1756-enbt connection issue

[jtashaffer]

I can't connect with my controllogix plc over Ethernet. I have talked to tech support over a 2 day period and they told me to change it out. I have one on order. what am I missing. If I connect directly to the unit it works fine but not through the network! It will also take hmi's along time to pull data from this unit, I guess because of the same issues. Has anyone ran across this. I will say that the controller doesn't fault and works great besides trying to connect to it and the slow recognition from it to the hmi's

 

[Ken Roach]

Clarify the difference between "connecting directly to the unit" and "connecting to the network".

The cables you use and the traffic that might be on the local switch are going to be good troubleshooting tools.

The fact that you can connect directly and get good speed suggests it's a problem in the cable, the network, the traffic, or the application.

Did this problem just start recently ?

One thing I did encounter a few months ago was a version of RSLinx that would send out browse packets every few milliseconds; I don't recall the exact issue because it happened to a co-worker. When that particular computer was connected to the network, our HMIs slowed way down. When we looked for the problem, it was obvious on Wireshark.

 

[jtashaffer]

Directly From the laptop to the Ethernet module. Through the network is through a unmanaged switch in the cabinet to the Ethernet module or somewhere else in the plant to the unit. I changed cables, I changed what main switch it went to. Still had the same results. The connection problem where it wouldn't connect at just happened. It has gave me issues in the past where I could pan down through the back plane to select the controller in linx's. I could hit the + symbol or I couldn't connect if I did. We have been adding several hmi's to this plc that pull data. There is about 12 or so. Rockwell said that was the problem.

 

[Geospark]

...If I connect directly to the unit it works fine but not through the network!...

...Directly From the laptop to the Ethernet module. Through the network is through a unmanaged switch in the cabinet to the Ethernet module or somewhere else in the plant to the unit. I changed cables, I changed what main switch it went to. Still had the same results. The connection problem where it wouldn't connect at just happened. It has gave me issues in the past where I could pan down through the back plane to select the controller in linx's. I could hit the + symbol or I couldn't connect if I did. We have been adding several hmi's to this plc that pull data. There is about 12 or so. Rockwell said that was the problem.

With that much traffic exchanging between the Controller/Ethernet module and the HMIs and whatever else, an unmanaged switch in the cabinet could be bottlenecking the network?

What else is plugged to the unmanaged switch in the cabinet?

Are all the devices that communicate with this controller connected to a managed switch?

Is the managed switch Layer 2?

Is it configured correctly?

Have a read of this...

22044 - EtherNet/IP Switch Considerations
Access Level: Everyone

and here...

24380 - Ethernet/IP, Switches, and Multicast Frames
Access Level: TechConnect

Regards,
George

 

[rocksalt]

Who made the cable end connections? If they are wired pin to pin it will not work right.

 

[Ken Roach]

We have been adding several hmi's to this plc that pull data. There is about 12 or so.

That would be my first guess, too. The whole point of distributed HMI software like Ignition or FTView SE is to reduce the number of devices hammering away at the controller for the same data. PanelView Plus is particularly notorious for consuming CIP connections; one PV+ can take up to five CIP connections.

The first few things I would do are:

1. Capture the connection counts and CPU utilization data from the 1756-ENBT's built-in webpage.

2. Capture the CPU utilization and connection counts for the 1756-ENBT and the ControlLogix using the Logix 5000 Task Monitor utility.

3. Check the configuration of the Overhead Time Slice on the ControlLogix to see if you can dedicate more controller resources to communications.

4. Examine the HMI applications to see if their data requests can be slowed down or optimized.

If the CPU utilization in the 1756-ENBT is a potential problem, a 1756-EN2T might be a solution with its faster processor and higher capacity.

But if the controller or the backplane buffers are the bottleneck, the solution is going to have to involve reduction of the communications load that the HMIs are putting on the controller.

 

[jtashaffer]

I can't get to the webpage unless I connect directly. I have a 1756-an2t on its way that is what Rockwell suggested. I also changed out the unmanaged switch in the panel

 

[Ken Roach]

Do you have an available slot in the chassis ?

If so, I recommend installing the 1756-EN2T when it arrives, and using that to bridge to the backplane so you can run the Logix 5000 Task Monitor to evaluate the CPU utilization on the existing system.

If it were my system, I would set up the 1756-EN2T for its own IP address, then re-target my HMIs to the new module one at a time, measuring the impact on CPU loading on the controller and the existing 1756-ENBT.

The only thing I like less than not knowing why something broke is not knowing why it was fixed.

 

[rdrast]

What kind of HMI's?
Having 12 independent HMI's all polling the same data would definitely be a problem. This is where a Archestra/Wonderware Galaxy would be fantastic, as it only needs to pull data from a single connection to the PLC.

FTView SE can also do that, but I wouldn't recommend it.

 

[Geospark]

Also worth noting...

28973 - Maximum Number of PanelView Plus HMIs Per ControlLogix Controller
Access Level: TechConnect

Regards,
George

 

[jtashaffer]

It says no more than 5!!! I have one Panelview plus and 14 proface hmi's. So I am way over the limit if I am reading that last tech note right. Even upgrading to a en2t won't help? By what that said.

 

[Ken Roach]

Not all HMIs work the same way. PanelView Plus terminals can use between 1 and 5 connections, depending on what features and how much data you use.

But twelve HMIs is almost certainly a heavy load on the controller and a significant element in your problem.

 

[jtashaffer]

Update: I changed the Ethernet card to a 1756-EN2T and all my connections picked up and started working. I was able to connect to everything even the webpage. Thanks for all your help