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BlurDavinci

Continuous Weighing

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Hi: I'm wondering have anybody wrote any program on continous weighing? What and how the calculation look like? Scenario: a moving conveyor (control by Inverter ) ferrying example sand or any powder where a load cell is weighing the weight continously, the belt travel distance can be measured by means of Encoder. Now If I set a weight Target say 1000 kg, how can I create the formulation to achive the set target? by Kg/meter ? if so if the weight varies from time to time then the value become dynamic? Can someone share some thought ?

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Hi, maybe the use of the OMRON CJ1W-F159 weighing unit might help in this matter. regards, MPM

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Hi I have made continous weighing system with Omron PLC. But this system is with a bin placed on 3 loadcell. The feeding is with a screwfeeder. Screwspeed controlled by VFD. I take a sample from the weighing transmitter every 200 msec. Make som calculation and transfere the result to a PID. Not Omron PID. The Omron PID can't do Aut./man bumpless. Try to make small diagram and post it. Banker

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That is not quite true, it all depends on how you setup your code! Whilst the Omron is not like other platforms, that make things so much easier, there is ways to achieve the same things.

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A lot of thoughts lets see if I can lay this out in sensible order. Assumptions : Weighing Belt from Head to Tail Roller centers is 1m. Weighing Belt is 0.1 m wide. Square Area distribution is uniform, but depth varies with time. Density of the Powder is uniform at 800 kg / m3 {an average sugar} Initial Thoughts: Belt area is 0.1 m sq and if depth is 0.1 m then you have 0.01 m3 or 8 kg on the belt. If belt speed is 1 m / sec then you will get 8 kg per second. Assuming you sample 10 times per second you add 1/10 of the belt weight each sample. Final thoughts; Use two speeds Major weigh and Minor or bump weigh. When you get close to target switch speeds and change fractions added to sum. You'll want to have a "freefall" or fudge factor in your calculation for the amount that drops during decel or stop.

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It is rough and my first program for Omron in 8 years and the first using CXProgrammer. Have a look and see. CheckWeigh1.cxp

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following this idea, you could just use a K3HB (eventually with devicenet) to get the value into the plc (high sample speed), and do a simple PID (I think even a P system with deadband would do it) You could even eliminate the PLC in the control loop and just send out the set value by achieving the control loop in the inverter (for instance V1000/CIMR-E7/CIMR-F7 ) I did this for pressure and for flow control. Beegee

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To MrPLC Admin,

I just want to know, if it is only me or other members are also unable to see / download the file attachments.  I have tried logging in / out, but still I could not open any file attachments in members post.

Thank you.

Leo

 

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A while back, the site went through an upgrade.  After that point, the attachments were not attached properly.  It is easy to repair, but has to be done on a case by case basis.  If you report it to a moderator, it can be restored.  I will restore the file in this thread for you.

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Thanks Michael.  I was able to download the file.

Leo

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