One tag provider per PLC or not?

[peter]

@nminchin

@peter

not so uniform coding practices

This way, if another contractor comes along and doesn't care for our standards, we can still use our generic templates as we can simply set the descriptive values up to suit

Well to start, I am the contractor and I'm complaining about the company's lack of standards

But there are a bunch of things that are working for and against me in this project:

Against:

• I'm talking to Rx3i PLCs so there is no nice hierarchical OPC data. Instead all 3000 published variables are presented in a single list (which makes finding particular variables in Ignition fun)
• There are 10 to 15 different prefixes applied to these variables within the PLC, and for this project I need to pick things from about 12 different prefixes.
• For fun, in several cases the data I want is duplicated under different prefixes, but sometimes updated under slightly different conditions, so I have to be careful in which variable I use.
• There are multiple spellings for the same type of data in different functional locations. EG "WaitForThing" and "WaitThing2" are wait times for the same thing but in two different locations (and there is no "Wait" variable with a "1" suffix)

For:

• I am very familiar with the PLC code, so over the years I have learnt most of the in's and out's.
• I can change the PLC code and I am solving the "against" points in the PLC by installing a new block and mapping all of the required variables to a new set of names under (yet another) a new prefix
• This new block will become the standard for the interface to this set of data and eventually rolled out to at least 110 systems at just this one customer site.

[nminchin]

Sounds like a nightmare!

[peter]

You don’t know the half of it

[everardohr]

If tag providers are only organizational tools, I am assuming that creating a new one does not create a dedicated process to update the tags within the provider. Do you know if a single process is dedicated to update all tags in providers, or there are as many processes as Tag Groups executing?

[scott.corbett]

We are having a problem with one tag provider failing to load tags (initial value unknown) while other tag providers continue to work. If tag providers are only organizational tools, why would one tag provider have issues while others continue to work normally?

[Chris_Bingham]

@scott.corbett

why would one tag provider have issues while others continue to work normally?

It might be worthwhile posting specifics of your setup. As @Kevin.Herron mentioned, tag providers can be more complicated than just an 'organizational tool', especially when considering remote tag providers, service security, etc.