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Low-cost circuit controls outside lights AUTOMATIC LIGHT Wont to switch on outside lights automatically when someone approaches your house at night? This automatic light controller will do the job. By BRANCO JUSTIC Many householders are now installing automatic light controllers to monitor driveways, pathways and other approaches to their homes. These units typically employ a passive infrared movement detector to detect the presence of body heat and then automatically switch on outside lights, usually for a preset time. Such systems enhance the safety and security of your home as well as adding convenience. You can forget about fumbling for keys in the dark or leaving outside lights on for guests. Leaving lights on is often a dead giveaway that a house is unoccupied. With this type of system, there is no need to leave lights on; they will turn on automatically when you or anyone else approaches. And the reaction of any intruder when lights suddenly switch on outside a home that appeared to be empty is obvious. The automatic light controller described here can be built for around half the cost of commercial units. It marries the Passive Infrared Movement Detector described in the December 1987 issue of SILICON CHIP with a simple control circuit. For the prototype, both circuits were housed in a sturdy electrical junction box fitted with a couple of floodlights, but this could be varied to suit your particular application. In fact, many readers will probably elect to delete the floodlights and simply use the controller to switch existing outside lights. An optional override switch allows the lights to be switched on manually if required. Commercial sensors Another option is to use the control board with a commercial PIR detector or, depending on circumstances, with other types of movement detectors. For example, you could combine the control board with the ultrasonic movement detector described last month to automatically switch on hallway lights or to light a stairway. For outdoor use, the infrared sensor is the one to go for. This is because it triggers only when it detects body heat and cannot be false triggered by other moving objects (eg, swaying tree branches). Other types of movement detectors would be virtually useless for outdoor use. Naturally, the range of the unit will depend on the type of detector used. The passive infrared sensor used here will give a useful range of about 12 metres when fitted with the wide-angle lens. To make it as versatile as possible, the control board has two inputs, one for normally-open relay contacts and the other for normallyclosed contacts. This means that it should work with most types of sensors. A light dependent resistor (LDR) on the control board monitors the ambient light level and disables the circuit during daylight hours. Perimeter monitoring The Automatic Light Controller uses a passive infrared sensor and is built into a sturdy plastic case fitted out with a couple of floodlights. The lights switch on for 40 seconds whenever the infrared sensor detects body heat. 56 SILICON CHIP Provision has been made on the control board for connecting several units together in parallel, for perimeter monitoring. When this is done, all the controllers will be activated if there is movement in any one of the covered areas. The lights then switch off only after the CONTROLLER +1 4V PASSIVE INFRARED MOVEMENT DETECTOR MODULE t ,-- 0 11 47k 47k ® _fL INPUT 1 u 240V LAMP(S) D1 0 1N4148 INPUT 2 0.1 MANUAL OVERRIDE Sl 0. 1 LINK 0.1 250 VAC 47k 1M GND .,. X GND D6 TO OTHER CONTRDLLER/S 08 B FROM OTHER CDNTRDLLER/S t DELETE IF N/C CONTACTS NOT USED AT INPUT 1 AUTOMATIC LIGHT CONTROLLER SCD3·1-0688 .,. Fig.I: the control circuit can accept either high or low logic inputs from an external movement detector. When movement is detected, pins 3 and 4 of IC2 switch high, the MOC3021 triggers, and Triac Qt turns on and lights the lamps. timer in the last activated control board has expired. The units are interconnected using inexpensive low-current alarm cable but note that each unit requires its own mains power connection. Of course, running two or mor e units in parallel is entirely optional and can be ignored if you require only a single automatic light controller. How it works Refer now to Fig.1 which shows the circuit diagram of the control board. It's built around a 4093 quad Schmitt NAND gate, a MOC3021 optically coupled Triac driver, and an SC151 Triac to switch the lamp(s). PARTS LIST 1 PIR movement detector (as described in the December 1987 issue) 1 Clipsal No.265/4 Series H.D. IP56 plastic case 1 printed circuit board, code OE12 1 1 mains transformer with 11 VAC secondary 1 MPY 76C569 LOR 1 or more floodlights (see text) Semiconductors 1 SC151 D Triac 1 MOC3021 Triac driver 1 40 93 quad NANO Schmitt trigger 4 1 N4004 silicon rectifier diodes 6 1 N41 48 silicon signal diodes Capacitors 1 4 70µ.F 25VW electrolytic 3 0 . 