Can a case structure execute multiple cases?

So I have a VI set up with a mutiple option case structure to select which input a voltage is read from (there are 32 options). Now that I have it made, I realize that sometimes I may want to read from multiple inputs at once.. Is there an easy way to change my setup so that it executes multiple cases at a time? Right now my control is a slider to choose the case. What would be a good front panel control choice to be able to select multiple options? Thanks
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You can build an array of your options and loop through the required cases. As mentioned, a case can only perform 1 case per loop.
A good front panel control would be a cluster or an array of booleans (e.g. a tick box per option), easy to loop through.
/Y
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How to implement Case Structure for multiple inputs to Pic Ring?

So I have a reasonably simple program which I am almost completeed with. Basically the data of an array is read and then is indexed and a new array is created from the indexed data. And then I use Match Pattern to see if elements in the new array match certain words. And if they do then a number value is allocated to a Pic Ring at the end. And depending on the final number value the Pic Ring changes from one pic to another.
However, I have the problem that I will be using multiple Match Pattern functions to compare elements in the final array, but I can't attach multiple Match Patterns and their subsequent logic statements to a single Pic Ring, only one. I've been trying to work this out by implementing a Case Structure or Event Structure. But the Event Structure isn't working and with the Case Structure, it is very messy with multiple True/False Case Structures inside of each other. Anyway, hopefully this all makes some sense. I'm attaching the VI program to this post. Thanks.
Attachments:
ArrayTest2.vi ‏495 KB
ArrayTest2.vi ‏495 KB

Obviously, you can only display one picture. So then the question becomes which picture to show. Therefore, you will have to create some sort of preference of one pattern over another.
I would use a FOR loop so that you can loop through your available patters and their possible results. Use the Conditional Terminal on the FOR loop so that you can stop the loop on the first match. Then you just wire up the selected value for the ring outside of the loop.
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Case structure run other case structure

HI all,
I have a big programme in LabVIEW, but what I want to do is very simple to describe with simple example on picture bellow.
I need to make that when 1. case structure will be true to start "second" case (but I also need to start second case manually with switch "START"). Is there any "property node" which will tell me when 1. case is on true?
If this exist I then only need to add "OR" boolean to second case.
I hope that is clear what I want to do.
Rookie; LV 2011 on WIN 7

Switch when release will keep that switch set as True until you come back and switch it off yourself. Latch when release will keep that switch as true until the terminal is read by LabVIEW at which time LabVIEW will return the switch to false automatically.
Well I need button which goes automatically back to same position as it was after it was pressed, so I used "switch when released", it's also working with "latch when released". It's make no sense.
Case structure 1 will execute the true case as long as X=1. Are you saying that you don't want the True case of the 2nd case structure to continue to execute as long as X=1? Only execute on the first time that X becomes 1? If so, you will need a shift register or feedback node to keep track of that boolean wire and only execute the 2nd case when the boolean wire is True AND when the boolean wire in the previous iteration is NOT True.
Yes exactly that, I will try to use " shift register", so I can get previous iteration.
So I need gate which will do next:
wire | button | OUTPUT
1         0            1
0         1            0
1         1            0
0         0            0
Which gate must I combine to get what I want?
Rookie; LV 2011 on WIN 7

How can I have multiple inputs into the selector terminal of a case structure

Hi everyone
I have a question on how to wire multiple inputs in to the selector terminal of a case structure.
Currently, I have three switches, each switch determines different case. So if I switch the switch 1 is on, the numeric indicator will show 1. If the switch 2 is on, the numeric indicator will show 2, so on and so forth. However, the selector terminal will not allow me to wire multiply inputs into the case structure, I tried Bundle by Name, Bundle and Array to Cluster, but they did not work. I set the case structure with 3 cases, they are 1, 2 and 3.
Could someone help me please. I have attach an image and the VI of the work I did so far.
I have another question, is there a function which can toggle other switches to off when there is a switch has been toggled on.
Thank you very much
Tommy
Attachments:
Trial - Case Structure.vi ‏7 KB

Tommy, attached find a cheeseball way of doing this that has given me a LOT of mileage over the years. IT lends itself nicely to a couple of really good practices that NI recommend, but I have given you the bare-bones to "see under the hood".
The recommended practices:
1. You can make this a nice tight sub-vi where you can put it into a core library of routines that you'll use over the years, even extending the logic to look only for changes, etc.
2. If you are thinking about Front Panel design considerations, you'll want to use arrays of controls where possible, as that's a nice neat way of containerizing your switch for both the FP and Block Diagram.
Have fun. I have TONS of these types of things, so feel free to PM me if you have any other needs.
Wes
Wes Ramm, Cyth UK
CLD, CPLI
Attachments:
Boolean Switch Logic.vi ‏11 KB

