February 2000 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Use those Safety Switches for extra protection
Review: Marantz SR-18 Home Theatre Receiver by Leo Simpson
Review: The "Hot Chip" Starter Kit by Peter Smith
Project: Build A Multi-Sector Sprinkler Controller by Ned Stojadinovic
Project: A Digital Voltmeter For Your Car by John Clarke
Project: An Ultrasonic Parking Radar by Branco Justic
Feature: Light Emitting Polymers For Flat-Screen Displays by Julian Edgar
Project: Build A Safety Switch Checker by John Clarke
Project: A Sine/Square Wave Oscillator For Your Workbench by Rick Walters
Order Form
Product Showcase
Serviceman's Log: Projection TV from many angles by The TV Serviceman
Vintage Radio: The Hellier Award; Pt.1 by Rodney Champness
Book Store
Back Issues
Market Centre
Advertising Index
Outer Back Cover

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FEBRUARY 2000 1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.emona.com.au Contents Vol.13, Vol.13, No.2; No.2; February February 2000 FEATURES 4 HiFi Review: Marantz SR-18 Home Theatre Receiver 5.1 channels plus Dolby Digital plus THX. And we love the gold finish – by Leo Simpson 10 Review: The “Hot Chip” Starter Kit “Hot Chip” Start Kit – Page 10. An easy way to get started with microcontrollers – by Peter Smith 42 Light Emitting Polymers For Flat-Screen Displays Imagine a flat-screen display that’s flexible and made out of plastic. That’s the promise of semiconducting polymers – by Julian Edgar PROJECTS TO BUILD 14 Build A Multi-Sector Sprinkler Controller At last: a multi-sector sprinkler controller that’s easy to program – by Ned Stojadinovic 24 A Digital Voltmeter For Your Car A PIC microcontroller makes it a snack to build – by John Clarke Multi-Sector Sprinkler Controller – Page 14. 38 An Ultrasonic Parking Radar Build it and avoid those parking mishaps – design by Branco Justic 53 Build A Safety Switch Checker Simple unit lets you check that each power point is covered. It also verifies the Earth connection – by John Clarke 58 A Sine/Square Wave Oscillator For Your Workbench It uses a switched capacitor filter IC to give very good envelope stability – by Rick Walters Digital Voltmeter For Cars – Page 24. SPECIAL COLUMNS 75 Serviceman’s Log Projection TV from many angles – by the TV Serviceman 82 Vintage Radio The Hellier Award; Pt.1 – by Rodney Champness DEPARTMENTS 2 9 68 70 71 Publisher’s Letter Mailbag Circuit Notebook Subscriptions Form Product Showcase 80 91 93 94 96 Electronics Showcase Ask Silicon Chip Notes & Errata Market Centre Advertising Index Build A Safety Switch Checker – Page 53. FEBRUARY 2000 1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Peter Smith Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0414 34 6669 Regular Contributors Brendan Akhurst Louis Challis Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2 Silicon Chip Use those Safety Switches for extra protection This month we feature an RCD Checker in our line-up of constructional projects. It is quite a simple unit and won’t take long to put together. It is the solution to a problem that we have been concerned about for some time – how do you do a proper test of an RCD or Safety Switch, as they are more commonly referred to? Sure, you can press their self-test button but that does not simulate the normal fault condition whereby Active current gets shunted to the Earth wire. So the RCD Checker is our answer and we think it could even become the basis for a standard tester to be included in any electrician’s toolkit. That’s all well and good but we are also concerned that many people (our readers included) still do not use Safety Switches where they are in hazardous situations. Perhaps the most common situation is where people are using power tools outdoors and running them from long extension leads. On building sites it is mandatory to use safety switches but people working at home are often more at risk, using older and less well-maintained power tools and often with dodgy extension leads. That’s bad enough, but the situation with musicians and amateur theatre groups is often much worse. At least most power tools these days are double-insulated but the equipment used by many bands and musicians is often quite unsafe. In fact, it is not at all uncommon for musicians to disconnect the earth on amplifiers to eliminate hum loops. These situations are just accidents waiting to happen. Potentially even worse is the situation where people bring their compact music system out of the house and down by the pool so that they can have music while they frolic. But frolicking generally means splashing about, meaning that water can get splashed over the music system. If it does get splashed, nothing might happen but there is also the possibility that water finding its way into the equipment might create a leakage path between the 240VAC Active and the exposed metal parts of the case. If that happens, the appliance could be live and lethal. Paradoxically, that is more likely if the equipment is “double insulated”, because there will not be an Earth connection to safely shunt leakage current away. The more you think about it, Safety Switches are a good idea. While they won’t necessarily protect people who are stupid, they are good insurance against unforeseen malfunctions in mains-powered equipment. If your home does not have a Safety Switch, now is the time to have one or two fitted. They are relatively inexpensive. Why have two? It is a good idea to have the power circuits split up with the kitchen and laundry protected by separate RCDs. That way, if a fault develops in the laundry and trips the RCD, it won’t kill the power to your fridge and freezer in the kitchen and possibly cause food spoilage. And if you often use power tools away from home, it is probably a good idea to buy a portable Safety Switch as well. What’s the point of being fully protected at home if you get fried elsewhere? Leo Simpson USB Digital Camera You will be up and running in minutes with this easy to install, Plug & Play, affordable digital camera. A simple, yet powerful way to capture AVI movie clips & still images effortlessly. Include still images & video clips into presentations, place them on the World Wide Web or e-mail them to friends. Cat. 21038 USB Digital Camera $149 USB Ethernet Adapter 10/100Mbps Web-Based Training from $14.95 per month* New courses now available! Including Windows 98, Quicken 98, Lotus Notes, Internet Tools (Netscape) and more courses on TCP / IP. USB Ethernet 10/100Mbps Adapter $149 Now over 300 courses on offer *Full details at www.tol.com.au 55 Key Programmable POS Keyboard Top of the line Point of Sale keyboard featuring very robust construction, compact size, down loadable key assignments (eg switch menus), multi-level programming, the ability to download an entire 55 key template into internal non-volatile memory in 7 secs!, keyboard wedge interface with optional RS-232 interface & internal 2KB nonvolatile memory. The USB to Ethernet converter allows a notebook or PC to connect to an Ethernet 10BaseT or 100Base-T LAN via a USB port. It will automatically negotiate 10 or 100Mbps con- Cat. 8356 nection rate, depending on speed of the network. Cat. 2816 A number of courses are “Microsoft Certified Professional - Approved Study Guides” 55 Key POS Keyboard $309 Cat. 8897 Cat. 8898 POS Cash Drawer POS Cash Drawer - RS232 $209 $239 POS Customer Display This POS customer display is driven from the serial port and has a vacuum fluorescent display with two lines of 20 characters. It is ergonomically designed with a 270 degree viewing angle . POS Customer Display Cat. 8728 $369 Citizen Docket Printers Hi- Scan Bar Code Readers High resolution CCD scanners Citizen printers offer 3 or 3.6 USB Active Extension Cable featuring multi-interface communicalines/sec bi-directional printing, Extend the distance between tion with RS-232C, and Keyboard friction feed with 6K bytes input your PC & USB peripherals. Emulation in one unit. Simply buffer, 2 colour ribbon This cable is 4.8m long and release the RJ-45 jack to change cables! Offering optical (red/black) or single colour includes an active amplifer to performance with a minium resolution of 0.125 mm & max- (black or purple) and use a 76mm paper roll. All boost the signal level. It imum reading distance of 20 mm they can read high-densi- printers will control 2 cash drawers and have operates in accordance with USB Specification Ver ty, laminated & acrylic-covered bar codes. added features of CBM, ESC/POS, Star emulation. 1.1 at 12Mb/Sec. Up to 5 cables can connect in Hi Scan Bar BCR KB Wedge AT or PS/2 Cat. 8458 / 59 $699 Cat. 5694/95 Citizen IDP3420 40 Col Parallel /Serial $530 series for extensions to 24m. Cat. 5697/96 Ciitizen IDP3421 40 Col Parallel / Serial $615 Also available, Long Range CCD bar code scanners. Cat. 9115 USB Active Extension Cable TBA Relay Output & Opto Digital Input Cat. 8489 / 8704 CCD BC Scanner Long Range KB AT or PS/2 CCD BC Scanner Long Range KB Stand Cat. 8675 Suitable for use with Windows 95/98 & NT these 8 As well as our standard range. CCD BC Scanner KB Wedge 80mm or 16 channel cards feature input signals that can Cat. 8196 Or pick from our Manual / Auto Trigger laser range. be completely floated to prevent ground loops. Cat. 17067 Cat. 17066 8 CH Opto DI 8 CH Relay 16 CH Opto DI 16 CH Relay $199 $319 TV & Capture PCI Card Cat. 8770 / 8767 Cat. 8771 Cat. 8772 TV & Capture PCI Card $199 Compact Keyboard When desk space is at a premium an 80 key keyboard with full 101 key functionality will come in handy. It has dimensions of only 297(W) x 152(L) x 30(D) mm. Cat. 8403 $259 $599 $599 $35 Omni-Directional Laser Scanner Turns your PC into a television with an IR Remote Controller. Watch TV programs in a window while you are working in other applications or switch to full screen TV display. Capture still frames & movie clips, channel surf, or Cat. 8521 Cat. 8573 create your own TV transcripts. Cat. 3399 Laser BCR Gun KB Wedge AT or PS/2 Laser BCR Gun Serial Laser BCR Gun Stand $469 $69 Compact 80 Key PS/2 $73 An affordable, vertically mounted, OmniDirectional laser scanner, which is ideally suited to reading bar coded products at supermarket checkouts. Depth of field is 300mm. Bar Code Laser Omni-Direct. KB Wedge Bar Code Laser Omni-Direct. Serial $2119 $2119 Cat. 5698/99 Citizen IDP3546 40 Col Parallel / Serial $690 Cat. 5673/74 Citizen IDP3550 40 Col Parallel / Serial $610 Cat. 5675/76 Citizen IDP3551 40 Col Parallel / Serial $715 POS Touch Systems & Peripherals Get ready for GST! Start with a compact all-in-one terminal with 12.1” TFT colour touch screen and add the peripherals you need to customize your requirements. The basic system consists of a Pentium motherboard with 133MHz MMX CPU, 16MB RAM, 4 serial ports, 2 parallel ports, 2 USB ports, VGA port, cash drawer port, 10Base-T Ethernet port, 1 free PCI slot, KB/mouse. Cat. 8755 POS Touch System with LCD & Swivel Base $4,490 Optional add-ons include a magnetic card reader, a magnetic I-Button POS Cash Drawers reader with 5 operator keys for POS cash drawers with robust metal construction casing security access, an external FDD and a pearl white ABS fascia with a slip deposit slot. The kit, Customer Display and cash drawers. bill tray has adjustable dividers for 4 or 5 compartments & POS Touch System MCR Track 2 Cat. 8756 $299 spring loaded bill clips. A separate coin tray has adjustable Cat. 8757 Magnetic I-Button Reader /5 keys $190 dividers for up to 9 compartments. Compatible with Epson, Cat. 8758 External FDD Kit $219 Star & Citizen POS printers. E & OE All prices include sales tax MICROGRAM 0200 Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 FreeFax 1 800 625 777 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 FEBRUARY 2000 3 SR-18 Home Theatre Receiver Over the last decade or so it could be said that audio equipment has not really developed or improved much. But the increasing emphasis on DVD and home theatre products has changed all that. There have been some big strides made recently, as demonstrated in the Marantz flagship, the SR-18 Home Theatre Receiver. M arantz is back! Or rather, the Marantz styling and cham pagne finish is back. In the long decade or so of the dominance of black as the accepted finish on high fidelity equipment, owners of older Marantz “champagne finish” gear have languished. They loved their older gear and they were loath to change over to black. Now the “dark ages” could be said to be over and a number of manufacturers are offering equipment in champagne or gold finish. So Marantz should find that this model SR-18 will sell in big numbers. Not only does it have the trademark gold finish but it also has other Marantz styling cues: two big knobs, one at each end, for input selection and a large flywheel knob in the centre of the panel, the so-called Gyro-Touch, for tuning. About the only thing missing is the little blue scope screen for signal strength and multipath indication. Maybe Marantz will bring that back in a future state-of-the-art FM/AM tuner? Actually, I have to say that while the various knobs look impressive, they really are a bit superfluous these days now that everything is remote-controlled. Apart from initially turning the unit on, you don’t ever have to touch the SR-18 in normal day-to-day use, any more than you need to touch your TV set to use it – you just point the remote control at it and press a button. And while some people may hanker for the old-style flywheel tuning for FM and AM stations, it really is a bit pointless once you have all your normal stations programmed in. Where it is good is when you are occasionally tuning across the dial looking for all those other stations. In fact, if you live within about 200km of Sydney or Melbourne and you have a sensitive tuner, it really is surprising just how many stations are dotted along the FM band. It is at those times when you want to listen to radio but you don’t like the current fare from any of your usual stations that the Marantz flywheel tuning knob comes into its own. You can creep along (in 50kHz steps – it is still full digital tuning) or whirl from one end to the other in a flash, something you can’t do in conventional FM tuners with synthesised tuning. And it makes the process of tuning and storing stations simpler. Marantz has kept the front panel clean and uncluttered but has a large drop-down door which reveals no less than 22 push-buttons, the stereo headphone socket and auxiliary inputs for a video camera or camcorder. We don’t have the space to mention all 22 buttons or indeed the endless features of this complex receiver but we’ll touch on some of them as we proceed. The SR-18 front panel also has the obligatory vacuum fluorescent dot matrix display to indicate all the operating modes but for a variety of reasons it is less effective than it otherwise could be. For example, it apparently does not have enough characters accessible, so that, when indicating CD Direct mode, it displays “CD-DIRCT” and yet it can also display “THX CINEMA” which requires more characters (ten, including spaces). In a large room, when you are sitting quite some distance away, the display is not all that readable but again, that is not really that important because the remote control handpiece, which we’ll come to in a moment, is very comprehensive and has its own LCD panel. In any case, you can always resort to the on-screen display which works in the same way as for DVD players and late-model VCRs. While there is little clutter on the front panel there is plenty on the rear panel. This is inevitable on any large receiver and more so on a home thea- Review by LEO SIMPSON 4 Silicon Chip The big Marantz SR-18 has virtually all features controllable via its equally large remote control. All those button light up each time one is pressed. The drop down door on the front panel (inset right) reveals the headphone socket and the 22 buttons for a range of functions including the tone controls. Note the Aux inputs (and S-video socket) for easy connection of a camcorder. Long-time Marantz fans will love the flywheel tuning knob. tre receiver which caters for so many operating modes: Dolby surround, Dolby Digital (AC-3),THX Cinema and DTS (Digital Theatre Systems). Hence, there is a large array of RCA sockets for all the program sources, including the video inputs from DVD, VCRs, TV (presumably cable or Pay-TV decoder boxes) and laser disc players. These are accompanied by S-video and optical fibre sockets where applicable. There are also quite a few audio and video outputs and there is no getting away from the fact that any home theatre receiver or amplifier must do a lot of video switching. How they manage it without any sign of video or sync buzz breakthrough must be a story in itself but it is routinely achieved in all of these products. We really did like the large binding post terminals for the five power amplifier outputs (did we mention that it was a fully Dolby surround receiver with the usual 5.1 output channels: front left & right, centre, two rear and the sub-woofer line output?). These binding post terminals are fully shrouded and are reasonably spaced so that connecting up thick speaker cables is easier than it is on a lot of other surround sound systems – on some, it can be a real chore. Inside the SR-18 is a labyrinth of PC boards which you would expect from its operational complexity but even so, it does appear as though it would be relatively straightforward to disassemble and service. All the PC boards are single-sided, with lots of wire links, which is the usual approach for consumer products designed and made in Japan. That approach also makes for much easier servicing when the time comes! Another good point is that a great deal of the circuitry appears to rely on discrete semiconductors and there is not so much in the way of surface-mount components – another plus. The power supply features a very large toroidal transformer which must be rated at well over 1kVA. It is accompanied by two large filter capacitors which feed all five power amplifiers. The filter capacitors are 56000µF at 71V which seems like an odd voltage rating but that’s what it is. Obviously the main DC supply rails must be in the vicinity of ±70V which would be necessary for power amplifiers of this rating. As with a number of other high power surround sound amplifiers we have seen, the SR-18 has the five power amplifiers around a tunnel heatsink assembly with a thermostatically-controlled fan at one end. This fan would also cool some of the power supply components such as the bridge rectifier which has its own heatsink. Each power amplifier has just two very large bipolar transistors in plastic encapsulation. We have remarked on the size of these power transistors in a previous review but they never fail to impress. In the Marantz receiver they have also managed to work some technical magic because the overall distortion level is very low, as we shall see. Perhaps part of this is due to a circuit feature of the Marantz SR-18, their so-called HD-AM PC board. This stands for “high definition amplifier module” and there are two visible in FEBRUARY 2000 5 Inside the Marantz SR-18. The toroidal transformer is a whopper. The HD-AM PC board with their copper shields can be seen in the centre of the picture. the internal photo. We have not been able to find out anything about them apart from the fact they are discrete preamplifier stages used instead of op amp ICs. Remote control handpiece There are remote controls and there are remote controls! This one must be one of the largest we have come across and it is also one of the most impressive. While it does have quite a few buttons there are not so many that you would shrink from 6 Silicon Chip it as being too complex. They are also legibly marked which makes a nice change and to top it off, they are all illuminated for a few seconds, each time a button is pressed. You can vary the time of illumination, by the way. Button illumination is highly desirable in a home theatre’s remote control because it is a fair assumption that it will often be used in a darkened room. Mind you, it should be possible to temporarily turn the illumination off and save the batteries as it will also often be used in normally lit rooms. Note that it is possible to turn off the illumination entirely but then you presumably have to go through the routine to turn it on again. By the way, under normal usage, the four AA cells can be expected to last about four months but that really does depend on how long you have the illumination set for. A major feature of the remote control is the LCD panel which is backlit every time the buttons are illuminated. Our photo shows the CD source selected and there are a bunch of buttons down both sides of the screen which can select various features. In This side view of the chassis shows the heatsink tunnel for the five power amplifiers. The fan is at the other end and also provides cooling for the power supply components. fact, with each program source there are normally four screens (or menus) of commands which can be accessed. Furthermore, it is a “learning” remote so it can take the place of the remote controls of all your audio and video program sources and as can be seen there are buttons for controlling CD players, VCRs, DVDs, TV tuners, FM/AM tuners and you name it. The SR-18’s remote can also use “macros” which let it store and carry out a series of control functions. This is a desirable feature, say, if you want to turn on all the equipment and make settings to watch a DVD movie or cable television program. In fact, as you learn about the features of the remote control and read about it in the owner’s manual you start to realise just how complex and how capable the Marantz SR-18 is. In reality we think that there are not a lot of owners who will fully comprehend all the features and thought that has gone into this top-of-the-line home theatre receiver. One point that could be improved is the range of the remote. This is stated as five metres and within an angle of 60° and in a fairly large room it is not enough, particularly since other ordinary remotes have no problem and can even work by bouncing off the walls. OK, so the remote does virtually everything except bring you chips and a drink (Toohey’s Red thanks, in a glass) but I still had some difficulties getting the machine to do what I wanted. For example, I could not get it to work with my CD player until I realised that you had to select analog (instead of digital) mode with the A/D button behind that aforesaid door in the front panel. To give it its due, it did try to tell me by flashing “no data” on the front panel but I had to read the manual several times before realisation dawned. On the other hand, it did not take long for us to realise that the SR-18 gave its best sound quality when switched to “Source Direct” which bypasses the tone control stages and presumably other signal processing. Another interesting touch is that when you connect an audio source to the Aux input sockets on the front panel, the SR-18 applies a steep bass cut below 100Hz. We found this out during our measurements. It probably is a good feature to minimise hum when you are connecting a video camcorder but we could find no mention of it at all in the owner’s manual. In fact, let us have a moan about the manual. It is nowhere Fig.1: frequency response of the power amplifiers taken at 1 watt into 8Ω. This is taken in Direct mode which bypasses the tone controls. Fig.2: total harmonic distortion versus power at 1kHz with the two front channels driven. Maximum power is 185 watts at the onset of clipping. Fig.3: total harmonic distortion versus frequency at a power of 100 watts per channel into 8Ω (Measured with a bandwidth of 20Hz to 80kHz). Note that there is no rise in the figure at frequencies above 5kHz. This is an excellent result. FEBRUARY 2000 7 near comprehensive enough – a complaint that can probably be directed at the manuals for all home theatre products. In fact, while the manual is in English and Japanese, it only has 35 pages to describe all the features in English. Just how inadequate that is becomes clear when you compare it to the owner’s manual for a typical car. My new car’s manual has 350 pages and yet it does not make any attempt to describe functions which are as complex and varied as those possible with the Marantz SR-18. So far then, we have really only touched upon some of the features of the big Marantz. We have not mentioned how each program source can be set up, how the time delays for the speakers are set, how the FM and AM tuners are programmed, the multi-room/multi-source capability, the 96kHz/24-bit decoding for DVDs and so on. We can’t hope to devote enough space for the all features so let us just acknowledge that this is a necessarily brief review. So how did it perform? We first put it though a battery of audio tests and even here we were pretty selective, testing only the stereo performance of the front channels. All five channels are identical so it can be assumed that the stereo performance is repeated for all channels. The SR-18 is rated to deliver 140W per channel into 8Ω loads with all five channels driven simultaneously. Alternatively, it is rated for 200W into 6Ω loads under the same conditions. 4Ω loads are not specified and so we did not test for this condition. Rated harmonic distortion is .05% and signal to noise ratio is 105dB. Frequency response is rated as within 2dB from 10Hz to 50kHz. This rear view of the SR-18 shows the complexity of a typical large home theatre receiver catering for a very large range of inputs. Note the large well-paced speaker binding posts. They are fully shrouded to reduce the risk of stray wires causing shorts. 8 Silicon Chip A close-up view of the large remote control. Each program source has a number of screens with all sorts of functions which can be selected. Fig.1 shows the frequency response of the SR-18 and it is about 0.5dB down at 10Hz and 2dB down at about 58kHz, so it comfortably meets the specification (as it does on every other measurement we made). Fig.2 shows the distortion versus per output and as can be seen, the onset of clipping (where the graph suddenly takes a steep rise) is about 185W. This was taken with both front channels driven. Under these conditions the top of the cabinet became quite hot but as far as we could tell, the internal fan did not cut in. It was silent during all our testing and listening sessions. Fig.3 is the standout performance graph and it shows that Marantz have done something special with their amplifiers. It shows the distortion versus frequency for both front amplifiers and as can be seen, it is virtually constant right across the range from 20Hz to 20kHz. The reading is close to .01%. How do they avoid the usually unavoidable rise as the frequency goes above 5kHz? We would love to know. That is one of the best performances we have ever seen, for any amplifier or receiver. Signal to noise ratio measurements came in right on the button, at 105dB unweighted (from 20Hz to 22kHz). Listening tests confirm that the Marantz SR-18 is a very fine performer. It has bags of power, and dare we say it, far more than virtually anyone would ever need. It is very clean (particularly in Direct mode) and once you work out how to drive it, it is very satisfying. It is expensive but when you consider all the technology and power output housed within its covers, it is fairly priced at $4990. Oh, and you can buy it in black, if you really must. For further information, contact the Australian distributors for Marantz products, Jamo Australia Pty Ltd by phoning (03) 9543 1522; email info<at> SC marantz.com.au MAILBAG AC voltages more dangerous I wish to bring to your notice a boo-boo in the November 1999 Mailbag letter from Jonathon Waller. He maintains that the danger from a DC electric shock is greater than a shock from the same voltage on AC. He goes on to say that this is because AC tends to throw the person away, while DC tends to paralyse the muscles, making it difficult for the victim to escape the shock. Now this is a very dangerous boo-boo because it is the exact opposite: DC tends to throw the person off or away and AC paralyses the victim. Please check on this and you will find I am correct. Now don’t get me wrong; they are both dangerous but AC is more so. Having been brought up on DC power supplies and having had a belt or two from DC, if it has been AC possibly I would not be here today. The other item I would like to comment on refers to the use of alternative power when connected to the grid and there is a power failure. Do as most rural families do: invest about $1200 - $1400 on a 5kVA engine-driven power plant and you can run the full house from it. Rural areas do have quite a few blackouts, sometimes for days, and the 5kVA plant is the most practical alternative. Keith Lang, Esperance WA. Solar regulators not expensive I read with great interest your feature on a solar panel regulator in the December 1999 issue of SILICON CHIP. Although I get great pleasure from constructing kits myself, I feel that this project needs some consideration. I wish to point out a few things mentioned in your article that need highlighting. First, the article says that solar regulators are expensive. This is NOT true. The cost of a solar regulator is only a very small part of the overall system cost. Take for example the BP solar panel featured in the article, with a recommended retail price of $795. Although we sell many of these panels, a system usually consists of several of these and sometimes more than a dozen or so. This is expensive indeed, not to mention the cost of quality battery storage, which can be around the same. Secondly, 5A current capability is all but useless except for the hobbyist, which is probably who you are targeting anyway. Thirdly, there are no current draw figures for the featured regulator. By using a relay, I guess that it is reasonably high, compared to commercially available units. The reason I say this is because when using solar energy, especially on small systems, such as this regulator would have been designed for, you need to be aware of ALL loads, including the regulator. For example, if the regulator is drawing 100mA on standby, this will equate to 2.4 Amp-hours per day (24 hours) at 12V. This will require a 12W solar panel just to provide the power to run the regulator during winter, not to mention the relay as well. This could be an expensive regulator if extra power is needed to run it. Fourth, the regulator provides no equalisation charging, which is required for any system using multiple wet/flooded cells (ie, more than 2V – a 12V battery has six cells). Equalisation charging is required because when cells are discharged and recharged repetitively, they must be slightly over-charged to equalise all cells. This will prolong the battery life substantially. Also quality deep-cycle batteries should be charged at 14.1V, not 13.9V as this regulator does, to prolong their life. However, if used with SLA batteries, this regulator will work OK. Fifth, always check with the battery manufacturer concern ing their required charging characteristics, as you may void the battery warranty if you are not charging correctly. This should have been explained at the start of the feature, as some companies will not warrant batteries unless they are charged with anything but a quality regulator/charger. I believe this to be very important. The solar regulator could easily have the current increased, if the user does not wish to use the current reading capability of the display, by increasing the relay’s rating and why not use the excess power from the panel/s to do something else, such as run a pond pump or charge a second battery, by removing R1 and dumping the solar power to an outside device, rather than just burning it off with a resistor. You would need a diode in series with the solar panel if charging another battery though, as the second battery may discharge back through the solar array overnight, as well as requiring another regulator. Another idea: why not make it suitable for charging 32V or even 48V systems, by increasing C10’s voltage rating, and putting in an over-voltage circuit before REG1, using a 47kΩ or 51kΩ resistor (for 48V or 33kΩ for 32V) in place of R5 or R6 and upgrading any other component that may need its voltage rating upgraded (I haven’t looked at it too closely). The most used solar regulator by us would have to be the P1.20 or P1.40, manufactured by Plasmatronics, in Melbourne. They consume as little as 8mA, will switch up to 40A current and are programmable with up to fourstage charging, with adjustable set points and time. They retail for $245 (20A model) and $345 (40A model) plus tax if applicable, so these are not expensive after all, considering the features. K & C Stork, Solar Power Consultants, Bacchus Marsh, Vic. FEBRUARY 2000 9 Review by Peter Smith HOT CHIP? Do you want a drink with that? Are you currently learning about microcontrollers? Thinking about a project that has real potential? Need to do something more than flash a LED or sound a buzzer? The “Hot Chip Starter Kit” is worth a close look. This new micro kit from Dick Smith Electronics will interest both the beginner and expert alike. Beginners will find that they can write and test a simple program, using the BASIC programming language, within an hour or two of connecting it up. Experts will like the power and flexibility of the Atmel microcontroller, as well as the ease with which the little Hot Chip board can be “designed-in” to a project. What’s in the box? The Hot Chip Starter Kit includes just about everything you need to get up and experimenting right away. On the hardware side, there’s a pre-assembled microcontroller PC board with both parallel and serial cables for connection to your PC. Software on CD-ROM for Windows 3.1, Windows 95 and Windows 98 is included, and features an Assembler, BASIC compiler and in-system programmer. What is a microcontroller? A microcontroller integrates a microprocessor core with key peripherals such as RAM, ROM, I/O ports, counter/timers, serial ports, A-D converters, etc – all on a single chip. The kit uses the AT90S8535 microcontroller IC, one of the latest and greatest from Atmel Corporation. 8KB of program (“Flash”) memory, 512 bytes of non-volatile data Hardware The Hot Chip PC board measures just 20 x 70mm but using surface mount components and a powerful microcontroller, it packs an incredible amount of functions into a small space. 10 Silicon Chip memory (EEPROM) and 512 bytes of RAM are all included on-chip. The program memory can be electrically erased and reprogrammed up to 1,000 times (throw away that old EPROM programmer!), whereas the EEPROM can be reprogrammed up to 100,000 times. Using the in-system programming (ISP) features of “Hot Chip” Microcontroller Starter Kit from DSE the microcontroller, the Hot Chip software can erase and reprogram both program and data memory via your PC’s parallel port, all in a matter of seconds. Table 1 lists all the major features of this little powerhouse. Further information can be downloaded from the Atmel web site at www.atmel.com – look under the “AVR 8-bit RISC” Microcontrollers section. (As a matter of interest, we used a similar, though smaller, Atmel microcontroller IC back in the November 1999 issue to control our LED Christmas Tree project). So far we’ve only talked about the microcontroller chip itself, but the Hot Chip PC board includes a number of other components to make it easier to use “out of the box”. DC power between 9 and 12V is supplied to the board via a 2-pin connector. This supply is regulated and filtered to 5V. The kit includes a power cable for connection to a 9V battery (it draws only 30mA), but any DC supply within the specified range could be used. A series diode provides polarity protection at the input. Power-on reset and brownout (low voltage) protection is provided for the microcontroller and a 32kHz crystal has been included to make it easy to set up a “real time” clock. A Maxim RS-232 IC converts the microcontroller’s serial port signals to RS232 levels, which are then made available on a 10-pin connector. A cable is supplied with the kit for connection to COM1, 2, 3 or 4 on your PC. (Your computer only has COM 1 and 2 and both are used? Have a look at your PC’s instruction manual – you’ll almost certainly find that COM 3 and 4 are also available.) As mentioned above, programming the microcontroller’s memory is performed via your PC’s parallel (LPT) port. All hardware support for this feature is provided within the microcontroller chip itself, with the necessary signals brought out to a 5-pin connector via current-limiting resistors. A cable is supplied with the kit for connection to either LPT1 or LPT2 on your PC. Similarly to COM ports, many computers only have LPT1 brought to an outside Table 1: AT90S8535 Microcontroller Features • AVR ® - High-performance and Low-power RISC Architecture – 118 powerful instructions – most single clock cycle execution – 32 x 8-bit general purpose working registers – Up to 8 MIPS (Millions of Instructions Per Second) throughput at 8 MHz • Data and Non-volatile Program Memories – 8K Bytes of in-system programmable flash memory SPI serial interface for in-system programming endurance: 1,000 Write/Erase Cycles – 512 Bytes EEPROM endurance: 100,000 write/erase cycles – 512 Bytes internal SRAM – Programming lock for software security • Peripheral Features – 8-channel, 10-bit A-D converter – Programmable UART (Universal Asynchronous Receiver and Transmitter) (Serial Port) – Two 8-bit timer/counters with separate prescaler and compare mode – One 16-bit timer/counter with separate prescaler, compare and capture modes and dual 8-bit, 9-bit, or 10-bit PWM – Programmable watchdog timer with on-chip oscillator – On-chip analog comparator • Special Microcontroller Features – Power-on reset circuit – Real Time Clock (RTC) with separate oscillator and counter mode – External and internal interrupt sources – Three sleep modes: idle, power save, and power down • Power Consumption at 4 MHz, 3V, 20°C – Active: 6.4 mA – Idle mode: 1.9 mA – Power down mode: <1µA • I/O and Packages – 32 Programmable I/O lines – 40-pin PDIP, 44-pin PLCC and 44-pin TQFP (Hot Chip uses 44-pin TQFP package) • Operating Voltages –VCC: 4.0 - 6.0V AT90S8535 (Hot Chip uses +5.0V) –VCC: 2.7 - 6.0V AT90LS8535 • Speed Grades: – 0-8MHz AT90S8535 (Hot Chip speed is 8MHz) – 0-4MHz AT90LS8535 FEBRUARY 2000 11 What’s in the box? The Hot Chip Starter Kit includes just about everything you need to get up and experimenting right away: a pre-assembled microcontroller PC board with both parallel and serial cables for connection to your PC. There’s also software on CD-ROM for Windows 3.1, Windows 95 and Windows 98 which features an Assembler, BASIC compiler and in-system programmer. wouldn’t recommend extending the parallel cable as programming errors may result. Design-in The Hot Chip PC board has two rows of 20 pads that provide convenient access to all microcontroller pins. It’s no accident that these pads have the same spacing as a 40-pin IC! If two 20-way SIL (single in-line) pin headers are installed, the board can be plugged into a 40-pin IC socket as part of a larger project. Does it get any easier than this? Alternatively, if you want to use the board in “stand-alone” mode, you can do that too. Individual pins or stakes can be soldered into whichever pads you desire – loose pins are provided with the kit. The Hot Chip on-line documentation includes a circuit diagram and PCB layout that can be printed for ease of reference. Software socket at time of manufacture (to save a few cents!). As most printers are hooked up to LPT1, you’ll find it much more convenient to use LPT2 if it is available. Again, check your PC operating manual. The parallel cable supplied is only 80cm in length and the serial cable is even shorter, so you’ll need to position the Hot Chip PC board right next to your PC. Although you could easily extend the serial cable without problems (simply use an appropriate male/female serial cable), we Software for Windows 3.1x, 95 and 98 is provided on CD-ROM, along with a complete technical manual for the AT90S8535 microcontroller in Windows help file format. The software consists of several major components, all of which are accessible from a simple to use graphical interface called “Debug ABC” ( Fig.1). Programs are entered using any text editor (Fig.3). Windows Notepad is preferable to using your normal word processor: most word processing programs can be a trap for young players, especially if you forget to save in text-only mode. Most word processors embed codes in your text which are invisible to you – but not the software! By the way, if you don’t already have a good text editor, we suggest giving Programmers File Editor (PFE) a try. It is available for free download from www.simtel.net/pub/ Fig.1: all software functions are accessible from the main window. Fig.2: likewise, all preferences are easily set from a sub-window. 12 Silicon Chip simtelnet/win95/editor/pfe101i.zip Programs can be written in BASIC or Assembly language (or both). Before BASIC programs are ready to run they must go through a two-step process. First, the BASIC compiler converts (compiles) the program into lower-level (but functionally equivalent) instructions in Assembly language (Fig.4). Then the Assembler translates these instructions into machine code (binary) format (Fig.5), ready for programming into the microcontroller’s Flash memory. If you’re familiar with BASIC programming, you’ll find most of the syntax quite familiar. Even if you’re not, one of the best things about BASIC is that you will have your first program up and running in quick time. Note that although compiled BASIC programs are notorious for their slow execution speeds, the Atmel AVR series of microcontrollers are specifically tuned for running compiled code (‘C’ in particular but we can’t see why this wouldn’t apply to BASIC as well). So unless you have a time-critical application that requires microsecond accuracy, you will probably find that BASIC does the job just fine. Once you have a program that you are ready to commit to memory, it’s simply a matter of clicking the Erase button, then the Program button to write it to the microcontroller’s Flash memory (Fig.1). Support is also provided to enable reading and writing of EEPROM memory, either as individual bytes or from data stored in a file. Once programming is complete, execution begins when you click on the UNreset button, releasing the microcontroller’s reset line. If your program reads and/or writes to the microcontroller’s serial port (UART), you can ‘talk’ to it via the serial communications module (Fig.6). Once again, this is accessible from the main (Debug ABC) window. This is of course the purpose of the serial cable connecting the Hot Chip board to the PC’s COM port. Fig.3: both BASIC and Assembler programs are entered using your favourite text editor. The default editor is Windows Notepad but this can be changed in the Preferences dialog box. Fig.4: clicking on the Assemble button launches the Compiler. Any errors that are detected are displayed along with the line number that generated them. Summary The only negative comment about the kit is that the software lacks any kind of real debugging tools or support for industry-standard tools such as those found in AVR Studio. If you need to do any serious debugging, you’re on your own… Nevertheless, we think that the low cost, power and versatility of the Hot Chip Starter Kit makes it an excellent SC choice for students, hobbyists and professionals. Fig.5: the output from the compiler is automatically passed to the Assembler, which produces the binary file ready for programming into the microcontroller. Where do you get it? The Hot Chip Starter Kit is available through all Dick Smith Electronics stores (including the PowerHouse stores), most DSE resellers and through the DSE “direct link” mail order/internet order service (www.dse.com.au; Freecall 1300 366 644). Retail price is $129 (plus p&p if not purchased over-the-counter). The Hot Chip system was developed by Investment Technologies Pty Ltd. You can visit their website at www.hawknet.com.au/~invtech Fig.6: the simple demo program we wrote in Fig.3, compiled in Fig.4 and assembled in Fig.5 is now “talking” to the PC via the COM1 port. FEBRUARY 2000 13 SPRINKLER CONTROLLER Multi-sector sprinkler controllers don’t have to be difficult to drive. This unit controls up to six sectors, has an easy-to-set clock and is programmed using simple switches and knobs. It’s also based on a PIC microcontroller and that means relatively few parts. By NED STOJADINOVIC 14 Silicon Chip T HEY SAY THAT necessity is the mother of invention but this invention was necessitated by my mother. Although the sprinkler timers currently available are wonders of modern technology, they can be rather formidable to operate. Alternate cycles, independently programmable sectors, the ability to set times months in advance and the like are all excellent features for those who want them. However, the extra complication can be a serious barrier to those who simply want to regularly water the lawn and a vegie patch a couple of times a day. This completely new design is the answer to this problem. It’s a timer that avoids programming as much as possible and is controlled by old fashioned switches and knobs, just the way mum and people of her generation (and some of mine) like it. Despite this, the timer is capable of controlling six independent solenoids (or sectors). You can individually set the watering period for each sector, turn individual sectors on or off and set which days watering takes place. The design uses a fairly new and quite high-powered piece of technology in the form of a PIC16C74A micro con troller. This device packs in a tremendous amount of complexity where nobody ever has to see it and greatly simplifies the external circuitry. And that allows us to keep the cost down. Operation Naturally, there is some programming to be done and this involves first setting the clock and the watering start times. You can set two watering start times per day, typically one for early morning and one for late afternoon. This is very easy to do, as we shall see later on. If you can set the time on a digital clock, you will have no problems because the operation is self-evident. The watering duration is controlled by a row of six knobs, each corresponding to a sector. For those not familiar with the terminology, a sector is an area controlled by an electrically-operated water valve, commonly called a “solenoid”. Sector 1 might be your front lawn, sector 2 a garden bed, sector 3 the vegie patch and so on. Each knob can set the watering duration of its sector from a few min- It’s pretty much self-evident how you drive this Sprinkler Controller. Once the two watering start times have been set (on the LCD clock), you use the knobs to set the watering duration for each sector (0-60 minutes) and the toggle switches to set the days of the week that watering takes place. utes to about one hour. Furthermore, turning the knob fully anticlockwise means that the corresponding sector will be off and no watering will take place. Similarly, turning it fully on (clockwise) turns that solenoid on continuously. The seven toggle switches (one for every day of the week) allow you to choose the days that watering takes place. This is handy if you only want to water on alternate days, for example, or to comply with any council regulations which may restrict watering to certain days of the week. Flicking a switch off means that there will be no watering at all on that day. An important point to note is that the sectors operate sequentially; ie, only one sector is on at a given Main Features • • • • Controls up to six 24V AC water solenoids (ie, six sectors). • • • Individual sectors can be turned fully off or on. Easy-to-set LCD clock with two watering start times per day. Toggle switches for day of week selection. Sector times independently variable from 0-60 minutes using rotary controls. Sectors are turned on sequentially to ensure adequate water pressure. Backup battery maintains settings during short-term power interruptions. FFEBRUARY ebruary 2000 15 16 Silicon Chip time. In operation, Sector 1 starts at the preset time(s) and completes its watering period before switching off and allowing Sector 2 to start. Sector 2 then completes its watering period, after which Sector 3 starts and so on until all sectors have been stepped through. In practice, this means that if all six sectors have been set to 30 minutes (say), the total watering time will be three hours. The reason this has been done is that, depending on the installation, there may not be enough capacity in the water lines to run all sectors simultaneously. Operating them one at a time ensures that each sector operates with good water pressure. Where To Buy A Kit Of Parts Parts for this design are available from the author, as follows: (1) PC board plus all on-board parts (includes LCD module, programmed microcontroller and switches but not the battery, optional fuseholder or optional reset switch) .....................................................................$125.00 (2) Programmed microcontroller .......................................................$45 (3) Plastic case and front panel .........................................................$50 All prices include postage. Payment by cheque or money order only to: Ned Stojadinovic, 23 Harricks Crescent, Monash, ACT 2904. Email: vladimir<at>u030.aone.net.au Note 1: 24V AC plugpack power supplies are available from garden supply shops or from Altronics (Cat. M9714). Note 2: copyright for the PC board and microcontroller program associated with this design is retained by the author. Circuit description Fig.1 shows the circuit details of the Programmable Sprinkler Controller. It’s all built around the PIC16C74A microcontroller (IC1). The PIC16C74A is a very capable chip which allows the elimination of a great deal of support circuitry such as A/D converters, serial transmitter/receivers, clock generators and buffers, etc. Indeed, there is so much packed into it that you might like to download the data on this device from Arizona Microchip and study it carefully when reading this article. Don’t be too dismayed at the seeming complexity of the chip. It’s true that there are so many functions that the pins are almost all multiplexed but once the desired function is programmed into the appropriate registers, they all work the same way as simpler devices. A/D converter The first really useful function is the 8-channel A/D converter. In this design, six channels are used to read the voltage on pots VR1-VR6. The microcontroller converts each voltage to a number ranging between 0 and 255 and the values from 0-240 are Fig.1 (left): a PIC16C74A microcontroller forms the basis of the circuit. This takes its inputs from the sector pots and the day switches and sequentially activates power Triacs via MOC3021 optoisolators. The PIC microcontroller also drives a 2-line LCD which displays the time and the watering start times. then divided by four to give values of 0-60 which are loaded into a minutes counter. The values between 240 and 254 are used as a buffer zone, as 255 tells the microcontroller to turn that sector on continuously. Note that I didn’t have to do anything similar at the zero time end as I found that all pots apparently drop to zero resistance long before they get to the end of their travel. By the way, the data sheet shows that there is only one A/D converter in the PIC16C74A and this is multi plexed eight ways by appropriately selecting the converter’s control register. The speed of the microcontroller means that we effectively have eight converters but it does have the limitation that you cannot do all eight conversions at once, such as might be required when doing high speed data processing. Port B internal pull-ups PIC processors are CMOS devices and so have a high resistance looking into their input pins. This means that stray static electricity can switch the pins rapidly from high to low and back again, which can cause the inputs to overheat. To counteract this problem, it’s standard practice to “tie” any unused inputs to either ground or Vcc (in this case +5V) via a reasonably large resistor; eg, 10kΩ. However, the PICs can do this internally and configuring the Port B pins as inputs ties each to +5V via its own 200kΩ resistor. Switches S1-S7 take advantage of these internal pull-ups by simply isolating the Port B input pins when the switches are open, leaving the corresponding inputs at +5V (logic high). Closing each switch grounds the pins through a common 250Ω resistor, forcing them to a logic low. Why include the 250Ω resistor? Well, it’s like this: the ports on a PIC can be configured as either inputs or outputs. As inputs, they look like high resistances to ground but as outputs they can supply up to about 20mA of current (per pin) to the outside world and not much more. If you configure a port as an output (either accidentally or otherwise) and it shorts directly to ground, that port will be destroyed and possibly the entire micro con troller as well. Another “gotcha” is that noise can cause the pin to reconfigure itself as an output in mid-program. In this case, the 250Ω resistor will limit the current to a safe level until the port settings are revised by the running program. Pull-down resistors The Set (SET) and Increment (INC) inputs at pins 30 & 29 both require pull-down resistors. For convenience and to allow for later expansion, these resistors are part of a resistor array package (RP1). This handy little component contains five 10kΩ resistors, all connected at one end to a single pin (in this case, pin 1). In this design, pin 1 is grounded, while the resistors at pins 3 & 4 go to FEBRUARY 2000 17 Fig.2: install the parts on the PC board exactly as shown in this wiring diagram. Note that the Reset switch (S10) is optional and won't be needed in most cases. The panel mount fuseholder is also optional. pins 29 & 30 of IC1, respectively. This means that pins 29 & 30 are normally pulled low via the 10kΩ resistors in RP1. Pressing the Set and Increment switches pulls these inputs high via a 250Ω resistor (R15). In a similar vein, pin 6 is open collector and is normally pulled high via R16. In this case, however, pin 6 functions as an output. A high output results in the pin remaining high resistance, allowing R16 to pull it to +5V. Conversely, a low effectively 18 Silicon Chip shorts the pin to ground. Pin 1 (MCLR) is also normally pulled high, in this case via R13. Switch S10 resets the microcontroller by pulling pin 1 low. This clears the time settings and restarts the program. The clock If you’ve dabbled before with micro controllers, you’ll know that they accept a variety of clock signals. Crystals, ceramic resonators and resistor/capacitor timing can all be used, depending on how accurate the clock has to be. For example, serial data transmission and reception requires good clock accuracy and so a ceramic resonator (at least) is necessary, or even a crystal for high baud rates. A look at the circuit diagram reveals a crystal lurking between pins 15 and 16 but this crystal has nothing to do with the microcontroller’s clock. Instead, the microcontroller’s clock is based on a simple RC timer consisting of R7 and C1 (pin 13). Such a rudimentary timer is quite sufficient for such simple functions as switching solenoids and updating registers, etc. However, it’s not good enough for the real time clock, which is where the crystal oscillator comes in. The crystal oscillator operates at 32.768kHz and the resulting square wave is fed to an internal counter which divides by 216 to give a frequency of 1Hz. This signal triggers an interrupt routine that updates the seconds, minutes and hours counters. Serial ports The more sophisticated PICs, including the 16C74A used here, all have hardware serial receiver/ transmitters, commonly referred to as USARTs (universal synchronous asynchronous receiver transmitters). The most common application is as an asynchronous receiver/transmitter which is the protocol that the average modem uses. The ability to do serial communication in hardware is enormously useful. Although it’s possible to write software that performs this function, it’s difficult because the timing of the individual bits needs to be very precise, especially at high baud rates. Not only that but the time between bits can get very short at high rates and the software has to constantly hover, waiting for the next bit to have its turn, making it difficult to do anything else. By contrast, a hardware USART allows you to simply dump in the byte to be transmitted and set the “send” bit. Similarly, reception of a complete byte causes a “message received” byte to be set and this in turn can trigger an interrupt. The receive buffer is three layers deep so two complete bytes can be received before the buffer needs to be unloaded. Having said all that, the USART is not used in this project. However, if there is sufficient interest in the Sprinkler Controller, a future expansion that uses serial transmission is planned. The display 16 x 2 LCD displays are quite cheap these days and go a long way towards making the operation of electronic equipment nearly foolproof. In this case, the LCD is used to show the time and day and to guide the operator when setting the watering start times. The data is shifted into the LCD in two 4-bit chunks via inputs D7-D4. This saves four pins on the micro controller but is a fraction slower and makes it a tad more difficult to program. Note also that I have not used a trimpot to set the contrast of the display. Instead, a fixed contrast voltage of about 0.25V is used and this is set by the resistive divider formed by R8 and R9 on pin 3 (VEE). Triac switching A complicating factor in sprinkler timer design is that the systems run off 24V AC, which is necessary to avoid corrosion in the lines to the solenoids. Consequently, there is no easy way to use simple DC components such as transistors to drive the solenoids; the drivers have to handle AC and in this design we use Triacs to switch the power. In greater detail, the six sector outputs from IC1 appear at pins 23-28 and drive MOC3021 optically-coupled Triac drivers (OPT1-6) via 300Ω current limiting resistors. These in turn drive six power Triacs (Triacs1-6). The MOC3021s serve to isolate IC1 from the inductive voltage spikes generated when the solenoids switch on and off. When a sector output goes high, the LED inside the relevant MOC3021 turns on and this turns on its companion optically-triggered Triac. This in turn applies bias to the gate of a power Triac which then switches on and applies power to the solenoid. Power supply The transformers available for use with sprinkler timers are rated at 24V AC and this gives a nominal 34V DC after rectification and filtering. However, this creates a small problem because standard voltage regulators only operate safely up to 30V. The answer is to use a pre-regulator, in this case based on resistor R10 and zener diode ZD1. Bridge rectifier BR1 rectifies the incoming AC and feeds the resulting DC voltage to R10 and ZD1, which provide a regulated +10V rail. This rail is filtered using C5 & C6 and fed to 3-terminal regulator REG1 which provides a +5V rail for IC1 and the LCD. Note that it is good practice to use high-quality capacitors in power supplies such as this (remember they are on for 24 hours a day for years) and these are rather expensive. Because the settings are stored in volatile RAM (in IC1), the circuit requires battery backup so that the set Parts List 1 PC board (available from author) 1 plastic electrical case to suit 7 SPST PC-mount toggle switches (S1-S7) 2 momentary contact pushbutton switches (S8,S9) 1 MF-R050 polyswitch 1 V100ZA3 metal oxide varistor (MOV1) 1 32.768kHz crystal (X1) 2 M205 fuseholder clips plus 100mA fuse (F1) 2 6-way PC-mount screw terminal blocks 1 battery snap connector 6 10kΩ PC-mount miniature potentiometers (VR1-VR6) (Farnell Cat. 697-990) 1 16 x 2 LCD module 1 6-pin SIL 10kΩ resistor array, pin 1 common (RP1) Semiconductors 1 PIC16C74A programmed microcontroller (IC1) 1 78L05 5V regulator (REG1) 6 MOC3021 optoisolated Triac drivers (Opto1-6) 6 2N6075B 600V 4A Triacs (Triac1-6) 1 DIL 200V diode bridge (BR1) 1 1N4740 10V 1W zener diode (ZD1) 1 1N4001 silicon diode D1 Capacitors 2 1000µF 16VW electrolytics (C4,C6) 4 0.1µF monolithic (C5,C7-C9) 1 15pF ceramic (C1) 2 12pF ceramic (C2,C3) Resistors (0.25W, 1%) 3 10kΩ 6 300Ω 1 2.2kΩ 2 250Ω 1 470Ω 5W 1 68Ω 6 390Ω times are not lost during blackouts. This is provided by a 9V battery via diode D1. Normally, D1 is reverse biased and no power is drawn from the battery. However, if mains power fails, D1 becomes forward biased and the battery supplies power to regulator REG1. Note, however, that the battery backup is only intended to cater for short interruptions to the power supply. FEBRUARY 2000 19 A conventional fuse could also be used here and indeed the circuit shows a 750mA slow blow type (F2) wired in series with the polyswitch. In most cases, this fuse won’t be necessary and can be replaced with a wire link. Construction The front panel is secured to the PC board by placing it over the switches and pot shafts and doing up the switch nuts. Take care with your soldering to ensure that adjacent tracks or IC pads aren't bridged. Varistor MOV1 across the AC power input is there to protect the diode bridge from switching spikes generated by the solenoids. This device acts like a high resistance to the “normal” voltages from the 24V AC power supply but breaks down at about 100V. As a result, switching spikes from the solenoids are effectively clamped to 100V and this protects the bridge rectifier (BR1) which is rated at 200V. As a further precaution, fuse F1 is included to protect against short circuits and other faults in the electronic circuitry. The solenoids and Triacs are separately protected using a polyswitch (or self-resetting fuse). These devices use a conductive polymer that melts internally and becomes a high resistance when too much current passes through them and then returns to normal when the overload is removed. The reasons for using a polyswitch are mainly to do with reliability. Many people use sprinkler controllers to keep their plants alive during holiday periods and if an intermittent problem develops in a solenoid, a conventional fuse would bring the whole system down. A polyswitch can recover from such problems so that the owners don’t return to a desert. However, it can’t prevent the unit from shutting down if a solenoid or the wiring to it develops a permanent short. Because of the simplicity of the circuit, the construction is very straightforward. Virtually all the parts, including the LCD, mount on a single PC board measuring 152 x 123mm and this is housed in a waterproof electrical instrument case. The main exceptions are the Set and Increment switches which are mounted on the front panel. The Reset switch and panel-mount fuseholder (both optional) can also be mounted on the front panel. Fig.2 shows the assembly details. Begin by installing all the wire links and resistors, followed by the power supply circuitry (at bottom right) including the fuses, battery snap connector, varistor and polyswitch. Watch the polarity of the electrolytic capacitors and note that the resistor array must be installed with its dot towards the optoisolators (Opto 1-6). Next, install a socket for IC1 and fit the screw terminal blocks along the bottom edge of the board. Don’t install IC1, the optoisolators or the LCD at this stage – that step comes later after you’ve tested the power supply and confirmed that it works correctly. As mentioned above, the panel-mount fuse (F2) is optional. Install a wire link across the fuseholder pads on the board if you don’t intend to include this fuse. At this stage you should have a fully functioning power supply and this should now be tested before installing any more parts. To do this, connect the leads from your 24V AC plugpack supply to the relevant screw Resistor Colour Codes         No. 3 1 1 6 6 2 1 20 Silicon Chip Value 10kΩ 2.2kΩ 470Ω 5W 390Ω 300Ω 250Ω 68Ω 4-Band Code (1%) brown black orange brown red red red brown not applicable