Ensayos acelerados de dispositivos electrónicos LED

El objetivo de este proyecto es el de determinar, a través de una serie de medidas, los tiempos de vida y causas de fallo de diodos LED. Para ello, se someterá a los dispositivos a condiciones extremas de temperatura y humedad dentro de una cámara climática, con el objetivo de acelerar su edad, su tiempo de uso, hecho que provocará la aparición de los fallos mucho antes que en condiciones normales de funcionamiento. Se tomarán medidas tanto de su tensión y corriente para el análisis de las gráficas I-V, dentro y fuera de la cámara, como de las potencias luminosas de cada uno de ellos. Estas medidas se realizarán en dos ocasiones al día, en intervalos de no menos de 6 horas. Para las medidas de tensión y corriente se utilizará un programa desarrollado en el entorno de LabView, tanto para las medidas en el interior de la cámara, lo que nos permite un seguimiento específico del estado de los dispositivos en cada momento, como para las medidas fuera de ella. Para las medidas de la potencia luminosa de cada LED se utilizará un medidor de potencia óptica. Cada ensayo constará de 15 dispositivos LED, que se evaluarán en las mismas condiciones de temperatura y humedad. El resumen de los 8 ensayos realizados es el que sigue: - Ensayo 1: 140ºC 85% HUMEDAD a 10 mA. - Ensayo 2: 140ºC 70% HUMEDAD a 10 mA. - Ensayo 3: 120ºC 85% HUMEDAD a 10 mA. - Ensayo 4: 120ºC 85% HUMEDAD a 30 mA. - Ensayo 5: 140ºC 70% HUMEDAD a 30 mA. - Ensayo 6: 140ºC 85% HUMEDAD a 30 mA. - Ensayo 7: 140ºC 60% HUMEDAD a 30 mA. - Ensayo 8: 140ºC 85% HUMEDAD a 20 mA. Una vez tomadas las medidas, se analizarán los datos, de cara a obtener una ley de degradación del LED a través del análisis de Weibull y se estudiarán las diferentes causas de fallo. ABSTRACT. The aim of this Project is to determine, based on several measures, the lifetime and the causes of LED’s failures. The devices will be tested under extreme both temperature and humidity conditions in a Pressure Cooker, attempting to make faults to appear earlier. Voltage and current measures will be taken, inside and also outside the Pressure cooker, in order to use them in I-V graphs. In addition, luminous power measures for each LED will be taken. All those measures will be obtained twice a day, with 6 hours delay between both of them. A program based on LabView environment will be used to take voltage and current measures, inside and outside the pressure cooker, which allow us to follow the performance of the LED at each moment. The luminous power of each LED will be taken by a measurer. Each test consists of 15 LED devices, which will be evaluated under the same conditions each time. The 8 tests are as follows - Test 1: 140ºC 85% relative humidity at 10 mA. - Test 2: 140ºC 70% relative humidity at 10 mA. - Test 3: 120ºC 85% relative humidity at 10 mA. - Test 4: 120ºC 85% relative humidity at 30 mA. - Test 5: 140ºC 70% relative humidity at 30 mA. - Test 6: 140ºC 85% relative humidity at 30 mA. - Test 7: 140ºC 60% relative humidity at 30 mA. - Test 8: 140ºC 85% relative humidity at 20 mA. When the measures are completely taken, data will be analyzed, in order to obtain a LED’s degradation law using Weibull’s distribution. Also the causes of the failures will be evaluated.

