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Positive Edge doesn't work anymore?

Created by: jruz at: 4/8/2014 7:14 PM (6 Replies)

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4/8/2014 7:14 PM	Rate (0)
jruz Posts: 3 Rating: (0)	Hi Guys, I am totally new to Siemens and I'm on the process of converting my ladder program from other PLC brand, GE for a certain project using S7-300. And I also have difficulty with this positive edge detection. I used DB addresses for several of my positive edge, and it works perfectly into my first FC. However, as I go through creating other functions, suddenly it just doesn't work to the new FCs and this includes the very first FC. I tried using M address, and it works into some networks, but not all, its unpredictable. I have no clue where did it went wrong, and I'm following just the same pattern with the first FC which works before. I must mention that FC40 has been inserted to my blocks recently, but I cannot see any relations to it, I just thought of telling you guys because you're the expert. I will be using this positive edge into a lot of my network, and so I would appreciate for your help. Thanks. new to siemens, jruz
jruz Posts: 3 Rating: (0)	Last edited by: CS Moderator at: 4/10/2014 1:55 PM new subject after splitting from /tf/WW/en/Posts/31903#top
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4/8/2014 7:39 PM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 10/17/2024 Posts: 5697 Rating: (715)	Hello, Maybe it's a goo idea to post your code (or part of it) that way we can maybe find the reason for your problems. You know FC has not it's own memory area outside the FC and that Temp variables have to be initialized (means first write to temps and then read)? 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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4/9/2014 12:32 PM	Rate (0)
jruz Posts: 3 Rating: (0)	Marcjan Hello, Maybe it's a goo idea to post your code (or part of it) that way we can maybe find the reason for your problems. You know FC has not it's own memory area outside the FC and that Temp variables have to be initialized (means first write to temps and then read)? Regards, Marcjan Thanks Marcjan for the reply. I really don't know that FC doesn't have its own memory. What I did is to program the way I'm doing in my other PLC. Its very simple which eventually did work on my first FC luckily, but not now, you happen to remember the example from S7 help, where (P) = DB address, (JMP) = another DB address under the same DB and my inputs are almost momentary. Now, I use this (JMP) address bit as NO to the corresponding network. I didn't use any temp vars. I attached part of my program. The FC99 is my first one, and the FC101 consists of so many other networks on my real application, but I just entered some. Again, I would appreciate for your help. Sorry, it maybe a big file, I just thought you might want to see the whole thing. Thanks. Jruz Attachment myprojec.zip (363 Downloads)
jruz Posts: 3 Rating: (0)
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4/10/2014 4:20 AM	Rate (0)
jruz Posts: 3 Rating: (0)	Hi All, Any thoughts on this? Thanks. Jruz
jruz Posts: 3 Rating: (0)
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4/25/2014 12:06 PM	Rate (0)
Slade aka ND Experienced Member Joined: 4/15/2009 Last visit: 6/30/2023 Posts: 5 Rating: (0)	Hello, jruz. Could you point network of FC101 where positive edge give no result. I simulate your project a little bit and it must work. Are you sure that you use edge memory bit only one time? In FC101 network 8 use positive edge detection at the end of some logic. I think this is not good way to use front detectoin. Better use front detection exactly for one bit but not for logic. Also in FC99 network 20 better to have four different edge detection. I think you know that new posive edge detected only when signal go down and then rise again. Best regards, anbron.

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4/25/2014 2:50 PM	Rate (0)
Piotr.M Platinum Expert Joined: 6/24/2013 Last visit: 11/4/2024 Posts: 1652 Rating: (425)	Hi Please check and ensure every posiutive or negative edge (FP or FN) instruction has its own memory bit in the data block. That bit must be used by one and only one Edge instruction. What I do for program structure is 1. for each big part of machine create FB which controls it 2. smaller tasks are controlled by FCs and bits which are to be remembered (STATIC) are passed to the FC as the in/out. These are declared as STAT in parent FB which calls the FC. this makes program structure clearer - plant is divided into self-contained objects and all variables for each part of plant are in FB interface. For data exchange between parts I use data block called "GLOBAL" which is divided into parts (STRUCTs) - one STRUCT for each machine part, one general (for all), etc. HMI/SCADA and ALARMS - again two data blocks divided with STRUCTs - first general then one struct for each major machine part. This makrs debugging/changes/understanding by maintenance easier and quicker. also when db is modified STEP 7 updares addresses so it is not possible to make symbols which overlap and write each other i.e. MD400 and MD402 WARNING - when the above method is used please change Address Priority to "Symbol has priority" (right click on blocks then select object proporties-->address priority and bottom right option)

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4/26/2014 5:44 AM	Rate (0)
jruz1 Regular Member Joined: 4/26/2014 Last visit: 4/29/2024 Posts: 26 Rating: (0)	Hi, Same guy here Jruz/Jruz1, I appreciate so much for your inputs and tips for guys new to siemens. I have actually did fixed this issue, I messed up with my DB that's why. I thank you for testing it anbron, and letting me know other tips handling this positive edge. And Piotr for programming structure tips, I appreciate that. Thanks again. I'm moving forward and trying to test some other functions that I need. Regards, Joel

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