Many high-rise buildings in the city are glass curtain wall structures. This is a good outdoor advertising carrier. Through the LED transparent screen technology, the building has become a three-dimensional optical advertising carrier, which has become popular at home and abroad in recent years.
When designing the screen, the glass curtain wall LED display should consider the important factors such as display content, space conditions, screen size, pixel, etc. At the same time, it is necessary to ensure that the production process and technical indicators are suitable for the actual application requirements of the glass curtain wall, and then combined with the project cost. Reasonable design.
First, the point spacing
The dot pitch is the distance between the centers of two adjacent LED beads, in mm. Visual graininess mainly comes from the human eye has a certain resolution, watching two points at a certain distance, when the two points are close to a certain degree, the human eye will not be able to distinguish. In the past two years, with the improvement of LED transparent screen manufacturing technology, the resolution of glass curtain wall LED display has been continuously improved. The design of glass curtain wall display has been upgraded from the initial selection of * small dot pitch specification scheme to the selection of suitable dot pitch specification scheme.
So how do you choose the right point size specification?
1. The dot pitch is an important basis for the LED curtain wall screen model, and also determines the final display effect of the screen*. The smaller the model size, the smaller the dot pitch and the higher the pixel density, the more suitable for HD content playback.
2. Point spacing and permeability are the dilemmas. The smaller the dot spacing, the lower the permeability. This is because the smaller the dot pitch is, the higher the pixel density is. The LED lamp bead is arranged more per unit area, which will inevitably lose part of the permeability, and the high passthrough rate is just *the LED transparent screen* has the advantage, and the improvement The cost of permeability* is the expansion of the dot pitch, which affects the sharpness and display of its picture.
3. The viewing distance is an important basis for selecting the model. The farther the viewing distance is, the larger the screen area is, which is suitable for selecting large models; the closer the viewing distance is, the smaller the screen area is, and the small model products are selected.
However, with the advancement of technology, the dot pitch and the permeability can be further improved to reach a large ideal balance point, such as a permeability of more than 90% and a pixel density of 3 to 6 mm.
Second, packaging technology
One factor that determines LED quality is the main materials, such as cabinet materials, chips, lamp beads, power supplies, etc. Another factor is the packaging process. The pixel packaging technology is related to the color saturation, viewing angle and other display effects of the entire transparent screen, production cost, quality stability, etc. The transparent LED curtain wall packaging technology is mainly for the surface mount SMD mode, and the surface mount refers to the paste of the packaged light-emitting tube. On the circuit board, the integrated circuit soldering process is then processed into a screen body. It has good heat dissipation and uniform color, and the entire screen can be maintained on the front side, which greatly reduces the maintenance cost and difficulty. At the same time, the metal compound is filled in the packaging process, the color mixing effect is good, and the light is soft.
Third, the LED control part
The LED control part is the core part that determines the display effect. The control circuit has a built-in high-performance single-chip micro-control chip. The controller sends control signals and data to the LED driver chip through the internal control program. After receiving the signal, the LED driver chip generates corresponding actions, thereby implementing separate control for each of the red, green and blue LED light-emitting chips.
3.1 drive system
The function of the LED driving part is to receive the color data and drive the LED transparent screen to display the brightness value represented by the data. Generally, there are three ways of constant current, voltage regulation, constant voltage-constant current.
The current output from the constant current drive circuit is constant, and the output DC voltage varies with the load resistance. The entire circuit is not afraid of load short circuit, but the load is completely open. The voltage regulator circuit outputs a fixed voltage, and the output current changes with the increase or decrease of the load. The whole circuit is not afraid of the load being open, but the load is completely short-circuited. The first constant voltage and then constant current mode is an ideal driving circuit. It is necessary to detect the LED current and control the LED voltage, which is beneficial to improve the life of the LED and reduce the power consumption. It is generally used in *LED products.
3.2 Control system
The display effect of the LED depends on the magnitude and time of the current and voltage passing through it, so the control system mainly controls the power output of the LED. At present, the PWM power supply designed by the PWM (pulse modulation) control method has a conversion efficiency of 80% to 90%, and the output voltage or current is very stable, and is a high reliability power supply.
