Psychedelic light organ of 80s style, developed with an Arduino and the FIX_FFT library for the analysis of the signal obtained by an analog input.
The idea is to use a sound source, in this case a microphone, bring it into line with the level of the entries of the Arduino, apply a FFT process to separate the different frequencies, grouping these into three channels (bass, mid and treble), and depending on which exceed a certain level, activate the outputs of the Arduino. These outputs can attack some leds initially, but to make it more authentic then use a triac output stage with some bulbs.
For the microphone, i use a Dealextreme module, the SKU: 135533: a sound detector module. To adjust the input signal to the Arduino i use a u741 as signal amplifier. As the Arduino analog input signals need 0 to 5V, the voltage divider formed by R1/R2 creates an offset of approximately 0.5V so that the signal has a range of 0-1 V approx.
Warning! the voltages are high and may cause damage. The power stage should be mounted on a PCB or prototyping board properly insulated.