Newbie

Hey guys, I just started doing plc work and had an issue. I tried to update the file via rspogix 500 and it asked if I want to save although the chart value may have changed, and I said yes. Now a pid value is stuck at negative!! Major fault!! How do I change it back to a positive??

Thanks, probably a stupid simple problem.

J

Any chance you can change back what you did? did you save it as a different name or did you save as the same and over write?

If you clear the fault does it go back into fault? what is the fault code?

Oh boy. Welcome to the forum.

What is the catalog number of the Allen Bradley controller you're dealing with?

Further define "I tried to update the file "?

"Major fault!! How do I change it back to a positive??"

You should be able to over write the value with the proper one and hit enter while the CPU is in program mode, but if it's a low level Micrologix, then it might require a download. In either case you may need to clear the fault first or afterward you will.

To clear the fault, with RSLogix 500 software, when online you can click on the FAULT red indicator toward the upper left, and a little menu pops up, and you can then choose "Goto Error" This will open up a window for the processor status, and there you can see the error and a description of it. A button is provided to Clear Major Error, and then the controller should return to program mode (unless its a model with a keyswitch set to RUN.)

Cont

Sorry for the perhaps vague statements. Basically I opened the .rss file to view it. Then I added a 4-20ma signal to tell the fans to run in the program. At that point I uploaded the program to the Plc and it prompted me if I wanted to continue although the table values may have changed since downloading. I said yes, foolishly it seems. It went into fault right away.

I then looked at the error and went to the rung that had the error. It was a PID value error. Or a bad value for the instruction, I can't remember the exact wording.

I opened the data table and saw that there were negative values in the table, for the blower motor speed function. This must have been the number that was messing things up.

I then at that time put the program in remote program mode and cleared the fault, opened the table with the negative values and changed them to zero, as the blowers were off so the speed should be zero.

At that point I hit enter to enter zero as the value and closed the window...

Now I don't know how to transfer the new data to the program... I can upload it but it goes right back to fault, even once I change the values....

Am I doing something wrong when trying to change the data? I can't get rid of the negative value in the table...

Thanks in advance for the help....new to this stuff, I guess I should have never hit ok when prompted that the values could be different.

The Plc flashes 00 then 80

Cheers,

After you change the values save the program.

What is the processor you have?

Since you were online when you changed the values, the correct values are now in the PLC and you can switch back to run mode. Like Mickey said, save the program from the PLC to your PC to update the offline program with the new values.

In the future, the best practice is to extract the current program from the PLC first. Your offline copy did not have the same values as were in the PLC. Why they were negative is a mystery though...

One other thing... Most of us refer to 'uploading' as transferring the program FROM the PLC TO the PC, and 'downloading' as transferring the program FROM the PC TO the PLC.



-Eric

Changing value

Ok I will give I a try and see what happens. Hopefully I can get this fault cleared. Is there a way I can see what the value should be? If I assign 0 to the value will it clear the fault and eventually set the value to what it needs? Thanks a lot I appreciate it as I am brand new to all this.

Regards,

If you will tell us the catalog number of the controller, more specific advice will be given.

If you zip and post the rss file, we can help you determine what (if anything) will put the correct numbers back into your PID function.

Thanks

Ok, I will be at the computer in An hour and can get more details.

Thanks

OkiePC said:

If you will tell us the catalog number of the controller, more specific advice will be given.

If you zip and post the rss file, we can help you determine what (if anything) will put the correct numbers back into your PID function.

Click to expand...

So if I open the program in remote programming mode And change the value in the table from the negative number, when does it actually change in the program? What I tried was to look at the fault, change the number, clear the fault, and go into run mode, and it faults once in run mode... Am I doing it in the wrong order?

Jonas Zimmer said:

So if I open the program in remote programming mode And change the value in the table from the negative number, when does it actually change in the program? What I tried was to look at the fault, change the number, clear the fault, and go into run mode, and it faults once in run mode... Am I doing it in the wrong order?

Click to expand...

Zip the rss file and attach it to a post. It is impossible to tell what is causing the fault without being able to see more of the bigger picture.

here is the rss. please let me know how to clear this, i cant get it to clear... on a friday too!!

controller is a slc5/05 CPU

the error desc. is "an invalid value is being used for a PID instruction parameter"

now I am thinking that it is a value that is below the min of the SCP in conjuction with the error I am getting... the value is 2048 and the min is 3277... hmm....