Do you know the secret of the LED display signal transmission
Aug 24, 2021
First, LED display signal transmission classification
1, wireless transmission: the primary reliance on wireless signal operation of different frequencies to classify, such as long wave, medium wave, short wave, microwave, etc.. Mobile phone signal is a wireless access method, many mobile phones today use GSM operating frequency at 900MHz. There are many varieties of TV signals, such as cable TV: the general transmission of analog signals, digital TELEVISION is the transmission of digital signals; Satellite TV signals are LED display signals of digital signals.
Two, LED display large signal transmission project
In addition to signal attenuation, another factor that affects signal transmission is signal reflection.
Impedance mismatch and impedance disconnection are the two primary causes of rS-485 bus signal reflection. Impedance mismatch, impedance mismatch is the primary impedance mismatch between 485 chip and communication line. The reason why the reflection is because in the communication line idle, all communication line signals at random, once this kind of reflection signal triggered 485 chip input comparator, will occur fault signal.
The usual solution is to add A, B line of RS-485 bus with A certain value of the bias resistance, and then separate pull high and low, so as to prevent the disorder signal is not predictable.
Impedance disconnection is analogous to the reflection of light from one medium into another.
The signal at the end of the transmission line suddenly encountered the cable impedance is very small, the signal at this point will cause reflection. The most common way to eliminate this reflection is to cross a terminal resistance at the end of the cable to the same size as the characteristic impedance of the cable.
Three, how to ensure the safety of the LED display signal transmission process
We can develop a simple and reliable RS-485 communication protocol. When the communication interval is short and the use environment is troublesome, one-way communication can complete the function of the project, but most of the use environment is not so ideal. Therefore, it is very important to draw up a perfect communication protocol. The specific method is to subcontract data transmission, and the data is packaged by adding the frame header and the frame tail to each packet, during which a byte is left at the end of the frame as the parity byte. The next machine after the verification byte of their own accounting and the host computer transmission over the verification byte for comparison, so as to announce instructions to the host computer, in the end is sent from the beginning just that packet of data is still next to the next packet of data, so that a packet of hair and then send the next packet, until the end of the hair stop. With such a verification resend mechanism, we can reduce the probability of error and make the communication system work properly.
In short, the signal in the transmission process, with the increase of the interval and weakened.
Therefore, in order to ensure the playback effect of THE LED screen, the performance of the LED screen is relative to other advertising communication methods, the selection of the transmission medium of the LED screen is particularly important.
