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Introduction:

LCD (Liquid Crystal Display) is nowadays embedded with many of the electronic gadgets like TV, Phone, Computer, Laptops, Watches etc. The display that we see is a liquid crystal sandwiched between two polarized glasses. It has both the properties of solid and liquid and both of them try to maintain their states regardless of one another. The LCD does not produce any illumination but it is entirely dependent on the illumination falling on it from the outside source.

The main principle behind liquid crystal molecules is that when an electric current is applied to them, they tend to untwist. This cause a change in the light angle passing through them. Due to this there is a change in the angle of the top polarizing filter with respect to it. So little light is allowed to pass through that particular area of LCD. Thus that area becomes darker comparing to others.

If the polarized glasses are both transparent then it is known as Transmittive type cell and when one glass is transparent and the other has a reflective coating then it is called Reflective type cell.

Usage:

We can see the usage of LCD everywhere nowadays. TV, Laptops, Computer, Watches, Phone. LCD have become soul of most of the electronic gadgets as of now.

Application:

http://invent.module143.com/earthquake-detector-using-arduino/

Project for Reference:

Code:

File -> Examples -> LCD -> Hello World.

/*
  LiquidCrystal Library - Hello World

 Demonstrates the use a 16x2 LCD display.  The LiquidCrystal
 library works with all LCD displays that are compatible with the
 Hitachi HD44780 driver. There are many of them out there, and you
 can usually tell them by the 16-pin interface.

 This sketch prints "Hello World!" to the LCD
 and shows the time.

  The circuit:
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)

 Library originally added 18 Apr 2008
 by David A. Mellis
 library modified 5 Jul 2009
 by Limor Fried (http://www.ladyada.net)
 example added 9 Jul 2009
 by Tom Igoe
 modified 22 Nov 2010
 by Tom Igoe
 modified 7 Nov 2016
 by Arturo Guadalupi

 This example code is in the public domain.

 http://www.arduino.cc/en/Tutorial/LiquidCrystalHelloWorld

*/

// include the library code:
#include <LiquidCrystal.h>

// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("hello, world!");
}

void loop() {
  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(millis() / 1000);
}