Staging - Demand Feeder

BBarnhart1

Member
Join Date
Jul 2018
Location
Ohio
Posts
7
I need help with what most of you find probably simple, but it has me perplexed, I'm very, very new at this.... I have the basics down but I'm confused about how to do this...

1. Output
2. Two Inputs


Input #1 sends signal and says RUN (demanding)
Input #2 sends signal and says STOP (staging)
Input #1 sends signal and says RUN (however, it now OVERRIDES, Input #2 LONG ENOUGH that it clears itself) and the very next piece of paper coming down the line is STOPPED by Input #2.

Input #1 sends a signal when it is triggered, wanting a piece of paper
Input #2 sends a signal when it SEES a piece of paper under its eye

both Inputs are Photoelectric eyes.

I ALWAYS need the paper to STOP at Input #2, getting it STAGED and ready to enter the machine. As long as that photoeye is reading the paper, it is sending a 24v signal, which in essence has OPENED the contact on the PLC to STOP the motor. BUT... when Input #2 says, "I'm ready for it, send it NOW, the PLC needs to IGNORE that Input #2 is still sending its signal, OPENING its contact. BUT..... as soon as the eye is CLEARED..... it needs to make sure to catch the very next piece of paper coming.

The Input #1 that says FEED NOW, it may only be activated for a split second, so do not assume that it will be active the same amount of time as Input #2 is still sending its signal CLOSING the contact.

Also.... understand that there may be only 1/8" piece of clearance between sheets of paper, so it could be a quick BLIP between the eye Freeing itself up and CLOSING its respective contact, and then OPENING back up again.

In case this matters, after Input #1 says FEED NOW, and it releases the paper out from under OPEN PLC contact and Input #2 the machine needs to continue to feed paper until Input #2 reads the next sheet and STOPS IT.

So we are always feeding paper until Input #2 opens up and stops the sheet with sending its 24v signal, then Input #1 says, FEED NOW, and its 24v signal may only be for a split moment, but once it says FEED, the motor needs to run until Input #2 CLEARS itself, and keeps running until Input #2 says STOP, seeing the next sheet... THUS, staging it.
 
Create a one-shot for each signal. Use the RUN one-shot to set a latch. Use the STOP one-shot to release the latch.


If you state the PLC and software someone may be able to provide a specific example.
 
Click PLC.... "I think it has 1-shot" I'm looking now, seems as though I saw it. I know it has "Set" and "Release" But I wasn't sure if after I "Released" the eye.... BUT that it was still sending its signal, if it wouldn't quickly relatch again.
 
Click PLC.... "I think it has 1-shot" I'm looking now, seems as though I saw it. I know it has "Set" and "Release" But I wasn't sure if after I "Released" the eye.... BUT that it was still sending its signal, if it wouldn't quickly relatch again.

That is an issue with the hardware you will need to work out to do it properly in my opinion. If the eye doesn't go off with every cycle it isn't in a position to reliably control the process.

You also need to correctly reset the bit after the cycle is done, so that the eye can reset the cycle.

I take back what I said before. You will want to use a sequencer for this. I don't know if the click has an instruction, but if you google it you can find lots of tutorials on how to make a sequencer with ladder logic. That way you can use your photo eye conditions to advance the sequence, and use the state in the sequence and the photo eye state to perform a desired action.
 
Last edited:
Here is what I came up with.... I make the Staging eye "One Shot" like you suggested, AND when the Demand eye temporarily latches the motor, it also RESETS the Staging Eye.

What do you think?

Final Ladder.jpg
 
Each eye DOES go off with every cycle, the issue being that when eye #2 is OPEN, it is sending a 24v signal the entire time it sees a piece of paper. So when eye #1 says FEED, it needs to "temporarily" override Eye #2, at least until the paper comes out from under it, and then resets itself and IMMEDIATELY "Opens" or STOPS the next one coming again.

So it is:
Start
Stop
Overide & Run
Stop
Overide & Run
Stop

With it catching EACH and every piece of paper at the leading edge, STOPPING it, but then feeding it at a precise moment, and then catching and stopping the very next, which must keep feeding until it hits the STOP eye.

It's a process of "staging" the sheet at Point A our of a pile feeder, so that there is alway a piece of paper just on the verge of getting, "Shot on Demand" into an unrelated machine, at the very precise moment.

it would be too unreliable to just shoot the paper from the feeder onto machine #2 right out of the feeder.... because any "lack of pulling" from the pile would delay the precise moment it needed to land "right in front" of 2 push dogs that are going around, and around and around..... on machine #2.

Don't want to land on TOP of them (crunch) (crash).... and its not good enough to land correctly "most of the time"... this method ASSURES a consistant timing between the two units.

Lastly.... IF a piece of paper does get jammed up and does not feed and it MISSES a cycle, or 2 or 3... it is not a problem... machine #2 just keeps running without issue, but at ANY POINT Paper feeder starts to "finally" pull paper, it will STOP at the staging eye, and then not get sent until machine #2 triggers it to "demand or feed" at the exact timing point.

The DEMAND Photo eye #1.... might only send a 24volt signal for a split second, which shouldn't be an issue, as it latches the coil. I just need to make sure that Eye #2 (the staging eye) doesn't stay in its current OPEN position.... which it WILL BE when the Demand eye says to SHOOT.
 
Rising Trigger

In this example: I just figured out how to use a RISING TRIGGER.

So the Contact is closed, the Eye #2 sends Signal and OPENS eye (a Rising Signal) and then we should be back into position for Photo Eye #1 to Latch and run the machine until Eye #2 on its "next go around" receives its "Rising Signal" and stops it again.

Do you like this better than the first?
or does it not really matter.

You guys have NO IDEA how much appreciate this help, been pounding my head for two days. But learned a lot of stuff inthe meantime, just not how to solve this problem... LOL

Final Ladder 2.JPG
 
I'm not sure I fully understand what is going on.
(A requirement for making this work.)

So, the Start button (input X001) starts it up and moves the paper to the staging area
where X002 stops the movement until input X003 calls for the paper to be shot into the second machine? At which point X003 also needs to restart the paper feeder to move the next sheet into position.

Maybe X003 needs to set a latch to run the feeder until X002 has cleared the eye?

Or maybe X002 needs to use a normally closed contact that says "If no paper is at the
staging point, run the conveyor till paper is at the staging point then stop". Then X003
says "spit the paper out to the next machine (and X002 will feed the next piece of paper)?"

Just thinking out loud. (Time to go home.)
Poet.
 
yES, you have it Mad... my last script is working PERFECT.... if you look at it the guys before who commented had me change it to a "1 shot" but then I got to looking at my PLC logic and they have "Rising Contact" so I used that and it works good as well.

When X003 tell it to SHOOT, it also RESETS X002 WHICH THEN waits for its next "Rising Contact"

Thanks evreryone for you help.
 

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