DHT21 AM2301 Digital Temperature Humidity Sensor Module

The DHT21, also known as AM2301, is a trusted digital sensor for measuring temperature and humidity. Its user-friendly nature and reliability make it a popular choice across various applications.

General Overview

The DHT21 (AM2301) is a dual-purpose sensor that provides digital readings of both temperature and humidity. It employs a capacitive humidity sensor and a thermistor to gauge the ambient air, outputting a digital signal on the data pin.

Key Features

• Temperature Range: -40 to +80°C (accuracy of ±0.5°C)
• Humidity Range: 0 to 100% RH (accuracy of ±3% RH)
• Resolution: 0.1 for both temperature and humidity
• Power Supply: 3.3V to 5.5V
• Low Power Consumption: Suitable for battery-operated applications
• Digital Output: Utilizes a single-bus communication protocol
• Response Time: Typically less than 2 seconds

Pin Configuration

The DHT21 sensor usually comes with three pins:

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

Applications

• Weather Stations: For ambient temperature and humidity measurements
• HVAC Systems: For regulating heating, ventilation, and air conditioning systems
• Home Automation: For environmental monitoring
• Agriculture: For greenhouse conditions monitoring
• Industrial Applications: For tracking environmental conditions in factories and warehouses

Wiring Instructions

Here's how to connect the DHT21 to an Arduino:

• Link the VCC pin of the DHT21 to the 5V pin of the Arduino
• Link the GND pin of the DHT21 to the GND pin of the Arduino
• Link the DATA pin of the DHT21 to a digital pin (for instance, pin 2) on the Arduino
• A pull-up resistor (4.7kΩ to 10kΩ) is necessary between the VCC and DATA pins

Example Code

To operate the DHT21 with an Arduino, the DHT library by Adafruit can be installed via the Library Manager in the Arduino IDE.

#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 2DHT 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(" %	");
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" *C");
}

Calibration and Usage Tips

• Ensure the sensor is located in an area with adequate airflow for precise readings
• Avoid positioning the sensor in direct sunlight or near heat sources to prevent inaccurate readings
• Regularly verify and recalibrate the sensor if used in critical applications

The DHT21 (AM2301) is a versatile and dependable sensor that is well-suited for a broad range of applications requiring precise temperature and humidity measurements.