Browsing by Author "Senanayake, S. V."

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Comparison of different methods for generating SPWM signal for the development of a pure Sine wave inverter
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Hemal, S. B. N. H.; Dilshan, G. K. D.; Karunarathna, M. A. D. D. S.; Morawakaarachchi, K. N.; Senanayake, S. V.; Premasiri, R. H. M. D.; Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.
An inverter is an electronic device which is used for converting Direct Current (DC) to Alternating Current (AC) because AC is the predominant form of electrical power used in homes, businesses, and most electrical appliances. Inverters can be categorized based on the type of waveform that they produce, such as Pure Sine Wave Inverters, Modified Square Wave Inverters and Square Wave Inverters. This paper discusses the development of a Pure Sine Wave Inverter with an output voltage of 230 VRMS and a frequency of 50 Hz using the Sinusoidal Pulse Width Modulation (SPWM) technique. Three SPWM signal generation methods, including analogue comparator, microcontroller, and SPWM driver module methods, were tested. This study presents a method to obtain a 230 VRMS, 50 Hz output sine wave in three steps. The first step involves the generation of an SPWM signal with frequency control, utilizing the DC source supply. The analogue comparator method uses op-amps as the analogue comparator. Then, it compares a reference sinusoidal wave with a high-frequency (in kHz range) carrier triangular wave. The output of the op-amp comparator is SPWM. The frequency of this reference sinusoidal wave is chosen based on the required inverter output frequency (50 Hz). In that process, the comparator gives out a pulse when the voltage of the sine waveform is greater than the triangular voltage, and this pulse is used to trigger the respective inverter switches. When designing a circuit that involves op-amps, the slew rate of the op-amp is a critical consideration. To generate an SPWM signal using an ATmega328p microcontroller, the microcontroller was used to generate a series of PWM signals by digital high and digital low. The corresponding time of each pulse's delay is added using the microsecond function. Increasing and decreasing duty cycle, and then a series of PWM signals. As the pure sine wave inverter SPWM driver module EGS002 was used and, that method was the more accurate method, and a clean SPWM signal was generated with less harmonics. Although this type of inverter board has more features, the circuitry was not complex because of the module. Secondly, we employ the MOSFET H-bridge stage to obtain the desired sine wave output. Finally, the third step focuses on supplying a high DC voltage to the H-bridge circuit, which the DC-DC PWM boost converter generates. Several circuit protections were included to ensure the device's safety and reliability. In the process of SPWM generation, although in the analogue comparator method, op-amps offer a low-cost option, a microcontroller is favoured for its superior precision and ability to handle high-power applications effectively. However, the EGS002 module stands out as the preferred method due to its user-friendly nature, comprehensive protection features, and ability to provide valuable feedback, making it a more economically efficient choice in the overall design.
Harvesting energy from human-body movements for ultra-low power appliances
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Gunarathna, T. G. L.; Rupasingha, U. S. D. B. M.; Gunasekara, H. S.; Thennakoon, S. E. R. T. M. M. I.; Senanayake, S. V.; Leanage, H. B.; Kumarage, W. G. C.; Ranaweera, A. L. A. K.
Energy harvesting from human body movements presents a promising approach to sustainably power wearable devices and sensor nodes. This study explores the potential of capturing energy from footsteps using piezoelectric technology. A critical aspect of this technology involves designing an efficient interface between the piezoelectric elements and the electrical load to maximize energy conversion. The irregular and low-frequency nature of human footsteps poses a significant challenge, resulting in low energy extraction. Moreover, achieving a self-powered circuit adds another layer of complexity. To address these challenges, a novel Parallel-Synchronous Switching Harvesting on Inductor (P-SSHI) circuit is proposed. This circuit increases the energy extraction efficiency of piezoelectric elements. Since the output of a piezoelectric element is in the form of alternating current (AC), a MOSFET-based full-bridge rectifier circuit is proposed to convert AC to direct current (DC). As proof of concept, a shoe insole integrated with multiple piezoelectric elements connected in parallel was developed, and the energy conversion circuit was rigorously validated. The system was tested at a frequency of 1 Hz, which corresponds to the typical walking frequency, using a person weighing 60 kg. Under these conditions, the proposed system achieved an average power output of 550 µW per step with a 10 kΩ resistive load and a 10 µF storage capacitor. The effectiveness of the system was further validated by demonstrating its ability to charge a 1 mF capacitor to 2.1 V in 18 steps and a 10 µF capacitor to 7.0 V in a single step. Notably, the circuit is self-powered and capable of initiating operation without the assistance of an external battery, highlighting its potential for autonomous use. The circuit was prototyped using simple discrete components, emphasizing its practicality and feasibility for real-world applications. The proposed MOSFET-based rectifier circuit offers a significant advantage in converting AC to DC with minimal voltage drop, compared to conventional diode full-bridge rectifiers. Furthermore, the system's capability to charge a Li-ion battery (3.7 V, 300 mAh) was demonstrated, showcasing the potential of the wearable piezoelectric energy harvesting system to provide a sustainable power supply for wearable wireless sensors. Future studies will focus on optimizing energy harvesting under different walking conditions, integrating energy storage devices, and enhancing durability. The proposed technology also shows promise for applications in diverse fields such as healthcare, fitness monitoring, and environmental sensing, where reliable, self-sustaining wearable power solutions are in high demand.
