LCD 20×4 Arduino: Larger Display Projects

The LCD 20×4 Arduino combination provides 80 characters of display space, more than double what a standard 16×2 offers. When your project needs to show multiple sensor readings, navigation menus, or detailed status information, this larger format becomes essential.

I’ve built dozens of projects using 20×4 displays, from environmental monitoring stations to CNC controller interfaces. This guide covers everything from basic wiring to advanced menu systems and multi-display configurations.

Why Choose a 20×4 LCD Over 16×2

The 20×4 format excels in applications where information density matters.

Display Capacity Comparison

Feature	16×2 LCD	20×4 LCD
Total Characters	32	80
Lines	2	4
Characters per Line	16	20
Typical Use	Simple readings	Complex interfaces

Four lines allow you to display labels and values together without cramming everything onto two rows. Twenty characters per line accommodate longer descriptions without truncation.

LCD 20×4 Technical Specifications

The 20×4 LCD uses the same HD44780 controller as smaller displays, making the programming identical.

Standard Specifications

Parameter	Value
Operating Voltage	5V DC
Backlight Voltage	5V DC
Controller	HD44780 or compatible
Character Matrix	5×8 dots
Interface Options	4-bit, 8-bit parallel, or I2C
Operating Temperature	-20°C to 70°C
Viewing Area	77 x 25.2 mm
Module Dimensions	98 x 60 x 13.6 mm

The larger physical size requires more mounting space but provides significantly better readability from a distance.

Understanding 20×4 LCD Memory Mapping

The HD44780 controller contains 80 bytes of DDRAM organized in a way that seems counterintuitive at first.

DDRAM Row Addresses

Row	Starting Address	Ending Address
Row 0	0x00	0x13
Row 1	0x40	0x53
Row 2	0x14	0x27
Row 3	0x54	0x67

Notice that rows 0 and 2 are consecutive in memory, as are rows 1 and 3. If you write more than 20 characters starting at row 0, text continues on row 2, not row 1. The LiquidCrystal library handles this automatically when you use setCursor(), but understanding the underlying mapping helps when troubleshooting.

I2C LCD 20×4 Arduino Wiring

The I2C interface reduces wiring to just four connections, making it the preferred method for most Arduino projects.

I2C Connection Table

I2C Module Pin	Arduino Uno	Arduino Mega	Arduino Nano
GND	GND	GND	GND
VCC	5V	5V	5V
SDA	A4	20	A4
SCL	A5	21	A5

The PCF8574 I/O expander on the I2C backpack converts serial data to the parallel signals the LCD needs. A small potentiometer on the module adjusts contrast.

Finding Your I2C Address

Most modules ship with address 0x27 or 0x3F. Run this scanner if you’re unsure:

#include <Wire.h>

void setup() {

  Wire.begin();

  Serial.begin(9600);

  for (byte address = 1; address < 127; address++) {

    Wire.beginTransmission(address);

    if (Wire.endTransmission() == 0) {

      Serial.print(“Found device at 0x”);

      Serial.println(address, HEX);

    }

  }

}

void loop() {}

Basic LCD 20×4 Arduino Code

Install the LiquidCrystal_I2C library through the Arduino IDE Library Manager, then use this starter code:

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);

void setup() {

  lcd.init();

  lcd.backlight();

  lcd.setCursor(0, 0);

  lcd.print(“Line 1: Row 0”);

  lcd.setCursor(0, 1);

  lcd.print(“Line 2: Row 1”);

  lcd.setCursor(0, 2);

  lcd.print(“Line 3: Row 2”);

  lcd.setCursor(0, 3);

  lcd.print(“Line 4: Row 3”);

}

void loop() {}

The init() function replaces begin() used with the standard LiquidCrystal library. Always call backlight() to illuminate the display.

Displaying Multiple Sensor Readings

The 20×4 format handles multiple data points elegantly:

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);

void setup() {

  lcd.init();

  lcd.backlight();

}

void loop() {

  float temp = 23.5;

  float humidity = 65.2;

  float pressure = 1013.25;

  int lightLevel = 780;

  lcd.setCursor(0, 0);

  lcd.print(“Temp:     “);

  lcd.print(temp, 1);

  lcd.print(” C”);

  lcd.setCursor(0, 1);

  lcd.print(“Humidity: “);

  lcd.print(humidity, 1);

  lcd.print(” %”);

  lcd.setCursor(0, 2);

  lcd.print(“Pressure: “);

  lcd.print(pressure, 0);

  lcd.print(” hPa”);

  lcd.setCursor(0, 3);

  lcd.print(“Light:    “);

  lcd.print(lightLevel);

  lcd.print(” lux”);

  delay(1000);

}

Aligning values to the same column position improves readability.

