Kids love alarms - or anything else that seems cloak and dagger for that matter. Although a sophisticated home alarm system is beyond your typical hobbyist, it is easy to make a door alarm with your kid that will go off with aloud buzzing should anyone enter his bedroom. The only tricky part is setting up the contacts so that, when someone opens the door, it closes the circuit. This article will show you one way to do it, but there are many more.
Instructions
1. Get your electronics. Buy a small, low-voltage piezo electric buzzer such as the one linked to below, and a battery holder that provides enough voltage to power it. The buzzer will include a voltage rating, which will make it easy enough to get a battery holder with the right power rating.
2. Attach the exposed end of one of the wires from the battery holder to one of the terminals of the buzzer. Soldering is the best way to make a connection, but twisting it on and taping it with electrical tape will work too.
3. Attach lengths of copper wire to the other wire of the battery holder and the unoccupied terminal of the buzzer. Strip enamel off the ends of the wire first so that you get a clean connection.
4. Test the circuit. Put in the batteries and touch the two exposed ends of wire together. The buzzer should make a loud beep, wail, or whatever.
5. Attach one exposed end of wire to the north pole of a neodymium magnet. Attach the other exposed end of wire to the south pole of another magnet. Use glue or a small piece of electrical tape to make the attachment. Be sure to not get anything on the other side of the neodymium magnet.
6. Position the circuit so that, when the door opens, the magnets snap together, triggering the alarm. Tape one wire to the bottom of the door with the south pole of the magnet sticking out. Place the other magnet in the path of the door with the north pole sticking in so that, when the door is opened, the two snap together.
Tags: battery holder, that when, Attach exposed, door with, electrical tape, ends wire