You don’t want to buy an expensive alarm system but still would like to have some? Well, you can make a stupid-simple door alarm for just couple of bucks and in no time. All you need is a peg, two AA batteries, couple of electric wires and a small signal buzzer electronic component which you can buy online or in a shop. Check it out.
First, attach batteries to a peg like this, make sure that you put the + and – sides of two batteries in opposite direction
Attach two small screws to the top of your peg, they will be used as contacts for alarm ignition
This is the kind of signal buzzer you need to buy
Attach the buzzer to a peg like this
And connect its wires to a battery and to one screw at the top of the peg exactly like this
At the other side of the peg, connect two different battery poles (+ and -) with a wire like this
And, by now, your door alarm should look something like this
You need to connect also the other battery end with the screw on its top-side of the peg using a wire (the yellow one) like this:
Now take a piece of cardboard
Fold it like this and connect a small piece of rope to it (this will be used as a trigger for your alarm)
Put the peg on one side of the door and connect the trigger on the other like this, and your alarm is ready to use!