PLC not staying online, sometimes not connecting at all..

[Wilsonn15]

Hello everyone, so I have an issue with a plc on a crane not wanting to stay online for longer than 5 or so minutes. And sometimes not even wanting to connect at all once it takes itself offline. The Plc is a GE PACsystems RX3i, with 12 slots, with a CPU315 in slot 3. On this same network is a bunch of different Ethernet devices that all eventually plug into an “N-Tron” Ethernet switch module.. I have an HMI also on this network that seems to be communicating just fine, and not going out. I’m trying to connect to the plc and make it stay online through a pc which is also plugged into the Ethernet switch. I’ve changed Ethernet cords, and did some other testing and everything seems to be okay, but I can’t get the plc to stay online through the pc at all times and as mentioned above sometimes it doesn’t even want to connect after taking itself offline.. I’m using Proficy machine edition program through my pc also. any help is very much appreciated!! I will be glad to give someone some more information on it also!!

 

[Steve Bailey]

Is there anything in the PLC fault tables that points to network problems? Are all devices on the network fixed IP addresses? Check for duplicate IP addresses. Are any or all of the "bunch of different Ethernet devices" communicating with the PLC? The Rx3i is limited to 32 simultaneous connections. Is the PC going into hibernation or taking any power saving action when you lose the connection?

 

[Wilsonn15]

Is there anything in the PLC fault tables that points to network problems? Are all devices on the network fixed IP addresses? Check for duplicate IP addresses. Are any or all of the "bunch of different Ethernet devices" communicating with the PLC? The Rx3i is limited to 32 simultaneous connections. Is the PC going into hibernation or taking any power saving action when you lose the connection?

Okay so there is less than 32 simultaneous connections, I’m not sure about fixed IP address because I can swap devices around on the N-tron module and they still communicate no matter what port they are in. To view the fault table I’m thinking I’m gonna have to get the plc to stay online long enough to do that. I thought if duplicate addresses was the issue then it wouldn’t come online at all, correct? I’m familiar with everything but not an expert on the ip addressing and everything..

 

[Ken Roach]

Welcome to the PLCTalk forum community !

How does the Ethernet connection get to the crane ? Sometimes festoon wiring is used, but WiFi, dedicated IP radio, and even power carrier line modems are other methods.

Are the other Ethernet devices on a wired LAN on the crane, or offboard and elsewhere in the facility ?

What model of N-Tron switch is it ? Some have diagnostics, some don't.

 

[Wilsonn15]

Welcome to the PLCTalk forum community !

How does the Ethernet connection get to the crane ? Sometimes festoon wiring is used, but WiFi, dedicated IP radio, and even power carrier line modems are other methods.

Are the other Ethernet devices on a wired LAN on the crane, or offboard and elsewhere in the facility ?

What model of N-Tron switch is it ? Some have diagnostics, some don't.

So all the ethernet devices are connected through fiber optics, so for example the cab plc has an Ethernet cord that plugs into an ntron module and that ntron module is connected back to the main plc through fiber optics. All of that looks okay for the most part. The ntron module is an FX2 I believe(could be wrong on that)

 

[RET]

Make sure the ethernet port on the plc is configured to auto negotiate the bit rate and duplex mode.

 

[p8p8]

Could it be ip address conflict?

 

[Ken Roach]

Your problem probably isn't one that can be solved by checking a software box that says "work better", of course. You've got a network with a bunch of devices and media, and you need to understand and analyze it.

You mentioned an "FX2" in the N-Tron part number. That probably means that it has two 100 megabit fiber optic ports, like the popular 708FX2 model.

Those switches have a good proprietary management and diagnostics viewing tool called "N-View 2". You can download it from NTron/Red Lion.

Access to the diagnostic counters and features for the various fiber and Ethernet cable ports on your switch may help you identify media that is failing, if that's part of your problem. Or they might help you diagnose a speed/duplex mismatch or a malfunctioning device. Most duplicate IP conflicts are not intermittent or transitory: they knock the involved devices off the network until the conflict is resolved.

While link lights and flickering data indicators are helpful to establish basic connectivity, you really can't diagnose a complex thing like an Ethernet network by visually looking at the cables and plugs. You need to understand the layout and examine the settings and diagnostics of all the devices.

 

[CanSpellPLC]

To add to this discussion, if the following is true:
1) Your PC is a laptop
2) The PLC is physically accessible
3) The PLC can be taken off of the network without issue (which is presumably true if nothing catastrophic is happening with it taking itself offline)

You should physically connect an ethernet cable directly from your PC to the PLC and verify that it can go online and stay online. That way you can at least rule out hardware problems with the two devices.

If it works, you may have cable issues or, like others have mentioned, your issue my be IP addressing or protocol conflicts.

 

[CanSpellPLC]

You could also try switching the CPU to "stop" and see if it is accessible on the network. If it gets on and stays on that way, it may be due to excessive CommReq initiations.

 

[CanSpellPLC]

One last thing until I see updates, and my apologies for the rapid influx of messages.. A quick and dirty way to check for IP conflicts would be to ping it, if you haven't already tried. Then unplug the one from the PLC and see if it can still be pinged.

 

[Wilsonn15]

Your problem probably isn't one that can be solved by checking a software box that says "work better", of course. You've got a network with a bunch of devices and media, and you need to understand and analyze it.

You mentioned an "FX2" in the N-Tron part number. That probably means that it has two 100 megabit fiber optic ports, like the popular 708FX2 model.

Those switches have a good proprietary management and diagnostics viewing tool called "N-View 2". You can download it from NTron/Red Lion.

Access to the diagnostic counters and features for the various fiber and Ethernet cable ports on your switch may help you identify media that is failing, if that's part of your problem. Or they might help you diagnose a speed/duplex mismatch or a malfunctioning device. Most duplicate IP conflicts are not intermittent or transitory: they knock the involved devices off the network until the conflict is resolved.

While link lights and flickering data indicators are helpful to establish basic connectivity, you really can't diagnose a complex thing like an Ethernet network by visually looking at the cables and plugs. You need to understand the layout and examine the settings and diagnostics of all the devices.

Correct; lots of devices on this network. The n-tron modules are 710FX2’s. They have 8 ports on each of them and fiber optics that jump between them and also fiber optics through the crane network. The plc and all other devices are tied into these 2 n-tron units.
I would like to download that software tool and explore it, if I download it onto a laptop and then hook to the n-tron with Ethernet cord, will it discover it pretty easily? Thanks for your input also!

 

[Wilsonn15]

One last thing until I see updates, and my apologies for the rapid influx of messages.. A quick and dirty way to check for IP conflicts would be to ping it, if you haven't already tried. Then unplug the one from the PLC and see if it can still be pinged.

Thanks for your help!! The plc can be pinged at times, which is times the plc stays online. And at other times cannot be pinged which is in turn why I can’t go online with it. I connected directly to the plc with a laptop and it did recognize my CPU however;the proficy machine edition is a newer version on the laptop compared to the main pc in the crane therefor it wanted me to update the cpu which I didn’t feel comfortable doing because it would make all my hardware configuration unequal. I’m thinking it could be the actual pc itself, so tommorrow I will change pcs with another crane that’s the exact same thing and see if the problem is resolved.

 

[Wilsonn15]

Could it be ip address conflict?

I don’t believe so because at times it lets me go online. I think of duplicate addresses were an issue then it wouldn’t let me go online at all. Just my opinion but I could be wrong on this.

 

[chelton]

How many network connections do you have running? Are you on WiFi as well as LAN? Make sure you only have 1 gateway address set.