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Add extra touch switches to your room An extension for the Touch-Lamp Dimmer If you are building the Touch-Lamp Dimmer described in last month's issue, you can add one or more extension units so that you can dim your lights from several positions. These can be simply wired in place of 2-way switches. By LEO SIMPSON Dimming from one point is OK for small rooms but if you have very large rooms or a hallway you probably want to be able to dim or turn your lights on and off from several points. For example, there may be several entrances into a large room or hallway and it is convenient to have a touchplate near each doorway. Another room where it is convenient to have two touch plates is the bedroom - put one near the doorway and another near the bedhead, so you don't have to get out of bed to turn off or adjust the light. No modifications are needed to the the Touch-Lamp Dimmer in order to add the extensions. It is just a matter of wiring them to the connection terminals on the TouchLamp Dimmer board. The Dimmer extensions are built behind the same standard plastic grid and decorative plate from the HPM Decorator range. In that way the extensions look exactly the same as the Dimmer itself. How it works Fig.1 shows the circuit details. It consists of one PNP transistor, two zener diodes and a few other bits. It is wired between the Active and Extension terminals on the TouchLamp Dimmer. As with the Touch-Lamp Dimmer circuit, the common reference in the extension circuit is the Active line of the mains. The circuit works quite simply. When you touch the Touch Plate, you "pull" the junction of zener diode ZD1 and diode D1 low with respect to the Active line. This causes a 50Hz voltage to be impressed across zener ZD1 and this signal is rectified by D1 to produce several volts DC across the .01µ,F capacitor. This small DC voltage then biases on transistor Qi via the 2.2MO resistor. So Q1 switches on and effectively connects the "Extension" line to the Active line. The two zener diodes are included in the circuit for voltage limiting. ZD1 limits the voltage developed across the .01µ,F capacitor and thus helps define the response time of the circuit. ZD2 limits the voltage across Q1 to a safe value so that there is no danger of transistor failure. Construction The Touch-Lamp Dimmer Extension is built behind the same blank grid as used for the main Dimmer. The PC board is secured to the grid using a 12mm-long raised head screw and two nuts (one either side of the board). 32 SILICON CHIP As mentioned earlier, the TouchLamp Dimmer Extension is built behind a standard HPM blank Decorator grid. We suggest that you use the same grid and decorative plate as for the main Dimmer. .--------------------oA PARTS LIST 250VAC 1 PC board, code SC10107892, 53 x 71mm 1 HPM white Decorator blank grid and gold plate, DR770GF/WE/G 1 2-way insulated terminal block 1 3mm dia. x 12mm-long countersunk raised head machine screw 2 3mm dia. nuts 1 3mm washer ZD1 s,-iv J 3.3M .01 01 BC559 D1 1N4148 B EOc VIEWED FROM BELOW ,___ _ _ _--OEXTENSION TOUCH LAMP DIMMER EXTENSION Semiconductors 1 BC559 PNP transistor (01) 2 6.8V 1 W zener diodes (ZD1 , ZD2) 1 1 N4148 silicon diode (D1) Fig.1: when you touch the Touch Plate, a 50Hz voltage is impressed across ZD1. This signal is rectified by D1 and switches on PNP transistor Ql which effectively connects the Extension line to the Active line. The few components are all mounted on a small printed board measuring 53 x 71mm and coded SC 10107892. The wiring diagram can be seen in Fig.2. Note that the board uses the same Philips VR37 4.7MO high voltage resistors as specified for the Touch-Lamp Dimmer. These must be used otherwise the safety of the circuit may be jeopardised. The assembly procedure is as follows: Step 1: inspect the board careful- Capacitors 1 .01 µF 1 OOVW metallised polyester (greencap) ly for any defects such as shorted or open circuit tracks and correct drilling of the holes. Make sure that the board will fit over the 8 locating lugs on the HPM plastic grid plate. Step 2: insert two PC stakes into the board and solder them. These provide the connection points for the 2-way insulated terminal block. Step 3: install the resistors and the .OlµF capacitor. The colour codes for 4-band (5 % ) and 5-band (1 % ) resistors are listed in the table associated with the wiring diagram Resistors (¼W, 5%) 2 4. ?MO (Philips VR37 high voltage; do not substitute) 1 3.3MO 1 2.2MO 1 2200, 1W of Fig.2. The capacitor may be labelled .OlµF, 10n or 103K. Step 4: install the diodes and Fig,2: it should only take you a few minutes to install all the parts on the PCB. Do not substitute for the two 4.7Mrl resistors specified in the parts list. If they're not Philips VR37 types, don't use them. TOUCH PLATE .