Movable Infrared Reflector for PIR Occupancy Detection
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Solution Overview
Problem
PIR sensors are not practical for occupancy detection due to their reliance on motion, making it difficult to detect stationary individuals, despite their low cost and power efficiency advantages over more complex technologies.
Innovation Solution
A device utilizing a passive infrared (PIR) sensor with a fixed field of view and a controllable-angle infrared reflector that redirects infrared radiation to simulate motion by altering the pointing angle, allowing detection of stationary occupants through periodic sweeping of the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a PIR sensor is used for occupancy detection, then cost and power consumption are reduced, but the ability to detect stationary occupants is lost
Solution Approach 1:
The patent applies the dynamics principle by making the infrared reflector movable rather than fixed. The reflector is rotated to different angles periodically, transforming the static detection system into a dynamic one that can detect stationary occupants by changing the angle at which infrared radiation is reflected back to the sensor.
Solution Approach 2:
The patent implements periodic action by rotating the infrared reflector at predetermined intervals or during predetermined time periods. This periodic rotation creates time-varying detection patterns that enable the system to distinguish between stationary and moving occupants, solving the detection reliability issue while maintaining low power consumption.
2Device complexity
If a PIR sensor with fixed field of view is used, then device complexity is reduced, but the field of view coverage is limited
Solution Approach 1:
Instead of using multiple fixed sensors to cover a larger area, the patent makes the reflector dynamic and rotatable. This allows a single PIR sensor to effectively sweep its field of view by changing the reflector angle, achieving broader coverage without increasing device complexity.
Solution Approach 2:
The patent makes the infrared reflector serve multiple functions: it acts as both an optical element for directing infrared radiation and as a mechanical component that can be rotated to change the field of view. This multi-functionality allows a single sensor to cover a larger effective area without adding multiple sensors.
3Reliability
If the infrared reflector is rotated frequently to detect stationary occupants, then detection reliability is improved, but power consumption increases
Solution Approach 1:
The patent uses periodic action by rotating the reflector only at predetermined intervals or during specific time windows, rather than continuously. This intermittent rotation maintains detection reliability for stationary occupants while significantly reducing power consumption compared to continuous operation.
Solution Approach 2:
The patent applies partial action by rotating the reflector only when necessary (e.g., during detection cycles) rather than continuously. The rotation occurs at predetermined intervals, providing sufficient detection capability while minimizing energy expenditure during non-detection periods.
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
Enables reliable occupancy detection using a single PIR sensor by simulating motion, maintaining low power consumption and cost-effectiveness, suitable for battery-operated applications.
Implementation Method 1
The PIR sensor includes at least two pyroelectric infrared elements
Implementation Method 2
an infrared reflector positioned proximate to the PIR sensor for re-directing infrared radiation received from within a monitored space toward the PIR sensor
Data Source
AI summary
A device for occupancy detection of a space includes a passive infrared (PIR) sensor having a fixed field of view; an infrared reflector positioned proximate to the PIR sensor for re-directing infrared radiation received from within the space toward the PIR sensor; an electromechanical device coupled to the infrared reflector and operative to alter a pointing angle thereof in response to a control signal; and, detection and control circuitry (or a microcontroller), coupled to the PIR sensor and the electromechanical device, operative to receive a signal from the PIR sensor indicative of motion of a person within the space, and further operative to selectively alter the pointing angle of the infrared reflector, using the electromechanical device, whereby the relative position of the person is shifted within the fixed field of view of the PIR sensor, thereby simulating motion of the person even when stationary.