Faulted PLC in Field

[ZamoraE]

Hi,

I have been using Directsoft PLC`s for sometime now (DL05`s and 06`s), and recently I had a problem with a DL06-DD1 being used in a control panel for an injector machine. After connecting and powering up the system, with progam downloaded and I/O wired to it, it happened that while making some changes on the fly, after the 3rd or 4th Run Mode download, it faulted, showing the red LED on the PLC. After powering off/powering back on, the Fault LED was off but I was never able to communicate with this PLC again. I am using a GS2 inverter located in the same panel, aprox 10 inches away from the PLC. After testing during a time, the Fault LED turned on again. My 2 questions basically are: 1) Is it possible that an error in the program could lead to this unrecoverable fault condition on the PLC? I was using some GOTO instructions, and thinking that perhaps the program jumped out to some unprogrammed or bad memory location, I decided to take out this instruction from the program. I replaced the PLC with another of the same model, and has been working fine ever since. Question 2) Is it possible that the inverter`s operation frequency could be corrupting the memory in the PLC? I am planning to add Line reactors to the GS2 at input and output, EMI and RF filtering, but this will help the inverter not the PLC.

Thanks in advance. Your valuable input will help me design panel component location layout in a better way and also understand if the issue could be caused or not by the way it is programmed.

-EZ       

[MikeS]

Programming errors usually don't cause permanent damage to the PLC, they may cause a condition that kicks the watchdog timer which does turn on the CPU led, but it's not a permanent fault. I've seen bugs in comm protocols that cause stuff like this to happen, but again they weren't permanent, the PLC would come back after a power cycle.

Does the afflicted PLC work at all now? Is the comm still broken? Is it powering up in RUN mode? If so, does powering up in PGM mode change anything - use the RUN/PGM switch to force it to power up in the desired mode?

Invertors can cause a wide range of weirdness in PLC systems, ranging from mild interference to causing the PLC to crash. IMHO, putting PLC and invertors in the same panel should be discouraged, there just aren't many good ways to keep them the invertor from interfering with the PLC.

[marksji]

Have you connected to the PLC using DirectSoft and seen any program corruption?  If the program appears corrupt when you look at it with DS try updating the DL06 firmware to 2.30.