Diseño de un sistema automático de medida de la constante de Planck en diodos LED

En este proyecto fin de carrera se ha diseñado y construido un equipo de medida automático que permite realizar la medida de la constante de Planck utilizando los principios de Funcionamiento de los diodos LED. El equipo de medida es totalmente automático gracias a la utilización de una placa controladora Arduino MEGA 2560, que se encarga de realizar la iluminación secuencial de cada LED, medir sus tensiones de funcionamiento, y de realizar los cálculos necesarios para hallar la constante de Planck. Todos los datos se muestran por una pantalla LCD de 16 caracteres por 2 lineas. Para comprender el funcionamiento del sistema de medida automático se ha realizado un estudio detallado de cada uno de los sistemas que componen el equipo de medida. Se ha explicado el funcionamiento teórico de los diodos LED y el funcionamiento de los semiconductores. Se ha explicando los diversos tipos de semiconductores que se utilizan para los LED y las modificaciones que se les aplica para mejorar su eficiencia. Para poder comprender en qué consiste la constante de Planck se ha explicado los principios teóricos en que se basa, y se ha realizado una pequeña demostración de su cálculo. Una vez visto todos los principios teóricos se ha pasado a realizar la explicación de cada uno de los grandes bloques que componen el sistema de medida automático. Estos bloques son la placa controladora Arduino, el sistema de iluminación LED, el sistema de control mecánico de LEDs, la pantalla LCD, el sistema de interrupciones y el sistema de alimentación. Para poder observar el espectro de emisión de cada uno de los LED se ha utilizado un analizador de espectros óptico (OSA), el cual ha sido explicado con detenimiento. El código de programación de Arduino ha sido explicado en forma de diagrama de flujo para una mayor facilidad de comprensión. Se ha desarrollado un manual de usuario para facilitar el uso del sistema a cualquier usuario, en el que se ha introducido un ejemplo completo de funcionamiento. ABSTRACT. In this final Project has designed and built an automatic measuring equipment which is able to measure the Planck`s constant using the operation principles of the LEDs. The measuring equipment is fully automated thanks to the use of an Arduino Mega 2560 controller board, which is responsible for conducting sequential illumination of each LED, measure their operating voltages, and perform the necessary calculations of find the Planck constant. All data is displayed by a LCD screen 16 character by 2 lines. To understand the operation of the automatic measuring system has been made a detailed study of each of the systems that make the measurement equipment. It develops the theoretical performance of the LED and the operation of semiconductors. It explains the different types of semiconductors that are used for LEDs and the changes applied to improve efficiency. In order to understand what is the Planck constant has been explained the theoretical principles in which it is based, and a small demonstration of its calculation has been performed. After seeing all the theoretical principles has been made the explanation of each of the main blocks that compose the automatic measuring system. These blocks are the Arduino controller board, LED lighting system, the mechanical control system LEDs, LCD screen, the interrupt system and feeding system. To observe the emission spectrum of each of the LED has been used optical spectrum analyzer (OSA), which has been explained in detail. The Arduino programming code has been explained in flowchart form for an easy understanding. It has developed a manual to facilitate the use of system to any user, which has introduced a complete example of operation.

Newer optics efficiently mix, dim, and color-tune LED light

Low-cost, plastic-injected optics mix light from different color LED dies without a significant decrease in average brightness, simplifying luminaire design both optically and electronically. In solid-state lighting, high-flux and high-color rendering index (CRI) light engines may be achieved by arraying and mixing the light from different color dies or phosphors, or a combination of the two, in the LED package. However, these nonhomogeneous sources, when combined with luminaire optics, tend to produce patterns with undesirable artifacts such as spatial and angular nonuniformities and color separation.

Variable impedance LED matrix control system for lamps in PV applications

The interest in LED lighting has been growing recently due to the high efficacy, lifelime and ruggedness that this technology offers. However the key element to guarantee those parameters with these new electronic devices is to keep under control the working temperature of the semiconductor crystal. This paper propases a LED lamp design that fulfils the requ irements of a PV lighting systems, whose main quality criteria is reliability. It uses directly as a power supply a non·stabilized constant voltage source, as batteries. An electronic control architecture is used to regulate the current applied to the LEO matri)( according to their temperature and the voltage output value of the batteries with two pulse modulation signals (PWM) signals. The first one connects and disconnects the LEOs to the power supply and the second one connects and disconnects several emitters to the electric circuit changing its overall impedance. A prototype of the LEO lamp has been implemented and tested at different temperaturas and battery voltages.

LED bulb lamps technical specification and testing procedure for solar home systems.

