"For my cooling scheme I plan to control the exhaust fan proportional to a temperature setpoint. The humidifiers will operate according to a humidity setpoint which I would increase on hot afternoons and then set lower in the evenings."
I see. I'm going to interpret your words above in strict control system language as opposed to everyday dictionary language. I believe that's what you mean.
Proportional control of the fan(s) (for the uninitiated) is just on/off control with a gap between on and off setpoints to avoid control system instability. It's pretty much the same as your home furnace control and much less complex than deviative and integral schemes, but cheaper and much more common in non-industrial use. In effect it will just turn the fan(s) on and off when certain setpoints are reached. Derivative control takes into account the rate of change of the error signal and integral control takes into account the area under the time/error curve. All three together are super good but expensive to implement.
It appears to me that, unless you left something out, operating the fans on temperature control and the foggers on humidity control, will at times allow fogging without the fans running. Depending on the location of the humidity sensor, this could quickly shut off the foggers or maybe not. Nonetheless, operating the foggers with no fans decreases drop flight time and evaporation rates increasing the likelihood of rain in the GH. But as I said before I never see humidity like 12%. Looks like you could operate the foggers on humidity control, but also turn them off when the fans stop without much effort at all.
Looks like you are dropping a lot of money into this effort and I wish you the best. Believe me I worried about my own design choices when I dumped over huge bucks into my GH. Fortunately most of it worked well. I hope you get the same result.
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