Arduino - Cooling System using DS18B20 Temperature Sensor

In this tutorial, we are going to make a cooling system using a fan and DS18B20 temperature sensor. When the temperature is too hot, turn on the cooling fan. When the temperature is cool, turn off the cooling fan. If you want to use DHT11 or DHT22 instead of the DS18B20 sensor, see Arduino - Cooling System using DHT Sensor .

Hardware Required


1×Arduino UNO or Genuino UNO
1×USB 2.0 cable type A/B
1×Temperature Sensor DS18B20
1×4.7 kΩ resistor
1×Cooling Fan
n×Jumper Wires
Please note: These are affiliate links. If you buy the components through these links, We may get a commission at no extra cost to you. We appreciate it.
Or you can order electronic components from

About Cooling Fan and DS18B20 Temperature Sensor

The cooling fan used in this tutorial uses the 12v power supply. If power is supplied for the fan, the fan on and vice verse. To control fan by Arduino, we need to use a relay in between.

If you do not know about temperature sensor and relay (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

Arduino cooling fan system wiring diagram

Image is developed using Fritzing. Click to enlarge image

How System Works

  • Arduino reads the temperature from the temperature sensor
  • If the temperature exceeds an upper threshold, Arduino turn on the fan
  • If the temperature falls below a lower threshold, Arduino turn off the fan

The above process is repeated infinitely in the loop.

If you want to turn on and turn off the fan when the temperature is above and below a specific value respectively, you just need to set the upper threshold and lower threshold to the same value.

Arduino Code for Cooling System with DS18B20 sensor

/* * Created by * * This example code is in the public domain * * Tutorial page: */ #include <OneWire.h> #include <DallasTemperature.h> const int TEMP_THRESHOLD_UPPER = 25; // upper threshold of temperature, change to your desire value const int TEMP_THRESHOLD_LOWER = 20; // lower threshold of temperature, change to your desire value const int SENSOR_PIN = 13; // Arduino pin connected to DS18B20 sensor's DQ pin const int RELAY_FAN_PIN = 3; // Arduino pin connected to relay which connected to fan OneWire oneWire(SENSOR_PIN); // setup a oneWire instance DallasTemperature sensors(&oneWire); // pass oneWire to DallasTemperature library float temperature; // temperature in Celsius void setup() { Serial.begin(9600); // initialize serial sensors.begin(); // initialize the sensor } void loop() { sensors.requestTemperatures(); // send the command to get temperatures temperature = sensors.getTempCByIndex(0); // read temperature in Celsius if(temperature > TEMP_THRESHOLD_UPPER){ Serial.println("The fan is turned on"); digitalWrite(RELAY_FAN_PIN, HIGH); // turn on } else if(temperature < TEMP_THRESHOLD_LOWER){ Serial.println("The fan is turned off"); digitalWrite(RELAY_FAN_PIN, LOW); // turn on } delay(500); }

In the above code, the Arduino turn on the fan when the temperature exceeds 25°C, and keep the fan on until the temperature is below 20°C

Quick Steps

  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • On Arduino IDE, Go to Sketch Include Library Manage Libraries
  • Arduino add library
  • Search “OneWire”, then find the OneWire library by Paul Stoffregen
  • Click Install button to install OneWire library.
  • Arduino onewire library
  • Search “Dallas”, then find the DallasTemperature library by Miles Burton.
  • Click Install button to install DallasTemperature library.
  • Arduino Dallas Temperature library
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Make enviroment around sensor hotter or colder
  • See the state of fan

Advanced Knowledge

The above controlling method is the on-off controller, also known as a signaller or "bang-bang" controller. This method is very simple to implement.

There is an alternative method called the PID controller. With the PID controller, the desired temperature is more stable but very difficult to understand and implement. Therefore, the PID controller is not popular in temperature control.

If this tutorial is useful for you, please give us motivation to make more tutorials
We are available for hire. See how to hire us to code for you