Previous in Forum: Replacing a Servo Motor & Drive with AC Motor and Inverter.   Next in Forum: Three-Phase to Single-Phase Transformer
Close
Close
Close
7 comments
Rate Comments: Nested
Associate

Join Date: Jul 2007
Posts: 37

S7400/ET-200 PLC system, Communication problem

09/29/2008 2:59 AM

We have 19 station S7-400/ ET200 system having continuous Profibus communication problem in one of ET200 system(last station with end resistor ON). We have done following:-

  1. Checked and replaced Profibus cable.
  2. Replaced DP connectors.
  3. Reload PLC program after refreshing memory.
  4. Checked power cable .
  5. Add filter in power supply.
  6. Replaced ET200
  7. Checked all I/Os

...... but all in vain, any one has any idea for rectification of this problem.

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Active Contributor

Join Date: Jul 2008
Location: Finland
Posts: 22
#1

Re: S7400/ET-200 PLC system, Communication problem

09/29/2008 5:14 AM

Even though PROFIBUS is relatively noise immune, poor earthing or very high noise levels (variable speed drives etc.) can cause significant errors. Check that the installation complies with PROFIBUS guidelines – it is a good starting point.

Above text is from a profibus guide. Almost allways the problem is bad earthing.

Register to Reply
Power-User

Join Date: May 2008
Location: Europe
Posts: 285
Good Answers: 9
#2

Re: S7400/ET-200 PLC system, Communication problem

09/30/2008 2:48 AM

Syed Ziauddin, can you advise the following:-

  1. Has this problem just started to occur - upon re-reading your post I would think that the system was functioning and then you encountered this issue.
  2. Were there any recent modifications made to the system (Masters/Slaves added/removed)
  3. Are you sure you have the correct GSD files loaded.

Regards

Mr. W.A Snow

Register to Reply
Associate

Join Date: Jul 2007
Posts: 37
#4
In reply to #2

Re: S7400/ET-200 PLC system, Communication problem

09/30/2008 5:25 AM

Thanks for your interest,answers are:

1. This problem started since few days.

2. No modification being done recently.

3. GSD files are OK and sometimes system run for hours without any fault some time with continuous fault.

Best regards,

Syed Ziauddin

Register to Reply
Power-User

Join Date: May 2008
Location: Europe
Posts: 285
Good Answers: 9
#6
In reply to #4

Re: S7400/ET-200 PLC system, Communication problem

09/30/2008 5:58 AM

Syed Ziauddin, no problem. I trust that someday you will also assist me.

You might check out (alindsay81 also made reference to this):

http://www.automation.siemens.com/WW/forum/guests/PostShow.aspx?language=en&PostID=88172

Kind Regards

Mr. W.A Snow

Register to Reply
Member

Join Date: Jul 2008
Location: N.Ireland
Posts: 9
#3

Re: S7400/ET-200 PLC system, Communication problem

09/30/2008 3:44 AM

I've seen problems like this a million times and its almost always a cable/earth problem

1. Have you changed the profibus plug on the last device, and the one before last?

2. How long is the profibus cable? you could install a repeater to give more length

3. what baud rate is your network running? if at 12mb try it at 1.5mb for a while and see if that helps

4. There is a Siemens device called a BT200 which can diagnose problems on profibus networks. get hold of one and see what it comes up with

5. What size is the 24vdc powersupply - it may be getting pulled down every now and again - install a 10amp supply and see what happens ?

Register to Reply
Associate

Join Date: Jul 2007
Posts: 37
#5
In reply to #3

Re: S7400/ET-200 PLC system, Communication problem

09/30/2008 5:48 AM

Thanks,

Answers are,

1. We already have changed both plugs.

2.It is about 80mtrs. We are now asking Siemens to provide signal repeater.

4.We have heard about it ,but we will definitely try to get hold of it.

5.Power supply is PS407 on Master and PS307 on last and 2nd last slave.

Register to Reply
Commentator

Join Date: Oct 2007
Location: Caribbean
Posts: 79
Good Answers: 2
#7

Re: S7400/ET-200 PLC system, Communication problem

09/30/2008 9:08 AM

We have many S7/400 ET 200 stations.

Whenever I have to troubleshoot problems like these, I have made up a Profibus test cable which I use to communicate to every ET 200 station directly.

In this way I can verify communication to the rack directly.

Of course you need a modified PLC simple program to do this testing.

I will highly recomment you do that . It comes in reallty handy when troubleshooting.

__________________
Learn more, Do more , Be more
Register to Reply
Register to Reply 7 comments
Copy to Clipboard

Users who posted comments:

alindsay81 (1); djacob (1); Flux (1); HoleInTheSnow (2); Syed Ziauddin (2)

Previous in Forum: Replacing a Servo Motor & Drive with AC Motor and Inverter.   Next in Forum: Three-Phase to Single-Phase Transformer

Advertisement