How to change the frequency of a finite pulse train?

Hi all? I Know I’ve asked once a similar question, but I need a better answer. I would like some ideas or examples on how to modify the example in LV; "Finite Pulse Train Generation - Intermediate for AM9513-Based Devices",so that the frequency can be changed while the VI is executing.
Will i have any problem with I use this VI in a DAQ-STC-Based Devices(E-series)?

Tiano,
I will try to better explain the paragraph on LabVIEW. The original paragraph reads ...
"While in a loop for continuous pulse train generation, make two calls to Counter Set Attribute.vi to set the values for "pulse spec 1" (constant 14) and "pulse spec 2" (constant 15). Following these calls you would make a call to Counter Control.vi with the control code set to "switch cycle" (constant 7). The attached LabVIEW programs demonstrate this flow."
You can make two calls to Counter Set Attribute or you can make a call to Set Pulse Specs which, if you open this VI, you will see that it is just making two calls to Counter Set Attribute. What you are doing with the Counter Set Attribute VIs is setting two registers called "pulse s
pec 1" and "pulse spec 2". These two registers are used to configure the frequency and duty cycle of your output frequency.
The example program which is attached to this Knowledge Base demonstrates how to change the frequency of a continuous generation on the fly. Why continuous? Because changing the frequency of a finite train would be easy. When the train completes it's finite generation you would just change the frequency and run a finite train again. You would not care about the time delay due to reconfiguration of the counter.
If you would like to change the frequency of the pulse train using a knob, this functionality will have to be added in the while loop. The while loop will be continuously checking for the new value of the knob and using the knob value to set the pulse specs.
LabVIEW is a language, and as with learning all new languages (spoken or programatic) there is a lot of learning to be accomplished. The great thing is that LabVIEW is much easier than mo
st languages and the learning curve should be much smaller. Don't fret, you'll be an expert before you know it. Especially since you're tackling a challenging first project.
Regards,
Justin Britten

Similar Messages

How to change the frequency of a finite/continuous pulse train in the program?

Hello!...
I am trying to modify the Finite pulse train vi example to change the frequency with respect of a ratio (1:2) of the data of a spreadsheet file as they are read one by one.
My aim is to get the pulse train to clock a stepper motor controller, in such way that the speed of the motor increases when the data of the spreadsheet increases and vice-versa.
I think that if I want to get the clock to change its speed, I must change the frequency and if I want it to increase/decrease like the data in the spreadsheet, I must tell the frequency that the data is increasing or decreasing in value.
Obviously the program must do it while it is running
Can anyone see wh
ere I have gone wrong and/or give any suggestions?
I have attached my vi and the spreadsheet file.
Thanks
Tiano
Attachments:
My_VI.vi ‏99 KB
wave.txt ‏18 KB

Tiano,
Try to build the pieces of the program separately. Get a VI running that reads the spreadsheet and reports the data in it sequentially in an indicator (forget about the pulse generation at this time). This indicator will be wired to the frequency input of the pulse generator VI.
You have read the data and have a transposed array. Now you must learn to use the Index Array function in a For Loop to extract the data sequentially. You will wire the increment output [i] of the For Loop into Index Array to shift from one data point to the next.
You have a For Loop with no constant wired to [N] to tell it how many times to run. If you use Array Size to extract the number of entries in the spreadsheet data, this can be the constan
t that tells the For Loop how many times to run.
You are using the Tab Control in a way I have never seen before (I don't think it will work this way either. Tab Control is for presenting and hiding controls, indicators, labels, etc. on the front panel, before running the VI. They are not used to control the program functionality itself. Typically you would use a Boolean to choose between 2 options for a Case Structure.
You can also change the path constant which selects the spreadsheet file into a control. This would allow you to browse for any file you want and eleiminate the need for the Case Structure altogether.
Mike

How to change the frequency of pulse train on the fly using an array of values?

Hi all!
First I want to thank U for the great job you are doing for this forum.
Iam still busy trying to control a stepper motor, by sending pulses from my E-series 6024 to a compumotor s6- stepper Driver. I've managed to get it working. I desperately need to control the motor using the values from an array. I believe we can use two approaches for that:
1st - I can get an array of the "numbers of pulses". Each element must run for 10 milliseconds. Using that we can calculate the array of frequencies to send the number of pulses within 10 milliseconds for each specific element. Could we use the arrays of "number of pulses" and frequencies in a "finite pulse train " and up
date with each element every 10 millisecond?
2nd - Or Could we use of the frequency array in a "continuous pulse train vi" and update it every 10 milliseconds?
Please note that I must use the values as they are.
Can someone please built a good example for me? Your help will be appreciated.
Regards
Chris
Attachments:
number_of_steps.txt ‏17 KB
frequency.txt ‏15 KB

