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Low-Cost Capacitive Sensor Front-End Circuit Based on Phase-Locked Technique
(2025-12-15)
Wongprommoon, Natapong
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Chimnoy, Jirat
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Prommee, Pipat
This research presents an efficient front-end circuit for grounded capacitive sensors (GCSs), based on a phase-locked technique. An all-pass filter serves as a phase shifter to obtain the desired 90° phase difference, enabling the sensor capacitance to be calculated from the locked frequency regardless of parasitic capacitances. For long-distance capacitance measurements (remote sensors), the proposed circuit integrates an improved active shield technique, allowing real-time measurements using only a low-cost microcontroller unit (MCU), display, and commercially available electronic components, without the need for expensive or bulky instruments. The design is fully automated and does not require manual adjustments. Simulation and experimental results are consistent and validate the effectiveness of the proposed method. Comparative experiments with standard instruments demonstrate accurate measurement within the 1–500 pF range through shielded cables up to 10 m, while maintaining a maximum nonlinear error (NLE) of only 0.04% full-scale span (FSS). The proposed circuit architecture effectively mitigates the effects of parasitic cable capacitance and the input capacitance of operational amplifiers. This approach provides a low-cost, compact, fast, and highly accurate solution, making it suitable for applications of liquid-level measurement in hazardous or hard-to-access environments through remote capacitive sensor measurement.
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Grounded Capacitive Sensor Readout Using Improved Guard Driving Circuit
(2025-01-01)
Chimnoy, Jirat
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Karawanich, Khunanon
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Prommee, Pipat
A remote capacitive sensor is necessary in hazardous locations such as liquid boilers and chemical facilities. The connection of the capacitive sensor and coaxial cable is integrated with the readout circuit, encompassing intrinsic noise and parasitic capacitance limitations. This work presents a grounded capacitive sensor with an economical architecture incorporating an RC lowpass filter and an enhanced guard driving circuit. The proposed technique effectively achieves minimal parasitic capacitance and reduced noise at the output. The sensor capacitance can be readily calculated by measuring the output signal's amplitude at the cutoff frequency. Both simulation and experimental findings corroborate its efficacy and precision. The capacitance range can be quantified between 1-100 pF with less than 2% relative errors.
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Extracting the Single-Dispersion Fractional Cole–Cole Bioimpedance Model Based on Low-Pass Filter Technique
(2025-01-01)
Prommee, Pipat
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Chimnoy, Jirat
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Wongprommoon, Natapong
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Karawanich, Khunanon
This article presents a simple approach to extracting the parameters of the single-dispersion Cole–Cole bioimpedance model. The main advantage of the proposed technique is that it is low-cost but accurate in identifying the bioimpedance models. The Cole–Cole model is simplified as a fractional low-pass filter (LPF) using a few electronic components. Based on a low-component count, the circuit can be realized using only a single operational amplifier (OPAMP), two resistors, and two potentiometers (POTs). The proposed technique can achieve a minimal error compared to the theory, ensuring accuracy. The Cole–Cole model parameter values can be extracted by measuring the filter magnitude and phase responses. The LPF topology inherently provides a low-noise output signal. Experimental results using different fruits are carried out to verify the method and compared with measurements from a commercial impedance analyzer to confirm the accuracy of the results, with the maximum errors of R<inf>0</inf>,R<inf>∞</inf>, α, and C<inf>α</inf> being 0.94%, 2.41%, 0.85%, and 1.52%, respectively. The proposed new efficient technique provides excellent results in extracting the Cole–Cole parameters and agrees with the theoretical expectations.
