April 2000 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Internet companies an unknown quantity
Review: Jamo Concert 8 Loudspeaker System by Louis Challis
Feature: How To Run A 3-Phase Induction Motor From 240VAC by Peter Laughton
Project: A Digital Tachometer For Your Car by John Clarke
Project: RoomGuard: A Low-Cost Intruder Alarm by John Clarke
Back Issues
Project: Build A Hot Wire Cutter by Leo Simpson
Order Form
Feature: Atmel's ICE 200 In-Circuit Emulator by Peter Smith
Product Showcase
Project: The OzTrip Car Computer; Pt.2 by Robert Priestley
Project: Build A Temperature Logger by Mark Roberts
Review: Mitsubishi's Diamond View DV180 LCD Monitor by Peter Smith
Book Store
Market Centre
Outer Back Cover

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Large LCD Flat-Screen Monitors: WOW! SILICON CHIP APRIL 2000 6 ISSN 1030-2662 04 $ 00* NZ $ 7 50 INCL GST PRINT POST APPROVED - PP255003/01272 9 771030 266001 www.siliconchip.com.au PROJECTS TO BUILD - SERVICING - COMPUTERS - VINTAGE RADIO - RADIO CONTROL ROOMGUARD NIFTY INTRUDER ALARM ADD-ON FOR A SMOKE DETECTOR HOTWIRE CUTTER AUTO TACHO SLICES THROUGH FOAM RUBBER & STYRO PLASTICS LIKE BUTTER! RE FFR EEE 3 08 PA E 3 J0A YPCAG 8 R C A A GEG* JA*NYewCsT-AstaAn LO d R c CScApaetaTcilaoAlgdooLfufebr2loeipn0bieos0nuo0snly side for subscOG ribers* TINY, ACCURATE DIGITAL TACHOMETER FOR YOUR CAR THERMaLOGGER PC-PROGRAMMABLE, SELF-POWERED PORTABLE RECORDING SYSTEM OzTrIP CAR COMPUTER April 2000 1 BUILDING, INSTALLING AND CALIBRATING OUR NEW DESIGN SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.mitsubishi-electric.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SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.mitsubishi-electric.com.au 2 Silicon Chip Contents Vol.13, No.4; April 2000 FEATURES 6 Review: Jamo Concert 8 Loudspeaker System Interested in surround sound? This loudspeaker system has to be heard to be appreciated – by Louis Challis 10 How To Run A 3-Phase Induction Motor From 240VAC It can be done but with some loss of efficiency – by Peter Laughton 54 Atmel’s ICE 200 In-Circuit Emulator You can use it to develop and debug software for the AVR series of microcontrollers. It’s ideal for novices too – by Peter Smith 76 Mitsubishi’s Diamond View DV180 LCD Monitor A Digital Tachometer For Your Car – Page 14. If you see it, you’ll want it – by Peter Smith PROJECTS TO BUILD 14 A Digital Tachometer For Your Car Compact design features a 4-digit LED display and a bargraph. It can also provide gearchange indication and drive a rev limiter – by John Clarke 28 RoomGuard: A Low-Cost Intruder Alarm Simple design interfaces to a battery-powered smoke detector – by John Clarke 48 Build A Hot Wire Cutter RoomGuard Intruder Alarm – Page 28. It’s easy to build and lets you cut plastic foam without mess – by Leo Simpson 64 The OzTrip Car Computer; Pt.2 Building, installing and calibrating this brilliant new car computer – by Robert Priestley 72 Build A Temperature Logger Standalone unit can record up to 2048 measurements and display the results on your PC – by Mark Roberts SPECIAL COLUMNS 42 Serviceman’s Log Hot Wire Cutter – Page 48. The fault that fixed itself – by the TV Serviceman 60 Vintage Radio The Hellier Award; Pt.3 – by Rodney Champness DEPARTMENTS 4 53 59 82 Publisher’s Letter Subscriptions Form Electronics Showcase Product Showcase 88 Ask Silicon Chip 94 Market Centre 96 Advertising Index Temperature Logger – Page 72. April 2000 3 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. 4 Silicon Chip Internet companies an unknown quantity Anyone who follows the sharemarket cannot fail to be amazed at what is happening to company valuations, depending on whether they are perceived to have an internet strategy or not. And even companies which are not internet-based, such as media companies, can also get a huge lift, because they are perceived as being sources of “internet content”. And it seems that every time a big conventional company such as a major retailer, bank, developer or whatever announces a big profit lift, their share prices tend to go down rather than up. While if an internet company announces a loss (as they generally do) their prices tend to rise. Frankly, I am as baffled by the whole process as anyone else. It seems crazy to me that a company such as Ecorp, which is really not much more than a ticketing agency and a discount broker and has yet to make any money, has a bigger market capitalisation than say, the giant construction firm Leighton Holdings. Or that Sausage Software should be more highly valued than Caltex which has real refineries, service stations and so on. It seems as though large companies which actually make goods or provide services are no longer valued as they should be. Not that this is confined to Australia; it is a world-wide trend at the moment. The pundits put it down to the fact that the internet is seen to be the way of the future and that those internet companies which are making the running now and building a large customer base, are the ones that will be positioned to make big profits in the future. This may well be so but many of those internet type companies which are losing money in really large amounts right now probably won’t exist in a few years time. In fact it appears that the only internet companies which are presently making any money are those that provide pornography or financial services; interesting juxtaposition, that. And while people can now buy all sorts of goods via the internet it does seem as though it will be a while before a major portion of retail sales becomes netbased. There are problems with deliveries and people still do like to inspect goods before they buy, in most cases. So where will the boom in internet business come from? It beats me. If I had any really worthwhile ideas on the subject I’d be out there hustling along with all the others. For example, SILICON CHIP could make all its editorial content available on the net as well as all sorts of related electronics information but it would seem unlikely that enough people would be prepared to pay for the services we could provide. It would certainly cost a heap of money to set up. Ask yourself the question: would I be prepared to pay something like $50 to $100 a year for wide-ranging access to SILICON CHIP material? If enough of you answered yes (and are prepared to tell us that) we might have a good chance of doing it. If not, then as far as we at SILICON CHIP and a great many other companies are concerned, the internet will remain a tantalising vortex, sucking in huge numbers of people and vast quantities of money. That is not to say that the internet itself is useless. We use it all the time and our activities on the internet will naturally continue to grow. And email is quickly replacing conventional mail and fax as the standard means of communication to SILICON CHIP. Just look at all the letters in “Ask Silicon Chip” which come in via email now. For the moment though, the internet remains enigmatic. For those companies and organisations who figure it out, the rewards will be large. Leo Simpson FireWire to PCI Host Adapter Connect your digital video camera to your PC. Our Firewire card allows IEEE 1394 FireWire devices (most digital camcorders available today) to connect to your PC at speeds up to 400Mbps. The card has three external & one internal IEEE 1394 ports to allow connections to hard drives, scanners, VCRs, HDTV, printers etc. Editing your videos is simplified with bundled Ulead Video Studio DV SE software. Cat. 2621 FireWire to PCI Host Adapter No Ball Mouse with Scroll Wheel Mouse with Sroll Wheel & No Ball $79 115 Key Programmable POS Keyboard Ideal for any Point-of-Sale situation, this robust, 115 key programmable keyboard supports 2 x 20 line text or 160 x 32 graphic LCD and has a magnetic swipe reader built-in. It has both PS/2 and RJ-45 connectors, modelock with five keys & 7 positions and programs 8 characters per key. Cat. 8783 115 Key Programmable POS Keyboard PS/2 Multi-PC Controller 2 Way New courses now available! Including Windows 98, Quicken 98, Lotus Notes, Internet Tools (Netscape) and more courses on TCP / IP. *Full details at www.tol.com.au Printer Cards Bi-directional parallel ports with an 83 byte FIFO buffer, configurable from LPT1 to LPT6 and set on interrupts 3 to 15. Achieve data transfer $199 rates up to 1Mb/sec with ECP/EPP. Both ports provide 7 selectable I/O port addresses & 10 selectable IRQ’s. The single port ECP/EPP card provides 7 DMA channels & the dual port provides 2 DMA channels. This is an innovative new mouse is compatible with the Microsoft IntelliMouse. It uses a new technology that avoids the need for a mouse pad, as there is no ball to gather dust. The mouse will even work on glass. A RISC 8 bit 12MHz CPU module decodes the movement to provide a resolution of 625 dpi. The smooth and continuously scrolling wheel provides better micro positioning than standard gear type scrolling wheels. Cat. 8784 Web-Based Training - Unlimited access to all courses in Group 1 from only $14.95 per month* Cat. 2314 Cat. 2315 Cat. 2316 Cat. 2235 Cat. 2236 Bi-directional 1 Port Bi-directional 2 Port Bi-directional 3 Port ECP/EPP 1 Port ECP/EPP 2 Port $61 $97 $65 $69 1 Port Printer PnP PCI 1 Port ECP/EPP/SPP PnP PCI 2 Port Printer PnP PCI 2 Port ECP/EPP/SPP PnP PCI $79 $83 $119 $125 All-in-one: Internet Access / Email / Print / Fax Server + 7 Port UTP 10 /100Mb Hub An internet access server combined with a 10/100 ethernet hub with 7 ports and 1 uplink port as well as a printer server, a fax server and a virtual email server, all in one box. There are two RS232 ports to provide additional bandwidth to the Internet. Up to 253 users on the network can have simulta$689 neous access to the Internet. A hardware-based firewall ensures security, while dial on demand minimises connect time. It also has a built in DHCP server. This sophisticated controller allows one keyboard, monitor, mouse to control 2 PCs. Single DB25 connectors on the controller & multi-core extension cables allow for simple connection (2 x PS2 cables supplied). Auto scan and manual selection of the PCs is provided. Cat. 10118 Intelligent Network tester with LCD Display An intelligent continuity tester for LAN cables that saves time on the job. It tests a range of Modular cables including 10Base-T (Category 3-5). Four numbered remote terminators allow testing, tracing and identification of in situ cables. The LCD display shows the pin connections as well as $45 the wiring scheme detected. Also available, are Plug & Play PCI printer cards. Cat. 2618 Cat. 2687 Cat. 2619 Cat. 2688 Now over 300 courses to choose from Internet Access / Fax / Print / Email Server & 7 Port UTP Hub 10/100Mbps $699 Cat. 11518 Cat. 11519 Intelligent Network Tester Network Tester with LCD $229 $239 Hot Swap IDE Mobile Rack HDD Kit The Mobile Rack is the perfect solution for data backup & transporting data between computers. A kit consists of a 5.25" mounting rack & a removable tray for a 3.5" hard disk & simply mounts in a standard 5.25" half-height bay. The tray is easily removed so data can be taken off site or locked in a safe for security. Move data between home & office or swap easily between multiple operating systems. The hot-swap model has a software utility, enabling you to remove & replace the drive in the PC without having to reboot or shut down. Mobile HDD Kit IDE Hot Swap Mobile HDD Kit IDE Mobile Rack IDE Tray Only Mobile HDD Kit IDE Ultra DMA Mobile HDD Kit SCSI Mobile HDD Kit SCSI Wide Cat. 6614 Cat. 6610 Cat. 6611 Cat. 6615 Cat. 6612 Cat. 6613 $159 $69 $39 $89 $79 $129 Hot-Swap IDE RAID Array Avoid downtime delays when your hard drive fails! This unit enables VGA Surveillance Monitoring Hub the user to replace the hard disk Plug in up to six cameras and diswhile the PC is operating and it play them on a PC monitor. Video automatically resynchronizes itself to full operation. recording can be configured to The RAID unit fits into two continuous 5.25" bays turn on with motion detection. and includes a controller & two removable frames. Cat. 11613 2-Way Multi-PC Controller PS/2 & Cables $299 Captured video can be compressed and stored on the hard disk and time and date The array accepts two EIDE, Ultra DMA 66/33 or Multi I/O ISA Card stamped. The unit can be monitored or controlled remotely PIO 4 hard drives. The controller provides RAID A versatile interface card that supports 2 FDD, 2 with individual camera control. The included software runs Level 1 disk mirroring. It can also be used as an HDD As well as 2 16550 compatible serial ports, 1 on-line hard drive copier. under Win95 or 98. ECP/EPP printer port and 1 games port. HDD Hot Swap IDE RAID Disk Array Cat. 2808 $1299 Cat. 2055 Multi I/O Card $50 Cat. 3410 Video Surveillance Monitoring Hub $2349 E & OE All prices include sales tax MICROGRAM 0400 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 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 April 2000 5 Hifi Review JAMO Concert 8 Loudspeaker System The Concert 8 Series main front speakers are beautifully made and give outstanding performance for their size. Designing loudspeakers has tended to be more of an art than a science. However, this review of the Jamo Concert 8 home theatre speakers demonstrates that the Dolby Digital system encompasses a lot of science and this is incorporated into the Jamo design. Review by LOUIS CHALLIS 6 Silicon Chip J AMO HAS BUILT its reputation as Denmark’s preeminent manufacturer of loudspeakers. Having tested many of its more innovative products, I have been consistently impressed by the manner in which they have been prepared to break new ground in the “quest for the Holy Grail”. To create a good loudspeaker, you have to start with appropriate drivers and then the cabinet also plays a significant role in the resultant sound quality. The underlying reason for this interaction between the cabinet and its drivers relates to cabinet resonances which degrade the purity and integrity of the reproduced sound. That interaction is frequently extended beyond the initial transient when the walls of the speaker cabinet exhibit resonances with minimal damping characteristics. When that occurs, an initial transient excitation can be extended for periods of as much as 50 milliseconds or more. The net result is a pronounced coloration of the sound. There are many ways through which such problems can be minimised. B&W in England have developed their modular foam-filled honeycomb structure, which has proved very effective. A simpler (and less expensive) way is to add mass combined with an efficient damping mechanism. Jamo have adopted this strategy and applied it to the design of some of their latest loudspeaker cabinets. The Jamo approach involves the use of a double-plastic layer wall structure, whose internal cavity is filled with a special mixture of high density mineral sands and what Jamo describes as “a resonance deadening binding agent”. This structure results in an extremely heavy cabinet which then displays very good control of cabinet ‘coloration’ and other less obvious anti-resonant characteristics. Why am I bothering to tell you all this? Well, the Jamo Concert 8 and the Jamo Concert Center are the centrepieces as it were of the 5.1 channel loudspeaker system that I have just been reviewing. Those three speakers were supported by a pair of small Jamo Concert Surrounds for the rear speakers of the system, with a Jamo SW3015 Subwoofer providing the low bass content. Home entertainment is currently undergoing a dramatic change as more and more homes install a DVD player with that ubiquitous 5.1 channel audio capability. The aim of the game is to replicate your local cinema’s Dolby Digital Sound System in your living room. While that sounds like a tall order, it is now far easier to achieve than one might think. The basic elements that the latest generation of home theatres have are: a reasonable size screen, a good DVD player, five channels of sound amplification and the five speakers that go with it. Lastly, a self-powered or externally powered subwoofer is desirable. The Jamo Concert series are among the most visually attractive home theatre loudspeaker systems currently being marketed in Australia. Each of the cabinets has been carefully designed to neatly fit on bookshelves, attach to the wall or to sit on stands. The rear of the Concert Center features foam backing, whilst the tops and bottoms of the Concert Surrounds have a soft rubber surface which allows them to be slid or moved without damaging them or the supporting surface. The Concert 8 Series left and right main front speakers are beautifully veneered, conforming to the highest Danish furniture standards. At just a modest 380mm high, they achieve an outstanding level of performance for their size. They employ a 165mm combined woofer and midrange driver that covers the frequency range from 40Hz to 2.5kHz. A 25mm diameter fabric dome tweeter then covers the top end and provides an unusually flat output response. The cabinet has a neatly contoured rear port. A rear ported vented enclosure can be an asset or liability, depending on how close the cabinet is placed to the rear wall or bookshelf; too close and the low frequency response will suffer. The Concert 8s have four sets of speaker terminals on the rear panel and they are designed for bi-wiring when required. With 4Ω impedance and a claimed 180W peak power rating, they are particularly potent, delivering sound level peaks that frequently exceed 110dB at your intended listening position. The front centre speaker, or Concert Center, as it is described, is a 3-way system with a cabinet construction very similar to the Concert 8. It utilises a pair of 165mm diameter woofers to cover the frequency range of 65Hz to 1100Hz. A separate 38mm diameter mid-range driver then covers the frequency range of 1100Hz to 3.5kHz and a 25mm diameter tweeter serves the top end of the spectrum. The Concert Center also has a 4Ω impedance and is similarly designed for bi-wiring where adopted or preferred. The rear of the cabinet features an impact absorbent foam lining while the rest of the cabinet is veneered. The Concert Surround speakers are based on design principles laid down by THX. They provide a diffuse sound field by virtue of their V-front configuration, with two sets of speakers on each of the angled speaker faces. The speaker line-up comprises a pair of 130mm diameter woofer/midrange speakers together with a pair of 25mm diameter soft dome tweeters. This composite speaker configuration provides a wide lateral sound field over the frequency range from 100Hz to 20kHz. The adoption of a rubber top and bottom surface enables the speakers to be inverted without fear of damage and provided the most convenient cable feed to the internally recessed angle speaker terminals. The acoustical outputs of the five speakers in the Jamo Concert series line-up are precisely matched, as you would expect. They only require the addition of a good The Jamo SW3015 subwoofer uses a 15-inch driver and has a 300W amplifier. It has no difficulty in providing wall-shaking sound level over the frequency range from 30Hz to 150Hz subwoofer to fulfil the more demanding requirements of a “fully fledged” Dolby Digital or the alternative DTS Sound Decoding System. 15-inch subwoofer I already had a Jamo SW3015 subwoofer and this will team up with the Jamo Concert system. The SW3015 uses a 15-inch motional feedback controlled subwoofer capable of working without any sign of cone break-up to a frequency four times its upper intended operating limit. The voice coil is designed to accommodate a 20mm movement and is driven by a 300 watt amplifier. The amplifier has an outstanding 85% efficiency (presumably it is switchmode design) so that the heatsink and the size of the cabinet may be appropriately reduced. When producing a 100dB sound pressure (at 1m) the total April 2000 7 The Concert Center (front, centre) loudspeaker system matches the styling of the Concert 8. The cabinet houses four drivers: a pair of 165mm diameter woofers, a 38mm diameter mid-range driver and a 25mm diameter tweeter. harmonic distortion is claimed to be less than 1%. With that sort of performance, the SW3015 has no difficulty in providing wall-shaking sound level over the frequency range from 30Hz to 150Hz. A particularly nice feature is its “Auto On/Off” function that shuts the unit down automatically after 10 minutes with no input signal. each of the side walls and approximately 500mm from the rear wall of my listening room. The Concert Center was located directly between the two main speakers and all with a common height of 1.2 metres above the floor and 3.5m from the central listening position. Initial tests The two Concert Surround Speakers were located at matching positions at the rear of my listening room, separated by 5m and approximately 1.6m above the floor and 2m to the rear of my listening position. The first test disc I used was “DVD Spectacular” Delos DV7001 issued by Dolby Laboratories, who worked with Delos on its development. It makes it possible to test the swept frequency response of each of the five main channels, as well as the subwoofer. With all six channels connected correctly in phase and with inputs correctly balanced, the measured frequency responses appeared to be exceptionally good; in fact, almost too good to be true. What surprised me was that each of the five separate Jamo speakers appeared to have a uniformly flat response all the way down to 30Hz. How could this be? It turned out that the subwoofer was the critical source of all the low frequency energy. I then realised that Dolby Laboratories had been more innovative than I had thought. By deactivating the sub woofer chan nel, I confirmed that Dolby Laboratories had designed a system that did not rely on any of the five primary channel speakers being flat below 100Hz. All the output below 100Hz is supposed to come from the subwoofer. So if you don’t own a subwoofer, you are forced to rely on the output from your two main (front, left and right) speakers to provide an extended low frequency response. Whilst the Concert 8s are adequate in that regard, they simply cannot match the performance of the SW3015. Obviously, Dolby Laboratories haven’t publicised this feature, as they saw no need. Their licensees however, are well aware of this critical design characteristic. When designing their loudspeakers for an integrated 5.1 channel Dolby Digital compatible system, the five main speakers only need to cover the nominal frequency range 100Hz through to 20kHz. As it happens, the Jamo Concert main speakers offer a relatively wide frequency response that extends well below the 100Hz criterion. The Concert 8s provide a remarkably smooth response down to below 40Hz. That response was measured with the subwoofer inactive, to ensure that I didn’t fool myself. For my initial assessment of the Jamo Concert system, I connected the five loudspeakers to a Yamaha model DSP-E492 3-channel amplifier coupled to a Yamaha M80 amplifier which served the two front channels. The Yamaha audio-visual processor/amplifier has a neat sequential reference tone to make it easy to adjust the five channels for equal output. Subsequent checking with a sound level meter confirmed that my subjective adjustment was accurate to within 2dB. I placed each of the Concert 8 loudspeakers on stands at one metre from The Concert Surround speakers provide a diffuse sound field by virtue of their V-front configuration, with two sets of speakers on each of the angled speaker faces. The driver line-up includes a pair of 130mm diameter woofer/ midrange speakers plus a pair of 25mm diameter softdome tweeters. 8 Silicon Chip Too good to be true Fig.1: this graph shows the frequency response of the Concert 8 left and right speakers, with the sub-woofer active (red). The green line shows the response of the subwoofer by itself at two metres. Fig.2: this graph shows the frequency response from the right front at 1.4 metres with the sub-woofer active (red) and the right front at 1.4 metres with the sub-woofer active. The subwoofer’s high frequency cut-off was set to 100Hz for my testing. However, the SW3015 can cover a significantly wider frequency range, up to 180Hz. The Concert series do not incorporate protection circuitry. Instead, each is designed to withstand short-term transient power inputs exceeding 150W. I used a 300W per channel stereo amplifier to drive the Concert 8s and a five-channel amplifier (5 x 150W) and although I subjected the speakers to some pretty nasty input signals, they never missed a beat. With peak inputs of 130W there were no problems at all, although at that input level, harmonic distortion is readily detectable. With unweighted peak and pressure levels exceeding 110dB, I was able to replicate the sound levels currently heard in cinemas. There is a surprisingly large amount of Dolby Digital software available in Australia. By contrast, there is relatively little DTS material around, although the first ‘dribs and drabs’ are now trickling into Australia. Fortunately I was offered a sample of the latest DTS audio material produced by Telarc, a 5.1 DTS Surround Sampler with which I evaluated a Kenwood model D 1888 DE 5-channel amplifier. This provided the opportunity to make a comparison with comparable Dolby Digital material. My assessment is that well recorded DTS encoded material is every bit as good as equivalent Dolby Digital encoded software. Irrespective of which source input you choose, the Jamo Concert 8, Concert Center and Concert Surrounds supplemented by the SW3015 subwoofer provide an audible performance that has to be heard to be appreciated. Irrespective of the software, the frequency response is impeccable. With a choir singing and organ playing, a bass drum being struck, a cannon firing or an orchestra playing, I had no difficulty in replicating the subjective feelings that I frequently experience when sitting in a concert hall at the Sydney Opera House. In short, the Jamo Concert series look impeccable and sound very impressive. For more information, contact SC Jamo Australia on (03) 9543 1522. 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. www.siliconchip.com.au SILICON CHIP’S 132 Pages $ 95 * 9 ISBN 0 95852291 X 9780958522910 09 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 NO AVA W Hints o Tips o Upgrades oDFixes IL IREC ABLE Covers DOS, Windows 3.1, 95, 98, NT T FRO SILIC M ON just $ CHIP 1 5O 2 INC o 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 P&P April 2000 9 How to run a 3-phase induction motor from 240VAC Over the years, many readers have wanted to run a 3-phase 415V AC induction motor from a single-phase 240V AC supply. It CAN be done, although with some loss of efficiency. This article discusses how to do it. By PETER LAUGHTON W HY WOULD YOU want to run a 3-phase 415VAC induction motor from a single phase 240VAC supply? The short answer is “because a 3-phase supply is not available!” Other answers are that 3-phase motors are typically found on lathes and other pieces of equipment and are generally cheaper to buy than equivalent single phase motors. Before we talk about how to do it, let’s look at some of the problems. The first one is that the starting torque is reduced from what it oth- erwise would be. This means that if the motor is connected to a load that needs a large starting torque (like an air compressor that isn’t fitted with an unloading valve), the motor will probably just sit there humming and eventually burn out. In practice, the starting torque is typically reduced by about 20%. My experiments show that some motors are better than others and indeed it is the older types that are usually better than newer ones. This is probably due to the fact that older motors gen- erally have a larger laminated core in the magnetic path and they have more copper in the windings. In other words, older motors are more conservatively designed. Examples of loads that can be successfully started and run are saw benches, band-saws and fans that start up under virtually no-load conditions. Some types of lathes can also be successfully run because they start with no load. Bear in mind that running a 3-phase motor from a single phase supply is far less than optimum because the 3-phase rotating fields will not have the correct 120° relationship to each other. The motor will therefore make more noise, will run hotter than normal and will not produce as much power. Also the pitch and strength of the noise will change ac cording to the load on the motor, as the phase vector from the artificially created 3rd phase Fig.1(a) shows the phasor diagram for an ideal 3-phase system. Each phase has a 120° separation from the other two. Fig.1(b) shows the likely phasor relationship with the third phase created by the connection of capacitors across a 3-phase motor with no load. Fig.1(c) is the likely phase diagram when the same motor is under load. These less than ideal phase relationships mean that the motor will not be as efficient or produce as much torque and it likely to also produce more noise. 10 Silicon Chip Fig.2: this is how capacitors are connected across a deltaconnected 3-phase motor to artificially produce 3-phase operation. Note that the motor must be capable of deltaconnection 240VAC operation. A 415VAC star connected motor will not have sufficient voltage to start and run properly. The capacitors should be rated at 440VAC. changes under load (see Fig.1). This could induce vibrations into a drive under certain conditions of load and might possibly cause damage. There are commercial devices which can provide the correct 120 degree spaced phase voltages for a 415VAC motor but we will confine ourselves to the passive solution which just uses high-voltage AC-rated capacitors. WARNING: DANGEROUS VOLTAGES! First, we need to make a few safety comments. We are deal ing with mains voltages here, so if you are not a licensed electrician, don’t attempt to try any of the ideas presented here. Even when the motor is switched off and disconnected from the 240VAC mains supply, there could still be appreciable voltage left on the capacitors, enough to kill the unsuspecting person. Remember that even if you don’t necessarily have all the leads connected to the motor, the unused ones will still be energised due to induction and transformer effects within its windings and core. I also suggest that you obtain a secondhand motor to experiment with, as you may burn it out if you get the connections wrong. Also be aware that a 3-phase motor, driving a load that still keeps it spinning after the power is removed, such as a drive equipped with a large flywheel, becomes a capacitively-excited induction alternator. Such a spinning motor is capable of killing you with the voltage produced at its terminals, even though it is completely disconnected from the mains supply. As already mentioned, all that is needed to run a 3-phase motor from a 240VAC single phase supply is a few capacitors. But what values? Too much capacitance and we create a leading power factor (which doesn’t usually go down too well with your local electricity supplier), while too little capacitance won’t give a strong enough field when operating under load and the motor will slow down and burn out. How much capacitance do we need? First, we need to briefly review how a 3-phase induction motor works. It has three separate stator windings which are connected in star or delta mode to the three phases of the mains supply. If we are thinking of the star connection, each phase can be regarded as 240VAC, separated by 120°. This is shown in the phasor diagram of Fig.1(a). This crude method of obtaining three phases from a single-phase supply uses a number of capacitors connected as shown in Fig.2, for a delta-connected motor. In effect, we are using the inductance of the stator winding in conjunction with the capacitors to provide the desired phase shifts. Strictly speaking, the amount of capacitance required varies with load because the inductive reactance of the motor varies as the speed of the motor varies. This is because of the varying “slip”. To explain further, the speed of the rotating magnetic fields in a 4-pole motor is 1500 RPM and 3000 RPM for a 2-pole motor, etc. This is the so-called “synchronous speed”. But the actual rotor speed isn’t constant, as it varies with load and even at “no-load” is always less than the synchronous field speed due to the stator windings. The April 2000 11 Fig.3: this is a delta-connected 3-phase motor. Each winding has 240VAC applied to it. Most new 3-phase motors can be run in this mode, as detailed on their nameplate. difference between the two is called “slip” and it typically varies from 2 % to 10 % or more in specially designed motors. For example, a motor rated at 1440 RPM will have a synchronous speed of 1500 RPM and the slip in this case is 4%. As the motor is loaded, the slip increases; ie, the rotor runs slower and slower until it eventually stalls. This change of speed with load affects the back-emf of the rotor and is reflected in the stator inductive reactance and is why the amount of capacitance needed varies according to load. Some commercial units use thyristors to switch in different capacitors but this is really beyond our aim of doing things simply. Note that, of necessity, the above explanation is much simplified. How do we work out the inductive reactance of the windings to allow us to provide the same amount of capacitive reactance in order to give the correct phase shifts? There are several ways. One is by measurement. You can use an AC ammeter and excite the winding from a low voltage AC supply. You can then calculate the reactance from Ohms Law, having measured the voltage and current flow through the windings. This gives a starting point for experimentation. You can also take full load current and volt ratings from the motor’s name-plate and use those to calculate the impedance of the windings. Once again, this only gives an approximate figure. Generally though, the calculation is not critical and the range of tolerances in capacitors is greater than the error anyway. For instance, say you want to use a small motor on a sawbench. It is rated at 1.1kW, 4.1A, 240VAC (delta-connected) at 2870 RPM (ie, 4.3% slip relative to 3000 RPM). We can use these figures to calculate the inductive reactance of the windings, using the following formula: Reactance = √[W2 - (VA)2] = √[(1100)2 - (240 x 4.1)2] This gives a result of 492Ω. We then calculate the value of capacitance to give the same reactance, using the formula: Capacitance = 1/(2π.f.Xc) where f is 50Hz and Xc is 492Ω. The result is 6.47µF. The voltage rating should be at least 440VAC and the capacitor must be rated for continuous duty. Motor-start capacitors are not suitable as they are only rated for a short duty cycle, typically several seconds. Oil-filled motor-run capacitors should be suitable. We now have to connect capacitors to the motor to create a rotating magnetic field. In fact, we only create an unbalanced field and let the motor’s Fig.4: a starting switch and extra capacitors will provide more initial torque from the motor but the additional capacitors must be switched out when the motor comes up to speed. 