The worst performer was an ultra-cheap LED bulb. Not bad for a simple DIY sensor and an existing mobile phone app intended for audio.

Instructables shows you how to make a home air quality sensor out of a giant balloon, an LED light, and some low tech accessories.

Note that, this steam sensor circuit offers two outputs; Digital (DO) and Analog (AO). If you only want a logic-low (L) level output when a threshold is reached, just use the Digital (DO) output. But ...

German engineer Gaurav Singh has designed and built an industrial USB box camera in a custom 3D-printed case that not only accepts interchangeable lenses, but the image sensor can also be swapped ...