Electronic Watch Rotor Rotation Detection Using Variable Pulse Width
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Solution Overview
Problem
Conventional electronic watches face challenges in accurately detecting rotor rotation with indicating hands of large moment of inertia and reduced stepper motor driving power, leading to erroneous detection and increased current consumption.
Innovation Solution
The electronic watch employs a detection pulse change factor detection system that adjusts detection pulse width based on elapsed time and power supply voltage, using multiple detection pulse widths to control electromagnetic brake strength, ensuring accurate rotation detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed-width detection pulse is used to detect rotor rotation, then the detection circuit is simple, but accurate rotation detection cannot be achieved with indicating hands of large moment of inertia and reduced stepper motor driving power
Solution Approach 1:
The detection pulse width is made variable rather than fixed. The control circuit dynamically adjusts the detection pulse width based on the operational state of the stepper motor, allowing the system to adapt to different loading conditions (including large moment of inertia hands) and driving power levels, thereby achieving accurate rotation detection under varying conditions.
Solution Approach 2:
The pulse width parameter of the detection signal is changed according to specific conditions. When the stepper motor is driven with reduced power or when indicating hands with large moment of inertia are used, the detection pulse width is extended to allow sufficient time for the rotor to respond and generate a detectable signal, ensuring accurate rotation detection despite the challenging conditions.
2Measurement precision
If the detection pulse width is extended to improve detection accuracy, then rotation detection becomes more accurate, but current consumption increases
Solution Approach 1:
The detection pulse width is dynamically adjusted based on operational conditions rather than being constantly extended. The control circuit determines the appropriate pulse width in real-time, using longer pulses only when necessary (e.g., when reduced driving power or large moment of inertia hands are detected), and shorter pulses during normal operation, thereby balancing detection accuracy with energy conservation.
Solution Approach 2:
The pulse width parameter is adaptively changed based on the operational state. When the stepper motor operates with reduced power or drives indicating hands with large moment of inertia, the detection pulse width is extended to ensure accurate rotation detection. Under normal operating conditions, a shorter pulse width is used to minimize current consumption, achieving an optimal balance between detection accuracy and energy efficiency.
3Measurement precision
If multiple detection modes are implemented to handle different rotation scenarios, then detection accuracy improves, but the detection system becomes more complex
Solution Approach 1:
Rather than implementing multiple separate detection modes with different circuits, the system uses a single detection circuit that dynamically adjusts the pulse width parameter. The control circuit monitors operational conditions and automatically modifies the detection pulse characteristics, achieving adaptive detection capability without the complexity of multiple dedicated detection modes.
Solution Approach 2:
The detection circuit is designed to perform multiple detection functions through parameter adjustment rather than through separate specialized circuits. By varying the pulse width based on operational conditions, the same detection circuit can effectively handle different rotation scenarios (normal operation, reduced power, large moment of inertia hands), reducing overall system complexity while maintaining high detection accuracy.
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
This approach allows for precise detection of rotor rotation even with large moment of inertia indicating hands and reduced driving power, preventing erroneous stoppages and conserving energy by optimizing detection pulse widths.
Implementation Method 1
a detection pulse is output to abruptly change the impedance value of a coil of a stepper motor, and an induced voltage generated in the coil is detected at the coil ends, to thereby determine the pattern of free oscillation of the rotor
Implementation Method 2
a detection pulse is output to abruptly change the impedance value of a coil of a stepper motor... determine the pattern of free oscillation of the rotor
Data Source
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AI summary
Provided is an electronic watch capable of, even if an indicating hand having a large moment of inertia is used, accurately determining success and failure of rotation. The electronic watch detects rotation by using a first detection mode determination circuit (12) and a second detection mode determination circuit (13). In the electronic watch, a timing counter (14) for measuring a time after an output of a normal drive pulse is followed by a detection pulse selection circuit (151) provided as changing means for changing a width or a frequency of a detection pulse in accordance with an output time of the detection pulse. The detection pulse detects the rotation and simultaneously serves as an electromagnetic brake for a rotor (10). The electromagnetic brake for the rotor (10) is controlled by changing the width or the frequency of the detection pulse in a predetermined period, thereby achieving an accurate rotation detection. Alternatively, the setting of the width or the frequency of the detection pulse may be changed in accordance with a determination result in a first detection mode, an output voltage of a power supply, and a driving power of the normal drive pulse, instead of the output timing of the detection pulse.