Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

Interesting behavior when detecting falling edge using SCL and Ladder logic

Created by: Sava at: 7/15/2022 1:27 PM (3 Replies)

Rating (1)

Thanks 2

4 Entries

7/15/2022 1:27 PM	Rate (0)
Sava Experienced Member Joined: 9/6/2011 Last visit: 10/18/2024 Posts: 22 Rating: (9)	FIY Found interesting behavior when detecting falling edge using SCL and Ladder logic. After power on, variable is Set to TRUE in SCL and remains FALSE in ladder. Bug/Feature ? ------------------------------------------------------------------------------------------ Split from Falling edge detection. Attachment F_EDGE_TEST.png (226 Downloads)
	Last edited by: The Helping Hand at: 07/15/2022 13:51:01 New subject after splitting
Suggestion To thank Quote Answer

7/15/2022 2:01 PM	Rate (0)
jacek d Platinum Expert Joined: 9/23/2005 Last visit: 11/13/2024 Posts: 4787 Rating: (731)	Isn't it your code which behaves oddly ? Shouldn't you ask yourself then ?
	Regards, Jacek What is confusing you is the fact that you never see a number but always its digit representation. So you end up thinking that the number is the representation. - Andrej Bauer Any claims against me - based on whatever legal reason - resulting from the use of any code and/or ideas presented on this forum shall be excluded. #StayWithUkraine
Suggestion To thank Quote Answer

7/15/2022 2:08 PM	Rate (1)
PetrNowak Experienced Member Joined: 8/3/2021 Last visit: 11/5/2024 Posts: 124 Rating: (4)	You have a bug in SCL 8th line: during first cycle both inputs are false (DI0 and #mbit3) so the result is true and Q1 is set to true. At the end of the first cycle is #mbit3 set to right value for evaluating falling edge. But its too late. Why do you use negated value of #mbit3 ??? Thats wrong. Use non-negated value in rows 8 and 12 and the code will work correctly...
	TIA Portal V13/14/16 S7-1200/1500
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Sava

2/24/2023 6:06 PM	Rate (0)
Sava Experienced Member Joined: 9/6/2011 Last visit: 10/18/2024 Posts: 22 Rating: (9)	Thanks for a hint. That was my mistake :) sometimes things are simpler, than we may think.

Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Jen_Moderator

|

Share this page:

Share this page on...

Follow us on