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Thieves often target locked houses. This door guard circuit detects any vibration in its vicinity when somebody tries to break open the door. A simple circuit to protect all your valuable things.
Learning from this project
Things which you can learn:
- Application of UM3561 IC.
- Working of the transistor as an amplifier.
- Working of MOSFET BS170.
- Application of piezoelectric sensor.
This is a simple door guard circuit which is based on piezo electric sensor to detect changes in the vibration caused due to the opening of doors.
The heart of the circuit is the piezo transducer (PZ1), which is the sensor element. If anyone attempts to open the door, the piezo element vibrates and the developed voltage drives transistors T1 and T2 into conduction. Then the alarm sounds for 20 seconds, which is taken care of by MOSFET T3 along with capacitor C1 and resistor R4 wired as a monostable timer.