ESP32 - Cooling System using DHT Sensor

This tutorial instructs you how to make a cooling system using ESP32, DHT11/DHT22 temperature sensor and fan. In detail:

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×Micro USB Cable
1×DHT11 Temperature and Humidity Sensor
1×(Optional) DHT22 Temperature and Humidity Sensor
1×Relay
1×12V Cooling Fan
1×12V Power Adapter
n×Jumper Wires
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Introduction to the Cooling Fan and DHT Sensor

We have specific tutorials about temperature sensor and fan. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

  • Wiring Diagram with DHT11 module
  • wiring diagram between esp32 cooling fan system

    This image is created using Fritzing. Click to enlarge image

  • Wiring Diagram with DHT22 module
  • wiring diagram between esp32 cooling fan system

    This image is created using Fritzing. Click to enlarge image

How System Works

  • The ESP32 reads the temperature from the DHT11 or DHT22 temperature sensor
  • If the temperature is above an upper threshold, ESP32 automatically turns the fan on
  • If the temperature is below a lower threshold, ESP32 automatically turns the fan off

ESP32 keeps checking the temperature infinitely.

The lower threshold and upper threshold can be the same value.

ESP32 Code

ESP32 Code for DHT11 sensor

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-cooling-system-using-dht-sensor */ #include <DHT.h> #define RELAY_FAN_PIN A5 // ESP32 pin connected to relay #define DHT_SENSOR_PIN 12 // ESP32 pin connected to DHT sensor #define DHT_SENSOR_TYPE DHT11 #define TEMP_UPPER_THRESHOLD 30 // upper temperature threshold #define TEMP_LOWER_THRESHOLD 15 // lower temperature threshold DHT dht_sensor(DHT_SENSOR_PIN, DHT_SENSOR_TYPE); void setup() { Serial.begin(9600); // initialize serial dht_sensor.begin(); // initialize the DHT sensor } void loop() { float temperature = dht_sensor.readTemperature();; // read temperature in Celsius if (isnan(temperature)) { Serial.println("Failed to read from DHT sensor!"); } else { if (temperature > TEMP_UPPER_THRESHOLD) { Serial.println("Turn the fan on"); digitalWrite(RELAY_FAN_PIN, HIGH); // turn on } else if (temperature < TEMP_LOWER_THRESHOLD) { Serial.println("Turn the fan off"); digitalWrite(RELAY_FAN_PIN, LOW); // turn off } } // wait a 2 seconds between readings delay(2000); }

ESP32 Code for DHT22 sensor

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-cooling-system-using-dht-sensor */ #include <DHT.h> #define RELAY_FAN_PIN A5 // ESP32 pin connected to relay #define DHT_SENSOR_PIN 12 // ESP32 pin connected to DHT sensor #define DHT_SENSOR_TYPE DHT22 #define TEMP_UPPER_THRESHOLD 30 // upper temperature threshold #define TEMP_LOWER_THRESHOLD 15 // lower temperature threshold DHT dht_sensor(DHT_SENSOR_PIN, DHT_SENSOR_TYPE); void setup() { Serial.begin(9600); // initialize serial dht_sensor.begin(); // initialize the DHT sensor } void loop() { float temperature = dht_sensor.readTemperature();; // read temperature in Celsius if (isnan(temperature)) { Serial.println("Failed to read from DHT sensor!"); } else { if (temperature > TEMP_UPPER_THRESHOLD) { Serial.println("Turn the fan on"); digitalWrite(RELAY_FAN_PIN, HIGH); // turn on } else if (temperature < TEMP_LOWER_THRESHOLD) { Serial.println("Turn the fan off"); digitalWrite(RELAY_FAN_PIN, LOW); // turn off } } // wait a 2 seconds between readings delay(2000); }

The above ESP32 codes automatically turn the fan on if the temperature is above 30°C, and keep the fan on until the temperature is below 15°C

Quick Instructions

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
  • Do the wiring as above image.
  • Connect the ESP32 board to your PC via a micro USB cable
  • Open Arduino IDE on your PC.
  • Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
  • On Arduino IDE, Navigate to Sketch Include Library Manage Libraries
  • ESP32 add library
  • Type “DHT” on the search box, then look for the DHT sensor library by Adafruit
  • Install the library by clicking on Install button.
  • ESP32 DHT sensor library
  • A windows appears to ask you to install dependencies for the library
  • Install all dependencies for the library by clicking on Install All button.
  • ESP32 Adafruit Unified sensor library
  • Copy one of the above code and open with Arduino IDE
  • Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
  • Make the sensor colder or hotter. For example, putting the sensor near a hot cup of coffee
  • Check the fan's state

Advanced Knowledge

  • The algorithm used on above tutorial to control the tmperature is called the on-off controller (also known as the "bang-bang" controller, or the signaller). This algorithm is simple to implement and works well in temperature control.
  • An alternative for the above algorithm is the PID controller. The PID controller makes the desired temperature more stable. However, it is very difficult to understand and implement. Therefore, the PID controller is not widely used in temperature control.

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