Arduino Thermostat Includes Vacation Mode


When [William’s] thermostat died, he wanted an upgrade. He found a few off-the-shelf Internet enabled thermostats, but they were all very expensive. He knew he could build his own for a fraction of the cost.

The primary unit synchronizes it’s time using NTP. This automatically keeps things up to date and in sync with daylight savings time. There is also a backup real-time clock chip in case the Internet connection is lost. The unit can be controlled via the physical control panel, or via a web interface. The system includes a nifty “vacation mode” that will set the temperature to a cool 60 degrees Fahrenheit while you are away. It will then automatically adjust the temperature to something more comfortable before you return home.

[William’s] home is split into three heat zones. Each zone has its own control panel including an LCD display and simple controls. The zones can be individually configured from either their own control panel or from the central panel. The panels include a DHT22 temperature and humidity sensor, an LCD display, a keypad, and support electronics. This project was clearly well thought out, and includes a host of other small features to make it easy to use.

19 thoughts on “Arduino Thermostat Includes Vacation Mode

    1. For a lot of climates, 15 degrees Celsius is just about a perfect idle temperature. It does not take much energy to maintain or much time to increase to something more comfortable. During away time and the night, we pretty much let it cool to a nice 15 degrees C as well. This means we only have to bump the temperature once or twice a day for a short amount which will last us long enough. It’s not like he’s going to let the ambient temperature control the house.

    1. This is really not true in most cases with modern equipment and insulation. My central ac is 20+ seer vs even localized window units would be no comparison, likewise my 99% efficient gas furnace vs electric ceramic heaters scares the crap out of me just thinking about that electric bill.

      Theres also the safety aspect with ceramic or other portable electric heaters, in that it is very easy to cause a fire with those things if you put something too close. I wouldnt want to make my 6 year old move it around to stay warm.

      Its more about efficiency unless you want to run around only heating the space immediately around you, not very practical when there are 4-5 people in the house.

    2. Really on the window AC? I went from paying $150.00+ a year in electric to less than 75 a month when I moved to a central AC. If you run the central AC correctly, it can save money versus the window AC. When the rooms would warm up, not a rare occurrence given that the two rooms I am in the most are plastered by sunlight, the compressors on the AC’s would stay on constantly with the thermostat set at 80F. With the central AC, I can keep the house at 75F for less than cooling two rooms with window AC’s to above 80F.

  1. There is very little point of having battery backup RTC if the power is out and you can’t control the heating/cooling at that point anyways. I supposed the internet and power interrupted and subsequently restored, so it still stuck in the previous mode (or at least should be in a fail-safe mode.)

  2. @Waterjet: I don’t know what the humidity accuracy of a DHT22 is but it’s good enough for my purposes. In the case of my heating system it only exists to satisfy my curiosity. Humidity comes for free with temp measurement in a DHT22 and the LCD real estate is free, so why not?

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