Capacitive Door Handle Sensor Water Rejection
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Solution Overview
Problem
Touch and proximity sensors face challenges in operating reliably in harsh outdoor environments, particularly when wet, as water interference can lead to erratic sensor operation and incorrect detection of water as a hand or vice versa.
Innovation Solution
A door handle proximity sensor system with a specific electrode configuration and signal pattern arrangement that differentiates between water and a user's hand, using drive signals and shield electrodes to distinguish between water and hand presence, enabling reliable operation even in wet conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a capacitive touch sensor is used in a door handle, then the sensor can detect hand proximity and enable contactless operation, but water on the door handle causes erratic sensor operation and incorrect detection
Solution Approach 1:
The sensor surface is divided into multiple independently controllable electrode segments. By selectively activating different electrode segments with different signal patterns, the system can distinguish between water and hand proximity. Water typically affects all segments uniformly, while a hand creates localized capacitive coupling on specific segments, enabling reliable detection despite water presence.
Solution Approach 2:
Different regions of the sensor (electrode segments) are assigned different signal characteristics or weighting factors. This allows the system to analyze spatial patterns of capacitive changes and differentiate between water (affecting all regions similarly) and hand proximity (affecting specific regions differently), thereby maintaining reliability in wet conditions.
2Measurement precision
If the sensor attempts to detect all capacitive changes, then it can detect both water and hand presence, but it cannot differentiate between water and hand, leading to incorrect detection
Solution Approach 1:
The sensor applies periodic signal patterns to different electrode segments at different time intervals. By analyzing the temporal response patterns and comparing capacitive changes across multiple measurement cycles with different signal configurations, the system can distinguish between water and hand proximity based on their different capacitive coupling characteristics.
Solution Approach 2:
The system continuously monitors capacitive changes on multiple electrode segments and uses this feedback to adjust signal patterns and determine the nature of the detected object. By analyzing the pattern of capacitive changes across different segments and comparing against known water and hand signatures, the system achieves accurate differentiation between water and hand presence.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively differentiates between water and a hand, ensuring accurate detection and reliable operation of the sensor, allowing for secure communication with a vehicle even in heavy rain conditions.
Implementation Method 1
the touchpad circuitry 20 obtains a value from the sense line 16 using a mutual capacitance measuring device 26 that indicates which row electrode is closest to the pointing object
Implementation Method 2
When a pointing object creates imbalance because of capacitive coupling when the object approaches or touches a touch surface
Data Source
AI summary
A system and method that provides a proximity sensor disposed within a door handle of a vehicle to enable one or more commands to be transmitted to the vehicle by a user's hand, wherein the door handle is in a harsh outdoor environment such that the door handle may be wet when the proximity sensor is used to detect the touch or presence of a user's hand, and wherein the proximity sensor is able to compensate for the presence of the water and enable reliable operation of the proximity sensor and thereby enable commands to be sent to the vehicle.