This is what the guys in Australia call our Catalogue, It’s full of electronic goodies and is soqoqo seductive it’s like pornography without the viscera. You might be titillated but won't be offended! Grab a free one, all products priced in pounds sterling, at: www.jaycarelectronics.co.iift/elektor Check our website! ■ Ail of our 6,000-3- products with search facilities, £ " 128-bit secure on-line ordering - safe & secure. £; * Over 3,500 product datasheets & application notes. ■ And we're from Australia, so you can trust us* ^ - * Postage and Packing includes airmail to the UK HOfBflfO? iGS S S fa ■nsif . jayca re J =c tfonits. c u±l LLsafeais^Li Performance Electronics for Cars Book BS-50S0 £6.95 + post & packing Australia's leading electronics magazine, Silicon Chip, has developed a range of projects for performance cars. There are T6 projects in total, ranging from devices for remapping fuel curves, to nitrous controllers, and morel The hook includes all instructions, components lists, colour pictures, and circuit layouts. There are also chapters on engine management, advanced systems, DIY modifications, and more. Over 150 pages? All of the projects described are available in kit form, exclusively from Jaycar. Check out our website for all the details. JUST ONE OF OUR MANY GREAT PRE- BUILT & TESTED PRODUCTS! Map Reading Made Easy! XC-0377 £12.50 + post and packing. All you need to do is program the scale of your map, then roll the wheel top along the intended route. It will then display the ACTUAL REAL WORLD DISTANCE in miles (or kilometers). It also works in nautical miles for marine and aviation 0 applications, has a f^\ backlit screen and a ) small torch. Measures 6 1/8” x 1 3/S ’ x I ft/ j' 15/16". Theremin Synthesiser Kit KC-5295 £17.50 + post & packing The Theremin is a weird musical instrument that was invented early last century but is still used today. The Reach Boys" classic hit "Good Vibrations featured a Theremin. By moving your hand between the antenna and metal plate, you create weird sound effects like in those scary movies! Kit Includes a silk-screened, and pre-drilled case, circuit board, all electronic components, S ^^and clear English instructions. 10 Amp 12VDC ^ ^ Motor Speed Controller Kit KC-5225 £7.75 -5- post & packing This project allows you to take control of DC motors, or dim incandescent lights. Control the speed of a fuel injection or water pump on your car, and a whole lot more. With the components supplied, it can handle up to TO amps. By fitting an optional extra MOSFET transistor, it can handle up to 20 amps. Kit includes circuit board, all electronic components, and _ • dear English instructions, ' “;2 I Jl i# Optional extra MOSFET “ ^ § transistor - ZT-2450 £2.50. dbv 9VDC wall adaptor required (Maplin #MG BOB £5.99). Universal High Energy ignition Kit KC-5247 £1695 + post arid packing o Get better fuel efficiency and /Ca performance from your car! It produces I** y " a very intense 0.9ms spark which results — in more complete fuel burning, lower emissions, and increased performance. It works with points, twin points, and reluctor Ignition systems. Kit supplied with weatherproof diecast aluminium case, circuit board, and all electronic components. ■ Works great on points ignition (ie. older ears). Can be used on newer cars with Hall-effect sensor. We Stock Get the Video Quality You Paid For With Our Doctor Video Kit KC-5390 £31,95 + post and packing Copy protection is put in place an videos and DVDs for a good reason, but this robs you of the true high quality reproduction that it is capable of. Get the quality you paid for and strip out these annoying signals! It supports composite and 5-video signals and can be configured for NTSC or PAL format. Kit includes case, circuit board, all electronic components, and clear „ English instructions. Note: Some 5MD soldering required. { 3 ) CiLiSon: During, signal conditioning, thi* unit removes copyright protection. Piracy U a crime, & Jay car Electronics takes no respontiblfty for Its polenta a I for unlawful use. Log on to www.jaycareiectronics.co.uk/elektor for your FREE catalogue! 0800 032 7241 (Monday - Friday G9.0B to 17.30 GMT + 10 hours only). For those that want to write: 100 Sifverv/ater Rd Silverwater NSW 2123 Sydney AUSTRALIA Equipment Power Products and Accessories Audio & Video Equipment & Accessories Computer & Telecoms Security & Surveillance Equipment iPost and Packing Charges; Order Value Cost £20 - £49,99 £5 £50 -£99.99 £10 £100 - £199.99 £20 £200 - £499*99 £50 £500+ £40 Max weight !2tb (5kg)- heavier | pare eit PDA. Minimum Of tier £20. j j “ f37T7m DrDAQ Data Log ge e ■Z1 -it ir< IKS H Light level Temperature External sensors. l ow cosU^jn d e r £ 8 0 (+vat) Built in sensBrsJor light, temperature and sound \ (level and waveforms) Use DrDAQ to capture fast signals Outputs for control experiments Supplied with both PicoScope (oscilloscope) and PicoLog (data logging) software Humidity Temperature 02 In Air Reed Switch For more information on DrDAQ, please visit: www.picotech.com/drdaq121 PC . - - n ( " ■ Oscilloscopes 7 • Scope and spectrum analyser functions • A fraction of the cost ^pf benchtop scope • Save multiple setups', for ease of use • Save, print and e-mail your traces • FREE technical support for life • FREE software and upgrades • Automated measurements Instrument ■ >■ J * For more information on our scopes, please visit: www.picotech.com/0cope272 Tel: 01480 396395 Fax: 01480 396296 : sales@picotech.com SJDJr 1 the way Welcome TO YOUR ENVIRONMENT z:: : ■ \25ja ■ zoo — 20.000000 exposure Kmrt tor UMTS (DoH) — 1 0 SXpO . OQO evposur e fimil for UMTS (ICNRP) — 4.500.000 GSM motjfe measured at head and bar?;! 44 Z DQ0 160.000 DECT bas& station at 0.3 m tf^iartce DECT base stafe&n at 0.5 m jtfistance il .... 17 5 UQ 16.000 Ratebook with WiFi card, measured at head DECT ^Si5 statin at ".5 m m^tertee GSM (2G) base station (sngk 10 W) ±il 5 -j m z -t : 650 _ 4C0 Dxjldh T?;0 COFA.M report i'OV jn) DECT base stats-n at 3 m dsstsnce 1 nr f h , Zsz 3rd e^pcsara — t . : : 20 <0/ Bluetooth dev^.narhafiifi&fi&d, at 1 m tSsiance Extreme twcfiogicet d/renproe ( 0_2 Wm) Satzbujg outdoor exposure tmrt Strong baofogacal divergence 10.043 V/m) SafctSxcsg %Ktoor' exposure timt _ z : =; re z re-re - re 0 T: . - — 0.000001 Raima] bzcjtg round ra^aton level firsLxantim} It will be hard to overlook that this month s issue of Elektor Electronics has a Focus on electronics and the environ- ment The environment is omni- as v/ell as ever-present yet surprisingly hard to define, It's largely subjective — deafen- ing noise to some is music to others — while some factors said to affect your personal wellbeing are beyond the Immediate detection capacities of human organs. You may reel great after smoking a cigarette but the cumulative and long-term effects of nicotine and ash are worrying to say the least. The same, basically, when you're getting good news through your mobile, or when you re happily WLANnlng or UMTSing oway the odd kilobyte. Blissfully unaware, but just took at the above radiation thermometer' to check how the use of wireless gizmos may affect your and other people's environments, ness comes with age awareness wiih information. Page 14. Jan Suiting, Editor According to a cautiou work will eventually i prising that an incr electromagnetic i Elektor Electros rising fieldstre the most rai we also si free turn 1 4 Electrosmog: can't be that bad An article with contri- butions from scientists, journalists, editors, researchers and other correspondents from various countries, aim- ing to present a bird's eye view over the con- fused and worrying situations created by radiation from mobile phone transmitters. The paradox: every- body wants to use his/her mobile phone but not the mast in the street or near the schoolyard. In good Elektor tradition we examine the problem from various disciplines including politics and research, not forgetting some interesting results of a poll-style Survey conducted on our four international websites. Volume 31 June 2005 no. 344 r rosmog Tester estimate, the roll-out of the UK’s nationwide 3G net- juire some 50,000 masts to be erected. It is not sur- sing number of people worry about the extra dose of Jiation produced by 3G base stations. The sensitive log Tester not only allows you to provide evidence of gths in your neighbourhood and home, but also to find ition-free spots up and down the country. On page 33 m w you how to make wideband electrosmog audible — almost everywhere! 42 Solar Power Made simple Complicated charge controllers and inverter circuits can be used to squeeze the last drop of energy out of a solar panel Contrary to pop- ular belief, however, it is also possible simply to connect the battery directly to the panel. In the UK, too! 60 GPS Receiver on USB r. \ ? jj 1 1 K i tWjt v _ tj i i -4-- 1 ii In this article we show that building a GPS receiver your- self is finally possible, and if has been worth the wait. The newest generation of GPS receivers are not only outstand- ingly small, but also offer con- siderably better reception per- formance and lower power consumption than their predecessors. We also offer a complete kit of parts! know-how 1 4 Electrosmog: can't be that bad 20 What is Electrosmog — Survey 50 Energy Saving Tips 68 Labial k (3): Lead-Free Electronics hands-on 24 Electrosmog Tester 33 Tune In To Electrosmog Solar Powered Charger (Mini Project) 54 Temperature Logger 6€ GPS Receiver on USB 09 Design Tips resistors a lo carte shift registers — a different approach DVM without isolation technology 42 Solar Power Made Simple 70 Delphi for Electronic Engineers (6) info & market 6 Colophon 8 Mailbox Corrections & Updates News & New Products 82 Elektor SHOP 84 Sneak Preview infotainment 36 WiFi Eavesdropping 77 Retronics: Elektor Vocoder (1980) 78 Quizz'away 2 is y uiiUjus rayl-iluia uiidto-ijumJv. U Ubiiljll. it U333 a l) if ni jliiyr. /'ju tilin' i h]l YJi^JrJ JLisijjns j ffifij y/an yu ihpLii^ Ur IfbiiU'Ju&j Y2 ii» ilUiljiyjy iiiyUiis « inin ff/Llryij'Jj; iiuDr lari'll e iJUS) diiaiuiSl JU) siisjuial ijiiiijS /slsd ami -JaJuys i |ill)| rai US $450 (UK £235 approx) b ruits j/LJlll 4iJ ferfcfi UOVJJI ib ^Urte: l U/iil -JAiJun ui impulse mill fryiju^jjdyi/S^ii'jn 'Jjjiliijj fur VJU Jb ttlbb. nl, r JU, pi/iiHT supply m* J ulJ riirjfe]. ui \ Iv.'J, itUsi iteiud {nuiu^bh^iml liitU iirdufiny informull'Jii at: *vv/;/.oaiiliu.com/3u|Jpnitra/aanr/G[!jNa(vitiiii'J2.him itirurmuti'Jii Real-time g; Up to 8 fflte Off-line filter Includes bo: ! i-’- ;- . A lectron Volume 3 1 t Number 343, May 2003 EJzktcr Bzctfcnics aims zi inspiring people to master electronic* at any personal level by presenting construction projects and spotting developments in electronics and information technology, El ' it Etn m " :z e ii: _ ::i z~ i p-jt E^-ed by Bettor Bectron.cs (PubSshaig). EG. Box 1 90s. Tianbrwjge WeSs TM5 TWfj England. Teh: (^44) (0) 1 5SQ IOQ657. rax: (+44) (0)1 5B0 2005 1 6, ErrtjJ: sa’esfSJe z - 1 c ■-- z :: : n :e . Tbe magazine k a vapteife from bookshops arx i eSectrGfics retail owfete, or on iUPsCrptaXi Sefacf Seo^its is ptiirf^ed 1 1 ijmesayearv^atkjufeteiss^fbr|uiy & Ai^si Unoecthe tsre Sfekior and ifSgfifizgg the rregszjne is sfeo ptisSsfted in Frer^cti. Gsnnar and Dutch, Tpg^ber v^h frsjxh^ed etEiions the rrsgazine & go c r rtJbti nfi m more than 50 as International Editor L 4s: Hedes Editor, l" r.. : "i :- : . . International editorial staff: --: jensNkicef, Guy Raetferadod. Baggen, Thtjs Beckers, Emst Krennpds= -- Design staff: KareJ Weaver :l: r- cebgn) r Ten Ge-bert*. GoosseftS. LjL Lerrrr.s'-i ■-- -- . = ■■■■ - '■ Editorial secretariat: ec.l n + '+■ : 'z Graphic design . DTP: >- G> Vers. Ce ! Dc> Managing Director Publisher: -,z_ E r .-_■ a s % ■ > p Subscriptions ViforcSvide StiKonption Service Lid.. Unit 4, Gabs Reed Farm, fehSey Reed. 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I e - r ' : £ : - cx.se Ess - ' : -e La - e G'-ertssy, Storey KTI 6 9Ai^ Er^ncL Tdeahoffie: 444 (0) 1 932 564999 r fee +44 (0)1932 56499B r’errec - . . . : - i i : ; e- : ee^e e s s: e ts Intemationaf Advertising ■ EEs _ e _ e i z _ eE e e e — ea z Era: * . . - ' - ' - 1 " ■: - ■ ‘ .zZ: “;a - -i a : "'E e.e a>'e _ “ 'ec^er c= * Copyright Notice ThecarOiTS efesoibed an ths n^ ^Ti he are faf dcimegMz use oriy. sAB t 5 rg - photo? : ■ : : ■ • >. . bcsnf feyszs, pro^arnsned rEe^Eied droits cfefes, 03404 =, scxf.'/sj^ aft srd artsfe teds puky fefed iri ols- books ard rmgzzres (cehs - thsnflwd-pertyadvoTJS^^ are co^g^t Begrs^ b.v. and may ntx be r^xodoced ortisfisTiiited in ary bm or by sry means, indudng pfto&ooopr/ng, sc^vwg an Tcccrtiirjg, art vufwfe orffi p^z ptier wnSen pemntssbn from the f\jfcfeheflE, Such wiSeci perms- ■ _ 'TTjgr be ■cfetaff^pd h^-rjF- y:y pgrf rf ft*; pi k cfnmprt m 7t trtnpu&%y+p?r, my ryfflim. f^zHTlp3 dtsgf^ airi T3t> use the cocteos it other S^sirec: psIft^SHns zrd edL^es. 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Est Great Dun mow, Essex CM6 1XG Telephone: 01371 875644 email: sales@cms.uk, com 6/2005- tick loi dartre nits mailbox info 11 market VOX AC-30 query {2] Dear Editor — in response to Greg's query in Mailbox, April 2005 , The AC3G had many variants, most of which did not catch on — there was on AC50 ond I believe an AC 100 that bath used E!_34s this may have caused the con- cision Greg wrote about; bd.) The younger engineers might be interested to know that valve radios etc were marked AC r DC or AC/DC because She UK mains volt- age could be AC or DC and even at different voltages. However os this changed in my childhood 1 realty can't remember the voltages used. The AC30 is an iconic design that remains popular to this day, it would make an interesting article, putting it through its paces with mod- ern test equipment and an explanation of what that tremaio/vibrata circuit is about! f have never found an AC30 with the trem/vib working. Good articles could be writ- ten about many other iconic designs, like the Fender Sfra- tocoster. For exampele, why are the pickups on the old ones so revered? It's rumoured they were wound with second rate copper with the best copper going to the war effort in Korea? The Quad tl HiFi amplifier would make on interesting article as well, other readers might have suggestions for iconic designs? Andre James Howard (UK) Thanks for that Andre James . An article on upgrading the VOX AC30 appeared in the April i 969 issue of Elekior Electronics. Hex format( s} Dear jan — there seems to be a problem with the hex file for the SC Analyser 2005 published in the April 2005 issue of your magazine. The programs I use to load the hex file to the PEC16F8 76 (Proteus VSM simulator, Pica II v/, Winpic] all report invalid addresses in the hex file. Con you verify this please. Le Var Cabey (UK) This question is asked at least a few times every month. Pfease hove a look at the hex file using any text editor like Notepad or Word, Each line starts with: ? 0 (meaning ?0H data bytes in this fine) and the next 4 positions are the starting addresses tor the data. As you can see , the addresses range from 00C0 to 3535H, Also , address 40G0 holds the ' options' information fi.e., what kind of oscillator etc) ror the FiC processor If your programming software does not accept this format please feel free to edit the file with any hex editor You can easily find a freeware hex editor on the Internet (for example, trial ver- sions of HexWorkshop and Ultra Edit). Remove any data above 3B00H. As on aside , the PIC 1 6F87XA devices have a 13 -bit program counter capable of addressing on 8 kword x 1 4-bit program mem- ory space. The catch however is that each location is not 14- bit wide instead of 8-bit . Expressed in bytes, this means a maximum address of 3800H. The maximum address of 3535 in our hex fife is well within this range . if you find this complicated fwe da, but memory space is optimally used this way), feel free to blame Microchip . Cuk Converter criticisms Dear Editor — I was interested to read your article about Cuk converters (Elektor 1/2005, page 22), as I made a careful study of these myself some years ago. I felt that your article did not really explain the merits of the Cuk converter: why it was such a ground-breaking topology, and why it has not been commercially successful. The article by Georg Gerads concentrated only on the volt- age and current waveforms but, since these are similar to those for existing topologies, they do not reveal anything par- ticularly interesting. One could be left wondering exactly why is there a claimed advantage over existing topologies, which are now very well developed? One paint you did not mention is that controller ICs specifi- cally designed for Cuk converters are available; and that the Cuk topology is closely related to the SEP1C (single-ended pri- mary inductance converter) topology that has emerged in recent years. But, in particular you did not fully explain why the two induc- tors in a Cuk converter are coupled. In fact, they do not need to be: the basic Cuk converter uses two uncoupled inductors and the topology is that of an inverting converter but with continuous input and output currents. We can note that a buck converter has a discontinuous input current and a continuous output current; for the boost converter it is the other way around, whilst a conventional inverting converter has discon- tinuous input ond output currents. So the Cuk converter allows us to make a power supply with the inherently better ripple performance that Is obtained by operating with continuous currents at both the input and the output. But that is just a first step in understanding what the topology offers. Because the two inductors have the same current waveform they can be wound on the same former without 'interfering' with eoch other, which gives a possible saving in space. This, in itself, is not particularly significant, but what the inventor showed was that if the turns ratio of the resulting transformer bears a certain relationship to the coupling coefficient between the windings, then it is possible to steer all the ripple current to one side of the converter. In other words, the input or the output ripple current can be zero! In this situation the converter does not need a smoothing capacitor an the zero- ripple side (or, at least, only a very small one!]. Unfortunately, your project cannot demonstrate this important aspect of the converter. Jf the two inductors have a turns ratio of 1 :1 then the coupling requirement for zero ripple is k~l , i.e, perfect coupling. Of course, this cannot be achieved in practice, and it does not work in theory either, so the ripple- current performance of such a converter is unpredictable. The fact that the converter needs a special magnetic circuit in order to achieve zero ripple is a drawback. However, in some situations, the behaviour can be suitably modified by using an additional series choke. Another simple way of achieving the desired behaviour is to use a magnetic circuit based around two stacked toroids. One winding is wound around both cores, the other around just one core. With a 3 ekltlor dfdnmirs - 6/2005 suitable turns ratio, the desired relationship between coupling and turns can be achieved. The need For specialised mag* neilc designs has lead to the concept of "integrated magnet* ics' which Cuk has been promoting. Another disadvantage is that the design requires a very high* quality capacitor for the storage element. But neither of these disadvantages can explain why the converter has not been commercially successful because, In a commercial market- place, components would have evolved to meet the require- ments. (Much in the same way that very low ESR capacitors hove evolved to cope with conventional topologies). There are several advantages to the Cuk converter, which all relate to transfer functions of, for example, line to output volt- age, duty cycle to output voltage and so on. The converter is daimed to be more stable than other topologies and easier to control. Part of the reason for this is that it works with continu- ous currents, os your project article does mention. At one lime, I was an enthusiastic supporter of this topology. It is certainly very Impressive to run a PSPICE simulation and see the ripple current disappear from one port without ihe need for a smoothing capacitor. But in practice, it appears to be difficult to make a Cuk converter live up to its promise * especially when it is competing against the very highly evolved designs that we can buy off-the-shelf from semicon- ductor manufacturers such as Maxim and National, Much of the reason for the lack of commercial success of the Cuk topology can perhaps be explained because the design was so well patented. It was in a niche market where there were no evolutionary forces 1 to develop It further For other than a very specialised application, 3 can see no reason why the Cuk converter needs to be considered at ail, especially when an incomplete understanding of Its rather peculiar behaviour can lead to a design that does not truly take advantage of its characteristics. On the other hand, it is o fascinating topic for home experimenters. David Gibson (UK) VVfe are very grateful to Me Gibson for his critical observations, which have been copied to the author/designer hr hi $ consideration. Mean- while the Cut Converter has turned out fa be very popular project The discussion may be continued an our Forum . ELI 56 Audio Power Amplifier Dear Fiektor — 1 believe an error could cause output valves to draw very excessive anode current. Destructive failure could even occur a long time after amplifier has been put Into service. In Figure 1, decoupling capaci- tor C8 in the amplifier schematic is shown with the positive end connected to neg- ative-biased grids of output valves (cathodes and negative end of capacitor essentially grounded). IF the electrolytic fails due to reverse connection, this could present low resist- ance to ground that causes lower negative bias on the con- tra! grids. AlsOj C7 is the wrong way around [valve cathode will be positive an an auto*bias arrangement); not very danger- ous but possibly upsetting the operating conditions causing very loud and distorted output C3 has no voltage rating. This device needs to be rated at least as high as C9 by the same criteria as C9 (see later). Adequate consideration or the effects of HT being supplied to components connected to cold valves and of powering with some valves unplugged does not appear to have been made. (Do you unreservedly trust switch-on delay circuits? I don't). For example, if C6 needs to be rated ai 500 V (questionable in view of the zener diodes) then so do C5, C3,C9,CIG & possibly others Also readers unfamiliar with the high voltages may not be aware of the power dissipa- tions involved, for example RIO dissipates 1 .25 W in nor- mal operation. Can I suggest (with the best or intentions since I enjoy your magazine!) that you get an old hand" with practical valve experience to examine the 'tube/ valve" designs before publishing? Someone who's never handled mere than a few tens of volts might pick up the article in years to come and get a loud bang & smelly smoke for their trouble! PS, love the magazine, & let's have lots more Hi-tech Audio. What about some valve/tran- sistor hybrids [best of bath worlds if done properly). Peter Hague (UK) Mr Hogues critical comments have been copied to the author/ designer and we a won his answers Valves versus transistors ( I ] Dear Editor — -t found the arti- cle "Opinion on Valves, Valves versus Transistors (page 25 of the Morch 2005 issue) very interesting Surely, that topic is the source of never-ending debates and discussions. I found the technical aspect of the discussion a bit simplistic, however, as Mr, Ton Giesberts sounded like he was compar- ing the very best transistor amplifier with mediocre valve amplifiers; " that's not actually the fault of the valves, but instead comes from the fact that most valve amplifiers are poorly designed (change both Valve' words to "transistor' in that sentence and it will remain true]). He claims that transistor amplifiers "'add almost nothing to the sound [ almost nothing" is "something", nevertheless), but in my opinion what they add plays a more important 6/2005 - elds lor tletfrcria 9 mailbox info & market role in the final quality of the perceived sound reproduction. Also, there are features in an amplifier that are more impor- tant than the damping factor. Having designed, built, and more importantly listened to both valve ond transistor ampli- fiers, i just can t agree with Giesberts general opinion about valve amplifiers: if they were simply not good", people wouldn't be listening to them! Yes, they colour the sound, and so do the transistors. There is no such thing as o 'neutral' amplifier, at bast I haven't yet found two different amplifiers that sound exactly the same. Every amplifier distorts, and the harmonic distribution of the dis- toftion components plays a major rob in the final sound quality. Take, for example, the spec- trum analysis of the distortion graph of the ELI 56 Valve Amplifier (page 35, figure D), and compare it with the corre- sponding plot of the transistor- ized High-End Power Amplifier (page 1 7, figure C), Noie the distribution of the different har- monic components: the EL 156 valve amplifier distortion is dominated by the second har- monic, and the amplitudes of the remaining even harmonics gradually decrease, until the 8 r ^ and high er virtually disapn pear. Something similar hap- pens with the cdd-numbered harmonics: their amplitudes gradually decrease from 3 r£ * to 9 ?r , which is the last one dis- cernible on the plot. Now look at the harmonic signature of the High-End Amplifier: again, ihe distortion is dominated by the second harmonic, with the barely visible, the 6™ and higher practically missing. But look at what happens with odd harmonics: the amplitude of the 5 in is actually higher than the third (l), the 7 3 ^ harmonic has the same amplitude as the 3-b; the 9 iK is fortunately smaller. the 1 r h and higher disappear. Clearly, the distortion products of this amplifier are dominated by odd, high-order harmonics. And it is well known that odd harmonics tend to produce a rather unpleasant, strident, sound; ihe higher-order ones are believed to be responsible for the listener's fatigue' effect. Such harmonic signature is typ- ical of transistor amplifiers, they create that characteristic 'tin-can' sound. A similar phenomenon can be seen in the distribution of the hum components: as one would expect, the valve amplifier pro- duces mare hum, and it can be seen that the amplitude of the hum harmonic components also gradually decrease especially for the evenorder components. In the other hand, the transistor amplifier shows and 3 r< *- order hum harmonics with lav/ amplitude, but again higher- order ones experience a rela- tive boost, (incidentally, where does that 80 Hz component come from? The valve amplifier plot does noi show if). My final guess is that the EL 1 56 Valve Amplifier will pro- duce the best, more pleasant ond enjoyable sound of the two, despite the higher overall THD figures. BuE mat s only a guess I actually prefer to listen to an amplifier before making any definitive conclusions. The distortion graphs shown for both amplifiers ore taken for o modest outpui of only one watt. If would be nice to compare distortion components near or at, clipping levels (clipping can happen when listening to low volume levels, often during ihe note attack phase), it would be also interesting to see the distor- tion and frequency response plats far both amplifiers when connected to a realistic (reac- tive, and not purely resistive) load. I have been very often disappointed by amplifiers whose characteristics look extremely nice on paper, but in p ractice badly misbeh ave whe n connected to o complex load such a real speaker system. In general, I think it would nice if designers or audio amplifiers paid as much attention to the distribution of distortion har- monic components as they do to lowering the THD levels. Blindly lowering THD figures does not necessarily result in a good sounding amplifier. Below are a few links with infor- mation about distortion and amplifier sound that I found interesting and would like to shore, if possible, with other readers. Although they are valve-minded, some concepts could be of interest to transistor amplifier designers as well: http:/ /normonkoren.com/ AudEo/Peedbackridellty.html Feedback and Fidelity , by Nor- man Koran http:/ v, mvmyfshe Ihif com/ librarv/FindinaCG.html The Sound of the Machine. The Hidden Harmonics behind THD , by Lynn Olson. There is a very interesting sec- tion on power supply-gener- ated noise (Tower Supply and Noise Spectra ). Other articles of the same auihor ihat ! found interesting, although again valve-minded, ore illusion Engines and Design Philosophy , available from the same web site by following the corresponding links. Hector Peraza (Belgium)* We are grateful to A-fr. Peroza hr expressing his vie.. points. Tran- sistor advocates ore invited to reply! The discussion men/ be con- tinued in our on din e Forum, Valves versus transistors (2) dear Editor — as I am on audio nut into valves, 1 could not resist buying the March 2005 edition of your maga- zine as it had Valves or Transis- tors across the Front cover. Although for amplifying audio analogue waveforms I regard transistors as a temporary step backwards (as surely ihe Inher- ently more linear Inode valve must reign supreme in the future), 1 studied the circuit of the High End Solid Stole Power Amp. 3 might be suffer- ing from cathode poisoning but as drawn, wouldn't the negative feedback loop be in phase with the input? Should- n't the base of T8 be con- nected to Tl pin 6, T7 base to TT pin2 and the some changes to T9 and Tl 0. I enjoyed reading the valve versus transistor article although I can't say S agreed with all the opinions expressed. Jerry (UK) E/oquenfly written Jerry but our audio designer Tan Giesberts replies that there ore no errors in the design. The High End Power Amp has been built by a good number of readers with excellent results. MailBox Terms - P ub : cat i o n o t rea d s r ' s cc r res oc n - dence is as. the discretion of Uis Editor. - Vi s Vi co nts expressed b\ co rre s- pondents are rot recess y : nose of ire Editor c? Publisher, - Correspondence may be Iran staled or etf U&d f o r ! & n gth c • arity a nc style. VJnec. replying to Mailbox corre- spondence, please quote Essue number, - P ease send your Mai’ Box corre- spondence tb: ? cjfrc n ii r s.jg.m-- o r EEektor Electronics, The Editor RO. BOX *90. Tun bnCge .Veils T.N5 7\VY. England. 