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Views: 234 Author: Kelai Publish Time: 2024-08-16 Origin: Site
Content Menu
● 1.Overall analysis of LED display control system
● 2.Analysis and Design of Computer Software Modules
● 3.Control Technology of LED Display Screen
>> 3.1 Energy saving and consumption reducing technologies
>> 3.2 Single point detection technology
>> 3.3 Single point brightness and chromaticity correction technology
LED display control system, also known as LED display controller or LED display control card. It is the core component of LED display screens, mainly responsible for receiving image and video display information from computer serial ports or DVI interfaces, storing it in frame memory, and generating serial display data and scanning control timing that can be recognized by LED display screens according to partition driving methods.
By analyzing the dot matrix module and control circuit, determine the component composition of the LED display screen; By analyzing the microcontroller and intelligent control module, the composition structure and scanning drive mode of the LED display screen are determined to achieve the display of the LED display screen.
Based on the application of LED display control system, the architecture and workflow of LED graphic display screen have been designed. The software system and the wireless transmission control hardware main system use serial communication to download programs and transmit text information.
The LED display system consists of software control system, wireless transmission system, equipment main controller, LED display dot matrix, power supply and other parts. The basic structure is shown in the following figure:
System working process: The main tasks completed by the software control system are graphic and text editing, font extraction and saving, image preview, and file transfer; The wireless transmission system mainly completes the transmission of file information from the PC to the LED display. In the hardware control system, the main task of the LED dot matrix is to display information through current control, and to drive the rows and columns of the LED dot matrix through the scanning and driving mode of the microcontroller, realizing the driving of the device and ultimately achieving the function of receiving graphic and text display.
The software module is divided into an editing part and a control communication part. The editing part implements the editing function of graphic and textual files, while the communication part completes the transfer of files to the microcontroller storage module through RS-232C serial communication. The communication section will be introduced in detail in Chapter 3. The system design adopts the Windows operating system, opens the text editing window, and the pixel points in the customer area are the same as those of the actual LED dot matrix display screen, with functions similar to Word document editing tools, including editing module, drawing module, text editing module, color control module, display effect loading module, preview module, and information download module.
1) In addition to the self generated cutting, copying, and pasting functions of Windows, the system has added undo and duplicate functions.
first. Selecting the undo function allows for step-by-step cancellation of previous editing work. Then, selecting the duplicate function can implement the most recent operation command of the previous editing work.
2) Drawing: graphic drawing functions including lines, rectangles, ellipses, circles, etc.
3) Text editing: including editing of various fonts, glyph shapes, font sizes, effects, and colors of text, and adding editing of specified position text according to the special purpose of the application.
Firstly, select the text function and a font selection box will pop up, allowing you to choose various fonts of text for editing. Then, the specific text position editing dialog box will be called up, and the text and the abscissa and ordinate of the required display position will be entered.
4) Color control module: Due to the specific characteristics of the application field, it mainly uses three colors: red, green, and yellow, which can achieve color control.
By adding display effects and transferring files from multiple screens to a single screen in communication, the control system's functionality has been improved.
1) Normal effect, static display of information on the screen.
2) The scrolling effect can achieve left to right information scrolling display and can be interspersed with static information display.
3) Single screen information transmission enables the saving of edited information to be transmitted.
4) Multi screen information transmission enables the merging and saving of pre edited single screen information into a single file, greatly reducing the tedious process of transferring files.
Implement the preview function of font information before file transfer, which can preview any form of font information saved before transfer and directly integrate it into the toolbar file open function button.
1) The display effect can be adjusted in the order of static and scrolling display effects through preview before file transfer.
2) Display time, showing the time interval between different screens displaying information.
With the development and implementation of the fifth generation "array style" control system, the birth of this generation of control system has further enhanced the technological advantages of Yuanheng Optoelectronics in screen control and improved the processing technology of display signals. After adopting the "array style" control system.
Firstly, the frame switching frequency of the display screen can be increased from around 60Hz to over 120Hz, far exceeding the human eye's resolution ability, so that there is no flicker or water ripple phenomenon when watching, improving the quality of the display.
Secondly, the grayscale levels of the red, green, and blue primary colors on the display screen can be increased from the current 256 levels to 1024 levels, making the colors more vivid, the color reproduction better, and the displayed image more realistic.
Finally, LDVS signal is used for transmission, which maximizes the avoidance of signal loss, synchronizes the display content of the entire screen, and improves the consistency of the screen. There is no color difference or color block appearing on the entire screen.
