LabView simple counter

Question

I am having real troubles with a seemingly easy task in LabView. So the task is, that you have some kind of a counter which goes from 0 to 60 and a push button. If you press the button, the counter should go up by one, this should continue until 60, where with the next button press the counter resets to 0 to start all over again.

I already have some kind of solution, but my problem is, that it keeps counting way to fast. If I press the button the counter jumps up 10-12 times and not one-by-one.

My solution: https://www.pic-upload.de/view-32620107/Counter.png.html

Answer 1

Never use a local variable in LabVIEW.

Ok, that's overstating it, but it's an advanced tool that should only be employed as a last resort. If you ever find yourself using a local variable, you're probably doing things as inefficiently and riskily as you can in a dataflow language. Local variables break dataflow and introduce data copies and the risk of race conditions. So let's ditch that.

There are two tools that you seem to be missing from your toolbox: the Event structure and the shift register. Here's your fix: (You may need to change that frame to 61 instead of 60... I was unclear from your directions whether you meant 60 button presses or the displayed value "60". I went with 60 button presses.)

By the way... the image below is a VI Snippet. You can literally drag the PNG onto your block diagram if you have LV 2016 or later and the embedded meta data will turn it into working code.

Here is how the code would be written prior to 2001 using polling instead of events. There are rare cases where polling is useful today, but generally, a good LabVIEW programmer will avoid this solution because it wastes so much CPU bandwidth.