayed Record). Similarly, Q6008 is driven by pin 42 DA-REC (Delayed Audio Record). Apart from the two transistors there was no other apparent damage so why did they get so hot and fail? This wasn’t easy to deduce but with the common denominator being the regulated 12.3V supply, the source of the problem had to be in the power supply itself. Access to the power supply is not easy, with a lot of short leads and metalwork in the way. Once it was out, I decided to adopt a blanket approach and replace all 10 electrolytics with EXR 105° types. It was a fiddly job but most of the capacitors looked pretty sorry anyway, especially C1101, C1107 and C1104. Finally, I left it on soak test and I’m pleased to report that there were no more pyrotechnics. Mr Peterson is once again a happy man though I did advise him to get a new one if it played up again. He would be surprised how cheap they are now compared with what he paid some 13 years ago. Mitsubishi stereo TV Mr Crane requested a service call for his 1992 59cm Mitsubishi CT2584AS (ASV59S/AS2 stereo chassis), which he said had an intermittent crackle in the sound. Initially, I was emphatic that an intermittent fault would have to be fixed in the workshop but he was equally emphatic that it really wasn’t intermittent and that because he was 76 years old, he couldn’t possibly get it down the stairs of his duplex and into his car to deliver it to me. I saw his point and relented. When I arrived the next afternoon, I switched it on and sure enough, there was a faint crackle on all channels. He assured me that it was normally a lot louder. I knew I was going to regret it later but I decided to take a quick look anyway, in the hope that I could fix it on the spot. I pulled the set away from the wall, removed the back and started tapping around, looking for a dry joint or a bad connection. After a few minutes, I emerged from behind the set having achieved nothing except that when I looked at the picture it was line tearing. “Oh yes”, said Mr Crane, “it does that too sometimes”. I secretly sighed with relief – I hated to think I might have been held responsible for this “new” problem. “Well”, I said authoritatively, “that settles that, I will have to take it back to the workshop”. I lent him a portable set and with immense difficulty finally got his set into the car and back to the workshop. The set must have enjoyed the ride because when I switched it on, all the faults had cleared and the picture was excellent. Such is life, I thought and left it to soak test. The crackling in the sound refused to come back but the line tearing did occasionally. I took the chassis out and reworked the soldering for any potential dry joints – there were none that were significant. I also noticed that the heatshrink tubing on some of the electrolytics had peeled back. Initially, I replaced three capacitors in the power supply secondary – C917 and C453 on the 28V rail to the vertical output IC (IC451) and C920 on the 15V input to the two 12V regulators (IC902 & IC103). I also replaced C552 (1µF 160V) which connects to the line driver Q551/T552. The two significant capacitors were C917 and C920 as they smelt “fishy” when I unsoldered them. They had spilt their electrolyte and this had attacked the copper tracks on the board. Anyway, this finally fixed the line tearing but I didn’t know what to do about the sound. I left it on soak test for another two weeks before Mr Crane finally demanded I return it. Reluctantly, I agreed but didn’t have much faith in the long-term reliability of the set and told him so. The set bounces As I expected, Mr Crane was back on the phone just two months later to let me know that didn’t last long. And despite my previous explanations, he seemed to think that it was all my fault (which I also expected). I called the next afternoon and listened attentively to the elusive crackle. This time I established that it wasn’t due to interference from an DON’T MISS THE ’BUS www.siliconchip.com.au SILICON CHIP’S Do you feel left behind by the latest advances in com puter technology? Don’t miss the bus: get the ’bus! Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. ORDER NOW: Use the handy order form in this (02) 9979 5644, 8.30-5.30 Mon-Fri with your 132 Pages 9 $ 95 * ISBN 0 95852291 X 09 9780958522910 09 9 780958 522910 COMPUTER OMNIBUS INC LUD ES FEA TUR E LIN UX A collection of computer features from the pages of SILICON CHIP magazine o Hints o Tips o Upgrades o Fixes Covers DOS, Windows 3.1, 95, 98, NT NO AVA W DIRE ILABLE C SILIC T FROM ON issue or call just $ CHIP 125O INC credit card details. RT P&P external source. Instead, it sounded as though it was due to arcing somewhere inside the set. With the speakers switched off I couldn’t hear it at all but I thought it might have been arcing internally inside the flyback transformer or even the deflection yoke and that the interference was finding its way into the audio chain. I disconnected the yoke momentarily and it wasn’t that. I also unplugged the CRT socket in case it was arcing inside the tube guns but it wasn’t from that either. Finally, I decided that it was the flyback transformer that was the cause of the problem and told Mr Crane that it would be expensive to replace. It was time now for him to put up or shut up. He decided to invest in a new transformer. It took the set back to the workshop to wait for a new flyback transformer. And although I had sounded confident, it was really only an intelligent guess. I knew that if this didn’t fix it, I would have to keep at it until I had cracked it. Finally the new part arrived. I unsoldered the old one using a solder sucker but I ran into problems when I tried to remove the EHT final anode/ ultor cap to the tube. The type of rubber that Mitsubishi uses is quite hard and resilient compared to others and getting a screwdriver underneath it was difficult. Then I had to push in the side clips that hold it on to the tube before one side came away and I finally got it off. The reason I had problems removing it was that it was extremely rusty underneath, with heaps of fine brown-red rust powder everywhere. This mystified me, as there was absolutely no sign of rust or water damage anywhere else but it got me thinking – was this the cause of the invisible arcing and crackling in the sound? I cleaned up the rust with a wire brush and CRC 2-26 and fitted the new flyback transformer – I didn’t have the time or patience to refit the old one and because of the intermittent nature of the fault, I felt that the result would have been inconclusive. As additional insurance, I replaced all the electrolytics feeding the audio output stages and reworked the sound module. Once again I soak tested the set before returning it to an anxious Mr Crane. It is now over three months since it went back so I feel confident that it has really been fixed. SC March 2000 69 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 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. 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. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Build A Windows-Based Logic Analyser. 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. 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. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80Based Computer; A Look At Satellites & Their Orbits. June 1991: A Corner Reflector Antenna For UHF TV; Build A 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled Cockroach. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. 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. 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. 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. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. 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. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. December 1993: Remote Controller For Garage Doors; Build A LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. 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. 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. 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. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags In Cars – How They Work. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; 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. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple Electronic Die; A Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: A Low-Cost 3-Digit Counter Module; Build A Simple Shortwave Converter For The 2-Metre Band; The Bose Lifestyle Music System (Review); The Care & Feeding Of Nicad Battery Packs (Getting The Most From Nicad Batteries). January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. 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. 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. November 1990: Connecting Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; 6-Metre Amateur Transmitter. 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. December 1990: 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. August 1992: Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; The MIDI Interface Explained. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Engine Management, Pt.6. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8. 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. ORDER FORM Please send thethe following back issues: Please send following back issues: ____________________________________________________________ Enclosed is my cheque/money order for $______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 70 Silicon Chip Note: prices include postage & packing Australia ....................... $A7.70 (incl. GST) Overseas (airmail) ............................ $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. Email: silchip<at>siliconchip.com.au ✂ Card No. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Build A Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); How To Plot Patterns Direct to PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote Control System for Models, Pt.1; Index to Vol.7. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Preamplifier. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; Remote Control System For Models, Pt.2. 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. 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: Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. August 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. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Prog rammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory To Your PC); Build The Opus One Loudspeaker System; Simple I/O Card With Automatic Data Logging; Build A Beat Triggered Strobe; A 15-Watt Per Channel Class-A Stereo Amplifier. S eptember 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A Waa-Waa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. November 1996: Adding A Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. October 1998: CPU Upgrades & Overclocking; Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. 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. November 1998: The Christmas Star (Microprocessor-Controlled Christmas Decoration); A Turbo Timer For Cars; Build A Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Setting Up A LAN Using TCP/IP; Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (For Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Cathode Ray Oscilloscopes, Pt.7. April 1997: Avoiding Win95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. May 1997: Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. 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. September 1995: Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Keypad Combination Lock; The Vader Voice; Jacob’s Ladder Display; Audio Lab PC-Controlled Test Instrument, Pt.2. 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. 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. 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. 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. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. 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. 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 Audio Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. May 1996: Upgrading The CPU In Your PC; High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluorescent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell; Relocating Your CD-ROM 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. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. February 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Demonstration Board For Liquid Crystal Displays; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Adjustable Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator; Build A Laser Light Show; Understanding Electric Lighting; Pt.6; Jet Engines In Model Aircraft. May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. June 1998: Troubleshooting Your PC, Pt.2; Understanding Electric Lighting, Pt.7; Universal High Energy Ignition System; The Roadies’ Friend Cable Tester; Universal Stepper Motor Controller; Command Control For Model Railways, Pt.5. July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem And Sorting Out Problems); Build A Heat Controller; 15-Watt Class-A Audio Amplifier Module; Simple Charger For 6V & 12V SLA Batteries; Automatic Semiconductor Analyser; Understanding Electric Lighting, Pt.8. December 1998: Protect Your Car With The Engine Immobiliser Mk.2; Thermocouple Adaptor For DMMs; A Regulated 12V DC Plugpack; Build Your Own Poker Machine, Pt.2; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Glider Operations. January 1999: The Y2K Bug & A Few Other Worries; High-Voltage Megohm Tester; Getting Going With BASIC Stamp; LED Bargraph Ammeter For Cars; Keypad Engine Immobiliser; Improving AM Radio Reception, Pt.3; Electric Lighting, Pt.10 February 1999: Installing A Computer Network (Network Types, Hubs, Switches & Routers); Making Front Panels For Your Projects; Low Distortion Audio Signal Generator, Pt.1; Command Control Decoder For Model Railways; Build A Digital Capacitance Meter; Remote Control Tester; Electric Lighting, Pt.11. March 1999: Getting Started With Linux; Pt.1; Build A Digital Anemometer; 3-Channel Current Monitor With Data Logging; Simple DIY PIC Programmer; Easy-To-Build Audio Compressor; Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12. April 1999: Getting Started With Linux; Pt.2; High-Power Electric Fence Controller; Bass Cube Subwoofer; Programmable Thermostat/ Thermometer; Build An Infrared Sentry; Rev Limiter For Cars; Electric Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft. May 1999: The Line Dancer Robot; An X-Y Table With Stepper Motor Control, Pt.1; Three Electric Fence Testers; Heart Of LEDs; Build A Carbon Monoxide Alarm; Getting Started With Linux; Pt.3. June 1999: FM Radio Tuner Card For PCs; X-Y Table With Stepper Motor Control, Pt.2; Programmable Ignition Timing Module For Cars, Pt.1; Hard Disk Drive Upgrades Without Reinstalling Software; What Is A Groundplane Antenna?; Getting Started With Linux; Pt.4. July 1999: Build The Dog Silencer; A 10µH to 19.99mH Inductance Meter; Build An Audio-Video Transmitter; Programmable Ignition Timing Module For Cars, Pt.2; XYZ Table With Stepper Motor Control, Pt.3; The Hexapod Robot. August 1999: Remote Modem Controller; Daytime Running Lights For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting, Pt.14; DOS & Windows Utilities For Reversing Protel PC Board Files. September 1999: Automatic Addressing On TCP/IP Networks; Wireless Networking Without The Hassles; Autonomouse The Robot, Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5; Peltier-Powered Can Cooler. October 1999: Sharing A Modem For Internet & Email Access (WinGate); Build The Railpower Model Train Controller, Pt.1; Semiconductor Curve Tracer; Autonomouse The Robot, Pt.2; XYZ Table With Stepper Motor Control, Pt.6; Introducing Home Theatre. November 1999: USB – Hassle-Free Connections