> I would like to build a Digital Readout (DRO) for a minilathe, and was
> thinking of using the slotted wheel inside an old mouse with
> the IR led and
> photo transistor. Couple the slotted wheel to the lathe
> saddle and couple it
> somehow to the bed of the lathe.
>
> The question is what sort of resolution can I expect to
> achieve using this
> set-up.

As high as you want. You get as pulses for turn as slots has the wheel, so
you can mechanicaly multiply the saddle displacement and measure it with the
wheel.

> I was thinking of counting the pulses generated when the
> wheel spins, using
> a PIC and sending the result out via RS232 to a computer where further
> calculation can be carried out, and the result displayed.

See Microchip's AN520 "Implementing a Simple Serial Mouse Controller" locate
in http://www.microchip.com/10/appnote/category/16c5x/00519/index.htm for
ideas.

...mmmmm but I could be ambitious... think on add a LCD for direct readout.

Sergi. (sorry for my english)

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