With the consolidation of the new solid state lighting LEOs devices, te5t1n9 the compliance 01 lamps based on this technology lor Solar Home Systems (SHS) have been analyzed. The definition of the laboratory procedures to be used with final products 15 a necessary step in arder to be able to assure the quality of the lamps prior to be installed [1]. As well as with CFL technology. particular attention has been given to simplicity and technical affordability in arder to facilitate the implementation of the test with basie and simple laboratory too15 even on the same SHS electrification program locations. The block of test procedures has been applied to a set of 14 low-cost lamps. They apply to lamp resistance, reliability and performance under normal, extreme and abnormal operating conditions as a simple but complete quality meter tool 01 any LEO bulb.

LED bulbs technical specification and testing procedure for solar home systems

The definition of technical specifications and the corresponding laboratory procedures are necessary steps in order to assure the quality of the devices prior to be installed in Solar Home Systems (SHS). To clarify and unify criteria a European project supported the development of the Universal Technical Standard for Solar Home Systems (UTSfSHS). Its principles were to generate simple and affordable technical requirements to be optimized in order to facilitate the implementation of tests with basic and simple laboratory tools even on the same SHS electrification program countries. These requirements cover the main aspects of this type of installations and its lighting chapter was developed based on the most used technology at that time: fluorescent tubes and CFLs. However, with the consolidation of the new LED solid state lighting devices, particular attention is being given to this matter and new procedures are required. In this work we develop a complete set of technical specifications and test procedures that have been designed within the frame of the UTSfSHS, based on an intense review of the scientific and technical publications related to LED lighting and their practical application. They apply to lamp reliability, performance and safety under normal, extreme and abnormal operating conditions as a simple but complete quality meter tool for any LED bulb.

Merit function for the evaluation of color uniformity in the far field of LED spot lights

The scope of the present paper is the derivation of a merit function which predicts the visual perception of LED spot lights. The color uniformity level Usl is described by a linear regression function of the spatial color distribution in the far field. Hereby, the function is derived from four basic functions. They describe the color uniformity of spot lights through different features. The result is a reliable prediction for the perceived color uniformity in spot lights. A human factor experiment was performed to evaluate the visual preferences for colors and patterns. A perceived rank order was derived from the subjects’ answers and compared with the four basic functions. The correlation between the perceived rank order and the basic functions was calculated resulting in the definition of the merit function Usl. The application of this function is shown by a comparison of visual evaluations and measurements of LED retrofit spot lamps. The results enable a prediction of color uniformity levels of simulations and measurements concerning the visual perception. The function provides a possibility to evaluate the far field of spot lights without individual subjective judgment. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Optimization of optical systems for LED spot lights concerning the color uniformity

Spotlighting is one illumination field where the application of light emitting diodes (LED) creates many advantages. Commonly, the system for spot lights consists of a LED light engine and collimating secondary optics. Through angular or spatial separated emitted light from the source and imaging optical elements, a non uniform far field appears with colored rings, dots or patterns. Many feasible combinations result in very different spatial color distributions. Several combinations of three multi-chip light sources and secondary optical elements like reflectors and TIR lenses with additional facets or scattering elements were analyzed mainly regarding the color uniformity. They are assessed by the merit function Usl which was derived from human factor experiments and describes the color uniformity based on the visual perception of humans. Furthermore, the optical systems are compared concerning efficiency, peak candela and aspect ratio. Both types of optics differ in the relation between the color uniformity level and other properties. A plain reflector with a slightly color mixing light source performs adequate. The results for the TIR lenses indicate that they need additional elements for good color mixing or blended light source. The most convenient system depends on the requirements of the application.

