k The leaders in PIC development ♦ ♦ ♦ ♦ Alt you need to get started with PIC Industry standard/quality board Open the box and get coding Available with C compiler or use our PicScript to write programs using simple commands... NO ASSEMBLER, NO COMPILER, JUST WRITE AND RUN AUTOMATION SCRIPTABILITY PicDev Board with PicScript PicDev Board with C Compiler £99.00 (plus p+p) £165.00 (plus p+p) This is a complete development suite This is a complete development suite for for the novice or non programmer. the more advanced programmer. It is shipped with: | Cfj! It is shipped with: • PicDev Board . PicDev Board • PicShell and PicScript software • PicShell and PicScript software • Breakout, board • C compiler • Cables • Breakout board • Example scripts • Cables . Example scripts * [ C D 1 B ot h i terns require J Q q pf p ■ PC with serial port available Power supply adapter www.p agin, c 0*11 k sales® pagm.co.uk Tel: -44 (0)1792 S91927 Polarising colours As I write this, our UK subscribers have had their April 2004 issue far about a week, and the magazine has been on sale in UK newsstands for just three days. So far, two dozen or so emails have been received on our "feedback' address in response to the rather dramatic layout changes v/e made to the magazine. I expect a good deal more feedback to arrive once the magazine reaches our overseas readers on subscription or via newsstands, distributors and bookshops all over [he world. Although I've been privi- leged to see most of the layout changes evolve during the page layout phase, I must admit that nothing heats the real thing: a printed magazine on your desk. If the feedback received so far is anything to go by, it is not just proof that there's no accounting for taste, but also a fairly accurate reflection of our own diverse opinions on the new layout, which has been the subject of hot debates these past few weeks. Most readers emailed brief comments, but o few analysed the new magazine in such derail v/e had to use a typography manual to make sense of it all. We were glad to see that a small majority applauds the new layout: Elektor has always kept up with times and the new format is no exception — A picture tells a thousand words — Makes competitive mags look decidedly drab and doted in comparison — Good to see that Elektor never rests on its laure/s — / Me the articles and presentation — Component overlays in green underline the quality of your PCBs which is second to none. Of course we also met with disapproval: Your use of colours degrades serious articles — The paper is too shiny — What's the connection between cigars and electronics ? — tf the new layout is this year's April spoof I'm not amused — Not so bad , but I still like the old format better — Date isn't easy to read on the cover. In general, you seem to approve of the new layout, although the new logo and the abundant use of colours is often queried or described as something to get used to. We will carefully evaluate oil feedback and make adjustments over the coming Few months. For example, many of you like to copy circuit diagrams and parts lists on paper for use on the workbench and admittedly that has become difficult owing to the use of colours. Our mission however, is to make the magazine attractive la a wider audience, not just by enhancing the technical contents, but also by proving that electronics is an exciting field to work in. Jan Suiting, Editor. elektor electronics Volume 30, Number 332, May 2004 ISSN 0268/45 1 9 Elektor Electronics aims at inspiring people to master elec- tronics at any personal level by presenting con sc ruction proj- ects and spotting developments in electronics and informa- tion cechnology. Efe&tor Hhameks is produced ar«d punched by BskSor Becfroracs (ftjbfehiig). RO- Box J90, T trfaidfee TN5 7WY! &$ar*L TMi 044} (0)1 580 200657. fee (-5-44) £0)1580 2006$ 6- Emai The magazMie e avafeibAe from newsagents. bookshops ^rtd efedronks n^sl out- lets. : _ Bettor Beetroots is pubfehad 1 1 times s ysr with « doufefe is&je for Jiiy St August _ : : ra.-~e - : Ge — l .it: - « :c - and e _ it. - 3 aa re _ : . : j :-r - — r : - Together with frarechsed editions the m^zihe is on ortuD tKjfi in more then 50 uXtfitrieS- Iniernaiional Editor ;n :i- m, : -i” Merer*; Editor: :-zr B^r-z = = - Irtiernatjona I editorial staff: Hi: ■ W--;-- Da : Lire r c " znsz vrempelsi jer. 3 _■ -Hz-dendtyf : f ./in - Design staff: Xa/eJ ',7a! ns* -- “ . Tc- r Desbsrts. rbii Glossers. L .. : _l rrn-. ere : . zb : : :: : •: £~- : - : - Editorial 5 Ercrctiriat — - ■ z — - -- t- - -a' .1 : Graphic dsiign DTP: 7: ■ G_ *£fs. Gjc Dos M anaging Director PubtishEr: "i. SmH.s i Circulation Control: ' ‘ v:~f' Hoe ' Subscriptions Wfcuidwide S o fa ^cnpD on Service ltd. . Unit 4, " i _ i ?eea Farm Pssr; e . Re: : T n _ '.£ “ - _ Er g sr : TeHpbooe D t5£v 203657 r i< I EzZ ZZZi-i- Em,i Lt" :: _■ &ite$ tuod terms are on the 5ri»aipbcn Order Form Head Office: 5eg RO. Bex J- »_-6 73— "3 zee-. - - ve'rf sr z. Telephone: (+3 1)^64389444. Fax: -31J46 4jj : - Dlsni birtion: SeyiPtw, 86 iStewman Street* London Wl P 3LD, Er^rxf UK AdTEJtliing r.z- :i : 3 De-ice - : ■;= C' -i - r&rr. GL5<} J?c. . TetetttcnE { -44 0 242 510760. 0 2-2 226626 Errs: r : i - • '4 :: . --.t-- ■ ce rali= i r : i,c .± - c cn i_“ ■ In^matisna] Advertising 1 ■. Ci :r "zv : ■ ’ess as H5=d I “ i., - if : _i 2 - £ nue-i ir-: gvsfe&fe or- Copyright notice The rb mit*. desoiaed h tm rregasne are for domesic ise only. AB drawing, pheao- gn^ihs, printed snost board feyofts artkfe texs peiblfehed in Ihe ecfeoftd sertioo of the n\=£=z>-:- ire S=-gm=r*L h:, ire me* net be c-t - r - -- : : -- - : _i - £ : ::: — : -■ : v ' ■ - : e v si part widioUt prior wttoee permesez bom me FU-- S-jch wrffiten permission - .r: .tzc i- sbEired : i - pen z - r : r~_ llm : n e rer^-.n - - of ir- / nsnre. ”i:e - : rr.iy =.■ r ^ ■ :_ n de. :ei comports sic :ii-f re: r. ; tv :e' : - - - = .l =■ = tfcei i::ei: r eir-"'' '=' fe. "£:c r..m paients) _■ other prc-tec&cr — - -■ e: : ■ : z - - — - " =; ' . -i : i ■ " n : " :: - lie z :: .--t. i : n i" I zn~ ~~~ ~ -l iz^.ztj De Dz-ire." Z7z-rzfi. gjareraes io re^m et ■ ::-c t:- tr:£-m c S^gmcpL b,v. 2C04 Pc red re 14 etc a ri an d 5 I lOOI-ehkttiukrircniB 3 30 First Steps Stepper motor ABC with control board 10 Design a* your own 1C and burn it into a CPLD 1 r~ Tf Vi 227 08 / Kj r ■ : 11 ill 24 Wind Speed & Direction Meter wiih a clever sensor High-end Preamp (2) Construction and software-customising M Project (+ Solved The solution to our April spoof elektor electronics Contents VOLUME 30 MAY 2004 * no. 332 m Sensors for Humans Sensor technology at MIT if Wireless Tyre Pressure Monitoring New sensors For your safety Construction Projects 10 Design your own IC 16 High-end Preamp (2) 24 Wind Speed & Direction Meter 30 First Steps 56 kitchen fable resounding truth 36 Project c+ Solved 39 review copy 44 Sensors go Systematic 50 Sensors for Humans 60 start here combi-gate oscillator IC - global power supply - self-tapping screws - pressing mutters with flolcable connectors 64 Software? Well do that ourselves! 69 inside out wireless tyre pressure monitoring 3 Editorial & Colophon 6 News & New Products 72 Mailbox 77 Readers Services 8 1 PCB layouts 82 Sneak Preview 82 Index of Advertisers www.eliktor-uectrohics.co.uk news & Pew products FASTER & LOW- VOLTAGE READY MulfiMediaCard (MMC) specification version 4.0 is released Version 4.0 of fhe MultiMediaC- □rd specification, offering wider bus width, dual voltage opera- iron and the highest transfer speeds available, was recently introduced by ihe MultiMediaC- ord Association [MMCA], a stan- dards organization that pro* motes the worldwide adoption of MultiMediaCards (MlMCs). The new r feature-rich version 4.0 specification represents a major expansion of the MultiMedioC- ard standard, opening new lev- els of sophistication and market- ing opportunities to the digital imaging and mobile phone industries. To ensure smooth transition from previous versions of the MMC standards, the new specification defines backward compatibility paths for both legacy cards and host devices that accept MultiMe- diaCords. The specification is provided to all MMC A members. Three key features of the new specification are: Wider bus-width: The new multi- ple (x 1 bit, x4 bit and x8 bit] bus-width feature now allows for host design flexibility and higher data transfer bandwidth at a given dock speed, to accommo- date the more data intensive content in cell phones and digi- tal cameras. Higher clock frequency: Extend- ing the maximum clock frequen- cies from 20 MHz to 26 MHz and 52 MHz allows higher data transfer rate and better compat- ibility to mobile phone architec- tural requirements. Operating ot 52 MHz in x8 bit mode, data can be transferred at up to 52 Mbyte/ sec. a 2 D-fold improve- ment from the previous stan- dards. This is the highest dota transfer rate of all flosh memory card farm factors available today. Duo! voltage operation: The MMC specification is the first smalt farm factor memory card standards to define both 3.3 V and IT 8 V operations. 1.8 V compatibility is especially impor- tant tor the new generations of cel! phones and small mobile devices that operate at lower voltages for lower power con- sumption. Definition of the specification is the culmination or the work and major contributions from Nokia, Hewlett Packard, Renesos Tech- nology Samsung Electronics, Infineon Technologies Flash, Micron Technology, SanDisk, and other member companies in the Association. It was approved and adopted by the full body of the MMCA Execu- tive Membership. VAYW.mtTico.org Fluxes for Flip Chip Bonding Designed for use in both air and nitrogen reflow and halide free. Indium Flip Chip Bonding Fluxes can be obtained individually or as part of a research kit, avail* able in two series, IT and HT. Indium Series LT is for high per- formance eutectic soldering such os 5n63Pb37 and 5n62Pb36Ag2. Series HT ts designed far high melting point solder alloys, for example Pb90Snl 0 and Pb95Sn5. Each series consists of fluxes with different viscosities and specifications depending on the processing conditions. For exam- ple, a flux 'with low or medium viscosity can be sprayed onto substrates followed by flip chip placement. Fluxes can also be dispensed onto the side of ihe flip chip, allowing the flux to work across the bottom of the chip. Fluxes with higher viscosities can be printed onto the pads or the chip can be dipped into the flux prior to placement. Both series offer superior wetting ability, wide re Row temperature ranges and extremely law to no residue for no-clean applica- tions. Custom fluxes con also be pro- vided to meet specific require- ments. 04 ? 1 j: - Indium Corporation of Europe, Tel: +44 (0) 1 908 580400, 9 Newmarket Court, Kingston, fax: +44 (0) 1 908 5 804 T 1. Milton Keynes MK1 0 QAG. Internet: www.mdium.com dektor eletfrcnio - 5/2004 PCB-mounfed Current Transducers LEM has introduced the HAIS series or PCB-mounted current measuring transducers that oper- ate from a single -3-5V supply. Permanent available rms ratings are 50, 100, 150, 200 and 400 A, wiih a measuring span of up fo -3 x IPN. The Irons- ducer aperture accepts bus bars □ s targe as 8x1 5mm, in a very compact design a! only 33x29x1 4mm. The heart or the HAIS series is a LEM ASIC, which provides a number of performance improve- ments, in particular an extended operaiing temperature range f- 40 to + B5"C) compared to tra- ditional discrete technology. With the standard HAIS, the interna! reference voltage or the ASIC is used fo provide a fixed output offset of -2.5V. This volt- age reference is also mode available on on external pin to alloy/ it to be fed fa the refer- ence of an converter or a . The SP1 version provides a ratiomet- ric output offset Vc/2 when the Ref pin is not used. The can also apply me system s voltage reference (between ' 7 V) to in, in which case the out- put offset is equal to the external refer- ence. This mode ollav/s reference thermal drift to be cancelled. An optional bus bar models) is available for nominal ratings of 50 A and inn -E marked and conforming to the EN 50178 standard, transducers are designed fai industrial applications. LEM Components o Iters o fi ve-year warranty for each transducer. ,0-Cj3 I JIM HEM! Ltd, I Fenkefh Place, V/esf PImbo, Skebiersdole, Imrn.hircWHS 9QX, IBM +44 [0)1695 720777. E-Mdfc kvvi@lem.com. Infemeh VAVwJem.com Low Pincount PIC Micros The PIC12F683, PIC16F684 and PIC16F688 microcontrollers offer up to 7 r l 68 byEes of Flash program memory, making use of Microchip's PMOS Electrically Erasable Cell (PEEC) Flash tech- nology offering one million erase/ write cycle endurance. The devices also include on- board EE PROM Data Memory, and offer several peripheral options with integrated nano Watt technology. Standard analogue peripherals include single or duo! comparators, and up to 8 channels of 1 0-bii A/D. In addition, they support a wide operating voltage of 2.0 - 5.5 volts. ThePIC12F683 features a stan- dard Capture/Compare/P WM module, while the PIC16F684 features an Enhanced C a ptu r e/C o m a a re / P WM m od- u!e with deadband control, up fa 4 outputs ond emergency shut- down. The FIC16F688 featu res an EUSART peripheral to suppori R5232/485-lype communica- tions and the UN protocol. Microchip s existing 8- and 14* pin Flash devices already offer nano Watt technology features such as nanoAmp standby cur- rent, fast-startup internal oscilla- tor, and Brownout defection for reliable operation. These new devices offer additional power- management features such as so ftwa re-selectable clock speed, s a ftw a re-c on tro II e d B rown-o u t detection, u f tra To w-p a v/e r wakeup on change, a lower- power Real Time Clock timer ond an extended Watchdog Timer. These provide maximum flexibility in managing power consumption, without sacrificing system reliability. The three new PIC microcon- trollers come in small-footprint 8- pin SOIC and 14-pin TSSOP packages. The devices are sup- ported by Microchip s develop- ment tools,. Including the PlCkit™ 1 Flash Starter Kit, MPLA0® IDE (Integrated Development Environ- ment), and me MPLAB ICO 2 (In- Circuit Debugger). Ariiona Microchip Technology UtL, Microchip House, 505 fksdde Rood, Y/Innersh Triangle, Y/okltigham R64I 5TU. Tel (+44) (0)118 921 5858. F QX (+44) (0)1189215835. www, miCTQchip.com . (047051-3) 5/2004-ddctsr Eledranks 7 news & new products SMART Ships One-Mi Blionth Bluetooth Module SMART Modular Technologies, Inc. recently shipped its one-mlk lionfh Bluetooth module since January 2003. an important milestone that demonstrates the relative success of the Bluetooth technology in the short-range wireless module market. SMARTs Bluetooth modules have been designed into PC, PDA, medico!, consumer and industrial products. SMARTS communication prod- ucts division jCPD) has devel- oped a broad line of Bluetooth- enabled modules and devices to support OEM/ODM designs or at! stages of the development cycle. SMARTS current product and service portfolio includes USB ond R5-232 Bluetooth adapters, mini-modules and developer boards, as well as complete product lifecycle sup- port built with next generation technology. According to a recent report from In-Stat MDR titled Bluetooth 2003: Are PMGs Another Dri- ver, aver three million note books vdth Bluetooth are forecasted to ship in 2003, which indicates a significant increase from the pre- vious year. SMART Modular Technologies, Inc., P0 Box 1 757, Fremont, CA 94533. Tel. (+1) 510-623-1231, fox (+1)51 0-623-1434, intern eft wwwj s m art m odulartedu tom • “03 ■ Protection Against Solder Fume n technology used in these uniis ihat pe< ensures le □ re Pur ex International, Purex House, Farfield Park, Mmwm, Rotherham ■N tecled against developing med- ical conditions such as occupa- tional asthma. S63 5DB. Tel. +44 (0)1709 763000, Fox +44 (0)1709 763001 , Internet: wvAv.purexlld.co.uk * A ttj,* -= •• ■r * % ¥ » i To combat the health and safety issues surrounding solder fume, Purex International have devel- oped a new tip extraction and filtration unit for use by people who solder by hand* These units are designed ra remove hazardous fumes from up to 10 soldering irons and with low capital and running costs they are ideal for schools and colleges home workers, rework, repair and prototyping work, light production soldering and hobby workshops. To protect the operator from haz- % * / ordous material a powerful vac- uum blower draws the solder fume directly from the tip of the soldering Iron ond then through a sub-micronic filter* High quality HEPA media is used in ihe filters to remove hazardous particles from the air stream, capturing 99*99/ % of particles at =0.3 pm and 95% of =0.01 pm In size. A large chemical layer in the filter then adsorbs toxic gas before dean air is returned to the workplace. The combination of excellent build quality, materials ond filter & clekler eletifcr'ts - 5/2Q04 Nano watt PIC Microcontrollers Microchip's new PIC 1 6f7 37/7 47/767/777 microcontrollers offer up to 8K words of reprogrammable Flash program memory and 368 bytes of RAM, They con operate at up ro 5 MIPS at 20 MHz. In addition, they feature three enhanced nanoWan Technology modes that allow total contra! of system power consumption. These new devices are socket- compatible with existing PIC© microcontrollers, and yet con offer up to 10x power reduction using the new power manage- ment features with minimal addi- tional software. The family also offers three Pulse-Width Modulation (PWM) modules with safe shutdown fea- iures for 3-phase motor control, 1 Ckbit Analag-to-Digital Conver- sion (A DC | and Real Time Clock functionality. Additional nano Watt Technology features include: an on-chip multi-fre- quency oscillator operating at up to 6MHz (with rast startup], flexible clack switching, 2-speed startup from reset, □ fail-safe dock monitor and a low-current programmable watchdog timer for safety critical applications. Serial interfaces include a USART module, SPP 1 ' and 12©™. These new PIC microcontrollers come In 28- and 44-pin QFN, SOIC, SDIP, SSOP PDIF and TQFP packages. The devices ore supported by Microchip s development tools, including MPLAB© IDE (Integrated Devel- opment Environment), the MPLAB [CD 2 (In-Circuit Debug- ger), the MPLAB ICE 2000 (In- Circuit Emulator), the PRO MATE© II modular device pro- grammer, and the PIC START© Plus low-cost programmer. i -5 Ariions Microchip Technology Lti, Microchip House, 505 Eksdde Road, Winnersh Triangle, Wokingham RG4 1 SHIM (+44)(0)11892I 5858. Fax (+44) (0)118 921 5835. wvAV.mTcrochIp.com . WIRELESS AND AIRBORNE Telemetry system helps reproduce Wright flyer A century after Ohio brothers Orville ana Wilbur Wright first flew fheir Wright Flyer at Kitty Hawk. North Carolina, Ohioans again played a major role in the history of Bight. The Sensotec Test and Measurement business of Honeywell Sensing and Con- trol provided instrumentation that helped test the reproduction plane built by The Wright Expe- rience of Warrenton, Virginia, for the Experimental Aircraft Association. Other teams have simply con- structed o plane similar to the Wright Flyer. But the Wright Experience flight engineers examined the original plane (now in the Smithsonian Institu- tion) and used nates left behind by the Wright Brothers, com- puter simulations, and air-runnel testing to build the world's most accurate reproduction. Honeywell provided an essentia! piece of the highly reliable test and measurement instrumenta- tion that helped the team suc- ceed. The firm's wireless teleme- try system enabled the flight engineers to measure how effi- ciently the plane s engine wos able to turn its propellers. The Wrights' propeller design enabled them to get the maxi- mum possible power from their small engine and was the key factor that made iheir plane fly in 1903. Modern engineers hove found the Wrights' design to be very nearly as efficient as that now used In modem air- craft. Although weather prevented the reproduction model from becoming airborne at the December 1 7, 2003, Centen- nial Celebration attended by President Bush the little 605- pound plane did actually fly on the earlier test flights. t- For more information about the :76- i Wright Flyer, visit www. wrlg htex peri e nc e. com . Honeywell Sensotep 2080 Arlingate Lone, Columbus, Ohio 43228, USA 5 20 “4 - Efrklor elsctrorocs 9 Prototyping with CPLDs (part 1 ) Designing a circuit always involves several somewhat disagreeable tasks, such as soldering, looking up the pinouts of ICs and laying out a maze of tracks on a printed circuit board. All of this is now no longer necessary, since you can program your own digital circuit in a CPLD. 1 ^ ekfctor etottk* - 5/2QQ4 Experimenter's b features CPLD version: EPM7128 JTAG interface all I/O lines available via box headers supplementary I/O can be disabled using jumpers 7-segment display 8 LEDs - 8 switches with debouncing circuitry - on-board supply voltage regulator - Eurocard format - extensive development environment available free of charge from Altera The CPLD experimenter's board pre- sented here makes an excellent start- ing point for sitting down at the key- board and directly designing your own circuit. For most people, experimenting with digital logic brings to mind an image of an experimenter’s board stuffed full of IGs interconnected by countless wires. Anyone who has ever worked in this manner knows that such an arrangement usually takes many hours to construct P not to mention the modifications that have to be made if the circuit does not work properly right off the bat. A CPLD can be used to replace such a ‘forest' of digital logic ICs. CPLD ICs contain a large number of digital building blocks that can be intercon- nected in a vride variety of manners simply by programming. Such an IC can actually be considered to be the modern version of an experimenters boaid full of ICs. Instead of soldering all sorts of little wires in place, designers and experi- menters can now conveniently design circuits while seated in front of a PC, and then program their latest designs into the IC in a trice. This clearly saves a lot of time, and it has the advantage that it isn't neces- sary to document modifications after- wards on paper or in some other man- ner. This is because the circuit is drawn (or described, as discussed later on) on the computer, after which the PC computes how the design must ultimately be realised in the IC. CPLD organisation Our experimenter’s board is based on the Altera MAX7000 family of CPLDs. The organisation of these CPLDs is shown in Figure 1. At the top of the drawing you can see the four special ,’lPut c-z" : 7 _ r PrA • Ccnrz. E&tx - - -u Fig ure 1 . Ove ro /I a rg on /. s a ti on of A iAXJOQ 0 L PIDs. ■_ l! C JL Li i-C.Er !_OTC Array Figure 2. The structure of c ALA X70CQ macroce!!. S/2004 - il jVfor aferlrcnio 11 ■Jilt | 4 p:|] \_VS_ ift fl g "S ft 1ft 1ft T - =■ \-vvy_\vv\- a is la L rr vS-S-S-N-S-S^- d :a ;a 2 a : a 2 -a ^ 15 ® ■_ j. J = L “ C 3 jTi )=: ,3 ■& T*r ’» |T"C ^ 6666666 6 6 6 TC 5* f5 ■H z r^- 1 n ” J- = n s w, a -% - S- V V 5 r^-i J2 S ^ *• "W V -i V < 1 i ! U ■ L < 1 p s |i I? |> [s Is rr i - = = — m f := = j. 2 « Jj* --i. e r =: ; r - — 3 ’■ “ ■3 = 2 ill I = V 5 0 iZ h® I 1 — 1 — 1 — 1 1 — I — 1 1 V V V V V V V V » 0 (I Q 0 0 0 0 0 0 O 0 0 0 0 Z -rr “ i” ti ■>_ a v u \\\\\_ 5 s i 2 “ 6666666606 9000000? P_ ^ = = i .=- : = : = r ZZzz ,, -f - i !u ■ = rj f «n, o j n ■— - - ■» L^ZZ/ TTTTWT E E E ; P p * • . • . i .r ,c 13 .a i- ■ ! i 'J @2 6666666666 C‘ O G C C C D p C 0 »i* _ o >: T-: 5 - - “ r— i— 3 irr 2 £- i; ~ 1 C Z Z “3 ’ z W [v l”“ ' ■ B,k ** r«- 1 * !,c ■ //// / ^ L 3 jJ ™ M - 5* j.4 i ” Figure 3. Besides the CPLD, the circuit of the experimenters hoard includes several indicators (D1-D8 & LD1} and switches wtih hardware debouncing (51-58 & IC5-IC8). 12 deVl# ^{Erenlu - 5/200-1 COMPONENTS LIST Resistors: Rl.R10 f R20 .R23.R26* lOkD R2£9,R25 = Ikn R1 1-RIB - 6 8CQ R19 R24 = 10kQ 8-v.oy SIL array R21 = lOOkO R22 - IGOU Capacitors: Cl, Cl 2 - iGjiF 16V radial C2 = IOOliF 16V radial C3-C6 r CflCl 1 Cl 5-C20 = lOOnF C7 = 22uf 16V radial C]3,CU - 22pF Semiconductors: Dl-DS r 0IO = LED, red, low current D9 - 1N4GD1 LD1 = 7-seament-displQy, common anode, e.a., HD fl 3 I O) ' ICI = EPM7128SLC84-10ar EPM71 28SLC84-1 5 1C2 - 7805 IC3JC4.IC9 = 74HCT563 1C5-IC8 = 74HCT74 5mm K2 - 1 0-way baxheader K3-K6 - 20- way box header SI -58 = slide switch, 1 changeover contacts, e g., AFE :M A2 XI = 4,000MHz quartz crystal 84-way PLCC socket PCB, order code 030385-1 Miscellaneous: JPI JP 2 = 2 -way header with jumper K 1 = 2 ‘Woy PCB terminal block lead pitch Figure 4 * Component layout of the double-sided through- pi a ted PCB for the experimenter's board . Tne associated copper track layouts cart be retrieved tram the Free Downloads section of our website (file no . 03U385- l.zip). inputs for the CPLD. These signals are connected to the macrocells in the IC in a manner that allows them to opti- mally perform their intended functions (CLK, QE, and CLEAR). The inputs and outputs of the various macro cells are connected to each other as desired via the Progr am m e hie inter- connect Array (PI A), There are also inputs and outputs that are connected to the various I/O Control Blocks. Their job is to connect the internal signals to the 10 pins of the IC. Four Logic Array Blocks (LABs) are also shown in Figure 1. These LABs contain the actual programmable logic. Each LAB consists of 18 macro cells. Various CPLD versions are available in the MAX7000 family. Toe type number of the IC indicates how many macro- cells are present in the 1C. Macroceffs The actual programmable logic is located in the macro cells. The struc- ture of a macrocell is shown in Fig- ure 2. Each macrocell has its own Logic Array, which consists of 36 inputs connected using a program- mable AND function. Four of these AND functions are combined into a single signal in the Product. Term Select Matrix. The capabilities of the IC can be increased by further increasing the number of product terms. If you want to know more about this, we recommend reading the data sheet for these CPLDs. 5/2004 - e! defer efcdicrits 13 Figure 5. This photo of on assembled prototype of the circuit board shows that the switches can be fitted as desired; in this case five are fitted . The signs] generated by the combine - tioo of AMD and OR operations then arrives at the register and its surround- ing logic. This portion can be used as a D-tvpe, T-type + JK or SR flip-flop, or it can be completely bypassed if no regis- ter is needed Fortunately, as designers we do not have to be overly concerned about exactly how our designs can be imple- mented in this manner. This is where the (free) software comes to our aid But before we delve into the software, let's First take a closer look at the experimenter's board. Exp ©f im ess f@r's board Our experimenter’s board has a rea- sonably simple design. Nevertheless, it has more than enough I/O for per- forming our initial experiments with CFLDs. Naturally all of the relevant pins of the CPLD are brought out via several connectors, to allow external hardware to work together with the board afterwards. The schematic diagram, which is shown in Figure 3, is fairly simple. The supply voltage of approximately 3 V DG is applied to connector Kl. 1C 2 and its surrounding components provide the 5-V operating voltage for the entire cir- cuit. LED Dll and R25 provide a ’power on’ indication. The CPLD is shown in the schematic diagram as ICL The JTAG program- ming interface is brought out via K2. The pin layout of this connector is com- patible with the Alters ByteBlaster, which means it is also compatible with the Elector Electronics Parailel-to- JTAG interface (see the September 2002 issue, page 34). The reset circuit is formed by RC network R1/G12. Finally, an oscillator is implemented using R21, R22 T C13, C14 and XL The manner in which these components can be used together with the CPLD to make an oscillator is described later on in the examples. A certain amount of simple I/O is indispensable on every experi- menter's board, IC3 is a buffer that boosts several signals from the CPLD and uses them to drive LEDs Dl-DS. 104 performs a similar function for driving a 7- segment display. If these I/O functions are not desired, they can be decoupled from the CPLD by removing jump er JP 1 , We decided to use eight switches for the inputs. To make your initial experi- menting relatively easy these eight switches (Sl-SB) are equipped with a debouncer circuit. This function is pro- vided by IC5-ICB. These inputs are connected to the CPLD via IC9, but here again this part of the circuit can be decoupled from the CPLD. In this case, JP2 is responsible for coupling the signals to the CPLD. Finally, connectors K3 through K5 make all relevant CPLD signals available to the outside world. Construction The double-sided printed circuit board shown in Figure 4 is generously dimen- sioned in order to keep everything readily accessible. All connectors axe placed a: the edge of the circuit board. Fitting th= components to the circuit board should not present any difficul- ties. Anyone who is interested in CPLD s vrill certainly have already built other circuit boards. 