Thermistors are inexpensive and easy to use for temperature measurement.  The only complicated part is the math used to translate the voltage output level to the measured temperature, but we have provided that for you in the Arduino sketch below.

Software used in this tutorial can be downloaded here:

Arduino Thermistor Software

Hardware used in this tutorial:

- Thermistor temperature Sensor (you also need a 10k resistor).

- Arduino board (Uno, Mega, Duemilanove, etc.)

Instructions:

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If this is your first Arduino project, first go through our “Arduino: Getting Started” tutorial.

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We will use an LCD to read the temperature from the thermistor.  Follow our Arduino LCD tutorial to get the LCD working with your Arduino.  If you don't want to use an LCD to get the temperature readings, you can always just change the sketch to use the Arduino's serial connection to your computer to read the temperature from the serial monitor.

Use your solderless breadboard to make the thermistor connections:

Software:

Download the example Arduino thermistor software here, and unzip the file.

You will now have a folder called “arduino_thermistor”

Start the Arduino software and load the Arduino thermistor example program by clicking File->Sketchbook->Open

Navigate to the arduino_thermistor folder and select the “arduino_thermistor.pde” file.

Transfer the Arduino thermistor sketch to your Arduino board by clicking the “Upload to I/O board” button. After uploading, you should see the current temperature displayed on the LCD.

Here is the code:

/* 
    Arduino thermistor example software
    Tutorial:  http://www.hacktronics.com/Tutorials/arduino-thermistor-tutorial
    Copyright (c) 2010 Mark McComb, hacktronics LLC
    License: http://www.opensource.org/licenses/mit-license.php (Go crazy)
*/

#include <LiquidCrystal.h>
#include <math.h>

/*

LCD Connections:
rs (LCD pin 4) to Arduino pin 12
rw (LCD pin 5) to Arduino pin 11
enable (LCD pin 6) to Arduino pin 10
LCD pin 15 to Arduino pin 13
LCD pins d4, d5, d6, d7 to Arduino pins 5, 4, 3, 2
*/

LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);
int backLight = 13;    // pin 13 will control the backlight



void setup(void) {
  pinMode(backLight, OUTPUT);
  digitalWrite(backLight, HIGH); // turn backlight on. Replace 'HIGH' with 'LOW' to turn it off.
  lcd.begin(20, 4);              // rows, columns.  use 16,2 for a 16x2 LCD, etc.
  lcd.clear();                   // start with a blank screen
  lcd.setCursor(0,0);            // set cursor to column 0, row 0
}

double Thermister(int RawADC) {
  double Temp;
  // See http://en.wikipedia.org/wiki/Thermistor for explanation of formula
  Temp = log(((10240000/RawADC) - 10000));
  Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp));
  Temp = Temp - 273.15;           // Convert Kelvin to Celcius
  return Temp;
}

void printTemp(void) {
  double fTemp;
  double temp = Thermister(analogRead(0));  // Read sensor
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Temperature is:");
  lcd.setCursor(0,1);
  lcd.print(temp);
  lcd.print(" C / ");
  fTemp = (temp * 1.8) + 32.0;    // Convert to USA
  lcd.print(fTemp);
  lcd.print(" F");
  if (fTemp > 68 && fTemp < 78) {
    lcd.setCursor(0,3);
    lcd.print("Very comfortable");
  }
}

void loop(void) {
  printTemp();
  delay(1000);
}

Happy hacking!

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