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The Thunderbird Battery Charger This charger has automatic voltage selection for 6V, 12V & 24V lead-acid batteries & is electronically regulated to deliver just the right amount of current. It features output short-circuit & reverse battery protection & has LEDs to indicate the state of the battery. By HERMAN NACINO,VICH 56 SILICON CHIP . Most of us have experienced, at some time, the frustration of trying to start a car only to find that the battery was flat. Apart from the annoyance of this situation, Murphy's Law practically guarantees that when it does happen, it will do so at the worst possible time. The best way to avoid this kind of situation is to have a good battery charger on hand and to use it regularly, not just for charging a battery after it has gone flat but to keep the battery fully charged during periods when it is not in use. Of course, lead-acid batteries are used not only in cars but in a wide range of other applications as well, such as ride-on mowers, emergency lighting systems and portable transceivers. Battery maintenance is just as important in these applications as it is for the battery in your car. In some cases, the battery is used on an infrequent basis and requires regular recharging to keep it in good condition. Regardless of the application, a good charger, correctly used, will ensure maximum performance from your battery (or batteries) when needed. It may also save money by ensuring maximum battery life. Lead-acid batteries are not cheap, so it makes sense to take care of them by investing in a good charger. Unfortunately, many battery chargers on the market are built to a price. They are relatively cheap but lack features that ideally should be included in any charger worthy of the name. One of the worst aspects of some cheap battery chargers is that, incorrectly used, they can damage a battery and shorten its life expectancy. Most battery chargers provide a "fast" charge rate, typically 4-6 amps. Some chargers also provide a much lower "trickle" charge rate which is selected by a switch. The idea is that the "fast" charge rate is selected when charging a flat battery and the "trickle" charge rate is selected to keep the battery topped up once it has become fully charged. The main problem with this type of charger occurs if it is inadvertently left on the "fast" charge setting for prolonged periods after the battery has fully charged. In this situation, the battery will be overcharged, resulting in gassing and drying out of the electrolyte inside the battery. Permanent damage to the battery can result with consequential shortening of battery life. There could also be a serious safety hazard due to the highly explosive gases generated when a battery has been overcharged. The solution to this problem is a battery charger which monitors the battery voltage and automatically reduces the charging current as the battery approaches full charge. This is the principle behind a regulated battery charger and is the basis for this project. Commercially-built regulated battery chargers are hard to find and are The two power transformers used in the unit are mounted on an L-shaped aluminium bracket which also serves as a heatsink. The remaining electronic circuitry performs voltage, current & temperature regulation. expensive because of the extra circuitry that's involved compared to conventional (unregulated) battery chargers. This project, however, uses low-cost, readily available components to minimise the overall cost but without compromising on performance. In addition, it offers a combination of features that are difficult to find in commercial chargers. Main features This charger will charge 6V, 12V and 24V automotive type lead-acid batteries. However, it is not intended Specifications • Automatically charges 6V, 12V & 24V lead-acid batteries. • LED indicators show high, medium or low battery charge. • Electronic regulation of voltage & charging current. • Features temperature, shortcircuit & reverse battery protection. • 1OA maximum output current; 8A continuous output current at 12V. for charging sealed (gel) type leadacid batteries which have different charging requirements. Its main features include electronic output voltage regulation, output current limiting, output short circuit protection and protection against reversed battery connections. A LED display on the front panel indicates the level of battery charge either LOW, MEDIUM or HIGH. This eliminates the need for a more expensive, and mechanically more fragile, moving coil ammeter or voltmeter. The heart of the battery charger is the electronic regulator circuit. This uses an SCR which operates in a switching mode to control the output current. This type of regulator circuit is much more efficient than the linear regulator circuits used in some battery charger designs. In practical terms, this higher efficiency translates into a higher output current capability for a given size of input transformer and a smaller heatsink for the output regulating element (SCR). And, in case the heatsink gets too hot, the circuit also incorporates thermal shut-down to protect the SCR from damage. Unlike conventional battery chargers, this unit does not require a bat. O CTOBEH 1992 57 Cl CXl ~ Cl'.) i:=1 ~ R ~ F1 A~ 2 1.5A 1 7 0 T1 ' . ... SCR1 MCR264-4 ~ + t i ! A~ i ~ r 0--o-~r 15A i T ' 1'.. 240VAC .,. NO J , D3 !1N4002- .,. RB ! 10k' 02 BC546 .., R13 82k E El, BATTERY VCC R7 100k VCC 6/12V SENSE ADJUST 6V VR1 20k r-1 +5V I B -:- ,ffio E1LJc I I RTH1 +5V R14 100k 1ii .J.: 12/24V SENS ADJUST 24V R19 100k VIEWED FROM BELOW fNv-- I I +5V +5V ~ ~ R2l 150!.1 5W I I I ECB' .,. TEMPERATURE SENSE +5V c1.i: 10! .015!.1 COPPER TRACK ON BOARD .,. R12 8.2k A I R16 22k I :--•--~ .,. 35VWJ A~K .....J! C5..,,; R17} 47k R20f 47k ........... ~ b-+5V 1+ +5V R22· 2.2k t. VCC B R18' 1.8k .,. +5V .,.