LED is how to realize the display function

23 May

What is a led strip lights?

In some semiconductor materials PN junction, injection of minority carriers and majority carrier composite, they’ll put extra energy to light form released, and thus the energy directly convert light energy. PN junction and reverse voltage, minority carriers to infuse, it does not shine. This kind of make use of the basic principle of electroluminescent made diodes that light emitting diode, films LED.

The emitting light colors and LED the luminous efficiency and production of materials and the process LED, is now widely used there are red, green, blue three. Because LED lower voltages (only 1.5 3 V), can have certain brightness and active luminous, brightness and can voltage (or current) regulation, and its resistance, impact resistance, vibration, long service life (100000 hours), so in large display device, at present there is no other way showing the way and LED display on top.

The red and green LED Light Bars put together as a pixel display called double color screen made of or color screen; Red, green, blue three LED tube put together as a pixel display that three color screen or a full color. Make indoor the LED screen size is usually the pixels 2-10 mm, often use several can produce different gezer LED the core package as a body, outdoor LED screen size of pixels for 12-more than 26 mm, each pixel consists of several a all kinds of monochromatic LED, common finished product says pixel tube, double color pixel tube is general by three red 2 green composition, three color pixel in 2 red cone of aram 1 1 green.

No matter use LED production monochrome, double color or three color screen to display images of each pixel to constitute the brightness LED light must can adjust and the control of delicate degree of gray level is display screen. Gray level, the high, show the picture more exquisite, colour is also more rich, the corresponding display and control system is also more complicated. General level 256 shades of the image, color transition already was very gentle, and 16 of gray level color image, color transition boundary is very clear. So, color LED the current requirements are made of gray level 256.

Second, the method of control LED luminance:

There are two methods of control flexible led strip. One is to change the current flows through LED, in general, the continuous working current allowed LED in 20 ma or so, besides red LED a saturation outside, other LED brightness and flow of current basically in proportion; Another method is to use the human visual inert, with pulse width modulation method to realize the gray control, also is cyclical change a light pulse width (i.e. occupies emptiescompared), as long as the repeat the light cycle short enough (i.e. refresh frequency is high enough), the human eye is not feel light pixels in the wobble. Due to the pulse width modulation is more suitable for digital control, so in the widespread use of the microcomputer to provide LED display content today, almost all the LED screen are using pulse width modulation to control the gray level.

LED by the control system usually main control box, scanning board and display control device composed of three. Master control box from the computer graphics CARDS in get a screen pixel all kinds of brightness data, then re-assigned to some piece of scanning board, each scan board is responsible for control of the LED screen on several row (column), and each row (column) LED display control signal is the way with serial transmission. There are two serial transmission display and control signals by means of: one kind is scanning board centralized control each pixel gray, scanning the board will come from control box in all the pixel luminance values decomposition (i.e. pulse width modulation), and then will all LED the opening of the signal to pulse form (light is 1, not bright 0) in line with serial mode to the corresponding LED, control whether the light. This way, using device less, but large quantities of serial data, because in a repeat of the light cycle, each pixel in 16 level gray to 16 pulse, and in the 256 level under 256 pulses to gray, because the devices work frequency restriction, general can only make the LED screen do 16 level gray.

Another method is the content of the serial transmission scanning board not every LED the switch of the signal but a 8 bit binary brightness values. Each LED all have a his pulse width omdulatros to control the light of time. So, in a repeat of the light cycle, each pixel gray level in 16 under four pulses only need to level 256 under a pulse 8 gray only, and greatly reduce the frequency of serial transmission. In this distributed control LED the method of gray can be easily realized gray control level 256.


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