orange white brown brown orange black brown brown red green brown brown blue grey black brown 5-Band Code (1%) brown black black red brown red red black brown brown not applicable orange white black black brown orange black black black brown red green black black brown blue grey black gold brown If the unit is to be moved about, it would be a good idea to fit a couple of stand-offs between the main PC board and the LCD module, so that the header pins don’t lift the copper pads on the PC board. terminal block and switch on. This done, switch your multimeter to a low voltage range and connect the negative lead to the negative side of one of the 1000µF capacitors (either C6 or C4). The main supply rails can now be checked by probing with the positive lead. The righthand lead of the 470Ω 5W resistor should have +10V on it and this is the voltage across zener diode ZD1. Similarly, the positive lead of C4 should be at +5V which represents the output from REG1. Pins 11 & 32 of the microcontroller socket should also be at +5V, while pins 12 & 31 should be at ground (ie, 0V). Pins 17, 18, 29 & 30 are pulled down to ground by the resistor array and so these pins should also be at 0V. Pin 1, the reset pin, should be at +5V. The LCD has two unused pins on the righthand side (labelled A & K) and then it’s ground, +5V and contrast in that order. Because the LCD is not yet installed, it’s easier to carefully flip the board over and check for the required voltages. The contrast pin should have a fairly low voltage on it – around 0.25V. Checking the Triac circuitry If everything checks out so far, check the remaining pins of the micro controller socket. These should all be at 0V and the same goes for the LCD. Assuming everything is OK, switch off and install the MOC3021 opto isolators and the Triacs, taking care of their orientation. This done, reapply power and connect a couple of solenoids to the lefthand screw terminal block (CON1) and also a flying lead to the positive side of C4; ie, the +5V power supply rail. Now touch this flying lead to pins 23-28 of the microcontroller socket in turn. Provided you have a solenoid hooked up to the appropriate output, you should hear a satisfying click as the solenoid switches on. Note that pin 23 controls solenoid 1, pin 24 controls solenoid 2 and so on. If you only have a couple of solenoids, just move them to successive positions on CON1 so that you can test all the Triac drive circuits. Assuming that the circuit passes all these tests, switch off and install the microcontroller, the LCD, crystal X1, toggle switches S1-S7 and the six pots (VR1-VR6). Note that the micro controller is static sensitive and will need to be treated carefully. You will find that the pins of the microcontroller need to be bent slightly inwards before it can be inserted into its socket. This is best done by holding the device between its ends and pushing one row of pins against a metal ruler. This done, turn it over, do the other row and test to see if it will fit in the socket. If it doesn’t, just repeat the above procedure until it fits correctly. The LCD is mounted on a 16-pin header socket before it is installed on the PC board. Push the assembly down onto the PC board as far as it will go (ie, push the pins of the header socket all the way through the plastic) before soldering the pads. FEBRUARY 2000 21 The PC board assembly is housed in a plastic electrical case and this can be fitted with a lid for waterproofing. This lid prevents easy access to the front panel controls but that doesn’t matter if the settings are seldom changed. You can now complete the board assembly by wiring up the Set and Increment switches (S1 & S2). The Reset switch (S3) is optional. In most cases, it can be omitted but we’ve made provision for it in the unlikely event that severe electrical noise sometimes causes the microcontroller to malfunction – in which case, the switch can easily be added. That said, the circuit is designed to tolerate electrical noise, so you shouldn’t have any problems along these lines. There certainly haven’t been any such problems with the prototype to date. Final testing Once the assembly is complete, clip in a battery – you should immediately be rewarded with a display that says 12:00 am, Monday. If not, the first thing to check is whether the microcontroller is running. Try turning Pot 1 to the “On Now” position. This should immediately result in pin 23 of IC1 going to +5V (check this with 22 Silicon Chip your multimeter). If that works, then the problem is most likely in the LCD. When the timer starts up, there is a flurry of activity on the data lines to the LCD and so the next step is to look for that, preferably using a logic probe. Another possibility is the contrast setting on the LCD. If you suspect that this is a problem (or if the contrast is poor), remove resistors R8 and R9 and replace them with a 5kΩ pot. The wiper of the pot should go to the contrast pin on the LCD while the other two pins go to +5V and ground. By suitably adjusting the pot, the dots that make up the digits should become visible. If they do and there is only one line of digits, then the interface to the microcontroller is faulty. No display at all probably means that the LCD is either defective or has no supply rail. Operation The operation of the Programmable Sprinkler Controller is self-evident with the possible exception of setting the clock. To set the current time, press the Increment button until the clock setting cursor pops up (at the minutes digit) and hold the button down until the value is correct. Pressing the Set button then cycles the cursor to the next digit which is then adjusted using the Increment button and so on until the time setting is complete. The next press of the Set button then takes you to the day of the week field and this is again altered using the Increment button. By the way, if you want to change the “am” indicator to “pm” or vice versa, position the cursor to the right of the “<” sign and press the Increment switch to toggle it. Pressing the SET button sets the watering start times. The defaults are for a morning (8.00am) and evening (7.30pm) watering. If you only want to water once per day, make the two start times exactly the same. Once all the clock settings have been completed, use the toggle switches to select the days that watering is to take place and adjust the watering period for each sector using the pots. Final assembly The completed board assembly is attached to the front panel (the panel is fastened using the switch nuts) and secured inside the plastic case using self-tapping screws. Before doing this, you will have to drill a hole in the bottom of the case to take the leads for the solenoids. Fit a rubber grommet to this hole to prevent lead damage. If necessary, this hole can later be sealed with silicone sealant (after you’ve installed the leads) to make the assembly waterproof. Once everything is working, connect the solenoids. To test each sector, simply turn the appropriate knob to “On Now” and watch for the sprinklers to start operating. Just remember that only one sector can be turned on at a time, so turn off each sector before trying the next one. Similarly, remember that the sectors operate sequentially in automatic mode, so don’t expect to see them all come on simultaneously at the starting times. Instead, only one sector will come on and this will complete its watering cycle before the next SC solenoid switches on. IT’S ON AGAIN...(Sun 27 Feb. 2000) CENTRAL COAST FIELD DAY PELTIER EFFECT DEVICES. … AUSTRALIA’S BIGGEST HOBBY ELECTRONICS MARKET DAY Could be used for cooling overclocked PC CPUs. All 40 X 40mm. sales<at>oatleyelectronics.com Lots of stalls including well known suppliers with new & used items. 4A T 65deg. Qmax 42W $25 If you have had trouble getting through Just 5min. walk from WYONG rail station at the WYONG Race Course. 6A T 65deg. Qmax 60W $27.50 on our main number 02-95843563 Some of our Special bargains for the day will be listed on our web site. 8A T 65deg. Qmax 75W $30 Be there..... we will!!! Comes with info to build cooler / heater.. then try 02-95843564 Some used heatsinks available. 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(barley visible) Sharp LTO26 limited life! our viewers use a sensitive CCD camera, a high power IR illuminator Features precision voltage ref., Hi eff. Requires 65mA.Diode and a 4” monitor. the unit is hand held but requires a rechargeable gel battery in saturating MOSFET, Shotky diode isolation, charge indicator and a current plus focus lens a shoulder bag / bum bag to operate. You don’t need moonlight or even starlight, limiter so it can be used with car battery (no housing) $18....constant it will work in total darkness with a range of up to 30meters!! what’s more it is not chargers, generators etc. Low cost due to current driver kit $10 fragile. The unit can even be used in full sunlight!! incredible low introductory the use of some unused recycled LITHiUM-ION BATTERY PACK prices! Click on CCD NIGHT VISION at... components. complete kit inc. case $29... AUDIOVOX BTR600R 400mAh 7.2V See our bargain solar panels in this ad.. These battery packs contain two UHF AUDIO / VIDEO TRANSMITTER KIT rechargeable Lithium-Ion cells, with an ***NEW KITS***..........Three new remote control kits Kit includes all components needed...... amazing 400 mAh capacity in such a small 8 CHANNEL IR REMOTE: PCB plus all on-board components, (pictured) cell (51mm X14mm). Ideal for use as R/C Features include: professionally connectors, switch, metal case, telescopic receiver batteries etc. $4ea antenna, twin RCA A/V lead, all that is built transmitter slim case, 8 RADIO CONTROL MODEL SERVOS changeover relay outputs (6 momentneeded to complete the full kit. 12Vdc Ideal for robotics projects <at>10mA operation. ary or latching, 2 latching). $50.... with good speed & high Ideal for trans(coming soon digital volume control for this kit) torque specs. They mitting audio and 4 CHANNEL UHF REMOTE: are supplied with a video around you Features include: 433MHz X-tal / saw resonator locked, selection of output suitable home.. 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Composite video in a time)all you have to do is CMOS SUGAR CUBE CAMERAS $70 (K80) reduced from$40 to &25 Res. 450 TV lines select the right one from the ALL WITH A FREE VHF MODULATOR ***NEW*****NEW*****NEW*****NEW*** & SUITABLE PLUG PACK chart supplied. 3 for $60 Weight 650g QUALITY AUSTRALIAN MADE look for video switcher / Intro price of $145 FEATURE PACKED MINI ALARM remote special in this ad SYSTEM. Features inc. boot release, NICAD 7.2VCHARGER / DISCHARGER *** KIT SUPER SPECIAL *** central locking Drawn in proportion 4 CHANNEL AUDIO/VIDEO SWITCHER Professional, built & tested fast NICAD output, imobiliser This is the most comprehensive video charger and discharger PCB assembly. in output, indicator switcher kit we have seen. Features inc 4 a desktop case Switch mode circuit, Has 6 flash relay. 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We supply a 55mm x 5mm...Flying lead: Dual cable 65mm (W) X 150mm kit could be used to put a security channel thermistor for temperature sensing plus a 25cm. Place under glass for outdoor (L) X 94mm on your TV to see who’s at the door or in cigarette lighter lead to use in a car use.$10ea. or 4 for $36... HTRY A 7 (H),+ suitable T the yard or to monitor the kids playing $7ea or 3 for 18. PANAFLOW 60mm 12Vdc fans. L BA 12L V CEL trickle GEL outside. Unreal price of $45 COUNTERFEIT STAMP MICRO. $3 ea or 4 for $10 charger. 5 in 1 remote $15 when bought with this kit. Stamps are simple but powerful R.I.S.K. Or 1Fan + 1 Solar Panel for the combined (reduced instruction set controller) micro bulk prices...$11.50...One of these solar Many more batteries on our web page See 5 in 1 remote elsewhere in this ad. CAMCORDER AND ACCESSORIES processor that can be programed with it’s panels will run one of these fans in ONE / TWO CHANNEL UHF REMOTE NiCad. BATTERIES 6V 2400mAh. 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Post & Pack typically $6 $23or 2 for $40 Prices subject to change without notice All $5 Ea. or 5 for $20 (can be mixed) SPECIAL 1 inverter & 3 CFLs: $45 SC_FEB_00 NEW PHONE NUMBER & E - m a i l a d d r e s s PC MOTHER BOARD $60 CCD NIGHT VISION!!! oatleyelectronics.com $145 $25 $160 $99 $70 $25 **LOOK AT THIS** OATLEY ELECTRONICS $23 $45 Keep tabs on your car's battery with this: Digital Voltmeter This digital voltmeter will let you keep tabs on the condition of your car’s battery & charging system. A PIC microcontroller shrinks the circuitry into the smallest available jiffy box and makes it a snack to build. By JOHN CLARKE Flat batteries usually happen at the most inconvenient time, in the most inappropriate place and when the weather is being totally disagreeable. In fact, the battery is probably the most unreliable component in a modern vehicle. To alleviate this problem, some battery manufacturers incorporate a backup unit within the same case, to allow the vehicle to be started if the main unit fails. 24 Silicon Chip A car battery can only deliver peak performance if it is properly maintained. This not only involves keeping an eye on the electrolyte level but also ensuring that the charging voltage operates within strict limits. That means a charging voltage of 13.8-14.4V for a 12V battery, or 27.6-28.8V for a 24V battery. If the battery voltage never reaches 13.8V, then either the charging voltage is too low or the battery is on the way out. This means that the battery will be marginal when it comes to delivering the necessary current during starting, particularly in cold weather. Conversely, if the battery is being overcharged, the electrolyte will gas excessively, leaving the plates dry and reducing the battery’s amp-hour (Ah) capacity. This can not only dramatically shorten the life of the battery but in severe cases (eg, if the voltage regulator has failed) could damage various electronic equipment in the car. So how can you be sure that your car’s battery is being properly charged and that it is in good condition? The answer is to build and fit this Digital Voltmeter. It monitors the voltage across the battery terminals and thus provides an accurate indication of the charging voltage. It also indicates how well the electrical system and the battery cope with extra loads such as lighting, fans and audio systems. In addition, an accurate voltmeter can quickly indicate the overall condition of the battery. For example, if the battery voltage regularly drops below its nominal value of 12V (eg, when the engine is idling or if the engine has been turned off for some time), it indicates that the battery is unable to maintain a charge (assuming that the charging system is OK). Another time to watch the battery voltage is during starting. During this time, the starter motor draws substantial current and the battery voltage will fall below its nominal 12V value. Wouldn’t it be nice to be able to accurately monitor the minimum battery voltage when the vehicle is started? Well, with this Digital Voltmeter you can because we’ve incorporated a minimum hold facility. All you have to do is press the Min/Hold button on the front panel at any time after starting and the lowest measured voltage will be displayed. The display then reverts to normal mode when the button is released. The minimum voltage, which is stored in volatile RAM, is automatically cleared the next time the ignition is turned off. Normally, with a good battery, the voltage should only drop to around 10.5V when starting the engine, although this will depend on the temperature, the cranking current and on the battery itself. In any case, it’s just a matter of using the Min/Hold button to establish a benchmark minimum voltage for your car’s battery and then checking it occasionally to make sure that the battery is in good condition. Be aware, though, that it’s normal for the voltage to go down during cold weather, so keep this in mind before suspecting a faulty battery. In summary, there are good reasons for carefully monitoring the battery voltage and this unit is ideal for the job. It boasts high accuracy, negligible drift with temperature and a 3-digit LED display that reads to the nearest 0.1V in 12V mode. It also features automatic display dimming to suit the ambient light conditions. Only three wires are required to Fig.1 (right): the PIC microcontroller does most of the work. It accepts inputs from the battery (via IC2a) and the Min/Hold switch and drives the 7-segment displays in multiplex fashion. FEBRUARY 2000 25 Parts List 1 processor PC board, code 05102001, 78 x 50mm (150 holes) 1 display PC board, code 05102002, 78 x 50mm (93 holes) 1 front panel label, 80 x 53mm 1 plastic case utility case, 83 x 54 x 30mm 1 4MHz parallel resonant crystal (X1) 1 LDR (Jaycar RD-3480 or equivalent) 3 PC stakes 3 7-way pin head launchers 2 DIP-14 low-cost IC sockets with wiper contacts (cut for 3 x 7-way single in-line sockets) 1 PC board mount click-action push-on switch (S1) 1 9mm tapped brass spacer 3 6mm tapped spacers 2 M3 x 6mm countersunk screws or Nylon cheesehead 2 M3 plastic washers 1mm thick or 1 M3 plastic washer 2mm thick 2 M3 x 15mm brass screws 1 2m length of red automotive wire 1 2m length of yellow automotive wire 1 2m length of black or green automotive wire (ground wire) 1 5A 3AG fuse and in-line fuseholder (optional) 1 1kΩ horizontal trimpot (VR1) connect the device to the car’s wiring (+12V, 0V and battery +ve) and the unit is easily calibrated by adjusting a single trimpot. A second trimpot sets the minimum display brightness at night. Circuit details Refer now to Fig.1 for the circuit details. It’s dominated by IC1, a PIC16F84 microcontroller, which forms the basis of the circuit. This device accepts inputs from the battery and switch S1, processes this information and drives the LED displays to give a voltage readout. If you think that the circuit looks similar to the Speed Alarm featured in the November 1999 issue, you’re dead right – it is. The major change, at least 26 Silicon Chip 1 500kΩ horizontal trimpot (VR2) Semiconductors 1 PIC16F84P microprocessor programmed with DVM.HEX program (IC1) 1 LM358 dual op amp (IC2) 1 LM2940-T5.0 5V 1A low dropout 3-terminal regulator (REG1) 3 BC328 PNP transistors (Q1-Q3) 1 BC338 NPN transistors (Q4) 3 HDSP5301, LTS542A common anode 7-segment LED displays (DISP1-DISP3) 1 20V 1W zener diode (ZD1) Capacitors 1 47µF 16VW PC electrolytic 1 22µF 35VW PC electrolytic 1 10µF 35VW PC electrolytic 1 1µF 16VW PC electrolytic 2 0.1µF MKT polyester 2 15pF ceramic Resistors (0.25W, 1%) 3 10kΩ 3 680Ω 1 3.3kΩ 8 150Ω 1 1.8kΩ 1 10Ω 1W Miscellaneous Automotive connectors, heatshrink tubing, cable ties, superglue. Extra parts for the 24V version 1 PC stake 1 22kΩ resistor 5 820Ω 1W resistors as far as the hardware is concerned, is to the input circuitry around IC2a (plus we’ve eliminated some of the switches). And that’s the beauty of using a PIC processor – we can use similar circuitry but get it to perform a completely different function by rewriting the software that controls the internal “smarts” of the device. As a bonus, we can shrink the parts count and that in turns means lower cost. OK, let’s start with the voltage sensing circuit based on IC2a. As shown in Fig.1, the battery voltage is applied to a divider consisting of a 10kΩ resistor and a 1.8kΩ resistor in series with a 1kΩ trimpot (VR1). Assuming a 12V battery, the battery voltage is divided by a factor of 5.1, filtered using 10µF capacitor and applied to pin 2 of comparator stage IC2a. In operation, IC2a compares the voltage on its pin 2 input with a DC voltage on its pin 3 input. This DC voltage is derived by applying a pulse width modulated (PWM) square-wave signal from the RA3 output of IC1 to a 1µF capacitor via a 10kΩ resistor. As a result, pin 1 of IC2a switches low when ever the voltage on its pin 2 is greater than the voltage on pin 3. This signal is then fed via a 3.3kΩ limiting resistor to the RB0 input of IC1. The resistor limits the current flow from IC2a when its output goes high to a nominal 12V, while the internal clamp diodes at RB0 limit the voltage on this pin to 5.5V. A-D converter Most of the complexity of this circuit is hidden inside the microcontroller (IC1) and its internal program. However, among other things, IC1 functions as an analog-to-digital (A-D) converter. In operation, it converts the comparator signal on its RB0 (pin 6) input into a digital value which is then used to drive the 3-digit LED display. The A-D converter used here is a little unusual and only requires two connections to the microcontroller. As mentioned above, the output at RA3 produces a PWM signal and this operates at 1.953kHz with a duty cycle ranging from .075% to 90%. Note that the high output level is at +5V while the low output level is at 0V. The 10kΩ resistor and 1µF capacitor filter the output from RA3 to derive a DC voltage that is the average of the duty cycle waveform. This means that if the duty cycle is 50% (ie, a square wave), the output voltage is 50% of 5V, or 2.5V This voltage is applied to pin 3 of IC2a. Other DC voltages are obtained by using different duty cycles. This DC voltage is connected to pin 3 of IC2a which is used as a comparator. Operation of the A-D converter is as follows: initially, the RA3 output operates with a 50% duty cycle and this sets the voltage at pin 3 of IC2a to 2.5V. At the same time, an 8-bit register inside IC1 has its most significant bit set high so that its value will be 10000000. The 50% duty cycle signal is produced by IC1 for 65.5ms, after which the comparator output (pin 1 of IC2a) is monitored by the RB0 input. Pin 1 of IC2a is low if the divided battery voltage at pin 2 is greater than 2.5V and high if the divided voltage is less than 2.5V. What happens now is that if the divided voltage is less than 2.5V, the PWM output at RA3 is reduced to a 25% duty cycle to produce 1.25V. The internal register is now set to 01000000. Alternatively, if the divided voltage is greater than 2.5V, corresponding to a low comparator output, RA3’s output is increased to a 75% duty cycle to provide 3.75V. The register is thus set to 11000000, with the most significant bit indicating a 2.5V 50% duty cycle and the next bit indicating the 1.25V 25% duty cycle (adding the two bits gives us the 3.75V). The comparator level is now again checked after 65.5ms, after which the microcontroller adds or subtracts a 12.5% duty cycle (0.625V) and checks against the divided battery voltage again. The register is then set at X1100000 (with the X value a 1 or 0 as determined by the previous operation) if the input voltage is higher than the PWM waveform. If the input voltage is lower than the PWM voltage, the register is set at X0100000. This process continues for eight cycles, the microcontroller either adding or subtracting smaller amounts of voltage (0.3125V, 0.156V, 0.078V, 0.039V and 0.0195V) and the lower bits in the 8-bit register being either set to a 1 or a 0 to obtain an 8-bit A-D conversion. The A-D conversion thus has a resolution of about 19mV (0.0195V) at the least significant bit. In addition, there are 256 possible values for the 8-bit register, ranging from 00000000 (0) to 11111111 (255). In practice, however, we are limited to a range from about 19 to 231. This is because the software must have time for internal processing to take place, to produce the waveform at RA3’s output and to monitor the RB0 input. The two values (ie, 19 & 231) correspond to 1.9V and 23.1V for the 12V measurement mode. This restricted measurement range is not really a problem for a car voltmeter since we only need to measure within a narrow range from about 6-16V for a 12V battery. Following the A-D conversion process, the binary number stored in the Fig.2: the top waveform in this scope shot shows the output from pin 2 of IC1. In this case, the peak-to-peak output is 5.12V and the duty cycle is 50%. The bottom trace shows the resulting filtered waveform on pin 3 of IC2. 8-bit register must be converted to a decimal value before it can be shown on the 3-digit display. Once again, this takes place inside the PIC microcontroller. Note that, in the 24V mode, the 8-bit register value is multiplied by two before being converted to the decimal value. This gives a resolution of 200mV for the measured voltage. The A-D conversion relies on several factors to produce a consistent reading. First, the reference voltage must remain stable and this means that the output from RA3 must swing to the full positive supply rail and all the way to ground. If it doesn’t, then the filtered output from RA3 will vary and give inaccurate results. For the same reason, the duty cycle of the PWM waveform at RA3’s output must remain accurate over each 65.5ms period. In this case, the reference uses the supply from an LM2940T-5 regulator which has excellent long term stability Main Features • • • • • Compact case. 3-digit LED display with automatic dimming. 12V or 24V operation. Optional remote voltage sensing. Minimum hold voltage display. (20mV/1000 hours at 150°C junction temperature and at maximum input of 26V). Its temperature variation is just 20mV over a 100°C range. In addition, the output at RA3 is CMOS and swings to within a few millivolts of the supply rails at no load. As for the duty cycle, this is set by the software and is controlled using a 4MHz crystal oscillator on pins 15 & 16. This means that the resultant voltage reading should be accurate to ±1 digit (±2 digits for 24V operation). The minimum hold switch (S1) is monitored at the RA4 input. Normally, the RA4 input is held high via a 10kΩ resistor to the 5V supply. However, when the switch is closed, it pulls the RA4 input low. This low is then detected by the software which subsequently loads the 7-segment data for the minimum voltage reading into the display register. When S1 is released, RA4 is pulled high again and the current battery voltage is again displayed. LED displays The 7-segment display data from IC1 appears at outputs RB1-RB7. These outputs directly drive the LED displays via 150Ω current limiting resistors while the RA0-RA2 outputs drive the individual displays via switching transistors Q1-Q3. The displays are driven in multiplex fashion, with IC1 switching its RA0, FEBRUARY 2000 27 and off at 1.96kHz, they appear to be continuously lit. Display brightness Fig.3: install the parts on the PC boards as shown here. Note particularly the orientation of switch S1 and be sure to use a BC338 transistor for Q4. The 820Ω resistors (shown in green) are used only in the 24V version. IC2b is used to control the display brightness. This op amp is wired as a voltage follower and drives a transistor buffer stage (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 drives Q4 which in turn controls the voltage applied to the emitters of the display drivers (Q1-Q3). During daylight hours, the voltage on pin 5 (and thus on pin 7) is close to +5V because the LDR has a low resistance in strong light. This means that Q4’s emitter will also be close to +5V and so the displays are lit at full brilliance Conversely, as the light level falls, the resistance of the LDR increases and the voltage on pin 5 of IC2b decreases. In fact, when it’s completely dark, the voltage on pin 5 is determined by the setting of trimpot VR2 which sets the minimum brightness level. As before, this voltage appears at Q4’s emitter and so the displays are all driven at reduced brightness. Note that, in practice, VR2 is adjusted to give the desired display brightness at night. Clock signals RA1 and RA2 lines low in sequence. For example, when RA0 is brought low, transistor Q1 turns on and applies power to the common anode connection of DISP1. 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 RA0 output is taken high and DISP1 turns off. The 7-segment data on RB1-RB7 is then updated, after which RA1 is brought low to drive Q2 and display DISP2. Finally, RA2 is taken low and new 7-segment data presented to DISP3. This cycle is repeated for as long as power is applied to the unit and because the displays are switched on Clock signals for IC1 are provided by an internal oscillator circuit which operates in conjunction with crystal X1 (4MHz) and two 15pF capacitors. The two capacitors are included to provide the correct loading for the crystal and to ensure reliable starting. The crystal frequency is divided down internally to produce separate clock signals for the microcontroller Resistor Colour Codes          No. 1 3 1 1 3 8 5 1 28 Silicon Chip Value 22kΩ 10kΩ 3.3kΩ 1.8kΩ 680Ω 150Ω 820Ω 10Ω 4-Band Code (1%) red red orange brown brown black orange brown orange orange red brown brown grey red brown blue grey brown brown brown green brown brown grey red brown brown brown black black brown 5-Band Code (1%) red red black red brown brown black black red brown orange orange black brown brown brown grey black brown brown blue grey black black brown brown green black black brown grey red black black brown brown black black gold brown operation and for the display multi plexing. Power Power for the circuit is derived from the vehicle’s battery via the ignition switch. A 10Ω 1W resistor and 22µF capacitor decouple this supply rail, while 20V zener diode ZD1 protects the circuit from transient voltage spikes above this value. The decoupled ignition supply rail is then fed to regulator REG1 which provides a +5V rail. This rail is then used to power all the circuitry except for IC2 which is powered directly from the decoupled ignition supply. A 47µF capacitor and a 0.1µF capacitor are used to decouple the regulator’s output. For 24V systems, the supply input is applied via five parallel-connected 820Ω 1W resistors which provide a voltage drop to limit dissipation in the regulator. Note that a low dropout regulator is used to allow the voltmeter to operate down to about 5.5V for 12V systems. A standard regulator would have only allowed measurements down to about 8V before REG1 began to drop out of regulation. OK, so much for the circuitry. Of course, most of the clever stuff takes place inside the PIC microcontroller under software control. For a broad overview of how this software works, take a look at the accompanying panel. Construction Fortunately, you don’t have to understand how the software works to build this project. Instead, you just buy the ready-programmed PIC chip and “plug it in”. All the parts are mounted on two small PC boards: a processor board coded 05102001 and a display board coded 05102002. These are stacked together using pin headers and cut down IC sockets. Fig.3 shows the assembly details. Before installing any of the parts, check the PC boards carefully for etching defects and undrilled holes. Two large holes are required in the display PC board to accommodate a screwdriver to adjust VR1 and VR2. These are just below DISP3 and to the left of S1. Note that two small pilot holes are provided in each location to suit two different trimpot sizes – just drill out the holes to suit the trimpots supplied. The display board (in case at top) plugs into the pin header sockets on the processor board (above). Notice how the bodies of the electrolytic capacitors on the processor board are bent over, so that they lie parallel to the board surface. You can now start the assembly by installing the parts on the processor board. Begin by installing all the wire links, then solder in all the resistors using the accompanying resistor colour code table as a guide. It’s also a good idea to use a digital multimeter to measure each one, just to make sure. Note that the seven 150Ω resistors Capacitor Codes    Value IEC Code EIA Code 0.1µF 100n 104 15pF 15p 15 are mounted end on. Note also the different values for the resistor immediately below VR1. The two horizontal trimpots (VR1 & VR2) can go in next, followed by PC stakes at the four external wiring points. This done, solder in a socket for IC1 (but don’t install the IC yet), then install IC2 by soldering it directly to the PC board. Make sure that both the socket and IC2 are correctly oriented. This done, install zener diode ZD1 and 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. Zener diode ZD1 can now be FEBRUARY 2000 29 How The Software Works We have already described the operation of the A-D converter in the main article and this forms a major part of the software operation. Other sections of the software come under two headings: (1) MAIN and (2) INTRUPT. The accompanying flowchart shows the MAIN and INTRUPT programs. The MAIN program operates when the processor is reset after first powering up. It sets up the RB0 and RA4 ports as inputs and the RB1-RB7 and RA0-RA3 ports as outputs. It then reads the value stored in memory for 12/24V mode and places it in a flag register. After this, it looks for a pressed switch which is used to change the 12/24V option. If the switch is pressed, it toggles from the current option to the other (ie, if the unit was in 12V mode, it toggles to 24V mode and vice versa). The new option is then written to memory for storage. Interrupts are now allowed which starts the program skipping to the INTRUPT section when ever the internal timer triggers an interrupt. We interrupt via an internal timer which can be preloaded so that the period between interrupts can be adjusted. This feature is used to generate the pulse width modulation output at RA3. If we want the RA3 output to be low for a short time, we load the timer with a value close to 255. Then, when the counter increases and overflows from 255 to 0, we have another interrupt. The converse happens for a high output from RA3. In this case, the timer is preloaded with a value of 255 minus the value used for the RA3 low output time. When the next interrupt occurs (ie, when the count rolls over from 255 to 0 again), RA3 goes low and the cycle start all over again. The value that is loaded into the counter is called LOW_TIME and is the same value as used in the 8-bit register for the A-D conversion. This A-D conversion is detailed in the circuit description and its operational block is shown in the MAIN and INTRUPT program flowchart. The display is updated in the multiplex routine when the total 255 counter period has expired. This occurs on each second timer overflow interrupt. The multiplexing lights the next display and switches off the previous one. The left digit is blanked if the value for the display is below 10.0V. After the A-D conversion, in the Main program, the software tests the minimum hold switch. If it is pressed, the LOW_1 value (ie, the lowest value) is displayed. If the switch is open, the REAL_V value, which is the value arrived at during the A-D conversion, is compared with the current LOW_1 value. If the REAL_V value is the lower of the two, it replaces the current LOW_1 value (ie, the LOW_1 value is updated). A check as to whether the 12V or 24V flag is set determines whether or not the value for display is multiplied by two, as required for the 24V setting. Finally, the values are converted to decimal for the display. The process then continues with another A-D conversion to measure the voltage again. Full software for the Digital Voltmeter can be obtained from our website and is called DVM.ASM. This may be used by readers who are interested in the programming details. 