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January 2001  1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.circuitmaker.com Contents Vol.14, No.1; January 2001 FEATURES 4 LP Resurrection: Transferring LPs & Tapes To CD PC multimedia technology makes it easy to transfer your LPs and tapes to CD. You can even clean up the sound in the process – by Greg Swain 14 Biorecognition: Checking Your Identity Keys and access cards are on the way out. Biorecognition machines can check that you really are who you say you are – by Jon Reid 32 Look Mum, No Cables Wireless networks are gaining in popularity and costs are coming down. Here’s one that’s a cinch to install – by Greg Swain LP Resurrection: Transferring LPs & Tapes To CD – Page 4. PROJECTS TO BUILD 22 The LP Doctor: Cleaning Up Clicks & Pops It cleans up clicks, pops and noise on LPs and even includes a stereo RIAA phono preamplifier – by Leo Simpson & John Clarke 36 The WaveMaker: An Arbitrary Waveform Generator Use this simple circuit with your PC to generate oddball waveforms. It does standard sine, triangle and square waves as well – by David Sibley 66 2-Channel Guitar Preamplifier, Pt.3 The LP Doctor: Cleaning Up Clicks & Pops – Page 22. Final article shows you how to build the preamps and reverb module into a metal rack case – by John Clarke 72 Digital Reverb – The Missing Pages We messed up and two pages from last month’s article went missing. The person responsible has been sent to a Siberian salt mine. 76 PIC Programmer & TestBed Got a concept you’d like to try before building a full prototype? This unit lets you test new PIC circuits and is great for learning too – by Barry Hubble. The WaveMaker Arbitrary Waveform Generator – Page 36. SPECIAL COLUMNS 56 Serviceman’s Log Ain’t no mountain high enough – by the TV Serviceman 86 Vintage Radio The 32V 5-Valve Operatic Mignon – by Rodney Champness DEPARTMENTS 2 53 55 61 64 Publisher’s Letter Product Showcase Electronics Showcase Circuit Notebook Mailbag 75 91 93 94 96 Subscriptions Form Ask Silicon Chip Notes & Errata Market Centre Advertising Index PIC Programmer And TestBed – Page 76. January 2001  1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Peter Smith Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0408 34 6669 Regular Contributors Brendan Akhurst Louis Challis Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Technology has its benefits – and its drawbacks OK, how many of you noticed the obvious mistake in the December issue? There were no prizes for spotting it and it caused a great deal of chagrin, if you can use such a mild term, in the SILICON CHIP offices. If you didn’t spot the error, I’ll put it down to having flitted over those two pages (twice) and not being particularly interested in the affected article on digital reverberation. For those who spotted it and wondered just how such a pain­ful mistake could occur, the answer is, all too easily. Nor can we fall back on the standard excuse, used countless times by publishers in years past, that it “was a printer’s error”. These days any mistakes you see are entirely ours, apart from the occasional page having poor colour because of registration prob­lems. No, since our magazine is produced CTP – computer to plate – the printer has very little input into the final product. The entire editorial contents of SILICON CHIP and the advertising content is all compiled as computer files and sent to the printer on a CD-ROM. Any corrections to the proofs are either emailed or sent to our FTP (file transfer protocol) site and they are then zotted into the computer at Dubbo in the blink of an eye. And that’s how the error occurred. Some small changes needed to be made to the proofs on pages 84 & 85 and these were quickly made to the original file and zapped up to the printer. Trouble was, the pages were laid out using the previous month’s pages as a template. That’s a pretty standard procedure but the previous month’s equivalent pages were 42 & 43. This was not noted, the changes were made and sent and no-one realised that pages 42 & 43 had just been changed – for the worse. This story has been a little simplified but that is the gist of it. Could it happen again? I sincerely hope not but you never know. That is one of the drawbacks of computer technology. You can make changes so easily and without careful checking (which did not happen) things can go awry. As soon as we discovered the error we placed the missing pages on our website and they are reproduced this month, starting on page 72. We apologise to all those readers who were inconven­ienced. Having said all the above, we don’t shrink from continuing to adopt the new technology. It has given us considerable produc­tion benefits, better print quality and helped to control costs. We could not and would not wish to go back to the old days when everything was in the hands of the printers. But it would have been nice to use the excuse “because of a printer’s error”. Since most of you will be reading this at the end of Decem­ber, I wish all of you a very prosperous New Year. We are very much looking forward to the new millennium. Leo Simpson                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       We welcome Bankcard,                 Mastercard and VISA               NO SURCHARGE!             The missing link        Website, online catalogue                 and shop: www.mgram.com.au                  Phone: (02) 4389 8444              sales<at>mgram.com.au                 info<at>mgram.com.au            Fax: (02) 4389 8388                                                                         FreeFax: 1 800 625 777 MicroGram Computers    Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 Vamtest Pty Ltd trading as MicroGram Computers ABN 60 003 062 100. January 2001  3 MGRM0101 All prices subject to change without notice. LP Resurrection How to transfer LPs & tapes to CD Dust off your old collection of LPs and tapes! If you have a CD writer, you can transfer some of them to CDs and even clean up the sound in the process. It’s easy to do and doesn’t cost the earth. I F YOU’RE OVER 30, you probably have a large collection of LP records and cassette tapes. It’s also probable that you no longer listen to them, mainly because CDs are easier to use and have better sound quality. Few people these days can be bothered trying to maintain a record By GREG SWAIN player in good nick. Nor can they be bothered with the cleaning rigmarole that goes with vinyl LPs, to keep dust and lint from clogging the stylus and degrading the sound quality. Inevitably though, there are lots of “old favourites” scat­tered through our LP collections. And despite their inherent limitations, LPs are still capable of producing excellent sound quality – provided they’re not too worn and the record player and pickup stylus are in good nick. For this reason, it makes a lot of sense to transfer some of those old favourites to CDs. These are not only much more con­venient to play but can be used in a car CD player as well. What’s more, the sound quality is “locked in” to the CDs and your LPs are protected from further wear. What’s required CD writer prices have tumbled over the last two years, so burning your own CDs is now very affordable – assuming you have the right equipment. The inventory reads like this: a turntable (or tape deck), a phono preamplifier, the right connecting ca­ b les, audio recording software, and a Pentium-based (or equival­ ent) PC equipped with a CD writer, a decent sound card and lots of hard disk space. The sound card is a critical element here because it’s used to convert the analog signal from your LPs to digital format. This means that the sound quality will depend on the card’s on-board A/D (analog-to-digital) converter. Don’t expect to get good results from an old Sound Blaster 16 or any of the cheaper cards of that era. 4  Silicon Chip Fig.1: the turntable output must be fed to the line input socket of the sound card via a phono preamplifier, as shown here. Most recent brand-name sound cards should provide good re­sults, however. These include Sound Blaster 64 and Sound Blaster Live, plus sound cards from Diamond (eg, Diamond Monster Sound), Turtle Beach and CrystaLake. Conversely, the CD writer is not critical and all brands should give similar results. It’s the quality of the digitised audio on your hard disk that you have to worry about – not the CD writer itself. By the way, if you’re buying new, go for a CD-RW drive so that you can also use the new re-writable CDs. The write speed of the drive isn’t critical but try to choose one with a read speed of 24x or better. An IDE drive will be cheaper than a SCSI drive but note that your PC’s motherboard must have a reasonably fast IDE interface. The record player The record player (or turntable) really is a vital link in the chain. Examine it carefully – the stylus should be in good condition, all the controls should operate smoothly and there should be no audible “wow” and “flutter” (ie, pitch variations due to turn­table speed variations). If the turntable speed varies as a record is played, check the condition of the belt or idler wheel. These rubber parts deteriorate over time and may require replacement. Check also that the tonearm operates freely and that the tracking weight and anti-skating settings are correct. The turntable speed should be accurately set using a stroboscope disc, if you have one. If the player hasn’t been used for some time, it will prob­ably need a good clean up. Depending on the brand, you may also want to apply some machine oil to the moving parts of the mechan­ ism underneath the platter, to make sure it all operates correct­ly. Don’t hesitate to replace the stylus if it’s worn or coated with gunk (examine it under a magnifying glass). Replacement styli and cartridges are readily available from hifi stores and from Tandy Electronics. New record players are also readily available and at quite reasonable prices. For example, Tandy Electronics has a fully-automatic belt-drive turntable for less than $200.00. This unit even includes a switchable phono preamplifier, which means that you can couple it directly to the auxiliary input of an amplifier (or even directly to the line input of your sound card). Connecting it up As already mentioned, the sound card digitises the analog audio that comes from the turntable. However, you can’t directly connect the turntable to the sound card. Instead, the turntable’s output must first be fed to a phono preamplifier, which amplifies the weak signals from the pick-up cartridge. During this process, the phono preamp equalises the signal Fig.2: this is the setup for an integrated amplifier with an inbuilt phono preamp. The sound card goes in the tape loop of the amplifier. January 2001  5 Fig.3: here’s how to set the Play and record line levels of the sound card. Any unused inputs should either be muted or not selected, to prevent unwanted noise. by boosting the bass and cutting the treble frequencies. This is necessary because LPs are recorded with the bass frequencies heavily attenuated, while the treble frequencies are boosted. The phono preamp reverses this situation, to give Fig.4: when recording for CD, you should sample at 44.1kHz and choose 16-bit stereo sound. a level frequency response (hence the term “equal­isation”). In most cases, it’s just a matter of feeding the turntable outputs into the “Phono” inputs of a stereo amplifier (or pream­plifier). The “Tape Out” or preamp out signals are then fed into the line input socket of the sound card – see Fig.2. Alternatively, you can use a separate phono preamplifier (eg, as described SILICON CHIP, April 1994). The output from this is then fed into the sound card as shown in Fig.1. Of course, if your turntable includes a phono preamplifier (eg, the Tandy unit noted above), then you can go direct to the sound card. Another option is to build the “LP Doctor” project de­scribed in the current issue. This not only has the necessary stereo phono preamplifier but also includes circuitry to filter out clicks and pops. It can be used for cleaning up the sound before it goes to your sound card, or you can simply use it with your hifi system. An audio cable with two RCA plugs at one end and a stereo 3.5mm jack plug at the other will usually be required to make the connection from the preamplifier. The RCA plugs go to the left and right output sockets on the preamp, while the 3.5mm plug goes to the line input socket on the sound card. These cables are readily available from electronics retail­ers for a few dollars. Alternatively, you can buy a cable with a 3.5mm plug and two RCA sockets, if that is what you require. If you don’t have “Tape Out” sockets on your amplifier, try taking the output from the headphone socket. In that case, you may need to use a cable with 3.5mm stereo plugs on either end and possibly also a 3.5mm to 6.5mm adapter for the headphone socket. Note, however, that the signal level from a headphone socket varies in response to the volume control setting. This means that you’ll have to carefully adjust the line-in gain of the sound card using the volume control panel on the PC, to prev­ent signal overload (Fig.3). What if you’re using a cassette recorder? In this case, the output is already at line level, which means that you can feed the output signal directly into the line input socket of the sound card. Monitoring the sound Fig.5: CoolEdit 2000 comes with an array of filters for noise reduction and other special effects that let you “operate” on the recorded sound. 6  Silicon Chip To complete the setup, you need some way of monitoring the music that’s being recorded. If you’re using a separate phono preamp, simply Looking for a top-notch sound card with lots of bundled software? Creative’s Sound Blaster Live Platinum provides Dolby Digital 5.1 surround sound and includes a microphone, a remote control unit and a device called “Live! Drive IR”. The latter functions as the IR receiver and also provides a range of front panel inputs so that external devices can be easily connected. The bundled software includes Sound Forge 4.5 XP, Creative PlayCenter 2 for encoding and decoding MPS and WMA files, and Creative Media RingTalk for PC-to-PC voice calls and messaging over the Internet. connect the sound card’s line output to a line input on a separate amplifier (eg, to an auxiliary or tuner input), as shown in Fig.1. As before, you’ll need a cable with a 3.5mm stereo plug on one end and two RCA plugs on the other. Alternatively, if the phono preamp is integrated into the amplifier, you’ll need to connect the sound card’s output to the tape monitor input of the amplifier – see Fig.2. In other words, the sound card is effectively connected into the tape loop of the stereo amplifier. Stopping noise pickup Computer monitors can easily induce noise into sensitive audio equipment, so position your monitor as far away from the rest of the gear as possible. This particularly applies to the turntable – the pickup cartridge can be rather sensitive to stray electromagnetic fields. If hum still proves to be a problem, try earthing the base of the turntable directly to the metal case of the preampli­fier. Another tip is to plug everything into the same power point (via a multiple socket strip) to reduce the possibility of hum due to earth loops. Naturally, you must use shielded audio cable for all con­nections between the turntable, preamplifier and sound card. Cleaning the records To minimise surface noise, it’s vital that you thoroughly clean your LPs. A soft bristle brush and some warm Creative’s sound card includes all the usual inputs and outputs on the backplane connector, plus onboard connectors for CD-ROM and DVD drives and for the Live! Drive IR unit. January 2001  7 Fig.6: the Audio Cleanup Plug-In for CoolEdit includes filters for click and pop removal, for hiss reduction and for clip restoration. You can either use one of the presets or tailor the filter to requirements. water can be used to remove any dirt that may have found its way into the grooves. Be careful not to damage the LP – brush carefully in the direction of the grooves and don’t scrub too hard. Don’t use a detergent, as this can leave a film residue on the surface of the LP. An antistatic cloth and a record cleaning brush will also come in handy. Once again, these are available from hifi stores and electronics retailers. Getting ready An audio CD accepts about 650Mb of data, so you’ll need to set aside plenty of hard disk space when making audio recordings. As a minimum you will need about 1Gb but 1.5Gb is better. Basically, there are five steps involved in transferring the material across: (1) select the line input of the Fig.7: CoolEdit’s dynamic noise reduction filter works by loading a noise profile – usually sampled from the beginning or end of a track – and subtracting this from the rest of the recording. sound card and set the signal level; (2) record and save the LP tracks to the hard disk (in wav format) using suitable recording software; (3) process the audio to reduce noise or to apply special ef­ fects; (4) assemble the tracks in order using CD writer software; and (5) burn the CD. Of these, step 3 can be regarded as optional, particularly if you’re getting good sound straight off your LPs. If that’s the case, you’re probably better off not applying any filtering at all to avoid any impact on the music. Conversely, LPs that are worn or scratched will need to have some filtering applied (and perhaps some other pro­cessing as well), depending on the type of material and the severity of the problem. Before trying to record anything, you need to turn up the gain controls for the line input of the sound card. You do that by first double-clicking Fig.8: CoolEdit’s graphic equaliser comes with a number of presets for changing the sound, or you can adjust the sliders yourself. 8  Silicon Chip the loudspeaker icon in the system tray (at the end of the taskbar) to bring up the “Play Control” mixer panel (Fig.4). Make sure that the Play Control (master), Wave and Line-In are not muted and that their volume sliders are turned well up so that you can monitor the sound. Next, click Options, Properties, Recording and OK to bring up the “Record Control” dialog box. Select Line-In and again make sure its volume slider is well up the scale. It’s a good idea to mute the other inputs and outputs (CD Audio, MIDI, etc), so that they cannot add to the noise. Recording software It’s the job of the recording software to set the sampling rate for the incoming audio signal and to save the recorded file to the hard disk. There are lots of programs available and these invariably include level indicators and controls to play, record, stop and (sometimes) pause the audio. What’s more, many programs include a staggering array of filters and effects that let you tailor the sound to your tastes. Want more bass? No problem – just load the bass-boost filter or a graphic equaliser. What about some treble cut, or a 50Hz notch filter, or some reverberation or flanger effects? They’re all there for you to try. Want to filter clicks and pops, reduce surface noise or cut tape hiss? There are filters to do these jobs as Fig.9: if your recording needs a bit more bass, CoolEdit’s FFT filter can take care of that too. well. You can even copy, cut and paste sections of the recordings to produce special effects if you want. A popular software choice is Adaptec’s Easy CD Creator 4 Deluxe which features a utility called “CD Spin Doctor”. CD Spin Doctor can perform all the basic tasks required to transfer LPs to CD, including the ability to save audio files in the required wav format. It can also perform fades and includes some basic filtering software to reduce pops, clicks and hiss. If you want something a bit fancier, consider programs like Syntrillium’s Cool Edit 2000 and Sonic Foundry’s Sound Forge 4.5 XP. Trial copies of these programs (and other programs mentioned in this article) can be downloaded from their respective websites (see panel). One program that’s easy to drive and doesn’t cost the earth is Diamond Cut’s Audio Restoration Tools – either DC-Art or the better-featured DC-Art32. The latter features a comprehensive array of filters and special effects and is certainly very effec­tive when it comes to getting rid of clicks. An alternative package is Dart PRO 32 from Digital Audio Restoration Technology However, if you’re into serious audio restoration and want the very best results, you’ll need to step up to the “Diamond Cut Millennium” package which can simultaneously run multiple filters for fast audio processing. Another package in the same league is Dart PRO 98 but you’ll Fig.10: the FFT filter is also handy for filtering out 50Hz and 100Hz hum. And there are lots of other filters to try. need to be serious – these packages retail for around $450.00 and $500.00 respectively. Making the recording Whichever program you use, the act of recording LP tracks and saving them to disk is a straightforward exercise. Usually, the first thing that you have to do is set the sampling rate. To record CD stereo sound, you’ll need to choose 16-bit stereo and sample at 44.1kHz – see Fig.4. The next job is to set the recording level. All decent audio-recording programs come with sound level meters and you have to adjust the line level control (Fig.3) while a record is playing but with the recording paused. Basically, the level is set so that the left and right channel signal peaks just fall short of activating the overload indicators. Anything more than that and you run the risk of introducing distortion due to clipping. On the other hand, don’t set the level too low as this will give a poor signalto-noise ratio. Don’t let any nasty clicks and pops fool you into turning the gain down too far. It’s OK for these to trigger the overload indicators as they can be filtered out later. Once the level has been set, it’s just a matter of clicking the record button to start the recording. Before doing that though, make sure that you’ve turned off your screen saver. If a screen saver activates in the middle of a recording, it can leave a gap in the music. Generally, it’s best to record each track in turn and save it as a separate file. This not only cuts down on individual file sizes but makes it far easier to edit the tracks later on. The way in which you go about this is up to you. However, the easiest method is to simply lower the stylus onto the lead-in grooves of the track What About Copyright? Many LPs and tapes are still protected by copyright and, as far as we can determine, you are not entitled to copy these to other media – not even for your own use. That even applies to LPs and tapes that you have paid for and which are your personal property. Of course, you are at perfect liberty to copy material if there is no copyright, or if the copyright has expired, or if permission has been obtained from the copyright holder. In addition, there can be exceptions under the Copyright Act for educational and professional bodies. By contrast, consumers in the United States have had the right to copy music they have purchased to other media for personal use, ever since the Home Recording Act of 1992. It seems that Australian copyright law is behind the times in this regard. January 2001  9 P.C.B. Makers ! • • • • • • • • If you need: P.C.B. High Speed Drill 3M Scotchmark Laser Labels P.C.B. Material – Negative or Positive acting Light Box – Single or Double Sided – Large or Small Etch Tank – Bubble Electronic Components and Equipment for TAFEs, Colleges and Schools Prompt and Economical Delivery FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE We now stock Hawera Carbide Tool Bits KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 ALL MAJOR CREDIT CARDS ACCEPTED Silicon Chip Binders REAL VALUE AT $12.95 PLUS P&P  Heavy board covers with 2-tone green vinyl covering  Each binder holds up to 14 issues  SILICON CHIP logo printed on spine & cover Price: $A12.95 plus $A5 p&p each (Australia only) Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. 10  Silicon Chip Typical of the CD rewriters that are now available, Creative’s CD-RW Blaster 121032 can burn CD-R disks at 12x speed and CD-RW disks at 10x, while playback speed is 32x. The unit comes bundled with blank CD-R and CD-RW disks, a CD carry case and four software applications for recording, drag-anddrop file copying, creating digital photo albums and MP3 playback. to be recorded and click the Record button. Then, at the end of the track, you click the Stop button to stop the recording. Don’t worry if you accidentally record part of the follow­ ing track before hitting the Stop button. This unwanted material can easily be discarded later on. The same goes for any unwanted material at the start of the track and for any noise between the tracks. Once the recording has been made, it can be saved to a file on the hard disk. It can then be played back (just load the file and click the Play button) so that the sound quality can be checked. Alternatively, some programs record to a temporary file on the hard disk so that it can be checked before actually being saved. A worthwhile feature of the better programs is that they let you preview the waveform of the recorded audio – see Figs.5 & 11. The important thing here is that there be no flattening of the signal peaks, as this indicates clipping. If this occurs, the track should be discarded and re-recorded at a reduced level. By the way, be sure to save your files in the “wav” format if you intend to burn a conventional audio CD. Some programs also give you the ability to save your files in MP3 format, which is fine if you have an MP3 player. Alternatively, you can run the wav files through a dedicated MP3 ripper/encoder (eg, Music­Match or easy MP3). Cleaning up the sound As stated previously, if you’re getting clean sound straight off an LP, you won’t need to do much signal processing. However, one thing you’ll want to do is completely silence (or mute) the sound between tracks. In Cool Edit, you do that by zooming in on the track “lead-in” portion of the waveform, highlighting it with the mouse and then clicking Transform (on the Toolbar) and selecting Silence from the drop-down menu. The same is then done for the “lead-out” section at the end of the track. DC-Art32 uses a slightly different method. In this case, the highlighted segment is silenced by clicking Edit and select­ing Mute from the dropdown list. While you’re at, you might like to also shorten the lead-in and lead-out times by deleting certain sections. If there’s a lot of noise in the recording, then you’ll want to clean up the sound using various filters. There’s usually a strict procedure for going about this, however. Clicks and pops are usually dealt with first. In DC-Art32, you run the Impulse Noise Filter with the “Vinyl LP” option checked. This filter doesn’t just chop out the clicks, though. As it eliminates each click, it also fills in the “hole” by mathematically calculating what the waveform should be at that position and inserting this instead. In other words, it effectively interpolates the waveform across the brief gap that’s left by eliminating the click, to eliminate any audible effects. Equally effective “de-clickers” are included in other pack­ages, although sometimes these are available only as extra-cost plug-ins. Cool Edit 2000, for example, requires the Audio Clean­up Plug-In for click removal and this plug-in also does hiss remov­al. Sometimes, particularly nasty clicks and pops will require manual editing. Typically, you do that by zooming in on the waveform at the click location (confirmed by playing back that section of the waveform), then selecting the click and interpo­ lating the waveform across the selected area. Many programs also include a dynamic noise reduction filter and this is run after click filtering. The procedure usually involves sampling the noise from the track lead-in or lead-out grooves to build up a noise profile which is then subtracted from the rest of the recording. The idea here is to reduce the noise as much as possible while leaving the music intact. Fairly obviously, you have to perform this type of noise reduction before muting the beginning and end of the track. If you perform the muting first, there will be no noise left to sample and the dynamic noise reduction filter won’t work! On the other hand, dynamic noise reduction should be carried out after click removal, so that no large clicks are present in the noise profile. Problems like rumble can often be eliminated by running a high-pass filter, while notch filters can be employed against 50Hz and 100Hz hum in the recording. Similarly, a low-pass filter may prove effective in reducing DC Audio Restoration Tools – Making It Easy Fig.11: the trial version of DC-Art32 lets you record only the first 90 seconds of a track. This program is easy to drive and comes with lots of filters for cleaning up the sound. BEFORE Fig.12: the waveforms at right show the effect of running DC-Art32’s impulse filter on a track with lots of audible clicks. Note that the clicks are missing from the bottom two waveforms (on the yellow background). The remaining “spikes” are musical transients (they look like spikes due to the compressed horizontal scale of the waveforms). AFTER Fig.13: if you yearn for a valve sound, you’ll love this Virtual Valve Amplifier filter. You even get to choose between different types of valves and amplifier output configurations. January 2001  11 Burning the CD Fig.14: Adaptec’s Easy CD Creator really is easy – you just drag the tracks to be recorded into the workspace window. You can then drag the tracks around to rearrange their order and even play individual tracks back prior to burning. high-frequency noise. At each stage in the process, you should play back the filtered track to make sure you’re happy with the result before saving it to file. If the filter doesn’t have the desired effect, reset the parameters and run the filter again. Once you’ve cleaned up the noise, you might want to run a graphic equaliser or a preset filter to enhance the bass or treble, to liven up the sound. This can help revitalise the sound if an LP is worn, for example. Many programs also have filters for fade in and fade out and for adding compression and expan­sion. Another thing that you’ll probably want to do is run the “normalise” or “normalise gain” filter over each file. This filter searches for the highest peak in a file and adjusts the gain so that it just reaches the maximum recordable level. Just remember that the recording should be fairly close to this level in the first place, to get the best signal-to-noise ratio. It’s important to save your files to a separate folder, to make it easy to assemble the tracks when you run the burner software later on. Depending on the track length, you can expect files sizes in the 25-60Mb range and they should add up to no more than about 630Mb to allow sufficient overhead for the burner to write the contents. 