On Thu, 03 Sep 2015 15:35:06 -0700, Don Y
wrote:

It depends on the functionality that you want to provide. E.g., if
you wanted your pool/solar controller to assume a higher degree of
utilization on *holidays* than on WORKdays, you'd be hard-pressed to
do this with discrete logic.

This all came about from work I did with a few IBM engineers way back
in the Jimmy Carter solar age. Guys were designing very complicated
controllers and in the end it was decided that this was a very simple
thing. You really only needed a photo cell to get about 90% efficiency
and a couple of temperature sensors (in and out) really bumped that
up.

In the case of the pool and my solars I just use a timer and assume
that in the winter in Florida the sun will be shining all day. I have
a garden variety Honeywell thermostat to decide when it gets too cool
to keep running them in the evening.