A Tinker Birthday Party: Making a Simple Alarm System

My son likes making and tinkering, and so do several of his friends. So we decided to have a “Tinker Birthday Party.” Searching for inspiration of what to make together with a dozen children, I found the “Talking Booby Trap” in Bob Knetzger’s  Make: Fun, in which he uses a clothes pin as switch for activating a sound playback. Replacing the sound playback unit with a simple buzzer gave me something that was simple enough and cheap enough to use as project for the birthday party: a small alarm system.

For each child, I prepared a bag with the parts required for the alarm system – though I decided to hand out the battery after each child had completed the circuit so as to prevent the children from accidentally shorting the battery.

I started out the project by demonstrating the alarm system to the children. I had built two examples and used them to secure a book on a shelf and a door, then asked two children to “steal” the book and open the door, respectively … buzzzzzz!

Then I cut the cable binder, took apart the clothes pin and demonstrated the circuit to the children as follows:

The tricky part of making the alarm system is building the two contact areas at the tips of the clothes pin: The cables have to be wrapped tightly into aluminum foil and then secured with adhesive tape. By providing the children with several choices of adhesive tape, they were able to decorate their alarm systems in different colors (though, this being an alarm system, red was the color of choice for many).

Once each circuit was ready, we put in the battery, reassembled the clothes pin, and tied everything together with the cable binder.

Things went well, though I wish my the battery in my voltmeter had not died just then and there. Not all circuits worked right away and troubleshooting without the voltmeter was cumbersome. But finally, all alarm systems worked and we used them to build a small obstacle course, which the children had to traverse as fast as possible without triggering an alarm. After all that tinkering, some running about was a welcome change! Looking at how much fun we had, I have the feeling that this was not our last “Tinker Birthday Party.”