SLYA063 August   2022 DRV5032 , TMAG5170 , TMAG5170-Q1 , TMAG5273

 

  1.   Abstract
  2. 1Problems With Mechanical Knobs and Rotary Encoders
  3. 2Hall-Effect Sensors for Rotational Sensing
  4. 3Design Considerations for Magnetic Dials
  5. 4Conclusion
  6. 5Reference

Abstract

Dials and knobs for user interfaces traditionally use a rotary encoder or potentiometer to determine the change of rotation or absolute angle. These methods have internal metal contacts that can wear out over time and provide a point-of-failure in long-life applications.

Reducing the number of electromechanical contacts in a system reduces the points of failure and results in a more reliable design. Dials that use electromechanical contacts may have a shorter life span compared to those that use other contactless implementations such as Hall-effect sensors and magnets.

There are different ways to implement a dial with a magnetic sensor, but using a sensor with an integrated coordinate rotation digital computer (CORDIC) calculation can provide angular position data through register reporting, reducing the need to process data externally and simplifying the design process while still providing accurate results. Otherwise, sensors that just provide the magnetic field strength must have an MCU perform calculations to determine the angle of the magnet. Hall-effect sensors also offer a variety of different full-scale measurement ranges to enable the use of various magnets.

This white paper briefly introduces magnetic sensors, describes their use in a contactless dial application, and explains the benefits of a contactless method.