Who would’ve thought a cheap AliExpress emergency light could be packed with such crafty design choices? Found for about $5, this unit uses simple components ... a smart circuit that defies ...

A great example is this simple wireless AC current detector from [NEW PEW]. The circuit is a simple one, and a classic. The spring from a ballpoint pen is soldered to the base of a BC547 ...

A simple circuit with a bulb and battery. A series circuit where the bulb doesn't light up. A circuit with three batteries, a bulb and a buzzer.

It's a simple string of miniature light bulbs ... but not all. The other type of circuit light strands use is a parallel circuit. In this setup, each bulb is on its own circuit to the power ...