Is it possible to learn PLC's yourself??

[dogleg43]

Your question ASSUMES that STOP buttons are wired to some type of contact. I say that a better assumption is that STOP buttons usually OPERATE a normally closed contact. The STOP button is not wired to any contact, but the contact is an integral part of the button and is operated by the button - no wiring required here! The wiring is in the next part, from the STOP button contact to the PLC Input terminals.

Where you made the wrong assumption is: that you wire this Normally Closed Stop button to a PLC input, and then inside the PLC program, you would use a NORMALLY OPEN contact to examine the Normally Closed Stop button input.

You're right. A poorly worded sentence on my part. Mea culpa

 

[swapped]

really?

 

[Timbert]

I hope from all this confusion the OP can learn about writing clear, concise code. What assumptions are anyone working on the machine going to make.

Because PLCs evolved from hired-wired relay logic. Most technicians will expect to see an NC stop button and an NO start button. While the configuration may be logically equivalent, they don't follow the expected norms. So, you've just managed to confuse the technician working on the equipment with no real gain.

 

[MarkNightingale]

What assumptions are anyone working on the machine going to make.

When working on a new machine or one that I haven't worked on before I make NO assumptions.

Assumptions can have devastating consequences and I have seen a few times when assuming has cost production time and worse injury.

I hope from all this confusion the OP can learn about writing clear, concise code.

I totally agree. Good documentation and clearly written code will help in all situations.

Mark

 

[Lancie1]

What happens if things are switched and you use a normally open stop switch with an XIO instruction or vice versa and normally closed start switch with an XIC instruction?

You get the same effect..............right?

Bottom line: No, you do not get the same effect. XIO always gives you the OPPOSITE effect of whatever type (NO or NC) of start or stop button you are using.

really?

Yes, really-really!

 

[Timbert]

When working on a new machine or one that I haven't worked on before I make NO assumptions.

That's obviously the right answer.

Perhaps, I should have said, "What assumptions is Bubba gonna make at 2AM."

 

[MarkNightingale]

Bottom line: No, you do not get the same effect. XIO always gives you the OPPOSITE effect of whatever type (NO or NC) of start or stop button you are using.

Lancie1,

I think you missed my point. I wasn't saying it was correct, I was putting it out for discussion, I would have liked it if the OP would have contributed again since he is the one wanting to learn.

Mark

 

[WildeKurt]

Back to the original subject: PLC programming is 'just another language.' You can apply those same good practices of well designed structural programming to PLC programming for the most part. You could also make a real nightmare too. I've seen both.

Orignally, I learned PLC programming 1st through OJT. Later I went back to school and studied procedural programming in other languages (COBOL, C, C++, etc). I was able to apply most principles to PLC programs. The 'quality' of my programming increases dramatically too.

 

[plcisgreat]

Motor Control systems and Ladder Logic

I would recommend taking a course in motor controls systems. Take the time to learn the fundamentals of relay logic, timer on , timer off, interlocks,NC,NO, and understand the transfer of relay ladder logic to PLC logic. I firmly believe you will have a much better understanding of PLC systems and the effects programming will have on various systems.

 

[OkiePC]

I would recommend taking a course in motor controls systems. Take the time to learn the fundamentals of relay logic, timer on , timer off, interlocks,NC,NO, and understand the transfer of relay ladder logic to PLC logic. I firmly believe you will have a much better understanding of PLC systems and the effects programming will have on various systems.

YES. Build some start/stop stations with real buttons and real relays first. This will not only be necessary to understand in the real world, it will give you a new appreciation for hte evolution of the PLC. I remember my first PLC class, being stunned by how crude and limited ladder logic appeared at first. "You mean to tell me that these million dollar man-eaters are controlled by a 16k processor with a 20-50ms scan time? And they cost thousands of dollars?" I expected something much more high tech. I was lucky to have been a home computer hobbiest as a kid (before DOS), so I had no trouble with binary and hex numbering systems...octal was easy to pick up on.

Many of the same things apply, with the exception of structure. PLCs don't wait. They are not event driven by nature, they go in an infinite loop as fast as possible. Understanding that structure is already there for you to work within, is perhaps the most important apsect. But, as already said, don't assume anything, rather study and examine everything. Get good at reading technical manuals, and pore over them all for all of the hardware involved.

 

[leitmotif]

Without training from a company or experience in designing PLC's systems?? And be a proffessional. Further to my other thread:
http://www.plctalk.net/qanda/showthread.php?p=465817#post465817

There may not be a limit to what you can do by yourself
BUT
It is easier with the help of others.

Uhhh the physician who treats himself has a fool for a patient? Is that appropriate I wonder??

It is better to learn from the mistakes of others ??

Dan Bentler

 

[uptown47]

You can teach yourself. It is quicker to be taught. However, at a certain point you will need to 'go it alone'. In my experience (I stress - in my own humble experience) there has never come a point where I've thought - "right, that's it, I've learnt everything".

Every day you learn new things. You are forced to develop better techniques for over-coming real world problems.

Your programming part of your brain is like a muscle, the more you use it the more it develops and becomes better.

Learning from other software is a great way to go. Learning from your mistakes is a must. Being open-minded and having the humility to listen to other opinions and other ways of doing things is a necessity.

The main thing is enjoying it. If you enjoy something you'll naturally try and get the most out of it and want to know more about it.

If you don't enjoy PLC programming and all the problem solving and tricky situations which it involves then you'll never be great at it.

Good luck ;-)

 

[L D[AR2P#0.0]]

if you don't enjoy plc programming and all the problem solving and tricky situations which it involves then you'll never be great at it.

+1

 

[trcash2]

That is how I learned AB software. I was given basic instructions in Modicon as my first PLC, but all the AB I learned on my own. After a couple of years started contracting out my programming skills and the rest is history. The only requirements are dont be scared to take a risk and you have to dedicate a lot of time. Forty hour weeks will not cut it if you really want to learn the PLC's.

 

[ajay34]

hai all...
i m not good as you all but i did learn PLC by book and pratice..
since i always to design on electrical work ..and when i start too get attch to PLC..i start doing by convert my electrical control from switch,contactor,relay and etc ..start from basic like control s/valve.motor starter and so on
till i could understand other ppl program and rewrite and modify it.

and i still learning new things from all the expert.

basicly i would say can but surely need mentor for better programing

bu