30 Silicon Chip Specifications Range: about 5.5-23.1V when powered from a 12V battery; 1846.2V when powered from a 24V battery. Display Resolution: 100mV in 12V mode, 200mV in 24V mode. Update time: 0.52s The pin headers are installed on the copper side of the display board using a fine-tipped soldering iron. These headers plug into matching sockets on the processor board. 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 an adjacent PC pad to the right of transistor Q2. Finally, the three 7-way in-line sockets can 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. Display board This view shows the completed module, with the two PC boards stacked together in “piggyback” fashion. Make sure that none of the parts on the processor board contact the back of the display board. installed, followed by REG1. The latter 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. Be sure to accurately align the hole in the regulator’s metal tab with its hole in the PC board. The capacitors can go in next, mak- ing sure that the electrolytic types are all correctly oriented. Note that the electrolytics must all be mounted so that they lie parallel with the PC board. In particular, the 22µF & 47µF capacitors at bottom right lie across the regulator leads, while the two 10µF capacitors lie across the adjacent 1.8kΩ and 10kΩ resistors. Now for the display board: install the seven wire links and the resistors first, then install the three 7-segment LED displays with their decimal points at bottom right. Note that the links all go under the displays, which is why they’re shown dotted on Fig.2. The 820Ω 1W resistors (shown in blue) are required for the 24V version only. The LDR is mounted so that its top face is about 3mm above the displays. Install it now (it can go in either way), then install S1 with its flat side oriented as shown. Finally, complete the display board assembly by installing the pin headers. These are installed from the copper side of the board, with their pins protruding about 1mm above the top surface. You will need a fine-tipped iron to solder these pin headers. You will also have to slide the plastic spacers along the pins to give sufficient room for soldering. Preparing the case Fig.4: the two PC boards are secured together using spacers, a 2mmthick washer and several machine screws. Work can now begin on the plastic case. First, use a sharp chisel to remove the integral side pillars, then slide the processor PC board into place and use it as a template to drill two mounting holes in the base – one through the hole in REG1’s metal tab and the other immediately below the 0.1µF capacitor on the far lefthand FEBRUARY 2000 31 small dabs of super glue along the inside edges. Finally, a hole is also required in the rear (base) of the case for the power leads. Testing Fig.5: this full-size front panel artwork can be used as a drilling template. It’s a good idea to check the power supply before plugging the microcontroller IC into its socket. To check the supply, first unplug the display board and put it to one side. Now connect automotive hookup wire to the +12V and GND (chassis) inputs on 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 (you can use the metal tab of REG1 for the negative connection). If this is correct, disconnect the power and install IC1 in its socket, ensuring that it is oriented correctly. This done, plug the display board back into the pin headers on the processor board and reapply power. The LED displays should light and show “L0”, indicating that the input voltage is below 1.9V (ie, not connected). You can test the dimming feature by holding your finger over the LDR. Adjust VR2 until the display dims. Calibration Fig.6: check your boards carefully against these full size PC artworks before installing any of the parts. side. This done, use an oversize drill to countersink these holes at the rear of the case, to suit the specified M3 x 6mm CSK screws. Next, plug the display board into the processor board and secure them together as shown in Fig.4. Check that the leads from the parts on the display PC board do not interfere with any parts on the processor PC board. If necessary, trim the leads of the parts on the display board to avoid this. The front panel artwork can now be affixed to the panel and used as 32 Silicon Chip a template for drilling the LDR and switch holes and for making the display cutout. It’s best to drill a small pilot hole for the switch first and then carefully enlarge it to the correct size using a tapered reamer. The display cutout is made by first drilling a series of small holes around the inside perimeter, then knocking out the centre piece and filing to a smooth finish. Make the cutout so that the red Perspex or Acrylic window is a tight fit. This window can then be further secured by applying several The calibration procedure for both versions is straightforward. Basically, the procedure involves applying a suitable input voltage and adjusting trimpot VR1 until the reading on the display matches the reading obtained on a digital multimeter. Let’s look at the 12V version first. The step-by-step procedure is as follows: (1). Connect the “To Battery +ve” terminal to the “+12V Via Ignition Switch” terminal using a short length of wire. (2). Connect a 12V (approx.) supply to the “+12V Via Ignition Switch” terminal and ground. (3). Compare the reading against a digital multimeter and adjust VR1 for the same reading. Note that the Digital Voltmeter only updates about every 0.5 seconds, so adjust VR1 slowly during this procedure. If you don’t have a digital multimeter, connect the “To Battery +ve” terminal to the output of REG1 and adjust VR1 for a reading of 5.0V. This should give a reasonably acc urate calibration, to within ±150mV. 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 The Perspex window should be a tight fit in the front panel cutout and can be further secured by applying spots of super glue along the inside edges. The calibration procedure for the 24V version is only slightly more complicated. In this case, you have to “switch” the unit to 24V mode first before calibration can take place (the 12V mode is the default). The step-bystep procedure is: (1). Connect the “To Battery +ve” terminal to the “+24V Via Ignition Switch” terminal. (2). Press (and hold down) the Min/ Hold switch and apply 18-30V to the Digital Voltmeter. The display will show an “H” to indicate that the 24V mode has been set. This setting will now remain even if the supply is subsequently switched off and on again. (3). Compare the Digital Voltmeter reading against the reading obtained on a digital multimeter and adjust VR1 for the same reading. Be sure to adjust VR1 very slowly – as before, the Digital Voltmeter updates only about twice every second. Note also that the reading will only show an even number after the decimal point (ie, it indicates in 200mV steps). This means that a 24.1V supply may show 24.0 or 24.2V but not 24.1V. (4) If you don’t have a digital multimeter, connect the “To Battery +ve” terminal to the output pin of REG1 and adjust VR1 for a reading of 5.0V. Once again, this should give a reasonably accurate calibration. By the way, if you want to revert to the 12V mode, all you have to do is again press the Min/Hold switch as power is applied. The display will now show an “L”, indicating that the 12V setting mode has now been selected. ELECTRONIC WORLD Pty Ltd ACN 069 935 397 Ph (03) 9723 3860 Installation Be sure to use automotive cable and connectors when installing the unit into a vehicle. The +12V supply is derived via the ignition switch and a suitable connection can usually be made at 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 a solder eyelet and a self-tapping screw. The “To Battery +ve” input can also go to the fused side of the ignition switch. Alternatively, this connection can be run directly to the positive terminal of the battery via an in-line automotive fuseholder (mount this fuseholder close to the battery terminal). This reduces the voltage drops across the wiring of the ignition supply and gives a more accurate reading of the battery voltage, particularly when starting. The only drawback with the direct connection method is that there will be a constant 1mA drain from the battery. However, this current is so low that it really shouldn’t cause any problems, even if the battery is left for extended periods without recharging. Note: When using the voltmeter with 24V vehicles, the five 820Ω resistors will become quite hot. To alleviate this, we recommend replacing them with 10 1.8kΩ 1W resistors. The five added resistors can be installed on the SC underside of the PCB. Amidon Stockist 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 ! • • • • • • • • • 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 FEBRUARY 2000 33 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.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 Ultrasonic PARKING RADAR Do you park by the “touch and go” method – touch the car behind you, go forward a bit, touch the car in front, go back a bit . . . ? Shame, shame, shame! But even if you’re not a careless parker, this little radar warning unit could help get you into tight spots! Parking a car is a real problem for many people. They can’t! Unless there is a shop window to reflect off they simply have no idea how to judge the distance between the back of their car and the front of the next. They either make life very hard for themselves, making what should be a three-point parking a ten or twenty point saga (you think we’re joking?) or, worse still, stop reversing when their tow bar has made a nice little scallop in the number plate of the car behind. Even a slight touch on a modern car can cost thousands of dollars to 38 Silicon Chip repair, especially where integral, moul-ded (or non-existent) bumper bars or too-sensitive air bag sensors are involved. So what’s the answer? Here it is – a small ultrasonic transmitter/receiver which warns you when you’re getting too close. It’s designed to fit to the back bumper (or other suitable location) of your car and sounds a buzzer or closes a relay when you’re within the range you set – anything from about a metre down to just a few centimetres. While designed for the specific purpose of parking, there are other Design by Branco Justic* applications where you might want to sense objects that come within range – security is one which springs to mind, perhaps even things like vehicles or other objects going past or through a small opening. It’s all housed on one PC board (even the ultrasonic transducers) which can all fit into a small disposals plastic case, ready for mounting on the car. Circuit description The circuit can be divided into three sections – a high gain amplifier based on transistors Q1 & Q2 and the ultrasonic transducers, a rectifier (D1&D2) and an output switch (actually two output switches) based on IC1c and IC1d. Two cascaded amplifier stages based on Q1 and Q2 form a potentially high gain amplifier, with its gain set by VR1. This amplifier has a 40kHz ultrasonic receiver transducer connected to its input and a 40kHz ultrasonic transmitter transducer connected to its output (ie, Q2’s collector). So there is a potential feedback path between output and input. Normally, the overall loop gain is set to be less than one but if an object comes into reasonably close proximity and reflects enough energy from the ultrasonic transmitter to the ultrasonic receiver, the gain increases to the point where it exceeds one and the amplifier will then break into oscillation. The loop gain includes the acoustic feedback between the transducers (loss) and the gain of the amplifier (gain). The distance at which the oscillation will first occur depends on the mechanical setup, acoustic isolation between the ultrasonic transducers and the setting of VR1. We'll look at the mechanical considerations shortly. The oscillator output is rectified by C4, D1, D2 and C5 which form a “diode pump”. The detected voltage across C5 is added to the voltage across C6, which is set by trimpot VR2 connected across the 6.2V supply. The total voltage is applied to the input of NAND gate IC1d. When this exceeds approximately 3.1V (half the supply voltage), IC1d’s output goes low which allows capacitor C7 to quickly charge via diode D3. When C7 is charged the input to IC1c goes low so its output goes high. Transistor Q3 is turned on, energising the load connected to its collector. This load could be an electro-mechanical buzzer or a relay with diode D5 connected across it. At the same time, the LED connected to Q3’s collector lights up. The high output from IC1c also enables the 3kHz oscillator based on gates IC1a and IC1b and therefore the buzzer “buzzes”. C7 will begin to discharge via R6 after the input amplifier (Q1 & Q2) stops oscillating; ie when the object that caused the oscillation is moved away from the transducers. When the Ready to mount on the bumper bar or other suitable location, the Ultrasonic Parking Radar is simple to build, automatic in use and could save you $$$! voltage falls below 3.1V the output from IC1c goes low and the LED, buzzer and/or relay turn off. There is a test link on the PC board to assist in setting the unit up. With no test link it takes C7 about 10 seconds to discharge. With the test link in place R10 is in parallel with R6 and the time is reduced to about one second. If you wish to adjust the time later, it is simply a matter of changing R6 – smaller values for shorter times, larger values for longer times. Construction Start by checking the PC board for any flaws, defects or undrilled holes. Then it is simply a matter of mounting and soldering the lowest components (resistors and diodes) first, followed by the capacitors, the trimpots and finally the transistors, IC and LED. Note that all semiconductors and electrolytic capacitors are polarised and must be inserted the way shown on the component overlay. The test link should be installed at this stage – use one of the resistor pigtail cut-offs. PC stakes can be used for external connections – the + and - power wires and the wires to the buzzer and/or relay. The ultrasonic transducers can be soldered directly to the PC board or mounted remotely via suitable lengths of shielded (coaxial) cable. If you mount them on the board, they can be on either the component side or copper side of the board. On the component side, though, you will need PC stakes as the leads will not be long enough to allow mounting on edge (ie, facing off the edge of the board). The transducers are not polarised but there is a difference between the transmitter and receiver: one is branded “S” and the other “R”. Guess which is which? (A clue: R stands for receive). The ultrasonic transmitter and receiver transducers are mounted flush with the case edge. Alternatively, they could be mounted externally to give even wider acoustic separation, thus increasing the range of the unit. FEBRUARY 2000 39 Fig. 1: the complete Ultrasonic Parking Radar. It's your choice whether the output is a relay or buzzer. Fig.2 (above): the PC board component layout. Use this in conjunction with the same-size photograph below and you should have no problems at all assembling the board. 40 Silicon Chip Setting up The range of this unit depends to some degree on the acoustic separation between the transducers. With them mounted as shown in the plastic box, the circuit works quite satisfactorily but it would probably work even better with more separation. Some experimentation may be necessary to achieve maximum range. We have also found that, in this box, a small piece of polyurethane foam placed between the transducers will improve the range of the system. Before you get to that point though, you will need to set the trimpots (VR1 and VR2) to at least get the circuit operational. Turn VR1 and VR2 fully anticlockwise. These settings correspond to minimum amplifier gain (VR1) and minimum trigger threshold voltage (VR2). Rotate VR2 clockwise until the LED just lights, then back it off slightly until the LED extinguishes. This procedure sets the threshold of the trigger point. At this stage the unit still cannot be triggered by approaching objects as the amplifier gain is set to zero (VR1 is fully anticlockwise). Increase VR1 (clockwise) by small increments, checking with a solid object brought in front of the transducers at a distance of say, 500mm. You should find that a point is reached where triggering is reliable. If you want a shorter range, back VR1 off a little. Conversely, a longer range can be achieved by increasing the amplifier gain (ie, increasing VR1) but beyond a certain point the unit will be permanently triggered, even with no objects placed in front of the transducers. This is because the loop gain Parts List 1 Ultrasonic Radar PC board, 96 x 50mm 1 plastic case to suit 1 panel label to suit 1 piezo or electro-mechanical buzzer and/or 12V coil relay (see text) 2 10mm M3 screws and nuts 2 5mm M3 spacers Here’s how it all fits together in the disposals case from Oatley Electronics. The buzzer shown is mounted under the dash or similar location inside the car. is now greater than one, producing permanent oscillation. If you need higher range, the only way that this oscillation can be stopped is to introduce more acoustic separation between the transducers. When the desired settings are achieved, the test link can be removed and the unit mounted in an appropriate position on the vehicle. Note that both the case (or the transducers if mounted remotely) will need to be fairly well waterproofed if placed in a position where they can be rained on or splashed (and that’s most useful positions on the rear of the car!). Waterproof ultrasonic transducers may be available shortly but at a higher cost. Power for the unit is most sensibly taken from the reversing light circuit, so that it is powered only when you are reversing. Identifying a reversing light Where to get the kit This kit is available only from *Oatley Electronics, who hold copyright on the design and PC board. A complete kit of parts including the case, label and some cable is available for $24.00. A short-form kit, including the PC board, all on-board components and transducers, is $19.00 Oatley Electronics sell by mail, phone and email/internet. You can contact them on (02) 9548 3563, Fax (02) 9584 3561, PO Box 89, Oatley NSW 2233, or by email sales<at>oatleyelectronics.com. The website is located at www.oatleyelectronics.com shouldn’t be too difficult and you can tap into the wiring using a “Scotchlok” or similar connector. These need no soldering – they pierce the wiring insulation and make contact as you squeeze them into position with a pair of pliers. A fuse is probably unnecessary as the reversing light circuit itself is fused. The buzzer will need to be mounted within hearing range – under the dashboard seems to make sense. Ordinary (thin) figure-8 cable is quite OK for this purpose. The buzzer shown in our photographs is probably inadequate for most cars because of its limited output. However, there are plenty of piezo and electro-magnetic buzzers around which would be more than loud enough. We wouldn’t suggest using an alarm piezo though – not if you value your hearing, that is. With most of these alarms designed to make a lot of noise (around 100-110dB output), that’s just a bit too loud for comfort! SC Semiconductors 1 4093B quad 2-input NAND gate (IC1) 3 C8050 NPN transistors (Q1, Q2, Q3) 2 1N60 germanium signal diodes (D1, D2) 2 1N914 silicon signal diodes (D3, 34) 1 GIG or 1N4004 power diode (D5) 1 6.2V 400mW zener diode 1 5mm LED (any colour) 1 MA40A3S or equivalent ultrasonic transmitter transducer (TX1) 1 MA40A3R or equivalent ultrasonic receiver transducer (RX1) Resistors (0.25W, 1%) 3 1MΩ 1 100kΩ 1 12kΩ 3 10kΩ 2 2.2kΩ 1 470Ω 2 10kΩ trimpots Capacitors 1 10µF 25VW PC electrolytic 3 10µF 16VW PC electrolytic 1 0.1µF polyester (code: 104 or 100n) 4 .012µF polyester (code: 123 or 12n) Miscellaneous Suitable lengths of hookup wire, figure-8 cable and shielded cable, “Scotchlok” or similar wiring connectors, suitable mounting nuts and bolts, solder, etc. Resistor Colour Codes       No. 3 1 1 3 2 1 Value 1MΩ 100kΩ 12kΩ 10kΩ 2.2kΩ 470Ω 4-Band Code (1%) brown black green brown brown black yellow brown brown red orange brown brown black orange brown red red red brown yellow violet brown brown 5-Band Code (1%) brown black black yellow brown brown black black orange brown brown red black red brown brown black black red brown red red black brown brown yellow violet black black brown FEBRUARY 2000 41 Light Emitting Polymers . . . the new flexible flat-panel display technology By JULIAN EDGAR Imagine a flat panel display made out of plastic. Or how about a panel that’s flexible and can made to conform to any shape such as a car dashboard? That’s the promise offered by new display technology based on semiconducting polymers. 42 Silicon Chip O VER THE LAST 30 YEARS, there has been increasing interest in the use of plastic polymers as conductors or semiconductors. Polymers that have semi conducting characteristics are called “conjugated” polymers and they behave as semiconductors for reasons that are different to those of inorganic devices. Despite this, semiconductor polymers are engineered using many of the lessons learned with traditional semiconductors. As a result, progress in the use of semiconducting polymers has been quite rapid. This prototype light emitting polymer display screen has been developed by Cambridge Display Technology. How it started Polymer semiconductor technology was invented in 1989 at the Cavendish Laboratory at Cambridge University in the UK. It began when physicist Richard Friend and chemist Andrew Holmes were experimenting with organic polymers. Quoted in the Cambridge “Alumni Magazine”, Holmes says: “we started with a plastic material called PPV, made by a process that allows it to be coated in thin films over large surface areas. If the material is chemically ‘doped’, it can conduct electricity nearly as well as a good metallic conductor”. However, the two scientists were interested in seeing how good the ‘undoped’ material was as an insulator. “We sandwiched a thin film between metal electrodes and subjected it to a high voltage. What happened next was pure serendipity. Someone switched out the lights by mistake and the plastic was seen to emit a yellow-green light. We had discovered the plastic version of a light-emitting diode.” In 1992, a company called Cambridge Display Technology was formed to develop commercial applications for light-emitting polymers (LEP), sometimes also called organic light emitting diodes (OLED). Joint ventures have since been signed with Seiko-Epson, Philips, DuPont, Hoechst and UNIAX. Conductors Conjugated polymers have found their first uses as conductors. In fact, doped conjugated polymers have achieved conductivities close to that of copper! The potential commercial applications include battery electrodes, conductive coatings for electrostatic speakers, capacitor electrolytes, transparent conductive coatings, through-hole plating of PC boards and electrostatic discharge coatings. Japanese company Matsushita is currently using polypyrrole in the manufacture of polymer capacitors, for example. Another major goal is to use conducting polymers to replace the copper tracks on PC boards. However, it will be necessary to improve the stability of the highest conductivity plastics before this can occur. Another promising use for conducting polymers is in electromagnetic shielding. That’s because of their relatively high conductivity and dielectric constant. It’s also easy to control these properties through chemical processing. Polyaniline is an especially good candidate for electromagnetic shielding. How they work Light emitting polymers sandwich a thin-film semiconducting polymer between two electrodes. Electrons and holes are injected from the electrodes and the recombination of these charge carriers leads to luminescence. The bandgap – ie, the energy difference between the valance band and conduction band of the semiconducting polymer – determines the wavelength of the light that is emitted. Fig.1 shows the basic layout. To make a device, a very thin (50300nm) uniform coating of polymer is spin-cast or extruded onto a glass or plastic film substrate that has been precoated with a transparent electrode material. The substrates can be chosen freely, with flexible and even 3-dimensional substrates suitable for use. The electrodes are either conducting oxides (indium tin oxide is often used) or conducting polymers, with one electrode transparent to allow the light to escape. In order to define the final configuration, the transparent electrode is patterned before the polymer layer is added. The other electrode is deposited by vacuum metallisation FEBRUARY 2000 43 TOP ELECTRODE ORGANIC LAYER BOTTOM ELECTRODE GLASS SUBSTRATE Fig.1: light emitting polymers consist of a polymer layer which is sandwiched between two electrodes, one of which is transparent. and patterned. The device is then encapsulated in a hermetically-sealed package. In practice, multiple devices can be fabricated on a single large substrate which is then scribed and broken before the leads are attached. By manipulating the structure of the polymer, light in the full colour spectrum of 450-740nm can be obtained. Display technology One hot topic of interest is the use of conjugated polymers in display technology. Five years ago, light output efficiencies of only 0.01 lumens/W were being reported but recent developments have seen efficiencies 10,000 times higher. Indeed, the polymer mat erials now being used have efficiencies close to that of inorganic LEDs. The display lifetimes that are now being quoted are also impressive. For example, Philips recently measured a display lifetime of more than 30,000 hours using light-emitting polymers. The display has high brightness and contrast and operates from only The UNIAX company has recently completed a prototype manufacturing line to produce this flexible alpha numeric display. 3.3V. Another company, UNIAX, has recently completed a clean room and prototype manufacturing line for its first light emitting polymer product – a flexible alphanumeric display. One major advantage of polymer displays is that the light emitting device can be patterned by simple pixellation of the metal. Large area pixellated displays made from one Table 1: Benefits Of Light Em itting Polym ers Feature LEP Processing Benefit Fast Swi tching Speed Fl exibl e substrates possible; large area coatings. No backlights required; no colour fil ters; no aperture loss; 180° viewing angle. Simple to define complex light emission patterns; very high resolution possible wrequired; any pi xel size and shape possible. Battery dri ven devices; DC dri ve. Innovati ve designs for end products; di spl ays shaped to products; easy manufacturing i ntegration wi th product; continuous coating for manufacture. Video displ ay capabili ty. Light Emi tting Pattern Formation Low Vol tage Operation Formabl e Substrates Light Weight Portabili ty. Solid State Devices Ruggedness. Thin Films Allows use of pol ari sers to gi ve high contrast. 44 Silicon Chip sheet are possible. Dot-matrix alphanumeric displays can also be made. The commercial collaboration between Cambridge Display Technology and Seiko-Epson is aimed at using ink-jet technology to print the pixels of the display directly on top of the pixel switching elements in the active matrix. It is hoped that this will lead to the development of a fast-switching, robust solid-sate device with a wide viewing angle, that can be used as a flat-screen display. When developed, it should combine both thinness and light weight with the look and feel of a traditional colour CRT. Thus far, this technology has only been showcased in a small (50mm square) b&w TV display that’s just 2mm thick! However, it’s being suggested that when combined with polysilicon TFT technology and inkjet printing, light-emitting polymers will deliver superior performance to existing display technologies such as LCDs. Cambridge Display Technology suggest that the advantages of the light emitting polymer displays are varied and many. Table 1 shows some of the advantages cited by the company. Recently, researchers at Princeton in the US replaced the ink cartridges of a conventional inkjet printer with a polymer solution containing the semiconducting polymer polyvinyl carbazol (PVK) and a light-emitting dye dissolved in a chloroform solvent. This solution was then “printed” onto a thin polyester film coated with indium tin oxide, which served as one of the electrodes. Finally, they deposited a metal film over the polymer layer to form the other electrode. This technique produced a light-emitting polymer that emitted green light. They then used the inkjet printer to make dot patterns of PVK mixed with either red, green or blue dyes on the coated polyester film. While this latter process has not yet been used to develop light-emitting polymers, it’s possible that this technology may lead to the development of a large, flat screen with mixed red, green and blue dot patterns. This in turn could lead to full-colour plastic TV screens, or even car indicator and dashboard lights that blend seamlessly into the bodywork and become visible only when they are on. It could even lead to the development of flexible TV and PC SC display screens. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au Build a “Safety Switch” Checker By JOHN CLARKE Many homes now have “Safety Switches” installed on their mains switchboards and these give a high level of protection against electrocution from faulty appliances. But how do check that the safety switch is protecting every power point? By using our RCD Checker which is simple to build and even simpler to use. S INCE THE INTRODUCTION of mandatory installation of RCDs in all new homes, there has been a huge increase in the availability of these products. There is no doubt that RCDs increase overall safety when using mains power and are a vital piece of equipment when using power tools. Indeed, under WorkCover regulations, all tradesmen on building sites are required to use RCDs when running power tools. Before we go too far in this article, we should explain what an RCD is. Features * Suitable for home use, tradesmen, electricians, musicians, etc * Creates an Earth leakage current to test RCD * Push to test operation * Neon indicator shows presence of power and checks internal components * Neon indicator to check Earth connection and Active/Neutral terminals * Suitable for type II RCDs (10-30mA rated residual current) * Applies residual test current from 32.5mA at 192VAC to 45.5mA at 264VAC. * Complies with Australian Standard AS 3190-1994 for RCD to trip at or above rated residual current of 100% +5% -0% between 80% of rated supply to 110% of rated supply (240VAC). FEBRUARY 2000 53 Our RCD or “Safety Switch” checker is built into a plugpack supply case. It simply plugs into the outlet to be checked. “RCD” is an acronym for “Residual Current Device”. While sometimes called a “Current-operated Earth leakage device” most people refer to them as a “safety switch”. They protect the user from electrocution by disconnecting the 240VAC supply if there is current flow to Earth. The RCD does this by monitoring the current flow between the Active and Neutral lines for the 240VAC mains supply. In a normally operating appliance there is current flow from the Active lead through the appliance and then back through the Neutral lead. This is shown in Fig.1a. Both currents i1 and i2 should be exactly the same value. If there is a fault in the appliance, as shown in Fig.1b, some of the current flowing from the Active lead may flow to Earth (i3) instead of to Neutral. If this is the case it may be that either there is a breakdown in the appliance between Active and Earth or someone is conducting current away from Neutral via their body. In other words they Fig.1a shows an appliance in normal condition – earthed but with no leakage. Fig.1b shows the same device with a fault. Fig.1c shows the “self test” in an RCD and Fig.1d shows how our checker can tell whether the RCD is operating correctly. All of these diagrams are fully explained in the text. 54 Silicon Chip are suffering electrocution. The RCD detects this difference between the Active and Neutral current and disconnects the power should the difference reach a predetermined level. The difference between the Active and Neutral current is called the residual. An RCD cannot protect against electrocution if the current flow through the person is between Active and Neu- tral. This is because the RCD cannot differentiate between appliance current and current through your body. (The moral of this is never to work on an appliance which is connected to the 240VAC mains supply!) Note that any appliance with exposed metal parts can become an electrocution hazard and this includes many appliances which are labelled as “double insulated”. All that has to happen is a for a leakage path to develop between the Active mains terminal in the equipment and the exposed metal parts; ie, usually the case. Then, if the case is not earthed, it will be live and a potential cause of electrocution if a person touches it. There are several types of RCDs. Type I RCDs have a rated residual current of 10mA and a 40ms tripping time. Type II have a rated residual current of between 10 and 30mA and 40ms tripping time at 500% residual over-current. It takes some 300ms to trip at the rated residual current. Type III RCDs have a rated residual current of between 30 and 300mA and a 50ms tripping time at the 500% residual current. Finally, type IV has type III current characteristics with selectable tripping times. Type II RCDs are the most frequently encountered. You should test your RCDs periodically with their own self-test switches. But this does not tell the whole story. Firstly, the self-test switch on the RCD merely tests its own operation. It does Fig. 2: the circuit of the RCD Checker could hardly be simpler: three resistors, two neons and a switch! Just remember that all this is at mains potential and no RCD Checker can protect you against an active/neutral path. Never work on a plugged-in RCD Checker. not tell you which power points are protected. If you have an RCD installed in your switchboard, you can use the checker to test each power point for its operation; not all power points will necessarily be connected. Secondly, power points which include an RCD do protect other power points connected to it but only those that are “down line” from it – that is, further along the mains circuit from the switchboard than the power point concerned. You can use the RCD Checker again to find out those which are protected and those which are not. Third, if you are using power in a premises where you are uncertain about the presence of an RCD, you can test for this on each power point. Finally, electricians can use the RCD Checker to verify that their installation is effective on each power point. Using the RCD Checker to trip out an RCD is a very convincing test of its effectiveness. there is no access to the Neutral input side of the RCD at the power point. The full circuit is shown in Fig.2. It comprises two Neon indicators, some resistors and a pushbutton switch. The “Valid Earth” Neon connected between Active and Earth lights to show there is an Active supply and a connection to Earth. This indicator is useful to verify that the Earth circuit exists on the power point. If there is no Earth connection, the RCD Checker cannot trip the RCD under test and the power point should be checked before using it. The “Power/Test” Neon monitors the Active and Neutral supply via the test current resistors, R1, R2 & R3. The Parts List 1 3-pin plugpack case (Jaycar HB-5900 or equivalent) 1 RCD Checker label, 40 x 32mm 1 250VAC plastic pushbutton momentary SPST switch (S1, Jaycar SP-0716, DSE P-7568, Altronics S-1080) 2 plastic Neon bezels with resistor (Jaycar SL-2630, DSE P-8116, P-8117, Altronics S-4016) 1 small cordgrip grommet to fill hole in case 1 100mm length of blue 250VAC 7.5A 250VAC wire 1 200mm length of brown 250VAC 7.5A 250VAC wire 1 100mm length of green/yellow 250VAC 7.5A 250VAC wire 1 20mm length of 1mm insulating tubing 1 20mm length of 3mm heatshrink tubing 1 100mm length of 12mm ID heatshrink tubing 1 small cable tie Resistors 2 2.2kΩ 5W wirewound resistors 1 1.5kΩ 5W wirewound resistor Miscellaneous Neutral-cure silicone sealant Test method So how does the test switch for an RCD work? Fig.1c shows the circuit for the internal self-test method used on an RCD. When the test switch is closed, the Active current passes through resistor R1 to the Neutral on the input side of the RCD. Thus all the current through R1 is assumed by the RCD to be the residual. R1 is chosen to trip the RCD between 80% to 110% of rated voltage (eg, from 192VAC to 264VAC for a unit rated at 240VAC). Fig.1d shows the circuit for the SILICON CHIP RCD Checker. In this case the test current flows from the Active to Earth. We have used this method for two reasons. First, because it simulates a true Earth fault and also because Compare this “opened out” photo of the RCD Checker with the wiring diagram (Fig.3,) while building your checker. While it is very simple, take extra care – it is a mains device, after all! FEBRUARY 2000 55 Neon will only light if the three resistors are in circuit and there is power from the Active to Neutral. When the test switch is pressed, the Power/Test Neon will go out and residual current will flow from Active to Earth. The Valid Earth Neon will stay alight until power is disconnected. So if you are using the RCD Checker and you press the button, both Neons will go out for an RCD that is working properly. Note that the switch must be held down for at least 300ms (1/3rd of a second) to ensure that the RCD is given sufficient time to trigger. Construction The RCD Checker is constructed in a plugpack case with the switch and two Neons mounted on the case lid. The three resistors mount around the mains pins inside the case. Fig.3 shows the wiring details. Begin construction by drilling the holes for the switch and two Neons. These are drilled as shown in Fig.4. Insert and secure the two Neons and pushbutton in place. The front panel label (Fig.5) fits into the rectangular moulding above the Neons and switch. Use the wiring diagram of Fig.4 when connecting up the components. Assembled and ready to go, this side-on shot shows how neat a package the plugpack case makes. The cord entry grommet (on the bottom) is not used and for safety, the hole should be sealed with silicone sealant. The resistors are placed around the plug pins with a short length of insulating sleeving on the resistor lead connecting to the Active pin. Solder the resistor leads together and secure a brown mains wire to the free end of the 1.5kΩ resistor and insulate it with a short length of heatshrink tubing. The wiring to the Neons and switch must be followed carefully and use 250VAC-rated wire. Slip a short length of heatshrink tubing over the Neon and switch body before connecting the wires. Then pull the tubing up over the terminals and shrink it with a heat gun. Secure the resistors with some silicone sealant (neutral-cure acid free, eg, roof and gutter sealant) and cover the resistor wires with a dob as well. Leave to cure overnight. Secure the wires together with a cable tie. The case has a cord entry point at the lower righthand side which must be filled to prevent accidental contact with any internal wiring. We used a small cord grip grommet in the hole which effectively sealed off the opening. Alternatively, the hole could be “plugged” with some more silicone sealant. Secure the case together using the supplied screws, with the two longer ones at the top. Checking operation Fig.3: wiring the checker should take no more than about half an hour – ten minutes to assemble, then twenty minutes to check your work before it is plugged in. 56 Silicon Chip Plug the RCD Checker into the power point and switch on the power point switch. Both Neons should light. The power/test Neon will light to indicate supply between the Active and Neutral and that the test resistors are in circuit. If it does not light, check SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Fig. 4 (left): drilling details for the front half of the Jaycar HB-5900 case. 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  Fig. 5 (above): the samesize label which fits the cut-out in the Jaycar HB-5900 plugpack case. the resistors for continuity and correct value and that there is power available. The Earth Neon will light to show there is an Earth connection on the power point. If this does not light, you either have the Active and Neutral connections in the power point transposed or there is a faulty earth connection. Either way, you should engage a licensed electrician to correct the problem. Pressing the Test switch for half a second (ie, more than 300ms) should trip the RCD. Both Neons should extinguish and the RCD should show that it has tripped. If it has not tripped, check that the RCD can be tripped with its own self-test switch. Any faulty RCD should be immediately replaced. If the RCD can be tripped with its own test switch but not with the RCD Checker, check the rated trip current. The SILICON CHIP RCD Checker is for use with 10-30mA RCDs only and will not test type III RCDs which will take a higher residual current before SC tripping. 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 Silicon Chip Binders REAL VALUE AT $12.95 PLUS ACTIVE/NEUTRAL TRANSPOSITION Until fairly recently, the connection of the Active and Neutral lines to a power outlet was not given the careful attention that it is today. In many older houses (say, pre 1950) you often find the Active and Neutral lines transposed, or swapped at the power point. (In a correctly wired outlet, when you look at the three “holes” from the front, the active is on the left side and the neutral on the right. Earth, of course, is ALWAYS at the bottom (vertical). Indeed, until the late 1960s "double adaptors” were sold which themselves transposed Active and Neutral! Of course, devices still work when plugged into transposed outlets and RCDs also work. It’s normally only a combination of appliance and earth faults which brings out the horrors of an Active/Neutral transposition. This device will not check RCDs where the Active and Neutral are transposed. However, it is very useful for determining whether you have an Active/Neutral transposition. If you have a power point which is known to work but the “valid earth” neon does not light, treat it with suspicion. It could be a broken or high resistance earth – which of course must be fixed immediately – or it could be an Active/Neutral transposition. It’s worth having the outlet checked out by a licenced electrician – for your piece of mind and your safety. P&P  Heavy board covers with 2-tone green vinyl covering  Each binder holds up to 14 issues  SILICON CHIP logo printed on spine & cover Price: $A12.95 plus $A5 p&p each (Australia only) Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. FEBRUARY 2000 57 By RICK WALTERS Build this sine/square wave oscillator for your workbench Do you want a good quality audio oscillator that does not go “boingg” when you switch ranges? And has constant output amplitude as you sweep over each range and from range to range? If so, this could be the oscillator for you. It covers the frequency range from 2Hz to 20kHz and is suitable for a wide range of audio applications. 58 Silicon Chip N ORMALLY, THE FIRST choice of anyone contemplating building or buying an audio oscillator is a Wein bridge type. These have the advantage of low distortion (usually) but their output amplitude often bounces all over the place as you sweep over each frequency range and is even worse when you switch ranges. It is possible to avoid these problems with careful design but the circuit will end up being more com- Fig.1: block diagram of the oscillator. IC1c is a high frequency oscillator and its output is divided by 1, 10, 100 or 1000 by IC7b or IC8. It is then further divided by 2 and 5 before being applied to a divide-by-10 ring counter (IC2a, IC4 & IC5). This drives a resistor network which produces a stepped waveform which is fed to switched capacitor filter, IC6. plicated (see our low distortion design in the February & March 1999 issues). The second choice for an audio oscillator is typically a function generator but while these usually have good amplitude stability, their distortion content is usually fairly average. But now you have a third choice with this design which uses digitally generated sinewaves and employs a switched capacitor filter. While thumbing through the Jaycar Electronics catalog some time ago, I came across an “IC bargain”, an MF4CH-50 4th order switched capacitor Butterworth low-pass filter, for the trivial sum of $1.50. This set me thinking (I do that occasionally) about what level of distortion we would get if we fed a pseudo sinewave (digitally generated) into that sort of filter. Many moons later, this low cost audio oscillator is the outcome of those profound thoughts. The oscillator is housed in a plastic zippy box measuring 157 x 95 x 50mm. It has three knobs on the front panel and these are the 4-position range switch, the frequency control and the sinewave output control. As well, there is a toggle power switch and three RCA sockets for the sinewave output and two square wave outputs. The circuit is battery operated but could be run from a plugpack if you wish; more on that later. Theory of operation Before we go too far, we need to explain just what is a 4th-order switched capacitor Butterworth lowpass filter. Let’s do the low-pass filter first because it’s easy: as its name sug gests, a low-pass filter is one that lets low frequencies through (passes) but progressively blocks (attenuates) the higher ones. The frequency at which the response is 3dB down is called the turnover frequency. Now what does 4th-order mean? A 1st order low-pass filter has an attenuation slope of 6dB per octave above the turnover frequency and so a 4th-order has four times this or Performance • • • • • Sinewave output ...............................................2Hz - 20kHz, 0-2V RMS Square-wave output ................................2Hz - 20kHz, 5V peak-to-peak Square-wave x100 output ....................200Hz - 2MHz, 5V peak-to-peak Sinewave distortion ....................................................... less than 0.85% Current consumption............................. 15mA from +5V, 6mA from -5V 24dB per octave. This steep rolloff of high frequencies is used to get rid of the higher harmonics of our digital sinewave. The term Butterworth describes a filter response which is flat (0dB) until it begins to roll off. Other types of filters have a peak or ripples in the response before the rolloff begins. For audio work, the Butterworth response is usually the best and most suitable. Switched capacitor filters Any conventional filter circuit can be designed to roll off at any given frequency but this frequency can only be altered by changing the relevant resistor or capacitor values. For a 4th-order filter, this would mean changing the values of four resistors or four capacitors in precisely the same ratio. This makes things very complicated because an oscillator based on a variable 4th-order filter would then need a five ganged potentiometer, or a five ganged capacitor (if we include one for the actual frequency control). In practice, this approach would be just too expensive. This is where the MF4CH-50 switched-capacitor filter comes into the picture. It has four internal capacitors which are rapidly switched in and out of circuit to vary their values. Furthermore, the more rapidly they are switched, the less the effective capacitance. FEBRUARY 2000 59 60 Silicon Chip More specifically, the turnover filter frequency of the MF4CH-50 is 1/50th of its clock frequency, so if we clocked it at 50kHz it would begin to rolloff at 1kHz. Fig.1 shows the general concept of the oscillator and IC6 is the MF4CH-50 switched capacitor filter. IC1c is a high frequency oscillator and its output is divided by 1, 10, 100 or 1000 by IC7b or IC8. It is then further divided by 2 and 5 before being applied to a divide-by-10 ring counter (IC2a, IC4 & IC5). This drives a resistor network which produces a stepped waveform which is a very rough approximation of a sinewave which is 1/50th of the frequency output from IC2b. IC6, the MF4CH-50, is also clocked by the output of IC2b and so its turnover frequency exactly matches the output of the ring counter. It effectively removes the switching hash from the waveform, leaving a clean sinewave. Circuit description The circuit of Fig.2 is a little more complex but operates as we have just explained. While it may look to have a lot of circuit elements, it uses only nine low-cost ICs. Let’s start with IC1c, the master oscillator. It is a 74HC132 quad NAND gate with Schmitt trigger inputs configured as an oscillator, with the maximum and minimum frequencies adjusted using trimpots VR2 and VR3. These are set so that the sinewave frequency varies from just under 2kHz to just over 20kHz on the highest range and potentiometer VR1 then becomes the main frequency control. The frequencies for the other three ranges are generated by successively dividing this main frequency by 10 in IC8 and IC7b. These four frequencies are fed to range switch S1a which directs the selected frequency to IC2b (one section of a 4013 dual-D flipflop) and also Fig.2 (left): the master oscillator is IC1c and since it is a Schmitt device it requires trimpots VR2 & VR3 to set the maximum and minimum frequencies. Both IC1a & IC1b are unused but their inputs have been tied to related parts of the circuit. The circuit can be powered from a 9V plugpack, as shown in Fig.12. to IC1d which inverts and buffers the signal and feeds it to the front panel as SQUARE x 100. This signal is only an exact square wave on the lower three ranges which come from IC8 and IC7b. The top range comes direct from IC1c and its output is not a true square wave but has a high time of around 45% (the low time being 55%) of the oscillator’s frequency. As the oscillator output is inverted by gate IC1d, the high and low periods are also inverted (55:45). IC2b divides the selected frequency from S1a by two, giving an exact square wave which is required for the clock input of IC6, the switched capacitor filter. IC2b also drives IC3, a 4017 connected to divide by five. The output of IC3, pin 10, is fed to the clock inputs of flipflops IC2a, IC4b & IC4a and IC5b & IC5a. These five flipflops are connected as a twisted ring counter which divides the clock frequency by 10. The Q outputs of four of the flipflops are summed by the 10kΩ and 16kΩ resistors to produce a stepped waveform and this is fed to the input of the switched capacitor filter, IC6. The stepped input waveform and the filtered output can be seen in the scope waveforms of Fig.3. Quite a dramatic improvement, eh? Twisted ring counter What’s a twisted ring counter we hear you asking? In a normal D-type flipflop (such as IC2b), the Qbar output (pin 12) is connected back to the D input (pin 9). This causes the Q output to change from high to low and back to high again on sequential low to high transitions of the clock signal at pin 11. In our twisted ring counter the Qbar output of IC5a is tied back to the D input of IC2a. Assuming the Qbar output of IC5a was low, the Q output of IC2a would be low and this low would then be propagated through the chain until the low level was applied to IC5a. This would cause the Q output to go low and the Qbar output to go high. Thus a high would be presented to pin 5 of IC2a and it would be propagated through the chain. It is “twisted” because a low level on IC5a’s Q output (the main output) propagates a high through the chain and vice versa. While it is hard to visualise, what happens is that a high is moved Parts List 1 PC board, code 04102001, 149 x 71mm 1 plastic box, 50mm x 90mm x 150mm with aluminium lid 1 front panel label, 150 x 85mm 1 2-pole 6-position PC mount rotary switch with two nuts (S1) 1 DPDT miniature toggle switch (S2) 3 panel-mount RCA sockets 2 25kΩ linear potentiometers (VR1, VR4) 3 knobs to suit 1 2kΩ horizontal mounting trimpot (VR2) 1 200kΩ horizontal mounting trimpot (VR3) 2 9V batteries 2 battery snap connectors Semiconductors 1 74HC132 quad NAND Schmitt trigger (IC1) 3 4013 dual D flipflop (IC2,IC4,IC5) 1 4017 decade divider (IC3) 1 MF4CH-50 switched capacitor filter (IC6) 2 74HC390 dual decade divider (IC7,IC8) 1 TL071 op amp (IC9) 1 78L05 5V regulator (REG1) 1 79L05 -5V regulator (REG2) Capacitors 1 100µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 4 0.1µF monolithic ceramic 1 .033µF MKT polyester 1 .0033µF MKT polyester 1 820pF 10% ceramic 1 330pF 10% ceramic 1 220pF 10% ceramic 1 33pF 10% ceramic Resistors (1%, 0.25W) 1 68kΩ 3 10kΩ 1 47kΩ 2 3.3kΩ 1 33kΩ 1 1kΩ 2 16kΩ For 9V AC plugpack operation Delete 9V batteries and snap connectors 1 panel mounting connector to suit 9V AC plugpack 2 1N4001, 1N4004 power diodes 2 100µF 25VW PC electrolytic capacitors 1 tag strip FEBRUARY 2000 61 The PC board is mounted on the back of rotary switch S1 which in turn is mounted on the front panel. However, you may prefer to further secure the board to the front panel by fitting a mounting pillar at each corner, particularly if the unit is going to be moved about. through the ring and this is followed by four more highs. As each Q output goes high, the stepped waveform of Fig.3 is produced by summing the Q outputs. Once the first high reaches pin 1 of IC5a (pin 2 will be low), a series of lows is shifted through the ring, causing the steps to fall towards 0V and this cycle repeats over and over. The clock frequency fed to the ring counter is also divided by 10 in IC7a, giving a true square wave output at the same frequency as the sinewave output. We found that the output amplitude from IC6 (MF4CH-50) increased on the highest range, starting from around 10kHz. The resistor/capacitor network between the output of IC6 and the sinewave level control VR4 help to flatten the output in this region although even with these components the response is still +1dB at 20kHz. Op amp IC9 is used as a sinewave output buffer with a gain of 3, to 62 Silicon Chip make up for the losses in IC6 and the two 3.3kΩ resistors in series with the output level control (VR4). It also sets the maximum output level to 2V RMS. While the switched capacitor filter does a good job of producing a clean sinewave, there is still some switching hash present and we do some more filtering in IC9. This is done by using S1b, the second pole of S1, to switch a capacitor across the feedback resistor of IC9 on each range. This helps to attenuate the high frequency switching spikes. This causes a rather interesting effect. The measured distortion actually decreases slightly as the frequency increases on each range, rather than the normal case where the distortion increases as the frequency increases. Mind you, since the hash is 50 times the fundamental, it is not the slightest bit audible until the fundamental frequency drops below about 200Hz. The sinewave output is symmetrical above and below the 0V line (ground) and is variable from 0V to 2V RMS which should be sufficient for any normal audio work. We fitted two voltage regulators on the PC board and these are fine for battery operation. If you plan to use a plugpack you will need to add two capacitors and two diodes which can be wired to a tag strip. This is explained in more detail later. Output & distortion waveforms As noted in the performance panel, the distortion content of the sinewave output is less than 0.85% but this depends on the frequency and the bandwidth of the measurement. The scope wave forms of Figs.4, 5, 6 & 7 demonstrate this. Fig.4 shows a 1.1kHz waveform on the top trace and the lower trace is the modulated distortion product which is mainly the 50kHz switching hash. This is equivalent to a harmonic distortion content of 0.83%, taken with a measurement bandwidth of 80kHz (ie, all Fig.3: these scope diagrams show the operation of the switched capacitor filter (IC6). The top trace is the stepped waveform and the lower trace is the sinewave output. Fig.4: the sinewave output at 1.1kHz (top) has a very slight “jagginess” due to 50kHz switching artefacts. The lower trace is the modulated distortion product – mainly the 50kHz switching hash (0.83% THD <at> 80kHz bandwidth). Fig.5: a 1kHz waveform is shown on the top trace, while the lower trace is the distortion waveform, measured with a bandwidth of 22kHz. (THD 0.26%). Fig.6: the top trace is a 10kHz sinewave while the lower trace is the residual harmonic content measured with an 80kHz bandwidth (THD 0.285%). Fig.7: the top trace is the sinewave output at 19.6kHz and the lower trace is the distortion which has a level of 0.76%, measured with a bandwidth of 80kHz. Fig.8: the 20kHz sinewave output (top) and the squarewave output. The lefthand cursor is not set correctly and so the frequency measurement of 20.7kHz is wrong. FEBRUARY 2000 63 Fig.9: this is the component layout for the PC board and it also shows the wiring to the front panel. harmonics and noise up to 80kHz are included in the measurement). Fig.5 shows a 1kHz waveform on the top trace but this time the distortion waveform on the lower trace has been measured with a bandwidth of 22kHz. This has removed most of the 50kHz hash from the measurement and results in a THD figure of 0.26%. The top waveform of Fig.6 is a 10kHz sinewave and the lower trace is 64 Silicon Chip the residual harmonic content measured with an 80kHz bandwidth. The result is a distortion measurement of 0.285%. Note that for an output at 10kHz, the switching hash would be at 500kHz and this would be well and truly eliminated by an 80kHz filter. Fig.7 shows the output waveform at 19.6kHz and its accompa nying residual distortion which has a level of 0.76%, measured with a bandwidth of 80kHz. In this case the switching hash would be at 980kHz. Finally, Fig.8 shows two waveforms at 20kHz. The top is the sinewave output and the lower trace is the accompanying square wave output. Construction All the circuit components, with the exception of the two potentiometers, are mounted on a PC board We used double-sided tape to secure the batteries but you might prefer to use battery holders fastened to the bottom of the case. measuring 149 x 71mm and coded 04102001. The component wiring diagram and the connections inside the case are shown in Fig.9. While we have made provision for mounting pillars at each corner of the PC board, our method of mounting is somewhat simpler – we just supported it on the back of the rotary switch, S1. It is a good idea to check the PC board against the artwork of Fig.11 before beginning the assembly. Check for any undrilled holes or broken or open circuit tracks and fix any defects that you find. Capacitor Codes         Value IEC Code EIA Code 0.1µF 100n 104 .033µF 33n 333 .0033µF 3n3 332 820pF 820p 821 330pF 330p 331 220pF 220p 221 33pF 33p 33 Resistor Colour Codes         No. 1 1 1 2 3 2 1 Value 68kΩ 47kΩ 33kΩ 16kΩ 10kΩ 3.3kΩ 1kΩ 4-Band Code (1%) blue grey orange brown yellow violet orange brown orange orange orange brown brown blue orange brown brown black orange brown orange orange red brown brown black red brown 5-Band Code (1%) blue grey black red brown yellow violet black red brown orange orange black red brown brown blue black red brown brown black black red brown orange orange black brown brown brown black black brown brown FEBRUARY 2000 65 The connections between the PC board and the front panel hardware can be run using light-duty hookup wire. Keep the lead lengths reasonably short to maintain a neat appearance (you can use cable ties if you wish). tion correct (not upside down) before soldering the 12 outer lugs. The locking tab on the switch can now be set to position 4 (so that the switch has only four positions). This done, solder the battery leads to the switch and complete the wiring, as shown in Fig.9. By the way, we used a zippy box with an aluminium front panel as the frequency control is sensitive to hand capacitance. If you wish to use a plugpack instead of batteries, you will need a 9V AC plugpack and a rectifier circuit wired to provide positive and negative supplies, as shown in Fig.12. This circuit consists of positive and a negative half-wave rectifiers, each feeding a 100µF electrolytic capacitor. The extra components can be wired onto a length of tagstrip. Testing the oscillator This view shows how the PC board is supported on the back of the rotary switch. Note that this switch mounts on the copper side of the board. Begin by installing the PC pins, wire links and resistors, followed by the trimpots and IC sockets, which are optional. This done, insert the smaller capacitors, followed by the two electrolytic capacitors which must be installed the right way around. Next, solder in the CMOS ICs. To do this, earth the barrel of your soldering iron to the 0V line on the PC board and solder the supply pins of each IC first, followed by the other pins. You can now install the two regulators. Make sure that you put each one in the correct position otherwise the circuit definitely