In the LED display industry called the gray can also be called LED brightness. Also known as a halftone gradation, mainly used to transmit images, pictures, screen, respectively, 16, 32, 64 in three ways, which uses a matrix approach to the pixels of the file handle 16,32,64 grade level so that the transmission of the picture sharper. Whether it is full color, or color screen, to display images or animations are required for each pixel LED light gray constitute adjust, the adjustment of sophistication is what we usually refer to the shades of gray.
Get a screen pixel control box from the computer's graphics card in each color luminance data, and then reassigned to the number of pieces of scanning plate, each scan board responsible for controlling the number of lines (columns) LED screen, and each row (column) the LED display and control signals are transmitted by serial fashion.
There are two serial transmission control signal display mode:
A pulse width modulation. Content scanning board serial transmission is not every LED switching signal but an 8-bit binary gray value. Each LED has its own pulse width modulator to control the lighting time. Thus, in a repeating cycle of light, each pixel in the 16-level gray scale needs only four pulses, only eight pulses of 256 gray scale, greatly decreasing the serial transmission frequency. This method of distributed control with LED gradation can easily achieve 256 gray scale control.
Second, the scan board centralized control of each pixel grayscale scanning plate from the control box for each gray value pixel rows decomposition (i.e. pulse width modulation), and then the opening of each row LED signals in pulses (lit 1, off = 0) by serial transmission line to the corresponding LED on, control it is lit. This approach uses fewer components, but the large amount of data serial transfer, because in a repeating cycle of light, each pixel requires 16 pulses at 16 gradation, 256 gradation required in 256 pulse, because the device operating frequency limit, generally only the LED screen to achieve 16 gray levels.
There are two control LED grayscale method:
A changing current flowing.
Second, the pulse width modulation:
1) Change the current flowing through the LED. General LED tube allows continuous operating current of about 20 mA, in addition to the red LED has saturation, the other LED gray substantially proportional to the current flowing through;
2) the use of the human visual inertia with a pulse width modulation method to achieve gray scale control, that is, periodic changes in light pulse width (duty ratio), as long as the repeated cycle of light short enough (that is, the refresh rate is high enough ), the human eye can not feel light-emitting pixels in the jitter. Since the pulse width modulation is more suitable for digital control.
So in general the use of computer to provide LED display today, almost all the LED screens are controlled using pulse width modulation gradation. LED control system typically consists of three parts, the main control box, scanning plate and display and control device.