Subscribe to Make Magazine Today!

Long before the dawn of digital music, folks employed the power of the electric color organ (aka “light organ”) to add some synced visuals to their hi-fi experience. Schematics for building such a beast based on AC power and incandescent bulbs can be be found fairly easily on the web, but plans for comparable LED-based designs seem a bit harder to come by.

Adapted from Aaron Cake’s 3 Channel Spectrum Analyzer, I built my own analog LED Color Organ to enhance the aural experience. The circuit uses 4 operational amplifiers plus ultra-bright 5mm LEDs to respond visually for bass, mid, and treble frequencies. A parts bundle for building your own incarnation of the project is now available from Jameco.


Schematic updated 11/1/10, Larger size available here

In order to simplify the construction process, I drew up and printed a label specifying the pinout for quad op amp ICs. Those interested in printing their own can download the design here.

Quadopamp Label 400

I’ll likely continue tweaking the design as I continue the unusually groovy process of testing this thing. I predict a second channel plus somewhat more dramatic display option may be in my future ;)

Subscribe to the MAKE Podcast in iTunes, download the m4v video directly,
or watch it on YouTube and Vimeo.

Collin Cunningham

Collin Cunningham

Born, drew a lot, made video, made music on 4-track, then computer, more songwriting, met future wife, went to art school for video major, made websites, toured in a band, worked as web media tech, discovered electronics, taught myself electronics, blogged about DIY electronics, made web videos about electronics and made music for them … and I still do!

  • Qasim Mian

    Wow this is awesome. I’m an electronics student and I really want to get into DIY electronics in my spare time, and this feels like a good first project. Just a few questions though, if someone could help:

    1. What is that virtual ground bit doing

    2. Where does it go in the circuit? i.e how does the other stuff connect to it.

    3. What do the numbers around the op-amps mean? Is it possible to add more to have an extra set of 4 LEDS (more frequency ranges)?

    Lol, just noticing some american/uk differences (or am I imagining them) Soder/Solder, Squiggly line for resistors/rectangles. NO too fussed but is there a components list? As I’m gonna be hunting them down in maplins.

    Sorry for being an epic noob (but hopefully not for long), Thankful for any help.

    • Collin Cunningham

      Scott’s explanation of virtual ground (see below) is well put – thanks, Scott!

      I believe the numbers around the op amps you speak of are the pin numbers (these assist in translating the schematic to an actual circuit board)

      I’ll add the parts list here soon – thnx for the reminder!

      And for the record my dictionary says –

      solder |ˈsädər|


      • aster yeyo

        i am unable to fin mc33204p IC in pakistan . so tell me any other IC which can do the same work or canbe used instead of this ??? :((((((

        • scarygood536

          I don’t see why you can’t use a LM324, available at radioshack. you can probably use most quad op amps

          • J

            I have used an LM324 with no problems at all. I also skipped using the virtual ground, and so far I haven’t noticed any odd behavior.

      • Nozar kasad

        hey can u clarify the that gnd except the v-gnd are the same,
        the one near the input and the battery gnd are the same ?
        please also carify that v+ represents what in ic2

  • Scott

    1. The circuit operates from a single sided supply, but the audio goes positive and negative. The voltage divider provides a voltage halfway between V+ and GND, but it’s high impedance. The op-amp buffer after the divider gives you a low-impedance ground.

    2. All of the VGnds are connected together.

    3. You can design and add as many filters as you like.

    4. Numbers around the op-amps? Do you mean the component values?

    • emihackr97

      Hi, just a quick question, why is the audio input signal connected to the ablsolute gnd instead of the virtual gnd if all the op amps are connected to the virtual gnd?

  • troykyo

    How many volts does the circuit need?

    • Collin Cunningham

      I was using a 12V 500mA supply in the vid.

      wow … amazing what you can forget to put on a schematic, eh?

      • troykyo

        Lol, I know the feeling. I just want to make the circuit wearable. Thanks!

