Physics
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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 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.Item Pentacene acoustic charge transfer devices(2011) Kalingamudali, S.R.D.; Shao, H.; Woods, R.C.; Neelam, R.; Singh, V.Acoustic charge transfer (ACT) devices use a charge transfer channel formed from a thin-film of the organic semiconductor pentacene deposited on the surfaces of either LiNbO(3) 0r Bi(12)GeO(20)substrates. Organic semiconductor is chosenbecause of the low costof deposition. Insulating Bi(12)GeO(20) substrate is favored over LiNbO(3) since it has a comparable piezoelectric constant, so that efficient surface acoustic wave generation is readily obtained. In addition, the Bi(12)GeO(20)substrate has a higher acoustic potential coefficient so that a pentacene acoustic charge transfer (PACT) device requires a lower power input compared to LiNbO(3) substrate.Item Development of electronics from vacuum tubes to intergrated circuits(Science to Society (YSF Science Magazine, NASTEC), 2004) Kalingamudali, S.R.D.Item Thermally Stimulated Current-Voltage Characteristics of Cu2O/CuxS Diode(1988) Kalingamudali, S.R.D.; Siripala, W.A simple method was developed to fabricate a p-n junction diode of CU20/CuxS and it Was observed that the stability as well as the current-voltage characteristics of the diode could be improved significantly by controlling the system parameters at the fabricating stage. The diode characteristics of the fabricated diode was compared with a commercial germanium diode. High temperature measurements under the reverse bias conditions revealed that there are two distinct current transport mechanisms that would lead to high leakage current across the junction. Namely, two distinct current peaks were observed at the reverse bias. This was interpreted as the thermally enhanced tunneling at the junction due to the existance of defect interface states. We beleive that proper surface treatment might reduce the density of interface state, and then lead to better diode characteristics. Comparing with the ideal diode equation, it was observed�that the current transport mechanisms are complicated in the CU20/CuxS diode. �Item New Experimental Interpretation for the Emitter-size Effect of AIGaAs/GaAs heterojunction bipolar transistors.(1995) Kalingamudali, S.R.D.; Woods, R.C.; Wismayer, A.C.AIGaAs/GaAs heterojunction bipolar transistors (HBTs) have an excellent frequency performance. One of the major limitations of these devices is current gain degradation with decreased emitter-base junction size, which is known as the emitter-size effect. Several experimental and theoretical studies have been reported on the emitter-size effect in AIGaAs/GaAs HBTs. These papers suggest that it is due to the extrinsic base surface recombination current. However, in thts paper. experimental evidence is reported which suggests that it is the perimeter recombination current which causes the emitter-size effect. Further analysis or previously published results, from rectangular geometry AIGaAs/GaAs HBTs fabricated with and without an overgrown A1GaAs layer approximately 0.5 um thick around the emitter-mesas, has been carried out. This analysis suggests that the perimeter recombination current rather than the extrinsic base surface recombination current causes the emitter-size effect. Devices with the overgrown layer and with the same emitter-base area. but significantly different perimeters, had similar current gains and n=2 recombination current values. In addition, for similar geometry devices without the overgrowth layer, the n=2 recombination current was roughly proportional to the device perimeter and due to the emitter-size effect current gains were decreased when the perimeter was increased. Since the reduction in the perimeter recombination current leads to a reduction of the emitter-size effect, it is suggested that the emitter-size effect is not due to the extrinsic base surface recombination current. Consequently, these results suggest that the emitter-size effect is due to the perimeter recornbination current.Item IV characteristics of ITO/Cu2O/ metal junctions(1996) Perera, L.D.R.D.; Siripala, W.; Kalingamudali, S.R.D.; Jayanetti, J.K.D.S.; de Silva, K.T.L.Cuprous oxide is an inexpensive and non-toxic semiconductor material having the potential for use in low-cost photovoltaic devices. Electrodeposition is a low-cost method t0 produce thin Cu2O films and electrodeposited CU2O has been reported to be n-type, In order to investigate the possibility of using electrodeposited Cu2O in solar cells, Cu2O/metal junctions were studied using their I-V characteristics. Thin films of Cu20 were electrodeposited on Indium tin oxide (ITO) coated glass substrate using an aqueous solution of cupric acetate. Electrodeposition was carried out under potentiostatic condition of -250 mV vs SCE at 55"C for a period of 1 h. These Cu20 samples were used to make junctions with Al, Hg,Cu, Ag and Au. The I-V plots of these junctions were obtained in dark and when illuminated. The I-V characteristics of the Cu2O/Hg junction show good rectifying properties.The plots for the junction in dark and under illumination indicate that the electrodeposited Cu2O behaves as an n-type semiconductor. The I-V profile fits into the standard diode equation with I0 = 2.8 x 10 -10 A, ideality factor n=0.48 and series resistance Rs = 40U. Also, the Junction exhibits a contact potential of about 150 mV.Item 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.Item 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.