Net-Eni (MicroLogix 1200) Communication loss over time with Third-Party scada

JPS_BPR

Member
Join Date
Jan 2011
Location
Montreal
Posts
15
Hi,


I am having problem with communication via third-party Scada (Citect 7.10) to a 1761-Net-ENI, connected to a ML1200.


The Scada is running on a PC, linked to the Net-ENI, retrieving data directly to the PLC (with Citect's built-in A-B communication driver, using port 44818).


We tried 2 different method of communication:

1. Radio linked
2. Cellular linked, over internet


The problems observed were:


Loss of communication over time (1 day to 1 week) between scada and NET-ENI/PLC and...

* Net-ENI web page still available.
* RSLinx would not recognize unit (yellow "?" with a red cross)
* Ping could be done
* No apparent error (fault LED)
* PLC still worked fine (for controlling automation part)
* Only way to get comm back was to power up the whole unit (PLC and NET-ENI)

Some local A-B retailer told me that my problems could come from the fact that both of my link weren't completely "reserved" for the communication link (to be more clear, radio link had a camera also, PC, printer, etc., compared to a "reserved" link that would be PC <--> Comm cable <--> PLC only, no other network equipment, and internet linked was not protected with something like a VPN) (hope that was clear enough). That was due to the fact that NET-ENI had a limited amount of inc/outgoing connection (2 in, 2 out, 2 mixed) and that some network equipment would use those (like a camera or printer) and have my scada get a loss of communication over time.


I have 3 questions regarding that.


First...


What way could i setup that in order to have less problem on both of my communication method:

1. Radio-linked: Have a VLAN only for PLC and PC? Get all other network equipment out of that VLAN?
2. Cellular-linked: Have a VPN? Have a firewall restricting only some port and some IPs?

Second...


Is there any way i can have a clear diagnostic of what's happening when the Scada stops communicating? I have no error on NET-ENI, PLC do still works, web page is ok, just can't connect data to scada...


Third...


I heard, looking into various forum, that NET-ENI could have problem dropping connection that aren't active anymore. Like if my PC is having a communication glitch, the NET-ENI would then use a new connection and not drop the first one, so after 3 glitch it would loss communication. Could that be true?


Some more information:

* Scada's error is something like "Can't communicate, channel (I/O device) is disconnected"
* Testing my setup while it was working fine, i could have RSLinx, Remote PC with SCADA and a local laptop also with scada, all connected to PLC, all working fine. That was done with electrical and network failure simulation, rebooting, cable disconnecting, etc...
* I think my NET-ENI is a "D" revision, could get that confirmed if needed.
* My scada is polling data at a good rate (let's say something like once every second, for about 15 tags)

Besides my main questions, if anyone has any clue on what could be happening, please feel free to add replies!


Thanks a lot for looking into that,

JPS


PS: I do have searched on many forums, have found some similar problems but without clear answers, so if i missed one, will be happy to be redirected to it.
 
Have you tried cycling power to only the NET-ENI module?

I have one connected to the serial port of a SLC 5/04 that had similar symptoms and it would recover by cycling power only to the NET-ENI module.

Later, I found a poorly crimped CAT5 cable, replaced it, and it hasn't happened since.
 
If it is a Rev D and firmware 3.21, update the firmware to 3.22. I've had similar problems and the firmware update fixed them.
 
Net ENI's can only have 3 connections theses can be seen on the web pageand tes it does do double ups to the same address

Another option is change the ML1200 to an ML1100 or a ML1400 and do comms with ethernet without the need for the NetENI.
 
We also use the Digi One IAP and have found it to have some superior qualites too.

I already used Digi One IAP for other project and they work pretty good (actually managed to do some magic things with those.

I did not know i could connect one with DF1 port tho, or am i missing somthing?

Is there any place i could get an explanation on this? I'll check today, but if anyone has somewhere they know.

If it is a Rev D and firmware 3.21, update the firmware to 3.22. I've had similar problems and the firmware update fixed them.
3

Need to check this, it will be done next week. To be continued...

[...]it does do double ups to the same address

Sorry i don't get that one. What do you mean?

Another option is change the ML1200 to an ML1100 or a ML1400 and do comms with ethernet without the need for the NetENI.

I know that was my first talked to OEM on startup of project, but they never wanted to do it for multiple reasons. I'm currently asking them to propose us a way to replace PLC with 1100, but i would not commit myself that this would correct the problem, as i still can't say 100% that NET-ENI is the actual REAL problem. What do you think?


Thanks all!
 
I've had the exact same problem with a Micrologix 1200 connected to a supervisory network through a 1761-NET-ENI using radios. It is definitely a timeout issue that causes the ENI to quite responding on the Ethernet port. The only permanant solution we could find was to go to a wired network. Even then if we were doing maintenance on the supervisory system you could usually count on it ceasing to respond.

If I recall it still did respond on the serial side. It seems we put some heartbeat code in one of them that we couldn't hard wire. If it timed out X amount of times in a row it would reset the ENI which would bring communications back online. Not a real fix but I can hunt and see if I can find it if you are interested
 
If I recall it still did respond on the serial side. It seems we put some heartbeat code in one of them that we couldn't hard wire. If it timed out X amount of times in a row it would reset the ENI which would bring communications back online. Not a real fix but I can hunt and see if I can find it if you are interested

I would be definitely interested in how you are doing the reset of the ENI. How are you monitoring the comm. with the ENI so you know when to reset it? We have installed several ENIs for our customers along with cell modems. There are times when we cannot get data but we can pull up the web pages. In our case we are pulling data into Excel on a periodic basis, usually 2 times a day. We also use the ENIs for sending emails when alarms are activated. If I had my choice I would never use these things because they are very erractic in operation. We recently installed one in a panel that has a SLC 5/05. We could have gotten web pages from the 5/05 but it doesn't do email so we went with the ENI. Would be nice to have a better solution.
 
I've had the exact same problem with a Micrologix 1200 connected to a supervisory network through a 1761-NET-ENI using radios. It is definitely a timeout issue that causes the ENI to quite responding on the Ethernet port. The only permanant solution we could find was to go to a wired network. Even then if we were doing maintenance on the supervisory system you could usually count on it ceasing to respond.

Just to make sure, the timeout issue is a timeout built-in the NET-ENI or from the comm driver? In other word, is it something i can change or not?

If I recall it still did respond on the serial side. It seems we put some heartbeat code in one of them that we couldn't hard wire. If it timed out X amount of times in a row it would reset the ENI which would bring communications back online. Not a real fix but I can hunt and see if I can find it if you are interested

Surely i'm interested, that would be great help!

thanks
 
If it is a Rev D and firmware 3.21, update the firmware to 3.22. I've had similar problems and the firmware update fixed them.

Firmware is 03.21, i'll have it updated next week.

Was your setup exactly the same as me, or was it a bit different?

Thank you
 

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