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Make sure that the bevelled cor- ner of the PLCC socket is correctly positioned on the circuit board (refer to the component overlay), since it can also be fitted incorrectly into the holes in the circuit board. Incidentally, the CPLD fits into the socket in only one orientation. Portions of the circuit that are not used can be disconnected from the CPLD by means of jumpers JP1 and JP2. Natu- rally, you can also simply omit the unneeded components. For instance, 1C4 along with LD1 and R11-R18 can be omitted if the 7-segment display is not necessary. The same holds true for ICS together with D1-D8 and R2-R9 if you don't need any LED indicators. As for the switches, you only need to hi the ones that are needed for the initial experiments. The voltage regulator (IC 2) is fitted flat against the board and secured using a small screw and nut. An additional heat sink is not necessary, at least as long as any additional hardware con- nected to the board does not draw too much current. The supply voltage can be provided by a mains adapter that supplies approx- imately 9-15 V at a current of at least 100 mA. This value applies to the experimenter's board by itself and must be increased by the amount of current drawn by any additional hard- ware that may be present . §@$ tware PC software that can generate the nec- essary programming hies and program them into the 1C is required for pro- gramming the CPLD. Fortunately, the manufacturer of the CPLD has a nice (and free) software package for this purpose (see Figure 6). This software is called Guartus, and it can be down- loaded from the manufacturer's web- s ire ( http ://w\ tw. alt era . com/) . On the home page of this site, select Design Software under the Products heading. This will cause a new win- dow to appear, where you should select Quartus II Web Edition. After this, follow the instructions displayed on the screen. However, you shouldn't overlook the size of the download. The file is a hefty 144.9 MB, so if you have a dial-up link, it might be more conven- ient to have someone else with a faster Internet connection download this file! After installing the software, you must request a free license. Exactly how to do this is clearly explained on the Altera website. mmsfth Next month we will use several exam- ples to explain how you can design a circuit using Guartus. and of course we will describe how to try out these examples using the experimenter’s board. For progr ammin g the CPLD, you will need a JTAG interface in addition to the experimenter’s board. The previously mentioned Parallel JTAG Interface from the Septem- ber 2002 issue of Elektor F/ecnonics is suitable for this purpose. While you're waiting for the next issue of Elektor Electronics , we recommend that you read the Guartus tutorial. It can be found under the Help menu. Using this tutorial, you can already familiarise yourself with the organisa- tion of the software and examine the features of the software. 7 7 ' ' : 5/2004 -eldcfer flcflronks 15 Benjamin Hinrichs The modular design and flexibility allow the preamplifier to be built c individual requirements of its user, program The multitude of options for construct- ing your ‘personalised' high-end pre- amplifier mean that you must read this second part of the article before you order the parts and take up your sol- dering iron. This is because your requirements determine how many cir- cuit boards of which type you will need, as well as which components you will need* You can connect several volume controls in parallel as illus- trated in Figure 1, in order to adjust more than two channels at the same time. If you do this, you must intercon- nect the CS, Mute, SCLK f f& V and Ground terminals of the circuit boards. SADATO from the first circuit board is connected to SDATI of the next circuit board, and so on. This causes the vol- ume level setting to be communicated to all of the circuit boards. You can choose from traditional audio signal switching, switching the ground leads together with the signal leads, or switching balanced signals.. If you know how, you can also give the microcontroller additional functional- ity or modify the details in the soft- ware, such as the designations shown on the display. What we need now are a few instruc- tions for populating the main preampli- fier board. This is because the circuit board shown in Figure 2 is quite com- pact, The closely spaced, narrow tracks are not particularly forgiving of mistakes, so the components should be fitted properly the mat time, and solder splashes and overheated joints should be assiduously avoided. On the main circuit board, only JP1 and JP3 can be implemented as jumpers. JP2 {directly underneath IC2) is a wire bridge. There is another wire bridge at the inner edge of K5. which should be fitted immediately: done is done! Now you should consider whether the programming and/or paralleling con- nections are necessary. If you arrive at a positive conclusion after studying the two text boxes, then you must fit the associated connectors (refer to the components list) and the solder pins for the audio signals. Despite ail the claims to the contrary, it certainly makes sense to fit the solder pins before the other components. Gener- ally speaking, they need a bit of coax- ing, and sometimes they can only be pressed into the holes using (brute) force. Besides this, a L3-mm diameter silver-plated steel pin requires a con- siderable amount of heat to achieve a reliable bond with the solder. And if you find a solder pin standing at an angle to the board, you can start all over again. This can be the kiss of death for small, sensitive components that have already been fitted in the immediate vicinity. If you use a decent stuffing frame, it doesn't matter very much if the low- profile components (resistors, capaci- tors, and diodes) are only fitted after- wards. As always, proper polarisation is important for some of the compo- nents. Besides the diodes and small electrolytic capacitors, tins also includes the resistor arrays and the PLCC socket, which is bevelled on one comer. This marking must match the component overlay on the circuit board, Now it me right time to not fit LED D1 if you want to use it as a pilot light on the front panel. This LED, along with IK receiver IC3 f should only be soldered in place after the circuit board has been securely fitted in the enclosure and the two components have been fastened in holes drilled in the front panel. If your enclosure layout doss not permit the circuit board to be placed direcrlv behind the front panel and you thus must fit the 1R receiver off the hoard, a screened connection cable is mandatory. The fixed voltage regulators IC4-IC6, which should be soldered in place after pin headers K3-K5 and the high- quality DIL socket for the PGA2311 have been fitted, do not require heat sinks. The soldering work is completed with the fitting of the three large elec- trolytic capacitors and the two circuit- board terminal strips (K1 and K2). If you wish to control several volume control boards in parallel, fully popu- 5/ 2004 -ddkr eleffronio 17 ( 020046 - 1 )) Resistors: R1 - 27Q R2,R9 = 4 7Hl R3 = 8 -way 1 0kQ SIL array R4 = 4-way 1 0 kQ SIL array R 5 - lkQ 5 R6,R7,R8,R10 = 10kQ PI = I Old) preset P2 = iCOll preset Capacitors: Cl C2.C3.C20 = 10^F 25V radial C4-C11C14.C15- lOGnF Cl 2 r Cl 3 = 27pF a6.C17.C18 = 220 GjjF 25V radial Cl 9 ~ lOOnF ceramic, lead pitch Omm Semiconductors: Dl = low-current LED (+ 2-way pinheader) D2.,D3 D4 - zener diode 5V6, 1 3W IC1 - PfCl 8LF452-I/L (PLCC) Stank ICs: Fame If # 400-9654. Programmed ICs: order code 020046-41 3C2 = RGA23 1 1PA From Texas Snslroments/Burp Brown or CS3310 from Cirrus Logic (Crystal) IC3 = SFH51 10 (TSOP1836) (+ 3 -way pin header) IC4JC6 = 7805 IC5 = 7905 p = BC550C Miscellaneous: JP1 JP3 = 2-way pinheader jumper JP2 = wire link K1 = 3-v/ay PCB terminal block,, lead pitch 5mm K2 = = 2-way PCB terminal block lead pitch 5mm rC3 = 1 6- way pinheader late one main circuit board and fit only the portion with the PGA2311 (includ- ing the peripheral circuitry and the voltage regulator circuitry) on the other boards. The system has been tested using a single controller board and two paral- lel circuit boards. Ah of the necessary connection points are located in a row on the circuit board. The input channels are switched on the relay board. The circuit shown in Figure 3 allows two different wiring options. With the traditional option, all eight inputs from the Cinch sockets are used, with a single output to the main circuit board. This requires JP2 and JP3 to be fitted. Each relay is then responsible for one stereo channel. If st andard twin screened audio cable is used, one channel is connected to A and the other to B. and the screen braid is soldered to the bottom of the circuit board. Ground isolation, which may be desired to improve charm el separation or avoid interconnecting the grounds of different items of equip- ment connected to the preamplifier, can be achieved by switching net only the signal lines, but also the associ- ated ground potentials. In this case, for each channel the 'live' lead is soldered to A and the ground lead is soldered to B, In addition, jumpers JP2 and JB3 are left open. In this mode, each pair of relays (RE1 & RE5. RE2 & RES, RE3 & RE7, and RE4 & RE8) belongs to a sin- gle signal source. This yields four stereo inputs and two sets of outputs (0UT1A & OUT IB and QUT2A & OUT2B). Here again A corresponds to the 'live : lead and R to ground. The 18 eleklej electT erics - 5/2 GDI K4 = 10-way boxheader, vertical K5 =* 2 6 - way boxheader, vertical XI — I OM Hz qua dz crystal 1 2 solder pins External parts: LCD, 2x16 characters vvith backlight 1 2 pushbuttons for chassis mounting 2 Cinch sockets for chassis mounting, isolated and gold-plated Mains on/off switch, chassis mount IEC mains appliance socket, chassis mount Disk hex and source code files, order code 020046-1 1 or Free Download, (020046-2) Resistors: R 1-8 = iokn R9-R 1 6 - 47kD Semiconductors; D1-D8 = 1N40G4 D9-D 1 6 = bw-current LED T1-T8 = BC550C Miscellaneous: JP1 = 2- way pinheader -r jumper JP2JP3 - wire link K 1 = 1 0-way boxheader, vertical K2 = 2-way PCB terminal block, lead pitch 5mm RE1-RE8 = RY5W-K (Takamisawa), Conrad Electronics # 502852 (5V/167Q) 16 Cinch sockets For chassis mounting, isolated and gold-plated EMJT1 QUT2 Figure 3, iher&lcy circuit also allows ground isolation and connecting balanced signal sources. only other thing you have to do is to change the Input Type option in the Set-up menu to 'Double 1 . In order to handle balanced signals, we simply switch two relays simulta- neously. In this mode, you also have to add a second, parallel volume control and then connect the balanced signals to one of the input channels (such as Left In) on both volume controls. This works well - quite well, in fact. Fujitsu (formerly Thkamisawa) type RY- 5W-K relays aie used here. Naturally, other pin- compatible types could also be used, but the specified line has excellent characteristics and is avail- able for less than 2 euros (approx. £1.40), for example from Comad Elec- tronic (www.conrad.de). This is a plas- tic-encapsulated relay, which prevents any dust from accumulating inside. The contacts axe made from a silver-palladium alloy with supple- mentary gold plating. Power for the relay board is taken from the main circuit board via connector K1 (which requires jumper JP1 to be fit- ted), If you wish to treat the channel switching board to its own power sup- ply or you want to use this board in a different project, you can also connect a 5-V supply to the K2 terminals. In order to avoid overloading the microcontroller outputs, transistors with base resistors are used as relay drivers. Diodes D1-D8 act as free- 5/2001 - tickler tbtfrania 19 Microcontroller programming is normally not the Forte of audiophiles who have dedicated themselves to DIY con- struction, Consequently, most people will probably be quite pleased fo know that the microcontroller can be obtained ready- programmed from Readers Services under order number 020046-41 . However, anyone who has a suitable development package for the PIC1 8LF452- l/l will certainly not have any problems downloading the hex code for the control program into the microcontroller (item number 020046-1 l, available at no charge from the Free Downloads page of the Elektor Electronics web- site or on diskette from Readers Services], The easily con- structed JDM programmer (see reference [4]) is an exam- ple of a suitable programmer. The software package also contains the source code, so interested users can get an idea of how it is constructed and/or make iheir own modifications (assuming they have suitable programming experience). The software is written in the JAL high-level language (see reference [5]), which is available from the Internet as freeware, JAL is an excellent choice for getting started with PIC microcon- troller programming, particularly since there ore also very informative newsgroups on this subject [see reference 6]). Nevertheless, it was necessary to make a few modi- Ications to the JAL files in the assembly code since JAL BOTX5J3 g i 020046-2 ]*JT*3,S P) 020046-2 wheeling diodes, while LEDs D9-D16 provide a visual indication of the relay states* The LEDs do not necessarily have to be fitted to the circuit board {Figure 4); they can of course be fitted to the front panel instead if you want to do without the display or they can simply be omitted (along with their series resistors). JP1 can be implemented as a jumper, but JP2 and JP3 should be imple* mented as wire bridges. Otherwise there's nor anything particularly remarkable about populating the cir- cuit board, particularly if you use the components specified in the compo- nents list and everything fits perfectly. A large part of the stabilisation, decoupling and hum suppression for the supply voltages takes place locally on the main circuit board, for both the digital portion (-5 V) and the ana- logue portion (5V). The only other thing you need is a sufficiently stable source of symmetrical DC voltages (which shouldn't be a problem with the low current consumption). This provides an opportunity to use a gen- eral-purpose low-power mains power supply (Figure 5). The power supply is designed to use Talema 10-VA encapsulated low-pro- file toroidal transformers (see refer- ence 1 2)). which can be obtained from DigiXev (among others •. Partic- ularly for audio applications, toroidal transformers are preferable to other types of transformers due to their low stray fields. The power supply circuit board is gen- eral-purpose because it can be config- ured to provide either an asymmetric supply voltage {V- and ground) or sy mm etrical supply voltages (V- T ground and V-) by simply fitting either wire bridges W (for asymmetric out- put) or (for sy mm etric output). Nat- urally C6 and R2 are not needed if it is configured to provide an asymmetric supply voltage. The output resistors (R1 & R2) should be wire-wound types, since this fur- ther reduces the hum voltage. Fast diodes with a recovery time of less than 200 ns are used as rectifier diodes (Dl-04) — for comparison, the recovery time of standard 1N4004 diodes is 1.2 jJs T which is more than six times as long. If you wish to use ultrafast diodes (< 50 ns), you are of course free to do so. Small foil capacitors are connected in parallet with the rectifier diodes to effectively suppress high-frequency noise, which primarily arises from diode switching transients. Each cir- cuit board is protected by a slow -blow fuse rated at 125 mA. Fitting the components to this board 20 eid.itr tl=r!rcd{S - 5, 2004 doss nof provide native support for storing code in the EEPROM of the PtCl 8F452. Ail of the modified fifes ore included in the project, if you wish to make changes to the source code, you should adjust the path names in the accompanying JAL.BAT file and use them for compiling* The software was compiled against JAL G.4.59.Wm32. The software was entirely written by the author, except for a few functions such as driving the display, for which JAL provides native support. Functions such as the SP1 interface code and acquiring RC5 signals were specifi- cally developed for this project. Modification and/or reuse of parts of this software, including in your own projects, is explicitly desired, as long as the author is named and the software is used for non -commercial pur* Doses (which means at home). More on this subject can oe found in the file WJAL The PIC18LF452 can easily be programmed in-circuit. For serial in-circuit programming, a number of conditions must be satisfied: the PBGA231 1 must be removed from its socket, and the connectors for the display and relay board must be disconnected. The programming interface comprises five connections: MCLR, RB6, RB7, +5 V, and Ground, These connections are arranged in a row on the circuit board and fitted with solder pins* (Figure 6) is also about as simple as could be imagined. First solder the wire bridges in place (one circuit board Y. 7 ith the three A' wire bridges and a second one with the three wire bridges). Then fit the remainder of the components in any desired order. Mount the series resistors vertically. Before inserting the microcontroller and the PGA2311 into their sockets and connecting the display, you should painstakingly check all the boards for incorrectly fitted compo- nents, dubious solder joints and solder bridges* The first test should be per- formed with the boards outside of the enclosure. To hold the boards securely in place for testing, screw them to the workbench using standoffs under each of the boards. First connect the power supply boards and check the voltages at their outputs. Due to the high open-circuit voltage and the combination of recti- fication and filtering, the measured voltage will naturally be somewhat higher than the 7 V specified for the transformer* Next, connect all of the boards together and switch on the power. Nothing will happen, but the following voltages should be present at the appropriate IC pins and the display module connect or: +5 V: 0-2. ICl-12, 1C 1-35, IC2-4, IC2-12 -5 V; IC2-13 uK‘-45- 13 If everything is OK, wait a few minutes to allow the capacitors to discharge, and then insert the ICs and connect the display. The display, the microcontroller and the volume control IC are highly sensi- tive to static electricity. As all of these components are not exactly inexpen- sive, you should work at a suitably earthed workstation. Figure 7 gives a deep insight into the laboratory prototype of the digitally controlled high-end preamp. The mains niter was fitted because it was 'already on hand', but it is hilly ade- quate. The power supply boards and the main board are separated as far as possible. Nevertheless, the FFT analy- sis (see Part 1) shows that induced 50-Hz noise is responsible for the majority of the distortion. If you want to improve matters and are not afraid of a bit of effort, you can fit the sensi- tive audio portion into a suitable tin- plate enclosure. At the rear, besides the mains input socket there are two sets of eight audio inputs and two audio outputs, ail using isolated gold-plated Cinch sockets. After the 'official' completion of the device in the Elektor Electronics lab, further tinkering revealed that small RG networks on the inputs suppress induced RF noise on the cables, and that a 100-Q series resistor in each of the output lines assures the stability of the PGA2311. As shown in Figure 8, these components should be soldered directly to the Cinch sockets using the shortest possible leads, or even fitted in the connecting cable, in order to maintain the highest possible degree of screening. In contrast to the audio connections, which employ high-quality twin screened cable, the keypad (which 5. 2004 - elrkfur E^dmrrfci 21 (020046-3) Resistors: R1 - 0Q1 5W Capacitors: C1-C4 = 47nF, lead pitch 5mm C5 = 47G0pF 25V radial, max. dia. 16mm Semiconductors: D1-D4 = BY50Q-2O0 Miscellaneous: = = fuss 125mA, slow, wiih PCB mount holder K1 = 2 -wo y PCB terminal block, [sod pitch 5mm K2 = 2-v/ay PCB terminal block, lead pitch 7.5mm TR 1 = mains transformer, 2x7 V 1 OVA, low profile, e.g. Talema 70 040 (RS- Components, Digikey) Fit wire links 'A' Da not mount R2, C6 Cr\ T Jiijt ij ^ j fj [ t (020046-3) Resistors: R 1 ,R2 = 0Ol 5W Capacitors: C1C4 - 47nF C5,C6 - 4700fjF 25V radial, max, dio. 16mm Semiconductors: 014)4 = BY500-20Q Miscellaneous; FI = fuse, 125mA, slow with PCB mount holder K1 = 3^way PCB terminal block, lead pitch 5mm K2 = 2-way PCB terminal block, lead pitch 7.5mm TR 1 = mains transformer, 2x7 / 1 OVA, low profile, e.g. Talema 70040 (RS Com pon en ts , Dig \ key) Fit wire links ' 8 does not have a circuit board) and the front-panel LED are connected using simple Hat cable. This allows a rela- tively large amount of freedom in the layout of the front panel. For example, the volume buttons can be arranged in a diamond pattern (if sufficient room is available). You can spare yourself the trouble of looking for a distributor for the attractive metal buttons used for the prototype - they were personally turned by the author. The bright red cable between the main circuit board and the LC display came from a computer shop. But be careful: many of the cables available in such shops have crossed lead pairs. In case of doubt, a ’normal' fiat cable is also perfectly satisfactory. rcv-K-2 h6 DQWBr ~ - I- cu f'r board. [1] www.f cl. fu [it5u.com/en/ products/relay/in dex.html [2] www.talema.de [3] www.avtechpulse.cam/ a ppnote/techbrief9 [4] www.jdm, fiomepage.dk/ newpic.htm [5] http:/ / ja! .sourcef orge, net [6] http://graups.yahoo.eam/ group/ [alii st 22 eJshci etectrcrTcs - 5/20D4 HowfoiJf (flr FlCffliife^ ! snkrfrctBltelletf Rowt&de is a program mirtg system Fra PlCmkra microcodtroUEtt baiedl ■on flowcharts. flawcode Includes maans to fa dli( ale the ton trot of cofnptex devices like 7 -segment and tea displays, Flawcode allows complete novices to design control systems without getting bogged down in Uie programming involved. ■ Requires no programming experience * Full on screen simulation * Produces PfCmicro hex code for a range □f S t i8» 28, and 40 pin devices * Full suite of demonstration tutorials * Allows complex Pltmicra designs to he produced in minutes for full specification see: www.matrixmultimedia.co.uk Allows users with no programming skills to design complex electronic systems or contact us for a full colour brochure email; safesSmalrixrnuLtimedia-co.uk iri: 0S70700 1831 fax; 0870 700 1832 matrix multimedia ! 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I ! h P y i N 4 c 3 * * ( i One advantage of the specific design of the combined sensor is that the mechanical construction of the anemometer is far simpler than that or traditional meters while also reducing the risk of wear and tear as well as breakdowns. The in si rumen t readout showing wind speed and direction is on an LCD as well as via a serial out- put that allows a PC or an (NMEA compatible) navigation instrument to he connected. Even if mounted in a single enclosure, wind speed and wind direction meters typically employ two different sensors. Several solutions have become commonplace for the wind speed (anemometer) function, includ- ing optical sensors, generators and reed contacts. However, the classic design comprising a rotor with three half spheres causing a magnet to pass across a Hall sensor has the smallest number of disadvantages. The sensor type UGN3503 used in this project supplies a voltage of the order of I mV per gauss. These sen- sors, which are discussed in some detail, in the inset are impervious to dirt ingress and may be totally encap- sulated. They consume little energy and unlike reed switches cause hardly any electrical noise. Wind direction meters are usually realised using potentiometers and optical Gray encoders, but here, too, the linear Hall sensor is a good choice. The circuit presented in this article is a simplified version of the Hotavecia system whose main advantage lies in the total absence of mechanical parts for the wind direction meter, leaving us just with the three-blade anemometer part. Tho principle The crux of the system is the little vane on one of the half spheres on the rotor. The vane causes a small acceleration or deceleration of the rotor, depending on its position relative to the wind direction. It we assume an angle refer- ence point relative to the wind (on the fixed part) then it has to be possible to determine the wind direction using two sensors fitted at an angle of 90 degrees. The calculation method con- sists of first measuring the average value (of each sensor) over a couple of revolutions. Each change in the wind direction will result in a small variation of these two average values. Next, using an angular reference table with two inputs, the microprocessor is able to figure out a 'wind vane' angle expressed in degrees. Hence in our wind speed and direction meter, only two Hall sensors are used supplying voltages proportional to their magnetic field. Each sensor supplies a sine wave* like voltage (Figure 1) whose frequency increases with wind speed while the average value Is an indirect indicator for the wind direction. Black diagram No remarkable things are seen in the block diagram in Figure 2. The start- ing point is the pair of Hall sensors arranged at an angle of 90 degrees. Two amplifiers, one for each sensor, condition the sensor signals for use by an ADC and then on to the processor. The limiter' block prevents overdriving of the capture/compare input on the PIG16F876 The processor is also busy driving the LCD as well as outputting an NMEA compatible serial signal for use by a PC or suitable navigation equipment. That wraps it up as far as the block diagram is concerned and we're ready to have a look at the Circuit diagram The schematic in Figure 3 can not be said to be overly complex, can it? At the heart of the circuit we find a PIC 16F876 and a double opamp. There's a 218-page document on the PIC family waiting to be downloaded from the Microchip website men- tioned at the end of this article. The PIC usd here has Flash memory and is simple to program over a serial link. On board we find a i 0-bit ADC of which two inputs are used, as well as a capture/compare module with one input used to measure the period of the reference signal. Using opamp IC1 (an LM358) the signal amplitude is adjusted for optimum use of the input span afforded by the ADC inside the PIC. The two UGN35Q3 sensor chips, IC5 and ICS, are linked to the main board by way of 4- way connector K3. Together with two small loading capacitors, quartz crystal XI provides a 16 -MHz clock frequency. Connector K1 allows the circuit to be hooked up to the PC's serial port. The LCD drive employs the R TV signal pair, besides Enable and RS. all on con- nector K2. Only four datelines are 5, 2094 - eld ter dalnnkr 25 G. Samblancat The author was born in T968 and graduated in electronics at a French polytechnic. He is currently active in the educational field while also studying network engineering at the Conservatoire National des Arts en Metiers. This article is his second publication P Figure 2. Block diagram of the combined wind speed & direction meter : required in our case as the LCD is operated in 4-bit mode. Jumpers JP1 and JP2 serve to select between NMEA mode (JP1) and CALibratkm mode (JP2), The on-board power supply gets its raw supply voltage from a 12-VDC mains adaptor. Alternatively, the instrument may be powered from a 9- V battery, in which case C7 and regu- lator chip IC3 are omitted and a wire link installed between the holes nor- mally provided for the input and output pins of the 78LG8. Building it Figure 4 shows the component overlay, Tne copper track layout may be found on the PCB Layout pages towards the back of this issue. The board consists of a main section and a sensor section. The elongated shape of the board allows it to be mounted in a 32-mm PVC tube, just under the sensor part. Note that presets P1-P4 are accessible from the top side. The actual popula- tion of the board is straightforward. It is best to start with the smaller parts. Xi is a quartz crystal in a miniature case. The PIC chip is the most expensive part and therefore best installed in a quality IC socket. Sensor construe f /on The Hal sensors are accommodated on the small round board that T s separated from the main board by cutting. The sensors are fitted at exactly the same height. Next, the board is fitted in the open end of the PVC tube and secured in place with epoxy glue. The spindle is made from a metal pin with a diam- eter of 3 mm, passing though a ball bearing or a Teflon sleeve bearing. In the prototype we used epoxy glue to secure the little magnet on to the spin- \ y Hall sensors at90 : Shaping amplifier I CAM inputs Shaping amplifier Clipper Cap lure/ Com pa re input Microcontroller PIC16F876 NMEA bus vessel equipment or PC LC display 050371 - 13 26 elektor s!