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8 Google Earth Preampliîier - Page 26. Ever wanted to zoom in on your house from 450km out in space? Google Earth will let you do it . . . and it's free! - by Ross Tester OcroBEn 2005 14 NetComm NP210: Ethernet Over Power You don't have to run new cables. Ethernet Over Power (EOP) lets you network your PCs via the 240VAC power wiilng - by Ross Tester 86 The iButton - A Hard \"Nut\"To Crack This family of devices comes in 1ãmm-diameter stainless steel cans.You can build a simple project to read their serial numbers - by Clive Seager 91 The DSl921 iButton Datalogger The D51921 houses an embedded computer chip with a temperature sensor, cloclc/calendar and memory . . . all in a 16mm steel can - by Clive Seager 22 Dead simple USB Breakout \"Box\" Do your USB devices misbehave or suddenly stop working? Here's an easy way to find out if your PC's USB ports can meet the demand - by Stan Swan 26 Studio Series Stereo Preamplifier Designed for the audio pertecilonis[ this superb preamplifier uses the latest high-peiormance op amps for ultra-low noise and distortion - by Peter Smith 38 Video Reading Aid For Vision lmpaired People It uses a small CMOS TV camera to produce an enlarged positive or negative image with boosted contrast - by Jim Rowe 66 Siniple Alcohol Level Meter It might not stand up in court but this simple device will give a good indication of alcohol on your breath (and therefore in your bloodstream) - by John Clarke 76 Ceiling Fan Timer It runs the fan in your bathroom or toilet for a fixed time after you turn it on and has two modes of operation - by John Clarke St 48 Serviceman's Log M You can't have enough protection - by the TV Serviceman at 61 Circuit Notebook (1) Discrete Dual-Tracking Power Supply; (2) PICAXE-Controlled Bird Brooder; I (3) Electronic Nim Game; (4) Trickle Charger Uses An Optocoupler 94 Salvage lt! A $5 2-channel vibration sensor - by Julian Edgar 100 Vintage Radio The Harbros 12/548 fire brigade transceiver - by Rodney Champness 2 Publisher's Letter 106 Ask Silicon Chip 4 Mailbag 108 Notes & Errata 37 Order Form 109 Market Centre 83 Product Showcase 111 Ad lndex siliconchip.com.au
PuilisneF's letter Valve amplifiers and Publisher & Editor-in-Chief self-delusion Leo Simpson, B.Bus., FAICD Well, we certainly seem to have struck a Production Manager chord with the publication of the Mudlark valve Greg Swain, B.Sc.(Hons.) amplifier design in the preceding two issues, ' Technical Editor '\\ugust and September. We have had some very enthusiastic one level, Peter Smith letters from readers. At I can understand the enthusiasm. With their Technical Staff glowing valves and the heat rising from them, John Clarke, B.E.(Elec.) Roçs Tester valve amplifiers can seem almost animate, in Jim Rowe, 8.4., B.Sc, Vj<2ZlO much the same way as a steam locomotive at Reader Services rest can seem almost \"alive\". Ann Jenkinson But on a pure performance level, I really calnot understand the attraction. Many people claim to love the sound of valve amplifiers, citing their \"soft\" Advertising Enquiries overload and tendency to produce low-order harmonic distortion instead of the \"highly undesirable high order\" harmonic distortion of modern solid- Lawrence Smith state amplifiers. Now it is one thing for a musician to prefer a vaÌve amplifier Benedictus Smith Pty Ltd because of the particular sound it can be made to produce when playing a guitar. It is quite another for someone listening to CDs to prefer the sound of Phone (02) 9211 8035 a valve amplifier over modern solid-state hifi designs which DON'T suffer Fax: (02) 921'l 0068 at alÌ from high-order harmonic distortion. lawrence @ benedictus-smith.com Unfortunately, there is lot of myth-making out there in the hifi market- Regular Gontributors place and too many people just swallow it. For example, among some Brendan Akhurst valve enthusiasts, single-ended amplifiers such as the Mudlark are much Rodney Champness, VK3UG preferred over far superior class-AB push-pull valve designs. Partly, this is Julian Edgar, Dip.T.(Sec.), B.Ed, because single-ended valve designs have predominantly second harmonic distortion which is preferable to higher order harmonics. But what people Grad.Dip.Jnl do not realise is that these single-ended amplifiers have LOTS of second- Mike Sheriff, B.Sc, VK2YFK harmonic distortion. Stan Swan Furthermore, if you have high harmonic distortion in a circuit, you will SrLlcoN CHIP ispublished 12 times ALWAYS have high intermodulation distortion. This is never mentioned a year by Silicon Chip Publications when you hear people waxing lyrical about valve amplifiers. Intermodulation Pty Ltd. ACN 003 205 490. ABN 49 003 205 490-All material copyright is the product of two different tones fed to a system - sum and difference @. No part of this publication may be reproduced without the written frequencies are the result and these are never harmonically related to the consent of the publisher. input tones. On complex orchestral and choral music, high intermodulation sounds horrible. Printing: Hannanprint, Noble Park, Victoria. Interestingly, before the advent of solid-state amplifiers, high quality Distribution: Network Distribution push-pull valve amplifiers were the order of the day - single-ended designs Company. were regarded with disdain. Subscription rates: $83.00 per But forgetting distortion - and many valve amplifier enthusiasts seem year in Australia, For overseas happy to do this - there is a huge amount of nonsense being circulated about rates, see the subscription page in valve amplifiers. For example, printed circuit boards are regarded þy some this issue. self-appointed gurus) as undesirable because they can lead to earth loops while supposedly, such problems do not exist in amplifiers with point-to- Editorial office: Unit8, 101 Darley point wiring! In fact, some amplifiers are assembled with silver wiring be- St, Mona Vale, NSW 2'103. cause this supposedly minimises earth loop problems. What utter drivel! Postal address: PO Box 139, By all means, build and listen to valve amplifiers if that is what you enjoy. Collaroy Beach, NSW 2097. They do sound quite different to the best solid-state amplifiers. They can Phone (02) 9979 5644. even sound very pleasant. But to genuinely believe that typical valve ampli- Fax (02) 9979 6503. fiers with low orclers of feedback are more \"hifi\" and sound better than the E-mail: silchip@ siliconchip.com.au best solid-state amplifiers is merely self delusion, rssN 1030-2662 Leo Simpson . Recommended and maximum price only. siliconchip.com.au SILIC)N CHIP
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MAITBAG OK, we gave in. . . corded music and valve amplification, listen\" situation t}rat is aII too common I was ¡eading some old Stllcou Cmp and there seems to be no good reason these days. magazines when I came across the JuIy to withhold a project that could lead to The following are a few off-the-cuff 1994 issue and had to laugh at your much pleasure for these readers. avenues for those interested enough to Publisher's Letter, \"I (Leo Simpson) actually build the Mudlark: There are a number of aspects of can state right now that SLICoN CHIe the published design that deserve How many push-pull voltage am- wiII never publish a design for a valve more than a passing look. Although plifying stages has the program signal some of these would appeil to fly in been subject to during the recording hifl amplifier - never, They have no the face of conventional knowledge process? Every one of tlese has can- place in today's technology\". What regarding circuit design, many have in celled even harmonic information do they say about never? Never say fact been conceptualised through years and proliferated odd harmonics. What nevel. of empirical experimentation, rather has this done to the integrity of the 'performance? Would it be better to re- Kevin Taylor, than following tle agreed scientific ap- Auckland, NZ. balance the signal by putting it tbrough proach that would have resulted from a circuit such as a single-ended valve Comment: to be prccise, the quote the implementation of the \"high-tech\" power amplifi er which will accentuate even harmonics and possibly restore should be, \"I can state right now that proposition suggested in your editorial Satco¡,t Catp wiII never publish a de- a measure of \"authenticity\" before it in the August issue. sign for a hifi valve amplifier unless it reaches the ear? I have a sneaking feeling that your is for academic intercst only. In fact, Remembering that an electronically Iet's be even more absolute and just idea of ahigh-voltage op amp followed reproduced listening experience is a by an ultra-linear valve output stage composite of all distortions encoun- say NEVER.\" with bags of added negative feedback, tered along the signal route (some In fact, the reasons for writing that would have resulted in a \"worst of both additive, some subtractive) and that worlds\" design that might have meas- editorial, that valve amplifiers perform they are many and varied, what does poorþ by compailson with really good ured quite reason.ably but produced a poor sonic result when connected it matter if the final amplifier intro- solid-state models, are unchanged. to real-world speakers in a domestic listening environment, duces a few percent more, provided But as you say Kevin, never say never! You can see why we were so reluctant As you have pointed out on numer- always that it is configured so as to to do it. ous occasions, if you want an exem- mathematically reduce the corruption Valve sound with solid-state plary set of measurements, SucoN With all the current discussions to the information arriving at the ear CtilP's recent solid-state offerings are and projects featuring valves, can the virtually unbeatable, That said, there of the listener? \"valve sound\" be obtained by having are still many reasonably sane ald It should be noted that recording a valve preamp ald solid-state power studios and their systems, pick-up amplifler? If the answer is yes, why not intelligent folk out there who have no justgo dor,rm this road arld don'tworry cartridges, D/A converters, Ioudspeak- hesitation in selecting an amplifier that about 2 O-watt valve p ower amplifl ers. ers, etc inherently contribute up to After all, a 100W solid-state amplifier offers a lamentable set of figures but a couple of percent distortion to the is easier to make; eg, your UItra-LD is capable of delivering an enthralling chain, so what is so appealing about a Stereo Amplifier, musical experience. In my experience, power amplifier that only adds .005% Ian Stewart, via email. there are in fact very few solid-state at the end? At best, it will do no more designs that can boast likewise in a Comment: the valve preamp followed harm; but neither has it the potential to by the Ultra-LD would give much bet- head-to-head \"shoot-out\" under con- ter sound than a valve amplifier with add a modifiiing factor that may undo transformers and not much negative trolled listening conditions. feedback. However, valve sound en- some of the existing damage. thusiasts don't seem to want that. Of course, agood amplifier ca¡r send For those who would follow this what appear to be the right electrical Publishing the Mudlark impulses to the speakers ald thence to line of reasoning and are prepared to an inspired move the listenerbut in reality, there is often think outside the conventional square, Your decision to publish the \"Mud- a huge difference in the enjoyment la¡k\" valve amplifier project seems to be one of those inspired moves, As you level of the resulting musical experi- point out, there are quite a number of readers who have more than a pass- ences. I feel that it is long overdue that ing interest in the reproduction of re- technology was better applied just to give sheer listening enjoyment (as was the case in the early days of Radio & Hobbies and John Moyle's Playmaster valve circuits) rather than the \"mine is bigger/better/more powerful/less distorted than yours, so shut up and Stuco¡rt Cutp siliconchip.com.au
it is worth reading some of the papers order was placed the same day I got Atmel's AVR, from written by Eduardo de Lima (and oth- JED in Australia ers) on the subject of distortions in hold of your magazine. audio equipment. There are pìenty of I'd like to say one more thing. Read- JED has designed a range of folkwith a deep appreciation of music single board computers and who feel strongly that the commonly ing your magazine is a pleasure and a referred to scientific principles do not joy. I feII in love with electronics when modules as a way of using the provide aÌl the answers to listening AUR without SMT boatd design I turned 10 (46 years agoJ and I am still satisfaction. The AVR570 module (above) is a way of going strong. using an ATmega128 CPU on a user base StlIco¡l Cnp is to be congratulated board without having to lay out the intricate, for its preparedness, no matter how Bob Bozanic, surface-mounted surrounds of the CPU, and reluctaltly, to provide this avenue for Tra¡algon, Vic. then having to manufacture your board on the enquiring hobbyist; after all, isn't an SMT robot line. lnslead you simply layout Circuit wanted for a square for four 0.1\" spaced socket strips that what DIY magazines are supposed Grundig \"Satellit\" receiver and plug in our prelested module. The module has the crystal, resetter, AVR-ISP to be about? I have a need for a circuit diagram programming header (and an optional JTAG Kerry Williams, for my Grundig Satellit 800 receiver. ICE pad), as well as programming signal Applied Physics, Grundig Australia say they have never switching. For a little extra, we load a DS1305 School of Applied Sciences, heard of it and Grundig US,\\ have not RTC, crystal and Li battery underneath, RMIT University, Bundoora, Vic. replied to my query, which uses SPI and port G. See JED's www site for a datasheet, Comment: we had to check the date I have searched the internetbut have çome up with the Users Marual, which AVR573 Single Boatd Gomputer on your email to confirm that it does not have a schematic. Is anyone wasn't April lst. You're winding us This board uses the AVR570 module and able to help? The radio is dead and wilÌ adds 20 An./Dig. inputs, 12 FET outputs, LCD/ up, right? become an expensive boat anchor if I Kbd, 2xRS232, 1xRS485, 1-Wire, power reg. cannot repair it! etc. See www.jedmicro.com,au/avr.htm The idea of addinglots of even-order h armo nic d i sbrtion during p layb ac k, Ray Reaburn, $330 PG-PROM Ptogtammer Mont Albert Nth, Vic. to compensate for any distortion This programmer plugs into a PC printer ray3 [email protected]. au port and reads, writes and edits any 28 ot added duringthe recording process is problematical, to say the least. What Digital cameras more 32-pin PBOM. Comes with plug-pack, cable convenient than 35mm and software. people do not realise is that if a sys- I must say I was very surprised at Also available ¡s a multi-PROM UV eraser tem has a high degree of supposedly your negative reaction to digital cam- with timer, and a32132 PLCC converter. eras (Publisher's Letter, July 2005), \"good\" low order harmonic distor- especially in Ìight ofthe fact that you JEll Microprocessors Pty ttd tion, iI will also hove a high degree of use (have) one in your office. Only 173 Bolonia Rd, Bo¡onia, Victoria,3155 intermo dulation. Intermo dulation i s a couple of years ago, I would have Ph. 03 9762 3588, Fax 03 9762 5499 never good! agreed with you. But not now. www.¡ednicro.com.au I agree you will pay more for digital InterestingLy, there is a precedent for adding disbrtion. In RCA's Dyna- than 35mm but five years ago, 35mm groove process, the recorded signal SLRs were about the same price as a was pre-distofted and dynamically good quality digital is now It is unfair equalised to compensate for the poor to lump all digital cameras as bad be- performance of cheap phonograph cause of a single bad choice, players . At the time, most audiophiles Recently, I went to Antarctica and judged the sonic results to be poor. took two digital cameras and one Cost of valve amplifiers 35mm SLR. I could view my digital not the issue photos full size within minutes if I wanted and preview them seconds Your Publisher's Letter in the August after taking them. I did a backup at issue is everything that a level-headed the end of each day and at maximum audiophile should agree with. Except quality and image size, never ran out one thing: \"using high quality output tralsformers, such a design would cost of \"film\" [ie, memory card). I used a single 512Mb card and two 256Mb well over $1000, which is the main cards (one as an emergency). My laptop could directly read the cards, reason we did not proceed.\" so I needed no extra cables. I could For some of us (non-level headed), select the good shots and erase the price is not the main consideration. It bad ones. is about choice and I hope I wiÌl live long enough to see your $1000 plus My 35mm film had to wait until I design and have a chance to build it, returned. There aren't too many film as I have built a hundred or so projects labs in Antarctica! One of my rolls was from yours and other magazines. I can- not wait to start on the Mudlark - my síliconchip.com.au OCTOBER 2OO5
