LED display knowledge

     LED Display (light emitting diode), light-emitting diodes English acronym LED. It is a semiconductor light-emitting diodes by controlling the display, which is probably the way by a number of red light-emitting diodes are usually composed by the bright lights off to show character. Display screen for displaying text, graphics, images, animations, quotes, video, video signals and other information.
       LED display classification, can be classified from the following criteria:
Color
LED display is divided into full-color display, monochrome (single color) display (one red, one white, one yellow) and color (two-color) display (red and green, blue and green)
Use of the environment
LED display can be divided into: indoor LED display, semi-outdoor LED display and outdoor LED display.
Installation
LED display can be divided into: Column LED display (single column and double column), wall-mounted LED display, ceiling-mounted display, embedded displays.
Use
LED display is divided into: information dissemination screen, traffic guidance screen, advertising screen, car screen, stadium screen, stage rental screen and stairs screen, etc.
Shape
LED display screen can be divided into conventional and special-shaped screen.
Single-color display
Single color (red, green, yellow, white, blue, etc.).
Dual color display:
Red and green dual-color, 256 or 512 gray gray, you can display 65,536 colors.
Full color display:
Red, green and blue color, 256 grayscale full color display can show more than sixteen million kinds of colors.
Indoor display:
Luminous point smaller, usually Φ3mm - Φ8mm, to show the general area of ​​a few dozen meters.
Semi-outdoor display:
Pixel sizes between the indoor and outdoor display; common in banks, shopping malls or hospitals lintel.
Outdoor display:
The general area of ​​a few dozen to several hundred square meters, high brightness, can work in the sun, with wind, rain, water resistant.
Technical advantages comments
Existing common indoor full color scheme of comparison:
1. Dot matrix module program:
The first design, the pseudo-color dot matrix screen indoor evolved
Advantages: the most advantageous cost of raw materials and the production process is simple, stable quality.
Cons: poor color consistency, mosaic more serious, showing poor results.
2. Single lamp program:
To solve the problem of color dot matrix screen, draw a plan outdoor display technology, while the pixel multiplexing (also known as pixel-sharing technology, virtual pixel technology) transplanted to the indoor outdoor display.
Advantages: Good color consistency than dot matrix module approach.
Disadvantages: blending effect poor little perspective, about the horizontal viewing with color. More complex processing, antistatic demanding. The actual pixel resolution more difficult to achieve 10,000 points.
3. SMD program:
Using SMD LED display element solution.
Advantages: color consistency, perspective and other important indicators are displayed in the best kind of existing programs, especially triple paste the mixing effect is very good.
Disadvantages: cumbersome process, the cost is too high.
4. Asia paste the program:
Is actually a single lamp program improvements, is still being improved.
Advantage: the display color consistency, perspective and other primary indicators and sticker program is not very different, but the lower cost, showing good results, the resolution is theoretically possible to achieve more than 17,200.
Disadvantages: Processing is more complex, requiring high antistatic


