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![Soldering point temperature measurement location [10] While using a thermocouple, the general guideline for thermocouple attachment is to place the thermocouple as close to the LED as possible, mounted directly on a metal pad connected to the neutral thermal trace, if possible. Fig. 3 is an image showing the proper location for a thermocouple. Thermally conductive epoxy or solder is recommended to ensure good heat transfer from the board to the thermocouple. All thermocouples must be out of the optical light path or photons will interfere with the readings, giving extremely inaccurate results [10]. IV. E XPERIMENTAL STUDY AND R ESULTS](profile/Amrutha-Thomas-3/publication/287195921/figure/fig3/AS:307495701630978@1450324096345/Soldering-point-temperature-measurement-location-10-While-using-a-thermocouple-the.png)
Soldering point temperature measurement location [10] While using a thermocouple, the general guideline for thermocouple attachment is to place the thermocouple as close to the LED as possible, mounted directly on a metal pad connected to the neutral thermal trace, if possible. Fig. 3 is an image showing the proper location for a thermocouple. Thermally conductive epoxy or solder is recommended to ensure good heat transfer from the board to the thermocouple. All thermocouples must be out of the optical light path or photons will interfere with the readings, giving extremely inaccurate results [10]. IV. E XPERIMENTAL STUDY AND R ESULTS
![Fig. 2: Heat transfer path for an LED [8]](profile/Amrutha-Thomas-3/publication/287195921/figure/fig2/AS:307495701630977@1450324096319/Heat-transfer-path-for-an-LED-8_Q320.jpg)
![Fig. 3: Soldering point temperature measurement location [10] While...](profile/Amrutha-Thomas-3/publication/287195921/figure/fig3/AS:307495701630978@1450324096345/Soldering-point-temperature-measurement-location-10-While-using-a-thermocouple-the_Q320.jpg)
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Context 1
... most common and simplest method to obtain accurate data and are recommended for precise absolute LED system measurements. While using a thermocouple, the general guideline for thermocouple attachment is to place the thermocouple as close to the LED as possible, mounted directly on a metal pad connected to the neutral thermal trace, if possible. Fig. 3 is an image showing the proper location for a thermocouple. Thermally conductive epoxy or solder is recommended to ensure good heat transfer from the board to the thermocouple. All thermocouples must be out of the optical light path or photons will interfere with the readings, giving extremely inaccurate results ...
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Citations
... Higher ambient temperature leads to higher junction temperatures [11]. The ambient temperature and the drive current both affect the junction temperature of LED [12]. Higher LED die junction temperatures, resulting from increased power dissipation or changes in ambient temperature, can have a significant effect on light output [10]. ...
... As indicated in [12], as junction temperature increases LED's current decreases, which in turn cause decrease in light output. ...
Temperature effects on luminaires is usually referred to light output, that is luminaire efficiency. However, the effect on electrical magnitudes as power, current and third current harmonic is not widely studied. One major technology, Light-emitting- diode (LED) is fast replacing the other types of lighting all over the world, this opens the interrogate of how is temperature affecting LED luminaires development and how different is this effect compared to other technologies. This paper analyses these effects on LED luminaires of different wattage and one high pressure SODIUM luminaire. Luminaires were measure in two different environments, the first stage with a constant temperature-controlled system (±1°C) and the second one without a temperature-controlled system. The tests were performed on three samples of LED luminaires with different power ratings and one sample of SODIUM luminaire. It was found that the third current harmonic is directly related to temperature while power and current are inversely related.
... Especially on the red LED which seems the most affected by the increase in junction temperature [15]. In fact, high power LEDs used for illumination run at high drive current leading to high junction temperature which cause signal power degradation over the time [19]. However, the thermal effect is not treated in this paper. ...
The integration of powerline communication (PLC) with visible light communication (VLC) has attracted the attention of many researchers. Cascading these two techniques offers the possibility of performing a wired transmission over existing powerline infrastructure and a last-mile energy-efficient wireless transmission through pre-installed LEDs for indoor illumination. Therefore, VLC should be deeply analyzed to optimize its integration with other systems. So far, most research has only modeled the channel and modulation bandwidth of the VLC system. However, the electrical and optical aspects are rarely taken into account and there is no explicit expression of the received signal as a function of that emitted. So in this paper, An explicit expression is proposed allowing a direct calculation of the photo-current as a function of the transmitted current taking into account the optical, electrical, and frequency behavior of the VLC system. This expression is validated using measurement results.
... The monochromaticity property of LEDs limits the propagation of radiant heat, making them even more suitable for the horticultural sector, since they can avoid the harmful effects of radiant heat on the quality of agricultural commodities. Although LEDs are relatively efficient, about 65-70% of the supplied electric power generates heat instead of light because of low IQE and light extraction efficiency [193]. One of the major factors in determining the lumen output of an LED is the p-n junction temperature. ...
