Fabrication of a Novel Contactless Switch Using Eddy Current Displacement Sensor for Safer Vehicle Brake System

Abstract

Conventional brake systems using a mechanical-structure-based contact switch with a metal spring suffer from frequent malfunction problems over time caused by unstable contacts stemming from loose tension of the spring, a faulty air gap, and damage to the contact point due to overcurrent from load. In this paper, a novel contactless switch for brake systems using an eddy-current displacement sensor is proposed, fabricated, and verified to have reliable performance that overcomes conventional contact switch problems. A proposed contactless switch was fabricated using automotive-grade surface-mount devices (SMDs) on both sides of an FR-4 printed circuit board for low-cost implementation. The measurement result shows a switching speed of less than 49.7 mu s, on average, which is approximately ten times faster than conventional mechanical-structure-based contact switches. The overall dimension of the proposed switch is 36 mm x 26 mm x 64 mm, which can fit into most brake switch housings. The operating input voltage range is from +8 V to +22 V, with the temperature ranging from -40 degrees C to +85 degrees C, showing reliable performance under harsh environment test for automobile applications.