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 July 6th, 2016, 10:31 AM   #1
ry_fern
Member
Philippines

ry_fern is offline
 
Join Date: Jan 2008
Location: Caloocan City
Posts: 44
S7-400 CPU 414-5H Load Memory Sudden Increase

Dear Experts,

We are currently in a project commissioning stage now of a Biomass Plant. The above mentioned CPU is used.

2 days ago, our load memory is only 42%. There were no major edits, only online monitoring and some bypassing of signals and adding some "always open" contact. When we checked the load memory again, we were surprised to see that it increased 67%. User memory is only 11%

I would like to ask for your opinion regarding the following:

1. Considering the minor changes, what other things could have caused the sudden increase in load memory?

2. Extra question, one bit, remains ON when the actuating switch is only momentary action and we are certain that it is not latching. I experienced this thrice (3X) already with Siemens systems. Because of the urgency, I wasn't able to find the root cause, only a work around. Now I'm experiencing it here again.

May I request for your technical opinion? It will be highly appreciated.

Thank you.

Ryan
  Reply With Quote
Old July 6th, 2016, 11:39 AM   #2
sigmadelta
Member
Canada

sigmadelta is offline
 
Join Date: Apr 2016
Location: From Canada - Living in Bulgaria
Posts: 1,290
If you go into STOP mode and Compress the memory, does it go back down?

Whenever you download a block in RUN, there must be enough space to receive the block again... which means the existing block and new block exist in the Load memory at least for some time. Can you send a screen shot of the Memory tab from the CPU's Module Information?
__________________
Automation Programmer
PLC / HMI / SCADA / SQL
New Systems, Modifications
System Upgrades & Conversions
------------------------
Visit: contrologica.com
Email: info@contrologica.com
  Reply With Quote
Old July 7th, 2016, 01:15 PM   #3
mk42
Member
United States

mk42 is offline
 
Join Date: Jun 2013
Location: MI
Posts: 2,293
Quote:
Originally Posted by ry_fern View Post
2. Extra question, one bit, remains ON when the actuating switch is only momentary action and we are certain that it is not latching. I experienced this thrice (3X) already with Siemens systems. Because of the urgency, I wasn't able to find the root cause, only a work around. Now I'm experiencing it here again.
No experience on the memory question.

For your 2nd question, there is always a cause for something like that, but they can sometimes come from crazy places.

Is the bit that is sticking on the input, or is it in a DB (or M memory)? If the input bit itself is sticking on, I'd recommend checking the LED on the card, as well as the physical wiring with a meter. You might also want to make sure it is in a process image, as opposed to being part of the periphery. If the input bit responds correctly, then I guess you either need to cross reference on your internal bit, or hope you haven't screwed up in some STL pointers somewhere.
  Reply With Quote
Old July 8th, 2016, 02:02 AM   #4
ry_fern
Member
Philippines

ry_fern is offline
 
Join Date: Jan 2008
Location: Caloocan City
Posts: 44
Sigmadelta,

Attached is my screenshot yesterday, I now have a 14% load memory. We are doing the same things that we did 2 days ago, minor edits, PIDs in Auto Mode, pumps are running.

mk42,

The bit is inside a DB. It is a button linked to the HMI to start the pump. We are certainly sure that it is not being shared. However, we'll still double check our references. Can you clarify the idea you mentioned about the periphery?

Thank you.
Attached Images
File Type: png Memory area.png (220.0 KB, 33 views)
  Reply With Quote
Old July 8th, 2016, 02:10 AM   #5
sigmadelta
Member
Canada

sigmadelta is offline
 
Join Date: Apr 2016
Location: From Canada - Living in Bulgaria
Posts: 1,290
Quote:
The bit is inside a DB. It is a button linked to the HMI to start the pump.
What function are you using on the HMI? Is it "Set Bit in Tag" or "Set Bit"?

Right click the address in your logic, and choose Go To -> Location, and it will show you a cross reference of where the address is used. Click the checkbox "Overlapping locations" to see if this bit is a part of a byte, word or double-word that is being used elsewhere in a write instruction.
__________________
Automation Programmer
PLC / HMI / SCADA / SQL
New Systems, Modifications
System Upgrades & Conversions
------------------------
Visit: contrologica.com
Email: info@contrologica.com
  Reply With Quote
Old July 8th, 2016, 02:15 AM   #6
sigmadelta
Member
Canada

sigmadelta is offline
 
Join Date: Apr 2016
Location: From Canada - Living in Bulgaria
Posts: 1,290
In SIMATIC Manager, right-click on the Blocks folder, and click Properties, then select the Blocks tab it will show you how much load and work memory should use. However, I believe downloading of blocks in RUN mode will increase this amount. I am not sure how/when the CPU operating system decides to delete the replaced blocks in the load memory RAM... it could be on a restart of the CPU.
__________________
Automation Programmer
PLC / HMI / SCADA / SQL
New Systems, Modifications
System Upgrades & Conversions
------------------------
Visit: contrologica.com
Email: info@contrologica.com
  Reply With Quote
Old July 8th, 2016, 08:49 AM   #7
mk42
Member
United States

mk42 is offline
 
Join Date: Jun 2013
Location: MI
Posts: 2,293
Maybe I'm misunderstanding the memory issue, but that shows you have 14% USED, not 14% available. What's the problem? You have tons of space to spare.

On the periphery, I was saying that if the bit you were concerned about was inside the process image (updated every scan, accessed by I6.0) or in the periphery (only updated when accessed by PIW300). Complicating things, the 400H often uses many Process Images, updated with different OBs. My concern is that the IO bit might be updating slower than expected, or not at all if you access it wrong.

If the bit you're concerned about is in a DB, then that isn't an issue. Can you take a screenshot of the code (while monitoring), so we can see the error?
  Reply With Quote
Old July 12th, 2016, 01:09 AM   #8
ry_fern
Member
Philippines

ry_fern is offline
 
Join Date: Jan 2008
Location: Caloocan City
Posts: 44
@Sigmadelta,

The only reason that we can think of with the sudden increase in load memory is the online edits we made. I believe this is the same thing that you were saying in your previous reply.

@mk42,

Yes, we have 14% memory and plenty to spare but what puzzled us is the sudden increase in the load memory that spiked up to 67%.

I'll keep you updated if we find something.

Thank you.
  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
SIEMENS PLC CPU memory stevenPLC LIVE PLC Questions And Answers 14 April 10th, 2006 10:52 AM
Siemens S7-400 Series CPU Load Memory. Mr Dave LIVE PLC Questions And Answers 13 September 14th, 2005 04:04 PM
s7 314 CPU replace by s7 315 CPU dwcy LIVE PLC Questions And Answers 2 June 21st, 2005 06:39 AM
Siemens PLC program lost after power down TEOWK LIVE PLC Questions And Answers 24 May 30th, 2005 02:17 AM
S7 CPU Parameterisation problems after loading program RMA LIVE PLC Questions And Answers 12 October 7th, 2004 10:12 AM


All times are GMT -5. The time now is 05:34 PM.


.