-.--=!=4.=7M=l-e-<at>----------, m24~VAC imtJ t.o,o~fi1 ~ 6- ~ EXTENSION METALLISED POLYESTER CAPACITORS ~ZD~ 0 Z 1~ No. □ 0 1 Value .01µF IEC EIA 1 On 103K RESISTORS No. □ □ □ □ 2 Value 4 .7MO 3 .3MO 2 .2MO 2200 1W 4-Band Code yellow violet green yellow* orange orange green gold red red green gold red red brown gold 5-Band Code not applicable orange orange black yellow brown red red black yellow brown not applicable * Note: the two 4 . ?MO 5% tolerance Philips VR37 high voltage resistors do not have a gold tolerance band - it is yellow. If the two 4. ?MO resistors you have been supplied with do not have a light blue body (10mm long) and a yellow tolerance band, you have been supplied with the wrong type. Do no use them! JULY 1989 33 Step 7: electrical check. This is the same test as for the TouchLamp Dimmer. Switch your multimeter to the highest resistance range and measure between the Active terminal and the touch plate screw. The resistance should be infinite in one direction and 15MO in the other (ie, do the measurement once and then reverse the leads to do it again). If you have an analog multimeter, you should get zero or negligible pointer deflection for both measurements. If this measurement is not right, check that you have the right value resistors installed. Installation A small washer or solder lug must be soldered on the copper side of the board for the touch plate screw connection. Check your work carefully before mounting the board on the blank grid. When the board is mounted on the blank grid, the washer on the copper side makes contact with the nut used to secure the touch plate screw. A second nut is then used to secure the board. transistor into circuit. Note that their polarity must be correct. The cathode of all three diodes is shown by the band at one end. Install the diodes as shown and make sure you use the correct type at each location. Step 5: solder a washer or solder lug on the copper side of the board. This is for the touch plate screw connection. Now carefully inspect all your work and soldering before the next step. Are all components correctly positioned and soldered in? Good. 34 SILICON CHIP Step 6: fit the board to the blank grid plate. You will need to drill one 3mm hole in the grid plate for the touch plate screw. Locate the board over the 8 lugs to mark the position of the hole to be drilled. The hole should be countersunk slightly on the dress panel side and fitted with a raised head countersunk 3mm machine screw 12mm long. The screw is secured to the grid plate with one nut. Do it up tight, then fit the board and secure it with a second nut over the screw. Make sure it is tight. If you have an existing 2-way switch for your lights, as shown in Fig.3(a), it is a relatively simple matter to install the Dimmer Extension. Fig.3(b) shows the details. If you want to install the Dimmer Extension in a home where there are presently no 2-way switches, you will need to have a licensed electrician run a 2-way cable from the Touch-Lamp Dimmer board to the proposed extension touch plate location. Note that you can have as many extensions as you like although we doubt whether more than three would ever be needed for one Dimmer installation. One point to be watched is that you must not transpose the wires for the Active and Extension inputs. If you do so you will probably burn out the 2200 1W resistor and possibly do other damage. Cleaning After some period of time, the Dimmer touch plate may collect dust and grime on the polycarbonate grid plate. This can cause false triggering of the dimmer. The cure is easy - just give the grid plate a wipe over with a clean cloth. Troubleshooting Now a few words on troubleshooting the Touch-Lamp Dimmer and extension circuits are appropriate. One thing you can't do is attempt to make any checks on the TouchLamp Dimmer while it is connected MAIN SWITCH REMOTE SWITCH LAMP l - - - < l NEUTRAL ACTIVEO----~- (a) NORMAL TWO-WAY SWITCH TO OTHER EXTENSIONS (OPTIONAL) A ~ ~ --,-p-~-----.....;:i.