Problem with a mic for a clap switch

Discussion in 'The Projects Forum' started by Melawrghk, Sep 9, 2010.

  1. Melawrghk

    Thread Starter New Member

    Sep 9, 2010
    5
    0
    Hello everyone,

    I'm building the circuit here: http://www.electronicsforu.com/efylinux/circuit/may2003/ci4-clap.pdf

    I started building it without the mic and simulated a mic with a piece of wire (short circuit vs open circuit) - everything seems to work after a fix up of the Decade counter circuit.
    I then bought several condenser mics and tried it with them, but I can't get a response if I clap (or any sort of response).
    Currently this is one of the mics I have: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=102-1732-ND

    The voltage drop across it is about 8V.

    Does anyone have any suggestions as to what I should try? Another mic? Thanks in advance!
     
  2. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    605
    24
    Are you sure you have the polarity correct?
     
  3. Melawrghk

    Thread Starter New Member

    Sep 9, 2010
    5
    0
    Pretty sure. Red wire +, black is ground. I've tried switching them, but I didn't notice any response either.
     
  4. Dyslexicbloke

    Active Member

    Sep 4, 2010
    420
    19
    Asuming the polarity IS correct, which would have been my first question too.

    Try increesing the 3.3k, quite a bit I would expect, and reduce / remove the 4.7K to test.

    Once you have a pulse, of some sort, on the transistor base add back seriese resistance before the cap to slow things down a little.

    (I would be working by experimentation here due to lack of knolidge,
    Sorry I cant be more spaciffic.)
     
  5. Dyslexicbloke

    Active Member

    Sep 4, 2010
    420
    19
    The mike datasheet, link from your link, recomends 2V bias 'standard'.
    It also states operating current of 500uA!!
    You need to redesign the input stage, it will not be sensative enough as is, considder a buffer amp, freferably FET inputs. (Also see datasheet test circuit) should be simple with modern opamp or a FET perhaps?
    Al
     
    Last edited: Sep 10, 2010
Loading...