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LED Light Box Troubleshoot

Discussion in 'LEDs and Optoelectronics' started by Desirae, May 10, 2012.

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  1. Desirae

    Desirae

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    May 10, 2012
    Ok, so I'm working on a sound reactive light box and I am having an issue. When I connect the negative light wire to either side pin on the TIP31, I get constant light, but nothing when it's attached to the center pin. I thought maybe it was a bad transistor, but I switched it out with the same results. There is something I am missing... Any ideas?
     

    Attached Files:

  2. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    Where did you get this circuit design? What is the theory of operation?
     
  3. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    What is the current requirements for that LED strip? Does it have a built in limiting resistor?
    The TIP31 seems like a lot of overkill to light LEDs unless they are high power. The TIP31 requires a lot of base drive to saturate it as the hFE is only 50 MAX and typically only 35. If this LED strip pulls under 100mA you'd be far better off with a 2N2222. They have an hFE>=235. The base should have a limiting resistor too and you should insure that the audio signal does not exceed -5V.
     
  4. Desirae

    Desirae

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    May 10, 2012
    12v and yes

    It lights up when the neg wire is on either side pin. Solid and bright, but is not sound reactive. The center pin produces nothing
     
    Last edited by a moderator: May 10, 2012
  5. Desirae

    Desirae

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    May 10, 2012
  6. KJ6EAD

    KJ6EAD

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    I'd advise you to use a real sound to light circuit design and stay far away from "destructables". You're risking serious damage to your stereo, MP3 player or whatever you're using to light up a few LEDs.

    I see the writer of that destructable hasn't responded to you or anyone else having difficulty with that "circuit".
     
    Last edited: May 10, 2012
  7. BobK

    BobK

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    What is the source of the sound? Perhaps the voltage is not high enough. It needs to be about 1V.

    Bob
     
  8. Desirae

    Desirae

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    May 10, 2012
    The audio source right now is my netbook, but ideally I'll hook it up to an ipod
     
  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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  10. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    That's because the Internet is rife with bad designs, that are designed by people that know about as much as the people building their stuff. ;)
     
  11. Desirae

    Desirae

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    May 10, 2012
    KJ6EAD- do you have a rec on a better design that is beginner/intermediate?
     
  12. Desirae

    Desirae

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    May 10, 2012
     
  13. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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  14. Desirae

    Desirae

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    May 10, 2012
  15. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
     
  16. Desirae

    Desirae

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    May 10, 2012
    Aaah! I'm sorry. Bear with me, I'm new at this. :)
    No just one long strip. I wasn't counting the LEDs in the drawing, there are 15, so 5 segments in all.The packaging says "built-in current limiting resistor, which protects the LED from reversed polarity" so I assumed the answer was yes.
     
  17. KJ6EAD

    KJ6EAD

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    Last edited: May 11, 2012
  18. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    OK, I read the sales data the link you posted. They say that their led strips can be cut at every 3 led cut point which they say is about 1" segments. If they're 3 led segments I think the circuit would look like this, which is a series parallel circuit. If anyone is familiar with these strips and thinks I'm mistaken please speak up.
     

    Attached Files:

  19. Desirae

    Desirae

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    May 10, 2012
    Sorry, to clarify, you mean replace the LEDs on the MK103 with a MOSFET and connect the strip via the transistor?
    Can I connect the MK103 to a 12v supply?
     
  20. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    Don't bother. Use the MK186. See my edited post above.
     
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