Rotary Encoder Module KY-040

A rotary encoder has a fixed number of positions per revolution.   These positions are easily felt as small “clicks” you turn the encoder.
The Keyes module that I have has thirty of these positions.

On one side of the switch there are three pins.   They are normally referred to as A, B and C.   In the case of the KY-040,  they are oriented as shown.

Inside the encoder there are two switches.  Once switch connects pin A to pin C and the other switch connects pin B to C.

In each encoder position, both switches are either opened or closed.  Each click causes these switches to change states as follows:

• If both switches are closed,  turning the encoder either clockwise or counterclockwise one position will cause both switches to open
• If both switches are open, turning the encoder either clockwise or counterclockwise one position will cause both switches to close.