DHT22 Temperature Sensor

DHT22 Temperature & Humidity Sensor

High Accuracy Digital Output Environmental Monitoring

What is DHT22?

The DHT22 (also known as AM2302) is a digital temperature and humidity sensor that provides high accuracy readings compared to basic sensors.

It measures:

• Temperature

• Relative Humidity

Commonly used in:

• Weather stations

• IoT projects

• Smart home systems

Working Principle

The sensor contains two main components:

• Humidity Sensor (Capacitive type)

  • Measures moisture in air

  • Capacitance changes with humidity

   

• Temperature Sensor (Thermistor)

Internal microcontroller:

• Converts readings into digital data

• Sends via single-wire communication

Pin Configuration (4-pin)

• Pin 1 (VCC) 3.3V 6V

• Pin 2 (DATA) Digital signal output

• Pin 3 (NC) Not connected

• Pin 4 (GND) Ground

Requires pull-up resistor (4.7k10k) on DATA line

Technical Specifications

• Operating Voltage: 3.3V 6V

• Temperature Range: -40C to +80C

• Humidity Range: 0% 100% RH

• Temperature Accuracy: 0.5C

• Humidity Accuracy:

• Humidity: 0.1%

Sampling Rate: ~0.5 Hz (1 reading every 2 seconds)

Output Type

• Digital signal (single-wire protocol)

• No need for ADC (unlike analog sensors)

Data is transmitted as a 40-bit digital message

Data Format (Simplified)

• 16 bits Humidity

• 16 bits Temperature

• 8 bits Checksum

Key Features

• High accuracy compared to DHT11

• Wide measurement range

• Digital output (easy to interface)

• Long transmission distance (up to ~20m with proper wiring)

• Stable and reliable performance

Applications

• Weather monitoring systems

• Smart home automation

• Greenhouse control

• IoT environmental sensors

Arduino Connection

• VCC 5V (or 3.3V)

• GND GND

• DATA Digital pin (e.g., D2)

• Add pull-up resistor between VCC and DATA

Advantages

• Higher accuracy than basic sensors

• Wider temperature and humidity range

• Digital output (less noise interference)

• Reliable for long-term monitoring

Limitations

• Slower sampling rate (2 seconds)

• Slightly more expensive than basic sensors

• Requires timing-sensitive communication

• Performance affected by condensation

Important Notes

• Do not take readings faster than every 2 seconds

• Use

• Avoid placing sensor in direct sunlight or water exposure

• Allow time to stabilize after power-up

Summary

The DHT22 sensor is a high-accuracy digital sensor for measuring:

Temperature Humidity

Ideal for:

• IoT projects

• Environmental monitoring