Browsing by Author "Kalingamudali, S.R.D."

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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.
Advantages of the use of solar cells and light emitting diodes (LED) for traffic signal lights for the current power crises in Sri Lanka
(2002) Kalingamudali, S.R.D.; Kalingamudali, M.L.
During power failures and power cuts road users suffer immense difficulties due to non-availability of traffic signal lights. Use of solar cells with lead acid accumulators to provide required power and the use of light emitting diode (LED) displays to function as signal lamps to reduce the stored power consumption will be a feasible solution for the same. In addition to the low power consumption of LED displays, it is possible to use the same display to indicate different directions by having different switching circuits. Since the LED display consists of a number of LEDs, visibility from side ways is better than the conventional signal lamp having a single light source. Failure of the lamp in the conventional signals halts the entire operation of the signal lamp but in the case of failures of few LEOs in a matrix will not cease the entire operation. The other major advantage is during the installation of new signal posts; it is possible to erect the same as a wireless installation. Solar panel with an accumulator (lead acid battery) can provide power while infrared sensors and diodes could be used to transfer signals between each signal post; hence it is not necessary to dig across the road for control and power cables.Considering the signal light requirement for the whole country, the above solution will have a considerable impact on the national power grid.
An inexpensive universal serial bus interfaced home automation system
(IET Sri Lanka Network-19th Annual conference, 2012) Wijesundera, R.P.; Abeyratne, M.D.G.M.; Kalupahana, I.U.; Buddhika, W.A.P.; Kumara, S.D.; Jayatissa, N.W.K.; Harambearachchi, J.C.; Kalingamudali, S.R.D.
Analysis of Impedance Matching Technique for Novel Supercapacitor Assisted PV Systems
(IEEE Computer Society, 2020-10) Piyumal, P.L.A.K.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.; Kularatna, N.
To extract the maximum power from a photovoltaic (PV) system, the maximum power point (MPP) of the PV array must be tracked continuously. A directly coupled load with the PV array does not track the MPP of the PV array because the load has a constant resistive value. Therefore, to track the MPP of the PV array, a technique called impedance matching is used. This is done by continuously matching the load impedance to the instantaneous impedance of the PV array. Switch mode DC-DC converters are widely used for this purpose which also helps to interface the DC output of the PV array with power distribution systems in order to deliver the power to the consumer end. However, the efficiency of these converters lies around 90% which degrade the end to end efficiency of the PV system. In this context, novel supercapacitor (SC) assisted PV systems have been introduced, which were able to enhance the end to end efficiency of PV systems. However, existing impedance matching technique is no longer valid for SC assisted PV systems. Therefore, still it is a challenge for these systems to track MPP of the PV array continuously while in operation. This paper presents a study on impedance matching technique for the novel SC assisted PV systems. Previously, it has been experimentally shown that a series connected SC bank between PV array and DC-DC buck converter of a PV system could deliver higher end to end efficiency than typical systems. This study validates the impedance matching technique for SC assisted PV systems by connecting a SC bank in series with buck, boost, and buck-boost converters. Simulation results indicate that this can be achieved by carefully designing the system with given parameters. © 2020 IEEE. https://ieeexplore.ieee.org/document/9254315
Challenges of Defending Maritime Domain of Sri Lanka
(University of Kelaniya, 2012) Kotakadeniya, H.M.S.K.B.; Kalingamudali, S.R.D.; Bulathsinghala, G.
The Indian Ocean is rapidly surpassing both the Atlantic and Pacific Oceans as the world’s busiest and most critical trade corridor, triggering several dramatic changes in the region. With the growth in legitimate international commerce in the maritime domain, escalation of criminal activities has also proliferated. Human and drug smuggling, weapons, and other contraband, as well as piracy and armed robberies against vessels, pose a serious threat to maritime security. The existing level of protection given to the maritime assets and the sealines is grossly inadequate. The Sri Lanka Navy (SLN) is conducting surveillance in brown water ranging from 50 Nm to 100 Nm as and when required. Due to the limited number of blue water ships, SLN’s capacity is restricted to continuous surveillance. All ships that sail on the international waters are fitted with the Automatic Identification System (AIS) which emanates position, identity, course and speed over ground, heading and rate of turn as well as navigational status and the destination of the ship. The information received is easily plotted on an electronic chart display system which has the capability of identifying rogue ships in the Exclusive Economic Zone, but the existing shore based sensors’ are restricted with poor coverage due to range. To overcome this limitation surveillance aircraft can be fitted with the AIS to cover a larger sea area. The objective of this research study is to establish the possibility of using indigenous mechanisms to upgrade the capabilities of the Sri Lanka Air Force’s (SLAF’s) existing Unmanned Aerial Vehicles (UAV) with minimum capital commitment. The research team has carried out in-depth analysis of the existing reconnaissance procedure of SLN. A number of interviews have been conducted with senior Naval officers who are directly involved in the operation and had identified its limitations. There is a possibility of fixing an airborne AIS system to available UAV’s and the engine power/aircraft weight ratios have been calculated for the modification. It has been determined to position the available Ground Data Terminal on a SLN ship. This will facilitate the UAV to extend its range. As follow up to this study, the team intends studying the possibility of linking up the UAV Uplink/Datalink with a satellite to gain more range since Sri Lanka will have one of her own very soon. The time is ripe to integrate the SLAF’s and SLN’s capabilities to strengthen surveillance mechanisms, effectively arresting the emerging transnational threats in the Maritime domain.
