What ?

Easy to make, durable and from just 3 elements - alarm device.

Why ?

This is great toy for kids. My son loves to set this alarm to his toys, doors to his room etc. He plays with that with his colleagues.
I've used this alarm to catch the dog, who knocks my wastebasket (trash bin) every night :)

What is needed ?

Batteries - I've used 2 AA batteries, but it could be any other battery, 4,5V or even 9V. Just use something that You have at home.
Clip - normal, ordinary clip which is used to hang the washing

Aluminum foil

Wires

Buzzer - You can buy it for less than 50 cents, or get it from an old PC computer

Box - ane type of box big enough to fit all of above things. The box should be durable, since we are building the toy for the kids.

Glue - any type of good glue. I've used hot glue gun.

Step 1: Alarm Trigger

Alararm trigger is made from clip and from small wooden desk.
Put aluminum foil on both clip clamps and attach one wire to clamp.

Take a small wooden desk and drill the hole in it. Now take a string and attach it to the desk using the whole.

Step 2: Electronic Circut (how to Connect Everything)

Connect batteries to buzzer, buzzer to clip and clip to batteries. This is easy serial connection. Remember to isolate connections (i used duct tape to do that).
It will work because opening the clip will break the circuit and current won't flow through the buzzer. If You close the clip, the current will flow and the alarm sound will be generated.

Step 3: Mounting It All Toghether

Take the box and make a two holes: one for the buzzer, and one for the little wooden desk which will be putted in clamp between clamps.
Now take all elements and mount them in the box using glue.

Step 4: Arm Your Alarm

Now Your alarm is ready. Attach the string to the something You want to be monitored, and put the small desk into alarm device. If You still don;t know how, just watch my video - there is everything explained.

If You like this tutorial and You want more, just subscribe my youtube and instructables channel.