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Build this unit into your next power supply project A general-purpose 31/2-digit panel meter Looking for a general-purpose 3½-digit panel meter that doesn't cost the earth? This unit has switchable decimal points and can be built to read either current or voltage. By DARREN YATES There are many situations where a moving coil meter just isn't accurate enough. For example, have you ever tried to set a power supply accurately when using a moving coil meter? You've probably found that you were about half a volt out if you bothered to check it later with an accurate digital voltmeter. And when you're working with TTL circuitry, any inac- curacies can spell the end of an IC or two. Of course, there are still places where moving coil meters are useful, particularly when you wish to see the rate of change in a voltage or current. But for accuracy and precision, a digital panel meter module is definitely the way to go. Building this panel meter is straight- Power for the 3½-digit Panel Meter can be derived from a 9V battery or from any convenient 9V rail. By changing a few onboard components, the unit can be configured to read voltages up to 200V or currents up to 2A. forward thanks to the use of an Intersil ICL7106 3½-digit A/D converter IC. In fact, many digital multimeters are built around this very IC. The manufacturer takes the basic chip and adds extra circuitry and switching so that the multimeter can read resistance, voltage, current and capacitance over several ranges. This project is essentially a stripped down multimeter that can be customised as a panel meter to read voltage or current. By simply selecting a few resistor values , the unit can be configured to read any voltage up to ±200V DC and currents up to 2A (actually 1.999A). There are many potential applications for the unit. For example, it could be built into a variable power supply for monitoring voltage or current (or both with suitable switching). It could also be used to display the output from a transducer in an industrial application (eg, temperature measurement). You could even use it to monitor the track voltage of a model railroad layout or as a car voltmeter to monitor the charge on the battery. Inside the 7106 Let's take a closer look at the internals of the 7106 3½-digit A/D converter. Essentially, the IC has everything necessary to make a simple 3½digit LCD meter. It has 7-segment decoders and drivers a 4-digit counter, a voltage reference, a clock circuit and an AID converter all built into the device. The AID converter is based on the dual-slope conversion technique. This technique relies on charging and discharging an integrating capacitor, and allowing a counter to count up during the time that the capacitor voltage is 78 SILICON CHIP ,l; tl. 'I" 10 + 9V : 16VWI _,_ + IN !'._UT ·1 - Rx1 35 32 1M Ry2 15 A1 e114 3 C1 01 2 36 REF HI VR1 10k Rx2 o-Ry1 1 15k .,. RA REF LO E1 8 F1 6 COM 31 IN HI .01: 61 7 A2n2 = 30 IN LO 0-- 82 11 CREF 01L 34 IC1 7106 C 10 9 02 E214 F213 38 OSC3 100pF: = 100k 62 25 A3 23 39 l,o OSC2 B316 4o OSC1 29 A/Z ... o.47: : *47k *SEE TEXT 28 BUFF 0.22:: 27 INT BP 121 TEST 37 29 C3 24 11 03 15 10 E3 18 9 F3 17 31 63 22 32 K19 3 y 20 2 -!;6 l1 ~6 13 14 15 124 25 23 22 n1 na 1~ 120 21 r-e/ / / /- / 3-1/2 DIGITLCD A K _v_ K/ F/ 6 E,-::, ,-, ,-, •-OP3 OP2 •2 DP1• 1OP3 8 np? 12 DP1 16 1 38 39 40 +9V ,_J4 4070 ◄ 3-1/2 DIGIT PANEL METER 7 ~" - ~~ 5,- ~)1c2~ 6'8·- 4 fr--"~ _/ .... - ----=l~ 9· ' '-- 100k~ 100k3 100k Fig.1: the circuit is built around an ICL7106 3½-digit AID converter IC which has its digit & segment driver outputs linked directly to the LCD. XOR gates IC2a-lC2d buffer & invert the backplane signal to drive the decimal point. above a set threshold level. When the voltage falls below this threshold level, the counter is stopped. Because the capacitor discharge is linear (it forms part of an integrator circuit), the counter reading is proportional to the input voltage. It's then just a matter of scaling the reference voltage so that the reading is correct. The external components on pins 38, 39 & 40 set up the internal inverters to provide the clock signal. This clock signal controls the timing of the digital logic and is applied to the conversion section as well. When the output of the final comparator stage in the A/D converter is set, the 4-digit counter counts up at the rate of the clock frequency divided by four. When the comparator output is subsequently reset, the internal latch stores the current reading and loads it into the 7-segment de- coders and the LCD phase driver. The phase driver now supplies a square wave signal to the appropriate segments of the LCD. At the same time, a backplane signal is applied to the LCD from the divide-by-four output