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-• TIMEOUT ULTRASONIC APPLIANCE MINDER Ultrasonic switch for mains appliances Are you one of those people who goes to sleep while watching TV or who inadvertently leaves mains appliances on? This project monitors an area using ultrasonic sensors & if no movement is detected for a preset period, it switches the controlled appliance off. By JEFF MONEGAL Switching a lamp off after the baby has falle n asleep is just one of the many uses for this proj ect Other possible uses include automatically switching off outdoor lights along a path, or turning off an iron, a radiator or a desklamp. And why leave the TV going while you drift off into slumberland? After all, the life of a TV tube depends on the hours of use. This project can automatically switch your TV off if you pass out on the couch or if the kids lose interest and abandon the set. 70 SILICO N CH IP To op erate the project, you simply plug it into the mains , plug the appliance to be controlled into the mains socket mounted on one end of the case, and press the ON/ OFF button. The green STANDBY LED now goes off, the appliance turns on and the red MOVE LED flash es each time movement is detected. The movement detector used h ere is a proven design but instead of triggering an alarm system , it simply resets a timer. If this timer is reset before its time limit expires , the controlled appliance remains on. However, if no movement occurs for a preset time , then the detector will not reset the timer and the applianc e turns off. The time for which no movement can occur before the appliance is turned off is set during construction and can be anywhere in the range from 230 minutes. Once the controlled appliance has been turned off, it can only be turned on again by pressing the ON/OFF button. Repeated pressings of the ON/OFF switch simply toggle the appliance between on and off. A small warning lamp on the front panel flashes just before the time-out expires. This is useful for those times when no movement has occurred in front of the TV (eg, during a gripping susp_ense movie) and you want the TV to remain on. Alternatively, the lamp can be replaced with a buzzer so that you get an audible indication that the time-out period is about to expire. How it works Refer now to Fig.1 which shows the circuit details of the Ultrasonic Ap pliance Minder. It can be roughly split into four sections: an ultrasonic receiver (ICl, ICZ & IC3a); an ultrasonic transmitter (IC3d, IC3e & IC3f); a timer circuit & relay driver (IC4, IC5, Q3Q5, etc); and a power supply (Tl, D8D12, REGl) . Ultrasonic waves generated by the transmitter bounce around the room and eventually find their way back to the receiving transducer. Its output is fed to ICla which is connected as a variable gain amplifier due to the presence of trimpot VRl in the feedback loop. The non-inverting input of ICla is biased to half supply (½Vee) by two lO0kQ resistors, while the associated lOµF capacitor provides decoupling. This sets the outpl!lt at pin 1 to half supply when no signal is applied, so that we get maximum signal swing in both the positive and negative directions. VRl varies the gain ofICla from about 13.5 (at maximum resistance) to about 4.5. Following ICla, the amplified signal is coupled to inverting amplifier stage IClb. This stage has a gain of 39, thus giving the total maximum gain of approximately 500. From there, the signal is applied to a level detector circuit consisting of Dl, Rl, RZ and Cl. Cl charges on the positive going peaks of the amplified signal and discharges at a slower rate through RZ on the negative signal peaks. What happens is that a DC paten- tial is established across Cl. This potential remains steady as long as the signal picked up by the receiving transducer is at a steady level. However, if an object disturbs the ultrasonic field, the varying signal levels reaching the transducer cause the DC potential across Cl to vary. These signal variations are coupled through CZ to pin 2 of