He used this knowledge to design a device called Op Art which generates Spirograph shapes on your oscilloscope using just a handful of op amps. To draw either a hypotrochoid or an epitrochoid ...
When you compute the number of vertices in a spirograph shape, you take the least common multiple of the two gears (or sets of gears) and divide by the small gear. So a 60-tooth turntable turning ...
The spirograph has been around since the mid 60s, putting it firmly in the class of being a 'retro' craft toy, but it's never really gone out of fashion. The clever cog and ring design can help ...