LED Indicator Circuit for AC Plug State Detection

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Solution Overview

Problem

Existing AC power plug and socket indicators, such as neon lamps, have limited lifespan and cannot accurately detect correct electrical connections or short circuits between wires.

Innovation Solution

An LED indicator device is introduced, featuring a circuit with a capacitor providing reactive power current-limiting impedance, connected in parallel with AC power sources, which includes multiple LED lighting circuits to indicate on/off states and incorrect connections, with LEDs offering long lifespan, low power consumption, and various colors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If a neon lamp is used to indicate power state, then the indicator can show on/off state, but the lifespan is limited to about 30,000 hours

Engineering Contradiction:

Improvelifespan of indicatorVSAvoidreliability of indicator

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent changes the fundamental parameter of the lighting element from neon lamp to LED, which has a significantly longer lifespan. The LED indicator device is designed with specific circuit components (capacitor, resistor, diode) that enable it to operate reliably for extended periods, directly addressing the lifespan limitation of neon lamps.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If simple tests are used to detect wire connections, then the testing process is simple, but it is impossible to identify correct electrical connection or short circuit

Engineering Contradiction:

Improveaccuracy of connection detectionVSAvoidcomplexity of detection circuit

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the detection function into multiple independent LED indicator circuits, each corresponding to a specific wire connection (hot wire, neutral wire, grounding wire). Each circuit independently detects its respective connection status, enabling precise identification of correct connections and short circuits without requiring a single complex testing system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses different colored LEDs to indicate different connection states. For example, green LEDs indicate correct connections while red LEDs indicate incorrect connections or short circuits. This color-coding system provides clear, intuitive visual feedback that enhances measurement precision without significantly increasing device complexity.

Inventive Principle:

Principle #32Color changes

3Temperature

If conventional indicators are used, then they can show power state, but they generate heat during voltage energy conversion

Engineering Contradiction:

Improveheat generation of circuitVSAvoidpower consumption of indicator

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The patent replaces the thermal-based neon lamp with an LED-based electrical indicator. The LED circuit uses a capacitor to store electrical energy and discharge it through the LED, eliminating the need for continuous voltage conversion and heat generation. This substitution dramatically reduces temperature rise while maintaining indication functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 LED indicator device effectively indicates the on/off state and correct electrical connections of AC power plugs and sockets, while also detecting incorrect connections, with LEDs lasting up to 100,000 hours and consuming minimal electricity.

Implementation Method 1

can be driven by a capacitor that provides a reactive power current-limiting impedance to light the light-emitting diode

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

LED indicator device includes an LED lighting circuit having an LED and can be driven by a capacitor that provides a reactive power current-limiting impedance to light the light-emitting diode

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS7855514B2LED indicator device for AC power plug or socket

Publication Date: 2010.12.21 YFC BONEAGLE ELECTRIC CO LTD

AI summary

An LED indicator device is mounted in an AC power plug or socket and electrically connected in parallel with an AC power source. The LED indicator device includes a driving/current-limiting circuit to which an LED lighting circuit is coupled. The driving/current-limiting circuit includes a driving/current-limiting capacitor and a discharge resistor connected in parallel with the driving/current-limiting capacitor. The LED lighting circuit includes an LED, a protective instantaneous current-limiting resistor coupled to the LED, a rectifying diode connected in parallel with the LED, and a protective instantaneous voltage-limiting capacitor connected in parallel with the LED. The LED is lit to show the position and on/off state of the AC power plug or socket. Three LEDs emitting different colors and associated driving/current-limiting circuits and associated LED lighting circuits can be utilized to indicate incorrect power connection or short circuit of the AC power plug or socket.