TO Your PC; Electric Lighting, Pt.15; Setting Up An Email Server; Speed Alarm For Cars, Pt.1; Multi-Colour LED Christmas Tree; Build An Intercom Station Expander; Foldback Loudspeaker System For Musicians; Railpower Model Train Controller, Pt.2. December 1999: Internet Connection Sharing Using Hardware; Electric Lighting, Pt.16; Index To Volume 12; Build A Solar Panel Regulator; The PC Powerhouse (gives fixed +12V, +9V, +6V & +5V rails); The Fortune Finder Metal Locator; Speed Alarm For Cars, Pt.2; Railpower Model Train Controller, Pt.3. January 2000: Spring Reverberation Module; An Audio-Video Test Generator; Build The Picman Programmable Robot; A Parallel Port Interface Card; Off-Hook Indicator For Telephone Lines; B&W Nautilus 801 Monitor Loudspeakers (Review). February 2000: Build A Multi-Sector Sprinkler Controller; A Digital Voltmeter For Your Car; An Ultrasonic Parking Radar; Build A Safety Switch Checker; A Sine/Square Wave Oscillator For Your Workbench; Marantz SR-18 Home Theatre Receiver (Review); The “Hot Chip” Starter Kit (Review). PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, December 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992, December 1992 and March 1998 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc for $10 including p&p, or can be downloaded free from our web site: www.siliconchip.com.au March 2000 71 Into powered models? Get into this If you’re into fuel-powered model aircraft, boats or cars we might just have solved that age-old problem: how to heat the glowplug to its required temperature from a car or gell battery. by ROSS TESTER Glowplugs come in many shapes and forms but they all have one function to perform: to provide a source of combustion inside a model engine to allow it to start when given a quick turn. Without the glowplug to start things “cooking” inside the engine, the engine would normally refuse to start. It’s a similar process to a diesel engine (which, by the way, also normally have glowplugs). When the engine is cold there simply isn’t enough energy to force the fuel to combust. So the glowplug supplies this energy by heating the fuel vapour to its combustion point while starting. Once started, the engine relies on its own heat and the fact that there is a lot more energy being generated in the compression process – simply because the engine is running fast. To make the glowplug operate it must be connected to a heavy-duty but low voltage (1-2VDC) power source. This brings about a couple of wrinkles. First of all, finding a battery of that capacity and second, matching it to the type of glowplug. Those who remember the old manual telephones used in “the bush” until about the early ’70s may recall they were powered by large 1.5V cells, capable of delivering many amps. If the phone didn't work, the chances were the cells had been purloined by a model aircraft enthusiast for their glowplugs. (Honest, mum, it wasn’t me!). Aah, the good old days . . . While many enthusiasts now make up battery packs to suit their models, most dream of being able to use the battery they take with them everywhere – their car battery. MUFFLER GLOW PLUG HEAD IDLE ADJUST SCREW NEEDLE VALVE IDLE MIXTURE SCREW THROTTLE ARM PROP SHAFT There are many different types of glowplug but they all have one purpose: to ignite the fuel and get the motor started. 72 Silicon Chip CARBURETTOR A typical 2-stroke model engine with various parts identified. The glowplug screws into the head – clearly seen at the top of this photograph. But car batteries are 12V and would make short work of most model glowplugs. The usual answer is to drop the voltage via some high wattage resistors – not only wasteful but also a bit hit-and-miss. Many enthusiasts have also tried gell cells (6 or 12V) but the problems are much the same. Another problem with using a standard battery for a power source is that different glowplugs will glow at different brightness levels. Some glowplugs operate barely red hot, while others are made to work much brighter. As brightness (and therefore heat) equates to the amount of power being delivered to the glowplug, if you are running various model engines it doesn’t take much to realise that a variable supply is required. Another advantage of being able to increase the heat of the plug is that a flooded engine can be started more easily. The ideal brightness level for most glowplugs is a bright orange that can be seen in normal daylight conditions. There are however some glowplugs that are normally used at lower brightness levels. An example of this is the ENYA number 3. It has a very thick element and is normally operated at lower levels of brightness. At the other end of the scale is the OS number 8. It is normally operated at much higher brightness levels. The circuit described here is capable of powering the vast majority of glowplugs in use today to their correct brightness, simply by varying one control. This control can be a preset potentiometer if you only run one model – or it can be changed to a standard pot with a pointer and markings to indicate various heat settings. For general model use the glowplug would be operated at a brightness level that can clearly be seen during daylight conditions. To set this level, the glowplug would be removed from the engine and connected to the circuit described here. With power applied the required brightness level is set. Once this level has been established the glowplug would be disconnected then installed back in the engine. The process could be repeated for as many glowplugs or engines that you want, with each marked on a scale. It would be a simple matter of “dialling up” the required heat, connecting the Housed in a disposals case (which is actually much larger than needed!) and with a suitable front panel, the Glowplug Driver is ready for action . . . unit – and flying! A felt pen marker would then be used to mark the front panel indicating the ideal position for the control knob. After any variations of plug heat it would then be a simple matter to return the knob to the previously set position. Circuit operation. NAND gate IC1a in conjunction with its surrounding components The circuit is quite simple: one IC, one MOSFET and a handful of parts. March 2000 73 Compare the PC board component overlay above to the larger-than-life photo at left. Note that we did not use PC stakes (though these are recommended) nor did we connect the external meter in this photo. forms a variable duty cycle oscillator with a frequency around 3kHz. The frequency, though, is unimportant. What is important is the on time to off time ratio at the output of the oscillator. When power is first applied, capacitor C2 discharged so the inputs to IC1a are low. Therefore the output is high. This provides a charging voltage for C2 via D2, R2 and VR1. When it reaches the threshold voltage of IC1a, the output goes low again, discharging the capacitor via R1 and D1. When its voltage reaches the lower threshold of IC1a, the output goes high, starting the process over again. This continues as long as power is applied. Even if C2 was still charged from the last time power was applied, the same process happens. The IC output would be low, so C2 would discharge until IC1a’s lower threshold was reach-ed, when the output would go high, charging the capacitor, etc etc. The ratio of charging time to discharging time, or the duty cycle, is set by VR1. With VR1 at the lower end of its resistance, charging time is very short and discharge time longer. The charge time increases as VR1 is increased but of course can never equal or exceed the discharge time because of the much higher resistance of R1. With the values shown, the duty cycle varies from 17% on in the minimum position to about 60% in the maximum position. The remaining gates, IC1b, c and d square up the variable duty cycle waveform with the resulting waveform at R3 effectively being only high or only low – the transition between the two states is very fast. This high and low waveform is then used to switch MOSFET Q1 on and off. When the voltage at Q1’s gate is high, Q1 turns on. If it stayed this way it would apply almost the full supply voltage to the glowplug and the glowplug would quickly burn out. But Q1 doesn’t stay on for long: it turns on and off rapidly, the period depending on the setting of VR1. With Q1 “off” most These waveforms show the operation of the Glowplug Driver. The upper trace is the gate voltage of the Mosfet while the lower trace is the waveform across the Glowplug. Note that it is set to produce an average voltage of 2V from a 12V input. 74 Silicon Chip of the time, the glowplug is powered only a fraction of the time. The average power is within the heat range of the glowplug. The very low value resistor (R5 – 0.1Ω) is in series with the supply to the glowplug. The average voltage across this resistor is proportional to the current flowing through it. By connecting a moving needle meter (eg, an analog multimeter – but not a digital multimeter) across this resistor we can get an indication of current flowing through the glowplug. This can be useful as a blown glowplug cannot be detected unless it is removed from the engine. Why not a digital multimeter? Simply because the moving needle (or more correctly, moving coil) multi-meter is not capable of responding to the rapid changes in voltage across the resistor as Q1 turns on and off. Instead, it produces an average reading of the voltage – exactly what we want. The reading on a typical digital voltmeter would depend on precisely when the meter sampled the voltage In this case, the Glowplug Driver is operating from 6V and the duty cycle has been increased by adjusting trimpot VR1 (ie, for longer pulse times) so that the output is maintained at 2V. Note that while the frequency has increased, that is not important. and in all likelihood would produce completely meaningless readings. Construction All components are mounted on a single PC board, with the possible exception of VR1. As previously mentioned, “serious” modellers may care to make VR1 a standard, as distinct from preset, potentiometer and mount it off the board with a scale indicating various glowplug brightnesses. That we’ll leave up to you – however, a preset pot will normally be supplied in the Oatley Electronics kit. After giving the PC board the usual inspection for defects, solder the low-profile components in first (resistors and diodes) followed by the 5W resistor, LED, electrolytic capacitor and finally the IC and MOSFET. Take care with the polarity of all components which matter – diodes, electrolytic, MOSFET and IC. Given the very fast rise and fall times and modest current through it, the MOSFET should not need a heatsink. However, you could fit a small one to it if you wish. There are four connections to the board – power (+V and 0V) and of course the glowplug. These should be Parts List 1 PC board 80 x 41mm 1 case to suit Semiconductors 1 4093B quad NAND gate (IC1) 1 BUK453 N-channel Power MOSFET (Q1) 1 5mm LED (any colour) (LED1) 2 GIG or 1N4004 power diodes (D3, D4) 2 1N914 small signal silicon diodes (D1, D2) Resistors 1 47kΩ 1 6.8kΩ 1 2.2kΩ 1 22Ω 1 0.1Ω 5W 1 10kΩ potentiometer (see text) Capacitors 1 100µF 16VW electrolytic 1 0.01µF polyester Miscellaneous 6 PC stakes 6 lengths insulated hookup wire (including red and black) The PC board mounts upside-down on the assembly pillars in this disposals case from Oatley Electronics. No extra screws are needed. made via PC stakes for convenience but there is nothing to stop you soldering the connecting wires direct to the PC board, as we have done. If you are going to use a moving-coil meter (or multimeter) you’ll also need to solder two wires in for that. The prototype was housed in a small disposals-type case which we understand will be available with the kit if required. The PC board mounts upside down in this case, with the two mounting holes drilled out to be a snug fit on the recesses in the case assembly pillars. No screws are needed – the board sits in position when the case halves are assembled. Testing There is no need to connect a glowplug or anything else to the unit to test it. Simply connect power and ensure the LED lights. Varying the pot to its maximum and minimum should vary the brightness of the LED somewhat (but certainly not from full on to full off!). If this works, you can be reasonably confident your Glowplug Driver is working correctly. Now for the acid test. You may care to remove the glowplug from the motor for this part! Connect the glowplug to the glowplug leads (they’re not polarised so can go either way around) and turn the pot to its minimum. Apply 12V DC power and note the colour of the glowplug. As you wind the pot up, the glowplug should glow brighter and brighter – if you go too far it might say “enough” and give up the ghost. Leave the pot at the point where the brightness is at the required level. If fitting an external pot, make sure you mark the position on a scale of some type so you can return to that setting. And that’s just about all there is to this simple project. Happy flying (or SC boating, or car racing, or . . .) Where to get the kit: This project design and PC board are copyright (C) Oatley Electronics. They will have a complete kit available, including case & label, for $14.95 Contact Oatley Electronics on (02) 9584 3563, fax (02) 9584 3561; email sales<at>oatleyelectronics.com; website www.oatleyelectronics.com March 2000 75 T MAILBAG Criticism of Publisher’s Letter I am writing concerning the Publisher’s Letter in the Janu ary 2000 issue, entitled “Switch Off Those Monitors When Not In Use”. As it stands I would have typically ignored the article but I am motivated to write this note because one or two members of staff (at work) were influenced by it. My motivation resides not in a desire to criticise but with a desire to save my time from negating heresies. If I was inclined to “attack” the article I’d make the point that the article is about seven years out of date. This topic was hammered to death from about 1984 to about 1991; suf fice to say that leaving the computers running in an environment which has a fairly constant temperature prevents power supply failures and disk failures. Indeed electronic equipment is designed to run continuously. Take for example switchers, hubs and servers which have run for five years plus or have been off for a total number of hours not amounting to more than five days in as many years. In the next few weeks we will be upgrading two such servers. There is still nothing “wrong” with these servers; they have just been overtaken by technology and I hope someone will have a use for them because they will run for many years yet. Moreover, the operating temperature range of IT components is tending to increase rather than decrease, thus supporting the above strategy. Having made the case for “leaving equipment on” it is College policy to switch off for security reasons and it is interesting to note that the chief cause of failure for PCs is power supplies and hard disks. Reversing the policy (if we had 24-hour air conditioning) would correct this problem. As to monitors catching fire this is a possible (and yes I have seen this - back in 1989 – and it was a terminal and NOT a monitor) albeit highly improbable event nowadays and one could say with some confidence: impossible on a good quality monitor nowadays. In fact, I’d say the possibility of a burglary (of the entire kit) is more likely. 