DHT22 Temperature and Humidity Sensor

Description

DHT22 Temperature and Humidity Sensor

The DHT22 is a digital temperature and relative-humidity sensor. It uses a capacitive humidity element and a thermistor for temperature, and provides digital readings to microcontrollers such as Arduino.

Specifications

• Temperature range: −40 °C to +80 °C (as stated in the source listing)
• Temperature accuracy: ±0.5 °C
• Humidity range: 0–100% RH
• Humidity accuracy: ±2% RH
• Operating voltage: 3.5–5.5 V
• Current: up to 2.5 mA during conversion
• Data output: digital single-wire protocol
• Sampling rate: 0.5 Hz (one reading every two seconds)

How it works

An onboard microcontroller converts the temperature and humidity readings into a digital signal that can be read by a compatible microcontroller.

Applications

• Local weather stations
• Automatic climate-control systems
• Environmental monitoring
• Educational and hobby projects

Pinout

The DHT22 may be supplied as a bare sensor or as a module; check the pin labels and arrangement on your version.

• VCC: 3.5–5.5 V supply
• Data: digital data output
• NC: not connected (on the bare 4-pin version)
• GND: ground

Using it with Arduino Uno

Basic example

#include "DHT.h"


#define DHTPIN 2     // Broche à laquelle le capteur est connecté
#define DHTTYPE DHT22   // Définir le type de capteur


DHT dht(DHTPIN, DHTTYPE);


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


void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  
  if (isnan(h) || isnan(t)) {
    Serial.println("Échec de lecture !");
    return;
  }
  
  Serial.print("Humidité: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Température: ");
  Serial.print(t);
  Serial.println(" *C");
  
  delay(2000);
}

Advanced example with I2C LCD

#include "DHT.h"
#include <Wire.h>
#include <LiquidCrystal_I2C.h>


#define DHTPIN 2     // Broche à laquelle le capteur est connecté
#define DHTTYPE DHT22   // Définir le type de capteur


DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 16, 2);


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


void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  
  if (isnan(h) || isnan(t)) {
    lcd.setCursor(0, 0);
    lcd.print("Échec de lecture!");
    Serial.println("Échec de lecture !");
    return;
  }
  
  lcd.setCursor(0, 0);
  lcd.print("Hum: ");
  lcd.print(h);
  lcd.print(" %");


  lcd.setCursor(0, 1);
  lcd.print("Temp: ");
  lcd.print(t);
  lcd.print(" C");


  Serial.print("Humidité: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Température: ");
  Serial.print(t);
  Serial.println(" *C");
  
  delay(2000);
}

Advanced-example wiring

• DHT22 VCC: Arduino 5 V
• DHT22 Data: Arduino pin 2, with a 10 kΩ pull-up resistor
• DHT22 GND: Arduino GND
• LCD VCC/GND: Arduino 5 V/GND
• LCD SDA/SCL: Arduino A4/A5

Library installation

1. In the Arduino IDE, open Sketch → Include Library → Manage Libraries.
2. Search for DHT sensor library by Adafruit and install it.
3. For the LCD example, search for and install LiquidCrystal_I2C.

Keywords: DHT22 temperature sensor, humidity sensor, relative humidity, Arduino weather sensor.