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BUILD 'I'Hf: PROTECTOR -CAR BURGLAR ALARM This refined car burglar alarm has just about every feature you could want but is easy to build. It incorporates internal and external siren alarms, back-up battery, ignition killer and dashboard flasher. Design by JOHN CLARKE Over the years there have been many refinements in the design of car burglar alarms, so much so that the best commercial alarms are now highly effective deterrents to car thieves. That fact is recognised by some of the larger insurance companies who give small discounts in premiums to those who have approved alarms fitted. The problem is that most approved alarms cost many hundreds of dollars to purchase and have fitted; money that the average motorist can ill afford. With that in mind, we at SILICON CHIP have examined the features of the best car alarms· and have come up with a design which incorporates the most desirable and effective features while still keeping the overall cost to a manageable figure. We've also included a number of features which, to our knowledge, are not included in commercial alarms but which are very effective theft deterrents. Alarm features Let's list the major features of the Protector: • Delayed input to monitor all doors. This let's you safely enter and leave your vehicle without setting the alarm off and disturbing the whole neighbourhood. Entry and exit delay times can each be adjusted to ten seconds. 18 SILICON CHIP The PC board is designed to fit into a standard plastic case and can be assembled by an experienced constructor in an hour or so. The two relays are used to drive an external siren and to disable the car's ignition, so that the thief can not drive away with the alarm sounding. All external connections are via multiway insulated terminal blocks. • Non-delayed (instant response) input to monitor your car's boot and bonnet. As soon as the boot or bonnet are opened, the alarm will sound. • Automatic alarm cut-out and reset: after the alarm is triggered the sirens will sound for 90 seconds and then stop. The alarm resets automatically. The alarm time is adjustable. • Ignition killer: as soon as the alarm is triggered the ignition circuit is disabled so that the thief cannot drive away with the alarm sounding. • Separate siren alarm: since car thieves often cut the wires to the horn, by gaining access underneath the vehicle, the Protector has provision to switch on a separate siren alarm which can be mounted in a more inaccessible position in the engine compartment. • Separate internal alarm: as well as having a conventional siren alarm under the bonnet, the Protector has an extremely loud piezoelectric siren mounted inside the vehicle. When it goes off inside the confines of your vehicle, it is so loud and painful that any thief will instantly break into a sweat and panic. No-one could possibly stay in the vehicle while the alarm is soun- This is what the completed alarm looks like. It should be mounted in an inaccessible location under the car's dashboard or under the rear parcel shelf. ding. It is the feature that we're particularly proud of. • Back-up battery and battery sense: since car thieves also often cut the wires to the vehicle's battery, the Protector has a back-up battery and monitors the input from the main car battery at all times. If the battery wires are cut, the alarm will sound. • Ignition sense: any attempt to start the vehicle (supposing that the thief has entered by opening a door, letting the alarm time out, and then coming back to have another go) will trip the alarm and immobilise the vehicle. • Dashboard flasher: this is a most effective deterrent in a car alarm. While ever the Protector is enabled, its dashboard lamp will flash. FEBRUARY1988 19 and Q4 to turn on while it is pressed. Q3 discharges the 0.047 µ,F capacitor at the base of Q2 and 2 1 N5404 3A diodes thereby causes Q2 and Ql to turn 2 1N4002 1A diodes off. Q4 discharges all circuit 10 1N4148, 1N914 signal capacitances via its associated diodes 2700 resistor and thereby makes 1 1 6V 1 W zener diode sure that the circuit is completely Capacitors