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Introduction 

The DHT-11 is a digital-output relative humidity and temperature sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin.
In this tutorial you will learn how to use this sensor with Arduino uno. The room temperature & humidity will be printed to serial monitor.

About the  DHT-11 sensor

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 spits out a digital signal on the data pin (no analog input pins needed).
Connections are simple, the first pin on the left to 3-5V power, the second pin to your data input pin and the right most pin to ground.
Technical details:
  • Power: 3-5V
  • Max Current: 2.5mA
  • Humidity: 20-80%, 2-5% accuracy
  • Temperature: 0 to 50°C, ±2°C accuracy

What you will need - Hardware

For this tutorial you will need:

The Circuit

The connections are pretty easy, see the image above with breadboard circuit schematic.

The code

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/* How to use the DHT-11 sensor with Arduino uno
   Temperature and humidity sensor
   More info: http://www.ardumotive.com/how-to-use-dht-11-sensor-en.html
   Dev: Michalis Vasilakis // Date: 2/7/2015 // www.ardumotive.com */

//Libraries
#include <dht.h>
dht DHT;
//Constants
#define DHT11_PIN 2     // DHT 22  (AM2302) - what pin we're connected to

//Variables
float hum;  //Stores humidity value
float temp; //Stores temperature value

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

void loop()
{
    int chk = DHT.read11(DHT11_PIN);
    //Read data and store it to variables hum and temp
    hum = DHT.humidity;
    temp= DHT.temperature;
    //Print temp and humidity values to serial monitor
    Serial.print("Humidity: ");
    Serial.print(hum);
    Serial.print(" %, Temp: ");
    Serial.print(temp);
    Serial.println(" Celsius");
    delay(2000); //Delay 2 sec.
}
Download the code from here and open it with Arduino IDE. Inside you will also find and the DHT.h library.
dht11_tutorial.zip
File Size: 9 kb
File Type: zip
Download File
Open the serial monitor from tools menu of Arduino IDE.

​The result:

Well done!

You have successfully completed one more Arduino "How to" tutorial and you learned how to use the DHT-11 sensor.
I hope you liked this, let me know in the comments.

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