Multiple boolean values to be used in case structure

Hi,
I am trying to implement a case structure with multiple boolean cases and am having trouble with that. What I want to do here is : I have a set of 5 values, each of them being "true" or "false". For each "true" value, I have a certain set of steps to be executed. The "false" of each can be ignored. Ideally, I would like to have a case structure for the 5 "true" cases. I am not sure how to go about wiring these boolean outputs to my case structure. Also am using LabView 6.1.
Any ideas?
Thanks,
Sukanya
Solved!
Go to Solution.

Additional comments regarding code:
It is a mistake to configure the serial port inside the loop. This is a waste of time and resources. Configure outside, read in the loop, and close outside after the loop is done. The flushing of the buffer would be part of the "configure outside".
The default values of the controls for the VISA Configure Serial Port VI are such that the termination character for reads is enabled, and the character is set to a linefeed. This means the VISA Read will read until it sees a linefeed or reaches the value wired to its byte count input. Thus, the VISA Bytes at Serial Port isn't really necessary.
You should not rely on the settings in the LabVIEW option for automatic error handling. You should explicitly handle errors in your code. Thus, you probably want to stop the loop on an error and provide a dialog via the Simple Error Handler.

Event structure or case structure

I have some case structures wired to buttons. When each button is true, code inside the corresponding case structure executes. `What are the advantages/disadvantages of using an event structure instead of a case structure?
Ron Deavers, CLD

Place an indicator for the iteration terminal of the main loop to see an obvious difference
Your case structures must be in a loop that constanty runs. If you don't put a delay in the loop, it consumes all CPU, but if your delay is too long, it takes a moment to react to the button changes. The loop spins all the time, no matter if you press buttons or not.
Your event structure also sits in a loop, but nothing happens until you press a button. Now the event structure triggers IMMEDIATELY, executes the event case, and then waits for the next event. The loop does not spin unless needed.
You can even mix the functions by using a timeout event. Code in the timeout event occurs at regular intervals, but at any time, any of the other events can take over.
LabVIEW Champion . Do more with less code and in less time .

Possible to do this with case structure?

Essentially I want the case structure to do: If case1 = run OR case2 = run, do this, else do case3++
I'm using a string case structure right now, where for example, the inputs could be SWEEP_A or SWEEP_B but I want the case structure to use case SWEEPAorB. This is so I can have different names for the input string BUT run the same case (this is to avoid redundant code for what I'm doing).
Thanks.

For more complex logic use can use create a boolean array and convert it to a number.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot

Trying to clear an array inside a case structure

Good morning all. I am trying (unsuccessfully, obviously) to clear an array inside a case structure. (See case structure at right side of vi, I colored it green to make it easy to find). Here's (briefly) what I'm trying to do. I have 6 test probes in the process. All six probes are connected to the Alcatel Detector through a 6-solenoid manifold. As I run the test, I want to sample 1/second, for let's say 3 minutes. For the first 30 seconds, I want to pull a sample from from probe 1, so I turn on solenoid one and leave it open for 30 seconds. Now all 30 values are tagged as having come from Probe 1, and they're stored in array 1. I can now compute an average value for probe 1. Then I close solenoid 1 and open solenoid 2, saving the next 30 values to array 2. (and so-on, until I have measured all 6 probes for 30 seconds each). Then I wait a pre-determined amount of time and repeat the process. Here's my problem. I want to clear out each array as I begin the second iteration, so that I can easily compute the average of the last 30 values. If I initialize the array by connecting a constant 0 to the shift register on the for loop insid ethe case structure, it does not work, nor does it work to place the 0 outide the overall for loop (the next for loop going out, NOT the OVERALL for loop). I know my programming skills are still crude, but I'm putting everything into this. Anyone have any suggestions?
Attachments:
HCMF rev 1 25 Apr.vi ‏485 KB

Altenbach, I definately understand your approach, and I like it much better than my own. But I still have no luck making it work. I get the same result as before (my original attempt). Value 0 of the array simply changes each iteration, with nothing "saved". Each new value simply overwrites the last value. Can you take a look at my new vi, with changes, and see if you can find the error of my ways. I am but a rookie Jedi in the vast reaches of LabVIEW Space, and you are no doubt a Jedi MASTER
Attachments:
HCMF rev 1 25 Apr pm.vi ‏374 KB

Generating a report w/ block diagram & programatically specified case structure?