Mailbag: continued is always poor because, in aperture from the water meter, Earths don't priority mode, the lens aperture is completely blank - the fiIm had not come much better than that! normally wide open at f2.8. Although Also, I just happened to have some caught on the sprocketwhenwinding on. With film, I had no choice about this might be so with a 35mm film off-cuts of \"monster cable\" that you selecting which shots I wanted; I had camera, with a small digicam this is could start a truck motor with and a to pay for them all, even the blank handy pack of assorted hose clamps not actually the case. The depth of fleld from a $2 shop! After some quick work ones. of llne C725 is quite large, in line with with some sandpaper and application other small-sensor digicams, and it is of the clamps and monster cable, that There has been a lot of comparison much greater than in DLSRs or 35mm mast was about as grounded as you between the cost of film and the cost film cameras. of digital. They all assume that you are Did it fix the digital TV dropouts? going to print every photo you ever The reason behind this is that the WeIl not completely, although it cer- take. What about when you only want C725 uses a liny 1.12.7\" CCD, whose tainly improved the situation. But one photo? Is it reasonable to process an entire film? What about photos for dimensions are about 5,3mm x 4.Omm, what it did do was clean up all the email or screen-savers? Scanning film assorted random interference I used which is much smaller than a 36 x or a print is inconvenient and to do it 24mmframe of 35mmfilm. Compared to get on the analog channels! to a 35mm film camera, the cropping Like manypeople in Sydney's outer- at good quality is expensive. factor for the lens on the C725 is 6.56. west, I get better reception of SBS and The weight of an SLR and fiIm As the C725 ]¡ras a lens whose focal the ABC from Wollongong than Artar- would likely be similar to a digital length range is 5.9-59mm, when this mon, so I have a band III VHF antenna camera, memory, charger and cables, cropping factor is applied, the lens pointed at Sydney and a high-gain so there wouldbe no real saving when has a field ofview equivalent to a 38- going overseas. The only issue is for- UHF antenna pointed at Wollongong, getting bits. 380mm lens on a 35mm fi.lm camera. This also gives me the regional ver- One of the by-products of this is that sions of the commercial channels. I I have never needed to use the eye when the C725's lens is set to f2.8, it used to get intermittent patterning viewflnder - the LCD is sufficient for will have depth of field approximately viewing in direct sunlight with only on most of the channels which I put equivalent to a 35mm film camera set minor difficulty. Besides,I carr always to f(2.8 x 6.56) = 1'J.8.4. That is a lot of down to meteorologically-induced check my photos in the shade of my depth of field! If you stop down to f7 body after taking them. Most cameras va¡iations in signal strength. have many assistance features on the on the C725, then that's equivalent,to But since I've earthed the mast, I f45,9 on a 35mm flIm camera. display - a histogram, a manual focus haven't seen a sign of the interference As it turns out, producing a shallow and the Wollongong commercial chan- assist area, horizon guide lines, etc. depth of field for creative purposes nels are now almost indistinguishable is one of tlre inherent problems with Digital carneras still need work in small-sensor digicams. Apart from from the Sydney ones! the areas of reaction time (time be- other image quality and performance The intriguing thing is, I later dis- tween pressing the button and taking issues, it is one of the reasons why covered that there's no electrical con- the photo) but pre-focusing can cut nectionbetween the antenna coax and this dramatically. many professional photographers tend the mast. Earthing the coax itself is a Most of all, I want to know when my to prefer DSLRs, which either offer the bit tricky as separate UHF and VHF photos have turned out, rather than same or slightly greater depth of field waiting several thousand kilometres tha¡ a 35mm fllm camera, cables are run to the antenna amplifier (and dollars) to find out I had a finger which is mounted in a fairly inacces- smudge on my lens! Witold Waldman, sible spot under the roof tiles. What via email. I'11 probably do is strip back the outer Despite having both 35mm and jackets of the cables and clamp them Earthing TV antenna masts digital carneras, I have used my 35mm I'd like to thank Neil Hecker for his to the mast but I want to make sure I camera for about 30 photos in the tip on reducing STB electrical interfer- can waterproof everything properly time I have used my digital camera ence (Possible Cure for STB Electrical before I try that! for about 4000. Interference, Mailbag,,â.ugust 2005), Anyway, it was an unexpected and Owen Scill, amazing improvement for very little although it didn't produce quite the Canberra, ACT. outlay! results I was anticipating! Comparing digital cameras Rather than earthing the coax, I de- Keith Walters, with 35mm equivalents via email. cided to first try earthing the antenna I read your recent editorial on low- Induction loop mast instead, simply because this was interference to video cost digital cameras in the luly 2005 easier to do, My antenna is mounted directly above a garden tap which is I read with interest the letter from issue of Sucotrt Crlrp and have some \"first cab offthe rank\" after the 20 me- correspondent G. C. in the \"Ask Sili- tres of buried copper pipe that comes con Chip\" pages of the August 2005 comments. You stated that, on a digicam like issue, in regards to induction loop the Olympu s C7 25 , the depth of field interference to a video projector. StLtcoN Cntp siliconchip.com.au
As background, I have worked for as the rest of the video system. www.oz¡tron¡cs.com 20 several years for Audio Telex Com- munications who sell the Ampetronic If feeding audio from the video ITel: (03) Email: range of hearing induction loop drivers system to the audio system, try using and currently work for a sister com- Kl73. Tx with serial data input an isolation transformer to break the Kl74. Rx with serial data output pany - Crestron Control Solutions. At Kl75 Tx w¡th parallel data input the contemporary church of which I earth connection between the two Kí76. Rx with parallel data output am a member, I have set up a reason- sub-systems Each receiver has a 4-bit address set by an onboard DIP switch, allowing up to 16 ably complex video projection system It may be possible that the loop is rece¡vers to be used in a nelwork being over-driven and is producing Documentali0n ¡ncludes examples of how that runs alongside a high-power hear- much more fleld than is required by t0 use w¡th other kits for remofe operation ing induction loop fed from a 24-chan- AS 1088.4. Valuable insights into the K174. K1 workings of hearing induction loop nel audio mixer. We feed all computer systems can be obtained from the Prices include GST - sh¡pp¡ng extra. Ampetronic web site (www.ampet- andvideo sources into aKramer scaler Full documentat¡on available from websile. ronic.com), which converts numerous formats e 100kHz - 750MHz @ 1 OmV sens. (usable to 1.5GHz) into RGBFIV (SVGA) and then send I would strongly advise using a standard. up t0 70v RMS (100v ,-;. that signal to the projector over 35m professional installer for a loop system o Use with any of high-quality cable. as they will have access to design and RF Probes Pqt Ltd Here are some extra insights that analysis toóls to correctly set up the system and deal with problems such P0 Box 6, Greensborough 3088 may be useful to G, C. I am assuming as interfering fields from bad mains Phone:(03) 94321936 Faxì(031 9444 7750 that he is sending data to the projec- tor via RGBHV: I have found that it is installations or freld reduction caused Email: admin@rlorobes,com.au by structural steel elements. It is also important to use S-core coaxial cable worthwhile to procure a loop listen- not 3-core, with data. It sounds as if ing dgvice for testing and confidence he has induced noise on the horizontal or vertical sync signals (or both). He issues. should ensure that the red, green and From my reading of G. C.'s letter, blue signals in particular do not have he was sending RGBHV (ie, VGA or their earth connections tied together better) to his projector, not composite in the cable as this defeats the purpose of the transmission line, allowing in- video. I believe that you c anget2,4GHz gress of nasties such as ghosting and KVM switches that are good for up to smearilg. Horizontal and vertical sync 30 metres or so but would be nervous about that solution, particularly with are effectively digital signals and so their sharing an earth is not so much the crowding of the 2,4GHzband that we've seen recently. Call me a Nean- of an issue. derthal but I prefer cable over wireless Cables that I have used with gieat any day. success are Calare V5-1.5C and Euro- A number of manufacturers have cable RGBYCD3, These can be termi- systems that convert RGBHV into a nated directly onto HD-15 connectors format that can be transmitted down but it is a diffrcult job fltting everything Cat.5e or Cat,6 cable (and be reconsti- into the backshell without shorting tuted cleanly at the other end). One things out (heatshrink is your friend hereJ. These cables are also quite ex- is the Crestron QuickMedia system pensive (about $10 per metre) but in my experience, worth every cent. that can encode RBGHV (1600x1280), composite video, Y/C or component No cabling shouldbe run parallel in close proximity (withintwo metres) to and send it (along with audio) down a hearing loop. Cables should cross the up to 100 metres of Cat.5e cable in a loop at 90\" to minimise interference. balanced format. This includes audio and mains cabling These products are more than where possible. just baluns; they involve serious If at all possible, the projector amounts of signal processing and are should be \"flown\" (suspended), as not generally end-user installable. this removes it as much as possible They are, however, finding homes in maly university lecture theatres ald from the plane of the loop where the classrooms, as the systems can be field strength is at its greatest. It also monitored remotely (via an Ethernet helps remove the signal cable from connection) using Crestron's Room- harm's way, view software. Again, if at all possible, run the Phil Moore, projector from the same mains circuit Crestron Control Solutions, Silverwater, NSW' siliconchip.com.au OCT)BEî 2OO5
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Everyone who has seen q demonstrotÍon of Google Earth is gobsmacked. Mind boggled. Blown qwey. Hey, we're not gÍven to exqggeratÍon - but we've got to agree. It is gobsmacking, mind boggling and blowing awqy! And the best port of all obout Google Eorth: it's free! T-lor computer users in the 2Lst by Ross Tester Not surprisingly (considering where century, it's hard to imagine life Ifi before Google. Only invented in for words, phrases and acronyms. it was developed, it shows North Google Search by location - Restrict 1998, Google has already entered the America, , . fiom sea to shining sea. But your search to a geographic area. lexicon as a fully-fledged verb in its you can also \"turn\" the globe in any We could go on listing all day - but direction to reveal the whole planet. own right. You don't search on line that would hardly leave room for the It looks pretty spectacular. any more, You Google! Ho-hum? You're not turned on by real feature of this article: Google Even if its name is an accident Earth. If you'd like to go through all this? Anyone can display a nice pic- (Google was supposed to have been that Google itself has to offer, have a ture? spelled Googol, a number with 1 and look at fhundred zèros, or 1¡100), Google it- Google Groups. Come on down to my house... selfis no accident! But there is far, far Google themselves say their com- What if I told you that with the click pany philosophy is built on a 7 O / 2O / LO of a mouse button, you can \"fly\" fiom more to Google than \"just\" tìe world's rule: they spend 7o% of company re- right out in space to onypoint on that sources on core business - like search globe - right down to your own neigh- most popular search engine. Whether bourhood, almost right down to your engines; 2Oo/\" on closely related areas or,rm backyard fin some cases, info your by acquisition or in-house develop- (Iike news), while the remaining 10% own backyard!). You can zoom in, and is where their engineers run amokpro- ment, Google has become an enormous ducing oddball projects which don't in, and in - down to virtual ground flt anywhere but which are fun and/or powerhouse in the computing world. interesting and/or groundbreaking. level, in near-perfect clarity? Not quite Here's just a small selection of Google's But wait, there's more! so ho-hum any more? Some time back Google bought add-ons and other \"products\": Twist it, tilt it, move it . . . a little organisation called Keyhole Google News - aggregated headlines Here's another of Google Earth's and a search engine of many of the Corporation. Reports suggested the absolutely amazing features. With another click or two, you can tilt the world's news sources. main reason they bought it was that view from straight down (plan) right Froogle - a product search engine Keyhole was working on, and had just through any angle down to horizontal about completed, a highly innovative (elevation). It's not yet perfect - but by and shopping directory. Assists con- project. Google renamed that project the same token, it's not bad! sumers with locating products for sale Google Earth. And if you don't like the view you're online by presenting photos ofrelevant Without too much fanfare, Google getting, you carl turn it through any Earth was announced to the planet at products. the end of June this year. And without point of the compass, You can flick wanting to get into hyperbole, I would back arrd forward between plan and Blogger - a tool to make Web log describe Google Earth as \"mind blow- elevation. There's even a one-button \"back to north\" setting. publishing very easy. ing\". Everyone who has seen it (and And at any time, you can move the Google Toolbar - a toolbar featuring I've shown anyone who wouldwatch!) whole view in any direction with four a Google search bar, as well as other is astounded. compass points on the toolbar, Hitting Google tools, As of luly 2005, Google Google Earth is over-simply de- the red button at their centre will lock the centre of the screen so if you turn Toolbar is available for two browsers, scribed as al image of the Earth, a globe or tilt you stay viewing the area you if you will, which sits inside your PC four operating systems and in ten monitor. are interested in. You can reveal terrain, main roads, languages. When Google Earth fully loads, (and it can take a good half minute on a typi- country and state borders . . , Google Deskbar - search tool which calbroadband connection), abeautiful runs from the Microsoft Windows view of the Earth against a star back- As you move around or up and ground is revealed fiom some 38,500 down, you will note that the screen is taskbar, without a browser having to miles [62,000km) out in space, constantly updating. Google Earth is be open, refereshing images \"on the fly\" from its obviously immense image database. Google Desktop - where your search is internal; that is, within your own Note that as yet, you cannot access computer. OcroBEn 2oo5 Google Groups - join [or even create) discussion groups, mailing lists and newsgroups, Google News Alerts - Specify a topic and receive email updates when news breaks. Google Web Alerts - Find out about new web pages on a topic of interest. Google Glossary - Find definitions siliconchip.com.au