12 Silicon Chip rotor produce a moving field as it turns. How do we unbalance the field? We connect the capacitors in the ratio C to 2C, as shown in the diagram of Fig.2. This creates our unbalanced field. But this will only work from a 415VAC 2-phase supply which is not practical when we only have a 240VAC single-phase supply! How can we run a 415VAC motor from 240VAC? Fortunately most new small 3-phase motors (rated up to 3.7kW or 5 HP) are now designed to work anywhere in the world, from 60Hz supplies at 220/240VAC (as in America) to 50Hz, 380VAC to 440VAC supplies (as in Europe and Australia). So the solution is to connect one of these motors to run in “delta” rather than “star” mode. This is shown in Fig.3. Note that the capacitors don’t have to be connected right at the motor terminals but should be reasonably close to reduce the effects of lead resistance. To reverse the rotation, it is simply a matter of changing any two connections to the motor, as in reversing a standard 3-phase motor. Improving the starting torque The usual way to do this is to switch in more capacitors at starting and disconnect them when the motor is up to speed, to prevent the power factor problems above (see Fig.4). The switch could be the motor’s inbuilt centrifugal throw-out switch or even a manually-operated toggle switch. What about operating a bigger 3-phase motor? Once you have the 3-phase field from a small motor, you can start a larger motor after the small one is running, as the rotating field is real and available at the small motor’s terminals. No extra capacitance is needed as the already running motor supplies the field. Note that there are limits set by your local supply author ity on the size of the motor you can start on the domestic power grid. The idea presented above also allows you to run 3-phase motors from a single phase petrol or diesel generator but it really gives the generator a workout during the starting period, so be careful or you may damage the genset. I can successfully start and run the 1.1kW 3-phase motor described above (on a sawbench) from a 5kVA, 240VAC SC single-phase diesel genset. 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 readout * Digital plus bargraph be used as * Can a gearchange indicator drive a rev * Can limiter auto* Display dims at night Keep tabs on engine revs with this: Digital Tacho This versatile Digital Tachometer has a 4-digit LED display plus an analog style bargraph to indicate engine rpm. The displays automatically dim at night and there’s even a limiter output, so that you can limit engine revs. By JOHN CLARKE Tachometers are a “must have” item for driving enthusiasts. If you prefer a manual car, a tacho lets you know when to change gear and can help you keep engine rpm within the best operating range. An accurate tachometer is also a vital tuning aid if you have an old car and you prefer to do the engine tune-ups yourself. 14 Silicon Chip Traditionally, analog tachometers have been circular in shape with a needle (or pointer) which sweeps in a clockwise direction as the engine speed (rpm) rises. The scale behind the needle is usually marked in 100s of rpm and there’s also often a colour scale to indicate the normal rpm range (green), a high rpm range (orange) and an “over-the-limit” range (red). In recent years, digital tachometers have also become quite popular with car enthusiasts. These directly show the engine speed on 7-segment LED displays or on an LCD but they do have one disadvantage – the forbidden red zone, where you can do serious engine damage due to over-revving, isn’t indicated on the display. Instead, it’s up to the driver to remember the where the redline is and drive accordingly. This design overcomes that problem by including a bargraph display. This display operates in conjunction with the digital display and has 10 LEDs – seven green and three red. As the engine speed rises, the seven green LEDs progressively light and then the three red LEDs all light together. In effect, the bargraph has eight steps – seven for the green (normal) range and one for the redline. These eight steps can be programmed to operate at any value within a 0-9900 rpm range, so the new Digital Tachometer can be used with virtually any engine (provided its redline is less than 9900 rpm). By the way, a reading of 9900 is also the limit for the digital readout but that should be more than enough for any normal engine. Beyond 9900rpm, the 7-segment LED displays show a value of “-00” to indicate the over range. Basic features The Digital Tachometer is a compact unit which is much smaller than any of our previous tachometers. In fact, it is about as small as you could expect, considering that there are four 7-segment displays and a 10-LED bargraph housed in the case. That’s all been made possible by basing the design on a PIC16F84 microcontroller – the same device as used in the Speed Alarm (November 1999) and the Digital Voltmeter (February 2000). In fact, this circuit completes a trilogy of car project designs based on the PIC16F84 microcontroller. As before, the PIC controller has allowed us to dramatically reduce the required parts count and this in turn makes the unit easy to build. Even the circuits are quite similar – we’ve “simply” made a few hardware changes and rewritten the software that’s programmed into the microcontroller, so that it now functions as a tachometer. The new Digital Tachometer is also very easy to install and calibrate. It connects to the ignition supply and ground for power and obtains its signal from the ignition coil or from an engine management computer. It shows the engine rpm in 100 rpm increments on the 4-digit LED display, while the bargraph indicates engine rpm in an analog format. One nice feature is that the display brightness varies according to the ambient light. In bright light, the display is at its maximum brilliance so that it can be easily seen. However, as the ambient light falls (eg, at night time), the display automatically dims so that it won’t be too bright. Before using the tachometer, you have to select the calibration profile for your particular engine and adjust Main Features • 4-digit LED display showing up to 9900 rpm; 10-LED bargraph with redline indication. • • 100 rpm display resolution. • LEDs 8-10 (red) in bargraph display light up together for redline indication. • LED rpm indication thresholds in bargraph can be individually set (eg, to allow the unit to be used as a gearchange indicator). • Automatic calculation and setting of the LEDs 1-7 rpm thresholds when the LEDs 8-10 rpm threshold is set. • • Optional dot or bargraph display. • • Adjustable rpm hysteresis for limiter output and bargraph display. • • Automatic display dimming during low light conditions. Works with 4-stroke engines with up to 12 cylinders and 2-stroke engines with up to 6 cylinders. Rev limiter output signal (can drive the SILICON CHIP Rev Limiter switcher board described April 1999). Three switches for setting calibration, bargraph and hysteresis values (Mode, Up and Down). Rpm sensing directly from ignition coil or via low voltage signal from engine management computer. the bargraph display range. We have made this process very easy to do using just three pushbutton switches. These switches are located on the circuit board just below the bargraph display but are not accessible when the lid is on since calibration is normally a “set and forget” function. The first time you apply power to the unit, the unit will be ready to display the engine rpm. In addition, the internal program loads a number of default values for the calibration, bargraph display and hysteresis. Initially, the unit is calibrated for a 4-cylinder 4-stroke engine, the redline is set at 4000 rpm and the hysteresis is set at 100 rpm. The first LED in the bargraph lights at 0 rpm but you can change this and the other green LEDs to light at what values ever you like (eg, to indicate gear change-down points). Note that the default values remain in place unless changed by pressing the calibration switches. We’ll tell you how to do this later in the article. Dot or bargraph display In case you’re wondering, the style of the bargraph display can be changed from bar to dot mode – hey, we are using a microcontroller after all! The major difference here is that in the dot mode, only one LED from LEDs 1-7 will light at a time. However, LEDs 8-10 always light together so that aspect remains the same. The Dot mode is selected by holding down the Mode switch while power is applied to the unit (ie, when the ignition is switched on). The display will then show a “d” to indicate dot mode. Similarly, the bargraph mode can be reactivated by again pressing the Mode switch during power up. This time, the display will show a “b” to indicate that the unit is now in bar mode. Note that the adjacent digit will also show a “0”, so the display actually shows “d0” or “b0”. The dot mode can be used to provide some unique display results. For example, if you program more than one LED to light at the same rpm value, then only the LED that’s on the right will light. You can use this feature to set up the tachometer to provide gearchange indication, whereby a series of three LEDs light in sequence to indicate when to April 2000 15 Fig.1: (left): a PIC microcontroller does most of the work in the Digital Tacho. It accepts input pulses from the coil (via a pulse conditioning circuit) or from the tacho output of an engine management computer and drives the LED displays. change up. The lower four LEDs can be blanked out by programming their rpm settings to the same value as for LED 5. The hysteresis for the LED bargraph display in dot or bar mode can also be selected to give the best bargraph display and limiter results. The hysteresis sets the rpm difference between when a LED first turns on and when it is switched off. If the hysteresis is set at 0, then each LED and the limiter output will switch on at the preset rpm and also switch off at this same rpm value. This means that a LED will continually flicker on and off if the rpm remains fairly constant. Adding hysteresis (eg, 100 rpm) ensures that the engine rpm must fall by a preset amount before the LED extinguishes after first switching on. This prevents display flicker which can be distracting. Hysteresis is also useful for the limiter output. This must stay low for a certain length of time to give the ignition limiting circuit a chance to work. The hysteresis is initially preset to 100 rpm and this value should be suitable for most applications. However, if your engine doesn’t maintain a constant rpm value at a given throttle setting, a greater hysteresis value may be required. In practice, you can set it to any value from 0-900 rpm in 100 rpm steps. One feature that is fixed in the software is the display update time. This is nominally set at the count period for the ignition coil pulses and is 0.3 seconds for a 4-cylinder 4-stroke engine. However, engines with more sparks per revolution will have a calibration which gives a faster count period and this would cause the display to become a blur as the digits rapidly changed, particularly the 100 rpm digit. The software compensates for this problem by only changing the display reading at a maximum of once every 0.3s regardless of the count period set by the calibration value. The 16 Silicon Chip bargraph display update time is also fixed at 0.3s. The accompanying calibration table (Table 1) shows the correlation between the number sparks per revolution, the count period and the display update time. Note how the count period becomes very short for 6-12 cylinder 4-stroke engines. Circuit details Refer now to Fig.1 for the complete circuit details. It’s dominated by IC1 which is the programmed PIC16F84P microcontroller. This device accepts inputs from the ignition coil (via a pulse conditioning circuit) or from the tacho output of an engine management computer and drives the LED displays. OK, let’s start with the pulse conditioning circuit. First, the voltage pulses from the ignition coil are attenuated by a factor of three using a voltage divider based on 22kΩ and 10kΩ resistors. The attenuated signal is then filtered by a .056µF capacitor which shunts signals above about 400Hz to ground and then AC-coupled via a 2.2µF capacitor to diode D1 and zener diode ZD2. ZD2 limits the peak signal level to 20V, while D1 allows only positive-going pulses to be fed to the inverting input (pin 2) of IC2a. A 10kΩ resistor between this input and ground holds the voltage low in the absence of any signal via D1. Alternatively, an ignition signal which swings from ground up to a maximum of 20V can be applied to the low input if this type of signal is available on your vehicle (eg, the tacho output of the engine management computer). IC2a functions as an inverting comparator with hysteresis. Each time a positive-going pulse is applied to pin 2, the output at pin 1 swings low. Alternatively, when no signal is present, pin 1 of IC2a swings high to almost 12V. Pin 3 of IC2a is nominally biased to about 1.6V by a voltage divider consisting of 4.7kΩ and 2.2kΩ resistors, while the 47kΩ positive feedback resistor provides the hysteresis. This sets the high-going threshold for the comparator to 1.7V and the low-going threshold to 1.5V and prevents false triggering due to noise. IC2a’s output drives pin 6 (RB0) of IC1 via a 2.2kΩ limiting resistor. Specifications • • • RPM accuracy typically 0.5% plus 100 rpm. • Bargraph rpm LED threshold values and limiter output rpm level can be set at any value from 0-9900 rpm. • Bargraph and limiter output hysteresis (rpm on to rpm off) adjustable from 0-900 rpm in 100 rpm steps. • Limiter output time set at a minimum of 0.3s. Linearity and repeatability within 100 rpm. Tachometer display update time: 0.6s for 2-cylinder 4-stroke calibration, 0.3s for 4-12-cylinder 4-stroke calibration settings. This resistor limits the current flow from IC2a when its output swings to a nominal 12V, while the internal clamp diodes at RB0 limit the voltage on this pin to about 5.6V (ie, 0.6V above the supply). Pin 6 (RB0) of IC1 is set as an interrupt and the internal software responds whenever this input goes low. on and applies power to the common anode connection of DISP3. Any low outputs on RB1-RB7 will thus light the corresponding segments of that display. After this display has been on for a short time, the RA2 output is taken high and DISP3 turns off. The 7-segment data on RB1-RB7 is then updated, after which RA1 is brought low to drive Q2 and display DISP4. Finally, after a short time, RA0 is taken low to drive Q3 and LEDs1-7 of the bargraph. Note that displays DIPS1 and DISP2 always show “00”. These displays have their a-f segments commoned and connected to ground via 150Ω resistors. DISP1 is switched by transistor Q2 and so it lights when DISP4 lights. Similarly, DISP2 is switched by transistor Q1 and lights when DISP3 lights. But why multiplex DISP2 and DISP1 if they always show “00”? Why not just leave them on all the time? The answer is that we multiplex them so that they will have the same brightness as the other displays. This LED displays The 7-segment LED displays and the LEDs1-7 of the bargraph are driven directly from the RB1-RB7 outputs of IC1 via 150Ω current limiting resistors. As shown, the corresponding segments of displays DISP3 and DISP4 are connected together, as are the segments for DISP1 and DISP2. In addition, the cathodes of the first seven LEDs in the bargraph (LEDs17) are each tied to a DISP3/4 display segment. The displays are driven in multiplex fashion, with IC1 switching its RA0, RA1 and RA2 lines low in sequence to control switching transistors Q1-Q3. For example, when RA2 is switched low, transistor Q1 turns Table Table 1: 1: Calibration Calibration Data/Update Data/Update Times Tim es N o. Of Cyls. (4-stroke) 1 N o. Of Cyls. (2-stroke) 2 1 3 4 2 5 Pulses/Rev Count Period Update Time 0.5 1.2 1.2 1 0.6 0.6 1.5 0.4 0.4 2 0.3 0.3 2.5 0.24 0.3 6 3 3 0.2 0.3 8 4 4 0.150 0.3 10 5 5 .06 0.3 12 6 6 .05 0.3 April 2000 17 limiting resistors when the reline has been reached. Second, it provides the limiter output signal. This output is normally at +5V but goes low to drive an external limit circuit whenever the redline is reached. Switch inputs Fig.2: install the parts on the PC boards as shown here. Note that switches S1-S3 on the display board must be installed with their terminals oriented as shown, while the electrolytic capacitors must all be mounted parallel to the board surface (see photo). is particularly important when the displays are dimmed. Multiplexing them also means that we only need six 150Ω current limiting resistors for the two displays rather than the 12 that would be needed if they were not multiplexed. The output at RA3 performs two functions. First, it switches low and drives LEDs 8-10 via 470Ω current Switches S1, S2 & S3 are all monitored at the RA4 input. The other sides of the Mode, Down and Up switches connect to the RA0, RA1 & RA2 outputs respectively. Normally, the RA4 input is held high via a 47kΩ resistor which connects to the +5V supply rail. However, when a switch is closed (pressed), the RA4 input is regularly taken low by one (and only one) of the RA0-RA2 outputs. The microcontroller then determines which switch has been closed by checking to see which one of the RA0, RA1 & RA2 outputs is low when RA4 is low. For example, if RA4 is low when RA0 is low, then it’s the Mode switch that’s been pressed. Similarly, if RA4 is low when RA1 is low it’s the Down switch that’s pressed and if RA2 must be low then it’s the Up switch. The 1kΩ resistors in series with the Mode and Up switches are there to ensure that the RA0, RA1 & RA2 outputs can not be shorted if more Capacitor Codes     Value IEC Code EIA Code 0.1µF 100n 104 0.056µF 56n 563 15pF 15p 15 Resistor Colour Codes  No.  1  1  1  2  1  2  2  1  3  2  13  1 18 Silicon Chip Value 47kΩ 22kΩ 22kΩ 10kΩ 4.7kΩ 2.2kΩ 1kΩ 680Ω 470Ω 220Ω 150Ω 10Ω 4-Band Code (1%) yellow violet orange brown red red orange brown red red orange brown brown black orange brown yellow violet red brown red red red brown brown black red brown blue grey brown brown yellow violet brown brown red red brown brown brown green brown brown brown black black brown 5-Band Code (1%) yellow violet black red brown red red black red brown red red black red brown brown black black red brown yellow violet black brown brown red red black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown red red black black brown brown green black black brown brown black black gold brown than one switch is pressed at the same time. This could otherwise produce strange display results. Dimming IC2b is used to control the display brightness. This op amp is connected as a voltage follower and drives buffer transistor Q4 which is inside the negative feedback loop. Light dependent resistor LDR1 controls the voltage on the pin 5 input of IC2b according to the ambient light level. IC2b in turn controls Q4 and thus the voltage applied to the emitters of display drivers Q1-Q3 and to the commoned anodes of the red LEDs in the bargraph. The circuit works like this. When the ambient light is high, LDR1 has low resistance and so the voltage on pin 5 of IC2b will be close to +5V. This means that the voltage at Q4’s emitter will also be close to +5V and so the LED displays will operate at full brightness. Conversely, in low light conditions, the resistance of the LDR will be higher and so the voltage on pin 5 of IC2b is lower than before. In fact, when it’s completely dark, the voltage on pin 5 is determined by VR1 which sets the minimum brightness level. As before, the voltage on pin 5 appears at Q4’s emitter and so the displays are driven at reduced brightness. Note that, in practice, VR1 is adjusted to give the requisite display brightness at night. Clock signals Clock signals for IC1 are provided by an internal oscillator circuit which operates in conjunction with 4MHz crystal X1 and two 15pF capacitors. The two capacitors are there to provide the correct loading and to ensure that the oscillator starts reliably. The crystal frequency is divided down internally to produce separate clock signals for the microcontroller operation and for display multi plexing. The crystal frequency is also used to give a precise time period over which to count the incoming ignition pulse signals at RB0. The number of pulses counted in a given time indicates the engine rpm. Power Power for the circuit is derived from the vehicle’s battery rail via the ignition switch. A 10Ω 1W resistor and 47µF capacitor decouple this The display board (in case at top) plugs directly into the pin header sockets on the processor board (above), eliminating wiring connections between the two. Notice how the electrolytic capacitors on the processor board are bent over, so that they lie across the regulator leads and across ZD2. 12V supply rail, while zener diode ZD1 protects the circuit from transient voltage spikes above 16V. The decoupled supply rail is then fed to REG1 to derive a +5V rail and this in turn is filtered by the 47µF and 0.1µF capacitors. The +5V supply rail is used to power all the circuitry except for IC2 which is powered directly from the decoupled 12V ignition supply. OK, so much for the electronic hardware which is fairly straightforward. As you’ve probably gathered by now, most of the complicated stuff takes place inside the microcontroller under software control. We’ll describe how this software works next month. Construction Fortunately, you don’t have to understand how the software works to build this circuit. Instead, it’s all programmed into the PIC chip. You just buy the preprogrammed chip and “plug” it into the socket on the circuit board. All the parts for the Digital Tacho meter are mounted on two PC boards: a processor board coded 05104001 April 2000 19 The pin headers are installed on the track side of the display board using a finetipped soldering iron. Note that it will be necessary to slide the plastic spacers along the leads to allow room for soldering. This view shows how the two boards are stacked together in “piggyback” fashion to make a compact assembly. Make sure that none of the parts on the processor board contact the back of the display board. and a display board coded 05104002. Both boards measure 78 x 50mm. They are stacked together and the connections between them automatically made using pin headers and cut-down IC sockets. Fig.2 shows the assembly details. Begin the construction by checking both boards for shorts between tracks, open circuit tracks and undrilled holes. This done, you can install all the parts on the processor board as shown in Fig.2. First, install all the wire links, then install the resistors using the accompanying resistor colour code table as a guide to selecting the correct values. It’s also a good idea to use a digital multimeter to measure each 20 Silicon Chip one, just to make sure. Note that the 150Ω resistors on the processor PC board are mounted end on. The horizontal trimpot (VR1) can go in next, followed by a socket to accept IC1 – but don’t install the IC yet. IC2 is soldered directly to the board and can go in now. Make sure that both IC2 and the socket for IC1 are correctly oriented. Next, install diode D1 and zener diodes ZD1 & ZD2, followed by transistors Q1-Q4. Be careful here – Q4 is a BC338 NPN type while Q1-Q3 are BC328 PNP types, so don’t get them mixed up. Now for regulator REG1 – this is installed with its metal tab flat against the PC board and with its leads bent at rightangles to pass through their respective mounting holes in the board. Make sure that the hole in the metal tab lines up with its corresponding hole in the PC board. The capacitors can now be installed, making sure that the electrolytic types are correctly oriented. Note that the electrolytics must all be mounted so that they lie parallel with the PC board, as shown in the photograph. The two 47µF capacitors at bottom right are bent over so that they lie across the regulator’s leads, while the 2.2µF capacitor below diode D1 lies across ZD1. Crystal X1 also mounts horizontally on the PC board. It is secured by soldering a short length of tinned copper wire between one end of its metal case and a PC pad immediately to the right of Q1. The three 7-way in-line sockets can now be fitted. These are made by cutting two 14-pin IC sockets into single in-line strips using a sharp knife or a fine-toothed hacksaw. Clean up the rough edges with a file before installing them on the PC board. Finally, install PC stakes at the five external wiring positions (near the bottom edge of the board and adjacent to D1). Once they’re in, trim these stakes on the component side of the board to prevent them from shorting against the display PC board later on. Also, the coil input PC stake needs to be shortened to prevent it from arcing to adjacent tracks on the display board due to its high voltage. Display board assembly Now for the display board. Install the wire links and the resistors first, including the six 150Ω resistors that sit beneath DISP1 and DISP2. The four 7-segment LED displays can then be installed with their decimal points at bottom right. Note that all the displays are mounted slightly proud of the board because of the 150Ω resistors. Make sure that they are all correctly aligned before soldering all their pins. Switches S1-S3 must be oriented correctly, so that there is normally an open circuit between the top and bottom terminals of each switch. These switches have leads which are rectangular in shape and it’s simply a matter of installing them with their leads oriented as shown in Fig.2. The LED bargraph mounts so that the anode leads are to the left. Install Fig.3: follow this diagram when stacking the boards together and be sure to use plastic washers where indicated. Note the small heatsink attached to the brass spacer. Fig.4: the full-size artworks for the front panel and PC boards are shown above and at right. it so that the green LEDs are to the left and the red LEDs to the right and you can’t go wrong. It should also be installed so that its top face is 19.5mm above the PC board, so that it will later sit flush with the front panel. The LDR should be mounted with its face about 1.5mm above the displays. Finally, complete the display board assembly by inserting the pin headers. These are installed from the copper side of the board with their leads just protruding above the board surface. You will need a fine-tipped soldering iron to solder them to the copper pads on the PC board. It will also be necessary to slide the plastic spacers along the leads to allow room for soldering. Final assembly The plastic case requires a minor amount of work before installing the PC boards. First, use a sharp chisel to remove the integral side pillars, then slide the processor PC board into the case and drill two mounting holes – one through the metal tab hole of the regulator and the other below the 0.1µF capacitor near IC2. An oversize drill can then be used to countersink the holes on the outside of the case, to suit the specified M3 x 6mm CSK screws. Two holes are also required at the rear of the base of the case for the power supply wiring and for the ignition coil lead. These holes can be drilled so that they line up with the relevant PC stakes. The next step is to fashion a small heatsink from sheet copper and solder it to the 6mm brass spacer – see Fig.3. This heatsink must be shaped so that the copper sheet cannot make contact with any components on the processor PC board and cause a short. The main component to watch out for here for is ZD1. The display board can now be plugged into the processor board and the assembly secured exactly as shown in Fig.3. Be sure to use plastic washers and spacers where specified and note that you must use an M3 x 15mm Nylon screw on one side of the assembly, while the other side uses a metal screw. Check that the leads from the parts on the display PC board do not interfere with any of the parts on the processor PC board or with the copper heatsink. Some of the pigtails on the display PC board may have to be trimmed to avoid this. The front panel label can now be affixed to the front panel and used as a template for making the display cutouts and for drilling the hole for the LDR. The main display cutout is made by first drilling a series of small holes around the inside perimeter, then knocking out the centre piece and filing the job to a smooth finish. Make the cutout so that the red Perspex or acrylic window is a tight fit. The window can be further secured by applying several small spots of super glue along the inside edges. Similarly, the cutout for the LED bargraph can be made by drilling a row of small holes and then filing so that the bargraph is a neat fit. Test & calibration It’s a good idea to check the power supply before plugging the microcontroller IC into its socket. To do this, first unplug the display board and connect automotive wires to the +12V and GND inputs of the processor board. This done, apply power and use a multimeter to check that there is +5V on pins 4 & 14 of IC1’s socket, using the metal tab of REG1 for the ground connection. If this is correct, disconnect the power and insert IC1 in place, ensuring that it is oriented correctly. Now attach both PC boards together and reapply power. The 7-segment LED displays should show “000” rpm, April 2000 21 Parts List 1 processor PC board, code 05104001, 78 x 50mm 1 display PC board, code 05104002, 78 x 50mm 1 front panel label, 80 x 52mm 1 plastic case utility case, 83 x 54 x 30mm 1 dark red transparent Perspex or Acrylic sheet, 59 x 20 x 2.5 1 4MHz parallel resonant crystal (X1) 1 LDR (Jaycar RD-3480 or equiv.) 5 PC stakes 3 7-way pin head launchers 2 DIP-14 low cost IC socket with wiper contacts (cut for 3 x 7-way single in line sockets) 3 tactile switches (S1-S3) (Jaycar SP-0730 or equiv.) 1 500kΩ horizontal trimpot (VR1) 1 6 x 20 x 0.5mm sheet copper for heatsink 1 400mm length of 0.8mm tinned copper wire 1 2m length of red automotive wire 1 2m length of black or green automotive wire (ground wire) 1 2m length of 250VAC wire for ignition coil connection 3 6mm tapped spacers 2 M3 nuts 2 M3 x 6mm countersunk screws or Nylon cheesehead cut to length 3 M3 plastic washers 1mm thick 1 M3 x 15mm Nylon screw while the first seven LEDs of the bargraph should be lit. Pressing the Mode switch (at far left) selects the first calibration function (or mode). This mode shows the calibration value which is a number ranging from 1-12, corresponding to 1-12 cylinders for a 4-stroke engine. Note that the display also shows the two fixed righthand “00” digits but these are ignored. Initially, the display should read “400” which is the default value for the number of engine cylinders; ie, the default is for a 4-cylinder engine (as previously stated, the two righthand digits are ignored). The calibration number is changed using the Up button (far righthand side) which selects the next value. 