- OPTIONAL RELAY BATTERY SELECT RELAY CONTROLLER REGULATED BATTERY CHARGER C6.i: 10J R29 56Dn .,. tery selector switch. Instead, it automatically sets the output voltage to suit the battery being charged. This feature makes this charger more convenient to use than ordinary battery' chargers - all you have to do is connect the leads to the battery. It also prevents the possibility of damage to the charger or to a battery that might otherwise result if a switch was set to the wrong voltage. How it works VB VREF__/ /1 [/ /1 [/ /1 L VB VREF VOUTLJLJLJl VOUTU7Jlf1 Fig.2: this diagram shows how the sampled battery voltage (V 8 ) on pin 4 ofICla interacts with a reference voltage (VREF) on pin 5 at intermediate battery voltages. As the battery voltage rises, ICla's output (VouT) goes high later during each mains half cycle and thus the SCR turns on for shorter periods of time. The circuit for the battery charger is shown in Fig, 1. Let's see how it battery voltage is compared with a reference voltage to derive an error works. Power for the circuit is obtained signal. This error signal is then used from the mains via a pair of trans- to control the SCR. When the battery formers, Tl and TZ. Each transformer voltage is low, SCR1 turns on early in has a pair of tapped 15V secondary each half-cycle of the mains AC wavewindings which can be connected in form, so that a large current flows into various configurations for different the battery (see Fig.7). At the end of output voltages. Relay RLY1 connects each AC half-cycle, the unfiltered DC the secondary windings of Tl and TZ voltage to the SCR drops to zero, alin a parallel configuration for charg- lowing the SCR to turn off in readiing 6V and 12V. batteries, and in a ness for the next half cycle. As the battery voltage approaches series configuration for charging 24 V batteries. The transformers are each the value set by the reference voltage, rated at lO0VA, giving a total input SCR1 is progressively turned on later in each half-cycle so that the average rating of Z00VA. current is reduced. When the battery For those who may be wondering, the main reason for using two trans- . voltage reaches the set value, SCRl is formers instead of one is that' high off for most of each half-cycle so that only sufficient current flows into the power transformers are quite expensive. It was cheaper to use two smaller battery to maintain its charge. A voltage divider (R13 & R34) betransformers than a single transformer tween the positive and negative terwith the same total VA rating. Diode bridge BR1 converts the AC minals is used to sample the battery output voltage from the transformers voltage and is adjustable by means of to an unfiltered DC voltage which is VRl. Op amp ICZa acts as a voltage follower and buffer but, due to the applied to the anode of SCRl. This DC voltage is also fed to a voltage effect ofC4, ignores the ripple voltages divider and filtered by capacitor Cl to generated across the battery terminals derive a supply rail (Vee) for the regu- by the battery charging current. This lator circuit. Diode Dl isolates the ensures a smooth regulating characfiltered DC voltage from the unfiltered teristic and avoids some of the adverse affects that can occur with more DC voltage ar.plied to SCRl. conventional circuits. During operation, a sample of the Voltage regulation is accomplished by ICla which is part of an LM339 quad comparator IC with open collector outputs. In this type of comparator, a pull-up resistor must be fitted to Fig.1 (left): the circuit uses op amp get a high output. comparators ICla, IClb & IClc to ICla compares the sampled battery phase control SCRl to provide voltage voltage on its pin 4 input with a refer& current regulation. ICla generates ence voltage applied to its pin 5 inthe voltage control signal; IClb the put. This reference voltage is derived temperature control signal; & IClc the from 5V regulator IC4 (via a voltage current control signal. IC2b & IC2c divider consisting ofR12, R17 & R18) provide the automatic voltage and carries a superimposed ramp selection feature (6V, 12V or 24V), waveform voltage which is generated while IC3b, IC3c & IC3d drive the three indicator LEDs. by ICld and capacitor C5. This ramp waveform is synchronised to the half cycles of the AC mains waveform. When the battery voltage is low, the voltage at pin 4 ofICla is less than the reference voltage at pin 5. ICla's output is therefore high and this turns on QZ, Ql and SCRl so that current is supplied to the battery. Conversely, when the sampled battery voltage exceeds the reference voltage, ICla's output goes low and QZ, Ql and SCR 1 turn off. At intermediate battery voltages, the voltage on pin 4 intersects the ramp waveform on pin 5 to give a pulsed waveform at the output of ICla - see Fig.2. As the battery voltage rises, the output of IC la goes high later in each half cycle and SCRl is turned on for a proportionately smaller fraction of the time. Current limiting Current limiting is achieved using current sense comparator IClc. During operation, the charging current flows through a resistance of 0.015Q (formed by a copper track on the PC board). This resistance is in series between the negative battery terminal and ground and so the voltage across it will be proportional to the charging current. The resulting voltage is then filtered by R19 and C7 and applied to pin 6 of IClc for comparison with a reference voltage on pin 7. This reference voltage is derived from the bottom tapping of voltage divider R12, R17 & R18 and again carries _a superimposed ramp waveform which is derived from ICld. As the voltage across the 0.015Q resistor rises, it interacts with the ramp voltage and IClc narrows its output pulses. This proportionately reduces the on-time of SCRl during each mains half-cycle, thus limiting the average current into the battery. Temperature limiting is achieved · OCT0in·: ll 1992 59 a 6V or 12V battery, the normally closed (NC) relay contacts connect the transformer secondary windings in parallel. If a 24V battery is connected, the output of IC3a goes high and turns on Q3. This, in turn, activates the relay, which then connects the transformer secondary windings in series. LED indicators Use plastic cable ties to keep the wiring tidy & check all wiring before applying power. The relay on the regulator board switches the transformer secondary windings·in parallel for 6V/12V batteries & in series for 24V batteries. using IC1b and this works in a similar manner to IC1c. In this case, however, the sensing device is a thermistor (RTH1) which is mounted next to SCR1 on a heatsink. It forms part of a voltage divider network (along with R24) and varies its resistance according to the temperature. The resulting voltage developed across R24 is then applied to pin 8 of IC1b and compared with a ramp voltage on pin 9. At low temperatures, the voltage on pin 8 will always be below the ramp voltage and so IC1b has no effect on the output current. If, however, the heatsink temperature rises, IC1 b progressively increases the phase angle of SCRl to reduce the output current. This means that the current is reduced smoothly rather than abruptly as the heatsink temperature approaches the set limit. Voltage selection Comparators IC2b & IC2c provide the automatic voltage selection feature. As previously stated, IC2a generates an output voltage that's proportional to the battery voltage. Its output at pin 2 is then connected directly to pin 10 of IC2b and to pin 8 of IC2c via a voltage divider consisting ofR14 & R15. 