10 ehktoi slECIrottfts - 6/2005 info & market corrections & updates RFfD Defector lor 13,56 MHz February 2005, p. 38-42, 040299-1. On the PCB copper frock lay* out, all three pins of preset PI are connected to ground instead of just two. The problem is easy to solve: the copper pad of PI com nected to pin 7 of !C I [of the edge of the board, near the 'Elektob print) has to be discon- nected from the ground plane by cutting the three thin tracks between the pad and the ground plane. SC Analyser April 2005, . p. 34-41, 030451-1. Unfortunately,, an early version of the PCB artwork is shown sn Figure 5 . Although if will pro- duce a properly working Instru- ment, the PCB design shown locks the extra decoupling for the PLED display mentioned in the article. The PCB supplied through our Readers Services does have space and copper frocks for the extra decoupling network and comes with a cor- responding note to customers. The correct PCB artwork is shown here. Opamp fester March 2005, p. 74-75, 030386-1, Unfortunately the printed circuit beard for the above project contains a mistake concerning the supply voltage to the opamp in position 1C4. How- ever, the problem is easy to solve. Using a sharp hobby knife, completely isolate pins 11 and 4 of IC4 from the rest of the cir- cuit by cutting all copper tracks to these pins. On the JC socket, bend out pins 4 and 1 1 side- ways and solder a short wire to each pin. Solder the 1C socket In place (at the under- side of the board). Connect the wire on socket pin 4 to the pos- itive supply voltage. Connect the wire on socket pin II to the negative supply voltage. Populate the rest of the board as indicated by the component mounting plan. Please note that sockets tC2, 1C3, IC4 and LEDs D1 through D1 6 have to be fitted at the sol- der side (underside] of the board. This allows the board to be better mounted In a case. h 20 OS - debar chdrarirs 1 I info & market news & new products USB IT -channel data logger Pico Technology announces the latest addition to their data acquisition range, the USB ADC- 1 1 Data Logger The new prod- uct has USB connectivity to allow Fast sampling rates and addi- tional digital outputs For use os control or alarm outputs. Avail- able in two variants ( the USB ADC-11 /tO (10 bit] and USB ADC-1 1/12 [12 bit) are bath compatible with the multi-pur- pose terminal block, providing a substantial enhancement to its Flexibility, The USB ADC-1 I provides a cost effective solution for meas- uring and recording voltage sig- nals onto any Windows based PC or laptop. When used with Pico Log© data logging software, which is able to record up to 1 million readings; the data can be viewed in real-time or stored on hard disk for later analysis. The popular PicoStope© can also be used with both models. Both variants of ihe USB ADC- 1 1 are capable oF measuring up to 1 1 channels of voltage ot up to 20,000 samples per second. Resolution and accuracy depend upon the model used; she USB ADC-1 1/10 provides 1024 dis- crete voltage levels giving 1% accuracy, whilst the USB ADC- 11 /1 2 offers considerably higher accuracy with 4096 volt- age levels and 0.5^ accuracy. Using the optional terminal block significantly expands the func- tionality of the USB ADC-1 1 * An area of PCB is reserved for the design and implementation of custom sensor circuits such as high precision thermister, stan- dard thermocouple or current and light measurement. Both USB ADC-1 1 models ore available immediately directly from Pico Technology or any authorised Pico distributor. The product can be purchased with the optional terminal block with prices starting from £ 95. Furlher information can be accessed through the Pico Technology web- site wwv/.picatech .com or by calling +44 [0)1480 396395. Q57CSI-4 PIC Micro for intelligent power conversion designs Microchip recently announced the P1C16F785, which provides large complement of onboard analogue peripherals, including analogue-to-digitol converters (A/Ds), comparators, a voltage reference and two operational amplifiers (op omps). These make it ideal For cost-effective digital control in power conver- sion designs, as well as a bread ronqe of sensing and closed- loop control applications. The 20-pin PIC 1 6F785 can cost effectively address a wide range of power-conversion parameters in applications such as Switch Mode Power Supplies (SMFSUs) and battery chargers. Today's electronic systems require intelli- gent control of multiple power rails, startup conditions, fault detection, exception handling, and complex battery-charging algorithms, and the P1C16F785 provides the familiar analogue building blocks within o pro- grammable microcontroller, mak- ing it easy for power-supply designers to utilize digital con- trol in their power-conversion applications. The two general-purpose op amps feature a 3-MHz Gain Bandwidth Product (GBWP) and 5 mV input offset voltage, ideal to implement fillers, input gains stages and other functions. These two op amps,, with the integrated 1 .2 V bandgap voltage- refer- ence and two high-speed [4U nanosecond) comparators, pro- vide unrivalled integration for input sensing. The PIC16F785 is supported by the full suite of Microchip's high- performance development tools, including: PICkit T "' 1 Flash Starter Kit, MPLAB© IDE [Inte- gra led Development Environ- ment),. MiPlAB ICD 2 (In-Circuit Debugger), PRO MATE© II and MPLAB PM3 universal device programmers, and the PIC- START© Plus cosheffiective device programmer. Application notes related to power conversion are Output Comic! currently being prepared. 3. Mi tro chip Ltd., Microchip House, 505 ikstfde Road, Wokingham RG41 5TIL TeL (+44) (0)118921 5369, Fox (+44) [0)1 VS 921 5820. vAvw.microthip.com . 12 tibia ell&clrcrtcs - -6/2QD5 j Isgh(er) density sEEPROM in 2x3mm package Microchip is Introducing 2x3 mil- limetre DFN (dual Fiat no leads] package options across Its product line of t^C extremely small foot- print and low profile for space- constrained applications such as portable devices and laptop com- puters. Its new 64-Kbit I^C and ] 6-kbit Microwire serial E EP- ROMs m the tiny DFN package offer the highestdenssty serial EEP- ROMs in the smallest standard package available icday. With a PCB footprint of just 6 square millimetres, the new DFN package Is 8G% smaller than an BJead SOIC package; 59% smaller than an 8-lead MSOP package; and 27% smaller than a 5-lead SOT-23 package. In addition, For applications requir- ing a very law profile, the DFN package is only 0.9 millimetres tall — between 20 and 40% tower than other standard pack- ages. The new DFN package is available for Microchip's 24xx series of I^C serial EEPROM products in densities from 128 bits to 64 Kbits, and for the 93xx series of Microwire serial EE PROMs in densities ranging From 1 kbit to 1 6 kbits. The 2x3 millimetre DFN package Is lead (Pb)-Free f and compatible with both higher temperature lead- free reflow processes, ond exist- ing tm/lead (Sn/Pbj processes. C5T" 53-5 Microchip Ltd., Microchip House, Teh {+44} [0)1 18 921 5869. 505 Eksdde Road, Fat (+44) (0) 11 8 92 1 5820. Wokingham RG41 5TU. www.microchip.cpin . pPFC™ 1C lor 75 W to 4kW power International Rectifier have started to supply (he IR1 150 family of pPFC " for AC-DC power factor correction (PFC) circuits. The com- pact SO-8-packaged device cuts PFC control board space in half, and enables a simplified and flex- ible high density solution for com- puting consumer electronics and home appliances from 75 W to 4 kW. IR's new One Cycle Con- trol (OCC) approach In the SRI 1 50 delivers the performance of continuous conduction mode [CCM) PFC with the simplicity, reliability and low component count of o discontinuous current mode [DCM] circuit for PFC appli- cations. Power factor (PF) is the relationship between AC voltage and current waveforms and is a measure of ' power quality that afreets ihe efficiency of electrical transmission networks. With unity PF as the ultimate goal, the IR I 150 enables 0.999 PF with only 4% total harmonic distortion, enabling AC-DC applications to conform to international legisla- tive requirements. The IR1 150 is an elegant solution to PFC legislation such as IEC 1 000-3-2 in Europe, JIC C 61000-3-2 in japan and [he China Compulsory Certificate (CCC) for products using more than 75 W. As manufacturers implement PFC in response to these energy standards, the IR 1 150 control 1C simplifies effec- tive PFC solutions, and enables a single design that can be used worldwide . 1057053 - 7 . Four digits For any The new OEM 4-LED is an extremely compact, 4 -digit, LED data display module from Lascar Electronics. Communication with the display Is via o serial interface making this product ideally suited to microcontroller based applica- tions, Each of the 7-segment dig- its (8 mm height) and ihree deci- mal places can be addressed indi- vidually and use low power red LEDs to produce a display that application whilst highly visible has o typical current consumption of just 20 mA at 5 V. Connection to the display is via a ] 2-pin DIL with Industry stan- dard 2.54 mm (0. ! ) pitch. This cost effective display option is on excellent choice for appli- cations where space and power consumption ore considerations. Already proven In high volume applications, the OEM 4-LED is available now with prices start- correction International Readier, European Regional Centre, 439/445 Gadstone Road, Whytelerie, Surrey CR3 GBL TeL +44 (0)20 3545 8003. www.irfcom ing at £10.90 (£6.40 at quanti- ties of 250-5- pcs). £ 37053-1 !■ Lascar Electronics limited, Module Hose, Whifeparish, Salisbury, Wiltshire SP5 2SJ. TeL (+44) (0)1794 384567, Fax (444) [0)1794 8B4616. wvAvJascareledionlcs.com 6/20 05 - tbkter dfttmrits 13 cover story know-how A study conducted last year by physicians in the German city of Wail a caused a lot of commotion. They sifted through theii card files and compared a group of patients living near a mobile telephone network base station with another group. The results were not so good; there were approximately twice as many cases of cancer among the group located dose to the transmitting tower. The "Reflex' study commissioned by the European Union [1]), which cosled more than 3 million euros also caused a great stir. It was concluded that high- frequency electromagnetic radiation at UMTS and GSM frequencies causes an increased number of breaks in DMA strands: involuntary gene modification; modified genetic characteristics In more concrete terms: it was noticed that the herd produced less milk and lost weight after a GSM tower was placed in the vicinity of their pasture. The number of miscarriages and still- bom calves also increased. Moving the herd to a different pasture outside the range of the new GSM tower improved milk production, and the other com- plaints also decreased significantly. To put things to the test, the herd was again moved back to the first pasture, and sure enough: milk production stalled again and medical complaints also increased. [2]_ Can't be that serious? Mr. J, Houtenbos of www.straling.nl finds these wild stories a bit exagger- ated. Although in his opinion the haz- ard cannot be considered to be totally References 1 wvav, s * o r we a ve . co m /re f lex/ 2 Repachali MH h Basten A, Bebski V, Finnic J r Harris AW. Lymphomas in E mu-Ptml hansgenic mice exposed \o pulsed 900 MHz eleclromagneiic Helds. Radio! Res 1997; 147:631-40 3 Journal of the Physical Society of Japan, Vol. 7 r p, 432 4 Hyland, G., The Lancet November 25 2000; 356:1833-40. 5 vAvw.rivm.nl/biblIolheek/ digilaa!depol/2wamborn20Q3CGFA Mrapport.pdf Mobile telecom operators are rolling out the systems they hope will recover the billions invested in 3G licences for the new UMTS services. The blessings: watching TV on your mobile, videophones, surfing, 70,000 extra masts, worrying electromagnetic radiation... insignificant, since there's a lot to be said against holding a mobile tele- phone with its 2 -watt transmitter right next to your head, he points out that the radiation from the antenna towers generally remains within the limits and well below the maximum levels speci- fied by the standards, with a few exceptions. For instance, if a large num- ber of calls are made from a single loca- tion, additional power is necessary so everyone can phone at the same time. The Japanese physicist Tsuyoshi Hoo- don, a member of the staff of Tohuku University in Sendai, carried out a study of the use of mobile telephones and field strength in trains. He found that the standard was already exceeded if 30 people made calls at the same time and their telephones trans- mitted with an average power of 0.4 W. Tn at was naturally related to reflec- tions of the signals and the small, enclosed space, which acted as a Fara- day cage. Just imagine the radiation level in a full train in Japan with every- one phoning at the same time. If in addition they all have 'poor reception; the radiation level vrill be even higher, since each transmirter can, is allowed to, and will increase its power up to 2W |3|. That puts things in a different perspective. What's up? Mobile telephones use the same type of radiation (microwaves) as microwave ovens. Microwaves can thus be used to heat things. And if microwaves in a microwave oven can heat material, the microwaves from a mobile telephone can do the same thing. Naturally, the amount of heating is less, due to the lower output power (2 watts for a mobile telephone versos 750 watts for a microwave oven), but still occurs. There’s no problem with a single mobile phone* but what about when several mobile phones are being used at the same time? And what about the other equipment in your everyday environment: cordless (DECT ) telephones , WLAN, Bluetooth, microwave ovens, wireless (security) cameras, radar, point-to-point trans- mission systems used by telecommu- nications companies, communications satellites, the taxi dispatch office around the comer, the w alky -talkies used by the police, fire department and ambulance personnel, the radio- controlled model car belonging to the boy next door, and now UMTS (which stands for ‘Universal Mobile Telecom- munications System)? A nice word has been invented for all of this: electrosmog (where 'smog' is borrowed from the word for a more vis- ible and odorous form of air pollution, which was originally formed from the combinaiion of smoke" and 'fog ). In terms of physics, it’s all relatively simple. Transmitters (including mobile phones) generate electromagnetic fields. In human tissue, a portion of the received energy is absorbed and con- verted into heat. This is referred to as Thermal effects’. These effects have been thoroughly investigated, and the processes are well understood. The statutory regulations specify that for health reasons, body tissue Is not 14 elsVtc-j c!criio"ics ■ fi/ It 05 (hi# frequencies above 2 GHz, such as UMTS base stations, the threshold value is 61 V/m, which corresponds to a power density of approximately 10 W/m 2 . If a network operator wishes to erect an installation with a power of 10 W or more, an additional permit is required Based on the antenna radia- tion characteristics and the structural situation, the responsible (govern- ment) authority determines a safe dis- tance beyond which the threshold value is in no event allowed to be exceeded. As this authority only oper- ates on a random-sample basis and is not aware of all sources of radiation, a safety factor is also applied according to the number of antennas already present and several other parameters. In addition, inspection departments make measurements over the entire KF spectrum in sensitive locations, such as schoolyards. i i • f f m » ii f i allowed to be heated up more than one degree Celsius by radiation (see the Tower density and $AR T inset). Any- thing more than this is prohibited. Under control! To he sure of entirely eliminating health hazards due to thermal effects, specific field strength thresholds apply to stationary transmitters with a power of more than 10 watts in areas where people stay for prolonged lengths of time. For transmitters with Studies ond research To provide objective information about emissions in the immediate vicinities of transmitters for mobile telephone systems, extensive studies have been carried out by various levels of govern- ment during recent years, as well as studies commissioned by network operators. For instance, in North Rhine-Westphalla the renowned l Insti- iut fin Mobil- und Sa telh ten fun ktech - nik' (1MST GmbH) made measure- ments in ten German cities, and the measured values inside and in the vicinity of buildings proved to be well below the threshold values, even close to the antennas. With a few excep- tions, the measured power density was less than 1% of the permissible power density. Nevertheless, the experts also obtained some surprising results. For instance, the power den- sity by no means decreased gradually up to around 100 metres; in that region the difference in the heights of the transmitter and the measurement point had a much larger influence. "Just like a lighthouse, the antennas radiate most of their power in the pri- mary direction, but there are also sev- eral side lobes r h explained IMST employee Christian Bornkessel, who coordinated the measurements. These side lobes are what negate the prevail- ing doctrine that the region directly below the antenna should be practi- cally free of radiation. "To our surprise, you can't automatically assume that there’s practically nothing to measure under the roof of a building with a transmitting antenna for mobile tele- phones', said Bornkessel. That depends a lot more on the structural situation." Nevertheless, even in the worst case the values proved to be well below the threshold value. According to Bornkessel, there are thus no grounds for 'honor stories". On the other hand, opponents contend I ) Bose station locations Probably as a result of political pressure and concern expressed by several organisations. Ofcam, fhe Office for Communication [formerly ihe DTI s Radio Agency) are supplying a mobile phone base station locator that's acces- sible by ihe Internet. Until recently, this informa- tion was either classified or only obtainable by cutting ihrough a lot of red tape. The Sitefinder webpages also have an Information Sheet that's quite useful although neutral in terms of radiation hazards presented by fhe 70-k or so base stations eventually active up and down the country. The Sitefinder database is updated at a remarkably slow rate of once every three months. Compare that with fhe time it takes a crew of experienced suite building verligofree engineers to erecr a most ond commission the equipment and you should not be surprised io suddenly see masts not yet identified by Sitefinder. SiteFinder provides the following Information on each base station: type of transmission, ontenna height, frequency range, irons miner power and maximum licensed power. In Germany, a similar government s office goes at least one better than OFcam by also show- ing measured (!) energy levels and associated safe distances. Ofcom Siiefinder at: svww.sitehnder.fQ dio .gov.uk/ German equivalent wvAv.emf-forschung5proqrQmm.de/hQme Antennas are not only hidden on the Internet] Dutch equivalent: wvAv.antennebureQu.nl/stQrt.htm A/2DQ5 - dsktor eltrtroma 15 cover story know-how that the question of whether a measure- ment justifies a horror story depends entirely on the threshold values. 'In the direction of the main beam, the field strength is still 6 V/m at a distance of 100 m.\ argued instrumentation engi- neer Rainer Muller, who is also a con- sultant to the environmental organisa- tion Bund fur Umwek und Naturschutz Deutschland (BUND), The expert put his findings m perspective by saying: "According to the legally permitted held strength, 90% of aU Elektor Electronics circuits would fail the test!". At the same time. Bornkessel thinks that the controversy regarding more restrictive threshold values, such as the frequently cited Swiss threshold value of 6 V/m, only fosters the uncer- tainty of the general public. That cer- tainly became clear to him after con- versations with Swiss colleagues. l Tne primary need for precautions is with mobile telephones, not base stations', said the mobile telephone expert. By way of exception, environmental activist Muller fully agreed with him on this point. When you’re phoning with a mobile telephone, the field strength inside your head can be as high as 300 V/m, which - as die master of visu- alization put it - is 'enough to ignite an explosive mixture of gasses'. The elec- tromagnetic field of a household DECT base station can also easily reach the level of a mobile telephone base sta- tion transmitter Manufacturers are keeping mum According to the recommendations of the International Commission on Non- Ionizing Radiation Protection (ICNTRP), mobile telephones should not be able to radiate more than 2 W per kilogram of body weight into the user's head. Some of the current mobile ohones are ■fe well below this threshold value for the specific absorption rate (SAR; see inset), but the manufacturers aren't saying this out loud. Toe industry has also refused to endorse the 'blue angel' environmental label for low-radiation mobile phones (with SAR values below 0.6 VV kg). As measurement engineer Bornkessel explained, L The manufac- turers are in a difficult position. If they make too much of a hiss about low 3AR values, than could he regarded as an admission that the radiation from mobile phones Is in fact hazardous. 1 In the opinion of BUND expert Muller, there is a major need for additional studies of what happens mside chil- dren s heads when they use mobile phones. As he pointed out, 'Now that even three-year-olds are phoning, you can't rely on measurements made with a water-filled model the size of an adult head, 1 To be on the safe side, the BUND argues for reducing the value to 0.5 V/m in order to account for the non-thermal effects on the organism. It appears that such effects do exist, but up to now it hasn't been possible to prove them. According to Muller, research more specifically focused on such effects Is necessary. He said that in any case he missed this ‘central theme T in the stud- ies currently being conducted by the Deutsche Mohilfunk Forsch un gspro - gramm (German Mobile Communica- tions Research Programme). Side effects Muller has a point, because the current rules are based on the thermal effects and ignore the non-thermal effects. For example, why are people not allowed to have their mobile phones switched on in hospitals? The sensitive equip- ment' in the hospital won't be both- ered by any thermal effects caused by a phone. That means there must be Why so many base stations? In the UK, the number of base stations carrying mo bite phone services is eventually expected to almost double to a staggering 50,000 - 70,000. Alarming? Maybe not. Forgetting tor the moment ihe line-ofsEghl effect applicable to SHF radio waves., let's assume you'd want to use a single antenna to cover the entire UK, You then build a massive antenna radiating an equally massive amount of power. The EF power levels produced would turn □ large area around the antenna into o hazardous area because the locally present radiation level would far exceed human life conditions. The alternative using lots of antennas radiating lower power (20-100 watts each) results in restricted areas of just 3 metres or so. With even mare transmitters conse- quently with even lower power, there ts no restricted area at di — after all you hold your mobile against your head. So r 'more' base stations is not necessarily more dan- gerous because at feast in theory it causes the local power fo drop. The "no masts- near-schools' campaigners are also faced with this dilemma. Summary of wireless systems frequency Pulse Terminal unit Base station Max. peak / average {MHz) frequency time slats power (Hate 9* terminal unit power GSM-900 network 890-960 217 Hz 1 or 8 5-50 W (Note l) 2 W / 250 mW] (Note 2) GSM-1800 network 1710-1 880 217 Hz 1 or 8 5-20 W (Nose 1) 1 W / 1 25 mW] (Nots 2| UMTS |G3) 1900-2170 various methods 5-50 W (Note 1) 1 VV ( Nc >te 2 > DECT 1880-1900 100 Hz 1 or 24 250 mW max. 250 mW/lOmW WLAN 2400-2483 10 Hz 100 mW max. (^ 3ts M 100 mW (Note 1) Bluetooth 2402-2480 1 600 Hz 1 or 2 ( Na ' s 6 ) 1; 2.5; 100 mW max. (Noto5| 1; 2,5; 100 mW (Note 5) Lite kU:! pifi-sr dsys-rk m tdl end d-:U .uYtss. 