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Build A High-Performance FM Antenna SILICON CHIP MARCH 1998 $5.50* NZ $6.50 INCL GST C I M A N Y D 'S A I L AUSTRA E N I Z A G A M S C ELECTRONI BONUS 236-PAG E JAYCAR CATALOG * *AUST. O NLY SERVICING - VINTAGE RADIO - COMPUTERS - SATELLITE TV - PROJECTS TO BUILD PRINT POST APPROVED - PP255003/01272 Guitar Sustain Unit Nifty Inverter For Compact Fluoros ISSN 1030-2662 03 Building The Multi-Purpose Fast Battery Charger Wiring The Train Controller CommandM Station 1998  1 Build A PC-Controlled LCD Demonstration Board arch 9 771030 266001 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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 Contents Vol.11, No.3; March 1998 FEATURES  4 Understanding Electric Lighting; Pt.5 The tricks and techniques behind floodlighting – by Julian Edgar   9  Labview Ver.5 Virtual Instrumentation Software New version is easier to use than before and has lots of features 40  Special Subscriptions Offer Buy a subscription before June 1998 and get a bonus data wallchart 42  Review: Norbiton Systems PC Bus Digital I/O Kit Do-it-yourself data acquisition – by Rick Walters 62  Feedback On The 500W Power Amplifier We take a look at the DSE kit – by Leo Simpson & Bob Flynn Sustain Unit For Electric Guitars – Page 18 83  Auto Detect & Hard Disc Drive Parameters Find out why auto detect doesn’t always work – by Jason Cole PROJECTS TO BUILD 18 Sustain Unit For Electric Guitars Easy-to-build sustain unit features low distortion – by John Clarke 23  Nifty Inverter For Compact Fluorescent Lamps It operates from a 12VDC power supply and can drive up to three CFLs at full brightness – by Branco Justic 34  Build A 5-Element FM Antenna Clean up your FM reception – by Leo Simpson & Bob Flynn Nifty Inverter For Compact Fluorescent Lamps – Page 23 46  Multi-Purpose Fast Battery Charger; Pt.2 Second article has all the construction details – by John Clarke 54  Command Control System For Model Railways; Pt.2 Power supply plus Command Station wiring – by Barry Grieger 66  PC-Controlled Liquid Crystal Display Board Use your PC to produce moving messages on an LCD – by Rick Walters SPECIAL COLUMNS 28  Serviceman’s Log Those summertime lightning blues – by the TV Serviceman 74  Vintage Radio A fault with a difference – by John Hill Build A 5-Element FM Antenna – Page 34 80  Computer Bits Norton Utilities V2 for Win95; Pt.3 – by Jason Cole 84  Radio Control Jet engines in model aircraft; Pt.3 – by Bob Young DEPARTMENTS   2  Publisher’s Letter 44 Mailbag 60  Circuit Notebook 70  Product Showcase 88  Ask Silicon Chip 93 Order Form 94  Market Centre 96  Advertising Index PC-Controlled Liquid Crystal Display Board – Page 66 March 1998  1 PUBLISHER'S LETTER Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Brendon Sheridan Phone (03) 9720 9198 Mobile 0416 009 217 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Mike Sheriff, B.Sc, VK2YFK Ross Tester Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $59 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. ISSN 1030-2662 and maximum * Recommended price only. 2  Silicon Chip Getting on top of the correspondence mountain As I write this editorial, it is Aus­ tralia Day. I have spent most of the day answering letters to readers. It’s been good really, because I have had the whole day to do it without interruption from the telephone or other workday distractions. It’s been good too because it drives home to me just how enthu­ siastic readers are about SILICON CHIP and electronics in gener­al. It’s good to be appreciated. But today I have had to finally admit that I and we at the magazine have a big problem with correspondence from readers. Quite a few letters have gone unanswered in the last year and there is little prospect that I can answer some of those older letters. I apologise here and now to those readers but perhaps I can explain why it has happened. Everyday there is a batch of letters from readers and many of them can be answered quite readily, although not necessarily on the same day. As you can imagine, there are times during the magazine’s production cycle when there simply isn’t any time at all to answer letters; the magazine must take precedence other­wise we will miss deadlines and the magazine will go on sale late. Generally though, most letters are answered within a week or so of their arrival in the office. Some miss out though and I would like to explain how this comes about. Some letters get passed over merely because they are too long to read at the time. They can easily be three or four (or many more) pages of closely written script and they can be loaded with questions. You see some of these letters featured in the “Ask Silicon Chip” pages and it is not unusual for a reader to ask six or more questions, often on unrelated topics. Such let­ters take a great deal of time to read and then formulate the answers. One letter can easily take an hour. I or someone else might be able to answer four out of five questions easily but the fifth might take half an hour or more and that is after doing a considerable amount of looking at older issues, data books and so on. Even an apparently simple request can take an inordinate amount of time. For example, one the letters I’ve answered today concerned the 2A SLA Bat­ tery Charger published in the July 1996 issue. The reader wanted to know how to alter it to drive a laptop computer and how to reduce its output to 12V. By the time I had read the letter several times to make sure I understood the problem, then referred back to the original article, worked out the circuit changes and wrote the letter, it had taken me 20 minutes. And that was for a straightforward letter. Some of them are really curly. Quite often we also get letters where people ask about designs featured in other magazines, some of which are no longer published. In some cases we can answer but in others we just can’t. Nor can we provide design information on topics which have not been published in the magazine. We are always happy to re­ceive suggestions but some we cannot respond to. If this sounds like a great long moan, it is not meant to be. We love to see those letters come in, even though we may shudder at the time it might take to answer them. So perhaps readers can help make sure their letters will be answered. First, keep the letters brief, to no more than one page, if possible. Second, please don’t ask too many questions or for lots of de­tail. Remember contiued on page 45 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.mgram.com.au Pt.5: The Floodlighting Of Buildings Electric Lighting Floodlighting a building or monument requires special techniques to produce an impressive result. In this chapter, we look at the various tricks employed and the lamps used for flood­lighting. By JULIAN EDGAR Buildings are usually floodlit so that their appearance can be aesthetically appreciated at night. Floodlighting is quite different to other specific forms of illumination (eg, for roads), which means that the criteria employed for floodlighting are also quite different. Floodlighting is not used to simply light every surface of a building even­ ly but instead to emphasise certain ar­ 4  Silicon Chip chitectural characteristics. A designer who created a floodlighting system that gave a natural stone building a strong green colour cast and made it look bland and boring wouldn’t be classed as very suc­cessful! Lamp types A wide variety of lamps can be used for floodlighting, with the most appropriate lamp type depending on the actual applica­tion. Incandescent lamps that are fitted with a built-in reflec­ tor (eg, PAR lamps) can be used for temporary installations where only small areas need be illuminated for short periods. However, the poor luminous efficacy of incandescent lamps means that they are not an ideal light source for long hours of use. Tungsten halogen lamps have higher efficacies than ordinary tung­ sten lamps and their availability in compact shapes and with built-in reflectors allows them to be used in small luminaires. Both tungsten and tungsten halogen lamps are easily dimmed although, of course, the lat­ ter’s lifespan suffers with dimming. However, the excellent colour ren­ Fig.1: a symmetrical floodlight spreads its beam equally in all directions from the central longitudinal axis – see Fig.3 Fig.3: the light distribution for a symmetrical floodlight. Here, the horizontal and vertical patterns are the same, so only one line is shown. dering of both types of lamps pro­ vides significant advantages in some situations. Fluorescent lamps have some limited floodlighting applica­ tions, where they can be used to illuminate linear features such as low walls or parapets. By contrast, high pressure mercury lamps are used for both gen­ eral floodlighting and for highlighting certain features. They are especially suitable where their ‘cool’ light can be used to accentuate blue or green objects. Metal halide lamps have a higher efficacy than high pres­sure mercury lamps and also give better colour rendering. Sodium lamps in high pressure form can be used to give a warm colour ap­pearance to brown, red or yellow objects. By contrast, low pres­ sure sodium lamps, with Fig.2: a bi-symmetrical floodlight has different beam spreads on each axis, but each spread is symmetrical either side of a cen­tral plane – see Fig 4. Fig.4: the pattern of light distribution for a bi-symmetrical floodlight. In this case, the horizontal spread is broader than the vertical spread. Fig.5: an asymmetric floodlight can sharply attenuate the beam in certain directions, as shown by the solid line on this graph. Fig.6: an asymmetric floodlight has different beam spreads along each axis and can sharply attenuate the light in one or more directions – see Fig.5. March 1998  5 Fig.7: the Philips building in Eindhoven has been very carefully floodlit. Note the different colour temperature lamps employed at both the extreme right and left of the photo, and the fountain in the foreground which has been brightly lit. Fig.8: the building can be broken up into its architectural components, each of which is illuminated differently: (A) low, wide, flat vertical surfaces (facades); (B) tall, narrow vertical surfaces (columns); (C) specific architectural features (accents). their monochromatic yellow spectral output, are suitable only when you want everything to appear yellow! By far, the most commonly used lamps in floodlights are the metal hal­ ide and high pressure sodium types. Luminaire types Fig.9: when illuminating facades, medium beam projectors should be placed at a distance (d) that’s one quarter the height of the building (h). 6  Silicon Chip Floodlights are classified on the basis of their general pattern of light distribution. They fall into three basic groups: (1) rotationally symmetrical; (2) bi-symmetrical; and (3) asym­ metrical. A rotationally symmetrical beam spread is produced by a floodlight that has a round face, as shown in Fig.1. This type of floodlight produces the same angle of spread in both the horizon­tal and vertical planes (and at all other angles in between). Fig.3 shows the photometric out­ line for a version that has a medium width beam. On this diagram, ‘y1-y2’ is represented by the dotted line and shows the vertical spread of light, while ‘x1-x2’ (solid line) shows the horizontal spread. As it is a symmet­ rical floodlight, the spreads are the same and so just a single (solid) line is shown. A bi-symmetrical floodlight (Fig.2) Fig.10: the Philips Atria SVF100 is suitable for the illumination of columns. It has a beam spread of only 12 degrees and uses a high pressure sodium lamp with a maximum power rating of 100 watts. has a rectangular face. In this case, the width of the beam differs between the vertical and the horizontal planes (Fig.4). Finally, an asymmetric floodlight is one that typically has a wide beam in one plane but throws the light much further in one direction than the other in the other plane. It is easier to see this on the photometric diagram than it is to describe it – see Fig.5. A typ­ ical asymmetric floodlight is shown in Fig.6. Architectural considerations Buildings can be broken down into a number of different elements which require different floodlighting techniques or equipment. Fig.7 shows the Philips building in Eindhoven at dusk, while Fig.8 identifies the different architectural elements that are individually illuminated. Facades are best lit by using high pressure sodium or metal halide projector luminaires, depending on the colour rendering required. When using medium spread bi-symmetrical floodlights, the projectors should be placed at a distance from the building one-quarter that of its height. Fig.9 shows this in diagrammatic form. A suitable floodlight for this appli­ cation is the Philips 616 Decoflood (Fig.12). This unit can use lamps rated at up to 150 watts, has a light output ratio of 0.58 and a bi-symmetrical beam spread. The electrical control gear for the lamp is built into the housing. Columns need a different type of floodlight and luminaire location if they are to be shown at their best. In this case, narrow-beam projectors are placed much closer to the building to illuminate the columns, with Fig.11 showing the recommended ap­proach. A suitable luminaire for this type of application is the Philips SVF100 (Fig.10). This can be fitted with a high pressure sodium lamp having a maximum power of 100 watts and gives a symmetrical beam spread of just 12°. The luminaire is aimed so that the maximum beam intensity is at the top of the column. Architectural accents – such as statues or other relatively small highlights – are illuminated by sym­ metrical beam projec­ tors, with the Fig.11: columns are illuminated with narrow-beam projector lumi­naires, positioned quite close to the building. It is recommended that ‘d’ be 1/12th of ‘h’ and that the beam be aimed at the top of the column. object bathed in one or more pools of light. An example of such a luminaire is the Philips 607 Decoflood, which is available in either high pressure sodium or metal halide forms with lamps of up to 400 watts power. It has a light output ratio of 0.83 and its aluminium reflector gives a very narrow beam. Several of these floodlights are March 1998  7 Table 1: Typical Illuminance Values Surroundings (Illuminance in Lux) Building Material Luminaire location The direction from which the build­ ing or monument is to be viewed will help determine the position of the lights. If glare and distraction are to be reduced, the lights should be kept out of sight of the viewing points and this is sometimes done by par­tially locating the luminaires underground. Alternatively, asym­metric floodlights can be used which direct no light at all behind the body of the luminaire. Floodlights are often aimed so that Metal Brightly Halide Sodium Clean Dirty Li t Lamp Surface Surface Lamp Poorly Li t Well Li t Light Stone 20 30 60 1.0 0.9 3.0 5.0 Dark Stone 100 150 300 1.0 1.1 2.0 3.0 Aluminium Cladding (natural finish) 200 300 600 1.2 1.1 1.5 2.0 Fig.12 (left): the Philips 616 Decoflood is suitable for illuminating building facades. It is available in either high pressure sodium or metal halide lamp forms. The control circuitry is contained within the housing. often used in a given situation so that the feature can be “modelled” by the light. Correction Coefficient they act differently on adjoining parts or planes of the building. Fig.13(a) shows the lights positioned so that the each facade will each appear to have a different brightness when viewed from position ‘V’. Using these lighting angles will also help bring out any textures that may be present on the two surfaces. Conversely, Fig.14(b) gives equal illuminance across both surfaces and will make any surface texture less visible. Illuminance values The illuminance required to give the right degree of visual impact depends on a number of factors, in­ cluding the environment in which the building is situated. If it stands alone in a dark space, less illuminance will be needed to give the same impact. Conversely, a bright environment will require a higher degree of illuminance to give the same visual impact. If the building has a dark surface finish, a higher illu­ m inance will be needed. A dark surface can be a characteristic of the materials from which the building is constructed or can be the result of fouling over a period of time. Another aspect to consider is the texture of the building material. In a normal installation where the light is directed up at the building, the smoother the surface, the lower the amount of reflected light that will reach the viewer. Finally, if the lamp chosen has a high spectral output that’s close to the colour of the build­ ing, less illumination will be required. Table 1 gives some recommended illuminance values, with the values valid for tungsten lamps having a col­ our temperature of 2800K. If you were designing a floodlighting system, you would certainly hope to be illuminat­ ing a light-coloured stone build­ing! Conclusion The floodlighting of buildings requires careful planning and con­ sideration of the luminaire and lamp types to be used. Next time you pass a floodlit building at night, it’s worth studying how the designer has gone about the task. Next month, in Part 6, we will take a look at the low pressure sodium vapour lamp. Fig.13: with the floodlights positioned at ‘S’ and the viewer at ‘V’, in (a) the relative brightness of the two walls will appear different and the textures will be strongly modelled. In (b) the brightness will be even and the lighting flat. 8  Silicon Chip Acknowledgement: thanks to Philips Lighting for making available the illustrations used in this article. SC Fig.1: LabVIEW 5.0 features a new Instrument Wizard that simplifies the configuration of GPIB, VXI and RS-232 instruments. The Instrument Wizard automatically identifies and tests the instruments connected to the system, installs the required driv­ers and then generates application examples using these drivers. New version has more features and is easy to use Labview 5.0 Virtual Instrumentation Software LabVIEW has been around for 11 years and has become known as the leading software package for instrumenta­tion and control. Any engineer or technician familiar with Wind­ows 95 should take to it like a duck to water. It is now over a decade since Lab­ VIEW was first released. This graph­ ical programming software from Na­ tional Instruments was introduced as a development tool to design, develop and modify instrumentation systems. The goal of LabVIEW has always been to simplify programming tasks so that scientists and engineers could fully utilise the capability of PCs and at the same time get their jobs done quickly and easily. Since its first release, LabVIEW has grown to become the industry-lead­ ing development software for data acquisition, test and measurement and analysis applications. National Instruments refers to LabVIEW as a programming environment, in much the same way as Windows 95 is an environment. So much so, that quite a few third parties have developed LabVIEW applications and these have been updated with the release of Version 5. So there is effec­tively a whole suite of new software and applications. As PCs continue to find use in more and more demanding applications, software developers are constantly looking for ways to get more out of them. Many software developers are also taking advantage of software de­ velopments that include ActiveX and Java to enhance their applications. Some of the features of the new version of LabVIEW are as follows: Instrument Wizards Used in some other Windows 95 programs such as Microsoft Word, Wizards are incorporated into Lab­ VIEW 5. These simplify the con­ figuration of GPIB, VXI, serial and computer-based instru­ m ents. The Instrument Wizard automatically identifies and tests the instruments connected to the system, installs the required drivers and then generates application examples using these drivers – see Fig.1. March 1998  9 Fig.2: LabVIEW 5.0 features a new ActiveX automation server that gives the users the ability to remotely call LabVIEW programs from other programming languages such as Visual Basic, Visual C/C++, Lab Windows/CVI, standard C languages, Microsoft Excel or even another copy of LabVIEW. Not only does the Data Acquisition (DAQ) wizard automati­cally generate a solution for the user, it also creates the LabVIEW block diagram so that users can modify the application as their needs change. These DAQ Wizards have also been added to the Macintosh platform. ActiveX Containers This feature of LabVIEW allows peo­ ple to share code across programming environments. Reusable components or objects of code that are written in one language but can be called from a variety of other environments are important simply because they allow code to be reused that would otherwise need to be completely rewritten. The most common type of reusable component is an ActiveX control and these can be embedded into any ActiveX container – see Fig.2. Today, the most popular ActiveX containers are Visual Basic and Visual C++. With the introduction of Version 5.0, Lab­ VIEW is now an ActiveX Container. 10  Silicon Chip This means that users can easily drop any ActiveX control or document onto a LabVIEW front panel, edit it by clicking on it and control it using a graphical approach on the block diagram. Thus, a user might embed a National Instruments Com­ponent­­ Works control, a web browser control, a HiQ Notebook, an Excel spreadsheet, a Word document, a calendar control or any of more than a thousand other controls and documents available over the Internet and in software worldwide. This means that users are no longer limited to the built-in controls available in Lab­VIEW but can take advantage of controls written in other languages. Equally important, they do not need to do any complicated programming to take full advantage of these other controls. Automation Servers These allow integration of LabVIEW programs into other applications. For example, Visual Basic is often used as a tool for developing front-end appli­ cations for databases. LabVIEW, on the other hand, is an industry-leading software tool used to develop data acquisition and production test sys­ tems. If a user could integrate the two applications together, or call LabVIEW programs from Visual Basic, then they would have the flexibility to use both tools in an application that stores production test data in a database. LabVIEW 5.0 features an Auto­ mation Server that gives users the ability to “remotely” call LabVIEW programs from outside the LabVIEW environment. Thus, the user can call a Lab­ VIEW Virtual Instrument (VI) from any ActiveX Automation client, such as a program written in C, Visual Basic, a Microsoft Excel macro or even from another copy of LabVIEW. Thus, much in the same way that a user calls a DLL from a program, now they can call a LabVIEW program from another appli­cation. In addition, the user can control the entire LabVIEW development environment itself from another program. Distributed Computing Tools These are used to easily create dis­ Fig.3: another feature of LabVIEW 5.0 is Translation Tools for multilingual user interfaces and software translation. This enables the same LabVIEW program to be run in numerous languages. tributed LabVIEW appli­cations that will execute on computers across a heterogeneous network. Certain applications require that their execution take place on multi­ ple machines. If users must quickly execute ex­tremely intensive routines, they may want the ability to divide the tasks onto different computers. Or if remote acquisition requires the user to collect data from various locations, a distributed system may also be the best approach. Typically, distributed systems are complex to write because they require a great amount of overhead code to pass data between the computers or to execute calls on remote machines. With LabVIEW 5.0, users can create distributed systems with ease. Suppose a user has a collection of acquisition routines and wants to call each of them at any time from any of several loca­tions. Many programming environments require networking functions to send commands and data to other computers; those remote com­puters must constantly listen for a connection. To send and receive data, the user must perform tedious data conversions to send information across the network. With LabVIEW 5.0, users simply create their initial pro­ grams, load them on all machines where they might execute and then write a simple program to call them at a specified location. When users execute the “controller” program, it simply reads the specified target and executes the function at that location. When using the ActiveX interface the server automatically launches LabVIEW if it is not already open, so LabVIEW does not need to run constantly on the target computer. The user can choose to display the program on the target machine as it runs or have the program execute in the background. worldwide are well documented and easy to use. In addition, as interna­ tional markets continue to grow, it becomes ever more important that both documentation and software be translated into the end-user’s native language – see Fig.3. With the new documentation tools in LabVIEW 5.0, users can automat­ ically generate software documenta­ tion in the form of HTML (hypertext mark-up language) and RTF (rich text format) formats. Thus, with the click of a mouse, an entire user manual, function reference manual or online help system can be generated. No other tool makes the tedious task of this documentation so simple. Translation tools These help large application de­ velopment by providing the ability to compare graphical code to determine the differences between them – see Fig.4. These are used to create multilin­ gual user interfaces and facilitate the translation of software. Software developers face several challenges to make their software successful worldwide. Good docu­ mentation is often a time-consuming task which some people choose to ignore. However, studies indicate that the most successful software packages Graphical differencing tools Multi-threading To address the requirement of high-performance, very reli­able ap­ plications on PC platforms, modern operating systems, such as Windows March 1998  11 Fig.4: the Graphical Differencing Tool in LabVIEW 5 enables the differences between two programs to be highlighted. This enables new versions of instrumentation programs to be generated quickly. Fig.5: the LabVIEW-based Intellichart from Densitron (Kent, England) is a paperless chart recorder with a TFT colour display, touch screen controls and LAN interface in a robust case. It was designed for clean room environments as encountered in activities such as microchip production or food processing. The graphical tools in LabVIEW 5 mean that users can easily set parameters such as trigger level, scan speed, paper speed, X scale and so on. For further information, contact National Instruments or the web site at www.densitron.com 12  Silicon Chip SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. OR D ER FOR M PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏  3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________  Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ NT and Windows 95, as well as Sun Solaris, are “multi-threaded”. Applications that take advantage of multi-threading have a number of benefits, including better CPU utili­ sation, better system reliability and user interface response and the ability to take advantage of multiprocessor machines. However, only a few applications today are multi-threaded, simply because it is difficult to implement. LabVIEW Version 5.0 solves this problem because, as a dataflow pro­ gramming language, it is inherently parallel in nature. This makes it nat­ ural for users to create code that can execute simultaneously in separate threads. Thus, it is the ideal language in which to develop multi-threaded applications. LabVIEW multi-threading technol­ ogy is built into every virtual instru­ ment (VI), or LabVIEW program, so it is not neces­sary for the user to learn any new programming techniques. In fact, the user does not even need to know what multi-threading is to ben­ efit from it. However, for expert users who want to have specific control over threads, such as changing thread priori­ties, the flexibility is available in a straightforward dialog box option. All of the complex tasks of thread management are transpar­ently built into the LabVIEW execution system, such that users need never concern themselves with the tedious details of thread management. Thus, while tex­ tual-based programmers must learn new and confusing programming practices to create a multi-threaded application, a LabVIEW user simply writes a VI (virtual instru­ment) as he or she always has. And to make an existing LabVIEW VI multi-thread­ ed, users simply have to load their LabVIEW programs into Version 5.0. For a more complete explanation of multi-threading and its benefits, there is an Application Note titled “Creat­ ing Multi-threaded Applications to Maximise System Performance and Reli­ability.” For further information on Lab­ VIEW 5.0 or the full range of instru­ mentation products, contact National Instruments Australia, PO Box 466, Ring­ w ood, Vic 3134. Phone (03) 9879; fax (03) 9879 6277. Readers can also access information by email at: info.australia<at>natinst.com or at http://www.natinst.com SC March 1998  13 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 Sustain Unit for electric guitars Are you playing electric guitar without a sustain pedal? What? In this day of electronics and technology, you don’t have a sustain pedal? Add one now and have a more fulfilling musical life and set out on the path to fame and fortune. By JOHN CLARKE If you’re a guitar player without a sustain pedal you must be feeling pretty deprived. But now you can fix all that by building this new design. It can give you really long sustain notes and will help make the sound much more live. 18  Silicon Chip Sustain is just one of many effects that can enhance the sound from a guitar. Some effects produce deliber­ ate distortion – eg, distortion pedals (previously called fuzz pedals) – so that they sound harsh, while others are more subtle and add in frequency response shaping or envelope modula­ tion. The sustain effect works by con­ trolling the signal from your guitar so as to maintain a constant level of sound. When you pluck the string on your guitar, it initially produces a high level of oscillation which ultimately dies away to nothing. This is reflected in the volume of the note – quite loud when initially plucked and then decay­ ing away quite fast. A sustain circuit modifies this natural decay so that the volume remains fairly constant as the sound from the string itself dies away to nothing. Some guitar sustain pedals are rel­ atively crude and provide the sustain function by amplifying the guitar signal and clipping the waveform Fig.1: some guitar sustain pedals work simply by clipping the waveform when the level becomes too high. The top waveform is a sinewave signal with 12dB higher bursts occurring every 125ms. The lower trace is the waveform with a clipping circuit added. This degree of clipping can sound pretty awful. Main features •  Low distortion •  Separate Attack and Decay controls •  Sustain/Bypass (In/Out) switch •   Matched in and out levels (adjustable) when the level becomes too high. The oscilloscope waveforms of Fig.1 show this type of sustain. The top waveform is a sinewave signal with 12dB higher bursts occur­ ring every 125ms. The lower trace is the waveform with a clipping circuit added. Note how the higher signal bursts are clipped hard to provide flat top limiting which con­ stitutes considerable distortion – it can sound pretty awful. Such a clipping circuit cannot be considered to be a pure sustain unit since it adds in very high distortion. If distortion is wanted, this can be added in with a distortion pedal. The Sustain pedal circuit described here produces much lower distortion than the clipping circuit but still maintains the output level over a wide signal range. The oscilloscope wave­ Fig.2: these waveforms show the response of the sustain circuit with the same input waveform as in Fig.1. Note how the lower waveform remains sinusoidal over its full duration. forms of Fig.2 show the response of the sustain unit under the same type of pulse waveform as the clipping cir­cuit referred to in Fig.1. The upper trace is the pulsed input. Note how the lower waveform remains sinusoidal over its full dura­ tion. Note that the initial attack of the waveform is more or less preserved and that the waveform does still decay away eventually. These times can be adjusted with the Attack and Decay controls. How it works Fig.3 shows the block diagram of the circuit. The guitar signal is applied to a gain-controlled amplifier which provides the output signal. The sig­ nal produced at the amplifier output is full-wave rectified and filtered to produce a DC level which is depend­ ent on the signal level at the gain controlled amplifier output. This DC level is compared against a reference level set by VR3 in the error amplifier IC2a. The error signal is then fed back to the gain controlled amplifier in order to maintain a constant output. Fig.4 shows the full circuit. It comprises six op amps, four in IC1 (a TL074) and two in IC2 (an LM358). Q1 is a 2N5484 JFET which provides the variable gain feature for IC1. Fig.3: the block diagram of the circuit. The guitar signal is applied to a gain-controlled amplifier which acts to provide a more constant output signal. March 1998  19 Fig.4: the circuit employs op amp IC1a and Mosfet Q1 as the gain controlled amplifier while