60 SILICON CHIP The resulting voltages on pins 10 & 8 are then compared with a +5V reference on pins 11 & 9. If a 6V battery is connected, the outputs of IC2b & IC2c will both be off and the output of IC2a is fed directly to pin 4 of the voltage sense comparator (IC1a) via R7. However, if a 12V battery is connected, the output ofIC2b will go low. This effectively connects one end of R10 to ground and so R7, VR2 and R10 now form a voltage divider on pin 4 of IC1a to set the correct charging voltage for a 12V battery. If a 24V battery is connected, the output of. IC2c also switches low and pulls Rl 1 to ground, thus setting the correct voltage divider ratio for charging a 24 V battery. Comparator IC2d sets the output current limit when charging 24V batteries. When a 24V battery is connected, the output of IC2d goes low. This pulls resistor R9 to ground and thus halves the reference voltage on pin 7 of IClc. This, in turn, reduces the current limit to half that used for 6V/12V batteries. Comparator IC3a controls relay RLYl and this, in turn, switches the secondary windings of the mains transformers in series or in parallel, depending on the battery voltage. For Comparators IC3b-IC3d control th e LED indicators. The inputs of IC3b are in parallel with the inputs ofICla. For low and high battery voltages, the output ofIC3b swings close to OV and +5V, respectively. For intermediate battery voltages, the output of IC3b is a pulse waveform with a duty cycle that increases with battery voltage. This waveform is smoothed by R28 and C6 and applied to the non-inverting inputs of IC3c and IC3d. IC3c and IC3d form a window comparator. When the battery voltage is high, the output of comparator IC3c turns off and Q4 turns on (via R31) and lights LED 2. At the same time, the current through LED 1 is bypassed since there is insufficient forward bias to turn the LED on due to the presence of D5. Similarly, when the battery ·voltage is low, the output of IC3d turns off and Q5 turns on and lights LED 3. For intermediate battery voltages, both comparator outputs are low and LEDs 2 and 3 are off. LED 1 is now no longer bypassed by either of the other two LEDs and consequently turns on. Construction This project is housed iri a moulded plastic case which consists of a base and cover. The transformers and 240V wiring components are mounted on an aluminium L-shaped plate which also serves as a heatsink for the SCR and bridge rectifier. Most of the remaining parts are mounted on two PC boards. The larger board is used for the regulator circuitry _and relay, while the smaller board carries the LEDs. Before commencing the assembly, use a piece of wet-and-dry sandpaper to smooth the mounting areas for the rectifier bridge and SCR on the vertical face of the aluminium plate. This is especially important in the case of the SCR because it must be insulated from the metal plate with a thin insulating washer. If there are metal burrs, ON HEATSINK- + BR1 ~ Fig.3: install the parts on the PC board & run the wiring as shown in this diagram. The external wiring connections to the board are made using quickconnect spade terminals. Be sure to use heavy-duty (10A) cable for all wiring connections on the secondary side of the transformer. they may cut through the insulating washer and cause a short circuit between the SCR and the plate. Fig.3 shows the wiring details. Start the assembly by mounting the 240V fuseholder and terminal block on the base of the aluminium plate. This done, solder a length of 240V 2-core flex to the fuseholder and cover the solder joints with a plastic or rubber sleeve. The fuseholder terminals, incidentally, have holes through which the wire ends should be looped be- fore they are soldered. This way, if the solder joints come loose for any reason, the wire ends will not come away from the terminals. Now bolt the two transformers and the earthing connector lug to the aluminium plate. Run the wires from the fuseholder and the primary windings of the transformers together and slip a 75mm length of 10mm diameter plastic sleeving over these wires. The free ends of these wires are now fitted with quick-connect spade terminals using a suitable crimping tool. Important: all the quick-connect spade terminals used for the 240VAC connections should have plastic insulating sleeves, to minimise the possibility of human contact with live terminals. For the sake of your own safety, do not use non-insulated terminals. Connect the primary leads of the transformers to the terminal block as follows: blue wire to blue wire and brown wire to brown wire. Now connect one of the wires from the fuse holder to the terminal for the brown wires, then connect the other wire from the fuseholder to a separate terOCT0BER 1992 61 - Power Supplies Bench-Top Instruments FUNCTION GENERATORS GW GFG 2 MHz SERIES] GFG SERIES COMMON FEATURES Frequency Range 0.2 Hz to 2 MHz, continuously variable. Output Waveforms sine, triangle, square, TTL pulse and ramp Output Level > 20 Vp-p open circuit, 10 Vp-p into 50 ohms VCF Oto 10V input for 1000:1 output frequency variation DC offset of± 10 VDC GFG-8016G ► Frequency Counter & 2 MHz Function Generator Special Functions Frequency Counter • Internal or External operation • Frequency range 0.1 Hz to 10 MHz • Sensitivity s; 20 mV rms 10 MHz • 6 digit LED display GFG-8017G ► Sweep Function, 2 MHz Function Generator Special Function Sweep Generator Operation • Auto or Manual sweeping • Sweep width is 1000:1 ratio • Sweep time is variable from 