Stop multiple while loops in Vision Aquisition

Hi, I want to close multiple while loops with one stop button. I'm using the Vision Acquisition software for recording from multiple cameras and I want to close this recording from all cameras simultaneously. Since I'm knew to LABView I don't know how to do this. I'll include my VI here and maybe someone can help me. Thanks!
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Attachments:
Aquire Images 2 with Cameras.vi ‏410 KB

A local variable should be enough for your implementation. Look at the following article:
Stopping Parallel While Loops in LabVIEW With One Stop Button
Adnan Zafar
Certified LabVIEW Architect
Coleman Technologies

Similar Messages

Starting stopping multiple while loops

I have a rather large VI that runs multiple while loops with case strutures inside.
I would like to be able to shut off and on the while loops programmatically depending on events.(cycle complete or cycle started)
I need to store my measured data in a table but everytime I shut off the while loop the data I gathered is lost.
So it goes like this- measure analog voltage-put it in a numeric indicator...now I want to put in a table only once per cycle of my machine.
If the opeator pushes the reset button the table is available for a report generation acquisition.
Any help would be appreciated.
Thanks
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Do you want something like this?
Attachments:
Loop_Control_Multi.vi ‏109 KB
Loop_Control_Multi_Demo.vi ‏177 KB

Code golf: stop two while loops with guaranteed iteration ratio

Proposal
In the vein of the Perl tradition, I'd like to see if there's any interest in solving short programming puzzles in LabVIEW. Anyone can post a problem and define the rules for solving it.
Here's a beginning/intermediate question to whet your "palette".
Description
With one user-action, how would you stop two while loops such that the ratio of their iterations is the always the same? One concrete way to visualize this situation is in taking measurements: two instruments use the same timing source to take measurements, but second divides the clock down so that it is an integer factor slower than the first. For example, if the slower instrument is four times slower, then at the end of the VI, if the slower instrument takes 100 measurements, the faster instrument has taken 400.
Rules
You may only use vi.lib
You cannot include any other subVIs
Your solution must pass for loop1 interval as low as 25 ms
Template (attached in LabVIEW 2009)
If folks are interested in this, then let's figure out how to make future problems better. Please post your suggestions and critiques, but only if you also post a submission ;-)
Solved!
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Attachments:
Multirate Loop Code Golf.vi ‏11 KB

Norbert_B wrote:
a) You work with an integer factor of speed. While this matches many application areas, there are still cases where the factor has to be floating point (e.g. 2.5). Additionally, the factor might "invert", so the master loop runs slower than the slave (factor 0.5 for instance).
It sounds like you're about to post another code golf question. If you think the problem scope is too small, you're welcome to fashion one to your taste. Thanks for volunteering :-D
Norbert_B wrote:
b) This example does not take into account that the hardware has to be synchronized with more accuracy than the software supplies (PXI?). If hardware synchronization is required, there are two possible ways:
- The factor can be included in the synchronization (using PLL for instance)
- The factor has to be software implemented by data reduction for the task running at the lower pace.
Hrm, maybe puzzles aren't really your thing after all. You are correct: I did not define every constraint that can lead to a provable best closed-form solution, but that does not prevent people from stating their assumptions and forming creative, well-reasoned, and still correct designs. I overlooked this reading of the description and neglected to add a statement that said solvers were free to add their own conditions. I will do so in the fugure :-)
If we choose the first of your suggestions, the VI must still retrieve the data at different rates. You can dedicate a loop for each instrument to decouple any jitter and latency introduced by their connectivity or internal operation; this adds some margin of safety when there is thread and driver contention. You can also implement a single counting loop like altenbach and forego the multiloop complexity.
Norbert_B wrote:
c) You don't state anything about "what happens with the data". Is this time consuming? Does it introduce additional delay in loop iterations? Is it OK to have data loss?
I don't know -- you decide, you disclose, and you solve :-)
In my specific situation, the measurements are time consuming and do add delay (each data "sample" is 5-20 megabytes), none can be lost, and the data must be available for others to analyze later. In addition, the amount of data is saturating the hard disk throughput. If a particular write takes too long, the instrument driver may overwrite a yet unfetched sample, which is unacceptable. I did not add these details to the problem discripton becuase they don't impact the puzzle.
I don't want to burden people with my situation and ask them to solve my problem: I want to encourage them to bring their intuition and experience to a discussion. This is the design process at its heart: understanding why and how constraints affect your decisions. If a person states the additional conditions they've assumed, readers can learn why, and more importantly, when a Notifier might be more desirable than an Occurance or a Queue more robust than a Data Value Reference.
The best NI-published advice for stopping multiple while loops (https://www.google.com/search?q=labview+stop+multiple+while+loops) is laughable (and is the "solution" in my template).
Would you care to re-approach and contribute to this puzzle? I suspect you have a lot to offer :-)

