Homemade Noise Alarms

Principles

• The alarm system needs to be triggered when door or window opens. You set the trigger by completing, then interrupting, a simple electrical circuit. A wedge or barricade between components of the circuit---between two wires for example---can break the circuit and thus keep the alarm from activating. All you need to do is arrange for the act of opening the door or window to knock the wedge out. Knocking the wedge out then connects the wires, sending electricity into the buzzer.

Components

• Connect the positive outlet on the battery pack to the negative outlet on the buzzer using a length of electrical wire; depending on the precise model of buzzer, you can either solder the wire into place or simply secure it by tightening the appropriate screw in the buzzer. Then connect one end of a second wire to the negative outlet on the battery pack in the same manner. Strip the insulation off the other end of the wire and wrap it around the upper jaw of a spring-loaded wooden clothes pin (i.e., the upper half of the end that pinches closed). Take a third length of wire, strip the insulation off the end and wrap it around the lower jaw of the clothes pin. When the two jaws are closed, the wires come into contact with each other. Then connect the free end of the third wire to the positive terminal on the buzzer. You now have a completed circuit which you can break simply by opening and closing the jaws of the clothes pin. You then only need something between the jaws which can be easily pulled out when the door opens.

Mounting

• Glue all of the components to a piece of wood and tape or nail the wood into the wall next to the door or window you want to arm. Cut out a piece of cardboard from a cereal box (or use a bit of thin packing cardboard), then place it between the jaws of the clothespin, just firmly enough to prevent the connection from being made. Use a thumbtack to punch a hole in the cardboard and run a piece of string through it. Then nail or glue the free end of the string to the door or window---taking care to place it towards the outer edge or the end which opens first---and put a battery in the battery pack. Your alarm is now armed: The next person to open the door or window will set off the buzzer.