Physics
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Item Smart Automation System for Controlling Various Appliances using a Mobile Device(IEEE Xplore Digital Library, 2019) Gunarathne, S.B.M.S.S.; Kalingamudali, S.R.D.This paper outlines the methodology of designing and developing a smart control system for controlling light, air conditioning and ceiling fans in a room. This system considers the requirements of the users appropriately and makes a comfort zone for the users. An android application with a user friendly Graphical Interface, which is easy to communicate with the smart control system, has been developed. The application is connected with the control system through Wi-Fi across a cloud network and it can respond quickly. RGB LED panel light system that controls the color, color temperature and luminance was designed by considering the requirements of the instances and lighting conditions. Although there are RGB LED panel lights available, there are no systems defined for the activity based color modes. An IR Remote module controller system was built for controlling inverter type air conditioners by giving commands from a smart phone application. This system considers the mean value of the preferences of many users to control the air conditioning system. The running mode of the air conditioner is chosen from the data given through the application by many users in a same place. Although the inverter type air conditioners continuously regulate the temperatures, the fan does not do it. Because of this problem, a ceiling fan controlling system with two modes, automatic and manual, was designed. Automatic mode utilizes the users skin moisture related hybrid system to set the room temperature. Manual mode works according to the suggestions given by the crowd just as the air conditioning system. This air conditioning and ceiling fan control system that works according to the suggestions of crowd is better than the individual preference system using a conventional remote controller.Item Improving the Energy Storage of Standalone PV Systems while Enhancing the Charging Efficiency using Supercapacitors(IEEE Xplore Digital Library, 2019) Piyumal, P.L.A.K.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.; Kularatna, N.Usually a battery is used as the energy storage device in typical standalone solar photovoltaic (PV) systems. It is charged by a solar charge controller. The charging efficiency of the system depends on the efficiency of the DC-DC converter of solar charge controller. However, a considerable amount of usable energy is wasted during the charging process. In this work, a method is proposed to utilize this wasted energy and thereby to enhance the charging efficiency. In the case of an empty capacitor being charged by an external source, it stores only half of the energy delivered by the source as compared to that of an electrochemical battery. Therefore, it wastes 50% of useful energy. A portion of this wasted energy can be collected and utilized if a useful resistive load is connected in series to this capacitor charging loop. In this study, a DC-DC converter and battery bank is connected as the useful resistive load in the capacitor charging loop. A supercapacitor (SC) bank is used replacing the conventional capacitor. Therefore, total energy loss in capacitor charging loop can be minimized by storing energy in both battery bank and SC bank. This concept is introduced into a typical PV system for reducing its energy losses. Experimental results show an enhancement in charging efficiency when this new method is employed. The energy stored in the SC bank could be used for driving loads with required electronics.Item Novel Approach for Harnessing Maximum Energy from PV Systems using Supercapacitors(IEEE Xplore, 2018) Piyumal, P.L.A.K.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.; Kularatna, N.Typical standalone solar photovoltaic (PV) systems use battery bank as the energy storage device. The battery bank is charged by using a solar charge controller connected to a solar array. For similar PV systems, charging efficiency mostly depends on the efficiency of DC-DC converter available inside the charge controller. However, considerable amount of usable energy will be wasted during the charging process. In this work, a method is proposed to utilize this wasted energy while enhancing the end to end efficiency of standalone PV systems. When an empty capacitor is charged by an external source, it stores only a half of the energy delivered by the source as compared to the case of an electrochemical battery. As a result, 50% of useful energy is lost in the charging loop of a capacitor. If a useful resistive load is connected to this loop, some amount of energy can be utilized by doing a beneficial work. In this study, a DC-DC converter and battery bank has been chosen as the useful load in the capacitor charging loop, and a supercapacitor (SC) bank is