Home Automation FTW!

Temperature Graph

Although we’ve been living in this house for almost six years now, I never really bothered to figure out how the heating system works. Not until I bought a wireless energy monitor. What a surprise. I had no idea a house could use that much energy! I started to search old documents we inherited from the previous house owner, and finally I read up on the heating system. Left unattended the heat pump had gathered a lot of air and the circulation pump had come to a complete stop. I realized that I needed to get in control. Enter home automation.

At work we monitor software systems in order to (hopefully) act proactively before things go out of hands. It’s as simple as this: if you don’t know, you don’t know! I liked to apply the same principles to the systems at home. Inspired by my colleague Christian Lizell (@lizell) who not only build our monitoring system at work but made his own home monitoring system based on the realtime graphing system Graphite and home automation technology from Telldus, I went out and bought a Tellstick Net unit.

The Tellstick Net is a fairly small device that connects to a cloud based service, and can be accessed with a web interface and an Iphone app. You can connect an array of 433 MHz devices, like on/off switches and dimmers to it and then control them individually and as groups. Schedules can be made so that lights turn on and off, let say on at sunset and turn off at sunrise. Better still the Tellstick Net can recognize a number of wireless sensors. I ended up buying 8 temperature sensors that I connected to outside, inside, the two attics, workshop, fridge, and freezer.

What I had i mind was to read temperature sensor values from Telldus every minute and then send those values to a Graphite backend. Telldus who open sourced their software, offers a REST API with which sensor values can be read. So I started out hacking on the Telldus tdtool.py and Graphite example-client.py and put the code on Github. How I love Python for tasks like this! Installing a Graphite server is quite a task so I ended up downloading a prebuilt VirtualBox Graphite server. Preferably I would like to create a server somewhere in the cloud.

With a graph showing the temperature over time I could tune the fridge, freezer, and workshop (notice the repeating form of the freezer graph). I expect the attic temperature to tell how well the insulation works, but I need more time and freezing temperatures outside to make that analysis. The workshop just need to be a few degrees above freezing.

Next step: When the farming season begins I want to automate irrigation and monitor humidity in the ground. Enter farm automation…

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