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

The DHT11 is a digital sensor designed to measure both humidity and temperature, making it an essential component for environmental monitoring and control applications. It provides accurate and reliable readings, making it suitable for a wide range of projects, including weather stations, HVAC systems, and IoT-based environmental monitoring.

The DHT11 is compact, easy to use, and communicates via a single-wire digital interface, making it ideal for integration with microcontrollers like Arduino, Raspberry Pi, and other development boards.

• Humidity Range: 20% to 90% RH (Relative Humidity)
• Humidity Accuracy: ±5% RH
• Temperature Range: 0°C to 50°C
• Temperature Accuracy: ±2°C
• Operating Voltage: 3.3V to 5.5V
• Max Current Consumption: 2.5mA
• Communication Protocol: Single-wire digital signal
• Sampling Period: 1 second (minimum interval between readings)

The DHT11 sensor typically has 3 or 4 pins, depending on the module version. Below is the pinout for the 4-pin version:

Note: For 3-pin modules, the NC pin is omitted, and the pinout is VCC, DATA, and GND.

1. Connect the Pins:

   • Connect the VCC pin to the 5V or 3.3V power supply of your microcontroller.
   • Connect the GND pin to the ground of your microcontroller.
   • Connect the DATA pin to a digital input pin on your microcontroller. Use a 10kΩ pull-up resistor between the DATA pin and VCC to ensure stable communication.

2. Install Required Libraries:

   • If using an Arduino, install the "DHT sensor library" by Adafruit from the Arduino Library Manager.

3. Write the Code:

   • Use the library functions to initialize the sensor and read temperature and humidity values.

// Include the DHT library
#include <DHT.h>

// Define the pin where the DHT11 is connected
#define DHTPIN 2  // Connect DATA pin to digital pin 2

// Define the type of DHT sensor
#define DHTTYPE DHT11  // Specify the sensor model (DHT11)

// Initialize the DHT sensor
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);  // Start serial communication at 9600 baud
  dht.begin();         // Initialize the DHT sensor
  Serial.println("DHT11 Sensor Initialized");
}

void loop() {
  delay(2000);  // Wait 2 seconds between readings

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

  // Check if the readings are valid
  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Print the readings to the Serial Monitor
  Serial.print("Humidity: ");
  Serial.print(humidity);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");
}

• Sampling Interval: The DHT11 requires at least 1 second between readings. Avoid polling the sensor too frequently.
• Environmental Factors: Place the sensor in a location free from direct sunlight, condensation, or strong airflow for accurate readings.
• Pull-Up Resistor: Always use a pull-up resistor (typically 10kΩ) on the DATA line to ensure stable communication.
• Cable Length: Keep the cable length between the sensor and microcontroller as short as possible to avoid signal degradation.

1. No Data or Incorrect Readings:

   • Ensure the sensor is connected correctly (check VCC, GND, and DATA connections).
   • Verify that the pull-up resistor is in place on the DATA line.
   • Check the power supply voltage (must be between 3.3V and 5.5V).

2. "Failed to Read from DHT Sensor" Error:

   • Ensure the correct pin number and sensor type (DHT11) are defined in the code.
   • Verify that the sensor is not being polled more frequently than once per second.

3. Inconsistent or Fluctuating Readings:

   • Ensure the sensor is placed in a stable environment without rapid temperature or humidity changes.
   • Check for loose or poor-quality connections.

Q1: Can I use the DHT11 with a 3.3V microcontroller?
Yes, the DHT11 operates within a voltage range of 3.3V to 5.5V, making it compatible with 3.3V systems.

Q2: What is the maximum cable length for the DHT11?
The recommended maximum cable length is 20 meters. However, for longer distances, use a lower pull-up resistor value (e.g., 4.7kΩ) to maintain signal integrity.

Q3: How does the DHT11 compare to the DHT22?
The DHT22 offers a wider range and better accuracy for both temperature and humidity but is more expensive. The DHT11 is sufficient for basic applications.

Q4: Can I use multiple DHT11 sensors in one project?
Yes, you can connect multiple DHT11 sensors to different digital pins on your microcontroller. Each sensor will require its own pull-up resistor.

By following this documentation, you can effectively integrate the DHT11 sensor into your projects for reliable humidity and temperature measurements.