Capacitive Airflow Sensor for Electronic Cigarette
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Solution Overview
Problem
Conventional electronic smoke apparatus, such as electronic cigarettes, suffer from unreliable inhaling detection due to environmental vibrations and noise, leading to false actuations, and their air-flow sensors are complex and costly.
Innovation Solution
An improved air-flow sensor using a conductive membrane and back plate with a capacitive structure measures deformation to determine air-flow rate and direction, integrated with a processor to measure capacitance or oscillation frequency, providing a cost-effective and compact solution to prevent false triggering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional air-flow sensor with JFET and electret layer is used, then the sensor can detect air flow, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and removes the complex JFET amplification stage and electret layer from the sensor structure. Instead, it uses a simple capacitive sensor with a flexible substrate that directly measures air flow-induced capacitance changes, eliminating unnecessary components while maintaining detection functionality
Solution Approach 2:
The patent employs inexpensive materials such as flexible substrate, conductive layer, and dielectric layer that can be manufactured using low-cost techniques. The simple capacitive structure uses readily available materials rather than expensive specialized components like JFETs and electret materials
2Reliability
If a conventional air-flow sensor is used, then air flow can be detected, but false actuations occur due to environmental vibration or noise
Solution Approach 1:
The patent introduces a dynamic detection mechanism that measures capacitance changes over time and calculates deformation rate. By analyzing the temporal derivative of capacitance changes, the system distinguishes between genuine air flow (which causes rapid deformation) and environmental vibrations (which cause slow, gradual changes), thereby preventing false actuations
Solution Approach 2:
The patent implements a feedback-based detection algorithm that continuously monitors capacitance changes, calculates deformation rates, and compares them against threshold values. This feedback mechanism allows the system to adaptively distinguish between valid air flow signals and noise, improving both precision and reliability
3Device complexity
If a simple capacitive sensor is used, then the device complexity is reduced, but the sensor cannot distinguish between air flow and environmental vibration
Solution Approach 1:
The patent compensates for the simplicity of the capacitive sensor by introducing dynamic analysis of capacitance changes over time. By calculating the rate of deformation (derivative of capacitance with respect to time), the system extracts meaningful air flow information while filtering out static or slowly varying environmental vibrations, thereby maintaining high detection accuracy with a simple sensor structure
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 solution effectively reduces inadvertent triggering by children or environmental noise, offering a reliable and cost-effective air-flow detection system for electronic smoke apparatus, ensuring accurate activation of the smoke generating circuitry only during intended user inhalation.
Implementation Method 1
the variation in capacitance between the baffle surface and the base surface is indicative of the direction and rate of air flow
Data Source
Figure 1~2
Figure 3~4
Figure 5~6A
AI summary
An electronic smoke comprising an inhale detector and a smoke effect generating circuitry. The inhale detector comprises an air-flow sensor which is arranged to detect direction and rate of air flow through the smoke apparatus, and the smoke effect generating circuitry is arranged to operate the smoke effect generating circuitry to generate smoking effect when the air flow direction corresponds to inhaling through the apparatus and the air flow rate reaches at predetermined threshold. Such an electronic smoke alleviates the problem of inadvertent triggering due to environmental vibration or noise or children playing by blowing into the device.