AB ML1200 Multiple S:4/Timer Use

[SNK]

Guys, I have posted 2 programs that are identical, other than I have added multiple instances of the same S:4/xx flags in the same routines.
I am writing code to ramp and decelerate VFDs, and I am looking at using only a few ramp rates. I have to complete this task in the ML1200, not the drive.
Ladder 5 is where the changes are.
If you run the logic in Program called MAR_EXHAUST_SINGLE_MTR, the ramping works perfectly.
If you run the logic in Program called MAR_EXHAUST_TRIPLE_MTR, the Deceleration ramping is almost instantanious, on all timer flags.
I am completely worn out trying to find out what is causing this problem,
So I as the experts.....what is going on?
I am using an ML1200
RSLogix500 version 7.00

 

[SNK]

Just for the record, I know that there are a couple ONS that are repeated on SC2 and SC3, but they have been changed with no effect on the processor.

 

[Ron Beaufort]

check your use of the ONS bit B3/161 (also known as B3:10/1) ...

 

[Ron Beaufort]

looks like we're "posting over" each other here ...

so in your last post, are you saying that you've already "corrected" the multiple ONS bit usage and you still have the same problem? ... if so what are the new bit numbers? ... in the meantime, we're still looking ...

 

[SNK]

Yes, I have updated the ONS as indicated, b3:10/0, B3:10/1 SC1
b3:10/2, B3:10/3 for SC2, and B3:10/4 and B3:10/5 for the SC3.
Still, no change.

 

[SNK]

I think I found the problem. The DECREASE Enable bit is used in all 3 instances of the SC1, SC2 and SC3. It really shouldn't make any difference, but I changed them accordingly to B3:8/1, B3:8/3 and B3:8/5 and it appears to work again.
I don't know why this has any effect on the process.
Either way, it works.
Is this the best way to handle a ramp function, in your opinions?

 

[Ron Beaufort]

what's controlling those "enable" bits? ... an HMI? ... or are you just toggling them manually for now to test the system? ... if they are being "flip/flopped" off and on by something like an HMI, then that MIGHT be repeatedly triggering the ONS instructions ...

as for "technique" ... why did you choose to SUBtract from the Counters' Accumulators for the "ramp down" function? ... a CTD instruction might be cleaner ... and that would be a little more consistent with the use of the CTU that you're using for each of the "ramp up" functions ...

glad you got it working ...

 

[SNK]

Thanks for your help RON. Yes, in this part of the development stage I am just setting up the bits from the HMI. When it is all ready to go, I will remove these bits and use other logic to latch and unlatch accordingly.
We have a very sensitive enviroment that requires that the fans ramp down when commanded in order to keep sterility, and we could not find an appropriate drive that would ramp with multiple ramp setpoints that control Italian made slit capacitor 220vac motors.
CTD instruction....I looked at it. I rarely have used it in the past. I will change it, it does seem right to keep consistency.
Thanks for the help again...