RSLogix 500 Ladder Logic Please Help!

[ASF]

Welcome to the forums Jay

I understand what you're trying to say about outputs affecting inputs - as one forum member's signature has it "an output is a PLC's way of getting it's inputs to change"

As the others have said, if you post what you've done so far, and some "this bit is working, but it gets to here and doesn't do this, I can't work out what's stopping this bit from turning on..." comments then a lot of folks on here will jump in to help you out. We're a friendly bunch generally but we like to know that you're at least making a concerted effort before we volunteer our time to help out

 

[jaywillnot]

Its quite okay sixstrings

Thank you for the link Mark. I will definitely look at it. Also, I ordered the PLC programming and lab books from the store on this site.
It will take time, but I will get this...then I will be unstoppable....no, not really

First I must learn from the masters here

 

[jaywillnot]

I'm having a bit of trouble transferring a saved picture of the rungs from my LogixPro simulator.
This is the curse of "newbies"

 

[JordanCClark]

Hi Jay,

If you click on the "Go Advanced" Button at the bottom of the Quick Reply section, you can upload your pics as attachments.

Hope this helps!

 

[jaywillnot]

Ah okay, thanks for the information Jordan.

 

[Lancie1]

I have been working on the LogixPro simulator. Some I can figure out but the elevator is killing me.

The LogixPro simulator Elevator Exercise is similar to many real-world PLC problems, because it uses a fairly long series of sequential logic, with many branching paths. However, if you follow the hints in the official Elevator Exercise problem, you will eventually arrive at a working program. The key is to set up the subroutines exactly as instructed. For a working version of the Elevator program, you can go to the "Downloads" area of this site (yellow "Downloads" button above, located on the line below "RSLogix 500 Ladder Logic Please Help!") , then look under "Allen Bradley".

http://www.plcs.net/downloads/index...t4&direction=0&order=&directory=Allen_Bradley

Look for this file: LogixPro ELEVATOR_EX_4.rsl, by Lancie1
Another well-written version is: Elevator - Exercise #4 113.zip, by member RWS8086

 

[jaywillnot]

----|NC|-------------|NO|------------|NC|--------------|NC |--------------( L )--
B3:0/1 l:3/1 O:4/1 l:3/2 O:4/0
close indicator close clamp solenoid on cylinder retract close clamp

---|NO|------------ |NO|----------------|NO|-----------|NC|----------------( L )-
B3:0/0 l:3/3 O:4/1 l:3/4 O:4/2
open indicator open clamp solenoid on extend cylinder open clamp

Let's assume these two rungs are a small portion of a spot welding robot cell routine. B3:0/0 and B3:0/1 are being used as clamp open / close indicators and are tied in with O:4/0 and O:4/2.

My question is this: If B3:0/1, l:3/1, O:4/1, and l:3/2 are energized, will O:4/0 come on and close the clamp? Then when the next rung is scanned, will the clamp open up again?
I realize that this interpretation isn't very well mapped out, but I'm sure you all get the idea.
Any suggestions and opinions are welcome.

 

[Lancie1]

My question is this: If B3:0/1, l:3/1, O:4/1, and l:3/2 are energized, will O:4/0 come on and close the clamp?

No, because if bit B3:0.1 is energized or "1", then the first instruction "NC B3:0/1" will be false or 0, making the remainder of the first rung also false. "NC O:4/1" and "NC I:3/2" will also be false.

 

[JaxGTO]

When using HMI epically, use device drivers for each output device. There should be some examples of this on this site. Device drivers take all the HMI Hand/Off/Auto or Auto/Manual code and put it in a routine you never have to trouble-shoot. Then when your auto logic needs to open a valve or start a motor, it just turns on one bit and the driver does the rest.

I always make separate routines for Discrete and Analog drivers. Then like rdrast said break the auto logic down into sections or areas. A lot of the way you break it down will have to do with the type of system it is. A discrete manufacturing machine will differ greatly from a baking oven etc. But the device drivers can remain very similar. Also the device drivers you can use on the next project and you will have consistency in your development for both PLC and HMI.

 

[GlenGineer]

My first project was designing an automatic/manual elevator. My boss wrote the original program and left me to troubleshoot it. Nothing seemed to work and I could not figure out why. The problem was his mindset. He was used to sequential programing (like basic). Although there are some tricks to be done with the "scan" the entire ladder including the sub-ladders are all active at the same time. His program did not recognize this.

I think you have already had some programing tips but basically figure out what action you want the device to do and then figure out what unique conditions you need in order to get there. Sometimes sketching it helps and sometimes writing it in English helps.


Roll Tide

 

[Lancie1]

Jaywillnot,

Thanks for your service to our country. Veterans are my heroes.

 

[jaywillnot]

Thank you all soooo very much for your help. You guys rock!!!!!

Hey Lancie, thank you; it was my pleasure and utmost honor defending you all and I would do it all over again at the drop of a hat!!!

ROLL TIDE ROLL GlenGineer!

 

[seth350]

You may already know this from reading you have done, but the PLC-5 & SLC processors scan logic differently than the 5000 series processors. It was a bit of a learning curve or adaptation when I started programming the 5000s.

The SLCs will scan the rungs from left to right in succession or synchronously.
The 5000 series will scan the rungs left to right but in an asynchronous manner.

First know how the PLC scans the logic and how it interprets the rung, before writing a program. Otherwise, you will wear your delete key out.

Or if delete keys are sacrificial to you, then get a PLC hooked up in the shop and get online with it. Then just start playing around with it.

To practice, pick a machine out on your plant floor and write a program for it the way you think it is wrote. Use timer done bits to simulate limit switches and proxes. When your done, and it's working, check and see how different yours is from the machines program. If it is the exact same, then you cheated. lol
There are a thousand different ways to skin a cat, don't favorite any of them just yet.

 

[jaywillnot]

That is a very good idea Seth.
I was actually looking through a 5000 program the other night for one of our more precise machines. It took me most of the night just to figure out what the "mapping" term means on some of the conditions. Needless to say, I'll be sticking with the SLC for a while.....

 

[seth350]

Not real sure what you mean by "mapping", but I did find this for you and it talks about synchronous and asynchronous scans. May also be relevant to your mapping term as well. Programmers will often "map" their field inputs to tags much like mapping a field input to a B:0/0 bit in 500. Except in 5000 you will use a tag to address this "bit".
Some people stick with the 500 addressing in 5000 and give tags names like B:0/0, N7:0/1, F8:1, etc..

Although, it is much better to give it an actual meaningful tag. "MCR_Ready", "Feeder_Retracted", "Extend_Pusher", etc. As these will stay with the PLC, so in the middle of the night when the new packing line they just commissioned goes down and no-one has bothered to send out the finalized program. You are able to hookup to it, upload, and there are all the meaningful tag names, less descriptions. You find that the "Conveyor_Outfeed_Full" tag is on, and then you can find the broken sensor on the outfeed conveyor. Lot less headache than searching through an uploaded 500 program.

Another thing I have seen, many people dwell on what to call their tag. Whereas, in 500, the bits are addressed for you, so its easy to assign a tag. No staring at a computer screen at an XIC with a question mark above it, trying to conjure a purely professional looking tag like you are trying to name the Queens pet ferret.

Just don't get hung-up on tagging, give it some kind of name so that YOU know what it is, then move on. Once you have the concept, you can refine it later.

http://www.contactandcoil.com/rslogix-5000-tutorial/mapping-your-inputs/