IC2 . This stage operates as a high-gain inverting amplifier with its bias set to about 1V by the lMQ & 150kQ resistors on the non-inverting input (pin 3). If the detected voltage across Cl rises above this 1V reference, pin 6 of ICZ swings low, thus turning on Ql and QZ. The 4.7µF capacitor at the input ofIC3a now quickly charges via QZ and its 470Q collector resistor. Thus, pin 2 of IC3a switches high and so Q7 turns on and lights the MOVEMENT LED to indicate that movement has been detected At the same time , the high on pin 2 of IC3a resets counter stage IC4 via DZ. When movement ceases, Ql and QZ switch off and the 4. 7µF capacitor at the input of IC3a discharges via its parallel lO0kQ resistor. Pin 2 of IC3a then switches low again and Q7 and the MOVEMENT LED turn off. Refer now to IC5a; this is one half of a dual 4013 D-type flipflop which operates in toggle mode due to the lO0kQ resistor connected between its Q-bar output and the Data (D) input at PARTS LIST 1 PC board, code ACT ONE 1 plastic utility case 1 pushbutton switch 1 12V miniature relay with 240VAC 1OA contacts 1 11 VAC mains transformer 1 pair 40kHz ultrasonic transducers 1 12V miniature lamp or buzzer 1 mains plug and mains cord 1 surface-mount mains socket 1 1OA fuse and fuseholder 1 miniature 40kHz crystal 2 200kQ miniature vertical trim pots (VR 1,VR2) 4 rubber feet 4 6mm-long standoffs 11 nylon screws & nuts 12 plastic cable ties Semiconductors 1 TL072 dual op amp (IC1) 1 TL071 op amp (IC2) 1 40106 hex inverter (IC3) 1 4040 binary counter (IC4) 1 4013 dual flipflop (IC5) 1 78L08 8V regulator (REG1) 2 BC558 transistors (Q1 ,03) 3 BC548 transistors (Q2,Q5,Q7) 2 80437 transistor (Q4,Q6) 61N4148 diodes (01-06) 61N4001 diodes (07-12) 1 5mm red LED (LED1) 1 5mm green LED (LED 2) Capacitors 2 1OOµF 16VW electrolytic 2 22µF 16VW electrolytic 2 1OµF 16VW electrolytic 1 4.7µF 16VW electrolytic 2 1µF 16VW electrolytic 7 0.1 µF monolithic 1 .001 µF ceramic 2 680pF ceramic 1 220pF ceramic 1 1OpF ceramic 1 4.7pF ceramic 1 2.2pF ceramic Resistors (0.25W, 5%) 21MQ 1 560kQ 1 390kQ 1 270kQ 2 150kQ 13 100kQ 1 47kQ 1 27kQ 4 22kQ 7 1OkQ 3 4. 7kQ 3 1kQ 1 470Q Miscellaneous Most of the parts are mounted on a small PC hoard & this in turn is secured to the lid of the case using nylon screws & washers. The relay is mounted on a separate outrigger board if mains appliances are to be controlled. Insulated hookup wire, mainsrated cable, heatshrink tubing . SEPTEMBER 1991 71 signals then drive the 40kHz transducer for high power operation, or the transducer can be connected between pin 10 of IC3e and ground for low power operation. Power for the project is derived from the mains via transformer Tl. Its secondary output is applied to bridge rectifier DB-Dl 1 which then drives an 8V 3-terminal regulator (REG1) via D12 . D12 is there is isolate the current pulses drawn by the lamp and relay from the regulator circuit. Construction ·{' The bodies of the two ultrasonic transducers, the pushbutton switch and the fuseholder are sheathed in heatshrink tubing to provide additional mains isolation. Mount the fuse lower down than shown here, to clear the PC board. pin 5. Actually, the two flipflops inside IC5 are connected in parallel but that doesn't affect the way the circuit operates. The RC timing circuit on the D input (pin 5) provides debouncing for the switch contacts. Each time Sl is pressed , it pulls the clock (CK) input high and the flipflop toggles. Assume initially that IC5 is set with its Q output (pin 1) low and its Q-bar output high. When Sl is pressed, IC5's clock input (pin 3) is pulled high and so the Q output switches high and Qbar goes low. This turns Q5 and the STANDBY LED off. At the same time, Q6 turns on and the relay closes to power the external appliance. The low on Q-bar (pin 2) now reverse biases D3 and thus pin 11 of IC4 is pulled low by the associated 100kQ resistor. IC4, a 12-stage binary counter, is now free to count the pulses on its clock (CK) input from Schmitt trigger oscillator of IC3b. If