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.
Computational Study of I-V characteristics of ITO/Cu2/Metal junctions
(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.
Construction of a Near Ideal Nanoammeter
(1998) Wijesundera, R.P.; Kalingamudali, S.R.D.; Jayasuriya, K.D.
A near ideal ac/dc nanoammeter was constructed using two operational amplifiers (op-amp) and a voltmeter. Small currents were converted into a voltage by the first op-amp and this was amplified into a larger voltage by the second op-amp. The amplified voltage was measuredby the voltmeter. The constructed meter has 10 and 100 nA ranges for the dc current measurements and 100 nA range for the ac current measurements.All the ranges were calibrated using a digital picoammeter. As compared to commercially available nanoammeters with similar features this meter has higher advantages such as almost zero internal resistance and negligible operating bias current. The construction cost of the meter is very low compared to a commercial ac/dc nanoammeter.
Current gain increase in AlGaAs/GaAs heterojunction bipolar transistors using AlGaAs layer overgrowth
(Applied Physics Letters, 1994) Kalingamudali, S.R.D.; Wismayer, A.C.; Woods, R.C.; Roberts, J.S.
Reduction of the surface recombination current components in Npn AlGaAs/GaAs heterojunction bipolar transistors has been achieved by overgrowing the emitter?mesas with an AlGaAs layer approximately 0.5 ?m thick. It was observed that the n=2 recombination current was reduced by ?90%, to about 10% of the original value, with a corresponding 13?fold increase in current gain for 270?20 ?m2 devices. In addition, devices with the same emitter?base area, but significantly different perimeters, were observed to have similar current gains and n=2 recombination current values. This was in contrast to devices fabricated without an overgrowth layer. These results suggest that the overgrowth layer causes a very significant reduction in the perimeter recombination current.
Design and characterization of a parametric speaker using Pulse Width Modulation method
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Jayawardana, D.G.D.D.,; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.
This study focuses on designing and characterization of a parametric speaker. It is used to convert sound waves that spread out in all directions emitted from a sound source into a narrow sound beam to reduce noise pollution. The designed parametric speaker consisted of a parametric acoustic array. The operation of the device is based on nonlinear acoustic characteristics of sound in air. An ultrasound wave that can be modulated by any audio signal is radiated from a transducer array into the air. As a result, an audio signal is produced by the self-demodulation effect of the modulated sound in the air due to the nonlinearity of the air. Typical parametric speakers use different amplitude modulation methods to produce the parametric acoustic array. There is a high cost to produce parametric speakers using those methods. In this work, a method is proposed to produce the parametric acoustic array using the pulse width modulation method (PWM). PWM techniques were used for modulating the input signal. Mainly TL494 IC was used to realize the modulate system. In that process, input audible sound waves were converted to digital high frequency sound (ultrasound) waves which contains information of the audible sound. The proposed design consists of an array of ultrasound transducers each with 8 mm radius that produces ultrasound wave of 40 kHz frequency as the carrier frequency and a class D power amplifier to amplify the sound level of the modulated output sound. The operation of the proposed parametric speaker was tested by changing the carrier frequency and audio signal and measuring the sound pressure level of the parametric speaker for the different distances. It is identified that this method will be a suitable and cost effective method to produce the parametric speaker. Further the directness of the parametric sound beam depends on the carrier frequency and slightly on the input signal. Hence, the parametric sound beam can be more narrowed by using the (30 kHz – 80 kHz) high-frequency range ultrasound emitters and carrier frequencies for the parametric speaker array. It is concluded that the pulse width modulation method based parametric array used for this research is cost effective method and has a great potential to be further developed for designing commercial scale parametric speakers.
Design and Implementation of a Web-Based Faculty Information System
(University of Kelaniya, 2006) Kumara, K.H.; Munasinghe, L.; Jayasuriya, K.D.; Dias, N.G.J.; de Silva, C.H.; Kalingamudali, S.R.D.
