ETI ELECTRONICS TODAY INTERNATIONAL TOMORROW'S TECHNOLOGY TODAY Technology behind the robot muscles of the future Designing and building switch regulator PSUs 4 channel touch switch for the ETI 80188 SBC - Adding circuitry to a PC's parallel port Build a PC controlled PIC programmer *LIPS Exploring Saturn with Cassini Stamp based analog input Build a bicycle loop alarm The laser tag controller r0 r *44,445A 4,A% C. 40 ye SHAPE M MORY ALLOYS 0 'N Pi JUNE 1995 E 2.15 06> x NEXUS
Transcript
ETIELECTRONICSTODAY INTERNATIONAL
TOMORROW'S TECHNOLOGY TODAY
Technology behindthe robot musclesof the future
Designing andbuilding switchregulator PSUs
4 channel touchswitch for the ETI80188 SBC
- Adding circuitry toa PC's parallel port
Build a PCcontrolled PICprogrammer
*LIPSExploring Saturn with Cassini
Stamp based analog input
Build a bicycle loop alarm
The laser tag controller
r0 r*44,445A
4,A% C. 40ye
SHAPEM MORYALLOYS
0'N Pi
JUNE 1995 E 2.1506> x
NEXUS
"moving from schematic to layout could not be easier"Electronics World & Wireless World Jan 1995
Time is money. That is whyQuickroute 3.0 for Windows 3.1 wasdesigned from the start to be aseasy to use as possible, withoutsacrificing the power professionalengineers need to get the jobdone. Available with SchematicCapture, support for busses &power rails, 1-8 layerauto -routing, and our newextended libraries (surface mount,CMOS, etc). Network versions ofQuickroute are available for largerinstallations, and all versions includecomprehensive on-line help.
*Schematic & PCB Drawing *1/2 layer auto -router*Supports Windows printers/plotters *Full set oflibraries *Clipboard support *Designer Special (manualon disk) also available.
Shape MemoryMetals 10Nick Hampshire takes a look at thestrange properties of certain metalalloys and how they could be used ina wide range of robotics applicationsas artificial muscles
Bicycle LoopAlarm 18A project by Terry Balbirnie that willappeal to every bike owner who isworried about theft
Analogue SignalMeasurement 24A project cased upon the versatileParallax BASIC Stamp computer toinput, digtise and retransmit inserial digital from one or moreanalog signals
MakingUse of PCParallel Ports
26
Stephen Smith shows how to buildyour own PC interfaces
Saturn'sSecrets 34The forthcoming Cassini mission toSaturn and its moons should greatlyexpand our knowledge about theplanetary giant. Douglas Clarksontakes a look at the technologybehind the mission and themission itself
SwitchRegulators 42Simple efficient powerful switchmode power supplies can now beeasily constructed using readilyavailable ICs. Dave Bradshaw takesa practical look at how to design andbuild such power supplies
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ELECTRONICS TODAY INTERNATIONAL3
FourChannelTouch Switch
46
Richard Grodzik offers a usefuladdition to the ETI 80188 singleboard computer
PICProgrammer 52This project by Robin Abbott showshow to construct a PC controlledprogrammer for the widely used, and\ery versatile, PIC miciocontrollerchip. Part 1 shows how the projecthas been designed
Light GunCentral 60In part 4 of ETI's Laser Tag systemRobin Abbott concludes his look atconstruction of the light gun central
Regulars
News and event diary 7
PCB foils 70
ff. Open Forum 74
Pico Releases PCPotentialPico's Virtual Instrumentation enable you to use yourcomputer as a variety of useful test and measurementinstruments or as an advanced data logger.
PicoScope'Virtualinstrument'software.
f enrwo at L. a
Hardware and software are supplied together as a package- no more worries about incompatibility or complex set-upprocedures. Unlike traditional 'plug in' data acquisition cards,they simply plug into the PC's parallel or serial port, makingthem ideal for use with portable PC's.
Call for your Guide on 'Virtual Instrumentation'.
PicoLogAdvanced data
logging software.
r'New from Pico TC-08 Thermocouple to PC Converter8 channel Thermocouple Amplifier Connects to your serial port - no power supply required. Supplied with PicoLog datalogging software
for advanced temperature processing. min/max detection and alarm. 8 Thermocouple inputs (B,E,J,K.R.S and T types) Resolution and accuracy dependant on thermocouple type.
For type K the resolution is better than 0.1 C and accurate to±0.1 C over -270' C to 4-1300"C.
TC-08 199complete with PicoLog, software drivers and connecting cable.
S4,4-/6with software, powersupply and cables £ 219
fire- /01 Channel 8 bit Lowest cost in the Pico range Up to 22kHz sampling 0 -5V input rangeCarriage UK free. Overseas £9 Oscilloscope Probes ( x1, x10) £10
412)e-/00 Virtual InstrumentDual Channel 12 bit resolution
Digital Storage ScopeSpectrum AnalyserFrequency MeterCh art RecorderDz.:ta LoggerVoltmeter
The ADC -100 offers both a highsampling :ate (100kHz) and a highresolution. It is ideal as a general
purpose test instrument either in thelab or in the field. Flexible input ranges
(±200mV to ±20V) allows the unit toconnect directly to a wide variety of signals.
ArDe-/OG with PicoScope £199with PicoScope & PicoLog £209
The ADC -10 gives your compJter a single channel ofanalog input. Simply plug into the parallel port.
AiDe- /0 with PicoScope £49PicoScope & PicoLog £59
Tel: 01954 - 211716 Fax: 01954 - 211880Phone or FAX for sales, ordering information, data sheets, technical support. All prices exclusive of VAT
ELECTRONICS TODAY INTERNATIONAL4
MONO VGA MONITORSSome with slight screen bums but OK at E19.96 RefEF40 and some without burns at E29.96 Ref EF39.
A4 DTP MONITORS Brand new, 300 DPI. Completewith diagram but no interface details.(so you willhave to work it out!) Bargain at just E12.99 eachIlllOPD MONITORS 9' mono monitor fully cased complete withraster board switched mode psu etc. CGA/TTL input (15way D). IECmains £1599 ref DEC23 Pnce including lot to convert to compositemonitor for CCTV use etc is E21 99 ref DEC24PC CONTROLLED 4 CHANNEL TIMER Contrd (on/ciftimes etc) up to 4 items (8A 240v each) with this kit Complete withSoftware. relays. PCB etc E25 99 Ref 95/26
COMPLETE PC 300 WATT UPS SYSTEM Top of the rangeUPS system providing protection for your computer system andvaluable software agenstmainspowerfluctuationsand cuts New andboxed. UK made Provides up to 5 mins running time in the event ofcomplete power failureto allow you to run your system down correctlySALE PRICE lust (119.00.RACAL MODEM BONANZA! 1 Racal MPSt223 1200/75modem. telep hone lead. mains lead. manual and comms softwa re. thecheapest way onto the net' all this for just El3 ref DEC13HOW LOW ARE YOUR FLOPPIES? 3 5' (1 44) unbrandedWe have sold 100 000. so NO Pack of 50 E24 99 ref DEC16BRITISH TELECOMM MULTIMETERS SA9083 These are'returns' so they may have faults but look ok Complete with new leadsand leather case Pnce for two meters 8 1 case is E10 ref DEC896mw LASER POINTER. Supplied in kit form complete withp ow.er adiuster 1-5mw a nd bearn divergence adjuster Runs on 2 AAAbattenes Produces thin red beam ideal forlevels. gun sights. expen-ments etc Cheapest in the UK' just E39 95 ref DEC49
SHOP WOBBLERSI Small assemblies designed to take D sizebattenes and Wobble' cardboard model signs aboutin shop windows,£3 99 Ref SEP4P2
RADIO PAGERSBrand new. UK made pocket pagers clearancep nceis I ust E4 99 each 100x40x 15mm packed with bits! Ref SE P5
BULL TENS UNIT Fully built and tested TENS (TranscutaneousElectrical Nerve Simulation) unit. complete with electrodes and fullinstructions TENS is used for the relief of pain etc in up to 70% ofsufferers Drug free pain relief. safe and easy to use can be used inconiunction with analgesics etc £49 Ref TEN/1COMPUTER RS232 TERMINALS. (LIBERTY)Excellentquality modem units.(likewyse 50,$) 2xRS232, 20 function keys. 50tnro to 38.400baud. menu dnven port. screen. cursor, and keyboardsetup menus (18 menu's) E29 REF NOV4OMRON TEMPERATURE CONTROLLERS (E6C2).Brandnew controllers. adjustable from -50 deg C to .1.200 deg C usinggraduateddial, 2% accuracy. thermocouple input. long life relayoutput3A 240v o/p contacts Perfect for exactly controlling a temperature.
Normal trade £50.. ours E15 Ref E5C2ELECTRIC MOTOR BONANZA? 110x6Omm.arand newpreasion. cap start (or spin to start), virtually silent and features amoving outer case that acts as a flywheel Because of their unusualdesign we think that 2 of these in a tube with some homemade fanblades could Joan the basis for a wind tunnel etc. Clearance once isjustE4 99 FORA PAIRI (note-thesewill have to be wiredin series for 240voperation Ref NOV1
MOTOR NO 2 BARGAIN 110x9Omm.S,mitar to the abovemotor but more sonablefor mounting vertically(ieturntable etc) Againyou will havelowire 2 insenes for 240v use Bargain pnceisjustE4 99FOR A PAIR,' Ref NOV3
OMRON ELECTRONIC INTERVAL TIMERS.MInature adjustable timers, 4 pole c/o output 3A 240v,HY1230S, 12vDC adjustable from 0-30 secs £9 99HY1210M, 12vDC adjustable from 0-10 mins £999HY1260M, 12vDC adjustable from 0-60 mins £999HY2460M. 24vAC adjustable from 0-60 mins £599HY241S, 24vAC adjustable from 0-1 secs £5 99HY2460S, 24vAC adjustable from 0-60 secs, £5 99HY243H, 24vAC adjustable from 0-3 hours £899HY2401S. 240v adjustable from 0-1 secs £9 99HY2405S. 240v adjustable from 0-5 secs £9 99HY24060m, 240v adjustable from 0-60 mins £12 99PC PAL VGA TO TV CONVERTER Converts a colour TV intoa basic VGA screen Complete with bu!tin psu. lead and sAvare£4995 Ideal forlaptops or a cheap upgrade We also can supplythisin lot form for home assembly at £34 95 ref EF54DRINKING BIRD Remember these' hook onto wine glass (sup-plied) and they dnnk. standup.dnnk. standup ETCi E4 each Ref EF1
EMERGENCY LIGHTING UNIT Complete unit with 2 doublebulb floodlights. built in charger and auto switch Fully cased 6v BAHlead aad req'd (secondhand) E4 ref MAG4P11GUIDED MISSILE WIRE. 4.200 metre reel of ultra thin 4 coreinsulated cable. 28lbs breaking strain, less than 1mm thick' Idealalarms intercoms. fishing, dolls house's etc E14 99 ref MAGI 5P5300v PANELM ETER 70X60X5OMM AC. 90 degree scale Goodquality meter E5 99 ref MAG 6P14 Ideal for monitoring mains etcASTEC SWITCHED MODE PSU BM41012 Gives .5 0 3 75A.1201 5A. -1204A 230/110. cased. BM41012 E599 ref AUG6P3TORRODIAL TX 30-0-30 480VA. Perfect for Mosfet amplifiersetc 120mm dia 55mm thick E18 99 ref APR19AUTO SU NCHARGER 155x30Ornm solar panel with diode and3metrelead fitted with a agarplug 12v 2watt E999 ea ref AUG1OP3FLOPPY DISCS DSDD Top quality 5 25' discs these have beenwritten to once and are unused Pack of 20 is E4 ref AUG4P1ECLATRON FLASH TUBE As used in police car flashing lightsetc. full spec supplied, 60-100 flashes a min E9 99 ref APR 10P524v AC 96WATT Cased power supply New E13 99 ref APR 14MILITARY SPEC GEIGER COUNTERS Unusedanstraghtfrcrn Her majesty's forces £50 ref MAG 50P3STETHOSCOPE F ugly functioning stethoscope. ideal for listeningto hearts pipes motors etc E6 ref MAR6P6OUTDOOR SOLAR PATH LIGHT Captures sunlight dunng
the dayand automatically switches on a buillin lamp at dusk Completewith sealed lead aad battery etc E19 99 ref MAR20P1
ALARM VERSION Of above unit comes with built in alarm and putto deter intruders Good value at just E24 99 ref MAR25°4
CARETAKER VOLUMETRIC Alarm, will cover the whole of theground floor against forcred entry Includes mains power supply andintegral batterybackup Powerful internalsounder will take external Del
req'd Retail £150.. ours? E49 99 ref MAR50P1
TELEPHONE CABLE White 6 core 100m reel complete with apack of 100 dips Ideal 'phone extns etc E7 99 ref MAF!8P3
MICRODRIVE STRIPPER Small cased tape drives ideal forstnpping. Ids of useful goodies including a smart case. and lots ofcomponents £2 each ref JUN2P3
SOLAR POWER LAB SPECIAL You get TWO Fre 6v 130mAsolar cells, 4 LED's. wire, buzzer, switch plus 1 relay or motor Superbvalue lutjust E5 99 REF MAG6P8
SOLID STATE RELAYS Will switch 25A mains Input 3 5-26v DC57x43x21mm with terminal screws E3 99 REF MAG4F 10
BUGGING TAPE RECORDER Small voice activated recorder.uses micro cassette complete with headphones E28 99 ref MAR29P1
ULTRAMINI BUG M IC 6mmx3 5mm madeby AKG 5-12v electretcondenser Cost £12 ea. Ours? just four for (9.99 REF MAG10P2RGB/CGA/EGA/TTL COLOUR MONITORS 12' in goodcondbon Back anodised metal case £79 each REF JUN79
ANSWER PHONES Returns with 2 faults. we give you the bits for1 fault. you have to find the other yourself BT Response 2005E18 eaREF MAG18P1 PSU E5 ref MAG5P 12
SWITCHED MODE PSU ex equip. 60w .5v Q 5A. -5v@ 5A..12v02A-12ve 5A 120/220v cased 245x88x 55rnm 'EC:input socketE6 99 REF MAG7P1PLUG IN PSU 9V 200rnA DC (2.99 each REF MAG3P9PLUG IN ACORN PSU 19v AC 14w £299 REF MAG3P 10POWER SUPPLY fully cased with mains and oh leads 17v DC900mA output Bargan once E599 ref MAG6P9
ACORN ARCHIMEDES PSU .5vQ 4 4A on/aff sw uncased.selectable mains input 145x 100x45mm E7 REF MA37P2GEIGER COUNTER KIT Low cost professional twin tube. complete with PCB and components Now only El 9 REF AUG19
9v DC POWER SUPPLY Standard plug in type 150ma 9v DC withlead and DC power plug pnce for two .5E2 99 ref AUG3P4AA NICAD PACK encapsulated pack of 8 AA. aced battenes(tagged) ex equip. 55x32x32mm E3 a pack REF MAG3P 1113.8V 1.9A psu cased with leads Just E9 99 REF MAG10P3
PPCMODEM CARDS These are high spec plug in cardsmadelorthe Amstrad laptop computers 2400 baud dial up knit complete withleads Oearance pnce E5 REF: MAG5P1
INFRA RED REMOTE CONTROLLERS °ovally made forhi spec satellite equipment but perfect for all sorts of remote controlprojects Our clearance pnceis just E2 REF: MAG2
200 WATT INVERTER Converts 10-15v DC I ito either 110v or240vAC Fully cased 115x36x156mm, complete with heavyduty porterlead. agar plug, AC outlet socket Auto ovenoad shutdown. auto shortcircuit shut down. auto input over voltage shutdown. auto input undervoltage shut down (with audible alarm). auto temp control. unit shutsdown if overheated and sounds audible alarm Fused reversed polantyprotected output frequency within 2%. volt age withtn 10% A extremelywell built unit at an excellent price Just E64 99 re AUG65
UNIVERSAL SPEED CONTROLLER KIT Designed by us forthe C5 motor but ok for any 12v motor up to 30A Complete with PCBetc A heat sink may be required E17 00 REF: MAG17MAINSCABLEPrecutolack 2core2metrelengAsideal for repairs.projects etc 50 metres for El 99 ref AUG2P7COMPUTER COMMUNICATIONS PACK Kit contans 100mof 6 core cable 100 cable dips. 2 line dnvers with RS232 interfacesand all connectors etc Ideal low cost method of communicating be-tween PC's over a long distance Complete kit E699MINI CYCLOPS PIR 52x 62x4Omm runs on P03 battery completewith shnll sounder Cheap protection at only E5 99 ref MAR6P4ELECTRIC MOTOR KITComprehensiveeducatonal kit includesall you need to build an electnc motor £9 99 ref MARI OP4VIEWDATA SYSTEMS made by Philips. complete with internal1200/75modem keyboard. psu etcRGBand corrposrleoutputs menudnven. autodaller etc E18 each Ref EF88BOOMERANG High tech. patented poly propylene. 34cm wingspan Get out and get some exercise for E4 99 ref E F83AIR RIFLES.22As used bytheChmese army fortraining puposes.so there is a lot about, £39.95 Ref EF78 500 pellets E4 50 ref EF80PEANUT TREE Complete kit to grow your own peanuts, fullinstructions supplied E3 Ref EF45
PLUG IN POWER SUPPLYS Plugs in to '3A socket with outputlead three types available. 9vdc 150mA E2 ref EF58 9vdc 200mAE2 50 ref EF59. 6 5vdc 500mA £3 ref EF61
VIDEO SENDER UNIT. Transmits both audio and video signalsfrom either a video cam era. video recorder, TV or Computer etc to anystandard TV set in a 100' range' (tune TV to a spare channel) 12v DCop Pnce is EIS REF: MAG15 12v psu is E5 extra REF: MAG5P2' FM CORDLESS MICROPHONE Smalt hand held unit with a500' range, 2 transmit powerievels Reqs PP3 9v battery Tuneable :oany FM receiver Pnce is £15 REF: MAG15.1LOW COST WALKIE TALKIES Par of battery operated unrtswith a range of about 200' Ideal for garden use or as an educational tcyPnce E8 a par REF, MAG BP1 2 x PP3 req d
' PA INATU RE RADIO TRANSCEIVERS A pair of wake talkies'SOME OF OUR PRODUCTS MAY BE UNLICENSABLE IN THE UK
MAIL ORDER TERMS: CASH PO OR CHEQUEWITH ORDER PLUS £3.00 PCST PLUS VAT.
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with a range otup to 2km in open country UNts measu re 2262x 155mmIncluding cases and earp'ces 2aPP3 req'd E30 OOpr REF: MAG30COMPOST - E VIDEO KIT. Con reds composite video into sepa-rate H sync sync and video 12v DC E8.00 REF: MAG8P2.LQ3600 PRINTER ASSEMBLIES Made by Amstrad they areenthemechanicalpnnter assemblies induding pnnthead, steppermo-tors etc etc 11 fact everything bar the case and electronics. a goodstnppert E5 REF: MAGSP3 or 2 for E8 REF: MAGBP3LED PACK of 100 standard red 5m leds E5 REF MAG5P4UNIVERSAL PC POWER SUPPLY complete with flyleads,switch fan etc Two types available 150w at E15 REF MAG15P2(23x23x23mm) and 200w at E20 REF MAG20P3 (23x23x23mm)GYROSCOPEAbout 3' Ngnand an excellent educational toy loranages' Pnce with instruction booklet E6 Ref EF15
FJTURE PC POWER SUPPLIES These are 295x 135x6Ornm4 Znve conrectors 1 mother board connector 150watl, 12v fan lerin'et and on/off switch £12 Ref EF6VENUS FLYTRAP KIT Grow your own carnivorous plant with thissrnple kit E3 ref EF34
PC POWER SUPPLIES (returns) These are 140x 150x9Ommps are .12. 12.5 and -5v Built in 12v fan These are returns so theymay well need repanngt E3 50 each ref EF42'FM TRANSMITTER KIT housed in a standard working 13Aadapter', the bug runs directly off the mans so lasts forever, why pay£700? or pficeisE15 REF EF62 Transmits to any FM radio (this is inIhtforrn wit1 full instructions )
'RI BUG KITNewdesgnwth PCB embedded col for extra stabilityWorks to any FM radio 9v battery req d E5 REF MAG5P5FM BUG BUILT AND TESTED supenor design to kit Suppliedto detective agenaes 9v battery req d E14 REF MAG14TALKING COIN BOX STRIPPERongmallymade to retail at E79each these units are designed to convert an ord nary phone into apayphone The units have the locks missing and sometimes brokenhinges However they can be adapted for their on ginal use or used forsomething else?? Pnce is just £3 REF: MAG3P1
TOP QUALITY SPEAKERS Made for HI FI televisions these are10 watt 4R Jap made 4' round with large shielded magnets Goodquality E2 each REF: MAG2P4 or 4 for £6 REF: MAG6P2TWEETERS T diameter good quality tweeter 140R (ok with theabove speaker) 2 for E2 REF: MAG2P5 or 4 for E3 REF: MAG3P4AT KEn1 BOARDS Made by Apncot these quality keyboards needjust a small mod to run on any AT, they work perfectlybut you will haveto put up with 1 or 2 foreign keycaps' Pnce E6 REF: MAG6P3H EA DF HONES Ex Virgin Atlantic 8pairsforE2 REF: MAG2P8DOS PACKS Microsoft version 3 3 or higher complete with allmanuals or pnce just E5 REF: MAG5P8 Worth it just for the verycompretensvemanuall 5 25' onlyGAS HOBSBrand new made by OpOmus bacthreebumer suitablefor small fiat etc bargain pnce lust E29 95 ref EF73GAT AIR PISTOL PACK Complete with pistol darts and pelletsE12 95 Ref EF82 extra pellets (500) E4 50 ref EF80CHRISTMAS TREE KIT Start growing it now' E3 ref EF53DOS PACK Microsoft version 5 Onginal software but no manualshence only E599 35' only.PIR DETECTOR Made by famous UK alarm manufacturer theseare hi spec, long range internal units 12v operation. Slight marks oncase aid unboxed (although brand new) E8 REF: MAG8115MOBILECAR PHON EE6.99 Well almostt completem carphoneexdudmg the box of electronics normally hidden under seat Can bemadeto illuminate with 12v also has built Inlight sensor so display onlyilluminates when dark Totally convinangl REF MAG6P6ALARM BEACONS Zenon strobe made to mount on an externalbellboebutcould beuseclfor caravans etc 12v operation. Just connectup arc it flashes regularly) E5 REF MAG5P116-X1r AMORPHOUS SOLAR PANEL 12v 155x310mm130rn.h Bargain pnce just E5 99 ea REF MAG6P12FIBRE OPTIC CABLE BUMPER PACK 10 metres for (499ref MAG5P 13 ideal for expenmentersI30 m for £12 .99 ref MAG13P1
HEATSINKS (finned) TO220 designed to mount vertically on a pcb50x40x25mm you can have a pack of 4 for Et ref JUN1P11STROBE LIGHT KIT Adjustable from 1 hz nght up to 60hzi(elecdonic asssernbly kit with full instructions) £16 ref EF28ROCK LIGHTS Unusual things these two pieces of rock that glowwhen rubbed togethert belived to cause ranlE3 a par Ref EF29
NEW HIGH POWER LASERS15rrtW Helium neon 3 switchablew avelengths 63um,1 15um 3 39urn(2 orthem are infrared) 500 1 polanzer built in so good for holographySupplied complete with mains power supply 790x65mm Use withEX, REME CAUTION AND QUALIFIED GUIDANCE E349.Vat.
WE BUY SURPLUS STOCK FOR CASH
FREE CATALOGUE1995 100 PAGE CATALOGUE NOWAVAILABLE, 45P STAMP OR FREE
WITH ORDER.
PORTABLE RADIATION 6 OR
WITH NEW COMPUTER INTERFACE.
£59.00Hand held personal Gamma and X Ray detector.
his unit contains two Geiger Tubes, has a 4 digit LCDsplay with a Piezo speaker, giving an audio visual
ndication. The unit detects high energy electromag-tic quanta with an energy from 30K eV to over 1.2Mand a measunng range of 5-9999 UR/h or 10-99990
r/h Supplied complete with handbook. Ref . NOV 18
3
1.
Is your PCB design package notquite as "professional" as youthought? Substantial trade-indiscounts still available.
Boa CaptorSchematic Capture Design Tool
Direct netlist link to BoardMaker2Forward annotation with part valesFull undo/redo facility (50 operations)Singe -sheet, multi -paged and hierarchical designsSmooth sc-ollingIntelligent wires (automatic junctions)Dynamic connectivity informationAutomatic on-line annotationIntegrated on -the -fly library editorContext sensitive editingExtensive component -based power controlBack annotation from BoadMaker2
PCB and schematic draftingEasy and intuitive to useSurface mount and metric support90. 45 and curved track cornersGround plane fillCopper highlight and clearance checking
BoardMaker2 - Advanced level
E95
All the features of BoardMakerl rFull netlist support- BoardCapture. ErOrCad, Schema, Tango, CadSta'Full Design Rule Checkingboth mechanical and electricalTop down modification from the schematicComponent renumber with back annotationReport generator- Database ASCII, BOMThermal power plane support with full DRC
Gridless re-entrant autorouter
Simultaneous multi -layer routingSMD and analogue supportFull interrupt, resume, panand zoom while routing
Output drivers - Included as standardPrinters - 9 & 24 pin Dot matrix,HPLaserjet and PostScriptPenplotters - HP, Graphtec & HoustonPhotoplotters - All Gerber 3X00 and 4X00Excellon NC Drill and Annotateddrill drawings (BM2)
From the FOX range of low-cost, high quality, vehicle alarm systems from MaplinElectronics comes the expandable remote vehicle alarm with battery back-up. This top -of -the -range vehicle al lrm system incorporates a host of features: such as LED statusindicator, built-in parking light flasher, and an in-built engine ignition disable facility.
The lead from the ignition switch to the ignition co I is cut and the two leads areconnected to two wires on the alarm. When the alarm is armed, the ignition coil isdisabled, the engine will turn, but not start. An alkaline 9V PP3 back-up battery (notincluded) provides additional security. When armed, if the main power - or earthconnection to the alarm is broken - then the alarm will be triggered. A key operatedswitch is provided on the back of the alarm that will bypass all the alarm functions whenoperated; this is useful when for instance, the vehicle is being serviced or valetted.
The range of optioial extras that can be used with the alarm provides a verycomprehensive and sophisticated vehicle alarm system. Complete with comprehensivefitting instructions, fixing kit, remote transmitter and warning stickers. A spare transmitter(£9.99) is also available.
Available from Map in shops price£64.99 (Inc. VAT) or by mail order.
For further information,please contact Maplin
Electronics on01702 55291 1.
New Remote Vehicle Alarm
Myriad Solutions 's launching the alpha drive CPU sub -system for use in highperformance parallel and multiple processing computer systems.
Designed specifically to provide superior F.ISC performance for the parallelsystem developer, the Myriad alpha drive features the Digital Alpha DECchip21064 running at 166, 233 and 275MHz and offers performance figures of upto SPECint 92 175.6 and SPECfp 92 272.8. Packaged in a durable steel case,alpha drive communicates with PC and workstation host computer systemsusing industry standard transputer and C40 comport links.
Its 64 -bit RISC super scalar super pipelined architecture can provide apeak instruction execution of 550 million operations per second! Inharnessing this performance, Myriad has devised the MaxCache memorymanager to provide up to 800 MB per second burst read/write cache accessof up to 32MB of memory. DRAM access of Jr) to 128MB is available tosupport larger applications and data files.