0.5s to 30s • Sweep modes LIN, LOG (.HULo) - FUNCTION GENERATORS GFC-F SERIES l ► Competitively Priced ► Professional Quality GFC-8010F/8010G 120 MHz Frequency Range: 1 Hz to 120 MHz Sensitivity: S20 mV 10 Hz to 100 MHz s;30 mV 100 MHz to 120 MHz Display 8 digit display and Gate Time 0.1 s, 1s, 10s GFC-8055F/8055G 550 MHz Frequency Range: 1 Hz to 550 MHz Sensitivity: Input A s;2Q mV <at> 100 MHz Input B S150 mV<at> 550 MHz 8 di! LED and Gate Time 0.1 s. 1s and 10s 11, I ii !!MM!NT COUNTERS 1• GFC-G SERIES 1 ► Frequency, Period and RPM Ranges The GFC-8131G is an economically priced 1.31 GHz counter. Additional features include a continuously variable Gate Time control as well as adjustable variable Level/Sensitivity. Front panel switches include AC/DC input coupling. LPF and attenuator controls. GFG-8019G Multifunction 2 MHz Function Generator Special Functions 3 units in 1 • Inbuilt Frequency Counter, same as GFG-8016G • Inbuilt Sweep Generator, same as GFG-8017G • AM and FM Modulation, internal or external ► GFG-80200 Digital Readout 2 MHz Function Generator Special functions large 0.5 inch, 4 digit LED display for frequency indication ► AUDIO SIGNAL GENERATOR ► Low Distortion Oscillator The GAG-808G is GW Instruments' latest general purpose audio oscillator. Being an RC type oscillator ensures a pure, low distortion sinewave output over the entire frequency range. A switchable output attenuator, calibrated in steps of 10 dB, makes the GAG-808G ideal in teaching as well as service applications. Both the sinewave and square wave outputs can also be varied by a continuous ampl~ude control. GAG-808G Frequency Range: 10 Hz to 1 MHz, in 5 ranges Sinewave Output: >20 V pk-pk; Distortion < 0.1 % Squarewave Output: >10 V pk-pk; Rise time< 200 ns Output Impedance: 600 ohm Stepped Attenuator 0 to -50 dB in 10 dB steps GFC-8131F 1.3 GHz Frequency Range: 0.01 Hz to 1.3 GHz, AC or DC coupling Period Range: 0.6 rpm to 7,200 rpm Sensitivity: Input A 10 mV<at> 80 MHz I utB50 mV<at> 1.3GHz 11 AA ;t-f ■ 1 ): IN Escort GW POWER SUPPLY BASIC FUNCTIONS Continuously variable voltage and current from zero to rated limit with FINE and COARSE controls. Outputs are electronically protected against short circuit or overload conditions. The input is fuse protected, with a true 240V AC input. Automatic Constant Voltage - Constant crossover with LEDs 1• GPG-8018 Frequency Range: 0.5 Hz to 5 MHz Pulse width and spacing independenUy variable 100 ns to 0.1 s Functions Run, Trigger, Gate, One shot, Square, invert Outputs TTL (Fanout 40) Variable Output (0,5 to 10V) for CMOS Synchronisation Output (Fanout 10) CAT. No. MODEL PRICE CAT. No. MODEL PRICE 10003 10004 10005 10006 10009 GW-GFG-8020G GW-GFG-8017G GW-GFG-8016G GW-GFG-8019G GW-GAG-808G 398.50 408.50 485.50 552.50 269.50 10011 10012 10013 10015 10016 GW-GPG-8018G GW-GFC-80100 GW-GFC-8055G GW-GFC-8131G GW-ESC-2200 369.50 276.50 405.50 558.00 553.50 GPS & GPR-DIGITAL SERIES 1 1• GPC-DIGITAL SERIES SINGLE output DC Supplies 2 Analogue Panel Meters, V and A The GPR-Series includes Floating Output, allowing either side to be linked to ground. FINE and COARSE voltage and current control. Clearly marked analogue panel meters, CLASS 2.5 1• Low ripple noise components, typically 0.5 mV rms to 1 mV rms. Excellent line and load regulation, typically 0.01 %. Dual and Quad output supplies with SERIES and PARALLEL functions. Guaranteed for 12 months, with 9 years experience in Australia 1 1• GPC-SERIES 1 ► ► SINGLE Output, DC Supplies ► Two 3'/, Digit LCD Panel Meter, V or A The GPR-D Series includes Floating Output, allowing either side to be linked to ground. FINE and COARSE voltage control. An inbuilt, autoranging 200V DC Digital Voltmeter (100VA models). 1 ► TRIPLE Output DC Supplies ► TRIPLE Output DC Supplies ► Two 3'/, Digit LED Panel Meters ► 4 Analogue Panel Meters Dual Variable Outputs Dual Variable OU1puts Switch selectable configurations Switch selectable configurations Independent both outputs controlled separately Independent both outputs controlled separately Dual Tracking provides Master/Slave control voltages Duel Tracking provides Master/Slave control voltages Parallel doubles output current range Parallel doubles output current range Series doubles output voltage range Serles doubles output voltage range Single Fixed OU1put Single Fixed OU1put Each output has an overload indication LED. Both Variable and Fixed outputs are floating. SPACE SAVER SERIES Inbuilt Logic Probe 5V DC Power Supply Output GPS & GPR-SERIES ► il!t•X•l: ii AA ;t-W EUC-2200175 MHz Frequency Range: 5 Hz to 175 MHz (CH A), 5 Hz to 2 MHz (CH B) Period Range: 0.5 µs to 0.2s, 5 Hz to 2 MHz (CH A) Frequency Ratio Measurement: 11 (CH B)/f2 (CH A) Totalise Range o to 99999999 (CH A) Time Interval Measurement Range 0.5 µs to 0.2s Sensitivity: Input A <150 mV <at> 175 MHz Input B <30 mV <at> 2 MHz Di a 8 . HED ► ► ECONOMICAL LABORATORY DC POWER SUPPLIES Iskra MODEL RANGE CAT No. PRICE GPS-1830 GPR-1810H GPS-2020 GPR-3060 GPR-6030 GPS-3030D GPR-6030D GPC-1850D GPC-3030D GPC-1850 GPC-3030 0-18V 0-3A 0-18V 0-10A 0-30V0-3A 0-30V 0-SA 0-60V 0-3A 0-30V 0-3A 0-60V 0-3A 2x0-18V 5A, 1x5V 3A 2x0-30V 3A, 1x5V 3A 2x0-18V 5A, 1x5V 3A 2x0-30V 3A, 1x5V 3A 10201 I0202 10203 10204 10205 10206 10207 10208 10209 10210 10211 282.50 723.50 395.50 479.50 535.50 489.50 654.50 742.50 742.50 714.00 714.00 HSG-SERIES, 1 phase Single Phase, Panel Mount The HSG-Series are open frame type variable transformers, designed to be incorporated in control panels and other dedicated equipment. They can all be mounted vertically or horizontally, except for the high power HSG-0602 which must be installed vertically. Front panel includes dearly labelled scale and control dial. A screw type terminal block is used to connect input and output leads. Input voltage is 240V Ac, 50 to 60 Hz. W·i;J,., :j! Ii ;H: M:(•) ;1f'ii3;t-i I ,i1'l ~K HSG 0022, 0052, 0102, 0202 and 0602 ELECTRONIC KITS & MODULES BI-FET PRE-AMP WITH 3 WAY TONE CONTROL $72.00 This super low distortion stereo pre-amplttier uses high slew rate wide bandwidth TL-074 op-amps for 0.005% total harmonic distortion. RIM curve deviation is 0.2 dB. Tone controls can be switched in and out. Fully regulated power supply. Low, High and Mid tone controls. SPECIFICATIONS Frequency response: 10 Hz to 100 KHz, ±0.5 dB CAT No. S0307 