Validación de HP UV-LED para la detección en continuo de contaminantes en aguas continentales mediante fluorescencia

La preservación del medio ambiente, el avance en las técnicas para que el impacto de la actividad humana sobre la fauna y flora sea lo menor posible, hacen que se deban monitorizar los diversos indicadores de calidad. El presente estudio viene motivado debido a que actualmente existen sistemas de medida y control en continuo de la calidad de las aguas, al margen de los estudios de laboratorio por toma de muestras, a través de los cuales se obtienen indicadores de calidad. El desarrollo tecnológico en analizadores en continuo para la medida de fósforo, amonio, DBO y otros, hacen que cada vez se consiga un control más exhaustivo de la calidad en tiempo real. Sin embargo, la detección temprana de contaminantes que no deben encontrarse presentes en el agua, hacen que el desarrollo de sensores de detección de estos contaminantes sea de gran utilidad. A este respecto, las técnicas mediante fluorescencia presentan enormes ventajas, ya que no existe contacto directo con la muestra, reduciéndose el desgaste y alargando el tiempo entre mantenimientos, como se ha comprobado en numerosos desarrollos con tecnología láser. Para la producir fluorescencia, tradicionalmente se vienen utilizando en el laboratorio principalmente lámparas de gas y monocromadores. Los nuevos LED de alta potencia en el espectro ultravioleta son una alternativa muy interesante que además puede ser aplicada en los mencionados sistemas de medición en continuo. En este trabajo se realiza un estudio de viabilidad de estos dispositivos como fuentes de excitación para la producción de fluorescencia tomando como contaminantes los hidrocarburos. El funcionamiento en estaciones en continuo hace que se tenga que realizar además ensayos de vida acelerados, así como estudios de modos de trabajo. Al respecto de la fluorescencia producida, se estudia la influencia de factores que pueden afectar a las medidas, tales como la temperatura. El estudio del espectro y su análisis para la identificación del contaminante es otro de los puntos desarrollados en este trabajo. Por último, y dado que la monitorización se realiza en modo continuo, es necesario un sistema de comunicaciones compacto y fiable: en este apartado se analizan los metamateriales como solución tecnológica, ya que se adapta perfectamente a la filosofía de estas estaciones de medición. ABSTRACT Currently the monitoring of quality indicators is a need to preserve the environment and minimize the impact of human activity on the fauna and flora. Currently there are measuring systems and continuous monitoring of water quality, regardless of sampling laboratory studies, through which quality indicators are obtained. Technological development in continuous analyzers for the measurement of phosphorus, ammonia, BOD and others increasingly make a more comprehensive real-time quality control is achieved. However, early detection of contaminants that should not be present in the water, make the development of sensors for detecting these contaminants is very useful. In this regard, fluorescence techniques have huge advantages, since there is no direct contact with the sample, reducing wear and extending the time between maintenance, as has been demonstrated in numerous developments in laser technology. To produce fluoresce, traditionally are being used mainly gas lamps and monochromators at the laboratory. The new high-power LEDs in the ultraviolet spectrum are a very interesting alternative that can also be applied in the above continuous measurement systems. In this paper a viability study of these devices as excitation sources to produce fluorescence using hydrocarbon as contaminants is performed. The stations in continuous operation makes it necessary to also perform accelerated life tests and studies operating modes. In regard to the fluorescence produced, the influence of factors that may affect the measurements, such as temperature is studied. The study of the spectrum and analysis to identify the contaminant is another of the points developed in this work. Finally, since the monitoring is carried out in continuous mode, a compact and reliable communication is necessary: in this section metamaterials as a technological solution is analyzed since it fits perfectly with the philosophy of these measuring stations.