Working closely with Digital engineers, Myriad have designed and built thesmallest and fastest Alpha sub -system in the market. The Alpha Drive is aself-contained Lila housed in a steel case with integral fan cooling andcustomer power management. A single unit is designed to Ut compactly intoa PC tower case with a simple cable attachment providing the hardwareinterface to the host PC through a transputer or C40 link adapter card. Foruse with works-ations or small footprint PC machines, single or multiplealpha drives are supported in the external stand-alone Myriad Drive Box.
The alpha drive facilitates the development of multiprocessor applicationswith the use of the Parallel C / AXP software tools from 3L Ltd in Edinburgh.Incorporating the DEC Alpha C compiler, Parallel C supports an advancedmicrokernal to provide true multitasking, multiple threads and multiplepriorities with are-emptive scheduling. Run - time library support forinitialisation, communication, load balancing and memory managementallows the development of a distributed application running on one or moreMyriad alpha crive units. Standardised 3L communication functions providethe tools to bL ild heterogeneous networks of alpha drive, transputer (TRAM)and TI 320C40 (TIM) processor mode modules.
For furtherinformation,
contact MyriadSolutions
01223 421181.
ELECTRONICS TODAY INTERNATIONAL7
The problem with trying to c-ortrol electrostatic damage (ESD)ias alwais been identifying arc, measuring something which.:annot be seen. Now, 3M El ac rival Specialists has found away of makinq visible the invisiile with its new Static EventDetects r.
The lean el the new kit is tie 715M clactor, a one -inchsquare electrct-tatic sensor module designed to monitor staticevents z s they occur at ail stag ?.s of production on
Lsigrounded ob.ects such as PCBs, parts trays or smallassembles. The detector car also be L sed to monitor parts-svorage 'acilities, field servicE o aerations and to verify staticcontrol Prosessas.
The sensor a- easures the difference be-v.een voltagestr nsmitted to i s backplate and is sma I concuctive internalantenna. The arthnna is -hen capacitive y coupled to earthground. Curing ri ESD event, a t rief difference in potentialexists between -he baci4 late and antenna, triggering thesensor, and activating an amplifytng and latch
When trigger -3d, the Static Event Detector indicates tooperators where and when an ES) event hz s occurred,allowing then to collect rueastresnent data with which toaucit their proce 33 using statistical methods already incommon use in rtany con panies.
When it a-riues on the market, he detector will be availablealore (in packs o- We) or as part of a turnkey audit kit, bundledwith resette rs, test boards, simuf atcrs, mounting clips and tapes.
For furtherinformation
contact 3M on01344 858739.
NEW MICRO MIDGET CPU ENGINEThe new Micro -Midget for CMS is a small (3..? x 2"approx.) very powerful 16132 bit controller. It is ideal as acomponent in intel igent trol systems, with an advancedroyalty free real time operatng system and ful support forhigh level languages includi-g C.
The controller has up to 22 digital 1,0 lines which can oeconfigured for inpu- outoLt as required, a single sels1 portoperating at up tc 38400 baud with RE -232 or RS -485driver options and two 1E-bi- timer/counters. The peribheralexpansion bus can be used with 6800C type devices, 8)51devices or 12C bus peripherals.
Applications are develcpe1 on a PC, downloaded tc theMicrc -Midget and tested ii RAM. Up to 1 Mbyte of proq-amspace is available on board with up to 512 kbtye of Sta:cRAM. The PC uti'ities are provided to allow the applicati:nscode to be EPROMed arc -u1 from power up.
The Micro -Midget can be considered as a corponen-and can be plugged into the user's board as a CPU engine,with digital and serial I/0. Al' connectors are brought out ona 0.1" pitch to cod pin heade-s.
The board is vicec at a remarkable 4295 one -cif andPC starter pack coitainirg all he software suppomoperat rg system, C compiler PC utilities and a Vicro-Midget from £295
For further details contact Cambridge MicroprocessorSystems Ltd on 01371 87564.
ELECTRONICS TODAY INTERNATIONAL8
Brain Boxes have now added on -board diodes to thei- RS422/485 twin serialport card, thus offering transient spike protection for the line drivers. Protectionfrom +ve spikes >12V and -ve spikes> -6.8V is now provided on the improvedversion of this half size card.
The card provides 2 RS422/485 serial ports independently configurable asRS422 with/without handshaking or RS485 full/half duplex, all optically isolatedto 1500 Volts DC/1000 Volts AC. Each serial port may/ be jumper configured asCOMI-COM8 with interrupt line jumper set to IRQ 2-7, 10-12, 14-15.
By adding the optional LPT adapter cable, a non-isclated parallel printer portset as LPT1-3 when interrupt 7 may be used. Thus alowing OS/2, Novell andUNIX full interrupt driven printer output. A buffered vers on of the card isavailable for Windows users. The top line card is unctr £200, including uti itydisk with sample programs, source code and terminal software, plus informative55 page manual; the optional adapter cable under £10.
More information: contact Brain Boxes on: 0151 220 2500.
Super thin LCDsA range of Super -low profile Chip On Flex LCD dot matrix modules, ideal for any application
where space is at a premium, is now available from Anders Displays.With a thickness less than 2.0mm, they are suitable for a wide range of markets, such as
mobile comms, telecommunications, hand-held instrumentation, metering, medical andautomotive. As stand alone modules, the devices allow users to use in-house mounting andbacklighting techniques, thus offering the possibility of a more cost-effective approach tnanusing a standard dot matrix module. Tooling a mounting bracket, complete with integre'backlight, is also possible if required.
Requiring an operating voltage of between 2.7V - 5.5V or 4.5V - 5.5V, the modules areeasily customised, allowing icons to be modified to suit user requirements and pin -outconnection to segments relocated to suit customer software listing. Extremely competitivelypriced - in line with existing dot matrix modules - the devices are expected to eclipse bezel
type modules completely.
For more informationcontact Anders
Electronics Plc, on0171 388 7171.
16-18 May20 May
6 June
12 June
26 June
4 July
10 July
24 July
Starting in Contesting. Sunbury and District Radio Amateurs, Wells Hall Old School,Great Cornard. Tel: 01787 312212Working wartime CW Shortwave station to celbrate VE day. Puckpool Park Wireless Museum,
IOW. -fel: 01983 567665Internet World, Wembley Centre, London. Tel: 0171 976 0405.Ipswich Computer Show. 1A ills Corroon Sports and Social Club, The Street,Rushmere St Andrew, Ipsw ch. Tel 01473 272002.Using Thermionoic Valves, Sunbury and District Radio Amateurs Weds Hall Old School
Great Cornard. Tel: 01787 313212Open House, Stratford upon Avon and District Radio Society, St-atford uponAvon. Tel: 01789 740994.Top Band Foxhunt, Stratfo-d upon Avon and Cistrict Radio Society, Stratford upon Avon.
Tel: 01789 740994.Operating QRP, Sunbury and District Radio Amateurs, Wells Hall Old School,Great Cornard. Tel: 01787 313212Summer School, Stratford upon Avon and District Radio Society, Stratford upon Avon.
Tel: 01789 740994.Construction Competition. Stratford upon Avcn and District Radio Society, Stratford upon Avon.
Tel: 01789 740994.
If you are organising an event which you would like to have included in this sec'.ion please send full details to: ETI,Nexus House, Boundary Way, Hemel Hempstead, Herts HP2 7ST. Clearly ma -king your envelope Even-. Diary.
ELECTRONICS TODAY INTERNATIONAL9
rtillifrEittEMORY
New types of metal alloy can changeshape when heated by an electriccurrent and are being used to replacetraditional actuators. Nick Hampshiretakes a look at this revolutionarytechnology and examines how theycould be used to make muscles forfuture generations of robots
In virtually every piece of electrical equipmentthere are devices which convert electrical energyinto mechanical energy. The drive motor andhead positioning actuator in a disk drive, theloudspeaker on a radio or TV, the fan in your
PC, the compressor in the refrigerator. All these, and manymore, use one of three different techniques for energyconversion - electric motors, solenoids, and piezoelectric materials.
To these three basic techniques we now need to add a
fourth, potentially the most powerful, easy to use, cheapestand versatile technique of them all. A technique based upon astrange phenomenon known as Shape Memory Alloys (SMAs).A phenomena in which certain special metal alloys undergochanges in shape or hardness when heated or cooled and doso with great force.
LONGER
SHORTER
TRANSITIONTEMPERATURE
RANGE4
0 TEMPERATURE I
Fig.1 . Temperature vs SMA wire length
What areShape Memory Alloys?Certain alloys of two or more metallic elements exhibit aproperty known as Shape Memory Effect. This effect meanssimply that they have a crystal structure which will completelychange to another structure at a distinct temperature. In otherwords, one may completely deform a piece of such an alloybut when it is heated past a certain temperature, usually wellunder 100C and way below the melting point, it will return tothe shape it had prior to being deformed.
Below the transition temperature a piece of SMA can beeasily stretched and deformed. If it is then heated above thetransition temeperature it will return to its unstretched,undeformed shape Hence the reason why they are calledshape memory alloys.
A typical SMA wire can thus be stretched by up to about8% and still contract to its original length when heated abovethe transition temperature (it will not properly recover fromexcessive stretching or deformation). In contracting it iscapable of generating a considerable amount of usable force.Indeed, they are being widely talked about as the muscles forfuture generations of robot.
The usable force generated by a piece of SMA wire can bequite substantial, but is of course only generated by thecontraction of a stretched wire. This means, of course, that ina practical SMA based actuator the wire must contract againstan opposing force which will then stretch the wire as soon asthe temperature of the wire drops below its transition point.
The transition temperature depends on the type of alloy,and can in fact be very precisely defined during manufacturingby careful control of the percentages of the different elements.Thus, the most common SMA is made from nearly equalproportions of nickel and titanium, and a 1% difference in the
ELECTRONICS TODAY INTERNATIONAL10
ratio of these two metals can lead to changes in the transitiontemperature in the range -100C to +100C.
The commonest SMA alloys are designed for use at roomtemperature and have transition temperatures of about +70C.However, higher transition temperatures are used where thecycle of contraction and stretching needs to be at a muchhigher rate than normal, the standard maximum cycling ratebeing about 50 cycles per minute.
The transition temperature is in fact spread over a smallrange, with the contraction temperature being slightly differentfrom the relaxation temperature. A gap which is referred to asthe temperature hysterisis, and which can be seen clearly in Fig.2.
The development of shape memory alloys.We have said that SMAs are a new development, but this isnot, strictly speaking, true since the shape memory effect of agold cadmium alloy was first noted by the Swedish scientistArne Olander in 1932, and he even went as far as predictingthat it had potential use in converting heat into motion.Olander's discovery remained little more than a scientific
curiosity until 1950 when L C Chang and T A Read of NewYork's Columbia University used X-rays to study this alloy andunderstand the changes in its crystal structure which accountfor the shape memory effect. Not only did their studies sparkoff a lot more research into SMAs but they actuallydemonstrated that the shape memory effect could be put touse and perform actual physical work.The further research into SME was centred around the searchfor other alloys which exhibited this effect. This search whichled to the discovery of another SMA, an alloy of indium andtitanium. However, both these SMAs used very expensivemetals and, in the case of the gold cadmium alloy, one whichwas very toxic. Factors which limited any further research intoSME until 1963. It was then that the US Naval OrdnanceLaboratory discovered that the shape memory effect wasexhibited by an alloy of nickel and titanium that they wereexamining for use in non -corrosive marine applications.This alloy was called Nitinol I Ni for nickel, Ti for titanium, andNOL for the Naval Ordnance Laboratory) and had none of thedrawbacks of the two previous SMAs, it was relatively cheap
An electronic interface for SMA wireThe explosion in applications for SMA are primarily due to the development of electrically activated SMA wire.Electrical activation involves simply passing an electric current along an SMA wire so that it heats the wireabove its transition temperature and thus causes it to return to its undeformed state.
Simply connecting a piece of SMA wire to 3 battery or other power source will work, but there is a seriousrisk of overheating the wire and thus potentially annealing it and in so doing destroying its existing 'memory'. Afar better way is to use a driver circuit which controls the amount of current flowing through a wire andtherefore the temperature of the wire.
The simplest form of SMA wire driver circuit is a passive current regulator which simply uses a resistor ofsuitable value in series with the wire as a means of limiting the current flow through the wire. The problem withthis technique, though, is that different resistor values will need to be calculated for different wire lengths anddifferent wire diameters. In other words the dr ver circuit will have to be taylored for each SMA actuator.
One way round this problem on computer controlled SMA actuators is to use pulse width modulationcurrent limiting. This essentially means regu wing the current flowing through tha wire by rapidly turning it offand on, with the average current being determined be the percentage of time that the current is on. With thistechnique the average current delivered across the wire can be very precisely controlled by altering the onpulse width with respect to the off pulse width.
By far the best form of current driver, for a'l applications, is an active current driver. This is a simple circuitwhich will deliver a constant current for any length or diameter of SMA wire, with the only limit being that ofthe power supply. It essentiallyconsists of a voltage regulator anda resistor. The resistor determinesthe current level and the voltageregulator adjusts its output tomaintain a constant current. Thecircuit in this box shows a practicalactive current regulator for SMAwire actuators.
Of course there may be arequirement for other specialisedactuators, which control acivationor relaxation speeds or even holdactivation. Thus rapid actuationcould be initiated by quickly sendinga very large current through thewire and drop the current to a lowlevel which would maintainactivation without overheatingthe wire.
-12V
SWt
LI
Vin
Rt
Vout 5R 1/2W
e
<XX> SYMBOL JSED FOR SMA(SHAPED MEMORY ALLOY) WIRE
Fig.2. SMA wire driver circuit
MW1
200umJ2 10cm
CURRENT i = 1.25R1
MPSA13NPN DARL.
e b c
317TREGULATOR
0
i5 Eno o
ELECTRONICS TODAY INTERNATIONAL11
HIGHER
LOWER
MOROMOMNOM
HIGH TEMPERATURE PHASE(AUSTENITE)
LOW TEMPERATURE PHASEIMARTENSITEI
ARdIA141
/UMW
I
SHORTER 4% 8%
STRAIN (STRETCHING)
Fig.3. Typical stress vs strain curve for SMA
LONGER
and non-toxic. On top of this, it possessed a much betterdeformation/recovery ratio than either of the other two SMAs.This discovery renewed interest in SMAs and their use and, by1973, researchers in various centres around the world haddiscovered the shape memory effect in a range of other alloys.These included iron -platinum, copper -zinc, copper -tin, copper-
aluminium -nickel, copper -zinc -aluminium, copper -gold -zinc,nickel -aluminium, and manganese -copper. Of all of theseSMAs, the two most widely used because of their low cost,
strength, and forge deformation/recovery ratios are nickel-titanium and copper -zinc -aluminium.During the late 60s and early 70s researchers started todevelop applications for SMAs, and in the forefront of thiswork were NASA and the world's major defence companies.Indeed, the Soviet Union considered SMA technology soimportant that they developed the ability to produce nitinol inquantity. It was regarded as a strategic material and tons of itwere stockpiled. A lot of work on SMAs was done by the militaryand much of it is only just starling to leak out into public domain.Amongst the non-military applications for SMAs that weredeveloped in the 70's and 80's, NASA devised a system forunfolding satellite antennas when they were exposed to theheat of the sun. Other university and corporate researchersused SMAs to create small heat engines running on hot andcold water, electrically operated pipe valves, automobile fanclutches which engaged when the engine reached a certaintemperature, and greenhouse window openers which wereactivated at specific greenhouse temperatures.Many of these applications were initially not very successfulbecause the quality of the available SMAs (they primarily usednitinol) was not good enough. But as metalurgical processesimproved and the quality became more consistent and reliable,so the engineers became more successful in their attempts toput the shape memory effect to practical use.
CONNECT SENSORAND MUSCLE WIRETO THE CIRCUIT ASSHOWN IN THESCHEMATIC
LOW FORCEPOSITION SENSOR
MUSCLE WIRE
Fig.4. SMA wire based servo mechanism
LED1
RED LED
LEDs(ANODE)
LEDc
(CATHODE)LEAD WITH FLAT EDGE
ON BODY
01 PHOTOTRANSISTOR
Fig.5. Low force position sense circuit
Olc (COLLECTOR)
018 (EMITTER)LEAD WITH FLAT EDGE
An SMA wire basedservo systemDriver circuit may be called upon to hold the activation ofan SMA wire based actuator at a certain level using someform of position sensing feedback loop. This is a similarapplication to those employed in servo controlmechanisms, such as those used in radio controlled models.
This type of application needs two components, a lowforce position sensor and a driver circuit. If we are goint touse an SMA wire based actuator in place of a standardradio control servo then we can use the a standard servoR/C circuit can be used, with the wire connected in placeof the conventional motor and a special position sensor inplace of the potentiometer. (there are some very low costR/C servo mechanisms on the market today and it isprobably cheaper and easier to buy one of these and usethe internal electronics tather than buying the componentsand building your own control circuitry.
A low force position sensor can be constructed from aphoto transistor and an LED as shown in theaccompanying diagrams. Note that the elastic banddetermines the force needed to extend the sensor andchanging the force is simply a matter of changing theelastic, the paper tube acts as a guide and as a means ofexcluding any external light.
In the diagram for the R/C interface circuit note howthe position sensor is connected to a typical R/C servoPCB, the variable resistors VR1 and 2 are used to adjustmovemeny in the 'up stick' and 'down stick' positionsrespectively.
(The ideas here were drawn from Roger Gilbertson'sMuscle Wires Project Book, available from MilfordInstruments - Tel: 01977 683665. - this book is an excellentsource of practical SMA based ideas and circuits)
ELECTRONICS TODAY INTERNATIONAL12
Thus by 1971 two researchers in Brooklyn, New York,P.N.Sawyer, and M.Page, were able to build an artificial heartthat was activated by 500um nitinol wire. But low cycle timesmeant that it could only run at about 12 beats per minute asopposed to 80 or 90 beats in a real heart. The SMA technologyavailable today would mean that a version could now be builtwhich would very nearly beat at the proper rate and thus couldbecome a viable prospect in medical applications.A lot of the early development work was related to the
CONNECTING WIRES(LABELLED TO HELPIDENTIFY THE LEADS)
THIN ELASTICLOOP
PAPERTUBE
1:7SHRINKTUBING
01IR PHOTOTRANSISTORTi - 3/. SIZE
LED1RED LEDTi- 3ASIZE
SHRINKTUBING
CONNECTING WIRES(COLOUR CODED)
THE SENSORIN ACTION
EPDXYHERE
RELAXED
IL
EXTENDED
Fig.6. Construction of low force position sensor
construction of pumps of various sorts since it was quicklyrealised that the ability of SMAs to perform useful work givenvery small temperature gradients made it the ideal techology forconstructing heat engines. Such engines would be capable ofturning very low grade thermal energy, in particular solar,geothermal, or waste industrial/domestic thermal energy, intouseful high grade mechanical or electrical energy.One of the earliest working SMA heat engines was developedin 1974 at the Lawrence Berkeley Laboratories in California andis based upon the differential pulley. A commercial version ofthis design which employs just a single coil of nitinol wire iscapable of speeds of up to 1000PRM with a power output of1 watt using just hot and cold water as the power source.In 1980 McDonald Douglas demonstrated a scaled up versionwhich employed one hundred 50um mechanically connectednitinol wires. This also used hot and cold water as the powersource and was capable of developing a power output inexcess of 32watts. In building this engine, the designersdiscovered no fundamental reasons why it should not bepossible to build very large and economically viable SMA basedheat engines. Indeed it is rumoured that such engines arecurrently being designed in several parts of the world.
Commercial applications for SMAsOne company which began research into SMAs in the late 60swas the Californian based Raychem Corporation. They alsojoined the search for new SMAs and in the early 1970slaunched two products, Betalloy, a copper -zinc SMA and Tinel anickel -titanium SMA with an unique sub -zero transition temperature.
Raychem have used the sub -zero transition temperature oftheir Tinel SMA to oroduce a range of high performancecouplings for aircraft hydraulic lines. These couplings are madeof Tinel and both shipped and installed at about minus 200C(the temperature of liquid nitrogen). Once it is installed thecoupling warms uo and in so doing shrinks by about 8% indiamete,r thereby making a very tight leakproof seal (so far theyhave sold over one million units and not one has either leakedor failed, thus making it one of the most successful SMAproducts to date).
In the UK, one company which was an early researcher intoSMAs and a developer of SMA basedproducts was Delta Metals. Using nitinolthey developed a range of automaticthermally operated vents for use inapplications such as greenhouse windows.They also developed a range of fan clutchesand hot water valves.Not surprisingly the Japanese quicklyrealised the commercial potential for SMAsand in 1985 the Toki Corporation of Tokyostarted manufacturing high quality nitinolwire under the trade name BioMetal. Thetechnology for producing this wire had beendiscovered by Dr Homma whilst researchingSMAs at Tokyo University and wasimportant because it allowed the wire to beelectrically activated, and in properlydesigned mechanisms operate predictablyover millions of cycles without failure.The BioMetal wires produced by Toki couldnot only be electrically activated (in otherwords heat was applied by sending anelectric current along the wire) but couldalso be elongated by a very low deformation
\./
STANDARD R C
TRANSMITTER
STANDARD FICRECEIVER
O
+V
POWER
MOTOR OUT
GROUND
RED POWER
WHT
I(
BATTERY PACK
SIGNAL
Cl)
GROUND -
PCB1
SENSOR IN
INPUT
+V R1
T 1k
RV10k
R24k7
BLU
RV2STANDARD R/C 50k
SERVO PRINTEDCIRCUIT BOARD
(SEE TEXT)R3
4k7
I
MW1
150µm10cm
LEDa
LEDc
01c
Ole
POSITION
Fig.7. SMA servo circuit using R/C system
ELECTRONICS TODAY INTERNATIONAL13
force. These two factors led to an explosion in the range ofapplication for the BioMetal nitinol wire, including acting as themuscles for robotic arms.
Throughout the late 1980s Toki and other Japanesecompanies, including Hitachi and Furukawa Electric,demonstrated a range of small to medium sized robot armsand hands which operated entirely using electrically actuatedSMA wire. Hitachi even produced a four fingered robotic handthat was capable of lifting and manipulating objects in almostexactly the same way as the human hand. The hand unit waspowered by twelve groups of 200um electrically actuated nitinolwire, four per finger. These wires were housed in the forearm.
When powered the wires contracted and closed the hand,gripping any object, when the power was removed from thewires a spring extended the wires and the hand opened.Under computer control any of the wires, in other words thefinger joints, could be activated individualy to produce complexhand and finger movements
The production of BioMetal wire in Japan was very quicklyfollowed by the production of similar products from UScompanies, including Dynalloy with its range of Flexinol pretrained nitinol SMA wires. These have also been extensivelyused in robotics. In 1989 Oaktree Automation Inc, ofAlexandria Virginia, started development of ananthropomorphic robotic hand, the Fingerspelling Hand, whichwas designed as a tactile communications aid for deaf/blind
people who are unable to read BrailleThe Fingerspelling Hand was developed in conjunction with
Gallaudet University, and partly funded by the US Departmentof Education. It is constructed from one hundred and eight250um Flexinol wires that are housed in the forearm. The wiresact in parallel with opposing wires providing flexion and extensionas well as side to side motion where applicable, for each joint.
In use the hand functions as a kind of computer display.The user places his/her hand lightly on the Hand, reading acharacter at a time by feeling the hand shape, the device usesa common finger spelling alphabet. The data used to controlthe hand comes vie the controlling computer from a variety ofsources, it could be a keyboard, a page scanner with OCR, ateletext decoder, a modem, etc.(SMA wires have also beenused to create a computer controlled Braille character display).
Researcher's understanding of how SMAs behave and thetechniques for making them has improved to a degree whereSMA actuators are now being scaled down and used ascomponents in micromecanical systems. In the US TiNi AlloyCompany has now developed ways to use thin films of nitinolwhich have been formed on top of silicon wafers to createmocroscopic mechanisms.
In 1990 they demonstrated a microscopic electronic thinfilm SMA valve which used a chemically etched silicon baseand a film of nitinol just 2um thick. It is capable of opening andclosing in just 15milliseconds and allowed air at a pressure of
An SMA based programmable tactile arrayA new application for SMA wires are the 'tactors' now being utilised in some advanced virtual reality andteleoperator systems to give the user a sense of virtual touch. This is very important in arease such astelesurgery where a remote surgeon often needs to feel texture and force feedback as well as see what he isdoing. Other applications are in telerobotics, micro -robots, molecular modeling, control functions such astraining and simulation cockpit, computer aided design, and sophisticated computer interfaces - super miceand joysticks.
Tactors fall into three categories, single tactors, and tactor arrays. Single tactors are used by and large usedin vibratory mode and used to give simple warning messages. Tactor arrays on the other hand are used to givefull tactile feedback and also for Braille communications systems. Such arrays will either have vibratory pointsunder a stationary finger or raised points that are stroked by a finger tip
A tactor array has to be made small enough so that it will fit on a fingertip as perhaps part of a glove wornby the user, or some form of hand held device. The need to make them very small by and large precludes theuse of conventional solenoids, although piezo electric resonators can be used for vibratory mode applications.However, SMA based miniatureactuators are ideal for tactor arrays bothin vibratory and raised point mode.
The design of an SMA tactor array isvery simple - as can be seen from theaccompanying diagram. It just consistsof tiny spring levers made from a sheet ofberellium copper that are bent at one endto protrude through holes in a top plateto provide the tactor sense points. Apiece of SMA wire is attached to eachlever and angled upwards to a connectorblock, so that when they contract thelever is angled upwards and the endprotrudes through the hole, thespringiness of the lever metal will thenstretch the SMA wire as soon as poweris removed.
TOP PLATE
4C)
flE)
1E)
BERYLLIUM -COPPER LEVEF S
Fig.8.SMA tactor array construction
ELECTRICAL LEADS
CONNECTOR BLOCK
SHAPE MEMORY ALLOY WIRE
ELECTRONICS TODAY INTERNATIONAL14
20psi to flow through it at a rate of l litre per minute, and has avery high reliability, being capable of operating over millions ofcycles. This is the first of many potential micromechanicalapplications for SMAs.
Another electronic application is the development byBetaphase Inc, of Menlo Park in California, of a range of veryhigh density electrical connectors, with up to 190 signal linesper centimeter. They incorporate a special internal heatingelement which causes a SMA actuator to press back a springand thus allow insertion of the circuit board.
Into the future.The success of the Fingerspelling Hand has led to a lot ofresearch, primarily in the US, into uses of electrically activatedSMA wire in the field of robotics, teleoperator systems, muscleamplifiers, and medical prosthesis. By using multiple electricallyactivated SMA wires working in parallel it is possible to createactuators which can exert very considerable force in a smallrelatively light weight and low power package (see Table 1 forstrengths of multiple wire systems)
Such totally integrated multiple SMA wire actuators are nowbeing developed commercially and will allow enginers to createthe robotic equivalent of biological muscles. Robots (andmedical prosthesis units) which use these actuators will have askeleton to which groups of actuators are connected to givequiet efficient linear motion without all the problems associatedwith hydraulic and pneumatic systems and the weight/ sizeproblems assoiciated with electric motors. These SMA linearactuators will have their own in-built intelligence and will becontrolled by a communications and power network fromsome form central motion control processor.
With light weight efficient, silent all electric linear actuatorsconnected to a lightweight skelital framework it should bepossible to design and build artificial limbs which will veryclosely resemble the biological equivalent in both form andfunction. The electronic limb would be controlled using signalsderived from actual nerves which are then interpreted usingadvanced signal processing techniques (scientists are alreadyworking on such systems with considerable success).
