Doorknob Proximity Alarm for wooden door


Posted on Jul 12, 2012

Reverse engineered circuit diagram of a popular retail doorknob alarm. It contains a small transmitter and the doorknob acts as an antenna so it will not work on a metal door. When a person comes close to the doorknob this loads down the oscillator and the alarm sounds. The proximity sensor circuitry is perfectly capable of driving 74HCT series CMOS logic in place of of the sound effect IC`s shown in the circuit diagram.


Doorknob Proximity Alarm for wooden door
Click here to download the full size of the above Circuit.




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