Strain Gauge Keyboard for Portable Data Carrier
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Solution Overview
Problem
Existing portable data carriers with input devices, such as keypads and keyboards, face challenges due to complex structures and electronics, which increase production costs and mechanical height, especially in compact designs like chip cards, and require complex wiring and continuous key interrogation.
Innovation Solution
A portable data carrier with a sensor arrangement of strain gauges connected in series, where each button area is assigned a strain gauge, allowing pressure detection through resistance changes, reducing the number of supply lines and simplifying the monitoring process by using only two end taps for all keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If membrane keyboards or touch-sensitive displays are used for input devices, then input functionality is provided, but the structure becomes complex and production costs increase
Solution Approach 1:
The patent replaces complex mechanical membrane keyboards or electronic touch-sensitive displays with a simplified mechanical button structure. Each button is a discrete mechanical element that directly actuates a contact point, eliminating the need for complex membrane layers, conductive inks, or touch-sensitive display electronics while maintaining input functionality.
Solution Approach 2:
The keyboard is segmented into individual discrete buttons rather than a continuous membrane or display surface. Each button is an independent mechanical element with its own contact point, allowing for simplified construction and easier manufacturing compared to integrated membrane or touch-sensitive solutions.
2Difficulty of detecting and measuring
If separate signal generators or continuous interrogation electronics are provided for each button, then button actuation can be detected, but the electronics become complex and supply lines increase
Solution Approach 1:
Multiple button contacts are electrically connected in parallel to a single common contact point. This merging of multiple individual button circuits into one shared electrical path eliminates the need for separate signal generators or continuous interrogation electronics for each button, significantly reducing electronic complexity while maintaining the ability to detect individual button actuations through the common contact point.
3Difficulty of detecting and measuring
If two lines per button are used to query and control buttons, then individual button detection is possible, but the number of supply lines increases and wiring becomes complex
Solution Approach 1:
Multiple button contacts are electrically connected in parallel to a single common contact point, merging multiple individual button circuits into one shared electrical path. This reduces the number of supply lines from two per button to a single common line serving all buttons, dramatically simplifying wiring while maintaining individual button detection capability through the common contact point.
4Device complexity
If diode bridges are used for cross-polling to reduce leads, then the number of leads decreases, but the number of components increases and production costs increase
Solution Approach 1:
The patent extracts and eliminates the need for complex diode bridge circuits and cross-polling mechanisms by using a simpler parallel connection topology. Instead of using active components like diodes to manage multiple leads, the invention uses passive parallel electrical connections that naturally reduce lead requirements without adding components, thereby lowering production costs.
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 solution reduces manufacturing complexity and cost, allows simultaneous monitoring of multiple keys, and minimizes energy requirements by eliminating the need for constant key querying, while enabling efficient actuation detection and key recognition.
Implementation Method 1
each area of the multiplicity of areas designed as a button being assigned at least one strain gauge of the sensor arrangement... a suitable pressure exerted on the key area results in a change in the electrical resistance of the strain gauge assigned to the key area
Data Source
Figure 1~3
Figure 4
AI summary
The invention relates to a portable data carrier (1) having a data carrier body comprising a sensor arrangement (7) having a multiplicity of strain gauges (4, 4.1, 4.2) connected in series and a multiplicity of regions (3) which are embodied as keys and to each of which at least one strain gauge (4, 4.1, 4.2) of the sensor arrangement (7) is assigned.