Reliable folding PLC does not require a large number of active components and connected electronic components. Its connections are greatly reduced. At the same time, the maintenance of the system is simple and the maintenance time is short. Plc adopts a series of reliability design methods for design. For example, redundant design. Power outage protection, fault diagnosis, information protection and recovery. PLC is a control device specially designed for industrial production process control, which has a simpler programming language and more reliable hardware than general computer control. Adopting a refined and simplified programming language. The programming error rate is greatly reduced. Easy to fold and operate PLC has high operability. It has the characteristics of simple programming, convenient operation, and easy maintenance, and is generally less prone to operational errors. The operation of PLC includes program input and program change operations. The input of the program can be directly displayed, and the operation of changing the program can also be directly searched or searched by the program based on the required address number or contact number, and then changed. PLC has multiple programming languages available for use. Used for ladder diagrams that are closer to electrical schematics. Easy to grasp and understand. The self-diagnosis function of PLC reduces the requirements for maintenance skills of maintenance personnel. When a system malfunction occurs, maintenance personnel can quickly locate the location of the malfunction through self diagnosis of hardware and software. Flexible folding The programming languages used by PLC include ladder diagram, Boolean mnemonic, function diagram, function module, and statement description programming language. The diversity of programming methods makes programming simple and expands its application scope. The operation is very flexible and convenient, and it is very easy to monitor and control variables. Siemens PLC S7-300 series PLC installation and precautions: 1、 The auxiliary power supply has low power and can only drive low-power equipment (such as photoelectric sensors); 2、 Generally, PLCs have a certain number of occupied points (i.e. empty address wiring terminals), do not connect the wires; 3、 PLC has the issue of I/O response delay, especially in fast response equipment, which should be paid attention to. 4、 There are relay type and transistor type outputs (suitable for high-speed output), and the output can directly carry light loads (LED indicator lights, etc.); 5、 The input/disconnection time should be greater than the PLC scanning time; 6、 There is no protection in the PLC output circuit, so protective devices such as fuses should be used in series in external circuits to prevent damage to the PLC caused by load short circuits; 7、 Do not connect the AC power cord to the input terminal to avoid burning out the PLC; 8、 The grounding terminal should be independently grounded and not connected in series with other equipment grounding terminals. The cutting surface of the grounding wire should not be less than 2mm2; 9、 The input and output signal lines should be routed separately as much as possible, and should not be in the same pipeline or bundled together with the power line to avoid interference signals and misoperation; The signal transmission line adopts shielded wire and the shielded wire is grounded; To ensure signal reliability, the input and output lines are generally controlled within 20 meters; Expansion cables are susceptible to noise and electrical interference, and should be kept away from power lines, high-voltage equipment, etc.