Temperature controlled light-emitting diode lamp for photovoltaic rural applications

In recent years, interest in light-emitting diode (LED) lighting has been growing because of its high efficacy, lifetime and ruggedness. This paper proposes a better adaptation of LED lamps to the technical requirements of photovoltaic lighting domestic systems, whose main quality criteria are reliability and that behave as voltage power supplies. As the key element of reliability in LED lamps is temperature, a solution is proposed for driving LED lamps using voltage sources, such as photovoltaic system batteries, with a control architecture based on pulse width modulation signal that regulates the current applied according to the LED lamp temperature. A prototype of the LED lamp has been implemented and tested to show its good performance at different temperatures and at different battery voltages.

A VLC-based beacon location system for mobile applications

This paper proposes a low cost and complexity indoor location and navigation system using visible light communications and a mobile device. LED lamps work as beacons transmitting an identifier code so a mobile device can know its location. Experimental designs for transmitter and receiver interfaces are presented and potential applications are discussed.

Implementación de sistema domótico con servidor Raspberry

Este proyecto consiste en el diseño e implementación un sistema domótico que puede ser instalado en una vivienda para controlar distintas variables ambientales y conseguir así la máxima comodidad de los habitantes de manera automática o manual según los gustos y necesidades de los usuarios. La característica principal de este sistema, es que cuenta con un funcionamiento distribuido donde entran en juego un servidor, encargado de tomar las decisiones generales para el comportamiento de la casa, y una serie de controladores esclavo cuya función es mantener constantes las variables ambientales con los valores fijados por el servidor. Así se consigue mantener la vivienda en una situación de bienestar constante para cualquier persona que se encuentre dentro. El sistema ha sido pensado de manera que se intenta reducir al máximo el cableado para facilitar su instalación por lo que la comunicación entre los distintos dispositivos se hace de manera inalámbrica por medio de un protocolo descrito en la norma IEEE 802.15.4 llamado ZigBee. Para ello se ha utilizado un módulo de comunicación wireless llamado Xbee, el cual permite la comunicación entre dos dispositivos. Para el control de dicho sistema distribuido se cuenta con una aplicación web, que mediante una interfaz gráfica permite al usuario controlar los distintos dispositivos dentro de la vivienda consiguiendo así controlar las variables ambientales a gusto del usuario. Dicha interfaz gráfica no depende de un software específico, sino que sólo es necesario un cliente http como podría ser Internet Explorer, Mozilla Firefox, Google Chrome, etc. Para integrar dicho sistema se ha usado un mini ordenador de bajo coste llamado RaspBerryPi, en el que se encuentra alojado un servidor Apache con el fin de gestionar y automatizar las variables ambientales. El control de los dipositivos encargados de modificar y estabilizar las variables ambientales se realiza mediante unos controladores genéricos implementados mediante mcontroladores 80C51F410, pertenecientes a la familia 80C51, y una serie de componentes y circuitería que permiten el correcto funcionamiento de éstos. Existen dos tipos de controladores distintos, los cuales son: Controlador Sensor: Encargados de las tomas de valores ambientales como puede ser la luz y la temperatura. Controladores Actuadores: Encargados de actuar sobre los dispositivos que modifican y estabilizan las variables ambientales como pueden ser la calefacción, tiras de leds de iluminación, persianas, alarmas, etc. El conjunto de la RaspBerryPi y los diferentes controladores forman el prototipo diseñado para este proyecto fin de carrera, el cual puede ser ampliado sencillamente para abarcar una amplia gama de posibilidades y funcionalidades dentro de la comodidad de una vivienda. ABSTRACT. The project described in this report consisted designing and implementing a home automation system that could be installed in a house in order to control environmental variables and thus get the maximum comfort of the inhabitant automatically or manually according to their tastes and needs. The main feature of this system consists in a distributed system, formed by a server which is responsible for making the main decisions of the actions performed inside the house. In addition, there are a series of slave controlers whose function consists in keeping the environmental variables within the values established by the server. Thus gets to keep the home in a situation of constant wellbeing to anyone who is inside. The system has been designed in order to reduce the amount of wire needed for the inter-connection of the devices, by means of wireless communication. The devices chosen for the solution are Xbee modules, which use the Zigbee protocol in order to comunicate one between each other. The Zigbee protocol is fully described in the IEEE 802.15.4 standard. A web application has been used to control the distributed system. This application allows users to control various devices inside the house and subsequently the different environmental variables. This implementation allows obtaining the maximum comfort by means of a very simple graphical interface. In addition, the Graphical User Interface (GUI) does not depend on any specific software. This means that it would only be necessary a http client (such as Internet Explorer, Mozilla Firefox, Google Chrome, etc.) for handling the application. The system has been integrated using a low-cost mini computer called RaspBerryPi.This computer has an Apache server allocated which allows to manage and to automatize the different environmental variables. Furthermore, for changing and stabilizing those variables, some generic controllers have been developed, based on mcontrollers 80C51F410. There have been developed mainly two different types of controllers: Sensor Controllers, responsible for measuring the different environmental values, such as light and temperature; and Actuator Controllers, which purpose is to modify and stabilize those environmental variables by actuating on the heating, the led lamps, the blinders, the alarm, etc. The combination of the RaspBerryPi and the different controllers conform the prototype designed during this project. Additionally, this solution could be easily expanded in order to intake further functionalities adapted to new needs that could arise in the future.