of the clock and a further divideby-200 stage. Circuit details Fig. l shows the complete circuit details. As you can see, most of the connections are between the 7106 IC and the 3½-digit LCD. ICl contains a number of inputs that can be varied to allow the meter to do different things. Of particular importance is the internal reference voltage (VREFL which is set by the external 15kQ resistor and trimpot VRl. The internal oscillator frequency for ICl is set by the lO0kQ resistor and the l00pF capacitor on pins 38, 39 & 40. These components give a clock frequency of approximately 48kHz, which produces a rate of three readings per second. In addition to the clock setting components, IC1 also requires three external components to set up the AID converter and provide the auto-zeroing function. The 0.47µF capacitor on 'pin 29 sets the auto-zeroing, while the 47kQ resistor and 0.ZZµF capacitor set the integration time constant for the AID converter. These last two components also set the noise immunity of the IC and should be changed for different full scale voltages. Decimal points Because the 7106 IC does not have the necessary drive circuitry to support the decimal points on the LCD, SEPTEMBER1992 79 ► Phone Your Order To Us Toll Free We guarantee our Jetservice Courier will deliver to 'your door faster than any other Australian supplier (including that local supplier just up the road). If we fail, I'll give you your money back plus $5.00 for your inconvenience. 2 Sector Alarm System Kit Here's a simple project that monitors the power drawn from a 'master' socket and automatica ll y switches o n a 'slave ' socket. It wil l monitor one or several appliances plugged into the 'master' and switch on o ne o r several devices plugged into the 'slave·. Ideal for Hi-Fi's or co mputers w ith peripheral hardware. K6070 $59.95 Solar Generator Kit (ET I Dec '87) Charge Your Batteri es Free Fro m , l ~· c The Sun. T he So la ~ Generator charges and maintains your standa rd 12V lead .· acid ca r battery via the sun. Ideal for boats, caravans and remote data acquisition stations etc . Must be used in co njunction with a suitable solar panel. Four Digit Combination . Lock Kit K 1925 $44.so (EA March/April '89) Features : • Includes 12V 1.2 Amp hour inbuilt sealed leadacid backu p batte ry • E.!sy to build , assembles on a single PCB • Two sectors delayed and insta nt inputs • Entry and ex it delay • Panic alarm input• Line monitoring • Soft pre alarm • Lamp te ll -tale output • Auxilliary relay for external siren etc • Key switch operation • Operates on vi rtua lly any type of sensor (SC Dec '90) This 4 Digit Combination Lock is bound to prove useful in many applications. Such as accessing alarm system s, e lectron ic doors, ignition ki llers or just about anyth i ng that comes to mind. Momentry or latched relay output. New 4-Channel Lighting Desk (SC June/J ul y '91) M■k• your at■ge production • profeulon■ I lhow with thla new Lighting Mixer. ldHI for amateur thHtre groupa band• etc. This 4-chan nel lighting desk is intended for theatre, disco and music group applications. It has heavy duty circuitry and is able to cope w ith spotlig hts rated up to 1000 watts or more. It has been designed and b uilt for the rigours of commercial use . You can flash each channel up to any brightness as set by the 'Flash Master' fader. Similarly, the 'Channel Master' cont ro l fades all lights up or down , to or from their individual fade settings. Two chaser faders co ntro l the rate and lamp brilliance when the unit is operated in chaser mode. The lights can be flashed to fu ll brilliance or to an intermediate setting as set by the 'Chaser Master' K1910 $89.oo _. 4 Channel Guitar Mixer & Preamp Kit K1680 $13.95 (SC Jan 1992) T his project takes advantage of the ~~:~~w fader. ... low cost •· . •· •i• · •· ••• ,. ,. • .-.-11P1- rw, ""'B ,,,...a'"'b _ y.....,R ,,,...o_o _m _""'M ,..,,..o - n""'i""'t_o_r_-4 ;~~~~~i "ltter features separate bass, midrange and & FM Transm trebel controls, very low noise and Kit a: ~~ -. 0 OABVAOOM This Baby Room ~QN.!JO_ R Mon itor all ows you to liste n to your baby from a remote location using a conventional FM receiver. It runs from a sing le 1.SV AA battery and incl udes a muting facility so that it only transmits sounds above a certain level. K 1180 .95 $ 24 Ni-cad Battery Discharger Kit Designed to rid yo ur ni-cad batteries of the 'memory effect' and rega in fu ll re -charge pote ntial. It discharges your nicad batteri es correctl y to enable a fu ll and p roper re-charge. Suits most battery packs. Great for mobile phones, rechargeable dr ills, re m ote co ntro lled toys etc. K1640 $24.95 I i:~~o~t~o~~t;t1a1r:::1i~g~:r~~~T~i~,n,~~ ~se with most musical instruments from keyboards to guitars to tape decks. In