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endless counter

Created by: HSCD at: 11/1/2013 4:37 PM (11 Replies)

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11/1/2013 4:37 PM	Rate (0)
HSCD Posts: 49 Rating: (0)	Dear friends How to write a FC or FB to count a pulse (just positive/negative edge)? according to siemens: 1- when use the S_CU command "the count value is incremented by 1 when the count value is less than 999." and 2- "If the counter is set and if RLO = 1 at the inputs CD, the counter will count accordingly in the next scan cycle, even if there was no change from a positive to a negative edge or vice versa." those aren't good to my point. I need to count a pulse (edge not the level) endlessly. any idea?
HSCD Posts: 49 Rating: (0)
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11/1/2013 5:26 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 5/4/2023 Posts: 722 Rating: (40)	Hi! You can use a positive edge detection on the input. In stead of using a counter, use a int or dint and just add one for every positive edge detected. Nothing is indefinetely in the binairy world, but a dint will give you a very large number. Ton

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11/1/2013 6:06 PM	Rate (0)
HSCD Posts: 49 Rating: (0)	Dear Sir P and N, yes, detect the edge but their address keep the state. means if P detect the edge P address will be 1 after that. it isn't working like as a shot.
HSCD Posts: 49 Rating: (0)
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11/1/2013 6:16 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 5/4/2023 Posts: 722 Rating: (40)	A pulse will only remain high for one cycle I believe? I havent got S7 on my machine, but the easiest way to implement from my little mind: Put a ADD_DINT block in your network. Input 1 is your tag where you want to store your counter value. Input 2 is 1 Output is the same tag as input 1. Add an positive or negative pulse detection to the EN input. And input the bit you wish to count. Make sure you don't use any TEMP tags for any of these signals.

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11/1/2013 6:20 PM	Rate (0)
HSCD Posts: 49 Rating: (0)	I did. i'm saying what i'm seeing. P address keep the state and Add block's out is increasing. what's wrong with the temp?
HSCD Posts: 49 Rating: (0)
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11/1/2013 6:27 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 5/4/2023 Posts: 722 Rating: (40)	a temporary value wouldn't know what happened the last cycle, and your result would be random. sometimes it works, usually it doesn't. also using an address that is used elsewhere is a common mistake. can you post a screen shot of your code?

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11/1/2013 6:30 PM	Rate (0)
HSCD Posts: 49 Rating: (0)	please download the attached file. i called the FC in OB35. Attachment 2.JPG (85 Downloads)
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11/1/2013 6:32 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 5/4/2023 Posts: 722 Rating: (40)	Try to replace temp with m54.0 (or any other memory bit) and it will work. Never use temps for pulses. They are reinitialised every cycle

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11/1/2013 6:34 PM	Rate (0)
HSCD Posts: 49 Rating: (0)	check it out please /tf/WW/en/Posts/99758#top
HSCD Posts: 49 Rating: (0)
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11/1/2013 6:41 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 5/4/2023 Posts: 722 Rating: (40)	I answered the same thing there.. Don't use temps unless it is to carry a value from a higher network to a lower network. FB's with STAT values are your friend.

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