Hall Effect Sensor.

[Greg Ross]

Originally Posted by Al Skierkiewicz

When the pulses change places you have reversed direction.

Al, there's a problem with your graph. The way you've drawn it. Each sensor is always low whenever the other sensor goes high. Without keeping track of time intervals between pulses, it won't be possible to tell the direction of rotation.

To reliably get direction information, you would need to position the sensors just far enough out of phase that the pulses overlap as illustrated below. Then when you see one of the lines go high, you can just check the other one, and immediately know the direction.