I cannot find my controller... only the ethernet module.

[JKanyce]

So, I have an Allen Bradley ethernet module, two DC input cards, and one DC output card on a 7 slot rack (1756-A7). I work in a huge plant and I have no idea where the controller is.

When I try to "upload" or "go online" with the ethernet module in Who Active, those options are grayed out (along with everything else except for Close and Help.) I am still green to a lot of this stuff, but I feel like I have gone online with ethernet modules, as opposed to the controller, on more than one occasion. The only difference is that, usually, the controller and ethernet modules are sitting next to each other on the same rack.

There is also a Flex I/O Ethernnet/IP Redundant Media Adapter (1794 AENTR) in this panel. Both the Ethernet card and the Flex I/O Adapters are connected to a Stratix. I don't know if this would have any effect on anything, I'm just wondering if this adapter "is" the controller in a sense... or if I must hunt down the "actual" controller.

I have attached pictures of the rack and adapter if that helps any.

Any help with this would be greatly appreciated. Thanks in advance for your response.

 

[Ken Roach]

Welcome to the PLCTalk forum community !

I feel like I have gone online with ethernet modules, as opposed to the controller, on more than one occasion. The only difference is that, usually, the controller and ethernet modules are sitting next to each other on the same rack.

It's a difference of one click on a communications path, or a device with a built-in Ethernet port.

For old PLC-5E or SLC-5/05 or MicroLogix 1100/1400 controllers, the Ethernet features are part of the PLC's operating system and handled entirely within the user program. So when you go online with those controllers, you browse them in RSLinx Classic, highlight just the icon, then go online.

CompactLogix controllers, and some of the newest generation of ControlLogix (1756-L8xE), have an Ethernet module built right into the CPU, so for those you can do the same.

But the rest of the 20-year history of the ControlLogix 1756 controllers involves a separate Ethernet module. Its configuration (IP address, subnet mask, gateway address) are stored onboard in nonvolatile memory, not in the user program.

For those, you have to browse *through* the Ethernet module, to the backplane, then to the CPU in its own slot.

In your situation, plug your computer into the Ethernet switch closest to that 1756 chassis and the FLEX adapter, open a web browser, and type in the IP address of the 1756-EN2T.

There should be a navigation tree on the left side of the embedded web page, with a Diagnostics folder and an I/O Connections tab.

That I/O Connections tab should show you the IP addresses of the Ethernet interface (probably a 1756-EN2T) that the controller running that chassis is using.

You should have a similar webpage in the 1794-AENTR as well, but I'm less familiar with those.


While the 1756-EN2T helpfully scrolls its own IP address across the face of it, the 1794-AENT doesn't. Now is a great time to make a sticker and label those devices with their IP addresses (and maybe a note to the next guy about the IP address and controller name that controls them).

 

[Ken Roach]

Edit: on the -EN2T the tab is labeled "Bridge Connections" not "IO Connections" like on the -ENBT I peeked at in my lab.

Advice: Never, ever, ever expose your ControlLogix to the Internet like the guys who I searched out just to look at the embedded web page on their Ethernet module, shown below:

 

[JKanyce]

Edit: on the -EN2T the tab is labeled "Bridge Connections" not "IO Connections" like on the -ENBT I peeked at in my lab.

Advice: Never, ever, ever expose your ControlLogix to the Internet like the guys who I searched out just to look at the embedded web page on their Ethernet module, shown below:

First, thanks for your response! Unfortunately, I followed your instructions, but nothing is displayed under Bridge Connections. See image.

 

[Ken Roach]

[Scratches head]

I don't know for certain if a "Rack Optimized" connection shows up under "Application Connections" or "Bridge Connections" on an -EN2T. I'm only accustomed to seeing Redundancy Module application connections on the Application Connection page. Is it possible that Rack Optimized connections don't show there at all ?

The photos you posted clearly show outputs being controlled on both the 1756 chassis and that one FLEX module, so they have to be under the control of *something*.

Are you 100% sure you are looking at the web page for that specific module ? Any chance that when you plugged into the nearest switch, you plugged into a different VLAN ?

You can also use the "browse backplane" feature to see if the backplane you're physically looking at matches.

There's an excellent Application Technique document about using various statistics, many of them on the embedded webserver, to do diagnostics on EtherNet/IP networks. But it doesn't describe in detail the Application Connection and Bridge Connection tabs.

https://literature.rockwellautomation.com/idc/groups/literature/documents/at/enet-at003_-en-p.pdf

There's also an "ARP Table" under the Advanced Diagnostic folder, which should tell you all the IP addresses that are communicating with this 1756-EN2T.

 

[Ken Moore]

I think he is unplugging the EN2T from the network, plugging into it and, thus sees zero connections.

 

[JKanyce]

I think he is unplugging the EN2T from the network, plugging into it and, thus sees zero connections.

Nope.

 

[I_Automation]

There is also the possibility that there is NO PLC in the system.



If a SCADA HMI is programmed to read the inputs and write directly to the outputs it is running the show. Also there can be a soft-PLC in a computer somewhere, Unless it is a PanelView product then RSLinx will not recognize it.

 

[Aardwizz]

You don't suppose all the I/O is being controlled by a soft PLC, do you?

If you plug your laptop into the Stratix (with a good IP address) so that you are IN the network and not just talking to it, can you browse the network via RSLinx ?

 

[I_Automation]

Your best bet is monitor the network with WireShark and see what other devices there are and try to connect with them in a browser or Windows Explorer in the network connections

 

[Ken Roach]

I'm very confused about why the I/O connections don't show up on the Bridged Connections tab.

That's definitely where they go, even for the Rack Optimized connections.