Although Information Systems (IS) are valuable elements for organizations, the private and public sectors in Sri Lanka are reluctant to use IS for decision making, organizing and classifying data, processing transactions, and for many other activities. This is caused by the lack of computer literacy and conventional attitudes of the majority of the Sri Lankan community. Even in the higher education institutions in Sri Lanka, majority of both staff and students who are well aware of information technology, rely on conventional ways of handling information. One major reason for the above issue is lack of availability of application software well suited for their needs. On one hand, such types of software are rarely used by institutes because of their high cost; on the other hand, they are highly organization dependent. Hence steps have been taken to build a Faculty Information System (FIS) for the Faculty of Science, University of Kelaniya. The FIS was developed in a network environment, with the active participation of all those involved by means of continuous dialogues with the aim of both promoting and demonstrating its benefits and by catering to the different needs arising from the faculty community. The FIS consists of three major subsystems, namely FIS Web Based Subsystem (FISW), FIS Intranet Sub System (FISI) and FIS Examination Sub System (FISE). FISW provides www access to FIS users at any time from anywhere. FISI enables the capability of access to FIS via the Faculty office local area network with security restrictions. FISE processes the examination data in a highly secured environment which is separated from both FISW and FISI. FISI and FISW eventually connect with FISE under security restrictions as required. It is clear that development of this type of tool has social, cultural and technological dimensions. What we planned is one thing, what happened in reality and how the stake holders respond to the tool is another. An evidence of the neediness of this type of tool to the faculty is the number of accesses, 41784, in two years. The above figure is not a complete measure of acceptance of FIS. To detect its defects and limitations, in addition it is necessary to take into account the number of pages requested by each registered user in the FIS. These statistics can be used to enhance the features of FIS.
Design and Implementation of Smart Standalone Gas Fire Security System for Domestic Usage
(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Rajapaksha, R.M.I.U.; Perera, P.S.H.; Nandasena, P.K.D.M.; Gunarathna, E.P.G.T.K.; Pieris, T.P.D.; Kanishka, G.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.
Liquid Petroleum Gas (LPG) fire security system for domestic gas cylinders has been designed and prototype is implemented. The proposed system automatically takes preventive measures in case of gas leakage. It includes an electronic circuit designed with 8-bit AVR microcontroller for emergency shut-off of the regulator for domestic gas cylinders, a control circuit for switching off the power nearby area and a transceiver unit for sending SMS to the corresponding people. In order for firing to occur LPG concentration should at least be reached to 200 ppm level. This level of LPG is detected with commercially available LPG sensor (MQ-5). A commercially available gas regulator is modified by attaching a spring and a solenoid valve. The spring is compressed when the regulator is ON in domestically available gas cylinders. Once a gas leakage of appropriate ppm is detected a pulse is send to solenoid valve such that, the attached spring gets rest by removing off the regulator from the cylinder. At the same time warning messages will automatically be sent to relevant consumers via GSM module attached to the circuit. The circuit is operated with battery power so that it will work even in power failure. Additional gas sensors are installed in electrical switches located near to the gas cylinder to cut-off power to prevent any spark. Integrating all these sensors through IOT platform is the subject of an on-going study
Design of an auto disconnecting regulator and a safety switch to prevent domestic gas leakages
(Department of Industrial Management, Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Rajapaksha, R.M. I. U.; Perera, P.S.H.; Nandasena, P.K.D.M.; Gunarathna, P.S.T.K.; Kanishka, P.P.D. Gihan; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.
There is a growing demand for research in various aspects of smart homes. Automated security systems are an integral part of smart homes. Liquid Petroleum Gas (LPG) is one of the popular fuels used in domestic cooking. Therefore, there is a very high demand for LPG fire security systems. In this study, an automated LPG fire security system for domestic gas leakages has been designed and a prototype model is constructed. The designed system automatically takes preventive measures in case of gas leakage. It includes a newly designed automatically disconnecting regulator from the cylinder which shuts OFF gas supply from commercially available gas cylinders, a control circuit for switching OFF the power supply of nearby area of gas leakage and transceiver unit for sending SMS to the corresponding people. It has been designed to operate automatically when LPG concentration reaches to 200 PPM, a value well below the LPG gas inflammable concentration. LPG concentration is sensed by the MQ-5 gas sensor and fed into the microcontroller. The commercially available gas regulator is modified by attaching a spring and solenoid valve. The spring is compressed when the regulator is ON. Once an LPG leakage of appropriate PPM is detected, a pulse is sent to the solenoid valve such that the attached spring gets rest by removing the regulator from the cylinder. At the same time, a warning message will automatically send to the corresponding users and security personnel through a GSM module attached to the circuit. The circuit is embedded with a rechargeable battery to work even in power outage. Additional gas sensors are installed in electrical switches located near to the gas cylinder and kept in connection with the microcontroller through the Bluetooth module to cutoff electrical power to prevent any spark.
