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Arduino Practical Workshop: LCD1602 Liquid Crystal Display Module

Experiment: LCD1602 Liquid Crystal Display 1602A Module Blue Screen Yellow Green Screen Gray Screen 5V 3.3V Soldered Pin IIC/I2C
'''1602 LCD'''

[https://www.unikeyic.com/search?keyword=PCF8574 The 1602 LCD] is a dot matrix module for displaying text and symbols. It has multiple character positions, each with a 5x7 or 5x11 dot matrix, displaying one character per position. Spacing between characters and rows ensures readability, but limits graphic display. The "1602" refers to its 16x2 display format, showing two lines of 16 characters each. Most character LCDs use the HD44780 controller, allowing similar control principles and easy application of control programs across different modules.
LCD
LCD, or Liquid Crystal Display, is a technology used in flat-panel screens. It consists of a liquid crystal layer between two glass plates, with TFTs on the bottom and a color filter on top. Adjusting the signals to the TFTs controls the liquid crystal molecules, allowing light to pass through and form images. LCDs have largely replaced CRT screens due to their lower cost and popularity.

Liquid crystal displays (LCDs) are advantageous due to their low voltage requirements, energy efficiency, reliability, and capacity for large information display. They provide flicker-free color display and are safe for health. Production is automated and cost-effective, allowing LCDs to be produced in various sizes and types, making them portable and versatile. This has led to more compact computers and televisions. LCD technology has significantly influenced display imaging product design and advanced microelectronics and optoelectronic information technologies. Liquid crystal materials are commonly used in electronic watch and calculator displays, converting electrical signals into visible characters or images using their electro-optical properties. Under normal conditions, liquid crystal molecules are arranged in an ordered, clear state. Applying a direct current electric field disrupts this order, altering light propagation and allowing for the display of numbers and images through color intensity variations.
LCD Composition

Backlight (or backlight module) is essential for LCD monitors, as liquid crystal molecules cannot emit light on their own. A specialized light source provides illumination, which is modulated by the liquid crystals to generate colors. The backlight supplies the necessary light energy. Older LCDs used cold cathode fluorescent lamps (CCFL) similar to fluorescent tubes. Modern LCDs use more energy-efficient and durable LED backlights. The emitted light is evenly distributed using a light guide plate, with a back reflector directing all light toward the liquid crystals. Prism sheets and diffusion plates then ensure uniform brightness across the display.

Upper and lower polarizing films - The function of polarizing films is to allow light to pass through in only one direction.

Upper and lower glass substrates - Glass substrates are not merely two pieces of glass; they feature grooved structures on their inner sides, coated with alignment layers to align the liquid crystal molecules neatly along the grooves. TFT thin-film transistors and color filters are attached to both sides of the upper and lower glass layers.

ITO transparent conductive layer - It provides a conductive path, divided into pixel electrodes (P level) and common electrodes (M level). In the next page, we will delve into more details about the structure of the liquid crystal panel.

Thin-film transistors, commonly known as TFT-LCD, are switches that control signal voltage on the IC control circuit and deliver it to liquid crystal molecules, determining their deflection angle and magnitude, making them a key component.

Liquid crystal layer - The liquid crystal layer is the most important element in changing the polarization state of light, with its arrangement and polarization state jointly determined by electric and elastic forces.

Color filters use RGB filters to mix red, green, and blue to create various colors and shades. Liquid crystal panels have pixels made up of red, green, and blue sub-pixels with different grayscale levels.
The Differences Between LCD and OLED

While color distortion may occur when viewing an LCD screen in certain environments, it does not mean that LCD has no advantages at all. After all, existence is reasonable, and LCD still has many benefits. For example, one of the most important concerns for consumers is power consumption, and LCD screens typically have low power consumption. Moreover, LCD displays generally use digital interfaces, making them very convenient to use.

OLED uses transparent ITO glass and metal electrodes as anode and cathode. Voltage causes electrons and holes to combine in the exciton layer, emitting light. This self-luminous property is crucial for OLED displays. OLED provides faster response times and wider viewing angles than LCDs, without the need for backlighting. It displays true black, offering better contrast and color range. OLED screens can be flexible and integrated into various materials, enhancing their versatility. OLED excels in image quality and thinness, making it a leading trend for future displays. However, its high production costs restrict its use in large screens, leading to a focus on small-screen applications. Despite this, OLED remains a significant player in the display market.
LCD1602 LCD 5V display module

The 1602 character LCD, also known as the [https://www.unikeyic.com/products/108090131564231/LCD1602.html 1602 LCD], is a type of dot-matrix LCD module specifically designed to display letters, numbers, symbols, and more. The character LCD can simultaneously display 16x02 or 32 characters. It consists of several 5X7 or 5X11 dot matrix character positions, with each dot matrix character position capable of displaying one character. There is a spacing between each character position and between each row, which serves the purpose of character spacing and line spacing. Due to this design, it does not display graphics well (even with custom CGRAM, the display effect is not ideal).
The 1602 module adopts a standard 16-pin interface, where:
Pin 1: [https://www.unikeyic.com/products/108090131564231/LCD1602.html GND] is the power ground.
Pin 2: VCC connects to the positive pole of a 5V power supply.
Pin 3: V0 is the LCD contrast adjustment terminal. When connected to a positive power supply, the contrast is weakest, while when connected to a ground power supply, the contrast is highest (excessive contrast may lead to "ghosting", which can be adjusted by using a 10K potentiometer).
Pin 4: RS is the register select pin. A high logic level 1 selects the data register, while a low logic level 0 selects the instruction register.
Pin 5: RW is the read/write signal line. A high logic level 1 indicates a read operation, while a low logic level 0 indicates a write operation.
Pin 6: The E (or EN) pin is the enable pin. A high logic level 1 reads information, and it executes instructions on a negative edge transition.
Pins 7 to 14: D0 to D7 are the 8-bit bidirectional data lines.
Pins 15 to 16: Unused pins or backlight power.
Pin 15: Positive pole of the backlight.
Pin 16: Negative pole of the backlight.

Schematic diagram of the [https://www.unikeyic.com/products/108090131564231/LCD1602.html 1602 module]
IIC/I2C Interface [https://www.unikeyic.com/products/108090131564231/LCD1602.html LCD1602] Adapter Board
The control board has only 20 I/O ports. If you add sensors, SD cards, relays, and other modules, the I/O ports may not be sufficient. The original 1602 screen requires at least 7 I/O ports to drive it, but this module can help you save 5 I/O ports.

[[Specificationshttps://www.unikeyic.com/products/108090131564231/LCD1602.html|Specifications]]:
Power Supply Voltage: +5V
Supports I2C Protocol
Comes with backlight and contrast adjustment potentiometer
Simplified with 4-wire output
Device Address: 0x27
[https://www.unikeyic.com/search?keyword=PCF8574 PCF8574] is an 8-bit I/O expander for the I2C bus, designed to operate with VCC ranging from 2.5V to 6V. This 8-bit input/output (I/O) expander for the two-wire-bidirectional bus (I2C) is intended for remote I/O expansion with most microcontroller series through the I2C interface [serial clock (SCL), serial data (SDA)]. The device features an 8-bit quasi-bidirectional I/O port (P0-P7) that includes latch outputs with high-drive capability for directly driving LEDs. Each quasi-bidirectional I/O can be used as an input or output without the need for a data direction control signal. When powered up, the I/Os are in a high-impedance state, and only the current source for VCC is activated in this mode.
Tag：LCD1602 Module; PCF8574 expander; Electronic component;