A Variac looks like a sci-fi laboratory prop. For some reason, I have three of them in my shop, and yes, one is just a book end. But they do have a useful purpose.
Variac is a generic trade name for a variable autotransformer. If that doesn't help explain much, let's look at what a regular transformer is, and how they relate to a collection of vintage arcade games.
You remember calculus, right? In a time before mechanized computing was performed by computers, complex (or sometimes just clever) machines were used to automate calculations. One example that has always impressed and fascinated me is the wheel-and-disk integrator, a simple machine capable of solving the calculus equations you labored over in high school without breaking a sweat. While this concept was used most impressively in Vannevar Bush's differential analyzer, an analog computer built in 1931, the chances are good that you've seen one in a more mundane application around your house: the power meter. Click on the photo gallery to see inside one and how it works, and follow the jump for more in-depth electro-geekery.
Much of the quality and variety of what I build depends on the quality and variety of parts and materials that I can source. To this end, I collect and semi-religiously thumb through catalogs. (Yes, most of these places also have Web sites, but sometimes catalogs are just easier, or at least more fun.) Whether for selection, esoterica or service, here are my six favorite vendors for all my project needs. Got a favorite of your own? Tell us about it in the comments.
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.