«ir&nia - 5/2004 Figure 3 . The circuit diagram remains happily uncluttered. Nearly all functionality is hidden inside the FIC micro t die, as well as to secure the ball bear- ing. The rotor with its three half spheres has to be fixed securely on to the spindle (such rotors are available as spare parts from appointed Auto- helm dealers). Home construction of a rotor from Ping- Pong bails cut in half look attractive is far from easy. An unexpected difficulty yon may run into is the need for perfect mechanical balancing, which is hard to achieve because of the little vane attached to one of the half spheres. The programs The program VElSMPU.hex (in 1NHX8 format) may be blown into the PIC if you have a suitable programmer. The PC programs called TUNE and ANEMO, written in Delphi, serve for the wind speed/direction adjustments and the PC readout respectively. The subject will be reverted to under the paragraphs on calibration. The program file, ref. 030371-11. may be obtained from the FYee Downloads section of our website, or on disk under the same order code. If you are unable to program a blank PIG t a ready-programmed one may be obtained through our Readers Services under number 030371-41. Amplifier adjustments The first thing you need to do after switching on the supply voltage is adjust the four multitura presets P1-P4. Your goal will be to make the ICla and IClb output signals cover the full range of 0.5 V to 4.5 V. This may be done with the aid of either an oscillo- scope or the TUNE software. In the first case you closely watch the signals at pins 1 and 7 of IC1 while the rotor is made to turn continuously by, for example, a hair dryer. Adjust P1/F4 (amplification) and P2/P3 (offset) to the best of your ability Do make sure the sinewave signals remain between 0.5 V and 4.5 V and free from clipping. Aim to achieve the optimum setting shown in Figure 1. If you don't have an oscilloscope, use the software instead. TUNE offers a min/max function that draws a line along the discrete values measured. This requires the working meter to be connected to a PC. After starting the program, click on l Min/Max and view the message ”'Mm/Max*'“ after a few seconds. Wind speed calibration Tne wind speed meter measures the period of one rotor revolution and then computes 5/2HM - elefrof efedronks 27 COMPOI ENTS 1ST Resistors; R1 - lkQ8 R2,R3 - lkI25 R4 r R5 - 5k Q6 R6.R8R1 1 = IQkil R7 - IkO P] P4 - 4> kQ mullilum preset with top adjustment F2 P3 = 4kQ7 mullilum preset with top adjustment Capacitors; C 1 ,C6 = UiF 16V C2/C3 = 15pr C4,C5 = IGOnF C7 - luF 25V Semiconductors: Dl r D2 = 1N4148 II - 8C547 IC1 = LM 358 SC2 = P1CI6F876, programmed, order code 030371-41 EC 3 - 78L08 EC4 - LM78L05 \C5,\C6 = LiGN 3503 (Allegro) Miscellaneous: XI - 16M Hz quartz crystal, miniaiure case K1 = 9-way subU socket (female), PCB mount K2 - 1 0-way pinneader K3 = 4 way pinheader JP1 JP2 = 2-way pinheader with jumper Standard LCD, 2x16 characters Figure 4, Component mounting plan on the elongated PCB. The small section is intended for the two Hall sensors speed = K anama / period The displayed speed is dependent on the constant K which takes a default value of 35500. The adjustment pro- gram TUNE calculates the constant based on a comparison between meas- ured speed and real speed (obtained, for example, with the aid of a car speedometer). Adjusting the speed factor K anemo (if necessary, adapt the initialisation value in the .hex file) boils down to comparing (a) the speed shown on the LC display with (b) the real speed and (c) the speed already stored in memory. In each case it is necessary for the PIC to be read out first, The program TUNE will then show l x.y (z) ? where z — speed factor — y + 256 x Sensor c&lihrati&n Due to the small differences in force and direction of the magnets we're forced to create individual calibration curves for each UGN3503 sensor chip. The process places rather high demands on the test wind ' quality'* The air stream produced by a hair dryer is too concentrated for an accu- rate direction measurement — nothing beats a real air stream. Here we avail ourselves of the adjust- ment software* To enable the system to calculate the wind direction, each sensor is linked to a lookup table with 72 values {for 5-degree steps). The adjustment program employs 8 points for the interpolation of each curve, so a total of 16 values is needed. In other words, two values have to be meas- ured with each angle of 45 degrees. This calibration method may take a while. In between two measurements, the wind meter has to be turned 45 degrees while making sure the readout remains stable. The values may be viewed continuously on the LCD or on the PC display (via the COM port) after the command Tead PIC 1 . They have to be entered in a table like the one shown in Figure 5. Once the table is complete, the function 'Curve 1 com- putes the 72 values we need, on the basis of the 16 actually measured ’/sl- ues. Next, the curves are actually plot- ted using 2 times 72 reference points. Pa asetital use After an initial phase in which the sys- tem has to determine a number of average values, the wind speed & direction meter will transmit its data to the LCD as well as the NMEA output. Although the NMEA 0183 (or NMEA183) standard is a bit old, it sees wide use in marine electronics. In our case, the NMEA sentence reads: 8 WTVWR , dir f L , vit , K where SVVIVWE should be taken to mean 'Weather Instrument'; 'VWR' is the standard prefix for anemometer information; *dir r is the wind direction 28 dehor dedmriifi - 5/2004 F VC Cube, dia, 32mm r length approx. 200mm PCB, available through The PCBShop Disk, o reject saitv/are, order code 030371*1 1 or Free Download PCB copper hack layout on 'PCB layout" page elsewhere in this issue. PCB artwork file also available as a Free Download. Th® UGN 3 S 03 iKsmx&j a™ L J — 0 i i ryi ■ - 1 * l-V Characteristics The type UGN35G3 Hall sensors (models IT, U and UA( are capable of delecting magnetic fiux changes o- a magnitude so small they can not he measured with a reed switch. Every sensor contains a Hall ehecT detector, o linear amplifier and on open-emitter output stage. A magnetic field perpendicular to the chip produces a current change, the resultant potential difference causing the Hall effect volt- age. This voltage is proportional with, among others, the magnetic field strength. Operation In the Inactive state. (B = 0 Gj, the output voltage level is normally half the supply voltage. A mag- nslic South pale opposite ihe active pari of the sensor produces a voltage above this level, and a North pole, o voltage under this level. Mode! -J Is not recommended for new design. £$6*fffc £ogrpc rgi jjui - V- : Vd i £f£d C4ici hi-jti 1X0 Speed | ftcdi?esd| E:gFh£* p~j2£ flU IB |^ \*& 1 50 * [ 135 - ISC 1 C5E1J C iy .1 j:o fitK -He \23 3 2*n 17 TjV \m* i'v 37 AQ 62 33 67 7t_ 2s !2 H Figure 5. Once TUNE has been launched you can start collecting calibration data . Figure 6 . An example of the ANEMO software in action . The values are simultaneously shown on the LCD. Anemometer Port Quit Speed Direction 6.5 nm/h in degrees and '\ht s is the wind speed in km/h. The program ANEMO allows everything to be viewed on your PC in real time. Admittedly the construction of our wind speed & direction meter requires due attention to mechanical details, but once calibrated the instrument will reward and surprise you with its totally efficient operation. Web pointers PIC16F876 family datasheets: www.micro chip.com/ download/lit/pline/ picmicro/families/ 16f87x/30292c*pdf Beaufort scale: wwWiietnet*co.uk/s]gs/weatlier/Met_Codes/beaufort.htm The Beaufort scale 0 Calm <1 knot I light air 1-3 knots 2 Light breeze 4-6 l63 knots 5/20114 * elsklor Eisdro[Ei(s 29 Horst Hubert Everything you need to know to drive a stepper motor Stepper motors have found their way into Elektor Electronics many times, most recently in the November and December 2003 issues. In contrast to previous articles, well keep it practical and won't go into the theory, if you want to know more about the background, have a look at some previous articles (listed in the reference section at the end of this article). 30 dektin eledmnjG - 5/2004 To get an unknown motor to work you really need to do two things: find out what properties your motor has and choose the right driver electronics. With the help of this article you will find that it’s not that difficult. The fol- lowing three steps will help you dis- cover the most important properties of a motor. The first step helps you determine whether you have a bipolar or unipolar motor. I <. Type ei motor A bipolar motor (Figure 1) has wind- ings whereby the current alternately flows in one direction, then in the opposite direction This creates a mag- netic field that also changes direction, causing the motor to turn. The '.'finding of this type of motor has two connec- tions. The driver electronics therefore has to continuously reverse the voltage to the winding. This requires a bridge circuit using four transistors, A unipolar motor has a winding with a centre tap. This winding therefore has three connections. The centre tap has to be connected to the positive supply voltage. If we now connect the start connection to ground (and leave the end connection open) t there will be a current flow through the first half of the winding. If we connect the end to ground (and the start is left open), there will be a current flow through the second half of the winding. Since the current in the second half of the I bipolar Figure 1. Bipolar or unipolar motor? Figure 2 , Finding out what the connections are. DO o 75 :©! 75 ■O DO 15Q o~b< 75 a 7= o ;©! 75 ■O O 155 75 O 155 winding flows in the opposite direc- tion, the magnetic field will also be reversed. The driver electronics can therefore be simpler, since we only need to connect either the start or the end of the winding to ground. Two transistors are sufficient for this. A stepper motor has at least two pairs of windings, so 22 or 2J3 connections. When a motor has four leads it is almost certainly a bipolar type. And when it has five or sis leads it is almost certainly a unipolar type* It's as simple as that. Should you find a motor with more leads, then you have a problem. There is nothing left but to open up the motor and hope that you can see what the internal wfiring is. This is usually not successful. In that case you ’ll just have to use a different motor! 2. €@mtestmns Once you have determined what type of motor you have, it T s time to find out which leads belong to each of the windings. Measure the resistance between the connections using a multi-meter. Go through all possible combinations and make a note of the results. The resistance between the ends of a winding will be low. Between the centre tap and one of the ends of a winding you’ll have half the value measured for the full winding. Between separate windings you’ll find an infinite resistance, or at least several megohms. In this way you can determine which two or three connec- tions belong to each winding. When a unipolar motor has a common centre tap (5 leads), it is unfortunately not possible to find out which connec- tions belong to which windings. In that case, the centre tap will have an Identical resistance to the remaining four leads. But as you will see later, we have come up with a solution for that as well. 3 . Operating voltage Unless it’s written on the motor, there is no way of telling what the operat- ing voltage of the motor is by looking at it. Often you do know what the supply voltage was to the circuit where the motor came from, A step- per motor from a floppy drive will work at either b or 12 V. If you have no idea what the voltage was, you can estimate it using the following method. For a bipolar motor connect one of the windings to a variable power supply* For a unipolar motor you connect two of the windings as shown in Figure 3. Set the output to a several volts and wait a few minutes. Feel if the motor becomes warm, if not. increase the voltage and check the temperature again after five min- utes. Repeat this until the motor becomes alm ost too hot to touch This should give you the maximum operat- ing voltage for that particular motor* 5; 1004 ■ detiroma 31 Figure 3. What is the maximum supply Figure 4a. Circuit diagram of the stepper motor driver, voltage ? Hardware Now that we have determined what the properties of the motor are, we nave to choose the right hardware. But don't panic, we'll work through this in a few simple steps as well. Our driver stage has several limita- tions. The maximum operating voltage is IB V (preferably a bit less, such as 15 V) and the maximum motor current is 2 Amps. If your motor requires a higher voltage or current then this cir- cuit won't be suitable. The current con- sumption of the motor can be read from the power supply during the pre- vious test, or calculated by dividing the motor voltage by the resistance of the winding. The supply voltage chosen for the cir- cuit should be the same as the required motor voltage. The circuit in Figure 4a consists of a bridge, so that it can drive bipolar motors. It is also possible to use the same board to drive unipolar motors. In that case the Top' transistors aren't mounted. Instead of these, a reverse biased diode is put between the collec- tor of the remaining transistors and the positive supply. That means that the cathode, the side with the line, goes to the positive. The other sides go to motor connectors A, B, C and D. Remember to connect the centre tap to the positive supply for a unipolar motor. The complete circuit diagram can be downloaded from the Elektor Electronics website (Figure 4b). Tne next question is which type of semiconductor to use. It happens that both transistors and FETb are suitable. Transistors are often cheaper and more robust, but have greater losses. In fact, we don't use ordinary transistors, but darlingtons. These consist of two tran- sistors after each other in one case. They behave just like ordinary transis- tors, but with a much greater gain, usually about 1,000 times. Their disad- vantage is that they have a greater voltage drop of about 0.8 V. FETs are usually a better choice, but take note: P-FETs (for the ‘top r semi- conductors in the bridge) are a bit harder to find. Their voltage drop is minimal, which makes the FET ver- sion particularly suitable for 5 V motors. In the transistor version there would only be It may be that you're told to buy so- called logic FETs. These FETs can function with a lower driving voltage on the gate. You can use logic FETs, but they're not strictly necessary, as can be seen from Figure 5. With a S V supply even a 'normal 1 FET can switch over 5 A. which is more than enough. In case of a 3530 type P-FET this is less favourable, but 2 A should still he possible. Tne choice of either the darlingtons or the FETs isn't critical. If you can’t find 5 - 0.8 - 0.8 - 3.4 V left for the motor. 32 el&ktor Elaltonm- 5/ 2 QO 4 25 v GE =iov V GS = 8V V GS = 7V PULSE DURATION = 80(15 DUTY CYCLE = 0.5% max Vqs = 6 V V GS = 5V V GS =4V 10 20 30 40 50 — ► V DS , DRAIN TO SOURCE VOLTAGE [V] — I E to : \ r i r i i i i i i i 1 \ ■ i i r 1 1 1 i i 1 1 i i J I l i 1 -5V 052203 * 17 C3G2G3 - IB Figure 5, Most FETs can easily pass 2 Amps with o 5 V gate/source voltage (Vq$ )_ Figure 6 . Two square waves are required to drive a stepper motor. the types in the parts list or if you have some spares, you should use a type that has a minimu m working voltage of 50 V and a minimum current of 4 A. Many types satisfy these criteria. ©per&tiom i The driver circuit for the stepper moior consists of two identical halves, so we only need to look at one half. The signal at the input is converted by T9 into a square wave with an amplitude equal to that of the supply voltage to the circuit. This is neces- sary because the driving signal usu- ally has a much smaller amplitude, such as 3.3 or 5 V. So T9 adapts the voltages to each other. The signal then goes to NAND gate 102b, once direct and once delayed by 10 us via R7/C2. There is a purpose to this of course. The trick here is that a transition from T to O' is fed through immediately, whereas a transition from O' to l V is delayed. The same occurs via !C!a and IC2a, but on the other diagonal because ICla has inverted the signal. This exercise is required so that the transistors turn off immedi- ately, but only turn on after a short delay. In this way we avoid that two transistors above each other conduct at the same time, which would short the supply. If you dare, you can leave C1/C2 from the hoard: you'll then find current spikes of several Amps! Dining normal operation only two diagonally opposite placed transistors will conduct. For example, when Ti and T4 conduct point A is positive and point B is connected to ground. LED D1 lights up and there will also be a current through the winding of the stepper motor. If T2 and T3 conduct instead, the polarity is reversed and the current flows t Inrough the stepper motor in the opposite direction. Now D2 will light up. At the time of switching {when the transistors stop conducting) voltage spikes occur because the stepper motor winding is a coil (self induc- tance). These spikes are suppressed by the LEDs and R5. These compo- nents should therefore not be left out. The darlingtons and FETS also have internal protection diodes. Driving the circuit The stepper motor PCB has two inputs. These are connected to our 8958252 Flash Micro Board (see refer- ences at the end of the article). To make a stepper motor turn requires two square waves that are 90 degrees out of phase with each other. If the waves are -90 degrees out of phase, the motor will turn in the opposite direction [see Figure 6). The software on the Flash Micro Board generates these square waves. Figure 7 shows how the board connects to the driver circuit. Push-buttons connected to the board make the motor change direc- tion, although with a little ingenuity they could also vary the speed. The input circuit around FETs T9 and TIG has been added to make sure that the 5 ¥ square wave from the Flash Micro Board connects seamlessly with the (usually) higher supply voltage of the stepper motor driver. The software, which can be down- loaded from the Elekior Electronics website, is an example so you can familiarise yourself with the tech- niques involved and perhaps try your hand at ivriting your own programs. Connecting the motor For a bipolar motor you should connect one winding to A and B, and the other winding to C and D. Should you find that the motor turns the wrong way round, you need only exchange the connections to A and B. For a unipolar motor with 6 leads the centre taps are connected to the — Ve supply. The ends of one v.finding are connected to A and B, and the ends of the other winding to C and D. If the motor turns the wrong way round, just swap A and B. For a unipolar motor with 5 leads the common centre tap is connected to the positive supply and the lour ends of the windings are arbitrarily connected to A, B, C and D. If you are very lucky, the motor will turn. However, it is more likely that the motor will just vibrate a little bit. This is where plan B comes into action: keep swapping the con- nections untfl the motor turns! You won’t cause any damage to the circuit or motor. Remember to turn off the 5/2004 - ddttor 33 COMPONENTS For 5-9 V (values for 9-1 5 V in bracket) Resistors: R1-R4.R8-R1 1 = 7VQ2 )4kn7] R5.R12 - 560D (ikliS) R6,R7,R 1 3.R14 - lkfl R15.R16 = 1LQ (2kn2| Ri7,R1 8 = IMfi Capatifors: C i -C4 = 1 0nF LIST C5,C6 = IGOnF Semiconductors: D1,D3 = LED, red, high efficiency D2,D4 - LED, green, high efficiency II ,T3 J6J8 = TIPI 27 or IRF9520 or diode MBR745 * T2J4 P T5,T7 = TIP ! 22 or IRF520 T9 ,110 = BS170 SCI - 4049 IC2 = 4093 B Miscellaneous: 1 4-way EC socket 1 6-way EC socket Flash Micro Hoard software. Free Download file no. 030203-1 1 T if you do not use bipolar iransistcrs cr FETs, diodes must be fitted! This applies to the u 2 * at a unipolar motor. + + 030203 - 18 Figure Z This is how the Flash Board should be connected to the stepper motor driver FCB . supply before changing any connec- tions. Swap A and B and turn the sup- ply on again. If the motor still doesn't turn, swap A and C. If you still don't get a result, swap A and B again. The associated program is described elsewhere in this edition in the article Software? We'll do that ourselves!' . References: Stepper Motors Uncovered, part 1, Elektor Electronics November 2003, Stepper Motors Uncovered, part 2, Elektor Electronics December 2003, S9S8252 Flash Microcontroller Board, Elektor Electronics December 2001 . Internet' The full version of the circuit dia- gram, as well as the PCB layout and software for the Flash Micro Board can be downloaded from: www.elektor-electronics.co.uk/ dl/dkhtm, select month of publication. 34 dak! or detirorncs - 5/2U04 Simply send your fib cni ankf OHUHE WWW.PCB-POOL.COM *o rc-5 d WOlt! pg Servicing Your Complete Prototype Needs O Prototypes at a fraction of the cosf O Tooling and setup mckided O Any contour O Fr 4 i 6 mm, 35 pm Cu ^i-.'£ iXWFLE BUROQARD k m + Tooling + Photopfols + VAT * £ 29 . ■Stel&sg jth£ss m&y v- 3 r/ Fines 0 O Fo/Zov up series runs O CAVf CAB consulting ZL*3S3B8&17$li& t- UoL- ’xTss? 0 » 0 ° 8 S 6 ® r^aSTW^TT n itnxr See /our design in print! Elektor Electronics (Publishing) are looking for Freelance Technical Authors/ Designers If you have # cm Innovative or otherwise origma/ design you would like to see in print in Europe's largest magazine on practice/ e/e cf rentes # above average $Jd//s In designing electronic circuits # experience in writing electronics-related software # basic skills m complementing your design v/ith an explanatory text # a PC, email and Internet access for efficient communication with our in-house design staff then do not hesitate fo contact us for exciting opportuni- ties In getting your designs published on a regular basis, Elektor Electronics K. Wat raven. Head of Design Dept * fia Box 75 , NL-6190-AR Beek, The Netherlands, Faxt (+3!) 46 4370161 Email : k w watraven@segmenhnt Based on the Atm el AVR controller Flexible? and powerful ^ \ Simple to configure . 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Cambs, Pe27 3Wi Tel ephorre: 0148 0 3 0 0 69 5 Fax: 0148 0 4 616 5 4 info@itp101.com wwwiitpl01.com www.tiepie.com 1 5/2(10-1 - irkklOf t;£[1ruuES 35 r- -VriActd ii-rVi m ' «- -.- .. r-jfj 1 - r » >, TFT* 4 V* w . fcy y- .^vf , .-, ,;v. 3 T : ••* -' “«-_ ^ 7-*:-- V*. '. &c&2$5ESG£' -- -• ' ■ , *&hr ■*#■*■' :^‘ ■" -* < 1- 1/ ■: ■ "■*?■•' y -■ 1 ■• ,,-r . 4 ■. .. -i ■ ■ ■ - ’ , , ' y . “•'j - -v 'J-f< -/^r- * >■ ;-. 'i ■gpr ’ * J * • ■ ., , , „ ■ *- -■?. r. ' r.4 IjT ~ T ,i,J k- 4 j ^ - % -:_ ■ V'.v^y • J '^4 •‘-J’.’ ' L, ir t ]J. "f A t . *y *■- ■ < • ,- ' V - ■- - - fc ; 1 -41 ■K “- - ■"» ■ ^Ci/* i r ■' , - : :' j *' ■' ' >_ • . * « "^TC*. ■'/j vt , c, ~ •— - 4 - ■ I Z-f-dfiy? j fj— -~ — - _jr > >*V ' /> . - fL Prof. Martin Ohsmann fe •»_ .^) -: * r- ; 1- Ll. - + f ' ) - _ 1 "U - Vz_ *> — *fr gj” . 4 7- V^fe^-T A ' / ' V. -%v ..- •: . /v 'V-^f._ 7 - ^ - ' • V T - ',< cVr ■ im?: ; ; ?&r *. ' ...-^: I >' r* ,//> ! • •’ -.V-.i2.>- . j|L '» . m j£% WiMf ' £ - J. '■- . ••, J • . - ” ’ •> y- “ , -V I'R— V v J y v f-j - ■ ' r, 1 -- '.7^-. - c? V J*. '/ '>' T .-» fc ’w - r - »>f- " ' * . >' -• r ". » “ .>•!>-*- ^ <■ - " f s i'- • jr.* \£u.W£3 :?%'■: v • - . /V- &■? > ’•' _ I. * r*-ri J F wi SSS^y: T - * ' • • •- &K i rrtj** .-'V. v':_/ -■ ,*I P7* -r.< V; - . " ? :>: »■.- ,<0 . C- V r - ' . J A M ■••O - .7.:?, 3 0" : 4^:^- ^ l-V >i« w vS&b ■ t'Z r r-" ■ '<- l'- , . V tV- f£ s }*■ -1 M ■ ■ > ■. / ;^r.V k*c^h;c- • “ 4 ^ “ m t'A.' -£~JC4-**- 'Vi' r-,U.r :• ' '_y-. i."