TRAPPING AND RECORDING AN EVENT

[Tim_56]

Hi,

I'm trying to trap and record the event whenever the emergency stop button is pushed on a particular machine. The VI I created does do that but the problem is that it continuously writes into the file while the emergency stop is engaged (False condition). I am trying to record only the first intances, but being completely new to Labview, I am struggling a bit. Any help would be greatly appreciated

Tim

[Diell.it]

With this simple structure you can convert the continuously true output in single true output

with this you can remove che chase structure and convert the boolean output to (0-1) for control directly for loop

[BertMcMahan]

First off get rid of the For loop, it's not doing any good. Second, either use a feedback node (like Diell said) or a Shift register.

You want to compare logic states- you want to trigger the write if (Value = True) AND (LastValue = False)

[Mancho00]

You can use 'Boolean Crossing PtByPt' to detect a T-F or F-T transition

[crossrulz]

As of LabVIEW 2018 (or maybe 2017), there is a new function called Value Changed.vim.  You can use that to AND with your read value.  When both are true, you write to your file.

[Tim_56]

Many thanks Diell

[Tim_56]

Many thanks

[wiebe@CARYA]

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@Diell.it wrote:

With this simple structure you can convert the continuously true output in single true output

with this you can remove che chase structure and convert the boolean output to (0-1) for control directly for loop

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Comparing a Boolean with true is redundant.

If a==true then b= false else b=c is basically a=!a and c

= 

This reads better. If Boolean is true and previous Boolean is false, result is true.

[Tim_56]

Hi,

Still can't work out where this fits in. I tried it as the input to the True/False loop, but the input to the file remains continuous

Thanks for you assistance

[wiebe@CARYA]

Time to post your updated VI.

The shift register should go between the DAQ read and the case structure (NKA True\False loop).