dead. 1 4 70µF 16VW PC electrolytic While S1 can be combined with 1 4 7µF 16VW PC electrolytic the dashboard flasher, the OFF 2 1 Oµ,F 16VW PC electrolytic switch S2 should be concealed in a 2 2 .2µ,F 16VW PC electrolytic spot not easily found by the poten2 0.22µ,F metallised polyester tial thief. (greencap) An alternative arrangement 1 0.1 µ,F metallised polyester which could be used to switch the 1 .04 7 µ,F metallised polyester Protector is a radio transmitter and 2 .022µ,F metallised polyester receiver. This has the advantage Resistors (0 .25W, 5%) that the alarm can be controlled 2 4 70k0, 2 x 220k0, 3 x 1 OOkO, remotely so that the exit and delay 2 x 47k0, 1 x 22k0, 5 X 10k0, 3 times can be eliminated or minimisx 3.3k0, 2 x 2.2k0, 1 x 2700, 1 ed. It would improve the security of X 330, 1 X 220 5W, 2 X 0 .470 the alarm, since the burglar will not 5W, 2 x 220k0 vertical miniature be able to find the OFF switch. trimpots, 1 x 22k0 vertical We will be publishing a suitable miniature trimpot UHF radio switch in a future issue. Miscellaneous With Ql turned on, most of the Machine screws and nuts, circuitry is fed via a 330 resistor hookup wire, alarm stickers, l while zener diode D3 protects the spring-loaded switch (for I circuitry from any voltages above bonnet). 16 volts. The associated 0.1µ,F capacitor is used for decoupling the supply. The alarm is enabled by pressing Having discussed the power inthe ON switch S1. This provides a put circuitry, let's flick up to the top kick start to Ql and Q2 to get the left-hand portion of the circuit to circuit going. Before S1 is pressed, the delayed input. This uses D4 and Ql and Q2 are off and neither can exclusive-OR (XOR) gate ICla. As conduct because Q2 controls Ql with all XOR gates, IC1a's output is and Ql provides base current to low unless its two inputs are difQ2 . When S1 is pressed, this Mex- ferent; ie, one high, one low. ican standoff is ended as the 10µ,F The delayed input monitors the capacitor feeds a pulse of current door switches and will work with into the base of Q2 , enabling it to door switches which short to turn on. This allows Ql to conduct chassis (OV) or those that switch and from then on Q2 obtains its + 12V to the cabin lights. In the base current from the collector of former case, the delayed input will Ql via a lOkO resistor. always by high when all doors are The reason for the lOµF closed. This means that pins 1 and 2 capacitor is so that a push-on/push- of ICla will both be high and its outoff switch can be used for S1 rather put will be low. than a momentary contact switch. When a door is opened, D4 will These are available with integral pull pin 2 low and pin 3, the output, lamp indicators which would will go high until the 2.2µF enable the ON switch to do double capacitor at pin 1 discharges via duty as the dashboard flasher . Note the associated 470k0 resistor. that if a push-on/push-off switch is With door switches that switch used for S1, it must be pushed off + 12V, the delayed input is wired to before it can be pushed on again to the lamp side of the switches. This power up the circuit. means that when all doors are closThe alarm is disabled by pressing ed, the delayed input is low and the OFF switch S2. This causes Q3 both pins 1 and 2 of ICla will be PARTS LIST ~ 1 PCB, code SC3-1-0188, 178 x 89mm 1 plastic· box, 195 x 113 x 60mm 1 Scotchcal front panel, 1 O7 x 191mm 1 12V relay, 1 OA OPOT contacts 1 12V relay, 5A SPOT contacts 1 1 2V push on/push off switch with integral 1 2V lamp 1 momentary contact pushbutton switch 1 piezo siren horn 1 self-driven weatherproof horn 1 in-line fuse holder 1 3A fuse 1 12V, 1.2AH gel battery 1 1 0-way PCB terminal block 1 8-way PCB terminal block 4 4mm PCB standoffs Semiconductors 1 4093 quad NANO Schmitt trigger 1 4030 quad XOR gate 1 4027 dual JK flipflop 4 BC33 7 NPN transistors 5 BC54 7 NPN tr~nsistors 1 BC557 PNP transistor We have not used a keyswitch to turn the alarm on and off. Keys are a hassle in this regard and no-one wants to fumble with keys if they have inadvertently set the alarm off or they know the alarm will go off any second. With that potent