Rotary Encoder

Description

Rotary Encoder

This listing describes a KY-040 electromechanical incremental rotary encoder. Its quadrature outputs allow a controller to detect relative rotation and direction. An integrated push switch can be used for selection or confirmation.

🔧 Listed specifications

• Supply: 5 V DC as stated in the listing
• Type: incremental rotary encoder with quadrature signals
• Resolution: multiple pulses per revolution; no exact count is given
• Integrated normally-open (N.O.) push switch
• Compact form for control panels and robotics projects

⚙️ How it works

As the shaft turns, the CLK and DT signals change state in sequence. Comparing them indicates direction; counting transitions provides relative movement. Press the shaft to operate the SW switch.

💡 Applications

• Rotary user-interface controls
• Relative motor-speed adjustment
• Robot navigation
• Interactive interfaces
• DIY electronics projects

📌 Pinout

• GND: ground
• VCC: supply (5 V as listed)
• SW: push-switch output (N.O.)
• DT: quadrature output B
• CLK: quadrature output A

🔌 Using it with an Arduino Uno

Connect GND and VCC to Arduino ground and a compatible supply. Connect DT and CLK to digital inputs to read rotation, and SW to a digital input to detect a press. The examples below are retained from the source listing; debouncing may be needed for stable readings.

Basic Arduino example

#define CLK 4
#define DT 3
#define SW 2


int counter = 0;
int currentStateCLK;
int lastStateCLK;
String currentDir = "";


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


void loop() {
  currentStateCLK = digitalRead(CLK);
  if (currentStateCLK != lastStateCLK) {
    if (digitalRead(DT) != currentStateCLK) {
      counter--;
      currentDir = "CCW";
    } else {
      counter++;
      currentDir = "CW";
    }
    Serial.print("Direction: ");
    Serial.print(currentDir);
    Serial.print(" | Counter: ");
    Serial.println(counter);
  }
  lastStateCLK = currentStateCLK;


  int buttonState = digitalRead(SW);
  if (buttonState == LOW) {
    Serial.println("Button Pressed");
  } else {
    Serial.println("Button Released");
  }
  delay(50);
}

The sketch reads rotation direction and count and reports whether the push switch is pressed in the Serial Monitor.

Advanced example with an I2C LCD

#define CLK 4
#define DT 3
#define SW 2


int counter = 0;
int currentStateCLK;
int lastStateCLK;
String currentDir = "";


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


void loop() {
  currentStateCLK = digitalRead(CLK);
  if (currentStateCLK!= lastStateCLK) {
    if (digitalRead(DT)!= currentStateCLK) {
      counter--;
      currentDir = "CCW";
    } else {
      counter++;
      currentDir = "CW";
    }
    Serial.print("Direction: ");
    Serial.print(currentDir);
    Serial.print(" | Counter: ");
    Serial.println(counter);
  }
  lastStateCLK = currentStateCLK;


  int buttonState = digitalRead(SW);
  if (buttonState == LOW) {
    Serial.println("Button Pressed");
  } else {
    Serial.println("Button Released");
  }
  delay(50);
}

This example displays relative position and direction on an I2C LCD and reports the push-switch state.

Components

• Arduino Uno
• KY-040 rotary encoder module
• I2C 1602 LCD
• Connecting wires

Code overview

1. Include libraries: #include <Wire.h> and #include <LiquidCrystal_I2C.h> for the LCD.
2. Initialization: Starts serial communication, initializes the LCD, and configures the encoder pins.
3. Read and display: Reads encoder signals and shows direction and relative count on the LCD and in the Serial Monitor.

Advanced wiring

• VCC: 5V (Arduino)
• GND: GND (Arduino)
• CLK: D4 (Arduino)
• DT: D3 (Arduino)
• SW: D2 (Arduino)
• LCD VCC: 5V (Arduino)
• LCD GND: GND (Arduino)
• LCD SCL: A5 (Arduino Uno)
• LCD SDA: A4 (Arduino Uno)

Library installation

Install the LiquidCrystal I2C library through Arduino IDE’s Library Manager: open Sketch → Include Library → Manage Libraries, search for “LiquidCrystal I2C”, and install it.

Check the pin labels before connecting the module. The exact pulse count is not provided in the source listing.