Hi all,
I am replacing a simple thermostat-type control that has rusted out on our 300Gal Gas Fired Hot Tub.
My first pass at the problem is using a DS1820(havent gotten the onewire support libs working with the DS18B20 yet) in the intake line to the boiler to measure water temp coming from the tub, eventually I will measure the temperature of the exhaust flow from the boiler and the tub water itself to determine system efficiency.
The tub motor itself is controlled by a 24 hour mechanical timer.
The boiler is allowed to be activated by a flow switch and the former thermostat. I will have 2 mode(s) in which the PID controller will be used, initial heatup, 4-5 hours not on the timer, and daily for one
hour topoff heat.
I will be using a 328p arduino to read the DS1820 sensors , run the PID loop and control a DC SSR to handle the 400-600mv required to switch the boiler on.
I presently have shamelessly copied the BBCC while changing temperature goals(200F is a bit warm) and I am changing both the temp input from ADC to DS1820 and replacing the output from PWM to min of 5 min flame on with ability to extend to continuous flame on and mandatory cool down time before relighting flames to minimize shock to the boiler.
OR
would the PID library with the same approach be just as versatile?
(prolly would, its just more of a blackbox to moi..)
clues for the clueless here?(especially about tuning)(guess its time to study auto tune approaches for PIDs)
gwen
ps the arduino PS will be plugged into a surge protector that is turn on by the same 24 hour mechanical timer/switch.