Capacitive Proximity Sensor for Dental Light Curing Device
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Solution Overview
Problem
Light curing devices face challenges in minimizing initialization delays and ensuring reliable operation, particularly in dental applications where dentists are often distracted, leading to battery discharge or incomplete curing cycles due to omitted calibration steps and system checks.
Innovation Solution
A capacitive proximity sensor is used to detect the approach of a user's hand, switching the device to standby mode, with an active shield to reduce parasitic capacitances and enhance detection accuracy, allowing for immediate readiness when needed and preventing accidental activation by non-user objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the light curing device is switched on manually using a power button, then the device can be activated when needed, but there is a start-up delay of several seconds that is unacceptable for efficient operation
Solution Approach 1:
The device performs preliminary actions by automatically switching to standby mode when a hand approaches (detected by capacitive sensor) and completing initialization in advance. This allows the device to be ready for immediate operation without waiting for manual power button activation, thus reducing the perceived start-up delay while maintaining complete system checks.
2Ease of operation
If the device automatically switches to standby mode when placed on the charging station, then charging is convenient, but the device may be accidentally activated or deactivated when the dentist places it down
Solution Approach 1:
The capacitive sensor is positioned specifically on the upper side of the housing to detect hand approach, while a separate sensor on the lower side detects placement on the charging station. This localized sensing approach allows the device to distinguish between intentional user interaction (hand approach from above) and incidental placement (on the charging station from below), preventing accidental activation while maintaining charging convenience.
3Speed
If calibration steps and system checks are omitted or performed less frequently to reduce delay, then activation is faster, but incomplete curing may occur leading to liability risks
Solution Approach 1:
The device performs complete calibration steps and system component checks during the automatic standby initialization that occurs when a hand approaches, before the user actually triggers the curing cycle. This preliminary action ensures all safety and quality checks are completed in advance without adding delay to the actual curing operation, maintaining both speed and reliability.
4Extent of automation
If a capacitive proximity sensor is used to detect hand approach, then automatic standby activation is achieved, but parasitic capacitances and external interference may affect detection accuracy
Solution Approach 1:
An active shield is introduced as an intermediary element between the capacitive sensor and the external environment. The shield electrode, controlled to have the same potential as the sensor electrode, acts as a mediator that blocks parasitic capacitances from ground and surrounding objects while allowing the sensor to detect the genuine capacitive change caused by hand approach, thus improving detection accuracy.
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 solution enables rapid and reliable activation of the light curing device, reducing the risk of incomplete curing and battery discharge, while maintaining error-proof operation and ergonomic handling.
Implementation Method 1
the sensor is designed as a capacitive proximity sensor. It distinguishes between the capacitance of a user's hand or finger and the capacitance of the curing surface
Implementation Method 2
the active shield can be controlled so that there is no voltage difference between the active shield and the capacitive proximity sensor. The shield electrode also protects the proximity sensor electrode from environmental influences
Data Source
Figure 1
Figure 2~3
AI summary
A light-curing device with a control circuit by which the light-curing device can be switched on and/or off, in particular from a standby mode to an operating mode and back, and with a sensor for triggering the switching on and/or off, characterized in that the sensor is designed as a capacitive proximity sensor (36) which has a sensitivity of less than 1 pF, and that the control circuit (40) distinguishes between the approach of a user's hand to the light-curing device (10) and the approach of the light-curing device to a surface.