Total harmonic distortion: ±0.005% at rated output Intermodulation distortion: 0.005% at fated output Sensitivity: · 2.5mV<at> 47K Phono: 100mV<at>100K Aux· and tape: RIM deviation: ±0.2 dB, 20 Hz to 20 KHz Signal to noise ratio: Phono: 75dB Tuner, aux and tape: 90dB Output: Tone controls: ±10 dB at 50 Hz Bass: Mid: ±5dBat 1 KHz Treble: ±10 dB at 15 KHz Dimensions: 8"x4.13"x 1.38" 15 V DC<at> 0.5to 1 amp. Power requirements: 36W PURE CLASS A MONO POWER AMPLIFIER $64.00 Audiophiles will instantly recognise the unchallenged superiority of pure class A operation. The circuit uses full complementary driver stages and a quasi-complementary darlington transistor output stage. If you desire extraordinarily dean sound this amplifier is for you! CAT No. SPECIRCATIONS Power Output: 36 watts into 8 ohms Frequency response: 10 Hz to 20 KHz Less than 0.01% Total harmonic distortion: Voltage gain: 30dB 22 VAC x 2, 3 amps Power requirements: 5¾"x3"x1'/a" P.C.B. Dimensions: 51/a" X 25/e°' X 3" Heat sink: 250W (BTL 320W) ALL FET, DUAL DIFFERENTIAL, SYMMETRICAL STEREO DC FINAL AMPLIFIER CHARACTERIsTIcs: CAT No. S0314 $199.00 • Equipping loudspeaker protector, ensuring speaker safety. • Equipping a rectifier section for power supply, with 2 powerlul filter capacitors, maintaining powerfully supply voltage during high output • DC circuit design without input and negative feedback blocking capacitor, the lowest frequency response • reaching DC (0 Hz), making the bass more sonorous and powerful and the treble clearer. ' • FET and MOSFET integrated design. incorporating the advantages of both vacuum tubes and transistors. • 12 inches black and big heatsink without leads for exterior connection. • 6 pairs of 120W N. channel and P. channel MOSFET with class AB power outputs, extra low transient distortion, new circuit design. MAIL ORDERS WELCOME: CHEQUE, MONEY ORDER, BANKCARD, MASTERCARD, VISA OR AMERICAN EXPRESS PHONE OR WRITE TO US FOR A COPY OF PRICE LISTS SHOP HOURS: Mon-Fri: 9.00-5.00. Sat: 9.00-1.00 All prices include Sales Tax STATE OF THE ART FULLY COMPLEMENTARY SYMMETRICAL FET STEREO PRE-AMPLIFIER $159.00 Significant features of this outstanding stereo preamplttier are the use of fully complementary and symmetrical FET transistor stages. Employs 1% metal film resistors. Power supply is fully regulated. Has a time delay circuit which prevents turn-on thumps. Power supply components are on board so that It requires only an external transformer. SPECIFICATIONS Frequency response: RIAA curve deviation: Total harmonic distortion: Intermodulation distortion: Channel separation at 1 KHz: Hum and noise: Phone: Aux: Phono sensttivity: Output: Record output: Maximum output at 0.1% distortion: Power requirements: Power consumption: 10 Hz to 100 KHz ,0.2 dB, 30 to 15,000 Hz Less than 0.007% at rated output Less than 0.005% at rated output Better than 70 dB Better than 70 dB Better than 90 dB 2mV<at>47K 1.5V (0.01% T.H.D.) 150mV 15V External transformer, 30V x 2 12W <at> 400 0-SOV 6A HIGH EFFICIENCY, CUT-OFF AND AUTO-RESET, ELECTRONIC-PROTECTED, REGULATED POWER SUPPLY CHARACTERISTICS: Employs professional regulator IC ()IA723) for high stability, reliability and low ripple. Auto input regulator decreases the dissipation at about one-fourth the other. Efficiency is increased and the wasted heat is decreased. Sophisticated protector device is a cut-off type protection. The reaction is faster than fuses. Do not damage the loaded device or regulator tt..W. Built-in testing circuit. No need to press reset button. All-purpose identifying sound indicator uses sound and LED to indicate varied operating status. Over-load indicator, voltage adjuster and current-protector selector switch. Has current adjustable circuit. High power output transistor is mounted on a larger U-pit heat sink. Output is sufficient and cooling effect good. Rectifier circuity also has larger heat sink. Only needs to connect a power transformer. 0-30V 10A PROFESSIONAL HEAVY-DUTY REGULATED POWER SUPPLY WITH PROTECTOR CIRCUIT CAT No. S0008 $89.00 CAT No. S0009 $84.00 CHARACTERISTICS Employs professional regulator IC ()IA 723) for high stability, reliability and low ripple. Multi-Purpose IC protector is equipped with cut-off protection and current limited protection and is selected by a switch. It is suitable for all kinds of conditions. The protector circuit employs fully IC and the design is elaborated. It operates at very high speed and is faster than fuse and conventional transistor protector circuits. Do not damage any load or regulator itself. It is durable and reliable. IC protector circuit is a new design. (The protector circus is completed and tested). IC protector besides protects from overload, it recovers automatically after the overloading is gone. Don't need to reset. The operating status of the protector is displayed by an indicator. Equipped with output rejustor, protecting-current selector (divided into 2.5A, 5A, 7.5A and 10A) and status selector. The design is made whole. It includes rectifier, filter and noise suppression circuits. The rectifier circuit is equipped with heat sink that keeps the operator in safely. Only need to connect power supply. Four high•current power transistors are mounted on a professional heat sink, cooling effect is good and output is stable. · RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 No. Value 4-Band Code 1% 5-Band Code 1% 5 1 2 1 4 3 2 1 1 6 2 2 1 1 100kO 91kn 82kO 56kO 47kn 22kO 10kO 8.2kO 5.6kO 2.2kO 1.8kO 5600 150O5W 1200 1000 10W 560 brown black yellow brown wt,ite brown orange brown grey red orange brown green blue orange brown yellow violet orange gold red red orange brown brown black orange brown grey red red brown green blue red brown red red red brown brown grey red brown green blue brown brown not applicable brown red brown brown not applicable green blue black brown brown black black orange brown white brown black red brown grey red black red brown green blue black red brown yellow violet black red brown red red black red brown brown black black red brown grey red black brown brown green blue black brown brown red red black brown brown brown grey black brown brown green blue black black brown not applicable brown red black black brown not applicable green blue black gold brown minal on the terminal block. The aluminium