You can do what the simple mouse encoder does. If you open up a common mouse you will see that it uses two LED-photo-detector channels per encoder to determine the direction of rotation. The direction can be determined by recording which channel gets the first pulse.

check this link out...It gives how to make a very cheap rotary encoder by hacking a mouse:

http://www.boondog.com/tutorials...seHack.htm

What really confused me was when I opened up
my old Logitech an found only one emitter-detector pair per encoder...?!??! I saw the same thing in several other newer mice.

Any idea how that works? I am thinking the emitter does not glow continuously but instead emits a certain series/code of pulses that allow the direction to be decoded, but I cant think how...

kundi