The KY-040 Rotary Encoder is a mechanical incremental encoder that converts rotational position and direction into electrical signals. Designed with a 360-degree mechanical angle and a built-in knob, it is ideal for precise control of motors such as steppers and servos. It is commonly used in automation systems, robotic interfaces, and user input controls.

Specifications:

• Operating Voltage: 5V DC

• Mechanical Rotation Angle: 360° (continuous rotation)

• Output Format: 2-bit Gray code (quadrature output)

• Positions Per Revolution: 30 detents (steps)

• Output Type: Digital square wave pulses

• Shaft Type: With detents for tactile feedback

• Switch Type: No integrated push-button switch

Pin Configuration:

The KY-040 module includes five pins for power and signal transmission. Below is the pin description:

Working Principle:

The KY-040 encoder works by generating two square wave signals (channels A and B) as the knob rotates. These signals are offset from each other and represent incremental changes in the encoder’s position. The phase difference between the signals determines the direction of rotation:

• If Channel A leads Channel B, the encoder is rotating clockwise.

• If Channel B leads Channel A, the encoder is rotating counter-clockwise.

By counting the pulses and determining the signal sequence, a microcontroller can measure both rotation and direction.

Wiring Instructions:

To interface the KY-040 with a microcontroller:

• VCC → Connect to +5V supply on MCU/MPU

• GND → Connect to ground on MCU/MPU

• CLK → Connect to digital input pin on MCU

• DT → Connect to another digital input pin on MCU

The encoder generates digital pulses, so standard interrupt-based or polling methods can be used for signal reading and position tracking.

Applications:

• Rotary input control in embedded user interfaces

• Robotic arm positioning and feedback

• Servo or stepper motor precision control

• Menu navigation for digital devices

• Industrial automation controls