2. Topic: Physics - Electronics
Purpose:
Design a portable color organ that will
take the frequencies from a song and
represent the music using three
differently colored LEDs.

3. Hypothesis:
If the circuit is built correctly, when music
is played, the LEDs should light up in
accordance with the frequencies in the
songs. Red will represent the treble
frequencies, blue the bass, and green the
midrange.

4. Color Organ
• A color organ is an electromechanical device that is
used to represent sound or accompany music. They
respond to frequency inputs with exhibits of light
that flash along with the music. The display device
uses a plurality of light bulbs, in this case LEDs,
which are set in distinct groups.
• Each group of LEDs is illuminated as a response to a
corresponding frequency range of audio input. The
brightness of the LED is directly proportional to the
amplitude of the signal coming from the
corresponding frequency channel.

5. Project Outline
• Define the project
• Research and order parts
• Analyze options and design
circuit
• Construct circuit
• Test and modify

6. Procedures:
1.) Solder the LEDs together in the desired pattern, paying
attention to where each color LED is being placed.
2.) Connect the spaces between the LEDs to form the bar graph
ladder circuit.
3.) Solder all connections and test before proceeding.
4.) Assemble the filter circuits and insert in the remaining
spaces between the LEDs.
5.) Construct a circuit board to mount the microphone and
trimmer potentiometers. Test connections again before
proceeding.
6.) Complete the preamp circuitry and the rest of the wiring.
7.) Mount the circuit board and circuit assembly to the battery
case.

7. Materials
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Solder
Soldering Iron
Wire
Wire Strippers/Cutters
C Cell Battery Holder
Perf Board
1.0K Ohm Audio Microphone
50K Potentiometers
200K Potentiometers
.01 uF Capacitors
.1 uF Capacitors
1000 pF Capacitors
2200 pF Capacitors
4.7 uF Capacitors
47 uF Capacitors
220K Ohm Resistors
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Blue Water Clear LED
Green Transparent LED
Red Transparent LED
33K Ohm Resistors
2.2K Ohm Resistors
100K Ohm Resistors
4.7K Ohm Resistors
10K Ohm Resistors
47K Ohm Resistors
470K Ohm Rresistors
100V Diode
PNP Epitaxial Transistors
200mA 60V NPN
Tranistors

8. Conclusions
• The potentiometers need to be adjusted to each
song and each volume to achieve preferred
results.
• Adding more LEDs should produce a more
interesting light display.
• When the circuit is attached to a 555 Audio
Oscillator circuit, the ‘frequency in’ displays a
measurable input frequency, but the ‘output
voltage’ is not defined enough for accurate
measurement.