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JULY 2011 ISSN 1030-2662 11 9 771030 266001 PRINT POST APPROVED - PP255003/01272 We test the latest One for the 9 serious boaties: Aussie company’s new digital technology that you can program yourself – and they’re half the price! REMOTE RUDDER POSITION INDICATOR D-I-Y Hearing Aids $ 30* NZ $ 11 90 INC GST INC GST HANDHELD CONTROL SMART I/O MODULE SENSOR DATA SMART I/O MODULE SMART I/O MODULE CONTROL & DATA Control your world using CONTROLLING COMPUTER SMART I/O MODULE SENSOR DATA CONTROL LINUX Our new Ultra-LD Mk.3 200W Module 0.0006% DISTORTION siliconchip.com.au J 2011  1 The lowest distortion class AB amplifier ever published – anywhere in the world! uly Winter Projects at Jaycar TEST & MEASUREMENT Mini Wireless Weather Centre Keep up-to-date with current and forecasted atmospheric conditions at a glance. With two small outdoor weather sensors, it precisely measures, records and forecasts all the basic weather parameters and displays them on an LCD screen. Handy features include three forecast icons based on changing barometric pressure. LCD screen comes with inbuilt desk stand and can be easily wall mounted. A must for anyone involved with food preparation, archiving or storage. This USB datalogger logs temperature and humidity readings and stores them in internal memory for later download to a PC. The measurement interval is adjustable - you simply set up the recording parameters then download the data when you need it. • Easy USB interface • Mounting bracket included • Windows compatible software • Dimensions: 100(L) x 22(W) x 20(H)mm QP-6013 WAS $119.00 99 00 $ SAVE $20 00 Also available: USB Temperature/Humidity Datalogger with LCD QP-6014 WAS $179.00 NOW $159.00 SAVE $20.00 Sound Level Datalogger Designed for recording and logging sound pressure level measurements for quality control, illness prevention, acoustic design or any other type of environmental sound measurement in domestic or industrial applications. Battery and windsock included. • USB interface 00 $ • Over-range indication • Dimensions: 140(L) x $ SAVE 40 00 28(W) x 21(H)mm QM-1599 WAS $149.00 109 Semiconductor Component Analyser Intelligent semiconductor analyser that offers simple identification and testing of a variety of 2 or 3-pin devices. Type and lead identification as well as forward voltage, test current and other parameters for transistors. NETWORK 16 CHANNEL H.264 DVR WITH 500GB HARD DRIVE This H.264 DVR incorporates a 16 channel multiplexer and is fitted with an on-board Ethernet connection allowing you to access the DVR remotely. Connect to a network and access the recorder with a standard browser or via a smart phone app for iPhone®, iPad® HD, Android, or Windows Mobile. The system utilises password authentication to avoid unauthorised use and you can enable offsite access if a broadband connection is present on site. The DVR supports large SATA hard drives and is fitted with a 500GB drive. 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J-B Weld Epoxy Easy, convenient and inexpensive alternative to welding, soldering and brazing. Two part epoxy resin and when mixed together forms a compound as tough as steel. Bonds metal, wood, plastics, fabric, paper - just about anything. 14 $ 95 UGlu Industrial Glue Strips Easy-Tear Magnetic Mounting Tape Simply cut a strip to the size you need, then fix just like doubleSimply apply sided tape to create a tape to a permanent, instant bond. Nonsupporting toxic, acid free, no mess. Pack surface and contains eight 75 x 30mm strips. another piece to the item then • Waterproof and stick it anywhere you like. Ideal for weatherproof craft projects, calendars, kids’ • Made in USA artwork or to-do lists. NA-1522 $ 95 • One side magnetic, one side adhesive 00 $ SAVE 4 • Easy tear-off, no $ 95 scissors DEAL • 3m x 12mm roll LM-1608 WAS $9.95 Buy all 3 for $22 SAVE $10.85 5 7 To order call $$$ MONITOR YOUR WINTER WEATHER USB Temperature/Humidity Datalogger • 25ml NA-1518 SAVE Don’t forget to check out our BRAND NEW 508 page catalogue. Available in stores & stockists for only $3.95 JULY 2011 1800 022 888 www.jaycar.com.au Prices valid from 24/06/2011 to 23/07/2011. Limited stock on sale items. No rainchecks. 99 00 $ • Storm warning indicator • LCD screen: 135(W) x 34(D) x 140(H)mm • Outdoor wind sensor: 110(H) x 180(D)mm • Temp/bar/humidity sensor: 57(W) x 57(D) x 160(H)mm XC-0349 DEAL Buy both for $120 SAVE $18.95 Wireless rain gauge to suit sold separately XC-0347 $39.95 INSPECTION CAMERA WITH RECORD & DETACHABLE WIRELESS SCREEN This inspection camera can capture video and pictures in confined and dark locations with its 9mm diameter and four white LEDs. The head and flexible boom being IP67 rated enables them both to be submerged in water during operation. Included is a 2GB MicroSD card (accepts up to 16GB) on which video and pictures can be recorded. 299 00 $ • 3.5" detachable colour LCD • Wireless transmission frequency 2.4GHz • Video memory usage approx. 27MB/min - With 2GB MicroSD card approx. 75 min can be stored • Lithium-ion battery in LCD - 3 hour charge, 2 hour usage • Strong plastic carry case • 4 x AA batteries required for camera handle • USB & video cables included • Power supply 5VDC 1A included • Dimensions: Monitor 100 x 70 x 25mm Camera handle 86 x 145 x 41mm Flexible boom 1m long QC-8712 SILICONE RESCUE TAPE Wrap this around your leaky pipe and it will bond in seconds. A self fusing tape for a permanent air-tight and water-tight seal. Designed for quick plumbing repairs, sealing hoses in your car/truck/boat, coating the ends of rope, wrapping tool handles etc. • Measures: 1" x 12ft (approx 25.4mm x 3.6m NA-2829 19 95 $ See demo video on website All Savings are based on Original RRP Contents SILICON CHIP www.siliconchip.com.au Vol.24, No.7; July 2011 Features 14 Australia Hears . . . And So Do I New digital hearing aids developed in Australia are now available for a fraction of the cost of other aids. You can even program them yourself – by Ross Tester 21 Could There Be A SIM-LEI Electric Car In Your Future? The evolution of electric cars continues. This one has in-wheel motors, does 0-100km/h in just 4.8s and has a range of 300km plus – by Ross Tester 22 Control Your World Using Linux PCs running Linux are quite open to the experimenter. Here’s how to use your computer to control external equipment – by Nenad Stojadinovic 72 A Look At Amplifier Stability & Compensation Ultra-LD Mk.3 200W Amplifier Module – Page 30. Portable Lightning Detector – Page 42. The Ultra-LD Mk3 amplifier described in this issue has a new frequency compensation arrangement to lower distortion. We explain why amplifier frequency compensation is necessary and how it works – by Nicholas Vinen Pro jects To Build 30 Ultra-LD Mk.3 200W Amplifier Module Upgraded design has even lower distortion than before. It also boasts much improved thermal stability, has a flatter frequency response and can deliver 135W RMS into 8Ω or 200W RMS into 4Ω – by Nicholas Vinen 42 A Portable Lightning Detector This device could literally save your life. It gives advance warning of approaching thunderstorms, giving you time to take shelter if out in the open or to disconnect valuable gear from the mains if at home – by John Clarke 62 Rudder Position Indicator For Power Boats Easy-to-build unit senses the rudder position and sends the information to a companion receiver unit via a 433MHz RF link – by Nicholas Vinen 82 Build A Voice-Activated Relay (VOX) Turn devices on or off by speaking (or by using some other sound) with this simple VOX circuit. It features adjustable sensitivity and delay– by John Clarke Special Columns 57 Serviceman’s Log Restarting after the Christchurch earthquake – by the Serviceman 87 Circuit Notebook (1) Surf Sound Synthesiser; (2) Geiger Counter Uses Cockroft-Walton Multiplier; (3) PICAXEL The Electronic Cricket; (4) Wein Bridge Oscillator Uses An LM386 Power Amplifier; (5) Synthetic 5-Segment Potentiometer Rudder Position Indicator For Power Boats – Page 62. 62. 92 Vintage Radio Hotpoint Bandmaster J35DE console radio, Pt.1 – by Maurie Findlay Departments   2   4 40 98 Publisher’s Letter Mailbag Product Showcase Ask Silicon Chip siliconchip.com.au 101 Notes & Errata 102 Order Form 103 Market Centre Build A Voice-Activated Relay – Page 82. July 2011  1 SILICON SILIC CHIP www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc. (Hons.) Technical Editor John Clarke, B.E.(Elec.) Technical Staff Ross Tester Jim Rowe, B.A., B.Sc Nicholas Vinen Photography Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Kevin Poulter Stan Swan 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 is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $97.50 per year in Australia. For overseas rates, see the order form in this issue. Editorial office: Unit 1, 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. Fax (02) 9939 2648. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 Recommended and maximum price only. 2  Silicon Chip Publisher’s Letter The quest for ultra-low distortion This month, we present the first article on the Ultra-LD Mk.3 amplifier module. This is the second time we have revisited this class-AB amplifier design and it’s almost getting monotonous, as we announce even lower distortion. Exceedingly low! In these days of iPODs and MP3 players, why do we bother? The reason is that those sound sources are so mediocre. Why put up with mediocrity? The same comment can be made of the vast majority of hometheatre systems and indeed, virtually any sound source that most people listen to. Compared to where we were with high-fidelity sound systems based on CD players 25 years ago, we have gone backwards. Furthermore, it can safely be said that the vast majority of people under the age of 30 probably have never experienced a good hifi sound system. If they have, it was probably years ago while they were still living with their parents. We at SILICON CHIP, on the other hand, believe that the best quality sound is still worth striving for. We also have better tools and design methods to help us get there than we did years ago. Our benchmark is the standard of performance available from the best CD players available today, such as the Marantz CD player reviewed in last month’s issue. So in designing a no-holds-barred amplifier, our task is to produce something that does not degrade the sound quality of such a CD player in any way. Or for that matter, the sound quality of a premium Blu-Ray DVD player. Ideally, this means that its total harmonic distortion across the entire audible spectrum up to 20,000Hz must be less than .0015% and its signal-to-noise ratio should be better than -110dB. If we get more distortion or more low-level noise, we are degrading the signal quality. It turns out to be a very difficult task to achieve such a standard. Indeed, home-theatre equipment, from even the best brands, is hard-pressed to achieve .01% harmonic distortion – about 10 times worse. And the typical home-theatre system with class-D amplifiers is a good deal worse again. Our 20W Class-A Amplifier has been our best attempt to date and its distortion is far below that of the best CD and Blu-ray DVD players, for frequencies below 10kHz at least. We have always aimed for the same standard with our more powerful class-AB designs and that is a much more difficult task. But with the Ultra-LD Mk3 amplifier module we have come tantalisingly close, as readers who like to closely compare performance graphs will attest (the relevant graphs for our 20W Class-A amplifier were featured in the May 2007 issue). The difference is that the Ultra-LD module is a great deal more powerful than the class-A design. Significantly, the new module typically has half the harmonic distortion of the module it supersedes. And while we are very pleased to be able to present it, we have not left all those people who built the previous module in the lurch. We intend to bring out a small adaptor PCB which will bring it up to the same standard. Is this the ultimate in amplifier design? In the true sense of the word, it is but only for now. Who knows what new devices and new techniques may bring in the future. In the meantime, our challenge is to produce a complete integrated amplifier featuring the new module and with facilities for analog and digital sound sources. If the development of the new Ultra-LD amplifier module is anything to go by, that could take some time. Stay tuned. Leo Simpson siliconchip.com.au siliconchip.com.au July 2011  3 MAILBAG Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to “Ask SILICON CHIP” and “Circuit Notebook”. Anti-glare glasses are useless at night I noted your comments on glare from headlights. Anti-glare glasses are useless in this scenario. Night vision is mainly processed by the rods in the retina. They are the receptors that respond to low-intensity light. Unfortunately they also stay refractory for 30 minutes after exposure, ie, they take 30 minutes to recharge before being able to fire again at low intensity. Rods also do not respond to light in the red/orange wavelengths but cones do and they have a short refractory period but require higher intensity light to activate. That is why submarines and night cockpits are illuminated with red light to allow the rods to respond to other low intensity (night) light sources. Yellow driving glasses sit on the edge wavelength of rod responsiveness, ie, headlights will just begin to depolarise the receptors but will not make them as refractory for as long as white light and will make it easier to see detail in the situation where there are oncoming headlights. Unfortunately, they will also change the perceived colour of stop lights etc. This is known to car manufacturers as they used to make yellow fog lights to illuminate the side of the road and not blind other drivers, unlike Why medical devices are so expensive In the Mailbag pages of your June 2011 issue, a reader wrote wondering why hearing aids are similar in price to vastly more complicated consumer equipment, such as a laptop. In general, medical equipment is priced between two and 10 times the consumer equivalent. The three main reasons are quality, safeguards and regulation. Medical devices (including hearing aids), should be compared to industrial electronics rather than consumer electronics. 4  Silicon Chip nowadays when fog lights are used as a status symbol, often illegally. Early cataract formation will further refract light and make it harder to see in the context of oncoming headlights but protecting the responsiveness of your rods will lessen the risk of an accident due to temporary blinding. Name & address supplied but withheld at writer’s request. No need to wait for Thorium reactors Luke Biddle (Mailbag, May 2011) is right to propose the use of Thorium in new designs of nuclear reactors but his enthusiasm might need some tempering. As Luke says, there is no expensive isotopic separation required. The only isotope of Thorium to occur naturally is Thorium-232. It is slightly radioactive with a half-life of 14.05 billion years; much longer than that of the naturally occurring isotopes of Uranium, which may account for its greater abundance. The mantles in portable gas camping lamps are made from Thorium dioxide, a ceramic that glows brilliant white when heated and with the highest melting point of all oxides: 3300°C. Many websites advocating Thorium as a nuclear fuel do not make it clear that the various reactor designs are still They are designed to be used day and night, with as little downtime as possible, typically for a lifespan of about 10 years. If a medical device is used in intensive care, operating theatre or on high-risk patients, it must have alarms, interlocks and fail-safe systems to protect patients. Lastly, for a medical device to be sold legally in Australia, it must meet very stringent regulations. For instance, to manufacture a hearing aid, a medical device company must certify every building, room, measurement, very much at the research stage. They also do not indicate clearly that Thorium, unlike that well-known isotope of Uranium, U-235, is not itself fissile, an essential property for an element to become a nuclear fuel. An atom of Thorium-232 must first absorb a neutron to become the Uranium isotope U-233, which is fissile. www.ga.gov.au/minerals/mineralresources/Thorium.html offers a good summary of the situation. It also confirms that there are large amounts in Australia in the form of Monazite sands in Queensland, NSW and WA. To kick-start a nuclear reactor containing Thorium, the Thorium has to be placed in the reactor as a blanket around a fuel load of a fissile isotope, such as U-235 or U-233 and remain there for some months during normal reactor operation so that the absorption of the neutrons and conversion from Th-232 to U-233 can occur. Then, if it is in a current design of watercooled reactor, the blanket material has to be removed, the newly-created U-233 is separated from the unconverted Thorium, then the U-233 is fabricated into new fuel rods to then be used as nuclear fuel. Note that U-233, like U-235 and Plutonium-239, can be used to make a nuclear weapon. Luke’s claim in that respect is not correct. process, machine and material involved, show that the device is safe and effective and be accountable for any death or injuries it causes. It all depends on what purpose a device is sold for: $100 at a pharmacy buys you a heart-rate monitor for jogging. Similar technology sold to a hospital specifically for diagnosis or therapy might cost $1000. Michael Smith, Technical Officer, Clinical Support, Flinders Biomedical Engineering, Flinders Medical Centre, Bedford Park, SA. siliconchip.com.au Thorium advocates concentrate on the possibility of the use of liquidfuelled, high-temperature reactor designs where the Thorium is present as a fluoride salt. This design is known as the Liquid Fluoride Thorium Reactor (LFTR). As with the above design, the reactor still requires a start-up fuel load of fissile Uranium, usually U-233, present in columns as fuel in the form of Uranium fluoride within the Thorium fluoride salt blanket. All of this material, both fuel and blanket, becomes liquid at an operational temperature of some 600°C. The fuel and blanket do not mix, being contained in separate ceramic tubes. The Thorium converted to U-233 is subsequently extracted from the blanket by a jet of fluorine gas, then cleaned up outside the core and reinjected. Again, as with present reactor designs, there is the possibility of diversion of the extracted U-233 into weapons production. On the matter of fission product waste production: while the mix of fission products may have somewhat shorter half-lives than siliconchip.com.au Standard-8 film could have had sound added at processing With respect to the article on the Projector Speed Control (SILICON CHIP, April 2011), I noticed the comment in the panel on page 64: “Note standard film did not include sound”. I thought this was wrong as my aunty was a camera buff back in the sixties when I was in high school. She had a clockwork dual-8 movie camera which would not have had sound but the finished film was magnetic striped; not sure at processing or afterwards. She had a Eumig sound projector. I thought my memory might be slipping so checked the web. If you go to www.8mm16mmfilmcollectibles. that extracted from conventional U235/U-238 fuel, it is still a nasty mix that has to be properly processed and stored as nuclear waste. I am not sure what Luke means where he says “radioactive waste can com you will find a listing of standard 8mm projectors (and super-8 and 16mm), many with sound and for sale. From this, the film and cameras may not have had the capabilities at that stage but the projectors could record/play from a magnetic stripe. Stephen Rawlins, Peterborough, SA. Comment: standard-8 film did not have the facility for sound since the camera did not provide an audio record function with a light exposure soundtrack on the film. Sound, as you suggest, would have been separately recorded. The comments relating to sound in the article would apply to any film with sound whether using magnetic tape or modulated film exposure. be fed back into the process to fuel the system . . .”. The only thing that is fed back in is the absolutely necessary U-233 fissile fuel. It is indeed radioactive but is not “radioactive waste” in the usually accepted sense. July 2011  5 DYNE INDUSTRIES PTY LTD Now manufacturing the original ILP Unirange Toroidal Transformer - In stock from 15VA to 1000VA - Virtually anything made to order! - Transformers and Chokes with Ferrite, Powdered Iron GOSS and Metglas cores - Current & Potential Transformers DYNE Industries Pty Ltd Ph: (03) 9720 7233 Fax: (03) 9720 7551 email: sales<at>dyne.com.au web: www.dyne.com.au Mailbag: continued The claim that “One tonne of [Thorium] produces as much power as 200 tonnes of Uranium . . .” is only correct in the sense that current US policy is not to reprocess spent fuel. Only a small part of the U-238 in the spent fuel is used as fuel on the first Cassette recorders not needed In the “Ask SILICON CHIP” pages of the June 2011 issue, B. P. wrote that he wanted a substitute for a cassette recorder. Our church abandoned the option of recording services on tape nearly five years ago. We were using a laptop and projector at the time to have our service orders projected at the front of the church. I then went the one step further and tested the option of recording the service on the same machine with great success. We have been recording the services since 2006 and editing them. I start the recording up to 30 minutes before the service to avoid interference with the PowerPoint service order. At the end of the service I save pass through a conventional reactor, the rest being either still present as U-238 or converted to various isotopes of Plutonium, all of which are useful as fissile fuels but by a US policy decision are not recycled. This point becomes important when it is realised that there are a number of so-called Generation IV reactor designs, all based on the same high temperature/non-pressurised operation model as the LFTR, that do indeed consume the U-238 as fuel. The Integral Fast Reactor (IFR) design, for example, which can use any of the nuclear fuels, including Thorium, is also similarly supposedly incapable of a meltdown and is able to extract the total recording and edit it. This involves trimming off pre-service and post-service sound and this then becomes the final saved file. I also trim out the sermon and save this separately and this is emailed to the “shut-ins”. This is all done in MP3 format using a mono low-quality setting to reduce file size. As we are all aware, these can be replayed on any number of devices. We use “Wavepad” for the editing but there are any number of programs available (see the USB Stereo Recorder article in the June 2011 issue of SILICON CHIP). It takes less than 10 minutes to do all the editing and multiple copies are very easy to make. Ray Saegenschnitter, VK3UCB, Huntly, Vic. all the energy of U235/U238. If the IFR is commercialised, then the oft-quoted one tonne versus 200 tonnes advantage of Thorium disappears because the U238 is then used up rather than removed as spent fuel. In pointing out these errors, I am not attempting to bury Luke’s enthusiasm for the Thorium reactor; quite the contrary. By all means, advocate a particular reactor design – and the Thorium concept has a great deal going for it – but do not potentially destroy a very good concept in its infancy with statements that are wrong. For example, to suggest that the LFTR cannot be used to produce weapons is simply wrong – this reac- Your Reliable Partner in the Electronics Lab ab LPKF ProtoMat E33 – small, accurate, affordable Hardly larger than a DIN A3 sheet: The budget choice for milling, drilling and depaneling of PCBs or engraving of front panels – in LPKF quality. www.lpkf.com/prototyping Embedded Logic Solutions Pty. Ltd. Ph. +61 (2) 9687 1880 6  Silicon Chip Email. sales<at>emlogic.com.au siliconchip.com.au siliconchip.com.au July 2011  7 Mailbag: continued Comment on XLR connectors in USB recording interface I refer to the article on the USB recording/playback interface project in the June 2011 issue. I may be wrong but haven’t you got the sex of the XLR connectors wrong? As I remember it, the convention was SOURCE is MALE. This applied to any TV or broadcast studio I ever worked on in an installation capacity. This convention applied to any “professional” equipment I had anything to do with. Unfortunately, changing the sex of your connectors is a major task as you can’t just fit a female connector as pin 1 (ground or earth) will finish up on the wrong side. You probably have to live with it now and use a Female/Female adapter cable, particularly if a balanced microphone is already fitted with a cable. If not it won’t really matter as a tor design, while not very efficient at it, can also produce Plutonium as well as U-233. Both are used in nuclear weapons. But let’s be clear in our thinking. The current models of pressurised water reactors (PWRs) are very safe and intrinsically safer than the old Fukushima plant design. They are far less polluting than coal-fired plants and deliver real, base-load power. Unlike Generation IV designs, of which Luke’s favoured LFTR reactor is but one, they are commercially available now, as opposed to at least 20-30 years into the future. cable will have to be made or purchased and can be organised to suit the connectors used. Robert Rayner, Willow Vale, Qld. Comment: thanks for the feedback. With hindsight we should have used female XLR connectors for the microphone inputs on the USB Recording/Playback Interface. However, this mistake is actually not difficult to correct. Female XLR connectors can be fitted to the front panel and the connections between pins 3 & 1 of each connector “swapped over” between the connector’s rear lugs and the pads on the PC board – instead of passing straight down. This can be done fairly easily if short lengths of insulated hookup wire are used to make these connections, ensuring that there will be no accidental shorts. Resources: (1) www.world-nuclear.org/info/ inf62.html is an authoritative source. (2) There is a very good article and excellent discussion, contributed to by some of the world’s leading nuclear power experts, on the pros and cons of the Thorium reactor at http:// bravenewclimate.com/2009/12/17/ lftr-in-australia/ There are also many excellent blogs on this site on the IFR, other reactor designs and energy issues in general. (3) Kirk Sorensen’s YouTube video at http://www.youtube.com/watch? v=N2vzotsvvkw provides both an excellent perspective on mankind’s need for energy as well as his own enthusiastic support for the Thorium reactor concept. Paul Miskelly Mittagong, NSW. Phone line polarity checker does work I read your article regarding the line polarity and the tester (SILICON CHIP, May 2011) and thought, “Yeah right!” The devices should comply with Telstra Service Interface Specification (TSIS) for ADSL Access. Then recently I was remote testing a DSL install (from the DSLAM) and the service would not meet our minimum SNR Margin of 8dB. Before messing with line profiles or logging a fault with Telstra, I got our field engineer to swap the A and B wires. Wow! It now gave 14dB SNR margin, I’m a convert! By the way, the modem was a Siemens 4200. Rod Beech, Fernvale, Qld. Grid-connect inverters cannot be used in stand-alone mode In the Mailbag pages in the April 2011 issue, you commented in your reply to the author of the “Solar Panel Generation Report” that you were investigating how a grid-connect inverter might be used as a standalone inverter in the event of a mains failure. “With extreme difficulty . . . ” might be a suitable answer! As a TAFE lecturer who is delivering the “GridConnect Installer” course in Adelaide, I would like to pass on the following information. Hakko FX888 Hakko FX951 Hakko FR803B General purpose soldering iron Advanced lead-free soldering iron Hot Air SMD Rework Station • • • • Compact Lead or lead-free solder Excellent thermal recovery With tip conical shape T18-B, cleaning sponge and wire • Heating element and tip in one • With sleep mode, auto shutdown, lock out card, quick tip replacement. Proudly distributed in Australia by HK Wentworth Pty Ltd • Digital station with 3 steps temp profiles • Vacuum pickup • Adjustable 100o-450oC • Optional stand, pre heater and vice www.hakko.com Hakko Specials this month: see your Hakko distributor! 8  Silicon Chip siliconchip.com.au Grid-connect inverters receive DC from the solar array (or wind generator or small hydro system) and use it to generate an AC waveform. While the grid is available, the inverter tracks the grid sinewave and generates its own sinewave at a fraction of a volt above the grid voltage and a degree or so ahead of the grid waveform. This forces energy to flow into the grid. The first problem with stand-alone operation of a grid-connect unit is that in the absence of a grid sinewave, most inverters will lose their synchronising AC reference signal and “free-run” well away from the 230V, 50Hz ideal. The second problem with standalone operation is that grid connect inverters MUST have several features called “anti-islanding” built into them or connected to them, if they are to conform to the Australian Standard covering them (AS4777 Parts 1, 2 & 3). “Islanding” is defined as the continued operation of the inverter if the grid is disconnected or the inverter output goes beyond the limits defined by the inverter manufacturer for proper operation for paralleling with the grid. Anti-islanding systems prevent inverters from continuing to operate online or off-line if the mains from the grid is out of normal limits for voltage or frequency, or is just not available. This may be due to a generation or distribution fault, or perhaps due to the grid being cut so the supply author- Vintage radio production photos were magnificent My congratulations to Kevin Poul­ ter for his Vintage Radio article in the June 2011 issue of SILICON CHIP. This was a great story of bygone times, supported by a large array of magnificent photos. As reported by Kevin, photos of radio production lines were rarely taken, let alone made available outside the factories. These outstanding photos are the results of Kevin’s exceptional skills with things photographic and they should now live forever. Thanks for sharing them. I wonder if we do still have any photos hidden away in this country of our own radio manufacturing factories? Probably sadly not but perhaps a comment which appeals to SILICON CHIP readers who may have photos to share might prove ity’s workers can safely work on the system. If an inverter continued to run on-line under the latter condition and back-fed into the grid, it could prove fatal to a line worker. Also, the inverter would attempt to power the loads in other premises that were still on the disconnected or failed grid and would promptly overload and shut down. Even in lightload conditions and with a number of other inverters back-feeding into the my suspicions wrong. I certainly hope so. Graeme Dennes Bunyip, Vic. Kevin Poulter comments: I have four excellent photos of Pye 2-way radio production in Clayton, Vic, circa 1960s and there are a few of AWA production in collectors’ hands. The September 1964 issue of Radio, TV & Hobbies had a Pye UHF Tx/Rx being inspected in the factory. The HRSA also has some photos of the EMI/HMV TV production lines in the mid-late 1960s. After extensive searches, I can advise that libraries around Australia including the National Archives have almost zero – just one or two of the Astor TV production and AWA TVs in about the 70s. I would love to hear of anyone who has production photos. grid at the same time, the inverter(s) must sense that the other inverters powering the loads are NOT the “real” grid and that the “real” grid source is no longer available. The inverters must disconnect themselves from the “false” grid in less than two seconds if other inverters are attempting to maintain the grid by back-feeding. This is a requirement of the basic design of the inverter protection system laid down in AS4777 Part 3. Australia’s Best Priced DSOs Shop On-Line at emona.com.au RIGOL DS-1052E 50MHz RIGOL DS-1102E 100MHz RIGOL DS-1202CA 200MHz 50MHz Bandwidth, 2 Ch 1GS/s Real Time Sampling USB Device, USB Host & PictBridge 100MHz Bandwidth, 2 Ch 1GS/s Real Time Sampling USB Device, USB Host & PictBridge 200MHz Bandwidth, 2 Ch 2GS/s Real Time Sampling USB Device & USB Host Sydney Brisbane Perth ONLY $439 inc GST Melbourne Tel 02 9519 3933 Tel 03 9889 0427 Fax 02 9550 1378 Fax 03 9889 0715 email testinst<at>emona.com.au siliconchip.com.au ONLY $769 inc GST Tel 07 3275 2183 Fax 07 3275 2196 Adelaide Tel 08 8363 5733 Fax 08 8363 5799 ONLY $1,422 inc GST Tel 08 9361 4200 Fax 08 9361 4300 web www.emona.com.au EMONA July 2011  9 Mailbag: continued Persuading the retailers to market a kit I was admiring the 12V 100W DCDC Converter project (SILICON CHIP, May 2011) and considering the uses I could put it to. I started looking for who would be putting a kit out for it and have not found anyone as yet. I was talking to some workmates and we all had the same complaint that we have to wait for someone to start marketing a kit and often a kit doesn’t become available. Living in a regional area makes shopping for individual components a bit of a task. What would be nice is somewhere we could register our interest in a project to show that there is a market for a kit. It would help the retailers who could take the risk knowing that there are X number of customers waiting. I build one kit a month and have done so for many years. I Typically, grid-connect inverters use both passive and active systems to check for the presence of the grid. Passive systems look for values of inverter voltage and frequency that are outside the preset grid limits. If the grid fails, the free-running inverter quickly goes outside of the pre-set voltage and frequency limits. The passive anti-islanding system detects the erroneous conditions and would be happy to build a few more. I recently lobbied several retailers to produce a kit for the Solar Panel Simulator. I did not have any positive replies. Chris Ryan, Dubbo, NSW. Comment: whether or not a kit is available is a decision for the kitset retailers, as you are aware. While we make the project information available to them before publication, it’s up to them to decide whether to produce a kit for a particular project or not. We sometimes think they miss a golden opportunity to do some kits but maybe we are just biased. If enough people ask for a kit, it might sway their decision. If a kit is not available, most if not all parts are available from Jaycar and Altronics on-line and the PCBs are also are available. initiates inverter shut-down. Active systems attempt to gently push either the voltage or frequency (or both) of the grid away from the present value, which, of course, they cannot succeed in doing if the big alternators in the power station are sourcing the supply. However, if another inverter or a small “putt-putt” alternator is the source, that source WILL track the change and the inverter will find that Presensitized PCB & associated products it CAN cause the grid to vary – so the source can’t be the grid! This will also trigger a shut-down. Another active system involves the inverter determining the impedance of the grid from the V/I characteristics of the AC source, and if the source impedance is too high, the inverter will also shut down on anti-islanding protection. Excessively long, small crosssection AC inverter output cables can cause this system to give false alarm shut-downs with some inverters, as well as allowing shut-downs with genuine islanding situations. The third problem is that all the settings for grid-connect systems be “secure” so the user or even a skilled technician can’t get in and change them (AS4777 again). That means you’ll have a lot of un-designing to do to overcome the anti-islanding systems if you want to run the inverter as a stand-alone unit – and then it will be illegal, irresponsible and downright dangerous to run it as a grid-connected system once the mains returns. You will be much better off having a separate inverter system and either a second AC distribution system, or an approved AC change-over system to let you power your home from either the grid-connect inverter or the stand-alone inverter – but only from one at a time. There ARE inverters that can gridconnect and run in both grid-available and grid-absent modes. These “special” units have an AC grid input/out- IN STOCK NOW! •Single Sided Presensitized PCBs •Double Sided Presensitized PCBs •Fibreglass & Phenolic •UV Light Boxes •DP50 Developer •PCB Etch Tanks, Heaters & Aerator Pumps •Thermometers •Ammonium Persulphate Etchant •PCB Drill Bits (HSS & Tungsten) For full range, pricing and to buy now online, visit 36 Years Quality Service 10  Silicon Chip www.wiltronics.com.au Ph: (03) 5334 2513 Email: sales<at>wiltronics.com.au siliconchip.com.au put, an AC load output and a DC system input/output. By comparison, a simple grid-connect system has an AC grid input/output and a DC input only. If the grid is present, the “special” inverter will power the AC loads and back-feed any excess generation to the grid. If the grid is missing, the “special” inverters will disconnect themselves from the grid and use the inverters and DC sources to power only the loads. Most of these systems use batteries, as well as the solar array, to keep the loads running, even in low-light conditions. If you use batteries to allow the inverter to operate under low-light conditions, you have created an Uninterruptible Power Supply (UPS) system. AS4777 says that a UPS installation needs separate switchboards for its AC loads, special battery storage areas, heavier DC cabling, fuses etc to cope with possible battery shortcircuit currents (from the batteries right back to the solar panel protection), and a special ($$$) grid-connect inverter that will back-feed if the grid is there but won’t back-feed if it isn’t. Brian Spencer, Seaford, SA. Comment: our investigation had centred on the concept of using a change-over contactor to isolate the home system from the grid and then tricking the gridfeed inverter into supplying power when the grid was down. When the grid came back, it would be up to the householder to switch the contactor back. But as your letter demonstrates in detail, this approach is simply not practical. Thanks for the information. Save Up To 60% On Electronic Co Components New ET-Easy T A Arduino Stamp Includes ATMega168 with Installed Bootloader Direct USB Program Download Up to 22 I/O Points, 10-Bit ADC Included Compact, Easy to Use and Program Only $24.90 Ultrasonic Range ge F Finder ind der Only $14 $14.90 90 Ideal for use on Robots and Water Tanks Measures from 3cm to 3m High Accuracy Ready to Run, No Set-Up Required 1 A So 10 ar Regulator for Lighting 10A Solar Only O Onl nly ly $$36.90 36.90 Hig Efficiency PWM Charging High Cha es Batteries During Daylight and Charges Switches Lights on at Night Sw S wii Suitable for 12V and 24V Systems S uitt LED D Status Indication for Charging, Low Battery etc We aare re e yyour ourr on ou oone-stop one ne-stop sh shop for Microcontroller Boards, PCB Manufacture aand Electronic Components www.futurlec.com.au Noise-cancelling headphones on commercial flights In these columns last year, I elicited advice on noisecancelling headphones on commercial flights. None was forthcoming! Pity! With another Australian holiday looming in June 2011, I couldn’t bear the thought of using the poor headphones issued by all major international airlines. Recapping, readers may remember that I “borrowed” a pair of Singapore Airlines issue in 2010. These were of 300Ω impedance, with fully isolated left and right earpieces. Incidentally, I returned these to S.A. at Heathrow, much to their amusement. We flew Qantas this time. I took a DMM with me and measured their headphones. Apart from the logo, they were identical to S.A. and I suspect to those in all other airlines. However, prior to departure, I bought a cheap pair of SilverCrest Model KH3447 stereo noisecancelling headphones, 32Ω impedance, complete with long lead, two AAA batteries and an aircraft 2-pole adapter. These gave a huge improvement, especially as I’m slightly deaf in my left ear. Although I can’t quantify the results, with noise-cancelling switched on, engine noise was considerably reduced. Any disadvantages? Yes! The cheap but well-padded ear pads, sat “on” my ears. As I wear glasses, within an hour, my head felt as though crushed in a vise. Obviously, more expensive “around-the-ear” types are required but these are also usually bulky. siliconchip.com.au July 2011  11 Details of Commodore 64 power supply A recent letter to Ask SILICON CHIP concerned replacing the power supply unit for a Commodore 64 computer. The suggestion was that a 12V DC input might substitute for the 9V AC. Unfortunately, this won’t work. According to the schematic, the 9V AC input is used to generate a second +5V supply (via a conventional bridge rectifier/ filter/linear regulator), used mainly by the audio and video output circuitry. This would still work with a DC input. However, the 9V AC also feeds a voltage doubler, via a series capacitor, to provide +12V from another regulator. This is used by the audio chip. A “+9V Unreg” supply is also generated, for the cassette motor. The 9V AC signal is also used to provide a 50Hz timing reference to the CIA chips. The 9V AC and 5V DC supplies should be derived from separate transformer windings, Jaycar MM-2014, or the MT2082 toroid. One winding would provide the 9V AC, with a simple linear regulator circuit for the +5V DC. I hope this information is useful. Mike Phillips, Adelaide, SA. Mailbag: continued Technically, I pose the question again. Why are 300Ω headphone sets standard issue? If many more people used 32Ω sets or even 8Ω, would it overload the aircraft audio system? It begs some reader in the aircraft industry to do a technical article on aircraft entertainment systems. How about it? Robert Gott, Normanton, UK. Technical standards are not mandatory In the Mailbag pages of the May 2011 issue, Collyn Rivers raised a matter of standards and I would like to add my tuppence worth. I have spent a life as a Mechanical Engineer specialising in Fluid Power (hydraulics & pneumatics), to which the inclusion of electronics as a control element was a wonderful development. Throughout, I have been a strong advocate for standardisation. Standards have been developed in many disciplines with benefits to manufacturers, end users and after markets. The adoption of standards is voluntary, not mandatory. As a member and later as chairman of Standards Australia, Committee ME35 – Fluid Power, over many years, I can attest to the difficulty in communicating these benefits. So I have some sympathy with Collyn. What bugs me 12  Silicon Chip most is the use, by people who should know better, of the word meter to refer to a length. They never say which meters they use for the measure – was it a wattmeter or voltmeter used singly time and again or was it a string of ammeters, flow meters and pressure gauges side by side. To Collyn I would say “Let it go mate and take consolation in the knowledge you would not have done it that way”. Kenneth W. Pilley, Bonnells Bay, NSW. Cassette recorders still wanted I’d like to endorse B.P.’s comments on page 101 of the June 2011 issue of SILICON CHIP, about the need for a digital “tape” recorder. As an example, a friend of mine is a piano teacher who regularly used a cassette recorder as part of her program. She says that her old machine is beyond repair and that she can’t find anything affordable that will do the same job. Another acquaintance is a speech therapist who reports similar problems. Sangean recently came up with a portable digital radio (model DPR-17) with an SD-card socket for recording. It works very well but if they had included provision for a microphone as well I think this would have greatly increased the unit’s versatility and appeal to purchasers. Thus, may I strongly support B.P.’s request for you to produce a “high-quality recorder based on an SD card”. I’m sure it would be of interest to both the technically and non-technically minded! Stuart Hodgson, SC Selby, Vic. siliconchip.com.au Read th e MSO-X review of the 2024 4channe oscillos l c o p e i n Aprill 2 011 iss the ue of SILICON CHIP Hello future. Goodbye status quo. Oscilloscopes Redefined Starting at $1,328* ex-GST for 2000 X-Series DSO $2,083* ex-GST for 2000 X-Series MSO $3,034* ex-GST for 3000 X-Series DSO $4,275* ex-GST for 3000 X-Series MSO © 2011 Agilent Technologies, Inc. *All prices are in AUS dollars and subject to change siliconchip.com.au Agilent 2000 X-Series (MSO and DSO) Tektronix TDS2000C Series (DSO) Agilent 3000 X-Series (MSO and DSO) Tektronix MSO/DPO2000 Series Bandwidth (MHz) 70, 100, 200 50, 70, 100, 200 100, 200, 350, 500 100, 200 Max sample rate 2 GSa/s 2 GSa/s 4 GSa/s 1 GSa/s Max memory depth 100 kpts 2.5 kpts 4 Mpts 1 Mpt Max update rate (waveforms/sec) 50,000 200** 1,000,000 5,000 Fully upgradable Yes No Yes No Function Generator Yes No Yes No Notes: Agilent and our Distributor Network Right Instrument. Right Expertise. Delivered Right Now. **Refer to Agilent Pub 5989-7885EN for update rate measurements Data for competitive oscilloscopes from Tektronix publications 3GW-25645-0 and 3GW-22048-1 Measurements taken on same signal using Agilent MSOX2024A and Tektronix TDS2024B Screen images are actual screen captures and scopes are shown to scale Buy from an Authorized Distributor www.agilent.com/find/distributors See the difference today. www.agilent.com/find/morescope July 2011  13 Australia Hears – and so do I! Not too long ago we heard of an Australian company offering high performance digital hearing aids, based on new technology developed in Australia, at a fraction of the cost of other aids. I was intrigued – it’s been a subject close to my heart ears for decades! Were they any good? Were they value for money? Did they work? And what is this latest technology in hearing aids, anyway? SILICON CHIP likes to look at electronics that are slightly out of the ordinary! By Ross Tester R egular readers will be aware of the series of hearing loop projects which we published during the latter part of last year and early this year to help the hearing impaired. That prompted several requests for a build-it-yourself hearing aid. But as you would realise, miniaturisation of this magnitude is way beyond the skill level of most people! Just to prove the point, we obtained a “dead” hearing aid, broke it open and photographed its innards. Apart from the near-impossibility of anyone constructing the ultra-miniature PCB, where are you going to get the appropriately-shaped “case”, the tiny speaker, the ear tube? You get the point, I’m sure. So no, this is not a build-it-yourself hearing aid. However, it is a “do-ityourself” hearing aid – an apparent contradiction which we’ll get to shortly. But first, let’s background this story a little. It’s a sad, personal tale so keep the tissues handy. For nearly four decades (since January 1973 in fact – I can still remember the day) I have had significant hearing loss in one ear. 14  Silicon Chip It all started with a very loud – and painful – audio tone from a two-way radio earpiece in the laboratory at Electronics Australia. For a couple of months I heard nothing but ringing in my right ear. When that subsided and my hearing eventually “returned” in that ear I was very aware that my high-frequency hearing was virtually non-existent. At my age then (early twenties) I should have been able to hear to at least 15-16kHz. I was flat out hearing 2kHz. Over the ensuing months, some higher frequencies were restored but it was virtually a brick wall at 4kHz – where We broke open a modern hearing aid to show what’s inside it. The “works” is on that tiny PCB (centre) while in this model, the miniature in-ear speaker is at the top of the picture. it has largely remained to this day. It’s been something I (and, regrettably, everyone around me) have put up with ever since. And as I have aged, my “good” ear has also started to deteriorate, to the point where an audiologist described my hearing (especially in the right ear) as bordering on clinical deafness. If you have never suffered from high frequency hearing loss, you could never understand just how difficult it is to decipher speech, in particular, with such a loss. Radio and TV programs particularly are terribly muffled (and turned up much too loud, according to everyone else!). Trying to understand conversations, particularly in a crowd or noisy environment, is almost impossible at times. The closest thing I can think of to describe the problem is either an offfrequency AM radio station, without the sibilance or perhaps someone mumbling while speaking softly, But apart from a couple of audiology tests done over the years (the most recent just on two years ago) I’ve done nothing about it. Why? In the first of the hearing loop articles referred to above (October 2010), siliconchip.com.au Where’s the hearing aid? If you look closely, real closely at the photo at left, you can just see the tiny tube entering Sarah’s ear. It’s a bit clearer in the shot above, because her hair has been pulled out of the way so you can see it! Inset above is the hearing aid body behind the ear, again with Sarah’s hair pulled out of the way. It would normally cover the aid completely. we said “But there are many people in greatest wholly-in-ear models for only while bushwalking and then I would the community who have hearing loss $12,000. Each! buy myself some decent hearing aids. I figured (alas incorrectly so far) that Or I would wait until I retired and get and, for various reasons (cost, denial and vanity are the main ones!) don’t one day I would win Lotto, or perhaps the pensioner’s specials! stub my toe on a giant gold nugget own or want a hearing aid.” In the meantime, I’d persevere (or I guess I fitted into the everyone else would!) with first and last categories. what was an annoyance but I certainly didn’t deny I something I could live with, had a hearing problem albeit often with difficulty. but equally I didn’t want Then it all changed a hearing aid – “they’re only for old people . . .” etc Late last April, several TV etc. (Someone reminded news programs carried a story me the other day that if I on an Australian company wasn’t there already, I was who were introducing quality rapidly approaching being hearing aids at a fraction of a member of that august the price of existing models. group!). But chief amongst They were based on new techmy objections was that of nology called ADRO which, cost. as far as I could understand At the time of the last from the news reports, was audiology test, the specialdeveloped in conjunction ist told me that I needed at with the people responsible least one, and preferably for the cochlear ear transplant two, hearing aids – and program. then proceeded to show Unfortunately we missed me models ranging from the press launch but I saw around $2,000 – “but you the story on TV, with some wouldn’t want one of them, The computer-plotted audiology tests shows quite significant interest. And so did the Editor hearing loss below 2kHz in my right ear (red plot), the result they’re not real good” – of a very loud tone in that ear, in the Electronics Australia of this esteemed publication right up to the latest and laboratory nearly 40 years ago. – and next day he asked me siliconchip.com.au July 2011  15 MODEL: SIE-312 ($1250.00) MODEL: LOF ($990.00) right. Just Google free hearing test or somesuch words. Australia Hears Dimensions: Weight (inc battery): Battery: Battery life: Speaker technology: Frequency channels: Processing: Volume control: Program selection: Telecoil option: Microphone: Noise suppression: Feedback canceller: Summary: 25 x 14 x 8mm 34 x 14 x 8mm 2g 4g Size 312 Size 13 100+ hours 160+ hours Speaker-in-the-ear Thin acoustic tube 32 32 ADRO ultra-low delay ADRO ultra-low delay Automatic plus manual dial Automatic plus manual dial Magnetic wand Magnetic wand plus program button No Yes Dynamic directional Dynamic directional Multi-channel Multi-channel Dynamic Dynamic Smaller, with speaker Slightly larger, longest battery life in-the-ear Comparison of the two models of ADRO hearing aids from Australia Hears. There’s not much between them – the SIE with in-ear speaker is slightly smaller and lighter but the LOF model offers longer battery life and an extended hearing range. The LOF also has a Telecoil – we believe a very useful feature. Otherwise they’re very similar in performance and usage. to investigate further to see if there was the makings of a feature article for SILICON CHIP readers. Now we’re not saying we think all SILICON CHIP readers are in the “need a hearing aid” category. But of course many are, or are heading that way (or know people who are). Just as important, though, are the younger readers who might have parents who would benefit. And let’s not forget that a huge proportion of younger readers in particular are almost certain to have significant hearing loss from (a) live music [why do bands have to play their music so damned loud?] and (b) excessive volume levels from the ear buds associated with their iPods/MP3 players/CD players etc [why do they have to play music so damned loud!]