The LED display is an electronic display made up of an LED dot matrix. It can display contents such as text, animation, pictures, and video in time by switching on and off the LED light bead on the screen.
The module display control is carried out through the modular structure. Mainly divided into a display module, control system, and power supply system. Their main functions are:
- The display module is made up of LED lamp dot matrix screen luminescence;
- The control system is to control the area of the light on the situation to achieve the conversion of the screen display content;
- The power supply system is to convert the input voltage and current to meet the needs of the display screen.
LED screens can realize the transformation between different forms of a variety of information presentation modes, and can be used indoors and outdoors, which has incomparable advantages over other displays.
It has the characteristics of high brightness intensity, small work power consumption, low voltage demand, small and convenient equipment, long service life, stable impact resistance and strong resistance to external interference, and has been rapidly developed and widely used in various fields.
The luminous color and luminous efficiency of LED are related to the materials and processes used to make LED. The bulb is blue at the beginning, followed by fluorescent powder. According to the different needs of users, different light colors are adjusted, and there are four widely used: red, green, blue and yellow.
Because the LED working voltage is low (only 1.2~4.0V), can actively emit and have a certain brightness, brightness and can be adjusted by voltage (or current), itself and impact resistance, anti-vibration, long life (100,000 hours), so in large display equipment, there is no other display way to match the LED display.
LED, Light Emitting Diode abbreviation. It is a semiconductor light-emitting diode by controlling the display way, by gallium (GA) and arsenic (AS), phosphorus (P), nitrogen (N), indium (IN) compounds made of the diode, when the electron and hole compound can emit visible light, so can be used to make the light-emitting diode.
Used as an indicator light in circuits and instruments, or as a text or digital display. Phosphorus gallium arsenide diodes emit red light, gallium phosphide diodes green light, silicon carbide diodes yellow light, and indium gallium nitrogen diodes blue light.
A display that combines red and green LED chips or tubes as one pixel is called a three-color or dual-color screen, while a display that combines red, green and blue LED chips or tubes as one pixel is called a three-color screen or full-color screen.
If there is only one color is called the monochrome or single color screen, make indoor LED screen pixel size is generally 1.5 to 12 mm, often using several can produce different colors of the LED tube core is encapsulated as a body, LED outdoor screen pixel size of 6-41.5 mm, each pixel is made up of several kinds of monochrome LEDs, the common product according to the pixel tube, double color pixel tube generally consists of 2 red 1 green, three color pixels of tube with 1 red 1 green and 1 blue.
Whether using LEDs to make a monochrome, two-color, or three-color screen, to display an image, the brightness of each LED that constitutes a pixel must be adjustable, and the degree of adjustment is the gray level of the display. The higher the gray level, the more delicate the displayed image is, the richer the color is, and the more complex the corresponding display control system is. Generally, in 256 grayscale images, the color transition has been very soft, and in 16 grayscale color images, the color transition boundary is very obvious. Therefore, color LED screens are currently required to be made into 256 to 4096 levels of gray.
Basic principles editing
LED display is a new type of information display media, it is the use of LED dot matrix
A flat display screen consisting of modules or pixel units. Figure 2 shows the structure diagram of an 8×8 dot matrix LED display. From the figure, a total of 64 LEDs are needed for an 8×8 dot matrix, and each LED is placed on the intersection of the row line and column line. When a corresponding row is set at a high level and a corresponding column is set at a low level, the corresponding diode will be lit.
For example, to display text, the corresponding diode can be lit according to the strokes that compose the text, so as to achieve the purpose of displaying text, as shown in Figure 3. The complete dot matrix can be composed of 16×16, 32×32 display modules.
Each pixel of a monochromatic LED display is composed of 1 monochromatic LED light-emitting diode, that is, each pixel contains 1 LED light-emitting diode; Each pixel of dual primary color LED display is composed of two kinds of monochrome LED LEDs, that is, each dual primary color pixel contains two LED LEDs; For a three-color, full-color LED display, the pixels consist of three or more diodes,
For example, it is composed of three diodes emitting red light, green light, and blue light respectively, so that it can achieve the purpose of the color display according to the principle of three primary color matching; Some screens may have four LEDs for better display: two red LEDs, one green LED and one blue LED.
LED display common classification method introduction
LED displays are classified in various ways, generally in the following ways:
(1) According to the display device
LED digital display:
a display device for 7 code digital tube, suitable for making a clock screen, interest rate screen, and other digital display electronic display.
LED dot matrix graphic display:
the display device is a dot matrix display module composed of many uniformly arranged light-emitting diodes, which are suitable for playing text and image information.
(2) According to the use environment
The indoor screen area is generally less than ten square meters, the point density is high, in the non-direct sunlight or lighting environment use, watching distance a few meters away, the screen body does not have the ability to seal and is waterproof. The luminescent spot diameter is small, the general diameter is 3 ~ 8mm.
