Quote Originally Posted by bobmcj View Post
I do not know why anyone would want to use the PC (linux or windows) for actual control, they are not made for that type of control.
I do not know why anyone would use a PLC for a home pool; they are not needed for that!

Actually there is an application for a PLC in *commercial* pool ops, managing a bleach & acid feed system, a bleach chiller, and ORP & pH electrode inputs. Conventional ORP / pH controllers don't do well on pools, because it's too hard to keep them from over-controlling, and because the relationship between ORP electrode mV output and free chlorine levels is highly variable. I worked on developing a system using a chem feed system I'd developed, that had a consistent service life, allowing manageable PM intervals.

I was trying to couple it with a control system that had inputs from ambient temps, ORP, pH and some other things. By properly locating the feed inlets in relation to the probes, you could BOTH clean the probes AND use them for chem feed proving. If I'd been able to finish and market it, it would have dramatically reduced operational costs and increased pool water quality for small commercial pools that don't have a dedicated pool staff. Now, the cost benefits would not be so great, since SWCG provide an increasingly viable alternative.

Nothing's ever been marketed however, with a control concept that is as simple and comprehensive, and self-alarming. But, I didn't have the money to market the product or the time to develop the programming expertise needed. (Still have a couple of working PLC's though!)

I did learn how to use $80 time clocks, and predictive dosing, to outperform $5,000 pH/ORP controllers!