EC12-type encoder 

https://www.aliexpress.com/item/32748889074.html?spm=a2g0s.9042311.0.0.27424c4dV7N7fL

{{:arduino:pasted:20190919-235422.png}}

{{:arduino:pasted:20190928-182343.png}}

<code c++>
const int pinA = 2;
const int pinB = 3;

void setup() {
  Serial.begin(115200);
  pinMode(pinA, INPUT_PULLUP);
  pinMode(pinB, INPUT_PULLUP);
}

void loop() {
  Serial.print(digitalRead(pinA));
  Serial.print(",");
  Serial.print(digitalRead(pinB));
  Serial.println();
  delay(10);
}
</code>



using lib: https://github.com/PaulStoffregen/Encoder

<code>
#include <Encoder.h>
Encoder knobLeft(8, 9);
void setup() {
  Serial.begin(115200);
}
void loop() {
  Serial.println(knobLeft.read());
}
</code>

{{:arduino:pasted:20190928-193355.png}}