A Portable Rgb Led Light Source with Color Control Mechanism for Backlighting Application

Tesis ini mengemukakan pembangunan mekanisme kawalan warna untuk sumber cahaya oleh Diod Pemancar Cahaya (LED) Merah Hijau dan Biru (RGB). Pencampuran secara penambahan daripada LED asas tersebut memerlukan mekanisme kawalan kerana warna yang dihasilkan tertakluk kepada variasi. Ini adalah disebabkan peningkatan suhu ambien dan pemanasan sendiri oleh LED tersebut. Titik warna akan berubah kerana penurunan keluaran keamatan sinaran tiap-tiap LED adalah tidak sama. Pengawal mikro dicadangkan sebagai unit pusat untuk mendapatkan set titik permulaan pencampuran warna seterusnya mengawal setiap LED apabila sisihan titik warna baru berubah melebihi had. Kaedah ini bergantung pada jangkaan voltan ke depan terhadap setiap LED dan sisihan ukuran sinaran oleh penderia optik. Mekanisme kawalan warna yang telah dibangunkan boleh mengekalkan gabungan titik warna dengan berkesan apabila tertakluk kepada ujian suhu ambien terpecut menerusi penenggelam haba yang dilekatkan pada LED. Sistem ini diuji pada dua jenis LED RGB. Sistem ini berupaya untuk mengurangkan 83 % ralat relatif untuk LED jenis pertama dan 78.6 % ralat relatif untuk LED jenis kedua. Ralat relatif diperolehi semasa proses mengukur dengan mekanisme kawalan tertutup mengurangkan ralat sistem kawalan terbuka daripada set titik permulaannya. Gangguan cahaya ambien juga berjaya dihapuskan semasa penderia beroperasi. ________________________________________________________________________________________________________________________ This thesis presents the development of color control mechanism for Red, Green and Blue (RGB) Light Emitting Diode (LED) light source. The additive mixing by the primary LED requires a control mechanism since a color produced is subjected to variation. This is due to the influenced of elevated ambient temperature and selfheating of the LEDs. The color point will vary because the individual LEDs output radiant intensity degradation is not the same. A microcontroller is proposed as a central unit to obtain an initial set point of the color mixing thus controlling each LED when the difference of new color point exceeded tolerance. The method relies on the forward voltage prediction to the individual LEDs and the radiant intensity measured by an optical sensor. The developed color control mechanism can effectively maintain the mixed color point when it is subjected to an accelerated ambient temperature test through heating the heat-sink attached to the LED. The system is tested on two types of RGB LED. The system is able to reduced 83% of relative error for the first type LED and 78.6 % of relative error for the second type LED. The relative error is obtained during the measuring process with the closedloop control mechanism reducing the open-loop control system error from its initial set point. The ambient light disturbance is also successfully eliminated during the sensor in operation

Building a Bidirectional Visible Light Communication Link: Challenges and Contributions

Visible Light Communication is a new information transmission method that involves sending data through light emitting diodes and photo-diodes via the visible light spectrum. It has strong applications in improving security for IoT (Internet of Things) devices. This paper describes a hardware-first approach to building a visible light communication (VLC) link. A VLC link was designed by choosing the simplest possible circuit and software and then incrementally improving it as challenges such as ambient lighting noise and data rate limitations were encountered. This link was used with two main communication protocols: On-off keying (OOK), and Frequency-Shift Keying. The paper describes a design for a fast, robust system using both protocols that also allows for an adjustable data rate. Because many issues were encountered along the way, the paper presents several possible sources of noise and data rate limitations and how to remove this noise and limitations. Finally, the paper also describes extensions to the design to make it bidirectional, more robust, and faster.Electrical and Computer Engineerin

Optimizing Exterior Lighting Illuminance and Spectrum for Human, Environmental, and Economic Factors.

With the recent widespread adoption of LED lighting in outdoor areas, numerous concerns have been raised about the potential for harmful effects on humans, animals, plants, and the night sky. These stem from the high blue light content of some LED bulbs and an incentive to increase lighting levels caused by higher efficiency and lower costs. While new lighting installations are often described as environmentally friendly due to their energy efficiency, factors such as light pollution are often neglected or not given enough weight. This research focuses on optimizing the design of exterior lighting for human, environmental, and economic factors using a multi-criteria decision analysis. Based on data in the literature and survey research, illuminance and spectrum alternatives were scored relative to each other using the analytic hierarchy process and multi-attribute utility theory. The findings of this study support the use of artificial illumination at levels similar to a full moon (0.01 fc) and a warm white spectrum (2700K or 2200K), with amber LED becoming a better choice if its energy efficiency and cost effectiveness improve in the future. This methodology can be used in the future as a framework for lighting design optimization in different settings

Virtual restoration and visualization changes through light: A review

This article belongs to the Special Issue Optical Technologies Applied to Cultural Heritage.The virtual modification of the appearance of an object using lighting technologies has become very important in recent years, since the projection of light on an object allows us to alter its appearance in a virtual and reversible way. Considering the limitation of non-contact when analysing a work of art, these optical techniques have been used in fields of restoration of cultural heritage, allowing us to visualize the work as it was conceived by its author, after a process of acquisition and treatment of the image. Furthermore, the technique of altering the appearance of objects through the projection of light has been used in projects with artistic or even educational purposes. This review has treated the main studies of light projection as a technique to alter the appearance of objects, emphasizing the calibration methods used in each study, taking into account the importance of a correct calibration between devices to carry out this technology. In addition, since the described technique consists of projecting light, and one of the applications is related to cultural heritage, those studies that carry out the design and optimization of lighting systems will be described for a correct appreciation of the works of art, without altering its state of conservationThis work has been funded by project number RTI2018-097633-A-I00 of the Ministry of Science and Innovation of Spain, entitled 'Photonic restoration applied to cultural heritage: Application to Dali's painting: Two Figures.

Using an LED as a sensor and visible light communication device in a smart illumination system

The need for more efficient illumination systems has led to the proliferation of Solid-State Lighting (SSL) systems, which offer optimized power consumption. SSL systems are comprised of LED devices which are intrinsically fast devices and permit very fast light modulation. This, along with the congestion of the radio frequency spectrum has paved the path for the emergence of Visible Light Communication (VLC) systems. VLC uses free space to convey information by using light modulation. Notwithstanding, as VLC systems proliferate and cost competitiveness ensues, there are two important aspects to be considered. State-of-the-art VLC implementations use power demanding PAs, and thus it is important to investigate if regular, existent Switched-Mode Power Supply (SMPS) circuits can be adapted for VLC use. A 28 W buck regulator was implemented using a off-the-shelf LED Driver integrated circuit, using both series and parallel dimming techniques. Results show that optical clock frequencies up to 500 kHz are achievable without any major modification besides adequate component sizing. The use of an LED as a sensor was investigated, in a short-range, low-data-rate perspective. Results show successful communication in an LED-to-LED configuration, with enhanced range when using LED strings as sensors. Besides, LEDs present spectral selective sensitivity, which makes them good contenders for a multi-colour LED-to-LED system, such as in the use of RGB displays and lamps. Ultimately, the present work shows evidence that LEDs can be used as a dual-purpose device, enabling not only illumination, but also bi-directional data communication