1µ.F monolithic 1 0 .1µ.F 250VAC metallised polycarbonate Resistors (0 .25W, 5%) 1 x 1 MO , 1 x 1 OOkO, 3 x 4 7k0, 2 x 2 .2k0, 2 x 4700, 1 x 1 OOkO miniature trimpot Miscellaneous Screws, nuts , solder, hookup wire, cable clamps, silicone sealant. JUNE 1988 57 In this version, the passive infrared movement detector was mounted on the lid of the case (right) while the control board is mounted on the base. Note the insulating material covering the mains transformer terminals. Keep mains wiring neat and tidy. Power for the circuit is derived from a mains step-down transformer. Its 10V AC output feeds a bridge rectifier and 470µF 25VW electrolytic capacitor to produce a smoothed DC voltage of about 14V. This DC voltage powers the control board and the external movement detector feither PIR or ultrasonic). The control logic has two inputs, designated Input 1 and Input 2 on the circuit diagram. Input 1 is used with external sensors employing normally-closed relay (NC) contacts, while Input 2 is used with sensors employing normally-open (NO) contacts. Let's consider Input 1 first. Normally, this input is held low by the NC relay contacts and thus pin 12 of IC2c will also be low. This means that pin 11 of IC2c will be high, pins 3 and 4 of IC2a and IC2b will be low and the MOC3021 (ICl) will be off. So Ql and the external lamp(s) will also be off. When the relay contacts open (ie, when movement is detected), Input 1 is pulled high via a 47k0 resistor and the resultant pulse applied via D9 and a 100kn resistor to pin 12 of IC2c. Assume for the moment that pin 13 of IC2c is also high. Pin 11 of Where to buy the parts Parts for this project are available from Oatley Electronics, 5 Lansdowne Pde (PO Box 89), Oatley, NSW 2223. Telephone (02) 579 4985. Prices are as follows (mail orders add $3.50 p&p): PCB plus on-board parts for PIR Movement Detector as per December 1987 SILICON CHIP (lenses supplied) ................ $54.95 PCB plus on-board parts for Control Board (includes transformer, terminal strip and the LOR) .... ... ...... ........... .... .. ... $24 .95 Note: copyright for the PCB artwork associated with this project is retained by Oatley Electronics. 58 SILICON CHIP IC2c will now go low and the outputs of paralleled inverter stages IC2a and IC2b will switch high. These drive the LED inside the MOC3021 which in turn triggers the internal diac. This then turns on Triac Ql via a lkO resistor to light the lamp( s ). Input 2 works in similiar fashion except that it is normally held high and is pulled low when the external sensor is triggered (ie, a set of relay contacts close, or a transistor turns on). This low signal is then inverted · by IC2a and the resulting high applied to pin 12 of IC2 via DlO and R7. After that, the sequence of events is exactly as set out above for Input 1. Note that D9 and DlO together form a simple diode OR gate (ie, input 1 or input 2 can deliver a. high signal to pin 12 of IC2c). The 10okn resistor and associated O. lµF capacitor on pin 12 of IC2c form a low pass filter. This stops false triggering due to noise and RF pickup when long interconnecting cables are used between the sensor and the control board. Daylight inhibit Now let's look more closely at the function of IC2c. Pin 13 of IC2c is connected to a voltage divider consisting of VR1, a 2.2k0 resistor, a 4700 resistor, and the light dependent resistor LDR1. LDR1 is there to stop the circuit from working during daylight hours. This happens in the following way. For IC2c to pass signals through from its pin 12 input to its output, pin 13 must be high (ie, close to Vee). For this to happen, the combined resistance of the 4700 resistor and LDR1 must be much greater than the combined resistance of VR1 and the 2.2kQ resistor. This means that LDR1 must be in darkness (so that its resistance will be very high). During daylight, when light illuminates LDR1, its resistance will be low and so pin 13 will be low and no signals will pass through IC2c. Trimpot VR1 sets the light level at which the circuit will trigger. When the lights turn on, the LDR circuit is disabled by the O. lµF capacitor connected to pin 13 of IC2c. This works as follows. When the outputs of IC2a and IC2b go