How to Use DHT11 Humitidy and Temperature Sensor: Examples, Pinouts, and Specs

The DHT11 is a widely used digital sensor that measures ambient temperature and humidity. It is known for its ease of use, affordability, and reasonable accuracy. The sensor is encapsulated in a small package with a single digital output, which makes it an excellent choice for hobbyists and makers for integrating into weather stations, HVAC systems, and home automation projects.

• Voltage: 3 to 5.5V supply voltage
• Current: 0.5-2.5mA (measuring), 100-150μA (standby)
• Temperature Range: 0 to 50°C
• Humidity Range: 20% to 90% RH
• Resolution:
  • Temperature: 1°C
  • Humidity: 1% RH
• Accuracy:
  • Temperature: ±2°C
  • Humidity: ±5% RH
• Sampling Rate: Not more than 1 Hz (once every second)

1. Connect the VCC pin to a 3-5.5V power supply.
2. Connect the GND pin to the ground of the power supply.
3. Connect the DATA pin to a digital input pin on a microcontroller, such as an Arduino UNO.

• Use a pull-up resistor (typically 4.7kΩ to 10kΩ) on the DATA pin.
• Avoid placing the sensor in direct sunlight or near heat sources to prevent inaccurate readings.
• Allow the sensor to acclimatize to the environment for accurate readings.
• Ensure the sensor is not exposed to condensing levels of humidity.

#include "DHT.h"

#define DHTPIN 2     // Digital pin connected to the DHT sensor
#define DHTTYPE DHT11 // DHT 11

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");
}

Note: The above code uses the DHT library, which can be installed via the Arduino Library Manager.

• Inaccurate Readings: Ensure the sensor is not exposed to direct sunlight or heat sources. Allow it to acclimatize to the environment.
• No Data: Check connections and ensure a pull-up resistor is in place. Also, verify that the correct pin is defined in the code.
• Sensor Heating Up: Ensure that the power supply voltage is within the specified range (3-5.5V).

Q: How often can I read data from the DHT11? A: The DHT11 should not be read more than once every second.

Q: Can the DHT11 sensor be used outdoors? A: Yes, but it should be protected from direct sunlight, rain, and condensation.

Q: Is calibration required for the DHT11 sensor? A: The DHT11 comes pre-calibrated from the factory and does not typically require additional calibration.

For further assistance, consult the datasheet of the DHT11 sensor or reach out to the community forums for support.