View Full Version : Blown 1771-IFE/IXE cards
May 15th, 2002, 07:55 AM
We were recently attempting to test some power-up and configuration logic (BTR/BTW). We wanted to simulate a power failure to a single card, and not an entire rack. While our PLC was running with power to the modules, we pulled the cards out of the backplane one at a time and reseated them, acting like a power failure. Needless to say, we fried two 1771-IXE and one 1771-IFE cards, and I am afraid to test this again.
Does anyone know a better way to simulate a power failure to one card (say 1771-IXE) and not another (say 1771-IFE)?
May 15th, 2002, 08:15 AM
Loss of backplane power to an individual module is a pretty unlikely mode of failure. It's much more likely that all modules in the rack will be affected.
I can understand wanting to check the behavior if external power fails to an individual module, but not backplane power.
May 16th, 2002, 11:57 PM
Doesn't anyone read the manuals these days. - hee hee
I have heard of thorough (can't spell it) but this is rediculous.
- sorry, did not mean to offend, but I had to say something. This post had me rolling on the floor.
May 17th, 2002, 01:21 AM
I agree with you, ganutenator....
I guess A-B wasn't "thorough" enough with their explanation?
May 17th, 2002, 06:34 AM
I am pretty sure we have quite dissimilar backgrounds, so maybe one of you can tell me how to simulate the loss of power in one card and not the rest, and simulate how the software will respond? This may sound silly to you, but there are certain places in which the reliability of manuals is not to be trusted, regardless of how "thorough" you can read.
May 17th, 2002, 07:15 AM
What you are attempting is called a HOT SWAP. Most PLC manufactures do not allow you to do a hot swap because it could damage the equipment. AB does not allow you to do a hot swap, because they did not design or build the equipment to do so.
I do not believe that you will lose back plane or rack power to one card. I have been working with PLC's for over 20 years and have never seen this happen, but this is not to say that it could not happen.
I think you are looking at too many possible ways the units can fail. PLC's are very robust and should not fail very offten, even if you are using AB.
May 17th, 2002, 07:48 AM
I think you may be focusing on an answer to the wrong question. You are asking: what happens if you loose power to a single I/O card? Who knows or cares? Never say never, but as others have pointed out the probability of this happening is incredibly low. If you truly need that level of reliability then you should be looking at hot back-up and redundant PLCs.
Now, for process or safety reasons, you may need to answer the question: What happens if I loose all of the signals on one I/O card but not the others? This is a different matter entirely, certainly possible, and fairly easy to simulate. You can simply drop out the external power supply to the I/O. If the module has a removable terminal strip you can even pull the terminal strip "live" while leaving the module in place (after verifying through the manual that this is not disallowed, and making sure you aren't working with dangerous voltages or explosive environments.) Just make sure you power down before you re-install the strip, since it is easy to be off by just one position and let the smoke out of the card.
I hate to pour salt in your wound, Dustin, but I have to add that I also got a laugh out of your predicament. Rule number one - don't pull components under power unless you are certain of what is going to happen!
January 16th, 2008, 10:32 PM
Well Dustin, there is a saying about the "School of Hard Knocks".
While I always shut down when possible sometimes you really need to avoid the shut down, gracefull or otherwise. No point taking needless risks that the OEM says not to...
I've spent 20 years working with a single large installed base of over 2000 racks with 300+ processors (PLC-2, PLC-3 and PLC-5)of 1771 equipment and have never seen a failure to one slot like you may have tried to simulate. Rack failures are very rare but P7's do routinly kill some 5/40e's (but not classic 5's)
On numerous occasions though I have hot swapped cards with predictable results. The only one I know of that WILL cause a problem is a 1771-SIM module. Swap it hot on a remote rack and it WILL kill the 1771-ASB. Tested that one several times, never on a processor and never again.
Discreet cards never caused a problem and analog cards would lock the PLC-5 about 30% of the time, often with a corrupted program.
Why do it? Some applications really do not lend themselves to be shut down. In that case prepare a loaded spare processor and go for it. If it works, you've avoided the shut down. If it doesn't, shut it down and swap or reload the processor.
With my experiences I can't figure out how you killed the analog cards but unless your boss has deep pockets (like mine) I doubt if you'll do it again.