The rotary encoder is a great user input device with a satisfying tactile feedback. A lot of user interfaces are slowly transitioning towards button-less devices, but when in need of a physical system, I always love to use encoders.
However if you have ever worked with one, you know they are not so easy to interface; and the culprit is input bounce.
Bounce coupled with fast changing signals is a nightmare. There are libraries out there that solve this issue in software but with a 8 bit micro-controller like the ATMEGA328 of Arduino fame, all the processing power will be lost in trying to get a clean signal. This can be solved with a few passive components.
Hardware Debounced Rotary Encoder
This module completely eliminates the need to filter anything in software. Signals coming through are clean, bounce free. Saves me future headaches.
Bonus: a clean, bounce free edge captured on a scope