Help with wien bridge diagram

Discussion in 'The Projects Forum' started by hadoque, Jul 24, 2007.

  1. hadoque

    Thread Starter Member

    Jul 24, 2007
    10
    0
    Hi
    I'm very new to electronics, and I thought a fitting first project would be a Wien-bridge oscillator. Since I have a lm386 amplifier lying around, I thought I'd use the circuit discribed in the datasheet of this component (attached, see page 5). Now I have some questions about this diagram.
    What kind of component is the round thing marked "ELDEMA CF-S-2158"?
    What is R_{L}, V_{S} and V_{O}?
    What is the "Bypass"? What voltage should I use and where do i connect the output (speaker or whatever)?

    Many thanks for help with answering these probably simple questions.
     
  2. hadoque

    Thread Starter Member

    Jul 24, 2007
    10
    0
    Forgot the attachement...
     
  3. hgmjr

    Moderator

    Jan 28, 2005
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    The round thing is a light bulb. It is used in this application because it exihibits negative resistance.

    Vs is the positive power supply input.

    Vo is the output of the oscillator.

    hgmjr
     
  4. hadoque

    Thread Starter Member

    Jul 24, 2007
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    ok, thanks
    what kind of bulb can I use? The specified bulb seems to be hard to get, aswell as any bulb with the 3V 15mA specs. Can I use a bulb with higher voltage or higher current?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    Mouser carries lamps and has no minimum order. It is possible to substitute bulbs with different ratings by experiment. The filament voltage should be no more than about 15, and the rated current should be no more than 40 ma. You just have to find a resistor for the feedback that works with the bulb, using more current - smaller resistor as the basis.
     
  7. hadoque

    Thread Starter Member

    Jul 24, 2007
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    I live in Sweden, so I'd rather not order from the US. I found 3V 10mA bulb in sweden though, do you think that might work?
     
  8. hadoque

    Thread Starter Member

    Jul 24, 2007
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    Thanks for the help everyone. Here are some images of the final construction, it's working perfectly.
     
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  9. DanRilley

    Senior Member

    Jan 13, 2008
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    This post is real old but maybe the poster still reads. Where do you buy bulbs from in Sweden? I'm also here and looking to complete the same project.
     
  10. t06afre

    AAC Fanatic!

    May 11, 2009
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