"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.