On Wed, 16 Nov 2005 21:18:20 +0000 (UTC), "Bob"
wrote:

The disk must be very slow moving so a stepper motor would have to be put
through a gearbox I guess (perhaps as high as 250:1).

Is there any circuit diagram on the internet that you could recommend for
this application?

---
I can show you exactly how to do it, but you have to decide on what
you want.

For example, if you can tolerate a resolution of one degree, then
for a seven day period the motor would step once for every 360th of
seven days, or once every 28 minutes. For the same resolution over
a 24 hour period the motor would have to step once every four
minutes. If you wanted a resolution greater than that then you'd
need a stepper which could step in 0.5°, 0.25°,... increments or
you'd have to get a gearbox. But whatever you want to do you need
to decide what the smallest increment of rotation of the wheel needs
to be.

--
John Fields
Professional Circuit Designer