@▷ wire loop alarm | Diagram for Schematic

wire loop alarm

This circuit is a simple wire loop alarm that can be used in doorways, hallways, or any other place the tripwire will be broken by intruders. The circuit has a built in siren, but it can be replaced by a relay to drive an external siren, commercial alarm, etc.

alarm1 wire loop alarm
alarm1 wire loop alarm


1. Email Alex Meaden with questions, comments, etc.

2. The loop can be any type of hookup wire, with a maximum resistance of about 90K. Using very thin wire (40AWG, for example) will make a very sensitive trip wire, but will shorten the distance it can be strung due to the high resistance.

3. The siren can be replaced with a relay to drive external loads.