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Rotary Encoder with Esp32

23-07-2025

📌 What is a Rotary Encoder?

A rotary encoder is an electro-mechanical sensor that converts the angular position or motion of a rotating shaft into digital signals. Unlike a potentiometer, it can rotate infinitely in either direction and is commonly used in digital volume knobs, step selection, or menu navigation.

There are two main types:

Incremental (most common)
Absolute

The most widely used type with ESP32 is the incremental rotary encoder with a push-button switch.

🧠 Key Features of Rotary Encoder

Feature	Details
Rotation	Continuous 360° (no end stops)
Signal Output	Digital (Quadrature: A and B)
Additional Button	Built-in push button (optional)
Resolution	Typically 20 pulses per rotation
Operating Voltage	3.3V to 5V
Durability	Long life (up to 100,000 rotations)

⚙️ Pinout of Rotary Encoder

Pin	Name	Description
CLK	Output A	Channel A (primary output)
DT	Output B	Channel B (direction control)
SW	Switch	Push-button (active LOW)
VCC	Power	3.3V or 5V input
GND	Ground	Common ground

📦 How It Works

A rotary encoder generates two square wave signals (CLK and DT) slightly out of phase. By comparing the timing between these signals, the ESP32 can determine the direction of rotation:

Clockwise (CW): CLK leads DT
Counterclockwise (CCW): DT leads CLK

The SW pin is a built-in push button often used to select or confirm actions.

🧪 Applications of Rotary Encoder

Digital volume knobs
Menu navigation in embedded systems
Motor position tracking
CNC machines and robotics
Media players and audio mixers
IoT interfaces and control panels

🔗 Basic Example with ESP32

✅ Components Needed

ESP32 Dev Board
Rotary Encoder Module (KY-040 or similar)
Jumper Wires
Breadboard

📍 Where to Use a Rotary Encoder

🔊 Digital volume control for audio systems
📻 Tuning knobs in radios and receivers
📋 Menu navigation in embedded systems (LCD/OLED)
🔁 Infinite scrolling inputs (brightness, time, settings)
🧭 Direction and position control in robotics

🧾 ESP32 Code With Rotary Encoder

HOW TO OPERATE

#define CLK 19

#define DT 18

#define SW 21

int counter = 0;

int lastStateCLK;

bool currentStateCLK;

bool currentStateSW;

bool lastStateSW = HIGH;

void setup() {

pinMode(CLK, INPUT);

pinMode(DT, INPUT);

pinMode(SW, INPUT_PULLUP);

Serial.begin(115200);

lastStateCLK = digitalRead(CLK);

}

void loop() {

currentStateCLK = digitalRead(CLK);

if (currentStateCLK != lastStateCLK && currentStateCLK == 1) {

if (digitalRead(DT) != currentStateCLK) {

counter++;

} else {

counter--;

}

Serial.print("Counter: ");

Serial.println(counter);

}

lastStateCLK = currentStateCLK;

currentStateSW = digitalRead(SW);

if (currentStateSW == LOW && lastStateSW == HIGH) {

Serial.println("Button Pressed");

delay(50);

}

lastStateSW = currentStateSW;

delay(1);

}

❗ Important Notes

Debouncing: Mechanical rotary encoders may need software debouncing or filtering for smooth reading.
Interrupts: For better performance and smoother rotation, use hardware interrupts instead of polling.
Pull-ups: Some modules have built-in pull-up resistors; if not, use INPUT_PULLUP.
Power Compatibility: Works on both 3.3V and 5V logic—perfect for ESP32.
Wiring Tip: Keep wires short to reduce noise.