12  Silicon Chip Fig.15: the “Disc-At-Once” option closes the recording session and prevents further data from being added to the disk later on. A session must be closed before the disk can be played back but you must leave the disk open if you plan on adding further sessions. It might take some work to get your tracks sounding just right but burning them to a CD requires little effort. Programs like Easy CD Creator are a no-brainer to use, no matter whether you’re creating audio or data CDs. The main thing to remember is that you are recording audio, not data, so select the audio CD layout option. You must also “close” the recording session if you want to play the CD back afterwards. You can either select this option before burning the disk or you can close the session afterwards. If you have a full complement of tracks, select the Disk-at-Once mode if this option is present. This mode burns and closes the disk in one operation. Alternatively, you can elect to close the session but leave the disk open so that you can to add tracks later on. Assuming that you have Easy CD Creator, you assemble the tracks to be recorded by dragging them from the file list to the workspace window. This done, the track order can be rearranged (just click and drag) and you can even play back individual tracks by right-clicking them and selecting “Play” from the drop-down list. This launches a bare-bones CD player with Play, Stop and Pause buttons (Fig.14). Finally, click the Record button to start the burn. Most programs give you the option of doing a test run first but if you’re the impatient type, you can bypass this step. Provided you have a reasonably fast hard disk, you should be able to burn at speeds of 4x or higher. Don’t interrupt the computer during this process, otherwise you’ll end up with a drink coaster. If that all sounds too hard, just run Easy CD Creator’s wizard. It really is a matter of following the proverbial bouncing ball – right up to burning the CD. SC Check Out These Online Sites Diamond Cut Productions (for DC-Art32 and Diamond Cut Millennium http://www.diamondcut.com Syntrillium Software (for Cool Edit 2000) - http://www.syntrilli­um.com DARTECH Inc (for DartPro) - http://www.dartpro.com Sonic Foundry (for Sound Forge XP 4.5) www.sonicfoundry.com Multimedia’n’Music - http://www.multimedia-music.com.au (for retail copies of Diamond Cut and Dart Pro software (all version). They also have an excellent tutorial site at http://www.enhance­daudio.com.au January 2001  13 In the recent futuristic sci-fi film “Gattaca” an astronaut candidate was going for an interview. He was asked to place his hand on a scanner and, after a second or so, was told he could leave. “What about the interview?”, he asked. “You’ve just had it” was the reply. Far fetched? Perhaps. A long way off? Perhaps. But then again, perhaps not. With biorecognition technology, it could be a lot closer than you think. – Checking to see if you really is YOU! By JON REID* 14  Silicon Chip D o you use keys to enter your workplace? That is now old technology. In the not-too-distant future you can expect to have some sort of biological scan to enable you to enter your workplace, club or other organisation, to do a financial transaction or even use your workplace computer. All this comes under the heading of biometrics or biorecognition. Some people regard the digital age as dehumanising. But the joke is on them: the human body lies at the heart of plans to wire banks, streamline government payments, secure the workplace and even to protect computers, driver’s licenses and credit cards. So the age of the body-part password is upon us. Our unique biological characteristics, such as hand geometry, eye structure, fingerprints, voice patterns, even our odour – are being mapped and digitised as part of the booming new biometric business. Biometric technology operates much as portrayed in recent films such as “Mission Impossible”. Computer scanners confirm a person’s identity by scanning a biological feature, then matching it with a digital file containing those exact characteristics. Identifiable traits can be physical, such as a hand contour or retina patterns. They can be behavioural, such as voice modulation, or even typing methods. Some can seem a little outlandish; features being tested for singularity among the planet’s six billion people include knuckle creases, body odours and even acoustic head resonances The HP4 hand scanner. Note the finger guides which ensure the user places his or her hand in the right spot. (have you tapped your head lately?) So, are we ready to have the patterns of our fingers, eyes and speech stored in central databases and traded like commodities by direct marketers, insurance companies and government agencies? It is already being done. Currently in NSW, bailees submit to biometric fingerprint scanning at their local police stations for identification. If the bailee is wanted or needs to be detained by police, the doors can be automatically locked. In the USA, travellers between the state of Montana and Canada are verified by voice recognition before access back and forth is granted. At Los Angeles international airport, US residents do not have to wait in long queues for passport verification; they simply place their hand into a reader and then they may pass through. At the recent Gartner Group’s IT Expo Bill Gates made the comment that “biometric technologies – those that use human characteristics such as fingerprint, voice and face recognition, will be among the most important IT innovations of the next several years”. Authentication One of the most important ethical issues of this technology is to acknowledge that its purpose is not only to confirm a person’s identity, but more importantly, to authenticate that person’s eligibility to access a particular service. Essentially, there are three components to authentication: Identification: this is a one-time process to establish an individual as a unique, named person. Confirmation of Eligibility: again, this is a one-time process to confirm that the named individual is eligible for the benefit or service to be accessed. Authentication Credential: this is something that identifies the individual as eligible and permits them to access the service or benefit on a recurring basis. Traditionally, these credentials have been in the form of cards, passwords or PINs. Now bi- The V-20 finger scanner in use. Here the finger is placed on the optical window and recognition normally takes less than a second. January 2001  15 This Fingerscan has both finger sensing and card swiping for increased security. ometrics are being used, with greatly enhanced results. Privacy To some people the need to identify themselves is intrinsically distasteful and demeaning. It is symbolic of the power that any organisation they are dealing with has over them. Having to present a biometric is considered by some as not just a form of moral submission to authority but also physical submission. To them, biometric identification represents the ultimate invasion of personal privacy. Certain biometric techniques do require touching a communal reader, which may be unacceptable to some, due to cultural norms or religious beliefs. Others are apprehensive about interacting with a machine because they are not familiar with the technology or are afraid that biometrics may cause them discomfort or harm. As noted earlier, the biometric techniques that have gained the most user acceptance are fast, easy to use and perceived as the least intrusive, such as fingerscan, hand geometry and facial recognition systems. There is no evidence that any biometric system has adversely affected or injured any user. In addition, no commercially used systems present health risks, leave marks or take physical samples from users. Use of biometric identification is interpreted by some as a questioning of their reputation and trustworthiness. They perceive a requirement to give a biometric as a reversal of the pre16  Silicon Chip sumption of innocence – shifting the burden of proof. Without pre-existing evidence of wrongdoing, organisations are requiring them to sacrifice their personal privacy. These privacy concerns are heightened by the fact that fingerprints are strongly associated with law enforcement. As a result, finger scanning may be seen not only as an invasion of privacy but also as an indignity and an embarrassment. Some people feel they are being treated like criminals. However, this concern does not appear to be shared by the majority of people. For example, one Australian survey found that 87% of respondents thought finger scanning was a legitimate identification requirement, 91% believed that the use of finger imaging was justified to control entry to high security areas, 77% to verify the identity of persons cashing personal cheques for large amounts, and 76% to identify persons using credit cards for major purchases. More than four out of five (83%) respondents rejected the view that using finger imaging to verify a person’s identity was akin to treating them like presumed criminals. Applications Biometrics was originally developed (in the 1950s), for secure access control, initially to sensitive military sites and intelligence organisations. Today, this remains a core application for the technology, due to the unique benefits it offers. First, security can be greatly enhanced, as the system is not assumptive. All other access technologies assume that, if a person possesses the correct key, card, token, code or password, then he/she must be that person. Biometrics is reality-based, in that it requires the physical presence of the person in question. Second, the costs, time and complexity of managing an access control system are greatly reduced, as no infrastructure needs to be issued – people require only their fingertip to gain access. Third, security levels are maintained, as unauthorised or accidental ‘handing-on’ of cards, keys, etc cannot occur. Time and Attendance In the past decade, employers have recognised the unique benefits of replacing traditional work-reporting practices (time clocks, attendance books, etc) with biometric devices. Because it requires the physical presence of the correct individual, it eliminates the potential for an employee to clock on or off for a colleague or for them to overstate the number of hours worked – some employers have reduced their total payroll by about 2%. As an example, Woolworths Australia uses Fingerscan devices for its 75,000 employees in almost 500 stores – and has done so for over three years. Another application is providing access to the rear of ATMs across Australia by Armaguard. IT Security Information Security Biometrics is now replacing managed password and other access methods to IT systems containing sensitive or secure data. Oracle, the world’s largest database company, has recently released an optional software module which enables access to its databases via a Fingerscan device – the only biometric device it has ever endorsed. Other manufacturers such as Key-tronic have incorporated biometric scanners into their keyboards. Compaq have recently released the first laptop with a built-in scanner. Securing workstations and servers with fingerprint login instead of passwords also reduces the amount of time wasted by computer help desks. In some cases the savings can more than 20% of total time spent by the help desk. Available technology Biometric equipment is currently available in Australia in the following formats: * Fingerscan * Iris Scanning * Handscan * Vein Scan * Voice Scan * Facial Scan * Eye Scan * Retina scan * Signature Scan * Odour Scan Fingerscan Fingerscan does not take a fingerprint, which is prohibited by privacy legislation in Australia (other than used by police). Instead, it takes a 3-dimensional optical scan of a person’s finger-tip, looking at such features as colour, width, height of ridges in the skin, etc. The scanning is performed by a CCD camera. A person is ‘enrolled’ by placing their finger a number of times against a glass square – this process takes about 30 seconds. A unique file, or ‘template’ of that person’s finger is then stored in the device’s memory. To verify their identity, a person simply calls up their ‘template’, and places their finger, once again, against the glass. A comparison is made between the stored file and the live finger and verification is made in less than a second. An electronic log of all transactions is recorded, to provide an irrefutable audit trail of events. The Fingerscan is usually mounted against a wall or suitable vertical surface. Earlier units consisted of a All of the information on authorised persons can be held in a central data base with virtually un-limited numbers. Some systems are so clever they automatically upgrade the data base if the person’s scan reveals changes (eg weight loss!). microprocessor board with an inbuilt communications front end. Today it uses miniature embedded 486-based computers. The Fingerscan V20 has an Ethernet 10BaseT interface, a multi-language screen and is capable of remote administration via modem. It can also connect to common alarm panels. Moreover, it is secure from illegal penetration and override from the unsecured side as the unit is not capable of switching the correct signals to the alarm panel if the unit is ripped off the wall. Handscan This technique uses a three-dimensional image of the hand and measures the shape, width and length of fingers and knuckles. A user places a designated hand on a reader, aligning the fingers with positioned guides. First, each employee is “enrolled” in the system. Three hand images, measuring more than 90 three-dimensional characteristics, are taken and averaged to become the initial master record or “template” for that employee’s hand. The enrolment process takes between 30 seconds and two minutes for each employee. After that, every time an employee uses the Hand Reader, the template is updated by recomputing the measurements to include the most recent hand image. By continually updating the template, the Hand Reader automatically adjusts for the normal changes in a person’s hand, caused by gaining or losing weight, aging, etc. More than 32,000 templates can be stored in each Hand Reader. The time/attendance software contains a template management system, which stores the templates on a central database. Employees are assigned to the Hand Reader(s) that they are authorised to use. Since many Hand Readers can be networked to the central computer, a virtually unlimited number of templates can be stored. Hand placement is simple, and the Hand Reader provides visual feedback, with a series of LEDs, to help users position their hands correctly. The need to reposition a hand disappears after the person has used the reader a few times. Once an employee learns proper hand placement, verification takes less than a second. The scanner disregards surface details, such as fingerprints, lines, scars and dirt, as well as fingernails, which may grow or be cut from day to day. Hand scanning is widely used in Australia in security situations. The most well known application of this technology was at the 1996 Summer Olympic Games in Atlanta, USA. Hand geometry was used to identify about 150,000 athletes, staff and other participants. Handscan is currently installed at more than 50,000 sites worldwide. Costs of biometric equipment Finger scanning units can be purchased commercially for approximately $2000 to $3000 each while hand scanners are sold for about $2500 to $3500 per unit, depending on the options required. Retina scanners still are rather expensive at about $5500 to $8000. Voice scanning hardware can be purchased from $300. Further information can be obtained from the following web site: www. bio-recognitionsystems.com.au SC *Jon Reid is CEO of Bio Systems who can supply, install a full range of Bio Equipment. Phone (02) Fax (02) 9487-5771. Recognition support and Recognition 9489-9379; January 2001  17 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 Clean up the clicks & pops on your vinyl records with the Gotta lotta records? Never play ’em because of the dreaded clicks and pops? Well, now you can start enjoying your records again. How? Just play them through the LP Doctor and it will get rid of most of the clicks and pops so you can enjoy them at any time. By LEO SIMPSON & JOHN CLARKE M any people have big collections of vinyl records but they can’t be bothered playing them because of the surface noise, clicks and pops. The truth is, we’ve all been spoilt by the pristine, noise-free sound of CDs. In fact, if you have not listened to some of your old LPs for a while, you might be shocked at just how bad they sound... There used to be two solutions to the problem of clicks, pops and noise on LP (long-play) records. You could (try to!) ignore them – not particularly satisfactory. Or you could download your ! LP to your computer via your ! sound card and use one of the ! many software programs which ! allow you to edit audio files before you dub them to CDs. You ! can then play the new disk on ! your home CD or DVD player, in your car or portable disk player, and never have to play the old vinyl record again. To find out more about this approach, go to our feature article on this subject starting on page 4. For many people, the above approach is the complete answer. They get a CD which sounds better and they can play it any time they like. But as always, there are drawbacks to the computer/software/CD approach. First, you do need a reasonably fast Pentium or equivalent computer 22  Silicon Chip with a late model sound card, a CD Writer and the necessary software, all of which can add up to a pretty big investment. Second, as good as these sound editing programs are, only the more expensive let you listen to the disk as the processing takes place. In other words, they don’t all do this magic processing “on the fly”. Instead, you have to play the record into your computer via an RIAA preamplifier and sound card and store the various Features Stereo RIAA preamplifier included Bypass mode Treble filter for noisy recordings Output level adjustment Signal clipping indicator Indicators for click muting in each channel tracks as .WAV files on your hard disk. Then you set the software to work to process the .WAV files and finally, they can be dubbed onto a CD with your CD Writer. By the way, you are going to need a pretty big hard disk (say with at least 1 or 2 Gigabytes to spare) to store and process these .WAV files. Third, and this is more of a subjective problem than a technical one, even if you do create CDs to replace your old vinyl records, you will not have the satisfaction of looking at the sleeve notes while you are listening or deciding which track to play next. That’s one of the nice features of the old 12-inch disks. Sigh... Finally, even if the process of CD dubbing is entirely satisfactory, who is going to go to the trouble of dubbing their entire LP collection to CD, just for the benefit of being able to listen to any or all of them occasionally? So if you a large collection of records, you need an alternative to CD dubbing, one where you can listen to any of them at any time, substantially free of clicks and pops. You can do this by playing them through the LP Doctor. LP Doctor + CD Writer Maybe you don’t have computer but you may want to consider a CD Recorder such as the Marantz DR6000 pictured elsewhere in this article. These make dubbing all sorts of audio material to a CD a real doddle but they do not include any means of removing noise, clicks and pops from your LP records. This is where the LP Doctor can also play a part. You dub your LPs to a CD Recorder via the LP Doctor and get a very worthwhile sound improvement, especially on jazz and classical music records; ie, those with quiet passages The LP Doctor can be teamed with any turntable having a magnetic cartridge so you can listen to your LPs without clicks and pops or you can feed its signal into a PC sound card for processing and dubbing to CD. which can be really plagued with clicks and pops. Or maybe you do have a computer, CD Writer and so on but you are without a sound editing program. Here again, you can dub your records to CD on your computer via the LP Doctor. LP Doctor – what it does OK, we’ve talked about where and why the LP Doctor might be used but we have not been specific about what it does, apart from the general Fig.1; this block diagram shows the left channel only. The signal from the RIAA preamplifier is fed via a delay so that the click detector has sufficient time to detect and fully mute signal transients. theme of click and pop removal. Let’s describe specifically what it does. The LP Doctor has two independent channels which monitor the left and right signals. When a click or pop is sensed, the signal is muted for a brief interval to greatly reduce its amplitude or completely remove it. At the same time, it can apply a slight degree of treble cut filtering, to reduce surface noise and also make the click attenuation more effective. While it does work well at greatly reducing bad clicks and pops, it does not do well on low level clicks which are difficult to discern from the general program signal. In other words, if you have trouble hearing clicks and pops unless you listen up close to the speakers (or wear headphones) then the LP Doctor will also have trouble. On the other hand, while many pop and rock records might have a fairly serious amount of clicks and pops, the general signal level is usually so consistently high that it does not matter – the music masks the noise. So really it is records that have a wide dynamic range, such as classical music and jazz, with quiet passages among the louder ones, that are more likely to be plagued with clicks and pops. This is where the LP Doctor can work very well. But the LP Doctor does not fix bad surface noise which may be caused by lots of dirt being ingrained into the record grooves or may be the result of fungus attack on records which have been stored for long periods in fairly humid conditions. In fact, if you have a record which has January 2001  23 Fig.2: this is the circuit of the left channel. IC3 is the digital delay which is set to 1ms at switch-on by ICs17, 18, 19 & 20. 24  Silicon Chip January 2001  25 There are also three indicators on the front panel. Two indicate whenever a click is detected in either channel while the third is a clipping indicator. The output level control needs to be adjusted so that there is normally no clipping. As well as providing click suppression, the LP Doctor includes a high performance RIAA preamplifier, making it compatible with virtually any amplifier, PC sound card or free-standing CD Recorder. The preamplifier is designed to suit the majority of moving magnet cartridges but may not have enough gain to suit moving coil cartridges. On the rear panel, there are two pairs of RCA sockets. One pair is for the magnetic cartridge signals while the other pair is for the line level output signals to a stereo amplifier, sound card or CD Recorder. Fig.3: the overall performance of the magnetic cartridge preamplifier, measured by applying an inverse RIAA signal to the input. Our preamplifier is not ideal but it is pretty close – the curve deviates by no more than ±0.3dB over the whole frequency range from 20Hz to 20kHz. been subject to a bad fungus attack, there is nothing you can do because the damage is permanent. And even if you do use the LP Doctor on a regular basis, there is still no substitute for keeping your records as clean as possible and also making sure that your stylus is free of any gunk that may be picked up from the record grooves. In fact, you really need to examine the stylus after every record side has been played, to make sure that it is clean. By the way, if you do lots of critical listening to CDs via headphones, you probably still won’t enjoy vinyl records after they have been processed by the LP Doctor. Let’s be honest: there is still going to be a huge difference in sound quality between an old LP and a pristine CD. Operating features The LP Doctor is housed in rack-mounting case measuring 426mm (W) x 44.5mm (H) x 277mm (D), not including the side-mounting flanges. Of course, you don’t have to mount a rack-mounting case in a rack! There are three knobs on the front panel: an output level control, a click sensitivity control and a selector switch with three positions: Bypass, Process (click suppression) and Filter. The latter setting adds treble cut to the click suppression, as noted above. Operating principles So how does the LP Doctor eliminate record clicks and pops? Essentially, each channel has a comparator which looks for the sudden large signal excursions which produce a click or pop. When the click signal is detected, the audio signal is muted (switched off) to prevent the click from passing through to the output. The signal is shut off for a short period (about seven milliseconds) so that it is more or less unnoticed by the listener. The problem is, by the time the comparator has detected the signal and has muted it, some of the click will have already passed through to the output. So only part of the click or pop will have been muted, resulting in a shorter click but still just as loud and annoying. Specifications Frequency response of RIAA phono preamplifier.... within ±0.3dB from 20Hz to 20kHz (see Fig.3) Signal-to-Noise........................................................... -83dB unweighted (20Hz to 20kHz) with respect to 10mV input at 1kHz and                       560mV; -88dB A-weighted (-84dB and -89dB in Bypass mode, respectively) Total Harmonic Distortion (THD)................................ 0.3% at 1kHz and 1V, 3% <at> 10kHz <at>-20dBV (0.008% <at> 1kHz and .01% <at>                      10kHz in bypass mode) Separation between channels.................................... -67dB at 100Hz; -73dB at 1kHz; -58dB at 10kHz Treble filter................................................................. -3dB at 10kHz, 12dB/octave slope Maximum input signal................................................ 190mV RMS at 1kHz Signal delay time....................................................... 1ms Click muting time....................................................... 7ms 26  Silicon Chip Inside the LP Doctor. It uses a digital delay in each channel for effective muting of clicks and pops. Therefore, we need to incorporate a delay circuit. This allows for the response time of the comparator and muting circuit such that the delayed signal has the full muting applied to it. In this way, the comparator/muting circuit can attenuate the whole of the click or pop instead of just the latter part of it. Block diagram Fig.1 shows the block diagram of the LP Doctor. For simplicity, only the left channel is depicted; both channels are completely separate and identical. First, the signal from the magnetic cartridge is fed to the RIAA (Recording Industry Association of America) preamplifier. From there, the amplifier signal is fed via four separate paths: (1) straight through to the output via the bypass position on switch S2; (2) to the one-millisecond digital delay unit (IC3) which converts the analog signal to a digital signal, feeds it into memory, shuffles it out again with the required delay and converts it back to analog; (3) to the click detector which operates switch IC4 where click muting takes place and (4) to the clipping detector which drives a front panel LED to indicate that the signal level is too high. Circuit description The full circuit of the LP Doctor, apart from its power supply, is shown in Fig.2. As with the block diagram, we are only showing the left channel. The equivalent IC and other device numbers for the right channel are shown in brackets. The phono (magnetic cartridge) signal is fed directly from the input socket via inductor L1, a 150Ω resistor and a 47µF bipolar capacitor to the non-inverting input, pin 3, of op amp IC1a. The inductor, series resistor and shunt 100pF capacitor form a filter to attenuate RF signals which may be picked up by the phono leads. The RIAA equalisation is provided by the feedback network comprising 16kΩ and 200kΩ resistors and the .0047µF and .015µF capacitors, connected between pins 1 & 2. This network provides the standard equalisation time constants of 3180µs (50Hz), 318µs (500Hz) and 75µs (2122Hz). The circuit also includes the IEC recommendation for rolloff below 20Hz. This is provided by the 1kΩ resistor in series with the 10µF capacitor and by the 10µF coupling capacitor to the 10kΩ potentiometer VR1. There is also rolloff in following stages to ensure that the signal below 20Hz is attenuated. This rolloff prevents amplification of record warp and rumble which occur at sub-audible frequencies but could possibly overload an amplifier and loudspeakers. The gain of IC1a is 22.45 (27dB) at 1kHz with a boost of +13.1dB at 100Hz and a cut of -13.75dB at 10kHz. With a typical magnetic cartridge output, the gain provides us with a nominal 100mV of signal. This is further boosted by op amp IC2a, by a factor of 11, to produce a nominal signal level of 1.1V. The frequency response graph of Fig.3 shows the overall performance of the RIAA preamplifier. It was measured by applying an inverse RIAA signal to the preamplifier. The response should be a dead-flat line if the RIAA preamplifier is ideal. Our preamplifier is not ideal but it is pretty close – the curve deviates by no more than ±0.3dB over the whole frequency range from 20Hz to 20kHz. IC6a & IC6b are comparators which form the clipping detector and they monitor the signals from IC2a (left channel) and IC2b (right channel) via 10kΩ resistors and a 10µF coupling January 2001  27 Fig.4: this is how the click detection works. The top trace is the averaged signal at pin 5 of IC12a, while the lower trace is the rectified signal at pin 6. When a transient occurs, pin 6 goes above pin 5 and the comparator output goes low to trigger the monostable timer IC13. Fig.5: these scope waveforms show only a short click being detected and muted but they can last a lot longer than this so we have settled for a compromise muting time of 7ms. capacitor. The non-inverting input of IC6a is held at +1.14V while the inverting input of IC6b is held at -1.14V. Thus, IC6a monitors positive swings of the signal while IC6b monitors negative swings. So if the audio signal to the comparators exceeds 2.3V peak-to-peak (800mV RMS), LED1 will light. 