Adding chassis to SLC

ASF

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Jun 2012
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Australia
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Hi all,


First thing in the new year I'm off to a remote site to add a second chassis to an existing SLC installation. All of the hardware is already in place (by others), I just have to turn up and commission it.

I've looked through the manual and the PLC program, and it really does seem quite straightforward. Plug it in, select the right model of chassis for rack 2 in the I/O configuration in Logix 500, and define the new cards in the new slots that appear.

But, having never performed this specific task before, I thought I'd put out a call for any things I might need to be aware of, any gotchas, anything you learned the hard way working with an SLC expansion chassis. The reason being, the site is remote in every sense of the word. The last time I went to this site, I arrived to find that mobile and internet service on the entire island had been down for three weeks. If I run into any especially creative problems, there's no guarantee I'll have google to help me solve them, so I thought I'd best prepare for the worst!

Anyone got tips, tricks or horror stories to share?
 
here's one potential gotcha ...

are they just connecting the new chassis by running a cable from the old to the new? ... if so, be aware that you MUST connect the END (the right-hand side) of the old chassis - to the BEGINNING (the left-hand side) of the new chassis ...

some guys order the wrong length cable - and try to hook up the END of the old chassis - to the END of the new chassis ...

so - specifically - left-to-left won't work ... right-to-right won't work ...

and each chassis has to have its own power supply ...

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

page 59 might be handy ...

DISCLAIMER: it's been awhile since I've had to deal with this setup ... Ken Roach will be along shortly and confirm - or deny - whether or not I'm right ... good luck with your project ...
 
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The last time I went to this site, I arrived to find that mobile and internet service on the entire island had been down for three weeks.


I didn't think Tassie was that bad :ROFLMAO:



Make sure the "others" have correctly seated all the cards and cables without bending any pins or forcing the card locators onto the chassis incorrectly.
 
I didn't think Tassie was that bad :ROFLMAO:
Hey, Tassie is quite nice this time of year. I was there this week on another project, and it was quite pleasant!


Thanks Ron, the right-to-left arrangement and PS in each chassis is indeed documented in the manuals I have - the cables are apparently "keyed" so they can only go one way (i.e. I don't believe you can physically make it go left-left or right-right). But on reflection, it would still be possible to go from left to right with the cable backwards. In any case, they've left the interconnect cable disconnected for me to plug in when I arrive, so hopefully all will be well on that front!
 
If my memory serves correct you don't have to enter the cards you can do a scan to determine what cards are in the chassis. The exception is a special module by a 3rd party like modules from Prosoft for example. Those special modules require you to put in information manually.

I hope they were careful installing the chassis connector cable and did not bend any pins.

Make sure the power supply has enough magic to hold the load of the cards. It has a built-in estimator but is only based on AB cards and if you have 3rd party cards in the mix the power supply estimation may be off by quite a bit.

Having a power supply that is too small or right on the line can cause a lot of intermittent problems so I always go for the largest size model 1746-P4 as long as it will fit in the physical cabinet.

If it's a 5/05 and using Ethernet there is an issue with the CIP settings when using the Ethernet IP driver and it may be a problem using the standard Ethernet driver also but not 100% on that one. Mickey has posted on that issue a bunch of times though so it should be easy to find.

I always try to make sure nobody is using or planning to use the 24 VDC sensor power from the SLC power supply. When I see it being used I try to change it if possible. A field fault could damage that power supply and it's more expensive and more trouble to replace than having a standard 24 VDC power supply.

If there is a partial field fault on sensors using the 24 VDC SLC power supply or an intermittent field fault it can cause processor faults and other things and be very difficult to find for the uninitiated.
 
If my memory serves correct you don't have to enter the cards you can do a scan to determine what cards are in the chassis. The exception is a special module by a 3rd party like modules from Prosoft for example. Those special modules require you to put in information manually.
Ah yes, I think you're right - I've not done that with an SLC but have done it with a Micrologix so the procedure should be the same.

I hope they were careful installing the chassis connector cable and did not bend any pins.
The customer was instructed not to connect the cable and to leave it for me to do when I arrive, so hopefully no issues on that front.

Make sure the power supply has enough magic to hold the load of the cards. It has a built-in estimator but is only based on AB cards and if you have 3rd party cards in the mix the power supply estimation may be off by quite a bit.

Having a power supply that is too small or right on the line can cause a lot of intermittent problems so I always go for the largest size model 1746-P4 as long as it will fit in the physical cabinet.
There is only one DI and one DO in the new rack, so no dramas there.

If it's a 5/05 and using Ethernet there is an issue with the CIP settings when using the Ethernet IP driver and it may be a problem using the standard Ethernet driver also but not 100% on that one. Mickey has posted on that issue a bunch of times though so it should be easy to find.
I did a quick search but all I could find was this thread which doesn't seem to be quite what you're referring to? Perhaps I just need some better search terms, can you give me any more detail to help me find it?

I always try to make sure nobody is using or planning to use the 24 VDC sensor power from the SLC power supply. When I see it being used I try to change it if possible. A field fault could damage that power supply and it's more expensive and more trouble to replace than having a standard 24 VDC power supply.

