[sdiy] Improving LED response when driven from half-wave rectifier

[rburnett at richieburnett.co.uk]

Regarding using bi-colour LEDs to show bi-polar signals, and 
exponential scaling for brightness, etc....

Paul Maddox had a really neat bi-colour LED on one of his products at 
SynthDIY this year that blinked and throbbed in brightness to depict the 
chosen LFO waveform and rate.  All I know is that it was done with a 
handful of discrete PWM duty-ratios, but it certainly seemed to vary 
smoothly in brightness and was perceived as looking very organic and 
natural.

-Richie,