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January 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 1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.jaycar.com.au Contents Vol.13, Vol.13,No.1; No.1;January January 2000 FEATURES   4  Protel 99: Much More Than A PCB Design Tool It takes the circuit diagram and lays out the board for you. Also included are circuit simulation and automatic design checking – by Peter Smith 11  Review: B&W Nautilus 801 Monitor Loudspeakers It’s got the looks, it’s got the sound and it’s got the technical magic – by Louis Challis Spring Reverberation Module – Page 24. PROJECTS TO BUILD 24  Spring Reverberation Module Build it and get great concert hall effects for your guitar or keyboard instrument – by John Clarke 38  An Audio-Video Test Generator Use it for testing VCRs, video monitors and the continuity of video cables – by Leon Williams 56  Build The Picman Programmable Robot Audio-Video Test Generator – Page 38. A PIC microcontroller lets you program in the commands – design by Andersson Nguyen 66  Parallel Port Interface Card A Windows-based program makes this simple I/O card easy to drive – by Peter Smith 80  Off-Hook Indicator For Telephone Lines A “busy” indicator to prevent annoying interruptions to Internet access – by John Clarke SPECIAL COLUMNS 18  Serviceman’s Log They came in two by two – by the TV Serviceman 74  Vintage Radio Picman Programmable Robot – Page 56. Building a vintage radio replica – by Rodney Champness DEPARTMENTS   2  Publisher’s Letter 17  Mailbag 53  Product Showcase 65  Subscriptions Form 78  Circuit Notebook 84  Electronics Showcase 90  Ask Silicon Chip 93  Notes & Errata 94  Market Centre 96  Advertising Index Parallel Port Interface Card – Page 66. January 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: Macquarie Print, 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 Switch those computers off when not in use One of the questions that we are commonly asked is whether computers should be switched off when not in use or whether they should be on permanently. It’s a fair question, particularly when you see that so many professional organisations leave their machines running 24 hours a day – they never turn them off. However, just because these large organisations do it does­n’t make it the right thing to do. Unless computers need to be accessed 24 hours a day, they should not be on permanently. Why? First, and this is a topic that we have touched upon in the past, if a fault occurs in a computer or more likely, in the video monitor, and if no-one is present to turn it off, it could cause a fire. It does happen! In fact, this month one of my own TV sets had a component failure which produced a lot of smoke and un­doubtedly it would have caused a fire if my wife had not been in the room to switch it off. I have seen banks of machines left on in rooms where there are sprinkler systems – so if one machine catches fire, a whole lot of them get a bath! Second, if machines are left on after hours and a thunder­storm occurs, they are vulnerable. And you can have all the electrical protec­tion that money can buy and it won’t mean a thing if the electri­cal supply outside the building gets a direct hit. There is only one sure way to protect a computer against lightning strikes and that is to disconnect it from the mains supply. Third, computers use a lot of electricity if they are left on permanently. In our office at SILICON CHIP there are 11 com­puters and they are only switched on during the day. Only the server is left on permanently, to do after-hours backup. And if a thunderstorm is likely to hit overnight, we switch the server off too. Just think about the power consumption of 11 computers left on permanently. A typical computer with its monitor will consume around 200 watts or more. Leaving 11 of them on perma­nently would be equivalent to running a 2.2kW radiator all the time. Now if we left such a radiator on in the office all the year round, you would say we were insane! You’d be right. The cost of running all our computers for 24 hours a day instead of about 10 hours a day, at 10 cents a kilowatt-hour, is over $1100 for one year. That is not allowing for the extra power we would use for air-conditioning and yet some organisations run hundreds of computers all the time. Sure the dollar cost may not be huge relative to their overall expenses but it probably also reflects their generally slack approach to cost control. One of the arguments commonly raised in favour of running computers continuously is that because they run at the same temperature all the time (not being cycled on and off), they are more reliable. Nonsense. A CRT in a video monitor has a typical brightness “half-life” of about 10,000 to 15,000 hours. 10,000 hours is not much more than a year. In effect, leaving a monitor on permanently (with or without screen-saver) reduces its life by a factor of about three. Hard disk drives also have a finite life – why shorten the time to their ultimate failure? Even if the cost of replacing a failed computer is regarded as small, the time and cost of getting a computer back in use with all its software loaded can be very considerable. Most organisations do not take that into account when they take out insurance. No, whether you have one computer or a hundred, it does not make sense to run them all the time unless they are being used all the time. Switch them off and pull the plug out of the wall socket. And if you must run computers all the time, at least switch off the monitors. Leo Simpson M croGram Computers Infra Red Serial Link This easy to install IR adapter connects to the serial (COM) port of the PC and provides wireless data transfer between desktop PCs and mobile computing devices that have a built in IrDA infrared port. Cat. 8421 $99 Infra Red Serial Link PCMCIA 10/100Mbps Ethernet Adapter Web-Based Training from $9.95 per month* New courses now available! 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The A-Shot Cat. 17035 8 Opto 8 Reed Relay $219 Expansion Kit $109 laser gun is equipped with an Metrologic 100 scan/sec laser Cat. 17036 module. Pressure Sensitive Pen Tablet The PCMCIA Ethernet card is a credit card size Ethernet adapter that connects a notebook PC to an IEEE 802.3 standard Ethernet network. It features 16-bit PCMCIA architecture and automatically negotiates 10 or 100Mbps connection rate, depending on the speed of the network. Cat. 8897 Cat. 11300 PCMCIA 10/100Mbps Ethernet Adapter $159 SCSI HDD Controller Cards Our high performance PCI bus SCSI-III Ultra2 Wide adapter with data transfer rate up to 80 MB/s features 32-bit PCI Bus Master DMA SCSI-3 transfer rate up to 133 MB/s. It also supports SCSI-1, SCSI-2 and SCSI-3 peripheral devices including HD, removable HD, CD-ROM drive, MO disk drive,optical k, WORM, Tape Drive, CD-R, scanner, etc. Cat. 2693 HDD Cont. PCI SCSI-III Ultra2 Wide $475 Cat. 8767 Cat. 8770 Cat. 8771 Cat. 8772 Bar Code Laser Gun Auto KB Wedge PS/2 Bar Code Laser Gun Auto KB Wedge AT Bar Code Laser Gun Auto Serial Bar Code Laser Gun Auto Stand $599 $599 $599 $35 At last an affordable pressure sensitive pad with an active Cat. 2585 HDD Cont. ISA SCSI-II Fast 16 bit $89 area of 146 x 108mm. Two butCat. 2584 HDD Cont. PCI SCSI-II Fast $109 Cat. 2587 HDD Cont. PCI SCSI-III Ultra Wide $249 tons on the stylus pen enable Remote Power Control Kit via Internet you to simulate clicking on the Smart Card Reader/Writer - Serial Control computers, swimming pool right, left or middle button of a Identical in size and feel to credpumps, security lighting, heating, cooling 3-button mouse. It is sensitive it cards, smart cards store inforetc. over an intranet or the internet. The to 512 pressure levels which allows you to vary line mation on an integrated microkit includes a PCI PnP Digital I/O interface width according to pressure using your favourite processor chip located within the card, power control box & eight-in-one application software (Photo Impact 4 Light body of the card. The Smart connecting cable. Fully functional software included). The tablet can be set up to a Card reader/writer connects to demonstration software, with source code in VB and C++, is resolution of 4064 lpi . the PC via a serial port and included as well video monitoring software. Cat. 8896 Pressure Sensitive Pen Tablet $169 takes power from the keyboard Cat. 17064 Remote Power Control Kit via Internet $579 UPS & Power Supply port with a T type cable. The reader is compliant FireWire to PCI Host Adapter with ISO7816/3 with T=0,T=1 and APDU protocols. It’s not just a UPS but also a A software library for DOS, Win95/98 and Connect your digital video camera to your PC. Our Firewire 300W power supply. The UPS card allows IEEE 1394 FireWire devices (most digital cam- is actually built into a standard WinNT4.0/2000 is included. corders available today) to connect to your PC at speeds up size power supply and the batteries & front panel Cat. 8899 Smart Card Reader/Writer - Serial $169 to 400Mbps. The card has three external and one internal occupy a 5.25in drive bay. The UPS is rated at Multi I/O ISA Card 1394 connection ports to allow connections to hard drives, 500VA. Apart from power failure, the UPS also A versatile interface card that supports 2 FDD, 2 scanners, VCRs, HDTV, printers etc. Editing your videos is protects against over voltage, under voltage, overHDD As well as 2 16550 compatible serial ports, 1 simplified with the bundled Ulead Video Studio DV SE load & DC short circuit. ECP/EPP printer port and 1 games port. software. Also available, Cat. 2055 $50 Multi I/O Card Cat. 2621 FireWire to PCI Host Adapter $199 Cat. 8588 UPS / PS (ATX) Int 500VA/300W E & OE $439 All prices include sales tax MICROGRAM 0100 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 Protel 99 . . . much more than a PCB design tool Protel 99 is much more than just a printed circuit board design tool. Among its many features, it provides automatic design checking, circuit simulation and the ability to preview the completed board in 3D. And of course, it can take a circuit diagram and automatically lay out the board for you. vantage of Windows’ improved mem­ ory management and user interface. Protel 99, the latest offering, is packed with all the features that any designer could wish for and at first sight is simply overwhelming. There are so many features that it is just not possible for us to cover them all in a review of reasonable length. Instead, we’ll concentrate on the key elements and see how they work together. By PETER SMITH In Protel 99, circuit diagrams are drawn using the “Schematic Capture” (or Schematic Editor) module. These schematics are drawn in a familiar WYSIWYG (what you see is what you get) format. If necessary, complicated designs can be simplified in appearance because Protel 99 has the ability to organise and display designated circuit sections as blocks. This is particularly handy when dealing with complex circuits that extend over many pages. The symbols of all commonly used components (over 60,000 of them) are supplied in libraries (see Fig.1). These libraries can be modified and expand­ ed using the integrated library editor Printed circuit board (PCB) design has come a long way since Protel’s Easytrax first appeared. This simple yet effective DOS-based package, along with the more advanced Autotrax, gained much popularity back in the 1980s and they’re still in use today. Until Protel arrived on the scene, PCB layout and most similar EDA (Electronic Design Automation) tasks had been the exclusive domain of UNIX-based software running on minicomputers and mainframes. This kind of hardware was out of the question for small operations, so layouts 4  Silicon Chip 4  Silicon Chip had to be done manually. Manually laying out PCB designs is laborious, involving the use of stencils, black tape and scalpel on paper or transparent sheets. As with text from a typewriter, editing the completed output is nigh on impossible. By attacking the problem from the designer’s viewpoint, Protel came up with an effective system that ran on available desktop hardware and cost a fraction of the price of high-end solutions. Later, Protel were one of the first companies to develop EDA applications for Windows, taking ad- Schematic capture and free updates are available on a regular basis from Protel’s website. Point-to-point connections can be made both manually and automatically. In automatic (or “AutoWire”) mode, it’s a simple matter of clicking on the start and end points and the connection is automatically routed (see Fig.2). In manual mode, “hot spots” at each connection point make sure that the wires actually connect, allowing the user to work at a lower zoom level than might otherwise be possible. Designs are edited using standard Windows concepts (cut, copy, paste, drag, etc). Multi-level undo/redo is also supported – a feature that I find indispensable. As you might expect, designing with a program such as Protel 99 brings many advantages. One of these is the ability to perform automatic checks on your schematic design before moving to the PCB layout phase. Protel 99 includes an Electrical Rules Checker (ERC) that examines designs for common drafting errors such as unconnected power/ground pins, floating inputs, duplicate component references, etc (Fig.3). Any problems that are identified can be highlighted directly on the schematic so that they can be easily spotted and fixed. Fig.1: browsing the schematic component libraries. Over 60,000 symbols are supplied, ready to be placed on the diagram. PLD design PLD (Programmable Logic Device) design often goes hand-in hand with the schematic layout and Protel 99 has the bases covered here too. So let’s have a quick look at PLD basics and the support offered by Protel 99. It is rare to see designs these days that consist of just a few logic devices like the 74xx or 40xx series. As miniaturisation techniques advance, chip manufacturers are squeezing more and more onto silicon wafers. Consider a typical PC motherboard for example – almost all logic external to the microprocessor is contained in just two or three chips (commonly referred to as the “chipset”). The functions of these “super” chips are fixed (or hard-wired) at the time of manufacture. But although this is the most cost-effective method for volume production, what about small production runs or prototypes? PLDs fill the gap. These devices integrate from just a few to many thousands of logic functions (or building Fig.2: using the AutoWire function to automatically connect two nodes in the Schematic Editor. Fig.3: setting up the Electrical Rules Checker. It checks the design for common drafting errors. blocks) onto a single chip. As shipped from the factory, PLDs are effectively “blank” (much like EPROMs) and must be programmed to connect their building blocks in a meaningful way. This technique allows the circuit designer to significantly reduce the physical size, power consumption and cost of the end product. Using PLDs in any design requires selecting a suitable device, then defining its internal logic connections (and hence its overall function) by using a dedicated programming language. One of the most popular is the CUPL Hardware Description Language. These high-level language instructions are then compiled into binary format, ready for download to a PLD programmer. Protel 99 greatly simplifies PLD January 2000  5 Fig.4: Protel 99 running a circuit simulation for a 555 timer IC which has been “wired” as a monostable multivibrator. language file, which is then compiled ready for PLD programming. Circuit simulation Fig.5: browsing the PCB component footprint libraries. design by allowing the engineer to draw a schematic representation of the internal logic connections, rather than having to define them with a programming language. It then automatically translates the schematic into a CUPL Simulation provides a means of verifying a design before it is even proto­typed. Protel 99’s simulator is based on the latest SPICE kernel. SPICE is the industry-standard analog circuit simulator. Developed at the University of California and released to the public domain in 1972, it has since undergone several revisions and is currently at major release 3. This release forms the kernel of most SPICE-compatible simulators. SPICE simulators can perform a host of functions, including transient, noise, distortion and Fourier analyses. They can also calculate local poles and zeros for transfer functions, calculate DC operating points and find signal transfer functions. Designing A Typical PCB In Protel 99 (1)  Define project concept. (2)  Schematic capture – the circuit is drawn and edited. (3)  Schematic design verification – errors like floating inputs and unconnected power pins are automatically detected. (4)  Circuit simulation (optional) – all or part of the circuit is simulated and the results analysed to ensure that it functions as expected. (5)  PCB layout – design information is transferred from the Schematic Editor to the PCB Layout Editor. Components are then placed and tracks are routed manually and/or automatically within the editor. (6)  PCB design verification – rules are applied to ensure design integrity and manufacturing viability. (7)  Result – output files are generated ready for direct input to the PCB manufacturing process. 6  Silicon Chip Simulating mixed analog and digital circuits in some simulators requires that the designer insert A/D and D/A converters between the analog and digital sections. In Protel 99, this process has been made more straightforward because direct support is provided for simulating digital circuits. Three steps are required to perform a simulation in Protel 99. First, the circuit schematic is drawn using the components supplied in the simulation libraries. Second, all the signal sources (AC/DC power, input signals, etc) that would be present in the real-world situation are added and finally, the simulation is run. The results are displayed in easy-to-interpret graphical form. Protel 99 includes a library of 5800 simulation-ready components, each linked to a standard SPICE model. In addition, component manufacturers usually provide SPICE models of their analog components (as files) and these can be used to update or expand the existing Protel 99 libraries as necessary. PCB layout – it’s automatic Now we really come to the heart of the matter. With the schematic design complete, wouldn’t it be nice to make use of all the information on how everything is connected together for the PCB design phase? Well, the people at Protel are more than one jump ahead of us here. Protel (and other) companies have designed PCB layout software that can import connection and component package information from the schematic, place the components on a board layout and connect them together – all automatically if desired. But let’s take a step back for a moment to the schematic entry phase. Each component in every schematic has various attributes associated with it, such as position in the schematic (X and Y coordinates), designator, library name, footprint, etc. It is the “footprint” attribute that we are interested in here, as this name assigns an appropriate footprint (or template) to the component for use during PCB layout. Component footprints are simply groups of correctly sized and spaced pads, together with overlays to suit System Requirements Protel 99 runs on Windows 95/98 and NT4. The minimum hardware requirement is a Pentium-class PC with 32MB of memory, SVGA display at 800 x 600 resolution with 256 colours and 200MB of free hard disk space. However, while Protel 99 will run on the minimum hardware spec­ified, we agree with Protel’s recommendation of a Pentium-II class PC, 64MB of memory, SVGA display at 1024 x 768 resolution with 16-bit colour and 300MB of free hard disk space. the pin size, spacing and package outlines (Fig.5). Each footprint is given a descriptive name, such as “TO-92A” (a typical small transistor package). Protel 99 also includes a PCB Lib­ rary Editor, complete with a component creation Wizard, for modifying and expanding the PCB footprint lib­raries. Updates are also available from the Protel website. Look Mum, no hands! When a schematic design is completed, a list of all the components used, their footprints and how they are connected (called a “netlist”) can be exported from the Schematic Editor into PCB layout software. Protel 99 provides a direct link between its schematic and PCB editors, so separate import and export steps are not required. Instead, the “Design Synchronizer” performs this function, as well as keeping the schematic and PCB layouts “in-sync” as the project progresses. By using the Design Synchronizer, modifications to the schematic layout are immediately reflected in the PCB layout (Fig.6). We should also mention here that the schematic and PCB layouts are “linked” in another important way. With a click of the mouse, the designer can jump from a particular point in the circuit schematic to the same point in the PCB layout and vice-versa. This is called “cross-probing” and it saves a lot of time. is done either by using the Board Wizard (which includes a handful of predefined board templates) or by manually drawing the outline (Fig.7). The basic design rules, such as default track sizes and minimum track/ pad clearances, can also be defined at this point. This done, the Design Synchronizer is invoked (from the Schematic Editor) to load and place all components onto the PCB layout. Initially, these appear outside the board outline, ready for manual or automatic placement. At this point, all component connections are shown in an aptly named “rat’s nest” configuration – see Fig.8. As each connection is made on the PCB, the associated rat’s nest connection disappears, making it easy to keep track of work yet to be done. Protel 99 includes a host of automatic component placement and routing tools that cater from the simple through to the most complex of designs. Naturally, the designer can also manually place part (or all) of the design if required. The designer can also define sets of rules to be adhered to during the layout process. Rules in over 25 classes such as component placement, clearances, net impedance and routing topology can be defined and enforced automatically in real-time, even during manual track routing (Fig.9). The familiar click-and-drag concept is used for manually placing and editing tracks. In addition, objects can be globally edited, making board-wide design changes a snap. Panning at higher zoom levels has been made easier too, using a new fea- Fig.6: selecting Design, Update PCB from the main menu displays the Design Synchronizer options. ture called “Slider Hand”. By clicking and holding the right mouse button, the PCB layout can be positioned smoothly beneath the viewing window. In practice, this is quicker and more accurate than using the scroll bars or shortcut keys. Gridless routing Protel 99 supports grid-based routing but gridless routing is also possible with a little help from Protel’s electrical grid and rules-driven design methodology. The electrical grid is an invisible grid that snaps the cursor to valid electrical connection points, regardless of the current routing grid setting. This is especially useful when working with a mixture of Imperial and metric-pinned components, for example. When working in tight spots, designers can place tracks without regard to their spacing and Protel 99 will automatically enforce minimum Fig.7: running the board Wizard to define the board outline and other basic design information. Starting the layout The first step in any PCB layout is to define the board outline. This January 2000  7 pleted, the final step is to generate the necessary output files so that the board can be manufactured. Several output files are involved and these are used to: (1) plot each layer photographically; (2) provide hole size and position information for a numerically-controlled drilling machine; and (3) provide component type and position information for mechanised assembly, if required. Protel 99 generates all of these files in industry-standard formats that should be acceptable by all PCB manufacturers. It also supports all Windows-based printing and plotting devices. Compatibility Fig.8: after creating the board outline and running the Design Synchronizer (see text), all components appear outside the board outline connected in a “rat’s nest” configuration. clearance rules. It can also move existing tracks to make way for new ones (Fig.10). Once completed, PCB layouts can be subjected to detailed design rule checking. These would generally be more comprehensive than the “online” checking done during placement and routing. As well as generating a detailed report, the Design Rules Fig.9: on-line design rule checking flags problems as they occur. In this example, the designer is routing a track that will exceed the minimum clearance rules to neighbouring tracks and pads and these are flagged by being highlighted in green. 8  Silicon Chip Checker can highlight any problems detected directly on the board (Fig.11). For high-speed digital design there is Protel 99’s Signal Integrity Analyzer. This feature can be run as part of the design rule check and provides crosstalk, reflection, impedance and other related analyses. Any problems can be further analysed and resolved with the help of the Signal Integrity Simulator. Once the PCB layout has been com- Protel 98 and Protel V3 files can be imported directly into Protel 99. However, if you need to import and edit files from earlier products than these, you might run into problems. For example, although Protel 99 will read PCB files created using Protel DOS products, it is not possible to directly import the associated libraries. If you do need to import older files like these, talk to the Protel support people – they will either do the conversions for you or provide the necessary tools for you to do the job. In summary, Protel 99 can import the following file formats: Netlist (Protel & Protel 2 format), Autotrax, DOS PCB 3, Protel PCB 2.8 (ASCII & binary), Gerber, AutoCAD DXF/DWG and OrCAD V7.x DSN. The following file formats can be exported: Netlist Fig.10: Protel 99’s “Avoid Obstacle” mode automatically moves existing tracks to make room for new ones in real time. The diagram at left shows the existing drawing, while the diagram at right shows how the centre track automatically moves when a new track is added immediately below it. This is a great time saver since you don’t have to manually move tracks out of the way. Fig.11: setting up the PCB Design Rules Checker. Where To Buy Protel 99 Protel 99 is available from Protel International Ltd, PO Box 1876 Dee Why, NSW 2099. Phone (02) 9984 0016; email sales<at>protel.com.au Alternatively, you can order a licensed copy on-line from the Protel website at www.protel.com.au A 30-day trial version is also available. In addition, Protel has announced that Protel 99 SE (second edition) will be available from January 2000 with even more features. (Protel format), Protel PCB 2.8 (ASCII), AutoCAD DXF/DWG and HyperLynx. Major new features Compared to earlier versions, Protel 99 also offers a number of important new features, particularly in the areas of multi-user support and document management. For example, all documents related to a project are now stored in a single design database. This even includes non-Protel documents like spreadsheets, AutoCAD drawings, etc. Multiple users can access these design databases simultaneously (without overwriting each Fig.12: using 3D PCB Viewer to display a board as it will look when assembled. It can be rotated to see it at any angle. This is a free plug-in that can be downloaded from Protel’s website. other’s work) and access rights can be assigned to each database on a per-user basis. A core program called Design Explorer brings all these elements together under a common interface. This program looks something like the familiar Windows Explorer and works in a similar manner. Using Design Explorer, you can open, navigate and organise your Protel databases (Fig.13). Multiple documents can be opened and viewed together and windows can be split into regions for side-by-side display. Protel has used a lot of the Windows Explorer shortcuts, so driving it all is quite easy. Add-ons Because it uses what Protel calls “open, client-server architecture”, a range of useful add-ons can be “plugged” into Protel 99. A good example of an add-on is the 3D PCB Viewer. As the name suggests, 3D Viewer generates an image of how the board will look when it is assembled. You can even rotate the board and view it in 3D from different angles – very impressive! The 3D PCB Viewer and a number of other useful add-ons can be downloaded free from Protel’s web site. Getting Help Fig.13: the Design Explorer looks like Windows Explorer and works in a similar manner. It lets you open, navigate and organise your Protel databases Protel 99 has a comprehensive online help system. If you can’t find the answer there, their web site is also a valuable source of help. It includes a searchable knowledge base, FAQ and updates download area. Check it out at http://www.protel.com.au In conclusion, we were very impressed with Protel 99. It’s a mammoth program that must have taken a huge number of man-hours to produce and it really does provide a comprehensive approach to electronic circuit design. To get more information, check out Protel’s free 30-day trial offer (see SC panel). January 2000  9 MORE FROM YOUR EFI CAR! Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication EFI TECH SPECIAL Here it is: a valuable collection of the best EFI features from ZOOM magazine, with all the tricks of the trade – and tricks the trade doesn’t know! Plus loads of do-it-yourself information to save you real $$$$ as well . . . HERE ARE JUST SOME OF THE CONTENTS . . . n Making Your EFI Car Go Harder n Building A Mixture Meter n D-I-Y Head Jobs n Fault Finding EFI Systems n $70 Boost Control For 23% More Grunt n All About Engine Management n Modifying Engine Management Systems n Water/Air Intercooling n How To Use A Multimeter n Wiring An Engine Transplant n And Much More including some Awesome Engines! AVAILABLE DIRECT FROM SILICON CHIP PUBLICATIONS PO BOX 139, COLLAROY NSW 2097 - $8.95 Inc GST & P&P To order your copy, call (02) 9979 5644 9-5 Mon-Fri with your credit card details! FROM THE PUBLISHERS OF “SILICON CHIP” Review by LOUIS CHALLIS It’s got the looks. It’s got the sound. It’s got the technical magic! Nautilus 801 B&W’s massive new monitor speakers are not for the faint-hearted. They are very big, very efficient, very expensive and their looks are hardly conventional. But according to Louis Challis, they are one of the very best loudspeaker systems ever made. He was so impressed he just had to buy a pair. The Nautilus 801s are large and heavy loud-speakers. Note the curved construction of the cabinet. Top of page is the exploded view of the Nautilus 801’s tweeter and midrange drivers. January 2000  11 W hile a few loudspeaker manufacturers do produce ‘monitor speakers’ very few deserve such an accolade. Following my recent involvement in the equalisation of three television sound-dubbing studios, I am aware of just how critical the quality of a pair of monitoring loudspeakers has become to the recording industry. Although studio monitor loudspeakers are expected to offer a flat frequency response, few achieve that aim. B&W’s 801 loudspeakers were first released in 1979. They were an instant success and I was but one of many international technical reviewers who adopted them as my reference against which all other loudspeakers were then compared. B&W’s use of woven Kevlar diaphragms in the mid-range drivers and the application of laser holography to iron out the bugs associated with diaphragm and edge termination reson-ances gave it (and the 801 series speakers) an initially unassailable edge over virtually all its competitors. In the ensuing 20 years, the 801 series 1, series 2 and most recently, the series 3, have been adopted by more than 80% of classical recording studios for their mix-down and dubbing suites. A limitation in the original 801 loudspeaker was the presence of discernible cabinet resonances in the frequency range from 50Hz to 500Hz. B&W resolved that problem in the mid-1980s with their ‘Matrix’ composite foam and internally stiffened enclosure structure. This was featured in the 801 series 2 and 3 and was based on a honeycomb of rigid internal bracing elements filled with foam. The results were dramatic, with the cabinet resonances reduced to a very low level. Then, in the early 1990s, B&W developed its controversial Nautilus loudspeakers. The Nautilus had a decidedly unusual appearance, with a stacked array of loudspeakers in what looked like four spiral conch shells of decreasing size, stuck one above the other. The tapered form at the rear of each loudspeaker driver provided an effective damped termination. This worked but its unusual appearance, weight and cost meant that relatively few enthusiasts were willing to accept it. B&W have now taken a different tack, incorporating the Nautilus system into the 801 series 3 monitor speakers. During my visit to B&W’s factory in Steyning, Kent, work on the development of the Nautilus 801 loudspeaker was in its final phase. On return from England, I was told that I would have to wait at least a year before a pair could be provided for review. When they finally turned up in two extremely large cartons attached to timber pallets, they were so heavy that specialist removalists were required to get them into my living room. Before I could start to review them, I found myself in the perplexing position of having to unpack them myself, even though I had been assured that the carriers would perform that task. Having unpacked them, I can confirm just how time-consuming (and at times daunting) that task was. Each cabinet weighs 104kg and my wife The quality of monitoring loudspeakers in the recording industry is critical. A pair of B&W Nautilus 801s have been chosen for the mixdown room at the famous EMI Abbey Road studio in London. 12  Silicon Chip tapered tail extends to the very rear of the cabinet at which point an aluminium venting cover provides a controlled impedance element for the taper’s exposed exit. The tweeter is centrally housed above the speaker in its own tapered assembly. Foam ring surround Fig.1: 1/3-octave pink noise listening room response of the Nautilus 801s. and I took about an hour to complete the job. There are few visual or functional similarities between the 801 series monitor loudspeakers and the Nautilus 801. The only significant element of the series 3 that was retained is the matrix concept in the construction of the low-frequency driver cabinet. Even the bass driver has been changed, from 300mm (12") to 380mm (15"). The more obvious differences are the curved sides and back for the lower portion of the enclosure. Curved panels are inherently stiffer than flat panels of the same thickness and they also reduce diffraction problems. The extremely thick curved plywood panels in the Nautilus 801 are manufactured by a Danish company. The woofer has a massive diecast aluminium chassis and its rigid cone is a composite of Kevlar and paper pulp. The dust cap is also unusual and is made from carbon fibre. The woofer voice-coil has two separate spider elements at its rear to maintain axial linearity during the extremely high excursions which can occur as a result of the extended low-frequency response. conventional loading ports produce is suppressed. The base of the cabinet also has a thick cast aluminium assembly on which the crossover networks are mounted. The aluminium casting acts a heatsink for the crossover and the base also incorporates four ball-bearing roller glides to enable moving the cabinets across a smooth floor. The roller glides are not intended to provide the final support though and B&W advocate their replacement by four long machined aluminium spikes with stainless steel points that should be inserted in the floor at the selected monitoring location. When I tentatively suggested that approach to my wife, the negative vibes convinced me that it might not be appropriate. . . The most striking feature of the Nautilus 801 is its midrange and tweeter assembly. The 150mm dia-meter midrange driver is housed in a shiny black, extremely rigid tear-drop plastic enclosure. The enclosure’s The mid-range driver utilises what B&W describe as a “fixed suspension transducer assembly”. This has a woven Kevlar diaphragm without the traditional foam or rubber surround. In its place is a 3mm diameter ring of foam that B&W claim removes the dominant surround resonance that plagues most conventional mid-range drivers. Those resonances can result in disturbing peaks and dips in the frequency response curves. B&W claim that the foam ring provides an optimum match between the travelling wave impedance of the bending waves in the cone and thereby minimises reflections that would otherwise occur at the outside of the cone’s rim. The foam edging results in a lower excursion capability when compared with conventional drivers but B&W claim that the driver’s operating frequency range negates the need for a greater excursion. In the place of the conventional dust cap, the mid-range driver has a stationary bullet-shaped cone and this is claimed to improve the off-axis response. Also provided is an alternative bullet-shaped cone with a central screw to which the protective black speaker cloth and wire-framed cover is attached. The mid-range enclosure is actually a long-tail reverse horn. With its carefully shaped internal cavity, it greatly reduces internal reflections, whilst Dimpled loading port The base of the enclosure incorporates an unconventional tapered loading port, with a rectangular aperture at the front and with tapered slots on the two sides of the cabinet. The upper and lower surfaces of the flared port are dimpled. B&W’s research showed that dimpled surfaces in the loading ports reduce boundary layer turbulence. As a result, under high drive conditions, the audible ‘chuffing’ that Fig.2: manufacturer’s frequency response curve for the Nautilus 801. January 2000  13 isolation material, with characteristics more like those of rubber. The crossover has three separate PC boards which are physically separated to minimise any coupling or interaction between them. Each coil is air cored, the capacitors are primarily polypropylene, with supplementary capacitors that are more effective at high frequencies and each thin film resistor has its own heatsink. The crossovers are designed for bi-wireable connections and two pairs of terminal posts are provided at the rear of each speaker enclosure. The gold-plated brass posts are designed to accept banana plugs, spade lugs and bare wires. For those people who choose to use only a single pair of wires for connection, B&W supplies short jumper cables with the speakers to simplify the task. Fig.3: near field frequency response of the Nautilus 801. Objective testing simultaneously providing a smooth, diffraction-free external surface that further improves off-axis response. at their points of fixing to avoid unwanted inter-modulation products. They use a newly developed plastic When reviewing speakers I normally do the objective testing in my anechoic chamber but the sheer weight and size of these Nautilus 801s made The 25mm diameter aluminium tweeter uses a small neodymium-iron-boron magnet assembly with an edge-wound, copper-coated, aluminium ribbon voice-coil and it has magnetic fluid cooling. The tweeter’s frequency response and rear loading is enhanced by a tapered aluminium tube filled with wadding. The tube acts as a heatsink while simultaneously absorbing the rearward directed sound waves. The wadding density behind each tweeter is carefully tweaked during manufacture to ensure the correct frequency response. The tweeter and mid-range assemblies have been carefully decoupled Fig.4: measured impedance curve of the Nautilus 801. 14  Silicon Chip that impossible. As a consequence, I had to do the objective and subjective testing in my listening room. The assessments included a third octave band analysis of the space-averaged pink noise response, measurements of the individual drivers’ frequency response in the near field using MLSSA procedures, impedance characteristics, peak level and distortion. Fortunately, each Nautilus 801 comes with a frequency response graph recorded during final testing in a small anechoic room. This shows the response differences relative to the company’s primary reference speaker which has been separately measured in a large anechoic chamber. The pink noise response reveals an unusually smooth characteristic with a relatively small (±2dB) variation over the critical frequency range from 200Hz to 20kHz. Between 20Hz and 200Hz, the listening room’s Eigentones (standing waves) dominate the peaks and null characteristics of the measured pink a pair of Nautilus 801s was used for the left and right channels of a home theatre system, there would be little measurements showed that the low frequency response was reasonably smooth (even though a flat response noise response. For example, there is a significant 7dB rise in the response in the third octave bands centred on 31.5Hz and 40Hz. Between 50Hz and 200Hz there is another smooth rise in output of approximately 7dB, whose peak is centred in the 100Hz third octave band. There is a discernible droop in the pink noise response above 16kHz, although the speakers still provide useful output at 20kHz (which few people can hear). At the other end of the frequency range, the low frequency drivers in the Nautilus 801 speakers will out-perform the majority of subwoofers that I have recently evaluated. In fact, if point in buying a subwoofer. Objective performance testing with a 12mm Bruel & Kjaer reference microphone, preamp and measuring amplifier coupled to an MLSSA system confirmed that even in the listening room, the frequency response (measured at 1 metre) was still within ±2dB over the frequency range 200Hz to 20kHz. The primary peaks and dips were all attributable to near-field reflections from the floor, ceiling and the walls behind the speakers. Longer path reflections in the listening room make the recording of a quasi-anechoic frequency response impractical. However, near-field could not be confirmed). Even the waterfall responses revealed smooth decays, whose peak-iness is primarily, if not entirely, attributable to room mode responses. Although the B&W literature talks about impedance adjusting elements in the crossover, the measured impedance curve still displays some significant peaks. For example, there is an unusually high peak of 42Ω at 15Hz, with a second peak of 16Ω at 40Hz and still another nominal 16Ω peak at 2.2kHz. The minimum impedance was 3.3Ω at 200Hz. However, the 801’s impedance characteristic would not cause any problems with the vast Fig.5: spectral decay response of the Nautilus 801. These are notably smooth curves. January 2000  15 majority of modern amplifiers. Having completed the objective tests, I had to conclude that the Naut-ilus 801 offers one of the flattest and without a doubt the highest peak output of any monitor loudspeaker system I have ever tested. I was mightily impressed by their ability to provide transient peak outputs exceeding 120dB at three metre distance over the frequency range 100Hz to 10kHz, without my risking the destruction of any drivers. At those extremely high levels, the distortion is both measurable and frequently audibly detectable. In case you’re wondering, I wore earmuffs for that phase of the testing, as peak levels of 120dB are painful and can cause permanent hearing loss. Subjective assessment For subjective tests, I used my listening panel, who were already familiar with the B&W 801 series 1, 2 and 3 loudspeakers. We compared the Nautilus 801s with a pair of B&W 801 series 2 and also with a pair of Quad Electrostatics supplemented by a subwoofer to broaden their low frequency response. In hindsight, that test might be considered patently unfair. In fact, the Nautilus 801s out-performed the other two systems in every single department. With a rated sen- sitivity of 91dB at 1 metre for 1 watt, the Nautilus 801 is one of the most efficient loudspeakers of its class. The difference in efficiency is quite marked when compared to the 801 series 2 – they required a 30° shift in the volume control to provide comparable output. The Nautilus 801’s frequency response is far broader than that of the Quad Electrostatics, even with the supplementary subwoofer and they provide a peak output power capability that exceeds the Quad’s by more than 15dB. More importantly, they provide a smoother and far less coloured frequency response, when assessed with broadband pink noise, than any other speaker I have yet heard. Our subjective assessment then involved a series of vocal and instrumental music. The vocal assessment made use of Ghillian Sullivan’s Vocal Gems (Walsingham Classics WAL 80322) and specifically track 8, Vilja from The Merry Widow and track 15 Voices of Spring by Johann Strauss. The recording and mix-down process adopted during the production of this particular disc has proven to be effective, even though unusual. The orchestral recording was made in the Eugene Goossens Hall, with Ghillian Sullivan’s vocal lead added during a subsequent mix-down. Having heard music and vocals in the Eugene Goossens Hall on many occasions, I know its sound quality very well. When listening to this recording through the B&W 801 Nautilus loudspeakers in my listening room, with eyes closed, I could easily convince myself that I was sitting in a central position in the Eugene Goossens Hall. The second disc I used featured Yo-Yo Ma as a soloist playing various modern works from Zoltan Kodaly, David Wilde, Alexander Tcherepnin and Mark O’Connor’s Appalchia Waltz (Sony Classical SK 61739). The stereo imaging was razor sharp and absolutely brilliant. While much of the music was not to my taste, the reproduction was outstanding. The third disc was a new release entitled Amiel: the chase, “mixes by Josh Abrahams and hifi bugs” (Festival Records D 1936). All five tracks but particularly the last two provide a low-frequency output that sorely tested the two comparison speakers, but presented no hurdles to the Nautilus speakers. And as noted above, the Nautilus 801s provided a smoother, more clearly focussed and less distorted, high-level low-frequency output than the quality sub-woofer that I had been using. Any purist who takes delight in organ recordings or cannons firing in Tchaikovsky’s 1812 Overture will revel in the 801 Nautilus’ sound reproduction. I have yet to test any loudspeaker that can approach or equal their performance. The B&W Nautilus 801s have a recommended retail price of $26,000 per pair. Many people would consider that a lot of money to spend on a car but there are quite a few people who would be prepared to swap that car for a set of these outstanding loudspeakers. I am one of those people. For further information, on the B&W range of loudspeakers, contact the Australian distributors, Convoy International. Phone 1 800 817 787. For a demonstration, visit the Len Wallis Audio showroom at 64 Burns Bay Road, Lane Cove NSW 2006. SC Phone (02) 9427 7655. Fancy a pair of Nautilus 801s in your listening room? You’ll need a lot of space, strong floors, rather deep pockets and a v-e-r-y understanding spouse. 16  Silicon Chip MAILBAG Letter of appreciation This is a letter of thanks, first to the staff of SILICON CHIP for an excellent magazine. I have been getting it since it first started 12 years ago and enjoy most articles but especially those on Vintage Radio. Now for my special thanks to Greg Swain and his computer articles. I have recently changed two hard drives in my 486 computer and his article on hard disk upgrades led me through this operation without any problems. When I went to install a 4.3GB hard drive, his article told me to down-load a program called EZDRIVE. Once the program was activated, it did the job for me. I enjoy the magazine nearly from cover to cover but don’t always agree with Leo Simpson, especially when he knocks valve amplifiers. I have been in the trade now for about 55 years and think valves still make the best outputs. Never mind; we can’t agree on everything. John Breden, Te-Puke, NZ. Pros & cons of the AC/DC controversy Your editorial in the October 1999 issue returns to an old controversy in the Solar/Renewables/RAPS field that has been going on for some time, whether to go for DC, AC or a combination of both. Thanks to modern electronics most electrical equipment could run on DC, motor drives included. After all, the only reason for running household appliances on AC has been the historical problem of distribution, voltage increase and decrease, motors and generation, all of which can be overcome these days with the help of solid state physics. The general consensus in the industry at the moment is that it is less messy to remain with AC and go with inverters on separate circuits. So the basic configuration would be gas cook­ ing, photovoltaics, batteries, inverters and AC appliances. This may now attract more attention in rural areas for water pumping and house power, now that the Federal Government is set to introduce a new rebate on photovoltaic installations this year. I believe this is somewhere in the region of $4000 to $5000 per installed kilowatt (peak) as part of the GST package. Could this lead to more interest in solar-related projects and articles? One solution that might be of interest in the situation described in your editorial would involve battery storage for about 18 hours of use, with charger and inverters. The charger would be permanently wired to your off-peak mains circuit and could then run the house entirely from batteries. Here in Queens­land the difference is about 8 cents per kilowatt-hour. This would result in an immediate reduction in power bills but would need about 30 years to pay it off, if then! You could also add photo­voltaics from time to time to improve the system considering the new rebate. If this sounds expensive, then what price do you put on the inconvenience of blackouts? As regards DC appliances and their availability, check out the US website at www.realgoods.com Geoff Dawson (via email) Caution on PC Powerhouse article I read the article on the PC Powerhouse in the December 1999 issue of the magazine and have to agree with you, “Why didn’t someone think of this before?” Great project. I built the 6V section (I had a plastic bag full of 7806s on hand) hanging in “3D” off a heavy back plane to power my son’s amplified speakers last night and got rid of the hum from the DC plugpack! But perhaps I can shed some light on why this idea is not used more frequently. In this example it’s used for a powered set of PC speakers. The ability to use this idea relies on the fact that the negative connection of the DC input socket is connected to the sleeve of the 3.5mm stereo lead, ie, negative earth. Say a manufacturer from Outer Slobovia decided to connect the positive of the DC supply to the sleeve (ie, positive earth) and the computer power supply is used – then there is a direct short on the PC’s supply. This is not common, I’ll admit, but it is possible, with embarrassing consequences. With batteries or a plugpack it doesn’t matter but with this project it could. Perhaps you could publish a note to this effect in the “Notes & Errata” section, getting people to check the grounding with their multimeter before connection. Yes, the article does mention the fact that the centre pin of the DC sockets must be positive and the sockets are to be insulated from the chassis. You also refer to powered speakers with the centre pin wired to the negative rail. However, merely reversing the leads at the other end of wire does not solve the problem if the manufacturer of the device being powered has connected the positive side of the power socket to the shield of the audio cable which goes to the computer’s earth. This will result in short circuit between the hot of the power wire and the cold of the audio cable. This may blow the 3-terminal regulator and possibly do more damage. Brad Sheargold, Collaroy, NSW. Smart Fastcharger works well I own a corporate event business and good batteries are essential for the equipment we run. One week out from an event and I found that 24 of my 35 NiCd batteries had developed severe memory problems. I searched the Internet and found some highly promoted battery chargers from the USA and Europe. Then while checking around the electronics stores I heard about Smart Fas­tchargers, in Devonport, Tasmania. I was sceptical about their claims but I went ahead and ordered one of their chargers. Within 48 hours I had recovered 23 or the 24 suspect batteries. Since then our office has gone recharge mad. Someone found an old video camera in our store room. It was at least 12 years old and hasn’t been touched for about eight years. At first, the batteries would not even take a charge but the Smart Fastcharger fixed that and now there are very embarrassing home videos being shot on my time. Everyone’s mobile phone batteries have been reconditioned and the search continues to try and defeat the charger, to no avail. It is wonderful to see a small Australian company taking on the giants and triumphing, with great products, fantastic service and keeping Australians employed. Mike Sheehan, Thunderbird Events, Chatswood, NSW. www.thunderbird.com.au January 2000  17 SERVICEMAN'S LOG They came in two by two Some of my jobs arrived in “twos” this month or at least that seemed to be the pattern. There was also a reminder of the problems than can be left by someone who has gone ahead. And of course, there always seems to be at least one unhappy customer. I was trapped into fixing Mrs Cartland’s Philips CR635 TV set. This set is over 10 years old and of course I am familiar with the old Australian-made KL9-A3 (and KT3A-3) chassis which, in my opinion, were very well built. And I say “trapped” because I try to steer clear of such old sets but she laid on the flat­tery and praise – tactics to which I’m quite susceptible. There was no sound or picture, although it was hiccuping or motor­ boating, the sound coming from the speaker. However, it didn’t seem to be quite the same kind of motorboating sound that comes from a faulty audio amplifier circuit. Instead, I felt that it was more likely to be a faulty tripler or horizon­tal output transformer and so I agreed to have a look. First, I disconnected the tripler (1570) but it made no difference. I then removed the horizontal deflection plug, which also links the 140V rail to the horizontal output stage (plug/ socket 4M5/2M5) and measured test point M2 (marked on the board but not the circuit) to check the voltage there. This voltage had previously been pulsating but was now steady. Next, I shorted the base and emitter leads of the horizontal output transistor (7562). There was still voltage (335V no load condition) but again, the pulsating stopped. Most of the noise was coming from the loudspeaker and by turning down the bass and treble controls this could be stopped, but the horizontal output stage could still be heard hiccuping or pulsating. All I had proved was that there were no DC shorts on the main 18  Silicon Chip supply rail but there could be a problem within the inductive load of the horizontal output transformer circuit. It was at this stage I realised that the set had to go to the workshop. This was a nuisance but Eileen’s praise for my techni­cal skills somehow made it all worthwhile. To settle any lingering doubts, I fitted a new horizontal output transformer (5564) which made no difference. I also dis­ connected the deflection yoke without removing the voltage rail links and ran it very quickly to see if there was any change (I didn’t want to incur screen burn from the dot) but there wasn’t. Having eliminated these two major items, I also unplugged the CRT socket in case there were any shorts inside the tube. In order to check the main HT rail, I connected a dummy load (consisting of a 100W globe) from the collector of the horizontal output transistor to chassis and again shorted its base to emitter. This time the voltage read a steady 141V on M2, which was what I was hoping for. I then checked R3561, the limit­ing resistor to the base of the horizontal output transistor, as well as all the components in that circuit. I was beginning to think that there was a problem on the secondary side Sets Covered This Month •  Philips CR635 TV set •  Mitsubishi HS621 VCR •  Mitsubishi HS-M60 VCR •  National M15L TV set of the horizontal output transformer (5564) and so I decided to disconnect each pin, one by one, and check the effect. Disconnecting pin 18 restored the HT without it pulsat­ ing. This pin supplies three 32V rails and the significant one was 32b, to pin 10 of the sync IC (7375, TDA2577), which should be at 12.3V. By disconnecting this one leg I could get sound and hori­zontal deflection but no vertical deflection. I now felt sure that this was where the trouble was (ie, around IC7375) and I spent a lot of time trying to find a fault in this IC or the circuits connected to it. As far as I could work out, its pin 10 was a secondary supply that was switched on following the start-up voltage (10.6V) being applied to pin 16. But I could not see what effect it could have had on the vertical timebase. Eventually, I forced myself to stop thinking about IC7375. I had already disconnected all of its pins to no avail. So the basic fault was that the set was unable to deliver a stable 140V rail and this in turn affected the 26V rail to the audio amplifier, which oscillated with the tone controls turned up. I followed the waveforms from pin 11 through to the chopper transistor 7463. I also disconnected D6317 and R3384D – a current limiter – to prevent any red herrings coming from that quarter (this power supply runs at 15.625kHz). It was then that I noticed that the CRO waveform on the base of transistor 7322 (ie, out of IC7375) wasn’t exactly as shown on the circuit, in diagram 19. And in the process, I also found that with the dummy load connected, the 140V rail could be adjusted with R3325, which