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use positive edge

Created by: saeedplc at: 1/17/2012 3:38 PM (7 Replies)

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1/17/2012 3:38 PM	Rate (0)
saeedplc Posts: 288 Rating: (4)	hello. i have seen many s7 programs but in most of them "positive edge detection" have not been used. is there any special reason? what is benefit of using "edge detection" and applications of it? best regards.
saeedplc Posts: 288 Rating: (4)
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1/18/2012 9:11 AM	Rate (1)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi The use of the Postive edge coil depends on the program that you do. See the P coil or the Postive Edge coil is used in program where you want only the high edge or the postive edge to trigger a particular logic. For an example A M10.0 AN 10.1 FP M10.2 = M10.3 on the above example you will find that when the status of the M10.0 changes to true or 1 the m10.3 will energise the coil with address M10.3 . M10.3 will be energised only for the postive edge and not when the status changes from 1 to 0. I hope you now understand, if any further query please post it in the forum.... Have fun...
	Jazz
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This contribution was helpful to 1 thankful Users Dren Bejtullahi

1/18/2012 6:57 PM	Rate (0)
Marciano Bronze Member Joined: 4/30/2007 Last visit: 3/9/2023 Posts: 231 Rating: (23)	One typical exampleis incrementing an accumulator, since ready to use Counters only go up to "999", anything bigger you need to create an accumulator logic using Add_Int for instance. (onlyone increment for each RLO=1 before theedge detection)

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1/18/2012 8:09 PM	Rate (1)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 2/21/2023 Posts: 6794 Rating: (1341)	Dear saeedplc, I am using edge evaluation instructions when I want to avoid long-term contribution of semi-permanent on/off signal in a given logic.In those cases edge detection provide easily implementation of logic and shorten the contribution of long on/off signals. I hope this concept helps Best regards, Hamid Hosseini
	Demo Channel on Youtube
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1/19/2012 4:48 PM	Rate (1)
saeedplc Posts: 288 Rating: (4)	hello dear hdhosseini. thank you for your reply. i can't understand your mean. if it is possible please explain in more detail with an example. (i use positive edge in programs in which network is depend on previous one and whenever previous network( for example a timer) was executed then next network or timer start to execute.) best regards.
saeedplc Posts: 288 Rating: (4)
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1/19/2012 5:34 PM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 12/15/2022 Posts: 5697 Rating: (702)	Hello, Let me give a practical example. There is an alarm in machine and that sets a claxon, operator wakes up and want to get rid of the noise If theClaxon is set without a positive edge instuction the reset only can be done if cause off alarm is taken away or keep pushing the reset button. If edge instruction is used to set claxon', alarm stays but claxon can be reset. A "alarm" FP M 10.1 S "claxon" A "reset_claxon" R "claxon" regards, Marcjan
	Last edited by: Marcjan at: 1/19/2012 5:52 PM Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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This contribution was helpful to 2 thankful Users ericson hdhosseini

1/19/2012 7:12 PM	Rate (1)
BeVee Gold Member Joined: 7/18/2011 Last visit: 3/16/2023 Posts: 520 Rating: (88)	Maybe another practical example: Lets take same claxon setting of Marcjan A "alarm" FP M 10.1 S "claxon" A "reset_claxon" R "claxon" A 'smart' operator can block the "reset_claxon" pushbutton with for e.g. a toothpick. This would disable the claxon so that it never signals an alarm and the operator can sleep all night long. Changing the code like this A "alarm" FP M 10.1 S "claxon" A "reset_claxon" FP M 10.2 R "claxon" would make this smartass trick useless and the horn would signal the alarm, even with 'continuously pressed' reset button. Kind regards, BV

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This contribution was helpful to 3 thankful Users ericson Marcjan Dren Bejtullahi

1/21/2012 4:31 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 3/15/2023 Posts: 1410 Rating: (146)	Yes, a lot of programmers don't use edge functions, I am one to try using them as minimum as possible. I do use it on manual buttons for start, on special case I do use edge functions on self retain in series to prevent accidental behaviour of machine: A( A #ManBtn FP #Pos O #out ) A #ManBtn A #LimSwitch = #out The same logic is: A #ManBtn A #LimSwitch = #out except if limit switch overruns in first case operator has to release and push button again, in second case it will continue as nothing happened. In program I try to minimize use of edge functions, as well use of set/resetbits is prohibited, there are maybe just few in entire program, others are self retaining bits. But you can use it as long set and reset are close together, once you will set a bit in one part of program and reset someware else, then you get quickly lost with large amount of bits.
	Last edited by: Marko Bursic at: 1/21/2012 4:34 PM
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