What is a DHT22 sensor ?

The DHT22 (or AM2302) is a combined digital temperature and humidity sensor, of better quality than the DHT11.

It integrates:

• a high-precision capacitive humidity sensor,
• a calibrated thermistor,
• and an internal microcontroller that ensures conversion and digital transmission.

It maintains the same simplified 1-wire interface, making it software-compatible with the DHT11 while offering greater accuracy and stability.

Operating principle

The sensor sends a 40-bit digital frame (identical to the DHT11):

8 bits for the whole humidity, 8 bits for the decimal humidity,

8 bits for the whole temperature, 8 bits for the decimal temperature,

and 8 bits for the checksum.

Decoding formula:

Humidity = [(data[0] × 256) + data[1]] / 10

Temperature = [(data[2] × 256) + data[3]] / 10

Example of digital conversion (Arduino)

#include "DHT.h"
#define DHTPIN 2
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

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

void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  Serial.print("Temp: "); Serial.print(t, 1);
  Serial.print(" °C | Hum: "); Serial.print(h, 1);
  Serial.println(" %");
  delay(2000);
}

✅ Example output:

Temp: 23.7 °C | Hum: 47.8 %

Principle diagram

+5V
 │
[DHT22]
 │ DATA ───────┐
 │ GND         │
                └── MCU (Arduino, ESP32, STM32…)

💡 Recommended pull-up resistance of 4.7–10 kΩ between DATA and VCC.

Application areas

🌦️ Home weather stations and IoT

🧠 HVAC home automation systems

🌿 Environmental monitoring (greenhouses, cellars, laboratories)

🏠 Indoor comfort control

🧪 Advanced educational projects (Arduino, ESP32, Raspberry Pi)