"Continous Pulse Train" Output - PWM Control with Duty Cycle

[Waterppk]

Alright, so the latest project is to drive a throttle body type valve with Pulse Width Modulation (http://en.wikipedia.org/wiki/Pulse_width_modulation). I have a number of PCI cards to choose from (using PCI-6123 counter 0), and am able to correctly run my valve through MAX. I'm having trouble running a VI and controlling the duty cycle through it.

The valve needs to be driven at 128 Hz and varying duty cycle between 5% and 95%, which I've tested through MAX and it works great. The attached VI will run the valve, but it won't update: so I can input a duty cycle, run the VI and it will move to the requested position, but when I change the duty cycle in the front panel control it doesn't change the valve position or the PWM output. I have any test tools available if they're needed, but this looks to be a problem with my understanding of how to control a counter's output duty cycle in a VI. Any ideas?

Available hardware devices are (if you have something against using a 6123 for some reason):

PCI-6122

PCI-6123 (currently using ctr0 and works fine)

PCI-6601

cRIO:

9211

9481

9481

9203

9265

9411

SCXI: (Can't use, too slow)

1102B

1102B

1520

1124

1520

Gen_Dig_Pulse_Train-Continuous-Variable_Freq_LV86.vi

[Daryl]

Here is an example that I think I downloaded from NI.com a while ago or something. It works good.

PWM_Output.vi

[Waterppk]

Here is an example that I think I downloaded from NI.com a while ago or something. It works good.

Works great and makes sense, thanks for the VI and the help!

[Daryl]

Works great and makes sense, thanks for the VI and the help!

No Problemo, enjoy!