The DHT22 Sensor and AM2302 are the same sensors is designed for measuring the relative humidity and temperature of its surrounding air. It has an inbuilt humidity sensor and thermistor to detect the humidity and temperature. In this article I’m sharing the details of Pinout, electrical characteristics and specifications.
Pinout
Pin Configuration
| Pin | Function |
| 1 | VDD – positive supply voltage |
| 2 | DATA data pin |
| 3 | NC (Not Connected) |
| 4 | GND is ground pin |
Features
- The DHT22 delivers a pre calibrated digital signal.
- The Measurement Ranges of Humidity and Temperature is about,
- Humidity: 0 – 100% RH
- Temperature: -40°C to 80°C
- The measurement value is high Accurate and it is about,
- Humidity: ±2% RH (max ±5%)
- Temperature: ±0.5°C
- Long Term Stability and Low Power Consumption
- Long Transmission Distance of Up to 20 meters.
- Fully Interchangeable with no need for additional components.
Applications
- HVAC systems
- Weather stations
- Environmental monitoring
- Greenhouses
- IoT projects
Internal Structure and Technology
This DHT22 sensor is designed with two types of sensors which are capacitive humidity sensor and a thermistor. The capacitive humidity sensor which senses the humidity and thermistor will check the temperature of the sensor’s surrounding area. The detected signal is passed to the micro controller for further processing of the data.
Technical Specifications
| Parameter | Value |
| Voltage Supply | 3.3V to 6V DC |
| Output Signal | Digital (Single-wire bus) |
| Humidity Range | 0 – 100% RH |
| Temperature Range | -40°C – 80°C |
| Accuracy | ±2% RH; ±0.5°C |
| Resolution | 0.1% RH; 0.1°C |
| Dimensions | Small: 14×18×5.5mm; Large: 22×28×5mm |
| Sampling Rate | Every 2 seconds |
Communication Protocol
The DHT22 uses a single-wire serial communication protocol. The data packet sent from the sensor includes:
- 8 bits integral RH
- 8 bits decimal RH
- 8 bits integral temperature
- 8 bits decimal temperature
- 8 bits checksum
Data Transmission Process:
- Start Signal: The MCU sends a low signal >1ms.
- Sensor Response: DHT22 sends a response signal followed by 40 bits of data.
- Bit Encoding:
- ‘0’ bit: 26–28 µs high level
- ‘1’ bit: ~70 µs high level
The sensor returns to standby mode until the next start signal.
Electrical Characteristics
| Condition | Min | Typ | Max | Unit |
| Voltage | 3.3 | 5 | 6 | V |
| Measuring Current | 1 | 1.5 | – | mA |
| Standby Current | 40 | – | 50 | µA |
Best Practices and Precautions
- Avoid operating outside the recommended RH and temperature ranges.
- Protect from chemical vapors and strong light and UV exposure.
- Use shielded cables to improve communication quality.
- Avoid using it under dew conditions or in critical safety systems.
- Recommended soldering temperature is < 260°C.