How do i stop a while loop

I'm new to labview and I'm having a problem stopping a while loop (running windows XP/2000 with the student edition of labview express 7).
I'm doing a data acquisition program where I'm constantly reading in voltage and comparing it to a set point value, when the input voltage goes above the set point, i want the while loop to stop. How do I do this? I already have an LED going on when the criteria is met, but I'm not sure how to actually stop the loop (i.e. change the iteration value from true to false-i guess). If anyone can please assist me with this I would very much appreciate it.
I've included my program too.
Attachments:
CO_Detection_Monitoring_System_Modified.vi ‏60 KB

Hello Everyone-
I've just posted a message about stopping a while loop and it was answered accurately and quickly- thanks to LV_Pro and PauloM- thanks much- its nice too see that there are many helpful people out there! Unfortunately, I have 2 more questions to ask of the forum.
My application is almost completed- I just need to add an elapsed time counter that will tell me how long it took for my LED to trigger (from my set point-i.e. when from 0:00:00 until when my loop stopped).
Now I've found a perfect elapsed time counter on the NI web site contributed from Mike Hall from Ohmeda Medical- the page is here.... http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=D37E2493DC333076E034080020E74861&p_node=DZ52032&p_source=external
So my first question is, it looks like I can just extend the while loop box in my 'CO detector... .vi' and paste just the code from the 'elapsed time.vi' while loop into my loop and I will be set- but do I need to change my wait until next multiple to be a 1000 too in my program? Probably, but I'm not sure hence the question- or other ideas would appreciated.
My second question is now that my application is complete (after I add the elapsed time above), I need to exactly duplicate this process for 7 other DAQ inputs (i.e. right now I'm using only 1 of 8 analog inputs on the FP-AI110). So should I make my 'CO detector.. .vi' a separate program (I remember reading something about this in one of the posts earlier).
Any help is very appreciated.
Thank you again,
Daniel
Attachments:
CO_Detection_Monitoring_System_Modified.vi ‏60 KB

I have a for loop inside of while loop.when i press stop for while loop, i also would like to stop for loop.how can i solve this problem?thanks

i have a for loop inside of while loop.when i press stop for while loop, i also would like to stop for loop.how can i solve this problem?thanks

Hi fais,
Following through with what JB suggested. The steps involved in replacing the inner for loop with a while loop are outlined below.
You can replace the inner for loop with a while by doing the following.
1) Right-click of the for loop and select "Repalce" then navigate to the "while loop".
2) Make sure the tunnels you where indexing on with the for loop are still indexing.
3) Drop an "array size" node on your diagram. Wire the array that determines the number of iterations your for loop executes into this "array size".
4) Wire the output of the array size into the new while loop.
5) Set the condition terminal to "stop if true".
6)Drop an "OR" gate inside the while loop and wire its output to the while loops condition terminal.
7) C
reate a local of the boolean "stop" button, and wire it into one of the inputs of your OR gate. This will allow you to stop the inner loop.
8) Drop a "less than" node inside the inner while loop.
9) Wire your iteration count into the bottom input of the "less than".
10) Wire the count (see step 4 above) into the top input of the less than. This will stop the inner loop when ever the inner loop has processed the last element of your array.
Provided I have not mixed up my tops and bottoms this should accomplish the replacement.
I will let others explain how to takle this task using the "case solution".
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

