I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?

Thanks

Bob

On Wed, 16 Nov 2005 12:21:55 +0000 (UTC), "Bob"
wrote:

I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?

---
Something like a 4060 with a couple of switchable crystals on the
front end eventually driving a stepping motor would do it, but what
kind of resolution are you looking for at the disc? 1°? 0.5?


--
John Fields
Professional Circuit Designer

"Bob" wrote

I have a project that requires turning a plastic disc (about the same
size
as a CD) through 360 degrees in 7 days or 24 hours using a battery
powered
system of some sort. The smaller and cheaper the better! Can anyone
suggest
the best way I should approach this problem?

If you don't need much torque, an old 5 1/4" floppy stepper motor would
give you 1.8 degree steps (200/revolution). You would need some kind of
logic to sequence the motor power wires. The nice thing about using a
stepper motor is that even with the power off, the motor will want to
hold its position.

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?

Bob

"John Fields" wrote in message
...
On Wed, 16 Nov 2005 12:21:55 +0000 (UTC), "Bob"
wrote:

I have a project that requires turning a plastic disc (about the same
size
as a CD) through 360 degrees in 7 days or 24 hours using a battery
powered
system of some sort. The smaller and cheaper the better! Can anyone
suggest
the best way I should approach this problem?

---
Something like a 4060 with a couple of switchable crystals on the
front end eventually driving a stepping motor would do it, but what
kind of resolution are you looking for at the disc? 1°? 0.5?


--
John Fields
Professional Circuit Designer

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

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).

Not if it makes a single step every 2-3 minutes, and is a high res
stepper.
--

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Thanks for all the help. Another news group has suggested I use a clock
mechanism and gearbox. This sounds simple so I think I will try this first.

Bob


"Bob" wrote in message
...
I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone
suggest
the best way I should approach this problem?

Thanks

Bob