In this project we will measure the temprature and humidity with the DHT 11 temperature and humidity sensor with an arduino and a 20×4 LCD display.
Some characteristics of this sensor are:
| 1 | Can detect the environmental humidity and temperature |
| 2 | Humidity measurement range: 20% 95% humidity |
| 3 | Humidity error +-5% |
| 4 | Temperature measurement range:0-50 °C |
| 5 | Temperature error ±2°C |
| 6 | Supply voltage 3.3-5 Volts |
| 7 | One wire digital output form |
| 8 | Fixed bolt hole for easy installation |
| 9 | 3.2×1.4 cm |
You can use this sensor to measure temperature and humidity in relative restricted environments because the temperature range is between 0 to 50 degrees. It is perfect for rooms, garages, storehouses etc where temperature do not go under zero.
Why we choose this sensor???? Because being calibrated and with only 2 degrees error it is perfect for cheap and pretty precise monitoring sistems.
A picture of this sensor is below:
For easy in installation we will use a library you can download from here. This zip library can be installed by selecting from arduino software sketch-include library-add zip library .
Now let’s see how to connect the sensor from arduino. As you can see in the image the shield sensor has 3 pins:
“+” connect to 5V from arduino
“-” connect to GND from arduino
“S”connect to any digital pin(we choose digital pin number 4).
Before to start the program with the LCD you can upload a example sketch that you installed with the library and you can find it in arduino software at Examples-DHTlib-dht11_test. It’s working with serial monitor.
To install the 20×4 LCD display see this tutorial.
The program with LCD is presented below or you can download from here:
#include <dht.h>
dht DHT;
#define DHT11_PIN 4 //digital pin 4 is the input pin for sensor
#include <Wire.h> // Comes with Arduino IDE
#include <LiquidCrystal_I2C.h>
// set the LCD address to 0x27 for a 20 chars 4 line display
// Set the pins on the I2C chip used for LCD connections:
// addr, en,rw,rs,d4,d5,d6,d7,bl,blpol
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); // Set the LCD I2C address
void setup()
{
Serial.begin(115200);
lcd.begin(20,4); // initialize the lcd for 20 chars 4 lines, turn on backlight
lcd.backlight(); // finish with backlight on
//first row and first column is indexed with 0
lcd.setCursor(0,0);//starting to display from character 0 line 0
lcd.print(“Temperature:”);
lcd.setCursor(6,1); //starting to display from character 6 line 1
lcd.print((char) 223); //ASCII code for degree
lcd.setCursor(7,1); //starting to display from character 7 line 1
lcd.print(“C”);
lcd.setCursor(0,2); //starting to display from character 0 line 2
lcd.print(“Humidity:”);
lcd.setCursor(6,3); //starting to display from character 6 line 3
lcd.print(“%”);
}
void loop()
{
updateDHT(); // call function updateDHT
}
void updateDHT() // the function that read the sensor and display data
{
int chk;
chk = DHT.read11(DHT11_PIN);// READ DATA
lcd.setCursor(2,1);
lcd.print(DHT.temperature,1);
lcd.setCursor(2,3);
lcd.print(DHT.humidity,1);
delay(1000);
}
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A small video with the sensor and the LCD display is:
