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