used replacing the conventional capacitor. Therefore, total energy loss can be minimized by storing energy in both battery and SC bank. The energy stored in the SCs could be used for driving loads with required electronics. Consequently, it leads to an improvement of end to end efficiency of the PV system.Item Simultaneous control of multiple line-loads each connected separately in series with a designed unit (Control using Radio Frequency and a Mobile device)(2016) Cooray, B.N.P.; Perera, W.S.K.; Kalingamudali, S.R.D.A unit which can be connected separately in series with each load to control multiple line-loads simultaneously using Radio Frequency (RF) and a mobile device has been developed during this study. Series connected remotely controllable regulators are not widely available commercially and the few available do not have the facility to control the multiple line loads using a mobile application along with a RF remote controller and also they are very expensive and even require an alternative wiring system. The designed regulator provides the convenience of controlling the current flow through appliances connected to a single line power supply. A triac is used to control the power supplied to the load, since it can control the current flow in both halves of an AC current. The gate terminal is triggered by using a diac. A Switch Mode Power Supply, powers the active components of the regulator using the voltage drop across the triac. The Bluetooth (HC-06) and RF (315 MHz RF receiver) modules are programmed to receive inputs from the user to switch ON/OFF or control the voltage supplied to appliances such as fans and light bulbs. The Graphical User Interface enables the user to control the appliances easily and much faster than in normal usage of mechanical switches. The timer which allows the user to define time intervals for predefined output levels, can set desired levels of outputs for the appliances. This feature is not currently available in normal regulators. The suggested method facilitate simultaneous use of RF and the mobile devices as well as the ability to control several appliances with a single unit enabling energy conservation and ease of use. The cost of designing the unit with discrete components being less than US$ 17, it can be concluded that the model is cost effective since this method suggests two modes of control of the appliances along with timer settings. [1-9].Item Effects of lightning and possible health hazards due to the erection of telecommunication towers(Wayamba University of Sri Lanka, 2016) Maduranga, J.A.K.; Kalingamudali, S.R.D.; Jayaratne, K.P.S.C.The health hazards due to lightning and electromagnetic radiations in the neighbourhood of telecommunication towers were studied. Six tower sites were selected for the investigations from the areas covering the Sri Lankan lightning belt in Gampaha (Delgoda, Gonawala, Madarawa and Udupila) and Kaluthara (two in Poruwadanda) districts. Initially, a survey was conducted with a questionnaire based interviews. The earth resistance was measured using a digital earth tester according to the fall of potential method inside the region of 15m from the tower for studying the contribution to the lightning effects. The electromagnetic radiation power density was measured using a broadband field metre. The readings were obtained at 10m intervals along the direct line-of-sight of the antennas from the tower to about 80m distance. According to the literature and from the observations it was revealed that the most important factors related to the induced lightning current effect are the earthing systems utilised at the tower site, locations of the power feeding transformer and the houses in the neighbourhood. It was also observed that the earth resistance was near to threshold value in the Kaluthara district, and severe lightning hazards were prevented by installing the Surge Protection Devices (SPD) by the service providers. However, installing SPDs into houses was a temporary solution for the induced lightning current effects. The results of power densities showed that they were significantly below the recommended threshold values according to the guidelines of Telecommunication Regulatory Commission of Sri Lanka; such that the maximum and minimum were 0∙001% and 0∙0001% respectively. The measurements also revealed that distance from the tower is not the sole criteria to determine radiation hazards. In some regions the power density was independent from the distance from the tower because it was not proportional to the distance. In rural areas, the radiation power density emitted by the telecommunication towers is considerably low compared to that emitted by in-use mobile phones. Also, the radiation pattern is critically dependent on inclination and tilting direction of antennas. Thus, this study revealed that the effects of radiation emitted from telecommunication towers are negligible in the immediate