IC1b, IC1c and diodes D2 & D3 act as a precision full-wave rectifier. Signal input from the guitar is AC-coupled via a 1µF ca­pacitor to pin 3, the non-inverting input of op amp IC1a. The 22kΩ resistor biases pin 3 to +5V while the 10Ω series resistor acts as a “stopper” to reduce the possibility of RF breakthrough. JFET Q1 is used to dynamically vary the gain of op amp IC1a; this is the gain-controlled amplifier referred to earlier in Fig.3. The gain of IC1a is set by the 10kΩ feedback resistor between pins 1 & 2, in conjunction with the drain-source resist­ance of JFET Q1 and the 100Ω source resis­ tor. If the JFET is biased on hard, the drain source resistance is low and the corre­sponding gain is high. Note that the JFET does not pass DC because of the asso­ciated 47µF capacitor. As well as blocking DC and effectively setting the DC gain of the circuit to unity, the 47µF ca­ pacitor also sets the low frequency 20  Silicon Chip rolloff of the circuit. High frequen­cy rolloff above about 16kHz is provid­ ed by the .001µF capaci­tor between pins 1 & 2. Rectifier & envelope control Op amps IC1b & IC1c, plus diodes D2 & D3 and associated resistors form the full wave rectifier. When the sig­ nal from IC1a goes negative, the out­ put of IC1b goes high, forward biasing D3. The gain for negative signals is set by the 20kΩ input and 20kΩ feedback resistors to a value of -1. The signal at the cathode of D3 is coupled to the inverting input, pin 9, of IC1c via the 10kΩ resistor. Gain for IC1c is set at -10 by this 10kΩ input resistor and the 100kΩ feedback resistor. Overall gain for the input signal is therefore -1 x -10 = +10. However, there is an extra path for the input signal via the 20kΩ resistor to pin 9 of IC1c. This path gives a positive signal at the output of IC1c with a gain of -5. Adding the two gains gives us +5. So when the input signal is negative, the output at pin 8 of IC1c is negative. For positive input signals diode D2 conducts and clamps the output of IC1b to +5V. Signal then passes via the 20kΩ resistor connecting to pin 9 of IC1c. IC1c inverts the signal and provides a gain of -5. Therefore, posi­ tive input signals result in a nega­tive output at pin 8 of IC1c. So, regardless of whether the input signal swings negative or positive, the output at pin 8 of IC1c always swings negative. Thus we have a full-wave rectifier. The 10pF capacitor across the 20kΩ feedback resistor for IC1b prevents instability while the 0.1µF capacitor across the 10kΩ feedback resistor of IC1c provides a measure of filtering. The full-wave rectified signal is filtered using D4, VR1, VR2, the 10kΩ resistor and the 10µF capacitor. Diode D4 allows the 10µF capacitor to be charged via VR1 but only discharged via VR2 and the series 10kΩ resistor. This allows separate control over the attack and decay times. Error amplifier IC2a is the error amplifier. It compares the rectified signal from D4 with the DC voltage (Vadj) at its pin 2 and it amplifies the difference between these two signals by a factor of 5.7, as set by the 10kΩ input and 47kΩ feedback resistors. Reference. Vadj, the DC reference fed to the error amplifier, comes from op amp IC2b and is set using trimpot VR3. The error amplifier drives the gate of JFET Q1 via a 10kΩ resistor and switch S2. The 10kΩ resistor between the gates and drain of Q1 has the effect of linearising the signal and thereby reducing distortion. Slide switch S2 is used to select Sustain (in) or Bypass modes (out). When Sustain is selected, the voltage from pin 1 of IC2a controls Q1’s gate. When S2 is in the out position, the gate is held at a voltage set by VR4 and the 10kΩ resistor between gate and drain. In this mode, the drainsource resistance of Q1 is constant and so the gain does not vary. In use, trimpot VR4 is adjusted so that the same volume is experienced whether the switch is in or out as the guitar string is first plucked. Power for the circuit is derived from a 12V DC source which will usu­ ally be a plugpack. Diode D1 protects against reverse polarity connection, while the 100µF capacitor decouples the supply. LED1 indicates power when S1 is switched on. Most of the op amps are biased from a 5V DC supply. This is de­ Fig.5: all the components mount on the PC board, including the input and output jack sockets. Note that IC1 and IC2 are oriented in different directions. rived with zener diode ZD1 which is supplied via a 1kΩ resistor from the 11.4V rail, following D1. The resulting regu­ lated voltage across ZD1 is filtered with a 10µF capacitor and then buffered with op amp IC1c. Construction Typically, a guitar sustain circuit such as this would be pedal operated and perhaps the electronics would all be mounted in the pedal housing itself. However, some guitar players would be just as happy mounting the circuit board in a simple plastic utility case and with simple switches to operate it instead of a pedal. With those thoughts in mind, we are presenting this project in the simplest possible form, as a PC board with all circuit components mounted on it. The PC board measures 105 x 60mm and is coded 01302981. It has been designed to fit into a standard UB3 plastic utility case measuring 130 x 67 x 43mm (Altronics Cat. H-0153 or equivalent). Fig.5 shows the component layout. Before you install any parts on the board, check it thoroughly against the PC artwork shown in Fig.6 and make sure that all holes have been drilled. That done, install the two Capacitor Codes ❏ Value IEC Code EIA Code ❏ 0.47µF   470n   474 ❏ 0.001µF   1n0   102 ❏ 10pF   10p   10 Resistor Colour Codes ❏ No. ❏  1 ❏  1 ❏  3 ❏  3 ❏  6 ❏  1 ❏  1 ❏  2 ❏  1 Value 100kΩ 47kΩ 22kΩ 20kΩ 10kΩ 2.2kΩ 1kΩ 100Ω 10Ω 4-Band Code (1%) brown black yellow brown yellow violet orange brown red red orange brown red black orange brown brown black orange brown red red red brown brown black red brown brown black brown brown brown black black brown 5-Band Code (1%) brown black black orange brown yellow violet black red brown red red black red brown red black black red brown brown black black red brown red red black brown brown brown black black brown brown brown black black black brown brown black black gold brown March 1998  21 Parts List Specifications 1 PC board, code 01302981, 105 x 60mm 2 DPDT slider switches (S1,S2) 2 6.35mm PC mount mono unswitched sockets 1 10kΩ linear PC mount pot (VR1) 1 100kΩ linear PC mount pot (VR2) 2 knobs 1 5mm red LED (LED1) 2 PC stakes 1 40mm length of 0.8mm tinned copper wire Total harmonic distortion (1kHz) ................... 0.7% at 10mV input, 2% <at> 20mV, 0.02% <at> 200mV Semiconductors 1 TL074, LF347 quad op amp (IC1) 1 LM358 dual op amp (IC2) 1 2N5484 N-channel JFET (Q1) 1 1N4004 1A 400V diode (D1) 3 1N914, 1N4148 signal diodes (D2-D4) 1 5.1V 400mW zener diode (ZD1) Signal to noise ratio at maximum gain (with respect to 100mV)............................-60dB with 20Hz to 20kHz filter (better noise figure at lower gains) Output level versus input level............................. flat from about 10mV to 170mV input Attack time ................................................................................. 5ms (max) Decay time ................................................................................ 25ms (min) Maximum gain ...............................................................................18 times Frequency response .....................................-1dB at 20Hz; -3dB at 16kHz Capacitors 1 100µF 16VW PC electrolytic 1 47µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 2 1µF 16VW PC electrolytic 1 0.47µF 63V MKT polyester 2 .001µF 63V MKT polyester 1 10pF ceramic Resistors (0.25W, 1%) 1 100kΩ 1 2.2kΩ 1 47kΩ 1 1kΩ 3 22kΩ 2 100Ω 3 20kΩ 1 10Ω 6 10kΩ PC stakes, two links, resistors and diodes, followed by the capacitors, the LED and the two trimpots. Make sure that the diodes and electrolytic capacitors are installed with correct polarity. Next, install the two ICs and note that they are oriented differently. Pin 1 of IC1 is adjacent to the two jack sockets while pin 1 of IC2 faces the other end of the board. Slide switches S1 and S2 are in­ stalled by inserting the switch pins into the PC board and soldering in place. If the pins are difficult to in­ sert, crimp them with pliers first or use tinned copper wire through the 22  Silicon Chip Fig.6 actual size artwork for the PC board. It has been designed to slip into a standard plastic utility box (UB3). switch pins which then insert into the PC board. The JFET (Q1) is mount­ed with its package oriented as shown on Fig.5. The Attack and Decay potentiome­ ters, VR1 and VR2, are PC types and are soldered directly into the board. Note that they have different values so don’t get them swapped around by mistake. Finally, mount the two 6.35mm PC sockets in position. They are PC types too and solder directly into the board. Testing, testing Connect up a 12V DC power supply to the PC stakes on the board and check that there is about +11.4V at pin 4 of IC1 and pin 8 of IC2 when S1 is on. Pin 7, pin 10 and pin 12 of IC1 should have about +5V present. You are now ready to test the sus­ tain unit with your gui­tar. Switch S2 to the Sustain setting (towards S1) and play a few notes. Adjust VR3 for best effect on the sustain. You may also need to adjust the volume level from your guitar to suit the input range of the sustain unit which operates best between 10mV and 200mV. Adjust the Attack control to set the rate at which the note is reduced in volume when the string is first plucked. Then adjust the Delay control to ensure that the note’s volume is main­tained as much as possible. SC A nifty inverter for compact fluorescent lamps Want to drive a number of compact fluorescent lamps (CFLs) from a 12V supply? Here’s a low cost way of doing it. The finished product fits into a small plastic case yet will drive up to three 11W CFLs at full brightness. Design by BRANCO JUSTIC* We have published a number of inverters for fluorescent lamps in the past but this is certainly the simplest. It makes use of the internal circuitry of CFLs and the result is a simple low-cost inverter. Before we go any further, perhaps we had better explain what we mean by a Compact Fluorescent Lamp or CFL. If you visit the electrical section of any large retailer or hardware store you will find a range of CFLs rated at between 10W and 40W. They have an March 1998  23 Fig.1: the inverter consists of a CMOS oscillator with complemen­tary outputs, two Mosfets to drive the step-up transistors and a bridge rectifier with ultra-fast diodes. The unsmoothed DC is then applied directly to the CFL which normally runs from 50Hz 240VAC. Edison screw base and run from the 240VAC 50Hz mains supply. But you don’t have to run them from 240VAC 50Hz. They can be run from a high voltage DC supply of about 340V. How can this be? Inside the circular plastic base of the CFL is a bridge rectifier to convert the incoming 240VAC supply to about 340V DC. This is then fed to an elec­ tronic ballast circuit inside the CFL to drive the folded fluorescent tube. So because there is a bridge rectifier inside the CFL, that means we can power it from 340V DC (or therea­ bouts) rather than 240VAC. But the high voltage supply does not even need to be smoothed DC. It can be unfiltered DC, direct from the inverter’s own bridge rectifier. Fig.2: this is the voltage waveform at the drain of Mosfet Q5. You can see that the waveform is close to 24V peak-to-peak. Ignore the oscilloscope measurement of 32.2V peak-to-peak because that includes occasional overshoots which are not depicted in this waveform but are clipped by the 16V zener diodes. 24  Silicon Chip So the fact that the high voltage DC does not need to be filtered means there is a further saving because high voltage electrolytic capacitors are not required. Neat, huh? But if the CFL has a bridge rectifier in it, why does the inverter need a bridge rectifier at its output too? Well, it is necessary and we’ll explain why later. Circuit details Fig.1 shows the inverter circuit. It uses an oscillator to drive a pair of power Mosfets and a step up trans­ former. Its output is then rectified and fed to the CFLs. Only one 74C14 hex Schmitt trig­ ger, IC1, is used in the circuit. IC1a and IC1b plus frequency determining components C1, R1, and R2 form a simple two-gate oscillator that pro­ duces a square wave output at about 20kHz. IC1e and IC1f are connected in parallel to invert and buffer the output of IC1b. Then IC1c and IC1d, also connected in parallel, invert and buffer the oscillator signal again. So now we have complementary (ie, 180° out of phase) signals and these are used to drive complementary emitter follower pairs, Q1 & Q2 and Q3 & Q4. We could have used the outputs of IC1e, etc to drive the following Mos­ fets, Q5 & Q6, but the emitter follower drive gives faster and cleaner switch­ ing because it is better able to charge and discharge the gate capacitance of the Mosfets. By ensuring fast switch­ ing, there is less stress and power loss Parts List 1 PC board, 115 x 36mm 1 plastic utility box, 129 x 68 x 41mm 1 Edison screw socket 1 or 2 11W compact fluorescent lamps (CFLs) 1 step-up inverter transformer (T1) 1 prewound inductor (L1) 3 rocker switches (S1,S2,S3) Fig.3: this the voltage appearing between one side of the trans­former secondary and 0V. This is 320V peak-to-peak and the full output is 640V peak-to-peak. in the Mos­fets and that leads to better efficiency. Because of the complementary signals driving the Mosfets, each one turns on alternately to drive its half of the transform­er primary winding. The Mosfet effectively switches the +12V across one half of the transformer and transformer action in the other half means that 24V peak-to-peak appears at each Mosfet drain. The transformer primary is 7.5 turns centre tapped (ie, 3.75 turns each half) and the secondary has 100 turns. So with 24V peak-to-peak across each pri­ mary half, the total voltage appearing across the transformer secondary will be 640V peak-to-peak. This is confirmed by the waveforms shown in Fig.2 & Fig.3. Fig.2 shows the voltage waveform at the drain of Mosfet Q5. You can see that the wave­ form is close to 24V peak-to-peak. (Ignore the oscilloscope measurement of 32.2V peak-to-peak because that includes occasional overshoots which are not depicted in this waveform.) Fig.3 shows the voltage appearing between one side of the transformer secondary and 0V. This is 320V peakto-peak, exactly as theory suggests. By the way, this waveform was recorded with two 11W CFLs connected. Note that the waveform frequency was recorded as just over 20kHz. We mentioned overshoots in the primary waveform and these are clamped, to protect the Mosfets from voltage punch-through, by 16V zener diodes ZD1 and ZD2 plus diodes D1 and D2. The fact that two 16V zener diodes are employed, explains why the oscillo­ scope produced a meas­ urement of 32.2V peak-to-peak for the over­shoots. The transformer secondary drives a bridge rectifier con­sisting of four ultra-fast 1000V diodes, D3-D6. The rectified output is fed to the CFLs via a low-pass filter consisting of R5 & R6 in parallel together with capacitor C5. R5 and R6 also limit the peak current when charging any load capacitance; eg, the filter capacitor in the CFL. Semiconductors 1 74C14, 40106 hex Schmitt trigger (IC1) 2 C8050 NPN transistors (Q1,Q3) 2 C8550 PNP transistors (Q2,Q4) 2 2SK2175 N-channel Mosfets (Q5,Q6) 2 16V 1W zener diodes (ZD1, ZD2) 6 1NH42 ultra-fast diodes (D1-D6) 2 1N4148 diodes (D7,D8) Resistors (0.25W, 1% or 5%) 1 47kΩ 2 205Ω 2W 1 10kΩ 2 4.7kΩ Capacitors 2 220µF 25VW PC electrolytic 1 0.1µF metallised polyester (greencap) or monolithic 1 .0015µF metallised polyester (greencap) 1 680pF 3kV ceramic Miscellaneous 240VAC figure-8 or sheathed twin cable, hookup wire, sold­er. All parts for this project are available from Oatley Electronics who own the design copyright. Their address is PO Box 89, Oatley, NSW 2223. Phone (02) 9584 3563; fax (02) 9584 3561. The prices are as follows: Earlier on we raised the issue of whether there was any need for the inverter to have its own bridge recti­ fier when the CFLs have an internal bridge. The reason the second bridge recti­fier is required is that the invert­ er runs at 20kHz and this is done to enable high efficiency and a small step-up transformer to be used. If the 20kHz output from the inverter was fed directly to the CFLs, their bridge rectifiers would immediately blow. So we use ultra-fast diodes to do the rectification and then the CFL internal bridges can handle the unsmoothed DC without problems. PC board plus on-board components plus one 11W CFL ................$25.00 Building it Extra CFL...............................................................................................$11 All the components for the CFL inverter are accommodated on a Where To Buy The Kit March 1998  25 Above: the inverter board steps up 12V DC to drive one, two or three compact fluorescent lamps (CFLs). Make sure that all parts are correctly oriented. Fig.4 (right): this is the component layout for the PC board and the wiring to the switches. Both the stepup transformer (T1) and the supply induc­tor (L1) will be supplied ready wound. small PC board which measures 115 x 36mm. It is then mounted in a stand­ ard plastic utility box measuring 129 x 68 x 41mm. This has a panel on it with three rocker switches, one for each CFL to be driven. Fig.4 shows the component layout for the PC board and the wiring to the switches. This project will be supplied as a kit from Oatley Electronics and both the stepup transformer (T1) and the supply inductor (L1) will be sup­ plied ready wound. When assembling the board, install the resistors and diodes first. Make sure that you don’t mix up the diodes 26  Silicon Chip and zener diodes otherwise the project will have a very brief life. Then install the four transistors, followed by the capacitors. Again, make sure that you install the transistors in their correct positions and that the electrolytic capacitors have the correct polarity. Next, install the transformer and inductor L1, followed by the two Mosfets and the CMOS IC. Finally, connect all the external wiring to the rocker switches and the Edison screw sockets for the CFLs. Check all your wiring very carefully and then connect one CFL. Connect the inverter to a 12V power supply or battery. The CFL should imme­diately light up. As is normal with any fluo­ rescent lamp or CFL, they will take a couple of minutes to reach maximum brilliance. Be careful not to come in contact with the inverter’s out­put. It bites! *Branco Justic is Managing Director of SC Oatley Electronics. LASER POINTER KIT SPECIAL!!! 650nM 5mW, 3-4V, case 125 x 39 x 25mm, lens, battery holder NOW JUST:$20 12V DC LIGHTING SPECIAL Very efficient and properly driven fluorescent white light! Tubes last because the filaments are heated! Inverter kit can drive up to three 11W Compact FluoVISIBLE LASER DIODE MODULE KIT rescent lamps (CFL’s). Kit plus one 5mW/650nM The same as our "visible 11W CFL$25. extra CFL $11Ea. laser diode kit" but a much smaller PCB. 2Hrs 4Hrs Dimensions are 15mm X 40mm: $20 AMPERE-HOUR END 6Hrs CHARGER KIT 12 CHANNEL UHF REMOTE SPECIAL Just set the required 8Hrs Ref: EA Mar 93. This system features a Amps - 0.1, 0.3, 0.5 10Hrs 12 channel keypad operated transmitter, and the time. Shuts 12Hrs AMPERE-HOUR CHARGER 12 channel receiver supplied with a UHF off automaticly. END CHARGING receiver module & 2 channel relay driver Charges any cell or kit (can be used in multiples) All the battery from 0 - 15v. 0.1A 0.3A 0.5A PCBs are solder masked & silk supplied with all screened, the transmitter fits into a hand parts, box, knob, held commercial case which has a switches, plugbattery compartment. At near1/2 price: pack, timer, label, Transmitter kit: $22, Transmitter case: PCB & all components:$18 $11, Receiver kit: $28, Rly driver kit: $18 IF YOU WANT OVER 500M RANGE NEW SMALL 650nM LASER MODULE JUST ADD $20 TO THE TX-RX KIT laser diode module, 35x10mm diam. PRICE. 3-4.5V: $32 NETWORK 2 COMPUTERS FOR $50!! New Windows/95 compatible (DEC (DE101) etherworks LC/TP) DIGITAL brand Ethernet computer cards with software and booklet in original box. Cards include boot ROM so one of the computers does not even require a hard CASE AND SWIVEL disc. We don’t supply the commonly A small plastic case available cable which can also be made suitable for enclosing the up with RJ45 connectors and two CCD camera, plus a very strong multi angle and position twisted wire pairs: Diagram included. adjustable universal joint swivel bracket Limited quantity: $50 for a pair. AUTOMATIC LASER LIGHT SHOW KIT plus screws: $6 - $4 The display changes every 5-60 sec, GIANT MOVING MESSAGE DISPLAY Adjustable time. Countless possible USED. Scrolls, flashes and reveals text displays from single to multiple flowers, UHF A-V MODULATOR in all directions and much more. Now collapsing circles, rotating single and Professional tuneable with software, programming info and multiple ellipses, stars, etc. PCB + all UHF A/V modulator with schematic diagram. Has 12 large 5x7 PCB components, three motors & built in Antenna booster and a test pattern generator: As used in LED dot matrices (38 X 52 mm), very mirrors : $65 Or with above kit for $79!! VCR’s. With each unit we also supply bright, in housing, 240Vac, 3 wire control lead: $60. parts for a 5V regulator $18 - $14 AUDIO LASER SCANNER KIT Great patterns that depend on the sound UHF A-V TRANSMITTER or music picked up by an electret Metal enclosed with telemicrophone. Inc. PCB, components scopic antenna, A/V leads microphone, 2 motors & 2 mirrors: $44 12V/7Ah GEL BATTERY BARGAIN supplied: $35 - $25 Fresh stock standard battery plus one 650nM LASER POINTER SPECIAL GEL/LEAD-ACID BATTERY CHARGER Light weight (2XAAA) pen sized pointer AUDIO PREAMPLIFIER Small kit which includes a microphone. for: $30 with 5mW/650nM laser diode, 140mm Gives Line level output for use with the long, 18mm diameter: $32 NEW!!! COMPUTER CONTROLLED above Modulator or transmitter: $8 - $5 STEPPER MOTOR KIT LONG RANGE UHF REMOTE CONTROL New improved kit that can drive larger New very small UHF Super-hetrodyne AUDIO POWER AMPLIFIER KIT A small LM386 based power amplifier kit motors and has optoisolation between receiver modules and matching that can directly drive a speaker, needs the circuit and the computer. DB25 Saw resonators connector provided on PCB. Needs a on 433.92 MHz. the above Preamplifier: $9 - $6 standard cable for connection to a PC, (25mW power TIME LAPSE RECORDING INTERFACE and a power supply for the motor drive limit!).The range of New kit, now has relay contact outputs! section. PCB and all on board com- our proto.Tx-Rx was approx. Can be directly connected to a VCR or ponents kit plus software and notes: $39 1Km! The first will be a 2 ch. remote via a learning remote control: $30 - $20 or $49 with two used 1.8deg. motors !!! control. $65: (1 Tx + 1 Rx.) avail. March PIR MOVEMENT DETECTOR module CGA COLOUR MONITOR to suit,very small: $16 - $12 10mW 640nM LASER DIODE!!! New 12V DC-1A 6" colour monitor, Finally a diode to suit LASER LIGHT ready for enclosing, no box, just the tube SHOW. brighter than large He-Ne tubes! LED IR ILLUMINATORS KITS and driver PCB’s: $65 10 LED: $14 - $10, 30 LED: $30 -$20 Avai. April: $69 . Driver kit, housing & lens avail. ReDC MOTOR SPEED CONTROL duced prices when purchased HIGH RESOLUTION MONITOR Brand new 240V 30cm enclosed EXPERIMENTERS PACK with the two laser (pattern computer monitor + a video conversion ONE 20A motor speed controller kit generators) on this page. (similar to SC - Jun.97-$18) plus two kit. Gives small new 12VDC motors (40mm dia., STEPPER MOTOR DRIVER KITS better res40mm length) plus one used car Kit includes a large used 1.8deg. (200 olution than windscreen wiper motor (which have step / rev) motor & used SAA1042A IC. TV’s!! Avail. internal gear reduction) for: $32 early Feb. Can be driven by external or an onLimited but board clock; has a variable frequency NEW SEMICONDUCTOR BARGAINS good qty. clock generator. Ext switches (not inc.) 2SK2175 - MOSFETS 15A, TO220, 60V, or logic levels from a computer etc set BARGAIN 30W: 10 for $15, CA3140 - MOSFET CW or CCW rotation, half or full step PRICE. input op amp : 5 for $5, TL494 - operation, operation enable/disable, MINIATURE FM TRANSMITTER (33 x switchmode power supply IC : 5 for $5, clock speed. PCB and onboard com23 x 10mm) enclosed in a small black NE555 - timer IC : 10 for $5, ICL7106 - ponents:$18 with 1 motor, $28 with 2 metal case. Built in switch & LCD display driver : $5, ICL7107 - LED motors. microphone. Specifications: 88 to 108- display driver : $5, IRFZ44 MOSFETS 60V,0.028ohm on resistance,50A: 10 for SWITCH MODE POWER SUPPLY MHz (adjustable), has a $30 C8050 and C8550 transistors: 20 Compact ( 145 X 80 X 50mm ), in a wire ant. attached, for $5, CMOS IC’S 4001/ 11/ 13/ 16/ 17/ perforated metal case, 240V AC in, 12V bat. life 60 hrs, 20/ 24/ 28/ 40/ 46/ 60/ 66/ 69/ 93 Any DC/2A and 5VDC/5A out: $17 Range 50M: mixture 10 for $8 $39 (Std. watch battery LR44, inc.) BRAND NEW LASER ENGINE SWITCH MODE POWER SUPPLY laser engine as used in laser printers. Compact ( 145 X 80 X 50mm ), in a With Polygon scanner motor with Xtal 4 CHANNEL LIGHT FLASHER Light flasher-chaser for flashing 20W perforated metal case, 240V AC in, 12V controlled driver PCB, 5mW/780nM Halogen lamps. 12/24V - 2A AC DC/2A and 5VDC/5A out: $17 laser diode in collimated housing, operation for flashing 4-8 lamps. Suit mirrors, lenses etc. Info on how to run shops, discos etc. Even has adjustable UNIDIRECTIONAL ELECTRET motor and laser included: $35 rate & sound trigger circuit. We supply MICROPHONE the microphone, PCB plus all on board New quality product REED SWITCHES NEW!!! components:$27 20W Halogen down- with clip, 3M lead, Quality "Bell telephone" brand 28mm x light lamps$4, Lamp connectors to suit 2.5mm plug: $4 Make 3.5mm. A great buy at: 10 for $3 $2.50. We should have some suitable a stage quality wireless used inexpensive transformers to suit microphone by combining mirrors, lenses etc. Info on running it with our FMTX MK2 transmitter kit: SPRING REVERB UNIT NEW!!! $16 for the kit plus the microphone motor & laser included: $35 Professional quality large 3 spring reverb unit with 425 X 100 X 35mm DOG SILENCER KIT- NEW IMPROVED metal housing and female MASTHEAD AMPLIFIER KIT Our famous MAR-6 based masthead High power swept ultrasonic generator RCA connectors amp. 2-section PCB (power supply sec. kit that can drive up to 4 piezo tweeters. plugs. Typical can be indoors): kit $15. Plugpack: $6 Works on dogs & most animals. PCB & circuit Weather-proof box:$2.50. Box for power all on-board components and horn piezo supplied. supply: $2.50 Rabbit-ears ant: $7 tweeter: $33, extra tweeters $7 ea. clearance Suitable 13.8V-1A DC plugpack $10. (MAR-6 avail. sep.)available price of ;$40 $50 /$70 OATLEY ELECTRONICS DEMO BOARD FOR LIQUID CRYSTAL DISPLAYS This is the actual 16 x 1 character display used in a project in this issue. No problems!!!: $16 Ea. or 3 for $40 OATLEY ELECTRONICS CCD CAMERA SPECIAL + BONUS!!!!!! The best "value for money" CCD camera on the market! Tiny CCD camera, 0.1 lux,IR responsive, high resolution. It has a metal lens housing and glass lenses, & performs better than many cheaper models. . WITH YOUR CHOICE OF ONE OF THE FOLLOWING LENS Pinhole (60deg.), 78 deg.; 92 deg.; 120 deg.; $89 or $99 with a 150 deg. . THE BONUS??? IF YOU PURCHASE THE CAMERA YOU CAN BUY UP TO ONE OF EACH OF THE FOLLOWING ITEMS AT THE REDUCED PRICE SHOWN. SUPER BRIGHT BLUE LEDS THE BRIGHTEST WE’VE OFFERED, Super bright at 400mCd $1.50 ea. 10 for $10...5mm LEDS AT SUPER PRICES 1Cd red 10 for $4,..300mCd green $1.10 ea. or 10 for $7,..3Cd red $1.10 ea. or 10 for $7,..3Cd yellow also in 3mm: 10 for $9 ; Super bright...FLASHING LEDs: $1.50 ea. or 10 for $10...(Make small torch! mix the red green & blue) MORE KITS Geiger counter:$40,...Breath tester: $40,..Music box: $11,..Ding dong doorbell: $3.50, Siren using a 10cm speaker: $14,..Electric fence using used car coil: $25,..Ultrasonic car alarm: $35,..1ch UHF Central locking, Tx and Rx: $35,...4 door Central locking: $60,..2 Channel UHF Remote Control, 1Tx + 1Rx: $45. LCD CHARACTER DISPLAYS In stock! Std 4 line X 32, NEC D7227G IC’s.: $18 NEW DIGITAL BAR CODE WANDS USA made wands. Sapphire tip, curly cord & 5pin DIN plug. converts bar codes to a digital pulses, 0.19mm spot size is. Open collector output TTL / CMOS compatible needs 5V supply. $45 INDUSTRIAL CONTROLLERS / MONITORS ( QUALITY DUTCH MADE) MOTOR PROTECTORS / MONITORS: suits 3 phase motors up to 1000V / 1000A against thermal & mechanical overload & electrical fault conditions, can be used as a shearpin, consists of motor protection unit with built in current transformers (wires pass through, no physical connection motor wires), with a 3m cable linking it to a monitor unit with a 6 digit LCD display for motor data, settings and the cause of any trip if it occurs, new, at a fraction of new cost: $200 for the pair.. GROUND FAULT UNIT For high power applications: 2-3 phase from a few Amps to over 1000A. can be set to trip at 0.01 to 6.4A, has adjustable trip time, N.O. & N.C. 440VAC/8A relay contacts, 46mm diam. hole for core balance, 2KV isolation etc., output terminals for linear meter etc. 6 CHANNEL RTD TEMP. MONITOR This unit is designed to monitor up to 2 groups of 3 temp. sensors and diplay on a remote LCD controller (included with above) user setable alarm states etc. from -50 to +350 Deg.C. Requires 240VAC supply: $180 MAGNIFIERS / LOUPES jewellers eye- piece with a plastic lens: $3,... 50mm $8, 75mm $12,... 