won’t work. must fit two wire links on the back of the switch as shown in Fig.10. This done, insert it in the PC board from the copper side. The lugs should be flush with the laminate side. Check that you have the orienta Calibrating the oscillator Rotary switch mounting The rotary switch is mounted on the copper side of the PC board (as shown in the photos) and this means that it is impossible to solder the two centre pins of the switch to the PC board. Therefore, before you mount it, you 66 Silicon Chip You will need a multimeter and a frequency counter or an oscilloscope to calibrate the oscillator. Turn on the batteries or plugpack. Check for +5V at pin 7 of IC9 and -5V at pin 4. These voltages should be within 0.5V. If the voltages are correct turn off the power and insert the ICs if you used sockets. Power up again and check for +5V on pin 14 of IC1, IC2, IC4 & IC5, pin 16 of IC3, IC7 & IC8, and pin 7 of IC6. Also check for -5V on pin 4 of IC6. With the sine level control fully clockwise and the 200Hz - 2kHz range selected, you should measure about 5.6V peak-to-peak with your oscilloscope. If using your multimeter, you should be able to measure 2V RMS at the sinewave output. Using an oscilloscope or a frequency counter check that the X1 square wave frequency is the same as the sinewave frequency and that the x100 output is also correct. Fig.10: the two centre pins of the rotary switch must be wired as shown before it is installed on the copper side of the PC board. The last step is to calibrate the oscillator. Turn VR3 and VR1 fully clockwise and adjust VR2 until the sine wave frequency is 20.5kHz on the 2-20kHz range. Now turn VR1 fully anticlockwise and adjust VR3 until the frequency is 1.95kHz. There will be some interaction between the two presets, so you may have to make these adjustments a couple of times to get the frequencies just right. As the lower ranges are generated by digital division they will track exactly. Fig.11: here are the actual size artworks for the PC board and the front panel. If you cannot get the frequency adjustment right, set VR3 and VR1 fully clockwise and VR2 to centre. Check the oscillator frequency then alter the 220pF capacitor on pin 10 of IC1c until you are close to 20.5kHz. Then follow the calibration instructions once again. If the frequency is too high, fit an extra capacitor in the holes adjacent to the 220pF capacitor. If the frequency is 20% high, add a 47pF capacitor. Conversely, if the frequency is low you will have to reduce the 220pF to 180pF or less, then perhaps fit a small SC value as described above. Fig.12: use this circuit if you wish to power the oscillator from a 9V AC plugpack. FEBRUARY 2000 67 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Using a photo-interrupter as a train detector The most common approach to detecting trains on model rail way layouts is based on detecting the current drain of locomotives on sections of track (Twin-T detectors etc) or uses reed relays under the track with magnets attached to the rolling stock. A more convenient approach is to use light beams but this means you usually have to devise your own optical detectors. This approach makes use of the photo interrupters used in many printers. The interrupter is a slotted module with an infrared light emitting diode in one half and a photo transistor in the other. By cutting the inter- rupter in half and positioning the two halves on either side of a section of track, you have a good train detector. The circuit feeds the voltage from the emitter of the photo-transistor to the input of a Schmitt trigger gate and its output drives a transistor and relay. The idea can be extended to suit a range of model railway applications, with the Schmitt trigger being used to trigger flipflops for signalling and automatic reversing circuits and so on. Suitable photo interrupters are available from Jaycar Electronics (Cat. ZD-1901). SILICON CHIP. How to cut clean holes in plastic front panels Monitor for 12V SLA batteries One of the disadvantages of sealed lead acid (SLA) batteries is that if they are too far discharged they become permanently damaged and cannot be recharged. Therefore it is good practice to make sure that 12V SLA batteries are not discharged below 11V. This little circuit monitors the output of a 12V SLA battery and can be set to light a flashing LED when the voltage drops below 11.3V. IC1 is an LM336 2.5V reference and is connected to the noninverting input (pin 3) of op amp IC2 which is connected as a com68 Silicon Chip parator. The battery being monitored also powers the circuit and a portion of its output is fed to pin 2 via trimpot VR1. When pin 2 drops below pin 3, the output at pin 6 goes high to turn on transistor Q1 and the flashing LED. The base of Q1 is fed via a voltage divider consisting of the 15kΩ and 10kΩ resistors, to ensure that Q1 does not turn on when the output of IC2 is low. VR1 should be set so that the LED flashes when the circuit voltage drops to around 11.3V, to give adequate warning of exces sive discharge. Laurie Marshall, Barrack Point, NSW. ($30) This method for cutting round holes came about as a result of the article on making front panels in the February 1999 issue. The suggested method of cutting the holes using a sharp scalpel can be rather tedious, especially if quite a few holes are required. My method is to use a wad punch (a hollow punch), rubber mallet and a block of wood to make the holes. If the sizes of the holes in the artwork are made so as to be just visible around the circumference of the wad punch, a perfectly placed hole will be achiev ed every time without the danger of slipping and ruining the whole panel. A set of 12 cheap wad punches covering the range 3.2mm to 19mm can be obtained for around $15 and are adequate for this application. For smaller holes (eg, for LEDs and screws), a handheld leather punch can be used. I apply a self-adhesive laminate (no laminating machine required) to both sides of my artwork to make them stiffer and more durable. Small panels don’t need to be glued on and can be held in place by the hardware. Barry Hubble, Moulden, NT. ($25) 12V fan controller for lower noise If you wish to use a 12V computer fan for general cooling or you want to add it as an extra to your computer, you may find it worthwhile to cut the speed as it can make a big difference to the noise it produces without cutting the airflow too much. This circuit provides an extra benefit of temperature control by incorporating a thermistor so the fan will be run at full speed as necessary. Op amp IC1 is connected as a comparator and the thermistor is connected to its inverting input, pin 2. The non-inverting input, pin 3, is connected to trimpot VR1 and this provides the means for setting the temperature. The thermistor has a negative temperature coefficient (NTC) and when the temperature is high its resistance will be low. This causes the voltage at pin 2 of IC1 to be low. If pin 2 is below the set-point of VR1, the output at pin 6 will be high and this will switch on transistor Q1 and the relay. As the thermistor is cooled by airflow from the fan, its resistance will rise, the voltage at pin 2 will also rise and the op amp’s output will switch low, causing Q1 and the relay to switch off. Since the 741 op amp cannot switch its output to 0V but only to about +2V or so, a 4.7V zener diode is connected in series with the base of Q1 to prevent it turning on when the output is low. The 1MΩ positive feedback resistor between pins 3 & 6 of op amp IC1 provides a degree of hysteresis so that the relay does not chatter at close to the switching point. The 30Ω 1W resistor may need to be varied to suit your 12V fan but should be selected to give around 8V across the fan motor when the relay is off. The thermistor should be mounted on the object to be cooled or in the airflow from the fan. Paul Walsh, Montmorency, Vic ($30) Constant current load for power supply testing While resistive loads can be used when testing power supplies and driver circuits, if the current is DC, it is better to use a semiconductor constant current load. This has the advantage that it can be set to provide any desired current and it will maintain it even in the supply voltage varies. With this circuit, taken from a Maxim application note, you can select a current within a range up to 1A or 10A with switch S2 and then precisely set the current with potentiometer VR3 which ideally should be a 10-turn type for high setting accuracy. IC1 is a 1.2V bandgap reference and it provides a very precise voltage reference for the circuit. Its output is fed via resistors to trimpots VR1 and VR2 and then to pin 3 of op amp IC2. These trimpots are adjusted to provide 1V for the 10A range and 100mV for the 1A range. IC2 and Mosfet Q1 are connected so that the voltage across the 0.1Ω resistor is maintained at the same level as that set at pin 3; ie, it maintains a constant current. The Mosfet needs to be mounted on a large heatsink and the circuit is suitable for testing at supply voltages between about 2V and 50V. Note that it could not handle a 50V supply at 10A; the total dissipation of 500W would vaporise Q1! Note that the op amp must be able to switch its output to 0V and its input common mode range must be able to go to 0V. SILICON CHIP. FEBRUARY 2000 69 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. No.________________  Gift subscription  RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. GST)**  $A159  $A83 New Zealand (airmail)  $A145  $A77 Overseas surface mail  $A160  $A85  $A250 Overseas airmail  $A125 **1 binder with 1-year subscription; 2 binders with 2-year subscription YOUR DETAILS Your Name_________________________________________________ GIFT SUBSCRIPTION DETAILS Month to start__________________ Message_____________________ _____________________________ _____________________________ Gift for: Name_________________________ (PLEASE PRINT) Address______________________ _____________________________ (PLEASE PRINT) Address___________________________________________________ State__________Postcode_______ ______________________________________Postcode_____________ Daytime Phone No.____________________Total Price $A __________ Signature  Cheque/Money Order  Bankcard  Visa Card  Master Card ______________________________ Card No. Card expiry date________/________ Phone (02) 9979 5644 9am-5pm Mon-Fri. Please have your credit card details ready 70 Silicon Chip OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia PRODUCT SHOWCASE Pro Soldering Setup from Altronics Whether your interest is at advanced hobbyist level or perhaps more in the manufacturing/assembly area, two new products from Altronics Distributors are worth a second look. Together they could form a very professional soldering set-up. First is the Micron Soldering Station (Cat T2438), offering electronic temperature control to ±2°C over a 200° – 500°C range, with digital temperature display. The station features a long-life Japanese ceramic heater element and new tip/heater design and the iron itself has an iron-clad long-life tip. Zero-voltage switching is used. This not only minimises RFI but also helps prevent voltage spikes at the iron tip which may damage sensitive devices. Incorporated into the station is a sponge tray and a soldering iron holder. With fast heat-up and recovery time the soldering station is highly suitable for repetitive assembly work as well as most other electronics construction and service tasks. Recommended retail price is $239. Replacement tips in 0.8mm micro chisel, 1.6mm mini chisel and 3.2mm standard chisel are available at $12.95 each. The second product is a fume extractor (Cat T-1290). For some time concerns have been raised about the dangers of long-term exposure to fumes given off by soldering processes – not just the fumes released by the flux but also the melting of the solder itself (which of course has a high lead content). This simple mains-operated device Ultrasonic Parking Sensor Elsewhere in this issue there is an Ultrasonic Parking Radar to build. But if you don’t have the time, the inclination or the energy to do-it-yourself, Jaycar Electronics might just have the answer – a built-up version. It works in exactly the same way as the do-it-yourself version except this one also has a coloured LED scale to show you the distance before crunch time. The ultrasonic transmitter and receiver are mounted in the one block which makes mounting a lot easier, even if distance is sacrificed. Mounting and operating instructions are included. The Jaycar Ultrasonic Parking Radar (Cat LR8860) is priced at $89.95 and is available from all Jaycar Electronics stores and authorised resellers. consists of a hood containing an open-mesh foam filter (similar to those used in fish tanks) through which air is drawn by a fan. The idea is that the fumes of soldering will be sucked in, trapping the larger particles in the filter but in any case directing the fumes away from the user. Recommended retail price is $139.95 Both products are available from Altronics Distributors retail and mail order centre in Perth (freecall 1800 999 007), via their website (www.altronics. com.au) or from Altronics resellers throughout Australia. Keeping in touch – the CB way Gone are the dull black or silver hand-held CB radios! This new Kenwood UBZ-LF48 UHF CB from Dick Smith Electronics doesn’t need a licence to use and is ideal for short-range communications, whether it is for pleasure or business. With just 300mW output it’s not going to set any distance records but that’s not the idea. The small handheld is intended for applications where the person you want to talk to is out of shouting range – say up to a couple of kilometres or so. It operates on three “AA” batteries, giving up to 40 hours use. An auto power-off function will help conserve the batteries when not in use. It also has a keylock, a swivel antenna and belt hook – and an inbuilt voice scrambler if you want to maintain privacy. You can use any of the 40 UHF CB channels, selectable via up/down push buttons, while using it is as simple as pressing the “talk” button to talk. Priced at $199 (Cat D-1744), the Kenwood transceiver is available from all Dick Smith Electronics stores, DSE PowerHouse stores, authorised resellers, via mail order or the website, www.dse.com.au And by the way, you can get it in black if you really want to! FEBRUARY 2000 71 Fluke’s new ScopeMeter 190 hand-held ’scopes The new 190 Series of handheld oscilloscopes from Fluke is designed to meet the needs of service professionals and electronic engineers involved in systems integration, installation and second-line services. The top model in the range offers up to 200MHz bandwidth and 2.5 GS/s real-time sampling using separate digitisers on both isolated inputs. In addition the 190 Series has a memory of 27,500 points per input for long, high-resolution recording. This continuous roll mode stores signals for up to 30 hours while still capturing past intermittents and glitches as fast as 50 nsec. They will operate for four hours on a single battery and, without the need for forced draft cooling, it is possible to put the ’scope in a sealed, dust and drip proof case. The ScopeMeter 190 Series features automatic triggering which provides a stable and accurate display of virtually any signal, whatever the signal complexity or dynamics, without the need for setting up the instrument. The series also offers various manual triggering modes such as edge, pulse width, video (line count and field select), delay and external triggering. This gives the engineer the trigger power to capture virtually any signal. A replay button is also provided which provides access to the last 100 screens. These can be re-displayed one by one or played continuously as a “live” animation. With the advanced trigger capabilities, the same feature automatically captures up to 100 predefined intermittent glitches and signal anomalies. Other features include cursors, 24 automatic scope measurements, a real-time clock, real-time sampling per input, a zoom function for detailed signal analysis of single sample measurements and 2 x 100 waveform. 10-setup memories allow for easy storage, recall and analysis, making printing or documenting waveforms quick and easy. Included is a 5000 count true RMS multimeter and a “paperless” recording mode for graphing meter and automatic scope measurements, with the possibility to use cursors and store recordings for later analysis. For more information, contact Fluke Australia, 26/7 Anella Ave, Castle Hill, NSW 2154. Phone (02) 8850 3300, fax (02) 8859 3300 or www. fluke.com/scopemeter As well as full product specs, a virtual demonstration also is available on this web page. Sony launches new SACD format and equipment to suit According to Sony, their new Super Audio CD (SACD) will be the “next generation” audio carrier, differing from conventional compact discs by not only reproducing the music but also recreating every detail of the atmosphere, nuance and space surrounding the original music source. SACD, which was released in Australia just before Christmas, is initially targeted mainly at audiophiles who are seeking the highest level of sound quality. Sony Australia’s Managing Director, Haruyuki Machida, said that his company’s aim was to establish SACD as a format which offers a significantly enhanced listening experience compared to any current technology, compact disc included. “We could conceivably implement SACD playback capability into our entire line of CD players,” he said. Sony started work on the new 72 Silicon Chip technology back in 1991, resulting in the development of Direct Stream Digital (DSD) – the heart of the new SACD. Using a sampling rate of 2.8224MHz to directly record a 1-bit signal, Sony claims the reproduction is infinitesimally close to the original source material. The need for decimation filtering in both recording and playback is eliminated and with a theoretical frequency range of 100kHz and dynamic range of more than 120dB across the audible range, recordings in DSD can reproduce even the most minute high range musical elements. SACD also contains advanced anti-piracy and copying protection including both visible and invisible watermarking on the disc (SACD players will reject invalid discs) and, if required, content encryption. SACD will be available in several disc formats including a hybrid construction which will allow playback on standard CD players. Along with the discs, Sony has announced equipment designed to handle the full potential of SACD. Included in the range is the TA-E1 preamplifier, the TA-N1 power amplifier, the TA-FA777ES integrated stereo amplifier and a speaker system, the SS-M9ED. A new Super Tweeter System (SS-TW100ED) is also available which will extend the range of conventional speaker systems to 100kHz. Sony make no pretence that this equipment is intended for a very limited (up!)market: the preamp-lifier, power amplifier and speaker setup alone carries a retail price of around $55,000. If you only want the Super Tweeter System to add to your existing system, be prepared to pay about $2000. For more information, visit the Sony website, www.sony.com.au or call (02) 9878 9712. dScope III audio test & measurement The new Prism Sound dScope Series III offers high precision generation and measurement of analog and digital audio signals as well as digital audio carrier analysis, all in a compact and convenient package which operates with any IBM-compatible notebook or desktop PC. No special interfacing software is required. The software operates under Windows (95, 98, 2000 or NT) and while the user interface is highly versatile, operation is delightfully simple. For more information, contact the distributors, Control Devices at Level 1, 150 William St, East Sydney NSW 2011; telephone (02) 9356 1943 or email controldevices<at>mira.net Test & measurement catalog Nutek Australia have available a free catalog containing a large range of Leader test and measurement equipment. Intended for all levels from the hobbyist through to the engineer, the catalog contains everything from multimeters and oscilloscopes through to waveform monitors and vectorscopes, wow and flutter meters and TV pattern generators. For your copy, contact Nutek Australia on (02) 9894 2377, fax (02) 9894 2386. Flexiglow Cable – it glows! A new range of electroluminescent cable called “Flexiglow” has been released by Dick Smith Electronics. The cable, originally developed for military use, has a chemical coating which glows when a current is applied. Unlike other cable lighting, illumination is constant throughout its length. Applications include advertising, signage and display work or even some pretty neat Christmas decorations (you’ve only got about 330 days to work on them!). The cable is only 3.2mm in diameter and can therefore be formed into any shape you wish – even around tight corners. Colours available are red, green, yellow and ultramarine blue. It is sold by the metre with a retail price of $19.25 per metre. To power the wire, a DC adaptor and inverter are required. There are two inverters available, one to suit 5 to 25 metre lengths (Cat. No. S 4596 <at>$79) and the other for 25 to 100 metre lengths (Cat. No. S4597 <at> $169.) An appropriate 12V DC adaptor is the Cat. No. M9670 <at> $33.50. You won’t find Flexiglow in your local DSE store because it is only available from the DSE “PowerHouse” stores at Moore Park, Bankstown and Penrith (NSW) and Carnegie and Nunawading (Vic) or from the Direct-Link mail order service (1300 366 644) or website, www.dse.com.au Central Coast Amateur Field Day Just a reminder – the Central Coast Field Day is on this month. It will be held at Wyong Racecourse (about 1 hour north of Sydney) on Sunday, February 27 from 8am. For futher information see last month's SILICON CHIP or contact the Central Coast Amateur Radio Club: PO Box 346, Woy Woy NSW 2256, phone (02) 4340 2500, email bobfitz<at>ozemail.com.au, website www.ccarg.org.au AUDIO MODULES broadcast quality Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 New semis from REC Electronics REC Electronics, Australian and New Zealand distributors of Linear Technology semiconductors, have a number of new LT devices in their range. In brief, these include: LT1402, a 2.2Msps A-D converter which features a high-speed serial interface. 80MHz sample-and-hold bandwidth with 72dB SINAD and 89dB THD. 16-pin SSOP package (SO-8 footprint). LT1578, a 200kHz monolithic buck mode switching regulator offering a compact DC/DC convert solution for 5V to 3.3V or lower conversions (adjustable to 1.2V). Incorporates all oscillator, control and protection circuitry for a complete switching regulator. 8-pin SO package. LT1721, a 16-pin SSOP- or SO-packaged ultra-fast quad comparator with 4.5ns propagation delay and 2.7V – 6V operation. It draws only 4mA per comparator. LT1886, containing two high-gain bandwidth, high-speed op amps capable of providing a minimum of 8.6VP-P at 200mA on a ±6V or single 12V supply with extremely low total signal distortion. SO-8 package. LT1986, a micropower charge pump which provides the smallest power supply for dual-voltage SIM cards in GSM cellular phones. VOUT stays within the 3V SIM VCC specification even when the VIN is as low as 2.6V. 6-lead SOT-23 package. For more information, contact REC Electronics, Unit 1, 38 South St, Rydalmere NSW 2116. Phone (02) 9638 1888, fax (02) 9638 1798. FEBRUARY 2000 73 AMD x86 chip hits 800MHz . . . . . . while the K6-2/3DNow reaches 533MHz AMD has released the world’s fastest and most powerful x86 processor with its new Athlon CPU running at a rather brisk 800MHz! This translates to unequalled performance for high-end computer applications, particularly in video, graphics, CAD, audio and digital content creation. The 800MHz chip is based on AMD’s aluminium 0.18-micron manufacturing process. This shrinks the size of the die, enabling faster speeds and lower power consumption. The AMD Athlon chip is an x-86-compatible, seventh-generation design featuring a superpipelined, nine-issue superscalar microarchitecture optimised for high clock frequency. It includes 128KB of on-chip level (L1) cache and a programmable, high-performance backside L2 cache interface. Computer manufacturers using, or planning to use, the new chip include industry leaders Compaq and IBM. They’ll be paying $US849 for each chip in 1000-unit quantities (about $AU1300). POSTSCRIPT: 1GHz reached! AMD and Compaq demonstrated a 1GHz Athlon at the Winter CES. Air block alarm system from DSE Hioki’s new non“No-shield” variablecontact thermometers speed drive filter Where most security systems use either motion detectors or physical switches to detect intrusion, a new alarm system from Dick Smith Electronics uses the change in pressure when a door or window is opened to trigger the alarm. The fully portable and self-contained Air Block Alarm System is therefore suitable for use in any type of property from homes and offices to cars, boats and caravans. Along with its 110dB alarm siren, the system also has a pleasant chime “alarm” for applications such as shop or office “door minders”. Sensitivity is adjustable to protect any area from two square metres up to five hundred square metres. It is powered by six “AA” batteries and is controlled by one key. The Air Block Alarm is priced at $199 and is available from all Dick Smith Electronics stores, Dick Smith PowerHouse stores or via the Direct Link mail order service (freecall 1300 366 644). For more information or to order on-line, visit www.dse.com.au Hioki have released three non-contact thermometers with applications in the food, scientific and hazardous goods industries. Because they measure temperature by reading the radiant flux emanating from the object to be measured, no contact with the object or surface is required. This results in zero contamination of the object or exposure to the user. Each measures from –50°C to +500°C with a resolution of 0.1°C. A 95% temperature change can be read in 1.6 seconds. An optional computer interface is available which allows data logging and massaging. The three models released are: Hioki 3443 – 24mm diameter measuring field at a distance of 1m. Has on-board memory for 130 temperature readings. Hioki 3444 – same field and distance but with real-time output is suitable for continuous monitoring. Hioki 3445 – also with real-time output but is intended for spot measuring with a 2.5mm field at 70mm. For more information contact Nilsen Technologies, 150 Oxford St, Colling-wood, Vic 3066. Freecall 1800 623 350, freefax 1800 067 263. 74 Silicon Chip At the same time as the very fast AMD Athlon release, AMD announced its popular Intel-alternative, the K6-2 with 3DNow technology, has reached an impressive 533MHz. The 9.3-million transistor K6-2 is manufactured on AMD’s 0.25-micron, five-layer metal process technology. The K6-2 chip is intended for machines for the small business and consumer markets which are significantly more price-sensitive than those for top-end applications. It is packaged in a Super7-platform compatible, 321-pin ceramic pin grid array. This also adds to its appeal for socket-7 motherboard manufacturers. The K6-2 sells for $US167 ($AU265) in 1000-off quantities. The Schaffner FN 5100 series of filters for variable speed drives eliminates the need for expensive shielded cables. This makes them ideal for retro-fitting in existing drive installations or in new installations requiring long cable runs. They represent an economical solution to the need for EMC-compliant installations. The filters not only minimise the emission of RF interference but also help protect the motor by limiting sharp voltage slews (dV/dT). The FN5100 is available for line voltages to 480V AC and in current ratings from 6A to 63A. For more information about Shaffner filters contact their distributors, Westek Industrial Products Pty Ltd, Unit 2, 6-10 Maria St, Laverton Nth, Vic 3026. Phone (03) 9369 8802, fax (03) 9369 8006 or email info<at> westek. com.au The company’s website is at www. SC westek.com.au SERVICEMAN'S LOG Projection TV – from many angles In the course of my service career, I have come across quite a few projection TV sets. Normally I shun these because of the logistics involved in servicing them. In-situ servicing can be difficult in many cases while the sets are just too big to easily transport back to the workshop. I was once asked to repair a projection TV set in a hotel and being more naive (and hungrier) than I am today, I attended the set to find that although it worked, it had no green. But the real problem was that it was switched on and the drinking clients were waiting to watch a world heavyweight title fight. The hotel manager had not mentioned this; he had simply told me that the set was in the lounge and left me to fix it. However, as I started to work on it, one belligerent and somewhat intoxicated customer decided that I was about to damage the set and felt that it was incumbent upon him to protect it. I count myself lucky that I was able to get out of there without personally being readjusted – and projected! Thereafter, I made it a strict policy: no house calls to pubs – ever. If they want their sets fixed, they can deliver them to me at the workshop and handle the delivery costs. I have also been forced to apply the same policy to property managers and other time wasters. The scenario normally goes along these lines. It starts with a request to pick up keys from a real estate office (usually in a busy street in a long No Stopping zone) and go immediately to flat 27 on the third floor in an old building (with no lift) and fix an ancient unnamed TV set with an unspecified intermittent fault – straight away. They then want you to return the keys and submit your account for payment within 90 days. Oh yeah! – if I’m lucky. And then only after them first questioning and whingeing about the cost. Many of my colleagues know how to deal with this – they charge like wounded bulls. Personally, I prefer to just politely refuse – it’s not worth the hassle or my time. If they want the set fixed, they can bring it to me and pay when the job is done, just like everyone else. However, I did make an exception recently when Mr Schultz, a well-spoken businessman, asked me to attend to a rear projec tion TV set he had just imported from Germany. It was a 117cm (46-inch) RP46 Thomson employing an ICC9 chassis, about four years old. Apparently it had been working perfectly in Germany but the picture was distorted and blurred when workmen had unpacked it and installed it in its new location in Australia. A local company had sent a technician along and he reported that one of the boards had been cracked and that the set was probably a write-off. I was asked to check it out and give a second opinion Sets Covered This Month • • • • Thomson RP46 projection TV set Seleco SVT 150 projection TV set Dual Digital Concept TV4170 TV set Sony KV-X2931S TV set on behalf of the insurance company. Fortunately, I already had experience with this series of sets and have had similar problems with cracked convergence boards which are held along one edge, needing only one quick jar to put an unacceptable strain on the mounting. And so I agreed to call and make a brief examination, to confirm or refute this diagnosis. Sure enough, the picture on the screen had colour but was distorted in all geometric settings. In addition, both the static and dynamic convergence settings were way off. To get to the convergence module, I had to remove the loudspeaker baffles and find the concealed screws that allow the front panel to come off. This done, access to this board is easy. However, although none of the controls worked, the board looked pristine with no sign of a crack. I replaced the front panel and removed the back. The irritating part of this is the need to use a Torx anti-tamper screwdriver for some screws and a 4BA spin-tight for others. That done, I was able to locate the convergence power supply on the righthand side. I measured voltage going in but none coming out and decided that this was where the problem might be. I removed this unit and told the client that I would take it back to the workshop. The power supply was a conventional switchmode