The outdoor screen area is generally from a few square meters to dozens or even hundreds of square meters, point density is sparse (more than 1000 ~ 4000 points ㎡), luminous brightness in 3000 ~ 5000cd㎡(towards different, brightness requirements are different), can be used in direct sunlight conditions, viewing distance in dozens of meters away, the screen body has good wind and rain resistance and lightning protection ability.
The basic unit of outdoor screen luminescence is a pixel, and the center diameter of the component pixel luminescence points is larger, such as P10mm, P12mm, P16mm, P20mm, P24mm, P26mm, etc. outdoor screen is between outdoor and indoor, with high brightness, can be used in non-direct sunlight outdoor, screen body has a certain seal, generally under the eaves or in the window.
(3) According to the way of control or use
Synchronization means that the LED display is basically equivalent to the computer monitor. It can map the images on the computer monitor in real time at a rate of at least 30 fields /s. It usually has the ability of multi-gray color display, which can achieve the effect of multimedia advertising.
Asynchronous (or communication) means that the LED screen has the ability to store and automatically play, in the PC edited text and no grayscale pictures through the serial port or other network interface into the LED screen, and then the LED screen automatically plays offline, generally no more grayscale display ability, mainly used to display text information, can be multi-screen networking.
Classification of performance characteristics
- High-intensity luminescence. Under the refraction of sunlight, the content on the screen surface can be presented in high definition within the visual range.
- The gray control level is high.1024 ~ 4096 level gray control can be used to clearly and realistically display the color of 16.7m or more, to ensure that the picture has a strong three-dimensional sense.
- The driving power is large, and the scanning mode is mainly static latching to ensure high-intensity light.
- In order to ensure the best playback effect, the light can be reasonably controlled through the automatic adjustment function under different background environments.
- circuit integration mainly relies on large-scale imported devices to improve the reliability of operation, which is conducive to maintenance and debugging.
- The use of modern digital processing technology to process video, scanning mainly chooses the way of distribution of technology, design rendering modular, static constant current drive, automatic adjustment of light, and then achieve high fidelity of the picture, no ghosting and moving, improve the clarity of the image picture.
- Various types of information display, such as icons, videos, texts, animations, pictures, etc., and various forms of reality, such as networking, remote reality, and the combination of common colors and techniques.
Technical Advantage Editor
- Equipped with full-color display screen, the introduction of a more high-quality LED imported core, makes the screen imaging high-definition, uniform color, less power consumption, light screen body, thin screen layer, wide area perspective, so its failure rate is small, easy maintenance.
- It mainly adopts a multimedia display card PCTV card with multiple functions in one, with more excellent performance, more advanced collection method, accurate video capture, and Studio editing software matching with the display card.
- DVI interface technology is relatively advanced. Without the A/D and D/A conversion, to ensure the integrity of the picture image, and reduce the possibility of details, in the display screen completely reproduce the computer image.DVI can support all display modes to ensure stable and reliable data display while having a variety of integration functions.
- The use of indoor full color system to alleviate the hidden danger of the system display transmission of a large number of complex data fully carries out full true color restoration. The chip is used to complete the task of data distribution and display, and the received data is converted to pulse output. The 8-bit (8bit) display data is converted to 12-bit PWM, which is upgraded to 4096 (12bit) level gray control, so as to realize the display of non-linear 256-level visual gray level on the screen, and fully create the enjoyment of full true color vision.
- The constant current system is adopted in the drive mode. Through its high cost performance, improve the LED tube’s existing pressure drop dispersion, overcome the problem of the mosaic, and ensure the texture of the picture.
- Combine the mode of optical fiber transmission to reduce signal loss during transmission.
Classification of performance index
Color, brightness, and perspective
With the combination of diode system and semiconductor, its production material and production process are gradually upgraded, breaking through the limitations of original brightness and color, and a large number of blue diodes and pure green light-emitting diodes are applied to improve the display brightness.
Thus, the advantages of LED display screens in outdoor environments are improved, which can adapt to different display requirements and enhance the effective value of LED in different environments. The evaluation of LED display performance must be the result of comprehensive consideration because its related performance indicators are closely related, brightness, perspective, resolution and other indicators affect each other.
At present, LED devices are used to improve the viewing Angle and brightness performance of high-density, full-color indoor display screens.
Greyscale
The gray level of an LED display screen is mainly used to evaluate the color reality. The brightness level is judged from the darkest single primary color brightness to the brightest, and the gray level is used as the standard to evaluate the display color.
