Almost all inexpensive commercial LED flashlights use a 4.5V power supply—three AA or AAA batteries—because white LEDs require 3.3 to 3.5V to fully turn on. Thus ...

This light activated remote switch circuit could be operated using a flashlight beam and could eb used for toggling a specified load from a distance using an external light source such as a flashlight ...

Those portable shake-to-charge devices seem like a good idea, especially for the battery challenged, but how well does this sort of thing really work? Engineer Dave Johnson took this flashlight to the ...