Joule Thief LED Flashlight

I do love a Joule Thief, but without an on/off switch and an enclosure, they can be clumsy to use. I designed this flashlight to provide protection, and on/off switch capability, and easy battery swapping. Simply unscrew to power off, or fully unscrew to remove and replace the battery. If you're not sure about what a Joule Thief is, have a read: https://en.wikipedia.org/wiki/Joule_thief . Basically it is a simple (few components, light soldering) DC-to-DC converter which allows you to harvest the ample current producing capabilities from voltage-impaired "dead" batteries. One easy way to make them is by harvesting parts from a dead CFLight bulb. PLEASE BE CAREFUL, all flourescent light bulbs contain mercury vapor. Mercury is a dangerous neurotoxin and once it has entered the body it cannot be removed. It is particularly dangerous for growing/developing humans. Alternately, you can make similar converters with inexpensive discrete components found at your favorite electronics supplier without any risk of exposure to mercury vapor. Newer (v3) front end is shorter and tighter than the v2, this may be preferable.