So I converted to the BBB method the end of last year and I wanted to get some automation for the chlorine. I got a Stenner 45mp5 for injection. I was planning on sending to liquid chlorine into my old tab feeder to inject the chlorine. I know most people figure out how much the pool uses per day then calculate the stenner output and put a timer to inject the right qty of chlorine per day.
I was thinking of doing a step further and incorporate a ORP probe and controller into the mix. I got one off eBay and it will switch 120V depending on the ORP voltage. All I need to do is calibrate the voltage to what my chlorine level needs are and if it drops, it turns on the outlet and hence the stenner to inject chlorine.
Since this is a feedback loop, the problem is the slow amount of time from injection of liquid chlorine until it registers enough to move the ORP voltage to shut off the stenner which could lead to injecting too much chlorine. I was thinking of adding a On/OFF mechanical timer to fix the lag. So if the ORP turns on the outlet and then the timer will get voltage and go on for say 15,30,45 minutes and power the Stenner to inject. I will set the off for say 30,45,60 minutes, whatever I find it takes the ORP to sense the increase and shut the outlet off. I think once this on/off is close I can set the timer to the on/off that works.
My injection point would be my old chlorinator, drill a hole in top and put tube in and since there is water flowing into the chlorinator and getting sucked in this seems like a ideal place for injection. For the ORP probe I was thinking of doing it at the suction side of the pump so its seeing the skimmers and main drain combined so should be a good average of what's really in the pool from a chlorine level.
Anyone that has done something like this I would appreciate input, or if I am off base or crazy to try and make this work. I think if I can get this close it will be a great way to keep the levels pretty consistent throughout the day and night.