Nice diagram but I think it'd be better if you start a new thread.I'm trying to integrate the control valve into an existing system. I want to use this application to learn a few things like UDT, AOI, Aliases, PID, etc.
I need the PID to control the modulation of the valve base on a predetermine set point and the feedback from the level sensor in the bottom.
Originally posted by ELake20:
When used in a UDT I will create a SBR for these IO moves and move the alias'd tag I/O tag to the UDT like Pump[1].Running and then use the UDT in my AOI libraries.
Originally posted by robertmee:
Why? If you're mapping the io to a UDT what's to be gained by aliasing to a tag? Just map the local directly to the udt.
Sure, but you can only have one symbol assigned to I0.0. Can't create two.In S7 it was easy. In symbol table you define these and do your aliasing that way so I0.0 is Pump1_Running.
I don't see the value of creating an alias if you intend to map the I/O point into a UDT. The alias won't be generally visible anyway.
Keith
Only if you are REALLY careless and undisciplined when it comes to tag naming convention...
I look at most of this like I look at most other tools. If you like them, use them. If you don't, don't.
I do this because in my opinion it helps with diagnostics.
My aliased IO tags generally match my wire numbers, so when trying to fault-find an IO point what you see on the drawing is what you look for in the PLC. This is not as straight forward with straight UDT/AOI's tags though.
Here is a real world example from a recent project I did. I have a lifting table on a machine, and for the cylinder position sensors I have wire tags L1_LFT_RET and L1_LFT_EXT.
I alias these local IO points as follows:
diL1_LFT_RET is an alias for Local:1:I.Data.3
diL1_LFT_EXT is an alias for Local:1:I.Data.4
The AOI that these points are mapped to is the P_ValveMO object from the PlantPAx library. The AOI tags for these two inputs are L1_LFT.Inp_OpenLS and L1_LFT.Inp_ClosedLS.
Now when someone comes along later down the track and is having issues with the position sensors on this device, it makes much more sense for them to look at the drawings, then look at the program for the same tag L1_LFT_RET as opposed to L1_LFT.Inp_OpenLS.
You could argue that it is not necessary, but for me when designing a program I make an IO list either way, and it is super easy to assign tag names / aliases my local IO points in this spreadsheet and import straight into Studio5000.
I do this because in my opinion it helps with diagnostics.
My aliased IO tags generally match my wire numbers, so when trying to fault-find an IO point what you see on the drawing is what you look for in the PLC. This is not as straight forward with straight UDT/AOI's tags though.
am I missing something or do alias really screw you if you are doing online edits? If you alias and have that alias in logic, you cannot change the alias tag online. the only option would be to go and change the alias in the logic to a different tag, delete the old alias tag, then recreate it with the new reference, then go back and put it back where it belongs. so am I missing something?
Yes, except many times this can't be done. You can't delete the alias if your HMI is using the tag. If you had used a second tag instead of the alias tag, then all you would need to do is change the copy to use the new source.
It seems like everyone that likes using aliases are people writing code that they do not support. The people that hate aliases are the people that are maintaining that code.