110mm $15. SPECIAL: The set of four for $25 ************ALL OF OUR KITS************ All kits come with quality made PCB’s with screen printed component designation & solder mask. OATLEY ELECTRONICS PO Box 89 Oatley NSW 2223 Ph ( 02 ) 9584 3563 Fax 9584 3561 orders by e-mail: oatley<at>world.net http://www.ozemail.com.au/~oatley major cards with ph. & fax orders, Post & Pack typically $6 SERVICEMAN'S LOG Those summertime lightning blues Every summer, after the hot humid days, there follows the inevitable storm and whether it is the El Nino effect or not, these storms seem to be getting more violent. Or is it that electronic devices are becoming more vulnerable? One would have thought that, after all these years, lightn­ing would be better understood but it doesn’t appear to be. I watched a program recently that went on to show that lightning does indeed strike the same place twice – sometimes even more. And with older TV sets, the high humidity causes insulation breakdown in the EHT transformers and focus circuits. The day after a storm is always hec­ tic, with many confused people on the phone. Some are surprised that their electronic equipment isn’t working and fail to make any connection with mother nature’s major disturbance the night before. Most of them just want their gear fixed immediately but of course, that’s not always possible. For my part, I organise a stack of loan sets so that people don’t become too impatient. I never cease to be amazed by the path lightning takes through a set – it never seems to be logical or in a straight line to earth. Sometimes the damage can be particularly serious on a set that did not appear to be near the strike, while others right next to the hit remain totally unaffected. The fireball One such case occurred when Mrs Williams anxiously asked me to call. She was certain that the whole lot would be a complete write-off. When I arrived at her house, she told me that she was walking into the lounge room when the lightning struck, hitting the garage roof only a few metres outside the front door. 28  Silicon Chip And, according to the lady, a fireball had come through the front door and moved horizontally until it hit the TV set. I must admit that I was a bit sceptical about the fireball bit but, even so, I half-expected the AWA 2C6346 to be burnt to a frazzle. I removed the back at arm’s length to avoid getting soot on my clothes but, to my surprise, it was exceptionally clean for an 11-year old set. I poked about, removed the chassis and looked everywhere. There was no sign of any damage and the fuse was intact. In the end, there was nothing for it but to switch it on. Fearing the worst, I hit the power switch and stood well-back but it was a total anticlimax. The set came on perfectly except that it gave a snowy picture, which was fixed as soon as I recon­ nected the antenna. I then checked the VCR, a Panason­ ic NV-G16A. Neither the controls on the unit, nor on the remote control, were working. I switched it off while Mrs Williams brought in a cup of tea and after 15 minutes I switched it back on again. The controls were now working perfectly, as indeed was the remote control. The one explanation appears to be that a lightn­ing surge can tem­ porarily disable a microprocessor, by applying false voltages to a wide range of pins. And if one is lucky, it will restore itself after a few on/off cycles. Either that or there is a subtle in­ termittent lurking in it somewhere. In either case, there wasn’t much I could do about it then. If, or when, it reappears it will be time to try again. So Mrs Williams was exceptionally lucky; the only thing that had failed completely was the Foxtel STV-100 cable decoder, which was Telstra’s responsibility. A weak effort The next customer was lucky too, as mother nature’s effort here was also a pretty weak one. This time, the set was an Italian-made Fujitsu General, model FGS211 (BS950 chassis). This too was dead and I soon discovered that the mains fuse (F451) had blown. There was no visible damage and the cause turned out to be switching transistor T401 (BU508A), which was shorted. The bridge rectifier hadn’t been damaged, as I would have ex­ pected. There was, however, one weird side effect. The sound was fractionally low and this turned out to be transistor TR702 (BC547C) in the audio preamp circuit. This transistor had become leaky and so that problem was easily fixed. No lightning The next problem was not quite so easy. There are some customers who insist that their equipment was dam­ aged during a storm but subsequent investigation proves that this was not the real cause. In this case, the customer brought in a VCR that was now showing fine horizontal interference lines when playing tapes. Initially, it looked to me as though an electro had dried out in the power supply, thereby causing ripple in the power supply to the video head preamplifier. As it turned out, the true cause was rather sneaky. Underneath a small metal can, soldered as a component screen onto the printed board, was some of the no­ torious brown goo. It was completely concealed and it had corroded and shorted the tracks underneath a drop­ out compensation circuit. Removing it and cleaning the board restored the picture, so the problem was hardly due to a lightning strike! The 76cm Toshiba There was no doubt about the next job. Mr Johns owns a 1989 76cm Toshiba (model 329P8A) and lives on the first floor of a block of units. This is a huge set and weighs in at around 50kg. Faced with this, I elected to go to the mountain. The fault was described as a horizontal line across the screen. I removed the back and quickly dis­ covered that R327, a fusible 6.2Ω 1W resistor feeding 27V to pin 7 of the vertical output stage (IC303, AN5521), was open circuit. Access to most of this circuit is not easy but nevertheless, I decided to replace the resistor and IC together to save time. When I switched it back on, it only took a second or so before the resistor burnt out again. Naturally, it was the last resistor of that type in my toolbox. This time, I looked more carefully at the set and soon noticed that IC361 (TDA8145) on the U905B DPC-2 board was very hot. In addition, the PC board was dark all around it. I decided to leave the set where it was and lend Mr Johns a portable until I could order in the necessary parts. A few days later I returned and re­ placed IC361 and resistor R327. This time the resistor lasted a few seconds longer before failing and the IC was still getting extremely hot. It was then that I spied what had to be the real culprit: coil L464 on board U905C DPC-1. This coil (TLN3061) had be­ come so hot it had melted its plastic insulation and was burnt black. Well, I knew I didn’t have a replace­ ment coil and it might be a long wait for another one. Because the part was in the hori­zontal deflection correction circuit I decided to try it without the coil in circuit to see if I had some sort of vertical deflec­tion. This turned out to be a colossal mistake. Initially, at switch-on there were a few noises I hadn’t heard be­ fore, then a very loud one. After that, there was silence and all life ceased to exist inside the set. I had blown the line output transis­ tor (Q404) and vapourised the 145V rail which feeds Q404’s collector via resistor R444 (0.82Ω, 2W) and pin 2 of the horizontal output transformer. Again, the thought of negotiating a 76cm TV set down a flight of stairs, lifting it into a vehicle big enough to carry it and then getting it into the workshop was too horrible to con­ template. I left the set where it was and went home. The next day I ordered the parts which arrived almost immediately. Third time lucky? No, you guessed it; there was more trouble to come. Despite replacing all the parts, the line output transistor (Q404) got very hot and failed yet again. There had to be another short nearby and after a while I found that diode D440 (ERC0615) in Q404’s collector circuit was shorted. I didn’t have one of these to hand but I did have an FR307, another line output transistor and a 0.82Ω resistor for R444. Pincushion distortion This time, success at last! The pic­ ture was restored and I checked the HT rail, refitted the back and recon­ nected the exter­nal speaker and AV connections. With it all back together again I was enjoying a nice cup of tea, when Mr Johns and I both noticed that the tennis wasn’t quite right. No, I don’t mean that someone was chucking a wobbly; instead, I mean March 1998  29 Serviceman’s Log – continued lightning strikes. One way of quoting for such sets, where damage appears to be severe, is to price a replace­ ment chassis rather than fixing it to component level. Sometimes it is a safer proposition but in some cases, the cost of a re­placement chassis is simply too high to make it econom­ ically viable and the set either has to be repaired at component level or written off. The unluckiest victim that the picture was all wrong in the east/west direction, with noticeable pincushion distor­tion. “Oh bother!” I said (rather untruth­ fully) as I removed the back again. I quickly found the three east/west controls – R358 width, R356 keystone (trapezoid) and R359 DPC (pincush­ ion) – and marked their positions with a felt-tip pen before twiddling each one in turn. This had no effect; all three appeared to be totally inop­ erative. This seemed to suggest that IC361 had failed again; either that or I was indeed going to have to manhandle it back to the workshop so that I could use the CRO to trace the waveforms around this circuit. Please – not that! A stroke of luck Well, it was at this stage that my luck turned for the better. Earlier in the piece, I had sensibly had the foresight to fit a socket for IC361. This 30  Silicon Chip meant that I could easily replace it without having to first unsolder the module that it was on (U905B) in or­ der to gain access to the copper side. As it turned out, the IC had failed again and the new one finally fixed the last problem. But why had IC361 failed the sec­ ond time? The answer is that it was almost certainly a byproduct of L464’s failure and/or any of the other failures that occurred after replacing IC361 the first time. I realigned the three controls using a crosshatch generator and settled down to a replacement cup of tea before replacing the back. I then had another cuppa to make sure that it was still working – while watching the tennis – and I would probably have stayed for a third if Mr Johns hadn’t made some subtle comment about how busy I must be. The above story just goes to empha­ sise the good and bad luck aspects of The unluckiest of the lightning victims was undoubtedly Mr Evans, with Yours Truly suffering collateral damage on the side. He was watching the spectacle that night when there was a strike a few streets away. The lights and power flickered and his Fujit­su General TV set, an FG2012 with a Goldstar PC-04A chassis, went completely dead. When I called, I removed the back, expecting just the fuse to have gone. However, not only was fuse F581 in­ tact but the switchmode power supply was actually working. But that was as far as it went and I noticed that some of the printed wiring had evaporated. That was enough for me; it was back to the workshop. Later, I found that the missing print­ ed wiring involved the sub-switch on the mains power switch, SW851. The latter is a pushbutton toggle type which opens or closes the two con­ tacts directly in the incoming 240V power line to the power supply. It also performs several functions via the sub-switch (P801). These functions involve the various rails out of the power supply and also include the control of relay RL801 in the 112V rail from pin 17. The vaporised sub-switch wiring led to four NPN transistors – Q704, Q705, Q713 and Q714 – in the standby/on switching circuit and this had also been destroyed. All this damage was duly re­paired but this only allowed the standby LED LD701 to turn on. By this stage, there should have been 112V on the collector of the horizontal out­ put transistor (Q402), applied via relay RL801. However, the relay was not being activated. This set provides a test function here although this is not shown on the circuit. A 2-pin male connector, P702, is connected between pin 41 of the main IC (IC701) and chassis (pin 41 drives the damaged NPN transistor circuit mentioned above). By bridging these pins, the relay could be switched on via Q801S and Q713. Unfortunately, the horizontal output stage started but then died. My next stop was Q401, the hori­ zontal driver transistor. A waveform check at its collector indicated that it was delivering only low ampli­ tude pulses. The collector voltage is derived from pin 6 of the EHT trans­ former (T801) which should be at 28V. After following a number of false leads, I finished up at D401 which connects between the 18V rail from the switchmode power supply and the 28V rail. This diode was short circuit. At last, I seemed to be getting somewhere, as a snowy raster now appeared. Unfortunately, no control functions were available at the front panel or via the remote control and I still had no sound. On the other hand, I now had clear confirma­tion that IC701 was faulty; pin 41 still needed to be bypassed, whereas it should have been doing the job itself. So, regardless of any other faults in the set, this IC it had to be replaced. In fact, I finished up replacing two IC701s. No, I didn’t replace the same one twice; there are two separate ICs marked IC701 on the circuit – the original 42-pin PCA84C640P/030 device and an 8-pin PCD8572 device connected to it. But just to confuse matters, the 8-pin device in the set was marked X24C02P and designated IC702. Anyway, I now had a picture but there was still no sound and the au­ tomatic tuning wouldn’t lock in. It took the replace­ment of IC401 to fix most of this. This IC is a TDA1940 and, among other things, provides sync separation, a burst generator and vertical and horizontal sync outputs. Next on the replacement list was IC601 (TBA-120T) which provides the sound IF functions. Changing this restored the sound. I now had a working set – well, sort of. No remote control The one thing left not working was the remote control. This involves a 3-terminal package (PA1) which contains an infrared sensor and a preamp­ lifier. One terminal goes to chassis, one is fed from a 5.6V source and the other delivers pulses to pin 35 of IC701. At least, that is what should hap­ pen but no pulses could be seen on the CRO. I removed the PA1 and disassem­ bled it. It was fitted with a GL3274 IC (IC1) which is not obtainable. However, I was able to purchase the entire package for $32 plus tax. This fitted, the pulses could now be seen at pin 35 but there was still no remote control action. I checked the 5V rail for ripple and replaced ZD701, a 5.6V zener, as it was down to 4V but I was getting nowhere. I confirmed that the remote controller was working properly and transmitting the correct data patterns, using another TV set. And this is where the exercise came to an abrupt halt. I was forced to the conclusion that the faulty pre­ amplifier (IC1) had damaged the new microprocessor (IC701), this probably involv­ing the internal circuitry asso­ ciated with pin 35. And this meant that the microprocessor would have to be replaced a second time to restore the remote control function. But enough was enough. This IC is an expensive item and is time-con­ suming to fit. And even if I did fit it, I could not be 100% sure that that was the only fault still involved. So I had to call it quits. It was a difficult decision, con­ sidering the amount of time, money and frustra­ tion that had been expended but I had to make it. I told the owner that I couldn’t economically repair the set and advised him to settle with his insurance company. I would make no charge, of course; the loss was mine. By mutual agreement I acquired the set which was working but without the remote control function. I hoped that I might be able to salvage it in the long term and recoup some of my losses but right now, it was a write-off. In fact, this is a classic example of how a repair can get out of hand; the time taken to diagnose and repair each succes­sive stage eventually exceed­ ed the value of this 1992 48cm TV set. Sometimes, it is hard to decide where to stop; the next component replaced may be the last one needed to complete the job. And it is virtually impossible to estimate the total cost of the repair without actually making it. Talk about a catch 22 situation! It’s not the end End of story? Well, I thought so when I put the set aside a few weeks SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. SMART ® FASTCHARGERS Brings you advanced technology at affordable prices As featured in ‘Silicon Chip’ Jan. ’96 This REFLEX® charger charges single cells or battery packs from 1.2V to 13.2V and 110mAh to 7Ah. VERY FAST CHARGING. Standard batteries in maximum 1 hour, fast charge batteries in max. 15 minutes AVOID THE WELL KNOWN MEMORY EFFECT. NO NEED TO DISCHARGE. Just top up. This saves time and also extends the life of the batteries. SAVE MONEY. Restore most Nicads with memory effect to remaining capacity and rejuvenate many 0V worn-out Nicads EXTEND THE LIFE OF YOUR BATTERIES Recharge them up to 3000 times. DESIGNED AND MADE IN AUSTRALIA 12V-24V Converters, P. supplies and dedicated, fully automatic chargers for industrial applications are also available. For a FREE detailed technical description please Ph: (03) 6492 1368 or Fax: (03) 6492 1329 2567 Wilmot Rd, Devenport, TAS 7310 March 1998  31 ago and then, more recently, when I had finished writ­ing the above notes which I have left exactly as I originally wrote them – ready to go to the Editor. In fact, it was only the intervention of a weekend which held them up. Boots and all And then, quite by chance, a similar model set came in for a minor service. I was sorely tempted – could I solve the mystery once for all? It wouldn’t cost anything, except time, so I jumped in, boots and all. I “borrowed” IC701 from the new arrival and fitted it to the written off set. The moment of truth had arrived; I switched it on and tried the re­ mote control. It still didn’t work – everything was the same as before with normal pulses into pin 35 of IC701 but with no response. Obvi­ 32  Silicon Chip ously, the fault wasn’t in the IC as I had thought. But where was it? The preamp had been replaced and was generating normal pulses; or was it? More to the point, did I have the correct preamp? I began to recall some discussion over the part number. Fujitsu’s spare parts division had been most helpful and had quoted me for a type 106-042A. I noted at the time that the unit in the chassis was a 106-042B and this was also shown in the manual. I did draw attention to this difference but I was assured that the “A” ver­sion was a direct replacement. Nothing unusu­ al about that; it happens all the time. But now I was more than a little suspicious. I went back to Fujitsu and began delving a little deeper. In fact, it didn’t take long to confirm my suspicions; the two units were not interchangeable. They both did the same kind of job and generated similar – but not identical – pulses. In greater detail, the pulses from the type “A” preamp are inverted compared to those from the type “B” unit. That’s fine for an IC designed to accept that type of pulse train but not for IC701. Fujitsu were most apologetic and promised to send a re­ p lacement immediately. But I couldn’t wait. I “pinched” the preamp from the set on the service bench and fitted it in my set. And bingo, it worked – at long last the set was complete and working normally. It’s hard to describe one’s feelings in situations like this. After all the hard work, there was finally a happy ending and I would be able to SC recoup some of my losses. 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 By LEO SIMPSON & BOB FLYNN Build this 5-element FM antenna for better reception What’s your FM reception like? Pretty poor? Does the music sound distorted or are there lots of sibilants on voice? If so, you need a proper FM antenna, not a bit of wire hanging out the back of your tuner. Why not build this 5-element Yagi antenna which is designed specially for the FM band? You’ll be amazed at how good those stations can sound. 34  Silicon Chip It’s amazing isn’t it. People spend thousands of dollars on their hifi equipment and then just hang a bit of wire out the back of the gear to pick up the FM stations. Well, the music might sound first class from CDs but it will definitely not be up to par from the FM stations. This doesn’t make sense really. Most people know that they need a good antenna for TV reception; the same applies to FM. The same recep­ tion problems that plague TV also Fig.1: this diagram shows all the details of the 5-element antenna. At top is a plan view while the other diagrams show hardware and element mounting details. March 1998  35 Bill of Materials Aluminium 2.3 metres of 19mm square aluminium tubing with 1.8mm wall thickness 8.5 metres of 10mm diameter aluminium tubing with 1mm wall thick­ness Hardware 1 piece of thick Perspex, 120 x 40 x 3mm 1 U-bolt and clamp to suit mast 4 8G x 13mm screws 2 8G x 32mm screws 2 3/16-inch Whitworth or M4 roundhead screws 70mm long 1 3/16-inch Whitworth or M4 roundhead screw 60mm long 2 3/16-inch Whitworth or M4 roundhead screws 32mm long 2 3/16-inch Whitworth or M4 roundhead screws 19mm long 7 3/16-inch or 4mm ID split or lockwashers 7 3/16-inch Whitworth or M4 nuts 2 3/16-inch Whitworth or M4 wing nuts 2 3/16-inch or 4mm ID flat washers Note: all screws, washers and nuts should be stainless steel Miscellaneous Mast and wall mounts or bargeboard mount (hockey stick style), 300Ω-to-75Ω in-line balun (for outdoor use), semi-air spaced coax cable (Hills SSC32 or equivalent), plastic cable ties, silicone sealant. affect FM stations. You wouldn’t put up with just a bit of wire hanging out of your TV so why compromise with FM signals? If you do, you are bound to get weak signals and multipath reception which is the same effect as “ghosting” on TV. Multipath causes bad distor­ tion and you can only cure it with a good anten­na. Sure, if you live in a strong signal area, you might get away with just a tap off your existing TV antenna but a separate FM antenna will always give better results. And if you changed over to a UHF TV antenna or pay TV, you 36  Silicon Chip What Is A Yagi Antenna? The Yagi is not a new antenna design by any means. It was developed by H. Yagi and S. Uda at Tohoku Imperial University in Japan in 1926. In the VHF (very high frequency) bands, of which the FM band (88108MHz) forms a small part, most antennas depend on electrically resonant elements; ie, elements which are a half-wavelength at the frequency of interest. In its simplest form, the Yagi consists of a dipole element and an additional slightly longer parasitic element behind it, called the reflector. More complex designs have shorter parasitic elements in front of the dipole and these are called directors. The reflector and directors are referred to as parasitic elements because they also resonate over a frequency range simi­lar to that of the don’t have that option. So what FM antenna to buy? There are only a few available and of those that are, few are suitable for fringe areas. To be specific, the most common FM antenna available is a 3-element Yagi which gives, at best, about 6dB gain with respect to a simple dipole. These are OK in strong signal areas but if you want more than just a couple of stations at reasonable signal strength, you need more gain; ie, you need a “fringe-area” anten­na. You also need more directivity to cope with poor reception conditions where multipath is a real problem. After looking at what’s available, we decided to design and build our own. Actually, we ended up building a number of varia­tions before settling on the design presented here. The new antenna is a 5-element Yagi array. It has a folded dipole, a single reflector and three directors. It has an esti­mated gain of between +8dB and +9dB with respect to a dipole and an improved front-to-back ratio compared to a 3-element array. Narrow acceptance angle As well as an improved front-toback ratio, this antenna is also more directional. To put it another way, it has a narrow­er acceptance angle. This dipole. Part of the electromagnetic energy they capture is re-radiated and picked up by the dipole. Hence the director and reflectors add considerably to the signal which is picked up by the dipole on its own. By suitably dimensioning the reflector and directors, it is possible to determine the overall frequency coverage of a Yagi antenna, its gain and its directional characteristics. In gener­al, the more elements in a Yagi array, the higher will be its gain and the smaller the forward acceptance angle. There is a law of diminishing returns though. Above a cer­ tain number of parasitic elements, no useful increase in gain is obtainable. There is a definite trade-off between the practical size of a Yagi and the amount of gain it provides. means that reflected signals coming in from the side of the antenna will be suppressed. This is worth­ while because the more suppression you can obtain for reflected signals, the less distorted the resulting stereo sound will be. In other words, if you have prob­ lems with distorted sound from FM stations (due to reflected signals or “multipath”), you should get a notice­ able improvement with this antenna. Apart from reducing multipath problems, the big reason to build this antenna is to obtain lots more signal than you would get from a random piece of wire or the common twinlead dipole wire antenna that is supplied with many tuners. Furthermore, be­ cause it will be installed outside your home, the signal pickup will be even better. In fact, our observations show that with a good FM antenna such as this, it is possible to pick up stations (in stereo) which may be more than 160km away. Finally, by feeding more signal to your tuner, even from your strong local stations, you will improve the re­ ception. There will be less distortion, better separation between channels and less hiss in the background. In fact, with a good FM tuner combined with a good antenna, it can be difficult to pick the difference between a CD player and the same piece of music “off air”. Does that sound outra­geous? Well, it’s not, as far as average CDs are concerned even though CD players have far superior noise and distortion compared to signals broadcast on FM. Tools you will need Most enthusiasts will have all the tools needed for this project. You will need a hacksaw, electric drill and a vice. It would also help if you have a drill press but you can do without this. Apart from an antenna clamp (U-bolt and V-block bracket), no spe­ cial hardware or fittings are required. Making this antenna is very straight­ forward. If you have all the materials available you can probably do it in a single afternoon. Fig.1 shows all the details of the 5-element antenna. It shows the di­ mensions of all the elements and the various hardware bits you will have to make to assemble the antenna. At top is a plan view showing the length of all five elements and their spacing along the boom. The dipole insulator plate has wing nut terminals to connect 300Ω ribbon or a 300Ω-to-75Ω balun. The plate is made from Per­spex, Lexan or other acrylic material. The square boom makes mounting easy. Screws & nuts After a few years’ exposure to the elements, many antennas are in a poor state. Aluminium may not “rust” but it does corrode, particularly in seaside areas or in metropolitan areas where there is a lot of industrial fallout. This corrosion can be a lot worse if you don’t use the right screws and nuts. We recommend the use of stain­ less steel screws, nuts and washers throughout, whether for machine screws or self-tappers. They do cost more but they last indefinitely. Don’t, on any account, use brass screws. When used to attach aluminium elements these will corrode away almost before your eyes. Nor do we recom­ mend galvanised, bright zinc or cadmium plated steel screws. In seaside areas these can be visibly cor­ roded with just a few days’ exposure. In rural areas, well away from the sea or city pollution, you can probably get away with galvanised screws but the antenna will last longer if you paint it. Starting work Before you start, make sure you have obtained all the alu­minium and hardware listed in the Bill of Materi­ This topside view of the antenna shows how the folded dipole is attached to the square boom. Note the short section of aluminium tubing which acts as a spacer between the underside of the boom and the dipole insulator plate. Whitworth or other machine screws hold it all together. als. After all, you will be frustrated if you get half-way through and find you can’t progress further because you lack screws or some other item. Get ‘em all before you start. Cut the boom to length first. It is 2222mm long. It is made of 19mm square aluminium tubing which makes drilling and assembly easier. If you are experienced in metalwork and have access to a set of V-blocks and a drill press, you could substi­ tute 25mm diameter tubing for the boom. In fact, you could use 25mm stain­ less steel round tubing which is readily available from plumbing supply stores. While you’re at it, cut the folded dipole spacer which also uses the 19mm square tubing. It is 50mm long. March 1998  37 The ends of the folded dipole are fabricated using 42mm lengths of aluminium tubing shaped to mate with the upper and lower pieces. They are held together with a 70mm long machine screw, nut and split washer. will have the elements skew-whiff. A few words of advice on drilling is appropriate here. Drilling in thin wall aluminium tubing can be a problem and many people tend to end up with holes that are more triangular than round. The way around this problem is to drill all the large holes (ie, all 10mm holes) undersize and then ream them out to the correct size using a tapered reamer. Be careful when reaming holes out though because it is quite easy to get carried away and then end up with holes that are oversize. Use a scrap piece of 10mm tubing to test when the holes specified at 10mm are the correct size. Each director element and the reflector is held in the boom with a self-tapping screw, as shown in dia­ gram A of Fig.1. Drill a 3mm hole at the centre point of each element but only through one side. Don’t mount the elements on the boom yet though because the dipole should be assem­ bled and mounted on the boom first. Making the dipole The mast clamp and V-block assembly can be purchased from elec­tronic parts or automobile accessory retailers. We strongly recommend hot-dip galvanised types if possible. Avoid cadmium plated or zinc plated clamps which can rust quite quickly, par­ticularly in seaside areas. You should have a piece of tubing about 120mm long left over as scrap. Don’t throw it away. It will come in handy later. Now cut the 10mm diameter tubing for the director, three reflectors and parts for the dipole. Remember the old adage about “measure twice and cut once”. It’s hard to lengthen elements that are too short. Note that the three directors are all the same length (ie, 1270mm). Next, centre-punch the boom for all holes prior to drill­ing. Note that the 38  Silicon Chip boom is 2222mm long and the total of the element spacings along the boom is 2182mm – see the plan diagram on Fig.1. Mark the hole centre position for the reflector element first, 20mm from one end of the boom, and then work your way along. If you have a drill press which lets you drill all the element holes square through the boom you are fortunate. If not, mark the hole centre positions on both sides of the boom and drill from both sides. If you don’t get the element holes lined up properly, you The folded dipole is made from five pieces of 10mm alumini­um tubing, three long and two short. The detail of its assembly can be seen from the diagram at the bottom of Fig.1. Two short tubes, shown as diagram E on Fig.1, are cut and shaped so that they key in with the top and bottom ele­ ments of the dipole. Further detail is shown in the accompanying photos. The top and bottom pieces of the dipole are held at each end with a 70mm long 3/16-inch Whitworth or M4 screw, together with a nut and lock washer. At the centre, the lower halves of the dipole are terminated on an insulating plate (shown in dia­ gram D of Fig.1). This plate is made of 3mm acrylic (Perspex or Lexan). The dipole halves are each secured to the insulating plate with a 19mm long 3/16-inch Whitworth or M4 screw, nut and lockwasher. Terminals for the dipole are pro­ vided with two 32mm long 3/16-inch Whitworth or M4 screws, each fitted with a nut and lockwasher plus a wing nut and flat washer. The insulating plate is secured to and spaced off the main boom via a section of square tubing, shown as a “folded dipole spacer” in diagram F of Fig.1. The insulating plate is secured to the spacer with two 8-gauge 32mm Do you have trouble drilling round holes? You’ll do better by drilling the holes undersize and then reaming them out to exact size with a tapered reamer. long self-tapping screws which go through the spacer and into the boom. The top piece of the dipole is then se­ cured to the boom with a 60mm long 3/16-inch Whitworth or M4 screw, nut and lockwasher. The details of the dipole insulating plate and fixing to the boom can be seen in the accompanying photos. Note that while we used white Per­ spex, you could use a piece of clear material if that is what you have on hand. However, note our remarks on painting, later in this article. By this time the antenna looks just about complete. You need to add the antenna clamp, to enable it to be at­ tached to the mast and you will need a 300Ω-to-75Ω balun to match it to 75Ω coax cable. You can use 300Ω ribbon if you wish and omit the balun but to obtain the most interference-free signal, we recom­mend coax cable for your installation. Unfortunately, many antenna clamps are sold with a cadmium plat­ ed and passivated finish. These have a “gold” finish. This is barely adequate for inland areas but rusts quickly in sea air. We may seem to be paranoid about corrosion but since the SILICON CHIP editorial offices are only a few hundred metres from the seaside we are very aware of just how quickly metal hardware can rust and corrode. If you can, buy antenna clamps that are hot dip galvanised. These last a The reflector and director elements are attached to the boom using self-tapping screws. Ideally, all screws, nuts and washers should be stainless steel to avoid corrosion. lot longer than the cad-plated jobs. U-bolts and clamps intended for auto exhaust systems are generally quite good in this respect. But be aware that zinc “plated” fittings are not as rust resistant as galvanised types. Zinc plated fittings have a smooth bright appearance while hot dip galvanising is unmistakable – it has quite a rough appearance. If you really want to gild the lily, go to a ship’s chan­dlers and buy stainless steel U-bolts and clamps. They’ll last forever; well just about. We suggest that the ends of all the elements and the boom be stopped up with silicone sealant. This will stop them from whistling in the wind. Better still, you can buy Delrin plugs to suit the square aluminium tubing. These look neater. It is also a good idea to paint your antenna, if you live in an area where corrosion is a problem. If nothing else, the dipole insulating plate should be painted as acrylic material does dete­ riorate in sunlight (ie, UV). We suggest you leave the antenna for a month or so to weather it and then paint it with an etch primer. Finish it with an aluminium loaded paint such as British Paints “Silvar”. Installation When you have finished your an­ tenna you need to carefully consider its installation. There is no point in going to a lot of trouble making it if you don’t install it properly. Try to install your new antenna well away from existing TV antennas as these can have quite a serious effect on the perfor­mance. Similarly, nearby metal guttering, electric cabling, metal roofing or sarking (ie, reflective insu­ lation such as Sisalation) can have a bad effect on antenna performance. And don’t forget the effect of a hot water tank which may be lurking just beneath the roof tiles. If you live on a busy street, try to install your antenna as far away as possible from the traffic side of your house. That way you will minimise ignition noise from passing traffic. Finally, install the antenna as high as possible above the roof and gutter­ ing. If that is a problem, try to install the antenna so that it is at least a half wavelength away from the nearest metallic object such as guttering or roofing. This means a distance of about 1.5 metres away from guttering. Take care when installing the an­ tenna. Safe working with ladders is particularly important. Take your time and don’t take risks. You don’t want to end up in hospital. Line up the antenna so that it is aimed at the main FM stations of interest. If you are really keen, you could consider installing a rotator, to obtain the very best reception from SC all stations. March 1998  39 3 1 2 GREAT REASO SUBSCRIBE NO Every new or renewing subscriber* between now and June 30 gets a FREE copy of the superb SILICON CHIP/JAYCAR Wall Data Chart. THAT’S WORTH $10.95 ALONE! Every new or renewing subscriber* between now and June 30 qualifies for an EXCLUSIVE 10% discount on ANY SILICON CHIP merchandise: books, software, EPROMS & microprocessors, binders, back issues, etc 40  Silicon iliconCChip hip * This offer applies to Australian subscribers only ONS TO OW TO 3 The best reason of all: you’ll actually save money! Not only will you get your copy of SILICON CHIP BEFORE it’s on the news-stands – it’s cheaper getting your copy mailed direct to you – and you’ll never miss an issue! HURRY! TAKE ADVANTAGE OF THIS STRICTLY LIMITED OFFER TODAY! Yes Please! I want SILICON CHIP delivered every month to my letterbox and I want to take advantage of the exclusive subscribers’ offers. Name............................................................................................. PLEASE PRINT Address.......................................................................................... ....................................................................Postcode..................... ❑ New Subscription (month to start....................................) ❑ Renewal (Sub No from wrapper.......................................) I want ❑ One Year <at> $59 ❑ Two Years <at> $112 or ❑ 1Yr with binder <at> $72 ❑ 2 Yr with binders <at> $138 This is a YES! This offer also applies to GIFT SUBSCRIPTIONS: Call SILICON CHIP to place your order for a gift subscription. Here’s how to order: or or Fax this coupon (or a copy) to SILICON CHIP on (02) 9979 6503 – 24 hours a day Post this coupon (or a copy) to SILICON CHIP, PO Box 139, Collaroy, NSW 2097 You can even order by phone with your Bankcard, Mastercard or Visa Card: Call SILICON CHIP on (02) 9979 5644 9am-5pm, Monday to Friday FAX or POST ORDERS: Card No: Expiry Date:_______/_______ Signature:__________________________ (Yes, we do accept cheques or money orders by post!) M March 1998  41 Norbiton Systems PC bus digital I/O kit Norbiton Systems, based in Western Australia, has re­leased a range of PC boards which, when interconnected, provide a complete data acquisition system. The individual PC boards are available as kits or can be purchased assembled and tested for a reasonable additional cost. Review by RICK WALTERS All the PC boards appear of the highest quality, being double-sided with plated-through holes and silk screened over­lays. This type of board is not recommended for beginners to learn to solder on. The currently available boards are the computer interface card (NS_PC101), a LED interface card (NS_LED), a system condi­ t ioning card (NS_16_8), 2 power supply cards (NS_DC_DC and NSDC_DC1) and a 42  Silicon Chip utility card (NS_UTIL1). The computer interface (I/O) card must be plugged into an empty slot on your PC motherboard and jumpers set to assign it a free address. The as­ sembled board is supplied jumpered to 170 Hex but if this address is cur­ rently in use (often by a sound card) then the supplied software allows you to locate a free address. This interface card allows your program (in Basic, Pascal, Assembler or any other) access to 48 lines, pro­ grammable in groups of eight as either inputs or outputs. Forty of these lines are fed via a 50-way ribbon cable to the power supply card. The other eight are brought out to a header on the I/O card. The power supply card produces 5V DC for the rest of the Norbiton system from an external 11-35V DC power supply or a suitable battery and prevents any loading of the computer’s power supply by these additional cards. If ±12V are needed (for the conditioning or utility cards), then an inverter module (NSDC_DC1), which generates these voltages, can be plugged onto the power supply card. The output from the power supply card can be connected to the LED card, again via a 50-way cable which loops the I/O card outputs through the power supply and picks up the power supply voltages. The LEDs on this card monitor the status (high, low) of 40 output lines from the I/O card. The LED card is connected to the utility card, again with a 50-way ca­ ble. The utility card has a 1580-hole prototyping board mounted on it along with a 25-way “D” connector and a stack of jumpers. It has access to any three of the five I/O groups by using these jumpers and can use the internal 5V supply for loads up to 2A or an external supply if higher currents are needed. The conditioning card, believe it or not, is connected to the utility card with a fourth 50-way cable. This type of connec­tion is relatively cheap and simple, the only drawback being the limited current capacity, as already mentioned. This card has 16 opto-isolated in­ puts which can be operated by 12V or 24V equipment. 