Introduction: Easy Door Alarm!

About: I'm a school student who aspires to pursue robotics. I love working on DIY projects and am learning programming and algorithms.

Hello! This is my first instructable

It is unfortunate that burglary is not uncommon these days. So, I decided to do something about that. Although this is a kind of primitive door alarm, it can help you detect trespassing when you are present in your house.

This instructable is going to help you make a cheap door alarm using minimal technical devices. It does not use any kind of sensors or specialized switches made for Door Alarms.


A cell is connected to a switch, which is used to turn alarm off/on. A wire "W" is placed near the hinge of the door and is connected to the switch. Another wire "Z" is placed on the knuckle of the hinge(the part which is attached to the door) which touches "W" when the door is opened and does not touch when the door is not opened. "Z" is connected to the alarm and finally to the cell. Thus, the circuit is complete when the the door is opened and the alarm sets off.

The alarm will sound only till the door is opened. As soon as the door is closed again, it will be silent.


  • Wire 40 cm
  • Buzzer(alarm)
  • Cell-9 Volt
  • Switch (Just to turn alarm off and on)
  • Wire stripper, pair of scissor and Cello/Duct Tape
  • A cylinder with diameter not more than 3 mm

Step 1: Shape the Wire

Cut 2 wires of 20 cm length each. Strip 4 cm wire at one end only. This is to be done with both the wires.

Twist the long stripped part of the wires and wrap them around the cylinder to make a loop. This loop is the main part of the alarm using which the door alarm is going to work.

Step 2: Placement

Place one of the wire on the wall such that its looped end is near to the knuckle of the hinge. Hold it on that place by sticking it to the wall with cello tape or duct tape. Place the other wire on the knuckle hinge of the door such that the looped end of the wire is just near the looped end of the other wire when the door is closed.

Also, make sure that the ends are in contact when the the door is opened. The quick response of the alarm depends on this!

Place the cell, switch and the buzzer on the wall using tape.

Step 3: Connecting Wires

Connect one wire with the switch, which is to be connected with positive terminal of the cell. Join the positive terminal of the buzzer with the other wire and connect the negative terminals of the buzzer and the cell.

Turn the switch on...And you are done!

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