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How many PID blocks can support a s7-1200 CPU?

Created by: zaxos at: 10/21/2014 7:49 AM (5 Replies)

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10/21/2014 7:49 AM	Rate (0)
zaxos Experienced Member Joined: 5/10/2013 Last visit: 7/17/2023 Posts: 19 Rating: (0)	I am working with a project and i want to control 20 points of temprature with the compact PID block (PWM output).Also i have 4 tension forces which i want to control via PID with the help of 4 asychrononous motors+ frequency drive. So i have sum 24 PID points. Can i use 24 PiD compact blocks with 1215c cpu or there is restriction? Best Regards Gogoulos Zaxarias

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10/21/2014 8:06 AM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 11/1/2024 Posts: 10229 Rating: (1181)	Hello, Officially there has not info. But you could start checks all the threads here which are related to the subject.Clcik Best regards, Hristo Mihalev

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10/21/2014 8:17 AM	Rate (0)
hdhosseini Diamond Member Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	zaxos I am working with a project and i want to control 20 points of temprature with the compact PID block (PWM output).Also i have 4 tension forces which i want to control via PID with the help of 4 asychrononous motors+ frequency drive. So i have sum 24 PID points. Can i use 24 PiD compact blocks with 1215c cpu or there is restriction? Best Regards Gogoulos Zaxarias Hello, Please read more the clustered posts related to max number of PID controllers in S7-1200: HD_Maximum permissible number of PID controllers for a given S7-1200 But in my point of view 24 loops of controllers belong to a machine in middle size and personally I suggest more investment on controller (at leat an S7-300).Normally processing of loops are not limited to just a block.You need to think of protections, scale and unscaling and selection logics on actuators. I hope this helps, Hamid Hosseini
	Last edited by: hdhosseini at: 10/21/2014 8:37 AM Demo Channel on Youtube
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10/21/2014 11:21 AM	Rate (1)
Denilson Pegaia Platinum Member Joined: 9/23/2005 Last visit: 11/12/2024 Posts: 4352 Rating: (1452)	Hi, if you don't need to commisioning more then one per time, the limit is the size of the memory and the run time scan. Both are strongly dependent of your application.
	Denilson Pegaia Siemens Industry Sector Technical Support
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10/21/2014 11:40 AM	Rate (0)
zaxos Experienced Member Joined: 5/10/2013 Last visit: 7/17/2023 Posts: 19 Rating: (0)	My thoughts are to create a cyclic interrupt block, in which will run the 24 PID control blocks. Is it possible ? Thank you for replies!! Best Regards Zaxarias Gogoulos

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10/21/2014 3:41 PM	Rate (0)
0_Einstein Diamond Member Joined: 7/7/2010 Last visit: 11/12/2024 Posts: 15392 Rating: (2443)	zaxos My thoughts are to create a cyclic interrupt block, in which will run the 24 PID control blocks. Is it possible ? Thank you for replies!! Best Regards Zaxarias Gogoulos Possible, but will greatly depend on your application needs versus the processing capabilities of the s7-1200 you have chosen - plus the non PID work it must also do, like communications, I/O handling, and other controls. The key is understand if you are handling very slow or very fast processes. Very fast processes with 24 PIDs in a cyclic interrupt is likely to crash your s7-1200 either on watchdog or the cyclic interrupt is not finished processing before it gets called again - which will eventually crash the plc. Very slow processes with a long cyclic interrupt, or even better, 24 cyclic interrupts with 24 phase shifts so the work is distributed rather than run all at once. If it is fast coordinated motion control, you have selected too much of the tiny entry level PLC. Just my opinion and you may find a way to make it work.
	science guy
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