How to Use DHT22 (Wokwi Compatible): Examples, Pinouts, and Specs

The DHT22 is a reliable sensor for measuring temperature and humidity. It is a digital sensor that provides high accuracy and long-term stability, making it suitable for a wide range of applications, including weather stations, home automation systems, and environmental monitoring.

• Home and building automation for climate control
• Weather monitoring stations
• Environmental data logging
• Agricultural and soil monitoring
• HVAC systems

• Humidity Measurement Range: 0-100% RH
• Humidity Measurement Accuracy: ±2% RH
• Temperature Measurement Range: -40 to 80°C
• Temperature Measurement Accuracy: ±0.5°C
• Operating Voltage: 3.3 to 6V DC
• Max Current: 2.5mA during conversion (while requesting data)
• Sampling Rate: ≤ 0.5 Hz (once every 2 seconds)
• Interface: Digital, Single-bus

1. Powering the Sensor: Connect the VDD pin to a 3.3V or 5V power supply, and the GND pin to the ground.
2. Data Pin Connection: Connect the DATA pin to a digital input pin on your microcontroller.
3. Pull-up Resistor: A pull-up resistor (typically 10kΩ) is required between the DATA pin and VDD for reliable communication.
4. Reading Data: Initiate a data reading request from your microcontroller and wait for the DHT22 to send back the temperature and humidity data.

• Avoid placing the sensor in direct sunlight or near heat sources to prevent inaccurate readings.
• Ensure the sensor is not exposed to condensing humidity conditions.
• Allow the sensor to acclimate to the environment for accurate readings.
• Use a decoupling capacitor close to the sensor's power supply pins to stabilize voltage.

#include "DHT.h"

#define DHTPIN 2     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT22 // DHT 22 (AM2302)

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  dht.begin();
}

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

  // Reading temperature or humidity takes about 250 milliseconds!
  float humidity = dht.readHumidity();
  // Read temperature as Celsius (the default)
  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;
  }

  // Compute heat index in Celsius (isFahrenheit = false)
  float heatIndex = dht.computeHeatIndex(temperature, humidity, false);

  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.print("%  Temperature: ");
  Serial.print(temperature);
  Serial.print("°C  Heat index: ");
  Serial.print(heatIndex);
  Serial.println("°C");
}

• Inaccurate Readings: Ensure the sensor is not in an environment with rapid temperature changes and is not affected by heat sources.
• No Data: Check the wiring, especially the pull-up resistor on the data line. Ensure the power supply is stable.
• Erratic Data: Make sure there is a decoupling capacitor to filter out noise on the power supply line.

• Sensor Not Responding: Reset the power to the sensor and ensure the microcontroller pin is correctly configured.
• Long Cable Runs: Use shielded cable for long runs to prevent signal degradation.
• Intermittent Communication: Verify that the timing of the data request is in accordance with the sensor's sampling rate.

Q: Can the DHT22 be used outdoors? A: Yes, but it should be protected from direct sunlight and water.

Q: How long does the DHT22 last? A: With proper care, the DHT22 can last for several years, although the accuracy may degrade over time.

Q: Is calibration required for the DHT22? A: The DHT22 comes pre-calibrated from the factory. However, for critical applications, periodic recalibration may be necessary.

Q: Can I use multiple DHT22 sensors on the same microcontroller? A: Yes, each DHT22 sensor can be connected to a separate digital pin on the microcontroller. Ensure each data line has its own pull-up resistor.