Light Fence Security Alarm Circuit Schematic


Posted on Feb 6, 2014

A simple light fence security beeper is presented here. This circuit can be used as a door alarm, gate alarm, pathway alarm, etc. Any 12 Volt dc power supply can power the whole circuit. Working of this circuit is straight forward. In standby mode photo transistor T1 receives light from the green LED (D1) and T1 conducts to disable the gated low-frequency astable built around IC1(4093). When this light path is


Light Fence Security Alarm Circuit Schematic
Click here to download the full size of the above Circuit.

interrupted by any object in the path, T1 stops conducting and IC1 is switched by the low level at its input point (pins 12&13). As a result the piezo-buzzer starts beeping at a slow rate determined by the in circuit values of R3, R4 & C1. Red LED (D2) is a visual warning indicator. With the help of suitable reflector and lens assembly, length of the light path can be increased. A minimum of 1 to 2 metres is possible with a high-bright green LED as D1. A laser pointer can also be used as the light source.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    RC Charger
    Transmitter-oscilloscope coupler for CB signals
    Radio Beacon Converter
    NiMH Battery Chargers
    fm radio ic tda7000 schematic
    0-50v 2a bench power supply
    Isolated Fuse Fail Indicator
    Handy Bright Light Circuit
    Electronic Roulette wheel with 20 LEDs and with 36 LEDs
    Secure lock circuit (CD4017) schematic
    Tube amplifier input voltage input



    Top