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If you like lights and music, you’ll have fun building this LED Color Organ. You plug your music into it, and the circuit divides the sound into high, mid, and low frequencies and then flashes 3 different colors of LEDs according to those frequencies. Blinky!

When Collin Cunningham published his fancy LED Color Organ in MAKE’s Circuit Skills video series, one reader was inspired to build a simpler circuit to achieve the same goal. Akimitsu Sadoi designed this bare-bones version that works great and uses only about 30 components. You can find the schematic right here and build it on a breadboard with no soldering required!

Assembly is broken into 4 parts:

  • The audio input — the circuitry that takes the signal from the audio jack.
  • High frequency — blinks the blue LEDs when high-frequency tones play.
  • Mid frequency — blinks the green LEDs when mid-frequency tones play.
  • Low frequency — blinks the red LEDs when low-frequency tones play.

Photo-Jun-18,-11-10-32-AM
easy-LED-color-organ_circuit

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Steps

Step #1: Jumper the power and ground rails.

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  • Install jumpers as shown, to provide power and ground all across the breadboard.
  • Install the 9V battery connector. Red to red, blue to black.

Step #2: Connect the audio jack.

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  • Insert a 10kΩ resistor (brown, black, orange) from the power rail of the breadboard to an arbitrary row. Remember, resistors aren't polarized, so it doesn't matter what orientation it's inserted in.
  • Insert the 2N3904 transistor (it should have a small "3904" labeled on the front) into the breadboard, with the flat side facing toward the breadboard’s central “trough”. Looking at it in this orientation, the left leg is called the "emitter," the middle leg the "base," and the right leg the "collector."
  • Connect the negative column to the leftmost pin of the transistor, the emitter, with a jumper.

Step #3:

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  • Connect a 1kΩ resistor (brown, black, red) from the power rail to the rightmost pin of the transistor.
  • Wire the second 10kΩ resistor from the one you installed earlier to the base of the transistor.
  • Connect the diode from the row with the two 10kΩ resistors to the leftmost pin of the transistor, noting the polarity (the black stripe of the diode should be nearest the transistor).

Step #4:

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  • Connect the 10µF capacitor from the base of the transistor to the other side of the breadboard, again noting the polarity: the positive side, without the black stripe, should be connected to the transistor.
  • Connect two 100Ω resistors (brown, black, brown) to the negative leg of the capacitor and insert their other legs into 2 separate rows. This is where the left and right audio inputs will connect.
  • Use alligator clips to attach jumper wires to the 3 legs of the audio jack, or solder them on directly, as I did here. The one sticking out the bottom of the jack is ground, and should go to the ground rail on the breadboard. The other 2 pins are for the left and right audio inputs, and should each be connected to one of the 100Ω resistors we installed earlier (it doesn't matter which).

Step #5: Build the high frequency filter.

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  • Insert a 2N3906 transistor into the breadboard (flat side facing forward, again).
  • Connect power to the emitter leg (the left one) with a jumper.
  • Connect power to the base of the transistor with a 2.2kΩ (red, red, red) resistor.

Step #6:

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  • Insert the 0.047µF cap into the board, connecting one leg to the base of the transistor and the other to an arbitrary spot on the other side of the breadboard, over the trough.
  • Connect the other leg of the capacitor to the collector of the 2N3904 transistor with a jumper wire.

Step #7:

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  • Connect the positive leg of a blue LED (usually the longer leg) to the collector of the transistor.
  • Hook up a 100Ω resistor (brown, black, brown) from the negative leg of the LED (indicated by the flat spot on the LED casing) over the trough to the other side of the board.
  • Connect the positive leg of the second blue LED to the 100Ω resistor, and the negative leg to ground. You can insert the LED’s negative leg right into the ground rail or use a jumper.

Step #8: Build the mid frequency filter.

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  • Insert another 2N3906 transistor into the breadboard, with the flat side facing the trough again.
  • Connect the emitter of the transistor to the power rail with a jumper wire.
  • Connect the base of the transistor to the power rail of the breadboard with a 2.2kΩ resistor.

Step #9:

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  • Hook up the 0.01µF cap between the base and emitter legs of the transistor. Polarity doesn't matter with a ceramic capacitor.
  • Now connect the positive leg of the big 0.47µF cap to the base of the transistor, and the negative leg across the trough of the breadboard.
  • Connect a 1kΩ resistor (brown, black, red) from the negative leg of the 0.47µF cap to the "hub" — the positive leg of the second blue LED you installed earlier. This connects all parts of the circuit together so they can work together; you’ll connect other sub-circuits to this "hub" later on.

Step #10:

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  • Connect a green LED’s positive leg to the rightmost leg (collector) of the transistor.
  • Connect the 180Ω resistor (brown, grey, brown) from the negative leg of the LED across the trough.
  • Connect the positive leg of the remaining green LED to the 180Ω resistor, and the negative leg to ground.

Step #11: Build the low frequency filter.

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  • Insert a 2N3906 transistor into the breadboard, with the flat side facing the trough as usual.
  • Connect power to the emitter leg of the transistor with a jumper.
  • Connect a 2.2kΩ resistor from the power rail to the base of the transistor.

Step #12:

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  • Insert the 1µF cap into the board, with its negative leg connected to the base of the transistor and its positive leg connected to the emitter.
  • Connect another 2.2kΩ resistor across the trough of the breadboard, from the negative leg of the 1µF cap to an arbitrary spot on the board.
  • Connect this 2.2kΩ resistor back to the "hub" with a long jumper wire. This connects the low frequency sub-circuit to the rest.

Step #13:

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  • Insert a red LED into the breadboard, with its positive leg connected to the collector of the transistor.
  • Connect the negative leg of the LED, across the trough of the breadboard, with the 270Ω resistor (red, purple, brown).
  • Connect the positive leg of the remaining red LED to the 270Ω resistor, and the negative leg to ground.

Step #14: Now you are ready to rock!

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Plug one of the male ends of the audio splitter into the audio jack, and the other male end into your audio source (stereo, computer, etc.). Now plug your audio output (headphones, speakers) into the female end of the splitter, plug the 2 ends of the 9V battery clip into the ground and power rails of the breadboard, and start pumping the tunes!

Conclusion

Thanks to Akimitsu Sadoi for his original circuit, on Instructables.

Eric Weinhoffer

Eric is a Manufacturing Engineer at Other Machine Co., where he uses large machines to make smaller machines. When not building things, Eric enjoys skiing, cycling, and climbing.


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