Slc 5/04 I/o

cds

Member
Join Date
Oct 2003
Posts
4
We have a conveyor system controled by a slc 504 that isn't shutting off in the auto mode when it gets a hopper full signal. The stop input gets to the 504, but the appropriate output does not turn on. With limited program documentation for the system - the uncommented uploaded program. How do I match up the I/O wiring schedule with the program?

Thanks --- CDS
 
Hi CDs,

With the uncommented program, life is going to be miserable. Try to get the documentation from the vendor. OR -

If it not a complicated operation, then start to do the documentation, starting from key in the comments for the I/O - of course referring to the wiring diagram or I/O list.

That was the easiest part. Now you have to figure out the machine scqueance and try to understand what each rung is going to accomplish and punch in the appropriate comments. It is tedious, but not only you, any one look at the program will appreciate that.
 
The best way is to work backwards. If you know what output should be turning ON, search the program and find the rung that controls that output.

Now see what's missing on the input side of that rung. Keep going backwards and you will probably find that the problem may not be with the input you are looking at. It may require another condition, or another input, to enable the desired output.

Going to the [View] Menu options in RSLogix and turning on the Cross Reference options will help you to work backwards though the logic.

.... good luck
 
Documentation

It sounds like you need to spend a fair bit of time physically verifying the i/o and listing comments. After this you can work back through the ladder, commenting as you go.

It's certainly not the most pleasant task but it yields great benefits long term.
 
Dont you have at least a printed program listing ?
If the program was made specially for your plant, then I do believe that this is a requirement for the original vendor.

Contact the original vendor and ask for the program file (including comments). Second best is to get a printed listing.

The stop input gets to the 504, but the appropriate output does not turn on
This sentence confuses me. Shouldnt the output turn off ? I assume that it is the output that activates the contactor for the conveyor drive motor.
 
no biggie

Your question is contradictory. Rather than to guess your problem I will guess a solution. Open the file for the program in the software. Follow the program through the process. Softwares track the scan differently. So when the scan gets to point in the program where your having the problem and you can see if the contact is passing/ not passing power to the output. More than likely the rung w/ the output on it isn't getting closed/opened.
 
At this point, I've managed to comment about half of the program. I'll have to search for updated prints as mine don't account for all that I find in the program. What we're talking about is an newspaper inserter with dual heads fed from a storage system by conveyor. The conveyors are staged allowing for stream aligners, fold compressors, and delivery sections. I have not been able to determine if we're dealing with an inhibit to stop the delivery, or simply an enable output that drops out to stop the delivery. The program runs 28 subroutines. The sequential stop/start aspect involves a complex timing scheme that (this is a guess) input data words to analog output cards to control the delivery drives. I'm handling RS500 better having some time with it now.

Thanks for everyones help - CDS
 

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