. One recent report said that at least 21% of people between 48 and 59 showed serious hearing loss. The researchers measured hearing loss as the 16  Silicon Chip ability to hear certain tones, and also as the ability to recognise words at different sound levels and words spoken by male and female voices. They found that 14.1% of the 3,285 study participants of all ages had some level of hearing loss. Another study surveyed a sample of children aged 12 to 19 in 2005 and 2006 and found that 19.5% had some hearing loss. One expert said that listening to loud sounds through earbuds – the tiny electronic speakers that fit into ears, for use with personal music players – is probably the main reason that more adolescents are losing some of their hearing Incidentally, if you even think you might have a hearing problem, there are any number of web sites where you can do a free rudimentary hearing check. It won’t replace the audiologist test , but it could give you the impetus to go and have that fair-dinkum test if it tells you that something is not quite But back to the subject at hand. The company concerned was Australia Hears Pty Ltd, (now called Blaymey & Saunders Hearing) based in Melbourne and the snippets we saw on the news was courtesy of a PR company which must be said, did a pretty good job. So much so that my first few phone calls were met by a recorded message saying that they had been overwhelmed by the reaction to the publicity and they’d get back to me as soon as possible. The contact-via-the-website method also had a similar message. However (with more prompting from he who must be obeyed!) I eventually managed to get in touch with the company and more importantly, spoke with Dr Daniel Taft, their Chief Technology Officer. I explained who I was and the fact that I would like to “review” their hearing aids for SILICON CHIP. Daniel was most accommodating with information and agreed that they would like to co-operate. First of all, Daniel asked if I had an audiogram which I could send him. I explained that the most recent one was two years ago and he said that would do, so I sent him a PDF which I had obtained from the audiologist. From this, he would “program” hearing aids to suit my particular hearing pattern. While this would tend to obviate any requirement for programming myself, we also got their “IHearYou” programmer package, which includes a USB programmer box, cables to connect the hearing aids and instructions – just so we could play. They also wanted to know the size of my lug-holes because there are four different sizes to choose from. They have a cut-out template which you place over your ear and read off small, medium, large or extra large sizes. Now just in case you think this was just a “freebie for Rosco” type of deal, I would point out that I paid full retail price for the products purchased from Australia Hears. Program it yourself Australia Hears’ main claim to fame (or at least the message that we got from the news reports) was that they had developed digital hearing aids which were the latest technology but siliconchip.com.au These are the “templates” which you use to check the size of your ears. Both ears must be measured because they are often different sizes. The pointer which lines up with your ear canal gives you the ear size. (www.archive.australiahears.com.au/Ear-size-A4.pdf) were about half the price (or even less) of comparable models on the market. Coupled with that was the fact that you, as a user, can “tune” them to suit your particular circumstances. Hence the “do-it-yourself” comment earlier. Of course, with the hearing aids pre-loaded with your audiogram, most people won’t want or need to do that but it’s comforting to know that, with the programmer box, you can. We’ll look at the programmer in a bit more detail shortly. Models They offer two different models, the $1250.00 SIE-312 and the $990.00 LOF. The first thing you will notice, if you have been in the market for a hearing aid, is those prices. SIE-312, the slightly smaller model, stands for speaker-in-the-ear and 312 is the battery size it takes. It has a very tiny “speaker”, a tube about 2mm in diameter x 5mm long, at the end of ultra-thin wires. LOF (which, incidentally, stands for liberty open fit), has its speaker within the body of the hearing aid connected to a thin (almost invisible) tube which feeds audio into the ear canal. Operationally, they are quite similar but the LOF battery life is longer (160 hours vs 100 hours) and its sound output is slightly greater. Both have similar electronics, offering 32 digital frequency channels, adaptive automatic directional microphone, dynamic feedback cancellation and ultra-low delay. According to Australia Hears, there is very little to choose from when selecting the model, apart from the price difference. If appearance is important, they suggest the SIE-312. It’s the lighter of the two at just 2g and measures 25 x 14 x 8mm. If longer battery life is your aim, siliconchip.com.au then the slightly larger and heavier LOF is better. It’s 34 x 14 x 8mm and weighs 4g. Having said that (and after wearing both) you don’t notice the difference at all. Characteristics of the hearing ranges are very slightly different at the low end (the LOF has a 10dB greater range at 250Hz) but this would not be of importance to the vast majority of users with high frequency hearing loss. Both can have up to four programs stored in them (for different ranges, amplification, etc, to suit different environments, for example) and both have program switching via a small magnetic wand, packed with the hearing aid. The LOF also has a push-button switch on the body to achieve this. Volume setting on both can be done via a tiny dial on the body but once set, you’ll probably find you’ll never touch it again as they have an automatic level control built in. The miniscule dynamic microphone is directional. The only other major difference that I noticed, having an obvious interest in the subject, is that a Telecoil is an option on the LOF but is not available on the SIE-312. So which one? I didn’t know which one to go for either, so at Australia Hears’ suggestion, I purchased a pair of each to compare them for this feature. I used them for a week at a time and, to be honest, I still cannot recommend one over the other! I will be returning one of the pairs shortly (within the 14 days satisfaction guarantee) for a full refund. But I can assure you I won’t be returning both! Wearing them For someone who has never worn hearing aids before, I wondered whether they would be physically annoying. The first fifteen minutes convinced me there was nothing to worry about there. First of all, though, you have to load the batteries. That’s not difficult to do – the batteries only fit in one way and there’s a card packed with the units to show how. Closing the battery doors immediately turn them on – there’s no on/off switch as such. Needless to say, there is a right and a left aid. This is not only for the physical reason of having the speaker/sound pipe emerging on the correct side to go into the ear but most importantly, the two hearing aids will very likely be programmed differently to take into account differences in the hearing loss. It takes a bit of fiddling around the first time to find where they go and get the ear-canal part seated properly but once you’ve done it a couple of times, it becomes second nature. After the first few minutes, it’s very easy to forget that you a wearing a hearing aid (or two). They really are that comfortable to wear. Moreover, most people don’t even notice you have them unless they get very up close and personal! I have quite short hair so if they were going to stand out they would do so on my head. But they don’t. And anyone with longer hair (especially females) would have them pretty-well completely hidden, as you can see from the two photos at the start of this article. As I mentioned before the wires (SIE-312) or tube (LOF) which go into the ear canal are themselves so small they are almost invisible. There’s a range of small “ear tips” which slip over the end of the speaker or tube to hold it in the right place in the ear. Usage of the tips (and the type of tip) is optional – I found them to be very comfortable with and without. The biggest problem I had was when one ear canal was itchy and had to July 2011  17 ADRO©: a new approach to amplification in hearing aids . . . Professor Peter Blamey, the founder and managing director of Australia Hears, has spent the past 30 years researching ways to improve the sound quality of cochlear implants and hearing aids. Blamey is also deputy director of The Bionic Ear Institute. He has long been aware of the limitations of conventional digital hearing aids designed to compress a wide range of input sounds into a narrower output range. In 1998, he hit upon the idea of using a processing chip within the aids to select the most informative parts of a sound range and present them at comfortable levels at each frequency for the listener. The Adaptive Dynamic Range Optimisation (ADRO) technology he invented splits sound into 32 different frequency channels, then uses statistical rules as part of the digital amplification strategy to optimise the audibility, comfort and intelligibility of sounds without compromising sound quality. The rules are set for each individual user and keep the audibility and comfort levels the same as those of a person with normal hearing. If the sound falls below the audibility target, it is made louder, while if it rises above the comfort target, it is made softer. Each individual can set his or her own comfort levels for different environments with an easy-to-use software program. This eliminates the need to fit hearing aids on the basis of the averages of a sample population as done with conventional hearing aids — a boon for individuals whose hearing preferences are not typical. Even the software used to customise the hearing aids is evidencebased, using data collected from 176 ears to predict and suggest amplification levels to the individual. “Conventional compression technology can match ADRO technology in terms of audibility or comfort but not both simultaneously unless very high compression ratios are used. However, application of these high compression ratios can reduce speech intelligibility in background noise and adversely affect sound quality in quiet surroundings,” Blamey notes. Fuzzy logic makes sense ADRO hearing aids work on four ‘fuzzy logic’ statistical rules, which can be true for part of the time rather than always being true or false. Each rule has a critical role and is applied independently to each of the 32 frequency channels in an individual’s hearing aids. The comfort rule ensures that sustained sounds are not too loud more than 10% of the time. The audibility rule ensures that sustained sounds are not too soft for more than 30% of the time. The hearing protection rule stops sudden loud sounds from being amplified beyond a maximum level for the listener. The background noise rule prevents low-level background noise from being over-amplified and annoying to the user. The result is that soft sounds are more audible, loud sounds are more comfortable, intelligibility for speech in background noise is improved while preferred sound quality is provided. Applying four standards Hearing aids from Australia Hears include four standards that enable easier and more flexible customisation. 1. The ADRO processor optimises sound for a listener across 32 different frequency channels. 2. An automatic adaptive directional microphone reduces the loudness of background noise from some directions. 18  Silicon Chip Research shows that these microphones provide better speech perception than either omnidirectional or fixed directional microphones. 3. Incorporation of adaptive feedback cancellation that prevents the highpitched whistles of feedback loops that occur when the microphone of an amplifier is too close to its speaker. 4. Ultra-low delay processing technology to eliminate perceptible distortions or echoes caused by sound Professor Peter Blamey, inventor delays as sound is processed of ADRO and founder of “Australia from analog to digital sig- Hears”. nals. The Australia Hears technology has the shortest delay of any device in the industry. Clinical trials The ADRO amplifier has been evaluated against an alternative amplifier in several clinical trials, which were conducted by the Cooperative Research Centre (CRC) for Cochlear Implant and Hearing Aid Innovation in Melbourne. 42 experienced hearing aid users preferred hearing aids with ADRO sound processors over conventional compression processors in most situations. Noted were improved sound quality, improved speech perception in quiet and in noise, and improved loudness control. Additional uses ADRO also has the flexibility required to improve hearing for any level of hearing loss, whether it’s a person with normal hearing using headsets and telephones, a person with mild hearing loss who needs hearing aids, or a person with severe-to-profound hearing loss who requires a cochlear implant. “ADRO is being applied in headsets and other devices for listeners with normal hearing to provide improved audibility and intelligibility to compensate for poor telephone transmission lines, and to protect hearing from loud sounds and acoustic trauma,” Blamey explains. In 2007, Blamey was honoured by the American Academy of Audiology with the International Award for his work in hearing and language research. Product heritage The products of Australia Hears are based on research conducted at the Bionic Ear Institute, funded by the CRC for Cochlear Implant and Hearing Aid Innovation. ADRO is copyright© Dynamic Hearing Pty Ltd and is the technology used in cochlear implant sound processors made by Cochlear Limited of Sydney. The digital signal processing algorithms were developed at Dynamic Hearing in Melbourne and the House Ear Institute in Los Angeles and are licensed from Dynamic Hearing Pty Ltd. The hearing aids are manufactured in Thailand using high-quality components including digital signal processing (DSP) chips from Sound Design Technologies in Burlington, Canada, and microphones and speakers from Knowles of Itasca, Illinois. siliconchip.com.au remove the aid to scratch it. But as any ear specialist will tell you, the smallest thing you should put in your ear is your elbow! I am very much a beach/water person and I live in dread of the day I will forget to take them out before swimming, or even showering. They really are that comfortable! If this happens, perish the thought, I take some comfort in the fact that Australia Hears offers a repair service – if they are damaged at all (I read a comment from one user who forgot to take them off before showering but simply dried them off and they continued to work perfectly). How do they sound? Obviously, I have no yardstick to judge them by (except years of poor hearing). I’ve only ever worn earphones or earbuds before. As an aside, I have to say earbuds annoy the life out of me! Give me a comfy set of conventional earphones anytime – and I am delighted to report that you can use headphones [not earbuds] with these hearing aids. While you can adjust the individual levels of most headphones, with hearing aids adjusted properly, you’ll never have to do so. My first reaction was, I have to say, shock. Not bad shock, just . . . shock! Everyday tasks such as typing on a keyboard, running a tap, stirring a cup of tea, picking up a set of keys, even walking, had so much more “sound” to them than I had been experiencing. In some cases, a jangly, jarring sound. In fact, for an hour or two, I found it quite unnerving. But as I got used to it, I started to realise it was simply what I had been missing all these years. What I had been missing was obviously not only the high frequencies but the harmonics present in virtually every sound. These harmonics go right up through the “normal” human audio passband of 15-20,000Hz. Wearing glasses That was one area I was worried about – I wear glasses virtually all the time and I thought that the glasses might interfere with the hearing aids, might rub on them creating a lot of unwanted noises or might prevent them being located properly. siliconchip.com.au None of these worries has proved to be warranted. Sure, if I move the glasses over the hearing aids (they normally sit on top of them) I can sometimes hear a sound but it’s certainly nothing to be concerned about. Some observations My greatest hearing problem has been listening to people in a crowded room or with lots of background noise. That, I am happy to say, is very much alleviated. Even one-on-one speech is much easier to understand now – and I don’t have to ask people to speak up (in fact, I’ve asked a few people to speak more softly!). I also used to have trouble listening to soft radio (particularly voices) and TV sound – it was always muffled and half the time, I couldn’t make out what was being said – female voices, especially, were a real problem. That too is now much better and as I get more used to the hearing aids, is getting better all the time. I can hear sounds/noises I simply couldn’t hear before. In fact, just about everything seems to be louder – while it is great most of the time, if I find it distracting, I simply remove the ear tube. At long last, I can actually hear the buzzer in my multimeter! It’s been a bane of my electronics life for years . . . My partner has become used to talk- What’s a Telecoil? We mentioned that the LOF model can be programmed to work with a Telecoil. But you may be wondering what the Telecoil is and why it is important. Hearing aids with a Telecoil option can take advantage of (a) special telephones (intended for hearing impaired) that have a coil fitted which inductively couples the hearing aid to the phone, allowing clearer phone calls; and (b) halls, churches, offices and the like which are now increasingly being fitted with “hearing loops”. Here audio signal (the same as normal-hearing people are hearing) is fed into a large wire loop which can also couple into a Telecoil-enabled hearing aid. The series of “hearing impaired” projects run in SILICON CHIP between October 2010 and April 2011 were all Hearing Loop/Telecoil devices, including installing such a loop in your own home. ing very loud to me and also having the TV etc volume way up. Now I find that obtrusive! In fact, the first night I had the hearing aids in she asked me to turn the TV up because I had it too low! I’ve also discovered my car has squeaks and rattles I didn’t know about. They’re quite disconcerting! I’ve found a loose floor tile in my bathroom – it has a squeak I had never heard before. Traffic and wind noise while driving is more accentuated. I have a soft-top car so this is probably something I should have been hearing all along . . . Feedback, once the bane of hearing aids, is almost – but not quite – eliminated. If you, or something, covers the area over the hearing aid (obviously creating a feedback path), you might get a quick “chirp”. It’s not all that loud, certainly not loud enough to cause discomfort, but it can occur. I notice it when I put on or take off the hearing aids sometimes; other times when my ear is too close to the car window. Perhaps the worst thing, believe it or not, is the noise our dog makes! Tessie loves playing with empty PET drink bottles, attacking them, For comparison, here is the audiogram for my pushing them around a tiled floor, hearing with the LOF hearing aids fitted. The big biting into them, banging them dip at 6kHz is almost certainly the result of my onto furniture and so on. But now, reprogramming the aids to reduce the “jarring” I find the noise a real problem. The sounds I mentioned. Otherwise the measured differences are quite subtle – most noticeable is the barking also seems to be much more intense. 5dB increase at 8kHz in the right ear (red trace). July 2011  19 IHearYou programmer with its software and connecting leads. In all cases, the right hearing aid is coloured red and the left is coloured blue. The small adaptor leads almost underneath the programmer are the connectors to your hearing aids – we originally had them upside down and they didn’t work! I have since fiddled slightly with the hearing aid programming (see below) to try to reduce this harshness – it’s something that I will continue to experiment with as I get more and more used to hearing aids. IHearYou programmer I mentioned earlier that if you supply your audiogram, Australia Hears will pre-program your hearing aids for you and the odds are that you will be completely happy with them. However, we like to tinker, don’t we. We like to see if we can improve on perfection. Or we might want to set up a particular profile for a specific application (perhaps something to do with work, for example). That’s where the IHearYou programmer is used. It’s another $275 so it might be considered a bit extravagant for many users but . . . what the heck. We wanted to see what we could do with the hearing aid program. It’s a USB device and comes with software to make programming quite simple. All you do is load the software, plug the unit in and then connect it to your hearing aids. Ahh – problem. It didn’t work! So the usual solution applies – if all else fails, read the instructions. The problem was that I had the tiny hearing aid connectors upside down. I had taken the instructions saying “shiny side up” to mean the shiny (plastic) side up. Somewhere else I found they actually meant the copper 20  Silicon Chip side up. Woops. Those connectors are quite fiddly to get inserted properly but once I succeeded, the software told me that the AHPRO3 programmer was communicating with the hearing aids and then presented me with a range of options – all of which are quite intuitive. I found the original program for the hearing aids was fairly close to ideal but I did take the opportunity to knock the treble back just a tad, to overcome that jangly noise thing I mentioned earlier. If I didn’t have the programmer, I certainly wouldn’t have worried about it and I may even reverse it later. Incidentally, the other use for the programmer is to set up the parameters for Telecoil operation, which you simply load as one of the programs. I also mentioned eariler that the program selection is achieved via a small magnet which is packaged with your hearing aids and/or, in the case of the LOF model, a tiny pushbutton switch. • rapid speakers • competing speakers It is said to be especially valuable for anyone new to hearing aids but I also understand LACE to be valuable for anyone who might have problems understanding speech. I downloaded a free demo version from the Australia Hears website and it looks to me, American voices notwithstanding, something that could really help comprehension. You can read several reviews and testimonials about LACE at the same source. Priced at $99, it’s available for Windows 7, XP and Vista, Apple OSX10.4 or newer computer systems and as well, is available on DVD for use on a home TV system. OK, the verdict . . . After wearing the hearing aids for little over a week, I’m sold. I have found my hearing rather significantly improved (as I would hope!) and apart from the itchy ear I mentioned before (which lasted only a day), have found them extremely comfortable to wear (indeed, I forget they are on most of the time). It is obviously impossible for me to to an A:B:C comparison with any other hearing aids as far as clarity or overall audio is concerned but they’d have to go a long way to beat these from Australia Hears. And at the price paid, they’re streets ahead. SC Contact: Blaymey & Saunders Hearing Pty Ltd 384-388 Albert St, East Melbourne, Vic. 3002 Tel: (03) 9667 7563 Fax: (03) 9667 7571 Website: www.blaymeysaunders.com.au LACE software One thing I didn’t order with my hearing aids – but may get in due course – is a specialised software program called “LACE”. That stands for Listening and Communication Enhancement and is designed to retrain the brain to comprehend speech up to 40% better in difficult listening situations such as: • noisy restaurants siliconchip.com.au by Ross Tester The evolution of electric cars: Could there be a SIM-LEI in your future? C orrespondents in the May and June issues of SILICON CHIP made comment about the Mitsubishi i-MIEV (reviewed in the March issue) and electric vehicles in general. In the main, they were critical of the performance offered and in some cases, the design. At least some of those criticisms may have been allayed with the announcement in late May of the “SIM-LEI” a new electric vehicle design from a Japanese consortium, Shimizu Inwheel Motor-Drive, or, as they abbreviate their name, SIM-Drive. Interestingly, the purpose of the company is not to manufacture electric vehicles themselves but to provide the highest level of electric vehicle technology and information, at the lowest cost, to all those involved with electric vehicles. The SIM-LEI is not the first electric vehicle produced. In fact, they have developed 10 electric car prototypes over a 30-year period based Beauty IS in the eye of the beholder! It may not be the prettiest thing you on in-wheel motor drive technology. SIM-Drive ever saw but low drag coefficient and in-wheel motors contribute to its believe they have overcome the traditional ob- 300km+ between charges. It’s scheduled for production in 2013. stacles of enclosing the motor within the wheel, Power consumption rate is 77Wh/km, equivalent to 70km/L mainly an increase in unsprung weight, contributing to poor of the fuel efficiency rate of petrol. ride and increased wear and tear. Several approaches combined to achieve this perforThe consortium planned to announce the SIM-LEI on mance. The most important is the in-wheel motor. The allMarch 29 but this was delayed – not by technical considerasteel but super-light monocoque body reduces both body tions but by the Japanese earthquake and tsunami. SIM-LEI, weight and drag, while super-low-rolling-resistance tyres by the way, comes from the consortium name plus “Leading reduce friction resistance. Finally, braking regeneration Efficiency In-Wheel motor”. contributes significant energy savings. At the moment it’s a concept car but it is scheduled to go The SIM-LEI is roughly the same length as a medium-size into production in 2013. With the backing of some pretty sedan and as wide as a compact car, with roomy leg space heavy hitters in the consortium (including Mitsubishi and and a large boot space. engineering firm IHI), one would be excused for believing that it just might happen. Target range of 300km plus Performance The acceleration performance, which is one of the outstanding features of the SIM-LEI, is 4.8 seconds for The target performance of SIM-LEI was over 300km 0-100km/h (standing start). This is equivalent to, or even of range per charge, which is generally acknowledged as better than, many petrolthe major concern for powered prestige sport cars. the electrical vehicle Developers were happy market. The prototype with both the long range and exceeded this target, energy consumption of the with 333km of range per Overall size (length/width/height): 4700mm/1600mm/1550mm 4 SIM-LEI. charge under the “JC-08 Number of seats: By using off-peak elecmode” which represents Vehicle weight: 1650kg tricity, they believe vehicles general urban traffic Drive system Outer rotor direct drive in-wheel motor such as the SIM-LEI could condition in Japan. Drive: 4WD use excess generating caThe battery capacity (a) 333km (b) 305km pacity with no additional to achieve this target Range per charge:* (a) 77Wh/km (b) 84Wh/km power generation plants is 24.5kWh, almost the Driving energy consumption:* needed but at the same same level as other elec- Standing start to 100km/h: 4.8 seconds time, significantly reduce tric vehicles presently in Maximum speed: 150km/h a country’s dependence on the market. The battery          * (a) JC-08 mode (b) at 100km/h constant petroleum. itself is lithium-ion. SC Specifications of SIM-LEI siliconchip.com.au July 2011  21 Penguini with Mint: the Linux Mint desktop, from a distribution supplied by P. J. Radcliffe of RMIT. The root versions of the file browser and terminal provide you with unlimited power but no handrails or safety net. The tool bar pops up when the cursor hits the bottom of the screen. Control Your World Using Linux By NENAD NENAD STOJADINOVIC Microcontrollers are becoming more powerful and sophisticated, to the point where they are challenging the supremacy of the PC. On the other hand, PCs running Linux are quite open and accessible to the experimenter. Yes, your computer can control your air-conditioning and lights and this article will show you how. T HIS ARTICLE is basically the first step (actually there are only two steps) to embedded computing using single-board computers (SBCs). SBCs are generally just 5-8cm square and cram a complete PC onto a single circuit board. They are extensively used in applications requiring small size and/or resistance to vibration, such as automated teller machines, motor vehicles and portable machinery etc. These days, many run a version of Linux as the operating system due to its low cost, flexibility and range of development tools (some instead use one of the BSD-based Unix clones or Microsoft Windows). 22  Silicon Chip They do tend to be rather basic, so it’s much easier to do all development work in the luxury of your desktop PC, then stuff the finished software into the SBC when it’s all debugged and running. Technology directions In the last year or two, SILICON CHIP has presented several spectacular examples of just what can be done with the newest generation of powerful microcontrollers. There has been the Web Server In A Box (WIB), the Data Logger and just recently, the Maximite computer. It gives an indication of the direction that technology has taken and it’s amazing to think that a tiny piece of plastic and metal with a silicon “brain” can present you with seemingly endless pages of full-colour web content. PCs have mirrored this upward trend but in so doing, have made themselves more and more inaccessible to the casual experimenter. It’s harder to interface with USB than the older serial and parallel ports; even if you still have one of the latter, the latest Microsoft operating systems make writing software to access it a difficult task. But then there’s Linux. Linux is most certainly not such a black box. siliconchip.com.au In fact, everything is out in the open and it’s really quite easy to access the various PC communication ports. By using Linux as the operating system (OS), you once again have a PC that you can experiment with. Want to log data, surf the web, flash LEDs or switch relays in response to varying light levels? No problem at all. You may never have found much need to use to Linux and I certainly hadn’t. But during the course of this work, I found that Linux is the number one choice for an embedded operating system, with “Android” (now commonly used in mobile phones) being perhaps the most famous derivative. This and many other embedded operating systems are based on the Linux kernel, which is the core component that provides all the basic functions. The kernel is now up to version 2.6, and has a well-deserved reputation for functionality, stability and security. CONTROL SMART I/O MODULE SENSOR DATA SMART I/O MODULE SMART I/O MODULE CONTROL & DATA CONTROLLING COMPUTER Fig.1: a simple supervisory control scenario. Smart modules run a process while a central supervisory computer provides broad operating parameters and responds to any alarms. SMART I/O MODULE SENSOR DATA CONTROL Linux control paths There are three clear paths to Linux control and it’s worth spending some time to explore them. The first is the simple, old-fashioned use of the serial and parallel ports. Yes, I know that they have been largely phased out but rumours of their deaths have been greatly exaggerated. Suitable interface cards are readily and cheaply available (including USBto-serial or USB-to-parallel adaptors) and the average desktop PC has lots of space to fit them. Likewise, many embedded applications still use them and a glance through the Ocean Controls catalog will quickly illustrate the point. The second path involves the use of USB I/O (input/output) devices. They come in every imaginable configuration, from simple USB converter cables to boxes full of relays, ADCs and digital outputs – all driven from the USB port. For a (very) good example, take a look at the Arduino-compatible I/O controller featured in the April 2010 issue of SILICON CHIP. However, while the above approach is very useful, it has two failings: (1) the devices are generally “brainless”; and (2) it is difficult to use a PC in real time for such tasks. Your controlled system can be going haywire and overrunning its limit switches while the computer is blithely servicing some trivial interrupt. A better approach is “supervisory siliconchip.com.au control” (see Fig 1). It can be used with a bewildering variety of busses and protocols but let’s assume for the moment that it’s all USB. In that case, the PC and one or more USB I/O devices are linked together in a network, except now the USB I/Os are intelligent. An an analogy, imagine a ship’s captain and engine room crew. The captain (supervisory computer) drives the boat according to a plan involving high order functions such as navigation, sea state, schedule etc. The captain issues orders to the engine room for a certain speed and the engine room crew (USB I/O modules) takes care of monitoring and adjusting for steam pressure, engine operating parameters, lubrication and all the myriad functions that the captain does not want (or need) to worry about. The point is that each control module can monitor and adjust for its own feedbacks in real-time so the PC can then interact with them on its own schedule. The battle plan Let’s start with a simple example of PC hardware control, a basic serial/ parallel control system. While there are many more complex systems, this has the potential to occupy the ardent experimenter for some time. As mentioned above, using Linux is essential to making this easy. The Linux interface is not hugely difficult to master but it has some important differences compared to Windows (and many similarities). An article in the March 2009 issue of SILICON CHIP (“Reviving Old Laptops With Puppy Linux”) covered the basics quite well and is recommended for the new chum (thanks Warrick). In my case, I chose to purchase a Linux disk from P. J. Radcliffe of RMIT, who presented an intelligent USB I/O Interface in the October 2009 SILICON CHIP. As part of the development, he produced a live DVD that is set up specifically for this sort of work and is furthermore stuffed with all sorts of tools and data (see http://interestingbytes.wordpress.com/hello/openusb-io-interface-board/). Selling for a paltry $8.80, it is one of the world’s few remaining bargains. For this project, I obtained a PC built in 2005 with both parallel and serial ports and set it up near my usual computer so that I could hop onto the net at any time to check up on some arcane Linux command. It would also let me experiment without the fear of “killing” my good computer. The total cost of the set-up was just the price of the Linux DVD plus the computer, which still came to a total of $8.80, ie, the computer was scrounged for free (I did have to duck the hordes of people that also tried to “donate” their excess computers). Now Linux is available in many July 2011  23 less familiar beyond this point (but if you’re old enough to remember DOS, this will be nostalgic). Open up a root terminal using the desktop icon and enter the following commands: user ~ # cd /media user media # cd work user work # A relay board with a parallel port interface. These are available from many sources, eg, Ocean Controls. Setting an output bit high on the parallel port closes the corresponding relay. different “flavours” (called distributions). These contain the same basic components (kernel, graphical user interface etc) but they are pre-configured in various different ways. Just about any distribution will do for this task but I rather like Ubuntu. Also many distributions (Ubuntu included) provide a “live CD” or “live DVD” mode where the operating system is booted off the installation disk. The advantage of working this way is that if you make a mistake and cause it to lock up or you mess up some critical system file, you simply reboot and all will be pristine again. And if you use P. J. Radcliffe’s DVD in this manner, you will find that the desktop and the directories are prearranged for ease of use in this mode. Into the breach The first step is to make sure you can boot from the DVD. Reboot your computer and watch for the message that tells you how to get into BIOS – generally you must press DEL, ESC or F1 early on in the boot process. Once in the BIOS menu, wade through the options until you find the setting for “Boot Order”, then follow the onscreen directions to move the DVDROM to the first line (if it isn’t there already). Next, go to the peripherals set-up menu. There you will find several options for the parallel port and you will need to set it to “SPP” mode (or bi-directional or compatible, depending on the BIOS). Having done that, put the Linux DVD in the drive, then save and exit the BIOS settings, which should reboot 24  Silicon Chip the computer. Booting from DVD is a bit slow but you will eventually be rewarded with the Linux Mint desktop (assuming that you are using the recommended distribution; see lead photo). Note the terminal and Dolphin icons – they will become your friends. Booting the machine from a DVD means that you will have to store your working files elsewhere. If you have an old 1GB USB stick laying around, it will be more than sufficient. Plug it into your favourite computer and rename it something simple like “work” because you’ll be typing it a lot (it’s easier if there are no spaces in the name). Watch out – unlike Windows, Linux is also case sensitive, ie, “work” and “Work” are treated differently. Next, download the files you will need from the SILICON CHIP website (see the panel for a list of files and sources) and save them to the USB drive. That done, plug the USB stick into the Linux machine and open up the Dolphin (or other) file browser. Note that Linux does NOT identify disk drives with letters like Windows (C:, D: etc), though it does show you your disk as an icon for convenience. The topmost directory level is root, denoted by a single forward slash (/). Everything else is then under root as in /bin or /usr etc and you will find your drive mounted as /media/work (depending on what exact name you assigned to it). Rummage around and make sure it is there, as it’s harder for beginners to do this when working in the terminal. Things now terminal For Windows users, it all gets much The hash (#) in the prompt shows that you are working as root, which means you have full access to the computer. Otherwise, you would see a $ (dollar) sign (a bit ironic given that Linux is free) and would have more limited access. You will need to learn the following commands: ls -1 (list the files and do it neatly) pwd (print working directory, ie, current location) cd .. (go up one directory level) ./my_program (run my_program from this directory) Note that you don’t normally use the root terminal, as it does not have any safety constraints. Instead, it is more usual to prefix a command with sudo, which has the same effect but only for that command. Linux has various levels of permissions for reading and writing files and executing programs but the root (or “super user”/administrator) rules them all and can do anything and everything (including trashing important files!). That’s why we’re operating from a DVD. Also, some programs are not usable without root access, so it’s easier in this case to simply use the root account. The terminal will now have access to the directory that holds your USB drive. Type ls -1 to see if your files are all present and accounted for. The provided programs are all written in the “C” language, so they will need to be “compiled” into executable program files before they can be run. Linux generally has a C compiler ready to go and you can invoke it by typing “gcc” (which stands for Gnu Compiler Collection) at the command prompt: user work # gcc -O -o lp_tty_start lp_tty_start.c This compiles the C program lp_tty_ start.c into an executable binary file called lp_tty_start. The “-O” flag tells the compiler to perform an optimisation pass, producing a faster program. This is not to be confused with “-o” which tells it that the output file name follows. siliconchip.com.au Sources For Information, Hardware & Software (1). http://linuxgazette.net/118/chang.html (interface ADC with parallel port) (2). http://linuxgazette.net/112/radcliffe.html (general introduction to interfacing serial and parallel ports) (3). www.interestingbytes.wordpress.com (Linux Mint development system on DVD-ROM and intelligent USB IO) (4). www.oceancontrols.com.au (network and control hardware, for industry and hobby users) (5). www.siliconchip.com.au (download site for the software relating to this article in zip format) Do the same for port_write_then_ read.c, port_read.c and tx_rx_serial.c, remembering to change both the C source file and executable file names for each; ie, Now type in the following (mind the spaces and underscores): user work # ./pp_serial_check run user work # gcc -O -o port_read port_read.c Note that the serial check part only checks for the presence of a functioning serial port. It does not test the data transfer (see below). If that’s all successful, then try outputting a value via the parallel port: user work # gcc -O -o tx_rx_serial tx_rx_serial.c user work # ./lp_tty_start ./port_ write_then_read 888 85 Finally, create an executable called pp_serial_check, which combines no less than three separate C source files. To compile it type: That outputs a value of 85 (decimal) or 55 (hex) or 01010101 (binary) onto LPT1, which is located at port 888 (often written as 378 hexadecimal). You can then connect the ground lead of your multimeter to any of pins 18-25 (all ground) and measure the port’s output. Pin 2 is the bottom bit (D0), which should be 1 and the remaining bits run through to pin 9 (D7). The voltages should alternate as you scan the pins. For this type of programming, it helps to become familiar with converting between decimal (base 10), hexadecimal (base 16) and binary (base two) numbers. Sending the number 1 (decimal) to the port will result in 00000001 (binary) going to the output pins (D0 high). Sending 128 (decimal) gives 1000000 (binary), ie, D7 high. If your calculator can’t handle the maths, there are lots of web sites that will do the job. You can read the state of the port pins by invoking ./port_read; eg: user work # gcc -O -o port_write_ then_read port_write_then_read.c user work # gcc -O -o pp_serial_check main.c pp_access.c serial_access.c It is worth noting that the source code listings of these serial programs are useful items in themselves and are neatly commented to make them as easy as possible to understand and use. Limited hair, proceed carefully If, like me, you don’t have much hair left, you can’t afford much in the way of frustration and need to consider each step with care. First, check the operation of the ports with a loopback test. To do this, connect serial and parallel cables to the PC and look closely at the free ends of these cables (or peer into the ports at the back of the computer if you’re a masochist). You will see little numbers and you need to connect pin 14 to pin 15 on the parallel cable and pin 6 to pin 7 on a 9-pin serial cable (or pin 6 to pin 4 on a 25-pin serial cable). In my case, I used a paper clip to short the relevant pins for the parallel port and I got my daughter to hold a screwdriver to short out the relevant serial pins. siliconchip.com.au user work # ./lp_tty_start ./port_ read 889 This will read the input of LPT1. Why 889? Parallel ports were originally designed for printers and the input port is at a different address to the output port. There are only five Helping to put you in Control Control Equipment Digital Spirit Level Has the normal liquid bubble vials and a digital inclinometer to give you an accurate 0-360degree readout. Also fitted with a laser to assist with alignment. SRS-105 $119.00+GST Dual Axis Inclinometer using the latest MEMS technology the sensor mounts flat and provides two orthogonal 0 to 5 V outputs for X and Y tilt from -45º to +45º. SRS-038 $159+GST Infra-Red Temperature Sensor Non contact sensor measures temperature over 0 to 400degC. 4-20mA output STW-080 $179.00+GST CNC Controller This is a 4 Axis stand alone CNC Controller which can execute GCode from a USB memory stick or its internal memory, eliminating the need for a separate PC running Mach3 or EMC. CNC-703 $995+GST MP3 Player Shield Fitted with a SD micro card your arduino controller can become a fully functional MP3 player SFA-405 $39+GST JPEG Trigger interfaces with the LinkSprite JPEG Color Camera to simplify picture taking. Activate one of six I/O lines to take a picture and save it to a onboard SD micro card SFC-060 $29.00+GST Industrial Grade Pushbuttons with screw terminals and NO+NC contact HER-201 $9.95+GST Contact Ocean Controls Ph: 03 9782 5882 www.oceancontrols.com.au July 2011  25 #409 N 6 CO TRO L 6 DATA #409 SENSOR MODULE #4096 MASTER SERIAL MODULE SENSOR DATA SENSOR MODULE #4097 CONTROLLING COMPUTER SENSOR DATA PARALLEL PORT RELAY BLOCK SENSOR MODULE #4098 CONTROLLED HARDWARE Fig:2: a more advanced control system. In this case, a radio serial transceiver module (eg, from Ocean Controls or Parallax) sends commands to remote stations which return data to be processed by the PC. A parallel port relay interface then switches pumps, valves etc. input bits for a parallel port, located at pin 15 (D3), pin 13 (D4), pin 12 (D5), pin 10 (D6) and pin 11 (D7). Yes they are scrambled and the data for bit D7 is inverted! There were plans afoot to make port 888 bidirectional but my computer certainly doesn’t have that option. It’s worth a try, though – just read port 888 while using a resistor to pull the pins high or low. Serial comes to us Serial data is much harder to deal with at first, because the data goes past in a blink and so you must capture it to debug it. The solution is to use another computer to send and receive test messages. I scrounged an old laptop that runs Windows 3.1 (guess how much it cost!), with the Hyperterminal program for serial port I/O. I also splashed out and bought a null-modem interface cable (which connects one serial port’s transmit pin to the other port’s receive pin, and vice versa) from Jaycar for about $12 (Cat. WC 7513). Serial ports are composite in that the serial data goes in and out of pins 2 & 3 while the rest of the pins are for handshaking signals and so are in fact quite like a little parallel port! However, it’s complicated by the fact that the application must decide which is 26  Silicon Chip the master and which is the slave; the master cues up data and signals when it is ready to transmit, while the slave is generally sending data and must signal when it’s ready to receive. This can make life a bit complicated, especially when sending from peer to peer, but it’s usually possible to simply ignore the physical handshaking functions and arrange for control signals to be embedded in the data if it becomes really necessary. Linux serial ports are prefixed with “tty”, which is from its early days as Unix, where the ports were used to drive teletypes. What is referred to as COM1 in Windows is ttyS0 in Linux (S is for serial). For USB, it is ttyUSB. Linux also differs in that the serial ports are accessible as files, eg, the first port is /dev/ttyS0. There is a huge variety of serial software available for Linux, most from amateur programmers who needed a particular function or had a good idea that they pursued. I found that GTKterm (an improved version of Hyperterminal) is very useful for testing, as it will display any data that passes by. It is included in many Linux distributions (or “distros”) and Mint makes it available from the toolbar which is at the bottom of the screen (under “Utilities”). Fig.2 shows a sample system that I built, with a number of microcontroller modules sending serial data to my control program which then switches pumps, heaters or valves as appropriate. I used radio modules for the serial link, because the remote sensors were in awkward positions. For the serial communications, I started by running the program tx_rx_serial with port pins 2 & 3 linked together so that the data sent was immediately looped around to the data input. Once I knew that the port was running correctly, I simplified the program and set it up to send the appropriate commands to each sensor. This version is called serialstim.c and it will need to be compiled in the usual way. Run the compiled program and immediately the number 4096 should appear on the screen (why 4096? In binary it is 100000000000). To test this, I then connected the laptop via the null modem cable and fired up Hyperterminal. With the appropriate port speed selected, I made up a text file with a number in it (actually it was the number 11) and cued it up with “send a file”. It was then a simple matter of starting serialstim at the same time as I pressed the <enter> key on the laptop. Success was getting the number 4096 to appear on the laptop and the number 11 on the Linux machine. siliconchip.com.au LISTING 1: BASIC SCRIPT FILE (PASSWORDNDATA) #!