Audio - Auto Detection of Line In / Mic In

Discussion in 'General Electronics Chat' started by csumod, Feb 6, 2009.

  1. csumod

    Thread Starter New Member

    Feb 6, 2009
    Hi All,
    My project needs auto detect requirement for distinguishing Line In or MIc In after the audio equipments has been connected. Please let me know how it can be done.
    Sumod C.
  2. italo

    New Member

    Nov 20, 2005
    the jack when not in use is shorted when you plug it in it opens. that can be detected and light a LED.
  3. Externet

    AAC Fanatic!

    Nov 29, 2005
    Distinguishing or self adjusting to any ?

    It would be detecting/reading the self-setting condition of an automatic volume control circuit. But that would not work moments when input is silent.

    AudioPrecision test equipment has autoscaling. Some multimeters too. Try an autoscaling circuit, and read its status.

  4. csumod

    Thread Starter New Member

    Feb 6, 2009
    Thanks for the quick reply, my requirement is to distinguish whether the connected device to be treated as Line in or Mic in through a 3.5mm connector
  5. flat5

    Active Member

    Nov 13, 2008
    Line in is usually 10k ohms, I think.
    Mic in will be much lower for dynamic or electret mic.
    For electret mic input there very often will be a voltage available to power the mic. You could detect this.

    Good luck.
  6. Externet

    AAC Fanatic!

    Nov 29, 2005
    ????? :(:(:(
  7. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    My local TV station has a circuit that automatically adjusts sound volume to the signal's level.
    When a new picture occurs the audio gain is maximum for about 1 second then it drops to normal sound. It is deafening.
  8. Søren

    Senior Member

    Sep 2, 2006

    That might be a better solution than just checking the amplituide, since you won't know if you have a line in until the signal gets positively above a certain level for a short time (longer than any possible transient). And if the level goes down, it will up the gain once more... Bad solution.
    It has to be quite a clever design to give a high quality on both mic and line level signals.
    I'm much more in favour of a switch - possibly one that defaults to line in level.
  9. csumod

    Thread Starter New Member

    Feb 6, 2009
    I did some search on the net. I found Universal Audio Jack and Jack Sensing performs the need I require. But Iam not sure how to implement.
    Please any body let me know regarding these technologies. I also learnt Jack Sensing works on Impedance sensing.