tracking how fast a treadmill like project is moving

Hi All,
I have this project that I am doing and it involves taking the speed of 2 treadmills. The premise is that two people get on opposite treadmills and push them under their own power to play a simple game of Tetris against each other. How would I go about reading the speed of the treadmill moving? I have explored the thought of taking apart computer mice and using the optical laser, but could not find and instruction on how to interface the two together. Any help on this matter would be greatly appreciated.


There are tons of ways to do this. One would be to glue a small magnet on one of the rollers and have a hall effect switch or reed switch nearby which is triggered each time the magnet passes by them. Then the arduino would be used to count the times the switch is triggered in a certain amount of time to calculate the speed and display it.

Oh that makes sense the reed sensor would be cost effective as well. Next question would there be any way of making it where if someone stopped rapidly that it would be read by the arduino?

Absolutely, you'd need to program it so when the speed drops to zero (the reed switch isn't triggered in a certain amount of time) it does whatever you're looking for it to do.

ok so the triggering bars would have to be close together to be sensitive enough to read that. I know this is a newbie question but could you give me an example sketch so i would have to run? Or maybe steer me in the direction that I could find the examples that I could use.