Humidity and Temperature Measurement using Arduino
![Humidity and Temperature Measurement using Arduino Arduino Uno Humidity Sensor Project](http://circuitdigest.com/sites/default/files/projectimage_mic/Arduino-Humidity-Measuremen.jpg)
Humidity
and temperature are common parameters to measure environmental
conditions. In this Arduino based project we are going to measure
ambient temperature and humidity and display it on a 16x2 LCD screen. A
combined temperature and himidity sensor DHT11 is used with Arduino uno
to develop this Celsius scale thermometer and percentage scale humidity
measurement project. In one of my previous project, I have also
developed a digital thermometer using temperature sensor LM35.
This project consists of three sections - one senses the humidity and temperature by using humidity and temperature sensor DHT11.
The second section reads the DHTsensor module’s output and extracts
temperature and humidity values into a suitable number in percentage and
Celsius scale. And the third part of the system displays humidity and
temperature on LCD.
Working of this project is based on single wire
serial communication. First arduino send a start signal to DHT module
and then DHT gives a response signal containing temperature and humidity
data. Arduino collect and extract in two parts one is humidity and
second is temperature and then send them to 16x2 LCD.
Here in this project we have used a sensor module namely DHT11.
This module features a humidity and temperature complex with a
calibrated digital signal output means DHT11 sensor module is a combined
module for sensing humidity and temperature which gives a calibrated
digital output signal. DHT11 gives us very precise value of humidity and
temperature and ensures high reliability and long term stability. This
sensor has a resistive type humidity measurement component and NTC type
temperature measurement component with an 8-bit microcontroller inbuilt
which has a fast response and cost effective and available in 4-pin
single row package.
![DHT11 sensor](http://circuitdigest.com/sites/default/files/inlineimages/DHT11-Sensor.jpg)
DHT11 module works on serial communication i.e.
single wire communication. This module sends data in form of pulse train
of specific time period. Before sending data to arduino it needs some
initialize command with a time delay. And the whole process time is
about 4ms. A complete data transmission is of 40-bit and data format of
this process is given below:
8-bit integral RH data + 8-bit decimal RH data + 8-bit integral T data + 8-bit decimal T data + 8-bit check sum.
Complete Process
First of all arduino sends a high to low start
signal to DHT11 with 18µs delay to ensure DHT’s detection. And then
arduino pull-up the data line and wait for 20-40µs for DHT’s response.
Once DHT detects starts signal, it will send a low voltage level
response signal to arduino of time delay about 80µs. And then DHT
controller pull up the data line and keeps it for 80µs for DHT’s
arranging of sending data.
When data bus is at low voltage level it means
that DHT11 is sending response signal. Once it is done, DHT again makes
data line pull-up for 80µs for preparing data transmission.
Data format that is sending by DHT to arduino for
every bit begins with 50µs low voltage level and length of high voltage
level signal determines whether data bit is “0” or “1”.
One important thing is to make sure pull up
resistor value because if we are placing DHT sensor at <20 meter
distance, 5k pull up resistor is recommended. If placing DHT at longer
the 20 meter then use appropriate value pull up resistor.
Circuit Diagram and Explanation
![Arduino Humidity Sensor Circuit Diagram Arduino Humidity Sensor Circuit Diagram](http://circuitdigest.com/sites/default/files/circuitdiagram_mic/Arduino-Humidity-Circuit.gif)
A liquid crystal display is used for displaying
temperature and humidity which is directly connected to arduino in 4-bit
mode. Pins of LCD namely RS, EN, D4, D5, D6 and D7 are connected to
arduino digital pin number 2, 3, 4, 5, 6 and 7. And a DHT11 sensor
module is also connected to digital pin 12 of arduino with a 5k pull-up
resistor.
Programming Description
In programming, we are going to use pre-built libraries for DHT11 sensor and LCD display module.
Then we haved defined pins for LCD and DHT sensor
and initialized all the things in setup. Then in a loop by using dht
function reads DHT sensor and then using some dht functions we extract
humidity and temperature and display them on LCD.
Here degree symbol is created by using custom character method.
Code:
#include<dht.h> // Including library for dht
#include<LiquidCrystal.h>
LiquidCrystal lcd(2, 3, 4, 5, 6, 7);
#define dht_dpin 12
dht DHT;
byte degree[8] =
{
0b00011,
0b00011,
0b00000,
0b00000,
0b00000,
0b00000,
0b00000,
0b00000
};
void setup()
{
lcd.begin(16, 2);
lcd.createChar(1, degree);
lcd.clear();
lcd.print(" Humidity ");
lcd.setCursor(0,1);
lcd.print(" Measurement ");
delay(2000);
lcd.clear();
lcd.print("Circuit Digest ");
delay(2000);
}
void loop()
{
DHT.read11(dht_dpin);
lcd.setCursor(0,0);
lcd.print("Humidity: ");
lcd.print(DHT.humidity); // printing Humidity on LCD
lcd.print(" %");
lcd.setCursor(0,1);
lcd.print("Temperature:");
lcd.print(DHT.temperature); // Printing temperature on LCD
lcd.write(1);
lcd.print("C");
delay(500);
}
#include<LiquidCrystal.h>
LiquidCrystal lcd(2, 3, 4, 5, 6, 7);
#define dht_dpin 12
dht DHT;
byte degree[8] =
{
0b00011,
0b00011,
0b00000,
0b00000,
0b00000,
0b00000,
0b00000,
0b00000
};
void setup()
{
lcd.begin(16, 2);
lcd.createChar(1, degree);
lcd.clear();
lcd.print(" Humidity ");
lcd.setCursor(0,1);
lcd.print(" Measurement ");
delay(2000);
lcd.clear();
lcd.print("Circuit Digest ");
delay(2000);
}
void loop()
{
DHT.read11(dht_dpin);
lcd.setCursor(0,0);
lcd.print("Humidity: ");
lcd.print(DHT.humidity); // printing Humidity on LCD
lcd.print(" %");
lcd.setCursor(0,1);
lcd.print("Temperature:");
lcd.print(DHT.temperature); // Printing temperature on LCD
lcd.write(1);
lcd.print("C");
delay(500);
}
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