  • Mathias

    Realy cool project.
    I’d like to integrate this into a project I’m working on, so a parts list would be nice.
    In the video at 4:57 there are changeable resistors, where are they in the schematics?


    • Collin Cunningham

      the potentiometers are located before the input of each bandpass filter, labeled with a value of 20K

  • circuitnewb

    Hey Collin,

    I’m a long time Make Blog reader. I have got to say that this type of post adds so much to the community. I’m still learning electronics and the detailed videos of putting circuits together is exactly what I need to advance my skills.

    Thanks for the Circuit Skills series, hope you keep it going for us circuit newbs.

  • Mathias

    I’ve done a quick and dirty parts list. Maybe someone would like to use it. But I’m not 100% shure about IC2 cause it’s named “TS921?” in the scheme. I think TS921IN should work for this.

    Partslist LED Organ Scheme:

    2x .1uF
    1x 4.7uF
    3x .047uF
    2x .01uF
    2x .0022uF
    3x 2.2uF
    1x 1uF
    1x 4.7uF
    1x 22uF
    1x 3.3uF
    1x 4.7uF
    1x 10uF

    1x 47K
    1x 1M
    5x 1K
    3x 560K
    3x 680K
    3x 39K
    5x 100K
    2x 470
    2x 160
    3x 20K (potentiometer)

    3x 1N4002

    3x 2N3904

    4x MC33204PG
    1x TS921IN

    4x red
    4x blue
    4x green

    1x perfboard
    1x DC plug
    1x stereo plug
    ??x cables

    • Mathias

      sorry I got it wrong. You only need 1 MC33204PG !

    • jared

      TS921? = MC34072P

      • Collin Cunningham

        MC34072P is a dual operational amplifier. It should work fine for this and will leave you with an extra op amp for use with a second channel of audio.

        • aster yeyo

          i m unable to find this IC in pakistan mc33204p tell me which i IC can be used instead of this . tell me 2 or 3 ok

  • elixeroflife

    I’m considering making a SMT version of this and in stereo to make it fit inside my laptop, and put the LED’s around the trim bezel of the screen!

  • jared

    On Aaron Cake’s 3 Channel Spectrum Analyzer he’s using line level inputs, I was wondering if you have changed this to speaker level inputs or if the circuit is still designed with line level input?

  • DCProductions

    Hello Masters of Circuitry!
    I am very interested in this Color Organ but have one question about it. What would I have to do to run more LEDs with the same ICs? I’m hoping to run up to 50 for each color (I know that’s a little much, maybe 25 with 2 kits?).
    Also, I would like to have a larger frequency difference between 3 op-amps. How can I change that?

  • elixeroflife

    just build a separate light board with its own power source and connect via “header pins”

    the more LED’s you add to the onboard circuit will be too heavy of a draw for the op amps out puts

    Like using speakers on an amplifier that are rated too high for the amplifier. will either be weak, or act as a short on the amplifier out put and burn it up, or both.

    • DCProductions

      Those header pins your referring to are the same ones in the video correct? I was wondering what those were for. Do I need to run any LEDs in the circuit at all or do I go straight to the header pins?

  • robodude666

    This is awesome. I’ve been wanting to build something like this for a while, but haven’t gotten to it yet. Now I absolutely will.

    Collin, could you please post some high-res photos of the front/back of the perf board? I’m looking at stills from the video but I don’t understand how you managed to route all of the connections so smoothly. In many cases the output of a pin or a connection magically gets across to the other side of the board.

    Speaking of which, I’d love to see a more detailed/slower overview of laying out parts on a perf board and routing the connections. I know you did perf boards in a Circuit Skills episode, but it would be nice to see more. I’m sure it’s something you learn with experience, but it’s very frightening at first.

    In either case, awesome work! I’ve been loving every one and plan to get a few of the kits in the coming weeks (Birthday, woot!).

  • Alex W.

    This circuit is so simple it’s amazing how fussy it is. PSPICE hated the virtual ground though.

