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simple alarm car Circuit

2015-01-08 16:25  
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Here is simple alarm car circuit. This circuit features exit and entry delays, an instant alarm zone, an intermittent siren output and automatic reset. By adding external relays you can immobilize the vehicle and flash the lights. The alarm is “set” by opening Sw1. It can be any small 1-amp single-pole change-over switch – but for added security you could use a key-switch. Once Sw1 is opened you have about 10 to 15 seconds to get out of the vehicle and close the door behind you. When you return and open the door the buzzer will sound. You have 10 to 15 seconds to move Sw1 to the “off” position. If you fail to do so, the siren will sound. The output to the siren is intermittent – it switches on and off. The speed at which it switches on and off is set by C6 and R10. While any trigger-switch remains closed, the siren will continue to sound. About 2 to 3 minutes after all of the switches have been opened, the circuit will reset. The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction. Fit a 1-amp in-line fuse AS CLOSE AS POSSIBLE to your power source. Here is a schematic drawing:

simple alarm car Circuit 400x286 simple alarm car Circuit

The fuse is there to protect the wiring – not the alarm. Exactly how the system is fitted will depend on the make of your particular vehicle. Consequently, I CANNOT give any further advice on installation. The circuit is designed to use an electronic Siren drawing 300 to 400mA. It’s not usually a good idea to use the vehicle’s own Horn because it can be easily located and disconnected. However, if you choose to use the Horn, remember that the alarm relay is too small to carry the necessary current. Connect the coil of a suitably rated relay to the “Siren” output. This can then be used to sound the Horn, flash the lights etc. The design has a number of advantages. It operates automatically when you turn the ignition off – so there’s no need to remember to activate it. The relay uses no current while the ignition is off – so there’s no drain on the battery. To de-activate it you’ll need to have the ignition key and you’ll need to know the whereabouts of the push-switch. Sw2 only requires a single wire because its return is through the chassis. It carries no load other than the current required by the relay-coil. So almost any small “momentary-action, push-to-make” switch will do. For extra security Sw2 could be key-operated.

source: http://www.zen22142.zen.co.uk

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