movement is detected by the ultrasonic receiver, IC4 is reset by IC3a and counting starts again. However, if no movement is detected, IC4 continues to count the clock pulses from IC3b until eventually its Q12 output (pin 1) goes high. This reverse biases D6 , thus enabling Schmitt trigger oscillator IC3c. IC3c operates with a frequency of about 1Hz. It drives Q3 which then drives Q4 to flash the TIMEOUT lamp 72 SILICON CHIP (or pulse a buzzer). This indicates that the timing period has almost finished, which means that you must move (if you are still awake) to prevent the appliance from switching off. If movement is still not detected, then a short time later pin 13 of IC4 will also go high. When this happens, the associated 100kQ resistor (on the anodes of D4 & D5) pulls the RESET pin ofIC5 high. IC5 now resets with Q low and Q-bar high and so the STANDBY LED turns on and the appliance switches off. Trimpot VR2 sets the period for which no movement must be detected before the appliance switches off. By using the component values shown, that time can be varied from about 2 minutes to 30 minutes. If longer or shorter times are required, it's simply a matter of changing the value of the timing capacitor. Fig.2 shows the parts layout on the main PC board. Begin construction by inspecting the PC board for any open or shorted tracks. When this has been done, install the two links on the top of the board but don't install the three bottom links at this stage. If you have decided to use IC sockets , now is the time to install them. This done, install the passive components (resistors and capacitors), then the diodes and transistors. Check that all polarised components are correctly oriented. Fig.1 shows the pinout diagrams for the transistors. When installing the transistors , push them down onto the PC board as far as they will comfortably go before soldering their leads. Be sure to use the correct transistor at each location, as the circuit uses a mixture ofNPN & PNP types. Note also that diodes D8D12 are 1N4001 types, while the remaining 'diodes are all 1N4148s. The remaining components can now be installed, along with the insulated links on the underside of the board. Make sure that the ICs are correctly oriented and don't overheat the crystal, otherwise it could be damaged. Although there is provision on the main PC board for the relay, it must be mounted on a small "outrigger" board if mains appliances are to be switched Ultrasonic transmitter IC3d and IC3e are wired as a standard 2-gate oscillator. This operates at 40kHz due to the 40kHz crystal in the feedback path. Note that the crystal is fed from a voltage divider network (100kQ and 22kQ) to keep the drive within safe operating limits. IC3finverts the output from IC3e so that we get complementary output signals (ie, signals that are 180° out of phase). These complementary output Fig.1: the circuit consists of an ultrasonic receiver (ICl, IC2 & IC3a); an ultrasonic transmitter (IC3d-f); a timer circuit & relay driver (IC4, IC5, Q3-Q5, etc); and a power suppy (Tl, DB-D12 & REGl). VR2 on IC3b sets the timing period. If no movement is detected, QB & Q12 of IC4 eventually both go high & reset IC5, thus turning off the appliance. +BV !+ luF 10pF 4.7pf 1M 4.7 100k 10k 390k ULTRASONIC RECEIVER 10D~ 1!220p R2 , 47k Cl 0.1 100k 02 0.1 ·sc54B E 100k 101 .. t I D2 1N4148 D3 I~· l ">o• ' T T • ) ) ,olcK as 13 __. VR2 200k IC31 ~ EICIB ULTRASONIC tri -0 tri ::0 HIGH POWER I TRANSMITTER (/) tri 0. 680p Q LOW ,POWER ELJc o(1_) I co co '-' ULTRASONIC APPLIANCE REMINDER w 0 4 0.1' +BV fi'h -012 , .... 01 l ) 8< r > •iM "( I 17 100k + F1 A 10A --0--.0---.---- 8 '-' ""-I ~- IC5a 4013 !!ISET 22'' ~ 0:, 5 100k 1 I 1 3:: J 8D437 -6. PLASTIC SIDE -3 Tt - t ' 680pf'! 