hi-res images everywhere - this is an become, well, buildings. (A tip : try this take immense undertaking and will on London and New York City). You can also highlight major roads, some time - if ever - to complete (it's actually still in beta form). They are places ofinterest, show the terrain or turn it off (it's less confusing that way), obviously concentrating on the major show state and country borders, show restaurants andhotels (we'Ìl lookmore population areas and working down. closely at that feature later), The lonely planet from 30,000 miles. Deja Vu? Änd before I forget, one of the most Some SntcoN CHIP readers will be Almost home! 15,ooo intriguing features of Googìe Earth: as experiencing a sense of deja-vu. Some- you might expect (being ftom GoogÌe), We've zoomed in to just 3,500 miles , . . thing sounds familiar about all this? it has search featutes. But they're Here's the view from 1o00 miles uP. Back in May 1999, we introduced extremely powerful: for example, the At 100 miles, starting to see features. you to the \"Terrasetvet\" website \"Fly to\" search. Simply type in the 10 stLtcoN cntp which also offered \"pictures fiom name of the place you walt to go to space,\" with quite good resolution in some areas (especially if you paid (eg, Paris, France) and Google Earth \"flies\" you there. Up, .,p and away for theml. That website has undergone quite a - across countries, oceans, even the downgrade, where now it appears to poles, until you descend into your offer USA images onÌy - but even in destination. ,\\nd I mean into - right its heyday it was nothing like Google Earth. For ease of use, features, clar- down to ground level! You really do have to experience this one! itv, value - Google Earth beats it every Resolution time. Terraserver never had anything In high resolution, the images, like the features of Google Earth we've already covered, let alone the bits we which appeaÌ to be taken from a vari- ety of satellites, are stunning in their haven't looked at vet. cÌarity. Individual buildings, even houses, are clearly visible. So are cars What about World Wind? and trucks on city streets. Many are so You may or may not have heard good that you can clearly pick out car of another, somewhat similar, site to Google Earth, set up by NASA. it's windscreens - and some even better! called WorÌd Wind and it's an B0MB It would appear that the image reso- download from worldwind.arc.nasa. lution/quality has a lot to do with the source; also the \"haziness\" ofthe day eov/download.html. But in our briel in the particular city would affect it. lookwe found it doesn't offer anything In low resolution, you cannot see like the features of Google Earth. It individual buildings. The general \"lie is free, though, so you might like to ofthe land\" is relatively clear and you can pick out major landmarks such as have a play. The biggest difference between the big bridges and so on. In hi-res, there is an optimum point two is that World Wind has all its im- ages pre-downloaded; Google Earth to view detail - about 500 feet above updates its images literally \"on the fly\" ground level appears to be best. Any - more on this aspect shortly. lower than this and images tend to become grainy and show artefacts' And while mentioning alternatives, That's not to say you can't go lower there is yet another Googie offering, at the moment still in beta and certainly - of course you can. not complete, callecl GoogÌe MaPs' When I first saw Google Earth, about Like Google Earth (even yet) it is very six weeks prior to writing this, it was much more \"finished\" when it comes not long aftei the London terrorist at- to the USA but even it its limited state tacks. At the time, there was consider- it looks very promising. However, at able (misguided!!) newspaper and TV the moment there are other \"map\" sites which offer far more, such as reporting about the fact that on Google whereis,com,Yahoo and MSN' Earth you could see the ANSTO atom- ic reactor at Lucas Heights (south of Fly to Paris . . . Sydney) in great detail - and theY In some major world cities (particu- showed it on the evening news, to larly US and UK) most major roads are prove itl \"Authorities\" wete calling on named. Click on \"buiidings\" and all the reactor site image to be pixellated of the major buildings are outlined. on Google Earth. When you tilt from plan to elevation In their typical \"grab a story and beat it at (near) ground level, the buildings up\" malner, the media failed to mention siliconchip.com.au
Google Earth gets a lot of its imagery from Digitalclobe's \"QuickBird\" eye-in-the- sky. This satellite orbits the planet at 450km and has a resoìution as low as 6Lcm on the Earth's surface. Even this will be greatly improved early next year when the their \"WorldView\" satellite is launched. It will have a much higher orbit but even better resolution, the fact that you could type \"ANSTO\" where the cursor is located is shown into whitepages.com.au and get the at the bottom of the screen - I've made street address, then go to whereis.com, a note of various ihings I m.ight want type in the street address , , , and up to go back to. ,\\nd when I say exact, it is that: comes a map with the word \"ANSTO\" actually shown in place! Hmmmm. it's calibrated to degrees, minutes, I digress. At tlat time, some capi- - seconds, tenths and hundredths of tal cities (Brisbane, Adelaide, Perth, seconds. (At the equator, a degree is Canberra especially) fared very weÌl about 69,16 miles or 111.11km, so a when it came to hi-res images. Much of minute is about 1,B5km and a second Melbourne was, at least then, lo-res, a about 30.8m. That makes a hundredth lot more obscured by cloud. Even some ofa second just 3Ocm - about a foot in major centres like the Gold Coast were the old money!) in hi-res (but not the Sunshine Coast). Unfortunately for me, Sydney was Oooh -it's changed! Very recently, I was idly \"playing\" also about 50% lo-res. For those who know Sydney, everywhere south of the with Google Earth (it still fascinates city was brilliantbut the city itself and me!), once again looking at Sydney. Hey, what's this? All of Sydney City anywhere north were not, 10,000 ft and the city streets are visible. Not being able to view my own area now in hi-res - you could even see the 1,000 feet above the Opera flouse at the time, I decided to find my mum's shadows of the Harbour Bridge on the Finally, 500 feet - yep, those are people! place on the Gold Coast, Zooming in water! Oh, bliss! OcroBEn 2oo5 77 and following the Pacific Motorway So I quickly \"flew\" up the northern north was dead easy - then I got to the beaches and, sure enough, hi-res im- familiar exit ramps at Mudgeeraba. I ages greeted me for at least most of the followed the road along until I turned way. ,A.s (good!) luckwould have it, the off towards Mum's retirement village. hi-res images ended about 500 metres Next I zoomed right in and was easily beyond my place! Yayl able to pick out her villa. And I must admit our publisher was It was so clear I almost.expected to pretty chuffed when I showed him his see her standing in the front garden mansion in glorious hi-res . . . waving to the satellite . . . This demonstrates the evolving na- The above paragraph gives us ture of Google Earth. As new images land-bound novices a good clue on become available (and obviously the how Google Earth is best navigated. time to work on them) they will be \"Flying\" over large areas and finding implemented into Google Earth. Our objects is not quite as simple as it deductions, from looking at homes ãnd sounds - just ask any pilot who's had buildings under construction in our to learn to navigate. The view is a lot area, is that the image was captured different from \"up there\"! about February or March of this year. The trick is to frnd something that The image of southern Brisbane, while you do know and follow roads, rail- hi-res, is about two years old. I can see ways, rivers etc, to where you want a town house I now own still \"under to go. const¡uction\" (in fact it is just a patch The exact latitude and longitude of of dirt!) - and I've been paying for it for siliconchip.com.au
A section of lower Manhattan, New more than a year since completion! square kilometers (200,000 square York City, from l mile up, The b¡own Who supplies the images? miles) per day of half-metre imagery. EarthSat, on the other hand, uses area top centre-left of the pic is where All of the images which come up on the World Trade Centre once stood. a variety of satellites including the Google Earth are copyrighted to various They are a bit indistinct at this various Landsats, SPOT, IRS, IKONOS, size- but each one ofthe labels organisations, Brisbane closeup, for ex- shows either a restaurant or hotel, ample, is copyrighted to DigitalcÌobe, Terra, JERS, AVHRR, OrbView and Advertisers pay to have their business DigitalGlobe's QuickBird. Depending while as you zoom out, the copyright on the swath, and therefore the reso- names appear. Ìution, some of these satellites have a changes to EarthSat. revisit time as short as 1 day (Spot-4, Here's what happens when you DigiialGlobe appear to oum their own 2200km swath) while fERS-1 has a highlight the \"buildings\" button: all of much narrower 7Skm swath and takes the major buildings in New York City satellite - QuickBird, launched in !001, appear, complete with shadowsl which orbits at an altitude of 450km, in 44 days to revisit. a 98o, sun-synchronous orbit. Some areas, especially the USA, appeæ to switch to aerial, as distinct They claim it is the only spacecraft lrom satellite, imaging at low heighis able to offer sub-metre resolution im- (for example, New York City close-up agery, industry-leading geo-locational images are from The Sanborn Map accuracy, l2BGBits ofdata storage and Company, Inc). an imaging footprint 2 to 10 times larger With these images, you can actually than any other commerciaÌ high-resolu- tion satellite. see people on the city streets, even street light poles! You can't quite see Its resolution is 61cm panchromatic the leaves on the trees but you can and 2. llrrrrrultispectral. With a swath certainÌy pick out branches . . . (image capturing path width) 16.skm What does it cost? wide, every year QuickBird collects over 75 million square kilometres of We have already mentioned that the imagery data. basic version ofGoogle Earth is, at least But even that will be overshadowed currently, a free download. But using by DigitalGlobe's next satellite. Sched- it does have a cost! uled to launch no Ìater than 2006, The price you pay is in the band- WorldView will be the world's only width you are paying for as you use it. commercial satellite to snap pictures ofthe Earth at 50cm resolution. And that can cost you plenty, depend- ing on the particular broadband pÌan The satellite's higher orbit, at nearÌy you are on. B00km, will allow it to revisit collec- When talking to some friends about tion areas more frequently - about once a day. The WorldView system will in- Google Earth, one made a comment about itbeing a \"bandwidth muncher\" clude more efficient image processing systems and multi-satellite collection and very costly to use. planning, shorter tasking timelines and So I did some investigating on this al expanded network of remote ground terminals. DigitalGlobe's imaging con- line and, as they say in the classics, stellation combining WorldView and QuickBird wiÌl be capable of collecting there is good news and bad news. more than 4.5 times the imagery of any current commercial imaging system. We'll start with the bad news. We mentioned earlier' that the pages By late 2006, WorldView alone will update \"on the fly\" using streaming be capable ofcollecting nearly 500,000 technology, A general rule of thumb for streaming And now look what happens when To prove the point, here's the elevat- |ust 150 féet above a bus stop in The you \"tilt\" the image, We're at about ion view of Manhattan from 90 feet. Battery area (lower left of other pics). 45o here - you can go down almost to This actually has the \"terrain\" feature The clarity ofview is sensational ground level if you wish! switched on but NYC is fairly flat . , . - one day it may all be this good! 72 SntcoN Catp siliconchip.com.au
video usage is about 2MB per minute, What you need Using a downloaded shareware Google Earth itself is a free (and relatively small - around 10MB) download utility called Networx (www.softper- You can find it on httpl//earth.ggggle.com. fect.com) we monitored Google Earth However, you're going to need some reasonable firepower to run it usage and confirmed this to be about lf your PC is, say, over four years old (even two years old in the case of right: usually about 25-35K8 per sec- many notebooks), forget it! ond, which does equate to roughly 2MB per minte. The minimum hardware configurat¡on is: So if you were constanfþ using 'CPU speed: lntel@ Pentium@ Plll 500 MHz 'System memory (RAM): 128M8 Google Earth for an hour, you could '200M8 hard-disk space easily eat up 120M8 of your allowed - 3D graphics card: 3D-capable video card with 16MB VRAM bandwidth - not very good if you're on one of the cheapie 150M8 or 200M8 ' 1024x768,32-bit true color screen per month plans! - Operating system: Windows 2000 Windows XP But here's where thè good news comes in. Unless you are constantly Recommended configuration : ' CPU speed: lntel@ Pentium@ P4 2 4GHz+ or AMD 24o0xp+ changing positions or views, the ' System memory (BAM): 512M8 streaming doesn't continually occur. '2GB hard-disk space In fact, for significant periods of time, our usage meter was saying perhaps \" 3D graphics card: 3D-capable video card with 32MB VRAM or greater 1-5KB per second, an average of per- - haps 100K8 per minute: much more . 'l 280x1 O24, 32-bit true color screen user (and wallet) friendly. Operating system: Windows XP The moral of the story is that like any lnternet Connection streaming source, you should keep your eye on your usage. It's easy to exceed As we said earlier in the article, Google Earth downloads its image data as you your plan limits and some ISPs charge go to that location (it's called \"streaming\") A broadband connection is essential like wounded bulls once you do so. - preferably a fast one. Minimum speed for practical use would be 128kbps More Google Earth power? but you will get much more satisfactory results with a 768kbps - or even faster Google Earih is also available in - broadband (ADSL/Cable/Wireless) connection. two higher-featured versions, neither research and presentation easy, com/earth pro.html along with a lot more information about Google Earth of which is fiee (but one is pretty Google Earth Pro costs $US400 but itself. there is a 7-day free trial offer to flud cheap), How does Google Earth make out if it is what you need or want. Google Earth Plus is an optional money? Google Earth Pro itself has a number upgrade adding GPS device support, I cannotbelieve the number of people of add-on modules, each priced at the ability to import spreadsheets, who have said \"if it's a free download, $US200 - Movie Making Module; how does Google make money?\" drawing tools and better printing. It Premium Printing Module; GIS Data Google Earth is more or less an ex- costs $US20,00. Importing Module; GDT Traffic Counts tension of Google's search engine tech- Further upmarket is a version for nology. Just as restaurants currently professional and commercial uses, Data; and NRB Shopping Centre Google Earth Pro. It is described as pay to advertise in the media, they will Data. the ultimate research, presentation and pay (and already are paying) to have collaboration tool for location informa- You'll flnd more information about tion. Google Earth Pro makes location these modules on http://earth.google. Hi, mum! One ofthose villas their name - and location - come up on is her place on Google Earth when you are looking for the Gold Coast. soriewhere to eat in that area (again, The images, from 450km away, check out New York CityJ. That's just one example, Google rates are so clear I are low by comparison to other forms almost expected of media - as a global organisation they to see my mother don't have to charge much because the stalding in the market is so huge - and growing. front garden waving to the And frnally, you may have heard satellite , . . recently reports that Google founders siliconchip.com.au Larry Page and Sergey Brin recently knocked back an offer of $3 billion fiom News Ltd. Is there money in Googling? We think there might be a few cents here andthere.., sc OCT)BER 2OO5 13
Fñhere's a rather clever ad on TV power, supplies the network connection. what they seem. Yes, there is a Power I at the momenl which has the tag supply built into them, But they also I \"isn't it nice when things jusì In other words, the data stream is super- contain the \"smarts\" which turn them imposed onto the mains at significantly work\". I'm sure you've seen it, While higher frequency that ihe 50Hz mains into network adaptors. this review has nothing to do with a Each terminal on the network requires Honda car, it has everything to do with - in fact, it's in the several MHz range. things \"just working\". one ofthese plugpacks. The basic pack- Using power lines for networking has age contains two plugpacks;you simply It's so nice to find a product which been in the pipeline (no pun intended!) buy as many as you need, uP to the not only delivers what it promises - it for some years, with various systems set does it without any hassle, any setup up here and overseas to test it out. maximum of 15 terminals. Also, each of the terminals needs to difficulties. It just works! To our knowledge, this is the first Over the yeaÌs, we've looked at manY system to actually reach it to market, at be on the same wiring circuit, or phase, That's usually not so much of a problem types of computer networks, some in least here in Australia, There are other in a home setup because most homes considerable depth, power line systems currently becoming are fed by a single phase. In an office, it This month, it's another type of net- available which offer broadband over might notbe quite so simple because all work. But it is quite different in that, three phases are used in many cases to while it is wired, the wiring is already power ìines - we understand trials have distribute loads - and this system cannot in place in your home or office. This been conducted in Australia but so far, cross from one phase to another, network uses the power lines running we haven't heard of anything further' NetComm claim a range of uP to 200 though the building (and even beyond) as the network. It's called Ethernet Over First, let's explain the NetComm metres, which is far more than most LANs would need. We weren't able to Power (EOP) HomePlug system. As our photo shows, conflrm that range because we couldn't Ethernet over power does exactlY it looks like a pair of plugpacks and a easily get two houses 200m apart on the same phase! However, we did conflrm a what its name suggests - there is no couple of Ethernet connection cables' range of more than 70m Pius, with the And, apart from a CD loaded with soft- aid of a long extension lead and a pair wireless, no Cat5 , no coax - the 240VAC ware and manuals-on-disk, that's exactly siliconchip.com.au power wiring, as well as supplying what you appeil to get when You open 74 stLtcoN cntp the package. But those \"pÌugpacks\" are not quite
