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Old February 21st, 2018, 11:56 AM   #1
Petr_Broza
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L24ER increasing number of nodes

Hello,

is there any way how to increase number of nodes of L24ER, which supports up to 8 Ethernet nodes? I'm thinking about additional Ethernet card module.

Thanks for suggestions
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Old February 21st, 2018, 12:12 PM   #2
Contr_Conn
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No, this is hard coded limit for the processor.
L27 or L30 can do 16
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Old February 21st, 2018, 03:54 PM   #3
PBuchanan
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As Contr_Conn said they are hard coded limits and align with the memory and other specs for small machine usage.

Most machines that would not exceed the memory of the L24ER would not have over 8 nodes.

Remember these are nodes /devices and not connections like in the past as with the old model a single device could consume multiple connections and this method was put in place to help simplify calculations and simplify the equipment selection process.
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Old February 21st, 2018, 04:06 PM   #4
Petr_Broza
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Thank you
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Old February 21st, 2018, 07:26 PM   #5
Geospark
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Soft, not Hard...

A slight correction, and in the interest of folks fully understanding the subtleties involved in such features...

The newer method of restricting the number of Ethernet nodes allowed for a particular controller is not hard coded into the controller. The Node Limit is a soft limit applied to the project in Logix Designer. If you add more Ethernet nodes to the I/O Configuration than are allowed for a particular controller then the project will not verify and so cannot be downloaded to the controller. Once downloaded we could, I suppose, then call the limit "hard coded" in the controller, but it it does not come "out-of-the-box" node limited. Nor is it restricted in firmware.

Theoretically, the controller may continue to open connections as requested until it has reached its total connections limit, which is 256 for the CompactLogix 5370 L1, L2, L3 controllers. Nothing has been changed in the controllers to limit connections. On the contrary, their connection limits were increased.

The software Node Limit for each controller is set in line with the expected size of the project and average Ethernet node count for applications suited to the specific controller. The L1, L2 or L3 each have 256 connections max. but the L16 is limited to 4 nodes whereas the L36 is limited to 48 nodes. As the L36 has far more memory and resources available it has the potential for larger projects with larger I/O node counts. Allowing 48 nodes on an L16 would place too great a burden on its resources, but not on it's connection count as we know it has the same 256 connections available to it as the L36. Also, while the CompactLogix controllers are considered medium range controllers, especially with respect to ControlLogix, and the L1 and L2 controllers are somewhat limited, I would not go so far as to say they are all just intended for "small machine usage". An L3 can quite easily, and often, run whole processes or production lines.

The reason for this software Node Limit is to prevent users from saturating the controller connection limit with implicit I/O by continuing to add Ethernet nodes (devices) unrestricted to the I/O Configuration in the project, as was the case of old. This could potentially leave little to no connections free for non I/O based Ethernet communications, such as HMI or MSG instructions.

In the past, nothing prevented a user from over burdening the controller with I/O nodes, even beyond its then somewhat more limited total connections. Only at runtime would it be realized that the controller could not handle all the communications placed upon it. It was also experienced to the point where a user could not even go online to certain controllers as there were no free connections. The 1769-L32E, in particular, is/was notorious for this. Either the controller was underrated for the application from the outset, or users continued to add communications without realizing the total connection limit for the controller. The SLC5/05 suffered a similar fate. These somewhat older, but Ethernet endowed controllers, were designed during a period where Industrial Ethernet was still in it's infancy and there were few to little Ethernet capable devices available to add and eat into their modest connection count. As more and more Ethernet devices were eventually introduced, these legacy Ethernet controllers quickly became inadequate.

By limiting the number of Ethernet nodes allowed in the project for a controller, it ensures that those I/O nodes will only use up a fixed maximum of the total connections for the controller. This then ensures that there should always be sufficient remaining connections to service non I/O communications.

Note: As the software Node Limit is placed solely on devices placed in the I/O Configuration, there is, in theory, nothing to stop users from saturating the remaining connections with non implicit I/O communications, such as a large number of HMI/SCADA clients or large volume of MSG instructions, for instance.

However, while these are unrestricted, they tend to be the lesser communication type in most projects. Besides, the new larger connection limit for these controllers has been designed to ensure that in cases where users have correctly sized a controller, based on the Node Limit, then the remaining connection count should not only meet but exceed normal requirements.

Another way to can the above information -

If they gave us the option to disable the Node Limit feature in Logix Designer, then there would be nothing else to prevent us from continuing to add nodes to the I/O Configuration and so potentially revert to type.

