Dither in PWM

Discussion in 'The Projects Forum' started by manuatl, Sep 25, 2015.

  1. manuatl

    Thread Starter New Member

    Sep 25, 2015
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    0
    Hi,
    Can any one please share some useful document on adding dither to PWM, for proportional control valve.

    Rgrds,
    Manu
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    I assume the dither would be just to add a small AC signal to the DC control signal value going to the PWM modulator.
    Where did you read about adding "dither" to the valve signal?
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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  4. BR-549

    Well-Known Member

    Sep 22, 2013
    1,986
    388
    mcgyvr, thanks for that first sheet. I bought that board, but haven’t started on it yet. The manual has 1700+ pages.

    I read those other links.

    I know nothing on this, but if the TS didn’t want the software solution, could one separately pwm the other end of the solenoid for dither?

    Both pwms would be independent and adjustable.
     
  5. dannyf

    Well-Known Member

    Sep 13, 2015
    1,792
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    If you were to run your PWM at 4/256 duty cycle 50% of the time, and then 5/256 duty cycle another 50% of the time, you have effectively had a 4.5/256 or 8/512 duty cycle -> dithering.

    Algorithms that accumulate historic errors (PID for example) are inherently dithering.
     
  6. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    Back around y2k, I managed to run the 10 bit pwm on the PIC16C774 at 14 bits/20khz using this technique.
     
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