"JERD" wrote in message
...
I am wondering if anyone has managed to convert/use a standard antenna
rotator for tracking purposes? I know that very expensive antenna rotators
are available for this use but hey there is no fun or challenge in that!

Want to use it to automate tracking the sun - have two solar panels
mounted
on one, currently using manual control.

I invented such a thing in my head but have never built it. My idea could
be adapted to what you already have. It is quite difficult to describe
without diagrams, but I'll give it a shot.

Imagine that your rotator is reset by you each sunny morning, pointing east
at the rising sun. You flip a TRANSFER switch and westward rotator power
is then applied through the contacts of a normally-closed (NC) relay . At
that moment, however, the relay is held open with coil current provided by
the amplified signal of a photosensor which is collocated with the collector
panels. It is aimed in the same direction as the panels, but it has
blinders on it so it has only a narrow field of view in the east-west
direction. Thus, the photosensor is illuminated because it is pointing in
the direction of the sun. First thing in the morning, with the panels and
the photosensor pointing at the sun, nothing happens when you throw the
TRANSFER switch.

But wait ...
As the sun rises, it gradually moves to a point where it is NOT illuminating
the photosensor. The relay drops and energizes the rotator. The rotator
moves but an instant later, the whole rig is again aimed at the sun, which
illuminates the photosensor. The relay re-energizes, removing power from
the rotator and movement stops. This process might repeat ten or twenty
times a day, depending on the angle of view of the photosensor.

For the fans of disclaimers, let me say I fully realize the relay could be
of the normally open (NO) variety and be pulled closed when the sensor is in
shade. (I had to pick one possibility for the description.) Photosensor
means any one of several types of light-to-electricity transducers. Relays
have solid-state alternatives. The TRANSFER switch is a minor
modification of the rotator control box he's probably using now.

Clouds will louse this up. With no sunshine, the tracking process should be
halted; thus, the circuit requires the addition of an all-seeing photosensor
(no blinders) to test whether the sun is shining and interrupt the power if
it's not.

This is hardly the only autotracker design that would work and you could
even add elevation tracking.(However, in addition to all the mechanical
things, elevation tracking control would require at least another pair of
sensors and possibly a lens system rather than simple blinders. Probably
too hard.)

Automatic daily resetting could be accomplished with a dedicated
sunrise-sensing photosensor and additional modification of the control box.
This would enable you to sleep in. (You could involve the "all-seeing
photosensor," above, in this, but the logic would have to include a test for
the approximate time-of day, so the daily reset could happen only in the
morning.)

Lest anybody be concerned this has nothing to do with antennas, let me
hasten to state that my last unconventional use for an antenna rotator was
to make a true tracking polar mount for a Ku-band satellite dish. Looks
like crap but tracks the arc perfectly. So there is a tenuous connection.

"Sal"