simple Sound pressure level meter

Discussion in 'The Projects Forum' started by engy, Jun 19, 2009.

  1. engy

    Thread Starter New Member

    Mar 27, 2009
    7
    0
    i have some problems with operating the microphone . . .
    here's the schematic i want to know whether it's right or not ? ? ? ?
    and the true connections of the mic. because the circuit didn't work yet :(
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    282
    Do you have an "EM-80 electric mic"? The circuit is made to use the characteristics of that device to produce know (or predictable) levels of output.
     
  3. engy

    Thread Starter New Member

    Mar 27, 2009
    7
    0
    no , i didn't find it , i bought the standard mic that's available, what can i do to make this mic match the circuit
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    I fear it's the other way around. If you can find the performance characteristic of the EM-80, and the same for the mic you have in hand, then you may be able to analyze the circuit and make the changes that let it function with your mic.

    There are several types of microphone available, and the label "EM-80" gives no clue as to the type it was. There is no low voltage out, so it may not have been an electret type - but I used to have some that had batteries to bias the element. It's almost certain that the EM-80 is not the same type as your "standard" type.
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    Of course the microphone is an electret type because it is biased.
    The circuit will work with any two-wires electret mic.
    The mic will not work if its polarity is connected backwards. The pin connected to its case is supposed to connect to ground and the other pin is its output.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    I looked right at and did not see that 3.3K bias resistor. Good thing someone else reads these things.
     
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