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

Similar Messages

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.)

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

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

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..

Throttle body PID control using pulse width modulation

Hello all,
I am trying to do a PID control for a throttle body (using pulse width modulation) for a set value of feedback voltage. The process variable is the pulse width duty cycle. The throttle body is expected to be fully open at a feedback voltage of 5V and pulse width duty cycle of 42.5%. When I use the highlight execution using the attached file, I can see the throttle body fully open (the values observed are: PID output 42.5 %, feedback voltage approximately 4.7V). However, when the highlight execution is unclicked, the throttle body flutters in the closed condition (still PID output 42.5%, feedback voltage approximately 0.9 V). Can any one please help by suggesting any modification to this attached file to make this throttle body respond to the set value of feedback voltage.
Many thanks
Ajith
Attachments:
Throttle body control using PWM technique - PID.vi ‏525 KB

How did you determine your P, I, and D gains? If you have not tuned your controller, you'll get poor performance. Running with execution highlighting will slow down the execution, which will change the effect of the gains. I would start with pure proportional control (I and D = 0) with a small proportional gain, and see if it responds in approximately the way you want. If so, then your code is probably correct, and you just need to do a full tuning to get good performance. There are many resources available on the web, on this forum and elsewhere, for PID tuning. Note that since your code uses a simple PID example, and not the one from the PID toolkit, the gains do not have the units that are used in many tutorials so you'll have to correct the calculations to compensate.

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

Lenovo x240 and PWM (Pulse Width Modulation)

Hello everyone!
Does Lenevo Thinkpad x240 use PWM (Pulse Width Modulation) to control screen brightness?
If so, is there a flickering effect like in this video?
https://www.youtube.com/watch?v=SpDdy9jSx7Y

There is an analog modulation with which there is no pulsation at low brightness levels. For example, HP Elitebook 8740w. Watch video: http://www.youtube.com/watch?v=Dk4ckdQ9rvE
How poor the implementation of PWM (if x230 has PWM) is in this model?

Does the new ipad use pulse width modulation to control the brightness of the display?

Does the new ipad use pulse width modulation to control the brightness of the display? I have photophobia and migraines and am unable to use displays that use this technology due to it triggering a headache.

You'll have to go to an Apple Store and view the screen to see if it's OK for you. If a store is not convenient, buy one from Apple online and check it out. You have 14 days to return it for a full refund, no questions asked.

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.

Cannot Find Pulse Width Modulation(FPGA, Use in SCTL)

Hello All,
Can someone tell me where I can find Pulse Width Modulation (FPGA, Use in SCTL).vi? I couldn't find it in LabVIEW Example Finder.
Thanks
Message Edited by John Edwards on 02-01-2009 09:30 PM
Solved!
Go to Solution.

Here it is...
Attachments:
Pulse Width Modulation (FPGA, Use in SCTL).vi ‏43 KB

Pulse width modulation with daq mx

Im trying to change the pulse width modulation on the fly with daq mx. All I have found so far are examples useing traditional DAQ, but not DaqMX. It would be a lot easier if I were to use DaqMX since I will be useing other daq applications in my program and would rather use mx.

Does this help?
Attachments:
PWM-Counter_Output_Folder.zip ‏63 KB

Measure pulse width of signals generated by DAQ

Eventually, I would like to:
Start a counter pulse width measurement and analog out at the same instant.
Stop the pulse width measurement with an external digital signal.
My current plan is to use a digital out on the DAQ to go to a digital input and the counter start input. The digital input will be a start trigger for the analog output. This works, except for the counter.
While trying to implement this, I tried a simpler test of just generating a digital pulse with the DAQ and wiring that to the counter inputs. That doesn't work, even though it looks fine on an oscilloscope. Then, without changing the software at all, I connect a function generator to my counter inputs, and it measures pulse widths flawlessly.
I'm actually implementing this with a Python wrapper around the DAQmx C API, but I recreated it in LabVIEW, and it behaves the same. VI attached. I have the latest DAQmx drivers.
Attachments:
meas_pulse_width_simple.vi ‏32 KB
screenshot.png ‏99 KB

ColeTrain wrote:
apaulsen,
Just a
friendly heads up, but this is more of a DAQ post and you will
generally get more replies to these types of questions by posting in
the proper forum.
That being said, try taking a look at
the Example Finder and look under the DAQmx examples at
synchronization/multifunction as this would be a good place to start
working on what you're trying to wind up doing down the road.
I am actually the OP. apaulson is my coworker, and he was logged in to the forums on the workstation from which I posted.
I
realized that it ended up in the LabVIEW forum, so I reposted on the
DAQ forum:
http://forums.ni.com/ni/board/message?board.id=40&thread.id=7185.
I understand why there is a search-to-post policy, but it's rather
unintuitive and clunky, and I got confused. IMHO, ubuntuforums.com
does this the right way and automatically searches before you submit
your post.
Anyway, I figured it out. See the other post for solution.

Harmonics analysis with Pulse Width Modulation

I stuck in how to show the harmonics contents of the PWM Inverter.
Which is the right input connect to the signal in port of FFT power spectrum component? and then that can show the PWM inverter harmonics contents.
Please help me , this is my final year project
Attachments:
1.jpg ‏31 KB
PWM_2013_10_16.vi ‏30 KB

Dear Lynn,
Thanks for your useful information. I was successful to obtain the power spectrum from the FFT component, But I would like to know how can I get the power spectrum exactly same as my attached picture?
( In my VI, all the parameters and type of control and carrier signal are same as the picture, but the power specturm is not the same. )
Which is show the x axis and y axis is modulation frequency ratio and modulation amplitude respectively, and the modulation amplitude will be changed in different harmonics frequencies.
The formula also is attached. I have no idea how to apply those equation in the FFT power spectrum analyzer.
In the other hand, I would like to know how to use harmonics analyzer to get the THD, since I connected the wire from modulation output to singal input of harmonics analysis and then show error.
Thank You!!'
Jason
Attachments:
1.jpg ‏31 KB
formula.jpg ‏14 KB
PWM_2013_10_30.vi ‏156 KB

Pulse width modulation with a PCI 1200 board

Hello,
I Have a PCI 1200 board and I try to generate a pulse train with a period
of 500 ms and a variable duty cycle between 10% and 100% by step of 10%.
Does anyone know how to do this.
Thanks in advance
Michel Kocher

Does this help?
Attachments:
PWM-Counter_Output_Folder.zip ‏63 KB

Pulse width modulation signal generation for ULx

Similar Messages

Maybe you are looking for