adccommunitymod (AutomationDirect) asked a question.
Diameter Calculation
Created Date: April 10,2015
Created By: JimG
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I have a turret that is unwinding a roll of paper. I have 2 4-20mA signals available. One is proportional to the fpm line speed (20mA = 1500fpm), the other signal is proportional to the rotational speed of the unwind. (1 pulse per revolution) I want to use a Do-More PLC to calculate a diameter reading out to a C-more panel. I'm not sure how to do the programming and math. Can someone provide me with an example of this type of measurement programming. Thanks.
Created Date: April 10,2015
Created by: Shimmy
The formula you need is to divide the known feet/min line speed by the revolutions/min of the unwind. Then divide that result by pi to get the diameter of the roll.
To find the rev/min of the unwind, set up a timer and copy the value of the timer to a register for every revolution. For example, let's say the line speed is 1000 ft/min, and the unwind takes 1.5 seconds to do a revolution.
First convert 1.5 seconds to 0.025 minutes. Now multiply 1000 ft/min * 0.025 minutes = 25 ft (the circumference of the roll). To get the diameter, divide 25 ft / pi (3.14...) = 7.96 ft in diameter.
Hopefully that will get you started.
Created Date: April 11,2015
Created by: Dean
Great solution!
Created Date: April 11,2015
Created by: bcarlton
I like it. In my mind I was creating something much more complicated. If the diameter of the core is known can this be expanded for a display of time or feet left?
Created Date: April 11,2015
Created by: Dean
This is how I would do it for the Do-More. Many thanks for the challenge, and to Shimmy for throwing on the light switch.
Created Date: April 13,2015
Created by: JimG
To all,
Thank you for the responses.
Shimmy, thank you for the start. I see it now.
Dean, if I understand the math expression correctly, the value R200 is the memory location where I would put the core diameter in inches? (I 've only played with the Do-More, this would be my first actual project with one.)
bcarlton, I probably will expand it out to show time and feet left.
Have a good day.
Created Date: April 13,2015
Created by: Dean
Yeah, that register was a remnant of me playing around a bit with some of Bernie's ideas. Not really necessary unless you are trying to figure feet remaining etc. I was picturing using this to stop the line once the diameter got below some minimum value. Having spent quite a few years in wire and cable manufacturing industry, nobody likes to re-string a production line because somebody let the payoff material run out.
Created Date: April 13,2015
Created by: Shimmy
I like it. In my mind I was creating something much more complicated. If the diameter of the core is known can this be expanded for a display of time or feet left?
Great idea. If you knew the inner diameter of the roll you could do this. I would assume the ID of his rolls is a constant. I'm going to write a program for this addition when I get a chance (it gives me a good reason to use the DoMore software).
What Dean has already written looks like it will work. I don't understand what the R200 register is though. ***Dean just explained what R200 is..nevermind.
Created Date: April 16,2015
Created by: Cap
Very nice and Tidy..
I think see an error on X0.. I think X0 needs to be Edge Triggered.
Else the Timer will not start counting again until the Sensor falls off it's mark, and you will get an error the 'Length ' of the Sensor in your calculations..
Cap
Created Date: April 16,2015
Created by: Dean
Nice catch. I thought about that, but as I said, I was imagining a line stop at some minimum diameter, and figured the little bit of slop wouldn't matter.
Created Date: April 17,2015
Created by: Cap
As most things in life.. lesions learned the hard way are remembered..
It's not that I'm smart or Nuthin..
I 've been bit by that one before.. Just trying to pass it along..
Cap