Capacitive Touch Pad Proximity Sensing Using Shared Electrodes
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Solution Overview
Problem
Integrating a proximity detection function into systems with capacitive touch pads poses challenges due to the large size and increased cost and current consumption of dedicated electrodes, making it difficult to implement without expanding the system's dimensions, cost, and power consumption.
Innovation Solution
A method and device for capacitive touch pads that utilize a proximity detection mode by determining capacitance measurements between specific electrode pairs, using a sampling capacitor with higher capacitance than in locate mode, and executing charge and transfer cycles until a threshold voltage is reached, allowing for object detection at varying distances without increasing system size, cost, or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dedicated electrodes are added for proximity detection, then object detection capability is improved, but system size and cost increase
Solution Approach 1:
The patent makes the existing touch pad electrodes serve dual functions: both touch input detection and proximity detection. By configuring the touch pad in proximity detection mode, the same electrodes that detect finger touches also detect objects at greater distances, eliminating the need for separate dedicated proximity electrodes and thus avoiding increased system size and cost.
Solution Approach 2:
The touch pad electrodes perform self-service by simultaneously executing touch detection and proximity detection functions. The control circuit enables the electrodes to adaptively switch between detection modes, allowing the existing hardware infrastructure to serve multiple purposes without requiring additional components.
2Adaptability or versatility
If dedicated electrodes are added for proximity detection, then object detection capability is improved, but manufacturing cost increases
Solution Approach 1:
The patent makes the existing touch pad electrodes serve dual functions: both touch input detection and proximity detection. By configuring the touch pad in proximity detection mode, the same electrodes that detect finger touches also detect objects at greater distances, eliminating the need for separate dedicated proximity electrodes and thus avoiding increased system size and cost.
3Adaptability or versatility
If dedicated electrodes are added for proximity detection, then object detection capability is improved, but current consumption increases
Solution Approach 1:
The patent makes the existing touch pad electrodes serve dual functions: both touch input detection and proximity detection. By configuring the touch pad in proximity detection mode, the same electrodes that detect finger touches also detect objects at greater distances, eliminating the need for separate dedicated proximity electrodes and thus avoiding increased system size and cost.
4Measurement precision
If charge and transfer cycles are executed until threshold voltage is reached, then measurement precision is improved, but detection time increases
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit monitors the voltage at the sampling capacitor during charge and transfer cycles. When the voltage reaches a predetermined threshold, the circuit automatically stops further cycles and proceeds to measurement. This feedback-controlled approach ensures precise capacitance measurement while minimizing unnecessary cycles, thus optimizing the balance between measurement precision and detection time.
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
Enables efficient detection of objects near the touch pad at different distances, including several centimeters, without increasing system dimensions, cost, or current consumption, by optimizing the use of existing electrode configurations and control circuits.
Implementation Method 1
the presence of an object on the touch pad can change the capacitance on pairs of electrodes located near the object
Implementation Method 2
determining a measurement representative of the capacitance between one or two electrodes and one or two other electrodes of the touch pad
Data Source
AI summary
The present disclosure relates to a method for controlling a touch pad, comprising an object locate mode for locating an object on the touch pad comprising steps of: determining a measurement of capacitance of each of the pairs of electrodes of the touch pad, each pair comprising a row electrode and a column electrode transverse to the row electrode, comparing each measurement with a first detection threshold, and if the comparison of at least one measurement with the first threshold reveals the presence of an object on the touch pad, locating the object on the touch pad according to the capacitance measurements, the method comprising a proximity detection mode comprising steps of: determining a measurement representative of the capacitance between one or two electrodes and one or two other electrodes of the touch pad, and comparing a measurement obtained with a second detection threshold different from the first threshold.