DIY: Wireless Alarm

Turn the wireless doorbell receiver over so that the back is facing you. Open the battery compartment on the back of the wireless doorbell receiver. If a screw attaches the lid, loosen the screw with a Phillips jeweler's screwdriver.

Insert the correct number of required batteries into the battery compartment. Close the lid and tighten the screw, if there is one.

Place the wireless doorbell receiver on an end table by your bed, or mount it on the wall by your bed using wood screws and a Phillips screwdriver. Slide the switch on the side of the receiver to the "On" position.

Loosen the two screws on the remote doorbell module with your fingers. Strip 1/2 inch of insulation from the ends of the two wires attached to the hobby alarm bell, using a wire stripper. Wind each wire around one of the screws. Tighten the screws with your fingers.

Turn the remote doorbell module over so that the back is facing you. Open the battery compartment lid on the back. If a screw attaches the lid, loosen the screw first with a Phillips jeweler's screwdriver.

Cut two 10-inch lengths of electric wire from the spool, using a utility knife. Strip 1/2 inch of insulation from each end of the two wires with a wire stripper.

Heat up a soldering iron for five minutes. Solder an end of each wire to one of the two contacts on the inside of the battery compartment. Let the solder cool for two minutes. Tape the button on the module in with a piece of duct tape.

Place the module and the doorbell against the wall near the door frame. Cut two 2-by-2-inch squares from the foil with a scissors. Solder the free ends of the two wires to an edge of a foil square each. Let the solder cool for two minutes. Unplug the soldering iron.

Place white glue on one side of one of the foil squares. Place the foil square against the bottom edge of the door, opposite the door frame. Press the foil against the door until the glue takes hold. Let the glue set for an hour.

Place the other foil square against the edge of the door frame so that the foil on the door will touch it when the door is opened -- you will need to bend the foil slightly toward you. Your DIY wireless alarm will now sound from both the hobby alarm bell and the receiver if the door is opened.