fact, you can feed it with just about any audio signal - it's not just lim ited to gu itar outputs. K5535 $49.95 Transistor Tester Kit K5815 Normally $3?,0'.'oo T h is Month $299 .00 Playmaster "Pro Series One" High Power Mosfet Amplifier Kit (EA Dec '89/ Jan '90) K $599 5070 This design has been carefully developed to produce a high definition audio output with reliability, ease of construction and low cost. Kit comes complete with all components, toroida l tra nsforme rs and case. Features: • Individua l toroidal transformers for each channe l f:Jr low residua l hum • Mosfet tec hno logy for ultrahigh performance• Power Output of 140W RMS into 8 Ohms. Studio 200 Stereo Control Unit Kit (SC June/ Ju ly '88) K5015 $229.oo Outperforms Commercial Unit• Coating $600 Or Morel The Studio 200 features slim 1u rack mount profile. treb le, stereo mono switch and volume control. Inputs include phono, tuner, VCR and tape loop. Ideal mate to K 5070 Amp (EA Aug '83) Checks transistor in circuit. " No need to unsolder suspect transistors". Have you ever de-soldered a suspect t ransistor, on ly to find that it checks out OK? Features: • Tests both NPN and PNP transistors in c ircuit at the touch of a switch • Tests Diodes and SCRs as well • No need to switch between NPN and PNP - it's automatic • LED indication to show co nditio n of device. Th is Digital Recorder delivers astonishing ~,:.::.~:.:,.:;::;;..;;.:;:.:"------, reproductio n of vo ice and/or music without any movi ng parts. It can store 4 different 30 second messages or 1 recording up to 2 mi nutes . Typical applications include • Alarm system messages • Sales messages for customers put on 'hold' • Talking Displays for shops • Emergency warning messages • And countless other applications where voice or music is required • K 9550 PCB alone version• K9555 Inc ludes fully punched & screen printed inst rument case. K253o$17.5o K9550 Adjustable 0-45V, 8 Amp Bench Power Supply (SC Jan / Feb '92) K 3360 $375 .00 Using state of th e art circ uitry this supply wi ll be a great asset to the enthusiast and professional ali ke. It uses switc h mode principles wh ic h allows fo r smaller transfo rmers, and heatsi nking wh ic h means greater efficiency, less heat and lighte r weig ht. feature,: • Var iab le output • Variab le cu rre nt limit • Separate Earth Terminal • Individual Volt and Amp Meters• Constant 13.8V setting• Short circuit proof Speclflcatlona: • Output voltage 0-45V • Output current BA <at>35V, 6A .<at>. 40V • . Load regulation 1% • Ripp le and Noise 40mVp-p at 8A 35V • Current lImIt 800mA8.6A • Over c urre nt limit 9A • Fold back c urrent less than 2A Digital Voice Recorder Kit PCB Format $129.95 K 9555 With Laboratory Power Supply (EA May '85) Instrument Case K 3300 $149.95 $195.oo 3-50 Volta at up to 5 Amp• This supply has been one of our most popular. It includes the latest refinements and is now housed in a tough 'A BS' instrument case. This compact version uses a high efficiency toroidal transformer resulting in less heat and weight • Exclualve to Altronlca • Deluxe instrument case • Attractive silk screened front panel • Pre-dri lled and punched chassis - No holes to d rill • Front panel drilled fo r K3302 option . Speclflcatlona: • Output Voltage: 3 to 50V • O utput Current: 5 AmP,s Max • Floating Output • Ripple: less than 5mV • Dual Meters 10 Turn Pot For Precision Voltage Control Option K3301 $4.so Fixed +/-12V Rai ls lndepe ndant of Main Output K3302 $14.50 Famous Get 240V AC from your ca r, truck or boat battery. The Al tron ics range inc ludes an inverter for nearly every application . Fantas ti c for camping . boating, farms and anywhere else 240V AC isn 't available. Each size in verter is available in kit form or fully built and tested . The 300 and 600 Wat t Inverters now feature new improved circuitry usi ng multiple mosfet outputs making them even more reliable with a genuine 300 or 600 wattC ontinuous power rati ng. Our latest model, the 1200 Watt Powerhouse offers excellent va lue fo r money and pe rformance. It features crystal locked c ircuitry and a massive 2400 watt power surge making it ideal for smal l fridges. vacuum cleane rs, power too ls etc. Any model an absol ute necessity where 240V isn't available. Cal l Altronlca today for more informati o n on freeca ll 007. 