HELP required for sound activated switch

Discussion in 'The Projects Forum' started by assuc, Oct 19, 2012.

  1. assuc

    Thread Starter Member

    Mar 23, 2012
    77
    1
    Assalam o alaikum,
    Guys i want some help regarding making a sound activated switch.
    Now first of all sound can be a clap, a whistle or me myself saying "Switch ON".
    Now what i have thought that i would need to implement a band pass filter according to the varying frequency of the input sound for instance take a clap now the clap has approx 2khz-3khz frequency according to what i have looked over the web.
    The basic idea for the ckt to work is when the input appears on the mic it will compare the voltage level and if it is the required level it will forward the input to d flip flop which in turns activates the ckt for instance starts the motor.
    NOW i want to know should i use the band pass filter to detect levels or should i directly use the comparator.
    Do provide the schematic or links related to it if anyone have it.

    REGARDS
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
    745
  3. assuc

    Thread Starter Member

    Mar 23, 2012
    77
    1
    can i test the ckt virtually? on proteus or related software?
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Why bother simulating the circuit?
    It will not be a reliable circuit because it responds to each half-cycle of sound frequencies. If you talk or if a dog barks then it will turn on and off and on and off many times with the frequency.

    It is too simple. It should have a peak detector that produces a single output with each sound burst.
     
  5. assuc

    Thread Starter Member

    Mar 23, 2012
    77
    1
    to build a ckt directly not suitable for me... and how a peak detector would work... means it would use a comparator to detect levels.... how many comparators are u talking about..?
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A peak detector uses a diode (a transistor or opamp can be added) to quickly charge a capacitor for each sound burst. The capacitor slowly discharges (one resistor determines the discharge speed) and its voltage drives a transistor that activates the motor.
     
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