Alarm sound output played when value from instrument exceeds threshold

[tmarshall07]

We are trying to have a program produce an alarm noise whenever the value of the force read from a pressure sensor exceeds a certain threshold. We have a bridge setup going through USB to the computer. The program works fine and displays a force anywhere from 0-4 Newtons, depending on how much pressure is placed on the instrument. I tried wiring the numerical indicator into a case structure which has '3..', with a play waveform chunk inside the case structure. It seems that this works except that when it gets above the threshold, it doesn't stop playing. It gets stuck in the case and won't read any new values from the instrument. Its most likely a simple fix, I just don't have enough experience with labVIEW to know what the problem would be. Any help would be much appreciated!

[Christian Mergl]

You are playing the waveform with the condition if VALUE = 3 then ALARM, but you need if VALUE >= 3 then ALARM.

Christian

[tmarshall07]

How do I denote VALUE >= 3 in the case structure? Isn't that the same as '3..'?

[Coq_Rouge]

Post your code. A picture is not much to work on 😉

[tmarshall07]

Yep, of course, I don't know why I didn't post it in the first place.

[NIquist]

You're unrealistically expecting that the value will drop back below 3 in the instant the event structure times out and checks for that condition.  If it happens at any other time (almost a certainty), the case structure switches to its default case where there is NO code.  That's why the the music keeps playing. 

[NIquist]

After looking in more detail at your code I'm seeing 3 embedded loops all with boolean switches to stop them.  Your logic seems a bit convoluted if you're trying to do what I think you are.  Why not change the audio part into a simple boolean indicator for now and see if you can get that switching correctly before you add the wave file alarm.

[tmarshall07]

Okay, I played around with booleans and without the sound file and loop I can get the indicator to show "true" if over 3 and "false" otherwise. I guess the discrepancy comes with my misunderstanding of case structures. How do I get the sound to only play when true?

[CarlosOtiniano]

I leave an example that can provide, use it in your program