plate and the parts mounted on it may now be fixed to the plastic base using two self-tapping screws. These are installed from the outside of the case and are adjacent to the bend in the bracket. When that is done, attach the four rubber feet to the underside of the plastic base with four 12mm-long self-tapping screws installed from the top of the base. Note that two of these screw_s pass through the corners of the aluminium bracket. grommet into the hole in the aluminium plate. Note: this cordgrip grommet is installed from the underside of the case. The next step is to use short lengths of heavy-duty hookup wire to connect the secondary windings of one of the transformers in parallel. Make sure that the terminal marked "OV" on one winding is connected to the terminal marked "OV" on the other winding. Similarly, check that the two 15V terminals on opposite sides of the transformer are connected together. Fig.3 shows the details. Mains cable The mains cable can now be installed by running it through a 12mmdiameter hole in the aluminium plate. Run this cable between the transformers and under the wires from the primary windings of the transformers. Crimp quick-connect terminals to the wire ends and connect them as follows: Active (brown) to fuse terminal on connector block; Neutral (blue) to transformer primary (blue) terminal on connector block; and Earth (green) to the earth lug bolted to the aluminium plate. Note that all the crimp connectors must be fitted with insulating sleeves. At this stage, you should also connect a 3-pin plug to the opposite end of the cable if one is not already fitted. S_ecure the cable by pushing a cordgri p 64 SILICON CHIP WARNING! Hydrogen gas is generated by batteries under charge. For this reason, always charge batteries in a well-ventilated area and do not generate sparks by connecting high-current loads directly to the battery terminals. When using the battery charger, always connect its output leads to the battery before switching on the mains power. Any failure to observe this simple precaution can lead to dangerous arcing at the battery terminals when the charger is connected and, in extreme cases, could even cause the battery to explode. When this job is completed, connect the two secondary windings of the other transformer in parallel (ie, connect the two OV terminals together and the two 15V terminals together). The terminals marked "12V" are left unconnected. Voltage checks Check all wiring thoroughly, then use the "ohms" range on your DMM to verify that there is good electrical continuity between the Earth pin on the mains plug and the aluminium plate. Check also that there are no shorts between any of the plug pins. You can now do a quick test by plugging the unit into a power point and switching on. Measure the voltages across the secondary windings of the transformers using an AC voltmeter to confirm that all is correct. You should get a reading of around 16-17VAC. If any of the voltages are incorrect or if the fuse blows, recheck the mains wiring and the transformer secondary connections. · Main board assembly No particular order need be followed when installing the parts on the main PC board, although it's best to leave the larger components until last. Make sure that all polarised components, such as the ICs, transistors, diodes and electrolytic capacitors, are with plastic tubing before connecting them to the header, socket. Heatsink assembly This close-up view shows the bridge rectifier & the heatsink bracket that's used to secure the SCR & thermistor. Tighten the bracket mounting screw firmly but don't overtighten it, otherwise you risk damaging the SCR. The 4-pin header strip on the PC board (in front of the fuse) connects to a matching socket & 4-way cable that runs to the LED indicator board. Be sure to plug the socket in with the correct polarity, otherwise the LEDs won't work. ALUMINIUM PLATE -----(HEATSINK) ---ALUMINIUM BRACKET ALUMINIUM BRACKET SELF-TAPPING SCREW ~~~1', 'scR---- o~'J~:i\i:• \ (~~THERMISTOR .):f'....,._'J I RUBBER WASHER C~UIT BOARD / . . _ __ _ _ _ _ _ _ ____. APPLY HEATSINK COMPOUND TO BOTH SIDES OF RUBBER WASHER Fig.4: this diagram shows the mounting details for the SCR & the thermistor. Install the thermistor so that it lines up with the midpoint of the SCR body & smear all mating surfaces with heatsink compound before attaching the bracket. correctly oriented. The SCR is mounted at full lead length, while the thermistor must be mounted so that its body lines up with the centre of the SCR. A 4-pin header strip is also mounted on the board and this mates with a complementary socket that's wired back to the LED board. These headers come supplied in strips of eight (or more) pins and it's simply a matter of snapping off the number of pins required. External wiring connections to the board are made using quick-connect spade terminals. There are six such wiring points and you should solder a male spade lug to the board at each location. The three indicator LEDs can now be installed on the small board. Use a yellow LED for LED 1, a green LED for LED 2 and a red LED for LED 3. Make sure that all the LEDs are correctly oriented - the anode lead is always the longer of the two (see Fig.1). The four wiring leads between the LED board and the header socket are run using 200mm lengths of lightduty hookup wire. Begin by soldering these four leads to the board, then bundle them together and sleeve them The PC board is supported on the base of the case by four plastic mounting posts. The mounting posts used here each have a clip-in end which locks automatically when pushed 1nto the mounting hole. When these posts have been fitted, clip the board into position and slide the thin rectangular thermal washer supplied with the kit behind the SCR. Position the thermal washer behind the SCR exactly as shown in Fig.4, then trace around its outline with a pencil. This done, remove the PC board and apply heatsink compound to the back of the thermal washer. The thermal washer should now be mounted on the metal bracket by using the heatsink compound to hold it in position. Next, clip the main board back onto the mounting posts. Adjust the position of the rubber washer if necessary and position the thermistor as close to the SCR as possible. Apply generous amounts of heatsink