£v . r 4 The circuit described in the April 2004 edition of Elektor Electronics certainly gave rise to a lot of head scratching and raised eyebrows when it was shown to produce an output pulse ahead of the input pulse. Is it possible that such a simple circuit can turn the principle of causality on its head? Read on... 36 titV,fcr dfditmia - 5/2004 :;■ • . y^ste * 03D-305 - 11 Figure 1 . The lead filler with negative group delay. The idea for this article began when a studeni asked me if it was possible to build a niter that produced a neg- ative group delay’. A quick trawl of the Internet (Google: ‘negative group delay 1 ) soon gave some interesting hits. In Darticular Professor Kitano in ■ Japan had published just such a cir- cuit that apparently exhibits a nega- tive group delay fi). With kind per- mission from him we were able to use his ideas and circuit (slightly modified) in last month’s article. So much for the background r now on to the details... . ■ SOnettfrf us£ S[0&&d If we consider the transmission of information In a co m mu n \ cat ion channel, the first characteristic we need to look at is phase velocity. With a pure sinusoidal carder wave this is equal to the propagation speed of any point (i.e. T constant phase) on this wave. Without any form of modulation it is not possible to send information, so we can see that the phase velocity has no influ- ence on the speed at which we can send information (i.e. t the group velocity). Information can, for exam- ple, be transmitted on narrow-band signal pulses or envelopes and the speed of the envelope will be gov- erned by the group velocity through the medium. Now back to the origi- nal question: if a circuit possessed a negative group delay this would imply that the information acceler- ates in the medium and travels back- wards in time to arrive at the output before it was introduced at the input. A B LPF — ► LEADING Lo* i 0304G5- i2 Figure 2. Block diagram of the experiment. This indeed is what appears to hap- pen in our circuit. This phenomenon has apparently been observed in the field of optics where anomalous dispersion (in a narrow spectrum) has seemingly produced a negative group delay and a refractive index smaller than 1. It is often the case that these effects occur when the circuit or medium is in resonance and an equivalent elec- trical experiment is described in a paper [2] which shows an output AM envelope leading the input sig- nal thus yielding an apparent nega- tive group delay. It is easier to observe these effects by using a filter with negative group delay at low frequencies and DC. The circuit shown in Figure 1 is a (low-pass) lead filter and produces the necessary effects. When a low frequency pulse from the generator described In the first part of this arti- cle is introduced to the lead filter, it should produce an output 'before' the pulse is introduced. This basic idea has been perfected by Mr, Kitano [1] in a circuit that maintains the pulse shape through the transmission medium and pro- duces a negative propagation delay. The pulse envelope travels at the group velocity and the pulse appears at the output of the filter before the input signal! Causality Causality states that in our physical world the flow of events is always the same: first, cause, then effect. You are aware of pain in your thumb after you hit it with a hammer and not before the unfortunate accident. If this prin- ciple is universal, is it possible in our simple circuit that a signal arrives at the output of a filter before it was applied to the input? Clearly not. lb understand what really is going on in the circuit we need to take a closer look. Figure 2 shows a block diagram representing the main parts of the cir- cuit. A rectangular pulse is generated when the switch is momentarily closed at t = 0. A low-pass Filter (LPF) is used next to filter out the high frequency components and pro- duce a smoothed Gaussian impulse at S, The pulse Is now introduced to the medium and recovered by the lead filter to produce the output pulse 0. The recovered pulse is amplified to produce the output pulse G so that its shape is similar to the input pulse. The circuit doubles-up the pulse shaping and lead-filter stages to optimise the effect. Additional com- ponents in the Lead Filter help reduce noise In the circuit. The more observant among you will have noticed that the output pulse rises more quickly than the input pulse. It was found to be Impracti- cal to increase ‘negative group delay' effect further by adding more lead filters. So there really is noth- ing unusual about the circuit, the effect is produced using just con- ventional components. The need for 400 m of cable was also something of a red herring. The circuit demonstrates that in this case the group velocity is not rele- vant to the (negative) time difference 5/2004 ■ eliklof tktfrsnits 37 literature []] M, Kitano, T* Nakamshi/K.Sugiyama, Negative Group Delay and Superluminal Propagation: An Electronic Circuit Approach/ IEEE Journal of Selected Topics in Quantum Electronics/ Jan/Feb 2003 (check the Internet). [2] M.W, Mitchell, R.Y, Chiao, Causality and negative group delays in a simple bandpass amplifier. Am. J. Phys. 66(1), January 1998 (also on the Internet). [3] J.DF. Jackson, Classical Electrodynamics, Wiley and Sons, New York 1975. observed between the input and output pulses, here the front veloc- ity (the propagation speed of an abrupt change or front) of the sys~ tem is more important. The effects produced here are still the subject of hot debate on the Internet but in any case you will no doubt be pleased that causality is still intact (at least for the time being) and this experiment under- lines how careful you need to be when interpreting test results espe- cially in systems using slow pulses. A similar phenomenon to that shown here occurs with a Mach Zehnder interferometer (no, honest), where light pulses appear to arrive 4 too early'. For more information on this subject refer to [2]_ If you are still curious about propagation speeds and anomalous dispersion then the classic work by Jackson [3] should fill in any gaps. ■.0j3=C£-£ Prof. Marlin Ohsmonn mos$mann@l-onime,de 8051, ARM7, TriCore Ci6x/STio,MPC5xx/8xx MPC82xxlPIII,Sc52cljHl Hitex BigChip 8, 16 or 32-bit microcontroller modules are the easiest way to increase the performance of your embedded design. By concentrating the CPU/memory sub -system into a BigChip, there’s more time low-cost, high for getting your 10 hardware and application software right first time. Their small size and guaranteed low EMC will get your project into great shape fast. Hitex (UK) Ltd. TeS: 074 7 fa 6970 66 Fax: 014 76692131 Em ail rsales^b i tex. co uk Web: www.hitex.CiO.iLk/bigchrp Tn components BfgChip starter kits aie available for all modules and include C compilers, debuggers and example applications. 33 ekktof EledTonks - 5/2D04 Lia r^iiLt! jraat^m rf T \ it inJcMoltri ihc a-jti mi fav OjJ a received frero T A M 4 &-Q5J1 HI. IT A Dfum 9th Telemetry Data: Ldiitadt : « 07.55 LnjiM Hf M! 4ifi> t ^nofr uik H; * SaliUrfj*; Ml no Tempera! ur* 1*0: 7A A-ttHUJe (Bit LTA JOD 70 David Daamen Telemetry applied to modelling sometimes pro- duces astounding results — especially if elec- tronics is part of the payload... Model construction and electronics seem to get on like a house on fire, new challenges appearing any time these two fields of interest are combined. The results are often rather spe- cial. For example, Olivier Humez on his website [1] describes lots of equipment to enable photo or video cameras to be attached to model planes and even bal- loons. The images captured during the flight and beamed down to the ground are often stunning. Of course we do not have to limit ourselves to 'shooting pictures', as Humez proves by the equipment he devel- oped to convey telemetry data. Height, temperature and battery voltage are among the quantities that can be measured in real time and transmitted to * earth’ by a radio link, possibly backed up by a video link you can watch using an on-screen display Mr Humez is of course not the only person active in this most interesting held. A team lead by Maynard Hill managed to make a model plane cross the Atlantic ocean. The take-off and landing were accomplished in the traditional way using radio-control transmitters. However, during the actual flight above the vast ocean waters, a microcontroller was in total control of the plane, continuously adjust- ing its course with the aid of GFS information. A few details: total distance trav- elled 3,000 km s in 39 hours with a total fuel consump- tion of just 5.7 litres) More about the flight and the technology used on the team's website at |2), Among lots of other we b b e d iniormatio n on telemetry and data logging we found Dietrich Meissner s site at [3], com- plete with circuit diagrams and software for PICs T Palm and Windows PCs. If you are now anxious to learn more about telemetry, have a look at the sites dis- cussed here, or do your own search using Google and the search words [model | in com- bination with [telemetry] . :4i07a-r [1] Olivier Humez' aerial photography: ww w. k a p e : ec .com / [2] Trans Atlantic Model Homepage: http; / / fa m . p! a n net2 1 .ca m/ index Jitrn Dietrich Meissner's circuits and software: h :: □ : 7'bome.ge rm a ny n e : lOai 73822/ dJcgg2_engLhfm 5/2D0I - eMlar extreme 39 review copy FlexiPanel IR Snfmred glue for micros and PDAs jon Buiting and Luc Lemmens IrDA sure looks like an attractive medium for conveying data across small distances. Unfortunately, the associated hardware gener- ally causes sour faces, and is not just 'playing' hard to get. Those days are over. Paris-based Hoptroff sail (in the UK: FlexIpanel Ltd.) recently announced the release of an IrDA module (also called ’irGUl module' or ’FlexipaneT) designed for easy connection to micro con- troller circuits. Tills triggered our curiosity and within days a sample of the module arrived in the post along with a hefty information pack. We were not disappointed. To begin with, free software is available for devices such as handhelds, mobile phones and (portable) com- puters. In the case of micro- controllers. the FlexiPanel module allows user access to any of these remote devices using a single, sim- ple I 2 C interface. As we writs this, the module should be available as a one- off, as well as software for Po eke t P C h andheld s . Product distribution has been arranged with Parallax Inc. (and its European dis- tributors such as Milford Instruments). A tentative price of USS 80 has been given for the module, US$ 25 for the chip set and USS 6-8 for licensing. According to Richard Hoptroff, software for Palm devices, Nokia and Ericsson mobile phones and Windows laptops is sched- uled for release later this year. A Bluetooth version is also under development and we hope to report on its release some time in the near future. Applications Applications for the FlexiPanel ER module broad- ly fall into two categories: The first category is 'big guns’ comprising handhelds, mobile phones etc, that can employ the generic Virtual Control Panel (VCP) soft- ware that’s available free of charge from Hoptroff. On the device, a graphical user interface (irGUl) provides the link to the VCP In this way, the irGUl acts as the IrDA server and the VCP as the IrDA client. To connect low- volume (100’s) and medium- volume (1000’s) products to VCPs, manufacturers should use an irGUl module or a cliipset which will manage the user interface, VCP tech- nology licensing is recom- mended for bulk volume products (1 0,000' ’s and up) with help available from Hoptroff with the implemen- tation on he host controller. The second category is much more interesting to the occa- sional user and lab worker as is comprises a multitude of individual microcontrollers and development systems for which tailored software needs to be written. In prin- ciple, any MGU or MGU sys- tem may be used as long as it talks and understands I 2 C {this will include many Elekior Electronics microcon- troller boards). Fortunately, Hoptroff have made the com- plete communications proto- col for ’FlexiPanel' freely available as part of an impressive and neatly organ- ised 70 + -page datasheet {which is too modest, ’docu- mentation set’ would have been a more apt description). FlexiPanel allows electronic products to create an opera- tor interface on remote devices such as handhelds (PDAs), mobile phones and other computers, using an infrared link. The remote device asks the product what controls it wants displayed and then it displays them. The operator reads the dis- play and modifies the con- trols as required, sending any changes back to the product. The Flexipanel documenta- tion, then, goes into great depths, discussing every- thing from product ordering and suggested product development methods down to the nitty-gritty of the (fairly complex) command syntax, not forgetting the hardware specific ation of the two avail- able FlexiPanel core proces- sors. Towards the end of the manual, lots of example pro- grams are found for functions including the Message box, file control, calibration, test, array control, password con- trol and many more. All this should allow microcontroller enthusiasts to slap together their own iiDA interface fairly easily on just about any MGU system sporting I 2 C connec- tivity. Our conclusion is that Hoptroff have not only released a module that avoids many pitfalls associ- ated with IrDA hardware construction, but also a good amount of software to back up the product. BASIC Stamp Not just to underline their business relation with dis- tributor Parallax Inc., but 40 etckbi =!a1[C'h - 5- 200 ‘ 1 also to encourage lab work- ers, Hoptroff provide lots of information on linking the Flexipanei to the famous BASIC Stamp. And a very welcome bit of information it is because the BASIC St am p (BS2pJ is widely known and extremely popular among budding programmers (and a lot of professionals, too...) if only because it can be pro- grammed in,,. BASIC! Figure 1 shows the really simple connections between the BS2p Demo Board and the irGUI452 module. The practical assembly is shown in the photograph in Figure 2. LEDs may be added to mon- itor the CD, Ready, Data and Test pins (shown dotted in Figure 1). If so, 4k7 current limiting resistors should be used to prevent overloading the power regulator on the Basic Stamp. The 10k resistor between Attn and Vss is only required if nap mode is to be used — it ensures that the Attn pin is not pulled high when Stamp resets. The 4k7 pull-up resistors on the SDA and SCL pins are required in all cases. In the example application. two check boxes are dis- played on the PDA. When Send is pressed, the state of the second check box is dis- played on the LCD display, the value is inverted and written to the first check box. Thus if a Read opera- tion takes place after the Send operation, the first check box's state will be the opposite of the second. The required resource script is shown in Listing 1. It is read using the irGUI config- uration tool and used to pro- gram the irGUI. Correct irGUI programming can be verified using a PDA to read the controls. Once the irGUI is config- ured, the Basic Stamp can be programmed. The required code is found in the Flexipanei documentation. Correct operation may now be checked by pressing the Send button. It is also possible to connect the irGUI452M directly to the BS24p without the Demo Board. The 40 mA voltage regulator on the BS2p mod- ule is then usually sufficient to power the IrGUI device, whose consumption peaks at 30 mA during infrared communication. However, if additional components are added, a more powerful reg- ulator may be needed. . 333557-1 Contact information Hop! raff s.o.rJ., \-r.v\vhoptroff. corn UK distributor: Flexipanei Ltd., \ wav . Fsxipan e I. coni Listing 1, irGU1452M resource script //- ^ // // 00 1 Check Box.rs // // X2C test an basic stamp check box control // // PARTNER! irGUl 452 H DEVXCEHAKE "OQI Check Box" SERIAL RANDOM RESET I2C 0x68 X2CADDRESSING IBYTE_INDEX CONTROL CHECKBOX ID chkl FIXED STORE ROM VAR STORE RAM TITLE "Check Box 1“ VALUE 0 // Initial value is 0; when starrsp starts, / / gets inverted TEXT "I'm what he's not" CONTROL CHECKBOX ID chk2 FIXED STORE ROM VARS TORE RAM TITLE "Check Box 2 " VALUE 0 TEXT "Try Me" 5/ 2004 - ekhor efecfrom 41 get three issues (without obligation) for jus £ 7.50! Try out the new elektor electronics and get the next 3 issues (June, Juiy/August double issue and September 2004) delivered at your doorstep. YOUR SAVING: MORE THAN 41%! The trial subscription expires automatically. Fill out the reply card with this issue. Helmuth physical quantities/ integrated electronics mare rch, it is now pcfssibleto any physical quantities for e In thinkable only a few measure sensors mine a** imples of ijew pro Figure J. Block diagram of the H ALSO 5 Hal! senior. The measurement parameters ore configurable. {Micro no 5} Under the increasing rime and cost pressures imposed on developing instrumentation devices, building preamplifiers for sensors is increasing!} coming to be seen as an irksome secondary task. They mu si be exactly matched 10 the sensor output signals, which are usually weak, and if a different type of sensor is used, the entire job has to be done all over again. A lar more user-friendly approach is to employ sensors whose signals have been preconditioned to remove distortion factors (such as temperature dependence, offsets and the like) and give them a standardised output format, such as 0-1 QY or -1-20 mA. This makes it easy to swap sensors. Fitting the sensor components and measurement electronics into the same package has been common practice for a long time already, in order to further reduce costs, the present trend is increasingly heading in the direction of integrating both of these elements onto a single silicon chip. This requires rinding ways to construct the actual sensor dement in silicon. In many cases, this has already been successfully accomplished. For temperature sensors, it is especially easy. For pressure sensors, in which the membrane often already consists or a silicon structure bearing pie zoresi stive tracks, the solution is also simple. Even if such a sensor system may appear to be expensive at first glance, overall costs are reduced Lhanks to savings realised in development effort. Another rea.se n for integration is failure prevention. Human lives can depend on the reliable operation of censors. such as in the case oi ABS and ESP sy stems in cars. In the automotive area a special challenge is provided by the extreme range of tempera- ture variations, which extends from below -20 C to the engine temperature of 4- 125 : C As has been shown by experience, fail- ures of soldered joints are much more common than internal fail- ures oi ICY Efforts to achieve increased levels of integration are thus primarily driven by considerations of safety and security. Htecost savings that arise at the same time (assuming large- scale mass production) are a welcome ride effect. Another bene- fit is increased interference immunity, If sensor signals must pass through long cables before they are amplified, as was the case in die past, interference will be coupled in. With everything on the same chip, this hazard is eliminated. Signal conditioning Amplify ing the signal is not the only task of signal condition- ing. Many of the physical effects utilised for sensors are tem- perature dependent. To compensate for this, a temperature sensor that suitably adjusts the gain can be incorporated inio the system. In many cases, the transfer characteristics are non-linear and must be linearised. This is especially true for conventional temperature sensors, such as NTC and platinum resistors, as well as thermocouples. Regardless of whether linearisation is performed using con- ventional analogue electronics or software in die signal evalu- ation computer, it always requires additional effort and expense. If a silicon-based temperature sensor is available, it can be housed on the same chip and the linearisation can be implemented directly adjacent to the sensor. Such compo- nents are now In widespread use. One example is the National Semiconductor LM35. which has been manufactured for many y ears already. It generates an output signal that pre- cisely and lineally increases with temperature at the rate of 10 mV/K. Over the years, it has been joined by a whole group of relatives that operate in similar manner (for more informa- tion, see w w w. nati onal .c om/ ap pi n fo/ie m ps e n sors/prod uc ts . h mil 1 . Sensor / controller combos Once a sensor has already become an 1C. the next step is to integrate functions that were previously wired externally in the form of "discrete* circuits. An example of such functions is comparators driving outputs that switch if the temperature crosses a certain threshold temperature. The threshold values can be provided externally in analogue or digital form, inte- grated A/D converters are also commonly present, usually with serial output in order to save pins. The next logical step is to add a microcontroller to the chip. This makes a multitude of additional functions possible, including externally pro- grammable parameters such as sensitivity and measurement range, calibration, and many others. An E EPROM (also on the chip ! can store the calibration data. In this wav. the sensor is transformed into a miniature computer. A significant advantage of such Intelligent' sensors is » £—■ ^ t.- reduced type diversity . Instead of making a large variety of types that differ only in their detailed specifications, manufac- turers can make just a few basic types, w hich can then be pro- duced in much larger quantities. The parameters required for operational use are entered by the user, and in many cases they can also be subsequently modified. A typical example of this type of sensor is the family of Hall sensors made fay Microtias, The first model of this family was the HALS0O. which was further refined to yield the derivative types HALS05, HALS 10 and HALS 1 5 ( ww w. m i c ron a > x o m/p rod ucis /o ve rv i ev, /s e n so rs / i n dev . p ho 1 , 5/2004 - eh r ,, | of dedrorifcs 45 Figure 2, eioek diagram o f the it A 87 supervisory 1C. The temperature sensor on the chip (lower left) plays Only a secondary rah. [National Semiconductor) SVSCL< SVEjilT-L R£5£"r rigere 3. iVtofiom sensitive coma structures in the ADKL202 micromschanlcal c c cetera tic n s e rr s c r. (Analog Devices) Figure 4, In the ADXRS15Q rotational rare sensor, the paths c : vibrating mechanical structures are altered when the device is rotated. (Analog Devices] excursion sensing rotation drive direction 1 resonator drive finger excursion due to Coriolis force Id this case, processing the measurement signal is especially difficult. The signal voltage from the Hall dement is extremely small, and it is superimposed on a large off set volt- age. In addition, both voltages are highly temperature depend- ent. Temperature compensation requires complex circuitry , and optimum results can only be achieved using a switching technique, similar to a chopper amplifier. With these sensors, users can configure a whole range of parameters according to their wishes: sensitivity, the upper and lower limits of the measurement range, measurement band- width and the amount of temperature compensation. A special feature here is that the temperature dependence can either be entire! v eliminated (even including its nonlinearity, for which ■ *-■ * purpose a quadratic correction network in included), or a cer- tain proportion of the temperature dependence can be inten- tionally retained. This can be useful if i for instance) the sensor is used with a magnet that has its own temperature depend- ence. Id this w ay, the temperature dependence of the overall system (and thus the temperature dependence of the sw itching distance, for example) can be reduced to nearly zero. In normal measurement operation, this sensor is operated from a 5- V supply voltage and generates an analogue signal that is proportional to the local magnetic flux density. It can be programmed by increasing the supply voltage to a higher level and modulating the voltage, A voltage in the range of 5.6-6 V corresponds to a logic Low level while the range of 6.8-S.5 V corresponds to a High level. The data are v. ritten serially. In this mode the sensor output operates digitally, and the internally stored parameter v alues can be requested and read out serially v ia the output. The sensor is electronically 'sealed' on conclusion of the programming process, and sub- sequent programming is no longer possible. The output signal is again analogue after programming. Tliis approach allows die number of leads to be kept to an absolute minimum: ground, supply voltage and output. This keeps down the cost, which essentially depends on the pack- age ty pe used and thus the number of leads. The packaged 46 ehklct dcUi emits ■ 5/2004 Author profile Heiffiuth E*Wi Lemme read Physics and Economics in Monster, Saarbrucken and Munich. Having start- ed out as an electronics designer he became editor of a magazine covering industrial electronics in 1978. Since 1986 he has been a free-lance journalist specializing in science and technology. Email: hewlem me@aol.com sensor. v. iih dimensions of 4 x 4 x I .5 mm, looks like u plas- tic-cased transistor. Its block diagram is show n in Figure 1. ■ — “ Bus connection In systems with many sensors. It is economical to connect all of them to the computer via a common bus, rather than using individual cabling. This means that each sensor must hav e a bus coupler, which in many cases can also he housed on the chip. An early example of this type of component was the National Semiconductor LM75. which had a delta/sigma AID ■wr converter and an I-C bus interface on the same chip. A large demand for JCA of this type quickly arose, so nevv tv pes were continuously developed and their range of functions was con- stantly enlarged to meet the wishes of users. They ultimately evolved into complex monitoring components, which (for example) can be used in PCs to monitor not only the tempera- ture but also a whole range of other quantities, such as fan speeds. Figure 2 show s the block diagram of the LM87, which has so many functions that it has become a General- » *i_ purpose 'early warning system' for all possible types of faults. Here the actual temperature sensor i at the bottom left I is only one of a host of elements, MEM5 Now that w e have learned how to accurate!} produce mechan- ical structures with micrometre dimensions, it’s possible to integrate sensor dements that operate using moving pans, such as sensors for pressure, force, acceleration, and rota- tional motion. Where we previous!} encountered metallic or ceramic parts with dimensions in the millimetre or centimetre range, we now find miniature structures made from monocrystal Ike silicon, which together u ith their associated electronics form a monolithic block. This combination of micromechanics and microelectronics forms a micro-electro- mechanical sv stem (MEMS i. The first products of this type to be manufactured in large vol- umes were acceleration sensors for m^erinv; air baes in cars. •tor ■*«*- S_- to- They contain two interleaved comb structures made from sili- con, with one of them be in* firm I v attached and the other being suspended such that it can move. Capacitances in the femtofarad range 1 1 femtofarad = Iff - F » are created between these two structures. When the sensor is subjected to a mechanical impact, the movable comb is slightly displaced due to its inertial mass. This causes one capacitance to become larger and the other one to become smaller, which is sensed using an electronic bridge circuit. Such sensors have proved to be extreme!} reliable, and more than 100 million pieces have been produced by now. Some of them are even sensitive in two directions, such as the Analog Dev ices ADXL2G2 illustrated in Figure 3 t vvww analog.com k Airbags in cars have already saved many lives, but electronic sta- bilisation systems can make an even greater contribution. They sense the rate of rotation of the vehicle about its vertical axis as the primary variable, and if it exceeds the maximum permissible value tas occurs with a skid}* they initiate suitable steering and braking manoeuvres. In the event of rotation about the longitudi- nal axis fro I lover l the airbags must i nil ate immediately. Sensors for use in cars must be produced in large quantities at low costs. The glass-fibre gyroscopes used in avionics and space flight systems would be unaffordable. Here again com- ponents containing movable micromechanical structures have proven to be quite suitable, and they are already being pro- duced by many manufacturers. They are based on the physical phenomenon of the Coriolis force: if a mass in a rotating sv *- tern is displaced linearly in a radial direction, it experiences a deflection in the tangential direction. In the Analog Devices to^ ADNRS150, a flexibly suspended mass is excited into reso- nant vibration bv electrostatic forces, with an amplitude of ±3.5 pm and a frequency of approximately 15 kl lz. If the chip is subjected to rotation, a force perpendicular to the direction of oscillation is exerted on the vibrating element, and in a manner similar to the previously described acceleration sen- sor. this causes a change in the capacitance measured between two interleaved comb electrodes. In Its practical implementation, the IC uses two sensor cells whose masses oscillate in antiphase. Not only does thi* neu- tralise the external vibration of the IC, it also makes it less sensitiv e to disturbance from vehicle vibration. Figure 4 shows a portion of the chip, which measures only 3 x 3 mm. It is housed in a BGA package with dimensions of 7x7x3 mm. Modular construction Despite its considerable success, there is a problem with microsystem technology, which is that the large from-end development costs can only be recovered if the components are produced in large quantities. Tills is difficult to achieve for small and medium-sized sensor manufacturers. One solution to this problem is to construct die sensors in modular form using several independent functional blocks, which can then easily achieve large production volumes. A concept employing three modules, which has been developed by AM A Fachverband fur Sertsorik e. V. < www.ama-sen- sorik.de I in close cooperation with industry, is show n in Fig- ure 5. It consists of the following modules: 1 ) the measure- ment module with the sensor element and signal conditioning. 