About sound reactive LED's with TIP31C

Discussion in 'General Electronics Chat' started by Janciius, Apr 14, 2012.

  1. Janciius

    Thread Starter New Member

    Apr 14, 2012
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    Hi my friends,
    I'm new in this forum. I wanted to ask. Yesterday I buyed TIP31C transistor, and connected all wires like in this scheme :
    http://www.google.lt/imgres?um=1&hl=...67&tx=72&ty=58
    So, I wanted to connect my LED strip (12v), which has 24LED's, to tip31C. So, it's working, but LED strip is not bright, like a connect it with 12v charger without any transistors. (That LED's strip bright not belong to high-volume, I tried to put high volume but that does not worked, led strip blinking is not bright).
    So, can someone help me? Maybe I must to use Tip31, not Tip31c?
    P.s I buyed tip31c from http://www.ebay.com/itm/2-x-TIP31C-T...item3a683f4dd1 Or maybe I need to use other scheme? Please help me, thanks. (I want to connect about 100 LED's, is this possible?)
    Sorry for my bad English
     
  2. chrisw1990

    Active Member

    Oct 22, 2011
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    the reason that works is the bass.. the DV level of the signal is high enough to turn the tip31 on. it doesnt matter 31c or 31. have you tried with 5 leds? you can try playing that video through your speakers and see if you get the same sort of response...:)
     
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  3. Janciius

    Thread Starter New Member

    Apr 14, 2012
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    So, this scheme i'ts just for 4 LED's? :)
     
  4. chrisw1990

    Active Member

    Oct 22, 2011
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    yes maybe dont know? the sound is for that transistor, my problem is the transistor, if you try your system using the same music, then you know it works.. my theory is, your trying to drive too many leds and theres not enough voltage, but if you test the tip first, then you know its too many leds.
     
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  5. Janciius

    Thread Starter New Member

    Apr 14, 2012
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    Thanks :) Maybe can you suggest me other scheme, where I can connect a about 5 LED strip, which are connected in 12v?
     
  6. chrisw1990

    Active Member

    Oct 22, 2011
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    5 leds should be fine? the video is with 5 leds? whats the forward voltage drop of your leds?
    if you say its 2.5v, the maximum number of leds you can have is supplyVoltage/Forward Voltage. (in this example 12/2.5 = 4.8, call it 4)
     
  7. Janciius

    Thread Starter New Member

    Apr 14, 2012
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    Sorry, i think you don't understanded what i say. I keep in mind, that i want to connect 5 strips, each of them have 24 leds. These leds are for car accumulator (12v) so, maybe you know any scheme for 12v led strip?
     
  8. chrisw1990

    Active Member

    Oct 22, 2011
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    yes. and im saying. try your tip31 set up. with normal leds. make sure its working. then try figure out why the strips arent.
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    The circuit is garbage. It was an Instructable posted (or copied) by a 10 years old kid who knows nothing about electronics:
    1) The transistor's base-emitter burns out and/or the stereo output feeding it also burns out because a current-limiting resistor at the input is missing.
    2) A protection diode is missing. The transistor is damaged when the input voltage swing is more than 5V peak (only 1.5W into 8 ohms) because its max allowed reverse voltage is only 5V.
    3) The LEDs burn out because they are also missing a current-limiting resistor.
     
  10. Janciius

    Thread Starter New Member

    Apr 14, 2012
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    Thanks a lot for you observation. Can you tell me other scheme, where I can use LED strips and TIP31?
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    Post the detailed datasheet for your LED strips.
     
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  12. Janciius

    Thread Starter New Member

    Apr 14, 2012
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  13. chrisw1990

    Active Member

    Oct 22, 2011
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    ahhh they arent series leds, theyre parallel groups of leds
     
  14. Janciius

    Thread Starter New Member

    Apr 14, 2012
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    Or maybe, can I use LPT port, to connect my LED strip? And with computer program (DiscoLitez) control that strips blinking. :)
     
  15. Audioguru

    New Member

    Dec 20, 2007
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    When you buy cheap LEDs on ebay then you get a bad Engrish description (the spelling is horrible) and NO datasheet. They don't even say how much current they use.

    Blue LEDs are about 3.5V and will burn out instantly when used with the 13.2V from a car. They might be connected in groups of 3 in series and in series with a current-limiting resistor.
     
  16. Janciius

    Thread Starter New Member

    Apr 14, 2012
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    I suppose you be right.
     
  17. Audioguru

    New Member

    Dec 20, 2007
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    Quote: "The weird thing about my audio source is I hooked in an adapter to give me a stereo jack and plugged in a pair of headphones and played a CD. The volume level through them was a very comfortable listening level. Is this typical of line level?"

    Line Level is designed to drive the input of a power amplifier that has an impedance of about 10k (ten thousand) ohms. Most headphones are only 32 ohms so are like a dead short.

    A headphones output is designed with a small power amplifier so it can drive low impedance headphones.

    A comfortable level on headphones is about 0.1V peak which is much too small to turn on a transistor. Loud sounds can be 1V or 2.5V peak.
     
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