Using Python to Control a Pop Can Solar Furnace

Hans Kelson

Audience level:
Embedded Systems


This poster tells the story of how I control and monitor a homebrew solar furnace using Python. This has been an opportunity for me to learn python and build an embedded system.


My Mom and a friend built a solar collector from pop cans to help save energy by harnessing the power of the sun to help heat our home in winter. Using solar heat to supplement our furnace will help us save money and reduce our carbon footprint. The heater directly heats air that moves through the solar collector, and you can't count on the air to simply move itself through the heater, so you need a fan. If you leave the fan on too long, the heater cools off and can't heat the air fast enough, instead it can cool the air, defeating the purpose of the heater. Also, the collection capability of the heater depends on the position of the sun, cloud cover, and other factors beyond my control. We need a way to regulate the fan based on the air temperature inside the heater. We could simply use a thermostat, but we want to measure to find out how well the heater works and what we're saving. Besides, a thermostat wouldn't be that much fun! I built a Raspberry Pi control system and used an I2C temperature sensor to read the temperatures of the air flowing in and out of the heater. I used the GPIO breakout to drive a relay that turns the fan on and off. Then I wrote a python program that monitors the temperature and makes decisions about whether the fan should be running or not. I learned to write a multithreaded Python program to control the system: 1. A thread that controls the fan system 2. A small web server interface that lets me monitor the system and change the settings for the controller from my laptop. 3. A data logger that stores the temperatures and the fan state once per minute My poster will show how the heater is set up, how I installed my controller, and what the web interface looks like. If I'm lucky and the wireless works at the conference, I can show it to people live over the Internet. I expect that people who are interested in solar power and makers in general will be interested in my poster. I especially hope to meet other kids who want to make cool things.