First, the classification of LED display signal transmission
1. Wireless transmission: The first thing to rely on the frequency of wireless signal operation is to classify, such as long wave, medium wave, short wave, microwave, etc. Cell phone signal is a wireless access method, and many mobile phone GSM operating frequencies are now 900MHz . There are many varieties of TV signals, such as cable TV: generally, analog signals are transmitted, digital televisions are digital signals ; satellite signals on satellites are LED display signals of digital signals.
2. Wired transmission: It can be divided into analog signal transmission, digital electrical signal transmission, and digital optical signal transmission.
Second, LED display large signal transmission project
In addition to signal attenuation, another element that affects signal transmission is signal reflection. Impedance mismatch and impedance discontinuity are the two primary causes of RS-485 bus signal reflection. Impedance mismatch, impedance mismatch is primarily the impedance mismatch between the 485 chip and the communication line. The reason for the reflection is that when the communication line is idle, all the communication line signals are in a mess. Once such a reflected signal triggers the comparator at the input of the 485 chip, a faulty signal will occur.
The usual solution is to add the bias resistors of the resistors of the A and B lines of the RS-485 bus , and then pull them low and pull low to prevent unpredictable messy signals. The impedance is not continuous, it is similar to the reflection caused by light entering from one medium to another. At the end of the transmission line, the signal is very small, and the signal will cause reflection in this area. The most common way to eliminate this reflection is to connect a terminating resistor of the same size as the cable's characteristic impedance at the end of the cable.
Third, how to ensure the security function of LED display signal transmission process
We can develop a simple and reliable RS-485 communication protocol. When the communication interval is short and the usage environment is disturbed for a small amount of time, one-way communication can complete the project function, but most of the usage environments are not such ideals. Therefore, it is particularly important to draw up a complete communication protocol. Specifically, the data is sub-packetized, and the data is packed by adding a frame header and a frame tail to each packet of data, and one byte is reserved as a check byte at the end of the frame. The lower computer compares the check byte that it has calculated with the check byte transmitted by the host computer, so as to announce the command to the upper computer, in the end, the data is sent from the beginning of the packet, and then the next packet of data is sent. After the package is sent, send another packet until it stops. After such a verification retransmission mechanism, we can reduce the probability of error and make the communication system work normally.
In short, the signal is weakened during the transmission process, followed by an increase in the interval. Therefore, in order to ensure playback LED display, LED display performance relative to other advertising to convey, and to select transmission media LED display is very important.
Stainless Steel Sanitary Pipe,Sanitary Pipe Material Stainless Steel Tube,Astm 409 Saintary Stainless Steel Pipe,Ss Seamless Saintary Pipe
ShenZhen Haofa Metal Precision Parts Technology Co., Ltd. , https://www.haofametals.com