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Arduino: Testing a Thermistor

Winter is upon us! And I thought to myself, its cold, but I do not know exactly just how cold it is. So I went online and found a

Tools for Thermistor test

Tools used for Thermistor Sketch

sketch (on the Arduino website) which experiments with a thermistor.

A thermistor  is a electronic component that registers a change in resistance in relation to the change in temperature. So the sketch requires:


  1. Arduino
  2. 10k resistor
  3. 10k Thermistor
  4. breadboard
  5. Jumper connectors.

I did not have a 10k thermistor, but a 1k thermistor. So I substituted the 10k resistor with a 1k resistor, in the hopes of decreasing the current requirements proportionally.


The code for the sketch on the arduino site (http://www.arduino.cc/playground/ComponentLib/Thermistor2) used the Analog Pin 0 as an input. This pin will then register the voltage and update by sending serial data to my laptop.


Measuring the Resistance of a Thermistor (Room temperature)

Measuring Resistance of Thermistor with heat (using fingertips)


As can be seen from the pics, the resistance of the Thermistor decreases the warmer it gets. So after testing the resistance I hooked up the components on the breadboard, uploaded the sketch to the Arduino, and turned on the serial monitor.


Thermistor hooked up to the Arduino

Ambient Room Temperature (A Toasty 17 degrees)


The room temperature is 17 degrees Celcuis which is quite chilly. I then apply some heat to the thermistor using my fingers. The temperature rose from 17 degress to a nice warm 27 degrees. I then removed my fingers, and the temperature then slowly dropped till eventually it was on 17 degrees again. This is the first experiment I have done using analog input pins. I was gong to test a photo-resistor, but it works along the same principle of adjusting resistance depending on the amount of light it receives, so I do not feel it will be necessary to test.


From here I think I can put together a app that will email me when the temperature drops below 20 degrees. All the processing will be done on my laptop, and when successful planning on shifting the processing to the Arduino further down the line.

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