Neil Baylis wrote:

> This is a brush commutated DC servo, and has a built in DC tachometer. In
> addition, someone has atached an optical encoder on the back. The
> encoder has only moderate resolution as far as I can tell by visually
> inspecting. Maybe 100 pulses per rev. Also, the encoder has only 3
> wires, so no direction info in there. 

> I want to begin by building a simple servo controller that will use this
> encoder for position feedback, and use the tach for velocity. I would
> obtain direction info by sampling the tach output voltage on every
> transition of the encoder signal. Obviously, the direction is the sign
> of the tacho signal. 
> 
> Will this work? 

For a servo controller, I would very much like a better direction signal,
and also an absolute position signal. The way this sounds, the controller
doesn't have a clue where the shaft position is on power-up.

Gerhard
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