360-degree Rotary Encoder Module KY-040 with Aluminum alloy hat

Operating Voltage: 5V
Number of Pulses per Revolution: 20

A rotary encoder counts the number of output pulses during rotation in both the forward and reverse directions. Unlike a potentiometer, this rotational counting is unlimited. Using the buttons on the rotary encoder, it can be reset to its initial state, starting the count from 0.

Working Principle:
An incremental encoder is a rotary sensor that converts rotational displacement into a series of digital pulse signals. These pulses are used to control angular displacement. In the Eltra encoder, the conversion of angular displacement uses the photoelectric scanning principle. The reading system is based on the rotation of a radial indexing disk (code disk) consisting of alternating transparent and opaque windows, simultaneously illuminated perpendicularly by an infrared light source. The light projects the image of the code disk onto the surface of a receiver. The receiver is covered with a diffraction grating with the same window width as the code disk. The receiver's function is to sense the changes caused by the rotation of the disk and then convert the light changes into corresponding electrical changes. The low-level signal is then raised to a higher level, generating square pulses without any interference, which are processed by electronic circuitry. Reading systems typically employ a differential method, comparing two identical signals with a 180° phase difference to ensure output signal quality and stability. The reading is based on the difference between the two signals, thus eliminating interference.

Incremental encoders output two-phase square waves with a 90° phase difference, commonly referred to as channels A and B. One channel provides information related to rotational speed, while the direction of rotation is obtained by sequentially comparing the signals from the two channels. A special signal, called the Z or zero channel, indicates the encoder's zero position; this signal is a square wave whose line coincides with the square wave of channel A.

The accuracy of incremental encoders depends on both mechanical and electrical factors, including: grating indexing error, optical disc eccentricity, bearing eccentricity, errors introduced by the electronic reading device, and inconsistencies in the optical components. The unit of measurement for encoder accuracy is electrical degrees, which determine the pulse division produced by the encoder. The rotation of the mechanical shaft is represented by 360° electrical degrees, where one complete cycle is represented. To determine how many mechanical angles correspond to 360 electrical degrees, the following formula can be used: Electrical 360 = Mechanical 360° / n° pulses/revolution

Figure: Signals during A and B reversal
Encoder indexing error is expressed as the large offset between two consecutive pulse waves, measured in electrical angles. Errors exist in any encoder, caused by the aforementioned factors. The maximum error for an Eltra encoder is ±25 electrical angles (under any stated conditions), equivalent to a ±7% offset from the rated value. For two channels with a 90° (electrical) phase difference, the maximum deviation is ±35 electrical degrees, equivalent to approximately ±10% of the rated value.

UVW Signal Incremental Encoder
Besides the traditional encoders mentioned above, there are also incremental encoders that integrate with other electrical output signals. An example is the incremental encoder integrated with UVW signals, typically used for feedback in AC servo motors. These magnetic signals are generally present in AC servo motors, and UVW signals are generally designed to simulate the function of magnetic components. In Eltra encoders, these UVW signals are generated optically and appear as three square waves offset from each other by 120°. To facilitate motor starting, the starter used to control the motor requires these correct signals. These UVW magnetic pulses can be repeated many times during the rotation of the mechanical shaft because they are directly dependent on the number of magnets of the connected motor, and are used for UVW signals of 4, 6 or more motors.