12 are wired for logic high input, the other four have toggle switches to select active low or active high input. All inputs have LEDs to monitor their status. The card also has eight single-pole changeover relays with a contact current rating of 10A. Again the relay drivers are opto-isolated from the logic and each relay has a LED to show its state. The board’s inputs (16) and outputs (8) are link selectable to any of the 5 groups in the 50-way cable and only use 24 of the 40 lines, leaving 16 free for other functions. What can it do? So much for the introduction. What can it do? This is certainly where the beginner can become unstuck. The documen­ tation is sparse but adequate for an­ yone used to PC interfacing and STE or VME bus equipment but for those (such as schools) who have purchased the system for beginners, the materi­al supplied is inadequate. There needs to be a set of instruc­ tions which take you, step by step, from opening the computer and plug­ ging in the I/O card, through program­ ming the interface (probably in Basic as this is often taught in schools), right through to explaining in much greater detail how the individual ports are addressed. This should be followed with code examples which allow single instruc­ tions to be issued which, for example, will turn one individual LED in a selected group on and off. As I have said previously, it’s all there, it just needs to be much more readily accessible and user friendly. I guess this last statement really sums it up: a great system, well thought out and flexible, but lacking the documenta­tion which makes it a pleasure to use instead of a chore. From our discussions with Norb­ iton we understand that they have arranged to have the documentation upgraded as soon as possible. Some of the pricing is as follows: The interface card kit (NS_PC101kit) is $129, the LED interface card kit (NS_LED-kit) is $99, the system conditioning card kit (NS_16_824K5) is $265 and the utility card kit is $245. These prices include sales tax and there are reductions avail­ able during March and April. Fully assembled versions of all the boards are available. Where to buy it Further information on pricing and availability can be obtained from Norbiton Systems, PO Box 687, WA 6968. Email Norbiton<at>bigpond.com SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. March 1998  43 MAILBAG Internet a boon to business Your correspondent Bob Young (Mailbag, January 1998) be­moans the fact that his tightfisted customers are now using the Internet “free to scour the world for the cheapest source of supply”. I find it ironic that your correspondent rightly criti­cises the heavy government and taxation bur­ den on small business in this country and then goes on to give his solution to the problem – the replacement of one tax with another! High tariffs were OK in the 1950s when Australia’s population doubled to buy all the tariff-protected goods and commodity prices were high. But today when Australia insists on sell­ ing its services and commodities into a free market, then selective tariffs on low volume manufactured items make no sense whatsoever. He has overlooked the only practi­ cal solution to his prob­lem. He must follow his customers onto the Internet and sell worldwide too. He must set up and promote his own website and his R/C products. If that is not enough, then he must assemble his products overseas in more friendly manufac­ turing environments. Please do not tell me that this cannot be done by a single businessman in present-day Australia. I can offer two electronics examples of people who have done it and done it successfully. The first is Don McKenzie at don­ tronics.com. You will have seen his ads for years in the classifieds of the electronics maga­zines. In the last few years his market has moved from being entirely Australia-based to one where today more than 60% of his business is overseas. He relies on his website to do the selling for him. His current classified ads just give his website address and nothing else. Increasingly he just sells electrons; he never sees the physical goods he advertises. He just takes the order from one country, arranges delivery from the supplier in a second country, and takes the credit card payment infor­ mation in a third country, Australia. The second case is my own, kitsrus. com, where I am based in Australia 44  Silicon Chip along with my major designer Frank Crivelli, yet all kit assembly, banking and shipping is done by my three girls in Hong Kong. I have almost no sales in Australia (the major retail­ers have their own in-house kits and do not want a second range). I sell worldwide. Orders come to me by email to my home/office in Melbourne. I pass the orders by email to Hong Kong. Most correspondence to customers is done by me at my lei­sure from our holiday house at Lorne or my home. When I visit Hong Kong it takes me at most two minutes to redirect all my email from my Melbourne server to my Hong Kong server. My Com­ paq Armada laptop contains all my business data and communication programs. The location of my man­ agerial, screen-based activity can be anywhere on Earth where it is convenient for me at any particular moment. You can easily check the detailed activity on our websites by looking at the access statistics. You can do this for yourself at http://dontronics.com/ stats, and http://kitsrus.com/stats No passwords or ‘www’ are needed. Don & I try to offer services to our customers equal to those provided by much larger companies. Conversely, our customers cannot readily guess from our websites whether we are a big or small business. What your correspondent has miss­ ed is that about five years ago the world began a communications revolution. Distance is dying. Country borders are eroding. The cost of voice & data communication whether next door or around the world is fast approaching zero. The convergence of a whole range of technolo­gies is changing the world we live in general and the way busi­ness and government are conduct­ ed in particular. These tech­nolo­gies include high-capacity fibre optics telephone links, digital, interactive and switched TV, digital compression, falling cost of computing, satellites, mobile telephones and the Internet. It has already been shown that young (under 40), affluent and edu­ cated people are the most receptive to these rapidly emerging technolo­gies. For expansion of the ideas men­ tioned above see “The Death of Dis­ tance”, by Frances Cairncross, 1997, Harvard Business School Press. I bought my copy on the Internet from amazon.com using a Mastercard issued by a Hong Kong bank and it was deliv­ered straight to my door in Melbourne by courier. Peter Crowcroft, peter<at>kitsrus.com EMC regulations and big business The letter from H. Nacinovich in the January 1998 issue of SILICON CHIP regarding EMC regulations posed the question whether big manufacturers were likely to be concerned with the costs associated with EMC. At the risk of appearing highly cynical, I would suggest big busi­ ness probably has (as always) had significant input in the framing of these regulations. Obviously larger manufacturers can readily absorb the additional cost burden involved yet they always seem to influence the regulators to the detriment of smaller concerns. You can bet that any aspects of the regulations unacceptable to them have been firmly stamped on whilst those aspects which are likely impediments to small business would be refined and enhanced. Whenever did Joe Blow Small Manufacturers P/L have any real in­ put to government except at election time and then only to be patted on the head with glib reassurances of government’s total dedication to the ideal of small business. Thirty something years of listening and talking to politi­cians regarding the concerns of small business have left me sufficiently disillusioned about serious government interest in us let alone the impact of regulations on the viability of our businesses. No wonder H. Nacinovich has not seen any comment from big business, they are simply unconcerned at another nail in our coffin! The real truth is that governments of all persuasions as well as the executive public service are totally addicted to the concept that big is good and that multinational is even better. If you consider that EMC regu­ lations are a burden, wait for GST which is being openly pushed by big business. Whilst superfi­ cially GST is probably a more equitable system, the cost benefits to big business will be enormous yet small business will encount­er an administrative and cost burden nightmare or have I simply become paranoid? I. Purdie, Pendle Hill South, NSW. Upgrade article was timely I’ve just had to change a mother­ board so Ross Tester’s article entitled “A Heart Transplant For An Aging Computer” in the December issue was timely. Now the reason for the change was that the CMOS battery in the real-time clock (RTC) chip (“Odin” OEC­12C887) failed and the chip is no longer obtainable except at some ridiculous price. There was no sep­ arate battery in the system and no provision to add one externally. It struck me that in the photo of the ASUS board on page 5 of that issue, here was an identical-looking RTC chip down on the bottom edge, also without any sign of a separate battery. I don’t know if this particular board has a socket for one but it exposes a trap for new players. Anyone buying a new or secondhand comput­er or buying a new motherboard should make sure either that there is a CMOS battery external to the RTC chip or there is a socket on the motherboard to take one or, like me, they could end up with an orphan when the battery gives up the ghost. Now I have read somewhere that these batteries are supposed to last 10 years. Well, mine lasted 14 months (just outside the warranty). I also have another older machine with a similar type of plug-in RTCplus-battery chip, only this one is the “Dallas” chip. I’m told that these are somewhat more readily available but in any case are not interchangeable with the Odin. It could be argued that by the time the battery fails it’s time to upgrade the computer or its motherboard but that seems to be a pretty drastic solu­ tion for what is normally a $6 problem and we shouldn’t have to accept it. The second bit of advice, which may seem pretty irrelevant at the time you are all fired up to buy a new computer, is to get memory chip-sets of a size such that whatever your total RAM size is to be, you don’t fill the four available banks. Ross explained it but it needs emphasising. If you fill the available space with the smaller RAM “sticks” at the start it will be slightly cheaper at the time, but when you eventually decide to increase the RAM you will have to throw all those old chips away. Sure, you could try to find a buyer for them, but that will not be easy because by then every­body else will be having the same problem. If you don’t specify the bigger chips when you buy the computer, you may be given the smaller sticks (4Mb or 8Mb) or the smallest size that will fill the four banks. That is because they are the cheapest option for the dealer to supply. He’s unlikely to explain it to you because it’s money in the bank for him further down the track. The trouble is, you will be paying twice over at some further time when you upgrade. A final bit of advice is to ensure that you get a board whose BIOS handles the transition to the year 2000 – and fully. It’s easy to forget these things in the heat of the moment. Both the BIOS and the software must be “compliant” but at least if the BIOS is correct it’s something. P. Dawes, Orange, NSW. Publisher’s Letter – continued from page 2 that we will need to refer back to the article concerned and this can take a lot of time. You may be very famil­iar with the article, having just read it, but if it’s more than a couple months old we will need to take time to refresh our memories and then formulate the answers. Second, please type the letter or use a word processor, if at all possible. We do have trouble with handwritten letters – often, we cannot even decipher people’s names. Finally, please be patient. Remember that even though we may have received it within an instant of you pressing the button to send it to our fax machine, it could take a day or two before we can even read it. In fact, this desire for instant replies is one reason why we have not yet published our email address or set up a Web page – we know it will increase correspondence and we know that readers will be frustrated because they have not re­ceived an instant response. So there you are. I have come clean. I do apologise for not answering some readers during 1997 but eventually reality dawns. If you can help us by being brief and to the point, we will have a much better chance of replying to your queries. Finally, I must make comments about two articles in this month’s issue. The first is the one on floodlighting of build­ings. Now while the article is presented in a straightforward technical fashion, it is a subject that arouses strong feelings in many people and I’m one of them. Simply put, a great deal of floodlighting is extravagant, wasteful and unnecessary. While there are good reasons for lighting up some buildings for some of the time, most of the time it is just a serious waste of energy. If Australia is to make any progress at all on greenhouse gas emissions, this is one issue that should be addressed. Second, I know that many readers enjoy the regular articles by John Hill on Vintage Radio. After exactly 10 years of unbroken contributions, John has decided to retire. We thank John for his great contribution over the years and wish him many years of happy retirement. For those of you who really look forward to reading Vintage Radio in every issue, I am glad to announce that Rodney Champness will take over the Vintage Radio column, starting next month. Leo Simpson March 1998  45 Build this multi-purpose Fast Battery Charger For tools, camcorders, R/C equipment & car batteries Last month, we presented the circuit and operating de­tails for this charger. This month, we conclude with the con­struction details and parts list. Pt.2: By JOHN CLARKE The Multi-Purpose Fast Battery Charger is housed in a plas­tic instru­ ment case measuring 257 x 190 x 85mm. All the circuitry is mounted on one PC board coded 14302981 and measuring 121 x 173mm. Two versions of the TEA1102 battery management IC are being made, a 20-pin dual inline package (DIP) and a 20-pin surface mount package. We have made pro­ vision for the surface mount version of the TEA1102 by means of a small 46  Silicon Chip carrier PC board coded 14302982 and measuring 29 x 16mm. We’ll talk more about this aspect later on. The power transformer (T1) is mounted sideways on the rear metal panel of the case, as shown in the photographs. Note that the inte­ gral ribs and bushes within the case will need to be removed in the area where the transformer mounts. The ribs can be removed with a sharp chisel while the bushes are eas­ ily cut out with a large, sharp drill bit. The main PC board is secured with self-tapping screws into the four bush­ es under the corner mounting holes in the PC board. Remove the other integral bushes under the board with a large drill. The component layout for the main PC board is shown in Fig.1. Before you install any parts on the PC board, it is wise to check it against the pattern of Fig.5. There should not be any shorts or breaks between tracks or any undrilled holes. Fix any defects before proceeding. Then you can begin by installing the PC stakes at the various external wiring connection points on the PC board. Next, install the wire links and resistors and then the diodes and zener diodes. Take care with their orienta­ tion and be sure to put each type in its correct place. As already noted, the TEA1102 (IC1) Fig.1: this component layout shows IC1 as a conventional dual in-line package but it may be supplied as a surface mount package. In that case, you will need to use the carrier PC board at right. may be supplied as a conventional dual in-line package (DIP) which can be soldered directly into the PC board or it may be a surface mount type. If you have the surface-mount type, you will need to mount it on the carrier board. This is coded 14302982 and measures just 29 x 16mm. It is assem­ bled as follows. First, check the pattern for shorts between the tracks and then pre-tin the copper lands where the IC pins will be placed. This done, insert and solder the two 10-way pin headers into the PC board so that the plastic holders are on the opposite side to the copper pattern. Next, place the surface-mount IC in position and, using a fine-tipped soldering iron, apply heat to each pin so that it melts the solder on the PC land. Check that each pin is soldered by measuring between the pin header connection and the IC pin with a mul­ timeter set to read Ohms. Check also that there are no shorts between pins. When the carrier board is complete, March 1998  47 Resistor Colour Codes ❏ No. ❏  1 ❏  3 ❏  1 ❏  3 ❏  1 ❏  1 ❏  4 ❏  2 ❏  2 ❏  1 ❏  1 ❏  1 ❏  2 ❏  1 ❏  1 ❏  4 ❏  2 ❏  1 ❏  1 ❏  1 ❏  1 Value 330kΩ 220kΩ 150kΩ 100kΩ 82kΩ 68kΩ 33kΩ 27kΩ 22kΩ 18kΩ 15kΩ 12kΩ 10kΩ 4.7kΩ 3.3kΩ 2.2kΩ 1kΩ 680Ω 470Ω 68Ω 10Ω Fig.2: the main switching inductor is bifilar wound, with two strands of 1mm enamelled copper wire. it can be inserted into the main PC board and soldered in position. Make sure that the IC is oriented correct­ ly. The remaining ICs can now be installed, taking care to orient them correctly, as shown in Fig.1. The two power transistors and two power diodes are mounted with their metal flanges towards the edge of the 48  Silicon Chip 4-Band Code (1%) orange orange yellow brown red red yellow brown brown green yellow brown brown black yellow brown grey red orange brown blue grey orange brown orange orange orange brown red violet orange brown red red orange brown brown grey orange brown brown green orange brown brown red orange brown brown black orange brown yellow violet red brown orange orange red brown red red red brown brown black red brown blue grey brown brown yellow violet brown brown blue grey black brown brown black black brown PC board. Do not cut their leads short because you will have to bend them to enable the flanges to be mounted on the rear panel for heatsinking; we’ll come to that later. You can install the capacitors next. The electrolytic ca­pacitors must be oriented with the correct polarity ex­ cept for the 3.3µF bipolar type which can go in either way. The five LEDs are installed so that they stand with about 12mm of lead length above the board. Later they will be bent over to protrude through the bezels in the front panel. Be sure that they are oriented correctly. Winding L1 L1, the main switching inductor, is wound on a plastic transformer bobbin which is then soldered into the main board. Fig.2 shows how it is wound. Two lengths of 1mm enamelled copper wire are bifilar wound from one side of the bobbin to the other. You need to strip the enamel from the ends of two lengths of 1mm wire and then solder them to pins on the one side of the transformer bobbin. The actual pins used on each side of 5-Band Code (1%) orange orange black orange brown red red black orange brown brown green black orange brown brown black black orange brown grey red black red brown blue grey black red brown orange orange black red brown red violet black red brown red red black red brown brown grey black red brown brown green black red brown brown red black red brown brown black black red brown yellow violet black brown brown orange orange black brown brown red red black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown blue grey black gold brown brown black black gold brown Capacitor Codes ❏ Value IEC ❏ 0.1µF 100n ❏ 0.0018µF 1.8n ❏ 820pF 820p EIA 104 182 821 the bobbin are not important since the pins on each side are connect­ed together by the PC pattern. Now bifilar wind on 10 turns (ie, both lengths of wire at the same time), with each turn placed neatly on the bobbin Once wound, terminate the wires onto the pins on the opposite side of the for­ mer. Again, the actual pins used are not important and you will need to ensure that the enamel is stripped off the wire ends before soldering. Insert one of the core halves in place and secure it with a clip. Now place the 1mm spacers on the two faces of the inserted core and install the sec­ ond core half in place and secure it with a clip. You now have a finished inductor and it can be soldered into the main board either way around. The large finned heatsink on the rear panel is necessary to keep the output devices (Q1, Q2, D1 & D2) cool. Use cable ties to keep the wiring neat and tidy. Rear panel hardware Now insert the PC board into its correct position in the case and mark the centres for the power transistor and diode mounting holes on the rear panel. Remove the rear panel and drill out these holes plus two holes for the cord­ grip grommet and fuseholder in the position shown on the wiring diagram. Also 4mm holes are required for the transformer mounting and the earth termination plus the bridge rectifier which mounts above D1. Do not forget the holes to mount the thermal switch THS1. Holes for the transistors, diodes and rectifier must be deburred with a larger drill to pre­ vent punch-through of the insulating washers and to ensure a flat contact to the heatsink. Fig.3: the power transistors and power diodes are mounted as shown here. After mounting, use a multimeter to confirm that their metal tabs are indeed isolated from the rear panel. Place the heatsink against the rear panel and mark the hole positions on it for drilling. Note that you must line up the heatsink so that the screws for Q2, D1 and the rectifier pass through the heatsink between the heatsink fins. Drill out and deburr all the holes. Attach the PC board to the case with the supplied self-tapping screws. Ap­ ply a smear of heatsink compound to the flat face of the heatsink and secure each of the transistors and diodes to the rear panel and heatsink with a screw, nut, insulat­ing washer and in­ sulating bush. Fig.3 shows the details. If you use mica washers apply a smear of heatsink compound to the mating surfaces before assembly. The silicone impregnated washers do not require heatsink compound. Check that the metal tabs of the devices are indeed isolated from the case by measur­ing the resistance with a mul­ timeter. Apply a smear of heatsink compound to the face of the rectifier before securing it to the rear panel. It is not necessary to insulate the rectifier case from the rear panel. Fit the AC power cord into its cordgrip grommet and secure it into March 1998  49 Fig.4: this diagram shows all the details of the wiring from the PC board to the front and rear panels. Take care with the mains wiring and shroud all exposed mains terminals with heatshrink tubing. 50  Silicon Chip Fig.5: check your etched PC boards against these full-size artworks before mounting any of the parts. Below: the thermal cutout (THS1) is mounted on the rear panel above Q1, Q2, D1 & D2, along with the bridge rectifier and power transformer. March 1998  51 Parts List 1 PC board, code 14302981, 121 x 173mm 1 PC board, code 14302982, 29 x 16mm (required for SMD version of IC1) 1 front panel label, 244 x 75mm 1 plastic instrument case, 257 x 190 x 85mm 1 aluminium rear panel to suit above case 1 heatsink, 109 x 75 x 33mm (DSE H-3460 or equivalent) 1 18V 6A mains transformer (T1) (DSE M2000 or equivalent) 1 ETD29/16/10 transformer assembly with 3C85 cores (L1) (Philips 2 x 4312 020 37502 cores, 1 x 4322 021 34381 bobbin, 2 x 4322 021 34371 clips) 1 NTC thermistor (DSE R1797) (NTC1) 2 3AG panel mount safety fuse holders (F1,F2) 1 630mA slow blow 3AG fuse 1 7A fast blow 3AG fuse 1 SPST neon-illuminated mains rocker switch (S1) 1 SPDT centre-off toggle switch (S2) 1 DPDT toggle switch (S3) 1 4P3W rotary switch (S4) 1 2P6W rotary switch (S5) 1 80°C thermal cutout (THS1) 1 momentary pushbutton switch with normally open contacts (S6) 1 black 4mm banana panel socket 1 red 4mm banana panel socket 1 black 2mm micro banana panel socket 1 red 2mm micro banana panel socket 1 black 4mm banana plug 1 red 4mm banana plug 1 black 2mm micro banana plug 1 red 2mm micro banana plug 5 M4 screws x 10mm the rear panel hole. Also, secure the fuseholder and transformer with 4mm screws, star washers and nuts. Attach the earth wire (green/yellow stripe) to the solder lug or crimp lug and secure to the rear panel with a screw, star washer and nut. 52  Silicon Chip 6 M4 nuts and star washers 4 M3 screws x 10mm and nuts 1 M3 screw x 25mm and nut 4 self-tapping screws to mount PC board 4 insulating bushes for TO-220 and TO-218 packages 2 TO-218 insulating washers 2 TO-220 insulating washers 25 PC stakes 1 7.5A mains cord with 3-pin plug 1 mains cordgrip grommet 2 1mm spacers, 10 x 5mm, to gap L1 1 600mm length of red hookup wire 1 600mm length of green hookup wire 1 600mm length of blue hookup wire 1 600mm length of yellow hookup wire 1 600mm length of black hookup wire 1 300mm length of red heavy duty hookup wire 1 300mm length of black heavy duty hookup wire 1 150mm length of 0.8mm tinned copper wire 1 2m length of 1mm enamelled copper wire 1 55mm length of 15mm diameter heatshrink tubing 1 50mm length of 25mm diameter heatshrink tubing 7 small cable ties 1 solder lug for earth terminal 2 10-way single in-line pin headers (if IC1 is surface mount) 5 5mm LED bezels Semiconductors 1 TEA1102 or TEA1102T fast charge controller (IC1) 1 4093 quad Schmitt NAND gate (IC2) 1 4020 binary divider (IC3) Front panel details The front panel can now be drilled out to accept the switches, terminals, fuseholder and the LED bezels. The front panel artwork can be used as a template for drilling. Attach the label in place after drilling and cut out the 1 TIP147 PNP power Darlington transistor (Q1) 1 TIP142 NPN power Darlington transistor (Q2) 2 BC337 NPN transistors (Q3,Q5) 1 BC548 NPN transistor (Q4) 2 MUR1550 fast recovery diodes (D1,D2) 1 1N4004 1A diode (D3) 2 1N914, 1N4148 diodes (D4,D5) 1 35A 400V bridge rectifier (BR1) 1 12V 1W zener diode (ZD1) 1 11V 400mW zener diode (ZD2) 5 5mm red LEDs (LED1-LED5) Capacitors 1 1000µF 25VW PC electrolytic 1 100µF 25VW PC electrolytic 1 100µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 1 10µF 100VW MKT polyester (Philips 373 series) 1 3.3µF bipolar electrolytic 1 1µF 16VW PC electrolytic 1 0.1µF MKT polyester 1 0.0018µF MKT polyester 1 820pF MKT polyester or ceramic Resistors (0.25W 1%) 1 330kΩ 1 12kΩ 3 220kΩ 2 10kΩ 1 150kΩ 1 4.7kΩ 3 100kΩ 1 3.3kΩ 1 82kΩ 2 2.2kΩ 0.5W 1 68kΩ 2 2.2kΩ 4 33kΩ 2 1kΩ 1W 2 27kΩ 1 680Ω 2 22kΩ 1 68Ω 1 18kΩ 1 10Ω 1 15kΩ 2 0.1Ω 5W Miscellaneous Heatsink compound, solder, machine screws and nuts, etc. holes with a sharp hobby knife. The two rotary switches require their shafts to be cut down to about 12mm long, with a hacksaw. Their shaft rotation should be adjusted for only five positions for S5 and two positions for S4. This is done by (+) + + + + + Fig.6: this full-size artwork can be used as a drilling template for the front panel. FAST + + PROTECT REFRESH 6 + OUTPUT (-) THERMISTOR NO BATTERY 100% NICAD & NIMH + + + 12 7.2 9.6 (NICAD & NIMH ONLY) + + 2Ah 1.2Ah 14.4 + SLA (6V&12V) + 30 15 4Ah 60 Battery Capacity Mins TIMER BATTERY VOLTAGE REFRESH MULTI-PURPOSE FAST BATTERY CHARGER Testing Check your work carefully before doing any voltage tests. Then apply power and measure the voltage between the TP GND on the PC board and pin 12 on IC1. You should measure about +12V DC. Check that pin 14 and pin 16 of IC2 and IC3 are at +12V. Pins 1 & 16 should be at + 4.25V. Switch S3 to the NiCd & NiMH position and check that the “no battery” LED lights. Measure the output voltage on the plus and minus termi­ nals. It should measure about 10V on the 6V battery selection. When connecting the thermistor, check that the voltage at pin 8 of IC1 is at about +2V when the temperature is around 25°C. If you heat up the thermistor slightly by holding your finger and thumb tightly around its body, the voltage should drop. If the temperature rises, then it is either a very hot day and your body temperature is lower than that of the air or you have the wrong type of thermistor. When charging a battery, make sure you select the correct battery type and voltage on the front panel switches. Also set the timer for the closest timeout period for the particular battery capacity. If you are charging a lead-acid battery, the timeout set­ting does not matter. You may wish to check the charge current which should be made with an RMS meter or a digital oscil­ loscope which reads RMS. If a standard multimeter is used, you can expect the read­ing across the two 0.1Ω resistors in parallel to be about 200mV. An RMS reading should show about 300mV which is equivalent to 6A. To vary the current slightly, change the value of the 3.3kΩ resistor at the IB input of IC1; larger for less current, smaller for more. Note that the heatsink and Q1 will run hot on fast charge and so the charger should be provided with sufficient venti­ lation to prevent the thermal cutout operating. The TP CELL and TP GND PC stakes can be monitored to measure the cell voltage of the connected battery. Note: charging current is best determined by checking the charging time of a discharged battery. If it's too long, the current can be increased slightly by using a larger value resistor at pin 2 of IC1. A 3.9kΩ resistor will increase it by about 10%. If the charge time is too short, the battery may be suffering from memory effect. Try a few discharge & charge cycles. The timeout period can be increased to suit larger batteries by increasing the value of the 820pF oscillator capacitor. SC + FUSE (7.5A) + POWER 6V & 12V LEAD ACID NIMH, NICAD & SLA removing the locking collar from beneath the star washer and nut and rotating the switch fully anticlockwise. Now re-insert the locking washer into position five for S5 and position two for S4. Now