Capacitive Input Key Matrix Electrode Merging
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Solution Overview
Problem
The increase in the number of input keys in electrostatic capacitance-based input devices leads to challenges in forming smaller electrodes and conductive wires, resulting in manufacturing difficulties and higher costs, as well as potential malfunctions due to unintended key inputs.
Innovation Solution
The input device features a matrix arrangement of input keys with electrodes surrounding intersections, an input key detecting unit that includes a clock signal generator, delay unit, logical conjunction unit, smoothing unit, and A/D conversion unit to identify operated keys based on electrostatic capacitance changes, and non-touch sensitive parts on electrodes to prevent malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of input keys increases, then the input device can provide more functions, but the number of electrodes and conductive wires increases making formation difficult
Solution Approach 1:
Multiple electrodes are combined into a single integrated electrode structure. Instead of providing separate electrodes for each input key, the patent uses one electrode that faces multiple input keys simultaneously, detecting capacitance changes across multiple keys through a single electrode-conductive wire connection.
Solution Approach 2:
A single electrode serves multiple functions by facing multiple input keys and detecting capacitance changes for each key. The electrode structure is designed to universally detect input across multiple keys rather than being dedicated to a single key, reducing the total number of electrodes needed.
2Adaptability or versatility
If the number of input keys increases, then more keys can be input, but the substrate area must be enlarged making the device bulky
Solution Approach 1:
The electrode structure merges multiple detection functions into a single electrode, allowing multiple input keys to be detected without proportionally increasing substrate area. The shared electrode configuration enables compact layout.
Solution Approach 2:
The electrode is positioned to face multiple input keys in a spatial arrangement that optimizes area utilization. By strategically positioning the electrode to detect capacitance changes across multiple keys simultaneously, the substrate area required is minimized while maintaining full key detection capability.
3Area of stationary object
If the substrate area is reduced to maintain slim profile, then the device becomes more compact, but forming small electrodes and thin conductive wires becomes difficult and costly
Solution Approach 1:
By combining multiple electrodes into one, the patent reduces the total number of small electrodes and thin conductive wires that need to be formed on the substrate. This merging approach maintains manufacturability even with reduced substrate area, as fewer precision-critical components are required.
4Ease of operation
If separate electrodes are provided for each input key, then key detection is straightforward, but the number of electrodes increases making the device complex and costly
Solution Approach 1:
Multiple electrode functions are merged into a single electrode structure that can detect capacitance changes for multiple input keys. This reduces device complexity by eliminating the need for separate electrodes and their associated connection circuits for each key.
Solution Approach 2:
The single electrode is designed with universal detection capability across multiple input keys, allowing it to serve multiple functions simultaneously. The electrode structure and detection method are optimized to accurately identify which specific key is pressed despite using a shared electrode.
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
This design allows for easier formation and reduced manufacturing costs of electrodes and conductive wires, while preventing malfunctions by effectively identifying operated keys and reducing the number of electrodes needed, making it suitable for slim portable devices.
Implementation Method 1
an input key detecting unit that identifies operated input keys among the plurality of input keys depending on combinations of the electrodes having a change in electrostatic capacitance
Data Source
AI summary
An input device includes a plurality of input keys arranged in a matrix of three or more rows and three or more columns; electrodes facing parts of or all surfaces of the input keys that surround intersection of rows and columns formed by the arrangement of the input keys; and an input key detecting unit that identifies operated input keys among the plurality of input keys by combinations of the electrodes having a change in electrostatic capacitance. With this structure, the number of electrodes can be less than that of the input keys.