further implied that all this circui­ try was working. I checked transistor 7322 and D6322, as well as D6323, D6325, R3317 and a host of other parts but could find nothing wrong. To cut a long story short, it is always the last component checked that is the culprit! I just wish there wasn’t quite such a long queue. Anyway, the culprit was C2317, a 330pf ceramic decoupling capacitor to the base of transistor 7322. It had gone leaky and a new one restored everything. Apparently, this leaky capacitor was applying forward bias to transistor 7322, switching it hard on. The exact sequence of events following that is quite complicated. Suffice it to say, that was it. And I think it is extremely unlikely I will ever see this particular fault again. Eileen, although happy to have her set back, really had no idea of the angst it had caused me. I think I deserve whatever praise she gave me! Two Mitsubishis I recently had two Mitsubishi video recorders arrive in the workshop, both of which came via other service departments. The first was a 1996 HS621 which employs a U deck. Mr Ford was fairly annoyed; he insisted that he had hardly used it since it was new. His complaint was that there was only a blue screen on playback. Perhaps I should explain what the blue screen condition means. This is a purely cosmetic function; a visual and audible muting system. In older sets, a blank channel produces a bright screen made up of multiple white dots (snow) and a blast of noise from the speaker. This can be objectionable. To overcome this, modern sets are normally programmed to present a blue screen when they encounter a blank channel or a very weak or varying one. But the control system can be used to turn the blue off, if the viewer elects to persist with a poor picture. In addition, a blue screen can also indicate a fault in the signal chain. In this case, I thought the fault could be a simple case of dirty heads muting the picture and so I used the remote control to turn off the blue screen, using its menu system. That done, I could now see what was really happening. The picture was flicker­ ing, with tracking bars moving fast down the screen. The tracking control didn’t work. What’s more, when I put the tape in, I noticed that I had some difficulty in making it go all the way into the machine. With the cover removed, I could see the cassette as it was low­ ered onto the deck. Unfortunately, the take-up arm did not always pick up the tape and wrap it around the ACE head, resulting in no sound, no control pulses and a jumping picture. Because it was intermittent, it was difficult to understand why the takeup arm was missing the tape. Initially, I suspected that the loading gears were out of alignment but I was also becoming more aware of the symptom the owner hadn’t mentioned – the difficulty the machine had in accepting tapes, especially on the lefthand side where it often jammed completely. On the earlier F decks, the cassette tray holder didn’t always hold the tape cassette firmly, resulting in the tape not always going in and staying in. However, because I’m not at all familiar with the mechanics of this particular machine, I eventu­ally had to seek help from the Technical Support people at Mitsu­bishi, who put me on the right track immediately. And “track” was the operative word. The tray slides in along moulded plastic rails on either side but somehow, over the years, these had fractured, causing the runners to run slow over the bumps – despite being lubricated with a pink grease. The result was that the tray with the tape cassette arrived too late at the bottom of the action and the take-up arm had January 2000  19 Serviceman’s Log – continued to pay for my work but I decided it wasn’t worth pushing my luck. The Mitsubishi HS-M60 already left its station! Unfortunately, there was no easy solution to this problem. The plastic cannot be replaced and the two side rails are an integral part of the U-deck assembly. The only approach is to change the deck main plate assembly. The good thing is that the chassis is quite cheap (about $20) but the labour involved in fitting it would be prohibitive and I certainly didn’t have all the jigs and adjusting gauges required to set it up. Mr Ford was furious. He claimed that he had played only about five tapes since he’d bought the machine and he had chosen Mitsubishi because he thought it was a reliable brand. I hastened to assure him that the latter is true but I couldn’t help him with his assertion that he had played only five tapes – a claim which I felt was rather far-fetched. In an attempt to find someone responsible for his predica­ment, he then suggested that a previous repair, which was done under warranty, had not been performed properly. I invited 20  Silicon Chip him to fax me the account and I would chase it up. The copy of the account duly arrived and this made it easy to work out what had happened. He had forced a tape in the wrong way around and broken the bottom cassette housing unit, which had nothing to do with the rails. The repair had been carried out two years ago and could not have been responsible the present fault. My theory is that the VCR had probably been kept near a window where it was directly exposed to the hot summer sun and temperature variations has caused the plastic to crack. In short, his problems were all of his own making. However, Mr Ford was in no mood to accept any culpability or explanation and stamped out of the shop cursing everything in sight. I had suggested that he take it to Mitsubishi who would obviously be the best and most experienced people to swap the decks but somehow I think he will just leave it for the council clean-up. I was somewhat miffed that he didn’t bother The second Mitsubishi was an even earlier model, an HS-M60 J deck from about 1994. This machine had also been to another service centre, who regularly serviced a local club’s Mit­ subishi video recorders. They had given up on this particular machine and returned it still faulty. It too was producing only a blue screen but in this case, if one wiring harness plug (GR/MR) was unplugged from the head amplifier, the picture would be restored, without colour. This was an intriguing fault which, once again, I thought would have a simple solution. But I should have been cautioned by the fact that someone else had had a go and abandoned it – and I didn’t even know what the original complaint was. I decided to tackle the no colour problem first. And almost immediately I noticed that the 4.433619MHz crystal on IC2AO had long pigtails and had obviously been replaced. This was my first suspect but equally obviously, someone had already tried that. Anyway, I measured the waveform on pin 18 of IC2AO on the YC/CG module and found that I had plenty of reference oscillation at what looked like the correct frequency. I also checked all the other waveforms and voltages marked on the circuit dia­ gram. Almost all were spot on, the exceptions being pins 5 & 15 on record. These were so weak as to be almost non-existent. I then spent a lot of time checking this board and replaced all the ICs, to no avail. I felt a bit stupid about this later when I found out that the whole board was available for not much more cost and in the end that is what I did. This new board fixed the colour problem and then, because the board doesn’t look very complicated, I thought that I should be able to fix the old board by comparing the two. Fruitless and totally uneconomic exercises like this are one reason why I seem to be perpetually poor but I really wanted to know why one board worked and the other didn’t. This indulgent luxury was eventually satisfied when, more out of desperation than anything alse, I swapped the crystals over and transferred the fault. Well, obviously both crystals work­ed so what was the dif­ference? Elementary, my dear Watson; one was nearly spot on fre­quency but the other was on 4.432185MHz, which was 1.434kHz out. This represents an error of only 0.032% but is marginal for the capture range of the APC discriminator circuit, to enable it to pull in. In fact, some authorities quote 1kHz as the limit. Because there is no tuning capacitor, if the crystal is not within tolerance, one has to choose one that is, so that the discriminator will lock. In this case, I had to try two or three before I found one that would work. I kept the old crystals; they may work in other circuits. Next, I concentrated on the video muting problem. I disen­ gaged the blue screen via the remote control on-screen menu so that (hopefully) I could look at the real situation. Alas, the picture was still blank but now black. I traced the video mute circuit and could find no fault with it. There are two wires running from IC301 on the head amplifi­er board to the motherboard, via connector GR/ MR. One wire, from pin 8 to GR pin 3, also connects to chassis via RJ306 (a wire link). When this was removed, the picture was fine. Or rather, the PC board shows a position where RJ306 could be added but RJ306 is not actually shown on this particular circuit. If it was fitted, pin 8 and the connection on the moth­ erboard would connect to chassis. If it isn’t fitted, the mother­board termination would be above chassis and connected directly to pin 8 on IC301. So what did all this mean? I wasted more time chasing this and trying to comprehend the circuit and how it was supposed to work. Finally, I gave up and contacted the long suffering techni­cal staff at Mit­subishi. If I had looked more carefully at the circuit I would have noticed a small table alongside each one, showing the differences between each model. It was now fairly obvious that the deck had been swapped with that from an HS-M50. And the HS-M50 chassis uses an RJ306 but the HS-60 does not. All I had to do was convert it back to an HS-M60 to make it all work properly again. It is comforting to know that some organisations, such as Mitsubishi, still have professionals who know their product well and can offer advice when needed. TO GR3 A couple of Panasonics The 1990-1992 M15 series of Panasonic TV sets have been excellent for reliability. I had only seen a few of these sets until quite recently, when suddenly I had quite a few to repair. Perhaps it’s because they are beginning to reach their use-by dates or perhaps it’s just fate – who knows? Anyway, the M15 series comes in two basic packages: (1) the M15L for sets up to 51cm and (2) the M15D for larger screens. Both are an improvement on the M14 series except for access, the M15D in particular being quite difficult. Usually this chassis has a tall vertical small signal board on the lefthand side which, along with the short lead wiring harness, prevents access to the power and deflection board. Because of the size and weight of the larger screen sets, I have been forced to repair them on site. Most have had short circuit horizontal output transistors but I cannot be sure what causes this, as I have never had a recall after changing the 2SC1175 (Q501). I always try, where possible, to resolder any suspect joints and replace C816, a 47µF 50V electrolytic, as it has often dried out from the heat. I also had one such house call on a TC2670V, where D620 had gone short circuit, causing the same symptoms. However, the main dramas have all concerned the M15L chassis, which fortunately are easily manhandled into the workshop. The easy ones involved replacing the regulator IC (IC801, STR50213) and the horizontal output transistor (2SD154LB), plus the fuse or R841 (a 4.7Ω resistor) where necessary. It was Mr Rodrigue’s set that gave the most grief. It was not quite dead in that it was making a screaming noise but there was no picture. The main HT rail, normally at 113V, was down to only a few volts at TPE1, out of the power supply. I replaced the horizontal output transistor Q501 (2SD­1541­LB) and IC801 in the power supply but this made no difference. It was very hard to determine where the noise was coming from but I assumed it was T801, the chopper transformer. This made me think it was an overload problem on the power supply. I disconnected Q834 and hung additional electros across C808 and Fig.1: this circuit section from the Mitsubishi HS-M60 J VCR shows IC301 on the head-amp/audio board. Note the terminals for component RJ306 (off pin 8). C847 before eventually realising that I was looking in the wrong area. The jungle IC (IC601, AN5601K) is fed from the 113V rail via R519, a 6.8kΩ 5W resistor supplying 8.5V to pin 42. Without this voltage, the set closes down and there is no horizontal oscillator or indeed anything. Also connected to pin 42, via R536, is a safety shutdown circuit consisting of Q451 (which monitors the vertical output deflection), Q504 and Q503 (which monitors the beam current and secondaries of the horizontal output transformer and vertical deflection). This shutdown circuit was obviously denying voltage to IC601. To test this theory, I desoldered R536 and isolated the shutdown circuit and suddenly things started to happen. We had sound but no vertical deflection. The vertical output IC (IC401) was the likely suspect and a new IC fixed every­thing – until I resoldered R536 that is, after which the set started screaming again. So the fault was in the shutdown circuit but where? Voltage measurements around the shutdown circuit, starting at Q503 and back-tracking from there, indicated that all was not well around Q451, which monitors the vertical January 2000  21 IC401 Fig.2: the safety shutdown circuit in the Panasonic M15L TV receiver is based on transistors Q503, Q504 & Q451. Q451 monitors the vertical deflect­ ion output via resistor R411. output. This transistor moni­tors the current flow in the 24V rail to pin 7 (Vcc) of the vertical output IC (IC401). It does this by means of a 1.2Ω resistor (R411), inserted in this rail. The base/ emitter junction of Q451 is connected across this resistor, with the base to the negative side. This establishes the operating conditions for Q451 which, under normal conditions, would be turned off. Only when the voltage across R411 rises above normal would Q451 turn on and initiate a shutdown sequence. However, IC401 appeared to be functioning normally, in that the set was working perfectly OK without the shutdown circuit. So either IC401 was drawing excess current – which seem­ed to be ruled out – or R411 had gone high. And the latter assumption proved to be correct; R411 had been damaged by the previous faulty IC401. The only flaw in this explanation is 22  Silicon Chip to query why, if R411 in the 24V rail was high, was IC401 still functioning normally? The answer is that it had gone only a little bit high, as they say in the classics – high enough to upset the shutdown system but not high enough to upset IC401. A new R411 allowed R536 to be reconnected and the set to remain fully operational. I fitted it back into the cabinet, replaced the back, put it on the soak bench and switched on. To my extreme annoyance, the shutdown circuit appeared to be falsely activating again. Feeling rather miffed, I put it back on the workbench and took the back off again, whereupon the set resumed working. A faulty back? I hoped so but it was more serious than that. It only required the chassis to be tapped for it to switch itself off and gradually I found the sensitive spot to be around IC401. I checked whether I had sol- dered the IC correctly and it was OK but there were suspect joints on the heatsink, which is also the chassis return for the safety circuit. I resoldered those but it was still intermittent when tapped. Again, this spot was still around IC401. I examined the area very carefully and eventually found that the chassis end of the copper track to R531 (22kΩ) from Q504’s base was fractured. I repaired this and put it back onto the soak bench where it worked until the next day before failing yet again. Once again I delved into it and went through the previous procedure, including disconnecting R536 and measuring each tran­sistor to find which was switching what on. The problem this time was that it would take 10 minutes or so before it occurred, suggesting a heat-sensitive component. To accelerate this, I used a hairdryer to make the fault happen and freezer to stop it. This time, it was Q503 that was being switched on falsely but not via Q504’s base. Possible suspects were Q504 being leaky, D520, D502, D522, R529 and the horizontal output transformer. The picture was still perfect and there was no sign of distress anywhere else. Gradually, I pinpointed it to D502 (MA4360), a zener diode to the base of Q503. Heating and freezing this would switch on Q503. Now I am not averse to ordering the correct zener from the Panasonic spare parts agents but this time I didn’t want to wait. So what value is an MA4360? Fortunately, I have some notes on other Panasonic nomenclature and the code for this series of zener diodes works like this: the first significant digit is the power rating – 2 = 1W; 3 = 150mW; 4 = 400mW; and 5 = 500mW. So in this case, it is a 400mW zener diode. The last three digits represent the operating voltage, with the decimal point going between the last two digits. This gives a value of 36.0V for D502. A new one allowed me to leave the set on for more than 10 minutes. In fact, two weeks later, Mr Rodrigue finally had his set back. These have been just two of several stories out this ser­ ies. Tomorrow I have to go to see a little old lady’s TC1400A set. She is complaining there is “an echo in the sound”! I do hope there isn’t another similar problem SC involved. 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 for more details. (We'll even call you back if STD). Or fax us on (02) 9979 6503. Or if you already have web access, email silchip<at>siliconchip.com.au or www.silchip.com.au A blast from the past – authentic spring reverb SPRING MODULE Add this spring reverberation module to your guitar, keyboard or organ amplifier and get that great “concert hall” effect. No longer do you have to practice in your bedroom, attic, basement or backyard shed. By turning up the reverb effect you can be transported to the concert hall of your dreams. By JOHN CLARKE 24  Silicon Chip B ACK IN THE “good old days” before digital effects became the vogue for musical instruments, electric guitars were often used with “spring reverberation” to get the echo effect of a large concert hall. Not only did the reverberation sound great but it could also make an average performer sound a lot better. And judicious use of reverb could make a small venue sound much larger and more impressive. But why bother with old technology when digital effects can be so much more flexible, more compact and not subject to any acoustic feedback? b The answer is to that like trying to explain why Hammond organs are so popular in modern bands when digital key­ boards are in so many ways superior. Spring reverb does have a particular “authentic” sound that isn’t quite duplicated by digital effects boxes. And anyhow, this little spring reverb module is cheaper than a digital effects box. A spring reverb unit consists of a box containing two or three stretched springs which are driven at one end by a voice coil – just like a loudspeaker but without the paper or plastic cone. The audio signal travels down the springs and is reflected back and forth and then is picked up at the other end by another voice coil unit. The echo signal can then be mixed with the original signal to produce a range of reverberation effects. For this project, we have arranged for Jaycar Electronics to import a compact 2-spring module which is much more compact than the spring modules used some 20 or 30 years ago. It measures just 264mm long x 52mm wide x 33mm deep. The spring reverb module has two characteristics which determine its overall reverberation effect. The first of these is the signal delay time and this is determined by the springs themselves at 22ms and 27ms. Then there is the decay time and this is typically around 1.2 to 2 seconds, depending on the circuit settings. We have a designed a PC board which fits over the metal chassis of the spring module and the complete assembly can then be suspended within your musical instrument amplifier, whether it is used for electric guitar, keyboard or any other musical in­strument. The spring reverb unit requires an unusual drive circuit. This is because the driving voice coil is an inductor Main Features •  2-spring reverb unit •  Input level control •  Reverb depth control •  Reverb in/out switching •  Wide frequency response and it has an impedance which is directly proportional to frequency. For example, it has an impedance of 8Ω at 1kHz but at 10kHz it is 80Ω. Down at 100Hz, the impedance is only 0.8Ω. To obtain a reasonably flat frequency response for signals fed through the module, we therefore need to apply ten times the signal level at 10kHz than at 1kHz and so on. And while the actual power levels are quite low, the drive current requirements are relatively large and so we have added a buffer stage which can do the job. Block diagram Fig.1 is the block diagram of the circuit. The input signal is applied to attenuator VR1 and then to driver amplifier IC1a which provides the rising frequency response. IC1b is the buffer stage which provides the drive current to the reverb module. The reverb output is then applied to switch S1 and then to recovery amplifier IC2a which amplifies the resultant signal. From there, the reverb signal goes to the depth control VR2. IC2b is a stage which mixes the reverb signal Fig.1: the block diagram of the spring reverb circuit. There is quite a lot of signal loss in the spring reverb module and this is made up in the recovery amplifier. January 2000  25 Parts List 1 PC board, code 01402000, 251 x 51mm 1 2-spring reverberation unit 2 knobs to suit potentiometers 1 push on/push off switch (S1) 2 RCA plugs (one white, one red) 1 1m length of shielded cable 1 500mm length of 0.25mm enamelled copper wire 1 50mm length of 0.8mm tinned copper wire 6 M3 x 6mm screws, nuts and star washers 8 PC stakes 1 50kΩ log potentiometer (VR1) 1 10kΩ log potentiometer (VR2) 1 1kΩ horizontal trimpot (VR3) Semiconductors 2 LM833 dual op amps (IC1,IC2) 1 BC338 NPN transistor (Q1) 1 BC328 PNP transistor (Q2) 1 7815 15V 3-terminal regulator (REG1) 1 7915 -15V 3-terminal regulator (REG2) 4 1N4004 1A rectifier diodes (D1-D4) Capacitors 2 1000µF 25VW PC electrolytic 6 10µF 35VW PC electrolytic 1 2.2µF bipolar electrolytic 1 0.22µF MKT polyester 2 0.15µF MKT polyester 1 .039µF MKT polyester 1 .033µF MKT polyester 1 .015µF MKT polyester 3 .01µF MKT polyester 1 .0039µF MKT polyester 1 100pF ceramic or MKT polyester 1 33pF ceramic 1 10pF ceramic Resistors (0.25W, 1%) 1 820kΩ 3 1kΩ 1 470kΩ 3 220Ω 4 220kΩ 2 100Ω 4 100kΩ 2 10Ω 6 10kΩ 1 6.8Ω 1W with the input signal. Switch S1 can be a foot-switch which enables or disables the reverb effect. Circuit details Fig.2 is the complete circuit for 26  Silicon Chip The Spring Reverb Module is based on this compact 2-spring unit from Jaycar Electronics. It is much more compact than the spring modules used 20-30 years ago, measuring just 264mm long x 52mm wide x 33mm deep. The two springs provide signal delay times of 22ms and 27ms. the spring reverb module. The input signal is applied through a 100Ω resistor and .0039µF capacitor which attenuate frequencies above 400kHz. This prevents the possibility of radio frequency breakthrough. From there the signal goes to 50kΩ level pot VR1 and then to pin 5, the non-inverting input of IC1a, via a .01µF capacitor. This capacitor and the 100kΩ resistor provide a low frequency rolloff below 160Hz. IC1a provides a rising frequency response by virtue of the 1kΩ resistor and .01µF capacitor connected to pin 6. These pro­vide a rolloff below 16kHz, while the 100kΩ resistor and 100pF capacitor between pins 6 & 7 roll off signals above 16kHz. The result is a response which peaks at 16kHz with a nominal gain of 40dB (100) and rolling off above and below this at a rate of 6dB per octave. Fig.3 shows the actual response of the driver amplifier. Buffer & output stage Op amp IC1b and transistors Q1 & Q2 make up the buffer and output stage. IC1b drives the complementary transistors and they are included in the feedback network of the overall amplifier. The signal from IC1a’s output is fed to pin 3 of IC1b via a 1kΩ resistor while 100% feedback from the emitters of Q1 & Q2 is fed via a 1kΩ resistor to pin 2, giving an overall gain of 1. Q1 & Q2 are slightly forward biased using the 10kΩ and 220Ω resistors at their bases. Their 10Ω emitter resistors apply local negative feedback to Fig.2: the complete circuit details for the Spring Reverb Module. IC1a, the driver amplifier, has a rising frequency re­sponse to compensate for the inductive reactance of the spring reverb’s voice coil drive. IC1b, together with Q1 & Q2, drive the reverb unit while IC2a makes up for its considerable signal attenuation. January 2000  27 AUDIO PRECISION FREQRESP AMPL(dBV) vs FREQ(Hz) 40.000 30 AUG 99 14:19:48 30.000 20.000 10.000 0.0 -10.00 -20.00 50 100 1k 10k 50k Fig.3: this is the frequency response of driver amplifier IC1a which peaks at 16kHz. The nominal gain at this frequency is 40dB (100), the response rolling off above and below this at a rate of 6dB per octave. stabilise their quiescent cur­rent. The 220Ω resistor between IC1b’s output and the junction of the 10Ω resistors allows the op amp to drive the load directly at very low signal levels and it has the effect of lowering the overall distortion of the buffer amplifier. The buffer stage drives the spring reverb via a filter network consisting of inductor L1, a 6.8Ω resistor and 0.15µF capacitor. This filter and the .01µF capacitor connected across the 1kΩ feedback resistor ensure high frequency stability in the buffer amplifier. DC offset adjustment Trimpot VR3 is included to adjust the offset voltage at the output of the buffer stage. This should be as close to Fig.4: signal delay through the spring reverb unit. The top waveform is a burst input signal while the lower trace is the output which contains the original burst and the delayed signal from the springs. One spring provides a 22ms delay while the second spring gives a 27ms delay. 