2
HHydrogen la
Li Be
Nasodium
19
Kpotassium
37
RbnIim
Cs87
Fr7 francium
12
Mg
Cacalcourn
38
Srtroniturn
Babanurn
88
Raraj
Fig. 9. Periodic table showing SMAelements
IIlb21
Scscandium
39
Yylnurn
Lalanthanum
89
Acactinium
1Vh
Zrzirconium
Hfnettaurn
104
Vb V 1 b
Vvanathum
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6
7
It would also be possible to use such actuators to createmuscle amplification systems which would give an ordinaryhuman superhuman muuscle force or someone with reducedmuscle function the ability to move without recourse towheelchairs etc. Such muscle amplifier systems have been thesubject of work in the past by the US military, but in a civilianversion would take the form of an active externally worn bracewith belt mounted power pack and control processor thatwould be able to sense the wearer's motion and be able totake corrective action to prevent a fall.
The ability to use SMA based linear actuators to build robotsystems that very closely model human muscle based systemsalso means that they are an ideal candidate for use inteleoperator robots. These are robots which will exactly mumicthe movements of a human operator, even though theoperator may be thousands of miles away. In many ways theultimate in virtual reality systems, but something which is beingvery closely examined for space and deep sea exploration aswell as applications such as telesurgery (see ETI May 95 issueon virtual reality, and Feb 95 on electronics in medicine).
Finally we come to the application of SMA actuators inrobots, this could be a minuature surgical robot no bigger thana pea, or an autonomous robot designed to construct andmaintain some space based facility. Such actuators are idealfor use in subsumption based robot systems which currentlylook like the best bet for autonomous operation in distantlocations (see ETI Marcn 95 and November 94).
In short SMA based actuators in conjunction with advancedcomputer technology could give us the robot systems thathave so far been pure science fiction.
Sources of SMA wireMilford Instruments. Milford House, 120 High Street,South Milford, Leeds LS25 5A0. UK Tel: 01977683665orMondo-tronics Inc. 524 San Anselmo Ave. #107San Anselmo, CA 94960. USA. Tel: 415 455 9330.
26
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66
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67
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68
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69
Tmthulium
70
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71
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90
Ththonum
91
Paprotactinium
92
Uuranium
93
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94
Puamericium
95
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96
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ELECTRONICS TODAY INTERNATIONAL15
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SMA wire specificationsThe following table gives some of the main specifications for Flexinol wireproduced by Dynalloy. There are two main types of wire, the HT series and the LTseries. The difference between the two lies in the transition temperature, the HTseries has a higher transition temperature and because it cools 50% faster istherefore used in applications needing a faster cycle rate (note that the cyclerates quoted are for cooling in still air at 20C, moving the air or immersing in aliquid will increase cycle rates by up to ten times).
Wirediameter(p meters)
Linearresistance(Qs /meter)
Typicalcurrent(milliamp)
Deformation Recoveryweight weight)(gms) (gms)
LT cyclerate(cyc/min)
HT cyclerate(cyc/min)
37 860 30 4 20 52 6850 510 50 8 35 46 67
100 150 180 28 150 33 50150 50 400 62 330 20 30
250 20 1000 172 930 9 13
Notes: The contraction speed on all wires is about 1/1000sec The annealing temperature for nitinol is 540C and the melting point 1300C To convert recovery/deformation weight to Newtons multiply by 0.0098 Maximum deformation ratio is 8%, recommended deformation ratio 3-5%
Table 1Strength of multiple nintinol wires lifting in parallel
Anritsu MG642A Pulse Pattern Generator £1500Avo VCM 163 Valve Characteristic Meter £400Ballantine 323 True RMS Voltmeter £350Data I/O Model 298 (with 12 fixtures) + Logic pack £995Datalab DL 1080 Programmable Transient Recorder £350Dyanpert TP20 Intelliplace - Tape peel Tester - immacualte condition £1950Farnell RB 1030-35 Electronic load 1Kw £450Farnell 2081 R/F Power meter POAFarnell TSV 70 Mkll Power Supply (70V -5A or 35V -10A) £200Ferrograph RTS-2 Audio Test Set with ATU 1 £500Fluke 8010A/8012A/8050A Digital multimeters - from £125Fluke 5101A AC/DC Calibrator £3500Fluke 5101B AC/DC Calibrator £6500Fluke 5220A Transconductance Amplifier (20A) £3000Fluke 720A Kelvin-Varley Voltage Divider £450Fluke 750A Reference Divider £450Gould TA 600 - Thermal Array Recorder £400Gould K100D - 100MHz Logic Analyser with Pods £350Heiden 1107 - 30V -10A Programmable Power Supply (IEEE) £650Hewlett Packard 334A - Distortion Analyser £250Hewlett Packard 436A Power meter +8481A sensor £950Hewlett Packard 3437A System voltmeter £350Hewlett Packard 3456A Digital voltmeter £850Hewlett Packard 3760/3761 Data gen + error detector each £300Hewlett Packard 3762/3763 Data gen + error detector each £350Hewlett Packard 5420A Digital Signal Analyser £350Hewlett Packard 5423A Structural Dynamics Analyser £350Hewlett Packard 544708 Digital Filter £100Hewlett Packard 54410A Analogue/Digital Converter. £100Hewlett Packard 7402 Recorder with 17401A x 2 plug -ins £300Hewlett Packard 8011A Pulse gen. 0.1 Hz-20MHz £500Hewlett Packard 8406A Frequency comb. generator £500Hewlett Packard 8443A Tracking gen/counter with IEEE £300/400Hewlett Packard 8620C Sweep oscillator mainframe £400Hewlett Packard 8750A Storage normaliser £375Hewlett Packard 8684A 5.4GHz to 12.5GHz Sig -Gen £3000Hewlett Packard 3785A !tier Generator + Receiver £1153Hewlett Packard 86408 - AM/FM Signal Gen (512MHz) £850Hewlett Packard 5340A - 18GHz Frequency Counter £900Hewlett Packard 5356A - 18GHz Frequency Converter head £450
Hewlett Packard 432A - Power Meter (with 478A Sensor) £275Hewlett Packard 435A or B Power Meter (with 8481A/8484A) from £750Hewlett Packard 3438A Digital multimeter £200Hewlett Packard 6181C D.C. curent source £150Hewlett Packard 59501B HP.18 isolated D/A powersupply programmer £150Hewlett Packard 3711A/3712A/3791B/3793B Microwave LinkAnalyser £3500Hewlett Packard 5316A Universal Counter HP1B £550Hewlett Packard 53168 Universal Counter HP1B £775Hewlett Packard 5385A Frequency Counter - 1GHz - (HP1B)with OPTS 001/003/004/005 £995Hewlett Packard 86578 2060M-lz synthesised signal generator
(as new) c£71020500
Hewlett Packard 3779C Primary Multiplex AnalyserHewlett Packard 6623A Triple output system power supplyHewlett Packard 6453A Power supply 15v -200A
£c11295500
Hewlet: Packard 3764A (Opt CO2) Digital Transmission Analyser £3500Hewlett Packard 3586A Selective level meter £1750Hewlett Packard 3488A HP - , B switch control £500Hewlett Packard 3325A - 21MHz Synthesiser/Function Gen £1500Hewlett Packard 8152A - Optcal Average Power Meter £1250Hewlett Packard 81588 - Optical Attenuator (OPTS 002 + 011) £1100
HEWLETT PACKARD 6261BPower Supply 20v -50A £500 Discount for Quantities
International Light - IL 1700 Research Radiometer with Erythermal SensorHead £1250Krohn -Hite 2200 Lin/Log Sweep Generator £995Krohn -Hite 4024A Oscillator £250Krohn -Hite 6500 Phase Meter £250Leader LCR 745G LCR Meter (as new) £1150Lyons PG73N/PG75/PG28/PG Pulse generator from £225Marconi 2432A 500MHz digital freq. meter £200Marconi 2337A Automatic cist. meter £150Marconi 2356 20MHz level oscillator £300Marconi 2306 Programmable interface £450Marconi 2830 Multiplex tester £1000Marconi 2831 Channel access switch £400Marconi 2019 - AM/FM Signal generator - 1040 MHz £1800Multicore "Vapourette" Bench Top Vapour Phase SMD Soldering Machine(New 4 Unused) £650Philips 5390 1GHz R/F Synthesised signal gen £1250Philips PM 5167 10MHz function gen £400Phoenix 5500A - Telecomms Analyser with various Interface Options ...£3750Racal Dana 9242D Programmable PSU 25V -2A £300Racal Dana 9246S Programmable PSU 25V -10A £400Racal Dana 3100 40-130MHz synthesiser £750Racal Dana 5002 Wideband evel meter £650Racal Dana 5003 Digital -n/meter £150Racal Dana 900C Microp-ocessing timer/count. 520MHzRacal Dana 9081 Synth. sig. gen. 520MHz ££555500
Pacal Dana 9084 Synth. sig. gen. 104MHz £450Racal Dana 9303 True PMS/RFevel meterRacal Dana 9341 LCR databridge ££265500
Racal Dana 9500 Universal timer/counter 100MHz £200Racal Dana 9917 UHF frequency meter 560MHz £175Racal Dana 9302A R/F millivoltmeter (new version) 1375Racal Dana 9082 Synthesised am/fm sig gen (520MHz) "500Racal 9301A - True RMS R/F Millivoltmeter £300Racal 9921 - 3GHz Frequency Counter £450Rohde & Schwartz BN36711 Digital 0 meter £400Rohde & Schwarz - Scud Radio Code Test Set £995Rohde & Schwarz - LF M 2 Sweep Generator 0.02 - 60MHz £1500Rohde & Schwarz SU,' 2 Noise Generator £300Rotek 3980A AC, DC Precision Calibrator with Rotek 350A HighCurrent Adaptor £130ASchlumberger S.I. 4040 Stabilock - High accuracy1GHz Radio Test Set. - £7000Schlumberger 4923 Radio Code Test Set £1500Schlumberger 2720 -'.250 MHz Frequency Counter £500Solarton Schlumb 1170 Freq. response analyser £250Systems Video 1258 Waveform Analyser + 1255 Vector Monitor + 1407Differential Phase and Gain Module + 1270 Remote Control Panel £2250Systron Donner 1702 Synthesised Sig. Gen 1GHz £990Systron Donner 6054B or D 18GHz or 24GHz Freq. Counter from£800Telequipment CT71 Curve Tracer £250Tektronix 1480 Waveform Monitor POATektronix 651 HR Monitor POATektronix DAS9100- Series Logic Analyser £500Tektronix 577 Curve Tracer with Fixtures £950Tektronix - Plug-irs - many available such as SC504, SW503, SG502,PG508. FG504, FG503, TG501, TR503 + many more
E £600P°ATime 9811 Programmable Resistance£750Time 9814 Voltage Calibrator
Wayne Kerr B424/4 LCR Component Meter Set £200W& G SPM12 Leve: Meter (200Hz 6MHz) £500W8G PS12 Level Oscillator (200Hz 6MHz) £500
Wiltron 560 Scala: Network Analyser£17500Weller D801/D802 Desoldering station
Wiltron 352 Low Frequency Differential Input Phase Meter £350EIP 331 - Frequency counter 18GHz £700
MANY MORE ITEMS AVAILABLE - SEND LARGES.A.E. FOR LIST OF EQUIPMENT
ALL EQUIPMENT IS USED - WITH 30 DAYSGUARANTEE.
PLEASE CHECK FOR AVAILABILITY BEFOREORDERING - CARRIAGE & VAT TO BE ADDED TO
ALL GOODS
ELECTRONICS TO DAY INTERNATIONAL17
B
M
I
any people rely on a bicycle as their chief meansof transport to and from work. Some use one toyo shopping or simply to ride for exercise andpleasure. With bicycle theft now a growingconcern, some means of protection is
becoming essential.The Bicycle Loop Alarm will provide good protection.
However, it must be remembered that no alarm can providecomplete security. If the bicycle is particularly valuable, it wouldbe wise to consider buying a commercial unit which may offer ahigher degree of protection but is possibly more expensive anddifficult to use. Note that if the alarm is to be used in the rain, awaterproof enclosure would be needed and some careexercised to protect other components from the effects of theweather. With a little ingenuity, this circuit could be used to protectother items such as bicycle racks, boats, vehicle trailers, etc.
In some ways, this alarm resembles the mechanicalcombination lock which will be familiar to many readers. Thishas a barrel section attached to a chain. Four wheels on thebarrel, bearing numbers 1 to 9, are lined up to show somesecret code. The free end of the chain is then passed betweenthe spokes of a wheel or round a post and inserted in the barrel.The wheels are then rotated to some random position therebysecuring it. To remove the chain, the wheels must be set to thesecret number again. As many will testify, this is a fiddly process- especially at night - and the combination can easily pass intothe wrong hands. Since the secret number is determined whenthe lock is manufactured, it cannot be changed by the owner.
Permanently attachedInstead of the chain, this alarm uses a wire loop. If it is broken,an alarm will sound. The main unit, which is permanentlyattached to the bicycle frame, houses the circuit panel, batterypack, high -power sounder and key -operated switch. There arealso two miniature line phono-type sockets on short pigtails (seephoto). The loop itself consists of a length of insulated wire witha phono plug connected to each end. In use, a plug is insertedin one of the sockets and the loop passed between the spokes
Terry Balbyrnie shows how to constructa simple electronic device that willprotect your precious bike from theft
of a wheel. The other plug is inserted into the remaining socket.Alternatively, the loop may be passed around a post, railings,etc. Before leaving the bicycle, the alarm is armed using thekey -operated switch. The whole operation is easy to performeven under dim lighting conditions and only takes a few seconds.If a plug is now removed from one of the sockets as will happenif the bicycle wheel rotates - or if it is snapped or cut - thecircuit triggers and a 'yelping' type siren will sound. It will thenoperate for approximately 1 minute 40 seconds (100 seconds)or some alternative time chosen by the user. It can only besilenced before the end of its natural timing cycle by using thekey -operated switch. When the alarm is disarmed, the wire loopmay be removed and stowed away ready for further use. Spareloops are easily made to suit the purpose or when worn out andthe key -operated switch may be changed quickly if a key is lostor gets into the wrong hands.
Carried awayIf the lid is partially removed in an attempt to tamper with thecircuit, this will trigger the alarm. Note also that the unit mayonly be removed from the bicycle frame by first removing the lid.
If the bicycle is moved slightly or if it falls over, this is unlikelyto remove a plug or break the wire so false triggering should notoccur. Note that this is the reason for using phono plugs in theloop rather than jack or other type of connector - the formerneed more force to disconnect them. This immunity from falsetriggering sets this alarm apart from those which rely on amovement or vibration sensor. Unfortunately, this type issometimes activated by accidental movements as when thebicycle falls over.
The circuit draws no current while the alarm is off. Whilearmed, it needs less than 100mA (85mA in the prototype unit)on standby rising to about 150mA when the alarm is actuallysounding. In normal use, the 12V 'AAA' battery pack will providemany months of service even if the alarm sounds occasionally.The batteries should be tested every so often by triggering theunit for a few seconds. Poor battery condition is indicated by aweakening of sound, not by a reduction in the time period.
ELECTRONICS TODAY INTERNATIONAL18
Circuit descriptionThe complete circuit for the Bicycle Loop Alarm is shown in Fig.1. Assume for the moment that key -operated switch, S2, is on(contacts closed) so that a supply is established from the 12Vbattery pack, Bl. Assume also that a wire loop interconnectssockets, SK1 and SK2 via the loop and matching plugs PL1and PL2 and that switch S1 contacts are closed. Thesecontacts are held in the closed position while the lid of the caseis in position and this provides the anti -tamper facilitymentioned earlier.
The circuit is based on a monostable comprising integratedcircuit timer IC1 and associated components. Once triggered,101 output - pin 3 - will become high (positive supply voltage)for a certain time. It then reverts to its original low state.Triggering is achieved by making pin 2 (trigger input) less thanone-third supply voltage (nominally 4V) for an instant. In theabsence of a trigger pulse, the low state of pin 3 will have nofurther effect. Normally, pin 2 is kept high (positive suppIy voltage)through fixed resistor R2 which prevents false triggering.
Quick pulseThe time period is set by the values of fixed resistor, R5 andcapacitor C3. The higher the value of either or both, the longerwill be the timing cycle. With the values used in the prototype,the time will be about 100 seconds. No adjustment is providedsince the exact period is not thought to be particularly important.However, for a shorter timing, R5 could be reduced in proportion.
With the loop plugged in, each plate of capacitor C1 will bemaintained in a high state - the left-hand one via the loop andswitch 51 and the right-hand one via resistor, R2. With eachplate of the capacitor at the same voltage, it is discharged.When the loop is broken, or when S1 contacts 'break' due tothe lid being lifted, the left-hand plate of C1 will assume lessthan 4V due to the potential divider action of R1 and R2. Thispulse will be transferred briefly to the right-hand plate andhence to pin 2. The specified value of R1 is sufficiently high toprevent an excessive current flowing continuously through theloop when the alarm is armed. This is a less than 2mA. and maybe regarded as negligible.
The reason for triggering 101 via capacitor C1 (so called
"a.c. coupling") rather than direct is that there is a highpossibility of a potential thief or vandal setting off the alarm,running away and leaving the wire loop disconnected. Directcoupling would result :n a ccntinuous low state being applied topin 2. This would cause the alarm to re -trigger when the timingcycle ended and the warning would sound continuously.
Short delayWhile IC1 pin 3 is high - that is during the course of timing -current enters Darlington transistor TR1 base through resistorR6. The transistor turns on and collector current flows from thesupply through electronic siren, WD1. It is essential to use asiren of the type specified in the components list. It must beloud enough and sufficiently small for the purpose, coupled witha low current requirement.
Capacitor C2 maintains 101 reset input (pin 4) low for a shortwhile after switch S2 is operated. It works in the fo:lowing way.When the supply is established, the voltage across thiscapacitor will be zero since it is uncharged. It then chargesthrough resistor R4. It will eventually develop a voltage of about3.8V across it this being set by the potential divider R3 and R4.When the voltage rises to about 1V (which takes a fraction of asecond), the i.c. is enabled. This provides a short delay duringwhich time the i.c. is insensitive to triggering. If jti;r. 4 were notheld low during power -up, there is a strong possibility that thecircuit would self -trigger when switched on whicn would be anuisance. Resistor R3 allows C2 to discharge quickly when thecircuit is switched off.
Using a car exhaust bracket, as described, is a convenientmethcd by which the unit may be attached rigidly to the bicycleframe. These brackets may be purchased from any car accessorystore such as Halfords. The diameter of the frame at the intendedfixing position will need to be measured so that the correctbracket may be bought - they are available in a variety of sizes.
ConstructionMost of the components for the Bicycle Loop Alarm aremounted on a single -sided printed circuit board ;PCB). Fig. 2shows full topside details (parts placement diagram).
Resistors R2 and R5 have a particularly high value - 33M
PL1 SKIOHO
WIRE
LOOP
Si
1R2
ci
I100n
PL2 SK2I
S2
33MR410M
R3R1 4M76M8
I
Fig.1 . Bicycle loop alarm circuit diagram
C222n
ICI
R547M
mim C32u2
R622k
WD1
01
B1".12V
NOTE:ICI ICM755501 MPSA1 4
ELECTRONICS TODAY INTERNATIONAL19
and 47M respectively. They are available from certain mail ordersuppliers - see Buy Lines. Alternatively, they could be made up(or nearly so) by connecting 3 off and 5 off 10M unitsrespectively in series zig-zag fashion (see Fig. 4).
Begin by drilling the single mounting hole in the positionindicated. Follow with the soldered on -board components. Therecommended assembly order is as follows. Firstly, solder thei.c. socket, then all resistors in position as indicated. Note thatsome resistors are mounted flat on the board while others areperpendicular to it. Add the three capacitors, noting that theseshould be of the specified type having 5mm pin spacing or theywill not fit the layout without modification. Solder the Darlingtontransistor in position - this is the only on -board componentwhere orientation is important (see Fig. 5).
Make up the output pigtails - one about 20 cm long and theother about 10 cm longer. The best wire to use is the extra -flexible type often used for test instrument probes. This will have30 to 50 strands of 0.1mm diameter copper wire. Such wire willsurvive a lot of bending as will happen in the normal course ofuse. Do not use singe -strand wire which would break after avery short time.
Complete construction of the PCB by soldering the negative(black) connection of one of the battery snap connectors to thepad labelled "Bi-" (this will need to be extended). Solder a 10cm piece of light -duty stranded connecting wire to the padlabelled "S2". Solder one end of the shorter pigtail to the padlabelled "SK2". Solder the sounder wires to WD1 + and WD1 -pads, taking care over the polarity or it will not work.
Getting readyPrepare the box to receive the internal components. Begin bydrilling the two holes in the base for the exhaust bracket whichwill be used to secure it to the bicycle frame later. After that,
hold the sounder in place and mark out the holes for themounting bracket. Note that when the unit is in position, thesounder points downwards. In the prototype, the bracketsupplied with the sounder was raised on 5mm long spacers sothat it took up a more suitable position in the end panel. Markthe position of the hole through which the sound will pass. Formaximum sound output a matrix of small holes will not besatisfactory and the whole of the front face should be exposed.To do this, drill a circle of small holes around the circumferenceas marked out then join them together using a small hacksawblade. The edge may then be smoothed using a half -round file.Drill the holes for the bracket, for PCB mounting and for thepigtails. Fit this latter one with a rubber grommet.
Drill holes for key switch S2 and for microswitch 51mounting (see photograph). Attach the microswitch and adjustthe lever so that the contacts are held in the closed position(that is, the switch is heard to click) when the lid is in place. Thiswill ensure that the alarm will trigger when the lid is lifted a little.
A bit of supportAttach all remaining components apart from the circuit panelitself and, referring to Fig. 3, complete the internal wiring.Holders for 8 off 'AAA' cells do not appear to be readilyavailable. In the prototype, the 12V supply was thereforeobtained by connecting two sets of four cells in series as shown(hence the need for two snap connectors). The commonconnection should be sleeved or taped over to insulate it. Thetwo cell holders were joined together using adhesive fixingpads. It is important to note that there are exposed connectionson the ends of the battery holders and these must be insulatedfrom the metal box. This may be done with a thick layer of PVCtape. If the specified enclosure is used, its height is such thatthe lid section will press on the top of the battery snap
Fig.2. Bicycle loop alarm PCB
component overlay
B1 12V
INSULATE THIS JOINT
PL2 SK2
WIRELOOP r-
PLI SKI
S2KEY OPERATED SWITCH
SIMICROSWITCH
NORMALLYOPENCONTACTS
WD1
L
Fig.3. Bicycle loop alarm wiring diagram
ELECTRONICS TODAY INTERNATIONAL20
PCB R2 POSITIONConnecting three 10M resistors in series
Fig.4. Resistor connections
PCB R5 POSITIONCo. -II -lading five 10M resistors in series
Pin connections for darlingtontransistor - looking at flat face
e b c
Fig.5.Darlington transistor pinconnections.
connectors and give firm vertical support. Lateral support maybe given using a small bracket. Make sure that the batteries aresecure because they will be subject to considerable vibration andjotting in use. The wiring may be tidied up by using small cable ties.
Connect the longer pigtail to one of the microswitchnormally -open contacts as shown. Knot the two pigtadstogether and pass them through the grommet. Adjust them sothat there is some slack left on the inside. Cut them to the samelength outside and fit the line sockets making sure these aresecure. Note that, for this purpose, it does not matter if the tipand sleeve terminals are connected together. Insert the i.c. intoits socket observing the orientation and mount the circuit panelusing a single fixing in the hole drilled for the purpose. The panelwill need to be raised about 10 mm using a plastic stand-offinsulator to provide clearance for the knot in the pigtails.
Note that all components are mounted in the lower sectionof the box since this method imposes least strain on the wiring. Withswitch S2 off, place the batteries in the holders and secure them.
Prepare the loop itself by cutting off a suitable length of wireof the same type as already used for the pigtails. Solder theinner (tip) connection of a phono plug to each end cf the wire.As with the sockets, it does not matter if the sleeve connectionis used too. Secure the wire and make sure that puling on it willnot dislodge the soldered connections. Attach the unit to thebicycle frame. Some PVC tape wrapped around it at the pointof attachment will protect the paintwork.
Warning: operating this device in an enclosed space andclose to the ears can cause temporary discomfort or evenpermanent damage to the hearing. Testing should therefore becarried out with the sounder hole taped over to reduce the noise.
Attach the lid and plug the loop into both sockets. Arm thealarm by switching S2 on. The sounder should remain silent.Unplug one end of the loop. The alarm should sound andcontinue doing so even when the plug is replaced. Check that ittimes out after about 1 min. 40 sec. Arm the alarm again andcheck that it is triggered by partially lifting the lid.
If all is well, the Bicycle Loop Alarm may be put intopermanent service. Remember to operate the alarm for a shortwhile every few weeks to check the condition of the batteries.Happy cycling!
Buy LinesMost of the components for the Bicycle Loop Alarm are readilyavailable. The only ones which may cause sourcing difficultiesare resistors R2 and R5. These are available from Maplin as"high voltage" resistors order code V33M and V47M respectively.They are also available from Electromail as "High Ohmic" resistorsorder code 158-187 and 158-193. They could also be made upusing 10M resistors in series as explained in the text
Resistors
R1 5M6
R2 33M
R4 10M
R5 47M
R6 22kAll resistor 0.25N 5% except R2 and R5 which will beas available - see text.
Capacitors
C1 100n polyester film C2 22n polyester film C3 2m2 polyester filmAll capacitors 5mm lead spacing
mini FM transmitter, viers high gain preamp,supplied complete with 11 1 electret microphone.Designed to cover 88-108 Mhz but It is easy tochange it to cover 63- 130%lhg V. orks with A com-mon% (PP.)) battery. 0.2W RF. 18.22 Kit no 11)01.
I lectronic siren kit with an impressive 5 wattpower output. Ideal for car/bike alarms etc. 6-12, dc, MAX current 1.1, tone frequency 1.2khg1'.05 Kit no 1003.
3-30v Power supply, variable, stabilized powersupply for laboratory use. Shorlcircult protected.suitable for professional or amateur applications.24v JA transformer is also needed to complete thekit. £16.45 Kit 1007.
Powerful 1 watt FM transmitter supplied consplete with plezockctric microphone. 8-3th dc. At25-311, you will get nearly 2 watts' f 14.10 Kit no1009.
FAVAM Scantier, well not quite you have to turnthe knob yourself but you will hear things on thisradio (even TV) that you would not hear on anordinary radio'. Receiver corers 50.160 Mhz bothAM and FM. Built in 5 watt amplifier. 117.62 Kitno 11)13.
Mosquito repeller, modern way to keep midges atbay! Runs for about a month on a I.5v battery.88.22 Kit no 1015.
3 channel wireless sound to light so stem mainsoperated, separate sensitivity adjustment for eachchannel, 1,200 watt power handling. MicrophoneIncluded. 116.45 Kit no 1014.
Motorbikery (le trembler alarm, adjustable suen-*hit,. preset alarm lime, auto reset. Could beconnected to bikes horn etc. 114.10 Kit no 1011
0-5 minute timer, adjustable from 0 to 5 min s. willswitch up to LA mains. Perfect for alarms, photo-graphic laboratoriesetc. 12vdc. 18.22 Kit no 111211.
4 watt FM tr ms ranter, small but powerful trans-mitter, 3 RI. stages, microphone and an audiopreamp Include In kit. 123.50 Klt no 11128.
25 watt FM transmitter 4 RF stages, promorequired (our tit 1068 is suitable). Due to Use
complexity of the transmitter it is supplied le auntup form only. £92.82 Kit eo 1031.
41
Strobe light adjustable frequency from I- to 6011z(a lot faster than cons entional strobes) mains op-erated. 118.80 Klt no 1)137.
I lirasonic radar ideal as a movement detectorwith orange of about 10 metres, automate) our catflap' 12s operation so ideal for cars carat' ant etc.116.45 Kit 1049.
011
......---I lquld level detector useful for detecting fluidlevels in tanks, fishponds, baths or u s. rain or leakACM. Will switch 2A mains. 15.87 Kit no 1)181.
