Sound reactive LED and FAN, NEED HELP WITH POTENTIOMETER

Discussion in 'The Projects Forum' started by sirpatch, Apr 21, 2012.

  1. sirpatch

    Thread Starter New Member

    Apr 21, 2012
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    Hello everyone :) First off Allow me to introduce myself. I am from portugal, my name is Nuno, its my first post here :)
    I registered because im doing a project and i need help. Im pretty much an electricity noob, no idea what ohms are, no idea how many volts, or amps i need nor how to calculate nor how to get values, its pretty much trial and error.
    Anyways i have my subwoofer, i opened it, wired a cable to its speaker PWR and another to the GND, and to the other end of that cable i wired a FAN. FAN works perfectly, even on a lot of volume it doesnt fry, just spins and not at it max rotation it seems. Fan is 12V. Then, i also wired a LED to the cables (GND AND PWR) comming from the speaker. Led works fine, reacts to music, thing is, and as i expected, louder volume and led burns. So i put in another one, also my last one. I have 2 potentiometers laying around i got from Fanatec's Standard pedals (some i dont use anymore and had hanging dont know what for). Those potentiometers read 10K 38 on them, not sure whatever that means. So with the rotating "shaft" of the potti facing to me, i used its 3 pins, from left to right as 1,2,3, being 1 the GND, 2 the OUT, 3 the PWR IN. I wired a cable from the speaker PWR to the PWR in on the Potti, and connected the LED's GND to the potti's GND, and the LED's PWR to the potti's PWR OUT, but nothing happens, led does not work, with any of the potties, they worked last time the pedals were used lol. I spin the little shaft, but i get no results.. I need some help on this lol. The subwoofer is from Logitech X530 Sound system.
    EDIT: BTW, LED works without potentiometer
    Incase i wasnt clearn, here's a scheme:
    [​IMG]

    Thanks in advance, incase anyone can help me out :)
    :p
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Audio from the sub's amplifier is AC. But your 12V fan might need only DC and all LEDs use only DC, not AC. AC reverses its voltage each cycle and the reverse voltage can blow up an LED.

    Your sketch with the pot has only a single wire from the sub's amplifier. Two wires are needed.

    A 10k pot is 10,000 ohms. If the sub's amplifier has a 12V output then only 500 ohms is needed then the 10k pot will need to be turned down to almost nothing.
     
  3. sirpatch

    Thread Starter New Member

    Apr 21, 2012
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    0
    Hmm i see, but how would i do that wiring? since the Pot only has 3 pins?
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    896
    If you used a 1000 ohms or 100 ohms pot then it could be used to control the speed of the fan and the brightness of the LEDs.

    But first you need 2 wires to the parts from the amplifier.

    Ther pot has an input terminal, an output terrminal (the middle one) and a ground terrminal.
     
  5. sirpatch

    Thread Starter New Member

    Apr 21, 2012
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    0
    So i connect the amplifier's ground to the pot's ground, the amp's PWR to the Pot's pwr input, and the led's pwr to the pot's pwr output, and leave the led's GND unwired?
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    How is it possible that a DC motor is runing on audio freq AC? Is there more to this than has been posted?

    EDIT: Late thought.. Maybe Universal motor? But still.. those frequencies?
     
    Last edited: Apr 23, 2012
  7. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Of course not.
    All grounds connect together.
    Why use a variable resistor? If the music is loud and the resistance is turned too low then the LED will burn out. Calculate a suitable resistance and use a resistor with that value.
    A rectifier diode is needed to be in series with the LED to block damaging reverse voltages.
     
  8. sirpatch

    Thread Starter New Member

    Apr 21, 2012
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    0
    Oh god too much for my 0.1% knowledge, and @CDRIVE, i just wired the fan to the subwoofer's speaker PWR and GND^^
    btw i think i wrote its 12v but i may be wrong, its not written on the fan, my other one is 12V but its not wired, i tried and it also works xD
    Currently, the one wired to the woofer is
    Nox Acid Blaster
    Video of it by me here:
    Clicky, actually i dare you! I DOUBLE DARE YOU!
     
  9. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    A universal motor can be operated on AC or DC but a DC motor will just sit there and buzz when powered by AC.
     
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