Duty cycle to frequency

Discussion in 'General Electronics Chat' started by Tobias, Jul 20, 2011.

  1. Tobias

    Thread Starter Active Member

    May 19, 2008
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    I need to measure an incoming PWM and convert it to a specific frequency.
    460hz/1% duty cycle.

    I am going the PIC route now. I am learning about how to config the timers to get a frequency. I am getting there but curious if there are other options to this project.
     
  2. tom66

    Senior Member

    May 9, 2009
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    You could divide the frequency by two. This would give you 230 Hz at 50% duty which is much easier to measure using a small microcontroller.
     
  3. Tobias

    Thread Starter Active Member

    May 19, 2008
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    I should clarify the incoming PWM is operating at a fixed 1000hz too.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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  5. tom66

    Senior Member

    May 9, 2009
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    So you want to convert the 1kHz to 460 Hz?
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    If I understand OP correctly, the idea is to take a PWM input signal of 0-100% and convert it to a variable frequency AC signal of 0-460Hz
     
  7. tom66

    Senior Member

    May 9, 2009
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    Voltage to frequency converter?

    (With voltage being the result of the PWM being filtered.)

    Problem is, I know no V-F converters that go down to 0 Hz... most are 10 or 1 Hz.
     
  8. Tobias

    Thread Starter Active Member

    May 19, 2008
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    Incoming PWM is 1000hz.
    I want to equate the duty cycle of the PWM into a frequency.
    For every 1% duty cycle is 460 hz.
    So 1% is 460 hz
    50% is 23000
    100% is 46000

    I am not stuck with the mentioned calibration.
     
  9. Tobias

    Thread Starter Active Member

    May 19, 2008
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    I was thinking the V-F route, yet the amplitude of the PWM might vary with battery level.


     
  10. strantor

    AAC Fanatic!

    Oct 3, 2010
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    wait, so you are trying to accomplish this with a PIC? IE have the pwm signal go into the pic, pic reads the duty cycle, then pic outputs the frequency?
    so are you looking for code?
     
  11. Tobias

    Thread Starter Active Member

    May 19, 2008
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    I am getting closer and closer with a PIC, I am just wondering if I am missing some other option.
     
  12. tom66

    Senior Member

    May 9, 2009
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    If you use a comparator or a logic buffer (two logic inverters in series) then the amplitude will stay constant no matter what the battery voltage is.
     
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