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.

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.

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.

LED Jitter-Induced Limitation Effects in the Baud Rate of VLC

In this paper we show that the effect of jitter due to driver and LED is the limiting factor in the baud rate in L-PPM formats for VLC systems.

Testing of fluorescent DC lamps for Solar Home Systems

With the advent of the Universal Technical Standard for Solar Home Systems, procedures to test the compliance of SHS fluorescent lamps with the standard have been developed. Definition of the laboratory testing procedures is a necessary step in any lamp quality assurance procedure. Particular attention has been paid to test simplicity and to affordability, in order to facilitate local application of the testing procedures, for example by the organisations which carry out electrification programmes. The set of test procedures has been applied to a representative collection of 42 lamps from many different countries, directly acquired in the current photovoltaic rural electrification market. Tests apply to: lamp resistance under normal operating conditions; lamp reliability under extreme conditions; under abnormal conditions; and lamp luminosity. Results are discussed and some recommendations for updating the relevant standard are given. The selected technical standard, together with the proposed testing procedures, form the basis of a complete quality assurance tool that can be applied locally in normal electrical laboratories. Full testing of a lamp requires less than one month, which is very reasonable on the context of quality assurance programmes

LED backlight designs with the flow-line method

An LED backlight has been designed using the flow-line design method. This method allows a very efficient control of the light extraction. The light is confined inside the guide by total internal reflection, being extracted only by specially calculated surfaces: the ejectors. Backlight designs presented here have a total optical efficiency of up to 80% (including Fresnel and absorption losses) with an FWHM below 30 degrees. The experimental results of the first prototype are shown.

Emissions and economic costs of cycling compact fluorescent lamps with integrated ballasts

This paper proposes a way to quantify the emissions of mercury (Hg) and CO2 associated with the manufacture and operation of compact fluorescent lamps with integrated ballasts (CFLis), as well as the economic cost of using them under different operating cycles. The main purpose of this paper is to find simple criteria for reducing the polluting emissions under consideration and the economic cost of CFLi to a minimum. A lifetime model is proposed that allows the emissions and costs to be described as a function of degradation from turning CFLi on and their continuous operation. An idealized model of a CFLi is defined that combines characteristics stated by different manufacturers. In addition, two CFLi models representing poor-quality products are analyzed. It was found that the emissions and costs per unit of time of operation of the CFLi depend linearly on the number of times per unit of time it is turned on and the time of continuous operation. The optimal conditions (lowest emissions and costs) depend on the place of manufacture, the place of operation and the quality of the components of the lamp/ballast. Finally, it was also found that for each lamp, there are intervals when it is turned off during which emissions of pollutants and costs are identical regardless of how often the lamp is turned on or the time it remains on. For CO2 emissions, the lamp must be off up to 5 minutes; for the cost, up to 7 minutes and for Hg emissions, up to 43 minutes. It is advisable not to turn on a CFLi sooner than 43 minutes from the last time it was turned off.

