Change parameters in thermistor



  • Hi
    I just want to say that I'm totally new on this so my question might be stupid. However I have looked for a z-wave thermometer for my smoker, barbecue but I haven't found one, then I discovered this "mysensors" and "nodemanager" and start reading about it. I have several meat probes at home, the probes are actually simple thermistors and I thought maybe this could be a solution. I bought some stuff from China and start a little project. As I don't know anything about coding or programming I was glad to find nodemanager. I measured the reference resistance on the probe at 25 degrees (100k) and also measured the resistance at some other temperatures to get the B-coffistence (4169).
    I hooked up a simple test project on my board and put in the following code:

    nodeManager.setSleep(SLEEP,1,MINUTES);
    int temp = nodeManager.registerSensor(SENSOR_THERMISTOR,A2);
    SensorThermistor* tempSensor = ((SensorThermistor*)nodeManager.getSensor(temp));
    tempSensor->setNominalResistor(100000);
    tempSensor->setNominalTemperature(25);
    tempSensor->setBCoefficient(4169);
    tempSensor->setSeriesResistor(100000);

    The sketch uploads to the ardruino and delivers a temperature but I don't think it considers the changes I try to implement, whatever values I put in I get the same result. Can anyone help me with this?

    Thanks in advance!


  • Mod

    What changes are you referring to?



  • What I understand from the Nodemanager documentation the standard values are:

    ""// resistance at 25 degrees C (default: 10000)
    void setNominalResistor(long value);
    // temperature for nominal resistance (default: 25)
    void setNominalTemperature(int value);
    // The beta coefficient of the thermistor (default: 3950)
    void setBCoefficient(int value);
    // the value of the resistor in series with the thermistor (default: 10000)
    void setSeriesResistor(long value);
    // set a temperature offset
    void setOffset(float value);""

    But since i use a different thermistor I want to change them to values I'm using


  • Mod

    Only @user2684 can answer that 😀



  • @gohan OK, thanks!


  • Contest Winner

    Hi, @Getz99 sorry for the delay. Your understanding about those functions is correct, they are there exactly for customizing those parameters. Your code looks correct as well. If I look at the source code (https://github.com/mysensors/NodeManager/blob/master/NodeManager.cpp#L455) looks like the values set through those functions are actually used and when I did test them, I got coherent results. May you try running some tests by changing one value per time so to understand if the temperature will be always the same? Thanks!



  • Hi @user2684 thanks a lot for your reply! I started to put in different values first for the Beta-c, nothing happened. Then I tried to change the value of the resistance of the probe, noting happened but when changing the reference resistance then I got a change. I started to measure and I found that the 2,5mm female connection (bought from China) for the probe was extremely high resistance so I soldered the probe connections directly to the board and now it works!!! Sorry for taking your time but I must say that nodemanager is amazing! I have no kompetente or skills in electronics or programming and still I got this to work (with a little help from you)! Now I just have to solder everyiting togheter and put in a box and start using it! I will follow the development and for sure do more projects using Node Manager!

    Thanks again for for taking your time!


  • Contest Winner

    @Getz99 cool, and don't worry, this is good use of the time, ensuring something which is supposed to work actually works is worth of any effort 🙂


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