2 \ a microcontroller for additional signal processing < includ- 5/7004 - ehklor e-stlrcriB 47 F'jgureS, A modular microsensor technique using defined inter luces (PrimSeas ana B u see up ier). (AA \A Fadwerbond fun Sensorik e. V!J analogue sensing K> processing I I Prim Sens recommendation system connectivity bu=, coupling recommendation Figure 6. Temperature measurement using fibre-op fic sensors Aside a 13Q0-MW generator with extremely high electrical and magnetic field strengths, (Photo: Siemens} F inure 7 .A wireless Ujr sensor using surface acoustic a ■ es. The response signal is affected by the attached sensor element. antenna InHnrogatian signal converter ecnvsft=r p;52oe!ec)ric cry$fc*i leatf iropetisnee {switch or externa] sensor] ing digitising ), and 3 ) a bus coupler if necessary, The modules are separated by two standardised interlaces. The first inter- face is called PrimSensA and the second is called ‘Buscou- pler’. The first products of this type were show n recently at the Hanover Fair Another modular concept defines a component system w ith small, square circuit boards with dimensions of 10 x 10 to 45 x 45 mm, which can be stacked on top of each other f w \vv, .matcii-.v-ors r Interferencedree measurement without electricity The sensors we have examined up this point are all ‘normal' sensors that work with electrical cables, but there are some places where it is not possible to run such cables, such as where there is an explosion hazard or where there is a risk of voltage discharge in a high-voltage installation - or in envi- ronments where there are strong electromagnetic fields, such as in radio transmitters or electrical venerators. a_- In such situation, a different approach must be taken, A big hly promising technique is optical measurement using light instead of electricity. The light is conveyed by a glass or plastic optical fibre to the measurement location, where it is affected b\ the quantity to be measured and then returned via die same optical fibre or a second fibre. The evaluation instrument determines the measurement value from the returning light. An example is die Lumidiemi instrument made by the US company Ipitek. w hich transmits light pulses from an LED through a fibre to a measurement probe, w here they excite luminescence in a fluo- rescent material. The duration of the luminescence depends on the temperature, and tins effect is exploited to make measure- ments tisinv the luminescent liuhl returned to the instrument. «_■ *i_- Systems of this son. In which the fibre only acts to convey the light, are called extrinsic' fibre -optic systems. However, it is also possible to use the actual fibre as the meas- uring element. Such intrinsic' fibre-optic systems exploit the miniscule but still present effects of external ph>sical quanti- ties on the propagation of light through die fibre. If the w ave nature of the light is also taken into account, very high sensi- tivity and resolution can be achieved. A w idely used technique involves writing a Bragg grating' into the fibre. A Bragg grat- 48 t'sktor e!«fro‘!K - 5/Z30I ing h a periodic series of regions having an elevated refractive index, which is sreneraled bv means of UY irradiation. Liuht W «' Hu- with a wavelength that exactly corresponds to tw ice the grat- ing spacing is reflected back to the optical source, while all other wavelengths pass through unaffected. If the fibre is stretched, light with a somewhat longer wavelength will be reflected, and this can be measured optical Iv. This yields a highly sensitive elongation sensor that operates without elec- tricity. cannot be affected by extremely strong ambient electro- magnetic fields, and cannot itself interfere with anything else. There are very many physical effects that can influence the propagation of light in a fibre. Quantities that can be meas- ured in this manner include elongation, tensile stress, vibra- tion. flow, tilling level, pressure, angle of rotation, tempera- ture. ionising radiation and many others. This makes it possi- ble to make a wide variety of measurements under difficult ■r conditions, in situations where such measurements were pre- viously considered lo be out of the question - such as deep inside the 1300-MW generator shown in Figure 6. Passive RF sensors ith rapidly rotating machine pans, a sensor link via com mu- tator rings is frequently not sufficiently reliable. In such situa- tions, it is possible to use another sensor technology drat does not require a local power source: surface acoustic wave chips. These components, which are made from piezoelectric cry stals l such as lithium niobaten are used as bandpass filters in radio receivers. An RF alternating voltage applied to the input comb electrodes (typically with a frequency of several hundred mega- hertz to a few gigahertz) generates a shallow mechanical w ave on the surface of the crystal. This wave propagates over the length of the crystal until it is reflected at the other end and returns back to the electrodes, where it again generates an alter- nating voltage that Is slightly delayed from the excitation pulse. If a sensor (for example, a capacitive pressure sensor) is con- nected to a second set of electrodes at the far end of the cry s- tal. the reflection of the waves will be affected bv the sensor in a manner that depends on the pressure. Hie pressure can then be determined bv evaluating the returned signal (Figure 7 j. If an aerial is connected to the input, the sensor can be queried using radio waves. This technology has been studied in the research departments of tyre manufacturers as a means of acquiring measurement data from rotating tyres l pressure, temperature and traction ) without using a batten as a power source. For more on this subject, ^ee the article ‘Wireless tyre -pres sure monitoring' elsew here in ihri issue. 14 1: 79- i - I.-:'" FRUSTRATED ! Looking for ICs TRANSISTORS? A phone call to us could set a result. We offer ail extensive range and with a world- wide database ai our fingertips, we are able to source even more. 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EIT prints hard copy via the Windows printer driver Order now using the Order Form in the Readers Services section, or WRITE TO P.0, Efli 150 - 1 F i(&ril$e Vfck m 7\’ff * TikpStre +44 [OM 2M e57 * Fci +44 (0) 15 SO iwm Interne! www.elektm- efecironlcs-co.uk 5/2104 - ebtlof eh monla 49 Delano L Klipstem Sensors ~ - r Sensor technology at MIT Polymer electronics for sensors: a new expected. The first results include nanotechnology sensors that chemical compounds such as incredible level of sensitivity. TliT with an i K . _L _ 1 1 — ■ - — »-t K. 1 The ‘hath ■•■=j hoik' c 'is E* /. ) 21 12 c " j' 5 e ~i ilih’lfiJIc Of. Techno : coy. . imune: Da. MpifeinJ Polymer Electronics for Chemical Sensors' was the topic for ihe lemh research and development conference at the Massa- chusetts Institute of Technology (MIT), which gave an overview of current developments in the field of plastic elec- tronics. The name of one speaker made us prick up our ears: Professor Timothy M. S wager is associate director of the Institute for Soldier Nanotechnologies at MIT. What was he seeking to achieve? The MIT professor came straight to the point, summing k up in one sentence: “We want to build sensors so small that they could in principle be constructed from a single molecule". An ambitious target, and certainly noL one that can be achieved in the foreseeable future. Or can k? Some substances, such as nitric oxide (NOj are relatively simple to detect using poly- mer sensors. NO is a colourless, poisonous gas which increases the conductivity of certain polymers. \Y "iih a good sensor it is already possible to detect as little as a few nanograms. Using more sophisticated polymer systems, more complex mixtures of substances can be detected. Swager and his colleagues have, as an example, developed a prototype of a detector which can respond to as little as ID -6 grams of TNT explosive. With that a very sensitive land mine detector could be built. What interests potential users more at the moment, though, is the possibility of dramatically improv- ing the sensitivity of baggage monitors at airports. In a com- mercial product such a detector could be more than ten thou- sand times more sensitive than those eurrenth used. And the ■r chances of being able to smuggle explosive on board an aero- plane in the heel of ones shoe would fall to zero at a stroke. At MIT they are well aware that a lot of development w ork lies ahead. At the moment it is only possible to make polymer sensors in the shape of a one-dimensional ^trip. whereas effective chemical sensors need to have a three-dimensional structure. Tw o-dimensional planar sensor structures will have to be made before w e can even consider going into the third dimension. Chemistry is being brought to bear on electronics in other areas too. Swager and his colleagues have developed a tiny laser made from a polymer, capable of delivering an output power of up to 7 5 nW. A ring laser has also been built using mi cios true tures made from dmitrobenzene. Using cunning molecular design techniques signal gains of up to I0 5 have been achieved. The MIT professor is absolutely certain that new results in chemistry will have a dramatic impact on the future of electronics. Phil Shakis. research assistant in the Department of Mechani- cal Engineering, agrees. He reported a sensor in the form of a linger ring which can measure blood pressure and oxygen sat- uration levels and transit them wirelessly to a monitoring station. The challenge in this case is not the instrumentation technol- ogy itself, but the problem of minimising power consumption. The data are measured on an anerv in ihe fineer. The rins »■- itself was designed usins finite element methods to euaramee i— ■*.- reliable operation: ii must not press too hard against ihe bones in the fin sen or errors will be introduced into the readings, ■— -fc_r T 5/2Q04 - cTeVtc-i dsdronics 51 Microscopically small grids Term, a cell trap. This allows Individual cells to be cb served red moved using electrical impulses. (Imngs: Voldmon/MfT) ultimately giving rise to incorrect measurements of blood pressure; bm on the other hand, ihe better the ring tits, the better the signal-to-noise ratio achieved Pressure is therefore only applied locally on the linger in the spots where the anen in question lies. The pressure itself is measured using infra- red sensors. What can we do v. iih a sensor like this in everyday life? This is being researched ai the Massachusetts General Hospital (MGH) in Boston, located opposite MIT on the other bank of the Charles River. Similar measurement devices for these Fiaure 3. Professor Timothy ‘A. Swager: “We wonf to build sensors so small that they could be ccnsrrvcied from j singh molecule ", (Image: private) kinds of data are already used in hospitals, and although they are very advanced the} are also comparatively large; the ring developed at MIT is a thousand times smaller. At present it is used in parallel with traditional instruments, including at a stress EKG unit. Early results are already available: identical measurements are obtained from patients at rest, while under stress the ring sensor gives much more accurate readings and. mo s i i mportan 1 1 y, fe we r arte fa els . Many different approaches were taken in trying to minimise the power consumption of the ring. A high modulation rate is used during data transmission to keep the transmit time as short as possible, A 'sleep mode" for the ring saves yet more power; there is no need to take measurements continuously. For special applications like thri one a dual- architecture processor has been developed at MIT which meets the extreme performance requirements better than conventional processors. The device also has an interesting market in the area of fitness. Once the system has proved itself in hospitals, the next project is to create a monitoring system for intensive training. Other experiments are being carried our to record stress situa- tions while driving. There is a close relationship between brain function and cardiac activity. Stress, anger and physical tiredness are reflected in an increased heart rate. For example, a system which provided continuous medical monitoring of rhe driver of a long-distance coach could increase safety. As well as this sensor ring, active sensors have been placed in cuffs to be worn on ihe arm: so-called wearable cufts'. Many people require continuous monitoring of the most important body functions in order to be able to call for help quickly in case of an emergency. Another approach to monitoring such patients is to use "smart shirts', which connect together a whole network of body sensors. At present they require too much wiring to be used inconspicuously; development work is in progress to reduce the number of connections to just two i tor the power supply). The power supply v, ires can be used simultaneously for signal transmission, forming a bus system for the data to be communicated. Such unprotected bus sys- tems are susceptible to interference, in particular to the inevitable noise. An initial analysis of Lhe noise spectrum indicates that this idea is practical ov er a wide range of fre- quencies, certainly above 100 kHz. MEMS for biosensors Joel Yoldman. Assistant Professor of Electrical Engineering at MIT reported on BioMEMS. Cells contain a large quantity of useful pieces of information w hich are not only of interest to doc tori. Modern criminology is also dependent on cell research. Today's typical experiments use cell cultures con- sisting of more than a million individual cells. The cells' envi- moment is poor: the cells die during the experiments, which changes the nature of ihe culture. What are wanted arc biosensors which can extract die same information, and possi- bly much more, from just a few cells. MEMS (micro-electro mechanical sensors ) look as if they might make suitable biosensors. Using such microminiaturised experimental methods it is pos- sible to aim for better results. For example, micromanipula- tion of samples can help extract desired information. Ihe problem with experimenting on single cells lies in optical screening: one can only study what one can screen lor, and 52 cleklflf decficrits - 5/2004 one can only screen for vv hat one cim see. The classical microscope always shows the same section. If the sample being studied is oil a glass slide, then there is no difficulty. However, when using dynamic >ereenlng. the cell material being studied flows across the screen, and thus there is always the danger that an interesting part of the sample might be lost for even \ old m an and his colleagues are looking for a solution between these two extremes of dynamic and static screening *_r 3 where there might be the possibility of repeating an observa- tion to obtain reliable data. Using MEMS one individual cell can be studied. The cells are kept alive in a transparent nutri- ent fluid. They can be studied using optical and electrical techniques, as well as by using ultrasound. Using microscopi- cally small grids cell traps can be constructed in which cells can not only be observed, but can also be moved around using electrical impulses. Using these technologies we hope to gain insight into a secret that also concerns quantum physicists. Today we know very little about what influence observation from outside has on a cell. As in quantum computing, we have to be wary of the problem that when reading or writing information one always runs the risk of distorting ihe information itself. .■i.i.uii : - hi", E ET9 rtUMjAl TOTB0S ra ssrree sw tf** tm ■ L^Zr : - z T j i’tio:n r n = ^ PtlSO-fH -Lf.T'l TTV^ : _^fc ■ FH1 r - , - 1 : ■ : : : = { T\ v V - j r . •: • ■ X \ i v : : ■ ■ : : : \ V = \ 93UH , -=.-i=.- -f ef RC i G..0 H UJCTR 0 l E TRA C KER V : : ^ . . Partab "=]5=W .... Just In ... Spectrum Analysers OSCILLOSCOPES h p. ps 1 :-za HP. cSHS FSU Q-I Sff 0-3K H P, 3$K£Q PSU ttotf O-tSV G-lttHJYG-laA r.f H P. £3e5a PSU TnffSt Cujm I C-T, :: I- II , £-:■ HP. 4,j , sa I-H:-- lMU 55eg= HP. M7^ lWJ s; dcT 17*7. L«S iJ^r GW Ha n::i tn £27* RJME^GUUEta^Dqd^ KHTHLET £}13 L-UV 73 > .GJTFLFf Z- “-:•■■= -s-ij . 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HARM 'll 1U1 Fte -5 C-xrts J J-I -r hp. sane rei ccukqt soat K.F, 5KZA HHt - TBSHd^c PMt fr' HP. ttsa Ldic A-.i'rii- i-L >.l V-:; UJUMGMl 22.15 tor li=t V-. ■ - ; 2-r ■n;E3 tm £3::^ £i:: sitei 475* Parnell DTV 12-14 Oscilloscope 0 cal Tra cs 1 2 MHz TV Co tipliji a On ' y Fame]] LFI Sine/Sq GscldoscopB IOKi-1 MHz Dnty ope 1 Hf al UdIIIHHU TDSS30 Didt Tn« 3AVSL IBS n*a»i rirmoaox 213533 Etaj Tk 5£* iDCMLz^mS TsJtHOHlX TOSStO 0aai TzSB SSJHi 2S LE99 j f SAIGA -j.-l T-^z iTIVrtr II] tfflAOfl VCSS5 Sax Treat 2PUSZ2Q? Prjj PU5>32 n r r, : :■ U.f MI-' ' J ' '■* aKfa . , • r ' in : £27 £ LEM - IT: . £2fL 27 ■19L HZ Cz~&Fr=.T T*£St F 5CM-Z fracE 9jLL-iJ toqfcnsnr Taos' i Dr Oscilloscopes Available 5/2004 - dcklor =!=drc"i(5 53 Visit our website 1 www.distei.co.uk | THE ORIGINAL SURPLUS WONDERLAND! 1 THIS MONTH'S SELECTION FROM OUR VAST EVER CHANGING STOCKS Surplus always 1 wanted for cash! | GIANT 10" 7 SEGMENT DISPLA YS I IC's -TRANSISTORS - DIODES A bui pirEfiSS.3 ertebes is in bring to you trese <3 ALT 7 jGurd iticite dspfe/a toa raw aifortiabta prfaen Tho AT dWrfry tbs g.es &r£Ctor^ ^ad- stiwy 3 trig dances sxf s hce cf acc < jCS- xns r dudrc score boeros cOgtel docks, coun- ters, event timers sto- As tiro urfe aro a s&nipfe efecrcrredtericEi risers ard ooerie Sram 12 V DQ, arriis avrhhg wa Bwxhes, RC cr PC may he teed to tijrrri srae crmi/xte efgb. Unfs tosLre rtnora! Tero Ftwsr' memoy whm ffssjy arpEres desgn Fof an exeaUertt DtY practical article, Eee trie Slay 55-5 of '^wayday & Practical Efectrorecs' magaa in e . (deal School I Co ’c^ coo sfrucbon project Scfpfed to good RFE ecndbon, complete w9i (fete sheet. Less than 30% of makers price OBSOLETE - SHORT SUPPLY - BULK 10,000,000 items EX STOCK Eot MAJOR SAVINGS CALL or see web site www.d IsteLco.uk Only £29,95;e) or 4 / £99.0Q(D) Otis- RWM Oroof PH25 THE AMAZING TELEBOX TV SOUND & VIDEO TUNER CABLE COMPATIBLE * Converts your colour monitor into a QUALITY COLOUR TV!! The TELEBOX fe an etoate.e Ltfy cased mans cohered uni Gcntenro si etoCTKs reedy to pjg rtoa host d vidao rrcntoirt cr AV eqUipmeri which are fifed wtii a qxrrpoefe or SCART rpi i The compeers ^ttoo o."c" wl aso plug creed/ into moat video recorders, ekwrig raceccxh c? TV chamste not rwrmaJy recavaUe on most teiffiision roesvers* P"B BOX fiBl PiuSi tx£cn ccnrofe on re rat pans slew reca^on, or t 1 tireacfs 'nh a* LHF ocfcur i= e.tfcn m[ I f | COMPUTER MONITOR SPECIALS Legacy products High spec genuine muitysync, CGA, EGA, VGA, SVGA .Mitsubishi FA341 SETKL U* SVGA Multisync octet? morfcr wfr me C2S rict pfcro Lte etc JEsaiOTs of 1 024 x 753 A vsrt roy of Tel'S afeviS correesm to a host cr comcufers IrrAjaba IBM PC 1 * h CGA, EGA, VGA & SVGA mates. BBC, COMMODORE fectidha Amca 1200), n — ARCHIMEDES snd APPLE. *.tery features: E'cr^c tectoate, tati sv.^totirg aid LOW RADIATION WR BsecTiPcajcn Ft '/ cyjsranteert to EXCELLENT brite lied ccrtoxn. TBt & Swivel Rasa £4.75 voa^^ibhpci™^ only £129 ( E) TST External cct-fesfor other types of computers svaftble- CALL -CH70H of 8 "Jh 0MT5 iilte ahy ai ^.^Eton ^bos Vr? and UKF ocsurOng the HYPERBAHD as used by most TV opa^ton. Tted tor desktop computer video sys- tems & PP (psoLra h pdi}dbr$. For compts'a cDrrpa±u:/ - e,t’ Lr mcTEJi v.tiout sour! - an Tasgrsi 4 aijoampKtor and tw hdUE 5ucio njto£ 3^ as &-ard new - 1*/ garariaea Generic LOW COST SVGA Monitors We eft cose the make, which includes Compaq. Milstibtishi, IBM. etc, Supplied ready to run with all cables. Standard RTB SO day guarantee. 14 SJ 15" 17 n £59.00 £69.00 £79.00 order TDS4 □nierTG21 ordsr TJ63 Supplied in good used condition, Shipp ng cods (D) TELEBOX ST fc? corrpcsiie sides Input type men tors ritii hte< Slate of Ifie art PAL (UK spec) UHF TV tun&r module & H\ £2e.gs TEL E B OX STL as ST but Ftted wSi I *q ml najear 09.50 TELEBOX MB M A and VH FAi H Ft Ca^ l e r Hyps.xand tu ner ES9.95 Fc: erverseas PAL versions state 5.5 c? 6 m Hz sc tra specT-caccri. t Fl - cah' e l hypoband signal nece-pLc-n Te'sbox J.'B sh-ould be cen- neded to a cab’s type seMoa. ShtppLng on a L Te ’a box's, coda (3) rtrii com pcs He W p -p’ video & HICAM hi fi steiBO sound outputs. Micro aledronlcs ail cn one small PCS only 73 x ‘ 60 x 52 mm erab'e fti ] tuning, control v^a a simple 3 wire link to Bn iEV pc type computer. Suppled corrptete yiHn simp's wcrWng pic g ram and documentation, RsquTss +1ZVi + 5VDCto operate. BRAND NEW ■ Ortfer as AfYOO. O/l// £39.95 code (B) Sbb rtW'jVrd^sfef. co, uLtofate_myC0.htm fiarp/cVt/jre + fulT tfe/eiTs HARD DISK DRIVES 2%" - 14 T : TOSHIBA MK1CS2VAV 1.1Gb !actsiM«2j5 mm H) New £59.95 2\j TOSHIBA MK431 3MAT 4.3Gh la|Mop [S2 mm H) lfov£ 105.00 2' .’ TOSHIBA MK&409MAV 6.1Gb teptop (12.7 pm H i New £95.00 2W TOSHIBA MK1SMGAV 16 Gb Septop (\2 rrm H Now £149.95 2Vi to 3 V" COriv&rBxm ?dl fc-r Pc's, ccmpteto with ccnr.entnrz £15.95 3 :/ CO M P AQ 3 13706-021 (ffl M) B gb U LT/SCS13 New £1 99.00 3 J4" FU J \ FK-3^25 20n* MFM Ur flr= ES9.95 5 i T CONNER CP3024 20 mb 10= l/F fo-r equw.) R^E £^.05 3J4’ CONNER CP3044 40 mb IDE tir (c: equY.) Ft-E £69.00 3‘ Y QUANTUM 40S Frodrtve 42mb SCSI L7 l Her. PFE £49.00 5 / MIH1SCRIBE S425 28mb P/.FM Ur (or equjv.) RFc £49.95 5ii* S EAG ATE ST-233R 30 mfa RLL UF Rsfti rb £69 .95 5 V CO C 942D&5 1 40Hib HH MFM b¥ RFE tested £69.95 5Va' HP 97543 B50 IS) SCS I RFE tasted £99 .00 5'/+' HP C3010 2 Givis SCSI tSfvmtlal RFE tested £195.00 S' NEC D2246 So Mil SMD fnMce New £99 .0 0 S' FUJITSU M2322K ; S0h*b SMP LF RFE tested £195.00 S' FUJITSU M23S2K 2 GO SVD Lr RFE tasted £345.00 Many other (loppy A H drnres, IDE. SCSI. ESDI eic from sfocJe, sc? .vciisrHc for full stock list Shipping on ail drives is code (C) VIDEO MONITORS PHILIPS HCS35 ^ESfr.E sijte as CVE333) atlrac£vely itjted U' Kilour mender wui both RGB and standard composite 15.B25 Khz video inputs via SCART social and separate pboT/3 isctos. frtegrsl audio power amp and spesiar for all audio visual uses. WH orated direct to Amiga and Atari BBC computers. Ideal tor a' ! video mortlioring / sacunty applc^tters with direct conn acti on to most colour cameras. Kgh qua! it/ with rr^ny feateTBS such as front (tonceaisd flap controls, VCR correct = n ti triton etc. Goad u&ed condtton - fcily tested - guararteed t w pQ Q D n Khtendcrts: Wt 4' x H12KF x \b'A M D. U,U J tM ' uu [DJ PHILIPS HCS31 Udra compact 9" ccjolt video monitor with stan- dard composite 15,625 Knx video input «a SCART sxkst kteal ='’ ^ i ''I I' - '' - ; ' ^• 11 --':. ezz 'ia'.= - E. LZ 'z'" •::= Tj idy f ffsf p rf & guaranteed (pokshte izinpr screen bums). In attrac- tive square fc^ack case messutoig WlfT x HID" x 1314" D. 240 V AC mains pew ered. Only £79*00 (dj INDUSTRIAL COMPUTERS Tmy shoebox s^zed aKiustrial 40 l. r hz 385 FG system measuring only (mm) 2€6 w X 6S h X 272 d loeal for dad hated canlrcf; ap^i- Gsdcns ranoirg DOS, Linux or even Vi.r.dows I Steel case OCH- tains fl5 to 26a V AC 50 / SO hz 70 Watt FSLL a 3 ski* ISA p&ssiva beedep' ane and a Rockv 31 £ < PCI 04 ) stendeto . ' e^ticaro com- SIMM, AVI BIOS, battery backed up real time cock. 2 s 9 ptoi D 16550 serial ports. EFP.ECP printer port, mini DIN XeytKK/d con- ne^w, (loppy port IDE port fra hard drives up to 528 VSyte capadbf, watebd og timer and PC f 1 04 bus sock sL i r«e 8 MByte sc ”d state 'ask on a chip’ has its own E£OS. and can be fosked, fotmetted 5 booted. Suppded BRAND NEW fuSy tested and guar- anteed. For fuJ cate see featured item cn aebste. Order as QG55 1 GO’S of appSicattoos inc; r Q.,:en firewall. ters. robotics eic Only £99.00 d: TEST EQUIPMENT & SPECIAL INTEREST ITEMS this wetkm are pro owned. V3T5UBUSHJ PA3445ETKL 14' !nd. spec SVGA monstora PARNELL ‘>60', DC I 50 Arnps, bench Fewer S-jcc'. ss FARNELL4F . ZZ z zi -~zz z= z Z.zz. K1NGSH1LL CZ40V1 ^50V ©DC 200 Amps - NEW tkWto4DalW - 403Hi3ph^pov^recLGxes-exEtDck IBM 6230 Type 1, Token rtog bsso unit driver Wayne Kerr RA2Q0 Aud >o frequeovy respc^iSe srvs yser INFODEC 1U, 24 port, RJ45 nsfwwk patchpanak ^THB2 3COM 1€o7Q 12 Fcrt Ethernet hub - RJ45 conns ctcrs -LD37 3CO?tl 16671 24 Port Ethernet hub - RJ45 comsdrvs 3COM 16790 8 Pori Ethernet hub - RJ45 cocrscays KEV* IBM 53 F 5 501 Tcksn R'rg ICS 20 port to-be modules IBM tf AU Token mg dAuSon panel 622>2>5CtoON AIM 501 Low lUmn Orator 9 Hz to 33CKhz. IEEE l O ALL G ON 6360.11601885 MHz hytorid power osr.b nsrs Trend DBA 274 Data Analyser vrlh G703{ZM] c-4 L'o Marconi 6310 Frogrommabte 2 to 22 GHz sweep genereto? Marconi 2022C ICKHZrlGHz. RF Ssgnai generator HP 1 650B Log c Analyse? HP37SIA Pattern geitercter L HP3782A E~-: Z e'.ed '. or HP 6621 A Dual Psografttr^ate GF = F3U 0-7 V 1E0 HP6264 Rack mount varfatoie 0-20'/ © 20A motored PSU HP54121A DC to E2 GHz four channd test set HPS13DA opt 02 Q 3W MRzpuisa gensrator. GPiS sl; HP At hQ B pen HPCL hreb speed drum pte-tera -from HP DRAFTMASTER 1 S pen high speed cotter EG+G Broofcderl 95035C PredsJcn Sock In ajr.p Koithtey 5 SO CV ca padicr ^ vofte-ge a^aiji-er Ratal 1CR40 cuaJ 40 channel votoe reoofd-er system Fiskere 45KVA 3 ph On Une UPS - t lz,\ hatisrees is Em ere on API 30 2.5KVA Industrial spet.UFS Mann Tally 147 645 Htoh Ine prnte - Intel SBC 48£i133SEnRtWMB 489 system. E-Mb Ram £245 £995 £1650 £3950 £PQA £760 £2500 £49 £69 £69 £39 £POA £45 £550 £250 £POA £4500 £1550 £3750 EPOA £1B00 £475 EPOA £7900 £550 £750 £1600 £POA £3750 £4500 £1499 £2200 £945 Trip >16 vds Sneer, metered 30 amp bench F5U. Now Fujitsu M3041R 600 LFM Kzh sceed band c rir:a-r Fuji Is u MOW ID 600 LPM p dr^Ytth nat^rt Slcmsns K44C 0 64 Kb to 14CMb demgat analyser Perkin Elmer 299 B Ercf^red fipedrophotomsie? Perkin Elmer 597 In6erod apecBQCihotenBtef VG Electronics 1035 TELETEXT Dsoodtog k!arg'“ Meter 19 n RACK CABINETS Europe's Larges! Stocks of quality rack cabinets, Jr enclosures and accessories. Over 1000 Racks from stock This month's special 33/42/47 U - High Quality All steel Rack Cabinets Marie by Eurocraft Enclosures Ltd to the highest pos- sible spec, zaz< fe ature s ^11 steel construction ^vtei rsmovsste skfo, from! and back doors. Froni and [lack doofs are hinged for easy access and all to-ckabte ^ioi rrie secure 5 lever barrel locks. Tria froni dDcr is constructed of double wa! ad s'.&stwrJi a 'designer style' smoked soryito froni -\ zanat to enable status indicators to tie saor through the panaL yet remain unublrusive. Internally tha rack features fu’ly slotted re?n- krood vertical fodng members to lake trio heavi- est of 19 a rock equfpmenL Trss tAO movaLte .ordeal fixing stmts (extras avaUebte) ere pre p-j- chad for standard 'cage nuts'. A mains dit- tnbulfon pans! intern aly moimted to the bdridm* near, provides B x I EC 3 pin Eero Backed and 1 3 13 amp 3 pin switched utility s ockeL Gvsral vantia- tidn is provided by fi4y towered back door and doubts sJcnred top seefen w3h top and site towres. Tha top panel may be remewse for Idling of Integral fans to Ihe sub plate ale. Other features incftjrie: fitted csi'.^rt a.'ti f:c-' tovetert, preparer ec .ti ty pane! ai rt-rtrtr rear for esbte ! ccnns^c-r access €?to. SuppFed : n excellerTt- ^ =' : .- iiarfl Lcrtdrbon 'rt-ih '^.G:_: j jr R^,£i: t.jc. ^crr.e crey gyaSahfe - CALL - Can be suppfted in many other nmfkjuratteos. 33U ' 42 U 47U Order as BC44 Order as DT20 Order as RV36 Externa' c menstens External dimensions External dimensions m“=lc25H .