DHT22 Temperature & Humidity Sensor Module (AM2302) – Single Wire Digital Output for Arduino & ESP32

DHT22 Temperature & Humidity Sensor Module (AM2302) – Single Wire Digital Output

The DHT22 Sensor Module — also known as the AM2302 or RHT03 — is a high-precision, low-cost digital temperature and humidity sensor widely used in embedded systems, IoT projects, and environmental monitoring applications. It integrates a capacitive humidity sensing element and an NTC (Negative Temperature Coefficient) thermistor along with an internal 8-bit microcontroller that delivers fully calibrated digital output over a single-wire interface — no ADC pins or signal conditioning circuits required.

Compared to the DHT11, the DHT22 offers a significantly wider measurement range, higher accuracy, and finer resolution, making it the preferred choice for precision-critical applications such as weather stations, HVAC systems, greenhouse automation, smart home monitoring, and industrial data logging.

Key Features

• Sensor IC: DHT22 / AM2302 (RHT03)
• Sensing Technology: Capacitive humidity sensor + NTC thermistor with internal 8-bit MCU
• Output Type: Calibrated 40-bit digital serial data (Single-Wire protocol)
• Interface: Proprietary Single-Wire Digital (NOT compatible with Dallas/Maxim 1-Wire)
• Supply Voltage: 3.3V – 5.5V DC
• Onboard Pull-up Resistor: Yes (no external resistor required when using module version)
• Calibrated Output: Yes — factory calibrated with OTP memory coefficients
• Sampling Rate: Once every 2 seconds (maximum)
• Long Transmission Distance: Up to 100 metres (with appropriate cable)
• Low Power Consumption: 40µA standby, 1.5mA measuring

Technical Specifications

Pin Description (Module)

Compatible Platforms

• Arduino Uno, Nano, Mega, Leonardo, Pro Mini
• ESP8266 (NodeMCU, Wemos D1 Mini)
• ESP32 DevKit (3.3V logic — use 3.3V VCC)
• Raspberry Pi (all models — via GPIO)
• STM32, Teensy, MSP430, Nucleo
• MicroPython and CircuitPython boards

Supported Libraries

• Arduino IDE:DHT sensor library by Adafruit (with Adafruit Unified Sensor)
• ESP-IDF: Custom single-wire driver
• MicroPython: Built-in dht module (dht.DHT22(pin))
• CircuitPython:adafruit_dht library
• Raspberry Pi (Python):Adafruit_DHT or pigpio library

Arduino Sample Code

#include <DHT.h>
#define DHTPIN 2         // GPIO pin connected to DATA
#define DHTTYPE DHT22    // Sensor type
DHT dht(DHTPIN, DHTTYPE);

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

void loop() {
  delay(2000);  // Min 2s between readings
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  Serial.print("Humidity: ");    Serial.print(h);    Serial.print(" %\t");
  Serial.print("Temperature: "); Serial.print(t);    Serial.println(" °C");
}

Applications

• Weather Stations: Ambient temperature and relative humidity monitoring
• HVAC Systems: Climate control feedback and automation
• Greenhouse Automation: Humidity and temperature regulation for plant growth
• Smart Home / IoT: Home assistant integration (Home Assistant, Blynk, ThingSpeak)
• Industrial Monitoring: Server room, warehouse, and cold storage environment logging
• Data Loggers: Long-term environmental data recording systems
• Wearables & Portable Devices: Personal weather monitors and comfort indicators
• Educational Projects: STEM kits, Arduino labs, IoT coursework

Important Notes

• Wait at least 1 second after power-on before sending the first read command.
• Maximum sampling rate is 1 reading per 2 seconds — do not query faster.
• The DHT22 single-wire protocol is NOT compatible with Dallas/Maxim 1-Wire protocol.
• If multiple DHT22 sensors are used, each must have its own dedicated GPIO data pin.
• A 100nF decoupling capacitor between VCC and GND is recommended for stable readings.
• Avoid exposure to condensation, chemical vapors, and direct sunlight for accurate long-term performance.

Package Contents

• 1 × DHT22 / AM2302 Temperature & Humidity Sensor Module (PCB mounted)

Upgrade Note: The DHT22 is the recommended upgrade from DHT11 — offering nearly 4× wider temperature range, double the humidity accuracy, and sub-degree temperature precision for professional and semi-professional applications.