008 999 300 Watt $279 K 6755 Built-up $379 K 6750 Kit Version These k its use quality Vita speakers made in Denmark and specially engineered enclosures for optimal performance. Black wood grain veneer make them ideal for any decor and situation. These two way models include high grade crossovers, speaker terminals and removable front grille. Simpl~ construction with only basic tools and skill required. These kits are complete a:,d incl ude speal<.er cloth, damping materia l, grille clips, speaker term ina ls, screws and parts. Outstanding performance for the fraction of the cost of commercia l equ iva lents . VIFA SA-50 2 Way Bookshelf System, 50 Watts RMS Now Only w,oe. I ...,.. $299.oo pr Jip.t'I';,:iJ' Powe1tH01.1s!" ~ 600 Watt " $499 K 6770 Kit Version K 6774 Built-up 12V Input K 6775 Built-up 24V Input $ i -,:~ • ~ ... ,"'-'c. ._, ~ I ' \ , \ ' -' Normally $ 7 ~ o 1200 Watt $799 K 6792 Bui!t- up 12V Input $999 K 6793 Built-up 24V Input K 6790 Kit Version Now Only $699.oo pr ..•----.:.= = =:!...---------1 Stereo Extension Ceiling Speaker Kit Want a set of high grade extension speakers for the back patio, games room, den, workshop, kitchen? Well here at Altronics we have put together this great kit which includes speakers, grilles, cable, screws and even a wall mounted volume contro ller. The speakers are our high qua lity 4" C 0626 dua l cone drivers, with stylish wh ite gril les - ideal for mounting in the cei li ng. Volume contro l mounts in standard electrica l wa ll box and includes 6 volume settings as well as off. Includes 2 x 20m cable. 300 Watt Economy Inverter Turn 12V DC lo 240V AC. This fantastic inverter wi l l power lights, TV's, A fine dri ve r using only high quality components and techno logy. For example barium ferrite magnets, revolutionary Kapton voice coil and unique c arbon fibre cones. C 0988 Normally $9J'6o. Now Only $69.oo 3034 $ This Month Only Weather Proof Monitor and Sound Column Speakers This fantastic new range of monitors and columns just have to be heard to be believed. Designed by the Altronics engineer team with extensive consultation from audiophiles and architects, these speakers are absolutely ideal for hi-fi extensions and P.A. Constructed from rugged extruded aluminium and UV resistant plastic makes these units both weatherproof and built to last. The drivers used are 4" carbon fibre with an inbuilt coxial tweeter. Ported design makes bass response incredibly smooth and deep. Two sizes available, 30 and 60 watts RMS, in a black or white powder coat finish. Mounting these speakers are made easy by employing the new "Wacki " bracket system. Call Altronics today for a free colo u r brochure. Proudly Ma.de in Australia 30 Watt Monitor Serles Normally $23fr6o ~,._,,s $169.oo ea ,io 0924 8 Ohm White !149 .00 ea 60 Watt Column Serles Vo lt Line Wh ite $2 $160 0928 .00 ea CC 0936 0937 100 100 Vo lt Li ne Black 45 .00 ea Audio Frequency Generator RF Signal Generator This new bullet tweeter looks and sounds great . Genuine Motorola KSN 1165A. Features 400 watt max imum po wer capability frequency response 1.BkHz to 30kHz and SPL at 93dB (2 .83v/ 1 m). 91 x 91 mm mounting hole centres. Specifications available on request. Simply wires in paralle l to your woofer. No crossover or capacitor required. As it presents al most no load to your amp it doesn't effect the overall speaker system's impedance. Fantastic for hi-fi or disco speakers. C C 0925 8 Ohm Black C 0927 100 Vo lt Li ne hite C 100 Vo lt Li ne Black a 1540 Normally $3~.oo Now $25O.oo .• Motorola Piezo Tweeter M 8120 Output Level: Sine: 8V rms Square: 10V P-P Output Attenuator: -20dB, -40dB and fine adjust - 59.ss These Poly Emulsion Coated Cone I PECC) woofers offer excel lent quality and performance. With a max imum power rating of 200 watts or 120 watts continuous and a frequency response down to 30Hz these drivers make an ideal sub-woofer or rep lacement bass speaker. Massive 2.5kg nett weight. See Altronics ·92 catalogue for full details . c 3032 Waveforms: Sine/ Square ' (/ fibre these speakers are ideal for boats an automotive use . Max input power 70 watts or 30 watts RMS. Resonant frequency 65Hz. See Altronics '92 catalogue for full details . C Normally $ 8 ~ T~ is Month Specifications: Frequency: 10Hz - 1MHz Accuracy: +/ -3% + 2 Hz Output C ~e~7;t~~~ ~:r~~~u~~g~f:!~~on I 625 tools, electric shavers and a whole host of other appliances. Great for camping, out in the bush and any place where 240V is not avai lable. Features: • Complete with over current circuit breaker• Fused 240V output• Built in panel meter to monitor output vo ltage • panel meter to monitor output voltage • Strong steel case and chassis. pf\\C1' fflO f>.' 