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
Connections
Here is the breadboard layout
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
[c]
#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);
}
[/c]
Output
Upload the sketch above and open the Serial Monitor window
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