of notebook computers, room, it worked like a charm. NP2l O TEGHNICAL But we are getting slightly ahead of As far as speed is concerned, 1Obase- SPECIFICATIONS ourselves. At the outset, we said that the T and 802.11b networks are more than PROTOGOL/STA]IDARIIS systems simply works, And it does. . l-lomePlug 1.0 specification, IEEE 802.3 There is a Quickstart card in the box adequate for surfing the 'net - therefore 10 Base-T Ethernet (1()Mbps) compliant which basically tells you what to do: Netcomm's HomePlug system was too, . 10Mbps AutoMDl/MDlx Support Ioad the driver software, plug the adap- For the vast majority of users, speed .14 Mbps HomePlug 1.0 compalible would not be al issue. . CSMA/CA MAC ConIroI tors into power and the Ethernet cables into the appropriate (RJ45) sockets on Butif you are aftermaximumthrough- MODULATION SUPPORT put (or more likely have a lot of high- . OFDM, DQPSK, DBPSK, ROBO your PC and on the adaptors - and level users trying to use the network at the same time), the speed limitation Carrier Modulation Suppott that's it. might start to become relevant. FBEQUENGY BA]ID It iust works! .4.3MHz - 20.9MHz So I The question will obviously ariser - afowllaoyweitdwtheentQ! uNicoksptraorbtlecmarsd QIIALITY OF SERVIGE and what happens if your next-door-neigh- . Forward Error Correction (FEC) support whatsoever. The two computers found bour decides to put in.the same system? . Channel Adaptation ensures that signal At the risk of sounding smart, nothing each other without any problems at all integrity is maintained even under harsh -if not onlybecause the way powerwir- and I was able to transfer data back and noise environment ing is distributed in Australia, adjacent forward, examine one's hard drives from homes are almost always on different . CSMA/CA with prioritisation and Automatic Repeat Request (AR0) for the other, etc etc - exactly as I could phases. reliable delivery of Ethernet packets have done had they been connected via But that's not tÌre only reason - the via Packet Encapsulation my wireless network (which of course I NetComm HomePlug has 56-bit DES encryption with key malagement; it also . Four Level prioritised random access disabled first) or via a \"normal\" Ethernet operates on a large number of channels method (wired) network. over its 4.3-20.9MH2 operating band, . Segment bursting and contention-free One curious thing: on one PC the Netcomm's marketing is directed at access ensures high throughput while signal strength meter told me I had people who (a) cannot or do not want maintaining low latency response and excellent signal [100%, in fact); on the to instaÌl a wired network - such as flat jitter performance other PC, it told me the signal strength dwellers, renters, etc; and/or (b) want SEGUBITY SUPPORT was low. No, I don't have a clue why! Internet access fiom various rooms as simply as possible. .56-bit DES Encryption with key Working from one to the other and vice management for secure powerline The system is highly suited to both communications (Use Windows versa appeared to be pretty much identi- platform to enable encryption) these groups - as it is to small busi- cal, with plenty of speed, etc. nesses, conferences, consultants - in PLATFORM SUPPORT Speaking of speed, how fast? The fact, anyone who needs to set up a net- . Windows 98SE, Me^2000 or XP specifications say that they are up to work quickly and easily. POWER SUPPLY 14Mbps - faster than 1Obase-T networks Recommended price of the NetComm . lntegrated 240V AC supply via power but not as fast as 100base-T; faster than NP210 HomePlug system is around socket 9199, although we have seen it adver- 802,11b wireless but not as fast as EXTER]IAL GOTINEGTORS tised up to $45 cheaper! BO2.11g wireless. I was able to confirm . 1 x electrical power socket For more information, including . 1x RJ45 for 1 0 Base-T ethernet this as pretty accurate. online suppliers, visit (Auto MDI/MDlx) Like any network, speed depends to a Sc APPROUA S large degree on distance; as I mentioned . C-Tick before, I wasn't able to stretch mine out . Energy Authority Approval - 0050207 to the 200m maximum but room-to- SYSTEM BEQUIREMETITS: It really is as simple as 1-2-3: . Windows operating syslems w¡th Ethernet (t) Connect a HomePlug to your connection, Pentium ll 300MHz MMX- Compatible PC or greater, minimum ADSL or cable modem using the 64MB hard disk space and memory, CD-R0M drive supplied cable; . Maximum of 15 devices connected to (2) Plug that HomePlug into a power line network convenient power socket and the . All HomePlugs must be on the same other HomePlug into a socket close by your PC (or game console); and power c¡rcuit (3) Connect the other PC to the PAGKAGE GO]ITETITS . 2 x NP210 HomePlug Adaptors HomePlug. . 2 x RJ45 1 0/1 00 ethernet cables . 1 x configuralion/manual CD OK, there is are 4 - All you need to . 1 x Ouick Start Guide do now is run the driver software contained on the CD supplied with OCT)BER 2OO5 15 the kit - and that's pretty much it! (Gr ap hi c c ou rte sy N etC omm) siliconchip.com.au
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and kits specialists Take youl'ctvvn ECGI! Electrocardiograph Kit Easy to build piojea, lets you take your own electrocardiograph (eCG) and displals it on a-PC (v¡a USB). You can read, display, save to disk and print the electrical waveform generated by your heart. lncludes all components, hardware, PCB, a specially manufactured case that has been fully drilled, powder coated and screen printed as well as a set of ECG pads to get you started. K 3704 NEVER REPI.ACE ATO BT'IBAGANI LED Torch Kit Build a solid-state torch with a white LED. Receive high brightness with cool white light, low battery drain and you will never need to Battery Monitor Kit replace a torch bulb again. Supplied with all Simple and functional kit to monitor components, including white LED, PCB t:i;,,î* battery' s149/\" s17s4 and mini torch. K 3018 IT'S E¡ACK II\\I.STCIFIE I\\lclw! S¡licon Ch¡p Magazine Get your copy every month from your local Dick Smith Electronics store. B so2o Pnomotion fnorn 2A/O9/O5 Ëo 25,/1O/O5
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The USB port has made PC expansion so deligþtfully simple it's a wonder no-one thought of it befor€ . . . but it has its limitations. Most PC users are completely unaware of this and wonder_why the computer starts giving error messages or the USB devices themselves either stop working oi misbehave. Here's a really simple way to find out what those devices are doing. . . omputer interfacing via Uni- tech USB data lines (middle pins 2 Cold coffee, when trying to tame a and s) being ignored and just the low late night spreadsheet macro, can eas- versal Serial Bus (USB) ports, voltage DC being exploited at (outer) ily ruin one's concentration! in either 12Mbps (Version 1.1) pins 1 and 4. The USB specifi.cation allows up to or more recent +AOMbps [Version 2.0) The PC's USB port can supply up 5m of connecting cable, since signal offerings, has deservedlybecome such to 500m,t @5V; however, downstream timing issues may give data corruption an indispensable connection method ports on LISB devices are generally with longer lengths. However, basic that it's hard to realise USB has only limited to 10omA maximum. DC electrical issues also arise, with been in use for just five years. heavier currents giving unacceptable Although it may be considered supply line voltage drops that infringe Apart from seamless \"smart\" data typical 5V +0.25V load electronics connections for digital cameras, flash frivolous to use a $1000 PC to just RAM dongles, WiFi adapters, modems power a light or charge batteries, the needs. and mice, etc, the availability of a computer may be on anyway and regulated 5V DC supply at relatively equipment powered by the 5V USB As an example, Ohm's law tells us supply is often conveniently associ- if 250m4 is flowing through a wire of generous currents has also lead to such ated with one's needs at the time. resistance 0.5Cl, then a tolerable drop diverse \"dumb\" devices as mobile by Stan Swan* of I x R = O.25 x0.5 = 0.125 Volts will phone chargers, coffee cup warmers, cooling fans and inspection lights. OCCUI. Dumb, of course, refers to the hi- This wire with the 500m4 maxi- 22 StLtco¡rt CutP siliconchip.com.au
mum load, however, would drop llere's Stan's prototype USB breakout \"box\", potted in some hot-melt glue. The idea is to poke your multimeter probes into the terminal block (avoiding shorts) 0.25V and deliver only a borderline 4. 75V to the load, which may therefore for voltage measurements; for current measurements, you remove the header work unreliably. pin shorting block and bonnect your mulitmeter in series. An additional issue relates to the (instead usually having power quoted - just ensure the data wires (usually power needs of the numerous items in dBm llbdBi - 101.s - aomW]), green and white) and the braid are now in use. Even with short cable increasingly popular USB WiFi adap- neatlv resoldered and heatshrink cov- lengths, multiple USB devices (and tors also differ significantly in their erdd,\"with no mischievous whiskers 'npto 127 are possible!) can eventually transmitter output power, from the braided shieldl demand more current than is permit- This is especially important when ted, with resulting port shutdown. A small terminal block makes for some distance fiom an Access Point Unpowered hubs are particularly since you may be able to \"hear\" its convenient voltage test points across prone to this, which explains the need strong signals - but it may not sense the red and black supply wires - even for powered USB hubs that will cater your weak out-going ones, though a DMM won't be worried by Given these issues, it's surprising for multiple energy-hungry add-ons. reverse polarity, we painted our termi- Alternatively, a simple USB power USB supply breakout adaptors haven't nal block red and black with a Texta become readily available, since sim- injector couldbe used with anunpow- ple current and voltage measurement pen to identily \"+\" and \"-\". ered hub to achieve the same result, of assorted loads cqn be extremely For current measutement (which of revealing, especially if device specs course mustbe in series), we included StllcoN Curr published such a are being stretched. a 2-pin header pin base in the +ve project in the October 2004 issue, Make your own! (red) wire. capable of supplying 5V DC @1,t to a To measure current, the shorting USB device. Need more power than With the cheapness of short USB M-F cables and DMMs, a simple sup- block is removed revealing a handy this for other devices? Add more ply breakout adaptor can quickly be pair of terminals for our multimeter organised by just cutting the cable. clip leads. power injectors! Position of the cut is unimportalt Overleaf are some samplemeasured Even though itself now threatened currents, using a short 600mm cable by other advances in technology, to typical loads, supplied from a Bluetooth is finally making a solid mains-powered Toshiba laptop - showing, Pa¡ticular interest in verify- ing the output power of USB Bluetooth adaptors has therefore arisen. The three Bluetooth classes have de creasing wireless power and range, and innocent purchase of a low power Class 2 adaptor may frustrate when Pin 3: Data 2 Pin 4: 0V The connections to a USB type-A plug (the one that goes into your PC). range has to be maximised. The most powerful Class 1 is typically good to 100m, with Class 2 some 10m and Class 3 just a metre \"across a motherboard\". Although not specified in classes, USB This diagram shows how it can be done - slightly more permanently socKET (F) than the glue version above. We US8 CABTE used a small block of timber to mount it on - but just about any non-conductive base would be fine. The header pin base was glued to the timber using hot melt; small woodscrews hold both cable clamps and the 2-way terminal block in place. siliconchip.com.au OCT)BER 2OO5 23
Deuice Measuled load cultent which accounts closely (may vaty with load demands| with the example above, ,\\dding another 5m ex- Pocket 40GB 300m4 tender dropped the load USB Hard Disk voltage to almost 4.5V with Atmel \"b\" WLAN 270m4 the PC then reporting \" USB adaptor DSE XH7947 (2002) 9OMA device not recognised\", 63mA DSE ''b,'WLAN presumably because of tim- adaptor XH6822 (2004) ing and low supply voltage WLANGenius \"9\" issues. 'E adaptor GW-7200U Given the lowered sup- Srr-rcoN Culp's ply voltage at the end of USB Power Injeclor Logitech 0uick Cam(2000) 60mA these lengthy USB cables, from the October 2004 it's feasible that heavier issue. It doubles the amount of power available from a USB port. (paralleled?) DC supply cables could be used if longer runs are needed and data propagation timing is not energised via cheap CÄT-5 cable. \"My Flash\" 256MB 50mA Aside from the tedious energy is- an issue - perhaps to serve a rooftop Flash RAM USB webcam ot \"sweetspot\" WiFi sues, ultimate cable lengths really are DSE Class 1 BlueTooth 48.5m4 adaptor. Iimited by the data speeds. ,\\lthough Some of the now-common external such signals travel near the speed dongle (2003) XH4104 USB hard disks and CD/DVD writers of light in cables, even a few extra lamp\"ltsy-Bitsy\" USB LED 30mA actually have two USB connectors metres of conductor can delay things at the PC end, wired in parallel to unacceptably. (ref Srr-rcotu CHre, March 2002) The recently-announced Wireiess achieve the currents required. They rely on the fact that (hopefully!) most USB still only offers modest ranges Genius Mini Traveller l0mA PCs these days have several USB port (3-10m) but given the lack of wires[!), there certainÌy won't be any voltage USB mouse sockets close together. D9Prolific USB-serial 8mA Remote DC supplies via compietely drops - or convenient 5V supplies. separate lines and a 7805 voltage Active Extender and doubled \"Bus\" adaptor (Picaxe use) regulator, perhaps with higher voltage power cables (laycar XC4B39 and Olympus C-1 digital camera < 1mA (9V?) initially, may serve to stretch WC7750 respectively) may of course (64M8 Smarl Media). Perhaps runs as well. better suit demanding USB setups, camera batteries supplying too? This is precisely the scheme in- But if only modest extensions are This laptop PC's unloaded.USB supply was measured at 5.04V which volved in the SIucoN CHtp USB Power needed, cheap passive extending techniques are well worth consider- dropped when loaded by the power- Injector mentioned above; however it hungry Atmel WLAN adapter (draw- ing - if only to keep your coffee warm ing 27OmA) to 4.BBV with a 600mm also included line sensing to turn the while lounging some distance away cable and just 4.75V when at the end power on and off in sympathy with the of a 5m USB 2.0 extender. power at the USB port itself. from the PC! This 5m cable was measured as hav- ing 0.5f) resistance in the supply wire Perhaps even a small photovoltaic With the breakout adaptor shown solar panel could be used to charge (therefore 1f), considering return too), above and a DMM, you can at least a rooftop battery, providing a regu- lated 5V supply. It's rather akin to be easily informed of your loads' DC \"corporate\" power over ethernet demands, something that currently is largely unknown, sc (POE) approaches - well known for * s.t,swan@massey,ac,nz rooftop/masthead WiFi Access Points This active USB 5m extension cable uses some of the power Where you have power-hungry USB devices, a USB Bus available from the USB port to amplifo the data signal. Up to Power Cable can give them a boost, connecting to two USB 5 can be connected in series, It's from faycar (Cat XCaBS9)' ports to double power. Also from |aycar (Cat WC7750). 24 Suco¡rt Cutp siliconchip.com.au
