Algorithms for light applications: from theoretical simulations to prototyping

[eng] Although the first LED dates to the middle of the 20th century, it has not been until the last decade that the market has been flooded with high efficiency and high durability LED solutions compared to previous technologies. In addition, luminaires that include types of LEDs differentiated in hue or color have already appeared. These luminaires offer new possibilities to reach colorimetric or non-visual capabilities not seen to date. Due to the enormous number of LEDs on the market, with very different spectral characteristics, the use of the spectrometer as a measuring device for determining LEDs properties has become popular. Obtaining colorimetric information from a luminaire is a necessary step to commercialize it, so it is a tool commonly used by many LED manufacturers. This doctoral thesis advances the state-of-the-art and knowledge of LED technology at the level of combined spectral emission, as well as applying innovative spectral reconstruction techniques to a commercial multichannel colorimetric sensor. On the one hand, new spectral simulation algorithms that allow obtaining a very high number of results have been developed, being able to obtain optimized values of colorimetric and non-visual parameters in multichannel light sources. MareNostrum supercomputer has been used and new relationships between colorimetric and non-visual parameters in commercial white LED datasets have been found through data analysis. Moreover, the functional improvement of a multichannel colorimetric sensor has been explored by providing it with a neural network for spectral reconstruction. A large amount of data has been generated, which has allowed simulations and statistical studies on the error committed in the spectral reconstruction process using different techniques. This improvement has led to an increase in the spectral resolution measured by the sensor, allowing better accuracy in the calculation of colorimetric parameters. Prototypes of the light sources and the colorimetric sensor have been developed in order to experimentally demonstrate the theoretical framework generated. All the prototypes have been characterized and the errors generated with respect to the theoretical models have been evaluated. The results obtained have been validated through the application of different industry standards by comparison with calibrated commercial devices.[cat] Aquesta tesi doctoral realitza un avançament en l’estat de l’art i en el coneixement sobre la tecnologia LED a nivell d’emissió espectral combinada, a més d’aplicar tècniques innovadores de reconstrucció espectral a un sensor colorimètric multicanal comercial. Per una banda, s’han desenvolupat nous algoritmes de simulació espectral que permeten obtenir un nombre molt elevat de resultats, sent capaços d’obtenir valors optimitzats de paràmetres colorimètrics i no-visuals en fonts de llum multicanal. S’ha fet ús del supercomputador MareNostrum i s’han trobat noves relacions entre paràmetres colorimètrics i no visuals en conjunts de LEDs blancs comercials a través de l’anàlisi de dades. Per altra banda, s’ha explorat la millora funcional d’un sensor colorimètric multicanal, dotant-lo d’una xarxa neuronal per a la reconstrucció espectral. S’han generat una gran quantitat de dades que han permès realitzar simulacions i estudis estadístics sobre l’error comès en el procés de reconstrucció espectral utilitzant diferents tècniques. Aquesta millora ha implicat un augment de la resolució espectral mesurada pel sensor, permetent obtenir una millor precisió en el càlcul de paràmetres colorimètrics. S’han desenvolupat prototips de les fonts de llum i del sensor colorimètric amb l’objectiu de demostrar experimentalment el marc teòric generat. Tots els prototips han estat caracteritzats i s’han avaluat els errors generats respecte els models teòrics. Els resultats obtinguts s’han validat a través de l’aplicació de diferents estàndards de la indústria o a través de la comparativa amb dispositius comercials calibrats

Desenvolupament d’una lluminària multicolor amb LEDs amb sistema de control intel·ligent

Treballs Finals del Màster d’Energies Renovables i Sostenibilitat Energètica, Facultat de Física, Universitat de Barcelona, Curs: 2013-2014, Tutor: Blas GarridoThe aim of this project is to develop a system able to reproduce the visible light emitted by a blackbody in a temperature between 1000 and 8000K using the LED technology. This light has an ideal color rendering index (CRI), so it can be used for any application. The traditional and obsolete incandescent light bulbs, acting as a blackbody radiator, offer a very poor efficiency converting the electricity into light, producing only 10-20lm/W. The developed smart system is controlled by an Arduino Nano equipped with an ATmega 328 microcontroller. It contains 6 different LED types: red, cyan, green, blue, warm white and neutral white. This selection of colors covers almost the whole visible band of the electromagnetic spectrum , allowing to fit the LED global light to the blackbody curve. The color temperature can be selected through two different graphical user interfaces (GUI) and they are programmed in MATLAB and App Inventor, a programming language for Android devices developed by the Massachussets Institute of Technology (MIT). On these interfaces the user can control the main parameters of the light, such as the color temperature and the global intensity. The intensity of the individual LED, the luminous efficacy and the CRI of each selection is given for informational purposes. Furthermore, the GUI developed in MATLAB shows a graphic with the color diagram and the planckian locus plotted inside, changing the position of a pointer for each color temperature selected. Moreover, the MATLAB GUI requires a USB connexion while the Android GUI needs the bluetooth technology. This microcontroller used can only provide 40mA of electrical intensity per pin. It causes several restrictions on the prototype, resulting in a low luminous flux (10-30lm) and a greater eficiency (30-50lm/W) than a halogen light bulb but smaller than a CFL. These issues can be solved changing the circuit, adding transistors and an external power source able to provide 700mA per pin, the nominal intensity of the used LED. This improvement increases the efficiency to values between 50 and 60lm/W, the typical performance of the CFL light bulb. Finally, the economical study shows that the cost of the prototype is approximately 180€, but an industrial process can reduce the price more than 130€, giving a final cost of less than 50€ per unit. This can be archieved due to the reduction of the connections board cost and the use of the microcontroller instead of the entire Arduino

Multichannel LED systems: from humans to animals and plants

Trabajo presentado al Seminario del CRAG (Special Webinar), celebrado Online el 2 de octubre de 2020.Peer reviewe