22 Silicon Chip 1 M3 x 15mm brass screw Semiconductors 1 PIC16F84P microprocessor programmed with TACHO.HEX program (IC1) 1 LM358 dual op amp (IC2) 1 7805, LM340T5 5V 1A 3-terminal regulator (REG1) 3 BC328 PNP transistors (Q1-Q3) 1 BC338 NPN transistor (Q4) 4 HDSP5301, LTS542A common anode 7-segment LED displays (DISP1-DISP4) 1 10-LED bargraph (Jaycar ZD1702 or equiv.) (LEDs 1-10) 1 16V 1W zener diode (ZD1) 1 20V 1W zener diode (ZD2) Capacitors 2 47µF 25VW PC electrolytic 1 2.2µF 50VW bipolar electrolytic 2 0.1µF MKT polyester 1 .056µF MKT polyester 2 15pF ceramic Resistors (0.25W, 1%) 1 47kΩ 2 1kΩ 1 22kΩ 1W 1 680Ω 1 22kΩ 3 470Ω 2 10kΩ 2 220Ω 1 4.7kΩ 13 150Ω 2 2.2kΩ 1 10Ω 1W Miscellaneous Automotive connectors, heatshrink tubing, cable ties, etc. You simply press this switch until the required value appears. So, if you have a 6-cylinder car, press the Up button twice so that the display reads “600”. The Down switch (middle) does not operate for the calibration adjustment. Note that if you are calibrating for a 2-stroke engine, you should select a value that is twice the number of cylinders. Pressing the Mode switch again lights the lefthand LED in the bargraph display. This corresponds to the lower rpm LED setting which is initially “000” rpm. It can be adjusted using the Up and Down switches if you wish to alter the default value. Pressing the Mode switch again cycles to the next LED in the bargraph display and so on until the final 8, 9 & 10 (red) LEDs of the bargraph display all light up. As indicated at the start of the article, the initial pre-programmed redline value is 4000 rpm and this will be indicated on the display. This value should be altered to suit the redline limit for your engine using the Up and Down switches. Once this had been done, the lower rpm settings for LEDs 1-7 are automatically calculated to provide a linear progression. You can go back and check this by pressing the Mode switch until you return to the rpm setting modes (after three Mode switch pressings) for each LED on the bargraph display. Note that you must change the 4000 rpm setting, otherwise the automatic calculation process won’t take place. This means that if you wish to set the redline limit at 4000 rpm (ie, to the default value), you must first press the Up switch and then the Down switch to return to 4000 rpm again. Once this has been done, the automatic calculation will take place. OK, so that’s the basic setup procedure for the Digital Tachometer. Note that all these settings now remain in place unless they are altered using the switches – even if the power is removed. Advanced features While most users will be happy with the basic setup, there are some added features for those who would like to customise their tachometer. One of the obvious changes that could be made is to individually adjust the rpm setting for each LED in the bargraph display. This could be done to compress the rpm range for the middle LEDs where most of the engine action takes place. For example, the lower LED could be set to indicate the engine speed at which to change down, to prevent the engine from labouring. The middle LEDs could then be programmed to light over a narrower range of rpm values compared to the linear progression that is automatically calculated. The only thing to note here is that it is important to adjust the LEDs 8-10 (redline) value first before changing the lower rpm values for the remaining LEDs. If you don’t do this, the settings will be overwritten by the automatic recalculation process that takes place each time the LEDs 8-10 rpm value is changed. Simply cycling through the LEDs 8-10 rpm setting using the Mode switch will not activate the automatic recalculation process, however. Automatic recalculation only occurs when the Down or Up switch is pressed in this mode. In fact, you can cycle through all the modes without changing any of the settings. The hysteresis setting mode is selected by repeatedly pressing the Mode switch until the display shows “H100” (ie, the default is 100 rpm). If necessary, this can be altered using the Up switch. As you do this, the display indicates hysteresis in 100’s of rpm. Note that the Down switch does not operate in this mode. Further tests & installation You can test the dimming feature by holding your finger over the LDR to simulate darkness. Unfortunately, you will need to unplug the display board (with the power switched off) to make adjustments to VR1, so adjustments will have to be done on a trial and error basis. The best time to make this adjustment is at night – just set VR1 to give the correct minimum brightness in the dark. You can further test the Digital Tachometer with a signal generator set to give a 3V rms sinewave output. Attach the signal generator output between ground and the low voltage input of the tachometer. The unit should show a reading of 3000 rpm per 100Hz input (4-cylinder, 4-stroke calibration only). Use automotive cable and connectors when installing the unit into a vehicle. The +12V supply connection is derived via the ignition switch and a suitable connection point will usually be found inside the fusebox. Be sure to choose the fused side of the supply rail, so that the existing fuse is in series. The ground connection can be made by connecting a lead to the chassis via an eyelet and self-tapping screw. The coil input for rpm sensing can connect directly to the switched side of the ignition coil using 250VAC rated wire. Alternatively, you can use a low voltage signal if this is available from the vehicle’s computer; eg, a low-voltage tachometer output signal. A 0-5V signal will directly trigger the Digital Tachometer if the signal is Using The Rev Limiter Output A S MENTIONED the Digital Tach ometer limit output can control an engine limiter. This will reduce the number of sparks per revolution at the rpm limit and thus prevent the engine from revving past this limit. We published a suitable Rev Limiter circuit in the April 1999 issue but note that you don’t have to use the whole circuit. Instead, you only have to use the Ignition Switcher circuit which was assembled on a separate PC board. The Ignition Switcher uses a single 555 timer IC and several transistors to drive a high-voltage Darlington output transistor. When the rev limit is reached, this transistor shorts out the main switching transistor in the car’s ignition system for about 50% of time, thus reducing the engine power and thereby limiting the engine rpm to the redline. The two circuits are easy to marry – all you have to do is connect the limit output from the Digital Tachometer directly to the terminal marked “From Rev Limit Controller” on the Ignition Switcher. A suitable value for C1 must be chosen for the Ignition Switcher from the table published in the April issue. This sets the requisite number of sparks that are blocked out during the limiting action. Note that if the Digital Tachometer derives its input signal from the coil, it will sense that the rpm has dropped as soon as the coil is prevented from sparking via the limiter action. This means that the limit action may not be as smooth as it would be if the tachometer signal was derived from a different source, such as the tachometer output from the engine computer. However, the limit output from the tachometer will remain low to disable the spark for at least 0.3s, regardless of the input source for the tachometer. This should provide sufficient time for the limit action to take place. The limiter output from the Digital Tacho can be used to drive this Ignition Switcher board (SILICON CHIP, April 1999), to restrict engine revs to the “red-line” setting. connected to the low voltage input. Note that some cars, including late-model Holden Commodores and Ford Falcons, use double-ended ignition coils, with each coil simultaneously firing two spark plugs (ie, three coils are used for a 6-cylinder engine). Similarly, some cars use individual coils for each cylinder and these are usually located at the ends of the HT leads, directly on the spark plugs. Invariably, these types of coils are fully encapsulated and their terminals are not accessible. The answer here is to use the tacho output from the engine management computer. You will need to refer to the wiring diagram for your vehicle to identify the correct lead or check with an auto SC electrician. April 2000 23 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 How to Protect Life AND Property: ROOMGUARD Smoke alarms are very common nowadays – in fact, in many states they’re required by law in all new homes. But why have just a smoke alarm? Here’s how to make one do double duty as an effective but low cost intruder alarm. by JOHN CLARKE F ITTING A SMOKE ALARM makes a lot of sense. For not much more than $10 – including a battery – they offer peace-of-mind and security, especially while the family sleeps. Typically though, the one place they are not normally fitted is the one place they should be – in bedrooms. That extra few minutes (or even seconds) of warning time could literally be the difference between life and death. But smoke detectors in bedrooms, especially teenage kid’s bedrooms, aren’t cool. They don’t want ’em! What they really want is something to keep little brother or sister out while they’re not home. The “keep out” sign on the door doesn’t work real well, even if it does threaten some exotic disease to anyone entering except the occupant. Where is all this leading? Well, how do you think they’d like an alarm system which will keep a sibling at bay? It just happens to look like a smoke detector and yes, it will shriek its head off if there is smoke in the room 28 Silicon Chip (darn! now they can’t smoke in their bedrooms...). Well, here it is. The SILICON CHIP ROOMGUARD looks and works just like a typical smoke detector – mostly because it is a typical smoke detector with its normal action completely unchanged! But it’s much more. By wiring in a suitable control circuit (and even pinching power from the detector’s 9V battery) we can make the detector sound an alarm when triggered by virtually any alarm detection device – switches on the doors or windows, pressure mats outside the door, light beam relays, even passive infrared (PIR) movement sensors and so on. But more on these devices anon. The features available on low-cost smoke alarms include a loud siren, a test input to sound the alarm, a low battery warning and of course a battery supply. These are all used as the main alarm section for the RoomGuard. Connections to the smoke alarm are deliberately kept very simple. Take one low-cost battery-operated smoke detector, add a little extra circuitry and an intruder detection device or two . . . and you have a low cost, battery-operated smoke detector which screams its head off when there’s smoke or intruders. It’s simple to build, too! They include the battery connections mentioned above and just two other connections which go to the “test” button. Normally this button is simply used to sound the alarm and so check the battery. We bridge it out to sound the alarm to indicate an intruder. What we have added to the smoke alarm to make up the RoomGuard system are two instant alarm inputs, a delayed input, an exit delay and an arm/disarm switch. The instant inputs make the smoke alarm sound immediately while the delayed input gives you time to get in and turn off the alarm side before the smoke alarm sounds. Alarm sensors are usually one of two types: at rest they are open circuit and they close when tripped or triggered – this is the normally open (NO) variety. The opposite, normally closed or NC type, is normally a short circuit which opens when triggered. The inputs to this alarm can be either normally open (NO) or normally closed (NC) types and more than one can be used per input if connected in parallel or series respectively. You cannot mix NO and NC types together on one input but you can have NO sensors on one input and NC sensors on the other input circuit. The intruder circuit has been designed to minimise current consumption so as to conserve the smoke alarm battery as much as possible. Actual life of the battery will depend on the amount of use the RoomGuard is given. It typically draws 250µA when armed and zero current when disarmed. A 1Ah (1000mAh) alkaline battery will provide a nominal 5.5 months of continuous use. In practice, if the RoomGuard is armed for 12 hours per day you could expect the battery to provide over eight months of use, including the consumption of the smoke alarm itself. This is significantly longer than the recommended time for batteries in smoke alarms: fire authorities say they should be changed every time you change your clocks for daylight saving (ie, roughly every six months). What readers in states without daylight saving do we’re not sure! The RoomGuard circuit is housed in a small plastic case which can be mounted anywhere practical: inside a cupboard, behind a bedhead, in fact, in any “hidden” location. The wires from the RoomGuard to the smoke alarm need to be hidden as much as possible – ideally, they should be taken up the wall and into the ceiling cavity. The wires could then be brought out to the smoke alarm unit (which is normally mounted on the ceiling). Wires to the sensor inputs could run down the wall to the floor and then under the floor to the sensor switches – or perhaps these could also run through the ceiling cavity, especially if they went to devices such as PIR detectors. Anyway, we’re getting a little ahead of ourselves. Let’s look at how the system works. The block diagram (Fig.1) shows the general arrangement of the Room April 2000 29 Fig.1: follow this block diagram and the text – and you should have no trouble working out just what the RoomGuard does. Guard alarm. It consists of three sensor inputs and three timers – a delay timer for one of the inputs, an exit delay timer and an “alarm on” timer which keeps the alarm sounding even if the input sensor is quickly returned to its normal state. The two instant alarm inputs (IC1a and IC1b) directly trigger the alarmon timer (IC2) immediately while the delayed input (IC1c) activates the delay timer which triggers the alarm-on timer after about 25 seconds. When activated, the alarm-on timer drives an optocoupler which is used to short out the “Test” switch on the smoke alarm to sound the siren. The arm/disarm switch (S1) incorporates an exit delay so that the RoomGuard is initially disabled for a short time (about 24 seconds) to allow exit from the room; this stops the sensors from having any effect even if they are triggered. After this delay the RoomGuard becomes fully active. A bi-colour LED (LED1) shows the two states – disabled and armed. The delay circuits do not affect the smoke alarm operation in any way – if there was a fire in that 24 seconds (or any time thereafter) the smoke detector would scream its head off! Of course the siren is shared between the smoke alarm and the Room Guard and so when the siren sounds, you have to decide if it is an intruder or a fire that caused the alarm. Here’s a clue: fires are hotter than intruders and have lots of smoke. The circuit for the RoomGuard is shown in Fig.2. It uses just four lowcost ICs, several resistors, capacitors and diodes, a switch and the bi-coloured LED. IC1 contains four exclusive-OR gates. The output of these gates (eg, pin 4) is only high whenever one of its inputs (eg, pin 5 and 6) is at a different logic level to the other. So if pin 5 goes high before pin 6, we get a short-duration high output. If pin 6 reaches the same logic level (its upper threshold voltage), the output then goes low. Both instant inputs work the same way, so we will concentrate on Input 1. It can operate with either normally open (NO) or normally (NC) contacts in the sensors. If the contact is initially closed both inputs to IC1a are low and the output is low. When the switch opens, the 0.22µF capacitor and 1µF capacitor both start to charge to the positive supply voltage via the 1MΩ resistor. But the smaller 0.22µF capacitor charges faster than Inside the RoomGuard controller box. Everything is mounted on a single PC board with connections to both the smoke detector (left side) and alarm sensor devices (right side) via on-board terminal blocks. At this stage no sensors were fitted. 30 Silicon Chip the 1µF capacitor and so pin 5 reaches its upper threshold before pin 6. Therefore the output (pin 4) goes high. Should the switch close again, pin 5 will be low but pin 6 will stay high until the 1µF capacitor discharges via the 100kΩ resistor. Thus we get a high output when the switch closes. Note that for this type of circuit to work we must have the delay from the 1µF input longer than the delay for the 0.22µF input. The time constant (the time it takes for the capacitor to charge to 63% of the applied voltage) is set at 0.22 seconds for the 0.22µF capacitor (time constant T = R x C where R is in ohms and C is in Farads – or 1,000,000 x .00000022) when the switch opens. Similarly, the 1µF capacitor time constant is 1.1 seconds when the switch opens ([1,000,000 + 100,000] x .000001). When the switch closes, the 0.22µF input goes low virtually instantly, while the 1µF capacitor must discharge via the 100kΩ resistor, giving a time constant of 100ms. A reverse operation occurs if the sensors have normally open contacts. Both gate inputs are held high by the charged capacitors but if the sensor contacts close, pin 5 goes low immediately while the capacitor at pin 6 must discharge through the 100kΩ resistor. Therefore the gate output goes high. The outputs of IC1a or IC1b drive gate IC1d via diode D1 and/or D2. IC1d is set up as a buffer so when pin 9 goes high, so does pin 10. When this happens, pin 10 charges the 0.15µF capacitor to the 9V supply rail. When pin 10 goes low, pin 2 of IC2 is pulled low to trigger the alarm-on timer. The .015µF capacitor charges via the 560kΩ resistor so that the trigger input goes high after about 10ms. Diode D5 prevents the pin 2 (trigger) input from going above the 9V supply whenever pin 10 of IC1d goes high. Without D5, the trigger input to IC2 could be damaged by excessive voltage. IC2 is a 7555 connected as a mono stable timer. The 220µF capacitor at its threshold input (pin 6) is charged via the 560kΩ and 10kΩ resistors towards the positive supply. During the charging period, the output (pin 3) is high. After about 138 seconds, or a little over two minutes, the 220µF capacitor is charged to 2/3rds the supply voltage. Pin 3 then goes low and the 220µF capacitor is discharged via the 10kΩ resistor and pin 7. The 10kΩ resistor limits the discharge current through pin 7. IC4 is an optocoupler which contains a LED and a phototransistor. When the LED is off, the photo transistor is off and when the LED is on, the phototransistor is on. But there is no electrical connection between the two devices. Fig.2: there’s not a great deal to the RoomGuard because the alarm itself is actually in the smoke detector. All we need to do is sense the intruder and tell the smoke alarm’s siren to sound. Operation of the smoke detector remains unaltered. April 2000 31 3* 2* Parts List 1 battery-operated smoke detector (see text) 1 PC board, code 03303001, 62mm x 105mm 1 front panel label 127 x 63mm 1 plastic case 130 x 68 x 44mm 1 6-way PC terminals 1 4-way PC terminals 1 SPDT toggle switch, S1 1 50mm length of 0.8mm tinned copper wire 2 10mm rubber grommets 3 PC stakes Semiconductors 1 4030 quad XOR gate (IC1) 2 7555, LMC555CN, TLC555CN, CMOS 555 timer (IC2, IC3) 1 4N28 optocoupler (IC4) 6 1N4148, 1N914 switching diodes (D1-D6) 1 5mm bicolour (red/green) LED (LED1) Capacitors 1 220µF 16VW PC electrolytic 1 100µF 16VW PC electrolytic 2 47µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 3 1µF 16VW PC electrolytic 3 0.22µF MKT polyester 2 0.1µF MKT polyester 2 .015µF MKT polyester Resistors (0.25W 1%) 5 1MΩ 5 560kΩ1 470kΩ 3 100kΩ 3 10kΩ 1 1kΩ 1 470Ω Misccellaneous Suitable length 4-core cable Suitable alarm detection devices (see text and panel) 32 Silicon Chip 1* The high pin 3 output of IC2 drives the LED within IC4. This in turn switches on the internal transistor which is connected across the “test” switch in the smoke alarm. The smoke alarm is tricked into believing the test switch has been pressed – and sounds its siren. The output transistor in IC4 is fully floating with respect to the power supply, which means that it can operate the test terminals of the smoke alarm regardless of whether it is connected to switch to ground or to the positive supply. However, it is important to have the polarity correct when connecting to the test switch terminals so that the optocoupler transistor will operate. This can be easily determined with a multimeter. Entry delay Timer IC3, which is triggered by the delayed sensor circuit (IC1c), operates in a similar manner to IC2, charging a 47µF capacitor to give a nominal 24-second time period which gives you enough time to enter and turn off the (hidden!) “arm” switch, S1. Like the other input circuits, its output also triggers IC2 (the alarm-on timer), in this case via diode D4 and IC1d. The 100kΩ resistor holds pin 9 of IC1d low when the diodes are not conducting, preventing false alarms. Exit delay The exit delay is provided by holding the pin 4 reset inputs to IC2 and IC3 low for a short period. This prevents these timers from being triggered immediately after the circuit is armed. To initiate the exit delay, when S1 applies power the 100µF capacitor (C1) charges via the 1MΩ resistor Fig.3: this is the component overlay of the RoomGuard with the PC board pattern shown underneath. Use this diagram in conjunction with the photograph when assembling the PC board. toward the positive supply. When the reset inputs of IC2 and IC3 (pin 4) reach about 1V, the timers are free to operate normally. Moving S1 to off disconnects the exit delay circuit from the 9V supply and connects it to ground. This will discharge capacitor C1 via the 10kΩ resistor and D6. LED1 is included to indicate the RoomGuard status. When switched to the armed position, the red LED in the bicoloured LED1 lights briefly as the 47µF capacitor charges towards the ground supply rail via that LED and 1kΩ resistor. When the switch is moved to off, the +9V supply is removed and the green LED within LED1 lights momentarily as the 47µF capacitor discharges through it. Note that the bicolour LED only confirms the status of the RoomGaurd as you switch it on or off. At all other times the LED is off. If you use a key operated switch instead of the toggle type, it will only have a single pole switch contact. Connect it between the common and armed positions for S1. A 1MΩ resistor will be required to discharge capacitor C2 when power is switched off. The green disarmed LED will not momentarily flash with this arrangement but the red armed LED indication will still operate. The resistor has been catered for on the PC board and is designated R1. In this case, the more expensive bicolour LED could be substituted with a standard red LED. Construction The RoomGuard is housed in a plastic case measuring 130 x 68 x 44mm. The components are mounted on a PC board coded 03303001 and measuring 62 x 105mm. Begin construction by checking the PC board for shorts between tracks and for any hairline cracks. Check that the PC board is a neat fit into the integral side clips in the case (no screws are required for mounting the PC board). The sides may need to be filed slightly so that the PC board fits easily in the case. You can begin assembly of the PC board by inserting the resistors and link. Use the accompanying resistor colour code table to assist you in selecting the correct value for each position. A digital multimeter could also be used to measure the values. Insert the diodes and ICs next, taking care with their orientation. The capacitors can be installed next. The accompanying capacitor code table shows the possible labelling for each value. The electrolytic capacitors are marked directly in µF and must be oriented with the polarity shown on the overlay diagram. Solder in PC stakes for switch S1 and the 6-way and 4-way PC terminals. LED1 is mounted so that the top of its lens is 31mm above the PC board, while switch S1 is mounted by soldering the terminals to the top of the PC stakes. Resistor R1 will only be required if you intend to use a single pole single throw (SPST) switch for S1 (for example, a key-type switch). Connect the switch between positions 1 & 3. Testing You can test the RoomGuard operation without connecting it to a smoke alarm. First, connect power between the +9V and 0V terminals using a 9V battery or power supply. (Any voltage from about 6-12V can be used without changing the circuit operation). Check that the ICs have power by measuring between the 0V terminal and the positive supply pin. This is pin 14 on IC1 and pin 8 on IC2 & IC3. Check that LED1 lights when switch S1 is toggled between on and off and note the comment earlier in the article about the LED operation if a single throw key-switch is used for S1. Connect your multimeter between the test terminal outputs with the plus side to the positive lead on the multimeter. Set the multimeter to read resistance. Switch off the alarm and then switch it to the armed position. The meter should read over 10MΩ. Try to trigger the alarm by momen- We haven’t been too specific about how to connect the RoomGuard to a Smoke Alarm because there are so many on the market. However, all have “Test” buttons to check the battery. We simply wire across this switch and to +9V and 0V. tarily shorting the GND and input 1 terminals. These are the instant terminals but do not expect anything to happen since the delayed exit timer should still be operating. Continue to short these terminals every second or so until the multi meter reads a low resistance value. This should occur after about 20-25 seconds. The low resistance indicates that the circuit has triggered. The multimeter reading should be about 4.7kΩ. Check that this alarm time lasts for about two minutes after which the resistance reading should again go high. Now switch the alarm off again and then on to arm the circuit. Check the second input by waiting for 25 seconds and triggering between ground and input 2. The resistance should again go low. Finally, the delayed input can be tested by waiting until the resistance goes high again and retriggering the alarm by shorting the ground and input 3 terminals. Check that the resistance goes low after about 24 seconds from triggering. The case will require drilling at each end for the wire entry grommets. Also the lid needs two holes – one for the LED and the second for the switch. Use the front panel artwork as a guide to the positioning of these holes or refer to the photograph if using the Jaycar plastic case with the grid on the lid. The label can now be glued to the front panel. Installation Before we look at the alarm detection devices, we’ll examine how the RoomGuard is connected to your smoke alarm. First of all, though, we should point out that the RoomGuard is designed to be used with a low-cost battery-only powered unit – it should not be installed on a mains-powered, battery-backed smoke alarm. Having said that, the RoomGuard should operate with virtually any battery-operated smoke alarm available. It will be very difficult, if not impossible, to attach the wiring to the smoke alarm in situ (ie, on the ceiling). So if you’re connecting to an existing smoke alarm, first of all carefully remove the April 2000 33 At left is a full-size front panel which can be glued to the case lid, shown above. You can see how the “armed” switch and indicator LED holes have been lined up on the lid’s dot grid in this plastic case from Jaycar. If you use another case (without a grid) use the label as a drilling template. screws holding your smoke alarm in place (some smoke alarms simply twist to remove them). Take out the smoke alarm battery then carefully remove the PC board. Sometimes this is a little tricky – there are often hidden catches which must be pushed back. Few modern smoke alarms use screws to hold the PC board in place (screws cost money!) There are four wires which connect the RoomGuard to the smoke alarm. The first two, the “+” and “-” battery connections, are very easy. Simply solder the wires to the points on the smoke detector PC board where the battery wires connect. Some smoke alarms use an integral battery connector but even this is not hard to identify. Just make sure you get the polarity right: “+” to “+” and “-” to “-” (or red to red and black to black). Now for the more difficult (though not too difficult) part – identifying the test button connections. In many cases you will find little more than a piece of spring metal which shorts out when a tab or button on the outer case is pressed. Line up the PC board with the test button and see where it lies on the PC board. Turn the board over to the track side and identify which two points are shorted when the test button is pressed. As we mentioned before, you need to know if the test button connects power to the test button, or whether it shorts to ground. With a multimeter (preferably digital) check the polarity of the two terminals of the test button. The more positive terminal connects to the + terminal of connector 2 in the RoomGuard and obviously the more negative terminal to the – terminal of connector 2. Some test buttons short to the radioactive smoke detector case itself which is often stainless steel or aluminium. Resistor Colour Codes No.  5  5  1  3  3  1  1 Value 1MΩ 560kΩ 470kΩ 100kΩ 10kΩ 1kΩ 470Ω 34 Silicon Chip 4-Band Code (1%) brown black green brown green blue yellow brown yellow violet yellow brown brown black yellow brown brown black orange brown brown black red brown yellow violet brown brown 5-Band Code (1%) brown black black yellow brown green blue black orange brown yellow violet black orange brown brown black black orange brown brown black black red brown brown black black brown brown yellow violet black black brown This may be difficult (or impossible) to solder to so an alligator clip might be used to clip to the case. Alarm sensors/detectors You will need to install the Room Guard in a hidden place that is also convenient for access. Note the method of wiring normally open (NO) or normally closed (NC) switches: NO types all connect in parallel while NC types connect in series. Some types of sensor are only available in one type but if you have the choice of using either normally open or normally closed sensors, we recommend normally open devices because these will have the lowest current drain in our circuit, thus making the battery last longest. While we have called this alarm a RoomGuard, it can protect a whole home. You should divide the house or home unit into three sectors for the three inputs on the alarm. The instant inputs can be used for the windows and most doors except for the main door that you need to make your entry. This door sensor should be connected to the delayed entry input. Reed switches are commonly used for alarm sensors. These are tiny, magnetically-activated switches which can be hidden inside door jambs and window frames, with small magnets hidden in the door or windows them- Capacitor Codes    Value 0.22µF 0.1µF .015µF EIA 224 104 153 IEC 220n 100n 15n Fig.4: the full-size artwork for the PC board pattern. This can be used to make your own board or as a checking aid for commercial boards. selves. Reed switches are (usually) normally open but when the magnet is brought close by, they close. Thus an opening window or door can remove the magnet and so cause the reed switch to open, triggering the alarm. Note, however, that some reed switch- es are normally closed and some even have both NO & NC contacts. Another possibility, usually even easier to mount, is one of the small passive infrared (PIR) detectors which detect the movement of people. These can be either normally open or normally closed devices but the disadvantage is that they will require their own power supply (usually 12V). Any passive infrared unit which will be triggered when you enter the house to switch off the alarm must be also connected to the delayed entry input. There are many other types of detection devices – pressure mats which go under carpets or doormats, light beam relays which you can buy or make yourself, even the old spy novel trick of tying a piece of very, very fine wire across a doorway or entrance so that anyone walking through will break it. (It has to be extremely fine so they cannot see it and also to ensure it breaks when disturbed). You may come up with even more ideas to protect your room. Finally, when you’ve completed installation of both the RoomGuard and your alarm sensors, testing the unit is simply a matter of triggering all of the sensors you have connected. Get ready to turn it off quickly, though: smoke detector sirens are SC designed to be loud! Alarm Intruder Detection Devices Here are a few devices from the Jaycar Electronics catalog (free in this issue of SILICON CHIP) which are commonly used to trigger alarm systems. As mentioned in the text, magnetic reed switches are commonly used to alert an alarm system when an intrusion takes place. As their name suggests, these switches are magnetically activated – when a magnet is brought into close proximity to the switch a reed inside it makes (or less usually breaks) a contact, which activates the alarm. Where wood-framed doors and windows are used, a completely “invisible” reed Photo 1 switch can be used, as shown in photo 1. The magnet is housed in a hole drilled in the door or window itself while the reed is housed in the architrave or frame so that when the door or window is closed, the two parts line up. The connecting cables can go inside the cavity and no-one will know there is an alarm in place. Where aluminium or steel doors or windows need protection, the reed Photo 2 switches can be the surface-mount type shown in photos 2 and 3. Naturally these can be seen which usually means slightly less security. Reed switches are usually normally-open (NO) devices but the reed switch set shown in photo 3 is different: it is both NO and NC – you select which way you want it to work by wiring the appropriate terminals. The door Photo 3 switch shown in photo 4 is similar to that found in cars to turn their interior lights on and off. It is actually a nor-mally closed device but is held in the “NO” position by the closed door. When the door opens a Photo 4 spring causes two parts to short together. These are cheap, reliable switches but are sometimes more difficult to fit than other types. The last detection device shown here is a Passive Infrared (PIR) detector (photo 5) which senses the movement of people. They used to be very expensive but are now relatively cheap. PIRs usually have both NO and NC contacts but also require Photo 5 a 12V DC supply. They can also sometimes be triggered by pets, etc. Finally, note how NO and NC devices are wired: NO are always wired in parallel, while NC are always wired in series April 2000 35 Silicon Chip Back Issues September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High-Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple 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). October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. November 1990: Connecting Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; 6-Metre Amateur Transmitter. December 1990: 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. ORDER FORM Please send thethe following back issues: Please send following back issues: 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 Z80-Based 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. 