The DHT21 (AM2301) is a popular digital sensor for measuring temperature and humidity. It combines a capacitive humidity sensor and a thermistor to provide digital signal output, making it convenient for use in electronics projects and IoT systems. Below is a detailed overview:

Key Specifications:

1. Temperature Measurement:

   • Range: -40°C to 80°C
   • Accuracy: ±0.5°C
   • Resolution: 0.1°C

2. Humidity Measurement:

   • Range: 0% to 100% RH
   • Accuracy: ±3% RH (typical)
   • Resolution: 0.1% RH

3. Power Requirements:

   • Operating Voltage: 3.3V to 5.5V
   • Average Current: 0.5 mA (approx.)

4. Output:

   • Digital signal (single-bus communication protocol).

5. Response Time:

   • Temperature: ≤1 second
   • Humidity: ≤5 seconds

6. Size:

   • Compact design for easy integration into systems.

Features:

• Factory-calibrated sensor ensures accuracy.
• Long-term stability and reliability.
• Low power consumption.
• Compatible with microcontrollers like Arduino, Raspberry Pi, and ESP series.
• Encased in a protective housing, making it more robust than DHT11 or DHT22.

Applications:

• Weather monitoring systems.
• Home automation (HVAC systems, humidifiers).
• Agricultural and industrial environmental monitoring.
• IoT devices.

Interfacing:

To interface the DHT21/AM2301 with microcontrollers:

1. Connect the VCC pin to a 3.3V or 5V power supply.
2. Connect the GND pin to ground.
3. Connect the Data pin to a digital I/O pin on the microcontroller. A 4.7k-10k ohm pull-up resistor is often required between the Data pin and VCC.

Example Libraries:-

• Arduino: Use libraries like DHT or Adafruit DHT Sensor Library.
• Python: For Raspberry Pi, libraries like Adafruit_DHT are commonly used.