Method for operating a safety-critical function using a touch sensor
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Solution Overview
Problem
Conventional cooking appliances face challenges in meeting the Two-Steps-On and One-Step-Off safety requirements for safety-critical functions, as they often rely on costly touchscreen displays or less visually appealing physical knobs, and there is a need for a method that uses an independent touch sensor not integrated with a touchscreen display to ensure compliance with UL standards.
Innovation Solution
A method and appliance design that utilize a touchscreen display for initiating a safety-critical function, requiring a second user input from a separate, adjacent capacitive-touch button via a wired connection to a UL 60730 Class B compliant microcontroller, which cannot be manipulated externally via wireless communication, ensuring compliance with safety standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a touchscreen display is used to control safety-critical functions, then visual appeal and user interface quality are improved, but cost increases and wireless manipulation vulnerability occurs
Solution Approach 1:
The control system is segmented into two independent parts: a touchscreen display for user interaction and a separate UL 60730 Class B compliant controller for safety-critical function control. This segmentation allows the touchscreen to provide visual appeal while the separate controller ensures reliability by being isolated from wireless communication vulnerabilities.
Solution Approach 2:
A wired connection acts as an intermediary between the touchscreen and the Class B compliant controller. This intermediary transmission path ensures that control signals for safety-critical functions cannot be manipulated wirelessly, while still allowing the touchscreen to serve as the user interface.
2Reliability
If a physical knob is used to control safety-critical functions, then wireless manipulation vulnerability is prevented, but visual appeal deteriorates
Solution Approach 1:
The solution merges the advantages of both touchscreen and physical knob approaches: the aesthetic and ease-of-use benefits of a touchscreen display with the security and reliability benefits of a wired, isolated control path used in physical knobs. The touchscreen provides visual appeal while the wired connection to the Class B controller prevents wireless manipulation.
3Reliability
If a UL 60730 Class B compliant touchscreen is used, then safety compliance is improved, but cost increases
Solution Approach 1:
The system separates the expensive UL 60730 Class B compliant controller from the touchscreen display, allowing the touchscreen to be a standard, lower-cost component. The Class B controller handles only the safety-critical control functions through wired connections, while the touchscreen serves as a separate user interface, reducing overall system cost.
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 allows for safe and compliant initiation and cancellation of safety-critical functions, such as pyrolytic cleaning, while preventing external wireless manipulation, thus enhancing user safety and visual appeal without the need for costly touchscreen displays.
Implementation Method 1
a capacitive-touch button adjacent to the touchscreen display
Data Source
AI summary
A method for initiating a safety-critical function in an appliance. The method including receiving a first user input for the safety-critical function via a touchscreen and receiving a second user input confirming the safety-critical function via a first separate input element adjacent to the touchscreen. The operation of the touchscreen can be manipulated externally, directly or indirectly, via wireless communication while a safety-critical function is active. The first separate input element communicates via a wired connection to a control device that is not capable of being manipulated externally via wireless communication while a safety-critical function is active, wherein the control device controls initiation of the safety-critical function. In the method, both the first user input and the second user input are required to initiate the safety-critical function.