16 provides the demodulation of the digital back to analog after the delay within the IC. The 22kΩ and 11kΩ resistors plus the 560pF and 150pF capacitors at pins 13 & 14 form another low-pass filter which removes the 500kHz digital switching artifacts from the now-delayed analog signal. Digital delay The output signal from IC3 passes through a final filter comprising a 270Ω resistor and .001µF capacitor and is then fed through a 10µF DC blocking capacitor to the analog switch, IC4. This is an optically controlled FET which has a low impedance when the internal LED is lit and a very high impedance when the LED is off. IC4 is controlled by the click detection circuitry involving IC11, IC12 & IC13. When switch IC4 isclosed, the signal passes through unaffected to pin 3 of op amp IC5a which is connected as a unity gain buffer. However, there is a wrinkle here because the 10kΩ resistor and .01µF capacitor following IC4 form a sample-and-hold circuit and the capacitor is constantly following the audio level as it is charged and discharged via the 10kΩ resistor. When switch IC4 is turned off, in response to a click, the voltage at pin IC3 provides the digital delay and this is set to provide a time delay of one millisecond by data fed into its pins 4, 5 & 6 at the moment of switchon. This initialising data is provided by ICs 17, 18, 19 & 20. We’ll briefly describe their operation later in this article. For the moment, though, all we need to know is that IC3 (IC7 in the right channel) are set to provide a one-millisecond delay. The input signal from IC2a is coupled into IC3 via some low-pass filter components comprising the 22kΩ and 11kΩ resistors at pins 23 & 22 of IC3. This filter rolls off at 12dB/octave above 36kHz to prevent quantisation errors in the analog-to-digital conversion process. The .068µF capacitor series 27Ω resistor between pins 20 and 21 form the integrator used in the analog to digital (delta-sigma type) conversion. The .068µF capacitor at pins 15 and 28  Silicon Chip Muting switch 3 of IC5a remains roughly where it was until the switch closes again. In this way, the signal is not muted down to zero but to its average level. This results in a less-audible muting effect and it duplicates the muting action of the best software packages in removing clicks. The signal voltage from the sampleand-hold circuit is applied to pin 3 of IC5a via a 10µF bipolar capacitor. This is included to avoid having the input bias voltage for IC5a from being applied to the output side of IC4. If it was, then an audible click would be produced each time IC4 switched on or off. IC5a’s output is applied direct to switch S2a and becomes the “Processed” output. It is also fed to op amp IC5b which provides the “Filter” output to switch S2a. IC5b provides a gentle treble cut at 12dB/octave above 10kHz. Click detection circuitry Apart from the delay circuit just described, the click detection circuit is really the heart of the LP Doctor. It takes the signal from IC2a and further amplifies by 4.7 in IC10a. It is then AC-coupled via a 1uF bipolar capacitor to a precision full-wave rectifier comprising op amps IC11a and IC11b, diodes D6 & D7 and associated Fig.6: the loading process for the delay codes which are fed into IC3 (and IC7) at switch-on. Serial data (lower trace) is transferred on the negative edge of SCK (centre trace). The REQ line (top trace) must be low before the following 12 clock pulses. The positive edge of REQ signals the end of the serial data stream. On the first clock pulse, the sleep data is input and this must be a low. The following six pulses are the delay codes while next are the low mute and ID1 and ID2 (identification codes). resistors. When the input signal goes positive, the output of IC11a goes low, biasing on D7 so that the gain is set by the 10kΩ input resistor R1 and the 10kΩ feedback resistor R2; thus gain is -1. This signal is coupled to the inverting input of IC11 via the 5.1kΩ resistor. Gain for IC11b is set by the 5.1kΩ input resistor and 10kΩ feedback resistor between pins 6 and 7 and is therefore -2. Overall gain of the input signal for positive signals is therefore -1 x -2 = + 2. However, there is another path for the input signal via the 10kΩ resistor R3 to pin 6 of IC11b. This signal gives a negative signal at the output of IC11b with a gain of -1. Adding the two gains Fig.7: this is the effect of the delay through IC3 and IC7. The top trace is the input signal and the lower trace is the delayed signal. gives us +1. For negative input signals the output of IC11a is clamped high, due to conduction of diode D6 and the cathode of D6 is held at ground, effectively switching the output of IC11a out of circuit. Signal then passes via the 10kΩ resistor R3 to pin 6 of IC11b. IC11b inverts the signal and provides gain at -1. Since the input signal is negative, the signal at pin 7 of IC11b is positive. Thus pin 7 of IC11b always goes positive, for both positive and negative swings of the input signal and so we have a precision full-wave rectifier. Trimpots VR2 and VR3 provide offset trimming for IC11a and IC11b respectively. These are set so that pin 1 and pin 7 of IC11 are at ground (0V) when no signal is applied. Comparator has floating threshold The rectified signal from IC11b is applied via the 27kΩ resistor and potentiometer VR4a to pin 6, the non-inverting input of comparator IC12a. It is also applied to pin 5 via a filter network comprising a 4.7kΩ resistor and 1µF bipolar capacitor, before being applied to the inverting input of IC12a. So IC12a has a slowly varying DC level at pin 5 and the rapidly moving signal level at pin 6 and it is looking for a sudden transient, ie, a click or pop, which will cause its output at pin 7 to go low. The Marantz CD Recorder is an attractive alternative to dubbing your LPs to CD via a computer. You don’t need a computer or to learn about new software and the result is much the same, when you process your LPs via the LP Doctor. January 2001  29 The oscilloscope waveforms of Fig.4 show how the click detection works. The top trace is the averaged signal at pin 5 of IC12a, while the lower trace is the rectified signal at pin 6. When a transient occurs, pin 6 goes above pin 5 and the comparator output goes low to trigger the monostable timer IC13. IC13 is a CMOS 555 connected as a monostable. It works in two ways. Normally, when pin 7 of IC12a is high IC13 is untriggered (as pin 2 is high) and the .0068µF at pins 6 & 7 of IC13 will be discharged and the output at pin 3 will be low. When pin 7 of IC12a goes low, it turns on transistor Q1 to maintain discharge the .0068µF capacitor and low at pin 2 of IC13 triggers the beginning the timing period. The result is a seven-millisecond positive pulse from pin 3 of IC13 and this turns on transistor Q2 which turns off IC4. IC13 also drives LED2 which gives a visible indication of the muting action. This is shown in the scope waveforms of Fig.5. This shows only a short click being detected and muted but they can last a lot longer than this so we have settled for a compromise muting time of 7ms. If IC12a detects a longer transient, it will hold Q1 on and keep the .0068µF capacitor discharged for longer and this will extend the muting period beyond the nominal seven-millisecond period. Comparator IC12b is there to provide power-on muting via IC13 and IC4. Initially, the 10µF capacitor at pin 3 of IC12b is discharged and pin 1 is low. When the 10µF capacitor charges via the 100kΩ resistor, its voltage goes above pin 2 and so pin 1 of IC12b goes high, to let IC4 unmute via IC13 and Q2. The scope waveforms of Fig.7 show the effect of the delay through IC3 and IC7. The top trace is the input signal and the lower trace is the delayed signal. Delay Control Power IC3 (and IC7 in the right channel) are set to the 1ms delay time via their REQ, SCK and DATA inputs at pins 4, 5 & 6 at switch-on. IC17 to IC20 are used to provide these clock and data codes and after they have done this, they have no more function in the circuit, until it is next switched on. They function in exactly the same way as in the Digital Reverberation circuit described in last month’s issue so we won’t go into the detail here, except to say that IC20, the 74HC165 serial shift register, is responsible (can we say that about a lowly IC?) for loading in the eight bits of data at switch-on. It is clocked by IC17, the 4060 oscillator/ counter while IC18 & IC19 perform related house-keeping tasks. The scope waveforms of Fig.6 show the loading process for the delay codes. The serial data (lower trace) is transferred on the negative edge of SCK (centre trace). The REQ line (top trace) must be low before the following 12 clock pulses. The positive edge of REQ signals the end of the serial data stream. On the first clock pulse, the sleep data is input and this must be a low. The following six pulses are the delay codes while next are the low mute and ID1 and ID2 (identification codes). The power supply circuit is shown separately on Fig.8. It uses a transformer with two 9V windings connected in series to give an 18V centre-tapped supply. This feeds a full-wave rectifier (diodes D1-D4) and the two 470µF 25VW capacitors. The resulting DC voltage is around ±12V. This feeds adjustable 3-terminal regulators set to give ±7.5V supply rails. The +12V supply is also applied to a 5V regulator, REG3, via diode D5. The diode isolates the supply to the input capacitors of REG3 when power is switched off. The idea is to maintain the +5V supply to the delay ICs (IC3 & IC7) to avoid switch-off thumps. The mains power switch is bypassed with a 250VAC-rated .001µF capacitor. This prevents arcing across the switch when it is switched off. The mains earth connects to the circuit earth via a 0.47µF capacitor to prevent hum in the signal where there is no connection to mains earth in any accompanying amplifier. Should the power amplifier be earthed, then the capacitor will minimise any resulting hum loop. Next month we will complete the presentation of the LP Doctor with all the constructional information and the parts list. SC Fig.8: the power supply of the LP Doctor provides +5V and ±7.5V rails. The 5V rail powers to the two delay chips. IN 0.001F 250VAC F1 150mA A SLOW BLOW 2200F 16V D1 - D4 4 x 1N4004 D5 1N4004 S1 250VAC 0V 470F 25V SC LP DOCTOR POWER SUPPLY 30  Silicon Chip +5V 10F 16V +7.5V 1k 4.7k 100F 16V 4.7k 100F 16V 470F 25V IN 2001 OUT ADJ 0.47F CHASSIS 2200F 16V OUT GND REG1 LM317 IN 9V N E T1 20VA 9V 0V 240VAC IN REG3 LM2940-5 ADJ OUT REG2 LM337 10F 16V 10F 16V 1k -7.5V SILICON $ 95* 10 CHIP’S inc GST Electronics TestBench ISBN 0 958522 9 2 8 A selection of from the page the best test equipment s of SILICON C www.silic HIP magazine onchip.c . om.au January 2001  31 Wireless networking LOOK MUM, NO CABLES By GREG SWAIN Fig.1: a simple Adhoc network. Here’s a wireless computer network that’s a cinch to install and get going. It works just like a regular network but without messy cables. W IRELESS NETWORKS have two big advantages: convenience and ease of set up. They’re convenient because there are no cables to install and they’re easy to set up for exactly the same reason. Usually, a wired network (LAN) is the most cost-effective method but it does tie the PCs to set locations. By contrast, a wireless LAN means that PCs can be moved from one location to another and still have network access – something that can be very useful for mobile users with laptops. A wireless LAN also has advantages in situations where it’s difficult to install cables or if you don’t want to drill holes through walls. And it can save you from digging up concrete paths if you want to “connect” two buildings together. In short, if you can’t go through it, over it or around it, a wireless network is the answer. Wireless network cards Although still relatively expensive, the cost of wireless networking is now on the way down. Diamond Multimedia’s HomeFree system has been 32  Silicon Chip popular at the bottom end of the market, although hampered by its rather leisurely 1Mb/s transmission speed. By contrast, this new system from Eumitcom Technology (and sold by MicroGram Computers) runs at a brisk 11Mb/s, which is far more useful for business applications. It’s based on PCMCIA wireless networking cards which plug straight into the PCMCIA slots fitted to laptop computers. Howev­er, by using a “PCMCIA-to-PCI Adapter”, they can be fitted to conventional PCs as well. Each PCMCIA card is actually a network card and radio tran­sceiver rolled into one. The omnidirectional antenna circuitry for the card is located at one end and protrudes from the laptop (or PC) by about 4cm when the card is pushed into place. The transceiver operates in the 2.4GHz band using spread spectrum wireless technology, to ensure security and reliability. What’s more, the cards don’t really need a separate base station (or access point) to operate. All you have to do is set up several computers with these cards and you have a working network (this is known as an “Adhoc” network). Of course, you still have to install the relevant network­ing protocols, set up workgroups and computer names, and share resources, just as you would for a conventional wired network. The setting up procedure for the PCMCIA card is straight­forward – just insert the card into its slot, reboot the computer and install the driver when prompted. You then install the con­ figuration utility software, which is supplied on a separate disk. Transmission mode Among other things, the configuration utility lets you set the channel number and the mode – see Fig.3. The mode is set to “Adhoc” for a small stand-alone wireless network or to “In­frastructure” if you intend using an Access Point. There are also options that allow you to encrypt the transmissions. The configuration utility also shows the current transmis­sion rate (or throughput), as well as the link quality and signal strength from an Access Point. The effective range for an Adhoc Fig.2: two or more Access Points can be using to create overlapping “cells” and to link networks together (eg, between buildings). An Access Point is also needed to interface a wireless network to a conventional wired LAN. This view shows the Access Point (centre) and two Wireless LAN PCMCIA cards. The PCMCIA cards function as a network card and radio transceiver rolled into one and can be used without the Access Point to create a simple “Adhoc” network – see Fig.1. January 2001  33 The PCMCIA cards can either be plugged directly into a notebook computer or used with a PC by installing a PCMCIA-to-PCI adapter or a PC Card Drive. network running at 11Mb/s is about 30 metres (line of sight), although greater distances are possible at reduced transmission rates. In operation, the system can automatically switch down to either 5.5Mb/s, 2Mb/s or 1Mb/s for line-of-sight ranges of 50m, 100m and 120m respective­ly. PCMCIA-to-PCI adapter Here’s a device that you probably haven’t seen before – it’s called a “Wireless LAN PCMCIA-to-PCI Adapt­ er” and it func­tions as a PCMCIA card to PCI bridge. In a nutshell, this card plugs into a spare PCI slot on your PC’s motherboard and accepts the wireless PCMCIA network card. The card slot is accessed through a cutout in the back­plane connector – you just slide the card in until it “clicks” home, just as you would with a laptop computer. Installing this card is straightforward enough, although your PC will need to have a couple of spare interrupt request lines (IRQs) – one for the adapter card itself and another for the PCMCIA card. The supplied setup diskette includes drivers for Windows 95 OSR2, Windows 98, Windows NT and Windows 2000. The setup program automatically identifies the operating system and installs the correct driver. You then slide the PCMCIA wireless LAN card into place and install the driver for this device. In case you’re wondering, the PCM- Fig.3: the Wireless LAN Configuration Utility, lets you set the channel number and mode. It also shows the transmission rate and indicates the link quality and signal strength from an Access Point. 34  Silicon Chip CIA-to-PCI Adapter works only with the wireless PCMCIA LAN cards. If you want to use other PCMCIA cards in a PC, take a look at MicroGram’s “PC Card Drive”. This device looks very similar to the other unit but has two slots and works with Type 1, 2 & 3 PCMCIA cards. In fact, it’s the PC Card Drive that’s pictured in this article. Naturally, it’s more expensive than the other adapter card (see below). Access Point An “Access Point” is required if you want to connect your wireless LAN to a conventional LAN. In addition, an Access Point effectively doubles the range between wireless PCs on the net­work, since it acts as a base station. You can also set up multi­ple Access Points with overlapping coverage areas so that mobile users can freely roam from one “cell” to the next. Similarly, two Access Points can be used to link two build­ing together, Fig.4: the Wireless LAN Configuration Utility is automatically launched at start-up and is minimised to the PC’s System Tray. Fig.5: the Access Point also comes with a configuration utility. Clicking the Scan button displays any detected Access Points, as shown here. Fig.6: double clicking an Access Point in Fig.5 brings up the dialog box shown above, so that you can assign it a temporary IP address. using Point-to-Point mode. Disarmingly simple in appearance, the Access Point is housed in a grey plastic box and is fitted with an omnidirection­al antenna at the back. Also on the back panel are an RJ-45 socket for connection to a standard network hub, plus an RS-232 socket which provides alternative connectivity direct to a PC. The Access Point also comes with a configuration utility which can be installed on any machine on the network – either wireless or wired. Clicking the Scan button in this utility detects the Access Point and displays it as shown in Fig.5. You then assign a temporary IP address to the Access Point (see Fig.6), after which you use the Access Point’s built in web server to assign a permanent address and to make other configuration changes (Fig.7). Alternatively, you can configure the Access Point to obtain its IP address from a DHCP server on the network. The bottom line We tested the system by fitting wireless PCMCIA cards to two computers – one a laptop, the other a conventional PC (via the PC Card Drive). To complete the setup, we plugged an Access Point into the hub on our wired network. Initially, we set the mode to Adhoc so that we could test the wireless network between the two computers fitted with the PCMCIA cards. The network came straight up – no problems. We then set the mode to Infrastructure” and scanned for the Access Point. It too came straight up and after running the configuration software, we had access between the wireless ma­chines and the wired segment of the LAN. In short, it all worked – what more can we say? Cost and availability Fig.7: the Access Point comes with an inbuilt web server. This lets you change the configuration settings, including assigning a permanent IP address, subnet mask and default gateway. The IP can also be obtained from a DHCP server. Unfortunately, you’re still paying for the R&D for this type of gear, so it’s not exactly as “cheap as chips”. At the time of writing, the Access Point (Cat. 11339) was priced at $1155; the Wireless LAN PCMCIA card (Cat.11340) at $490; and the Wireless LAN PCMCIA-to-PCI Station Adapter (Cat.11344) at $79 (prices include GST). The PC Card Drive (Cat.6523) retails for $259 but note that you don’t need this card unless you want to fit other types of PCMCIA cards to a PC. Normally, you would use the much cheaper PCMCIA-to-PCI Station Adapter instead. Further information is available from MicroGram Computers, Unit 1, 14 Bon Mace Close, Berkeley Vale 2261. Phone (02) 4389 8444. Their website is at www.mgram.com.au or you can email info<at>mgram.com.au SC for up-to-date pricing. January 2001  35 Need a weird signal waveform for testing a new circuit or to produce an unusual sound effect? Here’s a very low cost waveform generator which hooks up to the printer port of a PC and makes it easy to generate oddball waveforms at low frequencies. The software also lets you generate standard waveforms, just like a function generator – and even programmable DC voltage levels. By David Sibley The Wavemaker (or software-controlled arbitary waveform generator) fits into a small utility box and is connected to the PC’s parallel (printer) port via the multi-way cable coming from the rear. Power is supplied by a 12V DC plugpack. 36  Silicon Chip I f you’ve ever played with audio circuits (designing, servicing or whatever) you’ll know just how essential a signal generator (or function generator) is. But what happens if you want to generate a real “oddball” waveform – not your usual sine or square wave, not even a triangular or sawtooth. Perhaps it’s because an amplifier only misbehaves with certain types of signals. Perhaps it’s simply because you want a really unusual sound effect (eg for a theatrical production). Perhaps it’s for a host of other reasons. How do you go about it? The usual way to generate an ‘arbitrary’ waveform in R&D labs is by using an arbitrary waveform generator. Now that makes sense, doesn’t it! But these are usually big and complex instruments costing big bucks – and they can be very complicated to use, too. They’re a bit like a Formula 1 racecar: even if you could afford one, you probably couldn’t drive it. One or two home-brew arbitrary waveform generator designs have been published but they’ve generally used special components and these too have been pretty expensive. Sometimes you can get away with a low-cost function generator but (usually) these can only create standard waveforms – sine, square, triangle, sawtooth, etc. So if we can’t generate the waveform we want using a standard function generator, we’re forced to find another way of tackling the problem. When we need an unusual waveform it’s usually at a fairly low frequency — a few hundred hertz or so and often even less. In view of this, it seemed to me that you should be able to produce these waveforms using a really low-cost approach, based on using software running in a PC to send a ‘stream of digital samples’ out to a digital to analog converter (DAC). So I tried it. . . and it worked. That’s how this project came about. The hardware side is really just a ‘DAC in a box’, which hooks up to the PC’s printer port. The software in the PC does all the tricky part, preparing the waveform samples and sending them to the DAC. The project is called, for fairly obvious reasons, the “Wavemaker”. Speaking of software, I’ve written four separate programs to go with the Looking inside the case from the front. Note the cutout on the rear panel to allow room for the ribbon cable to exit. Wavemaker. One is a testing program, so you can quickly confirm which printer port the unit is connected to and check that the two are ‘talking to each other’. Another is a simple program which lets you use the Wave-maker as a programmable DC voltage source. A third program lets you ‘draw’ your arbitrary waveforms on the PC’s screen, and then save them as disk files. And finally there’s the Wavemaker program itself, which drives the generator box and gets it to ‘play’ either arbitrary wave files loaded from disk, or one of a range of standard ‘function generator’ type waveforms: sine, square, triangle, sawtooth falling or sawtooth rising. More about the software later. Let’s look first at what’s inside the little hardware box. Circuit description As you can see from the circuit, there isn’t much to it: the software does most of the work. Since we’re only working at frequencies up to 2kHz, I decided to use an ‘el-cheapo’ DAC rather than a fancy (expensive!) dedicated DAC chip. So in this case the DAC consists of just a low-cost CMOS octal latch (IC1) and the network of 20kΩ and 10kΩ resistors connected to its outputs. These form what’s usually called a ‘binary weighted ladder network’. The inputs of the latch chip are connected to the 8-bit lines of the PC printer port via 100Ω suppressor resistors, as you can see. (There are also 1.5kΩ pulldown resistors, to prevent the inputs being damaged – eg, by static – when the PC is disconnected.) The latch’s load enable input is also driven from the port’s strobe line, via inverter IC3a. So when the software running in the PC sends a data byte out to the port, the strobe pulse causes the eight data bits to be latched into IC1 and they accordingly appear at its outputs. Because IC1 is operating from a regulated +5V rail, the voltages at all of these outputs will therefore swing between +5V (for a digital ‘1’) and 0V (for a ‘0’). But the effect of the binary weighted ladder of resistors is to combine these into a single output DC voltage which automatically ‘scales’ the contributions of each output, according to its position along the ladder. Each position down the ladder contributes half that of the position above it, giving exactly the right proportions we need to produce the analog equivalent of the digital input. For example, when the top-most output (pin 12) goes high, this contributes exactly 2.50V to the output. But when the next output down (pin 9) goes high, it contributes only 1.25V. Similarly when pin 15 goes high, it contributes only 625mV; and so on, right down to pin 2 which contributes only a whisker under 20mV. If you work them all out you’ll discover this gives quite an accurate digital to analog conversion. The DC output voltage at the top of the ladder varies between a maximum of 5.00V (for a digital input of FF hex, or 255 decimal) and a minimum of 0V (for 00 hex input), in steps that are very January 2001  37 close to 20mV. To make the output from the generator a little more useful and also to minimise loading on the ladder network, its output is fed to IC2b, half of a TL072 dual op amp, connected here as a non-inverting buffer with a gain of two. So the output voltage at pin 7 now varies over twice the range from the DAC ladder: from 0 to 10V. This output is then fed through a simple low-pass filter network formed by the 100Ω resistor and 0.1µF capacitor, which filter out any sample clock components and ‘glitches’ in the DAC output. The smoothed output appears across the 20kΩ pot, which allows you to control the maximum output from the generator. From here the signal simply passes through IC2a, the other half of the TL072, which is used here as a voltage follower and output buffer. The 680Ω resistor in series with the output protects the output of the op amp against damage from accidental shorts. The rest of the circuit is to support this basic DAC and buffer amplifier system. IC3b re-inverts the PC port’s strobe pulse and drives the LED, to indicate when the generator is being driven with data. The same signal is then fed back via IC3c to the port as the BUSY/READY-bar signal, with the 100Ω resistor and .01µF capacitor providing a small amount of delay. This delay gives the DAC time to “digest” the information coming to it before more data is received. While this might marginally slow the DAC operation, it is essential when used with fast computers. The TL072 dual op amp is connected to the unregulated 12V DC input for its positive supply but needs a negative supply rail as well so that it can cope with output voltage swings right down Fig.1: a cheap CMOS octal latch forms the basis of the digital-to-analog converter. This is a much cheaper approach than using a dedicated DAC chip. 38  Silicon Chip to 0V. To provide this negative rail, I’ve used the other three inverters of IC3 as the heart of a simple negative voltage generator. IC3d operates as a relaxation oscillator, running at about 1.8kHz and driving the other two inverters in parallel. The resulting 5V peakto-peak square wave is then fed to a simple chargepump rectifier using D2, D3 and the two 33µF capacitors, to produce a negative rail of about -3.3V when loaded with the TL072. Diode D1 provides reverse-polarity protection for the main +12V power input, while the 7805 regulator (REG1) provides the regulated +5V needed by the DAC, hex inverter and LED. The complete generator runs from a nominal 12V This shot inside the case is reproduced with the PC board same size to make assembly easy. DC, which can come from Use this in conjunction with the component overlay below. either a battery or a mains power supply. As the curmount on a PC board measuring 105 x track breaks or shorts between tracks. rent drain and dissipation in REG1 76mm, and coded 04101011. As you It’s also a good idea to check that the are both quite low there should be no can see from the photos the board, corner holes are drilled 3mm diaproblem about using an unregulated together with the remaining parts, fits meter to take mounting screws, and 12V plugpack supply. in a readily available small low profile that there’s also a fifth 3mm hole ready Construction instrument box, measuring 140 x 111 for the screw used to hold down the tab of regulator IC4. Apart from the pot, LED and connec- x 35mm. Before fitting any of the parts on The board layout diagram shows tors for DC power and signal output, all the components used in the generator the PC board, check it carefully for where all the board-mounted parts go, Fig.2: there aren’t too many components to solder to the PC board, as this overlay shows. January 2001  39 together with their orientation. Where there’s any doubt the internal photo should help, as well as showing the off-board parts and wiring. I suggest you fit the header strip for IDC ribbon cable first, followed by the PC board pins used to simplify the other off-board connections. There are two of these for the LED, two for the output, two for the 12V DC input and three for the pot connections. Next, I’d fit the resistors, bending their leads carefully so they mount down against the board without straining the components. Then do the