There is a lot of information about LED screen equipment on the Internet, but in our opinion, it is not always presented as a whole, which brings inconvenience to readers. In order to solve this situation, we have prepared several articles and divided them as follows: In this material, you will be familiar with the basic concepts used, in the article “LED modules and cabinets” the components of the LED screen are introduced, and in the article “Control LED screen” has management types respectively.
Article content
1 What is LED screen
2 What is LED
3 What is the refresh rate
4 What are the pixels in the LED screen
5 LED screen resolution
6 pixel pitch LED screen
7 pixel configuration
7.1 Dial code configuration
7.2 Patch configuration
8 LED screen viewing angle
What is LED screen
Therefore, LED screens (also called LED screens, video screens, LED panels, etc.) are high-tech products based on LEDs that contain a large number of components and complex working principles. LEDs form pixels, the pixels are embedded in modules, and the modules are placed in the cabinet where the LED screen is manufactured.
What is LED
A light-emitting diode (LED) is a semiconductor device that shines when electric current passes through it. LEDs do not contain filaments like ordinary bulbs, and there are no fragile or burnt parts, and they have a long service life. According to the type of semiconductor crystal used, the color of the LED depends on: red, white, green, etc. If you slightly change the chemical composition of the crystal, the resulting color will change. Usually the housing (body) of the LED is painted. This is to determine what color it is without turning on the LED.
LED is the smallest component, but it is not important. In many ways, the cost of the LED screen itself is increased from its cost. In terms of technical characteristics, the cost of an LED model that has proven itself to be better may be several times that of similar products. So far, the Japanese manufacturer Nichia’s model is considered the highest quality, and the American-made Cree LED has a slightly lower rating. There are also Samsung and Jingdian (Taiwan)-their costs are similar, and China’s Absen, Silando and others are even lower. In most cases, in the production of LED screens today, China’s Silan LED is used. They are relatively affordable and have a long service life.
The rated continuous use time of standard LEDs is 100,000 hours (more than 11 years) and is not affected by the number of on/off occurrences. The brightness of the LED is called pulse width modulation technology, and its adjustment method is as follows-the voltage is not supplied to the LED constantly but alternately. And according to what brightness is needed, determine the current supply time, that is, if half of the brightness is needed, apply the voltage for half the time from the refresh frequency.
What is refresh rate
Refresh rate (refresh rate, Refresh) is the number of frame refreshes in a given time (in Hz). For example, if the refresh rate of a computer monitor is 100 Hz, this means that the picture is refreshed 100 times in 1 second. This indicator is very important, because the image quality largely depends on it. If the refresh frequency is not enough, then you will see the “jumping” of the image-flickering, which can be explained by the human visual perception of the light source. If the flickers happen quickly, add these flickers and perceive the light as burning. Today, the refresh rate of LED screens is at least 600 Hz, which is usually sufficient.
LEDs are truly undiscovered heroes in the electronic world. They can complete dozens of different jobs and can be found in various devices. Among other things, they form numbers on electronic clocks and tell us when our devices are turned on. Basically, LEDs are just miniature bulbs that can be easily incorporated into circuits. One or more LEDs are combined to form a pixel.
What are the pixels in the LED screen
Pixel-the luminous point, which is the smallest unit of the image. In order to create the various colors that pixels transmit, they usually only use three different color LEDs: red, green, and blue (represented by R, G, and B, respectively). In order to make large pixels up to 80mm in diameter (LED screens for media facades), increase the number of LEDs, for example: 2R1G1B-ie 2 red, 1 green and 1 blue. Consider the best approximation of the white balance to determine the number and color of LEDs to be used. Only when the ratio of red, green, and blue is 1:4.6:0.16, high-quality white can be obtained. If it deviates from this ratio, there will be deviations in white, such as blue-white or yellow-green.
LED screen resolution
LED screen resolution-the number of pixels per 1 square meter LED screen. The best resolution for 4m wide screen. And a height of 3m. The resolution is considered to be at least 256×192, which is 256 pixels horizontally and 192 pixels vertically. This value is achieved with a pixel pitch of 15.6 mm.
LED screen pixel pitch
Considering the equipment of the LED screen: the choice of pixel pitch is a very important point when buying: reducing the pitch by a few millimeters will significantly increase the density of the LED, thereby increasing the resolution of the screen. You can estimate the required pixel pitch as follows: it is proportional to the recommended viewing distance, that is, on a screen with a pixel pitch of 10 mm. It is recommended to look at a distance of 10 meters, for a screen with a pixel pitch of 16 mm to 16 meters, and for a screen with a pixel pitch of 25 mm to 25 meters. If the distance is smaller, the viewer will be able to distinguish individual pixels, if the distance is greater, on the contrary, small details will not be seen. Therefore, to determine the pixel pitch, it is necessary to know the distance between most viewers and the LED screen.
Pixel configuration
There are many ways to combine LEDs into pixels, which are called pixel configurations. Today, two main types are used: DIP and SMD.
Dialing configuration
The principle of DIP configuration is to implant each diode in its own package into the circuit board. The fact that one pixel is formed by a series of LEDs improves the reliability of the screen and the overall brightness level.
DIP configuration modules are most commonly used for outdoor LED screens. They have higher brightness, a reinforced mask to prevent mechanical damage, negative temperature resistance, moisture and dust resistance. In addition, they have good color stability and are committed to virtual pixel technology, which allows you to form so-called “virtual pixels”-it does not exist physically, but creates the illusion of its existence for the human eye. Therefore, the sharpness can be improved many times, and the image can be made more detailed and realistic. The disadvantages of the DIP module include the small viewing angle.
Patch configuration
Patch configuration. This is the latest development that has had a major impact on the design of LED displays. Its distinguishing feature is the combination of three LEDs of different colors into one housing, sometimes denoted as RGB (3 in 1). SMD technology provides better and clearer color reproduction. They are usually used for indoor LED screens with small pixel pitch-concert halls and stadiums, TV studios, train stations and airports. SMD configuration pixels usually have lower brightness, about 1200-3000 cd/m2, which is in contrast to the DIP configuration pixel brightness (6000-10000 cd/m2), but this is enough for indoor use, otherwise the audience will be dazzled. They consume less power, are thinner and lighter, have good color stability, large viewing angles, and a rich palette. Recently, this technology has spread to outdoor LED screens.
LED screen viewing angle
The viewing angle is the angle at which the viewer observes the brightness of the image from 50% to 100%. If you look at the screen plane vertically, the maximum brightness value will be. The viewing angle of the DIP configuration screen is 120 degrees horizontally and 60 degrees vertically, and the viewing angle of the SMD configuration screen is 120 degrees horizontally and 120 degrees vertically.
The LEDs that use DIP and SMD technology to implant the circuit board form the LED module, but in the next article that considers the LED screen device, it will be described in detail: “LED Module and Cabinet”.