Range Switching Amplifier for Raindrop Detection
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Solution Overview
Problem
Conventional state detecting devices, such as vehicular raindrop detectors, face challenges in accurately detecting raindrops due to a wide detection area leading to a small signal change, even with amplification, and require expensive components like offset power sources and semiconductor switches.
Innovation Solution
A state detecting device with a range switching amplifying circuit that amplifies the peak value of the received light signal in multiple ranges, allowing accurate detection of signal changes regardless of signal level, eliminating the need for expensive components by using a microcomputer-controlled operational amplifier circuit with resistive gain adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the detection area is made wider to ensure certain raindrop adhesion, then the detection reliability is improved, but the signal change ratio becomes smaller making detection more difficult
Solution Approach 1:
The patent applies dynamic amplification by switching between two amplification circuits with different gain values. When no raindrop is detected, a first amplification circuit with higher gain amplifies small signal changes. When raindrop is detected, a second amplification circuit with lower gain prevents saturation. This dynamic switching resolves the contradiction by adapting the amplification level to the current detection state, maintaining both wide detection area coverage and sufficient signal change detection capability.
2Measurement precision
If offset amplification is applied to increase output change, then the measurement precision is improved, but the device complexity and cost increase due to additional components
Solution Approach 1:
The patent makes the amplification circuits universal by designing them to perform multiple functions: signal amplification, adaptive gain switching, and saturation prevention. The switching mechanism automatically selects appropriate amplification levels based on signal characteristics, eliminating the need for separate offset amplification circuits. This multi-functionality reduces device complexity while maintaining measurement precision through adaptive amplification.
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 achieves high accuracy in detecting the state of a detection target with a wide dynamic range, reducing costs by eliminating the need for expensive semiconductor switches and offset power sources, while maintaining effective signal amplification across varying signal levels.
Implementation Method 1
light emitted from a light-emitting element is received by a light-receiving element
Implementation Method 2
range switching amplifying circuit for amplifying the peak value of the received light signal in a plurality of ranges
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(c)
AI summary
There is provided a raindrop detecting device using a light-emitting element and a light-receiving element, which can accurately detect a change of a received light signal in a wide dynamic range regardless of a high or low level of the received light signal. A light-receiving current of a photo diode as the light-receiving element is converted by a current to voltage conversion circuit, and a peak of the voltage is input to a range switching amplifying circuit from a peak hold circuit. The range switching amplifying circuit is configured such that a reverse input terminal of an operational amplifier is connected to a control terminal of a control component via a resistance and the control terminal is switched to Hi and Lo, thus outputting a Hi range amplification result Vout (H) and a Lo range amplification result Vout (L) that are offset from each other by Vos. The control component selects the output that is not saturated from a possible output range of the operational amplifier out of Vout (H) + Vos or Vout (L) to be used for determination on presence/absence of raindrops.