Problems regarding Oscillator design..

Discussion in 'The Projects Forum' started by Laguna, Apr 1, 2010.

  1. Laguna

    Thread Starter New Member

    Apr 1, 2010
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    Hi all
    I am dealing with some problem here.

    Regarding the attachment below..

    I can't seems to get a triangular wave..

    May i know whats the problem I'm facing?
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    The problem is that Multisim does not know if it is coming or going.

    The integration capacitor is supposed to charge and discharge with ramps but your schematic has a ramp in only one direction.

    Since the 555 does not produce a perfect square-wave (its timing is 5 periods positive then 4 periods to ground) then the triangle-wave will be only negative with the ramps at 5 periods and 4 periods.
     
  3. Laguna

    Thread Starter New Member

    Apr 1, 2010
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    Thanks for replying
    So what kind of modification should i do on my circuit?
    Is there anything to correct it?
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    A 555 needs a trimpot and two diodes to allow you to adjust its duty-cycle so its output is a perfect square-wave. Then the output of the intergrator will be triangle waves.

    I use an opamp as a Schmitt trigger to make the square-waves that feed an integrator.
     
  5. Laguna

    Thread Starter New Member

    Apr 1, 2010
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    Do u mean that the [​IMG]Schmitt Trigger is connected to output of the 555 to get a 50% duty cycle of square wave?
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    No.
    Get rid of the high current non-square-wave 555 and replace it with a symmetrical opamp (like an MC33171 or MC34071) Schmitt trigger instead. When the triangle wave's voltage gets high enough then it switches. When the triangle wave voltage gets low enough then it switches in the other direction. Then the triangle wave is perfect.
     
  7. Laguna

    Thread Starter New Member

    Apr 1, 2010
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    Did you have any example on it?
    I had read through an old post http://forum.allaboutcircuits.com/showthread.php?t=12405

    which my aim is similar like his..

    My goal now is to generate a square wave and change it to triangular wave and from triangular wave change to sine wave..
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    If you filter a square-wave or triangle-wave well enough then the output is a sine-wave. You don't need a triangle-wave.
    A 4th-order or 8th-order switched capacitor lowpass filter IC has very low distortion when fed a square-wave.
     
  9. Laguna

    Thread Starter New Member

    Apr 1, 2010
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    Alright man, thanks for your information =)
     
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