Electronic Watch Impact Detection Control for Magnetic Field Interference
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Solution Overview
Problem
Electronic timepieces employing electromagnetic braking schemes experience abnormal hand operation due to external magnetic fields, leading to incorrect time displays and increased battery consumption, as the system errantly detects rotor vibrations as impacts and applies locking pulses excessively.
Innovation Solution
An electronic timepiece with a stepper motor, an impact detecting unit, and a rotation detecting unit that controls the impact detection operation based on rotation status, using correction driving pulses to prevent errant locking pulses and allowing impact detection only when the rotor is rotating, thereby preventing abnormal hand operation in magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impact detection is continuously performed using rotor vibration detection, then impact protection is improved, but false detection under external magnetic fields causes abnormal hand operation and increased current consumption
Solution Approach 1:
A rotation detection unit is introduced as an intermediary to distinguish between normal rotation vibrations and impact vibrations. The unit detects whether the rotor is rotating by monitoring back electromotive force, and this information mediates the impact detection process by enabling it only during non-rotation periods, thereby preventing false detection under magnetic fields while maintaining impact protection
Solution Approach 2:
The impact detection operation is made dynamic by controlling it to execute only during specific time periods when the rotor is not rotating. This dynamic control adapts the detection system to the operational state of the rotor, allowing accurate impact detection during idle periods while avoiding false detection during normal rotation under magnetic field influence
2Reliability
If locking pulses are applied to brake the rotor during detected vibrations, then impact-induced time errors are prevented, but excessive locking pulses under magnetic fields cause abnormal hand operation and increased battery consumption
Solution Approach 1:
The locking pulse application is converted to periodic action by restricting it to specific time periods when the rotor is not rotating. Instead of continuous or frequent locking pulse application, the system applies locking pulses only during designated non-rotation intervals, reducing overall energy consumption while maintaining time display accuracy during impact events
Solution Approach 2:
The rotation detection unit serves as an intermediary that controls the application of locking pulses. By detecting rotor rotation status through back electromotive force monitoring, it mediates between vibration detection and locking pulse application, ensuring pulses are applied only when appropriate (during non-rotation), thereby preventing excessive energy consumption and abnormal hand operation
3Reliability
If the dead time period is extended to allow rotor vibration to settle, then false impact detection is reduced, but response time to actual impacts is delayed
Solution Approach 1:
The dead time period is made dynamic rather than fixed, adjusting its duration based on the actual rotation state of the rotor. The system monitors rotation status and adapts the waiting period accordingly, allowing shorter dead times when rotation confirms normal operation and longer periods when rotation status is uncertain, thereby optimizing both detection accuracy and response time
Solution Approach 2:
The rotation detection unit acts as an intermediary that informs the impact detection control when the rotor has settled. Instead of using a fixed dead time, the system waits for the rotation unit to confirm rotor status, dynamically determining when impact detection can resume with high accuracy without unnecessary delays
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
Prevents abnormal hand operation in magnetic fields by limiting the output of locking pulses and reducing current consumption, ensuring accurate timekeeping and extending battery life.
Implementation Method 1
an impact detecting circuit that detects occurrence of an impact using a counter-electromotive current that is generated in the coil 13 by a vibration of the rotor 10
Implementation Method 2
an electric current is immediately and forcibly caused to flow in a coil, applying a braking force to the rotor
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
An electronic timepiece includes a limiting circuit (116) that is controlled by the rotation detecting circuit (115) and limits output of a locking pulse PL. The electronic timepiece prevents the display of the incorrect current time due to impact, by executing impact detection when rotation is detected, and prevents errant hand operation in a magnetic field by not outputting a locking pulse PL by prohibiting impact detection when non-rotation is detected. The electronic timepiece controls the limiting circuit (116) using a ranking-down storing circuit (138) and if the electronic timepiece employs multi-stage load correction, executes impact detection when regularly occurring non-rotation is detected. Thereby, errant deviation in the display of the current time due to impact is prevented. The electronic timepiece prohibits the impact detection and causes the locking pulse PL not to be output when non-rotation other than those occurring regularly is detected. Thereby, errant hand operation in a magnetic field is prevented.