Implementación y análisis de luminarias LED

En este proyecto se abordan el diseño y análisis, con sus diferentes etapas, de varias configuraciones de prototipos para luminarias LED enfocadas al ámbito domestico e industrial. Se realizarán montajes sobre diferentes materiales para evaluar los resultados y decidir que soporte es más adecuado para cada circunstancia. Inicialmente expondremos el estado actual de esta tecnología y caracterizaremos, de forma preliminar, los dispositivos que vamos a utilizar para elaborar los prototipos que posteriormente analizaremos. Seguidamente detallaremos el proceso de construcción de cada prototipo, indicando especialmente las diferencias y similitudes entre ellos que, en siguientes secciones, serán analizadas. Trabajaremos con dos rangos de potencia para las luminarias. El primero de ellos se centra en obtener la máxima potencia lumínica, con valores comprendidos entre 40W y 50W, considerando un uso industrial, alumbrado público, etc. El segundo rango de potencias, se enfocará al ámbito doméstico, adecuando la temperatura de color a este entorno, para combinar la potencia, de entre 9W y 12W, con una iluminación más cálida. Finalmente someteremos los prototipos elaborados a una serie de análisis y, ante los resultados, concluiremos cuales serán aptos para el uso al que se pretenden dedicar y aquellos que deberán ser modificados. En el entorno de laboratorio, donde se llevaran a cabo análisis térmicos, eléctricos y lumínicos, emplearemos instrumental especializado para cada tipo de análisis así como su software correspondiente. A excepción de las mediciones relacionadas con el espectro de radiación lumínica, el resto serán obtenidas mediante la plataforma LabVIEW®, un completo software grafico para el desarrollo de instrumentación virtual. Como sección final, expondremos una evaluación sobre el cumplimiento de los objetivos establecidos para el proyecto, posibles mejoras o trabajos futuros y conclusiones obtenidas. ABSTRACT. This project concerns the design and analysis, with its different stages, of various configurations of LED luminaries prototypes focused on domestic and industrial environments. Mounts on different materials will be made to evaluate the results and decide which material is most appropriate for each circumstance. Initially we will expose the current state of this technology and characterize, in a preliminary way, the devices that we will use to produce the prototypes which subsequently will analyze. Later we detail the process of construction of each prototype, especially indicating the differences and similarities between them. In the following sections, we will analyze these characteristics. We will work with two power ranges for luminaries. The first one focuses on maximum light output, with values between 40W and 50W, thinking about industrial use, street lighting, etc. The second power range will focus on the domestic environment, adjusting the color temperature in this environment to combine power, between 9W and 12W, with warm lighting. Finally the prototypes will submit a series of analyzes and, with the results obtained, we conclude if will be suitable for the intended use and those that should be modified. In laboratory environment, where thermal, electrical and lighting analyzes were carried out, we will use specialized instruments for each type of analysis as well as the corresponding software. Except for measurements related to the spectrum of light radiation, the rest of information will be obtained by LabVIEW®, complete graphical development software for virtual instrumentation. As a final section, we will present an evaluation of compliance with the project objectives, possible future work, or improvements, and conclusions.

Trade policy issues in the Wider Europe – that led to war and not yet to peace. CEPS Working Document No. 398, July 2014

This paper looks at the trade policy landscape of the EU and the wider Europe, with a focus on issues arising from the signature on 27 June 2014 of Deep and Comprehensive Free Trade Agreements (DCFTAs) between the EU and three East European countries (Georgia, Moldova and Ukraine), and actual or prospective issues relating to the customs union of Belarus, Russia and Kazakhstan (BRK), and the Eurasian Economic Union whose founding treaty was signed on 29 May 2014. The huge expansion of intercontinental free trade area negotiations currently underway, in which the EU is an active participant alongside much of the Americas and Asia, stands in contrast with Russia’s choice to restrict itself to the Eurasian Economic Union, which is only a marginal extension of its own economy. Alone among the major economies in the world, Russia does not seek to integrate economically with any major economic bloc, which should be a matter of serious concern for Moscow. Within the wider Europe, the EU’s DCFTAs with Ukraine, Moldova and Georgia are a major new development, but Russia now threatens trade sanctions against Ukraine in particular, the economic case for which seems unfounded and whose unilateral application would also impair the customs union. The Belarus-Russia-Kazakhstan customs union itself poses several issues of compatibility with the rules of the WTO, which in turn are viewed by the EU as an impediment to discussing possible free trade scenarios with the customs union, although currently there are far more fundamental political impediments to any consideration of such ideas. Nonetheless, this paper looks at various long-term scenarios, if only as a reminder that there could be much better alternatives to the present context of conflict around Ukraine.