Phone bug detector. this device will warn you Ifsomebody is emesdru pping on your phone fine.17.115 Kfi no 1130.
Robot voice, interesting circuit that distorts youryoke' adjustable, answer the phone with a differ-ent Noire' 12s& 110.57 Kit no 1131.
Telephone bug, small tug powered by the tel-ephone line, starts transmitting as soon as thehandset is pie uo!uo! £9441101 no 1135.
function generator, produces sinusoidal, sawtoothand square oases adjustable from 20h1,20khEseparate level controls for each shape. Will pro-duce all 3 together. 24vac 117.62 Kit no 111101.
3 Channel 1101 chaser, 1100 watts per channel,speed and direction controls supplied with 12 ledand n,ains Wars, so you cm use mains light bulbsIf you want. 9-15vdc E19.97 Klt no 11)26.
[11t Alt T 1(1
N9 lits4,r2A
12. flourescent. A useful kfithal will enableyou tolight 4' flourescent tubes from your car battery!(you w ill also need a 9s 2A transformer, not sup-plied) £9.44.1 Kit no 1069.
VOA switch, sound activated naitch ideal for turn -Mg tape recorders on and off when sounds areheard. Makes the tape last a ic t longer' adjust ablesensitivity, built In delay. 19.411 Kit 1)173.
zatrcr.,--
Incar sound to fight, Put some at mosphere in yourcar with this mini 3 channel would to light. Fachchannel has 6 Iota 411.75 Kit no 1086.
11"1r .6.
1121-111'
'LS
7 watt ill Fl power amplifier useful, powerfulideal for intercomms audio synerns, car use etc.I 2-1Rvdc 5011mA. 18.22 Kit No 025.
Phone call relay, useful device that operates a relaywhen ever the 'phone rings, co 'Id be used tooperate more bells or signalling lights etc. Willswitch mains at 2A. 111.75 Kit no 1122.
Lead acid charger, two automatic charging rates,visual indication of battery slate, Ideal for alarmsy stems, emergency lighting etc. 100m1 12vdc.114.10 Klt no 11195.
Car alarm sy tens works on voltage drop and/orvibration, entry and exit delays plug adjustablealarm duration. Good for cars, caravanselc.114.10Kit no 1019.
Portable Alarm ty stern, based on a mercury' switch.1 he alarm continues to sound until the unit isdisabled by the owner. Ituuer Induced. L12.92Kit no 1150.
preamp mixer, 3 input mono mixer, separate bassand treble controls plus independent keel con-trols. 1801r. Input sens 150ms. 100m.6. £17.62Kit no 1052.
.
14:$01
Mini metal detector, suitable for locating pipes InNAM etc, range 15-20 cm complete with case 90operation. 19.40 Kit no 1)122.
o+v art 11.
8011 watt single channel sound to light kit, mainsoperated, add rhythm to y our parts for only 19.40Kit no 1006.
.assM,
-Aer
mm
Sound effects generator, produce sounds rangingfrom bird chips to sirens, complete with speaker,add sound effects to your projects for lust £10 57Kit no 1045.
Guitar preamp with tone controls, mull enough tofit inside any guitar, based on 11.082 I('. 9-12,dc,511mA. 19.40 Kit no 1091.
15 watt FM transmitter, 4 stage high power,preamp required. 12- I8sdc.Cm use either groundplane, open dipole, or Vogt Supplied inbuilt formonly m 181.07 Kit 1021.
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STAMP PROJECT
Using the STAMP computerto input analog signals
ne of the commonest requirements in anymicrocontroller application is to input and processanalog data. This could be simply a variablevoltage signal from some other piece ofequipment, or it could be the output from some
sort of measurement circuit, perhaps measuring temperature,pressure, strain, pH, etc. In this short article, we look at thehardware and software required to interface an 8 -bit serialanalog -to -digital converter to the Parallax BASIC Stamp.
The BASIC Stamp's instruction pot performs a limited sort ofanalog -to -digital conversion. It lets you interface nearly any kindof resistive sensor to the Stamp with a minimum of difficulty.However, many applications call for a true voltage -modeanalog -to -digital converter (ADC). One that's particularly suitedto interfacing with the Stamp is the National SemiconductorADC0831.
:Interfacing the ADC0831 requires only three input/outputlines, and of these, two can be multiplexed with other functions(or additional 0831's). Only the chip -select (cs) pin requires adedicated line. The ADC's range of input voltages is controlledby the Vref and Vin(-) pins. Vref sets the voltage at which theADC will return a full-scale output of 255, while Vin(-) sets thevoltage that will return 0.In the example application, Vin(-) is at ground and Vref is at +5;however, these values can be as close together as 1 voltwithout harming the device's accuracy or linearity. You may usediode voltage references or trim pots to set these values.
How it workshe sample program reads the voltage at the 0831's input pinevery 2 seconds and reports it via a 2400 -baud serialconnection. The subroutine cony handles the details of gettingdata out of the ADC. It enables the ADC by pulling the cs linelow, then pulses the clock (clk) line to signal the beginning of aconversion. The program then enters a loop in which it pulsesclk, gets the bit on pin ad, adds it to the received byte, and shiftsthe bits of the received byte to the left. Since BASIC traditionallydoesn't include bit -shift operations, the program multiplies thebyte by 2 to perform the shift. When all bits have been shiftedinto the byte, the program turns off the ADC by returning cshigh. The subroutine returns with the conversion result in thevariable data. The whole process takes about 20 milliseconds.
ModificationsYou can add more 0831s to the circuit as follows: Connecteach additional ADC to the same clock and data lines, butassign it a separate cs pin. Modify the cony subroutine to takethe appropriate cs pin low when it needs to acquire data from aparticular ADC. That's it.
' PROGRAM: AD_CONV.BAS' BASIC Stamp program that uses the NationalADC0831 to acquire' analog data and output it via RS -232.
Symbol
Symbol
SymbolSymbol
Symbol
Symbol
CS
AD
CLK
S_out =
data
setup: let pins = 255(deselect ADC).
let dirs = %11111101 ' S_out, CLK, CSoutputs; AD input.
0
pinl2
3
b0
b2
loop:gosub cony
' Pins high
' Get the data.serout S_out,N2400,(#b0,13,10)
data, CR, LF.pause 2000goto loop
conv:low CLKstarting state.
low CSpulsout CLK, 1
pulse.
let data = 0
for i = 1 to 8let data = data * 2
left.
pulsout CLK, 1
pulse.
let data = data + ADdata.
next
high CSdone.
return
' Send
' Wait 2 seconds' Do it forever.
' Put clock line in
' Select ADC.' 10 us clock
' Clear data.' Eight data bits.' Perform shift
' 10 us clock
' Put bit in LSB of
' Do it again.' Deselect ADC when
ELECTRONICS TODAY INTERNATIONAL24
HEWLETT PACKARD HP71BAs easy to use as a calculatorbut as powerful as acomputer
A powerful set of basic functions,statements and operators - over 230 in all- many larger computers don't have a setof basic instructions in this complete.
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HP -IL Interface pre -installed to create asystem that can print, plot, store, retrieveand display information. Control or readinstruments or speak to other computers,5030 bytes/set. Built in ROM includes 46separate commands. Interface to HP -1L,HP -1B, RS232C, GPIO or series 80.Includes connection cables
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BASIC Stamp -Stamp sized Computer runs BASIC
The Basic Stamp by PARALLAX measuresonly 4Cx6Omm yet is a true microcom-puter that runs BASIC programmes writtenon you- PC Its size, ecse of use andextensive I/O features make it an idealtool for both educational and inoustriolapplications as well as For the serioushobbyist.
TypicalApplicction
Writing programmes for the Stomp is easy. A3 -pin cable connects the Stamp to your PCprinter port. One piece of software is used toenter,debug and download your programme.Features include 8 I/O lines, non-volatilememory, serial comms, pulse measurementand PWM; all achieved with a minimum ofexternal components.
The BASIC Stamp Development Kit at £99 includes; 1 BASIC Stamp, instruction manual, PCcable, software and extensive application notes. Further Stomps are available from £29.
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All pr ces excl VAT and £3 postage per order. For further details of the Stomp, Muscle Wiresand ether products please call for our NEW colour catalogue
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£4.951/2AA with solder tags £1.55AAA (HP16) 180mAH £1.75AA 500mAH with solder tags £1.55C(HP'1)1.8AH £2.20D (HP2) 1.2AH £2.60PP3 8.4V 110mAH £4.95Sub C with solder tags C2.501/3 AA with tags (philps CTV)Standard charger charges 4 AA cells hours1 95
or.iCs or Ds in 12-14 hours 1.PP3 (1, 2. 3 or 4 cellsr' ray be charged at a time) £5.95High power charger as above but charges the Cs andDs in 5 hours AAs Cs and Cs must be charged in 2sor 4s 010.95Nickel Metal Hydryde AA cells high capacity with nomemory II charged at 100ma and discharged at25Orna or less 1200rnAH capacity (lower capacity forhigh cischarge rates) £3.75Special offers please check for availabilitystick of 4 42 x 16mm mad batteries ;71mmx16raimdia with red & black leads 40v C5.95Computer grade capacito9 with screw terminals58000u1 60v . .... . . £4.95115v ac 80v dc motor 4mm x 22mm shah 5Ornrn dia60 long body (excluding the shaft) it '-tas replacablethermal fuse and brushes £4.95 each £3.95 100.7 secrnent common anode led display 12mm .£0.45LM337k 703 case variable regulator C1.95C1.44 100.GaAs FET low leakage cLrrent 58873 £12.95 eachC9.95 10. 07.95 100.BS250 P channel rooster C0.45, BC559 transistorC3.95 per 10074LS05 hex inverfor £10.00 per 100. used 8748Mocrocontroller £3.50SL952 UHF Limiting aropItler LC t6 surface mountingpackage with data sheet £1.95AM27S02 £1.25 each 90p 100., C.D4007UB 10p100, 6p 1000.
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£6.00Airpax A82903 -C large stepping motor 14v 7 5' step27ohm 68mm dia body 6 3mm shaft C8.95 or £200.00for a box of 30Polyester capacitors box type 22 5mm lead pitch0.9u1 250vdc 18p each 14p 100+ 9p 1000.tut 250vdc 30p each. 20p 100+, 10p 1000.3.3u1 100vdc 30p each. 209 100.. 15p 1000.luf 50v bipolar electrolytic axial leads 15p each. 7.5p1000.0.22u1 250v polyester axial leads 15p each, 7.5p1000. Polypropylene tut 400vdc Wilma MKP10)27 Saw pitch32.29.17mm case 75p each 60p 100.Philips 123 series solid aluminium axial leads33u1 100 8 2 201 40p each. 25p 100+Philips 108 series lolg life 2201 63v axial 30p each15p 1000.Multilayer AVX ceramic capacitors all 5mm pitch 100v100p1, 150p1, 220pf 10.000pf (10n) lop each. 5pION, 3.5p 1000+500pf compression trimmer 60p40 of 370vac motor start capacitor (dialectrol typecontaining no pcbs) £5.95 or £49.50 for 10Solid carbon resistors very low inductance ideal forRF circuits27phm 2W. 68ohrn 2W 25p each 15p each 100. wehave a range of 0 25w 0 5w 1w arid 2w solid carbonresistors please send SAE for listPC 400W PSU (Intel part 201035-001) with standardmotherboard and 5 disk drive connectors, fan andmains inlet/outlet connectors on back and switch onthe side (top for tower case) dims212.49.149mm excluding switch £26.50 each£138.00 for 6MX180 Digital muttimeter 17 ranges 1000vdc 750vac2Mohm 200mA transistor Hfe 9v and 1/5v battery test
C12.95AMD 27256-3 Eproms £2.00 each. E1.25 1000DIP switch 3PCO 12 pin (ERG SDC-3 023) 60p each40p 100.Disk drive boxes for 5.25 disk drive with room for apower supply light grey plastic 67.268.247mm E7.95or £49.50 for 10Hand held ultrasonfc remote control E3.95CV2486 gas relay 30 x 10rnin dia with 3 wireterminals will also work as a neon light 20p each or£7.50 per 100
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ELECTRONICS TODAY INTERNATIONAL25
Making use of thePC PARALLELIn this tutorial project, Stephen Smithlooks at different ways in which the PCparallel port can be used to controlexternal circuitry
hen people think of interfacing to computers,visions of expensive expansion cards fittedwithin their PC are brought to mind. This idea offitting cards into a machine is scary for someand impossible for others. The interface that all
PCs have, as do many other types of computers, is the parallel(or centronics) printer port. You may have wondered exactlywhat this parallel port is capable of. This port is normally used totransfer data to a printer, a byte at a time (8 bits in parallel). Theparallel printer port on PCs have 8 data bits and 9 control lines(that is 5 inputs and 4 outputs). These input and output lines arecompletely user definable and, as such, can have uses otherthan printing. The low cost of multi -I/O cards (one parallel andtwo serial ports for £8 or £12 with hard and floppy diskcontrollers) compared to dedicated digital I/O cards (up to £80for a professional card giving 24bits of I/O) makes the parallelport very attractive to the cost conscious hobbyist.
Many copy protection dongles use the parallel port as dodata transfer packages to communicate between PCs or a PCand a peripheral (e.g. tape backup or scanner). The universalnature of the parallel port has led to numerous uses as anexpansion port. Analogue to digital converters, for instance, aremanufactured to talk to the parallel port of a PC (e.g. thedevices made by Pico Technology), and many EPROM anduniversal programmers use this port for data transfer and control.
The Printer Port.The pin out of a standard 25 way D type parallel port is given intable 1. The eight data bits D0(LSB) to D7(MSB), are used totransfer the data byte to the printer. The active low Strobe isgenerated by the PC to indicate that the data is valid. Theinputs Busy and Ack (active low) are used to tell the PC that adata transfer is welcome and data has been successfullyreceived. PaperEnd and Error warn the PC of any errors that theprinter has detected. Select selects the connected printer andSelectln, indicates that the printer recognises that it has beenselected. AutoFd advances the paper by one line while Init,when activated for more than 50ms, initialises the printer to aknown state. When the printer is initialised and selected, data transfer is
achieved by the following steps. Wait for Busy to go Low.
This is the printer saying OK send me data. Put data onto the data lines (D0-7).
Delay at least _ms. Pulse Strobe for at least _ms. PC's
saying data is valid now. Upon receipt of Strobe the printer pulls Busy high. Hold the data for at least another _ms. Sometime after this the printer will pull Ack low for 5ms
minimum.This is the printer saying that was OK.
Then, when ready, the printer lowers Busy to continuethe cycle.
Printer Port Handling In BIOS and DOSIBM has defined three input/output address ranges at whichparallel printer ports are recognised. This allows up to threeprinter ports labelled LPT1, LPT2 and LPT3. Thecorrespondence between LPT number and the base address isdefined by the PC's BIOS. Upon power up, the BIOS attemptsto identify printer ports at three address ranges (3BCHex onmono display cards, 378Hex and 278Hex on input/outputadapters). The BIOS tries these three in order and if a printerport is identified the base address at which it occurs is placed ina table, starting at memory address 408Hex. This table has fourpossible entries of 16bits each. Some software ignores thistable but DOS printing uses it, so it is a good idea to use it tokeep compatible. A parallel port at one of these addresses isidentified by writing AAHex to the base address (therefore thedata register) and reading back from the same address. IfAAHex is read back the BIOS considers this to be a parallel portand puts its base address in the table. If anything connected tothe parallel port (e.g. a printer that is turned oft) interferes withthis identification procedure the printer port may be ignored, orif another device that allows register feedback, is at a reservedaddress it will get incorrectly identified as a printer port.
The number of parallel ports identified is stored in the twomost significant bits of the byte at memory address 411 Hex. (Itis confusing to note that the table has four locations but thecount of ports can only go up to three.) The first parallel port isassigned to device LPT1. The second, LPT2 and the third,LPT3, if they are all present. Any ports not present are notassigned and, as such, cannot be accessed. When printingfrom DOS the PRN device is an alias for LPT1, although thiscan be changed with the use of DOS's mode command.
By swapping base addresses in the table you canswap between printer devices, as a number of printer swapping
i
ELECTRONICS TODAY INTERNATIONAL26
PORT
WRITE_CONTROL)
4 IC3 5
6 D 0 7
10
12
14 15
18
16
14
/12
READ_CONTROL )
DATA BUS
READ_STATUS>-
Fig.1. Generic printer port
+5i
1k
Dn° n
+12V
+5V
I1k
OPTO ISOLATOR
Fig.2. Optoisc lator circuit for computerinterface designs.
WRITE_DATAREAD_DATAREAD_STATUSWRITE_CONTROLREAD CONTROL
WRRE_DATA >
)STROBE
> AUTCFD
)SELECT
BUSY
<PAPEREND
<SELECTIN
<ERROR
41-> ACK
: WRITE TO BASE ADDRESS + 0: READ FROM BASE ADDRESS + 0: READ FROM BASE ADDRESS + 1: WRITE TO BASE ADDRESS + 2: READ FROM BASE ADDFESS + 2
READ_DATA>
NOTE:ICE 74'_S374
IC2. IC4 744_5244
IC3 744_5174
IC5 74LS125IC6. IC7 74LS05
ALL PULLUP RESISTORSARE 4k7
ELECTRONICS TODAY INTERNATIONAL27
Dn
+12V
1/8 OF ULN2801
Fig.3.Driving highervoltages from a standardoutput port
Fig.4.A 74LS based port extender
D6 >
D5>-
DO >
D1 >
02>
4
IC1A 3
5
9
/GIC1
V
133>
D4 >
BUSY >
ACK)
PAPE REND)
SELECTIN >
IC18
12IC1
A
-C /CS 0 2 P40
7c /FROG ,3
P41PORT41
P42
53 P43
IC20 P50
11 23 P51PORT51 22
P52
21P53
0 200 P60PORT2 19
P61
PORT6 18P62
173 P63
130 P70
14P71
PORT7 15P72
6P73
NOTE:ICIIC2
74LS1268243
0
rn
BUSY
ACK
PAPEREND
SELECTIN
STROBE
AUTOFD
INIT
/W1
/WO
/W3
/W2
/R1
/RO
/R3
/R2
NOTE:IC1 74LS139IC2 - IC5 74LS374IC6. IC7 74LS244
+5V
T III
18
16
14
12
7
5
IC6
IC6/0
A
2 /4 /
6 /
J1
</RI
DO - D7
/oc
O
Fig.5. 8243 based port extender.
2
5
6
9
12
15
16
19
5
6
9
12
15
16
19
/W2) 11 \>CLK
9
IC4
O
2
5
6
9
12
15
16
19
ELECTRONICS TODAY INTERNATIONAL28
programs do. Beware, 400Hex to 407Hex is used to store thebase addresses of the PC's COM ports (the serial ports), someserial port software supports more than four COM ports andcan overwrite the parallel port base addresses. This is rare, butbeware. Just to recap, table 2 shows the allocation of LPT's.Note that MDA is Monochrome Display Adapter.
ProgrammingWhen printing, DOS handles the allocation of printing devices toaddress (see above), but when using the parallel port as input oroutput, the programmer needs to know which address the LPTdevice is assigned to. Listing 1 gives a piece of code to find theBase Address of a port from its device number (1-3). This, likethe other programming examples given here, is written inQBasic as supplied with MS-DOS 5.0 and subsequent versions.This listing turns the LPT number into an address in the look uptable, then reads the Base Address of the port from thememory location calculated. From this Base Address, theaddresses of the Data Register, Status register and ControlRegister are derived.
INT17The PC's BIOS initialises both the hardware and the base
address look up table as described above. The BIOS supportsprinting with INT17 (which is used by INT5, the print screen
function). This is called
roc
I 11>CLK
16 INPUTS
\ 3
\_ 4 5
\ 7IC5 6
\ 8 9
\ 13 12
\ 14 15
\ 17 16
\ 18 19
32 OUTPUTS
with the required set up inspecific registers of themicro -processor. Theindex of the parallel portin the base address lookup table is put in DX. Thisis 0-3 representing LPT1-4. (Yes, you can accessthe fourth in the list here,but exactly what happensis BIOS dependent.) Thebyte to be sent To theprinter is put in AL ifnecessary. AH is given avalue of 0, 1 or 2.AH=0 Printercharacter in AL.AH=1Initialises the port, returnsthe status in AH.AH=2 Returnthe status in AH.
The status returned isthe state of the five inputs(the highest five bits of thebyte, see table 4 for thebit allocations) and theLSB is set if a time-outhas occurred.
InterruptsThe MDA parallel portand that at 378Hex areallocated IR07, and theport at 278Hex isallocated IR05. The ideabehind this was togenerate an interrupt
upon the Ack signal from the printer. This then can tell a printerdriver to send its next byte. Unfortunately, this is rarely possibleand is very infrequently used. IR05 and 7 are consequentlyconsidered free, and so are used by various other cards, e.g.network or sound cards. IROs are used by some otheroperating systems and some parallel port data transfer systems.
A Typical Printer PortFigure 1, shows a generic parallel port. The data bits are
latched together by a write to base address + 0 (see tables 3and 4 for register addresses and bit assignments) and can beread back at the same address. These and the other outputmay have capacitors to ground to remove fast transients. Thecontrol outputs are latched and inverted by open collectorinverters, except Init which is inverted twice to maintain thesame polarity. Each of these outputs are pulled up with 4K7resistors. These bits can be read back (with the same polarityas they were written) as they too are buffered at the sameaddress. The status of the printer can be read from the port bythe five inputs, of which only Busy is inverted. Twc of the otherbits of the control register are also used. The first (bit 4 of thecontrol register) enables the interrupt, passing the Ack signal tothe buses appropriate IRO line. The other (bit 5 of the controlregister) is only used in bi-directional parallel ports to enable ordisable the eight data lines,
Bi-directional Parallel PortsThe output latch used to handle the eight data bits has anoutput enable control which is, in the original IBM PC, tied toground to permanently enable the outputs. As mentioned abovethis output enable can be controlled by bit 5 of the controlregister, allowing software to control this output enable. Tri-stating the output, creates an input only port. This was firstintroauced on IBM's PS2 systems, but the original IBM PCcould be converted to this as all the required hardware ispresent; only the output enable connection needs to be made.This suggests that IBM considered the bi-directional port initiallyand abandoned it. This control over the direction of datatransfer allows a greater degree of communication with theprinter and a wide variety of other uses. The ability to send orreceive a byte of data creates a range of data transferapplications between two PCs or a PC and a peripheral. (Seecommunications below.)
DonglesOne of the non -printer uses of parallel ports are to talk to
copy protection dangles. These devices sit between the PC'sparallel port and the printer, monitoring the data being sent out.They usually only process data when the Strobe is high,therefore ignoring printed data allowing the printer to work inconjunction with the dangle. Dangles tend to be powered fromthe parallel port's data and control lines through a couple ofdiodes to sum the current from several outputs. When morethan a milliamp or so is pulled from an output, its voltage candrop significantly. These outputs are guaranteed to sourcecurrent up to 2.6mA, but also the voltage is within the range of5-2.4V. This is officially a definite no -no, but it does work if youare careful.
CommunicationsThe idea of transferring data to/from your PC in a high speedparallel form is very attractive, because it can provide anefficient means of data transfer at a very low cost. Manycommercial packages, such as LapLink or MS -DOS's interink,
ELECTRONICS TODAY :NTERNATIONAL29
Table 1Parallel port pin out and signal details
Pin No. Name Active High/Low Input/Output1 Strobe Low Output2 DO (LSB) High Output3 D1 High Output4 D2 High Output5 D3 High Output6 D4 High Output7 D5 High Output8 D6 High Output9 D7 (MSB) High Output10 Ack Low Input11 Busy High Input12 PaperEnd High Input13 Selectln High Input14 AutoFd Low Output15 Error Low Input16 !nit Low Output17 Select Low Output18-25 Ground
Table 4Bit definitions within the registers
Bit No. 7 6 5 4 3 2 1 0Data Register D7 D6 D5 D4 D3 D2 D1 DOStatus Register Busy Ack Paper End Select In ErrorControl Register Output Enable IRO Enable Select Int AutoFd Strobe
can use the parallel port for file transfer between PCs. A numberof storage systems, such as hard disks, floppy disks, CD-ROMsand tape back-up systems use the parallel port for data transferas an alternative to dedicated interfaces. These systems tend tobe more expensive than their dedicated counterparts and havesignificantly lower data transfer rates. Nevertheless, thesesystems are easy to connect and transport (i.e. to use on differentmachines) and can be invaluable to portable computer users.
Table 5 gives the connections for a nibble mode datatransfer cable. The use of bi-directional ports or the misuse ofthe open collector outputs can give the user byte transfers, butthese methods are not universally compatible or safe. The useof the lower half of the data bits and status lines to transfer dataa nibble at a time is slower, but works reliably. Data bit 3 andError are used to perform handshaking between systems. Justa warning; the D7 bit is inverted in transfer into the Busy line.
User Input/OutputWhen not in use for printing, the parallel port is ideal for thehobbyist to perform simple input or output tasks. Any of thestatus inputs could be used to read the status of a switch orother digital signal. As all the inputs are pulled up internally, aswitch only needs to pull the input to ground when activated.Relying upon the internal pull ups may prove to betemperamental in some cases so, if this is the case, useexternal pull ups to 5V. The control outputs are implemented
with open collector outputs. These, when outputting a logic lowpull the output to a low level. But when outputting a logic highthe output goes high impedance, being pulled up by 4K7resistors to 5V, and can be pulled low by external events. So ifthe outputs are forced to a logical 1, they can be mis-used asinputs, with internal pull ups, through the register feedbackbuffers. This does work, but is not recommended as it abusesthe outputs and some multi -I/O cards do not correctlyimplement the control outputs with open collector outputs.B:Using the digital outputs of the parallel port to drive digitalsystems, such as an ADC or DAC, is simply done but it is agood idea to pull up the inputs to your system to guarantee thelogic levels provided by the output. Examples of this form ofcontrol include a PC based controller for a model railway andaccess to devices over the l2C serial bus. The data outputs, asstated earlier, can only source 2.6mA (Max.) and this is onlyguaranteed for one output. You cannot hope to pull that from allthe outputs without damaging the device. Powering projectsfrom the parallel port is, as stated earlier, not advisable so anexternal power supply is needed for example take 5V from theGames Port (Pin 8).
Figure 2a shows how a LEDcan be controlled by a data output.These outputs can sink up to 24mA each and as such can bemore useful than sourcing current. So you think, "Ok I cancreate a pretty light show with my PC. So what?" Opto isolatorsare just a LED driven to cause a photo -transistor to conduct.
ELECTRONICS TODAY INTERNATIONAL30
Figure 2b shows how an opto isolator can be used to drive arelay. Once you can get a LED to flash, any other I/O is only asmall step further on. Non -isolated relay control is easy toachieve, as in figure 3, by using a Darlington driver, suchas the ULN2801.
