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Need help upscaling this circuit for leds.

  1. Aug 28, 2013 #1
    Hello everyone,

    I am currently a sophomore in computer engineering, so I don't quite know enough to figure this out on my own, so I was hoping you guys could help me.

    I really like the idea of a color organ to visualize music.


    That an example of one I would like to build. My only concern is that I want to use it for entertainment purposes in my dorm room, and the build they have is more of a hobby build. It features 4 leds of different colors that are placed directly on the protoboard.

    I would like to build one with 3 (or more) led spotlight type lights. (Anything that would look normal sitting on top of a dresser or behind a desk shining up.) And have these be wired down to the circuit.

    So basically what I need to know is how to change the circuit so that it can handle these more powerful lights.


    This is the circuit they used. Any help would be greatly appreciated. Also, if anyone has suggestion for lights, that would be great too. (My room dimensions are ~ 12 by 14 feet, with approximately 10 foot ceilings. Thank you guys so much.
  2. jcsd
  3. Aug 28, 2013 #2
    Well, that's very simple actually. First you should give us more info on those "led spotlight type lights".

    Basically what you have here:
    First OP amp acts as an audio amp, it filters DC components of a signal then amplifies it since most audio sources are about 3V peek to peek.

    Then you have 3 parallel OP amps that are configured to act as band-pass filters, upper one passes frequencies around 3khz, middle one 900hz and last one passes everything around 100hz.
    Signals you get from the output of these 3 filters drive those NPN transistors to saturation, and that turns on and off your led's.

    If you wish to use any other load (different leds and such, i would have to know their power, voltage, nominal current) and all you would have to do is modify the end of that schematic to fit your needs. If your light source uses more power you might want you use stronger output transistors, mosfets perhaps. Anyhow, it's simple enough.
  4. Aug 28, 2013 #3
    First off, thank you so much for your timely response.

    I've been trying to search for a light, but I haven't really found anything that works. I also don't know too much about led's so I don't know what would be overkill, and what wouldn't be enough.

    In my head, I was thinking something similar to this style, but most of the ones I have found are huge/expensive and are probably way to bright.


    I don't really know what I should be even calling them. Any ideas or suggestions?
  5. Aug 29, 2013 #4
    Ok I have few ideas. I checked DealExtreme for something you might use.
    They have bunch of really dirt cheap stuff that i wouldn't mind breaking apart.
    Check out this 10$ strobe. They probably come with small transformer inside you might use for power source, so you might fit everything inside this box, just put 3 small pot's on the back and plug it in.

    If you want 3 stages in everything, you could get bunch of different leds on ebay, or in your electronic store, since they are dirt cheap anyhow, why wait 1 month for delivery. Take out 2 rows of leds from this thing and put LEDs of different color instead, and make each of those filters in that diagram control one row of leds. That might be your treble, mids and bass.

    Or you could get 3 of those, just different color, and make one small box control all 3 of them,and put them around your room.
  6. Aug 29, 2013 #5


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    You can drive large 3 colored lamps for example. Say, 110 Volt, 100 Watt spotlights using 3 “solid state ac relay circuit”. You may Google using those search terms.

    You would disconnect the LEDS from the circuit, and put the triacs in their place. The 2N3904 transistors will then drive the triacs, and they in turn, allow the AC to drive your load(s). Here is one example to get you started:
  7. Aug 29, 2013 #6
    Well, if he knew what he wants to drive with that circuit, we might recommend something.
    I had a feeling he just wanted some backlight to fall on the wall of his dorm room, not 3x100 W spotlights, but who knows.
  8. Aug 29, 2013 #7
    Google SCR Light organ - there are a number of these for incandescent lights - from there a 110 LED bulb can be driven.
  9. Aug 29, 2013 #8
    Yup. I just wanted three lights (blue would by my preference) to shine up towards the ceilings and walls to be controlled by the circuit.

    I looked at the lights you suggested.


    It says they are a strobe light. I've never worked with strobe lights before, but can they be always on? Also, getting a light for 10 bucks sounds almost too good to be true. Any drawbacks?

    I like this idea as well.
  10. Aug 29, 2013 #9
    After doing a quick google search of a strobe light's circuit, I came up with this.


    I had a feeling it was using capacitors and such to achieve the pulsing effect. Would there be a way to bypass that circuit so that I could just have them on when power is given to them, and off when power isn't. Or is it not worth that much trouble?

    Also, what about these guys?


    Do you guys think something like these would be the right path? And what could I mount them in. (Other than building a custom mount box.)
    Last edited: Aug 29, 2013
  11. Aug 29, 2013 #10
    Don't worry, lol, it's simpler than that. the light source in that thing is simple led diodes, not xenon bulbs.
    There is probably some transistor that pulls cathodes of those leds to the ground, you could brake the original circuit before the base of that trans., and use that transistor as as the output transistors in the diagram you provided in the original post. You would take out most of the original circuitry inside.

    There aren't any drawbacks i can think of for 10 bucks. Keep in mind it's a toy made in china. Check out the pics, the case is probably made of cheap plastic, and I'm not sure how strong leds inside are. You could play and experiment, and if you want something stronger later, get high power leds.
  12. Aug 29, 2013 #11
    Alright. I think this is the approach I'm going to be further investigating. (strobe light)

    So I'm looking back at this original circuit,


    and trying to decipher what it all means.

    Would anyone be able to explain the purpose of the resistors and capacitors connected to ground. (The ones coming off of the line of the opamp and going to the transistors.)

    Also, I haven't had much experience with transistors, but I understand the general concept. If I use the transistors that are included with the strobe light, wouldn't I need to change the values of all the resistors, capacitors and other components of the circuit? If not, why?
  13. Aug 29, 2013 #12
    So I stumbled upon this build on youtube.

    More complicated, but I enjoy coding so I think it will be fun to figure out.
    Last edited by a moderator: Sep 25, 2014
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