FET type but the major problem was trying to match the component numbers from the circuits with those on the boards. For example, the chopper transformer is shown on the circuit as TR01 but on the board layout it is marked T7100. There is a note on the circuit and a small chart under the heading – and I quote – “Conv. of europ. Names to US names.”, where these items are shown. But it gets worse when identifying the connecting plugs and sockets. For example, BS02 becomes J7002 (mark ed J2 on the board), which connects FEBRUARY 2000 75 with J8204 on the convergence generator board, which then translates to J204 and then BE04. It was all very confusing. Anyway, there was no sign of the power supply even oscillating. I went straight to the start-up resistors RP09 (R9U) 100kΩ and RP18 (R18) 220kΩ and measured them. The former was OK but the latter was nearly open circuit. I replaced it and the whole thing fired up properly. I returned with it, refitted it to the set and after some adjustment of the controls, the set gave a very good picture. Mr Schultz was happy on one hand that his set was now OK – but unhappy on the other hand because he had to pay for the repair rather than the insurance company. However, it just wasn’t possible for him to claim on his insurance. After all, how could one faulty resistor be put down to accidental damage through shipping? Another projection set The next projection set I had to repair was for a club that had bought a secondhand Seleco, which wasn’t 76 Silicon Chip working. Unlike the Thomson, this was a front projection system, the picture being projected onto a wall screen. The set itself was a 1987 model SVT 150 and was worth around $12,000 new. This one had to go directly back to the workshop and I don’t know why I took it on, as I didn’t even have a circuit – I suppose I was just curious to see what one gets for $12,000. Removing the covers revealed immediately that it was very corroded. The only positive aspect was that I recognised the construction and layout of the boards as being similar to the Fujitsu General series of colour TV sets made in Italy at about the same period. Indeed, the main deflection board was marked BS950, the same as for a Fujitsu General FGS281PTXT. Even the remote control was the same (30D3). This was a stroke of luck because it meant that I now had a circuit. I started by switching it on and there was a brief display, then an “electronic click”, followed by silence – something had just died. After a more detailed investigation, I found the set had been endowed with two power supplies and the one marked BS820 had failed. Fortunately, it was a very conventional supply and I replaced the chopper transistor (BU508A, T601), four electrolytic capacitors and two resistors and fuse F451. Coils TR454 and TR453 (20µH) had been slightly melted but apart from that had held up to the strain. This time, when I switched on, it tried to start but closed down after a few seconds with just P30 displayed. Because this set was very corroded, I next looked at board BS776 which I deduced generated the EHT for the three tubes. After removing it, I went over it very carefully, testing all likely components I thought might fail. The only thing I could find here that was that R615, a 100kΩ resistor, had gone high. My broad plan of attack was to check each board, one at a time, looking for obvious signs of corrosion related failure or damage. However, after spending a great deal of time, I couldn’t find anything. The only thing I could work out was that something was killing the horizontal drive after a few seconds. I worked through all the boards until I reached the digital board (BS815). This is very similar to the BS816 in the Fujitsu General colour TV sets and indeed other digital TV receivers under names such as Schneider, Dual, Teac, Akai ITT and Nokia, to name a few. These all use the same chip sets but are not necessarily interchangeable as they are often encoded for the instruc tion set used within that model. The horizontal drive was generated from the DPU2553 deflec tion processing unit IC (CI5) which is in turn controlled by a central processing unit and its EEPROMs. Though this set was made in Italy, it was designed in Germany and there was another clue. The display constantly showed P31 or program 31, no matter which button of the remote control was pressed. This suggested that it was highly likely to be the CPU (or CCU as the Germans call it), or even more likely, the EEPROMs. The Fujitsu General showed these EEPROMs to be MDA2062s, whereas this set used a sub-board (BS842) soldered into the main board in location CI3. This sub-board carried a single 8-pin DIL EEPROM NVM3060 instead of the original 14-pin DILs. I thought I might be snookered here in not being able to get the spare parts but as luck would have it, the local agents were able to sell me the IC. When it arrived, the set powered up and stayed on and there was sound – but no picture – on all channels. It took another saga to locate and replace CI8 DTI2223, the “Digital Transient Improvement” IC, to finally bring up the picture. But that wasn’t the end of the matter. After it had been on for a while, the picture broke up into black and white horizontal bars and the Teletext no longer operated. With the aid of some freezer, this fault was traced to CI12, the Teletext RAM chip (TMS 416415N). Fortunately, I managed to find a replacement on an old computer motherboard. After that, I was home and hosed and the old projection set performed quite spectacularly. Dual TV set Reverting now to conventional TV sets, my next story concerns a 66cm Dual Digital Concept TV4170. This set uses a DTV2 chassis and is made by Schneider in Germany. It is also made under the brand names of Teac, NAD, Nokia, Salora and ITT. The entire chassis is no bigger than that of a 34cm portable set and when one looks inside, the first question one asks is “where is the rest of the set?” Apart from the control panel, which is about 10 x 10cm square, the motherboard is divided into two sections: (1) the power/deflection board and (2) the digital/small signal/audio board, that latter using the ITT digital IC chip set. As with a few other recent jobs, this set came to me via the tortured route of failed repairs from several other service centres who really didn’t want to know. However, that’s not surprising really, considering that there are not many of these sets in the country and the agency has closed. We would all prefer to work on easy faults that earn money rather than complex ones that don’t. The set was reported as dead but strictly speaking, it wasn’t. There was no sound or picture but the switch- mode power supply was working and delivering all the secondary voltage rails except for the 5V U3 rail which was low at 3.3V and delivering 1.5A. There was no horizontal or vertical drive because this rail fed the “digi board” where the oscillators are located. The problem was whether it was a load fault or a supply fault. When the interconnecting St.DT (play) plug was removed, the 5V rail recovered to its full value and this suggested that it was a load problem. And it seemed that the only way to locate the fault was to desolder each device in sequence until the short vanished. This is rather difficult as the 16 odd ICs are all hard wired/soldered close together on the double-sided PC board – not to mention the tuner, IF, audio, AV and control panels. In addition, many of the 40-pin ICs have multiple connections to the U3 rail, many of which are not marked. Nevertheless, I could see no easy alternative and so I persevered as best I could. Unfortunately, after spending a lot of time following this procedure, I had FEBRUARY 2000 77 signal never arrived at pin 23 of IC701. This turned out to be a fault of my own making; pin 23 had been poorly soldered when I fitted the IC socket. Because the IC is on the component side, it is very difficult to solder the pin from that side. All I could do was melt more solder onto pin 23’s pad from the other side until it finally connected with the pin. When this was finally achieved the whole set was trans formed into a well-behaved, responsive receiver with an excel l -ent picture. Everything worked, including the Teletext. The only thing that didn’t was the picture-in-picture facility and that was because the optional module wasn’t fitted. A weird fault made little progress. I could find no direct shorts, due partly to the amount of circuitry connected to this rail and partly because it is almost impossible to desolder awkwardly placed components on the double-sided boards. But the work wasn’t entirely wasted. I was beginning to suspect the Deflection Processing Unit, IC701 (IC1) DPU2553 and decided to remove it completely and fit a socket for it to the board. This was a drastic decision because it isn’t easy to fit a 40-pin IC socket to a PC board by soldering it on the component side – especially with virtually no room. However, I eventually managed to get the job done and then ordered and fitted a new IC. This turned out to be a good move, with the 5V rail making a big recovery – although not quite enough. And there were partial signs of life, with EHT and a white line at the top of the screen. I next suspected the two EEPROMs – IC1302 and IC1303 (MDA2062) – but then decided that IC1301 (CCU7916) was more likely to be the culprit, as neither the remote control nor any of the controls was having any effect. And I have to confess that I could only make intelligent guesses as to which section or IC might be faulty. 78 Silicon Chip Fortunately, my guess proved to be correct. When IC1301 (CCU7916) was replaced, the sound was restored and all the controls were working. However, there were still problems with the picture. The screen was intermittently trying to produce a full scan but there were huge quantities of what looked like hum moving up and down the screen. In addition, the horizontal deflection was off speed, as evidenced by picture tearing. The set was also suffering a great deal of stress, with a lot of heat being generated on the deflection module. I switched it off and had a think about the problem. The most valuable symptom was the horizontal deflection system being off frequency. Why should this be so on a digital set when the oscillator is crystal controlled and has AFC feedback? Because the frequency was only slightly off, a logical assumption was that the problem had to be in the AFC feedback loop. This is generated from pin 4 of the horizontal output transformer TR302 (TR2) and goes through CR410 (CR10) to pin 6 of the interconnecting harness plug St.DT. I followed this with the CRO to the anode of diode DT02 (D2) but the My final story this month describes one of the weirdest faults one could imagine. It was found in a set by our local Sony service agent. The set, a 1990 Sony KV-X2931S AEB1 chassis, belonged to an elderly couple and it had given good service for about eight years. Recently, however, it had started cutting out intermit t ently, giving no picture (black screen) or sound but leaving the channel number displayed on the screen. After a few abortive house calls to fix it, it ended up on their workshop bench. Subsequently, a number suspect solder joints were found which were duly attended to and the set was put aside for testing. Initially, they were quite confident that the fault had been scotched by this wide sweep but it wasn’t to be. This was the kind of fault that just keeps coming back and after a few days, they were right back to square one. Over the next couple of weeks, the set rocked back and forth from the soak-testing bench to the workbench and each time some suspect joints were discovered and resoldered. Finally, it was considered good enough to go home where it worked for about a month before the symp- toms returned. It then came back to the workshop where a couple of more joints were resoldered it worked OK for a week before going home again. This see-saw between home and workshop subsequently went on five times, with the set always being OK at the service centre and in trouble at home. Of course, you can imagine how the owners were beginning to get a little tetchy about this. In the meantime, all hell was breaking loose at the service centre as to how to fix such an intermittent fault. Finally, the boss, whose expertise is normally confined to audio equipment decided to have a go. To cut a long story short, the attention of all concerned had gradually been homing in on a particular board – the J1 board which carries the audio control, AV input, Y/C input, SCART video out and E/W correction circuits. This board is mounted vertically at the rear supported by a cream plastic rear support bracket (11) and the whole combination is hinged at the bottom so that it can fold down for service. The copper pattern side of the board faces inwards, against the plastic support – see Fig.1. It seemed that moving this assembly could bring on the fault – sometimes! It was eventually established that the set would always work with the back off, but intermittently fail with it on. A lot of time was spent examining the plugs and sockets and hinge connections J1-41 and J1-51, as pushing the assembly backwards and forwards could induce the fault. Finally, the boss confirmed that if the cream plastic bracket was removed from the J1 board, one could do anything with the board and the set still worked. But when everything was reassembled into the normal positions and the plastic back of the cabinet was replaced, the fault could be induced by pressing on this plastic back. The point here is that there is a plastic cover mounted inside the cabinet back, apparently to protect the component side of the board. So pressing the cabinet back can move the board/bracket combination. Simple solution Finally, he reached a dramatic conclusion – it wasn’t moving the board that caused the fault – it was just pushing the board against the cream plastic bracket that could do it! Fig.1: an exploded view of part of the Sony KV-X2931S AEB1 TV chassis. The J1 board (12) is supported by the plastic bracket (11). Note the fitting (13) and the cover inside the cabinet back. Apparently, this bracket had become conductive and with the back on, the cover pressed against the component side of J1 board. This in turn meant that the copper side of the board was pressed against the plastic bracket. So far, no one has managed to measure the conductivity of the plastic or determine precisely which circuit was affected. But the solution was quite simple – use insulating tape around the edges of the plastic bracket where it touched the J1 board. He had previously cleaned the bracket with acetone to remove any residual conducting chemicals but without success. This finally achieved a lasting repair and the set is still working months down the track. Of course, a new plastic bracket may have fixed the problem but why go to the expense when just a few centimetres of tape was all that was needed? Who would have thought that this board/bracket assembly could cause such a fault? Apparently, not all plastics are good insulators as we have been lead to believe! Finally, note that this fault could be very similar to one found in a run of 1992 Mitsubishi TV sets, models C3420/C3421. This produced a product recall when a white plastic PC board frame had to be replaced with SC a black one (BFC 3420-01). Silicon Chip Binders  Heavy board covers with 2-tone green vinyl covering  Each binder holds up to 14 issues  SILICON CHIP logo printed in gold-coloured lettering on spine & cover REAL VALUE AT $12.95 PLUS P & P Price: $A12.95 plus $A5 p&p each (Australia only; not available elsewhere). Buy five and get them postage free. Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. FEBRUARY 2000 79 CTRONICSHOWCASELECT 3990 FULL RANGE $ ELECTROSTATIC Now you can afford the legendary clarity, transparency, depth and precision of an electrostatic speaker. The new Vass ELS-5 is a full range electrostatic speaker, able to faithfully reproduce frequencies from 40Hz-20kHz. • 5 Year Warranty • Wide range of custom finishes. • Individually hand built & tested. 1/42-44 Garden Bvde, Dingley 3172 Pyramid subwoofer Ph 03 9558 0970 Fax 03 9558 0082 separately available email: vass<at>hotkey.net.au MicroZed Computers GENUINE STAMP PRODUCTS UNIVERSAL WIRELESS DEVELOPMENT SYSTEM FROM Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. Linx RF modules from Clarke & Severn Electronics offer a simple, efficient and cost-effective method of making a product wireless. Want to know more? Contact PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) CLARKE & SEVERN ELECTRONICS Ph (02) 6772 2777 – may time out to Mobile 0409 036 775 Fax (02) 6772 8987 PO Box 1, Hornsby NSW 1630 Ph (02) 9482 1944 Fx 9482 1309 http://www.microzed.com.au email: sales<at>clarke.com.au www.clarke.com.au Most Credit Cards OK Attention speaker builders and professionals World famous loudspeaker drivers make a return to the Australian Market. Call for information, data sheets, kit plans and free advice. Trade and OEM Enquiries welcome. Stock available mid December. Quantity discounts apply. Model RRP Peerless 811827 dome tweeter, wide angle $69 Peerless 811978 dome tweeter, shielded $89 Peerless 810665 dome tweeter, rectangular $99 Peerless 850122 woofer 6.5” CSX hi-end $135 Peerless 831709 woofer 8” thick PP cone $125 Peerless 831727 subwoofer, 10” thick PP cone $165 Peerless 850146 subwoofer, 10” CSX hi-end $189 Introductory special $59 $74 $85 $105 $95 $135 $160 ALSO STOCKING THE MOST COMPREHENSIVE RANGE OF REPLACEMENT SPEAKER FOAM SURROUNDS and parts including factory surrounds for Dynaudio, Tannoy, JBL, Scan-Speak, Cerwin-Vega and others. PHONE: (03) 9646 5115 FAX: (03) 9646 1574 POST: P.O Box 63 Port Melbourne VIC 3207 EMAIL: ortofon<at>labyrinth.net.au SWITCHMODE POWER SUPPLIES Extensive Range 25W500W SURPLUS ELECTRONIC COMPONENTS at CHEAP CHEAP CHEAP PRICES! ICs, LCD Displays,Transistors, Diodes, Leds, Books, Connectors, Switches, Transformers, Fans, Relays, Speakers,Terminals, Resistors, Buzzers, Leads, Knobs, Batteries, Computer Accs. etc. FOR A FREE MONTHLY MAILER PLEASE CONTACT 6 Sarich Court, Technology Park, Bentley WA 6102 80 S ilicon Chip Ph: 08 9470 1177 Fax 08 9470 2844 web: www.computronics.com 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 TRONICSHOWCASELECTRO • • • • • • • R.T.N Basic Stamps, SX chips and tools. OZ-made boards and development tools Best pricing on temp, a/d, rtc kits New Xilinx PLCC44 development system New OZ made serial LCD module 2*16 Stepper and R/C servo motor chips New super catalog on CD Rom with 40 meg of Stamp related data. Now available via SAE and our cost $4.50, or free with orders over $125 Phone/Fax 03-9338-3306 http://people.enternet.com.au/~nollet Email: nollet<at>mail.enternet.com.au NEW FROM QUESTRONIX DVS5 Video & Audio Distribution Amplifier DVS5 Video & Audio Distribution Amplifier 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 VGS2 Graphics Splitter Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. VGS2 Graphics Splitter High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email - questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC's, Converters, etc. QUESTRONIX All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only In your next issue of * March 2000 issue due on sale at your newsagent February 23 –or a few days earlier if you are a subscriber! Low Distortion 100W Amplifier Module You asked for it: here it is. A new, improved version of our incredibly popular “plastic power” module (April 1996). It has even lower distortion than the original! Glowplug Driver for Model Aircraft Into model aircraft? Aren’t glowplugs a pain in the *#*<at>^? Not any more with this nifty little kit. Use an ordinary 12V battery to heat the glowplugs without any danger of burnout. * These are just some of the items planned for the March 2000 issue but are subject to change. SUBSCRIBE TO AND $AVE $$$! Did you know that as a SILICON CHIP subscriber, you not only get your magazine days earlier AND cheaper, you qualify for a 10% discount on all SILICON CHIPmerchandise?* That's right! That's why so many SILICON CHIP readers are also SILICON CHIP subscribers. There's a handy order form on page 70 – or you can ring SILICON CHIP and become a subscriber by phone (02 9979 5644; 9-5, Mon-Fri). * Subscriptions, internet services not included FEBRUARY 2000 81 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The Hellier Award; Pt.1 Building simple valve radios from scratch can be a challenge and a lot of fun. Eight such radios were recently built by members of the Vintage Radio Club of North Eastern Victoria as part of a competition. All used just two valves but with lots of interesting variations. Back in 1989, when the Vintage Radio Club of North Eastern Victoria Inc. was formed, one of its aims was to foster a cooperative spirit in various areas of vintage radio – eg, education, restoration and the collection of historical information on our radio/wireless heritage. In addition, as part of the club’s activities, a com- petition has been conducted almost every year with a different emphasis each time. These competitions have included: building a 2-valve radio, restoring a wreck (and plotting your progress), building a “Little Jim”, building a “Little General”, building a useful piece of test gear and building a crystal set (Silicon Chip, October This little 2-valve TRF set had most of its cabinet made from a 2-litre ice-cream container! 82 Silicon Chip 1994), etc. This competition is known as “The Hellier Award” in honour of Les Hellier, one of our early radio broadcasting pioneers. Les Hellier established the first country-based broadcasting station in Victoria (and possibly in Australia), according to the club historian. That station was 3WR Wangaratta, which later became 3SR Shepparton on 1260kHz. 3SR has since closed down on the AM band but the transmitter is now operated by the racing fraternity. The last Hellier Award Back in April 1998, I proposed that the award should be for the construction of a small 2-valve (envelope) receiver – basically, a radio somewhere between a “Little Jim” and a “Little General” in complexity and performance. These sets appeared as constructional articles in “Radio & Hobbies” over many years and were built by enthusiasts between the late 1930s and the early 1960s. For those unfamiliar with these sets, the “Little Jim” was a 2-stage radio with a regenerative detector and audio stage (usually using a twin-triode valve). By contrast, the “Little General” was a more ambitious set, being a basic superhet with a converter, an IF stage and an audio stage. I proposed that perhaps the award for the year could be called the “Big Jim”. The name didn’t get off the ground but the concept certainly did. As for the technicalities, the valves could be single function such as a 6V6GT or multi-function such as some of the “Compactrons” that have up to three valves in the one envelope. Rectifier valves, if used, would not be considered in the valve count. The aim was to stimulate the members into looking at all the areas of importance This photo shows the eight entrants for the 1999 Hellier Award. Five of the sets are simple superhets, while the other three are TRF sets. in the production of a set and to really let their hair down and do something innovative if they wanted to. Key parameters The set was to be a mantle unit suitable for use in the kitchen or a bedroom. Some of the key parameters were: (1) it had to be easy to operate, (2) it had to be pleasing to look at and (3) it had to have adequate performance so that all local stations could be heard at good volume. In addition, the set should also be easy to disassemble for service and once disassembled, the electronics and mechanical aspects of the set should be easy to work on. Care was to be taken to ensure that inputs and outputs were well separated and that component values could be easily seen. After all, it is just as easy to put components in a circuit with the values showing as it is to have them facing the chassis! It was also suggested that a mockup be made before actually starting construction, to test various ideas and eliminate those that were unsuitable as far as the cabinet, chassis and electronics were concerned. Laying out the major components on a piece of paper is one way of making sure that everything fits and that certain areas of the radio aren’t going to be unduly crowded. After all, who likes delving under several layers of parts to get at a suspected faulty component? I don’t and I’m sure very few other people do either. It was expected that the contest would provide quite a learning curve for our members in various areas. Some are good at electronics while others are good at chassis construction, cabinet work or producing an aesthetically pleasing set, or providing good service and operational data. None of us excel in all these areas, so it was expected that members would ask others for advice if necessary. Finally, a year was allowed for members to get their entry up and running. Unfortunately, this didn’t prove long enough for some of the contestants and a couple of sets weren’t finished in time. However, now that the judging of the award is complete, these contestants are being encouraged to finalise their work so that each set really proves to have been worth the effort. Technical suggestions A number of suggestions were made as to how to obtain the best performance from two valves and yet still adhere to the KISS principle (Keep It Simple Stupid). These suggestions ranged from a regenerative detector with two audio stages (eg, using a 6N8 and a 6GW8) to a full superhet consisting of a converter, a single reflexed IF stage and a triode output (eg, using a 6AN7 and a 6BL8 or 6AN8). A small triode will certainly give adequate output, as demonstrated by the Chinese set described in the July 1999 issue. The circuits of typical receivers that could be used as the starting point for experimentation were subsequently published in the club’s newsletter. Of course, the contestants were free to adapt these or to develop something completely different, as the mood took them. As it turned out, some contestants did try something new while others felt more comfortable using the exFEBRUARY 2000 83 Two of the sets entered in the contest were housed in beautifully-made “Empire State” style cabinets. isting designs. Even so, no member slavishly copied any design – either electronically, mechanically or in cabinet style or construction material. The variations all proved quite interesting and this was reflected in the higher than normal attendance at the meeting when the sets were first displayed. What the contestants made From the accompanying photographs, it can be seen that eight very different sets were presented. For a start, the size variations are quite noticeable, the sets ranging from about the size of a brick to one that would be suitable only for a giant’s mantle piece. In the latter case, I can assure you that the set has a performance that equals its size. The cabinets were all made exclusively or partly of wood. It is easier to dress up than metal or plastic and when polished looks a million dollars. As can be seen, there are some very nice polished sets ranging from 1940s style back to “Empire State” style. Harvey, the owner of the large mantle set, ran into trouble with the finishing of his cabinet. Another club member explained what was necessary to get a good finish on pine and 84 Silicon Chip cabinet restoration and this will be described in a later article. Several other sets were painted (or were to be painted) to look like the typical 1950s kitchen mantle set. As for the little blue set, it had most of its cabinet made from a 2-litre icecream container! It may not have been intended to look the prettiest but Noel (the owner) decided that his set would use readily available bits and pieces. Because valve-radio power transformers are no longer manufactured, Noel decided to use two modern transformers, a 2155 and a 2853, to obtain the voltages that were required for his radio. The 2853 was wired backto-front across the 9V output of the 2155 to obtain a suitable HT voltage. What types of sets were built? Five out of the eight sets were simple superhets (commonly called “supergainers” in amateur radio circles). They used a converter (mostly a 6AN7) and a regenerative IF stage, followed by a stage of audio amplification. All were AC-powered, with one exception which could be powered either from 90V and 1.5V batteries or from an AC supply, as required. This latter set was a simple super het, using a 1A7GT and the marvellous little 1D8GT. Unfortunately, this was one of the sets that wasn’t operational at the time of the judging. The other three units are TRF sets, two of which are “Christmas Box” radios as described in “Radio & Hobbies” back around 1952. These Christmas Box radios consist of a 6N8 regenerative RF stage feeding another tuned section and a diode detector, which then reflexes back through the 6N8 to give additional audio gain. The 6N8 in turn drives a 6M5 audio stage which then drives the speaker (if reflex circuitry isn’t something that you fully understand take a look at the February 1996 issue of SILICON CHIP). The third TRF set used a 6J7G regenerative detector and a 6V6GT audio amplifier. Solving problems Have you ever done anything worthwhile that didn’t give some problems before success was yours? Well, that’s the way it proved to be for the contestants who built these sets. For example, Dennis who built the smaller more ornate Empire State cabinet ran into trouble with his bending and steaming. The result was a somewhat wavy rather than a smooth finish on the timber – and Dennis loves woodwork. He was disappointed with it but will no doubt sort the problem out. Nearly everyone ran into trouble getting the regeneration going in their simple superhets. They found that they needed to wind many turns of wire onto the IF transformer to get the reaction to work properly. There was detuning of the IF transformer in most cases, too. I built a similar receiver around 20 years ago and had no trouble with this but I did use a different method of obtaining the reaction. Hopefully, we’ll get to the bottom of this idiosyncrasy over the next few months. Next month That’s all for this month on this very interesting project. In the next issue, we’ll take a look at just how well each of these little sets works. One question that did arise during the course of the competition was which type of set performed the best – the TRFs or the simple superhets. At the moment the jury is still out on that one but there will be some answers SC for you next month. This photo shows the three winning sets. We’ll look more closely at these sets and describe their main features in Pt.3 of this series. FEBRUARY 2000 85 REFERENCE GREAT BOOKS FOR NEW NEW NEW NEW AUDIO POWER AMPLIFIER DESIGN HANDBOOK 77 95 NEW $ By Douglas Self. 2nd Edition Published 2000 A uniquely detailed and practical text on the design of audio amplifiers from one of the world’s most respected audio authorities. The new 2nd edition is even more comprehensive, includes sections on load-invariant power amps, distortion residuals, diagnosis of amplifier problems, reactive loads on amplifiers, how to make speakers draw higher currents and the practical side of variable temperature coefficient bias generators. 368 pages in paperback. VIDEO SCRAMBLING AND DESCRAMBLING for SETTING UP A WEB SERVER If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! Encoding/decoding systems (analog and digital systems), encryption, even schematics and details of several encoder and decoder circuits for experimentation. Intended for both the hobbyist and the professional. 290 pages in paperback. NEW 2nd Covers all major platforms, software, links and web techniques. It details each step required to choose, install and configure the hardware and software elements, create an effective site and promote it successfully. 273 pages, in paperback. Satellite & Cable TV by Graf & Sheets By Simon Collin. Published 1997. 59 $ Edition 1998 TCP/IP EXPLAINED 95 90 Assumes no prior knowledge of TCP/IP, only a basic understanding of LAN access protocols, explaining all the elements and alternatives. Combines study questions with reference material. Examples of network designs and implementations are given. 