Introduction to the basic knowledge of LED electronic display

1. LED

The most important part of the light-emitting tube is the selection of the light-emitting tube core inside the light-emitting tube. At present, the main manufacturers of medium and high-end light-emitting tube cores are Japan's Nichia, Toyota, the United States' Cree, HP, Germany's Siemens, Taiwan's Guolian, Dingyuan and Guanglei. Among them, the largest companies in the United States and Europe mainly produce pure blue and pure green light-emitting tube cores, while Taiwanese companies mainly produce red and green tube cores. From the current practical application and red and green color matching, the red tube uses four elements of red, and the green tube uses three elements of green. In the use of tube cores, it is recommended to use the red tube core of Taiwan Guolian Company's 712SOL, and the green tube core of Taiwan Dingyuan Company's 113YGU. The use and matching of this tube core is currently a higher configuration of dual-primary color indoor display screens. There is also a configuration of 2 reds and 1 pure green. (Outdoor dual color)

2. Integrated components

The photoelectric drive circuit receives the digital signal from the computer to the distribution card, drives the light and dark of the light source, and thus forms the text or graphics we need. Whether its quality is reliable and stable directly determines whether the light source can work normally. From the current operation of the outdoor screen, the failure rate is the highest in the photoelectric drive part, because the quality of the selected integrated IC device directly determines the quality of the photoelectric drive part. At present, the general chip used in the outdoor display screen is a pair of 4953 and HC595. In the outdoor display screen of Qingtai Foreign Language Power Plant, we recommend the use of a dedicated driver chip, the 6B series 595 produced in Texas, USA, which has a driving current twice that of a general chip and has the functions of latching and driving.

3. Power supply

The power supply used by our company is required to ensure that the failure rate is less than 1% in 5 years, that is, less than 0.02% per year. The quality of the power supply depends on the selection of its components and the quality control of the power supply manufacturer. There are many brands of power supplies on the market. Domestic ones include Changzhou Chuanglian, Star, Shanghai Hengfu, etc., and the imported ones are mainly Taiwan Mingwei. Our company has used products from these companies. From the actual use, the domestic power supply Changzhou Star has good stability, long service life, and a relatively well-known power supply brand. Our company uses a power supply that has passed 3C certification for this display.

4. Production process and construction process

The system's processes mainly include welding and installation. As for welding, this display system has as many as 100,000 welding points, and a poor solder joint can cause at least one pixel tube to not light up, so the welding process is very important. We use the current advanced wave soldering, and the entire welding process is completed by equipment to avoid human errors.

If it is an outdoor display screen, higher requirements are put forward for the installation process of the screen body, that is, the overall structure of the screen body is required to be resistant to typhoons, waterproof, and high temperature. This is because the system has a long working time, high power consumption, and the outdoor working environment is relatively harsh, so the screen body is required to have certain high temperature resistance, dustproof, and anti-fog functions. When the display screen area is more than 20 square meters, it is recommended to use double support. When it is less than 20 square meters, it is recommended to use a single support. This display screen is installed on the second gate of the power plant with a natural bracket. The overall structure of the display screen adopts steel structure, and the facade is edged with Taiwan Jixiang Industrial aluminum-plastic panel. In order to ensure the safety and reliability of the display screen structure, it is recommended that the design and construction of the structure be completed by a company with professional construction qualifications.

5. Production process

5.1 "Three-proof" treatment of power supply and circuit board

Outdoor electronic display screens are in an open-air environment for a long time and are located on the coast. Therefore, circuit printed boards, power supplies, solder joints, etc. are required to be resistant to water mist and corrosion. Our company comprehensively carries out "three-proof" treatment on circuit printed boards, components, solder joints, etc. in the outdoor electronic display screen system. We use military technology and carry out three-proof treatment according to the "three-proof" standards of naval shipborne radar. Our company is the only enterprise in the same industry in the province that truly carries out "three-proof" treatment according to military standards. As we all know, the quality of "three-proof" materials is crucial to the "three-proof" effect of the display screen. Its special ratio enables the display screen to withstand the test of harsh conditions. Our company adopts "immersion protection" according to the military-grade production process, which can ensure that the components of the display screen are reliably treated with three-proof. Our company believes that for a system such as a display screen with a long service life, a poor use environment, and a large number of components, in order to ensure the reliability of the display screen, it is necessary to strictly control the three-proof process of the display screen and adopt the "invasion protection" process. In addition, the use of current-carrying welding technology objectively eliminates the damage to the three-proof caused by the rosin left in the manual soldering, so as to achieve a truly full "three-proof" process.

5.2 The overall structure is typhoon-resistant, waterproof and high temperature-resistant

The all-weather working environment requires the outdoor screen to have waterproof function, so the screen must choose a unit box structure, each box is an independent unit. The box material is 1.5 cold-rolled plate, and the surface is black phosphating.

Haining is located in a typhoon-prone area. The front pressure that each square meter of the display screen needs to withstand during a level 12 typhoon is 80kg/square meter. The steel frame of the display screen is calculated to withstand typhoons above level 12, and a certain margin is given.