capacitors, taking care with the polarity of the polarised electrolytics (including the tantalums). The correct polarities are shown on the layout diagram. The three diodes can be fitted next. Note that D1 mounts with its cathode band end towards IC2, while D2 and D3 both have their cathode ends towards the edge of the board. Finally, fit the four ICs, again taking care with their orientation. Also be careful when you’re bending the leads of regulator (IC4) down at 90°, so that there’s no strain on them when the IC is mounted down against the board. I usually fit the leads through their holes and bolt the regulator down with an M3 screw and nut before soldering the leads to their pads. Your board should now be finished and can be put aside while you prepare We’ve unplugged the ribbon cable from its on-board connector to make this rear-panel shot much clearer. The socket at left is for DC power. the case. This doesn’t involve a great deal of effort. There are just the three holes in the front panel, a hole and slot in the rear panel and four holes to drill and countersink in the bottom of the case for the PC board mounting screws. A photocopy of the front panel artwork can be used as a template to drill the holes for the LED, pot and output connector. Similarly you can use a photocopy of the PC board artwork as a template for the board mounting holes. The lo- Parts List – Wavemaker Arbitrary Waveform Generator 1 PC board, 105 x 76mm, code 04101011 1 plastic case, 140 x 111 x 35mm    (DSE H-2512; Jaycar HB-5970) 1 panel label, 27 x 132mm 1 BNC socket, single-hole panel mount 1 DC power socket, 2.1mm 1 13 x 2 header strip 1 small control knob 1 26-way IDC ribbon connector 1 DB25 plug, IDC type 1 2m length of 26-way ribbon cable 4 10mm x M3 CSK head screws 1 6mm x M3 round head screw 13 M3 nuts 8 star lockwashers 9 1mm diameter PC terminal pins Semiconductors 1 74HC373 octal latch (IC1) 1 TL072 dual op amp (IC2) 40  Silicon Chip 1 74HC14 hex Schmitt inverter (IC3) 1 7805 +5V regulator (REG1) 3 1N4001, 1N4004 diodes (D1-D3) 1 red LED, 3mm Capacitors 1 1000µF 25VW PC electrolytic 2 33µF 16VW TAG tantalum 2 2.2µF 25VW TAG tantalum 2 0.1µF monolithic or MKT polyester 2 0.01µF MKT polyester Resistors (0.25W, 1%) 11 20kΩ 1% metal film 8 10kΩ 1% metal film 1 2.7kΩ 8 1.5kΩ 1 680Ω 1 470Ω 11 100Ω Potentiometers 1 20kΩ linear carbon cation of the hole and slot in the rear panel are not critical, and you should be able to use the photos as a guide. In view of the low profile of the plastic case, I elected not to use mounting pillars for the PC board. Instead it was mounted lower in the case using four 10mm-long M3 countersunk-head screws, coming up from underneath. Each screw has a star lockwasher and nut fitted first to fasten it inside the case, then a second nut to act as a spacer. The PC board sits on these second nuts, with a further lockwasher and nut on the top to hold it in place. If you have access to a photocopier you may be able to make your own front dress panel from the artwork, on adhesive backed aluminium or matt white plastic sheet. This can be stuck carefully on the front panel after the holes have been drilled, and before fitting the pot and other parts. At this stage I cemented the LED into its hole in the front panel using a dob of Araldite at the back, leaving it aside overnight to harden, before fitting the pot and connector to the panel. Once the LED is firmly cemented in place and everything else is fitted into the case you’re ready for the final step: the off-board wiring. This can all be done in light-duty ribbon cable wire, although I used resistor pigtail offcuts to extend the LED wires so they reached their PC board pins. These were insulated with sleeving to prevent shorts. Once the off-board wiring is done, the generator itself should be com- A sinewave at about 50Hz from Wavemaker; as you can see it’s pretty clean. Here’s a triangular wave at about 200Hz. It’s quite linear, and still quite clean. plete. All that should remain is making up a suitable cable to connect it to your PC’s printer port. This is easy if you use IDC connectors and 26-way IDC ribbon cable. All you’ll need are a 26-way IDC socket, an IDC type DB25 plug and a suitable length of cable — say 2m or so. Just be careful that you fit both connectors so their ‘pin 1’ ends are at the side of the cable marked with the red stripe; then the connections will be right. You should now be ready to power your generator up and connect it to the PC, to try it out with the software. The software A ramping-down sawtooth wave at close to 20Hz; again it’s very linear and good for testing amplifier linearity. This is a true arbitrary waveform, made using MAKEWAVE.EXE. The narrow negative spikes were programmed in, for scope triggering. As mentioned earlier, I’ve written four programs to go with the Wavemaker. They’re all written in Visual Basic for DOS and will therefore run happily on most IBM-compatible PCs. This means that you can use almost any PC to drive the generator, including those elderly desktops and laptops that many of us have gathering dust in our cupboards. Although you probably won’t want to run the software on a modern machine running Windows 98 or NT, it should run quite happily on these too, in a DOS window. You’ll probably get a ‘device conflict’ warning from time to time This is at 1kHz, showing how the waveform gets a little ‘segmented’ at higher frequencies. January 2001  41 Here’s the ‘control window’ for SOFTTEST.EXE, the program you use to check the printer port and save the generator’s config file. when the programs try to send data to the generator, but once you hit the ‘Y’ key to confirm that you want the DOS program to have access to the port, Windows usually backs away and lets them run. Zipped, free-running EXE versions of all four programs will be available on the SILICON CHIP website, for you to download, unzip and use ‘as is’. However for those who would like to see how they work, zipped text files with the VBDOS source code will also be on the website for you to download and inspect with a text editor/viewer. Here’s a quick rundown on each of the four programs, so you’ll know what each one does and how it’s used. There are a few screen shots to show what their ‘user interfaces’ are like, and also a couple of output waveforms captured via a digital storage oscilloscope. SOFTTEST.EXE: Normally SOFTTEST.EXE is the first program you’ll need to use, because it’s the one that lets you check the I/O address of the printer port the Wavemaker is connected to, and confirm that they’re talking to each other. It also lets you save the port address in a ‘config’ file (SOFTAGEN.CFG), which the other programs can read when they’re started up, so they’ll know where to find the generator. SOFTTEST.EXE also lets you set the value of a ‘delay constant’, which the main generator program SOFTARBG. EXE uses to set a software timing loop which controls the frequency of its output waveforms. This is necessary because the program will tend to run at different speeds on PCs with different processor chips and clock speeds, making it difficult to control absolute timing. To get around this problem I decided to have SOFTARBG.EXE use a timing loop to set the basic time-per-sample of the output waveforms, with this time set by a loop delay variable which is saved in the config file along with the port address. This makes it fairly easy to get the generator frequencies right, simply by adjusting the delay variable by trial and error using SOFTTEST.EXE. For example, on a 486DX2 running at 33MHz, a delay value of ‘3’ turned out to give generator frequencies that were within about 3% over most of the range, which is quite acceptable. On machines with faster processors and higher clock speeds you’ll need a larger value to achieve the correct frequencies. The third program is SOFTVOLT.EXE, which lets you use the generator as a programmable voltage source. This is very handy when you’re troubleshooting projects! 42  Silicon Chip When SOFTARBG.EXE is running, it gives you this window. You can select a waveform and frequency, and also control the generator. SOFTTEST.EXE gives you a screen window with five large control buttons, and a small ‘display panel’ which shows the current I/O port address you’re trying. To change this address you simply click on the top button, which brings up a dialog box to let you select one of the other common printer port addresses. To check whether the generator is at that address, you simply click on the next control button. If you’ve found the correct address, this will cause the generator’s LED to blink on and off five times, at a rate determined by the delay constant value. So finding the correct I/O port is simply a matter of trying the various addresses until the LED blinks when the second button is clicked. The third button down is the one which lets you set the software delay constant. This is explained in a message dialog which appears when you click on the button. You can then set the value via a second dialog box. The fourth button then lets you save the port address and current value of the delay constant on disk, in the config file ‘SOFTAGEN.CFG’ expected by the main generator program. Finally the fifth control button lets you quit SOFTTEST.EXE, and return This is the opening window for MAKEWAVE.EXE, the program you use to design your own waveforms and save them as disk files. When you enter MAKEWAVE.EXE’s edit mode, you get this screen to design your waveform graphically. to DOS — ready to try the main program and check its output frequencies, perhaps. SOFTARBGEN.EXE: This is the main generator program, which gives you a screen window with four control buttons and two ‘display panels’ — one to show the currently selected waveform and the other to show the waveform’s frequency. The two uppermost buttons let you set the waveform and frequency, respectively. Click on the Select Waveform button at top left and you get a small dialog box with six options to choose from: Sine, Square, Triangular, Sawtooth Down, Sawtooth Up or Custom. The last of these is to select an arbitrary waveform file on disk, and if you select this option you get another dialog asking for the name of the waveform file you want. These files have the extension ‘.SWF’, and some sample files will be available on the SILICON CHIP website to get you going. The top right Set Frequency button calls up a dialog button which, as you’d expect, lets you set the frequency of your waveform, in hertz. However, note that this button doesn’t work if you’ve selected a custom waveform, as the frequency of these is set by the length of the waveform in the loaded file. (If you want a similar waveform of a different frequency, you’ll need to make it using MAKEWAVE.EXE.) With any of the five ‘standard’ waveforms you can select a frequency between 1Hz and 2500Hz, although the frequency resolution and accuracy Finally, here’s how SOFTARBG.EXE’s window looks when you’re running an arbitrary waveform file. You can’t adjust the frequency; it’s fixed when you design the waveform. are not wonderful above 1kHz. Note that when you select a waveform and frequency, these are displayed on the ‘panels’ above the buttons — a bit like a hardware generator. The third button at lower left lets you start and stop the generator, running whatever waveform and frequency you’ve selected. Note, though, that because the selected waveform is either calculated or loaded in from disk only when you click on the button, there can be a short delay before the generator starts producing the waveform — especially for very low frequency waveforms, which have a lot of samples to calculate or load. The final button is again Quit Program, which is self-explanatory. SOFTVOLT.EXE: The third program is SOFTVOLT.EXE, which is designed to make it easy to use the Wavemaker as a programmable DC voltage supply. This one gives you a screen window with three small ‘display panels’ and three control buttons. The display panel at far right simply shows the I/O port that the program has loaded in from the config file, as a reminder. The other two show the current DC output voltage and the current ‘maximum’ (i.e., full digital scale) voltage respectively, and each of these figures can be set by clicking on the buttons beneath them. The idea of this ‘dual control’ system is that you can use the Wavemaker as a DC voltage source programmable over different ranges, depending on what you need. All you have to do is set the pot on the generator to produce the ‘full scale’ voltage you want, with the software set for full scale. Then if you set the ‘Max Volts’ readout to this figure (say 10.00V, 5.00V, 2.00V or whatever), the Change volts button can be used to set the scaled output voltage accordingly. In effect the program can allow for the setting of the generator’s pot. This makes it easier to use the program and generator to check multimeters, voltage comparators and so on. By the way, the display panel on the left shows not only the current output voltage, but the hex value being sent to the generator as well. Sometimes it’s handy to know! As before, the last button on the SOFTVOLT.EXE window is the escape hatch: Quit Program. MAKEWAVE.EXE: The final program is MAKEWAVE.EXE, which is pretty clearly the one that lets you design your own arbitrary waveforms and save them in disk files. These can then be loaded and fed to the generator by SOFTARBG.EXE. I confess that this program is fairly basic and needs a little patience, especially when you’re designing a complex low frequency waveform. That’s because it’s graphical and uses only the cursor arrow keys to adjust the sample values. However once you get the idea you can make many different kinds of waveforms, simply by flailing away at the keyboard. When you start MAKE-WAVE. EXE you get a fairly dull looking The front panel artwork can be copied and glued to the front panel and/or used as a drilling template for the three panel holes. The left hole is 3mm while the two right holes are 10mm. January 2001  43 screen window with just five control buttons — one of which is (you guessed it!) the Quit Program button. The other four are in two groups: the two on the left used to create new waveforms from scratch and the two on the right used to either save the current waveform on disk, or load in an existing waveform for further editing. To start producing a new waveform, you first click on the button at top left. This gives you two options: either setting the frequency This is the actual-size artwork for the PC board. of the waveform (1When you’re happy with the wave1000Hz), or its period form you’ve designed, you simply press in milliseconds (1-1000ms). the End key to exit from the editing Once you’ve done this, simply click screen and go back to the main window on the “New Wfm: Draw Samples” to save the waveform or whatever. button. This brings up the waveform I should warn you that this program editing screen, which is where you can manipulate the sample values to pulls a few ‘tricks’, in an effort to keep the program itself fairly simple ‘draw’ the waveform you want. A legend at lower right shows the keys you while also trying to make creating the waveforms as easy as possible. For exuse: the Right and Left arrow keys to move to the sample column you want ample, where the waveform only has to adjust in value, and then the Up and a relatively small number of samples due to its frequency (for example, a Down arrow keys to adjust the actual 1kHz waveform uses only 25 samples), value (from 0 to 255 decimal). Initialthese are ‘stretched’ so the waveform ly, the screen comes up with a green ‘horizontal line’ waveform of the right uses most of the screen horizontally rather than being squashed over at the wavelength, with the samples all set to midscale (127) to make it a bit easier to lefthand end. On the other hand, very low frequenset the values you want. As you’re working on the waveform, cy waveforms are not edited at their full resolution. A 1Hz waveform involves a list of parameter values is shown at lower left to help you. For example, 25,000 samples, which would be too you’re shown the current waveform difficult to edit on screen unless the program provided a ‘zoom’ function column you’re in and its sample value (which was too hard — sorry!). So in decimal. You can also see the time waveforms where there are over 600 value that the column corresponds to, samples (ie, with a frequency below in microseconds, and so on, including about 42Hz) are ‘decimated’ or reduced the waveform filename if you’ve saved in resolution, until their effective it (or a default name if you haven’t). resolution fits on the screen for easy editing. This means that you can’t get a waveform resolution higher than 600 effective samples, even for the lowest frequency waveform but I think this is a reasonable compromise. This still allows quite good ‘fine tuning’ of waveform shape, by the way, except on the highest frequencies where you don’t have many samples anyway. The two remaining control buttons on the MAKEWAVE.EXE screen are labelled respectively Save Current Waveform and Load & Edit a Waveform, and their use should be fairly self-evident. Here I should warn you of another small ‘quirk’ of MAKEWAVE.EXE. Although it can create and save quite complex waveforms, especially for low frequencies, the algorithms used for decimation (during loading) and restoration (during saving) of waveforms aren’t exactly complementary. This means that when you reload some waveforms back into MAKEWAVE. EXE, they can appear to have been corrupted — but this isn’t so. If you load them into SOFTARBG.EXE and run them, you’ll find they do deliver the waveform you designed. So it’s best to design your fancy low-frequency waveforms in one sitting and then save them to disk. Reloading them back into MAKEWAVE. EXE can produce confusing results. This only happens with waveforms below 42Hz, though. Higher frequency waveforms can usually be saved and reloaded for further editing, without any complications. SC Resistor Colour Codes No.  11  8  1  8   1   1  11 44  Silicon Chip Value 20kΩ 10kΩ 2.7kΩ 1.5kΩ 680Ω 470Ω 100Ω 4-Band Code (1%) red black orange brown brown black orange brown red purple red brown brown green red brown blue grey brown brown yellow purple brown brown brown black brown brown 5-Band Code (1%) red black black red brown brown black black red brown red purple black brown brown brown green black brown brown blue grey black black brown yellow purple black black brown brown black black black brown SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au PRODUCT SHOWCASE VGA into composite does go! Questronix have available a converter which accepts VGA signals, ie, from a computer, and converts them into composite or S-video output for displaying on standard video monitors. In fact, the CPT-370 unit accepts VGA signals in any of the three most popular modes: 1024 x 768, 800 x 600 and 540 x 480 and can superimpose these signals – text or graphics – onto another channel of live video if required. Output can be in both PAL and NTSC standards. It's ideal for demonstrations, classroom use, business presentations and software training where crowding around even a large VGA monitor isn't exactly convenient. When the converter is used in the Contact: overlay mode, it automatically converts underscanned monitor pictures into overscanned video so that the black band almost always found around the (DSE’s house brand) and according to the quality control people at DSE they are every bit as good as the big name brand batteries which now cost an arm and a leg. The packs, under Cat. S-4040, are available at all DSE stores. Contact: Dick Smith Electronics Pty Ltd PO Box 321, North Ryde NSW 2113 Phone: (02) 9937 3200 Fax: (02) 9888 3631 Website: www.dse.com.au Microgram has some real fans . . . To steal a line from Croc Dundee, “that's not a fan. THIS is a fan!” And this one is, well, huge! Specifically intended for Pentium III/ Celeron/Athlon/Duron processors – and even more specifically for those who want to overclock them – comes this huge Socket 370 “turbo”. For those familiar with the “run of the mill” fans found inside PCs, compare this one’s 70 x 70 x 50mm dimensions and you'll start to get some idea of just how big it is. Installation is simple – just a single contact point clip – and the unit is supplied with a now-standard 3-pin PC-socket DC connector. It sells for $39.00 Questronix PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Website: www.questronix.com.au email: questav<at>questronix.com.au Jaycar's Tape-in-a-can AA Alkalines <50c each from DSE If you’ve just forked out megabucks on the kid’s Christmas presents and have now found the “real” cost of all those battery-operated goodies (ie, batteries!), Dick Smith Electronics has some really great news for you. They have a pack of 40 AA-size alkaline batteries which retails for just $19.68 each (that’s less than 50 cents a cell.) They’re branded “Digitor” edge of a computer monitor screen is eliminated. You can also adjust the brightness and sharpness, freeeze frames, zoom into any of nine areas on the screen or pan the picture up, down, left and right. The CPT-370 is just one of the large variety of converters, processors, controllers and other video devices and fittings stocked by Questronix. Jaycar has released an electrical tape you don't stick on – you paint it on! The Liquid Electrical Tape is said to be ideal for cars, boats, trailers, around pools, underground wiring – in fact in any harsh environments where normal electrical tape won’t do the job. It won’t crack or peel but seals out moisture and prevents corrosion. It can be painted on or components etc can be dipped to coat them. The can of “tape” is available at all Jaycar Electronics stores and most resellers for $24.95 (Cat NM-2832). And if your hard disk runs hot? Cool it with this high performance dual 60mm fan. With ball bearing motors and airflow of 28cfm, it will help even the most-taxed hard disk drive keep its cool, which should result in significantly longer life and more importantly, less risk of a crash! The fan(s) screw to the hard disk drive using the standard mounting hole pattern and it has a male/female passthrough DC connector to make power connection very simple. It sells for $49.00. Contact: Microgram Computers Unit 1, 14 Bon Mace Close, Berkely Vale NSW 2261 Phone: (02) 4389 8444 Fax: (02) 4389 8388 Website: www.mgram.com.au FEBRUARY January 2001  53 Linux internet box In recent years, Linux has become more and more accepted in the wider community to the point where some experts have predicted that in the nottoo-distant future, Linux may actually threaten Windows’ almost universal dominance. This view is reinforced by devices such as Bio Recognition Systems’ Universal Internet Box (UIB), a Linux-based Internet web server which eliminates the need for a separate PC. The hardware contains an Intel 386 processor (yes, a 386!), 2 x 16 line LCD module, 8MB of RAM and 8MB of DiskOnChip flash memory. There are two modems built in (or one modem and an NE2000 LAN device). The unit also provides a very powerful software toolkit for developers, based on the very stable Linux OS and 2.0.x kernel. Using the toolkit, STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids developers can access all the hardware of the device and perform TCP/IP and email configuration from a touch-tone phone. All software fits into 4MB of DiskOnChip flash memory. Contact: Bio Recognition Systems 30 Osborn Rd, Normanhurst NSW 2076 Tel: (02) 9498 9379 Fax: (02) 9487 5771 www.biorecognitionsystems.com.au New Anritsu 3G spectrum analyser Anritsu have released a new spectrum analyser designed to provide the optimum performance required for the evaluation of third-generation mobile radio systems. These include W-CDMA as well as emerging systems such as Bluetooth and Hyperlan2. The Anritsu MS2683A covers from 9kHz to 7.8GHz with a dynamic range of 156dB, resolution bandwidth of 300Hz-20MHz and 20 times-per-second sweep. It is ideally suited to the development and manufacture of mobile terminals and their components –amplifiers, mixers, VCOs etc. The analyser includes a frequency counter, and can measure adjacent channel power, occupied frequency bandwidth, average power, channel power, time domain template evaluation and frequency domain mask evaluation. Contact: Anritsu Pty Ltd Unit 3, 170 Forster Rd Mt Waverley Vic 3149 Tel 1800 689 685 Fax (03) 9558 8255 2.5V op amp Linear Technology's new 8-pin SOIC-pack LT1806 offers 325MHz unity gain bandwidth, -80dBC (<at>5MHz) THD and an output stage that swings within 50mV of each rail. This makes the op amp perfect for applications in broad-band digital communications, high-speed data acquisition and high performance video applications. Maximum offset is less than 0.5mV, CMRR is 106dB and it has a large signal voltage gain of 300V/mV. Supply rails can be as low as 2.5V and up to 12V. Linear Technology semis are distributed in Australia by REC Electronics. 54  Silicon Chip Contact: REC Electronics Unit 1, 38 South St Rydalmere 2116 Phone: (02) 9638 1888 Fax: (02) 9638 1798 Website: www.rec.com.au Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 Central Coast Hobby & Communications Expo One of the “not to be missed” events on the amateur’s and hobbyist’s calendars is the NSW Central Coast Field Day, held each year on the last Sunday in February (25th). This year it has been renamed Expo 2001 – whatever the name, it promises to be the biggest and best ever with more than 2000 people from clubs and organisations all over Australia converging on Wyong Racecourse to display and trade equipment, new and “pre loved”. Just about every aspect of amateur and CB radio is represented, along with electronics as a hobby, vintage and historical radio collections, volunteer emergency communications, satellite reception, computers and more. Several seminar sessions and workshops will also be held during the day. Along with the displays by the nation’s leading radio and electronic equipment suppliers (and of course some bargains), one of the most-sought-after areas of the field day is the flea market and disposals where literally tonnes of equipment is sold and traded. Wyong Racecourse is about an hour north of Sydney with plenty of parking within the grounds. Gates to the public open at 8.30am. Admission is $10 for adults; $5.00 for students, seniors and pensioners; with children under 12 free. Food and drinks are available on site. More information is available via the Central Coast Amateur Radio Club website, www.ccarg.org.au, or by phone: (02) 4340 2500. E ELECTRONICSHOWCASELE NEW! HC-5 hi-res Vi deo Distribution Amplifier DVS5 Video & Audio Distribution Amplifier EMC Technologies' internationally recognised Electromagnetic Compatibility (EMC) test facilities are fully accredited for emissions, immunity and safety standards. EMC Technologies Melbourne: (03) 9335 3333 Sydney: (02) 9899 4599 Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. For broadcast, audiovisual and film industries. Wide bandwidth, high output and unconditional stability with hum-cancelling circuitry, front-panel video gain and cable eq adjustments. 