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DHT11 sensor example

In this example we will show a basic example of connecting a DHT11 Temperature and Humidity Sensor to your Arduino. This is a very nice little, low cost sensor which requires only a pull up resistor to VDD. This can easily be constructed on a mini bread board and then joined up to your Arduino. using some connecting cables

The DHT sensors are made of two parts, a capacitive humidity sensor and a thermistor. There is a chip inside that does some a/d conversion and outputs a digital signal with the temperature and humidity.

I wont go into the technical details of the DHT11, there is a link at the bottom to a PDF datasheet which explains all you need to know.

Schematic

Arduino and DHT11 schematic

Arduino and DHT11 schematic

Connections

Here is the breadboard layout

Arduino and DHT11 breadboard

Arduino and DHT11 breadboard

Code

You will need the DHT11 library from the DHT library. You could roll your own code but this saves a whole lot of time.

Download, extract and copy this to your Arduino libraries folder location. This is a simple example which outputs the humidity and temperature, place your fingers on the DHT11 and you will see the readings fluctuate

#include <dht11.h>

dht11 DHT;
//Pin 4 of Arduino to Data of DHT11
#define DHT11_PIN 4

void setup()
{
Serial.begin(9600);
int check;
Serial.print(“DHT11 STATUS – \t”);
check = DHT.read(DHT11_PIN);
//check status
switch (check)
{
case DHTLIB_OK:
Serial.print(“OK\n”);
break;
case DHTLIB_ERROR_CHECKSUM:
Serial.print(“Checksum error\n”);
break;
case DHTLIB_ERROR_TIMEOUT:
Serial.print(“Timeout error\n”);
break;
default:
Serial.print(“Unknown error\n”);
break;
}
}

void loop()
{

//humidity and temperature output
Serial.print(“Humidity is “);
Serial.print(DHT.humidity,1);
Serial.print(“\n”);
Serial.println(“Temperature is “);
Serial.println(DHT.temperature,1);

delay(1000);
}

Output

Upload the sketch above and open the Serial Monitor window

arduino and dht11 serial output

arduino and dht11 serial output

 

Parts List

Label	Part Type
DHT1	DHT11 Humitidy and Temperature Sensor	
Part1	Arduino Uno (Rev3)
R1	4.7k Ω

 

Links

DHT11 Humidity and Temperature Sensor from Amazon UK

DHT11 Humidity and Temperature Sensor from Amazon US

DHT11 Datasheet in PDF format

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