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This brand new easy-to-build preamp features many times more in comparable com- the latest high-performance audio op amps mercial units. for ultra-low noise and distortion. Its modular design incorporates five switched RCA inputs Having built one of our high-per- and support for a headphone amplifier. formance amplifiers, many readers have also asked us for a matching rTrHnSU DAYS, audio power ampli- formance than can be found in these preamplifier design. And so our de- mass-produced units, which explains sign brief was simple: a minimalist I fiers that produce low noise and why the discrete power amplifier approach, focused on achieving ul- projects described in Sucotl CHtp are tra-low noise and distortion, but with distortion a¡rd cost only a few hundred enough gain (with the \"wick\" wound dollars are relatively easy to find. In so popular. right up) to overdrive any ofour audio fact, they're built into many of the For example, the 15W Class-A power amplifiers, including the big latest multi-channetr home theatre 350W and 500W units. So, what were systems. Much of this gear is based Stereo Amplifler described in fuly and our options? around hybrid amplifier modules, August 1998 still gets a high ranking, which typically produce distortion as does the 100W \"UItra-LD\" class-AB Discrete versus integrated Ievels in lhe O.O2o/o realm, design described more recently. These Initially, we were aiming for a dis- Those serious about their audio will crete class-A amplifier design, specu- amplifiers are expensive to build but lating that this would be the best way demand a much higher level of per- offer performance that typically costs to achieve the ultra-low distortion 26 SnrcoN Cntp flgures that were required, Ânother option was to use boutique op amps siliconchip.com.au
specified for hifi audio use, such as ffieEm Feæüsscs t-hose ma¡ufactured by Analog Devices o High pefformance design - very low THD+N o Five on-board RCA inputs and Texas Instruments. . Passive-switched inputs maintain signal integrity High linearity and the lack of cross- . Switched headphone amplifier output over distortion are the major reasons for the use of class-A mode in audio @@6ætr@d PCrÉæeææ€@€ applications. However, when com- pared to an equivalent op amp design, Frequency response.....flat from 1OHz to 20kHz, -1dB @ 82kïz (see Fig.5) a discrete class-A amplifier would Maximum input signal 2.9V RMS (9.5V RMS output) have consumed a large amount of PC lnnr rl imna¡lonna -qnko board space, making the compÌeted ôr rtnr rt imnodanno l OOO module physically large and more prone to radiated noise. It would also Harmonic distortion . typically <.0005% (see Fig.7) be considerably more difficult to build, Signal-to-noise ratio -102d8 unweighted containing many more components Channel crosstalk...... than an equivalent op amp design. Source crosstalk...... -96d8 @ 1kïz, -73d8 @ 10kHz -110d8 @ 1k{z, -93d8 @ 10kHz We then looked at the current audio op amp offerings and their implemen- Note: all measurements were pertormed at the maximum volume sett¡ng w¡th the output driving a 50ld) load. lnput signal amplitude was 600mV RMS (2V tation. In many of our past designs, BMS output). For crosstalk measurements, non-driven inputs were back- we've used the industry-standard NE- 5534 and LMB33 devices. These are terminated into 600Q. relativeÌy cheap and easy to obtain, and dled by fitting a bunch of RCA sock- volume potentiometer, source selec- both typically produce about 0.002% ets to the rear panel and laboriously wiring these to a rotarlr switch on the tion switch and low-noise power total harmonic distortion (THD) at front panel with shielded cable. Al- lkHz when driving a 2kÇ) load. Don't ternatively, the RCAs are mounted on supply, all of which are described in get us wrong - this is a very good figure a PC board at the rear along with the detail in this article. -but it just wasn't good enough for our switch, which is then piped through to new preamp! Our intention was (and the front panel with a long extension In the pipeline is) to produce a preamp which causes shaft. While these methods work, they virtuaÌly no signal degradation when Over the coming months, we hope teamed with our benchmark class-A have their disadvantages. What's more, to describe a high-quality headphone 15W amplifier. amplifier module to suit. We're also de- they don't aÌlow for remote control veÌoping a companion control board, From the limited selection of au- which would feature an inlrared re- selection! mote control (motorised) volume pot dio-specific op amps available, most and remote source selection. were deemed either too expensive or We've opted for an eÌectro-mechan- In the final article, we'll show you too hard to obtain. However, the Burr- ical solution, using passive (relay) howto put all of these modules togeth- Brown (Texas Instruments) OP,\\134 switching forminimum impact on the er in a slim rack-mount case, In fact, we've heard rumours that Altronics series is not expensive and easy to audio signal, Each stereo input has its obtain and it produces an extremely own miniature relay, positioned right will have a very nice screen-printed Ìow 0.00008% harmonic distortion at next to the RCA socket. This gives and punched case to accept alÌ these lkHzl This is more than an order of absolute minimal source crosstalk and goodies. magnitude (25 times better!) beÌow less induced noise, even when com- How it works the figures for the op amps mentioned pared to some cabling schemes. earlier and with aÌl things considered, The preamp consists of two identi- The second feature is closely related cal signal paths from input to output, would give superior performance com- catering for the Ieft and right stereo to requests we've had for a high-qual- channeÌs. Therefore, to avoid duplica- pared to a discrete class-A design. ity headphone amplifler that runs off tion and reduce cÌutter, our circuits the preamp (rather than power amp) Incidentally, the output stages of show only the left channeÌ. We've these op amps do not run in class-A stage. In support of this idea, we've included a relay circuit that can route also divided the preamplifier circuit mode, despite their exceÌlent linearity. diagram into two sections, correspond- The manufacturer's datasheets do not the preamp's output to an RCA socket ing to the input signal switching (Fig.r) reveaÌ how they have achieved these at the rear or a terminal block on the and preamplifier functions (Fig.2). impressive results. inside, where it would connect to a Referring first to the signal inputs (Fig.r), no less than five RCA sockets Extra features separate headphone amplifi er board. OCT)BER 2OO5 27 We've stuck to our minimalist brief In summary, to operate as a fully and added just two features to the basic functioning unit, the Studio Series preamp, The first of these addresses Preamplifier module requires only a a common problem faced during preamp construction: how to switch the various signal inputs through to the preamp input while maintaining low noise and crosstalk. TypicalÌy, multipÌe inputs are han- siliconchip.com,au
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NOTES: +l 5V Rt {R2l I 00nF I. ONLY EFT CHANNEL SHOWN, BUFFER \\r1TI 221fi VATUES IN (I REFER TO RIGHT CHANNEL, 2. METAL BODY OF VRl MUST BE CONNECTED TO CHASSIS EARTH. tcl & tc2: oPA2l34 PREAtvtP ¿!Ë ¡-|IIFÍ TNRJT 35v I1 00k 56pF 2 row-PAss FITTER coNl AAMvPU=FgIE'¡R POWER INR'f CONó {cloNl40 TO HEADPHONE OI,JTR'T ATvIPUFIER lEFÍ RIGHT' GND ffi. STUIIIll SERIES STEREll PREAMPTITIER Fig.2: the amplifier part of the preamp is based on Burr-Brown high-performance OPA2134 audio op amps (ICl & IC2). To saveìpace, only the left audio channel is shown here - the right channel is identical. (CONB-CON1.2) arc provided for con- PNP transistors (Qr-Qs) from the +5V CD player was selected. This approach would have ensured low source cross- nection to various audio sources. \\.A/e've rail, such that when the base of a tran- talk but we felt that shorting some used labels such as \"CD\", \"DVD\" and sistor is pulled to ground it switches program sources may not be desirable. \"TAPE\", but of course, these inputs on, energisingthe relay. This closes the will accept any audio signal classed as In any case, we have managed to keep \"line-level\". The sixth socket (CON13) relay contacts and connects the signal source crosstalk very low, at around simply loops the selected input pair pair through to the amplifier input. -110d8, back out, duplicating the \"tape loop\" function found in some preamps ald We have not used the normally Thebases of Qr-Qs are connected to closed contacts of the relays. With a aheader [CON4] via 3.3kÇ)resistors, so control units. slightly different switching arrarge- it's simply a matter of grounding the ment we could have used these to designated header pin to select a par- Each input pair is connected to the short the outputs of the \"unselected\" ticular signal source. ,{ rotary switch normally-open contacts of a relay, can be used to perform this function, program sources to ground. For exam- as shown in Fig.3. with the poles of all relays connected ple, this would stop the audio from a together. The relays are driven with Note that the relay control circuits tuner being heard at l ow levels when a operate from completely separate TO IGWAY HEADER ON PREAMPUFIER BOARD power and ground rails. In fact, we've used a different ground symbol for I the relay circuits to indicate that ruNER-S) fll this rail is not connected to the srNGrE-POrE 5-POSÍIION amplifier ground rail on the ROTARYS,VITCH preamp PC board. Instead, Fig.3: a single-pole S-position rotary switch can be wired to the 10-way the two ground rails are header to provide source selection. connected only on the power supply siliconchíp.com.au board to mini- mise noise. Also shown on this circuit (FiS.1) are the coils for relays RLY6 & RLYT and their control circuit, These form part of the preamplifier's output signal OCTOBER 2OO5 29
t> J routing, which we describe in detail CL o-to ÉVJì3Pà-a È later. ;lf atÐ FET op amps Ì. ÉE The core function of the preamp- c- t lifler is performed by a pair of Burr- _o¡ã\\ Brown OPA2L34 duaÌ audio op amps CL (IC1 & IC2), as shown in Fig.2. The 43 I audio signal from the selected source is ËrÞ(! çh {zooT ozl l AC-coupled to the input of the first op 1t CEE amp (IC1a) via a 47pF capacitor, while 0) tø x xJI- IE ! = a 100kQ resistor to ground provides ¡i 5-lHl\" -ÈJ input termination. =ãË o5 Itz) il = A simple low-pass filter formed by dt) >d-cävE l¡l the 1.2kQ resistor and 56pF capacitor ã4UiNãb \"_¡¡9ro.Þlll+ôt Êo) ÈÊE attenuates RF frequencies ahead of the È oã Zu cEt op amp input. A relatively large resis- Cr¡El tor value can be used here because of ØØ jaSc c the OPA2134's true FET inputs, which <'ã6kç(;OËiJJÞHB6OL)ø! id h present an impressively large 10TÇ) ÉÉd att (Teraohms!) impedance. The -3dB point of the filter was chosen to be ;Ðoas.Høl:AC,JØ Eatt about 100 times greater than the high- est audio frequency, to have minimal i! gp I effect on the audio signal. ooÈ3dco5b)o.o(ãEJ CEE The voltage gain of the op amp is :øÈ((oõ6ú,É att set to about 3.3 [10.5d8) by virtue of the 4.7kf2 and zkÇ¿ feedback resistors. FËr¡drË.Ér cl) ct tI t The 4.7kC2 resistor and zzOpI'capaci- ØØ Ëoèo L-- tor combination roll off the top end (cõú ctl aD frequency response, with a -3 dB point !ç ã CIJ ,etä at 154kHz. 0) icr!)ã As can be seen from the fiequency èèDotr response graph (Fig.5), this gives a !øO0ahJJ)Èoõi!i:¡r,q¡Í flat response over the audio spectrum g oç'0) while eliminating the possibility of r<oÞf¡oo99õ.e hi gh-fre quency in stab ility. lr ¡, The output from ICla [pin 1) drives 30 Sn tco¡rt Cutp one end of a 10kÇ2 potentiometer (VR1a) via a 22¡t\"F non-polarised cou- pling capacitor. The pot acts as a sim- ple voltage divider, with more of less of the amplified signal appearing at the input of the second op amp (IC1b), dependent on wiper position. You'll note that the wiper of the pot is also AC-coupled, again with a non-polarised capacitor. This is done to prevent any DC voltage appearing across the pot, which if present would cause al irritating sound during wiper movement. We've used the second op amp in the package (IC1b) as a unity-gain buffer, allowing the preamp to provide a low-impedance output regardless of volume control setting. A 47pF non- polarised capacitor couples the audio signal to the output via a 1 00Ç) resistor, which is included to ensure stabil- ity when driving cable and amplifier input capacitance, Together with the ferrite bead, it also helps to attenuate siliconchip.com.au
i AUDIO PRECISION SCFREARE AMPL(dBr) vs FREQ(Hz) Ì r0.000 I i 8.0000 I i 6.0000 I l.oooo I I I i 2.0000 I I I 0.0 .2.000 ll 4.000 s.000 I {.000 I I -10.00 rok l00k 200k Fig.5: a plot ofthe frequency response for both channels Fig.6: crosstalk between channels is also very respectable. Increasing crosstalk at the higher end ofthe scale indicates shows a ruler-flat response over the entire audio spectrum, electrostatic coupling, due to the physical proximity of the after which the curve gently rolls off, with a -3dB point at L54kf[z. channels and the long PC tracks connecting the relays. RF noise that might otherwise find its music for awhile, so wire links are to drive the two relay coiìs. With a jack way back into the preamp circuit. in the socket, the switch is open and installed in these locations during the base of Q6 is pulled high via diode Impedance matching D6 and the two 1,5kO resistors. This construction, We suspect that most turns Q6 on and energises both relay As mentioned, op amp IClb is con- constructors won't bother to replace coiÌs, clirecting the output signal to figured for unity gain, so its output (pin the wire links! CON6 and the headphone amplifier. 7) must connect back to its inverting input (pin 6). Note, however, that we Output switching When the jack is unplugged, the show a resistor (Rr) in the feedback socket switch closes, grounding the Finally, provision has been made path. Those familiarwith op amps will \"SWITCH\" input on CONT and stealing to allow the preamp output to be Q6's base current. ,\\fter a short delay, know that a resistor can be included the transistor (and the relays) switch in this Ìoop to impedance match the switched between the RCA socket pair off, redirecting the output signal to two inputs. at the rear (CON14) and a terminal CON14 and the power amplifier. bÌock (CON6). The latter connector Like many op amps, the OPA2134 The diode, capacitor and resistors shows an increase in distortion in non- is intended for use with an ,internal high-quality headphone amplifier, are included in the base circuit of inverting applications if ihe imped- presently under development. Q6 to slow the circuit's response to ance seen by its positive and negative Two relays (RLY6 & RLYZ) are used inputs is not matched. Unfortunately, changes at the switch input. This helps the input impedance that the negative to allow the non-driven input to be to minimise relay chatter during jack insertion and removal. input of IClb \"sees\" varies with the grounded. Relay operation is dictated wiper of the pot. by the insertion and removal of the Power supply Despite this shortcoming, the distor- headphone jack, which operates a To ensure the best possible perform- tion leveÌs of the OPA2134 are very low even at the worst case wiper position, switch inside the jack socket. lok 20k where noise far outweighs distortion The jack switch is wired to CONT anyway. Nevertheìess, we've provided (Fig.f ), where it controls transistor Q6 positions on, the PC board for two Fig.7: all our audio impedance-matching resistors (R1 & tests were perform- ed in-house on our R2). Audio Precision System One, This If desired, you can instaÌl equaÌ val- graph shows total ue resistors [instead of wire links) in harmonic distortion these two locations that approximate & noise versus the wiper-to-ground resistance of the frequency. The volume pot at your typical Ìistening reading is mostly levels. This extra little feature allows below.0005%, you to obtain the very best perform- However, this figure ance from your preamplifier module! is barely above the noise floor ofthe Of course, the said wiper resist- test instrument, so ance can only be determined after the real value is you've used the preamp with your probably much lower! complete stereo system and favourite OCT)BER 2OO5 31 siliconchip.com.au
