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LED definition
In some PN junctions of semiconductor materials, the injected minority carriers recombine with the majority carriers to release excess energy in the form of light, thereby directly converting electrical energy into light energy. The PN junction adds a reverse voltage, and minority carriers are difficult to inject, so they do not emit light. The diode produced by the principle of injection electroluminescence is called a light-emitting diode, referred to as LED.
The color and luminous efficiency of LEDs are related to the materials and processes for making LEDs. Currently, red, green and blue are widely used. Due to the low operating voltage of the LED (only 1.5-3V), it can actively emit light and have a certain brightness. The brightness can be adjusted by voltage (or current), and it is resistant to shock, vibration and long life (100,000 hours), so it is large. Among the display devices, there is currently no other display mode that rivals the LED display mode.
A display made of red and green LEDs together as a pixel is called a two-color screen or a color screen; a display screen that puts three LED tubes of red, green, and blue together as a pixel is called a three-color screen or a full screen. Color screen.
Regardless of whether a single-color, two-color or three-color screen is made with LEDs, the brightness of each LED that is required to form a pixel to be displayed must be adjusted, and the degree of fineness of the adjustment is the gray level of the display. The higher the gray level, the finer the displayed image and the richer the color, and the more complex the corresponding display control system. Generally, the image of 256-level gray scale has a very soft color transition, while the color image of 16-level gray scale has a clear color transition boundary. Therefore, color LED screens are currently required to be 256-level grayscale.
LED display works
LED electronic display is a high-tech product integrating optoelectronics and computer technology.
Performance characteristics of LED products
The text LED display and the graphic LED display shall have the move in and out mode and display mode specified in the detailed specification.
The computer video LED display should have: an animation function. It is required that the LED display animation display is consistent with the area corresponding to the computer display; the text display function. Requires text to display stable, clear crosstalk; grayscale function. It is required to have the grade gray scale specified in the detailed specification. In addition to animation, text display, and grayscale functions, TV video LED displays should be able to display TV and video images. The market LED display has the corresponding market display capability.
How to classify LED display
LED displays can be classified according to the following conditions:
? Use environment LED display is divided into indoor LED display and outdoor LED display according to the use environment.
Display color LED display is divided into single primary color LED display (including pseudo color LED display), dual primary color LED display and full color (three primary color) LED display. According to the gray level, it can be divided into 16, 32, 64, 128, 256 gray LED display.
Display performance LED display is divided into text LED display, graphic LED display, computer video LED display, TV video LED display and market LED display according to display performance. The market LED display generally includes LED displays for securities, interest rates, futures, and the like.
? Basic light-emitting point non-line type LED display, indoor LED display can be divided into Φ3mm, Φ375mm, Φ5mm, Φ8mm, and Φ10mm display according to the single-point diameter of LED; outdoor LED display adopts pixel diameter Can be divided into Φ19mm, Φ22mm and Φmm26 LED display. In the market type LED display, the size of the digital tube can be divided into 2.0cm (0.8inch), 2.5cm (1.0inch), 3.0cm (1.2inch), 4.6cmm (1.8inch), 5.8cm (2.3inch), 7.6. LED display such as cm (3 inch).
How to evaluate the quality of LED screen?
The out-of-control point of the indoor LED display of the out-of-control point is not more than three-tenths of a percent, and the out-of-control point of the outdoor LED display should be no more than three thousandths, and it is discrete and strong;
Consistent LED screen consistency is better, the brightness of the whole screen should be balanced, no obvious color blocks;
Safety: no safety hazards, leakage current, ground leakage current should not exceed 3.5mA (AC RMS); anti-point strength, LED display can be 50Hz, 1500V (AC RMS) test voltage Lmin should not cause insulation breakdown At the same time, the LED display should have a warning sign at the fuse and switching power supply;
? Appearance, the LED display frame has no obvious scratches. The outdoor LED display pixel tube should be installed consistently, without looseness and cracked casing;
? Structure, LED display parts can be made of steel, aluminum, wood and other materials, requiring a strong structure and beautiful appearance.
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