Help Creating Pulse Frequency Modulated Signal

I'm trying to create a Pulse Frequency Modulated Signal ... I have seen the examples showing how to create a frequency modulated sine wave (using the function generator example, I believe) but am not sure where to look next.
Any suggestions?
For some context, this would be used to simulate the signals similar to those found traveling through/ transmitted through a nervous system.
Thanks for the help!

Hello Slow,
You can generate ECG signals using the Biosignal Generator by changing the Signal type in the pull-down menu. Take a look at this description.
Regards,
Alina M

Similar Messages

Using pulse width modulated signal (square wave) to control when a signal is turned on or off

Using pulse width modulated signal (square wave) to control when a signal is turned on or off
Greetings All
I'm trying to use a labview created pulse width modulated signal (square wave) to control when a signal is turned on or off.
Here's my logic and graphic example:
1) The source wave signal is continuous
2) Use a PWM (square wave) created in labview to control when the signal is turned on or off
3) If PWM signal (amplitude) is greater than 0 play signal if PWM is not greater than 0 don't play signal.
I'm actually using this to step sequence / pulse several separate magnetic coils using my audio card (which has several audio output channels), I have a signal in labview played constantly. Than compare it to the PWM (square wave) which controls if the signal gets played on each separate channel or not. That way I can control which coil is on and off and in what sequence they are activated.
I couldn't find an edge detection for a square wave created in labview so I tried Limits but that doesn't seem to work unless I change the phase manually and that only goes from 1 to -1. I'm just trying to compare the PWM (square wave edges) already created by labview / play a signal if the pulse is greater than 0 and it turns off the signal if it's less than 0.
Should I be doing this another way
Tia
Message Edited by sal22 on 08-16-2009 06:09 PM
Message Edited by sal22 on 08-16-2009 06:10 PM
Solved!
Go to Solution.
Attachments:
PWM control signal block.png ‏23 KB
PWM control signal front.png ‏48 KB
pwm test.vi ‏36 KB

Greetings,
I tried it two ways using amplitude and levels and fft spectrum. The values don't seem to update the way I need them to (basiclly showing a 0 or a 1). I compare the Y values like you recommended but they don't ever seem to update.
tia
Message Edited by sal22 on 08-19-2009 10:05 AM
Attachments:
pwm magnitude not updating.png ‏29 KB
pwm test.vi ‏41 KB

Pulse width modulated signals

Is it possible to generate a fixed frequency with variable duty cycle signals using counter/timer channels of my DAQ 700?
If yes, is there any example I could download?
If no, I am looking for a DAQ card that can handle
the job, I'd appreciate any recommendation.
Another part of my project is to read in a analog signal while generating this pulse width modulated
signal. So far I am not very lucky with one DAQ,
I am thinking of getting two. Does it sound overkill?
Please help.
Thanks

Could you provide a timing diagram for your digital signal?
I am a firm believer that a digital output device such as an NI timer can create any signal, given the proper software or hardware. I once did a high speed, gated, triggered data acquisition with only a single NI timer chip on the AT MIO 16E-1. It required about 75 feet of BNC cable, more PFI wires than you can imagine, four external logic devices (AND and OR, NAND and NOR boxes) all interconnected and basically tangled. I don't think I could repeat that setup without my documentation, but the point is, it worked.
The most important thing from that example is that I used a timing diagram. These are so vital in digital IO and timer applications that its not funny.
If you can't determine ho
w to do what you need from a timing diagram, just send me a copy, let me know what the basic specs are of the DAQ 700 (how many counters, interconnect capabilities, etc) and I can try to help.
Good luck.
As far as reading the analog signal at the same time...well, look at my example. I generated the trigger/gate signal with the card, and then read in the analog data (on several channels simultaneously.)

