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Paid attention | Design Led

2020/06/28


      LED display screens are widely used, with clear screen, long life and low energy consumption. Led displays are inappropriate in the design and will affect future usage. This article summarizes eight factors and tells everyone what to pay attention to in the design of led displays so that people can avoid these problems.


      ★  Heat dissipation design

      LED equipment will generate heat during operation. Excessive temperature will affect the attenuation speed and stability of the LED. Therefore, the heat dissipation design of the PCB board and the ventilation and heat dissipation design of the cabinet will affect the performance of the LED.


     ★  Mixed lights

      LEDs with different brightness files of the same color need to be mixed, or inserted according to the light insertion diagram designed by the discrete law to ensure the consistency of the brightness of each color of the entire screen. If there is a problem in this process, the local brightness of the large screen will be inconsistent, which directly affects the display effect of the large LED screen.


     ★  Design current value

      The nominal current of the LED is 20mA. It is generally recommended that the maximum current of the LED should not exceed 80% of the nominal value. Especially for large screens with a small dot pitch, the current value should be reduced due to poor heat dissipation conditions. According to experience, due to the inconsistency of the attenuation rate of the red, green, and blue LEDs, the current value of the blue and green LEDs is targeted to reduce the consistency of white balance after long-term use of the large screen.


     ★  Drive circuit design

      The arrangement of the driver IC on the driver circuit board on the large screen module will also affect the brightness of the LED. Since the transmission distance of the driver IC output current on the PCB board is too far, the voltage drop of the transmission path will be too large, affecting the normal operating voltage of the LED and causing its brightness to decrease. We often find that the LED brightness around the large screen module is lower than the middle, which is the reason. Therefore, to ensure the consistency of the brightness of the large screen, it is necessary to design a good driving circuit distribution diagram.


     ★  Control the verticality of the lamp

      For in-line LEDs, there must be sufficient process technology to ensure that the LEDs are perpendicular to the PCB board when the furnace is passed. Any deviation will affect the LED brightness consistency that has been set, and color patches with inconsistent brightness will appear.


     ★  Virtual welding control

      When the LED is not bright, the LED screen often has a probability of more than 50% caused by various types of virtual soldering, such as LED pin soldering, IC pin soldering, and pin header mother soldering. The improvement of these problems needs to be strictly improved the process and strengthened quality inspection to solve. The vibration test before leaving the factory is also a good inspection method.


     ★  Over-wave soldering temperature and time

      Strictly control the wave front welding temperature and furnace passing time. It is recommended that the preheating temperature be 100°C±5°C, and the maximum temperature should not exceed 120°C. The preheating temperature should be stable and the welding temperature should be 245°C±5°C. It is recommended that the time should not exceed 3 seconds. Do not vibrate or shock the LED after the furnace until it returns to normal temperature. The temperature parameters of the wave soldering machine should be checked regularly, which is determined by the characteristics of the LED. Overheating or fluctuating temperature will directly damage the LED or cause hidden quality problems for the LED, especially for small and round LEDs such as 3mm.


     ★  Anti-static

LED large screen assembly factories should have good anti-static measures. Special anti-static ground, anti-static floor, anti-static soldering iron, anti-static table mat, anti-static ring, anti-static clothing, humidity control, equipment grounding (especially foot-cutting machine), etc. are basic requirements, and should be regularly tested with an electrostatic meter.



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