1 800w•uoe,.. c,it~.,,., -::::, Si ... We have a huge ~~:lus of Vila C13WG-08-08 woofers. These quality drivers offer . high performance in both • . ported and sealed ,, enclosu res. Exceptionall y smooth response useable up to 5kHz. Caref ul desig·n and construction us ing rubber surround makes it possib le to obtai n an amaz.ing 50 watts RMS power ca labicity. Fa ntastic replacement or new construction speaker. C 3110 Normally $~00 Now $49.oo 6.5" Carbon Fibre · , 1,;.Jf>.l\.ft{~S Woofer r,10' C 0£ S Normally $3~oo pr Many Hundreds of Altronics l!7v~rters Now in use Australla ~~o~;•r sAvf:0°1,0· ., With provision for internal and external modulation. Specifications: Frequency Range: l00kHz - 150MHz in 6 ranges RF Output Level: 100mV rms Accuracy: +/ -3% Modulation: • Internal (30% depth): 1kHz • External : 50Hz-20kHz • Crystal Locked Oscillator Q 1550 Normally $ ~.00 Now $225.oo C 6160 $39.95 Proudly Made In Ausrralla Yet another Altronics innovation , proudly designed and made in Australia . These great new speaker mount brackets simply screw onto the wall and speaker allowing a universal 50° angle of adjustment . Su itable for speakers up to 5kg . No special tools required. Available in white or black. A must for any extension speaker. H Wh ite H Black pair 8010 8012 $39.95 Universal Battery Chargers High quality computer fans ideal for power supplies, amplifiers, computers etc. Reliable Sun non brand. Full . range available for almost any application. As a result of a bulk scoop purchase, we are able to offer to you these fantastic universal Ni-Cad t3attery chargers at a more than ridiculous price' It will charge any combination of up to 4 of AAA, AA, C or D size~batteries at one time plus a 9V. Features a LED indication to show each battery has made an electrical contact. Also has an added bonus of a battery tester function. Hurry. Stoc•s limited. Definately no back orders. 5 This Month Only $19.95 LID NOT SHOWN Passive Infra-Red Flood Light Control Just arrived , this new model PIA floodlight activates when it detects movement of a person or car approaching. Great to welcome visitors, ward off intruders or even to find the keys in the dark! Features daylight sensing circuit which means unit will not activate during daylight hours (save on your power bil l). Includes manual override facility to turn lights on continuously or automatically. Features . movement sensitivity adjustment, and turn on period. Great for the driveway or backyard. Complete with two screw in type sockets for standard 150W floodlight globes (not included). Amazing Value on Deleted UHF Alarm This UHF system contains one receiver and 3 wireless reed switches for doors and windows etc. T he ma,n controller simply plugs into 240V, the remote, reed switches are attached to your door/window frames and presto, the alarm is installed! Simple push button operation, 4 digit user selectable on/ off code, built-in siren makes this unit a pleasure to use. Includes 12V 1.2Ah backup battery and 9V batteries for remote reed switches. Because there is no need to drill holes in the wall or ceiling, making this unit just great for rented flats or units, or for those who don't want the trouble and hassle of a wired system. Also ideal for boats, caravans, the shed, garage or granny flat. Take the unit with you if you move - no wasted time and money. Remote Car Alarm 1020 80mm' $22.25 F 1030 120mm' $24.25 F 12V DC Model 30 Amp relays with individual fuses. Great for car headlights, spotlights etc. I S4335 Normally $1~o This Month Only $9.95 Chassis Mount RCA Sockets Australia Post. Allow approx 9 days from day you post order to when you receive goods. OVERNIGHT JETSERVICE Up to 3Kg is $10.00, 3Kg to 5Kg is $23.00 - We process your order the day received and despatch via . Overnight JetHrvlce Courier for delivery next day Country areas please allow additional 24-48 hours. PX f! 0235 Normally $3,..116 $1.50 Universal Remote Control PA This Month Only This universal infra-red remote control makes all other remote units superfluous. Will control CD players, videos, TV's and stereos etc. Controls up to 6 different appl iances. Easy to use and programme from an existing functional remote. 1000 $69.s5 Blank Rack Panels S'3" STANDARD DELIVERY I PACKING CHARGE $3.50 to 500gms, $5.50 500gms - 1Kg, $8 1Kg-5Kg AUSTRALIA WIDE - We process your order the day received and despatch via. These terminal blocks are ideal for 240V, speaker or DC voltage termination. Can be cut into shorter strips. Raised base for extra voltage protection. 3 rows of stereo (left and right) sockets. High quality. Bargain price. loud siren and visible warning of flashing headlights when the alarm system is triggered. Keyring remote control allows arming with 'beep' sound and disarming with headlights flashing signal. The alarm system will be triggered by unauthorised entrance through the car doors, boot, bonnet or removal of the car sound unit. The siren will sound and the headlights flash for 60 seconds. Ea■ y to ln1tall. S 4LTilOnlC.) Finger Guards ~i A 174 Roe St. Perth W.A. 6000 Phone (09) 328 1599 PHONE TOLL FREE 008 999 007 MAIL OROERS C/- P.O. Box 8350 Stirling Street PERTH W.A. 6849 1040 120mm' $23.so F F 1022 80mm $2 F 1032 120mm .45 1050 80mm' $17.50 Sturdy Spotlight 12 Way WireProduc:t Terminal Relay Blocks Includes two separate F With WlreleH Remote Control Audible warning with a 125 decibel 5220 $99 .00 24V DC Model 240V Models 2110 Normally$~ $3.50 or 10 up $3.oo Now Only Stationmaster CB Base Antenna earthed or unearthed. • 50 any height above the ground, Ohm impedance• V.S.W.R. 1.3:1 • Height 5.6m • Power 1kW L All $8.00 H 0422 Natural Aluminium H 0432 Grey H 0435 Black 1 . r· !.