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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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 Posted: 19/07/2013 08:38 Post subject: PLC sizing |
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Hello guys,
I´m new in this forum and id really appreciate your help. I have to do the stimation of a biogas plant automation system. The control system doesnt seem to be so difficult, 30 DO, 15DI, 10 AI from some field sensors and 8 AI from the biogas generator control cabinet (Ethernet conection). The analogic signal will be just monitored (using the necesary elements in the program to transform and storage them). For the program Clock timer, about 28 timers, signals trnsducers, comparators... (not so difficult).
The point is that I dont know how to size the PLC memory. Monitoring and storing trends and historical data will have to be done. The point is, Should I take into account the number of words stored every five secs in one month (as a example) for sizing the plc memory or the data is automaticatly stored in the server and deleted in the PLC memory?
Id really appreciate your suggestions coss i dont have too much idea about this.
Thank you a lot. |
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veliko
Member 3
Joined: 17 Jul 2013
Posts: 627
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| Posted: 19/07/2013 19:21 Post subject: Re: PLC sizing |
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| Keops wrote: | Hello guys,
I´m new in this forum and id really appreciate your help. I have to do the stimation of a biogas plant automation system. The control system doesnt seem to be so difficult, 30 DO, 15DI, 10 AI from some field sensors and 8 AI from the biogas generator control cabinet (Ethernet conection). The analogic signal will be just monitored (using the necesary elements in the program to transform and storage them). For the program Clock timer, about 28 timers, signals trnsducers, comparators... (not so difficult).
The point is that I dont know how to size the PLC memory. Monitoring and storing trends and historical data will have to be done. The point is, Should I take into account the number of words stored every five secs in one month (as a example) for sizing the plc memory or the data is automaticatly stored in the server and deleted in the PLC memory?
Id really appreciate your suggestions coss i dont have too much idea about this.
Thank you a lot. |
What PLC do you use and HMI? |
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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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| Posted: 19/07/2013 20:58 Post subject: Re: PLC sizing |
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| veliko wrote: | | Keops wrote: | Hello guys,
I´m new in this forum and id really appreciate your help. I have to do the stimation of a biogas plant automation system. The control system doesnt seem to be so difficult, 30 DO, 15DI, 10 AI from some field sensors and 8 AI from the biogas generator control cabinet (Ethernet conection). The analogic signal will be just monitored (using the necesary elements in the program to transform and storage them). For the program Clock timer, about 28 timers, signals trnsducers, comparators... (not so difficult).
The point is that I dont know how to size the PLC memory. Monitoring and storing trends and historical data will have to be done. The point is, Should I take into account the number of words stored every five secs in one month (as a example) for sizing the plc memory or the data is automaticatly stored in the server and deleted in the PLC memory?
Id really appreciate your suggestions coss i dont have too much idea about this.
Thank you a lot. |
What PLC do you use and HMI? |
I have to choose them, I was thinking about omron, siemens and Wago. Couls you help me with this? |
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veliko
Member 3
Joined: 17 Jul 2013
Posts: 627
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| Posted: 20/07/2013 15:25 Post subject: |
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On SIEMENS forum there are some clues...
https://www.automation.siemens.com/WW/forum/guests/PostShow.aspx?PageIndex=1&PostID=263177&Language=en
https://www.automation.siemens.com/WW/forum/guests/PostShow.aspx?PageIndex=1&PostID=184833&Language=en |
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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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| Posted: 20/07/2013 16:31 Post subject: |
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| ok, thank you for the links, they clarified the data loging issue. Anybody could please give an idea about stimating the memory plc usage? |
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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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| Posted: 20/07/2013 16:52 Post subject: |
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Would this stimation be correct?
lets say that i want to storage 40 events (20 analogic+20digital) every 5 secs:
- Analogic:
16 bits for the signal
16 bits for time stamp
5 bits for 20 events codification
8bits for backup
= 45 bits/ event * 20 = 900 bits
- Digital:
1 bit for the signal
16 bits for time stamp
5 bits for 20 events codification
8 bits for backup
= 30 bits/event * 20 = 600 bits
Data memory= 900+600=1500 bits = 187.5 bytes
Data memory plus internal work (no the program) + future ampliation= lets say 1 kbyte?
