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02-05-2018 09:18 AM
Hi,
I am trying to use this example to create a 5V pulse to a device. http://www.ni.com/example/52071/en/. I want to use the 5V digital output line on a Virtual Bench to create a short laser pulse. (The laser is just driven by a 5V pulse of any length.) I can use it to output 5V manually (just by toggling the button), but I dont know how to incorporate the Output Array Control into a timed loop or something else.
Thanks,
Matthew
02-05-2018 09:44 AM
How fast of pulses do you need? And how accurate are these pulse widths?
I do not think the VirtualBench DIO can be used for pulsed outputs since they are software timed. You might be able to do something with the Arbitrary Waveform Generator though.
02-05-2018 09:47 AM
I am not yet sure how fast, but down to a millisecond would be very nice. And I would use the FGEN but that is being used to generate pulses down to 1us for a different part of the experiment sadly. The pulses dont need to be accurate as such, just reliable. If I can set it to 15ms and always get a 17ms pulse then that is fine, I can calibrate for that, but if the pulses vary much with the same settings then that would be a problem.
However even if they are not stable I would like to be able to pulse it at the ~100ms range. Does that help answer your question?
02-05-2018 10:26 AM
100ms might be doable mostly reliable, but on a Windows machine you cannot rely on software timing. What you really should do is get a simple DAQ that has a counter output that is capable of outputting pulses (double check in the data sheet). Then you can use simple DAQmx functions to tell the hardware to output a pulse. With the hardware controlling the timing, you will get a lot more consistent pulses.
02-05-2018 10:37 AM
Ok thanks, but in the meantime how would I get this working as intended? I have attached the VI im using. It can turn the laser on with the pulse button, but then not off. I am very new to labview so I think its a basic mistake.
Thanks in advance
02-06-2018 09:03 AM - edited 02-06-2018 09:07 AM
Hi Matthew,
I believe you can do what you need with VirtualBench, but it's a little outside the designed behavior of the hardware.
md12g12 wrote:
I want to use the 5V digital output line on a Virtual Bench to create a short laser pulse. (The laser is just driven by a 5V pulse of any length.) I can use it to output 5V manually (just by toggling the button), but I dont know how to incorporate the Output Array Control into a timed loop or something else.
crossrulz wrote:
I do not think the VirtualBench DIO can be used for pulsed outputs since they are software timed.
This is correct -- the VirtualBench GPIO instrument API is 100% software timed -- as fast as the program can write to the device is as fast as you can go. However, the GPIO also has another mode: SPI, which is hardware-timed.
md12g12 wrote:
The pulses dont need to be accurate as such, just reliable. If I can set it to 15ms and always get a 17ms pulse then that is fine, I can calibrate for that, but if the pulses vary much with the same settings then that would be a problem.
Try this example and use the scope to measure the SPI Clock's period (dig/0). If that is too fast, you can write a different digital pattern and measure the MOSI Signal's period (dig/1).
VirtualBench: Master SPI With the DIO
http://www.ni.com/example/52585/en/
VirtualBench Digital I/O Pinout and Connections
http://zone.ni.com/reference/en-XX/help/371526B-01/vbhelp/diopinout/
Joe Friedchicken
NI Configuration Based Software Get with your fellow OS users
[ Linux ] [ macOS ]Principal Software Engineer :: Configuration Based Software
Senior Software Engineer :: Multifunction Instruments Applications Group (until May 2018)
Software Engineer :: Measurements RLP Group (until Mar 2014)
Applications Engineer :: High Speed Product Group (until Sep 2008)
02-06-2018 11:00 AM
The speed is ok, for now I would be happy with any pulse at all really. I just need help with making labview output a pulse of true to the boolean array. Something along the lines of the VI I attached would be great, but I dont know how to use a timer to change a boolean value.