With a few easy steps build a trip wire!
Projects from Make: Magazine
A Simple Trip Wire
Make a trip wire that beeps when someone walks into it.
Make a trip wire that beeps when someone walks into it.
Solder a wire to one terminal of a beeper or buzzer.
Put two pins or nails into a board.
Put in a third pin with a photo hook pivoting on it. Position the pin so that when the hook swings it will contact one of the other two pins.
Solder the wire from the beeper/buzzer to the pin that the hook will touch.
Solder a wire from a battery pack to the hook.
Complete the circuit by soldering a wire that connects the remaining terminals of the battery pack and the beeper/buzzer.
Tie a string to the hook. Mount the board on one side of a doorway or walkway and stretch the string across to the other side.
Now wait for someone to walk into your trap!