240V AC, 120V AC or 24V DC VGS2 Graphics Splitter High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email: questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC’s, Converters, etc. QUESTRONIX All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only MicroZed Computers GENUINE STAMP PRODUCTS FROM Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 0409 036 775 Fax (02) 6772 8987 http://www.microzed.com.au Most Credit Cards OK Fluke OptiView Network Analyser Fluke Networks has introduced its new OptiView Integrated Network Analyser for comprehensive monitoring and analysis of complex and constantly changing enterprise networks. According to Fluke, Opti-View’s active, passive and drill down analysis capabilities offers insight you can’t get in a traditional protocol analyser. It collects information from a variety of activities including seven layer protocol analysis, active discovery, SNMP device analysis, RMON2 traffic analysis and physical layer testing. It can be used as a portable device or placed semi-permanently on a network link. The user interface on the OptiView portable unit is replicated when viewed remotely using a network connection and a PC browser. It is easy and economical to share know-ledge and expertise across an organization. The Remote Contact: User Interface allows Fluke Australia Pty Ltd up to seven operators to Tel: (02) 8850 3333 access a single OptiView Website: www.flukenetworks.com simultaneously. New Hot Chip goodies Investment Technologies have released a range of add-on modules for their popular “Hot Chips” modules. Here are just some: Quad N-Channel Logic Level Mosfet: the four MTP3055VL mosfets in this unit are logic level drive – TTL-compatible with an Rds(on) 0.18Ω, Id (cont) 12A and Vds 60. Each is configured as open-drain sink driver, zener-clamped to limit drain voltage excursions to 33.5V and will comfortably handle 2.5A without additional heatsinking. Quad Relay Module: provides four normally-open 12V relays for general purpose moderate duty output switching. The relays have a 5A<at>275VAC/30V DC rating. PSU: provides regulated 12VDC at 500mA as well as the unregulated supply from the rectifier. The 12VDC Contact: is used to power the Hot- Investement Technologies Pty Ltd chip platform board as Tel: (02) 4577 4893 well as to provide drive email: invtech<at>hawknet.com.au for the relays. FEBRUARY January 2001  55 SERVICEMAN'S LOG Ain’t no mountain high enough Returning to work after an overseas holiday can be a real shock, particularly when you have to lug TV sets up a mountain precipice. There was also a mountain of work waiting for me. Mrs Carruthers is in her seventies and is very fit. The reason for this is quite obvious, as I found out when I called. She lives in a house which is at the back of her property and the only access is via a very steep winding “path”. Actually, I use the word “path” quite loosely; it is more like a bush trail and is so steep that it looks almost vertical. (Memo: a machete is a useful implement to take with you when undertaking this voyage in order to get through the vegetation. And don’t forget your crampons and abseiling equipment). Well, OK; it’s slightly possible that I’m exaggerating just a touch here but you get the picture. Anyway, she had asked that I attend her 1996 Sharp CX-59ES TV receiver (25AR chassis), which was dead. And of course, she neglected to mention that she lived at the top of a mountain, so you can imagine my horror at being confronted with such a mara­thon climb. When I had finally been resuscitated after my arrival, I realised that I needed more than luck to fix this set. Because I was travelling light, I didn’t even have a circuit diagram, let alone any parts worth mentioning. The symptoms were fairly straightforward. When the set was switched on, you could hear the relay click in and the red LED would light up and then go off – but nothing else happened. There were no blown fuses, no noises from anything under stress and nothing else was obviously faulty. Power was getting in and the secondary 12V power supply for the remote control receiver circuitry was working. However, the primary switchmode rail was completely dead. Next, I shorted out the relay contacts and checked that there was +320V on pin 1 of IC701, which is the collector of an internal chopper transistor for the switchmode supply. I also checked the line output transistor for shorts and checked for shorts on the 120V, 18V and 17V rails at the cathodes of D711, D712 and D174. Unfortunately, these checks revealed nothing – everything was fine. By now, my luck had run out and I was in a bit of a pickle. Here I was on the north face of the Matterhorn, with a broken 32kg 59cm stereo TV and no service manual or parts. What’s more, it looked like I was faced with a rather difficult fault in the main switchmode power supply. Back to the workshop What was I to do? Ideally, the set should go back to the workshop but there was all that mountaineering to do. I must confess that it did briefly cross my mind that Mrs Carruthers, with her mountain goat fitness, might be able to help. However, I soon got a grip on myself – it really would be a 56  Silicon Chip Fig.1: the switchmode power supply circuit in the Sharp CX-59ES TV receiver (25AR chassis). Diode D730 (inside the red circle) was the cause of all my grief. bit much asking a 70-year old woman to carry her TV set down to the car for me! Plan B involved taking just the chassis back to the work­ shop and that’s what I decided to do (no, I didn’t get Mrs Car­ruthers to carry it for me). And so I left Mrs Carruther’s moun­tain retreat without actually speculating on when the job would be finished – I need time to think about this one and to train for the return climb. Back at the workshop, I immediately placed an order for a service manual and also for IC701 (STRS6309) from my nearest Sharp agency. I then set to work on the set. In the refined mess of my workshop, I felt that I could examine this simple circuit and crack it easily. I started by replacing all the small electrolytics and checking all resistors over 100kΩ. One part I did particularly notice is C710, a 10µF 35VW tantalum capacitor which is in parallel with a 100µF 25VW electrolytic (C712). What on earth is the designer trying to achieve here? Next, I ran DC checks with the ohmmeter on the primary and secondary sides of the chopper transformer (T701) but nothing really showed up. I then shorted out the main relay (PY751) to ensure a constant 240V AC supply to the power supply circuitry and removed L711, L712 and L713 which are in series with the three output diodes in the three secondary rails. Finally, I connected a 100W globe and meter to the cathode of D711 in the 120V rail and connected an oscilloscope to pin 1 of IC701 (ie, the collec­tor of the chopper transistor). Unfortunately, this was all to no avail as the circuit refused to oscillate when power was applied and remained stub­ bornly dead. I could measure +320V on pin 1 of IC701 but nothing significant on the rest of the IC. I subsequently spent a lot of time checking out the refer­ ence voltage feedback via IC702, Q741 and Q701 before concluding that it would be best to wait for the service manual. Well, I waited and waited until I could wait no more. When I chased up the order, I discovered that Sharp was now supplying manuals via CD ROM disks but I didn’t receive these either. Can’t win Lotto Finally, I abandoned the idea of ordering the manual and instead grovelled at the feet of our nearest Sharp service agent in order to borrow his. This demeaning process paid off and he obligingly lent me his only copy, which came with a bonus. It was already marked with the faults they had previously found in this model set. Surely, I thought, I’m home and hosed. Well, of course I wasn’t. I’m not one of those lucky bat­tlers. I’m the one who never wins Lotto! The agent had marked Q701, Q741, Items Covered This Month • • • • • Sharp CX-59ES TV set. Panasonic TC-25V35A TV set. Sony KV-S2911D (AE-2) TV set. Philips 28GR6776/75R TV set. Philips 28GR6781/75R TV set. IC702, IC701, T701, C726, C730, D715, D761, D707, D710 and D730 as all being possible candidates. I began by replacing IC701 and D761 and then checked Q701, Q741 and IC702 out of circuit. I also connected additional capacitors across C726 and C730 and disconnected zener diode D715, which is across the 120V rail, all to no avail. By now, I was beginning to suspect the chopper transformer (T701) but I had to eliminate any other possibilities before ordering a new one. Diodes D707, D710 and D730 all measured OK in circuit but D730 was definitely leaky out of circuit. This diode is a DX0027CE and is connected across the base-emitter junction of the chopper transistor, which measured less than 0.6V. At last – a major clue had surfaced! But what exactly is a DX0027CE? The diode looked like an 1N4007 but was marked SV 03 62. I substituted a BYV-96E high-speed switching diode but it still wouldn’t work. By now, two weeks had passed and Mrs Carruthers had phoned to let me know that she had finished reading her book and had become tired of listening to the cricket on her radio. I had to do something. D730 could only be there to clip the positive pulses on the base of the chopper transistor (or so I assumed), so what if I removed it altogether? It was worth a try. To my delight, the unit started to oscillate, the 120V rail came up on the cathode of D711 and the globe lit. Feeling rather pleased with myself, I ordered the correct diode, although I wasn’t too sure how long it would take January 2001  57 up for that final climb to fit the chassis and retrieve my loan set. A trip to the Old Dart to arrive. In the meantime, I decided to experiment with different types of diodes. This turned out to be a mistake. I chose a 1N4007 and switched the set on. There was a very loud bang as IC701 spat the dummy and the fuse and circuit breaker blew in unison. In fact, the IC blew the front of its face clean off! Ob­viously, the 1N4007 was a poor choice. After replacing the IC, I looked in the parts list and found two other diodes with same part number (DX0027CE) that were used in the set; ie, D517 in the vertical trigger amplifier circuit and D211 in the RF AGC circuit. These are both small signal circuits, so I thought I would try swapping diode D211 over. This time the power supply worked OK. I then substituted a 1N4148 for D211 in the RF AGC circuit and this also worked. Back to the mountain I could find no data on the DX0027­ CE and Mrs Carruthers was beginning to get demanding. I had to go with what I had. I trudged back up the mountain, reconnected everything and switched on. Well, it worked as expected but 58  Silicon Chip unfortunately there was now a new fault. The picture was only scanning to about 150mm wide and then the set switched off. There was nothing for it but to go back to the drawing board. “What about a loan set?”, said Mrs Caruthers unreasonably. What about one? – I had to admit she probably deserved one, if only for her patience, but it was down at street level and we were up in the clouds. I said I would go and see if I had one, which I already knew I did. Back on terra firma, I foolishly decided to let her have the loan set, so once more I tackled the mountain. Somehow, I made it back to the house before collapsing into a chair to recover from my vertigo and acute angina. During this time, Mrs Carruth­ ers made suitable soothing noises to reassure me I was still alive. Eventually, I recovered sufficiently to con­nect the loan set and then abseiled back to the car with the Sharp chassis. A week later, the new diode finally arrived (although the circuit still hasn’t) and the width problem turned out to be major dry joints around Q1604, the east west output transistor. All I’ve got to do now is psych myself Having just returned from a fabulous holiday around the world, it was interesting to compare TV sets in various different countries. Obviously, as we were touring, the sets we encountered were mainly in hotels, motels and bed and breakfast establish­ments. In Britain, the hotels we stayed in most were Holiday Inn or Radisson chains and they almost exclusively used Philips Hotel TVs (model TV­ 055.0208.AO 21HT3352/41Z). These sets had digital clocks on the front panel and featured remote control QWERTY keyboards with trackballs, as well as conventional remote con­ trollers. They had an excellent 2-way menu system connected with the hotel reception for messages, information event calendar, service and billing, as well as pay TV activation, Teletext and Internet access – not to mention radio, wake-up calls and games! Incidentally, I found Internet access to be available in places you would least expect - eg, in a Post Office in a pictur­ esque little village called Dingle Bay in South West Ireland. We also found that Internet access was available in video stores and roadside cafes. The terminals used were mostly freestanding slot machine types which consumed coinage at an alarming rate. Ironically, the least sophisticated TV receivers we encoun­tered were in a motel in San Francisco. They had Philips Magnavox’s installed but these were just basic TV receivers. In New Zealand, all the monitors at Auckland airport had wide-vision flat screens (but not LCD panels) and Rydges Hotel used Panasonic TVs with data cabling built in. I guess the days of interactive TV have well and truly arrived. The Panasonic TC-25V35A Sometimes, I have to complete jobs that were started by other technicians. One set was Panasonic TC-25V35A (C150A chassis), which was giving no sound or picture – just pul­sating. Or at least it was when I got to it. The original complaint was that the set was dead and the chopper IC (802 STR-56307) had been replaced, or so I was told. However, it was obvious that a lot more than this had been done. For a start, all the electros in the power supply had been changed, along with some of the transistors, as evident by the fresh solder on the board. It now appeared as though the protection circuit was oper­ating but for what reason? Was it due to overvoltage or overcur­rent or was there a fault in the protection circuit itself? Although there was no sound or picture, there was a dull pulsating raster and the main voltage was down to an average of about +85V instead of +125V. I began by disabling the line output stage by shorting the base and emitter terminals of the line output transistor (Q501). I then switched on but it was still pulsating, so I connected a 60W globe from the collector to ground and tried again. It still pulsated. This power supply is unusual in that it uses no less than three optocoupler feedback circuits: D803, D811 and D836. IC803/D803 is the comparator circuit for voltage control feed­back. In company with Q803, this switches the set to standby, while Q802 controls the +5V supply to the memory and remote control circuitry. The other two optocouplers, D836 and D811, along with Q827, Q826, Q804 and IC802 (pin 3), are the protection circuits for controlling over­ voltage and over-current conditions on the +125V and +24V rails. And as I quickly discovered, the 16V and 24V rails were, along with all the other rails (12V and 5V), also pulsating. This meant that the fault had to be in the power supply itself. I subsequently spent a lot of time checking the work done by the previous technician but it all looked perfectly OK. Next, I shorted Q805’s base and emitter terminals (to prevent it from switching on) and disconnected D830 and D837 which overrides half the protection circuit. Even more drastically, shorting pin 4 to pin 3 of D811 and shorting Q804’s base and emitter terminals completely overrides the effects of both opto­couplers. None of this made any dif­ference. A new approach had to be found. This time I decided to start by checking the +300V from the bridge rectifier. Fully expecting this to be spot on, I was extremely surprised to find that this too was very low and pul­sating. Something wasn’t quite kosher here so I checked the 240V AC into the set, Introducing direct from USA “Test-Um” TEST GEAR TM From the company that brought you the world-famous ’Lil’ Buttie’ comes an outstanding range of phone and data test equipment... TP200 Twisted Pair Tester The TP200 quickly tests 4-pair Cat.5 cables for shorts, miswires, reversals and split pairs. If a fault is detected, the failure can be isolated and identified using the LED indicators or by going into Debug mode.  Designed for testing Cat.5 cable  Local and remote units with RJ45 sockets (test leads included)  LED indicators shows pairs plus shield connection and indicate faults  Test/debug button plus low battery LED Available exclusively through: Call now for more info! Distributor enquiries welcome! Telephone Technical Services Tel (07) 3286 6388, Fax (07) 3286 6399 Shop 2, 55 Shore St West, Cleveland Qld 4163 just in case something silly was going on, but that was OK. By now, I was beginning to suspect that my ancient analog meter was playing tricks. Perhaps the poor thing had finally carked it; after all, it has been dropped on several occasions, the last time down a flight of stairs. I substituted another meter with less falls in its history but it too indicated that something was decidedly fishy. Next, I soldered another large electro across the main filter capacitor (C809). As before, this made absolutely no difference. “Good grief”, I thought, “have the laws of physics changed again? Perhaps the Chaos Theory has finally kicked in”. I now measured the AC input into the bridge rectifier and it too was low and pulsating. Well, apart from a couple of coils, the switch and fuse, what else could be causing this? I found a steady 240V AC into and out of the power switch and across coils L801 and L802. And that left R802 as the sole component between the steady AC coming out of L802 and the very unsteady AC applied to the bridge rectifier. After checking the soldering and www.ttservices.com.au inspecting the board for cracks, I measured R802 which is marked on the circuit as 2.7Ω 5W. In fact, this part had been changed by the previous techni­cian and appeared to be 3.3Ω. That should have been close enough, except that the ohmmeter read 3300 ohms (3.3kΩ)! Well, of course you’ve guessed it – the previous technician had fitted what he thought was a 3.3Ω resistor when in fact it was actually marked 3k3 (ie, 3.3kΩ). It’s easily done but what a night­mare to find. And yes, this was indeed the culprit! Sony KV-S2911D Coming back from a holiday really is a shock. It’s terrible having to face up to all those new jobs that had been booked in during my absence, not to mention returning favours for a couple of colleagues who helped out during this time. Faced with so much, I had to act like a Triage sister in hospital casualty and sort the jobs into order, from the unbe­lievably urgent down to extremely urgent. My first job was a set that should have been fixed the day before. It January 2001  59 was a Sony KV-S2911D (AE-2) which had come in with vertical timebase failure, leaving a line across the screen. IC1501 (TDA8179S) was the culprit and someone had replaced it (correctly) with a substitute designated STV9379. However, it was now pulsating, with no sound or picture. After a lot of hair tearing, I finally discovered that there was no +15V rail due to R853 (0.47Ω) being open circuit. That was the easy part because it took a lot more to find that the fault within the power supply was in fact due to an open circuit IC fuse (PS601 N75). Worse still, because access to this small fuse is appalling, it required a lot of plastic and metalwork to be removed before I could get close enough to replace the device. The next most urgent sets were a couple of Philips. The first was a 28GR6776/75R (G110 chassis) which had originally come in with no eastwest or pincushion correction. Naturally, the wretched thing had had the audacity to die on me while it was on the operating table. Actually, what had happened was the set had run very well for many years but dry joints had developed (mostly due to vibra­tion in the coils and transformers) and eventually something had to give. In this case, the 60  Silicon Chip east-west modulator coils had gone short circuit, causing a catastrophic chain reaction. First, the east-west amplifier Q7963 (2SA1359) had gone short circuit, blowing the button fuse (F1963, 315mA). Unfor­ tunately, this hadn’t happened fast enough because it also took out the entire protection circuit deep into the power supply. Worse still, they were nearly all surface mounted components. Measuring them, identifying their part numbers and then ordering them was a nightmare in itself. But finally I replaced D6963, D6964, D6197, Q7196 and Q7197. Due to a mix up, Q7193 (BC847C) didn’t arrive with the main order and so this job was left while I got on with the next one. Because of all the sets that had come in, my previously tidy workshop was now in a mess and I was forced to start the next job in the middle of all this. Unfortunately, while trying to plug in the new job, I inadvertently picked up the power cord from the previous job and plugged it in instead. Without Q7193 fitted, the optocoupler was unable to function correctly and the chopper transistor (Q7156, 2SC3973A) blew its insides out and took the main fuse with it. In fact, this was the second time I had blown this one up. Previously, I had started to remove some components using solder wick, unaware that the main electro was still fully charged at 320V. The copper wick ensured a bright spark and a loud bang as it discharged the electro into the guts of the switchmode power supply. Anyway, I was very stoic and kept my cool while I ordered the extra parts. Replacing them all, along with the previously ordered Q7193, finally fixed this troublesome repair. The next Philips was a 28GR6781/75R using a G111S chassis. This came in with a bizarre fault of intermittently muting and selecting channel 60. This turned out to be the EEPROM, which is now updated to a new type. However, as luck would have it, re­placing the IC now left me with no picture at all – even putting back the original didn’t restore the picture. So how had I done this? Using the CRO, I could see video going into the jungle IC but nothing was coming out. The sandcastle pulse was the other thing that was incorrect – it was now only a positive pulse and the sandcastle bit was missing. I changed the IC and horizontal oscillator but it made no difference. In the end, it turned out to be the TDA3566 SC IC which had failed on me. 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. Model Aeroplane Navigation Strobe/ Battery Level Indi­cator If you are interested in model aeroplanes and have the money, a radio controlled electric park flyer is a must have. An RC aeroplane under 400 grams floats around like the rubber models of old and contact with the ground doesn’t seem to involve that sickening crunch that comes with larger models. Finding a deserted park in which to fly one (that propeller can still be dangerous) and waiting for a windless day isn’t always easy but it sure beats driving an hour to a club field. Park flyers are definitely stress beaters and are also just plain fun. Two things I’ve discovered about calm days in Canberra: one is they tend to be a little damp, so make your park flyer water resistant. The other point is that the calmest time is twilight. In these low light conditions a navigation strobe would be both useful and practical. LEDs could have been used but have a narrow viewing angle, so I chose miniature lamps instead. Since the electric motor takes a fair amount of current anyway, the current drawn by this circuit has little effect on the battery endurance. Another aspect of park flyers is that they generally need some power to fly at all and (depending on the model) have an appalling glide angle (slow flight often equals lots of drag). You can tell the battery is about to go when the model loses its oomph but this can leave little time to set up a good landing approach. I decided that a strobe light with a frequency that rose as battery voltage fell would be the most effective solution to the problem. This circuit should work with 6, 7 or 8 cells as the zener diode ZD1 and trimpot VR1 make the duty cycle of the 555 timer chip adaptable to the battery voltage while transistor Q1 limits the lamp current to 50mA (duty cycle is less than 10%). R1 and ZD1 provide a near stable voltage so that C1 is charged through R2 and R3 at a rate independent of the supply voltage. Since not much current is used in biasing ZD1, the actual voltage across the zener is closer to 3.4V instead of 4V. Small zeners in the range of 3.3V up to 5.1V will probably work. The circuit is set up with a fully-charged battery using VR1 to trim the control voltage so that the 555 triggers when the voltage across C1 is about 95% of the zener voltage. This gives a strobe rate of about once a Silicon Chip Binders  Each binder holds up to 14 issues  Heavy board covers with 2-tone green vinyl covering  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p each (Australia only; not available elsewhere). Buy five and get them postage free. Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. REAL VALUE AT $12.95 PLUS P & P second. Capacitor C1 then discharges through R3 with sufficient duration for the lamp filaments to reach their operating temperature. For the sake of component count, C2 could be left out but it may prevent problems in the field. The lamps bulbs should give a reasonable life since most park flights tend to last only about 5 to 10 minutes (about 1000 strobe cycles). In an attempt to lengthen bulb life, Q1 is set up as a current limiting circuit. The voltage across LED1 and the Vbe of Q1 result in a constant 1.5V across LAMP1. LAMP2, being green, is placed in the starboard wing while LAMP3 (which should be red) is in the port wing. The white lamp is placed in the belly of the model (between the undercarriage). To reduce the weight of the wiring, I used very fine varn­ish insulated wire from an old solenoid. The current limiting circuit should prevent an inflight fire occurring but keep the wires apart just the same. For a one-metre wing, this wire weighed less than 0.5g and gave a resistance of about 3Ω. LED1 is placed to be visible in the cockpit and will flash even if all the bulbs have failed. Note that I used Orange (cataloged as Amber) instead of Red as they are much dimmer. Construction uses the 555 timer as a base on which all components are soldered top and bottom. The resulting circuit weighed 3g. Robert Parker, Curtin, ACT. ($100) January 2001  61 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au MAILBAG Petition form wanted for electrical licensing changes I’d like to respond to Peter Cairns’s letter in the Mailbag pages of the November 2000 issue. I’m glad to see that by pester­ing his boss he has managed to squeeze his way into what is currently a closed shop. I notice that process control is one of his skills; I do hope that this doesn’t involve any programming of computers or PLCs. You see, I don’t think he has listed that as one of his formal qualifications. But any time that he wants to get “legal” in computer programming he can go to university and do a 3-year degree, just like I have. I don’t think that anybody is seriously knocking some form of training but let’s get real and dare I say it, be Australian about it and give everybody a fair go. So please publish a peti­tion form in the next issue and start to liaise with the relevant politicians. Help us SILICON CHIP, you’re our only hope. I’d give my name, but seeing as I don’t want a visit from the plug and socket inspectors, I’d prefer that it not be pub­lished (Name withheld at writer’s request). Licensing reforms not desirable Oh dear, you do seem to have opened a can of worms with the electrical licensing debate. I feel that there are a few things that should be said before you start picketing the politicians to get the licensing laws tossed into the bin. Firstly, I must admit that I am a licensed electrician but I can see that the non-licensed fraternity has raised questions that deserve thoughtful answers. My personal opinion is that, where a mains-powered kit has been designed and outfitted by professionals and where there is information on correct wiring and layout provided, then ‘unli­censed’ constructors should be allowed to do their own mains wiring within the kit. That type of informed work presents a minimal hazard and most constructors would follow the instructions for the 240VAC stuff as well as they do for the extra-low 64  Silicon Chip voltage wiring. Similarly, if home handymen (handypersons?) want to replace a power cord or plug to an appliance and the plug or power cord comes with information about its proper installation, then they should be allowed to do it – on the understanding that if they get it wrong, then they are legally responsible for the death, injury or damage that they cause. When it comes to fixed wiring (the stuff installed inside the walls) however, I have seen too many jobs done by people who really didn’t have the proverbial clue – a job, for instance, which had the Active wire connected to the metalwork on a chande­lier and which had the chandelier’s switch turning all the other lights in the house off when it was turned off. There was another job that involved a replacement light switch which, with Actives and Neutrals looping at the back of the switch, took out the pole fuse after the un-handyman managed to put the Actives into the common terminal and the Neutrals into the normally open terminal on the switch. The first time he turned the switch on, it ‘popped’ the 15A rewireable fuse, so he put three strands of 20A fuse wire into the fuse carrier. The second time he turned the switch on, the pole fuse blew and the supply authority had to replace it – after getting the wiring fixed. How about a handyman-added socket-outlet (power-point) that had the Active and Earth swapped? The only reason that didn’t kill its installer was that the ‘electrician’ only tried plugging double-insulated stereo gear into it. Or how about a wiring setup in a shed that involved a severed earth wire “to stop the safety switch from turning the light in the car pit off sometimes”? No, there’s more to maintaining the high level of electri­cal safety which we currently enjoy than knowing how to ‘pull the wiring through the conduit’, as Mr Hoolhurst suggests. That attitude seems to me to suggest that, because I know the theory of flight and I can start a Cessna’s engine, I don’t need to demonstrate that I’m a competent pilot, with a license, before I get let loose on the airways – and I don’t think anyone would agree with that attitude. If you propose doing away with licensed electrical workers for household wiring, then you will also have to agree that there’s going to be a case to do away with licensed plumbers working on mains water, sewage and other waste water around the house. And of course, there will also be no need for licensed gasfitters in domestic premises either. (That crashing noise you just heard was our insurance premiums going through the roof!) It would be interesting to know if the number of electrici­ ty-related deaths, fires and electric shocks has, in fact, risen in New Zealand in the last eight years. Mr Hoolhurst made the statement that “the extremely low level of fatalities and the fact that none of the fatalities are related to incompetent house wiring or appliance repairs by householders makes the claims of the electricians’ lobby look ridiculous”. Mr Hoolhurst, can you please inform us of the reference for that rather sweeping sta­tistic? Brian J Spencer, Seaford SA. Comment: we hate to tell you this but plumbing and gas fitting by householders is also permitted in New Zealand. We also have a copy of “A Review of the Safety Regime for Electrical and Gas Work” carried out by the NZ Ministry of Commerce in March 1999. Total number of electrical fatalities in 1998 was 8; in 1997, it was 9 and in 1996 it was 6. In 1992 it was 7. These are extremely low figures and they are not showing any sign of rising. Everyone has seen horrible examples of wiring done by householders but the facts seem to be that few people die because of it. Vintage radio is old hat Now that I have joined the WWW, I have to get this off my chest. The Vintage Radio pages in your magazine are well past the use-by date. I have spent some time in my youth with this tech­nology but I adapted happily to the transistor age. I don’t like reading about revival of corpses; that’s what these old valve radios are. I like the rest very much and I have been a subscriber for a considerable time. Alfred Fischer, via email. Comment: we like your attitude. Vintage Radio is still popular though. We stated some years ago that we would never publish a new design for a valve amplifier (regardless of how they might be revered by some audiophiles) and got up some peoples’ noses because of it. What do other readers think? Household electrical work will become legal Your call for everyone to be able to legally do their own household wiring is bound to happen. Since the early 1970s the number of electrical trade traineeships seems to have fallen markedly. Given that many electrical people give up household work from their forties, the numbers of available electricians are due to fall. Another problem is obtaining electricians with the right qualifications; my builder went through five electricians to find one that could work on the house lead-in wiring to collect power from the drop cable from the street pole. Terry Collins, via email. House wiring inspections are a joke I too have always been somewhat bemused about the level of restrictions