Here's a new addition to our rotary-potentiometer-knob family. This knob has a nice soft-touch feel with an arrow on it, and its much 'slimmer' than the skirted knob we have been using, so good for compact layouts.

Note: This is just the knob. We have a breadboard-friendly rotary encoder here.

Rotary encoders are useful as rotation sensors or selectors and look similar to potentiometers. However, they are not like potentiometers at all, so it's important to realize the difference! These rotary encoders rotate all the way around continuously and are divided up into 24 'segments'. Each segment has a clicky feeling to it, and each movement clockwise or counter-clockwise causes the two switches to open and close. There is no way to know what the current 'position' is - instead you would use a microcontroller to count how many 'clicks' left or right it has been turned. If you need to detect rotational 'position' a potentiometer would be a better choice.