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OpAmp oscillator circuit

Discussion in 'General Electronics Discussion' started by eng.abu_muslem, Mar 18, 2015.

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  1. eng.abu_muslem

    eng.abu_muslem

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    Apr 18, 2012
    Kindly help me!
    What is the problem in this design?
     

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  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Welcome to electronicspoint.

    Typically we work the other way round: you tell us what the problem is and we try to locate it.

    In this case, look closely at the power supply of U1:A and at R4. This is not correct. A correct circuit is shown here.

    Also note: there is no NE555 in your schematic, so I changed the title. This is also not a microprocessor circuit, so I will move the thread to another of our fora.

    Regards,
    Harald
     
  3. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Also look at U2, which appears to be installed backwards: the supply, Vcc, is connected to the output, pin 3, while the oscillator/amplifier circuit is trying to draw power from the input terminal, pin 1, of U2. D3 also appears to be installed backwards if the intent is supply power from Vcc to whatever the round thingy is (piezoelectric transducer? speaker? connector?)
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Good find, escaped me.
    It definitely is.

    I should have spent more time with the schematic ;)
     
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    No, Harold, the OP should have spent more time with the schematic. And perhaps explained what this circuit was supposed to do, if it actually worked. TWOFT to spend any more effort trying to "analyze" it.
     
    Arouse1973 likes this.
  6. davenn

    davenn Moderator

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    Sep 5, 2009
    x
     
  7. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Clarification: TWOFT = Total Waste Of Free Time
     
    Arouse1973 and davenn like this.
  8. davenn

    davenn Moderator

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    LOL wondered what that acronym was for
     
  9. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Hello
    This is how I think your oscillator circuit should look, operating from a single supply. I assume this is some kind of PWM circuit driver?
    Thanks
    Adam

    COMP_OSC.PNG
     
  10. davenn

    davenn Moderator

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    why would you have the "out" there ?
     
  11. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    PWM controller. The following stage samples the RC time constant triangle ish wave, so you can vary the pulse width. I guess that's what he is doing?
    Adam
     
  12. davenn

    davenn Moderator

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    no, why would you have the output coming off an input pin of the op-amp instead of the output pin ?

    (maybe Im missing something?)
     
  13. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    I think what Adam is saying is the following stage (which he didn't show) uses the triangleish wave across C1 to compare with a DC reference to create the PWM waveform... or sumthin' like that. What the heck is the round thingy the MOSFETs are trying to drive? Arrgh! I said I wouldn't waste anymore of my free time on this!
     
  14. davenn

    davenn Moderator

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    Sep 5, 2009
    Presumably the motor ??? haha
     
  15. davenn

    davenn Moderator

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    Sep 5, 2009
    rereading that comment from you
    I bet that diode is probably supposed to be in parallel with the ummm motor ?

    as you have said ... wired as it is that thingy aint gonna work ;)


    ohhh dear
     
  16. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Yep correct,cheers Hop. The circuit I drew what the correct way to draw his original oscillator circuit.
    Thanks
    Adam
     
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