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Monitor value change

Created by: petermat at: 3/4/2009 2:31 PM (11 Replies)

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3/4/2009 2:31 PM	Rate (0)
petermat Posts: 15 Rating: (0)	Lets say I need to watch on values for several variables (MWs). How can I get values of this variablesper each cycle, so I can compare them? Thanks, Peter
petermat Posts: 15 Rating: (0)
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3/4/2009 3:24 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 11/18/2024 Posts: 12296 Rating: (2691)	Hello, Peter; The cyclic structure of the PLC program allows you to do this easily. Status of the digital inputs are read from the Digital Input Modules of the PLC at the beginning of every program scan, and placed in the Input Image Table for that cycle. So the value they represent is valid only for one cycle, and accessible in Ix.x addresses. Use the digital instructions available in the program editor to check their present value. Status of analog inputs are read from the Analog Input Modules on command, using the PIWxxx addresses. Use the Compare instructions available in the program editor to evaluate their present value. Or did you have something different in mind? Please explain in greater detail, if this is the case. Hope this helps, Daniel Chartier

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3/5/2009 7:34 AM	Rate (0)
petermat Posts: 15 Rating: (0)	Hello, Daniel, thanks for the response. Let me try to explain better. The problem is not with monitoring in general, but monitoring the change. Lets say I have one variable MW that can have a value range from0-10000. It starts from 0, and by the step I give it, it moves to 10000. The problem is that this stephas variable value, not constant, so I need to be able to obtain each value for each cycle. And I need this for several variables to comapre them. For example: cycleNoMW1 MW2 MW3 100 0 224 33 17 3 35 57 29 etc I hope you now understood what I meant.
petermat Posts: 15 Rating: (0)	Last edited by: petermat at: 3/5/2009 7:36 AM
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3/5/2009 12:38 PM	Rate (0)
uel123 Gold Member Joined: 1/29/2006 Last visit: 11/12/2024 Posts: 447 Rating: (64)	I would store actual values ofvariablesin each cycle in DB (array....). Pointer to array should simply be incremented each cycle, of course also tested on maximal value,...... . The easiest way to do it would be in SCL. Have fun! uel123
	Last edited by: uel123 at: 3/5/2009 12:38 PM
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3/8/2009 8:35 PM	Rate (0)
petermat Posts: 15 Rating: (0)	Hello, uel123, thanks for the response. So, this is not possible withavailable step7 monitoring options? How is this done with SCL? Can you point me to some article that explains how to achieve this? I need this to monitor speeds of several motors at the same time.
petermat Posts: 15 Rating: (0)
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3/9/2009 8:42 AM	Rate (0)
uel123 Gold Member Joined: 1/29/2006 Last visit: 11/12/2024 Posts: 447 Rating: (64)	petermat Hello, uel123, thanks for the response. So, this is not possible withavailable step7 monitoring options? How is this done with SCL? Can you point me to some article that explains how to achieve this? I need this to monitor speeds of several motors at the same time. Hello, petermat! Proposed sollution is based (at the end)onavailable step7 monitoring options. Your first question was, how to"remember and then see" the value of variable in each OB1 cycle. I proposed to youa creation of data block and then filling this data block withvalues of variableson every cycle. When data block is filled with values, you can than see it withavailable step 7 monitoring options. It is a principle of "firstmake a record and then see results". You must be aware that OB1 cycle can last from only few milisecondsto f.e.150 miliseconds. That means, you can receive f.e. 200 new values/second, if OB1 lasts 5 ms. The only possible way to see all values is to store them somewhere and then observe them in any possible way. If this is your goal, I can write a small example and post it here, but later in the afternoon. Or perhaps, describe your task a little bit more in details, so that I can help you. Have fun! uel123

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3/9/2009 9:56 AM	Rate (1)
Eastern Posts: 557 Rating: (64)	hi cycle No== MW0[0,2,4,6,8,10,...........n] DB1 [10,30,58,70........................N] Each information stored in memory word 16bits of data block if mw0=0then DB1=10. if mw0=2 then DB1=30. VALUE L MW0 0 SLW 3 0.0 LAR10.0 OPEN DB1 L DBW [AR1,P#0.0] DB1.DBW0 (10) L MW0 2 SLW 3 2.0 LAR12.0 OPEN DB1 L DBW [AR1,P#0.0] DB1.DBW2(30) REGARDS VIVEK
Eastern Posts: 557 Rating: (64)
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3/22/2009 11:33 AM	Rate (0)
petermat Posts: 15 Rating: (0)	Hello, friends, sorry for the late response, I was on the field job, so I could not answer. @uel123 Yes, this is what I am after.Ant pointer to some documentation concerning this issue is welcomed. Also any good reference about SCL is appreciated, since I have never programmed in it @Vivek As you can read above, I have never programmed in SCL, so if you can point me to some resource that I can read about it would be great. At the first look, the code should not be a problem. Since this is my first touch with SCL, I am not sure what to do with the code you have provided (I dont see how can I use SCL in Step7). Btw, I am just now downloading 3 manuals from siemens support, so you dont need to point me to these references. Thanks, Peter
petermat Posts: 15 Rating: (0)	Last edited by: petermat at: 3/22/2009 11:35 AM Last edited by: petermat at: 3/22/2009 11:34 AM
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3/22/2009 5:43 PM	Rate (1)
Eastern Posts: 557 Rating: (64)	HI petermat, i have written thatcodein STL, not in SCL. both are programming language & also you can use both langauge in SIMATIC MANAGER software....... for learning STL language,you can place the same code in simatic manager & when you willpress F1 you will get a help......... also in simatic manager if you go HELP in menu bar, you will get the help in LAD,FBD,STL........ SO you can understand STL by learning the help which is already their in simatic manager........ I will suggest you to first develop the logic in LADorFBDthen convert into STL.(IN simatic manager their is setting for conversion).....so you canlearn the STL language.... now if you want to learn SCL(high level language pascal base)........That is also possible in Simatic manager.......but in SCL There is a limited instruction like "if elese" ,"switch case","for loop" "repeat" in this language you can develop in SCL then this language you can convert into STLalso. if you have any more doubt about STL & SCL during learning , you can ask....... regards
Eastern Posts: 557 Rating: (64)
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4/4/2009 2:19 AM	Rate (0)
Survive Posts: 26 Rating: (0)	Eastern VALUE L MW0 0 SLW 3 0.0 LAR10.0 OPEN DB1 L DBW [AR1,P#0.0] DB1.DBW0 (10) L MW0 2 SLW 3 2.0 LAR12.0 OPEN DB1 L DBW [AR1,P#0.0] DB1.DBW2(30) REGARDS VIVEK Hello ! Using the example showed byVivek, I haveone question for all you, please. When I use the AR 1/2 don't I needto use e.g. P#2.0 ?Why the value 2 was converted to 2.0 with the SLW instruction ? The value 2.0 showed by Vivek is the same of P#2.0 ? Can someone help me explaining it ? VALUE L MW0 2 SLW 3 2.0 LAR12.0 Best regards !
Survive Posts: 26 Rating: (0)
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