Dispensing Device Nonlinear Circuit Motion Sensing
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Solution Overview
Problem
Prior diffusion devices with sensors fail to operate effectively in environments with varying ambient light conditions and are insensitive to motion at distances, often triggering false alarms due to high and low frequency environmental changes.
Innovation Solution
A dispensing device with a nonlinear circuit element coupled to a phototransistor, where the voltage level at the bias point varies non-linearly with current, and a band-pass filter to attenuate unwanted frequencies, allowing the device to accurately detect motion across a wide range of light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear sensor configuration (phototransistor with resistor) is used to detect motion, then the device can detect motion in stable low light conditions, but the sensor becomes insensitive to motion in high ambient light conditions and low light conditions
Solution Approach 1:
The patent transforms the linear sensor output into a non-linear relationship by applying a logarithmic function. The voltage at the bias point varies non-linearly with current through the phototransistor, specifically following a logarithmic relationship: V_bias = V_supply - I_phototransistor * R_load. This logarithmic transformation compresses the wide range of current values (caused by varying ambient light) into a manageable voltage range, enabling motion detection across diverse light conditions while maintaining sensitivity.
2Area of stationary object
If the sensor is positioned to detect motion in a large space, then the device can cover more area, but the sensitivity to motion at distances decreases and false triggers increase due to high and low frequency environmental changes
Solution Approach 1:
The patent extracts and eliminates unwanted frequency components from the sensor signal using a band-pass filter. The filter removes high-frequency noise (such as flickering lights) and low-frequency drifts (such as gradual changes in ambient light), allowing only the relevant motion-induced frequency components to pass through. This extraction of useful signal from unwanted environmental variations improves motion detection accuracy across large detection areas.
3Illumination intensity
If the phototransistor operates in high ambient light conditions, then the current through the phototransistor increases, but the voltage level at the bias point approaches the supply voltage level reducing the controller's ability to detect motion
Solution Approach 1:
The patent applies a non-linear transformation to the voltage-current relationship through the logarithmic characteristic of the circuit. When ambient light increases, the phototransistor current increases linearly, but the voltage at the bias point changes non-linearly according to the logarithmic relationship. This compresses the voltage range, ensuring that even in high light conditions, the voltage remains within a detectable range that maintains motion signal distinguishability.
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 device can accurately detect motion and dispense volatile materials in a wide range of environments, reducing false triggers and improving sensitivity to motion beyond the sensor's proximity.
Implementation Method 1
motion is detected by sensing light changes at a photodiode connected in series with a resistor
Implementation Method 2
A voltage level at the bias point varies non-linearly with respect to a current that flows through the sensor
Implementation Method 3
a band-pass filter to attenuate high and low frequency conditions
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A dispensing device includes a dispenser configured to dispense a volatile material, a sensor configured to detect an environmental condition, and a nonlinear circuit element coupled to the sensor to establish a bias point. A voltage level at the bias point varies nonlinearly with respect to a current that flows through the sensor, wherein the current that flows through the sensor represents the environmental condition. The dispensing device further includes a controller coupled to the bias point. The controller controls the dispenser to dispense the volatile material in response to the environmental condition.