2. Its odud penrer ikmtk ai istrp^n tonafionL 3. Visnt cse: ftridaen Li [hi mch been dtf&dki ct ihe antenna. 4. Beper fe or ::!o w&me, 5- fed V 111 I : - v i T ” ^ 'tf'S i : ■T iV - 25 hands-on cover story EU Council exposure limit reference levels for ihe genera] public; electromagnetic (£/H) fields; 0-300 GHz (1999), Frequency range E-componenr H-coirtp orient B-fie!d (jjT) Equivalent fields Ire-tig Ih field strenghl power density (V/m) (ft/m) for flat waves S*, (W/m 7 ) 0-1 Hz - 3.2 x 10 4 4 x 10 4 - 1-8 Hz 1 0000 3.2 x 10 4 f 2 4 x 10 4 /f 2 - 8-25 Hz 1 0000 4 000/f 5000/F - 0,025-0,8 kHz 250/f 4/f 5/F - 0.8-3 kHz 250/F 5 6.25 * 3-150 kHz 87 5 6.25 - 0.15-1 MHz 87 0.73/f 0.92/F - 1-10 MHz 87/EV2 0.73/f 0.92/f - 10-400 MHz 28 0.073 0.092 2 400-2000 MHz 1,375 R/2 0.0037 f>/2 0.0046 fV2 f/200 2-300 GHz 61 0.16 0.20 10 (noise-Free, average values) TABLE 2. Field strength / LED indicator. 1 LID# ?- u (dBm) E (V/m) Colour H (A/m) s IW/m*} 1 1 -70 5 m green 12 p 56 n 2 -62.8 1 1 m green 28 p 293 n 3 -55.6 25 m green 64 p 1.5 p 4 -48.3 57 m green 148 p 8.3 p 5 -41.1 1 30 m orange 340 p 43 p 6 -33.9 300 m orange 780 p 230 p 7 -26,7 680 m orange 1.8 p 1.2 p 8 -19.4 1.6 red 4p 6.4 p 9 -12.2 3.6 red 9.4 p 34 p If) -5 8.3 red 22 H 180 p Legend received power E; Wfelraiglfi of electrical component H: FieFdstrengtFi of magnetic component S; power density When oil LEDs remain off, ihe m ensured signal strength is below -70 dBm, now obsolescent W/m 2 unit, which may be found in older literature. Each LED on the scale represents a V/m value increment by a factor of 2.3. Using the W/m 2 unit, this scale rises even more rapidly — at the rate of 2,3 squared (approx. 5.3). The correctness of the indicator scale has been verified and approved by an independent test facility company (see inset). A logarithmic 1C Being able to pinpoint the major sources of SHF electrosmog requires a circuit capable of not only processing signal frequencies in excess of 2,000 MHz (2 GHz), but also offering sufficient dynamic range to reliably spot small and large fieldstrengths. The above is of course possible using a spectrum analyser or a special super- heterodyne receiver. Fortunately there are simpler ways, too. Besides the well-known AD 83 07, Ana- log Devices also produce a number of related ICs with extended frequency range, like the AD8313. This detector IC is suitable for use up to 2.5 GHz and also supplies an output voltage that’s proportional with the input signal strength in decibels. The available measurement range extends from about -73 dBm to 0 dBm. Figure I shows a block diagram of the AD8313 internal architecture. A cheaper alternative, the AD3314, is entirely pin -compatible. The fc 8314 is probably cheaper because of its reduced sensitivity of just 45 dB and it’s exactly this property that makes it unsuitable for our application. After all. it's the lower ranges of the tester that afford reassurance of low radiance lev- els around you. In conclusion, the AD8313 is well suited for our circuit, offering an accurate indi- cation wi thin the range -70 dBm to -5 dBm, A half-wave dipole antenna at the input will produce the folio wring rela- tions between received power (P r ) and electrical held strength E: P T = E 2 x 4.59e-6 and £ = V(P r x 218000) At the low end of the scale, -70 dBm - 1G- 7 mW = 10 10 W so E = 4.7 mV/m. At the high end, we have -5 dBm = 0.316 raW = 316 uW so E — 8.3 V/m Typically found SHF fields trengths of around 1 V are well within the tester's indicator range, making a pre amplifier superfluous and keeping ihe circuit as simple as possible. For the above range, ihe detector 1C supplies a matching direct voltage between 0,55 V and 1.7 V, where the lowest volt- age corresponds to -70 dBm and the highest, to -5 dBm. These voltage lev- els are sufficient to drive a readout without the need for an amplifier. The readout consists of a 10-LED bar- graph indicator. Because UMTS and other 2G/3G sendees are pulsed, we are looking at 100% AM modulation. The circuit Figure 2 shows that the AD8313 is the main component in the circuit, fol- lowed by an L M3 9 14 acting as the LED driver. Received signals are picked up by a dipole antenna with a length of about 70 mm (the wavelength of the signals we’re after is about 14.7 cm). This is small enough not only to enable the 26 ill he I dcdlEKLEB - 6/2005 Functional Block Diagram antenna to be fitted inside the case but also to print it in copper on the circuit board. The printed antenna has no construction problems, has no protrud- ing parts and makes the tester a truly portable instrument that T s easy to earn , 1 r around in your pocket. Because the measured frequencies are so high that parasitic inductances are FIGURE 1 . Interna! architecture of the AD8313. The circuit diagram of the Electrosmog Tester consists mainly of an AD8313 and an LM3914. 6/2005 -aid: to; entire 'la 27 hands-on cover story COMPONENTS LIST Resistors; R1 = 56Q R2,R3 = 10a R4 = m R5,R8 r R16 = Ika R6 = 4kil7 R7,R13,R15 = lOkil R9 = 36512 RIO - 3kDl6 R1I,R18 = TOOkn R 1 2 — 4700 R14 = 22ldl R17 = 560Q R19 = 15ka Capacitors (5MD 0805]; C1,C2,C3,C5,C11 = lOOnF C4 = 1 50pF C6,C7,C10 = InF C8,C9 - 270 pF Cl 2 = 2nF2 Cl 3 - 22nF Cl 4,0 6 = lOfiF 16V, 3. 3x3. 3mm or 4.3x4. 3mm Cl 5 - 47nF Inductors (SMD): 11 — 5nH6, type 0603 L2,L4 = 39GuH, type 1 21 0 L3 = 27G)iH, type 1210 Semiconductors (5MD); D1-D4 — LED, high-efficiency, green, right angle, type 0805 D5,D6,D7 D1 1 = LED, high -efficiency, yellow, right angle, type 0805 D8„D9,D1 0,.D 1 2 - LED., high-efficiency, red, ri ght angle, type 0805 D1 3 = DL41 48 (minimeif) T 'l ,T2 = BC847B, SOT23 T3,T4 = BC857B, SOT23 IC1 - AD831 3ARMZ 8-lead MSOP {Analog Devices, print: J 1 A) IC2 = LM3914V PLCC | National Semiconductor) IC3 = LP2951ACD SOICS (National Semiconductor, print: 5lAxBUL) Miscellaneous; S 1 - miniature pushbutton with make contact, 6x6 or 10x10 mm r height 18.5mm Case: SERPAC H- 65,9V TRANS RED SRH65-9VTR-ND (Digi-Key) 9-V battery with clip-on leads PCB (bore, see text], order code 050008-1 Ready-assembled and tested PCB: order code 050008-91 (see EEektor Shop pages or www.elektor-electranics.co.uk] quickly incurred, it is essential for the antenna to be a close as passible to the IC input. For proper matching, and to afford some protection against high levels at around 10D MHz (from FM broadcast stations) a resistor and an inductor are connected in parallel with the antenna The LED readout consists of an LM3914 and ten LEDs. Toe LM3914 has a linear readout (not to be con- fused with the LM3915 with its loga- rithmic output). The parts around the LM3914 are dimensioned such that the relations according to Table 2 are realised. Tne LM3914 offers the choice between ’bargraph' or dot' readout. In the inter- est of battery capacity we went for die "dot' option. As an added bonus, pulsed signals are much better seen because several LEDs will light briefly at the same time, Tne detector runs off a 5-volt supply voltage furnished here by an LP2951CN low-drop regulator in an 8- pin DIE case. This IC is capable of sup- plying up to 100 niA and allows the battery to be 'juiced*. A low-battery indicator (LED D12) will tell you when the battery is truly flat and in need of replacement. In addition to the detec- tor, the LP2951 also powers the LED readout, UMTS detection Because the process of installing 50,000 base stations for the new 3G networks is highly controversial all over Europe, we wanted to add an UMTS detector to be able to see if a base station is actually a 3G one. The idea was to employ the fact that the maximum bandwidth of a tradi- tional GSM signal (2G) is about 200 kHz, which, at AM demodulation, equates to a highest audio frequency of 100 kHz, By contrast, a 3G UMTS signal requires up to 5 MHz band- width. A high-pass filter allows 1800- MHz GSM demodulation to be blocked and UMTS to be passed. The 7 r — order HPF used here suppresses conven- tional GSM demodulation (100 kHz) by at least 80 dB. The Alter is followed by an amplifier, a transistor detector and a LED driver. In tins case we need to consider that the AD8313 can supply a maximum of about 1,2 V pp . Applied to traditional GSM signals, the filter action of 80 dB suppression results in a maximum signal level of 0.12 mV DP , or just 20 mV^- after amplification by 28 the first transistor. This is far too low to activate the transistor detector let alone the LED driver. However, signals greater than about 300 kHz can pass unhindered, As smiling a level of 1.3 Vpp to activate the transistor detec- tor and with it the detector, a signal of no less than 1.3 V pp /140 =10 mV pp is required from the AD8313. Unfortunately, practical experience shows that the indicator is not terribly reliable. The reason: a clear UMTS or GSM signal is hardly ever found, most base stations transmitting a mix of the two. Also, WLANs will often be found to be of a very wideband nature. At very small field strengths, the LED will also respond to detector noise. In con- clusion, the action 'UMTS' indicator should be interpreted with caution. In fact, the opposite applies: if the LED fails to light, you can be sure you’re near an exclusively GSM- 1800 base station. Because the antenna in our design is peaked at around 2 GHz, signals picked up from 2G (900 MHz) base sta- tions will be subject to some attenua- tion. Fortunately, the difference amounts to no more than two LEDs, Tie design was purposely optimised for the 'new' frequencies around 2 GHz and keeping the instrument as com- pact as possible. Remember, when optimised for 900 MHz the antenna and with it the in strum ent would dou- ble m size. During the design of the Electro smog Tester, we had to take into account that the relevant transmitters are pulsed. Initially, a large RC delay was installed after the detector In order ro stabilise the readout. Tnis worked fine, but unfortunately only on base stations with 100% occupancy. This is rarely the case — a DECT base for example will only transmit for a few percent of the time. Take the logarithm, and then the average results In... nothing, and it would appear as If the transmitter is not active at all. A solution was found in making the RC time much shorter. Although this results in a slightly more unstable readout, with some practice you're soon able to gauge the amount of traffic on a certain base station, to tell its type and approximate peak level (all relative, of course). Build it or buy it? Fro the fans of ultra-miniature work we’ve printed the artwork for the Elec- trosmog Testier PCB in Figure 3. elekter clstli e-nlts ■ 6/2005 Capper track layout and component mounting plan of the PCB designed for the tester. The dipole antenna is a stripEne circuit. Please feel nee to build the circuit all by yourself, but some caution is in order. The entire circuit is built from SMD parts and may be 'beyond' any- one with a good deal of experience and/or suitable equipment. Moreover, we hope and expect this tester to be a desirable item for many people less or not conversant with electronics. That is why the printed circuit board is supplied ready- built and tested through the Elektor Shop. All you need to do is install the board into the case, drill a hole for the on/off switch and connect the battery K’XCS-i . Out and Cibouf wit k the Electrosmog Tester S o how fo interpret the readings pro- duced by the Electrosmog Tester? A cordless phone is ideal fo practice a bit. If Its n old-fashioned Cl analogue phone, the LEDs wifi light continuously. Modern ECT phones, on the other hand, will cause the LEDs fo Rash. In this way you're soon able to tell one source from another, WLAN (WiFi) wireless networking equipment will show yet another partem. If you do not have one, just go to your neighbour's door. A WLAN or wireless camera Is perfectly detectable out in the street and yes r that means anyone with a suitable receiver can pick up and view the images transmitted by your security camera, Thar's why we advise against installing one in your bedroom as that will heavily compromise your privacy. The tester is not directional, Its antenna being simple and omnidirectional by nature. The advantage of it Is speed of testing and not accidentally skipping a transmitter or being confused by reflec- tions. If you want io know the direction the signal is coming from, it is usually sufficient to walk around for a bit. The LED indication will then tell you If the signal is getting weaker or stronger Try it on your microwave oven — if It's on, some LEDs ore sure to light if you hold the tester near the door. The flashing of the LEDs and their not lighting ot ihe same intensity Is a sure indication of pulsed signals being delected. For example, your DECT base station in the standby state will only transmit for a few percent of the time. If a connection is made, the activity increases fo about If you delve into hot debates in Internet news- groups and forums you know that pul- sating radiation is supposedly more dangerous than expo- sure to o constant ener- gy level over the same period. It is safe to say that most research has gone into the thermal effects of radiation, in other wards, the heat- ing up of the human body by radiation. The question is now what effect radiation has on individual body cells and if there is a dan- ger of co nee r growth or damaged genetic material. In the short term, these dangers are of course hard so prove, but many are afraid that illness will come after a goad many years. Our opinion is the research carried out so far is not conclusive. In the article on radiation hazards and electrasmcg elsewhere in this issue we discuss the matter In greater depth, and also the action taken so for by European gov- ernments. Whatever the case, our Electrosmog Tester allows you to see for yourself if the radiation Is of (he pulsating type, and what peak levels are reached. Depending on your views on the problem, feel free to take any action you see fit. If there's a mobile phone most In your skeet (or even on your roof) we recom- mend using the tester io check the radiation pattern for possible side lobes that may produce high radiation levels in your living area. On-site measurements in Germany revealed that certain mast locations had poorly designed antennas installed, radiating a part of ihe energy straight down — causing great concern among flat Inhabitants and other residents. With an assistant in the passenger seat of your car, a drive around your area is sure to make LEDs Eight on the fester if you pass a mobile phone base station. If you live near UHF broadcast TV transmitters, you'll find that these will also produce considerable field- strengths. To make it worse, these lev- els will be found to decay relatively slowly. 6/2005 -cl Alci electronics hands-on (over story To make sure you can perform meaningful measurements using the Elektor Electrosmog Tester, D.A.R.EI! Calibrations in Waerden, The Netherlands, kindly performed a calibration test on our prototype. D.A.R.EI! Calibrations is a state of the art laboratory accredited as number K063 by the RVA. Under this accreditation, the company performs calibrations on fieldstrength sensors, antennas, monitor receivers, attenuators amplifiers signal generators and power meters. Calibrations are performed up to 18 GHz. By Rene Dijkslra D.A.R.EI ! Calibrolions What does calibration entail? First of all, it is essential to know the error of test instruments. In the case of an electronic instrument, measurement results may often be compensated dur- ing the actual measurement. The instrument's discrete errors are used to build a correction-factor table that allows the measurement results to be adjusted on the fly. As an example consider a digital ther- mometer If the right temperature is applied for each degree, the error per degree can, be established. If the ther- mometer reads 19 degrees C when 20 degrees is applied, the error is 1 degree. If that error is constant across the range, the manufacturer may decide to shift the entire scale by 1 degree. In practice, however, this often results in an error with another discrete level. Consequently it would seem better to enter the deviation with each temperature into a table. If, for instance, 19 degrees is measured, the user or programmer knows that an amount of 1 degree should be added. The process of establishing an instru- ment's error is called calibration. What's the importance of calibration? First of all many important decisions are taken on the basis of measure- ments. This happens in cases where money is involved: the price of a prod- uct is determined on the basis of weight, volume and length. This is how it works in shops and at the petrol 30 elektor dvtlrottks - 6/2005 stance where dispensing and weigh- ing instruments aie certified and rele- vant laws apply to protect customers. How are guarantees obtained that a calibration has been performed prop- erly? Firstly, any calibration has to be reproducible and retrace able to a seam- less chain of references to international standards. The best and safest way of to prove this is the case is by way of accreditation swarded not only by gov- ernment institutions and standards like British Standards but also by independ- ent agencies, often operating across national borders. If a calibration is per- formed under accreditation it is by def- inition a reiraceabie calibration. Equip- ment calibrated in this way is marked as such, often by means of an adhesive with a logo or similar. How accurate is a calibration? As a matter of course, it will not be infinitely accurate. The deviation of a calibration, or rather of any measure- ment, is expressed by means of the so- called measurement uncertainty, which is subject to a large number of factors. Some contributing factors are ambient conditions like temperature, humidity vibrations, test equipment used, the test set up. cables and con- nectors, as well as variation in meas- ured values. All these contributing fac- tors are captured in a single formula which, in the end, supplies the uncer- tainty factor for each discrete meas- ured value. How is a ileldstrengfh sensor calibrated? This is done in a so-called anechoic room, essentially a Faraday cage not allowing radiation to enter or escape. The inner walls including the floors and the ceiling are covered with radi- ation absorbing material. The upshot is that it becomes possible to gener- ate an electromagnetic field with homogenic distribution. By applying a calibrated field strength to a sensor subject to calibration, it is possible to determine the error at a number of discrete frequencies. Also, the linear- ity may be determined at one or more of these frequencies. In this way we are checking if the sensor, responds with a linear output to a known-linear increase in fleldstreogth. In addition, in the case of three-direction sensors, calibration of the isotopic properties is possible. Beats commercial testers? To be able to make comparisons with regard to practical use we also walked around for a bit with the pop- ular HF32D from Gigahertz Solutions. This equipment goes by the name "High Frequency Analysed and looks impressive mainly thanks to Us loga- rithmic-periodical (patented) anienna mode from FR4 PCB material, just like our Electrosmog Tester, it is capable of measuring fiefdstrenghis, however it has a digital readout. The measured peak volue is displayed. I he digital readout is af course enviable, because it is accurate in principle. However, ihe integrator time is so short that the display never indicates the same value twice in a row (remember, most SHF mobile phone signals are pulsed hence vary con- stantly in time], so you have to guess the actually measured value. The instrument also has a range switch allowing you tom select between pW/m^ and mW/nrri. This suggests a larger measurement range but unfortunately the only thing that's actually switched is the decimal point on the display. The selection changes nothing in ihe way of indication or range. It is understandable that a short int^ graiion time has been implemented because the analyser comes with an attraciively styled wideband direction- al anienna. A directional antenna in together with a slow readout is an annoyance instead of a bonus. The antenna was found useful when deter- mining ihe direction of relatively dis- tant transmitters. To moke it even easi- er, an audio signal may be switched on — this even works with signals beyond the maximum level of 1 999 on the display. For serious fieldslrengih measurements the instrument needs to be mounted on a tripod. However, wherever accu- racy of a few dB is desired, such measurements are best left to trained experts. Returning to the measurement range, with 1 999 and 2 pW/rn^ as the respective highest and lowest indi- cation, the Gigahertz Solutions analyser has a lame dynamic range of just 30 dB. That's so poor we ini- tially thought the instrument was faulty because low fieldstrenghts simply weren't indicated while the Elektor Eledrosmcg Tester did not fail to indi- cate the weak source of radiation. To make the difference even dearer: 30 dB in this case equals a voltage ratio of 1 :3G, while the 70 dB range of the Elektor Electrosmog Tester cor- responds to a ratio of 1 :30,GG0! It is however possible to buy a plug-on antenna attenuator to extend the high end of the range. We believe the HF32D Is too limited in its options. Fortunately the manu- facturer also supplies more sophisti- cated versions like the HF35B and higher that do have a real range switch to improve the measurement process. On the down side, the enhanced instruments are more expensive, http:// www.g [gahertz-saluttQns.de e. iOQS - drktsr ebcticrin hands-on cover story frequency Range Fieldstrength (V/m) at wkh LED lights Helds Irenglli (V/m) at wkh LED goes out LED D1 0.0058 0.0057 LED D2 0.014 0.014 LED D3 0,030 0.029 LED D4 0.065 0.064 LED D5 0.14 0 1 4 LED D6 0.32 0.31 LED D7 1 .05 0.72 LED D8 1.6 1.6 LED D9 3.6 3.6 LED D10 8.2 8.2 (Measured accuracy: 1 ,5 dB) 1 Measured sensitivity q 1 2 GHi, 900 1000 1 100 1200 1300 1400 1500 1600 1700 Response {dB) | f (MHz) | Response (dB) “16.2 1800 1.5 -14.2 1900 0.9 -11.9 2000 0.0 -8.4 2100 -0.8 -7.2 2200 -1 .6 -3.3 2300 -3.0 -2.9 2400 -4.5 -2.0 2500 -6,2 -0.1 Measured frequency response. How is the Elektor fieldstrength tester calibrated? The sensor has been installed in the anechoic room and the fieldstrength was slowly increased. The power level was noted each time the next LED came on. Next, a calibrated fieldstrength sensor was used to measure the field associated with the power levels. Next, the process was also carried out in reverse order to check for hysteresis of the circuit. A fre- quency response curve was plotted by establishing the power levels required to make die lowest and highest level LED light up. The results of this calibration are shown in the tables. The calibration was not carried out under accreditation. Further information ON DARE!! CALIBRATIONS may be found at htlji://w ww.dare.nl, or requested by email to info@d 0 re.nl < " — On Screen Display Project Bpard Versatile, Programmable, Low Cost irm for Video Text Projects. A Ql/ * 1^^626 microcontroller ^ zo oy 11 character OSD * Fully programmable * Demo sofhva re available * I/O lines * RS232 st * PAL or NTSC compatible * Enclosure option a vailable WWW.STVS730A.C lectronics CD-ROM ECD Now extended with even more Ics, transistors , FfTs, thyristors and triacs! ISBN 9Q-53B1 -159-1 £12.95 {US$ 22.90) Elektors Components Database gives you easy access to design data for over 5, 700 ICs, more than 35,000 transistors, FETs, thyristors and triacs, just under 25,000 diodes and 1,800 optocouplers. All databank applications are fully interactive, allowing the user to add, edit and complete component data. Order now using l he Order Form in the Readers Services section in Ibis issue. Elektor Electronics f Publishing) R.O. Box 190 Tunbridge Wells TM5 7WY ENGLAND Tel. ^44 (0) 1580 200 657 More information on wvm.efektor-^lectronicsxo.uk deleter eledionks - 6,/iOQS hands-on I mini project Burkhard Kainka ■ - rr ; . , r - J The debate concerning the possible harmful effects of electrical and magnetic alternat- ing fields in our environment goes on. The only thing that everyone seems to agree on is that you cannot see or smell these fields. No longer true! Build this simple electrosmog detector and add two extra senses to the five that you already have. Electrosmog is a relatively nev; term referring to the electrical and magnetic fields (EMF) emitted by almost all the electrical equipment that we fill our environment with. Papers on the sub- ject indicate that we cannot hear or see these fields but their effects on our body may prove to be harmful in the long term. The electrosmog detector is a very simple portable design that allows you to listen in to both mag- netic and electric field activity Take the detector on a tour around your house or even around town, you will be surprised at just how noisy the invisi- ble worlds of magnetic and electric fields can be. The defector circuit The circuit diagram shown in Figure 1 consists of a sensitive LF (low fre- quency) amplifier with a headphone output socket. The three stage direct- coupled amplifier automatically adjusts its bias point via a DC feed- back path from the output through R4 and R2; any AC signal components are shunted to earth via capacitor C3. Tne output voltage level will be at 0.7 V with no input signal. Tne whole circuit runs from a supply voltage in the range of 1.2 to 1.5 V provided by a single bat- tery The amplification factor achieved by this configuration is so high that you can clearly hear the noise signal fi/2t!05 - Elrkipr eUctronlcs 33 hands-on mini project Figure l . The circuit consists of o sensitive LF amplifier with an earphone output socket produced by T1 In the headphones. For this reason it is a good idea to use a low noise transistor like the BC549C for the first stage of the amplifier. Input signals at the microvolt level are suffi- cient to produce an output: there is lit- tle point in increasing the amplification factor further. Tire low supply voltage ensures that even if high signal levels drive the amplifier into saturation, the headphone sound intensity will never be excessive. This circuit could also be used as a sensitive microphone amplifier but for this application it would he necessary to decrease the amplifier bandwidth so that unwanted HF signals will not be amplified. The detector circuit does not contain any low pass filters so it is sensitive to HF signals also. Non- linear transistor characteristics have the effect of demodulating these high frequency signals so that they also can be heard. The circuit PCB shown in Figure 2 greatly simplifies the job of construc- tion, A three-way terminal block is used to connect the pick-up coil and aerial wires to the PCB while solder pins provide connections for the head- phone socket and battery leads. A 3.5 mm jack socket (Kl) allows normal Walkman type stereo earphones to be used. The output signal is mono so socket connections to the left and right earpieces can be wired either in paral- lel or series; try both connections to see which one sounds best. It is also possible to use just a single earpiece providing it has an impedance greater than 32 II A pick-up coil or antenna can be con- nected to the input of the circuit to allow it to detect magnetic or electric fields respectively. The pick-up coil specification isn’t critical, a flat coil from a broken floppy disk drive mech- anism was used in the prototype but you can experiment with whatever you have to band, m this case a screw- driver is far more useful than a calcu- lator, A coil consisting of around 200 turns on a 20 mm diameter former can he wound up if you cannot find an alternative. Tne wire gauge is not crit- ical. A ferrite rod. or an open trans- former core can also be used. The pri- mary (230 V) winding of a small dis- carded mains transformer will also make an effective pick up coil because not all the magnetic field in a normal transformer is constrained to the core, it is these stray fields leaking from any transformer in operation that are picked up by the detector. Using an air-spaced 2 00- turn coil it is possible to hear magnetic field activity generated by: -Electrical appliances using mains transformers. Tnese emit magnetic fields that can be detected up to 20 cm away. - A power cord or mains vriring con- cealed in a wall will only produce a field when power flows through the wires. - All types of fluorescent tube lighting produce a buzzing note with over- tones. Low-energy lamps have a built- in voltage converter that produces a characteristic whistling. - An alarm clock with a quartz move- ment produces a double tick for each step of the second hand. - Svritched-mode mains adapters emit a humming whistling sound. - Televisions and CRT computer moni- tors produce different frequency sig- nals in the region around the screen and the power supply. - Loudspeakers and headphones emit magnetic fields as well as sound pres- sure waves, -DECT telephones periodically pro- duce bleeps when the phone is on- hook and send out a whole series of bleeps and twittering when you make a call. - An oscilloscope produces a detectable magnetic field with a repe- tition rate equal to its timebase setting (turn up the beam intensity). - Equipment that is apparently switched off or in standby mode may produce sig- nals; this indicates that the equipment is active and drawing current. Not so long ago you might have attracted some odd looks if you were to walk through town wearing ear- phones but now almost every other person you meet is plugged into their own source of personal entertainment so you will not cause too many raised eyebrows by taking i he detector out onto the street. It is quite surprising to hear all the EMF activity that you can pick up while walking through town or visiting public buildings. Mains trans- formers are everywhere and can be recognised by their characteristic mains frequency hum. Tire High Street and shopping malls also has many examples of switched mode power supplies and each has its own individ- ual spectrum of signals allowing rhe type of equipment to be identified with practise. Automated ticket dispensers and drinks machines also have their own characteristic sounds. Most muse- ums and public places are now The EMF aerial Magnetic-field noise sources 34 deklor e fed ionics - 6/1005 COMPONENTS LIST Resistors: R] r R3 = IGkn R2,R4 = IQOkQ R 5 = 1 kQ Capacitors: C1,C3,C4 = 1 OpF 16V radial C2 - 22GpF 16V redial Semiconductors: T1 ,T2 ,T3 = BC547B (for T1 aha BC549C, sse texl] Miscellaneous: 51 = on/orf switch . 