Rotary encoder: Difference between revisions

Revision as of 16:09, 13 February 2023

Revision as of 20:49, 13 February 2023

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[[Image:Odometergearcropped.jpg|thumb|[[Hall effect]] quadrature encoder, sensing gear teeth on the [[driveshaft]] of a robot vehicle.]]

* '''Mechanical''': Also known as conductive encoders. A series of circumferential copper tracks etched onto a PCB is used to encode the information via contact brushes sensing the conductive areas. Mechanical encoders are economical but susceptible to mechanical wear. They are common in human interfaces such as [[digital multimeter]]s.<ref>{{cite web |url=https://www.digikey.com/en/articles/techzone/2012/apr/a-designers-guide-to-encoders |title=A Designer's Guide to Encoders |website=digikey.com |date=19 April 2012 |access-date=23 November 2019}}</ref>

* '''Optical''': This uses a light shining onto a [[photodiode]] through slits in a metal or glass disc. Reflective versions also exist. This is one of the most common technologies. Optical encoders are very sensitive to dust. Its origins began over 150 years ago in 1862 with the D.H Baldwin Company of Cincinnati, Ohio. By the 1890’s, the D.H Baldwin Company became the largest piano dealer in the Midwestern United States. Baldwin vowed to build “the best piano that could be built.” Baldwin’s work in electronic organs led to the development of an optical technology to generate harmonics. Accurate patterns put down on glass and read optically were the “Tone Wheels” that made organs sound like particular instruments. This technology became the foundation and birth of the optical encoder. Today, [https://beiprecision.com/ Quantic BEI] in Maumelle, Arkansas is manufacturing the industry's leading optical encoders for military and aerospace industries.

* '''On-Axis Magnetic''': This technology typically uses a specially magnetized 2 pole neodymium magnet attached to the motor shaft. Because it can be fixed to the end of the shaft, it can work with motors that only have 1 shaft extending out of the motor body. The accuracy can vary from a few degrees to under 1 degree. Resolutions can be as low as 1 degree or as high as 0.09 degree (4000 CPR, Count per Revolution).<ref>{{cite web |url=http://massmind.ecomorder.com/techref/io/sensor/pos/enc/ENC2.htm |title=MassMind Magnetic High Speed Non-Contact Quadrature Encoder V2 |website=MassMind.org |date=10 January 2018 |access-date=12 July 2019}}</ref> Poorly designed internal interpolation can cause output jitter, 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 design and low cost for custom applications. Due to the flexibility in many off axis encoder chips they can be programmed to accept any number of pole widths so the chip can be placed in any position required for the application. Magnetic encoders operate in harsh environments where optical encoders would fail to work.