Handpress flash light

hand press, originally uploaded by hooying.

Occasionally you can come across some interesting gears through the train commercials when you are on board. So I bought this flash light when I took the train to Zhuzhou yesterday. As the name suggests, you’ve probably figured out this flash does not require any batteries. It has two LEDs pointing downward in the picture. I was in the pose of pressing a handle which gears the big wheel to spin the magnetic coil in the center. This spinning coil functions as a generator to charge up the reservoir (a big capacitor in this case) which provides energy to light up the LEDs. Because of the semi-transparent body, you are able to see the internal circuit structures. I was even able to read the color code of a 5% tolerance resistor, and therefore to derive its precise resistance. Really smart and elegant design!

BTW, it costs about a dollar fifty cents.