Building Menu Systems with 20×4 LCD

Four lines make menu navigation practical without scrolling:

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);

const char* menuItems[] = {

  “Set Temperature”,

  “Set Humidity Alarm”,

  “Calibrate Sensors”,

  “System Settings”

};

int menuIndex = 0;

const int menuSize = 4;

void setup() {

  lcd.init();

  lcd.backlight();

  displayMenu();

}

void displayMenu() {

  lcd.clear();

  for (int i = 0; i < 4; i++) {

    lcd.setCursor(0, i);

    if (i == menuIndex) {

      lcd.print(“>”);

    } else {

      lcd.print(” “);

    }

    lcd.print(menuItems[i]);

  }

}

void loop() {

  // Add button handling to change menuIndex

  // Call displayMenu() when selection changes

}

The cursor indicator clearly shows the current selection while all options remain visible.

Custom Characters for Data Visualization

Create visual indicators using the 8 available custom character slots:

byte thermometer[8] = {

  0b00100, 0b01010, 0b01010, 0b01010,

  0b01110, 0b11111, 0b11111, 0b01110

};

byte droplet[8] = {

  0b00100, 0b00100, 0b01010, 0b01010,

  0b10001, 0b10001, 0b10001, 0b01110

};

void setup() {

  lcd.init();

  lcd.backlight();

  lcd.createChar(0, thermometer);

  lcd.createChar(1, droplet);

  lcd.setCursor(0, 0);

  lcd.write(byte(0));

  lcd.print(” Temperature: 25C”);

  lcd.setCursor(0, 1);

  lcd.write(byte(1));

  lcd.print(” Humidity: 60%”);

}

Custom icons provide instant visual recognition of different measurement types.

Progress Bar Implementation

The extra width accommodates meaningful progress indicators:

byte fullBlock[8] = {

  0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F

};

void drawProgressBar(int row, int percent) {

  int fillWidth = map(percent, 0, 100, 0, 16);

  lcd.setCursor(0, row);

  lcd.print(“[“);

  for (int i = 0; i < 16; i++) {

    if (i < fillWidth) {

      lcd.write(byte(0));

    } else {

      lcd.print(” “);

    }

  }

  lcd.print(“]”);

  lcd.print(percent);

  lcd.print(“%”);

}

A 16-character progress bar leaves room for the percentage value on the same line.

Connecting Multiple 20×4 LCDs

Projects needing more than 80 characters can use multiple displays on the same I2C bus.

I2C Address Configuration

The PCF8574 module has solder pads (A0, A1, A2) to change addresses:

A0	A1	A2	PCF8574 Address
Open	Open	Open	0x27
Closed	Open	Open	0x26
Open	Closed	Open	0x25
Closed	Closed	Open	0x24

LiquidCrystal_I2C lcd1(0x27, 20, 4);

LiquidCrystal_I2C lcd2(0x26, 20, 4);

void setup() {

  lcd1.init();

  lcd2.init();

  lcd1.backlight();

  lcd2.backlight();

  lcd1.print(“Display 1”);

  lcd2.print(“Display 2”);

}

Power Considerations

The 20×4 LCD draws more current than smaller displays due to the larger backlight area.

Typical Current Consumption

Component	Current Draw
LCD Logic	1-2 mA
LED Backlight	40-150 mA
Total (typical)	50-160 mA

For battery-powered projects, control the backlight programmatically:

lcd.noBacklight();  // Turn off backlight

delay(5000);

lcd.backlight();    // Turn on backlight

Some Arduino boards struggle to supply enough current through USB. Use an external 5V supply for the LCD if you experience dimming or erratic behavior.

