Laser triggered waterbomb trap

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

laser

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:

here

So this is one way to have fun with your old CD-Drive!