PLC fault analysis
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I’m not very familiar with PLCs; could everyone please help analyze this: There is an S7-300 PLC system, and the SF light as well as the STOP light on the CPU module are on. What could be the cause of such alarms? (The operators all said they hadn’t touched it.)
This post was last edited by zlky2005 on 2012-6-30 21:28: SF Red – Hardware or software error; BF Red – Bus error (applicable only to some PLCs with DP and PN interfaces); DC5V Green – The 5V power supply for the S7-300 CPU and internal bus is normal; FRCE Yellow – Forced operation is active; RUN Green – The CPU is in RUN mode； The LED light flashes at 2HZ, indicating a restart ； The LED flashes at 0.5 Hz to indicate HOLD. STOP Yellow: The CPU is in STOP, HOLD, or restart state ； The LED flashes at 0.5HZ, and the memory is in reset request state ； The LED lights flash at 2HZ during memory reset. Use the above information to make a judgment; if it doesn’t work, it’s better to consult Siemens, as that might be faster!
There are many reasons why the CPU of a PLC system stops working, and most of these are caused by error interruptions. In such cases, you can reset the CPU and restart it; if the problem persists, you can perform an online diagnosis of the PLC to identify the cause of the stoppage and then resolve it.