INSERT UNK IN CONT IF JACK õ.: ance, we've designed a separate, low- SW-ÍCH IS NOT CONNECÏED. noise power supply for the preamp TO TO module, It provides regulated +15V HEADPHONE JACK Åø and +5V outputs for the preamp and AMHIFIER o(! $iltTcH any future add-ons. Foa The power supply board accepts tô õ b I(J 9 *INSÍAII UNKS TOR RI & R2 DURING ld)Àõ 6- rNfTrAr-coNsrRucnoN (sEETÐq. a 30VAC centre-tapped transformer -9 ;= input, typically formed by joining two 15VAC secondary windings of a ôU { o!i toroidal transformer - see Fig.4. Four Itr ÊE Ìd 5ôL diodes [D1-D4) and two 2200pF ca- z 5*q ol -i0) þacitors rectify and filter the input to Þ= H2é {szÉ Nf create +21V DC (nominal) rails. =2zu ^/. É LM31.7 and LM337 adjustable regu- :P 33tE!øç ì; (Ú o.) lators generate the complementary positive and negative supply rails. g ãf- EZ Their outputs are programmed to 7e¿È t15Vby virtue of the 1000 and 1.1kÇ) resistors connected to the \"OUT\" and tl=oo>ð ,Þs \" ADJ\" terminals. Uõú -ôEd9)'Þ We've used adjustable regulators ui4rt +- 3ËW¡PER g-É in this design because the \"ADJ\" dÉ GND Iog<EE terminals can be bypassed to ground =lõq Eã¿ :! POT éÞ to improve ripple rejection, which È EP> we've done using 1OpF capacitors. The -l5v À> -vÉtÉ0) associated diodes (D5 & D7) provide <=+d dJ *,¡¿ a discharge path for the capacitors GND ÉP should an output be accidentally JO +r5v =9ãq shorted to ground. otr o6i Two reverse-connected diodes (D6 =rËi & DB) across the output prevent their respective rails from being driven to dçy= the opposite polarity (eg, if a regulator '_ Ø fails), something that should never oc- cur during normal operation, PX o.Ë A 7805 regulator (REG3) is used to Ëåo-ø) generate the +5V rail. The 100Ç) resis- tor in line with REG3 reduces power Þ¡a dissipation in the regulator. While this resistor is not strictly necessary when 5 ãï powering only the preamp module, it z >È:ã will certainly be required for future zI hÉ add-ons, which will demand consider- lñlloont :oI9¡Þd> .. ably more current! - o,Þ cHASSTS FROM PREAJ,¡P lEsH': >É' As the +5V supply draws power EARIH POWER SUPPIY tËr!É from only the positive side of the un- regulated DC input, a 330Q resistor : ãÈ across the negative input is included to balance the rails so that they decay t;p at similar rates at power off. .:.' i! ô Preamp assembly 9P3!Ë)ãÉiP Assembly of the preamplifier board È9: is quite straightforward, as all com- qE P ponents (except for the volume pot) mount on a single-sided PC board i¡ 3õ measuring 73 x 1.92trrm. Use the 32 SILIC)N CHIP overlay diagram in Fig.B as a guide to component placement. If you won't be connecting a head- phone amplifier to the board later on, then installation of the associated output switching circuitry is optional. siliconchip.com.au
The components involved are RLY6, links in place of the relays, as shown be mounted about 2mm proud of the in Fig.B, RLY7, CON6, CON7, D6-DB, Q6, A board surface. 100¡rF capacitor and a few resistors. Install the two B-pin IC sockets and Fig.B shows these items encÌosed the 1O-way header (CON4) next, Note Take care with the orientation of within a dotted outline, for easy iden- that one side of the header housing the electrolytic capacitors, as all on tification. is keyed and this must be oriented this board are polarised. Also, be sure You'll find assembly much easier not to interchange the two adjustable if you install the wire links, resistors towards the centre of the board. Like- regulators (REG1 & REG2) and note and diodes first. Note that two of the wise, the notched (pin 1) end of the IC that they face in opposite directions! wire links pass partially beneath the sockets must be correctly oriented. Unlike REG1 & REG2, regulator 22OpF capacitors and these must be Follow with the screw terminal fashioned from 0.7mm tinned copper blocks, all of the capacitors and the REG3 mounts horizontally. Bend its wire or similar. transistors. Five of the electrolytic leads at 90o about 5mm from its bodY Zero ohm \"resistors\" can be used capacitors (100¡LF & 1O¡rF values) are and trial flt it in position to verifii that in place of wire links in the remain- ing 11 positions, if desired. These are polarised and must be insialled with cTd3O POT shaped just like conventional 0.25W their positive leads aligned as shown. resistors and are identified by their The remaining electrolytics are non- wpen brown body and single black band. polarised (marked \"NP\" or \"BP\") and Although they impart a neater appear- can go in either way. VRI b ance to the finished work, they have no eÌectrical benefits over ordinary The RCA connectors (CONB-CONI4) TO copper wire! For the time being, you should also install wire links in pÌace go in last of all. Be sure to push each coN2 connector all tlre way home and check of resistors R1 & R2. that it's sitting perpendicular to the TO board surface before soldering. cHASSTS Note that the two L00fl resistors Power supply assembly EARIH require special treatment. Slip a Smm The power supply PC board is a IOKO GANGED ferrite bead over one lead before bend- relatively simple design and should VOTUME COMROT ing and inserting each resistor into its not present any particular assembly POTENTIOMEIERS problems. Apart from the mains trans- PC board hoÌes, check out the Infrared Remote Volurne former and wiring, all components Conhol published in fune 2002. The reÌays (RLY1-RLY7) can go in mount on a single-sided PC board next, taking care to insert them the measuring 54.6 x B0mm, including right way around. The white line on the top of the package must match the the bridge rectifler, filters and voltage corresponding marking on the overlay regulators, diagram, Remember that RLY6 & RLYT As before, install all of the low- can be left out if headphone amplifier profile components first, starting with switching isn't needed, as explained the single wire link, resistors and earlier. However, you must flt two wire diodes (see Fig.10). To aid heat dis- sipation, the two 5W resistors should siliconchip.com.au OCT)BER 2OO5 33
The power supply board \"-=E board in the holes provided using M3 should only take a few minutes x 6mm screws. to assemble. All connections are Mains wiring made via screw terminal blocks. It's very important that the power 4T\\ supply is checked out before it's con- nected to the preamplifier module. To l9ì(JdF do this, first assemble the transformer into your metaÌ project case. urt2.z cr For best results, the mains trans- Pr\" former shouÌd be located as far away from the preamp board as possible Jo l0RüI ¡ minimise induced noise. A toroidal 5W modeÌ is recommended for its low ra- Fig.10: follow this diagram to assemble the power supply board. Take diated field and low physicaÌ profile. care not to $et the S-terminal regulators mixed up. Important: a full metal case is rec- the hole in the tab lines up with its hole with an M3 x 1Omm scre\\ I, flat washer ommended for this project. Plastic will in the board. Adjust as necessary, then not provide the necessary electrical slide a TO-22O heatsink between the & nut. Don't solder the regulator's regulator and the PC board after apply- leads until after the screw has been screening! ing a thin smear of heatsink compound Connect the mains (primary) side tightened, otherwise the PC board or to the mating surfaces. of the transformer, using the basic regulator package could be damaged. diagram in Fig.4 as a guide. Be sure Secure the assembly to the board Before moving on to the wiring, at- to adhere to any instructions provided tach four threaded standoffs to each with the tralsformer, particularly with regard to mounting, fuse ratings and wire colour coding. A1Ì work must be carried out pro- fessionally and in accordance with mains wiring practices. In particular, ensure that all live connections are properly insuLated, which includes the use ofrubberboots (or equivalent) over the rear of all switches and mains sockets. The mains wiring is not complete until the mains earth is secured to the metal chassis using the scheme shown in Fig.11. That done, use your multi- meter to verifir that a good electrical connection exists between the earth pin of the mains plug and all panels of the metal chassis. Power supply test The power supply test is uncompli- Efl@Gffi@hro@ us Po$mroWil@n@ G@aeffioms I G H-CAPAC ITANC E non-polarised (DA) than electrolytics; a major rea- sufficient board space and part avail- ability. Smaller capacitance values will lIJ!electrolytics are used for signal son for their use in sample-and-hold circuits, high{requency filter networks need to be used for polypropylene coupling throughout this design. The and speaker crossovers, for example. substitutes due to the sheer size and results are excellent, as reflected in the cost differences. To minimise impact various pedormance measurements. However, their benefits in low-level au- on bass response, a minimum of 2.2¡tF However, some hifi proponents will dio frequency circuits are much harder should be substituted for the 47¡iF and be unhappy with this choice, instead to quantify, especially considering their 2.2¡rF electrolytics and a 4.7¡rF value insisting that polypropylene capaci- for the 22pF electrolytic. lt would also tors somehow \"sound\" better than proportionally larger size, higher cost electrolytics when used in the audio and limited local availability in appro- be preferable to use a 20kO log pot signal chain. priately large values. for VR1. Note that the use of physically larger To explain, polypropylene capacitors Those with a personal preference for polypropylene capacitors can of coupling capacitors is likely to increase have a much lower dissipation factor (DF) and lower dielectric absorption course substitute these for the speci- noise and crosstalk. fied non-polarised electrolytics, given StLtco¡v Cntp sil¡conchip.com.au
DOUBTT-ENDED Farts [Est QUICKCONNECÍ 1 PC board coded 01109051, Additional items CASE BASE 73mm x 192mm 1 dual-gang 1Oka log potentio- lv{4x lOmm SCREW, 7 DPDT 5V DIL relays (RLY1- meter NI,IÍS AND STAR RLYT) (Altronics S 41288) 1 single-pole S-position rotary WASHERS 7 PC-mount gold-plated dual switch (eg, Altronics S 3021) RCA sockets (CON8-CON1 4) 1 1O-way IDC cable-mount Fig.1l: the mains earth terminal (Altronics P 0212) is secured to the case as shown socket here. The top nut serves as a 1 1O-way 2.54mm PC mount 10-way IDC ribbon cable lock-nut, so that the assembly shrouded header (CON4) 2-core shielded audio cable for cannot possibly come loose, (Altronics P 5010) volume pot connections cated and involves simply measuring 4 3-way 5mm/5.08mm terminal Medium-duty hook-up wire for the unloaded output voltage of the blocks (CON1-CON3, CON6) three supply rails. To do this, first low-voltage wiring connect the two secondary (15VAC) 2 2-way 5mm/5.08mm terminal block (CON5, CONT) Power Supply windings to the transformer input 1 PC board coded 01 109052, 2 Smm ferrite beads (L1, L2) (CON1) of the board. (Altronics L 52504) 54.6 x 80mm 1 Micro-U 19\"C4/V TO-220 heat- Apply power and use your muÌ- 2 8-pin gold-plated lC sockets timeter to measure the three rails at 4 M3 x 1Omm tapped spacers sink (Altronics H 0637) the supply outputs (CON2 & CON3). 4 M3 x 6mm pan head screws 2 3-way 5mm/5.08mm terminal Assuming all is well, the +15V, -15V 7 self-tapping screws (for RCA and +5V rails should all be within +5 % block (CON1, CON2) sockets) 1 2-way 5mm/5.08mm terminal of the rated values. Semiconductors block (CON3) Low-voltage wiring 4 M3 x 'lOmm tapped spacers 2 OPA2134PA dual FET-|nput 5 M3 x 6mm pan head screws Once you're satisfied that the power op amps (1C1, lC2) (Farnell 1 M3 nut & flat washer supply is working properly, discon- 7e1 -039) nect input power and wire up the +15V Semiconductols and 5V outputs to the preamp supply 5 8C337 PNP transistors (Q1-Q5) 1 LM317T adjustable positive inputs. Note that these suppÌies must 1 PN100 NPN transistor (Q6) be cabled separately, meaning that two regulator (REG1) wires are required for the 5V supply I '1 N4148 diodes (D1-D8) 1 LM337T adjustable negative (+5V & GND) and three for the +15V supply (+15V -15V & GND). Capacitors regulator (REG2) 1 7805 +5V regulator (REG3) Use medium-duty, multi-strand 3 100pF 16V PC electrolytic hook-up wire for the job and twist 2 1O¡t\"F 16V PC electrolytic I 1N4004 diodes (D1-D8) the wires tightly together to reduce 4 47¡tF 35Vi50V non-polarised Besistors noise and improve appeilance. ,A.gain, PC electrolytic (max. 8mm run the cable for the 5V supply sepa- diameter) 2 1.'1kO 0.25W 1% rately; do not tr¡¡ist it together with the 2 22¡rF 35V/50V non-polarised 2100C¿ 0.25w 1% +15V wiring. PC electrolytic (max. 8mm 1 330ç) 5W 5% diameter) 1 100c)5w5% For most installations, the preamp's 2 2.2¡tF 35V/50V non-polarised PC electrolytic (max. 5mm Capacitors common (GND) rail should be con- diameter) 2 22OO¡IF 25V PC electrolytic 5100nF 50V metallised polyes- nected to chassis earth. This is achiev- ter (MKT) 2 100¡rF 16V PC electrolytic 2 22OpF 50V ceramic disc 1 47¡tF 25V PC electrolytic ed by running a wire from the pad 3 1O¡rF 16V PC electrolytic marked \"EARTH\" on the preamp 2 56pF 50V ceramic disc 2 'l00nF 50V metallised polyes- board to the main chassis earth point. Do not connect any other part of the Resistors (0.25W 1%) ter (MKT) preamp circuit or power supply to chassis earth (except the volume pot, 21MO 2 2kA Additional items: 6 100ko 2 1.5ka 1 15V+15V 30VA toroidal trans- see below). 6 10ko 2 1.2kA The volume potmustbe a dual-gang former 2 4.7kA 2 100ç¿ 1 Mains switch and connection logarithmic type, preferably 1OkQ in 5 3.3kO 13 0a (for links) hardware value. If using a motorised pot, a 2OkQ value may have to suffice. Don't use section of the pot, wired as shown noise pickup. Do not connect the in Fig.9! body to either ofthe shielded cables! a larger value, as this will affect the The metal body of the pot must be Normally, the front panel wilÌ provide preamp's noise performance. Do use connected to chassis earth to reduce the necessary earth connection. If twin-core shielded cable for each OcroBER 2oo5 35 siliconchip.com.au
s wired to CON7. Many jack sockets have isolated switches built in, so all .@a you need to do is connect across the zo 0.(x)l normally-closed terminals of one of oft+- the switches. 0.0001 However, the switch contacts in Frequency (Hz) some sockets share a ground con- nection with the audio signal. If you Fig.12: at unity gain, the THD+N performance for these op amPs is almosl have this type of socket, then find invisible and certainly inaudiblel This graph is reproduced from the datasheets, which can be obtained from the Texas Instruments website at the contact that is disconnected from www.ti.com. ground when the jack is inserted and connect this back to the \"SWITCH\" in- putof CON7,Ieavingthe \"GND\" input disconnected. This avoids creating a certain earth loop in your system! Important: if the headphone jack switch isn't connected to the preamp board, then you must insert a short- ing link between the two terminals of CONT; otherwise, you'll get no signal from the RC,t output (CON1,4)! oPA2134 Source selection HE OPA134 series op amps include OUTA V+ ,A.s mentioned earlier, each RCA -IN A OUT B input pair is individually selectable f I single (OPA134), dual (OPA2134) via one control line on the 10-way +lN A -IN B header [CON4). To select a particular and quad (OP44134) versions. The V- +IN B input, simply connect the associated series is fully specified for audio ap- control line to ground (GND). Fig.13: our preamp uses the plications, boasting ultra-low distortion OPAzaS4 (dual) version, which While we intend to describe a mea¡.s and low noise. They include true FET input stages to provide superior sound follows the industry-standard of remotely controlling the preampli- fier's source switching [and volumel) quality and speed forexceptional audio package configuration. in a future issue of SucoN CHP, a far performance. tions, including high load capacitance. cheaper and simpler method is to use a The dual and quad versions feature mechanical switch. All that's required This in combination with high output completely independent circuitry for is a single-pole 5-way rotary switch, a drive capability and excellent DC per- formance allows use in a wide variety lowest crosstalk and freedom from 10-way IDC cable-mount socket and a interaction, even when overdriven or of demanding applications. ln addition, length of IDC cable. overloaded. the OPA134's wide output swing, to As the cable doesn't carry low- within 1V of the rails, allows increased Another strong characteristic of level audio signals, it can be routed headroom, making it ideal for use in this series is its extremely low signal anywhere you like within your case distortion. Total harmonic distortion any audio circuit. plus noise (THD+N) is below 0.0004% without regard to length. The equiva- OPA134 op amps are easy to use throughout the audio frequency spec- lent electrical circuit for the switch wiring is given in Fig.3. and free from the phase inversion trum (20H2 to 20kHz) w¡th a 2kQ load. and overload problems often found ln fact, the THD+N produced by these Final checks in common FET-input op amps. They op amps is below the normal measure- can be operated from -r2.5V to t18V ment limit of all known commercially Before connecting inputs and out- power supplies. lnput cascode circuitry available test instruments! puts, power up and with your negative provides excellent common-mode meter probe touching a handy ground rejection and maintains low input bias point, measure the voltage on the current over ¡ts wide input voltage power supply pins of the two op amps. range, minimising distortion. Obviously, pin B should measure +15V These op amps are unity-gain stable and pin 4 should measure -15V. In and provide excellent dynamic behav- iour over a wide range of load condi- addition, the outputs (pins r & 7) of both op amps should be within a few it doesn't, then connect the pot to a amplifier switching circuitry (RLY6, mV of ground. RLY7, etc) and have a suitable ampli- convenient chassis earth point using Finally, if you've connected a source hook-up wire. Note that solder won't fi er board, then connect the headphone selection switch, you should be able adhere to the plating on the pot, so to hear the relays clicking when you remove a small area of the plating audio output (CON6) to the input of with an ink rubber or scouring pad your headphone amplifier using twin- rotate the knob. prior to tinning. core shielded cable. OK, that's it - you should now If you've installed the headphone In addition, the switch contacts of have a working hifi preamp! Happy 36 StucoN Cntp the headphone jack socket must be listening! SC s¡liconchip.com.au
