PinoutSearch

Read a Rotary Encoder (KY-040 + Arduino)

Count clicks and direction from an endless-turn rotary encoder, and reset with its button.

Beginner20 min

What you need

Wiring

Arduino Uno
Rotary encoder

Hover a pin or a wire to trace the connection.

Code

rotary_encoder.ino
// Count direction from a KY-040 rotary encoder; button resets to 0.
const int CLK = 2, DT = 3, SW = 4;
int lastClk;
long counter = 0;

void setup() {
  pinMode(CLK, INPUT);
  pinMode(DT, INPUT);
  pinMode(SW, INPUT_PULLUP);
  lastClk = digitalRead(CLK);
  Serial.begin(9600);
}

void loop() {
  int clk = digitalRead(CLK);
  if (clk != lastClk && clk == LOW) {          // one detent
    counter += (digitalRead(DT) != clk) ? 1 : -1;  // CW vs CCW
    Serial.println(counter);
  }
  lastClk = clk;

  if (digitalRead(SW) == LOW) {                // press to reset
    counter = 0;
    Serial.println("reset");
    delay(200);
  }
}

Steps

  1. Wire: + to 5V, GND to GND, CLK to D2, DT to D3, SW to D4.
  2. Upload and open the Serial Monitor.
  3. Turn the knob — the count goes up one way, down the other. Press to reset.