Need Help on How to Generate Pulse Width Modulation signals

Hi,
I am New in using NI board and programming using LabView. I have no idea on how to start to generate, use what function in order to create a PWM signals.
My project needs:
-PWM signals with 15kHz frequency.
-Duty cycle varrying from 0%, 25%, 50%, 75%, 100%.
-By using the generated PWM signals to control the half-bridge (MOSFETs) of boost converter and buck converter to varying the voltage of 24V battery to feed in my DC motor.
The NI board that I use is (NI - sbRIO-9642).
Can I have a clear view on what to use, how to generate, and by using what functions to generate the PWM signals.
Sorry for the inconvienient, but I really desperate for help in this. Thanks a lot. I am appreaciate it.
The attached is the circuit the half-bridge motor controller that I will used.
Attachments:
half bridge.jpg ‏13 KB

Hi Ronald,
in this thread a very similar question came up. You can use the same approach on your sbRIO.
For the frequency you gave you should use the FPGA present on the sbRIO - as is shown/discussed in that other thread! I also suggest that other thread because of the "deadtime" feature used to prevent shortcut problems when switching your MOSFETS simultanuously...
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Pulse width modulation signal generation for ULx

Hello,
I am trying to produce an analogue waveform (i.e square wave) with an option to control the duty cycle.
I am outputting through a Measurement Computing card, which uses the ULx user libaries.
There are many examples to do what I want using DAQmx, but all those using ULx have no option to control the duty cycle.
Can anyone help?
Thanks in advance.
Solved!
Go to Solution.

Hi ben,
does your ULx hardware even support PWM outputs? Does it support counter output tasks?
It's not only the software, also the hardware needs to support your requirements!
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome

Frequency Modulation trick. How to solve?

Hello!
I have a VI which does Frequency modulation using two formula nodes. One node is for Message signal generation and second formula node - is for resulting FM generation. Observing FM equations, the function inside FM equations - should be instegrated and FM is like:
FM(t) = A*cos(2*pi*Fc + 2*pi*D* Integral( M(t) );
, where A - amplitude; pi - 3.14; Fc - Carrier frequency, M(t) - message signal; D - frequency deviation.
Thats why I use external Integration, then pass integrated signal into FM equation.
The problem is - Signal has very low voltage (amplitude) after integration - and the whole thing doesn't work anymore.
Should I multiply integrated signal until it be the same amplitude as the original signal?
What might I did incorrect here?
Thanks in advance.
Solved!
Go to Solution.
Attachments:
FM_modulator75.vi ‏90 KB

I have created a Polymorphic VI "FM Generation". This VI Generates Frequency Modulated signal output according to wired Message signal. FM Generation VI accepts two types of Message signal input - Waveform or Array. If you wire an array for Message intput - you also need to wire "Sampling Frequency" input. Now every one can place this polymorphic function on their Block-Diagram palette and use it.
Note: You should place on a block diagram VI called "FM Generation.vi", two other files "FM Generation (array).vi" and "FM Generation (waveform).vi" are function instances that are responsible either for Waveform input or Array input.
This function is designed for LabView 7.1 or higher.
Feel free to write feedbacks.
Attachments:
FM Generation.vi ‏12 KB
FM Generation (array).vi ‏49 KB
FM Generation (waveform).vi ‏61 KB

Pulse width modulation on sbRIO 9631

need to control 150 RPM DC motor with help of pulse width modulation from sbRIO 9631. need a simple VI in which i can take some DIO's and with help of a slider i can increase or decrease speed of motor simultaneously.

A 12V geared DC motor is hard time figuring out how to control or maintain it.Torque in from speed 0 to 150 RPM.

Is it possible to use "Delay Values" to create a frequency signal from digital "Count Edges" -task? (= are the results I'm getting correct?)

Hello.
I have a digital encoder from which I need freaquency information (to ultimately get rpm -infromation). The problem is that this task is inside a loop with 2 other DAQmx -tasks that are using "one sample on demand"-aquisition mode and if I configure this new counter task to be a freaquency task, it only updates once in ~ second which makes the whole loop lag.
I thus created an "artificial" freaquency signal by using "Count Edges" -aquicition mode and the "Delay Values" -block so that I substract the delayed signal from original "Count Edges" -signal. There is a 0,01s delay in the loop and I figured out that if the history of the "Delay Values" -block is 100 samples I would thus get the real edge-freaquency.
I tested this configuration and the results seem to be at least really close to correct but I have no idea if this idea is in any way correct...
This explanation was probably quite confusing so please see the picture attached.
Thanks a lot in advance!
Attachments:
are_the_results_correct.jpg ‏200 KB