How to stop a while loop of event structure from a main vi

Hello;
sorry for my english
I have to stop a subvi from my main vi, the subvi contains a while loop and an event structure so I need to stop this loop while directly from my main vi I have tried global variable but it did not work
any help please or example !!!
Solved!
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Attachments:
stop a while loop and event structure from main vi.png ‏16 KB

IYED wrote:
Hello;
sorry for my english
I have to stop a subvi from my main vi, the subvi contains a while loop and an event structure so I need to stop this loop while directly from my main vi I have tried global variable but it did not work
any help please or example !!!
If this is an example of how your code looks, I'd clean it up before the developer who has to work on it next hits you over the head with his LabVIEW Style Book.
Bill
(Mid-Level minion.)
My support system ensures that I don't look totally incompetent.
Proud to say that I've progressed beyond knowing just enough to be dangerous. I now know enough to know that I have no clue about anything at all.

How to stop a while loop in LabVIEW from a C program

How to stop a while loop in LabVIEW from a C code

hi
I think by creating dll you can stop the while loop from your C program.For that you just create dll (Dynamic Link Library) for the VI which has that while loop.
Anyway can u please explain ur requirement clearly.

How to stop a while loop after certain time using Elapsed time vi

how to stop a while loop after certain time using Elapsed time vi.

Hi Frankie,
Just place the Elapsed Time VI inside the WHILE loop, and wire the 'Time Has Elapsed' output to the conditional terminal in the lower right corner (which should be set to 'stop if true' by default).
In the future, please post your LabVIEW questions to the LabVIEW Forum. You have a much better chance of getting your questions answered sooner, and those answers can then help others who are searching the LabVIEW forums. Thanks!
Justin M
National Instruments

Stopping a while-loop in a sub-vi

Hello,
I want to stop a while loop that runs in a sub-vi. It does not work with a local variable, is there a possibility to implement this without using global variables?
Many thanks !

One way is to use a notifier.
See attached - Uses LV 7.1.Message Edited by NeilR on 05-04-2005 08:10 AM
Attachments:
stop2.zip ‏14 KB

Stopping a while loop with a button in cvi

Hi people,
I am a newbie with CVI but I have used LabView Heaps. The issue I have is I want to be able to use a toggle button or a command button to stop a while loop. I used GetCtrlVal on the toggle before the while loop. I then enter the while loop and then GetCtrlVal at the end to see if the button has been pressed. The issue I have is that once I enter the loop I am unable to press any buttons on the Panel. I would normally have put a delay in the loop but the issue is I am wanting to control a robot in "realtime", thus any delays in the program results in the robot moving further than what I wanted it to. Any ideas? If you have any suggestions that would be much appreciated thank you.

This should be in the CVI group but...
At the tail end of your while loop add a call to function ProcessDrawEvents():
When your program executes in a callback function or in code that does not call RunUserInterface or GetUserEvent, LabWindows/CVI does not update the user interface. Functions that are overly time-consuming can "lock out" user interface updates. To allow LabWindows/CVI to process these updates, call ProcessDrawEvents.

Multiple DAQ Cards, Multiple While Loops

I'm writing a code to support 3 small test stands that each have the same outputs and inputs as the others. I'm running them all off of an 8-slot DAQ. Each test stand has its own dedicated RTD Card and Analog Out card, but they all share a 32-channel Analog Input card.
I'd like to decouple the 3 test stands as much as possible - if I have to take out an RTD card or Analog Output card, I don't want the entire LabVIEW program to stop running. I want to be able to keep running and logging data on the other two test stands if I were working on the other test stand. Is there a way to do this with only 1 cDAQ? Is it simply a matter of creating separate, independent while loops for each test stand? If so, would LabVIEW have issues with each while loop writing its own measurement file in parallel with the others?
Thank You.

