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Reducing FB Inputs and achieving same functionality!

Created by: SK(2*A) at: 1/6/2012 9:55 AM (5 Replies)

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1/6/2012 9:55 AM	Rate (0)
SK(2*A) Posts: 140 Rating: (0)	Hi Experts, I need an advice on an issue. I am reading ROLL, PITCH and HEAVE values from a sensor. Based on the parameter's values I am calculating period for each of them. After getting the period of each parameter I have to implement some warnign limits corresponding to each period value. I have 9 period value for each parameter. For example roll has warning limits corresponding to period values from 3s to 11s.So at 3s period the warning limits to be implemeted will be different as for period of 4 seconds. At the moment I have made a FB to move warning limit values based on comparison of period values and I am calling same FB for Pitch and Heave also. But by doing so the Inputs of the FB look too much and if in future I need to implement more cases then these inputs will increase. Is there any other way to implement such scenario with lesser number of inputs to the FB, i want to make my FB look more compact and short. I have attached the FB call and FB itself for your reference! Please advice accordingly! Tahnks in advance! Attachment FB73.pdf (218 Downloads)
SK(2*A) Posts: 140 Rating: (0)
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1/6/2012 9:56 AM	Rate (0)
SK(2*A) Posts: 140 Rating: (0)	Attached is the FC where this FB is being called for ROLL, PITCH and heave for two sensors! FB looks too long. Please suggest any other method to make it compact by some intelligent coding technique. I am beginner in Siemens PLC programming, please elaborate your solution :) Thanks! Attachment FC76.pdf (205 Downloads)
SK(2*A) Posts: 140 Rating: (0)	Last edited by: Khyzer at: 1/6/2012 10:03 AM
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1/6/2012 10:06 AM	Rate (0)
playerslight Posts: 1064 Rating: (72)	looking at your call to the fb most of the information is coming from the same datablock ,you could eleminate those inputs and call the data block in side the fb this would reduce the size of your call this would reduce it to3 inputs and 2 outputs
playerslight Posts: 1064 Rating: (72)	Last edited by: playerslight at: 1/6/2012 10:32 AM Last edited by: playerslight at: 1/6/2012 10:07 AM
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1/6/2012 10:42 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 8/31/2025 Posts: 6874 Rating: (1368)	Dear Khyzer, All the operations simply can be implemented by using indirect addressing and loops.of course you have to store data correspond to each entry in cells of data blocks which can be accessed viaindirect addressing.Try it Also check the following: STEP 7 -- Creating S7 programs -- Indirect Addressing Best regards, Hamid Hosseini
	Demo Channel on Youtube
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This contribution was helpful to 1 thankful Users playerslight

1/6/2012 5:57 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (154)	I do use simple philosophy : inputs are peripheral inputs, outputs also. It is not clearly where allthosereal numbers come from for your inputs. As I can see,they are computedbefore from some input signals, so you will copy all these results when nesting them into FB, and you will loose memory and time copying them. I would do different: start from peripheral inputs as real inputs into FB and outputing peripheral outputs, if there are any, all other variables are stored like STAT, or used temporarily as TEMP. If you want to access variable in other FC or OB you can access it by instance DB. Another way is to use FC instead FB, by using STRUCT var as in_out. When you call FC vars are not copiyed, just pointer of them is saved in local stack. When you will access them the plc will load them by using indirect addresing (pointer + pointer offset), so you can define a large STRUCT and only those really accessed var will also be processed, no copying will take place.

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1/6/2012 8:10 PM	Rate (0)
BeVee Gold Member Joined: 7/18/2011 Last visit: 4/11/2025 Posts: 521 Rating: (91)	Hi Khyzer, Some general comments on your FB: - Not all inputs are used inside FB - The output variables are not always assigned, this can cause unexpected behavior. - Mixing real variables and bool variables increases memory size of the block - If you write same code in FC, you won't need instance DB per call. Personally i would pass all REAL parameters to the block witha STRUCT input parameter Kind regards, BV

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