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Unread 04-05-2008, 20:24
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Re: The 2009 Control System Q&A Thread

Quote:
Originally Posted by jhersh View Post
Also, with these PWM signals, not just the resolution is important, but also the range. This also needs to be a good fit for the devices you are controlling. In a test I did with one 322HD, the servo responded outside of its spec'd 0.9us to 2.1us range, which means the new control system's PWM signal can give you more range out of the servos than you could get previously.
Just FYI, as shown in that IFI post I linked, even the standard IFI signals range from .9ms to 2.1ms. And the user controlled ones could, in fact, be configured for nearly whatever range and resolution we liked. So this isn't actually an improvement, per se.
Quote:
Originally Posted by jhersh View Post
The encoders, pwm generators, etc are running at just over 150kHz on the FPGA. This means that any signal you have going in to or out of the NI-9403 should not have 2 transitions in the signal closer together than 6.625us. It's true that we would all like to be able to have faster transitions, but the trade-off for cost, space, and channel density seem like a good thing.
Erm. That was sarcasm. I'm fairly confident we won't actually be limited by the input frequency, especially given the current update rate of our motor controllers.
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