Simple and versatile door alarm

A very simple but extremely effective alarm system for your home will notify you of the intrusion of unwanted guests. And for this you need all a couple of details and very little time.

Necessary materials

Everything that we need can be very easily found and it will cost you literally a few rubles:

• Clothespin;
• Ordinary finger batteries (2 pcs.);

Kapron thread or rope;

• Buzzer;
• Small screws (2 pcs.).

Tools required:

• Glue (it is recommended to use a glue gun, it's just very convenient);
• Screwdriver;
• Small diameter drill;
• Soldering iron with the necessary soldering materials.

Construction process

To get started, take a clothespin and cover both sides with hot glue. Then we lean on two batteries and press for better bonding.

Next, we need to make holes at the clamping point of the two parts. Carefully, along the edges of the lips, we drill small holes. After that, screws must be screwed into them. They should be placed with their caps inside. That is, to touch them when clamping clothespins.

Now take the buzzer and cut off the excess flat part. And proceed to tinning the bare ends of the outgoing wires. We also tin out the peeking ends of the screws.

Again we take glue and fasten the buzzer from the side of the clothespin. Solder the black (minus) wire of the buzzer to the screw, and the red (plus) wire to the plus of the battery. We take a small piece of wiring and solder one end to the remaining free side of the battery, and the other end to the plus of the free battery. The remaining free screw and the untouched side of the battery are also connected with a piece of wire. As a result, we get a closed system.

From a piece of plastic we need to cut a jumper that will disconnect the circuit. We make a hole at the edge of the plate and fasten a nylon thread into it.

In principle, our signaling device is ready, it remains only to install it in the right place. To do this, grease the batteries and clothespin. We select a place at the edge of the door or door jamb and fasten it there. We fasten the thread coming from the jumper opposite the device in a taut state. Now, when you open the door, a fixed thread will pull out the jumper and thereby close the chain. The buzzer will immediately work and you will be notified of an invasion.