I bought a nest gen 2 thermostat to play with a open source project that revives old nest thermostats (https://nolongerevil.com/). Since I don’t want to install it into the home, because it will be a toy. I was thinking of building a test rig using a arduino or esp32 to simulate a HVAC and indoor temperature. I’m IT guy, not a HVAC guy, I think this would be a good learning project. Any suggestions?
Everyone is over thinking the hell out of this. Almost all thermostats use a cheap NTC resistor, just change the resistance so the hardware thinks its at the whacky temperature. Or you could figure out the bias voltage the system uses through the NTC then apply your own external voltage to trick the system.