Phase Shift Oscillator

Discussion in 'General Electronics Chat' started by traitorousdevil, May 29, 2010.

  1. traitorousdevil

    Thread Starter New Member

    May 24, 2010
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    Hi...
    According to the attachment, I'm wondering... If I would just want the phase to be shifted 120 degree only, is it that possible with I'm using 2 pair of RC?

    If it is possible, what will be the value of both pair of RC pair? Is that can be calculate through any calculation or...? The output frequency I wish to get is just 50Hz which is similar with my input frequency as well...

    Thanks... =)
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Jim,
    You seem to be working pretty hard on this.

    What's your ultimate goal? A 3-phase output?

    It would help us a lot to help you more quickly if we know for sure what you need.

    Phase shifting by a given amount of degrees is usually easier if it's done in a loop.
     
  3. traitorousdevil

    Thread Starter New Member

    May 24, 2010
    15
    0
    Yupz... The 3 phase output with each 120 degree phase shift...
    I'm trying combining 3 phase shift oscillator to convert the single phase to 3 phase... Although I'm not sure would it work... =P

    I have a confusion here... Where is the input for the oscillator in previous post's attachment? I have been searching lots of phase shift oscillator circuit but none of them shown the position of input signal should be...
     
  4. traitorousdevil

    Thread Starter New Member

    May 24, 2010
    15
    0
    I have done my circuit~! But there's some problem...
    As shown in attachment, my output voltage is damn low... what changes can i make 2 increase the output voltage... Also, the 3 output have different voltage... Any ways to make 3 of them have similar voltage range? * 0v-20V

    Next, that's the problem for my 3rd output... Why is my output like being clamp and move up apart from the previous? Arghhh~! How I'm gonna fix it?

    Lastly, how do i count whether my output waveform is that 120 degree? =P

    Thanks...

    **Hope the attachment is clear enough for you guys... =)
     
  5. Norfindel

    Active Member

    Mar 6, 2008
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  6. Audioguru

    New Member

    Dec 20, 2007
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    An oscillator starts oscillating from the noise in its components being amplified.
    An oscillator does not have an input signal.

    The first phase-shift oscillator needs a voltage gain of about 29 or 30 from its transistor.
     
  7. anany387

    New Member

    Feb 23, 2014
    1
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    i also want to make this project of single phase to 3 phase conversion for operating a three phase motor...plzz help me...send details to anany387@gmail.com....i will be highly obliged..regards
     
  8. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,234
    Here's a circuit to generate the second and third phase from a single phase signal using op amp all-pass filters. All-pass filters have a constant amplitude with frequency but can change the signal phase anywhere from 0 to plus 180° (capacitor in series) or minus 180° (capacitor to ground). The RC values to give 120° and 240° are shown for a 400Hz signal but you can adjust them for any frequency you need. For 50Hz, increase the RC time-constants by a factor of 8.

    3  Phase.gif
     
  9. tcmtech

    Well-Known Member

    Nov 4, 2013
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  10. LvW

    Active Member

    Jun 13, 2013
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    As already mentioned: An oscillator has no signal input. It creates the signal by self-excitation.

    As to the three-phase oscillator: For my opinion, a modified BUBBA oscillator (to be found via google) with three instead of four passive RC sections would be a good, simple and reliable solution.
     
  11. t06afre

    AAC Fanatic!

    May 11, 2009
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    This thread is about 4 years old people:rolleyes:
     
  12. tcmtech

    Well-Known Member

    Nov 4, 2013
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    but post #7 came in today so I answered todays question. ;)
     
  13. LvW

    Active Member

    Jun 13, 2013
    674
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    Wow - I didn`t notice.
     
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