Thermostat Failure

Posted 2011.04.14 16.51 in Computers/Internet/Technology by Stephanie

After nearly a full month of flawless operation, my DIY ethernet thermostat suffered some kind of stroke yesterday evening, and this morning slipped into a coma.

I don’t know what cause the glitch but it appears that the microcontroller that runs the whole thing has been fatally befuddled. And while 98.2% of the time, I use a socket for any IC in any project, in this case for some stupid reason I did not.

Indeed, everything is soldered, hot-glued, and taped in there so well that I’m not sure it’s even worth-while attempting to debug & repair. I think this is a back-to-the-drawing-board moment. Or at least, back-to-the-assembly-line moment.

So, I have a couple replacement parts on order (and you can bet I’m re-stocking my IC stocket supply), and I suppose I’ll have to rebuild the darn thing over the weekend. It wouldn’t be such an issue if this had happened closer to the summer months, but for now I can’t leave the house unheated for days-on-end.

Hopefully the parts will arrive tomorrow and I’ll be able to get at it. Otherwise it’ll probably be a week before I can recover from this tragedy.

In the meantime, my home heating needs are being serviced by this neolithic thermostat that was recovered from an archaeological dig, and has been on display in a dusty old museum somewhere. Or quite possibly I found it on a shelf in the storage closet.


  1. bemis says:

    If you live in an area where low temperatures occur, you might want to consider putting a manual thermostat in parallel with the wiring for the heat.

    The manual one can be set for some very low temp, say 50*, with the goal of preventing your house from ever getting too cold due to a failure or lock up with your unit here.

    Another option, if you’re into redundancy, might be a sort of a “watch dog” which is completely separate and designed only to watch for extreme highs or lows–for example if it senses a temp of 50* and no heat, it can activate… if it senses a temp over 85* and that your ‘stat is calling for heat it can interrupt that circuit.

    Or maybe you’ve already reviewed these things and I just haven’t seen them yet 🙂

    1. Stephanie says:

      Hello Bemis,

      I have tried to make the code as ‘fail-safe’ as I can. There are some sanity-checks on the temperature, that are supposed to prevent it getting below 60 or above 80, depending on the season. However, if the hardware were to fail it is still possible (hopefully a very remote possibility) for the thing to get locked ‘on’ which could cause it to run out of control until intervened.

      On the other hand, I am still tweaking things and have some ideas to add some more checks-and-balances into the works.

      Cheers, & thanks for writing!

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