sound activated led

Discussion in 'The Projects Forum' started by sharpy, Aug 7, 2010.

  1. sharpy

    Thread Starter Member

    Aug 7, 2010
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    Hoping this is faily simple, I want the build a simple circuit to test an audio output.

    Upon any audio being detected I want the LED to light, fairly simple I hope! I am going to plug this into a headphones output.

    Im a bit of a novice at this, would appricate any help including circuit diagrams, components etc... I can manage the soldering, just [​IMG]


    thanks
    sharpy
     
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
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    At what audio level do you want the led to turn on, and what is the impedance of the headphone output ?
     
  3. sharpy

    Thread Starter Member

    Aug 7, 2010
    10
    0
    approx 60 ohms for the headphones (would happen if this was too low or high? )
    the sounds are from 20dB to 100dB

    does this info help?

    thanks for the reply
     
    Last edited: Aug 7, 2010
  4. Externet

    AAC Fanatic!

    Nov 29, 2005
    758
    57
    Try TWO same color leds connected together in counterparallel to the earphone jack, with no series limiter resistor and be gentle with the volume control until they lit up.
    Red, orange, yellow, green, blue leds will lit up correspondingly in the range from -1 dBu to +4 dBu or 2 to 3.5 Vpp.
     
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    Not all headphone jacks put out a ton of power, you may need to add a simple buffer circuit using an op amp or transistors. A TL082 op-amp IC would be ideal for this and the circuit woud be a snap to build since the TL082 operates as single or dual supply.

    Still haven't figure out how to upload pix jhere, or do you just link to something you've put on some webspace?
     
  6. sharpy

    Thread Starter Member

    Aug 7, 2010
    10
    0
    counterparallel, sorry being really dim what do you mean?

    any pics or circuit diagrams re op amps would also be useful, will try the two leds today.
     
  7. Externet

    AAC Fanatic!

    Nov 29, 2005
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    Leds in counterparallel :

    A-------------------------|>|------------------------------B
    A-------------------------|<|------------------------------B

    Both A together to your audio signal; both B to ground
    For stereo, you would need another set, one for L; one for R.
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    I have not had a chance to test this idea, but it is something I came up for my LEDs, 555s, Flashers, and Light Chasers article.

    It is something I've been rewriting forever it seems.

    [​IMG]

    R2 sets the minimum level. The idea is this is a flame simulator. I'm planning on using an AM radio.

    .
     
  9. sharpy

    Thread Starter Member

    Aug 7, 2010
    10
    0

    thanks for this, will do some testing tomorrow
     
  10. sharpy

    Thread Starter Member

    Aug 7, 2010
    10
    0

    hi, a few questions

    what component is q1?
    i guess i connect the audio out to the + side of c1?
    and the opp side of r2 and q1 is the 9v battery?
    does the circuit need a ground from the headphone output too?

    thanks
    sharpy
     
  11. Ghar

    Active Member

    Mar 8, 2010
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    There's a paper clip icon in the bar above your post when you go into "advanced" posting mode.
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    Ground is a common lead as well as the negative connection for the battery. This is pretty much a universal electronic convention.

    Q1 is pretty much any conventional NPN transistor. I tend to use a 2N2222A, but it isn't that important.

    Your real problem is mono jacks vs. stereo. You going to have to figure out what you need to do on your side.

    Since you didn't fill out your local on the profile we can only guess what kind of parts you have access to, this is one of the reasons you see us do it.

    You can attach pictures as part of the post, or you can use the albums section AAC offers.

    How to Display Attachments Full Size
     
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