Optical Touch Switch Circuit for Sensor Malfunction Detection
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Solution Overview
Problem
Conventional touch-sensitive momentary-contact switches used in household appliances cannot identify malfunctions in their optical sensors, posing a safety risk when the switch becomes faulty and cannot be switched off.
Innovation Solution
A touch-sensitive momentary-contact switch design that routes a portion of electromagnetic radiation to the receiver even when not operated, with an evaluation circuit assessing malfunctions based on changes in the evaluation signal level during transmission and changeover cycles, and utilizing a measurement range changeover to detect saturation voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the momentary-contact switch is designed with a cover that is at least partially permeable to electromagnetic radiation, then the switch can be operated simply and cleaned easily, but it becomes impossible to identify whether the optical sensor is faulty
Solution Approach 1:
The system performs preliminary self-diagnostics by routing a portion of the electromagnetic radiation emitted by the transmitter directly to the receiver through a feed-through opening in the masking frame. This creates a reference signal path that allows the evaluation circuit to detect malfunctions in the optical sensor before they affect normal operation, resolving the contradiction between maintaining simple operation and enabling fault detection
Solution Approach 2:
The feed-through opening in the masking frame acts as an intermediary structure that allows a portion of the electromagnetic radiation to pass through directly from the transmitter to the receiver. This intermediary path provides a reference signal that enables malfunction detection without interfering with the normal operation through the cover, thus resolving the contradiction between operational simplicity and reliability
2Device complexity
If no device is provided for routing electromagnetic radiation to the receiver when not operated, then the device structure remains simple, but malfunction in the optical sensor cannot be identified
Solution Approach 1:
The system implements preliminary action by providing a feed-through opening in the masking frame that allows a portion of the electromagnetic radiation to reach the receiver even when the switch is not operated. This creates a baseline reference signal that enables the evaluation circuit to detect malfunctions, achieving reliable fault identification while maintaining relatively simple device structure
Solution Approach 2:
The feed-through opening in the masking frame serves multiple functions: it allows the optical sensor to be tested for malfunctions by providing a reference signal path, and it does not interfere with the normal operation of the switch through the cover. This multi-functionality resolves the contradiction between structural simplicity and malfunction identification capability
3Device complexity
If the evaluation circuit only detects signal changes during operation, then the evaluation circuit remains simple, but it cannot distinguish between normal operation and optical sensor malfunction
Solution Approach 1:
The evaluation circuit uses feedback from two signal paths: the normal signal path through the cover during operation, and the reference signal path through the feed-through opening. By comparing these signals, the circuit can distinguish between normal operation (where only the operational path changes) and optical sensor malfunction (where neither path produces the expected signal change), thereby achieving accurate malfunction detection without excessive circuit complexity
Solution Approach 2:
The system performs preliminary measurement by routing a portion of the electromagnetic radiation through the feed-through opening to establish a reference signal level before normal operation. The evaluation circuit compares this reference level with signals during operation to detect malfunctions, achieving precise malfunction detection while maintaining relatively simple circuit architecture through the use of a basic level detection mechanism
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
Enables the identification of optical sensor malfunctions, allowing for appropriate reactions and increased safety by ensuring the switch can be reliably operated or switched off, even if faulty.
Implementation Method 1
a transmitter emitting electromagnetic radiation and a receiver receiving electromagnetic radiation
Implementation Method 2
routing a portion of the electromagnetic radiation emitted by the transmitter to the receiver
Data Source
AI summary
A touch-sensitive momentary-contact switch has an optical sensor, particularly an infrared sensor, and an evaluation circuit. The evaluation circuit is able to identify a malfunction in the optical sensor, so that the momentary-contact switch can be switched off, for example, for safety reasons. Therefore, it is possible to identify a malfunction in the optical sensor.