high to turn the lights on (via IC1 and Triac Qt), the 0.1µF capacitor is charged via the 4700 resistor and diode D5. This effectively latches the circuit up until the timer in the sensor module turns the lights off. Inputs A, B and C and output X allow up to four controllers to be connected together in daisy-chain fashion. In this configuration, the output (X) _of each controller is connected to an input (A, B or C) of all the other controllers. Diodes D6, D7 and DB form an OR gate so that the controller can be activated by applying a high to any of the inputs (ie, input A or input B or input C). When an external controller is triggered, this high is applied via that controller's X output. Thus, when one controller is triggered, it automatically triggers all the other controllers and lights all the lamps. Construction Most of the parts for the controller are installed on a printed circuit board (PCB) coded OE121. j_ ---I......... SWITCHED 240V AC TD LAMPS • • • r:i ........... __._. ~ ~1-D:-,m~ 470uF + ~O.l 05 X <at> e . . , ; "'~ c'-!:' c::.. B(/) «::::)e ..cJ>,e 0.1\J ~ 8~-bJ§ 1 GNO 0 :c:Jj j ~\\ 1 r-. {illg)e QzDe 0.1 0~ • !;;: : • VR1 LDRl D7 D~6 ~ e[TI[)e {ill[]e ~t Dl~::;: tDELETE IF NORMALLY CLOSED CONTACTS NOT USED AT INPUT 1 PASSIVE INFRARED MOVEMENT DETECTOR FRESNEL LENS NOTE: CHANGE R15 TO 8.2M TO INCREASE OH TIME TO 40 SECONDS 1J Fig.2: mount the parts on the control board as shown here. Take care with the mains wiring and note that some of the tracks on the board operate at mains potential. Fig.2 shows the parts layout. Begin construction by installing all the resistors and diodes, then install the larger components. Note that the 47kQ pull-up resistor on Input 1 must be deleted if you don't in- tend using this input. (Diode D9 could also be deleted in this case). The resistor to be deleted is marked with an asterisk. The power transformer is mounted directly on the PCB and is JUNE 1988 59 CONTROLLER 3 Fig.3: here's how to wire two or three controller boards together for perimeter lighting. When one controller switches on, it automatically triggers the others. secured using screws and nuts. Four insulated wire links are then run between the transformer terminals and points on the PCB. An insulated terminal block terminates the A, B, C, X and ground connections from other controllers, while PC stakes are used for other external wiring connections. Once completed, the control board can be tested separately. Connect mains wiring to the board and connect the output to a 240V incandescent lamp. The LDR should be left disconnected at this stage. The board is now ready for testing but, before plugging in, check all wiring carefully. You should also note that some of the tracks on the PCB operate at mains potential, so exercise extreme caution. In fact, we strongly recommend that you position the whole assembly in the specified plastic case before plugging it into the mains. Now switch on. If the 47k!l resistor has been installed on Input 1, the lamp should light. The lamp should then extinguish if Input 1 is shorted to ground. If the 47k!l resistor has been left out, the lamp should initially be off but should light when Input 2 is shorted to ground. If eveything works OK, disconnect the unit from the mains and connect the LDR to its respective terminals on the printed board. Check that the unit now operates in darkness but not in a well lit room. VRl can be adjusted to set the ambient light level at which the lamp will no longer turn on. Finally, check that the DC output voltage is around 14V. The Passive Infrared Movement Detector should be constructed and tested as described in the December 1987 issue of SILICON CHIP. There's just one change to make - the value of R15 should be increased to 8.2M!l to increase the on°time to approximately 40 seconds. In you want the lights to remain on for longer than this, increase the value of C12 (use a lowleakage electrolytic of tantalum type). Final assembly The two PCB assemblies are housed in a sturdy plastic electrical junction box made by Clipsal (type No.265/4 Series H.D. IP56}. This type of box is readily available from electrical wholesalers and hardware stores (eg, BBC). continued on page 68 Take care with component orientation when wiring up the control board. Note that the 47k!J resistor on Input 1 must be deleted if you don't intend using this input. 60 SILICON CHIP PARTS LIST 1 PCB, .code SC14-1-588, 11-2 x 69mm 1 Scotchcal label, 1 1 0 x 40mm 1 folded aluminium case, 133 x 76 x 54mm 1 finned heatsink, 7 5 x 11 0 x 33mm 1 panel mount 3AG fuse holder 1 SA fuse 2 6mm grommets 4 6mm standoffs 2 metres red automotive cable (4mm dia). 