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. 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. 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. 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. 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 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. 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 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. 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. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 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. SPECIAL STOCK CLEAROUT: 4 ISSUES FOR $10 (incl. p&p)* June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: Automatic SLA Battery Charger; Miniature 1.5V To 9V July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor DC Converter; 1kW Dummy Load Box For Audio Amplifiers; TrouPreamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V bleshooting Vintage Radio Receivers; The MIDI Interface Explained. *Offer SLA applies Battery Charger; Electronic Pt.10. to all issues upEngine to andManagement, including December 1994. Applies to Australian orders only and subscriber discounts do not apply. Offer closes 31st May, 2000. ____________________________________________________________ Enclosed is my cheque/money order for $______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 36 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 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 Dark rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. May 1995: Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; How To Identify IDE Hard Disk Drive Parameters. 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. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Transverter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2. 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. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Programmable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. September 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A Waa-Waa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. 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. 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. 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. 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. December 1996: CD Recorders – The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. January 1997: How To Network Your PC; 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: 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. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget; Win95, MSDOS.SYS & The Registry. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell; Relocating Your CD-ROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1998: Protect Your Car With The Engine Immobiliser Mk.2; Thermocouple Adaptor For DMMs; A Regulated 12V DC Plugpack; Build Your Own Poker Machine, Pt.2; 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. December 1997: Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. 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. 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. 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. 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 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. 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 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. 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. 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. 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. 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). March 2000: Doing A Lazarus On An Old Computer; Ultra Low Distortion 100W Amplifier Module, Pt.1; Electronic Wind Vane With 16-LED Display; Glowplug Driver For Powered Models; The OzTrip Car Computer, Pt.1; Multisim Circuit Design & Simulation Package (Review). 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 April 2000 37 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 DON’T UTER COMP MISS OMNIBUS THE ’BUS! www.siliconchip.com.au SILICON CHIP’S 132 Pages $ 95 * 9 ISBN 0 95852291 X 9780958522910 09 9 780958 522910 IN LINCLUDES FEA U TUR X E A collection of computer features from the pages of SILICON CHIP magazine Hints o Tips o Upgrades o Fixes Covers DOS, Windows 3.1, 95, 98, NT o RT Do you feel a little “left behind” by the latest advances and developments in computer hardware and software? Don’t miss the bus: get the ’bus! THIS IS IT: The computer reference you’ve been asking for! SILICON CHIP's Computer Omnibus is a valuable compendium of the most-requested computer hardware and software features from recent issues of SILICON CHIP magazine - all in one handy volume. Here's just a sample of the contents: Troubleshooting your PC: what to do when things go wrong NO Choosing, installing and taming computer networks AVA W Upgrading and overclocking CPUs DIRE ILABLE C Hard disk drive upgrades, tune-ups and tips SILIC T FROM Windows 3.1, 95, 98 and NT tips and tricks ON just $ CHIP The Y2K Bug - and how to swat it 125O* INC All about Linux GST & P& P And much more!!! ORDER NOW: Use the handy order form in this issue or call (02) 9979 5644, 9-5 Mon-Fri with your credit card details. * Price includes GST 09 SERVICEMAN'S LOG The fault that fixed itself! In this game, frustration comes with the job. Apart from the purely technical aspects such as tracking down weird faults, there are the incidental frustrations – the search for a rare spare part or a vital circuit, to say nothing of awkward customers. All of these problems are par for the course. One tackles them as they come, normally to a successful conclusion. But that doesn’t always happen. Mrs Shirley brought in her 1990 Panasonic NV-F70A VCR which had been involved in a lightning strike, along with her TV set, which was dead. This VCR had the unusual symptom of not having any sound in the E-E (tuner) mode. It could play and record sound via its AV inputs but there was nothing coming from the tuner – neither was there any stereo LED display. Being a stereo machine, the sound IF is taken from IC701 (M51366SP) on the TV demodulator pack and fed into the audio decoder where it is split into 5.5MHz and 5.74MHz signals before going to separate sound IF amplifiers and FM detectors. The outputs of these are then fed into IC7301 (TDA 3803A), which is the Zweiton stereo decoder. Knowing how something works is one thing; fixing it, another. Unfortunately, I have no equipment that can accurately indicate whether the sound IF is working correctly although I do have an RF probe that just gives a lot of noise and there is the CRO, which shows the same. The decoder module is almost totally inaccessible when soldered into the main CBA (Circuit Board Assembly VEP1353B). All I could do Fig.1: part of the sound IF circuitry in the Panasonic NV-F70A VCR. All the symptoms suggested that IC701 was the culprit but in the end, there was no way to be sure. 42 Silicon Chip was measure the inputs and outputs of the module but that indicated only that the +12V was present and that the mute Audio Off was in the right mode. And before anyone asks “what about the simulcast mode switch”, yes, I checked that first and it was OK. At this stage, I felt that the decoder IC (IC7301) could be faulty and decided to change it. Doing this meant removing the entire module before unsoldering and replacing it with a new one. This all took time and patience and as is my wont, I scrubbed the module with methylated spirits to remove any unwanted flux and check for faulty joints. Everything looked fine and eventually I was able to solder it back into the main CBA. I also checked for faulty joints on the de modulator module, especially around the metal screening cans where they are soldered onto the board. I switched it on and was disappointed to find it still didn’t work. There were two possible courses of action now. One was to check the +12V rail and any other rails for ripple that might be affecting associated circuits; the other was to check the sound IF. I had already checked the +12V and +11V rails associated with the voltage stabiliser circuit, involving Q7305, on the decoder module and they were spot on. I turned my attention to the power supply. Many technicians use an oscilloscope to measure the extent of ripple on each of the rails while simultaneously reading the DC level. However, I’ve had many cases of misleading results and it requires too much mental agility to calculate the percentage and type of ripple to be expected on each rail – as well as recalling which rail is on load or on standby. My preferred approach is to examine the entire switchmode power supply and measure the ESR (Effective Series Resistance) of all the electros as, by now, most are probably in need of attention. In this case, the usual culprits, C1109, C1118 and C1121, measured faulty but the rest were reasonable. This approach is quite quick and I hoped that that would be the end of the matter. I fitted the power supply back into the machine and powered it up but it still wouldn’t work. To make sure, I checked all the voltage rails with a digital multimeter and then the CRO. This was a wasted effort; they were all correct. I had already checked the main CBA for cracks and faulty joints, especially all the modules, so I was now left with just the sound IF. I had already checked the 9V stabiliser Q712, so I reasoned it was probably IC701 (M51366SP), a jungle IC on the demodulator module that was the main suspect. I discounted the two IF amplifiers and FM detectors – IC7302 and IC7303 (AN5213) – on the decoder, as I thought the chance of both failing simultaneously was unlikely. So I put aside the VCR while I ordered a replacement IC701 and went on with other jobs. In the meantime, I contemplated making an FM IF detector probe to deal with such problems but in the end decided that it really wasn’t worthwhile. The other thing that plagued my mind was the line marked SYNC L between the decoder and TV demod ulator modules. This is a 4.3V line from pin 9 of IC7651 (AN5421) to the two SIF Limiter Amps via transistors QR7301 and QR7302. IC7351 checks whether the video sync pulses are OK before deciding whether or not to cut off the sound IF, presumably to reduce unwanted noise in other modes; eg, AV input or playback, as well as multipath stereo distortion. The replacement IC701 finally arrived and I psyched myself up to fit it and try out some of my theories. However, before doing this, I set everything up to make sure it was functioning as before. And it was but then, just as I was about to switch it off to replace the new IC, it suddenly decided to work! The stereo light came on and both audio channels were in stereo on all TV stations. I couldn’t believe it. I checked all the tape functions, switched it on and off repeatedly, hit it, tapped it and kicked it. You name it; I did it and it still worked. I know lightning does some strange things, as it also took out the lady’s Sony TV set, but it is hard to believe that a lightning strike could cause this condition. More to the point, it is impossible to describe my frustra tion at this turn of events. It is bad enough to have to battle through a complex and time-consuming problem like this without knowing what fixed it. Furthermore, what sort of warranty can one give for an unknown cure? I put the machine on soak test for a few weeks and it never missed a beat. After that, all I could do then was return it to the customer and it is still working after several months. Only time will tell whether the “fix” is temporary or whether it will return to haunt me. Such is life; watch this space! Sony TV set As already indicated, that was only half of Mrs Shirley’s problem; her Sony KV-2964AS TV set (GP-1A Sets Covered This Month • • • Panasonic NV-F70A VCR Sony KV-2964AS TV set Sony KV-C2911D TV set chassis SCC-D23H-A) was completely dead from the same storm. The effect of lightning strikes can vary from just blowing the main fuse to hitting every component, so one never knows what to expect. In this case, the main 4A fuse F601 had blown violently, smashing the glass, which was a bad omen. I began by checking for DC shorts with the ohmmeter around bridge rectifier D601 on the F board. This wasn’t easy as the board is tucked behind the AV jack module K and is next to the motherboard (“A”) and its horizontal output transformer. However, I could find nothing of significance. The dual posistor THP 601 to the degaussing coils sometimes gives trouble on this series, probably more due to faulty joints than anything else but unlike other makes and models, if these degaussing coils are unplugged the circuit is not disabled and this can cause R601 to get extremely hot and smelly. This dual posistor can often cause intermittent failure of the fuse too. The output of the bridge rectifier plugs into the motherboard via F4/A6, supplying 340V to the switchmode power supply, but I couldn’t detect April 2000 43 any low resistance across this with my multimeter. Eventually, I decided to substitute a 200W globe in place of F601 before switching the power on. As the average power consumption for this set is 170W, I knew this might be inconclusive, especially with the degaussing coils consuming even more at switch on. With some trepidation I watched the globe as the set powered up. Initially, the globe glowed brightly but after 15 seconds or so it began to dim and with a few pulsations it remained at approximately quarter brightness. There were signs of life within the set – not enough to produce sound or picture but I could hear the horizontal 15,625kHz whistle and the EHT static charge rush to the final anode of the tube. This was promising – I now knew that the bridge rectifier and main electrolytic capacitor were OK and that the degaussing circuit and 44 Silicon Chip the switch mode primary were not drawing excessive current. I now felt that it was fairly safe to replace the 4A fuse but I was wrong. The set did its best to start and then there was a very loud bang and a bright light as the fuse exploded. So it was back to square but I did wonder if the power surge had caused any extra damage. I repeated my original series of checks and was gratified (and somewhat surprised) to find that everything was still OK. This done, I disconnected the motherboard via plug F-4, replaced the fuse and switched on again. Nothing adverse happened; the fuse held and there was 340V across pins 1 & 4 of F-4. This meant this circuit had to be OK but I now had to use the globe to discharge the main electrolytic, C607, before reconnecting it to the main chassis. During the last fuse “explosion”, I thought I detected a puff of smoke coming from behind the switchmode chopper transis tor Q601 and near transformer T602. This made me wonder whether some component, including the IC, had spat the dummy while under full load. The only way to confirm this is to completely remove the “A” board for a close examination and this would also give me a chance to re-solder any suspect joints. Removing the “A” board completely is a fair undertaking, with lots of plugs to remove and plastic subframes to unclip and unscrew. Once the board was out, I resoldered it to within an inch of its life. It may have been dead but it was now well soldered – a bit like a healthy corpse. Anyway, I examined the power supply and checked its DC resistance everywhere but everything measured fine. However, capacitor C420 (2.2µF 400V) looked a little sorry for itself, with its aluminium end bulging slightly, so I thought that it would be a good idea to change it while it was still a cheap and easy operation. This time, instead of the globe/ fuse arrangement, I tried a different tack and used the Variac instead. I gingerly wound it up, expecting it to strike in at about 110V, which it did. As I continued to wind it up and monitor the 135V rail at TP91/R340, more and more signs of life appeared until eventually a raster came up on the screen. Finally, I reached 240V AC and still had 135V on R340. Encouraged by this, I tried selecting a TV station using the remote control but nothing further happened. However, I was happy that the power supply was now OK. It was now time to track down the secondary faults and I hoped there weren’t too many. I started by checking the other voltage rails from the switchmode supply, namely the 22V rail and the 14V rail to the microprocessor. Both were correct, so it was on to the horizontal output transformer (T602) for the 17V and 28V rails (it was obvious that the 200V, 1000V and EHT supplies were OK or there wouldn’t be a raster). Finally, there were various tertiary rails: 83.6V on the emitter of Q602, 12V on TP96 at the output of IC602 (17V on the input) and 9V on TP94 at the output of IC603 (derived from the 12V rail). Everything was fine until I reached IC001, which converts 14V into 5V for the microprocessor but there was no output. I checked for shorts but found nothing, so I concluded it was the IC itself. This is an unusual 5-pin 5V IC regulator (LM78LR05D) which also provides the reset 5V for the microprocessor. It is not the sort of component I keep in stock but I was able to “borrow” one from a colleague, mainly to determine what else might be wrong with the set. But that was it! The microprocssor was in good working order and the picture, sound and on-screen display were now all OK. And the 68cm picture was just great. Reflecting on the whole repair once again, it is extraordinary how lightning destroys some components and not others. C410 is in parallel and rated the same as C607 – why one and not the other? Similarly, the 5V regulator is a small component in the midst of hundreds of others. Why did the lightning select this one on which to vent its wrath? Mortals such as you and I can only speculate but my money is on the theory of chaos and random selection! Christmas rush The prospect of no TV (despite the dearth of quality programs) is next to the end of life as they know it for many customers. Even large organisations can run out of resources around Christmas time (which is when this was written) and are only too happy to pass disgruntled, impatient, clients on to those of us not so well fed. So it was that a local service organisation passed on to me a few house calls involving monstrously heavy TV sets, just to keep the demanding public off their back. And as much as I hate doing service calls on such big sets, my bank balance demands I go forth and earn my keep. Mrs Staniforth (not her real name) was a frail old lady to look at but not to listen to. Her home is right near the sea and I was welcomed enthusiastically. Her set was a 1989 Sony KV-C2911D with an AE-1C chassis. The fault was that it took “only” an hour for the picture to come on. Apparently one of the service agent’s technicians had recom mended me highly and suggested it was probably only a faulty solder joint in the tube filament circuit and that someone as experienced as myself would fix it easily. I didn’t really need all this empty praise at that moment. And it was empty because anyone could see, without even taking the back off, that the fault was not a filament problem – the tube was fully alight. But there was no picture, no display, no nothing. (Whoops! – sorry about the double negative. There was nothing). The set was situated in a dark corner surrounded by expen sive Ming vase lookalikes. Removing the back without smashing the vases was a feat in itself, especially as I kept tripping over the tangle of power leads that were overloading the mains socket. Finally, I removed the back and shorted one cathode to chassis to make sure there was a full raster – and there was. I fumbled around trying to measure this and that and wait ing for the picture to appear but nothing happened. As I was doing all this I was constantly being asked, “have you fixed it yet? Do you know what the problem is? The other technician said it was only the filament circuit”. I fielded these questions as best I could but the confidence in my voice was beginning to falter – not that the customer would know what a filament was, even if it hit her in the face! At this stage, I thought I would have a go at resoldering several of the low-voltage regulators that are sprinkled through the main chassis and modules. However, this turned out to be a mistake as it was so dark I couldn’t really see what I was doing. On top of that, although I prepared by bringing a service manual for an AE-1 chassis, this set used a later AE-1C variant which is significantly different in layout. Finally, after an hour, I had to admit defeat and announced that it would have to go to the workshop. Mrs Staniforth played the same record once again but I had reached the take it or leave it stage by then. Surprisingly, she allowed me to take it, provided I loaned her a set (I had a 34cm portable). And that led to the next problem. The Sony set weighs 52kg and as I said earlier, the lady was quite frail. It was quite out of the question to expect her to do more than hold a door open. The problem was to lift this beast and get it through the door. Although I could lift it (just), the set’s dimensions are such that both it and I together had problems getting through the door and I was beginning to despair. However, a little lateral thinking solved that problem. There was a small piece of carpet handy, so I lifted – or rather half-dropped – the set onto it so that I could drag it outside. Unfortunately, this dislodged the front control panel lid, right in full view of the client. Rather sheepishly, I assured her that it was nothing serious and that all would be fixed but I was praying that the hinges on the front panel lid hadn’t broken. Finally, I got April 2000 45 result. Eventually, however, I was surprised to find that it was board C, which carries the CRT socket, that actually responded to heating and freezing. This was mostly around the area bounded by plug C-72, Q702 and D713. It was difficult to be more precise than that but the fault was probably around D701, a 9.1V zener diode. I connected an oscilloscope and a DVM on pin 1 (Auto Cutoff) of connector C-72 and noticed that there was no waveform and no voltage when there was no picture. When the picture came on there was a 100V p-p pulse on a 6.5V DC level. Suddenly, the wheels and cogs began to turn – I was sure I had seen this circuit before. The penny dropped when I followed connector C-72 back to the decoder B board and IC301, which is a Philips TDA4580 video processor. This features an auto cutoff circuit and is used in Philips 2B-S chassis and others to control the picture drive. It turns the drive on only when the beam current lies within a certain range. This is monitored by transistors Q704, Q707 and Q710 on the CRT board, in each gun output circuit. Prime suspect the set into the truck, gasped that I would be back with the loan set and drove off. When I returned with the promised 34cm set, the customer was “under whelmed” to say the least. I was greeted with all sorts of unhappy comments about its size; that it was really not much bigger than a postage stamp and hardly worth it, though why she didn’t say so earlier, I have no idea. As a further complication, I had to retune the set because some channels were better on the UHF translator station than the VHF main transmitter. I also had to retune an ancient JVC HR7650EA VCR on which the display was no longer functioning (due, no doubt, to a faulty -28V supply internally). When I recovered back at the workshop, I opened the set as soon as possible. I didn’t think I could take any more whinging but I was wrong. 46 Silicon Chip Mr Staniforth was now back home and he phoned to give his informed gratuitous advice as to exactly what was wrong with the set. I had to restrain myself from asking him why he hadn’t fixed it himself if he knew so much about it. My first approach was a blanket resoldering job but this didn’t fix the problem. I then figured out a plan because it took an hour or so to come on, it was most likely a heat problem. Therefore, if I waited, I could freeze parts of the circuit and it would rapidly kill the picture; or so I surmised. When the picture finally came on, I could see it was washed out with poor greyscale, which is synonymous with a sick tube. The freezing idea almost didn’t work because I initially sprayed everywhere I thought the problem might be – the power supply, video and chrominance decoder, the Teletext circuitry and so on – without So apart from anything else, the CRT board was still a prime suspect. It had been affected by the salt air from the nearby sea, although the freezer had cleaned or diluted it to the extent that it was now taking only minutes for the picture to appear. I decided on a three-pronged course of action. First, I removed, re-soldered and cleaned the CRT board, scrubbing it with methylated spirits and CRC2-26 before blowing the excess off with the air compressor. This done, I fitted a 150kΩ resistor from the 12V rail to pin 1 (Auto Cutoff) of C-72. This modification is necessary if the tube has low emission and the auto-cutoff circuit operates (and disables the drive) because the beam current doesn’t fall within the required range. Basically, it fools the auto-cutoff circuit by increasing the apparent beam current, thereby restoring the drive to the tube. Finally, I boosted the CRT slightly with the rejuvenator (I had already checked the CRT filaments at 6.3V). The final effect was magic – the pic- 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 Amidon Stockist ELECTRONIC WORLD Pty Ltd ACN 069 935 397 Ph (03) 9723 3860 Fax (03) 9725 9443 27 The Mall, South Croydon, Vic 3136 (Melway Map 50 G7) email: truscott<at>acepia.net.au www.electronicworld.aus.as P.C.B. Makers ! • • • Fig.2: this diagram shows part of the neckboard circuitry (board C) in the Sony KV-C2911D TV set. The CRT socket is at top, while connector C-72 is at bottom left. ture came on in about 10 seconds from cold and the picture quality was excellent. I refitted the front control panel lid I had knocked off during the move – thankfully, it had not been damaged. The remote control, an RM-673 type 3, was dead and rattling. After opening it, I removed the leaking batteries and a broken loose crystal (Z1) and washed off all the liquid corrosion under the rubber switch pads. It was then that I noticed that the board was drilled and punched to take an extra LED, to indicate that it was transmitting. I fitted an appropriate red LED with a series 47Ω resistor to pin 6 of IC1 and drilled a small hole through the case where it was marked. Finally, the remote was reassembled and tested – it worked like a charm. I made sure that there was someone young and fit to accompany me when I returned the set, to help me carry it inside and lift it onto its stand. Mrs Staniforth, although still very suspicious, kept her composure during this procedure. She really couldn’t believe that her beautiful set which had gone out in pieces with a supposed incompetent (me) two days earlier was now working better than ever. And the remote control now even had the bonus of a little light in it – or perhaps that is what she was SC probably expecting all along! • • • • • • If you need: P.C.B. High Speed Drill P.C.B. Guillotine P.C.B. Material – Negative or Positive acting Light Box – Single or Double Sided – Large or Small Etch Tank – Bubble or Circulating – Large or Small U.V. Sensitive film for Negatives Electronic Components and Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE Prompt and Economical Delivery KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 • ALL MAJOR CREDIT CARDS ACCEPTED April 2000 47 Build a for styrofoam, foam rubber & Are you into modelling or upholstery? Then you probably have often wanted a hot-wire cutter for foam plastics – but didn’t know how to build one. Wonder no more as we show you how to build a very cheap hot-wire cutter from odds and ends. By LEO SIMPSON M ANY PEOPLE have a need to cut expanded polystyrene foam (you probably know it as “styrofoam” or “coolite”), foam rubber (which isn’t rubber at all!) and many other soft plastic materials. Generally they resort to using a Stanley knife, handsaw, bandsaw, jigsaw or even an electric carving knife . . . and the result is generally a lot of mess for not much cut! The ideal way to fashion this material is with a hot-wire cutter. Actually, that’s a bit of a misnomer. It should be called a hot-wire melter because that’s what it does – but invariably they’re called hot-wire cutters so we’ll stick to that name. The cutter will go through most types of soft plastic just like a hot knife through butter (same principle really) and the result is a very smooth cut with no debris to sweep up afterwards. You also can do the most intricate cuts which would be impossible using any other method. And the cuts can be angled. In addition, you can also cut very 48 Silicon Chip thick material. Our prototype cutter would easily cut foam over 400mm thick and it’s not hard to make a much larger one if you wished. A hot-wire cutter is made from a length of resistance wire which is held taut and heated to just below red-heat. At this temperature you can slowly feed the material through and you will get a very smooth cut. As you can see from the photos, we made our hot-wire cutter from a variety of materials we had lying around the place. The baseboard was made from Laminex-coated chipboard left over from a kitchen installation. The vertical element was made from a scrap of 16mm Formply while the horizontal 5/16-inch threaded rod came from a cable reel. The hinge, screw eyes, spring and other bits were also hauled out of the junk box. The important point to note about this project is that it does not have to look good; it just has to work. For example, we could just as easily have used some raw chipboard for the base and a piece of hardwood decking for the vertical element. Or we could have used a piece of 3mm steel strap bent at rightangles and hinged from the base to carry the vertical cutter wire. No doubt you have other bits and pieces which could be pressed into service just as effectively. But where do you get the resistance wire? Fortunately, that is easily answered as it comes in small packs of 28 B & S Nichrome or Cuprothal from Dick Smith Electronics and Jaycar. Three types are available and just which type you use will depend on what power supplies you have available and how big you want the cutter to be. We made our cutter quite big because we envisaged using it to cut quite thick styrofoam for use in scenery for a model railway layout. If you want yours to cut thinner sheet materials then you may opt for something smaller. The active length of wire used in our cutter is 430mm and is probably just a bit longer than we need. But let’s say you want a similar length, other plastics 400mm. What we found is that you need about 40-45 watts to heat the wire adequately. More than 50 watts will make the wire glow brightly and that is not want you want as it could set fire to some materials. Anyway, if you have a power supply capable of around 50 watts you are in business. Your power supply could be a conventional adjustable DC power supply such as the 40V 3A supply we described in the January & February 1994 issues of SILICON CHIP. Alternatively, if you have a computer power supply capable of 200W or more, it can probably be pressed into service. Or you could even use a 12V car battery. Either way, if the supply you use is not adjustable, you will need a means of adjusting it. After all, the amount of heat for effective cutting will depend on the type and thickness of material so you do need to be able to adjust the available voltage over a small range. Now you need to consider how much voltage and current your power supply can provide because that determines what type of resistance wire you need to use. OK. Let’s consider the easy approach first and that involves using an adjustable power supply such as the 40V 3A unit referred to above. Since this unit can only supply a maximum of 3A, that meant that the resistance would have to be reasonably high. OK, so it’s not pretty – but it works! We scrounged the baseboard from an old kitchen cupboard, the spring from an old bed, the screw eyes and hinge from the junk box . . . we’re sure you get the picture. Here we’re about to cut through this thick block of polystyrene foam in just a second or so. The result: a beautifully clean, straight cut with no mess! April 2000 49 Like a hot knife through butter . . . that’s exactly how our hot wire cutter works. On the left we’re cutting a complex shape from a sheet of polystyrene foam, with a hunk of foam rubber waiting its turn. To prove the point, on the right is that same hunk of foam rubber being cut. Notice how straight, clean and mess-free the cut is? You can’t do that with a Stanley knife! For this example, we decided to use some 28 B&S Nichrome from Dick Smith Electronics. This comes in a small pack with a few metres of wire (Cat. W-3205). This has a nominal resistance of 13.4Ω ±5% per metre and so a 400mm length will be 5.4Ω. We jury-rigged up a 400mm length of this wire under tension and found that