Hall Sensor Pressure Feedback for Resonant Toothbrush
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Solution Overview
Problem
Existing pressure-sensing systems in toothbrushes are often costly, inaccurate, and provide only intermittent feedback, lacking continuous pressure information, making them difficult to implement effectively in both power and manual toothbrushes.
Innovation Solution
A compact, simple pressure-sensing system utilizing a V-spring assembly, a Hall effect sensor, and a microprocessor to provide continuous feedback on pressure applied to the bristle field, with a magnet and mu metal shield to accurately detect changes in the magnetic field and filter noise, enabling real-time pressure monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional pressure-sensing system with spring, moment arm and switch is used, then pressure threshold detection is achieved, but the system becomes complex and costly
Solution Approach 1:
The patent replaces the traditional mechanical pressure-sensing system (spring, moment arm, switch) with a magnetic field-based sensing system using a Hall effect sensor. The Hall sensor detects changes in magnetic field strength caused by magnet displacement, converting mechanical pressure into electrical signals without requiring complex mechanical components. This substitution maintains measurement precision while significantly reducing device complexity.
Solution Approach 2:
The patent introduces a magnet as an intermediary element that couples the mechanical V-spring system to the Hall effect sensor. The magnet's displacement under pressure creates corresponding changes in the magnetic field, which the Hall sensor detects. This intermediary enables the conversion of mechanical displacement into measurable electrical signals with high precision and simple architecture.
2Loss of information
If a traditional pressure-sensing system is used, then pressure threshold indication is provided, but continuous pressure feedback is not available
Solution Approach 1:
The patent implements continuous pressure feedback by connecting the Hall effect sensor output to a microprocessor that processes the signal in real-time. The system provides continuous pressure information through visual indicators (LEDs) and haptic feedback (vibration motor), enabling users to maintain optimal brushing pressure throughout the brushing process. This continuous feedback loop eliminates information loss and improves brushing efficiency by guiding users to apply appropriate pressure continuously rather than relying on intermittent threshold alerts.
3Ease of manufacture
If a compact pressure-sensing system is implemented, then cost is reduced, but measurement accuracy may be compromised
Solution Approach 1:
The patent achieves both cost reduction and maintained accuracy by replacing expensive mechanical components (precision springs, moment arms, tactile switches) with inexpensive electronic components (Hall effect sensor, magnet, microprocessor). The Hall effect sensor provides high-resolution pressure measurement capability at a fraction of the cost of traditional mechanical systems, while the digital signal processing enables precise pressure quantification without complex mechanical linkages.
4Loss of information
If a Hall effect sensor system is used, then continuous pressure feedback is achieved, but magnetic field interference may occur
Solution Approach 1:
The patent uses the V-spring assembly and magnet as intermediary elements that isolate the Hall effect sensor from direct mechanical interference. The magnetic field serves as an intermediary carrier that transmits pressure information from the brushhead to the sensor without requiring direct mechanical contact, thereby reducing noise and interference while maintaining continuous feedback capability.
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 system offers continuous, accurate pressure feedback, allowing users to maintain optimal brushing pressure, enhancing dental care by providing perceptible signals for adjusting pressure levels, ensuring both minimum and maximum pressure thresholds are met.
Implementation Method 1
a Hall effect sensor mounted within the changing magnetic field produced by the magnet as the rear end of the V-spring moves, wherein the output of the Hall effect sensor changes from a no-load condition corresponding to the displacement of the rear end of the V-spring due to pressure on the brush element
Data Source
AI summary
The power toothbrush includes a handle portion which includes a power drive assembly and a brushhead assembly (32) which includes a brushhead arm (36) and a brush element (38) at a distal end thereof. A V-spring assembly (14) converts the action of the power drive assembly to drive the brushhead assembly in a back-and-forth action. A mounting member (55) at the rear end of the V-spring assembly provides a base for a magnet (56). The V-spring assembly and the brushhead assembly comprises a unit which moves about a pivot point at the forward end of the V-spring assembly, so that the back end of the V-spring assembly is displaced in accordance with pressure applied to the brush member. A Hall effect sensor (58) is mounted within the changing magnetic field produced by the magnet as the rear end of the V-spring assembly is displaced due to pressure on the brushhead. A processor (65) is responsive to the output from the Hall sensor and stored information to produce a signal indicative of the pressure on the brushhead and to provide an indication of when the pressure exceeds a threshold value.