0rder FormÆax lnuoice Silicon Chip Publications PtY Ltd ABN 49 003 205 490 www.si I i con Gh ¡ p. com. au PRICE GUIDE: SUBSCRIPTI0I{S (Note: all subscrlptlon prlces lnclude P&P). YOUR DETAITS (Ausr. prtces include GST) Your llame yrs .Please stale month to start. .. ....,$A160 (PLEASE PBINT) Australia: 1 yr .................$483 2 0rganisation (if applicable) 1 yr + binder ....... ....... $496.50 2 yrs + 2 binders $41 86 NZ (air): 1 yr ....................$489 2 yrs .....,.,............$4178 Address 0verseas (air): 1 yr ..........$4135 2 yrs ....................$4260 Postcode Daytime Phone llo. ( PRIGE GUlllE: 0THER PR0DUCTS Email address (if applicable) (all pr¡ces lnclude GST on Aust. orders). Method of Payment: .SlLlC0N CHIP BAGK ISSUES in stock: 1 0% discount lor 1 0 or more issues or photocopies. Australia: $48.80 ea (includ- EE Cheque/Money 0rder Bankcard E Visa Card E Master Card ing p&p). Overseas: $41 0 each (including p&p by air). cardNo I I I I I IIIII .ELECTR0NICS AUSTRALIA: project photocopies, limited back issues. 10% discount for 10 or more issues or pholo- Icard expiry date: I ll I I copies. Australia: $48.80 each (including p&p). Overseas: $410 ea (including p&p by air). Signature -BINDERS: BUY 5 or more and gel them postage ftee. (Available in Aust. only): $412.95 each plus $7 p&p per order. -ELECTR0NICS PR0JECTS F0R CARS, V01.2: Aust. $A14.95; NZ/Asia/Pad c $418.00 including p&p (ai0; elsewhere $21.50. (All prices include p&p). -PERF0RMANCE ELECTR0NICS F0R GARS: Aust. $A22.50; Overseas $426.00. (Prices include p&p & GST where ap- plicable). SUBSCRIBERS QUATIFY FOR 1fl% DISC(IUNT OiI Att SITICON CHIP PRODUCTS- * excepl subscriptionsirenelvals Qty Item Description Item P&P if Total Price extra Price il Subscribe to Stucùn Cnp on-line at: www.s¡liconch¡p.com.au \\l w/' -^-/ Both printed and on-line versians available \\ t Totat \\- / $A Phone (02) 9979 5644 oE Tãäf|nå\"åiti\" oR Mailthis form, w¡th your w¡th your credit card details cheque/money order, to: 9am-Spm Mon-Fri 24 hours 7 days a week Silicon Chip Publications Pty Ltd, Please have your credit PO Box 139, Collaroy, NSW card details ready Australia 2097
The on-screen video looks considerably better tlrarr this photo indicates. The contrast is better and the Moire patterning, a result of the interaction between the on- screen display and our digital camera, is absent, Do you have a family member with vision problems - like cataracts, or age-related macular degeneration? Here's a low- cost video reading aid that will make it much easier for them to read a book or newspaper. It combines a small CMOS TV camera with a video processor which boosts the contrast and allows them to select either a positive or negative enlarged image for viewing on a TV set or video monitor. E YE PROBLEMS like cataracts and cally and deprives them of important are often out ofthe reach ofthe people age-related macular degeneration sources of news, entertainment and who couLd benefit from them. ale all too common in Australia, es- information, Recently, we decided to have a go peciaÌly among those of \"mature age\". In many cases, however, reading at a video magnifier ourselves and In fact, it was recently estimated that this project is the result. It combines one in every four peopie over 75 has printed material can be made a lot symptoms of this kind of visual im- easier by using improved lighting to one of the verv small iow-cost black pairment, whiÌe one in every 10 lose increase the contrast, plus a magni- and white CMOS cameras currerrtly their centraÌ vision. fication system to enlarge the type. available from various suppliers with a Optical magnifiers with built-in light- verv compact video processing circuit, Understandably, those unlucky ing are available for use as reading and has a switch so you can select one enough to suffer from these problems aids but they're fairly pricey. You can of three image options: high contrast also get similar devices using video can find it very difficult to read a greyscaÌe positive, hard limited or magnification but these are even more 'digital' bÌack and white positive, or book, magazine or newspaper. This digital negative. And the output is Iowers their quality of life dramati- expensive. As a result, such devices siliconchip.com.au 38 stucoN cntp
standard video so it's compatible with **\"-E-5$¡4\" any normal PAL TV receiver. ü.qSÈo$st---- i The camera and video processor are a plastic skirt (actually both fitted inside a standard UB3-size the correct focal distance project box. Because a person with and makes the unit easy to operate, impaired vision doesn't want to be fiddling with camera focusing, we've across to CMOS analog switch IC2a, The Video Reading Aid is based on mounted it on plastic food container down to the pin 2 input of sync sepa- a miniature black & white CMOS to give it a fixed focal length, In use, camera such as this Swann unit from this plastic skirt sits directly on the rator chip IC4 (via a 100Q resistor and printed page and slides easily over the DSE. page, without marking, 100nF capacitor) and further down to the non-inverting (pin 3) input of video ed by IC3b and used to control switch Basically, it behaves a bit like a gi- IC2c. This forms an active clamP to amplifler stage IC5a, fix the blanking level of the incoming ant mouse - you just slide it so that ICa (the sync separator) is used to video to ground potential, the lens is over the text you want to extract the sync and \"back porchl The part of the circuit we've just gating pulses fiom the video signal, read. These ale then used to provide con- described is basically the control trol signals for video switches IC2a Illumination is provided via four section, which ensures that only the and IC2b. active video is subjected to processing' high-output white LEDs, which mount Now let's look at the actual processing on the underside of the box adjacent In greater detail, both the back porch circuitry itself, which involves IC5a, to the lens, In practice, the LEDs have IC6, transistor Q1 and IC2d. to be \"doctored\" to ensure that their and composite signals are combined in gate IC3c (used here as a negative- IC5a is simply a video amPlifier light output is reasonably diffused input OR gate) and used to turn on and operates with a fixed gain of two, over the camera's viewing area but this is easy to do, as described later switch IC2a, Ío allow the sync and as set by the two 510Ç) resistors in its feedback divider. Its output at pin 1 in the article. blanking information to pass straight becomes the \"high contrast analog The end result is an easy-to-build positive\" video signal and is fed to the tluough. At the same time, IC3a inverts first position of selector switch St' video magnifier which you can feed this signal to control switch IC2b. This into almost any old colour or B&W TV This same output signal is also fed set. You should be able to build it for latter switch allows the processed to the non-inverting input (pin 2) of less than $200. video through to the output buffer OCTOBER 2OO5 3S By the way this price estimate is (IC5b) dudng the \"active\" part of each based on using of one of the low-cost B&W cameras with a CMOS sensot video line. that are currently available fiom vari- In effect, IC2a and IC2b operate in ous electronics retailers. We've tried complementary fashion. When IC2a is it out using two of these: the Swann on (closed), IC2b is off (open) and vice unit sold by Dick Smith Electronics as versa. This means that when IC2a is Cal.L-5877 ($ao.eo1 and the Samsung closed, the sync and blanking pulses unit soid by Jaycar Electronics as the are fed through to IC5b while the QC-3474 ($as,ss). These both give good results, although the Swann unit active video is blocked. Conversely, requires a minor modification to dis- when IC2b is closed, the active video able its inbuilt IR LEDs, so that it runs is fed through and the sync signal is cooler fmore on this later). b'loTchkeed\".back porçh\" (or burst gatingl Of course, other mini CMOS cam- eras from other suppliers should also pulses from pin 5 of IC4 are also invert- be suitable. How it works Refer now to Fig.1 for the circuit details. The output of the CMOS cam- era is fed through a video processing circuit that's rather similar to some of our video enhancers but modified to enhance the contrast, The circuit can also generate a negative version of the image, without degrading the signal's sync pulses. As shor,r¡n, the video output from the camera is terminated in a 100O load, to provide matching, It then passes through a 1¡rF coupling capacitor, af- ter which it splits in three directions: siliconchip.com.au
Farts Lflst stage (IC5b) or in the TV set. The recombined sync and video 1 PC board, code 02110051, 1 40668 quad bilateral switch 122.5 x 57.5mm (rc2) signals from switches IC2a and IC2b are fed to pin 5 of ICSb via a simple 1 UB3 utility box, 130 x 67 x 1 40938 quad CMOS Schmitt 44mm NAND gate (lC3) low-pass filter comprising a series 1 mini CMOS B&W TV camera 1 LM1881 video sync separator 100O resistor and 22pF capacitor. This (see text) (rc4) removes any switching transients. The 2 L-brackets, 15 x 15 x 1Omm 1 MAX4451ESA dual video amp signals are then passed through video (lC5) (www.futurlec.com.au) - see text buffer ICSb, which operates with a 1 LM31'1 comparator (lC6) fixed gain of two, to compensate for tle 1 47¡tH RF choke (RFC1) 1 PN100 NPN transistor (Q1) 1 3-pole rotary switch (S1) 4 5mm high-brightness white losses in the 75Çl \"back termination\" 1 2.5mm PC board mounting DC resistor in series with the output. This LEDs (LED1-LED4) is the standard video buffer configura- connector (CONl ) 3 1 N4148 signal diodes (D1 ,D2, tion and is used to allow the output 1 RCA connector, PC board signal to be fed along relatively long D5) video cables with minimal degrada- mounting (CON2) tion. 1 4-pin SIL header strip 2 1N4004 power diodes (D3,D4) 4 M3 x 25mm tapped metal 1 1N752 5.6V/400mW zener Power supply spacers diode (ZD1) Both the mini video camera and the video processing circuitry are pow- I M3 x 6mm machine screws Capacitors ered fiom an externaÌ 12V DC source 1 220¡tF 16V RB electrolytic 2 M3 x 1Omm machine screws - either a 12V battery or a regulated 1 3m length of light figure-8 twin 1 1OpF 10V RB electrolytic 3 4.7¡tF 16V tantalum plugpack supply delivering L2Y aT shielded cable 1 1.O¡rF MKT metallised polyester up to about 150m4. The four white 2 RCA plugs, yellow 2 100nF MKT metallised polyester LEDs (LED1-LED4) used to provide 1 12V/20OmA regulated plug 6 100nF multilayer monolithic illumination are powered from the 1 2.2nF 50V disc ceramic pack supply with 2.1mm plug 1 220pF 50V disc ceramic same source. 1 2.1mm concentric DC line 1 22pF 50V disc ceramic Series diodes D4 and D5 prorride socket (to match plugpack) 680kOBesistors (0.25W, 1%) reverse polarity protection and also 1 Microsafe plastic food container, reduce the overall supply voltage to 1 1 2.2kA 10.8V which is necessary to protect 130 x 105 x 60mm (available both IC5 and the CMOS camera from from Woolworths) 33kO 21kA over-voltage damage. Because IC5 1 1kQ mini horizontal trimpot needs a balanced bipolar supply, IC1 (vR1) 4.7kA 4 510O and ZD1 are used to give the 10.8V 1 SkO mini horizontaltrimpot supply an acti.ve \"centre tap\", which (vR2) 3.9kO 4 270A is connected to the circuit's earth. The two main supply rails thus become Semiconductols 3.3kO 4 100c¿ +5 ,4V and -5.4V nominaÌ with respect 1741 op amp (lC1) 2.7kA 1 7512 to ground. IC6, an LM311 high-speed compaÌator. inverter. The inverted video signal ap- The CMOS camera and all of the This compares it with a reference DC pears at pin 11 and is fed to the third remaining ICs are connected directly voltage level on pin 6, as setby trimpot position of S1, to become the \"Digital between the +5.4V and -5.4V rails, as VR1, to generate a \"hard limitedl' or Negative\" video signal. are the illumination LEDs. The latter rectangular digital equivalent of the boosted video signal. Limiting circuit are connected in two series strings, with a 270f) resistor in each string IC6 has positive feedback applied via The processed video signal selected to limit the current to around L7mA. the 4.7kQ, 100Q and 33kÇ)resistors, to by switch 51 is first fed through a Provided high-brightness white LEDs simple diode limiting circuit involv- give it a small amount of hysteresis ing diodes D1-D3 and a 1kf) series are used, this modest current provides resistor. Diode D3 ensures that the pÌenty of illumination, and ensure cleari switching. Trimpot VR2 also allows fine adjustment of negative excursions of the signal (ie, Construction this feedback. The output from pin 7 is then fed to transistor Q1, which is iis black level) are clamped at 0.6V All of the video processing circuitry connected as an emitter follower to below ground, while D1 and D2 en- fits on a PC board measuring L22.5 x provide buffering. 57.5mm and coded 02110051. This sure that the positive excursions (ie, board has a rounded cutout in each From there, the buffered signal is peak white level) are clamped at 1,,2Y corner, so that it slips neatly inside a fed to the second position of selector standard UB3 jift¡ box. The video se- switch S1, to become the hard limited above ground. The processed video fed or \"Digital Positive\" video signal. This lector switch is located near the centre signal is aiso fed to the control gate to video switch IC2b is thus limited of the board, while the DC input and (pin 12) of IC2d, used here as an analog video output connectors at mounted to a fairly normaÌ voltage range, so it 40 StLtco¡'¡ Cutp shouldn't cause any overload prob- at one end - see Fig.2. lems, either in the video output buffer siliconchip.com.au
0q tX=Ba I çõ o z (J c e il âË 8 Ëå\" Eo.>l H il, .ÞúoÈ) HNrNÀ =i- h!{ 9E øl -(ÉJro = i\" l Þo =Ø N!e ÊOU¡ ã¿'=H c.!! ¡ k>(Ú-,(oo õH tästcf)Ë li_ Otr ..ÅèOø FÜ ñf-U-\"'N5l:Eõ.9-iE' il\" ã HO>ì ØtÊ KJ Îl;El E 6 Ë,Ë9 ð-=3 !Èt-!(oJf!?ldcl!ÈÈ.E9 Ê€ €-! øÞo) 9.€ s C\" 91 BE ecHD o-o É CÐ ÞO-N tú P9E ÊÈ U*'iÈ ê t¡ 9 ¡11- | oLN1-o> I OYo *a N !ÚPË È\\ Jh CÐ øbirÐÉotr) ! É3c ô E-- .ãh'cl E siliconchip.com.au NN EE cã,ô)tos¡H ãË i; ICÐ g(J(J á Q= EE .õEä = oPo ::õc! CsÐtcP 'j é é .9P Þo bô OCTOBER 2OO5 47
Fig.2: follow this assembly diagram to-install the parts on the PC board, taking care to erx¡ure correct component polarity. The four high-brightness LEDs and the MAX4451ESÂ device are instaìled on the copper side ofthe board (see Fig.3). This is the fully-assembled PC board, mounted on 25mm tapped spacers. Note how the high- brightress LEDs hang down from the underside. The CMOS camera module is mount- ting the passive components, starting all the way dor,rm onto the board before with the resistors and RF choke and soldering its pins. ed centrally inside the box (Fig,6). It following these with the two trimpots, sits under the PC board with its lens the smaller capacitors and finally the The next step is to fit IC1, IC4,IC6, polarised tantalum and electrolytic IC3 and IC2, in that order. Note that protruding through a 16mm hole in the the last two of these devices are CMOS capacitors. ICs, so be sure to take the usual pre- base and is supportedby two small alu- cautions to avoid subjecting them to minium angle brackets. The adjacent Follow these with diodes DL-D5, illumination LEDs are mounted on the making sure you flt each one the cor- electrostatic damage - ie, don't touch copper side of the PC board at full lead rect way around as shown in Fig.2. their pins, make sure the tip of your length, so that the body of each LED Also, make sure you use the larger protrudes through a matching 5.5mm soldering iron is earthed and solder hole in the box. power diodes for D4 and D5 and the their supply pins (pins 7 & 14) flrst, It's also a good idea to \"discharge\" Fig.2 shows the parts layout on smaller glass signal diodes for D1-D3. yourself by touching an earthed metal object before handling these devices the PC board, Begin the assembly by Zener diode ZD1 can then go in, again or, better still, wear an earthed wrist taking care with its polarity. fitting the 12V DC input and video strap. output connectors, then install the At this stage, it's a good idea to fit The board \"topside\" assembly can eight wire links, rotary switch S1. To do this, first cut its now be completed by fitting transistor Next, fit the 4-pin SIL header which Q1, Be sure to orient it as shown, then shaft to about Bmm long and carefully flip the board over so that you can fit is used to terminate the leads ftom file off any burrs. That done, it can be the CMOS camera. This goes just be- mounted on the board with its index- ICS - see Fig.3. low the Bmm hole that the leads feed through, That done, you can begin fit- ing spigot at the 12 o'clock position, as siliconchip.com.au 42 StLtcoN Cntp shown on the overlay diagram. Push it