Due to the use of an array control system, it can effectively reduce the loss of display screen brightness caused by the control system used to generate grayscale. According to comparative calculations, the system loss of traditional "centralized control systems" is between 30% and 40%, while the system loss of "array control systems" is between 8% and 10%. The reduction of control system loss is conducive to improving the brightness of the display screen or reducing the current of the display screen under the same brightness conditions, thereby achieving energy-saving and consumption reducing effects. Centralized control system, due to its large control range, has to reduce the scanning frequency and brightness to form grayscale in order to maintain a certain refresh rate; Due to the small control range of the array control system, the scanning frequency can be greatly increased, and the brightness loss will be reduced accordingly. The scanning frequency of the array system can reach more than 136 fields, while the centralized system can reach a maximum of 42 fields.
According to the principle of brightness loss, the calculation table comparison is as follows: a 200 square meter outdoor full-color display screen with a specification of 3906 points per square meter, if a driving current of 20mA is used, the theoretical maximum brightness can reach 15000cd/m2. If a maximum actual brightness of 6000cd/m2 is to be achieved, using a "centralized control system", with a system loss of 30%, the driving current of the display screen is 11.4mA/pixel, and the maximum power supply current is 607A; If an "array control system" is used to achieve a maximum actual brightness of 6000cd/m2, with a system loss of 10%, the display screen drive current is 8.89mA/pixel, the maximum current is 474A, and the energy saving rate reaches 21.9%. Calculated based on an average power consumption of 40% of the maximum power consumption, with a usage time of 10 hours per day and 300 days per year, using a "centralized control system" results in an annual power consumption of 160248 kWh. By adopting an "array control system", the annual power consumption is 125136 kWh, saving approximately 35112 yuan/year in expenses (calculated at 1.0 yuan/kWh)
To improve the reliability of the screen and increase maintenance convenience, Yuanheng Optoelectronics has developed a single point detection technology for display screens. Usually, the detection of LED pixels before leaving the factory for LED display screens is done through visual inspection (i.e. whether the human eye observes whether it emits light according to the debugging program). When watching LED pixels for a long time, it is inevitable to have some visual fatigue, missed or misjudged, and its work efficiency is not high. Now our company uses the single point detection function on the screen, which only requires running the corresponding program to determine the working status of pixels and carry out repairs, greatly improving the reliability of the screen. Meanwhile, with the continuous development of LED display technology, the market for ultra large LED screens has emerged. This type of screen is generally installed at a higher position and has a longer viewing distance, which brings inconvenience to the detection work of the display screen. The judgment of each pixel point can often only be based on human judgment. After using the single point detection function, maintenance personnel can easily find the coordinates of the fault point and replace it quickly.
The issue of brightness and chromaticity uniformity in LED display screens has always been a major challenge for industry professionals. It is generally believed that uneven brightness in LEDs can be improved through single point correction, while chromaticity unevenness cannot be corrected and can only be improved by subdividing and filtering the LED color coordinates. With the increasing demand for LED display screens, only subdividing and filtering the color coordinates of LEDs is no longer sufficient to meet people's discerning eyes. It is feasible to comprehensively calibrate the display screen to improve chromaticity uniformity. Firstly, due to the differences in the LED itself, the brightness and chromaticity are not consistent at a certain level (for example, if two green LEDs from the same production batch are lit with the same current, the brightness may vary by 30% and the wavelength may vary by 10-15 nm). Secondly, after a period of use, the blue LED darkens the most, while the red LED darkens the least. However, the biggest problem is that the degree of dimming of the LED varies after a period of time. Therefore, even if the consistency of the LED screen is very perfect in the factory, as the LED becomes darker, the consistency will be lost, and after three years of continuous use, the inconsistency of the LED screen will be significantly discovered.
In terms of display technology, LCD is a display screen composed of liquid crystals, while LED is a display screen composed of light-emitting diodes. Each pixel unit in LED digital display is a light-emitting diode, and monochrome LED display screens are generally red light-emitting diodes.
The overall design of the LED display software control system has determined the system's workflow and completed the system software control function. According to the specific communication requirements of the equipment, serial communication technology is adopted. By introducing the relevant knowledge of port communication and serial communication protocol, the communication between the control system and hardware devices is achieved, and the text information transmission function of the LED display screen is realized. The technical control of LED display screens is an important guarantee for determining the quality of products.