assemble all components onto the front panel. Begin the wiring as shown on the diagram of Fig.4, using coloured hookup wire. The mains wiring must be done using mains rated wire. Be sure to sheath the terminals for the fuse and power switch with heatsh­rink tubing. Use heavy duty wir­ ing for the connections between the rectifier and PC board, the thermal switch and to the output terminals and fuse F2. Tidy up the wiring with cable ties and insert the front panel into the case with the LEDs protruding through their be­zels. You will need to make up some leads with banana plugs and alligator clips to connect from the output terminals to a bat­tery. Also, the thermistor connections require a lead with miniature banana plugs. We sheathed the thermistor wiring in heatshrink tubing. March 1998  53 Design by BARRY GRIEGER Part 3: Power Station & Command Station Wiring Last month we covered the description of the Command Station which is really the encoder portion of the system. This month we describe the Power Station which takes the signal from the Command Station and feeds it to the track. Design by BARRY GREIGER I N ESSENCE, the Command Sta- tion is just a big power supply and it is modulated with the block signals from the Command Station (encoder). Fig.1 shows the circuit. It uses a 30V centre-tapped trans­former to drive a 10A (or 35A) bridge rectifier BR1. This feeds an 8000µF 75VW chassis mount electrolytic capacitor (C1). By the way, we specified the capacitor voltage at 80V, not because the voltage is high but because the capacitor needs to be physically large in order to give it an Run your model railway with Command 54  Silicon Chip Fig.1: the power supply is essentially an adjustable 3-terminal regulator which is modulated by the 5V signal from the encoder board. adequate ripple current rating. Ripple current is the AC current which flows through the capacitor as a result of it filtering the raw (un­ smoothed) DC down to smooth DC. As a rule of thumb, the ripple current in the filter capacitors of a DC supply such as this is roughly equal to the DC current drain. So if we require 5A DC we need filter capacitors with a total ripple current rating of at least 5A. The transformer is rated at 100VA and so it should easily be able to de­ liver up to 5A DC to the track. The DC voltage across C1 is about 21-23V DC, depending on the actual value of the 240VAC mains supply and the loading caused by the various locomotives on the track. Now, to get back on track with this article (pun intended), the smoothed DC from capacitor C1 is fed to an LM338K adjustable 3-terminal regu­ We used this large plastic instrument case to accom­modate both the Command Station (encoder) and Power Station components. The front panel carries the various indicator LEDs. Control March 1998  55 Fig.2: component layout for the Power Station PC board. Take care with parts orientation. lator. This is controlled by a circuit consisting of two NPN transistors (Q4 & Q5) and the associated resistors. The two transistors act to modulate the output of the ad­justable regulator, switching it between 11V DC and 16.9V DC, with the 5.9V difference Below: a large finned heatsink is required for the LM338K adjustable regulator. Note that this heatsink must be fully isolated from the heatsink using an insulating washer and TO-3 mounting kit. 56  Silicon Chip Fig.3: actual size artwork for the Power Station PC board. being the serial data stream from the Command Station (encoder). Q4 & Q5 work in the following way: When the signal from the Command Station is low, transistor Q4 is off and therefore Q5 is turned fully on, by dint of the 10kΩ resistor R3. With Q5 fully on, the voltage drop between its collector and emitter will be around 100mV or less and so the voltage de­ livered by the LM338K will be largely determined by trimpot VR1 and the resistor network attached to the ADJ termi­nal. During the setup procedure, VR1 is set so that the output from REG1 is 11V. When the signal from the Command Station is high, Q4 is turned on and Q5 is turned off. With Q5 turned off, trimpot VR1 is effectively out of cir­ cuit, since no current flows through. In this condition, REG1’s output is close to 16.9V, as set by the ratio of resistors R5 & R6. The average voltage from REG1 is effectively about half way between 11V and 16.9V and therefore lies around 14V DC. The light emitting diode LED7 func­ Fig.4: this diagram shows the wiring details for the Command Station and Power Station circuitry. Take care with the mains wiring and sleeve all exposed mains connections with heatshrink tubing. tions as a track power indicator while the 1kΩ 1W resistor R7 is there merely to ensure a minimum load current on REG1. The 30V zener diode (ZD1) across the output is to help prevent commutator hash from locomotive motors from upsetting the regulator in any way. Construction In presenting this project we are conscious that each model railway enthusiast will have his (or her) pre­ ferred way of in­stalling the system within the layout. If it is a small lay­ out, only one power station is likely to be required. On the other hand, if it is a large layout, more power stations March 1998  57 This inside view shows the almost completed prototype, without the wiring from the Command Station module (lower right) to the various hand controllers (see Fig.4 for details). will be re­quired. The Command Sta­ tion presented last month has outputs to drive four power stations. Each power station would be con­ nected to a portion of the layout and each track section would be isolated from the others by insulators in the tracks. When a locomotive crosses between sections, the relevant power station outputs would be connected together via the locomotive’s wheels and chassis. However, this would not represent a fault condition since each power station would put out the same track voltage. All of this amounts to a restatement of the operating con­cepts outlined in the first article in this series, in the Janu­ ary 1998 issue. While all that may be clear and obvious, it does present a problem of presentation in the magazine. Do we present a version which would be applicable to a small layout or a large layout? Our answer is 58  Silicon Chip to present it in a way suited to a small layout; ie, with the Command Station driving one Power Station. From this we then proceed to the logical decision to in­stall the Power Station and Command Station in one case, as our photos show. This leads to a much more professional approach than is used by many model railway hobbyists. In particular, many mod­ ellers are very casual about power supply construction and wiring. They often have a largish power transformer and the rest of the circuitry laid out on a piece of timber or sheet metal. Often there is no cover, with the whole assembly sitting on the floor underneath the layout. You don’t need to be a rocket scientist to work out that this is an accident waiting to happen but it is quite common­place. So rather than present this project with the Command Sta­tion and Power Station is separate cases, we are pre­ senting them both in the one large case. This is neat, safe and cheaper in the long run. We selected a large plastic instru­ ment case from Altronics (Cat H-0490). It measures 355mm wide, 122mm high and 250mm deep. It has plenty of room inside for all the power supply (Power Station) components and the encoder PC board (Command Station). Actually, there’s probably enough room in this case for two Power Sta­ tions, if you wanted to do it that way. The front panel is bare except for seven LEDs. Four of these come from the encoder board and indicate that the main clock is working (see circuit description last month). The other three LEDs are the track power indicator (LED7) referred to above and indicators for the +12V and +5V rails. To be frank, only the track power indicator (LED7) is really necessary but a few LEDs do add interest, don’t they? On the aluminium back panel, there is an IEC mains power socket, Fig.5: the mounting details for the LM338 3-terminal regulator. the on/off switch, the finned heat­ sink for the 3-terminal regulator and a pair of binding post terminals for connections to the track layout. There are also two access holes for cables to the throttle panel and to other Power Stations, if they are required. Inside the case there is a steel base­ plate which mounts the power trans­ former, the bridge rectifier and other hardware and it also makes it easy to properly earth these components. The small components of the power supply shown in Fig.1 are mounted on a PC board which measures 65 x 48mm (code 09103981). It is shown in Fig.2. You can see that we have made provision for an onboard filter capac­ itor but this is not used in the version we are presenting here. The capacitor would only be used if a smaller ver­ sion of the circuit without the large 8000µF capacitor was envisaged. So in effect, the PC board layout of Fig.2 shows only two transistors (Q4 & Q5), the trimpot VR1 and a few resistors. It will only take a few minutes to solder all the necessary compon­ents and the PC pins or stakes onto the board. When the board is assembled, you will need to start work on the case. You will need to drill seven holes in the front panel to accommodate the LED bezels. On the rear panel, there will be cutouts for the on/off rocker switch and the fused IEC power socket and various holes for the heatsink, binding post termi­nals, earth solder lug and so on. The steel baseplate will need to be drilled to take the power transformer, bridge rectifier, main filter capacitor (8000µF) and the two PC boards. The mounting positions of these compo­ nents are not critical and you can work out where you want to put them by reference to the photos. You will also need a hole in each corner of the baseplate for a screw into an integral pillar on the case bottom section. Fig.4 shows how all the connec­ tions are made between the two PC boards and the rest of the power supply components. We have specified a fused IEC power socket which makes the wiring easier to and safer, into the bargain. All the mains wiring should be run in 250VAC-rated hookup wire and all exposed connections should be sheathed in heatshrink tubing. The Earth wire from the IEC socket should be connected to an adjacent solder lug, as shown in Fig.4. All the connections to the Com­ mand Station (encoder) board and the Power Station board can be run in light-duty hookup wire. Do not make the hookup between the encoder and signal input to the Power Station board until you have made the first voltage check. Note that we have in­ cluded a series 56Ω 5W wirewound resistor in the 23V power connection to the encoder board. This reduces the power dissipation in the on-board reg­ ulators, without otherwise affecting the performance. When all the wiring is complete, check your work carefully and apply power. You should then be able to measure about 23V DC across the main filter capacitor C1. Check the outputs of the 12V and 5V regulators on the encoder board. Next, set trimpot VR1 on the Com­ mand Station board so that the output of REG1 is 11V. Then connect the signal input of the Command Station board to the +5V rail on the encoder board. The output of REG1 should now be close to +16.2V. Disconnect the +5V rail from the signal input and connect it instead to the S1 output on the encoder board connector strip. You are now ready to make up handheld throttles. We’ll discuss that next month. By the way, some readers have expressed concern about the ZN409CE encoder ICs. These will be available soon from Jaycar Electronics SC (Cat ZK-8827) at $29.95 each. Parts List For Power Station 1 instrument case, 355mm x 250mm x 122mm (Altronics H-0490) 1 steel baseplate (Altronics H-0492) 1 aluminium back panel to suit case 1 250VAC rocker switch (DSE Cat P-7700) 1 IEC chassis-mount socket with fuse holder (Altronics P-8324) 1 IEC mains cord (Altronics P 8410) 1 20mm 500mA fuse to suit IEC socket 1 100VA 15V-0-15V power transformer (Altronics M-2170) 1 8000µF 75VW chassis mount electrolytic 1 single-sided finned heatsink, 110mm x 33mm x 72mm (Altronics H 0560) 1 TO-3 insulating kit (Altronics H 7200) 1 red binding post 1 black binding post 1 16-pin DIL IDC line plug 1 1m length 16-way IDC ribbon cable 1 grommet to fit 12.7mm mounting hole 1 PC board, 65 x 48mm (09103981) 7 panel mount 5mm LED bezels 6 PC stakes 3 solder lugs 6 M3 screws 10mm long 11 M3 screws 15mm long 17 M3 nuts 2 M4 screws 10mm long 1 M4 screw 20mm long 1 1kΩ horizontal mount cermet trimpot Semiconductors 1 bridge rectifier 400V, 10 or 35A, (BR1) 1 LM338K adjustable positive regulator (REG1) 1 30V 5W zener diode (ZD1) 2 PN100 NPN transistors (Q4,Q5) 1 5mm red LED (LED7) Resistors (1% or 5%, 0.25W) 2 10kΩ 1 1kΩ 1 2.2kΩ 1 820Ω 1 1.5kΩ 1 120Ω 1 1kΩ 1W 1 56Ω 5W wirewound March 1998  59 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. RF noise generator This low-cost circuit converts a square wave input signal to wideband noise. It does this by shaping the in­ put waveform using an RC network to accentuate the high frequency harmonics. A feature of the circuit is a relatively flat (within 2dB) output noise spectrum in the band from 150kHz to 30MHz, which is one of the bands specified for EMC compliance testing by the current Austra­lian/New Zealand standards. In fact, the effective noise spec­ trum extends well outside this range, which may make this generator suitable for a number of applications such as tuned circuit alignment, fil­ ter testing and radio receiver input noise figure measurements. Another possible application is for calibration of a quasi-peak detector for EMI meas­ urements such as that published in “Circuit Notebook” in the February 1998 issue of SILICON CHIP. The input waveform is squared up by IC1a, a 74LS14 fast low-power Schottky Schmitt trigger to ensure fast leading and trailing edges. Q1 boosts the output current drive capability of IC1, producing a very fast positive-go­ ing leading edge in the waveform at its collector. This is applied to the inputs of transistors Q2-Q5 (connect­ ed in parallel) which further boost the output current level, featured by a very fast (nega­tive going) leading edge waveform. An RC network at the combined output of Q2-Q5 shapes the output waveform, giving very narrow nega­ tive going spikes, char­acterised by a uniform spectrum well into the tens of Megahertz. Although both positive and negative spikes (corresponding to the leading and trailing edges of the input waveform) are theoreti­ cally generated at the output, only the negative spikes are of significant magnitude. The way in which the pulse shaping is achieved may be seen by 60  Silicon Chip The circuit has a relatively flat (within 2dB) output noise spectrum in the band from 150kHz to 30MHz, which is one of the bands specified for EMC compliance testing by the current Austra­lian/New Zealand standards. In fact, the effective noise spectrum extends well outside this range, making the circuit suitable for a number of applications such as tuned circuit alignment, filter testing and radio receiver input noise figure measurements considering the output transistors as switches and by assuming that the time-constant of the RC output circuit is much less than the time between pulses. Assume initially that Q2-Q5 are off and that the 22pF capacitors are charged to maximum voltage by the 100kΩ collector resistors. In this off state, the output voltage is zero due to the low resistance path at the output to ground. Next, a positive voltage applied to the inputs of Q2-Q5 causes these transistors to switch on very rapidly, forcing the output to a negative val­ ue, due to the initial charge on these capacitors. However, the capacitors rapidly discharge via the output resistance, resulting in a very brief pulse at the output. Turning off transistors Q2-Q5 al­ lows capacitors C3-C6 to charge again, in readiness for the next cycle. The long time-constant for this charging process suppresses the for­ mation of significant positive spikes at the output. This is significant only in that it affects the pulse repetition rate, which might have to be set to a spec­ ified value for cali­bration purposes. In order to work properly, this cir­ cuit needs to be driven by a square wave pulse generator with a 50Ω out­ put impedance. A suitable circuit was featured in the “Circuit Notebook” pages of the November 1997 issue. The input pulse rate may typically be in the range 1Hz to 1kHz. H. Nacinovich, Gulgong, NSW. ($50) 240VAC-powered strobe lamp This mains-powered strobe lamp uses readily available com­ponents but will need to be installed on a carefully designed PC board. It is not a project for inexperienced constructors. There are two sections to the power supply: a high voltage section and a low DC voltage section which is tied to half mains potential. The high voltage section involves direct connec­tion of the 240VAC mains supply to bridge rectifier BR2, diode D1 and a 22µF 450VW filter capacitor to produce about 340V DC. This is used to charge a trigger circuit consisting of a .022µF capacitor and a C122D SCR. The storage capacitor across the xenon flash tube is also charged, via the two 330Ω 10W resistors in parallel. These must be mounted clear of the PC board as they become quite warm when the flash rate is high. The low voltage section of the power supply uses a 9V transformer, bridge rectifier (BR1) and a 100µF 16VW ca­ pacitor to derive 14V DC (approx.) to run the 555 timer. This is connected as a free-running multivibrator which os­ cillates over a wide frequency range. Its square wave output from pin 3 is cou­ pled via a 0.47µF capacitor to the gate of the SCR. Each time a positive-going signal arrives at its gate it turns on to discharge the 0.22µF capacitor via the trigger transformer, T2. Cheap ammeter using LEDs This is a low-cost alternative to the LM3914 bargraph driver IC. The circuit is intrinsically an amp meter needing a burden voltage of 2-3V for proper operation. Placing a resistor in series with the circuit This produces around 6kV to fire the xenon tube and this discharges the 16µF 450VW flash capacitor. The key parts are available from Dick Smith Electron­ ics stores: flash tube (Cat P-8164), trig­ ger transformer (Cat M-0104) and flash capacitors (Cat R-2857; two required). The flash tubes are also available from allows the unit to function as a voltmeter with a “suppressed zero” of about 2V. With the components shown, the circuit functions as an amme­ ter with a full-scale deflection of 100mA. The overload LED comes on at currents of over 100mA. The temperature coefficient of Altronics and Jaycar. WARNING: all of the circuitry is at lethal voltage levels and is capable of supplying a lot of current. Construction should only be attempted by those experienced with high voltage work. S. Williamson, Hamilton, NZ. ($45) the transistors’ Vbe (0.3% per °C) would need to be compensated if high accuracy was necessary. The cir­ cuit was applied successfully as a battery voltage monitor with a resistor and a zener in series the positive lead. G. LaRooy, Christchurch, NZ. ($30) March 1998  61 Handsome is as handsome does. The 500W amplifier is a big brute but is very-well finished throughout. Feedback on the 500W power amplifier Reader reaction to the 500W amplifier featured in the August, September & October 1997 issues have been very enthusias­tic and a good number have now been successfully built. But it is only recently that Dick Smith Electronics have released their version of the kit and we were interested to have a good look at it. By LEO SIMPSON & BOB FLYNN It’s one thing for us to labour to produce a complex design for publi­ cation and often quite another to see the versions built by readers from kitsets. Sometimes they’re not what we expect and sometimes they are very good. 62  Silicon Chip So we were very interested to fi­ nally see the Dick Smith Electronics kit version of the 500W amplifier, as built by one of their staff members. In brief, while the kit has been produced to a very high standard, it had not been assembled to get the very best performance of which it was capable. We thought we might pass on what we discovered. The external appearance of the kit­ set amplifier is quite professional and pleasing to the eye. All metalwork, except the front panel, has a black, powder-coat finish. The front panel is finished a wet sprayed charcoal and both front are rear panel legends are silk screened in white paint which is very easy to read, even in subdued light. All the cabinet panels are made of steel. The base plate is 1.5mm thick. The front sub-panel, back, sides and top are 1mm plate and the front panel is 2.5mm material. The turned over edges of the vertical panels are fitted with 4mm captive nuts and the top and bottom panels have matching 4mm clearance holes for the 4mm round head assembly screws. The panel holes and nuts are in good alignment, ensuring easy assembly. The complete amplifier is very rigid. Lifting at any corner does not flex the case. Five large rubber feet are fitted to the case to provide good support for what is a heavy unit. Removing the case top revealed a well constructed amplifier with good quality components throughout. Both PC boards have an epoxy substrate and the copper tracks are tinned. The large toroidal transformer is made in Australia by Harbuch Electronics Pty Ltd. The chance of accidental contact with the power supply electrolytics has been eliminated by the provision of a screen of Elephantide insulating material. Instead of an XLR socket, this am­ plifier had an insulated gold-plated RCA socket for the signal input but apart from that all the componentry is pretty much as we specified. Naturally, we were anxious to put it to the test and while we did not expect it to be below par, it was good to find that it equalled the power output of our prototype on both 8Ω and 4Ω loads. Nor did it become too hot. We understand that Dick Smith Electronics also subjected it to full power testing for long periods with­ out any significant problems showing up. There was some evidence of over­ heating but we will come to that later. Where the performance was below par was with respect to noise and distortion. For example, while our prototype gave a signal-to-noise ratio of 117dB unweighted, the DSE ver­ sion was only -100dB. “Only -100dB!” you might say but while that’s pretty respectable it is not as good as it might have been. Similarly, the distortion was not as low as it should have been. Wiring layout is important There are several possible reasons for these differences. First, the power transformer orientation probably was not quite optimum to obtain lowest possible noise. While toroidal trans­ formers do have low hum radiation compared to conventional E-I trans­ formers, their secondary winding ter­ minations are still responsible for the radiation of hum and rectifier buzz. Inevitably there will be some dif­ ferences in this regard between our prototype transformer and the pro­ duction transformers finally used in the Dick Smith Electronics version. So it is difficult for us to nominate the precise orientation. Anyhow, rotating the transformer for minimum hum radiation can give a reduction of several dB in noise. To find the best orientation for the trans­ former, you need an oscilloscope and better still, a sensitive AC millivolt­ meter or as we have, a distortion measurement test set. If you have a quiet location and very keen hearing, it is also possible to do it by ear. Doing the adjustment is not easy be­ cause you need the amplifier powered up and the transformer bolt loosened off so you can rotate it while watching the rectifier buzz on the oscillo­scope. The transformer leads are very stiff and they make it hard to obtain the optimum position. At the same time you must be ex­tremely careful not to come into contact with any high voltage yourself of cause any shorts. In other words, you need to do it very carefully. The pragmatic approach Putting ourselves in the shoes of a typical hobbyist con­structing this amplifier, we would not be inclined to worry about getting the absolute minimum noise out of the amplifier unless rectifier buzz was audible in the loudspeakers. As we said above, -100dB is pretty respectable. Second, and much more important to obtaining minimum dis­tortion and noise, the power supply leads to the PC board were not run in the same way as in our prototype. They looked neat and tidy but they were not right. On page 59 of the September 1997 issue we were quite spe­cific in stat­ ing that “it is important to follow the wiring details of Fig.5 quite closely” and we went on to give details of the transformer wiring. Well, perhaps we should have been even more specific and should have stated that the sup­ ply wiring layout should be exactly as shown in the photos. Why? Because the orientation of the supply leads and output wiring does have a major effect on the harmonic distortion. What happens is that the heavy cur­ rents in the supply leads and output wiring have an associated magnetic field and this is radiated into the early stages of the amplifier. This leads to higher harmonic distortion. In our prototype, the power supply LOUDSPEAKER SALE Limited stocks Prices include sales tax Australian Audio Consultants PO Box 11 Stockport SA 5410 Phone or Fax 08 85 282 201 Vifa D25AG-35-06 Vifa D19SD-05-08 Vifa D26SG-05-06 SEAS ExcelT25-001 Vifa M11WG-09-08 Vifa P13WH-00-08 Vifa P17WJ-00-08 Vifa P17SJ-00-08 Vifa M18WO-08-08 Vifa M18WN-19-04 Vifa M22WR-09-08 Vifa M22WR-19-04 Vifa M22WR-29-04 DVC Vifa M26WR-09-08 Vifa M26WR-19-04 Vifa M26WR-29-04 DVC Dynaudio 24W100 Scanspeak D3806/8200 Dynaudio 20W75 Dynaudio 15W75 Call for full specs. $69.00 $45.00 $49.00 $34.00 $62.00 $49.00 $194.00 $179.00 $99.00 $79.00 $99.00 $75.00 $99.00 $75.00 $109.00 $75.00 $145.00 $90.00 $149.00 $90.00 $195.00 $110.00 $195.00 $120.00 $210.00 $125.00 $229.00 $135.00 $229.00 $150.00 $249.00 $159.00 $399.00 $199.00 $181.00 $90.00 $296.00 $170.00 $257.00 $140.00 leads were run close to the bottom plate because this minimises harmon­ ic radiation. But on the Dick Smith Electronics amplifier the same leads are run about 50mm above the metal­ work and make a right-angled down turn to the PC pins. Re-routing those wires so that they can lie flat on the chassis will have a very worthwhile effect on the harmonic distortion. Some readers may have wondered why we go to the trouble of provid­ ing large colour photographs of our prototypes. It is not just to show off the project or to use up more space. We do it so that constructors can see precisely what we have done. In most cases, they should try to duplicate wiring and other details as closely as possible, unless they have the skills and measurement equipment to check the performance of the finished project. This applies particularly to audio equipment where wiring layout is extremely important. Even the best audio circuit will be below par if the wiring layout is not optimised. Mind you, there is a down side to having large clear photos of projects in the magazines and that is that it lets March 1998  63 needs to be found. Winding the coil with 1.25mm diam­ eter enamelled copper wire instead of the 1mm diameter wire listed in the parts list will also reduce the coil dissipation. Note: while we used and spec­ified a Philips 0.15µF, 275VAC capacitor at the output of the amplifier, this device is not rated for the continuous applica­ tion of the high­ er audio frequen­ cies at full power. A better choice of device for this position is a Wima MKC10 0.15µF 630VDC poly­ carbonate or if avail­ able a Philips MKP378 or MKP379 0.15µF 630VDC polypropylene capacitor. Alternatively, you could consider the Wima MP3-X2 range. These are metallised paper 250VAC or 275VAC RF interference suppressors for class X2 service. DC offset error We also noted that a 30Ω resistor was shunted across the emitter resistor of Q2, one of the input differential pair tran­ sistors. This had apparently been done in order to get the output offset voltage down to an acceptable level and should not have been necessary and indicated that one of the devices must be leaky or faulty in some other way. We pulled the pair out and meas­ ured them. One was made by National Semiconductor and had a beta of about 100 while the other was unbranded and give a beta reading of over 1000 and was probably leaky as well. No wonder the DC offset could not be adjusted to zero! We replaced the input pair with Mo­ torola (again!) devices and the shunt resistor was removed. The output offset voltage was then easily set to zero with VR1’s wiper only slightly off-centre. That is how it should be. All told though, we were very grat­ ified to see this ampli­fier. It is well presented and anyone who built it would be pleased with its perfor­ mance and finish. The complete kit is very good value at $799 (Cat K-5582) and is available from all Dick Smith SC Electronics stores. The interior of the assembled 500W amplifier from Dick Smith Electronics. While all the componentry was the best quali­ty, the wiring itself did not duplicate the exact layout shown in the photos of our prototype. keen-eyed readers sometimes see that we have made a mistake. Oh well . . . of the mounting; a smear of heatsink compound is all that is required. Voltage gain stage Heat buildup There is another factor which can be significant in the distortion perfor­ mance of an amplifier such as this and this concerns the driver and output transistors. The output and driver transistors can only be obtained from Motorola so there is no problem with substitutions – there aren’t any that we know of. However, we specified MJE340/350 transistors in the voltage gain stage and in our experience, none are as good as those made by Motorola; they may be rated the same but their distor­ tion is worse. For the record, we did not specify Motorola MJE340/350s in the parts list but perhaps we should have. There was one other point concern­ ing the MJE340/350s in the review amplifier. They were mounted on their heatsinks with interposing mica wash­ ers. These insulators are not necessary and only add to the thermal resistance One of the tests Dick Smith Elec­ tronics performed on their amplifier was to run it at more than 500W out­ put into a 4Ω load for a full working day. This is a severe test of the output coupling network but does not run the output transistors at their maximum dissipation. Maximum power dissipa­ tion actually occurs at around 40% of power output. During the full-power test, the for­ mer of the output choke (L1) melted and the three 18Ω 1W resistors also overheated. By any normal standard, a full power test for 8 hours is a long way from typical operating conditions. During extensive testing of our prototype, we had no prob­lems with individual components overheating. If the amplifier is intended to be run continuously at full power or at very high levels with program material of a small dynamic range then a coil former with a higher melting point 64  Silicon Chip Silicon Chip Bookshop Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1997 (4th edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 383 pages, in hard cover at $55.00. Guide to TV & Video Technology By Eugene Trundle. First pub­lished 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $75.00. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $55.00. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $69.00. Power Electronics Handbook Components, Circuits & Applica­tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Surface Mount Technology By Rudolph Strauss. First pub­lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Radio Frequency Transistors Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $95.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First published 1989. 6th edition. This just has to be the best refer­ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semi­-custom electronics & data communications. 63 chapters, soft cover at $125.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order  ❏ Bankcard  ❏ Visa Card  ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Prices valid until 31st March, 1998 tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $55.00. Understanding Telephone Electronics By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. This is a very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $49.95. Video Scrambling & Descrambling For Satellite & Cable TV By Rudolf F. Graf & William Sheets. First pub­lished 1987. This is an easy-to-understand book for those who want to scramble and unscramble video signals for their own use or just want to learn about the techniques involved. It begins with the basic techniques, then details the theory of video encryption and decryption. It also provides schematics and details for several encoder and decoder projects, has a chapter of relevant semiconductor data sheets, covers three relevant US patents on the subject of scrambling and concludes with a chapter of technical data. 246 pages, in soft cover at $50.00. ✓ Title o o o o o o o o o o Price Guide to Satellite TV $55.00 Servicing Personal Computers $90.00 Video Scrambling & Descrambling $50.00 The Ar t Of Linear Electronics $70.00 Digital Audio & Compact Disc Technology $90.00 Radio Frequency Transistors $95.00 Guide to TV & Video Technology $55.00 Electronic Engineer's Reference Book $160.00 Audio Electronics $75.00 Understanding Telephone Electronics $55.00 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ add $10.00 per book; elsewhere add $15 per book. TOTAL $A March 1998  65 A liquid crystal display driven from a PC printer port Last month we published a demo board which let you manu­ally feed text into a one-line alphanumeric display by manipulat­ing switches. This month we take the same one-line display and hook it to the parallel port of a PC to produce moving messag­es. By RICK WALTERS 66  Silicon Chip Fig.1: horribly complicated, innit? The display requires 8 bits of data, a register select line, a strobe line and a 5V supply. Fig.2: the component overlay for the PC board. Parts List 1 PC board, code 04104981, 81 x 58mm 1 Liquid Crystal Display with HD44780 controller 1 25-way “D” male PC mount connector 1 20kΩ PC trimpot 1 100µF 25VW PC electrolytic capacitor 1 0.1µF MKT polyester capacitor 1 15-pin “D” male connector (for +5V from games port) Fig.3: actual size artwork for the PC board. D ID YOU DECIDE to have a go at the demo board last month or did you feel that all those switches were just not worth the has­ sle? Well, some of us at SILICON CHIP are quite lazy too and they (no names, no pack drill) thought that this sort of drudgery is the sort of task that com­ puters are ideal for. So the boss told me, “Some readers won’t be bothered with all that. You’d better do a version which can be driven from the parallel port of a PC”. Naturally I saluted and said “It will be done”. And here it is. So if you want all the hard work to be done for you by a computer so that you can display moving messages or create, save and display your own symbols, get stuck into this extremely simple project. It uses the same one-line 16-char­ acter Liquid Crystal Dis­play (LCD) as previously with an HD44780 control­ ler. This is mounted on a small PC board with a 25-way male D connector to mate with a standard 25-way cable from the parallel port. A trimpot and a couple of capacitors complete the assembly. The trimpot is used to ad­ just the optimum contrast for different LCD operating param­ eters. The 5V for the display can be provided by a power supply or taken from the games port of the computer. You could even use the 9V battery and regulator setup as in the previous article. To get the display working requires eight bits of data, a reg­ister select line, a strobe line and a 5V supply. The circuit arrangement is shown Fig.1. The 8-bit data we use for the display is the same eight bits that a printer uses and we also use two of the printer control lines for the other functions we need; ie, register select (RS) and strobe. When the register select line is low (ground) it allows the computer to send internal commands to the LCD and when it is high (5V) we can write to the LCD screen. The printer port line we use to control the RS line is port C bit 3. This is the only line from this port that does not have inverted logic. When logic highs are output from the computer to port C, only bit 3 will be high; the other three bits (1, 2 and 4) will be low (inverted). From this you can see that when we require the March 1998  67 Listing 1: LCD Driver Program 10 REM Driver program for single line LC Display 11 ‘driven from the parallel port of a PC 12 ‘R.W. 23/11/97 V1.0 20 GOSUB 1000 ‘Initialise software routines 30 GOSUB 2000 ‘Initialise display 40 GOSUB 3000 ‘Write data to display 50 GOSUB 6000 ‘Scroll message back & forth 60 GOSUB 7000 ‘Scroll message to left & wrap 70 GOSUB 8000 ‘Create your own character 999 END’ CLS: SYSTEM 1000 ‘*********************** 1010 ‘Initialisation routine. 1020 ‘*********************** 1030 KEY OFF: CLS: DEFINT A,B,S: DEFSTR D,K 1035 ‘A,B,S integers, D,K are strings, rest single precision 1040 DEF FNCEOL$ = STRING$(79 - POS(Q),” “) 1050 DEF FNCENTRE$(M$) = SPACE$((78-LEN(M$))/2) + M$ 1400 PORTA = &H378 ‘This is LPT1, use &H278 for LPT2 1410 PORTC = PORTA + 2 ‘Define Port C. Port B is not used 1420 COMMAND = 0: CHR = 4: STH = 0: STL = 1 ‘Define function & STrobe 1999 RETURN 2000 ‘******************* 2010 ‘Initialise display. 2020 ‘******************* 2030 FUNCT = COMMAND: OUT PORTA,0 ‘Define RS & set LCD inputs low 2040 GOSUB 4040 ‘clock RS line low 2050 OUT PORTA,48: GOSUB 4000 2060 T = TIMER: WHILE T + .03 > TIMER: WEND ‘wait 30ms 2070 GOSUB 4000 2080 T = TIMER: WHILE T + .01 > TIMER: WEND ‘wait 10ms 2090 GOSUB 4000 2100 OUT PORTA,60: GOSUB 4000 ’16 character display 2110 OUT PORTA,14: GOSUB 4000 ‘display & cursor ON, UNDERLINE cursor 2120 OUT PORTA,1: GOSUB 4000 ‘clear home 2130 T = TIMER: WHILE T + .01 > TIMER: WEND ‘clear home can take 5ms 2999 RETURN 3000 ‘******************* 3010 ‘Write data to Port. 3020 ‘******************* 3030 FUNCT = CHR ‘Set register select line high 3040 GOSUB 4040 ‘Clock RS line high 3050 DAT = “Silicon Chip is a great magazine.” 3060 FOR A = 1 TO LEN(DAT): TOWRITE = ASC(MID$(DAT,A,1)) 3070 OUT PORTA,TOWRITE 3080 GOSUB 4000 ‘Clock full message into LCD from left hand edge 3090 NEXT 3100 GOSUB 5000 ‘Locate cursor at 64 decimal 3110 FOR A = 9 TO LEN(DAT): TOWRITE = ASC(MID$(DAT,A,1)) ‘Write nessage 3120 OUT PORTA,TOWRITE ‘starting at position 9 i.e. “C” for correct scroll 3130 GOSUB 4000 ‘Clock data into LCD 3140 NEXT 3999 RETURN 4000 ‘********** 4010 ‘Clock LCD. 4020 ‘********** 4030 OUT PORTC,FUNCT OR STL ‘Set R/S line & take strobe low 4040 OUT PORTC,FUNCT OR STH ‘Set R/S line, take strobe high. 4999 RETURN 5000 ‘*************************** 5010 ‘Shift cursor to Position 9. 5020 ‘*************************** 5030 FUNCT = COMMAND: OUT PORTC,FUNCT OR STH ‘Set command mode 5040 OUT PORTA,64: GOSUB 4000 ‘Set CG to 9 . . . continued next page 68  Silicon Chip strobe to be high we actually have to output a low and vice versa. If you look at Listing 1, on line 1420 you will see that STH (strobe high) is defined as 0 (low) and STL (strobe low) is defined as 1 (high). This allows us to forget about the logic inversion and just select the strobe logic level we want. The strobe line is normally held high and is taken low to transfer information from the data lines to the display. The LCD commands for the HD44780 controller are listed in Ta­ ble 1 and the character set is listed in Table 2, as published in last month’s issue. After initialising the LCD, the software (Listing 1), firstly writes a string of text, which is longer than the 16 character window, to the display. This message then scrolls backwards and forwards until a key is pressed, whereupon it will scroll in a contin­ uous loop, disappearing on the left side of the window, then scrolling in from the right. Another keypress will clear the display screen then write a custom symbol to the first eight positions. The Listing should make it clear how you code the symbol you want. With a little ingenuity you can create and place two or three symbols side by side to make a shape. With each of these functions writ­ ten as a complete subrou­ tine, you should have no trouble customising the Listing to suit your particular needs. Board assembly & testing We will not insult you by telling you how to assemble the PC board. It should be quite apparent from the overlay dia­gram of Fig.2 and should not take more than a few minutes. Be sure to double check the orientation of the electrolytic capaci­tor for correct polarity. The display will only draw 4-5mA from its power supply so it does not impose any significant load. If you intend to power the display from the PC, connect a wire from the battery positive terminal to pin 1 on the 15way “D” connector, then plug the PC board into the end of the cable, the cable into the printer port and the 15 way connector into the games port. Turn the computer on, load GW-Ba­ sic or Q-Basic and type in listing 1. If this gives you the horrors, you can get the com­plete listing from SILICON CHIP on a floppy disc at $7 plus $3 postage and packing. Make sure that you enter the printer port you intend to use on line 1400. When you run the program the results should be as previously described. To change the message just enter a different string for DAT in line 3050. Don’t forget to enclose it in quota­ tion marks and remember it is case sensitive. Understanding the display The single line display we have used has a few quirks. Instead of the addresses of the 16 visible characters being continuous from 0-15, the first eight characters reside in addresses 0-7, while the second visible group of eight reside at addresses 64-71. All addresses are given in decimal as this is how both versions of Basic communicate with the printer port. Note that we are talking about vis­ ible addresses but there are actually 80 addresses available, 0-40 and 64104. This is the reason for subroutine 5000. After writing the full string of 33 characters starting from address 0 (lines 3060-3090), only the first eight will display. We then call subroutine 5000 to move the cursor to display position 9 or location 64. We then write from the 9th character to the 33rd again but only the next eight (“Chip is”) will show. By changing or adding lines be­ tween 40 and 999, changing the mes­ sage in subroutine 3000 and creating your own characters, you should soon become an expert with Liquid Crystal Displays. Acknowledgement Our thanks to Branco Justic of Oat­ ley Electronics for assistance in the SC development of this project. How To Get The Software The software shown in Listing 1 is available on floppy disc for $7 plus $3 postage and packing. Send your remittance or credit card authorisation (Bankcard, Visa or Mastercard) to Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097. Don’t forget to nominate whether you want a 3.5-inch or 5.25-inch floppy disc. Listing 1: LCD Driver Program – continued 5050 OUT PORTA,192: GOSUB 4000 ‘Set DD to 9 5060 FUNCT = CHR: OUT PORTC,FUNCT OR STH ‘Restore character function 5999 RETURN 6000 ‘************************ 6010 ‘Scroll message to & fro. 6020 ‘************************ 6030 FUNCT = COMMAND: OUT PORTC,FUNCT OR STH ‘Set command mode 6040 LOCATE 25,1: PRINT FNCENTRE$(“Press a key to end this demon­stration.”); 6050 OUT PORTA,24 ‘Shift data left 6060 FOR A = 1 TO LEN(DAT) - 1: GOSUB 4000 6070 K = INKEY$: IF K > “” THEN 6990 6080 T = TIMER: WHILE T + .5 > TIMER: WEND ‘Wait 0.5 seconds 6090 NEXT 6100 OUT PORTA,28 ‘Shift data right 6110 FOR A = 1 TO LEN(DAT) - 1: GOSUB 4000 6120 K = INKEY$: IF K > “” THEN 6990 6130 T = TIMER: WHILE T + .5 > TIMER: WEND 6140 NEXT 6150 GOTO 6050 6990 LOCATE 25,1: PRINT FNCEOL$;: LOCATE 1,1 6999 RETURN 7000 ‘*********************************** 7010 ‘Scroll message to left continuously. 7020 ‘************************************ 7030 FUNCT = COMMAND: OUT PORTC,FUNCT OR STH ‘Set command mode 7040 LOCATE 25,1: PRINT FNCENTRE$(“Press a key to end this demon­stration.”); 7050 OUT PORTA,24 ‘Shift data left 7060 FOR A = 1 TO LEN(DAT) * 32: GOSUB 4000 7070 K = INKEY$: IF K > “” THEN 7990 7080 T = TIMER: WHILE T + .5 > TIMER: WEND 7090 NEXT 7990 LOCATE 25,1: PRINT FNCEOL$;: LOCATE 1,1 7999 RETURN 8000 ‘************************** 8010 ‘Create your own character. 8020 ‘************************** 8030 ‘000 01110 decimal 14 The 1’s represent pixels that will 8040 ‘000 11011 decimal 27 be written (black) 8050 ‘000 00000 decimal 0 The 0’s will appear as background 8060 ‘000 00100 decimal 4 so the character will have the shape 8070 ‘000 10101 decimal 21 of the 1’s i.e. a crude smiley face 8080 ‘000 01010 decimal 10 Only the right 5 rows are significant 8090 ‘000 00100 decimal 4 The left 3 rows are ignored 8100 ‘000 00000 decimal 0 8110 FUNCT = COMMAND: OUT PORTC,FUNCT OR STH ‘set command mode 8120 OUT PORTA,1: GOSUB 4000 ‘clear home 8130 T = TIMER: WHILE T + .01 > TIMER: WEND ‘clear home can take 5ms 8140 OUT PORTA,64: GOSUB 4000 ‘Set RAM address 01000000 8150 FUNCT = CHR: GOSUB 4040 ‘Set character mode 8160 OUT PORTA,14: GOSUB 4000 ‘Start sending your character 8170 OUT PORTA,27: GOSUB 4000 8180 OUT PORTA,0: GOSUB 4000 8190 OUT PORTA,4: GOSUB 4000 8200 OUT PORTA,21: GOSUB 4000 8210 OUT PORTA,10: GOSUB 4000 8220 OUT PORTA,4: GOSUB 4000 8230 OUT PORTA,0: GOSUB 4000 ‘After the 8th bit 8240 FUNCT = COMMAND: GOSUB 4040 ‘change the RS line 8250 OUT PORTA,1: GOSUB 4000 ‘and clear/home the display 8260 T = TIMER: WHILE T + .01 > TIMER: WEND ‘Clear home can take 5ms 8270 FUNCT = CHR: GOSUB 4040 ‘Revert to character mode 8280 OUT PORTA,0: GOSUB 4000 ‘and load our character stored at location 0 8290 FOR B = 1 TO 7:GOSUB 4000: NEXT ‘Then write it to the next 7 locations 8999 RETURN March 1998  69 PRODUCT SHOWCASE New mains filters with metallic flange Schaffner has released the FN 9226 series IEC mains filter modules. They are very compact, measuring 30.4 x 22.9mm and have a depth of only 22.9mm, making them suitable for a wide range of applications including computers, office automation equip­ ment and medical apparatus (a class B version caters for low leakage current requirements). The filters have a metal flange, al­ lowing them to be mount­ed directly onto the internal face of equipment panels, eliminat­ing panel pre-assem­ bly operations as needed for most IEC inlet filters. There is a choice of connections: PCB-mount, Fast-On or solder lug. The FN 9226 series filters are IEC 950 compliant. They have a maximum operating voltage of 250VAC, current ratings of 1, 3, 6 or 10A, and an operat­ ing frequency range from DC to 400Hz. For further information, contact Westek Industrial Products Pty Ltd, Unit 2, 6-10 Maria St, Laverton North, Vic 3026. Phone (03) 9369 8802; fax (03) 9369 8006. Low voltage amplifier delivers 1.5W Analog Devices Inc have released the SSM2211 which delivers up to 1.5W RMS into a 4Ω load and 1W into an 8Ω load. It employs a single supply of 2.7V to 5.5V and provides a rail-to-rail differential output. With its 4MHz bandwidth, the SSM2211 provides a flat response across the entire audio spectrum. Nor does it need any external heat­ sink to deliver its 1W output into a 8Ω load. At full power, harmonic distortion is quoted at 0.2% and at 500mW, distortion is less than 0.1%. Quies­ cent current is 8.5mA and in standby mode it consumes less than 100nA. With a 5V supply, the power sup­ ply rejection ratio (PSRR) is better than 65dB (from 4.75V to 5.25V). It comes in an 8-pin DIP or SO-8 surface mount packages. For further information on the SSM2211 low-voltage amplifier, contact Hartec, 205A Middlebor­ ough Road, Box Hill, Vic 3128. Phone 1 800 335 623. New technical standard released by the Australian Communications Authority According to a recent press release, the Australian Commu­ nications Authority has ushered in a major milestone with the release of new technical stand­ ards for customer equipment and cabling. These former Austel standards have been significantly revised and updated to reflect the intentions of the Telecommuni­ cations Act 1997 for a more open and freer marketplace. Unlike before, the new Telecom­ munications Act only empowers the ACA to adopt standards based on four specific criteria: for the protection of personal health and safety, network integrity, and to ensure inter-operability and ac­ cess to emergency services. 70  Silicon Chip As a result, the 30-odd previous Austel technical standards have now been rewritten and reduced to just 21 to reflect this limited scope. In line with the Government’s policy of industry self-regulation, the old Austel technical standards were revised by working groups of the Australian Communica­ tions Industry Forum, in cooper­ ation with Standards Australia. Standards Australia Technical Committee IT/17 was responsible for rewriting the ACA Standard TS008 dealing with cabling. Roger Lyle, Standards Austral­ ia’s Associate Director for Com­ munications Technologies, says the standards had to be revised by 31st December, 1997 otherwise they would have lapsed. “That gave the industry only a few months to actually review and rewrite them.” Mr Lyle said. “It’s a credit to the industry that it was able to respond and get them out within such strict time con­ straints. To ensure compliance with the new regu­latory regime, it’s vital that users of the old Austel Technical Standards now obtain copies of the new ACA Technical Standards”. The new standards can be purchased at Standards Australia sales offices and agencies in all state capitals or by phoning the Customer Service Centre on 1300 654 646. Wooden you like a new TV? German television manufacturer Dual has released a range of luxury TV sets with the rather unusual fea­ ture of genu­ine timber cabinets. This could be a refreshing change from the unremitting charcoal or black plastic cabinets used for virtually all TVs these days. Three models, known as the “Clas­ sique Range”, are available and they are finished in Mahogany or Oak. A matching stand/cabinet, also in mahogany or oak timber finish, is available as an option. Each set features a “Blackline S” picture tube and a digi­ tal chassis to ensure the best possible picture. All signals are processed in the dig­ ital domain, preventing unwanted interference degrading the original signal. A digital chassis also allows many convenience and performance features not possible in analog-only sets. In addition, the sets are mul­ ti-system, allowing the playback of video material from overseas. The model TVM-7050M also fea­ tures picture-in-picture (PIP) which allows the viewer to watch a dif­ ferent TV channel or another video source on a small inset section of the screen while watching their preferred program on the main screen. This requires the use of an external video source such as a video recorder. All three sets have Teletext and the “Joy-Jog” remote con­trol which has only six buttons and a jog dial. An on-screen menu shows the various functions. The Classique range is part of a complete line-up of Dual TV sets ranging in price from $1699 up to the 85cm set at $3499. Dual TV sets are available from selected stores around Australia. For further information, contact Scan Audio Pty Ltd on 1 800 700 708; fax (03) 9429 9309. ACN 073 916 686 NORBITON SYSTEMS NS_PC101 card for XT/AT/PCs allows access to 48 I/O lines. There are 5 groups (0 to 4) available on a de-facto industrial standard 50-way ribbon cable used in STEbus and VMEbus 19" rack mount control systems. The board uses 2 x 8255 ICs. Multiple boards can be used if more I/O lines are required. NS_LED PCB gives visual access to five groups (0 to 4) of the NS_PC1OX. There is a total of 40 status LEDs. The board offers a 25-way “D” type female socket. The lines are driven by 74244 ICs & configured as a parallel printer port. This socket gives access to printer port kits, eg, stepper motors, LCDs, direct digital synthesis. NS_16_8 PCB is a system conditioning card with 16 optically isolated inputs set-up for either 12V or 24V operation. The board provides 8 single pole, double throw relays with 10 Amp contact rating. KITS & CARDS NS_DC_DC is a step down converter with an input range 11 to 35V DC and an output of 5 volts DC at 5 Amps, with an output ripple of approx 150mV. There is an IN/OUT 50-way connector isolating the 5V and 12V+ & 12V- rails of the PC power supply. This segregates PC’s power when working on prototypes. NSDC_DC1 module used with NS_DC_DC & NSDC_DC4 converters is a 5V to 12V(+/-) step- up converter. The board utilises 743 switch mode IC with 2 x 12V regulators, with output ripple of approx 200mV. NS_UTIL1 prototyping board has 1580 bread board holes access to any 3 groups (0 to 4) on the 50-way cable pinout. Power is available from the 50-way cable format 5 volts at 2 Amps & 12V+ 12V- at 1 Amp. There is provision for array resistors with either a ground or positive common connection. For brochure write to: Reply Paid 68, NORBITON SYSTEMS, PO Box 687, Rockingham WA 6968 Email: norbiton<at>bigpond.com embedded computers designed for the real world Put some intelligence in your next project! MC112 - 68HC11 processor, 32k RAM, 32k EPROM, serial, parallel, timers, A/D converters, BUFFALO software with inbuilt assembler / disassembler and bootloader. $220 Postage and handling $10. Available soon - ARM-based RISC, DSP and PIC systems • RISC • DSP • Parallel • Microcontrollers • Ultra low power • High Performance • Data Acquisition • Control Systems • Neuro-fuzzy • 8, 16, 32 and 64 bit WE HAVE THE SOLUTION Embedded Pty Ltd Level 5 371 Queen St Brisbane GPO Box 2603 Brisbane 4001 Phone: Fax: (07) 3236 5977 (07) 3221 0549 March 1998  71 A 68HC11-Based Embedded Computer When most people think of a computer system, they think of a PC. But the most common form of a computer system is the embedded or dedicated computer. Everyone has embedded computers built into their TV, VCR, microwave oven and so on. By JOHN CATSOULIS Embedded Pty Ltd designs and manufactures embedded comput­er systems for industrial, scientific and consumer applications. Their work­ horse is the MC112, which is based on the Motorola 68HC11. It’s easy to program and has lots of features. Embedded Pty Ltd has been approached many times by elec­ tronics hobbyists wanting a simple controller for some project on which they were working. Typically, they were looking for a small, 8-bit mi­ crocontroller with EPROM, static RAM, parallel I/O and often analog inputs as well. Since such systems Multimedia projector does not need a PC Mitsubishi Electric has launched their LVP-X100A Multimedia Data/ Video LCD Projector which can run computer-based presenta­tions with­ out a computer. Its built-in PCMCIA (Flash Memory) card driver means the projector is self-contained. Software is sup­plied to enable pres­ entation contents to be downloaded onto a PC card which slots into the projector. The remote control unit allows full control of the projec­tor as well as providing an IR beam pointer for cursor control of the on-screen menu or for smooth writing and 72  Silicon Chip just aren’t available through the larger electronics retail chains, Embedded have decided to give away the design of their MC112 computer for non-commercial use, so that anyone can build their own embedded microcontroller. The MC112 is a small comput­ er system based on the Motorola 68HC11 microcontroller (MCU). In addition to the “standard features” of the MC6800 family, the 68HC11 has a 16-bit timer with four stage programmable prescaler, a serial communications interface (SCI), an 8-bit pulse-accumulator, real-time drawing. You can enlarge segments of your presentation to show detail during the show, or use the Pic­ ture-in-Picture function to display a second picture (data or video) on screen at the same time. The LVPX100E has six inputs, for two PCs, two video inputs and two PC cards. The picture size is 51cm to 762cm diagonal and contrast ratio is 200:1. Electronically controlled zoom, focus and keystone correction are also available. For further information, contact Mitsubishi Electric Austra­ lia Pty Ltd, 348 Victoria Rd, Rydalmere 2116. Phone (02) 9684 7777; fax (02) 9898 0484. Internet address: www. mitsubishi-electric.com.au inter­rupts, 256 bytes of static RAM, an 8-channel analog-to-digital con­ verter and onboard EEPROM. The MC112 also has a 32K EPROM and a 32K static RAM. 32K may not sound like a lot but in embedded applications, it’s huge. If you were using the MC112 to record 8-bit temperature values from a sensor once every 30 min­ utes, 32K corresponds to 1.8 years worth of data! The MC112 also has an optional MC68HC24 Port Replacement Unit (PRU) for additional parallel I/O. With the MC112, you get up to 32 parallel I/O lines or 16 parallel I/O plus 8 analog input channels and 8 timer channels. The MC112 meas­ ures just 65 x 90 mm (small enough to be included inside an electronics project) and runs from 5V DC. Its block diagram is shown in Fig.1. For those who would rather buy than build, the MC112 will be available as a complete unit from Embedded Pty Ltd. As sup­ plied by Embedded, the MC112 will in­ Register of Year 2000 compliant software Many businesses have done nothing to ensure that their software will have no problems when the clock ticks over to the year 2000. Now at least there is a register of Year 2000 com­-pli­ant products and organisations, launched by Standards Australia and the Aus­ tralian Computer Society. The register of compliant products can be accessed free of charge through Standards Australia’s web site at www. standards.com.au or directly at www. y2kregister.com.au The site provides a comprehensive list of Year 2000 compliant software and hardware products in Australia and New Zealand, as defined by the Standards Australia publication SAA/ clude the public-domain BUFFALO monitor software in its EPROM. This includes an inbuilt assembler which allows you to enter and run machine code and/or assembly language programs directly and to examine the contents of memory and the processor’s registers. BUFFALO also provides a set of software tools to make the program­ mer’s life easier. These subroutines include facilities for printing to the screen, reading from a keyboard, and so forth. The address and data buses of the 68HC11 are multiplexed and demultiplexing is achieved using a 74HCT573 octal latch (U4). The address strobe, ~AS, causes the 74HCT573 to latch and hold the low-order address lines at the start of the memory cycle. The interrupt lines (~IRQ and ~XIRQ) and ~RE­ SNZ MP77:1998, “A Definition of Year 2000 Requirements”. Non-compliant products generally depend on the date being represented by only two digits and when 2000 rolls around, they may interpret the “00” in the “2000” as “1900”, causing anything from wrong data entry to total system failure. Visitors to the web site can obtain further information about the com­ pliance of a product or a vendor by clicking on the name of the organisa­ tions listed on the register. Hyper links then take the visitor to the vendor’s home page. Vendors pay a one-time registration fee for entry into the register and a fee for each product. The register will be updated each week. Note that none of the products in SET have 4.7kΩ pull-up resistors. The MC112 also has a Low Voltage Inhibitor (LVI), MC34064, for gener­ ating a power-on reset. The LVI looks like a transistor and provides an active-low reset whenever power falls below a preset value. Thus, when power is applied to the MC­112, the LVI holds the system reset until it is stabilised. Port D is the serial inter­ face, with bit 0 as the receive data input and bit 1 as the transmit data output. The Tx and Rx lines are converted to RS232 levels by a MAX202 (U2). This is to allow the connection of the MC112 to a sim­ ple terminal or PC. The MC68HC11 has an onboard 8-channel, 8-bit ADC. This is made avail­able to the user through a 16-pin IDC header labelled PORTE on the PC board. This may also be configured as a general-purpose digital I/O port under software control. The MC112 is available as a complete unit, including ROM pre­ programmed with BUFFALO, user’s guide and cables, for $250. Postage and handling is $10. For further information, contact Embedded Pty Ltd, GPO Box 2603, Brisbane, Qld 4001. Phone (07) 3236 5977; fax (07) 3221 0549. the register have been independently tested for year 2000 compliance. The vendors must sign a self-declaration, declaring the products in question are year 2000 compliant, before they can be listed on the register. Low-cost laser diode module Oatley Electronics have a new laser diode module which has automatic power control (APC) circuitry but its PC board is much smaller than previ­ ous modules. The finished assembly is 44mm long and would fit into a tube with an internal diameter of 15mm. It requires 3-5V DC at about 45mA. Its output is 5mW at 650nm. Priced at just $20, it is available from Oatley Electron­ics, PO Box 89, Oatley, STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 NSW 2223. Phone (02) 9584 3563; fax (02) 9584 3561. Large LCD clock is easy to see How many times have you wished for a digital clock that you could see from a rea­ sonable dis­ tance across the room? So many digital clocks have such tiny figures that only the young and those with super acute vision can see them to tell the time. Now here is a clock which you really can see from a good distance. Its digits are no less than 65mm high and even this relatively middle-aged writer has no trouble seeing the time of day from a distance of more than 20 metres away. The clock can be set to display 12 or 24-hour time and has three minor displays, with 18mm high digits, for the date (day and month), day (eg, SAT) and the temperature in Celsius or Fahrenheit. It runs on two AAA cells and can be wall hung. Its overall dimensions are 210mm wide, 230mm high and maximum depth is 30mm although the fascia is curved so that its apparent thickness is less. Price of this wonder-clock? Just $89.95 from all Jaycar Electronics stores and dealers. (Cat XC-0230). March 1998  73 VINTAGE RADIO By JOHN HILL A fault with a difference One intriguing aspect of vintage radio repairs is the number of obscure faults that one has to deal with from time to time. Few repairs are straight­forward and there is often a hidden and challenging problem to solve. It’s not really surprising that vintage radio receivers can produce obscure faults. No doubt the age and poor con­ dition of some of these old receivers has some bearing on the matter. A classic example of this was a fault in an old 1932 model Precedent, an early 5-valve superhet with 2.5V valves and an 8-inch (200mm) elec­ trodynamic loudspeaker. The restoration had been without incident and the set worked quite well for an old timer. However, there was an annoying problem that resulted in noticeably distorted sound when the set was hot. Turn the set off and then on again a few hours later and it would be OK. It took quite some time to establish a connection between the fault and the length of time the receiver was in operation. The problem never be­ came apparent until the set had been operat­ing for several hours. From then on, the distortion would gradu­ ally creep in. After several unsuccessful attempts at locating the fault, the problem was finally traced to the loudspeaker. To cut a long story short, gradual heat build up in the field coil cre­ ated physical distortion between the speaker frame and the field coil housing. Twisting the housing with one hand would increase or decrease the audible distortion, depending on which way it was twisted. This heat induced warp eventually caused the voice coil to foul the centre pole of the electromagnet. Once that happened, the sound deteriorated until the unit was switched off and the speaker cooled. It was noticed that although the voice coil did not rub on the magnet when the speaker was cold, it was very close on one side. As there was no central “spider” on the cone, I de­ cided to reposition the pole piece to see if that would solve the problem. One favourable aspect of early elec­ trodynamic loudspeakers is that they are held together with good old-fash­ ioned nuts and bolts. This allows them to be taken apart for repairs. In later years, speakers were riveted or spot welded together, which made dismantling extremely difficult, if not impossible. Several nasties The large bolt head on this Precedent loudspeaker at top holds the central pole piece in place, making it easy to remove for repairs. 74  Silicon Chip The Precedent speaker was of the nuts and bolts variety and it required little effort to remove the field coil and the cen­tral pole piece of the electro­ magnet. This revealed several nasties. First, despite being plated, the pole piece was now very rusty. This had the effect of enlarging its diameter, thus reduc­ing the clearance between it and the voice coil. Second, the field coil was wound on a cardboard spool which was a loose floating fit on the pole piece. Vintage Radio This pole piece shows obvious signs of damage. Note the scuff marks at the end where the voice coil has been rubbing against it. 