Doorknob Proximity Alarm
HOMEFor wooden door - Alarms when someone reaches for the doorknob.
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.
Safety, accuracy and completeness of information provided herein is not guaranteed,
so be inspired by it but do not use it as a basis for experimentation or other actions.
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Version 20231217