Passive Optical Lamp Sensor With FET Switching Output
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Solution Overview
Problem
Existing systems for remotely monitoring human-readable status indicators in legacy equipment are impractical due to the need for electrical hazards exposure, rewiring, and limited space, especially when such equipment operates at mains voltages and lacks necessary interfaces for remote monitoring circuitry.
Innovation Solution
A passive optical sensor system using a field-effect transistor (FET) coupled with a photoelectric sensor that generates an electric potential in response to incident light, allowing for distinct on and off states without an independent power supply, and can be secured to the equipment housing without penetrating it, using a light pipe for optical coupling and optical filters for wavelength-specific responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a powered circuit is used to monitor the indicator light and create a switched output, then monitoring capability is achieved, but device complexity and safety risks increase due to required rewiring, power supply installation, and exposure to electrical hazards
Solution Approach 1:
The passive optical sensor uses the light from the indicator lamp itself to generate the electrical potential needed to operate the monitoring circuit. The photoelectric sensor converts incident light directly into electrical energy, eliminating the need for external power supplies or rewiring. This self-powered approach reduces device complexity while maintaining monitoring reliability.
Solution Approach 2:
The invention replaces active electronic monitoring circuits with a passive optical sensing system. Instead of using powered circuits that require electrical connections and power supplies, the system uses optical fields to detect the indicator light state and converts it to electrical signals through the photoelectric effect, simplifying the overall system architecture.
2Reliability
If rewiring and power supply installation are performed to enable monitoring, then monitoring function is achieved, but safety risks increase due to exposure to electrical hazards and potential damage to equipment
Solution Approach 1:
The monitoring system is powered by the indicator light itself through the photoelectric sensor, eliminating the need to connect to mains voltage or internal equipment circuits. This external, non-invasive power source completely avoids exposure to electrical hazards and potential damage to the monitored equipment.
Solution Approach 2:
The invention introduces an intermediary optical coupling system that transfers information from the indicator light to the sensor without direct electrical contact. The light pipe or optical path acts as a mediator, allowing the system to sense the indicator state while maintaining complete electrical isolation from the monitored equipment.
3Reliability
If a light dependent resistor is used to monitor the indicator light, then basic detection is achieved, but measurement precision is insufficient due to small resistance changes and ambiguous outputs
Solution Approach 1:
The invention changes the operating parameter from resistance variation (LDR) to voltage threshold switching (FET). The field-effect transistor operates in saturation region where small changes in gate voltage produce large, abrupt changes in drain current, creating a sharp on-off switching effect that provides clear digital output signals with excellent measurement precision.
Solution Approach 2:
The invention applies optical filtering to make the photoelectric sensor selectively responsive to specific wavelengths emitted by the indicator lamp. This wavelength-specific detection enhances measurement precision by filtering out ambient light interference and focusing only on the characteristic emission spectrum of the monitored indicator.
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 effective remote monitoring of indicator lights without the need for rewiring or power supplies, providing a clear on-off switch-like output, reducing the risk of electrical hazards and improving monitoring efficiency by using the light from the indicator itself to power the sensor.
Implementation Method 1
a passive photoelectric sensor generating an electric potential in response to incident light
Implementation Method 2
a field-effect transistor which switches between distinct on and off states at a threshold potential
Implementation Method 3
The photoelectric sensor may be responsive to a first wavelength of light to generate a current and not responsive to a second wavelength of light, so that the sensor will respond to a change in color of the indicator light. This may be provided by fitting the photoelectric sensor with an optical filter.
Data Source
AI summary
A passive sensor for detecting the operation of a light source includes a photosensor which, when illuminated by the light source, delivers a voltage to a field effect transistor (FET) which can switch a circuit to control a device at a remote location. The FET transitions rapidly between very low resistance (short circuit) and very high resistance (open circuit), allowing a binary indication to be given in the circuit. The circuit can be used to charge an electrical storage device to allow later download of recent status of the lamp by detecting the charge stored in the device.