Motion Control: Rotary Encoders

Explore encoders as feedback devices in motion control systems, understand closed-loop motion control, and review encoder classifications, including linear and rotary encoders.

Explore how motion control uses linear and rotary profiles to move objects with precise acceleration, velocity, and deceleration, and learn how encoders provide closed-loop feedback for accurate, repeatable performance.

Learn how encoders convert mechanical motion into electrical signals, providing position, speed, and direction for rotary and linear motion, using optical rotary encoders with code disks, light sources, and detectors.

Explore how application requirements determine encoder selection, considering form, size, resolution, precision, and interface with motion controllers. Compare absolute and incremental rotary encoders, their sensing technologies: magnetic, optical, capacitive IP67.

Compare linear and rotary encoders, showing how linear encoders use a head with optical or magnetic sensing to measure position, while rotary encoders use pulses to track speed and direction.

Identify the importance of encoders as the feedback element in motion control, define encoders, and compare different types, including linear and rotary encoders.

Learn to identify and describe incremental encoder output signals, including open collector, push-pull or HDL and line driver or TTL, critical for proper system integration.

Incremental encoders use optical disc with opaque and transparent sectors, a photoelectric sensor, and a converter to generate square pulses that measure travel distance, speed, and resolution from disc slots.

The AB encoder, also called a quadrature encoder, uses two signals with 90-degree phase offset to measure rotation angle, count pulses, and determine rotation direction.

Learn how the z index pulse, a single pulse per revolution, marks the zero position in incremental encoders, enabling homing, position within a revolution, synchronization, and detection of errors.

Sin/cos encoders output analog sine waves A and B with a 90-degree phase shift, delivering higher resolution than incremental encoders and improving servo motor motion, velocity control, and noise reduction.

You have learned how an incremental rotary encoder works, including A and B signals, the Z or N signal in incremental encoders, and analog signals with sine causa encoders.

Verify the output signal type of an incremental encoder to ensure proper system integration, and understand its electronic signals, including open collector, push-pull or HDL, and TTL.

Learn how incremental encoders generate square wave pulses for position data. Interface them with controllers using pulse counter and driver types such as open collector, push-pull, and differential driver.

Understand how open collector outputs use an NPN transistor to sink current and float when off, with pull up resistors establishing high levels and noise immunity.

Explore push pull hdl encoders that use a totem-pole of npn and pnp transistors to provide fast sourcing and sinking outputs with no external pull-up resistors.

Explain differential line driver outputs for motion control encoders, with two signals and one inverted to improve noise immunity, TTL or HDL levels, RS-422 compatibility, and common mode rejection.

Explore the electronic signal options offered by incremental encoders, including open collector, push-pull, and line driver or TTL outputs.

Explore the working principle of absolute encoders and describe how Gray code enables absolute encoders to function. Compare absolute, incremental, and multi-turn absolute encoders.

Explore gray code, a one-bit change representation used in rotary encoders to minimize errors. Compare gray code disks with binary coded disks, using a mask wheel to sense shaft position.

Absolute encoders use a gray or binary coded disk and scanning head to deliver a unique digital code for each angular position, with higher track counts boosting resolution.

Compare absolute and incremental encoders, showing how absolute encoders provide exact position in digital binary codes, while incremental encoders deliver relative position through pulse outputs.

Absolute multi-turn encoders pair an absolute encoder with a multi-turn counting mechanism to measure shaft position across multiple rotations for applications like wind turbines, conveyors, and elevators.

Explore how Gray code relates to encoder signaling, learn how an absolute encoder works, compare incremental and absolute encoders, and understand the concept of a multi-turn absolute encoder.

Explore the most common formats in a typical motion control system and learn to describe parallel output, encoder, hyper phase, encoder bias.

Explore parallel output for absolute encoders, where each track bit is transmitted on its own wire; higher resolution means more wires, increased wiring complexity, and noise, leading to serial alternatives.

Ssi encoders use a synchronous serial interface to transfer absolute encoder data. Clock and data signals run on twisted pair wires, enabling plc compatibility, noise immunity, up to 1.5 mhz.

Explore the EnDat bidirectional RS-485 interface for absolute and incremental encoders, using four signal lines and mode commands to transmit position, temperature, and diagnostics.

Explore hyperflex, a hybrid rs485 interface that transmits speed and position via digital and analog signals, enabling absolute and incremental positioning with robust motion control.

BiSS is a bidirectional synchronous serial interface enabling master-slave encoder communication, memory read/write, data frames with start bits and CRC checksums, and high-speed bus configurations.

Learned how parallel output interface works and gained an overview of popular absolute encoders output interfaces, including SSI and BIS.

Explore line and pulse counts to determine incremental encoder resolution, including PPR, CPR, LPR, and quadrature. Compare incremental and absolute encoders and their bit-based resolutions.

Assess rotary encoder speed and frequency to ensure the encoder's maximum frequency supports the required application, using pulses per revolution and rpm to calculate frequency.

Explore accuracy, precision, and resolution in rotary encoders. Learn how deviations, repeatability, and units such as degrees, arc minutes, and arc seconds impact CNC and robotics.

Learn how encoder resolution is defined and measured, and why speed and frequency matter for encoders. Understand the difference between accuracy and precision.

Explore the technologies used to build encoders, including optical, magnetic, and capacitive encoders, and understand how manufacturers apply these approaches.

Identify how optical encoders use a light source and a coded disc to convert light transitions into position and speed signals, outlining transmissive and reflective types and material trade-offs.

Explore magnetic encoders as alternatives to optical encoders, using a hall sensor and permanent magnet on a magnetic disk with alternating poles to set resolution and reliability in harsh environments.

Capacitive encoders detect rotor position and speed by capacitance changes with a high frequency reference and a sinusoidal rotor pattern. Pros: compact, low power; cons: condensation and EMI/RFI noise.

Explore the technologies used in encoder measurement, including optical, magnetic, and capacitive, as you complete lesson seven in motion control: rotary encoders.

Explore the forms and types of rotary encoders, and learn to understand and describe their physical construction, fieldbus interfaces, and datasheets.

Discover the physical forms of rotary encoders—solid shaft, hollow shaft, and ring encoders—and how secure installation, precise alignment, and the right housing and working distance impact accuracy.

Explore fieldbus encoders that use ethernet-based protocols to transmit position and motion data to PLCs and motion controllers, with deep dives into Ethernet IP, Profinet, Ethercat, Powerlink, and Drive Click.

Understand how rotary encoder datasheets list model and part numbers, performance, electrical and mechanical specs, pinouts, environmental limits, certifications, and fieldbus compatibility.

Learn the physical forms and shapes of rotary encoders, explore encoders with network interfaces, and identify what to look for in an encoder datasheet.

Explore how rotary encoders are applied in automated systems and how to choose the right encoder. Understand application categories, sizing, and selection for motion control.

Survey of rotary encoder uses in production, robotics, CNC, printing, medical, food, marine, energy, and mining. Highlights selection factors: accuracy, resolution, speed, durability, compactness, and multi-turn capability for precise motion.

Identify encoder options through selection criteria, sizing parameters, and non-technical factors. Match application type and class, shaft, housing, and interfaces, including absolute versus incremental, resolution, and IP and safety certifications.

Identify common applications and systems for encoders and outline the key factors in encoder sizing and selection.