Rotary Sensor basics and types | Rotary Encoder basics and types

This article covers Rotary Sensor basics and Rotary Sensor types.The encoder which senses angular position is known as rotary encoder or sensor.The working of this rotary encoder is also described with the output timing diagrams.

What is rotary sensor or rotary encoder?

Introduction:
It is type of position sensor used to determine angular position of rotating shaft. It generates electrical signal which is either analog or digital. The electrical output is sensed or used by micro-controller board or arduino to perform desired action.

The figure-1 depicts Keyes rotary encoder which provides indication of knob position and its direction. It is used for stepper and/or servo motor controls. Following are the mappings between various pins on the rotary encoder.
• CLK - Encoder Pin-A
• DT - Encoder Pin-B
• SW - NO Pushbutton Switch
• + is connected to 5V Supply
• GND - Encoder Pin-C

Rotary Sensor Types | Rotary Encoder Types

• The rotary encoder or sensor is classified according to output signal or sensing technology.
• Based on output signal, rotary sensors are of two types viz. incremental and absolute. Incremental type of encoder is also known as quadrature encoder or relative rotary encoder.
• Based on sensing technology, rotary sensors are of three types viz. magnetic, optical and laser.

Rotary Sensor Working

Following section describes working of rotary sensor.
➨The figure-1 depicts circular disk with evenly spaced contact zones which are connected to common pin "C". There are two contact pins designated as "Output-A" and "Output-B".
➨When the disc rotates, pins A and B comes in contact with the evenly spaced contact zones and two square wave output pulses are generated.
➨Either output-A or output-B is used to determine angular or rotational position.
➨But to determine direction, both the output signals and their signal transitions i.e. high to low (H-L) and low to high (L-H) are monitored or measured. As shown for clockwise movement of the shaft, output-A leads output-B in both H-L and L-H transitions.
➨Similarly anti-clockwise rotational movement can also be measured or tracked.

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