George,
What you say may be true in general. However, I have a circuit from
the PARALLAX stamp manual which shows a single stamp chip, a ULN2003
driver chip, five resistors and a unipolar stepper motor are all that
are required. It appears to be able to drive stepper motors requiring
up to 0.5 amps.
The software is trivial -- about 10 lines of coding. Easily fits
within the 256 bits of memory in the cheapest stamp chip.
But then again maybe it doesn't work. However, the growing crowd of
homebrew robot enthusiasts seems to have good luck with it.
I'd be glad to forward the circuit diagram to anybody who is
interested.
A downside is that 6 wires are required to run it.
73 de Brian/K3KO
"George K. Watson" wrote:
>
> >> Anybody out there successfully used stepper motors to power variable
> >> caps in remote tuners? The ability to have good
> >> precision/repeatability seems idea. Chief problem seems to be
> >> obtaining one with enough torque.
> Torque can be generated through gearing. I imagine this would work quite
> well.
> I have some significant experience with both steppers and DC servo motors
> (though
> not in this application) and either would work fine. Servos are harder to
> work with.
> The control software is interesting and the external circuitry (amplifiers)
> required are expensive
> and/or non-trivial to build.
>
> 73,
> George K. Watson
>
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