Thermally Insulated PIR Detector Layout for LED Heat Isolation
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Solution Overview
Problem
Occupancy and vacancy sensors are susceptible to thermal interference from heat-generating components, which can affect the accuracy of infrared detection due to transient temperature changes, and are also vulnerable to high-frequency noise interference.
Innovation Solution
A thermally-insulated detector design with a ground plane gap and slot configuration to reduce thermal transfer from heat-generating components like LEDs, combined with a shielded ground plane to minimize noise interference, ensuring accurate infrared detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heat-generating components like LEDs are positioned close to the detector for lens illumination, then the device structure is simplified and manufacturing is easier, but thermal interference affects the accuracy of infrared detection
Solution Approach 1:
The ground plane is segmented into multiple regions including a first ground plane region, a second ground plane region, and a third ground plane region. These segmented ground plane regions create thermal isolation zones that prevent heat from the LED from transferring to the detector, while maintaining electrical connectivity for signal grounding.
Solution Approach 2:
The ground plane acts as an intermediary thermal barrier between the heat-generating LED and the infrared-sensitive detector. The specific configuration of ground plane regions with controlled connectivity provides both electrical grounding and thermal isolation, mediating the conflicting requirements of proximity for simplified manufacturing versus distance for thermal isolation.
2Object-affected harmful factors
If the ground plane is continuous for optimal electrical shielding, then noise interference is reduced, but thermal transfer from heat-generating components to the detector increases
Solution Approach 1:
The ground plane is divided into multiple disconnected regions (first, second, and third ground plane regions) that provide electrical shielding in a segmented manner. This segmentation breaks the continuous thermal path while maintaining sufficient electrical connectivity through strategic placement of ground connections at critical signal points.
Solution Approach 2:
Different regions of the ground plane have different connectivity characteristics. The first ground plane region connects to the LED anode, the second region connects to the detector cathode, and the third region provides additional shielding. Each region is optimized for its local function, providing electrical shielding where needed while preventing thermal conduction to the detector.
3Measurement precision
If the detector is positioned close to the lens aperture for optimal infrared reception, then detection sensitivity is improved, but the detector is more susceptible to thermal interference from nearby components
Solution Approach 1:
The segmented ground plane structure creates thermal isolation zones around the detector while maintaining its close proximity to the lens aperture for optimal infrared reception. The ground plane regions form a thermal barrier that allows the detector to remain in the optimal optical position without suffering from thermal interference.
Solution Approach 2:
The ground plane regions serve as an intermediary thermal barrier that allows the detector to be positioned close to the aperture for sensitivity while blocking thermal paths from nearby heat-generating components. The ground connections provide electrical shielding without creating continuous thermal conduction paths.
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 design effectively reduces thermal interference and noise, maintaining the reliability and accuracy of occupancy and vacancy sensing by minimizing heat transfer and shielding from high-frequency signals.
Implementation Method 1
The gap in the ground plane configured to reduce a thermal transfer of heat generated by the light-emitting diode to the detector
Implementation Method 2
The detector may be part of a passive infrared sensing circuit that allows the sensor device to detect occupancy and/or vacancy conditions in the space in which the sensor device is installed
Data Source
AI summary
A sensor device configured to detect an occupancy condition in a space may comprise a thermally-insulated detector (e.g., a pyroelectric detector). The sensor device may comprise a heat-generating device, such as a light-emitting diode, that may be positioned within the enclosure at a location such that when illuminated, light from the light emitting diode illuminates a lens through the detector receives infrared energy. The printed circuit board may have a ground plane having at least a portion located between the detector and the light-emitting diode. The printed circuit board may comprise a slot extending from a front surface into the printed circuit board. The ground plane may comprise a gap surrounding slot. The slot and/or the gap in the ground plane may be located between the detector and the light-emitting diode to reduce the thermal transfer of heat generated by the light-emitting diode to the detector.