Ideas for checking and judging PLC faults during PLC maintenance

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Ideas for checking and judging PLC faults during PLC maintenance [Copy link]

The probability of PLC hardware damage or software running errors is extremely low. When checking for faults, the focus should be on the PLC's peripheral electrical components. Most PLC faults are peripheral interface signal faults. When repairing, as long as some of the PLC controls are normal, there is no need to doubt the PLC program problem. Confirm that the operation program has output, but the PLC interface has no output, then it is an interface circuit failure. PLC systems have more hardware failures than software failures, most of which are caused by external signal failures or actuator failures, rather than PLC system problems. The fault can be judged based on the PLC input and output status. The input and output signals of the PLC must pass through the I/O channel. Some faults will be reflected on the I/O interface channel. Sometimes the cause of the fault can be found by observing the I/O interface status. PLCs all have self-diagnosis functions. When checking faults, the cause can be found and the fault location can be determined based on the alarm information. This is also the basic means and method for checking and troubleshooting PLC faults. First determine whether the fault is global or local. If the host computer displays that multiple control components are not working properly and prompts many alarm messages, it is necessary to check the common parts such as the CPU module, memory module, communication module and power supply. Experience shows that most of the faults in PLC control systems are checked through PLC programs. The actions of the PLC control system are completed in a certain order. By observing the system's action process and comparing the fault and normal conditions, most of the doubts can be found and the cause of the fault can be determined. Some faults can directly display the cause of the alarm on the screen. Some have alarm information but do not directly reflect the cause of the alarm. Some faults do not generate alarm information, but some actions are not executed. In the above two situations, tracking the operation of the PLC program is an effective way to check the fault.

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PLC system hardware failure should be easier to handle than single-chip system hardware. Single-chip system hardware failure sometimes makes it difficult to check the running program.

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I remember working in PLC for a year when I just graduated.