Design options and common problems of full-color LED large screens

1. Screen size design When designing the screen size, there are three important factors:
(1) the need for display content;
(2) the site space conditions;
(3) the screen unit template size (indoor screen) or pixel size (outdoor screen).

2. Power consumption and power supply requirements
The power consumption of the display screen is divided into average power consumption and maximum power consumption. Average power consumption is also called working power consumption, which is the actual power consumption in normal times. Maximum power consumption is the power consumption in extreme situations such as startup or full brightness. Maximum power consumption is a factor that must be considered for AC power supply (wire diameter, switch, etc.). Average power consumption is generally 1/3 of the maximum power consumption.

The display screen is a large precision electronic device. For safe use and reliable operation, its AC220V power input terminal or the AC220V power input terminal of the computer connected to it must be grounded.
Note: The AC220V power input ground terminal of the computer is already connected to the computer case.

3. Issues to be considered for outdoor screens
The main issues for outdoor screens are as follows:
(1) The display screen is installed outdoors, often exposed to the sun and rain, and covered with dust by wind, and the working environment is harsh. Electronic equipment that is wet or severely damp can cause short circuits or even fire, leading to failures or even fires, causing losses;
(2) The display screen may be attacked by strong electricity and strong magnetism caused by lightning;
(3) The ambient temperature changes greatly. The display screen itself generates a certain amount of heat when working. If the ambient temperature is too high and the heat dissipation is poor, the integrated circuit may not work properly or even be burned, making the display system unable to work properly;
(4) The audience is wide, the viewing distance and the field of view are required to be long; the ambient light changes greatly, especially it may be exposed to direct sunlight.
In view of the above special requirements, outdoor display screens must meet the following requirements:
(1) The screen body and the joints between the screen body and the building must be strictly waterproof and leakproof; the screen body must have good drainage measures so that water can be discharged smoothly in case of accumulation;
(2) Lightning protection devices should be installed on the display screen and the building. The display screen body and shell should be well grounded, with a grounding resistance of less than 3 ohms, so that the large current caused by lightning can be discharged in time;
(3) Ventilation equipment should be installed to cool down the screen body, so that the internal temperature of the screen body is between -10℃ and 40℃. An axial flow fan is installed on the upper back of the screen body to discharge heat;
(4) Industrial-grade integrated circuit chips with an operating temperature between -40℃ and 80℃ should be selected to prevent the display screen from being unable to start due to low temperatures in winter;
(5) In order to ensure long-distance visibility under strong ambient light, ultra-high brightness light-emitting diodes must be selected;
(6) The display medium uses a new wide-angle tube with a wide viewing angle, pure color, consistent coordination, and a lifespan of more than 100,000 hours. The outer package of the display medium is the most popular square cylinder with a shielding edge, silicone sealing, and non-metallic assembly; its appearance is exquisite and beautiful, sturdy and durable, and has the "five protection" characteristics of anti-direct sunlight, dustproof, waterproof, high temperature, and circuit short circuit.

FAQ

1. What are the factors that should be considered when considering the screen area that can be allowed in the user's site?
(1) The relationship between effective viewing distance and actual site size;
(2) Pixel size and resolution;
(3) Area estimation based on units;
(4) Screen mechanical installation and maintenance operation space;
(5) The impact of screen inclination on distance.

2 What playback effects do users need?
(1) Text display: depends on the text size and resolution requirements;
(2) Ordinary video display: 320×240 dots;
(3) Digital standard DVD display: ≥640×480 dots;
(4) Complete computer video: ≥800×600 dots;

3. What are the brightness requirements for the screen in terms of ambient brightness?
The general brightness requirements are as follows:
(1) Indoor: >800CD/M2
(2) Semi-indoor: >2000CD/M2
(3) Outdoor (facing south): >4000CD/M2
(4) Outdoor (facing north): >8000CD/M2

4. What are the brightness requirements for red, green and blue in the composition of white?
Red, green and blue contribute differently to the color of white. The fundamental reason is that the retina of the human eye has different perceptions of light of different wavelengths. After a lot of experimental tests, the following approximate ratios are obtained for reference design:
Simple red, green and blue brightness ratio is: 3:6:1vGD-
Precise red, green and blue brightness ratio is: 3.0:5.9:1.1

5. Why do high-end full-color displays use pure green tubes?
In actual LED display production, three-primary color tubes with high luminous efficiency and rich and bright colors should be selected to make the color triangle area in the chromaticity diagram as close to the tongue-shaped color spectrum curve as possible to meet the requirements of rich colors and sufficient brightness. The top of the tongue-shaped curve is 515nm wavelength light, so high-end LED displays use pure green LED tubes with a wavelength close to 515nm, such as 520nm, 525nm or 530nm wavelength LED tubes.

