Hey guys, this project works together with Wes' controller but I thought I'd start a new thread to keep hardware and software separate.
This project is for a cheap temperature and pH controller and monitor. Shooting for under $25, but that won't get you the big screen I have
The Idea:
To build a simple but fail-safe controller to monitor pH and trigger an output once to meets a limit. This could be a solenoid for your reactor or an outside air pump.
To build a redundant temperature controller using two separate probes whose values are compared to one another(with an alarm that warns if they are too far apart) and averaged together many times a second to give an accurate temperature reading.
How it is done:
The setpoints will be set(heh) by simple potentiometers. Simply press and hold one button to enter the "SET" mode. One pot for pH, one for low temperature limit and one for high temperature limit.
You will select if you'd like your pH relay to trigger above or below your setpoint ( but I haven't found a reason to trigger above it yet )
At your low temp setting a transistor will bias allowing you to supply your own voltage to power your relay for your heater, likewise for the high limit to turn on chiller or fans.
Any temperatures 2 degrees above or below your set points will sound an alarm (or bias a transistor)
The beauty of this system is, even if power is removed, once it is restored the controller already knows your set points and will take the correct measures to adjust the temp or pH.
If there is significant interest I may include logging capabilities, this will add a few dollars to the cost.
Without further adieu!
(yes, it is cold in my house)
Have a great Holiday everyone, I'm looking forward to your feedback!