Creating global controls

[Andre55]

Hello,

I was wondering how I would go about creating a global control. I am not sure what is the conventional meaning of a global control, but I am specifically looking for a control that bypasses structures so that I can instruct an infinite loop inside a case structure to stop from outside the case structure. Thanks.

Andre

[amcolosk]

To make a global, you'd want to check for a change on the control then wire the control into a Global Variable.  A global variable in LabVIEW is a variable that can be used anywhere in your project.

[Darren]

And if you just need access to this value within a single VI, another option is to create local variables of a front panel control.  I've used this trick before...make a hidden control on the front panel, and use local variables (and its terminal) to share a value between parallel loops on my diagram.

If you need access to the value in multiple VIs, however, the previous suggestion of using a Global Variable is the easiest approach.  Just watch out for race conditions...

-D

[Mythilt]

Do a search for Functional Globals (Also called AE's or Action Engines).  They are a better way to implement what you want to do over a global control.  Another method is to use a queue.  But for what you are describing, the Functional Global is the easier approach.

[Andre55]

Thank you for all your suggestions, however, my program still cannot perform the tasks I want. I can't seem to figure out how to use the global/local variables for my purpose. Perhaps I don't completely understand your advice so I created a very simplified program so that I can explain what I want to do. My aim is to start this program with the numeric value of 0 on the front panel, once I begin executing the while loop I want to be able to change that numeric value to 2 and stop the while loop. For my program I need for this control to be outside the while loop, and it seems once I have started looping nothing outside the loop executes anymore. I want to bypass this. Could you please demonstrate how I can use global/local variables to achieve this goal. Thank you.

[Mythilt]

A very simple example using a functional global / AE is attached.  Let me know if you have any questions.

[Andre55]

Thanks again for your help, but I was wondering if I could ask one more favour of you. I only have Labview 8.2, would it be possible to convert your files so that I can view them using this earlier version of Labview. Thanks.

Andre 

[Mythilt]

Done.