piezo siren in mind, a hidden switch to disable the alarm is what is required. Circuit features Considering the number of features in the Protector, its circuit is quite simple. It uses just three low cost CMOS integrated circuits, ten transistors, two relays plus several resistors, capacitors and diodes. Let's begin the circuit description by looking at the power input from the car battery. This is connected via diode D1. If the car battery is disconnected, power is obtained from the back-up battery via diode D2 . The back-up battery is maintained on a constant floating charge from the main battery via a 220 5W resistor. 20 SILICON CHIP V2+ ENTRY DELAY VR3 220k 011 1N4148 16 470k 04 1N4148 220k 10 J 10 DELAYED INPUT 4027 IC2b 13 CK 220k ALARM TIME VR2 220k - 14 a .,. ':'" 0.22t 013 1N4148 010 1N4148 Vl+ + Cl 470 16VW? V2+ DASHBOARD FLASHER INSTANT INPUTS V2+ V2+ 01 6 J C2 47 16VW ALARM OUTPUT + - 3 V-0 c-.-0 07 BC337 4 E .,. .,. .,. V1+ PIEZD SIREN V1+ .,. .,. ---------v1+ OFF 09 .E. 01 1N5404 1,2 33!l 7B +12V0--4-*-J-!.::: • t----+---..-~,r""><'---+~W.-.---.--'°------+--V2+ FROM VEHICLE BATTERY 22 1l 5W .,. 0.47!l 5W 6 -...IIWI..-OGROUND 1N~iD4 6 .,. GRDUNDi .,. BC337 D.47!l E 5W 8 EOc 31 12V 1.2AH ; BATTERY 1 BACK-UP .J.. 1. 10k VIEWED FROM BELOW .,. CAR BURGLAR ALARM SC31-0188 Fig.1: the circuit diagram. Dual JK flipflop IC2 takes care of the entry and exit delays and the alarm duration. low. When a door is opened, D4 pulls pin 2 high and pin 3 then goes high and the 2.2µ,F capacitor at pin 2 charges towards + 12V. The instant (non delay) input using ICl b and D5 operates in exactly the same manner as ICla and provides a high pulse whenever the input goes high or low. Battery sense This input monitors the car bat- tery and while ever it is connected Q5 is conducting. If the battery is disconnected, Q5 turns off and provides a momentary positive pulse via the 0.022µ,F capacitor to pin 9 of IClc. This causes the output of IClc FEBRUARY1988 21 0 IGNITION COIL NEGATIVE GROUND ALARM OUTPUT IGNITI INSTANT IN~ DASHBOARD FLASHER DELAYED 1riful PIEZD SIREN 1~ 0 Fig.2: assemble the PC board exactly as shown here. Make sure that you use the correct transistor at each location and note that the ICs all face in the same direction. to go high for the duration of the pulse from the 0.022µ.F capacitor. The ignition input is used to sense any unauthorised attempt to start the engine. Therefore Q6 is normally off and only conducts once the ignition sustem is energised. Pins 13 and 12 of ICld are normally high and when Q6 turns on it pulls pin 12 low for a brief period, determined by the associated 0.022µ.F capacitor. This causes the output of IC1d to go high for a brief period. The outputs from IC1 b, c and d are coupled via diodes D7, DB and D9 to the clock input of IC2a, which is half of a dual J-K flipflop. When one of the instant outputs goes high the clock input is triggered and the Q output of IC2a latches high. This also triggers the clock input to IC2b, via D10. The output of IC1a, the delayed input, also connects to the clock input of IC2b via D6. So ICla or IC2a can trigger flipflop IC2b. IC2b provides both the exit delay and the alarm duration, via the circuitry associated with Cl. IC2a and IC2b provide the entry delay. Initial power up Now consider what happens when the circuit is powered up, by pressing the ON switch Sl. Initially, capacitor Cl is discharged and the output of IC3b, a Schmitt NAND gate, is high. This high output resets both IC2a and IC2b so that their Q outputs are low and their Q-bar out22 SILICON CHIP puts (the complements) are high. Cl begins to charge through two paths, via D11 and trimpot VRl and via the 220k0 resistor and trimpot VR2. The VRl path is dominant, however, because of its lower resistance and charges Cl after about 10 seconds. This causes the output of IC3b to go low. This is the exit delay and after this time the circuit is fully alarmed since the reset inputs of IC2a and 2b are no longer held high. When IC2b is triggered, either by ICla or IC2a, its Q-bar output (pin 14) goes low and Cl begins to discharge via VR2 and the 220k0 resistor. Note that the