DHT21 AM2301 Digital Temperature Humidity Sensor Module

The DHT21 (also known as AM2301) is a digital temperature and humidity sensor. It is widely used in various applications due to its reliability and ease of use. Here is a detailed overview of the DHT21 (AM2301) sensor:

General Information:

The DHT21 is a sensor that measures both temperature and humidity and provides digital output. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air and spits out a digital signal on the data pin.

Features:

1. Temperature Range: -40 to +80°C with an accuracy of ±0.5°C.
2. Humidity Range: 0 to 100% RH with an accuracy of ±3% RH.
3. Resolution: 0.1 for both temperature and humidity.
4. Power Supply: 3.3V to 5.5V.
5. Low Power Consumption: Ideal for battery-powered applications.
6. Digital Output: Single-bus communication protocol.
7. Response Time: Relatively fast response time, typically less than 2 seconds.

Pin Configuration:

The DHT21 sensor typically has three pins:

• VCC: Power supply (3.3V to 5.5V).
• GND: Ground.
• DATA: Data pin for digital signal output.

Applications:

• Weather Stations: For measuring ambient temperature and humidity.
• HVAC Systems: For monitoring and controlling heating, ventilation, and air conditioning systems.
• Home Automation: For environmental monitoring.
• Agriculture: To monitor greenhouse conditions.
• Industrial Applications: For monitoring environmental conditions in factories and warehouses.

Wiring:

To connect the DHT21 to an Arduino:

1. Connect the VCC pin of the DHT21 to the 5V pin of the Arduino.
2. Connect the GND pin of the DHT21 to the GND pin of the Arduino.
3. Connect the DATA pin of the DHT21 to a digital pin (e.g., pin 2) on the Arduino.
4. A pull-up resistor (4.7kΩ to 10kΩ) is required between the VCC and DATA pins.

Example Code:

To use the DHT21 with an Arduino, you can use the DHT library. First, install the DHT library by Adafruit through the Library Manager in the Arduino IDE.

cpp

#include "DHT.h"

// Define the type of sensor and the pin it's connected to
#define DHTTYPE DHT21   // DHT 21 (AM2301)
#define DHTPIN 2        // Digital pin 2

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println("DHT21 (AM2301) test!");

  dht.begin();
}

void loop() {
  // Wait a few seconds between measurements
  delay(2000);

  // Reading temperature and humidity values
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  // Check if any reads failed and exit early (to try again).
  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Print the results
  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" *C");
}

Calibration and Usage Tips:

1. Ensure the sensor is placed in an area with good airflow for accurate readings.
2. Avoid placing the sensor in direct sunlight or near heat sources to prevent false readings.
3. Periodically check and recalibrate the sensor if used in critical applications.

The DHT21 (AM2301) is a versatile and reliable sensor suitable for a wide range of applications requiring accurate temperature and humidity measurements.