surrounding simple house wiring. However, having just had a new house built last year, I’m now left wondering just what level of expertise they are protecting. Before the power could be connect- ed, the new wiring had to be “inspected” which, on the face of it sounded reasonable enough, although it meant I had to take a day off work to let the inspector in. The “inspection” turned out to consist of a “lightning tour” of all the rooms to ensure “there were no bare wires or power points hanging off the walls”, followed by a check that none of the circuit breakers had tripped when the mains was applied! The justification for this truncated procedure was that: “if anything didn’t work properly, you’d soon let us know . . .” Well, fair enough, but do we really need an electrician to tell us that? And no, it seems the guys who are entrusted with attaching 3-phase power to the house from the street main aren’t qualified to check house wiring either! As for the wiring itself, long gone are the days of cables being neatly stapled along the ceiling beams. It was all just “duct-taped” to rough strips of wood, (presumably scrounged from the site’s trash pile), crudely nailed to the rafters. Unfortunately, when governments have spent decades rigor­ ously enforcing what are essentially bogus regulations, it’s very hard for them to turn around and admit that it’s all been a waste of time. Remember all that bureaucratic garbage you had to wade through to get ANY sort of transmitting license? Now CB radios and many other simple communication devices don’t need any sort of license at all and our civilization still stands, but what a struggle that was. It wasn’t all that long ago that you could have been jailed for fitting a “non-PMG” telephone to a standard phone socket. Maybe you still can. Keith Walters, Riverstone, NSW. House wiring in the USA With regard to the current debate on house wiring, I thought you’d be interested to know that when I was in Ohio, USA for work at the start of the year I was speaking to a friend who lives there. I was intrigued to discover that in Ohio (not sure about the entire USA) they are permitted to do their own electri­cal wiring but not permitted to do their own plumbing! Obviously this is because water is so much more dangerous and deadly than electricity. Stephen Wilkey, Sydney, NSW. Comment: probably they don’t let people do plumbing because it also involves gas-fitting. Also sewage backflow into drinking water seems to be more of an issue in the USA. Comment on the New Zealand experience The recent Publisher’s Letter “Anyone should be able to do their own house wiring” in November 2000 issue has created dis­cussion at my place of work which is an electrical trade training school. I feel the problem of differences between New Zealand and Australia requires an alternative viewpoint and a social analysis based on some understanding of the academic philosophy of “democ­racy”. A philosophical analysis in this debate seems to have been neglected. Your “Letter” quite rightly argues that New Zealanders are similar to Australians in many respects and a tourist will agree with that sweeping statement. I have been fortunate to work and live in New Zealand in the 1960s and the 1990s; the latter occa­ sion as part of the air-conditioning commissioning team at Har­rah’s Sky City Casino, Auckland. On the job and during extensive travels, I was able to com­pare and contrast New Zealanders with Australians. I was able to look, listen and analyse aspects of New Zealand society at work and play; aspects that are usually overlooked and glossed over by outsiders who are content to generalise about the culture of a country, and by “culture” I mean the “way we do things here”. The core issue I argue is that New Zealand society is a much kinder, fairer, gender-equal and more protective of civil liber­ties than we are in Australia. It seems to stem from decades of New Zealand rural farm life where there was a strong “repair and fix” attitude of self-sufficiency, brought on by the seagoing isolation in the antipodes from the industrialised countries in UK, Europe and USA. continued on page 93 January 2001  65 2-channel guitar preamplifier Pt.3: Building the preamps and reverb module into a metal rack case The 2-Channel Guitar Preamplifier and Digital Reverberation Module can be coupled together to produce a classy unit. This article describes how they are inter­ connected and installed into a rack case. By JOHN CLARKE As shown in the photos, the completed pream­ plifier boards and the reverberation module fit neatly into a 2-unit rack case. The 2-unit high case is required to allow room to mount the second channel above the first channel. However, if you intend to build a single-channel version only, it could be housed with the reverb unit in a 1-unit case. Before putting the case together, you have to first drill the front and rear 66  Silicon Chip panels. Use the wiring diagram (Fig.1) and the front panel artwork (Fig.2) as a guide to positioning the holes. Starting with the front panel, you will have to drill holes for mains switch S1, the 10 potentiometers and the three 6.35mm jack sockets. The hole for switch S1 can be made by first drilling a series of small holes around the inside perimeter, then knocking out the centre piece and carefully filing to shape. Don’t make the hole too big – the mains switch must be a tight fit so that it is properly secured by its retaining tabs. The rear panel requires holes for the fuseholder and mains lead cord­grip grommet at one end and the XLR panel plug and two 6.35mm jack sockets at the other end. Take care with the hole for the cordgrip grommet. This hole is not round – instead it must be carefully profiled to match the shape of the grommet, so that the grommet can not later be pulled out. Case assembly Once all these holes have been drilled, assemble the case without the lid, using the machine screws supplied. Important: be sure to scape away the paint at the countersunk screw points, so that each section of the case makes good metal-to-metal contact. This ensures that each section is properly earthed (important for safety reasons) and stops hum problems. This done, fit the channel 1 preamp­ lifier board to the front panel and secure it using the potentiometer nuts (these should all be tight). Now mark the locations for the three standoff mounting holes (the board mounts on 10mm-long threaded standoffs). You will also need to mark out mounting holes for the reverberation module, the mains transformer (4mm), the earth lug (4mm), the 3-way terminal strip and the cable tie mount – see Fig.1. Next, remove the preamp board and drill all the marked holes in the base of the case. While you’re at it, scrape away the paint or anodising from the area around the earth screw hole. This is necessary to ensure a good earth contact with the bare metal. You are now ready to install the various hardware items in the case. First, cut the pot shafts on the two preamplifier boards to a length suitable for the knobs, then install the board in the case on 10mm standoffs. The reverb module also mounts on 10mm standoffs, while the channel 2 preamplifier board is secured to the front panel solely via its pots and jack socket. This done, mount the remaining hardware items as shown in Fig.1. Note that both the transformer and earth lug are secured using M4 x 10mm screws, nuts and star washers. Do not attach the earth lug to one of the transformer mounting screws – it must be separately bolted to the case as shown in Fig.1. We recommend that you use a second “lock” nut to secure the earth lug, so that it cannot possibly come loose later on. Once it’s fitted, use your multimeter to confirm a good earth contact between the earth lug and case. Final wiring Now for the final wiring. Begin by installing the shielded cable signal wiring – see Fig.1. You also need to connect a 0.47µF MKT capacitor between pin 1 of the XLR socket and an earth solder lug secured by one of the socket’s mounting screws. Once again, be sure to scrape away the paint around the mounting hole to ensure a good earth contact. Be sure to secure the signal wiring with cable ties and to the cable tie mount, as shown in the photos. This will prevent undue stress from being placed on any one connection. Exercise extreme caution with the mains wiring – your safety depends BELOW: this is the view inside the completed prototype. The two preamplifier boards are stacked one above the other at top, while the reverberation unit is in the bottom righthand corner. January 2001  67 68  Silicon Chip Fig.1: here’s how to install the modules into the chassis and complete the wiring. Be sure to use mains-rated cable for all mains wiring and check that the earth lug makes good contact with the chassis. Note that all exposed mains terminations must be sleeved with heatshrink tubing and the wires should be laced together using cable ties – see text. January 2000  69 2001  69 If you intend moving the unit about a lot, it would be a good idea to make up some metal brackets to support the rear of the channel 2 preamp board. This will prevent the tracks from cracking around the solder joints for the pots and headphone socket. on it. First, strip back 380mm of the outer sheath on the mains cord, then clamp the cord into position using the cordgrip grommet. Check carefully to ensure that the cord is properly secured by the grommet; you must NOT be able to pull it back out. The Active (brown) mains lead goes to the centre terminal of the fusehold- er (which must be a safety type) and the excess lead then run between the out­side terminal and switch S1. Slip a 40mm length of 15mm-dia. heatshrink tubing over the two leads before soldering them to the fuseholder. Once the connections have been made, push the tubing over the fuseholder and shrink it down using a hot-air gun. Parts List 1 2-unit (2U) rack metal case; Altronics H-5036 or equiv. 1 2855 30V centre tapped 5VA transformer (T1) 2 6.35mm mono jack sockets 1 XLR panel plug 1 3AG panel-mount safety fuseholder; Jaycar SZ-2025 or equiv. 1 500mA 3AG fuse 1 SPST mains rocker switch with integral neon (S1) 1 mains cable cord grip grommet 1 mains cord and plug 1 3-way 5A terminal strip 1 cable tie mount 2 crimp eyelets 3 fully insulated 6.4mm female spade connectors 70  Silicon Chip 3 M4 x 10mm screws, nuts and star washers 14 M3 x 6mm screws 2 M3 x 10mm screws and nuts 1 M3 x 15mm screw and nut 7 10mm brass tapped standoffs 8 M3 star washers 8 100mm cable ties 1 40mm length of 15mm diameter heatshrink tubing 1 600mm length of red hookup wire 1 400mm length of black hookup wire 1 200mm length of green hookup wire 1 1.5m length of single core shielded cable 1 0.47µF MKT polyester capacitor The Neutral (blue) mains lead is run directly to the mains switch and is wired in parallel with the blue primary lead from the power transformer. The other transformer primary lead (brown) goes to the remaining terminal on the mains switch. Note that all the connections to the power switch are made using fully insulated female spade terminals. Make sure that the various leads are all securely crimped to these terminals before installing them (use the correct crimping tool for the job). The Earth (green/yellow) lead from the mains cord is sol­dered directly to the earth lug. This should be left long enough so that it will be the last connection to break if the mains cord is “reefed” out. Finally, use four cable ties to lace the mains wiring to­gether, as shown in the photo. That way, if a lead does come adrift, it will be secured to the other leads and the “live” end cannot make contact with the case. The transformer secondary wiring is run to the 3-way termi­nal block in the centre of the case and from there to the 15V AC and 0V terminals on the channel 1 preamp board. The DC supply wiring to the other two PC boards can then be run using medium-duty hookup wire. Use red wire for the +15V DC connections, black for the -15V DC connections and green for the 0V (ground) connec­tions. SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Testing Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Before applying power, go over your work and check your wiring carefully, In particular, make sure that all the mains wiring is correct before installing the fuse in the fuseholder. Now apply power and check the supply rails on both the channel 1 and channel 2 preamp boards. First, check that there is +15V on pin 8 of IC1, pin 7 of IC2, IC3 & IC5 and pin 4 of IC4. Similar­ly, there should be -15V on pin 4 of IC1, IC2, IC3 and IC5 and on pin 11 of IC4. Now connect a multimeter between TP1 in the centre of the channel 1 preamp board and the 0V supply pin. This done, switch the multimeter to the mV range and adjust trimpot VR7 for a reading of 0V, or as close to this as the potentiometer will allow. Repeat this procedure for the channel 2 board. Now check the supply rails on the reverberation board. There should be +15V on pin 8 of IC1 and pin 7 of IC3; -15V on pin 4 of IC1 & IC3; and +5V on pins 1 & 24 of IC2 & IC4. If the supply voltages are all OK, the preamplifier can be connected to a suitable music source and an amplifier while you check out the various controls. Check that VR5 (Volume) adjusts the overall volume and that the tone controls all produce the expected results. Similarly, the Effects control should increase the amount of reverberation as it is wound up. Finally, the Level control (VR1) should adjust the signal level from each channel. Corrections: the circuit diagram on pages 34-35 of the November 2000 issue incorrectly shows S1 as a 2-pole (DPDT) power switch. It should be a SPDT type and it switches the Active mains lead only – just follow the wiring diagram in this article. In addition, the parts list for the main PC board contains some errors. First, there should be 6 x 2.2µF NP PC electrolytic capacitors (not five) and a 1 x 1µF NP PC electrolytic capacitor should be added to the list. Second, there should be 15 x 10kΩ resistors and 4 x 150Ω (not 14 & 3). Finally, the 4.7kΩ resistor connecting to pin 3 of IC3 on the overlay (Fig.4) SC should be 27kΩ. Use these REFLEX® chargers for all your Nicads and NIMH batteries: Power tools 4 Torches 4 Radio equip. 4 Mobile phones 4 Video cameras 4 Field test instruments 4 RC models incl. indoor flight 4 Laptops 4 Photographic equip. 4 Toys 4 Others 4 Rugged, compact and very portable. Designed for maximum battery capacity and longest battery life. AVOIDS THE WELL KNOWN MEMORY EFFECT. SAVES MONEY & TIME: Restore most Nicads with memory effect to capacity. Recover batteries with very low remaining voltage. CHARGES VERY FAST plus ELIMINATES THE NEED TO DISCHARGE: charge standard batteries in minimum 3 min., max. 1 to 4 hrs, depending on mA/h rating. Partially empty batteries are just topped up. Batteries always remain cool; this increases the total battery life and also the battery’s reliability. DESIGNED AND MADE IN AUSTRALIA For a FREE, detailed technical description please Ph (03) 6492 1368; Fax (03) 6492 1329; or email smartfastchargers<at>bigpond.com 2567 Wilmot Rd., Devonport, TAS 7310 Truscott’s • RESELLER FOR MAJOR KIT RETAILERS • PROTOTYPING EQUIPMENT • COMPLETE CB RADIO SUPPLY HOUSE • TV ANTENNA ON SPECIAL (DIGITAL READY) • LARGE RANGE OF ELECTRONIC COMPONENTS Professional Mail Order Service Truscott’s Amidon Stockist ELECTRONIC WORLD Pty Ltd Fig.2: this is the front panel artwork, reproduced here 50% of full-size. It can be enlarged on a photostat machine for use as a drilling template, or you can download the full-size artwork from www.siliconchip.com.au ACN 069 935 397 Ph (03) 9723 3860 Fax (03) 9725 9443 27 The Mall, South Croydon, Vic 3136 (Melway Map 50 G7) email: truscott<at>acepia.net.au www.electronicworld.aus.as January 2001  71 Digital Reverb . . . last month’s missing pages An error in the SILICON CHIP editorial office resulted in the wrong pages being printed on pages 42 and 43 of the December 2000 issue, slap bang in the middle of the Digital Reverb article. These are the missing pages. We won’t name the staff member responsible for this appalling error but if you ever visit us, he’s the one with the serious bruises on his neck and the large lumps on his head. As soon as we became aware of the error, we posted the two missing pages in Adobe Acrobat pdf format on our website. In addition, we are publishing the last three pages of the article here, starting from the beginning of the last paragraph of page 41. Our apologies to readers for this unfortunate error. IC1b and IC4 operate in a similar manner to IC1a and IC2 but without the delay control circuit. Instead, IC4 operates with the default 20ms delay period, as described previously. Mixing IC3 mixes the delayed signals with the direct signals from pin 1 of IC1a & IC1b. The delayed signals come in via R2 & R2', while the direct signals are applied via R3 and R3'. The values of these resistors set the amount of mixing in IC3, while R1 & R1' set the reverberation or decay time. The values chosen will depend on the application of the reverberation unit. When connected to the 2-Channel Guitar Preamplifier, only R1 and R2 are used because the Reverb Unit is in the effects loop. In other applications, however, you may want to include R3 and R3'. In this case, you must use a larger value for R2 so that there will be an audible effect at IC3’s output. Power supply The Digital Reverberation Unit requires regulated supply rails of ±15V and a single supply rail of +5V. The +5V supply for IC2 & IC4-IC8 is derived from 3-terminal regulator REG1. A 220Ω 5W resistor at the input is used to reduce the dissipation in the regulator, while the +5V output is fil­tered using several electrolytic capacitors and two 0.1µF ceramic capacitors. The circuit can also be operated from a single +15V supply rail (instead of ±15V rails) if the GND is connected to the -15V rail. In fact, you can use a regulated supply voltage down to 8V, although the 220Ω resistor at the input of REG1 will need to be replaced with a link. Construction The Digital Reverberation Unit is built on a PC board coded 01112001 The completed Digital reverb board can be built into the 2-Channel Guitar Preamplifier or built into a separate case and used as a freestanding unit. Take care to ensure that all polarised parts are correctly orientated. 72  Silicon Chip OUT BP 560pF 56k 150pF 560pF .0047F 1k 1k 10F 10k 0.1F 150pF .068F 47F 56k 56k 33 .068F IC4 M65830P 0.1F 0.1F 56k 27k 150pF 33 1 1M X2 56k BP 100F 56k 27k .0047F 560pF 1F 0.1F 27k 150pF X1 OUT 22k 10k 2x 100pF BP 100F 1M IC7 4022B 1 2 x 10F 150 IC3 TL071 R2' 1 10k IC2 M65830P REG1 7805 10F 1F R2 10k 10k 820pF BP 1F SIG GND BP 820pF BP .068F IC5 4060B 6.8k BP .068F 47k 1N 4148 BP 1F 0.1F D1 BP R3' R1' IN .001F 1 1F 10k 1 IC6 4093B 1 1F 1F IC1 TL072 820pF 1 2x 100pF 10F 1F 10F 10k 10k IC8 74HC165 0.1F 1F 10k R1 1 3.3F +15V 15V R3 1F BP 100k _ 0V IN SIG 220 5W  GND  0.1F 560pF 47F 56k 27k 56k 560pF Fig.6: install the parts on the PC board as shown on this wiring diagram. The ICs all face in the same direction. and measuring 173 x 109mm. Begin the assembly by installing the links and resistors. The resistor colour codes and are shown in Table 2 or you can use a digital multimeter to check each value before soldering it to the board. Note that if you are building the unit to go in the 2-Chan­ nel Guitar Preamplifier, use 10kΩ resistors for R1, R1', R2 & R2' but don’t install R3 or R3'. However, if the board is to be built into other equipment or used as a standalone unit, you must include R3 and R3' (10kΩ) to get a direct signal component. In that case, use 18kΩ resistors for R2 and R2'. The seven PC stakes can now be soldered into place, fol­lowed by the ICs. Take care to ensure that each IC is correctly located and orientated (the ICs all face in the same direction). The convention is that pin 1 is always adjacent a small dot or notch in the plastic body. Diode D1 can be installed next, followed by 3-terminal regulator REG1. Again, make sure that these devices go in the right way around. Finally, install the two crystals (X1 & X2) and the capaci­tors. Table 1 shows the codes for ceramic and MKT types. Now for a few preliminary checks. If you have a suitable power supply, con­nect it to the board and check the Table 1: Capacitor Codes          Value IEC Code EIA Code 0.1µF   100n   104 .068µF   68n  683 .0047µF   4n7  472 .001µF   1n0  102 820pF   820p   821 560pF   560p   561 150pF   150p   151 100pF   100p   101 Table 2: Resistor Colour Codes  No.   2   1   1   8   4   1  13   1   2   1   1 Value 1MΩ 100kΩ 47kΩ 56kΩ 27kΩ 22kΩ 10kΩ 6.8kΩ 1kΩ 220Ω 150Ω 4-Band Code (1%) brown black green brown brown black yellow brown yellow violet orange brown green blue orange brown red violet orange brown red red orange brown brown black orange brown blue grey red brown brown black red brown red red brown brown brown green brown brown 5-Band Code (1%) brown black black yellow brown brown black black orange brown yellow violet black red brown green blue black red brown red violet black red brown red red black red brown brown black black red brown blue grey black brown brown brown black black brown brown red red black black brown brown green black black brown January 2001  73 Fig.7: this is the full-size etching pattern for the PC board. Check your board carefully before installing any of the parts. supply voltages to the ICs. Assuming you are using a regulated ±15V supply, there should be +15V on pin 8 of IC1 and pin 7 of IC3. Also check for -15V on pin 4 of both IC1 & IC3. Pins 1 & 24 of IC2 & IC4 should be at 5V. Alternatively, if you are using a single supply rail (“-” input connected to 0V), there should be +15V on pin 8 of IC1 and pin 7 of IC3. There should also be 0V on pin 4 of IC1 and IC3. In addition, check for +5V on pins 1 & 24 of IC2 and IC4, pin 14 of IC6 and pin 16 of IC5, IC7 & IC8. Note that if you use a supply voltage lower than 15V, the 220Ω 5W resistor will have to be reduced in value or shorted out completely. The input voltage to the regulator needs to be at least 8V. Test & adjustment You can test the reverberation board by connecting a signal to the input (at around 1V RMS) and the output to an amplifier driving headphones or loudspeakers. Check that the sound has the reverberation added and that the signal is undistorted. Alternatively, if the board is built into the 2-Channel Guitar Preamp­ lifier, you can check its operation 74  Silicon Chip simply be wind­ ing up the Effects control. Of course, you will have to feed a suitable signal into the CH1 or CH2 input first and monitor the output using headphones or an amplifier. If you wish, you can alter the reverberation characteris­tics by changing the delay of IC2 and the values of resistors R1, R1', R2, R2' and R3 & R3'. The table shown on the main cir­cuit (Fig.2) indicates the ranges that can be used for the resis­tors. As mentioned in the text, the reverberation decay times can be made longer by decreasing the values for R1 and R1'. However, these resistor values cannot be made too small, otherwise the feedback signal will exceed the input signal and the circuit will become unstable. The R2 & R2' mixing resistors determine the reverberation signal levels applied to the final mixer (IC3). Similarly, R3 & R3' set the undelayed (direct) signal levels. Note that when used with the 2-Channel Guitar Preamplifier, the reverberation unit is in an effects loop, whereby the signal is mixed in with the main or direct signal. This means that R3 & R3' are not required in this situation. However, if the reverb unit is connected as an in-line effects unit, resistors R3 & R3' must be included to provide the direct signal. A value of 10kΩ works well with 18kΩ values for R2 & R2'. If you’re prepared to experiment, you can substitute trim­pots for these resistors so that you can adjust the reverberation unit to your liking. This done, the trimpots can be measured using a multimeter and replaced with fixed value resistors. Finally, the delay time for IC2 can be changed by alter­ing the connections to pins 3, 4, 5, 12, 13 & 14 on IC8. Table 3 on page 44 of the December 2000 issue shows the connections required for each possible delay time. Note that the initial setting has all these pins connected to +5V. To make changes here, you have to cut the thinned track sections connecting these pins to the +5V track (ie, the track connecting to pin 16 of IC8). You then have to apply a solder bridge to connect the disconnected pins to the GND rail (on either side of IC8) instead. Make sure that none of the pins connects to both +5V and GND or the SC supply will be shorted. Order Form/Tax Invoice Silicon Chip Publications Pty Ltd ABN 49 003 205 490 PRICE GUIDE- Subscriptions YOUR DETAILS (all subscription prices INCLUDE P&P and GST) Your Name________________________________________________________ (PLEASE PRINT) Organisation (if applicable)___________________________________________ Please state month to start. 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Folded: $A5.95 inc p&p within Australia; elsewhere $A10 inc p&p. *BOOKSHOP TITLES: Please refer to current issue of SILICON CHIP for currently available titles and prices as these may vary from month to month. SUBSCRIBERS QUALIFY FOR 10% DISCOUNT ON ALL SILICON CHIP PRODUCTS AND SERVICES* *except subscriptions/renewals and Internet access Item Price Qty Item Description P&P if extra Total Price Spec i SUB al Offer SCR IBE & COM PUTE GET R OM FO N Aust R FREE! IBUS ralia Only* Total $A TO PLACE YOUR ORDER Phone (02) 9979 5644 9am-5pm Mon-Fri Please have your credit card details ready OR Fax this form to (02) 9979 6503 with your credit card details 24 hours 7 days a week OR Mail this form, with your cheque/money order, to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy, NSW, MARCH 2001  75 Australia 2097 * Special offer applies while stocks last. 01-01 Got a concept you’d like to try before building a full prototype? New to microcontrollers but want to learn more about them? This combined PIC programmer and test bed could be just what you’ve been looking for. PIC TestBed Easy PIC programming and prototyping. Design by Barry Hubble Article by Peter Smith    Please note: The PicProg software described in this article is outdated and will not work on recent model PCs. A suitable alternative is WinPIC, which can be obtained from http://people.freenet.de/dl4yhf/winpicpr. html. Before use, configure WinPIC to use an interface type of “COM84 programmer for serial port” and select the correct COM port from the drop-down list. These settings can be found on the “Interface” tab. LO RES TO BE REPLACED I f you’re a regular reader of Silicon Chip, you’ll have noticed more and more microcontroller-based projects appearing in our pages – especially those using PIC microcontrollers. 76  Silicon Chip These little devices are extremely versatile, allowing much more functionality to be packed into less space than is possible with traditional components. Just as importantly, they’re cheap and easy to obtain, and are well supported with a wealth of free development tools and example applications. Back in the March 1999 issue, we described a simple PIC programmer all? One reason might be to really slow PIC can sink and source up to 25mA at that has proved very popular. Although down the action so that you can “see” its port pins (PICs rule, OK?). it includes a LED chaser circuit that what is happening on the PIC’s I/O To accommodate the two popular can be used to demonstrate PIC opport pins. This could be very handy LCD hardware interfaces, the PC board eration, it really is little more than a for tracking down elusive bugs or even has been designed to allow installation programmer. for learning PIC basics. of single or dual row headers (CON3 This new design integrates a proTo ensure orderly startup each time and CON4). The pinouts are compatigrammer with support for several power is applied, the PIC includes ble with the “Hitachi” standard as used popular I/O (input/ on virtually all alphanumeric LCD output) devices, along modules. Trimpot with header pins givVR3 provides disFeatures ing access to each Supports PIC16C84, PIC play contrast (also 16F84 and PIC16F84A mic rocontrollers individual port pin. Simple programming via called viewing anWindows-based software Space prevents gle) adjustment. ZIF (zero insertion force) socket provides easy PIC us from describing Note that no provichip insertion & removal Clock source can be crysta PIC microcontrollers l, resonator or variable RC sion has been made oscillator Header pins allow easy acc in detail, so we’ve ess to all port lines for connecting LCD Basic serial (RS232) inte assumed that you back-lighting, as this rface included have at least a baLCD module support tends to vary consic knowledge of siderably between 8 LEDs for PIC outputs (RB 0-RB7), jumper selectabl the subject. If we e manufacturers. Variable voltage on RA0 (fo r PICs with A-D inputs) lose you, don’t be RA0 (pin 17) and Push button input on RA disillusioned; vast 1 RA1 (pin 18) of the Reset button quantities of (free) PIC have been nomiinformation for exnated as receive (RX) perts and beginners and transmit (TX) alike is available on the Internet (see internal reset circuitry. Our circuit data for the serial inlink list below). If you prefer hardcopy, adds an external RC network and terface. Alternatively, the larger technical bookshops can pushbutton switch (S2) so that you these pins can be configured as variable often help, too. can reset the chip without having to voltage and momentary switch inputs, You might also like to review the remove power each time you want to depending on the positions of JP13 Silicon Chip March 1999 PIC Prorestart your program. Diode D2 isolates and JP14. grammer project, which describes the the reset circuit from the programming Whoa, what’s the variable voltage PIC16F84 in a little more detail. This interface but more on that shortly. input for? Let’s just say that it can be issue is still available – see page 75 for used for other 18-pin PICs, such as the ordering details. Input and output devices PIC16C71X series, which include onA whole string of jumper pins on board A-D converters. The programCircuit description the board allows selection of one of ming software doesn’t support these For ease of description, let’s break two functions for most of the PIC’s devices, however. the PIC TestBed circuit into three secinput/output pins. In addition, the Connection to the serial interface tions, as follows: jumper pins can be used to gain easy is made via an on-board 9-pin ‘D’ 1) Life support (power, reset and access to the port lines for connection connector (CON2). We’ve called it a   oscillator) to prototyping circuits, etc. Jumper “simple” serial interface because it 2) Input and output devices wires for this purpose can be fashioned doesn’t support hardware handshak3) Programming interface from matrix pin sockets, heat-shrink ing. RTS/CTS (pins 7 & 8) and DSR/ tubing and light-gauge hookup wire. DTR (pins 6 & 4) are simply looped Life support Alternatively, you can purchase the back to signal an “always ready” conReferring to Fig.1, you can see that ready-made Basic Stamp jumper kit dition. Conversion between the +12V a typical 3-terminal regulator (REG1) from Dick Smith Electronics (Cat and -12V levels on the RS232 lines and together with a sprinkling of filtering K-1406) or MicroZed Computers. the PIC (which works on 0-5V levels) capacitors and a polarity protection Port pins RB0 - RB7 can be indiis achieved with IC1, a MAX232. The diode (D1) provides 5V power to the vidually jumpered to drive the LEDs MAX232 includes an on-chip charge circuit. (LED1 - LED8) or in conjunction with pump voltage converter to boost the PICs have an internal clock oscilpins RA2 - RA4, an LCD (Liquid Crystal +5V supply to the higher RS232 levels, lator that requires only an external Display) module. Note, however, that eliminating the need for separate +12V crystal, resonator or RC network. All it is possible to have both the ‘a’ and and -12V supplies. three of these options are provided for ‘b’ jumpers installed together, as the on the Test Bed, with JP12 selecting Programming interface PIC can drive both the LEDs and LCD between the crystal/resonator and the without problems. The most important feature of the RC network. Trimmer pot VR2 allows As you can see, the LEDs are conPIC programmer we described in the you to quickly tune the RC network to nected directly to the PIC’s port pins Silicon Chip March 1999 issue was its the desired frequency. (via jumpers JP4 - JP11) without drivers simplicity. In fact, the designer calls Why bother with an RC network at or buffers. This is possible because the it the “No Parts PIC Programmer”. Of · · · · · · · · · · · January 2001  77 78  Silicon Chip Fig.1: the PIC programmer and test bed. It’s easy to build and just as easy to use! LO RES TO BE REPLACED Fig.2: follow this component overlay as an aid in assembly. The order is given in the text. course, it does have a few components. In fact, it has more than this design! First up, we should mention that PICs are programmed in a serial data format, requiring only two signal lines and a programming voltage. To enter programming mode, the MCLR pin is raised to 12-14V. Data to be programmed is then presented in a serial stream (one bit at a time) on RB7 and clocked in with pulses on RB6. The data format and timing used is of course important and is described in detail in Microchip’s “In-Circuit Serial Programmers Guide”. Microchip calls this programming method “ICSP”. All this means is that PICs can easily be programmed (or reprogrammed) while they are plugged in to the end product. On the PIC Test Bed, the MCLR, RB6 and RB7 pins are routed to a 5-pin header (CON5). In programming mode, these become the VPP, CLK and DATA signals, respectively. 