DHT22 Digital Temperature & Humidity Sensor Module

Introduction

The DHT22 (AM2302) is a calibrated digital sensor that provides high-accuracy temperature and humidity measurements. With its single-wire serial interface, it’s perfect for weather stations, greenhouse monitoring, and HVAC systems.

DHT22 Digital Temperature & Humidity Sensor

Key Features

Technical Specifications

Pin Configuration

Wiring with Arduino

// Basic Connections:
// VCC  → 5V
// DATA → D2 (with pull-up resistor)
// GND  → GND

Important: Avoid long wires (>20cm) without proper shielding to prevent signal issues

Library Setup

1. Install the DHT sensor library by Adafruit
2. Include the required libraries:

   #include <DHT.h>
   #include <Adafruit_Sensor.h>

3. Initialize the sensor:

   #define DHTPIN 2     // Digital pin connected
   #define DHTTYPE DHT22 // DHT 22 (AM2302)
   
   DHT dht(DHTPIN, DHTTYPE);
   
   void setup() {
     dht.begin();
   }

Basic Sensor Example

#include <DHT.h>

#define DHTPIN 2
#define DHTTYPE DHT22

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  dht.begin();
}

void loop() {
  delay(2000); // Wait between measurements
  
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  
  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }
  
  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print("%\tTemperature: ");
  Serial.print(t);
  Serial.println("°C");
}

Advanced Features

// Calculate heat index (feels-like temp)
float hic = dht.computeHeatIndex(t, h, false);
Serial.print("Heat index: ");
Serial.print(hic);
Serial.println("°C");

// Read temperature in Fahrenheit
float f = dht.readTemperature(true);
Serial.print("Temperature: ");
Serial.print(f);
Serial.println("°F");

// Check sensor status
if (dht.read() == DHTLIB_OK) {
  Serial.println("Sensor working properly");
} else {
  Serial.println("Sensor error detected");
}

// Put sensor to sleep between readings
digitalWrite(DHTPIN, LOW);
delay(60000); // Sleep for 1 minute
digitalWrite(DHTPIN, HIGH);
delay(2000); // Allow sensor to stabilize

Troubleshooting