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Thread: Duty Cycle vs. Freq?

  1. #1
    Join Date
    Aug 2010
    Posts
    14

    Duty Cycle vs. Freq?

    Hello,

    On a PWM, is Duty Cycle and Freq the same?

    What is the general rule for the best Freq setting of a PWM?

    Looking forward to your answer!
    Have a Great Day!

  2. #2
    Join Date
    Nov 2008
    Posts
    126
    Duty cycle refers to the on and off time of the pwm. So basically it controls the amperage of the cell up and down. Freq is debatable, I have never seen an increase in efficiency by changing the freq. So there is no real magic freq number, just play with it up and down and if you get better results from a specific freq then let us know.

  3. #3
    Join Date
    Nov 2009
    Location
    Bradenton, Florida
    Posts
    201
    Keith is correct about duty cycle being percentage of time the PWM is passing current to the cell (on and off). Frequency is how often that switching occurs, usually rated in MHz. I agree that I have not seen any changes in HHO output at different frequencies, but some claim there is a sweat spot for every cell -- perhaps I've just never been able to find it.

    Having said that, being able to control the frequency does have some advantages. 500 MHz is normally the preset frequency with the PWMs I used. Sometime they produce radio interference -- I've even seen it effect digital or electronic gauges (MPH & RPM). Changing the frequency will usually stop this problem. Keep in mind that running at very high frequency can cause the switching mosfats to run hotter as they don't have enough "off" time to cool properly.
    1991 Plymouth Acclaim 3L V6.
    1 dry cells with nineteen 6"x8" 316L ss plates, driven by constant current PWM set at 35 amps (13.3V at PWM). 28% KOH electrolyte. Total measured output 2.5 lpm. Mileage went from 18 to 26 mpg, all city driving (44% increase). EFIE set at .370 and I still need to play with ignition timing.

  4. #4
    Join Date
    Feb 2011
    Posts
    2

    John Kanzius

    When John Kanzius turned water into fire he was using 13.561 MHz. I think this frequency is best for splitting water. The Hebrew word for water begins with the letter mem which is the 13th letter in Hebrew. Interestingly 13.56 MHz is quite popular for rfid tags so it should be inexpensive to purchase devices for generating this frequency. I'd like to see an HHO generator use vertical discs inside a container of water that are free to spin kind of like a Tesla turbine. One disc positive and the next disc negative. Also dissimilar metals to take advantage of dielectric properties. As the disc spins it is easier to slough off the bubbles. The spinning action could turn a motor to help generate some of the electricity needed for splitting. Also the discs disrupted a magnetic field they could produce electricity. Just my theories. I haven't done any practical research yet.

  5. #5
    Join Date
    Feb 2011
    Posts
    2
    Quote Originally Posted by willie333 View Post
    When John Kanzius turned water into fire he was using 13.561 MHz. I think this frequency is best for splitting water. The Hebrew word for water begins with the letter mem which is the 13th letter in Hebrew. Interestingly 13.56 MHz is quite popular for rfid tags so it should be inexpensive to purchase devices for generating this frequency. I'd like to see an HHO generator use vertical discs inside a container of water that are free to spin kind of like a Tesla turbine. One disc positive and the next disc negative. Also dissimilar metals to take advantage of dielectric properties. As the disc spins it is easier to slough off the bubbles. The spinning action could turn a motor to help generate some of the electricity needed for splitting. Also the discs disrupted a magnetic field they could produce electricity. Just my theories. I haven't done any practical research yet.
    OOps I meant galvanic not dielectric.

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