Lesson 9 Thermistor

Introduction

A thermistor is a type of resistor whose resistance varies significantly with temperature.

Components

– 1 * SunFounder Uno board

– 1 * USB data cable

– 1 * Thermistor

– 1 * Resistor (10K)

– Several jumper wires

Experimental Principle

The resistance of the thermistor varies significantly with ambient temperature. It can detect surrounding temperature changes in real time. Send the temperature data to analog I/O port of SunFounder. Next we only need to convert sensor output to Celsius temperature by simple programming and display it on the serial port.

Experimental Procedures

Step 1: Build the circuit

The schematic diagram

Step 2: Program (Please refer to the example code in LEARN -> Get Tutorials on our website)

Step 3: Compile the code

Step 4: Upload the sketch to the SunFounder Uno board

Now, you can see current temperature displayed on the serial monitor.

Code

// include the library code: //#include <LiquidCrystal.h> // initialize the library with the numbers of the interface pins //LiquidCrystal lcd(4, 5, 9, 10, 11, 12); #define analogPin A0 //the thermistor attach to #define beta 4090 //the beta of the thermistor #define resistance 10 //the value of the pull-down resistor void setup() { // set up the LCD’s number of columns and rows: //lcd.begin(16, 2); //lcd.clear(); Serial.begin(9600); } void loop() { //read thermistor value long a = analogRead(analogPin); //the calculating formula of temperature float tempC = beta /(log((1025.0 * 10 / a – 10) / 10) + beta / 298.0) – 273.0; //float tempF = 1.8*tempC + 32.0; // Print a message of “Temp: “to the LCD. // set the cursor to column 0, line 0 //lcd.setCursor(0, 0); //lcd.print(“Temp: “); Serial.print(“Temp: “); // Print a centigrade temperature to the LCD. //lcd.print(tempC); Serial.print(tempC); // Print the unit of the centigrade temperature to the LCD. //lcd.print(” C”); Serial.print(” C”); Serial.println(); // set the cursor to column 0, line 1 // (note: line 1 is the second row, since counting begins with 0): //lcd.setCursor(0, 1); //lcd.print(“Fahr: “); // Print a Fahrenheit temperature to the LCD. //lcd.print(tempF); // Print the unit of the Fahrenheit temperature to the LCD. //lcd.print(” F”); delay(200); //wait for 100 milliseconds }

Video