OPTICAL/SHAFT ENCODERS

WHAT CAN YOU SENSE? The position of a motor, if you use them smartly. If you use there feedback, you can in turn use them to position a motor.
WHO MAKES THEM? #1
WHERE CAN YOU BUY THEM? Hosfelt or surplus places.
HOW DO THEY WORK? Encode: You can use a pot for a variable resistance and measure the R to know where the motor is.

Optical: Led positioned above a photodiode with space for a rotating disk with a slot cut out of it attached
to the motor to spin through that space. When the photodiode sees the light, you know what
position the motor is at. For finer control, make more slots.

Quadrature: Have two slots at 90 degrees so that you can determine direction of spin, too.

Shaft: You should remember the fancy pictures, I will try and get them from Joe P.

EXAMPLE CIRCUIT:
PITFALLS & SOLUTIONS:

Pots wear out.

Singularity of Rotation: Use a 5, 10, 15 or turn forever pot.