Thought controlled vvvvisuals

Updated 27.5.2010: This is a very roundabout way of doing things - don't do this.  There is a much better way. Eh, who knew there'd be a direct serial port on this thing?
Ok, "thought controlled" is saying too much, but there is a brain-computer interface involved.
I saw a promo video about the Star Wars Force Trainer something like a year ago, and immediately knew I wanted one. Check it out:



How cool is that? I also knew I wanted to interface it with my PC - and now I have. Here's a short demo video:

Force Trainer test run from dep on Vimeo.

I used an Arduino Duemilanove. In case you don't know, Arduino is an open (both software and hardware), multi-purpose microcontroller board. It made creating the interface exceedingly easy - in fact, the whole setup is essentially the same as in this tutorial by MrBenefit. For the interested, the fan in the Force Trainer is PWM controlled, with "high" levels of +5V - perfect for Arduino, as it is the default reference voltage of the analog input. I had some kind of grasp of the basic idea of PWM from using a ball mouse back in the day, but as I'm not very good with electronics, I turned to the helpful folks at the Arduino forums. Here is the very informative PWM tutorial that helped me figure out how to build a super-simple low pass filter (for converting the pulses into a floating voltage between 0 and 5V).
Some pictures of the construction process:

Measuring the voltage

 
The finished product. The switch turns off the sound of the device.

 Connected to the Arduino (no filter yet).

 
Close-up of the filter (and some related math)

Of course, this setup is really limited compared to something like the Emotiv Epoc (only three electrodes, only measures beta wave activity), but it works, and the effect is pretty cool. I'm looking forward to letting people play with this at upcoming Valmet Children gigs!