/bin/bash set_val=11 #Preset value return=$( ./serialstim ) #Send command, get data in response echo $return #Print received data to screen if [ $return -ge $set_val ] # Is reading above preset value? then (./lp_tty_start ./port_write_then_read 888 1) #Yes it is, set D0 else (./lp_tty_start ./port_write_then_read 888 128) #No it’s not, set D7 fi This basic script file (passwordndata.sh) sends a command to a remote terminal, receives data in return and switches a relay if a condition is met. The command went one way and data came back the other. Cool. Close the loop with a script Passing data back and forth is all very well but nobody wants to sit around and operate stuff manually. How about controlling those pumps and valves? To achieve that, I tied it all together with script files. When you type commands into the terminal, they are actually interpreted by a program called BASH (which stands for Bourne Again SHell). BASH is basically the command line interface between you and Linux and it was the only way of doing things in this operating system before its graphical user interfaces were developed. Some clever person(s) realised that to save effort, it would be useful to be able to run common sets of commands without having to type them in every time. This is achieved using files called “shell scripts” which are a bit like DOS/Windows batch (*.BAT) or command (*.CMD) files. Additional commands were added to BASH to allow these scripts to be smarter; commands like “if”, “while”, “do” etc. Suddenly the command line had a form of programming called “BASH shell programming”, based on script files. With a shell script, you can do most of the things you expect from any program, with the added advantage of being able to easily utilise other programs, written in other languages such as “C” or Python (as well as other shell scripts). Furthermore, you can “pipe” the output from one program (say, your serial reception program) to the input of another program, perhaps a data analysis and control program. Simple script file The subject of BASH programming is much too large for an article such as this. The Linux community has obviously spent a lot of time developing the software and there are boundless references on the internet, though it can take a bit of hunting to find stuff that’s written by a native of Earth. However, to demonstrate, I’ve written a short script that uses all of the aspects covered so far – see Listing 1. It does not need to be compiled and it is run by typing: user work # sh ./passwordndata.sh The script calls serialstim to send a command and then receives data transmitted from the remote sensor, which is then echoed (printed) to the screen. It compares the returned data to a set value. If it is equal to or above this value (ge = Greater than or Equal to), it activates the parallel port enabling program and the control program to send binary 00000001 to the port, thus activating the relay connected to D0. Conversely, if it’s below the set value, it sends 1000000 to activate the relay on D7 and make sure that D0 is switched off. It’s a simple script and it demonstrates what can be done by unskilled labour. Remember though that you are only pottering around in one corner of a powerful computer. This simple script could easily be extended to, say, write the data to a file with a time stamp and then FTP the files to an address of your choosing. Then it would be easy to install web server software like Xampp so that you can access the system from all over the world (remote control is also possible using a program called ssh or Secure SHell). In short, the applications are limitless, the software and support is all out SC there, and the price is right! Are Your Issues Getting Dog-Eared? Are your SILICON CHIP copies getting damaged or dog-eared just lying around in a cupboard or on a shelf? Can you quickly find a particular issue that you need to refer to? REAL VALUE AT $14.95 PLUS P & P Keep your copies of SILICON CHIP safe, secure and always available with these handy binders Available Aust, only. Price: $A14.95 plus $10 p&p per order (includes GST). Just fill in and mail the handy order form in this issue; or fax (02) 9939 2648; or call (02) 9939 3295 and quote your credit card number. siliconchip.com.au July 2011  27 WANT TO SAVE 10%? S C (PRINT EDITION) AUTOMATICALLY QUALIFY FOR REFERENCE $ave SUBSCRIBERS* CHIP BOOKSHOP 10% A 10% DISCOUNT ON ALL BOOK PURCHASES! SILICON ILICON HIP (*Does not apply to website orders) SELF ON AUDIO by Douglas Self 2nd Edition 2006 $69.00 PROGRAMMING and CUSTOMIZING THE PICAXE By David Lincoln (2nd Ed, 2011) $65.00 See Review A great aid when wrestling with applications for the PICAXE series of microcontrollers, at beginner, intermediate and advanced April 2011 levels. Every electronics class, school and library should have a copy, A collection of 35 classic magazine articles offering a dependable methodology for designing audio power amplifiers to improve performance at every point without significantly increasing cost. Includes compressors/limiters, hybrid bipolar/FET amps, electronic switching and more. 474 pages in paperback. along with anyone who works with PICAXEs. 300 pages in paperback SMALL SIGNAL AUDIO DESIGN By Douglas Self – First Edition 2010 $88.00 PIC IN PRACTICE The latest from the Guru of audio. Explains audio concepts in easy-to-understand language with plenty of examples and reasoning. Inspiration for audio designers, superb background for audio enthusiasts and especially where it comes to component peculiarities and limitations. Expensive? Yes. Value for money? YES! Highly recommended. 558 pages in paperback. by D W Smith. 2nd Edition - published 2006 $60.00 Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcontrollers. 255 pages in paperback. AUDIO POWER AMPLIFIER DESIGN HANDBOOK PIC MICROCONTROLLER – your personal introduc- by Douglas Self – 5th Edition 2009 $81.00 tory course By John Morton 3rd edition 2005. $60.00 "The Bible" on audio power amplifiers. Many revisions and updates to the previous edition and now has an extra three chapters covering Class XD, Power Amp Input Systems and Input Processing and Auxiliarly Subsystems. Not cheap and not a book for the beginner but if you want the best reference on Audio Power Amps, you want this one! 463 pages in paperback. A unique and practical guide to getting up and running with the PIC. It assumes no knowledge of microcontrollers – ideal introduction for students, teachers, technicians and electronics enthusiasts. Revised 3rd edition focuses entirely on re-programmable flash PICs such as 16F54, 16F84 12F508 and 12F675. 226 pages in paperback. PRACTICAL GUIDE TO SATELLITE TV OP AMPS FOR EVERYONE By Garry Cratt – Latest (7th) Edition 2008 $49.00 By Carter & Mancini – 3RD EDITION $100.00 Written in Australia, for Australian conditions by one of Australia's foremost satellite TV experts. If there is anything you wanted to know about setting up a satellite TV system, (including what you can't do!) it's sure to be covered in this 176-page paperback book. Substantially updates coverage for low-speed and high-speed applications, and provides step-by-step walk-throughs for design and selection of op amps. Huge 648 pages! PROGRAMMING 32-bit MICROCONTROLLERS IN C By Luci di Jasio (2008) $79.00 NEWNES GUIDE TO TV & VIDEO TECHNOLOGY By KF Ibrahim 4th Edition (Published 2007) $49.00 Subtitled Exploring the PIC32, a Microchip insider tells all on this powerful PIC! Focuses on examples and exercises that show how to solve common, real-world design problems quickly. Includes handy checklists. FREE CD-ROM includes source code in C, the Microchip C30 compiler, and MPLAB SIM. 400 pages paperback. It's back! Provides a full and comprehensive coverage of video and television technology including HDTV and DVD. Starts with fundamentals so is ideal for students but covers in-depth technologies such as Blu-ray, DLP, Digital TV, etc so is also perfect for engineers. 600+ pages in paperback. USING UBUNTU LINUX RF CIRCUIT DESIGN by J Rolfe & A Edney – published 2007 $27.00 by Chris Bowick, Second Edition, 2008. $63.00 Ubuntu Linux is a free and easy-to-use operating system, a viable alternative to Windows and Mac OS. Introduces Ubuntu, tells how to set it up, covers the various Open Office applications and gives troubleshooting hints and tips. Highly recommended. 222 pages in paperback DVD PLAYERS AND DRIVES by K.F. Ibrahim. Published 2003. $71.00 A guide to DVD technology and applications, with particular focus on design issues and pitfalls, maintenance and repair. Ideal for engineers, technicians, students of consumer electronics and sales and installation staff. 319 pages in paperback. The classic RF circuit design book. RF circuit design is now more important that ever in the wireless world. In most of the wireless devices that we use there is an RF component – this book tells how to design and integrate in a very practical fashion. 244 pages in paperback. PRACTICAL RF HANDBOOK See Review Feb 2004 by Ian Hickman. 4th edition 2006 $61.00 A guide to RF design for engineers, technicians, students and enthusiasts. Covers key topics in RF: analog design principles, transmission lines, couplers, transformers, amplifiers, oscillators, modulation, transmitters and receivers, propagation and antennas. 279 pages in paperback. ELECTRIC MOTORS AND DRIVES PRACTICAL VARIABLE SPEED DRIVES & POWER ELECTRONICS Se By Austin Hughes - Third edition 2006 $51.00 Intended for non-specialist users of electric motors and drives, filling the gap between academic texts and general "handbooks". Explores all of the widely-used modern types of motor and drive including conventional & brushless DC, induction motors, steppers, servos, synchronous and reluctance. 384 pages, soft cover. e Review Feb An essential reference for engineers and anyone who wishes 2003 to design or use variable speed drives for induction motors. by Malcolm Barnes. 1st Ed, Feb 2003. $73.00 286 pages in soft cover. BUILD YOUR OWN ELECTRIC MOTORCYCLE AC MACHINES by Carl Vogel. Published 2009. $40.00 By Jim Lowe Published 2006 $66.00 Applicable to Australian trades-level courses including NE10 AC Machines, NE12 Synchronous Machines and the AC part of NE30 Electric Motor Control and Protection. Covering polyphase induction motors, single-phase motors, synchronous machines and polyphase motor starting. 160 pages in paperback. Alternative fuel expert Carl Vogel gives you a hands-on guide with the latest technical information and easy-to-follow instructions for building a two-wheeled electric vehicle – from a streamlined scooter to a full-sized motorcycle. 384 pages in soft cover. NOTE: ALL PRICES ARE PLUS P&P – AUSTRALIA ONLY: $10.00 per order; OR FAX (24/7) OR NZ – $12.00 PER BOOK; PAYPAL (24/7) REST OF WORLD $18.00 PER BOOK PHONE – (9-5, Mon-Fri) eMAIL (24/7) OR To Call (02) 9939 3295 with Your order and card details to Use your PayPal account silicon<at>siliconchip.com.au Place 28  S ilicon C hip with order & credit card details (02) 9939 2648 with all details silicon<at>siliconchip.com.au with order & credit card details Your Or use the handy order form on P105 of this issue Order: 1-13 See Review March 2010 OR MAIL Your order to PO Box 139 siliconchip.com.au Collaroy NSW 2097 *ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. ALL PRICES INCLUDE GST WANT TO SAVE 10%? S C (PRINT EDITION) AUTOMATICALLY QUALIFY FOR REFERENCE $ave SUBSCRIBERS* CHIP BOOKSHOP 10% A 10% DISCOUNT ON ALL BOOK PURCHASES! SILICON ILICON HIP (*Does not apply to website orders) SELF ON AUDIO PROGRAMMING and CUSTOMIZING THE PICAXE By David Lincoln (2nd Ed, 2011) $65.00 by Douglas Self 2nd Edition 2006 $69.00 See A collection of 35 classic magazine articles offering a dependable methodology for designing audio power amplifiers to improve performance at every point without significantly increasing cost. Includes compressors/limiters, hybrid bipolar/FET amps, electronic switching and more. 474 pages in paperback. Review A great aid when wrestling with applications for the PICAXE series of microcontrollers, at beginner, intermediate and advanced April 2011 levels. Every electronics class, school and library should have a copy, along with anyone who works with PICAXEs. 300 pages in paperback SMALL SIGNAL AUDIO DESIGN PIC IN PRACTICE By Douglas Self – First Edition 2010 $88.00 by D W Smith. 2nd Edition - published 2006 $60.00 The latest from the Guru of audio. Explains audio concepts in easy-to-understand language with plenty of examples and reasoning. Inspiration for audio designers, superb background for audio enthusiasts and especially where it comes to component peculiarities and limitations. Expensive? Yes. Value for money? YES! Highly recommended. 558 pages in paperback. Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcontrollers. 255 pages in paperback. PIC MICROCONTROLLER – your personal introduc- AUDIO POWER AMPLIFIER DESIGN HANDBOOK tory course By John Morton 3rd edition 2005. $60.00 by Douglas Self – 5th Edition 2009 $81.00 A unique and practical guide to getting up and running with the PIC. It assumes no knowledge of microcontrollers – ideal introduction for students, teachers, technicians and electronics enthusiasts. Revised 3rd edition focuses entirely on re-programmable flash PICs such as 16F54, 16F84 12F508 and 12F675. 226 pages in paperback. "The Bible" on audio power amplifiers. Many revisions and updates to the previous edition and now has an extra three chapters covering Class XD, Power Amp Input Systems and Input Processing and Auxiliarly Subsystems. Not cheap and not a book for the beginner but if you want the best reference on Audio Power Amps, you want this one! 463 pages in paperback. OP AMPS FOR EVERYONE PRACTICAL GUIDE TO SATELLITE TV By Carter & Mancini – 3RD EDITION $100.00 Substantially updates coverage for low-speed and high-speed applications, and provides step-by-step walk-throughs for design and selection of op amps. Huge 648 pages! By Garry Cratt – Latest (7th) Edition 2008 $49.00 Written in Australia, for Australian conditions by one of Australia's foremost satellite TV experts. If there is anything you wanted to know about setting up a satellite TV system, (including what you can't do!) it's sure to be covered in this 176-page paperback book. PROGRAMMING 32-bit MICROCONTROLLERS IN C By Luci di Jasio (2008) $79.00 NEWNES GUIDE TO TV & VIDEO TECHNOLOGY Subtitled Exploring the PIC32, a Microchip insider tells all on this powerful PIC! Focuses on examples and exercises that show how to solve common, real-world design problems quickly. Includes handy checklists. FREE CD-ROM includes source code in C, the Microchip C30 compiler, and MPLAB SIM. 400 pages paperback. By KF Ibrahim 4th Edition (Published 2007) $49.00 It's back! Provides a full and comprehensive coverage of video and television technology including HDTV and DVD. Starts with fundamentals so is ideal for students but covers in-depth technologies such as Blu-ray, DLP, Digital TV, etc so is also perfect for engineers. 600+ pages in paperback. USING UBUNTU LINUX by J Rolfe & A Edney – published 2007 $27.00 RF CIRCUIT DESIGN Ubuntu Linux is a free and easy-to-use operating system, a viable alternative to Windows and Mac OS. Introduces Ubuntu, tells how to set it up, covers the various Open Office applications and gives troubleshooting hints and tips. Highly recommended. 222 pages in paperback DVD PLAYERS AND DRIVES by K.F. Ibrahim. Published 2003. $71.00 A guide to DVD technology and applications, with particular focus on design issues and pitfalls, maintenance and repair. Ideal for engineers, technicians, students of consumer electronics and sales and installation staff. 319 pages in paperback. by Chris Bowick, Second Edition, 2008. $63.00 The classic RF circuit design book. RF circuit design is now more important that ever in the wireless world. In most of the wireless devices that we use there is an RF component – this book tells how to design and integrate in a very practical fashion. 244 pages in paperback. See Review Feb 2004 PRACTICAL RF HANDBOOK by Ian Hickman. 4th edition 2006 $61.00 A guide to RF design for engineers, technicians, students and enthusiasts. Covers key topics in RF: analog design principles, transmission lines, couplers, transformers, amplifiers, oscillators, modulation, transmitters and receivers, propagation and antennas. 279 pages in paperback. ELECTRIC MOTORS AND DRIVES By Austin Hughes - Third edition 2006 $51.00 PRACTICAL VARIABLE SPEED DRIVES & POWER ELECTRONICS Se Intended for non-specialist users of electric motors and drives, filling the gap between academic texts and general "handbooks". Explores all of the widely-used modern types of motor and drive including conventional & brushless DC, induction motors, steppers, servos, synchronous and reluctance. 384 pages, soft cover. e Review Feb An essential reference for engineers and anyone who wishes 2003 to design or use variable speed drives for induction motors. by Malcolm Barnes. 1st Ed, Feb 2003. $73.00 286 pages in soft cover. AC MACHINES BUILD YOUR OWN ELECTRIC MOTORCYCLE By Jim Lowe Published 2006 $66.00 Applicable to Australian trades-level courses including NE10 AC Machines, NE12 Synchronous Machines and the AC part of NE30 Electric Motor Control and Protection. Covering polyphase induction motors, singlephase motors, synchronous machines and polyphase motor starting. 160 pages in paperback. by Carl Vogel. Published 2009. $40.00 Alternative fuel expert Carl Vogel gives you a hands-on guide with the latest technical information and easy-to-follow instructions for building a two-wheeled electric vehicle – from a streamlined scooter to a full-sized motorcycle. 384 pages in soft cover. NOTE: ALL PRICES ARE PLUS P&P – AUSTRALIA ONLY: $10.00 per order; eMAIL (24/7) To silicon<at>siliconchip.com.au Place siliconchip.com.au with order & credit card details Your Order: 1-13 See Review March 2010 OR FAX (24/7) Your order and card details to (02) 9939 2648 with all details OR NZ – $12.00 PER BOOK; PAYPAL (24/7) Use your PayPal account silicon<at>siliconchip.com.au OR REST OF WORLD $18.00 PER BOOK PHONE – (9-5, Mon-Fri) Call (02) 9939 3295 with with order & credit card details OR MAIL Your order to PO Box 139 July 2011  29 Collaroy NSW 2097 Or use the handy order form on P85 of this issue *ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. ALL PRICES INCLUDE GST Ultra-LD Mk.3 200W Amplifier Module Upgraded design has even lower distortion! The Ultra-LD Mk.2 (August-September 2008) was the lowest distortion class-AB amplifier board design ever published. But we have not rested on our laurels and have found ways to improve it significantly. The Mk.3 version has less than half as much distortion at frequencies of 2kHz and above. It also boasts much improved thermal stability, is slightly quieter and has a flatter frequency response. By NICHOLAS VINEN T HE NEW AND UPDATED Ultra-LD Mk.3 is by far the best class-AB amplifier module design published anywhere. It has an astonishingly low total harmonic distortion plus noise (THD+N) figure of 0.004% at 20kHz for 100W into 8Ω (20Hz-80kHz measurement bandwidth) and less than 0.0006% THD+N at 1kHz and below. The signal-to-noise ratio has also been slightly improved on the previous version (by 1dB) to -123dB with respect to 135W into an 8Ω load. The power output figures are unchanged with regards to the Mk.2 module. All power measurements were made with a mains voltage of 230VAC, which is now common in Australia (although by no means universal). In locations with a higher mains voltage, slightly more output power is available. For example, if your mains voltage is normally 240VAC, you can expect about 8% more power output, eg, 145W into 8Ω. The quiescent current accuracy, stability and thermal compensation have been dramatically improved compared to the Mk.2 and in fact are superior to any class-AB amplifier that we have tested. The new module has a trimpot so that the quiescent current can be set Specifications & Performance Output Power (230VAC mains).................................200 watts RMS into 4Ω; 135 watts RMS into 8Ω Frequency response.................................+0, -0.3dB (8Ω); +0, -1.0dB (4Ω) – 10Hz-20kHz (see Fig.5) Input sensitivity...................................... 1.26V RMS for 135W into 8Ω; 1.08V RMS for 200W into 4Ω Input Impedance.............................................................................................................................. 12kΩ Rated Harmonic Distortion (8Ω)............... <0.004% 20Hz-20kHz, typically 0.0006% (see Figs.1 & 3) Rated Harmonic Distortion (4Ω)............... <0.007% 20Hz-20kHz, typically 0.0006% (see Figs.2 & 4) Signal-to-Noise Ratio....................123dB unweighted with respect to 135W into 8Ω (22Hz to 22kHz) Damping Factor.....................................................................~180 with respect to 8Ω at 1kHz & below Stability......................................................unconditionally stable with any nominal speaker load ≥ 4Ω 30  Silicon Chip to the optimum (the Mk.2 was a bit hit and miss in this regard). The new thermal compensation arrangement keeps the quiescent current well under control, even during and after sudden changes in dissipation. This contributes to the low distortion as it means that the output stage is always correctly biased. Rationale Making these improvements to an amplifier that already had outstanding performance may seem like gilding the lily. But there are two important reasons why we decided to improve on the Ultra-LD Mk.2. First, we felt that we could produce a design that was even closer to that holy grail of amplifier design: a highpower class-AB module with the low distortion of a Class-A amplifier. In fact, the new design is tantalisingly close to the benchmark SILICON CHIP Class-A amplifier (May-Sept. 2007). Astute readers may have noticed that while the Ultra-LD Mk.2 was clearly superior to the original UltraLD amplifier (SILICON CHIP, March & May 2000), it actually had higher distortion for frequencies above 6kHz. This is because the original Ultrasiliconchip.com.au The Ultra-LD Mk.3 Audio Amplifier module features pluggable connectors, improved thermal stability and extremely low noise and distortion figures. It’s built on a double-sided PCB and is attached to a large finned heatsink which carries the driver and output transistors and a central VBE multiplier transistor. LD featured a more linear output stage, consisting of two complementary compound transistor pairs. By contrast, the Ultra-LD Mk.2 used a standard complementary Darlington emitter-follower output stage, for better current sharing between the output transistors (allowing it to reliably drive 4Ω loads). Since then, we have tweaked the emitter-follower output stage to improve its linearity at high frequencies (more on this later). The end result is that the Mk.3 has distortion lower than or equal to both the original Ultra-LD and the Ultra-LD Mk.2 at all frequencies. siliconchip.com.au It may seem that the distortion products of very high frequencies (10kHz & above) are irrelevant, since they will all be above the audible range. The second harmonic of a 10kHz signal is 20kHz and the third is 30kHz and these are not audible so why are we trying to minimise their level? The answer is intermodulation. While lower order harmonic distortion may be relatively benign, the associated and inevitable intermodulation distortion is definitely not benign; it is audibly unpleasant. To demonstrate, let’s say we have an audio signal consisting of a 10kHz sinewave mixed with an 11kHz sine- wave. Their second harmonics are at 20kHz and 22kHz respectively and are not audible, but the difference products of 1kHz, 2kHz & 12kHz certainly are audible and are musically unrelated. So by minimising harmonic distortion at high frequencies, we are also minimising intermodulation – a far more unpleasant distortion product. Quiescent current Second, we just weren’t satisfied with the quiescent current and thermal compensation arrangement of the Ultra-LD Mk.2. That was our first design using the On Semiconductor July 2011  31 THD+N vs Frequency, 8, 100W, 20Hz-80kHz BW THD+N vs Frequency, 4, 100W, 20Hz-80kHz BW 05/20/11 12:27:35 Ultra-LD Mk.2 Ultra-LD Mk.3 Ultra-LD Mk.2 Ultra-LD Mk.3 0.01 Total Harmonic Distortion + Noise (%) Total Harmonic Distortion + Noise (%) 0.01 0.005 0.002 0.001 0.0005 0.005 0.002 0.001 0.0005 0.0002 0.0002 0.0001 20 05/20/11 12:27:35 0.02 0.02 50 100 200 500 1k Frequency (Hertz) 2k 5k 10k Fig.1: total harmonic distortion plus noise across the audible frequency range for an 8Ω load driven at 100W. This is an “apples-to-apples” comparison between the old and new amplifier modules with an identical power supply and test set-up. The Mk.3 is superior at all frequencies but especially above 1kHz. “ThermalTrak” transistors, which have integral diodes. The literature for these devices claims that they eliminate the need for quiescent current adjustment as well as providing much better thermal tracking than a traditional VBE multiplier circuit. Our initial prototypes seemed to confirm both points. But as more people built modules based on that design, it became apparent that the ThermalTrak transistors vary somewhat from batch to batch and therefore we do in fact need a method to trim the quiescent current. Also, for reasons we shall explain later, many of the Ultra-LD Mk.2 modules built do not have good thermal tracking. That is to say, their quiescent current can vary considerably depending on the output device temperature, which can vary rapidly depending on the program material being played. Once we found out about these problems we took a closer look at the ThermalTrak transistor data sheets. It turns out that the ThermalTrak diode temperature coefficient doesn’t necessarily match that of the accompanying transistor and so using the diodes alone for thermal compensation is not satisfactory. In some cases, the diode temperature coefficient is so much lower than the transistors’ that the result can be thermal runaway – as the transistors get hotter, the quiescent current increases, making them hotter again 32  Silicon Chip 20k 0.0001 20 50 100 200 500 1k Frequency (Hertz) 2k 5k 10k 20k Fig.2: the total harmonic distortion plus noise across the audible frequency range for a 4Ω load driven at 100W. The performance improvement for the Mk.3 module is even larger with a 4Ω load, with less than half the distortion of the Mk.2 version across a large portion of the audio frequency range. until eventually they blow; definitely not a good state of affairs! Back to the drawing board Actually, building a class-AB amplifier with accurate thermal compensation that responds quickly to changes in dissipation is a very difficult task. The basic problem is that to get good performance, the standing current through the push-pull output transistors must be kept within a relatively small range (in this case, about 70140mA per pair). If the quiescent current is too low, the result is significant crossover distortion. As the output voltage passes through zero, the load current is “handed over” from one of the output transistors to the other. Without sufficient bias, one transistor turns off faster than the other turns on, resulting in a discontinuity in the output stage transconductance (ie, the ratio of its input voltage to output current). This makes the amplifier as a whole less linear and so increases its distortion. The opposite problem occurs if the quiescent current is too high. In this case there is actually a sudden increase in the transconductance in a voltage band around 0V. This is called “transconductance doubling” and again reduces linearity. When the quiescent current is in the correct range, these two effects tend to balance out and so the transconduct- ance curve for the output stage is as flat as possible, maximising linearity and thus minimising distortion. So we want to set it within that range and keep it there. High quiescent current also causes excessive dissipation in the output devices – we don’t have to explain why that’s undesirable. Thermal tracking If the transistors were all kept at a constant temperature, correct biasing could easily be arranged by simply placing an adjustable floating voltage source between the base of the two driver transistors and then trimming it with an eye on the current through the output stage. This bias voltage sets the VBE across the driver and output transistors, resulting in a constant standing current through the output stage. Unfortunately, the required VBE for constant current through a transistor depends on its junction temperature. Since the output transistors heat up and cool down during use in an unpredictable way (depending on the program material, load impedance, ambient temperature, airflow, etc), we must come up with a way for the bias voltage to vary with driver and output transistor temperature, to keep the quiescent current as stable as possible. In the Mk.2 amplifier, the bias was developed by passing a constant current through the four ThermalTrak diodes contained within the output siliconchip.com.au Total Harmonic Distortion + Noise (%) 0.05 THD+N vs Power, 8, 1kHz, 20Hz-20kHz BW 05/20/11 14:59:08 0.1 Ultra-LD Mk.2 Ultra-LD Mk.3 0.02 0.01 0.005 0.002 0.001 0.0005 0.0002 05/20/11 14:57:55 Ultra-LD Mk.2 Ultra-LD Mk.3 0.02 0.01 0.005 0.002 0.001 0.0005 0.0002 0.06 0.1 0.2 0.5 1 2 5 Power(W) 10 20 50 100 Fig.3: total harmonic distortion plus noise against power level for 1kHz into 8Ω. The slightly lower noise figure makes the Mk.3 marginally superior at low powers, with it pulling further ahead above 4W due to its lower harmonic distortion. Note that the maximum power available has hardly changed from the earlier design; the small variation is mainly due to the test procedure. transistor packages. As the output transistors heated up, the required VBE for a given current dropped and so did the forward voltage of the associated diodes. If the two thermal coefficients matched, then theoretically the diodes would correctly compensate for the changing transistor properties with temperature. Since that clearly wasn’t happening, we decided to ignore what the application literature said about these transistors and instead analyse the circuit from first principles. We are not the only people to notice this problem. Douglas Self experienced similar difficulties using this type of transistor, which he documents in his Audio Power Amplifier Design Handbook (Fifth Edition). In that book, he points out that if the ThermalTrak transistor data sheet is correct, the diode forward voltage temperature coefficient is -1.7mV/°C but the transistor VBE temperature coefficient is -2.14mV/°C. Clearly then, we cannot use a single ThermalTrak diode to compensate for a single ThermalTrak transistor without risking thermal runaway (or at least a wildly varying quiescent current). But that wasn’t the only problem. The four ThermalTrak diodes compensated for four transistor VBE drops but only two of those drops are from the base-emitter junctions of the power transistors that the diodes thermally siliconchip.com.au 0.0001 200 0.06 0.1 0.2 track. The other two are the driver transistors (Q10 and Q11, MJE15030/ MJE15031). So even if the diode thermal coefficients matched those of the output transistors, they wouldn’t necessarily correctly compensate the driver transistors. Also, there is significant thermal lag between the output transistors and the driver transistors, since during periods of high output power, the power transistors can get significantly hotter than the heatsink. It takes a while for the heatsink temperature to heat up in response to the increased dissipation and then there is a further thermal lag from the heatsink back to the driver transistors. Fig.5: the frequency response for the Ultra-LD Mk.3 module. Note that there is less roll-off at both the lowfrequency and highfrequency ends for the Mk.3 compared to the Mk.2. The high-frequency rolloff is greater for 4Ω loads (about -1dB at 20kHz). This can be slightly improved (to -0.7dB) by changing the inductor – see Pt.2 next month. 0.5 1 2 5 Power(W) 10 20 50 100 200 Fig.4: total harmonic distortion plus noise versus power for 1kHz into 4Ω at a range of power levels. Here the Mk.3 module really shines, providing significantly lower distortion across the entire range. The Mk.3 can easily produce the rated power of 200W into 4Ω. Note that the measurement bandwidth (20Hz-20kHz) is smaller than in Figs.1 & 2, so the figures are better. +1.0 We had to find a better solution. As a result, we came up with several ideas for circuits that would provide a bias voltage with more accurate and reliable thermal tracking, then ran them through circuit simulations before building a prototype incorporating the most promising. New design Our new solution harks back to that tried and true bias compensation scheme, the good old VBE multiplier. But we have also incorporated the ThermalTrak diodes as they are critical in allowing us to provide compensation for rapidly varying output device temperature. Frequency Response, 4 & 8, 1W 05/20/11 12:43:21 Ultra-LD Mk.2 (8) Ultra-LD Mk.3 (8) Ultra-LD Mk.3 (4) +0.5 0 Amplitude Variation (dBr) 0.0001 THD+N vs Power, 4, 1kHz, 20Hz-20kHz BW 0.05 Total Harmonic Distortion + Noise (%) 0.1 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 10 20 50 100 200 500 1k 2k Frequency (Hertz) 5k 10k 20k 50k July 2011  33 Fig.6: load lines for the Ultra-LD Mk.3 amplifier. The red line is the 1-second Safe Operating Area (SOA), outside of which transistor second breakdown becomes likely. The mauve and green lines represent realistic speaker operating areas for 8Ω and 4Ω units respectively, taking into account their reactance. Ultra-LD Mk.3 Load Lines (4 Output Transistors) 10 2 x ThermalTrak 1 second SOA, 90% Sharing 8 Resistive Load 8 Reactive Load, 135W (5.6+5.6j) 8  Resistive Load Collector Current (Amps)  Reactive Load, 200W (2.83+2.83j) 6 4 2 0 0 20 40 60 80 Collector-Emitter Potential (Volts) We are now using two ThermalTrak diodes to compensate for the two power transistor VBE drops, in series with a VBE multiplier to compensate for the driver transistor VBE drops. The VBE multiplier transistor is mounted on the heatsink, between the driver transistors, to best track their temperature. Now that we have a VBE multiplier, this allows us to easily provide an adjustment by placing a trimpot in the multiplier network. This means that the quiescent current can be configured correctly regardless of variations in the output transistors. The adjustment will however slightly degrade the thermal tracking, since in changing the absolute voltage contribution of the VBE multiplier (by changing the multiplication factor) we also change its thermal coefficient. But our testing shows that this is a relatively minor factor and the tracking is still more than good enough. Actually, because the temperature coefficient of the ThermalTrak diodes is lower than that of the associated transistors, in order to achieve correct compensation, the VBE multiplier must slightly over-compensate for changes in temperature. We found that if we used a BD139 for the VBE multiplier, we achieved the required over-compensation. Simulation shows that the resulting quiescent current variation with temperature is virtually flat. The prototype Ultra-LD Mk.3 modules were built from two different batches of ThermalTrak transistors and they bear this out. As a happy coincidence, it turns out that the 34  Silicon Chip 100 120 best current to use for the new bias generating arrangement is the current that we originally chose for the UltraLD Mk.2 (9.5mA) to provide the best performance. Parallel diodes While we stated earlier that we are only using two of the ThermalTrak diodes, we have actually wired up all four on the PCB, in two parallel pairs which are then connected in series. This makes it possible to build the amplifier with only two output transistors (the outer pair), for applications where less power is required. The supply voltage is also reduced in this case, to reduce overall power dissipation. Lower distortion As stated, the Ultra-LD Mk.3 has less than half the distortion of the Mk.2 at frequencies of 2kHz and above (see Figs.1-4). It also has lower distortion at low frequencies but there is so little to measure that it tends to be lost in the noise floor (not that there is much of that either). There are two main changes which reduce the distortion and these are the new frequency compensation arrangement and the new driver transistor emitter resistor configuration (ie, for Q10 & Q11). Of these, the latter is the most important but they both contribute to the excellent performance. With the Ultra-LD Mk.2, the driver emitters were connected to the output via 100Ω resistors. For the new circuit, the emitters are instead connected to each other via a 220Ω resistor which is bypassed with a 470nF capacitor. This allows the driver transistors to reverse-bias one pair of the output transistors to switch them off quickly, when the slew rate is high (ie, at high frequencies). This was not possible with the old arrangement. Reverse-biasing the output transistor base-emitter junction rapidly removes the charge carriers from it, preventing conduction which would otherwise occur for some period after the normal base drive was removed. The 470nF bypass capacitor assists in the switch-off process. The bottom line is lower distortion at high frequencies. Two-pole compensation The new compensation scheme also helps to lower the distortion. Instead of a single 100pF, 100V ceramic capacitor between the base of Q8 and the collector of Q9, we now have two 180pF 100V polypropylene (plastic dielectric) capacitors and a 2.2kΩ resistor. This dramatically increases the open-loop gain within the 20Hz20kHz frequency range without affecting stability. For more details on why and how this works, see the separate feature article titled “Amplifier Stability and Compensation” in this issue. We found that polypropylene capacitors gave measurably less distortion compared to C0G/NP0 ceramic capacitors of the same value, presumably due to their higher linearity. Ceramic capacitors can be used but the distortion at 20kHz will increase from around 0.0048% to about 0.0055% (with proportionally similar increases at lower frequencies, down to about 1kHz). Feedback network changes During the course of testing the prototypes, we ran into a problem with the capacitor in the feedback network (above and to the left of Q8). The purpose of this capacitor is to reduce the amplifier’s DC offset at the output, by reducing the DC gain to one. The original capacitor was specified as 220µF but we found that if the capacitor value was on the low side and/or the capacitor used had particularly bad non-linearity (as is sometimes the case), the result could be a significant rise in distortion below 50Hz. By changing this capacitor to 1000µF, we eliminated that possibility. This also improves the signal-to-noise siliconchip.com.au Fig.7: an oscilloscope screen grab illustrating the shape of the distortion residual waveform for a 20kHz sinewave at 100W into 8Ω. It is primarily second harmonic, with some third harmonic (how much depends on how well-matched the output transistors are in terms of beta). We have to demonstrate the distortion at a high frequency and power level otherwise it’s hard to see! ratio, by about 1dB, because it lowers the source impedance seen by the inverting input (the base of transistor Q2) at low frequencies. In addition, it flattens the low frequency response, as can be seen in Fig.5. Input filter changes We have increased the value of the RF filter capacitor at the input, from 820pF to 4.7nF. This allows it to better reject supersonic components of the input signal (eg, digital-to-analog converter switching artefacts). This value suits signals sources with low output impedance (0-220Ω). Virtually all CD/DVD/SACD/BluRay players, preamplifiers, computer sound cards and DACs should be within this range. If a volume control potentiometer is to be installed immediately before the power amplifier, with no buffering between the two, or if the signal source(s) will have an output impedance above 220Ω, reduce this capacitor value to 1nF. Otherwise, the high frequency response of the amplifier will suffer. PCB improvements As well as updating the board to include the circuit changes, we have made further tweaks to the PCB pattern itself. The most important is that we completely removed the three top layer tracks which connected Q12, Q13 and Q14 to their supply rails, which were on the bottom side of the board. siliconchip.com.au Fig.8: by contrast with Fig.7, this scope grab shows the extremely low distortion when delivering 100W into 8Ω at 1kHz. Note that the distortion is virtually buried in the noise (blue trace). Averaging the distortion product signal shows it to be mainly second harmonic at a very low level. This low-level harmonic distortion is virtually the same whether at 50mW or 100W. That current is now routed entirely through bottom layer tracks, eliminating 30 current-carrying vias, six wire feed-throughs and one signal via (a via makes an electrical connection between tracks on different layers of the PCB). We have also “tented” all the vias on the board, except for those which require wire feed-throughs to be installed (for robustness under fault conditions). This means that the solder mask layer goes over the vias, exposing as little copper as possible and thus reducing the chance of short circuits when probing around the board. Some vias have also been moved under components, further ensuring that you can’t accidentally make contact with them. For boards without plated through-holes or solder masks, feed-throughs can still be installed in these locations since the components they are under (the 5W resistors) are mounted proud of the PCB anyway. We also rearranged some components to take account of the range of sizes available. This includes the 220nF 400V capacitor at the output, the 470µF 63V bypass capacitor for the negative rail and the 47µF bipolar input capacitor. There should now be enough space for just about any components with these ratings. Note that the PCB retains the most important aspect of the previous design: the layout of the current-carrying tracks results in the induced magnetic fields being almost perfectly cancelled, keeping the distortion low even with a high output power. The updated output filter also improves the outputcurrent magnetic field cancellation, reducing high-frequency distortion by around 20%. Better connectors For the Mk.3 design, we have also changed the connector arrangement. All connectors are now pluggable, making it easier to install and remove the module and simplifying testing and repair. Making reliable connections to a terminal block can be awkward with the module inside a case. More than once we thought we’d made a solid connection but then found that we could easily pull the wire out. The new connectors eliminate that problem. We have replaced the signal input terminal block with a right-angle RCA socket. For the power input and speaker/headphone outputs, we are now using Molex “Mini-Fit Jr” plastic locking connectors (in horizontal or vertical format). The power connector has three keyed pins and the speaker/ headphone connector has four keyed pins, so that they can’t be swapped around or connected backwards. The Mini-Fit Jr connectors are rated at 9A per pin, which is sufficient for this application. In addition, the final version of the PCB (not shown here) can also accept July 2011  35 210mV Q3 BC546 B A K D1, D2: 1N4148 4.7nF† 100 E C B E C E C 210mV K 180pF 100V D1 470 F 63V D2 A Q4 BC546 A K B C E 180pF 100V 2.2k B B B E K A K A C E K A DQ14 K A 120 VR1 1k B 330 DQ12 Q7 BF470 Q9 BF469 C C E 68 2SA970, BC639 2.2k E Q8 BC639 22k C 12k 100nF B 2.2k 56.3V 1000 F 16V 510 6.2k 6.2k B Q6 BC556 * Q16 IN THERMAL CONTACT WITH HEATSINK NEAR Q10 & Q11 100nF 68 B Q1, Q2: 2SA970 68 C E 100 2.2k 47 F 35V ULTRA-LD MK.3 200W AMPLIFIER MODULE † USE 1nF IF Z source > 220  10 1M 12k 47 F NP 6.8k 1W B 47 F 35V E E C C C E Q14 NJL1302D B C B E BD139, BF469, BF470 B B C C 100nF E MJE15030, MJE15031 Q15 NJL1302D FUSE2 6.5A C E 0.1  5W 0.1  7-10 5W mV 7-10 mV E E C 0.1  5W B 100nF 0.1  7-10 5W mV E C Q13 NJL3281D FUSE1 6.5A 7-10 mV B Q12 E NJL3281D C Q11 MJE15031 B 10  1W BC546, BC556 B B Q10 MJE15030 470nF MKT 2.2V 56V 56V 100 DQ15 Q16* BD139 DQ13 100 100nF C B E 390  1W –57V (NOM.) 0V 0V SPEAKER OUT PHONES OUT CON3 CA K NJL3281D, NJL1302D 1000 F 63V 220nF 400V 6.8  1W L1 10 H 1000 F 63V +57V (NOM.) CON2 Fig.9: the complete circuit diagram for the Ultra-LD Mk.3 amplifier. Changes from the Mk.2 circuit are highlighted with yellow boxes. We have improved the output stage bias circuit and the compensation network, while a new driver emitter resistor configuration speeds output transistor switch-off, reducing distortion. A larger feedback capacitor (1000μF) lowers noise and extends the bass response. In addition, L1 has been increased from 6.8μH to 10μH which partially cancels the magnetic field produced by the output current, reducing high-frequency distortion. 2011 SC  CON1 SIGNAL IN C E 100 45V Q5 BC556 100 220 36  Silicon Chip siliconchip.com.au vertical connectors in two locations (ie, a vertical RCA socket for the signal input and a vertical 3-way Mini-Fit Jr connector for the power input). These let you build a stereo amplifier, with the two amplifier modules mounted on either side of the case. The new, slimmer power supply board (described next month) can then fit between them. Heatsinking As stated, the additional transistor for the VBE multiplier is located on the heatsink between the two driver transistors (Q10 & Q11). To make room, the output transistor pairs are now closer together. This allows us to position the mounting holes for all transistors so that they fall in between heatsink fins, with the board centred on the heatsink. It is therefore no longer necessary to blind-tap the mounting holes or to offset the board from the centre of the heatsink if the transistor machine screws are fastened with nuts, as was the case with the Mk.2 design. Note that if you plan to run the amplifier at continuous high power levels (100W or more) into a 4Ω load then it will probably be necessary to use a larger heatsink (with lower thermal resistance to the air) and/or fanforced cooling. If driven at full power (200W) into a 4Ω load continuously, the heatsink becomes too hot to touch even in free air (70°+) and this will be even worse if it is mounted in a chassis with limited ventilation. For continuous high power levels into 8Ω, a larger heatsink is also a good idea although it may not be strictly necessary if the ventilation is good. Note that in either case (4Ω or 8Ω), for music program material, if the amplifier is not driven into clipping then heatsinking should not be an issue. This is because even heavily compressed pop music typically has a dynamic range of at least 10dB, so even if the peak power is close to maximum, the average power will be significantly less. Load lines When we described the Ultra-LD Mk.2, we did not publish any load line curves. Such graphs show the range of transistor currents and dissipations that can occur with speaker loads (resistive and reactive) and the Safe Operating Area (SOA) of the transistors in the amplifier. siliconchip.com.au The relevant load lines and the SOA curve for the Mk.3 are shown in Fig.6. By comparing the SOA curve for a pair of ThermalTrak transistors to reactive load lines for typical 4Ω and 8Ω loudspeakers, we can determine whether the transistors are likely to exceed their ratings during periods of high power output. If they can be driven beyond the safe operating area, the output transistors may be destroyed by second breakdown. Second breakdown is a phenomenon which can occur in bipolar transistors, where high temperature and dissipation lead to thermal run­ away in a small area on the silicon die, ultimately resulting in the silicon melting. We need to ensure that this is not possible under normal conditions. As you can see from Fig.6, the load lines for 4Ω and 8Ω resistive and reactive loads are within the safe operating area. This curve is computed based on the ThermalTrak transistor data sheets and assuming that no single output transistor is required to carry more than 55.6% of the total load current. It is specified for signal durations of one second. Since the reactive load curves are within the SOA then the amplifier should be quite robust. Unless the load impedance is dramatically less than we are assuming (eg, due to a short circuit at the output), the power transistors should be safe from destruction. All in all, plotting the load lines gives us a reasonable idea of how close to the limits we are pushing the power transistors. Circuit description Let’s now look at how the circuit works in more detail – see Fig.9. As shown, the input signal is applied to CON1 and is coupled to the WARNING! High DC voltages (ie, ±55V) are present on this amplifier module when power is applied. In particular, note that there is 110V DC between the two supply rails. Do not touch the supply wiring (including the fuseholders) when the amplifier is operating, otherwise you could get a lethal shock. base of PNP transistor Q1 by a 47µF non-polarised capacitor. The intervening RC filter (100Ω/4.7nF) attenuates any supersonic signals present, eg, switching artefacts from a DAC. The 12kΩ resistor provides the bias current for Q1’s base. PNP transistors Q1 and Q2 are the differential input pair, with Q1’s base being the non-inverting input of the amplifier and Q2’s base being the inverting input. These are configured as a “long tail pair”, fed with current by PNP transistor Q5, which is configured as a current source. The 100Ω resistor at its emitter sets the current through this stage to around 6.5mA (0.65V/100Ω). Some of this current flows through Q1’s collector-emitter junction and the rest flows through Q2’s. How the current is split depends on the difference in voltage between the two bases. Most of this current then flows through NPN transistors Q3 and Q4, which are configured as a current mirror. This current mirror keeps the current through Q3’s collector-emitter junction equal to the current through Q4’s, so any difference in the current through Q1 and Q2 must then flow to the base of Q8. Thus the current to Q8 is proportional to the difference in voltage between the bases of Q1 and Q2, ie, the two amplifier inputs. The 100Ω resistors at the emitters of You Must Use Good-Quality Transistors To ensure published performance, the 2SA970 low-noise transistors must be from Toshiba. Be wary of counterfeit parts. We recommend that all other transistors be from reputable manufacturers, such as NXP Semiconductors, On Semiconductor, ST Microelectronics and Toshiba. This applies particularly to the MJE15030 & MJE15031 output driver transistors. During the course of our testing, we came across some BC556 transistors which, when used in the amplifier, resulted in excessive distortion. Despite this, their hFE figure tested as normal. Replacing them with a different batch returned the distortion to normal. Use good-quality transistors throughout to guarantee good performance. July 2011  37 Parts List 1 double-sided PCB, code 01107111, 135 x 115mm 1 black anodised aluminium heatsink, 200 x 75 x 45mm (L x H x D) 4 M205 PCB-mount fuse clips 2 6.5A M205 fast-blow fuses (F1,F2) 1 10µH air-cored inductor (L1) (or 1 20mm OD x 10mm ID x 8mm bobbin and 2m of 1mm diameter enamelled copper wire, plus one length of 10 x 20mm diameter heatshrink tubing) 1 1kΩ multi-turn vertical trimpot (VR1) 2 TO-220 mini flag heatsinks, 19 x 19 x 9.5mm 5 TO-220 silicone insulating washers 4 TO-264 or TOP-3 silicone insulating washers 2 transistor insulating bushes Screws, nuts, spacers & washers 4 M3 x 9mm tapped spacers 7 M3 x 20mm machine screws 2 M3 x 10mm machine screws 8 M3 x 6mm machine screws 9 M3 nuts 9 M3 flat washers Connectors 1 black PCB-mount switched RCA Q1 and Q2 are “emitter degeneration resistors” which provide some local negative feedback, increasing their linearity at the cost of reduced gain (which in turn reduces the overall open loop gain of the amplifier). The 6.8kΩ resistor simply reduces the dissipation in Q5. The 68Ω emitter resistors for Q3 and Q4 improve the accuracy of the current mirror. Voltage amplification stage The circuitry described above comprises the first stage of the amplifier and as explained, it converts the differential input voltage into a proportional current. This current is then converted back to a single-ended voltage, relative to the negative rail, by the following stage (the “voltage amplification stage” or VAS). This consists primarily of NPN transistors Q8 and Q9 as well as PNP transistor Q7. 