Tap Sensitive Alarm Clock Vibration Sensor Filter
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Solution Overview
Problem
Existing tap sensitive alarm clocks with audio units often experience unreliable snooze function activation due to unintentional triggering by sound frequencies, as the vibration sensors are sensitive to frequencies overlapping with those produced by audio units.
Innovation Solution
Incorporating a filter, such as a low-pass filter, that matches its frequency curve to block sound frequencies and only allow mechanical shock frequencies to activate the control circuit, ensuring the snooze function is not accidentally triggered by audio signals, while maintaining sensitivity to tapping frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the vibration sensor is made sensitive to tapping frequencies, then the tap function sensitivity is improved, but the risk of accidental activation by sound frequencies increases
Solution Approach 1:
The patent applies parameter changes by adjusting the frequency response characteristics of the vibration sensor and filter circuit. The filter is designed with specific cutoff frequencies that allow the sensor to respond to tapping frequencies while attenuating sound frequencies. This changes the operational parameters of the sensor system to resolve the contradiction between sensitivity and reliability.
Solution Approach 2:
The filter circuit acts as an intermediary between the vibration sensor and the control circuit. It processes the raw signal from the sensor by removing unwanted frequency components (sound frequencies) while preserving useful components (tapping frequencies). This intermediary element enables the system to maintain high sensitivity to taps while preventing accidental activations.
2Reliability
If the filter blocks sound frequencies, then the reliability of tap detection is improved, but the complexity of the control circuit increases
Solution Approach 1:
The patent replaces complex mechanical filtering solutions with an electronic filter circuit implemented through standard electronic components (resistors, capacitors, inductors) or digital signal processing. This substitution achieves reliable frequency separation while keeping the implementation practical and not excessively complex.
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
Enhances the sensitivity of the tap function to mechanical shocks without increasing accidental activations, allowing reliable detection of tapping without interference from audio signals, by filtering out sound frequencies and focusing on lower frequency components from tapping.
Implementation Method 1
a vibration sensor mechanically coupled to the housing for receiving a shock due to a user tapping the housing
Implementation Method 2
a filter coupled to the vibration sensor and the control circuit, the filter having a filter curve matched to filter frequency components that are present in the sound
Data Source
AI summary
A tap sensitive alarm clock has a housing (20), a vibration sensor (22) mechanically coupled to the housing for receiving a shock due to a user tapping the housing, and a control circuit (24) coupled to the vibration sensor for controlling a function of the alarm clock. An audio unit (26) is coupled to an audio circuit (25) for generating sound, e.g. a loudspeaker in an alarm clock or a wake up light. To avoid interference of the sound and the vibration sensor, the alarm clock is provided with a filter (23) coupled to the vibration sensor and the control circuit. The filter has a filter curve matched to block frequencies occurring in the sound. Advantageously it is avoided that the sound frequencies trigger the function, while the sensor is sensitive to other frequencies up to the frequency range of the sound for reliably detecting the tapping.