we needed about 40W to get it to satisfactorily cut a range of styrofoam in various thicknesses. That translated to a voltage setting of around 15V at 2.7A, comfortably within the 3A limit of the power supply under discussion. If you don’t have an adjustable power supply of sufficient current capacity, you might consider using a computer power supply or perhaps even a 12V car battery. Either way, you will need some means of adjusting the voltage fed to the cutting wire. We have a simple solution for that problem too and we’ll discuss that later. Diving into our junk box again, we came up with a 200W PC power supply that could deliver +12V at up to 8A and +5V at up to 20A. Such power supplies can be picked up very cheaply these days or salvaged from computers tossed out for council Fig.1: modified from the Glow-Plug Driver last month, this “power supply” enables you to heat the wire to just below red heat. 50 Silicon Chip cleanups. If we elect to use the 12V option (from a computer supply or car battery), it is appropriate to use the 28 B&S Cuprothal resistance wire pack from Dick Smith Electronics (Cat. W-3200). This has a nominal resistance of 6.09Ω per metre and so a 400mm length will be just under 2.5Ω (2.44Ω to be more precise). With 10V DC applied, the current will be just over 4A and again we have the right result of between 40W and 45W to achieve a clean cut with this length of wire. How do we get 10V from a 12V supply? Patience, now; we’ll come to that in a moment. But perhaps the computer supply you have scrounged cannot supply 4A from the +12V – some of them are a bit skimpy for this rail. The answer is to go to the 5V rail which even in a fairly modest machine will typically be able to supply 12A or more. So if we’re going to use the +5V rail, we need lower resistance wire again and in this case the 28 B&S wire from Jaycar could be the answer (Jaycar Cat. WW-4040). This has a nominal resistance of 3.77Ω per metre. A 400mm length will have a resistance of 1.5Ω. In this case we are in trouble because 5V across 1.5Ω will result in a current of only 3.33A and a power dissipation of 16.7W; not enough cutting power for a 400mm length. Clearly, we have to make other arrangements. One possibility is to double up, or better still, triple the wire. With three 400mm lengths paralleled up, we get Fig.2: the modified PC board component layout with the PC board itself at right for comparison. Both are reproduced same size. a total resistance of 0.5Ω. With 5V applied we’ll get 10A (in theory), or a power dissipation of 50W, more than enough for the job. Shorter cutting wire Alternatively, you could always compromise and go for a unit with a shorter cutting wire. We know that we need around 40W for adequate cutting from a 400mm length of resistance wire. That translates to 1W per centimetre. So if we decide on a 250mm cutting wire, we’ll only need 25 watts. Going back to that 28 B&S wire from Jaycar, a 250mm length will have a resistance of just under 1Ω (0.94Ω to be more precise) and when 5V is applied across it, the current will be around 10A and the power dissipation around 25W, right on the money for a 25cm cutting length. We could also repeat the exercise for the higher resistance wire. Using a 25cm length of the 28 B&S Nichrome wire from Dick Smith Electronics, we get a resistance of 3.35Ω. With 9.5V applied, we get just over 2.8A and a total power dissipation of 27W, which is OK for this cutting length. By now you should see how you can choose the length of the cutting wire and its resistance to suit the capabilities of your power supply. Of course, if you want a 1-metre cutting wire, you will need a cutting power of 100W and your power supply will need to be beefed up accordingly. (Hint: if you used the 6.1Ω/m Cuprothal wire, you would need a supply capable of about 25V and just over 4A). computer supply. It just so happens that we published a suitable circuit in last month’s issue under the guise of a “GlowPlug Driver” (see SILICON CHIP, March 2000, page 72). With a few minor changes, that circuit is ideal for our purpose. Fig.1 shows the modified circuit while Fig.2 shows the component overlay. If you compare the circuit of Fig.1 with the GlowPlug Driver circuit on page 73 of the March 2000 issue, you will notice that we have made three modifications. First (and second), we Adjusting the voltage We mentioned the need to adjust the voltage to the cutting wire if you are using the +12V or +5V rail from a This photo gives a good idea of the construction and in particular the tensioning method. The resistance wire “cutter” must be kept under tension to achieve a good straight cut. A healthy “twang” when plucked means the tension is about right! April 2000 51 swapped the positions of resistors R1 & R2 to change the output duty cycle. Whereas before the desired duty cycle was around 17% to obtain around 2V from a 12V supply, the modified circuit will give a range of duty cycles from around 75% to 85%. This is about right, if you want to use the examples quoted above and want around 9.5V to 10V from a 12V PC power supply or car battery. Our third modification was to remove the 0.1Ω 5W wirewound resistor R5 and replace it with a link. This resistor will otherwise cause too much voltage drop when you are using it from a 12V or 5V supply. Note that if you are using it on the 5V supply you probably will need to fit a small flag heatsink to the BUK453 Mosfet. You may also want to replace the 10kΩ trimpot with a conventional potentiometer if you want to easily adjust the wire temperature from time to time. It would also be a good idea to fit an in-line 5A fuse if you are going to power your hot-wire cutter from a 12V car battery. Foot-operated switch Another refinement to our circuit could be the inclusion of a suitable foot-operated switch to apply power to the hot wire at the appropriate time, leaving both hands free to guide the work. We’ll leave that part to you – just make sure any switch you use has high enough ratings (say 10A at 30V WATCH THE FUMES! When heating or melting any type of plastic (eg, with a hotwire cutter!), beware of the fumes which are given off. Always use the cutter in a well-ventilated area (preferably fan assisted) and avoid breathing the fumes. DC) and use heavy-duty connecting cables (again, at least 10A). Building the cutter While you can see the construction details from the photos, there are few points that need to be covered so we’ll briefly describe how our prototype was made. First, we made the baseboard from a piece of Laminex coated chipboard measuring about 700 x 300 x 18mm thick. The precise measurements are not important but ours was quite large so that it would have a large “throat” for cutting big slabs of material. Laminex or melamine coated pyneboard is ideal as it easily cleaned and suitable for sliding the material through the cut. It is also fairy heavy which means that the cutter does not move about when you are pushing material against the wire. We used an ordinary 100mm steel butt hinge for the vertical support which was made of 16mm Formply measuring 450 x 70mm. For the hori- zontal wire support, we used a 500mm length of 5/16-inch threaded rod. This has the advantage that it is easy to make the wire connections to it. The wire connection to the baseboard can be via a countersunk screw with the external wire connection underneath the board but we took the simpler approach with our prototype, as can be seen in the photos. The 28 B&S wire is held under quite a bit of tension by the small spring attached to the screw eyes on the baseboard and vertical support. Our spring came from an old wire bed frame. The vertical support needs to be hinged and under spring tension for two reasons. One, you need a fair amount of tension so that the cutting wire is not deflected as you push the foam onto it. Second, the resistance wire expands by about 10mm from cold to hot and the spring tension needs to take this up. A look at the photos will show that the threaded rod is under a fair amount of tension and can be seen to be noticeably bent against the load. Mind you, the wire should not be too tight otherwise it will tend to break. Ours made a pronounced “twang” when it was plucked. Inevitably though, the wire can be expected to break from time to time, so make sure you keep the leftover resistance wire in a safe place. Incidentally, the hotter you run the wire, the more likely it is to break. Finally, by using the threaded rod and the hinged vertical support, the hot-wire cutter can be easily dismantled and stored as a flat package. Where do you get it? It mightn’t look like the best cut in the world but hey, it was our first-ever attempt – and it’s a darned sight better than you could get with a knife! One trap for young players we found was to cut too slowly or leave the work in the one place too long. If you do this, the polystyrene starts to melt (as you can see happening near the hot wire). Adding a foot-switch to turn the power on and off could help prevent this. 52 Silicon Chip We’ve told you where to scrounge all the bits from in the cutter itself but so far haven’t said where to get the power controller. As we mentioned, this was published last month as a Glow-Plug Driver and the kit is exclusive to Oatley Electronics. So if you want to build the controller, simply buy the Glow-Plug Driver kit from Oatley Electronics (it sells for $14.95 including a case). They can be contacted on (02) 9584 3563, fax (02) 9584 3561, email sales<at>oatleyelectronics.com or visit their website: www.oatleyelectronics.com.au Just don’t forget to swap resistors R1 & R2 and leave replace R5 with a SC wire link. ORDER FORM 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 SUBSCRIPTIONS  New subscription – month to start____________________________  Renewal – Sub. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia April 2000 53 This photo shows the Atmel ICE 200 (at right) plugged into an STK200 development board. The development board is also available from Atmel. Atmel's ICE 200 in-circuit emulator What’s the best way to develop and debug microcontroller software? Answer – use an in-circuit emulator (ICE) that interfaces to a PC. An ICE offers all sorts of useful debugging tools and there’s no need to add water! By PETER SMITH The Y2K problem highlighted something that many of us weren’t previously fully aware of – just how many pieces of equipment contain embedded computer chips. With so much equipment now relying on computer control, if you’re involved in electronics then you will almost certainly be involved with embedded systems in some way. Most embedded designs are based on microcontrollers (MCUs). These devices integrate a microprocessor core with memory and input/output (I/O) ports, as well as a variety of other 54 Silicon Chip commonly used functions. Effectively, this means that what once would have occupied an entire PC board now fits in a single chip, consumes a fraction of the power and runs perhaps 10-100 times faster! Due to their ever-increasing memory size and speed, microcontrollers can now be programmed effectively using high-level languages such as C and BASIC. Of course, serious design calls for serious debugging tools and in this review we look at the ICE 200. This is an “entry-level” in-circuit emulator (ICE) for Atmel’s range of popular AVR Enhanced RISC microcontrollers and should also appeal to novices. Atmel AVR microcontrollers In my opinion, Atmel has a real winner with their AVR series of microcontrollers. Using a modified RISC (Reduced Instruction Set) architecture, the AVR series is specifically optimised for running complied C code. Other key features such as in-circuit programmable flash memory (up to 128KB), EEPROM data memory, high throughput (all instructions are single-cycle) and low power consumption make this series hard to beat. As is common with all micro controllers today, it includes functions like A-D converters, serial ports (UARTs), real time clocks (RTCs), pulse width modulation (PWM) outputs, 16-bit timers and brown-out detectors. Do I need an ICE? When a microcontroller program Fig.1: the major components of the ICE 200 in-circuit emulator. Connection to your PC is via a standard serial port. doesn’t work as expected, how do you find out why? One way is to debug the program with a software simulator. Simulators do just that – they simulate the operation of a microcontroller in PC-based software. Your compiled program runs just as it would on a real microcontroller, the advantage being that you have control over the execution of each line of code. Instructions can be executed line-by-line (called single stepping), or “breakpoints” can be inserted at desired points to halt a running program. In addition, resources such as registers, memory and I/O ports can be examined and modified at will. The major disadvantage of simulators is that they are isolated from the devices that a typical microcontroller-based system would interface with. For example, if a design includes a pulse width modulated (PWM) output to control servo motors, the best that you can do is view the PWM registers – a poor substitute for seeing actual servo movement. The answer to this dilemma is in-circuit emulation. This approach replaces the microcontroller chip with hardware that emulates its operation and at the same time allows the pro- grammer to “get inside” to see what’s happening. The Atmel ICE 200 kit includes both hardware and software components. Let’s take a look at the hardware first. ICE hardware The kit consists of several major hardware components (see Fig.1). A small PC board called a “pod” contains the actual emulation hardware – all in a single chip mounted on the Fig.2: the Project window keeps all related files and settings nicely organised. Source files can be edited, compiled and run directly from this window. Fig.3: doubleclicking on an error in the Project Output window takes you directly to the problem line in your source file. underside of the board. The pod plugs into the microcontroller socket on the system to be debugged via a so-called “personality” adapter. The ICE 200 supports 11 different microcontrollers from the AVR series, so adapters are required to convert the varying package types and pinouts to suit the pod. Note that the kit only includes personality adapters for dualin-line (DIL) microcontroller packages (8, 20, 28 & 40 pin). If your application uses surface mount packages, you will need to obtain suitable SMD-to-DIL adapters or purchase the Atmel SMD personality adapter kit. The pod automatically detects which micro it should emulate and configures itself internally, so there are no jumpers or switches to be set. A “tiny” exception to this rule is the ATtiny 12/13 microcontroller, which has special oscillator pin features. Two 0Ω resistors on the pod must be set accordingly – the user guide has the full details. The pod connects to the main ICE 200 board via two flexible cables. The main board measures just 70 x 90mm but Atmel has squeezed on the program memory, pod control and host PC communication logic, as well as a power supply. A standard DC socket accepts input power, which is regulated and filtered to 5V on the board. Note that although the ICE 200 starter kit documentation states that 9-12V DC or 9V AC can be applied, more up-to-date information on the Atmel web site recommends applying 9V DC only. Atmel has included a length of cable with a DC jack on one end for connection to a lab supply but a trusty April 2000 55 9V DC 500mA plugpack would probably be the preferred choice. Also of note is that as the pod draws power from the target board it is connected to, its supply voltage can be anywhere from 2.7V to 5.5V. On the other hand, the main board has a 5V supply, so level converters on the main board do the necessary logic level shifts. Finally, the ICE 200 kit includes a 9-pin serial cable (about two metres long) to connect the main board to your PC. ICE software A brilliant set of software tools called AVR Studio controls the whole show. AVR Studio runs on Windows 95, 98, NT 3.51 and NT 4.0 and is supplied on CD-ROM, along with a bunch of useful product guides and technical data sheets. Our kit also included a copy of AVR Studio on diskette but both it and the CD-ROM version were out of date as Atmel has just released version 3.00. We downloaded our copy from At mel’s website at www.atmel.com AVR Studio provides all you need to edit, compile and debug your code. A macro assembler is included in the package and an optional C compiler is also available. Third party compilers and assemblers can be plugged in too but if you want to debug at the source code level, they must be object file compatible. Fig.4: the first time an object file is loaded, AVR Studio detects the ICE 200 and displays this Configuration window. The first step towards a working program is to enter the source file. AVR Studio includes a project manager that helps you keep source files associated with a particular project together (see Fig.2). A handy assembler source file editor is included (see Fig.3) and this can be launched directly from the Project window. Source files in a project can be assembled/compiled with a single keystroke, with the results displayed in the Project Output window. If one or more errors occur during assembly, finding the problem line of code is a simple matter of double-clicking on the error and the line is immediately highlighted in the Source window (see Fig.3). Once you’re ready to debug the code, the output from the assembler/ compiler (called an object file) can be loaded manually from the File menu. Fig.5: a typical debugging session in AVR Studio. The real work begins here! 56 Silicon Chip Alternatively, the source file(s) can be assembled/compiled and the object file loaded in one step by selecting Build & Run from the Project menu. The first time an object file is loaded, AVR Studio automatically detects and configures the ICE 200 and a configuration window appears to confirm a few important settings (see Fig.4). If an in-circuit emulator can’t be detected, AVR Studio enters software simulation mode instead. After closing the configuration window, various debug windows can be opened from the menu bar in preparation for the actual emulation session. The emulation display Fig.5 shows what a typical emulation session might look like. Naturally, window positions and sizes can be set according to personal preference and the settings are saved between sessions. If you’re a newcomer to emulators the display in Fig.5 might look a little intimidating, so let’s talk briefly about the function of each window. The largest window, titled avr910. asm, is the source window – it lists the program being debugged. The small arrow on the left sidebar indicates the next line to be executed. Right-clicking on any line allows you to set or clear a breakpoint at that position, or a bookmark can be placed for easy location at a later stage. Note the small brown squares – these indicate the positions of active breakpoints. Breakpoints can be cleared globally from the main menu bar. Labels (or symbols) are listed in the source window just as they appear in the original program. This information is retrieved from the assembly or object file. If a file without this information is loaded (eg, a hex file), AVR studio lists the program in disassembly mode. The Memory window displays the contents of program, data, EEPROM or I/O memory. A drop-down menu lets you select one of the four types. Memory contents can be edited directly in this window by double-clicking on the desired location and typing a new value. Multiple Memory windows can be open at the same time. The Registers window displays all 32 general-purpose microcontroller registers and like the memory window, these can be edited by double-clicking on the desired entry. The Watches window provides a convenient way of displaying all the memory locations that you would like monitor. Rightclick in this window to enter a new location in symbolic form. AVR Studio updates the “Value” column each time program execution stops. If you are debugging a C program, both simple and complex (eg, structures and arrays) data types can be displayed. Key emulation information is displayed in the Processor window. The Program Counter field displays the address of the next instruction to be executed, while the Cycle Counter field displays the total number of cycles since the last reset. The Stack Pointer, Flags and X, Y and Z Register fields are all self-explanatory. As you’ve probably guessed, the Frequency field displays the target’s clock speed. All values except time elapsed and frequency can be changed when the program isn’t running. The I/O window is used to examine and alter the various I/O registers. Multiple I/O windows can be opened at the same time. Executing the code Basically, these windows are our view “inside” the microcontroller. They display the current state of every resource within the chip, as well as giving us the ability to modify many of them. Just as importantly, AVR Studio allows complete control over program execution. Using buttons on the menu bar or shortcut keys, you can single-step the program (execute a single line at a time) or run until a breakpoint is encountered or you click on the Break button. You also have the option of executing a subroutine (function call) until it ends (Step Out) or skip a subroutine completely (Skip Over). Other versatile options allow execution of a defined number of instructions (Multi Step), or executing each instruction and pausing for a predefined period before going on to the next (Auto Step). Fig.6: on-line help that really helps! All help menus should work like this. Documentation Documentation is often the weak link in technical products but Atmel have excelled with their HTML-based on-line help system (see Fig.6). We found it to be comprehensive, well organised and easy to navigate. Wrap up We mentioned before that AVR Studio enters simulation mode if an emulator (in our case, the ICE 200) is not detected. Simulation control and display is deliberately very similar to emulation, so much of the previous description still applies. Of course, simulation is very limited in comparison to emulation (as described above) but it does The underside of the pod reveals just one 100-pin IC and this is responsible for emulating all supported microcontrollers. Note the connectors on either side – these plug into the personality adapters. April 2000 57 T This photo shows a selection of the available DIL “personality” adapters supplied with the kit. provide an ideal introduction to the software and would be an excellent learning tool. AVR Studio is available for free download from the Atmel web site at www.atmel.com Sample assembler files are included with the installation (look in the Avrstudio\Appnotes directory), so you don’t even need to know AVR coding to give the simulator a go! Where to next? Experienced ICE users will have noticed that we haven’t mentioned tracers or triggers. To explain, in-circuit emulators often provide a program tracing feature. This feature records detailed information about the execution of each instruction (or even each machine cycle on some systems) in dedicated memory called a trace buffer, all in real time. The idea here is to allow detailed analysis of sections of code without interrupting program execution – something that can be important in real-time systems. In addition, trace buffer contents can be written to a file for later scrutiny. Triggers are associated with physical input and output pins, usually made available on a connector on the ICE pod. Output triggers are often used to trigger external test instruments like oscilloscopes and logic analysers. Markers are placed in the code to signal when the corresponding output pin should go high (or low). Input triggers can be used to halt program execution. They can also be used for simply logic analysis, as the pins are sampled and recorded in the trace buffer every cycle. Tracing and triggering is often used to solve difficult hardware and software design problems in advanced systems, hence it has not been included in the entry-level ICE 200. However, these features are available on the more advanced Atmel ICE Pro for those who need them. And the good news it that AVR Studio supports the ICE Pro and traces and triggers too, so there’s no need to learn a new platform if you decide to upgrade to the big guns later! Want further info? The main board shown approximately full size. All components except for the 9-pin D connector are surface-mounted. 58 Silicon Chip Further information on the Atmel ICE 200 in-circuit emulator kit, phone the REC Electronics office in your state (see advert on inside back cover for phone numbers). You can also visit their website at www.rec.com.au SC TRONICSHOWCASELECTRO MicroZed Computers GENUINE STAMP PRODUCTS FROM Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. 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Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au www.quest.au.com Email - questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC's, Converters, etc. QUESTRONIX All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only SURPLUS ELECTRONIC COMPONENTS at CHEAP CHEAP CHEAP PRICES! 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 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 Do you want YOUR product or service showcased to Australasia's most important electronics marketplace? CALL ME: RICK WINKLER on (02) 9979 5644 and let me explain how cost effective the SILICON CHIP ELECTRONICS SHOWCASE can be for YOU! April 2000 59 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The Hellier Award, Pt 3: Simple Superhets This month, we take a close look at the three winning sets in the Hellier Award and describe the technical details. The sets are all simple superhets using a converter, a regenerative IF on 455kHz and one stage of audio feeding a loudspeaker. The size of the three winning sets varied considerably, from a small brick-sized set to a very large mantle set. They were built by Gary Newton, Des Nunan and Harvey Utber and all three sets worked very well indeed. Of the three, the mid-sized set built by Des would probably be the easiest for anyone wanting to build a near copy. The little brick Gary’s brick-sized set is compact and utilitarian in concept, which aided construction, operation and service. Because it is small, it took a great deal of planning to get everything into the case while ensuring that inputs and outputs were kept apart. The set has “hand-span” tuning with a knob fitted directly onto the tuning gang shaft. This made tuning a little more exacting compared to the other two sets but it wasn’t really a problem. By the way, the overall IF (intermediate frequency) skirt selectivity of all three sets isn’t as good as that from a conventional superhet with four tuned IF coils (ie, two IF transformers). This meant that when tuned This is the view inside the giant’s mantle set, made by Harvey Utber. This set is large for a 2-valve receiver and its performance matches its size. 60 Silicon Chip to a weak station, a strong station on a nearby frequency could be heard behind the wanted station. That said, the overall performance of all three sets was very good, considering their simplicity. The circuits of the three radios were all very similar so only one generic circuit diagram is included with this article – see Fig.1. Gary used a 6AN7 converter which was fed from a loopstick antenna, as well as being connected to an external antenna/ aerial. The twin tuning gang was a padderless type which means that the two sections have different capacit ances and so no padder capacitor is required. A 6AB8 triode pentode was used for the regenerative IF and audio stages. The 6AB8 is not commonly used, having a triode with a gain of around 11 and an output pentode similar to half a 6AQ5 (it requires similar voltages but draws less than half the current). The cathode is common to both sections which makes the circuitry a little more complex to obtain correct biasing. All sets required a modified IF transformer and this involved adding a feedback winding. The reaction was controlled with a series trimmer capacitor, with another parallel capacitor across the trimmer to make adjustment easier in the conventional Reinartz circuit. It’s interesting to note that all the simple superhets used this system although there are a number of other methods for achieving regeneration that work well too. As mentioned previously, almost all the contestants who built the simple superhet receivers had trouble getting the regeneration working to their satisfaction. This problem was solved by jumble-winding the feedback winding close to the grid winding of the IF transformer as shown in Fig.2. In 6AN7-A REGEN. 27pF 7 15410pF .047F 5k LIN VOLUME 100pF 9 3 47k 1M 6GW8 .047F 1 47k 2 15-410pF .047F 3 8 .022F 1M 220k 15k 1W 10F 16VW 7 220 2.2k 1W 180V .047F 7k 6 470pF 47pF 220 425pF 3-30pF 10k 9 8 1 2 3-30pF 3-30pF 90V * CAPACITOR MAY BE IN POWER SUPPLY H.T. 200 to 250V DC * 10F 300VW 10F 300VW Fig.1: a typical simple superhet radio receiver circuit. All three sets described here used this general scheme. practice, this feedback winding consisted of 100-150 turns of about 37B&S (0.125mm) enamelled copper wire. The audio output stage of Gary’s set is conventional and uses the pentode section of the 6AB8. Although slightly lacking in performance compared to 6BM8, 6GW8 and 6GV8 output stages, this is hardly noticed and the heater drain is only 0.3A. The plate impedance is quite high, varying between about 10kΩ and 17.5kΩ, depending on the supply voltage. It’s not easy to find speaker transformers with a primary impedance in this range but using a 7kΩ:3.5Ω transformer into an 8Ω loudspeaker will give a reflected impedance for the valve plate circuit of (nominally) 16kΩ. The bass response of the transformer may not be wonderful but a small set like this with a small loudspeaker doesn’t have a good bass response anyway. The set is quite a reasonable performer but Gary realised during discussion after the judging that there were a few things that could be altered around the aerial circuitry to improve its performance. These modifications will, I believe, make Gary’s set a very good performer. The 1940s wooden mantle set Des stuck to a more conventional layout from the 1940s and achieved a set that is impressive in both looks and performance. To dismantle the set, it is necessary only to remove the knobs and two screws under the bottom of the cabinet and slide the chassis out – simple but effective. The converter is again the ubiquitous 6AN7(A) which This “under-the-hood” view of the giant’s mantle set reveals a well-laid out chassis, with all parts readily accessible. April 2000 61 Fig.2: this diagram shows how the IF transformer in each set was modified by adding a feedback winding close to the grid winding. The triode is used as a regenerative IF stage with the pentode once again the audio output. The IF stage is similar to Gary’s, the main difference involving the use of an old HMV screw adjustment beehive type trimmer as the regeneration control. This is extremely smooth – in fact, I don’t think I’ve seen such a smooth regeneration control before but this is probably unimportant as it is a “set and forget” control. However, due to variations in mains voltages, it did initially break into oscillation at times and had to be backed off a little to ensure reliable operation under all circumstances. Unlike Gary, Des used a conventional cord-drive dial system which works well. The layout of the chassis is quite conventional and the wiring is very open and easy to work on (see photo). By the way, this is the only set to use a 6X4 as the rectifier – the other two sets used solid-state diodes in the power supplies. The “Little Brick” made by Gary Newton was compact and utilitarian in concept. The giant’s mantle set This 1940s-style mantle set was made by Des Nunan and has a conventional layout. It uses a 6X4 rectifier valve, a 6AN7(A) for the converter and a 6GW8 triode/pentode output stage. A feature of the set is its very smooth regeneration control. is fed from a conventional aerial coil attached to an outside aerial. The second valve is a 6GW8 which is a 62 Silicon Chip triode-pentode originally intended for audio use in hifi amplifiers and TV audio stages. Harvey had a 12-inch speaker going begging so he decided to build his 2-valve receiver around it. This set is large but it its performance matches its physical size and it can easily receive most Melbourne stations in Mooroopna some 150km away during daylight hours. Indeed, the volume and quality of the sound from the 12-inch speaker was quite impressive. Who said that regenerative detectors have too much distortion for normal use? Harvey’s receiver uses a 6AN7(A) and 6GW8 in a similar circuit to the other two sets. In this set, however, there is extensive decoupling of the high tension (HT) supply. In addition, Harvey played around with the operating conditions of the converter to get the best conversion efficiency. The performance of the radio frequency (RF) section of a set depends on the operating conditions of the valves and the quality and matching of the wound RF components (coils and transformers). In my opinion, Harvey got everything just right and the performance certainly is impressive for such a simple set. By the way, most of the simple superhets used a resistor in series with a potentiometer in the cathode circuit of the converter to control the volume – see Fig.1. This was used as it would be easy to overload the detector near strong stations due to the fact that no automatic gain control (AGC) was generated in these sets. This meant that the volume control had to be “ridden” when tuning across the band from one station to another. However, this isn’t particularly difficult and in any case, most people usually listen to one favourite station most of the time. The inductance-tuned set As mentioned last month, one of the All parts are readily accessible in the 1940s mantle set and the layout is easy to work on. The conventional cord-drive dial system works well. other simple superhets (the one in the ice-cream container) used inductance tuning and this worked quite well. The inductance tuning system was originally designed for a Philips set from the early 60s. Apart from this, the circuitry was similar to the other three sets describe here and used 6AN7(A) and 6GW8 valves. Hopefully, this series will have whetted your appetite to build your own valve receiver, just for the fun of it. We’ll move onto another topic SC next month. ELECTRONIC VALVE & TUBE COMPANY The Electronic Valve & Tube Company (EVATCO) has relocated to new premises at 76 Bluff Rd, St Leonards on Victoria’s Bellarine Peninsula. EVATCO has been specialising in the supply of vacuum tubes to the audio and music industries for hifi and guitar amplifiers since 1995. They also stock a large range of valves for vintage radio, amateur radio, industrial and small transmitting use. Major current brands such as SOVTEK and SVETLANA are always stocked and they are able to supply some rare NOS (New - Old stock) brands such as Mullard, Telefunken, RCA and Philips. To assist designers, experimenters and hobbyists, they stock a wide range of books covering valve specifications and design or modification of valve audio amplifiers. Hard to get high-voltage electrolytic capacitors and valve sockets are also available. Proprietor Arthur Courtney has over 40 years of experience in the valve industry. For advice or assistance, call Arthur on (03) 5257 2297 or 0417 143 167. PO Box 487 Drysdale, Victoria 3222. Tel: (03) 5257 2297; Fax: (03) 5257 1773 Mob: 0417 143 167; email: evatco<at>mira.net New premises at 76 Bluff Road, St Leonards, Vic 3223 April 2000 63 By Robert Priestley Part 2: Building It! Last month we introduced our new OzTrip Car Computer – arguably the best car computer ever published. In this final part, we’ll look at some of the other features and then move onto construction, installation and calibration. As we mentioned last month, the OzTrip Computer can most easily be used in cars with standard electronic fuel injection (EFI) systems. The computer uses data already available within the EFI system. With modifications (involving the use of an optional PC board) it can also be used in vehicles with carburettors or non-standard EFI. This entails the fitting of a fuel flow sensor – not a difficult job at all. EFI operation The OzTrip Computer measures the fuel flow of an EFI engine by measur- The OzTrip Car Computer is easy to build, easy to fit and easy to calibrate. The best part: you save money! 