PIR Sensor Uniform Detection via Sum-Difference Signal Processing
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Solution Overview
Problem
Ceiling-mounted PIR motion sensors exhibit non-uniform detection capabilities along different lines of bearing due to signal cancellation, resulting in longer detection ranges in some directions and shorter ranges in others, which is undesirable for comprehensive motion detection.
Innovation Solution
A PIR motion sensor system utilizing two arrays of pyroelectric elements with alternating polarities, where signals from each array are combined through summation and subtraction to generate sum and difference signals, allowing for uniform detection independent of the object's azimuthal orientation, and enabling detection if either signal exceeds a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceiling-mounted PIR sensors use positive and negative detector elements, then the sensor can detect motion, but signals from objects cancel along some lines of bearing causing non-uniform detection ranges
Solution Approach 1:
The detector array is divided into multiple independent detector elements with alternating polarities arranged in a specific pattern. This segmentation allows the system to process signals from different spatial zones separately, enabling uniform detection coverage in all directions by combining outputs from elements with different polarity orientations.
Solution Approach 2:
The patent employs an asymmetric arrangement of positive and negative polarity detector elements rather than a symmetric alternating pattern. This asymmetric configuration, combined with specific signal processing, eliminates the directional cancellation effects that occur in symmetric arrangements, achieving uniform detection sensitivity across all azimuthal directions.
2Device complexity
If signals from detector elements are combined simply, then processing requirements are low, but detection uniformity across all directions is poor
Solution Approach 1:
The patent introduces a new dimension to signal processing by implementing separate summation and difference operations on detector element outputs. This dual-signal approach transforms the single-dimensional simple summation into a two-dimensional processing space, allowing the system to achieve uniform omnidirectional detection while maintaining relatively simple processing logic through straightforward arithmetic operations.
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 system provides omni-directional motion detection with uniform sensitivity in all directions, reducing directional selectivity and enhancing detection accuracy by combining the best detection directions from both signals, thus addressing the non-uniformity issue in ceiling-mounted sensors.
Implementation Method 1
first and second arrays of pyroelectric elements
Data Source
Figure 1~4
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Figure 8~8A
AI summary
A passive infrared sensor has two or more detector element arrays, each consisting of positive polarity and negative polarity elements. The signals from the arrays are both summed together and subtracted from each other, and if either the sum or difference signal exceeds a threshold, detection is indicated.