For the LED display screens with a wide variety of prices and huge price differences on the market, consumers are very headaches. The key is not knowing how to buy a good quality display. Because each manufacturer produces different LED display price positioning, the quality requirements are different, then what is the difference between LED display screens for different price points?
The factors that cause different prices for LED displays are as follows:
1, antistatic
LEDs are low voltage drivers and therefore sensitive to high voltage and antistatic capabilities. The anti-static large LED natural price is relatively high.
2, brightness
LED is a material that directly converts electrical energy into light energy. The luminous efficiency determines the value of the LED itself.
In addition, the larger the size of the LED chip, the higher the brightness, and the higher the brightness, the more expensive the price.
3, wavelength
After the LED emits light, a band is generated, and the closest distance to the farthest distance of the band is divided into different wavelengths. The display screen has strict requirements on the wavelength of the LED lamp. The effect of the display with the same wavelength is better. If the wavelength is inconsistent or the deviation is too large, the LED display will have different chromatic aberration feeling when viewed from the side.
4, leakage current
LED is a unidirectional conductive light-emitting conductor. When designing a circuit board, the reverse current of the circuit board is very strict. If there is reverse current, the life of the LED will be shortened.
5, LED illumination angle
The LED illumination angle directly affects the brightness and consistency of the display. The concept of consistency is to view the display from any angle, and the displayed color is the same. If the angles are inconsistent, there will be chromatic aberration.
6, LED life
LED lifetime is determined by LED chip, LED bracket, LED gold wire and LED package structure.
The key factor in LED lifetime is the extent to which the LED is attenuated during operation. The faster the decay, the shorter the life.
7, LED chip
In the market, there are many brands of LED chips. There are American CREE in foreign countries, Nichia in Japan, and Taiwan. In the mainland, there are also chip manufacturers. Different chips have different stability, brightness and life.
8, chip size
The chips come in different sizes and the chip size is defined by the length of the sides. The larger the size, the better the performance and the higher the natural price.
9, epoxy resin colloid
After the LED is packaged, it is a finished product. The conventional plug-in LED chip will become a finished product after being cooled by die bonding, wire bonding, dispensing, and epoxy resin packaging. Epoxy resin is a transparent solid with a high price of colloids with UV and fire resistance.
How to distinguish the quality of LED display?
First, the LED wavelength control range
The wavelength determines whether the color is pure and the color is consistent. The method of resolution is very simple; users generally do not have professional equipment, how to distinguish with the eyes? First: The whole screen is white, and the screen should be pure white without any other noise. If you think that there is a little reddish or blued, it's a big mistake, because the color cast proves that the display material and process quality control have problems. It will become more and more serious after using it for a long time. Second: the red, green, and blue colors are printed. The color of the center wavelength is the positive blue color that we usually say. If it is darker or lighter, it proves to be a partial wavelength. If a certain color is inconsistent, it proves that the wave difference is too large, the high-quality display screen is in the range of the center wavelength, the blue-green wave difference is controlled at 3 nm, and the red wave difference is less than 5 nm.
Second, the perspective of the luminous tube
The illuminating angle of view of the illuminating tube refers to the angle between the two viewing directions of the same plane and the normal direction when the brightness of the viewing direction drops to one-half of the brightness of the normal direction of the LED display screen. Divided into horizontal and vertical perspectives.
Vertical viewing angle of an elliptical tube with a horizontal viewing angle of an elliptical tube
Horizontal viewing angle of the SMD tube
For outdoor LED displays, elliptical tubes or patch tubes are generally used. The elliptical tubes have the characteristics of small angle and high brightness, and the vertical viewing angle of the patch tubes is much larger than that of the elliptical tubes, but the brightness is smaller than that of the elliptical tubes. From the user's point of view, the light pipes of different viewing angles should be selected according to the audience surface of the LED display and the surrounding light environment. For indoor LED display, because of its low brightness requirements, the audience is generally wider, so the SMD tube is the best choice. It should be noted that some manufacturers of LEDs in the market are now trying to reduce costs, confuse users, and make the brightness of the LEDs relatively high, while the viewing angle is smaller than that of conventional LEDs, which leads to LED displays. The brightness is very high on the front side, but the image is not visible when viewed from a large angle.
Small-sized LED chips are usually packaged in small angles in order to increase brightness. Large size does not require a small angle package because it does not require such high brightness. Therefore, high angle (110) high brightness and low current is the best.
Third, the maximum brightness
The maximum brightness refers to the brightness of each of the primary colors of the LED display at the highest gray level and the highest brightness under a certain ambient illumination. In short, use the software to set the brightness of the light gun in the normal direction when the display is 255 white.
For the outdoor LED display, depending on the environment used, there will be different requirements for the maximum brightness, because in the case of strong ambient light, the brightness of the LED display is required to be higher, so that the masses can see the content displayed on the screen. Under normal circumstances, the display screen is located south to the north, and the maximum brightness requirement is lower. As long as it reaches 4000CD/m2, the requirement can be met, while the north-facing display screen requires the brightness of the whole screen to reach 7000CD/m2, facing east and west. The south-facing request is the same, because there will be a part of the time when the sun will shine directly on the LED display. Theoretically, a brightness requirement of more than 5,500 CD square meters is sufficient.
