Editor’s note: This article will be in two parts. Part 1 is component-related and Part 2 is applications. Please also see Planet Analog blog “LEDs Are Photodiodes Too” as an intro to this article.

Ordinary red LEDs normally function as light emitters, but they can also function as photosensors. A single LED can even function as both a light emitter and a light detector in the same circuit ...

A naked flame is a complex soup of ionised gases, that possesses an unexpected property. As you might expect with that much ionisation there is some level of electrical conductivity, but the unusual ...