neighbourhood.Item Remotely Controllable Regulator Connected in Series with Resistive and Inductive Loads(Institute of Physics, Sri Lanka, 2015) Perera, W.S.K.; Kalingamudali, S.R.D.This work presents a simple design and implementation of a series connected remotely controllable regulator which can be used for both resistive and inductive type loads driven by AC power. Commonly available remote controlled regulators require access to both live and neutral connections. The designed regulator enables the single line power controlling which offers a high level of convenience to the user. The power supplied to the load is controlled by a Triac, because it can control the current flow over both halves of an alternating cycle. The trigger on the gate terminal is set by a diac. The active components of the regulator are powered by a Switch Mode Power Supply (SMPS) using the voltage drop across the Triac. Radio Frequency (RF) remote control module controls the device and improved user satisfaction at a much better range. RF does not require the typical IR point-and-shoot action. The regulator includes a timer which enables the user to control both the level and the period of power. A seven segment display unit is included in the design to indicate the supplied power level and the timersetting. PICmicro® 16F873 microcontroller is used to drive the system and the timer. When compared with remote controlled regulators which require alternative additional electrical wiring system, the designed regulator is much more user friendly. It has many advantages such as low power consumption, small in size and low manufacturing cost and etc.Item Remotely Controllable Regulator for Line-Loads(Tech. Sess. Inst. Phys., Sri Lanka, 2014) Gunawardana, K.D.B.H.; Kalingamudali, S.R.D.Item A Study of CuInS2 Thin Films for Photovoltaic Applications(Proceedings of the Technical Session of Institute of Physics, 1999) Wijesundera, R.P.; Nadesalingam, M.P.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.; Jayanetti, J.K.D.S.; de Silva, K.T.L.Thin films of copper indium disulphide (CuInS2) on Ti Substrate were prepared by annealing potentiastatically electrodeposited Cu-In alloy in H2S gas at 5500 C. Films were characteristised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectral response in a polysulphide electrolyte. XRD measurements revealed the formation of the polysrystaline CuInS2 thin films and the abscence of any other phases. SEM showed the formation of crystallites having the size about 0.2 ?m. Variations of spectral response, open-circuit voltage (Voc) and short circuit current (Isc) with annealing in air have been studied. As deposited CuInS2 films exhibit a direct band gap of 1.5 eV, and shows n-type behaviour when used in a Photoelectrochemical (PEC) cell. Heat treatment shows a considerable enhancement of the photoresponse.Item Computational Study of I-V characteristics of ITO/Cu2 O/Metal junctions, Technical Session of Institute of Physics(Processing of the Technical Session of Institute of Physics, 1999) Wijesinghe, W.M.P.L.; Siripala, W.; Jayasuriya, K.D.; Kalingamudali, S.R.D.A theoretical model for current-voltage (I-V) characteristics of back-to-back diode systems was developed using the ideal diode equation. A computer model was developed using the language C++ to fit the experimental data to the theoretical equation and to determine the ideality factors and reverse saturation currents of each diode. This model was tested with commercial back-to-back diode systems. The values obtained for the above parameters from the theoretical fits were in very good agreement with the standard values. The experimental I-V characteristics data obtained for fabricated ITO/Cu2O/Metal (Au, Ag and Hg) structures were fitted to the model and values for the relevent parameters were obtained. These values indicate that the fabricated systems are back to back diodes except the ITO//Cu2O/Hg structure. Using this model, a good understanding of I-V characteristics of metal-semiconductor-metal diodes can be gained and thereby the quality of junction devices can be tested.Item Observation of Defect Interface States at the Cu2O/CuxS Junction Using Thermally Stimulated IV Measurements.(Sri Lankan Journal of Physics, 2001) Kalingamudali, S.R.D.; Siripala, W.A simple method was developed to fabricate a Cu2O/CuxS p-n junction diode and I-V characteristics of the diode was measured at various temperatures. It was revealed that there are current transport mechanisms at the junction which are leading to high leakage currents. Namely, an oscillatory behaviour of the current with the temperature was observed under reverse bias conditions. This behaviour was interpreted as the thermally enhanced tunnelling at the junction due to the existence of defect interface states. We believe that proper surface treatment might reduce the density of interface states, and thereby improve the I-V characteristics of the diode.