What are Rotary Encoders

What is a Rotary Encoder?

A rotary encoder is an electro-mechanical device that converts the angular position or motion of a shaft or axle to an analogue or digital signal. Rotary encoders  are commonly used in various applications to provide precise position, speed, and direction feedback. Rotary encoders are integral components in many systems, from industrial machinery and robotics to consumer electronics, where accurate control of movement is essential.

How Do Rotary Encoders Work?

Rotary encoders work by translating the mechanical rotation of a shaft into an electrical signal that can be read by a control system. This is achieved through a combination of sensors, coding discs, and electronics. A typical rotary encoder consists of a rotating disc with alternating light and dark patterns (for optical encoders) or magnets (for magnetic encoders). As the disc rotates, sensors detect changes in the pattern or magnetic field, generating signals that correspond to the position, speed, and direction of the shaft. The signals are then processed to determine the exact rotational position or movement.

Types of Rotary Encoders

There are two main types of rotary encoders: absolute and incremental.

Absolute Rotary Encoders: Absolute encoders provide a unique code or signal for each position of the shaft, allowing the system to know the exact position even after power loss or a system reset. They are particularly useful in applications requiring precise and repeatable positioning.

Incremental Rotary Encoders: Incremental encoders generate signals only when the shaft is rotating and provide relative position information. They offer high resolution and are suitable for applications where speed and direction are more critical than the exact position. Unlike absolute encoders, incremental encoders do not retain positional information when power is lost; they only indicate movement relative to a known reference point.

Applications of rotary encoders

Rotary encoders are vital components in a wide range of industries, offering precise position, speed, and direction feedback in various systems. Here are some key applications:

• Industrial machinery: Rotary encoders are commonly used in automation systems, CNC machines, packaging, and manufacturing equipment, where they provide essential feedback for movement control and precision machining.
• Robotics: In robotics, encoders help monitor the position of robotic arms, drones, and autonomous vehicles, ensuring accurate movement and positioning in both industrial and research applications.
• Consumer electronics: Many everyday devices, such as gaming joysticks, computer mice, and volume control knobs on audio systems, rely on rotary encoders for precise input tracking.
• Automotive industry: Rotary encoders are employed in various automotive systems, including engine control, steering systems, and speed sensing for vehicle stability and safety.
• Medical devices: Precision control is essential in medical imaging equipment and laboratory devices, where rotary encoders ensure accurate movement of components like imaging heads and robotic surgical tools.

Key specifications to consider when selecting an encoder

When choosing the right encoder for a specific application, it’s important to evaluate several key factors:

• Resolution: This defines the number of distinct positions or pulses generated per revolution. Higher resolution encoders provide finer positional accuracy, making them ideal for applications requiring precise control.
• Accuracy: Accuracy refers to how closely the encoder’s feedback matches the actual position. For applications demanding high precision, such as robotic surgery or semiconductor manufacturing, accuracy is key.
• Durability and environmental resistance: Rotary encoders must be able to withstand harsh environments, including exposure to dust, moisture, extreme temperatures, and vibrations. Industrial applications often require encoders with high durability and protective enclosures.
• Output type: Rotary encoders can have analogue or digital outputs. Digital encoders provide more robust and noise-resistant signals, making them preferable in environments with electrical interference.
• Mounting and size: Rotary encoders come in various sizes and configurations. Consider the physical space available and the type of mounting that best suits the hardware setup.

Absolute vs incremental rotary encoders: which one to choose?

Choosing between an absolute and incremental rotary encoder depends on your specific application needs. Here’s a comparison to help guide your decision:

Technologies behind rotary encoders

Rotary encoders utilise different technologies to detect position and movement. Here are the most common types:

• Optical encoders: These encoders use a light source, such as an LED, and a rotating disc with transparent and opaque sections. As the disc rotates, light passes through or is blocked, and a photodetector converts this into a digital signal. Optical encoders offer high resolution and accuracy but can be affected by dirt or dust.
• Magnetic encoders: Magnetic encoders detect changes in a magnetic field using a rotating magnet and sensors. They are less sensitive to environmental conditions, making them more durable in harsh environments, though their resolution may be lower than optical encoders.

Frequently asked questions (FAQs)

How do rotary encoders differ from linear encoders?
Rotary encoders measure angular position, speed, and direction, while linear encoders measure linear movement along a straight path. The choice between the two depends on the nature of the motion being monitored.

Can an incremental encoder be used as an absolute encoder?
No, incremental encoders only provide relative movement information, whereas absolute encoders provide a unique position for every shaft angle. They serve different purposes based on application needs.

What happens if an incremental encoder loses power during operation?
If power is lost, an incremental encoder will lose track of its position. After power is restored, the system will need to re-reference to a known position before accurate feedback can resume.

Timken Rotary Encoders

We offer a variety of absolute position and incremental rotary encoders. 

Buy Timken encoders online here or contact us for more information.