Regards,
George
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Old February 22nd, 2018, 01:20 AM   #6
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Quote:
Originally Posted by Geospark View Post
A slight correction, and in the interest of folks fully understanding the subtleties involved in such features...

The newer method of restricting the number of Ethernet nodes allowed for a particular controller is not hard coded into the controller. The Node Limit is a soft limit applied to the project in Logix Designer. If you add more Ethernet nodes to the I/O Configuration than are allowed for a particular controller then the project will not verify and so cannot be downloaded to the controller. Once downloaded we could, I suppose, then call the limit "hard coded" in the controller, but it it does not come "out-of-the-box" node limited. Nor is it restricted in firmware.
Nowhere was it said that the limit was hard coded "in" the controller. Contr_Conn said it was a hard coded limit for the processor meaning the L24ER of topic.

It is hard coded in logix designer because you can't change it. The meaning of hard coded is a that it can not be changed by the user so yes it is hard coded in logix designer.


Quote:
Originally Posted by Geospark View Post
I would not go so far as to say they are all just intended for "small machine usage". An L3 can quite easily, and often, run whole processes or production lines.
An L3 can run a small process or small production line as it's intended usage for small machine or small production lines.

Could someone use it on something large? Sure but when changes to the process are needed or slight expansion of I/O or additional drives or HMI's are needed then you would be in trouble and so many of us come into situations where someone was trying to save a buck and in the end they spend thousands for that original person trying to save a couple hundred.

Use the controller designed for the task. Controllers are designed as different sizes for a reason and more than just connection and node limits.

This is a big problem today people trying to use things for something they were not designed for and in this field it causes damages to equipment, wasted money and many times injury to people and is not something I think we should be encouraging.
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Old February 22nd, 2018, 01:36 AM   #7
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Quote:
Originally Posted by PBuchanan View Post

This is a big problem today people trying to use things for something they were not designed for and in this field it causes damages to equipment, wasted money and many times injury to people and is not something I think we should be encouraging.
Do you have a source for that?
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Old February 22nd, 2018, 04:28 AM   #8
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I often wonder why, no matter how well I try to inform people of my intentions, they still take exception to those intentions?

In retrospect, and in an effort to try meet you/ye half way on this...

Hard coded -

"Fix (data or parameters) in a program in such a way that they cannot be altered without modifying the program."

I suppose it does fall down to the use of the word "for" here and how it may be interpreted...

Quote:
Originally Posted by Contr_Conn
No, this is hard coded limit for the processor...
This could imply that it is hard coded in the project for the controller, as I've explained, and perhaps ye both meant. But it can also be interpreted as meaning it is a fixed or hard coded limit set in the controller itself, in the firmware, which would suggest more a hardware limitation, rather than the traditional sense of hard coding in the program and then transferring to the controller.

For that reason, I would correct myself in the use of the words "slight correction" and apologize if I appeared to be negating yere statements. Instead, it would have been better if I had used another common statement of mine in these situations - "For the sake of clarity". I usually use this when I think there is something that may be confused as something else, but the comments were not untrue, just open to misinterpretation, which is how it read to me. A novice, or greater, could go away with the notion that the controller, itself, is enforcing the Node Limit feature here, when, as we know, it is not.

Quote:
Originally Posted by PBuchanan
...An L3 can run a small process or small production line as it's intended usage for small machine or small production lines...Could someone use it on something large?...
Size is a relative thing in this game. I would leave the words "small" and "large" out of this altogether. I did not infer size, I was inferring simply "more than one". By "whole", I meant just that - A whole process or whole production line. Not small. Not large. Just whole. Putting it at its simplest, and L3 can run more than a single machine, comfortably. You did not say process or production line initially. If you had I would not have made my comments. You initially said "machine" singular, which had suggested to me that you were classing these types of controllers as only capable of single machine control. Now you are saying process or production lines, which is better aligned with what I was inferring. So it appears that my point was taken on board while you were replying there. That's a good thing.

Because size has nothing to do with what I was pointing out - A whole production line does not mean a large production line, by whatever yardstick we might use, and the fact that I was in no way suggesting to use an L3 for a "large" application; the rest of your comments are somewhat moot, to me. So I won't comment further on them.

There is no animosity intended in that post, whatsoever. Only a "slight correction" for myself and hopefully more clarification for you on what I meant.

Regards,
George
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