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Adjustable frequency and duty cycle circuit .

Discussion in 'General Electronics Discussion' started by arg733, Feb 23, 2012.

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  1. arg733

    arg733

    89
    0
    Dec 14, 2010
    Hi
    I need an easy schematic for a pulse generator that i can adjust duty cycle ( 0% - 100% ) and frequency (1hz - 100khz or more) INDEPENDENTLY

    I tried several circuits using 555s but duty cycle was affecting frequency and vice-versa and i could not get it to 0% and 100% duty. I tried everything i could thing of, i don't know what else to do.
     
    Last edited: Feb 23, 2012
  2. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    You do realize that a 0% and 100% duty cycle is equivalent to 0Hz?
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    11,702
    2,717
    Nov 17, 2011
    jackorocko,
    you're right, of course, but that doesn't help, does it?

    Here is a description: http://www.edn.com/article/480947-Circuit_produces_variable_frequency_duty_cycle.php
    By the way: 0% and 100 % are ecluded explicitely, too.
    Unfortunately, the linked PDF and figures do not exist (at least I get an error message).

    An interesting circuit could be this: http://pdfserv.maxim-ic.com/en/ds/MAX038.pdf
    but it is limited to 15 % ... 85 % duty cycle.

    Another rather simple circuit is here: http://www.rmcybernetics.com/projects/DIY_Devices/homemade_signal_generator2.htm

    Google's your friend :)


    Harald
     
  4. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    No, but I am questioning why one needs a 0% to 100% duty cycle when they specify the need for a 1hz - 100khz freq. I guess what I was hinting at is are you sure you need 0% to 100% functionality and to what limits he could get away with? Didn't really see my post being that bad, but ok
     
  5. arg733

    arg733

    89
    0
    Dec 14, 2010
    Thanks

    Thanks for the quick reply.
    My original idea was to have a pot and trim it down to 0% (cutoff) but I can have a switch for this. So yes you are right, 0% and 100% is 0hz .
    I should be ok with 15%-85%
    Thank you very much.
     
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