28  Silicon Chip zero as possible so that no DC voltage is applied to the spring reverb input. Any offset voltage here would cause considerable current to flow in the spring reverb’s driver coil due to its very low DC resistance of 0.81Ω. For example, if the offset voltage at the output of the buffer stage was a mere 100mV, the current through the voice coil would be over 120 milli­amps. With VR3 adjusted for minimum output, it should be possible to keep the output offset to around 1mV or so. The two back-to-back 10µF capacitors connected to the wiper of VR3 are there to prevent latch up in IC1 as power is first switched on. Without the back-to-back capacitors, the effect of one of the supply rails reaching 15V faster than the other would mean that VR3 could possibly apply 100mV or more to pin 6 of IC1a and that would cause the op amp to latch up. If nothing else, the effect would be a very loud thump fed to the external power amplifier and speakers. OK. So the spring reverb is being driven with signals which race up and down the springs and then emerge at the output voice coil. The process involves quite a bit of signal loss and this has to be made up in the aptly named “recovery” amplifier, IC2a. After all, as you can imagine, the output signal is probably feeling a little wobbly after going through those Fig.5: this scope shot shows the signal decay from the circuit with maximum reverb depth. The top trace shows a burst input signal while the lower trace shows the output signal from the reverberation module decaying over a period of 2.5 seconds. Mixer stage The output from IC2a is fed via a 0.22µF capacitor to the 10kΩ depth control pot VR2. This sets the signal level applied to mixer amplifier IC2b via a .033µF capacitor and 220kΩ resis­tor. The input signal to the reverb module is also applied to the mixer amplifier via a .039µF capacitor and another 220kΩ resistor. Since the feedback resistor between pins 1 & 2 is also 220kΩ, the gain of the mixer is set at -1. Frequencies above 22kHz are rolled off by the 33pF capacitor connected across the feedback resistor. The output from IC2b is coupled via a 2.2µF bipolar capaci­ tor and 100Ω resistor. Power supply Power for the reverb circuit is derived from a 30V centre-tapped transformer which is rectified and filtered to provide a ±21V supply. This is regulated to ±15V with REG1 and REG2. The output of the regulators is de­coupled with 10µF capacitors. Also each op amp package has its supply decoupled with 10µF 35VW capacitors. Construction As already noted, we have designed a PC board which fits on top of the spring reverb unit. The PC board measures 251 x 51mm and is coded 01402000. You can start construction by checking the PC board for breaks or shorts between tracks and undrilled holes. Fix any defects you find. The centrally located holes at the far ends Fig.6: the component overlay and wiring connections to the PC board. This mounts on top of the spring reverb unit. Note that the metal cases of the two potentiometers should be connected together and earthed as shown. springs and does need a little time to recuperate. Before the output signal from the spring reverb can get to IC2a, it must first get past S1, the in/out switch. If S1 is switched to the “out” position, the signal from the spring reverb is shunted to the 0V line and that is the end of it. Conversely, if S1 is open, IC2a does its job, amplifying the signal by a factor of 83, as set by the 10kΩ and 820kΩ resistors in the feedback network. To minimise hum pickup from the spring module, the frequency response below 100Hz is rolled off by the 0.15µF capacitor con­necting the 10kΩ feedback resistor to 0V and the .015µF capacitor and 100kΩ resistor at pin 5. January 2000  29 Table 1: Capacitor Codes  Value   IEC EIA  0.22µF 220n 224  0.15µF 150n 154  .039µF   39n 393  .033µF   33n 333  .015µF   15n 153  .01µF   10n 103  .0039   3n9 392  100pF 100p 101  33pF   33p   33  10pF   10p   10 of the PC board need to be drilled out to 13mm so that they clear the neoprene mounting grommets on the spring reverb case. The two holes adjacent to these can be 3mm in diameter. The holes for the PC mounting pots need to be 2mm in diameter and the mounting holes for the regulators should be 3mm in diameter. Start by installing the wire link and all the resistors except for the 6.8Ω 1W resistor. Check the resistor values with a digital multimeter before you install each one or check the colour codes against those shown in Table 2. The two regulators are bolted to the PC board. Bend their leads at right­ angles so that the regulator tabs line up with the mounting holes on the board. Be sure that each regulator is in the correct position before soldering its leads. Next, install the capacitors and take care with the elec­trolytics which must be connected the right way around. Note also that the two electrolytic capacitors adjacent to IC1 and IC2 must have a voltage rating above 30V since they are connected across the 30V supply rail. The MKT types have a value code and these are shown in Table 1. Table 2: Resistor Colour Codes            No. 1 1 3 4 6 3 3 2 2 1 30  Silicon Chip Value 820kΩ 470kΩ 220kΩ 100kΩ 10kΩ 1kΩ 220Ω 100Ω 10Ω 6.8Ω 4-Band Code (1%) grey red yellow brown yellow violet yellow brown red red yellow brown brown black yellow brown brown black orange brown brown black red brown red red brown brown brown black brown brown brown black black brown blue grey gold brown 5-Band Code (1%) grey red black orange brown yellow violet black orange brown red red black orange brown brown black black orange brown brown black black red brown brown black black brown brown red red black black brown brown black black black brown brown black black gold brown blue grey black silver brown This view shows the completed PC board, mounted on top of the spring reverb case. You can either build the completed module into a case of its own and add a power supply or, if there’s room, build it into an existing amplifier. Trimpot VR1, the diodes, PC stakes and transistors can be installed next. Make sure you install the transistors in their correct positions. The two potentiometers are soldered directly into the PC board. However, if you wish to mount them off the PC board this can be done using shielded cable. The shield connec­tion is soldered to the terminal marked GND on the PC board. Cut the pot shafts to length suitable for the knobs before installing them. The 6.8Ω 1W resistor has the coil for L1 wound over it; 24 turns of 0.25mm enamelled copper wire. Strip the enamel off one end of the wire and tin it with solder. Wrap this around one of the resistor leads and solder it in place. Then wind on 24 turns along the resistor body. Cut and strip the enamel off the other end of the wire, wrap it around the resistor lead and solder it. Insert the resistor/choke into the PC board and solder it in place. All signal connections to the PC board are made using shielded cable and cables to the reverb unit will need to have RCA plugs fitted to suit the input and output sockets. Bolt the PC board to the spring reverb unit with 4 x M3 screws and nuts but do not connect the RCA terminals to the input and output sockets just yet. Power supply Before you can test the reverb unit you will need to have a suitable power Fig.7: follow this diagram if you are using the 240VAC mains transformer. All exposed mains terminals should be covered in heatshrink tubing and you should use cable ties on the mains wires so that if one becomes detached, it cannot contact other parts of the circuit. January 2000  31 Specifications Frequency response of undelayed signal ........................... -3dB at 22Hz and 19kHz Frequency response of reverb signal ................................. -3dB at 100Hz and 5kHz Delay times .....................................22ms and 27ms (see oscilloscope waveforms) Decay time ............................................. 1.2-2 seconds (depending on signal level) Sensitivity ................................................................................. 34mV RMS at 1kHz Signal-to-noise ratio (reverb off) ........................... -84dB unweighted (20Hz-20kHz) -88dB A-weighted with respect to 1V output Signal-to-noise ratio (maximum reverb) ............... -73dB unweighted (20Hz-20kHz) -76dB A-weighted with respect to 1V output Fig.8: actual size artwork for the PC board. Check your board carefully before installing any of the parts. Frequency response of driver amplifier ...................................................... see Fig.3 32  Silicon Chip supply. If you have one which can deliver ±20V you can use it to power the positive and negative regulators directly. Failing that, you will need to wire up the 2855 trans­former as shown on the circuit. Alternatively, you may be able to pick up the necessary ±15V supply rails from inside your music instrument amplifier or mixer. The extra current drain from each supply rail will be about 50mA. If you can take this approach, you will be able to omit the 15V regulators. On the other hand, if your music instru­ment amplifier has balanced supply rails between, say, ±18V and ±30V, you should leave the regulators in place. If you need to mount the specified 2855 transformer in existing equipment, try to locate it away from sensitive input circuitry. You should be able to pick up the switched mains voltage where it is connected to the existing power transformer input. Using a separate case If you intend to install the reverb unit into its own case, follow the diagram of Fig.7 when running the 240VAC mains wiring. All exposed mains terminals should be covered in heatshrink tubing and you should use cable ties on the mains wires so that if one becomes detached, it cannot contact other parts of the circuit. The metalwork of the case must be earthed. Use a screw, nut and star washer to secure the earth lug to the case. Some metal cases will require the paint to be scraped away from the earth terminal area before a good contact can be made to the case. Testing Now you are ready to test the reverb unit. Apply power and check that the op amps are supplied with 15V. You should obtain a reading on your multimeter of +15V between pin 8 of both IC1 & IC2 and the 0V (ground) line. A reading of -15V should be obtained at pin 4 of IC1 & IC2. Now connect your multimeter set to read DC millivolts across the “to spring reverb input” terminals on the PC board. Adjust VR1 so that the reading is as close to 0mV as possible. You can now connect the RCA plugs to the spring reverb unit and you are ready to test it. You will need a power amplifier and loudspeaker and a suitable music instrument as the driving signal. You could also plug a guitar straight in and avoid the need for a preamplifier. Adjust the depth control fully anticlockwise and adjust the level pot for a suitable volume. Now adjust the depth pot and check that you can hear the reverb effect. You will find that the reverb effect increases as the depth control is adjusted clock­wise. Note that if the reverb effect sounds distorted, you possi­bly have too much signal at the input and this can be adjusted down with the level pot. The transistors driving the spring reverb will also run warm. Too little signal will result in a poor signal-to-noise ratio. The optimum signal level is SC 22mV at the wiper of VR1. DON’T UTER COMP MISS OMNIBUS THE ’BUS! www.siliconchip.com.au SILICON CHIP’S 132 Pages 9 $ 95 * ISBN 0 95852291 X 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 9780958522910 09 9 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au This handy test generator produces a standard monochrome video signal with a 4-step greyscale pattern, as well as a 500Hz audio tone. It’s just the shot for testing VCRs, video monitors and the continuity of video cables. An Audio-Video Test Generator By LEON WILLIAMS W HEN INSTALLING or repairing video equipment or systems, a test pattern generator is a must. However, for this type of work you don’t need an expensive colour pattern generator with a myriad of options and settings. What is required is a simple signal source that allows a go/no-go indication. While the specifications for this project don’t put it in the professional instrument class, it is light and rugged, can be carried in a toolbox and has the distinct advantage of being cheap. It also uses common components, is easy to build and should work first time. There is no setting up to do and there are no controls to fiddle with. The circuit is powered from a 9V DC supply, which would normally be a 9V plugpack. It produces standard 38  Silicon Chip non-interlaced monochrome video and audio signals (see specifications) that are compatible with just about all TV sets that have a A/V inputs, VCRs and video monitors. Note, however, that this device is not suitable for testing most computer monitors. Circuit details Fig.1 shows the full circuit details of the Audio-Video Generator. The circuit operation may not be obvious at first glance, mostly because the way in which the video signals are generated is a bit more complicated than normal. In addition, some circuit simplification and trickery has been applied to reduce the component count and keep costs down. Clock signals for the circuit are derived from a 4MHz crystal oscillator formed around NOR gate IC1a. The 10MΩ resistor places the gate into linear mode and feedback is accomplished with the 4MHz crystal (XTAL1) and the two 22pF capacitors. Because we are using a crystal, the resulting clock signal is accurate and stable. Inverter stage IC1b buffers the oscillator output which then clocks pin 1 of IC2, a 74HC393 dual 4-bit binary counter. In this case, IC2 has been cascaded to form a single 8-bit divider. Three of its outputs (pins 8, 9 & 10) are used for video timing, while a fourth output at pin 5 (500kHz) is fed to a divider circuit to derive a 500Hz audio signal. The signal at pin 5 is also divided down to produce a 50Hz vertical sync signal. Greyscale generation Pins 8 and 10 of IC2 provide two January 2000  39 Fig.1: clock signals for the circuit are provided by a 4MHz oscillator based on IC1a and these are divided down by dual 4-bit binary counter IC2 to produce most of the video timing signals. Dual decade counters IC3 & IC4 further divide the 500kHz output from IC2 to produce the vertical sync and audio output signals. a result, a stream of low-going 5µs pulses appear on pin 5 of IC5d and this provides the horizontal sync signal (see Fig.3). Diode D3 limits the voltage on pin 5 when pin 8 switches high again, by clamping it to the +5V supply rail. This is done to protect the IC from possible damage due to voltage spikes. Note that because the width of the sync pulses is determined by a simple capacitor/resistor combination and the switching threshold of the exclusive-OR gate, they may not be exactly 5µs. However, this shouldn’t cause any problems in practice. Vertical sync The Audio-Video Generator produces a 4-step greyscale pattern surrounded by a black border, as shown here. Note that the on-screen pattern is off-centre due to design limitations. square waves at 15.625kHz and 62.5kHz, respectively. These two waveforms are the input signals for the greyscale generator. This generator is a simple 2-bit (4-level) D-to-A converter consisting of three 3kΩ resistors and the 1kΩ resistor to ground. If both inputs are low, there is no voltage at the output of this divider network. However, as each input is taken high, a progressive voltage is built up until the voltage is at maximum when both inputs are high. So this simple but effective circuit provides four voltage steps. Diode D1 level shifts the greyscale video waveform generated by the D-to-A converter by 0.6V. We’ll look more closely at this when we discuss the following output buffer stage (Q2 & Q3) later on. Horizontal sync As mentioned above, the output on pin 8 of IC2 is a square wave with a frequency of 15,625Hz. This has a period of 64µs and is exactly the length of a line of video (as used in Australia). The horizontal sync pulses are derived by feeding this 15,625Hz signal to pin 10 of exclusive-OR gate IC5b. IC5b’s other input, pin 9, is connected to ground and so this stage simply functions as a buffer, the signal on 40  Silicon Chip pin 8 following the signal applied to pin 10. Each time pin 8 of IC5b switches low, pin 5 of IC5d is also pulled low via the .001µF capacitor. The .001µF capacitor then charges via the associated 4.7kΩ resistor, so that pin 5 switches high again after 5µs. As Specifications Power Supply Supply voltage ..........9-20V DC Current drain ............15mA <at> 9V Video Output connector ......RCA female Output level ..............1V peak-topeak into 75Ω; 2.4V peak-to-peak unloaded Pattern ......................4-step greyscale Horizontal sync .........5µs negative sync every 64µs Vertical sync .............500µs negative sync every 20ms Audio Output connector ......RCA female Output level ..............840mV RMS; 2.35V peak-to-peak unloaded Output frequency ......500Hz The vertical sync signal is derived by first using the 500kHz signal from IC2 to clock IC3. This stage is a dual decade counter which is wired to divide by 100. The resulting 5kHz signal appears on pin 14 and in turn clocks IC4, another dual decade counter stage. This produces a 50Hz signal on pin 14 of IC4, which is the video frame rate. IC5c buffers this square wave signal and the .001µF capacitor and a 470kΩ resistor on pin 3 generate 500µs vertical sync pulses on pin 4 of IC5d in the same way as for the horizontal sync pulses. The frame period is the inverse of the frame frequency; ie, 20ms. Given that the line period is 64µs, this means that there are 312.5 lines per frame. This figure may seem rather odd but is quite normal. In fact, the picture we see on our television screens is constructed of two frames of 312.5 lines each, to give a total of 625 lines. The half line length allows the two frames to be interlaced, or placed on top of each other, so that the lines of one frame fit between the lines of the other frame, to form one complete picture. The horizontal and vertical sync pulses are combined using IC5d to form a single composite sync signal. An exclusive-OR gate is used here for a special reason. During the vertical sync period, the horizontal sync pulses remain active and this creates what is referred to as “serrated sync”. Normally, in the absence of sync pulses, both inputs to IC5d are high. Because IC5d is an exclusive-OR gate, this means that pin 6 of IC5d will be low. The rule is that an exclusive-OR gate only switches its output high when its inputs are at different logic Fig.2: this scope shot shows the 500Hz audio waveform generated by the unit. The waveform is quite clean and has a level of about 2.35V peak-to-peak or about 840mV RMS. levels (ie, one high and one low). If the vertical sync signal is not active (ie, pin 4 of IC5d is high), a (low-going) horizontal sync pulse applied to pin 5 thus causes the output (pin 6) to go high. This turns on Q1 and pulls Q3’s base to ground (ie, the sync voltage is equal to 0V). Conversely, when the vertical sync is active, pin 4 of IC5d is low for 500µs and a number of horizontal sync pulses also occur during this period. As a result, Q1 cycles on and off at the line frequency and so the vertical sync pulse on pin 6 of IC5d appears to be “serrated”. Blanking To enhance the appearance of the on-screen display, a black border is placed around the greyscale pattern. This black border is generated by the blanking circuitry. Note that the voltage level of this blanking is less than the video black level and so it is often referred to as “blacker than black”. There are two forms of blanking: (1) horizontal blanking on the sides of the screen; and (2) vertical blanking at the top and bottom of the screen. The horizontal blanking signal essentially blanks the video at the beginning and end of each line and it does this by pulling the video signal on Q3’s base to ground (or close to it). It is derived by feeding the outputs from pins 8 and 9 of IC2 into exclusive OR gate IC5a. The output of IC5a switches low when both inputs are the same (ie, at the beginning and end of each line) Fig.3: this composite video waveform clearly shows the horizontal sync pulses, the horizontal blanking signals and the 4-step greyscale signal. Note that the blanking signals before and after each sync pulse differ in length and this is why the on-screen display is off-centre. and this pulls the base of Q3 low via diode D2. Similarly, the vertical blanking signal pulls the video to ground at the beginning and end of each frame. This signal is derived by feeding the outputs from pins 12 and 13 of IC4 into NOR gate IC1c. This gate switches its pin 4 output high only when both inputs are low. IC1d inverts the output from IC1c and pulls the video signal down to 0.6V via diode D5 during the blanking period. Because we are producing a monochrome test pattern, there is no need to generate a colour burst signal. This is a burst of approximately 10 cycles of 4.433MHz which is normally placed on the blanking line (porch) just after the horizontal sync pulse, to allow the receiver to correctly decode the colour information. If the colour burst is absent (as in this case), a colour TV set simply dis- Parts List 1 PC board, code 04101001, 120mm x 80mm 1 plastic case, 158 x 95 x 53mm 1 panel-mount DC connector to suit plugpack 2 panel-mount RCA sockets 6 PC board stakes 1 4MHz crystal Semiconductors 1 74HC02 quad NOR gate (IC1) 1 74HC393 dual 4-bit binary counter (IC2) 2 4518 dual BCD counters (IC3, IC4) 1 74HC86 quad exclusive-OR gate (IC5) 1 LM358 dual op amp (IC6) 1 7805 5V positive voltage regulator (REG1) 2 BC548 NPN transistors (Q1, Q2) 1 BC558 PNP transistor (Q3) 7 1N4148 signal diodes (D1-D7) 1 1N4004 silicon diode (D8) Capacitors 1 470µF 25VW PC electrolytic 2 100µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 6 0.1µF MKT polyester 1 .01µF MKT polyester 2 .001µF MKT polyester 2 22pF ceramic Resistors (0.25W, 1%) 1 10MΩ 3 3kΩ 1 470kΩ 1 1kΩ 4 22kΩ 1 560Ω 3 10kΩ 1 470Ω 1 6.8kΩ 1 75Ω 1 4.7kΩ Miscellaneous Tinned copper wire for links, light-duty hook-up wire, 3mm machine screws and nuts. January 2000  41 Fig.4: install the parts on the PC board and complete the external wiring as shown here. Make sure that all polarised parts are correctly oriented and that the correct part is used in each location. plays a monochrome picture (the PAL colour television system is designed to be compatible with monochrome signals). Output buffer The waveform at Q3’s base thus consists of the 4-step greyscale signal, the horizontal and vertical sync signals, and the horizontal and vertical blanking pulses. Together, these signals make up the composite video signal. However, this signal needs to be buffered before it can be connected to a 75Ω load. Transistors Q2 & Q3 form the buffer stage and are connected in similar fashion to a class-B audio amplifier. These two transistors are wired as complementary emitter followers, with forward bias provided by diodes D6 and D7 to minimise crossover distortion. In operation, D6 & D7 maintain a constant 1.2V between the two transistor bases. A 75Ω resistor sets the output impedance, while the associated 100µF capacitor provides AC coupling to the video output socket. Note that when there is no blanking, no horizontal or vertical sync and the video is black, the video level will be slightly higher than 0.6V (the blanking level). This voltage is developed across D1 and the resistors in the D-to-A converter, due to the current that flows via the output buffer bias circuit (ie, through the 10kΩ resistors Table 2: Capacitor Codes  Value IEC Code EIA Code  0.1µF  100n 104  .01µF   10n 103  .001µF    1n 102  22pF   22p  22 and diodes D6 & D7). Audio generator Pin 5 of IC4 produces a 500Hz square wave and although its duty cycle is not exactly 1:1, this is of no concern in this application. This square wave is applied to a 500Hz bandpass Table 1: Resistor Colour Codes  No.   1   1   4   3   1   1   3   1   1   1   1 42  Silicon Chip Value 10MΩ 470kΩ 22kΩ 10kΩ 6.8kΩ 4.7kΩ 3kΩ 1kΩ 560Ω 470Ω 75Ω 4-Band Code (1%) brown black blue brown yellow violet yellow brown red red orange brown brown black orange brown blue grey red brown yellow violet red brown orange black red brown brown black red brown green blue brown brown yellow violet brown brown violet green black brown 5-Band Code (1%) brown black black green brown yellow violet black orange brown red red black red brown brown black black red brown blue grey black brown brown yellow violet black brown brown orange black black brown brown brown black black brown brown green blue black black brown yellow violet black black brown violet green black gold brown The completed PC board is secured to the bottom of the case using machine screws and nuts, with additional nuts used as spacers. Twist the output leads together as shown, to minimise noise pickup. filter based on IC6a, part of a LM358 dual op amp IC. A bandpass filter is used here rather than a low pass filter because it has a much greater filter slope than a low pass filter with the same number of components. The output from IC6a appears at pin 1 and is a 500Hz sinewave of reasonable quality. This signal is then buffered by IC6b, with the .01µF capacitor across the 22kΩ feedback resistor providing additional low-pass filtering. The output from this stage appears at pin 7 and is coupled to the audio output socket via a 560Ω resistor and 10µF capacitor. The 560Ω resistor provides short circuit protection for the op amp and sets the output impedance at about 600Ω. Note that the non-inverting inputs (pins 3 & 5) of IC6a & IC6b are biased to about 1.8V by a common divider network consisting of 10kΩ and 6.8kΩ resistors. A 10µF capacitor provides filtering for this bias voltage. Power for the circuit is derived from a 9V DC plugpack. This is fed to 3-terminal regulator REG1 via diode D8 which provides reverse polarity protection. A 470µF electrolytic ca- pacitor filters the input to REG1 and the regulated 5V output is decoupled using a 100µF electrolytic capacitor and a number of 0.1µF MKT polyester capacitors scattered around the circuit. Construction Construction is straightforward because all the parts are mounted on a PC board, the only exceptions being the DC supply socket and audio/ video output sockets. This PC board is coded 04101001 and measures 120 x 80mm. Fig.4 shows the parts layout. Start by checking the PC board for faults, as it is much easier to spot these now than when it is covered in solder and flux. This done, straighten some tinned copper wire by stretching it slightly. You can do this by clamping one end in a vyce and pulling on the other end with a pair of pliers. This wire can now be used for the five wire links. Install these first, then fit the resistors and six PC stakes at the external wiring points. Next come the diodes and the capacitors but double-check these to ensure correct polarity. The transistors (Q1-Q3) and voltage regulator REG1 can go in next. The transistors all look the same so make sure that you install Q3 (BC558) in the correct position. The 7805 voltage regulator (REG1) mounts with its metal tab facing towards the centre of the PC board. Finally, install the 4MHz crystal and the ICs. Remember that some of the ICs are CMOS types, so take the usual precautions against static discharge; ie, earth yourself before touching them and solder the supply pins first. Be sure to use the correct IC in each position and note that they all face in the same direction. Before mounting the completed PC board in the case, it’s a good idea to check that it is operating correctly. This will make it easier to do any fault-finding if necessary. First, connect a suitable 9V DC supply to the relevant PC stakes and use your multimeter to check the output voltage of REG1. If it is within 0.25V either way of 5V, you can proceed. If the output voltage is incorrect, switch off and check for construction errors. A low output voltage probably means that the regulator has a short on it’s output. Check for short circuits or components in the wrong way around. January 2000  43 Fig.5: this is the full-size artwork for the front panel. It can be cut out and used directly if desired. Note that the greyscale pattern will not be positioned in the centre of the screen. This is due in part to the simple circuit employed and will also depend to some extent on the characteristics of the video monitor. The reason for this is shown in the scope photograph of Fig.3. As can be seen here, the horizontal blanking signal immediately following the negative-going sync pulse (ie, just before the 4-step greyscale signal) is much shorter than the blanking signal that precedes the sync pulse. Final assembly Fig.6: check your PC board for defects before installing any of the parts by comparing it with this full-size artwork. If you cannot measure any output voltage, leave the power on and check that there is power at the regulator input. If there is no power here, D8 may be reversed or the power supply may be connected with reversed polarity. Once everything is OK, you can have a look at the video output with a CRO. If you don’t have a CRO, the best way to test the unit is to simply connect it to a video monitor using a patch cable. The screen should show a 4-level grey scale pattern surrounded by a black border (see photo). The 44  Silicon Chip lefthand bar should be black, the righthand bar white and two bars with shades of grey in between. You can also check the audio output at this stage using either a CRO or by feeding it into an audio amplifier. You should hear a clean 500Hz tone with good volume. If there is no output, you will probably need a CRO to trace the waveforms around the circuit. In particular, check the video timing signals at the various IC outputs. When all these tests are positive, you can finish the construction. The case has two RCA connectors at one end, one for the video output and one for the audio output. These can be purchased with different colour inserts. The standard is yellow for the video output and red for the audio output. The DC connector is a single hole type and is mounted at the other end of the case. The PC board is secured to the bottom of the case using 3mm screws and nuts. Place an extra nut between the case and the PC board on each screw to act as a spacer. This done, wire the connectors to the PC stakes using light-duty hookup wire, twisting each pair of wires together. Finally, screw on the lid and your audio-video test generator is complete. We’re sure that you will find it SC a handy test instrument. 