Tiano,
I will try to better explain the paragraph on LabVIEW. The original paragraph reads ...
"While in a loop for continuous pulse train generation, make two calls to Counter Set Attribute.vi to set the values for "pulse spec 1" (constant 14) and "pulse spec 2" (constant 15). Following these calls you would make a call to Counter Control.vi with the control code set to "switch cycle" (constant 7). The attached LabVIEW programs demonstrate this flow."
You can make two calls to Counter Set Attribute or you can make a call to Set Pulse Specs which, if you open this VI, you will see that it is just making two calls to Counter Set Attribute. What you are doing with the Counter Set Attribute VIs is setting two registers called "pulse s
pec 1" and "pulse spec 2". These two registers are used to configure the frequency and duty cycle of your output frequency.
The example program which is attached to this Knowledge Base demonstrates how to change the frequency of a continuous generation on the fly. Why continuous? Because changing the frequency of a finite train would be easy. When the train completes it's finite generation you would just change the frequency and run a finite train again. You would not care about the time delay due to reconfiguration of the counter.
If you would like to change the frequency of the pulse train using a knob, this functionality will have to be added in the while loop. The while loop will be continuously checking for the new value of the knob and using the knob value to set the pulse specs.
LabVIEW is a language, and as with learning all new languages (spoken or programatic) there is a lot of learning to be accomplished. The great thing is that LabVIEW is much easier than mo
st languages and the learning curve should be much smaller. Don't fret, you'll be an expert before you know it. Especially since you're tackling a challenging first project.
Regards,
Justin Britten

In NI-DAQmx, how to change the frequency of a pulse train?

I was using "GPCTR_Change_Parameter()" to change the frequency of my pulse train in Traditional NI-DAQ and Labwindows/CVI; is there any function can do the same thing in NI-DAQmx without restarting the task?

You can do this in one of two ways, depending on the version of NI-DAQ you are using. If you are using 7.2 or later, you can use the counter write functions (ex: DAQmxWriteCtrFreq()), which are available for each flavor of pulse generation tasks (Freq, Time, Ticks). If you are using NI-DAQ 7.0 or 7.1, you can modify the attributes directly (DAQmx_CO_Pulse_HighTime, DAQmx_CO_Pulse_LowTime, etc). Keep in mind that for each attribute pair, one of the attributes will cause the counter to load the new pair. The attribute that causes the load is LowTime, LowTicks, and Frequency.
I hope this helps!
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For PCI-4451,How to change the frequency of an output signal without any undefined state

I would like to generate a signal using output channels of PCI-4451 and at the same time capture data using the input channels. Is there any method that I can generate a continuous signal without any undefined state when the signal frequency is being changed?
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Input_Signal.bmp ‏729 KB

Wee,
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Attachments:
Cont_Gen_Voltage_Wfm-Int_Clk-With_Updates_for_DSA.llb ‏161 KB

Finite pulse train with different frequency

Hello,
I'm trying to modify the labview example "generate finite pulse train" to generate a finite pluse train with different frequencies. Each freq will run 400 pulses. The freqs are stored in an array, which is being fed into a for loop. Thus ramp up the freq each iteration. However the program only generate 400 pluse at first given freq. I'm fairly new to daqmx and not sure what is wrong. Anyone have some idea how to fix it?
Attachments:
pulse train finite mod.vi ‏38 KB

The best "fix" will depend a bit on the needs of your app.
Is it ok to have a fraction of a second without any pulses each time you change frequencies? If so, then there's a pretty simple solution:
1. Outside the loop you'd create a DAQmx virtual channel and configure for Finite Sampling (# samples = 400) using DAQmx Timing.vi.
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3. So for each freq in your array, you'll program the counter for that frequency, start the generation of pulsetrains, and then stop the task after 400 pulses have been generated.
If you must change frequency on-the-fly, producing *exactly* 400 pulses at each freq setpoint will be tricky, and maybe even impossible to do reliably.  Some techniques will get you closer than others though, so post back if you need to do this.
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vasus wrote:
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I amtaking sensor input signals through NI FPGA cRIO-9004. i am analysing this using wave graph. the problem is i am not getting accurate singal.How to decrease the frequency?
You are responding to a very old (8 years) thread, be aware that that might not be the best option.
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What is the code you are running?
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Hello;
I'm attaching an example VI that shows how to change the output rate on the fly.
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Attachments:
aochangeonthefly.zip ‏47 KB

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How to change the frequency of a finite pulse train?

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