1 contact Bi 1 = AA battery (preferably alkali' manganese) with holder K1 = 3,5-rnm jack socket, stereo (see texij K2 = 3-way FCB terminal black, 5mm lead pitch PCB ref, 040424-1 [Elekfor Shop) L I = pickup coil, if necessary with ferrite core (see text! ANT = length or wire (see text) Figure 2. Even though there ore only o few components , construction is much easier with a PCB Figure 3. The authors original pick-up coil . equipped with an inductive loop voice transmission system throughout the building (look for the blue sign with an ear symbol and the letter T r ). This sys- tem allows the hard of hearing to pick up information on theii hearing aid without any of the distracting back- ground noises, Tne electrosmog detec- tor can also listen in to these signals. The Electrical world The detector can also pick up electric field activity. To listen- in replace the Electrosmog in your ear El is noi only contemporary musicians and ambient/noise bands like Orbital, Nine Inch Nails and EinslGrzende Neubauten who use sound to express ihemselves artistically There is also a movement within contemporary art that specialises in locating recording and manipulating unconventional sounds in the environment to make sound sculplures' or 'soundscapes Far example, there has recently been UK media interest in the work of an artist who attaches sound sensors to railway suspension bridges. The German artist Christina Kubisch is also active in the Field of "sound art" and exhibited in Cologne in 2004 along with seven other arlists from seven different countries. Visitors were invited to don o set of special head- phones and lake o stroll through the city. The headphones enabled them to actual- ly hear magnetic fields in the busy city centre ond the environment. Engineer Manfred Fox developed the special headphones. Their design was based on inductive loop headsets used in museums and art galleries to provide vis- itor information. The inspiration for the project came when it was noticed that these headsets were also capable of picking up [unwanted) signals From ether magnetic Field sources in the exhibition area. the artists homepage is at: www*c hristi no kubisch, de pick-up coil with a small stub aerial or short 10 cm length of wire. Place the aerial close to a power cord that is con- nected to the mains and you will be able to hear the field even though the mains switch on the equipment is off and no current is flowing. It is quite difficult to rind any place at all where there are no humming or buzzing noises. Fluorescent tube lighting and low-energy lamps also have a charac- teristic sound with loud harmonic over- tones, Oscilloscopes use a very high voltage to accelerate the electron beam and this produces a higher level of electric field than magnetic. Waving the aerial around electrical equipment always produces surprising results for example the buzzing emitted by a vac- uum fluorescent display on the front panel of a stereo amplifier and more reassuring the relatively low Level of fields produced by modern low-emis- sion CRT monitors. It is also possible to make the detector sensitive to both electrical and mag- netic fields by fitting both the aerial and the coil at the input. Iby experi- menting with different lengths of aer- ial and other coils and don’t be sur- prised if you pick up radio broadcasts, radio transmitters also produce alter- nating magnetic fields. Two hundred years ago electrical storms and solar radiation were prob- ably the only source of electric field activity on the planet but nowadays you would be hard pushed to find any corner of the globe that is not continu- ally bathed in electros mogt 6/20 05 - dcfclor elsrtj&nks 35 infotainement I WiFi Eavesdropping WiFi Eavesdropping Is nobody safe any more? Fedde Hettinga If you want to keep up with the times you can buy a cheap WiFi/WLAN 'access point' and an expansion card or a plug-in device for your laptop. Have you done this already and do you use WiFi? You're not alone. In the last year ihere has been a huge increase m the number of WiFi access points not just in the author's country (Hol- land) but al! over the world. And why not? It is fast, simple, inexpensive and conven- ient, which ore the most important consider- ations for many users. It's just not very secure, as we should al I know by now. If you keep all the default settings during a WiFi access point installation, you know that you leave your network wide open to your neighbours, who then have the benefit of Free Internet access. If there is a digital 36 ciekicrr elttfrorJcs - t/?D05 peeping Tom amongst your neighbours, it may happen that your computer is searched For passsvords and other personal information. That lesson should have been learnt by now, and those who still don't configure their access point property shouldn't be surprised if their net- work is invaded. And then there are the open WiFi networks, also known as hotspots'. These have become a common sight in cafes, airports and stock exchanges. Anyone who has a laptop with a WiFi card con use these to access the Intemei and check his or her e-mails. Security doesn't appear to be a problem here. Aren't the hotspots open by design? There are other security holes in WiFi. All information between the laptop and access point travels via radio waves and these can easily be picked up. Would it be possible to listen in on these wireless connections? If that is the case then the websites you visit, the e-mails you send and your MSN messages ore no longer safe. Your private communications are simply left open to eaves- droppers. It's time to call in on expert! This expert is o first-year student in Artificial Intelligence. He has taken on the challenge to discover how WiFi communications work and if there is □ danger that users' communications can be intercepted. The conclusion was that it was possible and the next section shows how it was done l The theory A wireless network allows several devices to communi- cate wirelessly with each other. Far wireless computer networks WiFi [Wireless Fidelity, or 802.1 1] is the undis- puted king. The maximum range of ordinary WiFi devices is about 100 metres indoors and 300 metres out- doors. The usual configuration of a wireless network is an access point', which is the central transmitter/receiver, and one or more 'wireless clients 1 , which are computers equipped with a WiFi network card or a plug-in (USB) unit. In such a network, all traffic is routed through the access point. As long as wireless clients are within range of an access point, they can use that to communicate with each other. The access paint often provides a con- nection to the Internet, providing all wireless clients with an Independent Internet connection. If is also possible to set up o network without using an access point. These have direct connections between the WiFi cards. This method is sometimes used to quickly set up a temporary connection between a small number of wireless clients. The administrator of a network can give it a name, called the SSID (Service Set tDenfifier), to distinguish it from other wireless networks nearby [or to combine o number of networks). An access potni announces its presence by regularly transmitting its name, in this way the wireless clients can discover which networks are available and set up a connection with them. Protection Wireless networks can be made more secure in two areas. Firstly, you can prevent third parties from gaining unauthorised access to the wireless network. The trans- 8'gure ?. MSN ccw- eriafic^ of an unwary mer mission of the SSID con be turned off, hiding the pres- ence of the network to wireless clients. It is also possible to restrict access to just a select group oF wireless clients. This method makes use of o unique code stored In every network cord, called the MAC address. Another area that can be made more secure is the actual transmission of the data. Since all data is sent via radio waves it Is possible for It to be picked up by out- siders. To keep the information secure all data can be encrypted. WEP (Wired Equivalent Privacy) is the most common standard for encrypting the data. This effec- tively lets the network communicate in a secret lan- guage. Outsiders who don't know ihe WEP key will only see gobbledygook. The explosive growth in the number of wireless networks is due to the lower costs and their ease of use. Whereas in the past the setting up of □ wireless network would be a challenge, these days it s □ question of unpacking and connecting the equipment and then the software will do all the hard work for you. This ease of use often comes at Figure 2. The same conversa- tion captured cut o- thin air. fi/2005 - eftktor thrtrcrtiu 37 infotainement I WiFi Eavesdropping Fiaure 3. w ~r,E logon details in an e-mail client. tr'rrril I/-; 1 1 CKjoa -r ^ : tTt t j- - |=sa ';r. - £ 77 - 7 ? F= ■y : uit" f pi I fteEH 1 : . . r .. I 7 A iSVTi jwripa£ soon Eh Unpg fieri £ --L-L i - L 09 CC S*^*p'**»*^d [S?VV ■.ii > Cxsesz' j ■ -e the cost of reduced security. Worse still, most security set- tings are turned off by default and it is left to the user to enable them. Upsurge in the number of WiFi networks Wardriving' (□ term used to describe driving around with a notebook to search for open wireless networks) along the canals of Amsterdam three years ago resulted in dozens of wireless networks, an impressive number at that time. If you do the same today, you will quickly dis- cover hundreds of networks. Despite this growth the ratio of secure to insecure net- works has remained the some, which means that about half of all networks are insecure. work data; this includes everything from e-mail pass- words to %vhole MSN conversations. Whereas it's possi- ble to discover ihe first type of 'attack', it is virtually impossible to detect the second type of attack. The eaves- dropping of wireless network traffic is therefore called o 'passive attack'. But secure networks con be at risk as well. Some cafes nowadays offer their customers wireless access to the Internet. When WEP is used to encrypt the wireless data, the network would appear to be o lot safer. The cus- tomers have to request the WEP key from the counter before ihey can use the network. But we should nt forget that all computers on the network use the some key! Should you want to eavesdrop on the traffic of other cus- tomers, you only need to know the WEP key, which can be requested at the counter by anybody. A passive attack We mentioned earlier that every network card contains a unique code, called the MAC address. The same applies to every wireless network card. When data is transmitted over a network it is split up into one or more pockets. Each of these packets has an identifier consisting of the MAC addresses of the sender and recipient In a wireless network ihese packets will be received by all network cords that are within range of the transmitter. The net- work card will normally ignore all packets that are not destined for it. Jt is usually fairly easy to change this default behaviour of network cards. When a network card is put into o so- called 'monitor mode', it will accept all packets as if they were intended for it. In other words, a network cord in monitor mode wifi receive the data of all wireless net- works within range, which can then be stored on the computer. This information can be processed later. Information through the air There are two risks involved with insecure networks. Out- siders can use the network, which often gives them access to the Internet connection and network devices such os computers and printers. It is less well known that they can also tap into all net- Figure 4 . The some details in the log hie. Software The best free software available runs under Linux and is called Kismet [1 ]. This program was specifically written to listen in on WiFi networks and therefore has special functions that are only relevant to WiFi networks. As an example, Kismet can run in o 'channel hopping mode, whereby the WiFi receiver switches between the 1 3 available channels at a rate of 10 times per second. This increases the chance to discover wireless network traffic. Kismet can also detect hidden networks from the contents of the wireless network traffic. The security setting men- tioned earlier, where ihe transmission of the SS1D is turnea* off, is therefore circumvented. There is often so much traffic that it is impassible to see all e-mails and passwords on the screen. Fortunately, Kismet saves all received packets in a log file, which can be analysed al leisure at a later stage, A good [and free) program far this is Ethereal [2), which runs under Linux and Windows. One of the fea- tures of this program is to analyse log files, such as those generated by Kismet. E-mails, MiSN conversations and passwords are easily extracted with ihe help of a com- prehensive filter function. A realistic test At the end of the day we want to see hard facts that prove that this approach works. For this rest we used a 38 i ’skier elEdKFtits ■ 6/2005 simple selup with two laptops. One of the laptops has a normal wireless Internet connection via an access point; the other is used with its WiFi card in monitor mode. As soon as the first laptop transmits data, the second cap- tures it to the Kismet lag file. When we later open this file with Ethereal and apply the MSN Filter, we can see the whale conversation. We can't think of a better proof than this (Figures 1 and 2). Before we leave our test environment and venture into the outside world, we d like to carry out one more test. Here we try to capture the logon details of an e-moil account. The unsuspecting user checks his e-mails and all data ends up in the Kismet log File again. When we apply the POP3 filter tn Ethereal the user name and password appear on the screen within a matter of seconds (Fig** ures 3 and 4j. During the resting if became clear that not all packets were captured. The traffic between the laptop and access point uses just one of the 1 3 available channels because a WiFi card is incapable of using several chan- nels simultaneously for data communications. However, Kismet iries ia keep an eye on as many wireless net- works as possible. It does this using a process called channel hopping, where it switches channels a maxi- mum of 10 times per second. This is useful when you're trying to discover many networks. However, this can have a negative effect when you're trying to monitor a specific network, since Kismet will listen to the wrong channel 1 2 out of 1 3 limes. Fortunately there is a solution to this. In Kismet you should select the network that you want to listen to and press SHIFT + L. Kismet will then listen io the single channel for that network. SHIFT + H is used to make Kismet switch back to its normal channel hopping mode. In the real world And now back io the real world. The first trials with a 'sniff-bag (a rucksack with a laptop) returned a flood of data. A stroll through the residential areas of Amsterdam yields, apart from hundreds of access paints (more than half of which were insecure), a large amount of personal information. We captured all kinds of data: web accesses i'HTTP), received e-mails (POP3), sent e-mails [SMTP] and dozens of MSN messenger conversations. The captured surfing data tells you which sites are vis- ited. which is not terribly exciting. What is interesting is ihe e-mail traffic. This is where we enter the privaie domain oF the unsuspecting WiFi user. The username and password fly across the screen, along with the sent and received e-mails. The most intimate MSN conversations ore also there for the world to see. For our second experiment v/e targeted the business com- munity. This group appears to have its own working hours and hobbies. At Schlphol Airport, near the busi- ness class lounge, everything was quiet. Other WiFi hotspots in this airport didn't return many results either. But who was this 'Butch! 02 who sent this message: 'so when / join another carp t leave this one'? Is he really going to change his job? On Further Investigation we found that Butch 102 was happily ploying the game 'EVE Online'. Perhaps we have to get out of bed a bit earlier Io catch the first horde of businessmen and discover which games they play. Next we carried our equipment around the restaurants and cafes in posh Amsterdam, during lunchtime. In one crowded cafe there where many conversations going on but hardly any surfing was seen to take place, if you want to discover some commercially sensitive information you stand a better chance if you just listen to ihe conver- sation at a nearby table. Afterwards, on the way home, we achieved better results near o coffee shop. Here we saw a multitude of MSN mes- sages and a variety of web pages flew across the screen. The best results are therefore in normal residential areas, where members of the family use the notebook to check their e-mails. Do if yourself If you don't mind breaking the law and want to spy on your neighbour's surfing habits, e-mails and chats, you need a Linux computer that runs Kismet and Ethereal. For those of you who don't have much experience In installing Linux, there is Auditor, a free Linux distribution that doesn't require installing [3]. After downloading this distribution it has to be unzipped (using WinZip) and ihen burnt on a CD (from Nero you should use 'File Burn Image'). Next, the laptop or computer has to be configured to boat from the CDROM.. All you have to do now is Io turn an the computer with the CD in the drive. Internet addresses [1 ] www_ kismetwireless.net [2] www. elhereal.com [3] www. r e mate-exp I oi t. org £ ■ 2005 - ekLtM c'cdioEiks 39 MikroElektronika MICROCONTROLLER DEVELOPMENT TOOLS from Breac boardi g Systems Make PICmicro® development easy with the EasyPIC2 - only £99! The MikroElektronika EasyPIC2 Development Board combines a versatile development/experiment board with a built-in USB programmer. With its wealth of on-board I/O devices and support for virtually all 8 f 14, 18, 28 and 40-pin PICmicro* microcontrollers in the 12F P 16F and 18F families, we're certain you won't find a more versatile high quality board at such a low price. The EasyPIC2 Development Board is supplied with USB programming power cable, programming software and useful example programs. Also available are similar boards for the 8051 r AVR and dsPIC, each at the same great price of £99 including UK delivery and VAT — please telephone or see our website for further details. EasyPIC2 Development Board features: » High quality development/experiment board with built-in USB programmer. • Programming software compatible with Windows operating systems including 2000 and XP. • Comes with a PIC16F877A microcontroller but compatible with virtually afi 8, 14, 18. 28 and 40- pin PICmicro" devices in the 12P, 16F and 18F families. • On-board I/O devices including switches, LEDs, seven-segment displays, potentiometers and RS- 232 interlace, • Provision for easy fitting of optional LCD display and DS1820 temperature sensor. • All I/O lines available for off-board expansion. • Wide range of optional add-on boards available including ADC, DAC : EEPROM, Compact Flash, RTC, RS-485, CAN and IrDA. • Powered from your PC's USB port or optional mains adapter. • Supplied with example programs written in assembly language, BASIC, C and Pascal. • Supplied with Microchip Technology's MPLAB development software and demonstration versions of MikroElektronika's MEkroBASIC. MikroC and MikroPascal compilers. Learn about microcontrollers with our EasyPiC2 Starter Pack - just £149! We've taken the EasyPIC2 Development Board and added a 16x2 character LCD display, matrix keypad, DS1820 temperature sensor, RS-232 serial communications cable, various different PICmicro microcontrollers and our own easy-to-follow microcontroller tutorial to form a complete and self-contained Starter Pack — everything you need to learn about and experiment with microcontrollers! With this pack you will quickly become proficient in microcontroller programming and interfacing. Please see our website for list of covered topics. Please visit our website tor details of other MikroElektronika products We stock the full range of MikroElektronika development boards and compilers for PICmicro, AVR T 8051, PSoC and dsPIC microcontrollers. Products may be ordered on-line at www.breadboarding.co.uk or by telephoning 0845 226 9451 using all major credit and debit cards. 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Call 0845 226 9451 or order online at www.hreadboarding.co.uk TURES Instalments - Meters, Scopes, + |q NEW Transient Recorder, Function VIRTUAL Generator, Power Supply INSTRUMENTS Test mode, equivalent to the standard SPICE analyses and a separate continuous transient simulation mode that allows you to interactively alter device and circuit parameters and examine the results immediately Layered sweeps, meaning you can step almost any device or circuit parameter on top of any Test Monte Carlo analysis available for all tests Easier part selection, including a customizable Parts Palette UseMriendly interface with buttons and control tabs Live updating in Simulation mode Circuit wizard makes it easy to generate standard circuits including Attenuators, Power Supplies, Filters, Op-Amp and Tube-based Circuits Tabbed-based Windows Highly flexible graphing 3D graphing * NEW "realistic” models for caps, resistors, inductors * Interactive parts including switches, fuses, LEDs t etc. * Layered Sweep tests (expanded). * Expanded Monte-carlo tests B2 SPICE is backed by comprehensive technical support both local rate telephone and online, full user manuals and tutorials and a NO QUIBBLE, FREE 30 DAY EVALUATION OFFER mm. CALL 01603 872331 www.i ;; software.com VISA 1=1 - - technology solar power made simple Solar charging with and without a controller Jens Nickel with contributions by David Gibson Complicated charge controllers and inverter circuits can be used to squeeze the last drop of energy out of a solar panel. Contrary to popular belief, however, it is also possible simply to connect the battery directly to the panel. Figure 1- An iso 'died solar panel system tjiVss a degree ct independence from the maim, /photo. PnocGsj During a sunny doy the UK receives up to about 1000 W/m 2 of solar energy. It seems absurd to let this clean source of energy go to waste. Solar cells, of which the majority on the market are made from crystalline sili- con, convert sunlight directly into electrical current. The manufacture and purification of silicon suitable for solar cells from silicon dioxide (quartz sand] is energy-inten- sive and therefore expensive. Nevertheless, the widely- held opinion that a solar panel (in which a number of the fragile solar cells are mounted and wired together) can never recoup the energy expended In its manufac- ture is not correct. The energy amortisation time for a commerclolly-available large-scale pane! delivering 1 00 W to 200 W of power Is, depending on its con- struction (whether it has an aluminium frame of not), in the region of 2 to 3 years. Self-sufficiency with solar power If is possible to connect an array of panels on the roof of a house or in the open to the national grid via an inverter, and then sell the energy generated back to the electricity company. 