VRl path plays no part here because D11 is reverse biased. With the Q-bar output of IC2b low, the output of NAND gate IC3d (towards the bottom right-hand corner of circuit) goes high and switches on transistor Q9 and its relay, RLA2. This disables the ignition while the alarm sounds. The relay 3as two sets of 10A contacts which are connected in parallel and are used to short across the ignition points (or transistor switching element for electronic ignition systems) via the two series 0.470 resistors. This prevents the ignition coil from firing. Note also that the second input of IC3d is connected to the collector of Q6 at the ignition input. Thus, if the alarm has already been tripped, say by a door being opened, the alarm will sound again, immediately any attempt is made to start the car or hot-wire the ignition. This is a "belts and braces" aspect of the circuit which means that if the ignition is hot wired, or otherwise interfered with, the ignition cut-out relay will be permanently energised, regardless of whether the alarm is sounding or not. This stops the thieves from attempting to drive the vehicle away, in spite of its alarm sounding at intervals. After all, we must acknowledge that in some circumstances people will ignore an alarm and so the Protector has been designed to make things impossible for the potential thief. Alarm outputs Two alarm outputs are available, the high intensity piezo siren and a relay, RLA1 , for an external powered siren. Transistor Q7 drives RLA1, while transistor QB drives the piezo siren. These transistors are driven by the output of IC3a. IC3a goes high to drive the alarm outputs either immediately, if one of the instant inputs triggers the alarm, or after a period set by the entry delay trimpot VR3 and capacitor C2 , if the delayed input triggers the alarm. At the time the Q-bar output of IC2b goes low, C2 (associated with pins 1 and 2 of IC3a) begins to discharge via VR3 and its series zzokn resistor. When the voltage reaches the lower threshold of IC3a, the output, pin 3, goes high and the alarm outputs are activated (this assumes that the delayed input caused the alarm). When the instant input triggers the alarm, diode D12 at the Q-bar output of ICZa discharges CZ and the alarm output operates immediately. The alarm continues to sound until Cl discharges and allows IC3b to reset the flipflops, ICZa and ICZb. The Q-bar of ICZb thus goes high and charges Cl again. This means that the alarm can now be triggered again, if another attempt to made to steal the car. The dashboard flasher involves gated Schmitt trigger oscillator IC3c and transistor QlO which drives the lamp. Pin 8 of IC3c connects to Cl. When Cl is charged up to + 12V, IC3c is enabled and the dashboard lamp begins flashing. r- I= u -] we >z -::::, en a: i1:i + ~o I- w a: c., a: (.) ~ ci5 <( w c., I<( 0 z z Li [&j ...J 0 (.) z 0 I- z c., 0 (.) ~ a: <( ...J <( <( Ll) C 0:: a: <( 0 m J: en <( C w en Construction Building the Protector is a straightforward process and will probably take no more than an hour or so. All the circuitry is accommodated on one printed board measuring 178 x 89mm (code SC3-1-0188). All the connections to and from the board are made via multiway insulated terminal blocks (Utilux or equivalent). The printed circuit board is mounted in a plastic box measuring 195 x 113 x 60mm which is fitted with a label having a legend for all the board connections. You can begin assembly by installing the two wire links, the diodes, resistors and capacitors. Note that the diodes and electrolytic capacitors must be installed the right way around to observe correct polarity. The trimpots and transistors can be mounted next. Make sure that each transistor installed is the correct type and that it is oriented correctly, according to the parts layout diagram. Each transistor should be pushed down so that its lead length a hove the board is about 5mm or so. The large resistors and the three integra ted circuits can then be mount ed, followed by the two rela ys and the two insulated termina l blocks. The ICs are CMOS r-- CD u, -=:t M N ::::, LL <( C") >en a: Iw =:; I- > Ic.. <( m ::::, w ~ >...J (.) C a: <( (.) zW m ::::, IJ: 0 Iw >> a: a: ~ w c,wzt0 II- 1a:...JOZ> <( w (.) i= <( <( > m 3=--1N ..... 