First of all, thank you for quick reply. Unfortunately I don't have the acces to the vi. until tomorrow.
And yes, I think you understood correctly: essentially this arragement measures how many edges have been counted during one iteration. This is how I figured out that this could then be used as a frequency measurement:
1. From the "Edges - Delayed Edges" I get the information on how many edges have been counted during last iteration.
2. I "know" (really I don't?) that one iteration lasts ~0,01s because of the delay in the loop.
3. There is 2048 edges in one round of the encoder so I get the rpm as follows: rpm = (edges - delayed edges)/204,8*60(s)
(If I was using history size of one as you suggested it would be: rpm = (edges-delayed edges)/2048 * 60) However using history size of 10 and taking it account in the multiplication smoothens the response nicely.
But doesn't this arragement count on the fact that the vi runs smoothly and there is no additional lag?
I quess using another loop and notifiers for a dedicated freaquency measurement as you suggested could be worth trying. I just have to first learn how to use them.
If I do use them will the main loop run smoothly and not wait for every update of the notifier? This would be essential since the freaquency output refresses only about once in a second if I use the continious aquisition mode.
Attachments:
are_the_results_correct.jpg ‏198 KB

Want help in creating a chat module!!!

Hello!!!
I want to create a chat module for my website.
I am trying to develop this module like we have in gmail...
What I am doing is whenever a person login ,his status is changed to online and when he opens the chat module all the users with online status are shown to him.When he want to chat with anyone ;he simply clicks on the name and a new window is open with text box and a tet area.When he sends any data then that data should be visible to the receiver as well as in senders text area screen.
Can anyone help me wih the code.
Thaks in advance.

Dashing201 wrote:
I don't know anything about SMACK library.Can you help me!!!he already did
now go check out the SMACK library before you get SMACKED!

Frequency Modulation for Tuning Forks on FPGA

Hi,
I am relatively new LabVIEW and FPGA user. I am trying create frequency modulation on the FPGA to maintain a 90 degree phase shift between the input and output signals. Currently, I am having trouble in trying to calculate the phase difference between two analog signals. The two analog signals are coming from analog inputs on the FPGA card. At the end of frequency modulation, there is a VCO that will output a signal that is shifted 90 degrees relative to the input signal. That output signal will drive the tuning fork at resonance. I am not familiar with the FPGA card and LabVIEW so it would be very helpful if someone could tell me how to calculate the phase difference between two analog signals.
Thanks,
Jason Bryant
Solved!
Go to Solution.

Hi wade_bruant3-24,
Below are a few links to examples of how to calculate the phase difference of two analog signals. Both examples show how to do this on a real-time or windows operating system, rather than on the FPGA itself since the functions used cannot be run on the FPGA.
https://decibel.ni.com/content/docs/DOC-21131
https://decibel.ni.com/content/docs/DOC-18286
Catherine B.
Applications Engineer
National Instruments

Generating Multiple Modulated Signals

I was a bit surprised I didn't see this on the forums, though I am new to the RF gear. What I would like to do is generate two modulated signals, such as 802.15, on two different frequencies. I am already able to create the signals individually using the modulation toolkit. I am using a PXI-5671 RFSG. I have found how to generate with interferance two CW tones in the examples, but do not see how to generate the two modulated tones. I also need to be able to set one of the modulated signals to a lower power than then other. I am trying to test adjacent channel interferance with modulated signals. Any thoughts?
Troy

Hi Troy,
There are a few tricks you can play here but
they are completely independent of hardware and more on signal
processing. Basically you need to write both waveforms at the same time
with different frequency offset.
1) Frequency Shift. Assume you
have two completelly independent baseband signals s1[n] and s2[n]. Each
one should be the same lenght (time duration).
One of them will
be transmitted at Fc and the other one at Fc + df. s1[n] remains
unchanged and s2[n] will be shifted by df using the following VI:
The
trick here is to make sure that your sample rate is high enough to
support the shifting, otherwise you will be aliasing. If you create
your waveforms with Modulation Toolkit make sure they have enough
samples per symbol.
Finally you need to sum all signals s[n] = s1[n] + s2[n].
2)
Apply different Powers. Before you add the signals, you only need to
scale the data correctly. To do this, I recommend to normalize both
waveforms. This is s1[n]/max(sqrt(|s1[n]|). Thenscale the smaller power
one. Finally, you will add them together.
Here is a spectrum of the composed signal:
I have attached
an example to do this using 802.15 signals with a few modifications: I
am not normalizing data but applying headroom to each signal and I
hardcoded the number of samples per symbol so the maximum frequency
offset is about 12 MHz. Should be helpful to get started.
Message Edited by Yardov on 10-17-2008 06:05 PM
Gerardo O.
RF Systems Engineering
National Instruments
Attachments:
frequency shift.jpg ‏9 KB
Generation Multiple Channels.zip ‏32 KB
spectrum.jpg ‏79 KB

Frequency Modulation circuit simulation in Multisim Using 566.

