GuyMiller

EEPROM PLC's

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I thought only PLC5's had EEPROM, but I was told MicroLogix PLC's also have an EEPROM that need to be burned to... What are all the PLC's that have EEPROM and require an EEPROM burn to prevent the program from being wiped in a power cycle?

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The Micrologix has an optional memory module that's you can save the program to but it is not required. If you don't have a memory module installed it will retain its program during a power cycle.

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Just now, TimWilborne said:

The Micrologix has an optional memory module that's you can save the program to but it is not required. If you don't have a memory module installed it will retain its program during a power cycle.

Mostly true but, unless AB fixed it, if the power glitches it can clear the program in a Micrologix. It's not an "everytime thing" but I've seen it happen more than once. On the other hand (and I think this is just as bad), if you use the memory card and "auto reload" the program on powerup that has it's own issues. (1) If a tech makes a change and doesn't update the program on the memory card, the PLC will reload the old program when power cycled and you lose the change. That could have safety an/or operations implications (2) Updating the card will require interrupting the process. For these reasons, we stopped using the cards, installed and maintained small UPS systems to mitigate power blips, and as far as I know we don't have "program dump" issue anymore.

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At least in the times I've seen it, it was due to poor grounds.  They are really susceptible to grounding issues.  Think it comes up as error 6H but I'm not near a PC.

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That could very well be the case. It didn't happen at every site, only 2, maybe 3 out of 55 total. And, it just occurred to me that it was the Compact Logix PLC not the Micrologix that had issues with glitches. The Micrologix PLC's were tanks. I even had an electrician run a sawzall blade through one :/ but it didn't survive :) It would've made a great commercial for AB if it had.

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The MicroLogix PLCs are indeed tanks. At my previous employer, we had an 1100 controlling part of the wastewater treatment plant. Once, some caustic solution leaked into the cabinet and into the ML1100 and the Red Lion HMI (G306). The PLC and HMI soldiered on for at least another year with very obvious damage. We ended up having to replace both a while later, but I was very impressed with their sturdiness. It might have been nice to get a production window to replace them BEFORE they completely died but, alas, such was not the case.

I've seen power glitches wipe programs, but only on the SLC 500 modular units (5/02 thru 5/04) and usually then when the chassis or power supply was getting flaky. I don't think I've ever seen a MicroLogix or 5000-class PLC do it.

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12 minutes ago, Joe E. said:

The MicroLogix PLCs are indeed tanks. At my previous employer, we had an 1100 controlling part of the wastewater treatment plant. Once, some caustic solution leaked into the cabinet and into the ML1100 and the Red Lion HMI (G306). The PLC and HMI soldiered on for at least another year with very obvious damage. We ended up having to replace both a while later, but I was very impressed with their sturdiness. It might have been nice to get a production window to replace them BEFORE they completely died but, alas, such was not the case.

I've seen power glitches wipe programs, but only on the SLC 500 modular units (5/02 thru 5/04) and usually then when the chassis or power supply was getting flaky. I don't think I've ever seen a MicroLogix or 5000-class PLC do it.

Wow, that must have been the mightiest control system ever built.  By the way, did it happen to to be sitting in front of two 5000 gallon tanks with a filter press to the right of it and a few ROs to the left as you were walking it?   :-2

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30 minutes ago, TimWilborne said:

Wow, that must have been the mightiest control system ever built.  By the way, did it happen to to be sitting in front of two 5000 gallon tanks with a filter press to the right of it and a few ROs to the left as you were walking it?   :-2

I don't know the capacity of the tanks, but that all sounds about right.... ;)

Did you ever work with ProChem? They subcontracted a local integrator to do some of the controls work on that system.

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I built the control panel back in 2009.  I did the original install but never went back to do any work on it.  

We build a lot of systems for companies that claim to do it all "in house".  We usually stay quiet about them but I figured 10 years was long enough.

What is funny is when we get a call about one of them because the "builder" won't support it anymore and they don't have programs or drawings.  Yes we might be able to figure out how it works for a fee :-)

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Just now, TimWilborne said:

I built the control panel back in 2009.  I did the original install but never went back to do any work on it.  

We build a lot of systems for companies that claim to do it all "in house".  We usually stay quiet about them but I figured 10 years was long enough.

What is funny is when we get a call about one of them because the "builder" won't support it anymore and they don't have programs or drawings.  Yes we might be able to figure out how it works for a fee :-)

Cool!

ProChem still maintains that system via remote access (cell modem). When I started there in late 2010, the main part of the system was still controlled by a PLC-5, but ProChem upgraded it to a CompactLogix soon after.

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Slow brown outs to nothing will wipe a micrologix that runs off AC power.
Which is why I've switched to the 24vdc units.

 

Edited by NevergoldMel
clarity

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