·,.· 3215 Normally $11 ~ $99.oo This Month Only Top quality blank panel clearout. All stock must go at these crazy prices. Stock is limited with definately no back orders at these prices. 2 unit - I Extra wide bandwidth base antenna without ungainly size. Supplied with a fully pre-tuned and assembled DC grounded matching system and all mounting hardware. Waterproofed and useable at 3 Unit - All $12.95 H 0423 Natural Aluminium H 0433 Grey • HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road Please allow 7 days for delivery. $12.00 to 10Kgs. $15.00 over 10Kgs. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add $1.00 per $100 of order value (minimum charge $1 ). When phone ordering please request "Insurance" TOLL FREE PHONE OROER - Bankcard, Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight JetHrYlce we deliver next day. AL TRON ICS RESELLERS Chances are there is an Altronic Reseller right near ct1eck this list or phone us for details of the nearest dealer. De ■ lero are highlighted with a ■ These dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. you - Blue Ribbon WA COUNTRY ALBANY BP Electronics ■ (098) 412681 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097) 2162:!2 ESPERANCE Esperance Communications (090) 713344 MANDURAH Lance Rock Retravision (09) 535 1246 PORT HEDLAND Ivan Tomek Electronics (091) 732531 ROCKINGHAM TV Joe's (09) 5271806 NT ALICE SPRINGS Farmer Electronics (089) 522388 DARWIN Ventronics (089) 853 622 VIC All Electronic Components (03) 6623506, TECS (03) 6706474 BORONIA Ray Cross Electronics ■ (03) 762242~ CHELTENHAM Talking Electronics (03) 5842386 COLLINGWOOD Truscott Electronics (03) 4198208 CROYDON Truscott Electronics ■ (03) 7233860 FOOTSCRAY G.B. Telespares (03) 3179100 PRESTON Preston Electronics ■ (03) 4840191 COUNTRY BAIRNSDALE LH & LM Crawford (051) 525677 BALLARAT Ballarat Electronics (053) 311947 QLO Del sound PL ■ (07) 8396155 WEST END BAS. Audiotronics (07) 8447566 WOODRIDGE David Hall Electronics ■ (07) 8082777 COUNTRY GLADSTONE Gladstone Electronic Services (079) 724459, Electronic Enterprises (079) 726660 MAROOCHYOORE MALS Electronics ■ (074) 436119 MARYBOROUGH Keller Electronics (071) 214559 NAM BOUR Nambour Electronics (074) 411966 PIALBA Keller Electronics (071) 283749 ROCKHAMPTON Access Electronics (East St.) (079) 221058 TOWNSVILLE Super Solex ■ (077) 724466 SA Force Electronics ■ (08) 2125505 BRIGHTON Force Electronics ■ (08) 3770512 CHRISTIES BEACH Force Electronics ■ (08) 3823366 FINDON Force Electronics ■ (08) 3471188 HOLDEN HILL Force Electronics ■ (08) 2617088 LONSDALE Force Electronics ■ (08) 3260901 ENFIELD Aztronics ■ (08) 3496340 COUNTRY WHYALLA Eyre Electronics (086) 454764 TAS HOBART George Harvey ■ (002) 342233 LAUNCESTON George Harvey ■ (003) 316533 NSW David Reid Electronics ■ (02) 2671385 REVESBY Revesby Electronics (02) 7922295 SMITHFIELD Chantronics (02) 6097218 COUNTRY COFFS HARBOUR Coffs Habour Electronics (066) 525684 NEWCASTLE Novocastrian Elect.Supplies (049) 621358 WARNERS BAY Vilec Distributors (049) 489405 WINDSOR M & E Elect. and Communications (045) 775935 WOLLONGONG Newtek Electronics ■ (042) 271620, Vimcom Electronics (042) 284400WOY WOY Alphatran Electronics (043) 434919 we've added our own circuitry so that you can select the required decimal point via a switch. Let's see how this works. The backplane (BP) signal on pin 21 is fed to IC2d, which is a single dual-input XOR gate. This stage simply functions as a buffer. Its output at pin 11 is in phase with the backplane signal and drives gates IC2a, IC2b & IC2c, which are connected in parallel as a single inverter stage. These parallel inverters produce a square wave which is complementary to the backplane signal and this then drives the decimal points of the LCD via one of three linking options. Alternatively, you can use a single pole 3-position switch for decimal point switching. and REF LO pins) would be set to 0.316V. Current measurements o.47 ,ooiF ...::~~,~~s t .01 f 0 ~ DP2.,._..::,_ □P1,► -1-,~--® ggg ~ -~I ~ -~- F - _..: ~ - 10uF O· ~~ Voltage measurements In order to use the module as a 0200mV (actually, 0-199.9mV) voltmeter, VR1 is set so that the reference voltage between pins 35 & 36 is 100mV. The decimal point connection is made from the output of the paralleled inverter stages to pin 16 (DP1) of the LCD. For a 0-2V (0-1.999V) meter, VR1 is adjusted to obtain 1.000V between pins 35 & 36 and the