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BUILD TOUCI and off from more than one point in a room, just like 2-way switches. You can't do that with a knob type dimmer. In fact, if you have a large room or hallway, you can dim the one set of lights via one, two or three touch plates. If one of your family members is unfortunate enough to be stricken with arthritis, it is much easier for them to turn on a light with a touch plate than with an ordinary switch. Features Are you still persevering with one of those old knob-type light dimmers? You are! Well, get onto this Touch-Lamp Dimmer. You can turn your lights on and off or dim them just by touching the decorative plate. By LEO SIMPSON Touchplate dimmers are not new; they have been around for about 6 years now but they are still new enough to be a novelty item in most homes. They do have advantages over conventional knob-type light dimmers though. First, there is no switch or knob to fumble with in the dark, just the decorative plate. With no switch and no knob involved, there are no mechanical 48 SILICON CHIP components to wear out or fail. (Mains switches do wear out, of course, often after only a few years). Second, our circuit incorporates full mains suppression so the amount of radio interference is less than from typical commercial dimmers. Third, more than one touch plate can be connected so that the lights can be dimmed or turned on The Touch-Lamp is housed behind a standard plastic grid and anodised aluminium plate from the HPM Decorator range. In fact, if you go for the gold anodised plate, it will look very similar to HPM' s own touchplate dimmer (Dimamat Cat. DRM500). Naturally, by building the Touch-Lamp Dimmer yourself, you save about half the price of the commercial version. The Touch-Lamp Dimmer is intended for dimming incandescent lamps rated from 25 watts up to a total of 300 watts (individual lamps should not be rated at more than 100 watts). It is not suitable for controlling fluorescent lights or motors of any sort. The Touch-Lamp Dimmer may be installed on walls or in standard wall-boxes (ie, HPM Cat. 140P) but cannot be installed in place of miniature architrave switches. Installation is simply of matter of disconnecting the existing light switch and wiring the Touch-Lamp Dimmer in its place. We'll talk about this in more detail later. SLB 0586 dimmer IC The circuitry of the Touch-Lamp THE 1-L P DIMMER Dimmer is quite simple and is based on a new integrated circuit from Siemens, the SLB 0586. This chip supersedes and replaces the Siemens S576 chip which had three variants: the S5 76A, B and C. The SLB 0586 is quite a complex chip but briefly, it responds to signals generated when your hand touches the decorative plate and it distinguishes between a brief touch and a longer hand contact. In response to these signals, it delivers trigger pulses to a Triac which controls the actual power fed to the incandescent lamp. To read more about the internal function of the SLB 0586 see the panel accompanying this article. employs a Triac to vary the AC power fed to the incandescent lamp. The Triac is an AC power control device which can be made to turn on at any point in each halfcycle of the 50Hz AC mains waveform. If it is turned on early in each half cycle, the power fed to the load is high. If it is turned on late in each half cycle, the power fed to the load is low. Since the Triac is a switching device, it can control quite large amounts of power while its own heat dissipation is very small. For example, if the Touch-Lamp Dimmer is feeding 250 watts to an incandescent lamp load, the power dissipation in the Triac will only be about one watt. Precisely when the Triac is turned on during each mains half cycle is determined by the timing of the Phase controlled Triac As with any other light dimmer, the Touch-Lamp Dimmer circuit trigger pulses fed to its gate electrode. Since the timing is relative to the phase of the mains waveform, this method of control is referred to as "phase control". Radio interference One big problem with Triac circuitry, as used in light dimmers, is that it generates radio inter£erence. This is because the Triac turns on extremely rapidly, within a microsecond. The fast rising current waveform is rich in harmonics and these are easily picked up by radios, expecially in the AM broadcast band. If you bring an AM portable radio close to a conventional dimmer you can hear the "buzzing" sound which is caused by the Triac switching. The buzzing is loudest when the light is at half brilliance. EXTENSIOND----- - - - - - - - - - - - - - - - - > - - -....,__ _ _ _ _....,__ _ _ _ _ _ _ _ _ _ ____,_ _ _-OA LKl ,I 1M 01 1N4148 .00b8 3 02 1N4148 1 INTEGRATOR 100 16VW _ mJ 1W 03 1N4148 VOD 8 TRIGGER.t--- - t - - - - - + - - - - i - - - - i - - t --N-+ - - t - - - - - . 