comparison between plc and conventional control

joel

Member
Join Date
Aug 2002
Location
san fernando, pampanga, philippines
Posts
5
i would like to ask for a detailed discussion regarding the comparison between plc and conventional control using relays and contactors in terms of 1. efficiency 2. reliability 3. maintenance 4.flexibility 5. cost. can you also some pointers in the advantages and disadvantages of plc? thank you for your help!
 
Since it seems that you must have missed the New Here? Please read this important info!!! above, here's an excerpt...

<hr>
4. How can you get these professionals to help you?

Peer-to-Peer questions are self-evident. These questions will be answered without qualification except that it sure helps if the questions are clear and concise.

Student questions are also self-evident. Those questions will be answered IF, AND ONLY IF, it is clearly seen that the student has put in the effort to help himself!

Questions that are answered in Chapter 1 of any decent PLC book are not likely to be answered here.

“What is a PLC?” and “What is I/O?” will not be answered! At least, not directly. Be prepared for ridicule!

Lazy students are not tolerated! We will NOT do your homework for you!

<hr>
Get it?... :cool:

-Eric
 
ERIC

THANK YOU VERY MUCH FOR YOUR reply! i'm not a student, actually i have no deeper knowledge regarding plc, this is my first time to explore this type of controller.but anyway thank you very much for your help.
 
Joel I am willing to discuss it, I also (from your post) am not convinced you arent new to plc's (being new to this site is another thing).

Anyway to start the discussion/debate etc ...PLC's were designed to REPLACE relay logic...why? cost for one, a plc could replace many relays/timers/counters...ONE device to replace MANY,,,,awesome concept. They take up less space and can do the job of MANY devices.

Reliability? compared to what? PLC's are solid state devices,,no electromechanical devices can compete in this aspect.

Relays have a life expectancy dependent on how many times they are opened and closed, plcs do not have that. The timers, counters etc ALL software and cannot mechanically fail.

There are situations where an I/O with a plc can fail but the relationship to a relay etc is minimal.

If you ever had to troubleshoot a double cabinet ( each 6x8 ) that was all relay logic and analog devices then you would understand the difference.

As a project..if possible...use a small plc (10 I/O or so) and create the relay logic system to replace it. I am not as inept as the guys here when it comes to programming devices ( I have to bulldog my way) BUT I do understand WHY they are more efficient.

To make it simple a PLC can replace a LARGE cabinet of relays and at same timne be more reliablw/efficient.
 
To the Membership...

Believe it or not, some of us are as tired of repeating the same answers as some of us get tired hearing the same answers.

Wouldn't it be nice if we had a way to refer the new poster to "Answer #15" before he posts his question? Then, when he's read all of that, he can then post a question if he still has one.

Ken's response in an earlier thread did not go un-noticed.

What I'm suggesting is to come up with a way to organize the earlier threads in such a way that they can be more readily referenced and cross-referenced. Just so we don't have to re-invent the wheel, re-light the flame torches, and possibly plagiarize one's self yet again.

You all know that Search Engines are stuffy about what they will return. They tend not to know what it is one is really looking for.

I just think it might be better to put our efforts into newer questions than to continually rehash the old flame-bait questions.

This could be something we put to Phil as a suggestion, but then, maybe he's already doing plenty simply by maintaining this site.

Maybe there is a way they we could do something. Maybe the first one (of the regulars) to answer the post can classify it according to some scheme. He would then enter a code number or word into the title. Then the thread(s) would be much easier to find.

Well... something like that.

So...????
 
Great idea Terry! Hope you have better luck than I did with my multiple categories idea... :rolleyes:

I'm not sure what's possible with VBulletin, but an easily referenced database of previously answered questions would be a big help. Each time someone (usually YOU Terry) comes up eith a good answer to a common question, this answer could get stuffed into an archive with an easy cross-reference to it.

Now the problem is... Who decides what is a good answer... :mad:

And who wants to voluteer to manage it?... ;)

beerchug

-Eric
 
Q

Perhaps the way to handle it is to have a real FAQ section. Then all we need to do is have the FAQ quesiton ("How do I program a traffic light"), and instead of trying ave the "right" answer, provide links to existing posts wher the answer is discussed.

That way, if a topic for somne reason does get revisited (directly or through tangents), the topic will just get a new link.

Probably the easiest way to handle it in the existing forum is to add a FAQ FORUM, which would not be able to be added to by anyone but the moderators.

Then perhaps Phil might give some of us Forum-specific moderator rights. I'd certainly be willing to do some of it, and I think I saw Terry's hand being raised as a volenteer.

The first question would be - what are the Questions?

If this works, it might be expanded to include "Tips & Tricks & Programming Techniques". May of us print out certain threads that contain gems of code snippets or other techniques. It wouldn't surprise me i we all wind up printing the same few pages. We print them so we can find them again. Wouldn't it be nice to have a reference library where those could be gathered? I'm thinking along the lines of the "Free Software" thread that Steve started last Christmas.

Phil - what's your take on all this?
 
Great idea, Terry. We will still get the traffic light questions, but Phil (it's his site after all) can put the answers that seem best (or at least the most humorous) in a single link that we can then post in our answers. That way, if we ever think of something new to say about that old chestnut, we can still have some fun or convey some information, but not have to repeat ourselves!
 

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