5.1 LCD Display Interface

5.1.1 What is an LCD?

LCD (Liquid Crystal Display) is an electronic display device used to show text, numbers, symbols, and other information generated by a microcontroller.

LCDs are widely used in Arduino projects because they are:

• Easy to use
• Low-cost
• Easy to read
• Available in different sizes
• Suitable for displaying sensor values and messages

A common Arduino LCD is the 16×2 LCD, which can display 16 characters on each of 2 rows.

5.1.2 Common LCD Types

1. 16×2 LCD

It has:

• 16 columns
• 2 rows
• 32 character positions in total

2. 20×4 LCD

It has:

• 20 columns
• 4 rows
• 80 character positions

3. I2C LCD

An I2C LCD uses an I2C interface module attached to the back of the LCD. It significantly reduces the number of Arduino pins required.

Instead of many parallel connections, an I2C LCD normally uses:

I2C Pin	Function
VCC	Power supply
GND	Ground
SDA	Serial Data
SCL	Serial Clock

7.1.3 Basic LCD Pins

A standard 16×2 parallel LCD commonly has 16 pins.

Important pins include:

Pin	Name	Function
1	VSS	Ground
2	VDD	Power supply
3	V0	Contrast adjustment
4	RS	Register Select
5	RW	Read/Write
6	E	Enable
7–14	D0–D7	Data pins
15	A	Backlight
16	K	Backlight ground

5.1.4 How an LCD Works with Arduino

The Arduino sends information to the LCD through its interface pins.

For example:

Sensor → Arduino → LCD → User

If a temperature sensor measures 25°C, the Arduino can process the value and send:

Temperature: 25 C

to the LCD.

5.1.5 Simple Arduino LCD Program

For an I2C LCD:

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

 

LiquidCrystal_I2C lcd(0x27, 16, 2);

 

void setup() {

  lcd.init();

  lcd.backlight();

 

  lcd.setCursor(0, 0);

  lcd.print(“Hello Student”);

 

  lcd.setCursor(0, 1);

  lcd.print(“Arduino LCD”);

}

 

void loop() {

}

5.1.6 Important LCD Functions

Function	Purpose
lcd.init()	Initializes the LCD
lcd.backlight()	Turns on the backlight
lcd.print()	Displays text or numbers
lcd.setCursor()	Sets the position of the cursor
lcd.clear()	Clears the display
lcd.home()	Moves cursor to the beginning

5.1.7 Applications of LCD

LCDs are used in:

• Digital thermometers
• Electronic weighing machines
• Security systems
• Industrial control systems
• Arduino projects
• Digital clocks
• Vending machines
• Medical equipment
• IoT monitoring systems

Advantages of LCD

• Low cost
• Easy to program
• Low power consumption
• Good readability
• Available in many sizes
• Suitable for text and numerical information

Disadvantages of LCD

• Some types require many connection wires
• Limited graphics capability
• Viewing angle can be limited
• Backlight consumes additional power