Plant antioxidants are important compounds involved in plant defense, signaling, growth, and development. The quantity and quality of such compounds is genetically driven; nonetheless, light is one of the factors that strongly influence their synthesis and accumulation in plant tissues. Indeed, light quality affects the fitness of the plant, modulating its antioxidative profile, a key element to counteract the biotic and abiotic stresses. With this regard, light-emitting diodes (LEDs) are emerging as a powerful technology which allows the selection of specific wavelengths and intensities, and therefore the targeted accumulation of plant antioxidant compounds. Despite the unique advantages of such technology, LED application in the horticultural field is still at its early days and several aspects still need to be investigated. This review focused on the most recent outcomes of LED application to modulate the antioxidant compounds of plants, with particular regard to vitamin C, phenols, chlorophyll, carotenoids, and glucosinolates. Additionally, future challenges and opportunities in the use of LED technology in the growth and postharvest storage of fruits and vegetables were also addressed to give a comprehensive overview of the future applications and trends of research.
... However, a drop in LEDs Light bar's illuminance versus time is also mainly noticed for powers higher than 1W; about 15% of illuminance degradation after 15 min LEDs operating under a power supply of 2 W, whereas for low powers (0.25, 0.5 and 0.75) it remains un-changed. Thus, it was reported in other works [14] that as the junction temperature increases, the output light can be reduced due to the current decreases, and consequently the output lumen reduces. However, for LEDs light bar mounted on a fin heat sink there is less reduction in the illuminance that still about 5725 Lux after 10 min, which means that the used thermal heat sink has a pronounced effect on the performance of the luminaire, in particular for higher electrical powers ...
Thermal management of light emitting diodes (LEDs) lighting fixtures is a fundamental issue that can significantly affect the performance and life time of installed lighting products. Based on an experimental study, this paper outlines the vital role of passive heat dissipation in thermal management of low-power LED packaging. The aim of this present work is to give an appropriate model to evaluate the thermal resistance of the heat sink. For optimizing the heat sink dissipation, it is necessary to reduce its thermal resistance as same as improve its cooling capacity because the thermal resistance plays a major role in the total resistance of LED package. In addition, the experimental measurements associated to the LEDs' illuminances and temperatures are made using advanced equipment such as digital luxmeter, and IR camera, respectively, which the results are analyzed by Raycam reporting System software in real time.
In today’s lighting industry, with developing technology and a widened usage area, LEDs have become very popular due to their higher energy efficiency and longer life. In the present study, the effect of electronic components on printed circuits and the radiation level on light output was studied. The performed analysis was validated with an experimental method. For the finite volume method, FloEFD 2019, commercial software, was used. The ambient temperature was assumed to be 23 °C. The value of solar irradiance was taken as 1009 W/cm2. LEDs on a PCB were driven at 70 mA at first and then at 50 mA, and, by exerting power on all electronic components, analyses were performed. Both sides of the PCB were examined, and, in order to achieve efficient heat conduction, the power and distribution of the electronic components on the back side of the LEDs were optimized. With a new electronic circuit design, analyses were performed at 50, 55, 60, 65, and 70 mA. It was determined that the highest light output was achieved at 65 mA and that the distribution of electronic components on a PCB indirectly affects light output through junction temperature (Tj).
Thermal management of light sources based on Light Emitting Diodes technology is a fundamental issue that can significantly affect the performance and life time of installed lighting products. By conducting an experimental study, this paper focuses on the vital role of passive cooling method in thermal management of low-power SMD LEDs Light bars. The used approach in this work aims to give an appropriate model to evaluate the thermal resistance of the heat sink. In order to optimize the cooling performance of a heat sink, it is recommended to minimise its thermal resistance as same as improve its cooling capacity since the thermal resistance impact the total resistance of LED package. In addition, the experimental measurements associated to the LEDs’ illuminances and temperature distribution are made using advanced equipment such as digital luxmeter, and IR camera, respectively, which the results are analyzed by Raycam reporting System software in real time.
Chemical vapor deposition was used to coat boron-doped AlN thin film on Al substrates and used as thermal substrates in the fabrication of printed circuit boards (PCBs). Conventional screen printing method was used to deposit dielectric, conductor, and protective coating on thin-film-coated Al substrate for the printed metal PCBs (MPCBs). Commercial light emitting diode (LED) was fixed on MPCB and tested for thermal and optical properties under various driving currents. The observed results are compared with those of commercial metal-core printed circuit board (MCPCB). The measured total thermal resistance (R
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) of the LED was low for MPCB and recorded good difference in R
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(AR
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= 7.55 K/W) when compared with MCPCB. An impressive difference on rise in junction temperature (T
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) was noticed (ΔT
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= 13.72) with MPCB at 700 mA as compared with MCPCB. As a result of reduced T
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, an improved light output was recorded for MPCB in all driving currents and a higher value also with MPCB. Hence, B-AlN thin-film-coated Al substrate could be used as thermal substrates in PCB fabrication for efficient electronic packaging in LED industries.