38  Silicon Chip connector, or one vertical PCBmount RCA connector (CON1) 1 Molex Mini-fit Jr 3-pin rightangle PCB-mount male socket (Element14 order code 9963545); OR one vertical PCB-mount Mini-fit Jr male socket (Element14 order code 9963570) (CON2) 1 Molex Mini-fit Jr 4-pin rightangle PCB-mount male socket (CON3, Element14 order code 9963553) 1 Molex Mini-fit Jr 3-pin female line plug (CON2, Element14 order code 9963480) 1 Molex Mini-fit Jr 4-pin female line plug (CON3, Element14 order code 9963499) 7 Molex Mini-fit Jr female pins (for CON2 & CON3, Element14 order code 9732675) 1 MJE15031 PNP transistor (Q11) 2 NJL3281D NPN ThermalTrak transistors (Q12,Q13) 2 NJL1302D PNP ThermalTrak transistors (Q14,Q15) 1 BD139 NPN transistor (Q16) 2 1N4148 signal diodes (D1,D2) Semiconductors 2 2SA970 low-noise PNP transistors (Q1,Q2) 2 BC546 NPN transistors (Q3,Q4) 2 BC556 PNP transistors (Q5,Q6) 1 BC639 NPN transistor (Q8) 1 BF470 or 2SA1837 PNP transistor (Q7) 1 BF469 or 2SC4793 NPN transistor (Q9) 1 MJE15030 NPN transistor (Q10) Resistors (0.25W, 1%) 1 1MΩ 1 220Ω 1 22kΩ 1 120Ω 2 12kΩ 6 100Ω 1 6.8kΩ 1W 3 68Ω 2 6.2kΩ 1 10Ω 1W 4 2.2kΩ 1 10Ω 0.25W 1 510Ω 1 6.8Ω 1W 1 390Ω 1W 4 0.1Ω 5W 1 330Ω 2 0Ω 2 68Ω 5W (for testing) NPN transistor Q8 amplifies the current from the previous stage and feeds it to NPN transistor Q9. Together they form a compound transistor similar to a Darlington, which is set up as a common-emitter amplifier. PNP transistor Q7 is the current source load for this amplifier and the standing current is set to around 9.5mA by the 68Ω resistor (0.65V/68Ω). This current flows from Q7, through the output stage bias network (DQ12-DQ15 and transistor Q16) and thence to Q9. This common-emitter amplifier converts the current delivered to the base of Q8 into a voltage, at Q9’s collector. This voltage is then proportional to the input voltage differential at the base of Q1 and Q2. Transistor Q6 provides the negative feedback for both current source transistors (Q5 and Q7), regulating the current through them. The two 6.2kΩ Capacitors 2 1000µF 63V electrolytic 1 1000µF 16V electrolytic 1 470µF 63V electrolytic 2 47µF 35V electrolytic 1 47µF non-polarised (NP) electrolytic 1 470nF 63V MKT 1 220nF 400V MKT 5 100nF 63V MKT 1 4.7nF 63V MKT 2 180pF 100V polypropylene (Rockby Stock No 36350) resistors, in combination with the 47µF capacitor, form a bootstrapped current sink which turns on both Q5 and Q7. Once the right amount of current is flowing through each, Q6 turns on and reduces the base current to both in order to maintain it at that level. The two 180pF capacitors and the 2.2kΩ resistor between Q8’s base and Q9’s collector are the compensation network described earlier, which takes the place of the traditional Miller capacitor. This reduces open loop gain at high frequencies by reducing the gain in this stage, as well as linearising the operation of Q8 and Q9. The negative supply rail for this stage and for the previous (input) stage is filtered using a 10Ω resistor and a 470µF capacitor. This low-pass filter prevents 100Hz power-supply ripple from coupling into the signal path, especially when the output power is siliconchip.com.au Another view of the completed Ultra-LD Mk.3 amplifier module. The full constructional details will be published next month. frequencies where the load’s reactance may cause the amplifier to oscillate. The parallel 6.8Ω resistor acts as a “snubber”, preventing the output filter from oscillating in response to signal pulses from the amplifier. The inductor also prevents any RF signals picked up by the speaker leads from being coupled to the base of Q2 where they may be rectified to an audio frequency signal. The 220nF capacitor, in combination with the inductor and resistor, presents the amplifier with a constant load to high frequencies and keeps the output impedance low at high frequencies, even if no speaker is connected. This ensures that oscillation can not occur. Any output cable capacitance will be swamped by the 220nF capacitor across the output. This filter arrangement was developed by A.N.Thiele (Load Circuit Stabilising Network for Audio Amplifiers, Proceedings of the IREE 299, September 1975). Power for the output stage is filtered by 1000µF and 100nF bypass capacitors across each rail. If an output transistor fails, one or both of the 6.5A fuses will blow, protecting the power supply. Loudspeaker protection high. It’s the negative rail that requires filtering most of all because the output voltage of the VAS common-emitter amplifier is relative to this. Output stage The output stage is a current buffer/ unity gain voltage follower formed from two complementary emitterfollowers. These are arranged in Darlington configuration, with a single driver transistor for each half (Q10 and Q11) providing current to the bases of two output transistor pairs (Q12/Q13 and Q14/Q15 respectively). There is a 100Ω resistor in series with the base of each driver transistor, to limit current in the event of a (brief) output short circuit. The voltages at the bases of the two driver transistors are controlled by the common-emitter amplifier in the previous stage. The DC voltage between them is set by the bias generator described earlier. The 100Ω resistors also function as RF “stoppers” which reduce the possibility of parasitic oscillation in the emitter-follower output stages. The class-A amplifier (VAS) current passes through the bias generator and siliconchip.com.au the voltage across it is determined by the forward voltage of the two ThermalTrak diodes which have the lowest forward voltage within each pair, plus the voltage across the VBE multiplier. The voltage across the VBE multiplier is roughly Q16’s base-emitter voltage multiplied by a factor set by VR1. This bias voltage varies with the junction temperatures of Q10-Q15. The 0.1Ω emitter resistors for Q12Q15 force each pair (Q12-Q13 and Q14-Q15) to share the load current, as well as providing a small amount of current feedback. RLC filter After the output stage is the RLC filter consisting of a 10µH air-cored inductor, 6.8Ω resistor and 220nF capacitor. This isolates the amplifier circuitry from any load reactance (capacitance or inductance) caused by the cabling or loudspeakers. The 10µH inductor presents a low impedance to audio-frequency signals but a high impedance at supersonic frequencies, at which the amplifier might oscillate. Therefore it isolates the amplifier from the load at critical Note that it is necessary to connect a loudspeaker protection module between the amplifier and speaker terminals, so that the load is disconnected in the event of an amplifier failure. Failures usually cause the output to be connected directly to one or other of the ±57V supply rails and unless a protection module is present to immediately disconnect the loudspeaker, it may be damaged and quite possibly catch fire due to the resulting high current flow through the voice coil. More to come That’s all we have space for this month. Next month, we will describe how to assemble, test and adjust the amplifier module and also present an updated version of the power supply board. That article will also include some suggestions for putting it all together in a case, as a mono or stereo power amplifier. Finally, for those who have already built an Ultra-LD Mk.2 module, don’t despair. We plan to present a small adaptor board which will allow you to fully upgrade its performance to the SC Mk.3 standard. July 2011  39 PRODUCT SHOWCASE Vehicle “event” recorder records video, location, time and more! How often have you thought “where’s a camera when you really need one . . .” when something happens in your car! It may be an accident, it may be road rage, it may be any one of dozens of things. Now you can “capture the moment” with this new event recorder from Jaycar Electronics. Fleet owners, taxi companies, delivery vehicles – even Optiview XG network analysis tablet Fluke Networks’ new OptiView XG network analysis tablet is claimed to provide the fastest solutions for network and application problems for both wireless and wired access, anywhere in the network. The tablet expedites network and application problem solving by automating root cause analysis and providing guided troubleshooting to address problem areas. It is an instant, integrated window into organisations’ network in a tablet form factor, that you can take from the data centre, to the production floor, to the office desktop. The OptiView XG is designed to provide a wide range of functionality necessary to adapt to the dynamic and diverse networks of today through various features. It has a bright, easy-to-to read screen and features customisable dashboards that can be personalised for each user or help transform data into reports for employees at all levels of the organisation, from techni- Contact: cians to managers. Fluke Australia Pty Ltd More information Unit 26, 7 Anella Ave, Castle Hill, 2154 is available on the Tel: (02) 8850 3333 Fax: (02) 8850 3300 company website. Website: www.flukenetworks.com/au 40  Silicon Chip the private motorist can benefit from having a record of vehicle movements and any incidents that occur. It’s about the size of a GPS unit – and in fact has GPS built in – but this device will record any incident, inside or outside the vehicle (depending on mounting) along with a range of parameters such as the vehicle’s position, time and so on. It’s triggered automatically by a sudden change in vehicle speed (or can be turned on manually) and writes the data to an SD card. You can elect to keep the information indefinitely by inserting a replacement card, or if you wish the data will over-write the existing information. Depending on the size of the SD card, several hours of video and data can be stored (it supports up to 16GB SD cards). Video resolution is 640 x 480 <at> 30 frames per second and the field of view is 120°. Infrared LEDs allow night scenes to be captured and there is a video output for an external monitor. It’s normally powered by a cigarette lighter plug but there is also a backup NiMH battery just Contact: Jaycar Electronics (all stores) in case. Recommended PO Box 107, Rydalmere NSW 2116 r e t a i l p r i c e i s Order Tel: 1800 022 888 Fax: (02) 8832 3188 $249.00 (QV-3798). Website: www.jaycar.com.au First Arduino-compatible 32-bit micro development platform Microchip Technology Inc and Digilent, Inc. have launched the first 32-bit microcontrollerbased, open-source development platform that is compatible with Arduino hardware and software. The chipKIT platform is the first and only 32-bit Arduino solution in the industry to enable hobbyists and academics to easily and inexpensively integrate electronics into their projects, even if they do not have an electronic engineering background. The platform consists of two PIC32-based development boards and open-source software that is compatible with the Arduino programming language and development environment. The hardware is compatible with existing 3.3V Arduino shields and applications, and can be developed using a modified version of the Arduino IDE and existing Arduino resources, such as code examples, libraries, references and tutorials. The boards start Contact: at US$26.95 each. Microchip Technology Australia A video can be PO Box 260, Epping, NSW 1710. viewed online at Tel:(02) 9868 6733 Fax:(02) 9868 6755 www.microchip. Website: www.microchip.com com/get/D268 siliconchip.com.au 5km 5GHz 200MBit/s Data Link from WiFi Products Mikrotik’s new SXT 5HnD is a low cost, high-speed 5GHz wireless device ideal for setting up a point-to-point data link with fast throughput. Dualpolarisation 802.11n and Nv2 TDMA technology help to achieve a 200Mbit real throughput speed. It features a solid all-in-one design, with a ready-to-mount enclosure and built-in antenna. Powered by Mikrotik’s RouterOS, it is also a most advanced router, bandwidth controller and firewall. The SXT has signal-strength LED indicators making it easy to install and align. There’s also a USB 2.0 port and voltage and temperature monitors so you can keep an eye on the system remotely. This product has huge potential, ranging from extending your LAN to provide internet access, remote monitoring, IP camera surveillance, machinery control, etc on farms, stock monitoring in large warehouses and factories and so on. Or it can be an viable alternative when running a cable is just too difficult or expensive. The 16dBi antenna can give you up to 5km range while the SXT itself measures in at only 140mm diameter and 56mm deep. Retail price is less than $230 a pair delivered within Australia. EFM32 Tiny Gecko Starter Kit Energy Micro has released a starter kit for its ARM Cortex-M3 based EFM32 Tiny Gecko microcontrollers. Referenced EFM32TG-STK3300 and selling at US$69, the kit provides users with all the functionality that’s needed to create ultra low power system designs consuming a fraction of the energy of systems using rival microcontrollers. Achieving an active mode current consumption of only 160µA/ MHz, the energy friendly EFM32TG840 microcontroller featured in Energy Micro’s latest kit is the largest in a family of 23 Tiny Gecko devices now in full production. The starter kit includes a 8x20 segment LCD supported by Tiny’s sub µA LCD controller and a selection of light, touch and motion sensors, backed by the MCU’s innovative low energy sensor (LESENSE) interface. Tiny’s LESENSE interface with ‘wake-on-touch’ capability runs independently of the Cortex-M3 core and enables a mix of up to 16 resistive, capacitive or inductive sensors to be autonomously monitored while the microcontroller remains in its 900nA deep sleep mode. Other low power peripherals ofered by the kit’s MCU include a 150nA low energy UART and a 350µA 1MSPS 8-channel 12-bit ADC. The starter kit provides a comprehensive choice of GPIO pins, serial communication ports and debug connections. To support the development of the most energy efficient application code, the Tiny Gecko starter kit also integrates Energy Micro’s unique Advanced Energy Monitoring system (AEM), enabling system current consumption and voltage to be accurately viewed in real time, allowing code to be debugged for adverse energy drains. Visualisation and analysis of the starter kit system’s energy consumption data is via energyAware Profiler, one of a comprehensive selection of software tools and resources accessible through Energy Micro’s free-to-download Simplicity Studio. Providing immediate access to and updates on all the software tools, product documentation and other resources needed in the development of EFM32 Gecko microcontroller systems, Simplicity Contact: Studio aims to dra- APEX Electronics Ltd matically reduce em- PO Box 2357, 175 Vivan St, Wellington, 6140, NZ bedded development Tel: (0011) (64) 4 974 8943 Fax: (64) 4 385 3483 Website: www.apexelec.co.nz times. siliconchip.com.au Contact: WiFi Products 2/24 Windorah St, Stafford Qld 4053 Tel: (07) 3356 0588 Website: www.wifiproducts.com.au RS Branded Power Supplies With the increasing demands on power supplies, RS Branded Power Supplies are excellent alternatives to meet your needs. They will help you in saving money without compromising on quality. The range of enclosed supplies offer power outputs from 15W to more than 1500W with ef- Contact: ficiencies ranging RS Components from 77% right up 25 Pavesi St, Smithfield NSW 2164 to 91% for the larg- Tel: (02) 9681 8558 Fax: (02) 9681 8614 Website: www.rsaustralia.com est supplies. Amalgen’s range now made by Dyne Dyne Industries, designers and manufacturers of custom-made transformers, power supplies and wound components, has taken over the manufacturing and sales of the Amalgen range of power supplies and toroidal transformers at the retirement of Amalgen’s Frank Choate (who will remain as a consultant). The acquisition of the Amalgen products extends Dyne’s range of transformers and light electronic products into new markets. Amalgen power supplies have a high reputation in the mining and manufacturing industries and this matches the high quality of the Dyne products. The range now covers AC and DC power supplies, DC UPS’s single & 3 phase transformers, audio transformers, in- Contact: ductors, specialty Dyne Industries Pty Ltd wound components 41 Barry St, Bayswater, Vic 3153 and light electronic Tel: (03) 9720 7233 Fax: (03) 9720 7551 Website: www.dyne.com.au assembly. July 2011  41 This little device could save your life . . . You don’t want to be caught in a storm, especially if you are on a sports field, out boating, bushwalking or working in the open, on the farm or anywhere else where there is minimum shelter. If there is even a risk of a storm, take this Lightning Detector with you before venturing outdoors. Lightning Detector W hile most of us love the wide open spaces, they are definitely not the place to be if a thunderstorm is on the way. If there is a lightning strike nearby you could be in big danger of death or injury. And you don’t have to be hit directly – induction can kill you and so can the voltage gradient across the ground in the vicinity of a lightning strike. Our Lightning Detector can warn you of an approaching lightning storm and provides valuable time to take shelter safely indoors. And even if you’re not outdoors it can give you warning to disconnect vulnerable electrical appliances from the 230VAC mains supply. It provides audible and visual indication to warn of approaching thunderstorms. Lightning damage to electronic appliances Many people do not realise how vulnerable electronic equipment can be in a thunderstorm, even if it is not close by. Service organisations report a big surge in repair jobs 42  Silicon Chip by John Clarke after storms and just about all of this could be avoided simply by switching off and removing power plugs from the wall socket. Those appliances especially at risk include microwave ovens, TV sets, satellite receivers, mains powered computers (especially those also connected to the phone lines via a modem), washing machines and dryers. They should not be just switched off at the power point but the mains plug should be removed from the socket. TV antenna and satellite dish connections should be disconnected too. Many ovens incorporate electronic timers and power to these can be switched off at the “fuse” box. Apart from mains-powered computers, devices that are particularly prone to damage are fax machines and cordless telephone base stations. It is the fact that they are connected to both the 230VAC mains and the telephone wiring that provides a double whammy. During a big thunderstorm they should be disconnected both from the phone line and the mains power. siliconchip.com.au Of course, it is well known that any phones (apart from mobiles and cordless models) should not be used during a thunderstorm. So what to do? S1 +3V 1.5V POWER SUPPLY (Q1, LED3 & 4) LED2  BATTERY 3V POWER SUPPLY (2 x AA CELLS OR PLUGPACK INPUT) CONDITION To get a warning of imminent thunINDICATOR 1.5V derstorms, you need the SILICON CHIP Lightning Detector. It is a pocket-sized SINGLE CHIP PULSE unit that provides visual indication usOSCILLATOR AMPLIFIER AM RADIO EXTENDER (IC3) (Q2) ing a flashing LED and sounds an audible (IC1) (IC2, D3) PIEZO TRANSDUCER tone whenever lightning occurs in your COIL area. The greater the number of lightning DETECT  strikes, the more LED flashes and audible LED1 VR1 tone bursts are produced. SENSITIVITY For portable use it is powered with two alkaline AA cells, Battery life should Fig.1: the block diagram of the Lightning Detector. The early part looks be at least 1000 hours. For indoor use, similar to a radio receiver – which of course it is – but this radio receiver you can use a 6V-12V DC supply, such picks up just one thing: the RF pulse from a lightning strike within range. as a plugpack. One resistor needs to be chosen according to the DC supply voltage. When the exThe pulse extender produces a 200ms pulse and this ternal power supply is connected to the jack the socket, the lights the “detect” LED1. The pulse extender is necessary AA cells are automatically disconnected from the circuit. because the lightning strike pulses are too short in duration The principle of operation is based on detection of the to be noticed as a flash from the LED. broad-spectrum electromagnetic emissions produced by IC3 is an oscillator that runs for 200ms each time the lightning strikes. This is readily detected by a simple AM pulse extender produces a low signal and the resulting 4kHz (amplitude modulation) radio receiver. tone burst drives the piezo transducer which is resonant If you’ve ever been anywhere near an electrical storm at that frequency. with an AM radio turned on, you’ll have heard the crashes (static) of lightning strikes. Very large strikes can be heard Circuit details from a considerable distance away. The full circuit is shown in Fig.2. As mentioned, IC1 is We use a single AM radio IC which comprises a RF the TA7642 AM radio chip while CMOS 555 timers are used (radio frequency) amplifier, detector and AGC (automatic for the pulse extender IC2 and for 4kHz oscillator, IC3. The gain control). This was originally available in 1984 from circuit is powered from 3V but it will operate down to 2V. Ferranti Semiconductors as the ZN414Z but replaced by A 1.5V regulated supply powers IC1 while the amplifier, the MK484, now also obsolete. pulse extender (IC2) and the oscillator (IC3) are driven We have used the modern equivalent, the TA7642. It from the 3V supply. operates from a 1.2 to 1.6V supply and covers from 150kHz While most of the circuit is powered from the 3V supto 3MHz. This includes the normal AM radio broadcast ply rail, IC1 needs to be operated at between 1.2 and 1.6V. band (530kHz to 1.6MHz) but for our purposes, we are To provide for this we use a voltage regulator comprising not concerned with listening to broadcast radio stations. transistor Q1 plus infrared LED3 & LED4. These develop We simply monitor the whole spectrum covered by the a forward voltage of approximately 1V each which is reAM radio chip. markably constant over a wide range of current. Tests of several infrared LEDs from different manufacturers showed Block diagram that the forward voltage is around 1.09V at 1.6mA current The general arrangement of the Lightning Detector is dropping to 0.945V at 160A, ie, a current range of 10:1. shown in the block diagram of Fig.1. IC1 receives signals Stacking two infrared LEDs in series provides a reasonfrom a pickup coil. In an AM radio this pickup coil would ably stable 2V reference. The LEDs are fed via a 2.2kΩ normally be tuned to a particular frequency using a vari- resistor from the 3V supply and the 2V reference drives able tuning capacitor. the base of transistor Q1. This acts as a current buffer to We want to monitor a wide frequency range and so the supply IC1 with about 1.4V. This varies from 1.46V with a coil is left un-tuned. IC1’s output signal is noise bursts 3V supply down to 1.287V with a 2V supply. from lightning. IC1 is connected to the 1.4V Output from IC1 is typically supply via the 470Ω AGC resistor 15mV with a tuned coil but is at its output pin. A 100nF decouparound 2mV with the un-tuned ling capacitor at the output sets • Portable coil. This signal is amplified using the high frequency rolloff to 4kHz. • Battery or external power supply transistor Q2 and a sensitivity conOne end of the pickup coil L1 is trol sets the level applied to the fol• Visual and audible lightning indication connected to the high impedance lowing pulse extender comprising (around 3MΩ) input of IC1 while • Sensitivity control IC2 and diode D3. When lightning the other end is grounded via a • Battery condition indicator is detected, a noise-burst triggers 100nF ceramic capacitor. There • Reverse supply protection the pulse extender. is no parallel capacitor across Features siliconchip.com.au July 2011  43 +3V 2.2k C B A  K E LED3 (IR) 220k D3 1N4148 VR1 10k LIN 470 LED4  (IR) 10nF 8 7 C Q2 BC549C B TA7642 L1 I 100nF 100nF IC1 G E CER. 1 10k CER. 470nF 180k 22nF 6 5 1k CON1 A 22 A LED1 K POWER S1 PIEZO TRANSDUCER 1 1nF  OSCILLATOR A BATTERY  LED2 3V BATTERY (2 x AA CELLS) LIGHTNING DETECTOR K 100k K 10 F 16V A SC 5 +3V 180 D2 1N4004 B R1: FOR 12V INPUT -- 470  0.5W FOR 9V INPUT -- 330  0.5W FOR 6V INPUT -- 120  0.5W L1: STANDARD BROADCAST BAND FERRITE ROD ANTENNA 2011 3 IC3 7555 A DETECT K ZD1 3.9V 1W 8 4 2 PULSE EXTENDER D1 1N4148 R1 7 K AM RECEIVER 12V DC INPUT IC2 7555 2 100k 180k 4 3 6 O 100nF K A SENSITIVITY K 100k 100nF 100k 2.2k 100k 100nF A 100nF 470k Q1 BC547 10 F 16V 220k E BC547, BC549C, BC559 Q3 BC559 B C E TA7642 LEDS IN4148 A K 1N4004 A K K A C O I GND Fig.2: the three main functional areas of the circuit diagram are labelled the same as block diagram to enable you to trace the circuit operation through. As mentioned in the text, resistor R1 needs to selected depending on the DC power supply you use – it can handle anything from 6 to 12V. The battery supply is nominally 3V but it will operate down to 2V. L1. This means that the coil is un-tuned and will have a fully at 2V and we are inclined to assume that this IC does broadband response. Bias for the input of IC1 comes from also operate at 2V. a 100kΩ resistor connected to its output. Make sure you do not use bipolar 555 timers such as the IC1’s output is AC-coupled to the following common LM555CN or the TL555CP as these typically require 4.5V emitter amplifier, Q2. This has its emitter resistor bypassed or more for operation. with a 22nF capacitor to provide a gain of about 50 for freIC2 is the pulse extender which is set up as a monostable quencies above about 723Hz. Q2’s collector load comprises timer. Before triggering occurs, pin 3 is close to 0V and the the 10kΩ potentiometer VR1 and a 2.2kΩ resistor. VR1 is 470nF capacitor is held discharged at about 0.6V above 0V the sensitivity control. by diode D3. Pin 2 is held at 45% of the 3V supply, ie, at IC2 and IC3 are CMOS 555 timers and most manufacturers +1.35V, using the 220kΩ and 180kΩ voltage divider resistors. of these devices state that their version will operate down Triggering occurs when the noise signal fed to pin 2 pulls to 2V or less. These include the Intersil ICM7555IPA, Texas it below +1V. This sets pin 3 high and diode D3 is then Instruments TLC555CP, ST Microelectronics TS555CN and reverse biased. The 470nF capacitor then begins to charge National Semiconductor LMC555CN. The NXP (found- via the 470kΩ resistor. During this time, LED1 is lit (driven ed by Philips) ICfrom pin 3) When M7555CN guaranthe voltage across tees operation at 3V the 470nF capacitor over full automo- Supply voltage: reaches 2/3 of the 3V (2 x AA cells) [will operate down to 2V] tive temperatures. supply voltage, pin Plugpack: 6 to 12VDC at 30mA However, perfor- Current Consumption: 3 goes low and the Battery operation 1.5mA at 3V, 1mA at 2V, mance graphs show 470nF capacitor is DC plugpack operation 17mA at 12V operation with a Battery life: discharged via diTypically 1000h with Alkaline cells 2V supply at –55° IC1 supply: Typically 1.46V with 3V supply, 1.28V with 2V supply ode D3. C, 25°C and 125°C. Battery voltage indication: This is an unconDown to 2V Also samples of the Strike indication duration: ventional monosta200ms NXP ICM7555CN Transducer frequency drive: 4kHz ble timer arrangeoperate success- Frequency detection band: ment. Normally pin 150kHz to 3MHz Specifications 44  Silicon Chip siliconchip.com.au 2.2k 220k LED1 VR1 A K S1 A K IC3 7555 470nF 10 F 1nF 220k 180k 100k 10k 100k 2.2k PIEZO Q2 D2 CABLE TIES 22nF 10 F Q3 100nF 100nF 180 470k D3 4148 100nF IC2 7555 1k L1 10190210 R OT CETED G NI NT H GIL 10nF LED2 180k ZD1 D1 4148 22 R1* 100k 100k 100k 100nF CON1 470 LED4 LED3 A 100nF (-) 100nF IC1 + Q1 A * R1: SEE TEXT (DEPENDS ON VOLTAGE IN) + – TO BATTERY HOLDER TERMINALS Fig.3: everything (except the batteries) mounts on a single-side PCB. The component layout is shown above and, with the same-size photo at right, is self-explanatory. At right is Fig.4, the drilling guide for the end panel. There is no labelling on this panel; all controls are labelled on the front panel. Millimetre dimensions are the hole diameter required at each position. 7, the discharge, would be connected to pin 6 and would discharge the 470nF capacitor instead of using diode D3. Using D3 to discharge the capacitor frees pin 7 to perform another task. Because it can sink (pull down) to 0V, it is suitable for use as a reset control for the following oscillator, IC3. IC3 is connected in astable (free-running) mode, running at about 4kHzm to drive the piezo transducer. It is held in the reset condition, with its pin 4 pulled low by pin 7 (discharge) of IC2, when IC2 is not timing. Power supply As already mentioned, the Lightning Detector is powered from two AA-cells or a low voltage plugpack supply. When running from the AA cells, current flows via the closed contact in the power connector (CON1) and through the 22Ω resistor to the 0V supply. This resistor is included to prevent excess current if the cells are inserted back-to-front. When the cells are correctly inserted, the 22Ω resistor produces a minimal voltage drop (normally less than 33mV and less than 100mV with the detect LED lit). When running from a DC suppy, the AA cells are disconnected via CON1 (as noted above) and the incoming supply is regulated down to 3.9V using zener diode ZD1 and resistor R1. The value of this resistor depends on the DC supply voltage – anywhere from 6V to 12V will be suitable, with resistor values of 120Ω (6V), 330Ω (9V) or 470Ω (12V). The negative supply connects to the circuit ground siliconchip.com.au End Panel Drill Guide Switch 5mm LED 3mm LED 3mm Pot 7mm via the 22Ω resistor. Diode D1 reduces the 3.9V zener voltage supply to about 3.3V. We could have used 3.3V zener diode on its own without D1. However, we want to be able to run the circuit from two AA cells that provide a 3V supply. If a 3.3V zener diode were used, the cells would be discharged via the zener diode. So by including diode D1, current is prevented from flowing through the zener diode. The zener voltage is increased from 3.3V to 3.9V to compensate for the 0.6V diode drop. D1 also blocks reverse voltage to the circuit should the 12V supply be connected with reversed polarity. With reverse polarity, zener diode ZD1 is forward biased and clamps the voltage to no more than -0.6V below the 0V supply. D1 stops current flowing through the circuit backwards. Battery indication When the power is first switched on, LED2 provides indication of the battery condition. LED2 is driven via PNP transistor Q3 and its base is initially tied to 0V via the 10F capacitor. With the supply at 3V, Q3’s emitter is at about 0.6V and the LED is driven at maximum brightness. That is with about 2.4V (3V-0.6V) across the LED and 180Ω resistor. Assuming a LED forward voltage of 1.8V, this produces a current of about 3mA. At a lower supply voltage, the initial LED current is less and it will be dimmer. With a 2V supply, LED2 will be barely alight, indicating that the batteries should be replaced. July 2011  45 Parts List – Lightning Detector 1 PCB coded 04107111, 65 x 86mm 1 remote control case 135 x 70 x 24mm (Jaycar HB5610 or equivalent) 1 panel label 50 x 114mm 1 miniature PC mount SPDT toggle switch (Altronics S1421 or equivalent) (S1) 1 10k log potentiometer, 9mm square, PCB mount (VR1) 1 knob to suit potentiometer 1 switched 2.5mm PCB mount DC socket (CON1) 2 AA Alkaline cells 2 DIP8 IC sockets (optional) 1 tuning coil with ferrite rod (Jaycar LF-1020) 1 piezo transducer (Jaycar AB-3440, Altronics S 6140) 2 6mm spacers 2 M2.5 x 12mm screws 4 6mm self-tapping screws 2 100mm cable ties 6 PC stakes 1 50mm length of red light gauge hookup wire 1 50mm length of black light gauge hookup wire Semiconductors 1 TA7642 single chip AM radio (IC1) (Wiltronics X-TA7642) 2 7555 CMOS 555 timers (ICM7555IPA, TLC555CP, TS555CN, LMC555CN or ICM7555CN) (IC2,IC3) 2 3mm high intensity red LEDs (LED1,LED2) 2 5mm IR LEDs (LED3,LED4) 1 BC547 NPN transistor (Q1) 1 BC549C NPN transistor (Q2) 1 BC559 PNP transistor (Q3) 1 3.9V 1W zener diode (ZD1) 2 1N4148 switching diodes (D1,D3) 1 1N4004 diode (D2) Capacitors 2 10F 16V PC electrolytic 1 470nF MKT polyester 4 100nF MKT polyester 2 100nF ceramic 1 22nF MKT polyester 1 10nF MKT polyester 1 1nF MKT polyester Resistors (0.25W, 1%) 1 470k 2 220k 2 180k 5 100k 1 10k 2 2.2k 1 1k 1 470 1 180 1 22 1 of 120, 330 or 470 0.5W (R1 – see text) Whatever the supply, LED2 only lights momentarily and as the 10F capacitor begins to charge via the 100kΩ resistor, it dims and eventually goes out. The 220kΩ resistor across the 10F capacitor prevents the capacitor charging to any more than 2/3rds the supply. This provides a faster discharge of the capacitor when the supply is switched off. The 220 resistor is also used to discharge the capacitor when the supply is off so it is ready to flash the LED when power is reapplied. Construction The Lightning Detector uses a PCB measuring 65 x 86mm 46  Silicon Chip Here’s how the PCB fits inside the case. The top corners need to be shaped to fit the case mounting pillars but otherwise it’s a simple drop-in fit, secured by four selftapping screws . The two AA batteries which power the unit fit under the moulding at the bottom. and coded 04107111. The PCB and components are housed in a plastic case measuring 135 x 70 x 24mm. The PC board is designed to mount onto the integral mounting bushes within the box. Make sure the front edge of the PC board is shaped to the correct outline so it fits properly. It can be filed to shape if necessary using the PCB outline shape as a guide. Begin by checking the PCB for breaks in tracks or shorts between tracks or pads. Fix any defects, if necessary. Check the hole sizes for the PCB mounting holes and for the cable ties. These are 3mm in diameter. You can then insert the resistors and use the resistor colour code table to select each value and check each one with a digital multimeter. Then install the diodes; they must be mounted with the orientation as shown. Install the six PC stakes. IC2 & IC3 can be mounted on sockets or directly soldered to the PCB. When installing sockets and ICs, take care to orient them correctly – as indicated by the notch at one end. Capacitors can be mounted now. The electrolytic types must be oriented with the shown polarity. Make sure these capacitors are placed on the PCB so their height above the surface is no more than 12.5mm, otherwise the lid of the case will not fit correctly. Note that while provision is made for a capacitor across the L1 coil, as mentioned earlier one is not used in this circuit. It is included so that you can experiment with the radio IC by placing a tuning capacitor between the two PC stakes for the L1 coil and placing a fixed value (if required) capacitor to pad out the capacitor range. This will allow the reception of radio broadcast stations. Audio signal is available at the VR1 wiper. A coupling siliconchip.com.au plastic transducer tabs. Alternatively, two nuts can be used. Follow the wiring diagram to make the connections from the piezo transducer and battery terminals to the PC stakes on the PCB. Next, install the battery clips into the battery compartment. The two connected terminals are placed on the right hand side (as you look at the rear of the case with the compartment at the bottom). The spring terminal is placed to the top and raised section to the bottom. For the left side, insert the separate terminals with the spring terminal placed at the lower edge and the raised section to the top. On the compartment inside bend the two individual terminals to the outside of the compartment. You may need to stretch the contact springs so that the AA cells are held securely between the contacts. Looking end-on shows the two controls and two LEDs The PCB is secured to the base of the case using four M3 which mount on the end panel. Fig.5 (below right) is the x 6mm screws that screw into the integral mounting bushes same-size front panel artwork which can be photocopied in the box. Before fitting them in place, drill out the small or downloaded and printed, then glued in place. front panel for the LEDs, potentiometer and switch. A drill guide is available and is provided with the capacitor (say 100nF or so) is required front panel label. This can be used as a guide to connect this signal to an external Sensitivity Detect Power as to the drill hole positions. amplifier. The panel label for this project can eiMount IC1 and the transistors taking ther be photocopied (without infringing care to place each in its correct place. copyright) – see fig.5 – or for best results, If you happen to be using a Ferranti it can be downloaded from the SILICON CHIP ZN414Z from your IC collection for website (www.siliconchip.com.au). Go to IC1 note that the GND and Out pins the downloads section and select the month are reversed compared to the TA7642. and year of publication. You would have to place the IC in the When downloaded, print it onto paper, PCB oriented 180° to that shown on sticky-backed photo paper or onto plastic the overlay. film. For protection and long life, paper An MK484 has the same pin out as labels should be covered with either selfthe TA7642. The TA7642 has a greater adhesive clear film or (as we normally do) sensitivity in the lightning detector aphot laminated (laminators and sleeves are plication compared to the MK484 and very cheap these days and give a tough so given the choice, we recommend protective layer!). using the TA7642. We did not try a DC If printing on clear plastic film (overhead ZN414Z since this is not available. Input projector film) you can print the label as a The potentiometer (VR1) and the + mirror image so that the ink is behind the PCB-mounted switch S1 can now be film when placed onto the panel. Again, this soldered in. will give the label maximum protection. LED1 and LED2 mount horizontally Once the ink is dry, cut the label to size. but at a height of 6mm above the board The paper or plastic film is glued to the surface. Bend their leads 90° at 7mm panel using an even smear of neutral-cure back from the base of the LEDs, making silicone. For plastic film, if you are gluing sure the anode lead is to the left. it to a black coloured panel, use coloured L1 is a standard broadcast band coil silicone such as grey or white so the label pre-wound onto a small ferrite rod. can be seen against the black. There are actually two coils on the rod A hole in the panel is required directly but only one is used. Using your multimeter, find the coil that has the greatest above the piezo transducer. This can be first drilled in the plastic lid and then once the panel label is affixed, cut the resistance. With our prototype, the main winding measured about 11, while the separate antenna winding measured hole out using a sharp hobby knife. A small piece of dark fabric or loudspeaker foam 2. Connect the coil with the highest resistance to the PC (scrounged from an old pair of headphones) can be used to stakes. The ferrite rod is secured to the PCB using a pair of small cover the piezo transducer. Also a black bezel over the panel hole can improve the finish of the unit. These are secured cable ties. The piezo transducer is mounted using two 6mm long with a smear of neutral cure silicone. Our bezel came from standoffs and 12mm long M2.5 screws. The screws are the plastic dress plate that sits behind the nut of a Jaycar inserted from the underside of the PCB, pass through the PS-0192 stereo 6.35mm jack socket. Additionally, a cut out is required for access to the DC spacers and tap into the piezo mounting tabs. If you are using a different piezo transducer that has larger mounting holes socket. A rat-tail file can be used to make this hole in the lid. A suitable belt clip for the remote control box is available in the tabs, M3 screws could be used instead to tap into the SILICON CHIP siliconchip.com.au . July 2011  47 RESISTOR COLOUR CODES No. Value 4-Band Code (1%) 1 470kΩ yellow purple yellow brown 2 220kΩ red red yellow brown 2 180kΩ brown grey yellow brown 5 100kΩ brown black yellow brown 1 10kΩ brown black orange brown 2 2.2kΩ red red red brown 1 1kΩ brown black red brown 1 470Ω yellow purple brown brown 1 180Ω brown grey brown brown 2 22Ω red red black brown One of the following (R1): 1 470Ω yellow purple brown brown 1 330Ω orange orange brown brown 1 120Ω brown red brown brown 1 1 1 1 1 1 1 1 1 1 1 1 1 Capacitor Codes 5-Band Code (1%) yellow purple black orange brown red red black orange brown brown grey black orange brown brown black black orange brown brown black black red brown red red black brown brown brown black black brown brown yellow purple black black brown brown grey black black brown red red black gold brown Value F Value IEC Code EIA Code 470nF 0.47F 470n 474 100nF 0.1F 100n 104 22nF 0.022F 22n 223 10nF 0.01F 10n 103 1nF 0.001F 1n 102 the 22Ω resistor should be about 33mV with a 3V supply or less with a lower voltage supply. Check supply to IC1 at the emitter of Q1. This should be 1.46V with a 3V supply dropping to 1.287V with a 2V yellow purple black black brown supply. orange orange black black brown Adjust the sensitivity control fully brown red black black brown clockwise or back off if any indication persists. Test the Lightning Detector as from Altronics. The catalog number is H0349. (Contact a fluorescent light is being switched on. The switching on www.altronics.com.au). of conventional fluorescent tubes will cause the Lightning Detector to give a LED detect and tone indication with Testing each starter attempt to light the tube. Compact fluorescent Testing can be done with two AA cells or a DC supply. tubes tend to be indicated with a single flash and tone as Apply power and check that the power LED momentar- the tube lights rapidly. ily lights when the Lightning Dectector is switched on. The sensitivity control is included to prevent the Check the supply voltage by measuring across diode D2. Lightning Detector from producing an indication when This should be around 3V but may differ depending on there is no lightning. The control is adjusted clockwise the state of the cells or the tolerance of the 3.9V zener for maximum sensitivity to lightning but not so far as to SC diode when a DC power supply is used. Voltage across give false detection. What to Do in a Storm The best idea is to avoid getting caught outside in an electrical storm but sometimes, the best laid plans of mice and men. . . etc. How far away is the lightning? Watch for a flash of lightning. Then count or read off your watch the number of seconds until you hear the first crash of thunder (or crack if it is close!). Divide the number of seconds by three and you have a rough distance away that the lightning has struck. Anything less than 1km (ie, 3s) should be regarded as getting very dangerous. If you cannot get to shelter? If you are caught outside during an electrical storm, avoid conductors of electricity such as water, trees, poles, golf clubs, umbrellas and metal fences. If possible, keep away from open spaces (eg, the middle of a sports field) where you will be taller than the surroundings and definitely do not shelter under a tree. Crouch down, keeping your feet close together and wait out the storm. Groups of people should be spread out several metres apart. It is also a good idea to cover your ears with your hands to avoid hearing damage due to the noise of a close lightning strike. If possible, take refuge inside a vehicle or building. If inside a vehicle, close the windows and avoid touching the metal of the vehicle. Make yourself less of a target by lying down (eg on the back seat). Keep the vehicle away from trees or tall objects that may fall over in the storm. Avoid fallen power lines. Inside a building, keep windows and doors closed and keep 48  Silicon Chip away from windows, doors and fireplaces. Before the storm, unplug electrical appliances that may be susceptible to lightning damage. These include fax machines, telephones, microwave ovens, televisions and computers. To be doubly safe, unplug any computer communications devices from phone lines or cables (don’t forget routers etc). Avoid using electrical appliances and telephones until the storm has well and truly passed. (However, you can use a mobile phone if you have to – eg, to call for help). Avoid touching earthed fittings such as water taps, sinks, appliances and so on. If you are on a boat, keep low, dry, and away from metal conductors. Always check with the Bureau of Meteorology for storm forecasts before going out on a boat. In this way you could avoid boating in a storm. If you are a boat owner, make sure the boat is fitted with lightning protection that directs lightning safely to the water. This will help protect the occupants should they be caught out in a storm and also help protect the boat when left moored. And if someone near you is struck by lightning? Avoid the temptation to rush in and help – time is of the essence but there’s no point in two people being struck! As soon as it is safe to do so (ie, the danger has passed), commence standard A-B-C resuscitation. Check their response, clear the airway, and if necessary proceed with CPR. What? You don’t know CPR? Learn it today! siliconchip.com.au Winter Projects at JULY 2011 Check out the tools for DIY projects on pages 2 & 3. Jaycar DVR • Four channel split-screen or single channel switching display • USB 2.0 interface for external backups/mouse • Motion trigger alarms • Input/Output: 4-ch input/ 1-ch output • Video compression: H.264 • Mains power supply included • Dimensions: 375(L) x 265(W) x 60(H)mm Standard Colour CCD Camera A Stirling engine is a machine that converts heat into mechanical energy. The expanding air acts on a piston to provide mechanical force: simply heat up the air chamber, give the flywheel a whirl and away it goes. Made in Germany, our Stirling engine is beautifully engineered from stainless steel, brass and a genuine beech base. It has 2 ball 00 bearings and should become an $ heirloom. THIS IS A KIT, ASSEMBLY REQUIRED! 249 12/24VDC 20A MOTOR SPEED CONTROLLER KIT Refer: Silicon Chip Magazine June, 2011 Control the speed of 12 or 24VDC motors from zero to full power, up to 20A. Features optional soft start, adjustable pulse frequency to reduce motor noise, and low battery protection. The speed is set using the onboard trimpot, or by using an external potentiometer (available 95 $ separately, use RP-3510). 39 • Infrared LEDs for day/night capability • Weatherproof IP67 rated housing with integrated mounting bracket • Resolution: 520 TV Lines • Effective range: up to 15 metres $ • Dimensions: 90(D) x 60(Dia)mm • Kit supplied with silk-screened PCB and all onboard electronic components. • Suitable enclosure UB3 case, HB-6013 sold separately KIT OF THE MONTH KC-5502 Human Detection Colour Camera PURE SINE WAVE INVERTERS/CHARGERS 999 00 • Push notifications to mobile (via DVR) • Resolution: 520 TV Lines View live or • Effective range: up to 15 metres recorded • Dimensions: 90(W) x footage on a 3G phone or 145(D) x 30(H)mm iPhone® QV-8110 MINI CCTV 420 TV LINES CAMERAS Ideal for use in retail stores, home security, remote monitoring or covert applications. All feature adjustable focus lens and composite video output with audio, which can feed into the AV inputs on any DVR or TV. Requires a 12VDC regulated power supply. Three models to choose from. • Sensor: 1/3" SHARP • Resolution:420 TV Lines • Power required: 12VDC SENSOR INSIDE Mini Colour CCD Camera • Lens: 3.6mm • Dimensions: 36(W) x 36(H) x 15.9(D)mm QC-3690 $64.95 Mini Colour Pinhole CCD Camera Mini Colour CCD Camera with IR • Lens: 3.6mm • Dimensions: 36(W) x 36(H) x 15.9(D)mm QC-3694 $69.95 To order call Combining the functions of a pure sine wave inverter, battery charger and automatic transfer switch in one unit, these are the ideal power solution for mobile and recreational vehicle applications. When connected to the mains, the load is taken from the mains and the connected batteries are charged. If the mains is interrupted or exceeds the allowable limits, power is drawn from the batteries and mains power is provided by the inverter. This ensures a seamless supply of power in your caravan, 4WD or recreational vehicle - plug into mains power when it's available, and automatically flick over to battery power when mains is removed. No more manual switching from mains to battery power! FROM 00 • Battery voltage: 12VDC $ • Battery charge current: 20A 1499 1500W Sine Wave Inverter/Charger • Weight: 5.2kg • Dimensions: 520(L) x 200(W) x 88(H)mm MI-5260 $1499.00 2000W Sine Wave Inverter/Charger • Lens: 3.7mm • Dimensions: 36(W) x 36(H) x 15.9(D)mm QC-3692 $69.95 FROM 64 95 $ SAVE BIG! SAVE STIRLING ENGINE PROJECT KIT INTELLIGENT VIDEO SURVEILLANCE (IVS) 4 CHANNEL DVR KIT Supplied with Make your security measures 500GB HDD smart with the use of the Intelligent Video Surveillance (IVS) DVR kit. This DVR kit incorporates a human motion detection camera and three IR colour CCD cameras. Once the motion detection camera detects motion a push notification is sent to your smart phone, enabling you to look at live footage of the intruder as the incident happens. Push notifications are supported for most Smart Phones using the downloadable surveillance app. You can also monitor via Ethernet or Internet connections. See website for more details. Look for this icon & Inverter & Charger Combined! • Weight: 6.4kg • Dimensions: 615(L) x 200(W) x 88(H)mm MI-5262 $1799.00 All Savings are based on Original RRP 1800 022 888 www.jaycar.com.au Prices valid from 24/06/2011 to 23/07/11. Limited stock on sale items. No rainchecks. • Recommended for ages 12+ • Adult supervision recommended • Dimensions:156(L) x 108(W) x 70(H)mm YM-2923 5.8GHZ AV SENDER EXPERIMENTERS KIT WITH IR RECEIVERS All AV sender transmitters are limited to strict controls and output power. This unit is for qualified and licensed amateur radio experimenters only as it has ten times the output power of standard units (100mW). In keeping with the experimental nature of the unit, it is not ready to plug in. Several parts such as the supplied RCA sockets need to be soldered in. It also doesn't come with a set of cases. It uses a standard 9V adaptor that comes with the unit. The extra power works well with experiments in, say concrete buildings with lots of reinforcing steel. In all respects except output power, it's identical to AR-1840 AV sender. • Video input: Composite for NTSC or PAL • IR frequency: 433.92MHz • IR modulation: ASK 00 $ • IR carrier: 30 - 60kHz • Range: Up to 300m (line of sight) • Operating frequency: 5.76 - 5.86GHz (6 channels) • Transmission power: 20 dBm (100mW) • Receiver sensitivity: -85dBm • Operating voltage: 9VDC • Power consumption: TX: max. 500mA <at>9V RX: max. 400mA <at>9V • Dimensions: TX/RX PCB: 111(L) x 62(W)mm AR-1849 249 Caution: This product requires further assembly, which assumes technical competence. If you feel that this may be above your skill level, please return the unit in its original packaging, with receipt, under our standard satisfaction guarantee terms. Once construction or soldering has begun we will not accept the unit back under any circumstances. NEWS & EVENTS CASTLE HILL NSW Store Now Open Shop 2/2 Anella Ave (Cnr of Anella & Victoria Ave) Ph: (02) 9634 4470 Parking Available Do - It - Yourself SOLDERING EQUIPMENT • Measures: Angled & duckbill 120mm, superfine 135mm TH-1760 59 $ 19 95 • UV stability $ • Box measures: 250(W) x 180(D) x 40(H)mm HP-1216 Also available: 19 95 $ Releasable Cable 30 Tie Pack HP-1217 $6.95 GLUE LINED PRE-CUT HEATSHRINK TUBING - TRADE PACK 95 60W Soldering Iron - 12VDC Glue lined heatshrink in an array of sizes to suit all needs - 60 pieces in total. Supplied in see through nylon snap shut case. A quality 12V soldering iron. Plugs into your car cigarette lighter and with 60 watt, it's hot enough to solder terminals, heavy cable etc. • 2.5 metre lead length • Supplied with a length of solder as well. Box of 400 black cable ties in various sizes: 200mm, 150mm & 100mm. Supplied in a re-usable box with compartment storage. Set of 3 tweezers, duckbill head, angle fine and straight superfine enable you to manipulate surface mount components or other tiny items with ease. ESD coating on main body of tweezers reduces static discharge issues. the hobby user. Comes with a lightweight iron with anti-slip grip and tip cleaning sponge, with temperature adjustment from 150-450°C. • Dimensions: 135(L) x 82(W) x 70(H)mm TS-1620 CABLE TIE BOX - 400 PIECES STAINLESS STEEL TWEEZER SET - ESD SAFE FREE Spare 40W Temperature Controlled Tip (TS-1622) with Soldering Station every purchase An ideal entry-level valued at $8.95 soldering station for • 95mm long • Box measures: 205(W) x 108(D) x 35(H)mm WH-5521 17 95 $ 29 95 $ Note: Before use, check your car's wiring is enough to carry the current, or else connect direct to the battery. TS-1530 BUDGET DIGITAL VERNIER CALIPER Portasol Super Pro Gas Soldering Tool Kit The digital display is calibrated in imperial and metric units with a corresponding scale etched onto the caliper slide. Perfectly suited to the home handyperson and is the ideal caliper for woodworkers. Features 90 minute run time, 10 second fill, maximum 1300°C temperature and 40 second heat up. The kit contains a Portasol Super Pro Gas Soldering Iron, and all of the following: • 150mm measurement range • 245mm length (closed) • Internal and external jaws • 0.1mm resolution TD-2081 FREE Butane Gas (NA-1020) with every purchase valued at $5.95 • Quality storage case, cleaning sponge and tray, 2.4mm & 4.8mm double flat tips, hot air blow, hot knife tip, hot air deflector TS-1328 Everything you need to get into your gaming console and accessories. Includes tools for pretty much every console and handheld on the market today - WII®, X-Box®, Playstation® etc. Carry case included. See website for full contents. TD-2109 WAS $29.95 Also available: Computer Tool Kit 24 95 $ SAVE $5 00 TD-2150 WAS $19.95 NOW $14.95 SAVE $5.00 PENCIL BUTANE TORCH Pocket sized gas torch for heatshrinking, soldering etc and uses standard butane gas. Adjustable flame, all metal construction. 