Optics detailed analysis of an improved collimation system for LED light sources

Optics detailed analysis of an improved collimation system for LED light sources

Primary optics for efficient high-brightness LED color mixing

In SSL general illumination, there is a clear trend to high flux packages with higher efficiency and higher CRI addressed with the use of multiple color chips and phosphors. However, such light sources require the optics provide color mixing, both in the near-field and far-field. This design problem is specially challenging for collimated luminaries, in which diffusers (which dramatically reduce the brightness) cannot be applied without enlarging the exit aperture too much. In this work we present first injection molded prototypes of a novel primary shell-shaped optics that have microlenses on both sides to provide Köhler integration. This shell is design so when it is placed on top of an inhomogeneous multichip Lambertian LED, creates a highly homogeneous virtual source (i.e, spatially and angularly mixed), also Lambertian, which is located in the same position with only small increment of the size (about 10-20%, so the average brightness is similar to the brightness of the source). This shell-mixer device is very versatile and permits now to use a lens or a reflector secondary optics to collimate the light as desired, without color separation effects. Experimental measurements have shown optical efficiency of the shell of 95%, and highly homogeneous angular intensity distribution of collimated beams, in good agreement with the ray-tracing simulations.

Quasi-aplanatic free-form V-groove collimators for LED colour mixing

Two quasi-aplanatic free-form solid V-groove collimators are presented in this work. Both optical designs are originally designed using the Simultaneous Multiple Surface method in three dimensions (SMS 3D). The second optically active surface in both free-form V-groove devices is designed a posteriori as a grooved surface. First two mirror (XX) design is designed in order to clearly show the design procedure and working principle of these devices. Second, RXI free-form design is comparable with existing RXI collimators; it is a compact and highly efficient design made of polycarbonate (PC) performing very good colour mixing of the RGGB LED sources placed off-axis. There have been presented rotationally symmetric non-aplanatic high efficiency collimators with colour mixing property to be improved and rotationally symmetric aplanatic devices with good colour mixing property and efficiency to be improved. The aim of this work was to design a free-form device in order to improve colour mixing property of the rotationally symmetric nonaplanatic RXI devices and the efficiency of the aplanatic ones.

Refrigeración de LED's mediante "Heat Pipes"

El enfriamiento tradicional de los LEDs, mediante disipadores térmicos, se ve muchas veces comprometido al tener que disponer estos elementos refrigeradores justo en el punto de generación de la luz. Para evitar, en la medida de lo posible, este hecho, se presenta como una de las posibles alternativas el empleo de los ?Heat Pipes?. Los Heat Pipes son unos dispositivos autónomos, que permiten refrigerar los focos calientes, trasladando el calor generado por ellos a disipadores térmicos situados en zonas más accesibles y menos comprometidas. Los Heat Pipe, basados en técnicas termodinámicas, tienen un uso muy extendido en la tecnología aeroespacial. Son actualmente la solución ideal en aplicaciones de bombeo de calor y refrigeración de componenetes electricos y electrónicos. Con tamaños reducidos, pueden alcanzar flujos de refrigeración de 300 - 400 W/cm2. En esta comunicación se presenta y analiza este tipo de refrigeración aplicada a LED¿s utilizados en iluminación y alumbrado. La refrigeración de LEDs propuesta está compuesta por el Heat Pipe adosado por un extremo a la cara posterior del diodo LED, y por el otro, a una cierta distancia, al disipador térmico. La temperatura alcanzada por el LED dependerá del tipo y características del Heat Pipe así como de las cualidades del disipador térmico utilizado. También se utilizan en combinación con refrigeradores termoeléctricos (células de Peltier) cuando se desea controlar la temperatura de los dispositivos por debajo de la temperatura ambiental.