How to Use lcd 20*4: Examples, Pinouts, and Specs

The 20x4 LCD (Liquid Crystal Display) is a versatile display module capable of showing 20 characters per line across 4 lines. It is widely used in embedded systems for displaying text, numeric data, and simple graphics. This module is ideal for applications requiring a clear and compact display, such as industrial control panels, home automation systems, and educational projects. The LCD 20x4 can be interfaced using either a parallel or serial communication protocol, making it compatible with a variety of microcontrollers, including Arduino boards.

• Display Type: Character LCD
• Resolution: 20 characters x 4 lines
• Operating Voltage: 4.7V to 5.3V
• Current Consumption: 1mA (without backlight), ~15mA (with backlight)
• Interface: Parallel (4-bit or 8-bit mode) or I2C (with adapter)
• Backlight: LED backlight (usually white or green)
• Character Size: 5x8 dot matrix
• Operating Temperature: -20°C to 70°C
• Dimensions: ~98mm x 60mm x 12mm

The LCD 20x4 typically has 16 pins for parallel communication. If an I2C adapter is used, only 4 pins are required.

1. Power Supply: Connect the VSS pin to ground and the VDD pin to a 5V power source.
2. Contrast Adjustment: Connect the VO pin to the wiper of a 10kΩ potentiometer. Connect one end of the potentiometer to ground and the other to 5V. Adjust the potentiometer to set the display contrast.
3. Communication Mode:
   • For parallel mode, connect the RS, RW, E, and data pins (D0-D7) to the microcontroller.
   • For I2C mode, connect the SDA and SCL pins to the corresponding microcontroller pins.
4. Backlight: Connect the A pin to 5V through a 220Ω resistor and the K pin to ground.
5. Code Implementation: Use a suitable library (e.g., LiquidCrystal for parallel mode or LiquidCrystal_I2C for I2C mode) to control the LCD.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Initialize the LCD with I2C address 0x27 and dimensions 20x4
LiquidCrystal_I2C lcd(0x27, 20, 4);

void setup() {
  lcd.init(); // Initialize the LCD
  lcd.backlight(); // Turn on the backlight
  lcd.setCursor(0, 0); // Set cursor to the first column of the first row
  lcd.print("Hello, World!"); // Display text on the LCD
  lcd.setCursor(0, 1); // Move to the second row
  lcd.print("LCD 20x4 Demo"); // Display additional text
}

void loop() {
  // No actions in the loop for this example
}

• Ensure the power supply voltage is within the specified range to avoid damage.
• Use pull-up resistors for the SDA and SCL lines when using I2C communication.
• Avoid excessive backlight current by using an appropriate resistor.
• For parallel mode, unused data pins (D0-D3 in 4-bit mode) should be grounded.

1. No Display on the Screen:

   • Check the power connections (VSS and VDD).
   • Adjust the contrast using the potentiometer connected to VO.
   • Verify the backlight connections (A and K).

2. Garbled or No Text:

   • Ensure the correct communication mode (4-bit, 8-bit, or I2C) is configured in the code.
   • Double-check the wiring between the microcontroller and the LCD.
   • Verify the I2C address if using an I2C adapter (common addresses are 0x27 or 0x3F).

3. Backlight Not Working:

   • Check the resistor value connected to the A pin.
   • Ensure the backlight pins (A and K) are properly connected.

• Q: Can I use the LCD 20x4 with a 3.3V microcontroller?
  A: Yes, but you will need a level shifter or a 5V-tolerant I2C adapter for proper operation.

• Q: How do I find the I2C address of my LCD?
  A: Use an I2C scanner sketch to detect the address. This is especially useful if the default address (0x27) does not work.

• Q: Can I display custom characters on the LCD?
  A: Yes, the LCD supports custom characters. Use the createChar() function in the LiquidCrystal or LiquidCrystal_I2C library to define and display them.

By following this documentation, you can effectively integrate and troubleshoot the LCD 20x4 in your projects.