5 240VAC 01 SC142-M !Cl SLB0586 4 1.™ .SYNCl - ' - - + - - - 4 . . , . _ - - - - - + - - - - - ' t - - - ' , f \ N , , - -..... VSS 120k 04 1N4007 OPTIONS: LKl - DOWN /UP DIMMING LK2 - UP/DOWN DIMMING OPEN - STORED DIMMING 250V 300W MAX. L1 : 29T, 0.63mm ENAMELLED COPPER WIRE ON NEOSIO 17/732/22 IRON DUST TORDIO TOUCH LAMP DIMMER A2 Fig.1: the heart of the circuit is the Siemens S1B0586 dimmer IC. It responds to signals generated when your hand touches the touch plate and delivers trigger pulses to Triac Qt. The Triac then controls the actual power fed to the lamp. JUNE 1989 49 The Siemens SLB 0586 Dimmer IC The SLB 0586 is a new light dimmer control IC. It triggers a Triac directly and will thereby dim a lamp to any desired level or turn it on or off in response to signals from a single sensor, the touch plate. The SLB 0586 replaces the earlier Siemens dimmer chips, the S576A, S576B and S576C. However, the new chip is not exactly compatible with the S576 family. While it has the same pinouts, it runs from a lower supply voltage and so if it was used to replace an S576, the circuit components and layout vyould have to be changed. Since the SLB 0586 replaces the S576A, B and C, it can perform the functions of these three separate chips, depending on whether its pin 2 is tied to the + 5V rail, the 0V rail (ie, pin 7) or left open circuit. When pin 2 is tied high (LK1 on the circuit diagram, Fig.1). the SLB 0586 performs the "A" function. When the lamp is turned on, it is brought up to maximum brightness within 380 milliseconds which means the lamp filament gets a "soft start". It you hold your hand on the touch plate, the lamp will start at minimum brightness and will brighten to full brightness within 4 seconds. With repeated When the light is brightest or dimmest, the buzzing will be less. In the Touch-Lamp Dimmer circuit we have included suppression components to keep this "buzzing" interference to a minimum. Now let's have a look at the circuit shown in Fig, 1. This features the SLB 0586 dimmer IC, a Triac (Ql), and a handful of other components. The touch plate is shown on the left hand side of the circuit while the Triac is on the righthand side. The Triac is connected between the mains Active lead and one side of the lamp via the 100/.lH choke. The other side of the lamp is connected to the Neutral line from the mains. The 100/.lH choke and the 0.1/.lF 250V AC capacitor (Cl) con50 SILICON CHIP dimming, the lamp is always brightened. When pin 2 is left open circuit (no connection). the SLB0856 performs the "B" function. When the lamp is turned on, it will have the brightness set at the same level as when last used. It you hold your hand on the touch plate, the lamp will brighten from the stored setting and will then dim after maximum brightness is reached. The "B" function also gives a lower minimum brightness than is achievable tor the "A" function . If pin 2 is tied low, the SLB 0586 performs the "C" function . When the lamp is turned on, it is brought to maximum brightness within 380ms (soft start) . If you hold your hand on the touch plate, the lamp will start at minimum brightness and will brighten to full brightness within 4 seconds. With repeated dimming, the direction of dimming is reversed. The "C" function also enables a lower minimum brightness than is achievable with the "A" function. For all modes, the time to go from dim to bright and dim again is 7 .6 seconds. At first reading, the "A" and "C" functions might seem identical but the ability of function "C" to more easily fine tune the level of brightness is an advantage . We recommend either the "C" Junction (link LK2) which gives stored dimming or the "B" function (no link) which gives a soft start and better control of the dimming. For convenience, we prefer the stored dimming function (B). It you are concerned about getting better life from your lamps, you may prefer to use the "soft start" function (C). Fig. 2 is a block diagram which shows the main functions of the SLB 0586 dimmer chip. It contains logic circuitry to decode whether the lamp is to be dimmed (changed in brightness level) or turned on or off. It also decodes the position of the link at pin 2 which gives the three dimming functions already mentioned . The way the SLB 0586 distinguishes signals from the sensor is as follows. First, very brief pulse signals, less than 50 milliseconds, are disregarded. This is to make the unit insensitive to short t~rm disturbances in the mains voltage. Second , tor pulse signals between 50 and 400ms, the SLB 0586 will turn the lamp on or off. Third, for pulse signals longer than 400ms, the SLB 0586 provides the dimming function. nected between the Active line and the lamp are the interference suppression components mentioned earlier. The choke and