Four, square power consumption
The square power consumption refers to the power consumption generated by the LED display of one square meter, in watts. The unit of electricity we usually say is watts/hour. For example, the power consumption of a square meter LED display is 300 watts, and this display consumes 300 watts/hour of electricity per square meter per hour, which is what we often call 0.3 kWh. The power consumption of LED displays generally has two indicators, one is the maximum power consumption, and the other is the power consumption. The maximum power consumption refers to the power consumption of the maximum brightness of the LED display. How to use the eyes to distinguish the maximum power consumption? The method is very simple: look at the number of power sources behind the cabinet, multiply the maximum power of each power supply, and calculate the maximum power consumption of the square meter according to the size of the cabinet. There are two types of power supplies, 200W and 300W. The power consumption refers to the power consumption when playing video, text, and pictures. Because the power consumption is directly related to the content being played, it is difficult to have an exact value, but according to our experience, it is generally 1/3 of the maximum power consumption. Lower power consumption represents lower cost of use and less heat. The amount of heat depends on the current, which directly affects the life and stability of the display.
Energy-efficient LED displays use four 200-watt power supplies per square meter, so the maximum power consumption does not exceed 680 watts per square meter. Because the effective output of the power supply is basically 85%
Five, refresh frequency
Refers to the number of times the LED display shows the information displayed in seconds, in Hz. If the refresh rate is too low, the human eye will see the LED display vibrating, and a scan line will appear when shooting through the camera. Generally, the refresh rate requirement of the human eye is 300 Hz or more, that is, as long as the refresh rate exceeds 300 Hz, the LED display screen is generally not shaken when viewed by the naked eye, and if the camera is used for shooting, it is generally required according to different settings of different cameras. More than 600Hz can capture the scan line. High refresh can increase the brightness and color vividness of the display. It can be detected with a digital camera. If it is high refresh, the picture taken by the camera is very clear, there are no snowflake points and scan lines. This indicator is especially important when renting screens and TV broadcasts.
Figure 1 Comparison of different refresh rates
Figure 1 is obtained by taking pictures of LED display screens with different refreshing frequencies using the same camera. It can be seen from the figure that the refresh rate of the left screen satisfies the shooting requirements of the camera, and the right screen has obvious scanning lines because the refresh rate is insufficient. The black horizontal line in the right picture is the scan line).
Sixth, about contrast
Contrast refers to the measurement of different brightness levels between the brightest white and the darkest black in the dark and dark areas of an image. The larger the difference range is, the larger the contrast is. The smaller the difference range is, the smaller the contrast is. The effect of contrast on the visual effect is very important. Generally speaking, the contrast is larger, the image is more clear and conspicuous, and the color is more vivid and vivid; while the contrast is small, the whole picture is grayed out. In order to improve the contrast of the LED display, the use of all-black LED is currently the most effective method, which can be seen very intuitively from the following figure.
Figure 2 Comparison of different LED modules
The left LED module uses a traditional white light, and the right module uses a full black LED. The picture shows a non-lighting effect. It can be imagined that when the LED display shows a contrast between light and dark, the right module is much better than the left. The contrast can be doubled when the whole black LED is actually measured by our company.
Seven, circuit design part
The design and materials of the circuit board play an important role in the stability and display effect of the LED display. There are mainly the following requirements:
1. Requirements for materials: PCB thickness, generally 1.6mm thickness; material: FR-4 fiberglass board, some manufacturers may use FR-2 paper substrate to reduce cost; copper foil thickness: thickness of copper foil It has a non-negligible effect on the heat dissipation of the PCB board and the stability of the line. The normal copper foil thickness is 35um (1Oz), and some manufacturers will use 18um (0.5Oz) copper foil thickness to shoddy; then as consumption How do you tell the difference? You can take an empty PCB to distinguish by weight. Under normal circumstances, the heavier the better.
2, a few key points in the design: connectors, connectors refers to the connection between the module and the module, there are two main types of use on the market, one is the horn (Figure 4 red circle ), one is the pin header (red circle in Figure 3). The advantage of the horn is that the cable can be caught by the two card slots, and the fault caused by the connector problem is not easy to occur; the electrolytic capacitor (circle 3 yellow circle) and The choice of tantalum capacitor (yellow circle in Figure 4), for applications requiring long life, tantalum capacitor is undoubtedly the first choice, for low-cost applications, electrolytic capacitors are preferred.
Figure 3 pin header and electrolytic capacitor
Figure 4 horn and tantalum capacitor
Eight, automated production equipment
Most of the LED display is electronic components, and static electricity has a very serious hazard to electronic components. Sometimes static electricity directly penetrates the components to damage them. Sometimes it does not directly penetrate, but leaves hidden dangers and side effects. That is, the components are damaged after using them for a while. In the electronics manufacturing industry, people think of a lot of methods for the treatment of artificial static electricity, including wearing static rings, wearing electrostatic clothes, using dust-free workshops, and so on. In fact, the most effective way is to avoid manual contact with electronic components, and the use of automated equipment achieves this goal. As a user, how do you check if you are using automated equipment? It can be distinguished very intuitively by the following two figures.
Figure 5 automatic plug-in renderings
It can be seen from the red circle in Figure 5 that after the LED lamp foot passes through the automatic plug-in machine, the machine will automatically bend the lamp foot.
Figure 6, the effect of artificial hand insert light
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