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Image cryptography communication using FPAA-based multi-scroll chaotic system
(2024-03-01)
Karawanich, Khunanon
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Chimnoy, Jirat
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Khateb, Fabian
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Marwan, Muhammad
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Prommee, Pipat
This research presents an image cryptography communication system based on a novel 3D high-complex chaotic system. The chaotic system is implemented by field programmable analog array (FPAA), which is a conveniently reconfigurable system. The image cryptography communication system is realized using low-cost microcontrollers and commercially available devices. The proposed chaotic system based on the jerk model incorporated two different nonlinear functions that can generate single-scroll, double-scroll, three-scroll, four-scroll, and six-scroll attractors by adjusting only one coefficient. The fundamental dynamical properties of the proposed system are investigated, viz., equilibria and stability, dissipative, phase portraits, bifurcation, and Lyapunov exponent, etc. The four-scroll attractor of the proposed system is applied in image encryption. The multi-scroll attractor’s characteristic in this work can achieve relatively high complexity, with a high Kaplan–Yorke dimension of up to 2.45. The performances of the multi-scroll chaotic using FPAAs are proven by comparing the experimental and numerical results. The image cryptography communication system based on the chaotic masking method (CM) has been tested around 1 × 10<sup>7</sup> bits under 9600 bps. The measuring signals of the image cryptography communication system are demonstrated in different scenarios. The experimental results can be ensured that mismatched parameters give the complete cipher image if and only if the bit error rate is more significant than 490,000 × 10<sup>–6</sup>.
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Low-Cost Technique for Extracting the Cole-Cole Model Parameters
(2024-01-01)
Chimnoy, Jirat
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Karawanich, Khunanon
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Prommee, Pipat
This paper proposed a new efficient approach for extracting the parameters of the Cole-Cole impedance model. The main offered advantage is simple and low-cost but accurate in identifying the constant phase element from the bioimpedance models. The Cole-Cole model is simplified as a low-pass filter (LPF) by using a few electronic components. The magnitude and phase response of LPF characteristics are applied to calculate the fractional order (α) and value of the capacitor. This technique offers low complexity and low-cost equipment. The circuit can be realized by a low-component count based on a single OPAMP and four resistors. PSpice simulation with a Cole model is carried out to verify the method. The simulation results are in good agreement with the theory expectations.
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Realization of image cryptography using FPAA-based two chaotic systems
(2023-01-01)
Sanprang, Pitipat
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Amornsusawad, Chinnapat
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Boonmak, Kuntapong
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Chimnoy, Jirat
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Karawanich, Khunanon
This paper presents a data cryptography system based on chaotic systems (Lorenz and jerk). The system implementation consists of Field Programmable Analog Array (FPAA) and a microcontroller for transmit and receiver sides. MATLAB/Simulink provides the simulation results in various parameters. The experimental setup is exhibited by applying the data of digital pictures, which are encrypted by the selected chaos model and transmitted by using the serial port. The receiver can be correctly decrypted if and only if the chosen chaos model and parameters are perfectly matched with the transmitter. The experimental results of BER were measured around $42.39\times 10^{-6}$ for the Lorenz system and $38.29\times 10^{-6}$ for the jerk system with a time of approximately 24 minutes to recover all 10,002,432 bits
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A four-scroll chaotic generator based on two nonlinear functions and its telecommunications cryptography application
(2022-12-01)
Karawanich, Khunanon
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Kumngern, Montree
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Chimnoy, Jirat
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Prommee, Pipat
This paper describes a new chaotic jerk system based on two different nonlinear functions. The modified signum and rectangular functions are incorporated into the system at different positions. The system can generate double-scroll and new four-scroll chaotic attractors by adjusting only one coefficient (k). The chaotic behaviors of the proposed system are investigated by the Lyapunov spectrum and period distribution of state variable × of the bifurcations. The complexity of the proposed chaotic system is computed by the Kaplan-Yorke dimension of 2.30. The coexisting attractors and basin of attraction are also included to verify the system's dynamic to the initial conditions. The PCB prototype's commercially available OPAMP and passive components are realized to confirm the numerical studies. The experimental results and the numerical results are agreeable in signals and attractors. The chaotic masking method is applied for encrypting the data for secure communication. The efficient encrypted signal can be obtained, and the decrypted data can be correctly received after successful synchronization.

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