DHT22 Humidity and Temperature Sensor Module (AM2302)

🧠 What It Is
The DHT22 (also called AM2302) is a digital temperature and humidity sensor that uses a capacitive humidity sensing element and a thermistor to measure the environment and output calibrated digital readings.
It’s an upgrade over DHT11 offering wider range and better accuracy.
📊 Key Features
✔ Digital Output: Sends temperature and humidity data over a single digital data line — no analog conversion needed.
✔ Wide Temperature Range: Measures from about –40 °C to +80 °C.
✔ Wide Humidity Range: From 0 % to 99.9 % relative humidity.
✔ High Accuracy:
• Temperature: about ±0.5 °C
• Humidity: about ±2 % RH
✔ Resolution: 0.1 °C (temp) and 0.1 % RH (humidity)
✔ Power Supply: Typically 3.3 V to 5.5 V DC, suitable for Arduino, Raspberry Pi, ESP32, etc.
✔ Low Power Consumption: Good for battery‑powered systems.
📋 How It Works
The module reads temperature and humidity with internal sensors and outputs digital data in a simple protocol.
Only one pin (data) is used for communication with your controller — but it’s not Dallas One‑Wire compatible, so each sensor needs its own data pin in multi‑sensor setups.
Updates are available roughly once every 2 seconds (about 0.5 Hz sampling rate).
📌 Typical Applications
✅ Weather Stations & Environmental Monitoring
✅ Home Automation (HVAC control, smart thermostats)
✅ Data Logging Systems
✅ Greenhouse & Agriculture Climate Monitoring
✅ IoT Devices and Smart Sensors
✅ Consumer Electronics & Appliances
⚠️ Important Notes
⚠ Sampling Limitation: You can request new readings only about once every 2 seconds.
⚠ Careful Timing: Code must handle timing correctly to read data.
⚠ Environmental Limitations: Direct water or heavy condensation contact can affect humidity performance — sensors are best used where moisture won’t settle directly on them.
⚠ Better Alternatives: For higher accuracy and faster response, sensors like SHT3x/SHT4x are sometimes preferred.