Remote I/O

Just thought I'd throw this question out there. A couple of days ago a ongoing project that was being worked on was hooked up incorrectly. On the Remote I/O "blue hose" cable the shield and the clear were inadvertantly swapped, or so I was told anyway. What are the ramifications of this senario happening? The system ran fine after this new block was put in for a 24hr period of time. Obviously I do not want to hook up and run a test of what will happen if??? on our critical spare parts but I also realize that their is a lot of knowledge on this site and someone may have heard of or done it themselves. Looking for feedback. Thanks.

Ozone

Don't worry about it. DH+ and RIO are very forgiving of miswiring. I have shorted and reversed dozens of plugs on PLC-5 and I/O blocks and never had any damage.

Just keep the 120V off the wires.... that can get exciting.

That's what I thought as well. My co-worker got in a whole pile of trouble from our boss though. He says if you get it wrong it will damage the system. All this work was done on my days off so I can't be 100% certain exactly what happened but it sounds odd to me.

This is what happened that is for certain:

A 1791-8AC was added to the remote I/O complete with the proper end of the line resistor.

The system was autoconfigured and accepted the new "block"

It ran for 24hrs.

I came in for nightshift, my boss had been working on it for awhile and I had to do the folowing to get it running:

I moved the end of the line resistor to the old location and did an autoconfigure.
All came back but 1 1791-16AC
I Replaced the 1791-16AC that would no longer communicate
Redid the autoconfigure and then away it went.
I then put another 1791-8AC in and redid the "blue hose" and moved the end of the line resistor.
I then did an autoconfigure again and all was up and running.



If it was wired wrong in the first place why would it autoconfig and "see" the added "block".

Why would it run for 24hrs and then quit by itself?

Sound weird to anyone but me????

I had a small DH+ setup that was running fine at 57.6k but I wanted faster response so I switched it to 230k. When I did that it began faulting very sporatically with no particular rhyme or reason to it. I found out that the clear and sheild wires were reversed in the middle of the run at a programming port connection. When I put them straight, I got much more reliable, but not perfect, results. I've only done one remote I/O installation and I don't remember the baud of it or if it is changeable but I would guess these types of things would get worse as the baud rate increases.

on RIO

On remote I/O wiring, if you swap the non-shield wires on a single
station, you'll have difficulty seeing that station with
auto-config. If all stations are swapped, then the processor
will not see any of them.

I've hooked up plenty of RIO over the years, and, without
exception, if you have a wire swap, things don't work. As to
the 'it worked for 24 hours' deal, that does sound weird.

I have a friend who works in a quarry, and they have all kinds
of trouble with RIO/DH+ wiring because of the routing of it
in the quarry, the use of medium voltage switchgear, and
too many inverters without chokes or filters. All those
problems are self-induced, of course.

I had a similar problem on an encoder cable once. The shield and common pins were swapped at one connector. It didn't cause any lasting problems, but the cable ran in a bundle with a 30 A DC power cable. The controller was supposed to move the servomotor immediately after turning off the DC supply. Boy, did that cause an EMI problem. The servo drive monitoring the encoder would fault out every time.

I don't think the swap on RIO would cause any lasting damage unless you had a huge EMI pulse hitting the cable. It's a good thing you fixed it, though.

Try grounding the "blue hose" to the chassis but only where it hooks up to the SN card. Make sure you only have resistors on the ends of the "blue hose" runs. Also make sure you are using the proper resistor. (57.6 k 150ohm, 115.2 k 150ohm, 230.4 k 82 ohm) These all sound like minimal problems but with my experience with it those are the ones that make the RIO flakey.