capacitor Cl form an LC filter which attenuates the RF harmonics which otherwise would be radiated by the mains wiring. Secondly, the inductance in series with the Triac stops the load current from rising too rapidly and hence generating interference. Along the bottom line of the circuit is a lkO 1W resistor, a 0, 1/.lF 250V AC capacitor (CZ) and a rectifier diode D4. In conjunction with the 100/.lF 16VW electrolytic and the 5.6V lW zener diode ZDl, these components provide a 5V supply rail for the SLB 0586 integrated circuit. The workings of the DC supply circuit are interesting for a number of reasons. First, the 5V supply is derived from the 240V AC mains with very low power dissipation. This is achieved by dropping most of mains voltage through the impedance of the 0,1/.lF 250VAC capacitor CZ. Current flow for the DC supply takes two paths. For positive halfcycles of the 50Hz mains waveform, the current flows via the 100/.lF capacitor, through diode D4, the lkO 1W resistor and then via CZ and the lamp to the Neutral line. For negative half cycles, current flows via the lamp and CZ, the lkO 1W resistor and then via the zener diode ZDl to the Active line. For positive half cycles, the Programming Input o---------- Signal Evaluation anc Recognition Types A,B,C Brightness Memory Signal Element Counter (SEC) Control Logic for Timing and Safety Log ic Comparator Extension Input Sensor Input Sync Input Sync Trigger Pulse Output Reset Output Stage PLL Cycle Counter (CC) !NT - [ 1 Fig.2: block diagram of the SLB 0586 dimmer chip. It contains logic circuitry to determine whether the lamp is to be dimmed or turned on or off. The trigger signals to the Triac can be varied between 45° (high power) to 152° (low power) in each half cycle. To be able to distinguish the length of time of pulse signals from the touch plate, the SLB 0586 has internal counter circuitry and a phase lock loop (PLL). There is also a brightness memory which is effectively another counter which is stepped up or down in response to the signals from the touch plate. The IC has three inputs to determine its response: the touch plate already mentioned, the extension input (for additional touch plates) and the sync input which synchronises the voltage controlled oscillator of the PLL to the mains frequency , 50Hz. Synchronism is necessary at all times otherwise the trigger pulses to the Triac would be incorrectly timed and so the lamp would flicker badly. All the internal circuitry works to determine whether or not the Triac receives trigger signals to turn it on . The trigger signals can be varied from between 45 ° (high power) to 152 ° (low power) in each half cycle. The length of trigger signal fed to the Triac is just over 39 micro- voltage across the lOOµF capacitor and D4 is limited to the breakdown voltage of ZDl, so that effectively, the voltage across the l00µF capacitor is limited to 5V. Note that the + 5V line of the circuit is actually the Active line of the mains. This is important because the reference line for the SLB 0586 IC is the Active line. Pin 8 of the SLB 0586 is the output of the device and it triggers the Triac. It works by "sinking" a current out of the Triac gate, via diode D3. This is the most sensitive mode of Triac triggering and hence requires the least current. Pin 4 is the sync input of ICl. It gets a small filtered sample of the 50Hz mains signal from the A2 terminal of the Triac, via a 1.5Mrl resistor. Filtering is provided by the .0068µF capacitor connected between pin 4 and the Active line. Pin 2 is the programming input. It is tied high with link LKl , or tied low with LK2 or left open circuit (no link). Programming is discussed in some detail in the accompanying panel on the SLB 0586. We think most readers will prefer to have the unit programmed so that the dimmer comes on with the lamp at the same brightness as when it was last used. To achieve this, pin 2 is left open circuit. Pin 3 is the integrator input. This is the filtered voltage for the VCO (voltage controlled oscillator) in the internal phase lock loop (PLL) of the IC. Pin 5 is perhaps the most impor- seconds. Thus the CMOS output stage of the SLB 0586 has to supply trigger current only for a very brief period in each half cycle. If power is removed from the circuit briefly, for example during a blackout of a few seconds, the SLB 0586 will remember the brightness setting of the lamp and will come baok to that level when power is restored. For long term blackouts, when power is restored, the lamp will stay off until it is turned on by the touch plate signal. tant input of all, the sensor input for the touch plate. The touch plate works in an interesting way. In effect, the touch plate is connected to the Active line of the mains supply, but via a very high impedance formed by