Multiple Racks on SLC

alive15 · Jul 24, 2019

Good afternoon all,

I noticed in my plc program for my SLC 5/03, there is an option to have multiple racks (see pic below)? I thought it was very interesting, is this similar to flex or point i/o with compact logix? Has anyone ever used this option before with success? Very curious about this option, never noticed until now.

Thanks!

sparkie · Jul 24, 2019

Racks are connected via a ribbon cable. I don't know the right part number. There is also a limit on IO points and how many racks/modules can be daisy-chained this way.

The other way this is done is via RIO. Really, really, really stay away from RIO. You have to set a bunch of dip switches just right and deal with a bunch of cryptic settings to get everything working correctly and mapped correctly. It is very time-consuming and not something you want to mess with. Hope you never have to. Just as an aside, RIO is more equivalent to something like flexIO.

All your questions are answered in-depth here:

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/1747-um011_-en-p.pdf

rupej · Jul 24, 2019

sparkie said:
The other way this is done is via RIO. Really, really, really stay away from RIO. You have to set a bunch of dip switches just right and deal with a bunch of cryptic settings to get everything working correctly and mapped correctly. It is very time-consuming and not something you want to mess with. Hope you never have to. Just as an aside, RIO is more equivalent to something like flexIO.

Amen. I'm currently working on a project with a SLC 5/05 with a RIO scanner controlling 3 Flex I/O racks. What a pain- the address scheme is nuts and I still don't completely understand it, after reading both the scanner and the flex RIO adapter manuals. I think if I had to add I/O, I would just MSG a MicroLogix or another SLC rack, or as I call it "Poor man's remote I/O".

sparkie · Jul 24, 2019

rupej said:
Amen. I'm currently working on a project with a SLC 5/05 with a RIO scanner controlling 3 Flex I/O racks. What a pain- the address scheme is nuts and I still don't completely understand it, after reading both the scanner and the flex RIO adapter manuals. I think if I had to add I/O, I would just MSG a MicroLogix or another SLC rack, or as I call it "Poor man's remote I/O".

Dude, unless the IO was required to be deterministic, I would totally pack all of the data for periodic transmit with a heartbeat and fault state.

JaxGTO · Jul 25, 2019

I have put in several SLC systems with 3 13 slot racks. mostly conveyor systems with lots of motor starters and photo-eyes.
On a side note if you upgrade the SLC with a AENT to a ControlLogix you have to use version 21 or higher to recognize the additional racks.

alive15 · Jul 25, 2019

@All Thanks for the great info!

Ken Roach · Jul 25, 2019

the address scheme is nuts and I still don't completely understand it

This is the result of grafting on a network designed in 1977 to a controller designed in 1988 that should have been obsoleted in 1999.

You're not alone in being confused by the RIO addressing and configuration scheme. I barely dipped my toe into the PLC-2/3 era, but it was enough to remind me to think in Octal and appreciate the limited data table space in the old controller platforms.

The simple answer to the original question is "up to three physical chassis, up to 30 addressable slots, but limited to 256 words of Input and 256 words of Output data".

Each chassis needs its own power supply.

Ron Beaufort · Jul 25, 2019

here's something else that hasn't been made really clear ...

the cables that connect all of the chassis together are only about 3 feet long at most ... that means that all of the "expanded" chassis have to be really close together ... specifically, you can't mount an "extended" chassis in another panel the same way that you can set up "remote I/O" ...

James Mcquade · Jul 25, 2019

in any modular slc 5/02,03,04,05 system using the ribbon cable to connect chassis, you are limited to 1 plc processor and 29 I/o slots for a total of 30 slots ! yes, you can configure (3) 13 slot racks, but you will only be able to use 29 of them.

if anyone has used more than (3) 10 slot racks successfully, please post how.

james

EICS · Jul 26, 2019

when AB came out with the SLC platform we just kept buying PLC5's as they just worked. the SLC range was ****ty in my Opinion and only marginally just better than Micrologix 1000,1200 and 1500 paperweights.

cost us money initially but they are still in service to this day without issue (Ever)

i do like the ML1100 & 1400's

alive15 · Jul 26, 2019

@Ken Your first sentence describes the situation very well, thanks for your input.

@Ron Ah, I see, I thought you could place in a different cabinet much farther away, but looks like it is difficult. Rockwell didn't create any extension cable I am assuming.

@James From what I have read about these, I am unsure if many people have even used this option. But it would seem very useful on extremely large projects like Jax was referring to. If you can figure out all the addressing and keep the i/o organized, then this option could be very useful. But still very difficult to troubleshoot so many i/o slots.

@EICS We only have one plc5 in our plant now, but slowly going towards compact logix.

kwade · Jul 26, 2019

We have a couple 5/04 systems like this

Code:

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.      +-------------------------+
.      |                         |
.      |                         |
.      >                         >------------+
.      |                         |            |
.      +-------------------------+            |
.                                             |
.  +------------------------------------------+
.  |
.  |   +-------------------------+
.  |   |                         |
.  |   |                         |
.  +--->                         >------------+
.      |                         |            |
.      +-------------------------+            |
.                                             |
.  +------------------------------------------+
.  |
.  |   +-------------------------+
.  |   |                         |
.  |   |                         |
.  +--->                         >
.      |                         |
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.
[/font]

The addressing is sequential. No mention of specific rack, just the next card in series.
The systems have several unpopulated slots, so I cannot check/confirm the 29/30 slot maximum.

Multiple Racks on SLC

alive15

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sparkie

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rupej

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sparkie

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JaxGTO

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alive15

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Ken Roach

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Ron Beaufort

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James Mcquade

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EICS

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alive15

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kwade

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