Troubleshooting LCD 20×4 Arduino Issues

Common Problems and Solutions

Symptom	Likely Cause	Solution
Blank display, backlight on	Wrong I2C address	Run I2C scanner
Two rows of blocks	No initialization	Verify code uploaded
Garbled characters	Incorrect library	Use LiquidCrystal_I2C
Dim display	Insufficient power	Add external 5V supply
Text on wrong lines	Memory mapping confusion	Use setCursor() correctly
Flickering	Loose connections	Check wiring and solder joints

Contrast Adjustment

If characters are invisible or display appears all black, adjust the blue potentiometer on the I2C backpack. Turn slowly while watching the display until characters become clearly visible.

Practical Project Applications

The LCD 20×4 Arduino combination suits projects requiring detailed information display. Weather stations benefit from showing temperature, humidity, pressure, and forecast simultaneously. Home automation controllers can display room status, setpoints, and schedules without page scrolling.

Data loggers show current values alongside min/max readings and timestamps. CNC and 3D printer controllers display coordinates, speeds, and job progress on dedicated lines. Aquarium controllers monitor pH, temperature, and feeding schedules with room for alerts.

Parallel Wiring Alternative

When I2C isn’t suitable, direct parallel wiring provides faster updates at the cost of more pins.

4-Bit Parallel Connection Table

LCD Pin	Name	Arduino Pin
1	VSS	GND
2	VDD	5V
3	VO	Potentiometer wiper
4	RS	Digital 12
5	RW	GND
6	E	Digital 11
11	D4	Digital 5
12	D5	Digital 4
13	D6	Digital 3
14	D7	Digital 2
15	A	5V (through 220Ω)
16	K	GND

Use the standard LiquidCrystal library for parallel connections:

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {

  lcd.begin(20, 4);

  lcd.print(“Parallel Mode”);

}

Optimizing Display Updates

Avoid calling lcd.clear() repeatedly as it causes visible flicker. Instead, overwrite specific positions:

void updateValue(int row, int col, int value) {

  lcd.setCursor(col, row);

  lcd.print(value);

  lcd.print(”    “);  // Clear trailing characters

}

For static labels, print them once in setup() and only update the changing values in loop().

Memory-Efficient String Handling

Use the F() macro to store static strings in program memory:

lcd.print(F(“Temperature: “));  // Stored in flash

This preserves SRAM for variables, especially important on memory-limited boards like the Arduino Uno.

Useful Resources

Resource	Description
LiquidCrystal_I2C Library	Arduino I2C LCD library
HD44780 Datasheet	Controller specifications
Custom Character Generator	Visual pixel editor
LCD Memory Mapping Reference	DDRAM address documentation

Frequently Asked Questions

Can I use the same code for 16×2 and 20×4 LCDs?

Yes, just change the initialization parameters. Replace LiquidCrystal_I2C lcd(0x27, 16, 2) with LiquidCrystal_I2C lcd(0x27, 20, 4). The library functions work identically, though you’ll want to adjust cursor positions to use the additional space.

Why does text wrap from line 1 to line 3 instead of line 2?

This behavior results from the HD44780’s internal memory organization. The controller treats the display as two 40-character lines, mapped to create four 20-character rows. The library’s setCursor() function handles this automatically, so always use it rather than relying on text wrapping.

How many 20×4 LCDs can I connect to one Arduino?

Using I2C, you can connect up to 8 displays by configuring unique addresses via the A0-A2 solder pads on each backpack. Ensure your power supply can handle the combined current draw.

Why is my display very dim even with backlight on?

The Arduino’s USB power may be insufficient. Connect an external 5V supply directly to the LCD’s VCC pin or use a powered USB hub. Also verify the contrast potentiometer isn’t turned to an extreme position.

Can I use a 20×4 LCD with a 3.3V Arduino?

Most 20×4 LCDs require 5V for proper operation. With 3.3V boards like ESP32, you’ll need a logic level shifter on the I2C lines and a separate 5V supply for the LCD module. Some newer modules are 3.3V compatible but check your specific display’s datasheet first.

Choosing Between Display Sizes

Consider your specific project requirements when selecting a display format.

Selection Criteria

Project Type	Recommended Display
Simple sensor reading	16×2 LCD
Multiple readings	20×4 LCD
Menu-driven interface	20×4 LCD
Portable/battery device	16×2 LCD (lower power)
Dashboard/status panel	20×4 LCD

The 20×4 format costs slightly more but eliminates the frustration of cramming information onto inadequate display space. When in doubt, choose the larger display since you can always use fewer lines, but you cannot expand a smaller LCD after installation.