Force-Sensing Audio Keyboard Button With Interdigitated Contacts
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Solution Overview
Problem
Existing button configurations using force sensing resistors (FSRs) suffer from poor sensitivity, small dynamic range, and inconsistency in force detection, leading to suboptimal user experience and musical expression.
Innovation Solution
A button design featuring a contact pad with interdigitated fingers and a conductive layer independent of the actuator and contact pad, where the actuator base is shaped to increase the surface area of the conductive layer in contact with the contacts as force is applied, enhancing sensitivity and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gap between the conductive layer and contact pad is reduced to improve sensitivity, then the button activates at lower force, but the dynamic range is reduced
Solution Approach 1:
The invention transitions from a single-point contact mechanism to a multi-finger interdigitated contact pattern. Instead of reducing the gap in one dimension, the conductive layer is divided into multiple fingers that interdigitate with contact pad fingers, creating multiple contact points across a larger area. This dimensional expansion allows the button to maintain sensitivity while increasing the range of detectable forces.
Solution Approach 2:
The conductive layer is segmented into multiple interdigitated fingers that correspond to multiple fingers on the contact pad. This segmentation creates multiple independent contact points, where each finger pair can make contact at slightly different force levels. The cumulative effect of multiple contacts provides both high sensitivity (each individual contact is sensitive) and large dynamic range (multiple contacts engage across a wide force range).
2Measurement precision
If the gap between the conductive layer and contact pad is removed to increase sensitivity, then the button becomes continuously active, but this causes false triggers and reduces consistency
Solution Approach 1:
By segmenting both the conductive layer and contact pad into multiple interdigitated fingers, the invention creates a mechanism where full contact requires significant force. At rest, the fingers remain separated; as force is applied, the fingers progressively engage. This segmented approach prevents false triggers while maintaining sensitivity, as each finger pair acts as an independent contact point that only engages when sufficient force is applied.
Solution Approach 2:
The interdigitated finger configuration creates a dynamic contact mechanism where the degree of contact varies continuously with applied force. Rather than a static gap or continuous contact, the system transitions dynamically from no contact to partial contact to full contact as force increases. This dynamic behavior enables the button to remain inactive at rest while providing consistent activation thresholds and preventing false triggers.
3Reliability
If user adjustable trigger threshold is provided to overcome variations between buttons, then false triggers are reduced, but the dynamic range is further reduced
Solution Approach 1:
The interdigitated multi-finger design inherently provides consistency across buttons through standardized manufacturing of the finger patterns. Each button in an array uses the same finger configuration, ensuring uniform performance without requiring user adjustment. The segmented structure allows precise control of the contact mechanics, maintaining large dynamic range while eliminating the need for threshold adjustment that would otherwise reduce dynamic range.
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 solution improves sensitivity by allowing detection of low forces while increasing the dynamic range of the button, ensuring consistent performance across all buttons in an array, thus enhancing user experience and musical expression.
Implementation Method 1
the button comprising: a contact pad with at least two contacts, the contacts being arranged in a complementary pattern of interdigitated fingers with a separation therebetween; and an actuator and a conductive layer, the conductive layer being located between a base of the actuator and the contact pad... the base of the actuator being shaped to increase the surface area of the conductive layer in contact with the contacts as the actuator is pushed towards the contact pad, thereby increasing current flow between the contacts in use as the force applied to the actuator increases
Data Source
AI summary
There is provided a button for varying output based on force applied. The button comprises: a contact pad with at least two contacts, the contacts being arranged in a complementary pattern of interdigitated fingers with a separation therebetween; and an actuator and a conductive layer, the conductive layer being located between a base of the actuator and the contact pad and being independent of the actuator and contact pad, the base of the actuator being shaped to increase the surface area of the conductive layer in contact with the contacts as the actuator is pushed towards the contact pad. This increases current flow between the contacts in use as the force applied to the actuator increases.