DHT22 Temperature and Humidity Sensor (Generic)

Features:

• Full-range temperature compensation
• Measures relative humidity and temperature
• Calibrated digital signal output
• Excellent long-term stability
• No extra components required for basic usage
• 4-pin package for flexible integration
• Ultra-low power consumption

Principle of Operation:

• Asynchronous single-wire serial communication (not One-Wire)
• 5K pull-up resistor required between VCC and Data
• Outputs: 8-bit humidity integer + 8-bit humidity decimal + 8-bit temperature integer + 8-bit temperature decimal + 8-bit checksum

Pinout:

Note: Reversing VCC and GND will damage the sensor.

Applications:

• Weather monitoring stations
• Humidity controllers
• Air conditioning systems

Circuit Diagram:

Follow these connections:

• Place a 10K resistor between Pin 1 (VCC) and Pin 2 (Data)
• Pin 1 → Arduino 5V
• Pin 2 → Arduino digital pin 2
• Pin 4 → GND
• Pin 3 → Not connected

Library:

Install the SimpleDHT library: 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);
}

Technical Details:

• Temperature range: -40 to 80°C ±0.5°C
• Humidity range: 0 to 100% RH ±2%
• Resolution: 0.1°C / 0.1% RH
• Operating voltage: 3V to 6V
• Current consumption: 1–1.5 mA
• Sampling rate: Every 2 seconds

Resources:

• DHT22 Datasheet
• Tutorial

Comparison: DHT22 Sensor vs DHT22 Module