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How do I set a value to my device from my Xpress panel only when a button is pressed?

The communications server in the Interact Xpress product is set by default to update data (tags) when ever the data changes.  So, to only update a parameter in my device when an operator wants to requires using a particular button type.

The Set Value button type would seem to be the correct option, however this only allows you to set a 'constant' value and not a 'variable' value from another tag.  So . . .

The Increment or Decrement buttons will provide you this functionality.

This example shows you how:

Act_Pos is a tag getting actual position from my device.

Teach_Pos is a tag that I occasionally want to set with the actual position.

I create a button that is type Increment. 

My Switch Input field is set to Teach_Pos.  This is where the data will be written to when the button is pressed.

My Increment By field is set to Act_Pos.  This is the data I want to grab and then write to my Teach_Pos tag.

My Base Value is set to 0 (zero).  This way, each time I press the button it will take Act_Pos and add it to 0 and then update Teach_Pos with this value.

You could also use the Decrement button if you wanted to negate the value in Act_Pos as it would subtract it from 0 (zero) before writing it to Teach_Pos.


Or, another way...

Since the above would require 2 different buttons if the value is positive or negative, if you wanted to only transfer TAG1 to TAG2 when Trigger button is pushed:

TAG2= TAG2+ ((TAG1 - TAG2) * (ABS(Trigger)))

One example of an application is teaching a position from a motor to a controller:

Compax_Position_Register2 = Compax_Position_Register2 + ((MotorPosition2 - Compax_Position_Register2) * (ABS(Trigger)))

glh June 2013

updated jh July 2013