Port ExtendersThe main reason people buy or build a digital input/output cardfor their PC, is because they require more inputs or outputs thanthe parallel port can offer. This is where port extenders come in.They multiplex the inputs and outputs available on the parallelport to provide a more useful number of inputs and outputs (seeETI November '94 for such a project based upon shift registers).Figure 4 gives an example of how to provide up to 16 inputs and32 outputs with a relatively low chip count (7 chips in fact).Replacing the 74LS139 with two 74LS138's can double thenumber of I/O bits available (use Select as the next input of the74LS138). This circuit latches the data into one of the externallatches by putting the data into the data register and setting thecontrol register to select the appropriate external register. TheStrobe signal is then pulsed low to latch the data. The inputs aremultiplexed, in banks, onto the status lines controlled by thesame control lines as the outputs.Listing 2 shows how the discrete port extender is programmed.This code sends a Byte to the specified expanded por. and thenreads in a nibble from the separately defined expanded input.This nibble is processed to present it in the lower half of a byte,with the correct logic levels.Figure 5 shows an I/O expander based upon the 8243. Thischip is an I/O expander designed for use with the 8048 family ofmicro -controllers. It communicates via a four bit data bus and afew control signals. Data bits D0-3 are used to send data to the8243 through the 74LS126. This data buffer allows these bits tobe disabled and data from the 8243 to be read in to tne PC onthe status lines. The 8243 provides four, four bit I/O ports (16bits altogether).To talk to the 8243 an instruction is given to the data bus (D0-3)and the Prog line is taken from high to low (all this while CS islow of course). If the instruction is a write, the appropriate datanibble is placed on the bus and the Prog line taken high again. Ifa read instruction is used, the 74LS126 is disabled to allow datato be output by the 8243 without conflict and then the data isread into the PC. A port on the 8243 is considered to be aninput port if it has had a read instruction directed towards it. Thismeans that a dummy read of any input port is required to set upthe port before use. Also you cannot read back the status of anoutput, as it will be converted to an input by the read.If 16 I/O lines are not enough for you, it is possible to use anumber of 8243's with a different chip select (e.g. use D7 or D6and D7 via a 74LS139). This is not shown diagramatically or inthe example program, but should not prove difficult for theexperienced hobbyist. Listing 3 shows an example
Table 5Nibble mode transfer cable as used for
MS-DOS interink
Machine 1D4 (6)
Machine 2Busy (11)*
D3 (E) Ack (10)
D2
D1 (3)
DO (2)
Busy (11)*
Ack (10)
Paper End (12)
Select In (13)
Errcr (15)
GND (25)
* Note that Busy is ir verted
Paper End (12)
Select In (13)
Error (15)
D4 (6)
03 f,5)
D2 (4)
D1 (3)
DO 12)
GND (25)
Table 2Base addresses for each LPT device
LPT'
LPT2
LPT3
MDA Present
3BCHex
378Hex
278Hex
No MDAPresent378Hex
278Hex
N/A
programming for this form of port extender.One note on compatibility with printing; it is a good idea to storethe contents of the control register on start up, before it iscorrupted by your program, and then restore this value to thecontrol register when the program ends. This ensures that thecorrect configuration is present to allow printing to take placeafter your program has run.
WARNINGDo not connect any externally powered circuit to your parallelport unless you have checked and double checked your work.Use current limiting resistors (10K) in series with the signals if possible.
It is important to note that modern PCs have their parallelports on the same smal piece of silicon as the serial ports andfloppy, hard disk controllers. So, electrically, the parallel port isvery close to expensive parts of your system, like themotnerboard and hard disk. Damage to the parallel port putsthese expensive parts in danger. Please do not let this deter
Table 3Register definitions
NameData Register
Control Register
Status Register
Read and/or WriteRead and Write
Read and Write
Read Only
LocationBase Address
Base Address + 2
Base Address + 1
ELECTRONICS TODAY INTERNATIONAL31
you, just be careful. The electrical parameters given in thisarticle are correct for the original IBM parallel port, implementedusing discrete 74LS technology. Modern ASIC implementationsof the parallel port may not conform to these specifications, butcan sink reasonable current to drive LEDs, etc.
The circuits and systems presented here are not intended tobe full projects and, as such, no PCB or other support is available.These have been devised only as examples and ideas to informyou and invoke your imagination. The parallel port is an easy anduniversal way to interface to your PC, so have fun experimenting.
Listing 1REM This code shows how to read the bal. address
of a LPT portREM from the installed devices table.REM Set PORT equal to the LPT port number 1,2 or 3REM TableStart is the start of the base address
lookup table.REM The SEC is defined to access the bottom
segment.REM Then MemoryAddress is calculated from the
port number and start of table.REM This location is read and the word is put
together from two bytes.REM Using the BaseAddress from the table the
registers addresses are found.REM Data Register is at the Base Address itselfREM Status Register is the second location
ControlRegister = BaseAddress + 2PRIMP "The base address for LPT'; PORT; 'isHEX$(BaseAddress); 'Hex"
Listing 2REM Example of how to write to the Discrete Port
Expander.REM Set number of expansion port in ExpPort.REM Set Byte to the data to be sent.REM Put this data on to the data bits D0-7
DataRegister ).REM Define the port number onto the appropriate
bits of the Control RegisterREM Pull Strobe low to latch the data on to the
defined expansion port.REM Strobe goes High again and the data is
latched.ExpPort = 0
Byte = &H55OUT DataRegister, ByteOUT ControlRegister, ExpPort * 2OUT ControlRegister, 1 + (ExpPort * 2)OUT ControlRegister, ExpPort * 2REM To Read from the Discrete Port Expander.REM Set Expinput to the number of the expansion
input port
REM Put this Input port's address on the ControlRegister
REM Read the data inREM Then invert Busy bit and shift data down by
ListingREM To Talk to the 8243 Based Port Expander.REM Some consts required to drive 8243, common to
Write and Read.CONST CS = &H40CONST PROG = &H20CONST OE = &H10REM Write to 8243 Port Expander.REM PORT = number of the port to write to; 4,5,6
or 7.
REM Nibble = four bits to send.
REM Give instruction which is the same as PORTnumber for Writes.
REM Take Prog low.REM Put the Nibble of data on Port 2REM Take Prog High again to end write cycle.REM Put the Chip Select for the 8243 High at the
end.PORT = 4Nibble = 14
OUT DataRegister, PORT + PROG + OEOUT DataRegister, PORT + OEOUT DataRegister, Nibble + OEOUT DataRegister, Nibble + PROG + OEOUT DataRegister, Nibble + PROG + OE + CSREM To Read from the 8243 first send instruction.REM That instructLon is the PORT number with bit
2 reset.
REM Take Prog Low to indicate instruction on bus.REM Put OE Low, so data can be read in.REM Read in the data.REM Manipulate Nibble so it contains the data
with correct polarity.REM Take CS High at the end.PORT = 5
OUT DataRegister, (PORT AND 3) + PROG + OEOUT DataRegister, (PORT AND 3) + OEOUT DataRegister, C: REM i.e. disable OE with PROGLOWNibble = (INP(StatusRegister) XOR &H80) / 16OUT DataRegister, FROG + CS + OE
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The exploration of the Solar System beyond Marsby unmanned craft could well be described asnow being in its 'third' phase. During phase onethe Pioneer craft such as Pioneer 11 in 1979 inits flight towards the outer reaches of the solar
system, valuable information was obtained which was used todesign and direct the Voyager satellites I and II some tenyears later.
The extensive data of the Voyager craft in turn allowedspecific missions to be designed such as the Galileo missionfor Jupiter and the Cassini Mission for Saturn. While the Galileocraft is due to encounter Jupiter this year, the Cassini missionhas still some way to go before launch.
While Saturn is even farther away from us than Jupiter andmay be expected to present a cold and utterly barrenenvironment, scientists have long been curious about Titan,Saturn's largest moon. Titan is large enough to support andretain an atmosphere, although the gases present are quiteunlike those at present in our own atmosphere. A key part ofthe Cassini mission to Saturn will involve the launching ofaprobe through Titan's atmosphere in order to sample itscomposition. This Huygens probe is also designed to sendback any images it may capture during its descent or from itssurface if a landing is successfully achieved.
Figure 1 shows the large planet as imaged by Voyager 2from a distance of 13 million miles. The three small white dotsat the base of the picture are the moons Tethys, Dione andRhea. Saturn is widely accepted as the most beautiful planet inthe Solar System.
Saturn's secrets: Early observationshaving observed the rings of Saturn in 1610,
though without appreciating what they were, Galileo Galileiwas even more astonished in 1612 when the featureapparently vanished. It was however, the Dutch scientist
Christian Huygens, who, with the benefit of better opticsaround 1655, was able to identify the feature as a set of ringsaround the planet. As Saturn orbits round the sun every 29.5years and the axis of rotation of the planet (rings included) isinclined at 20 degrees, so on occasion when viewed fromearth the rings can appear to vanish. Huygens also discoveredthe largest moon, Titan.
During subsequent observations, the French -Italianastronomer Jean -Dominique Cassini was able to identify theadditional moons of Iapetus, Rhea, Tethys and Dione. Inaddition, in 1675, Cassini discovered that the rings of Saturnare divided by a narrow gap - termed the Cassini division.Thus, while Galileo and Huygens were involved in importantstages in discovering the first of Saturn's secrets, it wasCassini who through much patient observation addedconsiderably to the knowledge of Saturn and her attendantmoons and rings.
Saturn: Facts and figuresThe four giant gaseous planets of the Solar System, Jupiter,
Saturn, Uranus and Neptune form a family with sharedcharacteristics. Saturn is nearly ten times the diameter of theEarth and its volume would enclose 815 Earths. Its density,however, is less than that of water. The orbit of Saturn isperturbed somewhat by the attraction of Jupiter and as aresult the distance of Saturn from the sun varies between 9.0Astronomical Urits (AU) and 10.1 AU. The surface gravity ofSaturn is 1.16 of that of the earth.
The relatively great distance of Saturn from the sun resultsin the planet receiving about 1/100th of the amount of incidentsunlight as does the earth. In contrast to most earth orbitsatellites which can utiliseSaturn -bound probes need to carry their own on boardpower sources.
The axis of Saturn is inclined at 26 degrees to the horizontal
Douglas Clarksonlooks at theforthcoming NASAEuropean SpaceAgency probe toSaturn - the CassiniMission
Uncovering
SECRETSELECTRONICS TODAY INTERNATIONAL
34
Figure 11:Artist's impression of theCassini orbiter with deployedHuygens probe above Titai.
Saturn'sFigure 1:
Saturn as imaged by Voyager 2from a distance of 13 million miles.
The three small white dots at thebase of the picture are the moons
Tethys, Dione and Rhea.
ELECTRONICS TODAY INTERNATIONAL35
11M MAO BOOM4M HGA
RPWS ANTENNA
FGM (MAG)
RADAR BAY
VIMS (IR)
VIMS (V)
ISS NAC)
ISS (WAC)
UVIS
REMOTESENSINGPALLET
CI RS
Figure 12: Detail of theCassini/Huygens craft (Courtesy ESA)
LGA1
Table 1:Relationship between escape velocity and
atmospheric status of various planets of thesolar system.
Planet
Mercury
Earth
Mars
Jupiter
Saturn
Escape velocity(km/sec)4.25
11.2
5.02
59.5
32.26
AtmosphericStatusNONE
YES
NONE
YES
YES
Figure 3: Image of Enceladus taken from a distance of74,000 miles by Voyager II. There appears to be areas ofrecent ice melting.
RPWS SEARCH COILS
RPWS LANGMUIR PROBE
FP&W PALLET
INCA (MIMI)
INMS
LEMMS (MIMI)
CAL'S
CHEMS (MIMI)
HUYGENS TITAN
- even greater than Earth's inclination of 23.5degrees. The Saturn day is 10 hours and 40 minutesand the Saturn year 29.5 'Earth' years.
Saturn is a large planet - its equatorial radius is60,330 miles. In many ways, the structure of Saturnand its associated planets has been determined bythe sheer mass of material which has generated agravitational field strong enough to retain the lightestelements, Hydrogen and Helium, in its atmosphereand also in liquid and solid forms at depth within thefabric of the planet. If the total mass of Saturn hadbeen below a critical value then it would graduallyhave lost first its mass of Hydrogen and then its mass
Figure 4: Image of Iapetus taken by Voyager II,revealing sharply contrasting colour details of thesurface.
ELECTRONICS TODAY INTERNATIONAL36
Figure 5: Details of Titan taken by Voyager 2 in 1981.
of Helium as the associated gas molecules attained sufficientvelocity to escape from Saturn's gravity and venture out into space
Table 1 indicates the escape velocity of a range of planetsin the solar system with details of atmospheric status.
Saturn is considered to have a rocky core of probably thesame size of the Earth but contains material around threetimes as dense. With increasing depth beneath the top of thecloud layers, both the temperature and the pressure within theatmosphere increases. Hydrogen in a metallic state is consideredto start to exist at a depth of 32000km beneath the clouds ata level where the temperature is 9000K.The temperature at the
Figure 6: Picture of Titan taken by Voyager II which revealsdetails of the moon's thick atmosphere.
cloud tops of Saturn is estimated to be -180C.Saturn's magnetic field was discovered by Pioneer 11 in
1979. This field, which is around 1000 times greater than thatof the Earth, has a significant influence in the interaction ofSaturn with the Solar Wind - the stream of charged particlesstreaming out from the sLn. The area within this field - themagnetosphere is a key factor in atmospheric chemistry forSaturn's and also Titan. The interaction of Saturn's magneticfield with high energy cosmic rays of charged Hydrogen nuclei(protons) renders part of Saturn's surface relatively free ofcosmic ray radiation.
VENUS FLYBY20 JUN 1999
MANOEUVRE2 DEC 1998
VENUS FLYBY21 APR 1998 7 1 LAUNCH
6 OCT 1997
EARTH FLYBY16 AUG 1999
SATURN25 JUN 2004
JUPITER30 DEC 2000
PERIHELIA23 MAR 1998 0.68 AU27 JUN 1999 0.72 AU
Figure 9. details of the interplanetary trajectory of theCassini/Huygens spacecraft (Courtesy ESA)
Saturn's moonsOne of the major attractions of Saturn is that it has the
most extensive set of moons of any planet in the solar system.Over 20 have been identified. Table 2 summarises the principalmoons of Saturn.
The Voyager missions in their transit past Saturn and itsmoons made various surprising discoveries. Figure 2 shows amontage of the Saturnian system taken from images fromVoyager 1 during November 1980. In the upper left is Rheawith Enceladus below, just above Dione. Ringed Saturn isabove Dione; Tethys and Mimas with its large impact craterare to the lower right. Titan is in the upper right.
The moon Enceladus, shown in figure 3, while covered withice, displays abnormally smooth areas with the absence ofcraters as if there have been episodes of melting over parts ofits surface. Stranger still is the object Iapetus as shown infigure 4. One of its faces is exceedingly bright while its leadingside is exceedingly dark - consisting possibly of areas oforganic, carbon -based material.
Titan, however, remains Saturn's biggest secret. Figure 5shows details of the shrouded moon taken by Voyager 2 in1981 from a distance of 1.4 million miles. Titan lies hiddenbeneath an opaque atmosphere more than 50% denser than
that of the Earth. Nitrogen is probably the principal componentof Titan's atmosphere. Methane (a few percent) and Hydrogen(0.2%) are likely present. There may also be a highpercentage of Argon - as high as 20% - though this will needto be confirmed by direct atmospheric sampling. Figure 6indicates a picture of Titan taken by Voyager II which revealsdetails of the moon's thick atmosphere. Scientists haveobserved a brownish orange haze in Titan's atmosphere whichis considered to originate from complex organic molecules.This is considered to result from photolysis of methane causedby solar ultraviolet radiation, cosmic rays and particlestravelling within the magnetosphere of Saturn.
Titan is of very high scientific interest since it may hold vitalclues to the initial development of the earth's atmospherefrom 4.5 billion years ago to its present condition and also tothe development of the early building blocks necessary for theevolution of organic carbon -based life forms. Scientists havemade a range of speculations about conditions on Titan.These range from an interesting but lifeless terrain to thepossibility of lifeforms existing in covered lakes of liquidhydrocarbons warmed by the planet's internal heat. It willbe quite some time, however, before such scientificcuriosity is satisfied.
Seen in context, however, Titan could easily have existed inthe Solar System as an individual planet such as Mars orMercury. Therefore, rather than having to voyage to distantstar systems in the hope of finding 'interesting' planets ormoons, Titan is one in our own backyard.
The RingsThe Voyager mission provided a wealth of information
about Saturn's rings and, while some old problems weresolved, new ones were created. Figure 7 shows details of thering structure taken by Voyager II. The earth observationbased convention of banding the rings as A, B, C and D fromthe outside towards the centre considerably oversimplifies thefine detail observed by the Voyagers. Fine structured rings areobserved also to be present in the Cassini division. Thematerial within the rings of Saturn range from sub microscopicdust to lumps of ice the size of houses. The rings are dense
EARTHSUN 4 --
ORBITERENGINEERING/TURNS
ORBITERnREZMOTNEGSCIENCE
A
PROBEEVENTS
DOWNLINK 8CONFIGURE PSA
TURN IMAGINGTO TITAN
RECEIVE AND RECORD PROBE DATA
REMOTE SENSING IN SLEEP MODE. F 8 P IF MARGINS PERMIT
L
COASTPHASE PROBE DESCENT (2.5h1
PROBEENTRY
lin FROM°RORER C/A
-I day = -8h -4 Oh
PROBE AT EN -7Y
TURN HGATO EARTH
TURN ABOLT HGA AXISFOR TMC. X AXIS FOR MOSAICSINMS IN RAM DIRECTION FOR AERONOMY
PROBE
I 011CHDOWN
V
SURFACE SCIENCEG/6 WILL CONTINUE TO
' TRACK PROBE FOR 20IANuTES
I Sh -1.0 -0.7
ORBITERCLOSEST
APPROACH
0
Figure 14: Data capture and relay of Huygens probe data by the Cassini orbiter. (Courtesy ESA)
PLAYBACK _
FIELDS.PARTICLE
_AVfAVES
=1h
ELECTRONICS TODAY INTERNATIONAL38
Figure 2:Montage of theSatuniark systemtaken from imagesfrom Voyager 1 In theupper left is Rhea withEnceladus below', justabove Dicr e. R ngedSaturn is aboveTethys and Minaswith its la-ge impactcrater are to the lowerright. Tital is in theupper rigf t.
Satellite Diameter) Mean distance(I* .m fromSaturn
(km x 1000)
Atla 3 30 137
Promethius 100 139
Pandora 90 142
Janus 190 15'Epimetf i _IS 123 151
Mimes 39) 187
Encelack. s 503 233
Tethys 1080 295
Telesto 25 295
Calypsc 25 295
Dior e 1' 20 373
Electra 30 378
Rhea 1530 526
Titan 5800 1221
Hyperiol 300 14E1
Iapetus 1480 35E1
Pheobe 220 12SE 0
The major moonsof Saturn
V EW 11:10M SATURN NORTH POLE
AARIVAL-RAJECTORY
TITANORBIT
INITIALORBIT
LAFETUS ORBIT
Figure 10. Sequence ot orb is plarnec for the Cassilio-aiter craft 'Courtesy ESP).
ELECTRONICS TODAY INTERNATIONAL39
enough to cast deep shadows on the surface of Saturn.The rings are considered to interact with the retinue of
orbiting moons and moonlets although most of these liebeyond the outer extent of the ring system. Scientists areparticularly interested in the ring structure since that mayprovide clues relating to the condensation of dust and gas atthe birth of the solar system.
The Voyager mission captured flickering lights in sections ofSaturn's ring structure. These are thought to be caused bycharged particles in the planet's magnetosphere.
Saturn: Atmosphere and cloud systemsThe Cassini orbiter will be able to monitor the atmospheric
features of Saturn both in greater detail and for a longer timescale than the Voyager probes. This will give a betterappreciation of the natural cycles of development of weathersystems as observed in the swaths of circling clouds. Figure 8shows details in Saturn's northern hemisphere cloud structures.
While Saturn's atmosphere is approximately 94% Hydrogenand 6% Helium, traces of a range of other atmosphericcomponents have been identified. These include Ammonia,Phosphine, Propane, Methylacetylene and ethane. It is likelythat many more compounds await detection.
While on the Earth there are significant temperaturedifferences between poles to equator, on Saturn the equivalenttemperature differences are much smaller - around 5 K. LikeJupiter, Saturn radiates more heat than it absorbs from SolarRadiation though it is unclear what gives rise to Saturn'sinternal heating. Most of the energy that drives the cloudsystems on Saturn originates as heat convecting up from deepwithin the planet. The Cassini mission will afford ampleopportunity to monitor Saturn's cloud systems.
All about the missionThe Cassini probe is due to be launched in October 1997
by a Titan IV -Centaur rocket from Cape Canaveral in Florida.Since Saturn is farther from the sun than Jupiter, and payloadsrequire more energy to reach Saturn than Jupiter, because ofovercoming the gravitational attraction of the sun. Due alsoprimarily to limitations in payload capacity, the flight path toSaturn will take place via gravity assist encounters with severalplanets of the solar system. Two are planned for Venus andone each for the Earth and Jupiter.
Figure 9 shows the interplanetary trajectory of theCassini/Huygens spacecraft. Hopefully, Cassini will surviveunscathed as it traverses the asteroid belt between Mars andJupiter. If all goes well, Cassini should enter Saturn orbit duringJune 2004. The orbit of Cassini will be configured to allowobservation of polar as well as equatorial zones. Figure 10indicates the complex series of orbits planned for the Cassini craft.The craft will initially enter into a wide orbit and the Huygensprobe released towards the end of this initial orbit around Saturn.
The present mission plan dates from mid 1992 when amore ambitious NASA CRAF/Cassini programme approved in1990 was scaled down to reduce costs. The mission is apartnership between NASA, ESA (European Space Agency)and ASI - the Italian Space Agency. ASI is involved inproducing Cassini's high gain antennae and key parts ofseveral experiments. The main Cassini mission will becommanded from the Cassini Mission Support Area (MSA) atthe Jet Propulsion Laboratory (JPL) in Pasadena, California.The Huygens Probe Operations Centre (HPOC) will be atESOC Headquarters in Europe. Links to the Cassini craft willbe undertaken by means of NASA's extensive Deep Space
Network. Aerospatiale/Cannes was selected by ESA as themain Huygens contractor in November 1990. The initial orbitsof Cassini are planned to be at an altitude above Saturnequivalent of one sixth of its diameter. During its planned fouryear mission, the craft will undertake around sixty orbits of thelarge planet. On account of the principal interest in observingTitan, Cassini's orbit has been planned to allow over thirtyencounters with the large mysterious moon. Changes in orbitare undertaken either by propulsive manoeuvres or Titangravity assist encounters.
The Cassini SpacecraftAn artist's impression of the Cassini craft is shown in figure
11. The weight of the Cassini orbiter at launch includingpropellants will be almost six tonnes. The actual Huygensprobe itself weighs around 350 kg. Cassini will be poweredusing radioisotope thermoelectric generators which utilisePlutonium. Such power generators have already been used forthe Galileo and Ulysses missions. The details of theCassini/Huygens craft design are shown in figure 12.
The Cassini orbiter carries a total of twelve scientificexperiments witi the Huygens Titan probe carrying anothersix. The Cassini mission makes extensive use of developmentsin electronics. While previous planetary spacecraft such as theVoyagers used on -board tape recorders, the Cassini missionutilises new solid-state recorder technology with no movingparts. Extensive use is being made of very high speedintegrated circuit (VHSIC) chip technology for the on -boardcomputer. Application -specific integrated circuit (ASIC) are alsobeing utilised. The power systems of the Cassini orbiter havebeen upgraded to include innovative solid-state powerswitches which will eliminate current and voltage transientsand provide significantly improved component lifetime.
The Cassini orbiter carries a broad range of instrumentswhich include high resolution infra -red spectrometers, CCDdetectors for photometric images (200 nm to 1100 nm),synthetic aperture RADAR, Ultraviolet spectroscopy, electronspectrometers, dust particle detectors, magnetic fielddetectors, mass spectrometer, ion imager and radio andplasma wave detectors. Thus, the surfaces of Titan can beimaged in much the same way that Magellan mapped thesurface of Venus using synthetic radar techniques. Table 3indicates the components of the Cassini Craft at launch.
The Huygens Titan ProbeThe Huygens probe is being supplied by the European
Space Agency. The Huygens probe will be launched from theCassini orbiter in late 2004 and drop into Titan's atmosphere
Table 3Launch components of the Cassini craft
Item Orbiter(dry massincluding payload)
Mass (kg)2150
Probe (+ 5Ckg payload)
Probe Support equipment 30Launch adaptor 165
Bipropellani 3000Monopropellant 132
Launch mass 5820
ELECTRONICS TODAY INTERNATIONAL40
some three weeks later. Up to this time the Cassini craft canmonitor the condition of the instruments aboard Huygens andwhere necessary undertake calibratior checks and monitorbattery condition. The last operation undertaken beforeseparation is the activation of the battery circuits and theresetting of the probe's timer in order that it should beactivated before it enters Titan's atmosphere.
The probe will initially enter the top of the atmosphere andbegin making measurements in the layer of haze above thecloud tops. This study will be undertaken by an aerosolcollector pyrolyzer, a gas chromatograph and a massspectrometer. During the descent, various instruments wi Irecord temperature, pressure, atmospneric density and energybalance it tne atmosphere. The Huygens probe carries acamera tc capture pictures of the Titan landscape.
Scientists can only speculate what features may exist onTitan's surface.There is the possibility that the surface of Titanis covered by lakes or oceans of methane or ethane. TheHuygens probe is designed to functior even if it lands in I quid.
A surface science package has been designed by theUniversity of Kent at Canterbury to determine character stics ofany landing site. The Huygens probe is anticipated to land at avelocity of between 5 to 7 metres/sec. This is equivalent todropping the probe from a height of two metres above asurface in earth's gravity.
Information captured by the Huygens probe will be storedon board and relayed to the Cassini orbiter while it is st II withinrange. This data will in turn be relayed onto earth.
The Landing ProgrammeThe deployment and landing of the Huygens probe is
certainly one of the most complex manoeuvres undertakenduring space exploration. Initially, the Huygens probe will bereleased some 22 days before the Titan encounter. It will bereleased with a relative velocity of 30 cm/sec and with arotation rate of seven revolutions per minute. This gives adegree of stability of the craft during its coast phase to Titanand during its descent stage through Titan's atmosphere.
During the initial descent through Titan's atmosphere, theprobe is protected by a heat shield some 2.7 metres in
diameter using heat resisting components Proial and AQ 60.At initial impact into Titan's atmosphere the craft's velocity willbe 6000 m/s. This will rapidy be reduced to 400 m/s (Mach1.5) in less than two minutes at which stage the parachutedeployment stage will be initiated by the firing of a mortar.Some thirty seconds after the main eight metre diameterparachute has been deployed the front heat shield will bereleased so that it falls clear of any probe landing site andavoids instrument contamination.
At this stage, various of the sampling ports on the probeare opened and scientific investigation begins. In order,however, to speed the descent, after 15 minutes a smaller 2.5metre parachute is deployed. The landing sequence isindicated in figure 13.
One 01 the main limitations of the Huygens probe is thepower requirements of the on board laboratory systems. Atotal energy capacity of 1800 Wh will be supplied whichshould provide sufficient power for a 153 minute mission - 2.5hours of descent and three minutes on the surface. Datacaptured oy the various instruments will be buffered internallyprior to transmission to the Cassini orbiter.
The Cassini/Huygens Probe InteractionAs the flexibility of space craft increases. so also does the
associated complexity of mission control and co-ordination.Figure 14 indicates the main stages of the mission :o capturedata from the Huygens probe. Initially, the Cassini craft isturned so that the high gain antennae is pointing towards Titanin order to capture the probe descent phase and up to 30minutes of data after touchdown. The on -board Cassiniimaging systems are then directed to Titan and other Cassinispecific modules are activated for analysis of Titan data. Aroundone hour after closest approach, the Cassini orbiter turns itshigh gain antenna towards earth for the playback of data.
The Huygens probe is therefore launched ahead of theorbiter so that it touches down some 1.5 hours ahead of theclosest approach of the orbiter. Due to the limited battery lifeof the Huygens probe, there s no opportunity for a repeat run.It is a once only event. As a comparison, the Mars landerscould use solar cells tc maintain on -board systems.