64 Silicon Chip ing the time one injector is open. The main components of the fuel delivery system in an EFI engine include the fuel pump, pressure regulator, fuel rail and fuel injector valve. The fuel injectors are under the control of the engine management computer (EMC). This adjusts the time the injector is open and therefore the amount of fuel sprayed into the cylinders, according to the speed of the engine and the load on it, attempting to achieve maximum efficiency at all times. The pressure in the fuel rail, which feeds the injectors, is kept constant by the pressure regulator. Because of this, the fuel flow through each injector can be assumed to be the same (on average) so we only need to measure one injector to determine the total fuel flow. The fuel flow is directly proportional to the injector open time and by measuring the injector open time we can calculate the fuel consumption. Before we can determine fuel flow, the computer needs to be calibrated so it can relate fuel consumption to injector open time. This is achieved by measuring the total injector open time over a full tank of fuel, then entering the total fuel used during the calibration process into the computer. The computer has a special calibration mode which makes This photo of an early prototype shows the back-to-back method of construction. The microcontroller used in this shot was actually a reprogrammable type to assist in development, as distinct from the one-time programmable chip finally used. Some resistor values may also be slightly different – use the component overlays for construction! this easy to do. Calibration can be performed over several days if required. The greater the volume of fuel used during calibration the more accurate the calibration process is. The 68HC705C8A microcontroller has a timer input pin which is used to measure the pulse width of the injector signal. The computer’s fuel input can be directly connected to the injector. The injector has two connections: one side of the injector coil is connected to +12V DC and the other to the engine management computer (EMC). The OzTrip Computer must be connected to the EMC side of the injector. It is sometimes easier to make the injector connection directly across the vehicle’s EMC, which is usually located in the front passenger foot well or under the dashboard. Note that this method of fuel measurement is only suitable for EFI engines with one injector per cylinder and constant fuel rail regulation. Other engine setups may have to be treated as a carburetted engine and a fuel flow sensor fitted. terminals of the fuel sensor is connected to the input terminals via shielded cable – the shield itself connects to the “ground” terminal. There are various types of fuel flow sensors (or meters) available but the flow sensor used by Oztechnics produces 780 pulses for every 100ml of fuel which flows through it. This is its calibration number. The OzTrip Computer needs the calibration number entered into it (via the Fuel Calibration menu) so it can calculate the fuel flow. The flow sensor should be mounted in a vertical position with the fuel entering at the bottom of the sensor and leaving at the top for optimum operation. Diagnostic/calibration menus In addition to the 81 functions which can be selected, two-sub menus are available for Diagnostic and Calibration functions. When the diagnostic menu is accessed with the UP + Set/Clear key Speed alarm The speed alarm has a piezo siren and a visual “SLO” message to warn you that you are exceeding the speed limit. The alarm sounds 5km/h above the set speed – for example, if you set the alarm at 60km/h, it will trigger when your speed reaches 65km/h. The speed alarm can be set and cleared when the “speed” is displayed, using functions 1, 28 or 55. Pressing the SET/CLEAR key when the speed is above 40km/h will set the speed alarm at the current speed. To disable the speed alarm the SET/ CLEAR key is pressed when the speed is below 40kmn/h. Sprint timer Flow sensor operation Fitting a fuel flow sensor for non-EFI or non-standard EFI vehicles is quite simple: the fuel line is broken somewhere between the fuel pump and the carburettor and the fuel sensor is connected in series, securely clamped to the line by worm-drive hose clamps. Connection to the OzTrip computer is via optional PC board 3. Each of the sequence a “diAg” message is briefly displayed then the ENTER LED lights. You must enter a value between 1-5 into the computer to select the appropriate diagnostic function. The Diagnostic functions are listed in Table 4. When the calibration menu is accessed with the Down + Set/Clear key sequence a “CAL” message is briefly displayed then the ENTER LED lights. You must enter a value between 1-7 into the computer to select the appropriate calibration function. The Calibration functions are listed in Table 3. This fuel flow sensor is available from Oztechnics for those with carburetted or non-standard EFI vehicles. The sprint timer is used to calculate the time it takes for the vehicle to travel over a preset distance. Typically this distance would be 400m (roughly the old “quarter mile”) because that is the usual distance drag races cover. But if you want to time your vehicle over any distance – 100m or 100km, all you have to do is tell the computer. When the Sprint Timer option is selected from the Cal Menu/Option 7, April 2000 65 This photo and the diagram show the assembly details for board 1 (the display board). The connections all go to PC board 2, with links A-H actually 1kΩ resistors. All other connections are short wire links. Note the 10mm spacer position on the PC board. the computer asks for the distance to be timed (“Dist”) and then a 9-second countdown starts. When the count down reaches 0000, a BEEP is heard and the timer starts. When the vehicle has travelled the entered distance the timer is frozen, displaying the time duration with an accuracy of tenths of a second. Pressing the Mode/Enter Key returns the computer to normal operation. Journey counter The Journey counter is the main distance/timer counter and is represented by the Trip 1 Counter, F5 (distance) & F20 (time). The functions which are derived from the Journey counter are F2, F9, F11, F13, F15, F18 & F21. Parts List 2 PC boards, each 135 x 31mm, coded QIP1 & QIP2 1 4MHz crystal 4 PCB pushbutton switches (S1 -S4) 1 case 1 red acrylic (filter) front panel 1 10mm spacer 2 screws Semiconductors 1 68HC705C8A programmed microcontroller (IC4) 1 40106 quad Schmitt trigger inverter (IC3) 1 LM317 variable regulator (REG1/IC1) 1 LM78L05 5V positive regulator (REG2/IC2) 20 BC559 PNP transistors (Q1Q20) 1 BC547 NPN transistor (Q21) 3 1N914 diodes (D3, D4, D6) 3 1N4004 diodes (D1, D2, D5) 66 Silicon Chip 3 1N4733 5V zener diodes (ZD1ZD3) 4 FND506 7-segment LED displays (SEG1-SEG4) 8 3mm red LEDs (LED1-LED8) Capacitors 1 1000µF (C7) 2 100µF (C10, C12) 1 10µF (C11) 6 0.1µF (C5, C6, C8, C9, C13, C14) 2 .001µF (C1, C2) 2 22pF (C3, C4) Resistors (1%, 0.25W) 1 10MΩ (R5) 2 33kΩ (R1, R3) 9 10kΩ (R2, R4, R9, R11-R13, R33-R36) 23 2.2kΩ (R8, R14-R25, R37-R44, R58-R59) 10 1kΩ (R6, R7, R60-R67) 8 22Ω (R26-R32, R45) When the computer is RESET using the Mode/Enter + Set/Clear combinations, the Distance Travelled on the Trip1 counter is copied to the Distance Remaining Function (F6) and the Trip1 counters are cleared ready for a new journey. If the same trip is being travelled then the distance remaining in F6 is already set, otherwise it will have to be entered for correct operation. If the distance remaining of journey is not entered or is incorrect then the distance remaining of journey (F6) & Time remaining at current/average speed to complete journey (F23/F24) will be incorrect. That completes the description of the various functions of the OzTrip Computer. Now we’ll put it together! You may need to refer to the circuit diagram published last month if any of the following is unclear. There are some differences in the way components are marked on the PC board and in the text. For example, we refer to transistors as “Q1, Q2,” etc but the PC board shows them as “TR1, TR2,” etc. Likewise regulators REG1 and REG2 are labelled “IC1” and “IC2”, the 7-segment displays DISP1-4 are labelled “SEG1-4”, the LEDs are labelled “L” and some capacitors shown in µF on the circuit may be shown in nF. Construction There are two PC boards to assemble. This is made easy by following the component mask printed onto the PCBs. Here are the assembly details for PC board 2. The RED leads go to PC board 1, while the GREEN leads go to PC board 3 if it is used. The parts shown in red are installed first, on the reverse side of the PC board. IC5, R58 & R59 (shown in blue) are optional and not included in the kit. Note also that some of the parts adjacent to IC3 on the prototype are not used in the final version. Before mounting any components, check that the PC boards fit into the case and the case closes properly. It may be necessary to round the corners of the boards slightly with a file to en-sure the cases halves fits together. Start with PC board 1, the display board. This is the easier of the two main boards because all components are mounted on one side. Solder in the lowest profile components first (resistors), followed by the LEDs and transistors, taking care with the polarity of the LEDs (in all cases, the anodes or longer legs go to the right). The LEDs should all mount so that they are about 3mm above the PC board. The transistors mount hard down on the board. Next solder in the four LED displays – the decimal points all go to the bottom – and the four pushbutton switches or keys. Again, these must be inserted the right way for switching action to occur – the notches go to the top and bottom. The LED displays and switches mount right down on the PC board. Note that there are four diode positions marked on the PC board which are not used. PC board 2, the one containing the ICs, has components mounted on both sides. You must solder the components on the bottom side first as IC1 hides resistors R26, R37-R44 and transistors Q13-Q20, which are mounted directly under it. Resistors R37-R44 are mounted on their ends. Proceed with the assembly as per board 1. The piezo buzzer can either be mounted on the board or externally (eg, on the case) via flying leads. Note that there is provision for mounting a serial EEPROM (IC5) and two resistors (R58 & R59) on the bottom of the board but they are not used in this particular application. Eight 1kΩ resistors and 21 wire links are used to bridge the two PC boards (component lead offcuts can be used for the links). After carefully inspecting both boards for the usual soldering mishaps place both boards back to back and use the spacer and screws to join both Parts List For Non-EFI Option (PC Board 3) 1 PC board (coded QIP3) 10 63mm lengths tinned copper or hookup wire Semiconductors 1 4020 (IC8) 1 MAX232 (IC6) 1 TL082 (IC7) Capacitors 6 10µF (C15 - C20) Resistors 4 10MΩ (R46, R49, R54, R57) 8 1kΩ (R47-R48, R50-R53, R55-R56) 1 22Ω (R60) boards together. This done, install resistors R60-R67 (1kΩ), then install the wire links. The boards have plated-through holes so all soldering can be done from the outside but before final soldering make sure both boards are parallel to each other and aligned correctly. There should be exactly 10mm between the PC boards. If the third PC board is being used, assemble it in the same way. PC stakes should be installed on the back of the board for external connections. PC board 3 is mounted with its components facing forward and linked to PC board 2 via long lengths of tinned copper wire. The two boards should be exactly 60mm apart. There is an obvious danger of the tinned copper wire shorting but when assembled in the case, the wires can be bent out of each other’s way. They are rigid enough to stay in the same position. However, if you have any doubts at all, some or all of the tinned copper wire can be replaced with insulated hookup wire or you could slide an insulation sleeve over each length of tinned copper wire before soldering it in. Mounting in the case Before installing the two or three PC boards in the case, the bottom screw lugs need to be removed from inside the case so that the display board is clear of them. The lugs can be drilled or filed down. April 2000 67 This is the optional PC board 3 for non-EFI vehicles, also shown samesize. The connecting links (shown in green) back to PC board 2 need to be about 63mm long to allow the boards to mount 60mm apart and so fit into the slots in the case. IC8, shown in blue, is not required in this project nor included in the kit. Its job was to divide and shape incoming pulses but was found to be unnecessary. If the computer is to be used for general-purpose data logging applications (as it can be) this facility could be quite handy! You will need to drill out a small hole on the back panel of the case so that the 6-core cable can enter the computer from behind. Use a grommet on the back panel to secure and protect the cable. A logical colour code for the 6-core cable is given in Table 1. Testing Much of the testing is undertaken using the computer’s own diagnostic functions. These tests are undertaken BEFORE the computer is installed in a vehicle. Follow the steps below for a thorough testing procedure: Step 1: apply +12VDC and ground to the respective inputs. Nothing should happen Step 2: apply +12V to the accessory input. You should hear a BEEP out of the computer and a message displayed on the display “tRiP 1.0” – Trip computer, version 1.0. Disconnecting the accessory input from the +12V should shut the computer down. Step 3: check that the keyboard is functioning correctly by pressing every key; a BEEP should be heard every time a key is pressed. Use the Diagnostic Menu Option 4 to check all the key combinations. Step 4: check the display and use Diagnostic Option 5 to cycle through all of the display. Step 5: check the speed input by using Diagnostic Option 1 and pulsing the speed input with a voltage of 5-12VDC. The display should register the pulses. Remember the display might jump up very quickly because the input is very sensitive. Step 6: check the fuel input by using Diagnostic Option 2. If the computer has been configured for EFI operation, pulse the input with a 5-12VDC signal to trip the counter. If a Flow Sensor is connected blow into the sensor and it should register on the display. Step 7: test the display-dimming feature by connecting +12VDC to the headlight input. Testing is now complete. If all tests were satisfactory the computer can now be installed into a vehicle and calibrated. Speed calibration Speed sensor calibration can be achieved in two ways. The first method involves using the Cal Menu Option #1 automatic calibration mode. This requires you to drive a known distance while the computer counts the pulses from the speed sensor. Your local motor registry or transport department should be able to tell you where an accurate “speedo calibration” stretch of road is located (most are on freeways). Alternatively, most taxi companies have a known length of road for calibrating taxi meters. Also most new cars have a quite The two boards have to be exactly 10mm apart and exactly parallel. Here you can see how the 10mm spacer, resistors (which are actually 1kΩ now) and the wire links (cut-offs from resistors) achieve this spacing. It’s very rigid, too. 68 Silicon Chip Table 1: Wiring Colours Colour Connection Orange Green Blue Brown Black White +12V DC Ground +12V DC Accessories Speed Sender Fuel Injector Headlight accurate speedo (odometer) but older cars may not be so good. During calibration, the computer displays the message “DiSt”, “CAL”, “value” where “value” represents the number of pulses received from the speed sensor. Once the known distance has been travelled, the Mode/Enter key is pressed to end counting and the distance travelled is entered. The computer divides the distance travelled by the number of pulses counted and stores the value as a calibration number. It is a good idea to record the Distance Calibration number using Cal Menu Option #2 – View Modify Speed Sensor Calibration number, so that if power is lost you can manually enter the number into the computer without having to repeat the entire calibration process. The second calibration method is to manually calculate how many millimetres each pulse from the speed sender represents and entering the value in number of mm’s using Cal Menu Option #2. This number can be calculated by measuring the diameter of the tyre and dividing that by the number of sensor pulses per wheel revolution. This method is not normally as accurate as the first method. EFI Calibration Follow these steps to calibrate the Table 2: Resistor Colour Codes       No. 1 (or 5*) 2 9 23 10 (or 18*) 8 (or 9*) Value 10MΩ 33kΩ 10kΩ 2.2kΩ 1kΩ 22Ω 4-Band Code (1%) brown black blue brown yellow yellow orange brown brown black orange brown red red red brown brown black red brown red red black brown 5-Band Code (1%) brown black black green brown yellow yellow black red brown brown black black red brown red red black brown brown brown black black brown brown red red black gold brown (* extra resistors required if PC board 3 is used) April 2000 69 Here are the three PC boards mounted in the case, complete with the red acrylic filter. Note that the filter is in the first slot. The display PC board is not in any slot but is held in place by the second PC board 10mm behind it in the second slot. The optional third PC board is in the third slot with the back panel in the fourth. computer for EFI operation: Step 1: fill the fuel tank (ie, all the way to full. Step 2: ensure the “EFI” Mode is selected (Cal Menu Option #7). Step 3: select the Fuel Calibrate Mode from the Cal Menu Option 3 to start calibration. During calibration the message “Fuel”, “CAL”, “EFI”, “value” will be displayed. The “value” represents the total pulse width time. This value must not exceed “4294”. Drive the vehicle for as many trips as required until 80-99% of the fuel tank is used or the value approaches “4294”. If you exceed the value of “4294” then an error message will be displayed and you will have to start calibration again. When the value reaches “3500” the computer will beep to indicate that it is approaching the end of its calibration range. Step 4: fill the tank to the same point again and note exactly how much fuel was used. Press the Mode/Enter key and then the computer will ask you to enter the Fuel Used. This completes fuel calibration. It is a good idea to take a note of the fuel calibration number using Cal Menu Option 4 in case the computer loses its settings – you can manually input the calibration number without having to recalibrate the computer. Fuel flow sensor calibration To calibrate the computer for Flow 70 Silicon Chip Sensor Operation you will need to know the calibration number of the sensor being used which is number of pulses the sensor emits per 100ml of fuel used. The sensor used by Oztechnics, for example, has a fuel calibration factor of 780. Step 1: ensure the “FLO” Mode is selected (Cal Menu Option #7). Step 2: select the Fuel Calibrate Mode from the Cal Menu Option Step 3: enter the flow sensor calibration factor. That's all there is to sensor calibration. Engine tacho calibration (EFI mode only) The Engine Tacho is only operational in the EFI mode as the injector frequency is also used to determine the RPM of the engine. A calibration number, which for most engines will be 120, must be entered into the computer. Enter this number using the CAL Menu option #5. The maximum value is 255. The calibration number may be different for some EFI systems which fire the injectors more than once per cycle. The calibration number for these engines may need to be determined by trial and error. If the flow sensor mode is used, you can enter 1 to display the frequency of the flow sensor or 60 to display the RPM of the sensor. Serial data link & logging A Windows 95/98 Virtual Dashboard application can be used to display the OzTrip Computer’s Telemetry. It is also possible to control the OzTrip from this application. A 2-way serial data link is used between the OzTrip Computer and a PC and the data from the microcontroller needs to be RS232-translated. This is achieved via optional PC board 3. This PC board and the optional software are available separately. The Virtual Dashboard Visual Basic source code is also available separately so that it can be customised for individual applications. We plan to present another part to the OzTrip Computer in a future issue detailing the use of the Virtual Dashboard and describing remote monitoring/control. Errata The following recent amendments should be noted for the circuit diagram published on pages 90-91 of the March 2000 issue: the 10kΩ resistors to the bases of Q5-Q12 and Q13-Q20 have now been changed to 2.2kΩ. Also, power to the TL082 (IC7) pin 8 on board 3 has been changed: it is now taken not from the +5V rail as shown but from +12V via the ignition switch, through a 22Ω resistor (R60) decoupled by a 10µF electrolytic capacitor (C15). Finally, the 5V supply to the MAX232 (IC6) goes direct to pin 16, not pin SC 2 as shown. Where To Buy The Parts A full kit of parts can be purchased from Oztechnics Pty Ltd. You can place your order on-line from the Oztechnics secured web server or make inquiries via email. Visa, MasterCard and Bankcard accepted. All components, case and laser cut front panel filter are included in the kit. Note: this project and software is copyright to Oztechnics Pty Ltd. Description OzTrip Computer Kit (boards 1 & 2).......................................................$129 PC board 3 Kit........................................................................................$59 (a) (Signal Conditioning & Serial Data Comm’s PCB kit + PC software) Fuel Flow Sensor....................................................................................$119 (b) Proximity Switch (speed sensor)...........................................................$30 Oztechnics V2.0 Car Computer Kit (LCD Model)....................................$179 P&P........................................................................................................$10 (a) & (b) are required for fuel flow installation. (a) is required for data logging. Oztechnics Pty Ltd, PO Box 38, Illawong, NSW 2234. Phone: 02 9541 0310; Fax: 02 9541 0734. Website: www.oztechnics.com.au Email: info<at>oztechnics.com.au April 2000 71 Do you need to track temperatures inside a coolroom, a shipping container or inside a factory or warehouse? This low-cost logger is set up using a PC and can record up to 2048 measurements. The accompanying software lets you display the results as a table or in graphical form. Design By MARK ROBERTS Temperature Lo L OW COST, portability and versatility are the key features of this temperature recorder project. All components are mounted on a single PC board measuring only 57 x 60mm, which means that it could be placed just about anywhere that temperature monitoring is required. No external connections are required during operation, as the recorder is powered by an on-board battery and all measurements are logged in non-volatile memory. The recorder board plugs directly into the parallel port of your PC to allow setup and data retrieval. Windows-based software makes the task straightforward and even includes charting and graphing facilities. The measurement range is from -40°C to +85°C in 0.5°C increments and a total of 2048 measurements can be logged in memory. Also included is a histogram feature which provides 63 data bins with 2°C increments. Both temperature logging and histogram tabulation can be programmed for 72 Silicon Chip sampling intervals of once per minute to once every 255 minutes. Circuit details A Dallas DS1615 temperature recorder IC does all the work (see Fig.1). The actual temperature sensor is contained on-chip, as is a real time clock/calendar, non-volatile memory, a serial interface and the associated control logic (see Fig.2). The DS1615 can source power from either its VCC or VBAT pins. When the VCC pin is higher than VBAT, the entire chip is powered from VCC. When the VBAT pin is higher than VCC, the VBAT pin powers everything except the serial interface circuitry. Two TTL output lines from the PC parallel port supply power to the VCC pin via a 100µF capacitor. At first glance this might seem to be a rather unorthodox approach but as the DS1615 draws little current it does the job. A 3.6V lithium battery powers the temperature recorder when it’s not connected to a PC. With the serial interface powered down, current is really only consumed during a temperature conversion cycle, when it peaks at a maximum of 600µA. This drops to a couple of µA between conversions, which is probably less than normal battery leakage. As you can see, the sample rate ultimately determines battery life. Communication with the DS1615 is via the PC parallel port and a 3-wire synchronous serial bus. Transfers are initiated when the RST pin is driven high. Data is clocked in/out of the I/O pin by high-low-high pulses on the SCLK pin, with a maximum transfer speed of 2Mbps. On the PC side, data is received on parallel port pin 10 and transmitted on parallel port pin 6. When the DS1615 is transmitting data, the software writes a low to pin 6 of the parallel port to reverse bias diode D1. As a matter of interest, the DS1615 also provides an asynchronous serial interface (on pins TX and RX), suita- Fig.1: the circuit is based on the Dallas DS1615 temperature recorder IC. The device is self-powered and is plugged into the parallel port of a PC for setup and data retrieval. ogger ble for interfacing to a PC serial port or modem. However, neither the PC board nor software provide support for this connection method. Pushbutton switch S1 performs double duty. When it is pressed, data logging is initiated and the red and green LEDs flash simultaneously four times to indicate acknowledgment. Alternatively, if data logging is already under way, pressing S1 instructs the DS1615 to check its temperature alarm status. If all the samples recorded to that point are within the lower and upper temperature range (programmed during setup), the green LED flashes four times (INSPEC). If any sample exceeded the thresholds, the red LED flashes four times (OUTSPEC). Of course, the software can also perform all these functions and more but the switch and LEDs provide a quick way of checking temperature alarm status without having to plug the recorder into a PC. What about the yellow LED? This LED illuminates whenever the INT pin is driven low in response to a temperature and/or time of day alarm. Once active, the INT pin remains so until cleared under software control. You will probably want to disable this feature to maximise battery life. Alternatively, the INT output could be interfaced with other low-power CMOS logic for remote temperature alarm monitoring. Finally, a 32.768kHz watch crystal together with an internal oscillator provides the timebase for the DS1615s clock/calendar circuitry. If you would like to delve more deeply into the internal workings of the DS1615, the complete datasheet is available for download from the Dallas Semiconductor website at www.dalsemi.com Construction With only a handful of components, this could be the simplest project you’ve ever constructed! First, carefully check the PC board for shorts between tracks. This is particularly important as the battery is a high-energy lithium type and won’t cope well with a short circuit! Fig.3 shows the full-size compo- Fig.2: block diagram of the DS1615 Temperature Recorder IC internals. Even the temperature sensor is located on-chip. April 2000 73 you must, a word of warning - it will probably need to be quite short due to the low-cost design of the interface. Another point we should mention is that if you come in contact with any of the connections on the PC board while the DS1615 is recording, data corruption may result. To reduce the chances of this happening, a piece of insulating material could be attached to the solder side of the board, or you might opt to fashion a simple enclosure (open to free air, of course!). Fig.3: the full-size component overlay for the Temperature Recorder. Link L1 functions as the on/off switch. nent overlay. As usual, install the links, resistors and diode first, followed by the crystal and LEDs. Note that depending on the revision of PC board you receive, you may notice a diode (D2) shown on the silk screen overlay next to IC1 – do not install anything in this position. We recommend socketing the DS1615, so install the IC socket next. The D-connector and 2-way header pins for LK1 can be installed next but don’t install the jumper shunt just yet. Now install the capacitors, switch and battery. Finally, plug in the DS1615 IC (carefully noting its orientation) and install the jumper shunt on LK1. The Temperature Recorder PC board is designed to plug directly into the parallel port connector on your PC. We don’t recommend using a cable to make the connection but if Software Software suitable for Windows 95/98 and Windows NT is provided on four floppy disks. To install it, run the Setup.exe file on the first disk and follow the on-screen instructions. Click on the Start button and select Programs, DS1615 Temperature Recorder to launch the program. Every time the software is launched, a dialog box appears that allows you to select which port the recorder is connected to (LPT1 or LPT2). A total of six tabulated windows provide easy access to all software functions. First stop is the Time/ Alarm window, as this allows us to set the DS1615’s clock and calendar (Fig.4). Clicking on the red circle at the bottom of the calendar automatically sets the date to match the current PC date. The time must be set manually using the up/down arrows next to the time display. The Time/Alarm window also al- Fig.4: clicking on the red circle at the bottom of the calendar automatically sets the date to match the current PC date. 74 Silicon Chip Parts List 1 PC board, 57 x 60mm 1 DB-25 PC-mount male connector (CON1) 1 3.6V PC-mount Lithium battery 1 16-pin IC socket 1 32.768kHz crystal (X1) 1 4-disk software package Semiconductors 1 DS1615 temperature recorder IC (IC1) 1 1N4148 diode (D1) 1 subminiature red LED (LED1) 1 subminiature green LED (LED3) 1 subminiature yellow LED (LED2) Capacitors 1 100µF 16VW PC electrolytic 1 0.1µF monolithic ceramic Resistors (0.25W, 5%) 4 2.7kΩ 1 1kΩ Where To Buy The Parts Full kit (hardware & software.....$65 PC board only.............................