Power Tool Load Detection Circuit for Overcurrent Warning
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Solution Overview
Problem
Conventional power tools, such as cutting saws and chain saws, cannot predict the magnitude of current load during cutting processes, leading to unpredictable overcurrent shutdowns and rapid temperature increases in motor coils, affecting cutting performance and user experience.
Innovation Solution
A detection circuit for power tools that includes a main control unit, sampling resistor, voltage sampling unit, and alarm display unit, which samples voltage across the sampling resistor to determine load current and state, triggering a preset display state when the load state duration exceeds a set time, thereby alerting users to current load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If overcurrent protection shutdown is implemented during cutting process, then motor coil temperature rise is prevented, but cutting process is interrupted and user experience deteriorates
Solution Approach 1:
The detection circuit samples voltage across the sampling resistor to obtain load current information before overcurrent damage occurs. The main control unit processes this information and triggers alarm display in advance, enabling users to take preventive action before overtemperature protection shutdown is activated, thus maintaining cutting continuity while preventing motor damage
2Productivity
If load current detection and alarm system is added, then cutting process continuity is maintained through early warning, but device complexity increases
Solution Approach 1:
A sampling resistor is introduced as an intermediary component in the motor driving loop to convert load current information into voltage signals for detection. The voltage sampling unit and main control unit process these signals to generate alarm outputs, creating a modular detection system that adds functionality while maintaining clear separation of concerns and manageable complexity
Solution Approach 2:
The detection circuit establishes a feedback loop where load current information is continuously sampled, processed by the main control unit, and displayed through alarm indicators. This real-time feedback enables users to monitor load conditions and adjust operation accordingly, maintaining cutting continuity while preventing overtemperature shutdown
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 detection circuit intuitively informs users of load current levels during use, maintaining consistent cutting performance and enhancing user satisfaction and product competitiveness by preventing overtemperature issues.
Implementation Method 1
The voltage sampling unit is used to sample a voltage across the sampling resistor
Implementation Method 2
the alarm display unit includes a resistor R1 and a light-emitting diode LED1
Data Source
AI summary
The disclosure provides a power tool, a detection circuit and a detection method of a load state thereof. The detection circuit of the power tool includes: a main control unit, a sampling resistor, a voltage sampling unit and an alarm display unit. The sampling resistor is arranged on a driving loop of a motor. The voltage sampling unit is used to sample a voltage across the sampling resistor. The alarm display unit is connected with the main control unit. The main control unit is configured to control the alarm display unit to execute a preset display state according to a voltage signal across the sampling resistor sampled by the voltage sampling unit.