Arduino - Cooling System using DHT Sensor
In this tutorial, we are going to make a cooling system using a fan and DHT11 or DHT22 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 DS18B20 sensor instead of DHT sendsor, see Arduino - Cooling System using DS18B20 Sensor .
|1||×||Arduino UNO or Genuino UNO|
|1||×||USB 2.0 cable type A/B|
|1||×||Temperature Sensor DS18B20|
|1||×||4.7 kΩ resistor|
About Cooling Fan and DHT 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:
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 DHT11 sensor
Arduino Code for Cooling System with DHT22 sensor
In the above codes, the Arduino turn on the fan when the temperature exceeds 25°C, and keep the fan on until the temperature is below 20°C
- 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
- Search “DHT”, then find the DHT sensor library by Adafruit
- Click Install button to install the library.
- You will be ased for intall some other library dependancies
- Click Install All button all library dependancies.
- Copy the above code corresponding to the sensor you have 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
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.