< &35D *. mm=2019H x 6350 x itt;= 223 5h x 635 D x 603 Sri'. (£4* H x 25 T cd3 Vi. (79.5' H x 25^ 603 iV. i36‘ H x 25' D «: 23 ’ T v; D x 23YA V< □ * 23%' Vi Only Only Only I £245 £345 £410 Call for shipping quotation COLOUR CCD CAMERAS % HP 5030 A 0-200V DC % 1 7 Amp® bench port er s upp> , £ 1 9 50 Intel SBC 485712 SCO 3"E— zed khiSbus New £1 1 50 Nikon HFX-11 (Eprtpftol ) expostfo cunlrol unit £1450 PHILIPS FM551S pro. TV signal gensrafbf £1250 Motorola VME B_s Beards & Con^jcnsrris List EAE CALL EPOA ' ' £550 £1950 £1250 £2950 £500 £3500 £3250 SekonlcSD 150H 18 cKimof (ffgtel Hybrid chart racorci- £1995 BSK 2633 JjFcrophono pro amp £300 Tayl or Hobs o n t afysti rf amp-lifer f recorder £7 £0 ADC SS200 Csrosn c decide gas detector/ mcMutiMr £1450 BBC Alil20r3 PPM Meter lErr.vzl Turner) + drive efettrtnkte £75 AN RITE U 9 684 A Optical DC-2-5Gro v.’gvsfcm-- mcnitef £^.t 0 ANRITS U MLS3A optical p crwsr meter £990 ANRTTSU Fibre ep "ic characteristic tost sol £PO A RaS FTDZ Dual sotmd unit £650 RS.S SBUF-E1 Vgktfi rnoduteter £775 WILTRON 6©30B 12.4 / 2DGHz RF e.veec generate^ £5750 TEK 2445 ISO MH* 4 &BCO OSCflOSCOpe £1250 TEK 2465 300 Mhz 300 kL-Lz c.s : r scope rack mount £1955 TEK TDS3B0 4CCVr.z c g^tel reariime ^ ifek drive. FFT etc £2900 TEK TDS524A SOOMta^Hitel roaftime * cofoUMSsptay etc E5100 H P3 56 5A Opt 9*37 20Hz to 40 Mhz spectrum analyse r £3959 PHILIPS PW1730 10 60 KV X=LAV A a-=cssaatei £POA VARIACS - Large rangs from stock - call of we cur wab site CLAU D E LYQ N S 12A 240V stegle phase auto- vtfL reg^ £325 CLAU D E LYO N S 100A 24 G*4 1 5V 3 phass auto, vert reg3 £29 00 Undoubtedly s miracto- of m ode m technology L cur spec's! pc we: '. A qualify product tefi-4 turintj a fully cased COLOUR CCu camera at a grire sway price ! Uni teateros fill autoldht sefissig for ^ i^se in low light i high light ^ appllcEtions. A 10 rom fixed focus Mde angle lens gives MceSEont focus and resolution from cinsa up to ton-g range. The campcsfts video output v. svarificjl to any ccmpes-to mentor or T 1 .' \v\E SCART socket) and most videz- rer^croErs. Unh rum from 12V DC sc ideal tor security & portable applica- tions where mains ptr^er n^rt Hvaiable Overall dlmertstens E6 mm wide ill? deep x 43 High- SuppJjea BRAND NEW & hrify guaronteed wi* user date, IOC's df spplcs- fcrts hdiKSng Secunly, Home Vifeo. Web TV. Web Cams ofc, eto OtoEf LK33 ONLY £79.00 or 2 for £ 149.00 ( b } SOFTWARE SPECIALS NT4 Workstation, complete with service pack 3 and licence - OEM packaged. ONLY £ 89.00 s ENCARTA95 - CDROM, Not tho latest - but at this price I _£T95 DOS 5 u0ot 334" asks wtthcesneisa books o'tvQBssic. £14.95 Windows for Workgroups 3.11 +■ Do* 6.22 on 3.5” disks £55, DO Windows 05 CD ROM Only * Ho Licence - £19.95 Wc rdp Effect 6 :: D ZS suppled on 3V4' d^ska with manual £2495 shipping- charges for software Is code B SOLID STATE LASERS Vis. red. 6 7 Gran laser diode assemty. Unit rsir^ from 5 V DC at Epprox SO mA Cdgirrty made for ccrsvuous use In ind^rteal bar- coda scanners, the fester Is mounted In a remtwafcte sefid a.'ur.r'jm t'oek. ¥,Hrfi. ffeicikjfES as a heats id? snti rigid optisti mount Dims of fc-'oekare 50 ^x50 dx 15 h mm. Integral features ind-jdecvBrtem- r.teratoro shutobafe current corttroi, laser OK ouptrt, srd gated TTL OH / OFF. kterry uses for stperimenlaS optics, ootewb & s^htahews etc Euppifed cc-Tzte‘5 .vto date sheet Ofen-r as TD91 ONL Y £24.95 (A} DC POWER SUPPLIES Virtually every type of power supply you can imagine. Over 70,000 Power Supplies Ex Stock - Call or see our web site. I RELAYS - 200,000 FROM STOCK S 5 ,e ££ETs ty pboosing ycurn-M re's, tirt vi raw Massive Slocks zZYBd r r g r/ 7 -c s zt-zd as = y, Qctsi. Ora^e, tfermetic£$y Seated, Continerta!. Cc niBctors, Tune Da'ay Reed. fS± r cu.y iVedaz. SoTti Slate, Printed Circx-i /JoifrAlng elc. . CALL Of see our we fa site 'A~ww.dssttd.co.uk for mom infrxmatkm. Many obsolete types from stock. Ssvs ££££*8 • i • ■ • * « ft • f ft- ■ >1 ft * ft ft ft * 1 1 • ft I ft ft ft # ft ft ft ft ft ft ft ft ft ft ft •ft ft ft K V i ft )• ft ft ft ft I ft ft *• ■ ft# -ELECTRONICS- ALL MAIL TO Dept EK t 29 / 35 Osborne Rd Thornton Heath Surrey CR7 flPD, UK Open Mon - Fri 9.00 - 5:30 18 Million Items On Line Now ! Secure Ordering , Pictures, information 'A&gn www.distel.co.uk email = admfn@disteLco.uk ALL ^ ENQUIRIES 0208 653 3333 FAX 0208 653 8888 ft 26 i ^.=. ?, AI prices tr L : K and L.._ % , T _ _ . (D;p£ 1 SCO ^ElpEISTC}, (F/rtALL. AJc,v 3- cfeyri far dipping - feste - CALL AI gooefe axetoc to zu- S-tonfero Ccr utoc rs o Sse v.tocri esn ce vav.^ PM ui a to base bass. AI reps lasHvtd to d^ge prices / seel " l;:=_:o~s wnxxA ptr recce Orders to stoex D'sccurts fcr 'Lore Tap CASH pnets pfed tor surfes gooefe Ai ladrorarks, va%rs=rr^ etc ackraMpd S Dtectey Eterorxws ZjjZ. t&OE 54 dfklor c-=t5ni- : (i ■ 5/2004 1 : 1 Quasar Electronics Limited PO Box 6935 f Bistiops Stortford, CM 23 4WP Tel: 0870 248 1B26 Fax: 0870 460 1046 E-mail: saies@quasarelectronics,com Add £3,00 P&F to all UK orders or 1st Class Recorded -£5, Next Day (insured £2S0) - £3, Europe - £6, Rest of World - £10 (order online for reduced price UK Postage), We accept all major credil/debit cards. Make chequesJFO's payable to Quasar Electronics. Prices include 17.5% VAT. Cat! now for our FREE CATALOGUE with details of over 300 kits, projects, modules and publications, MAILORDER ONLY. QUASAR electronics ■Me^TO jcu jnoia rft* rigiV come Motor Drivers/Controllers Here are just a few of our controller and driver modules for AC, DC, unipofar/bipolar stepper motors and servo motors. See website for full details, DC Motor Speed Controller (5A/100V) Control the speed of almost any common DC motor rated up to 100V/5A, Pulse width modulation output for maximum motor torque at all speeds. Supply: 5-15VDC. Box sup- plied. Dimensions (mm): 6GWx1 GOLxSOH, Kit Order Code: 3Q67KT - £12.95 Assembled Order Code: AS 30 57 - £19.95 NEW! PC / Standalone Unipolar Stepper Motor Driver Drives any 5, 6 or 8-lead unipolar stepper motor rated up to 6 Amps max. Provides speed and direc- tion control. Operates in stand-alone or PC- controlled mode. Up to sex 3179 driver boards can be connected to a single parallel port. Supply: 9V DC. PCB: 8Cx50mm, Kit Order Code: 3179KT - £9.95 Assembled Order Code: AS31 79 - £16.35 PC Controlled Dual Stepper Motor Driver Independently control two unipolar stepper motors (each rated up to 3 Amps max.) using PC parallel port and soft- ware interface provided. Four digital inputs available for monitoring external switches and other inputs. Software provides three run modes and will half-step, single-step or man- ual-step motors. Complete unit neatiy housed in an extended D-shell case. A0 components, case, documentation and software are sup- plied (stepper motors are NOT provided) Dimensions (mm): 55Wx70b<15H. Kit Order Code: 31 13KJ- £15.95 Assembled Order Code: AS31 13 - £24.95 NEW! Bi -Polar Stepper Motor Driver Drive any bi-polar stepper motor using externally sup- plied 5V levels for stepping and direction control. These usually come from software running on a computer. HH-? fu Supply: 8-3GV DC. PCB: 75x85mm. Kit Order Code: 31 5BKT - £12.96 Assembled Order Code: AS31 58 - £26.95 Most items are available in kit form (KT suffix) or assembled and ready for use (AS prefix). CREDIT CARD SALES flf Controllers & Loggers Here are just a few of the controller and data acquisition and control units we have. See website for full details. Suitable PSU for all units: Order Code PSU203 £9.95 Rolling Code 4-Channel UHF Remote Slate-oMhe-Art. High security. 4 channels. Momentary or latching relay output. Range up to 40m, Up to 15 Tx’s can be leamt by one Rx (kit in- cludes one Tx but more avail- able separately), 4 indicator LED ’s, Rx: PCB 77x85mm, 1 2VDC/6mA (standby). Two and Ten channef versions aiso available. Kit Order Code: 3180KT - £41.95 Assembled Order Code: AS31 SO - £49,95 Computer Temperature Data Logger 4-channel temperature log- ger for serial port. ~0 or a F. Continuously logs up to 4 separate sensors located 200m -s- from board. Wide range of free software appli- cations for storing/uslng data. PCB just 38x38m m. Powered by PC, Includes one DS1 820 sensor and four header cables. Kit Order Code: 3145KT -£22.95 Assembled Order Code: AS31 45 - £29.95 Additional DS1 820 Sensors - £3.95 each NEW! DTMF Telephone Relay Switcher Call your phene number using a DTMF phone from anywhere in the world and remotely turn on/off any of the 4 relays as desired. User settable Security Password, Anti- Tampen Rings to Answer, Auto Hang up and Lockout. Includes plastic case. 130x110x30mm. Power: 12VDC. Kit Order Code: 3140KT - £39.95 Assembled Order Code: AS3140 - £59,95 Serial Isolated I/O Module PC controlled 8-Relay Board. 115/250V relay outputs and 4 isolated digital inputs. Useful in a variety of control and sensing applications. Uses PC serial port for programming (using our new Windows interface or batch files). Once programmed unit can operate without PC. Includes plastic case 1 30x1 00x3 0mm. Power Supply: 12VDC/500mA. Kit Order Code: 3108KT - £54.95 Assembled Order Code: AS31 08 - £64,95 infrared RC Relay Board Individually control 12 on- board relays with included infrared remote control unit. Toggle or momentary. 15m+ range. 112x122mm. Supply: 12VDC/0.5A Kit Order Code: 3142KT - £41.96 Assembled Order Code: AS3142 - £59.95 PIC & ATM EL Programmers We have a wide range of low cost PIC and ATM EL Programmers, Complete range and documentation available from our web site. Programmer Accessories; 40-pin Wide ZIF socket (ZIF40W) £16.00 18V DC Power supply (PSU216) £19.95 Leads: Parallel (LEAD 10 9) £4.95 / Serial (LEAD75) £4.95 / USB (LEADUAA) £2J5 NEW! USB 'All-Flash' PIC Programmer USB PfC programmer for all l F[ash r devices. No external power supply making it truly portable. Supplied with box and Windows Software, ZIF Socket and USB Plug A-A lead not incl. Kit Order Code: 31 28 KT - £29.95 Assembled Order Code: AS31 23 - £39.95 Enhanced "PICALL" ISP PIC Programmer Will program virtually ALL 8 to 40 pin PiCs plus a range of ATMELAVR, SCENIX SX and E E PROM 24C de- vices. Also supports In Sys- tem Programming (ISP) for PIC and ATM EL AVRs, Free software. Blank chip auto detect for super fast bulk programming. Requires a 40-pin wide ZIF socket (not included). Kit Order Code: 31 44KT - £54,95 Assembled Order Code: AS31 44 - £59.95 ATM EL 89xxxx Programmer Uses serial port and any standard terminal comms program. 4 LED's display the status. ZIF sockets not included. Supply: 16-13VDC, Kit Order Code: 3123KT - £29*95 Assembled Order Code: AS3123- £34,95 NEW! USB & Serial Port PIC Programmer USB/Serial connection. Header cable for ICSP. Free Windows software. See website for PiCs •supported. ZIF Socket/USB Plug “ A-A lead extra. Supply: 18VDC. Kit Order Code: 31 49KT - £29.95 Assembled Order Code: AS3149 -£44.95 L i * i -il j £" Leirf'A iSp- E V ffif i z — R i j 'J +■ ■ 0 lO. 1 KITS, www.quasarelectronics.com H Secure Online Ordering Facilities Full Product Listing, Descriptions & Photos Kit Documentation & Software Downloads : 17A ■ Mltf e'rctrcraks 55 kitchen table ; . £ > A V 4 Res An a Burkhard Kainka V f PL r- TT There are those cool-headed types, who can lie through their teeth with a straight face. But in the end it is just a matter of asking the right questions. Sooner or later everyone will get sweaty palms. Lie detectors are always a great deal of fun at parties. Who is prepared to face up to the challenge from technol- ogy? And also: who is able to defeat the machine! The latter is also very dependent on the actual situation — the questioner must not make it too easy for the test subject! When the ten- sion increases, even the best liar can't avoid a subtle but inevitable physio- logical reaction: sweaty palms. The operating principle of this lie detector makes use of this phenome- non. When the hands of the person in the hot seat become damp, the elec- trical resistance of the skin will reduce. This change is relatively easy to detect. In that respect we certainly don't want to claim that the circuit presented here is a feat of brilliant innovation. However, it is the manner in which this device signals the result that sets it apart. That is F this circuit will emit a tone, the frequency of which depends in the resistance of the skin. Five* five- five The design, of the circuit shown in Figure 1 is actually a relatively typi- cal application for the well-known 555. This timer-IC has been wired here as an astable multivibrator, that means that at the output there is a signal, the frequency and duty-cycle of which are determined by two resis- tors and one capacitor. In this case there are actually three resistors and one capacitor. The resistance of the skin is connected in series with Rl. In conjunction with R2 and C1 T this series connection determines the duration that the output (pin 3 of IC i) is high. When the power supply is switched on, the capacitor is charged, through these resistors, to 2 / 3 of the power supply voltage. An internal comparator compares, via pin 6, the voltage across the capacitor with this 56 ckklur c'edTc;.:u - 5/2004 COMPONENTS LIST Resistors: R1 ,R2 - 27kD Capacitors: Cl - 4n7 Semiconductors: IC1 - NE555 Miscellaneous: BZ 1 - buzzer 2 PC8 solder pins 2 solder pin receptacles soldered to long wires (stripped ends) 6 pieces of (bare) wire PCB. protatypinq board, order code UFBS-1 (see Readers Services page) 9 V-bottery with clip-on leads threshold value. When this threshold is exceeded, the output of the IC will change state. This means that the inverting output oi the internal flip- flop (Gin Figure !) will become high. This causes an internal transistor to conduct which results in the dis- charge of the capacitor via pin 7 and R2. Note that the length of time that the output remains low is not depend- ent on R1 or the skin resistance. Subsequently, the second internal comparator starts to play a part. Again, the voltage across the capacitor is compared with a threshold value (pin 2). When the voltage is V 3 of the power supply voltage, the internal flip-flop is set, the output changes state again and the whole process begins anew. Two pins of IC1 are not used in this configuration. Pin 4. the inverted reset input, can be used to interrupt the charging process of the capacitor pre- maturely. This can be very useful in other circuits but is not necessary in this design. Here, the reset input has been connected to V cc , so that the internal comparator alone determines when to reset the flip-flop. That leaves the control input (pin b). Via this input the upper threshold value can be changed. That function is not used here and the input is left open. Construction For this project too, we have designed a printed circuit board. However, this time not quite as you have come to expect from us. Figure 2 shows a PCB layout for our Universal Prototyping Board size-1 (UPBS-1) which can be purchased ready-made through the Elektor Electronics Readers Services. A normal piece of prototyping board, stripboard or Veroboard can be used as well, of course. +U b "inure I. The 555 as an asfahle multivibrator We can be brief regarding the actual construction, the only thing that may need some clarification is how io measure the skin resistance. Very sim- ple: attach two wires, one to the posi- tive power supply and one to Rl. The stripped ends are then loosely wrapped around two hug ers of one hand. That is ah. Component values In the inset you can read how the com- ponent values in the circuit are calm- Figure 2, Suggested construction on an UFBS- i prototyping board. 5/200-4 - eicktor electronics 57 ReCapping... When □ capacitor is charged through a resistor, the charging current is not con- stant, As □ consequence, ihe change of voltage across the capacitor follows a typical curve [Figure 3 refers): U(t) = U b (I - e- *' RC ) in this equation, the product of capaci- tance and resistance stands ouh the RC time constant. This determines how long ir will take before the capacitor is charged to a certain value. By rearrang- ing the equation we can determine this time accurately: * = log* (I ~U{t)/V ec ) Here U(t) is the desired voltage at instant t and is the charging voltage. The time it takes to charge the capacitor to V3 of Jhe power supply voltage is there* fore: f = -RC log e {1 ~( 2 / 3 / 1)) = 1.10 RC Once the circuit is operating, the capaci- tor only needs to be charged starling from V3 of the power supply voltage. If v/e subtract the time this takes from the value previously calculated, v/e then know the duration of the on-period: f on = 1.10 RC - 0*41 RC = 0*69 RC For the off-period (the discharging of the capacitor) we can write another equa- tion. In general: U{t) = U 0 e - t/M or t«ff = - l°g e (U(t) / U 0 ) RC Here we are looking For ihe time it will take to discharge the capacitor to V/ 3 U a , when the initial value is 2 / 3 : t oH = -fog e (V 2 ) RC = 0*69 RC Nov/ that v/e know exactly how long it takes for one cycle, i.e., what the period ts, we can determine the frequency of the signal at the output: f = 1 / T, where T s t on + t off Substituting the capacitance and resist- ance values into the equations for the on- and off-times [note: v/hen discharg- ing only R 2 is part of the RC network) v/e can calculate the frequency of the tone well hear: F ^ 1 / [t on + t 0 f|} f = K4 / Cl (R s[dn + R1 + 2 R2) Here: f = 319 106/(R skin 4- 81 103} GED: only the resistance of the skin determines the Frequency, 1 1 1 11 030 C 3 &- U Figure 3. The voltage across the capacitor (tap) and the corresponding output signal (bottom). lated. If you are only interested in the result, then only the last equation is of importance. Normally the resistance of the skin will be between 10 and 500 kD. With the component values as shown* this will produce a tone from buzzer Bzl with a frequency between 500 to 3500 Hz, The frequency is mainly dependent on the dampness of the skin: the more sweat, the better the conduction and therefore the lower the resistance Wien the resistance reduces, that is, ihe test subject becomes nervous . the pitch increases. Note that the pitch is not an absolute measure of 'die truth'. One person has a naturally better conducting skin than another. That makes no difference here, because it is the change that matters. Human hearing is actually quite sensitive to such changes in pitch. An additional feature is that the test subject can hear the tone as well. Tnis often leads from bad to worse. Despite the best intentions not to break under duress, this psychological feedback is usually the last straw that breaks the camel's back. www.elektor-electronics.co.uk 58 debar electro, nits - 5/2004 WUWWWl I fw prOAQ y.oitage • FREE software and upgrades • Automated measurements com W1E DrDAQ Data Lo Light level Temperature External sensors. Sender Built in sensors^for light, temperature and sound (level and waveforms) Use DrDAQ to capture fast signals Outputs for control experiments Supplied with both PicoScope (oscilloscope) ancl PicoLog (data logging) software Humidity Temperature 02 In Air Reed Switch For more information on DrDAQ, please visit: www. Dicotech. PC Oscillo HJ 3 071 ji E Scope and spectrum analyser functions A fraction of the cosLpf benchtop scope Save multiple setuos^ for ease of use Save, orint and e-mail your traces Ave-zts Virtual Instrument For more information on our scopes, please WWW. Tel: 01480 306395 j Technology Limited start here +1V6 ... -3-5 V5 2 3 74LVG1GU04 74LVC1G04 Xi o l|l — o Combi-gate Oscillator 1C Many of you will know that a dig- ital oscillator built from unbuffered inverters in □ 74xxG4U tC has to be followed by a J normal' gore. Both functions are now available from o single 1C produced by Philips, A quartz crystal oscillator built around an unbuffered logic gate type 74HC04U traditionally employs o high feedback resist- ance to be effectively turned into a high-gain linear amplifier (Fig- ure 1 ] , Th e fr eg u e ncyfoeie rmi n- ing quartz crystal is also inserted in the feedback path, its reso- nance characteristics forcing the circuit to oscillate at the crystal fre- quency. This works very well bur unfortunately there are also a few disadvantages: not only are five of the six gates in the HCG4U package left unused, bur you will also need one unbuffered gate to make the signal truly digital-com- patible because the output signal of the linear oscillator stage looks more like a sine wave. The above combination of an unbuffered and a buffered gate is now available in a single 1C package type 74LVC1GXG4 horn Philips (Figure 2). The new 1C may be used for oscillator cir- cuits operating at up ro 50 MHz and runs happily off supply volt- ages between 1 -65 V and 5.5 V. Its output is capable of 24 mA drive [at V cc - 3.3 V). The first inverter in the new 1C is unbuffered and the second one, buffered to ensure the norndigiral oscillator signal is properly shaped to meet TTi specifications in regard of swing and absolute high/low levels. The 74LVC1GXG4 requires only a quartz crystal and o small num- ber of external parts. Resistor R1 is the feedback resistance to which the crystal is connected in parallel Resistor R2 and capacitor Cl together act as voltage divider to keep the quartz crystal dissipation within limits. The dis- sipation spec may be found in the quartz crystal datasheets, or obtained from the manufacturer. If necessary, the value of R2 may be adopted to your requirements. In Figure 3, capacitors Cl and c2 together with the load capaci- tance C. form the load on the quartz crystal. The manufacturer will typically indicate that due to the crystal cutting and grinding method, the nominal crystal fre- quency is reached at a load capacitance of about 30 pF. Because C|_ is in parallel with the crystal, a mode called parallel resonance’’ is required. Here, the crystal 'sees' as its load two series connected capacitors. C I and C2 r not forgetting the circuit stray capacitance Q, which is essentially formed by the gate Input (XI , X2 in Figure 1). In practice. equates to about 5 pF. C L =[[C1 C2]/[C] * C2j] + C 3 Cl -C2 = C C L = a 2 + Q With Ci - 30 pr and Cl = C2 =C the latter takes a theoretical value of 50 pF, or 47 pF from the components drawer. C2 may hove a trimmer connected in par- allel if exact frequency adjustment is required. The value of C2 is then decreased by an amount equal to half the trimmers full capacitance. Cl decouples the supply voltage and has to be fitted os close as possible to the 74LVC 1C. If nec- essary, noise suppression may be enhanced by adding o small series resistor or a choke in the supply line. ' 44 : - 2 - ■: Web pointer v avw. phi I i ps fog i c . com / p red uc ts/ Ivc/pd f/7 4 1 vc i gxQ4 pdf 60 dskter detUorrcs - 5. 2004 1 S = open: 5V. 4A S -cfosed' SV£.„24V conti nuousfy vsrisbl-e Global Power Supply With continuously variable output voltage Bernd Oehlerking Small switch-mode power sup- plies are often available af a low price from jumble safes, electron- ics surplus outlets and high street electronics shops. Well show you how these units con be put to good use. These SMPSUs from surplus lots con handle any power line volt- age between I 00 V and 240 V, which makes them suitable for use oi! over the planet. They adapt automatically to the mains voltage measured. Not much larger than a cigarette pack, these SMPSUs are short-circuit and overbad proof, offering an output power of up to 50 watts depending on ihe type on offer. Usually the output voltage is adjustable over o wide range between 5 V and 24 V in 1-volt increments. The voltage adjust- ment is carried out using a small rotary switch or — as in our cose — with ihe aid oF labelled code plugs included in the package. These intriguing plugs contain no more than an SMD resistor and two contact pins. Even without o look inside the power supply (which is usually contained in □ fully moulded case you can't open without causing permanent damage to the supply) it's not dif- ficult to identify this resistor as port or a voltage divider that determines the voltage or the out- put of the switch-mode controller 1C. Simply by replacing the fixed SMD resistors with a suitable potentiometer, we obtain a con- tinuously variable power supply (Figure 1). The potentiometer takes o value of 50 kQ, linear law. The author used o pot with an end switch (Figure 2). When the switch is opened, the output voltage is 5 V. When closed and with the pat at maximum resist- ance, the level is 6.2 V. Turning the pot towards the zero position causes the output voltage to rise to Its maximum value of 24 V. If you use a pot without on end switch you can either fit a sepa- rate an/off switch for ihe 5-V set- ting or simply unplug the lead ta ihe pot. On the subject of plugs, you'll find that a 2-way pinheoder will fit the socket on the SMPSU. Jhe pot is best built info a small A8$ case and fitted with a knob and scale. Once you've meas- ured a couple of frequently used output voltages and marked the associated settings an the scale, any voltage may be adjusted with reasonable accuracy. The maximum current that con be drawn from the power supply h of course dependent on the out- put voltage, but inversely propor- tional for oil practical purposes. The SMPSU the author picked up from a shop and used for his experiments was labelled 35 watts 2 According to the equip- ment label, it supplies 1 .5 A at 24 V which equates to 36 watts. At 5 V, however, we see that the current spec is just 4 A which means 20 watts of output power. Apparently internal losses became significant in the lower output voltage range (roughly below 12 V), Figure 3 shows the actual output voltage os o function of bod current. The measurement was carried out in the Eiekfor Electronics design lab- oratory. : : 5 1304 -ebkluf ionics 61 start here Self-tapping screws Monty ABS but also aluminium, steal and other light mefal enclosures like dieca5t are dosed with se! happing screws secured directly into the car- rier material. In general, ibis works fine but yau may run into a problem when a screw has been removed and needs to be secured again. For example, when self-tapping screws are reinserted just like that after a repair or battery replacement, it may happen that the screw appears fo cut a new thread into the carrier material. If this happens a few times, the screw hole will be enlarged to the extent that the sere’,'/ will no longer provide the necessary farce to keep the case together. A simple trick of the trade may pre^ vent such problems: when the screw is reinserted, first turn it counter clockwise until you feel it rising and suddenly dropping again. With mefal enclosures this is even audible. Exactly at this point, start turning the screw clockwise cgoin and secure sL Of course, the thread cut into on ABS cr soft mefal case is subject to normal wear, hence the above trick cannot be repeated loo many times. None the less, the method will help to increase the life expectancy of the screw joint con- siderably. If things do go wrong. make the hole o bit smaller with a small piece of pbstic or a motch- stick, if necessary adding o drop of permanently flexible glue. Pressing matters with f laf cable connectors Although special tods are avail- able to press IDCs [insulation dis- placement connectors) onto Rat ca- bles. a small vise will also do the jab. Unfortunately the vise method cannot be applied to DIP 1C and mini DIP connectors without squash- ing the delicate pins. The trick is to insert the pins into a few layers of verobaard or stripbeard [the num- ber of layers you need depends on the pin length) and so protect the pins from the pressure exerted by the vise jaws. The holes in ihe stacked pieces of vero board have to be accurately aligned before inserting the connector pins. The 'assembly' is then ready for damp- ing in the vise. You may want to turn the makeshift solution into a permanent tool by using strips of vero board with lengths and widths to suit different types of IDC connec- tor. Secure the stacked strips wiih two-component glue. rDA, SPI, l 2 C, Analogue, Imers/Counters, RTC, etc I • Large Memory Capacity rl*~L rn am no aii/i Flash, SRAM, DRAM. • Supports:- Mono & Colour LCD's, f Touch Panels & Keypads, Very Low Power. <( ■ Target easily & quickly. ill ANSI ‘C’ compiler, assemble lihker all Windows32 based. .A Source Level Debug. f Futl Driver Support with '{s Libraries. ieiai Time Multitasking OS with a free run time licence. AfE Unlimited email support. nU 'j| IP I T la ] I Jil | MS S' Hjfli ■]. jiT ill M ■ j [fa 1* I * “ www. cms. uk. com see our web site for full details CAMBRIDGE ^CRGPROCESSOR SYSTEMS LTD Unit 17-18 Zone 'D' Chelmsford Rd. Ind. Esi Great Dunmow, Essex CM6 1XG | Telephone: 01371 875644 email; sales@cms.uk, com 62 CD flakier 0 n ea cb C D : u v, nd a a r'-d as p ub ! Ghed ' n tbs relevant year, irai circuit diagrams and PCS layouts, sedan extensive searcti program. The 1 957 and 1993 CD-ROMs a'so tide a v^rk ng demo of Bsctrcr zs Wurkbench for computer simulation of selected E eksor projects. CD flekloc 1996: Price £25.35 (US3 44.85) CD flrkter 1997: Price £25.35 (USS 44.85) CD Ekitor 1998: Price £16.25 {USS 2875) CD Elekl&r 1999; Price £16.25 (USS 28 .75) CD flfkler 2G0fc Pries £1 6.25 (USS 28.75) CD Mix 2001: Price £16.25 (USS 23.75 CD flsktar 2002; Price £16.25 (USS 28.75) CD Ekklcr 2003: Pries £16.25 (USS 28.75) pP-jK kriwete £ saltwore 97'98 A : _ s m ~' v i arinss : : tns 27, Aogjs: 1997 microprocessor competition: more than 100 rieagns RRP £14.95 (USS 26.45? PC Sftfonrt 93-99 W n n r .2 scires from srs jy , August 1938 PC software c : -t cer:; : ■ More Lh an 70 prize-wVrge ac ra ms DOS arc '.VirdO'rtsK RRP £12.05 (USS 21.25) F-RmIh 1 # 2 1 3 Vbf 1: 22 Elector Electronics projects covering t : ■ : i! r :■: a s ors. correlate ft ft !e xi . cra't z ig a m s e.r: PCS layouts in elector;: fcnnsL RRP £21.15 (USS 37.40) Vg 1.2: 19m c a z rose ss o '-based c o r at a :: c ?. p m; acts . complete with test, circuit diagrams ami PCR layouts In e'sctoric format. 