love noise. The more the better. In order to introduce a practical
application of a simple electrical circuit, I decided to show them
how to build their own alarm. One requirement is that the alarm
should stay running even if the person who enters closes the door.
The basic wiring diagram for any circuit is shown above. The little electric motor is just allowed to lie in the tin. When the battery is connected the motor rattles. The tin makes noise
switch can be included, by simply breaking the wire, baring the ends
and joining them or not.
peg can easily be converted into a spring switch. The bared ends of
the wire are wrapped around the peg as shown in the diagram. When the
peg is open, the circuit is broken. When it is closed, the circuit is
made. Tinfoil be used as well as the copper wire. This improves the
The peg can be held in the open position by placing a lollypop stick in the open end.
One end of the lollypop stick is tied to the door using a thumb tack at the other end of the string.
The peg itself is tied to the door frame.
When the door is opened, the stick is jerked from the peg. The peg closes, the circuit is made and the motor makes plenty of noise in the tin.
The peg remains closed even if the person who enters closes the door.