A smart thermostat is nothing new. But making one built a decade or more ago takes a few tricks. If you want to upgrade your thermostat without replacing it, [geektechniquestudios] shares their solution using a Raspberry Pi Zero to smarten up that dumb controller.
The hardware is decidedly simple: just a Pi Zero and a pair of relays. The relays act as button presses to the old thermostat. The software, though, is decidedly complex. There’s a React server and a Redis database along with some other bits and pieces.
The project is a work in progress, so you’ll probably have to figure a bit out for yourself. Even better, there is room to contribute back. In fact, the project page has a wish list of additions including Google home integration, scheduled temperature changes, and a few others.
Fake button presses takes a bit of finesse on the software side. After all, the computer can jam a button many times faster than a human with a mechanical switch can, and that’s bound to confuse an old circuit, especially if it denounces the switches.