Figure 13: Landingsequence of theHuygens probe.(Courtesy ESA)
54 Mt109-139 km1-1'.
SummaryThe Cassini mission is a
highly ambitious undertaking.The design of the craft farexceeds in complexity that ofthe highly successful Voyagervehicles. This addedcomplexity, however,introduces complication atthe human level in co-ordinating and controlling themission. As well as scientificskills being tested at thelimits of knowledge, it willalso be most demanding onhuman capabilities andresourcefulness.
Images courtesy of NASA and
European Space Agency
ELECTRONICS TODAY INTERNATIONAL41
Switchregulators
magine a regulator that will produce a regulatedoutput with more current than the input. Let's takea it a stage further: imagine being able to getseveral different voltages from one input unregulatedsupply, at high efficiency. Take a look at Figure 1,
which shows a 40V 1 A unregulated supply feeding threeswitching regulators giving a total of 3.5A of current at differentvoltages. Yes, 3.5A is perfectly possible form a 1A unregulatedsupply. The power is fine: the total input power is 40W and theoutput power is 29.5W, and the efficiency is just under 75%.
Using linear regulators, the total current from all threeregulators would be limited to 1 A and the efficiency would bearound 20%. This is because linear regulators act as cleverattenuators, regulating the output voltage by adjusting the voltagedrop across the input and output terminals of the regulator. Unlikeswitching regulators, they cannot increase the current available.
DIY switchersSwitched mode supplies are now widely used to powercomputers and they are getting increasingly common in audioand video equipment. However, they are still a no-go area forone-off and amateur designs. This is despite ETI, trailblazing asever, publishing a practical design in June 1983, when a certainlong -forgotten D. Bradshaw was editor. The ETI design was afull-blown PSU delivering 12V at 4A, but it required threetransformers, a couple of high -voltage MOSFETs and a heap oftransistors, diodes and passive components.
In contrast, Nat Semi's Simple Switchers make it a cinch toknock up a fixed or variable switching regulator. They cost alittle more, but they offer a broader input voltage range, higherefficiency and lower heat dissipation.
Like a linear regulator, this particular switching regulator takesan unregulated input and produces a regulated lower voltage.But because the switcher transforms power, the output currentis normally larger than the input current. Switchers can workefficiently from higher input voltages, so several switchers canbe used to supply different output voltages from a single inputvoltage with no efficiency penalty. Other switchers, like theLM2577, produce a higher voltage than the input, but I'msaving that for a future article.
How they do itSwitching regulators use the fundamental property of aninductor, which is the ability to store energy and, using the
Dave Bradshaw takes a look at the designand construction of some simple switchregulators power supplies which offer theuser more current and higher efficiency
stored energy, oppose any change in the current flowingthrough itself. The inductor's energy is stored in its magneticfield, built up while current is being passed through it. Turn offthe current, and the inductor will do its best to keep the currentflowing, making sparks jump across switch contacts (or acrossspark plugs in a car's ignition systems). The property ofresisting change gives inductors their frequency -dependentimpedance (the quicker the change, the more the inductorresists, so the higher its impedance).
The switching regulator exploits the inductor's property byturning the current supply on and off in a controlled way; this isshown in Figure 2. Inside the regulator IC is a 52kHz oscillatorwith a variable duty -cycle: the relative lengths of the 'on' and'off' periods can be changed while the total period is kept thesame. The oscillator output drives a transistor that acts as apower switch; one 'terminal' of the switch is attached to theunregulated input and the other terminal to one end of the inductor.
The duty cycle of the oscillator is set by a circuit whichmeasures the output voltage (at the junction of inductor Li andcapacitor C4) via the feedback connection to the IC. If theoutput voltage is too low, the duty cycle is lengthened, i.e. theswitch stays on tor longer so more current flows through L1 intoC4; if the voltage is too high, the duty cycle is shortened, sothat less current flows into the capacitor.
If the unregulated input were the only source of current, theswitcher would not be able to supply an output current that ishigher than the input current. Here's where the inductor'senergy storage comes into play. It stores energy in its magneticfield while the switch is 'on' and current is flowing from theunregulated input to the output. When the switch is turned 'off',the inductor keeps current flowing by drawing positive currentfrom the ground via the 'catch' diode, D5, as shown in Figure 3.
The best analogy I can think of is of a water wheel (Figure 4a)that feeds water from a higher level to a lower one. The flow ofthe water turns the wheel quickly, building up momentum. If thehigher level water is shut off via a tap, the wheel carries onspinning because of its momentum. If we supply it with waterfrom a level that is below the output level (Figure 4b), the wheelwill scoop up this water to the higher output level, losingmomentum as it does so.
The inductors acting like the water wheel, except that ratherthan mechanical energy (momentum), its energy is stored as amagnetic field. The energy makes the inductor 'scoop up'current from ground and supply it to the output.
ELECTRONICS TODAY INTERNATIONAL42
40V
OV
ACMAINS
UNREGULATEDSUPPLY
Fig 1. 3.5A output from 1A input - it is possibla!
CURRENT FLOW WHEN TRANSISTORSWITCH ON
5V
Fig.2. The essential elements of the switcher are the switchitself, an inductor, a capacitor and a controlled oscillator.
ACMAINS
*40V 1A
UNREGULATEDSUPPLY
.15V 05A
REG I- +12V 1A
REIG I-05V 2A
OV
Fig 4. The water -wheel analogy: while the top tap is open (Fig3a), the water wheel is pushed round faster and faster,building up momentum; when the top tap is shut (Fig3b), thewater wheel scoops up water from the lower tap, losingmomentum.
OSCILLATOR(52kHz)
MEASURINGCIRCUIT VOLT NGE
REFERENCE
SHUT
- 0 7
PATH OF WATER
PATH OF WATEF
Fig 3. Essential switcher action: In hile the transistor conducts,current flows through the inducto-, building up the magneticfield; when the transistor is off, ct.rrent flows from the dicde, butfrom ground lo positive due to the action of the inductor.
INPUTFEEDBACK
IC 1
0 JT PUT
GND ON/OFF
1F I . LI SEE TEXT
Fig 6. The switcher circuit for fixed 5, 12 and 15 V supplies.
NOTECI LAR2578T 5.12 x 15DI -134 1N501D5 IN5122
ELECTRONICS TODAY INTERNATIONAL43
The inductor used cannot be any old inductor. It has to be atype that is specified for switched mode use, and it must becapable of carrying the full current. The 'catch' diode also isspecial, a conventional rectifier diode is not up to the job. It hasto be a fast -recovery high -current device, but not all fastrecovery types are suitable, some will cause instability and/orelectromagnetic interference. Normally a Schottky diode is usedfor its 'soft' turn-off characteristics.
Input ripple and efficiencyIn most cases, the switchers are direct replacements for linearregulators, but they have some different characteristics. As wehave already seen, the switching regulator transforms power, so alarge difference between input and output voltages is not a problem.
With a linear regulator, high voltage difference means high powerdissipation, and the regulator will shut itself off to avoid frying.
As with linear regulators, you have to watch that theinstantaneous voltage on unregulated supply lines does notdrop below the minimum input voltage, otherwise some verynasty 100Hz ripple will feed through to the output. A step-downswitcher has a minimum overhead of around 2V, dependingquite a lot on current drawn and other operating conditions.
Unlike linear regulators, extra margin does not mean extra
dissipation; rather, we can use a wider margin to increasetransformer efficiency. In linear supplies, we normally use ahigh -value smoothing capacitor to achieve a low ripple on theinput voltage (as in Figure 5a). This enables us to keep regulatorheat dissipation 'ow by keeping the input voltage just above theminimum overhead required by the regulator. The penalty forthis is the high ripple current flowing in the transformer, rectifiersand capacitors - up to 50 times the average output current.Small internal resistances lower the overall efficiency markedlyand lower the output current capability.
The switcher's ability to take a higher input voltage enablesus to increasing the transformer voltage. Lowering the reservoircapacitor size produces a longer conduction period (Figure 5b),so reducing losses in internal resistances. The ripple voltage ismuch larger, but so long as there is a good safety marginbetween the minimum voltage the regulator needs and thelowest part of the wave form, the switching regulator works fine.The higher the input voltage, the higher the ripple voltage can be.
There is a absolute restriction on input voltage, which is thatit must not exceed 45V, the absolute maximum rating of theLM2575/6 series. Nat Semi does produce high voltageversions, LM2575HV and LM2576HV, with absolute maximuminput voltages of 63V. However, I was unable to find suppliers.
Table 1C1 and L1 values for 5V
Transformer voltage 9 12 15 18 22
C1 for 1A (uF) 4,700 1,000 470 330 220
C1 for 2A (uF) 10,000 2,200 680 680 470
C1 for 3A (uF) 12,000 3,300 1,500 1,000 470
L1 for 1A (uH) 220 220 330 330 330
L1 for 2A (uH) 100 100 150 150 150
L1 for 3A (uH) 68 100 100 100 100
25,28,30220
220
330
330
150
100
Table 2C1 and Ll values for 12V
Transformer voltage 15 18 22
C1 for 1A (uF) 3,300 1,000 470
C1 for 2A (uF) 6,800 2,200 1,000
C1 for 3A (uF) 10,000 3,300 1,500
L1 for 1A (uH) 330 330 470
L1 for 2A (uH) 150 220 220
L1 for 3A (uH) 100 150 150
Table 3CI and Ll values for 15V
Transformer voltage 18 22
C1 for 1A (uF) 2,200 1,000
C1 for 2A (uF) 4,700 2,200
C1 for 3A (uF) 6,800 2,200
L1 for 1A (uH) 330 470
L1 for 2A (uH) 220 330
L1 for 3A (uH) 150 150
25 28,30
330 220
680 470
1,000 680
680 680
330 470
220 220
25 28,30
470 330
1,000 680
1,500 1,000
680 680
330 330
220 220
ELECTRONICS TODAY INTERNATIONAL44
One final word before we get stuck into the nitty-gritty is thatthe LM2575/6 have an on/off control on pin 5. None of thecircuits here make use of this control, so they all take it to earth.
Fixed voltage regulatorsThere are five different fixed -voltage switching regulators circuitshere, with outputs of 5, 6.3 12 and 15, and 25V, and a variablevoltage options. There is fixed 3.3V version of the SimpleSwitcher that I haven't made use of, but which could use thesame circuit values as the 5V regulator.
Including a 6.3V version may seem quirky, but it is the reasonwhy I got involved with the Simple Switchers. I was looking foran efficient way of supplying valve heaters with 6.3V DC, so asto reduce mains hum in a valve preamplifier. The solution wasthe first supply I built using these devices, but I quickly realisedhow many other uses there were.
The circuits are shown in 1A, 2A and 3A versions, with a widerange of input and output voltages. Although the circuits hardlychange, the component values do vary a lot, so be sure to usethe right values. The 1 A version uses the LM2575 seriesregulators, while the 2 and 3A versions use the LM2576Tversions (there's no particular reason for using the LM2575series for 1A, except that it is a little cheaper).
Figure 6 shows the basic circuit for the fixed 5V, 12V anc 15Vregulators (the 6.3 volts and 25 volts versions are described below).Figure 7 shows the corresponding PCB layout. Figure 6 is drawnto emphasise the importance of short PCB track paths betweenIC1, C1 and 2 and D5, in particular short earth paths; if you donot use the PCB, you must keep these paths as short as possible.
For each output voltage, the inductor value and minimumsize of capacitor in the unregulated supply depend on the inputvoltage and output current. I have given the appropriate valuesfor C1 and L1 in Tables 1-3.
For the capacitor values, I have chosen commonly -availablevalues where possible; however, if you cannot find the valuespecified, use the next available value above; the circuit is not criticalin this respect. If you use a capacitor with tolerance greater than20%, you should use the next value up anyway.
At first sight, some of the C1 values may seem remarkablylow - for example, 330uF for a 5V 3A output from 25V - but thisis because I have allowed for quite a lot of ripple. Raise thevalues if they worry you, or if you find any ripplebreakthrough in the output.
The optimum value of L1 varies according tothe maximum current output. Some values of L1may be hard to get; use the next lowest valuethat you can find.
If you have a free choice of transformersecondary voltages, I suggest choosing a valuethat is mid -way or above in the table. If you everwant to use the same transformer to supplyother switchers with different voltage outputs,choosing a higher voltage adds flexibility.
The maximum input voltage to the IC is 45V,and this dictates a maximum transformersecondary voltage of 28V RMS. This gives arectified peak voltage of 39.6V with no load, i.e.a safety margin of just over 10%. This margin isneeded because under no or light load,transformers usually give a few extra volts.However, I have included 30V in the tables as itis a commonly available secondary voltage andshould be acceptable provided the supplyoutput will always be under heavy load. 30V
RMS gives a rectified peak voltage of 42.4V, leaving only a 2.6Vsafety margin, but with a heavy load there is an additionalvoltage drop of around 2V across the rectifier diodes, leaving a10% (4.6V) safety margin.
Because of the improved efficiency, transformer currentrequirements are lower than you would normally expect,particularly for the higher voltages. As a rough guide, thetransformer current rating (It amps) is given by:
It = 2 x Vc x Io/Vt
Where Vo is the maximum output voltage of the regulator,lo is the maximum required current in amps, and Vt is thenominal voltage of the transformer secondary. This assumes anoverall efficiency of 50%, including losses in other parts of thepower supply.
This relationship applies to all the different versions of the circuit.
Next Month...We will look at 6.3V, 25V, and variable voltage regulators.
CONDUCTION PERIOD
CONDUCTION PERIOD
Fig 5. In Fig 5a, a high reservoir capacitance valueleads to the very short conduction time; In Fig 5b, theconduction time is increased but so is ripple. So longas the unregulated voltage is above the operatingmargin needed by the regulator, high ripple can leadto higher efficiency.
ACINPUT
5
ICI
0
OUTPUT
Fig 7. PCB layout for the switcher for 5, 12 and 15V. Note the alternativepositions for different versions of L1. Note also that several holes are notused in this version. Be careful with the orientation of C1. The PCB trackingcornecting C2, L1, the output and the feedback may look odd, but it iscorrect (the shape is to minimise the effect of ripple current).
ELECTRONICS TODAY INTERNATIONAL45
Touch Switch
ontinuing a series of modules for the 80188embedded controller, this circuit features a touchsensitive keypad and tri-colour LED indicator.This interface is interrupt driven; switch 'presses'are checked at a rate of 100 times a second.
When a switch is touched, the LED colour will indicate whichswitch channel has been activated; a background program canthen determine what action to take dependent on the contentsof the AL register:AL register contains 00H; no switch has been pressed
If more than one switch is touched accidentally, no switchpress is registered to provide a fail-safe condition. The touchpads may be larger than shown, effectively increasing thesensitivity of the switch to a point that no contact needs to bemade with the switch; the proximity of the finger is all that isneeded to activate the switch. This switch interface then wouldbe ideally suitable in a intrinsically safe environment, since allconductive surfaces can be insulated from the user.
How does it work?The hybrid circuit (consisting of both analogue and digitalcomponents), relies on capacitance effect to introduce a phaseshift in a digital signal. In the block diagram shown, a 100Hzsquare wave signal generated by the 80188's timer is applied toan octal latch, so that the logic level at its inputs are changing ata steady rate. A phase shifting circuit - the 10K variable resistor,and a 100 pF capacitor form a simple integrator whichintegrates the square wave input: the slope of the output signal
InterfaceAnother useful add-on module forRichard Grodzik's 80188 single boardcomputer
depends on the value of the variable resistor. Increasing the CRvalue reduces the slope of the waveform and therefore modifiesthe time at which the Schmidt trigger will change its logic level.Note that these changes are barely perceptible and a good50Mhz storage scope is required to observe this effect.
The 10K potentiometer is adjusted to the point where thelatching signal (active high) applied to pin 11 of the 74373 latchcauses the clock inputs of the switches (10 - 4D) to be latchedthrough to the outputs (10 - 40) when the 100Hz signal is atlogic low. This cal easily be checked by means of a logicprobe. As the clock signal continues to toggle, the octal latchoutputs will remain low. A further CR network formed by a 10Kresistor and a 1000pF capacitor introduces a further phase shiftso that an active high interrupt signal is generated just after the74373 is latched.
The interrupt signal causes an interrupt service routine (ISR)to be executed which reads in the output logic levels of thelatch into Port B of the 8155, and hence to the 80188, where acheck is made of the logic levels which should be all low.
If one of the touch pads is touched, the extra capacitancegenerated by the finger produces a phase shift of the inputsquare wave to that channel, effectively 'widening' the pulse sothat, when the latch signal goes high, the logic level at this inputis at a logic high level - the remaining input channels being atlogic low. The activated channel causes a logic high signal to belatched to the output pin of the 74373, which is subsequentlyread by the CPU when an interrupt is issued.
An indication of which switch channel has been activated isthe function of the tri-colour LED, whose inputs are connectedvia FET buffers to Port C.
ConstructionA double -sided board was used for the touch interface circuit.Making a double -sided board is not beyond the realities of the
ELECTRONICS TODAY INTERNATIONAL46
TOUCH.A DS OCTAL
LATCH
1-0CI COCK
80188 TIMER 1-0 20 20
INTO
1-0 30 30
1-0 4 40 s
PHASE SHIFT LATCH
TSENSITIVITY
CONTROL
CR PHASESHIFT SWITCH INDICATOR
F g. 1. Touch switch interface bock diagram
-
PF30
8155
P81
P82
PB3
PC3
PC4
80188EMBEDDED
CONTROLLER
INTO
TIMER OUT 0 (80188)
IC1
10k
100Hz
3ICI
5IC
SENSITIVITYCONTROL
RV1
9
mim C101100p
10k+5V
LC102n
ICI
5V
Fig. 2. Touch switch circuit diagram
+5V
T0 TIMER 0 IN (80188)
SIL 33k
LATCH E
8
o b 6
INTO (80188)
T DUCH PADS
+5V
20
3 VCC
4 2,
7 3) 10
8 4 ) 2013 5) 30
6, IC2 4017 7) 50
18 8 ) 60
70
I' N 80
NOTE:ICI 74HC14IC2 74HCC 7301, 02 BS17C
10
.1. 3103100n
P80
60 P131
-C) PB29-0 PB312
15
26
19
+5,/
R270R
ELECTRONICS TODAY INTERNATIONAL47
Fig. 3. Touch switch PCB component overlay
home constructor. Who would have thought it possible 20 yearsago, that the design and programming of a smallmicrocomputer would be possible on a kitchen table?. I, for one,did not, I must admit. My initial response to the PC was that itwas an over -priced word processor, little realising that severalyears later, the PC would be an indispensable tool on which allmy microcomputer development would take place.
Back to making a double -sided PCB. We have all found thatdesigning a single -sided PCB, even with PCB CAD facilities is atime-consuming task if size constraints or many ICs have to beaccommodated. How to avoid too many links?. The answer ismaking a double -sided board where copper connecting tracksare placed on both sides of the board - the normal copper sideand also the component side. Electrical connections betweenbottom and top layers are then made with simple 0. 8 mm pinswhich are inserted into the 'pin-thru' holes and soldered on both sides.
The most common problem is making a double -sided boardis how to align the artwork on both sides of the board, so thatthere is correct registration between the component sides andthe copper side. A few millimetres out and the board becomesunusable. The following method has been tried and tested bythe author many times.
Offer the copperside artwork to one side of the UV sensitiveboard, having first removed the protective backing. Secure theartwork with a couple of small strips of Sellotape - having aslightly larger board than required will make this task easier - theboard is then later cut to final size. Drill two small diameter holes(0. 6mm) at diagonally opposite ends of the board, includingboth pieces of artwork. Now offer the component side artworkto the other side of the board - print side outwards - and line upwith the aid of the two pilot holes. Secure with sticky tape. Theboard can now be exposed to UV light and chemicallyprocessed as usual i. e developed in a solution of caustic sodaand then etched in ferric chloride. Since both sides of the board
need to be etched, turn the board periodically , making sure thatthe necessary safety precautions are observed. Use vinylsurgical gloves to protect the hand - the common kitchen'rubber' gloves tend to disintegrate in contact with ferric chlorideand should not be used. Finally, the board is washed and driedand the thru holes are pinned through with special 0. 8 mmtrack pins or wit-) wire.
All the components are now assembled on the 'component'side of the board with the exception of the tri-colour LED whichis mounted on the opposite side - the leads soldered on thecomponent side, so that when this interface is plugged into themodule of the 80188 embedded controller, all the componentssit face down, with the LED pointing up. A 'wander' lead issoldered to INTO pad on the interface card with connects to theINTO pin on the embedded controller board. Drill a 10mm holeso that the 10K cot can be adjusted when the circuit is matedwith the embedded controller.
SoftwareMost of the procedures to initialise the 80188 have been used indescribing the programming of the 80188 controller board sothey should not be too unfamiliar. Procedure INIT_PORTSconfigures the 8155 ports, Procedure Initialise enables the INTOinterrupt system and procedure VECTOR loads the address ofthe interrupt service routine (ISR) into the vector table located inthe RAM of the 8155.
The timer is configured at the start of the program and isidentical to the listing given in 'TIMERO. ASM' in the first part ofthe programming course. Once the timer, ports and interruptsystem has been initialised, the interrupt flag is enabled and theprocessor just 'sits' doing nothing. This is the backgroundprogram which is left for the user to program for their ownrequirements.
Every 20 Ms, an interrupt is issued and the ISR routine readsthe logic states of the switch outputs, switches on the LED thecorrect colour and returns to the background program.
;4 CHANNEL TOUCH SWITCH INTERFACE.;TRI-COLOR LED INDICATES WHICH SWITCH HAS BEENTOUCHED;INDICATING RED,GREEN,ORANGE OR OFF;SWITCH IDENTIFICATION (1,2,4,8) RETURNS IN AL;REGISTER IN BACKGROUND PROGRAM.CODE SEGMENTASSUME CS:CODEORG 0ORG 0400H
device programmerSYSTEM: ASK FOR OUR FREEPrograms 24, 26 32 p INFORMATION PACK.
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ogrammerRobin Abbott explains how aninexpensive PIC programmer can beconstructed for home use
D1
>17V 014
°-1
IC3
clC922u
IC4N OUT
GND
D2
D3
D4
0214.1V
> VDD
Fig.1 . PIC programmer circuit
XL1 3.58MHz
C7mm C815pI 15pI
o C5 C6
D6 R5
1
I.5R
1
R310k
I10p I 100n
R1
4k7
R2
01
R4
4k7
03
VDD RCO /MCLR'11÷3ni28
4VSS
/MCLR
RTCCRCI 19 mcldry
SKT1
28 pin
21 rtccdry2RC3 RTCCOSCI
RC2 20 oscldry 27OSC1
22 6RC4 OSC2OSC2
23RC5
IC1
VCC
24RC6
06 /
DO D11\ 6
RAO GND 4
7 / \ 725
11C78 / \ 8 RCO
/
RA3 9 / \ 9 RA3
10 10 20RBO RBO
1 / \ 11 21
12 / \ 12 22
13 / \ 13 23
14 \ 14 24NOTE.
15 / \ 15ICI PICI 6C57/XT RC7IC2 MAX232
16 IC3 7805 \ 16
17 / \ 17
/R87
IC401.03
78L12BC548 RB7
02 BC55701 1N4001
D2 D6 1N4148LDI RED LED 5mmZD1 5 6V ZENER DO D1I
RN112 x 1 0 k
I
LD1
R6
560R
ZD1
5V6
4
3
16
15
/MCLR
SKT218pin
RTCC
OSC1
OSC2
7RAO
18
1
2
6
7
8
9
10
12
RA3
RBO
RB7
ELECTRONICS TODAY INTERNATIONAL52
s readers of any of the electronics magazinesover the last couple of years will have noticed,the microchip PIC devices have becomeincreasingly popular with home constructors.They offer a fast RISC architecture, on board
RAM, PROM and peripherals offering use in a wide range ofapplications which previously may have taken considerableamounts of logic.
The development tools for PICs are available free of chargefrom Microchip, however the commercially available PICprogrammers are, unfortunately, quite expensive and often willonly program a small subset of the available PIC devices. Thisproject describes a PIC programmer for home or other smallscale use which can be constructed for a total cost (includingsoftware) of around 535.00. It has the following features: Reads, programs, and verifies PIC 16C54, 55, 56, 57,58, 64, 71, 74 84 and any other upcoming 18, 28, or 40pin PIC devices which conform to the current PIC serialprogramming specification.
1,C1
1007
I3 x100n
2
VDD
GND
1. T5
IMCLR
SKT340 pin
D10 39 RB6
011 40 RB7
Reads and programs EEPROM device data areas. Will program serial devices in circuit with a 4 wire
interface. Fully supports user data area and configuration fuses. Serial 'nterface to host PC. Windows host software available. Loads and saves Intel hex, hex text and binary file
formats produced by Microchip Assembler (MPASM). Host software supports automatic device
serialisation.The programmer is constructed on a fibreglass PCB which
is not cased to save costs. A standard 3 wire RS232 serialinterface running a simple command interface is provided tothe host PC. The programmer operates from an 18v supply, asuitable mains driven supply is described in this article.
Circuit DescriptionFigure 1 shows the circuit diagram of the programmer.Programming a PIC requires two power supplies, a 5v supplyfor the main circuitry of the device, and a supply between12.5V and 13.5V for the programming algorithm. 103 providesa 5V supply and IC4 provides a 14.1V programming supply(voltage drops in other parts of the circuit reduce this to 13.3Vat the RC).
The main functionality o4 the programmer is provided byIC1, another PIC device, the PIC16C57. This device is usedbecause it has 80 bytes of RAM which are needed to bufferinformation from the host PC, and it also has 20 I/O pins -programming the parallel devices requires a 12 bit interface tothe PIC being programmed. The design uses a cheap 3.58MHzcolour crystal as a main oscillator. The control signals neededfor programming are the RTCC and OSC1 pins of the devicebeing programmed, these are driven directly from 101.
The programming supply is switched from 101 by TR2 andTR3. TR2 enables the programming supply which isconnected to the MCLR pin of the device through D5 and R5(these are needed when devices are programmed in -circuit).TR3 provides a fast switch open collector to ground so thatthe programming supply is turned off quickly enough whenprogramming in -circuit. LD1, R6 and ZD1 provide a visibleindication that the PIC device in use has the programmingsupply connected and should not be inserted or removed. ZD1ensures that LD1 will not illuminate unless the programmingsupply is well above 5v.
The interface tc the device being programmed is providedthrough a 12 bit bus, DO to D11. 101 port pins RAO to RA3 arethe lower 4 bits of the bus, and port pins RBO to RB7 are theupper 12 bits of the bus RN1 provides a pull down to the bus.
IC2 is a MAX232 devte which provides an RS232 interfacefrom a 5v supply, it connects to port C of 101. The serial
interface is 3 wire, andoperates on a
D101
T1C101
+20V
GND
Fig.2. Circuit diagram of PIC prcgrammer power supply
request/acknowledge protocol.When the programming supplyis disconnected the MCLR,RTCC and OSC1 pins of thedevice being programmed areall held low by 101. Theprogramming bus is held lowby RN1, and so the only pin onthe programmed device whichis above ground is the powersupply pin. Normally it is notconsidered good practice to
ELECTRONICS TODAY INTERNATIONAL53
+12V
MCLRov
RTCC
OSC1
DATA<0:11,
r
Fig.3. Parallel programming interface
PROGRAMPULSE
READPULSE--*
C>
READ PC ANDINCREMENT ADDRESS
PROGRAM DATA READ READ(WRITE) PROGRAMMED
DATA
insert a device into a circuit with the power supply connected.However, in this case, as we can guarantee that all other pinsare held at ground or are open circuit then there is nopossibility of latch up.
To simplify the circuit separate sockets are provided for 18,28 and 40 pin devices. The host software allows fullconfiguration of device parameters allowing new devices to beprogrammed as they become available.
