Power Tool Indication Circuit Using a Zener Threshold

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Solution Overview

Problem

Existing motor control units in power tools have a limited number of output pins, restricting the amount of information that can be provided to users through LEDs, and adding additional control units increases complexity and cost.

Innovation Solution

A power tool condition indication circuit utilizing a Zener diode that becomes conductive at a threshold voltage to generate multiple indication signals, allowing a single output pin to control multiple LED indicators or alternative indicators like buzzers or speakers, thereby expanding the range of conditions that can be indicated without requiring extensive redesign.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If additional control units or digital electronics are added to expand LED control capabilities, then the amount of information provided to the user increases, but the complexity and manufacturing cost increase

Engineering Contradiction:
Improveinformation provided to userVSAvoidcontrol unit complexity
Core Design Contradiction:
Loss of informationVSDevice complexity

Solution Approach 1:

The power tool condition indication circuit is designed to perform multiple functions using a single output pin from the motor control unit. By monitoring voltage levels and generating multiple indication signals, the circuit enables one component to control multiple LED indicators, thereby providing comprehensive information feedback without adding additional control units.

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

Solution Approach 2:

The power tool condition indication circuit acts as an intermediary between the motor control unit and the LED indicators. It receives a single output signal from the motor control unit, processes the voltage information, and generates multiple indication signals to drive multiple LEDs, thus expanding information capacity without increasing control unit complexity.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Loss of information

If additional control units are added to expand LED control capabilities, then the amount of information provided to the user increases, but the manufacturing cost increases

Engineering Contradiction:
Improveinformation provided to userVSAvoidmanufacturing cost
Core Design Contradiction:
Loss of informationVSEase of manufacture

Solution Approach 1:

The power tool condition indication circuit enables a single output pin to control multiple LED indicators through voltage level monitoring and signal generation. This multi-functional design eliminates the need for additional control units, thereby reducing component count and manufacturing cost while maintaining comprehensive information feedback capability.

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

3Loss of information

If the number of output pins on the motor control unit is increased to directly control more LEDs, then the information provided to the user increases, but the device complexity and cost increase

Engineering Contradiction:
Improveinformation provided to userVSAvoidoutput pin requirements
Core Design Contradiction:
Loss of informationVSDevice complexity

Solution Approach 1:

The indication circuit segments the information feedback function into multiple LED indicators, each representing different power tool conditions. A single output pin is used to provide voltage information that the circuit then segments into multiple discrete indication signals, allowing comprehensive feedback without increasing the number of output pins required.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The power tool condition indication circuit enables a single output pin to perform the function of multiple output pins by generating multiple indication signals from a single voltage input. This allows the motor control unit to maintain its original pin configuration while still providing expanded information feedback through multiple LEDs.

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

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 motor control unit to indicate multiple power tool conditions using a single output pin, reducing complexity and cost while providing users with more informative feedback.

Implementation Method 1

a zener diode configured to be conductive at a threshold voltage; wherein the power tool condition indication circuit is configured generate a first indication signal when a voltage controlled by the control circuit exceeds the threshold voltage

Methodology Applied
Scientific EffectZener diode breakdown effect: Diode

Data Source

PatentEP4417373B1A power tool
Publication Date: 2025.10.22 BLACK & DECKER CORP
  • EP4417373B1 patent drawingFigure 1
  • EP4417373B1 patent drawingFigure 2
  • EP4417373B1 patent drawingFigure 3

AI summary

A power tool comprises a housing and an electrical power source. A control circuit is electrically connected to the electrical power source and configured to control at least one operation of the power tool. A power tool condition indication circuit is electrically connected to the control circuit comprising a zener diode configured to be conductive at a threshold voltage. Wherein the power tool condition indication circuit is configured generate a first indication signal when a voltage controlled by the control circuit exceeds the threshold voltage and generate a second indication signal when a voltage controlled by the control circuit is below the threshold voltage.