With the development of the Internet of Things (IoT), wireless pushbuttons are being increasingly used to control devices such as lights, fans, and air conditioners in smart homes and offices. In contrast to conventional systems, self-powered pushbuttons eliminate the inconvenience of cable arrangement and the cost of battery replacement. However, existing self-powered wireless pushbuttons can only send commands unidirectionally and lack an instant feedback mechanism. This limitation reduces system reliability and impairs the user experience. To tackle this issue, we propose ViPSN-button, a motion-powered wireless pushbutton that offers instant feedback. When the ViPSN-button is pressed, it can deliver instant feedback to the user. This feedback mechanism enables the user to confirm whether the host unit has successfully acknowledged their command. ViPSN-button is powered by a quasi-static-toggling energy harvester (QST harvester). The entire communication process of the ViPSN-button includes three steps: sending commands, receiving acknowledgments (ACK), and displaying an indication. All of these actions are carried out solely by utilizing the energy generated from a single press action. Experiments demonstrate that the ViPSN-button can achieve low-power, fast, private, and reliable bidirectional communication under the Enhanced ShockBurst (ESB) communication protocol. Field tests have been conducted, showing that the ViPSN-button can achieve reliable communication at a distance of 50 meters. ViPSN-button offers an innovative design concept for self-powered sensing nodes, facilitating bidirectional communication between host units and sensing nodes. This feature renders it highly suitable for a wide range of applications, including smart homes, smart offices, smart cities, and industrial IoT.

Synchronous switch (SS) technique has been extensively studied in piezoelectric energy harvesting (PEH). The SS circuits can significantly enhance the output power under the same vibration excitation. Some SS solutions have also been developed for an inductive electromagnetic (EM) source by referring to its capacitive PEH counterpart and taking a complementary design. This paper proposes a synchronized current inversion and energy extraction (SCIEE) circuit for EM energy harvesting (EMEH). SCIEE utilizes two switched capacitive branches to carry out the synchronized current inversion at the electromotive voltage negative-to-positive zero-crossing instants and energy extraction at the voltage positive-to-negative zero-crossing instants. Theoretical analysis shows that the proposed circuit is suitable to be used with an EM transducer, whose quality factor is relatively large. Experiments show that, under the same mechanical excitation, SCIEE can harvest 25% more power compared with the cutting-edge synchronized switch energy extraction (SSEE) circuit for EMEH.

Synchronous switch (SS) technique has been extensively studied in piezoelectric energy harvesting (PEH). The SS circuits can significantly enhance the output power under the same vibration excitation. Some SS solutions have also been developed for an inductive electromagnetic (EM) source by referring to its capacitive PEH counterpart and taking a reciprocal design. This paper proposes a synchronized current inversion and energy extraction (SCIEE) circuit for EM energy harvesting (EMEH). SCIEE utilizes two switched capacitive branches to carry out the synchronized current inversion at the electromotive voltage negative-to-positive zero-crossing instants and energy extraction at the voltage positive-to-negative zero-crossing instants. By inverting the transducer current, SCIEE increases the torque/force inside the transducer to extract more energy from the relative movement between magnets and coils. Theoretical analysis shows that the proposed circuit is suitable for use with an EM transducer, whose quality factor is relatively large. Experiments compared the output power of three harvesting schemes: SCIEE, synchronized switch energy extraction (SSEE), and conventional pulse-width modulation (PWM)-based harvesting scheme. When using the same prototyped EM harvester under the same mechanical excitation, SCIEE can harvest 38% more power, compared with the cutting-edge SSEE circuit for EMEH; and 900% more power, compared with the PWM-based harvesting scheme.

The literature on piezoelectric energy harvesting (PEH) systems underscores the role of circuit advancements in enhancing energy harvesting capability in resonance. Recent studies using phase-variable (PV) synchronized switch technologies have also shown potential in broadband PEH, thereby improving off-resonance energy harvesting. However, the electrically induced dynamics by existing interface circuits lack a comprehensive definition and demonstration, hampering the performance comparisons across different circuits. Regarding these gaps, this paper presents an impedance-based analysis and comparison of electromechanical joint dynamics in PEH systems employing various interface circuits. The focus is on their contributions to enhancing harvesting bandwidth. By introducing resonance tunability into the conventional ideal PEH model, this paper proposes a more generic impedance model. It reveals that the achievable dynamic ranges of practical interface circuits are subsets of the ideal arbitrarily tunable scenario. A detailed quantitative study on the attainable ranges of the PV synchronized switch circuit solutions is provided after the introduction of the ideal target. Simulation and experimental data from different interface circuits align well with theoretical findings. The paper concludes that resonance tunability hinges on the extent of the achievable reactive (imaginary) part of the equivalent impedance. Electromechanical coupling conditions and dielectric loss may further impact resonance tunability. The general ideal model and quantitative impedance analysis provided in this paper help guide the future design effort toward high-capability and broadband PEH systems.