Washer-Dryer Door Lock Circuit for Motor Stop Fail-Safe
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Solution Overview
Problem
Existing washer/dryer electronic control systems are prone to errors due to noise, irregular mains voltage, and electromagnetic interference, which can cause the safety algorithm to malfunction and fail to stop the drum rotation when errors occur, compromising user safety.
Innovation Solution
A control circuit that includes a relay, a triac for energizing the door lock, and a microprocessor to regulate the electric motor and door lock, which measures voltage differences to detect triac errors and cuts off power to the motor if an error is detected, ensuring the drum stops rotating when the door is opened.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a software-based microprocessor control system is used to regulate the door lock and motor operation, then the ease of operation and automation are improved, but the reliability deteriorates due to susceptibility to noise, voltage irregularities, and software bugs
Solution Approach 1:
The patent introduces an intermediary control circuit that acts as a mediator between the microprocessor and the critical components (door lock and motor). This control circuit independently monitors the triac state and can override the microprocessor to cut off power to the motor, providing a safety layer that is not susceptible to software errors or electromagnetic interference affecting the microprocessor.
Solution Approach 2:
The control system is segmented into independent functional blocks: the microprocessor for high-level control, the control circuit for intermediate monitoring and decision-making, and the execution components (triac, relay, door lock, motor). This segmentation allows the control circuit to independently verify the triac state and take corrective action without being dependent on the microprocessor's software integrity.
2Reliability
If the door lock is energized during washing to prevent door opening, then user safety is improved, but the device complexity increases due to additional control circuits and components
Solution Approach 1:
The control circuit continuously monitors the voltage across the triac and provides feedback about the triac's conduction state. This feedback mechanism allows the system to detect whether the triac is properly conducting power to the door lock and motor, and to take corrective action if the triac fails to conduct, thereby enhancing safety through active monitoring.
Solution Approach 2:
The control circuit autonomously detects triac errors and automatically cuts off power to the motor without requiring microprocessor intervention or user action. The system monitors its own critical components and self-corrects by de-energizing the motor when a triac failure is detected, providing self-service safety functionality.
3Reliability
If voltage monitoring is implemented to detect triac errors, then the reliability of safety functions is improved, but the device complexity and measurement precision requirements increase
Solution Approach 1:
The control circuit uses simple, robust voltage detection components that are inexpensive and reliable. The voltage monitoring approach uses basic electronic components to detect the triac's conduction state by measuring voltage across it, avoiding the need for complex sensors or high-precision measurement devices. The solution prioritizes simplicity and reliability over measurement precision.
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
Guarantees user safety by reliably halting the electric motor and preventing drum rotation when errors are detected in the door lock circuit, even if the microprocessor fails, thereby preventing accidental door opening during operation.
Implementation Method 1
measures the voltages on the triac (5) or the door lock (4) by taking the mains voltage as reference
Implementation Method 2
a door lock (4), for example the electromagnetic type, that prevents the door to be opened by being locked
Implementation Method 3
One end of the control circuit is connected to the line between the triac and the door lock, and the other end to the relay of the electric motor
Data Source
Figure 1
AI summary
The present invention relates to a washer/dryer (1) wherein user safety is maintained by ensuring that the electric motor (2) rotating the drum is halted when the door is opened or an opening command is transmitted. The washer/dryer (1) comprises a microprocessor (6) that allows the door lock (4) to be opened only after ensuring that the electric motor (2) has halted before the door is opened, and an extra control circuit (7) that cuts off the energy of the relay (3) operating the electric motor (2) in the case the microprocessor (6) is in error.