Make your own Burglar Alarm

Let’s begin!

Materials

1. Insulated Wire
   • Get 4 strands of wire, each 1 foot in length
   • You can find the wires around the house, inside battery-operated appliances that no longer work. Make sure that your parents give you permission to take them apart.
   • You can also buy the wires and other supplies listed from a Radio Shack, a hardware store, or the electrical section of big stores like Walmart.
   • Note: In order to make this alarm, you will need to peel off the rubber/plastic insulation from two of the wires. Try to peel the wires before starting this lesson. If it is too difficult for you, then you can buy non-insulated wire that does not need peeling.
2. 1.5-volt battery.
3. Kite string or button-and-carpet thread, 3-5 feet long.
4. Scissors
5. Electrical tape
6. 1.5-volt mini-buzzer
7. Spring-type wooden clothes pin
8. A scrap piece of board or plywood 4 inches by 12 inches or bigger.
9. Super Glue

---

Principles

The burglar alarm is made of three parts:

1. The device that makes noise - a buzzer
2. The battery
3. The buzzer switch

The Buzzer

We cannot have an alarm without something that makes sounds. That is why we use a buzzer, which is something that makes a loud sound. To make the sound, the buzzer needs to be connected to the battery.

The Battery

The battery is very important to the alarm. For the buzzer to work, it needs energy. This energy comes from the battery. If the buzzer is not connected to the battery, it will not work. You have a switch to control this connection.

The Buzzer Switch

See how the buzzer works by connecting your 1.5-volt battery to the buzzer directly. (The buzzer should come with two different wires. If the wire is insulated, you will need to peel a small length so that you are able to see the metal wire inside.) Get two other pieces of wire and connect them to opposite ends of the battery. Connect one wire to (+) and the other to (-). The battery should have the (+) and (-) labeled. Also, if you look closely, there is a (+) and (-) on the battery that you bought.

You may want to use electrical tape to hold the wires in place on the battery.

Connect the buzzer’s wires and the battery’s wires by twisting them, just like in the diagram 1. The buzzer should be making a sound; if it does not, check the connections at the ends of the wires to the battery.

Question :

• What happens when you disconnect a wire from the buzzer?
  Now, connect it again as often as you want and see how the buzzer turns on and off. By connecting and disconnecting the wires, what you have made is called a switch.

When you disconnect a wire and the buzzer stops sounding, we say that the switch is open. When it is open, no energy from the battery reaches the buzzer.

When you connect the wire and the buzzer sounds, we say that the switch is closed. When it is closed, the energy from the battery reaches the buzzer.