PWM through DI/O PCIe 6353

[homeauto]

Hello,

I have a quick question. For my rescent project i need to control 30 SSR by PWM. I am thinking to use PCIe 6353 board in a desktop Real TIME terget. i know this board has 4 counter which is easy to use but because i need 30 PWM out, is it possible to use this 6353's 30 DI/O as a pwm?

thanks in advance

[homeauto]

Forget to mention they have to be hardware timed. As I know this board has 32 channel hardware timed DIO. An example would be great if anybody has one. Thanks.

[PHarris]

Hi there,

The PCIe 6353 does provide hardware timed DI/O, but you would only be able to configure 4 separate PWM signals which utilise the counters as you describe. If you'd like to have 30 PWM signals of hardware timed accuracy, I would suggest considering a RIO FPGA card such as the 7851R as this would give you the most flexibility and speed.

Kind Regards,

[autohome]

Thanks Paul for the input. The Prototype machine I am working on, don't have to be hardware timed and my budget wont cover FPGA card,  I am not sure about the clock source yet,  I have few more question for you below,

For hardware timed: Is it not possible to use one clock source with same sample rate/frequency with 30 pwm for 30 pid output?  

For software timed: Is it possible to use 30 pwm for 30 pid output?

[Mcdan]

autohome,

Yes, you can use Digital Output to generate 30 PWM signals.  However, doing this and controlling the frequency/duty cycle of each line independently is a challenging task.  All of the digital output lines on your 6363 must share the same clock, which means all lines get updated at the same time.  In order to generate 'independent' PWMs on each line, you'll need to set your sample clock to a known rate, then calculate the pattern for each line based on this.  When you call DAQmx Write to update the pattern, you must calculate the relevant pattern for all lines, and write them all at the same time.  If all PWM patterns are known in advance, this can be fairly straight forward.  If you need to continuously update each PWM individually, this can be quite challenging (though possible).

Hope that helps,

Dan

PS.. If you're concerned with the accuracy of your frequency/duty cycle, I would advise against using Software Timed output.

[John_P1]

Here is an example you might find useful:

https://decibel.ni.com/content/docs/DOC-8010

The method to build the waveform in this example could certainly be optimized, but I think it gets the general idea across and should probably be good enough depending on the rates you need to achieve.

Best Regards,