There’s an inherent dilemma in purchasing a flashlight: The really bright and long-lasting LED models are pretty expensive, and the heavy, cheap traditional ones always seem to be dead just when you need them the most. Good thing it’s possible to build your own superbright, reliable and inexpensive hybrid light. With a bit of creative circuitry work—you’ll need to add a small circuit called a charge pump to increase the voltage—you can replace the bulb in any cheap lantern-style flashlight with several bright white LEDs. All you need to power your DIY version are three small AA batteries instead of that huge, heavy six-volt. Plus, LEDs will last far longer than regular flashlight bulbs, so you’ll never be left in the dark.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.