This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and ...

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.

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 ...