Introduction: The LCD module is a component that integrates the liquid crystal display device, connectors, integrated circuits, PCB circuit boards, backlight sources, and structural components together. The English name is “LCD Module”, abbreviated as “LCM”, and it is generally referred to in Chinese as “液晶显示模块”.
LCM Display Type
The LCD module is a component that integrates the liquid crystal display device, connectors, integrated circuits, PCB circuit boards, backlight sources, and structural components together. The English name is “LCD Module”, abbreviated as “LCM”, and it is generally referred to in Chinese as “液晶显示模块”. In fact, it is a commercialized component. According to relevant national standards in China, only integrated components that cannot be disassembled are called “modules”, while components that can be disassembled are called “components”. Therefore, the correct term should be “液晶显示组件”. However, due to long-standing habits, people usually refer to it as “模块”.
The liquid crystal display device is a fundamental component of high-tech technology. Although its application is already widespread, many people still find it difficult to use and assemble. Especially for dot-matrix liquid crystal display devices, users may feel lost. The special connection methods and required specialized equipment are not understood or possessed by everyone. Therefore, users of liquid crystal display devices hope that someone can assist in integrating the liquid crystal display device with control and drive integrated circuits to form a functional component, allowing users to assemble it into a complete system using traditional processes.
Broadly speaking, any component that integrates a liquid crystal display device and integrated circuits belongs to a “module”, but in practice, we usually refer to “modules” mainly as dot-matrix liquid crystal display modules. Particularly because for dot-matrix liquid crystal display products, except for some specialized high-volume varieties (such as electronic dictionaries and communication products), manufacturers supply liquid crystal display devices directly to users. Almost all general-purpose dot-matrix liquid crystal display devices are supplied to users after being processed into modules, so it is easy to form the misunderstanding that “液晶模块” is equivalent to “点阵液晶模块”.
1. Digital LCD Module
This is a functional component assembled from segment-type liquid crystal display devices and dedicated integrated circuits, capable of displaying only numbers and some identifiers. Segment-type liquid crystal display devices are mostly used in portable and compact devices such as pagers, telephones, electronic watches, calculators, MP3 players, etc.; they are also used in some instruments and meters, such as car audio systems and fuel dispensers. Due to the compact size of these devices, the display part is designed not to be a separate component. Even if some application fields require a separate display component, it should also have some functions for information reception, processing, storage, and transmission, as they are popular in the market due to their specific functions. Common digital LCD modules include the following types.
1. Counting Module
This is a counting display component assembled from seven-segment liquid crystal display devices of different digit counts and decoding drivers, or with additional counters. It has the functions of recording, processing, and displaying numbers. The main products available in the Chinese market include unit liquid crystal display modules driven by the CD4055 decoding driver, as well as 4-digit, 6-digit, 8-digit, 10-digit, 12-digit, and 16-digit counting modules assembled from integrated circuits such as ICM7211, ICM7231, ICM7232, CD14543, UPD145001, HD44100, etc. When selecting such counting modules, the following points must be noted:
Understand the function: Although they are all called “counting modules”, most of them cannot directly count. Their input ports may only be in BCD code interface form, some may have BCD code plus enable terminal input interface form, and others may have interfaces that can connect directly to serial or parallel ports, etc. If you need to calculate or record a string of numerical elements, you must also configure the corresponding circuit. Of course, there are also products with the counting circuit integrated into the module.
Identify the structure: Liquid crystal display devices have different installation methods and structures. Therefore, when selecting, pay attention to its structural characteristics. Generally speaking, these counting modules are mostly assembled with zebra conductive rubber strips, plastic (or metal) frames, and PCB boards that integrate the liquid crystal display device and integrated circuits. Their external lead terminals may have solder point types, pin types, and PCB header types. Pay attention to the power supply: a device should ideally use a unified power supply. Common liquid crystal display counting modules include single power supply types and dual power supply types, with different specifications such as 5V and 9V.
2. Measurement Module
This is a module composed of multiple segment-type liquid crystal display devices and integrated circuit chips with decoding, driving, counting, and A/D conversion functions. Since the integrated circuits used have A/D conversion functions, they can convert the input analog electrical signals into digital displays. We know that any physical quantity, even chemical quantities (such as acidity and alkalinity), can be converted into analog electrical quantities. Therefore, as long as certain sensors are equipped, this module can measure and display any value, making it very convenient to use. The integrated circuit models used in measurement modules mainly include ICL7106, ICL7116, ICL7126, ICL7136, ICL7135, ICL7129, etc. The functions and characteristics of these integrated circuits determine the functions and characteristics of the measurement module. As a measurement product, it must undergo measurement verification as per regulations. Products approved by measurement departments bear measurement qualification certificates.
