DHT11 Temperature and Humidity Sensor

Description

DHT11 Temperature and Humidity Sensor

The DHT11 is a digital temperature and relative-humidity sensor. It combines an NTC thermistor for temperature measurement with a capacitive humidity sensor, and sends digital readings to microcontrollers such as Arduino.

Specifications

• Temperature range: 0–50 °C
• Temperature accuracy: ±2 °C
• Humidity range: 20–90% RH
• Humidity accuracy: ±5% RH
• Operating voltage: 3.5–5.5 V
• Current: 0.3 mA while measuring; 60 µA in standby
• Data output: digital single-wire protocol
• Sampling rate: 1 Hz (one reading per second)

How it works

An onboard microcontroller converts the sensor 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 DHT11 is available as a bare 4-pin sensor or as a module; pin arrangements can differ between versions.

• Bare 4-pin sensor: VCC (3.5–5.5 V), Data, NC (not connected), GND
• Module: VCC, Data, GND

Using it with Arduino Uno

Basic example

#include "DHT.h"


#define DHTPIN 2     // Broche à laquelle le capteur est connecté
#define DHTTYPE DHT11   // 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 DHT11   // 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

• DHT11 VCC: Arduino 5 V
• DHT11 Data: Arduino pin 2, with a 10 kΩ pull-up resistor
• DHT11 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 and install DHT sensor library.
3. For the LCD example, also install LiquidCrystal_I2C.

Keywords: DHT11 temperature sensor, humidity sensor, relative humidity, Arduino weather sensor.