Hi,
I am trying to generate a report that shows the block diagram for a programatically specific case structure.
The case structure has ~90 cases and is selected by a custom control.
I'm on Labview 8.5
I've found with the Append Block Diagram to VI, I can print out all of the cases (setting hidden frames to true), or just one case. However, I cannot select which case it shows, it always prints out whatever case has been manually selected on the block diagram, but I want to be able to programatically select it.
I've tried to do the same thing by opening a vi reference, and using BD.Get Image Scaled, and cannot get that working as desired either. I've also tried setting the value of the control before getting the image, but that doesn't help.
Any thoughts?

Probably.
This VI is backsaved to 8.5 and has the basic functionality. I don't know if the traverse VI shipped with 8.5, but hopefully this should be enough. If not, LAVA has info on how to access the scripting features in older versions (although less between 8.0 and 8.6).
Try to take over the world!
Attachments:
Visible Frame.vi ‏10 KB

Case structure for comparing values

Hi,
i just wanted to know if there is a special way to use comparison in case structures.
I only kow how to create cases for things like if x=0 then ... if x=1 then ...
Now I want to make it if x<0 then ... if x=0 then ... if x>0 then ...
The only solution I found so far is creating a case structure inside a case structure.
Is there a way to keep it all in just one case structure?
Thanks and have a nice weekend,
Bernie

Case Structures are pretty flexible in how you can specify what triggers a particular case. You can specify ranges or various values per case.
In your situation, if you specify three cases with the following values, you'll get what you want.
'..-1' = x<0
'0' = 0
'1..' = x>0
The two periods before or after a number indicate that the case should run if the value is anything less than or greater than the specified number, depending on which side of the number you place it. You can also use this to specify a range of number. '1..10' would trigger the case for any value 1 through 10. Using a comma between numbers lets you specify different non-sequencial numbers. '1,5,10' would run the case only those specified numbers.
The same basic rules a
lso work with text based Case Structures.
Attached image shows the three cases you need.
Ed
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.
Attachments:
Case_Range_Values.gif ‏21 KB

Once I have sent an email I cant switch my case structure back to false

This may be a stupid question because nobody else seems to have had a problem with it, so sorry if this is the case.
Using the email Vi example provided with Labview, in a case structure, when the case structure goes true, it stays true as soon as the email vi is running, even after it has sent the email.
Is there any way to stop it or does it need a specific timeout period?
My very simple example is provided.
Thanks for any help
Alexi
Attachments:
mailtest[1].vi ‏28 KB

alexi wrote:
> This may be a stupid question because nobody else seems to have had a
> problem with it, so sorry if this is the case.
>
> Using the email Vi example provided with Labview, in a case structure,
> when the case structure goes true, it stays true as soon as the email
> vi is running, even after it has sent the email.
>
> Is there any way to stop it or does it need a specific timeout period?
> My very simple example is provided.
Are you sure hotmail.com has an SMTP server running? I really doubt
that. Or even if it does you may not be able to contact it, as most ISP
block outgoing port 25 on their network to reduce problems with virus
hyjacked boxens spamming the internet. Don't blame him, it is a very
sensitive thing to do.
If one of these p
roblems occurs the Open TCP Connection function will
timeout after 60 seconds and return with an error 56, network timeout.
You will probably have to use the SMTP server of your ISP to send the
messages to and this server will further send it to the correct receiver
even if that one is on hotmail.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

How to get a case structure to execute only once in a loop

I have a while loop that is monitoring temperature. Once the temperature meets or exceeds a given setpoint I want to start a timer. At this point I don't want to monitor the temperature anymore. That is, if the temperature should drop below the setpoint, I don't want to execute the case structure again when the temperture meets or exceeds the setpoint(the temp may oscillate about the setpoint for a given period of time). In any event, I need the case structure to execute only one time, not every iteration of the loop.

