PWM on digital output DAQ 6528

[martin3885]

Hi,

currently I am trying to control an electric motor through it's controller. This ontroller needs PWM signal 24V max as a speed control. Unfortunatelly I have the PXI with the NI card 6528 which doesn't have counter outputs. I need there 100Hz. Is ist possible to use this card to control this motor? If it is possible, how should I programm it? I have also a NI card 6230, which has counter outputs, thus there are only 5V on counter output, I prefere using 6528 card instead of going into electronic to build an circuit for 6230.

Thank you in advance for your help!

Martin 

[Maciej_Antonik]

Hi

If you insist on working with 6528, then you need to work with digital outputs, which are only software timed. In other works you would need to write a program, which would be changing the value on digital output every time that you need it. Here are benchmarks of what's realistic: http://digital.ni.com/public.nsf/websearch/624CD9E32E2C4076862570C10000B9DE?OpenDocument

You might also want to consider running Real Time operating system, which offers deterministic operation

[martin3885]

Hi,

i've tried PWM form this example http://digital.ni.com/public.nsf/allkb/1561D31534F07D608625727900391114 . I have placed this vi in a sequence structure. The result is, that it blocks the code in the previous frame of the sequence structure. In the first frame there are only 2 booleans that are written to the 2 digital outputs. When I change the state of these booleans, its results are written to the outputs only when I set the switch in the PWM vi. to stop.What can be the reason and how can I solve the problem to be able reliably set outputs?

Regards,

Martin 

[Maciej_Antonik]

Hi Martin

It is very difficult to guess what could be the problem without seeing your code. Do you think you could post here the VI which you have created?

[martin3885]

Hi,

I've attachen my vi. Maybe it's the probem of the loop outside sequence structure?

Regards,

Martin

[Maciej_Antonik · Accepted solution]

Hi

The example you are using has a while loop inside of it. So the VI you made will stay in the first loop (second page of Sequence Structure) as long as the subVI is running (=until you stop it or there is an error). I would propose to spend some time on learning basics of LabVIEW structures to understand it better. Here is one sample tutorial, which might help you understand, how loops are working: http://zone.ni.com/devzone/cda/tut/p/id/7588. This tutorial might also be helpful: http://decibel.ni.com/content/docs/DOC-1694. There are also other tutorials - just search on ni.com. 

[martin3885]

Hi Maciej,

many thanks for your post! Now it seems obvious for me:)

Regards,

Martin