If there is a partial field fault on sensors using the 24 VDC SLC power supply or an intermittent field fault it can cause processor faults and other things and be very difficult to find for the uninitiated.
As the field power is already established, I'd be surprised to find them doing this. But I will check and confirm.


Thanks for the detailed response!
 
I've done such things before, though it never occurred to me to go backwards before.

Back up program and get data table info if necessary. Make sure to check for the presence of an EEPROM. You may have to update the program on it as well, lest it copy the old program into memory on reboot.

Power down rack and install cable
Set switch to program
Power up rack. Go into IO configuration and autoscan IO
Copy program to EEPROM if necessary
Profit
 
I did a quick search but all I could find was this thread which doesn't seem to be quite what you're referring to? Perhaps I just need some better search terms, can you give me any more detail to help me find it?

This is it. You found the right thread or at least one of many. Those CIP settings will prevent or corrupt online edits and also not let you connect or keep knocking you offline when connected.

This problem if fairly common with 5/05 processors using Ethernet.

That edits fail PDF file in the thread shows the correct settings to modify to cure this.
 
To "expand" a little further...

ASF said:
...First thing in the new year I'm off to a remote site to add a second chassis to an existing SLC installation. All of the hardware is already in place (by others), I just have to turn up and commission it...

We'd have to assume you have already covered the programming side of things, but either way and for the sake of advising the Forum in general...

You've probably already headed to or started this project upgrade by now and have most likely no issue with the following consideration that I'm going to mention. So for the purpose of this topic in general, and for anyone reading it and looking for as much info as possible; one other thing that users should bear in mind when adding to an existing SLC modular system is the processor's current memory consumption, or more importantly, what is left.

Note: The SLC modular controllers have no memory expansion options. However, an upgrade to a higher memory capacity processor may be possible (8k > 16k > 32k > 64k)

Although, in this case, we are only talking about two additional digital I/O modules, there may also be cases where a more fuller expansion chassis, or two, are being added. However, in all of these cases, whether adding a little or a lot to the physical side of things, they may all, by the nature of any required additional programming logic for the I/O points, push a project size over the maximum memory capacity for the processor in question.

Now, of course, if an existing project's processor has sufficient spare memory then there is generally little need for concern. But if it happened to be quite close to its maximum capacity, or indeed not, but the amount of additional programming logic is considerable, then it could possible run out while you are adding the logic, if you have not considered it to begin with.

So my advice is to make sure to check the existing processor's memory has sufficient headroom to add whatever programming logic is likely required to service the additional I/O points. Also consider the future in estimating the required memory, as often many of the additional I/O points may be added as spares and will not likely be utilized until a later date.

There are no hard figures for estimating the likely required programming memory usage for additional digital, analog or speciality I/O points. For instance, a single input point could add just one programming rung to one particular project, whereas it could add an entire and sizable subroutine in another particular project. It is completely application dependent so that is why I would say that users should carefully consider this when expanding existing older systems where the processor's memory is not relatively huge to begin with, and may already be considerably used up. An example, and as has happened to me in the past, is where a 16k processor is running "tight" and adding even additional local I/O (not expansion) required more memory for the programming than was available. An upgrade to a 32k processor was necessary. I have also had to upgrade from a 32k to a 64k processor where expansion I/O was added.

Just keep it in mind is all I'll say.

While there are no hard "per point" figures available for estimating the amount of memory that will be used in an SLC modular processor, there is a worksheet that has been around for Donkey's years to aid users in this task...

29481 - Estimating Memory Remaining on a 5/03, 5/04 and 5/05 Processor
Access Level: TechConnect

If you are more experienced at estimating likely memory consumption based on previous project observations, then you will most likely not bother with that worksheet. But for those who cannot or do not want to guess as much, it may prove useful.

Also, and regardless of whether or not you are adding additional I/O points, there is extensive information available on the amount of word memory consumed per programming instruction type. For instance, an OTE instruction uses 0.75 of a user word in memory, an XIC uses 1 user word, an ADD instruction uses 1.5 user words and a BSL uses 2 user words.

Did-you-know? - A single SLC program may contain up to a maximum of 12k user words. That is, within a single "LAD 2" routine file. If using a 16k, 32k or 64k processor, and the overall program exceeds the 12k user words boundary, then you must start a new file (LAD 3, etc.). Of course, it is good practice to structure our programs into several organizational subroutines, regardless of size, but still, we many of us know of or have seen those programs out there where the entire program logic was written in one single LAD 2 routine. So that is another small but important fact to consider if physically expanding or programatically adding to existing projects.

As the technote above is "TechConnect" only - the worksheet and any memory usage information it mentions are available in the...

SLC 500 Instruction Set Reference Manual

Always a bit of "light" reading in there.

Regards,
George
 
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Well, I'm onsite now and it really was as simple as plug in, read I/O config, download. So that's a win. Also a win is the shiny new mobile phone tower bolted to the factory roof that means I have plenty of internet. It's on about a ten degree lean, but there's reportedly a cyclone heading this way so that'll probably straighten it back up nicely. Not sure what it'll do to the tiny little twin prop aeroplane I'm supposed to fly out on, but I'm sure nothing could possibly go wrong. I mean aside from the 300kW compressor motor that just caught fire, but that's only indirectly related to the cyclone so not a big problem.
 

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