-Jl.0-~l : C I < ~ } -J w DIMMER EXTENSION 0 ACTIVE ;--+--<at>-o NEUTRAL ~ ~ TOUCH LAMP DIMMER (b) TOUCH-LAMP DIMMER WITH EXTENSION(S) Fig.3: here's how to wire the Dimmer circuits in place of an existing 2-way switch arrangement. Don't transpose the wires for the Active and Extension inputs - you'll burn out the 2200 1W resistor if you do. to the mains wiring. That would be extremely dangerous. However, if your Touch-Lamp Dimmer fails to function as it should, it is possible to rig it up to a low voltage AC supply and ·then check it out in perfect safety. The method is as follows. You need a power supply or transformer which will deliver about 15 to 18 volts AC. You also need a 12V filament lamp, say around 18 to 21 watts, to substitute for the 240V AC lamp. Fig.4 shows how to wire the Touch-Lamp Dimmer to a mains transformer or power supply delivering 15 to 18 volts AC. One side of the 18V transformer, designated 0V, connects to the 12V filament lamp and then to the Load terminal of the Dimmer board. The other wire of the transformer then connects to the Active terminal on the Dimmer board. You also need a jumper lead to bridge out C2, a 0.lµF 250VAC capacitor. Fig.4 shows how the jumper lead is connected. Now apply power via the transformer. Nothing should happen although it is possible that the lamp may flicker. Now you should be able to get the lamp to turn on fully by touching the 0V wire with one hand and the "touch test" point with the other. The latter is marked on Fig.4 and is the junction of the continued on page 91 When the decorative plate is clipped into position, it should just make contact with the raised-head screw. We preferred the gold plate but you can use any colour you like from the HPM range. I I SC10-1-0789-2 Fig.5: here is an actual size reproduction of the PC artwork. TOUCH TEST Fig.4: by hooking the main Touch-Lamp Dimmer circuit up to a low-voltage AC supply, you can troubleshoot the circuit in complete safety. JULY 1989 35 Philips infrared image converter Dimmer extension ctd from page 35 Want to see in the dark? This Philips infrared image converter valve, type XX1080, could be used as the basis of an infrared vision experiment. You will need a lens system and a high voltage power supply. The tube is bargain priced at only $45 from D. Dauner who has all the data you need. See him at 51 Georges Crescent, Georges Hall, NSW 2198. Phone (02} 724 6982. 4.7MO and lMO resistors and functions in the same way as the touch plate during normal operation. If the Dimmer does not function, measure the DC voltage between pins 1 and 7 of ICl. The voltage should be close to 5V with pin 1 positive with respect to pin 7. If you can't measure this voltage, check the orientation of ZDl, D4 and the lOOµF capacitor. Don't worry about measuring the voltage across ZDl. If you do so, you will get a reading of about 2.5 volts which may suggest that ZDl is malfunctioning but it is not. If you get the right DC supply voltage and the Dimmer fails to function, check the polarity of Dl and D2. If you suspect that the Triac is faulty, you can easily check it by disconnecting D3 and then connecting a 1000 resistor between its A2 and G(ate) pins. This should light up the lamp while ever the 1000 resistor is connected. Don't do this For test while D3 is connected otherwise you run the risk of damaging ICl. You can also check the operation of the Extension input by momentarily connecting a jumper lead between the Active and Extension input. This duplicates the function of the touch plate. Remove the clip lead before reapplying the mains once you have the unit operational. ·1c Bookshelf - ctd from page 47 (shortwave listeners). Chapter 5 is on transceivers while chapter 6 gets into the nitty gritty of low band DX operation. Chapter 7 has Basic listings of computer programs discussed throughout the book. Chapter 8 is a comprehensive bibliography on all the topics in the first 6 chapters. This most useful book is available at a bargain price of $12 from the NSW Division of the Wireless Institute of Australia, PO Box 1066, Parramatta, NSW 2124. I~ RANGE .. . TECHNOLOGY ... and SERVICE TALK TO THE SPECIALISTS ABOUT YOUR BATTERY REQUIREMENTS! - BROADCASTING TEST EQUIPMENT HOBBY ELECTRONICS MEDICAL PROTOTYPING BATTERIES TO SUIT - BP90, NPI, ECLAIR , AARTON, ZENITH , AMPEX , FREZZOLINI. 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