This project by Collin uses a familiar schematic — the light-sensitive oscillator (aka “phototheremin”) as originally described in Forrest Mims’ book Timer, Op Amp and Optoelectronic Circuits & Projects.
Long before the dawn of digital music, folks employed the power of the electric color organ (aka “light organ”) to add some synced visuals to their hi-fi experience.
This project is a very straightforward guide for converting an old PC power supply box with a cooling fan into an AC powered, activated carbon fume extractor.