How to Use DHT 11 : Examples, Pinouts, and Specs

The DHT11 is a widely used digital temperature and humidity sensor that offers a simple interface and easy integration into various electronic projects, including DIY projects and home automation systems. It measures the surrounding air and provides a digital signal with the temperature and humidity readings. Its cost-effectiveness and simplicity make it an ideal choice for hobbyists and educators who are introducing concepts of environmental sensing.

• Home weather stations
• Environmental monitoring
• HVAC systems
• Incubators
• Consumer electronics

• Supply Voltage: 3.5 to 5.5 V DC
• Output Signal: Digital signal via a single data pin
• Humidity Measurement Range: 20 to 80% RH
• Humidity Accuracy: ±5% RH
• Temperature Measurement Range: 0 to 50°C
• Temperature Accuracy: ±2°C
• Resolution: 1% RH for humidity, 1°C for temperature
• Sampling Rate: No more than 1 Hz (once every second)

1. Connect the VCC pin to a 3.5-5.5 V 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 your microcontroller, such as an Arduino UNO.

• Ensure that the power supply is stable and within the specified voltage range.
• Place the sensor in an environment with good air circulation to get accurate readings.
• Avoid placing the sensor near heat sources or in direct sunlight.
• Allow the sensor to acclimatize to the environment for accurate readings.
• Use a pull-up resistor (typically 4.7kΩ to 10kΩ) on the DATA pin when connecting to a microcontroller.

#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();
  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 heat_index = dht.computeHeatIndex(temperature, humidity, false);

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

• Inaccurate Readings: Ensure the sensor is not placed near heat sources or in direct sunlight. Allow it to acclimatize to the environment.
• No Data: Check the wiring, especially the DATA pin connection. Ensure the pull-up resistor is in place.
• Erratic Readings: Ensure the power supply is stable and within the recommended voltage range.

• Sensor Not Responding: Reset the power to the sensor and check the connections.
• Consistently High or Low Readings: Calibrate the sensor in a known environment or compare it with another sensor.
• Intermittent Readings: Reduce the length of the wires if possible, and ensure there is no electromagnetic interference.

Q: How long does the DHT11 need to acclimatize to the environment? A: It is recommended to let the DHT11 sensor sit in the new environment for at least an hour before taking readings.

Q: Can the DHT11 sensor be used outdoors? A: The DHT11 is not waterproof and is designed for indoor use. If used outdoors, it should be placed in a protective enclosure.

Q: How often can I read data from the DHT11? A: The DHT11 should not be read more than once every second. Reading it more frequently may lead to self-heating and inaccurate readings.