My wife and I live in a big house that is expensive to cool down in the summer. I don’t sleep well when it’s too warm. Our bedroom is on the second floor and the thermostat is on the first floor which means that getting my bedroom to a good temperature is nearly impossible without cooling the entire house.

Ideal Solution

A programmable thermostat that turns the air on and off based on the temperature in my bedroom. It has a web interface so that it can be easily configured on the fly. It gathers data about how it’s used so that I can tweak the algorith to maximize comfort and minimize energy cost.

Smallest Useful Thing

A Raspberry Pi with a thermometer attached that logs the temperature in my room at regular intervals.

At this point I can imagine a number of the steps that get me to the ideal solution, but I know I need a raspberry pi thermometer in my bedroom, so that’s where I’m starting. My goal for this project will be to continually find the next small thing and iterate my way towards the ideal solution.


Hi! This is John from 2020. First of all, I hope you’re enjoying 2017. Sorry. That’s a little 2020 inside joke. Give Stan Lee a hug from me.

Second of all, I completed this project but I never completed the blog posts I intended to write. You can view the first couple posts here and then I will summarize everything else I did. Keep in mind that I was using an older OS version and so some of the steps I highlight there are outdated.

Once I was able to get temperature readings, I set up a web server so I could easily view the temperature for my room which was the end of the easy part.

Final Setup Looked like this


  • Raspberry pi wired to a relay wired into the house thermostat wiring
  • running a webserver that would accept requests to turn on and off the A/C and fan


  • Raspberry pi with thermometer attached
  • running a simple webserver that would return the current temperature in the room
  • also running a cron job that would check the temperature and hit the basement API to turn on and off the A/C


This project accomplished its task and was in use every day until we moved at the end of the summer. It definitely made our bedroom more comfortable but I don’t believe it accomplished the original goal of running the A/C more efficiently. It turns out that even if you close vents in your house, the A/C will work just as hard and cost just as much money to run. Closing many vents doesn’t really increase the flow of air into the desired room as more air will leak out of the ductwork with the increase in pressure. Any benefits to closing certain vents in the house were probably offset by the fact that I switched the A/C on and off more rapidly than the regular thermostat did which is inefficient. When we moved, I removed my Raspberry Pi and wired up the regular thermostat.