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 PRODUCT SHOWCASE It’s a Sony . . . but it’s a different! Sony Australia have released the first digital video Handycam cam-corder which not only records full-motion video but also “mega-pixel” still images. In other words, Sony’s DCR-PC100 combines the best of both worlds in video and still cameras into one compact unit. The camera uses the mini DV cassette format and, even more importantly, Sony’s “Memory Stick” flash memory (see below). On the video side, the camcorder delivers up to 520 lines of resolution, while in still mode it captures images at up to 1152 x 864 pixels – more than three times other digital camcorders. And this is in a lightweight (550g) unit which measures just 61 x 127 x 123mm. A 10x optical and 120x digital zoom is built in, with the precision optics sporting the Carl Zeiss brand name. It’s already suitable for digital TV with a 16:9 (wide-screen) recording format. The camera can record in total darkness (0 lux) with its inbuilt infra-red mode. Eight different picture effects are also available, including black and white, sepia, negative art, solarisation, pastel, slim, stretch and mosaic. Digital options include Old Movie, Luminance Key, Flash Motion, Still, Slow Shutter and Trail modes. Still pictures and video can be combined in a variety of Chroma Key modes. Analog and video inputs are provided, so the user can convert their libraries of analog videotapes to digital, regardless of format. And digital tapes can be easily edited via a PC. Included is a 2.5-inch LCD colour screen (of 200,000 pixels) for whatyou-see-is-what-you-record realism. The screen can rotate up to 270°, even allowing the user to video themselves while watching the screen. Supplied with a Windows-compatible photo manipulation and cataloguing program called PictureGear Lite, a wide variety of applications are possi- ble – everything from near-broadcast-quality video to still pictures for the ’net. Mind you, this doesn’t come particularly cheap. The list price for the DSCPC100 Handycam with a 4MB Memory Stick is almost $4600. Then again, quality single-frame mega-pixel cameras are still in the $1000$2000 range so to get an outstanding quality digital video thrown in, the value is certainly there. Memory Stick If the release of the DCR-PC100 wasn’t news enough, Sony also announced a 64MB capacity “Memory Stick” media to bolster its range of 4, 8, 16 and 32MB sticks. Sony believes the memory stick will become the standard flash-storage media of the future, especially with even larger capacities planned – 256MB by 2001. As it is, the 64MB stick can hold more than three hundred mega-pixel (1152 x 864) images in super fine, fine or standard modes. The memory stick is designed to link and transfer information between The 64MB variant of Sony's “Memory Stick” flash memory, shown close to actual size. 256MB versions are planned by 2001! a wide variety of audio, video and computer products. It is flash media, giving it high storage capacity but in an ultra-compact design. The durable stick memory case measures just 21.5 x 50 x 2.8mm and weighs just 4g. Read speed is up to 2.45MB/second while write speed is up to 1.5MB/second. Already the memory stick concept has been backed by a number of other major consumer electronics and computer manufacturers. Transferring data recorded on a memory stick to a PC is simple: Sony have an adapter which fits any standard 3.5-inch floppy disk slot. This disk drive reads the data from the memory stick adapter as if it were a disk. A parallel port adapter is also available. Memory Sticks sell for around $240 (32MB capacity) up to $429 (64MB), while the floppy disk drive adapter lists for $239. For more information, contact Sony Consumer Information Centre on (02) 9879 9712, or www.world.sony.com January 2000  53 Marantz “Century Design” range for new century Jamo Australia have introduced the new “Century Design” range from Marantz to coincide with the turn of the century. The CD6000 OSE CD player (pictured above) is part of this range which also includes four other CD players (two multi-CD), a new integrated amplifier offering optional Class A mode, two new tuners and a twin tape deck. The CD6000 OSE recently gained 5 stars in the “What Hi Fi” (UK) awards. Coming early this year will be the new DR-600 CD-recorder and DR-6050 dual-drive CD player/recorder. An even higher spec range, the Marantz “Premium Series”, has also been introduced for those who want the very best in audio performance and reproduction. New AV equipment is also being introduced. For more information, visit better hifi dealers or contact Jamo Australia, PO Box 350, Mt Waverley, Vic 3149, phone (03) 9543 1522; email info<at> jamo.com.au The Marantz website is www.marantz.com.au Let Jaycar shed some light on the subject . . . If your eyesight isn’t what it used to be – or perhaps if you don’t want it to go that way – Jaycar Electronics stores have a magnifying worklamp which should be of interest. It’s fitted with a 22 watt fluoro lamp and a large 3-dioptre lens which gives a superbly clear enlarged image for you to work by. The base can clamp to a workbench up to 45mm thick and it has a double-hinged extension arm that opens out to 990mm. It’s perfect for the hobbyist, technician or even production and assembly lines. Price is $125 from all Jaycar Electronics stores. Remote Power Control Via The Internet If you need to switch devices on and off from a remote location, this Remote Power On/Off Control Kit from MicroGram could be the answer. It lets you log onto the Internet and switch up to eight appliances via a central server. It might not be the complete answer to a “smart house” but this device is at least a step in the right direction. Let’s face it, you’re not really going to use it to start a coffee percola­ tor, although undoubtedly it could be used to do this. Instead, it’s more likely to be used for more serious purposes, such as switching security lights and burglar alarms, or switching com­puters on or off from a remote location. Other possible uses include controlling air-conditioning, transmitters and pumps, industrial process control and switching security monitoring equipment. What’s in the box? Well, you get a PCI “industrial” card (this plugs into a spare PCI slot on the server’s motherboard), a power control box and a 2-metre long cable to connect 54  Silicon Chip the two together. The cable has eight separate outputs (all BNC con-nec­ tors), which means that you can connect up to eight separate power control boxes. Each control box is capable of switching 240V at up to 10A. Also included in the package is the necessary software, supplied on a CD ROM. This includes the device driver for the card (Windows 95/98/NT) plus the application software to provide the switching function. Also included on the disk is the Visual Basic source code for both the server and client, so that you can develop your own application software. The software can be configured so that the server (ie, the PC with the controller) can register its IP address to an Inter­ net Location Server (ILS). Client computers at remote locations can then query the ILS when they log on to obtain this IP ad­dress. What this means in practice is that a user at a remote location only needs to know the server’s email address. The ILS then returns the server’s IP address so that the client can access the server, to switch devices on and off. Of course, this is only necessary where the server is dynamically assigned IP addresses by an Internet Service Provid­er; the ILS service isn’t necessary if the server has a fixed IP address. The Remote Power Control Kit (Cat. 17064), including one power control box, costs $579.00 (incl. tax) and is available from Microgram Computers, Unit 1, 14 Bon Mace Close, Berkeley Vale, NSW 2261. Phone (02) 4389 8444; email info<at>mgram.com.au; website www.mgram.com.au Additional power control boxes are also available if required for $259 each. Central Coast Field Day “The Biggest Field Day & Hamfest in the Southern Hemisphere”: that’s how the Central Coast Field Day is described. And with a huge range of attractions for amateurs and electronics hobbyists, it’s hard to disagree. Held on the last Sunday of February each year at the Wyong Racecourse (about 1 hour north of Sydney), the field day has a reputation as a bargain-hunter’s paradise with loads of pre-loved equipment in the flea market plus importers and distributors keen to dispose of superseded models (and to show off and sell their latest!). There are also many demonstrations, lectures, seminars and workshops during the day. Entry to the Field Day is $10 for adults, concession $5 and children under 12 free. Parking is free and food and drink is available at the venue. Gates open at 8.30am. For futher information 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 TOROIDAL POWER TRANSFORMERS Manufactured in Australia Comprehensive data available Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 Questronix Video Distribution Amplifiers Two Video Distribution Amplifiers for the audio-visual, broadcast and film industries have been released by Sydney-based Quest Electronics Pty Ltd. The compact, lightweight HC5 amplifiers appear and are functionally identical but one is designed to work from 240V AC and the other from 12-24V DC (or 9-36V DC in the “HC5C” model). The units feature a hum-cancelling input circuit to reduce interference caused by mains wiring, lighting dimmers, ground loops, etc, without impacting on bandwidth. Input is a standard BNC socket, 1V pk-pk nominal. Five 1V pk-pk nominal BNC outputs are provided, each at 75Ω, with gain New low-cost, high quality ‘dbx’ equalisers Jands Electronics, distributors of dbx, have available the new dbx Series 12 equalisers, the 1215 (retail price $995) and 1231 (retail price $1395). Offering 15 2/3-octave and 31 1/3octave bands respectively, the equalisers have a range of features normally found only in high-end models. These include 45mm faders, select-able ±6dB or ±15dB boost/cut, a choice of XLR, barrier strip and 1/4inch TRS connectors for installation ease, balanced inputs and outputs and chassis/signal ground lift capabilities. Contact Jands Electronics Pty Ltd, phone (02) 9582 0909, fax (02) 9582 0999. variable via a front panel control from 0dB to +6dB. Cable equalisation is also adjustable from the front panel. Hum rejection is better than 46dB at 50Hz and better than 26dB at 1MHz. The units also have internal links for 75Ω input termination on/off, AC or DC input coupling and whether the input shield is floating or grounded. Both units measure 140 x 122 x 35mm and weigh 650g (AC version) or 430g (DC version). A 240V plugpack supply is included with the DC version. For more information, contact Quest Electronics at PO Box 548, Wahroonga NSW 2076, phone (02) 9477 3596, fax (02) 9477 3681, or via their website at www.questronix.com.au Get your components from an online store A new Australian on-line electronic component store has been launched with more than 650 pages of electronic kits, components and equipment available. Ballarat-based Wiltronics Research Pty Ltd is an Australian-owned and operated company which has been in the wholesale component business for more than 25 years. Its new on-line store, www.wiltronics.com.au, is believed to be the largest regional e-commerce site in Australia. With its own inbuilt search engine it is very easy to find just what you need. The company plans to add more than 400 new pages over the next year. They offer very competitive prices, with payment made via credit card to a secure server. January 2000  55 Remember PACMAN, that ubiquitous computer game of a decade (or so) ago? Here’s the new millenium version – PICMAN 2000 – only this one doesn’t run around a screen and chomp dots. He runs around, well, anywhere you tell him to. That’s ’cause PICMAN 2000 is a programmable robot and obeys your every command. PiCMAN A PROGRAMMABLE ROBOT 56  Silicon Chip P ICMAN 2000 is driven by a single PIC16F84 microcontroller and will perform up to fifty combinations of manoeuvres involving left and right, forward and back movements and a pause. Like all good robots, he lets you know when he’s turning and stopping with his built-in turn indicators and brake light. It’s a simple project which we believe will be very popular with schools as they move into this new phase of the information technology age. PICMAN 2000 will not only give hours of entertainment, it will teach a lot about how basic microcontroller programs work. Build PICMAN 2000 now and you could become the twenty-first century’s Bill Gates! Apart from the PIC microcontroller, there are not very many other components – just a few to supply appropriate power to the robot’s drive motors. There are also a few switches which not only control various functions (such as power on/off, speed, etc) but also allow you to program the PIC (and therefore the robot). Finally, there are the previously-mentioned blinkers and stop light which are LEDs driven directly from the PIC chip. Unlike some previous robots, PICMAN 2000 has a single 6V supply derived from 4 x AA cells. This provides power for both the logic circuitry and the motors. And also unlike some previous robots, the motors power the back wheels with a free-turning front wheel (castor). With the exception of the battery pack, three switches and the rear (brake) LED, all of the electronics is assembled on a single PC board. Mechanically, everything is mounted onto two small pieces of clear acrylic sheet (although other materials could be substituted) which are themselves glued to two back-to-back stepper motors. The drive shafts from the stepper motors are fitted with cogs which friction-drive the large rubber-tyred wheels. Turning is achieved by driving one wheel faster than its mate or even one wheel in a reverse direction to its mate. The circuit Fig.1 shows the PIC16F84 to be the heart (or brains) of the circuit driving PICMAN 2000 with PORTB outputs (RB0 to RB7) driving the four windings in the two stepper motors through pairs of NPN/PNP power transistors in a bridge or “H” configuration. RB0-RB3 drives the two fields of the left stepper motor and likewise, RB4-RB7 drive the right motor. Each end of each stepper motor winding is connected to the common emitter of a BD139 (NPN) and BD140 (PNP) transistor pair. Their common bases are biased by a single 100Ω resistor connected to the PORTB terminals. In this way, a low signal from the port would allow grounding of the end of the associated field. PORTB also doubles as the programming inputs to the PIC, depending on whether S2 is set in the PROGRAM or RUN mode. S1 turns the robot on, connecting 2000 DESIGN BY ANDERSSON NGUYEN Above photo shows PICMAN 2000 going away from you, while the shot on the facing page is comin’ right at ya! The front wheel doesn't steer: all direction control is performed by the instructions you give to the PIC which in turn drives the stepper motors. January 2000  57 Fig.1: the circuit might look complicated but it really is very simple, thanks to the PIC microcontroller. both the motor drivers (directly) and also the PIC chip through a reverse polarity protection diode, D10. This diode also drops the IC supply voltage to around 5.4V. Although the PIC can handle 4.56V, it is better to keep the supply in the middle of these extremes. MCLR (main clear) is also held high by this 5.4V rail. When in RUN mode, 6V is applied to the collectors of all BD139s, with 58  Silicon Chip the collectors of all BD140s earthed. A high signal from any of the PORTB outputs would take the base of the associated BD139 and BD140 high. Take, for example, when RB0 (pin 6) goes high. This would turn on transistor Q1 (NPN – BD139) and ensure Q2 (PNP – BD140) is turned off. Therefore the emitters of both transistors, along with one end of the attached field winding, would be raised to about 5.5V (allowing for some voltage drop across the transistor). Since the PORTB outputs are usually low, the bases of transistors Q3 and Q4 would be pulled low by RB2 (pin 8). The BD139 would be turned off while the BD140 would be turned on, effectively grounding the opposite end of the field winding. The field winding is energised, causing the motor to step forward. Conversely, a high on the bases of transistors Q3 and Q4 (with Q1 and Fig.2: the component overlay shows just how simple the electronics are – just a microcontroller and a few other components. Inset below is the DIP switch showing which switches do what! Q2 bases low) will cause the field to be reversed. It is a requirement of the particular stepper motors used that one field is activated in one polarity, then the other field is activated with this same polarity. Then the first field is reversed followed by the second field being reversed. This cycle is repeated to cause the motor to run in one direction. In order to reverse the motor, the sequence is applied in reverse order. In moving forwards, the two motors are driven in the same direction. In turning one is driven forwards, the other in reverse depending on the turn involved. In this way, a very tight turn arc is achieved. All these motor sequences are possible thanks to our nifty PIC! But that’s not all! In the program mode (when S2 is switched to PROGRAM ), PORTB is converted to act as inputs, switching power to D1-D8 and causing RA0 to go high, previously held low by the 10kΩ resistor to earth. D9 drops the input voltage to match the supply voltage to the PIC. D1-D8 serve the same purpose, in addition to isolating the PORTB terminals from each other, which could happen via DIP switches DIPa-DIPh. The terminals of PORTB are each held low by a 2.2kΩ resistor. Being significantly higher in value than the bias resistors (100Ω), these have no bearing on operation in RUN mode. Each of the diodes D1-D8 is connected to the terminals of PORTB via the programming DIP switches DIPa-DIPh. These enable the instruc- tions to be entered, effectively as an 8-bit binary code. DIPa = back, DIPb = left, DIPc = stop (pause), DIPd = right, DIPe = forward while DIPf,g,h represent the 3-bit binary code for the number of steps the robot will take with that instruction. For example, if DIPe is set along with DIPf and DIPh, and this is entered as the instruction and then executed, the robot will turn right for five arbitrary preprogrammed units of angular displacement. The programming is such that a turn of five units brings the robot around 90° and so a turn of one unit will turn the robot about 18° (with allowance made for any slippage, whether in the drive mechanism or between the wheels and floor). Similarly, a setting of DIPa and DIPf will cause PICMAN 2000 to move back an arbitrary preprogrammed distance of almost exactly 15cm. With these variations in addition to the 50 possible instructions, an immense number of permutations of manoeuvres may be carried out. The program switch array may then be separated into two areas, one being the command switches, the other being the magnitude (steps) switches. The command switches operate on a lowest significant priority. For example, if DIPa and DIPd were both set and entered as the instruction, the accepted command would be a ‘back’ command since DIPa is lesser in significance. There is, however, one exception, which occurs when both DIPa and DIPe are set. This is recognised as a repeat command and when encountered, the robot will return to the beginning of the instructions and execute them again from there. It is possible to enter instructions after the REPEAT instructions but these will never be acted upon. It should be noted that the REPEAT is infinite although at least one of the magnitude switches must be set. Irrespective of what state the magnitude switches are in, if none of the command switches are set and this instruction is entered, this is accepted as an ‘end of instructions’ command and is registered by the two blinkers turning on and staying on. No more instructions are accepted after this. In practice, it is not necessary to enter this instruction since, whenever switching to RUN from PROGRAM, the last entered instruction is recognised as the last instruction. If none of the magnitude switches are on when an instruction is entered (other than the ‘end of instructions’ instruction), there will be an error message indicated by the flashing of the brake light five times in rapid succession. The instruction can then be reentered with alteration to the magnitude switches. This mechanism prevents the robot from being instructed to perform an illogical operation such as: ‘forward 0 units’. In PROGRAM mode, power to the collector of the BD139s is removed to ensure that the setting of the program switches doesn’t energise the motors. C3 serves to hold the supply voltage January 2000  59 when S2 is switched from RUN to PROGRAM because there is a brief instant when PORTB is still acting as outputs and if any of the program switches are set, then this results in a short. Without C3, the IC powers down briefly but enough to cause all memory to be reset. RA4 is normally held low by a 10kΩ resistor to earth. To enter/execute or pause, it is pulled high by the momentary-acting pushbutton switch, S3. This switch is responsible for entering the instructions in PROGRAM mode. After each entry, the brake light will turn on and stay on for a duration of about one second. During this period, another instruction may not be entered. This delay prevents switch bounce from causing incorrect entries. In RUN mode, S3 will start the execution of the entered program. While the program is running, pressing S3 will cause it to pause indefinitely until S3 is once again pressed. At the commencement of execution of a program, the brake light will come on for a brief moment before the robot actually acts on its first instruction. When paused, the brake light will again be illuminated briefly before extinguishing. When instructed to PAUSE (in programming), the robot stops and the brake light slowly flashes to distinguish it from an external instruction to pause. Fig.3: compare the mechanical drawings above with the photos below and you’ll get a good idea of how PICMAN 2000 goes together. Drive is directly onto the rubber tyres from the stepper motors – it’s essential to get a good tight fit! The photo at right shows where the battery pack goes. It’s held in place simply by the switch at the front. 60  Silicon Chip Fig.4: these diagrams will assist you in constructing the various pieces for the PICMAN 2000 robot. All are to scale so you can also use them as drilling templates. Saves a lot of messy measurement, doesn’t it? January 2000  61 Parts List 1 PICMAN 2000 PC board, code 11101001 1 acrylic chassis, cut to size from 126mm x 3mm diameter circle 1 acrylic plate, 60 x 50 x 3mm 1 aluminium angle bracket, 70 x 25 x 25mm; 2 wheel brackets, 40 x 25 x 3mm 2 50mm rubber-tyred trolley wheels, 1/4-inch axle 1 30mm wheel castor 2 4-wire stepper motors 1 8-way DIP switch 1 SPDT mini toggle switch 2 SPST mini toggle switches 1 momentary pushbutton switch, PCB mounting (eg DSE P-7572) 1 4 x AA battery holder (flat type) 4 AA batteries (pref. alkaline) 4 32 x 3mm bolts & nuts 4 22mm spacers 2 ¼” x 1¾” bolts 4 nuts to match 4 shakeproof washers 2 plain washers 20 PC pins 1 18-pin IC socket 1 16-pin IC socket Semiconductors 1 programmed PIC16F84 (IC1) 2 5mm yellow LEDs (LED1, 2) 1 10mm RED LED (LED3) 1 IN4004 power diode (D10) 9 IN4148 signal diodes (D1-D9) 8 BD139 NPN transistors (Q1, 3, 5, 7, 9, 11, 13, 15) 8 BD140 PNP transistors (Q2, 4, 6, 8, 10, 12, 14, 16) Resistors (0.25W, 1%) 1 15kΩ 2 10kΩ 8 2.2kΩ 3 220Ω 8 100Ω Capacitors 1 100µF PC electrolytic 1 180pF disc ceramic 1 100pF disc ceramic Miscellaneous   Solder, hook up wire, contact adhesive etc. RA1 and RA3 of PORTA drive the right and left blinker LEDs respectively via 220Ω resistors. These flash and indicate the appropriate turn. At the end of execution of all entered instructions, both will flash repeatedly to indicate the end of the task (unless a repeat instruction has been included). At this point, the robot may be instructed to execute again, or a new program may be entered by changing to RUN mode. After executing the 50th instruction, both blinkers and the stop light come on. This differentiates the “50th instruction” from an “end of instructions”. Similarly, RA2 drives the Stop LED. In addition to being activated in the abovementioned circumstances, between programmed instructions the robot comes to a brief stop, indicated by the stop light going on for that duration. C1, C2, S4 and the 15kΩ resistor comprise an external clock connected to the OSC1 input. S4 switches a second capacitor, C1, in parallel with C2 to increase the time constant, slowing down the rate of operations and hence the speed of rotation of the motors. There are a number of other aspects of operation, functions and limitations of the robot which may be further explained by referring to the ‘WHAT IF’ table. Construction The program on the PIC16F84 and the PC board artwork are both copyright to the author and so it will be necessary to attain these and the appropriate motors from the author. The PC board must be firstly assembled, following the component overlay diagram of Fig.2. Tracks and pads are close together on this board so care is required when soldering. Because of the fine trackwork, it’s even more important than normal to check the PC board thoroughly before commencing construction. The lowest sitting components, resistors and small-signal diodes should be installed first, followed by the Fig.5: a close-up diagram of the drive mechanism (obviously one side only). The opposite side is mirror-image. capacitors and right and left blinker LEDs which should be bent parallel to and in front of the PC board. PC pins are used to make the external connections – these include the switches, power, brake LED and motor connections. Power diode D10 is installed vertically on the PC board with its cathode (stripe) closest to S3. It is advisable to use IC sockets for both the PIC and DIP switch as this will allow for easy replacement should there be any problems. The transistors and pushbutton switch should be soldered last. Take care with both the polarity and location of the transistors: on one side of the PC board they face one way, on the other side they face the opposite way. The pushbutton switch, too, must be installed the right way around – its flat side is closest to the PIC. The chassis The chassis of the robot is fabricated from a slightly larger than half circle of acrylic with a diameter of 126mm (see Fig.4) The cuts are made with a coping saw then trimmed with a sander. While in the original one piece of acrylic was cut to size then bent at 90° using a heat gun, you might find it easier to cut two pieces of Resistor Colour Codes No.   2   3   2   2   1 62  Silicon Chip Value 15kΩ 10kΩ 2.2kΩ 220Ω 100Ω 4-Band Code (1%) brown green orange brown brown black orange brown red red red brown red red brown brown brown black brown brown 5-Band Code (1%) brown green black red brown brown black black red brown red red black brown brown red red black black brown brown black black black brown acrylic and glue them together using a small right-angle aluminium bracket, as we have shown. Contact adhesive is used throughout. Fig.4 shows the cutting and drilling details for the acrylic chassis, the acrylic vertical strip, the angle bracket, the wheel brackets (two required) and the motor plate. Start with the motor/wheel plate assembly. Each plate is made from 3mm x 25mm strip, available from most hardware stores. The two plates are 40mm long. Accurate drilling of holes in the plate is necessary to ensure that the motor cog meshes adequately with the rubber rim of the wheels once assembled. The wheel and bracket are fixed to the motors by fitting protruding screws on the motors through the holes in the brackets and tightening with nuts. The wheels used are typically available from hardware stores (eg, as used in very small trolleys) and have a rubber tyre. They are 50mm in diameter and have a shaft hole suitable for a quarter-inch bolt. They are fixed to the wheel brackets with two nuts, one each side of the bracket, and shakeproof washers. The wheel should spin freely on its axle when not in contact with the motor cog. The two stepper motors are glued end-to-end with contact adhesive. Make sure the alignment is perfect because this will affect how true your robot travels. We also glued on an aluminium strip, 75 x 25mm, across the back of the motors. It’s there for good looks as much as to ensure the motors stay glued together! Once the glue sets, an aluminium angle bracket 70 x 25 x 25mm is used to attach both the acrylic chassis and the vertical acrylic strip to the front end of the motors, again with contact adhesive. The acrylic chassis is not flush with the lower edge of the motors but instead is about 12mm above them so the aluminium angle bracket is glued in position to accept this. While the glue is setting, you can prepare the rest of the chassis. A small castor with wheel diameter of 30mm is glued to the underside of the acrylic chassis in the midline as far forward as possible without impinging on the installation or operation of the front “WHAT IF” TABLE 1. The robot is turned on. The brake light will go on for about one second, then turns off. If S2 is on RUN, and the ENTER/EXECUTE/PAUSE button is pressed, the blinkers will flash to indicate the end of instructions since none had been entered. S2 may be switched to PROGRAM or, if already in program mode, the robot may be programmed by firstly setting the DIP switch array and pressing the ENTER/ EXECUTE/PAUSE button for each instruction. 2. S2 is switched to RUN after having entered a set of instructions. The robot will now execute the entered instructions if the ENTER/EXECUTE/ PAUSE button is pressed. 3. The ENTER/EXECUTE/PAUSE button is pressed during the    execution of instructions The robot will enter into an indefinite pause (as compared to an instructed pause – which is definite). The brake light will come on for about 1s, then extinguish and the robot will sit idle. It will await for either the ENTER/EXECUTE/PAUSE button to be pressed again, whereby it will continue executing the program from where it left off, or S2 may be changed to PROGRAM to enter a new set of instructions. If no new instructions are entered and S2 is switched back to RUN, the robot will retain the previous program instruction set and can execute the program from the beginning if the ENTER/EXECUTE/PAUSE button is pressed. 