Capacitive Cursor Pad for Fine Direction and Force Sensing
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Solution Overview
Problem
Directional pads in game controllers lack angular resolution better than 45 degrees and cannot measure the depression force applied by the user, limiting the control of a cursor's movement speed.
Innovation Solution
A cursor control device with a printed circuit board featuring a plurality of sensing elements arranged in a circular manner, using capacitance changes between a conductive layer and sensing elements to determine the direction and magnitude of force applied, allowing for precise cursor movement control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a D-pad with four buttons is used to detect direction, then the device can sense movement in four primary and secondary directions, but the angular resolution is limited to 45 degrees and cannot measure depression force
Solution Approach 1:
The control surface is divided into multiple discrete sensing zones (at least four, preferably more) arranged radially around a central pivot point. Each sensing zone corresponds to a specific angular sector and independently detects contact or proximity, enabling angular resolution finer than 45 degrees while maintaining a simple mechanical structure.
Solution Approach 2:
A conductive layer is introduced as an intermediary between the actuator and the sensing elements. This conductive layer transfers both mechanical contact information and electrical signals, allowing the sensing elements to detect both directional information and depression force through capacitance changes without adding mechanical complexity.
2Measurement precision
If strain gauges or force sensing resistors are used to measure depression force, then cursor movement speed can be controlled, but the manufacturing cost increases significantly
Solution Approach 1:
Traditional mechanical force sensing elements (strain gauges, force sensing resistors) are replaced with electrical capacitance-based sensing elements. The capacitance between the conductive layer and sensing elements changes in response to depression force, providing force measurement capability through electrical measurements rather than mechanical sensing, thereby reducing manufacturing cost.
Solution Approach 2:
The sensing elements serve multiple functions simultaneously: they detect directional information (which sensing zone is activated), measure depression force (through capacitance magnitude), and provide angular resolution (through the radial arrangement of zones). This multi-functionality eliminates the need for separate force sensing components.
3Measurement precision
If more sensing elements are added to improve angular resolution, then direction detection precision improves, but device complexity increases
Solution Approach 1:
The sensing elements are arranged radially in a circular pattern around the pivot point, utilizing angular dimension rather than linear arrangement. This radial configuration allows multiple sensing zones to be packed efficiently in a compact area, improving angular resolution without proportionally increasing device footprint or complexity.
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 improved angular resolution and force measurement, allowing for controlled cursor movement speed and direction, potentially replacing expensive strain gauges or force sensing resistors with a more cost-effective solution.
Implementation Method 1
using capacitance changes between a conductive layer and sensing elements to determine the direction and magnitude of force applied
Data Source
AI summary
We describe an apparatus including a plurality of sensing elements, a conductive layer, and a compressive layer interposed between the plurality of sensing elements and the conductive layer. The conductive layer can include a plurality of segments. A user applies a force to an actuator positioned over the conductive layer. The actuator changes a capacitance of at least one capacitor formed by at least one of the plurality of sensing elements, the conductive layer (at least one segment), and the compressive layer by reducing the distance between the at least one of the plurality of sensing elements and the conductive layer responsive to the applied force. The device measures and calculates a magnitude and direction of the force by measuring the change in the capacitance.