newcomer to site and plc in general

Hi,
I have recently started PLC training at my place of employment.
I was basically given a crash course in logic relay and a RSLogix trainer CD. I was told to study the CD, which I did. Now I am faced with training scenarios and one particular involves move instuctions.
I get the general concept. But I am still confused. Say for instance........Move source: N7:10 1<
Destination: T4:2.Pre 5<.
what i don't understand is the signifigance of the source, where does the source come from besides the integer files.is the source from an outside source or what.
how does the source affect the timer that it is moved to.
the only answer i got from work is that we use them to move the speed from one motor to another motor.....and that is all i was told.
can some please shed some light on these move instructions beyond the typical textbook explainations.

Here's a quick answer... Others may get into more detail...

Realize that N7:10 is simple a location that can store a value (i.e. a number). When you MOV N7:10 to T4:2.PRE, you are simple moving whatever value that is currently in N7:10 to the Preset of timer T4:2.

Let's say N7:10 contains the value "500". If you MOV that to T4:2.PRE, timer T4:2 will now use "500" as it's preset the next time it's enabled.

Get it?

beerchug

-Eric

In this integer file, are placed values.

They can be placed by you, with the keyboard, as you program the ladders
Tehy can be placed there by an operator interface... the operator enters the values
They could be the result of a mathematical calculation
They could be the result of another ladder file or function block...

They are values to be used by ... something else...

So here you have the preset time of a Timer... which comes from this N file...

It could be a recipe.
It could be a fix value that you want to keep track of...

When you move the integer value to this timer pre. you Set the preset value of the timer... just has if you would have writen this value directly in the timer pre. box.

Why would you use an N file for timer preset value?

You tell me.

RMAAAAANN...

The SOURCE is a “Mail Box”. The Mail Box has something in it; even if that “something” is nothing.

“MOVE” says “Get what’s in the Mail Box and “Move” it to ... (such-and-such place)”.

More accurately, “Move” says, “take a picture” of the mail in the mailbox.

So, if you’re gonna “move” your mail from the “mailbox” to your kitchen table, you would go to the mailbox, take a picture of your mail and then bring the picture into your house (leaving the actual mail behind) and set it on the kitchen table. You then “read” your new mail (Gimme a break! It’s just a damned metaphor! But it does kinda cut down on the Anthrax-worry, doesn’t it?).

So, how did that mail get in the mailbox in the first place? Somebody “Moves” it there.

That “somebody” might be you, as in “Hey, Joe! Would you mind if I “MOVE” your mail into my mailbox? Thank you very much!”

Or, that “Move” might occur outside of your control; as in when the Mailman finally arrives and “Delivers” your mail. You didn’t request it... it’s just there... or, at least, “something” is there, even if that “something” is nothing!

If you have a “regular” mailman, you’ll always have new mail when you look in the box, even if the “new mail” is no mail. When the mailman comes he always gets rid of the “old mail” even if he doesn’t have “new” mail to deliver – in that case, he has delivered “no-mail”.

If he ain’t so “regular”, then you might see the same mail for a while; but you still keep taking those pictures and bringing them into the house and “reading” them!

Let’s say that your “mail” is the TV-Guide. You open the TV-Guide to your favorite show, look at the time and then see that you have 2-hours and 45-minutes to go until your show is on. You Preset your timer for 2-hours and 45-minutes. (Is this bogus? Or, what?)

The mailbox, “SOURCE”, is actually a Memory Location. Your kitchen table is another Memory Location, the “Destination”. Or, in the case of the TV-Guide, the actual "destination" was your Timer.

Either “you” (as the PLC) performs the “move” to the “SOURCE” location, or some "external device" “Delivers” to the “SOURCE” location.

An external device can be damned near anything... input from an analog card, a thumbwheel,...etc, etc.

Originally posted by ME!
Others may get into more detail...

Click to expand...

Or, as always with Terry's explanations, give an excellent analogy!...

beerchug

-Eric

Damn it! I knew it was an Analogy... just after I went to bed!

So Terry, using your analogy (which BTW was very good) The actual instruction MOV (move) is confusing in itself. Because MOVE means - 'take from here and place there' which implies that nothing is left where it was.

It would probably be better called COPY, dont ya think.

thanks for the replies

Thanks guys for the replies....it makes alot more since now that I got it explained simply and in analogy (thanks for the mental pictures,Terry).
And as far as Pierre's Question..."why use a N file for a timer preset....that I don't know the example I gave came straight off one of my training scenario programs(it was home made by the head electrical engineer) that i guess acquaints you with TON's. basically getting a series of outputs to fire in a certian order and delay and be able to change the presets by toggling certian inputs thats about all i know. i havent had much time to get into it yet.....after that i have to accomplish the same exact thing with only TOF's...then on to a product pusher scenario(that I actually hard wired correctly using logic relay, so I am eager to see the differences and similarities alike, and then to 1:2 lane diverter gate scenarios, then incorporating VFD's and using inputs to control motor speeds.
So as you can see, I am still kind of green and I have some bit of learning to do, so I hope you don't mind me calling on some help from you guys in the future.