How to Use NodeMCU ESP8266 with DHT11 Temperature Humidity Sensor

This tutorial shows how to connect a DHT11 temperature and humidity sensor to a NodeMCU ESP8266 board and read values through the Arduino IDE Serial Monitor. Simple setup with minimal components.

Required Components

• NodeMCU ESP8266 V2 with CP2102 chip
• DHT11 sensor with PCB breakout for easier wiring
• Micro USB cable for code upload
• 3x Male-to-Female Jumper wires

Wiring NodeMCU ESP8266 to DHT11

Connection is straightforward:

NodeMCU ESP8266	DHT11 (PCB)
5V	+ pin
GND	- pin
D4 (GPIO 2)	OUT pin

D4 on the board maps to GPIO 2 on the ESP8266 chip. You can change to other pins by editing the code later.

Installing the DHT11 Library

Install a DHT library before using the sensor:

1. Download a DHT11-compatible library
2. Open Arduino IDE → Sketch → Include Library → Add .ZIP Library
3. Select the downloaded library file

Different libraries may have different APIs, so check the example code that comes with your chosen library.

Code to Read Temperature and Humidity

#include <DHT.h>

#define DHTPIN 2     // GPIO 2 is D4 on the board
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  dht.begin();
  Serial.println("DHT11 Sensor Ready");
}

void loop() {
  delay(2000);  // Wait 2 seconds between readings
  
  float h = dht.readHumidity();
  float t = dht.readTemperature();  // Celsius
  float f = dht.readTemperature(true);  // Fahrenheit

  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C \t");
  Serial.print(f);
  Serial.println(" *F");
}

This code reads relative humidity, temperature in Celsius and Fahrenheit, then prints them to Serial Monitor every 2 seconds.

Changing the GPIO Pin

To use D1 (GPIO 5) instead, modify line 3:

#define DHTPIN 5     // Using GPIO 5 which is D1 on the board

Remember to reconnect the data wire to the D1 pin.

How to Upload and View Results

1. Select Board: NodeMCU 1.0 (ESP-12E Module)
2. Select the correct Port
3. Click Upload
4. Open Serial Monitor and set Baud Rate to 9600

If everything is correct, you’ll see temperature and humidity readings like 28°C with 65% humidity.

Testing with Heat Source

Try pointing a hair dryer near the sensor. Temperature values should rise, confirming the sensor works properly.

Summary

Using DHT11 with NodeMCU ESP8266 is straightforward. Key points: wire correctly, install a compatible library, and check connections if readings fail. For unstable readings, shorten wire length and ensure proper delay between measurements.