The system I installed at Madocke Brewing involves local control software on a dedicated Windows machine, and a slave device mounted to each fermenter.
The software performs all the control operations for the system and communicates with Brewers Chronicle transmitting temperature readings, and downloading the latest gravity readings and target ferment temperatures based on a brewer-defined ferment schedule based on gravity readings.
It sends target temperature instructions to the slave device which are connected via a local computer network. I am trialling devices which communicate via wireless network, which will reduce cabling requirements.
Each slave device is able to fire the glycol pump, and open and close the fermenter ball valve to allow cooling of the current fermentation. Multiple devices can turn on and off the glycol pump, but only the last device actually turns off the pump
Once the instructions have been sent to the slave device it will quite happily follow those instructions with no further interaction from the control software until the temperature needs changing. This means that if the control software is unavailable for whatever reason, the slave device keeps operating.
In the photo below, you can see the enclosure mounted to the fermenter containing the slave device, and some electrical components.
The control software also transmits information to the slave device. At the moment we have the following info being sent to the LCD screen attached to each slave device.
Temperature and cooling status
Current and target gravity readings
These details are refreshed frequently so you can always have a look at the fermenter to see how things are going. There is no need to go back to the control software to monitor operations.
Given that the LCD has 4 lines, we have now run out of lines. If more information is required, I'd probably cycle 2 screens of info every few seconds.
Gravity readings are read from a Tilt digital hydrometer which is transmitted by a Raspberry Pi device direct to Brewers Chronicle. These readings can be used to calculate the currently required fermentation temperature based on a ferment schedule Jimmy enters into the relevant ferment log in Brewers Chronicle.