555 Triangle wave PWM

Discussion in 'The Projects Forum' started by iONic, Aug 3, 2008.

  1. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    I'd like to design a PWM with a sawtooth wave output, the on time being half the off time with variable output. Would anybody have any ideas on how to accomplish this?

    Thanks
     
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  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    You could do this with a triggerable sawtooth generator, like the ones used in an oscilloscope.

    Greetings,
    Bertus
     
  3. iONic

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    Nov 16, 2007
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    Maybe Something like these???
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The right one from the first dwawing, you can convert to a one shot.
    This can be done by taking pin 2 free and give startpulses on it.

    Greetings,
    Bertus
     
  5. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    Or better yet, what about this?
     
    Last edited: Aug 3, 2008
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Do you mean a waveform like this? This is the result of a simulation of a circuit I designed.
     
  7. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    Yes, this is what I was initially looking for, but thought that the capacitive charge curve would be the kindest for the purposes of charging a 1,5V battery with a PWM scheme.
     
  8. reymund

    Member

    Sep 23, 2008
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    yes, can i do this using a 555 timer ic???...
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Pin 5 on a 555 is a neat VCO input if look at correctly, then work from there. Something like the function generator I was working on only using pin 5 as a input.

    http://forum.allaboutcircuits.com/showthread.php?t=12405

    There would be some interesting problems though, amplitude change is one of them.
     
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