Vampire Flashlight


A single fully-charged AA battery is incapable of powering high-flux LEDs. However with the aid of a toroid, bipolar NPN transistor, and the popular Joule Thief circuit, you can even turn "dead" batteries into a capable flashlight power source. Read more »

Super Simple iPod FM Transmitter


FM transmitters can be complicated to build, but not this one — it's about the easiest you can possibly make. And though the science of radio is well understood, there's a magical, emotional quality about it that we don't often stop to appreciate. Building your own radio receiver — or... Read more »

Infrared Pulse Sensor


Taking your pulse is as simple as holding a finger to your neck or wrist and timing the beats with your watch. But if you want to record the data or use it to trigger events, you need to turn that mechanical pulsing action into an electrical signal. This pulse... Read more »