Rotary Encoders

As-Salaam-Alaikum, Welcome to my blogger "World of Knowledge".Here we discuss the topic Rotary Encoders.

Points to be discuss in this Article are given below:
  • Rotary Encoder
  • Types of Rotary Encoder
  • Construction of Rotary Encoders
  • Incremental Rotary Encoder
  • Constriction: Incremental Type
  • How it works?
  • Absolute Rotary Encoder
  • Applications of Absolute Rotary Encoder 

Rotary Encoder:

  • Electromechanical device converts motion into electrical signal, this signal can be used to control a conditional event.
  • Converts the position of a shaft or axle into digital or analog code.
Types:
  • Absolute (Determine Angular position)
  • Incremental (Determine change in Angular position)
Construction of Rotary Encoders:

It uses a slotted wheel with single LED/ photo detector pair to generate pulses as the wheel turns. 
Figure 1

Incremental Rotary Encoder:

  • Incremental Type provides a series of high and low waves, which indicate movement from one place to next.
  • No special indication to show specific position
  • Only an indication that position is changed
  • Speed of an object is measured by counting the pulses for a period of time
  • To calculate the distance covered, pulses are counted starting from a reference point.
Constriction: Incremental Type

Figure 2
How it works?
  • The LED emits light beam which passes through a transparent disk, patterned with opaque lines
  • When photo sensor receives the light beam, it produces a sinusoidal waveform, which is transformed into a square wave or pulse train.
  • The pulse signal is then sent to the counter or controller which then send the signal to produce the desired function.
Absolute Rotary Encoder:
  • It uses a unique “word” for each position i.e. it provides both the indication that position has been changed and an indication of the absolute position of the encoder.
  • Information in the form of unique output for every moment of the shaft rotation.(Binary, BCD, Grey code)
  • Advantage over incremental encoder => position is maintained after a power-down
Applications:
  • Robotics
  • Photographic Lenses
  • Computer input device(Track ball)
  • Radar Platform
Figure 3


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