3n some countries, the refund is more per unit than the norma! cost of supply. Where the grid Is not available, for example on a boat or in o remote holi- day home, or for buoys, emergency telephones on motor- ways and similar uses, solar panels are used in a differ- ent way (Figure 1). Isolated systems like these need a battery. The best price-performance ratio Is still offered by lead-acid accumulators, although other types, such as NiCd cells, are used is smaller systems such os measur- ing devices. Special lead-acid batteries for solar use are available, with better charge-discharge cycle reliability 42 EteVlDf ebtfronits - 6/2005 and lower self-discharge than commercially-available automotive batteries. The scxalled charge controller con- nects together the components of a solar power genera- tion system: the solar panels, the batteries, and the load, Its most important function is to protect the batteries from overcharging; then, in decreasing order of importance, protection against deep discharge the maintenance or restoration of the capacity of the battery ond its ability to accept charge, the efficient use of solar energy and finally convenient operation and monitoring of the sys- tem. The greater the power demands on the system, ihe more worthwhile complex and expensive multi-function charge controllers become. As well as the cost of the sys- tem, the amount of power wasted must be taken into account. In very small systems the charge controller can even be dispensed with, os we sholl see later. Solar cells: the bastes An ideal solar cell con be modelled as on ideal current source with on ideal diode connected in parallel [Figure 2}. A part of the photocurrenf generated in the cell, which depends on the lighting level and on the area or tne cell, flows through the ideal diode and so the usable output photocurrent is given using the familiar diode formula; f = Hot ” fojeds = hhoi “ h [ exp (eL//kT) - 1 ] Plot U against I and we obtain the characteristic curves shown in Figure 3. The lighting level increases from below left to above fight. With no load connected the open-circuit voltage can be measured across the cells: in the case of silicon cells this is a little under 0.6 V (at a lighting level of 1000 W/m- and a temperature of 25 Cj. Short-circuit the cell, on the other hand, and a [theoretical) short-circuit current flows. The maximum power output is obtained af the marked points, ihe so-colled MPPs [maximum power points). In general a pone! contains cells wired in series and in par- allel to obtain both a higher voltage and a higher cur- rent. Depending on the cell and panel type up to between 80 W/m 2 and 150 W/m 2 of power can be obtained, which represents an energy conversion effi- ciency of between 8 % and 15 %. As temperature rises the power from the panels falls, typically by between 0.2 and 0.5 % per 1 C. Panels themselves can be connected together to form bigger power sources. Charging the easy way If nominal output voltage of the solar panel is greater than that of the battery there is no reason why the battery cannot be connected directly to the panel. This might ieem surprising at first sight, but let us dispose of a cou- pie of myths: - If the battery voltage is considerably less than the nomi- nal voltage or ;ne panel, a voltage divider or similar cir- cuif must oe used. In fact, a 1 2 V panel can be con- I — — O - 050031 -11 Figure 2 . Equivalent circuit of an (ideal) solar cell an (ideal) current source in para lie! with an (ideal) diode. Figure 3 Characteristic curves of a solar pone! of various light levels. The maximum po wer points (MPPs] are shown. neciea directly to □ 3 V battery without damaging it: see Figure 3. A 12 V solar panel does not work as a volt- age source with a constant output voltage of 1 2 V but rather as a current source. The only thing that will hap- pen is that the panel will be operated a tong way down its characteristic curve. - 1 he charge current must be controlled. In fact, the only criterion is that the panel power ond the battery capacity need to be reasonably matched to prevent damage from overcharging [see below}. In darkness □ directly-connected battery will partly dis- charge itself due to a small current flawing back into the solar panel This can be prevented using the very simple circuit shown in Figure 4. In practice this simple circuit, without any kind of charge controller, is suitable for use in very small systems where the current produced by the solar pone! is smaller than the maximum acceptable trickle charging current for the battery. NiCd batteries can be overcharged for up to I 00 hours if the current [in amps) is less than a tenth of the capacity (in amp-hours). A small panel with a nominal current of 2 A can there- fore be used to charge a 20 Ah battery without addi- tional circuitry os long as a load discharges the battery from time to rime, this is the case, for example, with an illuminated house number which comes on automatically - , * at night. Moderation in alt things Lead-acid batteries with a liquid electrolyte evolve gas when overcharged, which can ultimately result in dam- age to the battery. A charge controller can be used to prevent overcharging by disconnecting the battery. There l’iOS5 -ekSiturrl-itlGflES 43 ted nology solar power made simple Figure 4 . I'r.is circuit ade- quate for very- tow power panels. □ M k _ A 05GG31 - 13 C5003t-14a Figure 5, A charge controller provides protection ago ins t a v& rc n org - inn Charging is interrupted using either a series fieh) or shunt {right] tech- nique. 05CO31 - 14b Figure 6. Principle of a van- able DC-tO’DC con- verter for so! or charging: Observe that it is the input vc/tage, net the out- put voltage , that is varied. I array ► O OH charge controller with DC/DC converter •chaiige -O a halter? — O l ECO 31 - IE are two different ways this can be achieved (Figure 5). In a series regulator the controller breaks the charging circuit, whereas in a shunt regulator a low-value resistor is switched in parallel with the panel so that the current from the panel flows through if. The diode shown is of course essential in this circuit! Switching is normally done using a semiconductor circuit ideally, once the battery is fully charged, a small charge current should continue to Flow to maintain a constant ter- minal voltage. This can be achieved by the charge con- troller regularly and briefly connecting the pane! to the battery with timing determined by the battery voltage. In practice pulse-width modulated systems operating at a fixed frequency are used. Top-notch charge controllers Maximum power is obtained From the panels when they are operated continuously ot the MPP. In this case the panel voltage must vary continuously and be independ- ent of the battery voltage. This function is built into some charge controllers using on adjustable DC-to-DC con- verter (Figure 6), Adjusting the operating point to Follow the MPP as the light conditions change, typically every minute or so, is called MPP tracking. The efficiency gains from this technique are generally grossly overestimated: experiments show that the efficiency gain over an unregu- lated system is only about 5 %. Since any DC-tc-DC con- verter will involve losses and the MPP tracker makes the charge controller more expensive, this approach is only worthwhile in medium-to-large scale installations (from 200 W upwards), A simple method for determining the MPP voltage is ro measure the open-circuit voltage of the panel from time to time. The characteristic curves (Figure 3) show that the voltage ot the MPP is about 80 % of the open-circuit volt- age, For even more efficient charging the charge current must also be monitored continuously. The panel voltage is then adjusted so as to maximise the charging current. As already mentioned, modern solar charge controllers offer a range of extra functions (Figure 7 ), Almost all the devices offer protection against deep discharge and disconnect the bad if the battery becomes dangerously discharged. More expensive units include meters to indi- cate charge state, a display and even remote conlrol functions. ::: Figure 7. Two charge con- trollers one made by Steer: (felt) and another by Fr-ccos {right} V/ith over- charging and dee a discharge protec- tion MPP tracking and a host of extra functions, these units oher a complete chmae contra! solu- ficn (photos: Steco Phonos} 44 debar dsriitKHts - 6/2005 ! 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Our ANT8 and ANT16 Logic Analyzers feature 8/16 capture channels of data at a blazing 500MS/S sample rate in a compact enclosure. priced from £125 ( DS1MT2 & ANTS ) hands-on mini project Paul Goossens Solar- Powered Charger Solar cell lead-acid charger During the summer months they appear again all over the place: those solar powered garden lights. During the day they store the captured solar energy, which is used at night to provide lighting. If you'd like to use this energy for something different, such as listening to the radio or playing a CD, you'll find this circuit fits the bill. Dining the summer we all thoroughly enjoy the sunshine. In this way we also experience just how much energy we receive from this big star. AU those people on the beach who end up looking like a lobster can cer- tainly attest to this; a moment of care- lessness and you could be subject to an excess of thermal and radiation energy. We even pay to protect our- selves against this energy, buying suntan lotions and creams. 46 dtV.tor ehclicdu * 6/2005 Even the v.hnd and ocean currents are powered by the sun. Enormous amounts of energy are involved here as well We're not that interested here in chan- ging our skin colour to a bright red (a nice tan is welcome though), neither do we welcome stonns and dangerous sea currents. But all that energy that we could tap into for nothing is very appealing. Solar power Mankind has discovered a number of different converters' to change the sun's energy into a more useful form. This group of ‘converters' (after all, they convert energy from one form into another) is known as solar cells. The solar cell that converts the sun's energy into electri- cal energy is of course of most i n t e - rest to us. Such a photovoltaic cell produces an open- circuit voltage of about 0,55 V. This voltage drops as soon as a load is applied. These cells are in their element when the voltage has dropped to 0,45 V, since they are then working at iheii optimum efficiency. Storage The biggest problem with solar power is that it is not always available at the time when it is required. The solution to this is very simple: temporarily store this energy until such time that ii is required. A lead -acid battery is often used for the temporary storage of this energy. The advantage is that a lot of (camping) equipment is designed to run off 12 V. so that they can be powe- red directly from the battery. We can t just connect one or more solar cells directly to a lead-acid bat- tery to charge it. The voltage from one cell is too small to charge the battery, whereas the voltage from a number of cells connected in series depends very much on the load they drive and the amount of solar energy striking the cells. 01 Figure 1 . A simple siep up converter is sufficient to charge a lead-acid botfery using just a few solar cells. Charging voltage A charger should have an output of about 13.5 V to 14 V in order to provide a constant charge to the battery without overcharging it. We are out of harm's way as long as we regulate the voltage. For this we could use a standard series regulator, a step-up converter or a step-down converter, Both the series regulator and step-down converter require an input voltage that is higher than the output voltage. For both these options we have to connect a number of solar cells in series to provide an output that is greater than 14 V, This quickly takes us beyond 24 solar cells. This would be a costly option since solar cells don't come cheap. A step-up converter works with an input voltage that is lower or equal to the output voltage. This type of circuit can therefore be used with a smaller number of solar cells. This can always be expanded with more cells by con- necting them in parallel to capture more energy. The eireuit The circuit designed by us (Figure 1) couldn't be simpler. IC1 only requires a handful of components to make a step- up converter. The supply for the IC comes directly from the battery. This means that when the solar cells don't supply any energy, the circuit still takes its power from the battery. Since this current is very low, the battery won't discharge in a hurry. The voltage from the solar cells is con- nected to Kl. The IC makes FET T1 conduct, which causes a current to flow through Li. This turns the electri- cal energy into magnetic energy, which is stored in the inductor. When the cur- rent has exceeded a certain value the IC turns off the FET. At that instant the inductor attempts to maintain the cur- rent flow. In this way a voltage is indu- ced so that the current can flow via D1 to the battery. In this manner the mag- netic energy is converted back into electrical energy. The current through the inductor should not rise too far. The IC is provi- ded with current limiting to stop this from happening. The current through the inductor is converted into a small voltage via shunt resistor Rl. The IC turns off the FET as soon as this vol- tage rises above 0,1 V Resistors R2 r PI and R3 are connected as a potential divider. This means that the voltage at the wiper of PI is directly proportional to the output vol- tage. The IC attempts to keep this vol- tage fixed at 1.5 V PI can therefore be used to adjust the maximum output voltage. 6/2GQ5 - sfetar ektfrofiks 47 hands-on mini project Figure 2. PCS layout for the solar lead acid charger. Miscellaneous; K1 ,K2 = 2-way FCB terminal btac. lead pitch 5mm LI = lOpH high current (Dlgikey # M60Q7-ND] PCB r ref. 040474-1 from The PCBShop 3 solar cells [e.g. r Conrad Electronics # I9805dd2] COMPONENTS LIST Resistors; R1 = I OOmQ [e.g. Digikey # 12FR1QOOH- ND) R2 = 82kT3 R3 - tOfcil Pi - 2ilk5 presei Construction There is nothing much to say about the construction itself When the circuit has been built you must first calibrate it before using it. Connect a number of solar cells in series to connector K1 and place them in bright sunlight. Don’t connect the battery at this stage yet. Now measure rhe voltage on connector K2, Adjusting P 1 will vary this voltage slightly Set PI such that the output voltage is somew- here between 13.5 V and 14 V. A bat- ter/ can withstand these voltages con- tinuously without coming to harm. You can now connect the battery to K2, making sure that you have the polarity right The positive terminal of the battery should connect to tire - of the circuit 1 Experimentation It is perfectly normal that the output voltage decreases when the battery is connected. This doesn't mean that the Capacitor s: C1,C2- lOOnF C3,C4 = 47uF 16V radial C5 - 47 pF Semiconductors; D1 = MBR35Q (Diatkey # MBR350-ND) EC 1 = MAX 1 77 1 -CPA (Dla ikey # MAXI 771 EPA-ND] T1 - IRFU3708 (Digikey = IFFU37Q3-ND) battery isn’t being charged, just that the solar cells cannot provide enough power to charge the battery as quickly as possible. It is very easy to check that the battery is being charged. Disconnect the bat- tery from the circuit and measure (after waiting at least 30 seconds) the bat- tery voltage. Now reconnect the bat- tery to the circuit and make sure that sunlight strikes the solar cells. Mea- sure the batten/ voltage again and compare it with the previous measure- ment. If the voltage is now a bit higher, the battery is being charged. If tins isn’t the case than the solar cells are- n’t providing enough power. You may get some improvement if you place them in direct, bright sunlight. It also helps if the solar cells point directly towards the sun. More, I want more! The circuit wall work quite well with 8 solar cells connected in series. This is a reasonable compromise between the cost and the charging time /efficiency. You will always get an improvement if you connect more solar cells in series. You should limit the number of cells to 24, as the voltage could otherwise become too high, which would have nasty consequences! Once the output voltage is equal to the value set up during calibration, adding any more solar cells won't have any effect. The extra energy will just remain unused. But when the sun shi- nes less brightly, the voltage may drop, when a few extra solar cells would prove useful If you really want to connect more than 24 solar cells to the circuit, you should connect them in parallel. Tins won't cause a rise in the open-circuit voltage, but the solar cells will be able to pro- vide a larger current. 48 rlshc-r elsdrorics - 6/2005 WHY NOT VISIT OUR WEBSITE \v\v w.criddeAVODdelectronics.coiD Before phoning us - if you are looking for a hard -to -find part. We have over 2G.0GG items in stock - including obsolete and up-to-date parts. 2N 25 A 2SB 2SC 2SD 2P 2SJ 2SK 3N 3SK 4N 6N 17 40 AD ADC AN AM AY BA BC BD BDT BDY HDW BDX BF BFR BFS BFT BFX BFY ELY BLX BS BR BRX BRY BS BSS BSY BSW BSX BT BTABTB BRW BU BUK BIT BUY BUW BLX BUY BUZ CA CD CX CXA DAC DG DM DS DTA DTC GL GM HA HCF HD HHF ICL ICM IRF I KA RIAL LA LB LC LD LF LM M M5M MA MAE MAX MB MC MDAJ MTE MIF MM MN MRS MPSA MPSH MPSU MRF NJM NH OM OP PA PAL PIC PN RC 5 SAA SAB SAD SAJ SAS SDA SG SI SL SN SO STA STX STR STRD STRM STRS SV1 TTATAA TAG TB A TC TCA TDA TDB TEA TIC TIP TIPL TEA TL TLC TMP TMS TP U U UA UAA LC UDN ULN UM UFA UPC LTD VN X XR Z ZN ZTX+ many others We accept Mail* telephone & email orders. Callers welcome. 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Low cost USB PIC programmers {Staffing ai £27, ihoAn ££5) plus a wide range of add-on boards and accessories ... ......plus Incredibly easy to use software based on flow charts.,. ...equals extremely rapid system development like this mobile text messaging system bulit from E- blocks. Hands on training courses Resources for learning CPLD programming Complete courses in electronics and programming Equipment for datalogging control and PC 'scopes training courses v\ PICmkrr^R) programming. CPLD programming end ECAD and more at Matrix Multimedia Limited sa Ies@matri xmuHtm ed la , co ■ uk t. 0870 700 1 831 f. 0870 700 1832 r? ■*« i \ ■ TZ: ol ' £ I i-4 - - - - 6/2005 - tIAlor elfictrcnro 49 know-how energy saving tips Energy Savii trace energy wasting equipment Karel Walraven (Elektor Labs) Being mindful of our delicate environment starts at home with a thorough hunt for all electrical equipment large and small that's wasting energy and silently adding to your electricity bill. A direct reading or logging power consumption meter is very useful for this, and investing in one (perhaps together with your neighbour] gives peace of mind and possibly a financial return in the long term. Waitcmeiers or energy monitors or os they are sometimes called can be bought or reasonable prices these days and may allow you to achieve considerably electricity savings. Any household has a many electrical devices that silently conspire to odd considerably to your electric- ity bill simply because they are on all the time: the TV set [how many do you hove?}, the cordless phone, the mobile phone charger, the alarm dock, the kitchen radio, the list is endless. Lighting, too, often consumes more energy than you would expect. In your living room you may have halogen or low-energy lamps, but what about the stairway? Having the lights on there for an hour or so may well consume as much power as all of the living room lighting for the whole evening. Stealthy consumers OF course you wont to enjoy the comfort oF your home, at a price. However, unnecessary energy use is always bad, For your wallet os well as the environment. Signifi- cant savings may be earned simply by measuring the power consumption of every electrical appliance in your home. In your household, much energy is consumed by equipment that's left on all the time. Just tot up the power consumption of all small' loads and take a deep breath... We may point the finger to these stealth consumers: - firstly, all mains adapters (a La. battery eliminators) are prime suspects. These will typically consume I to 2 watts around the clock, silently powering telephones, ADSL, cable and other broadband modems, kitchen radios, battery chargers, even the front doorbell. - The second group comprises all equipment with remote control. To be able to respond to o remote control com- mand, at least a part of a TV set, video recorder or audio rack has be on oil the time. Maybe you've got one of those remote controlled lamps? The ywlll always consume a little power even when off! Or is the halo gen Sighting transformer permanently connected to the mains? Although microwave ovens rarely have remote control, most now have a display that's always showing a dock. What about the bread machine you use once a week? Add it all up and you II find that 10 to 50 watts of power is wasted, - Third, we have those larger consumers. Fortunately, refrigerators and 'washing machines are now sold with labels stating iheir energy doss. Note the actual use: a small wash load or 60 degrees easily eats up double the amount of power than one at 40 degrees. A badly defrosted freezer comportment with thick ice lining inside may raise energy consumption by half. - Finally, the trusty PC. You may have several, and think they are off, but we measured 3.6 watts in the off state, day and night. When switched on, a PC will wont os much power as an average TV set, its consumption 50 eSeklar Efedrtmiti- i/2003 varying between 150 to 400 waits. Of course, you will have a printer and a display to complete the set A TFT screen will amount lo 30-40 watts, but on old-fashioned CRT will weigh in at at least three times the amount. It all adds up and the only way to save money here is to completely disconnect the computer set from the mains using a dedicated, swifchable power ban Clearly, it is or the highest importance to trace ail these hidden energy eaters. Next, you can decide for your own if comfort outweighs the trouble of operating some switches from time to time, as the switched power bar is without doubt is the only remedy. With mains adaptors, there is an alternative, however Although not yet widely available from the high street shops, electronic (switch-mode) variants are available from mail-order outlets with an energy consumption we can safely describe as negligible. At the end of the day There can be no argument in favour of allowing energy to fritter away just like that. Being energy-wise is also good for your wallet. In most countries, electricity rotes are no longer flat, so get out a recent bill to see just how much one kilowatt-hour costs. Energy taxes may be levied at often surprisingly high rates. The actual bill will also include fixed amounts for your use of the power grid, the electricity meter and other items. The fixed costs may eas- ily double the actual kWh price. tf you manage fo save a total of 100 watts, it equals 0,1 kWh per hour, or 876 kWh per year and that's not to be sniffed at because a typical household will con- sume something of the order of 3500 kWh. Savings may easily work out at 100 pounds per year, a pretty penny I Maybe 1 00 watts worth of savings is foo ambitious for you. However, we would be surprised if any Elektor reader would not be able to scrape together energy reduction worth 25 watts. Even then the real savings at about 25 pounds (or even 40 pounds with all costs included] are still well worth the effort. Hidden energy eaters Mains adaptor 1 - 2 watts TV set 5-10 watts PC 2 - 5 watts ADSL modem 5-10 wafts Microwave oven 1-10 watts Video recorder 3-10 watts Figure 7. Power measure- ment ore easy — just insert the insiru- mem between the power outlet and the plug. You'll be surprised about the results of the test} Figure 2. A switch-mode battery eliminator is often more compact and invariably energy friendlier than older transformer based counterparts . Figure 3, £xomp/e of on electricity cos/ mefer. (Conrad Electronics) 6; 2005 ■ dikter e!cttrc‘ : c> 51 Visit our website www.disteLco.uk ] THE ORIGINAL SURPLUS WONDERLAND! 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High performance; 1 QGS/s sampling rate & 300MHz bandwidth * 1MB buffer memory * High speed USB 2.0 interface * Advanced display & trigger modes * Compact & portable * Supplied with PicoScope £ PicoLog software Tel: 01480 396395 www.picotech.com/scope271 3BIH SOVrtf H SpaUjv 50***. Dla 5 Sf/.TJ j SOatirii U asnfi lOTUSJx 1 3 fTlD&Hsinr 5 ±»I!