SLIA096 January   2022 DRV5021 , DRV5021-Q1 , DRV5023 , DRV5023-Q1 , DRV5032 , DRV5033 , DRV5033-Q1 , TMAG5123 , TMAG5123-Q1 , TMAG5124 , TMAG5124-Q1 , TMAG5231 , TMAG5328


  1.   Trademarks
  2. 1Introduction
  3. 2Design Process
    1. 2.1 Mechanical Implementation
    2. 2.2 Magnetic Implementation
    3. 2.3 Magnet Sensor Placement
    4. 2.4 Prototyping and Bench Testing
    5. 2.5 Layout
    6. 2.6 Bench Testing
    7. 2.7 Bench Results
    8. 2.8 Error Sources
      1. 2.8.1 Offsets
      2. 2.8.2 Roll, Yaw, and Pitch
      3. 2.8.3 Magnet Variation
      4. 2.8.4 Device Variation and Temperature Drift
      5. 2.8.5 External Fields
      6. 2.8.6 Nearby Material Influence
      7. 2.8.7 Bench Setup Error
  4. 3Summary

Mechanical Implementation

Typically, the design begins with defining a system that executes a particular set of actions. In this case, the goal is a three-state switch in which there are two action states achieved when the user applies some force and another resting state, when the user applies no force or returns the switch to the default position. This actually might be achieved with multiple different styles of switch and is therefore subjective to the user preference, aesthetic, space, or cost. Figure 2-1 shows three possible mechanical options. This document explores what is necessary to make a three-state switch with the bottom option, the rocker switch.
Figure 2-1 Mechanical Options

A rocker switch can be generalized into four basic mechanical components: a base, axle, springs, and a rocker. In this case the base holds the axle and has cantilevers that serve as springs for returning the rocker back to the resting state when the user is not applying force. While these cantilevers are not the primary focus in this design, note that traditional metal spring alternatives were intentionally avoided as many are typically composed of iron which can influence the magnetic field shape from a nearby magnet and thereby complicate design.

Figure 2-2 Mechanical Implementation