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AC to DC quick question — Parallax Forums

AC to DC quick question

ArchiverArchiver Posts: 46,084
edited 2003-08-11 15:45 in General Discussion
Hi i have mic output i want to conver to DC so i can
read it with an A/D. The elec condensor mic connects
to a preamp with ~100 gain. I need to connect this to
an A/D. I was thinking i just need to add a Diode to
split the wave in half(top half). is this all i need?
i was also thinking of just taking this
kit(http://www.electronics123.com/amazon/datasheet/k126.pdf)
and using the first half of the kit(up to the second
op amp.). does that provide a linear DC voltage for
direct input to an A/D? that is what i need. please
reply ASAP i need this info so i can order tommorow.

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Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-08-09 16:28
    Hi Jack,

    I'm not sure what type of audio you're trying to
    monitor and sample with an A/D, but adding a diode
    and/or a rectification circuit would horribly distort
    the sound. What you sample would have phase problems
    and most likely wouldn't be anything coldse to your
    original signal.

    A very simple solution would to be build your own mic.
    By simply using a high-quality electrit mic element (a
    couple bucks), clean DC power supple (9V battery works
    too), and a 10K resistor would give you a good, clean,
    DC biased audio source. If you don't need great sound
    quality, even Radio Shack parts will work. If you need
    more sensitivity, an op-amp could be added to boost
    the signal before sampling.

    An op-amp could also be used to remove the AC coupling
    of your existing mic and feed your A/D, but this is a
    little more involved.

    If you're interested in schematics, send me your email
    address and I can send you some samples (in
    PowerPoint).

    Regards,
    Dr. Diode
    --- Jack Wu <wulabshoo@y...> wrote:
    > Hi i have mic output i want to conver to DC so i
    > can
    > read it with an A/D. The elec condensor mic
    > connects
    > to a preamp with ~100 gain. I need to connect this
    > to
    > an A/D. I was thinking i just need to add a Diode
    > to
    > split the wave in half(top half). is this all i
    > need?
    > i was also thinking of just taking this
    >
    kit(http://www.electronics123.com/amazon/datasheet/k126.pdf)
    > and using the first half of the kit(up to the second
    > op amp.). does that provide a linear DC voltage for
    > direct input to an A/D? that is what i need.
    > please
    > reply ASAP i need this info so i can order tommorow.
    >
    > __________________________________
    > Do you Yahoo!?
    > Yahoo! SiteBuilder - Free, easy-to-use web site
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    > Text in the Subject and Body of the message will be
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    >
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  • ArchiverArchiver Posts: 46,084
    edited 2003-08-11 15:45
    I don't understand why you would want to convert analog (audio) to dc to
    read with an A/D converter. An A/D converter is an analog to digital
    converter and will output a digital level of the supplied analog signal at
    the sample rate provided the applied signal is within the range of the A/D
    converter. In other words, it samples the signal supplied at a certain
    clock rate, and outputs a corresponding digital signal of that level on each
    clock pulse. A sine wave would output a level which increases (not
    linearly) to some peak reading and then decreases to some low level and then
    repeats. You just need to adjust the supplied analog signal to be within
    the range required by the A/D and to do that a resistive divider or op amp
    will suffice.

    jim
    http://www.geocities.com/jimforkin2003/


    Original Message
    From: PH [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=vuufB4_zcnxfsQLh9OxpDPCnFsI9ZSaXcOAt2EtMUDuXJw3Qbd6_fJbKZdN2ZjqULihiUn91lAtcEICCV3EM]drdiode2002@y...[/url
    Sent: Saturday, August 09, 2003 11:28 AM
    To: basicstamps@yahoogroups.com
    Subject: Re: [noparse][[/noparse]basicstamps] AC to DC quick question


    Hi Jack,

    I'm not sure what type of audio you're trying to
    monitor and sample with an A/D, but adding a diode
    and/or a rectification circuit would horribly distort
    the sound. What you sample would have phase problems
    and most likely wouldn't be anything coldse to your
    original signal.

    A very simple solution would to be build your own mic.
    By simply using a high-quality electrit mic element (a
    couple bucks), clean DC power supple (9V battery works
    too), and a 10K resistor would give you a good, clean,
    DC biased audio source. If you don't need great sound
    quality, even Radio Shack parts will work. If you need
    more sensitivity, an op-amp could be added to boost
    the signal before sampling.

    An op-amp could also be used to remove the AC coupling
    of your existing mic and feed your A/D, but this is a
    little more involved.

    If you're interested in schematics, send me your email
    address and I can send you some samples (in
    PowerPoint).

    Regards,
    Dr. Diode
    --- Jack Wu <wulabshoo@y...> wrote:
    > Hi i have mic output i want to conver to DC so i
    > can
    > read it with an A/D. The elec condensor mic
    > connects
    > to a preamp with ~100 gain. I need to connect this
    > to
    > an A/D. I was thinking i just need to add a Diode
    > to
    > split the wave in half(top half). is this all i
    > need?
    > i was also thinking of just taking this
    >
    kit(http://www.electronics123.com/amazon/datasheet/k126.pdf)
    > and using the first half of the kit(up to the second
    > op amp.). does that provide a linear DC voltage for
    > direct input to an A/D? that is what i need.
    > please
    > reply ASAP i need this info so i can order tommorow.
    >
    > __________________________________
    > Do you Yahoo!?
    > Yahoo! SiteBuilder - Free, easy-to-use web site
    > design software
    > http://sitebuilder.yahoo.com
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed.
    > Text in the Subject and Body of the message will be
    > ignored.
    >
    >
    > Your use of Yahoo! Groups is subject to
    > http://docs.yahoo.com/info/terms/
    >
    >


    __________________________________
    Do you Yahoo!?
    Yahoo! SiteBuilder - Free, easy-to-use web site design software
    http://sitebuilder.yahoo.com

    To UNSUBSCRIBE, just send mail to:
    basicstamps-unsubscribe@yahoogroups.com
    from the same email address that you subscribed. Text in the Subject and
    Body of the message will be ignored.


    Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
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