Unitary, modular and rack mounted PLCs

I know everyone has probably heard this question a million times before, but i really need some help.

I have carried out a lot of research for the following question, and have found none, or very little information.

I have looked on the internet, which does not give me much information, and i have researched into several PLC books.

The troublesome question is as follows:

"Discuss the design characteristics, of Unitary, modular and rack mounted PLC's"

If anyone could provide any information, not necessaryily the answer, or any sites that i may be able to find related information, it would be much appreciated.

Regards

A search at this site gave me this

http://www.plctalk.net/qanda/search...d=161893&sortby=lastpost&sortorder=descending

You're right nursiejenny, we've heard the question more times than we can count. Do a search of this site using those keywords. You'll find plenty of hits. You'll also find our opinion of the British HNC exam and the people who seem to think that this is such an important point that it deserves to be include in the course syllabus.

I dare you to use this answer:
The memorization of little used terminology does not in any way contribute to the understanding of how to use PLCs as a tool in industrial automation. It is sufficient to say that there are different sizes and configurations of PLCs to suit different applications.

This should answer your question:
http://www.freestudy.co.uk/plc/outcome1.pdf

That site may help with your studies and future questions:
http://www.freestudy.co.uk/plc.htm

We need those links on the front page.

nursiejennie said:

I know everyone has probably heard this question a million times before, but i really need some help.

I have carried out a lot of research for the following question, and have found none, or very little information.

I have looked on the internet, which does not give me much information, and i have researched into several PLC books.

Click to expand...

It's good that you tried to convince us that you're really confused, and not just looking for a free ride. Most of the students who come here, post the question (with typos), and disappear. They don't get much help that way.

Follow Ron's (rsdoran) links. They're good ones. But remember, in the "real world" the answer to your question is useless trivia. We pick a PLC that is going to to the job we want it to do. Whether a PLC is rack, modular, unitary, or painted purple, it has to do what the project requires!

AK

Its like your car, when you go to register it, do you really care if it is a "sedan" or a "coupe"? No, you care about functionality after the fact, or 2 door vs. 4 door.


Greg

What is the pass mark for your class?
Is it 49% fail 50% you pass?
Is it 80% = A
70% = B
60% = C
50% = D
<49% = F?

If so, then you don't really have to answer this question, you can probably still pass without it.

BTW, the correct answer is "Don't Care".

Doug

Just checked Ron's reply.

Ron, you are a goodguy.

Doug

That is a great link, Ron. You have now confirmed my long suspicion that these guys just aren't reading the text!

<rant>
This has got to be the stupidest question I've seen on a test since... well, since I was in school.

I'm not saying the OP (original poster) is asking a stupid question. I'm saying the author of the original question has no idea about how to convey useful information from one person to another. That means the author of the original question doesn't know how to teach. If the professor or instructor comes to this forum, I'd be more than happy to show him some texts he can read to improve his abilities in this area.

And Nursie is paying money for this?!

Has ANYONE ever seen or written a design spec that used any of the three keywords? Of course not.

This is worse than trivia (useless information). It is designed to confuse the learner with pointless, non-standard jargon that no one actually uses. In other words, not only does it not convey information, it conveys inaccurate (non standard, unless someone can find me some IEEE link that defines the terms) and arbitrary information that will absolutely never be used by anyone after the pointless question is finished and the class moves on to other (and probably equally pointless) topics.

How about instead a question that says, "Name five items necessary to consider a device a PLC?" (Processor, data memory, I/O's, program memory, programming device) Hey.. that's useful information, isn't it? Why not ask about such things?

You don't ask because you don't think, instructor.
</rant>

Sorry about the rant. I happen to have very strong feelings when it comes to teaching. And they tend to boil over when I see things like this. Questions should be asked to reinforce key core concepts, not to see if the student read the text.

Hear-re Here-re... Don's da MAN!!

There is one thing I consider more stupid than asking the question:
Not providing the student the answer IN CLASS! How can you expect to be tested without being taught. This question should've been covered in class so it could be answered on a test instead of being answered here.

Mark,

Not so say that this directly applies to the stupid question, but I think it's good practice for the instructor to encoruage students to go out and find answers on their own. Whereas in the real world you will many times need to develop your own resoceses to answer your own questions. And guess what. This fourm is one of thoes resources! That stands for you and me both.

However the fact of the matter is that the "unitary" question belongs in the urinal. banghead

No argument there. But there is a line between thought/learning and robotically asking/answering questions. I agree there needs to be thought involved in learning. I couldn't go out and do your job without basic training to some degree. But if it's damned important for me to know the difference between a shift and a shaft, you better teach me that AND test my knowledge of it.