DHT22 Temperature and Humidity Sensor Module (Generic)

Features:

• Fully calibrated digital output
• Measures both relative humidity and temperature
• Excellent long-term stability
• Low power consumption
• Wide operating voltage range: 3.5V to 5.5V
• Long transmission distance
• Simple 3-pin interface

Principle of Operation:

• Uses a single-wire digital interface (not One-Wire compatible)
• Requires a pull-up resistor on the data line (typically 5K)
• Transmits 5 bytes: 16 bits humidity, 16 bits temperature, and 8-bit checksum
• Data request: host pulls data pin LOW briefly, then HIGH to initiate transmission

Pinout:

Note: Incorrect wiring (e.g., reversing VCC and GND) can permanently damage the sensor.

Applications:

• Weather monitoring systems
• Humidity regulators
• Air conditioners and HVAC control

Circuit Diagram:

Connect the DHT22 sensor to an Arduino as follows:

• VCC → 5V
• GND → GND
• Data → A0 (or any digital pin)

Library:

Install the SimpleDHT library via Arduino IDE: Sketch > Include Library > Add .ZIP Library

Example Arduino Code:

#include "SimpleDHT.h"

int pinDHT22 = 2;
SimpleDHT22 dht22(pinDHT22);

void setup() {
  Serial.begin(115200);
}

void loop() {
  Serial.println("=================================");
  Serial.println("Sample DHT22...");

  float temperature = 0;
  float humidity = 0;
  int err = SimpleDHTErrSuccess;

  if ((err = dht22.read2(&temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
    Serial.print("Read DHT22 failed, err=");
    Serial.println(err);
    delay(2000);
    return;
  }

  Serial.print("Sample OK: ");
  Serial.print(temperature);
  Serial.print(" *C, ");
  Serial.print(humidity);
  Serial.println(" RH%");

  delay(2500);  // DHT22 sampling rate is 0.5Hz
}

Technical Details:

• Supply Voltage: 3.3V to 5.5V
• Temperature Range: -40°C to +125°C
• Temperature Accuracy: ±0.3°C
• Humidity Range: 0% to 100% RH
• Humidity Accuracy: ±2% RH
• Data Format: Digital single-wire serial
• Size: 38 x 20 mm

Comparison with DHT11:

Resources:

• DHT22 Datasheet
• Arduino Tutorial