Single LED Audio Signal Monitor

Discussion in 'The Projects Forum' started by sylas, Aug 8, 2007.

  1. sylas

    Thread Starter New Member

    Aug 8, 2007
    2
    0
    I am trying to accomplish the following and honestly have very little clue as to how to accomplish it.

    Project goal:
    Use the speaker (audio/AC) signal from a bluetooth headset to illuminate a single LED when a signal is preset. Preferably pulsing with the signal and possibly with adjustable sensitivity.

    Considerations:
    Size and power. Physical dimensions need to be as small as possible. Power source needs to be 3V or less, hopefully using button-type cells. Another consideration is that there is now only one good electronics supply house left in town. The easiest way for me to obtain parts in a timely manner is good 'ol Radio Shack.

    Intended use:
    I have a radar detector audio output connected to a bluetooth transmitter. I use a bluetooth receiver/speaker/mic headset especially designed for motorcycle helmet applications. The speaker volume is considerably louder then most cell phone or audio bluetooth headsets. I would like a visual indicator in the helmet as well. I do not want to attempt to modify any of the internals of the bluetooth transceiver, including tapping it for power. I would like the visual indicator circuit to be self contained for mounting inside the helmet or on the headset connector.

    I hope this explains my needs clearly. I can solder, read schematics, and have a solid 12V electrical background. Unfortunately as professional 12V tech I always left the electronics repair and troubleshooting to the bench techs and never gained (or forgot) most basic electronics knowledge.

    Any help would be greatly appreciated!
     
  2. sylas

    Thread Starter New Member

    Aug 8, 2007
    2
    0
    I am wondering if this thread is not showing up or if I wrote the initial post in the language that my twin and I made up as children and only we understand?
     
  3. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    The simplest thing I can think of, if I understand you correctly and without using any powered device such as an op amp, is in the attached. However, the input signal will need to be in the range of +3vpk audio-in to the circuit.

    This is not expensive or difficult to build, so you can experiment and see if it fit your needs.
     
  4. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    An additional thought: the circuit as shown has a standard 20mA LED, but if you use a low-power LED specifically designed to operate at 2mA, with a 680 ohm resistor, it will place less strain on the batteries (assuming that is the power source).
     
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