Jayasvasti, Subhawat

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Jayasvasti, Subhawat
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subhawat.ja@kmitl.ac.th

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    Comparative study of QCM analyzers based on pierce oscillator and electromechanical impedance techniques
    (2017-02-21)
    Jayasvasti, Subhawat
    ;
    Isarakorn, Don
    ;
    Nundrakwang, Songmoung
    This paper presents a comparison between pierce oscillator and impedance analysis techniques for measuring the frequency of the quartz crystal. The QCM analyzer based on pierce oscillator is designed, realized, and then compared to the impedance analyzer (Type bode 100). The comparison is focused on accuracy and precision of measurement. The pierce oscillator in a completed-chip is employed in the QCM analyzing device in order to simplify the circuit of system. The frequency drift and standard deviation (SD) values which are obtained from resonant frequency measurement are studied in order to investigate the accurate and precise measurement of devices. In the experiment, an AT-cut quartz disc of crystal oscillator package HC49U is unloaded and loaded while it is being measured the frequency. From the experimental results, the QCM analyzer based on pierce oscillator and impedance analyzer have the approximate accuracy and precision of measurement. The QCM analyzer based on pierce oscillator has lower sensitivity due to the frequency drift.
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    Indoor positioning system on identification of neurodegenerative disease: A comparative study of BLE versus RFID
    (2019-07-01)
    Jayasvasti, Subhawat
    ;
    Isarakorn, Don
    This paper introduces the feasibility examination of indoor positioning system using the Bluetooth low energy (BLE) and the radio-frequency identification (RFID) devices to further apply in the diagnosis of neurodegenerative disease leading an unusual human body motion. Experimentally, a BLE module and a RFID tag are simulated to be the wearable devices mounted to human body, moving with common body motions. Their movements affecting on position tracking efficiency are investigated through smartphone and ultra-high frequency RFID reader, respectively. The results show that a BLE device presents the best position sensing ability.
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    Design and evaluation of double-stage energy harvesting floor tile
    (2019-10-01)
    Isarakorn, Don
    ;
    Jayasvasti, Subhawat
    ;
    Panthongsy, Phosy
    ;
    Janphuang, Pattanaphong
    ;
    Hamamoto, Kazuhiko
    This paper introduces the design and characterization of a double-stage energy harvesting floor tile that uses a piezoelectric cantilever to generate electricity from human footsteps. A frequency up-conversion principle, in the form of an overshooting piezoelectric cantilever, plucked with a proof mass is utilized to increase energy conversion efficiency. The overshoot of the proof mass is implemented by a mechanical impact between a moving cover plate and a stopper to prevent damage to the plucked piezoelectric element. In an experiment, the piezoelectric cantilever of a floor tile prototype was excited by a pneumatic actuator that simulated human footsteps. The key parameters affecting the electrical power and energy outputs were investigated by actuating the prototype with a few kinds of excitation input. It was found that, when actuated by a single simulated footstep, the prototype was able to produce electrical power and energy in two stages. The cantilever resonated at a frequency of 14.08 Hz. The output electricity was directly proportional to the acceleration of the moving cover plate and the gap between the cover plate and the stopper. An average power of 0.82 mW and a total energy of 2.40 mJ were obtained at an acceleration of 0.93 g and a gap of 4 mm. The prototype had a simple structure and was able to operate over a wide range of frequencies.
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    Study of Interaction between Operational Clock-Frequency and Energy Consumption of Microcontrollers for Wireless Sensor Applications
    (2018-08-14)
    Jayasvasti, Subhawat
    ;
    Isarakorn, Don
    This work focuses on the diagnosis of energy consumption of commonly used microcontrollers with various driving clock-frequency. The interaction among the driving clock-frequency, processing time and current consumption are determined to be a guidance for the design of low-power wireless sensor applications. In implementation, the microcontrollers are supposed to process the data following the operational procedures of wireless sensor application, which is programmed to solve mathematical equation with various driving clock-frequencies, and then sleep to reduce the power consumption. With a single circle procession, the current consumption at each driving clock-frequency are captured and analyzed. As the results, the current consumption is proportional to the driving clock-frequency, however energy consumption is minimized at highest clock-frequency.