SBAA632 April   2024 TMAG3001 , TMAG5170 , TMAG5170-Q1 , TMAG5170D-Q1 , TMAG5173-Q1 , TMAG5273

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Implementation and Testing
    1. 2.1 Build Configuration
    2. 2.2 Data Collection
    3. 2.3 Speed Calculation Methods
      1. 2.3.1 Continuous Sampling
      2. 2.3.2 Running Average
      3. 2.3.3 Zero-Crossing
      4. 2.3.4 Periodic Sampling
  6. 3Summary
  7. 4References

Abstract

Vehicle sensing systems including e-bike cadence detection and anti-lock brake systems function by measuring the speed and direction a rotating pedal crankset or wheel. Mechanical designs wear over time, and optical sensors can be cumbersome and difficult to keep free of dirt and debris.

An alternative approach using a fixed position back-biased Hall-effect sensor can provide a high degree of resolution to provide not only the speed of rotation, but the direction and relative angle measurements to detect small changes to the system as well. Back-biased sensors operate by measuring the interaction of a magnetic field and a moving ferromagnetic object.