Hand Dryer Airflow Control Using Segmented Capacitive Sensing
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Solution Overview
Problem
Capacitive sensors used in hand dryers cannot detect the position of a hand, leading to misoperation due to water adhesion and inadequate control of the drying process.
Innovation Solution
A hand dryer design incorporating a recessed hand insertion portion with a high-pressure airflow nozzle and a capacitive sensor with multiple electrode pairs to detect hand position and control airflow distribution based on hand detection patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor with a pair of electrodes facing each other is used to detect a hand, then hand detection is enabled, but the position of the hand cannot be detected
Solution Approach 1:
The sensor is divided into multiple electrode pairs arranged in different regions (first electrode pair in upper region, second electrode pair in lower region, third electrode pair in left region, fourth electrode pair in right region). Each electrode pair independently detects capacitance changes in its specific region, enabling both hand detection and position determination through segmented spatial coverage.
Solution Approach 2:
The sensor transitions from a single pair of electrodes (one-dimensional detection) to multiple electrode pairs arranged in a two-dimensional matrix pattern. This dimensional expansion allows the system to detect not only the presence of a hand but also its specific position by determining which electrode pairs register capacitance changes.
2Device complexity
If a single pair of electrodes is used for hand detection, then the sensor structure is simple, but the hand position cannot be determined for appropriate control
Solution Approach 1:
The sensor is divided into multiple electrode pairs arranged in different regions (first electrode pair in upper region, second electrode pair in lower region, third electrode pair in left region, fourth electrode pair in right region). Each electrode pair independently detects capacitance changes in its specific region, enabling both hand detection and position determination through segmented spatial coverage.
Solution Approach 2:
The multiple electrode pairs serve dual functions: they collectively detect hand presence while individually providing position information. The same sensor structure enables both simple detection and sophisticated position-based control, making the system multi-functional without requiring separate detection and control mechanisms.
3Reliability
If water adheres to the hand or sensor, then misoperation occurs, but the capacitive sensor is supposed to be resistant to extraneous light and surface uncleanliness
Solution Approach 1:
The sensor is divided into multiple electrode pairs arranged in different regions (first electrode pair in upper region, second electrode pair in lower region, third electrode pair in left region, fourth electrode pair in right region). Each electrode pair independently detects capacitance changes in its specific region, enabling both hand detection and position determination through segmented spatial coverage.
Solution Approach 2:
The controller receives capacitance change signals from multiple electrode pairs and analyzes the pattern of detection across different regions. By evaluating which specific electrode pairs register changes, the system can distinguish between water adhesion (affecting random electrodes) and actual hand placement (affecting specific regional electrodes), enabling discrimination between valid and invalid operations.
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
Prevents misoperation by accurately determining hand position and controlling airflow for efficient drying, ensuring effective water removal and user-friendly operation.
Implementation Method 1
The capacitive sensor detects a hand by measuring a change in capacitance between two electrodes based on the mutual capacitance type
Implementation Method 2
an air blower provided in the body casing to generate the high-pressure airflow; and the nozzle provided on a wall of the hand insertion portion to transform the high-pressure airflow from the air blower into a high-speed airflow
Data Source
AI summary
A hand dryer includes: nozzles each provided on a wall of a hand insertion portion, transforming a high-pressure airflow from an air blower into a high-speed airflow, and blowing the high-speed airflow into the hand insertion portion. The hand dryer includes: a hand sensor including a plurality of electrode pairs and detecting a hand inserted into the hand insertion portion from a change in capacitance between two electrodes included in the plurality of electrode pairs, each of the plurality of electrode pairs consisting of a first electrode and a second electrode having different polarities to each other; and a controller that drives the air blower on the basis of a combination of the two electrodes with which a hand has been detected by the hand sensor.