Back at school I built a little trap in order to fool some other pupils.
At first I took apart an old CD-drive and removed the laser-moving unit:
|the laser unit|
The laser unit will be used as our trigger mechanism.
Just solder a connection to the motor and add a needle to the moving part.
The needle will move forward and pop our waterballoon.
I used a laser and a photocell to build a lightbarrier which would activat the trap.
The light barrier was placed across the pupils' common room.
Here's the trap's schematic:
This is the laser and the receiver (both are battery powered) :
|receiver with relais|
If the laser beam is interrupted the relais will activate the CD-drive-trigger and pop the waterbomb right over somebody's head.
Here the mounted trigger armed with one waterbomb:
And here the first victim (of course with slowmow) :
And here's an old video about the whole thing:
So this is one way to have fun with your old CD-Drive!