Introduction of communication cables: The weak current cables commonly used in LED display projects include 4 pairs of super five twisted pairs (network cables), shielded flexible wires, optical fibers, coaxial cables, etc.
LED display
4 pairs of Super Category 5 twisted-pair cables are often called 8-core network cables in local area network wiring. They are divided into 4 pairs and twisted together by 8 wires of different colors. The effect of twisting in groups is to reduce electromagnetic radiation as much as possible. With the influence of external electromagnetic interference, twisted pair cables can be divided into shielded twisted pair (STP) and unshielded twisted pair (UTP) according to whether or not the shielding layer of the metal mesh sleeve is added. In the display screen project, it is used for the short-distance communication of the display screen signal (not greater than 100 meters), and can also be used for the transmission of other control signals of the display screen. The general length specification is 305 meters/box (1000 feet).
特点
Shielded flexible wires are similar to ordinary wires and have the same wire diameter specifications. The main reason is that there is a metal mesh shielding layer between the sheath layer and the inner cable. The characteristic is that the wire has a higher weave density and a softer wire. Easy to lay and prevent signal interference.
The coaxial cable uses hard copper wire as the core and is covered with a layer of insulating material. This layer of insulating material is surrounded by a densely woven mesh conductor, and the net is covered with a layer of protective material. There are two widely used coaxial cables. One is a 50-ohm cable, which is used for digital transmission. Because it is mostly used for baseband transmission, it is also called baseband coaxial cable and is often used for network connection. The other is a 75-ohm cable for analog transmission. It is often used for the transmission of cable television radio frequency signals and ordinary video signals.
optical fiber
Optical fiber is similar to coaxial cable, except that there is no mesh shield. In the center is the glass core through which light propagates. In a multimode fiber, the core diameter is 15μm-50μm, roughly equivalent to the thickness of a human hair. The diameter of the single-mode fiber core is 8 μm to 10 μm. The core is surrounded by a glass envelope with a lower refractive index than the core to keep the optical fiber in the core. On the outside is a thin plastic jacket to protect the envelope. Optical fibers are usually bundled and protected by a casing. The fiber core is usually a double-layer concentric cylinder with a small cross-sectional area made of quartz glass. It is brittle and easy to break, so an additional protective layer is needed. The transmission point modulus is divided into single mode fiber (Single Mode Fiber) and multimode fiber (Multi Mode Fiber). The core diameter of a single-mode fiber is very small, and it can only transmit in a single mode at a given operating wavelength. The transmission frequency is wide and the transmission capacity is large. Generally, the transmission distance is above 2Km. Multimode fiber is a fiber that can transmit multiple modes at the same time at a given operating wavelength. Compared with single-mode fiber, the transmission performance of multi-mode fiber is poor, and the general transmission distance is about 500m. The longest length is not more than 2Km. According to the different working environment, it is divided into outdoor optical fiber and indoor optical fiber. The length can be intercepted according to the actual situation.
