Circuit Skills: LED Color Organ Experience Level: Intermediate Time Required: 3-4 hours Color Organ Kit: P/N 2155541

Long before the dawn of digital music, folks employed the power of the electric color organ (aka "light organ") to add some synched visuals to their hi-fi experience. Schematics for building such a beast based on AC power and incandescent bulbs can be found fairly easy 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, Cunningham designed an analog schematic for the 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. To build your own LED Color Organ, we have a couple of options for you. Color Organ Kit (P/N 2155541) This Intermediate kit contains a custom PCB, labeled with component locations for a quicker build. The Customizable LED Color Organ Kit (P/N 2126272) Components bundle that contains the parts you'll need, but allows you to design your PCB layout and customize the organ however you like.

1) ICs U1, U2 Take note of the orientation of the ICs and IC sockets by looking at the notch and matching the notch of the IC to the notch of the PCB. See Figure 1.

Figure 1: IC Polarity

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2) Diodes D1, D2, D3 The correct configuration of the diodes is shown in Figure 2. Pay attention to the stripe on one end of the diode indicating the cathode end.

Figure 2: Diode Polarity

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3) Transistors Q1, Q2, Q3 Polarities of the Bipolar Junction Transistors (BJTs) are extremely important. Here, we use the 2N3904, 3-pin package. Match the component to the symbol in Figure 3.

Figure 3: Correct BJT Pinout

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4) Non-Polarized Resistor Color Code
R1, R2, R3, R16, R17: 1kΩ (Brown, Black, Red) R4, R5, R6: 560k1kΩ (Green, Blue, Yellow) R7, R8, R9: 6801kΩ (Blue, Gray, Brown) R10, R11, R12: 39k1kΩ (Orange, White, Orange) R13, R14, R15, R27, R28: 100k1kΩ (Brown, Black, Yellow)		R18, R19: 4701kΩ (Yellow, Violet, Brown) R20, R21: 1601kΩ (Brown, Blue, Brown) R22: 1M1kΩ (Brown, Black, Green) R23: 47k1kΩ (Yellow, Violet, Orange) R24, R25, R26: 20k1kΩ (Red, Black, Orange)

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5) Capacitors C1 through C7, C15 non-polarized capacitors. C1, C2 0.0022µF C3, C4: 0.01µF C5, C6: 0.047µF C7, C15: 0.1µF C8 through C14: These electrolytic are polirazied with the negative side (shorter lead) indicated by a strip on one side, see Figure 5. C8, C9, C10: 2.2µF C11: 2.2µF C12, C14: 4.7µ6µF C13: 22µF

Figure 4: Electrolytic Capacitor Polarity

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6) LEDs D4, D5, D6, D7: Yellow (represents the Treble) D8, D9, D10, D11: Red (represents the Mids) D12, D13, D14, D15: Blue (represents the Bass) Be sure to have the cathode end (shorter lead) facing the side with the flat edge. See Figure 5.

Figure 5: LED Polarity

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7) Audio Jack and Power Jack U4, U5 There is only one way to insert each of these components into the board, so just be sure to apply enough solder to ensure a good connection with each tab.

Figure 7: Audio Jack pinout

Figure 8: DC Power Jack pinout

Keep in mind that this project makes a mono-channel LED light organ, which means if you plug in your headphones, music will only come out of one side. If you wish to make it a stereo light organ, you will have to duplicate this circuit for the second channel. As always, remember to take extra precaution when soldering! And most importantly, have fun! Click here to enlarge We would love to hear how your build turned out. Let us know at MyStory@Jameco.com