Big science LED display function

Due to the light color of LED and LED luminous efficiency and production materials and related technology, widely used at present have red, green, blue three kinds. Because of the low voltage LED work ( Only 1. 5 - 3V) Brightness, can take the initiative to light and to a certain extent, brightness and in voltage ( Or current) Adjust, itself and impact resistance, resistance to vibration, long life, 100000 hours) , so in the large display devices, there is no other way of display and LED display.

the red and green leds together as a screen name is double color LED display pixel make or color LED display; The red, green, blue three kinds of LED tube together as a pixel or full color screen display name is three color screen. Production of indoor LED screen pixel size is generally 2 - 10 mm, often using several can produce different colors of LED tube core is encapsulated into a whole, the pixel size of the outdoor LED screen is 12 - more 26 mm, each pixel is made up of several kinds of monochrome leds, common product according to pixel tube, double color pixel tube usually consists of three red 2 green, three color pixels of tube in 2 red 1 green and 1 blue.

no matter made of LED monochrome, double color or 3 color screen, need to display the image pixels of each LED luminous intensity must be able to adjust, the adjustment of fine degree is the grayscale display, etc. Gray-scale order is higher, such as display image is more delicate, more colorful, the corresponding display control system are more complex. General order 256 gray-scale image, color transition is very soft, and 16 order gray color image, color transition boundary obviously. Color LED screen, therefore, the current required to make more than 256 order gray-scale.

there are two ways to control the LED brightness. Current through the LED is a kind of change, general LED tube allows continuous working current is controlled in 20 milliampere, besides red leds have saturation phenomenon, other LED brightness basically proportional to the flow of electric current; Another method is to use human eye visual inertia, using pulse width modulation method to realize gray-scale control, light pulse width (cyclical change The duty ratio) Cycle is short enough, as long as the repeated light ( The refresh rate is high enough) , the human eye is feeling less than glowing pixels in jitter. Due to the pulse width modulation is more suitable for digital control, so widely used in computers to provide LED display content today, almost all of the LED screen is use the order such as pulse width modulation to control the gray scale.

the LED control system generally consists of main control box, scanning board and display control device is composed of three parts. Main box from a variety of computer display card to get a screen pixel brightness information, and then reassigned to a number of scanning board, scanning each one is responsible for the control of the LED screen lines, Column) While each line ( Column) On the LED display control signal is transmitted by serial. There are two serial display control signals via a scanning board is centralized control of each pixel gray-scale, scanning board will come from the control box of the brightness values of all pixels decomposition ( The pulse width modulation) And then all LED the opening of the signal in the form of pulse ( Light is 1, not bright 0) In line with serial transmission to the corresponding LED on, control whether the light. This way using the device is less, serial transmission data amount is larger, but because in a repeated cycle of light, each pixel in the 16th order under the gray-scale need 16 pulse, under the order 256 gray-scale need 256 pulse, because the device operating frequency restricted, generally can only make the LED screen do 16 gray-scale.

another method is to scan the content of the plate serial transmission instead of each LED switch signals an 8 bit binary brightness values. Each LED has an own pulse width modulator to control the light time. Thus, in a repetitive cycle of light, each pixel in the 16th order gray-scale just under four pulse, just under 256 gray-scale eight pulse, greatly reduces the frequency of serial transmission. With this kind of decentralized control LED gray-scale method can be easily implemented 256 gray-scale control.

LED screen mesh