518 pages, in paperback. By Tim Williams. First published 1991 (reprinted 1997). $ 59 Includes grounding, printed circuit design and layout, the characteristics of practical active and passive components, cables, linear ICs, logic circuits and their interfaces, power supplies, electromagnetic compatibility, safety and thermal management.302 pages, in paperback. 95 LOCAL AREA NETWORKS: An Introduction to the Technology ELECTRIC MOTORS AND DRIVES Want to become more familiar with local area networks (LANs) without facing the challenge of a 400-page text? . Gives familiarity with the concepts involved and provides a start for reading more detailed texts. 191 pages, in paperback. For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. By Austin Hughes. Second edition published 1993 (reprinted 1997). By John E. McNamara. 2nd edition 1996. 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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 Silicon Chip Back Issues June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; The MIDI Interface Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High-Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. 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. 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. 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. 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. 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. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. 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. 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. 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. 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. 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. 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. 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. 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). November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. 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. 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. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled Cockroach. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. December 1993: Remote Controller For Garage Doors; Build A LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags In Cars – How They Work. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. 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. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. 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. 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. 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. 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. ORDER FORM Please send thethe following back issues: Please send following back issues: ____________________________________________________________ Enclosed is my cheque/money order for $______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 88 Silicon Chip Note: prices include postage & packing Australia ....................... $A7.70 (incl. GST) Overseas (airmail) ............................ $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. Email: silchip<at>siliconchip.com.au ✂ Card No. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. July 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. 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 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 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. 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 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. 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. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: Adding A Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. 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. 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 1998: CPU Upgrades & Overclocking; Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. December 1996: CD Recorders – The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. November 1998: The Christmas Star (Microprocessor-Controlled Christmas Decoration); A Turbo Timer For Cars; Build A Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Setting Up A LAN Using TCP/IP; Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. January 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. 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. 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. 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. 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. 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 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. 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. 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. 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. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Darkrooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. May 1995: Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. September 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. April 1997: Avoiding Win95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. May 1997: Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers. 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. 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. 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. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. December 1997: A Heart Transplant For An Aging Computer; Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. 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. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. February 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Demonstration Board For Liquid Crystal Displays; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. 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. 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. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. March 1999: Getting Started With Linux; Pt.1; Build A Digital Anemometer; 3-Channel Current Monitor With Data Logging; Simple DIY PIC Programmer; Easy-To-Build Audio Compressor; Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12. April 1999: Getting Started With Linux; Pt.2; High-Power Electric Fence Controller; Bass Cube Subwoofer; Programmable Thermostat/Thermometer; Build An Infrared Sentry; Rev Limiter For Cars; Electric Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft. May 1999: The Line Dancer Robot; An X-Y Table With Stepper Motor Control, Pt.1; Three Electric Fence Testers; Heart Of LEDs; Build A Carbon Monoxide Alarm; Getting Started With Linux; Pt.3. June 1999: FM Radio Tuner Card For PCs; X-Y Table With Stepper Motor Control, Pt.2; Programmable Ignition Timing Module For Cars, Pt.1; Hard Disk Drive Upgrades Without Reinstalling Software; What Is A Groundplane Antenna?; Getting Started With Linux; Pt.4. July 1999: Build The Dog Silencer; A 10µH to 19.99mH Inductance Meter; Build An Audio-Video Transmitter; Programmable Ignition Timing Module For Cars, Pt.2; XYZ Table With Stepper Motor Control, Pt.3; The Hexapod Robot. August 1999: Remote Modem Controller; Daytime Running Lights For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting, Pt.14; DOS & Windows Utilities For Reversing Protel PC Board Files. September 1999: Automatic Addressing On TCP/IP Networks; Wireless Networking Without The Hassles; Autonomouse The Robot, Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5; Peltier-Powered Can Cooler. October 1999: Sharing A Modem For Internet & Email Access (WinGate); Build The Railpower Model Train Controller, Pt.1; Semiconductor Curve Tracer; Autonomouse The Robot, Pt.2; XYZ Table With Stepper Motor Control, Pt.6; Introducing Home Theatre. November 1999: USB – Hassle-Free Connections TO Your PC; Electric Lighting, Pt.15; Setting Up An Email Server; Speed Alarm For Cars, Pt.1; Multi-Colour LED Christmas Tree; Build An Intercom Station Expander; Foldback Loudspeaker System For Musicians; Railpower Model Train Controller, Pt.2. December 1999: Internet Connection Sharing Using Hardware; Electric Lighting, Pt.16; Index To Volume 12; Build A Solar Panel Regulator; The PC Powerhouse (gives fixed +12V, +9V, +6V & +5V rails); The Fortune Finder Metal Locator; Speed Alarm For Cars, Pt.2; Railpower Model Train Controller, Pt.3. January 2000: Spring Reverberation Module; An Audio-Video Test Generator; Build The Picman Programmable Robot; A Parallel Port Interface Card; Off-Hook Indicator For Telephone Lines; B&W Nautilus 801 Monitor Loudspeakers (Review). 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 FEBRUARY 2000 89 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! NO-CATCH INTERNET ACCESS 2.7c PER MINUTE     NO NO NO NO download limits mysterious hidden charges long-term contracts fine print  YES - your own email address  YES - your own website space  YES - 100% peace-of-mind 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. Most capitals and many larger cities covered. INTERESTED? Call SILICON CHIP, totally obligation free, on (02) 9979 5644 9-5, Mon-Fri (We'll even call you back if STD). Or fax us on (02) 9979 6503. Or if you already have web access, email silchip<at>siliconchip.com.au or www.silchip.com.au for more 90 S ilicon Chipdetails. 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. Train controller transformer Can you please assist me with the Train Controller featured in the April 1997 issue? I purchased a kit from Dick Smith Electronics (K-3029) and I have assembled it but I cannot work out how to connect the 15V AC transformer I swiped out of an old controller. Your circuit shows three connections for a centre-tapped 9V per side transformer to the board but seeing as I only have two from my transformer (0V and 15VAC) I cannot figure out how to connect it. Can you help? (B. L., via email) • The circuit on page 67 of the April 1997 issue shows how a single winding 12VAC transformer can be connected. Simply connect the 0V terminal of the transformer to ground and the 15V terminal to one side of the bridge rectifier BR1. On the PC board you connect one transformer wire to the centre of the three input terminals and the other transformer wire to one of the other terminals to the left or right. The third terminal is left unconnected. In effect, you are connecting the transformer so that it drives just two Multi-Spark CDI timing queries I recently purchased the CDI kitset as featured in the September 1997 issue of SILICON CHIP and have some questions about the unit to help me understand how it works. What was the formula you employed to get the values for sparks presented as the product’s specifications? I am unable to see how the above information is related to Table 1 (RPM vs. Spark No. & Duration) on page 23. For example, please provide a mathematical formula on how to get: (a) four sparks covering 37° of diodes in the bridge rectifier; ie, you will have two half-wave rectifiers feeding the 4700µF capacitors. However, there is a problem in that 15VAC is a little too high for the application. You will probably find that the rectified DC voltage will be well over 20V and if you apply this voltage to your locos they will scream around the track. The DC voltage may also be a little high for the capacitors and it may be wise to replace the 4700µF 25VW types with a higher voltage rating, say 35VW. By the way, we published Notes & Errata on this circuit in the August 1999 issue on how to avoid a brief backward lurch from the loco when power is first applied. Clifford the cricket is comatose I recently purchased Clifford the electronic cricket, as described the December 1994 issue of SILICON CHIP. I’m having some trouble getting him to work. When I connect the battery, the LEDs light and then when I block out the light nothing happens and the LEDs stay on. Do you need a multimeter? Can you help me? (P. H., via email). crankshaft rotation at 4500 RPM for a 4-cylinder engine? (b) eight sparks covering 20° of crankshaft rotation at 1400 RPM for an 8-cylinder engine? (M. R., via email). • The spark duration table is based on the fact that the there are always multiples of two sparks produced. The duration and spacing was measured with an oscilloscope when driving a standard ignition coil. The times may vary with different coils and the calculations will vary slightly from the measured values due to differences in charging the timing capacitors. The crankshaft angle is derived • It should be possible to get Clifford going without a multimeter. It is possible that you have transposed the two transistors, Q1 and Q2, on the PC board. Check that Q1 is a BC548 or BC547 and that Q2 is a BC557 or BC558. Also check the diode orientation for D1 and D2. The anode (A) is the end of the diode with the stripe. Both anodes for D1 and D2 should be toward the 3.3kΩ resistor. The overlay diagram for this is a little tricky but if you place diode D1 with the stripe up and D2 with the stripe down and with the wire lead and body placed as shown, the orientation will be correct. If Clifford still does not operate, check the placement of the resistors using the published colour code as a guide to reading their values. 4Ω version of foldback loudspeaker I refer to your excellent foldback loudspeaker presented in the November 1999 issue. As I already have a suitable power amplifier which delivers 200W into 4Ω but only around 80W into 16Ω, I would like to modify the design so it has a nominal impedance of 4Ω. I assume the two drivers by calculating the rotation of the shaft over the total spark duration. For example, the four sparks at 4500 RPM for a 4-cylinder engine gives 37°. At 4500 RPM, the frequency of rotation is 4500/60 or 75Hz. This is a duration of 13.3ms. The duration of four sparks is about 1.3ms and so we have 1.3/13.3 x 360° = 35°. The result for eight sparks at 1500 RPM, giving 20° of crankshaft rotation, is calculated similarly: 1400 RPM is 23Hz or 43ms; eight sparks is 3.1ms and 3.1/43 x 360° is 25°. As you can see, the calculations do fit the measured values reasonably closely. FEBRUARY 2000 91 Signal loading problem in rev limiter I am building the Rev Limiter kit described in April 1999 to show three shift lights. I have an imported Nissan Skyline which is already factory rev-limited so I don’t need the Ignition Switcher as well. I have a second “interceptor” computer which controls fuel for different revs. It is hooked to the factory computer for positive, earth, revs, air flow, throttle position and fuel. I hooked the Rev Limiter up to my factory computer for positive, earth and rev wires, the same as the second computer. When powered up the Limiter circuit seems to sense the different speeds and the lights come on OK and the second computer continues to show correct revs. However, my in-dash tacho stops working. It starts working again if I cut the earth return to the Rev Limiter kit. I then changed to the Hall Effect/ Points/Distributor input which gives me back the tacho but doesn’t seem to detect revs for the shift lights. Do I need to isolate the Rev Limiter kit from the computer by putting in a diode on the input to allow one-way signals into it? Can you possibly shed some light on what I need to do to get it working? (G. J., via email). • It is possible that the loading from the low voltage input is upsetting the tachometer. The ignition coil input is not sensitive enough to detect the low voltage signal. You could try a diode connected in series with the 1kΩ low voltage input to isolate the signal and connect it with the anode to the low voltage input and the cathode to the 1kΩ resistor. Alternatively, you could connect to the ignition coil input if the 22kΩ resistor is reduced to 1kΩ. would be connected in parallel but how is the crossover modified? (G. D., via email). • The loudspeakers can be connected in parallel to provide a nominal 4Ω impedance. The inductor should be reduced in value to 450µH. Since the woofer sensitivity will increase by 6dB it is necessary to remove the 0.33µF capacitor in series with the tweeter and replace it with a short circuit. Make sure the phasing of woofers and tweeter is as shown on the diagram on page 73 of the November issue. Also both woofers should be connected with the plus terminals tied together. The plus side then connects to L1 and the two minus terminals to the common ground. seem to align fairly closely in three different positions. When I use the position which puts the white line or knob marker closest to the start of the dial selections on the panel, the first selection is not aligned to the first position of the knob by one click. What do I do? (S. D., via email). • The switch can be placed in any of the three possible orientations. This is because the poles of the switches can be interchanged and used for any of the switching functions. The type of knob must be able to be adjusted to align correctly with the panel markings. Some plastic knobs can be adjusted by removing the front pointer plate and repositioning correctly in place in line with the panel markings. Audio signal generator switch confusion Speed Alert for racing car I am trying to assemble the Audio Signal Generator described in the February & March 1999 issues. It has been about 15 years since I did any circuit board work and I must confess that I am puzzled with your rotary switch (S2) alignment instructions (page 66, March 1999). How do I know when I have the switch properly located over the drilled holes? You see, the holes I read with interest John Clarke’s Speed Alert project in the November 1999 issue. Is there any way of modifying this kit to indicate a higher speed? I noted that John mentioned that this kit was not suitable for racing cars but I do need an electronic speedo for my racing car. (P. M., via email). • The software could be changed to accommodate a higher reading of speed up to 255km/h but not without 92 Silicon Chip some major changes. If other readers are interested, we would consider producing a modified version however it seems likely that 255km/h would not be sufficiently high for a racing application. Pulse counting with the Stress-O-Meter I have made the pulse counting section of the Stress-O-Meter project in the October 1998 issue of SILICON CHIP, with both the connections to it from the games and printer port. It should work since I have checked all the components. The problem is that I can’t use it with the software on your website because you include the GSR section which I don’t want. How do I change the Q-Basic software so that it will display my average pulse rate on the screen without needing a GSR input? Can this be done easily or do I need the other section of the project? (D. T., via email). • All you should have to do is to delete lines 80, 100, 110 and 120. You will have to use CTRL+PAUSE to exit the program. Deleting these lines will allow the program to continually loop to subroutine 3030. Sensitivity of carbon monoxide alarm In the May 1999 issue, you published a circuit for a carbon monoxide sensor using a Nemoto sensing element. You incorporated the sensor into a voltage divider to obtain the right sort of levels to feed to a comparator. The problem is, from the manufacturer’s chart that I have, the sensor should have about 27kΩ resistance at 200 ppm CO but your design seems to use a value closer to around 20kΩ (it’s difficult to tell as you used a trimpot in the divider). Can you tell me how you arrived at your figures? (N. S., via email). • The CO Alarm is an uncalibrated unit and is set so that the alarm does not sound under normal driving circumstances. Trimpot VR2 does not allow the sensitivity to be set as low as 200 ppm since this would be too sensitive in our application. You could substitute a 10kΩ trimpot for VR2 to allow adjustment down 200 ppm. Note that the 27kΩ resistance of the CO sensor at 200 ppm is a typical value only and does not describe a precise calibration. 100W PA amplifier wanted I am contemplating constructing a PA amplifier with six inputs; five microphone and one auxiliary. I have searched through my older magazines but cannot find anything that meets my needs. I require 100 watts RMS into a suitable matching transformer for 100V line use. Have you at any time produced such a design? There are a number of good kits available for a main amplifier but none have a suitable preamplifier to match into. Have you any suggestions? (E. C., Bundaberg, Qld). • We published a 120W PA amp with 100V line transformer in the December 1988 and January 1989 issues. We can supply photocopies of these articles at $7 each including postage. No picture from PC monitor checker I constructed the PC Monitor Check er project published in the August 1999 issue from a Jaycar kit. The only problem I found was that a .01µF ceramic capacitor was supplied but both the layout and circuit call for a 100pF ceramic capacitor (I used a 100pF capacitor, as specified). My problem is that I am unable to get a picture in sync on a known working monitor. Your help would be appreciated. (D. B., via email). • The capacitor associated with pin 3 of IC3 is 100pF as shown. If you are not getting a picture there could be any number of faults which could stop the signal getting through. You really need to check for the existence of video signals at the emitters of the Class A amplifier questions I would like to ask several questions pertaining to the class A amplifier published in July 1998. (1) Apart from Altronics, are there any other places where kits can be obtained? (2) What is the openloop bandwidth of the amplifier? (3) How much could the supply rails be increased before the circuit would need altering (neglecting the need for increased heatsinking)? (A. B., via email). five transistors, using an oscilloscope. If you don’t have one, try setting the unit for 15kHz operation and then connect the composite video output to drive a normal video monitor. Longer ticking egg timer wanted I want to build the ticking egg timer described in the November 1990 issue but I want to have a longer time. How do I do it? (S. W., via email). • The way to increase the time is to increase the time constant of oscillator IC1a. This can be done by using a larger pot for VR1 (say 1MΩ) or a larger capacitor instead of the 0.1µF. Digital tacho adjustment procedure I purchased and assembled a digital tachometer from the February 1994 issue but I have now lost the calibration instructions. I need to know which resistor I have to adjust so that it can work on 4, 6 and 8-cylinder engines. If possible, could you tell me the re- • Altronics is the only source for this kit. We have not measured the open-loop bandwidth but it should be in excess of 20kHz. The main limitations on the supply rails are the ratings of Q11 and Q13, the small signal transistors used as drivers. If you wanted to run at high current and voltage, you would have to substitute much higher-rated transistors for Q11 & Q13. Trouble is, virtually any bigger transistor you find will have poorer frequency-gain product and so the performance will suffer. sistances that are required and which resistor it is? (D. B., via email). • There was no tacho project in February 1994 so we assume you mean the circuit in August 1991. The resistor marked Rx, in series with trimpot VR1, should be 82kΩ for 4-cylinder engines, 56kΩ for 6-cylinders and 47kΩ for V8s. We can still supply a photostat copy of the article if you wish, for $7 including postage. Notes & Errata Switching Temperature Controller, August 1999: two capaci t ors are marked C6 on the circuit. The 100µF capacitor associated with diode D1 should be C2. Also the text in the last paragraph on page 58 is wrong. It should read: the BUK453 is for cooling, the IRF9530 is for heating. Refinements To PC Monitor Checker, Circuit Notebook, November 1999: the rotary switch is incorrectly labelled 12345 in an anticlockwise direction from top to bottom. The correct labelSC ling sequence is 43215. 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. FEBRUARY 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 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $__________ or please debit my ❏ Bankcard ❏ Visa Card ❏ Master Card FOR SALE RAIN BRAIN AND DIGI-TEMP KITS: 8 station sprinkler controllers, 60 channel temp monitor uses DS1820s over 500 metres. Has PC Data logging. Mantis Micro Products, http://www.home.aone.net.au/mantismp TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. Melbourne 9806 0110. 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. WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. $420.00 complete plus sales tax if appli cable. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/Ecowatch ph: (03) 5968 4863 fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. Card No. KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com Signature ________________________ Card expiry date______/______ ACT REGION (CANBERRA) ELECTRONIC SERVICE & REPAIR BUSINESS offered for the first time $50K plus in annual gov’t service contracts, unlimited scope for expansion, currently run 2-3 days per week. Owner moving into other business interests. Enquiries at first to accountant. Ph 0418 603236. Name _____________________________________________________ Street _____________________________________________________ Suburb/town _________________________ Postcode______________ 94 Silicon Chip 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. DON’T MISS Australia’s biggest and best exhibition and sale of new and used radio and communication equipment at the Central Coast Field Day, Sunday 27th Feb, Wyong Race Course, just 1 hour north from Sydney. Starts 8.30am. Special Field Day bargains from traders and tons of disposals gear in the flea market. Exhibits by clubs and groups with interests ranging from vintage radio, packet radio, scanning, amateur TV and satellite comms. www. ccarc.org.au Ph (02) 4340 2500. 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. 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. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. 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 76.5F to 180F. Silvertone’s RC Receiver Still the best little performer available! AV-COMM P/L, 198 Condamine St, Balgowlah, NSW 2093. Tel: 02 9949 7417 or 9948 2667. Fax: 9949 7095; www.avcomm.com.au KITS-R-US PO Box 314 Blackwood S.A. Ph/fax 08 8270 3175 FMTX2A Universal Stereo Coder $49 FMTX2B 30mW Xtal Locked 100MHz Transmitter $49 FMTX1 1-3 Watt Free Running Transmitter $49 FMX1 200mW Full Broadcast Transmitter, built & tested $499 FM220 10-18 Watt FM BGY133 Philips Linear $499 FM1525 25 Watt Discrete Linear FM Band $499 FM2100 110 Watt Discrete Linear FM Band $699 FM3000 300 Watt Discrete Linear FM Band $1499 Philips 828E/A VHF Receiver Boards (6 metres) $9 AWA 721 VHF Receiver Boards (2 metres) $9 AWA 721 VHF transmitter boards 1 watt (2 metres) $19 Philips 323 UHF transmitter boards 500mW (70cm) $19 AEM 35 Watt Little Brick Audio Power Amp $15 Digi-125 200W RMS Audio Power Amp $39 CA Clipper Compiler, new in box $49 6dBd Gain Colinear FM Band Antenna $999 Roll Smart-1 FM Station Audio Processor $999 Free catalog on disk of discounted surplus components Same day shipping, credit cards OK, circuits supplied. SPECIAL STEAM BOAT KITS $14 FREE PC VIDEO RECORDER - TIME LAPSE - MOTION DETECTION Software with 4 Ch Capture Card from $113 * DIY PCBs: Video Memory from $94 * QUAD 4 Pix 1 Screen from $142 * Video Transmitter Kitsets & Complete Systems from $142 * IR Remote Control Extender Set $79 * concealed PINHOLE Mono or DSP COLOUR Camera, Microphone & Timer/Controller in PIR DETECTOR from $139 * BULLET 480 Line 0.05 lux SONY CCD or DSP COLOUR from $132 * HIRES better than SUPER-VHS Quality QUADS 4 Pix 1 screen from $208 * PCB Modules from $76 COLOUR Pinhole from $155 * MINI CAMERAS 36 x 36 from $85 - SONY CCD $102 - COLOUR $162 * DOME CAMERAS from $88 - SONY CCD $107 - COLOUR $164 * Video BALUNS from $7 * DIY PAKS 4 Cameras, Switcher & Supply from $461 with 12" Monitor from $575 * 4 COLOUR CAMERAS, SWITCHER & POWER SUPPLY from $769 - with COLOUR QUAD 4 Pix 1 Screen from $1168 * COLOUR QUADS from $474 * COLOUR DUPLEX MUX from $1329 * 14" MONITORS from $203 - with Inbuilt 4 Ch SWITCHER from $236 * SEE-inthe-DARK CAMERAS & INFRARED 50 x 120 mW LED ILLUMINATOR Kits from $19 * www.allthings.com.au * T 08 9349 9413. DESIGN SOFTWARE: Loudspeaker enclosures and equalisers. http:// www.users.bigpond.com/alphaelectronics Email: alphaelectronics<at>bigpond.com C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68 HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $155.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 and 68HC12 for $78. Debug monitors: $78 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 Simulator (fast, now incl. 80C320): $78. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $199, $37 tax, $10 p&p. 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 SOIC adaptors: 20-pin $90, 14-pin $85, 8-pin $80. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; Fax (02) 9631 1236; or Internet: http://www.grantronics.com.au RCS Radio is MOVING. For information, ring 0408-613-300. DUAL VARIAC 2 AMP 0-260V near new condition $120. 02 9948 5034. KIT ASSEMBLY ANY KITS assembled/repaired: professional, speedy service. Phone Neville Walker (07) 3857 2752. WANTED 3,000V x 0.1 amp transformer or neon transformer, at 240V input. Quote price & postage charge. Please phone (02) 6452 6396 evenings. FEBRUARY 2000 95 14 Model Railway Projects Advertising Index Acetronics....................................81 Av-Comm Pty Ltd.........................95 Shop soiled but HALF PRICE! Clarke & Severn Electronics........80 Computronics Corp......................80 Dick Smith Electronics........... 34-37 Dontronics...................................80 EMC Technologies.......................81 Emona Instruments...................IFC Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. Harbuch Electronics....................73 SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) Kits-R-Us.....................................95 Instant PCBs................................95 Jamo Australia Pty Ltd.............OBC Jaycar .............................. 45-52,95 Kalex............................................33 Microgram Computers...................3 MicroZed Computers...................80 This book will not be reprinted Yes! Please send me _____ copies of 14 Model Railway Projects at the special price of $A3.95 + $A3 p&p (p&p outside Aust. & NZ $A6). Enclosed is my cheque/money order for $A__________ or please debit my  Bankcard  Visa Card  MasterCard Oatley Electronics........................23 Pinfold Health Services...............80 Premier Batteries.........................85 Preston Electronics......................80 Printed Electronics...................... 95 Questronix...................................81 Robotic Education Products........80 Card No. RobotOz......................................81 Signature___________________________ Card expiry date______/______ R.T.N............................................81 Name Rocom Electronics.......................80 ________________________________________________________ SC Binders..................................79 PLEASE PRINT SC Computer Omnibus.............IBC ________________________________________________________ Silicon Chip Back Issues....... 88-89 Suburb/town___________________________________ Postcode_________ Silicon Chip Bookshop........... 86-87 Street Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). SC Internet Service.....................90 Silicon Chip Subscriptions...........70 Silvertone Electronics..................95 Smart Fastchargers.....................57 Solar Flair/Ecowatch....................94 Speakerworks..............................80 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 Truscott’s Electronic World...........33 Vass Electronics..........................80 _____________________________ 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. 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