    Tips for people working on this project:

    1)build it in stages, it makes it easier to debug if it doesn’t work.I started with verifying my virtual ground.

    2)Make sure to include the biasing capacitor on the inverter. It’s there to filter out any DC in your signal, and the virtual ground then gives you your offset half way between your rails. Even with my function generator with a 0 offset, it was still saturating at 12V until I added that capacitor (C1).

    3)If you use the opamp Jameco has listed for the virtual ground, do NOT use the pins listed in the schematic. I was lazy and just followed the pins listed, which is for a single opamp, jameco kit gives you a dual so even though it says pins 7 is the upper power rail, it’s actually the second output and it fried my IC.

    Video came out with amazing timing though, I’m using this as my final project for my microelectronics lab final after I make a few tweaks. Anyone have good suggestions for songs to demonstrate with? I wish Collin had a website he had his mixes on.

  • slamer123

    Wow this was a good catch. It’s not good when the pinouts are different.
    I think from looking at the data sheet that I should use pin 2 and pin 3 as listed on the color organ schematic but pin 1 should be the output (instead of pin 6) and pin 8 is 12 Volts (instead of pin 7) and pin 4 is still ground.
    Is this Correct?

    Pin 2 inverting input
    Pin 3 non inverting input
    Pin 1 output
    Pin 8 12 VDC
    Pin 4 ground
    Heres the data sheet I’m looking at

    • Alex W.

      yes. you’re completely correct. I also failed to mention If you need the bass to be blue, mid red and treble yellow the capacitor values are wrong for the bandpass filters. the .047 uF will give pass frequencies around 100Hz and the .0022 uF will pass frequencies around 3000 Hz, since F=1/[2(pi)RC].

      probably too much info for beginners but your first -3dB point is the equivalent resistance between the 1k and 680 ohm resistor, and your second -3dB point is with a R value of 560k ohms.

  • Marcel

    Hi Collin
    I was wondering if you would be kind enough to either put up or send me a close-up of the #2126272 board you constructed on you video “Circuit Skills: LED Color Organ”

    Thank you

    • Collin Cunningham

      Here are front & back shots of my board –

      Big thanks to everyone who’s been answering Q’s & sharing info on this project. More project vids are on the way!

      • Vipul Gautame

        Hello sir Collin, i am from India.. i have selected this project for my 12th standard’s electrornics project . Thank you very much for sharing this project and pictures..
        Now definitely i will get good grades in my college project. :-)

  • Scott H.

    Thanks for this! It’s surprisingly similar to something I’ve been working on myself. I’m still trying to figure out the optimum filter values for a light organ that will built into a guitar, like the Rickenbacker 331LS.

    A couple questions…

    Did you intend for the other side of these pots to be connected to real ground? Seems like they, as well as the positive inputs of your filter op-amps, should connect to V-GND, assuming you want a V-GND biased signal going into the filters.

    If the above is true, I’m also curious about the 4.7uf capacitor on the output of the amp. Wouldn’t any small DC offset from V-GND just get eaten by the bandpass filters?

    • Alex W.

      Scott, the pots should be connected to power ground, not virtual ground. the purpose of the pots is to be a voltage divider, so you’re basically controlling the sensitivity of the filters because he’s only using a single stage filter which means that if the input is too high, a 1000Hz signal could cause the bass LEDs to light, so you turn the pot so the input voltage is lower to the bass.

      The 4.7uF cap is doing just like you said, eating the DC voltage. Because these are active filters, they also amplify the signal. Think of the signal simplified to A*sin(wt)+DC. the filter amplifies all of that, which means your 6V will be amplified and cause your signal to saturate at the positive rail, which means your LEDs will stay on all the time.

      Don’t worry though, since the V-gnd is at the filters non-inverting inputs, it will add the offset back into your signal.

      • Scott H.

