SNOAAA5 April 2024 DRV8220 , FDC1004-Q1 , LDC3114-Q1 , TMAG5131-Q1 , TMAG5173-Q1 , TMAG6180-Q1
Automotive door handle systems continue to enhance user experience, safety, and reliability by incorporating new features and improving upon old ones. These features are enabled by different sensing technologies including magnetic sensors (anisotropic magneto resistive (AMR) and Hall-effect), capacitive sensors, and inductive sensors.
This document demonstrates the implementation of a deployable automotive door handle using magnetic and capacitive sensors to capture position data in a door handle demo design. Sensor design and testing methods are described, leveraging the hardware and software based demo, along with potential error sources and alternative sensing options, such as inductive sensing. The technologies covered in this app note include a Hall-effect sensor for detecting the open or close status of the door and an AMR angle sensor for the position of the handle. The application note illustrates the use and design of capacitive sensing for a touch button and the presence of a user's hand on the handle. This application note, but not the demo, also includes the use, design and implementation of an inductive sensor push button (as opposed to a capacitive touch button), as that is also a frequent option in today's vehicles.
All trademarks are the property of their respective owners.
This document provides a high-level overview of automotive door handles and the potential features, and how such features can be achieved using magnetic, capacitive, and inductive sensors. Design examples presented are based on a demo, which is also featured in the demo video Designing with position sensors: Automotive door handles and the Position Sensing in Automotive Door Handle Systems application brief.
The demo is used as a foundation to illustrate the use of Hall-based sensors to monitor door open/closed position, and discusses the design considerations and capabilities of Hall sensing technology for this application. This is supported by simulations in TI Magnetic Sense Simulator (TIMSS), TI's online simulator for magnetic position sensors.
The demo also illustrates capacitive-sensing technology as the basis for a touch button to detect a user's finger or hand, which can subsequently deploy a recessed door handle. Once the handle is deployed, a capacitive sensor can then detect the presence of a user's hand on the handle to prevent the handle closing on the user's hand. Approximate mathematical models are given to provide the user a starting point for a design, and the approximations are confirmed by the demo. References to other capacitive sensing application notes with supporting information are given throughout.
Also included in this application note is the use of inductive sensors for push-button applications (as opposed to a capacitive touch button). This technology is not included in the demo, but is a popular feature in many of today's vehicles. That section covers design and implementation-related considerations and provides a more detailed design example of a push-button sense coil using the Inductive Sensing Calculator Tool.