This is a collection of simple design ideas some of which date back to the 1960s. All of these have been tested recently with updated component types. Some use very unusual methods.

Today you can buy gadgets to do most of what these do. It is much more fun to build your own, try variations, and tailor them to do exactly what you want.

Copyrighted drawings are under a Creative Commons 3.0 license. Unmarked drawings are public domain.