Pyroelectric Sensor Shutter Mechanism for Human Detection
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Solution Overview
Problem
Existing lighting systems that use pyroelectric sensors to detect human presence struggle to distinguish between a human body and a fixed heat source, leading to unnecessary maintenance of lighting loads even when a human is not present, resulting in increased power consumption.
Innovation Solution
A lighting device comprising a pyroelectric sensor, a shutter mechanism, and a lighting control unit that differentiates between human presence and fixed heat sources by controlling the shutter to close and open for varying time periods, allowing the system to determine if the heat source is human-related or not, thereby adjusting the lighting load accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pyroelectric sensor is used to detect human presence, then the lighting load can be turned on when a human is detected, but the lighting load is turned off if a human does not move because the sensor cannot detect a human in an immobile state
Solution Approach 1:
The shutter performs periodic opening and closing actions to create time-varying infrared radiation changes. By mechanically modulating the infrared signal at regular intervals, the system can detect stationary human bodies that would otherwise produce no signal changes, resolving the contradiction between detecting immobile humans and avoiding false positives from fixed heat sources.
Solution Approach 2:
The shutter acts as an intermediary component between the human body and the pyroelectric sensor. It modulates the infrared radiation from the human body, converting a static thermal signal into a dynamic one that the sensor can detect, thereby enabling detection of stationary humans without requiring sensor movement.
2Measurement precision
If a shutter is added to close and open after human movement is detected, then a change in infrared radiation from a human body can be detected even if the human does not move, but the device cannot distinctively detect a simple heat source and a human body
Solution Approach 1:
The system uses feedback from the pyroelectric sensor to control the shutter operation and lighting load. When the sensor detects infrared radiation changes during shutter operation, the lighting is turned on and the shutter stops cycling. When no changes are detected after a threshold number of cycles, the lighting turns off. This feedback mechanism enables the system to distinguish humans from fixed heat sources by responding to actual detection events.
Solution Approach 2:
The system transitions from a static detection mode to a dynamic detection mode by implementing a state machine with multiple operational phases. The shutter control unit dynamically adjusts shutter behavior based on detection states, and the lighting control unit dynamically switches between on and off states based on cumulative detection results, enabling discrimination between human and non-human heat sources.
3Reliability
If the shutter closes and opens repeatedly to detect stationary humans, then the lighting load remains on for stationary humans, but the lighting load remains on unnecessarily for fixed heat sources like TVs or desk lamps
Solution Approach 1:
The lighting control unit uses feedback from the pyroelectric sensor to determine when to turn off the lighting load. By counting the number of shutter cycles without detecting infrared radiation changes, the system can confidently identify fixed heat sources and turn off the lighting, preventing unnecessary energy consumption while maintaining reliability for detecting actual human presence.
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
Effectively turns off lighting loads when a fixed heat source is detected, reducing power consumption and preventing unnecessary lighting retention, while maintaining illumination when a human is present.
Implementation Method 1
a pyroelectric sensor (5) which detects a change in infrared radiation
Implementation Method 2
a shutter (61) which keeps the infrared radiation out of the pyroelectric sensor (5)
Data Source
Figure 1
Figure 2
Figure 3A~3E
AI summary
A lighting device includes a pyroelectric sensor, a shutter and a lighting control unit. The lighting control unit is configured, when the lighting load is turned off, to turn the lighting load on if the pyroelectric sensor detects a change in infrared radiation. The lighting control unit is also configured, when the lighting load is turned on, to turn the lighting load off if a repetition count or time of a lighting retention time reaches a specified count or time, respectively, with no change in infrared radiation detected through the pyroelectric sensor within each lighting retention time per the passage of lighting retention time.