Converting 9VAC to DC

Discussion in 'General Electronics Chat' started by summersab, Jun 29, 2010.

  1. summersab

    Thread Starter Active Member

    Apr 8, 2010
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    First off, I'm a mechanical engineering graduate. It's been literally years since I've had an electrical class. Feel free to treat me like a bumbling moron.

    Second, I'm sure this issue has been covered before, but I can't find anything SPECIFIC. Perhaps I'm not using the right search terms . . .

    I'm modifying an alarm clock of mine. It is powered by a standard wall-wart type power supply with an input of 120VAC and an output of 9VAC @ 900mA. So far, I have been incorrectly assuming that the output was 9VDC - I've simply never seen a wall-wart that goes from AC-AC. My project requires 5VDC (though higher is fine - I already have circuitry in place to handle higher/unstable DC inputs using a Zener diode), and amps can be fairly low. How do I convert 9VAC to DC?

    Thanks!
     
  2. VoodooMojo

    Active Member

    Nov 28, 2009
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    [​IMG]
     
    Last edited: Jun 30, 2010
  3. ifixit

    Distinguished Member

    Nov 20, 2008
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    Hi Summersab,

    To expand on VoodooMojo's post see attachment.

    Good Luck,
    Ifixit
     
  4. VoodooMojo

    Active Member

    Nov 28, 2009
    503
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    [​IMG]
     
    Last edited: Jun 30, 2010
  5. summersab

    Thread Starter Active Member

    Apr 8, 2010
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  6. SgtWookie

    Expert

    Jul 17, 2007
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    Zener diodes won't provide decent regulation unless the current through them is fairly constant.

    If your circuits' current draw is low, and you take a 9v@900mA AC wall wart, you might be unpleasantly surprised at how much voltage you'll get out of it.

    Post your schematic as it exists now to establish a baseline, and so that we can get an idea of your power requirements.
     
  7. ifixit

    Distinguished Member

    Nov 20, 2008
    639
    108
    The 276-1152 should work, however, there is no data sheet to use to verify if temperature derating is required. I'm going to guess it would be okay at room temperature and soldered to a PCB.
     
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