76 Silicon Chip With regard to the service life of monitors, it is important not to have the phosphors incurring the same state, ie, it is important to have, as much as practicable, the monitor undergoing a change of state and a good screen saver is worth a lot here. Furthermore, modern monitors will draw about 5W when in “power-down”. Try it; after 60 to 90 minutes you’ll be able to place your hand on the top of the monitor and barely be able to detect the warmth. You may be interested to know that we have serviceable monitors which are 11 years old and at 600 x 800 are as good as any new monitor! In respect of thunderstorms, electronic equipment is vulnerable irrespective of it being switched on or off although it does stand a slightly better chance switched off; but only slightly better. May I ask you to retract the “pull the plug from the socket” remark which is contained in the last few lines of Mr Simpson’s editorial. The very small amount of power and hence heat dissipation actually prevents condensation from the electronic boards. That is to say that in respect of computer power supplies the power supply doesn’t entirely switch off (unless the plug has been removed from the wall) when the unit is switched off and this is a very good thing for the above reason. Indeed one is well advised, after satisfying themselves that all is well at component level to have the unit plugged in for a number of hours prior to powering up after a period of prolonged inactivity or after a “big” cyclone or where the ambient conditions have been damp. Up here in the north our equipment lasts us a long time in very adverse conditions. It has to, with budgets being the way they are. Moreover we have to buy wisely. Hopping in the car and dropping a unit back on the counter of the supplier isn’t an option whey you’re 1600km away. I think I can say with some confidence that we, at the College, know how to look after our equipment. I think SILICON CHIP extends a great service to its readers in regard to “electronics” per se and I’m sure that the authors of the more technical articles have them refereed for the sake of everyone. I think the IT trade has a bad enough name as it is so (in the interests of raising standards) perhaps you could have your IT articles refereed too? Kyle Hargraves, Information Systems Manager, Eastern Pilbara College of TAFE. Comments: (1) Any monitor which has been running for 11 years but is still as good as new must have been subject to a miracle. (2) We strongly advocate unplugging the equipment as the only effective protection against lightning strikes. (3)When a computer power supply is turned off it consumes no power at all, unless it is an ATX model with a standby feature. Even those with a standby mode consume very little power and hardly enough to mitigate the effects of high humidity. In any case, high humidity is most damaging in monitors and hard disk drives and they won’t be protected by standby power consumption which only takes place in the power supply module. (4) Making the statement that it is impossible for any modern monitor to catch fire is just inviting fate to strike! Shortwave interference from Optus cables Since the Optus phone connection in September 1999 to my home in Grays Point I have been virtually unable to pursue my hobby of listening to shortwave radio broadcasts. I find there is a loud pulsating beat interspersed with intermittent tonal bursts and this affects all bands up to 30MHz. I have contacted Optus on several occasions and a company technician called and conducted tests, including a complete disconnection. He agreed the problem lay within the Optus cabling. But since then, despite repeated efforts to obtain information or a remedy from Optus, nothing has been done. Does anyone else have this problem or is it peculiar to this area? Can anyone offer a cure? Ashley Huggett, Grays Point, NSW. TRONICSHOWCASELECTRO EMC Technologies' internationally recognised Electromagnetic Compatibility (EMC) test facilities are fully accredited for emissions, immunity and safety standards. EMC Technologies Melbourne: (03) 9335 3333 Sydney: (02) 9899 4599 3990 FULL RANGE $ ELECTROSTATIC Now you can afford the legendary clarity, transparency, depth and precision of an electrostatic speaker. 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DVS5 Video & Audio Distribution Amplifier Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email - questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC's, Converters, etc. QUESTRONIX MicroZed Computers GENUINE STAMP PRODUCTS FROM Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 0409 036 775 Fax (02) 6772 8987 http://www.microzed.com.au Most Credit Cards OK All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only SURPLUS ELECTRONIC COMPONENTS at CHEAP CHEAP CHEAP PRICES! ICs, LCD Displays,Transistors, Diodes, Leds, Books, Connectors, Switches, Transformers, Fans, Relays, Speakers,Terminals, Resistors, Buzzers, Leads, Knobs, Batteries, Computer Accs. etc. FOR A FREE MONTHLY MAILER PLEASE CONTACT ROCOM ELECTRONICS STORE ADDRESS: 56 RENVER ROAD, CLAYTON VIC. 3168 POSTAL ADDRESS: BAG 620 CLAYTON SOUTH, VIC. 3169 PH (03) 9543 7877 FAX (03) 9543 4871 Email: sales<at>rocom.com.au Attention speaker builders and professionals World famous loudspeaker drivers make a return to the Australian Market. Call for information, data sheets, kit plans and free advice. Trade and OEM Enquiries welcome. Stock available mid December. Quantity discounts apply. Model RRP Introductory special Peerless 811827 dome tweeter, wide angle $69 $59 Peerless 811978 dome tweeter, shielded $89 $74 Peerless 810665 dome tweeter, rectangular $99 $85 Peerless 850122 woofer 6.5” CSX hi-end $135 $105 Peerless 831709 woofer 8” thick PP cone $125 $95 Peerless 831727 subwoofer, 10” thick PP cone $165 $135 Peerless 850146 subwoofer, 10” CSX hi-end $189 $160 ALSO STOCKING THE MOST COMPREHENSIVE RANGE OF REPLACEMENT SPEAKER FOAM SURROUNDS and parts including factory surrounds for Dynaudio, Tannoy, JBL, Scan-Speak, Cerwin-Vega and others. PHONE: (03) 9646 5115 FAX: (03) 9646 1574 POST: P.O Box 63 Port Melbourne VIC 3207 EMAIL: ortofon<at>labyrinth.net.au March 2000 77 PRODUCT SHOWCASE CD-R/CD-RW recorder has HDCD copy/playback Marantz has announced the introduction of its Reference Series DR-17 Compact Disc Recorder, a CD-R/ CD-RW deck incorporating HDCD recording and playback capability and double-speed disc finalisation. The Marantz DR-17 can record on both write-once CD-R discs and re-writable CD-RW discs, which can be erased and re-recorded upon. It offers complete flexibility in recording both digital and analog sources, including direct digital-to-digital recording capability from any digital source. Its built-in sampling rate converter automatically converts digital audio recorded at different sampling rates, such as a 48kHz data stream from a DAT recorder, to the 16-bit/44.1kHz CD standard when transferring data to disc. When dubbing CDs, the DR17, unlike other CD recording decks, automatically bypasses the sampling rate converter for the highest possible sound quality. The Marantz DR-17 is one of the first CD recorders to feature High Definition CD (HDCD) copy and playback capability. Unlike most home audio CD recorders that cannot properly record the HDCD encoding when copying an HDCD disc, the DR-17 perfectly transfers the HDCD informa- tion to the copied CD-R or CD-RW. It is playback-compatible with all HDCD-encoded discs, which offer greater resolution and a more natural musical presentation than standard CDs. There are optical and coaxial digital inputs for direct digital recording, as well as a set of analog inputs for recording sources such as cassette or LP. It also includes optical and coaxial digital outputs that allow it to be played through an outboard D/A converter or the digital inputs of a receiver or preamp/processor, plus a set of analog outputs for connection to a receiver or preamp. Its CD sync feature automatically begins recording when a CD (or other digital source) is played or it can be operated in manual recording mode. The DR-17 can also either automatically assign index (track) numbers to a disc being recorded or the user can add their own index numbers at the touch of a button. Its CD-RW edit functions allow the Safety outlets from DSE A new double power point from Dick Smith Electronics has a builtin safety feature to protect young children with a penchant for poking things in the holes. To operate, the plug must be inserted gently then turned to the right before power is connected to the outlet. This action should be beyond most young children and even if it is not, the plug is inserted so nothing else can be pushed into the outlet. It comes with a 10-year guarantee and like all similar products, must 78 Silicon Chip be installed by a licenced electrician. Priced at $18.90, the outlet is available from all Dick Smith Electronics stores and PowerHouse stores throughout Australia and by mail order through 1300 366 644 or their website at www.dse.com.au user to either erase tracks one at a time from the end to the beginning of a disc, or erase an entire disc at once. The DR-17 is fully compliant with the SCMS Serial Copy Management System, which limits digital copying to one generation. A key feature is its double-speed finalisation function, making a once tedious and time-consuming task fast and easy. Other features of the DR-17 include a precisely calibrated recording level meter, remote control operation via the supplied remote, a headphone output with adjustable level control and a full range of CD programming and playback functions. For more information, contact Jamo Australia on (03) 9543 1522. Want a 650-page book on DSP? Download it! Analog Devices have released a 650page book delving into the mysteries of digital signal processing (DSP). The Scientists and Engineers Guide to Digital Signal Processing, by Steven W Smith PhD is directed at scientists and engineers who need the power of DSP but do not have time to learn the rigorous theory and maths. A soft-cover version of the book is available from Analog Devices for $US40 (call US 1800 262 5643). But if you have the time (!) it can be downloaded free of charge from www. analog .com/industry/dsp/dsp_book Additional information is available from the book’s website at www.dspguide.com PICtutor – multimedia training system Emona Instruments have released the PICtutor kit from Matrix Multimedia. This is a self-contained training course that will teach users how to write, test and implement assembly language programs for the PIC series of microcontrollers. The kit includes a multimedia CD-ROM with 39 tutorial sessions as well as a Virtual PIC to test programs on-screen plus a PIC development board, based on a repro-grammable PIC16C84 with a parallel PC interface for program download from the assembler and various user interfaces. The PICtutor kit will teach stu- dents how to write assembly language programs for the PIC series of microcontrollers. The CD ROM’s tutorial sections will guide users through basic PIC architecture, commands and programming techniques up to advanced concepts such as watchdog timers, interrupt, sleep modes and EEPROM data memory use. The CD contains over 80 exercises and on-screen programming challenges. The deluxe version also includes a 7-segment LED display and an alphanumeric LCD display. Assembler and download (via printer port) software is included on the CD ROM. For more information, contact Emona Instruments on (02) 9519 3933, fax on (02) 9550 1378 or e-mail testinst<at>emona.com.au Altronics 3-2/3 digit DMM has RS232C interface Altronics have recently introduced a new digital multimeter (DMM) which not only offers advanced features in its own right but also has an inbuilt optically isolated RS232C interface. The meter itself has a 3-2/3 digit (2500 count) LCD display which also has a variety of other information available. It features six basic positions, each auto-ranging or manual ranging as required. There is a volts AC/DC range (250mV–1kV DC, 250mV –750V AC) with 10MΩ//15pF input impedance; resistance (250Ω – 25MΩ); amps AC/DC in three ranges (250µA – 10A continuous or 20A/30 sec); and temperature (with optional K-type probe): 20°–300°C. However, the resistance range also has available a continuity sound-er, a diode tester and a capacitance meter (.0025 – 25µF). There are another two ranges available via pushbuttons – a frequency meter measuring from 20Hz to 200kHz and a wireless electric field detection range measuring fields for 30 to >700V with a bargraph display. This latter function is also ideal for tracing live wiring connections, locating wiring breaks and distinguishing between active/neutral or active/ earth lines. With all of these features, the multimeter would be very popular in its own right. But it is the optional but lowcost RS232C interface which makes it really outstanding. It plugs into any spare “COM” port on a Windows 95/98 PC and, with the software provided in the interface kit, enables the PC to display a digital meter, an analog meter, a comparator meter and a data graphical recorder display (ie, data logging). For production work, service and troubleshooting etc, having a permanent record of all measurements can be a blessing! However, we believe this meter will be just as popular with advanced hobbyists and enthusiasts, simply because of the exceptional number of features offered for the price. A 9-pin serial connector is supplied but if a 25-pin COM port is all that is available, 9-pin to 25-pin adaptors are commonly available. The meter automatically senses when the RS232C connection is made and disables its own auto power down function. Because the interface is optically coupled, there is no danger to the computer even in the case of catastrophic failure or gross overload. A protective rubber holster and large shrouded probes are supplied, as is a comprehensive manual. You do not have to remove the holster to attach the RS232C interface – it clips through a slot in the rear. The meter has a recommended retail price of $149.00 (Cat Q-1080) while the optional RS232C kit, containing the interface cable and software, sells for $25.00 (Cat Q-1082). It is available from Altronics retail and mail order centre in Perth (1800 999 007) or from most authorised resellers. 