Flex I/O Configuration and EN2T

h-townmobile

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I am contacting you in regards to erroneous readings from a 1794-IT8 after several oven cycles and a 1756-EN2T in your I/O configuration. There are two instances of 1756-EN2T OVENS02 Why was the second instances created? The second iteration of the EN2T is located just before the oven we are having problems with. That what's directing toword this as being the problem.

This is a system with fourteen ovens controlled by a centralized controller.

Why can't it be removed?

Could this be our culprit?

Attached are images of the I/O Configuration with the two instances of EN2Ts.

1st EN2T.JPG 2nd EN2T.JPG
 
Parent/Child Modules

Hi and Welcome to the Forum!

Your first paragraph reads like you've posted an extract from an email that a disgruntled customer sent you?

Anyway...

This is the centralized controller we are looking at, I take it?

When you add a local EN2T communications module to the backplane, you are effectively adding a port for which the backplane can access that particular network. The local EN2T is the Parent over all the modules that are added under its Ethernet port. When you expand the EN2T module, you can see the Ethernet port.

For the I/O Configuration, this Ethernet port represents everything that will be added to the network, and everything that may communicate with each other on that network. This includes the local EN2T module itself. So as soon as you add an Ethernet Child module, under the Ethernet port, the local EN2T Parent module is automatically added as well, as it too will be part of this network.

Once this duplicate instance of the EN2T is added you cannot delete it. It is an integral part of the local I/O Configuration and must be present under the Ethernet port, else all other added modules cannot communicate with this local EN2T. Only if you were to delete the last remaining module from under the Ethernet port would the EN2T module instance disappear again.

Note how it has the very same name "OVENS02" as the Parent EN2T module. You cannot add two modules with the same name or you will get a Duplicate Name error. If you double-click the apparently Child EN2T module, you will see that the properties for the Parent module will open and the same IP address will be displayed. They are one and the same. Both instances are of the Parent EN2T module.

So what you are seeing is normal, except for one thing...

What does look odd, however, is where it has placed itself in the I/O Configuration tree, midway down? Normally, when you add the first Child module, the second instance of the Parent module plants itself right underneath the Ethernet port and never budges? How it could get down there, I'm not sure?

The fact that, in the I/O configuration tree, it's right at the Oven that is giving the erroneous readings could mean it's a glitch, corruption, or it could be nothing at all? The I/O tree normally lists the modules in the order they were added, rather than alphanumerically. When the first Child module is created, the Parent module's second instance, that is automatically added, sits right under the port and then the first created Child module underneath that. All other Child modules created after that are added underneath the last, and so on.

But the second instance of the Parent module should stay at the top? The order that RSLogix 5000/Logix Designer displays the I/O modules may have no bearing whatsoever on how they communicate in reality. This I/O tree representation is just a GUI, after all.

So I just cannot say with any certainty whether this is an issue or not.

An original copy of the program would be useful to compare with. Or else you could rebuild the I/O Configuration. That's not necessarily my recommendation, just yet, but something to consider if other options run dry.

Another thing, but not so important, is the naming convention...

It is a little mixed up, by the looks of things?

In my opinion, the local EN2T should not really be named "OVENS02" if it...

1. Is part of a centralized controller over a number of "OVENS"...

...and...

2. There is already an apparently correctly named 1794-AENT "OVENS02..."

Something like "OVENS_ENET" would be more suitable, perhaps? Anyway, it can be renamed if needs be, but it is not that important, just confusing to look at.

To summarize...

The fact that the second instance of the parent EN2T is present under the Ethernet port is perfectly normal.

The fact that it is not present directly underneath the Ethernet port does not look right, but whether it is a problem or not, I cannot say for sure.

The name of the EN2T may need to be addressed, if you so wish.

What I would be interested in knowing, if the above all proves irrelevant, is what erroneous readings are they getting?

What exactly is not working correctly?

Are there any error messages, particularly for communications?

Regards,
George

Attached is how the I/O Configuration would normally look (minus Flex I/O modules)...

Parent_Module_Duplication.jpg
 
Last edited:
I'm not really sure what you are asking, but I wanted to comment that we have had many issues with the 1794-IT8 modules just plain going stupid, and reading incorrect temperatures out of the blue. Removing and replacing the module fixes the issue temporarily, but we've had to replace all of the older modules with new ones. Hoping that works.
 
FLEX I/O Configuration and EN2T

The erroneous readings are as follows:
OVEN 10 process thermocouple only reads 20°C when the actual temperature is can be anything from 20°C to 160°C where an independent temperature controller monitors and limits high over-temperature limit. If OVEN10 power is cycled off and back on again the process thermocouple reads correctly for approximately one to two heating cycles and then reads ~20°C againg. We have measured the oven temperature with a separate device where the ovens temperature was 150°C, but the temperature measured in the logic was only 20°C.
Its almost like its reading another oven thats not in use and at ambient room temperature.

I agree that the placement 2nd instance, EN2T Child module, shouldnot be located where it is. We believe this is the culpruit, but not absolutely sure.

We are trying to exhaust every effeort before rebuilding the I/O Configuration.

We did see the yellow triangles next to the iteration of the EB2T module and OVEN10 components, however the oven has been restarted since then and we haven't been able to repeat the warning traingles.

I am attaching the .ACD file.
 
I would agree with rdrast that it's very possible that the 1794-IT8 module is suspect here. If you've proven the temperature probe is not defective then it's going to be something local to that ovens Flex rack. The individual module, the base, or even the adapter could be suspect.

When you see the warnings this in an indication that the local EN2T and the Flex adapter have lost comms between each other.

I would swap out or swap around the components for this Flex rack, starting with the IT8, to try and either move the problem or eliminate it. Paying close attention to the pins and there alignment. I would concentrate on eliminating the existing rack as being the culprit first.

If you cannot eliminate the problem at the rack end, then, yes, an I/O Configuration rebuild would probably be the next thing to try. If you can correct the EN2T's position in the I/O tree, then you can be more sure the configuration is good. It's current position may indicate some type of corruption of the configuration.


P.s. I cannot review your program today as I'm on a day off and heading away soon. I'm sure someone else can oblige you though.

Regards,
George
 
Last edited:
Found the solution

After determining that the problem was not hardware by swapping the IP addresses between two ovens. We saw the temperature control problem move to the oven that we swapped IP addresses.

We noticed that there was an intentional break in the sequence of the IP addresses - Ovens 1 to 9 had IP addresses 192.168.1.101 to 192.168.1.109 and Ovens 10 to 16 had IP addresses 192.168.1.120 to 192.168.1.126

We tried to rebuild the I/O Configuration tree and use IP address 192.168.1.110, which the software would not allow us to create, because the address was already in use. However there was no evidence that the address was being used.

We changed the IP addresses to all the ovens to 192.168.1.2 thru 192.168.1.16 and this moved the 2nd instance of the EN2T to the bottom of the I/O Configuration tree. An image of the new configuration is attached

New IO Configuration with 2nd iteration of 1756-ENT2 OVENA02.JPG
 

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