MattS

I just tried the link and access was denied so I guess I don't have the Tech Connect authority. We should have received a code but this was sent to someone about 6 months ago who now works in Australia and he hasn't supplied it so I'm stuck on the outside. However, emailing works, after a fashion. Rockwell said I didn't need a code, though it appears it may have saved both them and myself some time. A bit of persistence in the right area and I could have solved it myself. I figured there had to be a place where I could turn on and off the various subterranean devices that grease the wheels automatically.

Finally I have an answer from Rockwell (not a technote). The solution to the conflict on COM1 is to access the services, through the control Panel\Administrative tools\services, or Start, Run, services.msc. Then turn of RSLinx Classic or RSLinx Enterprise, depending which one you need to use etc.

Rockwell has supplied the answer to the Token problem. This is to do with a timeout setting in the security branch of the System folder (technote 32566).

Thank you again. The technote is no longer available (I was looking on this site), which is curious, but I have been able to make some slow progress anyway. I obtained the correct cable, which is labelled PV to PLC, and followed the instructions in the previous download. There is still an issue with a conflict on COM1 which would be OK except that, once the FT View Studio program on the PC has used it to access the PLC, for making shortcuts and linking to variable addresses, it is next to impossible to restore it and go online. Even turning off the computer does not work but something does, sometimes. I'm not sure what it is. It appears random but a pattern may yet emerge. I have emailed Rockwell about this but so far no reply, so perhaps this is not common and there is a problem with my computer. For those that are curious, I have a Microlgix 1200 PLC linked to COM1 on my PC and a PanelView Plus 600 linked via ethernet to my PC. The PLC and PV link via a different serial cable, requiring frequent unplugging at the PLC, since it has only one socket. I am using RSLogix and Factory Talk View Studio. Another issue is that the Token expires on the FT View Studio and the program freezes, despite having correct activation etc. Hopefully these are both teething problems and can be resolved shortly. Answers may even lie somewhere in the mountains of Rockwell information so perhaps I will put on my tramping boots, get a big water bottle and start exploring.

Thanks Mickey, that looks good and I will try it out. The article also mentioned a technote and I can't work out how to access this. Perhaps a search on words in the title....

Hi there, Thanks for the interest. The RSLinx shortcuts shown on the PV appear correct, ie the ethernet link to the PC and the PLC on a serial-DF1. I simply aim to connect the PV to the PLC via an RS232 cable. I have been using one labelled Allen Bradley PC to PLC, (nine pin D connector at the PV and round 8 pin at the PLC) but now someone has mentioned that this may not be correct and indeed I find the correct one is a 2711 NC21. So I may make progress when I have one, which should be shortly. Here's hoping. I still have the problem of going online with the PanelView connected, since there is only one socket on the PLC, and when I use the PLC Panelview simulation it conflicts with the RSLogix at COM, and difficult to switch between the two.

Hello there, Now I am trying to Link a Panelview Plus 600 device with a Micrlogix 1200 via the RS232 serial ports. Both devices have programs working on them, ie the program that triggers the PLC from the computer is on the PVPlus. Apparently there are some settings to make this work. Does anyone know what they are?

Thank you for your responses. I like this area and will try to gain some experience. Just now I am occupied with a different project but I hope to return in a few weeks. <<One thing you can do with the PIDE is to place only the PIDE instruction with a valid tagname on a function block sheet in a periodic task.>> Thanks for that idea. I like it and I will try it, but I am on a different project for a few weeks so I may have some more queries after that. Whew! There's quite a bit of info there. Some of it I have seen before but it is very helpful to get relevant points adressed. Although I have fiddled with these things before I did not set them up so it is hard to get a feel for it without doing simulations or actual testing. At that point I will have a clearer picture but that may not be for a few weeks. I will report back on progress, assuming I am still involved at that stage of the project, which is what I am hoping.

Hi Paul, What we are trying to do is drive the pump using two different measurements, ie pressure or speed. Auto/manual may be superficial, as you suggest. With pressure, the desired value is loaded into the setpoint var, while the actual value is fed into the ProcessVr, as I understand it, since a variety of factors affect the speed/pressure relationship. But when a speed setpoint is required then this can be loaded into the .SO value directly and then .SWM is turned on, if I understand you right. Then to stop the .SO could be changed to zero, although resetting EnableIn is the correct method, I expect. Hmmm, maybe not. Outputs would not be updated! I would initially clock the PID loop at around 250ms, ie 4 Hz. Might be a bit slow. I expect that using an integral element could require a regular time delay so I will look at the CLX function. I remember using PIV loops when we first tried AC motors instead of DC and it did help a lot. The PIDE has been recommended here so I will give it a look. There are a lot of parameters and the Autotune is greyed out on the office version. Correction: giving it an autotune tag name allowed some access. Thanks for your help. It may be a while before we need to run the program but it is good to know there is some expertise available. If it is left to me then there may be some more questions coming.

Ron, Looking over the Instruction Help it looks a bit clearer than the first time. I expect it is fairly simple after the first few times. There are some obscure settings which may need some study, but not too many. Configuring the drives may or may not be complicated, depending on how suitable are the default settings, but I will come to that down the track and read the instructions. It should be possible to set up a basic simulation.....hmmm. MattS OK, just got the last post. That's good stuff. Thank you. MattS

Ron, Thank you for the comments. I believe we have a full development toolkit but I have not found the files you mentioned, though I will keep looking. I will leave the structured text out for now, though it should be part of my repertoire and it should be available somewhere. Perhaps it is easier than I think. If I label the PID, fill in the Process Variable with the pressure setpoint and the Tieback with the manual speed setpoint (zero at first) and feed the Control Var to the drive, with correct scaling, then something should happen. It may be that the gains etc are configured on the drive. I will start with a small one, not the 250 kW ones, and perhaps assume that the default settings are OK. By then I'm sure someone will know what to do. What is a bit frustrating is the search for documentation on the topic, which must be there somewhere, just buried amongst a lot of other stuff. The AB sample code facility requires a title, for example, but I only have a topic. Before we used Allen Bradley I had occasion to set A, B and K gains when we developed robotic drive systems. I believe these are related to the amount of feedback for the P and I and D loops. Pumps are a lot less critical than motion control in response times, but there may be some issues around switching from Auto to Manual etc. I have found bits and pieces about this but no coherent discussion or tutorial or, as yet, example, but I know it must be there somewhere. Cheers, MattS

Hello folks, I am trying to access the AB online Knowledge Base, chasing up TechConnect numbers etc and assuming that our toolkit is eligible for this, but I am also interested to know if there are examples of code elsewhere using PID loops to regulate pump drives and flow and level control valves with RSLogix 5000. Pumps are using pressure setpoints in Auto and speed setpoints in Manual. I noticed a recommendation to use PIDEs instead of PIDs so examples of these may be useful. I have used PIDs before to control linear axes (in SoftLogix) but I can't seem to make head nor tail of the current format. What is a tieback? Before AB we used A, B and K gains. Does anything equate to these? From browsing here I have found one tip, ie to put the PID block on its own rung.