Resistive Touch Screen Multiple Simultaneous Touch Detection
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Solution Overview
Problem
Existing touch screen technologies, such as resistive, capacitive, and surface acoustic wave systems, are unable to effectively detect multiple simultaneous touches, which is a limitation for portable devices due to high cost, complexity, and sensitivity to environmental factors.
Innovation Solution
A resistive touch screen system with electrically conductive columns and rows, utilizing an analog to digital converter and voltage source connected sequentially to each column and row, allows for the detection of multiple simultaneous touches by applying voltage to rows and columns and reading voltage levels, enabling high-resolution touch location identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a resistive touch screen is used, then the cost and complexity are reduced, but the ability to detect multiple simultaneous touches is lost
Solution Approach 1:
The touch screen is segmented into multiple independently controllable regions or layers, allowing different scanning patterns to be applied to different segments. This enables the system to detect multiple simultaneous touches by sequentially scanning different segments while maintaining the simplicity of resistive technology.
Solution Approach 2:
The system uses periodic scanning of rows and columns with alternating polarity voltage applications. By periodically switching the voltage polarity and scanning sequences, the system can distinguish between multiple simultaneous touch events while using the same simple resistive sensing mechanism.
2Adaptability or versatility
If capacitive or SAW touch screens are used for multiple touch detection, then multiple simultaneous touches can be detected, but the cost and complexity increase
Solution Approach 1:
The patent replaces complex capacitive sensing mechanisms or SAW transducer systems with a simplified resistive sensing mechanism combined with periodic voltage scanning. This substitution maintains multiple touch detection capability while dramatically reducing system complexity and cost by using basic electrical resistance measurements instead of complex electrical field or acoustic wave sensing.
3Adaptability or versatility
If capacitive touch screens are used, then multiple simultaneous touches can be detected, but susceptibility to electrical noise increases
Solution Approach 1:
The system applies periodic voltage scanning with alternating polarity to the rows and columns. This periodic action creates a time-varying signal pattern that allows the system to distinguish between actual touch events and random electrical noise, thereby reducing noise susceptibility while maintaining multiple touch detection capability.
Solution Approach 2:
The system uses feedback from the measured resistance values to determine touch locations. By continuously scanning and comparing resistance measurements against expected values, the system can identify actual touch events while filtering out electrical noise through the feedback mechanism.
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 the detection and identification of multiple simultaneous touches with high resolution, improving user interaction on portable devices while reducing costs and complexity compared to existing systems.
Implementation Method 1
The resistance between a wire at the edge of one sheet to another wire at the edge of the second sheet can be used to determine the location of the touch
Implementation Method 2
The controller includes an analog to digital (A/D) converter switchably and sequentially connected to each of the columns and rows
Data Source
AI summary
Various apparatuses, methods and systems for detecting simultaneous touches at multiple locates are disclosed herein. For example, some embodiments provide an apparatus for detecting a touch, the apparatus including a resistive touch screen and a controller connected to the touch screen. The touch screen includes a number of electrically conductive columns and rows. In various embodiments, the touch screen is an analog matrix, with the overlapping columns and rows forming a matrix of cubics that can each detect one touch at a time, and with the location of the touch detectable in an analog fashion within each cubic. The resolution of the analog matrix in these embodiments is thus higher than that of the columns and rows. The controller includes an analog to digital converter switchably and sequentially connected to each of the columns and rows. The controller also includes a voltage source switchably and sequentially connected to each of the columns and rows. The controller is adapted to connect the voltage source to one of the rows when the analog to digital converter is sequentially connected to each of the columns and to connect the voltage source to one of the columns when the analog to digital converter is sequentially connected to each of the rows.