Ian is more to expert than myself OFC.
However the 24vdc modules do offer a larger use of different inputs. All expansion modules need to the same base voltage.
I do have a pH controller signal linked to my PLC, which basically turns off my second CO2 injection for the rest of the 24hr cylce. Works well IMO as it drops the pH of tank in about 50mins, primary CO2 injection continues for rest of photo period, but I have that also tweeted with slight CO2 off periods whilst my lights ramp up in intensity. I use the DALI 0-10v ramping via the PLC software for my lights also. My rig wasn't cheap. Mine does temp monitoring also turning heater on and off plus slightly different temps for day and night and no heating on when dropping the pH off the tank. Works a dream and was great fun to make and program
However the 24vdc modules do offer a larger use of different inputs. All expansion modules need to the same base voltage.
I do have a pH controller signal linked to my PLC, which basically turns off my second CO2 injection for the rest of the 24hr cylce. Works well IMO as it drops the pH of tank in about 50mins, primary CO2 injection continues for rest of photo period, but I have that also tweeted with slight CO2 off periods whilst my lights ramp up in intensity. I use the DALI 0-10v ramping via the PLC software for my lights also. My rig wasn't cheap. Mine does temp monitoring also turning heater on and off plus slightly different temps for day and night and no heating on when dropping the pH off the tank. Works a dream and was great fun to make and program