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.

Surely it is much simpler than that, as long as you are only interested in
azimuth and not elevation. The trouble with photo-sensors and the like is
that there will be a problem when the sun is behind cloud, and that will
cause all sorts of 'hunting' problems.

The good thing about the sun is that you always know where it will be at any
time of the day, and the rate at which it moves, so all you have to do is
arrange a mechanism that rotates by 15 degrees an hour. If you are only
pointing solar panels the you could step in at say 15 or 30 minute
intervals, rather than have it continuously tracking.

73
Jeff

"Jeff" wrote in message
. com...
The trouble with photo-sensors and the like is
that there will be a problem when the sun is behind cloud, and that will
cause all sorts of 'hunting' problems.

No, there won't be hunting. First, there is one photsensor that has no
blinders. It senses the presence of sun -- anywhere. When a cloud obscures
the sun, it inhibits tracking.

Second, the tracker only goes in one direction, advancing ever-westward,
automatically following the sun by steps, assuming a sunny day. Recall, I
said the shining of the sun onto the photosensor is what stops the advance
and the loss of sunshine onto the sensor restarts the advance.


The good thing about the sun is that you always know where it will be at
any
time of the day, and the rate at which it moves, so all you have to do is
arrange a mechanism that rotates by 15 degrees an hour.

Describe your mechanism. Making the version I originally described requires
only two photosensors, a dual DC amplifier chip, two relay driver modules,
two relays, a switch, a small prototyping board and some wire.

that there will be a problem when the sun is behind cloud, and that will
cause all sorts of 'hunting' problems.

No, there won't be hunting. First, there is one photsensor that has no
blinders. It senses the presence of sun -- anywhere. When a cloud
obscures
the sun, it inhibits tracking.

Second, the tracker only goes in one direction, advancing ever-westward,
automatically following the sun by steps, assuming a sunny day. Recall, I
said the shining of the sun onto the photosensor is what stops the advance
and the loss of sunshine onto the sensor restarts the advance.


The system works unitil it gets out of sync for some reason. A leaf
obscuring a sensor, a bird sitting on it etc etc.
One the rotator gets ahead of itself it will never find the sun.


The good thing about the sun is that you always know where it will be at
any
time of the day, and the rate at which it moves, so all you have to do is
arrange a mechanism that rotates by 15 degrees an hour.

Describe your mechanism. Making the version I originally described
requires
only two photosensors, a dual DC amplifier chip, two relay driver modules,
two relays, a switch, a small prototyping board and some wire.


The actual system will depend on what type of rotator you are using, a
stepper motor would be the easiest since you know how many degrees each step
is. If you are using an 'normal' antenna' rotator then most have a feedback
pot, and a control pot. All you have to do is apply a voltage in place of
the control pot to get your desired position. There are many ways of doing
that from a computer, a micro controller, a counter chip feeding a d/a
converter. a series of relays switching in resistors, the list is almost
endless.

73
Jeff

"Jeff" wrote in message
. com...

snip

The system works unitil it gets out of sync for some reason. A leaf
obscuring a sensor, a bird sitting on it etc etc.
One the rotator gets ahead of itself it will never find the sun.

This is true.Perhaps multiple sensors to some OR gates would provide the
necessary redundancy. I provided only one fail-safe mechanism and that is
for a cloud.

snip

The actual system will depend on what type of rotator you are using, a
stepper motor would be the easiest since you know how many degrees each
step
is. If you are using an 'normal' antenna' rotator then most have a
feedback
pot, and a control pot. All you have to do is apply a voltage in place of
the control pot to get your desired position. There are many ways of doing
that from a computer, a micro controller, a counter chip feeding a d/a
converter. a series of relays switching in resistors, the list is almost
endless.

What, no hamsters? :-)

Seriously, OP "JERD" never said whether he wanted a complicated, highly
accurate setup or just something that works. I went for bare-bones, basic
El Cheapo, the most fun, IMHO.

(I have more of a history of jury rigging antenna rotators than most people.
My first [1968] was the building of a controller based on two doorbell
pushbuttons from the hardware store; I bought the correct transformer and
capacitor from the electronics store. No indicator ... We aimed it solely
by looking at the TV. The components were screwed down to a chunk of
plywood I found in the yard. Oy! But I was a young sailor living in town
on my own dime for the first time. After rent and utilities, there was beer
money and not much else.)

73
"Sal"