2 metres black automotive cable (4mm dia.) 4 3mm dia. x 1 5mm screws 4 3mm nuts 3 2.5mm dia. x 10mm screws 3 2.5mm nuts 1 solder lug 1 T0126 mica washer 1 T0-3 mica washer plus insulating bushes 1 socket to suit plug on 7. 2V Nicad battery pack 2 automotive battery clips 4 rubber feet tery pack. Since the timer is also going to be adjusted during this procedure, you should also note the precise time when the 12V source is connected. Assuming that the battery pack Semiconductors 1 2N3055 NPN power transistor 1 BD139 NPN transistor 1 BYX98-300(R) 1 OA 300V diode 2 5mm LEDs (1 red , 1 green) 3 1 N4148, 1 N914 diodes 1 LM324 quad op amp Capacitors 3 2200,uF 25VW PC electrolytic 1 1000,uF 25VW PC electrolytic 1 100,uF 25VW PC electrolytic 1 0.0 1,uF metallised polyester Resistors (0 .25W, 5%) 1 x 1 OMO, 1 x 470k0, 1 x 27k0, 2 X 22kQ, 1 X 2.2k0, 1 X 6800, 3 X 1000, 1 X Q. 10 5W, 2 X 20k0 miniature vertical trimpots Miscellaneous Solder, heatsink compound, tinned copper wire, etc. was flat to begin with, it should take about 20 minutes for the pack to recharge. During this period, you should carefully monitor the temperature of the battery pack. If the battery becomes hot, disconnect Automatic light controller The accompanying photographs show the general layout inside the case. As can be seen, the PIR movement detector is mounted on the lid of the case, supported on 18mmlong pillars. Before mounting the detector, you will have to make a cutout in the lid to clear the lens assembly. A 7mm hole will also have to be drilled in the lid to accept the LDR. The control board is mounted on the bottom of the case and secured using machine screws and nuts. Drill holes to accept the mounting screws plus an extra hole ih the bottom left corner (looking from inside the case) for the mains cord entry. You will also have to drill a hole in the adjacent end for the mains cord clamp, plus additional holes in 68 SILICON CHIP continued from page 60 the sides of the case to accept the lamp holders (or to pass wiring to external lamps, depending on requirements). It's best to complete the wiring to the control board before mounting it in the case. Light duty hookup wire can be used for connections between the two PCBs and to the LDR but note that the wiring between the control PCBs and the lamps must be run using 240V AC cable. Lace up the cables or use cable ties to keep the wiring tidy. The control PCB can now be mounted in the case and the mains cord secured using a suitable clamp. The prototype used a clamp fashioned from scrap aluminium and secured with a screw and nut. This same screw and nut also it from the charger immediately. Under normal circumstances, the battery pack should become warm and the "charged" LED should light at the end of the charging period (ie, after about 20 minutes). As soon as the "charged" LED comes on, disconnect the battery pack but leave the charger connected to the 12V source. Now quickly connect your multimeter (set to volts) between pin 1 of ICld and ground and adjust VR2 so that pin 1 switches high. This effectively sets the timer so that it disables the charger shortly after the end of the normal charging cycle. To check the timer action, disconnect the charger from the 12V source, leave it for a minute or so to discharge the circuit's capacitors and then reconnect it, without a nicad battery pack in place. Then check that LED 2 comes on after 20 minutes. When you are using the charger and want to charge several battery packs in succession, remember to disconnect the charger from the 12V source after each pack is charged. This resets the timer and the voltage monitoring circuit. Footnote: the Mega-Fast Nicad Battery Charger can also be used to charge lower voltage packs (eg, 5.6V nicad packs) without any changes to the circuit. lb secures a piece of insulating material to cover the mains terminations on the transformer. (In the kit supplied by Oatley Electronics, this material will be Presspahn or Elephantide ). We suggest that the cut-outs for the PIR lens assembly and the LDR be weather-sealed using a silicone sealant. If possible, try mounting the unit under the eaves of the house, out of the weather. A licensed electrician should be employed to connect the unit to existing house wiring. Note: on boards presently being supplied by Oatley Electronics, it is necessary to modify the pattern asssociated with the relay coil on the PIR movement detector. Instructions on how to do this are being supplied with the board (see Notes and Errata on page 95). lb