ladder scan question

[cking2729]

I have a 10ms periodic task (in ladder logic) set up in my Logix controller (v28.)

One of my routines is to MOV the decimal number "2" into a DINT tag when a motor isn't being told to run. When a start button is pressed and the motors aren't running, I need to MOV a "0" and then an "11" into the same DINT tag.
I have the logic set up to achieve the MOV's, but unfortunately the "2" is always being written and seems to always take precedence unless I AFI out the MOV "2" rungs entirely.

I am wondering what I can do or what features Studio 5000 might have to help me accomplish getting the 0 and 11 to take precedence when true. My routine to MOV the 0 and 11 comes first in the program schedule.

Thanks for the help!

 

[Operaghost]

Can you post a screenshot of your logic? Is all of this logic occurring in the same Task/Program/Routine?

OG

 

[Mark Buskell]

It sounds like you may have logic that states if motor is not running MOV a 2.
Try adding in about the start button not being pushed as well.
This should disable the rung and allow your other numbers.
As Opera pointed out, a screenshot would be helpful.

 

[cking2729]

Can you post a screenshot of your logic? Is all of this logic occurring in the same Task/Program/Routine?

OG

I will try to get a screenshot ASAP. But the MOV 2 logic is in the same task, but a different program & routine than the MOV 0 and MOV 11. Does it need to be in the same program or routine?

 

[nhatsen]

I think the problem is because there are only 2 states (not running and running) and the OP needs to do something when the system goes from the first state to the second one.

I'd add a third state: stopped, starting and running. This way it's possible to write the correct value in any case.

 

[Operaghost]

.......Does it need to be in the same program or routine?

Not necessarily. I'm more concerned with the logic preceding the MOV instructions. What are the conditions triggering the MOVs? That is what I want to see.

OG

 

[rdrast]

I'm not sure what you are trying to do, but just off the cuff, I would suggest that you use a one-shot (OSR) instruction just before each of your MOV's. That way, you don't have logic constantly writing to your status variable, but only writing when a condition changes.

 

[Operaghost]

See all the people guessing? Without a screenshot, that is all we can do.

OG