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 March 2000 79 Video to VGA Conversion We’ve often seen converters for VGA (ie, computer video) signals to composite video but one back the other way is much rarer. According to Allthings Sales & Services, there are many applications where composite video needs to be displayed on a VGA monitor. Security/surveillance monitoring is just one area. VGA monitors are usually cheaper than video monitors or even many TV sets and the images they produce are usually superior – better linearity (less distortion), better resolution (higher bandwidth) and minimal overscan (on a video monitor you can lose up to 15% of the image). That’s the rationale behind this VGA-Convert system. It will convert any PAL, NTSC or SECAM colour/ monochrome composite and component S-Video (Y/C) video signal into a standard VGA signal. Almost any video source can be used – CCTV cameras, VCRs, TV tuners, DVD players, video games, etc, with no software or even a computer required – just plug the signal into the converter and the converter into the VGA monitor. You may want to use your existing 300MHz hand-held frequency counter Olympus digital camera sports world firsts The new Thurlby PFM1300 is a compact battery powered frequency counter offering the convenience of a hand-held multimeter. With an 8-digit liquid crystal display, it measures 5Hz to 25MHz and 20MHz to 1.3GHz in two ranges, with high sensitivity across the whole frequency range. A low- pass filter can be selected to reduce high frequency signal noise and ensure stable readings at lower frequencies. The system yields at least 7 digits of resolution per second of measurement time and can measure low frequencies to a resolution of 0.0001mHz. Despite its wide frequency range, the PFM1300 has low power consumption, enabling it to operate for many hours from a 9V battery. It can also be operated via a DC adaptor. A push-to-measure capability gives a virtually instantaneous reading followed by an automatic power-down after 15 seconds. This provides greatly extended battery life where continuous monitoring is not required. For more information, contact the Thurlby-Thandar nation-al distributor Emona Instruments on (02) 9519 3933, fax (02) 9550 1378 or e-mail test-inst<at>emona.com.au 80 Silicon Chip Along with many advanced features, the recently-released Olympus C-2020 ZOOM digital compact camera is the world’s first digital camera featuring an LCD monitor with a wide viewing angle. Until now most, if not all, digital cameras with LCD screens had to be viewed from virtually straight on, otherwise the image deteriorated rapidly. The 1.8 inch TFT colour LCD monitor on the C-2020 does not have this drawback – a very handy feature when composing a shot from an unusually high or low angle. The C-2020 is the first CAMEDIA offering a QuickTime Motion JPEG motion image capability for extended recording. This can record 15 seconds at 1.5 frames per second with a resolution of 320 x 240 pixels. Lower resolutions can give up to 60 seconds. The 0.5-inch CCD with 2.1 million pixels delivers detailed, high-quality shots. The CCD is coupled to a large diameter 3x optical zoom lens. This can be combined with a 1.6x, 2x and 2.5x digital zoom for a maximum zoom of 7.5x. There are three optional conversion lenses available, a telephoto, wide-angle and a macro. In addition to aperture-priority, shutter-priority and programmed AE, there is a manual exposure mode for shooting difficult subjects. Any shutter speed from 16 seconds through to 1/800 second can be selected, with apertures from f2.0-f11 (wide angle) or computer setup to monitor camera outputs, for example: this could be done at the touch of a button. VGA-Convert is priced from $119 and is available from Allthings Sales & Services, phone (08) 9349 9413, fax (08) 9344 5905; website www.allthings.com.au f2.8-f11 (tele-photo). There is also both manual and automatic focusing and auto bracketing is available with three or five step brackets. A wide range of special effects and features are also built in, including sepia, whiteboard and blackboard and black and white photography. A remote control is also included. The C-2020 camera uses SmartMedia technology and is supplied with an 8MB SmartMedia card capable of recording 82 or more SQ/VGA standard mode pictures (640 x 480 pixels) down to one SHQ, non-compressed picture at 1600 x 1200 pixels. It can also use the new 64MB SmartMedia card. When used with Olympus’ proprietary SmartMedia cards, extra features in firmware are accessible, including the ability to seamlessly stitch a number of shots into one panorama image. Images can be recorded in TIFF (non-compressed) or JPEG (compressed) formats, including JPEG for QuickTime. The camera measures 107.5 x 74 x 66mm and weighs 305g without battery or card. Retail price of the camera is around $2050 and it is available at better photographic outlets. For more information, contact the Australian distributors, R Gunz (Photographic) Pty Ltd, phone (02) 9935 6600; fax (02) 9935 6622; email gunzmail<at>gunzphoto.com.au SC SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au 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. All other issues are currently i n stock. $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. e & Get Subscrib count is D A 10% on ther Silic e O ll A n O is d n a h rc Chip Me $A SUBSCRIPTIONS  New subscription – month to start____________________________  Renewal – Sub. No.________________  Gift subscription  GIFT SUBSCRIPTION DETAILS RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. GST)**  $A159  $A83 New Zealand (airmail)  $A145  $A77 Overseas surface mail  $A160  $A85 Month to start__________________ Overseas airmail _____________________________  $A250  $A125 **1 binder with 1-year subscription; 2 binders with 2-year subscription YOUR DETAILS Your Name_________________________________________________ Message_____________________ _____________________________ Gift for: Name_________________________ (PLEASE PRINT) Address______________________ _____________________________ (PLEASE PRINT) Address___________________________________________________ State__________Postcode_______ ______________________________________Postcode_____________ Daytime Phone No.____________________Total Price $A __________ Signature  Cheque/Money Order  Bankcard  Visa Card  Master Card ______________________________ Card No. Card expiry date________/________ Phone (02) 9979 5644 9am-5pm Mon-Fri. 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 March 2000 85 Is this the best car computer . . . ever? By Robert Priestley We believe this car computer is right up there with the very best commercial units – and is probably better. We say this because we have yet to find any car computer – commercial or otherwise – which will do as much as this. Would you believe it can even time quarter-mile drags? Just as important is that it is attractively housed and also very small – so it won’t look out-of-place in your car. 86 Silicon Chip M ost car computers can measure the distance travelled, speed, elapsed time, fuel used and engine RPM. Likewise the OzTrip Computer – but it’s how this information is interpreted and presented that makes this computer unique. It has to be the most comprehensive system ever available for the “ordinary” car user (as distinct from motor racing teams with millions of dollars to play with. Then again, with the features it offers, it’s a fairly safe bet that some OzTrip Computers will find their way into race and rally cars!). Want to know the amount of fuel used for a trip? How about the trip cost? How about speeds – current, average or peak? And then there’s fuel usage – current consumption, fuel left, distance until empty, and so on. OK, so any car computer worth its salt can handle many, if not most of these tasks. It’s the extra things that the OzTrip Computer can do that makes this one worth building – even if you already have a car computer. There are in fact 27 different functions available (or 81 if you count the three different quantity display modes!). It’s not limited to just a car computer, either. It can be used as a sprint timer (accurate to tenths of a second over any distance). Think about that for a moment: standing 400m (“quarter mile”) timing from inside the car – no dragstrip timing beams and tele-metry needed here! If you have FEATURES • 27 Functions covering distance, speed, fuel, engine RPM & time. • 3 display formats – metric, US & imperial (km/miles, litres/US gallons/Imperial gallons) • 8-LED function display • Sprint timer over any distance accurate to one-tenth of a second • 3 trip meters • 1 count down meter • Programmable speed alarm • EFI and fuel flow sensor compatible (software selectable) • 4-digit 7-segment display with day/night brightness control • Small low cost unit (140 x 110 x 36mm) • Simple 4-key user interface • Audible alarm • Diagnostic functions • Optional serial data interface for telemetry and control • PC software available for virtual dashboard data logging • Can be used as a car or rally computer • Can be used as a boat fuel computer • Can be used in many general applications for counting or measuring the closed-off road or other suitable track, the OzTrip Computer will settle any arguments! It can be used as a rally computer – or even a boat fuel computer. It has diagnostic functions, an optional serial data interface for telemetry and control and there is even PC software available for virtual dashboard data logging. It could even be used as a general-purpose data logger not even related to vehicle use. When we say the OzTrip is comprehensive, we mean comprehensive! Details of all the functions of the OzTrip Computer are listed in Table 1. Each of the 27 functions has three readings – metric, US and Imperial. (Just in case you didn’t know, there is a difference between Uncle Sam’s gallons and good Queen Bess’s gallons – 1US gallon (3.785l) = 0.833 imperial gallon (4.546l)). Every time a new function is selected, a brief message appears on the display indicating the Function Num-ber selected. Physically, the computer is assembled on either two or three small PC boards. The third board is only required if input from other than an EFI engine is needed and/or a March 2000 87 fuel-flow sensor is wanted. The two (or three) boards mount back-to-back, connected by either wire links or resistors. All boards are housed in a small (140 x 110 x 36mm) case which can be mounted wherever practical. Because of its size, the OzTrip Computer doesn’t look out of place even in a sub-compact. A screen-printed, red acrylic front panel completes the project, hiding all LEDs and LED displays underneath until they are lit. The four pushbuttons used to select the various functions emerge through the front panel. A small number of connections are required to the vehicle but these should not cause any significant problems. We’ll examine these more closely later. Block diagram Despite its versatility, the OzTrip Computer contains relatively few components, most of the hard work being undertaken by a Motorola 68H705C8 microcontroller. This 40pin one-time-programmable chip is perfect for this application. It has 4 88 Silicon Chip x 8-bit input/output (I/O) ports, 384 bytes of RAM, 8K EPROM, 16-bit internal timer, serial port, interrupt pin and one Timer Input Capture pin. Just Fig.1: despite its versatility, the OzTrip Computer can be broken down into just a few elements. about every resource of this controller is used in this application. We will not attempt to describe what goes on inside the microcontroller; suffice to say that it manages the data presented to it and presents it in an understandable form. Perhaps the best way to understand circuit operation is to refer to the block diagram, Fig.1. On the left are the inputs to the microcontroller: the distance input and the fuel input. It is this raw data that the microcontroller uses to give you the various output functions on the right: the tone generator with its piezo buzzer (used to acknowledge inputs and also to warn you that you are travelling faster than your preset speed, among other things); the status LEDs and 4 x 8 digit LED displays, which of course give you the information in an understandable form. Not mentioned yet is the four-button keypad which you use to select the various functions of the OzTrip Computer and also the optional serial interface (bottom left) which is used if you really want to get serious and input and/or extract data from the computer. A typical application here would be a laptop computer for diagnostics or perhaps even a radio data link – maybe back to the pits? There is also a 5V power supply – actually, two 5V power supplies. One powers the microcontroller and most of the circuitry while the second The OzTrip Computer is assembled on two small PC boards which slot into a tiny plastic case (the third PC board shown here is for pulse conditioning in non-EFI vehicles). A red acrylic panel hides the components but allows the LEDs and LED readouts to shine through. We’ll cover full construction, testing and fitting details next month. gives a reduced output if the vehicle headlamps are turned on, thus dimming the LED displays (both individual and 7-segment) for night driving. We’ll take a much closer look at these various functions a little later. Circuit description As mentioned above, the two main inputs to the microcontroller monitor the speed of the vehicle and the amount of fuel being used. Both of these are “real time” measurements – that is, they present the microcontroller with a continually updated reading of both speed and fuel use. For the moment, we won’t concern ourselves with how this data is read, only what is done with it. The Speed Input conditioning circuits consists of R2, C1, ZD1 & R1 which are used to protect the input to Schmitt trigger IC3f, which produces a clean digital signal to the Interrupt input (pin 2) of the controller, IC4. Similarly, the Fuel Input conditioning circuit consists of R4, C2, ZD2 & R3 and is identical to the Speed Input protection. Two Schmitt triggers are used, IC3e and IC3d, so that the pulse is not inverted. The output of IC3d is connected to the Timer Capture Input, pin 37 of the controller. The microcontroller oscillator circuit consist of C3, C4, a 4MHz crystal (X1) and R5. The microcontroller RESET and Electrical Specifications Characteristic Typical Supply Voltage 12VDC Supply Current Operating 150mA Switched Off 11mA Speed Input Trip Voltage 5V Injector Trip Voltage 12-0-12V Accessories sense circuitry is formed around R12, R26 and ZD3. Because of the likelihood of noise coming in from the ignition wiring, these components protect the inputs to the controller by clipping any voltages above about 5V. D5 & D6 provide additional protection while R13 and C14 form a delay network to the input of the RESET pin. When the accessories are switched off, the RESET pin is at 0V holding the controller in a low power RESET state. When the accessories are switched on, the voltage at the RESET input pin is pulled high by R12 after a short delay while C14 charges. Eventually C14 is charged to +5V taking the controller out of RESET. The controller uses PB5 pin 17 to hold the RESET pin high. When PD3 senses the Accessories have been switched off, the controller executes a shut down procedure and clears PB5, March 2000 89 90 Silicon Chip March 2000 91 causing the voltage at the reset pin to fall to 0 and placing the controller in RESET. If the accessories input was used to directly control the RESET input then correct controller shut down could not be guaranteed and data could be lost. Moving now to the controller’s output ports (there are four of them), we can see that portA is used to drive the individual segments of the four 7-segment displays via transistor buffers Q5-Q12. The controller multiplexes all of the segments. To switch a segment on, the controller drives the output pins PA low. Port B0-B3 is used to address the appropriate 7-segment displays via driver buffers Q1-Q4. PortB (B4) also drives the audible tone generator, formed around IC3a,b & c and a piezo buzzer. When IC3a input is pulled low by PB4, the three inverters hold the piezo input high. But when PB4 goes high the output goes low, allowing the piezo transducer to sound. PortC is used to drive the eight indicator LEDs via transistor buffers Q13-Q20. Eight 1kΩ resistors are used for current limiting of the LED indicators. These resistors are connected between the two PC boards, not only forming the circuit elements but also providing some mechanical rigidity. PortD 7, 5, 4, 3 is connected to the four pushbuttons or “keys” (S1-S4). Each input is normally pulled high by a 10kΩ resistor and pressing a key pulls its input line low. The controller samples the keyboard inputs 200 Project Details This project and software is Copyright to Oztechnics Pty Ltd. A full kit can be purchased from Oztechnics. You can place your order on-line from the Oztechnics secured WEB server or make inquires via email. Visa, MasterCard and Bankcard accepted. All components, case and laser cut front panel filter are included in the kit. Oztechnics Pty Ltd PO BOX 38 Illawong NSW 2234 Phone: 02-9541 0310 FAX: 02-9541 0734 WEB: www.oztechnics.com.au Email: info<at>oztechnics.com.au 92 Silicon Chip times per second, or every 5ms. This is much faster than anyone can press and release a push button. PortD 0,1 provide the RX & TX serial communi- Table 2: the eight indicator cations. This sec- LEDs are split into two tion of the circuit columns. Here are their is optional – IC6 functions. Table 4: four pushbutton and C16-20 – and switches enter data to the is only required Table 3: the ranges of computer. The table at right if serial commu- values displayed for the (Table 6) shows the various combinations of keys. nications will be various functions. required. If fitting as a standalone unit to a vehicle, don’t bother fitting any of these components. The power supply is split into two. A permanent +5V supplied by IC1, a 78L05 regulator, is used to supply the controller and logic while IC2, a LM317 Display values variable regulator is used to supply While the computer has only a the variable display voltage. 