3 1cK 04 TI MEOU T' r - ---------, T 14 LAMP OR BUZZER 150k 0.1 T 0.1I "I 11,R ~~4~0121 • · ~ 10k 22 T + l 116 1N4148 IC3b T T 100..: 11V 240VAC VI EWED FROM BELOW N • f ) 1our , 10 I , +Bv r--- - - - - - - -7 I <at> I i- - - - - - - - - - - - l I I I : I I I I I ELEPHANTHIDE MAiNS COVER I I <at> * \ f ~ V E T°WN) MAINS PANEL SOCKET Fl~ CORD GRIP GROMMET ULIBASOlilC * fj) <at> CASE LID LINKS UNDER PCB - - - * COVER WITH HEATSHRINK TUBING Fig.2: take care with component orientation when installing the parts on the PC board & use mains-rated cable for all 240VAC wiring. Don't forget the links under the PC board. (see Fig.2). This is done to keep dangerous main voltages away from the main board. Alternatively, for switching low voltages, the relay can be installed on the main PC board. The relay contacts are then used as a normally open switch. If you are using this option, 74 SILICON CHIP delete the mains socket and all associated mains wiring. When the boards have been completed, the case can be drilled to accept the hardware. Use the front panel label as a marking temr,late to locate the holes for the two LEDs, the pushbutton switch, the warning lamp and the transducers. The holes for the transducers are best made by first drilling small pilot holes and then reaming them out until the transducers are a tight fit. The main board is mounted on the lid of the case on 6mm plastic standoffs and secured using nylon screws and nuts. You will also have to drill holes in the base to mount the power transformer and relay board , plus l I!. . AM il ~1'"N'1'1:I I - - - - - - - - - ~ - C•i)' This view inside the completed prototype shows how the mains cables are bound so that if a lead does come adrift, it cannot short against anything. Note that nylon screws are used to mount all the hardware items in the case. holes in each end to accept a cordgrip grommet, fuseholder and surfacemounting mains socket. Mount the fuseholder down near the bottom of the case, to keep it away from the PC board (note: it should be further down than on the prototype). The front panel label can now be attached, the hardware mounted in position and the wiring completed as shown in Fig.2. Note that nylon screws & nuts are used to secure the relay board, mains terminal block and power transformer to provide isolation from the mains. As a further safety measure, the bodies of the two ultrasonic transducers and the pushbutton switch must be sleeved in heatshrink tubing (see photo). The front panel items are all wired using light-duty hookup wire but you must use mains-rated cable for all connections to the power transformer, fuseholder, mains socket and relay contact terminals. The mains cord enters through one end of the case and is anchored by the cordgrip grom- CAPACITOR CODES 0 0 0 0 0 0 0 0 Value IEC Code EIA Code 0.1µF .001µF 680pF 220pF 10pF 4.7pF 2.2pF 100n 1n 680p 220p 10p 4p7 2p2 104 102 681 221 10 4.7 2.2 RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 No. Value 4-Band Code (5%) 5-Band Code (1%) 2 1MQ 560k.Q 390k.Q 270k.Q 150k.Q 100k.Q 47k.Q 27k.Q 22k.Q 10k.Q 4.7k.Q 1k.Q 470.Q brown black green gold green blue yellow gold orange white yellow gold red violet yellow gold brown green yellow gold brown black yellow gold yellow violet orange gold red violet orange gold red red orange gold brown black orange gold yellow violet red gold brown black red gold yellow violet brown gold brown black black yellow brown green blue black orange brown orange white black orange brown red violet black orange brown brown green black orange brown brown black black orange brown yellow violet black red brown red violet black red brown red red black red brown brown black black red brown yellow violet black brown brown brown black black brown brown yellow violet black black brown 1 1 2 13 1 1 4 8 3 3 SEPTEM BER 1991 75 met. Leave sufficient cord inside the case to reach the fuseholder and mains terminal block. Install about 45mm of heatshrink tubing over the leads to the fuseholder before connecting them to the terminals. After soldering, push this tubing over the body of the terminals and shrink it to a tight fit using a hot airgun. Do not install the Active lead between the mains terminal block and the relay board at this stage. This lead is only installed after the unit has been