Is achieved in this report, develop a driver circuit to a lamp of 4 LED’s cold white and high brightness, as charge. This uses as current limiter a series combination of a polyester capacitor (1μF to 250V), and a resistance (3.3kΩ to... more
Is achieved in this report, develop a driver circuit to a lamp of 4 LED’s cold white and high brightness, as charge. This uses as current limiter a series combination of a polyester capacitor (1μF to 250V), and a resistance (3.3kΩ to 2watts). Between these, is connect 4 silicon diodes (1N4001) as rectifier bridge, to converter current AC in DC. At the exit, is placed an electrolytic capacitor (68μF to 200V) in parallel, reducing the ripple of rectifier wave on the charge. The software Multisim 12.0 was used to develop of circuit prototype, to confirm its good operation, and construction later. The consume power, was approx. determined as 2,4watts.
O objetivo desta apostila é iniciar o aluno no estudo dos dispositivos semicondutores, desde os diodos, com algumas de suas apresentações (retificador, de sinal, led, Zener) até os transistores bipolares de junção, com a teoria básica de... more
O objetivo desta apostila é iniciar o aluno no estudo dos dispositivos semicondutores, desde os diodos, com algumas de suas apresentações (retificador, de sinal, led, Zener) até os transistores bipolares de junção, com a teoria básica de funcionamento de cada um deles e algumas aplicações práticas. Duas das famílias mais populares de reguladores integrados (78XX e LM317) também são apresentadas, além de um capítulo dedicado a dispositivos ópticos como fotoacopladores. A interpretação das folhas de informações originais (Datasheets) dos fabricantes e das curvas características dos dispositivos é também comentada e utilizada no dimensionamento desses componentes. Uma extensa lista de exercícios é apresentada, incluindo diversos de testes de admissão em grandes empresas, de provas do ENADE e de outras apostilas, todos devidamente identificados e com respostas.
Flashing lights are next-generation tools to mitigate light attenuation and increase the photosynthetic efficiency of microalgal cultivation systems illuminated by light-emitting diodes (LEDs). Optimal flashing light conditions depend on... more
Flashing lights are next-generation tools to mitigate light attenuation and increase the photosynthetic efficiency of microalgal cultivation systems illuminated by light-emitting diodes (LEDs). Optimal flashing light conditions depend on the reaction kinetics and properties of the linear electron transfer chain, energy dissipation, and storage mechanisms of a phototroph. In particular, extremely short and intense light flashes potentially mitigate light attenuation in photobioreactors without impairing photosynthesis. Intelligently controlling flashing light units and selecting electronic components can maximize light emission and energy efficiency. We discuss the biological, physical, and technical properties of flashing lights for algal production. We combine recent findings about photosynthetic pathways, self-shading in photobioreactors, and developments in solid-state technology towards the biotechnological application of LEDs to microalgal production.
Biochemical components obtained by microalgal biomass can be induced by specific wavelengths and processed to high value food/feed supplements or pharma-and nutraceuticals. Two biotechnologically relevant microalgae, Nannochloropsis... more
Biochemical components obtained by microalgal biomass can be induced by specific wavelengths and processed to high value food/feed supplements or pharma-and nutraceuticals. Two biotechnologically relevant microalgae, Nannochloropsis oculata and Tetraselmis chuii, were exposed to non-tailored LEDs light sources emitting either mono-or multichromatic light with low red but significant blue (b450 nm) photon content, or tailored light sources with high blue or high red photon emissions: fluorescent light (FL), di-or multichromatic LED mixes. Growth of N. oculata and T. chuii under tailored light resulted in a ≈ 24% increase of the average biomass productivity as compared to cultures lit by non-tailored light sources. FL induced the highest C:N ratios in both algae (N. oculata: 7.91 ± 0.09 and T. chuii: 11.29 ± 0.03), highest total lipid (48.37 ± 1.07%) in N. oculata and carbohydrate (55.31 ± 1.02%) in T. chuii biomass. Among non-tailored light sources, monochromatic LEDs with emission peaks 465, 630 and 660 nm induced a ≈ 29% increase of carbohydrates and a ≈ 20% decrease of protein levels as compared to LEDs peaking at 405 nm and cool-and warm white LEDs. In conclusion, as FL have low photon conversion efficiencies (PCE), particularly within the red wavelength range, LEDs emitting at the 390–450 and 630– 690 nm wavebands should be combined for optimal carbon fixation, nitrogen and phosphate uptake.
Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants.... more
Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants. Moreover, we propose a general, simple, but accurate mathematical model of the irradiance pattern, valid for Lambertian and non-Lambertian LEDs at short distances. This model provides the irradiance profile as a function of both the LED-target distance and the coordinates of every point on the irradiated surface. The model is formulated in terms of simple sigmoid functions, in which LED size and light flux are fundamental parameters. The accuracy of the irradiance pattern model is tested both with theory and with experimental measurements.