Figure 2 shows the circuit diagram of the power supply. A15-0-15V transformer may be used as current consumption isso low that the input voltage remains above 19V at all times.The power supply is constructed in a small case with anintegral mains plug.
Programming interface to Parallel devicesThe older PIC devices - those in the 16C5XX series can onlybe programmed in parallel mode. These devices require a 12bit data interface together with a programming controlinterface, because of this heavy I/O requirement they cannotbe programmed in -circuit by this programmer.
To enter programming mode the MCLR pin of the devicemust be taken to at least +12.5V in less than 1uS whilst theRTCC pin is held high. Once in this mode the device can beread or programmed. To program the device, the word to beprogrammed MUST be placed on the data bus. The RTCC pinis then driven low to program the word. To verify the wordwhich has been written the RTCC pin is driven low again,
N=N+1
START
N=1
PROGRAM - 100us
READ VALUE
FAIL
N=N*3
PROGRAM LOOPS
N=N -1
Fig.4. Programming cycle for each word in UV EPROM devices
N=O?
SUCCESS
ELECTRONICS TODAY INTERNATIONAL54
IC4
IC3
D2; ;D3
01
+5V
10k P1
10k
10k
P2
P3
P4
/MCLR
RB6
RB7
GND
PIC TO BE PROGRAMMED
Header cable - connect 16 pinDIL header as follows:
Header pin Circuit pin
Fig.5. In -circuit programming
during this second period the data word is output on the databus. The programming/verify cycle is described below. Toincrement the program counter and look at the next word theOSC1 pin is used as a clock. Whilst it is high the currentcontents of the program counter are output on the data bus.The OSC1 pin may be used to step through the PIC readingits program without changing it.Figure 3 illustrates the programming interface for parallel devices.
Programming interface to Serial devicesThe more recent PIC devices can be programmed in a parallelor serial mode. For this programmer serial mode is used forthese devices, except for the bulk erasure of EEPROM deviceswhich is only possible using parallel mode. As for paralleldevices the PIC enters programming mode when the MCLRpin is taken to +12.5V. However, for these devices, the RB7pin is used as data, passing information into or out of thedevice. Pin RB6 is used as a data clock. These devices have a
6 bit command which is entered into the serial input, and isthen followed either by 16 bits of data which is either clockedin to the device for programming, or is clocked out of thedevice for reading.B:The commands available irclude reading and writingprogram, user and configuration data areas, as well asEEPROM data memory in those devices which includeEEPROM memory. The EEPROM devices have a bulk erasefacility which must be used if the code protect fuse has beenprogrammed. However the bulk erase procedure must use theparallel programming mode, and so is only available on 18 and28 pin devices.To adjust the device programming pulse width in thesedevices there is a start programming and an end programmingcommand which are given to time the pulse width accurately.
ProgrammingProgramming of the EEPROM devices is straightforward, theprogramming is self timed, and there is no need to explicitlyerase the device (unless the code protect fuse has been set).
Programming of the UV EPROM and OTP devices is morecomplex. These devices have a speed programming algorithmwhere repeated programming pulses of 100uS are used. Aftereach pulse the device is read to check if it has beenprogrammed successfully. Once the device has successfullyreturned the correct word then three times as many pulses asthose initially required are applied to overprogram the device.This procedure is illustrated in figure 4.
The host software reports the average number of initialprogramming pulses required. In the prototype only one initialpulse was ever required unless the power supply was reducedwell below specification. However, this may increase withdevices which have been programmed multiple times.
Please note that the only part of the programming algorithmnot implemented by this programmer is the verification ofprogrammed information at different values of Vdd. This haslittle practical impact but consequently Microchip would classthe programmer as 'development" only.
PL2
PL1
3
D-f R31-0
-{ R5 F-
2
Sk'1
I C31
I 1
LD1 7111U
SKT3
KT?
C4 1
Fig.7. PCB component overlay
ELECTRONICS TODAY INTERNATIONAL55
In circuit programmingIn -Circuit programming is only available with seriallyprogrammed devices, and will not operate with EEPROMdevices which have been code protected, or with UV EEPROMdevices which have been programmed. The currently availabledevices which can be programmed in -circuit are the 16C6416C71,16C74, and 16C84. The 16C84 can be reprogrammedin -circuit allowing updating of software in the field.
Figure 5 shows the circuit diagram of the application circuit.A 4 way header cable must be made up with a 16 pin DILheader connecting to RB6, RB7, MCLR and ground in theapplication circuit as shown in figure 5. The 16 pin header isinserted in SKT 2 so that pin 1 of the header is inserted intopin 1 of SKT 2. This will leave 2 pins of SKT 2 unconnected.The header cable must be as short as possible.
Note that in the application circuit the RB6 and RB7 pinsmust be capable of being driven by the programmeroverdriving any signals present in the circuit. Resistors Rs shownin figure 5 are used to allow the programmer to drive the PICregardless of any other signals driving the device. Note alsothat during programming the I/O pins of the PIC will all be floating.
ConstructionThe programmer is constructed on a fibreglass PCB with fourrubber feet which prevent the PCB from scratching anysurface on which it is used.The PCB overlay is shown in figure 7. Construction is notcomplicated, insert all the jumpers and horizontally mountedcomponents first, 101 and IC2 should be socketed. Insert thecapacitors, crystal, IC3 and PL1 last. Note the resistor networkRN1. RN1 can be made up from one 9 way SIL resistornetwork and one 3 way SIL network. However as these
FIGURE 9Serial Cable from
programmer to host PC
Programmer PC connector type:
PL1 9way 9way 25 way 25wayfemale Male Female Male
2 2 3
3 3 2
5 5 5 7 7
appear to be unobtainable then RN1 can be made up from 12individual vertically mounted resistors.SKT1, SKT2, and SKT3 are the device programming sockets.Zero Insertion Force (ZIF) sockets can be used here. Howeve,rthey are expensive and can be replaced with stacked DILsockets. If this is to be the case, then ensure that the deviceprogrammed is inserted into a DIL socket, and that the boardhas at least two stacked sockets. This will ensure that socketswith bent pins can be replaced without unsoldering from thePCB. 18 pin ZIF sockets are hard to find, and the prototypeused a 20 pin socket for SKT2. If ZIF sockets are used thenthey should be either long pin devices, or should be mountedon two stacked DIL sockets to raise them above the boardand components.A serial cable needs to be constructed, or a standard serialcable can be used. As there are a variety of serial portsconnectors available then it is likely that different host PCs willneed different connectors. If you choose to make up a cablefor the host PC then follow the connections shown in figure 9.The power supply is constructed in a small case with anintegral mains plug. There are only three components in thepower supply apart from the transformer. These are mountedon a small piece of veroboard. Ensure that the transformer andpower supply board are bolted firmly into the case. In theprototype, the exposed mains pins were liberally smeared withsilicone rubber sealant to insulate them.
Next Month...We will look at the PIC programmer software, as wellas testing and using the programmer.
* SURVEILLANC,T KITS *MTX MICRO TRANSMITTER 18x45mm includingsensitive electret mic., tuneable 70-115MHz, 500m plusrange. KIT £5.95 ASSEMBLED £9.95TTX TELEPHONE TRANSMITTER 15x45mm, poweredfrom line, transmits all conversations, 500m range, 90-105MHz. KIT £5.95 ASSEMBLED £10.95Supplied with all components & high quality PCB's. Pricesinclude P&P. Send 2 x 1st class stamps for our latest kits& ublications catalo ue. Che ues/P.O.'s a able to:
OUASAR ELECTRONICS .
(Dept. EPE) Unit 14 SunningdaleBISHOP'S STORTFORD Herts CM23 2PA
ASTRONOMICAL RANGE ATDOWN TO EARTH PRICESTRANSISTORS+ICs+SEMICONDUCTORSRESISTORS+CAPACITORS+INDUCTORSSURVEILLANCE+SECRECY+SECURITYPLUGS+SOCKETS+LEADS+CONNECTSTV & VIDEO SPARES (inc Video Heads)HIFI+DISCO+HIFI GADGETS+SPEAKERSAUDIOPHILE COMPONENTS (inc Capacitors)IN CAR AUDIO+SPEAKERS (inc Bass tubes)COMPUTER ACCESSORIES+BOARDSTOOLS+TEST EQUIPMENT+BENCH WARE
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Pay by PO, Cheque, Credit Card or tape Coins to PaperPlease send me copies of the 1995 Cricklewood Catalogue.! enclose £2.50 per copy (UK & Europe). £5.00 overseasNameAddress
Please Charge my Credit Card.noExpiry Date Tel no ETI
THE ORIGINAL SURPLUS WONDERLAND!THIS MONTH'S SELECTION FROM OUR VAST EVER CHANGING STOCKS
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FLOPPY DISK DRIVES 31/2"- 8"51/4" from £22.95 - 31/2" from £24.95
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Teac FD-55GFR 1.2 Meg f29.95(B)5%' BRAND NEW Mitsubishi MF501 B 360K £22.95(B) Data cable included in price.Shugart 800/801 8' SS refurbished & tested £195.00(EShugart 851 8' double sided refurbished & tested £250.00(EMitsubishi M2894-63 8" double sided NEW £275.00(EMitsubishi M2896 -63-02U 8" DS slimline NEW £285.00(EDual 8" drives with 2 mbyte capacity housed in a smart case withbuilt in power supply. Ideal as exterior drives! £499.00(F(
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THE AMAZING TELEBOXConverts your colour monitor Into a QUALITY COLOUR TV!!
g::=1
TV SOUND& VIDEOTUNER!
The TELEBOX consists of an attractive fully cased mains poweredunit, containing all electronics ready to plug into a host of video moni-tors made by makers such as MICROVITEC, ATARI, SANYO,SONY, COMMODORE, PHILIPS, TATUNG, AMSTRAD etc. Thecomposite video output will also plug directly into most videorecorders, allowing reception of TV channels not normally receivableon most television receivers' (TELEBOX MB). Push button controlson the front panel allow reception of 8 fully tuneable 'off air' UHFColour television channels. TELEBOX MB covers virtually all televi-sion frequencies VHF and UHF including the HYPERBAND asused by most cable TV operators. A composite video output islocated on the rear panel for direct connection to most makes ofmonitor or desktop video systems. For complete compatibility - evenfor monitors without sound - an integral 4 watt audio amplifier andlow level Hi Fi audio output are provided as standard.TELEBOX ST for composite video input type monitors £34.95TELEBOX STL as ST but with integral speaker £37.50TELEBOX MB Multiband VHF -UHF -Cable- Hyperband tuner £69.95For overseas PAL versions state 5.5 or 6mhz sound specification'For cable / hyperband reception Telebox MB should be connectedto cable t e service. Shi in code on all Teleboxes is B
FANS & BLOWERSMITSUBISHI MMF-D6D12DL 60 x 25 mm 12v DC £4.95 10 / £42MITSUBISHI MMF-09B12DH 92 x 25 mm 12v DC £5.95 10 / £53PANCAKE 12-3.5 92 x 18 mm 12v DC £7.95 10 / £69EX -EQUIP 120 x 38mm AC fans - tested specify 110 or 240 v £6.95EX -EQUIP 80 x 38mm AC fans - tested specify 110 or 240 v £5.95VERO rack mount 1U a 19' fan tray specify 110 or 240v £45.95 ivIMHOF 826 1900 rack mnt 3U x 19 Blower 110/240v NEW £79.95Shipping on all fans (A) Blowers (8) 50,000 Fans Ex Stock CALL
IC's -TRANSISTORS - DIODESOBSOLETE - SHORT SUPPLY -BULK
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Issue 13 of Display Nc
000 0000
000
000 0...0
-ELECTRONICS-
PC SCOOPCOMPLETE
COLOUR SYSTEMONLY £99.00
A massive bulk purchase enables us to bring you a COMPLETEready to run colour PC system at an unheard of price!The Display Electronics PC99 system comprises of fully com-patible and expandable XT PC with 256k of RAM. 5%' 360k flop-py disk drive. 12" CGA colour monitor, standard 84 key key-board, MS DOS and all connecting cables - lust plug in and goIt Ideal students, schools or anybody wishing :o learn the world ofPC's on an ultra !ow budget. Don't miss this opportunity.Fully guaranteed for 90 Days.
VIDEO MONITOR SPECIALSOne of the highest specificationmt monitors you will ever see -
At this price - Don't miss it!!Mitsubishi FA3415ETKL 14" SVGA MultIsync monitor with tine0.28 dot pitch tube and guaranteed resolution of 1024 x 768 A
variety of inputs allows connection to a hos' ofcomputers including IBM PC's in CGA. EGA, VGA &SVGA modes, BBC, COMMODORE (includingAmiga 1200), ARCHIMEDES and APPLE. Manyfeatures: Etched faceplate, text switching and LOWRADIATION MPR specrfication Full 90 day warranty.
Supplied in EXCELLENT little used condition Only £139(ElOrder as MRS -SVGATilt & Swivel Base £8.00 Leads for IBM PC £8.95 (A)External Cables tor other computers £ CALLPHILIPS HCS35 (same style as CM8833) attractively styled 14"colour monitor with both RGB and standard composite 15.625Khz video inputs via SCART socket and separate phono lacks.Integral audio power amp and speaker for all audio visual uses.Will connect direct to Amiga and Atari BBC computers. Ideal forall monitoring / security applications with direct connection tomost colour cameras. High quality with many features such as rontconcealed flap controls, VCR correction button etc. Good usedcondition - fully tested with a 90 day guarantee Only £99Dimensions W14' x H123/4' a 151/2' D.
)
Special Offer save 06.95 - Orde TELEBOX ST &HCS35 together - giving you a quality colour TV & AV
system for Only £122.50 (E)
KME 10" high definition colour monitors. Nice tight 0.28' dot pitchfor superb clarity and modem styling. Operates fromany 15.625 khz sync RGB video source, with RGBanalog and composite sync such as Atari,Commodore Amiga, Acorn Archimedes & BBC.Measures only 131/2' x 12' x 11'. Only £125 (E)Good used condition. 90 day guarantee.KME 10" as above for PC EGA standard £145.00 (E)PHILIPS HCS31 Ultra compact 9" colour video monitor with stan-dard composite 15.625 Khz video input via SCART socket Idealfor all monitoring / security applications. High quality. ex -equipmentfully tested with a 90 day guarantee (poss'ble minor screen turns).In attractive square black plastic case measuring W10' a H10' x131/2" D. Mains powered Limited Quantity - Only £79.00 (D)
20" 22" and 26" AV SPECIALSSuperbly made UK manufacture. PIL all solid state colour monitors.complete with composite video & optional sound inputs. AS -activeteak style case. Perfect for Schools, Shops, Disco, Clubs. etc.lnEXCELLENT little used condition with full 90 day guarantee.
20"....£135 22"....£155 26"....£185,F,
DC POWER SUPPLIESVirtually every type of powersupply you can imagine.Over
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Zeta 3220-05 AO 4 pen HPGL RS232 fast drum plotter £19503M VDA - Video Distribution Amps.1 in 32 out £375Trio 0-18 vdc bench PSU. 30 amps. New £470Fujitsu M3041 600 LPM band printer £1950VG Electronics 1035 TELETEXT Decocing Margin Meter £3750Andrews LARGE 3.1 m Satellite Dish 4 mount (For Voyager.) £950RED TOP IR Heat seeking missile (not armed !!) POA
Thurlby LA 1608 logic analyserf1200£375
KNS EMC / Line interference tester NEW
INTEL SBC 486/133SE Multibus 486 system. 8Mb Ram £1200GEC 1.5kw 115v 60hz power source £950Brush 2Kw 400 Hz 3 phase frequency converter £850Anton Pillar 75 kW 400 Hz 3 phase frequency converter POANewton Derby 70 KW 400 Hz 3 phase frequency converter POACOMPONEDEX T1000 Portable TELEX tester NEW £250Sekonic SD 150H 18 channel digital Hybrid chart recorder £1995HP 7580A Al 8 pen HPGL high speed drum plotter £1850Computer MCA1613APC 16mm auto iris lenses 'C' mount £125Seaward PAT 2000 dual voltage computerised PAT tester £585Densel MUD 0185AH 1KVa UPS system with baits NEW £575
19" RACK CABINETSSuperb quality 6 foot 40U
Virtually New, Ultra SmartLess than Half Price!
Top quality 19' rack cabinets made in UK byOptima Enclosures Ltd. Units featuredesigner, smoked acrylic lockable front door,full height lockable half louvered back doorand removable side panels. Fully adjustableinternal fixing struts, ready punched for anyconfiguration of equipment mounting plusready mounted integral 12 way 13 amp socketswitched mains distribution strip make theseracks some of the most versatile we have
ever sold. Racks may be stacked side by side and therefore requireonly two side panels to stand singly or in baysOverall dimensions are: 771/2' H x 321/2' 0 x 22" W. Order as:
OPT Rack 1 Complete with removable side panels £335.00 (GIOPT Rack 2 Rack, Less side panels £225.00 (G)
32U - High Quality - All steel cabinetMade by Eurocraft Enclosures Ltd to the highest possible spec.rack features all steel construction with removableside front and back doors Front and back doors arehinged for easy access and all are lockable withfive secure 5 lever barrel locks. The front dooris constructed of double walled steel with a -
'designer style' smoked acrylic front panel toenable status indicators to be seen through thepanel, yet remain unobtrusive. Internally the rackfeatures full slotted reinforced vertical fixing mem-ber-: to take the heaviest of 19" rack equip -melt. The two movable vertical fixing struts(extras available) are pre punched for standard'cage nuts'. A mains distribution panel internal-ly mounted to the bottom rear, provides 8 IEC 3pin Euro sockets and 1 x 13 amp 3 pin switchedutilty socket. Overall ventilation is provided by-,(fulla louvered back door and double skinned top sectionwith top and side louvres. The top panel may be removed for fittingof integral fans to the sub plate etc. Other features include: fittedcastors and floor levelers, prepunched utility panel at lower rear forcable / connector access etc. Supplied in excellent, slightly usedcondition with keys. Colour Royal blue. External dimensions 64" H a25 D x 233/4" W
Sold at LESS than a third of makers price !!
A superb buy at only £195.00 (G)
Over 1000 racks in all sizes 19" 22" & 24"3 to 44 U. Available from stock !!
Call with your requirements.
TOUCH SCREEN SYSTEMToe ultimate in 'Touch Screen Technology' made by the experts -bicroTouch - but sold at a price below cost II System consists ofa flat translucent glass laminated panel measuring 29.5 a 23.5 cmconnected to a PCB with on board sophisticated electronics. Fromtl-a board comes a standard serial RS232 or TTL output. The out-put continuously gives simple serial data containing positional X & Yco-ordinates as to where a finger is touching the panel - as the fin-ger moves, the data instantly changes. The X & V information isgiven at an incredible matrix resolution of 1024 a 1024 positionsover the screen size !!! So, no position, however small fails detec-tion A host of available translation software enables direct con-nection to a PC for a myriad of applications including: control pan-els, pointing devices, POS systems, controllers for the disabled orcomputer un-trained etc etc Imagine using your finger in 'Windows'instead of a mouse II (a driver is indeed available !) The applica-,ions for this amazing product are only limited by your Imagine -'Ion!! Supplied as a complete system including Controller. PowerSupply and Data at an incredible price of only El,RFE. Full Software Support Available Fully Guaranteod 45.00 (B)
LOW COST RAM & CPU'SINTEL 'ABOVE' Memory Expansion Board. Full length PC -XTand PC -AT compatible card with 2 Mbytes of memory on board.Card is fully selectable for Expanded or Extended (286 processorand above) memory Full data and driver disk supplied In goodused condition fully tested and guaranteedWindows compatible. Order as: ABOVE CARD £59.95(A1)Half length 8 bit memory upgrade cards for PC AT XT expandsmemory either 256k or 512k in 64k steps. May also be used to fillin RAM above 640k DOS limit Complete with dataOrder as: XT RAM UG. 256k. £32.95 or 512k £38.95 (A1)
OFFERS1 MB x 9 SIMM 9 chip 120ns only1 MB x 9 SIMM 3 chip 80 ns £23.50 7Ons1 MB x 9 SIMM 9 chip 80 ns £22.50 7Ons4 MB 7Ons 72 pin SIMM module onlySPECIAL NTEL 486-DX33 CPU
£19.50 (A1)£26.00 (Al)£28.00 (A1)
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NO BREAK UNINTERRUPTIBLE PSU'SEMERSON ACCUCARD UPS, brand new 8 Bit half length PCcompatible card for all IBM XT/AT compatibles. Card provides DCpower to all internal system components in the event of power sup-ply failure.The Accusaver software provided uses only 6k of baseRAM and automatically copies all system. expanded and videomemory to the hard disk in the event of loss of power. When poweris returned the machine is returned to the exact status when thepower failed It The unit features full self diagnostics on boot and issupplied brand new, with full, easifitting instructions and manual.Normally £189.00 NOW! E69.010 or 2 for £120 (B)
revisededition TRANSMITTAT LAST. A comprehensive, easy to followguide to building short range transmittersand surveillance devices. Packed withuseful information and circuits.* Only £3.95 inc p&p.(Some of the circuits included cannot be used legally in the UK)
RADIO KITSAll kits come with pre -drilled PCBs and high spec.components.MICRO FM TRANSMITTER (a). 1km range. 80-100MHz
preset inc. mic., very small (2x3cm) £6.95MICRO FM TRANSMITTER (b). Variable mic. sens., tunable 90-110MHz.
1km range C7.95FM TRACKER. Transmits an audio tone for direction finding, tracking etc.
80-110MHz C8.50ULTRA MINIATURE FM TRANSMITTER. Runs off watch battery (inc). only1x2cm, 200mtrs range. 80-100MHz C8.95FM RECEIVER (a). Tiny high quality FM radio. Will drive headphones
direct (not inc) 010.90FM RECEIVER (b). As (a) but with 3 watt audio output and tuning LED 013.50CRYSTAL RADIO. Includes tuner, earphone, ferrite aerial, etc. C7.50AM RADIO. Single chip radio for headphones (not inc.) C8.90
AUDIO KITSAMPS 15 WATT General purpose upgrade
40 WATT High quality, HD 0.003%, switchon mute ideal for compact disc
150 WATT Rugged and powerful MOSFETdesign. PA/sound systems
PREAMPS ETCGE ERAL PURPOSE PREAMP. Variable gain 9-25V 40mV max in £4.00ULTRA LOW NOISE. For high quality mixers, mics etc 9-25V C4.50ACTIVE TONE. 12dB c/b bass and treble with variable gain C8.957 BAND EQ. 150Hz-18kHz for E0 units and tone control,
includes on -board preamp and pots. Variable gain 012.95NOISE GATE. Dynamic noise reduction system. Variable input
and cut oft level. Will accept instruments, tape decks etc C15.95MUSIC KITS. Full range of on -board units for guitars and other instruments.
Tone boosters, active circuits, delay lines, transducers. Send for list.Prices include P&P. Mail Order Only. Make cheques and postal orders payable to:
19CD DesignerFor Windows 3.1Runs on any PC runningWindows in standard orenhanced modewith 2MBRAM
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Produce Single or Double sided PCBs. Print out to any Windows supported printer. Toolbar for rapid access to commonly used
components. Helpful prompts on screen as you work. Pads sizes fully customisable. No charges for technical support. Snap -to grid sizes 0.111, 0.05" 0.025" and
unrestricted. SMT pads and other pad shapes. Positive reviews by Robert Penfold and Paul
!lease Note. Since PCB designer is so easy to use, and to keep costs down. PCB Designer has an On -Linemanual, in Windows Help format. A FREE tutorial is also supplied.
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WAYNE IC 8424 DORI Crane.. ON. TOR 0200
HP 16330 43 Orannree 1750SORENSEN DCF1800-4 513 0 . MO Vole 0 . 4 5Arery 1700H P 6240 40 Vols. 3020 1500
MARION TF2153 Anomie DC -I GH2 1100H P 849513 AlwArlor DC -180W 0 11dEl te 113 Steps 1350
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KeTFIELD 2105 Allerragor 50 Oran 115
TEKTRONIX TOR1502 0250R 15 Vero Now MM. UP502 wa, uPSF2E2 M°R 3 S Mode Tara. SMSFP2 0 4 10001.1712
00250
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Delay in.,:,.,'AMEG Ora -efts, out 7T.Iree G.., Ira., raw: or..., -trate m,.HU/CB OSCILLOSCOPE 114303 Duat irr< 302H7 Camp Rs., 1392MMEG OSCILLOSCOPE...2033 Per Trace Meg Deem Swine L853
Al rarar tragee awdeble . all aerate:ran Nees] we 12 probes
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Al rater Nora SW we rnere swede
6505r....°POLARAD 641 I 101-47U Wee £4°°ANDO AC8281 wet AC8211 170014147 £1500HP 182 AO BEMS 1001(117-15001Ati £1500H P 141T we 855413 6 IMPS 500.2- I 2500.4ra £1200H P 141T ara 836313 8 05520 1e4 -1102e 0300WV103141 TF2370 33111 110MN 11000H P lel Mew Fames c.,, Goon Tees 1700
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Used Equipment - Guaranteed Manuals supplied If possible.This IS a VERY SMALL SAMPLE OF STOCK SAE or telephone for lists. Please check availabilety before
ordering CARRIAGE all units [16 VAT to he added to Total of Goods and Carnage
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STEVENAGEProfessional Sub -Contract Manufacturing & Suppliers to theElectronics IndustryDo you have a requirement for any of the following services:PCB Assembly (Conventional and Product Design/ConsultationSurface Mount) Full Procurement ServiceWave & Hand SolderingComplete EquipmentManufactureDevice Programming from handwritten shts or PC 3V discCable Harness Assembly/loomManufactureCard Cage and Module W.ringFull Inspection
PCB Test & "Burn in" FacilitiesEnclosure Design & ManufacturePCB Artwork ManufactureCircuits Drawn ProfessionallyKit Procurement & SupplyComponent SalesRefurbishment a specialityTop Quality Work at ReasonableRates
Phone Tracey on (0438) 363406 or fax details of your requirements to uson (0438) 352742EOT LTD, Cromer House, Caxton way, STEVENAGE. HERTS, SG1 2DF
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We offer below a selection of our CVC PREMIUM range of audio valves. These CVC BRAND valves arefrom ;elected world wide sources, processed in our special facility to provide lownoise/hum/microphony PRE -AMP valves and POWER VALVES burnt -in for improved stability andreliability. Use this sheet as your order form. If yoU require matched pairs, quads or octects etc. Pleaseallow £1.00 extra per valve for this service and mark alongside the valvas required.
KT77 12.00 MATCHING CHARGESPOST & PACKING (UK)TOTAL. EXC. VATVAT En 171/2% (UK & EEC)TOTAL TO PAY
KT88 12.50 3.00
KT88 (Gold Special) 19.80
2A3 (State 4 Pin or Octal) 14.50
211 22.00 £
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6V6GT 5.00
6080 12.00
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7581A 11.00
807 8.00811A 10.50
812A 34.00845 30.00
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..}_rri;. fLIJJdJJ
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13) New London Road, Chelm3ford, E.:;:;ex r:;i1/12. E.ngland. Te/ephone 0-a24rj .'.35529(.J2G)865 or FAX.
Gun Centrahis fourth part of the light gun project covers thecentral renewal station. The station provides thecapability to organise different game types, toadjust the length of the games and toautomatically provide scores for individual players
and for the teams. It also allows light guns to be programmedwith their Identities which are stored in EEPROM in the light gunmicro -controller
The central renewal station consists of two pieces ofequipment: the central and the external display. The central providesthe processing capability for the game and has a keyboard andLCD display for game control and reporting. It also has a serialport which drives either the external display or a printer.
Last month we looked at a general description of the central
Robin Abbot continues his projectto build the light gun central unit forthe ETI Laser Tag game system, helooks at building the unit andwriting the software for it.
unit and how it works, and how it communicates with the playerunits. We continue with a look at constructing andprogramming the central.