4. S2 is switched from RUN to PROGRAM and then back to RUN again without entering a new program. If this is done at the end of the execution of a set of instructions, then there will be no effect on the already entered program and the robot will execute the program again if instructed to do so. If the switch is actually changed during the execution of a program, the robot will stop and will retain the previous program instruction set which may be executed again from the beginning once in the RUN mode. 5. The robot is turned off, then on again at any time. If during the execution of instructions, the robot will obviously stop and all memory is lost and new instructions must be entered. 6. The speed switch is changed at any time. The speed at which the robot clocks and performs instructions is altered and so such things as the speed of blinkers, delay time of instruction entry and so on are altered. 7. S2 is switched from PROGRAM to RUN and then back to PROGRAM again. A new set of instructions can be entered from the beginning only. All previously entered data is lost unless S2 is once again changed to RUN without any programming changes. 8. ‘Repeat’ is entered as the first instruction. When switching to execute, the robot will go into an infinite loop and the brake light will remain on. There is only one remedy – switch the robot off to clear all memory. Watch this though. If you switch off and on too quickly, there is inadequate time for C3 to discharge and so memory can be retained. To avoid this, switch off and count to 10 before switching on again. 9. ‘End of instructions’ is entered as the first instruction. On switching to RUN and executing, both blinkers will flash to indicate the end of instructions since none were really entered. January 2000  63 (power) switch. The PC board can now be bolted to the chassis with 32mm long bolts with nuts and 22mm spacers. This provides adequate room under the PC board to house the 4xAA flat battery holder. The vertical acrylic plate, approx. 60mm wide and 50mm high, is glued to the aluminium bracket behind the PC board. This protrudes above the motors and the 10mm red LED is glued onto this to act as the brake light. Two fine holes are drilled through the acrylic for the LED leads. Glue the acrylic chassis/PC board assembly and the vertical acrylic plate to the inside of the aluminium angle bracket and set aside to dry. The three external switches are mounted in the places provided. Make sure S2, the program/run switch, is the SPDT type – the others can be SPST types. Of course, SPDT switches can be used as SPST if you ignore one terminal. The front switch (S1) also helps to keep the battery pack from slipping forwards. It’s best to leave S1 out until the battery holder (with batteries, of course) is inserted – but leave this until your robot is finished! Wire connections from the PC board to the switches, batteries and motors can now be made. Holes are provided in the acrylic chassis for the switch wiring to travel, in part, underneath the chassis. Twisting the wires together over their length is not only neater – it keeps them together. After this is done, tidy up all wiring with cable ties where required and you’re almost ready to go! Just make one last check that everything is where it should be, that all the nuts are tight and all wires are secured out of harm’s way. Then place your four AA batteries into the holder, slide it into position between the PC board and the acrylic chassis and then insert and tighten S1. Now you’re ready to go! Operation Naturally, you’re going to have to program the robot before it does anything. When you have that part nailed down, you’ll be amazed at how much control you can have over the PICMAN 2000’s actions. Get some friends together with your PICMAN 2000s and, laying multiple obstacles on the floor, attempt to navigate your path by guesstimate programming to avoid the obstacles through to the other side from a common start point. The first to achieve this wins! Remember that the robot will travel 15cm with each forward or back step and turns approximately 18° with each right or left turn step. With little slip, the robot is capable of very accurate and reproducible movements and having such big wheels, the robot has little trouble travelling over carpet and even relatively rough ground so you can have SC fun almost anywhere! WHERE TO GET THE PARTS Most components are commonly available at electronics stores. Specialised components (PC board, programmed PIC and stepper motors) are available from Andersson Nguyen, PO Box 338, Minto NSW 2566. Ph (bh) (02) 9820 4161. Prices are:   PC Board – $15.00   Programmed PIC - $20.00   2 x 5V stepper motors – $35.00   P&P on any/all items: $3.00 R VAL EAL UE AT $12 .95 +$ Or 5 ea P bu &P g y5 pos et themand tage free Order by phone or fax from SILICON CHIP - or use the handy order form in this issue 64  Silicon Chip ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. e & Get Subscrib count is D A 10% on ther Silic e O ll A n O is d n a h rc Chip Me $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  GIFT SUBSCRIPTION DETAILS RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia January 2000  65 Connect to the real world with this: Parallel port I/O card for PCs This easy-to-build input/output (I/O) card features 10 analog inputs, two analog outputs and eight digital outputs. It plugs into your PC’s parallel port and you can drive it with Windows-based software. By PETER SMITH If you have an application that would adapt well to comput­er control or would just like to learn about interfacing PCs to the real world, this project is for you. Connection couldn’t be simpler; just plug it in to the parallel printer port on your PC, hook up DC power and you’re ready to begin experimenting. The card’s eight digital outputs can be used to control devices such as 66  Silicon Chip relays, solenoids, motors and lamps. Ten analog inputs are provided too and these can be easily interfaced to a multitude of devices like temperature, pressure, light and posi­tion sensors. In addition, two variable voltages can be generated using the analog outputs. Software examples are available if you want to write your own control programs or you can download Windows software, writ­ten by James Rickard, from SILICON CHIP to get you off the mark right away. Low power consumption means that it can be battery powered or it will operate from any DC power source from 7.5V to 25V. In the following text, we take a brief look at the PC parallel port and how it connects to the interface board. We then look at how data is transferred from the parallel port to the interface board. Next, we examine how that data is used to gener­ate the digital and analog outputs. Last but not least, the analog-to-digital section gets the treatment. PC parallel port basics Software control of the interface board is carried out via the standard PC parallel printer port. Table 2 lists the function of each signal on the PC parallel port as related to its usage on the interface board. For reference, we also show the function of each signal when the port is used for its “normal” purpose – driving a printer! All signal lines in and out of the PC parallel port are at TTL or CMOS (05V) voltage levels. The port occupies three sequential addresses in the PC’s I/O memory map. The first ad­dress is called the “base” address. PCs support up to three parallel ports, commonly referred to as LPT1, LPT2 and LPT3. Generally, the first two ports are mapped to base addresses 378H and 278H, respectively. For example, to read the IC4 data out and EOC pins when the interface board is connected to LPT1, the software would read I/O address 379H (base +1). Communication The interface board is connected to the parallel port via connector SK6. The 1kΩ series resistors and 220pF capac­itors to ground filter the parallel port signals. The series resistors limit current flow into the IC pins to safe levels. High currents could occur when the PC is powered but the interface is not (or vice versa) or when the board or con­ necting cable is exposed to electrostatic voltages. In combina­ tion with the capacitor to ground, the series resistor also helps to remove high frequency noise. In addition, most lines are pulled up to +5V with 10kΩ resistors, ensuring that logic inputs always reach valid “high” voltage levels. Getting data in and out To keep the design as simple as possible, all data is transferred to and from the interface board in serial format (ie, one bit at a time). IC1, IC2 and IC3 are serial-to-parallel shift registers, connected in series (cascad­ed) to form a 24-bit shift register. This is done by connecting the serial out (or Qh’) pin of one 74HC595 to the serial input (SER) pin of the next. The software writes each data bit in turn to the serial input of IC1 (pin 14) and toggles the clock (pin 11) to shift it in. The clock inputs on all three 74HC595s are connected togeth­ er, allowing the entire 24 bits to be shifted together. The 74HC595 has a second clock input (pin 12) which is used to transfer data from the shift registers to an internal 8-bit output latch. This Fig.1: the Windows-based software is easy to drive, with everything controlled and displayed via this dialog box. “two-stage” method of update is used so that data does not change on the output pins until all bits have been shifted to their correct positions. Unlike the shift clock, the register clock (pin 12) of each 74HC595 can be individually controlled by the parallel port interface and software; this is the default configuration. Alternatively, they can be connected together and controlled via a single interface line by moving jumpers J4 and J5 from position 1-2 to 2-3. The Qa-Qh outputs of the 74HC595s can be enabled or disa­bled (switched to the high-impedance state) by controlling pin 13 (G). The output enable pin of each 74HC595 is controlled indi­vidually by the PC parallel port interface and software. Alterna­tively, connecting them to ground with jumpers J1, J2 & J3 will permanently enable the outputs. We recommend using the default positions (as shown Fig.2: this dialog box provides the setup options. on the circuit diagram) for all jumpers. A low-going pulse on pin 10 (SRCLR) zeros all 74HC595 out­puts on power up. This is generated by the RC network formed by R1 and C1. Transfer of data in and out of IC4, the A-D converter chip, is also performed serially. We describe how this works in the analog-to-digital section below. Digital outputs Fig.3: the output stage configuration for the ULN2083 driver IC. There are eight output channels in all. The interface board provides eight digital outputs, acces­ sible on connector SK4. All outputs are driven by a ULN2803A (IC5), a January 2000  67 68  Silicon Chip Fig.4 (left): the circuit connects to the PC’s parallel port. IC1, IC2 & IC6 perform D/A conversion, IC3 & IC5 provide the digital outputs and IC4 provides A/D conversion. high voltage and high current inverting buffer. A single output of IC5 is capable of sinking up to 500mA but for each additional output conducting simultaneously this needs to be derated by about 50mA. For more detailed information on derating, refer to the ULN2803A data sheet (see Table 3). Note that as the ULN2803A’s outputs are open collector, they can be connected together to increase sink current capability. Each output is protected by an internal diode, so inductive loads (such as relays) can be driven directly without any addi­tional protection. Zener diode ZD1 connects to the internal protection diodes on pin 10, clamping all outputs to a maximum of 33V. Fig.3 shows the equivalent circuit for each driver in the ULN2803A. Note that the cathodes of all the protection diodes have a common connection to pin 10. Additional protection is provided by R54, which helps to limit large current surges through the interface when switching heavy loads. It also provides some protection for the driver and PC board’s tracks should an output be momentarily shorted to the power rail. Digital-to-analog conversion Two digital to analog converters are provided on the paral­lel interface board. Both converters operate in an identical manner, so we’ll only look at channel 0. The eight outputs from IC1 give a total of 256 (28) possi­ble combinations. Each output is given a particular “weight” according to its connection point in the R-2R resistor network (or “ladder”). The result of adding all outputs in this way is a voltage on IC6 (pin 3) that increases by 20mV for each increment (or step) of the input byte. To find what the output voltage will be for a particular digital input, use the following formula: Vout = Digital input (in decimal) x Vcc/256. In our case, Vcc = 5V. For example, if our digital input value is 155, the output will be 3V (ie, 155 x 5/256). The output voltage is buffered by IC6, an op amp connected as a unity gain buffer. Note that this op amp cannot sink any significant amounts of current down to the 0V rail (see specs). This is due to the fact that the output needs to be about one diode drop above 0V to forward bias the on-chip high-current PNP output transistor. The designers recommend using the output as a current source (ie, resistive load to ground). Alternatively, you could replace the LM358 with a high-drive, rail-to-rail CMOS type op amp such as the MAX492. Note that IC6 is powered directly from the switched DC input (+Vb) rather than from +5V. In order to be able to drive its output all the way to +5V under load, IC6 needs a positive supply voltage at least 1.5V higher than the maximum output voltage. Analog-to-digital conversion The analog input section of the interface, made up of IC4 and a handful of resistors, appears to be the simplest part of our circuit – but looks can be deceiving! The TLC542 (IC4) is a complete data acquisition system on a single chip. Internally, it contains an analog-to-digital (A-D) converter, an analog multiplexer to connect the converter to one of 12 possible inputs and a serial interface for reading the digital result. The number of bits that an A-D converter can handle deter­mines its resolution. The TLC542 includes an 8-bit converter, giving a total of 256 (28) possible steps. This circuit uses +5V as the reference for the A-D converter and if we divide this by 256, we find that the resolution is around 20mV. When working with small voltages, the accuracy of the vol­tage used as the reference in the measurement and conversion process obviously becomes important. The TLC542 has separate reference supply pins (Vr+ and Vr-) but for simplicity these have been tied directly to the main supply rail. Fortunately, inaccu­racies in the 78L05 regulator’s output can be allowed for in software, so we can still maintain an accuracy of ±20mV over Fig.5: this parts layout diagram is shown 120% actual size. Note that some of the ICs face in different directions. January 2000  69 Table 1: Specifications Power Requirements Voltage range ........................................................................ +7.5-25V DC Current consumption ................................................. 8-10mA typical at 9V Analog outputs Voltage range ....................................................................0-5V (unloaded) Source current ................................................................ 20mA (maximum) Sink current ..................................... 5µA for 20mV (1 LSB) error at 0V out Resolution ...............................................................................8-bit (20mV) Digital outputs (open collector) Sink current ....................................500mA (maximum; derate by 50mA for each additional output – see text) Output voltage ..................................................................... 33V maximum Output protection .............................................. all outputs clamped to 33V Analog inputs Voltage range ......................................................................................0-5V Resolution ...............................................................................8-bit (20mV) Input protection ............................ 20mA absolute maximum for one input, 30mA abso­lute maximum total input current the entire 0-5V input range. Using a simple formula, we can calculate what the digital result will be for any given input voltage, as follows: Digital result (in decimal) = integer ((256 x (Vin - Vr-) / (Vr+ - Vr-)) As Vr+ = 5V and Vr- = 0V, we can simplify to: Digital result (in decimal) = integer (51.2 x Vin). Although the TLC542 has a total of 12 analog channels, only 10 of these are available on connector SK5. Each input has a 1kΩ series resistor that limits current flowing into the TLC542 pins if more that +5V is inadvertently applied. In fact, up to +25V and -20V can be tolerated for short periods before damage to the IC occurs. The eleventh input (pin 12) is wired to the switched DC input (+Vb) via voltage divider resistors R65 and R66. Software can read this input and report low voltage conditions – very handy for battery-powered applications. The 78L05 needs a minimum input of 7V to maintain output regulation. With the 4.1:1 ratio of R65 and R66, this equates to about 1.7V at the A-D input, for a digital reading of 87 (ie, 1.7 x 51.2). The TLC542 provides an additional twelfth channel that can be read by 70  Silicon Chip software but is not physically connected to an exter­nal pin. It is internally connected to a reference voltage of 2.5V, providing a simple “self-test” function. Reading this channel should always return a digital value of 128 ± 2 (ie, 2.5 x 51.2). Reading & writing Digital data is moved in and out of the TLC542 under soft­ware control, using signal lines on the PC parallel port inter­face. Basically, the software needs to be able to tell the TLC542 which channel to sample, wait for the sample and conversion process to complete and then read the result. A typical transfer sequence begins when the TLC542’s serial interface is enabled by driving CS (pin 15) low. As soon as CS goes low, the MSB (bit 7) of the previous data conversion can be read at DATA OUT (pin 16). Next, a 4-bit address for the channel that we want to read during the next conversion cycle is present­ed on ADDR IN (pin 17) and clocked in using I/O CLK (pin 18). As the address is clocked in, the next four bits of the previous data conversion (bits 6-3) appear at DATA OUT. Three more clock pulses are applied to I/O CLK to recover the final three bits of data (bits 2-0) from the previous conversion. Finally, one more clock pulse is applied to start the conversion cycle. The software now drives CS high and waits for the conver­sion to complete – about 20µs – which is signalled by the TLC542 driving the EOC (end of conversion) pin high. Power supply DC power for the board connects to SK1, with diode D2 pro­viding reverse polarity protection. Power is switched through to the regulation circuit under software control, using transistors Q1 & Q2 and a handful of biasing resistors. IC7, a 78L05 3-terminal regulator, brings the voltage down to a steady +5V, with C14 and C15 providing the usual filtering. Zener diode ZD2 shunts any stray voltages above +6.2V to ground – something that should­n’t occur during normal operation! The interface board accepts any regulated DC supply between +7.5V and +25V. Although the same supply can be used for powering external devices (relays, lamps, etc) driven by the open collec­tor outputs, this is not recommended if accurate A-D and D-A conversion is required. The board can also be powered from a single 9V battery. Construction All components, including the 25pin ‘D’ connector, are mounted on a single PC board measuring 144.8 x 67.3mm. The component layout in Fig.5 is shown 1.2 times actual size to make it easier to read. Begin by inserting and soldering all resistors. Note that instead of wire links, zero ohm resistors are used throughout. These are the same physical size as 0.25W resistors and are usual­ly brown in colour with a single black band. The only exceptions to this are the jumpers (J1-J6), which require the usual single-strand tinned copper wire. The jumpers can be installed in positions 1-2 or 2-3. The default for all is position 1-2 and this is what is required for the Windows software. To make test­ing a little easier, don’t install J6 just yet; we’ll come to that a little further on. Next, mount all the diodes, capacitors, transistors and 78L05 regulator in order. The six ICs should be mounted next, taking note that IC5 is mounted the opposite way around to ICs 1-4. These ICs are static sensitive, so use a soldering iron with an earthed tip and solder the ground and power pins first. Finally, mount connectors SK1 to SK6. Base 0 2 Write IC1 serial data in (pin14) Data bi t 0 Testing Base 1 3 Write IC1 to IC4 clock (pin 11) Data bi t 1 Once completed, it’s a good idea to do a few simple checks before connecting the interface board to your PC. First, temporar­ily solder J6 in the 2-3 position. This will allow transistors Q1 and Q2 to switch power through to the regulator. Now apply DC power to SK1 and using the circuit diagram as a reference, meas­ure the supply voltage across the power (Vcc) and ground (GND) pins of all ICs. This should be close to +5.0V. If not, check for problems around Q1, Q2 and IC7. If all is OK, remove power and remove link J6 from position 2-3 and solder it in position 1-2. To prevent possible damage to your PC’s parallel port, we also recommend checking that none of the interface signals on SK6 (pins 1-9, 14 and 17) are shorted to power or ground. The resistance between each of these pins and power or ground should be greater than 10kΩ. Base 2 4 Write IC1 l atch load (pin 12) Data bi t 2 Base 3 5 Write IC2 l atch load (pin 12) Data bi t 3 Base 4 6 Write IC3 l atch load (pin 12) Data bi t 4 Base 5 7 Write IC4 chip sel ect (pin 15) Data bi t 5 Base 6 8 Write IC4 address input (pin 17) Data bi t 6 Base 7 9 Write Power on/off Data bi t 7 Base + 1 3 15 Read Not used -Faul t Base + 1 4 13 Read IC4 data out (pin 16) Sel ect Base + 1 5 12 Read Not used Paper end Base + 1 6 10 Read IC4 end of conversion (EOC) (pin 19) -Ack Base + 1 7 11 Read Not used Busy Base + 2 0 1 Write IC1 output enabl e (pin 13) -Strobe Base + 2 1 14 Write IC2 output enabl e (pin 13) -Auto feed Base + 2 2 16 Write Not used -Ini t Base + 2 3 17 Write IC3 output enabl e (pin 13) -Sel ect - - 18-25 - Ground - Table 2: Parallel Port Pin Assignments I/O Address Software If you have computer hardware and programming skills, you might want to write your own software to control the interface board. Program examples written in QBasic are available for download from the SILICON CHIP website. Don’t want to write your own software? No problem. James Rickard has written general-purpose Windows 95/98 software which can also be down­loaded from the SILICON CHIP web site. To install the software, extract the downloaded file to a temporary folder and run the INSTALL program. The installation program is very basic but does get the job done. It copies two library files (called VB40032.DLL & WIN95IO.DLL) to the Windows directory and places the executable file K2805.EXE in a new directory on the C: drive named \K2805. It then copies a shortcut for the program to the default desktop in C:\Windows\ Desktop. Note that the shortcut will not appear on your desktop if you have profiles enabled in Windows (ie. Windows is maintaining desktop settings for more than one user); simply Bit D B 25 Pin No. Direction Printer Function Interface Function Table 3: Where To Find Additional Data Device Manufacturer URL 74HC595, U LN 2803A Motorol a http://scgproducts.motorol a.com TLC 542 Texas Instruments http://www.ti.com/sc/docs/schome.htm LM358 National Semiconductor http://www.national.com PC Parall el Port create a new shortcut to C:\K2805\ K2805.EXE. Double-click on the K2805 shortcut to launch the program. The main dialog box appears as in Fig.1. Before changing anything here, we have to tell the software which parallel port the inter­face is connected to. To do this, select Edit, Options from the menu bar to display the Options dialog (Fig.2). A useful feature of this program is its ability to record A-D samples in a text file which can later be imported to a database or spreadsheet for manipulation. The Options dialog box allows us to specify the location of this file, as well as the A-D sampling rate. Click the OK button to return to the main window. Driving the software is straightfor- http://www.rmii .com/~hi sys/parport.html ward, so we won’t go into the details here. Remember that channel 10 of the A-D con­verter reads the switched DC input voltage and channel 11 the A-D converter’s internal reference SC voltage. Where To Get It The complete kit is available from Dick Smith Electronics, Cat. K-2805. You will also need a cable with 25-pin male ‘D’ connectors on both ends to connect the interface board to your PC’s printer port. Dick Smith Electronics stock a suitable type, Cat. X-3574. To protect the completed board, it can be mounted in a plastic “Zippy” box, DSE Cat. H-2851. January 2000  71 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG Building a vintage radio “replica” Have you always wanted a 1920s or 1930s “cathedral” style radio. They’re as scarce as hens’ teeth these days – or are they? If you can’t get an original, what about one of the many replicas now coming onto the market? From time to time, “replicas” of early radio sets appear in catalog advertisements from various electronics and electrical retailers. Consoles and cathedral sets seem to be the favour- ites but of course, they’re not true replicas. First, the cabinets are nothing like the those from the 20s, 30s and 40s, usually being made from cheap ply or particle board with a lacquer finish of some sort. Second, a glance at the front panel reveals that these sets can receive FM transmissions as well as AM. In reali­ty, FM didn’t get under way in Australia until well after the era that the “replica” is supposed to represent. However, it’s not until you expect the “insides” of such radios that you realise just how far away they are from being a true replica of the era. Hidden inside the cabinet will be a small transistor radio and that’s hardly something that was around in the 1920s or 1930s! So these sets are in no way an accurate copy or replica of any early radio. The fact is, there are very few genuine 1920s (and not many more 1930s) sets now available on the market. Many collectors will never own radios of this vintage. But there is nothing to stop you from building a replica using the components (either originals or reproductions), wiring layouts and construction techniques of the era. The resulting set will look like a brand new 1920s or 1930s radio (not a restored set), although it still won’t be authentic. Building a replica requires a lot of work when it comes to sourcing the parts, selecting a representative circuit and plan­ning the layout. You then have to assemble it and get it to work properly. It may also be necessary to vary the original circuitry or layout somewhat, as some parts may just not be available any more. The Rice Neutrodyne This view shows the completed Rice Neutrodyne with its loudspeaker. 