4-digit display, it is capable of 6-digits When the headlights are switched resolution in many ranges. When a on, transistor Q21 is turned on via value exceeds the 4-digit display resD3 and the 10kΩ resistor. This effec- olution, the computer alternates the tively shorts the 2.2kΩ (R8) resistor, display between the first four digits which lowers the output of the LM317 and the last two digits on a 5:1 second voltage regulator. This has the effect of dimming the display for night-time driving. Provision has been made on the PC board for six components not used in this version of the computer: IC5, a 24C02 connected to PB6 and PB7; IC8, a 4020 divider and 4 x 1N914 diodes (D8-D11). Display interface The display consists of four multiplexed 13mm 7-segment displays and eight indicator LEDs. The 7-segment displays are used to display messages and values. The messages that can appear on the display are shown in Table 5. The eight indicator LEDs are split into two columns and indicate the current function being displayed, eg DIST REM for Distance Remaining of Journey. Table 5: here’s how to decode the various LED readout messages. March 2000 93 Reproduced life-size, this is the front PC board of the two (or three) in the OzTrip Computer. Two boards are required in EFI-engined vehicles, the third board required only for processing the output of a fuel-flow sensor (see below). ratio. The ranges that can be displayed are listed in Table 3. The LED indicators cover the main functions of the OzTrip computer. These functions are listed in Table 2. The ENTER LED lights when a numeric value is required to be entered into the computer from the pushbutton “keypad”. Keypad interface The keypad interface allows the user to enter all the data required to select the various modes of the computer and enter any required data. This is done through just four push-buttons or “keys”. Some actions require two keys to be simultaneously pressed. The key functions are shown in Table 4 while the various key combinations are listed in Table 6. Connections The computer requires a permanent +12VDC supply, an “Accessories” connection (ie, a +12V supply switched by the ignition switch), speed sender connection, fuel connection and a headlight connection so that the display can be automatically dimmed when the headlights are switched on. The speed sender connection to the computer can be taken from a number of sources. Many modern vehicles (most EFItypes) have an electronic speed sensor to drive the digital speedometer. This, or a speedo cable sensor can be tapped into on the back of the speedo A fuel flow sensor available from Oztechnics for those with carburetted or non-standard EFI vehicles. 94 Silicon Chip instrument panel. Alternatively, a wheel/tail shaft sensor can be installed to measure the vehicle’s speed. If the vehicle’s speed sensor is an analog (inductive) type then its output signal needs to be amplified and conditioned to drive the speed input to the computer. The optional PC board 3 has a high gain differential amplifier for this purpose. A typical speed sender unit produces eight pulses per wheel rotation. The engine type determines the fuel sender connection. Carburetted engines don’t have any fuel flow measurement and will require a fuel flow sensor to be fitted. Oztechnics have a low-cost fuel flow sensor available for this type of vehicle. It is an inductive type, which requires signal conditioning to drive the digital input to the computer. Signal conditioning for the flow sensor is also achieved on PC board 3. Entering values When a value is required to be entered into the computer the ENTER LED illuminates and the display clears to 0. The computer accepts the values entered according to the Function range selected; ie F1-F27 metric, F28-F54 US, F55-81 Imperial format. All values entered are converted back to metric and all calculations are performed in metric and displayed in the selected function range. Values are entered one digit at a time using the push-button “keypad”. There are four keys: a plus (+) and minus (-) key, a Set/Clear key and a Mode/Enter key. The + and - keys select the value of the digit (each time you press the + or key the value goes up or down by one, respectively). The Set/Clear key locks the current digit in and scrolls the display to the left to accept the next digit, while the Mode/Enter key either inserts a decimal point (first press) or acts as an Enter key (second press) and the value displayed on the screen is locked into the computer (see example below). If the Set/Clear key is pressed twice in succession within 0.3 second it clears the display ready for a new entry. Note that the computer will accept up to two decimal places. Enter any more and the computer will display the “Err” message and clear the display ready for another attempt. If no decimal places are required to be entered then the Mode/Enter key still has to be pressed twice to Enter the value. The first press inserts a decimal point, which has no effect on the value of the number entered and the second press of the Mode/Enter key acts as an Enter function. The computer can accept input values up to 999.99 even though the first digit scrolls off the display. For example to Enter “18.2” into the computer you would use the sequence of keys tabled below. This concludes the introduction to the OzTrip Car Computer. Next month we’ll conclude with the complete assembly, testing, installation and calibration procedures. SC Address http://www.oatleyelecrtonics.com PENTIUM MOTHER BOARDS with 70 MHz MICROPROCESSOR AND HEATSINK. Brand new from low profile cases with one bus connector but we supply a bus board from another system that fits. all for $40 SUPER LOW PRICE + LASER AUTOMATIC L A S E R L I G H T S H O W K I T: M K I I I . Automatically changes every 5 - 60 secs. Countless great displays from single to multiple flowers, collapsing circles, rotating single and multiple ellipses, stars, etc. (K115) + very bright 650nM laser module. $60 Kit+ case $75 Ph ( 02 ) 9584 3563 or 9584 3564 PO Box 89 Oatley NSW 2223 Fax 9584 3561 e-mail orders: sales<at>oatleyelectronics.com RADIO CONTROL MODEL SERVOS With good speed and high torque specs & a selection of output arms & disks + mounting screws. If you ask us we will send a free e circuit diagram to drive servos. $18 4IN VIDEO MONITOR SCREEN 81 X 59mm 12Vdc... 375mA 204 X 104 X 41mm Composite video in Res. 450 TV lines Weight 650g Intro price of $145 $145 $60 12V DC / 13W COMPACT FLUORESCENT TUBE: These CFL's must not be installed in 240V AC sockets. (Edison Screw), centre TWO MOTOR LASER LIGHTSHOW KIT positive. Equivalent to a 75W incandescent Inc. motors, mirrors, reversing switch & all lamp. 180mm long, 47mm maximum base ACN 068 740 081 electronic components. Lots of patterns, diameter: (CFL12) $25 flowers, stars etc. $16 24V DC / 10W Laser module $8 (AS ABOVE) Equivalent KEY-CHAIN LASER POINTER $10 . Line lens+$0.80...X-hair lens ( + ) to a 60W incandescent $0.80...Module (no case) only $8 IR LASER DIODE SECIAL 5mW 780nM lamp. : (CFL24) $23 (barley visible) Sharp LTO26 Req. 65mA.Diode plus focus lens (no housing) BRAND NEW! COMPUTER POWER $18....constant current driver kit $10 SUPPLIES...150W LITEON BRAND inc. BRAND NEW MICROPHONES!!! remote mains switch. +5V <at> 18A ...-5V <at> .03A DESKTOP MICROPHONE ...+12V <at>4.6A ...-12 <at> 0.3A...$12.50 Ideal for computers etc. DVE BRAND inc. onboard mains switch. +5V uni-directional electret mic. <at> 15A ...-5V <at> 0.3V ...+12V <at> 6A ...-12V <at> insert & terminated with a 0.3A...$15....IEC MAINS LEAD TO SUIT $2 stereo 3.5mm plug. for just $5 TWO TIECLIP TYPES "POWER LIGHT" MULTI TORCH: Great for mobile phones or computers.$3ea Great for the car! With warning $5 $3ea flasher and white defused light. Req. 3 x "D" cells not inc. (GT1) $3 NEW 80mm 12V FANS Ideal replacement for computer power supply fans. 12V <at> 0.15A...$4 or 4 for $12 NEW 5 IN 1 REMOTE CONTROL This remote is designed to work with 100’s of different TVs, VCRs etc.(max. 5 at a time)all you have to do is select the right one from the chart supplied. $22 or 3 for $60 (NEW) Drop Cable - RG11 Messengered Siamese: The F11 Series coax with (1) through (6) 22 AWG solid copper twisted pair conductors. Very low loss coaxial cable (10mm) with 4 cores (2 pairs) attached. With a >1Ghz bandwidth, Ideal for long spans between poles. Ea roll weighs 50Kg. (099939) $60 (per 300m / 1000' roll) HOUSED VIDEO CAMERAS CCD COLOUR IN SWIVEL CASE $190 CCD B/W IN SWIVEL CASE $99 PCB VIDEO CAMERAS B/W CCD CAMERAS $89 pinhole (60deg.), 92 deg,120 deg. add $10 for 150 deg. CAMERAS $70 PLUG PACKS TO SUIT $4 ASK FOR A FREE VHF MODULATOR and Plug Pack with each camera major cards with ph. & fax orders, *** KIT SUPER SPECIAL *** 4 CHANNEL AUDIO/VIDEO SWITCHER This is the most comprehensive video switcher kit we have seen. Inc. REC/PLAY output for VCR, put a security channel on your TV $45... Optional UHF modulator $18 Ask for a free plug pack with each A/V SW kit CFL INVERTER KIT our very popular inverter. Very Efficient Driver kit can drive a number of CFL’s from 12vdc. SPECIAL 1 inverter & 3 CFLs: $45 QUALITY AUSTRALIAN MADE FEATURE PACKED MINI ALARM SYSTEM CONTROL Features inc. boot release, central locking output, imobiliser output, indicator flash relay. Has with 2 key-fob transmitter keys. $99 CATALOGUE.... Ask for one with your next order. COMPUTER CPU HEAT SINKS Three types, 1st is a small self adhesive low profile $0.60...2nd is a larger clip-on type $1... 3rd type is larger still clip-on type $1... for pictures see our website UHF AUDIO / VIDEO TRANSMITTER KIT Kit inc all components needed to build A/V TX as pictured, 12Vdc <at>10mA operation. just $28 suitable plugcack $5 CAMCORDER AND ACCESSORIES NiCad. BATTERIES 6V 2400mAh. Multi-fit type. These are new and in original pack. Few types, Like (sbc5225) fits HITACHI, SABA, MINOLTA, RCA and equivalents. Just a fraction of the retail price at $22 FM TRANSMITTER MK 1 KIT: Our smallest transmitter. Range is about 50m. Stable design, Has high audio sensitivity. PCB: 46 x 1 5mm: (K10) $13 OPTO PACK: contains a total of 103 opto semiconductors, various colours, visible & IR PELTIER EFFECT DEVICES. All 40 X 40mm. 4A T 65deg. Qmax 42W $25 6A T 65deg. Qmax 60W $27.50 8A T 65deg. Qmax 75W $30 Comes with info to build cooler / heater NICAD 7.2VCHARGER / DISCHARGER Professional, built & tested fast NICAD charger and discharger PCB assembly. in a case. We supply a thermistor for temperature sensing + a cigarette lighter lead $7ea or 3 for 18. NEW AUSTRALIAN PLUG PACKS AT BELOW WHOLESALE PRICES G.E. 20VA 14VDC <at>700mA AUDIOVOX 9Vdc <at> 500mA AUDIOVOX 12Vdc <at> 400mA 9Vac <at>1A All $5 Ea. or 5 for $20 (can be mixed) (NEW) NEC Port Replicator 2400: Model #OP-560-65001. This is new in its original packaging. (099967) $25 Check out our “new look” website for more products. amazing cheap super bargains in our bargain corner & many items that we can not fit on this page NEW SUPER CHEAP PENTIUM NEW TV TUNER CARDS FOR PCs!!! $15 Watch TV on your computer while you work COMPUTERS. Throw away that old 386 / 486 computer. Replace it with one of these great hard. These cards are brand new & with S/W Prices subject to change without2000 95 notice March Post & Pack typically $6 ACN 068 740 081 SC_MAR_00 As you can see, the Interactor Aura amplifier module comes in an attractively finished plastic case. It has two thumbwheel controls and two slide switches to control its operation. There are two LED indicators, one for power and one to indicate the onset of clipping. A solution waiting for a problem Jaycar Electronics are selling Aura Interactor amplifiers for a knockdown price of just $5 and the challenge is to put them to good use. We’ve drawn out the circuit diagram and made some measurements. Now what can you do with them? By LEO SIMPSON For some time now, Jaycar Electronics have been selling an attractive little module which goes by the name Aura Interactor amplifier. The Aura Interactor was (is) intended to drive a body blaster cushion from a computer games console or perhaps from the subwoofer signal in a home theatre system. As sometimes happens, the product was a monumental flop and so Jaycar is selling them off by the bucket-load at $5 each. Probably most people will just buy them and throw them into the junk 96 Silicon Chip box to be “ratted” at some stage in the future. We thought that it was a shame that such a nicely finished module should end up wasted in this way. So we set out to draw up the circuitry and see if it has other applications. Fig.3 shows the complete circuit and right from the outset, we have to admit that we don’t fully understand how it functions. Nor do we have time to fully analyse it. Hey, it could have been interesting to run it through the Electronic Workbench simulator reviewed elsewhere in this issue. What would the simulator have made of it? Again, we didn’t do it simply because we did not have the time. Let’s just run through a brief description of the circuit. The input signal from a stereo source is coupled via a 3.5mm jack socket to switch S2a and then via a 1µF capacitor (C7) to the volume control R44. From there it goes to op amps U7a & U7d which provide about 75 times gain and function as a low pass filter, rolling off signals above 2kHz. The output of U7d drives comparator U6b which squares up the signal and feeds it to the two flipflops in U3, a 4013 dual-D flipflop. Thus if the output of U6b is 120Hz, for example, the two square wave outputs from U3 will be at 60Hz and 30Hz. These two signals are used to control two inputs, pins 10 & 11, on a 4051 1-of-8 demultiplexer, U4. As used here, the 4051 has eight inputs (pins 1, 2, 4, 5, 12, 13, 14 & 15) which can be switched through to pin 3 depending on the binary signals Inside the amplifier module. Note that it has quite a small heatsink for the class-B power stage and so it can only deliver its full power in short bursts. present at control pins 9, 10 & 11. We’ve already mentioned the signals fed to pins 10 & 11. The control signal to pin 9 comes from switch S1 and is high (+5V) in Music mode and low (-5V) in Games mode. By the way, all the ICs runs from ±5V supply rails so the CMOS chips effectively are running from a 10V supply. The signals to the eight inputs of the 4051 come from op amp U7d and via diodes D4 & D5 which considerably distort the signal and also via op amp U5b which provides a phase inversion of 180° (ie, it is a unity gain inverter). How does all this hang together? When the unit is in Music mode, the signal passes through the 4051 essentially unmodified to the following power amplifier. In Games mode though, the signal being fed to the power amplifier is practically unrecognisable, as can be seen in the lower trace of the scope waveforms Fig.1: these oscilloscope waveforms show the action of the 4051 in adding sub-harmonics. The top trace is a 120Hz sinewave while the lower trace is the mangled waveform which has a repetition rate of 30Hz. in Fig.1. The 4051 chops up the input waveform, adding bits that are out of phase and distorted, to obtain a waveform which has a substantial sub-harmonic content. As can be seen from the scope waveforms, the input waveform of 120Hz is turned into one with a repetition rate of 30Hz. This is just what would be required to rumble the Interactor cushion but it sounds pretty horrible if you feed it to a loudspeaker. The scope waveform of Fig.2 shows the frequency divider action of the flipflops. The top waveform is a 120Hz Fig.2: these waveforms show the action of the frequency divider circuit based on the 4013 dual flipflops, U3a & U3b. The top trace is a 120Hz sinewave while the lower trace is a 30Hz square wave, taken from pin 12, U3b March 2000 97 sinewave while the lower trace is a 30Hz square wave. Power amplifier Now let’s have a look at the power 98 Silicon Chip amplifier and like everything else in this circuit, it is unusual. Op amp U5a provides most of the voltage gain and it drives a complementary emitter follower pair, Q3 & Q4. These drive the output stage which is another complementary pair, Q1 & Q2, driven in common emitter mode. Neither of these transistor pairs has any quiescent current so the amplifier Fig.3: the circuit incorporates a frequency divider stage which provides control signals to a 4051 switching circuit and this adds sub-harmonics to the signal waveform when the unit is in Games mode. runs in pure class-B. Naturally there is some crossover distortion but the very substantial feedback applied back to the op amp’s input keeps the crossover distortion to fairly modest levels. Yes you can hear it and it means that it is not a hifi amplifier by any means but it is quite satisfactory for voice and other non-critical applications. The amplifier has two feedback net- works; one for AC signals, via C8, R36 and C101 and one for DC, via R12, C9 and R37. Why have they done it this way? It beats us. Much of the circuit seems unnecessarily complicated. March 2000 99 This view of the Interactor Aura amplifier module shows the two slide switches and the audio input socket (Source). Some readers have tried to modify the amplifier to provide some quiescent current but this is not really practical without re-designing the output stages. In any case, the amplifier can’t handle much quiescent current because it has a very small heatsink considering its nominal maximum output rating of about 20W into a 4Ω load. In fact, this level of output power would only be possible in very short bursts because the heatsink is just not capable of dissipating any appreciable power. Threshold muting One way in which the module does reduce the effective power output or duty cycle is with the threshold muting circuit, involving comparators U6a & U6d. U6a has its non-inverting input connected to the wiper of potentiometer R45. This is labelled as a “filter” control on the Interactor case but it has nothing to do with signal filtering. Instead, it acts as a signal threshold control for U6a; signals below the preset threshold do not pass through. Those that do pass through U6a are rectified by diodes D2 & D3 and the resultant DC voltage is fed to comparator U6d which is used to switch the Inhibit (INH) input, pin 6, of the 4051 demultiplexer, U4. Thus in the Games mode only high level signals from computer games, such as explosions, gunfire and so on, are fed through to be mangled by the signal chopping circuit and then to the power amplifier. 