Covertly monitor your property and distinguish between loiterers and passers-by

This is a unit that should find many applications within home and business security. Battery powered and about the size of a small brick, it can be simply placed at the area to be protected, switched on and left. Intruders entering the area will trigger a siren that is loud enough to alert anyone nearby.

The circuit features “pulse counting” that enables it to distinguish between passers by and someone loitering, perhaps with “intent”, in the protected area. The count can be adjusted by the user for the desired degree of immunity from false alarms. The battery life will depend upon the number of detections and alarms, but the circuit is a micro-power design and is capable of remaining “on guard” for periods well in excess of a year.

Simple construction means that several of these units can be built if needed, the author has three! There are various ways in which the circuit can be modified for individual requirements and a few suggestions are given in the article.