Hardware and Wiring
The system was developed on a Raspberry Pi4B, tested on a Raspberry Pi 3B, and ultimately deployed on a Raspberry Pi 2B. It has not been tested on a Raspberry Pi Zero, Pi 400, or compute models but I don't see why it wouldn't work on those. In addition to a Raspberry Pi, the system requires a minimum of one DS18B20 temperature sensor per zone, and a relay for each stage of equipment control desired and one relay for each zone the system will control. I used a Sainsmart 8 relay module for the initial deployment. This covers each of the typical controls of our subject system as follows:
- First stage heat
- Second stage heat
- First stage cool
- Second stage cool
- Fan only control
- Zone 1 damper (or valve or pump)
- Zone 2 damper
- Zone 3 damper
The sensors and relay module are all that are technically needed, but the following wiring diagram includes some emergency backup equipment to allow for the user to easily bypass the relay module and set the system to run with a regular two stage thermostat.