$6 Payment by cheque or money order to Softmark, PO Box 1609, Hornsby NSW 2077. Phone/fax (02) 9482 1565; email softmark<at>ar.com.au Please add $6 for postage. Website: www.ar.com.au/~softmark lows us to alter the DS1615 control register bits. Let’s briefly examine each of these settings: (a) The Disable Oscillator setting Fig.5: the temperature alarm is set here. If an alarm condition occurs, the respective indicator changes colour. The settings can’t be altered once recording is under way. The DB-25M connector mounts on the PC board, so that you can plug the unit directly into the PC’s parallel port. shuts down the DS1615s internal oscillator if it’s not in the process of logging data. The chip enters standby mode, drawing only about 0.2µA. (b) The Clear mem-Enable setting enables clearing of all internal memory including datalog and histogram memory (a clear memory command can be issued from the Graph window). (c) Pushbutton switch S1 (see hardware section) can be enabled or disabled with the Start Ext-Enable setting. (d) The Roll Over setting, if select ed, allows data recording to “wrap around” when memory is full (ie after 2048 samples). (e) Finally, hitting the SAVE NEW button saves the current settings (including the alarm time) in a file called DS1615.ini in the C:\Windows Fig.6: temperature sampling is set up and initiated from this window. Note that if a recording is in progress, clicking in the START LOGGING button actually stops recording. directory. This initilisation file is automatically loaded each time the software is started. Note that if recording is in progress when you change any of the settings, it will be terminated when the software writes the changes to the DS1615. As mentioned in the hardware description, the DS1615 includes a temperature alarm feature. This is programmed in the Temperature window (Fig.5). The indicators marked “THigh”, “TLow” and “Time” display current alarm status. Note that the “Time” indicator is associated with the time of day alarm, which is set in the Time/Alarm window. Recording settings are found in the Graph window (Fig.6). Both the sampling interval (Sample Ratio) and delay until first sample can be set Fig.7: a variety of graph types and colours are supported in the histogram-plotting feature. here. Clicking on the START LOGGING button initiates the recording cycle. Once at least one sample has been performed, clicking on the READ button retrieves datalog memory and displays the readings on the graph. Note that the Total Samples value is the total number of samples ever performed. This value can be zeroed by disconnecting the battery. Histogram memory is retrieved and displayed in the Histogram window (Fig.7). There are no surprises here, so let’s skip over to the Logging window (Fig.8). Clicking on the Read Log button reads datalog memory and creates a log file called DS1615.txt in the root directory of your C: drive. This file could easily be imported into a spreadsheet or database for further SC processing. Fig.8: log files can be created, viewed and printed from the logging tab. April 2000 75 Large-screen LCD monitors have arrived and they look great. We review the Diamond View DV180, the latest generation in flat-screen displays from Mitsubishi Australia. By PETER SMITH Mitsubishi Diamond View DV180 LCD Monitor A FTER USING A LAPTOP computer with a liquid crystal display (LCD) for a number of months and then moving back to a standard CRT monitor, I immediately became aware of just how easy on the eyes a good LCD can be. So naturally, I wasn’t complaining when one of the latest LCD monitors arrived on my desk for review. Not too long ago, the high cost of LCD panels prohibited their use in desktop monitors, at least for the mass market. In addition, design improvements needed to be made in areas like colour saturation, image persistence and viewing angle before they could 76 Silicon Chip compete directly with CRT displays. All that is now changing as improving manufacturing methods and technological advances push the price down and the display quality up. If you’ve been on the lookout for a new computer or monitor lately, you will probably have noticed the steady increase in the variety of LCD monitors being offered for sale. Manufacturers such as Dell, IBM and Compaq are now offering LCD monitors as options with their systems. Prices are on the way down but are still rather high by comparison – you’ll typically pay as much as 2-4 times more for an LCD monitor than for the “equivalent” conventional type. That’s outrageously expensive, I hear you say. But you do get a lot more (or should I say less?) for your money. So what are the advantages of LCDs? Well, they don’t suffer from the many alignment problems that plague CRTs, like pincushion distortion, colour misconvergence, poor focus, etc. What’s more, they don’t emit potentially harmful radiation, they consume much less power and perhaps best of all, they’re incredibly thin! Big screen If you prefer a large-screen monitor for work or play, until very recently you had no choice but to stick with the CRT variety. From a display viewpoint, the large-screen advantages are obvious but take a tape measure with you when you go to buy one – it might not fit on your desk (hey, this thing’s bigger than my bar fridge!). The good news is that LCD monitors with screen sizes of 21 inches or more are now available – and their image quality is nothing short of amazing! The Diamond View DV180 reviewed here has a generous 18.1-inch (46cm) screen size. Note that this is the actual viewable size, measured diagonally. By contrast, CRT monitors are not listed by their viewable size but rather the tube size, which is usually somewhat larger. This means that the DV180’s 18.1 inches is roughly equivalent to a conventional 19-inch monitor in viewable size. One of the first things you notice about LCD monitors is their size. In comparison to CRT monitors, they occupy only a fraction of the desk space. Of course, this also means that they weigh a lot less – a welcome change from my 21-inch CRT monitor, which is a two-person lift! Setting it up Unpacking and setting up the Mit subishi DV180 was a snap. It accepts analog (as opposed to digital) video input, so it simply plugs into your standard SVGA card. Driver software for Windows 95 & 98 is included on diskette, along with a utility that allows automatic adjustment of the display. Unlike some other models that have a separate power pack, the DV180 has an inbuilt power supply – the 240V cable plugs directly into the base of the stand. Having installed the driver software, we went into “Display Properties” to set the display resolution to 1280 x 1024 pixels – the monitor’s “native” resolution. As with most LCD monitors, the DV180 automatically expands lower-resolution images (800 x 600, for example) to fill the entire screen. Unfortunately, expanded images are nowhere near as clear as those displayed in native mode. Scaling images to fill the entire screen while still retaining reasonable picture quality is apparently quite difficult and there is some variation in the results between manufacturers. If necessary, auto-expansion (called “Zoom” in the DV180) can be disabled LCD panels lack the sheer bulk of conventional monitors which means that they’re far easier to fit on the desktop. They’re considerably lighter too! in the DV180’s on-screen set-up. Not all monitors allow you to disable this feature, so the DV180 scores here. The only other settings to consider are the refresh frequency and colour palette. The refresh frequency setting is not critical, as LCD monitors do not suffer from the annoying flickering that haunts CRTs at the lower (60Hz and below) rates, especially under fluorescent lighting. We set ours to 75Hz since the DV180 can handle this quite comfortably. Finally, the DV180 can display 16.7 million colours, so we selected the closest setting – True Colour. Adjustment The DV180’s auto-adjust feature makes display adjustment a simple task. The first step is to run the AUTO. EXE program to display the full-screen alignment pattern. You then push the “Auto” button on the front of the monitor and you’re done! Manual adjustment is also possible with the aid of the On-Screen Display (OSD) system and a single wheel located on the lower, righthand side of the display panel. This wheel also functions as a pushbutton, operating in a very similar manner to the scroll wheel on many mice. Pushing the wheel brings up the on-screen display (OSD) and it also enters your selection (like pressing the Enter key) within the OSD menus. Rotating the wheel moves among the various options, as well as allowing you to increase or decrease any setting you choose. I was about to complain about the lack of separate brightness and contrast controls (these can be varied from within the OSD menu, of course), when I discovered that simply rotating the wheel when the OSD menu isn’t on the screen does the job. Move the wheel in the anticlockwise direction and the contrast setting appears; move it clockwise and the brightness setting appears – brilliant! Next time, I’ll read the manual first, I promise! Subjective impressions Did we mention that the picture April 2000 77 DV180. We didn’t notice it during normal use but then we don’t run video applications. Another problem with some LCD monitors is that variations in the backlighting can cause light and dark spots across the face of the panel. We didn’t notice any evidence of this on the DV180 although we did notice some shimmering (or noise) when displaying certain fine-line dark images. This is probably an artifact of the analog-to-digital conversion process and was easily corrected by performing the auto-adjust procedure or by tweaking the “clock phase” setting in the OSD menu. Audio & USB The rear panel of the DV180 carries the audio input and output sockets plus four powered USB ports. A pair of multimedia speakers is also included in the stand, along with a 1W stereo amplifier. quality is outstanding? The high brightness and excellent contrast of the DV180 results in a really crisp, clear image that just can’t be matched on a conventional monitor. Lack of refresh-induced flicker is noticeable by its absence too, as images are rock steady. A common complaint about LCDs in the past concerned their narrow viewing angle – shift your body position slightly and the display appeared to fade. However, this is no longer a problem because current high-quality monitors have a wide viewing angle – 160° or more horizontally for most large-screen panels (the DV180 has 180°). CRTs still have the edge over LCD panels when it comes to image persistence. Fast-moving objects, such as those in video clips or animations can cause a slight smearing effect on an LCD monitor. This is due to the speed at which the crystal elements themselves can be switched (or polarised) and although this effect has been minimised, it is still apparent to a small degree on the latest panels. This effect seemed small on the LCD Monitors & Interface Standards The majority of LCD monitors on the market today accept analog video input. While this means that they connect directly to existing VGA/ SVGA graphics cards, the LCD panel is a digital device, so the incoming analog signal needs to be converted to digital. As you may be aware, the reverse process occurs at the PC side. The graphics card receives information in digital form and converts it to analog at the output stage (CRT monitors are analog devices). The downside to this double conversion (digital to analog to digital), 78 Silicon Chip apart from the cost of the redundant electronics, is some loss of signal information. This can result in lower-than-possible picture quality and side effects like pixel “jitter”. The solution, of course, is to use an all-digital system. Graphics cards based on a new standard called DVI (Digital Visual Interface) that provide both analog and digital support will be available in the near future. In the meantime, a few digital LCD monitor and graphics card bundles are available but the choice is limited and the cost is higher than otherwise. Included within the monitor stand is a pair of multimedia speakers and a 1W stereo amplifier. Input to the amplifier is via a standard 3.5mm stereo socket, situated at the rear of the stand. The volume control is located on the side of the stand and can be accessed without too much difficulty by reaching under the display panel. Two additional 3.5mm sockets are to be found at the rear of the stand; one is the headphone output and the other the microphone output. The microphone itself is hidden behind a tiny pinhole at the top of the display panel. Adding to its list of impressive features, the DV180 also includes a powered USB hub with four downstream ports – just the ticket for connecting up that ZIP drive, mouse, etc. The USB connectors are also positioned at the rear of the stand and while you need to reach around the back to hook things up, it’s not too difficult due to the super-slim LCD casing. Warranty The Diamond View DV180 is supplied with a full 3-year warranty, which includes the LCD backlight. This is a distinct advantage, as many other manufacturers cover the back light for the first year only. Why only one year? The backlight is actually one or more fluorescent tubes that have a limited life in comparison to the LCD panel itself. They are also quite fragile, although this concern applies more to portables than to desktop displays. It follows that to get the longest life out of your LCD monitor, you should set up power saving in Windows so Diamond D iamond View View DV180 DV180 Specifications Spec wications At At AA Glance Glance Displ ay type Thin film transistor (TFT) acti ve matrix panel Max. vi ewabl e size 46cm (18.1 i nches) diagonal Max. resolution 1280 x 1024 pixel s at up to 75Hz refresh rate Displ ay size 359mm (H) x 287.2mm (V) Pi xel pitch 0.28mm Colour depth Quasi-full colour (16.7 mil lion colours) Luminance 200 Cd/m2 (typical) Contrast ratio 200:1 (typical) Vi ewing angl e ±80° horizontal, ±45° verti cal Video We couldn’t help taking a peek inside the rear panel. The large vertical board is a switchmode power supply for the LCD panel. that it is powered down when not in use. By the way, it is probable that your LCD monitor will arrive from the manufacturer with one of more defects on the display panel. Defects occur when a cell is stuck on (creating a bright spot) or stuck off (creating a dark spot). Each pixel is composed of a group of three cells and with 1280 x 1024 pixels in all, that’s a total of over 3.9 million cells, so the chances of a defect must be high. Often, manufacturers consider not just the number of defects to be important but also their grouping and whether they are bright or dark. Generally, a maximum of about six defects is considered acceptable but policies and specifications do vary. Contact Mitsubishi Australia for a copy of their “Pixel Defect Specification” if you would like the whole picture. Horizonta yrequency 31.5 - 80.5kHz, auto scanning Verti ca yrequency 56 - 75Hz, auto scanning Synchroni sation Separate Vi deo bandwidth 135MHz Input signal Vi deo analog RGB (positi ve) Plug & Pl ay Compatible with Windows 95, Windows 98 and Windows 2000 (DDC-1 and DDC-2B) User control s On-Screen Displ ay (OSD) Audio Speaker output power 1W per channel (stereo) Input impedance 50k S/N ratio 50d B Mi crophone sensiti vity -68dB Frequency response 100Hz ~ 20kHz Power Requirements Power input 90-264 VAC (47/63Hz) Power consumption 75W maximum (supports VESA DPMS power saving modes) Input Connectors Vi deo 15-pin mini D-sub Audio Stereo audio input - 3.5mm jack Headphone j ack 3.5mm Mi crophone output j ack 3.5mm U SB 1 upstream, 4 downstream ports Physical Characteristics Dimensions (H x W x D) 457mm x 469mm x 217mm Weight 9.8kg net Final say The Diamond View DV180 is a fine example of current large-screen, stateof-the-art LCD monitors but at $6229 (incl. tax) it’s not for everyone. If you see one, you’ll almost certainly want it on your desk but of course, it will need to fit your budget too! Also available is the Diamond View DV150, a 15.1-inch LCD monitor with a more affordable price tag of $2440 (shop around for the best deal). Check out Mitsubishi Electric Australia Pty Ltd’s website at www.mitsubishi-electric.com.au for more details or phone (02) 9684 7777. SC April 2000 79 NOW WITH 30 E and st ternet in h t i w s s e c ac 2. PER M  NO download limits  NO mysterious hidden charges  NO long-term contracts  NO fine print *POPS (Points of Presence) NOW IN ALL THESE CITIES AND TOWNS VIC Bacchus Marsh, Ballarat, Balliang, Bendigo, Cranbourne, Emerald, Geelong, Gisborne, Healesville, Kilmore, Kinglake, Lara, Melbourne, Mornington , Nunawading, Pakenham , Romsey, Shepparton NSW Albury, Armidale, Bathurst, Camden, Campbelltown, Coffs Harbour, Dubbo, Gosford, Grafton, Lismore, Mulgoa, Newcastle, Nowra, Penrith, Port Macquarie, Sydney, Tamworth, Taree, Wagga Wagga, Windsor, Wisemans Ferry, Wollongong QLD Brisbane, Bundaberg, Cairns, Gladstone, Gold Coast, Mackay , Maroochydore, Maryborough, Mt Isa, Rockhampton, Toowoomba, Townsville WA Broome, Bunbury, Geraldton, Kalgoorlie, Katanning, Perth, Rockingham SA Adelaide, Gawler, Mt Gambier, Port Augusta ACT Canberra NT Darwin TAS Hobart 80 Silicon Chip EXTRA POPS* . . . till only COUNTRY .7c READERS TAKE NOT E! MINUTE     YES YES YES YES - your own email address your own website space 100% peace-of-mind 100% satisfaction g'tee You’ve seen all those other low-cost Internet access offers? The ones which look great until you read the fine print? Well, here's one without fine print! The only restriction to this service is a $10 minimum per month (5 hours included free) and payment may only be made by credit card. All capitals and many larger cities covered. INTERESTED? Call SILICON CHIP, totally obligation free, on (02) 9979 5644, 9am - 5pm Mon-Fri for more details. (We'll even call you back if STD). Or fax us on (02) 9979 6503. Or if you already have web access, April 2000 81 email silchip<at>siliconchip.com.au or www.silchip.com.au PRODUCT SHOWCASE Dual is back! Jamo Australia has recently been appointed the Australian distributor for the range of Dual turntables, made in Germany. Dual, founded in 1900, is celebrating 100 years of manufacturing. There are five models in the DUAL range. The midi size CS-400 retails for $349. The ‘standard width’ turntables start at $499 retail for the CS-415, a fully automatic, belt-driven model. The CS-435, also a fully automatic belt-driven model, sells for $599.00. The next model up, the CS-455, is supplied with an Ortofon cartridge and will also play ‘78’ records. Available in Low-cost DMM is packed with features gold or silver, it sells for $699. The CS-505, now in its Mark 4 version, sells for $899 and is also supplied with an Ortofon cartridge. For more information, contact Jamo Australia on (03) 9543 1522. External case runs IDE drives from parallel port Jaycar Electronics have recently introduced a product which allows any IDE device (hard disk drives, CD-ROMs, Zip/Jazz drives, etc) to be run outside the host computer via its parallel printer port. While removable drive drawers for IDE devices have been available for some time, they require access to the internals of the computer, not to mention a spare 5.25-inch drive bay. This is a similar system, allowing various devices to be fitted, but the computer does not have to be opened. All that is required is connection to the parallel printer port socket on the rear of the computer. The existing printer cable then plugs into the rear of the external IDE box in “pass through” mode. The box can stand horizontally or vertically and suits half-height 5.25-inch devices, or 3.5-inch devices with an optional 5.25 to 3.5 adaptor. It features an easily removable tray so the device can be mounted in a matter of seconds. Separate fascias are supplied suiting both hard disk drives (as photographed) or with a cut-out 82 Silicon Chip to suit CD-ROM and other devices with removable media. The 270 x 210 x 60mm case has its own 50 watt universal AC supply and inbuilt cooling fan and comes complete with all screws, connecting cables, plugs and sockets – even down to twin RCA sockets for CD-ROM audio outputs. A floppy disk containing appropriate driver software is also included. The XC-4572 External IDE Expansion Enclosure sells for $179 and is available through any Jaycar Electronics store, Jaycar mail orders (phone 02 9743 5222 or www.jaycar.com.au) or most resellers. A near-pocket-sized digital multimeter recently introduced by Altronics Distributors would be a most suitable choice for anyone wanting to buy their first digital multimeter – and for the more advanced student, hobbyist, technician or professional looking for a meter that is packed with features at a low price. The Q-1059 multimeter has all the usual DC and AC ranges – 200mV to 600V DC, 200 to 500V AC, 2mA to 10A DC and five resistance ranges to 20MΩ. It also features diode testing, a continuity tester with buzzer, transistor hFE and a temperature range with K-type thermocouple supplied suitable for 0-250°C. A “hold” button in the centre of the rotary selector freezes any reading currently displayed. The meter measures 135 x 70 x 35mm and is very comfortable in the hand with its sculptured case. Priced at $32.95 it represents very good value for money, especially considering a thermocouple is supplied. It is available from Altronics Distributors retail and mail order centre at 174 Roe St, Perth WA 6000 (Phone 08 9328 1599, website www.altronics. com.au) or through their authorised resellers. Test & measurement brochure is free The National Instruments Automated Test & Measurement Solutions brochure describes how test management software, test programs, instrument drivers and I/O interfaces efficiently work together. Also included is information on several I/O inter- PCB POWER TRANSFORMERS CCTV monitoring system from DSE The micromark CCTV Camera System from Dick Smith Electronics is a fully self-contained camera designed not only for indoor and outdoor use but day and night operation. With six infrared LEDs to improve night-time vision and a built-in microphone, the system allows the user to not only watch what is happening but listen as well. A wide-angle 92° glass lens gives a high quality picture. The system includes the camera itself with a 17m screened cable, fully adjustable mounting bracket, wall plugs, cable clips and a 9V DC power adaptor. Dual IGBT and MOSFET gate driver The new WSL2106 driver from Westcode will drive two IGBTs as a half bridge or as two independent switches. The IGBTs are provided with a ±15V and a 0-15V suppy in standard version. Saturation of the IGBTs is monitored and all logic inputs are of the Schmitt trigger type. Input level can be selected – 5V for HCMOS or 15V for CMOS. Error feedback can be activated by the driver or by an external signal. For more information contact Westek Industrial Products Pty Ltd, Tel (03) 9369 8802, Fax (03) 9369 8006; website www.westek.com.au faces from Nation al Instruments. For your free copy, call National Instruments Aust on (03) 9879 1566, fax (03) 9879 6277, email info. australia<at>ni.com Website is www.ni.com/australia 1VA to 25VA The system is available through all Dick Smith Electronics stores, mail order centre and PowerHouse stores at a retail price of $199 (Cat. L-5880). For further information visit any store or the DSE website, www.dse.com.au Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 Power boards with a difference Two new mains power devices from PowerQwest will be of interest to businesses, hobbyists and home users. First is the Zapcatcher, a heavy-duty power and telephone line filter intended for computers and peripherals, fax machines and modems, shop cash registers and POS terminals, and cordless phone and answering machines, etc. Built into a 215 x 97 x 37mm case and fitted with a 1.2m mains lead, it has four standard 3-pin outlets along with telephone line input and output sockets (standard RJ-12 connectors). The unit is designed to suppress power line surges and spikes with a peak rating of 6500A (8 x 20µs). An indicator neon and LED show normal operation, with a “strike” LED showing if the internal metal-oxide varistor protection circuit has been damaged by excessive surges. Fault conditions in the power outlet are revealed by another neon globe. A 10A circuit breaker is also included to protect against excessive loading. Maximum loading is 2400W (10A). There are also two large toroidal inductors for mains-borne noise suppression and these give better than 40dB of noise rejection. Second item is the Teleswitch, a music muting system which automatically cuts power to any mains-operated device when the phone rings and reconnects it when the call ends. Similar in size to the Zapcatcher, it also has spike suppression built in but does not have the range of indicators. Along with the four standard mains outlets, this also has an IEC outlet built in. Only one of the four outlets is cut off when the phone rings – presumably this would be the amplifier or other audio source. All four outlets have surge protection. A 10A thermal circuit breaker is also included while phone line connection is via standard RJ-12 connectors The Teleswitch is designed to work with the normal analog phone network. It may not operate with some PABX or digital phone systems. The Zapcatcher3 and Teleswitch are manufactured in New Zealand and both carry Australian electricity and Austel approval. They are available from selected retailers throughout Australia. Trade enquiries should be directed to PowerQwest: phone (02) 9979 4811; fax (02) 9979 4833. April 2000 83 80 minute minidisc and CD-R from TDK TDK has released new 80-minute versions of its popular MiniDisc magneto-optical recording media and its audio recordable CD (CD-R). The MiniDisc is claimed to be more portable and durable than either cassette tapes or CD-R and is considered to offer sound quality comparable to CD and DAT. TDK guarantees that the MiniDisc is capable of more than one million re-recordings due to its tough outer polycarbonate resin coating. To achieve the 80-minute playing time, the track pitch was reduced while still meeting the stringent specifications of the format. The 80-Minute MiniDisk (MD-XG80) sells for $7.95 at selected TDK dealers. The new recordable CD offers six minutes more recording time than a conventional recordable CD. It is designed specifically for home recording but contains a pre-formatted table of contents (TOC) and Serial Copy Management System (SCMS) which inhibits making copies from copies. The CD-RXA80 is compatible with all existing CD audio recorders. For more information contact TDK on (02) 8437 0600 or visit www.tdk.com.au Highly accurate Hioki power meters Hioki have introduced two new “Power HiTesters” ideally suited for the accurate evaluation of power drawn by a large range of electrical and electronic products, not only at full power but also on stand-by. They have applications in a wide range of home, communication and industrial electronic equipment. The Hioki 3331 is for single and 3-phase use and can measure power from as little as 7.5W single phase to 60kW, 3-phase, while the 3332 is for single phase only and can measure power from as low as 15mW to 120W. Both instruments can measure line voltage as high as 600VAC, line current as high as 60A and active power, apparent power, reactive power, power factor and phase angle, accepting a wide range of frequency inputs to 100kHz. D/A outputs provide waveform data which can be displayed on waveform recorders. For more information contact Nilsen Technologies, freecall 1800 623 350, freefax 1800 067 263. New acquisition systems reduce testing times The release of three new multi-channel data acquisition systems from Acqiris promises to reduce test times for applications that involve high frequency electronic signals. The Cougar systems, which are suited to monitoring signals up to 500MHz in frequency, deliver an exceptional measurement throughput, reducing test times by a factor of up to 10 when compared to using conventional test instrumentation (oscilloscopes, transient recorders, data loggers, etc.) or VXI based test systems. Typical applications include tele communications, LIDAR, radar, auto84 Silicon Chip motive, chemistry, computing, power measurement, ultrasonics, mechanics, physics, military and explosive-weapons and ballistics testing. This Acqiris’ Cougar 2000 system uses ultra-fast real-time digitiser technology and offers four full channels each with 2GS/s sampling rate, 500MHz analog bandwidth and long (up to 16 Mpoints) acquisition memories. Each channel input has a full front-end buffer/amplifier that can handle voltage ranges from 50mV to 5V full scale, with 50Ω and 1MΩ input loading, variable offset, internal calibration (that allows 1% voltage Mitsubishi’s tiny, bright LCD projector The new Mitsubishi LVP-X70U Multimedia LCD data projector might only weigh 3.2kg but it offers a brightness of 1100 ANSI lumens. Distorted images caused by projecting images from the wrong angle have been eradicated with the projector’s digital keystone correction system. It corrects the trapezoid effect within a range of 15°. High quality images with clear definition are achieved with the projector’s “Cineview” line-doubler. It stores the previous and next-image fields and processes the signals with extra motion detection to smooth out horizontal and vertical lines for finer, sharper moving images. Mitsubishi claim the projection of RGB and YMC colour spectra that are equal to those of CRTs – and all six colours can be manually adjusted. Other features include a built-in USB mouse port, a laser pointer built into the remote control and a long-life lamp. Recommended retail price of the projector is $8900 plus sales tax. For more information contact Mit subishi Electric on (02) 9684 7777 or visit their website at www.mitsubishielectric.com.au measurements), full input protection and fast recovery from out-of-range signals. Underneath the Cougar 2000 are the 1000 and 500 systems which offer four channels with 1GS/s and 500MS/s sampling rates respectively. The Cougar systems are housed in small 6U CompactPCI crate (around one-third the size of a regular benchtop oscilloscope) and come complete with all necessary software and a highspeed CompactPCI to PCI interface that boasts an impressive 100 Mbytes/s transfer rate. For more information, contact Acqiris Pty Ltd, phone (03) 9877 9322; fax (03) 9849 0861; website www. acqiris.com Video stabiliser fixes jittery pix! A recently released Australian-made video stabiliser is claimed to be the best available, offering features not found on any other model. The VCS2 Stabiliser is made in Australia by a new designer, Bamb! G (pronounced Bambi-G) and is the first in a new range of processors. It has both S-video and composite video inputs and outputs allowing high levels of connectivity. Both outputs are available from either input but if an S-video and composite video are connected to the inputs, the composite video signal takes precedence. More importantly, though, the device stabilises the video signal and removes any non-standard components in the signal. Conversion is undertaken in a “perfect filter” – and one of the features of this type of filter is that the output signal is a completely standard, rock-solid waveform. Any non-standard components of the video signal which may have been added along the way – either deliberately or accidentally – are removed, allowing a great deal of versatility in its use. One application of the stabiliser is with video projectors and the like which often fail to lock properly on signals from a DVD player or other device which has had proprietary components added. When fed through the VCS2 Stabiliser the signal is returned to standard video and video projectors work perfectly. Similarly, DVD signals can be fed through the VCS2 Stabiliser and into a VCR, allowing DVDs to be viewed on any TV set, not just those with video and audio inputs. The Bamb! G VCS2 is currently available from Questronix, Phone (02) 9477 3596, Fax (02) 9477 3681, with more information on their website, www.questronix.com.au Trade enquiries should be directed to Bamb! G via email: bambi_g<at>bigpond.com VCR springs ’n’ things from DSE Every now and then, a product comes along which makes you think “finally!” We’re sure service technicians, developers and even many hobbyists will think exactly the same about these VCR hardware assortments from Dick Smith Electronics. There are seven packs in the range covering a myriad of the small parts needed to repair VCRs (and many other devices). You’ll find compression springs, tension springs, washers and circlips, screws . . . all labelled in handy trays with see-through lids. No more searching, no more sorting to find that elusive spring or washer! Cat H-1670 pack contains 246 washers, circlips, springs and screws and sells for $16.80. The H-1671 pack has washers and circlips only, selling for $15.50. The H-1677 pack contains tension springs and sells for $19.70 while the H-1678 pack contains compression springs and also sells for $19.70. Not shown are various drive belts: Cat H-6016 contains 14 video drive belts for $10.75; a set of 11 belts for turntables (yes, that’s audio turntables!) selling for $29.40 (Cat H-6018) and the last pack is a set of 10 cassette player belts selling for $6.70 (Cat H-6015). The packs are available through all Dick Smith Electronics stores and most dealers, or through the DSE mail order service or website (www.dse.com.au). SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Use these REFLEX® chargers for all your Nicads and NIMH batteries: Power tools  Torches  Radio equip.  Mobile phones  Video cameras  Field test instruments  RC models incl. indoor flight  Laptops  Photographic equip.  