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HELP WITH A DOOR ALARM?

hey everyone. i had an idea. what if you could have a strip of foil running across your door. when someone opens the door and breaks the circuit, it sets off an alarm. any ideas for the circuit needed for this?

Burf3 years ago
Use a small magnet and a reed switch instead of the foil and you can make the one found here:

http://www.circuit-finder.com/categories/alarms-and-security/alarm/116/personal-alarm
EmmettO3 years ago
Have the gate of a Mosfet connected to your foil switch. As long as electricity is flowing to the gate of the Mosfet, it will not allow electricity to flow through the source and drain leads. Use this to interrupt the flow of current to a buzzer, light, whatever signaling device you want.
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