Rob_W

Looking for help with an FX3 fault

12 posts in this topic

I volunteer for a charity and have the remit to look after a piece of heavy equipment that's controlled by an FX3 series PLC.

Long term I need to understand how to reprogram it, but in the short term we have a problem: the PLC is displaying  a light on its "PLC fault" output. It has previously suffered from intermittent faults. Is this something that an inexperienced engineer (me) could attempt?

I have limited documentation, including a E1032 installation manual (operator terminal).

I'd appreciate any help!

 

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Dear @Rob_W It's broke I doubt you can make it worse if you proceed wisely and cautiously.

Welcome to MRPLC - Now for some basic questions - no insult to your education or experience intended.

Have you determined the exact model number by looking at the FX3 Nameplate and retrieved a copy of it's user manual from Mr. Google?

If so you'll most likely find a troubleshooting section that tells you how to interpret the fault light and some some common recovery steps.

IF those fail to resolve the issue post back here with a journal entry of what you've done and seen and you're likely to get relevant help.

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The manual for the hardware will indicate what the error means.  Sometimes the light is solid, sometimes flashing.  The manual will indicate what each means.  

The battery may have gone dead and the program may be lost.

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Thanks Bob, I'll follow your steps and report back if needed.

Rob

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Please see photo of front panel. Does anything look obvious?

I'll now go and get the manual from Mr G.

PLC panel_small.jpg

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It appears to be in 'run' mode with no error light. (unless it was flashing and you took the photo while it was off)

A output is on - so there is still a program in there.

You'll need GX Works 2 to go online and find the fault in the program.

 

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Thanks @Ron_S. That PLC output is described in the so-called documentation for the machine as PLC fault - I suppose the program just gave up!

Anyway, I will tackle GX Works 2 next. Not sure where/how to get this - I've seen some high prices but someone told me it's also shareware. Any advice on getting it please?

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GX Works2 is NOT shareware.  You need to purchase it from an authorized Mitsubishi distributor.  The older software GX-Developer had an FX-only version that was lower cost, not sure if GX Works2 offers the same or not.

So there is nothing wrong with the PLC.  If that output is the fault, that's based on the program inside the CPU turning that on.  If there was a PLC problem, the error light on the right would be on, and the run light would typically be off...

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Until PLC Power and Program leds are on and Batt and Error Leds are OFF PLC and program are fine! 

Y0 ("PLC Fault") is driven by the sequece program under specific conditions and no connection to PLC system status. More sound's like machine fault... E-stop button, door lock, safety relay... firt 4/8 inputs ( written as barieres)... missing input for fault reset.

Check machine wiring diagram to determine inputs status requered for normal operation of machine.

Not long ago i had a problem with Fx1N on chinese machine. 

There was timer sequence in the program, that brings the machine to stop mode after 3600 working hours nad there's no input or any other way to reset it.

Programmer or machine designer mistake i assume... off course the idea is maintenance every 3600 hourse.. oil, filters and so on, but no message on HMI or way to tell the machine, that it's done.

I had to modify that part of the program ( self reset ) to bring back the machine runing.

Edited by glavanov
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Thanks, I'm getting to learn this! It's also confusing that some logic is inverted - for example the documentation names an input as "Barrier loss" but it actually means Battery OK".

Agree that Y0 is only a function of inputs. I now think it should be on if everything is OK.

I also think we have an error signal from a battery charger which is also an input to the PLC - photo attached.I will debug that next.

Battery charger 13 Sep 3.37pm.jpg

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Hi, If the plc is FX3U series you should be able to use GX Developer and may be freeware from internet. First obtain s/w and try to download the program ladder from plc.

Have you tried to reset the plc when it is safe to do so. Run/Reset would do the reset.

Let us know where you are now once you have done above.

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Thanks, have done a rest, but still stopped.

I've now found a problem with a failed backup battery which could be stopping the program from running.

Will update here when I know more!

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