I don’t know exactly what to call this, but there’s one in my car’s centerstack, and of course the original iPod had something like it. It’s a clickstopped switch that can turn infinitely in either direction. Turn it in one direction, and you get one “up” pulse with each click; turn it in the other direction, and you get one “down” pulse with each click. I assume that inside there are just two SPST switches and some clever mechanism that clicks one of them when you turn the knob one way, and clicks the other one when you turn the knob the other way.
I’m thinking that this kind of switch hooked up to a couple of Arduino pins would be a nice input for a variety of projects: you could use it to scroll through options, increment or decrement values by specific amounts, etc.
I’ve looked through the ‘components’ section of the Sparkfun website and don’t see anything like this. Thoughts…?