5mm or 10mm LEDs will work just fine for most projects, but if you really want to light up a room, consider using some of the “high-power” variety. With forward currents of up to a full amp, you’ll need a way to dissipate heat – but the results are very much worth the extra effort.
I’ve had color organs on the brain since the last installment of the Circuit Skills series, so I decided try my hand at a new incarnation of the basic 3-channel sound-to-light machine using high-power LEDs. This time, I took advantage of the fact that I play all of my music from a computer, and created a ‘patch’ in MaxMSP to calculate high, mid, & low values of the outgoing audio stream. Max then sends these values out to an Arduino via serial connection over USB. The Arduino uses these values to set the PWM output levels of 6 pins – each of which are wired to a couple of Tri-Driver boards powering my display. Alternatively, a much more affordable low-power display could be created by simply connecting each of those PWM outs to a 5mm LED and resistor wired in series.
Update: Head over to Make: Projects for the Arduino code, Max patch & basic instructions for this one.