The main aim of this paper is "design and construction of automatic lamp post with parallel connected solar". This project includes a circuit of lamp post with automatic on/off state during day and night. The main aims to develop a system... more
The main aim of this paper is "design and construction of automatic lamp post with parallel connected solar". This project includes a circuit of lamp post with automatic on/off state during day and night. The main aims to develop a system which will lead to energy conservation and by doing and to automatically switch the lamp post to an on/off state utilizing the Light Depended Resistor. The module used for lighting is the LED. This project has designed the delay time because the light of surroundings suddenly. The beauty of the proposed research paper is that the wastage of unused electricity can be reduced, lifetime of the lamplights gets enhance because the lights do not stay ON during the whole time, and also helps to increase safety measurements.
We report on the achievement of high efficiency green, yellow, and red InGaN/AlGaN dot-in-a-wire nanowire light-emitting diodes grown on Si(111) by molecular beam epitaxy. The peak emission wavelengths were altered by varying the growth... more
We report on the achievement of high efficiency green, yellow, and red InGaN/AlGaN dot-in-a-wire nanowire light-emitting diodes grown on Si(111) by molecular beam epitaxy. The peak emission wavelengths were altered by varying the growth conditions, including the substrate temperature, and In/ Ga flux ratio. The devices demonstrate relatively high (>40%) internal quantum efficiency at room temperature, relative to that measured at 5 K. Moreover, negligible blue-shift in peak emission spectrum associated with no efficiency droop was measured when injection current was driven up to 556 A/cm 2. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
A method for modeling the irradiance spatial distribution by light-emitting diodes (LEDs) on near distance targets has been developed. The model can easily handle the complex simulation of non-homogenous emitting LEDs, multichip LEDs, LED... more
A method for modeling the irradiance spatial distribution by light-emitting diodes (LEDs) on near distance targets has been developed. The model can easily handle the complex simulation of non-homogenous emitting LEDs, multichip LEDs, LED arrays, and phosphor coated LEDs. The LED irradiation profile is obtained by image processing one photograph of the emitting LED, taken with a smartphone. The method uses image convolution or image correlation between the LED image and a special kernel. The model provides the irradiation spatial pattern in function of the irradiation distance. And the model is tested both with theory and with experimental measurements.
In this paper, we report our study on high-performance III-nitride nanowire light-emitting diodes (LEDs) on copper (Cu) substrates via the substrate-transfer process. Nanowire LED structures were first grown on silicon-on-insulator (SOI)... more
In this paper, we report our study on high-performance III-nitride nanowire light-emitting diodes (LEDs) on copper (Cu) substrates via the substrate-transfer process. Nanowire LED structures were first grown on silicon-on-insulator (SOI) substrates by molecular beam epitaxy. Subsequently, the SOI substrate was removed by combining dry-and wet-etching processes. Compared to conventional nanowire LEDs on Si, the nanowire LEDs on Cu exhibit several advantages, including more efficient thermal management and enhanced light-extraction efficiency (LEE) because of the usage of metal reflectors and highly thermally conductive metal substrates. The LED on Cu, therefore, has stronger photoluminescence, electroluminescence intensities, and better current−voltage characteristics compared to the conventional nanowire LED on Si. Our simulation results further confirm the improved device performance of LEDs on Cu, compared to LEDs on Si. The LEE of the nanowire LED on Cu is nine times higher than that of the LED on Si at the same nanowire radius of 60 nm and spacing of 130 nm. Moreover, by engineering the device-active region, we achieved high-brightness phosphor-free LEDs on Cu with highly stable white-light emission and high color-rendering index of ∼95, showing their promising applications in general lighting, flexible displays, and wearable applications.
Biochemical components obtained by microalgal biomass can be induced by specific wavelengths and processed to high value food/feed supplements or pharma-and nutraceuticals. Two biotechnologically relevant microalgae, Nannochloropsis... more
Biochemical components obtained by microalgal biomass can be induced by specific wavelengths and processed to high value food/feed supplements or pharma-and nutraceuticals. Two biotechnologically relevant microalgae, Nannochloropsis oculata and Tetraselmis chuii, were exposed to non-tailored LEDs light sources emitting either mono-or multichromatic light with low red but significant blue (b450 nm) photon content, or tailored light sources with high blue or high red photon emissions: fluorescent light (FL), di-or multichromatic LED mixes. Growth of N. oculata and T. chuii under tailored light resulted in a ≈ 24% increase of the average biomass productivity as compared to cultures lit by non-tailored light sources. FL induced the highest C:N ratios in both algae (N. oculata: 7.91 ± 0.09 and T. chuii: 11.29 ± 0.03), highest total lipid (48.37 ± 1.07%) in N. oculata and carbohydrate (55.31 ± 1.02%) in T. chuii biomass. Among non-tailored light sources, monochromatic LEDs with emission peaks 465, 630 and 660 nm induced a ≈ 29% increase of carbohydrates and a ≈ 20% decrease of protein levels as compared to LEDs peaking at 405 nm and cool-and warm white LEDs. In conclusion, as FL have low photon conversion efficiencies (PCE), particularly within the red wavelength range, LEDs emitting at the 390–450 and 630– 690 nm wavebands should be combined for optimal carbon fixation, nitrogen and phosphate uptake.
