How can I create a PWM from a digital output on a DAQ-1200 card?

[bknight83]

Hi, my name is Bryan and I'm trying to control a bunch of motors from the DAQ-1200 card using pulse width modulation (PWM). I've ruled out creating the PWM from the analog out as I do not have enough analog out pins to control all eight motors. I tried creating a PWM through a for loop in LabView but the frequency of the wave was greatly dependent on the computer's clock speed. Obviously, the more things I had running on the computer, the more fluctuation there was in the frequency. Is there a way I can develop a PWM generator that can run and not be affected by the load on the computer (sort of running in the background?). Thank you very much for you help.

Bryan Knight
Sophomore Computer Systems
Engineering
Rensselaer Polytechnic Institute

[kroth]

Bryan,

The DAQ-1200's digital lines are all static and thus cannot be HW timed. Running LV on a standard PC will not give you deterministic timing. The options you have would be to get a digital card with timing such as the 6533 or 6534, moving to a real-time operating system, or getting a sources card that could give you the channel count in analog output. Unfortunately there is no way to get deterministic timing with the static digital lines on the DAQCard-1200.

Kevin R
Applications Engineer
National Instruments