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 Analogue... VMX410 $1,899.00 - Very high quality video mixer for S-Video and Composite. Full-frame TBC, 60 wipes, borders, colours, mix, fade, cut, picture-in-picture, chromakey, freeze, etc. Fix colour bleed - H and V!, four memories, GPI trigger, etc. Stereo mixer with four inputs + mic input, headphone output and metering. The speaker cone on this unit is still attached to the frame. Note the “spider” in the centre of this model, which is used to posi­tion the cone. Shrinkage over the years had caused this problem. The cardboard spool is perhaps the cause of most faults that develop in electrodynamic loudspeakers. The spool absorbs moisture from the at­ mosphere when the speaker is not in use. When the field is operative, the heat generated within the coil drives the moisture out of the cardboard and it condenses on the cold pole piece. Even though the iron was originally electroplated, 60 plus years of heating and cooling can eventually result in severe rusting and a fouled voice coil. Moisture in the field coil spool can also cause electroly­ sis which was possibly the main cause of field winding failure. If moulded bakelite had been used instead of cardboard, ...or Digital? We've got it! The latest digital editing cards... DPS Spark & Edit Bay, Miro DV300, FAST DV and AV Master, etc. SCSI cards and drives. Whole systems too. Want prices, pictures and info? Visit our website at www.questronix.com.au/~questav - it's updated frequently - or come in. Kits, components, accessories - our list is growing all the time! 2/1 Leonard Street, HORNSBY, NSW, 2077 P O Box 548, WAHROONGA, NSW, 2076 Fax (02) 9477 3681 Ph. (02) 9477 3596 March 1998  75 This back view shows the speaker frame and voice coil. The coil is wound on a thin cardboard former which often goes out of shape over the years, especially if the cone has sagged. A typical field coil housing. Unlike the Precedent loudspeaker, this unit has the pole piece riveted in place which makes repairs more difficult. electro­ dyna­ mic speaker fields may have been more reliable. Proposed repair The proposed repair for the Pre­ cedent loudspeaker was to clean up the pole piece and reposition it centrally in the voice coil. However, the job would not really be complete unless something was also done about the moisture absorbent cardboard. So, after leaving the spool out in the Sun to dry for a few hours, it was given 76  Silicon Chip several coats of clear lacquer to seal it. A couple of thin cardboard wash­ ers were also made, so that the field coil would be held firmly in place and these washers were sealed from moisture too. All that remained was to reassemble the speaker and the distortion prob­ lem would be solved. Unfortunately, one cannot really expect to solve dif­ ficult problems as easy as that. It would appear that electrody­ namic loudspeakers were originally assembled from rear to front. In other words, the cone was glued into posi­ tion last. Putting a speaker together with the cone already in position is not so easy. No matter how the bolts that hold the frame and field housing together were jiggled and twiddled, the voice coil always rubbed on the pole piece. After going through this routine often enough to realise that it wasn’t going to work, the situation called for drastic measures. The pole piece was set up in a lathe and a quarter of a millimetre was turned off its diam­ eter at the front where it fits into the voice coil. After that, no further problems were experienced with the speaker’s assem­ bly. The cone moved freely without a hint of interference. Now one would expect that increas­ ing the clearance between the pole piece and the voice coil would reduce the speaker’s sensitivity. If that’s the case, it was by no means noticeable. What’s more, if the same problem arises again with other speak­ers, I will have no hesitation in taking a skim off the pole piece in order to give it adequate clearance. Because the voice coil is wound on a thin cardboard former, it is asking a lot to expect it to be perfectly round 50 or 60 years after it was made. Reducing the pole piece diameter is one way of compensating for an outof-shape voice coil. A cone that sags and loses its form is one reason that voice coils go out of shape. While on the subject of voice coils, remember that they are only glued to the speaker cone and a touch of lacquer to rein­force the area of at­ tachment is highly recommended. If you have ever encountered a speaker with a loose voice coil or voice coil winding, you will appreciate the need to pay attention to that part of the speaker while it is accessible. Other methods There are other ways of clearing fouled voice coils without having to resort to the drastic methods previ­ ously described. One way is to move the cone in and out while applying side­ wards pressure to the cone. In other words: try to loosen the dust, grit and barna­ cles by forcing the inside of the voice coil to rub gently on the pole piece. After that treatment, lay the working was used. Unfortunately, this speaker is of slightly different construction, which just goes to show that some may be easier to repair than others (note the “spider” shown in the photograph of this model). One pr o b lem t h a t would arise if doing a similar repair on this second speaker is the fact that the pole piece is riveted in place instead of being held by a bolt, as was the case with the Precedent speaker. No money In conclusion, I see little point in spending large sums of money on old radios, especially The hole in this backing plate is a neat fit around the voice coil. In some instances, this hole when the price of some may require enlarging so as to clear a coil that has gone out of shape. repairs exceeds the re­ ceiver’s value. This par­ speaker face down on the workbench Once again, give the speaker a run ticularly applies to re­placement field for a while so that any rubbish can in the face down position so that the wind­ings and speaker cones where work its way out of the gap. gritty granules can find their way out. one can easily spend $100 on an old If that fails to do the trick, slide a In my case, the repaired Precedent speaker restoration. thin piece of shim brass between the speaker was reinstalled in its cabinet Why pay to have these things done voice coil and the pole piece, work­ before I realised it had the potential when they can often be restored by ing it all the way around if possible. for a Vintage Radio story. So for the either a straightforward repair or by This procedure is likely to be more purpose of supplying photographs, combining various good components SC effective than the previous method. another electrodynamic loudspeaker into one working unit? This 2.5kΩ field coil is wound on a cardboard former. Sealing the card­board with lacquer will help to moisture-proof it. Most electrodynamic loudspeakers employed a hum-bucking coil which was used to neutralise hum induced by the field coil. March 1998  77 Silicon Chip Back Issues 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. 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. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. July 1990: Digital Sine/Square Generator, Pt.1 (0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; LowCost Dual Power Supply; Inside A Coal Burning Power Station. 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. 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. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. September 1990: Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band; the Bose Lifestyle Music System; The Care & Feeding Of Battery Packs; How To Make Dynamark Labels. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Operating an R/C Transmitter; Index to Vol. 2. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; MIDI Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. 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. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. April 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. 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. 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. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. June 1990: Multi-Sector Home Burglar Alarm; Build A LowNoise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. 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. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium. 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. ORDER FORM Please send me the following back issues: _____________________________________________________________________ _______________________________________________________________________________________________________________ ______________________________________________________________________________________________________________ Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 78  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A8 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. ✂ Card No. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; A Windows-Based Logic Analyser. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. 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: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. April 1995: Build An FM Radio Trainer, Pt.1; Photographic Timer For Dark­rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. May 1995: What To Do When the Battery On Your PC’s Mother­ board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder (Uses Pressure Sensing); Adding RAM To A Computer. December 1993: Remote Controller For Garage Doors; LED Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. September 1995: Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags – How They Work. 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. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. 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 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. 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. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. March 1996: Programmable Electronic Ignition System; Zener Diode Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. May 1996: Upgrading The CPU In Your PC; Build A High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. November 1996: Adding An Extra Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. December 1996: CD Recorders –­ The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. January 1997: How To Network Your PC; Using An Auto­ transformer To Save Light Bulbs; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (for Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. February 1997: Computer Problems: Sorting Out What’s At Fault; Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Audible Continuity Tester; Cathode Ray Oscilloscopes, Pt.7. April 1997: Avoiding Windows 95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; Installing A PC-Compatible Floppy Drive In An Amiga 500; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. May 1997: Windows 95 – The Hardware Required; Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How Holden’s Electronic Control Unit works, Pt.1. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home; How Holden’s Electronic Control Unit Works, Pt.2. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget; Win95, MSDOS.SYS & The Registry. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; The Flickering Flame Stage Prop; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Regulated Supply For Darkroom Lamps; Build A Musical Doorbell; Relocating Your CDROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. 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. 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. 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. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. December 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. 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. February 1998: Hot Web Sites For Surplus Bits; Build A 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. 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 Pre­ amp­lifier;The Latest Trends In Car Sound; Pt.1. September 1996: VGA Oscilloscope, Pt.3; Infrared Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­grammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; Infrared Stereo Headphone Link, Pt.2; Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc for $10 including p&p. 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); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. March 1998  79 COMPUTER BITS BY JASON COLE Norton Utilities V2 For Win95; Pt.3 No matter how big your hard disc drive is, it’s all too easy for it to become cluttered with obsolete or duplicate files. This is where Norton’s “Space Wizard” utility comes in handy. It goes through the drive and searches for files that can be safely deleted. When the Space Wizard utility is started, it asks you to choose between an Express deletion process or a Comprehensive deletion pro­ cess – see Fig.1. We will concentrate on the Comprehensive process here, because the Express method is in fact just a scaled down version. In the Express process, you are asked just a few questions such as “Do you want to empty the Recycle Bin now?” You are also asked to select which file types you want deleted. Space Wizard looks through the hard drive and also locates other files that it believes can be deleted, such as *.tmp files and any files inside a “Temp” direc­tory. As with all of Norton’s programs, you are taken systemati­cally through the process. However, no matter how advanced this program is, there are some things to watch out for. For ex­ ample, I have a Root Directory called Fig.1: Space Wizard offers two methods of creating disc space: Express and Comprehensive. The latter method will recover much more disc space. 80  Silicon Chip “Temp”. At first this directory was in fact just a temporary one, which held files that I could delete when required. However, I now use this directory to hold quite a few files that I want to keep. As you might expect, Norton’s Space Wizard automatically marks all the files in this folder for deletion. Initially, I got around this by manually deselecting the files I wanted to keep but this took quite some time as there was lots of files. So, if you make a habit of using the Temp directory to hold files that you might want to keep, then you have a couple of choices: (1) Temporarily change the name of the directory before running Space Wizard; or (2) Permanently change the name of the directory to something else and then create a new Temp directory. Note that you must create a new Temp Fig.2: Space Wizard selects all files which it regards as temporary but you have the option of deselecting any files you want to keep. Fig.3: Space Wizard also displays a list of “commonly discardable files”. These are not automatically selected for deletion; you choose the files to be discarded. directory because some programs rely on its presence in order to function correctly. The comprehensive method The Comprehensive method does much more than the Express method when it comes to recovering space on your hard disc drive. It includes all the functions already described for the Express method and, in addition, it searches the entire hard disc drive for infrequently used files, duplicate files and “commonly discardable files and folders”. Let’s take a closer look at what it offers. The operational procedure is quite Fig.4: Space Wizard can track down files which have not been used for a nominated period of time. Once again, you tick the files that you want to delete. straightforward. After starting Space Wizard, you choose the Comprehen­ sive method, press Next and then select which hard drive you want to find room on. Space Wizard then scans the hard disc drive and comes back with a series of questions. The first question is: Do you want to empty the recycle bin? Select yes so that it can delete the bin contents. Space Wizard will then select files which are generally temporary; eg, *.tmp and any files located in Temp folders (Fig.2). It is a good idea to check through these and deselect any files that you want to keep. Next, you are shown a listing of Fig.5: want to track down files larger than a certain size? No problem – Space Wizard can display all files larger than a nominated value between 1Kb and 999Mb. commonly discardable files (Fig.3). These are not selected for deletion but can be – the choice is yours. Many people will have files on their hard disc drive which haven’t been used for months, if not years. These files remain there mainly because they have been forgotten about but Space Wizard can track them down. All you have to do is choose the period of time since the files were accessed (from one day to 999 years). You then tick the files that you want to delete (Fig.4). What about large files? In this case, Space Wizard searches the drive for files larger than a nominated value between 1Kb and 999Mb and presents Fig.6: Space Wizard can locate files that have the same size, time and date. These are all checked using a binary comparison method to make sure they are identical. March 1998  81 Fig.8 (above): all other applications should be shut down before running Space Wizard to avoid error messages like the one shown above. Fig.7 (left): as a final step, Space Wizard displays all the files that have been selected for deletion. You then have a choice of actually deleting files, compressing selected files and storing them as a “zip” file, or moving certain files to a new location. you with a list, as shown in Fig.5. If you now click on the Allocated tab, the files will be sorted in size order, either from smallest to largest or vice versa. Another possibility is duplicate files. To track these down, Space Wiz­ ard goes through the hard drive and locates files that have the same size, time and date. These files are then checked using a binary comparison method to make sure that they are identical, even though their names may be different (Fig.6). Be careful what you delete here. A command.com file is stored in both the Windows directory and the root directory and both are used. Do not delete any files that you are unsure about. The final step The final step is crucial. Space Wizard displays all the files that have been selected for deletion and this will be your last chance to keep any wanted files. However, if you are unsure as to whether or not you can live without some of these files, you can compress them and store them as a “zip” file in a desig­nated location on the hard drive. That way, if you find that you actually needed a file, you can uncompress it. Save Network Hassles With Quick Log-On Do you have two or more computers on a small Win95 local area network with resources shared back and forth between them? If so, this can create problems during boot-up because one computer cannot connect to the resources shared on another computer until that computer has been switched on. If you do try to map the drives on a computer that is switched off, you will get an error message. However, depending on the setup, this may be unavoidable, because it is impossible to boot all the machines simultaneously. Fortunately, the way around the problem is quite simple. Here’s what to do: double click the Network icon in the Control Panel, then choose Client For Microsoft Networks from the list of installed components and click the Properties button. This brings up the dialog box shown at right. Now all you have to do is choose Quick Logon from the Network Logon Options list. From now on, Windows will simply log you onto the network when you boot but won’t try to reconnect the drives until you use them. 82  Silicon Chip For the remaining files, just select them and click the Delete button and they will be gone (Fig.7). Another option is to move all the files to a new location, so that you can easily delete them later on if they are not needed. By the way, while I was writing this article, I ran Space Wizard at the same time. When Space Wizard performed its first scan, it came up with the error message shown in Fig.8. This was because that particular file was in use by Word. It is therefore a good idea to shut down all other applications before running Space Wizard, to avoid SC similar messages. Computer hardware problems Auto detect & hard disc drive parameters Enjoy playing with your computer’s CMOS setup? Well, watch out. If you change the hard disc setup from a “User” type to “Auto Detect”, the machine may no longer boot. Here’s why auto detect doesn’t always work. When you buy a new hard disc drive, one of the first things to do is to check the manual for the drive’s “parameters”. Alter­ natively, these parameters are usually also printed on a sticker attached to the drive itself. Your Drive parameters consist of: (1) number of heads; (2) number of cylinders; (3) number of sectors (4) landing zone; and (5) write pre­ compression. These parameters are required by the computer so that it knows how big the drive is and, more impor­tantly, where to go on the drive in order to retrieve data. For example, to retrieve a certain string of data, it may read sector 7 head 3 on the drive. That’s fine but what if you change the parameters of the drive, either intentionally or accidentally? This can easily happen if you install a new mother­board or transfer the drive to another comput­ er, for example. The most common error is using Auto Detect (in the system BIOS) on a drive that’s come from a machine in which it was “assigned” it’s para­ meters by the person who originally installed it. If it’s a boot disc, you may find that the machine will no longer boot up. Alternatively, if it’s a non-boot disc, you may no longer be able to retrieve files or the files may be corrupted, with lots of lost clusters. The reason for this is quite simple. Auto detect doesn’t actually read the settings that have been manually assigned to the drive. Instead, it re­ trieves the drive’s parameters by read­ ing the manufacturer’s data from the drive itself. Because of this, it follows that if the original manually-assigned para­meters differ from the parameters stored in the ROM, then using auto detect will cause data errors. This doesn’t matter if it’s not a boot drive and you no longer need the data that’s stored on it. In this case, you can just reformat the drive and carry on. The drive will be auto-detected each time you start the computer and all will be well. If it is a boot drive and/or you do need access to the data, then you will have to manually assign the required drive parameters if auto-detect causes problems. How do you know if it’s wrong or not? The most simple checks to do are: (1). Try to boot the machine. If the settings are incor­rect, the machine won’t boot (because it can’t find the system). Be sure not to run Scandisk with the autofix option, otherwise you could trash your data; (2). Run CHKDSK or Scandisk (no autofix) on the drive. This quickly checks the drive and if the settings are incorrect then you will receive hundred’s of errors. Parameter selection is very im­ portant. If you lose your parameters you can spend hours trying different combinations and still not guess the correct settings. My advice is to al­ ways write them down. Before leaving this subject, it’s worth noting that many BIOS’s offer two different auto detect options. The first is the auto detect in the BIOS setup. You activate this in or­ der to automatically enter the correct drive parameters in the main menu when it is first installed. You then save those parameters so that the machine doesn’t have to auto detect the drive each time it’s started. This is used for most computer setups and the detected parameters can be written down and stored with the computer (so that they can be later manually re-entered in a different setup if necessary). The other method involves select­ ing ‘Auto’ as the drive type in the main menu. This way, the system will auto detect the drive every time you start up. This is a simple way of installing drives, however you are generally not presented with the set­ tings. Only the size is shown so that if you transfer the drive to another machine without auto detect and you don’t know the settings, it can’t be correctly set up. Finally, I have seen different moth­ erboards return differ­ent para-meters for the same hard disc drive when using auto detect. Admittedly, this only occurs with some older mother­ boards; I haven’t encountered any modern motherboards that give this sort of problem. So be careful when playing with hard disc drives – it’s all to easy to lose your precious data and wind up with a door stop if you don’t know SC exactly what you are doing. March 1998  83 RADIO CONTROL BY BOB YOUNG Jet engines in model aircraft; Pt.3 Last month we looked at the input of air to the jet engine via the compressor and we established that the radial or centrifugal compressor was the best choice for model jet engines. This month we look at the diffuser, combustion chamber and tur­bine. Having accelerated the air to the outside edge of the com­ p ressor wheel, it is now time to collect the air, achieve the full measure of com­ pression possible and remove as much tur­bulence in preparation for the entry of the air to the combustion chamber. To do this we use a diffuser (stator or collector ring). Here we are faced with some difficult choices. Essentially, diffusers may be divid­ ed into two categories, bladeless and bladed diffusers. Professional engine men refer to the bladeless diffuser as a bladeless annular space. They are easy to man­ ufacture and can be quite efficient if designed correctly. As there are no blades there is no flow breakaway. The main advantage of the bladeless diffuser is that the compressor as a whole has excellent self-regulatory characteristics. The disadvantages are that they must be of a larger diamet­er than the bladed diffuser and that they cannot smooth out the twisting motion im­ parted to the airflow by the compres­ sor. As the overall diameter of the finished engine is very important to the modeller, the increased diameter is a serious drawback. Therefore, the best solution for a model turbine is the bladed diffuser with the blades set back from the com­ pressor, leaving a clear annular space where the airspeeds are the highest 84  Silicon Chip and most unevenly distributed. The wedge-shaped diffuser blade can be useful for mounting the diffuser to the outer casing. Screws can be fair­ ed into the wedge with a minimum disturbance to the airflow. The action whereby the air is slowed and compressed in the diffus­ er is a complex mix of subtle factors. If you are interested in model aircraft jet engines, this book by Thomas Kamps and entitled Model Jet Engines is a good one to have. It’s published by Traplet Publications UK (ISBN 0 9510589 9 1). The spiral law governing action of a fluid in a centrifugal compressor states that the product of the radius (r) in the diffuser system and the speed (cu) in the peripheral direction is constant (spiral law: r x cu = con­ stant). Thus, as the radius increases, the speed is re­duced. This basic law plays an important role in model jet engines and an interesting analog is found in the common tea cup. As we stir a cup of tea we speed up the centre of the mixture but at the edge the speed is the slowest. This causes an increase in the fluid pressure and the level of the fluid at the wall of the cup rises, leaving a dish or well at the centre; the faster the rotational speed, the deeper the well. According to Bernoulli’s theorem, the total energy in the flow must al­ ways remain constant. Therefore, if the speed de­creases as the air moves out, away from the compressor into the larger diameter diffuser, the pres­ sure goes up, as in the tea cup. So contrary to what one might expect, compression is due largely to the centrifugal force applied to the air leaving the compressor and moving outwards into a space of a larger di­ ameter, and not due to the change in volume between the compressor and the diffuser. True, this change in volume will also cause a slowing of the airflow with the subsequent increase in pres­ sure but not of the order required. In fact, if the size of the annular non-bladed duct is increased, there is a danger of the airflow break­ing up into turbulence with a severe loss of efficiency. For this reason, some bladeless diffusers have a cross sec­ tion which tapers to a more narrow section as the diameter increases, This close-up view shows the JPX-T-240 turbine engine fitted to Kevin Dodds’ (Tingalpa, Qld) A-10 “wart hog”. The maximum engine speed is 122,000rpm! Note the discoloration on the rear of the fuselage from the exhaust. forc­ing the air to move more quickly to the outer edge. Here we come across another dis­ advantage of the centrifugal or radial compressor. To get a worthwhile increase in diameter in the diffuser we need to have a diffuser of ap­ proximately twice the diameter of the compressor. Practical experience has estab­lished that this figure may be cribbed somewhat but a minimum ra­ tio is around 1.6 times the diameter of the compressor wheel if we introduce vanes or guides into the diffuser. Thus it is the diffuser that most contributes to the dumpy appearance of the model jet engine. With blades in the diffuser, we now have real cause for concern because the path of the air leaving the com­ pressor rim is a very complex func­ tion. It requires careful calculation to get the diffuser blades set at the correct angle so as to minimise flow breakaway on the guide vanes. What must be kept in mind with these engines are the very high air­ speeds involved. In an engine using a shaft speed of 100,000 rpm and a 66mm diameter compressor, the rim speed (Rs) of the compressor is given by the formula Rs = n x d x π/60, where n is the shaft speed and d is the diam­ eter. This works out to 345.5 metres per second or 1243.44km/h. But wait, I hear you cry, that is in excess of the speed of sound! Not so, for we are working with air at higher temperatures and pressures, so the speed of sound in the medium is much high­er. Even at rim speeds as high as 450m/s, the sound barrier can­ not be exceeded inside these engines. However these are phenomenally high airspeeds and if the diffuser blades are set incorrectly then there are serious rami­ fications. Unfortu­ nately these are the sorts of speeds required if the Reynolds numbers are to be moved up into a reasonably efficient range. Yet model jet engines can be throt­ tled down successfully to much lower speeds, such is the amount develop­ ment work that has been poured into this the most difficult of all modelling dreams. If any reader is interested in a full mathematical analysis of the model jet engine then there is a very good book on the sub­ject written by Thomas Kamps and entitled Model Jet Engines, available from Traplet Publications UK (ISBN 0 9510589 9 1). If we can slow the air by 50% in the diffuser, we will convert about 75% of the speed energy to pressure energy, as the energy in the gas is proportional to the square of its speed. Thus, re­ turning to our motor using a 66mm compressor at 100,000 rpm, we find that typical throughput of air will be about 1.35 - 1.75kg. As the thrust of the motor rises in proportion to the throughput, the higher figure is the more acceptable. At this point the compressor will deliver a compres­ sion ratio of about 1.9:1. Another important factor in the compressor/diffuser design is the expansion angle of the diffuser blades. The blades start off more close­ ly spaced and gradually move apart as they move out to the rim of the dif­ fuser. This divergence angle is known as the expansion angle and it plays a large part in the compression of the incom­ing air. Too shallow an angle will mean more losses as the air will stay in the duct longer and boundary layer losses will rise. Typical expansion angles are around 15 degrees which calls for 24 blades in the diffuser. Smaller angles will call for more blades and more friction losses. For this reason it is better to use blades which are curved forward slightly, forming gently wid­ ening ducts. This type of diffuser and a radial compressor with retro curved blades will result in an engine capable of rapid throttle response and which will be quite resistant to surging. The compressed and stabilised air now passes to the combus­tion cham­ ber and we haven’t even got to the March 1998  85 Table 1: Model Jet Engine Fuels Densi ty (kg/l ) H0u (MJ/kg) Boi l i ng Range (oC) Diesel Petrol JP1/Jet A JP4 Propane Methanol 0.85 0.76 0.804 0.76 0.5(1) 0.79 42.8 42.5 43.3 >42 46.3 19.5 190-334 80-130 160-260 60-240 -42 65 Fuel tank Capaci ty (ml ) 880 990 920 990 1380 (5 mi nutes, 30N thrust) Fl ammabi l i ty/Fi re Low H i gh Low H i gh Very Hi gh Hazard (1) Li qui d under pressure; (2) Suffi ci ent for 5 mi nutes of powered fl i ght at a thrust of 30 Newtons (speci fi c consumpti on = 0.3kg/N/h) 2080 H i gh Source: Model Jet Engi nes, by Thomas Kamps hard part yet. Is it any wonder that the model jet engine took so long to develop? The combustion chamber Single stage turbines and compres­ sors take up little space but not so the combustion chamber. This is why model jet engines do not look at all like their full-size cousins from the outside. Actually, the proportions are almost reversed. In the full-size motor, the combustion chamber is a short section between the compressor and turbine, whereas in the model engine the combus­tion chamber is the largest component. There are other difference between model and full-size turbines in terms of specific power. Model size com­ pressors and turbines are less efficient than industrial aircraft engines. If the engine is to run at all, the turbine must extract most of the available energy from the exhaust flow at the turbine. As a result, there is little left in the residual exhaust flow to produce thrust. For this reason, the shape of the tail-cone is vitally important; a correctly shaped tail-cone can increase the thrust dramatically. The low residual thrust combined with the low compression ratios avail­ able in the model engine means that only 3 - 8% of the energy contained in the fuel is turned into thrust. Howev­ er, due to the low mass of the model engine, thrust to mass ratios are much the same as full-size engines. The drawback in the model engine is fuel consumption. Modellers wishing to use a jet in their new model should leave plenty of space for the fuel tank. Table 1 shows the most common fuels suitable for use in model turbines. Early model jets used propane gas but there was some risk with this fuel. Theoretically, the jet engine is not re­ 86  Silicon Chip stricted to one type of fuel, the main requirement being that the maximum energy is released during combustion. In practice, most jets are designed to run on one of the many mineral oil products commer­c ially available. Alcohol fuels such as methanol are not suitable due to their low energy densities. These days, most model en­ gine manufacturers choose kerosene. The design of the combustion cham­ ber is critical. If this component falls short in any way, there are serious conse­quences, the most drastic being the destruction of the motor. If combustion is uneven, then the incoming air will not be heated to full temperature in parts of the combustion chamber. The enthalpy of this portion of the air rises only slightly and con­ sequently does little work on its way through the engine. Worse still, to compensate, the rest of the air must become that much hotter to keep the engine running. The result is uneven speed distribution in the turbine and lower overall efficiency. In the worst case, the engine will not run at all. The purpose of the combustion chamber is to heat the air in order that it can do more work when it is decom­ pressed than was required to heat it. If the air is heated during decompression then this effect is largely nullified. For this reason, combus­ tion must be contained inside the combustion chamber as much as possible. If the flames are too long, they will extend into the turbine area and the turbine will overheat. The clue for this prob­ lem is high exhaust gas temperature. Mixture considerations Stable combustion can only be achieved if a stoichiometric mixture is present. This is referred to as an air surplus of one. A mixture is said to be rich if the air surplus is less than one and lean if it is greater than one. A lean mixture can result in the flame being blown out if the throttle is closed suddenly because the compressor is still delivering a large quantity of air to a weak flame. If the mixture is too rich, the flame burns yellow due to glowing carbon particles. These cannot be fully burnt because the necessary oxygen is ab­ sent. The result is a layer of soot depos­ ited on the combustion chamber walls. When using kerosene or diesel, sto­ ichiometric combustion occurs with a fuel/air ratio of 14.7:1 and results in burn tem­peratures of about 2000°C, even in model engines. To reduce this temperature to the desirable 650850°C, cool air must be introduced by dividing the combustion chamber into two parts. These are called the primary and secondary zones. In full-size engines, high combus­ tion chamber temperatures (900°C) are a real problem and nickel based alloys (Nimonic or Inconel) are the usual solution. In a model engine, this heating is not so severe due to the low­ er compression ra­tios. This means the air temperature is not as high from the compressor and therefore the cooling effect is much greater. A neat trick is to drill small holes (1-1.5mm dia.) in the primary zone to introduce cooling air. This air forms a thin, cool boundary layer and protects the combustion chamber primary zone from the stoichiometric temperatures. As a result, V2A sheet steel is OK for the combustion chambers. On the other hand, it is desirable that the cooling air in the secondary zone penetrates deeper into the com­ bustion chamber and this calls for larger holes. The number, size and location of the holes has a large effect on the overall exhaust gas tempera­ture and temperature distribution and is a key factor in the engine design. The aim is to obtain perfectly even heating with as short a flame length as possible and with all fuel completely burnt. The exhaust gas heat must be directed away from the root of the tur­ bine blades, as the stresses are highest at this point. Most heat is directed towards the centre of the turbine disc, towards the shaft and bearings. By now, the reader should be aware of why it took so long to make one of these engines run at all. Did Mr Ball ever have those engines running in SC 1947? I really doubt it. 