You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Reply
 
Thread Tools Display Modes
Old December 28th, 2016, 10:08 PM   #1
Kal_H
Member
United States

Kal_H is offline
 
Join Date: Dec 2016
Location: ND
Posts: 4
AB Micro 1400 TCP MODBUS Issue

I'm working with an AB Micrologix 1400 series B communicating with a Banner camera via MODBUS over TCP. I was able to get everything setup and communicating great, no issues. Until I cycled power, after I did a power cycle my MSG commands errored out with a communication timeout. After a lot of poking around, I finally unplugged the Ethernet cable from the PLC and plugged it back in. All of the sudden the communication started worked again. I forgot to mention I have the camera connected directly to the PLC, no switch or anything else in between. I have done a lot of experimenting and I found that every time I cycle power I wait 2 minutes and then unplug and plug this cable back in and it works. There is no power up sequence between the camera and PLC that changes this, and nothing I can do in the PLC code to change this. Has anyone else ever seen this behavior before? It is the craziest thing I have ever seen. Does anyone know what unplugging this cable from the processor would affect?
  Reply With Quote
Old December 28th, 2016, 11:50 PM   #2
scrambled
Member
Australia

scrambled is offline
 
scrambled's Avatar
 
Join Date: Jul 2015
Location: Brisbane
Posts: 108
When you power cycle, is it just power cycling the PLC or is it power cycling both the camera and the PLC?

If it's just the PLC, my wild guess is that the camera is somehow not resetting its TCP socket connection when the PLC power cycles.

If you have a dumb hub or a managed switch that can port mirror, I'd use that to perform some Wireshark sniffing to see what the TCP traffic is like between the PLC and the camera. It should give you some much-needed diagnostic info to narrow down the possible causes.
  Reply With Quote
Old December 29th, 2016, 12:01 AM   #3
Kal_H
Member
United States

Kal_H is offline
 
Join Date: Dec 2016
Location: ND
Posts: 4
Thanks for the response. I'm power cycling both devices, the entire panel to be exact. I'll check into that.
  Reply With Quote
Old December 29th, 2016, 12:02 AM   #4
Epy
Lifetime Supporting Member
United States

Epy is offline
 
Join Date: Jul 2012
Location: no
Posts: 371
Are you using the ML as TCP master or slave? I've had issues with the ML1400 as TCP slave, if you try to poll it too fast it will eventually timeout every single time. I had to slow the polling rate down to once/second to prevent it from eventually timing out.
  Reply With Quote
Old December 29th, 2016, 07:37 AM   #5
Kal_H
Member
United States

Kal_H is offline
 
Join Date: Dec 2016
Location: ND
Posts: 4
The ML is a TCP master, it polls the camera for information. They system works great once I get past my startup issue. I forgot to mention I do have feedback from the camera. As soon as the system powers up there is a a network light that is lit on the camera. It is lit like it sees the network but does not flash with network traffic. Also there is a TCP status page on the camera that says connected. I really think the camera is doing everything right. I think it's the PLC that's not, maybe it's waiting for the camera to renew it's socket connection? I think if I could re-initialize my TCP port on the ML everything would work. Is there any commamd for something like that?
  Reply With Quote
Old December 29th, 2016, 08:00 AM   #6
scrambled
Member
Australia

scrambled is offline
 
scrambled's Avatar
 
Join Date: Jul 2015
Location: Brisbane
Posts: 108
It does sound a bit like a timeout issue on the TCP layer of the comms.

If you want to narrow your investigation down to the MicroLogix side of things, you can test it out by connecting the MicroLogix to your laptop and using a slave simulator to replicate the camera.

For example, see if the MicroLogix is able to maintain Modbus comms when you stop then restart the TCP session on your simulator. Also, you can easily run Wireshark alongside the simulator to see the packets being sent out by the PLC - just to make sure everything is as you expect it to be.

Last edited by scrambled; December 29th, 2016 at 08:03 AM.
  Reply With Quote
Old December 29th, 2016, 08:11 AM   #7
damica1
Member
United States

damica1 is offline
 
Join Date: Aug 2015
Location: Illinois
Posts: 595
Since you are NOT using a switch, but "Device to Device" I really think the cable should be a "CROSSOVER" cable.
  Reply With Quote
Old December 29th, 2016, 09:37 AM   #8
Kal_H
Member
United States

Kal_H is offline
 
Join Date: Dec 2016
Location: ND
Posts: 4
SOLVED!! - I added an unmanaged switch between the devices and that solved the issue. I'm going to try a cross over cable yet to see if I can get away from using the switch, but it is solved. Thanks to everyone that contributed.
  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
AB micro 1400 remote programming roburn1 LIVE PLC Questions And Answers 4 June 1st, 2011 10:30 AM
Modbus TCP Steve Bailey LIVE PLC Questions And Answers 3 December 12th, 2010 06:30 PM
Modicon M340 Modbus TCP and Modbus Serial? northwest_trail LIVE PLC Questions And Answers 1 December 3rd, 2008 07:09 AM
Modbus TCP between Quantum PLC and MNS iS Motor Control Center booatoa LIVE PLC Questions And Answers 0 May 26th, 2008 05:17 AM
AB PLC, MODEM , MODBUS Connectivity gautham LIVE PLC Questions And Answers 8 April 25th, 2005 04:56 PM


All times are GMT -5. The time now is 07:28 AM.


.