74  Silicon Chip I haven’t personally built a replica of an early set but a few members of the Vintage Radio Club of North East Victoria have. In particular, I was most impressed with Jim Birtchnell’s replica of a 3-valve Rice Neutrodyne (you’ve heard of Jim and his vintage radios before in this column). The design for the Rice Neutrodyne was originally published in the 7th October, 1927 issue of “Wireless Weekly”. That article was quite detailed and covered more than four pages. Jim started from scratch, either sourcing or making the parts himself so that his completed replica very closely resembles the original. In the original article, the author began by discussing the Rice neutralising system as seen in an old publication of 1918, some nine years before! This publication discussed the various neutralised triode amplifiers that were used at that time. The problem is that triode valves, when used in tuned radio frequency amplifiers, are very prone to oscillate at the frequency of one of the two tuned circuits around the stage (ie, the grid circuit or plate circuit). This oscillation is due to the capacitance between the grid and the plate of the valve. This capacitance is actually quite small – only 4pF in the case of a 6SN7-GT. However, this value is more than enough for this triode to oscillate fiercely if used in a tuned plate and tuned grid amplifying circuit. In fact, this circuit is actually used as an oscillator in some transmitters! By contrast, a 6BA6 has a gridto-plate capacity of only .0035pF, which is over 1000 times less than for a 6SN7-GT. However, this low The completed Rice Neutrodyne replica closely resembles the original receiver described in “Wireless Weekly” in 1927. capacity is only realised when the screen grid is earthed to RF signals. Even so, the 6BA6 can still oscillate in some circuits and so the IF stages in quite a few HMV Little Nipper sets are neutralised (we’ll explain what neutralising is shortly). This was not done because the stage was inherently unstable but to make sure the stage was unconditionally stable. Of course, it is also important to isolate the input and output circuitry of an RF stage, to minimise any coupling between them. Neutralisation Radio experimenters of the early 1900s and into the 1920s did not have tetrode and pentode valves to amplify radio frequen­cy signals, so Fig.1: the circuit for the Rice Neutrodyne receiver. The neutralising capacitor (N.C.) is installed between the plate of the RF valve (V1) and one end of tuned winding L1. This capacitor effectively cancelled out – or neutralised – the grid-toplate capacitance of the valve, thus making the stage stable. January 2000  75 This view shows how the completed receiver fits into the home-made cabinet (it slides in from the front). The large socket in the top panel is for the external power supply connections. other ways had to be found to stabilise triode RF amplifiers. Neutralising, in the various forms that it took, was not always particularly easy to accomplish although the results were quite reasonable. Rice Neutrodyne The Rice Neutrodyne was one such circuit that employed neutralising (Fig.1). Essentially, this involved installing an additional capacitor between the plate of the RF valve and one end of tuned winding L1. This capacitor effectively cancelled out – or “neutralised” – the grid-to-plate capacitance of the valve, thus making the stage stable. The neutralising capacitor was made adjustable in most cases and is adjusted for optimum stability. It worked because the RF signal at the bottom end of coil L1 is 180° out of phase with the signal at the other end (ie, on the grid) and so the grid-plate capacitance was effectively “eliminated”. This system works well but having the tuning gang “float­ing” above earth can cause problems. Because the aerial, which is connected to the top of L1 via a 100pF capacitor, can vary in length, the capacitances around the circuit can also vary. For this reason, the value of the neutralising capacitor sometimes required adjustment which is why a variable type is used. By the way, this circuit can be slightly modified to make it much easier to achieve good results. How76  Silicon Chip ever, that is a story for another article in the future. Another common method of ensuring stability was to install a variable resistor between the grid of the valve and the tuned circuit. The value of this resistor was then adjusted until the set was stable (a value of around 850Ω was commonly used by Atwater Kent, for example). The big problem with this was that the gain of the stage was dramatically reduced. This meant that extra amplifying stages were required to make up for the low gain of an “un-neutralised” RF amplifier. It may seem surprising that not all manufacturers used neutralised RF amplifiers, as valves at that time were very expensive. They didn’t because patents on neutralising were held by Hazeltine and Rice and they weren’t going to let anyone else use this technique without paying a considerable royalty. Having talked about the neutralised RF amplifier stage, it can be seen that the rest of the radio is quite conventional, with a grid detector and a transformer-coupled audio output stage. The Rice Neutrodyne is really only a head­phone set but it can do a credible job on strong stations, as Jim can attest. Jim’s replica Jim built the set virtually as per the article in “Wireless Weekly”, with some slight modifications to suit the connection of the power supply to the set. Building a replica such as this doesn’t require enormous skill as the circuitry is quite simple and the article included detailed layout instructions. However, this is not meant to detract from the obvious skill Jim used in making this set and getting it to operate. Obtaining the parts to build such a set is quite another story. Where does the builder get 201A valves, or square section copper wire, UX valve sockets, 5:1 audio interstage transformers or the old style vernier dials? However, as can be seen in the photographs, Jim has succeeded in obtaining suitable parts. Jim told me that he imported most of the bits from America because of price and availability. However, if one is prepared to hunt around, most if not all of the bits can be found (or made) in Australia. For example, there are several advertisers in SILICON CHIP that cater for the vintage radio buff and contacting them should bring results. They have extensive stocks of all sorts of bits and pieces that are used to restore or build receivers. Members of the Historical Radio Society of Australia or the New Zealand Vintage Radio Society are also often able to assist when it comes to obtaining that special part. And bits and pieces can turn up in all sorts of other places – garage sales, second­ hand shops, deceased estates and “for sale” columns in local newspapers, to name but a few sources. Placing adverts in magazines such as SILICON CHIP, in local newspapers and on supermarket notice boards can also help track down the bits re­quired to make an authentic replica of a bygone age. Each vintage radio buff has his or her particular area of expertise, so it is quite reasonable to enlist the aid of others to help in areas where you are no expert. As can be seen from the photographs, the cabinet and the works of Jim’s set reflect the era that the Rice Neutrodyne came from. Jim is very good with cabinet work and with circuit layout, although he admits to getting a friend to help with any difficult electronic work on more complex sets. Other replicas Replicas can be made of sets from any era, from the very first sets made (with coherers and the like) up to transistorised radios of the 1960s. However, an enthusiast is more likely to build an early wireless set from the 1920s rather than a 1960s set. There are still many of these later radios around and if you can scrounge more than one unit of a particular model, it’s usually possible to make at least one good working unit using parts scrounged from the others. For this reason, I always endeavour to collect several sets of the model I want to restore so that I can make one “perfect” radio. There is of course another type of replica. This replica is not a slavish copy of any particular set but rather a copy of the style of set that was used during a particular era. For example I know of some enthusiasts who have built typical 4-valve mantle sets using octal valves and a wooden cabinet. They look the part, are similar to many commercially made sets of the era depicted and work much the same. Summary Above: the top of the cabinet is hinged to allow easy access to internal components. As we’ve seen, replicas can be direct copies of receivers from bygone times or can simply be representative of sets of a particular era while not copying any particular make or model. And although they are not true vintage radios, they can be inter­ esting and valuable sets in their own right. Other projects that have been held in recent times by various groups include building a “Little General”, a “Little Jim”, a “Hikers One” or some other radio, as described in popular radio magazines of the time. All of these are examples of replicas. Finally, my thanks to Jim for sharing with us the informa­ t ion on his replica Rice Neutro­dyne. The photographs in this article clearly show what can be achiev­ed with attention to detail. SC Vintage Radio Repairs Sales Valves Books Spare Parts See the specialists * Stock constantly changing. * Top prices paid for good quality vintage wireless and audio amps. * Friendly, reliable expert service. Call in or send SSAE for our current catalogue RESURRECTION RADIO 242 Chapel Street (PO Box 2029) PRAHRAN, VIC 3181 Tel (03) 9510 4486 Fax (03) 9529 5639 Truscott’s !RESELLER FOR MAJOR KIT RETAILERS !PROTOTYPING EQUIPMENT !COMPLETE CB RADIO SUPPLY HOUSE !TV ANTENNA ON SPECIAL (DIGITAL READY) !LARGE RANGE OF ELECTRONIC COMPONENTS Professional Mail Order Service Truscott’s Come In And See O New Storeur ELECTRONIC WORLD Pty Ltd ACN 069 935 397 Ph (03) 9723 3860 Fax (03) 9725 9443 27 The Mall, South Croydon, Vic 3136 (Melway Map 50 G7) email: truscott<at>acepia.net.au www.electronicworld.aus.as January 2000  77 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. Battery charging from a 1V or 2V solar panel For battery-powered applications, such as remote data logging, it is often necessary use solar power for battery recharging. Unfortunately, solar panels are expensive, currently retailing at around $50 to $90 for a typical 12V 2W panel. Many such applications only require a fraction of this power and this could be provided by much cheaper low voltage solar modules of 1V or 2V. However, the low voltage outputs of these modules are too low for directly recharging batteries. What is needed is a cheap circuit that will boost these low voltages to more useful levels. The circuits shown here will do just that. These two circuits can also run off one or two dry cells, for example. They will operate from voltages down to about 0.6V but also up to about 6V. In both circuits transistor Q1 and transformer T1, together with associated components, form a flyback converter. Feedback from the output of the converter back to Q2 regulates the output voltage. Fig.1 is the “bare-bones” circuit which works quite well. The circuit of Fig.2 is essentially the same but op amp IC1 and a voltage reference diode have been added to improve the voltage regulation. The efficiency of both circuits varies typically from 50% to 70%, depending on the load current. They can deliver up to 70mW of output power with 1V input and the output voltage can be adjusted with trimpot VR1 to as much as 12V, at light load currents. If used to charge a battery, either of these circuits will draw some current from the battery during periods when there is no input power. If this is a problem, then connect a diode between the output of the cir- cuit and the battery to prevent reverse battery current. H. Nacinovich, Gulgong, NSW. ($60) TTL decision maker Based on two readily available TTL packages, this Decision Maker drives two LEDs, red for NO and green for YES. Two NAND gates in the 74LS00 package are wired to provide a high frequency oscillator which clocks the 74LS76 continuously. However, neither of the LEDs is lit because the base of PNP transistor Q1 is held high. When pushbutton S1 is closed, the J & K inputs of the flipflop are pulled low and this stops its outputs at pins 14 & 15 from toggling. At the 78  Silicon Chip same time, the base of Q1 is pulled low, turning it on and lighting which ever LED has its cathode being pulled low by the 74LS76. The result should be completely random. The circuit will run from 3-6V, using AA cells. Luke Baldan, Wantirna South, Vic. ($25) Paralleling the output of 3-terminal regulators A common way of boosting the output of a 3-terminal regulator is to connect a power transistor in parallel with it so that the transistor becomes a current source under the control of the regulator. That circuit concept works but it does increase the input voltage requirement of the circuit. This circuit takes a simpler approach and merely parallels the outputs of two or more LM317 or LM350 3-terminal regulators. Their ADJ terminals are all connected to a common line so that their voltage output is adjusted by trimpot VR1. To ensure that the regulators share the output current evenly, they are each connected to the output line via separate 0.1Ω 5W resistors. If wired up on a circuit board, these 5W wirewound resistors will need be mounted at least 5mm off the board to ensure cooling. While a common heatsink could be used for the regulators, they will each need to be insulated from it. Steve Goebel, Tumbi Umbi, NSW. ($30) Buffered virtual ground generator Analog circuits often require split power supply rails but this can be a problem where batteries or a DC plugpack will be the power source. In low power circuits this can often be solved by having a bypassed voltage divider across the single supply rail to derive a half-supply reference. But where the requirements are more demanding, this circuit could be the solution. It provides a low impedance centre rail or ground to the supply. The output voltage remains halfway between the positive and negative rails, even if their voltage fluctuates. The supply voltage is divided in half by R1 and R2 providing a reference for the buffer amplifier IC1. IC1 has 100% negative feedback from the output so it operates as a unity gain buffer, or more precisely, as a voltage follower. Resistor R3 maintains stability of the feedback loop. Any current under 4mA sourced or sunk at the output is provided by the op amp via resistor R3. Currents greater than this are sourced (or sunk) by the complementary Dar-lington pairs of transistors Q1 & Q2 and Q3 & Q4. As the op amp has a finite slew rate, capacitors C1-C4 are required to absorb transients. The circuit is capable of sourcing or sinking 1A on a continuous basis, provided that Q2 & Q4 are fitted with suitable heatsinks. Maximum input voltage is 36V, as set by the op amp ratings. Julian Phillips, Christchurch, NZ. ($30) CONTRIBUTIONS WANTED! Got an original, unpublished circuit? We'll pay you good money for it! See page 2 for our address details. January 2000  79 OFF-HOOK INDICATOR for TELEPHONE LINES This little circuit will tell you when a phone line is in use, without you having to pick up a phone to listen in. It can avoid conflicts in your home and better still, avoid “crashing” a modem connection when downloading data from the Internet. H OW MANY TIMES have you been on the phone and some one else has picked up another phone and begun dialling? It’s pretty annoying, isn’t it? How many times have you done the same thing to them? That’s not so bad, is it? Or how many times have you been almost finished down-loading a large file from the Internet and someone has picked up an extension and started dialling? Now that’s really frustrating. Of course some people may argue that this is a good reason to get a second phone line and indeed it is but the same thing still occurs in homes with two phone lines. We can vouch for that. It happens in offices too, where a fax machine can be connected to the same line as a computer modem. 80  Silicon Chip It’s certainly happened in our office and there have been howls of anguish when the victim has realised what has been done. Mind you, in our office there’s no excuse because our telephone system indicates which lines are busy. Wouldn’t it be good if there was a similar doodad you could fit to any By JOHN CLARKE phone line? Well, now there is and you can build it. It will not affect telephone, fax or modem operation in any way and draws negligible current from the phone lines. Called the “Off hook Indicator”, it is a little plastic box which flashes a LED whenever your phone line is in use. As the name suggests, it also solves another problem with tele-phones and that is when they are left off-hook. The flashing LED will remind you that the phone is off-hook and will be “engaged”, preventing outside callers from reaching you. The Off-hook Indicator is housed in a small plastic case with a US modular phone socket (RJ12 6P6C) at each end. These enable the Off-hook Indicator to be connected in-line with your telephone, modem or fax machine. The indicating LED can be seen at the top of the lid. Note that some fax machines do indicate when the line is being used and in these cases the Off-hook Indicator would be unnecessary. The Off-hook Indicator works by monitoring the voltage across the DISCLAIMER Please note that the Off-hook Ind icator is NOT an Austel-ap proved devic e. The penalty for using suc h a non-appro ved device, if detected and subsequent prosecution took place, could be a h eavy fine, up to $10,00 0. phone line. When your phone is not in use (ie, on-hook or in its cradle) the line voltage is around 50V. But when a phone, modem or fax machine connects across the line, the voltage drops to between about 3 and 6V. Our circuit regards any voltage below 13V as the “off-hook” condition and flashes a LED when that occurs. LM3909 flasher The circuit uses an LM3909 IC which is specifically designed to drive LEDs and draw minimal power. It can drive a LED when operated from 1.2V even though the turn-on voltage for a LED is typically around 1.8V. It performs this neat trick by charging a capacitor and then connecting this capacitor in series with the 1.2V supply, effectively doubling the voltage. This then becomes the supply for the LED which flashes momentarily as the capacitor dumps its charge into it. Fig.1 shows the relevant internal circuitry for the LM3909 and the Shown here bigger than life-size, the Off-Hook Indicator is designed to connect “in line” between the wall socket and the phone via a pair of RJ-12 modular (American-style) connectors. Most modern phones now have these connectors. external LED and capacitor. When transistor Q3 is not conducting, the 100µF capacitor can charge via the 800Ω, 6kΩ and 3kΩ resistors. When the capacitor is fully charged, transistor Q3 is turned on and pulls the positive terminal of the 100µF capacitor to pin 4. The negative terminal of the 100µF capacitor ends up being about 1.2V below the negative terminal of the battery and so we effectively have about 2.4V between pin 5 and the cathode of the LED. The LED now lights as current flows via the 12Ω resistor and this discharges the 100µF capacitor. The cycle then repeats with Q3 off and the 100µF capacitor charging up. Battery-powered circuit Fig.2: basically, the LM3909 is a clever R/C timing circuit using its internal resistors and an external capacitor. It’s an efficient and effective way to make a LED flash. The full circuit for the Off-hook Indicator is shown in Fig.2. It comprises the LM3909 IC, a LED, two transistors, four diodes and several capacitors and resistors. There is also a 1.2V NiCd cell which provides power to the circuit. Having the NiCd cell means that there are no pulses of current drawn from the phone line as the LED is flashing. Instead, the current drawn from the phone line is very low and constant: around 0.27mA when the phone is not in use (ie, “on-hook”) and less than 40µA when the phone line is in use (ie, “off-hook”). By taking this approach, the Offhook Indicator will have no effect on any phone equipment and in fact will be “invisible” to the system. By the way, we said before that the Off-hook Indicator was to be connected in-line with your phone, modem fax or whatever. But that does not mean that any of its circuit components are actually connected “in series” with your phone equipment. What happens is that the two US phone plugs are connected in parallel so that they merely loop in and out of the box. The Off-hook Indicator then connects in parallel with the phone line, causing negligible loading on it. The circuit is connected to the phone line via a bridge of four diodes, January 2000  81 It's a pretty neat fit inside the Jiffy box but it does all go in! The large electrolytic capacitor must be laid over to enable the lid to fit on. The LED pokes through a hole in the lid. The shorting link (top left) is shown in the “off” position. D1 to D4. This copes with the fact that the line polarity can vary, one way or the other. Following the diode bridge, the 1.2V NiCd cell is charged via the 220kΩ resistor. This gives a nominal trickle charge of 220µA when the telephone line voltage is at 50V. The cell can be isolated from the circuit by removing a shorting plug on the PC board. This shorting plug is provided so that the cell can be disconnected from the flasher circuit if it is not connected to the phone line. After all, there is no point having the LED flashing if it is not monitoring the phone line. Transistor Q1 is switched on by the 50V supply via the 1MΩ resistor. When Q1 is on, it pulls the base of Q2 low which holds it in the off state. Q2 is actually in the negative line to the flasher IC, so if Q2 is off, the LED can’t be flashed. When the phone line voltage drops below 13V, the voltage divider consisting of the 1MΩ and 47kΩ resistor at Q1’s base causes its base voltage to drop below 0.6V and the transistor turns off. Bias current can now flow into the base of 82  Silicon Chip Q2 via the 100kΩ resistor to switch it on. This connects pin 4 of IC1 to the negative supply rail and the LED can now be flashed. The 470µF capacitor provides energy storage so that the supply to the IC does not fluctuate markedly as the LED is flashed on and off. Construction The Off-Hook Indicator is constructed onto a PC board which measures 50 x 79mm and is coded 12301001. This is designed to fit into a standard plastic case which measures 83 x 54 x 31mm (eg, Jaycar Cat. HB-6025). Begin construction by checking the PC board for shorts and possible breaks in the copper tracks. The four corners of the PC board need to be cut to shape to clear the integral pillars in the case. The outline is shown on the copper side of the PC board. You will also need to drill holes for the integral mounting pins on the 6P6C sockets so that they clip in correctly to the PC board. The Altronics socket (Cat P-1405) differs slightly to the one sold by Jaycar (Cat PS-1474), so we have provided hole positions for both. The plastic case has integral slots in the case sides and these need to be removed so that the PC board can slide into place. You can remove these with a sharp chisel or knife. Check that the PC board fits into the case without fouling. Insert and solder the diodes and resistors. Check each resistor value with your multimeter before it is installed. The two transistors, the IC and the capacitors can installed next. IC1 must be oriented as shown and the electrolytic capacitors positioned with the positive lead where indicated. The 470µF capacitor will need to be laid over on its side otherwise it will be too tall for the box lid to go on. LED1 is a high brightness type and it is mounted so that the top of its dome is 19mm above the PC board, which allows it to poke through a hole in the lid. It is oriented with the cathode toward the edge of the PC board. The US modular 6P6C (also known as RJ12) sockets can be installed next. Also insert and solder the PC stakes for the solder terminals on the AA cell. We used a standard NiCd cell and soldered tags to its end electrodes. However, cells with solder tag types are readily available and are prefera- Fig.2: there’s not much too the Off-hook Indicator – just a sensor circuit, a LED flasher and a battery with a few charging components. Fig.3: compare the component overlay above with the photograph opposite when assembling the board. The PC pattern itself (right) can be used to make your own PC board or to check a commercial board for defects. ble. These tags solder to the PC stakes on the board. Make sure you solder the cell in with the correct polarity otherwise the circuit won’t work. Insert and solder the 2-way pin header but do not insert the shorting plug yet. Now you need to cut the case so that there is a neat cutout in each end to clear the modular phone sockets. Place the PC board over the case and mark out the cutout positions for the sockets. We cut the box with a fine toothed hacksaw and broke off the pieces with pliers. The cutout was then filed to shape. Test the PC board for fit into the case and adjust any of the cutout sides accordingly. The lid will require a hole for the LED and also the flanges above the sockets will need to be filed flat so that the lid will sit flush on the case. Fit the label to the lid of the case and cut out the LED hole with a sharp knife. Measure the cell voltage with a multimeter. It should be at least 1.2V. If it is lower than this it will require charging before you can use the circuit. You can let the phone line do this for you by plugging the line into the socket. Charging via the phone line will require the shorting plug to be connected to the pin header. The telephone or appliance connects to the second socket using a 6P2C (or 6P4C or 6P6C) extension lead. You can test the unit by lifting the telephone handset. The LED should begin to flash. If it does not, check the cell voltage for at least 1.2V and the supply to IC1. There should be around 1.2V between pins 4 & 5. If so, then maybe LED1 or the 100uF capacitor is incorrectly oriented. If there is little voltage here, check that Q1 is off so that the base to emitter voltage of Q2 is around 0.6V. We recommend that you do not place more than three Off-hook Indicators on the same phone line, including extensions. This is to make sure that the extra loading on the line does not cause any operational problems. The typical current drawn from the Nicad cell when the LED flasher is operating is 450A. Since the cell is charged at about 200A when the phone line is on-hook, the maximum time that the telephone line can be in use per day without discharging the cell is around seven hours. This assumes that the seven hours is broken up into shorter times spread throughout the day and assumes a 66% SC efficiency in charging the cell. Parts List 1 PC board, 50 x 79mm, code 12101001 1 panel label 50 x 77mm 1 plastic case 83 x 54 x 31mm (Jaycar HB-6025) 2 6P6C PC board mounting modular sockets (Jaycar PS-1474, Altronics P-1425) 1 6P2C (or 6P4C or 6P6C) extension lead 1 AA NiCd (or NiMh) cell with solder terminals 1 2-way header with shorting plug 2 PC stakes Semiconductors 1 5mm high brightness red LED (LED1) 1 LM3909 LED flasher (IC1) 2 BC549 NPN transistors (Q1,Q2) 4 1N4004 1A 400V diodes (D1D4) Capacitors 1 470µF 16VW or 25VW PC electrolytic 1 100µF 16VW or 25VW PC electrolytic 1 0.1µF (100n or 104) MKT polyester Resistors (0.25W, 1%) 1 1MΩ 1 220kΩ 1 100kΩ 1 47kΩ Resistor Colour Codes This photo shows how we modified the Jiffy box to accept two phone sockets. Note the cutouts' bevelled inside edges.                      No. Value 1 1MΩ 1 220kΩ 1 100kΩ 1 47kΩ 4-Band Code (1%) brown black green brown red red yellow brown brown black yellow brown yellow violet orange brown 5-Band Code (1%) brown black black yellow brown red red black orange brown brown black black orange brown yellow violet black red brown January 2000  83 CTRONICSHOWCASELECT SURPLUS ELECTRONIC COMPONENTS at CHEAP CHEAP CHEAP PRICES! ICs, LCD Displays,Transistors, Diodes, Leds, Books, Connectors, Switches, Transformers, Fans, Relays, Speakers,Terminals, Resistors, Buzzers, Leads, Knobs, Batteries, Computer Accs. etc. FOR A FREE MONTHLY MAILER PLEASE CONTACT ROCOM ELECTRONICS STORE ADDRESS: 56 RENVER ROAD, CLAYTON VIC. 3168 POSTAL ADDRESS: BAG 620 CLAYTON SOUTH, VIC. 3169 PH (03) 9543 7877 FAX (03) 9543 4871 Email: sales<at>rocom.com.au Attention speaker builders and professionals World famous loudspeaker drivers make a return to the Australian Market. Call for information, data sheets, kit plans and free advice. Trade and OEM Enquiries welcome. Stock available mid December. Quantity discounts apply.             Model RRP Introductory special Peerless 811827 dome tweeter, wide angle $69 $59 Peerless 811978 dome tweeter, shielded $89 $74 Peerless 810665 dome tweeter, rectangular $99 $85 Peerless 850122 woofer 6.5” CSX hi-end $135 $105 Peerless 831709 woofer 8” thick PP cone $125 $95 Peerless 831727 subwoofer, 10” thick PP cone $165 $135 Peerless 850146 subwoofer, 10” CSX hi-end $189 $160 ALSO STOCKING THE MOST COMPREHENSIVE RANGE OF REPLACEMENT SPEAKER FOAM SURROUNDS and parts including factory surrounds for Dynaudio, Tannoy, JBL, Scan-Speak, Cerwin-Vega and others. PHONE: (03) 9646 5115 FAX: (03) 9646 1574 POST: P.O Box 63 Port Melbourne VIC 3207 EMAIL: ortofon<at>labyrinth.net.au Ultra DMA 66 Card 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 BUSINESS FOR SALE: Escape to the sun in beautiful Coffs Harbour! • Stable electronic retail business • Easily run by husband and wife team. • Agent for GSM carrier • Access to large electronics suppliers (niche market). • Very strong customer base inc Government depts   and schools etc. • Five year rental option on current highway premises. • Full figures available. • Current owners (12 years) are moving to a new   business. 84  S ilicon • Price only $55,000C+hip SAV. Enquiries: phone (02) 6652 5684 or fax (02) 6651 3731 Got a new Ultra DMA 66 hard disk drive but your motherboard is at least 3 years old? Get the most out of your new hard drive by installing an Ultra-DMA 66 add-in card along with your new hard drive. Vamtest Pty Ltd trading as Microgram Computers A.C.N. 003 062 100 Web site: Email: www.mgram.com.au info<at>mgram.com.au Cat. 2809 HDD Cont. PCI IDE Ultra DMA 66 Check our web site Cat. 9109 $129 HD Ribbon Cable IDE Ultra DMA 66 $15 Unit 1, 14 Bon Mace Close Berkeley Vale NSW 2261 Phone: (02) 4389 8444 Fax: (02) 4389 8388 TRONICSHOWCASELECTRO MicroZed Computers GENUINE STAMP PRODUCTS FROM Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 0409 036 775 Fax (02) 6772 8987 http://www.microzed.com.au 3990 Now you can afford the legendary clarity, transparency, depth and precision of an electrostatic speaker. 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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 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 CLARKE & SEVERN ELECTRONICS PO Box 1, Hornsby NSW 1630 Ph (02) 9482 1944 Fx 9482 1309 email: sales<at>clarke.com.au www.clarke.com.au Most Credit Cards OK FULL RANGE $ ELECTROSTATIC UNIVERSAL WIRELESS DEVELOPMENT SYSTEM DVS5 Video & Audio Distribution Amplifier 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 Do you want YOUR product or service showcased to Australasia's most important electronics marketplace? CALL ME: RICK WINKLER on (02) 9979 5644 and let me explain how cost effective the SILICON CHIP ELECTRONICS SHOWCASE can be for YOU! January 2000  85 REFERENCE GREAT BOOKS FOR VIDEO SCRAMBLING AND DESCRAMBLING for Satellite & Cable TV NEW NEW NEW NEW 59 95 $ TCP/IP EXPLAINED By Philip Miller. Published 1997. $ 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. SETTING UP A WEB SERVER By Simon Collin. Published 1997. 