This IC is in an SOIC-B surface Fig,3 (left): use fine-gauge solder mount package which measures and a fine-tipped soldering iron to install the SOIC device (ICs) on the only about Smm square and has a pin spacing of just 1.25mm. It is just underside ofthe PC oard. large enough to be soldered in place ORIGINr' by hand, provided you take your time ROUNDED and work carefully. SA DEDONEND This job requires a soldering iron O DIFFUSE UGHT with a very fine tapered bit, which is Fig,4: here's how the four high- also weìl tinned and clean. You should brightness LEDs are modified to use fine gauge (ie, 0.Bmm) resin-cored di se the light. wire solder, to ensure there are no soÌ- even ilÌumination. Fig.4 shows the Before actually installing the LEDs, der bridges between adjacent pins. basic idea. it's a good idea to fit 20mm lengths of 2mm sleeving over each lead, to The best procedure is to hold the It's quite easy to sand these flats prevent accidental shorts. You can device in position using a wooden by hand, because the LED bodies are use red sleeving for the anode leads moulded in a fairly soft \"water clear\" and green or black sleeving for the toothpick r,r'hile you carefully solder plastic. A small piece of medium gar- one of its supply leads - either pin 4 or cathode leads. B. This involves just touching the outer net paper wrapped around a piece of end of the device lead with the solder- After the LEDs have been fitted, flat wood will do the job quite nicely ing iron and feeding on the solder', so and you will only need seven or eight the board assembly can be completed that a tiny drop melts and bonds the by attaching four M3 x 25mm tapped passes to produce each flat at the cor- leacl to the pad underneath. spacers (one at each corner), using That done, you can quickly solder rect angle fthe exact angle isn't critical, by the way). 6mm long M3 machine screws. the other supply Ìead and then the rest Don't try to polish the surfaces after Box preparation of the leads, So the trick is to make one joint first, to hold the device in place sanding - just leave them with the The box needs to have a number of while you solder all the other leads. holes cut in the bottom and lefthand after-sanding matt finish, as this gives Doctoring the LEDs ftËlþa@ffi better light diffusion. Now for the LEDs. These are left un- Value ¡0rF.1Co¡drFe IE1C 0Co0dne EIA Code After aÌl four LEDs have been til last because, as mentioned earlier, treated, you can fit them to the un- 100nF 104 2.2nF .0022¡tF 2n2 222 they first have to be \"doctored\". derside of the board. They must aÌl be 220pF NA 220p 220 Äs supplied, the rounded end of 22pF NA 22p 22 mounted at full lead length (ie, with each LED's clear body produces a the shorter cathode leads just entering fairly narrow semi-focused axial beam. That's fine for most appÌications but their matching holes), so that the1,'ll not this one, as this would produce Iater protrude through the holes in very uneven lighting below the camera the bottom of the box when the board lens, with four bright spots separated assembly is fitted. by relatively dark regions, The cure is simple - by sanding four small \"flats\" on the end of each LED, its light output becomes much more diffused and this gives more ftËfblc[ffimmffi tr llo. Value 4-Band Gode (1%) S'Band Code (1%) 680kO blue grey yellow brown tr 1 brownorange orange orange blue grey black orange brown tr 1 33kO orange orange black red brown 4.7kA yellow violet red brown tr 1 3.9kO orange white red brown yellow violet black brown brown tr 1 orange orange red brown orange white black brown brown tr 1 3.3kO orange orange black brown brown 2.7kA red violet red brown tr 1 2.2kA red red red brown red violet black brown brown tr 1 brown black red brown red red black brown brown tr 2 kA browngreen brown brown brown black black brown brown tr 4 510f) green brown black black brown tr 4 27OA red violet brown brown red violet black black brown 100c¿ brown black brown brown brown black black black brown tr 4 violet green black brown tr 1 75O violet green black gold brown siliconchip.com.au OCT]BER 2OO5
. 225-l-22.5- {IfFT END OF BOX) AII DIMENSIONS IN MIIIIMETRES HOII A: I ómm DIAM WTH 5 x 1 .5 KEYWAY HOIIS B:5.5mm DlAlvt HOES C: 3.5mm DIAM SIOT D: 9mm WDE WTH 9mm DIAM SEMICIRCE HOIE E: 8mm DlAlrl HOE F: l0.5mm DIAM (TOP OF BOX UDI æ@ Fig,5: here are the drilling details for the plastic case. It's best to make the larger holes by drilling small-diameter holes first and then carefully enlarging them to size using a tapered reamer. 44 Sntcotrt Cøtp siliconchip.com.au
6^ Lo¡.rcJ 5mm WHTTE EDS )\\n/ ¡ WITH 4 X FLATS u[sÈox M3 SCREWS SANDEDON ENDS lcRoss sEcnoNl Fig,6: this diagram shows how it all fits inside the case. Note that the lid should sit firmly on tlre switch indexing ring, to keep it in place when everything is screwed down. end of the base, plus two holes in the neatly twisted together, sleeved and IvIATERIAL I mm lid. The positions and sizes of these tinned as well. ÆUMINIUM holes are shown in Fig.5. And that's basically all you have to HOIES A Depending on the box, you may also do to prepare a camera like the Sam- have to cut away some of the plastic 3mm DI,AMEIER ribs moulded on the inside at one end, sung unit sold by Jaycar, However, near tlre input/output connectors. This witl a camera like the Swann unit sold CAMERA MOUNTING BRACKEÍS (2 OFFI cal be done using a sharp chisel. by DSE, you also have to disable the inbuilt IR LEDs (originally intended Fig.7: here's how to make the two Mounting the camera for night illumination). That's done L-brackets that support the mini CMOS camera. Once you've drilled all the holes, by removing the back of the case (it's usually attached by two tiny screws) x 10mm machine screws, nuts and the mini camera can be prepared and removing one of the LEDs - either lockwashers. for mounting. First, remove the two by cutting its leads with side-cutters Final assembly screws which attach it to its existing or desoldering them from the internal Once the carnera is mounted, the U-bracket, then cut the camera's out- PC board. PC board (with its mounting spacers) put cable about 40mm foom the body can be lowered into position. Feed the (or its mini connection plug). Remove You don't have to worry about the camera cable through its board access about 15mm of the outer sleeving from others, because they're usually con- hole as you go and make sure the four the end, then separate the individual nected in a series string. LEDs aÌl pass through their respective holes in the base. The board assembly leads. In most cases, the positive The camera can now be mounted can then be secured foom underneath power lead has red insulation, while inside the box using two small L-brack- the video lead has yellow insulation. using M3 x 6mm screws into the The negative power lead usually qither ets, made fiom 1mm aluminium sheet has black insulation or is in the form tapped spacers, of a screening ground braid. - see Figs.6 & 7. The camera mounts Finally, connect the camera cable If the camera also has a¡r audio between the brackets using the same leads to their respective header pins on the PC board. The positive power output (many of them do), this is two screws which held it in its original lead (red) connects to the leftmost pin, usually a wire with white insulation. nearest the 1pF MKT capacitor, while U bracket, the video wire (yellowJ connects to the This output isn't used in this project, however, It's a good idea to fit an M2.5 flat OcroBER 2005 45 After separating the various leads, washer on each screw before passing strip about Smrn of insulation from the ends and tin the exposed wire ends, it through the hole in the L-bracket and then fit an M2.5 star lockwasher ready for connection to the 4-way on each screw before it enters its header on the PC board. If you camera tapped hole in the side of the camera. This anangement keeps the camera has a ground braid, this should be flrmly vertical when both screws are siliconchip.com.au tightened. The camera mounting brackets are then attached to the box using M3
Above: this close-up view shows the mounting details for IC5. Below: the plastic skirt has a clearance hole for the camera lens and is attached to the base of the case using double-sided adhesive Above: the CMOS camera is attached to the base of the case and its leads fed up through a smaìl hole in the PC board. rightmost pin. If present, the audio if there are four, the switch wiÌl need sÌots. The idea is to find the slot be- tweenthenumbers \"3\" and \"4\" andre- wire (white) is left disconnected - just to be reset. flt the indexing washer with its spigot tape it up so it can't make contact with in that slot. Check that the switch now To do this, first turn the switch anti- anything. has only three positions, then reflt the clockwise to its end position and then star lockwasher and nut. If there's a negative power wire remove the knob. That done, unscrew Fitting the plastic skirt fbiackJ separate from the ground braid, solder this to the second pin from the the mounting nut, and remove both it The plastic skirt fitted to the unit left and connect the ground braid to the is actually an upside-down food con- and the star lockwasher underneath. tainer, The recommended unit (see remaining pin - ie, the third pin from This will reveal the indexing stop Parts List) measures 130 x 105 x 60mm the left. Alternatively, if there's no deep and has an indent in the centre washer, which you then have to prise of its base which provides clearance separate negative power wire, simply connect the ground braid to BOTH of up using a small screwdriver. The for the LEDs. Thê unit is also curved the centre pins. towards the sides, which means that it underside of this washer has a small The only other possibility is that siliconchip.com.au your camera may have just a black spigot, which sits in one of the match- negative wire and no ground braid. ing slots in the switch body. In this case, connect the black wire to both centre pins instead. If you look closely you'll see that Switch indexing there are a series of numbers moulded Before testing the Video Reading into the switch body, between the ,\\id, you have to set the rotary switch so that it has only three positions and not four. To check this, fit its knob temporar- ily to the spindle and try turning it to see how many positions are available. If there's only three, you can relax. But 46 StLtco¡rt Cutp
naturally clears the four corner mount- ,Ml-l6G ooo ing screws that go into the spacers. o oo Attaching it is hardly rocket science 021 1005r - just cut a hole in the centre to clear Fig.B: check your PC board for defects by comparing it with this full-size etching the camera lens, attach some double- pattern before installing any ofthe parts. sided tape to its base and attach it to the bottom of the box, USE I 2V BATTERY OR REGULATED I2V DC SUPPTY ONIY Ifyou use a different food container from the one we used, then you may NEGATIVE...{ ?l- MEDIUM have to also drill holes to clear the HIGH ? 66¡1p451 -l66¡1p,451 LEDs and the mounting screws. UIIIEfl BTAIIIIIG AIII Testing Fig.9: this is the full-size artwork for the front panel. It goes on the Now for the smoke test! First, set the lid and can be protected using wide strips of clear adhesive tape. rotary switch to fuIly anticlockwise VR1 alone, you may also need to adjust ln¡ago shod Out? (Medium Contrast), set trimpot VR1 VR2 slightly one way or the other. to fully anticlockwise and set VR2 to Depending on the high-brightness Once the correct settings have been LEDs supplied and/or the amount of its mid-range position. That done, con- ambient light at the reading location, nect the Reading Aid's video output found, try switching 51 to the third you might find that the on-screen im- position (fully clockwisel, The image age is washed out (ie, over-bright). cable to the video input of a TV set should change into a high contrast and apply power. negative, with black type on a white ln that case, try throttling back background turning into white type the LED-brightness by increasing Note: you must use a 12V regulated on a black background, which many people with visual impairment find their series 270Q resistors to around plugpack or L2Y battery. Do not use 680Q. Alternatively, if you have plenty an unregulated plugpack, otherwise easier to read, of ambient light, you may get a better you'll damage the camera and IC5. result if the LEDs are taped over (or Final assembly the unit modified so that they can be If all is well, you should see a blu- switched out of circuit). ish-white glow from the illumination Assuming it all checks out, discon- LEDs underneath the Reading Aid bo¡. nect the power supply and remove Be prepared to experiment to get a Now place the unit on some printed the knob, mounting nut and star lock- good picture if necessary. material, The image will probably be washer from the rotary switch. The box ,\\ll that remains now is to fit the quite blurry initially - just adjust the four lid fastening screws and then lid can then be slipped into position lens until you get the correct focus by refit the star lockwasher and nut to rotating it clockwise or anticlockwise. over the switch shaft and should iest This will have to be done by trial and on tlre top of the box, with the switch the switch ferrule, YourVideo Reading enor, since the plastic skirt is in the locating spigot passing up through the way when the unit is resting on a small hole that's located just behind Aid should is now ready for use. Sc surface but it shouldn't take long to the main spindle hole - see Fig.5. ocroBER 2005 47 get it just right, You may also have to adjust the brightness and contrast controÌs on the TV to get a good image. If there's no image or none of the LEDs is alight, you've probably got the power supply the wrong way around, No damage will result from this - just reverse the connections and all should be OK, However, if the image does appeaÌ but only two of the LEDs are alight, the odds are that you've con- nected at least one of the dark LEDs around the wrong way. If all LEDs are alight and you have a clear image on the TV turn the rotary switchto its centre position. The image will probably go very dark but if you turn trimpot VR1 slowly clockwise with a small screwdriver, it should gradually turn into a very \"contrasty\" but still clear black-and-white image. The correct setting for VR1 will be quite obvious - just set it for max- imum clarity and best contrast, If you can't achieve this by adjusting siliconchip.com.au
SERVICEM'SLOG You can't have enough protection Protection circuits are a vital part of modern Items Govered This Month TV sets, to prevent widespread damage to o PanasonicTC29R20TV set expensive components when a critical fault (C1504 chassis) occurs. But sometimes, it's a protection . Teac Televideo l\\4V4822 (CP- circuit itself that causes problems. 420 chassis) Between 1992 and l-997, Pa¡rasonic changed to improve the tlueshold level . LG PF60A3Q rear-projection released a range of TV sets covering of the overcurrent protection circuit. These parts are RB35 (now 0;33e)), TV set (MP87A chassis) the MX1, MX2, MX3, M16 and C150 chasses. The C150 later became the RB4B (33kO), CB3L (3.3pF) and CB3B . Phil¡ps 46PP8621/79 rear C1504 when the B+ was increased (0,1pF). projection TV set (DPTV325AA from +115V to +1258. It was during chassis). These parts hadn't been replaced this period that Panasonic also began in this set, so this was a pretty good o Sony KD32DX40AX FD Trini- using more IC regulators and opto- place to start. Unfortunately, it made couplers (the C150 series has four IC tron TV set (FE-2, SCC-U784 regulators ald three optocouplers). no difference - the set was now com- - A chassis) Recently Ihad aPanasonic TC29R20 pletely dead, Anyway, this didn't flx the fault but come in with Mr Moss, who com- Even though the above modification it did change the symptoms slightly. plained that it kept \"cutting out\". didn't change anything, I thought it wise to also replace aII the common The set would now occasionally come WeII, when I switched it on, I components that cause the same on for a few minutes (with perfect pic- symptoms. There are nine all told ture and sound) and then cut out. couldn't even get it to \"cut in\". and I had already changed four. The When the set is on, the red LED is on, Most of the faults that occur in this remaining five are electrolytic capaci- being fed by the 5V rail from C1106, popular 9-year old set are well-known tors C817, CB2O,CB24, C455 & C1121 which is in turn fed by 16V from DB12 and Qaoz. This rail drops to 9V in the by now and this set was no exception. in the switchmode power supply. Even Staldby mode. The three optocouplers between the primary and the second- There is a series of modifications that in the event that this didn't fix the ary are for voltage control feedback are designed specifically to fix these fault, I couldn't send this set back to and standby switching (D803) and to Mr Moss with a warranty when these provide protection (D811 and DB36). particular symptoms (intermittent shutdown), which were released on components are known to fail. In this case, I was beginning to sus- Besides, they don't take very long pect that it was the protection circuits 11th JuIy, L997 by Panasonic Techni- to replace. cal Information. In particular, two resistors and two capacitors have been N\\t ó ?ANASONIC C\\6O PAI{ASANIC MX3 SntcoN Cutp siliconchip.com.au
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