19 95 $ • Size: 205(L) x 13(Dia)mm TS-1667 LOWER PRICE 159 00 11 95 $ $ MINI GLUE GUN - 240V ROTARY TOOL KIT WITH FLEXIBLE SHAFT 6W Soldering Iron - Battery Powered Battery powered soldering irons have come a long way. This 6W model will re-solder a dry joint or fix a solder lug, etc. It is ideal in potentially explosive situations, such as bilge, or where petrol fumes may be present. Reaches full temp 95 in about 10 seconds. $ • Uses 3 x AA batteries (not included) • Size: 175(L) x 36(W) x 18(D)mm TS-1535 GAMING CONSOLE TOOL KIT The kit consists of a powerful 32,000 RPM rotary tool that you can use with numerous attachments (210 pcs) in the usual way, plus a 1m 95 $ long flexible shaft that attaches in seconds to give extra versatility. SAVE $5 00 Suitable for model making, automotive, workshop, art, jewellery or sculpture. See website for full kit contents. TD-2459 WAS $39.95 19 34 FREE Batteries (SB-2425) with every purchase valued at $3.95 A handy tool to have around the house. It's fast, easy and simple to use with trigger controlled glue feed. Plugs straight into 240V power point. Perfect fix for toys, decorations, furniture, woodwork, cardboard etc. • Standards Australia approved • Requires glue sticks with 7.4mm diameter FREE Glue Stick 6pk TH-1990 (TH-1991) with Note: Intermittent use only, not for production use. 19 95 $ every purchase valued at $3.95 PROJECTS MADE EASY! Precision 5" Angled Side Cutters PCB Holder with Magnifying Glass Ideal for fine PCB work. They will easily cut leads flush with the board's surface. Made from quality carbon steel and have soft padded handles. TH-1897 An extra pair of hands and eyes for those fiddly jobs. Supports PCBs while soldering etc. Great for model builders and other hobbyists. • 145mm high TH-1983 12 $ 11 $ 95 3mm De-Solder Braid A quick & simple bulb type solder sucker that is affordable, compact and effective. Buy two or three and you will always have one handy. A specially treated piece of braid for removing solder from a PCB. Place the braid over the solder and apply soldering iron to efficiently remove solder. • Size: Approx. 50(D) x 110(L)mm TH-1850 95 DEAL Buy all 4 for $25 Save $10.10 Better, More Technical 2 Solder Sucker & Blower Bulb All Savings are based on Original RRP Limited stock on sale items. 6 $ 95 • 3mm wide, 120mm long NS-3020 3 $ 25 To order call 1800 022 888 Tools DIGITAL MULTIMETERS Cat II Autoranging DMM True RMS Autoranging DMM Compact Cat III Multimeter with Temperature Suitable for voltages up to 600VAC and has 15mm high digits for easy reference. Features include overload protection, 10A AC & DC current, diode check, data hold & backlit display. Features large 20mm high digits, True RMS measurement, temperature, capacitance, relative measurement, data hold, temperature and more. Includes holster and temperature probe. A budget-priced meter with everything you need - capacitance, temperature and 10A on AC and DC, compact and light weight with rugged double moulded housing. • Display: 4000 count • Category: Cat III 600V • Dimensions: 196(H) x 96(W) x 51(D)mm QM-1536 WAS $79.95 • Display: 4000 count 95 $ • Cat III 600V • Duty cycle, backlit • Non-contact voltage • Dimensions: 137(H) x 65(W) x 35(D)mm QM-1323 39 • Display: 2000 count • Category: Cat II 600V QM-1524 19 95 $ 59 95 $ SAVE $20 00 VACUUM BENCH VICE WITH 75MM JAW ILLUMINATED GOOSENECK MAGNIFIER STAINLESS CUTTER / PLIERS SET A robust bench vice with a powerful suction base. The vice consists of three-pieces; a vacuum base, ball joint clamp and a 75mm opening jaw with removable soft rubber jaw covers. The jaws have 'V' grooves for holding cylindrical or irregular shapes making it well suited to small bench jobs. This handy hobbyist's magnifier has a 2x main magnifier lens with 5x insert lens and 2 LED lights, all mounted on a flexible arm. Can be free-standing or clamped to a surface up to 38mm thick. Lens comes with a soft protective pouch. Set of five 115mm cutters and pliers for electronics, hobbies, beading or other crafts. Stainless steel with soft ergonomic grips. • Stands approximately 160mm tall TH-1766 • Lens: 110(dia)mm • Stands: 225mm high • Requires 3 x AAA batteries (SB-2413) QM-3532 WAS $29.95 29 95 $ IDC CRIMPING TOOL Suits all IDC cable connectors. Commonly used for connecting items such as SCSI and IDE computer plugs. Don't destroy connectors with a vice or a hammer, crimp them the easy way. • Crimping distance from 27.5mm to 6mm (with attachment). TH-1941 WAS $14.95 11 95 $ SAVE $3 00 24 $ This handy set will fit the bill for all those microscopic fasteners we come across in modern electronics. • Contains: Slotted: 1, 1.4, 1.8, & 2.4mm, Phillips: #000, #00, #0, #1, Torx: T5, T6,T7, & T8, Hex: 1.5, 2, & 2.5mm 95 $ • Drivers: 105mm long • Case size: 192(L) x SAVE $5 00 130(W) x 26(H)mm TD-2069 WAS $24.95 19 The advantages of a DSO gives you capabilities that simply aren't possible with any analogue oscilloscope, including trace capture, PC interface, storage of data on portable media etc. Visit our website for more detailed features. 7 PIECE CR-V SCREWDRIVER SET Made to last from an alloy of heat-treated chrome vanadium and molybdenum steel for high wear resistance and strength. The set contains: • Slotted: 2.5 x 75, 5 x 75, 5 x 150, 6 x 125mm • Phillips: #0 x 75, #1 x 75, #2 x 100mm $ TD-2088 25MHz Dual Trace DSO Ideal entry-level DSO for the advanced hobby user or technician and is particularly suited to audio work. Full data storage capabilities and USB interface so you can store traces on a flash drive. • Channels: 2 • Display: Colour TFT LCD 145mm • Weight: 2.4kg • Dimensions: 310(W) x 150(H) x 130(D)mm QC-1932 95 100 PIECE DRIVER BIT SET This is an excellent driver bit set that contains just about every bit you could ever use. It has a magnetic holder, adaptors, Phillips bits, slotted bits, torx, tamperproof, pin drive, and even a wing nut driver - Fantastic. See web site for full listing 95 $ TD-2038 Enhanced performance, professional level test instrument for the technician, design engineer or development laboratory. Full 100MHz bandwidth to keep up with the current digital chip technology, plus a host of features that make it a cost-effective addition or upgrade to your current test equipment. Big 7" screen, smaller, lighter more portable and with a host of extra features, and it even includes a carry bag. EASY DISTANCE MEASURING Professional Laser Distance Meter Measure distance quickly from a remote position. This ultrasonic measurer calculates area, sums total readings and stores data for later use in imperial or metric units. Laser pointer for accurate placement of the measurement point. Requires flat unobstructed surface to measure againts. This comprehensive measurement tool adds, subtracts and calculates area, volume and takes indirect measurements. The memory stores up to 20 historical records and these can be used for area and volume calculations. Invaluable for architects, estimators, builders or renovators. • Backlit LCD • Auto or manual power-off • Dimensions: 175(L) x 62(W) x 45(D)mm QP-2295 WAS $44.95 Case & Belt Clip included 34 95 $ SAVE $10 00 SAVE $$$ • Area and volume calculations • Add/subtract measurements 00 • Continuous measurement $ • Min/max distance tracking • Backlit LCD SAVE $20 00 • Laser accuracy • Dimensions: 110(L) x se Battery & Ca 47(W) x 28(H)mm included QM-1621 WAS $199.00 www.jaycar.com.au 599 00 $ 7" Screen 100MHz Dual Channel DSO 19 Ultrasonic Distance Meter with Laser 29 DIGITAL STORAGE OSCILLOSCOPES SAVE $5 00 9 15 PIECE MICRO DRIVER SET 95 • Contains: flush cutters, long nose pliers, flat nose pliers, bent nose pliers, round 95 $ nose pliers TH-1812 179 • Digital filter function and waveform recorder function • Pass/fail function • Screen-saver enables less power-consuming, prolong product lifetime • Channels: 2 00 • Display: Colour 7in TFT LCD 178mm $ • Weight: 2.4kg • Dimensions: 340(W) x 150(H) x 110(D)mm QC-1934 1149 Both models include probes, Easyscope software & a USB cable Limited stock on sale items. All Savings are based on Original RRP 3 Power Management Systems SUPER COMBI POWER MANAGEMENT SYSTEM These Rich Electric SuperCombi inverter/chargers are the ultimate solution to your power management needs for a wide range of applications. From caravans and motorhomes, to marine and household remote power systems, the SuperCombi is up to the task of supplying and managing your power needs whatever your application. Featuring super-rugged design and build quality to withstand harsh Australian conditions, these units are capable of delivering their FULL rated power output all the way up to an impressive 70˚C operating temperature. See website for more information. • True pure sinewave interactive inverter/charger • Auto-transfer switch (ATS) • Dynamic Power Shifting • Power support • DC generator input up tp 700 amps • Solar panel controller input up to 600 amps • Programmable DC control switches • Stackable • Interactive power sharing • Multi-phase supply • Green Power Smart feature SAVE 12V 1500W MI-5250 24V 1500W MI-5251 12V 3000W MI-5252 24V 3000W MI-5253 $$$ FROM Was Now Save $3199.00 $3199.00 $4399.00 $4399.00 $2999.00 $2999.00 $4199.00 $4199.00 $200.00 $200.00 $200.00 $200.00 Sydney Grid-Tie Installation Accessories to suit both SuperCombi and CombiPlus Units Multiphase data hub Parallel stack data hub Battery temperature sensor Remote control for SuperCombi Remote control for CombiPlus Linkable Solar Charge Controller 45A Linkable Solar Charge Controller 60A Also available: CombiPlus Power Management Systems. Was Now Save 12V 1500W MI-5270 $2899.00 $2699.00 $200.00 24V 1500W MI-5273 $3799.00 $3599.00 $200.00 Check our POWERSTACK HIGH PERFORMANCE BATTERY BANKS to suit these systems. See our friendly staff and or website. 3kWh Per Day with 1kW Solar Solar Panels Three days system autonomy at 3kWh per day usage. About 3.5kWh solar charging provided per day on average. MP-9005 WAS $13,990.00 NOW $12,500.00 SAVE $1,490.00 DC POWER AC POWER POWER FROM GENERATOR Solar Charge Controller 5kWh Per Day with 1.575kW Solar Note: Not stocked in all stores but can be ordered. Call your nearest store for details. Inverter / Charger Four days system autonomy at 5kWh per day usage. About 5.2kWh solar charging provided per day on average. MP-9007 WAS $22,990.00 NOW $19,990.00 SAVE $3,000.00 699 • Small footprint to suit installations in tight areas • Advanced AGM (absorbed glass matt) technology • Cycle life: 1800+ <at> 20% DOD, 500+ <at> 80% DOD • Voltage: 12VDC • Capacity: 150Ah (10hr rate), 164Ah (20hr rate) • Weight: 52kg • Dimensions: 123(W) x 556(D) x 296(H)mm SB-1822 12,500 POWERTECH MONOCRYSTALLINE SOLAR PANELS Bank As strong and tough as the better known brands, but at a more attractive price. Op�onal DC Load Controller DC Loads 240V Generator • Water pump • 12V LED lighting • Etc AC Loads • LCD TV • Fridge • Kettle • Etc Note: Due to size and weight of items in these packages, not all parts are available in-store. Please speak with our staff for more information. SAVE BATTERY-TO-BATTERY DC CHARGE CONTROLLER 12 - 24V 140A Fully programmable, battery-to-battery charge controller system with a variety of applications as a charge or load controller. It can be used as a bi-directional, fully programmable battery to battery charge controller. Alternatively, it can be used as an independent, fully programmable DC load controller low voltage disconnect / re-connect with programmable twin timer functions. Or finally, it can be used in conjunction with the SuperCombi power management system as the DC load controller or DC generator input. Suitable for 12V or 24V systems, up to 140A maximum current. • Operating voltage: 9-35VDC • Over-voltage protection • Dimensions: 111(W) x 90(H) x 58(D)mm MI-5282 Better, More Technical 4 $199.00 $199.00 $69.00 $439.00 $379.00 $389.00 $459.00 Designed to perform in harsh tropical conditions, and with a superior high rate discharge performance and higher cycle service life, this battery is perfect for a wide array of applications including remote solar systems, 4WD, caravan and RV, motorhome, and marine. See our website for a full specification datasheet. 00 $ For those living in locations where mains electricity isn’t available, or expensive to have connected, a remote power system is the best solution to household power needs. Whilst a remote power system can be a major investment, Jaycar offers packages to suit your needs and there are government incentives (Australia only) & rebates that may support your purchase*. Each packages contains the necessary number of solar panels, a fully featured inverter-charger power management system, FROM solar charge controller, high capacity deep cycle battery banks, cables, 00 $ connectors and cable-termination tooling. Just add the appropriate panel mounting hardware. *Must meet criteria for Solar Credits scheme. See www.orer.gov.au for details MI-5276 MI-5277 MI-5278 MI-5259 MI-5279 MP-3726 MP-3728 12V 150AH AGM DEEP CYCLE BATTERY REMOTE POWER PACKAGES Also available: 10kWh Per Day with 3.15kW Solar MP-9009 WAS $39,990.00 NOW $35,500.00 SAVE $4,490.00 2999 00 $ 279 00 $ • Sizes range from 5 watts to a massive 175 watts • For full technical spec ask in-store or visit online • QC tested - all come with test certificate • 20 year limited warranty FROM 32 95 $ SAVE $$$ $$$ Get 10% off on our solar mounting brackets with every panel purchased 12V 12V 12V 12V 12V 12V 12V 24V All Savings are based on Original RRP Limited stock on sale items. 5 Watt 10 Watt 20 Watt 40 Watt 65 Watt 80 Watt 120 Watt 175 Watt ZM-9091 ZM-9093 ZM-9094 ZM-9095 ZM-9096 ZM-9097 ZM-9098 ZM-9099 Was Now Save $39.95 $64.95 $119.00 $225.00 $359.00 $429.00 $639.00 $899.00 $32.95 $59.95 $115.00 $219.00 $349.00 $399.00 $579.00 $849.00 $7.00 $5.00 $4.00 $6.00 $10.00 $30.00 $60.00 $50.00 To order call 1800 022 888 Power MONITOR YOUR POWER BILL THIS WINTER Deluxe Mains Power Meter with CO2 Measurement Mains Standby Power Saver with IR Receiver Save power costs by monitoring what your appliances use. This meter tells you the cost of electricity consumption of an appliance plugged into it and the amount of power used in kilowatt hours, as well as how many cumulative kg of CO2 the appliance is putting into the atmosphere. This energy saving device eliminates the standby power consumed by most modern appliances. Simply program the power saver with the standby level for your system and it will shut the power off whenever the set level is reached. Program any IR remote control to turn the power saver on again for simple and effective operation. • Extra large LCD for easy reading • Dimensions: 120(L) x 58(W) x 40(H)mm MS-6118 Mains Wireless Power Monitor Monitor your household's electricity consumption simply and easily. With the sensor unit installed in your fuse box, your household power usage data is wirelessly transmitted to the indoor display unit up to 50m away. You can also scrutinise your week-to-date and year-to-date energy consumption. The indoor LCD receiver unit runs on 2 x AA batteries (included). • Electricity usage, cost and time displayed • Suitable for single phase only • Dimensions: Display unit: 101(H) x 80(W) x 42(D)mm Sensor unit: 75(L) x 95 $ 60(W) x 35(H)mm MS-6160 • Dimensions: 128(H) x 65(W) x 40(D)mm MS-6146 WAS $39.95 29 95 $ 99 29 95 $ SAVE $10 00 4 X AA SOLAR BATTERY CHARGER 4 OUTLET REMOTE CONTROL POWERBOARD The solar panel in the lid will charge up to 4 x AA Ni-Cd or Ni-MH batteries in a fairly short time. Ideal for yachts, campers or anywhere 240V is not available. Control up to 4 mains appliances individually. Simply plug them into the powerboard, and use the remote to turn each device on or off. Makes it easier to turn off devices behind cabinets like Hi-Fi or home theatre components. Each remote is coded to avoid interference. • Size: 67(W) x 30(H)x 96(D)mm 95 $ MB-3502 WAS $23.95 14 • One-touch synchronisation • Overload circuit-breaker protection • Surge and spike protection • LED power indicator • Each outlet switched individually MS-6150 SAVE 9 $ 00 MODIFIED SINEWAVE INVERTERS These modified sine wave inverters will produce mains power from a vehicle's battery. A 150W inverter will run some laptops, lights, small TVs & recharge batteries. Inverters 300W & above will also recharge power tools, run fluorescents & larger style TV's. Take your creature comforts with you when you go bush or on any road trip. 150W 300W 400W 400W 600W 800W 1000W 1500W 2000W 12VDC to 230VAC 12VDC to 230VAC 12VDC to 230VAC 24VDC to 230VAC 12VDC to 230VAC 12VDC to 230VAC 12VDC to 230VAC 12VDC to 230VAC 24VDC to 230VAC 3 IN 1 MOTION SENSOR LIGHT 59 95 $ Use it as a torch, a spotlight or as a motion sensor light! It will switch on instantly after detecting motion and illuminate the area for either 30 or 60 seconds before it goes off. Can be mounted on any surface and has motion sensitivity of up to 5m. A great idea for areas such as your kitchen cupboards or pantry, sheds & hallways. Mounting bracket and hardware included. • Eco-friendly - using LED & motion sensor • Requires 2 x AA batteries (not included) • Dimensions with bracket: 106(L) x $ 92(H) x 33(D)mm ST-3203 19 95 12VDC CCTV MAINS POWER SUPPLIES Note: This product is not suitable for use with inverters or UPS units. Mains power supplies suitable for CCTV installations, with multi-channel outputs for each individual camera. Housed in a rugged lockable steel enclosure designed for permanent professional installations. Must be installed by a licensed Electrician. 150 LUMEN MAGNETIC TORCH WITH GOOSENECK Great New Prices MI-5102 MI-5104 MI-5106 MI-5107 MI-5108 MI-5110 MI-5112 MI-5114 MI-5116 $49.95 $69.95 $99.00 $99.00 $169.00 $199.00 $299.00 $449.00 $549.00 Pure sinewave inverters also available. See in-store or on website. A tough & handy LED work light perfect for the home, in the car, garage and even in the office. Position light exactly where you need it with a flexible tube & powerful magnetic base, the high powered 3W LED will emit a very bright focused beam. Aluminium build, designed to last. Requires 3 x AA batteries. • Output: 150 lumens • Burn time: 15 hours • Dimensions: 35(D) x 180(L)mm ST-3460 49 95 $ DUAL BATTERY ISOLATORS WITH ADJUSTABLE DISCONNECT/RECONNECT This dual battery isolator, or voltage sensitive relay (VSR), is the link that allows both batteries to charge whilst your engine is running, but keeps your main engine cranking battery isolated from being discharged by your 12V accessories once camped. Cut-in and cut-out voltages are independently user adjustable, and it also features a manual override/jumpstart function. Two models available: MB-3680 for 12V batteries, and MB-3682 for 24V batteries. • 100% solid state technology with extremely low standby current and voltage drop • 10 user adjustable set points for disconnect and reconnect voltages • Over current, over voltage and over temperature protection • Emergency over-ride feature • Can be used independently as a low voltage 00 $ disconnect/reconnect for a 100A load each • Dimensions: 162(L) x 75(W) x 50(D)mm 119 4 x separate 12-14V DC channels MP-3850 $69.95 9 x separate 12-14V DC channels MP-3852 $129.00 Both units have: • Each DC power channel has secure, screw down terminals with rear panel wiring access • Mains hardwire connection via screw down terminals with safety cover • Each 12VDC output channel is individually fused, and can be switched ON/OFF with jumpers • Output voltage: adjustable from 11-13VDC • Output current: MP-3850 3.0A total MP-3852 5.0A total • AC input: 100-240V 50-60Hz • LED power on status on locked panel face • Dimensions: MP-3850 163(L) x 163(W) x 48(D)mm MP-3852 203(L) x 163(W) x 54(D)mm WARNING: FROM Whilst these 95 $ units have a secure plastic cover over the switchmode circuitry, mains wiring is still accessible. We strongly MP-3850 recommend that only licensed electricians are used to connect the unit to power mains. shown 69 12V batteries MB-3680 $119.00 24V batteries MB-3682 $119.00 Note: 24V version not stocked in stores but can be ordered. Call your nearest store for details. stock on sale items. Limited stock on sale items. www.jaycar.com.au Limited 5 Sight and Sound TWINKLE LASER LIGHT SHOWS BUILD-IT YOURSELF Produce spectacular lighting effects with hundreds of twinkling and constantly moving laser lights. Lightweight and compact, these laser projectors are suitable for portable lighting setups. DMX Controller USB Interface Kit Red & Green Mini Laser Show Red and Green Twinkle Laser Show with Blue Waterfall Feature Basic economy model provides red & green twinkle laser light display. Sound activated, auto or remote control with variable modulation. Manually controlled only. • Control mode: Sound active, auto, remote control • Mains operated from 9-12VDC plugpack (included) • Dimensions: 135(L) x 105(W) x 55(H)mm SL-3439 DMX control, red and green twinkle displays along with spectacular high power blue LED waterfall effect. Adjustable dimmer, rotation speed and stroboscopic function. 149 00 $ • Key protection safety function • Brightness 00 adjustment $ • Scattering function • Mains powered • Dimensions: 200(L) x 85(W) x 158(H)mm SL-3437 299 • 512 DMX channels with 256 levels each $ • 3 pin XLR-DMX output connector • Windows 98SE or higher compatible • Dimensions: 106(L) x 100(W) x 44(H)mm KV-3610 149 00 DMX Relay Control Kit ANIMATION GREEN LASER SHOW WITH ILDA ACTIVE PA SPEAKERS WITH MP3 CONTROLLER ILDA (International Laser Display Association) capability enables full software integration and complex animation of your laser show. The unit comes with pre-programmed displays and characters, but with the use of ILDA software such as Zion®, Millennium® or V3D® you can add PC control to create cartoon, letters, figures or other characters. Software is not included. 2- way active PA speakers that are not only powerful but also extremely portable. Incorporates a 12" or 15" woofer and compression driver, 3 channels with balanced XLR inputs and 1/4” unbalanced inputs, RCA line level inputs and an MP3 controller. Ideal for DJ, PA for schools, sports, churches, weddings, conferences etc. • SD card and USB inputs • Titanium tweeter • 2 band equaliser $$$ • 200WRMS power output • Weight: 20kg • Dimensions: 620(H) x 400(W) x 400(D)mm FROM CS-2529 $399.00 399 399 00 15" Active PA Speaker with MP3 Controller 99 00 • 512 unique addresses, selectable with DIP switch • Status LED for power and error detection • Stand alone mode for testing • Dimensions: 150(L) x 60(W) x 45(H)mm KV-3614 DEAL SAVE $20 00 Buy 2 for $799 SAVE $139 PAPER CONE PA DRIVERS PARTY LIGHTING LED Linkable Party Lights with Controller Rotating Disco Ball with LED Spotlights Turn a lifeless party into an exciting one with these linkable blue, amber and red LED party lights. They have a built-in sound modulator that allows for the lights to switch in time with the beat. Microphone sensitivity and light chaser speed functions are fully adjustable. Units are mains powered, easy to operate and designed to last. Two models available: This brilliant mirror ball and LED spotlights station features an automatic rotating mirror ball, two adjustable angle spotlights with 6 LEDs in each which alternate between red, green and blue. It also has an additional 4 LEDs on the base for maximum effect. Mains power adaptor included. 3 LED Linkable Party Light • Dimensions: 14(L) x 13(W) x 48(H)mm SL-2911 $49.95 • Dimensions: 260(L) x 130(W) x 230(H)mm SL-2916 6 LED Linkable Party Light • Dimensions: 35(L) x 13(W) x 36(H)mm SL-2913 $79.95 FROM 39 95 $ 49 95 $ Better, More Technical 6 49 79 • 300WRMS power output • Weight: 28kg • Dimensions: 690(H) x 460(W) x 400(D)mm CS-2530 $469.00 $ • 512 unique addresses, DIP switch settable • LED indication 95 $ for power supply, relay output and error status • Relay hold function in case of DMX signal loss KV-3612 Allows you to control a lamp or group of lamps through a DMX signal. Use the USB Controlled DMX Interface kit or any other control console compliant with the DMX-512 protocol as a controller. It will drive resistive loads 95 $ like incandescent lamps and mains voltage halogen lighting. Short form kit. Buy 2 for $699 SAVE $99 This unit projects thousands of dazzling green laser star like formations to your ceiling. Comes with an integrated amplified speaker to connect your iPod® and MP3s to blast your tunes through the stars. Control a relay with the DMX512 protocol. It is actually a bus-controlled power driver. The relay will be activated when the DMX value of the set channel equals 140 or more and turns off when the value is 120 or less. Short form kit contains DMX-512, XLR plug, PCB and all specified components. DMX Control Dimmer Kit $ DEAL GREEN LASER STAR PROJECTOR • Colour changing LEDs • 6W motion light • Dimensions: 140(L) x 140(H) x 110(D)mm SL-2931 WAS $119.00 SAVE 12" Active PA Speaker with MP3 Controller • ILDA software or DMX control • Control mode: Sound active, automatic, DMX (6 channels), master/slave • Mains powered • Dimensions: 270(L) x $ 00 80(W) x 174(H)mm SL-3438 Add computer control to your DJ or stage show. This kit controls DMX fixtures such as spotlights using a PC and USB interface. Includes software, USB cable and enclosure. DLL is provided so you can write your own software if you like. It can also be operated in stand-alone mode that outputs all 512 channels at the same time (9V battery required for stand-alone mode). All Savings are based on Original RRP Limited stock on sale items. Ideal for DIY PA bins or replacement drivers. With aluminium frames, high efficiency and power handling capacity, these drivers offer exceptional value. Full specifications on website. 10" Paper Cone PA Driver SAVE • Power handling: 150WRMS CG-2381 WAS $99.00 NOW $89.00 SAVE $10.00 $$$ 12" Paper Cone PA Driver • Power handling: 200WRMS CG-2383 WAS $119.00 NOW $99.00 SAVE $20.00 FROM 89 00 $ To order call 1800 022 888 IT & Comms NOTEBOOK ACCESSORIES USB 3.0 Portable Study Table with Notebook Cooler ExpressCard with 2 x USB3.0 Ports 4-Port Powered USB 3.0 Hub Achieve transfer speeds of up to 2.5Gbps with this ExpressCard to 2 x USB 3.0 port adaptor for your laptop. Though unable to reach the maximum theoretical speed of USB 3.0 due to ExpressCard bandwidth limitations it is still more than triple the speed of USB2.0 (480Mbps). This is more than enough for a significant reduction in transfer times. If you've made the upgrade to USB 3.0, you'll need a hub to run all your new peripherals. This one has four ports and provides a 4.8Gbps data rate, and significantly faster than USB 2.0. Lots of applications for this handy fold-up table. Features two work surfaces - the adjustable sloping and the flat surface. The legs are heightadjustable, has a pen and cup holder and cooling fans for your laptop. The whole lot folds up neatly for easy transport and storage. • Retractable USB cable included • Size folded: 285(W) x 316(H) x 36(D)mm • Size unfolded: 570(W) x 316(H) x 36(D)mm XC-5218 Note: Laptop not included $49 • Compatible with XP, Vista and 7 (32-bit and 64-bit) • Compliant with ExpressCard SAVE $10 00 standard release 0.95 • Dimensions: 95(L) x 68(H) x 14(D)mm Add USB 3.0 to XC-4141 WAS $59.95 your Laptop 95 MULTINETWORK CABLE TESTER WITH PIN OUT INDICATOR 29 95 $ This laptop security cable has a four digit combination that you can customise for security. It's 1.8m long and has a swivel on the end so moving it around your desk area will not be a problem. • Steel lock mechanism XC-4639 WAS $17.95 • Requires 1 x 9V battery • Dimensions: Main Unit: 104(L) x 62(W) x 26(D)mm Active Terminator: 100(L) x 30(W) x 25(D)mm 12 95 $ SAVE $5 00 Tiny 300k Notebook USB Webcam • Driverless, plug and play • 300k resolution • Dimensions: 28(W) x 59(H x14(D)mm QC-3231 19 95 Use this USB port powered light when looking inside a computer, or when on the road with a laptop. Twist the head to turn On/ Off, and it has a gooseneck for universal angle adjustment. DEAL ST-2808 14 $ Once the media player is connected to your TV just attach your USB hard drive or thumb drive with your movies or SD card from your digital camera and start watching. Two models available: 39 95 720p Media Player with USB & SD Ports $ Extremely soft ear pads with a fabric headband beneath the stainless band, which evenly distribute the weight of the headset on your head to ensure comfort. The microphone is an electret condenser type on a sturdy but flexible metal gooseneck. USB Powered Notebook Light 95 • Headphone transducers 40mm dia. • Cable: 2.5m long with 2 x 3.5 stereo plugs for headphones and mic connection 95 $ • In-line volume control AA-2078 Buy 2 for $20 SAVE $9.90 39 95 $ HIGH DEFINITION MEDIA PLAYERS COMFORTABLE COMPUTER HEADPHONE & MICROPHONE $ It's a rechargeable active speaker that can take a MicroSD card full of music files and it will play them in order or you can pause, play or skip to another track. It can be used as a laptop or computer speaker or plugged into a range of other devices such as iPods®, iPads® or any device that has an earphone jack. It also has an internal battery for charging via USB. • Dimensions: 74(L) x 50(W) x 52(H)mm XC-5176 Note: Not suitable for Live circuits XC-5076 FREE 9V battery (SB-2423) with every purchase valued at $3.95 Excellent for on-the-go online video conferencing or chatting. It has a built-in microphone to keep your setup as minimalist as possible. Comfortably mounts on top of a thin LCD laptop screen. 59 MINI SPEAKER Designed to quickly test UTP/STP/Coaxial/Modular network cables by manually or automatically scanning the wires for continuity, incorrect wiring and polarisation. It will sequence each connection and indicate the connections via two 9-way LED bar graphs. Main unit supplied with: Active RJ-45 terminator, 2 x RJ-45 to BNC adaptors and instruction manual. Combination Notebook Cable Lock • USB 3.0 lead and mains plugpack included • Windows XP, Vista and 7 • Dimensions: 85(L) x 32(W) x 18(H)mm 95 $ XC-4947 WAS $69.95 SAVE $10 00 19 • Supports AVI/MP4, DivX, Xvid, MPEG 1&2, RM, RMVB, DAT, MOV (not H.264) and VOB • Maximum resolution: HDMI/YPbPr up to 720p XC-4206 $89.00 Ideal for movie 1080p High Definition marathons on cold Media Player with USB, winter nights SD & LAN Ports • Supported video formats: RM/RMVB/AVI/MPEG4 /MKV/M2TS/DivX/Xvid/Dat /VOB/MP4/MOV/SWF • HDMI, YPbPr (YUV component) & AV outputs • Ethernet connectivity FROM (UPnP) 00 $ XC-4204 $139.00 89 AUTO REVERSING CAMERAS Rear View Mirror TFT Monitor with Camera A complete rear-view safety package including a 7" TFT LCD monitor and a flush mount weatherproof camera. The monitor fits securely over your existing rear vew mirror and can be quickly removed when needed. It has adjustable spring-loaded brackets to fit different sized mirrors and includes a slimline remote control. Additional camera (QC-3513) can be connected. • 7 inch screen • 5m video/power cable included • Power: 12VDC • Dimensions: 260(L) x 108(H) x 50(D)mm QM-3762 WAS $249.00 179 00 $ SAVE 70 $ 00 Note: Should not be used as a substitute for a conventional rearview mirror unless the normal view is blocked. www.jaycar.com.au Flush Mount Mini Waterproof Camera for Cars or Trucks Designed for use in vehicles to give drivers a clear view of car or truck blind spots. A lengthy 5m composite RCA cable, a 730mm power cable, and the appropriate sized hole saw are included making this colour CMOS camera easy to install. • 420TV Lines • Power: 12VDC • Dimensions: 31(L) x 20(Dia)mm QC-3513 89 95 $ DEAL Bus / Truck Camera with Infrared LEDs This tough unit can be firmly mounted inside as a surveillance camera or outside as a reversing camera. The camera is fitted to a solid bracket that can be rotated in a vertical motion for the optimal view. An RCA composite video and audio connection are fitted for compatibility with most in dash and security LCDs. Infrared LEDs will allow night vision so nothing will escape the cameras view. • Power supply: 12VDC • IP Rating: IP67 • Lens angle: 120 • Dimensions (including bracket): 73(L) x 45(W) x 53(H)mm QC-3519 WAS $149.00 119 00 $ SAVE $30 00 SAVE $$$ Buy QM-3762 & get the extra camera (QC-3513) for $69.95 SAVE $20 Limited stock on sale items. 7 Kits ARDUINO DEVELOPMENT KITS Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs (includes Jaycar stepper motors). Arduino projects can be stand-alone, or they can be communicate with software running on your computer. These Arduino development kits are 100% Arduino compatible. EtherTen (100% Arduino Compatible with Onboard Ethernet) Getting Started with Arduino 100% Arduino compatible board that can talk to the world. Do Twitter updates automatically, serve web pages, connect to web services, display sensor data online, and control devices using a web browser. Any project you would previously have built with an Arduino and an Ethernet shield stacked together, you can now do all in a single, integrated board. See website for more details. Arduino is an open-source development platform that enables experimenters to configure an open hardware design for a single board microcontroller. This book explains what it is and how it works, and what you can do with it. It also includes a project to build complete with how to write the code to make it work. • Gold-plated PCB • Top and bottom parts overlay • Top-spec ATmega328P MCU • Rounded corners XC-4216 • Softcover, 118 pages. 216 x 140mm BM-7130 69 $ 95 23 95 $ Practical Arduino Eleven (100% Arduino Uno Compatible) A copy of the exact Arduino Duemilanove board. It contains the ATmega328 microprocessor with a boot loader program so that you can communicate with it at switch-on. It has the standard I/O and is 100% compatible with the original Arduino concept. It contains some documentation and assembly instructions. See website for more information. XC-4210 95 $ PS-0749 A much larger and detailed book. It takes you beyond basics quite quickly and shows you how to make up a typical application / design. This is a necessity as it goes to the heart of Arduino. • Softcover, 422 pages. 235 x 190mm BM-7132 39 57 95 $ NEWS & EVENTS ProtoShield Basic for Arduino NEW STORE East Kew VIC 782 High St East Kew Vic 3101 Ph: (03) 9859 6188 Parking Available Fits directly onto an Arduino or Freeduino compatible board such as the Eleven and EtherTen so you can make more durable and permanent projects. The PCB is gold plated for durability, yellow solder masked, and features top and bottom overlay which clearly marks the GND and 5V rails. There is also mounting pads for a reset button, power on LED and current limiting resistor, and power supply capacitors. 4 $ 45 • Size 59(L) x 53(W)mm XC-4214 KITS - BUILD THEM! Headlight Reminder For Cars Refer: Silicon Chip August 2001 Nothing is more frustrating than getting into your car early in the morning, only to discover that you had left your headlights on the night before, running your car’s battery flat. Features include a modulated alarm, ignition and lights monitoring, optional door switch detection, time-out alarm and a short delay before the alarm sounds. Build and install this hassle-saving kit and enjoy a feature in your car that many luxury vehicle owners have long taken for granted. Kit includes quality solder masked PCB with overlay, case with screen printed lid and all electronic components. 12VDC. Learn everything there is to know about component recognition and basic electronics with this comprehensive kit. From test leads to solder, everything you need for the construction of this meter is included. All you'll need is a soldering iron. Excellent choice for first year trade apprentices. • Kit includes DMM case, LCD, solder, battery, test leads, PCB, manual and electronic components. • Meter dimensions: 67(W) x 123(H) x 25(D)mm KG-9250 • PCB: 78 x 49 mm KC-5317 Don’t get caught in the cold! 27 95 $ DAB+/FM Digital Radio Kit Digital Multimeter Kit 24 $ 95 There are very few digital radios available as Hi-Fi components and the few that are cost north of $700. Many Hi-Fi enthusiasts want to add a digital tuner to their system and want function and sound quality over bells and whistles. This kit covers DAB+ and FM, has analogue and optical audio outputs, IR remote (included), an external antenna connector and is powered by a mains plugpack. The kit is complete with everything, including the case. See website for full specs. • Digital station info display • RCA and optical audio output • External antenna connection • Station memory presets • 9VAC plugpack included KC-5491 Newcastle Ph (02) 4965 3799 Townsville Ph (07) 4772 5022 Sunshine YOUR LOCAL JAYCAR STORE Thomastown Penrith Ph (02) 4721 8337 Underwood Ph (07) 3841 4888 Australia Freecall Orders: Ph 1800 022 888 Werribee Port Macquarie Ph (02) 6581 4476 Woolloongabba Ph (07) 3393 0777 AUSTRALIAN CAPITAL TERRITORY WESTERN AUSTRALIA Rydalmere Ph (02) 8832 3120 SOUTH AUSTRALIA Belconnen Ph (02) 6253 5700 Maddington Sydney City Ph (02) 9267 1614 Adelaide Ph (08) 8231 7355 Fyshwick Ph (02) 6239 1801 Midland Taren Point Ph (02) 9531 7033 Clovelly Park Ph (08) 8276 6901 NEW SOUTH WALES Northbridge Tweed Heads Ph (07) 5524 6566 Gepps Cross Ph (08) 8262 3200 Albury Ph (02) 6021 6788 Rockingham Wagga Wagga Ph (02) 6931 9333 Reynella Ph (08) 8387 3847 NEW ZEALAND Alexandria Ph (02) 9699 4699 Wollongong Ph (02) 4226 7089 TASMANIA Christchurch Bankstown Ph (02) 9709 2822 NORTHERN TERRITORY Hobart Ph (03) 6272 9955 Dunedin Blacktown Ph (02) 9678 9669 Darwin Ph (08) 8948 4043 Launceston Ph (03) 6334 2777 Glenfield Bondi Junction Ph (02) 9369 3899 QUEENSLAND VICTORIA Hamilton Brookvale Ph (02) 9905 4130 Aspley Ph (07) 3863 0099 Cheltenham Ph (03) 9585 5011 Hastings Campbelltown Ph (02) 4620 7155 Caboolture Ph (07) 5432 3152 Coburg Ph (03) 9384 1811 Manukau NEW Castle Hill Ph (02) 9634 4470 Frankston Ph (03) 9781 4100 Cairns Ph (07) 4041 6747 Mt Wellington Coffs Harbour Ph (02) 6651 5238 Capalaba Ph (07) 3245 2014 Geelong Ph (03) 5221 5800 Newmarket Croydon Ph (02) 9799 0402 Hallam Ph (03) 9796 4577 Ipswich Ph (07) 3282 5800 New Lynn Erina Ph (02) 4365 3433 Labrador Ph (07) 5537 4295 NEW Kew Ph (03) 9859 6188 Palmerston Nth Gore Hill Ph (02) 9439 4799 Mackay Ph (07) 4953 0611 Melbourne Ph (03) 9663 2030 Wellington Hornsby Ph (02) 9476 6221 Maroochydore Ph (07) 5479 3511 Ringwood Ph (03) 9870 9053 NZ Freecall Orders Liverpool Ph (02) 9821 3100 Mermaid Beach Ph (07) 5526 6722 Shepparton Ph (03) 5822 4037 Maitland Ph (02) 4934 4911 Nth Rockhampton Ph (07) 4926 4155 Springvale Ph (03) 9547 1022 Arrival dates of new products in this flyer were confirmed at the time of print. Online Orders Head Office Occasionally these dates change unexpectedly. Please ring your local store to 320 Victoria Road, Rydalmere NSW 2116 Website: www.jaycar.com.au check stock details. Prices valid from 24th June to 23rd July 2011. Ph: (02) 8832 3100 Fax: (02) 8832 3169 All savings are based on original RRP Email: techstore<at>jaycar.com.au 399 00 $ Exclusive to Jaycar Ph (03) 9310 8066 Ph (03) 9465 3333 Ph (03) 9741 8951 Ph (08) 9493 4300 Ph (08) 9250 8200 Ph (08) 9328 8252 Ph (08) 9592 8000 Ph (03) 379 1662 Ph (03) 471 7934 Ph (09) 444 4628 Ph (07) 846 0177 Ph (06) 876 0239 Ph (09) 263 6241 Ph (09) 258 5207 Ph (09) 377 6421 Ph (09) 828 8096 Ph (06) 353 8246 Ph (04) 801 9005 Ph 0800 452 922 SERVICEMAN'S LOG Restarting after the earthquake Restarting a business after an earthquake isn’t easy, especially when the workshop and its equipment is damaged and there’s so much mess to clean up. However, I wasn’t about to sit around and have all my previous efforts go down the drain. After re-reading my article on the Christchurch earthquake in the May 2011 issue of SILICON CHIP, I realised that the story ended rather darkly. At that time, we did not know what would happen next and were not at all certain that our business would survive the quake. Since then, I’m happy to report some positive progress. Small businesses like mine (and for many others in the service industry) rely on cash-flow to stay afloat. It is the air we breathe and no cash flow equals no business. Unlike big business, we don’t have the resources to have accounts outstanding for months on end. That’s because we have to pay our suppliers and other outgoings siliconchip.com.au promptly, regardless as to whether we get money in or not. In short, our suppliers rely on us paying them and we rely on customers paying us to keep the money-go-round going round. After the quake, everyone was in shock and the city paralysed. After my initial inspection of the damage at my workshop, road closures meant that we could no longer even reach the building let alone get inside. When I closed the door on that day, the workshop was calf-deep in liquefaction and it was rising. In addition, large cracks through seemingly solid concrete floor slabs and wide-open “staircase” cracks up the concrete block walls Items Covered This Month • • • • • Restarting after the earthquake Do-it-yourself starter motor repair Optical drive fun LG RT-42PX1 106cm plasma TV set HP/Agilent 3458A multimeter meant the building might not be safe, so getting back in wasn’t at the top of my to-do list. Because I thought that the workshop was ruined, the outlook appeared bleak. I had to keep reminding myself that people had died and that others had lost everything they owned under the rubble. We were alive with an intact house and contents and therefore were extremely fortunate. Despite this, I was worried about my business and wondered how we could recover. There is nothing like a disaster to motivate people. Work crews toiling night and day soon had the roads and avenues cleared to at least one lane of traffic, while an army of students, farmers and other volunteers cleared thousands of tonnes of liquefaction and rubble from suburban footpaths and yards. Helicopter pilots donated flying hours and machines, while teams of chefs prepared donated food for free in order to fly hot meals in for the workers. Similarly, rival power companies banded together and in just over a week had an overhead cable strung clear across town; a job that would normally take many months. And drain layers rapidly replaced shattered sewers with above-ground pipes in an effort to keep the waste moving. Meanwhile, the government, in a rare show of actually doing something useful, offered wage subsidies to businesses unable to trade but having to pay staff. Although not normally being one to accept hand-outs, I nevertheless applied; we didn’t know how long July 2011  57 Serr v ice Se ceman’s man’s Log – continued we’d be down and I wasn’t about to forgo paying my employee. That relieved some of the financial pressure and although customers had already started leaving messages, we were initially in no position to help them. Once the roads had been cleared, I was able to return to my workshop to further assess the damage. It’s all very well sitting back and taking “free” money from the government but that’s a short-term answer only. Our customers needed us and if we weren’t there, they’d call someone else. I wasn’t about to sit on my hands and watch all my hard-won clients go elsewhere, so I decided that we really had no choice but to get the business running again as soon as possible. By now, I knew that the workshop wouldn’t fall on me, so I decided to try to clean it up and at least start answering the phones and booking in jobs. By that time, most of our suppliers had re-opened and power, phones and the internet were all restored, so I had everything I needed to start trading. I called my staff member and told him what I had in mind, assuring him we could get the building declared safe, though if he felt it too dangerous to work there, I would understand. He replied that he’d been thinking about it too and knew we had to get going or we’d likely not recover, so he would be there first thing in the morning. His loyalty and can-do attitude confirmed I’d made the right choice in hiring him. With two of us pitching in, 58  Silicon Chip we would soon be on our way. Unfortunately, every one of our specially-designed test rigs and workshop machines were still sitting where they fell and were thus waterdamaged and useless. Our server was also dead and our workbenches literally shaken apart. Even the overhead fluorescent tubes had smashed together and disintegrated into a million bits, adding noxious powder and broken glass to the sticking foetid mess on the floors and workbenches. Because we needed to conserve our available capital, we couldn’t replace everything up-front, so we sat down and worked out what we’d need as a bare minimum. We then assembled what we could from our remaining stock and known good used parts, buying only when absolutely necessary. We built a new server and because one of the old server’s RAID drives was still alive, it was up and running in no time. Within two days, we had a barebones but functional workshop up and running. The landlord would have to sort out the building. However, because he is elderly and lives in the country, he usually operates according to his own unique time, which us townies would call “dead slow”. I impressed on him that unless the building was declared safe, we couldn’t trade and if we couldn’t trade, we couldn’t pay rent. To his credit he was there the next day with a building inspector/engineer who went through and declared everything safe. The landlord also brought in a crew to clean the outside of the place up so that we didn’t have to tip-toe everywhere or wear gumboots to work. The workshop still looks like a bomb has gone off in there but at least we are trading and slowly rebuilding. Earthquakes may break the hardest stone, but the human spirit is something altogether tougher. Starter motor A few years back, my dad, being the technical one in his family, was roped into doing some work on a relative’s car. The car was having trouble starting and experience suggested that the starter motor was getting a bit tired. In the grand old days, one simply removed the starter motor from the engine, unscrewed the brush covers, replaced the brushes, gave the commutator a bit of a rub with some wet and dry and buttoned it up. You then threw some fresh grease on the pinion and slapped it all back together for another 10 years of reliable service. However, it wasn’t quite so easy on my relative’s car which was an expensive European model. This was at a time when the majority of cars on New Zealand roads tended to be an odd mixture of aging and fast-disappearing British marques and newer and much better equipped Japanese imports. In New Zealand, European cars have always tended to be relatively expensive to buy and maintain, with spares tending to be a bit on the pricey side. And even though the owner of this particular car was a man of some means, he baulked at paying the many hundreds of dollars they wanted for a new starter motor plus freight. Throw in a 4-week wait for the part to arrive and it’s easy to understand why he turned up at Dad’s workshop, wanting to know if anything could be done to fix his present unit. This particular starter motor, like a lot of European engineering, was a well-made unit. However, the rivets holding everything together, rather than the more usual screws, indicated that it was designed to be a throwaway item. Dad quickly dealt with the rivets holding the end covers in place by drilling them out. Gently easing the covers away then revealed the armature, brushes and commutator end of the motor. And the problem was evident straight away – the brushes had worn all the way down to their copper braids. Removing the old brushes simply involved lifting the springs and easing them out of their housings. To Dad’s keen eye they looked like a standardsized item and a quick trip to a local spare parts dealer and a few minutes spent comparing the old ones with several different brands soon produced a close match. While the new ones were a little longer than the originals, they fitted nicely into the brush-holders and a little extra initial spring tension siliconchip.com.au wouldn’t hurt, even though it might increase the wear rate slightly. The commutator was showing its age and was lightly scored, though it was considered not worth the hassle of splitting the case and removing the pinion gears just to give it a skim in the lathe. Dad made do with cleaning it up as best he could in-situ, then spent half an hour using a modified junior hacksaw blade to carefully under-cut the mica insulation sandwiched between the commutator segments. A few quick spins by hand with 100-grit wet and dry held to the commutator soon had everything looking good again. After drilling the old rivet shafts from the body of the starter, dad replaced the covers and secured them in place with some small “PK-type” self-tapping screws. A quick test using a car battery showed it worked and so the starter was returned to its happy owner. It’s still in the car and working many years later. The total cost of repairs, excluding labour, was $5.00 which was the cost of the brushes. So if you have a sealed unit that’s causing problems, you have nothing to lose by cracking it open and taking a look inside. You never know; it might be easy to fix and you could save yourself a small fortune over the cost of a new one. Optical drive fun It doesn’t seem that long ago I paid $1000 for a 2-speed CD writer. While that seems a lot today, I have to admit that I made the money back (and then some) during the halcyon disk-burning days of the late nineties. Only “professionals” and hard-core hardware nuts bought such gadgets and once word got out that I had one, the orders came in thick and fast for back-up disks. Of course, the boom didn’t last long; a scant few years later, anyone could fit a burner into their computer for a song and back up their own disks, so that little cottage industry tanked relatively quickly – as did the PlayStation 1 chipping craze of around the same time. While I didn’t chip any consoles, I knew of people making a lot of money doing nothing but. For those unfamiliar with the