5V (VDD) and GND (VSS) are also made available on the header. A number of commercial programming adapters are available that will plug directly into this header. This not-quite-same-size pic (no pun intended!) can be used in conjunction with the component overlay above when constructing the PIC TestBed. Fig. 3, the artwork for the board label which can be photocopied and glued to the board, as seen above. January 2001  79 Parts List: PIC Test Bed 1 PC board, code 07101011, 124 x 172mm 1 SPST PC-mount pushbutton switch 1 SPST tactile switch 1 2.5mm PC mount DC socket 1 9-pin female right angle PC mount ‘D’ connector 2 40-way dual row 2.54mm headers 1 40-way single row 2.54mm header 1 40-way header socket (Altronics cat P-5390 or sim.) 1 single row machine pin socket strip (6-way or larger) 24 jumper shunts 1 16-pin IC socket 1 18-pin ZIF (zero insertion force) IC socket 1 9V or 12V DC 300mA plugpack Semiconductors 1 MAX232A RS232 driver/receiver (IC1) 1 PIC16F84, PIC16F84A microcontroller (IC2) 1 78L05 5V regulator (REG1) 9 5mm red LEDs (LED 1 - LED9) 1 1N4001, 1N4004 1A diode (D1) 1 1N5819 Schottky diode (Altronics Cat Z-0040) (D2) 1 4MHz parallel resonant crystal (X1) Resistors (0.25W 1%) 1 100kΩ 3 4.7kΩ 1 470Ω 9 390Ω 1 100kΩ miniature horizontal trimpot (VR2) 1 10kΩ miniature horizontal trimpot (VR3) 1 5kΩ miniature horizontal trimpot (VR1) Capacitors 1 470µF 25V PC electrolytic 1 10µF 16V PC electrolytic 1 0.47µF monolithic ceramic 8 0.1µF monolithic ceramic 2 15pF ceramic But we’ve got an easier way! A tiny adapter board containing just a header plug and three resistors are all that we need (see Fig.4). The adapter board also provides termination for a serial cable that connects to your PCs serial port. How does such a simple scheme work? Well, the 12V signal levels on the RS232 interface are just what we need for the programming voltage. But what about the CLK and DATA signals, which should only be 5V maximum? The PIC clamps its port pins internally and with the aid of the 4.7kΩ resistors, current flowing into the pins in limited to a safe level. The Microchip people would surely frown on this method of programming their chips but we’re assured that in practice it works just fine (at least, in a hobbyist situation). A word of warning, though. Some serial ports, such as many found on older model laptops, do not generate true RS232 voltage levels. Signal levels may only reach between about 5V to 10V, which is clearly too low for the PIC programming voltage. The remainder of the magic is performed by Windows-based software, which reads your assembled PIC program code and drives the serial port lines in the necessary sequence to perform the programming. By the way, you will need to remove jumpers from JP10 and JP11 before connecting the programming adapter so as not to overload the signal lines. This also prevents potential damage to the LCD from the higher voltage levels present. Assembling the board Begin by checking the board for defects, in particular around CON3 where the tracks and pads are quite tightly Additional parts for programming adapter 1 PC board, code 07101012, 20 x 45mm (optional, see text) 1 9-pin or 25-pin female ‘D’ connector 5-core data cable, length as required 1 small cable tie Heatshrink tubing Additional parts for LCD (optional) 1 alphanumeric LCD module 150mm 14-way rainbow or IDC ribbon cable (see text) 2 14-way IDC sockets (Altronics Cat P-5314) (see text) Fig.4: here’s the circuit for the programming adaptor which can be built on the PC board as illustrated below (Fig. 5), or even as part of the cable (as shown overleaf). Misc. 200mm 0.71mm tinned copper wire 6 4G x 12mm wood screws or self tappers 1 190mm x 140mm wooden photo frame 4 small stick-on rubber feet Where to get the parts The only part that could present a problem is the 18-pin ZIF socket. We found a source at Futurlec (www.futurlec. com). A good selection of PIC chips, crystals and resonators can be found at MicroZed Computers. Jaycar, Dick Smith Electronics and Altronics also list a few types of PICs as well as LCD modules. 80  Silicon Chip Fig.5: the component overlay for the programming adaptor. Fig.6: samesize artwork for the adaptor PC board. Table 1: Useful PIC Resources On The Internet www.microchip.com The PIC manufacturers. Check here first! www.geocities.com/SiliconValley/Way/5807 Very comprehensive PIC resource list. home.iae.nl/users/pouweha/index.shtml How to control an LCD (the source of the LCD code in TESTBED.ASM) www.microzed.com.au Commercial site (Australian) www.dontronics.com Commercial site (Australian) spaced. Using Fig.2 as a guide, install the five wire links, followed by the resistors, diodes and capacitors. Note that capacitor C1 forms part of the RC oscillator and can be socketed for easy replacement. On the prototype, we snapped off a 3-pin section of a machined-pin socket strip for the job, then cut off the bottom of the middle pin. The crystal (X1) can also be socketed in the same manner. If you intend using a ceramic resonator rather than a crystal, you will note that there is no connection for the middle (ground) pin of the three-legged variety. No problems were found using resonators up to 10MHz without the ground connection. The socket for IC1 can be installed next, but don’t plug in the MAX232 chip just yet. Follow this with all LEDs, trimmer pots, switches and the 3-terminal regulator (REG1). All the jumper pin sets, as well as the LCD and ICSP connectors need to be made by cutting sections from the longer header strips shown in the parts list. The jumper pins (JP1 - JP14), as well as the pins marked “GND” (next to JP14), are made by cutting off two pairs of pins for each jumper pair. For the LCD interface, either CON3 (dual row header) or CON4 (single row header) can be installed, depending on which type of connector your LCD module supports. To hook up the LCD, a short length of ribbon cable (no more than about 150mm) is required. For single-row connector styles, you can make up the cable using a length of rainbow cable and two 14-pin header sockets. Once again, these are cut down from the 40-pin length shown in the parts list. For dual-row connector styles, use IDC ribbon cable and IDC sockets instead. Observe antistatic precautions when handling LCDs as they are particularly static sensitive. Install the ZIF socket (IC2) as the final step. Before plugging in IC1, apply power and use a multimeter to check that the 5V supply rail is OK. A good place to do this is between pin 15 (GND) and pin 16 (VCC) of the IC1 socket. The parts list specifies a MAX232A Fig.7: same-size artwork for the PC board, as viewed from the copper (ie, non-component) side. January 2001  81 Table 2: Some Of The Relevant Literature Available From Microchip Document No. DS30262C DS30277C DS35007A DS51025D AN555 AN587 Description PIC16F8XX EEPROM Memory Programming Specification In-Circuit Serial Programming Guide PIC16F84A Data Sheet MPLAB IDE, Simulator, Editor User’s Guide (includes tutorial) Software Implementation of Asynchronous Serial I/O Interfacing to an LCD Module for IC1. The ‘A’ at the end essentially means that the four charge pump capacitors (C2-C5) can be as small as 0.1µF, whereas on the non-‘A’ version, they are usually about 10µF. However, the non-‘A’ version works fine with 0.1µF capacitors up to around 64kb/s. also try TESTBED.ASM, which combines the LED chaser with an LCD test. It also provides an excellent example of how to program LCDs. So far we’ve only mentioned the .ASM, or assembly language versions of these programs, which must first be assembled into machine code before they can be programmed into a PIC. Despair not, we’ve also included the assembled versions (DEMO.HEX and TESTBED.HEX), all ready to be “burnt”. Which leads us to the programming software. A freeware program called PicProg handles the programming side of things (see Figs.9 and 10). PicProg runs on Windows 3.x and Windows 95/98, on any hardware with a 486DX processor and above. There are no special installation requirements; simply unzip PICPRG06. ZIP into your folder of choice, and set up a shortcut to the PICPROG.EXE file. By the way, all of the software mentioned (with the exception of MPLAB) The programming adapter The only parts needed for the programming adapter are three 4.7kΩ resistors, a length of 5-core cable, a 9-pin (or 25-pin) female ‘D’ connector and a 5-pin header socket. If you wish, you can use a PC board to mount the resistors and the header socket and to terminate one end of the cable. Alternatively, you can dispense with the PC board altogether and solder the resistors “in-line” with the header socket and cable. Figures 5 and 8 show how to construct the adapter using either method. As shown in our photos, we used a rather unconventional method to “house” the prototype; a wooden photo frame fitted with rubber feet! If you don’t like this idea, you could use plastic stand-offs or even large rubber feet. It’s a good idea to label the jumper pins, too. We’ve included a simple label (Fig.3) that you can photocopy and stick on. Software The software of choice for PIC program development is MPLAB, a complete collection of all the tools you need to edit, assemble and debug PIC code. Best of all, it is available free of charge from Microchip, on the web at www.microchip.com If you don’t have a lot of PIC programming experience, you might like to use the little programs we’ve adapted for testing the completed board. First of all, there’s DEMO.ASM, a simple LED chaser that will check out the 8 LEDs. If you’ve connected an LCD, you can 82  Silicon Chip Fig.8: alternative programming adaptor, with no PC board required. Be sure to insulate all components! Experienced PICers Read This! PicProg was developed as a 16C84 programmer. There are a number of small but important differences between the 16C84 and the newer 16F84 and 16F84A PICs that need to be considered. The most obvious differences exist in the Configuration word. The polarity of the PWRTE bit is inverted in the F84/F84A, so selecting this fuse in PicProg (ticking the “PWRTE” box) when programming a F84/F84A causes the Power-up Timer to be disabled. Bits 4-13 of the Configuration word are designated as Code Protection bits in the F84/F84A. However, on the C84, only bit 4 is significant. We’re unsure how PicProg handles undefined bits, so selecting the Code Protect fuse may not result in protection. You can, of course, perform a read after programming; if the resultant data is invalid (all zeros, for example) then code protection is working. We were able to successfully code protect our test PICs. The different Configuration word masking also means that PicProgs checksum computation will be incorrect on both the F84 and F84A. Most would consider this insignificant. The author has no intention of updating PicProg to specifically support the F84/F84A. However, we are aware of a second freeware programmer, called ICProg, which does support the newer PICs and is compatible with the TestBed. We were amazed by the enormous range of options provided by ICProg, but in use found that it was unable to successfully program EEPROM data memory in a PIC16F84A (we tried version 1.03A). If this problem is ironed out, ICProg could be well work a look. Check it out at www.h2deetoo. demon.nl ’Nuff said. Our tests convinced us that PicProg effectively programs both types of chips! Fig.9: the main programming screen: you should see this when you run the PicProg.exe program. As you can see, all parameters are set from this screen . . . is downloadable from the SILICON CHIP website, www.siliconchip.com.au After launching PicProg, select Setup from the main menu and choose which serial port you’ve connected to the TestBed (see Fig.10). Next, load the code (.HEX) file that you want to burn, then select the appropriate Fuse options. These are fully explained in . . . except the port parameters which are shown on this screen (fig. 10). It gives you the option of changing the port – and it also remembers which port you’ve set next time around. the PIC data sheets (hint: select “XT” if you’re using a 4MHz crystal). Finally, hit the Program Chip button, and if all goes well, programming will complete in a matter of seconds! PicProgs on-line help includes a couple of useful tips, so check these out if you get stuck. Note that the Test Bed programmer is compatible with the “LudiPipo” programmer mentioned throughout the PicProg documentation. All credits for PicProg go to Tord Andersson, who has been kind enough to make his software available to all for non-commercial use. Well, that’s about it for this project. SC Happy PICing! OMPONENTS Order by phone: 08 9479 4850 RADIAL ELECTROLYTICS (16V) 1-9 10+ 1uF $0.26 $0.22 2.2uF $0.26 $0.22 3.3uF $0.26 $0.22 4.7uF $0.28 $0.24 10uF $0.30 $0.26 22uF $0.32 $0.28 33uF $0.35 $0.28 47uF $0.38 $0.30 100uF $0.38 $0.30 220uF $0.40 $0.32 330uF $0.50 $0.45 470uF $0.55 $0.50 1000uF $0.70 $0.55 2200uF $0.90 $0.70 3300uF $1.35 $1.10 4700uF $1.50 $1.20 AXIAL POLYESTERS (630V) 1-9 10+ 0.001uF $0.60 $0.50 0.0022uF $0.65 $0.55 0.0047uF $0.65 $0.55 0.01uF $0.70 $0.60 0.022uF $0.85 $0.75 0.033uF $1.40 $1.25 0.047uF $1.55 $1.35 0.1uF $1.70 $1.45 0.22uF $1.85 $1.60 0.47uF $2.50 $2.20 RADIAL ELECTROLYTICS RADIAL ELECTROLYTICS (25V) 1-9 10+ (50V) 1-9 10+ 4.7uF $0.22 $0.18 10uF $0.22 $0.18 10uF $0.22 $0.18 22uF $0.22 $0.18 22uF $0.22 $0.18 33uF $0.38 $0.30 33uF $0.33 $0.26 47uF $0.38 $0.30 47uF $0.38 $0.30 100uF $0.60 $0.50 100uF $0.42 $0.32 220uF $0.75 $0.60 220uF $0.55 $0.45 330uF $0.80 $0.70 330uF $0.60 $0.50 470uF $1.20 $1.00 470uF $0.65 $0.52 1000uF $1.50 $1.20 1000uF $0.90 $0.70 2200uF $2.80 $2.00 2200uF $1.30 $1.00 4700uF $4.30 $3.75 3300uF $1.85 $1.45 4700uF $2.60 $2.00 Fax: (08) 9479 4417 Email: capacitor<at>bigpond.com Snail mail: PO Box 437, Welshpool, WA 6986 Aust. 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(To subscribe, see page 57) ALL PRICES INCLUDE GST UNDERSTANDING TELEPHONE ELECTRONICS SETTING UP A WEB SERVER By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. $ 59 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. 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 to date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback. $ 59 SILICON CHIP'S ELECTRONICS TEST BENCH First published 2000 A collection of the “most asked for” Test Equipment projects and features from the pages of Australia’s “most asked for” electronics magazine. Exceptional value at $10.95 O R D E R H E R E P&P  AUDIO POWER AMPLIFIER DESIGN...............................$85.00  INDUSTRIAL BRUSHLESS SERVO MOTORS..................$99.00  VIDEO SCRAMBLING/DESCRAMBLING..........................$65.00  TCP/IP EXPLAINED.........................................................$99.00  LOCAL AREA NETWORKS...............................................$69.00  SETTING UP A WEB SERVER..........................................$69.00  THE CIRCUIT DESIGNER’S COMPANION........................$65.00  ELECTRIC MOTORS AND DRIVES...................................$65.00  UNDERSTANDING TELEPHONE ELECTRONICS.................$59.00  AUDIO ELECTRONICS.....................................................$85.00  GUIDE TO TV & VIDEO TECHNOLOGY............................$59.00  EMC FOR PRODUCT DESIGNERS...................................$99.00  DIGITAL ELECTRONICS ..................................................$65.00  ESSENTIAL LINUX..........................................................$85.00  SILICON CHIP TEST BENCH............................................$10.95  SILICON CHIP COMPUTER OMNIBUS............................$10.95               ORDER TOTAL: $...................... Orders over $100 P&P free in Australia. AUST: Add $A5.50 per book NZ: Add $A10 per book, $A15 elsewhere By Simon Collin. Published 1997. $ 69 Covers all major platforms, software, links and web techniques. It details each step required to choose, install and configure the hardware and software elements, create an effective site and promote it successfully. 273 pages, in paperback DIGITAL ELECTRONICS – A PRACTICAL APPROACH By Richard Monk. Published 1998. With this book you can learn the principles and practice of digital electronics without leaving your desk, through the popular simulation applications, EASY-PC Pro XM and Pulsar. Alternatively, if you want to discover the applications through a thoroughly practical exploration of digital electronics, this is the book for you. A free floppy disk is included, featuring limited function versions of EASY-PC Professional XM and Pulsar. 249 pages, in paperback. 65 $ SILICON CHIP'S COMPUTER OMNIBUS First published 1999 Hints, tips, Upgrades and Fixes for your computer from articles published in SILICON CHIP in recent years. Covers DOS, Windows 3.1, 95, 98 and NT. A must for the computer user. $10.95 INC GST TAX INVOICE Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ___________________________________ Postcode_______________ Daytime Phone No. (______) __________________________________ STD Email___________________<at>_________________________________  Cheque/Money Order enclosed OR  Charge my credit card –  Bankcard  Visa Card  MasterCard No: Signature______________________Card expiry date PLUS P&P (if applic): $........................... TOTAL$ AU.............................. POST TO: SILICON CHIP Publications, PO Box 139, Collaroy NSW, Australia 2097. OR CALL (02) 9979 5644 & quote your credit card details; or FAX TO (02) 9979 6503 FEBRUARY JONLY. anuary 2001  85 ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ALL PRICES INCLUDE GST FEBRUARY 2001  85 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG The 32V 5-valve Operatic Mignon Valve radios designed for remote country areas were quite different from their city cousins. They had to have far more sensitivity to cope with weak signals and also ran from 32V battery lighting system supplies. And just to make it even more difficult, they had to cope with the interference from the vibra­tor used to generate the HT. As the majority of the vintage radio enthusiasts are city-based, many have not had the opportunity of seeing and being involved with sets specifically designed to operate in remote rural locations. They are quite different, as can be appreciated when all of the conditions that these sets had to work under are taken into consideration. In the 1950s, commercial AM broadcast stations had an aerial power of 2kW in country areas and 5kW in the city. Nation­al stations were up to 10kW and many are now 50kW. In most country areas, there were usually only two or three stations within a radius of perhaps 160km. If you wanted to hear more, it was necessary to have a large outside aerial and an earth – and a set that was quite sensitive. I lived near Bordertown in South Australia and the only stations of good strength were 3WV with 10kW 110km away at Dooen, 3LK (3WM) with 2kW 130km away at Lubeck, and 3SH with 2kW 250km away at Swan Hill. The typical mains-operated 4-valve set was totally inade­quate and the average 5-valve (including rectifier) mains receiv­er was still struggling to do a satisfactory job. To get the necessary sensitivity, 5-valve sets were used in rural areas. They worked from 32V DC (ie, battery-powered home lighting sys­tems), so no rectifier was need­ed and all five valves were amplifiers. Typically, these sets had an RF stage, converter, an IF stage, detector and first audio amplifier, and an audio output stage. In normal sets, AC mains operation was quite easily achieved using a trans­former with windings to supply the various voltages required for the valves and a vacuum tube rectifier to convert the AC to DC. On 32V DC sets, things were nowhere this easy. Nominally, the receiv­er could be like its AC mains brother but to supply the high voltage (HT) for the valves, it was necessary to use a vibrator power supply. Vibrator supplies The 32V Operatic Mignon, made in South Australia, was really equivalent to a 6-valve mains receiver since it did not use a rectifier. Its RF stage was highly desirable since it was often used in remote rural areas. 86  Silicon Chip A vibrator a is solenoid-driven mechanical switch which opens and closes its contacts at between 100 and 150 Hertz (depending on manufacturer). The pulsating DC is applied to a transformer specifically designed to The Operatic Mignon used a vibrator to derive the HT from the 32V DC input. As with all vibrator sets, there is a trap in that if the 32V supply is reversed, all the electrolytics on the HT rail will be damaged. In fact, a series silicon diode (rated at 3A) would be good insurance. be used with a vibrator. The transformer steps this up in its secondary where a much higher square wave AC voltage is developed. A second set of contacts on the vibrator “rectify” the secondary voltage to produce the HT (high tension) for the plates and screens of the valves. This sort of vibrator with two sets of contacts is said to be “synchronous” because the contacts work in unison. Asynchronous vibrators have one set of contacts, to switch the primary current, and the secondary voltage is recti­fied by a valve rectifier. One trap with vibrator supplies is that if the 32V supply is reversed, the electrolytic capacitors get charged up with the wrong polarity and the set won’t work. It doesn’t do the electro­ lytics much good either! The transformer must be “tuned” using “buffer” capacitors so that there is minimal sparking at the vibrator points, otherwise the vibrator will have a very short life. Even with buffer capacitors, there is still some sparking at the vibrator contacts (also called “points”) and radio interference is produced. This interference would wipe out all radio reception if it were not dealt with. Typically, the whole vibrator power supply is shielded, as can be seen in the Operatic. Some sets had double-shielded sup­plies and also single point earthing was commonly used to prevent interference currents circulating around the receiver chassis. Some areas are very remote from radios stations which means that daytime radio reception on the medium wave broadcast band is virtually non-existent. At night, many stations are heard but suffer from selective fading and often there is more than one sta­tion on the same frequency. So that day-time reception could be achieved, at least one shortwave band was installed. This allowed the domestic shortwave stations to make up for the lack of medium-frequency reception during daylight hours. These receivers also had to work off a very variable power supply, which could be as low as 28V and as high as 40V. Sometimes extra cells were added to the 32V bank of batteries to make up for voltage drop in the cables and the voltage could reach 45V. Some sets had a 3-position power switch marked “Off”, “Charge” and “On”. In the “Charge” position, a resistor was placed in series with the supply to reduce it to around 32V when the batteries were being charged. As can be understood, remote country listeners really had it tough in regard to getting reasonable radio reception. The radio set designers had quite a task to design suitable receivers for these remote locations. That they succeeded can be seen in the Operatic Mignon and sets produced by other manufacturers. The Operatic Mignon RF A12 Bland Radio of Adelaide may not be a manufacturer known to many but the Operatic brand name was well known in South Austra­lia and Western Victoria for many years. In country areas, their 32V radios gained a reputation, over several decades, as reliable and sensitive receivers that were well-suited to rural conditions. The Mignon was quite a standard set with nothing unusual in its appearance. It was a good solid brown Bakelite set of 1951 vintage. It is of January 2001  87 moved, then two screws, one at either end of the cabinet are removed and the chassis is just slid out with the dial and all the works attached. I wish all receivers were as convenient as this to disassemble. The chassis can be tipped onto its end where the vibrator box is located or even tipped upside down with no damage to components. A view underneath the chassis shows that it is not unduly cluttered, despite being dual wave and having an RF stage. Vibrator supply & series heater wiring The metal box on the righthand side of the chassis is the shielded vibrator supply. This shielding was crucial in minimis­ing interference to fringe area reception. average size, has the usual slide type dial, and four controls to operate the set. Yes, the wrong knobs are on this set, as it was purchased without them. I’m on the lookout for the right knobs. A view of the back of the receiver shows a metal box on the right which is the shielded vibrator power supply. To the far left is the 3-gang tuning capacitor. The set uses a 6N8 RF stage, 6AN7 converter, 6N8 455kHz IF stage, a 6BD7 detector/AGC and first audio stage, followed by a 6AQ5 audio output. The Mignon is very easy to remove from its case. The four knobs are re- How to Power A 32V Radio Power supplies that put out 32V at an amp or so are quite scarce. However, it is possible to build quite a simple supply that will easily power this and other sets. The following parts are needed: a transformer with a 24V <at> 2A secondary, a bridge rectifier rated at 100 PIV or higher and a current rating of greater than 2A, a 4700µF 50VW electrolytic capacitor and two .01µF 200V greencap or polyester capacitors, plus any necessary mounting hardware and cabling. This supply will comfortably provide up to 1.5A at around 32V DC. 88  Silicon Chip The vibrator power supply has been found to be quite reli­able. Some vibrator supplies are extremely reliable, rarely, if ever, needing a replacement vibrator while others need a new one relatively frequently. If you do replace a vibrator, it is a wise policy to replace the buffer capacitors as a matter of course. In this vibrator power supply, the buffer components are the .004µF capacitor and 10kΩ resistor in series and the 0.5µF capacitor – all these being connected to the vibrator trans­ former in the lower right of the circuit diagram. The voltage ratings of these capacitors must be strictly adhered to as must their capacitance values. The voltage rating on the .004µF capacitor may be as high as 2kV working. WES Components in Ashfield, NSW have suitable capacitors, which are normally used in TV receivers. A value of .0039µF is near enough to .004µF but a 0.47µF capacitor should have a .027µF capacitor placed in parallel with it to nearly equal 0.5µF. This is a 32V DC receiver but the vibrator is rated at 24V. However, this only applies to the reed drive of the vibrator and a 100Ω resistor is used to drop the voltage down from 32V to 24V. Throughout the receiver it can be seen that cathode bias is used, instead of the more popular “back bias”. With most vibrator sets, it is not possible to separate the low tension and the high tension circuits and they have a common negative which goes to chassis or earth. As a result back bias cannot be used. However, it does mean that it is quite practical to measure the current drain of each valve by checking the cathode to earth/chassis voltage. Note that the valve heaters are in