RC values on pins 28 & 29 are changed to 470kQ and .047µF. The decimal point connection is now made to pin 8 of the LCD (ie, to DP3). In both cases, all other parts to the left of the 1MQ resistor on pin 31 are deleted, except for Ryl which is made equal to 10Mil This 10MQ resistor ensures that the display returns to 000 when the input is removed. Higher voltage ranges are obtained by scaling the input using voltage divider resistors Rxl, Rx2, Ryland Ry2. For example, a 0-20V range can be obtained using a 10:1 voltage divider. We can do this and at the same time obtain a 1MQ input impedance by ~ ~ •3 •2 ·•1 INPUT - + • • 9V BATTERY --------' Fig.2: be sure to install all the wire links before mounting any of the other parts. Resistors Rxl, Rx2, Ryl, Ry2 & RA are selected from Table 1. making Rx (ie, Rxl/ /Rx2) = 900kQ and Ry = 100kil The decimal point connection is made to DP2 (pin 12) of the LCD, so that we get a full-scale display of 19.99V. Table 1 lists the resistor values for several other ranges up to 200V. In some measurement situations, it will be necessary for the meter to display a full-scale reading (ie, 1999) for some specific input voltage. Instead of using a divider network, this can be achieved by setting VREF to half the full-scale input voltage using VR1, provided that the input voltage is less than 2V. For example, let's say that a voltage of 0.632V from a transducer is required to give a reading of 1999 on the LCD. In this case, the reference voltage (ie, the voltage between the REF HI To give the meter added versatility, we've also left space on the PC board for 5W shunt resistor RA to allow the meter to read currents up to 2A. The way in which this works is quite straightforward. Resistor RA is wired in parallel with the inputs, while resistors Rxl, Rx2, Ryl & Ry2 are all deleted. If RA = 0. H2, 200mV will be developed across the resistor when the current through it is 2A. This voltage is then applied to the meter which is set up for the 200mVrange (ie, VR1 is set for 100mV between pins 35 & 36). At the same time, DP3 (pin 8) of the LCD is connected to the inverter outputs, so that the meter reads 1.999A full scale. The reason that you should choose the 200m V range is to limit the power dissipation in the shunt resistor for any given reading. For example, at the maximum reading of 2A, the power dissipation is P= I2 R = 2 x 2 x 0. 10 = 0.4 W. This figure is well within the resistor's 5W rating. Another reason to use the 200m V range for current measurements is to limit the "burden voltage" of the circuit. This is subtracted from the supply voltage to the external circuit and naturally, this reduction should be as small as possible. Note that because of the tolerances of the shunt resistor, it may be necessary to adjust the reference voltage in order to get the correct reading. For example, if the shunt resistor has a value of 0.090, then we will only obtain a voltage of 180mVacross it for a current flow of 2A. This means that the meter will only read 1.800 instead of 1.999 unless VREF is adjusted to 90mV. In practice, VR1 is adjusted so that the meter displays the correct reading for a known current. Power requirements TABLE 1 Range Rx1 Rx2 Ry1 Ry2 RA Decimal Vref 200mV - - 10M - - DP1 100mV 2V - - 10M - - DP3 1V 20V 1.8M 1.8M 100k - - DP2 1V 200V 1.8M 2.2M 10k - - DP1 1V 2A - - - - 0.1 ohm DP3 100mV Power for the unit comes from a 9V battery and this is decoupled using a 10µF capacitor. It directly supplies the two ICs and the voltage divider network (15kQ and VR1) that's used to set the reference voltage. In operation, the common input (pin 32) always sits 2.8V below the supply rail, which means that the reference voltage stays constant as the battery disSEPTEMBER 1992 83 PARTS LIST 1 PC board, code SC04110921, 120 x 71mm 2 32-way SIL sockets 1 10kQ miniature horizontal trimpot Semiconductors 1 7106 3½-digit AID converter (IC1) 1 4070 quad XOR gate (IC2) 1 3½-digit LCD (Altron ics Cat. Z-7297) Capacitors A more compact assembly can be achieved by cutting the PC board into two sections & then soldering these sections together at right angles. Alternatively, you can connect them together via a short length of rainbow cable. There is also sufficient room on each section for extra mounting holes, if necessary. charges. Alternatively, you can power the unit from a plugpack supply or from the equipment being monitored. In any case, the maximum supply voltage should not exceed 12V. The current consumption of the unit is about lmA. Construction All of the components for the 3½Digit Panel Meter are mounted on a CAPACITOR CODES 0 0 0 0 0 0 0 Value IEC Code EIA Code 0.47µF 0.22µF 0.1µF .047µF .01µF 100pF 470n 220n 100n 47n 10n 100p 474 224 104 473 103 101 single PC board coded SC04110921 and measuring 