Door Latch Alert System Circuit Diagram

Circuit Diagram

The door latch alarm circuits are simple and effective and easy to construct. Normally the alarm is in de-activated mode by keeping the switch s1 in off state which can be done with a lock and key kind of switch. Number of doors can be guarded against the intrusion by keeping or connecting the reed switch in series fitted with the help of a magnet.
The reed switch can be fitted in such an way that the magnet is fixed on the door, in normal conditions when the door is closed reed switch will be held close to the magnet and hence the reed switch is kept closed , when the door is opened the reed switch contact is opened , this triggers an SCR, the gate of an SCR is connected to its cathode through the reed switch as long as the switch is closed the SCR dose not fire but when the door is opened the SCR is fired supplying an voltage to the alarm circuit.

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