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. Controller modification for halogen lamps Currently I am working on a rather complex design, on con­tract. One of the many requirements is to supply power to 12V, 18W incandescent lamps, with constant brightness, from a supply which can vary from about 13V to 26V. This calls for a PWM power supply. Generally, I don’t like to reinvent the wheel. I thought, what a beauty, SILICON CHIP just published a cou­ ple of designs which I could draw ideas from (the high current speed controller for 12V/24V motors in the June 1997 issue and better still, the regulated power supply for darkroom lamps in the November issue). I must admit that at first I was impressed by the simplicity of these two designs by Rick Walters and I believed they would work, as claimed. So I duly bread-boarded the basic circuit and when I found that it did not regulate the brightness of the lamp at all, I copied the circuits, one after the other, precisely. To no avail. For hours on end, I checked and rechecked the component val­ ues, connections, different brands of the TL494, lamps, etc. The weird­est Golf buggy jumps when stopping I recently purchased and assem­ bled the kit for the High Current Speed Controller as described in the June 1997 issue and I am pleased to say that, with one minor exception, it works most satisfacto­ rily. I have it in use on my electric golf buggy and as the course on which I mostly play is quite hilly, it gets a good opportunity to demon­ strate its ability. The one exception I mentioned is that when it is switched off, a momentary surge of full power is 88  Silicon Chip thing, however, is the fact that all volt­ age measurements, and waveforms, are correct, according to the design, as it is, for what it is. In addition, I also used my digital light meter which shows more than three times increase in brightness, in the range of 13V-26V. All in all, it was a very frustrating exercise. (L. B., Springvale, Vic). •  We used tungsten lamps in the development of the regulated supply for darkroom lamps, although it was contained in a metal box to prevent us all going blind during the devel­ opment. Howev­ er, the anticipated supply voltage variations were in the order of +5% and -10%, not the 100% you are talking about. We have checked the circuit with a 50W halogen lamp and the com­ pensation resistors R3 and R4 are not quite correct for it. We fitted a 1kΩ 10-turn trimpot between the two resistors with the wiper to IC1 pin 1. With hindsight, we should have included it in the original unit to set the compensation exactly. With around 3V on pin 1 of IC1 the (analog) lightmeter barely moved over the range 210V to 260V. We set the output to 12V with the Variac set to 240V then varied the AC input. Each time the 10-turn trimpot is adjusted delivered. Any suggestions you can offer to solve this problem would be appreciated. (F. R., Hazelwood North, Vic). •  We are not able to explain how the circuit can deliver a surge at switch-off unless you are switching the supply to the 3-terminal regula­ tor while leaving the supply to the motor perma­nently connected. If this is the case, the solution is to switch off the supply to the motor at the same time as the rest of the circuit is powered down. If that is not convenient in your setup, try switching the supply line after the 3-terminal regulator. the output voltage needs to be reset, but it only took a couple of adjust­ ments to get it correct. We should also offer a caution about breadboarding a prototype of this circuit. If you are not careful about the circuit layout it is quite easy to obtain the situation where load current is flowing in the same common impedance as the feedback or compensation currents. If this happens, it will wreck the line and load regulation. Speakerphone desperation I am writing to you in sheer des­ peration. I have a problem with my project, the Speakerphone described in the May 1988 issue of SILICON CHIP. The problem I am experiencing is that when the unit is switched on, I can easily hear the other party’s voice through the speaker but the transmission of my voice through the electret microphone is very soft, from a distance of say, 30-40cm; when my mouth is only a few centimetres away, the other party can hear very well. I have followed the instructions to the letter except that some of the resistors are of 1% tolerance, which I assume causes no problems. The microphone is sealed at the rear and I even put some more Blu Tak on the rear for extra sealing. I have rechecked the circuit many times and also had a fellow electronics enthusiast go over the circuit but to no avail. Finally, I bought a new chip but this did not solve the problem. I was not able to do the initial check to test the output on the pins of the chip as I do not have a power supply with a suitable voltage. Once having solved the problem, my intention is to adapt a headset and mike to the Speakerphone. Would you please advise me where to connect the mike. My thoughts would be to perhaps attach the wires to where the electret mic is and a switch to switch High power enlarger queries I am very interested in the Regu­ lated Power Supply for Darkroom Lamps, described in your No­ vember 1997 issue. However, my enlarger is of larger format than the usual 35mm. It uses a 24V 250W halogen lamp, with corresponding­ ly higher current re­quirement to the design in the November issue (10.4A versus 8.3A). Could you advise whether the operating voltage can be in­creased to 24V and if so, whether the com­ ponent ratings of the components have the margin to handle the higher wattage? If not, could you indicate the order of modifications necessary to pro­vide for the 250W lamp. I suspect a 300VA transformer would be required with higher secondary voltage to provide the “overhead” for the control system. Maybe the diode heatsinking may need upgrading as well. I suspect that the control system will still be designed to “drop” about 15V, so a transformer secondary of about 30V is indicat­ ed. Beyond these comments, I seek your advice. (R. K., Wembley Downs, WA). •  We see no real problem with your modification. You will need a larger case to house the 300VA between the mic on the headset and the mic in the Speakerphone case. Would you please advise me as to whether there have been any notes or mods published that I have perhaps missed. I am also chasing a circuit which will enable me to attach a mic and headphone to interface with the standard Telstra issue phone. I un­ derstand there are commercial units that do this job. Finally, has S ILICON C HIP ever published a project to allow a fax machine to be operated on one phone line, allowing the fax to distinguish between the normal phone call and a fax call, in which case the fax inter­ cepts the fax call only? With my fax I have to switch my machine over to auto mode, in which case the machine transformer which should have a secondary voltage of 27-30V. The Jaycar MT-2136 should be fine. As you suggest, the bridge rectifi­ er may need a better heatsink, with perhaps a bigger aluminium plate for the trans­former, on which the bridge heatsink can be mounted. We also suggest that you use two Mosfets, both with heatsinks. The major problem will be the input voltage at REG1. This is specified as 35V maximum and you will end up with 45V, off load. A 12V 5W zener diode in series to the input should help. The resis­ tor feeding the power LED should be increased to 2.2kΩ. R3 should be increased to about 33kΩ and a 5kΩ or 10kΩ potentiom­eter fitted between R3 and R4. The wiper should be taken to pin 1 of IC1. Set the wiper of VR1 to 2.4V and adjust this new control until the light output is constant, as you vary the input voltage with a load connected. You will find one end of the new control will give increased light output as the input voltage increases and the other end will reduce the light output as the input voltage increases. The two controls will have to be “juggled” to keep the nominal output voltage at 24V with 240V input, while the light output is constant over -10% + 5% mains variation. answers all calls, or operate it man­ ually after I have been advised that a fax is about to be sent down line. (B. A., Mooroolbark, Vic). •  The electret volume is probably low because of the insen­sitivity of the particular microphone used in your circuit. Try another electret micro­ phone in its place such as the Jaycar Cat. AM-4008. This has a sensitivity of 66dB. Alternatively, Oatley Elec­ tronics (phone 02 9584 3561 or fax 02 9584 3561) have high sensitivity types of about 55dB which are better still. A circuit to add on a headset for the Speakerphone was published in the November 1988 issue. Photostat copies can be obtained for $7.00 (in­ cluding postage) by calling our office. Headsets for telephones should be available through tele­phone sales outlets such as Telecom and Optus. A headset phone is also available from Dick Smith Electronics. Unfortunately, a fax machine can­ not distinguish between a voice or fax call until it is answered and the fax tone is de­tected. This can be remedied by what is called a “Duet” line where you have two separate phone num­ bers for the same phone line – one for the fax and the other for the phone. The phone ring is different for a fax call and so the machine automatically answers it unless the call is voice in which case the phone rings normally. Contact your phone service provider for information on this facility. More bass punch for a music system Three months ago my 14 year old son saved up his “odd job” money and bought an Akai AC-MX 46 Mini System, twin cassette/CD/radio, with two fairly small speaker boxes. The amplifier output is only 5W per chan­ nel and the speakers have a quoted frequency response of only 95Hz to 18,000Hz. He thought that it would be OK but it’s not taken him long to realise that he needs lots of “bass boost” to sound even near good. So now he wants something better. His search through SILICON CHIP and the Jaycar and DSE catalogs have turned up the December 1993 25W amplifier module, to drive a 12-inch paper cone woofer (Jaycar Cat CW2125) in about a 4.5 cu.ft. enclosure, facing down, raised off the carpet about 10cm. The first problems are that the input sensitivity for the 25W amplifier is not stated and there is no provision for a volume control. How can he add one? On the input or as a variation to the feedback loop? The only outputs from his Akai unit are the 4Ω speaker clips. I assume he will need to some­ how mix these into one channel for the amplifier input, without upsetting the normal speak­ers. We have not “got into” the Akai amplifier. It may be possible to find a suitable point to pick up a line out and fit a socket on the back panel. I hesitate as the unit is still under guar­ antee, although it would probably be the better way to go. Your recom­ mendations please. (R. F., Laura, SA). •  The input sensitivity of the am­ plifier will depend on the maximum March 1998  89 Avoiding charger melt-down I noted the problems of a cor­ respondent with his 10A bat­ tery charger, as featured on page 82 of the January 1998 issue. He may find that changing the 4.7kΩ resis­ tor in the secondary of the driver transformer to 12kΩ will help keep the Mosfet saturat­ed and running cooler during prolonged heavy charging. Other suggestions include pot­ ting the inductor to stop the core whistling and insulating the 15V regulator from the heatsink to avoid the current sensor being bypassed. This situation can arise if the battery being charged happens to be earthed to the same source as mains earth; eg, a motor-home auxiliary battery. This brings me to the override switch and R1 (27kΩ). A 12V battery would have to be pretty sick not to initially set the 6V op amp output high. Its own 56kΩ pull-up resistor power output which in turn, is de­ pendent on the supply rails. If you build the amplifier with ±25V supply rails, its maximum (unclipped) power output will be 25W into an 8-ohm load. Under this condition, the input sensitivity will be 200mV RMS. A 10kΩ potentiometer may be installed at the input to serve as a volume control. The left and right signals from the 4-ohm music system speakers may be mixed together via 4.7kΩ resistors. However, if you want to use the 25W module as a bass chan­nel only, you really need a crossover network as well, so that the module only han­ dles bass frequencies. The closest we have come to meeting this need was the subwoofer crossover in December 1995. Super glue degrades FM circuit I built the FM Stereo Transmitter and did the alignment. It just would not work, as M. N., of Bankstown stated in the “Ask Silicon Chip” pag­ es of the December 1997 issue. The multiplex and pilot tones were pres­ 90  Silicon Chip would then be in parallel with R1. It seems therefore that R1 should be at least 56kΩ. Alternatively, for a dead-flat 12V battery, 56kΩ would be ideal to get things started since the initial charge rate should be limited. This would also get 6V batteries started. Come to think of it, a rather dead 24V battery charging at 12V and two op amps active could possibly be induced to greater effort with the override switch as well. One final point: I understand that pins 9 & 10 of the TL494 can sink up to 200mA and this is sufficient to drive a diode. It seems therefore that an optocoupler could well re­ place the transformer and switching transistors. With the zener being tied to 55V via a suitable limiting resistor and bypassed during the off cycle via the coupler output, this would reduce costs and provide the Mosfet gate with a genuine floating DC pulsed drive. (J. L., Ferny Hills, Qld). ent but no oscillation or RF output. The cause turned out to be that I had used a cheap super glue to fix the coil formers in position. Cleaning it off the surrounding tracks gave some output. The total solution was to scrape the surface of the board so as to remove any trace and use nail polish to glue them. Now the unit works well. (G. H., Fairview Park, SA). Speed control for fans I am considering building the 5A drill speed controller published in the September & November 1992 is­ sue of SILICON CHIP. I want to use it to control the speed of a ceiling fan. I am sick of replacing the existing controller which has burnt out several times. Do you foresee any problems? (M. B., Para Hills, SA). •  Don’t even think about it. The drill speed controller is only suited to mo­ tors with brushes and commutators. By contrast, virtually all 240VAC fans are shielded pole types; ie, a variant of an induction motor. The trouble with the drill speed con­troller is that it applies what is virtually chopped DC to the motor and this will not work with an induction motor. The solution is to use the fan speed control featured in the January 1990 issue. In essence, this is a conven­ tional light dimmer with snubber circuits and it is used in conjunction with the tapped iron-cored inductor which is the basis of the conventional fan speed control. The relevant back issue is available from the SILICON CHIP offices at $7 including postage. Model railway speed indicator I was wondering if it would be possible for you to design a kit for an HO scale speed indicator. I have seen one reviewed in “Model Railroader” magazine and would like to obtain one. (K. M., Altona, Vic). •  Such a project is certainly feasible but it is a little too specialised for us to feature it in SILICON CHIP magazine. Even if we did publish it, it is unlikely that any of the kitset suppliers would decide to make it available. In that case, the best way to obtain a unit would be to buy it direct from the US supplier. Query on Multi-Spark CDI I am building the Multi-Spark CDI described in the Septem­ ber 1997 issue and I am thoroughly confused. There is no value shown for C3 on the circuit or wiring diagram but the parts list quotes three different values. I’ve read right through the text and I can’t find any mention of this, so am I going nuts? (P. O., Oberon, NSW). •  Sorry about that. It is fairly easy to miss but the informa­tion you want is on the circuit diagram on page 20 of the Septem­ber issue, in the bottom righthand corner. C3 should be 0.47µF for a V8, 0.15µF for 6-cylinder and 0.12µF for a 4-cylinder. C3 determines how many sparks are produced for each firing, as shown in Table 1 on page 23 of that article. Amplifier PC board change I have a question concerning the 500W power amplifier re­ cently de­ scribed in SILICON CHIP. I am hoping you can explain why, on page 25 (August), page 55 (September), page 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” ORDER FORM B AC K IS S U E S MON TH YEAR MON TH YEAR P R IC E E AC H (in c lu d e s p & p ) Australia $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; Jun 89; Aug 89; May 90; Aug 91; Feb 92; July 92; Sept 92 & Nov-Dec 92 are sold out. All other issues are currently in stock. TOTA L $A B IN D E R S Please send me _______ S ILICON CHIP binder(s) at $A12.95 + $5.00 p&p each (Australia only). Not available elsewhere. ecial See Sp r – ffe Subs O 0 e g Pa 4 $A SUBSCRIPTIONS ❏ New subscription – month to start­­____________________________ ❏ Renewal – Sub. No.________________   ❏ Gift subscription ☞ RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia ❏ $A112 ❏ $A59 Australia with binder(s)** ❏ $A138 ❏ $A72 New Zealand (airmail) ❏ $A145 ❏ $A77 Overseas surface mail ❏ $A160 ❏ $A85 Overseas airmail ❏ $A250 GIFT SUBSCRIPTION DETAILS Month to start__________________ Message______________________ _____________________________ _____________________________ ❏ $A125 **1 binder with 1-year subscription; 2 binders with 2-year subscription YOUR DETAILS Your Name_________________________________________________ (PLEASE PRINT) Address___________________________________________________ Gift for: Name_________________________ (PLEASE PRINT) Address_______________________ _____________________________ State__________Postcode_______ ______________________________________Postcode___________ Daytime Phone No.____________________Total Price $A __________ ❏ Cheque/Money Order  ❏ Bankcard  ❏ Visa Card  ❏ Master Card 9am-5pm Mon-Fri. Please have your credit card details ready 92  Silicon Chip ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail coupon to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia Scanners and IRQs I recently obtained a Microtec scanner and a feature of this par­ ticular scanner is that you can loop the printer through the scanner. But the setup did not work too well. I am still not exactly aware what is going wrong but sooner rather than later the computer could not find the scanner again after using the printer. As my computer was still under warranty, I did the right thing and took it to the retailers and asked them to install another parallel port. When I got the computer back it worked for about 10 minutes and then crashed. It did not take long to work out that the reason for the crash was the new parallel port. This was after several restarts and a good deal of very bad language. All these troubles disappeared magically after pulling out the offending parallel port card. However, this left me with a scanner, a spare parallel port and about $400 down the drain. I got around the scanner problem for a while by plugging it into LPT1 so that the computer could find it at switch-on and then, after doing all the scanning, unplugging the scanner and plugging the printer in. Then I purchased the December 1997 issue of SILICON CHIP and lo and behold there was your article 59 (Septem­ber), page 69 (October) and page 73 (October) the photos show that Q4 & Q5 are positioned so that their flat surfaces are touching to achieve thermal bonding while Q1 & Q2 are positioned so that their round surfaces with the answer in full detail. You have to reserve the IRQ and DMA for PnP not to have a lash at it. Ten minutes after reading your article, what I thought was a useless spare parallel port was back in the com­ puter and after reserving the IRQ for it has been working like a beauty ever since. You realise, of course, that all of this is leading up to a question. I only have one (1) IRQ left on my computer. Does that mean that somewhere in the near future a program is going to fail for lack of IRQs or DMAs? As you can see I am not sure at all how it works. Why and what for have you got two versions of Quick Time on your computer? Tweak UI looked interesting too. What is it? Is there such a thing as a PnP parallel port? I always thought that if you set the jumpers on an addon card to occupy a certain IRQ, then the computer automatically reserved it for that device. (R. M., Robinvale, Vic). •  We will answer your questions in order. First, you should not have software problems because only one IRQ is left. IRQs are predomi­ nantly required by hardware devic­ es and unless you add additional hardware into your computer which requires IRQs there should be no problem. Unfortunately, the limited num­ ber of IRQs in a computer is a are touching? Have you inserted Q1 & Q2 incorrectly, because in the overlay drawing on pages 56 & 57 (September) Q1 & Q2 have their flat surfaces facing each other? (R. L., Melbourne, Vic). •  You are very observant. There is legacy of the good old days when designers believed that no-one would ever need more. Little did they know . . . QuickTime for Windows lets you play QuickTime video clips. It is generally loaded as an add-on to software requiring it and often comes on the same set of discs or CD-ROM as that software. The reason there were two versions on our computer is that one is the 16-bit version while the other is the 32-bit version. We’ve left the older 16-bit version there in case it’s required by some older programs. Tweak UI is a handy utility that’s included in Microsoft’s PowerToys. As its name suggests, it lets you tweak the Windows 95 interface. It’s often included on the CD-ROMs that come with some computer magazines or you can download it from the Microsoft web site. Printer ports are not regarded as PnP devices; they are usually set up as part of the basic operating system and stay there forever more. PnP devices are often switched around or upgraded as the user’s needs or demands require. Setting the jumpers on a legacy (ie, non PnP) card to occupy a certain IRQ is no guarantee that the IRQ will be reserved, as you have found with your parallel port. Reserving IRQs in the system BIOS is the only way to ensure success. no mistake. The photos show one of our prototype amplifiers while the published pattern and parts layout has been changed to enable the tran­ sistors to be mounted with flat faces together. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. March 1998  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly on a separate sheet of paper, fill out the form below & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my Signature­­­­­­­­­­­­__________________________  Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086 or 8096: $140.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 and 68HC12 now combined at the new low price of $75. Debug monitors: $70 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 or 80C320 Simulator (fast, now incl. 80C320): $70. Disassemblers for 12 CPUs only $75. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, the 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $189, $35 tax, $10 p&p. 20-pin SOIC adaptor only $70. Credit cards accepted. GRAN­TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150 or Internet: http://www.grantronics.com.au HOMEMADE GENERATORS: how to instructions. Eight pages free text and colour photos on the Internet at: http://www.onekw.co.nz/ RTN Parallax Australia distributor. Parallax Basic Stamp modules BS1IC, BS2-IC and BS1 chipsets all ex stock. Carrier boards for the above also stocked. PicBus and StampBus modules also avail­able. Guaranteed best pricing and technical back up. Email: nollet<at>mail.enternet.com.au http://people.enternet.com.au/~nollet Ph/fax (03) 9338 3306 SIMPLE PIC84 PROGRAMMER: various models available. Also PIC-driven moving message and digit displays. EST Electronics (02) 9789 3616, Fax (02) 9718 4762, or www.nettrade.com.au/sesame/ CAMERAS $99 TINY 36 x 36mm Robust Cast Aluminium Case (see p72 SC Dec). DOME $99. 32 x 32 PCB Modules $79! SONY CHIPSET 400 x 0.05 MODULES $99! COLOUR MODULES $239! 450 LINE COLOUR $369. Options/Accessories: 14 Lenses 2.1-12mm. Microfine Focus, Infra-Red Cut, Pass & Polarising Filters. 50 LED INFRA-RED or SUPER BRIGHT RED Lamp Kits $29! Our range includes 380-570 Line Resolu­ t ion, 0.2-0.05 lux Low Light & Infra-Red sensitive, 1/4" & 1/3" CCD Sensors from SONY, SHARP & SAMSUNG, 28 x 28 PCBs, Digital Signal Processing Colour & UP TO 24 MONTH WARRANTY!!! Before you buy ask for our ILLUSTRATED PRICE LIST with Ancillary Equipment & Application Notes. Allthings Sales & Services 08 9349 9413 Fax 08 9344 5905. ELECTRONIC ENGINEERING SOLUTIONS: No matter what problem what industry we will find you a solution that meets your needs. Specialising in schematic & PCB design, custom Windows based software, embedded control, Windows/PC based test equipment, turnkey solutions. Fast turn around with competitive rates. DAMUE PTY LTD, 46 Whitby Road, Kings Langley NSW 2147. Phone (02) 9624 2802. Fax (02) 9624 2651 or E-mail alovell<at>ibm.net THE ORIGINAL IS STILL THE BEST. Our CCTV - TV/VCR Video/Audio Inter­face Module combines 3 functions (Mod­ulator, Mixer & Antenna Booster) & features: a Phase Locked Loop for Stability/Accuracy, 48 Channels, Two-Stage Booster, Test Pattern, Proven Design & Reliability. Over 14 Years in Production. ONLY $20! All­things Sales & Services. Ph 08 9349 9413. PCBs MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics Ph/fax (02) 9554 9760. sesame<at>nettrade.com.au http://nettrade.com.au/sesame/ MicroZed has stocks of SX Key programming kit from Parallax. $320. See http://www.microzed.com.au/~microzed 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. MicroZed Computers BASIC STAMPS & PIC Tools SPECIAL STEAM BOAT KITS $14 A HOT SPOT FOR CHEAP PCB SUPPLIES, raw stock, drills etc plus quality manufactured boards is located at http://www.accsoft.com.au/~acetronics or phone 02 9743 9235. Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. SX Key Ver 1.0 now in stock. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 014 036775 Fax (02) 6772 8987 http://www.microzed.com.au/~microzed Most Credit Cards OK 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. HARD TO GET MODULES & KITS. Laser diode module, 650nm, 15mW, 3V-5V, easy adjustable focus, brass case, 31mm long, 10mm diam. 25cm wires. $140. Same LD module but 5mW, $40. Kit 113 control 2 unipolar steppers to 3A from a PC. All contained in RS232 D-shell case. $27. Kit 109 control one unipolar stepper with 5804 PRESTON ELECTRONIC COMPONENTS Now at 172 HIGH STREET, PRESTON, VIC (Corner of Bell and High Streets) Phone: (03) 9484 0191 Specialising in a wide range of: TV Antennas – Resistors – Cables – Circuit Boards – Capacitors – Sprays – PCB Artwork – Instrument Cases – Relays – Kit Sets – Semiconductors (all types) – Trimpots – Photo Sensitive – Transformers – Switches – Alarm/Security Equipment – CB Radios & Accessories. We are approved resellers for Altronics, DSE and RPG Products! IC. $27. P/P extra. All components, PCB & software supplied. Software may be d/l free from our web site at http://kitsrus.com Email: peter<at>kitsrus.com Fax: (852) 2725 0610 DIY Electronics. DONTRONICS can be found at: http://www.dontronics.com SILICON CHIP FLOPPY INDEX WITH FILE VIEWER Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. Price $7.00 each + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 9979 5644 & quote your credit card number; or fax the details to (02) 9979 6503. Please specify 3.5-inch or 5.25-inch disc. March 1998  95 14 Model Railway Projects Shop soiled but HALF PRICE! Embedded Pty Ltd.......................71 Harbuch Electronics....................73 Instant PCBs................................95 Jaycar .........................................33 SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) Norbiton Systems........................71 Microgram Computers...................3 MicroZed Computers...................95 Oatley Electronics........................27 Premier Batteries.........................43 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 Preston Electronics......................95 Printed Electronics.......................95 Quest Electronics........................75 Card No. Resurrection Radio......................75 Signature­­­­­­­­­­­­___________________________  Card expiry date______/______ Street Dick Smith Electronics..................... ................................ IFC,OBC,14-17 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. This book will not be reprinted Name Advertising Index ______________________________________________________ PLEASE PRINT ______________________________________________________ Suburb/town_________________________________ Postcode_________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). Rola Australia..............................95 Scan Audio..................................31 Silicon Chip Bookshop.................65 Silicon Chip Binders/Wallcht........87 Silicon Chip Software..................13 Smart Fastchargers.....................31 Zoom EFI Special........................91 Silicon Chip Binders ★  Heavy board covers with 2-tone green vinyl covering ★  Each binder holds up to 14 issues ★ SILICON CHIP logo printed in goldcoloured lettering on spine & cover REAL VALUE AT $12.95 PLUS P &P Zoom Magazine.........................IBC _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: Price: $21.95 plus $5 p&p each (Aust. only) •  RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. •  Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. 96  Silicon Chip R AUSTRALIA’S BEST AUTO TECH MAGAZINE It’s a great mag... but could you be disappointed? If you’re looking for a magazine just filled with lots of beautiful cars, you could be disappointed. Sure, ZOOM has plenty of outstanding pictorials of superb cars, but it’s much more than that. If you’re looking for a magazine just filled with “how to” features, you could be disappointed. Sure, ZOOM has probably more “how to” features than any other car magazine, but it’s much more than that. If you’re looking for a magazine just filled with technical descriptions in layman’s language, you could be disappointed. Sure, ZOOM tells it in language you can understand . . . but it’s much more than that. If you’re looking for a magazine just filled with no-punches-pulled product comparisons, you could be disappointed . Sure, ZOOM has Australia’s best car-related comparisons . . . but it’s much more than that If you’re looking for a magazine just filled with car sound that you can afford, you could be disappointed. Sure, ZOOM has car hifi that will make your hair stand on end for low $$$$ . . . but it’s much more than that. If you’re looking for a magazine just filled with great products, ideas and sources for bits and pieces you’d only dreamed about, you could be disappointed. Sure, ZOOM has all these . . . but it’s much more than that. But if you’re looking for one magazine that has all this and much, much more crammed between the covers every issue, there is no way you’re going to be disappointed with ZOOM. Look for the February/March 1998 issue in your newsagent From the publishers of “SILICON CHIP” March 1998  97