How can I get Frequency Modulation circuit simulation in Multisim Using 566? In Multisim I dont have IC 566.. And I have attached the image of the circuit i want... I dont want to use FM signal source directly.
Attachments:
FM CIRCUIT USING IC566.PNG ‏21 KB

Hello,
This component is not available in Multisim; I tried to locate a SPICE model for LM566 with no luck. It seems that the component is obsolete now.
Take a look of this old forum post, it explains an alternate method to build the FM circuit.
Hope this helps.
Fernando D.
National Instruments

Building delays in pulse width modulation

HI there I am trying to build a vi to control a speed controller for a motor.
The specification that the technician gave me is to produce a pulse width modulation waveform with constant gap time and variable "on" time.
This will give the motor a variable speed that can be manipulate.
I already build a pulse width modulation vi but I don't understand how can I make the gap time constant eg 20ms while varying the on time 1-3ms.
Is there a method that I could use or an example that I can look at? Any help will do thanks in advance.
ill attach my current vi.
Solved!
Go to Solution.
Attachments:
pulse.vi ‏20 KB

You want to vary the ON time between 1 to 3ms?
Did you do a search using the keyword "pwm"? There are many posts that have examples.
The idea is that you want to preserve the same frequency and change your duty cycle.
(Example)
Let say you want a waveform at every 20ms, which translates to 50 Hz.
2 ms is 10% duty cycle, 1ms is 5% duty cycle, and 3ms is 15% duty cycle.
Did I understand your question correctly? Somehow, I feel like I missed something..

Measure pulse frequency with 4.7 volt peak amplitude

used two shipped Measurment Studio Vb.Net 2005 Examples:
1-Example 1 : CountDigEvents "MEASURES PULSE COUNTS" and Example 2: MeasDigFrequency_LowFreq1Ctr "MEASURES PULSE FREQUENCY"
2-Example 1 works fine measuring pulse counts , however Example 2 did not recognize pulse frequency , the pulse amplitude voltage is 4.7 volt peak
3-during testing used counter ch0 channle by connecting Sorce0 and Dgnd pins to signal source.
4-using Nidaqmx 9 and MIO-16xe-10 daq
5-pulse frequency around 10 khz
QUESTION:
-please advice what to do to make frequency measures ?
Thanks

Hi MyKat,
Note that the connections are different for edge counting and low frequency frequency measurements with one counter. For the latter, you'll need to connect the signal to PFI 9 rather than PFI8 as you did for edge counting.
http://zone.ni.com/reference/en-XX/help/370466W-01/mxdevconsid/eseriessigcounters/
Regards,
-Jim B
Applications Engineer, National Instruments
CLD, CTD

Two harmonic signals with time difference to one modulated signal

Hi LabView experts,
I'm not realy good in using lab view, but I need the visualisation for my diploma thesis.
I know how to creat a sin wave and I know how to creat a modluated signal out of to different sin waves.
but I want to creat a modulated signal where the HF signal is starting later.
So first you have the low frequency sin wave and maybe after one sec. the high frequency signal will be modluated on top.
It would be great if someone could tell me how to do that.
unfortunately I'm using labview 7.1 so I will not be able to open newer files..
thank you very much!!

It's a bit long to explain what you did wrong..
First thing.. STAY AWAY FROM STACKED SEQUENCES!!! Sorry for shouting! But I keep praying that NI will remove those horrible things!
Stacked Sequences are annoying because they make you loose sight of the dataflow that goes on inside the code. Forcing sequential actions is not a good thing in Labview.
Have a look at the attached code. It will do what you wanted. It can still be improved, such as changing the For Loop to a While Loop and have the graph update as run run the VI, instead of a fixed number of iterations.
Let me know how it goes..
RayR
Message Edited by JoeLabView on 06-13-2008 08:43 AM
Attachments:
modulation.vi ‏30 KB
waveform.PNG ‏22 KB

Help Creating Pulse Frequency Modulated Signal

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