RSLogix 500 Ladder Logic Please Help!

Hello all,
I have been in the maintenance field for about six years now, and I work around many machines running with the SLC 5/03 and 5/04. We have a few machines with the 5000 but that's another thread later on.
Here is my dilemma in a nutshell. I can navigate through the ladder logic and troubleshoot the problem areas (most times) and I like to think I have a basic understanding of inputs and outputs, but for the life of me; I do not know how to actually write a program with multiple tasks and make the machine(s) operate in a specific manner. Something always seems to turn on or off at the wrong time or not at all. I've always heard to use the outputs to manipulate the inputs. Kinda confusing to me I guess. Can anyone please help with this? I want to further my technical skills.
Thank you all for hosting this site!
Jay

I'll figure it out. Thanks anyway

Hi, Jay.

Keep in mind that three hours is not a long time for people to respond to your posts. Heck, I've only been awake a short time myself, and the coffee hasn't started percolating through me yet...

That being said, feel free to post what you have tried (along with your code) and we'll be happy to help you sort things out. If you look at some of the other threads here, you'll notice there are more responses if you show your work.

Sorry about that, it's been a long night at work. We do not have the resources or management on 3rd shift to really help us when these situations arise

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

I will post some rungs of the program later on. It is almost time to go home

I start by breaking a machine down into logical sections, and writing down exactly what that section is supposed to do and when.
Does it run in speed mode? torque mode? position mode? Does it need to jog? forward/reverse?

Then I make a list of all inputs and outputs associated with that section, and write down how each of them should affect the machine section and when.

Only after that is done do I bother writing the code, and just to keep things consistent in my head, I start with interlock logic.. What must be satisfied to allow this section to run in coordinated mode? to run in independent mode? to jog? After the interlocks are done, I do my main logic sequencing. The final part of each section is the analog or reference logic.

Then move on to the next section.

When all sections are done, you just have to tie the 'whole line' parts in, which is usually almost complete by then.

I always use a PLC based ramp generator as well for coordinated, multi-motor systems, never the ramps built into the drives, but once written, it's pretty much done forever.

Your mileage may vary.

Hi rdrast,
That is very helpful knowledge. I never really thought of going that route.

jaywillnot said:

Hello all,
I have been in the maintenance field for about six years now, and I work around many machines running with the SLC 5/03 and 5/04. We have a few machines with the 5000 but that's another thread later on.
Here is my dilemma in a nutshell. I can navigate through the ladder logic and troubleshoot the problem areas (most times) and I like to think I have a basic understanding of inputs and outputs, but for the life of me; I do not know how to actually write a program with multiple tasks and make the machine(s) operate in a specific manner. Something always seems to turn on or off at the wrong time or not at all. I've always heard to use the outputs to manipulate the inputs. Kinda confusing to me I guess. Can anyone please help with this? I want to further my technical skills.
Thank you all for hosting this site!
Jay

Click to expand...

This sounds as if these multiple <tasks> might possibly all have an output to the same physical I/O address...which would give these observed results.

JW, take a breath, if you have been doing this for 6 years surely you know outputs don't control inputs. Look for things you want done in the process, but they have to be in sequence. You can't ask for something to happen if it hasn't happened in your code.

PLCnovice61 said:

JW, take a breath, if you have been doing this for 6 years surely you know outputs don't control inputs. Look for things you want done in the process, but they have to be in sequence. You can't ask for something to happen if it hasn't happened in your code.

Click to expand...

I didn't mean manipulate the hard inputs with outputs literally. I was talking about how an output sends a signal back to the processor, and the PLC must see that the output is made by a prox or limit switch. I'm just speaking about the scan cycle itself. Guess I should have worded it a little better...http://www.plctalk.net/qanda/images/smilies/smile.gif

hello all.
have anybody successfully conect a weintek hmi with a micrologix 1000?

@Zhandor, please start a new thread for your question. That way we can avoid confusion between topics.

Thanks!

Jay,
go here: http://www.thelearningpit.com/lp/logixpro.html

spend a couple dollars and buy the simulator, it is worth every penny.......

sixstringz said:

Jay,
go here: http://www.thelearningpit.com/lp/logixpro.html

spend a couple dollars and buy the simulator, it is worth every penny.......

Click to expand...

Already has it, as stated in post #3
http://www.plctalk.net/qanda/showpost.php?p=637021&postcount=3

JordanCClark said:

Already has it, as stated in post #3
http://www.plctalk.net/qanda/showpost.php?p=637021&postcount=3

Click to expand...

Did not catch that!

JW, what you heard about the plc using the outputs to control the inputs is from Bernie Carlton's sig line. What he means by that is based on the logic you have written if the inputs do not conform to what you want them to be, then the plc (based on the logic written) will change outputs to make the inputs conform. For example, a simple machine with just a cylinder... it is retracted and the prox that says it is retracted is on, and the one saying it is extended is off. Based on some other conditions (timers, push buttons, other sensors) the plc logic now needs the extended prox to be on, and if you wrote the logic correctly it will turn on the solenoid for extend cylinder until the input changes. This is overly simplistic, but that is the gist of what he is saying.

If you want to know the behind the curtain stuff on PLCs (particularly AB) then check out Ron Beaufort's website and watch the sample lessons and videos. They will give a good head start on knowing what is really going on in the PLC brain.


http://www.ronbeaufort.com/