LED display common terms explained
1. LED brightness
General brightness light-emitting diodes with emission intensity (Luminous Intensity) said that the unit is candela cd; 1000ucd (micro candela) = 1 mcd (milli candela), 1000mcd = 1 cd. Indoor single LED light intensity is generally 500ucd-50 mcd, and outdoor single LED light intensity should normally be 100 mcd-1000 mcd, 1000 mcd even more.
2. LED pixel module
LED arranged in a matrix or pen section, preformed into a standard-size module. Indoor display commonly used 8x8 pixel block, eight 7-segment digital module word. Outdoor display pixel module has 4 * 4,8 * 8,8 * 16 pixels and other specifications. Outdoor display with a pixel module because each pixel is composed of two or more of its LED tubes composed, so called for its bundle module set.
3. Pixel (Pixel) with pixel diameter
Each LED display can be individually controlled LED light unit (point) is called a pixel (or pixels). Pixel diameter ∮ means for each pixel diameter in millimeters.
For indoor display, usually a single LED, is circular in shape. Indoor display pixel diameter school are common ∮3.0, ∮3.75, ∮5.0, ∮8.0, of which ∮3.75 and ∮5.0 most.
In the outdoor environment, to improve the brightness, increase the line of sight, a pixel contains two or more cluster LED; due to two or more cluster LED generally not circular, so the outdoor display pixel diameter generally use two average distance between two pixels represent : □ 10, □ 11.5, □ 16, □ 22, □ 25.
4. Spacing, pixel density and information capacity
Between two pixels from the center of Hefei LED display manufacturer or point spacing (Dot Pitch); the number of pixels per unit area is called a pixel density; the number of units contained within the display area is called the information capacity. This is the essence of the three describe the same concept: the dot pitch is the distance between two pixels from room to reflect the pixel density, spacing and the pixel density is a physical property of the display; the information capacity is the information carrying capacity of a pixel density the number of units.
The smaller the dot pitch, the higher pixel density, the more information the capacity for closer viewing distance.
Dot pitch, the lower pixel density, the less information capacity, the farther the distance for watching.
5. Resolution
Ranks number called pixel LED display LED display resolution. Resolution is the amount of pixels of the display, which determines the information capacity of a display screen.
6. LED display structure
The LED module in accordance with the actual needs of the size of the pixels arranged in a matrix assembly, together with a dedicated display driver circuit, DC power supply, software, frameworks and outdoor decoration, constitute an LED display.
7. Grayscale
Refers to the degree of luminous gray pixel shading, and a color of gray generally 8-12. For example, if each of the color gray as 256, for a two-color color screen, the display color is 256 × 256 = 64K colors, also known as the 256-color display screen.


How to assess the quality of the LED screen
The quality of a full-color display is mainly from the following aspects can be signed:
1. Flatness
Surface roughness of the display to be within ± 1mm, in order to ensure the display image is not distorted, partial raised or recessed will lead to the display viewing angle appears dead. Flatness is mainly determined by the quality of the production process.
2. Brightness and viewing angle
Indoor brightness full color to the 800cd / m & sup2; image or because the brightness is too low to see more, to ensure the normal operation of the display, the display; more outdoor brightness full color to the 1500 cd / m & sup2. Size of the brightness by the LED die is good or bad decisions.
How much screen size of the audience directly depends on the viewing angle, and therefore the bigger the better. Mainly by the size of the viewing angle of the die packages to decide.
3. White balance
Balance effect is one of the most important indicators display. Red, green and blue color science fooled ratio of 1: 4.6: 0.16 out of pure white will show, if the actual proportion of the white balance a little deviation deviation occurs, usually pay attention to whether there are bluish white, yellow green phenomenon. White balance is good or bad is determined by the display control system, the die for the reduction of color is also affected.
4. Reduction of color
Color reduction refers to the color display of color reduction, both display a high degree of consistency with the source of the color, so as to ensure that the image realism.
5. Whether the mosaic, dead phenomenon
Mosaic refers to appear on the display lit or normally black small four-square, both modules necrosis, mainly due to the quality of its display connectors used, but off.
Always refer dead appear on the display or normally black single point, how good or bad from the die to determine the dead point.
6. Presence or absence of color
Color refers to the existence of obvious color difference between adjacent modules, the transition to color module as a unit, the color phenomenon is mainly caused by poor control systems, the gray level is not high, low scanning frequency caused.


