Watch Pointer Correction Using Coil Back-EMF Impact Detection
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Solution Overview
Problem
Analog electronic watches face challenges in accurately correcting pointer positions after impacts due to the lack of effective detection and correction mechanisms, leading to potential shifts and reduced product reliability.
Innovation Solution
A pointer device equipped with a stepping motor, a driving circuit, a detection unit, and a processor that detects electromotive force generated by impacts and corrects the pointer position based on the detected patterns, ensuring accurate alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If braking control is performed on a step motor at impact detection timing, then pointer shift is reduced, but pointer position accuracy after impact is insufficient due to lack of effective correction mechanism
Solution Approach 1:
The patent implements a feedback mechanism where the system detects electromotive force generated by the coil during impact, determines the direction of pointer shift based on the polarity of the detected signal, and applies corrective braking control in the opposite direction. This closed-loop feedback approach ensures accurate pointer position correction while maintaining system reliability.
Solution Approach 2:
The system uses the existing coil structure of the step motor to detect impact-induced electromotive force, eliminating the need for separate detection sensors. The same coil that drives the motor serves dual purposes: actuation and impact detection, thereby reducing device complexity while maintaining correction accuracy.
2Measurement precision
If impact detection is implemented using electromotive force detection, then detection precision is improved, but device complexity increases due to additional detection circuitry
Solution Approach 1:
The patent makes the motor coil serve multiple functions: it acts as both the actuation coil for driving the step motor and the detection coil for sensing impact through electromotive force generation. This multi-functional design improves impact detection precision without requiring separate detection circuitry, thereby avoiding increased device complexity.
Solution Approach 2:
The system leverages the inherent electrical characteristics of the motor coil during operation to detect impact. The coil's own electromotive force response to mechanical impact is utilized for detection purposes, eliminating the need for external sensors or complex detection circuits while maintaining high detection 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
The solution effectively corrects pointer shifts caused by impacts, enhancing the reliability and accuracy of the electronic watch by determining the direction and extent of shifts and adjusting the pointer position accordingly.
Implementation Method 1
a detection unit configured to detect electromotive force generated in the coil due to an impact
Data Source
AI summary
An electronic watch includes a pointer; a stepping motor including a coil and configured to drive the pointer; a driving circuit configured to drive the stepping motor; an A/D converter configured to detect electromotive force generated in the coil due to an impact; and a CPU configured to control driving of the driving circuit. The CPU determines a direction in which the pointer is likely to be shifted, based on the electromotive force detected by the A/D converter, determines whether the pointer is shifted due to the impact, and upon determining that the pointer is shifted, corrects a position of the pointer in accordance with the direction in which the pointer is likely to be shifted.