You can put a local Boolean variable "Flag" inside that case structure and
set "Flag" to False. Outside the case structure, use an "AND" function
output to control the case structure. The "AND" function has two inputs. One
goes to the comparison results between real temp and setpoint. The other
inputs connects to the "Flag" variable. In this way, once you entered that
case structure, the "Flag" will be turned to False, and then in next
iteration, you won't get into the case again because the "AND" function will
be False as your "Flag" is False now.
Hope this helps.
Rentian
1. Inside the case structure, put a
"BB Herman" wrote in message
news:[email protected]..
>I have a while loop that is monitori
ng temperature. Once the
> temperature meets or exceeds a given setpoint I want to start a timer.
> At this point I don't want to monitor the temperature anymore. That
> is, if the temperature should drop below the setpoint, I don't want to
> execute the case structure again when the temperture meets or exceeds
> the setpoint(the temp may oscillate about the setpoint for a given
> period of time). In any event, I need the case structure to execute
> only one time, not every iteration of the loop.

Execute Case Structure with Button Press Slows Down VI

Hi -
I'm fairly new to LabView, and I am having some issues with using a button to run a timed while loop.
I am writing a VI that outputs a timed voltage pulse to an output channel on a DAQ; meanwhile, the VI reads and graphs the voltage on three input channels on the DAQ. When I use a timed loop that automatically executes when the VI runs, the program works. However, I would like to include a button so I can control the timing and number of voltage pulses sent to the output channel, instead of sending only one voltage pulse each time the VI runs. I have tried to do this using a button wired to a case structure. If the button is 'true,' the VI should send the voltage pulse. If the button is 'false,' the VI should keep the voltage at zero.
When the button is 'false,' the VI runs normally; however, when the button changes to 'true,' the VI slows down and never sends the pulse. Why does this happen? How can I fix it?
Also, how can I send the voltage pulse only when the value of the button changes? I only want the timed loop to execute once when the button changes value.
Thanks for any help or advice!!!
Attachments:
Sensor Read6.vi ‏85 KB

The graph is in the same while loop as the case structure. The while loop won't iterate until all the code inside of it has completed. So the graph only gets updated once, and won't update again until the while loop iterates again. If you need more continual updating you may want to put that in a loop that executes a couple of times, or completely separate your code into 2 while loops. Is it that long of a wait considering your pulse length is 1 second?
Your analog output code is just writing a voltage out (7 volts) until it eventually writes out 0 volts. There is no reason for it to drop down unless you have some sort of electrical problem between your DAQ device and the device on the other end that is reading the 7 volts. What are you connecting that analog output too?
What if you don't use LabVIEW and try to test out that analog output using Measurement and Automation Explorer? Does it do the same thing?

Execute case structure a certain number of times within a while loop

Hi guys,
I was wondering if it was possible to execute a case structure a specified number of times within a while loop. Basically I'm running a camera where each iteration of the outer while loop displays a frame of a live video feed and I'd like to capture the next x amount of frames (specified by the user) each time the 'Start Capture' button is clicked. The block diagram within the case structure captures and saves an image frame. As the program is written right now, frames will continue to be captured until the 'Start Capture' button is clicked again. Instead of having to click the button again to stop the case structure from executing for each iteration of the while loop, I'd like it to only execute for the next x iterations of the while loop. Any help would be appreciated. Thanks.

Hello Uxorious,
A while loop has a iteration counter that gives an integer value of how many times the loop has iterated. You can utilise this to count the number of frames captured. I assume that the program could be running for any amount of time before clicking start capture, if that is the case then you will need to be able to detect when you have clicked the button and add the desired number of frames you wish to capture to the current loop iteration.
If you use a shift register on the outer loop with the start capture button connected to it (inside the loop) you will be able to compare its current value to its previous value. If it changes from false to true then you can add the desired number of frames to it to give you the loop iteration value where you need to stop.
Then you can compare the current loop iteration value to that number and once reached, you can use a property node to change the value of your start capture button back to false.
One final thing, don't forget to initialise the shift register I suggested to false so that you don't run the risk of missing the first time you press the button.
I hope that makes sense.
Alistair
Best regards,
Ali Bailey
National Instruments
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Execute case structure only once

Hi everybody.
I want to execute a case structure inside a while loop only once. The case strucutre is controlled by a counter, so that every time the counter has a value multiple of N, the program records an acoustic signal and calculate the main peaks of the FFT. The problem I have at the moment is that, every time the case is executed, it records and analyze the sound several times until the counter jumps to the next value. I want the case to execute only once every time the counter has a value multiple of N. I atttach the vi.
Thank you for your attention guys!!!
Attachments:
Pulsations2.vi ‏243 KB

GERD is right. You should use a feedback node to store the previous count value. If the current count is Not Equal AND the remainder is Equal To Zero run your case.
Since your counts are all integers, I would also recommend changing the representation to an integer type. I32 would likely be the most appropriate.
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Can a case structure execute multiple cases?

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