This is my MIT acceptance tube hack. MIT asked us to hack our tubes, and so I did.
"What does it do?" I am glad you asked! It falls over when something walks in front of it.
"Why?" As I said in my video, "because being stable is too mainstream." Watch the video to see how I made it, to see it in action, and to listen to a song from Youtube's audioswap that took me 20 minutes to find (most audioswap songs are terrible).
It has an ultrasonic Ping sensor for detecting something in front of it. The sensor is bolted in and there are some spacers on the inside to keep it sort of flush with the surface of the tube.
I used the very first PCB I ever made as the "brain." It has the 3 pin connectors necessary for a servo and Ping, which was all I needed. The circuit is basically just a bare bones Arduino.
I used a micro servo with a screw glued to its arm as the "falling over" mechanism.
The batteries and switch are housed at the top of the tube. Not only was this the easiest way to do it, but it also makes it top heavy.
Here is the inside of the tube:
And that's all I have to say about that.