Burglar Door Alarm
The last time I did an alarm that’s under a mat and it received a lot of likes. The link for that is here: How to Make a Burglar Alarm Mat. So today I have another alarm to make, and it involves a door. Make sure to follow the pictures and have fun.
Things you’ll need: String, a bottle cap, 9V battery, a small box, 3 alligator wires, speaker with sound or a piezo buzzer, a paper clip, and tape.
- Cut a hole outside of the box.
- Cut a piece of plastic from a bottle cap.
- Put tape on one “tong” of an alligator clip and leave the other alone as shown in the picture.
- Build a circuit in the box as shown below. Make sure the speaker is working and the alligator clip with tape needs to be next to the hole.
- Attach a string to the piece plastic from the bottle cap. Then, put the piece of plastic between the alligator clip and make the string go through the hole.
- Make sure you see the circuit from the hole and the string cannot be blocked or tight.
- Now the alarm is done. When you pull the string the speaker will be activated.
- The door needs to pull the string, so find a place that the door knob moves away from the alarm.
- Tape or place the box in the right position.
- Tie the string to the door knob.
- Now your alarm is ready. When someone opens the door, the door knob will pull the string, the wire will be connected to the paperclip, and the speaker will be activated.
The reason I put tape on only on “tong” of the alligator clip is because the speaker will be activated when it has the piece of plastic between the first tong. The tape and plastic is an insulator. An electrical insulator is a material whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily. The property that distinguishes an insulator is its resistivity; insulators have higher resistivity than semiconductors or conductors.
When the door knob pulls the plastic with the string, the metal will touch and the speaker will be activated.