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 - Interactive Q & A > - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Thread Tools Display Modes
Old December 20th, 2017, 09:19 AM   #1
United Kingdom

lanester is offline
Join Date: Aug 2010
Location: England
Posts: 22
PROFIBUS ProfiTrace Diagnostics Assistance

Hi All,

Looking for some advice in interpreting ProfiTrace Scope images.

The PROFIBUS network topology of the machine was as follows;

PLC(2) <-> ET200(3) <-> SEW_GW(50) <-> SEW_SERVO(55) <-> SEW_SERVO(56) <-> SEW_GW(51) <-> SEW_GW(52) <-> SEW_GW(53) <-> SEW_VFD(57) <-> SEW_VFD(58) <-> SEW_VFD(59) <-> ET200(7) <-> ET200(10) <-> TR Elec Encoder(70) <-> TR Elec Encoder(71) <-> TR Elec Encoder(72) <-> TR Elec Encoder(73) <-> TR Elec Encoder(74) <-> TR Elec Encoder(75) <-> TR Elec Encoder(76) <-> TR Elec Encoder(77) <-> TR Elec Encoder(78) <-> ET200(11) <-> TR Elec Encoder(79) <-> TR Elec Encoder(80) <-> ET200(12) <-> ET200(13) <-> ET200(16) <-> ET200(18) <-> TR Elec Encoder(81) <-> TR Elec Encoder(82) <-> TR Elec Encoder(83) <-> TR Elec Encoder(84) <-> ET200(14) <-> ET200(15)

Baud is 3Mbps. We were having constant bus failures all from station 12 onwards. All the interface modules and connectors for the ET200's were replaced as we chased bus fault lights around. All the wiring from station 13 on has been replaced.

We noted that the length of the run was probably greater than 100m and also that there were more than 32 stations on the the network. We then decided to split the network using a repeater from Station 13 on inclusive. The repeater was installed immediately after station 7. Terminator resistors for station 12, Repeater side 2 turned on.

This allowed the machine to run but still on the odd occasion would fault out with a bus fault. Generally the bus fault was from the new segment that had been created (Stn13-Stn15).

We purchased a ProfiTrace tool. Connecting to the PLC DB9 I get the following (see PDF or ProfiTrace file as fle too big) I therefore assume I am dealing with a wire break. Unless all I am looking at is the reflection from the stub connection.

What is also odd is that between station 71 and 72 there is a large drop in quality. We have replaced both the encoder back plates and cable between the two but this has not improved the quality between the two devices. station 72 and on the amplitude and quality of the signal is very degraded.

Now I am looking for some advice as to what the ProfiTrace tool data is telling me and wether my conclusion is correct?

All help appreciated.
  Reply With Quote
Old December 20th, 2017, 01:12 PM   #2
United States

jacoffey85 is offline
Join Date: Nov 2016
Location: NC
Posts: 70
I had a similar issue with a ProfiBus network before where I had an encoder fault out and cause some issues. Every node after the encoder would be totally faulted out, and the 4 or 5 nodes before it would have random faults that came and went. I imagine the reflection from not having a terminating resister caused the issues with the nodes in front of the encoder.

The way I troubleshot this (I didn't have a trace tool) was I went to the first node that was faulted out and unhooked the outgoing ProfiBus cable. If the comm fault cleared out, I would hook it back up and move to the next node. This was how I was able to narrow it down to a specific device. What I ended up doing was adding an external ground to the the encoder and have not had any issues since.

I don't know if this helps, but your diagnostic results seem similar to what I was have happening.
  Reply With Quote
Old December 21st, 2017, 02:29 AM   #3
United Kingdom

lanester is offline
Join Date: Aug 2010
Location: England
Posts: 22
Thanks Jacoffey85. I was thinking of doing this looking at the tracetool to see if the waveform improved. My issue is downtime on the machine is minimal so getting the time to do this is an issue. Hence why i was asking if anyone could take a look at the waveforms to assist me in narrowing down the issue until I can get to the machine.
  Reply With Quote
Old December 21st, 2017, 02:41 PM   #4
United States

Mad_Poet is offline
Join Date: Feb 2017
Location: Virginia
Posts: 288
Any chance there is a bad terminator switch?

The Profibus connectors I work around have little switches on them which are supposed to disconnect the bus and switch in the terminator . . . I flipped the switch one day to test and evaluate - got the expected trouble symptoms, then switched it back and had more problems. Till I pushed the switch back on then hard back off. Cleared that problem.
  Reply With Quote
Jump to Live PLC Question and Answer Forum


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
[Prosoft with ControlLogix] Trying to diagnose Profibus fault defcon.klaxon LIVE PLC Questions And Answers 5 March 23rd, 2016 04:56 PM
Profibus DP in SIVACON MCC installation Ken Roach LIVE PLC Questions And Answers 4 December 5th, 2009 12:55 AM
S7300 cpu314c-2dp and mp270b using profibus dp tomrobot11 LIVE PLC Questions And Answers 11 April 7th, 2009 06:23 PM
Codesys Profibus Diagnostics bestbier LIVE PLC Questions And Answers 0 March 23rd, 2009 04:51 AM
Diagnostics of Profibus PA devices on Step7 guilhermecgs LIVE PLC Questions And Answers 3 May 5th, 2008 03:59 PM

All times are GMT -5. The time now is 07:15 PM.