LED display Frequently Asked Questions
LED attaches great importance to anti-static measures, the following are a few instructions for static and anti-static:
1. static source:
Impact on the circuit's main sources of human electrostatic, plastic products and related equipment and instruments, from the use of the environment in which static power supply has the following:
1) objects, materials
2) floors, work desks and chairs
3) clothes, containers
4) the surface of the paint or wax, organic and fiberglass materials.
5) cement floors, paint or waxing floors, plastic or vinyl flooring tiles.
6) synthetic clothes, non-conductive work shoes, clean cotton overalls.
7) plastics, packaging, boxes, bags, trays, foam liner.
2. Electrostatic discharge failure modes:
Sudden failures and potential failures.
In the environment of use for more than 90 failures electrostatic potential failures, the performance of anti-circuit electrical overstress the ability to weaken and shorten life.
3. Anti-static measures:
1) the use of electrostatic sensitive circuit trainers static knowledge and related technologies.
2) the establishment of anti-static work area, for use in the area of ​​anti-static flooring, anti-static table, anti-static and anti-static equipment grounding wire, and relative humidity to go above 40.
3) damage to electronic equipment caused by static electricity may be released anywhere from the manufacturer to the field devices. Harm because there is no adequate, effective training and equipment failure caused by manipulation. LED is a static-sensitive devices. INGAN wafers are generally considered "on a" vulnerable to interference. And ALINGAP LEDS SHI "second" or better.
4) ESD damaged equipment can show dim, fuzzy, off, short or low VF or VR. ESD damaged equipment should not be confused with electronic overload, such as: due to an error in the current design or drive, chip hook, wire shield grounding or package, or general environment induced stress.
5) ESD safety and control procedures: Most electronic and electro-optical company ESD is very similar, and has successfully achieved so equipment ESD control, manipulation, and the main program. These procedures have been used since ancient ESD testing the quality of the effect of the instrument. ISO-9000 certification also had listed him as the normal control procedures.
4. Transportation and packaging
In the daily operation, ESD sensitive devices should always be stored in an antistatic bag or container. This includes reserves, transportation and inventory of WIP. Prevention includes consumption during transportation fleet, boxes or other devices, such as with conductive wheels or even drag in the delivery of ESD equipment is grounded.
LED business development opportunities facing First, although China in the upstream LED epitaxial wafers, chip production with the United States, Japan, EU production is technically a gap, but due to huge domestic and international market applications, and end-consumer market with diversified decentralized structure, not easy to form a market monopoly, thus giving LED downstream manufacturers to bring tremendous growth opportunities, especially for the relatively backward technology enterprises in China, have a greater survival and development.
Secondly, due to the Chinese government is actively promoting the industrialization of LED. 2003 established the National Leading Group of semiconductor lighting inter-ministerial coordination, launched the "National Semiconductor Lighting Project." "863" plan for the relevant enterprises and research institutions have invested the appropriate funds to support basic research and technological research.


LED display effect
1. Play commodity publicity attraction customers.
2. Play a storefront decoration, enhance the role of enterprise grade.
3. Play lighting, unconventional role.
4. Play the role of universal knowledge. (Can be used to play a small enterprise product information, relevant industry knowledge)
5. Play the role of bulletin boards. (Promotion, recruitment information release)
6. Heighten the atmosphere play a role. Can be played through superior leadership and various VIP display screen to visit, guide words of welcome, a variety of major festivals and other celebrations word.
7. Serve as a warning, often used for road navigation LED indication.
Admittedly, the ultimate goal of establishing businesses billboard product information is propaganda to attract target customers, the maximum extent possible to earn maximum profit. The LED billboard precisely to achieve this goal to become the first items of choice for enterprise promotion.


LED display features
Feature
A comprehensive understanding of the characteristics of the LED display is to select cost-effective LED display, compared with other large-screen terminal display, LED display has the following characteristics.
a, high brightness: Outdoor LED display brightness is greater than 8000mcd / m2, is currently the only large-scale display terminal can be used in outdoor weather; indoor LED display brightness is greater than 2000md / m2.
b, long life: LED life of up to 100,000 hours (ten years) or more, which generally refers to the design parameters of life, brightness dark can be considered;
C, viewing angle: indoor viewing angle greater than 160 degrees, outdoor viewing angle greater than 120 degrees. The size of angle depends on the shape LED light-emitting diodes.
d, vary in screen size, as small as less than one square meter, big is up to hundreds of thousands of square meters;
e, easy computer interface, support software rich.
f, common large display terminal contrast