How to Use Rotary Encoder: Examples, Pinouts, and Specs

The KY-040 Rotary Encoder is an electro-mechanical device manufactured by GIAK, designed to convert the angular position or rotation of a shaft into digital signals. Rotary encoders are widely used in various applications such as volume controls, scrolling through menus, and as input devices in user interfaces. The KY-040 is particularly popular among hobbyists and is often used with microcontroller platforms like Arduino due to its simplicity and ease of use.

• Operating Voltage: 5V
• Pulse Number for One Revolution: 20
• Detent Positions: 20 per revolution
• Shaft Diameter: 6mm
• Output: 2-bit quadrature code
• Switch Life: 200,000 cycles
• Operating Temperature: -30°C to +70°C

To use the KY-040 Rotary Encoder with an Arduino UNO, connect the pins as follows:

• GND to Arduino GND
• +5V to Arduino 5V
• Signal A (CLK) to a digital pin (e.g., D2)
• Signal B (DT) to another digital pin (e.g., D3)
• Push Button (SW) to another digital pin (e.g., D4)

• Use pull-up resistors on the CLK and DT pins to ensure stable readings.
• Debounce the rotary encoder in software to prevent false readings due to mechanical noise.
• Implement an interrupt service routine to handle the rotary encoder's signals without missing pulses.

// Define the connections to the Arduino
const int pinCLK = 2; // Connected to CLK on KY-040
const int pinDT = 3;  // Connected to DT on KY-040
const int pinSW = 4;  // Connected to SW on KY-040

// Variables to hold the current and last encoder position
volatile int encoderPos = 0;
int lastEncoderPos = 0;
boolean buttonPressed = false;

// Interrupt service routine for encoder CLK pin
void isr() {
  if (digitalRead(pinDT) != digitalRead(pinCLK)) {
    encoderPos++; // Clockwise
  } else {
    encoderPos--; // Counterclockwise
  }
}

// Setup function
void setup() {
  pinMode(pinCLK, INPUT_PULLUP);
  pinMode(pinDT, INPUT_PULLUP);
  pinMode(pinSW, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(pinCLK), isr, CHANGE);
  Serial.begin(9600);
}

// Main loop
void loop() {
  if (encoderPos != lastEncoderPos) {
    Serial.println(encoderPos);
    lastEncoderPos = encoderPos;
  }
  if (digitalRead(pinSW) == LOW && !buttonPressed) {
    Serial.println("Button Pressed");
    buttonPressed = true;
  } else if (digitalRead(pinSW) == HIGH && buttonPressed) {
    buttonPressed = false;
  }
}

• Jittery or Inconsistent Readings: This can be caused by mechanical noise or a lack of debouncing in the code. Implement software debouncing to mitigate this issue.
• No Response from the Encoder: Ensure that the encoder is properly powered and that all connections are secure. Check for any damage to the encoder or its pins.
• Button Not Working: Verify that the button pin is correctly connected and that the internal pull-up resistor is enabled in the code.

• Debouncing: Implement a simple debounce algorithm in the interrupt service routine or use a library that handles encoder debouncing.
• Check Connections: Use a multimeter to ensure that there is continuity between the encoder pins and the Arduino pins.
• Serial Output: Use Serial.println() statements to debug and monitor the encoder's output in real-time.

Q: Can I use the KY-040 Rotary Encoder with a 3.3V system? A: Yes, but the output signal levels will be lower, which may require level shifting for some 5V systems.

Q: How can I increase the resolution of the encoder? A: The KY-040 has a fixed resolution of 20 pulses per revolution. To increase the effective resolution, you can use gear ratios or employ software algorithms to interpolate between pulses.

Q: Is it possible to use the encoder without an interrupt? A: Yes, but using interrupts is recommended to ensure all pulses are captured, especially at higher rotation speeds.