GNP

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About GNP

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  • Country Canada
  1. pump speed pid control

    I was hoping someone here might have some input on what I’m trying to figure out as I am a bit stumped at the moment.   I am trying to control a pump (motor) speed based on the suction pressure at the inlet of a pump. I have a 4-20ma compound pressure transducer on the suction side of the pump connected to a CJ2M analog input and a 4-20ma output from the PLC to the pump VFD. I am using the PIDAT instruction with the transducer as the input  and the 4-20 to the VFD as the output for pump speed. I have set the SV as the maximum suction pressure to maintain. I have to finish testing and tuning the PID but I think I have this part basically figured out.   My issue is that in addition to the above I have another 4-20ma input from a separate control system that “tells” the pump to run at a certain speed, which will vary regularly. At times this control system will ask the pump to run at too high a speed causing too great a suction pressure (NPSHR > NPSHA) which in turn causes cavitation which will damage the pump and destroy the product we are pumping. The temperature (viscosity) of the products and liquid elevation vary significantly during the pumping process so we are not able to just pick a maximum speed to run.   So what I am struggling with is how to integrate the two control systems such that the pump will always attempt to run at the requested speed but Only if it does not exceed the SV suction pressure. If the suction pressure becomes to great the pump should slow down via the PID which in turn reduces the suction pressure. Basically run as close as possible to the requested speed but do not exceed the maximum suction pressure.   I had thought at one point to keep the two speed control methods separate so the the other control system would be the primary control and compare the value from the transducer to the SV ( maximum suction pressure allowed) and turn on the PID control on when the suction pressure dictated but i think this will only cause oscillating as the PID takes over corrects the the speed which will then in turn revert back to the primary control which will then potentially increase the pump speed (and suction pressure) an so on and so on.   Any help on this one would be greatly appreciated.
  2. Saving text in PLC memory

    I now have this working. Under display value (text)  I had put some characters there as place holders thinking this would change to what I input when I edited the text in runtime. My mistake, all I needed to do was put a single pound symbol. The display value text simply replaces anything from the pound symbol on with the information contained in the text point that is used.  
  3. Saving text in PLC memory

    Thank Garry but unfortunately not. choices are: Unicode Signed char binary Unsigned char binary Raw char binary  
  4. Hi, I am trying to enter a text value in CX-Supervisor and save in PLC memory. Basically liquid storage tanks that we want to put a product name on, which will change from time to time. I need to keep it in the PLC as there are two CX-Supervisor runtimes accessing the information via the internet. So I want any changes made on one to be reflected on both. When ever I try to make the change in the runtime the keyboard comes up, I enter my new text, press enter and the default remains as it was? I have tried with it only being setup as edit point value (text) and also as display point value (text) and edit point value (text) but the results are the same. What am I missing??? I have attached a PDF that has screen shots of my complete setup.   Any input would be greatly appreciated!   screen shots.pdf
  5. NC contact

    Thank you.....Again. G  
  6. NC contact

    What does a contact with a double line on the left side mean? and what have I done to get it there? I deleted the symbol, shut down restarted etc etc but every time I reinsert the contact with this address it comes up like this? Obviously operator error......    
  7. NB HMI update rate

    Innoaloe, Thank you for your input. I have everything working as expected now. I had originally imported a large tag file with the intent of using what I wanted through development and then just deleting anything unused. Your comments got me to thinking that possibly the entire tag list was being polled even though only a few items where on display. I deleted everything and just started again with no tag list and everything is now good. I am not sure if my theory is correct or if it was something else I did, or didn't do, but everything is now okay, Thanks again G  
  8. NB HMI update rate

    Any thoughts out there?  
  9. Forgive me if I have missed something obvious in the manual...... How do I specify an update rate for a float value that I display on the HMI from a CJ2M-CPU32 connected via Ethernet. The memory address is referenced directly, D7501, as opposed to a tag. I have it setup as a number display property and it works just fine. It is just the time that it takes from the change in the PLC to be reflected on the HMI, 120 seconds minimum? Bit values seem to be immediate. I see on the setup, basic property, it is defaulted at normal but it is greyed out so I can't select high or something else? if that is where I am supposed set it? Any input would be appreciated. G.  
  10. cj2m expansion rack issues

    So..... Won the lottery and found a II101 and a IC101 on the shelf here in Edmonton. No cable, but what are the odds. Swapped both boards, don't have time to sort out which is the issue   Put things back together and test... No go! ? On the phone with Omron tech support tried all the things we have already said plus a couple. Decided to strip both racks and install one board at a time and see what happens. To shorten the story. The fourth AD08-v1 in the main rack when not in the system the expansion rack shows up as expected..... What the *@&**%^* ? Removed  and replaced three times to prove the theory. Story checked out. Put the whole system back together as it is supposed to be be, less the AD board, power up the system, all is good. For the heck of it put the "offending board" back in the system physically and unit number where it was, just to see what happens.... It is now working? Been about 8 hours now with multiple restarts hasn't skipped a beat   Not feeling warm an fuzzy about this as I don't have a definitive  answer to the issues we saw, will replace the AD card even those van it is currently working.     
  11. cj2m expansion rack issues

    I think your right! I will post the outcome once I know it. By the time the rodeo happens I will probably be back home in the east........ maybe.   Thanks for the help    
  12. cj2m expansion rack issues

    yes, yes and yes. Thanks for the quick responses. I have read many of your posts. Actually I think I am using your Function block for scaling analog inputs to real values in this program for scaling 37 storage tank ultrasonic sensors into a volume for use in supervisor.    
  13. cj2m expansion rack issues

    did all the physical stuff.... in detail. I was hoping that there was some setup I was missing. If that is not the case I'm thinking I may have some bad hardware. Which I was, am, struggling with. I have been playing on and off playing with Omron gear for the last 20 years and I have only ever changed two boards. One of which I inadvertently blew up :)
  14. cj2m expansion rack issues

    Sorry my typo.  that is how it is.  Only "out" on the main rack "in and out" on the expansion rack.  Other than physically connecting it is there a setting required I am missing?  
  15. Hello, I am trying to get a system going, for it's first time, that has an expansion rack.  Hardware configuration is: MAIN RACK: PS = PA205R CPU = CJ2M-CPU31 CJ1W-II101 CRM21 7 X AD08-V1 1 X DA08-V1   EXPANISION RACK: PS = PA205R CJ1W-IC101 IA111 ID231 ID231 ID211 OD232 main rack seems to be working okay Expansion rack I/O led's on the boards appear to be indicating the I/O status correctly Both power supplies appear to be okay, displaying "FUL" The connecting cable is a CS1W-CN223 I have verified the II and IC boards are connected properly and the cable is properly seated. out to the in. Even tried reversing which end is plugged into II101 and IC101. Using automatic allocation but when we transfer the I/O table to CX Programmer the main rack comes back as expected but the expansion comes back as empty slots for all. I tried creating an I?O table and sending it to the PLC but that only created a fatal error because the CPU does not see an expansion rack..... I think. Am I being brain dead and missing something obvious that I need to do? From what I have read this part should be somewhat "plug and play" Any thoughts would be greatly appreciated as I am on site doing a start-up and short of replacing boards and cables, which I don't have, I'm stuck and Omron Tech support doesn't open until tomorrow. Thanks in advance :)