Simple Door Alarm

You can use this Simple Alarm to protect the door or Window. It gives a loud beep and switch on the room light when an intruder/burglar attempts to breaks the door lock. The alarm functions only after 5 minutes to confuse the intruder.

Working of this burglar alarm circuit is simple. IC1 is used to trigger the SCR after the delay of 5 minutes and a Reed switch (Normally Open) is used to control the working of IC1. CD4060 oscillates and gives high output only when its reset pin 12 is grounded. When the door is closed, Magnet is close to the reed switch and it closes. Reset pin of IC1 now becomes high through R1 and it remains off. When the door opens, magnet move away from the reed switch and IC1 starts tp oscillate with the components C1 and R3. After 5 minutes, its Q8 output becomes high and triggers the SCR. Relay and the buzzer then turns on. Relay can be used to drive an AC load like room light or AC buzzer. SCR remains latched until its Anode voltage is removed by pressing S2 (Normally closed push switch).

Reed Switch- Normally Open

Magnet and Reed switch arrangement

Red LED blinks and indicates the activation of circuit. Fix theReed switch on the door frame and Magnet on thedoor with exact positioning so that when door closes Reed switch make contact.