Design of an Inexpensive Digital Watt-hour Meter
(2003) Chandana, A.W.S.; Wijesundera, R.P.; Jayasuriya, K.D.; Kalingamudali, S.R.D.
An inexpensive digital watt-hour meter has been designed and tested using MCap 7 simulation package since commercially available digital watt-hour meters are very expensive. One of the major usages of watt-hour meters is to measure the power consumption of electricity consumers for billing purposes. Although digital watt-hour meters are commercially available,all electrical power supply companies through out the world including well-developed countries like the United States ofAmerica and the United Kingdom use analogue watt-hour meters to measure the power consumption. This is probably due the expensiveness ofdigital watt-hour meters. The designed digital watt-hour meter consists with analogue multiplier, analogue to digital converters, adder, registers, digital clocks, dividers, accumulators and digital displaying unit. Basically the current and voltage will be multiplied by using a four-quadrant analogue multiplier and then converted to digital signals using analogue to digital converters, which is clocked at a frequency significantly higher than mains frequency, to produce instantaneous values. The algebraic average of the output product per second will be the power consumption per second Finally, this will continuously be added and sent to the digital displaying unit to display watt-hour output. One of the major advantageous of the digital walthour meter is that the power consumption cannot be tampered like in analogue watt-hour meters where the power consumption can be very easily disturbed by changing the rotation power ofthe rotating disk.
Design of an Inexpensive GPIB Interfaced Voltage Source
(2006) Kalingamudali, S.R.D.; Jayasingha, A.M.R.
An inexpensive voltage source that can be controlled by a computer using the general purpose interface bus (GPIB) controller is designed since commercially available GPIB interfaced voltage sources are very expensive. The designed voltage source has been tested for regulation and compared with two commercial type power supplies. The power supply of the voltage source was constructed using the switch mode power supply (SMPS) method. Controlling the duty cycle of the pulse width modulator circuit the output voltage of the SMPS was regulated. PICmicroreg 16F877A microcontroller was used to control all operations of the GPIB interfaced voltage source
Designing of an Economical Computer Interfaced Current Source
(University of Kelaniya, 2008) Kalingamudali, S.R.D.; Nikapitiya, N.Y.J.B.
An economical current source which can be controlled by a computer using the parallel port is designed. The Switch Mode Power Supply (SMPS) technique is used to construct the power supply unit of the current source. The output voltage of the SMPS is regulated by controlling the duty cycle of the Pulse Width Modulator circuit, and thereby constant load current is achieved. The current source is capable of producing constant currents up to 2 A with an accuracy of 96%. This was tested under various load conditions and accuracy is compared using digital multimeters. The compared results of the interfaced current source suggest that the output current regulation values under different loads are very accurate, and noise filtering techniques were used to filter noises. The best operating temperature range will be 20-70° C. In addition, all the components used in the construction are economical and commercially available in the open market.
Development of electronics from vacuum tubes to intergrated circuits
(Science to Society (YSF Science Magazine, NASTEC), 2004) Kalingamudali, S.R.D.
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.
Efficiency Optimization of Supercapacitor Assisted Low Dropout (SCALDO) Regulators
(IEEE, 2020-12) Jayasekara, L. D. P. S.; Piyumal, P. L. A. K.; Ranaweera, A L A K.; Kalingamudali, S.R.D.
This study was primarily focused on presenting a novel method to enhance the eﬃciency of Supercapacitor Assisted Low Dropout (SCALDO) regulators. The main objective was to study SCALDO regulators under a speciﬁcally controlled condition where supply voltage is less than twice of the required minimum voltage for Low Dropout (LDO) regulators. Furthermore, design modiﬁcations to the switching controlling algorithm were performed to optimize number of capacitors with respect to the supply voltage in order to enhance the eﬃciency of SCALDO regulators. It was theoretically proven that the eﬃciency decline can be successfully reduced by varying the number of capacitors connected, according to the supply voltage and the minimum input voltages. The theoretical eﬃciency calculated for the proposed SCALDO technique falls within 81.5% - 88% range, which is well above the previously reported values. This was veriﬁed experimentally with the prototype developed using 2.7 V, 10 F supercapacitors, 5-3.3 V LDO. © 2020 IEEE.
Electronic Scoreboard for Basketball games
(2002) Kalingamudali, S.R.D.; Dedigamuwa, G.S.
An electronic scoreboard has bean designed and fabricated for the basketball game. Although this has been specifically designed for the basketbaU game. this can also be used for other games such as Rugby. Hockey, Boxing etc. Where both timing and scoring are required. This scoreboard is cost effective. easy to build, and more importantly judges can do scorinq, thereby removing the communication errors completely. Since the acquislnon speed of this scoreboard is very fast the current scores can be updated instantaneously pleaslnq both olavers and spectators. Therefore, this scoreboard can be fully utilised in a fast moving game like basketball.