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). Buy five and get them postage free. 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. 100 Silicon Chip REAL VALUE AT $12.95 PLUS P & P The remaining comparator in the LM339 package is U6c. This is used as a clipping indicator and it monitors the input signal to the power amplifier. The power supply is quite well designed, considering that this is a consumer product which would be normally subject to cost restraints. The separate transformer module provides 23V centre-tapped to the bridge rectifier and this produces about ±17V from the 6800µF 25VW filter capacitors. These unregulated supplies are fed directly to the output stages of the power amplifier. Low power 3-terminal regulators (U1 & U2) are used to provide ±5V to the op amps and CMOS chips, as noted above. Gift voucher That about wraps up the circuit description and we hope that readers can take the module and find interesting applications for it. In fact, Jaycar Electronics are offering an additional incentive for experimenters to put their thinking caps on. They are offering a $200 gift voucher, redeemable at any Jaycar Electronics store, for the best circuit modification or application for the Aura Interactor module. Send your idea together with a good description to Aura Competition, Jaycar Electronics, PO Box 185, Concord, NSW 2137. The offer closes SC on 31st May, 2000. VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The Hellier Award, Pt.2: the simple superhet vs the TRF Last month, we talked about the latest Hellier Award which was restricted to sets with just two valves. There were eight entrants and we asked which type of set would have the best performance – the TRFs or the simple superhets? Who were the judges for the award? Max Johnson and I took on the task and that eliminated both of us from the competition. Max and I worked together to assess the more technical matters while my wife Lyn judged the aesthetics. The judging was divided into six areas, which gave members with different skills an even chance of achieving the top marks in the award. All were marked out of 100, with 20 for the cabinet, 20 for the operation of the receiver, 15 for the chassis (mechanical), 15 for the chassis (electronic), 15 for innovation and 15 for the information supplied on the set. Cabinets As can be seen in the photographs, the cabinet styles varied. All were made of wood, except for one. Timber is much easier to work with than metal and who has the necessary moulding equipment for plastic or bakelite cabinets? In fact, several of our members are very good at woodwork as can be seen in the photographs. There were three polished cabinets, two painted, one stained and one with a leatherette covering. One innovative set used part of a 2-litre blue plastic ice-cream container as the significant part of its cabinet, although the baseplate was made of wood. Although the cabinets were excellent in many ways, some members dipped out when it came to enclosing the chassis. For example, some had open backs which would let mice or other pests into the sets, although these sets did have good ventilation! Others excluded the pests but the ventilation was poor, while others kept the pests out by using fly wire or by drilling small holes in the back and bottom of the cabinet. Most got the baffling of the speaker spot on, at least as far as the size of the cabinet would allow. Most sets were also easy to dismantle. Perhaps the best as far as service was concerned was the plastic-enclosed set made by Noel. Three screws in the front of the set allowed the set to be withdrawn with the dial and controls intact and with access to both sides of the chassis for service. Operation This innovative set used inductance tuning (which was quite effective) and a plastic icecream container as part of the cabinet. Now this is the real test as to whether a set is worth having or not – after all, if it doesn’t work what good is it? The sets were to be easy to use, with no cranky or critical controls so that they could be operated by all members March 2000 101 Des (left) and Gary (right) holding their winning entries in the 1999 Hellier Award. Both sets were simple superhets using a converter and a regenerative IF on 455kHz plus one stage of audio amplification. of the family. It was expected that the sets would need an aerial 15-20 metres long and about 5 metres high. The test aerial was around 23 metres long and 4.5 metres high. The performance of individual receivers varied from quite insensitive to “red-hot”. Because the club members had quite a bit of latitude in what they built, this showed up in the relative performance of the sets. One entry was a stock standard 2-valve regenerative set using a 6J7G and a 6V6G. To the best of my knowledge, it is based on “Tiny Tim II” circuit. It is a beautiful set to look at, being the larger of the two Empire State style sets in the photograph. Because it has only two active stages, it really needs to be quite close to stations if loudspeaker reception is to be realistically achieved. It could be considered a typical replica from the early 1940s and a very nice one at that. There were two sets which were nominally based on a design originally published in “Radio and Hobbies” around 1950/52. This set was called the “Christmas Box” and is a 2-valve TRF set using a 6N8 as a tuned RF amplifier and detector. One tuned circuit is in the grid and another in the plate circuit. The RF amplifier has regeneration applied to it but it is not a regenerative detector. The audio is applied back through the 6N8 in a reflex circuit and then passes to a 6M5 audio amplifier stage. The circuit is not unlike the socalled Astor “Football”, although the performance of the two sets entered in the contest was possibly not as good due to the fact that suitable aerial and RF coils were unavailable. One member, Eric, experimented with the Christmas Box circuit and found that it was very touchy in a couple of areas. The two tuned circuits were too closely coupled, with the RF stage being regenerative, so he isolated the tuned circuits by using a 6BL8 triode-pentode. The pentode took the place of the 6N8 and its output was RC coupled to the triode grid. The RF coil was in the plate circuit of the triode and this gave much improved stability – see Fig.1. By the way, the high plate voltages are applied to one side of the tuning gang via L3 so exercise due caution if experimenting with this circuit. The second problem he experienced was that the preset regeneration had to be set at the high-frequency end of the dial. If set near oscillation at the low frequency end, it oscillated at the high-frequency end. This meant that the set was not as sensitive at the low-frequency end of the dial as it could be. To overcome this problem, he experimented with a 3-gang tuning capacitor, using one gang in series with the regeneration control, in an endeavour to increase regeneration at the low-frequency end. He hadn’t finished experimenting with this arrangement at the time of the competition so hadn’t quite got it going to his satisfaction, but was confident that this would work quite well. Simple superhets The most common sets built by members were simple superhets. In amateur radio circles, these sets were called “supergainers” and were used right up to the early 1960s. One company, Raycophone, had a small set called a “PeeWee” which used this principle and others probably did too. In this competition, the radios consisted of a converter (typically 6AN7) and a regenerative IF with a pentode output (typically 6GW8). The con- Fig.1: the original Christmas Box RF circuit and the amended circuit (right). The triode stage serves to isolate the two tuned circuits, thereby giving much improved stability. Note that the high plate voltages do appear on one side of the tuning gang which could present a shock hazard. 102 Silicon Chip Vintage Radio Repairs Sales Valves Books Spare Parts See the specialists * Stock constantly changing. * Top prices paid for good quality vintage wireless and audio amps. * Friendly, reliable expert service. The two “Empire State” radios were housed in beautifully-made cabinets. verter circuitry is quite conventional and in each case is typical of what you would find in most radios using the 6AN7(A). A couple of sets used different valves – one used a 6AN7 and a 6AB8 and the other a 1A7GT and a 1D8GT. The IF circuitry is very different to that in most superhet receivers. There is one IF transformer at (nominally) 455kHz, as used in a conventional IF stage. This feeds the grid of the 6GW8 triode which is wired as a regenerative detector. The IF transformer had to be modified by adding a feedback winding near to the grid winding and this involved dismantling the IF transformer. Most had considerable trouble getting the regeneration to work properly but all ultimately succeeded, using 100-150 turns of thin enamelled wire to get it to operate effectively. The regeneration is adjusted to just below oscillation and as the IF (intermediate frequency) is fixed, the setting doesn’t alter with changes in the tuning as it does with Christmas Box sets. Following the regenerative detector, the pentode section of the 6GW8 amplified the signal to a comfortable speaker level. In fact, the “giant” mantle set with the 12-inch speaker was quite loud if the gain was turned up. No AGC Because none of the sets had AGC (automatic gain control), the volume control has to be adjusted when tun- ing different stations but this wasn’t a real problem. Most of these sets used a potentiometer in the cathode of the converter, with the moving arm to earth. The aerial is connected to one end of the potentiometer track, while the other end of the pot goes to the cathode of the converter via a low value resistor – see Fig.2. These sets performed quite well, the exception being the one with the battery valves which hadn’t been completed. The receiver that really set us all back on our heels was the “giant” mantle set. Harvey, the constructor of this set, really worked hard at it (not that others didn’t) and got results better than expected for such a simple set. In daylight, a few stations were expected but there were many Melbourne stations, both national and commercial, that provided com- Call in or send SSAE for our current catalogue RESURRECTION RADIO 242 Chapel Street (PO Box 2029) PRAHRAN, VIC 3181 Tel (03) 9510 4486 Fax (03) 9529 5639 fortable listening here at Mooroopna in Northern Victoria. Mooroopna, by the way, is about 150km away from these stations. As to which sort of set is better, the answer is unequivocal – the simple superhets thoroughly thrashed the TRFs. However, a better design for the TRFs would have made them stronger competitors. One of the very real advantages of the superhets was that the regeneration only had to be set once which made them easier to operate for non-technical people. Chassis details Fig.2: this is how the volume control was arranged in most of the simple superhets. One end of the pot went to the aerial while the other was connected to the cathode of the converter valve via a resistor All members had their own style of chassis construction but in general they were all conventional upturned boxes. Some were made out of aluminium and some out of thin galvanised iron sheet. All were well-made although one entry used metal that was a bit too thin (it was probably all that he could find in his junkbox). What’s more, the main chassis-mounted parts were all easy to access, so that they could be quickly removed and replaced if necessary. The soldering was also generally March 2000 103 of something innovative. Noel’s plastic (icecream container) cabinet was certainly different and he used parts in his radio that are readily available to anyone. He was also the only entrant to use inductance tuning (which was quite effective) and his set was the easiest to access for service. Information The winners – Gary and Des with the Hellier Award shield. good, with very few examples of possible dry joints. It was very pleasing to see that most entries had a logical progression of components, with short leads (wherever possible) and with most inputs and outputs kept well apart. The components were generally easy to get at for service and most of the contestants remembered to install the parts so that their values could easily be read in-situ. It usually takes no more effort to do this than to place the parts so that their values are hidden. Colour coded wiring makes servicing so much easier too. I have always endeavoured to use different coloured wires for different functions and this is particularly important when using a wiring loom. The attention to detail here helped to make many of the sets real winners in this area. The high-tension (HT) feeds to various parts of the circuits were also well decoupled which is important when it comes to extracting the best performance from the sets. Innovative ideas This is an area where it’s hard to come up with anything really new. However, slightly different ways of doing things, such as a better method of gaining access to a set or a different method of tuning, could be examples This is an important area as it is so much easier to operate and service sets if the appropriate information is available. In the past, many manufacturers supplied information on the circuit, technical specifications, operating methods, methods of disassembly, parts lists and anything else that they believed to be important. Wouldn’t it be wonderful if this happened all the time? It doesn’t, of course, as you will appreciate from the stories in “Serviceman’s Log”. He often has trouble even reading circuit diagrams because the reproduction quality is so poor and there are frequently errors in the diagrams. Most of the entrants supplied relevant information for their radios, although one or two needed to be just a little more careful to ensure that all the collated information was up-todate. This can be the boring side of a project but the job isn’t finished until the paperwork is complete! Finally, although all this may seem to be concentrating on just one club and its activities, the intention is to give readers an idea of what vintage radio buffs can do in a club SC atmosphere. MORE FROM YOUR EFI CAR! Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication  Making Your EFI Car Go Harder  Building A Mixture Meter  D-I-Y Head Jobs  Fault Finding EFI Systems  $70 Boost Control For 23% More Grunt  All About Engine Management  Modifying Engine Management Systems  Water/Air Intercooling  How To Use A Multimeter  Wiring An Engine Transplant  And Much More Including Some Awesome Engines! AVAILABLE DIRECT FROM SILICON CHIP PUBLICATIONS PO BOX 139, COLLAROY NSW 2097 - $8.95 Inc P&P To order your copy, call (02) 9979 5644 9-5 Mon-Fri with your credit card details! 104 Silicon Chip 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. Bridge operation for LM3886 Back in February 1995 you published a stereo amplifier module based on two LM3886 monolithic power chips. I have just obtained a couple of these modules and my question is can they operate in bridge mode to double the power output? (A. B., Marrickville, NSW). • The answer is yes. The module effectively only requires the addition of a 22kΩ resistor to enable two power amplifiers to drive a common 8Ω load. We published the details, along with the modified wiring diagram and a suggested power supply, in the June 1996 issue. In theory, this suggested setup could deliver 120 watts into 8Ω. Speed alarm has dis play problems I have built the Speed Alarm described in the November & December 1999 issue and it works well, except for a display problem. False triggering of segment “a” in Displays 1 and 2 make 10 and 100 look like 70 and 700. Is there a problem with the RB5 output of the PIC? TV pattern generator software I have obtained the software for the Colour TV Pattern Generator (SILICON CHIP June & July 1997) and I would like to know how I go about changing the type of patterns on the screen. I cannot understand the binary (hex codes in Basic program) coding and how they operate the encoder chip. Can you explain how each hex byte is used? (G. V., via email). • The Colour TV Pattern Generator hex codes refer to the graphical representation (Fig.5) shown on During “Up” and “Down” the display shows 0 and 9, 10 and 19, 20 and 29, etc. Is RB6 being driven in error? Display of what should be 50 indicates 90. Similarly, what should be 55 is 99, 60 is 80, 65 is 89 and so on. What is the problem likely to be? (D. H, via email). • You have a problem of shorts between the relevant segment lines on the PC boards. Check the tracks and also between the relevant pins of the headers. If you break the header connection for the faulty “d”segments and the fault is still present, the short will be on the display board. Look for very fine solder splashes. If you can’t see any, try scraping between the relevant tracks with a sharp knife. Problems with audio signal generator I am having a few problems with the Audio Signal Generator described in the February & March 1999 issues of SILICON CHIP. When I first assembled the circuit, I actually flipped the LEDs instead of just changing the K and A markings on the circuit board diagram. Obviously this did not work at all and could have damaged some other page 20 of the June 1997 issue. D0 is for the checkerboard pattern, D1 for the dot, D2 for the crosshatch, D3 for the raster, D4 for blue, D5 for green, D6 for red & D7 for the sync. A low value will be a 0 on the particular bit while a high value will be a 1 on that bit. The Fig.5 representation shows the high and low voltage required for each bit. The hex value then becomes the conversion from binary of D0-D7. Thus 00000000 is 00 in hex with 11111111 being FF in hex. The hex codes not only provide the information about signalling a dot on the screen but they also position the dot. The memory is parts. I discovered the error and put the LEDs in so that the flat side was to the right when one placed the board so that the knob panel was closest to the observer. I assumed that the “K” leg was the one that connected to the “cup” inside the LED. Now, with all the ICs removed from the board, I blow fuses almost every time I turn the box on using the switch supplied with the kit. However, if I leave the switch on, replace the fuse and turn the box on from the wall, the power stays on. With a line voltage of 254VAC, the transformer secondary windings produce 17.2VAC and 34.4VAC. With all the ICs in place, I get the same fuse blowing problem. The heatsink on REG3 is also really hot. On the lowest setting of S2, I get a maximum of 45Hz when the circuit is oscillating (which is only intermittently). None of the selections on S2 produce more than 5xxx values so the values I am getting are about half what should be there in Hz. I have peeked inside the LED - LDR chamber to see if I could detect any light from the LEDs and found none visible. In fact the voltage coming out of Q5 to the LEDs is a constant. While I was checking for voltage levels divided into 210 locations per line and there are 312 lines. The first 40 memory locations are for the line blanking interval while the remaining locations set the field or screen display. Each memory location in the field is a pixel or picture element and we must program each pixel along each line. For example, the 125th location is the centre of the screen while the 210th location is the far righthand side of the screen. This is why there are 210 hexadecimal codes per line even if we only want a single dot on the screen. The black parts of the screen must be programmed in as well. March 2000 105 Battery charger rates too high I’ve just purchased a Multipurpose Fast Battery Charger as featured in the February & March 1998 issues of SILICON CHIP. It is my understanding that this kit supplies a peak current of 6A, regardless of battery capacity (C). I am a little concerned as I understood that good practice for charging SLA batteries was to use a peak charge current of C/4 (or C/5 to be conservative – as used in your March 1990 SLA battery charger based on the Unitrode UC3906 IC). Is it possible to simply add a switched array of resistors to the project in place of the fixed resistor at the IB output (pin 2) to allow the maximum charge current to be between pins 1, 2 and 3 on IC4, the system started to oscillate again for a short while. I opened the LED - LDR chamber and flashed white light on and off to see if that would start the oscillations again with no joy. Can you give me a few clues? (S. D., via email). • We think you have a short somewhere on the PC board and this is causing a heavy current flow. Check the supply voltages carefully and also check each output from the regulators. You may have one of the electrolytic capacitors inserted with the wrong polarity, so check this carefully too. Incorrect orientation of the LEDs will not cause any de struction of components. The LEDs should be placed with the flat side toward VR1. Railpower setup confusion I have just got my Railpower Controller (October, November & December 1998) to work. However, could I suggest that you include an errata for those electronically challenged like myself? For the setup procedure you indicate pushing the speed up button until full power is reached and then adjusting the output voltage on the rails. To do this I put down the transmitter, picked up a suitable screw 106 Silicon Chip selected? I’d also considered the resistor on the Vref/Rref pin 20 but I believe that this resistor also has some bearing on the oscillator frequency. Sure this would negate a bit of the “fast” output of the charger but may be better for SLA batteries in the longer term. (P. J., via email). • The Multipurpose Fast Battery Charger does provide fast charge for NiCds and SLA batteries. If you do not need the batteries fast charged then they could be charged at a reduced rate. You could then use switched resistors at the IB input (pin2) as you suggest. In terms of battery life we have not heard of any problems associated with fast charging. In fact, the ability of the charger to sense the charging endpoint accurately prevents damage. driver and adjusted but to no effect. You might have indicated that it was necessary to keep the trans mitter button depressed. This might sound like a minor point but it would have saved me 20 hours looking for a fault that was not there. The controller seems to work well on all but one of my locos which is impossible to stop in any reasonable distance even with inertia off. I assume that this will have something to do with the back-EMF you discussed in your article and that the particular motor may be slightly different. It runs very well on a standard controller. Is there a fix for the loco as I want to try to run the whole layout with your controllers if possible? (B. N., via email). • The instructions for setting the maximum track voltage do mention holding down the speed up button and then adjusting VR1. However, we could have emphasised the point “to adjust VR1 with the button still pressed”. The loco back-EMF should not greatly affect the stopping rate as this is set by the rate of discharge of capacitors C1 and C2. However, you can adjust the back EMF effect by decreasing the gain of IC8c. Changing the 220kΩ resistor between pins 1 and 2 of IC8c to 100kΩ will reduce this gain from 3.2 down to 2 and this may be enough for your locomotive. Leading zero blanking for the 5-digit tacho I am using the 5-Digit Tachometer (SILICON CHIP, October 1997) with a dyno and have separated the display to operate in a portable handheld unit also containing LCD readouts of horsepower and car speed. The tacho works exceptionally well but the large number of connecting wires to the display makes the remote cable a little larger and less flexible than I would like. As the leading digit in the tacho readout only needs to be a “1”, can I reduce the number of interconnecting wires by multiplexing or using a 4½-digit LCD without effecting the performance or update speed of the tacho? (L. J., via email). • The 5-digit tachometer can be wired so that it will only show a 1 or a blank on the most significant digit. This would save you 5-wires. You would need to keep the connections for the “b” and “c” segments at pins 11 and 12 of IC12 connecting to pins 4 and 6 of DISP5. As it stands the circuit is not entirely suitable for driving liquid crystal displays. This is because the segments need to be driven from an AC signal at about 25Hz. Also you would need a backplane signal which is 180° out of phase to the drive signal. A 32Hz signal is available at pin 15 of IC14 and it could be used to gate the blanking inputs of IC8-IC12 via AND gates. An inverted 32Hz signal (via an inverter) could provide the backplane signal. However, the use of an LCD will not reduce the wiring count from main board to the display. How to wind the speed sensor I have a question about the speed sensor coil used in the Speed Alarm which was featured in the November & December 1999 issues of SILICON CHIP. I have never wound a coil before and I would like to know if I have more than the 500 turns will this matter? And does the shielded lead from the coil terminate on one side of the coil and the signal on the other or does the shield go to ground? (C. S., via email). • The number of turns is not all that critical but try to get 500 on. One side of the coil is connected to the shield – it does not matter which. The shield is effectively connected to chassis at the PC board end. Electronic rust preven tion kit wanted Do you have any information or a kit available for electronic rust prevention? I am very interested in making several for my car and motorcycle but have not been able to come across a kit or schematic. I have searched all over the net and have come across two commercial products made in Australia which are available but at considerable cost. Surely the electronics in such a project could not be that complex or costly. (H. M., via email). • We do not have any information on electronic rust prevention and nor do we see how it can be made to work on a car. Presumably there needs to be some sort of sacrificial anode as used in boats or hot water tanks but how such a system could be used on a car we are unable to say. Transformer for electric fence controller I am building the electric fence controller described in the April 1999 issue. I have everything except the E30 transformer assemblies. Could you please tell me where I can obtain these? (C. D., via email). • You may be able to obtain the E30 transformers from the Dick Smith Electronics kit department, at their head office at North Ryde. Phone (02) 9937 3200. Alternatively the ETD29 core assembly could be used but it will not fit readily into the PC board holes. It is a little larger but the cores are similar and so you can expect similar results. These cores, former and clips Capacitor failure in fence controller I have a rather odd problem with the electric fence controller described in the April 1999 issue of SILICON CHIP. I constructed it with no problems and it tested out OK on the bench as per the article. The 340V was easily set and the spark test was OK, so I installed it on the fence (three runs totalling about 450m) and left it happily ticking away. Unfortunately, some two hours later it was still ticking but with no EHT present. After some time I discovered that the dump capacitor had “lost” capacitance. A temporary replacement brought the unit back to life. All the rest of the circuit seemed to be operating as far as I could tell from measurements so I obtained another dump capacitor and fitted it. However, a few hours later it are available from Farnell Electronic Components Pty Ltd. Phone 1300 361 005. Their catalog numbers are 178-505 for the cores (2 required per transformer assembly), 178-506 for the bobbin (1 per transformer assembly) and 178-507 for the clips (two required per transformer assembly). How to repair a remote control Do you know of a way to repair a TV remote control in which it appears the button contacts have lost their conductivity? (D. M., via email). • WES Components have a rubber keypad repair kit, catalog code CW failed again. Because the two capacitors from the supplier were from the same batch and I knew that they didn’t have any more in Hobart, I bought a 6µF 440VAC motor start capacitor and fitted it, thinking the originals may have been from a bad batch. This ran overnight and then failed with the same symptoms as the others. I am completely at a loss to know why this is happening so would really appreciate any assistance you could give me. (K. R., via email). • The 7µF 250VAC capacitor should cope with the constant charge and discharge cycles. We have not heard of this problem before. You could try increasing the values of the 220Ω resistors which charge the capacitor to, say, 470Ω each. This will limit the charge current. Also wind more turns onto inductor L1 to limit the discharge current. 2611 at $15.95. You can phone them on (02) 9797 9866. Notes & Errata Digital Voltmeter For Cars, February 2000: the 10µF capacitor adjacent to pin 2 of IC2 on the component overlay diagram on page 28 should be 1µF, to agree with the circuit on page 25. Remote Modem Controller, August 1999: the circuit on page 19 shows the LED incorrectly. It should be connected between the +5.12V rail and pin 16, rather than between pin 16 and 0V, as shown. The PC board SC is correct. 