Two ways of controlling LED gray level led wall

Led gray can also be called led chroma. Gray level, also known as half tone, is used to transmit photos of the led video wall. There are three methods, 16, 32 and 64, respectively. The drainage matrix processing method is used to solve the definition of documents into 16, 32 and 64 levels to make the photos clearer. Whether it is a solid color, two-color, three-color screen, in order to display information images or animation, it is necessary to adjust the brightness of each LED that is composed of pixels. The level of adjustment is commonly referred to as the gray level.

There are two ways to control LED gray: one is to change the current through, the other is to adjust the pulse width.
1. Change the amount of current passing through the LED. Generally, the current flow of LED tube is about 20 MAH during continuous operation. Except for the saturation state of bright red LED, the gray level of other LED is mostly proportional to the current passing through;

2. Using the plasticity of the visual effect of human eyes, using pulse width modulation to complete gray level control, that is, regularly changing the light pulse width (i.e., the swing rate). If the cycle time of this repeated lighting is short enough (i.e., the screen refresh rate is sufficiently high), the human eye can not feel the bright pixels are trembling. Because the pulse width modulation is more suitable for data control, today, when microcomputers are widely used to show the information content of LED display, basically all LED screens use pulse width modulation to control the gray level. The control system software of
LED is generally composed of main control chip box, scanner board and display and control equipment. The
main control chip box obtains the chromaticity data information of a screen pixel from the display terminal of the electronic computer, and then distributes it to several scanner boards. Each scanner board controls multiple rows (columns) on the LED screen, and the display and control data signals of each row (column) are transmitted by serial communication.
at present, there are two methods of serial communication to transmit display information control data signal:
1. One is the centralized control of the gray level of each pixel on the scanner board. The scanner board dissolves the gray value of each big bank pixel from the control box (i.e. pulse width modulation), and then transmits the enabling data signal of each bank led to the corresponding LED in a single pulse mode (lit as 1, not lit as 0) by serial communication method to control whether it is on or not. There are few components used in this method, but the amount of information transmitted by serial communication is very large. In a period of repeated lighting, each pixel must have 16 monopulses at 16 levels of gray level, and 256 monopulses at 256 levels of gray level. Because the output power of components is limited, the LED screen can only guarantee 16 levels of gray. One is pulse width adjustment. The content of scanner board serial communication is not the power switch data signal of each LED, but an eight bit gray value. Each LED has its own pulse width modulator to control the lighting time. In this way, in a cycle time of repeated lighting, each pixel only needs 4 monopulses at 16 levels of gray level, and only 8 monopulses at 256 gray levels, which greatly reduces the transmission frequency of serial communication. The 256 level gray level control can be easily completed by using this kind of decentralized control method.

WhatsApp WhatsApp us