the lMO resistor and the two 4.7Mrl resistors, all in series. The sensor input is connected to the junction of the lMO and 4.7Mrl resistors. When your hand comes into contact with the touch plate, your body capacitance shunts away the mains voltage (which is at very high impedance remember, so you are safe). This shunting away of the 50Hz signal means that pin 5 is "pulled" towards Earth (which is not even shown on the circuit). When pin 5 is pulled towards Earth, JUNE 1989 51 Fig.3: here's how to install the parts on the PC board. Do not substitute for any of the parts specified otherwise safety will be jeopardised. L1 consists of 29 turns of 0.63mm enamelled copper wire on a Neosid iron powder toroid core. METALLISED POL VESTER CAPACITORS D D No. 1 Value .0068µF .0022µF IEC 6n8 2n2 EIA 682K 222K RESISTORS D D D D D D D No. 2 1 1 1 1 1 1 Value 4.?MO 1.5MO 1MO 680k0 470k0 120k0 0.5W 1k0 1W 4-band code yellow violet green yellow* brown green green gold brown black green gold blue grey yellow gold yellow violet yellow gold brown red yellow gold brown black red gold 5-band code not applicable brown green black yellow brown brown black black yellow brown blue grey black orange brown yellow violet black orange brown not applicable not applicable * Note: the two 4.7MO 5% tolerance Philips VR37 high voltage resistors do not have a gold tolerance band - it is yellow. If the two 4. 7 MO resistors you have been supplied with do not have a light blue body ( 1 0mm long) and with yellow tolerance band, you have been supplied with the wrong type. Do not use them! it sits at several volts below the mains Active line. Since everything in the circuit is referenced to the Active line, this is enough to cause the IC to respond. For very brief signals from the touch plate, less than 50 milliseconds, the IC does not respond. This gives the circuit high immunity from mains interference. For touch plate signals between 50ms and 400ms, the IC turns the lamp on or off. In other words, if you touch the touch plate for less than half a second, the circuit will turn the lamp on or off. For longer hand contact with the touch plate, the dimmer action will take place. This is detailed in the explanatory panel on the SLB 0586. Pin 6 is the extension sensor input. It allows the use of additional touch plates or pushbuttons. The additional circuitry required for extension touch plates will be described next month. Pre-production ICs We have yet to explain the purpose of the diodes Dl and DZ. 52 SILICON CHIP The SLB 0586 was originally developed in early 1988 and lab samples were sent to dimmer manufacturers and designers during 1988. SILICON CHIP received samples in the middle of 1988 and had a circuit ready to go for the August or September 1988 issue. Subsequently though, Siemens found that their early production chips had a problem which prevented them from properly resetting after the mains power was removed (as for example, during a power blackout). We therefore had to delay presenting the project. The symptom of this problem is flickering or flashing of the lamp when the mains power is first applied (ie, correct resetting does not occur). To solve this problem, Siemens suggested the addition of diodes Dl and DZ which we have duly incorporated. These diodes are necessary for early versions of the SLB 0586 which are now available as this issue goes on sale. Later, when modified ICs go into production, diodes Dl and DZ will not be necessary, as they will be incorporated into the IC die. Therefore, for kits of this project put together after January 1990, these diodes can be left in or omitted. Kitset suppliers can be expected to omit them as a matter of course. Other points of interest Just a few other points can be made about the circuit. The first is that the DC rectifier system involving D4 and zener ZDl only works when the lamp is off. This is because when the Triac is turned on, the voltage across it is only about 1 volt which is not enough to power the DC circuit for the IC. However, the Triac turns off at the end of each half cycle and in between this time and when it turns on, during the next half cycle, power is available to the DC rectifier circuit. Second, the circuit always draws power from the mains, whether the lamp is on or off. However, since most of the voltage drop to the DC supply is across the 0. lµF Z50V AC 11 PARTS LIST 1 1 2 1 PC board , code SC 11 106891 , 72 x 56mm HPM white Decorator blank grid and Gold plate, DR770GF/WE/G 3-way insulated terminal block Neosid iron powder toroid core, 17-732-22 metre of 0 .63mm enamelled copper wire 3mm dia, 1 2mm long countersunk raised head machine screw 3mm dia. nuts 3mm washer Semiconductors Push all the parts down onto the PCB as far as they will go before soldering their leads. To stop the coil from