120 x 71mm. This board has been designed so that it can be cut just below the LCD and the two pieces soldered together at right angles to make a more compact unit (see photo). Alternatively, the two pieces can be connected together via a short length of rainbow cable. There is also sufficient room on each section of the board for extra mounting holes, if necessary. Before beginning construction, check the board carefully against the published pattern for any shorts or breaks. If you do find any faults, repair them immediately before installing any of the parts. Fig.2 shows the parts layout on the board. Begin by installing the wire links - there are 15 in all plus an extra link for the decimal point option. These links should all be flush with 1 10µF 16VW electrolytic 1 0.47µF 63VW MKT polyester (.047µF for 0-2V meter) 1 0.22µF 63VW MKT polyester 1 0.1µF 63VW MKT polyester 1 .01 µF 63VW MKT polyester 1 100pF ceramic Resistors (0.25W, 1%) 1 10MQ (5%) - see text 11MQ 4100kQ 1 47kQ (470kQ tor 0-2V meter) 1 1SkQ 1 0.1n SW (RA - current meter only) Note: see Table 1 for values of Rx1 , Rx2, Ry1 & Ry2 Miscellaneous Solder, tinned copper wire for links, 9V battery the board and must be straight to avoid accidental shorts. You can straighten the link wire by clamping one end in a vyce and then stretching it slightly by pulling on the other end with a pair of pliers. When all the links are in, install the resistors, trimpot and capacitors on the board. Table 1 shows the resistor values for the various voltage and current ranges, plus the decimal point RESISTOR COLOUR CODES 0 0 0 0 0 0 84 No. Value 4-Band Code (1%) 5-Band Code (1%) 1 1 4 1 1 10MQ (5%) 1MQ 100kQ 47kQ 15kQ brown black blue gold brown black green brown brown black yellow brown yellow violet orange brown brown green orange brown not applicable brown black black yellow brown brown black black orange brown yellow violet black red brown brown green black red brown SILICON CHIP IOa~~~~ sc.... Never push down on the centre of the display - you may damage it if you do. You can determine the orientation of the display by angling it so that the reflected light shows a faint image of the digits. There is also a small ridge in the glass on the lefthand edge of the display. Finally, connect a battery snap connector to the board. The unit is now ready for testing. ~«;,;-;.-;--- 0_41_10....9~2~1 Fr..:~).=" 0 ~~~0 E~I i~~ IO a ""ci'O J> GO Testing SILICON CHIP 1992 Fig.3: the PC board is coded SC04110921 & measures 120 x 71mm. Check your board carefully against this full-size pattern before mounting any of the parts. ticularly that the ICs face in opposite directiqns on the board. Take care when installing the LCD panel because it's easily damaged. Check that it is correctly oriented and that all pins line up with the sockets before gently pushing down on the corners of the module. linking details. If you build the unit as a current meter, mount 5W resistor RA slightly proud of the board so that the air can circulate beneath it for cooling. The ICs can now be installed and two 20-pin SIL sockets soldered into position to accept the LCD. Note par- To test the unit, just snap the battery into place and check that the display turns on and settles down within a second or so to "000". If you don't get this, switch off immediately and check for assembly errors. For example, if you get incorrect segments appearing on the LCD , check the board carefully for shorts between the ·tracks underneath the LCD and ICl. Finally, note that if you are using a voltage divider on the input (ie, for voltage ranges greater than 2V), then the two outer pins (1 & 3) are used for the input. Ifno resistor is used for Rxl or Rx2 , then pins 1 & 2 are used. SC IAN J. TRUSCOTT'S ELECTRONIC WORLD 30 Lacey Street, Croydon, 3136. Phone (03) 723 3344; Fax: (03) 725 9443 Now also at: 200 Smith Street, Collingwood. Phone (03) 419 2808 Mail & Credit Card Orders Welcome *** SAVE ON OUR SEPTEMBER SPECIALS Exclusive to SILICON CHIP readers: *The Portasol Professional Soldering Iron* Normally $79.95. This month *** Cordless, Refillable Butane Gas-Power'd Soldering Tool Kit $67 .50 Safety Stand Hot Knife *PLCC Extractor Tool* PLCC Extractor prevents damage: th is new J-lead IC remover has a dual action to protect fragile PLCC packages when being extracted from carriers. First, its two steel fingers are inserted at diagonal corners of the package. Then, as hand pressure is applied, the steel fingers lock under the PLCC body. Finally, as further hand pressure is applied, the steel fingers apply a balanced upward pull to remove the package without damage. Normally $22.95. This month $17 .95 Cleaning Sponge Blow Torch accessory Hot Blower accessory Ask about our great range of kits & TV antennas SEPTEMBER1992 85