Tutorial 15: Arduino Serial Thermometer

The Arduino reads temperature from a MCP9700 temperature sensor IC and displays the temperature in the Arduino IDE serial monitor window.

Also see the Arduino LCD thermometer tutorial (tutorial 14).


Complete Tutorial 9: Using the Arduino Serial Port before attempting this tutorial.Tutorial 15 Arduino Serial Thermometer


Besides an Arduino Uno board, USB cable, wire links and a breadboard, you will need:

Qty Part Designator Notes Type
2 100n C1, C2 Non-polarized Capacitor
1 MCP9700 U1 Linear Active Thermistor IC Semiconductor


Circuit Diagram

The schematic for the Arduino serial thermometer and pinout for the MCP9700 is shown below. The MCP9700 temperature sensor is packaged in a TO-92 case – it looks like a transistor.

Building the Circuit

The circuit is very simple to build, click the picture below for a bigger image of the breadboard circuit.

Programming the Arduino

The serial_temperature sketch is listed below. Copy the sketch and paste it into the Arduino IDE.


Program:     serial_temperature
Description:  Reads the voltage from a MCP9700 temperature
sensor on pin A0 of the Arduino. Converts the
voltage to a temperature and sends it out of
the serial port for display on the serial
Date:         15 April 2012
Author:       W.A. Smith, http://startingelectronics.org
void setup() {
// initialize the serial port
void loop() {
float temperature = 0.0;   // stores the calculated temperature
int sample;                // counts through ADC samples
float ten_samples = 0.0;   // stores sum of 10 samples
// take 10 samples from the MCP9700
for (sample = 0; sample < 10; sample++) {
// convert A0 value to temperature
temperature = ((float)analogRead(A0) * 5.0 / 1024.0) - 0.5;
temperature = temperature / 0.01;
// sample every 0.1 seconds
// sum of all samples
ten_samples = ten_samples + temperature;
// get the average value of 10 temperatures
temperature = ten_samples / 10.0;
// send temperature out of serial port
Serial.println(" deg. C");
ten_samples = 0.0;

Tutorial 15 Arduino Serial Thermometer Schematic

Operating the Circuit

After loading the serial_temperature sketch to the Arduino, open the serial monitor window from within the Arduino IDE. The temperature will be displayed in the serial monitor window and will be updated approximately every one second. When heat is applied to the MCP9700 sensor (by touching it with a finger for example) the temperature reading will increase.

READ  Weather Station Receiver using Arduino


For more detail: Tutorial 15: Arduino Serial Thermometer

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