Working memory:
lets say 150 lines of code * 3bytes =450 bytes
20 AI*200 bits= 4000 bits= 500 bytes
40 D I/O*100= 4000 bits= 500 bytes
Working memory= 1.5 kbytes+ 100%(future ampliation) = 3 kbytes?
Loading memory= Working memory + Data memory= 4 Kbytes?
What do you guys think about this stimation? I´m a bit lost and I dont want to kill a fly with a cannon so I really apreciate your help. |
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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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| Posted: 20/07/2013 18:54 Post subject: |
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Thank you for the reply, i´m a bit lost with this so forgive my ignorance.
For tag logging in WinCC and WinCC flexible there is a limit in the number of tags right?
If I get the data from the Scada then, How should I do the PLC memory sizing? only the working memory? or also some data memory for the places and descriptions of the signals that are going to be taken?
Working memory:
lets say 150 lines of code * 3bytes =450 bytes
20 AI*200 bits= 4000 bits= 500 bytes
40 D I/O*100= 4000 bits= 500 bytes
Working memory= 1.5 kbytes+ 100%(future ampliation) = 3 kbytes?
would that be a good stimation?
How can I do a rough calculation?
Thanks again |
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veliko
Member 3
Joined: 17 Jul 2013
Posts: 627
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| Posted: 20/07/2013 19:40 Post subject: |
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| Keops wrote: | Thank you for the reply, i´m a bit lost with this so forgive my ignorance.
For tag logging in WinCC and WinCC flexible there is a limit in the number of tags right?
If I get the data from the Scada then, How should I do the PLC memory sizing? only the working memory? or also some data memory for the places and descriptions of the signals that are going to be taken?
Working memory:
lets say 150 lines of code * 3bytes =450 bytes
20 AI*200 bits= 4000 bits= 500 bytes
40 D I/O*100= 4000 bits= 500 bytes
Working memory= 1.5 kbytes+ 100%(future ampliation) = 3 kbytes?
would that be a good stimation?
How can I do a rough calculation?
Thanks again |
Keops,
I suggest you to forget about data logging on a PLC memory...for large amount of data....
No one use such a think...
Usually data storage are made on servers or HMI computers...
I suggest you to use a standard PLC let say S7 300 CPU and a WinCC Flexible or WinCC and you'll have a lot of options... |
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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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| Posted: 20/07/2013 19:49 Post subject: |
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| Thank you veliko again, ill do it in that way. But Could you please tell me how to stimate the memory necesary for an automation systems? I mean, when I asked some suppliers the offer me a "cannon to kill a fly" (of course they want profits). The thing is that the PLC that Omron (for example) offered me is too much for the project so I would like to have a rough stimation of PLC memory that I´m going to need in terms of selecting the proper PLC. |
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veliko
Member 3
Joined: 17 Jul 2013
Posts: 627
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| Posted: 20/07/2013 20:05 Post subject: |
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| Keops wrote: | | Thank you veliko again, ill do it in that way. But Could you please tell me how to stimate the memory necesary for an automation systems? I mean, when I asked some suppliers the offer me a "cannon to kill a fly" (of course they want profits). The thing is that the PLC that Omron (for example) offered me is too much for the project so I would like to have a rough stimation of PLC memory that I´m going to need in terms of selecting the proper PLC. |
The problem is not the memory..
For an CPU 315 2-DP from SIEMENS a 8MB memory for program is enough..
I saw a SIEMENS catalog CA01 on this forum where you can find out prices for a PLC system.
Again, PLC has nothing to do with the necessary memory for data logging.. |
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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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| Posted: 20/07/2013 20:25 Post subject: |
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I not mentioning the memory for data logging, I just would like to stimate the memory necesary for my system. You say 8 MB for program memory is enought, how you came to that? 3-4 bytes per intruction? How can I stimate it?
Sorry for keeping you so busy  |
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Keops
Junior
Joined: 17 Jul 2013
Posts: 11
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| Posted: 21/07/2013 13:44 Post subject: |
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The doubt about data logging has already become clrear, but could please anyone help me to make a rough stimation about my plc working and load memory?
Thank you in advance |
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