eCircuitbook

This circuit utilising a 555 timer IC can be used as an alarm system to prevent the theft of your luggage, burglars breaking into your house etc. The alarms goes ON when a thin wire, usually as thin as a hair is broken.

The circuit is straightforward. It uses a 555 IC wired as an astable multivibrator to produce a tone of frequency of about 1kHz which gives out a shrill noise to scare away the burglar.


The wire used to set off the alarm can be made of a thin copper wire like SWG 36 or higher.


You can even use single strands of copper form a power cable.

The circuit operates on a wide range of voltages from 5V to 15V.


The speaker and the circuit could be housed inside a tin can with holes drilled on the speaker side for the sound to come out.