checked for correct operation. Don't forget to connect the earth lead between the PC board and the terminal block - see Fig.2. After the wiring has been completed, use plastic cable ties to bundle the wires together, as shown in the photographs. In particular, you should ties the mains leads together so that if one lead does come adrift, it cannot move and short against anything. Final checkout To test the unit, first check your mains wiring carefully, then close the lid of the case and apply power. The STANDBY LED will usually now come on, while the MOVEMENT LED should flash briefly if there is movement in front of the transducers. Adjust the sensitivity control, VRl, to ensure that the ultrasonic range can be varied. Now press the ON/OFF button. The STANDBY LED should go out and the relay contacts should close. If this checks out, set VR2 to minimum (fully anticlockwise) and check that the relay drops out after about two min- Because there are exposed mains connections on top of the transformer, it should be covered with insulation to prevent accidental contact. This piece of insulation is secured by one of the transformer mounting screws & to the side of the case using a nylon screw & nut. utes if there is no movement in front of the sensors. Note: you can simulate this by disconnecting a lead to one of the transducers. Finally, install the active mains lead between the transformer and the relay board. The controlled appliance should now toggle between on and off when you press the ON/OFF button and should automatically switch off if there is no movement during the timing period. Troubleshooting If it doesn't work, first use your multimeter to check the supply rails. You should get +8V from the regulator and this voltage should also be present on the positive supply pins of Where to buy the kit Kits for this project are available from CTOAN Electronics, PO Box 33, Condell Park, NSW 2200. Phone (02) 708 3763. There are three variations : • Kit 1: includes PCBs, mains transformer, relay, 40-kHz crystal & ultrasonic transducers. Price $39.95 plus $4.00 p&p. • Kit 2: includes all of Kit 1 plus on-board components, pushbutton switch, LEDs & lamp. Cost $54.95 plus $4.00 p&p. • Kit 3: includes all of Kit 2 plus plastic case, adhesive front panel label, fuseholder, mains socket and mains cord & plug. Cost $69.95 plus $4.50 p&p. CTOAN Electronics offers a full repair service for this kit. The cost is $20.00 plus $5.00 return postage. Only kits built as described in this article and with good quality soldering will be accepted for repair. Note: Copyright of the PC board for this project is retained by CTOAN Electronics. 76 SILICON CHTP the ICs. A low rail indicates that either the regulator, a supply diode or an IC has been incorrectly oriented. It often helps if you can pinpoint the fault to a specific section of the circuit. Assuming that the supply rails are correct, here's what to look for: • Symptom: relay doesn't close on each alternate pressing of Sl. Check circuit around IC5 & Q6 and check D4 & D5 for correct orientation. If the Q output of IC5 goes high on alternate presses of Sl, check Q6. • Symptom: circuit times out regardless of movement; MOVE LED does not flash. Check that pin 6 of IC2 swings low when movement is present. If OK, check Ql & Q2. Ql's collector should swing high if movement is detected, while QZ 's collector should go low. If no signal is present at pin 6 of IC2, use a CRO to check for signal at the output of the transmitter. If this is OK, check for signal at the outputs of ICla & IClb when there is movement. • Symptom: MOVE LED flashes but circuit times out regardless of any movement. Check orientation of DZ & D3, • Symptom: warning lamp flashes continually during timing period. Check orientation of D6. • Symptom: warning lamp does not flash just before timing period expires. Check around IC3c, Q3 and Q4. • Symptom: circuit does not time out if there is no movement. Check circuit around IC3b & IC4. Check D4 & D5 for correct orientation. SC