The steps and principles of PLC programming

1. General steps of plc program design
(1) If the adopted PLC has its own program, it is necessary to understand in detail the existing functions of the program and the degree of satisfaction and modifiability of the program. Try to use the program that comes with the PLC.
(2) List all PLC-related input signals (buttons, travel switches, speed and temperature sensors), output signals (contactors, solenoid valves, signal lights, etc.) Each signal is assigned a certain number.
(3) Learn more about the requirements of the production process and equipment for the control system. Draw the working cycle diagram or flow chart, function diagram and timing diagram of related signals of each functional process of the system.
(4) Design the ladder diagram or write the program list according to the requirements of the PLC programming language. The text symbols on the ladder diagram should be marked according to the provisions of the on-site signal and PLC internal interface comparison table.
2. General Principles of PLC Program Design
(1) The design to ensure personal and equipment safety is never superfluous.
(2) The safety design of the PLC program does not mean that the safety protection of the hardware can be omitted.
(3) Understand the characteristics of PLC itself.
(4) The design debugging point is easy to debug.
(5) Modular design.
(6) Minimize the amount of program.
(7) Comprehensive notes for easy maintenance.

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