Rotary Encoders

Rotary encoders are essential components in industrial electronics and other applications. They help machines, devices, and systems track rotational movement with precision. From operating machinery to scrolling the wheel on your mouse, rotary encoders help ensure that machines and systems perform tasks with high accuracy, minimizing errors and improving overall system performance. In this article, we’ll explore rotary encoders, how they function, and the different types available, shedding light on their role in various applications.

Rotary encoders work behind the scenes in applications of all kinds, from everyday activities like dialing up the volume on your car stereo to advanced industrial applications like operating machinery or controlling robotic pick-and-place systems in assembly lines. A rotary encoder is a device that turns rotational motion into a readable electrical signal, which helps machines or computers understand the position or movement of the knob. Think of them like the ‘eyes’ of a system that needs to know how far something has rotated so it can translate the turning motion into information a system can use to control things like speed or position.

A rotary encoder detects speed and position by converting rotational mechanical displacements into analog or digital output signals, which are then processed. Although there are different types, they all operate on the same basic principles of rotation detection, signal generation, signal interpretation, and output. These components can be configured to send a shaft’s position in one of two ways: as an incremental measure or as an absolute value. Their basic working principle begins when a shaft or knob is turned, causing the encoder's internal mechanism, which can be mechanical, optical, or magnetic, to rotate. 

Mechanical rotary encoders include a disk with conductive tracks, typically segmented into specific patterns, and fixed contact points, such as brushes or wipers, that maintain physical contact with the tracks on the disk. As the shaft rotates, the brushes move across the conductive tracks, completing circuits at specific points during rotation and generating electrical signals. In optical encoders, a disk with patterns, such as lines or holes, passes through an optical sensor as the shaft turns. Rotary positional encoding occurs when the sensor detects changes in the light as the patterns move past it and converts them into electrical signals. Finally, the magnetic rotary encoder uses a magnetized disk or ring with alternating poles that rotate past magnetic sensors. The sensors detect changes in the magnetic field and convert them into electrical signals representing the rotation’s speed, position, or direction.

There are two main types of rotary encoders in industrial electronic applications: incremental encoders and absolute encoders. Both are used to measure the position angle in a variety of industries and applications, from industrial automation to navigating and communication systems and more. The main difference between these two types of encoders is how they provide position information. An absolute rotary encoder retains its exact position even after power loss, assigning a unique value to every shaft angle. This is ideal for applications where knowing the precise position at all times is critical, such as robotics or elevators. With an incremental rotary encoder, the pulse or signals are generated as the shaft turns, indicating position, speed, or direction changes. Therefore, the position is calculated relative to a starting point. These encoder types are suitable for speed measurement or applications where relative motion is sufficient, like conveyor belts or motor feedback. In short, absolute encoders share where you are, whereas incremental encoders share how far you’ve moved.

These components are instrumental across various industries for obtaining feedback on positioning, speed, and direction within applications and systems. In industrial automation, encoders play a critical role in controlling machinery, conveyor belts, and production lines. In robotics, they enable precise motion control, helping robots navigate, position arms, and accurately perform tasks. Rotary encoders are also instrumental to consumer electronics, providing smooth and responsive control for user interfaces while adjusting settings in everyday devices like volume knobs, computer mice, washing machines, and more. 

Once you have determined which type of encoder, absolute or incremental, meets your application’s needs, consider the following when narrowing down your selection.

First, consider the application’s space requirements, including the housing diameter, housing profile (height), and the shaft diameter

Consider the type of shaft that is required, e.g., hollow or regular shaft, as it pertains to the mounting space.

The resolution determines the rotary encoder’s precision. Higher resolutions provide more position data per revolution, which is essential for applications requiring fine control.

Based on environmental conditions, consider which rotary encoder sensor best suits the application, i.e., optical, magnetic, or capacitive.

Factors like temperature range, shock, vibrations, and protection (IP Rating) against dust and moisture must be considered.

Other important considerations include power requirements and compatibility with the existing control system’s connectivity and interface.

In modern electronic systems, rotary encoders are essential for providing precise, real-time feedback on the position, speed, and direction of mechanical components, which is crucial for the smooth operation of automated systems. This accurate motion control is essential in manufacturing, automation, and other industries to ensure safety, quality, and efficiency. 

Peerless Electronics is a stocking distributor for quality incremental optical rotary encoders from Sensata BEI Sensors, with a wide variety available to shop online. We are certified to stringent AS9100D / ISO 9001:2015 standards and have recently added CMMC compliance to our portfolio, so you can rest assured your requirements are handled with the highest level of professionalism in the industry.

What is the difference between rotary and mechanical encoders?

Rotary encoders are all encoders that measure rotation, regardless of their sensing method. A mechanical encoder, however, is a rotary encoder type that uses physical contact to detect movement.

How long do encoders last? 

The lifespan of a rotary encoder depends on its type, operating conditions, and usage. Mechanical encoders typically have the shortest lifespan, and magnetic encoders have the longest.

Can encoders handle high-speed applications?

Yes, provided the right type is selected. Optical encoders are common in high-speed applications due to their high resolution and fast signal response.