Touchpad Resistive Pressure Sensor With Wheatstone Bridge
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Solution Overview
Problem
Existing touchpads with force sensing functions struggle to accurately detect fine changes in force due to large differences in capacitance between the basic capacitor and the detected capacitance when an object presses down, making it difficult to identify subtle force variations.
Innovation Solution
A touchpad with a resistive pressure sensor incorporating a Wheatstone bridge circuit on a deformable circuit board, where the resistors in the bridge are oriented in specific directions relative to the deformation, allowing for an amplified output voltage difference when the board is pressed, enhancing force sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitance-based force sensing electrode is used to detect force changes, then the touchpad can detect force variations, but the fine changes in force are difficult to identify when the capacitance difference between basic capacitor and detected capacitance is too large
Solution Approach 1:
The patent replaces the capacitance-based sensing mechanism with a resistive pressure sensor system. The resistive sensor detects force through resistance changes in a deformation zone, converting mechanical pressure into electrical resistance variations. This substitution resolves the capacitance measurement complexity while maintaining force detection capability, enabling precise measurement of fine force changes without the limitations of capacitance-based approaches.
2Force
If the capacitance difference between basic capacitor and detected capacitance is large when an object presses down, then the force sensing electrode can detect force, but the fine changes in force cannot be identified
Solution Approach 1:
The patent changes the detection parameter from capacitance to resistance. The resistive pressure sensor operates by measuring resistance changes in the deformation zone rather than capacitance changes. This parameter transformation allows the system to detect both large downforces and fine force changes with high precision, as resistance variations can be measured accurately across different force magnitudes without the saturation issues inherent in capacitance-based systems.
3Force
If a Wheatstone bridge circuit with specifically oriented resistors is used in the deformation zone, then the output voltage difference is amplified for larger downforce sensing, but the device structure becomes more complex
Solution Approach 1:
The patent segments the force sensing function into multiple independent resistor units arranged in a Wheatstone bridge configuration. Each resistor is positioned in specific regions of the deformation zone, allowing the system to amplify output voltage difference through the bridge circuit while maintaining modular structure. This segmentation enables enhanced downforce sensing capability without creating an intractably complex overall device, as each resistor unit can be independently manufactured and assembled.
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
The design enables the touchpad to sense larger downforces with increased sensitivity by leveraging the Wheatstone bridge circuit's output voltage amplification, improving the detection of subtle force variations.
Implementation Method 1
a resistive pressure sensor... having a deformation zone, wherein the deformation zone of the circuit board deforms along a first deformation direction when the circuit board is pressed
Implementation Method 2
a Wheatstone bridge circuit formed on the circuit board and having: a first serial-connecting resistor unit positioned in the deformation zone
Data Source
AI summary
A touchpad with a force sensing function and resistive pressure sensor thereof are disclosed. The resistive pressure sensor has a circuit board and a Wheatstone bridge circuit mounted on a deformation zone of the circuit board. The deformation zone deforms when a touchpad body is pressed by a force. The Wheatstone bridge circuit has a first upper-arm resistor, a first lower-arm resistor, a second upper-arm resistor and a second lower-arm resistor. The four arm resistors are in the deformation zone. A direction of current through the first lower-arm resistor and the second upper-arm resistor is different from a direction of current through the second lower-arm resistor and the first upper-arm resistor. Therefore, when the deformation zone of the circuit board deforms by the force, an output voltage of the Wheatstone bridge circuit is relatively increased to enhance a force sensitivity.