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How we can decide which PLC is to be used for a particular application?

Created by: pachu at: 1/27/2012 9:12 AM (8 Replies)

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1/27/2012 9:12 AM	Rate (0)
pachu Advanced Member Joined: 7/15/2011 Last visit: 8/8/2024 Posts: 48 Rating: (0)	Dear All, Can anyone tell me, How we can decide which PLC is to be used for a particular application and also how to determine what will be the maximum IO modules and FC, FB and DB that a particular CPU can support?
	Last edited by: O_Moderator at: 1/27/2012 12:05 PM new subject after splitting from /tf/WW/en/Posts/41808#top
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1/27/2012 10:09 AM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 12/13/2024 Posts: 5697 Rating: (715)	Hello, You can read the CPU specifications for a start [url=http://support.automation.siemens.com/WW/view/en/12996906]S7-300[/url], [url=http://support.automation.siemens.com/WW/view/en/53385241] S7-400 [/url] Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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1/27/2012 10:55 AM	Rate (0)
pachu Advanced Member Joined: 7/15/2011 Last visit: 8/8/2024 Posts: 48 Rating: (0)	how to determine what will be the maximum IO modules and FC, FB and DB that a particular CPU can support?

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1/27/2012 11:02 AM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 12/13/2024 Posts: 5697 Rating: (715)	Hello, It's all in the manual i linked to. For example 312 CPU see attachment. Regards, Marcjan Attachment s7300_cpudata-example.pdf (285 Downloads)
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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1/28/2012 7:25 AM	Rate (0)
pachu Advanced Member Joined: 7/15/2011 Last visit: 8/8/2024 Posts: 48 Rating: (0)	Is it possible to determine the work memory even before we start programming? So that we can decide which CPU is to be selected?

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1/28/2012 11:48 AM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi See the Memeory concept is diffrentiated to three types Load memeory System memeory Work memeory Load memeory, it this place where user can store his user program eg. FC,FB, DB, Normally user can expand the load memeory with micromemeory cards, or RAM cards Work memeory, As the name suggests here the work is done on the user program, process image, communication etc are done. It can not be expanded System Memeory, The Timers, counter, Block stack System Blocks, etc are set here. This part of the memeory can not be expanded. See the selection depends upon your IO capacity of your project, if you have lot of PID and timers then it is advisable to go for a S7400 system than S7300 system. You will have to look into the ST 70 catalogue for more processor details. As marcjan suggested Have fun....
	Last edited by: Tagolover at: 1/28/2012 11:52 AM Last edited by: Tagolover at: 1/28/2012 11:51 AM Last edited by: Tagolover at: 1/28/2012 11:50 AM Jazz
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1/28/2012 12:28 PM	Rate (0)
pachu Advanced Member Joined: 7/15/2011 Last visit: 8/8/2024 Posts: 48 Rating: (0)	Hi, I understood the memory concept frm Marcjan and also further by u as well. But my doubt is regarding who we know how much memory is going to be consumed even before we start programming? supose if i decide to write a program with FC0 to FC10 with 20 networks each, then what will be the memory consumed for this? is it possible to know even before we decide the CPU?

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1/28/2012 3:36 PM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	pachu Hi, I understood the memory concept frm Marcjan and also further by u as well. But my doubt is regarding who we know how much memory is going to be consumed even before we start programming? supose if i decide to write a program with FC0 to FC10 with 20 networks each, then what will be the memory consumed for this? is it possible to know even before we decide the CPU? Hi well you can not start the FC no with "0", see the default size of the FC or a FB is 38 bytes, Before starting the programming, the user can only guess the size of the program can be. Then again depends upon the user programming skills and the number of logics that is written Normally if you write the program using the STL then the block size is less than writing the same logic with Lad or FBD. for calculating the rough estimate use the follwoing link. See the attached link for further calculation link1 Have fun...
	Jazz
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1/28/2012 5:05 PM	Rate (0)
Ganes10 Platinum Member Joined: 8/31/2010 Last visit: 1/9/2025 Posts: 1523 Rating: (230)	Tagolover for calculating the rough estimate use the follwoing link. See the attached link for further calculation link1 Hello Tagolover, Good Idea. Still in this method, you need to create the program blocks and then only check the work memory and load memory consumption. It's not possible to determine before creating pachu Hi, But my doubt is regarding who we know how much memory is going to be consumed even before we start programming? Hello pachu, Though it's an easy question (i like this question), the answer is not that easy and straight. It depends on many factors as Tagolover said, - Programmer skill - Programmer's way of thinking - Programming Language used - etc, etc Anyhow you can check with your local Siemens office / representative on the S7 family selection (S7-1200 / S7-300 / S7-400) or for CPU selection. They may give a better idea based on your application as they deal with variety of applications.
	Last edited by: Ganes10 at: 1/28/2012 5:06 PM Like it? Rate it!
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