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Display internal PID calculation values on HMI

Created by: Jsteve at: 5/25/2012 5:50 PM (6 Replies)

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5/25/2012 5:50 PM	Rate (0)
Jsteve Posts: 4 Rating: (0)	HI, I am working in an educational enviromnent and have constructed a demonstration system to teach how the Siemens S71214C and HPI can be used to explain how PID control works. I am using the TIA development system. I have linked the PV, Setpoint, and PID gain, integral time, derivative time, and output value to the HMI successfully. I woudl also like to display other parameters such as the calcuated integrator value PIDCompact_DB.sPid_Cmpt.r_Ctrl_IOutv to sho what is happening. This tag is availabe to be seen on the watch list but is not accepted as a legitamate tap name. Is there a way to do this or possibly a direct from the data block address and offset to the parameter. The PID block was assigned as DB1 but I do know its address.
Jsteve Posts: 4 Rating: (0)
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5/29/2012 10:46 AM	Rate (0)
Tweety Posts: 3037 Rating: (192)	Hello, Which Version of WinCC V11 do you use? Advanced or Professional? Do you use WinCC V11 SP2? Which data type has the tag "PIDCompact_DB.sPid_Cmpt.r_Ctrl_IOutv"? Which object do you want to display this tag? Can you post screenshots about this. Tweety
Tweety Posts: 3037 Rating: (192)
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5/30/2012 2:13 PM	Rate (0)
Jsteve Posts: 4 Rating: (0)	I am using TIA Portal WinCC Basic V10.5 SP2 The sPid_Cmpt is data type Struct. r_Ctrl_IOutv is type Real. The tag sPid_Cmpt .r_Ctrl_IOutv can be viewed on the watch screen under Technological Objects, PID_Compact_DB[DB1], right click, Open in editor, scroll down to sPid_Cmpt, expand and scroll down to r_Ctrl_IOutv . Unable to capture and send screens at this time. The development system is not connected to internet. I want to view this value on the HMI as an Output IOdisplay field formattes as s999. Under Process PLC tag, selecting Technological Objects, PID_Compact_DB[DB1], sPid_Cmpt, r_Ctrl_IOutv is not shofwn in the list of available tags. Thanks, Jsteve
Jsteve Posts: 4 Rating: (0)
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5/31/2012 5:45 PM	Rate (0)
FreakOnALeash Posts: 267 Rating: (24)	Hello, sPid_Cmpt.r_Ctrl_IOutv is an internal variable. You can't call it on STEP 7 (MOVE) or HMI side. Why do you need it?
FreakOnALeash Posts: 267 Rating: (24)
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6/1/2012 1:45 PM	Rate (0)
Jsteve Posts: 4 Rating: (0)	Thanks, It is not a necessity but it would be helpful in explaining to students what is happening in the internals of the PID algorithm. We could just look at the watch list though. However, this value seems like it is part of the PID data block and as such has an offset of so many bytes into the table. Knowing the address of the data block and then its offset it should be possible to access the vaue. 1) Is there a way to find the starting address of the data block? 2) Is there a listing of the PID data block structure to find the offset into any particular tag? Jsteve
Jsteve Posts: 4 Rating: (0)
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6/4/2012 11:16 AM	Rate (0)
FreakOnALeash Posts: 267 Rating: (24)	Hello, "1) Is there a way to find the starting address of the data block?" Sorry, but there is no possibility to select the instance DB of the PID_Comapctas not "Symbolic access only". 2) Is there a listing of the PID data block structure to find the offset into any particular tag? You can see the structure of the instance DB by "Open in editor". But the offset (which is perhaps calculatable) is useless because you have only symbolic access to it.
FreakOnALeash Posts: 267 Rating: (24)
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6/4/2012 5:12 PM	Rate (0)
Jsteve Posts: 4 Rating: (0)	Thanks. Then I will just have to display the integrator vaue in the editor watch screen and explain it to the students. Thanks for your help. Jsteve
Jsteve Posts: 4 Rating: (0)
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