Using a SLC505 to control remote Ethernet components

Hey all,

I am considering using Ethernet style valve packs for a new machine were building. They are priced reasonably, and would certainly save a decent amount of time wiring - especially on a primarily pneumatic machine.

Our customer has spec'd in an AB SLC505, and I called our vendor's tech to get his input on the subject. Without any hesitation whatsoever, he brought up a concern which has been puzzling me all weekend.

Now bear with me - I am no PLC guru, just a 'simpler is better' guy. And please don't quote me here, I'm just rephrasing what I heard and only partially understood.

His concern had to with the 5/05's somewhat limited capabilities in regards to ethernet control of components. He was refering to the SLC's evolution over the last 20 years and how Ethernet was sort-of 'added on'. And that while the SLC's ethernet is proficient at messaging, when it comes to controlling discrete devices via ethernet, it has it's limitations - limitations that don't exist in the newer Compact/Control/FlexLogix type PLCs designed only a few years ago.

He gets calls here and there from customers who bought a component 'that works with AB plcs via ethernet' only to end up having troubles programming them. He recommended that I contact the manufacturer of the valve packs, and see if they even have any example code specifically for the 5/05.

It's all a bit over my head. I'm looking to save time by using these types of devices, not spend more time trying to figure them out.

Anyway, before I say 'forget it', I thought I'd run it up the flagpole here for a your thoughts/feedback.

Thanks in advance

Ethernet IO control is not in the SLC controllers (unless it has been recently added - I don't think so).

If you want to control IO over Ethernet, then you would need the Logix5000 family of controllers.

Thanks Oakley, you saved me a bunch of time/trouble.

Now why in the world wouldn't the vendor's tech just tell me that? sheesh!

Originally posted by Control Freak:

Now why in the world wouldn't the vendor's tech just tell me that? sheesh!

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I suspect because in come instances you can perform a level of 'control' over Ethernet using the SLC 5/05. The SLC family is incapable of doing true producer/consumer I/O over Ethernet. However, if your device can accept AB Ethernet messages and respond to them then you may be able to 'control' it.

Most discrete devices, like valve banks, don't respond to messages. In any case control via messages is generally a bad idea since there is no structure in place to make sure the communication link is valid when you message. So you may turn the device on and not be able to turn it off.

Keith

Devicenet would be an option to control banks of pneumatic manifolds. Most Pneumatic manf. have a Devicenet control option. Only caveat is that you would have to add a Devicenet Scanner card into your SLC I/O rack.

I WOULD not do control over ethernet. Too much chance of there being a network problem and losing control or instrumentaion not responding when you really, really want it to.

One note about the CLX produced/consumed ethernet comm model - you CANNOT create or modify these online. Once the system is running, and it can't be shut down, you can't add or change anything.
Sucks, but its a 'feature' of CIP I guess.

I would go with DeviceNet, Profibus or Foundation Fieldbus if your serious about using some kind of bus system for your instrumentation.

Note on DeviceNet with SLC platform - you cant add or change devices while online. So again, you have to shut the process down.
CLX platform doesnt have this problem.

Thanks for your input, guys.

I looked into the DeviceNet and ControlNet options when researching the Ethernet possibility. It seems that in addition to the DeviceNet scanner, I'd also have to purchase RSNetWorx to setup the network, and also the appropriate cable.
Taking that into consideration, along with the limitations of the SLC's backplane (which I presume is the reason that one cannot add/edit devices while online) I believe that the good ol' fashion I/O is probably the best appoach.

In fact, rarely has it NOT been the best approach, IMHO

Thanks again -

Control Freak said:

Thanks for your input, guys.

I looked into the DeviceNet and ControlNet options when researching the Ethernet possibility. It seems that in addition to the DeviceNet scanner, I'd also have to purchase RSNetWorx to setup the network, and also the appropriate cable.

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You would not need a separate cable. You can now see the devicenet over the backplane of the SLC. But I would advice buying a copy of RSNetworx. You'd have to take the initial hit, but you would be able to use it for any other Devicenet applications you happen upon.

Have you looked at Compactlogix platforms, using the Controlnet or Ethernet I/O? You can do point I/O like you have requested...

http://www.ab.com/programmablecontrol/pac/compactlogix/index.html

Better than the ancient SLC line, not as great as a full blown Controllogix, but at least you are using some current software and features....
We use controlnet everywhere here. Stable, and fast.

In the original post the customer spec'd out the 5/05, so that's his only choice.

Many users have resisted the CLX migration because of the added software cost.
Sooner or later, they will be forced to migrate, but they are delaying as long as possible. Many will continue to use the SLC line as long as Rockwell sells/supports it.

Specs can change...
SLC platform will end up costing more....features not available...
Nobody ever thinks about software for cards.......wait until you have to purchase RSNetworks for DeviceNet......DeviceNet Scanner Card....
It all adds up.

LJBMatt said:

You would not need a separate cable. You can now see the devicenet over the backplane of the SLC. But I would advice buying a copy of RSNetworx. You'd have to take the initial hit, but you would be able to use it for any other Devicenet applications you happen upon.

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I love that I get more accurate info here than from my vendor's tech

Ken Moore said:

Many users have resisted the CLX migration because of the added software cost.
Sooner or later, they will be forced to migrate, but they are delaying as long as possible. Many will continue to use the SLC line as long as Rockwell sells/supports it.

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I too have resisted the migration - for now. Naturally, when I have to (IE a customer writes it into their spec, or when it becomes more cost effective for me to do so) then I most certainly will. Right now the market is pretty tight, and more and more customers are focused heavily on price. (sad when price becomes more important than quality/capability) But honestly, I'd love to switch over right now. I've heard MANY great things about CLX and it's improvements.

SNK said:

Specs can change...
SLC platform will end up costing more....features not available...
Nobody ever thinks about software for cards.......wait until you have to purchase RSNetworks for DeviceNet......DeviceNet Scanner Card....
It all adds up.

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I couldn't agree more. Especially with AB, the add-ons add up very quickly. I think the 5/05 I have to purchase for this machine costs nearly double what a CompactLogix processor with Ethernet would cost.