Welcome to our step-by-step guide on connecting a DHT11 temperature and humidity sensor to an ESP32 microcontroller. The ESP32 is a powerful, low-cost board with built-in Wi-Fi and Bluetooth, making it perfect for Internet of Things (IoT) projects. The DHT11 is a popular and inexpensive sensor for measuring basic climate data. By the end of this tutorial, you will learn how to wire the sensor to your ESP32, write the necessary code, and read temperature and humidity values, laying the foundation for more advanced projects like a web-based weather station.

Components and Tools Required

Before we begin, you'll need to gather a few essential components. You likely have most of these in your electronics kit already.

  • ESP32 Development Board: Any model of the ESP32 board will work.
  • DHT11 Sensor: This is a basic temperature and humidity sensor.
  • Breadboard: For creating a solderless circuit.
  • Jumper Wires: To connect the components on the breadboard.

Circuit Wiring Steps

Connecting the DHT11 to the ESP32 is straightforward. The DHT11 sensor typically has three or four pins. We will be using the 3-pin version for this guide. If your sensor has four pins, the one labeled "NC" is not used.

First, place the ESP32 and the DHT11 sensor on the breadboard. Then, use the following connections:

DHT11 PinConnects to ESP32 Pin
VCC or +3V3
GND or -GND
Data or OutGPIO 4 (or D4)

Important: Always ensure your ESP32 is disconnected from power while you are wiring the circuit to prevent accidental shorts.

Setting Up Your ESP32 Environment

To program the ESP32, we will use the Arduino IDE. If this is your first time using an ESP32 with the Arduino IDE, you'll need to add the ESP32 board definitions to it. This allows the IDE to compile and upload code to your board.

For a detailed, step-by-step guide on this one-time setup process, please refer to this excellent tutorial:

You will also need to install the DHT sensor library by Adafruit. You can do this directly in the Arduino IDE:

  1. Go to Sketch > Include Library > Manage Libraries...
  2. In the search box, type "DHT sensor library".
  3. Find the one by Adafruit and click "Install". The IDE may ask to install dependencies like the "Adafruit Unified Sensor" library; please accept and install those as well.

Code and Explanation

Below is the complete Arduino sketch for reading data from the DHT11 sensor. It's the code you provided, now integrated into our guide.

// Include the necessary libraries
#include "DHT.h"

// Define the GPIO pin connected to the DHT11 data pin
#define DHTPIN 4

// Define the type of DHT sensor
#define DHTTYPE DHT11

// Initialize the DHT sensor object
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  // Start the serial communication
  Serial.begin(115200);
  Serial.println("DHT11 Test!");

  // Initialize the DHT sensor
  dht.begin();
}

void loop() {
  // Wait a few seconds between measurements.
  delay(2000);

  // Read humidity
  float h = dht.readHumidity();
  // Read temperature as Celsius (the default)
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit (isFahrenheit = true)
  float f = dht.readTemperature(true);

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Compute heat index in Fahrenheit (the default)
  float hif = dht.computeHeatIndex(f, h);
  // Compute heat index in Celsius (isFahrenheit = false)
  float hic = dht.computeHeatIndex(t, h, false);

  // Print the results to the Serial Monitor
  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hic);
  Serial.print(" *C ");
  Serial.print(hif);
  Serial.println(" *F");
}

How the Code Works

  • #include "DHT.h": This line includes the Adafruit DHT library we installed earlier.
  • #define DHTPIN 4: We define a constant DHTPIN to specify that our sensor's data pin is connected to GPIO 4.
  • #define DHTTYPE DHT11: This tells the library that we are using a DHT11 sensor.
  • DHT dht(DHTPIN, DHTTYPE);: This creates a dht object that represents our sensor.
  • setup(): This function runs once when the ESP32 starts. It initializes serial communication so we can see the output on a computer and starts the DHT sensor.
  • loop(): This function runs continuously. It waits for 2 seconds, then reads the humidity and temperature (in both Celsius and Fahrenheit). It includes an error check to see if the readings were successful and then prints all the data to the Serial Monitor.

Uploading the Code and Testing

  1. Connect your ESP32 to your computer via a USB cable.
  2. In the Arduino IDE, go to Tools > Board and select your ESP32 board model.
  3. Select the correct Port under the Tools menu.
  4. Click the Upload button (the right-pointing arrow).
  5. Once the code is uploaded, open the Serial Monitor (the magnifying glass icon in the top-right corner).
  6. Set the baud rate to 115200. You should now see the temperature and humidity readings appear every two seconds!

Conclusion

Congratulations! You have successfully connected a DHT11 sensor to your ESP32 and are reading live environmental data. This simple project is a gateway to many exciting IoT applications. You can now expand on this by sending the data over Wi-Fi to a server, displaying it on a web dashboard, or triggering other devices based on temperature and humidity levels.

Frequently Asked Questions (FAQ)

Question 1: My Serial Monitor shows "Failed to read from DHT sensor!" What's wrong? Answer 1: This is a common issue. Check these things first:

  • Double-check your wiring. Make sure VCC, GND, and Data lines are connected to the correct pins.
  • Ensure you have a good connection. Sometimes jumper wires can be loose on the breadboard.
  • Some DHT11 sensors require a 10k Ohm pull-up resistor between the VCC and Data lines, although many modules include one. If you have a spare resistor, try adding it.

Question 2: Can I use a different GPIO pin on the ESP32? Answer 2: Yes, absolutely. You can use most of the other GPIO pins. Just remember to change the pin number in the code by modifying the #define DHTPIN 4 line to match the pin you choose.

Question 3: What is the difference between the DHT11 and DHT22 sensors? Answer 3: The DHT22 is a more expensive but more accurate version of the DHT11. It has a better temperature and humidity range and precision. The good news is that you can use the same code for the DHT22; you just need to change #define DHTTYPE DHT11 to #define DHTTYPE DHT22.