scene, Sony all but tied up disk copy and zone protection with the PlayStation 1 by putting a boot sector at the start of every game disk. This wouldn’t copy across to blank media in even the most comprehensive disk copy siliconchip.com.au process, meaning that copied PlayStation games would not even load, let alone play, on unmodified consoles. Then some bright spark came up with the idea of replacing the disk’s boot sector with a hard-wired one soldered directly to the console’s motherboard. This “fooled” the console into booting from that instead of the disk’s boot sector (which of course didn’t even exist in backed-up games) and so the chipping boom began. The Internet made it a global phenomenon and some technicians were installing chips into consoles as fast as they could program them. Of course, this modification voided any warranties and there was always the possibility that a console wouldn’t work at all after one of the dodgier “chippers” had had a crack at it. Being a computer gamer rather than a console gamer, the whole chipping thing didn’t affect me and while I didn’t agree with the rampant pirating of games this craze appeared to encourage, I did like the idea of being able to back up and play from those backups, given that the Playstation disks were quite costly at the time. It was also around this time that faster CD-ROM drives began appearing on the market. First came the 2x drive, then followed 4x, 8x, 12x & 16x drives and so on up to 52x drives. Things are going the same way with DVD drives today, with 22x drives the current flavour. The new speedier models brought their own problems though. On more than a few occasions, I was called out soon after installing a new optical drive to complaints of noise and it not working properly. In all those cases, old and obviously cracked or damaged disks had literally blown to bits inside the drive, damaging it in the process. It was sometimes a tough call as to which way to go when it came to replacing the dead unit – was it a warranty job or was it the client’s responsibility (especially if the disk was known to be defective)? LG plasma TV This next story could also have been titled “Waste not, want not”. It comes from P. C., a retired electrical engineer from One Tree Hill, SA. Here’s how he tells it . . . I was brought up in an era when, if something broke, you tried to fix it. It wasn’t always economical to do so of course but it gave me the satisfaction of knowing that I had extended a device’s useful life and saved it from the scrap heap. It always seems such a waste to throw away all the metals and plastics that something is made of, especially as the Earth’s resources are not unlimited. It was in this spirit that I approached the repair of an LG 106cm (42-inch) plasma panel TV (RT-42PX11) which was given to me by my son-in-law. This screen was larger than my own CRT TV but it was a 2006 model which had been superseded many times, even though it had good resolution. If I could fix the flat panel, I could use it with my HD set-top box and discard my dinosaur CRT set. The plasma panel had died with a click from the rear when the set had been switched on. My first move was to lie the panel face down on the kitchen table and take the back off. This revealed a number of PCBs. Some boards were related to input signal processing while one was obviously the main power supply PCB. Three others drove the plasma panel itself. Each of these latter PCBs had glass fuses and the fuse on the YSUS board had blown. This immediately narrowed down the problem to this particular board. A close examination of this board revealed some heavy discrete comJuly 2011  59 Serr v ice Se ceman’s man’s Log – continued ponents (electrolytics, transformers and transistors) and a large heatsink (about 75 x 50mm) obscuring what was probably a special-purpose IC. Initially, I thought that I could measure the voltages on the major components but the system was under microprocessor control and wouldn’t switch on because of the fault. Not having a circuit diagram was a hindrance as well, so I looked for one on the net. I eventually found a source and downloaded the manual. However, I was disappointed because it didn’t detail anything about the three plasma panel PCBs. Apparently, these boards are proprietary and are not regarded as serviceable. In the end, it seemed that the only way to repair the unit was to buy a new YSUS board. There were two numbers on the PCB but the number etched into the board is not the one used for ordering. Instead, a sticker attached to the board gave the part number as “YSUS 6871QYH029A”. A Google search turned up a source for this PCB from Big Warehouse. The site also provided some additional advice that the available PCB “6870GYE008C” was the correct replacement PCB for the one I wanted. Hoping that the advice was good, I ordered a new board and it arrived quite quickly. To install it, I had to re-attach all the other boards and I hoped that the new one would be OK after all my work. I switched on and was gratified when the panel sprang to life as good as new. 60  Silicon Chip Afterwards, I cut away the large IC on the old PCB and removed the heatsink to see what it was. There were four large slices of silicon, presumably transistors, on the IC, two of which had exploded. I was glad I had not wasted any more time on the old PCB as it would not have been possible to replace this unique IC. If I get another five years out of the unit for an outlay of $240, I will have done well. At the same time, the set has been kept from adding to our evergrowing electronic waste problem. The ultimate multimeter A. L. of Turramurra, NSW recently had an unusual failure in a high-end digital multimeter. Here’s what happened . . . A friend called me excitedly to tell This view shows the IEC socket/EMI filter at the back of the HP multimeter. The EMI components are housed in an oil-filled cover. me that a local medical research lab was closing because of lack of government funding and that we could visit them the same day to have a look at all the equipment for sale. With business being quiet, I decided I could leave the place for awhile, so we made an appointment with the accountant at the lab. It was the electronics gear that I was really wanted to see and one item that did interest me was a Tektronix 60MHz 224 oscilloscope which handles up to 1000V peak and is only slightly bigger than a house brick! The price was reasonable so I agreed to pick it up at a later date, when I had some ready cash. A couple of days later, the accountant rang and asked when I was coming to collect it. I went straight down to meet him and he explained that they now had to clear out the lab in a week and if I would agree to pay an extra $200, I could have all the other instruments no-one wanted. This seemed like a bargain as there was a very large digital multimeter, a digital counter and a large, heavy dual-tracking variable power supply. Unfortunately, Mrs Serviceman was not impressed since space is somewhat at a premium in our workshop. The large multimeter was an HP/ Agilent 3458A and the functions of its various buttons and controls were not immediately obvious. As a result, I spent some time wading through the three large manuals supplied with the instrument before I could even do a simple voltage measurement. I also “Googled” it and found, to my astonishment, that the same instrument was being sold for up to $8000.00. By now, I had spent an inordinate amount of time learning how to use it but had no idea as to whether I would ever need such a super-accurate and sensitive device – apart from checking out my other multimeters. The 3458A measures down to 10nV DC and 1pA and can measure RMS voltages at frequencies up to 10MHz. It is fully programmable and is apparently the “ultimate multimeter”. Now that I owned it, I just had to use it and so I always started it up as soon as I’d opened the workshop, to ensure sufficient warm-up time. And then one day, while I was repairing a microphone mixer for an old rock star from the 60s (another story), I became aware of the presence of thick black smoke. Unfortunately, it wasn’t comsiliconchip.com.au siliconchip.com.au ACOUSTICS SB ing from the microphone mixer but out of every pore of my prized HP multimeter! I quickly turned off the switch at the front of the instrument but the smoke came out even heavier! It wasn’t until I whipped the mains plug from the socket that the smoke stopped. I was so dispirited by this that I just left it in place for a couple of days before plucking up the courage to open it up. With all that smoke, experience told me that such a sensitive instrument must have suffered a terrible blow and may never display a nanovolt again. My fear was that the power supply had failed and taken everything else out with it but the fuse was still OK. Then, remembering that the on/off switch had had no effect, I suspected some sort of switch failure, possibly caused by excessive current welding the contacts together so I checked it out. To my surprise, the switch was perfect! So why did the smoke still issue forth when the switch was off? It didn’t take long to figure out that the only components before the switch were the fuse and the IEC socket. And the latter looked pretty black! In this case, the IEC socket is an EMI power-line filter type. It contains a filter that’s based on a network of inductors and capacitors in an oil-filled shell and is designed to reduce line-to-ground (common mode) interference. There was nothing for it but to remove it. However, that was easier said than done because it’s riveted into a confined space and I had to drill out all the tiny rivets before I could slide it out of the case. When I got it out, I immediately noticed some oil in the area below where the socket had been mounted. These sockets are oil-filled for cooling but because some of the oil had leaked out, the internal components had apparently overheated and brought the remaining oil to its “smoke-point”. As far as I can discover, HP/Agilent don’t list a replacement part for the IEC socket. I guess no-one ever suspected it would ever wear out, which is why the engineers designed it to be riveted permanently to the chassis. In the end, I replaced the faulty socket with a local version, after which the instrument fired up and passed all its (very complicated) self-checks – much to my delight. That was some time ago now and it has worked ever since. It really is an excellent instrument and is the last word when it comes to checking other multimeters, some of which can show errors of 20% or more. My friend, an electrician who paid good money for a “professional” multimeter, was shocked (no pun intended) to discover that it was reading 0.5V DC when it should have been showing 50V DC from my benchtop supply! “Better throw it out before you kill yourself”, I warned him. We tend to toss multimeters around in the toolbox without realising they can be damaged, so it was lucky he had it checked! Since then, I have never left any device with one of those IEC/filter sockets switched on and left unattended. And at knock-off time, I always switch all my instruments off at the mains and remove the plugs as well. It’s better SC to be safe than burn the house down! CEILING & IN-WALL TWO-WAY SPEAKERS SUPERIOR SOUND QUALITY AND PERFORMANCE dynamica July 2011  61 A Rudder Indicator For Power Boats, Pt.1 By NICHOLAS VINEN Manoeuvring a medium-sized or large boat at low speeds can be very difficult and it is even more difficult if you don’t know where the rudder(s) is pointing before putting the engine(s) into gear. Trouble is, in most boats, after swinging the wheel back and forth several times, you have no idea. Take the guesswork out of steering with this Rudder Position Indicator. H ERE IS A typical scenario. You are reversing your flybridge twinengined cruiser into a berth (doesn’t everyone have one of these?). You must do it at low speed (pretty obvious!) and you can’t use the rudder to steer with since rudders don’t work at low speeds. The only way to steer is to use the motors. Normally, in a twin-engined boat, you make sure the rudders are centred and then you manoeuvre the boat by nudging the motors into and out of gear and using very judicious (tiny!) amounts of throttle or none at all. For example, if you are going forward, you can steer to port (left, if you’re a landlubber) by putting the port engine into reverse and the starboard engine into forward gear. Or you might just leave 62  Silicon Chip the starboard engine in neutral while nudging the port engine in and out of reverse gear. Going in reverse is a whole different ball-game. Now you are looking at the rear of the boat while you manoeuvre it into a narrow berth. In this case, if you want to steer to the left going backwards, you put the starboard engine into reverse and the port engine into forward . . . or combinations of those settings. All the while, you have to cope with the effects of currents and wind. It can be a nightmare. It can be even harder in a singleengined boat. The rudder still doesn’t work at low speeds and you don’t have the luxury of two motors to do the steering. In this case, you do have to use the rudder but in order to get the boat to respond to the rudder, you have swing it hard over, in one direction or the other, and give the motor a quick stab of power in forward or reverse gear to push the stern of the boat in the required direction. Sounds tricky, doesn’t it? Well, it is. Going back to the twin-engined boat for a moment, before you can start these low-speed manoeuvres, you must have the rudder centred. But since typical boats require many turns from lock-to-lock, it is almost impossible to know when the rudder is centred. The practical way to do it, is count the turns from lock-to-lock and then halve it, to centre the rudder. So if it is six turns from lock to lock, you turn the wheel fully to port or starboard and then wind the wheel siliconchip.com.au back by three turns. Trouble is, it’s easy to lose count when you’re winding the wheel back and forth. How much easier it would be if you had an electronic rudder indicator! Commercial rudder indicators are fitted to some boats but they are very expensive. So that was the brief. The skipper of SILICON CHIP can’t steer his boat (hope I won’t get into too much trouble for this . . .) and he wanted an electronic indicator. Being the autocratic type that he is, who was I to argue? His justification is that the project would have other applications, so here is the result. This Rudder Position Indicator consists of two units, each of which mounts in a small sealed box with a transparent lid. The sensor unit monitors the movement of the rudder arm and transmits information to a receiver unit via a UHF radio link at 433MHz. The receiver display unit is portable so that it can be moved from the flybridge driving position to the helm inside the cabin. It shows the rudder position using an array of high brightness LEDs, with adjustable brightness to suit indoor and outdoor use. Features The rudder display can show one of seven positions: three steps to port, three to starboard and one when it is centred. The port, starboard and centre positions use different LED colours to Specifications & Performance Rudder Position Resolution................................................. seven steps, plus centre indication Sensor Type ...........................................................................................magnet and reed switch Communication Method ..........................................433MHz UHF digital wireless transmission (Amplitude Shift Keying) Range ...........................approximately 20m (depending on antenna orientation and obstacles) Power source ..................................................................... 4 x AAA cells or external 12V supply Battery life (sensor unit) ........................................approximately two years with 4 x AAA cells Battery life (receiver) .....approximately two years on standby or 2-8 hours in use, depending on LED brightness Size (each unit) ..................................105 x 75 x 40mm with a protruding 15cm whip antenna make the direction more obvious at a glance. For extra precision in setting the rudder straight ahead, the middle LEDs flash when the rudder arm is directly over the central sensor. Both the sensor and receiver units are fitted with short whip antennas (about 15cm) to provide sufficient range for use on larger boats. In most boats, the hydraulic steering arms are located in a compartment called a “lazarette” and this may or may not be lined with aluminium foil coated insulation, to cut down noise and heat. In this case, it may be necessary to run a coaxial cable from the sensor unit to a whip antenna mounted outside this compartment, to allow the signal to reach the helm position(s). The same comment applies if the boat has an aluminium or steel hull. Both the sensor and receiver units can be powered from an internal battery (which can be rechargeable) or from an external 12V power source. An external power source can also be used to trickle charge the internal batteries. The approximate charge state of both batteries is indicated on the display unit. The sensor unit is always powered, so you don’t have to switch it on and off each time. Even so, its low current drain means that it will run for at least a year on four AAA cells. Just how long depends on how often you use it and the cell type used. If you use goodquality alkaline cells, the transmitter battery could last two years or more. Many boats have a 12V lead-acid battery in the lazarette and in that case, you can omit the sender unit’s The sender unit (left) uses seven reed switches to detect the rudder position. It transmits data to the receiver unit (right) via a 433MHz wireless link. siliconchip.com.au July 2011  63 ACTUATOR PIVOT HYDRAULIC RAM RUDDER ARM ADDED ARM S1 MAGNET (UNDER ARM) S2 S3 © 2011 S4 CON5 SC RUDDER BEARING S5 CON6 S6 SENSOR UNIT S7 (HORIZONTAL PLATFORM) RUDDER So for the final design, each unit is based around a microcontroller which does virtually all the work, in combination with a wireless transmitter or receiver module. Most of the time, the micros are in a low-power sleep mode, keeping the battery drain down to about 15µA (including current for the regulator). When active, the micro wakes up and performs the necessary tasks before going back to sleep. Each unit comprises two PCBs: a lower control board which hosts the battery, micro and most other components, and an upper board which hosts either the reed switches (sender unit) or the display LEDs (receiver unit). All boards are the same shape and size and fit snugly into the sealed boxes, so only the top board is visible through the clear lid. Basic operation Fig.1: how the sensor unit is arranged. It’s mounted on a platform and is activated by a magnet on the underside of an arm that’s attached to the rudder shaft. internal battery and use that as a power source instead. The UHF link makes installation easy; there is no need to run wires from the rudder to the helm which can be a major task in a typical large power boat. Design concept The first aspect we considered was how to sense the rudder position. There are four obvious sensor types to choose from: a rotary switch, a potentiometer, an optical sensor or reed switches. In each case, either the sensor needs to be attached to the rudder shaft or an arm must be attached to the shaft with the sensors arranged in an arc above or below it, so that the arm triggers one at a time. Rotary switches and potentiometers tend to wear out fairly quickly with continuous use and they can also be fouled by water, grease or dirt in a marine environment, unless they are fully sealed. An optical sensor is a better choice but is the most power-hungry 64  Silicon Chip option and it also requires the most complicated wiring, as both the light source(s) and sensor(s) require power. So we settled on reed switches, with a magnet attached to a cranked arm that is mounted on the rudder shaft. Seven reed switches are arranged in an arc below the arm so that as the arm moves, the magnet passes over them, closing each reed switch in turn. Fig.1 illustrates this arrangement. While it is possible to design these circuits using discrete logic and special-purpose ICs (in fact, we initially tried to do just that), there are several advantages to a microcontroller-based solution. First, if we use a microcontroller in each unit, fewer parts are required. Since we want to fit the display unit into a small box with an internal battery (so it’s easily portable), this is important. Also, because the microcontroller in the sensor unit can drive current through the reed switches intermittently, the battery drain can be kept very low. For an overview of how the two units are configured, refer to Fig.2, the block diagram. The sensor unit (left) contains the reed switches for rudder position sensing and the microcontroller to monitor them. When the switch state changes, the micro powers up the 433MHz transmitter module and sends a data packet containing the new position. This packet is amplitude shift keyed (ASK) and bi-phase encoded. The receiver/display unit (right) is portable and only listens for packets when it is switched on. When it receives a valid packet, the microcontroller decodes it and extracts the new rudder position. It then displays this position by determining which row of high-brightness LEDs is lit. The display unit incorporates a boost regulator. This is necessary to drive the series strings of five LEDs that form the main display. With a typical forward voltage of around 2V, at least 10V is required to drive each string (slightly more due to the 100Ω series current limiting resistor they share). The boost regulator develops roughly 12V at 20mA when the LEDs are lit, from a nominal 6V battery (it can operate down to about 3V). It can also run off an external 12V supply, in which case very little or no boosting is needed. In this case, a series resistor in the power supply input ensures that the LED voltage doesn’t exceed 12V, even if the supply voltage is up to 14.8V (eg, when a lead-acid battery is on charge). Note that while the wireless modsiliconchip.com.au LED DISPLAY RUDDER ARM WITH MAGNET S N MICROCONTROLLER (IC1) REED SWITCHES 433MHz TRANSMITTER 433MHz RECEIVER BATTERY MICROCONTROLLER (IC2) DECODER/ DRIVER (IC3) BATTERY BOOST REGULATOR Fig.2: this block diagram shows how the sensor and receiver units are configured. The reed switch outputs are processed by microcontroller (IC1) which then powers up the 433MHz transmitter module to send a 16-bit data packet on the new rudder position. This signal is picked up by receiver and processed by another microcontroller (IC2). This then drives a LED display (consisting of series LED strings) via decoder/driver IC3. ules are referred to as operating at 433MHz, the actual frequency band used is 433.05-434.79MHz. Sensor unit details The micro in the sensor unit is in low-power “sleep” mode almost all the time. Its 32kHz watchdog timer (WDT) is continuously running and this “wakes it up” several times a second (maybe it sleeps quite poorly!) to check the reed switch state. To do so, it turns on an internal pull-up current source for each input and checks the voltage. The current sources are then immediately disabled and remain off until the next time, to conserve power. Further action is only taken if the switch states differ from the previous reading. Otherwise, the period the micro spends running is very short and the power consumed during these periods is negligible. When a change in reed switch state is detected, the 433MHz transmitter module is powered up. Several 16bit packet pairs are transmitted with a short delay between each, in case interference corrupts one or more of the packets. Each packet pair encodes the updated rudder position, battery charge state and a unique identifier number, which is randomly generated when the battery is inserted. Once five complete packets have been sent, the transmitter is shut down and the device goes back to sleep until another rudder movement occurs. Packet protocol The format of the 16-bit data packets is shown in Fig.3. The bi-phase data is encoded by the microcontroller before being sent to the transmitter module, which modulates the amplitude of its 433MHz RF output accordingly. Each packet contains 14 bits of data siliconchip.com.au along with two start bits. With bi-phase encoding, a zero is encoded with one level change between bits (low-to-high or high-to-low) while a one is encoded the same way but with an additional level change in the middle of the bit. The advantage of bi-phase encoding is that the bit timing and the data are encoded together, so the transmitter and receiver can re-synchronise the timing for each bit. The receiver records the signal level one quarter and three quarters of the way through each encoded bit and if they differ, it records the bit as a one. It also times the level changes before and after this, to determine when to sample the next bit. The first data bit value determines the meaning of the following three bits. If this first bit is a zero then the next three encode the rudder position, with 0-6 indicating one of the seven possible positions and seven indicating that the centre reed switch has opened but no other switches have closed. This is used to indicate whether the rudder is precisely centred. If the first data bit is instead one, then the following three bits encode the transmitter’s battery state. Zero means that it is fully discharged, while PACKET RUDDER START TYPE POS. OR BITS 0 or 1 BATTERY RAW DATA BIPHASEENCODED DATA TO TRANSMITTER MODULE seven indicates full charge. In either case, the next eight bits contain the transmitter’s unique identifier (ID), which is generated based on random noise sampled by the ADC module. This number does not change unless the battery is removed. The receiver remembers the transmitter’s ID and ignores any packets from transmitters with different IDs, until it too is power cycled. Finally, there are two checksum bits which are the bottom two bits of the total number of ones in the transmission (ignoring the start bits and the checksum). This is similar to parity and it allows the receiver to detect if any single data bit has been scrambled during transmission (or in some cases, when multiple bits are affected). If the checksum does not match the received data, the packet is ignored. This reduces the chance of an incorrect display as the result of interference or marginal reception. Display unit details When it is not in use, the micro in the display unit is in low-power sleep mode and so the drain on the battery is minimal. When the single pushbutton TRANSMITTER UNIQUE ID (8 bits, 256 combinations) CRC-2 1 1 0 1 0 0 0 1 1 1 0 1 0 0 1 0 32 x 200s = 6.4ms Fig.3: the 16-bit data packet format. The data is bi-phase encoded and each packet contains two start bits and 14 bits of data. Bits 4-6 encode either the rudder position or the battery state, depending the state of the first data bit (0 = rudder position, 1 = battery state). July 2011  65 Table 1: Battery Voltage Jumper Options Battery type........................................................................................................ JP1 pins shorted Four non-rechargeable AAA (nominal 6.0V)........................................................................1&2 Four rechargeable AAA (nominal 4.8V)................................................................................3&4 12V lead-acid (nominal 12.9V).............................................................................none (or 2&3) is pressed, the micro wakes up and activates the boost regulator, which it controls via software. This generates power for the LEDs (12V) and the 433MHz receiver module (5V, derived from the 12V rail via a linear regulator). Initially, only the battery state LED(s) are lit (indicating the unit’s own battery voltage) and it waits for a data packet. Upon reception, assuming that it is valid, the display is updated to show the new rudder position. The display remains in this state until the rudder moves again and a new packet is received, or the unit is shut off (either manually or through a long period of inactivity). Since the transmitter’s battery state is sent at the same time as the updated rudder position, this can be shown on the display unit. It is distinguished by the micro flashing the battery level LEDs while it is being displayed. After a few seconds, the flashing ceases and the display unit’s own battery state is once again shown instead. If no new packets are received for 10 minutes and the button has not been pressed, the unit automatically shuts down to conserve battery power. It can also be turned off by holding down the pushbutton for about one second. Short presses on the button cycle through three possible LED brightness settings, which suit indoor use and outdoor use, with and without direct sunlight. On the lower brightness settings, the battery lasts longer. One additional feature we have hinted at helps you to tell whether the rudder is dead centre. When the magnet is moved away from the centre, the middle reed switch opens before any of the adjacent switches close. In this case, we don’t know which way the rudder has moved, only that it is no longer centred. Taking advantage of this, the middle (yellow) row of LEDs initially flashes when the central reed switch is closed. When it opens, a packet is transmitted which causes the flashing to cease. If the rudder is moved back to the centre 66  Silicon Chip again, the middle switch closes and so the flashing resumes. Power supply options As stated, both units can be operated without external power connections, using their internal battery only (four AAA cells). These can be rechargeable and with an appropriate connector, can be recharged without having to open the unit up. Since the transmitter unit’s battery should last more than a year, alkaline cells are a practical proposition and the unit can be opened to replace them. However, the batteries in the display unit only last a few hours if it is used at maximum LED brightness. So in this case, either external power or low self-discharge NiMH batteries recharged from 12V are the most practical options. External power is practical for the transmitter, since it does not move and is usually located near a 12V lead-acid battery (its load on that battery would be minimal). On a boat with a single helm position, the receiver unit could be hard-wired too, although it’s more flexible to run it from its internal battery. If a charge connector is used for either unit, it should ideally be a sealed type, to prevent moisture ingress. If you use a regular connector, we recommend applying silicone sealant on the inside once it has been installed, to reduce the chance of water entering the enclosure. The sensor unit has provision for a PCB-mount DC connector. If this is used, a hole must be cut into the side of the box. This is not recommended if there is any possibility of water being present where it is mounted. Battery life For either module, when the micro is in sleep mode, the continuous 15µA current draw works out to around 473mAh/year. At this rate, four 900mAh NiMH AAA batteries should last about two years. Rechargeable cells must be low self-discharge types or else their own internal discharge will be much higher than this and they will go flat if left uncharged for more than a few weeks. Good-quality alkaline cells generally contain more energy than NiMHs so they should last even longer than two years. The sensor unit’s current increases to 15mA for about 100ms when the rudder position changes. This equates to an energy consumption of around 1mAh for every 2400 rudder position changes. If you take two trips a week and each trip involves 1000 position updates, that means a drain of just 43mAh/year, so rudder movements don’t really figure into the battery life. For the display unit, the situation is more complicated. Driving the highbrightness LEDs can consume 100mA or more continuously, depending on battery voltage and brightness setting. At this rate, with similar cells as we have described above, we would expect 6-9 hours of use per charge. Due to internal resistance and falling battery voltage, the battery life at full LED brightness will be more like 2-3 hours. As you would normally only turn the unit on when leaving the marina (or dock) or returning to it, that should be more than enough for a single trip. It’s probably a good idea to recharge the cells after each outing. It can be kept on trickle charge when it is not in use, so it’s always ready to go. When the display unit is switched off, the micro consumes about the same power as the sensor unit does. So a fully-charged battery will lose about half its charge per year if left untouched. Sensor circuit description The circuit for the sensor unit is shown in Fig.4 and the highlighted section shows the reed switches on the upper board. The battery holder for the four AAA cells is on the lower board. They can be trickle charged from 12V via CON1 or CON2, depending on which is installed. CON1 is a 2-way terminal block which can be wired to a separate chassis power connector, while CON2 is a PCB-mount DC connector. The same connectors can be used for permanent power if the unit is hardwired. When trickle charging the battery, the 390Ω resistor limits the charge siliconchip.com.au siliconchip.com.au K A LED 1.5k 3 4 5 6 7 8 9 10 11 12 3 4 5 6 7 8 9 10 11 12 K 2011 SC  REED SWITCHES ON UPPER BOARD *CHANGE VALUE TO 220 0.5W IF HIGH CAPACITY NiMH AAA CELLS ARE USED, OR TO 100 0.5W IF 12V EXTERNAL POWER IS USED PERMANENTLY. S7 S6 S5 S4 S3 S2 S1 CON2 RUDDER POSITION INDICATOR SENSOR UNIT 1 2 1 2 CON3 A CON5 100nF K ZD1 16V BATTERY B1 (6V) CON1 A 16 6 1N5819 AGND A 1.5k 11 PA7 GND IC1 ATTiny861 PB4 8 PB5 9 PB6 PB1 PB2 PB3 1 2 3 4 7 PB0 PA4/ADC3 14 20 19 PA1 17 PA3/AREF 18 PA2 13 PA5 12 PA6 PA0 K  LED1 2V 82k B A E ZD1 K Q1 BC547 C B 1.5k E C 12k Q2 BC327 2 VR1 5k TP1 100nF 10 5 15 RESET Vcc AVcc 100nF 100F GND OUT IN A (FAST BLOW) Fig.4: the sensor circuit is based on microcontroller IC1, an ATTiny861. It decodes the reed switch outputs on its PB0-PB6 ports, powers up the 433MHz transmitter module from its PA0 & PA1 outputs and sends data to the transmitter from port PA2. A 3V rail to power IC1 is derived via 3-terminal regulator REG1, while PA7 turns on transistors Q1 & Q2 as required to sample the battery voltage at port PA4/ADC3. JP1 is used to select the battery type. OUT GND IN E 1 4 433MHz TX MODULE 3 100nF LM2936Z B C BC327, BC547 4 3 BATTERY 2 VOLTAGE 1 JP1 CON4 ANTENNA WIRE +3V 100 Vcc REG1 LM2936Z-3.0 K D1 1N5819 F1 500mA 390* 12V + DC IN – current to about 20mA. Its value can be reduced if high-capacity cells are used, allowing them to charge faster. For example, if 900mAh AAA cells are used, a 220Ω 0.5W resistor increases the charge current to around 40mA. In either case, the charge time for a completely flat battery is around 24 hours. In practice, the battery will normally be only partially discharged so eight hours should be sufficient. If the module is to be powered permanently from a 12V supply (eg, an external lead-acid battery), use a 100Ω resistor instead. A 500mA fuse protects the power source from a board fault. Schottky diode D1 provides reverse polarity protection (it drops less voltage than a standard diode). Zener diode ZD1 protects the circuit from voltage spikes which may occur when a lead-acid battery is on charge (due to load dumps and so on). If the spike is particularly bad, the fuse will blow, protecting the unit from damage. REG1 regulates the incoming voltage down to 3V (or 3.3V depending on the exact type used). Microcontroller IC1 and the 433MHz transmitter module run off this voltage. The LM2936Z regulator specified is designed for automotive use, so it is robust enough for a marine application. It has a quiescent current of below 15µA with a light load such as a micro in sleep mode. The micro draws less than 1µA in sleep mode, hence the low current drain when the device is idle. Regulator stability is ensured by a 100nF input bypass capacitor and a 100µF output filter capacitor. While low drop-out regulators require capacitors with an ESR value within a certain range, the range in this case is very large (0.01-8Ω) so virtually any 100µF electrolytic capacitor is suitable. REG1’s 3-3.3V output is also bypassed with a 100nF capacitor. The microcontroller (IC1) is an ATTiny861. These are easy to obtain at a reasonable price and have all the necessary features for this application: low power consumption in sleep mode, plenty of program (flash) memory, an analog-to-digital converter (ADC) for battery voltage monitoring and enough digital I/O pins for our purposes. The micro consumes less current at 3V or 3.3V than at 5V. Its ADC power supply (AVcc) is filtered with a 100Ω resistor and 100nF capacitor, removing July 2011  67 68  Silicon Chip siliconchip.com.au (FAST BLOW) F2 500mA A ZD2 16V K D2 1N5819 A K 100nF Vcc 1 2 3 7 14 433MHz RX MODULE 4 47F IN 16 15 1.5k 12k +12V K C E Q5 BC337 A D3 1N4148 B 1.5k L1 100H C Q4 BC327 E C 1.5k 1k E Q3 BC547 12k B 4 82k 100F JP2 B 2.2k 1 BATTERY 3 VOLTAGE 2 GND OUT RUDDER POSITION INDICATOR DISPLAY UNIT CON9 ANTENNA WIRE 100nF 100F GND OUT REG3 78L05 +12V +5V IN REG2 LM2936Z-3.0 11 9 8 13 12 IC2 ATTiny861 A K 16 6 ZD1 AGND PB3 PB2 PB1 PB0 PB4 GND PA7 ADC9/PB6 OC1D/PB5 ADC4/PA5 PA6 18 PA2 20 PA0 14 PA4 PA1 PA3/AREF 13 12 3 4 A A 14 2 D3 D2 P3 P2 P1 P0 K K 8 GND +12V +5V O9 O8 O7 O6 O5 O3 O2 O1 O0 IC3 O4 74LS145 16 Vcc TO POWER SWITCH CON8 VR2 5k +5V 15 2V TP2 1 7 17 19 100nF 100 10 5 15 RESET Vcc AVcc 100nF +3V 1 E 11 10 9 7 6 5 4 3 2 B C BC327, BC337, BC547 100 100 IN OUT GND LM2936Z 12 11 10 9 8 7 6 5 4 3 2 1 TO LEDS CON7 Fig.5: the receiver circuit also uses an ATTiny861 microcontroller (IC2). The data from the 433MHz receiver module is fed to its PA7 port and processed, with the decoded binary data appearing at ports PB0-PB3. These drive a 74LS145 4-to-10 binary decoder with open collector outputs which in turn drive the LEDs on the display board (see Fig.5) via connector CON7. Inductor L1, diode D3, transistor Q5 and the 47μF capacitor at D3’s cathode form a boost converter which is controlled from IC2’s PA6 port using transistors Q3 & Q4. This provides a +12V rail for the LED display and drives REG3 to derive a +5V rail for IC3. SC 2011 BATTERY B2 (6V) 390* *CHANGE VALUE TO 220 0.5W IF HIGH CAPACITY NiMH AAA CELLS ARE USED, OR TO 100 0.5W IF 12V EXTERNAL POWER IS USED PERMANENTLY. CON6 12V + DC IN – A LED1 A LED2  A LED3 K LED4 A CON10 1 2 3 LED6 A LED8 A K A LED12 K K K A A A A LED15 K  A LED16 LED17 K A K A  LED22 A A LED26 LED28  A LED29 A A K A  A  LED31 K K  K  LED30 LED27 K A K  K K   LED25 A  LED23 K K  K K A  LED24 LED21 A   LED18 LED20 K  K A   LED13  K  K  LED19 LED14 tive divider and then to IC1’s ADC3 pin. When PA7 is high it also drives a high-brightness LED (LED1), indicating that the transmitter is active. Ports PA0 & PA1 also supply power to the 433MHz transmitter (Tx) module. With a 3V supply, the transmitter module receives at least 2.8V (0.2V is lost due to the internal resistance of the micro’s output transistors). When the transmitter is powered up, output PA2 is used to send the data burst to the transmitter module. When the transmitter is not powered, PA2 is kept low. The antenna is a ¼-wavelength whip, measuring about 164mm and soldered to a PC pin on the lower board. This gives a useful range of approximately 20 metres, even with the user’s body between the transmitter and the receiver. This can vary somewhat, depending on the obstacles between the two units and the relative antenna orientation. A K  LED11 A  LED9 LED10 K  K K   LED7 A  LED5 A K   A K  K 4 5 6 7 8 9 10 A LED32 11 12  K A LED33  A LED34 K FROM CONTROL BOARD SC 2011  K Display unit (+2V) (+10V) RUDDER POSITION INDICATOR LED ARRAY PCB CATHODE DOT LEDS K A Fig.6: the LED array board consists of seven strings of series LEDs (LEDs1-31) to give a visual indication of rudder position plus three LEDs (LEDs32-34) to indicate the battery condition. It’s driven from CON7 of the receiver board. digital switching noise injected by the other circuitry and hence improving ADC conversion stability. The reed switch sensors are connected to the PORTB pins PB0-PB6 (pins 1-4 & 7-9), via pin header socket CON5 on the upper board. IC1 has internal current sources for each reed switch which can be turned on and off by software. Each has a source impedance of 20-50kΩ, sourcing 60-150µA when enabled. IC1’s PA0, PA1, AREF, ADC3 and PA5-7 (pins 11-14, 17 & 20) are used to monitor the battery voltage. A jumper shunt placed on pin header JP1 tells the micro what type of battery is being used, so that it knows what voltage range to expect. There are three possible options, indicated by the different combinations shown in Table 1. The microcontroller (IC1) reads the jumper position using pins PA5 and PA6. PA0-1 and trimpot VR1 provide the ADC reference voltage (AREF). This siliconchip.com.au is set to 2V. No current flows through VR1 unless PA0 and PA1 are sourcing current (ie, they are driven high to +3V), saving power when the ADC is not in use. The ADC is only used for brief periods so the circuitry to supply AREF is only active during this time (and for one minute after power is applied, allowing VR1 to be trimmed). The battery/supply voltage is sampled at the ADC3 pin, via a 12kΩ/1.5kΩ divider. This converts the battery voltage (0-18V) into a range which can be handled by the ADC (0-2V). As with the AREF divider, current does not flow through it unless the battery voltage is actually being read, to save power, as controlled by pin PA7. This is driven high while ADC3 is being sampled, turning on NPN transistor Q1 and sinking current from the base of PNP transistor Q2, turning it on as well. This allows current to flow from the battery (after the fuse and diode D1) into the 12kΩ/1.5kΩ resis- Figs.5 & 6 show the circuit for the receiver unit. Fig.5 depicts the lower board circuitry, while Fig.6 shows the LED array circuit on the top board. The power supply for the receiver unit is identical to that used in the sensor unit, except there is no provision for an on-board DC connector. That’s because this unit is more likely to be exposed to spray and such a connector would be too likely to allow water ingress. As for the sensor unit, the 390Ω resistor in series with CON6 should be changed for use with high-capacity cells or permanent 12V power. This is important, since the receiver unit can draw significantly more current than the sensor unit. This resistor must not be omitted, otherwise the LEDs could be over-driven if the 12V battery supply is on charge. Microcontroller IC2 is the same type as before but its role is a little different. The PORTB pins PB0-PB3 drive IC3, a 74LS145 4-to-10 binary decoder with open collector outputs. This in effect gives IC2 10 open-collector outputs, one of which can be driven low at any given time (or they can all be turned off). The binary decoder’s outputs can handle voltages up to 15V (although the off-state leakage current can be significant even at 10V; enough to dimly light LEDs). Each output can sink up July 2011  69 Parts List: Rudder Position Indicator SENSOR UNIT 1 PCB, code 20107111, 98.5 x 68mm 1 PCB, code 20107112, 98.5 x 68mm 1 sealed ABS box with clear lid, 105 x 75 x 40mm (Altronics H0321) 1 433MHz transmitter module (Jaycar ZW3100, Altronics Z6900) 1 2-way mini terminal block, 5.08mm pitch (CON1) 1 PCB-mount DC connector (optional*) (CON2) 2 M205 fuse clips 1 M205 500mA fast-blow fuse 1 5kΩ sealed horizontal trimpot (VR1) 1 4 x AAA PCB-mount battery holder (Jaycar PH9270) 2 M2 x 6mm machine screws and nuts (Element14 507118/1419445) 4 AAA cells (Alkaline or NiMH) (optional*) 1 4-way pin header (JP1) 1 jumper shunt (for JP1) 1 40-pin header socket, 2.54mm pitch (cut down to 12-way [CON3] & 4-way sockets) 1 20-pin DIL socket 2 PC pins 1 200mm length 1.5mm diameter enamelled copper wire 1 300mm length 0.7mm diameter tinned copper wire 7 glass-encapsulated NO reed switches (Jaycar SM1002, Altronics S5150A) 1 reed switch trigger magnet 2 15mm tapped Nylon spacers 2 M3 x 20mm machine screws 2 M3 nuts 1 small crimp wire joiner 1 small IP67-rated chassis connector* Semiconductors 1 ATTiny861 microcontroller programmed with 2010711A.hex (IC1) (Altronics Z5110 or Futur­ lec ATTINY861-20PU) 1 LM2936Z-3 ultra-low quiescent current linear regulator (REG1) (Digikey**) 70  Silicon Chip 1 BC547 NPN transistor (Q1) 1 BC327 PNP transistor (Q2) 1 1N5819 Schottky diode (D1) 1 16V 1W zener diode (ZD1) 1 high-brightness red LED (LED1) Capacitors 1 100µF 16V electrolytic 4 100nF MKT Resistors (0.25W, 1%) 1 82kΩ 1 220Ω 0.5W* 1 12kΩ 1 100Ω 0.5W* 3 1.5kΩ 1 100Ω 1 390Ω* * Depends on power supply chosen, see text ** Alternative part LM2936Z-3.3 (Element14 1564641) DISPLAY UNIT 1 PCB, code 20107113, 98.5 x 68mm 1 PCB, code 20107114, 98.5 x 68mm 1 sealed ABS box with clear lid, 105 x 75 x 40mm (Altronics H0321) 1 433MHz receiver module (Jaycar ZW3102, Altronics Z6905) 1 2-way mini terminal block, 5.08mm pitch (optional*) (CON6) 2 M205 fuse clips 1 M205 500mA fast-blow fuse 1 5kΩ sealed horizontal trimpot (VR1) 1 100µH 250mA axial RF inductor 1 4 x AAA PCB-mount battery holder (Jaycar PH9270) 2 M2 x 6mm machine screws & nuts (Element14 507118/1419445) 4 AAA cells (alkaline or NiMH) 1 4-way pin header (JP2) 1 jumper shunt (JP2) 1 12-way header socket, 2.54mm pitch (or cut down a 40-way socket) (CON7) 1 20-pin DIL socket 1 16-pin DIL socket 2 PC pins 2 15mm tapped Nylon spacers 2 M3 x 20mm machine screws 2 M3 nuts 1 small IP67-rated chassis connector* 1 small IP67-rated momentary pushbutton switch (Jaycar SP0656, Altronics S0961) 14 ultra-bright 1206 or 1210 SMD red LEDs (Digikey 754-1165-1ND) 14 ultra-bright 1206 or 1210 SMD green LEDs (Digikey 754-11621-ND) 6 ultra-bright 1206 or 1210 SMD yellow LEDs (Digikey 754-11661-ND) 1 200mm length 1.5mm diameter enamelled copper wire 1 300mm length 0.7mm diameter tinned copper wire 1 50mm length red light duty hookup wire 1 50mm length black light duty hookup wire 1 100mm length blue light duty hookup wire 1 small crimp wire joiner Semiconductors 1 ATTiny861 microcontroller programmed with 2010711B.hex (IC2) (Altronics Z5110 or Futur­ lec ATTINY861-20PU) 1 74LS145 4-to-10 binary decoder (IC3) 1 LM2936Z-3 ultra-low quiescent current linear regulator (REG2) (Digikey**) 1 78L05 5V linear regulator (REG3) 1 BC547 NPN transistor (Q3) 1 BC327 PNP transistor (Q4) 1 BC337 NPN transistor (Q5) 1 1N5819 Schottky diode (D2) 1 1N4148 small signal diode (D3) 1 16V 1W zener diode (ZD2) Capacitors 2 100µF 16V electrolytic 1 47µF 16V electrolytic 4 100nF MKT Resistors (0.25W, 1%) 1 82kΩ 1 390Ω* 2 12kΩ 1 220Ω 0.5W* 1 2.2kΩ 1 100Ω 0.5W* 3 1.5kΩ 3 100Ω 1 1kΩ * Depends on power supply, see text ** Alternative part LM2936Z-3.3 (Element14 1564641) siliconchip.com.au to 80mA. Seven of the outputs (pins 1-7) are used to drive 5-LEDs strings, to indicate the rudder position, while the three remaining outputs (pins 8-10) drive individual LEDs to form a simple battery meter. The series LED strings have a common anode which is connected to the 12V rail via a 100Ω current-limiting resistor. The total forward voltage for each string is around 10V (5 x 2V), so the maximum DC current per LED is around (12V - 10V) ÷ 100Ω = 20mA. In practice, due to additional loss­ es, such as the saturation voltage of the 74LS145’s output transistors, the LEDs run at a slightly lower current than this. However, because we have specified very efficient LEDs, they are still very bright. It’s a compromise because we if we ran them at a higher current, they would dim somewhat as the battery discharged. That’s because the boost regulator generating the 12V rail becomes less effective as the boost ratio increases. A 5V rail is derived from the 12V supply using regulator REG3. This rail powers both IC3 and the 433MHz receiver module. This is a little wasteful of energy (its efficiency is 5/12 = 42%) but it allows us to operate the receiver even if the battery voltage is well below 5V. That can easily be the case with four standard cells, especially if they are rechargeable. Note that REG3 has a 100µF output filter capacitor and this doubles as a bypass capacitor for IC3. The battery indicator LEDs run off the 5V rail, since they are not connected in series. A second 100Ω current limiting resistor is shared between them; they run at a higher current of around (5V - 2V) ÷ 100Ω = 30mA. Because only one of IC3’s outputs can be active at any time, the battery LEDs must be multiplexed with the rudder display LEDs. Running them at a higher current allows them to be driven at a low duty cycle, keeping the rudder position LEDs as bright as possible with a high duty cycle. ADC9. This allows closed loop control. Transistor Q5 is driven with a 187.5kHz PWM signal from output pin OC1D (pin 8) via a 1kΩ resistor. If the 12V rail is too low, IC2 increases the PWM duty cycle to bring it up and vice versa. PNP transistor Q4 allows the boost regulator to be switched off by interrupting the battery current to it. This is important since a boost regulator’s output voltage can never be less than one diode drop below its input voltage and we need to turn the 12V rail fully off to conserve power in sleep mode. Q4 is driven by NPN transistor Q3 via a 2.2kΩ resistor, with Q3 in turn driven from output pin PA6 of IC2 via an 82kΩ current-limiting resistor. When PA6 is low, Q3 is off and so is Q4, so no voltage is applied to the boost regulator. Q3 and Q4 also control the current flow through the resistive divider which is used to monitor the battery voltage. This involves another 12kΩ/1.5kΩ divider, the output of which is monitored by the ADC4 port of IC2. This is done so that the power consumption is reduced when the unit is not operating. Boosted supply Battery monitoring The boost regulator which develops the 12V supply consists primarily of inductor L1, NPN transistor Q5, diode D3 and a 47µF capacitor (at D3’s cathode). The voltage across the 47µF capacitor is fed back to the micro via a 12kΩ/1.5kΩ resistive divider, to pin The display unit has similar battery monitoring circuity to the sensor unit. The connections are slightly different though; for example, the trimpot (VR2) to set AREF (VR2) is now permanently connected to +3V rather than ground, so the other end must be pulled to siliconchip.com.au This photo shows the lower board used in the sensor unit. It carries the microcontroller and its support circuitry plus the 433MHz transmitter module (top right). ground by IC2’s PA1 port to allow the ADC to operate. PA1 also serves as a digital input to detect presses of the pushbutton switch wired to CON8. In this role, VR2 acts as a pull-up resistor and pressing the button pulls PA1 low, which is detected by the microcontroller. If the power is off, this triggers an interrupt which wakes the micro up. If it is already awake, it uses an internal timer to determine the length of the press; longer presses send it to sleep while shorter presses step through the LED brightness settings. As with the sensor unit, a jumper shunt on 4-pin header JP1 determines the expected battery voltage – see Table 1. When the 433MHz receiver (Rx) has power (ie, when the boost regulator is switched on), data is fed through to PA7 (pin 11) of IC2. Since the receiver runs off 5V and the micro off 3V, the receiver’s digital output can swing up above IC2’s power supply voltage. This causes PA7’s clamp diode to conduct and the 1.5kΩ series resistor limits the current which flows under this condition. As with the transmitter, the receiver’s antenna is soldered to a PCB pin on the lower board. It is orientated so that the unit can be held with the LEDs facing the user while it is operating. That’s it for this month. Next month, we will give the full assembly details and explain how to set up and test the two units. We will also give instructions on installing them in a boat. SC July 2011  71 Getting to grips with . . . Amplifier Stability & Compensation By NICHOLAS VINEN Elsewhere in this issue, we present the updated Ultra-LD Mk.3 Audio Power Amplifier Module. It has a new frequency compensation arrangement which helps it achieve even lower distortion than the Mk.2 version. In this article, we explain why amplifier frequency compensation is necessary and how it works. A MPLIFIER FREQUENCY compensation and stability are complicated topics about which books can be (and have been) written. These issues are important when designing or modifying audio circuitry, yet they are widely misunderstood. Here’s a 72  Silicon Chip brief summary of the relevant fundamentals. Negative feedback Stability and compensation relate to systems with negative feedback. But initially, let’s consider a power amplifier (or op amp) with its feedback network disconnected. We connect the inverting input to ground and apply a small signal to the non-inverting input, as shown in Fig.1(a). This is known as “open loop” operation. Nominally, the output voltage is the siliconchip.com.au difference in input voltages multiplied by the open loop gain which can be as high as one million (120dB). So a 1µV RMS input signal could result in a 1V RMS output signal. Amplifiers operated in this mode aren’t very linear which is another way of saying that they produce a significant amount of harmonic distortion. Also, this is far too much gain for most purposes and it varies from device to device. Closed loop operation If we feed a portion of the output signal back to the inverting input to apply negative feedback, the amplifier now operates in “closed loop” mode. The simplest method is to connect the output directly to the inverting input, as shown in Fig.1(b). Assume for a moment that we have an “ideal” op amp. It has zero input bias current, infinite open loop gain at all frequencies, zero output impedance and no phase shift (ie, no signal delay) from input to input. If we configure it as in Fig.1(b), whenever the input signal swings positive, the input voltage difference (“+” - “-”) becomes positive. This is amplified by a huge factor and so the op amp’s output swings towards the positive rail. However, it stops when the output voltage equals the input signal voltage, as the input voltage difference is then zero. Similarly, if the input signal swings negative, the input voltage difference becomes negative so the output voltage decreases, tracking the input signal perfectly. Hence, this circuit is known as a “voltage follower”. Now consider what happens with the same circuit if we use a real op amp, which has a very high but finite open loop gain, say 1,000,000 times. We then apply 0V DC to the non-inverting input followed by a step change to +1µV. Shortly after that change, the output swings positive, towards 1V (ie, 1µV x 1,000,000). But again, this positive slewing slows and then stops before the output gets to 1V because the inverting input voltage approaches that of the non-inverting input. The differential input voltage approaches but does not reach zero. The output (and thus the inverting input) settles at around 0.999999µV. We know this because the input voltage difference is then 0.000001µV siliconchip.com.au INPUT OUTPUT 1 V RMS 1V RMS OPEN LOOP GAIN = 120dB (1,000,000) A OP AMP IN OPEN LOOP MODE INPUT OUTPUT 1 V RMS 0.999999 V RMS EFFECTIVE INPUT VOLTAGE = 0.000001 V B OP AMP IN VOLTAGE FOLLOWER MODE INPUT OUTPUT 0.1 V RMS 27k EFFECTIVE INPUT VOLTAGE = 0.000001 V 0.999990 V RMS 3k C OP AMP WITH A NON -INVERTING GAIN OF 10 Fig.1: (A) an op amp operated in open loop mode, with a large but ill-defined gain and poor linearity; (B) an op amp configured as a voltage follower, operated in closed-loop mode with a gain of one; (C) closed loop operation with a fixed gain of 10 (the output accuracy and bandwidth are reduced compared to unity gain). INPUT SIGNAL FEEDBACK SIGNAL LOW FREQUENCY: PHASE SHIFT <180° – NO POLARITY INVERSION INPUT SIGNAL FEEDBACK SIGNAL HIGH FREQUENCY: PHASE SHIFT >180° – POLARITY INVERSION Fig.2: (top) at audio and low supersonic frequencies, amplifier feedback is in phase with the input signal and so negative feedback operates normally. At high frequencies (bottom), the feedback signal phase shift (delay) increases and eventually the feedback becomes positive, thus destabilising the amplifier. and this, multiplied by the open loop gain, is 1µV (ie, almost exactly the output voltage). So in reality, the output tracks the input with an error factor of 1 ÷ open loop gain. Higher open loop gain means better accuracy, explaining why ideal an op amp would have infinite open loop gain. AC signal non-linearities are also reduced by the same factor (at low July 2011  73 Bode Plot for Ultra-LD Mk3 Front-end, No Compensation Open Loop Gain Feedback (Gain=26dB) Phase Shift 100 Gain (dB) 0 30 80 60 60 90 40 120 20 150 0 180 -20 210 100 1k 10k 100k 1M 10M Phase (Degrees) 120 100M Fig.3: gain and phase (Bode plot) for a simple twostage differential amplifier circuit with no Miller capacitor. It is marginally stable with a gain of 20 and not stable at unity gain. Note that there are two different vertical axes. Frequency (Hz) frequencies), vastly improving the distortion performance compared to open loop operation. At higher frequencies, the distortion cancellation becomes much less effective for various reasons, some of which will be explained later. Fixed gain operation We can achieve a fixed gain by dividing down the output voltage before applying it to the inverting input. Fig.1(c) shows how the gain is set to 10. Now let’s imagine a +0.1µV step change is applied to the non-inverting input (one tenth that of the previous example). Again, the output swings positive. This time, the output reaches 0.999990µV before the inverting input settles at about 0.099999µV. Again the open loop condition is satisfied, ie, the input voltage difference (0.000001µV) multiplied by the open loop gain equals the output voltage, more or less. While the input voltage difference and output voltages are the same as the last example, now the output voltage is low by 0.000010µV or 10 times as much. That’s because the output error is divided by the feedback network and so cannot be compensated for as effectively. So for an amplifier with negative feedback, the DC input voltage error is constant and determined by the open loop gain (ignoring input offset and bias errors), while the output error factor is equal to closed loop gain ÷ open loop gain which in this case is 1/100,000. The inverse of this is the feedback factor, ie, open loop gain ÷ closed loop gain. A higher feedback factor means less DC voltage error and less AC signal distortion. Any distortion produced by the amplifier circuit is also divided by the closed loop gain before being fed back to the input for correction. Thus it is the feedback factor which determines V+ Rfb1 Q4 Vin+ Q1 Q2 VinQ5 Q3 V– Fig.4: a 3-stage amplifier schematic which is similar in principle to virtually all class B amplifiers and operational amplifier (op amp) ICs. The key component defining the closed-loop gain bandwidith is the compensation capacitor between the base and collector of Q3. 