[TowerTalk] tuner/stepper motors?

[RCARIELLO]

Brian,

I have used stepper motors to tune small magnetic loop xmitting antennas.
Using an air valuable Cap adjustments become very critical requiring stepper
motor precision.  The motors are easy to get but the controllers are
expensive and I found very sensitive to RF. I would love to take a look at
the circuit and program that you have. Would you send it to me? The next
thought is to expand the program to set the motor to preset locations.
Rich AA2MF
aa2mf@arrl.net

----- Original Message -----
From: "alsopb" <alsopb@gloryroad.net>
To: "George K. Watson" <watson@sierracmp.com>
Cc: <towertalk@contesting.com>
Sent: Monday, August 27, 2001 12:24 PM
Subject: Re: [TowerTalk] tuner/stepper motors?


>
> 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
> >
> > List Sponsored by AN Wireless:  AN Wireless handles Rohn tower systems,
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> supporting towers up to 96 feet for under $1500!!
http://www.anwireless.com
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List Sponsored by AN Wireless:  AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!!  http://www.anwireless.com

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