Two-Terminal Switching Circuit for Reed Switch Replacement

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Solution Overview

Problem

Conventional reed switches are vulnerable to mechanical stress and have a limited lifespan, and their two-terminal configuration makes direct replacement with three-terminal electromagnetic switches, such as Hall effect or magneto-resistive switches, difficult due to compatibility issues with digital logic inputs and the need for additional components like comparators to convert analogue signals to digital.

Innovation Solution

An electrical switching circuit with a first and second terminal, incorporating an electromagnetic switch with a positive and negative power supply and an output terminal, where an electronic switch is connected between the terminals, and a diode and electrical storage means are used to manage power supply and generate a digital output signal compatible with reed switches, including a pulse generator to handle low-frequency operations and prevent discharge issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a reed switch is used, then the circuit is simple and compatible with digital logic inputs, but the switch is vulnerable to mechanical stress and has a limited lifespan

Engineering Contradiction:
Improveswitch lifespanVSAvoidcircuit complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical reed switch with an electromagnetic switch (Hall effect sensor or magneto-resistive sensor) that has no moving parts, eliminating mechanical stress and extending lifespan. The electromagnetic switch detects magnetic field changes to control the electronic switch, providing a non-mechanical alternative that maintains reliability while improving durability.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary electromagnetic switch that senses magnetic field changes and controls the electronic switch through electrical signals rather than direct mechanical contact. This intermediary component transfers the switching function from a mechanical system to an electromagnetic system, resolving the contradiction between reliability and complexity.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If a three-terminal electromagnetic switch is used to replace a two-terminal reed switch, then the switch has no mechanical stress, but additional components like comparators are needed to convert analogue signals to digital

Engineering Contradiction:
Improveswitch lifespanVSAvoidnumber of components
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the electromagnetic switch with the electronic switch into a single integrated circuit unit. The electromagnetic switch (sensor) and electronic switch are combined such that the sensor's output directly controls the electronic switch without requiring external comparators or additional signal conditioning components. This integration eliminates the need for separate analogue-to-digital conversion components while maintaining the benefits of the electromagnetic switching mechanism.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent creates a universal switching component that combines multiple functions: the electromagnetic switch serves as both the sensing element and the control element for the electronic switch. This multi-functional design allows the same component to perform both analogue signal detection and digital signal generation, eliminating the need for separate comparator circuits and reducing overall system complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Device complexity

If the electromagnetic switch output is directly connected to digital logic input, then the circuit is simple, but the output may not maintain a valid digital state under low-frequency conditions

Engineering Contradiction:
Improvecircuit complexityVSAvoidoutput signal validity
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent uses an electronic switch (transistor or MOSFET) that dynamically responds to the electromagnetic switch output signal. The electronic switch actively maintains a valid digital output state by switching between fully on and fully off states, even under low-frequency conditions. This dynamic switching action ensures the output remains in a valid digital state (either high or low) regardless of the frequency of the input signal, preventing indeterminate states that would occur with direct connection.

Inventive Principle:
Principle #15Dynamics

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

The solution enables pin-to-pin compatibility with reed switches, providing a digital output that maintains a valid state under low-frequency conditions and prevents glitches, allowing for direct replacement without additional hardware or software changes on the processing unit, ensuring reliable operation and compatibility with digital logic inputs.

Implementation Method 1

An electrical switching circuit, e.g. based on electromagnetic sensors or switches, such as Hall effect switches or magneto-resistive switches

Methodology Applied
Scientific EffectHall effect: Hall Effect

Implementation Method 2

electromagnetic sensors or switches, such as Hall effect switches or magneto-resistive switches

Methodology Applied
Scientific EffectMagneto-resistive effect: Magnetoresistance

Implementation Method 3

A diode wherein its cathode is connected (e.g. directly) to the positive power supply terminal of the electromagnetic switch and its anode is connected (e.g. directly) to the first terminal

Methodology Applied
Scientific EffectDiode rectification: Diode

Implementation Method 4

electrical storage means connected (e.g. directly) between the positive and the negative power supply terminal of the electromagnetic switch

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 5

An electronic switch connected (e.g. directly) between the first and second terminal, wherein the electronic switch switches between an opened (e.g. non-conductive) and a closed (e.g. conductive) condition as a function of a signal applied to a control terminal

Methodology Applied
Scientific EffectElectrical resistance control: Electrical Resistance

Data Source

PatentEP3419173B1An electrical switching circuit, corresponding method and apparatus
Publication Date: 2021.04.21 ILLINOIS TOOL WORKS INC
  • EP3419173B1 patent drawingFigure 1
  • EP3419173B1 patent drawingFigure 2A~2B
  • EP3419173B1 patent drawingFigure 3~4B

AI summary

An electrical switching circuit, includes a first (X1) and a second (X2) terminal; an electromagnetic switch (200) having a positive (V+) and a negative (V-) power supply terminal and an output terminal (O), the negative (V-) power supply terminal being connected to the second (X2) terminal; an electronic switch (T1) connected between the first (X1) and the second (X2) terminal and having a control terminal connected to the output (O) of the electromagnetic switch (200), that switches between an opened and a closed condition as a function of a signal applied to the control terminal, thereby varying the resistance between the first (X1) and the second (X2) terminal; electrical storage means (C1), connected between the positive (V+) and negative (V-) power supply terminal of the electromagnetic switch (200); and a diode (D1), with the cathode connected to the positive power supply terminal (V+) of the electromagnetic switch (200) and the anode connected to the first (X1) terminal, whereby: when the voltage (VOUT) between the first (X1) and the second (X2) terminal is greater or smaller than the voltage between the positive (V+) and the negative (V-) power supply terminal of the electromagnetic switch (200), the diode (D1) is closed or opened and the electromagnetic switch (200) is either supplied by the voltage (VOUT) between the first (X1) and the second (X2) terminal or by the electrical storage means (C1), the electrical storage means (C1) charging when the voltage (VOUT) between the first (X1) and the second (X2) terminal is greater than the voltage between the positive (V+) and the negative (V-) power supply terminal of the electromagnetic switch (200).