How to Make an Alarm

Do you have toddlers who wake up at night while you are sleeping and wander through the house? It would be great if you could make a simple alarm to alert you whenever they do. After all, you don't want them to sneak outside or get into household cleaners without adult supervision. Perhaps you need to know when anybody enters your bedroom especially just before a child's birthday or before a holiday when you are hiding gifts. You can make an alarm rather easily with supplies that you may already have on hand.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Aluminum foil
• 9-volt battery
• 2 10 inch pieces of wire
• On/off switch
• Buzzer
• Scissors
• Duct tape
• Cardboard approx 10 by 20 inches
• Electrical tape

1. Fold the cardboard in half so that when folded the piece is 10 by 10 inches and then open it back up.

2. 
   Cut strips of aluminum foil.

   Tape a strip of aluminum foil that is about three inches wide across both ends of the cardboard so that when you fold the cardboard in half, the two pieces of aluminum foil line up, and fully cover each other.

3. 
   Connect the wiring harness and stip plastic off the ends.

   Strip about half an inch of plastic coating from the ends of two 10 inch pieces of wire and from the wire ends protruding from the wiring harness. Attach the wiring harness to the 9-volt battery. Attach one 10 inch wire to one wire of the harness by wrapping the exposed ends together. Then wrap some electrical tape around the exposed wires that are twisted together.

4. Push one end of an exposed wire through the aluminum foil taped on an end of the cardboard and tape it into place. Push one end of the other 10 inch piece of wire through the other piece of aluminum foil on the other end of the cardboard and tape that into place.

5. 
   A complete circuit will set off the alarm.

   Wrap the exposed end of the remaining wire coming from the wiring harness on the 9-volt battery to one side of your buzzer. If there is a screw, wrap the exposed wire around the screw several times and then tighten the screw. Wrap the exposed end of the 10 inch wire that has one end tucked under the tinfoil to the screw on the other side of the buzzer. When the two pieces of aluminum foil touch each other, the circuit should be complete.

6. Fold the cardboard in half pushing the two pieces of aluminum foil together and see if the alarm goes off. The photo provided contains a light instead of a buzzer so you can see that the circuit is complete and the alarm works.

7. Hide your folded piece of cardboard under a rug that isn't quite heavy enough to push the two pieces of aluminum foil all the way together. Hide it just inside any doorway where you want an alarm. When someone steps on the rug, the two pieces of foil will touch and the alarm will sound.

Tips & Warnings

• Items such as wires, harnesses and switches come in children's lab sets and "Newton's Body Shop" kit for children's experiments.
• A single alarm of this type will not offer protection for your entire home.

Resources

• Burglar alarm fun experiments
• Super simple door alarm
• You build it door alarm