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generqte a PWM signal with LabVIEW using digitals outputs - foxone - 08.03.2006 18:01
I would like to generate a PWM signal (freq 50 hz Duty Cycle 10%) thanks to LabVIEW and NI-DAQ, on 5 digitals outputs in order to control 5 servomotors. Is it possible with LabVIEW, and how?
Thanks
generqte a PWM signal with LabVIEW using digitals outputs - cb - 08.03.2006 18:38
please take yoursef the time and take a look at the examples, which are shipped with LabVIEW:
help --> find examples --> the example finder opens
click on "index" in the left tab,
type "PWM" and
open The example
"PWM-Counter Output.vi"
generqte a PWM signal with LabVIEW using digitals outputs - foxone - 09.03.2006 11:20
Thanks i2dx, but I have ever seen the examples, and they use Analog or Counter output. I have to use Digital Output, because I need to control 6 servomotors, and there are 8 Digital output, therefore it matchs. But, there is only 2 Counter et 2 Analog output, so I con't use them, unless you could give me a solution. That's the reason why, I really want to knom if it's possible to create PWM with Digital output.
thanks
generqte a PWM signal with LabVIEW using digitals outputs - cb - 09.03.2006 13:26
yes, it is possible with digital output, too, but you have to do a lot of work "by hand" ...
take a look at my example. i hope, this will help you. be aware that the "calculate dutycycle algorithm" is a QUICK and DIRTY DRAFT. You will have to improve it, but i hope it gives you a hint, how it can work.
in my draft there are only 10 steps 0%, 10% .... 90%, 100%
you have to increase the number of steps, and the sample rate, etc ...
generqte a PWM signal with LabVIEW using digitals outputs - foxone - 09.03.2006 14:46
Thanks a lot, i2dx.
I'll try with your example, your are helpfull.
I just wonder how to change the frequence ?
generqte a PWM signal with LabVIEW using digitals outputs - cb - 09.03.2006 15:24
frequency depends on the sample rate.
the basic calculation in my example is:
i put 100 samples in the output buffer on each loop iteration. the output sample rate is 1000 Hz. i divide the 100 samples into 10 blocks of 10 samples ==> the frequency of one block is 100 Hz or one block lasts 10ms. and the output of one loop iteration are 10 pwm-signals ...
helpfull?
generqte a PWM signal with LabVIEW using digitals outputs - foxone - 09.03.2006 17:31
yes, it is really helpful for me, but I have still some troubles, because I confess, I am not very confident with LabVIEW, and I think I am bad too.
So, I need a frequence of 50 Hz, I have changed values and it work, but I need a much better accuracy concerning the duty cycle, it means, a step of 0.1%, but I can't chose the correct values :evil: Could you help me again, pls ?
For the moment, nothing works because "Device identifier is invalid" as it's written. But my device is number 1 too. I don't know why it doesn't work but I'll continu to look for solutions.
generqte a PWM signal with LabVIEW using digitals outputs - cb - 09.03.2006 19:01
ok, here it is.
it's up to you to understand, what's happening in there, maybe someone other will help (sorry, but i still have work to do ...)
generqte a PWM signal with LabVIEW using digitals outputs - foxone - 10.03.2006 17:51
hi i2dx, sorry to disturb you again.
Thank you again for your 50 Hz program, it's precisely what I need. But unfortunatly, it doesn't work yet. The problem comes from the link between NI-DAQmx and the PXI 6070E device. In fact, it works with the test panel, but I can't configure the VI "DAQ configuration" with LabVIEW, and when I lunch your program (or any other programs containing DAQmx VIs), the error 200220 occures. Have you ever had this kind of problem ? Isn't that a problem with software's versions ? (NI-DAQmx 3.1)
Otherwise, is it possible to create the same progam you have ever done (50Hz) but without using DAQmx VIs, just tradionnal DAQ VIs ? (I don't want you to create it, I just want to know if it's feasible in theory).
Thanks
Have a nice weekend end.
generqte a PWM signal with LabVIEW using digitals outputs - cb - 11.03.2006 09:05
please take a look at this:
Common NI-DAQmx Error Codes and Solutions: Codes -200000 to -200299 and -50103
DAQmx 3.1 sound very old. Can you upgrade to the current version?
Download NI-DAQmx 8.0.1
please look in the Measurement and Automation Exploer, which Device# your 6070E has, i guess you have to change the device#s here: