If you need a small flashlight, one can be had for a couple dollars, but, even with the use of efficient LEDs, all of them will eventually run out of power. The idea of generating power by turning a crank isn’t new, but hacker Ted Yapo put his own spin on things with his “forever flashlight” made from a continuous rotation hobby servo.
While new to readers, this actually isn’t a new project, as Yapo originally implemented this hack in (roughly) 2001 and is just now getting around to documenting it. The good news is that his design, which uses the servo horn to rotate the motor shaft through a series of gears and store energy in a pair of capacitors, has been proven out and could give you an emergency lighting solution that can last a lifetime in storage. While it wouldn’t make a good spotlight, the red LED is great for preserving night vision, perhaps for a quick peek at documentation while stargazing.
Not content to simply document his project Yapo is in the process of upgrading the design — including a circuit to help maintain the LEDs brightness, and a 3D-printed crank. The new design also utilizes an upgraded servo with metal gearing to accommodate the use of modern supercapacitors. Because they now take in charge more easily, this also causes extra stress on the gear train.