Rotary encoder

A rotary encoder which is also called a shaft encoder is an elector-mechanical device that converts the angular position or motion of a shaft or axle to analog or digital output signals. There are two main type of rotary encoder i.e. absolute and incremental. The output of an absolute encoder indicates the current shaft position, making it an angle transducer. The output of an incremental encoder will provides information about the motion of the shaft which typically is processed elsewhere into information such as position speed and distance.

Thus rotary encoders are used in a wide range of application that require monitoring or control, or both, of mechanical systems, including industrial controls, robotics, photographic lenses, and computer input devices such as opt mechanical mice and trackballs, controlled stress rheometers, and rotating radar platform

Encoder Technologies

• Conductive: Contact brushes are used to sense the conductive areas and this form of the encoder is now rarely seen except as user input in digital millimeter.
• Optical: This uses a light shining on a photo diode through slits in a metal or glass disc, also reflective versions exist. This is one of the most common technologies. This optical encoder is very sensitive to dust.
• On-Axis Magnetic: this technology use a specially magnetized 2 pole neodymium magnet attached to the motor shaft. This is because it can fixed to the end of the shaft and it can work with motors that only have 1 shaft extending out of the motor body. The accuracy can range from a few degrees to under 1 degree and resolution can be as low as 1 degree or as high as 0.09 degree. Poorly designed internal interpolation can cause output jitters, but this can be overcome with internal sample averaging.
• OFF-Axis Magnetic: this technology typically employs the use of rubber bonded ferrite magnets attached to a metal hub. This offers flexibility in many off-axis encoder chips they can programmed to accept any number of pole widths so the chip can be placed in any position required for the application.

Types of Rotary Encoder

Mainly there are two type of Rotary Encoder

• Absolute Encoder
• Incremental Encoder

Applications of Rotary Encoders

• Assembling machine
• Packaging
• X and Y Indication system
• Printers
• Testing Machine
• CNC Machine
• Robotics
• Labeling Machine
• Medical equipment
• Textiles
• Drilling Machine
• Motor Feedback

Advantages and disadvantages of rotary encoders

Advantages of encoder

• Highly reliable and accurate
• Low cost feedback
• High resolution
• Integrated electronics
• Fuses optical and digital technology
• Can be incorporated into existing applications
• Compact size

Disadvantages of an encoder

• Subject to magnetic or radio interference
• Direct light source interference
• Susceptible to dirt, oil and dust contaminates