Arduino - Cooling System using DS18B20 Temperature Sensor

In this tutorial, we are going to control temperature 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×DS18B20 Temperature Sensor (WITH Adapter)
1×DS18B20 Temperature Sensor (WITHOUT Adapter)
1×4.7 kΩ resistor
1×12V DC Cooling Fan
1×(Alternative) 5V DC Cooling Fan
1×12V Power Adapter
1×DC Power Jack
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino
1×(Recommended) Screw Terminal Block Shield for Arduino Uno
1×(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

Buy Note: Many DS18B20 sensors on the market are low-quality. We highly recommend buying the sensor from the DIYables brand using the link above. We tested it, and it worked well.

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 fan (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

  • Wiring diagram with breadboard
Arduino cooling fan system wiring diagram

This image is created using Fritzing. Click to enlarge image

  • Wiring diagram with adapter (recommended)
Arduino temperature sensor controls fan system wiring diagram

This image is created using Fritzing. Click to enlarge image

We suggest purchasing a DS18B20 sensor that comes with a wiring adapter for easy connection. The adapter has a built-in resistor, eliminating the need for a separate one in the wiring.

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 = 2; // Arduino pin connected to DS18B20 sensor's DQ pin const int RELAY_FAN_PIN = A5; // 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 pinMode(RELAY_FAN_PIN, OUTPUT); // initialize digital pin as an output } 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
  • Navigate to the Libraries icon on the left bar of the Arduino IDE.
  • Search “DallasTemperature”, then find the DallasTemperature library by Miles Burton.
  • Click Install button to install DallasTemperature library.
Arduino Dallas Temperature library
  • You will be asked to install the library dependency
  • Click Install All button to install OneWire library.
Arduino onewire 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.

Video Tutorial

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