Maximum output frequency USB-6XXX series

[Aaron L]

Hello,

I am looking at purchasing one of the following:

USB-6501

USB-6008

USB-6009

for controlling a stepper motor. However, I cannot find the maximum digital output frequency of these units. The timing says software controlled. Can these output a pulse stream in the ~20kHz range? This is what I need to run the digital portion of my stepper motor controller. I would like to use labview to develop my ramp up/down times and see what works best for my application.

Any help on this will be greatly appreciated. Thanks!

Aaron

[crelf]

QUOTE (Aaron L @ Jan 8 2009, 07:53 PM)

I am looking at purchasing one of the following... for controlling a stepper motor.

Buy a stepper motor controller - they're gauranteed to output what you need, they're easy to control, and they'll work out of the box - lower your engineering anxiety and get the right tool for the job.

[Aaron L]

QUOTE (crelf @ Jan 8 2009, 05:38 PM)

Buy a stepper motor controller - they're gauranteed to output what you need, they're easy to control, and they'll work out of the box - lower your engineering anxiety and get the right tool for the job.

I've got the electronics for the stepper controller, so I don't need to generate the sequencing. I really just need 2 digital IO lines for direction and hold. Any one of the DIO boxes above can do that for me. But the one thing I need is something that can generate a slowish (up to 20kHz) clock to activate the stepping. I'd like to control the clock speed with a slider, basic labview stuff, really. Will any of those actually do that?

[Yair]

I don't know the answer, but I doubt that at least the 600x will be able to do this. They're simply not designed for this and even if they will be, I'm not sure you'll be able to generate a reliable 20kHz software clock on a desktop OS. If you want to know the answer, you could try calling NI, but the simplest solution is probably going with crelf's suggestion.

[Jeffrey Habets]

You certainly won't be able to get the 20kHz deterministically since the devices you mention are all programmed I/O.

I don't know about the capabilities of the counter/timer on those devices. (I do know that with the counters on an M-Series device it's pretty easy to generate the digital pulse signal you need.)

As Yair said, I would give NI a ring, they should know.

[ned]

QUOTE (Aaron L @ Jan 8 2009, 10:52 PM)

I've got the electronics for the stepper controller, so I don't need to generate the sequencing. I really just need 2 digital IO lines for direction and hold. Any one of the DIO boxes above can do that for me. But the one thing I need is something that can generate a slowish (up to 20kHz) clock to activate the stepping. I'd like to control the clock speed with a slider, basic labview stuff, really. Will any of those actually do that?

EDIT to remove incorrect information.

Those boards have a counter input but do not provide pulse generation. What you want is something like the PCI-6601, which provides digital IO and counter/timer channels with pulse generation outputs. A quick search on NI.com suggests that the least expensive USB device capable of pulse generation is the http://sine.ni.com/nips/cds/view/p/lang/en/nid/203189' target="_blank">USB-6221.

[AnalogKid2DigitalMan]

Use an analog ouput on the DAQ card and drive a voltage to frequency converter circuit.

-AK2DM

[crelf]

QUOTE (Aaron L @ Jan 8 2009, 10:52 PM)

I've got the electronics for the stepper controller, so I don't need to generate the sequencing. I really just need 2 digital IO lines for direction and hold. Any one of the DIO boxes above can do that for me. But the one thing I need is something that can generate a slowish (up to 20kHz) clock to activate the stepping.

Oh - okay. That makes it clearer.

QUOTE (ned @ Jan 9 2009, 08:28 AM)

What you want is something like the PCI-6601, which provides digital IO and counter/timer channels with pulse generation outputs.

Yep - like others have said, you don't want to try to do the 20kHz clock in software, which is what you'd have to do with the USB DAQ modules you listed. You want to choose a device that has the clock generator as a chip on the device where you set the initial variables, start the generation, then just adjust the variable that you're interested in. Because you want to adjust it using a FP slider, then you're not trying to adjust it very quickly, so ned's right - the 6221 would work great.

[Aaron L]

QUOTE (crelf @ Jan 9 2009, 07:40 AM)

Oh - okay. That makes it clearer.

Yep - like others have said, you don't want to try to do the 20kHz clock in software, which is what you'd have to do with the USB DAQ modules you listed. You want to choose a device that has the clock generator as a chip on the device where you set the initial variables, start the generation, then just adjust the variable that you're interested in. Because you want to adjust it using a FP slider, then you're not trying to adjust it very quickly, so ned's right - the 6221 would work great.

Thank you very much for the 6221 suggestion! I'll give NI a call and see what else is available. Working on a laptop does limit the options somewhat, like PCI cards and such, but it's good to see there is an USB alternative.