Pulsed Digital Output with 9401

[MJHanagan]

I am trying to generate the same "pulsed" output on two lines of a 9401 module (I am using the +5V signals to "duty-cycle" drive two 2N3904 transistors).  How do I instruct these two DO lines to use a pulse train generated from a "CO Pulse Generation" task?

Ideally, I would also like to start this DO output/CO Pulse with and Analog Edge trigger (I need to start the output pulses to coincide with an AC voltage signal passing through its “zero point”).  I have a 9239 analog module in slot 6 of the 9172 chassis (I assume this is where it needs to be to generate a trigger, correct?).

Any help on how to get all of this accomplish would be greatly appreciated.

I am using LabVIEW 8.2.  Thank you!

[MJHanagan]

Ah ha!  I just figured out that having the 9401 in slot 5 or 6 of the 9172 chassis is what is needed to then set up the pulse generator to use either select counter "ctr0" (which is tied to line 3 of the 9401) or counter "crt1" (which is tied to line 7 on the 9401) in the DAQmx Create Channel VI.  This gets me the +5V output I need on the one 2N3904 transistor.

What I would like to do now is to figure out how to trigger start this task when a 60 Hz AC voltage on one of the 9239 module's channels passes through a "zero" point.  I also have a 9215 AD module if the 9239 can't generate an analog trigger start.  Any ideas how to setup an analog edge trigger with either the 9239 or 9215 module?

[Brad_K · Accepted solution]

Hi MJHanagan,

Neither the NI 9215 nor the NI 9239 has analog trigger circuitry built in. However, you can acquire data continuously and scan for a trigger condition in your application. DAQmx includes a shipping example that shows how to do this: LabVIEW\examples\DAQmx\Analog In\Measure Voltage.llb\Cont Acq&Graph Voltage-Analog SW Trigger.vi. It's also on the web: Continuous Acquisition with a Software Analog Start Trigger.

Brad

[MJHanagan]

Hello Brad - thank you for that valuable insight, I can now stop banging my head against the wall!  I'll give your software approach a try.