^ □are '• r--> WtMASz. S.Eit u ■tl*H U Mh , Du tMH 7 et hnology Umiwl 6/2005 -ekLloi e'Hfronits 53 measuring temperatures both indoors and outdoors Niklas Langmaack Th is temperature logger is a device which continuously records two temperatures for subsequent analysis on a PC. Thanks to its l 2 C bus it can also easily be used with a range of other types of sensor. This simple data recording device is designed to make a continuous log of two temperatures. The chief application is of course the measurement of temperatures indoors and outdoors over the course of t say, a year. The device includes a serial I 2 C bus interface to which an A/D converter can be connected, allowing a wide range of other types of sensor (pressure, humidity, and so on) to be nsed. In principle a com- 54 chlUsrdEtfrOiiks- i/2005 m 1N414B © 5CA IC4 AD SCL At O 5- A2 TON? 5 — 030447 - 11 Figure \ . Circuit of the temperature logger plete weather monitoring station could be built. ©mnis dl vises in partes tres The project as a whole is divided into three parts: the hardware, the firmware in the microcontroller, and the software running on the PC. The PC software allows the device to be configured and can read the data from the device’s memory. The data can be displayed as a table or graphically, and can be saved as a text file for further processing, using Excel for example. The hardware is very simple, and, thanks to the bus, general-purpose. Just a few simple modifications to the firmware are required to support a dif- ferent sensor. Source code for the arm ware and for the PC software can be downloaded for free from www. elekt or-electronic s.co.nk or from the author's homepage. For this rea- son, we will be looking in detail at the software later in this article. First, though, to the hardware. This comprises two digital temperature sensors, a non-volatile memory capa- ble of storing over 32,000 pairs of data values, and a serial interface to the PC. At the heart lies a Microchip microcon- troller. which is responsible for reading the sensors, managing the memory and attending to the PC interface. The logger has a particularly low current consumption (see box), is small and is child’s play to use. As we can see from Figure 1 , this is a typical microcontroller application. Tire device used, a PIC16F676, is a recent addition to the PIC 16 family of micro- controllers from Microchip with an 8- bit architecture. It offers 64 bytes of SRAM data memory, while program memory consists of 1024 14- bit words, Each instruction occupies typically just one word, and so the program memory is enough to hold a good 1000 lines of machine code. xAs the *F : in the pan number indicates, the program mem- ory is constructed from Flash ROM: in other words, the memory is non- volatile, and electrically erasable and reprogrammable. The controller is connected to two dig- ital temperature sensors and a 64 KB EE PROM over an I 2 C bus. It is also possible to add a small extra circuit to the microcontroller to allow it to meas- ure its own power supply voltage. It can then produce a warning when the voltage is too low and there is risk of logging being interrupted. The PIC16F676 microcontroller includes a built-in A D converter (Figure 2) con- nected to pins ANO (pin 13) and AN1/V PiEF (pin 12). The microcontroller monitors the supply voltage via the potential divider formed by R6 and R7, and a reference voltage is produced by Di and R5, The current through the Zener diode, and hence the reference voltage itself, is slightly dependent on the battery voltage, but for this pur- pose we have more than adequate accuracy. The two low-current LEDs D2 and D3 provide a visual indication of the state of the batten/ and the cur- rent mode of operation. UP Status none D3 D2 D2 and D3 Quiescent slate or operating from GoldCap backup supply Ac live. supply voltage goad Inactive, supply voltage low Aclive, supply voltage low — 6,/2005-Eleklof dedrquks 55 hands-on I temperature logger Vco I VCFG = P n Figure 2. The PIC 1 6F676 has a built-in A/0 converter. Start Interrupt (triggered by TTmerl every 8 sec) initialisation interrupts Timerl R5232 120 bus ext EEPRQM AD Converter address counter status battery status 1 Activate TTmert Interrupt Character 1 received ; (RS232)? i Finished Transmit OK 1 Transmit version Transmit status > Received time interval Start log Stop log Reset, all counters to 0 H Received addresses K Transmit data Output current temperature Reset counter y Store temperature LEDs , (X*H47-13 Figure 3. Firmware flowchart. Since the LEDs only blink briefly once every eight seconds (if at ail) they effectively consume almost zero cur- rent. Either three alkaline ceils (3*1.5 V} or loin NiMH cells (44.2 V) can be used to power the circuit. Alternatively, if mains power is available, a regulated mains adaptor can be connected via K4. The operating voltage of the ICs is from 3,5 V to 5.5 V; the 'official 1 operat- ing voltage for the whole circuit is thus set at between 4 V and 5 V. Cer ami c capacitors C4 and C5 smooth the power supply and remove interference, while GoldCap C8 Is used to maintain the supply during interruptions, for example when the batteries are changed. The serial interface is very straightfor- ward. There is no level shifting, just a resistor R2 at the input, which protects the PIC from damage. The interface does not, of course, meet the RS-232 standard but nevertheless works per- fectly as long as excessively long cables (over 3 m) are avoided. The Inverting driver integrated Into the PiC T along with 32 kHz watch crystal XI, Cl and C2 form an oscillator which acts as the time base for timer T1 in the microcontroller. The frequency of this oscillator, together with the supply voltage, largely determine the current consumption. Using the internal micro- controller dock, here set to 4 IdHz, the current consumption should be less than 500 pA at 5 V. SI and HI form the usual reset circuit for the PIC. Tills is not required for nor- mal operation, but it is sometimes use- ful to restart the microcontroller firmware execution in case of a fault or during program development. Bus sf©p The P1C16F676 does not have a built- in I 2 C bus interface* and so it must be emulated in software {just like the RS232 interface). Pull-up resistors R3 and R9 are required for communication on the 1 2 C bus; C3 is not strictly neces- sary, but serves to improve the signal quality on the clock signal SCL and improves noise immunity. Three ICs are connected to the bus: two temper- ature sensors and the EEPRGM for storing the pairs of measured values. Originally developed by National Semi- conductor, the well-known LM75 com- bines a temperature sensor, a 9-bit A/D converter and an I 2 C bus interface in an 8-pm S01C package. According to 56 ekktor alidioria ■ 6/2005 Figure 4. Controlling the temperature logaer using a PC . the data sheet, the typical error is 0.5 C. The device has three address pins which allow it to be configured so that up to eight sensors can be con- nected to a single bus. Microchip offers many variations on this component. The TCN75 is based on the original LM75 r but has a mlly- program rnable address and comes in an SOIC or MSOP package. The TC74, which can also be used, comes in a TO220 package with five pins, but has a resolution of only 1 C, It dispenses entirely with address pins and is sup- plied with a pre-programmed address (TC74AQ, TC74A1, and so on). One sensor is fitted to the printed circuit board of the data logger and directly measures the ambient temperature where the circuit is positioned; the other is connected by a cable with waterproof connections, and measures the temperature outside. Temperature data values, as received from the sensors, are nine bits long, consisting of a sign bit, seven bits to represent the integer part of the tem- perature value, and one bit to repre- sent the fractional part, which can be zero or half a degree. This gives a range of temperature values from —127.5 C to + 127.5 "C, which is much greater than we need for our applica- tion. We therefore convert these values in the PIC into a different format which encompasses a smaller temperature range, but which only requires eight bits. This saves precious space in the EEPROM. The 8-bit format starts at “32 Z C (zero) and runs up to -r95.5 C <255), The off- set can be changed if desired; the important value here is 32. In line 48 of the firmware source code file lm75.inc this value is added to the raw data; in lines 572 and 573, and 608 and 609 of Unit 1. pas 32 is subtracted from the 8- bit values to convert them back into real temperatures. It is easy to change the onset of the temperature window by modifying these lines suitably, Tli e serial electric ally-erasable memory used for the logged data is a 24FC512 EEPROM, also from Microchip. Tne device is organised as 64K 8 -bit words (512 kbits in total, or 64 kbytes). The 24FC512 : s address is configured using three address pins, allowing up to eight memory devices to be connected to the same bus. The 24FC512 comes in an eight-pin DEL package. Firmware The firmware in the PIC was written entirely m assembler nsing the MPLAB and MPASM development software provided free by Microchip. Although there are only 35 different assembler instructions, they are very flexible and powerful. The flowchart in Figure 3 illustrates schematically the functions of the firmware. Tne firmware consists of two almost completely independent parts. On reset the PIC automatically starts executing the routine which initialises all the various components and then waits for a command from the PC, Every eight seconds an interrupt is generated by timer 1; the interrupt rou- tine is responsible for actually storing the temperature data. Most of the work involved with the RS232 interface is done by the func- tions pure (for transmission) and getc (for reception). The routine putc trans- mits the byte stored in the working register W over a predefined I/O pin. The data format is *8NT (one start bit, eight data bits, no parity bit and one stop bit). The receive routine getc uses a polling technique: when called, the function waits until a complete data byte in 8N1 format has been received over a predefined I/O pin. The data byte is returned in the W register. Tim- ing for both routines Is handled by the delay loop rsdel which gives a data rate of 9600 baud with a processor clock of 4 MHz. All the routines which are concerned with the RS232 interface are collected together in the library soft rs.inc; only the definitions of which I/O pins are to be used (and their tristate control hits) have to be specified in the main source code. The library soft_i2c.inc is a little more complicated. In the I 2 C protocol the bus goes though a number of states, also called 'conditions 1 . Tnese corre- spond to functions in the code: 12c_start generates a start command; i2c res generates a repeated- start command; i2c stop generates a stop command and returns the bus to its quiescent state; i2c send transmits one byte; 12 c rec receives one byte; i2c ack transmits an acknowledge bit after reception; 12c nack transmits a negative- acknowledge bit after reception. This gives a very flexible set of com- mands, which is helpful when integrat- ing other 1-C devices Into the system. The functions allow various complex communication situations to be han- dled. Examples of using the functions can be found in the modules for inter- facing with the external EEPROM (eee24.inc) and with the temperature sensors (Im75.inc). 6/7005 - filter ehtir&raa 57 hands-c temperature logger fi? Temp Logger tl . cartd j rr.it i i-orji^js-jcrtriE hefc - -,x i - p *Aj ” r * cu^ri := insiclo 21.5'C outside: -2,&'C i.TCOE 1 &rt ry=. | 0 §15.5 J zz 1BJ 2 2Z5 sz IBS i 15.5 135 5 135 13 155 :75 155 13 155 Is IS 17.5 I'M 15 i 175 n 15.5 155 ■i 13 IBS n T 5 155 u i? 155 >: ■: : = 1=:-: IZVE i Figure 5. A series of measurements displayed in tabular and graphical form. PC The PC software controls the unit over the serial interface, and reads and analyses the stored data. It was writ- ten using Borland Delphi 6 and uses the Windows API to access the inter- face. Tnis means no extra DLLs are required: it is sufficient to simply install the interface under Windows using the standard driver. The application will work on ail 32-bit Windows systems {from Windows 95 onwards) using Internet Explorer 4.0 or above. A Pentium I system has plenty of processing power, ft is not possible to compile the program under Linux using Borland Kylix because the inter- face is accessed directly using the Windows APL As a minimum the rou- tines for handling RS232 communica- tion would need to be rewritten. The program window is divided into five pages accessed using tans. The first page, 'control' (Figure 4) gathers together all the functions for control- ling the data logger as well as the indi- cators that show the current state of the device (such as battery status and remaining EEPROM storage capacity). The second page, ‘data', (Figure 5) includes all the functions for reading out and displaying the scored data. The third page shows the complete contents of the configuration file set- tings, ini to simplify debugging. You should only make changes here if you know exactly what you are doing! The fourth page gives a brief summary of the program’s functions, and finally the fifth page leads (if a suitable Internet connection is available) to the author's website at http : / / wwt vX ancmi aack-TZ.de/ TbmnLoQgeg/ where further information can be found, along with a discussion forum. Figure 6 , Printed circuit board layout for the temperature logger with remote outdoor sensor. COMPONENTS LIST Resistors: R 1 ,R2,R5,R7 = 4/kQ R3,R4 = IkOS R6,R8,R9 = IGkn Capacitors: C 1 ,C2 - 1 2pF C3 = 39pF C4 r C5 = 33nf C6,C7,C9 - IGQnF C8 - GaldCop I F 5.5V Semiconductors: D1 - Zener diode 2.7V, 400m W D2 = taw-current LED, green D3 = law-current LED, red D4 = 1N4148 IC1 = PEC16F676, programmed, order cade 030447-41 IC2 = TC74 IC3 = 24FC512 EC 4 - TCN75 or LM75 Miscellaneous: 51 = on/off switch, 1 contact K1 = 3.5mm rack socket stereo, PCB mount K2 = 4-way 51 L p inheader K3 = 4-way RJ45 socket, PCB mount XI = 32.768kFiz quartz crystal PCB, order code 030447-1 Disk, project software, order code 030447 - II or free download from WWW- e ! e k ror— !ec rronics.co.uk 58 tkliter efecIrctiRs '6/2505 The most important functions of the program aie to start and stop a session of measurements. A precise record is made of when a session is started, so that different sessions can be kept sep- arate when the data axe subsequently processed. Before starting a session, the time interval between measure- ment samples can be set using two sliders. The available range runs from eight seconds to six days. These set- tings are also recorded so that the user can access them later. There are two ways to read the data out of the device. The first option offered by the program is automatic read-out. where the user selects one of the sessions from a list and the pro- gram determines the relevant region of memory to be read automatically. If the last log is selected and logging is not yet complete the program automati- cally loads all data available up to the last stored value. hi manual reading mode the user must manually select the region of memory to be transferred. The value 'now 1 indi- cates the position currently reached in the memory. For example, to read out the entire used area of memory, spec- ify 0 for the start address and 'now 1 for the end address. In manual mode the data can only be presented as a table or graphically: the extra information such as start time and sample interval are onty available in automatic mode. Once the data values have been read out they can be displayed in tabular or in graphical format. Tne table can be stored as a text ole which can then be loaded directly into a spreadsheet pro- gram such as Excel, where it can be processed further. Finally a few words on constructing the temperature logger. The printed circuit board is shown in Figure 6; as you can see, construction should pres- ent no difficulties. Be careful to ensure that all components are fitted the right way around. The microcontroller and the memory device can be fitted in sockets, while the temperature sensor is soldered to the back of the board. Connection to the external tempera- ture sensor is via air RJ45 socket (and yet another sensor can be connected to connector K2, where the I 2 C bus sig- nals are made available), and the reset button is connected across JPI. A mini stereo jack socket (Kl) is provided for the serial interface to the PC; this can be replaced with a sub-D connector if desired. The markings show the cor- rect connections. (G3Q447-1) Current consumption At maximum load, that is, with logging at eight second intervals and continuous status moniioring from the PC, the current consumption of the complete circuit is 1 .8 mA at 4.8 V. This gives a calculated maximum running time of 46 days using four 2000 mAh (AA size) NiMH cells, or 81 days using 3500 mAh (C size) cells. If the supply voltage drops below 4 V, the temperature logger indicates that the batteries need changing by flashing the red LED. The GoldCop wilt maintain o supply voltage between 3.7 V and 3.9 V for about a minute: if the batteries are changed within this time, logging will proceed svithout interruption. If power is lost completely, the logger will subsequently resume operation from v/here it left off: this can lead to gaps or time-shift effects in what should be continuous logs. The TCN75 The TCN75 is a seri- a I ly-p rag ram ma bte temperature sensor which converts tem- peratures in the range from -55 C C to + 125 "C into 9-bit words and stores them in a memory. This memory can be read out using a host controller over the t 2 C bus. It is also possible to set o threshold value T s ^- and o hysteresis value T h YSTh on the basis of which an interrupt signal can be generated and sent to the host. the TCN75 can operate in "interrupt mode" or in Tomparoror mode . fn both cases the 1NT/CMPTR output is active (the polarity is programmable) when the thresnola value is exceeded. In comparator mode the output is automatically reset again when the temperature falls below T hyst ; in interrupt mode, hov/ever, the out- put con only be reset by accessing a register. Then, when the temperature falls below T HY 5 t, the INT/CMPTR output again goes active [and must again be reset by a register access). In interrupt mode entering the shutdown state also resets the output Five registers control operation of the TCN75, The register pointer (2 bits) determines which of the four other registers will be accessed in the next operation. Tne configuration register (5 bits) sets normal or shutdown mode, comparator or interrupt mode, and the polarity or the INT/CMPTR output. Two bits determine how many times the threshold value must be exceeded before the INT/CMPTR out- put will be made active. These bits give a degree a noise immunity to the sensor. The read-only temperature register and the read/write registers for threshold and hysteresis are each 16 bits long although only the top nine bits are used. Tne L5B represents 0.5 "C f and a binary two's complement representation is used: Temp era tore Binary value HEX value - 3 - 1 25 °C onmoio 0FA +25 C C 0001 10010 032 +0,5 =C 000000001 Oil 0 c C 000000000 000 -0,5 a C 111111111 IFF -25 C C 1111001110 ICE -40 D C 1 1 10110000 180 -55 D C 1 10010010 192 fi/2005-elsklur nstirorjcs 59 hands-on GPS receiver on USB With contributions by Thomas Biel The lack of availability of integrated modules in small quantities has unt now been an obstacle to building a GPS receiver yourself. Now things changing, and it has been worth the wait: the newest generation of GP ’"'ceivers are not only outstandingly small, but also offer considerably Ter reception performance and lower power con- _ nption than their predecessors. as until itter _ GPS offer considerably lower power con- are gtw © if) ffi i«ss: Rt ifd £t*4? & swe >( 9 t © i ?_°.£ PC V rn r.ri r ^ L> V P si • -?=■ ^ nv - j J “T. i 1A -i //\ b * * V > 7 y/} Ly > | . 1 .-i * r ^ .*■" 3?? *# n * ■' « r 3 I b i — \ "V \ R. - J 0 © B ^JUvs*** <3°'" - 30 -s n li^i y &• &— **** t, S C^ 30 *>*» £if' m C WH 131 rire =** c£ ' to , ^ ?,**£**'* * , ° ^ el£0 ,'T t5 »' osi ARg T. i ■ ^ 6tf n vi*u* iiovro yC9^ y05W» esf^ 66 ja* 1 * . rjttc- 3 trirtf® 5 3I #U iS 7 TrtT^ 5 yo **** 63 VI t**** 5 |pr*^' ^t^ £5 t- 4 inr^ 6 * 2 7 tr^-- ^cftrti 55 Whether you are a fan of water sports, flying or amateur radio f a driver or a walker, whether for business or for pleasure, if you are interested in tech- nology you will no doubt have seen a 57 G-P8 receiver or marvelled at some system based on GPS technology. GPS technology was developed by the United States Department of Defense to provide military forces with a global navigation system. Twenty-nine satel- lites circle the earth to provide an almost complete coverage of the sur- face of our planet with the signals they beam out. Because of the curva- ture of the earth, a GPS receiver can never receive all 29 satellite signals simultaneously; fortunately this is never necessary and for basic opera- tion it is only necessary to be able to see three satellites to obtain accurate positional information for navigation in two dimensions. If more than three satellites can be seen the results can be more accurate and altitude can also be determined (for navigation in three dimensions). Until a few years ago GPS was expensive and not particularly accu- rate. For strategic reasons errors were deliberately introduced into the positional information made available to civilian users, so that the received GPS position was guaranteed to be out by up to a dozen metres or so. The rather involved DGPS {differential GPS) technology was introduced to compensate for this state of affairs: DGPS provides the nec- essary correction data to allow the system to measure position to an accuracy of one metre. 35 n* - **-' 5 In 2000, for global political reasons, the US administra- tion switched off the degradation of the signal. Errors are now of the order or one metre, and so we no longer need to pay the price for DGPS. In non- ideal conditions, however, the accu- Figure I . The GPS module is the size of o postage stamp - but a little bit thicken racy of the system can fall off rapidly: errors can amount to tens or hundreds of metres. DG-F3 is still used in appli- cations where the greatest possible accuracy is wanted, for example in air- craft landing systems or for marine rescue. Satellite-based systems, such as WAAS in the USA, EGNOS in Europe, and MS AS in Japan, are also used for DGPS: the correction signal is calculated at GPS reference stations (so-called ‘RIMS') on the ground and then transmitted via "normal' geosta- tionary communications satellites, such as the INMARSAT family. One of the channels of the GPS receiver can be used to receive this signal. WAAS is already in operation, and the other two systems are still in the test phase. After many delays EGNOS should be available by the middle of 2G05, although initially not for "safety of life 1 applications, that is, applications where human life would depend on the system, such as in air and sea transport. In general navigation should never rely exclusively on one individual system, and failure of GPS reception is not a rare event. The Trimble module The GPS project described here con- sists of a GPS receiver module and an interface to connect to the USB port of a computer. The printed circuit hoard is laid out to accept either of two mod- ules produced by Trimble, the Lassen SG and the newer Lassen iQ (see Fig- ure 1 }. The latter is a 12- channel GPS module, which means that it can simultaneously receive and process signals from up to twelve GPS satel- lites. The unir comes in a very compact enclosure with a footprint of just 26 nun by 26 mm and a height of just 6 nvm. It achieves an accuracy of 5 m in the horizontal plane and 10 mm the vertical direction (SO % points). This receiver is therefore as accurate as that 6/2005 -efeklor t!«fronits 61 GPS receiver on USB htnds-on 040264 it Figure 2. The FFDI chip connects the GPS module to the USB interface . of one of the market leaders* TomTom, who use the Motorola SIRE II chipset, but offers more in re mis of software. Compared to the pin-compatible 8- channel Lassen SQ module, the Lassen iQ offers more than just an improve- ment in positional accuracy. The time for a bold st an' has been reduced from 90 seconds to 50 seconds, that for a 'hot start' from 14 seconds to 10 sec- onds, The module also offers the user an additional sensitivity mode. Power consumption is, at 86 mW, around a third lower than the Lassen SQ, As well as the TSIB TAIP and NMEA 0183 protocols, which are supported by both modules, the Lassen iQ also supports RTCM SC-104, which is used to transfer COMPONENTS LIST Resistors: R 1 ,R2 = 27Q R3 - 1 kQ5 R4 = 2k02 R5.R7 = lOkQ R6 - 4700 Capacitors: C1-C7 = IGGnF Semiconductors: D1 = LED, red, low-current D2 - LED, green, 3rtim r low-current iCl = FT232BM [FTDI| 1C2 = LM1 1 1 7-3.3 (National SsmiconduLor) IC3 = 93LC46A/P (Microchip) Miscellaneous: BT! = 3V Lilhlum cell, 20mm [e g. CR2032) wilh holder (e.g, Digikey # 1026K-ND) K1 = USB-B connector, FCB mount K2 = 8-woy SMD connector (5am tec CUM 04-02-G-D^BE-PA] K3 “ 5-way 511 connector XI = 6MHz quartz crystal GPS receiver module. Trimble Lassen iQ or SG [see text, available from Framos, Geist or Molecular) 3.3V active antenna (see text) FCB, order code 040264-1, see Eiektor Shop pages* 9 wire links A kit or parts s available far this project; see this month's Elekfar Shop pages or w vav . el e k fore I ectro n \ cs , co „ irk DGPS data, and has a second serial port. The firmware for this protocol is available from Trimble* A data sheet and a detailed comparison of the two modules can be found at the website of Ramos, who are distributors for the Trimble modules: the address appears at the end of this article. The module costs around £35. interface chip The FT232BM from FTDI, which will be familiar from many previous Eiektor Electronics circuits, has been chosen to provide the USB interface (Figure 2). This provides a cost-effective USB UART, which allows us to send serial data over the USB. Offering data rates of up to 920 kbaud (RS232) or 2000 kbaud (E3422 or RS485), the FT232BM oners better performance than conventional ISA or PCI bus based UART systems, and also provides full plug-and-play functionality with a sim- ple connection to the USB port. As far as the PC is concerned data are transmitted using standard COM port functions, so that in the majority of cases no changes are required to appli- cation software. Its flexible architec- ture makes the 1C ideal for use in a wide range of applications. Virtual COM port (VCP) drivers are available for Windows 98, Windows 983E, Windows ME, Windows 2000, Windows 3CP, Linux, Mac QS 8, Mac QS 9 and Mac 05 X. Windows CE drivers can be obtained from third- party suppliers. The most recent VCP drivers for Windows XP are Microsoft WHGL certified. The circuit generally runs along the lines recommended in the FT232BM data sheet. Besides the FT232BM ihe circuit (Figure 2) includes just a 6 MHz crystal, a 93C46BP EE PROM, a fixed 3.3 V voltage regulator and a few pas- sive components. The GPS module is connected to the circuit id a K2. Not shown is tire active antenna, which is connected directly to the antenna con- nector on the GPS module. An optional five-way header (K3) is provided so that an alternative GPS module can he used. The EEPROM IC3 is also optional. The circuit will work without this non-volatile memory, but in this case the interface will just present itself as a standard serial device. The EEPROM allows for the storage and 62 daktoi clHtiOfiits - 6/1005 retrieval of specific data sach as the vendor and product identification num- bers (VID and P!D), serial number and so on. The EEPROM cannot be dis- pensed with if multiple USB -serial con- verters using the FTDI chip are to be connected to the same PC, since the driver will only create separate virtual serial ports for converters with distinct serial numbers. Without a stored serial number, only one virtual COM port is installed. A tool with accompanying guide to programming the EEPRQM can be found on FTD! s website. An exte rnal p ower s upply is not required: the circuit is powered from the USB port of the PC, An optional Lithium battery allows the receiver to store the most recently calculated posi- tion data along with the ephemeris when the unit is switched off. The module can then perform a 'hot start \ providing its first positional informa- tion after a much shorter delay than would be the case with a 'cold start 1 , SMD tonsiruttion A kit of parts for the project is available from the Publishers — see the Elektor Shop pages in this issue, or visit our website at WWW, elekto r- el ect ronic s.cq i ik . The nine wire links should be fined first to the printed circuit board (Fig- ure 3), Next, the FT232BM can be sol- dered to the underside of the printed circuit board: this device is only avail- able in an LGFP-32 package, and so a steady hand and a fine-tipped solder- ing iron axe required. SMD connector K 2 is also fitted, to the underside of the printed circuit board < Figure 4). Apart from these two components, populat- ing the board should not present any difficulties, A word of ad wee to home etchers: the enclosure of the GPS module is con- nected to ground. When the module is mounted on the copper side of the board, be careful not to cause a short to the tracks. A piece of insulating tape will serve to emulate the insulating function of the solder mask provided on the original Elektor Electronics printed circuit boards. The GPS module is compatible with active 3.3 V DC antennas, which receive their 3.3 V DC supply from the Figure 3. Layout and component mounting plan for the printed circuit hoard. Figure 4. The 1C and the GPS module are fitted to the underside of the printed circuit board . 