Switch detection issue

Hey all,

I am working on a Logixpro bottle line issue. However, I am trying to remove the bottle line as a whole at the moment and just get down some basic process.

On this conveyor is a "box detecting switch". I think it's a limit switch, but it doesn't really matter. The scenario I am trying to understand is this process:

Switch is on, there is a box here. Switch is off, no box.
So, I want to turn on the conveyor and move from box edge to box edge.
However, 50% of the time the switch is on because there is a box here (while it moves through)

I am struggling with the process/logic to turn on the conveyor (just hit the start button) and move to the next box beginning.

What instructions should I use to accomplish this? I've tried some timers to ignore the switch, I've tried various bit operations, and it seems I cannot get the conditions correct.

Thanks for the pointers.

Hi,

Look for a one shot rising.

OSR or ONS.

Hit the F1 key for the help menu, and you will find one of these instructions will help you.

Cheers

Mark

What instructions should I use to accomplish this? I've tried some timers to ignore the switch, I've tried various bit operations, and it seems I cannot get the conditions correct.

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The problem with using timers (and most other instructions that you would think should work) in the LogixPro Bottle Line simulation is that the entire project is timed by the encoder timing. If you use timers, then you might (after many hours of trial-and error) get the program to run at one exact "speed" (scan rate setting from 0 to 100%), but then if you nudge the scan rate even a hair, it will never run again because you cannot ever set that exact speed again (in this project). When you change the scan rate, it does not change the speed of your timers, but it does change the encoder speed and thus the bottle speed.

The LS10 Box Position sensor can be used to keep the Box Conveyor Motor O:2/1 running, but NOT to start the scrap conveyor. To start the scrap conveyor, you must use logic to anticipate WHEN the box will be full, based on the number of Large Broke and Small Broke bottles that have gone or will go into the scrap box. Count each type and multiply the Small by 10 and the large by 15, then add the results and save in N7:2. When N7:2 is greater than 145 and the next broken bottle is large, then advance to the next empty box (because there is not room in the box for another large bottle but a small bottle will fit). If N7:2 is already >= 150, then advance to the next box (because either Small or Large will overfill the box to greater than 155). On the first PLC scan (S:1/15 is ON), latch on B3:0/1 for 4 encoder pulses to move the conveyor until a new empty box is in position.

What you need to do is tie your bottle scrap conveyor to the bit-shift speed, so that it will work at any scan-rate setting. Here is how I did that using bits that go on 3 encoder bottle positions BEFORE (3B4) the scrap gate, up to 1 position before (1B4). See attached picture of Rung 6 (for LogixPro Exercise 5 using three BSL's) for the scrap converyor motor control.

Thanks for the comments! I was using a OSR, but obviously wrong. I looked at it again and got this working with OSR. I considered moving the box out of the way at first scan, because you do not know the contents. But, it's not in the instructions as a requirements (that I saw), and I have 1 week to complete exercises 1-5. Functionality first, features second!

I have 1 week to complete exercises 1-5.

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Good luck with that! Be sure to add comments to instruction and to each rung. That will save time and prevent you from continually having to figure out what each bit does.

I considered moving the box out of the way at first scan, because you do not know the contents. But, it's not in the instructions as a requirements (that I saw),...

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No, it is not a STATED requirement, but is an imputed requirement if you want to prevent broken glass on the floor. You will see as you run the program many times, if you do not always start with a new box, that the old box is sitting there partially filled but your program does not know how much is in the box from the previous run! There is no penalty for ejecting a partially filled box, but if your program overfills a box, the penalty will be spilled broken glass on the floor. Your instructor will count that as a program failure and someone may get a cut foot.

Some tips for the LogixPro Bottle Line, Exercises 1 to 5:

1. Run main conveyor only until unbroken bottle arrives at filling station.

2. Turn on Scrap Conveyor for 4 encoder pulses to move new box into positon on first PLC scan (S:1/15 ON).

3. Keep Divert Conveyor ON for 4 seconds after STOP pushbutton is pressed. Otherwise the full bottles on the vertical conveyor will fall and break.

4. Anticipate broken bottles, so that grinder can be started 4 bottle spaces before broken bottle arrives, and run until two spaces after grinder.

5. Large bottles = 1.5X Small. Scrap box can hold 15.5 units. Use counters for small and large broken bottles, then scale and add to get the total volume of broken glass. Reset broken bottle counters when full box leaves scrap grinder. It is not always possible to fill the box 100% full (if the next broken is a large bottle).

6. Timers can be used for the Fill Extend time and the Charge Delay time. If you do use timers, the maximum speed (without breaking bottles) will be about a 75% scan rate.