74  Silicon Chip Stability While the negative feedback is applied virtually instantaneously with respect to audio frequencies, there is a time delay involved. This is due to capacitance and inductance in the amplifier circuit as well as charge storage effects in the transistors. This fixed time delay (true to a first approximation) becomes a problem as the signal frequency is increased. You can see this effect in Fig.2. At low frequencies the delay in the feedback is slight but at a particular high frequency (and higher) the feedback is so delayed that it becomes positive feedback rather than negative. And if the feedback factor is greater than or equal to unity (ie, one) at this frequency, the output signal amplitude builds until it “bounces off” the supply rails (clipping). In other words, the amplifier becomes an oscillator. Typically, the phase shift (ie, the time delay) reaches 180° at a high frequency, around 1MHz or more, and the resulting oscillation causes a variety of problems. A marginally unstable amplifier can operate more or less normally but has increased distortion and dissipation. It will get much hotter than it should because of cross-conduction of the output devices. This occurs because at high frequencies, they can’t switch off fast enough. Apart from that, oscillation in a marginally stable amplifier can cause major RF interference. And if the oscillation is high enough, it will burn out the power transistors, even in the absence of an input signal. So clearly, any oscillation is bad. Preventing oscillation Vout Rfb2 how well distortion is cancelled by negative feedback. If we arrange for the feedback factor to fall with increasing frequency, so that it is below one at the frequency where the phase shift reaches 180°, there won’t be enough positive feedback for oscillation (but possibly still enough for overshoot and ringing in response to an input impulse). The open-loop gain and feedback factor fall with frequency anyway, because the same capacitances and charge storage effects that cause the phase shift also act as low-pass filters on the signal. But this isn’t usually enough to ensure stability. siliconchip.com.au Bode Plot for Ultra-LD Mk3 Front-end, 100pF Miller capacitor 120 Open Loop Gain Feedback (Gain=26dB) Phase Shift 0 100 60 80 60 60 90 60 90 40 120 40 120 20 150 20 150 0 180 0 180 -20 210 -20 210 100 1k 10k 100k 1M 10M 100M Gain (dB) 30 80 Phase (Degrees) Gain (dB) 100 Bode Plot for Ultra-LD Mk3 Amplifier, No Compensation 0 Open Loop Gain Feedback (Gain=26dB) Phase Shift 100 1k Frequency (Hz) siliconchip.com.au 100k 1M 10M 100M Frequency (Hz) Fig.5: Bode plot for the same circuit as Fig.3 but with a 100pF Miller capacitor added. As shown, the phase shift is increased and the open loop gain reduced at low frequencies. It is unity gain stable. To demonstrate this effect, we ran SPICE simulations on the Ultra-LD Mk.3 amplifier circuit described in this issue. To measure the open loop gain and phase shift, we modified the circuit by removing the input and output filtering and disconnecting the feedback loop. The base of Q2 is connected to ground while the test signal is applied to the base of Q1. We used a 0.1mV RMS signal with a DC bias of about +3mV, to make the output swing symmetrically about ground. The result of each simulation is a Bode plot. This is a graph with frequency on the horizontal axis and gain and phase on the vertical axes. One trace shows the open-loop gain in decibels (red) and the other, the phase shift in degrees (blue). We can judge the amplifier’s stability and bandwidth from these plots. (Bode plots are named after engineer Hendrik Wade Bode [1905-1982] who, while working at Bell Labs in the United States in the 1930s, devised a simple but accurate method for graphing gain and phase-shift plots). We have added a third line to each graph which represents the feedback factor for a closed-loop gain of 26dB (green), as this represents the operating conditions of the Ultra-LD Mk.3 (and many other power amplifiers). Because the plots are generated by simulation, they may not be 100% accurate. This is partly because we are not including parasitic capacitance and inductance effects. However, the results are quite similar to those of our prototype circuits, so we can draw useful conclusions, as long as we allow some margin for error. 10k 30 Phase (Degrees) 120 Fig.6: a Bode plot for a complete 3-stage power amplifier with no compensation. It is unstable even with a gain of 20 (26dB) due to the extra phase shift introduced by the output stage. For the output stage, we used transistor simulation models provided by On Semiconductor, which should be quite accurate. Results Fig.3 shows the Bode plot for the amplifier with no output stage buffer (Q10-Q15) and no compensation, ie, with the two 180pF 100V capacitors out of circuit. The output is taken from Q9’s collector. To explain further, Fig.4 shows the stripped down schematic of a typical power amplifier or op amp IC. Q1 & Q2 are the differential input transistors, Q3 (equivalent to Q9 in the Ultra-LD circuit) is the voltage amplifier stage and Q4 & Q5 are the output transistors. The critical component which largely defines the amplifier’s openloop frequency response and phase shift is the capacitor between base and collector of Q3. This is often referred to as a Miller capacitor, which is a reference to the Miller effect of capacitance between the grid and plate of a triode; after John Milton Miller, in a paper published in 1920. Getting back to Fig.3, the left vertical axis shows the gain in decibels and applies to the red (gain) and green (feedback) traces. The right vertical axis shows the phase shift in degrees and applies to the blue trace. The criterion for stability is that the amplifier gain must drop below unity before the phase shift reaches 180°. If the phase is more than 180° with a gain above unity, the amplifier will be unstable. For Fig.3, showing a closed loop gain of +26dB, the feedback factor reaches unity at around 45MHz while the phase shift does not reach 180° so this configuration appears stable. The open loop gain is around 120dB for low frequencies but rolls off from a -3dB point around 40kHz. Phase margin The “phase margin” is computed as 180° - phase shift, at the point where the feedback factor reaches 0dB. In this case it is 30°. The higher the phase margin, the more tolerant the circuit is of additional capacitance at its output, as this increases the phase shift and can destabilise the amplifier. 45° is generally considered sufficient; anything less is regarded as marginally stable. Compare this to Fig.5, which has been taken using a single 100pF Miller compensation capacitor between the base of Q8 and the collector of Q9. The open loop gain and feedback now begin to roll off at a much lower frequency, in fact from below 100Hz. The phase shift has been increased to around 90° below 50kHz (a result of the severe low-pass filter action of the Miller capacitor). Since the open-loop gain is now well below unity at the point where the phase shift reaches 180° (80MHz or roughly the same as for Fig.3), this configuration should be stable for any gain of unity or more. The phase margin is much healthier at around 60°. We can also measure the gain bandwidth for both cases, ie, the frequency at which the open loop gain reaches -3dB. It is around 22MHz for Fig.5 and the bandwidth for a closed loop gain of +26dB (20 x) is just above 1MHz. For the uncompensated circuit (Fig.3), July 2011  75 Bode Plot for Ultra-LD Mk3 Amplifier, Two Pole Compensation 30 100 80 60 80 60 60 90 60 90 40 120 40 120 20 150 20 150 0 180 0 180 -20 210 -20 210 Gain (dB) 100 100 1k 10k 100k 1M 10M 100M Gain (dB) 120 Phase (Degrees) 0 Open Loop Gain Feedback (Gain=26dB) Phase Shift 100 Open Loop Gain Feedback (Gain=26dB) Phase Shift 1k Fig.7: Bode plot for the same circuit as Fig.6 but with a 100pF Miller capacitor added. Once again, the phase shift is increased and the open loop gain is reduced at low frequencies. It is stable with a gain of 20 but not with unity gain. Adding the output buffer Now let’s add the output stage (Q10Q15) of the Ultra-LD Mk.3 module back into the equation. It’s a unity gain stage, ie, simply a current buffer. In an ideal world, it would have no effect on open loop gain or phase shift but this is not actually the case. Compare Fig.6 to Fig.3; the conditions are identical except for the presence of the output stage. It greatly increases the phase shift above 100kHz and so the frequency at which the feedback becomes positive has moved from 500kHz to about 200kHz. The open-loop gain rolls off at a slightly lower frequency, to a steeper slope. So with no compensation, the amplifier is even less stable with the output stage included, due to the additional signal delays. For Fig.7, we add a 100pF Miller capacitor again. This arrangement is very similar to the Ultra-LD Mk.2 76  Silicon Chip 100k 1M 10M 30 100M Frequency (Hz) Frequency (Hz) the gain bandwidth is above 100MHz. Theoretically, the bandwidth for a given gain setting is computed as gain bandwidth ÷ gain. In other words, as the gain is increased, the bandwidth is reduced, unless the compensation arrangement is changed. If we can change the compensation arrangement, we can adjust it to suit the closed-loop gain used, providing maximum bandwidth while maintaining stability. This is the main reason that some op amps provide pins for an external compensation capacitor (those with internal compensation are sometimes available in “decompensated” versions for use with higher closed loop gains). 10k 0 Phase (Degrees) Bode Plot for Ultra-LD Mk3 Amplifier, 100pF Miller capacitor 120 Fig.8: Bode plot for the complete amplifier with 2-pole compensation (compare this to Figs.6 & 7). It is also stable with a gain of 20 but open loop gain at audio frequencies is greatly increased at the expense of a higher phase shift above 3kHz. (August-September 2008) and many other power amplifiers. As with the earlier example (Fig.4), this pushes the feedback inversion frequency up but not as far; it is now around 5MHz. The open-loop gain roll-off is virtually identical to that in Fig.5 except for the sudden drop above 5MHz, due to the transition frequencies of the driver and power transistors (these are specified as 50MHz but that is the -3dB point; the roll-off actually begins at a lower frequency). As can be seen from the graph, for a gain of 26dB, the 100pF capacitor provides sufficient compensation, giving an excellent phase margin of around 80° and a bandwidth of about 1.5MHz. Interestingly, decreasing the closed-loop gain doesn’t yield as much additional bandwidth as we might expect, due to the output stage running out of steam at 5MHz. Two-pole compensation Now we get to the crux of the matter. In the Ultra-LD Mk.3 amplifier described in this issue, we are using a 2-pole compensation arrangement for the first time. This replaces the single Miller capacitor with two series capacitors and a resistor from the “centre tap” to Q9’s emitter. These capacitors can be different values but to simplify construction, they are both 180pF. For those unfamiliar with the term “pole”, in this case it refers to the effect of a single low-pass filter stage. Each low-pass filter pole adds a “knee” to the open-loop gain plot at the point where the frequency response rolls off. The pole also has an additional effect on phase shift. The simulated effect of the 2-pole arrangement is shown in Fig.8. Comparing this to Fig.7 we can see that the open-loop gain and feedback factor both roll off at a much higher frequency than with single pole compensation. The roll-off occurs after a peak, at about 3-4kHz. The gain then initially diminishes at 12dB/octave, rather than the 6dB/octave which is possible with a single pole. The result is that the feedback factor reaches unity at a similar frequency as for the single-pole scheme, despite the much higher corner frequency. The means a significantly greater feedback factor at higher frequencies in the audio band (in some cases by more than 30dB), allowing for better distortion cancellation. However, this benefit is limited by the additional phase shift introduced after the loop gain peak. The phase shift after this peak approaches 180° (nearly 90° from each pole), reducing the benefit of the additional feedback at high audio frequencies. However, our tests show that this scheme still results in much improved distortion cancellation up to 20kHz. The Bode plot does a good job of demonstrating how 2-pole compensation works. Below the gain peak, there is essentially no compensation, as the 2.2kΩ resistor shunts the feedback from Q9’s collector, via the 180pF capacitor, to the negative rail. Above the gain peak, the capacitor impedances drop so the 2.2kΩ resistance becomes less significant and both poles take effect. At very high frequencies, the capacitor impedances are so low that the resistor is taken out of the equation, giving the equivalent siliconchip.com.au Ultra-LD Mk.3 Output Clipping Behaviour, 2 x 180pF Capacitors Ultra-LD Mk.3 Output Clipping Behaviour, 2 x 100pF Capacitors 47.5 47.5 1 20 0 1 Potential (Volts) 30 Potential (Volts) Potential (Volts) 2 2 Output Base of Q8 Compensation Junction 30 1 20 0 1 0 0 -1 -1 150 200 250 300 350 400 150 200 Ensuring stability Looking at Fig.8, you may wonder why we can’t reduce the compensation capacitors somewhat, since we apparently have quite a large phase margin (around 70°) and there is a reasonable gap between the point where the feedback factor reaches unity (900kHz) and where the phase shift reaches 180° (5MHz). This would increase the open loop gain and reduce distortion. We performed this experiment on an Ultra-LD Mk.3 amplifier and examined its behaviour, in order to both confirm the accuracy of these simulations and to answer this question. The physical amplifier behaved essentially as predicted. It was stable during normal operation with ceramic capacitor pairs of 100pF, 120pF, 150pF and 180pF. As we changed the capacitors, the distortion at 20kHz (with 20Hz-80kHz measurement bandwidth) varied over a range of approximately 0.0045% (100pF) to 0.0055% (180pF). Things get interesting when we push the amplifier into clipping under load. With the 180pF capacitors (which we have selected for the final amplifier design), the waveform is simply clipped at the peaks where the output voltage reaches its furthest possible swing (see Fig.9). However, with the smaller capacitor values, there is parasitic high-frequency oscillation after siliconchip.com.au 250 300 350 400 Time (us) Time (us) Fig.9: the behaviour of the complete amplifier when driven into clipping with a low load impedance (3Ω). The supply rails are at ±48V to simulate a power supply under load. With 180pF compensation capacitors, there is a small step as it recovers from the clip but no oscillation. of a single 90pF compensation capacitor. As a consequence, the phase shift returns to a little over 90° and the gain slope drops to -6dB/octave before the feedback factor reaches unity. Potential (Volts) 40 40 Output Base of Q8 Compensation Junction Fig.10: with 100pF compensation capacitors, the amp­ lifier is stable during normal operation but not after recovery from clipping. Note how low the base drive for Q8 is during clipping, as the amplifier is operating in open loop mode. Recovery takes a finite period and triggers the oscillations which eventually die out. the recovery from clipping (Fig.10). This oscillation is at 450kHz or so and it is worse with smaller compensation capacitors. It significantly increases the output current consumption, due to cross-conduction in the output devices and as a result, we managed to blow the output stage fuses more than once during these tests. The reason that the amplifier behaves this way when it is normally stable is that once the clipping point has been reached, the amplifier is no longer operating in closed loop mode, as its feedback network is essentially out of action. For an amplifier with positive gain in clipping, the magnitude of the voltage at the inverting input (a divided down version of the output) has reached its maximum while the voltage magnitude at the non-inverting input continues to in­ crease. As can be seen from the figures, when this occurs for a positive excursion, the voltage from the base of Q8 to the negative rail drops dramatically (well below anything that’s experienced during normal operation), so that the output will swing as close to the positive rail as possible. But when the output voltage needs to drop, this means that the voltage at this point must dramatically increase in order to resume normal operation. This rapid change in base voltage, in combination with the compensation network from this point to Q9’s collector (which is also in a state that does not occur during normal operation), can trigger oscillations in a margin- ally stable amplifier. If you look very carefully at Fig.9, you can see that the amplifier’s output takes a short time to resume its normal slope after clipping; this same artefact is present in Fig.10 and the oscillation immediately follows it. Similar oscillations occur after the output clips to the negative rail (not shown). However, in this case, the base-emitter junctions in Q8 and Q9 limit the maximum voltage at Q8’s base to around 1.4V. As a result, the recovery is quicker and the oscillations are less severe. Note that while Figs.9 & 10 are produced by simulation, they bear an uncanny resemblance to what we saw on our scope while testing the real thing. That the SPICE simulator is able to reproduce this behaviour gives us confidence in its accuracy. Further research If you want to investigate stability and compensation yourself, the SPICE netlists, command files and component models are available as a download from the SILICON CHIP website (SPICE_Amplifier_Stability.zip). You will need SPICE simulation software (eg, ngspice or LTspice, both of which are available for free) and some experience with circuit simulation. We won’t detail how to run the simulations here. Once you figure it out, it is easy to change component values and configuration and then produce new Bode plots to gauge the effect of those changes on amplifier SC stability and feedback. July 2011  77 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ 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/ Triggers devices on and off with sound Build a VOX By JOHN CLARKE Traditionally, VOX circuits toggle a transmitter on as you speak into a microphone and off again when there is silence. But VOX circuits can be used anywhere you want to turn something on when a sound occurs or you speak into a microphone. You could use it turn on a light, an amplifier or maybe even unlock a door. VOX stands for Voice Operated eXchange and it is also the Latin word for ‘Voice’. A VOX circuit switches on a relay whenever a signal reaches a set threshold. The relay switches off once the signal level drops below the threshold and after a short delay. They are used in communications, public address systems, surveillance, security and general purpose electronics. For communications, a VOX switches a transceiver from receive to transmit whenever the person speaks into the microphone. This frees the operator for other tasks as a separate switch is not needed to talk. Many intercoms and public address systems are also automated in a similar way. 82  Silicon Chip A VOX circuit can be used to mute any sound until it reaches a set level. That way a public address system will ignore background noise and remain quiet, until someone intentionally speaks into a microphone. For security and surveillance, a recorder can be switched on whenever a noise is sensed by a microphone. But it doesn’t have to be a microphone which causes the VOX action. For general-purpose use, any audio signal can used to switch the relay. Our design In line with the above comments, our VOX design has two inputs, both of which will accept the same types of audio input. First is a stereo 3.5mm jack socket which will handle both mono and stereo signals, while the second input is for mono inputs only and is via screw terminals. You can connect an electret or dynamic microphone. Electret microphones require a bias voltage which can be selected with a jumper link (LK1). For stereo signals connected via the 3.5mm socket, a jumper link provides mixing of the left and right channels into a mono signal. Signal sensitivity can be adjusted to cover a wide range from microphone levels up to line levels of 2V RMS. With sufficient signal, the relay switches on and remains on until the signal level drops to below a threshold level. An adjustable delay sets the time taken for the relay to switch off once this threshold is reached. The relay has two sets of changeover contacts which will suit a variety of siliconchip.com.au Features • • • • • • • • • 12V operation Electret or dynamic microphone or line input 3.5mm jack socket or screw terminal inputs Mono or stereo signal Adjustable sensitivity Adjustable delay Hysteresis prevents relay chattering at threshold DPDT relay Power and relay LED indication switching applications. LEDs are included for visual indication of power and of relay switching. Because of the wide variety of possible uses for a VOX, our module is simply presented as a PCB which you can install to suit your application. Or if you wish, it can be fitted into a plastic “UB3” case measuring 130 x 68 x 44mm. As you can see from the features at left, our new VOX is quite a versatile beast! It can be used in practically any application which requires triggering from a sound source – and that sound source can itself be just about anything! a supply that is decoupled from the 11.4V supply via a 1k resistor and a 100F capacitor. This decoupling prevents supply variations entering the input to the amplifier to cause false triggering. If the electret microphone is connected via the stereo jack socket input, the electret is connected between the ground terminal (sleeve) and the tip of a mono jack plug. Again, link LK1 is inserted for electret power. If an electret is not used and signal is applied via the jack socket or screw terminals, the link (LK1) is left disconnected. Stereo signals can be connected via the stereo jack socket and the signal is mixed down to mono using 10k resistors for each channel. This stereo mixing occurs when link LK2 is inserted. Dynamic microphones do not require bias current; in fact they should not be connected to a circuit providing electret bias, hence the reason for LK1. A 100nF capacitor couples the mono signal to op amp IC1a. Its noninverting input, pin 3, is biased from the decoupled supply via two 100k resistors. This sets the ampli-fier output to swing symmetrically about Circuit details a nominal half-supply voltage. The The VOX comprises a dual op amp half supply will vary from about 5.3V (IC1) that functions as a signal amplito about 5.6V, depending on whether fier and threshold switch. The relay or not an electret microphone is conis driven from the second op amp via nected. a transistor. Diodes D1 and D2 are included to Input signals come in via the 3.5mm clamp any signal to +0.6V above the jack socket (CON1) or via a 2-way decoupled supply and -0.6V (ie, below screw terminal block (CON2). For the the 0V rail). They protect the IC1 input screw terminal input, if an excessive signal is one terminal is conapplied. nected to ground while IC1a is connected as a Power supply:.................... 12VDC at 50mA the other is applied to non-inverting amplifier Trigger sensitivity:............. Adjustable from 2mV (microphone) to 2V (line) the amplifier stage via with a gain of 2 when Maximum signal input: ..... 50V rms a 10k resistor. VR1 is set to zero ohms Signal frequency range: ... 16Hz to >600Hz When an electret and a gain of about 1000 Attack time:........................ 10 cycles with signal at threshold voltage microphone is used, when VR1 is set to its (faster attack if signal is above threshold) bias current is selectmaximum. The actual Hysteresis:......................... 0.44V at the 2.06V threshold ed when link LK1 is gain when VR1 is set to a Delay time:......................... Adjustable from 100ms to 10s closed. The 10k bias high value is dependent Electret bias current:......... ~320 A resistor is connected to upon the signal frequency Relay contacts (DPDT):...... 5A (maximum of 50V recommended) siliconchip.com.au July 2011  83 Specifications 1k 10k LK1 LK2 CON1 100 F 16V K 100k 100nF 3 8 IC1a 2 100 1 D4 1N4148 10 F 47k K A D3 1N4148 4 100 F 1k A SENSITIVITY 1k 7 IC1b VR2 100k K 1k VR1 1M 5 6 47pF LK1: ELECTRET BIAS LK2: STEREO 1M K NP K 100k 10k  POWER 2 x 10k 100 F 16V A LED1 A ALTERNATIVE ELECTRET OR SIGNAL INPUT 4.7k 100 F 16V A D2 1N4148 + 10 F 16V 100nF D1 1N4148 3.5mm JACK SOCKET CON2 +11.4V 2.2k 100nF IC1: LM358 10 F AC SIGNAL TO DC CONVERTER (RECTIFIER) AMPLIFIER SC 2011 VOICE ACTIVATED RELAY DELAY SCHMITT TRIGGER 1N4148 1N4004 A A K K 84  Silicon Chip D3 D4 4148 4148 47pF 4.7k 47k 10k 1k 4148 1k 100k 4.7k A K 100 F CON5 NO COM 1M VR2 100k 100 F NO COM NC X OV 4004 Q1 D6 10k 10k CON4 1k 2.2k 100nF D2 10 F 100nF 1k 4148 100k 10k 10k CON1 NC RELAY1 11170210 VR1 1M IC1 LM358 100nF 10 F LK2 SIG IN 100 F 10k GND LED2 NP 100 F LK1 0V 4004 +12V CON3 K 10 F 100 D5 A LED1 CON2 and the open- loop gain of the LM358 op amp. The 47pF capacitor is included to provide a steep roll-off at high frequencies, to ensure IC1 does not oscillate. However, it is the open-loop gain of the amplifier that sets the bandwidth. For example at a gain setting of 100 (when VR1 is 99k), the roll-off caused by the 47pF capacitor is about 34kHz. Roll-off due to the open-loop gain is at around 6kHz. With VR1 set for a gain of 1000, the 47pF rolls off frequencies above about 3.4kHz. But the open-loop gain begins to roll off beyond about 600Hz. Low frequency rolloff is set at about 16Hz. This is due to the 1k resistor and 10F capacitor connected in series to the inverting input. The output signal from op amp IC1a is fed to a rectifier involving diodes D3 and D4, to convert the AC signal to a DC voltage. As pin 1 swings above its resting position of 5.7V, the 10F capacitor discharges via diode D4 into the 100F capacitor at D4’s cathode. When pin 1 swings below 5.7V, the 10F capacitor discharges via D3. The 100F capacitor then charges with repetitive pulses provided by the 10F capacitor. Op amp IC1b is connected as a Schmitt trigger comparator, with the inverting input at pin 6 tied to a voltage divider comprising a 10k and 2.2k resistor across the 11.4V supply. Pin D1 Fig.1: complete circuit diagram of the VOX, or Voice Activated Relay. It’s all based on one IC, an LM358, which performs the dual function of signal amplifier and comparator/schmitt trigger. A handful of other components complete the circuit. Fig.2: everything mounts on the one PCB, shown here in both diagram and photo form. The only thing “missing” from the PCB is the microphone which must be mounted off the board, as it will “hear” the relay pulling in and releasing and more than likely trigger in error. It can be mounted on a short pair of wires if you wish, or as long away as necessary using a shielded microphone cable. siliconchip.com.au D5 1N4004 K A +12V A 0V RELAY  LED2 K RLY1 K D6 1N4004 4.7k CON5 A NC COM NO 10k B CON4 C Q1 BC337 NC COM NO E 10k RELAY DRIVER BC337 LEDS B K A E C 6 sits at about 2.06V and is bypassed with a 100nF capacitor. IC1b’s non-inverting input, pin 5, monitors the voltage across the 100F capacitor via a 47k resistor. When the 100F capacitor voltage is below pin 6, IC1b’s output at pin 7 is low; close to 0V. When the capacitor voltage rises above pin 6, pin 7 will go high to about +10V. So provided the AC signal fed to rectifier is enough to produce more than 2V across the 100F capacitor, pin 7 of IC1b will go high and this will turn on transistor Q1 and the associated relay. Now one of the problems with a trigger circuit like IC1b is that it will not switch cleanly from high to low since a very slight change in the voltage across the 100F capacitor could mean that it switches back and forth very rapidly. This would have the result that the relay would chatter, ie, also switch on and off very rapidly. We fix this by adding hysteresis to the circuit, by including the 1M resistor between pin 5 and 7. What now happens is that when the output switches high, it also pulls pin 5 slightly higher, 0.35V higher than the 100F capacitor voltage. This means that the capacitor has to discharge by this amount before the IC1b will go low again. This stops the relay chatter. The 100F capacitor is continually discharged via VR2 and the 1k resistor. So if signal from IC1a is not siliconchip.com.au Parts List – VOX CON3 1 PCB coded 01207111, 106 x 61mm 1 DPDT 12V relay, 5A contacts (Jaycar SY-4052, Altronics S4190C) (RLY1) 1 3.5mm stereo socket PCB-mount (Jaycar PS-0133, Altronics P0092)) (CON1) 2 2-way PCB-mount screw terminals with 5.08mm pin spacing (CON2,CON3) 2 3-way PCB-mount screw terminals with 5.08mm pin spacing (CON4,CON5) 1 electret microphone insert (MIC1) (if required – see text) 11M horizontal mount trimpot (Code 105) (VR1) 1100k horizontal mount trimpot (Code 104) (VR2) 2 2-way pin headers with 2.54mm pin spacing (LK1,LK2) 2 2.54mm jumper shunts 4 M3 tapped spacers (optional) 4 M3 x 6mm screws (optional) 1 length of hookup wire or single cored shielded cable Semiconductors 1 LM358N dual op amp (IC1) 1 BC337 NPN transistor (Q1) 4 1N4148 switching diode (D1-D4) 2 1N4004 1A diodes (D5,D6) 2 3mm red LEDs, 1 red and 1 green (LED1,LED2) Capacitors 3 100F 16V electrolytic 1 10F Non Polarised (NP) electrolytic 2 10F 16V electrolytic Codes: 3 100nF MKT polyester 1 47pF ceramic Resistors (0.25W 1%) 4-Band Code (1%) 1 1MΩ brown black green brown 2 100kΩ brown black yellow brown 1 47kΩ yellow purple orange brown 6 10kΩ brown black orange brown 2 4.7kΩ yellow purple red brown 1 2.2kΩ red red red brown 4 1kΩ brown black red brown 1 100Ω brown black brown brown continuously replenishing the 100F capacitor, the voltage will drop in level. VR2 sets the delay period from when IC1b is triggered high to when its output goes low in the absence of signal from IC1a. The VOX runs from a 12V supply and diode D5 is included for reverse polarity protection. LED1 indicates when power is present. Construction The VOX is assembled on a PCB coded 01207111 and measuring 106 x 61mm. All of the components are mounted on the PCB, apart from the microphone which must not be – it needs to be off the board so that it does not attempt to retrigger the F Value IEC Code EIA Code 0.1F 100n 104 NA 47p 47 5-Band Code (1%) brown black black yellow brown brown black black orange brown yellow purple black red brown brown black black red brown yellow purple black brown brown red red black brown brown brown black black brown brown brown black black black brown circuit whenever it “hears” the relay switch off. The PCB is sized to clip into the integral side slots of a UB3 utility box measuring 130 x 68 x 44mm. If you are using this box, make sure the left edge of the PCB is shaped to the correct outline so it fits into the box, clearing the internal corner pillars. That way the 3.5mm socket can pass through the end of the box. It can be filed to shape if necessary, using the PCB outline shape as a guide. Begin construction by checking the PCB for breaks in tracks or shorts between tracks or pads. Repair if necessary. Check hole sizes for the components and for the corner mounting holes. July 2011  85 Another view of the VOX PCB showing in detail the input and power sockets. It can be driven from an electret microphone (as shown here), a dynamic microphone (with the bias link LK1 left open) or indeed from virtually any audio source from 2mV (microphone level) right up to 2V (higher than most line levels). The sensitivity pot (closest to the input sockets) can be adjusted to cater for this range. The other pot (closest to the relay) adjusts the length of time the relay stays closed once it is triggered. Assembly can begin by the inserting the resistors. When doing this, use the colour codes in the parts list to help in reading their values. A digital multimeter can also be used to measure each value. Next come the diodes, remembering these must be mounted with the orientation as shown. There are two types of diodes; the smaller 1N4148s are D1-D4 while the larger 1N4004 types are D5 and D6. IC1 can be soldered directly into the PCB (or you can use a DIP8 socket if you wish). When installing the IC (and socket), take care to orient them correctly. Orientation is with the notch positioned as shown. Capacitors can be mounted next. The electrolytics must be oriented with the shown polarity except for the NP (non-polarised) type that can mount either way. Mount the transistors and trimpots VR1 and VR2. VR1 is the 1M trimpot and could be marked with its value or with the coding 105. The 100k VR2 could be marked as 104. LED1 and LED2 are mounted about 5mm above the PCB. The anode is the longer lead and is placed in the uppermost hole. The 2-way pin headers for LK1 and LK2 can be mounted now, followed by the 3.5mm socket, the relay and the screw terminals. CON1 and CON2 are 2-way terminals that are first attached by sliding the dovetail sections of each together. Similarly for the CON3 and CON4 terminals, these are slid together before being mounted on the PCB. Make sure the wire entry side face the outside of the PCB. 86  Silicon Chip We mounted the PCB on four 6mm long tapped spacers, held in place with M3 x 6mm screws but this is entirely up to you and your application. If using an electret microphone, this should be mounted so that it does not touch the PCB and connected via multi-strand hookup wire for short (less than 30mm) leads or using single core shielded cable for longer runs. The shield wire connects to the GND terminal (for the 3.5mm jack plug, the GND is the sleeve). Signal connects to the second screw terminal for the screw terminal input or the tip connection of the 3.5mm jack plug. For a signal input other than a microphone, apply the signal to either the screw terminals or via a 3.5mm jack plug. One channel connects to the tip terminal and the other channel to the ring terminal. Link selection depends on whether you are using an electret or dynamic microphone or a mono or stereo signal connection. LK1 should be linked only when the electret microphone is used and removed for a dynamic mic. LK2 should have a jumper link for a stereo signal. You wouldn’t normally have both LK1 and LK2 in position at once but there are stereo electret microphones around so it is possible (though why you’d want to use one in this application is a bit beyond us!). Apply 12V power and adjust VR1 so that the relay triggers at the required signal level. Similarly, adjust VR2 so that the relay switches off after the desired time period. The delay should be as short as possible but not so short that it drops out while speaking. If the Voice Activated Relay does not work, first check your soldering to make sure there are no dry joints, solder bridges or dags, etc. If the visual inspection looks OK, check voltages on the circuit. There should be about 11.4V between pins 4 and 8 of IC1. Pin 3 of IC1 should be around 5.7V to 5.3V. Pin 6 of IC1b should be at about 2V. Incorrect voltages may be because of incorrect resistor values or a short or open circuit connection. Check that LED 1 lights. Output of IC2 at pin 7 should be near 0V when no signal is applied (or when no sound is detected by the microphone). With sufficient signal applied, the pin 7 output should go to around 10V, the relay should switch on and LED2 should light. The relay should switch off after the preset time period when there is no signal. 9V operation? We know we will be asked the question! Some constructors may wish to use the VOX as a stand-alone device – so we’ll answer it already! No, operation from 9V would be quite unreliable, especially if the battery is a bit flat. And the 50mA current draw would put the battery in that state pretty quickly! Most of the circuit would be fine at 9V but the 12V relay would not be at all happy (if indeed it worked at all). Substituting a 5V relay may be an option, with a resistor in series with the coil but it may not be possible to get one which fits the PCB without modification. SC siliconchip.com.au CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. OUT 15k 470 100k 4 3 2 VR1 100k 100k 1 IC1a 150k 33k 100k 3 IC2a 47 0.5W 1F 100F 16V 2 GND 330F 16V A 220F 35V +18V DC 0V 15k 100F 16V 1M 47nF IC1: TL084 5 IC2: TL082 6 100k 8 IC2b 7 47nF 100k 5 7 IC1b VR2 2.5M E 220pF Q1 BC547 B 1 8 IC3 LM386N 2 220F 16V 5 7 8 SPEAKER 10 4 4.7F C 100k 6 3 4 6 K IN 1M 1 47F 16V 100k D1 1N5819 REG1 7815 1k 4.7nF 470k 10F 16V 100k 100k 100k 10 100k 9 IC1c 100k 12 8 82k 13 IC1d IC1d 100k 11 100k 1N5819 14 K A 100F 16V 7815 BC547 220F 16V 220k 680k IN E Surf sound synthesiser Many people who live close to the ocean have the benefit of being lulled to sleep by the sound of the surf. This circuit may provide a similar benefit to all those poor unfortunates who don’t live near the seaside but who do have the small consolation that they don’t have to worry about rust and corrosion in a salty atmosphere. The circuit consists of four unsynchronised oscillators which are mixed together to modulate a white noise source to simulate the more or less random nature of surf sounds. You won’t hear the waves crashing but the ebb and flow of the white noise will help mask other noises which would otherwise disturb your sleep. The four oscillators are based on four op amps in a TL074 or TL084 siliconchip.com.au quad op amp package (IC1). IC1a, IC1b, IC1c & IC1d are configured as Schmitt trigger oscillators with their operating frequencies defined by the resistor connected between their outputs (pins 1, 7, 8 & 14) and the respective inverting inputs (pins 2, 6, 9 & 13), as well as the electrolytic capacitors connected between these latter pins and 0V. The result is a triangle waveform at each of the respective inverting inputs and square waves at the same frequencies at the op amp outputs. We don’t use the square outputs but instead feed the four triangle waveforms to op amp IC2a which is connected as a mixer. Its output is used to drive and modulate a noise source based on NPN transistor Q1. This is operated with reverse bias across its base-emitter junction and the controlled reverse current is very noisy. GND B 470F 16V C GND OUT By varying the amount of reverse bias, we vary the amount of white noise produced. Since the amount of noise produced by the transistor varies markedly between types, the gain of IC2a can be varied over a wide range to produce the optimum output voltage to drive Q1. From there, the noise signal from the emitter of Q1 is fed via a 47nF capacitor to op amp IC2b which can also have its gain varied over a wide range to drive IC3, an LM386 power amplifier which drives the loudspeaker. In use, first adjust trimpot VR2 to set the volume level from the loudspeaker, then adjust trimpot VR1 to get the best range of white noise which simulates the surf sounds. Sleep well. Craig Kendrick Sellen, Pennsylvania, USA. ($50) July 2011  87 Circuit Notebook – Continued +500V WAVEFORM AT COLLECTOR OF Q1 D7 K S1 47nF 630V REG1 78L05 +5V OUT IN 9V BATTERY 10 F GND T1 10k 1 6V IC1: 40106B 14 3 2 IC1b 10k 1k 4.7 F 6 250V 47nF 630V D3 C 10k B LND 7312 8 A 47k +5V IC1d 9 47nF VR1 50k LND 712 ANODE (A) IC1e 10 SET METER – ANODE (A) CASE IS CATHODE (K) SET 500V 10k 11 A 100nF 100 F WINDOW 5 E VR2 5k 12 IC1f GLASS PIP SCR1 BT149 K 13 CASE IS CATHODE (K) G WINDOW PIEZO BC337, BC547 LED 1N4148 1N4007 A A K K K A The recent tsunami in Japan and the on-going calamity with the Fukushima nuclear power plant has apparently greatly increased sales of radiation meters, not only in Japan but elsewhere around the world. This device will allow an estimation of the level of radioactivity, being sensitive enough for background radiation monitoring or to provide an estimation of the level of radioactivity from sample objects such as Thorium gas mantles in LPG lamps. The circuit is compatible with several Geiger Muller tubes and three types of indication are provided: the good old-fashioned audible click with each discharge, a flashing LED or an analog meter providing a rough average of radiation levels. A normal background count in New Zealand with the smaller GM 78L05 E LND712 tube is around 30 counts per minute, while the larger and more-sensitive LND7312 pancake tube will count about four times this figure. Both GM tubes will detect alpha, beta and gamma radiation. Unless the tube is “filtered”, there is no way of knowing just what type of radiation is being detected, although a rough guess can be made. Alpha particles will be stopped by placing a sheet of paper between the tube and the source, Beta particles (electrons) will be stopped with a few layers of aluminium foil and the more lively Gamma rays will need a layer of lead. The circuit provides a regulated 500V supply for the Geiger Muller tube. This voltage places the tube into its linear operating mode so BT149 GND B Geiger counter uses Cockroft-Walton multiplier 88  Silicon Chip 10k 4.7M ERROR AMP LED1  K Q2 BC547 IC1c K 100 A METER K D4 Q1 BC337 B D2 1N4148 + K A E K A G-M TUBE A C 7 D1 1N4148 +9V A A 4 220nF A 10M D6 47nF 630V D5 K OSCILLATOR IC1a K 47nF 630V 47nF 630V 100nF K A +9V D3–D7: 1N4007 A C IN G OUT K A that a discharge inside the tube will occur when a particle enters through the mica window of the tube and causes the gas to ionise. The very short pulse produced is stretched and used to signal that a discharge has occurred. The power supply consists of an oscillator and small transistor driving the 6V secondary of a 240VAC mains transformer. The stepped up output of the transformer is fed to a Cockroft-Walton voltage multiplier consisting of diodes D3-D7 and the associated 47nF 630V metallised polyester capacitors. IC1 is a 40106 Schmitt trigger inverter and IC1a is connected as an oscillator running at several hundred hertz. This is buffered by IC1b and fed to the base of NPN transistor Q1 which then drives the abovementioned transformer. IC1c acts as an error amplifier to siliconchip.com.au + ELECTRET MIC 100nF LDR1  Q1 BC327 B E 4 LIGHT C 47k INVERT Q2 BC327 B 1 F 3 2.2M 47k P4 2 SER IN SOUND C 10k 10k P2 P3 E 22k 4.7k 1 Vdd IC1 PICAXE -08M P1 P0 5 SILICON CHIP has presented two electronic cricket projects: Horace the cricket (August 1990) and his cousin Clifford the cricket (December 1994). Horace only chirped if he heard a noise but otherwise kept mum; Clifford behaved the same, with eyes flashing as well, but only in the dark. PICAXEL is just as pesky as Clifford but is based on a PICAXE08M microprocessor rather than op amps or a CMOS hex inverter. PICAXEL can respond to either sound (electret microphone) or light (LDR) sensors and can produce a chirp sequence rather than a single chirp. Transistors Q1 & Q2 amplify the sound from the electret microphone which has bias provided by the 4.7kΩ resistor. Alternatively, ambient light is sensed by the LDR (light dependent resistor) and it produces a low signal in darkness, when its resistance is high. Either the electret or LDR signal is fed to the P4 input of IC1 via the jumper block. For the electret option, loud sounds will turn Q1 off and Q2 on regulate the high voltage fed to the GM tube. A portion of the DC voltage produced at the junction of diodes D4 & D5 is monitored by a voltage divider consisting of the 4.7MΩ and 47kΩ resistors, in combination with trimpot VR1. When the voltage from D5 is below the positive threshold of IC1c, its output will be high and IC1a will be able to oscillate. Hence, the oscillator will pulse on and off, to maintain the 500V set by VR1. siliconchip.com.au S1 220 7 Vss 4.5V BATTERY (3 CELLS) 'EYES' PROG SKT 10k PICAXEL the electronic cricket ON/OFF 220 6 8 10k 100nF PIEZO BUZZER (3.3kHz) + – A LED1 A LED2  K  K BC547 LEDS and the P4 input will switch high for a period set by the 1µF feedback capacitor. The two transistors will then revert to the quiescent state, with Q1 on and Q2 off, ready to react to the next sound. The P4 input of the PICAXE is operated in the A/D converter mode, allowing an accurate mid-rail switching level for both light and sound operation. Three pins of IC1 are configured as outputs. Outputs P0 and P1 drive the two LEDs, representing PICAXEL’s eyes. They light up each time he chirps. The P2 output drives the 3.3kHz piezo buzzer. The program pulses the piezo buzzer in a sequence of chirps, starting with a single 150ms chirp followed by eight short 20ms chirps, then a rest or pause time of two seconds before the next chirp sequence begins. Normally, PICAXEL will chirp when it is light, remaining quiet when it is dark. To