6, 2Q05 - tkifei dstfntda 63 GPS receiver on USB hands-on Figure 5 . Our final prototype board with miniature active antenna connected '. antenna socket op. the module. Thimble can supply an ‘ultra compact embed- ded antenna' with an 8 cm cable and an HFL plug that mates directly with the socket on the module. This antenna is shown in Figure 5. With an adaptor cable, 3.3 V active antennas with MCX or SMA plugs can also be used. Trimble also offer a suitable active antenna with a magnetic base and a 6 m cable, suitable for indoor or outdoor mounting, for example on the roof of a car. The active antenna cable must be con- nected to the antenna socket of the GPS module before the module is fitted into its socket on the printed circuit board. For permanent fixing, the mod- ule enclosure should be soldered to ground at the points indicated on the component mounting plan, to help hold the connector in place and pro- vide mechanical support. Configuration Once the circuit has been built and the soldering has faeen inspected, the GPS receiver can be connected to the USB port of a PC. Windows XP will now recognise a new USB device. The sim- plest course now is to let Windows find a suitable driver on the Internet. If you prefer (or if you are using a dif- ferent operating system), the relevant driver can be selected from FTDFs website and then downloaded. When installation is complete a new COM port will appear on the PC. As supplied the Trimble GPS module uses a manufacturer-specific protocol called TSIE The module must be con- figured (once) to make it emit data using the NMEA (National Marine Electronics Association) protocol. This is easily done using the program SQ Monitor, which is available for free download from Trimble. The window which shows the serial interface set- tings for the GPS module, and where the data output protocol can be set to NMEA, is available under the menu option 'Configure/Serial Port*. The HS232 interface should be configured with parameters 4800,8.1^,1, which is the standard for NMEA data and which is also used as a default inter- face setting by most PC-based naviga- tion or route pl annin g software, TS IP Chat If problems are encountered in config- uring the communication protocol, Trimble also provides a low-level con- figuration tool called ‘TSIPChat.exe*, which runs under DOS and communi- cates with rhe GPS module using COM! or COM2, To use this program, a virtual USB COM port must he installed on COM! or COM2. This is done in the Device lsipchflt_ 1 - 02 .es(e * tl * ctmf igure Contnanri; Set Set MCE I V tiH Port Gonf i {jurat iuit Band rate : + 1SOO €6> Dat.* bits' » <3> Par it ■/: HOME < 0 > t:o^ bits: I <0> Protocol in: Lessen S4 sup|iorts onljf TSIP I fth injmt . Press RETURN to continue. ProiQpdl iilit: NMEm C2> 1- ct receiver serial port? CY^tO YES Change PC serial configuration to natch? YES ...imitiny for reply <@kDO $GPUIG $GPGGG f HU. , » , - r * $GPU 1 G, M’OW $GPGGR ***, -HA $GPUJG, H* m Figure 6, Interface configuration using the TStPChat' program. 64 cl^lof electiojiks - 6/2005 GALILEO Europe's answer to GPS Hans Weber reliability far safety-critical applications, for example in sea and air transport; -an search and rescue service; and - a public regulated service' which is encrypted and offers a high degree of resistance against Interference. Users must be agencies with responsibility for security and pre- lection'. In order to reduce Ms dependency on the USA, the European Union, along with the European Space Agency, has initiated its own satellite navigation system. GALILEO should deliver better positioning data than GPS and, if things go according to schedule, be ready for full operation in 2008. GALILEO is based on 30 satellites which are positioned in three different orbits. Of the ten satellites in each plane nine are active, the tenth acting as a backup that can be switched in at any time. The altitude of the orbits is approximately 23600 km, and the satellites are therefore in medium earth orbit (MEG). GALILEO is exclusively designed far civilian applications, but there is also a security aspect. In services are planned: -a free basic service open to the public, comparable to the civilian GPS signal, but with better quality and reliability; - a commercial service offering, far a fee. extra information to improve accuracy and reliability (or 'integrity') and aimed at professional services such as logistics and fleet management; - a safety of life' service with especially high quality and particular, the following Originally GALILEO was conceived as a competitor to GPS. Under pressure from the USA an agreement was signed in June 2004 to ensure ihe equal status, compatibility and - in the civilian sector - Interoperability of GALILEO and GPS. Applications that use both systems ore therefore possible. !n any case the EU has already had to declare that the BOC (Binary Offset Carrier) 1.5 modulation scheme will not be used, being replaced by the BOC 1 .1 scheme, which will also be used in the next generation of GPS ( GPS III ). Arrangements were also made to cooperate in preventing enemy use' of the signals. This means that in crisis areas or 'in ihe interests of national security' of one of the partners, the service can be restricted or cut off completely. Critics who complain at the high development costs (estimat- ed at approximately four billion Euro), claim that after this agreement GALILEO is redundant. Also, the original schedule has slipped. Speed is of ihe essence, since if the first satellite is not launched before the end of February 2006, the fre- quencies allocated by the ITU may be forfeited. The planned start to operations In 2008 has already been moved; now II is said that GALILEO may only go into service '|ust before the end of the decade'. Manager under Torts (COM and LPT) 3 , where USB Serial Port (COM n) s can be selected with a double click. This brings up the properties of the USB serial port. Change from the tab marked General 1 to Tort Settings' and use the Advanced,./ button to reach the Advanced Settings’ window. The held ‘COM port number gives a choice from the available COM ports: here we choose COM2'. The list may show the port as in use/ this need not worry us as COM1 and COM2 are addressed via the computer's BIOS. If COM1 or COM2 were free the FTDI VCP would install itself as COM3 or, in the case of a laptop with a modem, as COM4. Note that on a laptop COM2 may be used for TrDA. Now confirm by clicking on 'OK 1 and restart the computer. The new settings should now be checked in the Device Manager. As well as T rimb le's TSIPChat.exe there are also older navigation pro- grams that will only work with port COM1 or COM2. A right click on TSIPChat, followed by selecting ‘Properties/ brings up the 'Properties' window. Since it is a DOS program, there is a 'Program' tab next to the ‘General 1 tab. Under this tab the option string *-c2’ must be added to the end of the command Line. The box ’Close on Exit 1 must not be checked. Clicking on OK' completes the config- uration as far as Windows is con- cerned. When TSIPChat is run a DOS window v/ill appear. First type U'. You will be asked if you wish to change the COM port settings. Confirm with *Y r and configure the interface to 4800 baud, 8 data bits, N (no) parity. 1 stop bit, TSLP input protocol and ‘NMEA T output protocol (Figure 6). When initialisation is complete GPS data will appear in the DOS window in NMEA format. To exit the program press ESC twice and close the DOS window. Navigation programs Many of the route planning programs available for PCs understand NMEA fr/20G5 - effkior ekdroriiu 65 GPS receiver on USB hands-on fcSrcii-iS Figure 7. In conjunction with a com merciallyo vaila ble navigation program running on o portable computer the GPS receiver forms a complete navigation system. protocol. The route planner can then he connected to a GPS receiver and dis- play the current location on a map. Some route planners can metamor- phose into fully -3 edged navigation sys- tems with speech output as soon as a GPS module is connected. It is thus a very simple matter to use a laptop it I IrtiMSrtK* fc jfctaf ILriatfil h (fc.-r T .da) Figure 8. The program YtsuaiGPS' can even display the movement of the satellites * along with the USB GPS receiver described here along with a route plan- ner to create a navigation system. Suit- able programs, such as ‘Route 66\ shown in the picture at the beginning of this article, are readily available from around twenty pounds In many cases there will be no cost involved at all: for example, Microsoft's Autoioute’ pro- gram is already delivered pre-installed on many notebooks and PCs as part of the MS Works package (Figure 7). To establish connection with the GPS receiver it is sufficient to simply enable the GPS function in the navigation pro- gram menu. In Route 66 the COM port number and baud rate must also be entered. In Autoroute you can click on ’Scan' in the GPS setting menu, and the program will then automatically find the GPS receiver connected to a USB port or the relevant virtual COM port. Visual GPS If you do not already have a navigation program or if you simply want to look in detail at the MMEA data, the free program ‘VisuaIGPS 1 can he used. This can be downloaded from the Internet (see link below). As Figure 8 shows, this interesting program can even pro- vide a display showing the movement of the satellites. An alternative for special applications is the DIY approach. In the box NIvIEA data decoded' we give a praciical example using Visual BASIC. The example program can he downloaded for free from the Elektor Electronics website, rei Q4G26441.zip. Elektor Electronics articles: Automobile Navigation Systems based on the GPS, December 1 997. GPS Receivers with NMEA output, October 2001 H p. 6E. USB-RS232 Inierrace April 2003, p_ 60. Links: USB interface chip www. fid i c hi p . cam / FID r i ve rs . h tm Information and firmware for the GPS module http://trl.trirnbie.cam/ docushare/ds ,veb /Get/ Document-! 84028/ lassen-f-iQ-i-v9.pdf h ttp : / / w ww. fr a m os . d e / p d f_ s h e eh/ LasseniGSGC o m pa risonRev 1 .pdf hiip: / /trl . tri m b ie.com/dscgi / d s . py / G et / File-3 1 5 60/ SQ_Monitor.exe 66 ddbr eklrwks - 6/2005 JMEA0183 data decoded using Visual BASIC One of ihe standards defined by ihe NMEA (National Marine Electronics Association] is NMEA 0183, which describes data interchange between various electronic devices used for navigation. This NMEA standard protocol is extremely widespread and allows almost any GPS device which generates NMEA data to be used in conjunction with navigational and mapping programs running on □ PC, PDA or laptop. The data are transmitted using ASCII characters. Each sen- tence" begins with the $ symbol and continues with a two- character transmitter or 'talker' identifier (in our case 'GP ), a three-character sentence type identifier ond a series of daia items separated by commas. At the end of the sentence is on optional checksum, follov/ed by a CR/LF (carriage return/line feed] pair. Each sentence can be up to 82 char- acters long. If the data expected in a particular field are not available, the value is simply omitted, with the comma sepa- rator remaining in place without extra space characters, A receiver can therefore extract the data it needs from each sentence simply by counting commas. Some common talker identifiers include: GP GPS 1C Laran-C (older positioning system] II Integrated Instrumentation (e.g. Autohelm Seatalk system and autopilots] The Trimble GPS module generates the following NMEA sen- tences: GPMRC: the recommended basic minimum message that any GPS receiver should support. GPZDA: contains data about the local lime zone. GPGGA: contains the most important information about the GPS position and accuracy. GPGLL a telle from the time of LorcmC receivers. It con- tains information about geographical position. GPVTG; includes information about speed ond course, GPG5A: Includes information about the satellites used to obtain the position fix. currently be in view, their position, signal strength ond so on. Since one sentence con only hold the doto for four satellites, there can be up to ihree sentences of this iype. At present there ore seventy-nine different sentence types defined. By way of on open source project we have created a small program in Visual BASIC that shows how to use software to extract information from the NMEA sentences. The program Is available for free download, either as source code or in installable form, from the Elektor Electronics website at http://wvAv,elektor-eleciron ics.co.uk . We will only look briefly here at the procedures and func- tions, since the source code Is thoroughly commented. Let us know about any extensions you might make to this program. Start up Visual BASIC and then... Using the MSComm.OCX control, three burtons, o text field, a timer, a check box, a few label controls and same code to run in the background it is very easy to set up a respectable GPS data analyser. After starting up Visual BASIC we begin a new 'standard EX E project. The main control used is MSComm.OCX, which is one of the standard controls provided with Visual BASIC, Under Project/Components' odd 'Microsoft Comm Control x.x' to [he project. The telephone icon should appear in the toolbox below, and we con now place this on the form. Next, we give the project o name and begin saving it regu- larly as errors con send our program into an unbreakable loop, for example if we forget to include a calf to DaEventsb Since the Elektor Electronics USB GPS Receiver is configured with parameters 'COM2:, 4300, 8, N, I , these are the settings that must also be entered on the Properties' page of ihe MSComm control. We con now create a control array from the three buttons, calling the button dick functions using a Select-Case block to improve the readability of the code. We now place the text field, ensuring that the Multiline property is enabled, since otherwise we will only see a sin- gle flickering line of text. The timer control is responsible for updating the data. The check box control allows the form to be increased or reduced in size, and determines whether the text control (ihe data window) is visible or not. The descriptive label controls are olso placed in the control array area. Displaying the individual data stems is also done by the label controls, which are implemented here as sepa- rate controls. The NMEA sentence is split up using special parsing functions grouped together in the module NMEA0183.BAS. There are nine subroutines associated with the form 'frm^aster' which together con read o complete data block from ihe Elektor Electronics USB GPS Receiver, GPGSV: includes information about satellites that may also Links: www. NMEA ora Visual GPS www. visualgps.net Overview of NMEA and GPS information hifp: / / vanc 0 uver-webpcges.com / pub / peter/index, him] www. gpstrn,CQTn/erg/d own loadeng.htm (GPS TmckMaker, free download) Component Sources: Frames Electronic Dauihendeysirasse 2 D-S 1 377 Munich - Germany Tel.: +49 89 71 06 67 69 Fax; +49 89 71 06 67 66 safest fro mos.ds h tip: / / wv/w Tramos.de / v a- .av.d I r / sn/ start enmiml Molecular Computer Bohnhofstrasse 33 D-63 i 10 Rcdaau Germany Tel.: +49 61 06 40 35 37 Fax: +49 61 06 6 15 12 http ; //va'av. mobculor.de 6/2595 - tldl nr eltdrcfurs 67 know-how lobtolk Lead-Free Electronics Luc Lemmens The big day is 1 July 2006. From then on, use of lead in electronic cir- cuitry will be prohibited by the Restriction of Hazardous Substances (RoHS) European directive. This involves much more man just switching to lead-free solder For instance, soldering methods must adapted to the higher tem- perature needed by lead-free sol- ders, components must be able to handle this temperature, and lead-based solder cannot be used for tinning component leads. It appears that manufac- turers are finally getting up to speed in making their compo- nents suitable for the Pb-free label during recent months, but it is certainly not inconceivable that a few older types at compo- nents may be temporarily unavailable next year. Doomsayers claim that quite a few electronics firms will have to dose shop because they waited too long to switch over to lead- free. Time will fell: similar pro- nouncements were made when the EMC directive was intro- duced, but there hasn't been much sign of the major shakeout that was feared at ihat time. Quire a few alternatives For lead- based solder ha ve now been developed, and it's hard to see the forest for the trees when you browse through the catalogues of the major suppliers. For Instance, there are alloys of tin with silver, tin with copper, and tin with silver and copper, all with various proportions and dif- ferent types of flux. We decided to put things to o test by simply ordering a few rolls of various olloys and trying them out. This wasn't Intended to be □ serious market study, but simply a way to find out what's available nowadays and how easy if Is to use in the lab, A colleague recalled the solder- ing test that wa s used in his tech- nical secondary school days: sol- dering a large number of wire bridges in series, with the work being assessed by the instructor with the help of a milliohmmeter. Since we anyhow needed some- thing to solder, this exercise pro- vided a perfect opportunity to compare the conductivity of the various types of solder. We could have saved ourselves the trouble because the resistances of oil the various types proved to be comparable. We could not measure any noticeable differ- ences. Lead-free solder does not Flow nearly as well as the familiar lead-tin alloy. You have use the tip of the soldering iron to push it a bit in ihe right direction, A lead-free solder joint always has a mat! surface, which mokes it difficult to judge whether ihe sol- der actually flowed well. How- ever, It's also o question of get- ting used to a material that reacts differently that what you re accustomed to. You get the knack of it after a few solder joints, and then you can work just as fast as before. Still old- fashioned lead-tin solder is the nicest to work with; no lead-free product can touch it in that regard. For bond soldering, there f $ hardly any noticeable dif- ference between the various types of lead-free solders - it's six of one and half a dozen of the other. But next year well sim- ply hove to accept it - or are things actually not so bad in practice? What's the official word? You con find oil sorts of informa- tion about lead free electronics on the Internet, but nothing at all about what It means in practice for the man in the street'. From the answers we received to ques- tions posed to government authorities, it appears that the consequences for hobbyists aren't that drastic. For instance, you can continue to use lead- based solder in your own proj- ects and for repairs to your own equipment after the RoHS direc- tive has been Introduced. Elec- tronics merchants won't have lo dump their old slocks of compo- nents on the rubbish lip next yeor, since these components are already on the market and the RoHS directive only applies to newly manufactured compo- nents and equipment. Production of lead-based solder wi 11 still be permitted, and it will only disap- pear from the market when its soles dry up. Even if you don't necessarily have to moke your hobby lead- free next year, you can certainly do the environment a favour by doing so. However, She enthusi- asm for Inis change will proba- bly be quite small, as lead-free solder Is much more expensive than the old familiar SnPb 60/40 and it isn't nearly as nice to use. It will most likely take quite □ while before it disap- pears entirely from the market. Link: Official version of the RoHS directive: http:/ / europa.eu.int/ e uf-1 ex/pri /e n/o j /d a t/200 3 / l_037/l_03 72003 02 1 3en001 90023. pdf 68 clrklDf tlrrironlcs- £.> 2005 hands-on I design tips Resistors a la carte Andreas Graf The extremely useful resistor cal- culation too! colled RCalc for use on PCs has three menu items and three tabs. The three tab sheets allow voltage dividers, poten- tiometers and resistive parallel/ series networks to be cal- culated, The program accepts real os well as desired voltages or resistor values to be entered. One click an the Calculate button does the rest and the values you require will appear instantly. Although really superfluous, a short user manual is available under HELP, The program file as supplied by the author includes two resistor series, El 2 and E24, that need to be stored in the same subdirectory. Because the resistor series tables are plain text files (with the extension GHM) r it is easy to add other, more (or less!] accurate series like ET92 and E6. Provided they hove the right for- mat and extension, any R series you've added will be included in the calcu- lations by RCalc. The author makes RCalc freely avail- able vio the publish- ers' website at www. e lek Eor-e Sec t rc n- icsxo.uk os item no. 050032- 1 1 .zip. The program is just one megabyte in size and runs without installation on all ver- sions of Windows from 95 through XP. i Shift registers — a different approach Vincent Himpe New technologies ore causing the number of ICs working at the long-established TIT (transistor- transistor logic) to decrease rather alarmingly. The process is not one or gradual substitution, designers being faced with ICs having dif- ferent voltage swings for their logic levels. It may happen that a certain type of shift register employing TTL levels is suddenly no longer available. This Design Tip presents an example of how to approach and solve the prob- lem. The circuit diagram shows the use of a 74x574 shirt register with serial input and parallel output. As an alternative, you could use the 74x374. Although the '374 is slower than the 74x574, it is compatible in respect of function os well as pinout. The 74x574 is on 8-way (octu- ple) D (data) HlpRop with low- power Schotiky TTL (LSTLL) com- patible inputs and outputs. Ie cut- puts are tri-stateable hence may be switched to high-impedance. This feature is not used here, how- ever, so the OE (output enable) input (pin 1) has to be perma- nently grounded. Here, we propose to use Df (pin 2] as the serial input. Ql (pin 19) is connected to D2 [pin 3); G2 (pin 1 8) is connected to D3 (pin 4), and so on. The clock signal for the 1C is applied to pin 1 1. One bit is shifted through' on each low-to- high clock transition of the CLK signal. Eight con- secutive shift oper- ations then allow 8-bit parallel data to be read from outputs G1X38. It is also possible to extend the shift register to 16 bits operation (or even more) simply by connecting she highest G output (Q8, pin 1 2) to the first data input of a further 74x574. On that chip, you connect Ql to D2, G2 to D3, and so on. The CLK inputs have to be interconnected and al OE inputs on the ICs have to be hed to ground (0 V). ]cn DVM without isolation Carsferi Weber Normally, commercial DVM mod- ules based on the popular ICL7I06/07 ICs require the measurement voltage to be elec- trically isolated ( floating ) with respect to the supply voltage. Without appropriate precautions, it is, for example, not possible to measure a potential in o power supply with reference to ground. The ICL7 106/07 datasheets will tell you that INLO pin is an output whose voltage is 2,8 V above V-k The operational amplifier shown in the circuit diagram may be just about any low-offset type like the OP07. It serves to adjust V+ (and v/ith it INLO) to a level that pulls INLO to o virtual ground (neglecting, of curse, the opomp s offset voltage). In this way, it becomes possible to measure the potential at INH1 with respect to ground. A supply voltage of 7,8 V is suffi- cient tor the DVM module. Alterna- tively, by connect- ing it to -6 V, the module supply volt- age becomes 8.8 V. As long as It is not too low, the positive supply voltage will not affect V-k x:: r - 6/2DOS - dtktQr ebrircntts 69 70 Detlef Overbeek, Anton Vogelaar and Siegfried Zuhr Last month we familiarised ourselves with a few topics that are essential for our project, which we conclude this month: a PC oscilloscope that makes use of the sound card. Unit2 from part 5 is used as the main element in this program. The WAV format is oFten used when we want to output something via the sound card. This was put into practice in the function generator in part 4, When we record a sound, the opposite happens. The information is recorded by the card and written to a data block in a WAV format. This is declared when the device is opened. It is then passed an empty data block, which it fills with the recorded da to. At the start of the data black is a header, which describes the format of the block. A type has been defined for this in the MMSysfem unit, the TwaveHdr type", which contains the details for the data. The header is part of the data block, whereas the recording/play- back format is set in the sound device. The TPCMWaveFormat type is used for configuring the recording device. This works with the PCM format that was used previously in the sound recorder. This contains extra information such as the number of bits per sample and how many samples per second were used. There js a TPCMWaveFormat type record, where we define that we use the PCM format, and set the number of channels (mono or stereo), the number of samples per second and a few other parameters. The code The source code for this project is divided into three sec- tions (units), where each unit deals with a discrete funo fiona! part of the program [Figure 1), Unit! deals with the display and contains the visible form. Unst2 holds everything to initialise the form when the program starts, as well as routines to draw on She form and to perform other tasks when the program is run- sfsklci ekfromts - 6/2005 ning. In this unif the background is calculated, the signal is drawn and ihe whale display is redrawn when a repaint is issued (e.g. after moving the window). This unit has already been described when we drew the sine wave. Unil3 deals with ihe collection of data. The MMSystem again appears in the 'Uses line, followed by the definition of a number of routines: Laginii, LogClose, LogStari and Log Stop. These are used to manage the col- lection of data. C4I24S -5 . 