Pete Keillor wrote:
On Wed, 09 Dec 2009 07:06:14 -0600, cavelamb
wrote:

Pete Keillor wrote:
On Tue, 08 Dec 2009 22:06:17 -0600, Don Foreman
wrote:

"Karl Townsend" wrote in message
anews.com...
You described the exact issue. Mechanically, I've got it geared down to
raise/lower 12"/minute with a total travel of 60 inches. Gets hard to gear
it much slower. My "plan A" is two stats so you have a dead band, then
play with % run to get response without oscillation. I suppose if you knew
exactly what percent on/off was optimum you could just gear it for 100%
on.
You can't know that because it will change significantly with cloud
cover, sun angle, wind, etc.


It ain't hard, it just ain't cheap. I used a double reduction
Sumitomo cycloid drive of 3400:1 to drive the continuous filter I
invented. Web movement maximum was 60"/hour, min was close to zero.
I'd mark the web, go have a cup of coffee, come back and stick a ruler
on it to make sure it was working.

Pete Keillor

Well, not to be contradictory, but it is both easy and cheep - in software.

Once you have the drive running that can handle the mechanical loads,
controlling the speed is simple stuff.

Richard

Yeah, you're right if discontinuous works, as in this case. I wanted
continuous motion in the case I described.

Pete Keillor


Pulse width modulate.

The motor will integrate that into continuous motion.

If the requirements get REAL slow, you may have to pulse both ways.
Drive forward Tx
Drive backwards Tc-n

Keep the motor energized so it doesn't wander off position.