When the gray level is higher, it shows that the vegetables are rich and gorgeous; When its gray level is low, the color change is single. Therefore, the improvement of the gray level is conducive to the increase of the color display level of the image and the improvement of the color depth.
contrast
The contrast of the display screen affects the visual imaging effect. High contrast improves the clarity of the picture, the color is bright, and effectively improves the detail texture, clarity and gray level of the image quality.
In addition, contrast also has a certain effect on the resolution conversion of dynamic video. High contrast makes it easier for the naked eye to distinguish the light and shade conversion process in the motion picture.
Refresh rate
The number of times the content of an LED display can be displayed repeatedly per second is called the refresh frequency. When the refresh frequency is low, the flicker of the image will appear, especially in the process of video shooting. Therefore, the refresh frequency must be maximized to ensure the stability of the display screen.
Classification of key technology
Image acquisition
The LED image display uses the electronic luminescence system to display the results of image conversion of digital signals. The special video card JMC-LED emerges at the right moment. Based on the PCI bus using a 64-bit graphics accelerator, it forms unified compatibility with VGA and video functions, which makes video data superposition VGA data to perfect the shortcomings of compatibility.
The full screen method is used to collect the resolution so that the video image can realize the full Angle resolution to strengthen the resolution effect, eliminate the problem of edge blurring, and can be zoomed and moved at any time, to different playback requirements in can timely response. Effective separation of red, green and blue colors, enhance the electronic display of the true color imaging effect.
Real image color reproduction
In general, the combination of red, green, and blue colors should meet the light-sensitivity intensity ratio tending to 3:6:1; Red is more sensitive to imaging, so it must be evenly distributed in the spatial display. Because the three colors of light intensity are different, people’s visual experience in the resolution of the nonlinear curve is also different, so different light intensities benefit white light, and correct the light inside the television; Color resolution varies due to individual differences and environmental differences, so color reproduction should be performed according to certain objective indicators, such as:
- Position the basic wavelengths of red light at 660nm, green light at 525nm, and blue light at 470nm.
- According to the actual situation of light intensity, 4 tubes or more white light units are used for matching.
- The gray level is 256.
- LED pixels must be handled with non-linear calibration. The hardware system and the player system software can be used to control the three primary color piping.
Brightness control D/T conversion
The luminescence of the pixel is controlled by the controller to promote its drive independence. When rendering color video, it is necessary to effectively control the brightness and color of each pixel, and make the scanning operation complete synchronously within the specified time. But large LED electronic displays have tens of thousands of pixels, which adds to the complexity of control and the difficulty of transmitting data.
However, it is unrealistic to use D/A to control each pixel point in practical work. At this time, A new control scheme is needed to meet the complex requirements of the pixel system. Based on the analysis of the vision principle, the ratio of pixels’ brightness to their brightness is the main basis for people to analyze the average brightness, and effective adjustment of this ratio can achieve effective control of pixel brightness. When this principle is applied to an LED electronic display screen, a digital signal can be converted to a time signal, and an effective conversion between D/A can be realized.
Data refactoring and storage
At present, the combination pixel method and level pixel method are common memory combination methods. The center plane method has more obvious advantages and effectively improves the best display effect of LED screens.
Through the bit plane data, the circuit is reconstructed, the RGB data is converted, the different pixels in the same weight bit are combined organically, and the adjacent storage structure is used for data storage.
ISP in logic circuit design
With the emergence of System Programmable Technology (ISP), users can repeatedly fix the deficiencies in the design and design goals, systems, or circuit boards by themselves, which realizes the designer application function of software integration. At this time, the combination of digital systems and system-programmable technology brings new application effects.
The introduction and use of new technology can effectively shorten the design time, expand the limited use of components, simplify on-site maintenance, and facilitate the realization of target equipment functions.
When the system software input logic, the influence of the selected device can be ignored, and the input element can be selected at will, or the virtual element can be selected for adaptation after the completion of input.
Notes Editing
1. Switch sequence:
Screen opening: Power on first, then screen opening.
Screen off: Screen off first, then power off.
(first, turning off the computer without the display screen, will cause the screen body appears high bright spot, and LED to burn the lamp tube, the consequences are serious.)
2. switch screen time interval should be greater than 5 minutes.
3. After the computer enters the engineering control software, it can turn on the screen and power.
4. Avoid opening the screen under the all-white screen state, because the impact current of the system is the largest at this time.
5. Avoid opening the screen in the out-of-control state, because the impact current of the system is the largest at this time.
6. the electronic display body part appears a line that is very bright, should pay attention to turn off the screen in time, in this state should not be a long time.
7. often appear the display power switch trip, should be timely check the screen or replace the power switch.
8. Check the firmness of the connection regularly. If there is a loosening phenomenon, pay attention to timely adjustment, re-reinforce or update the hanging parts.
9. When the ambient temperature is too high or the heat dissipation condition is not good, the LED lighting should be paid attention not to open the screen for a long time.
