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  1. Home
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  3. [SOLVED] Pro Mini 3.3v with DS18B20 sensor getting (-)127 Celsius!

[SOLVED] Pro Mini 3.3v with DS18B20 sensor getting (-)127 Celsius!

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  • G Offline
    G Offline
    gogopotato
    wrote on last edited by Yveaux
    #1

    I hooked up DS18B20 to Pro Mini 3.3v using Vcc (3.3v). But the temp reading is constant at -127 degree Celsius. Below is my wiring with 4k7 Ohm resistor across data and vcc. I did some googling and some say -127 C reading means incorrect wiring. Is my wiring wrong?

    alt text

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    • G gogopotato

      I hooked up DS18B20 to Pro Mini 3.3v using Vcc (3.3v). But the temp reading is constant at -127 degree Celsius. Below is my wiring with 4k7 Ohm resistor across data and vcc. I did some googling and some say -127 C reading means incorrect wiring. Is my wiring wrong?

      alt text

      A Offline
      A Offline
      AWI
      Hero Member
      wrote on last edited by
      #2

      @gogopotato the - 127 can either mean that your sensor is not working or is read in the wrong way. Which sketch are you using? (the connections look ok)

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      • A AWI

        @gogopotato the - 127 can either mean that your sensor is not working or is read in the wrong way. Which sketch are you using? (the connections look ok)

        G Offline
        G Offline
        gogopotato
        wrote on last edited by
        #3

        @AWI I'm using the example provided in https://www.mysensors.org/build/temp

        numSensors = sensors.getDeviceCount();
        

        The above statement is returning zero. So perhaps I have a faulty/dead sensor? I should have tested the sensor before soldering it in...

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        • G gogopotato

          @AWI I'm using the example provided in https://www.mysensors.org/build/temp

          numSensors = sensors.getDeviceCount();
          

          The above statement is returning zero. So perhaps I have a faulty/dead sensor? I should have tested the sensor before soldering it in...

          A Offline
          A Offline
          AWI
          Hero Member
          wrote on last edited by AWI
          #4

          @gogopotato The DS18B20 is a pretty solid device, but there is a chance that it's broken. Re-check your wiring and measure the resistor before breaking anything.

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          • A AWI

            @gogopotato The DS18B20 is a pretty solid device, but there is a chance that it's broken. Re-check your wiring and measure the resistor before breaking anything.

            G Offline
            G Offline
            gogopotato
            wrote on last edited by
            #5

            @AWI I will try that. Thanks!

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            • A AWI

              @gogopotato The DS18B20 is a pretty solid device, but there is a chance that it's broken. Re-check your wiring and measure the resistor before breaking anything.

              G Offline
              G Offline
              gogopotato
              wrote on last edited by gogopotato
              #6

              @AWI Turns out, I was using 47k resistor instead of 4.7k resistor. Now it's working with no issue :)

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