Touchpad Grounding Self-Test for Ghost Input Reduction
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Solution Overview
Problem
Touchpads in portable information handling systems experience difficulties in distinguishing between intended and incidental touches due to signal and ground continuity issues, leading to false touch detections known as ghost inputs, which disrupt user experience and can cause system failures.
Innovation Solution
The implementation of first and second ground devices, such as conical springs, extend from the touchpad circuit board to contact the system ground, and a low resistance ohmmeter measures resistance between these devices to adjust touch detection sensitivity, reducing ghost touch errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the touchpad pivots to accept press button input, then the touchpad functionality is improved, but signal and ground continuity becomes difficult to maintain
Solution Approach 1:
The ground connection transitions from a static rigid structure to a dynamic flexible structure that can accommodate the pivoting motion of the touchpad while maintaining continuous electrical contact throughout the range of motion
Solution Approach 2:
A flexible ground connection structure is used instead of rigid conductors, allowing the ground path to bend and flex with the touchpad movement while maintaining electrical continuity, thus resolving the conflict between mechanical adaptability and electrical reliability
2Measurement precision
If the touch detection surface is made sensitive to detect touches, then touch detection capability is improved, but false touch detections known as ghost inputs increase
Solution Approach 1:
The system continuously monitors ground resistance and uses this feedback to dynamically adjust touch detection sensitivity thresholds, allowing the system to maintain high sensitivity for valid touches while automatically raising thresholds to reject ghost inputs when ground connection degradation is detected
Solution Approach 2:
The touch detection parameters are dynamically changed based on measured ground resistance conditions, adjusting the sensitivity threshold parameter to match the actual ground connection quality, thus maintaining accurate touch detection across varying operational conditions
3Reliability
If ground interface is not optimal, then ghost input detection becomes a greater problem, but system complexity increases
Solution Approach 1:
The grounding system performs self-diagnosis by automatically measuring its own ground resistance and self-adjusts by modifying touch detection parameters based on the measured conditions, eliminating the need for external calibration or complex manual intervention systems
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
Improved ground contact through conical springs enhances touch detection accuracy and reduces ghost touch inputs by adjusting sensitivity based on measured resistance, ensuring reliable touch input detection.
Implementation Method 1
first and second ground devices, such as conical springs, extend from a touchpad circuit board to contact the system ground
Implementation Method 2
a low resistance ohmmeter measures resistance between these devices to adjust touch detection sensitivity
Data Source
AI summary
An information handling system includes a touchpad that accepts touch inputs to move a cursor on a display and that deflects at a front side to accept button inputs. A bracket is disposed between a touch detection surface and circuit board of the touchpad to bias the touch detection surface up and deflect in response to a push down as a button input. Conical spring ground devices coupled to the circuit board on opposing sides of the bracket interface with an ohmmeter included on the circuit board that detects a resistance from a first ground device through the system ground to a second ground device. Resistance across ground is applied by the touchpad processor to adjust touch detection sensitivity and avoid ghost inputs.