What is a DHT11 sensor ?

The DHT11 is an ultra-simple digital humidity and temperature sensor to use.

It combines:

• a capacitive humidity sensor,
• an integrated thermistor,
• and an analog-to-digital converter (ADC),
• all controlled by a small internal chip that transmits data in a 1-wire digital format.

It is an ideal choice for beginner projects, basic weather stations, or DIY home automation.

Operating principle

The sensor performs an internal conversion every 1 to 2 seconds.

The temperature and humidity values are then transmitted bit by bit via a single data pin (DATA), according to a precise timing protocol.

Message structure:

[8 bits HR int] [8 bits HR decimal]
[8 bits T int]  [8 bits T décimal]
[8 bits checksum]

💡 Each measurement lasts about 20 ms, with a minimum cycle of 1 second between two readings.

Example of digital conversion (Arduino)

#include "DHT.h"
#define DHTPIN 2
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

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

void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  Serial.print("Humidité: "); Serial.print(h);
  Serial.print("%  Température: "); Serial.print(t); Serial.println("°C");
  delay(2000);
}

✅ Example:

Humidity: 56.0 % Temperature: 23.0 °C

Principle diagram

+5V
 │
[DHT11]
 │ DATA ─────┐
 │ NC        │
 │ GND ──────┘
        │
        └── Pull-up resistance 10 kΩ on DATA

💡 The DATA pin requires a pull-up resistor between DATA and VCC.

Application areas

🌦️ Mini weather stations

🏠 Home automation projects (ventilation, air conditioning)

🧠 Educational IoT and ambient sensors

🧪 Prototypes and electronic models

🔋 Non-critical low-power systems