The disagreement!

BDKuhns

Member
BDKuhns
Join Date
Sep 2003
Location
KC, MO
Posts
78
OK, you should have seen it.

I said YES IT DOES. My brother said NO IT DOES’NT.

I hit him in the nose. He poked me in the eye.

IT WAS A REAL KNOCK-DOWN-DRAGOUT! bonkhead

Well….. :rolleyes: not really. At our age, we’ve learned to get along (even if we don’t agree).

The question is as follows. Will the diagram below work, and
will it serve any useful purpose?



|        I:3/0             B3:0/1            B3:0/0

|------| |----------|-----|/|----------------(  )

|                   |

|                   |                        B3:0/1

|                   |------------------------(   )


I used it in my last class project after reading that you
can’t bracket around a (OSR) on a SLC-500.
It worked just fine for what I needed.

What do you all think?
barry.
 
its a reference to Terry Woods...do a search on the site using that name...very informative.

Note...what u have done is NOT the same as a ONE SHOT

bottom line is...work with plc scan
 
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So what you want is when I:3/0 is "on", B3:0/0 is on for 1 scan and B3:0/1 is on until the input goes off? Is that what yer lookin for? That IS a one shot for B3:0/0 when I:3/0 is true, is that what the question is? :confused:
 
BDKuhns said:
I guess that was befor my time. Is there something I should know?
Click to expand...

Ron is referring to THIS THREAD by Terry, which Ron recently brought back into the limelight... :D

On topic with this thread's title, I disagree with you Ron... :p

What Barry has IS a one-shot. This is one way of doing it when you don't have one-shot instructions in a particular PLC.

Think about how it operates. When I:3/0 turns ON, B3:0/1 is OFF, causing B3:0/0 to turn ON. Before leaving this rung, B3:1/1 gets turned ON. OK, now both 'output' bits are ON.

On the next scan, when I:3.0/0 turns ON, B3:0/1 is already ON, so B3:0/0 turns OFF. Therefore, B3:0/0 is ON for 1-scan, or as Terry says "from the point of creation to the point of creation".

You can think of Barry's B3:0/1 bit like Terry's 'WAS' bit. It might help to remember that internal bits remain in their last state unless acted upon by an instruction. Before I get attacked, I'm not talking about through a power cycle, mode change, etc... :cool:

beerchug

-Eric
 
BK, a one shot is a ONE SCAN SHOT.

NOTE I am not an expert on this, each plc has a different approach to certain things.

What u have u done is FORCE the plc to LOOK to see if certain inputs are ON (TRUE) and act accordingly to certain outputs.

NOTE: There is nothing WRONG with this approach BUT it is NOT a ONE SHOT.

A ONE SHOT works for ONE scan, what you have done MAY work with more than ONE scan.

I wish I was good at explaining this as others.
 
Eric I disagree...depending on input conditions it MAY or MAY not WORK ONE SCAN.

A one shot, in AB terms, ONS (one shot)or OSR (one shot rising) should only work for ONE scan.

What was done MAY work for one scan...sometimes..it would depend on how long the condition was enabled...seems to me.

Terry has me spell bound in some cases, the aforementioned link is one. I still dont understand the WAS bit. I trust Terry tho, if he says something its reachable. Noone is infallible tho, you must LEARN what you can and use info here to assist.

Eric I agree that what was done is a "kinda" one shot...use that configuration with ONE PB to turn off and on an output..see how far u get. GEEZ u know this!

It all boils down to working with plc scan and ladder placement in the program to do what is needed when needed.

Wish I was as good as you and as prolific as Terry.

AS I SAID.....IT WILL WORK
 
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I would have to say that yes, that is a homemade ONS (One shot). At least it would work on an Allen Bradley, but then why not use an ONS or OSR and save a few branch words. I'm not clear on why you would want to branch around the one shot.

When the XIC goes true Bit 0 only sees it for one scan because bit 1 keeps it that way until the input is cycled again.
 
rsdoran said:
Eric I disagree...depending on input conditions it MAY or MAY not WORK ONE SCAN.
Click to expand...

Ron, I disagree with your disagreement, but mainly because this is "The Disagreement" thread!... :p

beerchug

-Eric
 
Eric
Ron, I disagree with your disagreement, but mainly because this is "The Disagreement" thread
Click to expand...

It would be nice if you explain this, I just bulldog my way thru to what I think is right.
 
All I can say is "Barry started it"... :mad:

beerchug

-Eric

By the way Ron, these are not your normal hours. Did you 'stay up late', or 'get up early'?... zzzzz
 
how astute of you to notice

Please dont take offense, yes this is NOT my regular hours from the past

Looks like I may be woking days ane nites...anyone need some to dignose a problem in the Alabama.

I cqan do many things
 
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Time for bed Ron...

rsdoran said:
Looks like I may be woking days ane nites...anyone need some to dignose a problem in the Alabama.

I cqan do many things
Click to expand...

"in the Alabama" what? Someone has been up WAAAAY too long... :D

beerchug

-Eric
 
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