compound between the rubber washer and the thermistor and the SCR, then stick a piece of foam rubber to the back of the SCR mounting bracket - see Fig.4. Finally, attach the metal bracket to the aluminium plate using a self-tapping screw to secure the assembly. Be careful not to overtighten the screw, otherwise you could damage the SCR. The bridge rectifier can now be installed on the metal plate, to the left of the SCR assembly. Smear its mounting surface with heatsink compound, then attach it to the metal plate using a 4 x 10mm bolt. · The wiring from the transformer secondaries to the diode bridge and to the main board must be run using heavy-duty (10A) hook-up wire. Solder the four leads to their respective transformer secondary terminals, then bundle them together and slip a 50mm-length of 10mm plastic tubing over them. The two leads that go to the bridge rectifier are now soldered to the AC terminals (see Fig.3), while the two remaining leads are fitted with quick-connect spade lugs and connected to the main PC board. The remainder of the wiring from the bridge rectifier can now be completed. As before, use 10A cable for OCT0 BER1992 65 PARTS LIST 1 PC board, code SC14110921, 177 x 72mm · 1 PC board, code SC14110922, 34 x 15mm 2 M-2170 30V CT mains transformers (Altronics) 1 3AG 1.5A 240V fuse (F1) 1 3AG 15A fuse (F2) 4 PCB fuseclips 1 3AG fuseholder 1 12V 10A DPDT relay 4 plastic PCB mounting posts 2 cordgrip grommets 4 plastic feet 6 plastic cable ties 1 200mm-length of 10mm-dia. heatshrink tubing 1 200mm length of 4-core light duty cable 1 plastic case 6 plastic rivets 1 aluminium baseplate 1 aluminium heatsink bracket 1 piece of foam rubber, selfadhesive, 10 x 8mm 1 packet of heatsink compound 1 mains lead with plug 1 4-pin header 1 4-pin socket 1 insulating washer, 30 x 20mm 8 PC mounting spade lugs 16 female spade lugs 1 5-way 240V terminal block with spade lug connectors 1 1.5m-length of heavy-duty hookup wire 1 1-metre length of heavy-duty (1 0A) figure-8 cable with battery clamps 1 front-panel label 4 self-tapping 4 x 12mm screws (to secure rubber feet) 3 self-tapping 4 x 6mm screws 5 4 x 10mm bolts (to secure transformers & earth lug) 3 4 x 15mm bolts (to secure the mains terminal strip & bridge rectifier) 8 4mm nuts 8 4mm washers 1 Philips 6.8kQ NTC thermistor (RTH1) 3 20kQ trimpots (VR1 ,VR2,VR3) Semiconductors 3 LM339 quad comparator ICs (IC1-IC3) 1 78L05 3-terminal regulator (IC4) 66 SILICON CHIP 1 35A bridge rectifier (BR1) 1 MCR264-4 40A SCR (SCR1) 1 BC556 PNP transistor (01) 1 BC546 NPN transistor (Q2) 1 BD679 Darlington transistor (Q3) 2 BC548 NPN transistors (Q4,Q5) 5 1N4002 silicon diodes (D1-D5) 1 1N4751 30V 1W zener diode (ZD1) 1 5mm yellow LED (LED1) 1 5mm green LED (LED2) 1 5mm red LED (LED3) Capacitors 2 100µF 35VW electrolytic 1 100µF 16VW electrolytic 2 10µF 16VW electrolytic 1 1µF 50VW electrolytic 1 .01µF monolithic Resistors (0.25W, 1%) 5 100kQ 1 91kQ 2 82kQ 1 56kQ 4 47kQ 3 22kQ 2 10kQ 1 8.2kQ 1 5.6kQ 6 2.2kQ 2 1.8kQ 2 560Q 1 150Q 5W 1 120Q 1 56Q Calibration circuit 1 1N5404 3A diode 1 10µF 50VW electrolytic capacitor 1 100Q 1OW resistor Where to buy the kit A short-form kit of parts for this project is available from the author for $65 plus $15 p&p. This kit includes a predrilled case, the metal baseplate & heatsink bracket, a front panel label, \ he PC boards, all the semiconductors, the thermistor, the PC mounting spade lugs, the thermal washer, the mains terminal block, mounting posts for the regulator board, & the battery cable & clamps. It does not include the power transformers, the mains cord, minor hardware items, the relay or minor PC board components (note: other parts available on request). Payment should be made by cheque or money order to: H. Nacinovich, Beryl Rd, Gulgong, NSW 2852. Phone (063) 74 1486. Note: copyright of the PC artwork associated with this project is retained by the author. these leads and fit them with spade lugs to make the connections to the board. Check all these wiring connections very carefully; it's all too easy to make a mistake here. Finally, feed the heavy-duty (10A) 2-core battery cable through a hole in the plastic base, fit the leads with quick connect terminals and connect them to their corresponding terminals on the PC board. Use a cordgrip grommet to secure the cable to the plastic base and fit the far ends of the cable with large battery clips. Calibration To calibrate the battery charger, you will need a voltmeter (preferably a digital multimeter) and a 0-30V DC variable power supply. You also need a 100Q 10W resistor, a lOµF 50VW capacitor, a 3A diode and some hookup cable (note: the power supply, resistor and capacitor are used to simulate the battery). The step-by-step calibration procedure is as follows: (1). Connect the lOOQ resistor, diode and capacitor across the output of the variable power supply as shown in Fig.5. Do not connect the charger at this stage. (2). Switch on and adjust the variable supply for 6.8V across the lOOQ resistor. (3). Connect the battery charger output leads across the resistor, as shown in Fig. 5. Switch on the battery charger and adjust VR1 so that the LED display just changes from "MEDIUM" to "HIGH". (4). Switch off the battery charger and adjust the power supply output to give 13.6V across the lOOQ resistor. Switch on the charger again and adjust VR2 so that the LED display just changes from "MEDIUM" to "HIGH" as in step 3. (5). Switch off the battery charger and adjust the power supply output to give 27.2V across the lOOQ resistor. Switch on the charger again and adjust VR3 so that the LED display again just changes from "MEDIUM" to "HIGH". That completes the calibration procedure. By the way, if your variable power supply only goes to 20V or so, you can obtain the extra voltage required for step 5 by connecting a 12V battery in series with it. Testing Before placing the unit into general service, it's a good idea to check that PCB and SCHEMATIC CAD 3A OIODE COVER REMOVEO +t - - - ~- -- - - - - - - + - IM-+-1+ 100n 10W BATTERY CHARGER 10 50VW + _ VARIABLE POWER SUPPLY (0·30V) :·· ,__ r .. _ Fig.5: this circuit is used to calibrate the unit, so that it charges the battery to the correct voltage on each of the three ranges (6V, 12V & 24V). Just follow the step-by-step instructions in the text. --- - - ·::t = UQlJID!I. I ~ ..... : - : TV IFAMPLIFJE •.:: , '" I ' \. F -~- ,,, '1'\lli':6",---ti . ~ !"'"'