Pokkrong Vongkoon

After harvesting and drying, areca nut (betel nut) processing requires shell cracking and separation of the kernel from the shell. Conventional processing often relies on manual sorting or additional separation machines after husking. To address this limitation, this study developed a mechanically simple machine that integrates husking and separation of full nuts, broken nuts, and shells into a single processing unit without cutting blades or complex control systems. The proposed machine employs all-terrain vehicle (ATV) tires as husking elements, providing a compliant and high-friction contact surface to promote shear-dominant shell detachment in combination with concave metal sieves. Dried areca nuts are fed through a hopper into the shearing zone formed between the rotating ATV tires and stationary concave sieves, where shells are detached through compressive and tangential forces. The husked material is then conveyed to an integrated separating system for in-line classification. Experimental results showed that, under selected operating conditions (tire pressure of 138 kPa, wheel-sieve clearance of 20 mm, husking wheel speed of 442 rpm, and separating system speed of 337 rpm), the machine achieved 80.2% fully husked nuts, 13.8% unhusked nuts, and 6.0% broken nuts. The results demonstrate the feasibility of a shear-based, integrated husking-and-separating approach for dried areca nut processing.

This study presents a modular battery charging system based on a DC–DC buck converter with proportional–integral (PI) control, developed to support hands-on learning in power electronics education. In response to the need for flexible experimental platforms, the system is designed to bridge theoretical concepts of power conversion and control with practical implementation. The proposed setup employs cascaded current and voltage control loops to achieve constant current (CC) and constant voltage (CV) charging modes, while its modular hardware architecture allows modification of key parameters such as inductance, capacitance, and circuit topology. The control algorithms are implemented on a microcontroller, and real-time data acquisition is integrated using the ThingSpeak platform for monitoring system behaviour. Experimental results show that the current control loop recovers to its reference value within approximately 6 ms under abrupt load variations, whereas the voltage control loop settles within approximately 15 ms, demonstrating stable closed-loop performance. In addition, the system successfully charges a 12 V lead-acid battery following a standard CC–CV charging profile. Overall, the proposed experiment kit provides an effective educational platform and a practical basis for further exploration of battery charging strategies and power converter control.

After arecanuts (or betel nut) are harvested and dried, the processing of arecanut involves cracking the shell and separating the kernel seed from the shell. In this process, traditional machines required full nuts separation by hands or other machines. For this reason, this study developed a low-cost machine to husk and separate full nuts, broken nuts, and shells simultaneously. In addition, this study also aimed to decrease the number of broken nuts from husking by reduction the power of the husking motor. Once dry betel nuts were fed through the hopper into the spaces between concave sieves and ATV (All-Terrain Vehicle) wheels. The shells of betel nuts were peeled by the shearing force of the tire’s surfaces and the sieves before being consecutively passed through the separating hopper to sort out full nuts, broken nuts, and shells. The experimental results presented the testing performance of 500 betel nuts that can simultaneously husk and separate for 80.2% of full nuts, 13.8% of unhusked nuts, and 6% of broken nuts based on the optimum setting (20 psi of tire pressure, 20 mm of the gap between the tires’ surface and the sieves, 442 rpm for husking tires, and 337 rpm for the separating system).

Maximizing solar energy capture requires the continuous alignment of photovoltaic panels perpendicular to incoming solar radiation. However, traditional sensor‐based tracking systems face challenges such as calibration issues, installation complexity, and environmental susceptibility, while sensorless tracking systems often require extensive datasets and incur high computational costs. To address these limitations, this study proposes a sensorless dual‐axis solar tracking system based on the whale optimization algorithm (WOA) to enhance energy generation while reducing computational complexity and tracking energy consumption. The WOA‐based tracking system is tested over 35 days (October 2023 to April 2024) at King Mongkut's University of Technology North Bangkok, Rayong Campus, Thailand. It is benchmarked against two systems: a particle filter (PF) system and a fixed system. The results indicate that the WOA‐based system achieves improvements in average daily net energy gain of 16% and 42% compared to the PF and fixed flat‐plate systems, respectively. Additionally, it reduces average time and energy consumption per tracking cycle by 13% and 14%, respectively, and memory footprint by 24% compared to the PF‐based system.

On the grid side, the half‐bridge topology of the microinverter is of interest for solar rooftop applications because of its high efficiency, low component count, and cost‐effectiveness. However, it has an inherent double‐line frequency ripple voltage on the dc‐link, which causes the injection of a third‐order harmonic current when the voltage control loop is closed. Furthermore, in practice, different average voltages or different capacitances of the two capacitors at the dc‐link produce a second‐order harmonic current that flows into the grid. In this paper, the analytical details of these harmonics are comprehensively described, and a simple and effective low‐cost technique using the cascaded connection of two modified notch filters is proposed in the voltage control loop to mitigate their effects. The simulation and experimental results of a 300 W microinverter indicate that the proposed filters represent an effective low‐cost solution and perform well in accordance with the IEEE 1547 standard, even if the capacitances at the dc‐link are mismatched by 20%. Besides, the prototype is tested when occurring of the changing +1% of the line frequency, or appearing of the distorted waveform of grid voltage with the composition of 6% of fifth‐order harmonic.

A single-phase phase-locked loop (PLL) is popular for line frequency estimation. However, the line voltage may not be a pure sinusoidal waveform in practice, which causes high noise in the estimated frequency signal generated from the PLL. An increasing system order using a digital RST controller is presented to enhance high-frequency rejection. Consequently, the estimated frequency signal is significantly improved to be precise and smooth, even under a distorted line voltage. The proposed control strategy was verified by simulation results.

The half-bridge inverter is attractively employed to be a second stage dc-ac converter of microinverter since it is low component count, low cost and high efficiency. However, the microinverter is usually connected to the single-phase utility grid and its instantaneous power pulsates with double-line frequency. This frequency also appears on dc bus voltage and propagates into voltage loop control, which consequently causes third harmonic occurring on the output current injected into the grid. This paper investigates the detail of dc bus ripple voltage and analyzes the reference output grid current thoroughly. Particular design of a PI controller in order to reduce the third harmonic complying with the grid standard IEEE 1547 is presented. Thanks to the feed forward technique, the dynamic response of dc bus voltage is drastically improved to be fast and steadily even under input power suddenly changed. Theoretical analysis and proposed control strategy are verified by experimental results.