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PID Loop Configuration

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Hi all

I am new to the Visilogic PLC platform and I have a PID question.


A little background on myself:  I have been using Allen Bradley / Rockwell products for the last 25 years and it is now time to change to a new platform.  The company that I work for will not buy in to the licence fees associated with their products, so here we are trying out Unilogics products.


My first project is a heat tunnel application using a V570-57-T20B controller.  I also plan on using a snap in I/O module to allow the use of a type J thermocouple.


My question is this:  I have set up the PID FB configuration.  No problem.  Now I want to incorporate the auto tune FB for the same PID loop. Must I configure the Auto Tune FB since the PID FB is configured?  

If so, do I use the same MI and MB in both configurations, or does the Auto Tune FB configuration need to have it's own MI and MB's?  It seems to me that they would both need to use the same memory addresses.  I have read through the manuals that I could find and watched a few vids on Youtube and I suspect that these are using older software revs. 


Also, do I really need to have the snap in I/O?  There is enough I/O on the controller for this application.  If I can use my J thermocouple some way without having to buy the snap in I/O, that would save me some bucks.


My hardware is on order and not here yet and I have nothing to download to and experiment with.


I have enjoyed using the Visilogic software so far.




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I'm glad that you have found the software enjoyable so far.


Within VisiLogic there are two sets of PID function blocks as you have noticed. The first is the original PID blocks which is generally only used when working with legacy code. We would not recommend using this, and would suggest using only the functions from the PID Auto-tune menu. The new one is titled PID Auto-tune, which has the same capabilities as the regular PID, yet has an additional function block that allows for auto tuning your system.


If you have set up the original legacy PID functions you will need to replace all of the existing PID functions (config, run, etc) with the same ones from the PID Auto-tune menu.


There is no requirement that you use the Snap-In I/O. It is an option for the V570 as it does not come with on board I/O, though if you are using a local expansion adapter it will work jut the same.

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