        I get it now, we’re both right :)

        The amp output, the pots, and the 1k/680 dividers could all be tied to any DC level, as long as they are all the same. It’s all AC-coupled to the op amp’s inverting input by the filter capacitors.

        So you could either zero the amp’s DC output and tie the dividers to ground (as in your circuit), or use the amp’s output directly and tie the dividers to +6V (which is what I had done in my circuit).

        I guess using real ground is better because it creates less additional current demands on V-GND, and then… if the only load on V-GND is the four op-amp inputs, you can maybe get away with just a simple resistive divider V-GND and save the extra op-amp.

        Thanks again, I learned something today!

  • Alex W.

    it’s not on perf board, but this is the layout of my PCB, i only had to use a couple jumpers and from left to right it’s bass, mid, treble

  • onix45

    Hi there, i was wonering if anyone could give me any guidelines how i could use this circuit to hoop up some high power leds instead of the existin ones, for example 3 1W leds? I think quite a few people would be interested in this aswell. I would greatly appreciate any help.

    • Scott H.

      Here’s an idea from a circuit I’ve been working on:

      It puts the peak detector inside an op-amp feedback loop to make adjustment simpler. It expects Vin to be biased around +6V. The current through the LED will be determined by the peak AC amplitude of Vin and by the resistor between the FET and gnd. The given value of 10 ohms pulls approximately 80mA based on a 1 volt peak-to-peak input signal. To increase the current, either increase the AC amplitude of Vin or decrease the resistor value. (for example, 1 ohm would pull 800mA through the LED).

      Brightness of the LED is proportional to the AC amplitude of Vin. You just need to make sure that the max expected Vin amplitude doesn’t cause the current to exceed the LED rating.

      The Trim pot is for fine adjustment of the “off” state current draw — too far the one way, and the LED will stay off for too much of the Vin amplitude swings. Too fat the other way, and the LED will never quite turn off. I’d like to find a way to have this set automatically, but haven’t gotten around to figuring that out yet.

      • Scott H.

        You should be able to hook this circuit up directly to the outputs of IC1 b/c/d (but you will need to choose the resistor value based on the expected amplitude of these signals and the current you want to pull through your LEDs).

      • AjaxOfTheRockies

        Hi, would you be able to post the schematic where we can see it? I’d very much like to examine and understand your circuit.


        – a -

  • slamer123

    Heh, it’s amazing how long it took me to get this circuit working. During building I left out a couple of power traces and a ground as well. Boy that drove me nuts for awhile. “Thank the Maker for creating Multimeters”, Anyways I tested the board after fixing the problems and it works well.

    The Jameco kit did not come with the (2) 160 ohm resistors that protect the Blue LEDS. So I replaced them with 2 220 ohm resistors that I had in my parts stash. I found the Proto board to be a little hard to see well when working on it. Too much silver color makes it a bit tough on the eyes.

    Other than that, I plan on driving a some Larger PNP Darlington transistors like the TIP125’s with the output from the NPN 2N3904’s so I can trigger lots more LEDS. More blinky lights = More Fun. Hopefully I’ll get some more parts and build the other channel next for Stereo Blinky light fun.

  • slamer123

    I updated the schematic for use with the MC34072P Duel Op Amp that comes in the Jameco Kit. I also put the .0022uF and the .047uF Caps in their correct positions. You can get the schematic here..

  • Veer

    the schematic and the part list will change or not.
    MC34072P is not easyliy avilb here and is expensive,
    and how can i add more LED COLOR ORGAN (bands)…..?
    not aware of frequency calcs

    I made PCB for COLOR ORGAN but unable to assemble cause of ICs >-(

    • Alex W.

      all the parts are readily available from Jameco.

      you can add more bands to it using the equation that i posted in an earlier comment where F=1/2piRC which I got from the wiki on bandpass filters, confirmed by my circuits textbooks.

      you can add more bands but your eventually going to run into problems due to the current limitations on the “preamp”

      • Veer

        i read it earlier but i’m confused, the value of which R or C should be varied to hv desired frequency….?

        is therm any solution for current limitation on preamp..

