Create any color, using 3 LEDs and the trick of pulse-width modulation.
On a shelf above my bed stands something highly unusual: a giant, translucent, crystalline chunk of salt (Figure A), given to me by a friend who imports gemstones from Pakistan.
Photography and diagrams by Charles Platt
Fig. A: By day, an 8" crystalline chunk of salt.
The salt was drilled with a ...