Is it safe to assume you've been running the three tests? Some of your post makes it sound like you've run them coupled while other parts make it sound like you haven't successfully had all three tests running simultaneously.
If you aren't running them, are you using hardware timing (counters) for your tasks? If you're looking to use counters, you're only using one per task, correct? The cDAQ will only have four counters total to be shared between your loops.
I can't remember off the top of my head if it is the task or the computer that reserves a cDAQ chassis. I want to say it's the computer so you can run multiple tasks from the same cDAQ. But, you'd still need to choose ctr0, ctr1, ctr2, etc in each task so that you don't share these resources between tasks.
Are you looking to pull the shared module out frequently? If not, are you gaining enough functionality to justify buying two redundant modules to gain decoupling?

Stop a while loop with a interrupt

I' m using a while with a delay time of 60 seconds to perform a sub vi.
So when I press the stop button it could take in extrem 2 minutes to stop the vi. I want to use something like an interrupt or jump order to stop the vi without waiting for the end of delay time.
How can I create an interrupt in lab view 6.1.
Thanks for help. bye uli

If the delay is in the calling VI using Wait (mS), you can run a smaller delay multiple times (a while loop inside your main while loop), checking Stop between each of the smaller delays until the smaller delays add up to your bigger delay. See the attached DelayWithStopCheck.vi.
But this technique doesn't stop the sub-VI: it just stops the loop in the main VI which will still run until the sub-VI is done. You could connect the Stop button to a global which the sub-VI checks in a loop to know if the calling VI pressed Stop.
Attachments:
DelayWithStopCheck.VI ‏41 KB

How to use one single boolean button to control a multiple while loops?

I've posted the attached file and you will see that it doesn't let me use local variable for stop button, but I need to stop all the action whenever I want but more than one single button on the front panel would look ugly... The file represents the Numeric Mode of
HP 5371A. thanks for your time
Attachments:
NUMERIC.vi ‏580 KB

In order to use a local variable, you can change the mechanical action of stop button (Switch When Pressed will work), or create a property node for it and select values. You'll also have to do a lot of work changing those for loops into while loops so that you can abort them.

How to use Boolean values from 2 different sources to stop a while loop?

I am working on a program for homework that states E5.4) Using a single Whil eLoop, construct a VI that executes a loop N times or until the user presses a stop button. Be sure to include the Time Delay Exress Vi so the user has time to press the stop botton.
I am doing this right now but it seems as though I can only connect one thing to the stop sign on th while loop. It won't let me connect a comparision of N and the iterations as well as the stop button to the stop sign on the while loop. So how would I be able to structure it so that it stops if it receives a true Boolean value from either of the 2 sources (whichever comes first)?
Basically, I cannot wire the output of the comparison of N and iterations as well as the stop button to the stop button on the whlie loop to end it. Is there a solution?
Thanks!
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Go to Solution.

Rajster16 wrote:
Using a single Whil eLoop, construct a VI that executes a loop N times or until the user presses a stop button.
Look in the boolean palette for something similar to the word hightlighted in red above.
LabVIEW Champion . Do more with less code and in less time .

How to stop a while loop when using tab control

How do you use a tab contol to stop what is happening on one tab when you switch to another tab? In the test example I attached, I have a while loop nested inside a case structure controlled by the tab control. When I tab to page two the elapsed timer starts but when I switch to another tab it does not stop. I can't come up with an easy way to stop or exit the while loop when I change tabs.
Thank you
Danny
Attachments:
tab control.vi ‏24 KB

I played with it a little more and came up with this fix. This fixes it but is not tied to the changing tabs as I was looking for. Is this just too many nested loops and a bad idea?
Danny
Attachments:
tab control fix maybe.vi ‏26 KB

Stop multiple while loops in Vision Aquisition

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