DESIGN AND CONSTRUCTION OF A LIGHT OPERATED DOMESTIC ALARM

Abstract

Alarm systems are systems which operate a warning device after the occurrence of an abnormal or dangerous condition. They are used to signal undesirable or dangerous situation such as the presence of an intruder or the existence of a runaway condition in a petroleum refinery process. In factories, these system detects such things as excessive process temperature, or pressure or rapid change in a process condition. Over the years, the use of intruder alarms to protect an area has become widespread in industrial, commercial and private uses. Its design, construction and application has also increased in sophistication and style. Alarm system can be grouped into classes VIZ: space intrusion detection, perimeter detection and contact detection. Space intrusion detection is three dimensional while contact detection is by touch. This project is on domestic alarm system and falls under the contact detection. It is based on the widespread use of photocell and amplifiers. This was achieved by using astable multi vibrator and electronic bulb and a relay. The signal processing which forms part of the detecting circuit is made up of a pulse amplifier and the astable multibrator