April 21, 2011

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


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!

April 9, 2011

Angular momentum 3d stabilizer

Some time ago I wanted to build a cube that could seemingly defy the law of physics and balance on its edges or corners. To achieve this aim I decided to use spinning weights which would create a large angular momentum. So if the angular momentum gets bigger than the gravitational force, the cube would remain in its position even if it was balancing on its corners.

So there had to be three angular momentum axis: X Y Z

I used three 600 6V DC motors:


piece of wood with metal weights

electric motor

I attatched the motors to square plates which would form a cube later.

This is the first result: I added some protection to enclose the spinning discs.
The video shows a rotating disc: The laser was used for measruring the disc's speed
I also had to calibrate the disc very accuratly in order to prevent vibrations.

Turn on the cube and you will need some force to move it!
You can take it and place it on its corner and it won't fall but remain in its position as long as the discs are spinning!
Not really useful but ... :)