Capacitive Sensing on Floating Metal Surfaces for Proximity and Touch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional capacitive sensing devices are limited in their ability to detect user proximity and touch on conductive surfaces, as they require a non-conductive outer surface, restricting their application in devices like metal-bodied electronics where transparency is not necessary.
Innovation Solution
A capacitive proximity and touch sensing system that utilizes a metal enclosure with an insulated gasket and electrodes to detect capacitance changes on a floating electrical potential, allowing for user input signals even on conductive surfaces by forming a parallel plate capacitor and using a capacitive sensor to convert capacitance to digital signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a non-conductive outer surface is used for capacitive sensing, then the sensing mechanism can detect user proximity and touch, but the device cannot utilize conductive surfaces such as metal enclosures for the same function
Solution Approach 1:
An insulated gasket is introduced as an intermediary element between the conductive enclosure and the sensing electrode. This gasket provides electrical insulation while allowing the electrode to sense capacitance changes through the insulating material, enabling capacitive sensing on conductive surfaces without direct electrical contact
Solution Approach 2:
The enclosure is segmented into conductive and insulated portions, with the insulated gasket creating distinct electrical zones. This segmentation allows different parts of the device to have different electrical properties, enabling capacitive sensing functionality on otherwise conductive surfaces
2Adaptability or versatility
If a conductive surface is used for the device enclosure, then aesthetic and structural benefits are achieved, but capacitive sensing of user proximity and touch becomes impossible
Solution Approach 1:
The insulated gasket serves as a mediator that transmits capacitive coupling signals from the user's body through the insulating material to the sensing electrode, enabling reliable detection of proximity and touch events on conductive surfaces
Solution Approach 2:
The sensing mechanism transitions from direct surface contact to sensing through the insulating gasket layer, adding a dimensional aspect to the sensing path that enables operation on conductive surfaces while maintaining detection reliability
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 user input detection on conductive surfaces, such as metal-bodied devices, by accurately measuring proximity and touch, enabling features like waking devices from sleep or initiating functions without direct contact, and allowing for invisible buttons and sliders that can be selectively visible through backlighting.
Implementation Method 1
sensing a capacitance in a circuit that includes the conductive surface
Implementation Method 2
an insulative gasket electrically insulating the conductive surface from ground potential
Implementation Method 3
forming a parallel plate capacitor
Data Source
AI summary
The present disclosure addresses methods and apparatus facilitating capacitive sensing using a conductive surface, and facilitating the sensing of proximity to the conductive surface. The sensed proximity will often be that of a user, but can be another source of a reference voltage potential. In some examples, the described systems are capable of sensing capacitance (including parasitic capacitance) in a circuit that includes the outer conductive surface, and where that outer conductive surface is at a floating electrical potential. In some systems, the systems can be switched between two operating modes, a first mode in which the system will sense proximity to the conductive surface, and a second mode in which the system will use a capacitance measurement to sense contact with the conductive surface.