On Tue, 1 Oct 2002, Alex wrote:

> I would like to build an improved controller for an amateur radio antenna
> that I use.
> It has a large variable capacitor that is motor driven.

Have you disconnected the motor from the cap to see how much force it
takes to move the cap?  I'm thinking you might be able to replace the
motor with a suitably sized R/C servo, and drive that from the PIC.  I
don't know if you could get close enough positioning that way, but it may
be worth the try.  Anyway, you could just replace the control box with the
PIC and still keep the same button arrangement.  I can almost see the QST
article coming now!  8-)

> The two things that change are capacitance and angular rotation. I suppose
> angular rotation would be easiest to store,but would mean adding something
> to the shaft that could be counted. The rotation is about 80 degrees and has
> switches that indicate the end of travel.

If you do want to use the existing motor, see if you could adapt something
simple to the shaft.  I'm thinking the optical guts from a mouse might
work, that will give you a slotted wheel you may be able to drill out and
secure to the motor shaft, then use an optical encoder to watch the holes
go by.  Again, not having seen the loop -- is it MFJ or AEA? -- I don't
know if the motor has a small enough shaft, or if there's enough exposed
to give you the half inch or so you'd need to get at.

Another idea would be to keep the same drive arrangement, but use a
stepper morot for the drive instead of a DC motor.  Steps from the limit
switch could easily be determined and stored.

> One last question. I have been using assembler and the Epic programmer, but
> would Basic or C make my life easier especially with bigger projects. I have
> some programming experience with both.

I know it made my life a lot easier.  I learned PIC assembler, having done
a lot of assembly programming in the past, but never did get really
comfortable with it.  I got a few projects done, but since I switched to C
it's been a lot better for me.  To each his own, some people are dyed in
the wool ASM devotees.  I'm right, of course, and so are they!  8-)

Dale

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