Temperature sensor conversion

Troubleshooting
1

I’ve put enough time into this and would love some fresh eyes on this.
I’ve got a Grove IoT Starter Kit connected to my Core, and it has a v1.1 Temperature sensor (Thermistor model NCP18WF104F03RC)
I haven’t been able to find the proper conversion of the analog reading (which is about 3200 at room temperature, higher when the temperature is higher) to a temperature.
The code samples I’ve tried usually expect a value of 1023 or less and convert to resistance accordingly, so I’m stumped.

Here’s my site with the temperature currently showing the analog value rather than temperature.

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2

hahaha the hamster wheel is awesome!

The readings from the particle devices will go from 0-4095 instead of the arduino’s 0-1023. thats the extra resolution (extra bits) on the analog to digital converter. the calculation for resistance takes that into account, so try changing it and see how you go.

3

Thanks! I tried changing the value to that, but it’s not fitting properly. That solves half my issue, I think. I’ve noticed that a a colder temperature relates to a lower analog value.

Here’s my code

void updateTemperature(){
    analogvalue=analogRead(temp_sensor);
    resistance=(float)(4095.0-analogvalue)*10000/analogvalue; //get the resistance of the sensor;
    temperature=1/(log(resistance/10000)/B+1/298.15)-273.15;//convert to temperature via datasheet ;
    
    tempC =     (int)temperature;
}
4

Maybe see if this works for you:

http://playground.arduino.cc/ComponentLib/Thermistor2

I’ve wrapped that code in a small library at https://github.com/wgbartley/spark-thermistor-library. You can also find it in the web IDE by searching for “thermistor”. It should be the top result in that search.

5

I tried out the example library, and now it’s the same result as what I currently have. The temp in C is between 49 and 51, which I believe is incorrect, since there is currently a hamster thriving in that spot. I am happy to report that heating the thermometer with my thumb does increase the temp, so that part’s correct.

6

The hamster tracker is cool :hamster:

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