~ ! .:: i _--------------- '------------_______ 1-10A AMNIETER .J BATTERY CHARGER LEAD-ACID BATTERY Fig.6: this test circuit is used to ensure that the current & temperature limiting circuits are working correctly. The 12A load can be made up by connecting several high-power automotive lamps in parallel. SCR1 INPUT VOLTAGE EASY-PC • Runs on PC/XT/AT/286/386 with Hercules, CGA, EGA or VGA. VOLTAGE PIN 13, IC1d • Design Single sided, Double sided and Multilayer boards • Provides Surface Mount support SCR1 CURRENT, FLAT BATTERY • Standard output includes Dot Matrix/Laser/Inkjet printers, Pen Plotters, Photo-plotters and NC Drill SCR1 CURRENT, BATTERY NEAR FULL CHARGE Fig.7: if you have an oscilloscope, you can compare the voltage waveforms on the input of the SCR & on pin 13 ofICld against those shown here. The bottom two waveforms show the SCR current for a flat battery & an almost fully-charged battery respectively. Notice how the SCR turns on later in each half-cycle as the battery nears full charge. • Award winning EASY-PC is in use in over 12,000 installations in 70 Countries World-Wide • Superbly Easy to use • Not Copy Protected Options: • 1000 piece Schematic symbol library the current and temperature limiting circuits are working correctly. To do this, you will need a 12V lead-acid battery in reasonable condition, a 0lOA ammeter (ie, a digital multimeter), and a resistive load which draws at least 12A. A suitable load can be made up by connecting several high-power 12V automotive lamps in parallel. If you don't already have the lamps in your workshop, try scrounging a couple of old sealed headlamp units for a few · dollars from a wrecker's yard. The required load can then be made up by connecting the high and low-beam circuits in parallel to give a total load of about 160-170W. Of course, you can also use eight 20W globes in parallel if you have them on hand. You can easily calculate the load current using the formula I= P/V, where I is the current, P is the total wattage of the globes, and V is the battery voltage. To test the charger, connect it to the battery with the 10A ammeter in series with the positive lead as shown • Surface Mount symbol library • Gerber Import facility For full info 'phone, fax or write: BTC PO BOX432 GARBUTT 4814 QLD. PH (077) 21 5299 FAX (077) 21 5930 OCT0HEH1992 67 The mains cord is installed from the underside of the base & is clamped using a cordgrip grommet. Be sure to fit insulating sleeves to all the quick-connect spade lugs that clip on to the mains terminal block, to protect yourself from accidental contact with the mains. TABLE 1: OUTPUT CURRENT VS. BATTERY VOLT AGE Battery Voltage Nominal Actual Charger Output Current (measured at actual battery voltage) 6V 10A (+/-1A) 6.9V* 200mA (max). 11 V 9A (+/-1A) 13.8V* 100mA (max) . 22V · 5.5A (+/·0.5A) 27.6V* 100mA (max). 6V 12V 24V An entry marked with an asterisk (*) indicates the voltage across the battery when it is fully charged. in Fig.6, but don't connect the resistive load at this stage. Switch on and check the current reading. This will depend on the state of charge of the battery but should be not exceed the limit specified in Table 1 (ie, 9A ±1A). If the battery is flat, the output current will probably be very close to the specified 9A limit, due to the current limiting action of th(l regulator circuit. If, however, the current exceeds the specified limit by an appreciable amount, switch the charger off immediately and check the main board for wiring errors and incorrect component values. In particular, check the 68 SILICON CHIP values of Rl 7 and R18. Assuming everything is OK, connect the load across the battery as shown in Fig.6 and note the ammeter reading. This should approach the specified 10A limit although, if the battery is fully charged, it may be necessary to wait a while for the battery voltage to drop sufficiently for the current limiting action to come into effect. In other words, a fully charged battery will initially supply part of the load current, thus giving a lower than expected current reading until the battery partially discharges. Do not disconnect the battery for this test; its presence is necessary to ensure that the charger switches to the correct output voltage. As before, switch off immediately and check the regulator circuit if the charging current exceeds the specified limit by a significant amount. Finally, check the voltage at pin 8 of IClb. At a heatsink temperature of 25°C, this voltage should be approximately 1. 2V. During normal operation, the heatsink temperature will rise above the ambient level and the voltage on pin 8 of IClb should rise accordingly. At high charging current levels, the heatsink temperature may rise to 65°C or thereabouts, at which point the voltage on pin 8 of IClb should be about 3.6V. IClb should now act to reduce the charging current to prevent additional temperature rise, as described previously. If, at any temperature, the measured voltage on pin 8 of IClb is significantly outside the range expected or does not increase with heatsink temperature, check the circuitry around thermistor RTH1 and R24. Note that, ideally, the charger should also be tested with 6V and 24 V batteries. However, this will not usually be practicable and it's generally safe to assume that everything is OK if the circuit checks out with a 12V battery. Final assembly The display board can now be mounted on the cover. Enlarge the holes if necessary until the LEDs are a snug fit and note that the green LED (HIGH) goes towards the top. A dab of adhesive can be applied to the sides of the LEDs to secure the assembly in position. This done, fit the label to the cover, plug the LED wiring connector into the main board, and fit the cover to the base. Finally, secure the cover using the plastic rivets supplied. These rivets come in two parts: a bush and a pin. The bushes are pushed through holes in the sides of the cover and matching holes in the .b ase flanges. The pins are then pushed into the centres of the bushes to prevent the rivet assemblies from coming apart. To remove the cover, use a punch to push the plastic pins out of the bushes. The bushes can then be removed by pulling them out of the cover. SC