An SCR Based Burglar Alarm


Posted on Feb 6, 2014

This is a simple SCR based burglar alarm circuit. Its features include automatic Exit and Entry delays - together with a timed Bell cut-off and Reset. It`s designed to be used with the usual types of normally-closed input devices such as - magnetic-reed contacts - micro switches - foil tape - and PIRs. The basic alarm has a single zone with `Exit/


An SCR Based Burglar Alarm
Click here to download the full size of the above Circuit.

Entry" delays. This will be adequate in many situations. However - larger buildings are better divided into zones. The modular design means that you can Add Any Number Of Zones to the system. These "Instant" zones may be triggered by normally-open as well as normally-closed input devices. It`s easy to use. When you switch on the alarm - you have about 30 seconds to leave the building. When you return and open the door - the Buzzer will sound. You have about 30 seconds to switch off the alarm. If you fail to do so - the Siren will sound. After about 10 minutes - the alarm will attempt to reset itself. If the trigger circuit has been restored - the attempt will be successful. But - if the loop is still open - the attempt will fail - and the alarm will re-activate. Of course - you can turn the Siren off at any time by switching off the alarm. A conventional bell uses up to about 400ma. An electronic siren generally uses less. If you intend to draw a heavier current from either the Buzzer or Siren terminals - the SCR in question will need to be bolted to a metal heatsink - and the relay contacts may need upgrading.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Laser Beam Alarm
    LX-800 LIGHTING SYSTEM
    Audio Function Generator
    Getting started with AVR development
    Digital Bike Tachometer Circuit Schematic Diagram
    Klee Sequencer Circuit Theory of Operation
    Capacitance Meter
    PLL Frequency Synthesizer
    Hakko 936 ceramic heater A1321
    TDA0161 metal detector electronic schematic
    Light Dimmers Circuits
    Phase shift and Wiens bridge oscillator
    2Digit up/down Counter



    Top