        • slamer123

          Lets just Look at the middle of the schematic for the op amp labeled IC1C. There is a 20,000 ohm variable resistor connected in series to a 1000 ohm resistor this gives a maximum of 21,000 ohms if you turn the pot all the way in one direction. These resistor are connected to the Capacitor thats rated at .01 uF(micro farads). The value of either the resistor or the capacitor is what determines the out put frequency Frequency out will equal 1 divided by 2 times (pi) 3.1416 times the resistor value (in ohms) times the Capacitor value in uF (micro Farads) for the center Op amp circuit you get
          pi times 2=6.28.
          Resistor value times capacitor = 210. 210 times 6.28 = 1318.8
          1 divide by 1318.8 =758 Hz (they call it a 900 Hz filter on the schematic)
          So the change the maximum frequency allowed you change the value of both of the capacitors connected (-) input for the Op amp. Then you turn The 20,000 om variable resistor for fine tuning of the output frequency.
          By the way heres an on-line calculator for Resistor and Capacitor filters.

  • slamer123
  • slamer123

    Lets do the math for a simple Resistor/Capacitor filter circuit.
    Look at the middle of the schematic for the op amp labeled IC1C.

    There is a 20,000 Ohm variable resistor connected in series to a 1000 ohm resistor this gives a maximum of 21,000 ohms if you turn the pot all the way in one direction. These resistors are connected to the Capacitor that’s rated at .01 uF (micro farads). The value of either the resistor or the capacitor are what determines the output frequency.
    The maximum Frequency out will equal 1 divided by 2 times (pi) 3.1416 times the resistor value (in ohms) times the
    Capacitor value in uF (micro Farads).

    For the center Op amp circuit you get
    Resistor value 21,000 Ohms times Capacitor value .01 uF = 210.
    (pi) times 2 =6.28.
    The Resistor Capacitor value 210 times 6.28 = 1318.8
    1 divided by 1318.8 =758 Hz (they call it a 900 Hz filter on the schematic)

    So to change the maximum frequency allowed you change the value of Both of the capacitors connected to the (-) input for the Op Amp IC. in this case the Capacitors connected to PINS 8 and 9.

    Then you turn The 20,000 Ohm variable resistor for fine tuning of the output frequency. Kinda like the valve on a garden hose. (The Higher the Resistance the smaller the hose)(Higher Resistance makes for a Lower Frequency)

    A Larger Value Capacitor will produce a Lower output frequency. (The bigger the bucket, the slower it fills)

    A Smaller Value Capacitor will produce a Higher output frequency. (The smaller the bucket, the faster it fills)

    By the way here’s an on-line calculator for Resistor and Capacitor filters.

    • Joe

      The equation that is being used would work but the correct equation is the following:

      ________________ = Frequency Output
      2π √(RpR3C1C2)

      where 2Ï€= aprrox. 6.28

      Rp = R1xR2
      R1 + R2

      If C1 and C2 are the same value then the equation would look more like:

      ________________ = Frequency Output
      2π C√(RpR3)

      C1 and C2 in the circuit are the capacitors after the voltage follower, example in the mid range is .01Uf
      R1 is the value of the 20K pot and the 1K resistor in series.
      R2 is the 680 ohm
      R3 is the 560K ohm

      In the mid range the 20K pot is adjusted to approx 1250 ohms to get a 902Hz signal as an output.

      Hope this helps any trying to configure different frequency ranges for their organ lights

  • mikeyjay

    I am planing on installing this into a set of speakers but I want to have only one power source.
    what would you recommended?
    Parallel with same voltage requirements or something different?

  • Veer

    • Nguyen Nguyen Trong

      You can send to me,file PCB ? .tks u

    • Matias

      Hi Veer, could you please send me the PCB? Thanks :)

  • riccardo

    Hi collin do you have the PCB of this project??

blog comments powered by Disqus

Related Supplies at Maker Shed