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Electret Mic to Drive Logic (Clap or Whistle)

Discussion in 'Electronic Basics' started by Ike, Nov 17, 2005.

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  1. Ike

    Ike Guest

    What is the easiest way to drive a logic high input pin on a
    microcontroller with an electret microphone?

    I want the microcontroller to be able to detect a clap or whistle or
    any spike in sound pressure. Sound quality and frequency are not
    important.

    The catch is that the circuit MUST run from a single 3v lithium CR2
    battery.

    The microcontroller is a 12F675 and it has an ADC, so I could use the
    ADC if it is not practical to get 2.5v to 5v for a digital input pin.
    But I think I still need to boost the electret's output for the pin to
    be able to detect a change.
     
  2. John Fields

    John Fields Guest

    ---
    View in Courier:


    +3V>-----+-----------+------+-------+
    | | | |
    [3k3] [1M] | |
    +----+ | | | |
    | |--+--[0.1µF]--+------|------|+\
    |MIC | | | | >--->Vout
    | |--+ | [1M]<---|-/TLV
    +----+ | [1M] | | 3701
    | | | |
    GND>-----+-----------+------+-------+----->GND

    The 3.3k resistor might have to be changed depending on the mic you
    use.

    With no sound into the mic, adjust the 1 meg pot until Vout goes
    high, (about 1/2 scale) then back off until Vout goes low. Then,
    with sound into the mic, adjust the pot for the sensitivity you
    want.
     
  3. Ike

    Ike Guest

    Hi John...

    Wow, I really appreciate your post with this circuit! This will work
    perfectly!

    I can't seem to find a TLV3701. TI lists it as obsolete, and I can't
    find a source at the standard outlets (Mouser, Newark, Jameco, etc.) or
    on Google. DigiKey lists them, but they don't have the PDIP as a stock
    item (I can't use SMD at this time).

    Is there another device that can be subbed?

    Thank you!
     
  4. John Fields

    John Fields Guest

     
  5. Ike

    Ike Guest

    Hi John...

    Excellent! Actually, when I searched for your reference to "TLV3702IP"
    I found the "TLV3701IP" which is not obsolete! I'm not sure how I
    missed that one. I have ordered samples from TI.

    Is there a way to achieve this functionality with transistors?

    Thank you!
     
  6. John Fields

    John Fields Guest

     
  7. Ike

    Ike Guest

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