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. By Tim Williams. First published 1991  (reprinted 1997). By John E. McNamara. 2nd edition 1996. 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. 65 $ HTML 4.0 MADE SIMPLE By PK McBride & Nat McBride. Publ. 1999. O R D E R H E R E 29 65 $ THE CIRCUIT DESIGNER’S COMPANION LOCAL AREA NETWORKS: An Introduction to the Technology $ NEW NEW NEW NEW by Rudolf F Graf & William Sheets NEW 2nd Edition 1998 If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! 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Uses a combination of tutorial approach, carefully focussed examples and quick reference guides. 198 pages, in paperback. 95  VIDEO SCRAMBLING/DESCRAMBLING.............$59.95  TCP/IP EXPLAINED.............................................$90.00  LOCAL AREA NETWORKS..................................$65.00  HTML 4.0 MADE SIMPLE...................................$29.95  SETTING UP A WEB SERVER.............................$65.00  THE CIRCUIT DESIGNER’S COMPANION...........$59.95  ELECTRIC MOTORS AND DRIVES......................$59.95  UNDERSTANDING TELEPHONE ELECTRONICS....$55.00  AUDIO ELECTRONICS........................................$79.00  GUIDE TO TV & VIDEO TECHNOLOGY...............$55.00  EMC FOR PRODUCT DESIGNERS.......................$95.00  THE ART OF LINEAR ELECTRONICS..................$80.00  INTERNET HOME PAGES MADE SIMPLE...........$24.95  DIGITAL ELECTRONICS .....................................$59.95  ESSENTIAL LINUX..............................................$85.00               ORDER TOTAL: $............. $ 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 ELECTRIC MOTORS AND DRIVES By Austin Hughes. 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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. 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Published 1998. P&P Add $A5.00 per book – Orders over $100 P&P free in Australia. NZ: Add $A10 per book, $A15 elsewhere $ 59 95 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 Steve Heath. Published 1997. By Tim Williams. First pub­­lished 1992. Second edition 1996. 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. 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. 95 $ Provides all the information and software that is necessary for a PC user to install and use the freeware Linux operating system. It details, step-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 CDROM 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. 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 January 2000  89 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. Turbo timer alarm override problems I have installed the Turbo Timer on my car and it works fine except for the alarm override relay switch. When I park the car I take the key and get out. I close the door and press the button on my alarm remote (my alarm is NOT auto-arming). The problem is that it doesn’t always work. When it does, the park-lights flash, the doors lock and the alarm is prepared to go on as soon as the engine shuts down. When it doesn’t work absolutely nothing happens. It never seems to work if I drive the car only a short distance and is happier if I drive for a longer time. Maybe it needs higher battery voltage or something? Do you have any idea on how I can fix this? Currently, when it doesn’t work I either have to wait around for the Turbo Timer to shut down the motor or I have to switch the car off with the reset switch and then lock up. (F. P., Joondanna WA). Beat-triggered strobe misses the beat I built the Beat-Triggered Strobe Light described in the August 1998 issue. The problem is that it’s not beat triggering well at all. It misses most of the beats and it seems to be a bit behind the beat of the music anyway. I have checked everything over and over again but can not figure out the problem. The oscillation mode was working perfectly until recently as well. Now, when you turn the oscillation control past halfway the Xenon tubes stop flashing but the little test neon is flashing well. When you turn down the oscillation rate, the Xenon tubes start flashing again but not as well as when we first finished it. Please help! (B. W., via email). •  The beat input sensitivity needs 90  Silicon Chip •   From your description of the problem it seems that the alarm can only be set when the Turbo Timer is running. This is after the engine has warmed up and the thermistor has opened, allowing the Turbo Timer to operate. You will need to test the alarm with its ignition input disconnected from the ignition output of the Turbo Timer. If your alarm does not operate correctly under these conditions, the alarm connections may be incorrect. The ignition signal input to your alarm should connect to the 87a terminal of relay RLY1. The second relay RLY2 is only required if the alarm system disables the ignition in some way which would prevent the turbo timer from running the engine with the alarm activated. Christmas tree LED malfunction I have just finished constructing the LED Christmas Tree as described to be adjusted rather carefully so that the strobe does flash in syn­ chronism with the music. You have not mentioned how you are connecting the line signal inputs to the music source and perhaps the signal is too low which would be indicated by having to turn the sensitivity fully up or clockwise. Alternatively, there may be excessive signal which would be indicated by having to turn the control close to fully anticlock­wise. If the signal is too low, you can increase sensitivity by increasing the value of resistance between pins 8 & 9 of IC1a. The existing 47kΩ resistor can be increased to 470kΩ and the .015µF capacitor reduced to .0015µF (1n5). On the other hand, if the signal is too large, you can reduce the signal level before applying it to the line signal inputs on the strobe. Use a in November 1999. One column of LEDs do not light up green although they will light up red. They are LEDs 4, 5, 12, 13, 20, 21, 28 & 29. Can you suggest what I should check to remedy this problem? (Kaye – via email). •  One of the transistor pair, Q7 or Q8, is not doing its switching job. Check your soldering around both transistors and you will probably find you’ve missed doing one or you have a poor solder joint. Programmable ignition timing for CDI system I recently purchased a programmable ignition timing kit (published in June 1999) from Jaycar Electronics in Perth. I’d like to know if this kit is compatible with a Crane Hi-6 multiple spark capacitive discharge unit. I’m running this device in a Holden VK 308 Commodore with electronic ignition and no vacuum advance. Do I need to make any changes to the circuitry on the igni­tion timing series resistor of 470kΩ to reduce the signal by a factor of 10. The problem with the flashing performance not being as good as before could be due to the trigger transformer having a short between windings. Alternatively, you may have arcing between the trigger transformer high tension output and the trigger connec­tions to the Xenon tubes. Check your wiring and separate the high tension wires to the anode and cathode connections to the Xenon tubes. Make sure the mains power is switched off and disconnected and the capacitors are discharged before working on the circui­try. Alternatively, it’s possible that the Xenon tubes are getting old and tired, particularly if they’ve been used a lot. Try replacing them if everything else checks out. kit to suit the above system? (S. L., via email). •  The Programmable Ignition Timing module could be used with the Hi-6 unit simply by placing it between the points and the Hi-6 ignition system. You would need to build up the input circuitry for the trigger coil on your distributor. The output from this circuit would then connect to the Programmable Ignition and its output would drive the Hi-6 module which would be set up for a points input. Details on programming the module for various advance curves were provided in the July 1999 issue of SILICON CHIP. Timing for slot car drag racing I have a need to measure times over a few seconds, down to a thousandth of a second, for slot car drag racing. Two lanes need to be timed, false starts indicated and the overall winning car identified at the end of each race. Can this be done with one of the interface cards designed to be plugged into the parallel port of a computer (I would like to use a notebook computer), or does the card need to do the timing and send the information to the software for display? If you have published anything which may suit my require­ments I would appreciate the information so I can get started. (B. K., via email). •  You are correct in your assumption that the interface card cannot be used for the timing function. However, it could be used to signal false starts, etc to the computer. The timing could be done with two 74HC390s driven with one section of a 74HC132 configured as an oscillator. Another section could be used to gate the counter. The 16 counter outputs could be switched in two groups of eight to the interface card inputs with 74HC4066 switches. UHF version of Railpower Being a model railway enthusiast, it is great to see the Railpower project in the October 1999 issue. I have built many of your model railway projects and found them all very successful. I built your last infrared controller of a few years back and have it working Garage door controller I have a problem with the Garage Door Controller featured in the April & May 1998 issues. I have completed the controller board and it works fine without a motor connected. I intend using the board to control a sliding gate and have a large, well-made DC motor from an old tape backup system to drive the whole thing. When running with this motor connected, the “up” relay operates normally but when I stop and reverse, the “down” relay produces arcing across the contacts as they are closing. This sends the logic into a total spin and causes the “up” relay to re-engage. It will do this 9 times out of 10, though if I wait for 10 seconds or so before reversing, it will usually operate fine. I am wondering, should I try a windscreen wiper motor to see if the problem disappears? By the way, I have not connected a lamp or the driver tran­sistor (for the lamp) as yet. Would this have any effect? I’ve looked at the supply rails with the CRO; the motor produces some hash but not much. I’ve tried running the relays and motor from a separate supply but this doesn’t work properly. I have also very successfully on my home layout. Your latest effort seems just as interesting and I look forward to the forthcoming editions to see how things progress. I only have one question and that is would it be possible to have the activation of the controller done by RF rather than infrared? There are RF-activated controllers on the market and these can be a great asset if one is operating layouts at an exhibition. (T. B., Glenroy, Vic). •  Yes, you could use the encoder in the remote to drive a UHF transmitter and then have a UHF receiver in the Railpower. You could base it on the UHF system published in the February 1996 issue. Radio interference in daytime running lights I recently built the Daytime Run- tried various capacitors across the relay contacts and more smoothing on the supply, to no avail. I have also tried running the logic from a 3-terminal 9V regulator while the relays and motor were on a separate 12V battery but this was no good either. (P. W., via email) •  We believe your problem hinges around the “large” motor. This means more current than the original design and this may mean that the over-current trip is causing the motor to reverse. The first thing to do is to short out the 0.1Ω resistor from RLY1 to ground. This will prevent the over-current trip from working. If things now work as expected you will have to reduce the value of the resistor by shunting it with one or two 0.1Ω resistors until the gate will close without reversing, unless you put an extra load on it. Alternatively, you may prefer to do away with the over-current limit altogether. One additional thing to watch is the current carrying capacity of the tracks on the PC board. You may have to run thicker wires from point to point on the heavy current tracks. It all hinges on the current that your motor draws. If it is too high, you may also be approaching the limit of the relay con­tacts. ning Lights For Cars as described in the August 1999 issue of SILICON CHIP. It is a brilliant project and works well on my Nissan 4WD wagon. However, I have one problem and that is radio interference. My favourite radio station that I listen to while driving is the NZ national station which broadcasts on AM at 819kHz and this is seriously degraded while the lighting kit is working. I have tried resetting L1 and even rewound it again but to no avail. I have also thoroughly rechecked the PC board. The problem is readily apparent if the radio is tuned off station on AM and then one can clearly the pulsed power frequency of the Mosfet. Is there any way I can overcome this problem? (J. N., Tauranga, NZ). •  You should be able to reduce the interference by connecting automotive suppression capacitors across the January 2000  91 Railpower model train controller I have two questions about the recent Railpower model trail controller articles. There is no mention in the article as to whether or not you can have two or more controllers on different frequencies. Can this be done? Secondly, why does the controller have an output of 6A. This is totally unnecessary as ALL commercial brands of motor available over the last 20 years at least, draw significantly less than 1A. Even multiple header trains don’t need 6A. I know the maximum output can be lowered by increasing the value of the sensing resister but why design for 6A in the first place? (K. M., via email). •  You can have up to four Rail­ headlamps and anoth­er between the 12V lights supply and chassis. Also a capacitor at the radio supply will help. Best results will be obtained if the antenna for the radio is extended to its fullest. This will give the best signal-to-noise ratio for the radio Increased power from FM stereo transmitter I recently bought the FM transmitter published in the October 1988 issue of SILICON CHIP. It works fine but I was wondering if you had any ideas for boosting its output. Do you have any designs for an RF amplifier that can be built onto the output of the BA1404? (P. J., via email). •  We don’t have any suitable RF amplifiers but you can in­crease the power output by operating the circuit from 3V instead of 1.5V. Guitar limiter has no attack or delay I recently built the Guitar Limiter as published in the October 1998 issue. The attack and delay functions don’t have any effect at all although the other functions do work. I can’t see any shorts or misplaced components. I had noticed the component overlay diagram has one of the capacitors not marked. The circuit diagram shows it 92  Silicon Chip powers on the one layout. All you have to do is use various combinations of links LK1 & 2 on the transmitter and main board, as mentioned in the text on page 80 of the November 1999 article. The Railpower has 6A capacity because it has been used on G scale and large outdoor rail systems that do require high cur­rent. We have seen past versions of the Railpower run up to six locomotives in very long trains – that is really something to see. In fact, the Railpower circuit has also been adapted in the past to golf buggies and electric wheel chairs. In any case, our past experience has been that it is better to design for more capacity rather than less. Readers are always wanting to adapt our designs for something bigger, better, etc. to be a 1µF electrolytic. Am I correct on that? (D. F., Salisbury, SA). •  The unlabelled electrolytic capacitor on the overlay diagram has a value of 1µF. The only reason that the attack and decay controls would not operate, apart from misplaced components, is that the gain limit control may be set too high or the output level is set incorrectly. Make sure that the output level pot, VR3, is set as per the instructions on page 73. Blackout feature for Discolight I have built the Discolight as published in the July & August 1988 issues and it works fine. On one of my other light chasers I have a switch called “blackout”. It blacks out the power to the lights while keeping every­thing else running, the indicator LEDs, the chaser sequence, etc. When I want the lights to reactivate, I flip the switch and it continues like nothing has happened. I have looked in the Discolight but I am unable to exactly relate the part of the circuitry where the switch could be wired in. Can you tell me how to do it? (Peter – via email). •  The easy way to provide a “blackout” feature would be to switch the 240VAC supply to the Triacs. This switch will need to be rated to carry the full load current of the incandescent lamps. Using the Speed Alert with a vehicle speed sensor The article on the Speed Alert in the November 1999 issue looks to be a great improvement on the original design published in December 1997. I built the original version but I couldn’t get it to work. It has been in the toohard basket ever since. However, I would like to build the new kit and here is my question. Most cars after about 1986 are fuel-injected and most of these have a computer and a VSS (Vehicle Speed Sensor). Some cars run an electronic speedometer as well although many still run a cable speedo. I have a JE Camira which runs a cable-driven speedo but has a VSS wire going into the computer. It would be much easier to hook the Speed Alert up to this wire instead of finding a place to attach magnets and the pickup coil. Could you suggest a simple modification to the sensor section which would allow this? (C. P., via email) I would like to know if the Speed Alarm published in the November 1999 issue unit could use the electronic speed sensor already mounted in my car’s transmission instead of one fitted to the drive shaft? The sensor was fitted for a VDO monitoring unit along with fuel and other sensors. The VDO unit has now been taken out but the speed sensor is still mounted and has three wires terminating to a Molex plug. (C. S., via email). •  For both of these cases, the installed sensor should be suitable. Just connect the signal wire to the signal input at the free end of the 1kΩ resistor connecting to pin 2 of IC2a. The calibration procedure remains the same. Faulty electric fence controller I have built the High Power Electric Fence Controller as described in the April 1999 issue of SILICON CHIP. At the output the spark jumps across a 5mm gap and gives a loud crack. But attached to fence wire using 60 feet deep bore casing as earth, it is not good. The fence wire is almost dead – I can hold it. My old mains-operated fencer easily handles the task – about half a kilometre. Please suggest what is necessary to make the unit opera­tional as it is needed for another paddock. (A. C., via email). •  The electric fence controller on its own appears to have sufficient energy as indicated by the loud crack and 5mm spark. The loss must be in the fence run. Note that the electric fence controller does have a very fast rise­time for the output pulse and this could be causing one or more of your fence insulators to break down or arc over. This would prevent the fence from deliv­ering the energy when you hold it. A slower risetime pulse such as from a different controller may not affect the insulators so much. Try it on your new fence run. If the insulators are newer it should work well. Satellite receiver modification I have built the Satellite Receiver published in the May, June & July 1995 issues of SILICON CHIP. I have set it up to a point and can’t zero the meter. Apparently the pre-built module has higher gain than the original. What can you suggest? (J. S., via email). •  It should be an easy matter to zero the meter if you follow these procedures carefully. First, measure the AGC voltage connecting to pin 5 of IC2a with respect to ground. Now check that the pin 7 output of IC2a is also this same voltage. The meter is set to zero when the pin 1 voltage from IC2b’s output is identical to the output from IC2a. If you cannot obtain the correct voltage you may need to change the resistor values on either side of VR6. If the voltage cannot be adjusted low enough, decrease the 1kΩ resistor. If Problems with Touch Lamp Dimmer Could somebody please help me out with the Touch Lamp Dim­mer published in the June 1989 issue of SILICON CHIP? It doesn’t want to work. I’ve checked everything from shorts to reversed/wrong components. I am wondering if the two high voltage capacitors, ie, 0.1µF 250VAC, would make difference to the over­all reference voltage of +5V. I’ve been given two MKT capacitors which are coded 275VAC 103. After cross-check­ing, I found their value to be .01µF and not 0.1µF. the voltage cannot be set high enough, decrease the 2.2kΩ resistor. The sensitivity of the meter can be set by using a higher value of resistance for VR5. Charging 3.6V batteries I am building your Multi-purpose Fast Battery Charger as described in the February 1998 issue. I would like to be able to charge several other NiMH batteries, in particular 3.6V. Could you please tell me the formula or method used so I can calculate my own resistor requirements? I will be changing SW5 to a 2-pole 8-position switch to accommodate the existing voltages plus three more. (D. E., via email). •  The value of resistance for lower voltage batteries can be calculated knowing the pin 19 input of the TEA1102 requires the equivalent cell voltage of 1.2V. So for a 3.6V battery The voltage at pin 1 of IC1 (SLB­ 0586A) is around 3.75V to 3.85V. Would this be the cause of the Triac not switching on? (S. F., via email). •  The use of two capacitors that are 10 times smaller than the circuit suggests will affect the operation of the dim­mer. C1 is a filter capacitor to reduce electro­mag­netic interference, while C2 is there to provide the current necessary for the power supply which is derived directly from the mains. Using a value of .01µF will cause the supply to be low in voltage and as you have found, well below the required 5V. Use the correct types and it should operate properly. we would set the resistance divider to divide by 3. The resistance from the positive terminal of the battery is fixed at 100kΩ and it is only the resistance from switch S5a connecting to ground which is altered. The formula works out as 120kΩ/ (Vbatt-1.2) = resist­ance value required. If Vbatt is 3.6V, the required resistance is 50kΩ ohm. Two 100kΩ resistors in parallel would be ideal. Notes & Errata PC Powerhouse, December 1999: if this project is used to drive powered loudspeakers for a PC, you should first check that the ground of the signal line (ie, shield connection) is not connected to the positive supply for the speakers. While we have not encountered this situation, it is not suitable for the PC Powerhouse as it would cause a short circuit to occur across the 5V output. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. January 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 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. 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. Card No. KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com Signature­­­­­­­­­­­­ ________________________  Card expiry date______/______ CHEAP 200MHz TEKTRONIX SCOPE THS-730A, “NEW” in box, factory warranty, $5899. Phone 0412 566100. Name _____________________________________________________ Street _____________________________________________________ Suburb/town _________________________  Postcode______________ 94  Silicon Chip PC-CONTROLS: Receiver 144148MHz (PLL), DS2401 ID-Reader, Temperature Recorder (DS1615), AF Generators, Temperature Measure- DIY PCBs: Video Memory from $39 * QUAD 4 Pix 1 Screen Time / Date from $149 * Video TX/RX from $149 * VIDEO TRANSMITTER/RECEIVER System $199 * IR Remote Control Extender Set $69 * FREE DIGITAL PC VIDEO RECORDER - TIME LAPSE MOTION DETECTION Software with 4 Ch Capture Card from $113 * 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 * QUADS 4 Pix 1 screen from $256 HIRES better than SUPER-VHS Quality * 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 $499 - with 12" Monitor from $582 * 4 COLOUR CAMERAS, SWITCHER & POWER SUPPLY from $807 - with COLOUR QUAD 4 Pix 1 Screen from $1211 * COLOUR QUADS from $512 * COLOUR DUPLEX MUX from $1329 * 14" MONITORS from $203 - with inbuilt 4 Ch SWITCHER from $236 * SEE-inthe-DARK CAMERAS & INFRARED 50 x 120mW LED ILLUMINATOR Kits from $19 * FULL RANGE * DISCOUNTS * Ask for our Catalogue & New Enquiry Offer * www.allthings.com.au * T 08 9349 9413. C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $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. Need prototype PC boards? We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. 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. 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. 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 ment, I/O cards, Data Logging, ActiveX. Ph/Fax (02) 9482 1565. http://www. ar.com.au/~softmark AV-COMM P/L, 198 Condamine St, Balgowlah, NSW 2093. Tel: 02 9949 7417 or 9948 2667. Fax: 9949 7095; www.avcomm.com.au Silvertone’s RC Receiver SOIC adaptors: 20-pin $90, 14-pin $85, 8-pin $80. Credit cards accepted. GRAN­ TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; Fax (02) 9631 1236; or Internet: http://www.grantronics.com.au SOLAR PANELS: 120 watt $995.00, 80 watt $650.00, 60 watt $510.00, 40 watt $395.00 (all with 25 year guarantee). UNBREAKABLE PANELS: 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 Still the best little performer available! 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 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. DATAMAN Softy S4 128K EPROM Programmer and Emulator – $500. ZILOG Z86CCP01ZEM Emulator and Programmer Board (qty 3) <at> $70 each. Ph (02) 9659 5695. feelgood<at>loom.net.au RCS Radio is MOVING. For information, ring 0408-613-300. KIT ASSEMBLY ANY KITS assembled/repaired: professional, speedy service. Phone Nev­ille Walker (07) 3857 2752. January 2000  95 14 Model Railway Projects Shop soiled but HALF PRICE! 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. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) 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 Card No. Signature­­­­­­­­­­­­___________________________  Card expiry date______/______ Name ________________________________________________________ PLEASE PRINT Street ________________________________________________________ Suburb/town___________________________________ Postcode_________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). 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 Advertising Index Acetronics....................................84 Altronics................................. 72-73 Av-Comm Pty Ltd.........................95 Clarke & Severn Electronics........84 Coffs Harbour Electronics............85 Dick Smith Electronics........... 34-37 Dontronics...................................84 EMC Technologies.......................85 Harbuch Electronics....................55 Instant PCBs................................95 Jamo Australia Pty Ltd.............OBC Jaycar ...................... 45-52,95, IBC Kits-R-Us.....................................95 Len Wallis Audio........................IFC Microgram Computers..............3,85 MicroZed Computers...................84 Oatley Electronics..........................9 Pinfold Health Services...............85 Preston Electronics......................84 Printed Electronics...................... 95 Questronix...................................84 Resurrection Radio......................77 Robotic Education Products........85 RobotOz......................................95 Rocom Electronics.......................85 R.T.N............................................84 SC Binders..................................64 SC Computer Omnibus...............33 SC EFI Tech Special....................10 Silicon Chip Bookshop........... 86-87 SC Internet Service.....................23 Silicon Chip Subscriptions...........53 Silvertone Electronics..................95 Smart Fastchargers.....................79 Solar Flair/Ecowatch....................94 Speakerworks..............................85 Telelink Communications.............84 Truscott’s Electronic World...........77 Vass Electronics..........................84 Willis Communications................85 Zoom EFI Special........................11 _____________________________ 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. 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.lenwallisaudio.com