buzzing, the wire should be wound on tightly and secured using molten candle wax. capacitor C2, which has a high reactive impedance (j31.8k0), the current drawn leads the mains voltage and so the actual true power drawn (as opposed to reactive power) is extremely small, considerably less than one watt. This will not register on a domestic watthour meter. Third, inductor L1 is wound on an iron powder toroid made by Neosid. Because it is a toroid it radiates very little interference, in contrast to inductors wound on rods which are common in commercial dimmers (or non-existent). And because the toroid is made of iron powder, it has a damping effect on the inductor. This, too, is important in reducing the amount of interference radiated by the circuit. Construction As mentioned earlier, the TouchLamp Dimmer is built behind a standard HPM blank Decorator grid and plate. We suggest white for the grid and a gold finish for the decorative plate itself. All the componentry is mounted on a small printed circuit board measuring 72 x 56mm and coded SC 11106891. The wiring layout can be seen in Fig.3. Note that the board is fairly well crammed for the most part but is more open on one corner where the two 4. 7MO resistors are mounted. These two resistors are mounted as far away as possible from the active circuitry to ensure high isolation between the touch plate and the mains. Note: the safety of this circuit can be jeopardised if you don't use the right components. Take special note of the specified components and the way they are installed. The two 4.7MO resistors are special high voltage types made by Philips, type VR3 7. They are light blue in colour and have a voltage rating of 2.5kV RMS. They are specified for your safety. Don't substitute other types. As a point of interest, VR3 7 resistors made to 5 % toletance do not have a gold band; it is yellow instead (as shown in our colour code tables). This is because metal par- 1 SC142M, BT1 37F-600 or MAC218A8FP isolated tab Triac (01) 1 Siemens SLB 0586 light dimmer IC (IC1) 1 5.6V 1 W zener diode (ZD1) 3 1 N4148 , 1 N914 small signal diodes (D1, D2, D3) 1 1 N4007 silicon diode (D4) Capacitors 1 1 OOµF 16VW PC electrolytic 2 0 .1µF 250VAC interference suppression capacitors (Wima MP3 or Philips MKT-P 2222 330) 1 .0068µF 1 OOVW metallised polyester (greencap) 1 .0022µF 1 OOVW metallised polyester (greencap) Resistors ( ¼ W, 5 % tolerance) 2 4. ?MO (Philips VR37 high voltage; do not substitute, see text) 1.5MO 1 470k0 1MO 1 120k0, 0.5W 1 1 kO, 1 W 680k0 tides would degrade the high voltage property of the resistor 's coating. Step 1: Three PC stakes are inserted into the board and soldered. These provide mounting and connection points for the 3-way insulated terminal block which can now be screwed into place. Step 2: solder in the two 0. lµF 250VAC capacitors, Cl and C2. Do not use capacitors which are not labelled 250VAC for Cl and C2. Step 3: wind the inductor Ll. J UN E 1989 53 The pen points to the two 4. 7MO Philips VR37 high-voltage resistors which are in series with the touch plate. The PC board is secured to the plastic grid plate using a 12mm-long raised head screw and two nuts (one either side of the board). 0 ,.... ,.... ,.... (.) en J!. Fig.4: above is the actual-size PC artwork. This takes 29 turns of 0.63mm enamelled copper wire . Wind it on tightly and secure it by running some molten candle wax over the winding. Strip the two ends of enamel, tin them with your soldering iron and solder the inductor to the PC board. To make the inductor mounting more rigid, use some contact adhesive or some more candle wax. Step 4: insert the diodes into cir54 SILICON CHIP cuit. Note that their polarity must be correct. The cathode of each diode (and the zener ZD1) is shown by the band at one end. Install the diodes as shown on the component diagram and make sure that you use the correct type at each location. Step 5: install the three remaining capacitors, making sure that the polarity of the 100µF capacitor is correct. The two metallised poly- ester capacitors can be marked in a number of ways, as shown in the table associated with the component overlay diagram. Step 6: install the resistors. The colour codes for 4-band (5%) and 5-band resistors (1 % ) are shown in the table associated with the component overlay diagram. The link LKl or LK2 may be inserted and soldered now, or left out, depending on how the Dimmer is to be programmed, as detailed elsewhere in this article (no link for stored dimming; LK2 for soft start and reversible dimming). Step 7: install the integrated circuit and the Triac. Note correct orientation of both these critical components. The specified Triacs are isolated tab devices which are a safer proposition than conventional Triacs with live tabs. Step 8: solder a washer