Innovative fence monitoring system to mitigate human-elephant conflict
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Bodaragama, B. T. P.; Athawuda, A. H. C.; Gunawardhana, M. A. W. S. N. T.; Senanayake, S. V.; Leanage, H. B.; Gunawardana, K. D. B. H.; Seneviratne, J. A.
Human-elephant conflict (HEC) poses a significant threat to communities and wildlife, prompting the development of an innovative standalone device to enhance electric fence monitoring and mitigate associated risks. This research introduces a system that determines breakage location by measuring fence capacitance, inductance, and resistance, and uses a mathematical model to map changes of these parameters to change of the fence length. This approach enables remote detection of both open and short circuit breakdowns without relying on expensive, failure-prone active nodes along the entire fence. The device can identify the distance to the breached location along the length of the fence approximately and immediately. It will send this alert via SMS to designated contacts using a GSM module, providing real-time monitoring and rapid response capabilities. This key feature ensures timely alerts and quick responses to potential breaches, enhancing the fence's effectiveness in preventing elephants from entering villages and reducing HEC incidents. The standalone nature of the solution simplifies installation and maintenance, eliminating the need for additional wiring or complex infrastructure, thereby significantly reducing overall costs associated with fence monitoring while increasing reliability and efficiency. Furthermore, the device functions accurately by minimizing the effects of weather changes, ensuring consistent performance in various environmental conditions. This innovative breakage detection system represents a significant advancement in fence monitoring technology for wildlife conservation, addressing many shortcomings of traditional solutions by offering a cost-effective, efficient, and reliable method for mitigating human-elephant conflict. The research underscores the potential of integrating advanced technology with traditional conservation methods to create more sustainable and effective strategies for managing human-wildlife conflicts, ultimately improving the effectiveness of electric fences in deterring elephants and reducing the incidence of fatalities and crop damage. Testing on a 150m fence demonstrated promising results, with the system achieving nearly 80% accuracy in detecting and locating both open circuit and short circuit breakages, as verified through manual simulations and observations recorded in the device's test results.
Mosquito detection and repellent system using acoustics signals for household use.
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Senanayake, S. V.; Warnakulasooriya, C. B.; Ranaweera, A. L. A. K.; Jayathilaka, K. M. D. C.
There are over 130 mosquito species in Sri Lanka, and this abundance may be the reason for the spread of several critical diseases. Therefore, an effective mosquito repellent system, including a mosquito detection mechanism, is essential for daily life. Using acoustic signals is a harmless and cost-effective method for detecting and repelling pests compared to other visual or thermal processes. Therefore, this research investigates a novel approach for detecting mosquitoes and creating an effective mosquito-repellent mechanism based on acoustic signals. A system capable of distinguishing mosquitoes from other sound sources based on their unique wing flapping frequency was built and repelling them using specific ultrasonic frequencies was realized. The system consists of several components, including microphones, amplifiers, and filters, tested in both simulations and experiments. The methodology involved in determining the wing flapping frequency of mosquitoes by concentrating mosquitoes in a soundproof container, which was found to be within the 800-900 Hz range, with slight differences between male and female mosquitoes. Additionally, the effect of ultrasound in repelling mosquitoes was explored, discovering an effective frequency range of 42 kHz to 44 kHz. The system was subjected to numerous iterations and improvements to enhance mosquito detection sensitivity and the band of repellent frequencies. The final design includes an instrumentation amplifier for cancelling the noises and a second order Sallen-Key bandpass filter for filtering the flapping frequency of mosquitoes. However, due to the limitations of conventional condenser microphones, the discrepancy between simulations and physical implementations appeared. Further, the interference from surrounding noise caused some complications. Despite these obstacles, the results showed the system's potential in detecting and repelling mosquitoes. The system can be improved further by incorporating more sensitive microphones and filter circuits. By providing power with rechargeable batteries, it can be made portable. The flexibility and adaptability of the system design offer exciting possibilities for future enhancements and optimizations. In conclusion, this research advances the field of mosquito detection and repellence, providing new insights into the potential of acoustic signal processing in pest detection and control. Future improvements to the system could significantly contribute to mitigating the risks associated with mosquito-borne diseases.