3. Timing Module
The timing module has the longest history of using liquid crystal display devices for timing. By integrating a liquid crystal display device with a timing integrated circuit, a complete timer is formed. Since it does not have the casing of a finished clock, it is called a timing module. Although timing modules have a wide range of applications, general-purpose and standard timing modules are difficult to purchase in the market; they can only be selected or ordered from electronic clock manufacturers for suitable movements. Although timing modules and counting modules look similar, their display methods differ. The numbers displayed by timing modules are composed of two-digit groups, while each digit of counting modules is arranged continuously. Since many timing modules also have timing and control functions, these modules can be widely integrated into various powered devices, such as tape recorders, CD players, microwave ovens, rice cookers, and other appliances.
2. Character Dot-Matrix Module
This module is composed of character dot-matrix liquid crystal display devices and dedicated row and column drivers, controllers, and necessary connectors and structural components. It can display numerical elements and Western characters. This type of dot-matrix character module has its own character generator, large display capacity, and rich functions. Generally, this module can display 8 characters in 1 row or more than 16 characters in 1 row. The dot-matrix arrangement of this module consists of groups of pixel dot matrices arranged in 5×7, 5×8, or 5×11. Each group is 1 digit, with a gap between each digit and a gap between each row, so it cannot display graphics. Its specifications are mainly shown in the following table:
Generally, the module control and driver have a built-in character library CGROM with 192 fixed character patterns and allow users to create custom characters in random memory CGRAM, permitting users to establish 8 characters with a 5×8 dot matrix.
3. Graphic Dot-Matrix LCD Module
This module is characterized by continuous arrangement of bitmap elements, with basically no gaps in the arrangement of rows and columns. Therefore, it can display continuous and complete graphics. Since it is composed of X-Y matrix pixels, it can display various texts in addition to graphics.
1. Row and Column Driver Type
This is a module that must be connected to a dedicated controller. The module is only equipped with general row and column drivers, which actually only have general output terminals for pixel driving. The input terminals generally have data input terminals of less than 4 bits, shift signal input terminals, latch input terminals, AC signal input terminals, etc., such as HD44100, HD66100, etc. This type of module must be connected to control circuits, such as T6963C, SED1335, etc., to connect with computers. This type of module has many models and is widely used. Although it requires a self-configured controller, it also gives customers the freedom to choose different controllers.
2. Row and Column Driver-Control Type
This is a module that can be directly interfaced with computers, relying on computers to directly control the driver. The column driver used in this type of module has an I/O bus data interface, allowing the module to be directly connected to the computer bus, eliminating the need for a dedicated controller, thus reducing costs for the entire system. This is very suitable for users with a small number of pixels, limited overall functionality, and familiarity with computer software programming. However, it will occupy part of the system’s resources.
3. Row and Column Control Type
This is a bitmap module with an embedded controller. It is also the most popular type. This module is equipped not only with row and column drivers like the first type but also with dedicated controllers like T6963C, SED1335, etc. This controller serves as the interface between the liquid crystal driver and the computer, controlled by the computer in the simplest way, receiving and feeding back various information from the computer, managing the display buffer through independent information processing, and providing the necessary signals and pulses to the driver, manipulating the driver to realize the display function of the module. This controller has its own set of dedicated instructions and its own character generator CGROM. Users must be familiar with the detailed manual of this controller to operate it. This module frees users from the design, processing, and production of controllers, and simplifies the complex control of displays by computers, saving internal resources of the host system. There are now products using single-chip integrated driving and control, mainly used in portable products such as mobile phones, MP3 players, PDAs, electronic dictionaries, handheld POS machines, etc.
Author’s Note:Peking University Shenzhen Graduate School’s School of Information Engineering provides a specialized academic platform for more advanced technical talents aspiring to transition into information display technology—(Information Display Technology Professional Part-time Graduate Class http://www2.pkuece.cn), which is open for enrollment to society, and enrollment for 2016 is ongoing.
