Encoder: Concept and Applications

Are you familiar with the concept of an encoder and what it entails? In this article, we aim to introduce the various types of encoders along with their applications. Please stay with us until the end of the article as we delve into important aspects of encoders.

Before fully understanding the operation of an encoder, it’s essential to grasp the concept and function of this device. Therefore, join us in this article to become acquainted with this topic.

What is an Encoder?

An encoder is a mechanical motion sensor that processes to produce digital signals in response to movement. As an electromechanical device, it can provide information about position, speed, and direction for users of motion control systems.

Main Types of Encoders

Linear and rotary encoders are divided into two main types: absolute and incremental. Both types are structurally similar; however, they differ in physical characteristics and motion properties.

1. Incremental Encoder

The incremental rotary encoder is also known as a quadrature encoder. These sensors use optical, mechanical, or magnetic indicators to measure angles.

How Incremental Encoders Work

The incremental rotary encoder uses a transparent disk containing opaque sections that determine motion distances. A light emitter diode is used to pass through the glass disk and is detected by an image tracker. This causes the encoders to generate pulses with consistent intervals during rotation.

Absolute Encoder

An absolute encoder includes components found in incremental encoders as well. They implement a light detector and an LED light source, but instead of a disk with equally spaced lines, they use a disk with concentric patterns.

1. Operation of Absolute Encoders

The output signal generated by an absolute encoder is in digital bits, each indicating a specific position. These bits are generated by the light received by the photodetector device as the disk rotates. Then, the received light is translated into gray code, resulting in each position having its unique bit configuration.

2. Linear Encoder

A linear encoder is a sensor, transducer, or reader associated with a scale that encodes position. This sensor reads the scale and converts the position into an analog or digital signal, which is then processed for digital reconstruction. Motion is determined from changes in position over time. Both types of linear encoders, optical and magnetic, operate using this method. However, their physical characteristics distinguish them from each other.

Operation of Optical Linear Encoders

The light source and lens create a parallel beam of light passing through four or five scanning windows. These four or five windows, scanned at 90-degree intervals, change position. Then, the light passes through the glass scale and is detected by light sensors. Subsequently, during unit movement scanning, the scale detects a beam of light. Light detection by the light sensor produces sinusoidal wave outputs. Finally, the linear encoder system combines shifted signals to create two symmetrical sinusoidal outputs, but out of phase by 90 degrees.

Controlling Encoders

Encoders are controlled through the rotation installed on them. The shaft makes contact with a ball inside the encoder. With the rotation of the shaft, the disk with transparent and opaque lines within the circuit of this device rotates. Its circuits include an LED that is picked up by a photovoltaic diode and transmits pulses to the user. The rotation speed of the disk depends on the rotational speed to which the encoder is connected.

Physical Specifications of Encoders

Linear Encoders:

The main components of linear encoders include a scanning unit and a transducer sensor paired with a transmissive or reflective scale that encodes position. The scale of a linear encoder is generally made of glass and mounted on a support. The scanning unit includes a light source, light cells, and a second glass piece called a scan network.

Rotary Encoders:

The main components of this model include light sources, detectors, and electronics. The disk consists of a unique pattern of concentric circles and alternates between opaque and transparent sections. This pattern provides unique bit configurations and is used to allocate specific positions.

Incremental Encoders:

The main components of an incremental encoder include a glass disk, LED (light-emitting diode), and a photoelectric sensor. The transparent disk has opaque sections that deflect light at a distance, while transparent sections allow light to pass through. The optical encoder uses a light-emitting diode to shine light through the transparent sections of the disk.

Controlling Encoders

Encoders are controlled through the rotation installed on them. A shaft, fitted inside the encoder, makes contact with a ball. As the shaft rotates, a disk with transparent and solid lines within the circuit of this device also rotates. Its circuits include an LED picked up by a photovoltaic diode, transmitting pulses to the user. The rotation speed of the disk depends on the rotational speed to which the encoder is connected.

Applications of Encoders

1. Automotive:

The automotive industry utilizes encoders as mechanical motion sensors may be used for speed control.

2. Consumer Electronics and Office Equipment:

In the consumer electronics industry, encoders are widely used in office equipment such as PC scanners, printers, and scanners.

3. Industrial:

In industries, encoders are used in labeling machines, packaging, and machine tools with motor controllers for single and multi-axis. Additionally, encoders are used in controlling CNC machines.

4. Medical:

In the medical industry, encoders are used for medical scanners, controlling microscopic or nanoscopic movements, automatic devices, and distribution pumps.

5. Military:

The military also employs encoders in positioning antennas.

Selection Criteria for Encoders:

1. Output: The type of output signal is crucial.

2. Desired Resolution (CPR): The number of pulses per complete revolution determines resolution.

3. Noise and Cable Length: The amount of noise produced and cable length can be influential.

4. Index Channels: The presence of additional channels for determining the index position.

5. Enclosure/Base: Protective enclosure and base type are important.

Advantages of Encoders:

– Highly reliable and accurate.

– High resolution.

– Integrated electronics.

– Utilization of optical and digital fusion technologies.

– Compatible with existing programs.

– Compact size.

Disadvantages of Encoders:

– Magnetic or radio frequency interference (for magnetic encoders).

– Direct light source interference (for optical encoders).

– Susceptibility to contamination from dust, oil, and dirt.

With the provision of this information, we thank you for staying with us until the end of this article. If you need to purchase industrial electrical equipment, you can contact our experts at Electrosheely.

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