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RRP £12.95 (US$22 .90) Oil fer now using the Order Form in the Readers Services section In this issue Elektor Electronics (Publishing) » P.O. Box 190 0 Tunbridge Wells TflS 7WY • England, Telephone +44 (0) 1580 200 657 ® Fax +44 (0) 1580 200 616 I [klrwks Kjilol CLnil lirtiv (1-2-3) Oavcl^e 1 Captains o\e r 300 circa Is complete v,ih digram a^j text. Zoom and print module. Fast search feo% r Error- totaran: '".dax searen E/siarr. .Many p - n iad-c:rcui beard layouts. RRP£1Z05IUS521ioi OaYC^Ee? A second selectman of over ECO circa its complete with : sc f sm and sext RRP £12,05 1 USS 21.251 Ol Y c\wz 3 A lino selection of ov ar 300 circuits comp ate ,v,:h ri a a 'am and text RRP £12.05 IUSS 21.25 j Th^ fldifw Dfflasbsf Cc’lediMt, DiVaW 1 ; Original arm unahririgsd datasheets, mo'e than 3 CO ICs iT^xx and 4Qx s vcAage rec^atcrs. near iCs. rriscei ! anaou3, RRP £ 12,05 (USS 21 - 25 ) Oa Vfes 2 ; Datasheets of ^ ore tnan iCG3 c Krete eorposisnts: d.\ h : gh-pi'W£ F Iranslslois. MOSFEFs irynsiens, triacs. varactors, zensr c ad as ^ED osoia 1 , s, etc. RflP£12C6(USS 21G5) Oa Yoira? 3: Datasheets of : Gpu'ar rlcroHj-ntro ars j a the S-2 51 series, Pic. ST6-7, AVR, COP. 6EHCG5GE 11 and SX. AGo Ga DSF21G0 seres. RRP £12.05 (USS 205) Oa Vctese 4 : Datasheets cf hequen: , used memeiy’ cr :e a r : modules. RRP £12.05 (USS 2125) Fi/jrwfujn™ Dmmi toimm > 1 •**" ! l a flv * r; 4 ■» „ ^ Oa V&3we 5: More than 400 datasheets covering rr caacntrc as Tom 4 to 32 bit ^ 8a in to 144 pin cases. RRP £12.05 (USS 21.25= 1 Cl ; ' ts r: : : f ?j K ’ - :: - : si: 1 urzz=n Fres 4 ShareYfse 2000-2003 Tr i saves cor.tafr,s hcroreds of frae,'ia r e arc shareware programs plated to elechonlcs. I rrie est r e :s rdurie audio, comparers, test sr.-j ms5SLi?emeni :a, efcpTera tools. sm:at;C-r; CAD and RF systems. AppGcatHms vary from schemahb caplum ictedhg dig -a ar j aoafogue s ; tj afcn right up to FCBriei grii cor: =:e -with calcolabcr teals and rr croretiiroller as , e-opmant tea s. Depeit-d ng c-r tbs r c gins ire programs run error VCro: ,vs, DOS era or Linux. Each CD-ROM (excap: .came 5000) centals a PDF file Vi “ = c-ca'c.5MSV. c ; crcc r e r 'E ' tbs CD- ROM RRP £12,05 (USS 21.25) per volume Toc&m 1 cod 2 On these CMC Vs yovf fed co L ecte: r formation ■ q a tee n sets an a a n : ' cat s n rates- and s sc-fft'i a ?e • co r : : s rad n d sp ins a: s v,he n n z n z vv :n mam-contrc ters' RRP £12.05 (USS 21_25i per vstT e See also www.elektor- elecfranks+co.uk i Software ? We'll do that ourselves! Three examples explained Karel Walraven and David Daamen Elsewhere in this issue is an article for a stepper motor driver. Th is article describes the demonstration software for this circuit. We explain how these programs came about and find that there are several ways of achieving our goal. We have purposely kept the so ftw are for the stepper motor driver as simple as possible. This makes it easier to follow and allows you to use it as a basis for vour own software. M- T Examples are given in assembler as well as C. These two examples are meant for use with the S9SS252 Flash Micro- controller Board I Elektor Electronics. December 2001 i. The third example is in Visual Basie and works on a PC. This lets you generate ihe required signals without the use of special hardware. Assembler We'll first cast our eye over die assembler program, which is the file that ends in .asm. The designer of the >iepper motor driver has developed the program using Proview32. which also includes an assembler. The program i Listing 1 > first specifies which inputs and out- puts are used. The pushbuttons connect to pins PL6 and PIT. and pins P3.4 and P3.5 output ihe square waves. If you choose different pin names, die microprocessor will use these as inputs and outputs. First we test Buttoo_17. If this button isnT pressed, the input is at logic High and the program jumps to label *ccw . The code then tests Bulion_16 and if this isnt pressed either the program jumps back to label *cw\ As long as no button is pressed, the processor follows this loop indefinitely. When a button is pressed the input at PL 6 or P 1.7 is con- nected to ground and the program doesn't jump, but executes the following instructions. The follow ing action now take place: L_1 goes high, delay L_2 goes high, delay, L_1 goes low, delav. L_2 goes low, delay. The routine has therefore gone through a complete cycle of a square wave. The pro- 64 sfejdnf ti&rif&riis - 5 20 G 4 Listing 1, Assembler program ; Stepper motor software for use with the 89SS252 flash board m r ; Horst Hubert # r ; Two switches are used to control the motor. One between ; Pi. 7 and GtJD (3utton_I7 for turning clockwise) and one between ; Pi. 6 and GND [Buttoii_lfi for turning counter clockwise) . ; Turning cw/ccw is an assumption; the actual direction is of course ; dependent on how the motor is connected, ; In the cw direction, the motor wil 1 turn at higher speed than in ; ccw direction. ; Declarations Buttdp_17 ecu Pi. 7 Button_l6 ecu Pi. 6 equ P3 * 4 L_2 equ P3 , 5 org OOOGh ; Turning cw cw: jb Hutton 17, ccw f cwl ; setb call L_I ;coil zsr 1 high setb call L_2 zsr ;coil 2 high clr call L _1 zsr ;coii 1 low clr call s jmp L_2 zsr cw ;coIl 2 low ; turning ccw ccw; jb Button 16, cw t setb L_1 jeoil 1 high call zsl clr L_2 ;coil 2 low call zsl clr L I ;coil 1 low call zsl setb L_2 ; coil 2 high call zsl S j-Rp ccw ; Delay ■ for turning cw zsr: ¥ mov RO, #255 mov Rl,#20 zsrl ; d jnz RQ, zsrl djnz ret Rl , zsrl ; Delay V for turning zsl ; 1 mov RO , 1255 mov Rl, =255 zsll : djnz RO, zsll djnz ret and Rl, zsll gram then tests if the buuon is still pressed and repeats the previous actions. Hie delay routine consists of two nested loops. The inner loop decrements register RO from 255 to 0. and this happens _G times i the value in R I ), Rv vary ing this value, you can gener- ate square waves of a different frequency, causing the motor to run at a different speed. This is just about die simplest driver program that can be written, C The C program [Listing 2 . the name of the file ends in ,ci is more compact than the assembler listing. This also starts with some declarations. The first line includes a complete file con- taining a set of standard declarations for our processor, Thi> type of file always ends in .h Many manufacturers make these files available for use with their processors. Next, we have to define the inputs and outputs, just as in the assembler program. Sbit tells the C compiler that L_1 is one bit in size and is connected to a single processor pin. with an interna] microprocessor address of B4. We won t go into fur- ther detail here, but more information can be found in the datasheet for the S9S8252 in the section 'special function reg- isters’. Later on in the program use is made of the variables i. j and k. The compiler needs to know about these in advance, since it ha> to reserve memory' space (2 bytes for an integers and also use the right t\pe of ninths routines, in this case rou- tines for integers jabbrev iated to ini). In this program the delav routine is implemented as an inde- pendent sub routine la function l which also has to be declared in advance. The size of the delav is given as an inte- 5/2004 - ddter ehdToma 65 Listing 2, C program /^Stepper motor software for use with the 89S8252 flash board Borat Hubert Two switches are vised to control the motor. One between PI. 7 and GKD (Buttan_l7 for turning clockwise) and one between PI. 6 and G1ID (Button_16 for turning counter clockwise). Turning cw/ccw is an assumption; the actual direction is of course dependent on how the motor is connected. The values of j and k determine the speed one of the two buttons is pressed. This source code is intended for use with */ 4 include sbit at GxB4 L_1 ; sbir at 0xB5 L_2 ; sbit at 0x96 Button_l6; sbit at 0x97 Button^!?; int i; int j; int k? void delay (int); //Function void main( ) { while(l) //infinite loop { while ( l Sutton_17 ) //turning cw { j-4000; L_1 “1 ; delay (j ) ; L_2 =1; delay( j ) ; of the motor. The motor only runs when FBI's ProView32 compiler L_1 =0; delay ( j ) ; L_2 -0; delay { j) ; } while ( !Button_16 ) //turning ccw { k=20G ; L_1 =1; de lay { k ) ; L_2 =0; delay (k) ; L 1 =0; delay (k) ; L_2 -1; delay (k) ; > > > void delay (int m) { for (1=0; i Figure J, Thk macro far MS Ward generates signals on the printer port. sc r after the name of the function, which is why we have int CT in brackets after the name of the routine. The delay routine doesn't return a value to the calling program. For this reason the word void is in front of the routine. Yon will have noticed that with higher level languages there are more declarations. This has the effect of shortening the program code. Every- thing is declared at the Stan, so you don’t have to worry about these tilings in the actual program. And now for the main program. In C this is always called main. It is through dtis convention that the compiler knows where the program stans. Since it is the main program it doesn't lake any arguments, nor does it return a result. For this reason there are empty brackets after main and it has void in front of it. This main program starts with a loop ( while* 1 )) that runs indefinitely. This statement really means: do Lhe following w hile T is equal to a logical one. Since the 66 eldrtot decTrcniQ ■ 5/2004 listing 3- Visual Basic program; the most important parts "silektor Example Square Wave Generator for use with Stepper Motor Driver J 030203-11 May 2004 'This examples employs inpout32 -dll * Copy this DLL to /windows /5ystem3 2 . ' See http : / /www , logixlu * net/ Public Declare Sub Out Lib x 'inpout32 « dll" Alias "Out 3 2" (ByVal Port Address As Integer, ByVal Value As Integer) 'use external library for direct LPT access Public Delay As Long Public Run As Boolean Public Ccw As Boolean Public Cw As Boolean Sub Sleep l Delay As Long) "count the value in Delay and do nothing ThisDelay = Delay While ThisDelay > 0 ThisDelay - ThisDelay - 1 DoE vents "pass control to the OS to 'prevent hanging Wend End Sub Sub Square_Wave_Generator ( ) "hide the main Word window and show the macro form 'show Word again after exiting Documents ( "Square_wave_gen .dac") , Windows { 1 ) * Vi sible = False form. Show Documents ( ■'Squnre_wave_gen.doc" ) .Windows ( i ). Vi sible = True End Sub Sub Output (Port As Integer ) "generate some square waves Out {Port ) r 0 While Run While Cw Out BBS, 1 Sleep Delay Out 088, 3 Sleep Delay Out 888 r 2 Sleep Delay Out 888, 0 Sleep Delay DoE vents Wend "reset printer port "turn clockwise; make "output 1 high first "pause for one half J period "switch on the second "output too (90 degrees!} "switch off first output 'switch off second output ' too "pass control to the OS "to prevent hanging While Ccw Out 888/ 3 Sleep Delay Out 888, 1 Sleep Delay Out 888, 0 Sleep Delay Out BBS, 2 Sleep Delay DoEvents W e nd DoEvents Wend 'reverse: both outputs J high " switch off second output "switch off first output " too ' switch output 2 on again - [S^i*e_Wair,Gen (Cade)] ^ ^ Fgrar Kj_n. Tp&s A-j+Srs £ri±w rfc^ -T-g 7 & r » II iM U m U*vdi.i ivewct ‘f 'itnnxii i | T. lain ; * Ssaar' ?s7e -iEiiia: ‘020103-11 Ms- r - ■ ■ _ ■ • : ; : r In z. 'Tills eieajUe tnpiiirt3S.dll* vapy ii4i I'LL E □ "it* i,3l^ Iir T ~ ‘r -■= - = 1 = J - talveiu ll I ccEEt Else vEiaa m *£!=£ ns/A io p=s= taftrlnl tfs tbs CS 'to prevent S/2DD4 - tVj.h' tlErtmnics Figure 2. Macro opened In Vh us! BASIC Editor. 67 Figure 3. How to connect the stepper motor control to ycvr PC. 13SK3-3-T5 “ T is never changed, this is always true and the loop w ill go on forever. We now come to another loop. This time there is a condi- tion to be met: while Button 1“ i> not equal to a logic one. The exclamation mark indicates the condition is negated: it is compared to a not logic one. When the condition is satis- fied (the button is pressed and a O' is at the input L the pro- gram will execute all statements within the following curlv brackets. The routine w iihin the curly brackets creates a square wave, just like die assembler program. First, j takes the value 4000. Then output L_ l is set to ' T and the delay routine now cre- ates a delay dependent on the value in j. This continues until a full square wave has been created. The pan of the program following this routine has the same function, but this lime the other button is tested. Hie final routine is the delay function. Since C programmers don't like ty ping (and seem to prefer to write compact, obscure code! it's written as a single-line function. As you may have guessed, this is a for- next loop, w hich begins at zero i i=U ) and i> incremented by one u-hh as long us the value is less than m i i_ This m has a value that was given as a parameter w lien die function w as called and in this case is either 4000 or 200. Visual Basic and the PC Our final example uses the printer port of a PC. This makes it possible to experiment with stepper motors if you don't have a Flash Micro Board, This example is also very convenient in use. since you are unlikely to need any special programming software: we make use of the Visual Basic environment that is nowadays integrated with Microsoft Office. The only extra software that needs to be in-tailed Is a little helper program that permits direct access to the parallel port. Window s NT and X? no longer let normal programs access this port. You therefore haxe to copy the file inpOut32.dll to die folder \win- dowyswemoV Thi> helper program works transparently w ith some other versions of Windows (9SSE and ME I: Lhe port will still be driven correctly. Unfortunately, this software won't work with older versions of Window %. The actual Visual Basie program is in fact a macro for Microsoft Word. The most important pans are shown in Listing 3. Here too w r e have declarations, a delay I unction, a lunction dial pops up the macro w indow i Figure 1 1 and temporarily hides Word, and finally a function that toggles the output pins in the correct order, just as in she other examples. There is some other code as well hut there is not enough space to go into details here. The document including the macro can be downloaded from the Elektor Electronics web- site (030203-11 ). Remember to turn off macro security before opening the document. Go to Tool- XI aero Security, Choose one of the lower two options, so don’t use high'. If you now open the document and permit the use of macro-, the program v, indow w ill appear automatically. W hen you close this win- dow’. Word will re -appear again. You can now open lhe Visual Basic Editor using ait-Fl 1 \ Fig- ure 2). To the right will be a small w indow show ing 'Project (Square_w ave_gen ) ' . Below this project are a tew folders w ith a document (the document containing the macro), the code and description of the form to control the suftw are, a module w ith the actual program and possible references to other files. If you inspect the code belonging to the form it should soon become dear how the macro operate-. Operation All softw are can be dow nloaded from the Elekioi -Electronics website. We assume that owners of Flash Micro Boards don t need to be told how to load a program into their boards. But if you do need more information, it can be found in the Decem- ber 2001 issue of Elektor Electronics. The Visual Basic software is hidden inside a Word file and is automatically started as soon as the document is opened. Its operation is \ery siraightlonvard. A number can be entered in a text box (defaults to f 0000 1. This \a!ue determines the fre- quency of the signals on the printer port. The effect of this value depends on the speed oi the PC's processor. It other programs are running at the same lime, they too will influence the output signal. You will have to find the best salue for your PC by trial and error. Finally. Figure 3 show s the pinout of the sub-D connector, w hich connects the stepper motor driver to the printer port. Connect pin 2 and 3 of the printer port to P3.4 and P3.5 of the stepper motor board. All software for this project con be downloaded under number 030203-1 1 at www.elektor-electromcs.corok/ dl/ dLhtm, select month of publication. 63 dAtor dedrania - 5/2004 inside out Figure 1 . Relation between tyre pressure and wearing. (Wabcoj Wireless Tyre Pressure M @ n i ft© [f i ei g Helmuth Lem me Sudden tyre failure is not only annoying but also downright dangerous. In the future, new technology will help to reduce the number of accidents caused by tyre problems, with recently developed sensor systems constantly guarding tyre pressure and issuing a warning signal well before disaster strikes. In 85% of all cases, tyre rup- ture or explosion is caused by too low pressure. The real cause, however, is increased friction leading to excessive tyre temperatures and mate- rial failure with often cata- strophic consequences. Slightly less worrying, even a small loss of tyre pressure causes not only increased wear but alos higher fuel con- sumption due to increased rolling resistance. Just as with too high pressure, the life expectancy of the tyre is sig- nificantly reduced (Figure 1). Since there are no tyres with zero rolling resistance, and pressure checks by the vehicle driver are insufficient, an elec- tronic alternative appears use- ful and more than welcome. The first systems are now in volume production. Each wheel contains a module measuring the tyre pressure and temperature at regular intervals and copying the resulting data to the vehicle computer. The computer responds to too low or too high values by lighting a warning indicator on the dashboard. In the USA. the National Traffic Safety AxLniln- is trail on has made the use of a TMPS (tyre pressure moni- toring system) compulsory for new cars as of November 2003. It is expected that Europe and Japan will follow suit in the not too distant future. From a point of view of tech- nology used, individual manu- facturers seem to follow their own ideas. The oldest orinci- 5/200-i - ekhei cintroniis 69 F inure 2. Forts constituting Sera's 755 (tyre safety system) Figure 3. No more batteries in the future: passive- sensor interroga tian using RFID techniques (Siemens/ Goodyear). pie works Indirectly: a micro- computer compares the rota- tional speed of all wheels, using data supplied by ABS (anti -bio eking system) sen- sors. This principle is used by, among others, Continental for their DDS (deflation detection system). If the tyre pressure on one wheel drops, the effective wheel radius becomes smaller causing a higher rotational speed. Although such systems are cost-effective, they suffer from a high detection thresh- old (approx 30 pressure loss). Also, gradual pressure loss on all tyres goes by unnoticed. Systems with real sensors inside the tyres are far more secure. The technical chal- lenge boils do vm to the ability to convey measured values from the rotating wheel to the vehicle chassis. Slip rings are too unreliable because they soil easily. Today, the standard principle is a radio link. The measurement module on the wheel not only contains a microcontroller that turns the values supplied by the pres- sure and temperature sensor into a digital data packet, but also a small RF transmitter operating in one of the ISM bands (usually 433 MHz, rarely on 2.4 GHz). The unit is powered by a Lithium battery which should last for a couple of years but is nonetheless a serviceable pan. The module should be up to harsh condi- tions: strong vibrations with dynamic peak acceleration exceeding 2000 g, dirt, water, salt, ice and snow, yet have the smallest possible dimen- sions and weight, A receiver antenna is fitted in each wheelcasfe, or a single antenna centrally located under the chassis. A second micro controller computes the measured values. The above systems are avail- able from Bern (T5S, tyre safety system. Figure 2), Wab co/M iche I in ( IVTM , inte- grated vehicle tyre pressure monitoring). Continental (IMPS, tyre pressure monitor- ing system) and a few other manufacturers. In principle they are similar, but different when ex amin ed in detail. For example, the Bern wheel mod- ule that forms a compact unit with the tyre valve is fitted inside the tyre on the -wheel rim — meaning It can only be built into a vehicle by the fac- tory. The Wahco/MIchelln module Is fitted outside the wheel rim, secured to the valve with small pneumatic tubes so it can be Tetro-fitted 1 without so much as having to remove the tyre. Other sys- tems for trucks and utility vehicles differ widely because of the large variations in tyre pressure. Batteryless systems The Lithium battery is a source of problems with all systems. Exchanging the battery is time-consuming. The battery is also heavier than the eutyxe electronic cir- cuit and it obviously requires a very stable mounting method in view or the cen- trifugal acceleration. When braking hard, the tempera- ture inside the tyre can reach up to 100 degrees G which may easily damage the bat- tery. Finally flat Lithium bat- teries are toxic waste hence have to be disposed of using the proper channels. A. solution to the above prob- lems was found in the use of passive sensor responders that are interrogated over radio. The RF energy allows the transponder to return the instantaneous tyre pressure ‘over the air 1 . The sensor goes inactive again until the next RF trigger arrives. The princi- ple is well established in RFID ('radio tagging 1 ) systems that have been around for years. The technology offers several options. One very elegant solution is called ' surface - wave elements'. A system using these devices was developed by the Siemens re search labs but never made it to volume production. Instead. Siemens in co-opera- tion with Goodyear are now working on a different system which reportedly is cheaper as well as less complex. Here, the transmission Is inductive: inductors axe fitted on the wheel and the wheel holder, the assembly producing a 70 shlbr efstlrcvlo - 5/2Q04 Figure 4. Quartz crystal based sensor; principle of the lyretronic : pressure ana temperature sensor system. [G Mobil) Qgure 5. The Darmstadt P/re sensor measures read contact by > nfe rp ref: ng ty re profi \e de form a i ion. transformer effect (Figure 3). A short RF pulse at a carrier frequency of 125 kHz supplies the energy for the measure- ment and returning of a data packet containing the current tyre pressure. The system is to be perfected for launching in 2006, Quartz crystal sensors Still another principle has been adopted by IQ Mobil (Munich, Germany) for their tyre pressure monitoring sys- tems. Trie central part is a quartz volume oscillator pro- ducing a controlled amount of ringing". The interrogator module emits a microwave signal (at 2,45 GHz) which is amplitude-modulated with a frequency between 6 MHz and 10 MHz. Inside the responder, the RF burst is rectified and the resulting voltage used to excite the quartz crystal (within approx, 1 ms), Next, the AM modulation is removed from the carrier. The quartz crystal will continue to oscil- late at its own frequency, but subject to the capacitance pre- sented by the pressure sensor. The result is crystal 'pulling' to a frequency removed from the excitation frequency. The resultant ringing (oscillation decay, lasting about 2 ms) is mixed with the carrier fre- quency, hence modulated by it and returned as an RF signal. The control module measures the modulation frequency of the responder signal and employs the deviation from the excitation frequency to calcu- late the pressure value. (Fig- ure 4). The entyre interrogate- and-iespond sequence is com- pleted wi thin 6 ms* The (small) temperature coefficient of the quartz element responsible for the pressure measurement is compensated. In this way, pressure measurements can be performed at an accuracy of ±0.1 bar (1,45 psl). The second measurement channel is for temperature and employs its own quartz crys- tal with a different cut angle and a much larger tempera- ture coefficient. In practice, it allows and accuracy of ± 1 K (kelvin) to be achieved. The return carrier is alternately modulated with the two crys- tal resonance frequencies. Extensive tests showed that the system is immune to other RF sources in the 2. 4- GHz band (say, from other cars). This is achieved by measures including frequency hopping after each sensor interroga- tion action. The usable range of the RF link s is about 1 m. The size of the module is 22 x 22 mm and its weight, approximately 14 g. The sys- tem will be taken into volume production by the Japanese company Alps, Reportedly the unit cost should remain under 1 USS, The chip could also be programmed to contain data on the tyre used. This may be useful for car production logis- tics or even to inform the car computer new tyres have been oiled. Road contact sensors Still more security is afforded by an additional tyre parame- ter which is actually the most important: road contact. Using this real-time information, anti- blocking and vehicle stabilisa- tion systems could be made to work even better. The Darm- stadt tyre sensor' (Figure 5) is a joint development by Conti- nental and the University of Darmstadt (Faculty of Vehicle Technology, Prof. Winner). It records deformation of the tyre profile elements when in con- tact with the supporting sur- face. The current version employs a surface- wave sen- sor in tire tyre profile and has not yet left the test bench. The adaptation to Teal life" on the road is problematic because the sensor is expected to measure as well as transmit when it is in contact with the road. At that instant, the RF contact is hindered by the wheel rim. There remains a lot to explore and research. It however, researchers are suc- cessful, they can pride them- selves in having reduced the number of road accidents even further. 