When the dot matrix LCD screen is interfered, we will see the splicing screen appear water ripples, vertical lines, wood grains, multi-line ripples, etc. The following Yicheng photoelectric analysis of common factors that cause interference with LCD splicing:
(1) Caused by the power supply of the power supply system. There are interference signals superimposed on the normal power supply, and the interference signals on this power supply mostly come from the equipment that uses thyristor in the power grid. The solution to this situation is relatively simple, as long as the entire system of the LCD splicing screen adopts a clean power supply or an online UPS power supply, it can basically be solved.
(2) Space radiation interference introduced by the transmission line. This kind of interference phenomenon occurs mostly because there are strong and high-frequency space radiation sources near the transmission system, the front end of the system, or the central control room. One solution to this situation is to understand the surrounding environment and try to avoid or stay away from the radiation source when the system is established.
(3) There is a strong interference source near the system. This can be judged through investigation and understanding. If this is the reason, the solution is to strengthen the shielding of the camera, and to ground the video cable pipe.
(4) Failure phenomenon caused by the characteristic impedance mismatch of the transmission line. The manifestation of this phenomenon is that a number of vertical bar interferences with equal spacing are generated on the monitor screen. The frequency of the interference signal is basically an integer multiple of the horizontal frequency. The solution generally depends on the "start-end series connection resistance" or "terminal parallel connection resistance" method to solve the problem.
(5) The quality of the video transmission line is not good, especially the poor shielding performance (the shielding net is not a good quality copper wire net, or the shielding net is too thin to provide a shielding effect); at the same time, the line of this kind of video cable The resistance is too large, which causes a large attenuation of the signal is also the cause of aggravated failure. In addition, the characteristic impedance of this type of video line is not 75Ω and the parameters exceed the regulations are also one of the reasons for the failure.
