For my networked Pong controller, I am attempting to create a device that senses inhalation and exhalation as methods of moving the Pong paddle left and right. To do this, I am using a simple fan to generate an induction current. The two conductors of the fan motor are connected to two Arduino analog inputs with 10k-ohm resistors bridging them to ground to create voltage dividers. In this sense the motor acts exactly like any typical resistance-based sensor, like a flex sensor, except that the motor is not connected to any voltage source, as it generates its own current.
This works surprisingly well! I just have to set a small threshold to ignore the small amount of noise generated if you touch the motor or an EM source is moved near it. The next step is to figure out a reliable way to move the fan with your breath; I’m going to try a computer fan with a blowing/sucking tube (har!) attached to it. It’s an unusual kind of action to try to sense.
Video here: http://vimeo.com/3152151
Images:
The DC test motor with plastic-cup fan blower