3D Keyboard Circuit Reducing Wire Count for Electric Music Instruments
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Solution Overview
Problem
Conventional keyboard switch matrices for electric music instruments face challenges in reducing the number of wires on a substrate, particularly when transitioning from two contacts to three contacts per key, leading to increased costs and complexity, especially when trying to maintain a single-sided substrate configuration.
Innovation Solution
A three-dimensional switch matrix configuration is implemented, where three layers of matrices are laminated, allowing 4 lines of scan output signals and 22 lines of input signals to cross each other, enabling detection of 88 switches per layer and 264 switches in total, while using transistors instead of diodes to manage signal flow and reduce wire count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of contacts per key is increased from two to three to detect key-pressing speed and intensity, then the detection capability is improved, but the number of wires required increases significantly
Solution Approach 1:
The patent transitions from a conventional two-dimensional switch matrix to a three-dimensional switch matrix by adding a vertical dimension (stacking multiple matrix layers). This allows 264 switches (88 keys × 3 contacts) to be detected using only 44 wires (22 row lines + 22 column lines), whereas a conventional 2D matrix would require 176 wires (88 rows + 88 columns). The third dimension enables space-efficient wiring by utilizing multiple layers stacked vertically.
Solution Approach 2:
The patent merges multiple matrix layers into a single integrated three-dimensional structure. By stacking multiple 2D matrix layers vertically and interconnecting them through wiring holes, the system combines the detection capability of multiple layers into one unified switch matrix, reducing the overall wire count while maintaining high detection precision for three contacts per key.
2Measurement precision
If a conventional two-dimensional switch matrix is used for three contacts per key, then the detection capability is achieved, but the substrate width requirement increases
Solution Approach 1:
By introducing a third dimension (vertical stacking of matrix layers), the patent reduces the horizontal footprint of the switch matrix. The 3D configuration allows the same detection capability to be achieved within a smaller substrate area by utilizing the vertical space for additional contacts and wiring layers.
Solution Approach 2:
The patent implements a nested structure where multiple matrix layers are stacked vertically within each other, similar to nested dolls. Each layer contains a subset of the total switches, and the layers are interconnected through wiring holes, allowing compact integration of 264 switches in a limited substrate area.
3Ease of manufacture
If the number of wires is reduced for single-sided substrate wiring, then the manufacturing simplicity is improved, but the detection of three contacts per key becomes more difficult
Solution Approach 1:
The patent uses the third dimension (vertical stacking) to reduce the number of wires required on the substrate surface. By routing some connections through the vertical dimension (using wiring holes between layers), the horizontal wire count is reduced to 44 wires, making single-sided substrate wiring feasible while maintaining full detection capability for three contacts per key.
Solution Approach 2:
The patent introduces wiring holes as intermediary structures that connect different matrix layers vertically. These wiring holes act as mediators, allowing signals to pass between layers without requiring additional horizontal wires on the substrate surface, thus enabling reduced wire count while maintaining detection capability.
Data Source
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AI summary
A keyboard circuit (15) of an electric music instrument includes contact transistors (TRk) having at least three terminals as input/output terminals for state detection for each of a plurality of contacts (14a, 14b, and 14c); and wiring units to the contact transistors (TRk) and the contacts (14a, 14b, and 14c). A selector (Sm) and the wiring unit for each of the plurality of contacts (14a, 14b, and 14c) are arranged to be divided into a plurality of layers in three dimensions. Then, the keyboard circuit (15) detects ON/OFF states for each of the contacts (14a, 14b, and 14c) for which the ON/OFF states change in response to a key-pressing operation for each of a plurality of keys (12) and for which at least one is provided to each of the plurality of keys (12).