0 zli:om Zen ijj + 1-ooc..>S:2~c r~ □ L:.. 1~"'"' .. "'"' . . =m~I _:J Fig.3: actual size reproduction of the front panel artwork. devices so their supply pins should be soldered first to enable their static protection diodes . For ICl and IC3 , solder pins 7 and 14 first. For ICZ, solder pins 8 and 16. When the board is complete it can be mounted in the plastic case. You will need a hole drilled in each end of the case to allow for cable entry and four holes for screws or standoffs for the board. Note that the corners of the board must be removed to prevent interference with the corner posts of the case. The Scotchcal panel can now be affixed to the lid of the case. FEBRUARY1988 23 input panel} needs to be tied high and then disconnected. The ignition input (terminal 8} needs to be pulled high while the other instant input (terminal 9} can be pulled high or low to test it. • Check that relay RLA1 is closed for 90 seconds after the alarm is triggered. This time can be adjusted with VR2 . . • Check that relay RLA2 is closed for the same length of time as RLA1. • Check that relay RLA1 closes ten seconds after the delayed input is triggered. This is done by pulling the input low and then disconnecting it, or pulling it high and then pulling it low. The ten second delay can be obtained by adjusting VR3. • Having triggered the alarm once with the battery input, check that when the ignition input is pulled high, RLA2 closes and stays closed after RLA 1 opens, as long is the ignition input is pulled high. • Connect the piezo siren to terminals 1 and 8 on the output panel. Muffle it thoroughly under a cushion before letting it sound otherwise your ears will be subjected to considerable discomfort and possible damage. We ' re serious about this. The piezo alarm is excruciatingly loud. Check that the piezo alarm sounds each time relay RLA1 closes. Installation Fig.4: here is the etching pattern for the PC board. Testing When the Protector is fully assembled, a number of tests should be made to ensure that all functions are working. The tests are as follows: • Connect + 12V to the circuit and check that no voltage appears across zener D3 until switch S1 is 24 SILICON CHIP pressed. After S 1 is pressed, the dashboard flasher lamp should stay illuminated for ten seconds and then begin flashing. This time can be adjusted using VR1. • Check that the three instant inputs instantly cause relay RLA1 to close when triggered. To do this, the battery input (terminal 7 on the Make sure you install the Protector alarm in a professional manner. Mount the case securely and use a 10 x 0.2mm (or thicker} hookup wire for external connections. It is a good idea to purchase a crimp connector kit for this job so that all your connections are secure. Probably the best and easiest place to mount the alarm will be under the parcel shelf inside the boot. The same goes for the back-up battery which should be securely clamped in a place where· it won't be damaged by miscellaneous boot debris. The self-powered siren should be mounted in the engine compartment but make sure that its wiring is inaccessible from underneath the vehicle. Finally, put warning stickers on your car. These are another effec• tive deterrent. ~ + VEll1CLE BAffiRY ALARM UNIT + 12V 8,7 --,,""'-- • IGNITION COIL NEGATIVE 6 ~ • , 680UND5 ~ . ..v ...1· -....!.l___,.!....~--- ALARM OUTPUT 4,3 • DASHBOARO FLASHER 2 PIEZO SIREN 1 • e-+-1-.. . . . ._--........ ~ I e ·•- - - -- - --------------' I'-----------~ 11 DASHBOARD FLASHER PIEZO SIREN BONNET • Fig.5: here's how to wire the Protector alarm into your vehicle. Use a crimp connector kit to terminate external leads as appropriate and note that S2 (off) should be hidden. S1 and the dashboard flasher can be a single switch/lamp combination. The complete alarm system (from top left): 12V 1.2Ah battery, 12V siren, pushbutton switches with integral 12V lamp, bonnet switch, alarm module, piezo siren and (centre) warning sticker. (Accessories kindly supplied by Jaycar Electronics). FEBRUARY1988 25