reverse this normal operation, place a jumper on the “invert” pins for the P3 input. He will now chirp when it is dark and remain quiet when it is light. This “invert” jumper should not be used with the “sound” jumper installed because false triggering will Each time there is a discharge in the GM tube, the resultant current triggers the BT149 SCR which discharges the associated 100nF capacitor and thereby acts as a pulse stretcher to drive the three remaining inverters in IC1. These in turn drive a high-brightness red LED (LED1), a piezo transducer and an analog metering circuit which is based on an old VU meter movement with a scale graduated in counts/ minute. K A B E C occur due to Ian R the drop-outs is this m obertson ont present in all of a Pe h’s winner a sound sources. Test Ins k Atlas trumen The circuit is t powered by a 3cell 4.5V battery pack and includes a standard PICAXE 3-pin programming socket. You could build PICAXEL without any sound input by deleting all the components to the left of the “sound” link. You can also modify the sound your cricket makes by tweaking the program. Enter different pause times in the chirp routines. For example, try 100 rather than 150 or perhaps use 15 rather than 20. While you are at it, try increasing or decreasing the number of chirps; eg, try six or 10 instead of eight small chirps. During development of this project I tried a wide range of settings and all sounded like a cricket to me; but perhaps not to another cricket! Ian Robertson, Engadine, NSW. The current drain of the circuit is 10mA and a small 9V battery should run the counter for many hours. Warning: do not touch the window of the GM tube. These are very fragile and made of very thin mica, to allow the low-energy alpha particles to pass through. With the LND 712, 200 counts per minute is roughly equivalent to 0.3 micro-seiverts. Dayle Edwards, Taylorville, New Zealand. ($70) July 2011  89 Circuit Notebook – Continued CON1 +Vcc 0V 3.3k 51 VR1 220 K 10 F 6 2 3 1 8 15nF 10k 22 F 16V D2 1N4004 1k 2.2 /1 OUT1 180 220nF 220 F 16V /10 K 15nF GND 470 F 25V 10k CON2 K 5 7 4 A  LED1 A IC1 LM386N 6V/20mA LAMP 220 F 25V 330nF D1 1N4004 OUT2 18 2.2 /100 OUT3 A 2.0 IC2b 3 1k 1 LED D1, D2: 1N4004 A K 5 IC2a 2 K 9 11 A 14 IC2c IC2d 6 IC2e 10 IC2f VR2 500 12 10 220 8 IC2: 40106B 13 GND 4 VR3 5k 220 OUT4 OUT5 OUT6 GND 7 Wein bridge oscillator uses an LM386 power amplifier Most audio oscillators are based on conventional op amp ICs but these are usually intended to drive a load of no less than 600 ohms and cannot deliver any useful power into lower impedance loads. This particular circuit was devised for testing cables, loudspeakers, headphones, transformers, inductors etc where rather more current and voltage is required. Using the LM386 amplifier IC meets the power requirement and it is connected in a standard Wein bridge oscillator configuration with the operating frequency of 1kHz Synthetic 5-segment potentiometer This simple circuit was devised to provide an easier way to ‘fine adjust’ the output level from my audio signal generator to a specific level. This was quite difficult with the generator’s inbuilt output level controls, which consist of just a 5090  Silicon Chip being set by the components connected between pins 3 & 5. The output amplitude is set to around 8V peak-to-peak by means of the incandescent lamp connected to pin 2 and by trimpot VR1. The 220nF capacitor and 2.2Ω resistor connected to the output (pin 5) comprise a standard Zobel network to ensure stability of the LM386 and the output is coupled via a 470µF capacitor and 2.2Ω resistor. Diodes D1 & D2 are included to enable the amplifier to safely drive inductive loads if it is overloaded. It will drive any load provided its ohm wirewound pot followed by a couple of switched decade dividers. I realised that fine adjustment would be much easier if I were to use a multi-turn pot but these are not available from the usual suppliers. So I decided to build up the equivalent of a multi-turn pot, using readily available parts. The circuit uses a 2-pole 5-posi- impedance is more than 4Ω. A low-power square wave output is provided by the 40106 hex Schmitt trigger inverter. IC2a is connected to the output of the LM386 via a 1kΩ resistor and it “squares up” the 1kHz sinewave. Its output is fed to the inputs of the other five inverters which are connected in parallel to provide a fixed output with relatively low impedance which is defined by the 220Ω resistor and the limited output current capability of each CMOS inverter. Potentiometer VR3 provides a variable output. Petre Petrov, Sofia, Bulgaria. ($50) tion rotary switch (S1), a 500Ω linear pot (VR1), nine 100Ω 1% metal film resistors and a 100Ω multi-turn trimpot (VR2). These parts are arranged in a circuit a little like the traditional multi-stage stepped potentiometer. Basically VR2 and one of the 100Ω resistors are connected in parallel with the 500Ω element of VR1, so that by careful adjustment of VR2 the siliconchip.com.au total resistance connected between the poles of S1 is “padded” down to exactly 100Ω. Then depending on the particular position to which S1 is set, this “100Ω pot” effectively becomes one of the segments in a 5-segment voltage divider, connected between the input (CON1) and ground. For example, with S1 switched to the “B” position as shown, the output pot forms the second-highest divider segment – with one 100Ω fixed resistor above it and three same-value resistors below it. As a result, the pot’s adjustment range varies between 60% and 80% of the input voltage. If switch S1 is set to the “D” position instead, the output pot then forms the second-lowest divider segment – with three 100Ω fixed resistors above it and only one below it. So it now has an adjustment range of 20-40% of the input. And so on, with the effective adjustment range of the five switch positions shown in the small table. By the way, the reason for using VR2 and its series 100Ω resistor to “pad” the effective resistance of VR1 down to 100Ω is to ensure that the five adjustment ranges are contiguous, with neither gaps between them CON1 INPUT (Rin = 500 ) 100 A 100 B S1a C 100 D 100 E VR1 500  LIN CON2 OUTPUT (Rout < 500 ) VR2 100  (25T) 100 NOTE: ALL FIXED RESISTORS 1% METAL FILM 100 A 100 B C D S1b 100 RANGE A: 80 – 100% RANGE B: 60 – 80% RANGE C: 40 – 60% RANGE D: 20 – 40% RANGE E: 0 – 20% E 100 nor overlapping at their maximums and minimums. This only happens when the effective pot resistance is 100Ω, matching the fixed resistors in the divider. The complete circuit was housed inside a small aluminium box measuring 111 x 60 x 30mm, to provide it with shielding. The input and out- put connectors were panel-mount BNC sockets, each mounted on one end of the box. Switch S1 and trimpot VR1 were mounted in the bottom of the box, which became the top when the box was inverted for use. Jim Rowe, SILICON CHIP. Contribute And Choose Your Prize SCR/TRIAC Analyser no longer available As you can see, we pay for each of the “Circuit Notebook” items published in SILICON CHIP but there are three more reasons to send in your circuit idea. siliconchip.com.au Each month, at the discretion of the editor, the best contribution published will entitle the author to choose a prize: either an LCR40 LCR meter or a DCA55 Semiconductor Component Analyser, with the compliments of Peak Electronic Design Ltd – see www.peakelec.co.uk ESR60 Equivalent Series Resistance Analyser no longer available So now you have even more reasons to send that brilliant circuit in but it must be original and not previously published. Send it to SILICON CHIP and you could be a winner. You can either email your idea to silicon<at>siliconchip.com.au or post it to PO Box 139, Collaroy, NSW 2097. July 2011  91 Vintage Radio By Maurie Findlay, MIE Aust, VK2PW The Hotpoint Bandmaster J35DE console radio Over the next few months, veteran radio designer Maurie Findlay will go through the process of restoring a good “1940s wireless” to its original performance – and for those who are interested, he describes how to make it perform even better than new. The radio to be restored is a Hotpoint Bandmaster which was made in console (J35DE) and table (T55DE) models. Maurie takes up the story . . . The Hotpoint Bandmaster J35DE was a 1940s console radio that offered quite good performance in its day. This example is still in good condition, although the grille cloth needs replacing and the cabinet requires work. 92  Silicon Chip W HILE THERE were many run-ofthe-mill radios produced during the valve era, those with better performance were considerably more expensive and are now hard to come by. And while the sets made by AWA were highly regarded, those branded Hotpoint would these days hardly rate a second glance by vintage radio collectors. However, they would be missing out. Hotpoint-branded radios were made by AWA Pty Ltd (Amalgamated Wireless Australasia), Australia’s biggest electronics company in the 1940s. Which just goes to show that “badge engineering” was not confined to the automotive industry. The Hotpoint Bandmaster T55DE/ J35DE is a 5-valve radio offering AM broadcast band and shortwave reception, with provision for a pick-up to play records. The chassis may also have been the basis for radiograms made by AWA at the time. The Hotpoint J35DE/T55DE chassis was virtually identical to that in the AWA 721-C console radio and the 618-T mantle (or table) radio. A set of this general type, in good order, will have a reserve of performance for local broadcast stations and will receive the stronger shortwave stations. With care and patience, the valves and other components can be tested, replaced if necessary and the set realigned for best performance using no more than a multimeter. That said, the meter needs to be a modern digital multimeter. Multi-range meters available at the time the Hotpoint was designed mostly used a moving coil meter which required a current of 1mA for full-scale siliconchip.com.au deflection (FSD). Such a meter would give readings very much in error in many radio circuits because of the high resistances involved. For example, take a look at the circuit diagram of the radio featured in this article. At valve V3’s plate, it would read about one third of the actual voltage on the 100V scale. That’s because the relatively low impedance of a moving coil multimeter loads down the voltage when attempting to measure such a circuit. By contrast, a modern digital multimeter has an input resistance of 10MΩ (100 times greater) and would have very little effect on the voltage. Apart from a good digital multimeter (DMM), you will need spare parts, small hand tools and most important of all, some skill with a soldering iron. Still, if you have assembled a typical PCB, you should have no trouble soldering parts in an old radio chassis. However, you will need a bigger soldering iron to do some of the work. The Hotpoint T55DE is typical of 5-valve sets made in the valve era. It used good quality components which were operated conservatively and offered what most owners wanted: reliable reception of the local broadcast stations. More elaborate receivers, for use in remote areas, would have had an extra stage of amplification between the aerial and the mixer stage. For those needing high volume, a more elaborate audio system, perhaps using push-pull valves, would be prescribed. In addition, shortwave reception could be improved by incorporating a bandspread system so that particular frequencies can be tuned more easily, while an extra RF amplifier stage is also a big advantage at the higher frequencies. And so it goes on. The aim of this article and the one that follows is to give enthusiasts, with only a basic knowledge of radio, a systematic means of restoring vintage receivers to full performance. A particular set has been chosen in order to avoid a string of generalities which could easily have been confusing. I have redrawn the manufacturer’s circuit diagram, with component values marked, to avoid the need to refer to the parts list when studying the diagram. Circuit details Let’s start by going through the varisiliconchip.com.au This view shows the neat arrangement of the major components on the top of the chassis. A label on the dial backing plate shows the drive cord arrangement. The old Hotpoint featured a rather elaborate glass dial which carried markings for the Australian states, New Zealand and the international shortwave band. ous stages of the Hotpoint T55DE. Fig.1 shows the circuit details. Valve V1 is the mixer, sometimes called the 1st detector, and is a 6J8G. It takes the signal from the aerial (antenna) and converts it to an intermediate frequency which makes it easier to obtain the amplification and selectivity required. The 6J8-G has a special “heptode” construction which consists of a fine helix grid close to the cathode, a screen grid surrounding that and yet another screen grid followed by the suppressor grid and then the plate. In between the two screen grids is another grid which is connected to the grid of a separate triode element. This sounds complicated but this construction allows the local oscilJuly 2011  93 Fig.1: the redrawn circuit for the Hotpoint Bandmaster J35DE radio. It’s a fairly conventional 5-valve superhet configuration with AGC and a 455kHz IF. The set can tune both broadcast and shortwave bands. lator, using the triode section, to function with full efficiency, while mixing of the two signals takes place in the electron stream from cathode to plate. Several frequencies appear at the plate but the one we want, the difference between the signal and the higher oscillator frequency, is selected by the 455kHz tuned circuit. 6J8-Gs cost more to manufacture than other valves designed to do the same job but this valve worked better than most, particularly on the shortwave bands. It was often used in quality receivers manufactured at the time. The next stage, V2, uses a 6SK7GT pentode. The internal shielding between the control grid and the plate is provided by the usual screen and suppressor and the valve is able to amplify in a stable fashion. Other valves, such as the 6U7-G, available at the time, could have done the job equally well. An important requirement for this 94  Silicon Chip stage is that the valve has a “variable mu” characteristic; the gain reduces as the negative bias on the grid increases, which allows for automatic gain control (AGC). An interesting point about the design of the Hotpoint circuit is that AGC control is applied to both the 6J8-G and the 6SK7-GT on the broadcast band but only to the 6SK7-GT on shortwave. This allows greater amplification for the weaker shortwave signals. Another special design point is the filter in the broadcast band aerial circuit. A 50pF capacitor in series with a high-Q inductor forms a series tuned circuit at 455kHz, effectively shorting out the receiver input at that frequency. Not many designers would have considered this necessary, because 455kHz is kept clear of highpower transmitters. As was conventional at the time, this set has four circuits tuned to the intermediate frequency of 455kHz, two before and two after the amplifier. Coupling between the circuits was loose enough for the circuits to be tuned individually without affecting each other. The resultant selectivity caused attenuation of the higher sidebands and hence a reduction in the higher frequency audio. At the time, few designers would have incorporated a bandpass arrangement. People seemed to think that radios should have a “mellow” tone. Detection & AGC The next valve, V3, a 6SQ7-GT, incorporates two diodes and a triode. It recovers the audio from the intermediate (IF) signal, provides the automatic gain control and amplifies the recovered audio signal. Other valve types capable of doing the same job were available at the time. For example, a pentode double-diode could have been chosen for higher gain. But the triode provides a reserve siliconchip.com.au of gain anyway, with a very simple circuit. The small amount of negative bias required is obtained from a high-value resistor in the grid circuit (10MΩ). The diode connected to pin 5 of V3 rectifies the 455kHz signal from the IF transformer and the recovered audio signal appears at the lower end of that transformer. At this point, the audio is mixed with the 455kHz IF signal and a filter, consisting of a 47kΩ resistor and two 100pF capacitors, removes this 455kHz component. With the function switch in the “radio” position, the recovered audio appears across the 500kΩ (0.5MΩ) volume control potentiometer. AGC is developed by the diode connected to pin 4 of V3. However, pin 4 is returned to a voltage that’s negative with respect to the cathode via a 2.2MΩ resistor and therefore does not start developing an AGC voltage until a certain signal level is reached. This is “delayed AGC” and ensures that maximum gain is available for very weak signals. Output stage V4, the audio output valve, amplifies the signal further and provides power to drive the loudspeaker. It is a 6V6-GT and was the best choice for the job at the time this set was designed. In this set, it is operated with a cathode bias resistor that’s slightly larger in value than usual. This reduces the power dissipation and audio output of the valve but would make for longer life. The optimum load resistance with the higher bias resistor would be higher than the usual 5kΩ and is probably somewhere around 7kΩ. Design fault This circuit has a serious design fault concerning the arrangement for connecting the speaker. The output transformer is mounted on the back of the speaker and is connected to the output valve via a plug and socket arrangement on the chassis. As a result, if the set were to be accidentally switched on without speaker connected, the 6V6-GT screen current would be very high and this would probably ruin the valve. A better arrangement would be to have the speaker transformer permanently mounted on the chassis and the voice-coil leads extended. Alternatively, a solution such as that described on page 91 of the August 2010 issue siliconchip.com.au The chassis mounts vertically inside the cabinet, so that the glass dial and control shafts face upwards. Note that the output transformer is mounted on the speaker frame. This means that the 6V6-GT output valve could be destroyed if the speaker cable is disconnected from the chassis while power is applied. of SILICON CHIP, for an Airzone 612 console radio, could be adopted. This is what we eventually did with this Hotpoint set. Power supply A power transformer and rectifier valve, V5, are used to derive the 240V DC high-tension supply for the amplifying valves. However, the usual approach has not been taken. V5 is a 6X5-GT and this valve has special insulation, designed to withstand the high voltage between the cathode and the 6.3V filament. The 6.3V heater winding on the transformer also supplies the other valve filaments and is effectively at chassis potential. The alternative approach, and the one mostly used in sets at this time, was to use a 5Y3-GT rectifier which has directly-heated cathode supplied from a separate 5V heater winding. This could then “float” at the HT voltage which could be anywhere from 100-300V or more, depending on the circuit requirements. The 100Ω resistors in each plate circuit of V5 are provided to limit the peak current. The 8µF capacitor connected to V5’s cathode also affects the peak current and hence the life of the valve. It should not be replaced with a higher value. To complete the circuit description, note the function switch which allows the set to be switched for radio or record pick-up operation. There are July 2011  95 By contrast with the top, the underside of the chassis is quite crowded due to the bulky old-style components used. Note the primitive technique used to anchor the power and speaker cables, ie, by tying knots in them. The underside of the chassis is protected by a perforated steel cover, a rather unusual feature for radios of that time. tone control positions for both radio and pick-up. In the pick-up position, the screen supply to V1 and V2 is disconnected so that “play-through” from the radio stage, due to stray coupling, is eliminated. The pick-up input was designed to accept the high-output signals from the crystal (piezoelectric) pick-up cartridges used in the 1940s with 78 RPM records. Not every restorer will want to bring this back to life! In addition, the treble cut applied for radio listening is probably too severe for modern ears and could be reduced by choosing a smaller value for the associated .01µF capacitor. A power socket for a turntable motor is mounted on the chassis and is alive even with the radio switched off. When replacing the power cord, we 96  Silicon Chip used the socket as a convenient termination. However, there is a safety issue here in that the metal terminations in the socket are close to the metal surface on which the socket is mounted. If the bare wires are not pushed right into terminations, there is the possibility of them touching the metal chassis with disastrous results. Such a socket would definitely not meet approval today. Preferred value components In the original service manual for the Hotpoint Bandmaster J35DE, all the passive components, ie, resistors and capacitors, are in “non-preferred” values. For example, one resistor is specified as 2.5MΩ while others are marked 1.6MΩ, 50kΩ, 32kΩ, 25kΩ and 20kΩ. In the capacitor list, there is a 50pF unit, a 70pF (actually µµF) unit, some .05µF units and so on. This is because this set was made before the introduction of the “preferred value” system, which is now universally used for small components. With preferred value numbering, a designer can adjust a circuit value to a desired order of accuracy while stocking the minimum number of components. The numbers in the ratios 10, 15, 22, 33, 47, 68 and 100 would be stocked by a design laboratory over most of the range, except for very small and very large values. On the other hand, for very critical circuitry, a designer may need to stock values in finer increments such as 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91 and 100. However, extended over the decades, this could involve a huge number of components. So what do we do about, say, replacing the 50kΩ resistor in the grid circuit of the 6V6-GT output valve? You cannot buy a 50kΩ resistor at your usual supply store. The answer is that the exact value is not critical and a 47kΩ resistor will do the job perfectly well. This also applies to most of the other components in the radio. The 2.5MΩ resistor could be replaced with 2.2MΩ, the 1.6MΩ with 1.5MΩ and so on. In addition, the .0025µF capacitor from the plate of V4 to ground can be replaced with a .0022µF capacitor with negligible effect on the way the radio works. With this in mind, the circuit presented in this article has been redrawn with “preferred values” for most of the passive components. There are, however, some components where accuracy must be maintained. The 4000pF (4nF) capacitor in the shortwave oscillator circuit is an example. It modifies the tracking of the oscillator frequency to give the desired tuning range. The same applies to the capacitors in the 455kHz IF coils (unmarked). Next month Next month’s article will describe the practical side of getting the Hotpoint Bandmaster into operation. It is now 60 or more years since the set was manufactured and that meant that a great deal more than defective valves had to be considered. Many capacitors, resistors and even the wiring had SC deteriorated badly. siliconchip.com.au Is your hip-pocket nerve hurting? We know how you feel – prices seem to be going up all the time. But you can save money by taking out a SILICON CHIP subscription. A 12-month subscription will get you 12 issues for the price of less than 11! For an even bigger discount, a 2-year subscription gets you 24 issues for the price of 20! Better still, a 2-year subscription gives you longer protection against price rises in the future. Count the advantages: q  q  q  q  q  It's cheaper – you $ave money! It's delivered right to your mail box! You can always be sure you'll receive it!! We pick up all the postage and handling charges!!! You will never miss an issue because it's sold out (or you forgot)!!!! $5200 6 months SILICON chip : 12 months SILICON chip : $9750 24 months SILICON chip : $18800 *These prices and comparisons refer to Australian subscriptions. Other countries are subject to exchange rates – please see page 102 of this issue. siliconchip.com.au July 2011  97 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 or send an email to silicon<at>siliconchip.com.au Recharging Apple USB devices I can’t quite fathom how a USB port can provide the biasing conditions for a variety of devices, assuming that these iPODs can be charged from a normal PC USB port. I have an Apple Shuffle and a Dick Smith MP3 player. How do I know what biasing is required? (E. J., Otago, Tas). • The reason that biasing is required for iPods to charge is that when the iPod is plugged into a computer, it communicates with the computer and checks that it can draw 500mA first. According to the USB standard, unconfigured devices are not allowed to draw more than 100mA. Since there is no computer or microcontroller in the USB charger for Cars & Bikes (SILICON CHIP, May 2010) an iPod can not communicate with it and so can not request the full 500mA. The biasing resistors tell the device that it is connected to a charger and it’s allowed to draw more power without having to talk to a computer. This is a common problem and unfortunately each manufacturer has addressed it in a different way (and in the case of Apple, a different solution for different devices). The USB3 standard provides a way to make third-party chargers work with any USB device but unfortunately few devices have adopted it yet. You may find that the Dick Smith MP3 player will charge without any biasing. Some devices skip the configuration process and just draw power from the port. We don’t know what bias voltages an iPod Shuffle needs but if it doesn’t charge with D+ and D- unconnected then try shorting those lines together (with a solder bridge). That is the new USB3 method for detecting a charger. If that doesn’t work, try the scheme in Fig.8 on page 72 of the May 2010 issue. One of these two approaches should do the trick. At least one report on the internet suggests that this scheme (or one very similar to it) works with 2nd generation iPod shuffles. However we have not tried it so we can’t guarantee that it will work. Soft-starter wanted for switchmode supplies Have you produced an article or project for “soft-start” switching 230VAC to transformers and computers? I have a problem occasionally when switching on the power to the power board that supplies the above equipment. It doesn’t happen every time but sometimes I see a spark coming from the power point switch at switch on. The total wattage of the devices connected to the power board is only about 450W, so they should be within the 10A rated capacity of the power point switch. My feeling is that there is an inductive and capacitive load from the conventional wirewound type trans­ former/s that power the modem etc that’s causing this. The power point has been replaced with a new one and I am still experiencing this problem which will eventually burn out the switch contacts again. What is needed is a “soft start zero current” device to place in front of the power board and after the power point that will eliminate the sudden rush of current at switch on. If such a device has not been produced as a project it could be considered for a future project for your magazine as I am unable to buy anything commercially from electrical suppliers that will give a “soft start” at switch on. Any suggestions that you could offer would be appreciated in solving my dilemma. (B. S., Warners, Bay, NSW). • Your dilemma is very common. In fact, we think that virtually every household has a similar situation in which the in-rush current to electronic appliances can not only burn out the switch contacts in typical power points but depending on the number of appliances being switched, can also On Modifying CD-ROM Motors For Higher Power I’m interested in electric models, mainly airplanes, and have been reading with interest on a few websites about using old CD-ROM drive motors to make brushless airplane motors. This involves re-winding the stator and replacing the magnets to get sufficient power. What are the chances of your techies coming up with a brushless speed controller? One which can have a range of power outputs by varying output components would be good, however there is a lot of interest in 98  Silicon Chip 36-inch wingspan models such as those designed by Peter Rake in the UK. These are suitable for a brushed Speed 400 electric motor, so a speed controller which would suit an equivalent power brushless motor would be great. I’m part way through the construction of a 36-inch Sopwith Pup and am getting to the stage where a decision on the motor etc is imminent. (B. L., via email). • We have serious doubts whether CD-ROM drive motors could be modified to produce anywhere near enough power for a sizeable model aircraft. Realistically, for the sort of aircraft you are considering you would need a motor capable of many hundreds of watts, or perhaps up to 1HP or more. A modified CD-ROM motor is highly unlikely to be capable of even a fraction of that. Secondly, we do not have plans to do a brushless motor controller. There are too many variables to cater for and nor do we have RC modellers on tap to do the considerable testing which would be required. siliconchip.com.au lead to nuisance tripping of circuit breakers in switchboards. In fact, we have a similar scenario in the SILICON CHIP offices where some desks have a typical desktop computer driving two monitors and other ancillary equipment, all with switchmode power supplies. Just as in your situation, the total rated power of the appliances is probably quite modest at maybe less than 400W but the initial inrush current over the first few cycles of the 50Hz 230VAC waveform can be very large, perhaps 30A or more. One way to reduce the problem is to avoid switching all the appliances on simultaneously at the power point. Switch on the computer first, followed by the first video monitor and so on. But we realise that few people will want to go to that much trouble. In fact, we have just such a soft-start module in the pipeline and it should be published within the next few months. Increasing door strike time in RFID module I built the RFID Security Module (SILICON CHIP, June 2004) which was designed by Peter Smith. How can I change the time the door strike output stays on for (ie, when a valid tag Disconnecting Loudspeakers When Headphones Are Plugged In I have a question regarding the Loudspeaker Protector and Muting Module described in the July 2007. This project uses NO (normally open) contacts for the thermostat. How can it be converted to make the contacts NC so that it can be used to disconnect the loudspeakers using the NC contacts in a loudspeaker socket, when a set of headphones is plugged in? This is the approach you took in the Ultra-LD 100W Stereo Amplifier of November & December 2001 and January 2002. I understand why you might not do it for the Class-A amplifier but it might be useful for a lesser unit such as my LM3886 amplifier. (I. F., via email). • There are several approaches to using the NC contacts of a headphone socket to disconnect the loudspeakers when the headphones is presented) from a few seconds to a few minutes? (J. H., Bankstown, NSW). • The door strike on-period can be extended by changing transistor Q3 are plugged in. For example, you could wire the NC switch contact in place of the 0Ω link for R2 or it could be placed in series with the 100Ω resistor between the collector of transistor Q1 and the base of Q2. In the latter case, when the headphone contact opens (ie, when the headphones are plugged in), transistor Q2 switches on (after a short delay to charge the 470nF capacitor via the 100kΩ resistor at Q2’s base) to ultimately prevent the relay from being driven via Q3 and Q4. Note that the headphone socket would need to have an isolated switch contact (eg, Jaycar PS0184 or Altronics P0074). Alternatively, the NO contact for the DPDT stereo insulated switch in the headphone socket could be used in parallel with the NO thermostat contact. to an IRF540N N-channel Mosfet. The Mosfet is installed with the same orientation as the transistor, with the Mosfet’s gate in place of the transistor’s Quality ISO 9001 siliconchip.com.au July 2011  99 How To Measure Subsonic Sounds From Wind Farms Has SILICON CHIP ever described a circuit to measure both the frequency and energy of infrasound? We are trying to measure the noise generated by wind farms due to serious concerns with the distress that they can cause to people living in the near vicinity. It is clear that a relatively cheap meter of some sort is needed to perform in-field measurements in the sub-audible range to test the various theories. (P. K., Mittagong, NSW). • We have had previous discussions with an acoustics consultant on this topic and he remarked that one of the mechanisms by which subsonic vibration becomes audible is that it rattles window panes and excites ceilings, walls and floors at base and the drain and source in place of the collector and emitter. The 1kΩ resistor at pin 9 of IC1 should be lifted and a 1N4148 diode placed in series with this 1kΩ resistor, with the anode at the pin 9 end (the anode end is the end opposite the stripe [K] end of the diode). A 10MΩ resistor should then be connected between the Mosfet’s gate and source. In addition, a 220µF capacitor must be connected between the gate and source (negative to the source). In this way when the door strike is to be activated, the high output at pin 9 of IC1 would charge the 220µF capacitor via the diode and 1kΩ resistor. This would switch on the Mosfet to power the door strike. When the output at pin 9 of IC1 goes low, the diode is reverse biased and the capacitor discharges via their own resonances which then amplifies the effect. By the way, the infrasound is produced each time the turbine blades pass the tower. It is an interference effect. It should be possible to calculate the frequency by simple observation of the number of times the blades rotate in one minute – and then do the calculations. We have not published an infrasonic meter as such but it would not be a big job to modify one our of previous sound level meter designs so that it has a response down to 1Hz or below. Ideally, you would want a readout of frequency as well. We published a sound level meter back in the December 1996 issue of SILICON CHIP. It was designed to be the 10MΩ resistor. When the voltage across the capacitor drops, the Mosfet switches off. The extra time would be 220 seconds or about three minutes. Change the capacitor value to set the time. Amplifier slew rate is generally unimportant Please can you tell me what the slew rate is of the Studio 350 power amplifier module (SILICON CHIP, January & February 2004). (S. W., Stowmarket, UK). • We did not publish data on the slew rate or gain bandwidth for this amplifier however we did publish a full power square wave, captured with an oscilloscope. Estimating the slope of the vertical edges on that square used with an external DMM. We have tried using a couple of standard sound level meters for such measurements and they also have an analog output which could be connected to an oscilloscope or frequency meter. However, we found it doesn’t work as the sound level meter outputs have no response to infrasonic signals. However, we have tried measuring infrasonic pulses (produced by partially opening and closing a door) with the high-performance microphone preamplifier featured in the September 2010 issue (it has a usable response to below 1Hz). To observe the infrasonic signal, you need a digital scope with a slow horizontal sweep speed at around 500ms/div. wave, the slew rate into 8-ohm loads is somewhere in the region of 20-25V/μs. It could possibly be as high as 50V/μs. An audio amplifier’s slew rate can matter to performance but if the amplifier is properly designed, it is not usually critical. The reason is that most audio amplifiers use dominant-pole compensation (in the form of a Miller capacitor in the “Voltage Amplification Stage”) in order to avoid high-frequency oscillations. This capacitor rolls off the open loop gain at higher frequencies. It also limits the slew rate. If an amplifier has excessive compensation (eg, due to inherent instabilities in the design) then it might have a low enough open-loop gain at high frequencies such that the negative feedback no longer works to cancel 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 Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. 100  Silicon Chip siliconchip.com.au Next month in SILICON CHIP: August 2011 3D Printing Ever want to make your own plastic prototypes of scale models, unusual hardware items or whatever? You would need a 3D printer wouldn’t you? But these are still horrendously expensive, aren’t they? Well actually, no and we review a 3D printer which is affordable for most businesses. Inclinometer That’s a fancy name for a digital spirit level. And why would you want such a thing? Well a spirit level will tell you if a surface is horizontal or vertical but if it is somewhere in between, it won’t tell you the slope in degrees. Our inclinometer will. It uses a 3-axis accelerometer chip and a microcontroller (inevitably) to drive a 4-digit LED display. Electronic Stethoscope Want to check out your heartbeat or trace some odd sounds in a car engine? This electronic stethoscope will do the job and you can listen on headphones or a loudspeaker. It has switchable frequency shaping in four bands so you can hone in on sounds which would otherwise be masked out. Ultra-LD Mk.3 Amplifier Module The second article on this ultra-high-performance amplifier will detail its construction and set-up. It will also provide some more details on its phenomenal performance. Note: these features are in the the process of preparation for publication and barring unforeseen circumstances, will be in the issue. ON-SALE: Wednesday, 27th July 2011 distortion. This would also result in a low slew rate, hence low slew rate can be an indicator of poor performance. However, if you have access to graphs of THD+N vs frequency, rather than using the slew rate as a means to assess the high-frequency distortion performance, you can simply look at the upper end of the graph and note how fast distortion rises with frequency. We publish these graphs for virtually all our designs as well as THD+N vs power graphs. We suggest that these graphs are the best means of determining whether an amplifier will sound good (in the sense of “clean”; ie, with no added harmonics to muddy the sound). We usually consider the THD+N figures for 1kHz and 10kHz or 20kHz as a way to estimate performance. Is it typical for the distortion at 10kHz to be around 10 times that at 1kHz. If you need a lot of power then the Studio 350 amplifier has very good performance, as stated in the article. Distortion is low, as is noise. However if you are happy with 135W into 8Ω or 200W into 4Ω (enough power to generate a lot of sound unless your speakers are incredibly inefficient) then take a look at the new Ultra-LD Mk.3. This has even lower distortion and is more compact. It also runs off lower voltages, simplifying the power supply. As a comparison, the Studio 350 has THD+N figures of 0.002% (1kHz) siliconchip.com.au and 0.02% (10kHz) while our updated Ultra-LD Mk.3 figures are 0.0006% (1kHz) and 0.0027% (10kHz). Not only does the latter have less distortion overall but the rise in distortion at higher frequencies is also much less. Tuning the Theremin Mk.2 I have built the new improved Theremin Mk.2 according to the project published in SILICON CHIP, March 2009. Unfortunately, it is not working. I am an experienced electronic builder and took care of all the details, including the correction of the errata which I found on your website. So far, I cannot make the thing work. First of all there is no sound. I suspect there is a problem somewhere in the volume control section. The volume oscillator is working but I am not able to do the volume alignment according to the directions published in the project. There is no voltage between TP GND and TP2, whatever I do with T4’s slug. According to the written directions, this voltage should be set to 2.5V. (M. F., Brasilia, Brazil). • The volume tuning must be done according to the procedure described on page 40 of the March 2009 issue under the heading “Volume Alignment”. You need to be able to get 2.5V at TP2 and 7V at TP3 before any sound will be heard. If adjustment of T4 does not Notes & Errata USB Recording/Playback Interface, June 2011: ideally the XLR connectors for the microphone inputs should be female, in line with the usual convention. Female XLR connectors can be fitted to the front panel and the connections between pins 3 & 1 of each connector swapped over between the connector’s rear lugs and the pads on the PCB – instead of passing straight down. This can be done quite easily if short lengths of insulated hook-up wire are used to make these connections, thereby ensuring that there will be no accidental shorts. provide any change in level at TP2, then try re-positioning the slug in T3 and readjust T4 again. No voltage at TP2 could mean that there is no oscillator signal applied to Q4 or that Q4’s T4 slope detection is not working. An oscilloscope would help in tracing the signal through to diode D6’s anode. Otherwise check that the parts are correctly placed and make sure that there is no short circuit between D6’s cathode (K) and ground. Check also that both D6 and the 2.2µF capacitor at D6’s cathode are orientated correctly and that D6 is SC still OK. July 2011  101 SILICON SILIC CHIP siliconchip.com.au YOUR DETAILS LOOK! EVEN Order Form/Tax Invoice Silicon Chip Publications Pty Ltd LOWER PRICES! ABN 49 003 205 490 High Aussie $ means imported books are now even lower in price! Your Name_________________________________________________________ PO BOX 139, COLLAROY NSW 2097 email: silicon<at>siliconchip.com.au Phone (02) 9939 3295 Fax (02) 9939 2648 This form may be photocopied without infringing copyright. 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IMAGECRAFT C COMPILERS ANSI C compilers, Windows IDE AVR, TMS430, ARM7/ARM9 68HC08, 68HC11, 68HC12 GRANTRONICS PTY LTD www.grantronics.com.au Hurry - stocks are limited. Call Avcomm now - (02) 9939 4377 Made in Australia, used by OEMs world-wide splat-sc.com 537 Kits, Modules and Boxes Innovative & affordable projects for hobby, school & industry Shop on-line at: www.kitstop.com.au electronics-the fun starts here FOR SALE MAXIMITE BREAKOUT BOARD: 10 channels, 2 relays per board. 2 boards can be cascaded to get all 20 channels. Each channel can be configured as Digital In, Digital Out or Analog In, Screw terminals. More information www.hamfield.com.au RCS RADIO/DESIGN is at 41 Arlewis St, Chester Hill 2162, NSW Australia and has all the published PC boards from SC, EA, ETI, HE, AEM & others. Ph (02) 9738 0330. sales<at>rcsradio.com. au; www.rcsradio.com.au PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone (02) 8005 6732. sesame<at>sesame.com.au www.sesame.com.au questronix.com.au – audiovisual experts solve home, corporate security and devotional installation & editing woes. QuestAV CYP, Kramer TVone (02) 4343 1970 or sales<at>questronix. com.au siliconchip.com.au Yes, it’s true! Don’t let its tiny size fool you. This powerhouse receiver covers the AM, FM, LW and entire SW bands from 35 to to30MHz 3.5 30MHz– –andandhashasgenuine genuinedigital Digitalsignal Signalprocessing! Processing! Exclusive to Avcomm, the Tecsun PL-310 DSP normally sells for $90.00 (plus p&h) but if you say you saw it in SILICON CHIP, Avcomm will give you an amazing10% off! CLEVERSCOPE USB OSCILLOSCOPES 2 x 100MSa/s 10bit inputs + trigger 100MHz bandwidth 8 x digital inputs 4M samples/input Sig-gen + spectrum analyser Windows 98/Me/NT/2k/XP WOW! A QUALITY DSP HF COMMUNICATIONS RECEIVER FOR 10% OFF? For more details visit www.avcomm.com.au Battery Packs & Chargers 3”,5” 7”,9” 10” Super Bright Displays MEAN WELL Power Supplies On The Net www.radioandelectronics.com Ph: 1300 495 211 Fax 08 9402 1287 Email: sales<at>radioandelectronics.com PO Box 780, Hillarys, WA 6923 Siomar Battery Engineering www.batterybook.com Phone (08) 9302 5444 LEDs! Nichia, Cree and other brand name LEDs at excellent prices. LED drivers, including ultra-reliable linear driver options. Many other interesting and hard-to-find electronic items! www.ledsales.com.au WANTED CUSTOMERS WANTED: Truscotts Electronic World – large range of semiconductors and passive components for industry, hobbyist and amateur projects including Drew Diamond. 27 The Mall, South Croydon, Melbourne. Phone (03) 9723 3860. sales<at>electronicworld. com.au WANTED: EARLY HIFIs, AMPLIFIERS, Speakers, Turntables, Valves, Books, Quad, Leak, Pye, Lowther, Ortofon, SME, Western Electric, Altec, Marantz, McIntosh, Tannoy, Goodmans, Wharfedale, radio and wireless. Collector/ Hobbyist will pay cash. (07) 5471 1062. johnmurt<at>highprofile.com.au KIT ASSEMBLY KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith 0409 662 794. keith.rippon<at>gmail.com July 2011  103 Do you eat, breathe and sleep TECHNOLOGY? Opportunities exist for experienced Sales Professionals & Store Management across Australia & NZ Jaycar Electronics is a rapidly growing, Australian owned, international retailer with more than 60 stores in Australia and New Zealand. Due to our aggressive expansion program we are seeking dedicated sales professionals to join our retail team to assist us in achieving our goals. We pride ourselves on technical expertise from our staff. Do you think that the following statements describe you? Please put a tick in the boxes that do:  Knowledge of core electronics, particularly at a component level  Retail experience, highly regarded  Assemble projects or kits yourself for your car, computer, audio etc  Have energy, enthusiasm and a personality that enjoys helping people  Opportunities for future advancement and development  Why not do something you love and get paid for it? Please email us your applicaton & CV in PDF format, including location preference. We offer a competitive salary, sales incentive and have a generous staff purchase policy. Applications should be emailed to jobs <at> jaycar.com.au Advertising Index Agilent Technologies........................ 13 Altronics...................................... 78-81 Avcomm......................................... 103 Digi-Key Corporation.......................... 3 Dyne Industries.................................. 6 Embedded Logic................................ 6 Emona Instruments............................ 9 EV Power....................................... 103 Jaycar Electronics is an Equal Opportunity Employer & actively promotes staff from within the organisation. Futurlec............................................ 11 Grantronics.................................... 103 Hare & Forbes.............................. OBC High Profile Communications......... 103 HK Wentworth.................................... 8 Instant PCBs.................................. 103 Jaycar .......................... IFC,49-56,104 Jimojo.............................................. 11 Keith Rippon.................................. 103 Kitstop............................................ 103 LED Sales...................................... 103 LHP.NET.AU................................... IBC Microchip Technology......................... 7 Ocean Controls................................ 25 CIRCUIT IDEAS WANTED DOWNLOAD OUR CATALOG at We pay up to $100 for contributions to Circuit Notebook or you could win a piece of test gear. send your circuit idea to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. www.iinet.net.au/~worcom Quest Electronics........................... 103 WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305 Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au Radio & Electronics Pty Ltd........... 103 RCS Radio..................................... 103 RF Modules................................... 104 Sesame Electronics....................... 103 Issues Getting Dog-Eared? Keep your copies safe with these handy binders Available Aust. only. Price: $A14.95 plus $10 p&p per order (includes GST). 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To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or fax (02) 9939 2648, or phone (02) 9939 3295. 104  Silicon Chip Silicon Chip Binders....................... 104 Siomar Battery Engineering........ 5,103 Soundlabs Group............................. 12 Splat Controls................................ 103 Switchmode Power Supplies............ 99 Truscotts Electronic World............. 103 Wagner Electronics.......................... 59 Wiltronics......................................... 10 Worldwide Elect. Components....... 104 PC Boards Printed circuit boards for SILICON CHIP designs can be obtained from RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0331. siliconchip.com.au e r o t s SOLAR ENERGY.com.au THE SMART CHOICE Solar Power BACKPACK Charge your iPhone, camera etc, while you walk. Complete set ready to use $49 NOW ONLY $35 LED 12vdc Bright Lights Great for camping tent, caravan etc.5m Roll easily cuts to size. Waterproof + adhesive back fast easy installed. Silent Sine Wave Generator Battery Charge Controller INFOMON COOLING FRIDGE - FREEZER Protect your battery from overcharging. PLUS: LCD display shows you the amount of power you are using and producing. Also lets you know battery VDC and Batt capacity Pecentage. 240VAC Power, 4.4KVA: $799 2kVA also available: $499 From $89 Solar Panels BEST PRICES IN AUSTRALIA! ONLY $49 INFOMON ECO CHARGER Compact small powerful laptop phone charger with Solar Cell recharge built in. Connect 2 devices in at the same time and charge within 2 hours. Complete Pack, ONLY $169 ready to use. Grid Inverters CEC Approved 5KW $2499 NOW $1999 2KW $1499 NOW $999 20w . . . . $59 Each solar 50w . . . . $150 panel 80w . . . . $250 features 100w . . . $300 a 25 year power SPEC 120w . . . $350 warranty. SILICONICAL OFFER for 200w . . . $599 FREE DHIP READERS: AUSTRALELIVERY IA WIDE! Folding Solar Panels All come in a carry bag, regulator, cable and leads -- READY TO USE! 60 watt . . . . $199 80 watt . . . . $350 100 watt . . . $399 120 watt . . . $499 160 watt . . . $599 200 watt . . . $699 60cm electric fan-forced oven with temperature, timer control AMAZING $299 $169 NOW ONLY $129 Petrol powered LAWN MOWER Infomon Wind Turbines One of the most technologically advanced Wind Tubines on the market. Sold in over 70 countries across the world!!! We have 2 models to choose from: Portable 500W Wind Turbine kit - complete with controller and tower for fast easy set up SALE Was $1599 NOW ONLY $699 4 Stroke Worth $899 Now Only $299 NOW ONLY $189 Pressure Washers Commercial grade Petrol Was $1300 60cm, 4 burner And Stove Petrol powered CHAIN SAW LIMITED STOCK Stainless Steel Cooktop JUST $99 gas with auto ignition This is one tough Fridge Built to Last. Latest technology interface + Design Great for mobile remote use. Micro Computer Temp Control energy saving system so it does not stress out your batteries. 45L was $1499 NOW $ 769 60L was $1699 NOW $799 80L was $1899 NOW $899 FREE BONUS : Insulation Cover, Wall charger and cigarette adaptor. NOW $499 For those who want to generate some serious power we have a 1000 watt system complete kit with stand and controller Dont Pay over $2000 SALE $1199 LIMITED STOCK Heavy Duty Diesel Was $2000 NOW $899 siliconchip.com.au July 2011  105 5/110 Station Rd, Seven Hills NSW 2147 (Mon-Fri 9am-5pm) Phone (02) 9620 9011 www.lhp.net.au