Topic: Physics - Electronics
Design a portable color organ that will
take the frequencies from a song and
represent the music using three
differently colored LEDs.
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
• 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.
• Define the project
• Research and order parts
• Analyze options and design
• Construct circuit
• Test and modify
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
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
6.) Complete the preamp circuitry and the rest of the wiring.
7.) Mount the circuit board and circuit assembly to the battery
• The potentiometers need to be adjusted to each
song and each volume to achieve preferred
• 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
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