The PWM can control the ratio of the time the LED is turned on and off. By dividing the time scale into several levels, the LED displays a corresponding number of gray levels (grayscale). The product of the gray level of the three primary colors is the number of colors that can be reproduced theoretically on the display screen, generally 256 levels, the number of colors reaches 16.7M, and * can display information of 24-bit true color.
Generally, the frequency of the PWM is greater than 100 Hz, otherwise there will be flashing and scanning lines displayed during viewing. Now the large screen with gray level of 10 digits, the refresh frequency is mostly 800 ~ 1000 Hz, and the refresh rate of transparent screen of LED industry is generally above 1920Hz.
Fourth, display demand
1) Unit modular planning, the whole screen is “without seams”. When playing a video, the image is not cut by the seam and then affects the visual viewing.
2) The color and brightness of the whole screen are highly consistent and uniform, and can be proofread point by point. Thoroughly avoiding chromatic aberration, vignetting, dark edges, and "patching".
3) Because the outdoor light has a large influence, the brightness of the LED curtain wall screen needs to reach 4000 cd/m2 or more. Moreover, it supports intelligent conditioning brightness, which can be changed according to the surrounding environment. The picture is more comfortable and the details* appear.
4) Wide viewing angle, support horizontal 140°/vertical 140° large viewing angle, satisfying the viewing effect at different angles, covering more audiences.
Five, installation method
Under the premise of avoiding damage to the appearance and structure of the glass curtain wall, the installation method will be different according to the actual situation on site:
Fully hidden frame: * The LED transparent screen is fixed on the aluminum alloy frame, and the upper and lower beams of the aluminum alloy frame are upper and lower, and the two sides of the glass correspond to the left and right vertical bars of the aluminum alloy frame.
Semi-hidden frame: Since the vertical and horizontal glass curtain wall and the vertical and horizontal glass curtain wall are called semi-hidden frame glass curtain wall, the semi-hidden frame curtain wall glass has two installation methods. The vertical and horizontal concealment is to fix the glass installation in the groove, and then fix it with glass glue on the left and right sides. The vertical and horizontal curtain wall glass should be placed in the aluminum alloy inlay groove of the cross bar, and then covered on the outside of the glass. Press the plate and hide the aluminum rods behind the glass.
Bright frame: The glass type structure of the exposed frame curtain wall Whether the frame and the glass frame made of special aluminum alloy profiles or the steel frame are used as the skeleton, the aluminum alloy frame in the entire curtain wall will be exposed.
Hanging type: This is a kind of mounting method of welding the column and the stainless steel hanging piece. The four claws of the hanging piece are connected with the glass hole of the curtain wall, and one hole corresponds to one claw. It can also be said that one hole is drilled in each of the four corners of the glass, and then the glass is fixed on the four claws of the stainless steel pendant.
No skeleton: The glass on the frameless curtain wall can also be called structural glass. This kind of curtain wall is mostly used in the first floor of the building. It is similar to the floor-to-ceiling windows of the building. The glass is installed in the form of lifting. It is a kind of hook with uniform spacing. Or a method of hanging a glass from a top with a special profile. The operation steps are firstly fixed on the main frame of the channel by special profile hooks, and then the channel steel is suspended and suspended under the bottom of the plate or the beam. To strengthen the rigidity of the glass, a support frame or a horizontal frame may be added on the upper and lower sides of the glass. files.
Sixth, the structure
For example, the glass curtain wall structure of a building is not a conventional flat shape, such as a curved, fan-shaped, triangular, or circular structure. At this time, * special design requirements are required. Make the LED curtain wall screen better adapt to the overall structure and use requirements of the environment.
Due to the different appearances and different structures, the requirements for research and development and production processes are higher. If the manufacturer's technology is not enough, the LED screens that are spliced will have many problems such as uneven layout and uneven layout, which will affect the viewing effect and undermine the aesthetics of the overall design. More importantly, the design of the circuit and structure of the LED shaped screen is more complicated, which puts high requirements on the R&D capability of the manufacturer.