series across the 32V supply and there are also resistors across some heaters. ELECTRONIC VALVE & TUBE COMPANY The Electronic Valve & Tube Company (EVATCO) stocks a large range of valves for vintage radio, amateur radio, industrial and small transmitting use. Major current brands such as SOV-TEK and SVETLANA are always stocked and we can supply some rare NOS (New - Old stock) brands such as Mullard, Telefunken, RCA and Philips. Hard to get high-voltage electrolytic capacitors and valve sockets are also available together with a wide range of books covering valve specifications, design and/or modification of valve audio amplifiers. PO Box 487 Drysdale, Victoria 3222. Tel: (03) 5257 2297; Fax: (03) 5257 1773 Mob: 0417 143 167; email: evatco<at>mira.net New premises at: 76 Bluff Road, St Leonards, Vic 3223 The under-chassis wiring is relatively uncluttered. Quite a few of the old paper capacitors were replaced with polyester or metallised polyester types. The resistors are there to balance the voltages across each valve. The 6BD7 and the 6AN7 only draw 0.23A of heater current and this is padded out to 0.3A by the 175Ω resistor. If a 6AN7A was to be used as a replacement, the heater equalising resistor would need to be changed so that it was only across the 6BD7 and be reduced to 90Ω. Likewise the 150Ω resistor bleeds off 0.15A so that the 6AQ5 gets the right current through it (0.45A) and the other valves get 0.3A through their supply line. The dial lamps are fed off their own series 62Ω resistor. Getting it up & running As has been said, the Mignon is a quite conventional re­ceiver designed for use on 32V DC. All of the usual critical capacitors were replaced. It is quite important before turning the set on to make sure that the negative line of the supply goes to the chassis. If it is positive to chassis the HT voltage will be reversed. The set was then tried out – it was rather sick, with the high tension (HT) relatively low. No shorts were found on the HT line so the vibrator was thought to be the culprit for the lack of voltage. The vibrator was removed from the power supply and the mechanism itself removed from its case. To do this, it was necessary to desolder the small lug on the side of the base. The next step was to remove the circlip inside the bottom of the base using a screwdriver and then slip the vibrator out of the case. Vibrators aren’t easy to come by so I decided to clean up the points. This was done by running a points file between each set of points until they appeared reasonably smooth. Fine wet and dry paper was then used to polish the contacts. During this process, the points were closed together under slight pressure to help the polishing action. January 2001  89 vibrators. If you have any vibrator set, I recommend that you always replace the buffer capacitors, except where they are mica and test OK. A general check-up The vibrator was removed from its metal case so that its con­tacts could be cleaned up with an automotive points file. There are a total of five gaps to clean in these synchro­nous vibrators. I checked that the points were reasonably smooth and shiny, by using a magnifying headset. If the points are very pitted, it will not be possible to get them into first class condition. Be careful not to bend the points out of position if you decide to overhaul a vibrator. This vibrator had obviously had a long and hard life, as there was quite a bit of black around the insides, and still is. The foam rubber buffers and the insulated rubber sleeves on the leads to the vibrator plug had all disintegrated. I used contact adhesive to glue some thin rubber strap to either side of the top of the vibrator to act as a buffer so that it wouldn’t bang against the side of the mounting can and make a noise when it was operating. It was not practical to re-sleeve the braid wires coming into the vibrator so 10mm plastic tubing was cut and placed so that all the flexible braid leads were kept apart. This work can be seen in the photograph. A vibrator in poor condition will not provide as much output voltage as a new one but since the receiver is unlikely to be used much, a slightly 90  Silicon Chip dodgy vibrator is not worth replacing. The vibrator in this set isn’t 100% but is still quite adequate. Another problem that sometimes occurs with vibrators is that they vibrate well but there is no output from the supply. I have found some that haven’t been used for years develop an insulating film on the contact points, hence the contacts never make electrical contact with one another. The exception is the reed drive circuit, so a thorough clean even of new vibrators is needed, if a fault like this shows up. As stated earlier, the buffer capacitors are critical to the long life of This circuit shows how the pick­up (crystal cartridge) connec­tions should have been wired, to avoid hearing the radio program when listening to records. Now that the supply was producing a voltage somewhere near the 160 volts expected the receiver started to perform. The IF stages were aligned and no problems were found, with all the adjustments being close. This was done by forcing a strong signal through the set with the signal generator on 455kHz attached to the aerial terminal, the receiver on the broadcast band and the gangs closed. By doing it this way, test instruments do not interfere with the tuning of the IF channel. The tuning peak can be located by placing a digital multimeter (with 10MΩ input resistance) across the volume control and tuning for maximum voltage. By the way, there is an error in the circuit diagram around the pick-up terminals; it won’t work without radio programs also coming through loud and clear along with the record you are playing. The correct portion of this circuit is shown separately. It just goes to show that draughtsmen and proof readers didn’t always get this correct. A liberty was also taken in the way that the IF transformers were drawn in that the resonating capacitors for each winding were omitted. It was always assumed that anyone reading the circuit would know this. The tuning of the RF sections is a relatively complex task which we don’t have space to cover here. Suffice to say that the stages all peaked nicely and the set performed well. Summary A receiver with an RF stage is always desirable; the extra stage of radio frequency amplification really does make a dif­ference on the broadcast band as well as on shortwave. The Oper­atic Mignon is no exception. It is sensitive, has a good delayed AGC system and a moderate audio output level. Operatic receivers do not have any whiz bang circuitry or anything that appears exotic but they work well and just keep on going. They are part of our rural radio heritage. I’m pleased SC to have it in my collection. 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. 12-to-24V inverter wanted I am inquiring about a 12V to 24V inverter. I have several Hella 24V revolving orange lights that I would like to operate on 12V. (M. L., via email). • We have not produced a suitable circuit for your applica­tion. It might be easier to change the lamps to run on 12V – the 24V motors would probably still run at 12V. Amplifier for sound card I am looking to build an amplifier to drive a pair of 4Ω loudspeakers to reasonable levels from my sound card. I want more level than the existing multimedia speakers but I don’t need hifi levels. And I would also like to build the amplifier into the PC itself and power it from the PC as well. I was thinking of using your “Mini Amplifier For Personal Stereos” which was pub­lished in the October 1992 issue. Would this be a good approach? (G. C., via email). • The Mini Stereo Amplifier featured in October 1992 used the TDA2822M dual 1W 8-pin IC amplifier. While it Rev limiter kills the tacho I have recently purchased the Rev Limiter kit described in the April 1999 issue of SILICON CHIP. I installed it as a simple shift-up light into my Proton M21 coupe. After tapping the signal from the triggering module, the shift light works but the car’s tachometer went dead. It seems that no two things can work at the same time. Is there any way I can get around this? I checked out the impedance from the tacho­ meter to be 150kΩ and the voltage from the triggering module to be at 5V. Could this be the problem? (J. M., via email). is still a current design, its output is quite low and probably not enough to suit your needs. Have a look at the MultiMedia Sound System amplifier featured in the October 1996 issue. This used three TDA1519A bridge amplifier ICs to deliver around 9W into two woofers and 1.5W into two tweeters and also included an electronic crossover. It was designed onto a PC card and was internally powered by the PC itself. Sounds ideal, eh? Jumbo clock is very slow I’ve built the Jumbo Clock described in the March 1997 issue of SILICON CHIP. The clock is running very slow or it doesn’t seems to be running at all. All the LED segments are working, as well as the hour and minute switches. Do you have any suggestions? I think it might be related to the crystal or 4060 chip. (A. W., via email) • The first thing to check is that the colon flashes at a one-second rate. If so, then the problem will be in IC2 or IC3. Check for dry joints, solder between IC pins or hairline cracks • The input impedance for the low voltage input for the Rev Limiter is around 10kΩ. However, this could be much lower if the 1µF and .056µF capacitors plus the 10kΩ resistor are still on the PC board for the ignition coil input. So first remove the above components from the PC board. If you still have problems running the tachometer, it is possible to increase the input impedance by changing the 10kΩ resistor across ZD2 to 100kΩ and the 1kΩ low voltage input resistor to 10kΩ. The .056µF capacitor should be changed to a value of .0056µF (5n6 or 562) or it could be removed altogether. in the PC tracks. If the colon does not flash or is very slow, check that the pin 14 output of IC1 does go high and low at a 2Hz rate. You can use a LED connected in series with a 2.2kΩ resistor to check this. Alternatively, use an oscilloscope, logic probe or even an analog multimeter. If IC1 is not producing the correct rate, then the problem could be with the crystal or components connecting to it. Note that it is unlikely that any of the ICs are faulty. Simply check for other problems either with the PC board or soldering. Alter­natively, the resistors for the oscillator could be incorrect or the capacitors the wrong value. RC speed controller is temperature sensitive I built the RC Speed Controller described in the May 2000 issue of SILICON CHIP. I had a problem in that the ZN409’s 1.5ms reference oscillator varied significantly from day to day and a hair dryer showed it to be a temperature thing. The nominal 1.5ms reference, adjusted at “room temperature” (about 18°C in my garage), varied between 0.5ms and almost 2ms when the PC board was heated or cooled (between maybe 40°C and 15°C). Even simply placing a finger on the capacitors caused the rise time to begin to drift. There’s not much in the way of external parts for the oscillator, so I replaced the two 0.1µF capacitors with tantalum types – now it’s rock steady, even at elevated temperatures. Measuring the two old capacitors out of circuit showed they had a room temperature capacitance of 0.1µF, which dropped down to under .05µF once warmed. All components have some kind of temperature coefficient, though I’ve never seen such a sensitivity before! (The supplied units were those small blue, non-polarised types, polyester I think?) Perhaps I received part of a bad batch? January 2001  91 Concern about mobile phone radiation I have been carrying my latest mobile phone around in my lefthand pocket for the past two years, instead of on my belt. I drive a forklift at work and the phone gets pushed up against the fork seat and it annoys me. I also have a mobile phone vibrator, because I have to go into a noisy factory and I cannot hear the phone ringing. The vibrator is supposed to vibrate when the mobile phone rings. It does that all right but it also vibrates when within 2m of a working microwave oven. Does this mean mi­crowave ovens leak microwaves? When the phone vibrator is goes off, does this mean I’m being zapped with microwaves from the phone? The front of the phone is facing toward my body. The reason I’m asking this is that I’ve been Also, I have a suggestion for people who want to use the controller with relatively light loads – rather than cut a hole in the case to fit the loaded PC board, cut off the MOSFET tags. This way, you don’t need to make any holes in the little case. The tags don’t add much in the way of heatsinking and with 20A loads or less, the MOSFETs don’t even get warm. Finally, this mod makes it possible to make the case water-resistant via a silicone seal around the case lid. (B. L., via email). • The blue capacitors are monolithic (stacked ceramic) types intended for supply bypassing on computer and logic boards. They are OK for that task but as with any high-K ceramic capacitor, they do have quite a large temperature coefficient and should not be used in any circuit involving critical time constants. Improving the Class A amplifier I have read with interest your recent project on the Ultra-LD Amplifier (March, May & August 2000) and as I already have a very good class AB amplifier I am interested in your July 1998 15W class-A design. Would it be possible to amend 92  Silicon Chip told I’ve got an enlarged prostate and no drugs I’ve taken in the last 12 months have made much difference. I thought my mobile phone might be causing my prostate problem. I’ve since turned my mobile off. Do you think my prostate became en­larged due to the microwaves coming from my phone? (O. M., via email). • Yes, some microwave ovens do leak and you certainly are being irradiated by your phone every time you use it. If you want a demonstration of this effect, have a listen to the rhythmic beepety-beep interference to a normal phone when anyone is using a mobile phone in the near vicinity. However, an enlarged pros­tate is a normal condition for anyone (male, that is) over 50. Is it likely to be made worse by a mobile phone? We don’t know and doubt if anyone does. this to use the later generation of transistors used in the output stages of the 100W class AB amplifier? Is it possible to raise the voltage with these new transistors to increase the output to about 25W? What changes would be required to increase the output of the 15W project by using paralleled output transistors? (C. M., via email). • Since the distortion is already extremely low, there is little point in going to the more expensive transistors. It would be possible to increase the supply rails to get more power but this would greatly increase the overall power dissipation. We have not done any work along these lines and therefore we are reluctant to recommend that it be done. Electric fence needs extra zap Some years ago I purchased an Electric Fence kit from Jaycar that I believe came from your magazine. It used a car ignition coil to produce the charge. I am having some difficulty gaining any real noticeable “boot” at the fence and need some pointers regarding what to look for to fix the problem. It may be as simple as replacing the coil (which was old) but that is a $30.00 fix that may be unnecessary. Can you help? (K. M., via email). • This project was published in the July 1995 issue of SILICON CHIP. Two errata on this project have been published. First, we recommended changing the 6.8Ω resistor to 1.2Ω to increase the output to 10kV. If you short out the resistor, the coil will deliver full output. Second, use a 500mA fuse as 250mA fuses can have high resistance. Shifting a sawtooth oscillator I’ve made up the Waveform Generator from Jaycar’s Short Circuits Volume 3 handbook and it works fine. But can I have it go down to say 20Hz (rather than the present 100Hz) so I could use it to test subwoofers? (G. K., via email). • You can change the minimum frequency to 20Hz by using a capacitor at pin 2 which is at least five times bigger; try .056µF or larger. However that will mean that the maximum frequency will also be five times lower, at around 4kHz. The sawtooth waveform is really not suitable for testing any loudspeaker since it has quite a high harmonic content. You need a low distortion sinewave oscillator for testing speakers. VU meter needs auto level control I have constructed a LED VU level meter for my car stereo, which is purely for aesthetic purposes; ie, regardless of volume, the display should work over most of its displayable range. The only problem is that the stereo does not have a constant volume output and therefore the input sensitivity of the VU meter must be varied each time the volume of the stereo is varied. Is there a way to obtain a constant volume level from the stereo, so that I won’t have to turn two dials each time I want to change the volume? (J. P., via email). • Short of building our CD Compressor described in the July 2000 issue, the only way to avoid the need to change the LED VU setting is to take the signal from across the volume control; ie, you have to access the signal inside the car stereo. Spark won’t climb Jacob’s Ladder I have built a kit for the Jacob’s Ladder de­scribed in the September 1995 issue of SILICON CHIP. I want to know why the spark only travels half the way up the wires? The length of my wires are about 220mm with a gap no bigger than 20mm. How can I make the spark go farther up the wire? (L. C., Albany, WA). • The spark will travel all the way up the wire if the following requirements are met. First, there can be no kinks in the wire as these Mailbag: from page 65 The strong work ethic and individualism brought by the NZ pioneers from the United Kingdom were reinforced in the isolation of NZ hinterland, increasing the concepts of self-worth, egali­tarianism and the importance of the individual to be self-directing. Thus many civil liberties are protected by the “cul­ture”. For these reasons, NZ “pollies” and regulators are reluct­ ant to write and enforce restrictive regulations. Australians have allowed AS/ NZS 3000-2000 Wiring Rules to be interpreted in a legalistic manner. Little imagination is needed with the Australian interpretation to see the work of insurance underwriters in league with powerful legal lobbies and with industry associations and employee unions for the stated purpose of “safety”. But the bottom line is dollars: income from electrical trade employment, consultants’ fees and legal argument and minimising the will cause the spark to stop at this point. Second, the flare or angle at which the wires slope outward towards the top must be very gradual. Also make sure the two wires are exact­ly vertical since the rising spark relies on convection of the heated air (above the spark). Finally the length of spark is ultimately dependent on the coil used. You may be able to obtain slightly more spark if you change the 0.33µF capacitor at pins 2 & 6 of IC1 to a slightly larger value. This will increase the dwell or charge time for the coil. Try a 0.47µF instead. insurance companies’ liabilities and pay­outs for injury and property loss. Quite rightly your “Letter” comments that New Zealanders are not dying like flies from electrocution and I add that if many NZ houses were burnt down due to electrical wiring faults, then restrictive regulations would be enacted. It seems to me that if the governments of Australia were really concerned about stopping “illegal” Notes & Errata Pink Noise Source, January 1997 & Electronics TestBench: the 22kΩ resistor shown connected between pins 1 & 2 of IC1 on the PC board overlay diagram on page 42 (January 1997) should be 220kΩ. The circuit diagram is correct. 2-Channel Guitar Preamplifier November 2000: the circuit diagram incorrectly shows S1 as a 2-pole (DPDT) power switch. It should be a electrical work then every hardware shop in the country would be banned from selling all electrical cable for fixed electrical wiring, and all switch­ es, socket outlets, batten holders and junction boxes. These items are exclusively made for fixed wiring installation. As everyone knows, these are available in “bubble packs” for retail sale to any person regardless of age, gender or qualification. Perhaps supermarkets should be banned from selling replacement light globes. The Australian community would not tolerate such an outra­geous and preposterous erosion of our liberty to “have a go” to make our own repairs. Your “Letter” mentions the need to lobby our politicians to get restrictive electrical worker regulations scrapped but our “pollies” only act on the advice of technical specialists when they see it is to their electoral advantage. I suggest that until we change Australian culture to be more like the New Zealand model, we will keep on the legalistic path (as USA copycats) of more control by bureaucrats who believe more control is good for its own sake. I. Morrison, Marleston, SA. SPDT type and it switches the Active mains lead only. In addition, the parts list for the main PC board contains some errors. First, there should be 6 x 2.2µF NP PC electrolytic capacitors (not five) and a 1 x 1µF NP PC electrolytic capacitor should be added to the list. Second, there should be 15 x 10kΩ resistors and 4 x 150Ω (not 14 & 3). Finally, the 4.7kΩ resistor connecting to pin 3 of IC3 on the overlay (Fig.4) SC should be 27kΩ. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. January 2001  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FRWEEBE YES! Place your classified advertisement in SILICON CHIP Market Centre and your advert will also appear FREE in the Classifieds-on-the-Web page of the SILICON CHIP website, www.siliconchip.com.au And if you include an email address or your website URL in you classified advert, the links will be LIVE in your classified-on-the-web! S! D E I F I S C LAS EXCLUSIVE TO SILICON CHIP! CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12 words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­ ________________________ Card expiry date______/______ Name _____________________________________________________ Street _____________________________________________________ Suburb/town _________________________ Postcode______________ 94  Silicon Chip FOR SALE VCR Controller use a standard home VCR for Surveillance Event Recording Wireless IR Control only $39 * DOME 480 Line 0.05 Lux SONY CCD & ChipSet from $81 * COLOUR DSP DOME: 400 Line from $139 * 600 + Line from $164 * COLOUR DSP PIN in PIR CASE from $152 * MINI CAMS from $67 * DSP COLOUR from $133 * PC REMOTE VIEW, PAGING, WEB-CAM, DVR System High 768 x 576 Resolution from $219 * QUAD 1024 H-Pixels from $175 * COLOUR QUAD only ! $380 * MULTIPLEXER 4 Ch from $633 * 4 Ch Switchers only ! $79 * COLOUR Bullet Cameras from $122 * Digital PC 4 Ch Video Recorder System from $159 * DOME VIDEO CAMERAS COLOUR from $77 ! Mono from $53 ! BULLET from $97 TWO YEAR WARRANTY * DIY PLUG-IN 20 metre AV Cables from $20 BLEMISH FREE & LOW BLEMISH CCDs * UP TO 5 YEARS WARRANTY * OVERNIGHT DELIVERY * www. allthings.com.au RAINBOW POWER COMPANY: Sol­ar Panels 80W $660, Batteries, Inverters, Regulators, Rebates available – call (02) 6689 1430. COVERT VIDEO SURVEILLANCE Tiny Sub-Matchbox from ~ 6 grams Wireless Video & Audio TRANSMITTERS from $77 * Pinhole Cameras from $67. Easily concealed in: Mobile Phone Case, Clock, VCR Cassette, Toys, Teddy Bear (Nanny-Cam), Smoke Detector, Ornament, Cap, Cigarette Pack, etc. www. allthings.com.au TELEPHONE EXCHANGE SIMULATOR: test equipment without the cost of telephone lines. Melb 9806 0110. http://www.alphalink.com.au/~zenere WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/Ecowatch phone: (03) 5968 4863; fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. KITS KITS AND MORE KITS! Check ‘em out at www.ozitronics.com SEE-in-the-DARK Camera with in-built IR LEDs in Water Resistant Case for disturbance-free Baby - Bird - Animal observation from $147 * DIY Plug-In 20 metre Cable & Plug Pack from $33 * www.allthings.com.au C COMPILERS: everything you need to develop C and ASM software for 68­HC08, 6809, 68HC11, 68HC12, 68­ HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $170.50 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 and 68­HC12 for $88. Debug monitors: $88 for 6 CPUs. All compilers, XASMs and monitors: $5280. 8051/52 Simulator (fast, now incl. 80C320): $88. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5.50 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x and 89Sxx series, and some AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $220 $11 p&p. SOIC adaptors: 20-pin $99, 14-pin $93.50, 8-pin $88. Credit cards accepted. GRAN­ TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150 or Internet: http://www.grantronics.com.au HOME CCTV Mono / Colour PAKS only ! $119 / $151 Full DIY Plug-In to TV / VCR 20 metre Cable, Plug Pack & Camera www.allthings.com.au RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production soon. Tel (02) 9738 0330; Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio www.procontechnology.com.au fischertechnik robotic kits, interfaces and Atmel AT90S8535 microcontroller boards from $66. Starter kits with cables and software, ready to program in ROLA AUSTRALIA PH/FAX (08) 8270 3175 WEB SITE WWW.BETTANET.NET.AU/GTD CHECK OUR WEBSITE FOR DETAILS ON KITS AND COMPONENTS • • • • Silvertone’s RC Receiver Still the best little performer available! TRANSMITTER KITS AND MODULES AUDIO MODULES COMPUTER INTERFACE KITS RADIO STATION AUDIO SOFTWARE NEW: Our MP3-CD player in short form for $169 inc GST. Includes the following: processor board, front panel display and tactile keypad; just add a case, cables, 12V power supply and a CD-ROM drive. Play CDs and up to 2600 MP3’s from a CDR. Great for car or home. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. Still only $129.50 AM or $149.50 FM. May be used with most ppm transmitters. This and many other radio control products available from: Silvertone Electronics, PO Box 580, Riverwood 2210. Phone/Fax (02) 9533 3517. www.silvertone.com.au AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Rhodes in Sydney. A genuine interest in electronics is a necessity. Phone 02 9743 5222 for current vacancies. compiled BASIC or assembler from $99. Design service available. Credit cards accepted. Phone (03) 9830 6288. DIY CCTV PAKS 4 Cameras & Switcher .................$354 as above COLOUR .....................$466 4 Cams, Switcher/Monitor ...........$495 as above 14" Monitor ................$528 4 Cams & QUAD .........................$478 4 COLOUR & QUAD ....................$752 Time-Lapse 24 hr VCR only $699 with CCTV Systems ! MORE at: www.allthings.com.au Fully Plug-In DIY Paks with Cables & Power Supplies ALSO PC Digital Motion / Sound detection & activated Video / Audio Recording systems 08 9349 9413 DON’T MISS Australia’s biggest and best exhibition and sale of new and used radio and communication equipment at the Central Coast Field Day, Sunday 25th February, Wyong Race Course, just 1 hour north from Sydney. Starts 8.30 a.m. Special Field Day bargains from traders and tons of disposals gear 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. in the flea market. Exhibits by clubs and groups with interests ranging from vintage radio, packet radio, scanning, amateur TV and satellite comms. www. ccarc.org.au Ph (02) 4340 2500. USB DEVELOPMENT KIT CY3650, Temperature/Voltage measurement via phone line, PC-controlled VHF Receiver http://www.ar.com.au/~softmark QUAD 4 pixs 1 screen from $247 * Real Time * High better than SUPER-VHS 1024 Pixel Resolution * Time * Date * Camera Title * Alarm Input / Output * Remote Camera Selection * FREEZE * www.allthings.com.au KIT ASSEMBLY ANY KITS assembled/repaired: professional, speedy service. Phone continued next page January 2001  95 DON’T MISS THE ’BUS Advertising Index Acorn Icon (Akhurst Calendar)....60 Altronics................................. 62-63 Av-Comm Pty Ltd.........................95 Do you feel left behind by the latest advances in com­puter technology? Don’t miss the bus: get the ’bus! Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. Dick Smith Electronics........... 18-21 Price: $12.50 (incl. GST) Order now by using the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. Investment Technology..............IBC Direct Components......................83 EMC Technologies.......................55 Evatco..........................................89 Harbuch Electronics....................54 Instant PCBs................................95 Special subscription offer available only while stocks last. Jaycar ................................... 45-52 Kalex............................................10 Silicon Chip Binders  Each binder holds up to 14 issues  Heavy board covers with 2-tone green vinyl covering  SILICON CHIP logo printed in gold-coloured lettering on spine & cover REAL VALUE AT Mass Technology.........................55 P MicroZed Computers...................55 $12.95 PLUS P & Price: $A12.95 plus $A5 p&p each (Australia only; not available elsewhere). Buy five and get them postage free. Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Microgram Computers..........3,OBC Printed Electronics...................... 95 Protel Australia..........................IFC Questronix...................................55 RF Probes...................................55 Rola Australia..............................95 R.T.N............................................13 Nev­ille Walker (07) 3857 2752 or email flashdog<at>optusnet.com.au NEG. Tel John<at>AER (03) 9482 4958 0415 305 470. WANTED WE PAY UP TO $60 for contributions to Circuit Notebook. Send your circuit with a brief description to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. PERSON WITH EXPERIENCE / APTITUDE able to fault find & repair PCBs – without diagrams. GENEROUS PKG Silicon Chip Binders....................96 Silicon Chip Bookshop........... 84-85 SC Computer Omnibus...............96 SC Electronics Testbench............31 Silicon Chip Subscriptions...........75 Silvertone Electronics..................95 HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. http://sites.netscape.net/solislp/ 96  Silicon Chip Smart Fastchargers.....................71 Solar Flair/Ecowatch....................95 Telephone Technical Services.....59 Truscotts Electronics....................71 _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334.