Capacitive Sensor Key Activation Detection
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Solution Overview
Problem
Mobile devices often experience unintended key activations due to accidental actuation while being transported or removed from carrying cases, leading to frustration and perceived device malfunction.
Innovation Solution
A method and device using capacitive sensors to differentiate between human touch and object contact by measuring capacitance levels at the keypad, with a processor identifying intended key activations based on thresholds and secondary indicators from non-keyboard locations, thereby preventing unintended key presses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If keyboard input is kept unlocked to permit easy access to device features, then ease of operation is improved, but unintended key activations occur when device is transported or removed from carrying case
Solution Approach 1:
A capacitive sensor acts as an intermediary between the key circuit and the processing system. The sensor detects capacitance changes caused by human skin contact and provides this information to the processor, which then decides whether to activate the key function. This intermediary layer prevents accidental activations from objects while maintaining easy access when human users interact with the device.
Solution Approach 2:
The system monitors capacitance parameter changes at the key switch to distinguish between human touch and object contact. By measuring and comparing capacitance values against predetermined thresholds, the system can differentiate between intentional key presses by users and accidental contacts during transport, enabling selective activation based on the detected parameter.
2Measurement precision
If capacitive sensor is provided between keypad and printed circuit board to detect capacitance levels, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The capacitive sensor serves multiple functions: it detects human skin contact, provides capacitance measurement data to the processor, and works with existing key circuit infrastructure. This multi-functionality justifies the added component by delivering measurement precision improvements while the sensor integrates seamlessly with the existing keypad and circuit board architecture.
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
Effectively reduces accidental key activations by accurately distinguishing between intended and unintended inputs, enhancing user experience by minimizing false activations and device misinterpretation.
Implementation Method 1
By measuring a capacitance level at the mobile device keypad, a determination may be made to distinguish between a human touch and abutment with an object. A capacitive sensor may sense a capacitance level at a location on the keyboard
Data Source
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AI summary
A method and device are provided for preventing unintended activation of one or more hard keys on a mobile device. A capacitive sensor senses a capacitance level at a location on the keyboard, to detect whether a hard key is being actuated by a human hand or human skin. If the sensed capacitance level exceeds a key activation capacitance threshold, a key circuit connection is identified as being associated with an intended hard key activation. If the measured capacitance level is within an uncertainty tolerance below the key activation capacitance threshold, a secondary capacitance level is measured at a non-keyboard location. The key circuit connection is identified as being associated with an intended hard key activation when the measured secondary capacitance level exceeds a key activation confirmation threshold. Additional secondary indicators can be obtained based on size and shape capacitance pattern, timing information, and an active application or device state.