If you are designing your own intelligent “Graden Computer” with an optional digital plant moisture sensor/water pump ... the analog output (AO) of the module, to one analog input (A0) of the Arduino.

Here is a motor speed sensor module ... and pre-flight test, the module was connected to an Arduino board and measured the rotation per minute (rpm) rate of a geared robo motor (150rpm@5V) with the ...

Rotary encoders ... Chinese Arduino 37 sensor kits. (By the way, if you are looking for documentation on those kinds of boards, look here.; in particular, this was a KY-040 module.) ...