or solder lug on the copper side of the board through which the touch plate screw will pass. The HPM blank plate has eight plastic lugs on which the printed board is located. One 3mm hole is drilled in the blank plate to take the touch plate screw. The hole is countersunk slightly on the dress panel side and fitted with a raised head countersunk 3mm machine screw 12mm long. It is secured tightly with one nut. A raised head screw is specified here so that is will make good electrical contact with the decorative plate when it is fitted. Step 9: fit the board to the blank grid plate. Before you do so carefully examine all your work. Are all components correct and properly located? Are all solder connections clean, with no bridges? Yes. Good. Now locate the board on the eight lugs and over the touch plate screw. Secure the board with a second nut on the touch plate screw. Make sure it is reasonably tight. Step 10: electrical check. You're The countersunk raised head screw should sit slightly proud of the grid plate surface to ensure good electrical contact with the decorative plate. almost finished at this point but don't rush it. Switch your multimeter to its highest range and measure the resistance between the Active terminal and the touch plate screw. The resistance should be close to l0MQ or there should be negligible pointer deflection if you have an analog multimeter which will not measure very high resistances. This test will ensure that there is no fault at the touch plate. If the circuit fails this test, check that the correct value resistors have been used and that there are no solder bridges or shorts on the board. Prices listed apply till August. OUR LA EST UHF REMOTE CONTROL (EA JAN 89 and APRIL 89) • • • Installation involves removing the old switch plate and replacing it with the Touch-Lamp Dimmer. Wiring involves only inserting the two switch wires into the terminal block of the PCB. Before doing this you must switch off the power at your fusebox. To ensure that you have pulled the correct fuse, try the light switch before removing it from the wall and touching its connections with a screwdriver. Once the connections are made, screw the Touch-Lamp Dimmer to the wall and re-apply power. Check that the dimmer responds correctly to hand contact on the touch plate. Once that has been established, fit the decorative plate and you are finished. After a long period of use, the Dimmer may collect dirt and an oily film on the polycarbonate plate. This can decrease the resistance between the touch plate and earth and cause false triggering. This can be fixed by a quick wipe over of the decorative plate surfaces with a clean cloth. In some cases, it may be necessary to remove the decorative plate and wipe over the whole plastic grid plate. Next month we will present the Dimmer extension circuit which will allow you to use a number of touch plates with the Touch-Lamp Dimmer. We will also show you how to wire in these additional plates and how to troubleshoot the circuit if it doesn't work. ~ High Security, Low Power Consumption. Switch and Indicator Relays. Up to 50 metre range. COMPLETE KITS TRANSMITTER & RECEIVER ONLY $49.90 Extra Transmitter Kits $17 .00 ea PASSIVE INFRARED IIE DETECTOR (EA MAY 89) • Installation Next month The decorative plate simply clips over the plastic grid plate and contacts the raised head screw. We used a gold plate but you can use any colour you like from the HPM range. LOOK AT THESE BARGAIN PRICED KITS • Uses Special Dual Element Pyroelectric Detector. Kit includes two Lenses. SPECIAL BARGAIN PRICE $34.95 Interface Components $7 .95 extra. CHANNEL UHF REMOTE CONTROL (EA NOV 88 and MARCH 89) • Package including Transmitter, Receiver and Four Channel Relay Driver, plus indicator. SPECIAL TILL END OF AUGUST $119.00 THE: MICROPHONE (EA NOV 86) • • • Profession al Quality Up to 1 V RMS Output, Drives any Amplifier, even HI-FI Line inputs. Touch Control. COMPLETE KIT $24.99 AINS MUZZLER (SC JAN 89) Short Form kit similar to the Mains Muzzler including the Torroid, 3x0.022uF/ 400V metallised polyester capacitors, 1M ohm 1 W resistor and a 275V/40joule Varistor THE PRICE? ... ONLY $7 .40 That's less than the price of the Varistor! UL ONIC MOVEMENT t TOR/ALARM • • • • High Quality Crystal Controlled Kit. Prewired Transducers. PCB & Components plus ABS Case. Relay Output. COMPLETE KIT $42.95 BANKCARD, MASTERCARD and VISA ACCEPTED WITH PHONE ORDERS. P&P FOR ANY OF THE ABOVE $2.50. OATLEY ELECTRONICS MAIL: PO Box 89, Oatley, NSW 2223 SHOP: 5 Lansdowne Pde, Oatley West. PHONE: (02) 579 4985. You can also buy some of our Kits at the following Distributors. Slightly higher prices may apply. NEWCASTLE - NOVOCASTRIAN (049) 62 1358 MELBOURNE - ELECTRONICS WORLD (03) 723 3860 WOLLONGONG - ITEC (042) 26 4044 JUNE 1989 55