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. March 2000 107 REFERENCE GREAT BOOKS FOR NEW NEW NEW NEW AUDIO POWER AMPLIFIER DESIGN HANDBOOK 77 95 NEW $ By Douglas Self. 2nd Edition Published 2000 A uniquely detailed and practical text on the design of audio amplifiers from one of the world’s most respected audio authorities. The new 2nd edition is even more comprehensive, includes sections on load-invariant power amps, distortion residuals, diagnosis of amplifier problems, reactive loads on amplifiers, how to make speakers draw higher currents and the practical side of variable temperature coefficient bias generators. 368 pages in paperback. VIDEO SCRAMBLING AND DESCRAMBLING for SETTING UP A WEB SERVER If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! Encoding/decoding systems (analog and digital systems), encryption, even schematics and details of several encoder and decoder circuits for experimentation. Intended for both the hobbyist and the professional. 290 pages in paperback. NEW 2nd Covers all major platforms, software, links and web techniques. It details each step required to choose, install and configure the hardware and software elements, create an effective site and promote it successfully. 273 pages, in paperback. Satellite & Cable TV by Graf & Sheets By Simon Collin. Published 1997. 59 $ Edition 1998 TCP/IP EXPLAINED 95 90 Assumes no prior knowledge of TCP/IP, only a basic understanding of LAN access protocols, explaining all the elements and alternatives. Combines study questions with reference material. Examples of network designs and implementations are given. 518 pages, in paperback. By Tim Williams. First published 1991 (reprinted 1997). $ 59 Includes grounding, printed circuit design and layout, the characteristics of practical active and passive components, cables, linear ICs, logic circuits and their interfaces, power supplies, electromagnetic compatibility, safety and thermal management.302 pages, in paperback. 95 LOCAL AREA NETWORKS: An Introduction to the Technology ELECTRIC MOTORS AND DRIVES Want to become more familiar with local area networks (LANs) without facing the challenge of a 400-page text? . Gives familiarity with the concepts involved and provides a start for reading more detailed texts. 191 pages, in paperback. For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. By Austin Hughes. Second edition published 1993 (reprinted 1997). By John E. McNamara. 2nd edition 1996. O R D E R H E R E 65 $ THE CIRCUIT DESIGNER’S COMPANION By Philip Miller. Published 1997. $ NEW NEW NEW 65 $  AUDIO POWER AMPLIFIER DESIGN..................$77.95  VIDEO SCRAMBLING/DESCRAMBLING.............$59.95  TCP/IP EXPLAINED.............................................$90.00  LOCAL AREA NETWORKS..................................$65.00  SETTING UP A WEB SERVER.............................$65.00  THE CIRCUIT DESIGNER’S COMPANION...........$59.95  ELECTRIC MOTORS AND DRIVES......................$59.95  UNDERSTANDING TELEPHONE ELECTRONICS....$55.00  AUDIO ELECTRONICS........................................$79.00  GUIDE TO TV & VIDEO TECHNOLOGY...............$55.00  EMC FOR PRODUCT DESIGNERS.......................$95.00  THE ART OF LINEAR ELECTRONICS..................$80.00  INTERNET HOME PAGES MADE SIMPLE...........$24.95  DIGITAL ELECTRONICS .....................................$59.95  ESSENTIAL LINUX..............................................$85.00 ORDER TOTAL: $............. 5995 $ Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ___________________________________ Postcode_______________ Daytime Phone No. (______) __________________________________ STD Email___________________<at>_________________________________  Cheque/Money Order enclosed OR  Charge my credit card –  Bankcard  Visa Card  MasterCard Signature____________________ Card expiry date PLUS P&P (if applic.): $.............. TOTAL$ AU.................... ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. BOOKSHOP WANT TO SAVE 10%? SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! ENQUIRING MINDS! (To subscribe, see page 65) UNDERSTANDING TELEPHONE ELECTRONICS THE ART OF LINEAR ELECTRONICS By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. $ By John Linsley Hood. First published 1993. NEW SECOND EDITION 1998. A very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $55.00. 55 80 DESIGNING INTERNET HOME PAGES MADE SIMPLE AUDIO ELECTRONICS By John Linsley Hood. First published 1995. Second edition 1999. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover at $79.00. $ By Lilian Hobbs. First published 1996. Second edition 1999. All you need to get started. Create and design your own Internet home pages that include both text and graphics, using this practical, easy to follow, jargon free guide. This edition has been enhanced and updated and now covers HTML 4.0. 182 pages, in paperback, at $24.95. 79 $ GUIDE TO TV & VIDEO TECHNOLOGY Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback, at $55.00. 55 EMC FOR PRODUCT DESIGNERS By Richard Monk. Published 1998. 59 95 By Steve Heath. Published 1997. Widely regarded as the standard text on EMC, this book provides all the information necessary to meet the requirements of the EMC Directive. It includes chapters on standards, measurement techniques and design principles, including layout and grounding, digital and analog circuit design, filtering and shielding and interference sources. The four appendices give a design checklist and include useful tables, data and formulae. 299 pages, in soft cover at $95.00. 95 $ P&P $ With this book you can learn the principles and practice of digital electronics without leaving your desk, through the popular simulation applications, EASY-PC Pro XM and Pulsar. Alternatively, if you want to discover the applications through a thoroughly practical exploration of digital electronics, this is the book for you. A free floppy disk is included, featuring limited function versions of EASY-PC Professional XM and Pulsar. 249 pages, in paperback, at $59.95. ESSENTIAL LINUX By Tim Williams. First published 1992. Second edition 1996. Add $A5.00 per book – Orders over $100 P&P free in Australia. NZ: Add $A10 per book, $A15 elsewhere 24 95 $ DIGITAL ELECTRONICS – A PRACTICAL APPROACH By Eugene Trundle. First published 1988. Second edition 1996. $ This practical handbook from one of the world’s most prolific audio designers has been updated and amended to make it the leading practical source of information for those interested in linear electronics and its applications, particularly in the world of audio design. 348 pages, in paperback, at $80.00. Provides all the information and software that is necessary for a PC user to install and use the freeware Linux operating system. It details, setp-by-step, how to obtain and configure the operating system and utilities. It also explains all of the key commands. The text is generously illustrated with screen shots and examples that show how the commands work. Includes a CD-ROM containing Linux version 1.3 and including all the interim updates, basic utilities and compilers with their associated documentation. 257 pages, in paperback, at $85.00. 85 $ POST TO: SILICON CHIP Publications, PO Box 139, Collaroy NSW, Australia 2097. OR CALL (02) 9979 5644 & quote your credit card details; or FAX TO (02) 9979 6503 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FRWEEBE YES! Place your classified advertisement in SILICON CHIP Market Centre and your advert will also appear FREE in the Classifieds-on-the-Web page of the SILICON CHIP website, www.siliconchip.com.au And if you include an email address or your website URL in you classified advert, the links will be LIVE in your classified-on-the-web! S! D E I F I S C LAS EXCLUSIVE TO SILICON CHIP! CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12 words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. 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No job is too small and can be to prototype or “turn key” stage, in one offs or for future production. Simply send us an email at vladimir<at> u030.aone.net.au with your questions or requirements and we will get back to you. PC-CONTROLS: Receiver 144148MHz (PLL), 2GHz Frequency Meter, Temperature Recorder (DS1615), Audio Generators, I/O Cards, Data Logging, ActiveX. http://www.ar.com. au/~softmark CHEAP USED HEATSINKS, semis, UV light, etching tank, Weller parts, etc. Phone (03) 6228 2600 or email altaego<at>netspace.net.au WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. $420.00 complete plus sales tax if appli cable. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/Ecowatch ph: (03) 5968 4863 fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. RAIN BRAIN AND DIGI-TEMP KITS: 8 station sprinkler controllers, 60 channel temp monitor uses DS1820s over 500 metres. Has PC Data logging. Mantis Micro Products, http://www.home.aone.net.au/mantismp TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. Melbourne 9806 0110. C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68 HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $155.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 and 68HC12 for $78. Debug monitors: $78 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 Simulator (fast, now incl. 80C320): $78. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $199, $37 tax, $10 p&p. SOIC adaptors: 20-pin $90, 14-pin $85, 8-pin $80. Credit cards accepted. GRAN TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; Fax (02) 9631 1236; or Internet: http://www.grantronics.com.au SOLAR PANELS: 120 watt $995.00, 80 watt $650.00, 60 watt $510.00, 40 watt $395.00 (all with 25 year guarantee). UNBREAKABLE PANELS: Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au Need prototype PC boards? Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Rhodes in Sydney. A genuine interest in electronics is a necessity. Phone 02 9743 5222 for current vacancies. Silvertone’s RC Receiver Still the best little performer available! 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. KITS-R-US PO Box 314 Blackwood S.A. Ph/fax 08 8270 3175 FMTX2A Universal Stereo Coder $49 FMTX2B 30mW Xtal Locked 100MHz Transmitter $49 FMTX1 1-3 Watt Free Running Transmitter $49 FMX1 200mW Full Broadcast Transmitter, built & tested $499 FM220 10-18 Watt FM BGY133 Philips Linear $499 FM1525 25 Watt Discrete Linear FM Band $499 FM2100 110 Watt Discrete Linear FM Band $699 FM3000 300 Watt Discrete Linear FM Band $1499 Philips 828E/A VHF Receiver Boards (6 metres) $9 AWA 721 VHF Receiver Boards (2 metres) $9 AWA 721 VHF transmitter boards 1 watt (2 metres) $19 Philips 323 UHF transmitter boards 500mW (70cm) $19 AEM 35 Watt Little Brick Audio Power Amp $15 Digi-125 200W RMS Audio Power Amp $39 CA Clipper Compiler, new in box $49 6dBd Gain Colinear FM Band Antenna $999 Roll Smart-1 FM Station Audio Processor $999 Free catalog on disk of discounted surplus components Same day shipping, credit cards OK, circuits supplied. SPECIAL STEAM BOAT KITS $14 COVERT Camera in PIR or Smoke Detector case from $94 * FREE PC VIDEO RECORDER - TIME LAPSE MOTION DETECTION Software with 4 Ch Capture Card from $113 * Video Transmitter Kitsets & Systems from $142 * Camera, Microphone & Timer/ Controller in PIR DETECTOR from $129 * BULLET 480 Line 0.05 lux SONY CCD or DSP COLOUR from $132 * HIRES better than SUPER-VHS Quality QUADS 4 Pix 1 screen from $208 * PCB Modules from $76 COLOUR Pinhole from $155 * MINI CAMERAS 36 x 36 from $85 - SONY CCD $102 - COLOUR $162 * DOME CAMERAS from $88 SONY CCD $107 - COLOUR $164 * Video BALUNS from $7 * DIY PAKS 4 Cameras, Switcher & Supply from $461 with 12" Monitor from $575 * 4 COLOUR CAMERAS, SWITCHER & POWER SUPPLY from $769 - with COLOUR QUAD 4 Pix 1 Screen from $1168 * COLOUR QUADS from $474 * COLOUR DUPLEX MUX from $1329 * 14" MONITORS from $203 - with Inbuilt 4 Ch SWITCHER from $236 * SEE-in-the-DARK CAMERAS & INFRARED 120 mW LED ILLUMINATOR Kits from $19 * www.allthings.com.au * 08 9349 9413 64 watt $550.00, 42 watt $420.00, 32 watt $340.00, 11 watt $190.00, 5 watt $120.00, 1.25 watt $80.00. WIND GENERATORS: 400 watt $950.00. INVERTERS: sinewave inverters, inverter/chargers, mod. Sinewave inverters, call with requirements. AUSTRALIA WIDE DELIVERY (Free on orders over $500.00). TASMAN ENERGY: (03) 6362 3050 Fax (03) 6362 3054. Circuit Ideas Wanted Do you have a good circuit idea. If so, sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We pay up to $60 for a good circuit so send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, 2097. Still only $129.50 AM or $149.50 FM. May be used with most ppm transmitters. This and many other radio control products available from: Silvertone Electronics, PO Box 580, Riverwood 2210. Phone/Fax (02) 9533 3517. www.silvertone.com.au KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com RCS Radio is MOVING. For information, ring 0408-613-300. KIT ASSEMBLY ANY KITS assembled/repaired: professional, speedy service. Phone Neville Walker (07) 3857 2752. WANTED WANTED: Operating manual or copy for a PATON VCT-V valve tester. Phone Allen Rowley (08) 8264 4984. WANTED: SILICON CHIP back issues: November, December 1987, January - August 1988, October - December 1988, January, March, August, December 1989, May 1990, February, July, September, November, December 1992, March 1998. Please call Chris (03) 9510 9921. March 2000 111 Silicon Chip Binders Keep your copies safe, secure and always available with SILICON CHIP binders: they’re cheap insurance! Advertising Index Acetronics....................................77 REAL VALUE AT Altronics................................. 49-64 PLUS P &P Clarke & Severn Electronics........77 $12.95  Heavy board covers with 2-tone green vinyl covering Av-Comm Pty Ltd.......................111 Dick Smith Electronics........... 12-15 Dontronics...................................77  Each binder holds up to 14 issues so that you can include catalogs EMC Technologies.......................77 Emona Instruments...................IFC  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Harbuch Electronics....................79 Instant PCBs..............................111 Price: $12.95 plus $5 p&p each (available Aust. only) Jaycar ........ IBC, 29-32, 81-84, 111 Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Kits-R-Us...................................111 Microgram Computers...................3 MicroZed Computers...................77 Oatley Electronics........................95 Printed Electronics.................... 111 DON’T MISS THE ’BUS Do you feel left behind by the latest advances in computer technology? Don’t miss the bus: get the ’bus! Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. Questronix...................................77 RALL Electronics.........................77 www.siliconchip.com.au SILICON CHIP’S 132 Pages 9 $ 95 * ISBN 0 95852291 X 09 9780958522910 09 9 780958 Resurrection Radio....................103 Robotic Education Products........77 522910 COMPUTER OMNIBUS Rocom Electronics.......................77 R.T.N............................................77 INC LUD ES FEA TUR E LIN UX Silicon Chip Back Issues....... 70-71 A collection of computer features from the pages of SILICON CHIP magazine Silicon Chip Bookshop....... 108-109 Silicon Chip Binders.............39,112 SC Computer Omnibus...........OBC Hints o Tips o Upgrades o Fixes NOW Covers DOS, Windows 3.1, 95, 98,ANT V o A DIRE ILABLE C SILIC T FROM ON just $ CHIP 125 ORDER NOW: Use the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. RT INC P&P O SC EFI Tech Special..................104 Silicon Chip Subscriptions...........85 Silvertone Electronics................111 Smart Fastchargers.....................34 Solar Flair/Ecowatch..................110 Speakerworks..............................77 HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. Truscott’s Electronic World...........34 Vass Electronics..........................77 _____________________________ PC Boards You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Printed circuit boards for SILICON CHIP projects are made by: Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. Email: tpeters<at>pip.elm.mq.edu.au 112 Silicon Chip • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. 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