Processor boardIt was decided to use a Z80 for the main processor of thecentral. This is a very cheap device which has plentifuldevelopment tools, and which is powerful enough for therelatively low processor load required in the central.Unfortunately, the relatively large amount of ROM and RAMrequired (14K of EPROM, 1K of RAM) prevents the use of anyof the readily available microcontrollers. The software for thecentral is written in a mix of assembler for the interrupt routinesand compiled C for the main functions of the central.
ENTER MONITOR 4
Fig.1 . Operation of the central
PRESS M
POWER UP
DISPLAY COPYRIGHTPRESS C
ANY OTHER KEY
SELECT GAME TYPE
SELECT GAME TIME
RECHARGE PLAYERS
PRESS ANY KEY
GAME RUNS
GAME END
PLAYERS DOWNLOAD
SCORES DISPLAY
ENTER PASSWORD(1986)
SELECT:
PRINTEREXTERNAL DISPLAYTEAM NAMESPROGRAM GUNS
ENTER GUN ID
INSERT GUN
ELECTRONICS TODAY INTERNATIONAL60
Byte1
Name
Start flag
Value (Hex)AA
NotesA'ways has the value AA, shows start of packet
2 Type 00-01 00 for a renewal packet01 to program the gun ICFor ID packets bytes 4 to 9 are set to CO
3 Shots 00-FF Number of shots per lifeFor an ID packet this the ID of the gun to procramFor ID packets bytes 4 to 9 are set to 00
4 Timelo 00-FF Lower byte of game time left in seconds5 Timehi 00-FF Upper byte of game time left in seconds6 Game type 00-07 Type 0 is normal
Type 1 is warriorsAll other types are spare
7 Lives 00-7F Number of lives for userNole numbers greater than 1F(Hex) are used only forspecial purposes, as the number of lives transmitted fromthe gun to the central is limited to 5 bits
8 MRC 00-9F ID of the most recently renewed user used to acknowledgetie gunBlt 7 if set shows that this user is a warrior
9 MRCBUT1 00-9F As MRC for the most recently renewed user but one10 Checksum 00-FF 8 bit checksum - lower 8 bits of the additive sum of bytes 2
to 9 (does not include start flag)
Fig.6. Renewal packet from central to guns
The processor board is based on the Forth single boardcomputer presented in ETI in the April 1994 issue. To recap,this board offers the following functions:
Z80 running at 3.7MHz 32K of EPROM 32K of battery backed RAM Two 10 bit output ports Two 1) bit input ports Bi-directional serial port
For the central only one input and one output port are used.The serial port is used to communicate to the external displayand the printer; it was also used to connect the monitor usedfor development. Regrettably, it is not possible to omit the serialport drive- IC if no external devices are in use because theunderlying monitor used in the central checks the serial portduring initialisation and will not proceed if it is absent.
The circuit has been modified from that shown in the originalarticle, and the modified circuit diagram is shown in figure 7.Please refer to the original article for details of the mainoperation of this board.
The modifications are concerned with the use of interrupts.The driver for the serial port used in the central requiresinterrupt operation to provide a bi-directional buffer andXON/XOFF signalling. The transmit and receive ready signalsfrom IC10 are combined by a spare OR gate in IC3 witn anopen collector output which drives the interrupt pin of the Z80directly. There is also an additional interrupt input provided forthe interrupt signal from the auxiliary board. This interruptoccurs every 1/16th of a second and is used in normaloperation for timing purposes and to trigger communicationwith the guns and bases.
There is one other important modification to the board - IC7.This is because the original board used a simple decodingscheme for I/O devices. IC7 enables the peripheral deviceswhenever the IORQ line from the Z80 is low, there is nodecoding of the read and write signals from the Z80. This isnormally acceptable - a read from one of the output ports willwrite a spurious value to the port, but as the input and outputports are at different addresses then they never need TO be readin practice.
However, when interrupts are used in the Z80, the processorprovides a special interrupt acknowledge cycle when IORQ isdriven low without WR or RD going low; this will write spuriousvalues to the output ports. To correct this, a new decodingdevice (10100) is included for the output ports.
The serial chip (1010) is p-ovided with its own decoding forread and write signals and is not affected by the interruptacknowledge cycles.
The other modifications to the card are that the serialconnector is now a 9 -pin device mounted off the board, there isa diode connected in series with the power supply (one reverseconnection to the power supply - and an open circuit regulatorwas enough!), and the reset button is mounted on the case.
SoftwareThe operation of the complete software is too complex forreview here. However, a brief consideration of the mechanismsused whilst the game is running may be of interest.
The Z80 is interrupted 16 times a second. This is used tokeep time during the game. On even interrupts the renewalpacket is transmitted to the guns, and on odd interrupts theZ80 will accept messages f-om any guns requestingtransmission. Any messages from the bases are built up overseveral seconds, the interrupts count the length of The data bitsto decode the message. Interrupts also read keypresses fromthe PIC and buffer them for use in the main program.
The main program runs in a loop which waits for the passingof a second to update the main display. In addition, when aninterrupt routine detects an incoming message from a gun or abase, it sets a flag wnich enables processing of the message inthe main program. On receiving a message from a gun therenewal packet is updated with the ID of the gun, and thechecksum is recalculated. The refreshed renewal packet is sentto the gun on the next interrupt.
The central keeps a record of all the players in the gamewhich is used to generate the secret agents and warriors, andto ensure that all the players have downloaded at the end of thegame. The player record maintains a list of all renewals and acount of the total lives used by a player. The team scores areupdated and displayed during the game, the player scores arecalculated at the end of the game. The scores are shown at theend of the game and updated once per second.
ELECTRONICS TODAY INTERNATIONAL61
Auxiliary boardThe auxiliary board provides the following functions:
Writing to the LCD display. The drive to theLCD module is fairly complex and requires adelay between commands which is as mu:has 4mS. The processor on the boardimplements a buffer for commands written tothe module.
Scanning the keyboard and translatingkeypresses andshift keys to ASCII codes. It also debouncesthe keyboard, and provides auto repeat if keysare held down.
Driving and flashing the LEDs. providing a 1/16th of a second interrupt to
the main board.
The auxiliary board is mounted in the top of thecase and all of the peripheral devices are connectedthrough it. This allows the main board to bemounted in the base of the case, and there is onlyone cable connection to the main board for all thefunctions of the central.
The auxiliary board is based on the PIC16C57micro controller (well we had to get one insomewhere!); its circuit diagram is shown in figure 8.This processor has 80 bytes of RAM which issufficient to buffer commands to the LCD module.
The LCD module is driven by port C, bits 1 to 7.The LCD module is set into 4 bit mode to reduce theI/O requirement on the PIC.
The keyboard consists of four rows and fivecolumns. Resistors R16 to R19 prevent dualkeypresses from causing excess current drain if ahigh and low output are connected together. Thered and green LEDs are driven by two of thekeyboard outputs (they are not driven duringkeyboard scanning, but this occurs only briefly every16th of a second and is not perceptible).
The interrupt output on RB5 drives the mainboard through TR4. This is to provide an opencollector drive, allowing interrupts from the auxiliaryboard and the serial port to be "wire -oar's" on themain processor card.
The two wire communication to the Z80 card isprovided on port bits RCO and RB7 of the PIC andprovides bi-directional communication andtransmit/receive request and acknowledgement.This is used to send commands and text for thedisplay module, to read the keyboard, to control theoperation of the LEDs, and to release the interruptsignal from the Z80 when the interrupt routine isexecuted. The scope of the operation of theprotocol between the Z80 card and the auxiliaryboard is too extensive for this article, but full detailsare available from the author.
The other components on this card areconcerned with the communication with the gunsand the bases. Note that all connections to theguns and the bases run through theauxiliary board.
IN
OUT
VCC
CENTRAL
Fig.3. Simplified renewal circuit
RING
TIP
GND
RING
TIP
GND
O
0-01
R12 1k7-I 0
0
O
GUN 2
SEAR
SERH
RX
SERR
SERH
RX
PIC
SERH
SERR HiZ
RO ACK
RINGLINE
[
1 REQUEST TX
TIPLINE
LSB
UnS 1 mS 1mS
MSB
nS lmS lmS
HiZ
_HiZ
HiZ I,msl HiZ
REQUEST ACK
PROTOCOL FROM GUNS TO CENTRAL
LSBSTART BIT
00uS 100,S
MSB
PROTOCOL FROM CENTRAL TO GUNS
Fig.4. Serial protocols
100uS 00uS
STOP BIT
ANBO2
FSGT4 5
KXL Y
7 8Shift
0Fig.11. Keyboard overlay
C P
3D Q
Yes
HU6
I VDel1-
M Z
9Shift
ERNo
J W
Space4_1Enter
ELECTRONICS TOD6
Y INTERNATIONAL
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ELECTR DNICS TODAY INTERNATIONAL63
ConstructionThere are two boards to construct in the central. The first is themain processor board, and the second is the auxiliary board.
The main processor board should be constructed with careas there are many narrow tracks. Our problem with the mainboard was very small track breaks which are extremely difficultto see. The overlay for the processor board is shown in Figure9. This is built in the same way as in the original article exceptfor the modifications. Cut the circuit board tracks from IC7 pins14 and 15 as close to the IC as possible. Drill holes in the boardabout 0.2" from IC7 to allow connection to the tracks whichhave just been cut. Drill small holes by IC10 pins 14 and 15,102pin 27, IC1 pin 16 (by R2). and IC3 pins 8,9 and 10. Be careful
not to cut any existing tracks.Fit all the wire links. Do not fit the RS232 socket, but fit
veropins into pins 1, 2 and 3 of the position for the socket.Now consult the circuit diagram whilst making the following
modifications.
Solder IC7 directly into the board. Now take a74HCT138, or a 74LS138 (IC100) and carefullycut off pins 9,10,11,12 and 13 at the IC. Bendpins 4,14 and 15 horizontally. and cut these pins sothat about 0.1" of the pin is left on the IC.
Fit IC100 over IC7 and solder the remaining pins ofIC100 to IC7.
onnonc-InnnIC 1 2
C./ u IJ U t.) U LI
+ . .
POWER9V DC
C3 C2
D2
CONNECT DI
I. I
Fig.9. Component overlay for main processor
I C17 1
SW1
RS232
Wire IC100 pins 14 and 15to the tracks whichoriginally connected toIC7 pins 14 and 15. WireIC100 pin 4 to IC2 pin 27.
Wire IC3 pin 8 to IC10 pin15 and 1C3 pin 9 toIC10 pin 15.
Wire IC3 pin 10 to IC1pin 16.
Fit a veropin andconnect to IC1 pin16 for the interrupt input.(We cut the copper landunder X1 in two, anddrilled two holes in thenow spare land, one forthe pin, and one for theconnection to IC1.)
Cut the track from thepower supply positiveinput, drill two holes andfit D100 in serieswith the positive input.
Fit veropins in the hole forthe reset switch (SW1).
Superglue the longer wirelinks to the board. Fit allremaining components, socketall remaining ICs, noting thatIC11 and IC12 are not fitted.Glue XL1 and the heatsink forthe regulator to the board usingsilicone rubber. Do not connectthe batteries or fit the ICs yet. Toincrease confidence in theconstruction it is worthchecking all of the narrowtracks for continuity.
The auxiliary board has widertracks and is slightly easier tobuild; its overlay is shown infigure 10. Please ignore thecomponents shown in thebottom right of the layout and theprototype card which areintended for later expansion.
There are three wire links, fitthese first. Fit a socket for 101.Resistor networks RN1 and RN2
RESET BUTTON / -12V MAIN SUPPLY RED BASEPHONO SOCKET
SERIAL LINK (PRINTER/EXTERNAL DISPLAY)9 P'N RS232 GREEN BASE
+12V - TO EXTERNAL DISPLAY PHOND SOCKETFig.12. Connectors on rear of case
ELECTRONICS TODAY INTERNATIONAL65
are made up by mounting resis-tors vertically and soldering to atinned wire connected across the other pins of the resistors anddown to the common connection.
The keyboard is supplied with its own connector PL2 whichcan be mounted directly to the PCB,. However, the keyboard tailis very short and we had to fit an extension on a small piece ofveroboard. PL2 is fitted so that the connectors are closest to101, Pin 1 of PL2 is the pin which connects to the keyboardtrack with no connection to any of the keys. The IDC connectorsPL1 and PL5 are fitted with the slot facing away from 101. PL1 isa 16 -way connector; remove two end pins to make it a 14 wayconnector. When fitting the IC sockets for PL3 and PL4, notethat pin 1 is the opposite direction from 101. Fit veropins for theLEDs and the interrupt output. Also fit the two veropins for thepower supply for testing.
Physical construction and cablingConsult the circuit diagrams throughout all the stages of wiringup the case. Photograph 1 shows the inside of the top of thecase. We used a plastic case 22x15x6cm. All of the connectors,the auxiliary board, the keyboard and LCD module are fitted intothe top. The serial connector, two power sockets, the baseconnector and reset switch are mounted at the back of the caseas shown in figure 12.
The keyboard is glued to the top of the case and the tail fitsthrough a slot cut in the top of the case. The keyboard isassembled by copying the overlay (figure 11) and gluing it betweenthe membrane and the mask which fits on top. As for all otherparts of the project silicone rubber is extensively used here.
Use an IDC connector for the LCD module; again remove thesame 2 pins as from the connector PL1 to convert theconnector to 14 pins and solder to the module so that theconnector protrudes behind the display; the slot points away
Pt
CIiC4 C2 RN2
VCCII
from the ICs on the back of the module. The LCD module isfitted into the front of the case and a hole is cut to view themodule from outside the case.
The two renewal sockets are fitted into opposite sides of thecase, flanked by one of the green and one of the red LEDs oneach side of the case. The renewal sockets are wired to PL3,common, tip and ring are wired directly to each other. Toconnect the renewal sockets, we used an IC socket and wiredthe renewal sockets directly to it; the IC socket plugs directlyinto PL3. In similar fashion, the phono sockets for the basecommunication links are wired to PL4. The LEDs and interruptline are wired directly to the veropins.
The main board is mounted on the bottom panel of the case.The two power sockets are wired directly to each other to allowthe external display to be powered. The sockets are thenconnected to the supply pins on the main board. The serial portconnector is a 9 pin socket; pin 2 of the socket goes to pin 3 ofthe connector on the board, pin 3 of the socket to pin 2 of theboard, and pin 5 of the socket to pin 1 on the board. The resetbutton is wired to the veropins which replace SW1.
Now use IDC connector cable to make up two data cables.The 16 -way lead from the auxiliary board to the LCD moduleuses IDC connectors which are pressed onto the cable with avice, or a large pair of pliers. Make sure that the red stripe on thecable goes to the left when the slot is held pointing downwardson the connectors. The lead from the Z80 card to the auxiliarycard is made up with 20 -way cable. Connect to the IDCconnectors so that the red stripe is to the left when the slot isheld downwards. On the other end of the cable, split the cablein half and wire the two 10 -way connectors so that the half withthe red stripe connects to the plug by IC9 with the red stripenearest pin 1 of IC9. The 11th wire of the cable (the first wire ofthe second half of the cable) is wired to the second connector
-1 n6 H-i R7 I-
PL2
Fig.10. Component overly for auxiliary board.
RV1
O04
INTERRUPTOUT
RED LED
GREEN LED
LED COMM.
ELECTRONICS TODAY INTERNATIONAL66
nearest pin 1 of IC8.The renewal leads are two back to back 3.5mm jack plugs.
They are connected using lm 3 -way coiled cable. Use the bestpossible construction technique for this cable as it will besubjected to considerable strain. The power supply leadconnects to spade terminals for a 12v sealed lead acid battery.
Testing and Set-upDo not insert any ICs yet. Connect only the cable from theauxiliary board to the LCD module. Do not make the connectionfrom the main board to the auxiliary board. The auxiliary beardhas a diagnostic mode to assist set-up independently of themain processor. Connect a 10K resistor from the end of bothRE and R7 (it doesn't matter which end) to +5v so that pins 17and 18 of IC1 are pulled up.
Use a multimeter to check that the frame of the LCD moduleis connected to pin 4 of 101 confirming that the power supply to
Main Processor Board, Parts ListResistors R1 1K5 R2,3 10K
Miscellaneous Battery holder Heatsink IC sockets 2 x 10way SIL plugs & sockets Veropins 2 x AAA batteries
Auxiliary Board, Parts ListResistors R6,7,15 10K R8,9,10 1K
R12 4K7
R13,14 56R
the LCD is correct. Do not connect 101 yet and wire theauxiliary board to +5V using the two veropins. The LCD moduleshould have one of its rows slightly darker than the other, thiscan be varied with VR1. Check the power supply to 101. Powerdown, insert IC1 and power up again. The display wil, show"OK!" Now check that if keys are pressed then the letter ornumber of the key is shown for 1 second in the bottcm right ofthe display. The letters are accessed by pressing the shift keys.Finally, check that the interrupt output on pin 15 of IC1 isproducing an 8Hz square wave (use an oscilloscope or analoguemultimeter); this is the diagnostic mode which indicates that themain processor is not communicating with the auxiliary card.
Now oisconnect the power supply from the auxiliary boardand the two resistors connected to R6 and R7. Connect themain 12V power supp'y and check that the main card has +5vat the correct pins on the ICs. Disconnect power. Now insert allthe main card ICs and the cable from the main board to the
R16,17,18,19 RN1 RN2 VR1
Capacitors C1,2 C3,5 C4,6,7 XL1
470R
4x1OK
4x10K10K
51pF
100uF
100nF
4.194304MHz
IC1 PIC16C57/XT-P TR1 BC557 TR4 BC547 LD1,2 Red LEDs LD3,4 Green LEDs
Miscellaneous PL1,5 PL2 PL3,4 Veropins
16 way IDC socketKeyboard connector16 pin IC sockets
Case & Connectors 20 way IDC 50cm 16 way IDC 50cm Coiled cable 2m
For full information, please write, phone or fax: -
Number One SystemsUK/EEC:
USA:
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auxiliary board. Check that the power supply pins on the ICs onthe main card are connected to the correct power pins on ,C1of the auxiliary card. This will confirm that the cable has beenwired correctly.
Connect the main power supply, wait for about 1 secordand the base should spring into life! Use light guns and basesto confirm operation in accordance with the instructions shownat the start of this article. Check operation of the LEDs aloboth renewal sockets. Note that to use the central the gunsshould be powered up in normal renewal mode. This isachieved by removing the power recharging plug from the gunwhilst NOT holding the gun trigger down. Remember that, untilprogrammed, the guns will all have an ID of Red 8.
To use a printer or an external display then enable them inthe configuration menu.
Finally fit the AAA batteries for RAM backup and confirm thatthe selected configuration is held through power down. Adjustthe contrast of the LCD with VR1.
If at any point in testing the base cannot be made to operateas expected then check power supplies to ICs, and check forcontinuity and ensure that there are no short circuits.
Other InformationSome of the HC and HCT devices specified in the componentslist for the main board can be very hard to obtain (in fact I'm notsure that the 'HC92 has ever been manufactured). With tneexception of IC3 and IC4 they can all be replaced by LSdevices with no penalty except for power consumption andnoise immunity - use HC/HCT devices wherever possible.Viewcom electronics are happy to sell to the hobbyist, and
stock nearly all of the devices and the crystal on the main card- 0181-471-9338. The PIC, LCD module and keyboad areavailable from Maplin - 01702-554161.
If a printer is used then it must be set to 9600 bps, 8 bit, Noparity. Select XON/XOFF signalling. If it cannot be made tooperate then try swapping pins 2 and 3 over in the caole. Reme-mber the printer must be selected from the configuration menu,and will only operate to display scores at the end ofthe game
If the base is used at night then a backlit LCD module maybe used. This requires a 5v supply connected at the rear of themodule at the opposite end to the data connector. This shouldbe connected to the main card power supply near Theregulator. However backlit LCDs are considerably moreexpensive than the normal modules.
The game type control is table driven and the author wouldbe pleased to accept suggestions for modifications,enhancements, or new game types within the limitationsimposed by the operation of the guns.
SoftwareThe author is prepared to program the EPROMs and PICs forthis project. Send erased 27C256 and PIC16C57/XTP devicestogether with a return SAE (at least A5) and a cheque for£20.00 to Robin Abbott, 37 Plantation Drive, Christchurch,Dorset, BH23 5SG. This includes fuller details on the operationand player scoring of the central and an explanation of theareas of protocols not covered in this article. This will enablefurther aevelopment and experimentation.
Seetrax CAE / Ranger / PCB DesignRanger 1 / £100Schematic capture linkedto PCB.Parts and wiring list entry.Outline (footprint) libraryeditor.Manual board layout.Full design rule checker.Black annotation(linked to schematic)Power, memoryand signalautorouter,£50.
Ranger 2 / £599All the featuresof the Ranger 1, plus,Gate and pin swapping(linked to the schematic).Track highlighting.Auto track necking.Copper flood fill.Power planes(heat relief and anti -pads).
Rip -upand retry
autorouer.
Outputsto:
Ranger 3 / £3500All the featuresof the Ranger 2, plus,UNIX or Dos versions.1 Micron resolutions andangles to 1/10th degree.Hierarchical or flatschematic.Unlimited design size.Any -shaped pad.Split power planes.Optional on line DCR.100% rip -up and retry,push and shoveautorouter.
Seetrax CAE / Hinton Daubnay House / Broadway Lane / Lovedean / Hampshire / P08 OSG.Call 01705 591037 or fax 01705 599036 for further information / demo packs.All systems upward compatible. Trade deals availaole. All trademarks acknowledged.
ELECTRONICS TODAY INTERNATIONAL69
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FOILS FORTHIS ISSUE
Bicycle Loop Alarm
Switch Regulator
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00
0 0
Light gun central
0001 0000000
i It111:1 I °
1-00of CO
gea 0 00 0 000000000000000
00 000 0
o o 0 0Or
CO
Channel Touch Switch
ILO
ELECTRONICS TODAY INTERNATIONAL71
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SEWING MACHINE MOTORBrand new 220/240v AC/DC SEW-TRIC 2 lead BrushMotor. Size L 100mm x H 70rnm x W 55mm Spindle1/4in die x 1,0 long E14.10 incl. P&P & VAT
GEARED MOTORS71 RPM 20Ib inch torque reversable 115V ACincluding capacitor and transformer for 240V ACOboe. Price Inc VAT & pap 227.73
SOLID STATE EHT UNITInput 230/240V AC, Output approx 15KVProducing lOrnm spark Built-in 10 sec timer.Easily muddied for 20sec. 30 sec to continuous.Designed for boiler ignition Dozens of uses in thefield of physics and electronics. eg supplying neonor argon tubes etc. Price less case 221.50 E2.40pap (C12.81 Inc VAT) NMS
EPROM ERASURE KITBuild your own EPROM ERASURE for a fraction of theprice of a made-up unit kit of parts less case includes12in 8 watt 2537 Angst Tube Ballast unit, pair of bi-pinleads, neon indicator. ortioff switch. safety microswitchand circuit C15.00 4. C2.00 pap (E19.98 inc VAT)
WASHING MACHINE WATER PUMPBrand new 240V AC fan coded. Can be used for a u:r,ety of purposes. Inlet Ilan. outlet 1 n. die. Price inc tr
p&p & VAT £11.20 arch or 2 for 220.50 inclusive
MICROSWITCHPye 15 amp changeover lever rnicroswi ch, type SI71Brand new price 5 for E7.05 inc VAT & pap
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EPROMS PLDs + MICROCONTROLLERS copied orprogrammed. We supplydevices/convert discrete logic toPLDs. PLDs for ETI PC PostCard supplied at £10/P.C.B. £12.PO Box 1561, Bath 0225 444467.
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ELECTRONICS TODAY INTERNATIONAL73
Open Forumhe British government, in the form ofScience Minister David Hunt, haspublished the first of a series ofreports which forms one of thecentral components of what has
been grandiosely entitled the TechnologyForesight Programme. The report contains acollection of futuristic ideas: the first five coverhealth, transport, financial services, chemicals,and construction. Another ten reports coveringother areas are due to be published shortly.The reports have been produced by a team ofacademics and industrialists under the auspicesof Hunt's Office of Science and Technology, andare designed to enable industrialists to identifymarkets and technologies which are likely to bemost lucrative over the next twenty years.Crystal ball gazing is always fun, and I am surethat the authors of these reports enjoyedthemselves greatly, but do we really want toreturn to the days of government -directedresearch and industrial development. I am surethat the readers of ETI, who are actively involvedin science and technology, can see theenormous flaws in this development, howeverwell intentioned.The areas of greatest commercial potential in thefuture are all too often those areas which defyidentification. Only a few years before YuriGagarin's first flight, eminent scientists were stillsaying that manned space flight was impossible.When Intel developed the first microprocessorchip for use in calculators and process controlequipment, very few people even remotelyforesaw the rise of the personal computer industry.With all respect to the individuals involved,academics are notoriously poor judges of whatwill be a commercial success, as for industrialists,I am sure that if they see a good commercial ideathey will keep it to themselves rather than tell thecompetition about it. Then of course we come topoliticians and civil servants. Here I am afraid thatthe level of ignorance about science andtechnology is, in my own experience, horrendous.We cannot take these reports seriously. They arean interesting read, but they cannot beconsidered as a science and technology roadmap to the future. When it comes to thecommercial application of science and technology
the future is far too complex, full of far too manyunforeseen events and interactions to be putunder the direction of a government committee.The only way to develop the science andtechnology that will be the basis of tomorrow'sindustries is to give scientists, engineers, andindustrialists a free rein. Mistakes will be made,money wasted, but in the long term the successrate for this approach will be infinitely better. Letscientists and engineers follow their instincts, todiscover whatever there is to discover, and letindustrialists use their judgement about whatmakes a commercial success.Instead of attempting to direct science,technology, and industry, the govemment shouldbe trying to make it easier for people to exploitnew ideas and developments, and turn them intocommercial products. This includes betteraccess to funding, better tax allowances for R&D,better education of scientists and engineers inthe workings of business and finance, and ofbusinessmen and accountants in some of themore general aspects of science and engineering.Let us try and create a culture in this country ofthe successful scientist/ engineer/ businessman,where the man at the top can talk to financiersand research scientists with equal ease.Instead of pointing at certain ideas as being theboom industries of the future, the governmentshould be improving the flow of informationbetween scientist and industrialist, and vice versa.The government should, for example, be fundingthe translation of foreign language researchpapers. Why are we all too often so ignorant ofresearch work, and industrial development, thatis going on in Russia, Japan, China, India, andeven our close EU neighbours such as Franceand Germany.Take the case of shape memory alloys featuredin this issue, we have been able to find out plentyof information about what has been done inAmerica, since we share the same language. Butthe enormous amount of published work fromJapan and Russia, is closed to most of us, andyet may well contain information which could bethe basis of an enormously successful product.If such information was easily available intranslation, then who knows what potentialcommercial successes might be uncovered?
Next Month...In the July 1995 issue of ETI we conclude the laser tag system with construction of a
large character score display board. We feature another of Richard Grodzik's add-onboards for his 80188 single board computer project, an analogue input. We will alsocomplete Robin Abbott's PIC programmer project, and Dave Bradshaw's practicalintroduction to switch regulators
We continue our series of projects built around the Parallax Stamp computer with alook at building a range of versatile pulse measurement system that will connect to yourPC. We will also be continuing the series of projects by Bart Trepak which use the PICmicrocontroller.
From Terry Balbirnie there is a practical look at a novel technique for making printedcircuit boards. The main feature article will look at one of the most successfulmicroprocessor designs of the last couple of years, the British designed ARM chip, andat some truly revolutionary future developments from this world leading Cambridge hightechnology company.
ELECTRONICS TODAY INTERNATIONAL74
ELECTRONICSTODAY INTERNATIONAL
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