Toys  Others  Rugged, compact and very portable. Designed for maximum battery capacity and longest battery life. AVOIDS THE WELL KNOWN MEMORY EFFECT. SAVES MONEY & TIME: Restore most Nicads with memory effect to capacity. Recover batteries with very low remaining voltage. CHARGES VERY FAST plus ELIMINATES THE NEED TO DISCHARGE: charge standard batteries in minimum 3 min., max. 1 to 4 hrs, depending on mA/h rating. Partially empty batteries are just topped up. Batteries always remain cool; this increases the total battery life and also the battery’s reliability. DESIGNED AND MADE IN AUSTRALIA For a FREE, detailed technical description please Ph (03) 6492 1368; Fax (03) 6492 1329; or email smartfastchargers<at>bigpond.com 2567 Wilmot Rd., Devonport, TAS 7310 New Jaycar store for Nth Queensland Jaycar Electronics has opened a new store in Townsville, Qld. Gary Johnston, Managing Director of Jaycar, said that Jaycar was pleased to be a part of this major administrative, defence and education-based city. The full range of Jaycar products will be available including components, alarm systems, test equipment, video surveillance, car audio, electrical and electronic tools, wire, cable and accessories. “Jaycar is known for its extensive range of electronic hobbyist kits and these will also be a feature of the new Townsville store,” said Mr Johnston. The store, employing up to five local staff, is located at 177 Ingham Rd, West End, Townsville. Phone number SC is (07) 4772 5022. April 2000 85 REFERENCE GREAT BOOKS FOR AUDIO POWER AMPLIFIER DESIGN HANDBOOK NEW NEW NEW NEW 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 $ 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: $............. 86 Silicon Chip 65 $ THE CIRCUIT DESIGNER’S COMPANION By Philip Miller. Published 1997. $ NEW NEW NEW 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 April 2000 87 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Tacho regulator burnout A friend of mine recently bought his second Digital Tachometer which I think was in SILICON CHIP. The first one he tried he fried and on this second one he burnt out the voltage regulator. For some reason it was getting too hot so I replaced it and put a heatsink on it. I tested it on a power pack set to 12V and the three zeros flashed up and all the voltages tested out OK, so we tried it on his car. He assured me it was calibrated. It worked once. The second time we tried we got 8000 revs without the engine running. So I set it up with the power pack again and it showed 8000. He is really annoyed because he has paid a total of $60. What could be wrong? (Damien, via email). • Without really knowing, we assume that you are referring to the 4-Digit Tachometer published in the August 1994 issue. The regulator should not burn out as these are short circuit proof. Perhaps there is a short circuit on the PC board somewhere causing the regulator to overheat. Also the short could be causing the display to show an “8” if FM Mini-mitter misbehaviour I have purchased and built three of the FM Mini-mitter kits (SILICON CHIP, October 1988) over the past 10 years, along with one Baby-minder. Most have been successful, bar this and the previous one. The previous problem was a centre frequency off the FM band and was solved by increasing the 47pF capacitor on pin 10 to 59pF. Now I’ve built the third unit. It delivers a stronger signal than the others but does not trigger the stereo lock on receivers. I’ve checked that the capacitor on pin 12 is 88 Silicon Chip there is a connection between the “g” segment and another segment on the most significant display. How to charge lithium ion batteries I have just built the Multipurpose Fast Charger from the February & March 1998 issues of SILICON CHIP and it works well. Now how can I get it to charge li-ion batteries which are popular in phones and cameras? (N. S., via email). • We published information on using the charger with li-ion batteries in the Circuit Notebook pages of the June 1998 issue. We can supply the back issue for $7 including postage Cordless phone backup battery project I’m keen to build the backup battery unit described in the October 1999 issue, for my new Panasonic cordless phone. The plugpack is nominally 13.5V but is actually putting out 22.5V. The base station handset charger puts out 8.75V (no load) with a 3.5V NiMH battery in the handset. I’m unsure how to set up the LM317 to achieve an output equivalent to .001µF as per the errata. I’ve also checked the components around the mixer (pins 12, 13 & 14). Also, there are about five points on the receiver dial around the best signal where a reasonable signal is heard. This leads me to suspect that I may be receiving a harmonic of the main signal and that the centre frequency is again off the band. I tried increasing the 47pF capacitor in the main oscillator to 59pF by adding a 12pF in parallel. This only gave about 10MHz shift. Can you suggest steps for further diagnosis? I have no CRO. (J. C., via email). • You are probably correct in assuming that the receiver is locked the existing plugpack. The R1 and R2 values in the article are all for lower voltages. What values should I use? (G. T., via email). • As far as we can see there is no simple solution to your problem since the plugpack output is a great deal higher than a 12V SLA battery. Reluctor problem with Multi-spark CDI I have just put together the Multis-park Capacitor Discharge Ignition as published in the September 1997 issue of SILICON CHIP and I have come across some problems. There is no output from the coil (standard type) and the transformer I wound makes a buzzing sound. Here are the DC voltages I measured (all taken from left to right (Q1 on the left) looking down on the devices bolted to the heatsink): Q1 – 9.5V, 12.3V, 15.5mV. Q2 – 1.4V, 12.1V, 17.1mV. Q6 – 13.8V, 298.3V, 14.1V. Q7 – 9.4mV, 14.2V, 9.1mV. IC1 – pin 1 8.3V, pin 2 8.0V, pin 3 0.9V, pin 4 14.7V, pin 5 1.5V, pin 6 15.7mV, pin 7 8.12V, pin 8 8.3V. IC2 – pin 1 15.3V, pin 2 22.2V, pin 3 12.5V, pin 4 9.1mV, pin 5 9.1mV, pin onto a harmonic. Try carefully tuning across the FM band with the receiver well away from the transmitter. You will find several spots where the signal is received. Select the one which gives stereo. If you cannot find any other positions on the receiver, then try retuning the transmitter to another frequency and try again. Another possible problem with lack of stereo reception concerns the 38kHz crystal. In the past some kits were supplied with 40kHz types by mistake. If you do not have any means of checking this frequency, try another crystal (38kHz). 6 13.2V, pin 7 13.2V and pin 8 15.1V. The current draw without the coil is about 3.04A. The ignition pickup is a standard magnet/reluctor from a late-model Chrysler 360 engine. (M. K., via email). • The 300VDC supply is being correctly produced by your cir cuit as there is 298V at the drain of Q6. This means that all the circuitry, including IC1 and Mosfets Q1 & Q2, is operating correctly. It is normal for the transformer to buzz as it is switched on and off to maintain regulation. We assume that the 14.7V at pin 4 of IC1 is actually 14.7mV as it should be close to zero. It would seem likely that your problem is in the reluctor pickup circuit. Check that ZD5 has 5.1V across it and that you have the correct value resistors inserted. You can simulate firing the coil by connecting a momentary short between collector and emitter of Q8. Alternatively, connect a momentary short between chassis and the anode of diode D12. The coil should give a spark provided that there is a pathway from the high tension output to ground. To provide that, insert a paper clip into the coil’s high tension output and bend it so that there is about a 2mm gap to the coil’s negative terminal. We do not recommend having an open circuit high tension output (no spark pathway) as the coil may break down internally. Revised software for Speed Alarm I have constructed the Speed Alarm as published in the November & December 1999 issues and it is great other than the 159km/h limit on the speedometer. I take my car out on the track occasionally and would like to use it to check the accuracy of my speedo at 200+ km/h and the 888 display isn’t really of great help. Have you written any software for the PIC that can accomplish this? (B. C. via email). • We have now revised the software so that it allows the speedometer to operate up to 254km/h. Speeds above 254km/h will be displayed as 888 to indicate overrange. The speed alarm feature can now be incremented in 5km/h steps from 0 to 255km/h. The 255km/h setting will prevent alarm operation for speeds up to 254km/h. LED ammeter has high earth strap resistance I built the LED Ammeter (SILICON CHIP, January 1999) which uses the earth strap voltage to display current status. I can’t fault the theory behind it but I can’t get it to work properly. On the bench it works perfectly using the testing method set out in the instructions, In the car I turn VR1 fully anticlockwise and adjust VR2 for the green and yellow LEDs. I then turn on the parking lights and try to adjust VR1 so that the yellow LED is on. This is where it all goes out the window be cause when you adjust VR1 it immediately progresses up the red LEDs; ie, the wrong way. I thought the circuit must have too much gain but looking at the input circuit (IC1a) it only has a gain of 10. So I changed the 10kΩ The hysteresis between the alarm switching on and switching off is now 1km/h rather than the previous 1.25km/h. Options such as repeat alarm and upper and lower alarm threshold selection as well as speedometer disable are still available. The calibration procedure remains the same. The revised software is called SPEED254.ASM and SPEED254.HEX and is available for download from our website at www.siliconchip.com.au Electronic house number with large LED displays Has SILICON CHIP ever published a circuit for an electronic house num ber? Something along the lines of a rechargeable battery powered circuit would be good, using those large 70mm LED displays, either flashing or stable. The circuit would come on automatically at night and the battery could then be charged by solar cells during the day. Is there any plan for such a project? It doesn’t sound too complicated. (P. L., via email). • We published a “LED light House Number” in the October 1988 issue. It could be adapted to 70mm displays without problems. It was powered from a plugpack but could be run from feedback resistor to 5kΩ and it worked better but still adjusting VR1 is of no use at all and turning on the headlights sends the meter off the scale. My vehicle has an extremely short earth lead of about 10cm but I thought this would mean that we would just need more gain, not less. I then swapped the two leads across the earth lead around and it did adjust up in the exact opposite way. Is there anything I can do to make this work? (K. S., via email). • Possibly the short earth strap in your vehicle has a higher impedance than the design allows for. This would mean you need less gain and the value for VR1 is way too large. Try using a link for the 10kΩ resistor at pin 2 of IC1a and change VR1 to a 22kΩ trimpot. Alternatively, you could try increasing the input resistor from 1kΩ to 10kΩ to reduce the gain. a solar charged battery. We can supply a photostat copy of the article for $7 including postage. Pro-Logic surround sound decoder I built the Prologic Surround Sound Decoder published in the November & December 1995 issues of SILICON CHIP and I have a weird fault. The processor seems to be switching between two modes all on its own. Hooking up a CD player into the 5200 and then some speakers out through the surround terminals, you would hear the CD playing for a few seconds and then it would seemingly switch into another mode. The switching is pretty obvious, as it is louder and clearer in one of the modes. The processor will stay in each mode the same length of time before clicking into the other. What do you suspect may be the problem and what are your suggestions? (M. L., via email). • The mode changing problem in your Prologic Decoder does seem to be a strange fault. You do not say at what rate the mode changes from one to another. At this stage we can only assume that it at the noise sequencer rate. April 2000 89 Fence tester only works at night I recently built the Fence Voltage Tester (SILICON CHIP, May 1999) which I purchased from Dick Smith Electronics. It works perfectly but there is one drawback. I finished building it at night and I wanted to test it out straight away. So I went and tested it out on one of our fences and for some unexplained reason you can only see the neon light flashing when there is a light source present. When you take that source away and it is pitch black, the neon light either does not work or is not visible. I tested out my theory with a torch and also with a light globe inside a shed and I found the same result. I am puzzled at this and would Check that the pushbutton switches (S5, S6 & S7) are not sticking on when pressed. Also check the mode switch S4b. The wiper of S4a will connect pin 31 of IC1 to 4V when in the surround mode and to 0V when in stereo mode. S4b should apply 5V to pin 33 of IC6 when in surround mode and 0V when in 3-stereo or stereo mode. Finally, check the wiring between processor IC6 and IC1, particularly the noise test inputs at pins 23, 24 & 25 of IC1. Connecting a ceramic phono cartridge Is the auxiliary (AUX) input on a modern audio amplifier suitable for the direct connection of a ceramic cartridge (for playing 78 rpm records) or is some additional circuitry advantageous or necessary? (L.B., Aspley, Qld). • Depending on the output of the particular cartridge and your amplifier’s gain, it may be possible to use the AUX input, provided each channel of the cartridge is shunted with a capacitor of say 470-1000pF to improve the bass response. This would be a “quick and dirty” connection which may be good enough. However, it is more likely that you will need a high impedance preamplifier with a gain of around 5 or so. 90 Silicon Chip appreciate it greatly if you explain it. (T. H., via email). • It turns out that since the high voltage pulses are so short, they are not enough to cause the tester to light up in total darkness. It actually needs the extra photons from daylight (or from your torch) for the neon gas to break down and discharge! Apparently, there is a similar problem in gas arrestors used for transient voltage protection. These devices have a relatively long response time and will not work with very short spikes. Some manufacturers incorporate a small amount of radon gas (a radioactive emitter) in the gas arrestors to improve their response times. Anyway, the circuit does work but only if there is some ambient light! To give good bass, typical ceramic cartridges need an input impedance of at least 2MΩ. It would be possible to produce a suitable stereo preamplifier using a dual low-noise FET-input op amp such as a TL072. Audio signal generator amplitude problem I have completed constructing the Audio Signal Generator from the February & March 1999 issues and it appears to be working, at least as far as my frequency counter and milli voltmeter can tell. However, without being “picky”, I do have some ques tions regarding its setting up. (1) Should VR4’s setting be critical? For mid-frequencies, the display either locks or it doesn’t. However, if VR4 is set for reliable operation on the highest frequency range (>50kHz) then for the lowest frequency range (<20Hz) it needs to be readjusted so that the display reads correctly; but then the display doesn’t lock on the highest frequency range. On the three highest ranges, frequency coverage is a multiple of about 77-106Hz (this after adding a 0.82µF capacitor to pin 2 of the 555). However, I cannot get the lowest range to work/display reliably below about 20Hz. Below 20Hz my millivoltmeter in- dicates a slightly rising low frequency output but the display shows all zeros. Adjusting VR4 will restore the display but then I have problems at the highest end of the high frequency range (as mentioned). (2) The amplitude of the output signal rises as frequency decreases; in fact, at 20Hz it is up by about 2-3dB compared to 1kHz. Attempting to adjust VR3 either kills the low frequency oscillation or allows the circuit to oscillate supersonically (the AC output hits 10V on the millivoltmeter). For stability (25Hz and up), trimpot VR3 is hard clockwise. (3) Using a digital frequency meter, I had to add a .082µF capacitor to pin 2 of the 555 timer to get the display to read within 5% of the frequency. Would you expect to need this amount of capacitance increase? I have checked component values and the DC voltages are all within spec. Incidentally, for the benefit of other constructors, my kit failed to function at switch-on because a track on the PC board was missing; it was the +5V supply to IC3 pin 11. (N. H., via email). • You cannot expect to obtain a flat response if the oscillator is not set up to operate over all the ranges. Some constructors of the Jaycar kits have needed to change the 12kΩ resistor connecting to LDR1 to a 560kΩ resistor with a .0047µF capacitor placed in parallel with it. This will allow the oscillator to be set up to oscillate over the full frequency range. VR4 will be critical to set if the output level does vary with frequency. Once you can set the oscillator correctly, this adjustment will be less critical. The capacitance change at pin 2 of IC11 to obtain a satisfactory frequency accuracy does seem extreme. Perhaps the original values are out of tolerance. VHF PAL demodulator circuit Have you published an RF VHF PAL demodulator circuit or project in SILICON CHIP? What I need is to convert a VHF signal in RF mode back to composite and/or S-video (Super VHS) output(s) so that they can be connected to a video camera for recording. Video cameras do not have a TV tuner built in. S-video output is not important; composite video output is mandatory. (M. O., via email). • We have not published a VHF PAL demodulator. In fact, what you are asking for is virtually a complete TV set front end. Have you thought about using a VCR to do the job? Even a machine in which the transport is no longer working could be used for your job. TVI caused by FM receiver Last year I became a listener to ‘tube radio’ in my home. The FM stereo decoder is solid-state, from Studio12 in . Wales UK. The receiver is a modified and realigned Kenwood W8, a stereo valved receiver, originally only ‘mono’ on FM, from the 1960s. The problem is as follows: when I’m listening to just one FM stereo station, on 102.3MHz, I get TVI (interference) on one VHF TV channel (TEN, picture centred on 182.258MHz) and on one UHF channel (UHF 31 picture 548.25MHz). Note that the FM stereo sound via the Kenwood on this station remains excellent, notwithstanding the RFI it is generating. The interference disappears if I disconnect the antenna lead from the Kenwood to the wall outlet. It is a “shot-silk” effect, very like FM transmitter sourced interference as pictured in various books on this subject. The tuner does not have this effect on any other local FM station. It seems to be the local oscillator in the stereo tuner, not the IF in the TV receiver. The tuned frequency is 102.3MHz and with an IF of 10.7MHz the local oscillator is 91.6MHz; its second harmonic = 183.2MHz, slap in the middle of VHF10 and the 5th harmonic is slap in the middle of UHF 31. A friend of mine says that the strength of the station is probably irrelevant and I’ve since confirmed this, at least with a variable attenuator. That particular frequency, 102.3MHz or very nearly, may be triggering some resonances somewhere in ‘my’ circuit. So is there really a resonant problem with the local oscillator when tuned at or near 102.3MHz? The following actions are possible. I could use separate FM cables from the TV cables, use two separate splitters and use single rather than combined wall-plates everywhere. Apart from Parking radar has low sensitivity I have built the Ultrasonic Parking Radar kit (SILICON CHIP, February 2000) with mixed results. I find the unit has low sensitivity due to the hysteresis on pins 12 and 13 of IC1d. This gate switches from high to low when the voltage on its input pins reaches 3.8V but will not turn off again until the voltage drops back to 2.5V. The result is very low sensitivity with poor long-range detection. Also, the LED on the output refuses to conduct with the values shown in circuit. Q3 switches OK but does not fully saturate. Also, I am only getting 5.7V across the zener diode instead of 6.2V. I cannot make out the zener numbers and it may be an incorrect zener as supplied in the kit. Any ideas? (B. C., via email). • The sensitivity of the radar is set by VR1 rather than the hysteresis of IC1d. You can obtain more range by separating the ultrasonic transduc- the extra expense, the disadvantages of this solution are having to crawl about under the house and get up on the roof and lastly, it doesn’t actually fix the RFI/TVI near the source. Alternatively, I could get someone skilled in the art to fiddle with the operating characteristics of the valve tuner. Unless it is radiating from the tuning gang, extra HT bypasses might help. I could also filter the harmonics from the FM stage so it doesn’t go back up the coax to the splitter, without affecting the signal strength going in; ie, a steep low-pass from about 109MHz up into the UHF band to 600MHz. Maybe Kingray could help here. What do you think? (T. B., via email). • We doubt very much that you can easily suppress the harmonic radiation from your tuner’s local oscillator. Valve local oscillators had a much stronger signal than transistor oscillators and they didn’t have a clean waveform; ie, harmonics were present. In fact, it is doubtful whether the designers actually ever saw the ers as described on pages 40 and 41 and increasing the value of VR1. To some extent the gain is set by adjustment of VR2 which sets the threshold trigger point for IC1d. Set this too high, however, and IC1d will remain triggered (output low) as its lower input threshold will never be reached. Perhaps your low sensitivity is due to the low supply voltage. You would expect the LED to light when powered from 12V and 2.2kΩ resistor even if Q3 does not fully saturate. Check that the LED is inserted the right way around on the PC board. You could reduce this value to 1kΩ for more brightness if you want. A 6.2V 400mW zener will probably be marked as 1N753A while a 5.6V zener will be marked 1N752. You can check the zener by placing it in series with a 2.2kΩ resistor across a 12V supply. Measure the zener voltage with a meter. If the zener voltage is OK, you may need to supply it with a little more current in the radar circuit. Try reducing R8 to 390Ω. waveform on an oscilloscope since that would have required scopes with bandwidth out to beyond 200MHz – such scopes probably did not exist when your tuner was designed. Even today, with a good scope you might have great trouble improving the oscillator’s waveform sufficiently to remove harmonic interference. Our first suggestion is to try the separate splitter approach and if that doesn’t work, an approach to Kingray might be the only solution. Spring reverb unit has phase reversal I have purchased and assembled the Spring Reverb unit described in the January 2000 issue of SILICON CHIP. I have achieved successful reverberation but now have a polarity reverse/ out of phase problem with respect to the input source. All connections seem correct. Do you have any suggestion to solve my dilemma? (A. C., via email). • The Spring Reverb module does invert the signal at IC2b which is an April 2000 91 Spring reverb frequency response I recently constructed the Spring Reverb kit for use with an electric guitar. The construction and electrical testing of the unit seemed to go pretty much by the book. However, I found that when it came to a comparison between plugging directly into the guitar amplifier and plugging in via the reverb unit, I did notice an appreciable attenuation of top end frequencies, although I was quite happy with the quality of the reverb effect itself for a unit in this price range, . I realise that this is not a highend professional unit but am wondering whether this is an idiosyncrasy of the circuit itself or maybe I’ve missed some detail in the construction. Any ideas? (C. M., via email). • The frequency response of the reverb signal is limited to 5kHz, as detailed in the specifications panel inverting mixer stage. You would need to add another inverting stage at the output to return the phase to the same as the original input. However, the phase inversion of the signal by the spring reverb should not present any problems. In fact many amplifiers invert the signal, as do mixers and preamplifiers. Increasing the turbo timer period I have just bought a Turbo Timer kit from Jaycar (SILICON CHIP, November 1998). Could you tell me how to on page 32 of the January 2000 issue. The response of the undelayed signal is up to 19kHz which should be more than adequate. Without too much reverb, the overall response will be dominated by the 19kHz bandwidth. If you find the high frequency end is dropping off without much reverb being mixed into the signal, you have possibly used an incorrect capacitor value across one of the feedback resis tors. Check in particular the capacitor between pins 1 & 2 of IC2b. It should be 33pF. The capacitor will either be marked as 33 or 33p. Also the capacitor across VR1 should be .0039µF (3n9 or 392 on the capacitor). There is no point in trying to increase the frequency re sponse of the reverb signal itself as the response of the spring unit is limited anyway; any increase in bandwidth would just increase the residual noise. modify it so that it makes my car idle longer, or even make it adjustable like the really expensive ones? (I. B., via email). • You can change the idle period by altering either the 220µF capacitor at pin 6 of IC1 or the 390kΩ resistor. Increasing either value will extend the period and reducing it will shorten the idle time. The capacitor should not be increased much past 1000µF in value while the resistor should be in the range from say 10kΩ up to 1MΩ. If you want to make it adjustable, you could use a 1MΩ potentiometer in series with a 10kΩ resistor, in place of the 390kΩ resistor. Query on cordless phone backup In the article entitled “Backup Battery for cordless phones” from the October 1999 issue of SILICON CHIP you have shown the charging circuit as simply being a diode and a 100Ω resistor. Would this be OK if the unit is working 24 hours a day; ie, charging the SLA battery continuously? I thought that SLA batteries should be charged gradually and when they reach full charge, the charger switches to trickle charge. I understand that the 100Ω resistor provides that trickle charge continuously. Isn’t that damaging to the SLA battery? It would take quite a while to initially charge the SLA, wouldn’t it? (O. N.) • It is OK to trickle charge an SLA battery and that is what this circuit does. Yes, it would be a good idea to have the battery fully charged before installing it in the circuit. Plastic stereo power amplifier wanted I like the 175W amplifier modules described in the April 1996 issue. Can I use two modules to a make a stereo amplifier? How do I go about it? (T. W., via email). • You would need to use the suggested power supply circuit on page 28 of the April 1996 article but with a 300VA transformer. The modules would need to wired up in the same sort of layout as we used for the stereo power amplifier featured in the February 1988 issue. We can send you a photocopy of this article for $7 SC including postage. 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. 92 Silicon Chip Own an EFI car? Want to get the best from it? Youll find all you need to know in this publication April 2000 93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FRWEEBE YES! Place your classified advertisement in SILICON CHIP Market Centre and your advert will also appear FREE in the Classifieds-on-the-Web page of the SILICON CHIP website, www.siliconchip.com.au And if you include an email address or your website URL in you classified advert, the links will be LIVE in your classified-on-the-web! S! D E I F I S C LAS EXCLUSIVE TO SILICON CHIP! CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12 words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ FOR SALE ELECTRONIC/MECHANICAL DESIGN AND CONSTRUCTION: we offer a complete design service for electronic and mechanical devices. Most work is done in house and you deal directly with the designers. No job is too small and can be to prototype or “turn key” stage, in one offs or for future production. Simply send us an email at vladimir<at> u030.aone.net.au with your questions or requirements and we will get back to you. 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 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 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, Enclosed is my cheque/money order for $__________ or please debit my ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ________________________ Card expiry date______/______ Name _____________________________________________________ Street _____________________________________________________ Suburb/town _________________________ Postcode______________ 94 Silicon Chip 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. 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. 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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. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; ROLA Australia (08) 8270 3175 www.bettanet.net.au/GTD Silvertone’s RC Receiver Still the best little performer available! MP3-CD Player: $699 Plays standard CDs & MP3s as well. Plays MP3 CDs made with a CD writer. Up to 2200 songs per CD. Car adapter available. ROLA 15U & 15UX: $325 Size: 15" (380mm). Freqency response: 30-3,000Hz (15U); 30-12,000Hz (15UX). Power handling: 250 watts RMS. SPL: 97db/1 metre. FS (resonant frequency) 30Hz. 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°. 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 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? 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. 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: 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. TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. Melbourne 9806 0110. KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com 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. New Component Supplier A new company, SQ Sources Pty Ltd, has recently been formed to supply active and passive electronic components to the Australian market, including: flash memory and EPROMs, microcontrollers, optocouplers, relays, logic devices, telecom circuits, power devices, PLA devices and tantalum and ceramic capacitors. The director of the company is Keith Chan and their Sydney head office is at Suite 22, Unit 4-5, Penrith Small Business Centre, 9-11 Abel St, Penrith, NSW 2750. Phone (02) 4732 5044; fax (02) 4732 5066. 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. April 2000 95 Silicon Chip Binders Keep your copies safe, secure and always available with SILICON CHIP binders: they’re cheap insurance! Advertising Index Acetronics....................................59 REAL VALUE AT Altronics................................. 38-40 PLUS P &P Dick Smith Electronics........... 24-27 $12.95  Heavy board covers with 2-tone green vinyl covering Av-Comm Pty Ltd.........................95 EMC Technologies.......................59 Electronic Valve & Tube Co..........63  Each binder holds up to 14 issues so that you can include catalogs Harbuch Electronics....................83 Instant PCBs................................95  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Jamo Australia.........................OBC Jaycar .........................................13 Kalex............................................47 Price: $12.95 plus $5 p&p each (available Aust. only) Kits-R-Us.....................................95 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. Microgram Computers...................5 MicroZed Computers...................59 Mitsubishi Electric................... IFC,1 Printed Electronics...................... 95 Questronix...................................59 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. Rall Electronics............................59 REC Electronics........................IBC www.siliconchip.com.au SILICON CHIP’S 132 Pages $ 95 * 9 ISBN 0 95852291 X 9780958522910 09 09 9 780958 522910 COMPUTER OMNIBUS Robotic Education Products........59 RobotOz......................................59 Rocom Electronics.......................59 R.T.N............................................11 Silicon Chip Back Issues....... 36-37 INC LUD ES FEA TUR E LIN UX Silicon Chip Binders....................96 Silicon Chip Bookshop........... 86-87 A collection of computer features from the pages of SILICON CHIP magazine SC Internet Access................ 80-81 o Hints o Tips o Upgrades o Fixes NOW Covers DOS, Windows 3.1, 95, 98,ANT V 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. SC Computer Omnibus...............41 SC EFI Tech Special....................93 Silicon Chip Subscriptions...........53 RT INC O P&P Silvertone Electronics..................95 Smart Fastchargers.....................85 Solar Flair/Ecowatch....................95 Truscott’s Electronic World...........47 HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. Email: tpeters<at>pip.elm.mq.edu.au 96 Silicon Chip Vass Electronics..........................59 Wiltronics.......................................2 _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. April 2000 97