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RGB LEDs dancing on music problem

Discussion in 'LEDs and Optoelectronics' started by Andrei Bului, Dec 20, 2016.

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  1. Andrei Bului

    Andrei Bului

    3
    0
    Dec 20, 2016
    Hi. I am new on this forum but I would really appreciate some help on this one.
    So basically I have this RGB LED controller that has a switch that switches between them being ON ( connected directly to ground ) and them dancing on music. It's just a transistor getting input to it's base from the sound input. I have 2 channels. Left and Right. The other jack is just for having a in-built spliter so I can connect some speakers to it and easier access to the Right channel. The transistor type is a TIP31C ( thus the base and collector being inversed ) and the Op-Amp is a LM386 and i marked the pins for you. The pin 1 and 8 are used only for gain which I don't care about and the 7-th pin is for bypass. I forgot to add a 220uF capacitor between the Vout's and the Stereo potentimeter which controls the reactivity of the LEDs to the music.
    Now what's not working:
    I've made this circuit before, a little bit modified ( Had only one channel ) and it worked. When I had the LEDs connected they where shining dimly. As soon as I connected a male jack into the female jack they went off completely and when I started the music, everything went fine. The LEDs were blinking properly on the music. I tried to redo the circuit step by step by adding the other channel and nothing is working anymore. When I switch to "music mode" they go off ( they dont shine dimly anymore ) and when I connect the male jack nothing happens, when I input music, also nothing happens. NOTE: My phone doesn't show the headphone in symbol if I have voltage in the circuit and the phone connected to it. If I turn the voltage ( the circuit ) off it shows me that it is connected. So is it something wrong with my circuit? Is something connected the way it should not be? I want to note that this circuit is made by me.I tried to draw it :
    [​IMG]
    And included a schematic: New.png
    I hope I included enough details and I also hope that I will find help on this forum. Please, I really need it to work!
    Thanks in advance and if more information is needed ask and I will try to provide.
     
  2. Audioguru

    Audioguru

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    Sep 24, 2016
    The LM386 amplifiers are overloaded by the base-emitter diode of the transistors so a series base resistor (try 100 ohms) should be added.

    The base-emitter diode will charge the input capacitor until the transistor is biased off then it does not work. Add a diode with reversed polarity from base to emitter.

    The LEDs will probably instantly burn out unless a resistor is added in series with them to limit the current.

    Your schematic does not show a stereo level control, how it is wired and its resistance.
     
  3. Andrei Bului

    Andrei Bului

    3
    0
    Dec 20, 2016
    Hi, Audioguru, thanks for your reply!
    I had this circuit done on one channel and it worked properly without the lm386 burning out.

    I'm not sure I understand since the capacitor is being charged by the amplifier since there is no current flowing from the base but into it since I have a NPN transistor.


    That one is a LED strip that runs on 12v. The pin 4 is common anode and thus the pins 1 2 and 3 are all cathodes, R G B colors that must be and are connected to ground through the collector-emitter connection of the transistor which is opened and closed with the frequency of the base with is the frequenvy of the audio comming from the amlifier.


    Thebonly control I have included is a 1k stereo pot that is put between the cap and base of the transistor to control the sensitivity of the LEDs. And each LED strip is connected to a different channel. One to the right channel and one to the left.

    That's all. Thanks for your reply and if you can help me out further based on those statements i've made, please do.

    I'd gladly appreciate it! Thanks!
     
  4. Audioguru

    Audioguru

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    Sep 24, 2016
    You should do it like this:
     

    Attached Files:

  5. Andrei Bului

    Andrei Bului

    3
    0
    Dec 20, 2016
    Great. Now it makes more sense. But I use the pot as a variable resistance not as a circuit divider. Should I use it that way? And do you see anything ede broken in my circuit? Thank you again for answering my questions! You are helping me a lot!
     
  6. Audioguru

    Audioguru

    2,834
    634
    Sep 24, 2016
    A level controller is always a voltage divider. A series potentiometer is called a rheostat and adjusts the current which can be much too high, not the voltage.

    Maybe you got the original circuit from An Instructable that was designed by a kid 10 years old who knows nothing about electronics.

    Your 220uF capacitor must have its negative wire at the pot, not at the output of the LM386.
    When you had everything connected wrong maybe the LM386, the pot or the transistor are burnt out.
     
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