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Thread: Output Current, PWM Freq, and Dither Freq

  1. #1
    Join Date
    Feb 2010
    Posts
    29

    Default Output Current, PWM Freq, and Dither Freq

    Using OUTPUT_CURRENT_CONTROL, there are certain combinations of PWM frequency and dither frequency that seem to result in causing the output to not turn on. What are the acceptable ranges of PWM frequency and dither frequency that are supported? What would cause the output to not turn on?

  2. #2
    Join Date
    May 2009
    Location
    Minneapolis, MN
    Posts
    300

    Default

    The range that will work for frequency is up to 2000 hz, don't do that though. The outputs are only rated up to 250 hz.

    If you look in the manual you will see how to calculate the frequency for dither frequency and amplitude based on the operating frequency.

  3. #3
    Join Date
    Feb 2010
    Posts
    29

    Default

    I just wanted to check I have found the correct reference:

    The manual states the dither frequency must be an integer part of the pwm frequency, which i take it means a integer factor of the pwm frequency? The manual suggests other dither values will cause the output to drift; however in my testing here it appears the outputs will simply stop working.

    so with a max pwm of 250, the largest supported superimposed dither is 125?

    I was not able to locate information on calculating dither value.

  4. #4
    Join Date
    May 2009
    Location
    Minneapolis, MN
    Posts
    300

    Default

    Not sure why you would want to run 125 dither. Even at 250 hz dither really isn't needed.

    This is the calculation from the manual:

    The dither frequency is 1/8 of the PWM frequency.
    The dither amplitude is 10 %.

    Its in the Hydraulic Library part of the manual.

  5. #5

    Default CR0032 output

    HI,
    I have been trying to supply current to Proportional valve with CR0032, and currently I am using the OCC FB, none of the application are successful.
    Glad if some hint / tips can be shared.
    Attached is my setup for your perusal.
    Thanks
    Attached Images Attached Images

  6. #6
    Join Date
    May 2009
    Location
    Minneapolis, MN
    Posts
    300

    Default

    For testing, remove the DITHER_FREQUENCY and the DITHER_VALUE.

    Everything else looks good. You can monitor the current with the OUTPUT_CURRENT function block.

    If you are still having issues you can try the PWM1000 to see if that works. Or you can just setup the output as digital to see if there is an issue with wiring.

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