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

The DHT11 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air and outputs a digital signal on the data pin. It's simple to use and ideal for environmental sensing and data logging and perfect for a weather station or humidor control system.

• Home environment monitoring
• Weather stations
• Automotive climate control
• Humidifiers and dehumidifiers
• Medical and health applications

• Voltage: 3.3 to 5V power and I/O
• Current: 2.5mA max current use during conversion (while requesting data)
• Humidity: 20-80% with 5% accuracy
• Temperature: 0-50°C with ±2°C accuracy
• Sampling Rate: No more than 1 Hz sampling rate (once every second)

1. Powering the Sensor: Connect the VCC pin to a 3.3V or 5V power supply. The GND pin should be connected to the ground on your microcontroller board.

2. Data Connection: Connect the DATA pin to a digital I/O pin on your microcontroller.

3. Pull-up Resistor: A pull-up resistor (typically 4.7kΩ to 10kΩ) is required on the DATA pin to pull it up to the level of VCC.

• The DHT11 is relatively slow and you should wait at least 1 second between readings.
• Avoid placing the sensor in direct sunlight or near a heat source to get accurate readings.
• Ensure that the sensor is not exposed to condensation or water.

#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 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 affected by heat sources or direct sunlight.
• No Data: Check the wiring, especially the pull-up resistor on the DATA pin.
• Erratic Readings: Ensure there's a stable power supply and the sampling rate is not too high.

• Sensor Not Responding: Reset the power to the sensor and ensure the correct pin is used for data.
• Consistently High or Low Humidity Readings: Calibrate the sensor in an environment with a known humidity level.
• Long Cable Runs: Keep the cable between the sensor and microcontroller short to prevent signal degradation.

Q: Can the DHT11 sensor measure temperature below 0°C? A: No, the DHT11 is limited to a temperature range of 0 to 50°C.

Q: How long should I wait between readings? A: Wait at least 2 seconds between readings to ensure accurate measurements.

Q: Can I use the DHT11 sensor with a Raspberry Pi? A: Yes, the DHT11 can be used with a Raspberry Pi using a suitable library for interfacing.

Q: Is the DHT11 sensor waterproof? A: No, the DHT11 is not waterproof and should be protected from moisture and condensation.