Intruder Alarm

Posted on Apr 4, 2012

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It`s 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.

Intruder Alarm
Click here to download the full size of the above Circuit.

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

Leave Comment

characters left:

New Circuits



Popular Circuits

Optical schmitt trigger
Stepper Motor Interface to Microcontroller
LM3876 - High-Performance 56W Audio Power Amplifier with Mute
hardware control with computer
relay circuit 9 second led timer
audio tone control 2 transistor circuit
improved 3 transistor audio amp
Metal Detector MkII
Novel multifunctional high-power amplifier module 01