Capacitive Laundry Humidity Sensing for Precise Dryer Control
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Solution Overview
Problem
Existing laundry drying appliances lack precision in measuring laundry mass humidity due to inaccurate impedance measurement methods, which are complex to implement and prone to errors, especially when the laundry is almost dry, and capacitive sensing solutions require cumbersome condenser arrangements.
Innovation Solution
A capacitive laundry mass drying degree sensing method using a capacitor with the laundry mass as dielectric, measured by electronic circuitry with a supply voltage and reference voltage, allowing for accurate control of the drying process by determining capacitance and adjusting parameters like power, drum speed, and drying time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laundry mass humidity measurement is based on electrical conductivity (resistivity) measurement, then the measurement system can be implemented with direct contact to laundry mass, but the measurement precision deteriorates especially when laundry is almost dry
Solution Approach 1:
The patent replaces the electrical conductivity measurement method with a capacitive sensing method. Instead of measuring resistivity through direct electrical contact with laundry mass, the system uses a capacitor where laundry mass acts as the dielectric between two plates. This substitution of measurement principle eliminates the need for direct electrical contact while providing more accurate humidity detection, especially for nearly dry laundry where resistivity measurements fail.
Solution Approach 2:
The patent introduces a capacitive sensing system with two plates (one fixed to the drum, one to the door) that act as intermediaries to measure laundry humidity indirectly. The laundry mass serves as the dielectric medium between these plates, allowing non-contact measurement of humidity through capacitance changes, thus avoiding the limitations of direct electrical contact methods.
2Measurement precision
If capacitive sensing is implemented with two plates arranged around laundry, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes existing structural components of the dryer serve dual functions: the drum and door serve both their primary functions (drying chamber and access closure) and as mounting structures for capacitive sensing plates. The drum inner wall and door inner wall become part of the capacitive sensor assembly, eliminating the need for separate dedicated sensor components and reducing overall device complexity.
Solution Approach 2:
The patent merges the capacitive sensing function with the existing drum and door structures. Instead of adding separate complex condenser arrangements, the system combines the sensing plates with the structural elements already present in the dryer, integrating multiple functions into existing components and simplifying the overall device architecture.
3Ease of operation
If drying program duration is predetermined according to user selection, then ease of operation improves, but productivity deteriorates due to excessive power consumption
Solution Approach 1:
The patent implements a feedback mechanism where the capacitive humidity sensing system continuously monitors laundry moisture levels during the drying cycle and provides real-time information to the control unit. Based on this feedback, the system automatically adjusts drying parameters such as heating power, drum speed, and cycle duration, optimizing energy consumption while ensuring complete drying without requiring users to manually adjust settings.
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 method provides reliable and precise humidity measurement, enabling optimal drying performance and reduced power consumption by accurately estimating water content and adjusting drying parameters in real-time.
Implementation Method 1
measuring a capacitance of said capacitor by means of an electronic circuitry electrically supplied by a supply voltage (Vcc) and a reference voltage (Vref), said reference voltage (Vref) being different from the first electric potential
Implementation Method 2
providing a capacitor in the laundry appliance, said capacitor having, as part of the capacitor dielectric, the laundry mass
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A method for measuring the humidity of a laundry mass (505) contained in a laundry treatment chamber (110) of a laundry appliance (100) comprises: providing a capacitor in the laundry appliance, said capacitor having, as part of the capacitor dielectric, the laundry mass; measuring a capacitance of said capacitor by means of an electronic circuitry electrically supplied by a supply voltage (Vcc) and a reference voltage (Vref). Providing a capacitor comprises: providing in the laundry appliance at least one conductive plate (205) which forms a plate of said capacitor, and exploiting, as a second plate of said capacitor, routing lines distributing inside the laundry drying appliance said reference voltage (Vref).