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Working principle and structure of the video LED screens and signs

LED video screens control system

Full-color video LED screens control system

Video LED screen is in fact a large television set. Unlike TV, LED systems are made of separate LED modules into video screens of different sizes and shapes.

Information is relayed to LED modules by controllers which are connected to the controlling computer. A video processor in a PC receives video signals from different sources - standard TV signal, signal from the VCR, DVD-player, video camera, another computer and so on.

Video clips prepared in advance could be recorded on hard drive of the controlling computer and could be displayed according to a required schedule.

When sufficient number of video LED screens was installed, a new idea of connecting all of these LED screens into a network with the unified control center emerged. Separate standing LED screens are controlled by a central computer through any of the available channels - modem, radio modem, fiber-optics, etc.

Modular construction of LED screens

Modular construction of the screens

As it was already mentioned, video LED screens are made of LED modules. On the picture there is an example of construction of the video LED screen's modules with the linear size of 240x240 mm, pixel pitch 15 and ratio of the sides (width : height) - 4:3.

Standard TV signal on a LED screen with different aspect ratio will be distorted or shown on the different parts of the screen.

If the LED screen is used only for the broadcasting of special video clips prepared in advance, then the aspect ratio does not play such important role and can be changed according to customer's request.

Table of a LED screen constructed from LED modules with the pixel pitch 15 mm
module size - 240x240 mm / 16x16 pixels (screen aspect ratio - 4:3)

Number
of modules
Screen sizes,
m
Image area,
sq. m
Screen
resolution
16 x 12 3,84 x 2,88 11,06 256 x 192
20 x 15 4,80 x 3,60 17,28 320 x; 240
24 x 18 5,76 x 4,32 24,88 384 x 288
28 x 21 6,72 x 5,04 33,87 448 x 336

Advantages of the modular structure:

  • Construction of screens of different sizes and resolutions
  • Possibility to increase size during upgrade
  • Construction of screens of different forms and shapes
  • Construction of high resolution screens
  • Easy assembly and servicing
  • Exchangeability of the modules
  • Easy localization of errors
  • Possibility of constructing mobile and easily assembling screens

LED modules of the video screens

Module of LED video screens

Pixels of LED video screens
LED module with 2R1G1B pixels
Module of LED video screens

Pixels of LED video screens
LED module with 1R1G1B pixels

LED modules are the elements from which LED screens are constructed to different sizes and shapes. The picture on the left shows module with the resolution of 8x8 pixels and pixel structure: 2 Red, 1 Green, 1 Blue. The bottom left picture shows enlarged pixel. LED modules - segments for building LED screens of all sizes and resolution (like building blocks).

Essential parameters of a LED module:

  • Pitch (distance between pixels, mm)
  • Resolution (number of pixels in a module)
  • Linear size (height and length)
  • Brightness in cd/sq.m (nit)
  • Construction - for the indoor or outdoor use
  • Energy consumption
  • Viewing angles (horizontal and vertical)
  • Pixel composition (number of LEDs that make up a pixel)

One of the main parameter of a LED module is pitch - distance between pixels (dots). The smaller is the distance between pixels the higher the resolution of the LED screen.

Three LEDs pixel

Initially the pixel composition was based on two red lamps (2R1G1B) due to low luminous intensity of red LEDs. The consecutive connection of two red LEDs was optimal in power consumption, while the 4-lamp pixel helped to uniformly fill the irradiating screen surface.

However, when brighter Red LEDs appeared on the market, the pixel structure of 1R1G1B became accessible up to pitch 38 mm. At large viewing distance the pixels 1R1G1B and 2R1G1B are perceived as being the same. But at close range the 2R1G1B could seem excessively reddish, created red background and distorted coloring. All these negative features were eliminated by the use of 1R1G1B pixel structure.

Another advantage of 1R1G1B pixel is the increase in black screen surface area that helps to improve contrast of the image in bright sunlight or with bright ambient street lights around.

SMD screens

With the appearance of SMD LED (3 LEDs - red, green and blue - in the same case) it became possible to start production of SMD modules with the pitch smaller than 10 mm.


 

Technical data of some LED modules for outdoor screens

Model Type Pixel
structure
Number
of pixels
Pitch,
mm
Size,
mm
Brightness,
cd/m2
Viewing angle Weight,
kg
Power,
W
Horiz. Vert.
m15-16x16 outdoor 1R-1G-1B 16 x 16 15 240 x 240 8000±10% 120 60 2,0 80
m19-16x16 outdoor 1R-1G-1B 16 x 16 19 304 x 304 7000±10% 120 60 2,2 80
m22-8x8 outdoor 1R-1G-1B 8 x 8 22 176 x 176 5000±10% 120 60 1,0 20
m22-16x16 outdoor 1R-1G-1B 16 x 16 22 352 x 352 5000±10% 120 60 2,0 80
m30-8x8 outdoor 1R-1G-1B 8 x 8 30 240 x 240 5000±10% 60 45 1,5 20
m38-8x8 outdoor 2R-1G-1B 8 x 8 38 304 x 304 5000±10% 60 45 1,7 20

Designation of module models in table:
m - Module XX - Pixel pitch YY x YY - Pixel quantity

Note: All data in table are for reference only. Assortment of the LED module models that is produced by our company is changing constantly, that is why if you want to get the latest information about LED modules you can send the request to info@atvoutdoorsystems.ru or simply call.