11 JiJjJzjUiij ujlarfuiia urn put LiJ-it jpliiy iflij y /ll j j n J This is followed by the declaration of a pair of variables, WavelnHandle and WoveHdr WavelnHandle is a han- dle for the recording device with a type of hWaveln. It is given a value of 0 and is linked in MMSystem to record- ing device 0, which is She sound card, Windows always uses handles to drive the hardware during its use. The handle for making the recording is therefore requested of Windows. The variable WaveFarmat is declared in the routine loglnit, where the format of ihe wave file is defined. Mere we establish that we work with a PCM format, in mono using 1 byte per sample. The value of BitsPerSample then becomes 8. The sample rote Is passed os a parameter to Loglnit, as is o handle to ihe colling procedure. Once these values hove been set up we use the routine WavelnOpen in Query mode to find out if the card sup- ports these settings, if this is not the case it will return an error code. We then generate an error message that shows where in the program the fault occurred. If oil went well then we open the recording device and link it to the handle, LogClose does the opposite. In here we look if the handle has a non-zero value. If that Is the case we reset the device, which frees up the memory blocks in use. We can then dose the device and set the handle to 0. It's in LcgStart where the real work starts To make a recording we have to prepare a data block and place it In the queue. An array with 700 elements of type byte has been defined for inis in Unit] [we will cover this in more detail later an). We then prepare ihe header by filling the fields of Wave- Hdr. The data block that was passed as a parameter to this routine is linked to the header and made ready for use by the WavelnPrepareHeader routine. This links the block to the sound card via the handle we requested ear- lier. The last stage is for fhe linked block to be put in the recording queue by the WavelnAddBuffer routine. We then start recording using the routine WavelnStar t(handle) , The final routine is LogClose. Its task is to stop the record- ing and moke the data block usable by running if through WavelnUnPrepareHeader. We now have ail the loots required to make □ successful recording. Al the bottom of the page is another section: Initialization / i this line is required by Finalization. // if y 0ii leave this line out it will result // in a compiler error Figure J. The oscilloscope pregram is divided into three units. The program The most important port of the program Is Unit! f as this is responsible for creating the display. It is also responsible for the control of all processes and it uses routines from both other Units. This keeps the program well organised, which is particularly important when the project increases in size. Let s start a new project (program) In Delphi: File/New/ Application. We are then greeted by a blank form. A standard unit actually consists of two parts: the Unit itself, which contains ihe pregram code, and a Form where we place all objects used by the program. We also have to reuse Unif2 from the previous project and add the routines for the third unit. The last two units con- tain only code and no objects. For this reason they don't hove an associated Form. We start with Unit 1 where we create the GUI (Graphi- cal User Interface) and we begin with the background of the form. In order to speed up the display we have used a bitmap that is displayed in Its entirety whenever the screen has to be redrawn. We take o TPaintBox (from the System tab of the Component Palette, Figure 2) and put it on fhe Form. (TPaintBox provides o canvas that can be used by appli- cations for browing an.). A PaintBox has the advantage that If draws directly onto ihe canvas of the form, but only In □ restricted area. When you load a Bitmap (Image) onto it, it is put onto the canvas In one go and therefore won't cause any flickering. We have to bear In mind that the coordinates of ihe canvas are [G;0] In the top-left cor- ner. Something similar also applies to the PaintBox, We set its top-left corner to Top-8 and Left=8. We set the Width to 510 pixels and the Height to 41 0 pixels. We now have the PaintBox in the top-left corner [see the example in Figure 3), We then add two buttons of type TButton from the Standard tab, a RadiaGroup (choose one item from several options) from the same tab and o Memo. From the Additional tab we finally add a Val- ueLIsfEdiior (o list of values). When v/e double-click on the onC reate event of the Events tab In the Object Inspector, Delphi will create this procedure and switch to the editor. We then have to enter the following: Procedure TFonnl , FonaCreate (Sender : TObject); a m •* - j Finalization LogClose; Figure 2 . TPaintBox can he round cn the System tab of the Component Palette. 6/200-5 - clcCtrenks 71 Figure 3. All hosts elements for the oscilloscope screen are placed here. (* These- settings c sn also be modified via the Object Inspector’’ J Begin Kith Paintbox 1 Do Begin Vvidth : = 510; Height : = 410; GnPaint : = PBxPaint; Co ritrol Style : = ControiStyle t fcsGpaqua] End; Hith Button! Do Begin Caption : = ’Clear"; OnClick := DgClear End; With Button2 Do Begin Caption ; = 'Sample'; OnClick i= BoSampie End; With RadioGroupl Do Begin Caption 'Tire base [ms/div]'; Columns . V | Items . ComnaText : = '20, 10, 5, 2, 1, 0.5"; Itemlndex := 0 End; Memol . Text ‘Use RECORDING CONTROL to set amplitude' ; ValueListEdifcorL.ColWidths [0] 80; OscBackground { Paintbox! } ; // Calculate bacic- c round End; Figure A. Unit2 one J 3 sfifi nave fo he added to the p reject. The above shows that fa is also possible to enter the set- tings in the program. The result is the same as if they were entered using the Object Inspector [FI 1 ), except that the result is nor visible during the development! This completes the creation of the form. We still have to include Unit2 and Unfa3 f so we can use their internal rou- tines. Unit2 already exists in last month s project, which makes it easy to include again. To do this, we first need to open it. Choose File/Open and select the folder where Unit2 is stored. Youll find that it is loaded into the current environment, but won't yet have been included in the new project. We do this as follows: Select the unit (click in Project Manager} and save it in the directory' or your current project with a right-click {Figure 4). You then have to use Alt+Fl 1 to let Unit! use Unit2. We have now made □ copy of Unit2 by storing fa and including it in the project. If you're not completely dear what you should do, have a look at the accompanying listing, which is available on the wwwJearningdelphunfo and Flekfor Electronics websites. Unfa2 contains everything to do with drawing and the bitmap. In the listing for the onCreate of the form we hove os the last line: Os c Background { Paintboxl } ; // Calculate back- ground This requires the inclusion of Unit2. This routine is port of that unit and it creates the background. The bitmap is cre- ated in the memory. This happens at the very end of Unif2 during the Initialisation [the variable BmpOscBockgr was declared in the Var section of Unit2). Unit Unit2; — — == Interface ===== *) Interface Uses ExtCtrls, Graphics; Var // Contains X-Y screen background BmpOscBackgr : TBitnap; // Buffer containing Y values OacDara : Array [0.^500] Or Integer; // Number of valuer in DalaArray GscDataN : Integer; f* End 1 Initialization BsapQscBackgr := TBitmap . Create ; This varloble is of the TBiimap type, which is defined in Delphi's libraries. The insiruction BmpOscBackgr : = TBitmap . Create creates a bitmap in memory, which can later be written to. This is done by the routine Osc Background ( Paintboxl ) . It mokes sure that the width and height of the bitmap are equal to that of the Paintbox ond it makes the pen [line colour) and brush (fill colour) black (cIBlock is a property within Delphi that refers to the colour black), A rectangle covering the whole bitmap is then drawn using a block pen ond fill colour. The subsequent draw- ing of the lines is the same as in the sine wave project and is described there. 72 eltkiDi dednmjB - 6/2 DOS We now have a useable bitmap available. When the program starts, onCreate will be processed first. After that the screen and its components are drawn. That also applies to the PaintBox. When this is drown we hook info this by calling the PbxPaint routine From the onPainf event. This was linked to the Paintbox during the onCre- ote of the form. PbxPaint in turn calk OscRepaint, a routine in Unif2, which finally puts the bitmap onto the screen and draws the samples, if any. At the start the display shows a dear screen containing the buttons, a rodiobutton section, a memo with a mes- sage, the blank 'scope screen and next to that an empty list. The Functionality still has to be added for the buttons. This is fairly simple for the Clear button (Button]). This is already pointing to the DoClear routine. In this two things happen: the counter for the number of samples is set to zero and the paintbox is made to draw Itself again using Invalidate. This results in a new, dear screen. The second button, Sample', does the real work. This has been linked in onCreate to the procedure DoSam- ple. Procedure TFoxml . DoSample (Sender : TObjeeii); Var SanplaRate : Integer; Begin Button^ .Enabled : = False; Case RadioGroupI.Iteinlndex Of 0 ■ S aiLLoleRafcs = 2500; // I >■ Sai^pleRate = 5000; U 2 Sai?.pleRate = 10000; // J ■*1 <* SampleRate = 25000; u 4 Mi m Bsir.pIeRate - 50000; u Else SampleRate : = 100000; // End; U Initialise sound card 2D ms/Div 10 ms/Div 5 ms/Div 2 ms/Div 1 ms / Di v 0.5 ms/Div rngir.it f Form I . Handle, SanipIeRate ) ; LogSt art ( S WaveD a t a , SiseOf ( Wav eDat a ) ) ; End; The local variable SampleRafe is used to store the value of the selected RadioButton, which lets us choose the sample rate We then coll the routine Loglnii from Unil3, if all went well, this should have been included in the project at the same time os Unif2, otherwise you have to repeat the process for Unit3. Lcglnit has the handle for the Form and the sample rate as parameters. The sound card Is then prepared as described when we covered Unit3. Next, the recording begins. This takes a pointer to the variable WoveDafo and the size of WaveData. The variable WaveData is declared in Unit 1 as a 700-element array of type Byte. This can store 700 values in the range 0 to 255. We decided to record 700 samples because during our tests we found that a lot of noise was present at the start of the recording. For this reason we fake ihe last 500 samples from the 700, which corresponds to ihe 500 pixel width of ihe bitmap. The recording now takes place and when the data block is full it is token oui of the queue and a MMWIMDATA message is generated. This mechanism is part of Windows and Delphi links info It. All of Windows is saturated with messages and events. It is often described as event-driven r a term we've men- tioned previously in ihis course. Programs can also send messages via SendMessage or PostMessage and other programs or another port of the some program can react Figure 5 . ft worksl The signal at ihe input of the sound card is mods visible on the screen. to those. That is what happens here. The Private section of the unit has a routine called MM In- Done, which listens for the MM_W]M_DATA Windows message. Procedure TEoml , HMXnDone (Var Msg : Tmessage); Const SndAdjust. - 65; // Sound card dependent // This value may be changed if necessary Var I : Integer; Begin LogStop ( Msg, LFarai:, ) ; LoaClose; Button2. Enabled True; / / Enable button after re cord ing has finished GscDataK := 0; // Reset display buffer 0 sc Repaint ( Paintboxl ) ; VaiueListEditorl .Strings .Text ; - ' 1 ; For I := 200 To 700 Do Begin OscAddY (Paintbox!, (WaveData [I] - 128} / SndAdjust ) ; VaiueListEditorl . InsertRow (IntToStr (I - 200}, IntToStr (WaveData [I]), True) End End; We first call LogStop, which has a pointer to the data block as its parameter, taken from Msg LPoram, This is part of the message MM_W!M_DATA. The recording is ihen stopped and the data is 'unprepared', or processed ready far use. Next we call LogClose to turn off the sound card. The Sample' button is enabled again. This was disabled when it was clicked so that it can only run once at a time. Next everything is cleared [OscDafaN is set to zero and a repaint is issued which results in a bfonk oscilloscope screen) and then we process elements 200 to 700 From the recorded samples. The routine OscAddY from Unil2 is used to draw each sample. Finally the sample is added to ihe ValueList. The image will be on the screen when all samples have been processed. It has been quite a lot of work, but we now have a func- tional oscilloscope (Figure 5). 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The publication of the Vocoder hardware in the January and February 1 980 issues of E/ek/or magazine must have been awaited with baited breath by many readers as., in good Etek- tor tradition, the Tea! thing was not published until after a solid dose of theory and market infor- mation contained in introduc- tory' articles published in late 1979. it was a time when com- mercial vocoders were simply unaffordable. The Elektor Vocoder Filtered the input signal into two bands, a lowposs of about 600 Hz (A), and a highpass of about 2500 Hz (B), and envelope detectors followed by simple decision logic to the effect that Voiced" was detected if A>8, and unvoiced if Aue for eleven issues) we will publish ihe above plus run a 3cm deep full colour image - e.g. a product shot, a screen shot from your site, a company logo - your choice Places are limited and spaces will go on a strictly first come, first served basis. 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USB INSTRUMENTS h ftp : A www.u s b - i n stru men tsx om USB Instruments specialises in PC based instrumentation products and software such as Oscilloscopes, Data Loggers, Logic Anal ays srs which interface to your PC via USB. VIEWC0M htto . 7, 727, . V [ 8 v« co m .19. c o . u k tel: 020 8471 9338 fax: 020 8552 0946 * Mail Order supplier of: * Integrated Circuits and Components. * Kit and pans for Elektor projects. * Transistors, FETs, Capacitors, Resistors, Crystals, etc and hard to find devices. View com Electronics. 77Upperton Road West. Plaistow, London El 3 9LT V1RTINS TECHNOLOGY http: 'wvtW.virfihs.com ^ PC based virtual instrument for electronics enthusiasts, students and professionals, including full-fledged sound card real time Oscilloscope, Spectrum. Analyzer and Signal Generator, Down loader and by. ELECTRONIC ENTHUSIASTS Only om magazfrte tests its projects and circuits in Its own iai> before publication ELEKTOR ELECTRONIC S THE ELECTRONICS & COMPUTER MAGAZINE Contact: Worldwide Subscription Service Ltd, Unit $ Gibbs Reed Farm, Paihley Road, Tlcehurat TIMS 7 HE Telephone: 01530 2006S7 Fax: 01 580 20061 6 www, e f efc to r~c re ctro n I«. co. u k 6/2005 - elddor elEctienia SI More information on www.eiektor-electronics.co.uk Order I www.elektor-u CD-ROM BESTSELLERS Elektor 2004 This CD-ROM contains alE editorial articles, with the exception of New Products items, published in Elektor Electronics magazine Volume 2004. Using the supplied Acrobat Reader program, articles are presented in the same layout as originally found in the magazine. The DiskMirror utility on this CD-ROM allows your earlier Elektor year volume CD-ROMs (1997-2003) to be added to a large archive on hard disk for fast access and easy reference, A built-in search function allows you to find refe- rences in any article from the archive on hard disk, or from individual year volume CD-ROMs you have available, El 6.25 {USS 28.75) The 3Qx series of Summer Circuit compilation books have been bestsel lers for many years. You can use these books not only for building the circuits described, but also as a treasure trove of ideas or circuit adap- tions for your own experiments. Many rea- ders have found in these books that new approach, new con- cept, or new circuit they were looking for. 307 CIRCUITS I 307 Circuits ISBN 0-905705-62-9 342 pages £18.20 iUSS 37.00) 308 CIRCUITS I I 308 Circuits ISBN 0-905705-66-1 367 pages £18.20 {USS 37.00) Order now using the Order Farm in the Readers Services section in this issue. Audio Collection 2 A unique CD-ROM for the true audio lover, containing no fewer than 75 audio designs from the past five year volumes of Efektor Electronics magazine. The articles on the CD-ROM cover test 8l measurement equipment, amplifiers, digital audio and loud- speaker technology. Highlights include the Crescendo Millennium Edition, Audio-DAC 2000 ; Audio-ADC 2000 and the IR-S/PDIF Transmitter and Receiver Using the included Acrobat Reader you are able to browse the articles on your computer as well as print texts, circuit diagrams and PCB layouts. £12.05 (USS 21.25) Robotics A large collection of data- sheets, software tools, tips, tricks and Internet links to assorted robot constructions and general technical infor- mation. AH aspects of modern robotics are covered, from sensors to motors, mechanical parts to microcontrollers, not forgetting matching program- ming tools and libraries for signal processing, El 2.05 {USS 21.25) Complete your 30x circuits series now! Visit www.elektor-electronics.co.uk for various springtime offers! BESTSELLING E OKS Top-S 308 Circuits ISBN 0-905705-66-1 £18.20 PC-Interfaces under Windows ‘ 1 ISBN 0-905705-65-3 £25.95 Build your own Audio Valve Amplifiers ISBN 0-905705-39-4 £15.55 307 Circuits ISBN 0-905705-62-9 £18,20 Handbook for sound technicians ISBN 0-905705-48-3 £20.75 308 CIRCUITS 302 circuits 302 Circuits ISBN 0-905705-25-4 354 pages £10,35 (USS 21.00) 304 Circuits ISBN 0-905705-34-3 366 pages £13.45 (USS 27.00) § C RCU rs 305 Circuits ISBN 0-905705-36-X 369 pages £15.55 (USS 31.00) Diline at lectroni co.uk Or call Elektor Customer Services on (+44) (0)1580 200657 or email sales@elektor-electronics.co.uk. SC (semiconductor) Analyser 2005 (Elektor Electronics April 2005) * Complete kit oi parts including PCB and programmed controller {without LCD) 030451-71 £ 29.65 / S 55.85 * 'standard’ back-lit LC display 030451-72 £7.25/5 13.65 * Poly-LED display 030451-73 £ 25.50 / S 48.05 Check www.elektor-electronics.co.uk for current pricing of the Electrosmog Tester! GPS Receiver on USB (Elektor Electronics June 2005) £ 62.05 S 116.95 Complete kit with Lassen iQ- receiver, extra long cable and waterproof antenna case 040264-71 LPC210X ARMee Development System (Elektor Electronics April 2005) • Processor board, ready-built and iested 040444-91 £ 25.50/ S 48,05 • Motherboard (bare, without components} 040444-2 £ 11.70/ S 22.05 Temperature Logger (Elektor Electronics June 2005) Complete kit of parts including components, PCB and program- med controller (available from mid May 2005) 030447-71 £ 25.85 / S 48.75 Further products from Elektor Electronics: READY-BUILT PROJECTS £ S CiariTy 300 -W Class-T Amplifier 030217-91 Ampler £- 2 3rd win SMDs pte-fiiea ceres fer Li i L2 34-50 55.70 Flash Microcontroller Starter Kit 01020801 r EEz,-EE££T:’EirCB rd sc-fovars, cafte aiapLe: a reiated artlcfes 69-00 112.50 Gameboy Digital Sampling Oscilloscope (GBDSO) 990032-91 reacy-assfifTtisted boarc in-: . etc PC software and rented aricies 103-00 153.0*0 LPC210X ARMee Development System 040444-31 Processor bcsrcj. read) made ar-d lestea Micro Webserver with MSC1210 Board 030060- 9 \ V ss . • 5 oar a, ready assetr z . e a 044026-91 Netvtc'* E^ens-cn Bc-aro ready-asssT'c'e-d 04402892 C:-= -*d pa^ga 1 030060-91 i G4402891 i relied arte 55: 25-60 75-90 44-50 117-50 48.05 14Z95 53.95 220.35 EVERGREENS £ $ Elektor Electronics Help Disk 9&6022-1 C 5* A rcdcAS .a r a 615 14.45 Elektor Electronics Item Tracer 1985-2003 046003- 1 1 an :c. r -!5 database (tU< W. " 2 Cas v efsln 1 8-15 14.35 Universal Prototyping Boards UP3S-1 PCE 2-45 4.30 UP33-2 2 FCBs 4-10 7.25 UrBS-4 4 PCBs 6-55 11.55 No. 343 JUNE 2005 £ S Electrosmog Tester &5fXX8-1 PC3. rare 5-15 9.75 050C08-91 FC5 read, cl : and tested, check cjnmebsite GPS Receiver on USB 040264-1 PCS. tara 4-30 9.15 04026-4-71 K;tof parts 62-05 116.95 Temperature Logger 030447-1 PCS. bare 3 -ao 7.15 03044 7-tl D : sk prefect so ftwa re 5-20 9.75 030447-41 PiC16FB7t. pregrer r~£-J 5-50 10.35 030447-71 Kl of Parts 25-65 46.75 Tune in to Electrosmog C43424-1-I PCS 3-40 6.45 1 No. 342 MAY 2005 £ Glow Plug Heater 040239-11 Disk STL program 5-20 9.75 040239-41 5T7FLfTE05. pregrairar&d 6-55 12.35 Magnetic Flux Density Meter 040253-11 C 5'v PIC source tora 520 9.75 040258-41 PtCl 6P 876-20 3 P. pfD§ ran. m-ed 16-55 31. 15 Programmer for DOC Model Railway Control 040422-1 PCB 18-60 3505 040422-11 D.sk. ATMega stwres i he* cods 520 9.75 046422^1 AT?.! s§a£51 5-8PL pf cgtamm e d 15-55 31.15 No. 342 APRIL 2005 £ s LPC210X ARMee Development System 0*0444-1 Processor board 470 8.85 040^-2 Mothefboard 11-70 22.05 040444-11 D=« ptc>:s software 520 9,75 SC Analyser 2005 020451-1 PCB 535 10.10 03045M1 Dev prefect softiY arc- 5-20 9.75 030451-41 PIG16FB782S 3?. c ' ci re t t e- j 13-75 2595 No. 341 MARCH 2005 £ s High-End Power Amp 040193-1 PCB 9-65 18,15 0401 93-2 Ifldsater PCB 7495 14.35 040193-3 Sua>p PCB 7m 14.95 Products for older projects (if available) may be found on our website www.elektor-electronics.co.uk home construction = fun and added value market sneak preview More than 100 small circuits/ design tips and weblinks The year 2005 marks the return of the TQQ-plus* articles version or Elektors celebrated and unique Summer Circuits Issue. Between 1988 and 2004 ihs English-language edition of Elektor contained 60-70 small circuits in ihe July/ August Issue, while the remaining 30-40 were published in the December issue. Both issues also contained regu- lar-size articles. New production methods at our interna Ilona I offices now enable us to reinstate a great publication none of our direct competitors has ever managed ta pull off these past 30 years. Here are a Few articles you can look forward to seeing: - PEC PWM Controller - MIDI Interace far SoundBlaster - Project D51 620 - Frequency Meter - 12-volt Regulator - 3-30 MHz Active Antenna - Servo Control Tester - To si Ink Boo s ter/ Splitter - and at least 92 other bits & bobs for your hobby or profession. May . .Sensors June ...... .Environment July/August , .Summer Circuits September . . Jest & Measurement October .... .Security November . . .CAD Software December . . .Optoelectronics OBD-2 Car Diagnostic Tool Our cars ore increasingly crammed with not-so- transparent electronics, enabling the vehicle to leg massive amounts of service information about what's happen- ing in and around it. The OBD-2 standard now implemented an most modem cars allows servicing staff to pick the car's brains not only to obtain interna! fault reports bur also essential data on important parameters like engine cooling, combustion efficiency, gearbox, battery voltage, and so an. Got a laptop PC? Then you, too, can view this information if you build our versatile OBD-2 interface. no not miss Theme Plan for 2005 January .... .Power Supplies February . . . .Wireless March Sound April ...... .Microcontrollers RESERVE YOUR COPY HOW! U?[ subscribers will receive the mcgciins a The July 2005 issue •::« ci w =• cr : Swfcy 25 hr-i 2005 (UK disbibiriicn or y). few days before this dale. Article titles and magazine ffifitenls subject to change. NEWSAGENTS ORDER FORM SHOP SAVE / HOME DELIVERY Please save / deliver one copy of Elektor Electronics magazine for me each month Name: ..... ...... A f S H tp sc * ■ - M - V-t %-jLX tjr 1-3 ■ T r r m mi mi ■mmmmmmmmmmummM t m * , fe § . Post code: Telephone: , . * . . . . . . ♦ * . . Date: ... .... .... Signature: 1 J© lister? iectronics Please cut our or photocopy this form, com- plete details and hand to your newsagent. Elektor Electronics is published on the third Friday of each month, except in July. Distribution S.O.R, by Seymour (NS). Index of Advertisers AiJgooti Tectinc-ogy, Showcase gtHjrftecrin&jgjLczm .............. .80 AudiOUfprBSS, Showcase ...... >vv/,v andnyprBBs.LQn ? 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Showcase aw. fain ■ka.cL~ ..... .80 [IP Electronics Limited, Showcase AAvsilpelBctrmics-coni .80 tpeva Limned, Showcase . .......... .AvAY.tpcYa.anTj JO Jaycsr Eieetrumes jrjvmjayca^/acZnM^.caiiA , .2 JLB EteCsTOnx-S: Showcase .......... w-w, i.Luk-nL'arJus.cGfn 80 Korn card. Sbo wcase .... ovvwv. ■ imcn-d.cn-- JO Uboenier ........ .ww. {ibcenierxv- uk JO London Sectromcs Co- &g&. Showcase _ y t v,wJBn.crg.nr 80 Matrix Multimedia Ltd ........ tra wjnstrjiniiiV me .... 49 Microchip ...... yrAwJtuy.fi ficmtJupxBm ....... .23 MQP Electronics. Showcase ... _ mw.mqp£lE£lrGnic$-cajik . . . New Wave Concepts, Showcase ■ . f : : ?<:? con Ftumber Gee Systems ...... .iKViKnumherooe.conj Krnve Networks ... _ _ ..w v: rgunmial : -? cc ~ PCB Wo ltd. Showcase ....... .',v 'AY..rztn zr; : Z nzg -J ....... FrffZX. Showcase ■. vc-vr n/zneo . - PiCtJos. Showcase ,A'A',v.sttzz. cq~ Rco WiW.picotezhtxim . Quasar ElecUDAics. Showcase Awcuas-refsci : -zs.Dur- . . RD Research ........ y,vr.\ nr -~z-: ! 7a--.-= - Robot Electronics. Showcase . jAvAvrutof-sIsnir-: - -oi.cn..:: . Showcase ... . ...... To in] Telematics awa iota '^{eiefuslicscom . . . . LTnrarnds, Sho wcase . iyavc_ ■■eTos. nn-.t.-. ....... University ot M anchester a-aw sae j... m USB Instruments, Showcase a . .. ,v .nsi}- sir v? : " tj . . , Vi ewe am. Showcase , e-i . (9. com Virtins Technotogy Showcase . .ri.is.cc~ .......01 ....... 81 .53 .32 ...... .fit 81 ...... .81 . ... . 3 . 53 76, 81 .41 at ...ao 3 ai .7 ai .... s .81 ...... .81 .81 fldverlisino space far the i ssue of 15 August 2005 may be reserved nol later than 19 July 2005 with Huson International Merfia— Cambridge House - Go g mom Lana - Chertsey , Surrey KT16 9AP - England - Telephone 01932 564 999 - Fax 01932 564993 - e - mail : : ^ r ~ ~ ~ ~ ~~ : r : to whom an correspondence , copy instructions end artwork should he addressed. 34 tfcklare'&ttrenks-i/200'5 P'^iiss supply the follow no For PC Bs. from panel foils, EPROMs RALs. GALs. microcontrollers asi/j diskettes, siaie the part number anti description: for books, stale toe full title: for photocopies of articles. state full name of article and month and year of publication. PLEASE USE BLOCK CAPITALS. 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Our account number is 3512 5225, Sorting Code 60-22-15. IBAN code: GB4Q NWB KQ 022 15 3512 5225 BIG code: NWB KGB 2L COMPONENTS Components for projects appearing in Eiektor Electronics are usually available from certain advertisers in this magazine. If difficulties in the supply Ql components are envisaged, a source will normally be advised in the article. Note, however, that the saurcore given is (are) not exclusive. TERMS OF BUSINESS Delivery Although ever/ error: will be made io dispatch your cr Jer within 2-3 weeks from receipt of your iraslrvstions, we rev not guarantee mis rime scale for ab orders Returns FairiL guess or goods sen: n error may ::a relumed for repfgcemeT or r ef jnd. but not before c-L-la nrng our consent A i gaods returned shou/J be packed securely in a padded bag or hex. endo-sino a covering ret ter stating the oispa-:: note cumber. if the goods are returrreif because a mistake on our pari, ;.e will refur.:: riie return oQsrege. 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Subscription rates and conditions may be found at the back of this issue. • Berkeley SPICE3F5 simulator with custom extensions for true mixed mode and interactive simulation. • 6 virtual instruments and 14 graph based analysis types. • 6000 models including TTL, CMOS and PLD digital parts. • Fully compatible with manufacturers' SPiCE models. • Textual library part search. • User defined keyboard map. • CADCAM output to ZIP file. • Bitmap import function. • Truetype fonts on PCBs. • Enhanced printer output. Mixed Mode SPICE Circuit Simulation Schematic & PCB Layout • Powerful & flexible schematic capture. • Auto-component placement and rip-up/retry PCB routing, • Polygonal gridless ground planes. • Libraries of over 8000 schematic and 1000 PCB parts. • Bill of materials, DRC reports and much more. Proteus VSM - Co-simulation and debugging for popular Micro-controllers www. labeenter. co. uh info @iabcenter. co. uk Supports PIC, AVR, 8051, and BASIC STAMP micro-controllers. Co-simulate target firmware with your hardware design. Includes interactive peripheral models for LED and LCD displays, switches, keypads, virtual terminal and much, much more. Compatible with popular compilers and assemblers from Microchip, Crownhill, IAR, Keil, and others.