5,1004 - d-fct ur cletfranJa 71 mailbox lAccess — accessible to anyone? Dear Editor, regarding the impressive iAccess project in your February 2004 issue I would be very interested to know how the i Buttons are encoded and how we can be sure that the code can not be traced back to the buyer. After all, I would like to be the only pen son authorised to open my own daori The question can be extended to other protec- tion systems like magnetic cards, transponders, etc. mentioned in She article. D. Kokta, Germany (by email} The author. Ike Joostens, replies: each {Button has a unique serial number consisting of six bytes. This number Is preceded by the family code which is 01 for the DS 1 990 A and followed by a CRC checksum (to delect reed errors). Dallas Semiconductor (now Maxim), ihe manufacturer of these (Buttons guarantees that every single (Button has a unique serial number, so there are no two iBufiam with the same serial number in the world Six bytes corresponding to 2,8 / ■. 707-4 possibilities, it is unlikely that problems will occur in pro- ducing unique i. Buttons in /he future ... Having said mat , it is possible to copy o DS 1 990A i But- ton . Some months ago I saw a circuit using an AT89C2051 microcontroller on a Russian web- site capable or emulating a DS > 990 A i Button, in fact you ecu! a store up to 30 serial num- bers in memory* and emulate one of your choke. It is possible to copy an IB often with this circuit , however c nances are small this will ever happen since some knowledge about n ikroco n fro Her circui fs is req w red and physical access to one of your i Burtons is needed in order to get the unique serial number to emulate. Other systems like magnetic cards and transponders have also a unique code, but can be copied, too. If is widely known that credit cards and other bank cards hove been copied... while even biomet - ric systems employing f ranspon- ders have some weaknesses. However, the : Button system still provides more security compared to traditional mechanical keys, if even more security h desired , you may consider combining systems, far example, you can combine a blomefric system with or. i Button system . Sound Generation using VB Dear Editor, ever since the Commodore 64 was introduced and per- haps even before that, users were capable of controlling the sound chip in their com- puters. I remember in those days when my hair was still black I created music and tones with various waveform and levels, even white noise and speech fragments, I designed a program to test the hearing response of my whole family by having them push the space key, once they heard a tone whose level was ramped up. Along came the PC and all changed. Users needed sound cards, which mode proper music and speech of course, but robbed small-time programmers and enthusiasts of their chance to control tones and sounds in self made games or small techni- cal computer applications, like electronic test programs, filter evaluation etc. Even under DOS BASIC, pro grams still allowed a sequence of tones to be cre- ated by using the 'play command. But then Bill Gates spoke again ond said let there be Windows and Visual Basic ond he saw that they were good. I bought many books to teach myself VB 3, VB 4 up to VB 6, never giving up againsi better presentiment to try to discover somewhere in a hidden chapter a way fo create a few modest tones apart From the ugly Beep command, but every time my hopes where crushed. So I gave up hope in books and combed the internet. Apart From ready-made shareware or commercial programmes the search machines eluded my quest for an answer. Having been o subscriber to Elektor for many years I checked thousands of pages hoping to find an article to deal with the generation of tones under the Windows environment, preferably using VB. It is utterly absurd to have o SoundBlaster card in your computer playing dozens of instruments simulta- neously ond no way to cre- ate a single tone by your own program code. And now I am coming to the point: will you hove mercy on us small-time programmers and show us how to extract tones from our thousand Pound machines? Klaus Boriges, Cairo, by email .A Google search using the words ' Visual BASIC sound ' produces a lot of educational web links s including complete tutorials . Here ore a few: www. v hexplorer. co m/ VBExpiorer/ sound I .asp h ftp :/ /us e rs . bigpon d. n et. ou / grad ley/ vb atufor/ VSAAesson 6 . h in ' Vi'\v% v. officecomp u te rfrai n mg. co m /vb tutorial, du ipag es/ paged 1 .asp h tip:/ /experts, a bo ui.com Zq / 1 04 8/3376 G05. h tm Also, our book PC interfaces under Windows (ISBN 0 905705 65 3) includes chapters on sound cord contra! at a very elementary level using Delphi , as well os a program to implement an auto- mated hearing threshold test sim- ilar to the one you produced way back in ihe C64 age. S9C equivalent, please Dear Editor, regarding the Rev Counter for R/C Models project (November 2003), I could only find the 89C205I-24PC in Malaysia — the 89C2051-12PC you specify is not available. Is it possible to use the -24PC as a substitute? According to the datasheets, the 1C specs ore identical and ihe only differ- ence is the range of supply voltages It can handle: the - 1 2 PC accepts 2.7 V to 6 V and the -24 PC 4 V to 7 V. And where can I obtain the hex files for the 1C? K. Cheah (by email) The 89C2051-2APC is suitable. The suffix (24) indicates the max- imum clock frequency in MHz. The hex hies ere available on disk or from our website as is mode abundantly clear in ihe article. Alternatively , the programmed controller can he purchased directly from us. Evergreen oscillates Dear people a Elektor, l recently built the Compact AF Power Amplifier from the May 1 997 Issue. With the quiescent current preset turned fully cow all measured values match those printed in the circuit diagram. Although I om sure there is no ground loop in my construction, both amplifiers (L and R] produce spurious oscillation between 72 cbklBr elcftionks - 5/20^ J I and 4 MHz when the pre- set is turned three quarters cw. Do you recognise this effect or did I moke a mis- take somewhere? Dick Flanderijn, Holland {by email] Although the project is now abiod seven years old., the Com- pact Amp has made it to Ever- green status hence we include this letter in this month’s Mail Box. Looking at the impressive FCB sales volumes achieved by this project, the problem can only be said to have been reported $po- radically. A suggested cure is to fit a WO-pF cap behveen the base of 116 and ground . This will however affect the amplifiers sank response to some extent. Tension rising! Dear Jan, can I osk two questions about the power supply with the Valve Final Amp from April 2003, please? The required alternating volt- age should be 340 V (| m03C = 0,7 A). I have had a match- ing transformer made which supplies 365 Vac under no- load conditions and 340 Voc when loaded with 0.7 A. Is 365 Vac too much of a good thing? Second, you state that the direct voltage after rectifica- tion is 440 Vdc. AAy calcula- tions fell nne that 340 x \2 ~ 480 Vdc, The two above factors couse a high tension of about 510 V in my circuit. Is that a problem? Patrick Gbrlach (by email) The designer of the amplifier Bob Stuurmon replies: Air. Gorlach's transformer is probably beyond reproach. As a safety precaution { would advise loading in the HT P5U with two parallel connected 23Q-V, 40-waft bulbs. This had will draw about 200 mA which is about the same as the amplifier under no signal conditions. Replacing the irons former should only be considered if the HT is hr off the 440-V mark wiih the amps connected. Those Elektor drawings Dear Editor, which drawing or CAD program do you use to make your schematics and PCBs? Vm curious because your drawing style appears to have been identical since the early 1 990s when there were no drawing programs f know of. Serdar Ulukonakci (by email) Well Serdar this question is asked at least once a week hence we print a reply here. We started drawing schematics on PCs as far back as 1 985 using OrCAD and FCB artwork using Ulti board. Today we employ versions of McCad (wvrw. mcca d. co mj and Ultiboard /Www. ukibcard. com } . both heavily customised and extended with our own libraries for circuit symbols and shapes. Corrections & ypPAfis FMS Flight Simulator Encoder January 2004, p. 22-26, 030066-1 In the parts fist, the CIS model number for mini joy- sticks PI and P2 belongs to the 1 OCTkO version. The cir- cuit diagram however shows IG-kU joysticks (model no. CIS 25A1 03A60TB). The 1 0-kQ and 1 00-kD versions function equally well in the circuit. LED Roulette January 2004, p, 52-55, G30I63-I the PCB has a short-circuit between the anode of D J 8 and the +5 V raiL To lift fhe short-circuit, two tracks have to be cut and a wire fink fitted as shown in the illustration. Seconds and Minuses Clocks from DCF77 July/August 2003, p. 40, 024005*1 The RC rime defined for IC2 needs to be increased by a factor of 10. This requires changing PI to 1 MQ and R7 to 330 kQ. Stepper Motors Uncovered (2) December 2003, p. 54-63, 0201 27*2 On ihe printed circuit board overlay, the symbols for FETs T1-T16 have been printed the wrong way around. The FETs devices should be mounted the other way around. Lambda Probe Readout for Carburettor Tuning July/August 2003, p* 36, 034052*1 In the circuit diagram, the anodes of D I -D 1 0 should be shown os connected to + 12 V. Mai [Box Terms - Fual oat on of reader's correspon- dence 's at the c screiion the Editor. - V\e .v points esc re ssed b y e :■ : res- pondents are no- ncosssaniy those of the Editor c? Put! she; - Correspondence may be Translated or edited for length, clarity and sty to - Ahen r ez to Va cz- core- spoedeecs p ease quote issue cumber - Please send , c u r 7. Ts t\ Bos rsr. r e- sponerence to: e tor : -• ectro nl^ cq.lt-: or Etoktor EtecLfontcs The Editor RO Bose 190. “j n e ri d ge W e I Is T ft 5 7 AY £ n g! ar d 5, 2004 - ctekior eEcdfonia 73 T lik§ To book your website space contact Bernard Hubbard Tel 44 (0)1242 510760 Fax: 0044 (0)1242 226626 ALLGOOD TECHNOLOGY \\ w \ v . al \ g mn la c h n ofo g co m Low-medium volume sub-contract assembly. SMT specialist since 1990. Customers include military, aerospace etc. 0402 io BGA capabilities, automatic assembly and hand built prototypes. BETA LAYOUT wwvwp cb-poQl. com Seta layout Ltd Award- winning site in both English and German offers prototype PCBs at a fraction of the cost of the usual manufacturers’ prices. BURN TECHNOLOGY LTD h tip. v i 'j /W. biJITlIEC.C o m Distributors of a wide range or device programmers, package adaptors, test and soldering equipment Order online and get free delivery on all orders over £30,00. 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The Peak Atlas family starts from £59. 74 bIeViw Entire: ■£* - 4 '2004 LINKS POND ELECTRONICS http: Vviiww.pqnd.Ie tel 4-353-1-821-5060 fax +353-1-320-9384 Innovate systems far PIC development & embedded applications, * p FI ash 87 6 ■ PIC C Compilers & Programmers * MicroStack * Basic Stamp * Custom development Service QUASAR ELECTRONICS a w w, Q u asaiEf eciro n its , c o m Over 300 electronic kits, projects and ready built units for hobby, education and industrial aep ! cations including HC/ATMEL programming solutions. Online orderino facilities. 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"■* ■■ 1 wish to promote m_\ company, please book my space: * Text insertion only for £120 + VAT • Text and photo for £300 + YAT NAME: ORGANISATION: JOB TITLE: « + +=* §■ + ■# BT ■ a «#.+ - - t-T TEL: ■+f Iti+ili PLEASE COMPLETE COUPON BELOW AND EYX BACK TO (KM4-(0)1242 226626 COMPANY NAME WEB ADDRESS 25-WORD DESCRIPTION --“---STB ■ *T- - B T ri - J - -- -- •■*lt4H + eiriririi'iri«iciiiiBB - - - -•■TBTBB'TBBI 1 t I I 1 J I I ] t 1 I 1 I I I [ 1 I l l I I I I I I I I t J ENTHUSIASTS Only one magazine tests its projects and circuits in its own lab before publication Contact: Worldwide Subscription Service Ltd, Unit 4 Gibbs Reed Farm, Pashley Road, Ticehurst TN5 7HE Telephone: (+44) (Oj 1580 200657 Fax: (+44J (0) 1580 200616 Or visit our Website: www.eleI(tor*eiectronics.co.uk 1 2L01 - E^klcr ciKftc-rifi 75 — Easy-PC from High performance Windows based PCB Design Capture, Simulation and Layout software at prices you'd expect from your local computer store! NEW! in Easy-PC 7 e Library Databook 0 Step and repeat plotting 0 Swap Connection Mode • Dimensioning • Copy to Metafile plus much more Vrtr^kriw^XP 2C&1 ME 55 .V-zift i L ti ■ _ : a i * 211 — . — * - — -- — Stop press... by customer demand, now with Tsien Boardmaker 2 design import... Numbsr One Systems delivers true 32 bit Windows software applications including features that a few short years ago would only have been available in software tools priced in the thousands! Test drive Easy-PC and Easy-Spice for yourself and be prepared to be amazed at the super value... Call for a brochure, price list and demo CD on +44 (0)1684 773662 or email sales@numberone.com a ELEKTOR Hardware^ Software The Flash Microcontroller Starter Kit costs I just £ 69.00 / U5$ 1 12.50 (plus postage). Step into the fascinating world of microcontrollers with the Elektor Electronics Flash Microcontroller Starter Kit. Contents of Starter Kit 1: 89S8252 Flash Microcontroller board (ready-assembled and tested PCB) 300-mA mains adapter Serial cable for COM port Software bundle on CD-ROM Article compilation on CD-ROM: • 89S8252 Flash Microcontroller Board (December 2001 ) • Microcontroller Basics Course parts 1-6 (January through June 2002) • Microcontroller Basics FAQ (September 2002) • Port Line and ADC Extension for 89S8252 Flash Micro Board (December 2002) • Chess Computer using the Flash Micro Board, Order now using the Order Form in the Readers Services section in this issue Elektor Electronics (Publishing) ® P.0, Box 190 0 Tunbridge Wells INS 7WY * England, Telephone +44 (0) 1580 200 657 • Fox +44 (0) 1580 200 616 THE E!4£TEO*HL5 £ COMPUTE! MACAT3KI lip | 1 See also www. elektor- eledronks.co.uk E 76 elefclw e!srtn;-is - 5 2C04 readers services Please Mote ScAmae ferns mertsa @ ere aytabUe from tfe Fr $5 D&a-fe-r^ tfftePtf&frgrs' w&stteEi - ^?Gfi^fefrDfas co ■ G :=>^i ete sapped lor the cofFi^nacOce of readers vrtffwut access. EVERGREENS Elektor Electronics Help Disk £ ys S6022-1 2,1k. \Vir&y^ \ zZ-jn Elektor Eleclronics item Tracer 1985-2003 315 U.45 ii4 C‘OD.3-7 ' ; : ~2~s {£.= ■ »V ;:.vs vs.'s c" | Medium pov/er HEXFET amplifier (December 1993) £-15 14.35 5301 92- T PCS Universal Prolntyping Boards 1S90 19 25 UF&6-T PlB 2-45 430 UPBC-2 2 FCSs 4-10 7J25 LFBS-4 4 PCSs £-55 11.55 110,332 MAY 2004 6EHERAL W I'rt'il ISStJI ■■ Ptifethjroal taftfe (PESs). SS-alissre trotf P&sS ton y if jfifeife, fog tnm --:-■ ‘.S3 ^.l-'V! :rr ,'f= FAU £- i “>..:-■ WciMrfiie S!&uvr;tiea Senice Ui Lteu 4 . GiS&s ' "L " EL "’"~ T: r: -'-‘ i: " ; -■- RSS3 Fan* Pas^sj Read TICEHURST TH5 7HL i: . ..._ : . gtyerf — -iy :■= v:-: =c -i-g fr;iJM t=T?^-:^5 f-i-4-ti ISi: 2-X::7. lei < - :--: S :•::•: = := = - -■:, - : 1553 2Dbfit6 T e®aiwwi@wira,(!«-irLcajji = :i: . : = ... - b l B ... Dscaniei), fcefotfcg postal for sja^s cop^ * *©* ^ tn^fag s PCS hfitfi b dec BrSiiF £4.75 (WKirtiBre); £550 (at mia Eojapsk D6L10 am iradjf-m3& thRHgk &e testers Serines (sn^ Europe). Pric^cJ pasr Jk^ 1 August nayteftailfeiBigreSaHfaliEia aal Etecctnig isaes wAifcj pndjy far tj ^tp , , „ _ _ CKite. s» tt.45 lift an) Bk) E7.15 iij-V : F -i T '^CHs. - .5 v r .- -_ L --:: ^5 E_-.: = - ' ':• " :‘3 jj= £_:■: ■-- r TE:.i-P T &' PAST ARTICLES Fr^ gs and fem i^g^ans to ctera^ The -■:- - - -^v-:: — E fl gfe ig Mm fag : : r-::= .::■_: ErBfflisf 5ixJ Adnfcfcfjsgre Offices te^me priorrage^^ftiett ^^ tii^ i| i e m air^ (M5S0| 300657; tu 200610, ?nai steagBUt*- tera federate those is pig j iam ; * 0£ a : :i :o • . DesEdji Your Own 1C © G3£©54 FCE High-End Preamp © 02CC4&-1 PCS — 3T 1 i Cv irii © £>5945*2 rZS — T'ij, tjQdrf © 02W45-3 PC-3 — PS'J tasiit © azaeJG-ii y-.EA OZ994S-41 PIC1 81^452-11^ progmmmEd WintJ Speed £ Directinn Meier I 073371-11 t>i£< proigci software ‘-■121 - - . i ■ pf{7| of 37 T p.'c.c : ht — ~ : no* 331 APRIL 2004 Dr o p-m IkU c roce ntmJ let Board H Q2j1^t PCS Z -11-7-' ' C-e- safi?|s4 prelect 0e Pandora's Sound & Music Box m OS^K-l FC3 ? ^ “ K -;■ sotr res oird c «te f ee 0-:C- 1 2-' 1 P Cl t F3 7 T P, 2K2'1T ~ Ed VHP- Low Explorer © Q2&41EP1 PCS No* 330 MARCH 2004 Build Your Own DRM Receiver © 0303*5-1 PC3 @030365-11 Dfitt^epafflam Code Lock © 02CH34-1 PC3 © J * Z,1.. T ifcs< :-^ J ee -'77-I--- 41 r->r75 = c-4 -- R c^rarmigit Hands-on CPLDs (2) © 03C&52-T PCS © PjD: 52-TT Sofarare 030052-41 ffM7l2£S.CS4-T5, progrsfimed Muitichannei Failsale for Sadia Conlrolfed Models W 0iGiB2- r ’ D©* iiXXEe axfe f = B - B3 52-4 7 A 7 E SC5 2-2— j i proeraiimed Muflihmclion Frequency Meier 7 0301^-1 f-[3 © DID 13-5-11 D-sA. p O'Ci s-ifyASic - 1 --’ P-5-f 1 ATS IS 2 Si 3-1 CP C p -r^rai'.Tir’j No. 329 FEBRUARY 2004 DEgilal Alarm Clock i 0331^- ‘1 D-- F'.C Educe £“3 r^i -;^T -- -C-5— 1 " Pi C 1 r -- l 2- Q pfOgia; — ^ iAccess ©£f20163-11 ---'" :: -'“ L 1 --T.I } :i-' Z = I : — e: Simple 12-fi]-23QV Power Inverter @ ISB433-1 PC-3 Toucb-conlrolled Switch © 3 IS- 1 4 - 1 7 I ;■ Pt C sosc r cede 035-2 1 - -4 1 PCI 2C503A04 SC5. prt^amsed No. 328 JANUARY 2004 64-K S0C552 Rash Board © 04-3042-1 FC-5 @ Cs3O042-1 1 Ofek. irc>c. prt^ect software iiL'JAi-ijT 'd'2'22 2 piCCf£Trrr*d 0 SICA 2-31 GAL 1 6VE 3 15 QR jsf ogj£Ttured Climate loggar © HOD 7 6-i PCS © 022076-11 2:?* Vh'.TKtOt'o fsttivare FMS Flight Simulator Encoder m OS4Si56-1 PC B 030^41 -57lF: 7673’i. pre :^-TE-d LED Houlelte © 03016,3-1 PC 3 ©- BI0 1 C3-1 1 D i.*; e otirce A _ d tet fl e.$ 15-65 2770 £ uss 5-45 14.95 9291 £3-41 E9C2051-12PC pjtotstlT^ 3-95 1425 7’50 1130 Multi-event Alarm Clock 670 1185 @ 020304-1 1 tfet, C (stEffca) fizz 4-90 3.65 4-=tD 3.S5 920304-41 MB9C20Sl-i2PC, pn®!raTifrsaS 6-19 : e; 2329 49 90 Stepper Motors Uncovered 929127-41 1^1^873-29 SP 1S-1Q 33 39 4-90 S.55 17-55 31.05 No, 327 DECEMBER 2003 FM Remote Control Transmitter & Receiver © 034044-1 PCS LED Christmas Decoration 10-20 15,65 3^60 I fVT: 15.20 © GIOI 57-1 FC5 7 ’55 1335 4-90 3.65 P87LPC76x Programmer 70 5-3 4-&3 1875 @ 030313-1 1 Cfek. prajKi sen^re Projecl Timekeeper 4-52 3 55 20-55 U.LU 35.40 Z 2121:1--- 2 ~z> : : . :t L :: • ■ -- *90 : :i L'20359^1 F.C‘6P£4-irp pfccrsrrrrcd 13-T5 23:25 B-^3 1650 Stepper Malors Uncovered (2) @ 929127-11 iMsfc, source ajife Efe 490 365 Universal Clock Generator © 020355-1 1 E e ■ ..tf crate FT* 4-99 !5t S-1G 15.10 Wireless RS232 Link 4-92 3.65 © 0352 94- 1 p-CS 670 15.40 969 16 5A No. 326 NOVEMBER 2003 493 3.55 Precisian Measurement Cenlrai 1479 26.00 m 039£6iM PC3 3-70 15.40 399 15 75 No. 326 NOVEfflBER 2003 490 £ 55 Rev Counter for R C Models 3340 5919 @ 0241 11-1 PCB 17-50 31 .00 924 11T-11 1)22 s»3ce add r-r< : :-:A 4-95 £ 65 *so 3.35 0241 1 Ml 6SC2S5M2PC, prupaamnsd 6-65 15.65 870 15.40 Running Text Display @ 0294&7-11 Ksk Stute asi hs; catia 3.65 &-35 16.55 USB Analogue Converter 4-90 3.65 © 920374-1 F£B 7-65 13.50 7S5 14.05 r 1 I - ■ "I :::£ r : 4"S9 3.65 0203r4-41 PH71 6C7E5 T proqrarttrrt&d 13-25 23.45 No* 325 OCTOBER 2003 4-9D 8.65 DOS RF Signal Generator 15-20 26.50 © 92&299-1 FC3 Mnasc-r 11^9 20.55 © 020293-2 FC5 * 1Z-1Q 21.45 7-59 T3.Si G202SS-4 1 4T96SB 5 1 5 £ FC t >z-z tzt —z-i B0-5-5 54.65 13-59 24.59 Minimalist tn duel Eon-8 atance Metal Detector •© 9292SO-1 FC3 S-55 15. £5 £-50 15.95 Xllinx PROM Programmer © 019109-1-; ic?TA-i r 5 4-90 3,65 490 £0-5 No. 324 SEPTEMBER 2003 6 15 !0j90 ATV Picture Generalnr @020296-11 setrree & hex code ffe 020296-41 M@0S85t6BPC c pmgismial I 335 1 6 55 020295-42 ATKJSl 200-1 2PC, pfDgrertffisd 4-39 8 55 DTMF Remute Telephone Swftch 19 00 1776 © 920284-1 PCS 610 10.60 © 92 1234-11 DeA prr i sotrw its 0292&M1 PfCI 9fB4A'2a«H psiigrammaf 775 1379 LC Display with J?C Bus 4^9 8.55 © 0»? FC8 PICProg 2003 10-20 18.95 @ 010202-1 =CE 1 7-95 mi 5 © 0 10202-11 Si=*; Vi i-n w s =aiiA .• ? C ' 920 2-4 1 RG1SFS '4-29 7 : s ~ T?r : 17’f’J 31.63 Polyphonic Doorhell 4^0 a 65 ©■ 026354- T 1 0 i h: pfH©L t s ^ ^ 4-90 S.65 1520 2690 13- 03 24.60 11-65 20.66 4£0 Bto 14 - F0 25-00 7 35 13.D9 9-C5 16 00 4 -SO 365 23 55 41 65 *90 3.55 5/2004 - =!-klflr cI:cHc*m 77 £ U$$ 02035441 P,CtcFS4A-1G E prEKpaifned 14-45 25.55 Precision Measurement Cenlral 030059-91 Beadr^snitesa tested toarf 6900 112.50 Valve Preamplifier (1) @ 020333-1 pea, mififer bwfd 11-55 20.40 @ §20333-2 PCS. paw s«pp.V board 11-40 2020 @ Q203S3-3 PC9. I G board 10-10 17.89 No, 323 JULY/ AUGUST 2003 Add a Sparkle @ 020293-1 1 Qisfc. ESC Ml saute fies 490 3 65 020233-41 W12C509A-04/Sl3k 7-40 13.1 D AT90S2313 Programmer @ 034036-1 FC6 9-05 16.00 Hard Disk Selector @ 034(50-1 PCS 9-45 15.75 Mm! Running Text Display @020355-11 te^sauKcedfr'Ra 44» 5.65 Mini Test Chert Generator @ 020403-n Dsk. RC stare code 4-90 e.es Programming Tool tor ATllnylS @ 030030-1 FCB 7-55 1135 @ 030030-11 Es*. profsct 4-90 365 Quad Bridge Car Amp @ G34039-1 PCS S-70 1535 Remote Light Control with Dimmer @ 020337- 1 1 Dck, HEX aod suture fifes 4-93 3.65 020337-41 AT6SC2Q51-12_ prooramned 6-25 11.05 No. 322 JUNE 2003 AVR TV Tennis @ 0300264 Man FCB 670 15.40 @ 030Q2&r2 PiStfetonPCa B-ffl 15.25 @ 030026-11 Das*, ANR source code 4-90 865 030026-41 M908515. programme 15-20 26.90 Electronic Knolled Handkerchiet @ 020390-11 Disl, FC sid confedfcf afiware 4 -9D 8.65 020308-41 JttMSaaiS-IOPC progrisniried 12H&0 22_30 Uw-Cost LCD Controller f2) @ 020 114- 1 PCS 6 70 1535 @ 020114-11 ifeitfffBiBct software 4-90 8.65 Right Light Contra! @026115-11 Dcfc, ha afri $G«t8 code 4-93 3.05 020115-41 At9BS2ail1QPC. programmed 12-65 22.75 Universe] XA Development Board @ 010103-1 PC 3 13-20 23.35 @ 01 0103-1 1 ffct GM. code. HWA ha fifes, XADEV 490 e.65 O10103-21 EPROM ICE. 27C256-90, programmed 1090 17,70 G10103-22 EFnO-M tCS. 27C255-SD, progflmmed 10-00 17.70 01 0103-31 GAL lBV8,pfDQr^JD£d 4-80 3.50 No, 32 T MAY 2003 Countdown Timer @ 026296-11 Osk. SoUffi and tusx code 4-90 3.65 020206-41 ATB0S1200.progrsnmed 1399 24.60 USA Audin Recorder @01201341 EPROM tet code 4-90 665 012013-21 EPROM 27C511 jraparana} 12-60 22,30 Valve Final Amp |2) @ 02GO7t-l Aofifi&r board {arte dannd) 1510 26.75 @ 020071-2 Power sti?i4y board 10-05 17.75 No, 320 APRIL 2003 8-Channel Disco Light Controller @ §10131-1 PCS 13-ID 23.15 £ uss 01 01 31 -41 5 7C 750 w 37C7 1 . programmed 23T3Q 40.70 Pice PLC @ 010059-1 FCB 1670 3310 @ 01 0059- 11 U ' s fc. test prapsm 4-90 B.&5 Singte-Chip Tone Central @ 020054^ PCS 1090 19,30 Switched-Oultet Rawer Bar with RS232 Centro! @ 020206-1 PC-3 1060 10.10 © 020293*1 T C.5‘. p'C-/E-:i i-m 865 Temperature Indicator ter the PC @02 C 330- 1 * EM-v asms 2r-a c *>Ttv 'ed C «te 490 865 025350-4 1 AT53C 2551 . pi^rcned 1025 10.15 No. 319 MARCH 2003 17 V 10 A Switch-Mode Power Supply @ O20554-3 PCS 945 16.65 Add-on Switch unit for R C Models @ 020126-1 RGB 8-S5 15.65 @ 020 1 26- : t (Esk. fen and souxe f.ts 4-00 8.65 020126-41 FiC IK712-G41 SO. prog^lVTted 15-20 26.90 AVRee Development System @ 02D351-1 FCB 13-20' 23 35 @ 020351-11 D'sk etSTpfe programs 4-50 865 Guitar Effects Switchbox @ 0201314 FCB 1315 23.30 Intelligent Fan Timer @020170-11 Os* piijstt soiwaie 490 B.65 020 1 7041 VI P43S f 1 1 21 . p? cammed 11-33 20.00 SAA3049 Replacement @ 029055-1 PCS 13-05 23.10 @ 020055-11 D£- and hex rate 4-90 8.65 0200S5-41 67LPC764BIL pnxpamnigj 9-0-3 17.55 Two-Colour Running Light @ 0 10134-1 PC 5 . Lv-ir C : s±j board 825 14.60 @ 010134-2 PCS. LED toard 1065 1B.80 @ 010134-11 CSV. px ; Mt sGtere 490 e.to 0101 34 -4 1 ATsy C2D51 -1 2PC, pr*-; craned MS 1265 No. 31 S FEBRUARY 2003 20 '40 MH7 Logic Analyser @ 020032-1 FCB 1520 26 85 ■3 C- 20D32- 11 0 e V teno z :r ;~ ■'-SO 3.65 Q2D032-41 AT0e^5l5-£PC. prcc-isirrsi 1510 26.70 Active Loudspeaker System (2J ■@ 020054-2 FCB 795 14.05 Autoranging Capacitance Meier B 020144-1 FCB 7-35 13.00 @ 020 '44-11 C-E";. scc-xe *~4 r lias 490 8.65 0291 44-4 1 RC16F&4A-20. F pfCv-'snnsQ 15 20 2qM Dimmer with 0-10 V Control Input (S D 10125- 1 CORtr&j FOB 960 17.00 © 010125-2 diiTuTcf PCB 8-S5 15.85 Electronic Hourglass B 020036-1 FCB 18-55 32.85 @ 029036-11 Cfct pi^ect soffw^ 490 5 65 02003641 R Cl GF 64-04 R prtgs^r.xtjd 15-26 26 SO Optimise your PC Soundcard @ 020134-11 fe* Ei :t ipresasAssS 490 865 No, 317 JANUARY 2003 Active Loudspeaker System (1) @ 02C054-1 FCB 1 22Q Electronic RPG Dice Roller & 020005-1 PC B 10-05 17.75 B 030005-n 0 ,ea. source cofis f ^ 490 5.65 CT20Qt&41 AT90E4433^PC. proorawr^ 3080 54 50 Rodeo! Deterrent @ 020110-1 FOB 12-35 21.30 SMS-Controlled Mains Sockets @ 020157-1 F’CB 1290 2265 No, 316 DECEMBER 2002 DCI PLC B €10113-1 FCB, cDuVcne? zom 540 14 55 @ 010113-2 PCB. teor.'-il board 12^0 22.10 @ B5011 3-1 1 t- z*_ pr:, sst s c-fr •vi'i & EESffC e c Kfe 4-5*3 5 55 01011 3-4 T AT9SBB5 ■ 5-F PC. pJcg-i-Tcj 21-20 37.55 Port Line and ADC Extension @ C2O307-11 Efe k, flASCO !,'.-5 1 p' v4T2 ts 430 5.65 Products for older projects (if available) maj he found on our web site http:lfwww.efektor~etectronics.co.uk 78 deleter Electronics - 5/2QQ4 Please supply I tie following, For PCSs. front panel foils, EPROMs, PALs, GALs. microcontrollers and diskettes, slate the perl number and description: for books state the full title: for photocopies of articles, slate full name of article and month and year nf publication. PLEASE USE BLOCK CAPITALS, Description Flash Microcontroller Starter Kit item Tracer 1985*2003 CD-ROM Elektor 2003 *353- fig* iSiS. 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Sorting Code 60-22-1 5, I B AN code: GB40 NWB K6 022 15 3512 5225 SIC code: NWB KGS 2L COMPONENTS Components for projects appearing in Eleklor Electronics are usually available from 'certain advertisers in this magazine. If difficulties in the supply of components are envisaged, a source will normally be advised in the article. Note, however, tfratths $ource($) given is (are) not exclusive. TERMS OF BUSINESS Delivery Although every effort will be made to dispatch your order within 2-3 weeks from receipt of your instructions, we can not guarantee this time scale for all orders. Returns Faulty goods or goods sen! in error may be returned for replacement or refund, but not before obtaining our consent. All goods returned should be packed secures* in a padded bag or box. enclosing a covering letter stating the dispatch note number. If the goods are relumed because of a mistake on our part, ■ a will refund ike return postage. 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Student applications, which qualify for a 20% (twenty per cent) reduc- i i o n i r c u rre n !. rates , must be s u p p o rte d by evi d e n c e o i slu de 1 £ b ' p signed by the head of the college, school or university faculty. A stan- dard Student Subscription costs £31.60. a Student Subscription-Plus costs £37,60 (OK only). F lease note that new subscriptions. take about lour weeks from receipt of order to become effective. Cancelled subscriptions will be subject to a charge of 25% (twenty-five per cent) of the full subscript price or £7,5 D, whichever is the higher, plus the cost of any Issues already dis- patched. Subsci prions cannot be cancelled after they have run for six months or more. January 2004 pcb layouts High-End Preamp — main board 020046- 1 High-End Preamp — PSU board 02CD46-3 Nig h - En cl Prea nip — relay boa rd 020046 - 2 All PCB layouts shown reflected and at true she (100%) unless otherwise stated. Wind Speed & Direction Meter 030371-1 5/2004 -elsilor electronic 31 sneak preview ££2 kimim rm,€Qmpu£zit£rs.cm 74 Content Electronics, Met IMks .VfWMConfonlelec.co. uk .74 Crtckfewned . . ... .49 Danbury, fid Links ......... ... .Hwv.-.mc- Fc j € ~l i.eo uk .74 Debug Innovations. Met Links .wAw.ffsh- z ~'~zzaLz~z.czn .... 74 Display Oedroracs co.xi 54 Easysync, Met Links y,v*w easyaj ~z.zz .■ ............. .74 EtexoL Met Links .um.e rxo/.Lsr ..... .74 ELM Bsctrofiics, Met Links. iv wa.e sz : v r- :a. : .74 Elwc. Met Links ................ mvze ‘esc cc.r ........... 74 Eimovi .tn*-,v,£7TftLh7 c o.l- -35 Err an [ntemaSonal, Met IMS ;v;vw.e r t v: co f n .74 Emocfecuits ........ .......... , ww.thepcbsttop. co ............. ,78 Forest Met Links .................. jflWJbfMdJ.fri: .74 Future TEchfitfogy Devices. Met Links . . JWiVr ftc. : ~ i of .74 Riturtec, Met Links m\~v ij-tL ■-’=■£.&/- .74 Hammond Electronics. 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