An 8x8 LED array which produces random display patterns from an audio source. Circuitry consists of an audio amplifier, serial A/D converter and counter/demux circuits to drive the 8x8 LED array.
The 8x8 LED display consists of 16 each of red, yellow, green and blue, T1 LEDs arranged in a diagonal pattern.
Theory of Operation:
The audio signal is fed into an audio amplifier. The output from the amplifier is capacitively coupled to the analog input of a Serial Analog to Digital converter IC.
Using the popular NE555 timer IC, it generates both the A/D sampling rate and display scan speed to produce the random patterns.
The display scan circuitry consists of a dual binary counter and 2, 3-8 decoder ICs to form the 8x8 matrix.
The serial digital data from the A/D chip is fed to the 3-8 demxes which randomly illuminate the LEDs at the scan rate set by the 555 timer.
Because the sound is not syncronis with the scan rate, this is why the pattern appears random. I however found this a fascinating operation. I initially used my MP-3 player as the audio source. Connected the output of the device to the DMD and switched in the sound (I used the song "Everlong" by the Foo Fighter in this experiment) After adjusting the audio level and reference voltage, it turned out successful.
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