6. Under the conditions of clear brightness and dot density requirements, how to calculate the brightness of a single tube?
The calculation method is as follows: (Take two red, one green and one blue as an example)
Red LED brightness: brightness (CD) / M2 ÷ number of dots / M2 × 0.3
÷ 2 Green LED brightness: brightness (CD) / M2 ÷ number of dots / M2 × 0.6
Blue LED brightness: brightness (CD) / M2 ÷ number of dots / M2 × 0.1
For example: 2500 dots per square meter, 2R1G1B, brightness requirement per square meter is 5000 CD/M2, then:
Red LED brightness: 5000÷2500×0.3÷2=0.3
Green LED brightness: 5000÷2500×0.6÷2=1.2
Blue LED brightness: 5000÷2500×0.1=0.2
Brightness of each pixel: 0.3×2+1.2+0.2=2.0 CD

7. Why choose the DVI display interface standard?
(1) The DVI display card interface is a display interface that complies with international computer standards;
(2) It can be easily installed without opening the computer case;
(3) It has a large video memory and strong dynamic image display capabilities;
(4) It has strong software and hardware compatibility;
(5) It supports all operating systems and application software, and has flexible and convenient display;
(6) It can be mass-produced, low cost, and easy to maintain.

8. Can the display be controlled by a laptop? Why
? No. The graphics card of the laptop is built-in and cannot be connected to the control system. Currently, BOE has a laptop with a DVI interface that can be controlled by the laptop.

9. What are the differences between using Nichia tubes and domestic tubes for full-color screens, except for the price?
(1) Tube core: Nichia produces its own tube core, while domestic tubes generally use tube cores from American or Taiwanese companies;
(2) Packaging: Nichia produces its own packaging, and there is no production factory in China. There are many domestic tube packaging manufacturers;
(3) Consistency: The wavelength difference of Nichia tubes in the same batch is small, and the consistency is good, while the consistency of domestic tubes is relatively poor;
(4) Service life: Nichia tubes have a relatively long service life, while domestic tubes have more serious attenuation;

10. What is the difference between indoor full-color modular screens and full-color SMD screens?
(1) Luminous part: The display module of the full-color modular screen is generally yellow-green, and the pure green module is more expensive; the full-color SMD screen generally uses a pure green tube core;
(2) Display effect: The pixel points of the full-color modular screen are visually coarse, the brightness is low, and it is easy to have mosaic phenomenon; the full-color SMD screen has better consistency and higher brightness;
(3) Maintenance: The full-color modular screen is not easy to maintain, and the cost of replacing the entire module is high; the full-color SMD screen is easy to maintain, and single lamps can be repaired and replaced;

11. Can surface mount LEDs be used for outdoor screens? Why
? No. Outdoor screens have strict requirements for installation structure, and surface mount LEDs cannot adapt to the harsh outdoor environment;
outdoor screens have high brightness requirements, and surface mount LEDs cannot meet the brightness requirements of outdoor screens at present.

12. Why is the production cycle of outdoor screens so long?
(1) Raw material procurement: The procurement cycle of LED tubes is relatively long, especially for imported tube cores, which require an order cycle of 4-6 weeks;
(2) Complex production process: PCB design, cover production, glue filling, white balance adjustment, etc. are required;
(3) Strict structural requirements: Generally, it is a box design, which needs to consider wind, rain, lightning protection, etc.

13. How to help users choose the right display screen?
(1) Display content needs;
(2) Confirmation of viewing distance and viewing angle;
(3) Screen resolution requirements;
(4) Installation environment requirements;
(5) Cost control;

14. What is the general aspect ratio of a display screen?
Graphic screen: Determined by the displayed content;
Video screen: Generally 4:3 or close to 4:3; The ideal ratio is 16:9.

15. How many points can a control system control?
Communication screen A card: monochrome, two-color 1024×64
Communication screen B card: monochrome: 896×512 two-color: 896×256
two-color screen: 1280×768
full-color screen: 1024×512

16. What are the installation requirements for the display screen?
Power supply requirements: The power supply connection point should be within the size of the screen. 220V mains power supply, live wire and 0 wire ground wire; 380V mains power supply, three live wires and one 0 wire ground wire; the cross-sectional area of ​​the live wire and 0 wire is the same;

display screens above 10 kilowatts should be equipped with a step-down starting device.
Communication requirements: The communication distance is defined by the length of the communication line.
The communication line should be installed according to the communication line length standard used for the model of the installed display screen.
The communication line is prohibited from running in the same wire tube as the power line.
Installation requirements: The display screen should be installed horizontally from left to right, and backward tilting is not allowed. Up and down adjustment rods should be installed for hoisting. Forward tilting drop hooks should be installed before wall-mounted installation. Positioning support bolts should be added for ground-mounted installation.