This is a
burglar alarm circuit
written by Ron J. Its features
include
automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It’s
designed to be used with the usual types of normally-closed input
devices such as – magnetic reed contacts – micro switches – foil tape –
and PIRs. But it can be Easily Modified to accept normally-open
triggering devices – such as pressure mats.
Hot It works
This
intruder burglar alarm is easy to use. First check that
the building is
secure and that the green LED is lit. Then move SW1 to the “set” position. The red LED will light. You now have about 30
seconds to
leave the building. When you return and open the door – the Buzzer will sound. You then have about 30 seconds to move SW1 to the “off” position. If you fail to do so – the relay will energize and the
Siren will sound.
While at least one of the switches in the normally-closed loop remains open – the
Siren will continue to sound. However, about 15-minutes after the loop has been
restored – the relay will de-energize – the Siren will Cut-Off – and the alarm will Reset. Of course, you can turn the
Siren off at any time by moving SW1 to the “off” position.
Posted in: Alarms
