If counterclockwise, the DOWN signal is registered at each step. Luckily, using the mouse scroll wheel encoder with an Arduino Uno proved to be easy after I made a slight modification (see below).

Every single (non-optical) mouse comes with a pair built in. On either side of the encoder wheel are some little boxes. One side is an IR emitter, and the other side is a pair of IR detectors.

Imagine creating a mouse that fits your hand perfectly, providing comfort and precision. You can make this a reality by combining the power of Arduino ... operated scroll wheel for ease of use.