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General Category => Do-more CPUs and Do-more Designer Software => Topic started by: belias on January 05, 2022, 10:20:11 PM

Title: One Shot Trailing Edge Applied to Xxx Input - Not Working?
Post by: belias on January 05, 2022, 10:20:11 PM

I've stared at this for 2 days now and I can't figure out what's going on.  I feel like I'm missing something obvious, so please be nice to me if it is...

This ladder logic comes from a task.  The top and bottom rungs work fine (the bottom run was actually just for my own testing).  The middle run that applies a trailing edge contact to the X38 input doesn't work.  Even when I provide a very slow (15 second) change to the X38 signal from ON to OFF, it still will not allow power flow.

As soon as I change the X38 to a C-bit and manually change it, it works fine.

Any idea what I'm missing?

Title: Re: One Shot Trailing Edge Applied to Xxx Input - Not Working?
Post by: RBPLC on January 05, 2022, 11:53:57 PM

Two things:
1) What command is on the output side of the rung?
2) What does your ENTASK look like for this Task?

Title: Re: One Shot Trailing Edge Applied to Xxx Input - Not Working?
Post by: belias on January 06, 2022, 11:11:55 AM

Sorry...the picture was apparently too large to show the whole thing (re-sized below).  The output is a simple STRPRINT command.

The ENTASK is set in the Main program:

ST1 ($On)  ---->   ENTASK (Interval 0)

And it's not like this is an intermittent thing...every single time, it works perfectly for a change in the C-bit, but not for a change in the actual input (X-bit).

Title: Re: One Shot Trailing Edge Applied to Xxx Input - Not Working?
Post by: BobO on January 06, 2022, 05:33:16 PM

I put this code in a task exactly as shown, and it worked as expected. Only thing I can think of is the input isn't really doing what you think. You could try forcing it on then off and see if that fires the logic.

Title: Re: One Shot Trailing Edge Applied to Xxx Input - Not Working?
Post by: ADC Product Engineer on January 07, 2022, 08:02:34 AM

Put a counter on the rung under this one and use the same logic to trigger it.  As Bob said, I would bet that it doesn't increment when you think it is.