The outdoor electronic display screen has a large area, the system has a long working time, high power consumption and a relatively harsh working environment, so the screen is required to have certain high temperature resistance, dust resistance and fog resistance functions.

Our company installs several axial flow fans according to the size of the screen, which can not only maintain air convection inside the screen, playing a cooling role, but also a purification role.

The entire steel structure is made of steel plate folding on all four sides to effectively prevent water droplets from penetrating. The surface decoration uses Taiwan Jixiang double-sided plastic aluminum plate, and the color selection is coordinated with the surrounding environment.

To ensure the flatness of the screen surface and the installation gap, our company uses CNC equipment for box processing. The frame design is commissioned to Hangzhou Light Textile Design Institute, and the frame is commissioned to Hangzhou China Electric Power 12th Bureau to produce, ensuring the reliability, safety and aesthetics of the overall structure.

Box size: 704×352×150mm

5.3 Lightning protection grounding

Electronic components in electronic display screens are highly integrated, and their sensitivity to interference is also increasing. Lightning can harm the display system in various ways. Generally, it directly concentrates on the screen and then discharges into the ground through the grounding device. Mechanical, electrical, and thermal damage is caused where the lightning current passes. The solution is to connect the ungrounded or poorly grounded metal casing, the metal sheath of the cable, and the metal frame inside the display screen to the grounding device to prevent these objects from being affected by high voltage or the transmission of high potential from lightning to the ground on the grounding device, causing a counterattack on the internal insulation of the equipment and the cable core wire. Adding a lightning arrester to a large display screen system can reduce the overvoltage that appears on the equipment during a counterattack and limit the lightning intrusion wave.

6. Editing and playback system software

The overall requirement of the system software is to provide a simple and interactive program production/playback environment, adopt a hierarchical and modular design approach in implementation, and have good reliability and scalability.

The software system includes several parts such as supporting environment, computer graphic display or multimedia program playback software, special effects software, multimedia database, etc. The functions and performances are explained below.

Support environment

The supporting environment includes three parts: operating system, Chinese environment and device driver:

Operating system: Windows series

Chinese environment: Use advanced TrueType fonts, with nearly a hundred fonts, and the fonts can be enlarged steplessly without jagged edges or deformation.

Hardware driver software: Under Windows, the system supports application software operations in the form of dynamic link libraries.

2. Computer graphic display software

Computer graphic display software can display various texts and images on the screen in a lively form and must have the following characteristics:

Rich display modes

There are dynamic and static display modes such as moving, rolling, flashing, highlighting, shutters, zooming, etc., which make the monotonous text and pictures more attractive.

Powerful editing tools

Text, images and other information can be input through keyboard, mouse, scanner and other different input methods. The input images and text can be zoomed in, out, copied, mirrored and other editing processes. Video signals can also be used as an input type.

2D/3D animation software

Animation is one of the most convincing and appealing means of computer presentation in advertising and publicity. Currently, the main animation software include Autodesk's Animator Pro (2D) and 3D-Studio (3D). These software packages have convenient interface, rich material library, shape library and advanced rendering technology, and can produce high-quality 3D animation, making advertising creativity a realistic reality.

3. Program control and playback software (network version)

The program playback software is a multimedia application software with full copyright, which works closely with large-screen applications, provides consistent support for multiple media objects such as sound, animation, text, video, etc., and has a good human-computer interface. It is a rare and powerful tool in publicity and news production.

The software should have the following features:

a. Automatically install various low-level driver modules, support Yucheng multimedia cards, sound cards, modems and other devices, support VGA synchronization, and support synchronous output of sound and image.

b. Multiple instances of the software can run simultaneously, that is, there can be multiple insertion and playback windows (under current hardware conditions, only one video window can be the active window, and the others are non-video ports).

c. The size of the video window can be adjusted steplessly without image distortion. This feature is especially important for large LED screens, because the number of rows and columns of a user's screen is usually smaller than that of a full-screen TV.

d. Full support for NTSC, PAL and other formats, which can be identified by software, without manual adjustment or additional decoder.

e. Capable of capturing video images, and performing various processing (filtering, smoothing, sharpening, color adjustment, etc.) on the acquired images before storing or printing them out.

f. New forms of expression are superimposed one by one. In multimedia technology, VGA images and videos can appear on the screen at the same time. First, it can produce an effect better than a subtitle machine, with TV and video programs as the background, and produce scrolling, moving, flashing and other text and image display effects on the screen; secondly, 2D/3D animations can be superimposed on videos to achieve an effect similar to that of real people and cartoon characters performing together.

g. Sound effects. Currently, animations on PCs generally do not have sound. To make the system more expressive, the playback software supports the synchronous output of sound and 2D/3D animations, so that characters can have dialogues, and there can be commentary during the performance. Background music, etc.

h. Full control of the playback process, similar to a general DVD player, you can jump to any program at any time during playback, play at normal speed or fast speed, or play in single step. You can pause the playback at any time during playback and then restart from the pause point. The system also indicates the current time and program at any time, which is very convenient to use. Similarly, you can also adjust the brightness, contrast, and color at any time to achieve the best viewing effect.

I. The control computer is equipped with a network interface, which can be connected to other computers and broadcast network information at the same time to achieve network control.