Help with music sensitive LEDs

Discussion in 'The Projects Forum' started by LFOtrumpeteer, Dec 7, 2012.

  1. LFOtrumpeteer

    Thread Starter New Member

    Dec 7, 2012
    This is my first time attempting any sort of circuitry and have run into some complications. I am attempting to create a series of LEDs that pulse in time with music. I am doing this with a TIP31 transistor. I followed the tutorial I found on this to the best of my ability and knowledge. However, when I plug in the circuit and start the music, the LEDs do not flash or even turn on. I have attached a very simple sketch of what I have done. If anyone is willing to tell me what I have done wrong it would be much appreciated, and I am more than willing to answer questions.
    Circut setup.png
  2. MrChips


    Oct 2, 2009
    You have two problems.

    1) You are likely to blow your LEDs because you do not show a resistor to limit the current.

    2) The voltage from your music source is probably not loud enough to turn on the transistor. You need to amplify the signal first before applying it to the transistor.
  3. LFOtrumpeteer

    Thread Starter New Member

    Dec 7, 2012
    Thank you for clearing that up. Do you have any suggestions on what specific parts I would need and an estimate of cost?
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
    Google "color organ" or "sound to light". Ignore any results with the word "instructables". This is your best avenue to success and the continued functioning of your music source.

    The Velleman kit MK103 is one example and the schematic is published with the other kit documents.
    #12 likes this.
  5. absf

    Senior Member

    Dec 29, 2010
  6. Audioguru


    Dec 20, 2007
    The transistor does not have a base current-limiting resistor so the transistor and maybe the stereo amplifier will blow up if driven from an amplifier.
    The transistor does not have a diode to prevent excessive reverse emitter-base voltage that might damage the transistor and amplifier.

    I think that is the Instructable that was designed by a little 10 years old kid who knows NOTHING about electronics.
    absf likes this.
  7. bertus


    Apr 5, 2008
  8. sheldons

    Well-Known Member

    Oct 26, 2011
    you could try this simple circuit