PIC (programmable logic controlen, programmable control cabinet, control cabinet refers to a complete set of control cabinets, which can realize the control of motors and switches. PLC control cabinet can be used in various industrial automation control occasions of various sizes. It is widely used in power, metallurgy, chemical industry, papermaking, environmental protection and sewage treatment industries.

PLC control cabinet generally includes five parts: air switch, PIC, power supply, relay and wiring terminal. The air switch controls the entire cabinet; PLC is the main functional component. Small projects can choose an integrated PC, large projects may require modules and card-type, and may also require redundancy. For PLC without power supply, the control may also need a power supply; generally, PC can directly send instructions to the control loop, but if If the power supply of the output port is not the power supply required in the control circuit, a relay is needed; another part is the terminal block, which is an indispensable component of each control cabinet. The control units in the control cabinet system are usually connected by terminal blocks to ensure the normal use of the control phase. In the wiring inside the control cabinet, when the equipment inside the screen is connected to the equipment outside the screen, some special terminal blocks must be used. These terminal blocks are combined to form a terminal block. The function of the terminal block is to connect the lines of the equipment inside the screen and the equipment outside the screen, and play the role of signal (current and voltage) transmission. With the terminal block, the electrical connection of the controller can be realized. The use of the terminal block can make the wiring lines in the control cabinet beautiful, It is easy to maintain, and can make the connection between long-distance commercial lines more reliable, making construction and maintenance more convenient and quick.

Under normal circumstances, when we open the keyboard of a general-purpose computer, we can see a soft film (flexible insulating substrate) with silver-white (silver paste) conductive patterns and key surface shapes printed on it. It is precisely because this pattern is obtained by the general screen printing method that we call this printed circuit board a flexible silver paste printed circuit board. However, the printed circuit boards on various computer motherboards, graphics cards, network cards, modems, sound cards and household appliances that we see in computer malls are different.

The base material used for the terminal block is a paper base (commonly used for single-sided) or a broken glass cloth base (commonly used for Han and multi-layer), pre-painted phenolic or ring gold resin, and one or both sides of the surface are glued with copper. Then laminated and formed. This kind of circuit board is called a mesh board. The circuit board made of copper plate is called a rigid circuit board. We call it a single-sided printed circuit board if there is a printed circuit pattern on one side, and a printed circuit board with printed circuit patterns on both sides and metallized on both sides is called a double-sided printed circuit board. If a printed circuit board with one double-sided inner layer and two single-sided outer layers or two double-sided inner layers and two single-sided outer layers is used, and the positioning system and insulating materials are interlaced together and then printed according to the design requirements, the circuit board becomes a four-layer or six-layer printed circuit board, which is also called a multi-layer printed circuit board. Now there are more than 100 layers of practical printed circuit boards.