WHY?

I moved into a two story house a few years ago, and it came with a heat pump for upstairs and for downstairs.  The thermostats were simple electronic thermostats that used relays, no schedules, just on/off and emergency heat.  I couldn't even run the fan manually.

I had a Nest thermostat at a previous house, and looked into that, but I couldn't justify $500 for thermostats.  So after a little research I decided to make my own.

Details on pause until op-amp challenge is done