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Influence of temperature on light-technical parameters of LED
Sláma, Pavel ; Štěpánek, Jaroslav (referee) ; Pavelka, Tomáš (advisor)
This thesis deals with LEDs and how temperature influences their parameters. In the first part it is analyzed how semiconductors and semiconductor junctions work, which is fundamental for understanding mechanisms of diodes. Next up is description of electroluminescence and basic description of physical principles, on which it works. Following part is supposed to introduce reader to electro-technical parameters and powering possibilities of LEDs. Following chapter focuses on description of lightning-technical parameters. It aims to describe their meaning and their relation to LEDs. Next part is about influence of temperature. Firstly, it names the parameters which are altered by temperature change. Follows the description of thermal management and its influence on right behavior of LED diodes. The last part contains construction of measuring workplace for analyzing temperature influence on lightning-technical parameters of LEDs. Measurement of chosen electrical and lightning parameters follows up.
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Light sources in extreme operational conditions
Martiš, Jan ; Krbal, Michal (referee) ; Pavelka, Tomáš (advisor)
The purpose of this work is to inform about how various external influences can affect the operational characteristics of light sources. In the first part of the work, the light sources are categorized based on their principle of operation and the basic parameters and properties of different light source types are listed. Then the individual influences (voltage changes, temperature, operational position) and their possible effect on the operational characteristics of different types of light sources are analysed. Further, possible procedures for measuring light sources under altered conditions are mentioned and the results of practical measurements on selected light sources are presented. The last part of the work deals with ways to decrease the influence of altered operating conditions on the operation of light sources.
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Design and construction of an interactive light sources panel
Žák, Martin ; Pavelka, Tomáš (referee) ; Škoda, Jan (advisor)
This semestral thesis deals with design and construction of the interactive light sources board and measurement of various parameters of those light sources. Using the given requirements, a solution is worked out (construction materials, behaviour, design, wiring etc. are given). Based on this, the interactive board was also constructed and put into operation. The thesis is also focused on the given light sources themselves (incandescent light bulbs, halogen lamps, compact fluorescent lamps, fluorescent tubes and LED lamps) and their measurement results are presented.
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LED failures
Doležal, Petr ; Krbal, Michal (referee) ; Pavelka, Tomáš (advisor)
This bachelor thesis is dealing with description of the principle generation light in the LED light sources. In the text we can find principle function of LED, history, possibilities of brightness control, power supply and various types of structures. There are described photometric and electrical parameters. Other part of this thesis is the description of effects leading to failure and malfunction of LED light sources. The practical part of this thesis contains measuring on samples of power LED emitting white light and verification of operational effect leading to the failure of LED light sources.
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Modern systems for lighting control
Klein, Tomáš ; Pavelka, Tomáš (referee) ; Bátora, Branislav (advisor)
This Master's thesis deals with intelligent installation systems, focused on lighting systems using the DALI bus system. Theoretical part of this work includes a list of currently available intelligent installation systems and its use in both households and industrial buildings. A summarizing description of KNX and DALI bus systems and their actuators and actuating units are a part of this paper. The practical part proposes two examplary boards designed for laboratories of UEEN VUT in Brno and describes its construction, as well as the programs necessary for its programming, control and monitoring. The outcome of this Master's thesis is a survey of possible remote control of DALI bus system's actuators and mutual compatibility of KNX and DALI bus systems. Furthermore, this paper includes background material for laboratory task, based on data found about remote control and DALI bus system's monitoring.
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The Influence of Temperature to Change Operational Parameters and Lifetime of Powerful LEDs
Zeman, Milan ; Pavelka, Tomáš (referee) ; Krbal, Michal (advisor)
The aim of this bachelor’s thesis is the introduction of changes in operating parameters and lifetime period of LED module. The theoretical part is dedicated to a principle of light, the development and use of LED. The main emphasis is placed on PN junction degradation due to temperature and lifetime period of the LED module. The practical part of this thesis contains measuring of LED diode Cree XLamp XR-E in the course of temperature from 0°C to 90°C in the current range of 0-300% of nominal value. Efficiency of LED operation is highly dependent on PN junction temperature. When powering the LED to approximately 65% of the rated power, the conversion of electric energy to light is the most efficient. It depends on junction temperature because increasing temperature decreases efficiency. A very important factor when designing the lighting system is cooling which helps to dissipate heat from the chip.
