This repository contains the design and production files that I used to build by own ESP32-based OpenTherm* and ON/OFF thermostats.
The devices is based on a ESP32-S3 microcontroller, and can include exclusively a OpenTherm driver circuit or a latching on/off relay to drive the boiler. Optionally, a BME280 sensor can be soldered onto the board in order to measure temperature, humidity and pressure (and use them for control).
Mounted by me by hand, imperfect but functioning.
I'm an not a PCB designer / electronics professional, everything here is provided for free and the user assumes all resposibilities of what they do with the material. This material comes AS-IS with ABSOLUTELY NO WARRANTY.
*I'm NOT affiliated with the OpenTherm Association in any way, the circuit has only been tested by me on my own boiler and is not guaranteed to work on every boiler.
The OpenTherm circuit part is heavily inspired by this StackExchange post.