topic Re : Re: Stop a while loop with array outside in LabVIEW

Stop a while loop with array outside

nousome — Fri, 21 Nov 2008 14:34:07 GMT

Hi,

I have a problem to stop running a vi which uses a while loop and outside an array with two values of intervals of time. I would like to stop the VI when the different values in the array are elapsed. I attached here the code if you like to help me please I thank you in advance.

Re: Stop a while loop with array outside

xdaf — Fri, 21 Nov 2008 14:54:33 GMT

If I understand correctly your application, I'd use a for loop instead, executing n times (obtain n with the "array size" function), activating indexing where the array enters the for loop, and timing with the "wait (ms)" function.

Re: Stop a while loop with array outside

smercurio_fc — Fri, 21 Nov 2008 14:57:41 GMT

You have a units problem. You seem to be specifying the time intervals in milliseconds (at least I think they're milliseconds), and then dividing by 1000. That makes them microseconds. You are then comparing to a difference calculation which is in milliseconds. I think you want to specify the time intervals in seconds, and multiply by 1000 to get milliseconds. Also, watch your coercion dots. The constant of 2 should have a representation of I32.

A better solution would be to use the Elapsed Time function.

Re: Stop a while loop with array outside

Pnt — Fri, 21 Nov 2008 14:59:44 GMT

"I would like to stop the VI when the different values in the array are elapsed"

It is not clear to me, what you want.

Does this help ?

Re : Re: Stop a while loop with array outside

nousome — Fri, 21 Nov 2008 15:25:29 GMT

I want to make a criterion to stop the Vi when the two values in the array are elapsed so here the Vi would stop after 2 seconds.

Re: Re : Re: Stop a while loop with array outside

Dennis_Knutson — Fri, 21 Nov 2008 15:46:07 GMT

As xdaf mentioned, all you really need to do is this:

If there is a reason to make it any more complicated, please explain why or should we just post your program to the Rube Goldberg thread?

Message Edited by Dennis Knutson on 11-21-2008 08:46 AM

Re : Re: Re : Re: Stop a while loop with array outside

nousome — Fri, 21 Nov 2008 15:52:18 GMT

Thank you very much all for your quick help.

Re: Stop a while loop with array outside

smercurio_fc — Fri, 21 Nov 2008 21:01:57 GMT

There is one caveat that you should be mindful of. When I looked at your time values it seemed as if you were wanting to wait for long periods of time. The simple implementation provided by Dennis will have the effect of not allowing you to stop the program when it's waiting unless you press the Abort button in the toolbar. My presumption was that you wanted to be in a loop waiting and be able to stop at any time. Of course, that was my presumption. I'm not really sure what your overall goal is.

Re : Re: Stop a while loop with array outside

nousome — Fri, 21 Nov 2008 21:30:28 GMT

Yes I would like to stop after all the values from the array pass the while loop.

Re: Stop a while loop with array outside

smercurio_fc — Sat, 22 Nov 2008 15:34:08 GMT

I'm sorry, I don't understand what you mean by that. Do you understand how the example provided by Dennis works? What does it not do that you need to do?

Re : Re: Stop a while loop with array outside

nousome — Mon, 24 Nov 2008 09:52:32 GMT

The solution given by Pnt works fine. Now I would like something a little bit complicated. I would like that first before each value from the array is running, that the user clicks to a button to start the waiting time (I know how to do this with event structure). After I would like that at the 90% of the time of waiting given by the differents by the array, some event appeared (I guess that I could do this in case structure) during 500 ms and then the remaining time has to be elapsed and another event appears. For example, for a value of 10s, at 9 sec, an event appeared during 500 ms and this event disappeared and following 500 ms another event appeared during 500 ms. After 1 sec, another value from the array is running.

Thank you for the help.

Re: Re : Re: Stop a while loop with array outside

RavensFan — Mon, 24 Nov 2008 14:12:37 GMT

What is "differents"?

Your description isn't too clear. Perhaps you can draw a picture or a timeline or something to describe this.

Re : Re: Re : Re: Stop a while loop with array outside

nousome — Mon, 24 Nov 2008 14:53:01 GMT

Okay I'm sorry I will try to make it clear.

Each value from the array represent an individual trial. At the beginning of each trial I would like that the user clicks to a button to start the wait time (I know how to programate a click on the button but I can't with this architecture program in the way that the button appears back with each new value from the array). After 90% of the time of waiting (so if the value in the array is 10 sec, after 9 sec) a stimulus appears during 500 ms and disappears. And after the value is elapsed (i.e., after 10 sec) another event appears. For these two events to program no problem. After the delay is elapsed i would like to have 1 second of waiting after the new trial (and make appear the circle).

My aim actually is to select randomly from the array one of the 9 values. When this value is selected it can't be used again. I would like the loop ends after a x number of trials. I wonder so if array is well suited for my problem. I know the random number function but I can not easily remove a value when it was used. I hope that I am clear.

Re: Stop a while loop with array outside

RavensFan — Mon, 24 Nov 2008 15:13:35 GMT

Sure, an array is perfect for this.

You would probably want another array of booleans where each index matches up with a value in your numeric array. Once you select a value and use it, set the same index in the boolean array to true. When you randomly choose a value in the numeric array again, check to see if the boolean flag is true. If it is still false, use the value and change the flag to true. If it is true, choose another random number and check again. Keep the number of values used in a shift register and stop the larger while loop after that number matches your desired "x" trials.

Re : Re: Stop a while loop with array outside

nousome — Mon, 24 Nov 2008 18:01:52 GMT

Thank you very much for the reply. I am not sure to understand could you give me a picture of this please if you have any time. I thank you in advance

Re : Re: Stop a while loop with array outside

nousome — Wed, 26 Nov 2008 13:57:32 GMT

Thank you very much for the reply. I tried your solution but it doesn't work. I guess I miss something could you give me a picture of this please if you have any time. I thank you in advance

Re: Stop a while loop with array outside

smercurio_fc — Wed, 26 Nov 2008 14:41:54 GMT

Which solution are you referring to? Why don't you go ahead and post what you've done so far.

Re : Re: Stop a while loop with array outside

nousome — Wed, 26 Nov 2008 16:44:18 GMT

The solution given by Ravens fan

Re: Re : Re: Stop a while loop with array outside

RavensFan — Wed, 26 Nov 2008 18:42:54 GMT

Take a look at this in LV 8.0

Re : Re: Re : Re: Stop a while loop with array outside

nousome — Thu, 27 Nov 2008 09:05:23 GMT

Thank you very much for the solution given. I tried to apply this in my program but it didn't work. I would like to use each value given by the array as time and when this time is elapsed a change in the font of the screen to yellow appears during 1/2 sec and after 1.5 sec I would like that the next interval given by the array is selected. I would like the array runs for 10 or more trials, so that after 5 trials and all values are selected the array of boolean returns to 0 to let select among all the values.

Here in the VI runs only for one value and stops even though I set the number of trials to 5. Thanks. I attached the code here