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Design and construction of advanced LED lighting system for aquarium
Novák, Pavel ; Škoda, Jan (referee) ; Pavelka, Tomáš (advisor)
The first part of this thesis is devoted to the presentation of light and the basic quantities describing the light and its properties. These quantities are then used to describe the light sources, which is the thesis engaged in in the following section. The light sources are divided into thermal and luminescent. Then, there are described the basic parameters that are monitored when choosing the light source, such as luminous flux, color rendering index, correlated color temperature, mean lifetime, beam angle. Next, the thesis engages in solar radiation, spectrum of radiation, process and the color temperature of daylight and turns to the requirements for the aquarium lighting. According to the requirements for the aquarium lighting, the lighting design is done and it is sought an ideal solution for the aquarium lighting using LEDs. In conclusion of this thesis, there is designed an effective cooling for the LEDs in order to maintain their lifetime and luminous flux as long as possible. Then, it is designed and realized control of the LEDs by the pulse width modulation, prepared software for controlling the lighting depending on the daytime to meet the demands on the aquarium lighting while monitoring the process of the daylight and to look natural.
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Evaluation of LED replacements
Bordovský, Lukáš ; Pavelka, Tomáš (referee) ; Škoda, Jan (advisor)
The aim of my thesis is to become familiar with LED replacements of light sources, possible problems, advantages and disadvantages. In the work are at first explained terms of light technology. Then are concisely described actual light sources, that can be replaced by LED. That concern: classic bulbs, halogen bulbs, linear fluorescents and compact bulbs. After that is described principle of LED light fittings and advantages, disadvantages nowadays to use LED light fittings. The main emphasis is placed on chapter 5. The compensations of linear fluorescents by LED moduls. The following chapters are dedicated to comparison of fluorescent lamps and LED moduls. Involving-photometrics parameters, luminous intensity, lumniance analysis and also economics comparison of lighting systems with fluorescent lamps versus the LED moduls.
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Design of an extraction steam condensing turbine in the Precheza company.
Pavelka, Tomáš ; Paseka, Bohumil (referee) ; Bok, Jaromír (advisor)
This diploma thesis is concerned with the design of the machinery with an extraction steam condensing turbine in Precheza corp. The theoretical part of this thesis describes the energetical situation in the company and the primary consideration about recovery of the heat, released at sulphuric acid production, for electrical power production. There is also presented brief description of the sulphuric acid production and the fundamental principles of the steam production at this process. In the practical part of this thesis there is performed the calculation of the heat-flow diagram of the steam turbine and the calculation of heat and producted electrical power at the basic operational states. There is presented the source code for the calculation of the heat-flow diagram using Matlab software. In the end there is mentioned the economical evaluation of the whole project, using the fundamental economical methods, such as net present value method, or profitability index, including the calculation of the pay-back period.
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Analysis of Electric Power Consumption of Public Lighting
Varmuža, Jan ; Pavelka, Tomáš (referee) ; Paar, Martin (advisor)
The thesis deals with analysis of the public lighting system from the point of view of light sources and luminaries. It focuses on the specifics of the lighting systems such as lighting for pedestrian crossings or decorative lighting. It analyzes the energy consumption depending on daylight and how it manifests a shift sunrise and sunset on the consumption of electricity. The work clarifies how the model can be simplified sunrise, sunset for the entire Czech Republic. Based on the distribution of municipalities with population over 10,000 and modeling of sunrise and sunset calculation is carried out power consumption of lighting systems and compared to the total consumption of the Czech Republic. Simplification is an estimate of the consumption of electricity to villages to 10 000 people on the basis of the estimate, the final consumption of electricity for public lighting for the entire Czech Republic.
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