Energy harvesting is expected to be used as a source of energy for tiny low power sensor nodes. Since the amount of harvested energy is unstable, an energy storage device is used with an energy harvesting system. With advancement in rechargeable batteries, ultra-low weight rechargeable lithium-ion batteries are used as energy storage devices with low power wireless sensor nodes at remote places. These ultra-low weight energy storage devices are expected to be charged efficiently with maximum harvested power. The mismatching of the electrical impedance between input (i.e. Piezoelectric Transducer (PZT)) and output (i.e. Load) gives inefficient power transfer. The piezoelectric energy harvesting circuit described in this paper focuses on the design and analysis of op-amp based inductor circuit for matching the impedance by presenting a conjugate impedance match to the Piezoelectric harvester. The values of inductor obtained for optimal power transfer from PZT to storage device tend to be prohibitively large. This becomes an inhibiting factor for Integrated Circuit(IC) realization of the interface circuits. The proposed work implements the required value of inductor using op-amp circuit to match the complex conjugate part of the impedance thereby making it cost effective and suitable for IC realization. Finally, comparison between pure resistive match and complex conjugate match is presented along with results.

Purpose The purpose of this research paper is to explore the possibility to enhance the power transfer from piezoelectric energy harvester (PEH) source to the load. As the proposed gyrator-induced voltage flip technique (GIVFT) does not require bulky components such as physical inductors, it is easily realizable in small integrated circuits (IC) package thereby offering performance benefits, reducing area overhead and providing cost benefits for constrained self-powered autonomous Internet-of-Things (IoT) applications. Design/methodology/approach This paper presents an inductorless interface circuit for PEH. The proposed technique is called GIVFT and is demonstrated using active elements. The authors use gyrator to induce voltage flip at the output side of PEH to enhance the charge extraction from PEH. The proposed technique uses the current-voltage (I-V) relationship of gyrator to get appropriate phasor response necessary to induce the voltage flip at the output of PEH to gain power transfer enhancement at the load. Findings The experimental results show the efficacy of the GIVFT realization for enhanced power extraction. The authors have compared their proposed design with popular earlier reported interface circuits. Experimentally measured performance improvement is 1.86×higher than the baseline comparison of full-wave bridge rectifier circuit. The authors demonstrated a voltage flip using GIVFT to gain power transfer improvement in piezoelectric energy harvesting. Originality/value To the best of the authors’ knowledge, pertaining to the field of PEH, this is the first reported GIVFT based on the I-V relationship of the gyrator. The proposed approach could be useful for constrained self-powered autonomous IoT applications, and it could be of importance in guiding the design of new interface circuits for PEH.

With increase in population, the problems related to transportation systems are increasing day by day, such as constrained car parking facilities, traffic congestion, and in particular traffic rules and road safety. The problem of traffic rules and road safety are becoming very critical for human being in existing metro cities and probably in future for smart cities. This paper discusses the implementation of smart vehicles which gather the information like the speed of the vehicle, the number of persons sitting on/in the vehicle, utilization of safety feature by owner/driver, the location of the vehicle, drunk and drive situation, etc. In case any rules are being violated, the information regarding vehicle will be sent to the central database system, from where the e-challan is generated and send to the concerned authority. Further, the implementation of such features avoids the accidents, provides the safe and secure ride to the persons driving the vehicle.

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Background: Most of the proposed interface circuits use bulky inductors to enhance the key performance parameter i.e., power transfer efficiency. This sets constraints on the design of power conditioning circuitry for constrained IoT applications. Objective: To replace the bulky physical inductor with area optimized components suitable for integrated circuit realization with reduced silicon footprint for constrained applications like Internet-of-Things (IoT). Method: This paper presents the implementation of Circuit Resonance with Active Inductor (CRAI) technique based interface circuit design to deliver the maximum power generated from the Piezoelectric Energy (PEH) source to the load. Results: Compared to the conventional FWBR technique, the proposed CRAI technique improves ≈2X power delivered to the load. Conclusion: The proposed work presents an inductor-less interface circuit for PEH. An active inductor (gyrator) is used to induce ‘IP’ rejection at the PEH circuit resonant frequency to enhance the performance parameters. Since the proposed technique is based on active inductor, it can be easily fabricated in small integrated circuit (IC) packages, allowing integration with state-of-the-art constrained IoT applications. CRAI technique based on the rejection of ‘IP’ at the resonance using active inductor is first reported here. The proposed concept is non-adiabatic, but it could be used for constrained self-powered autonomous IoT applications and it could be of importance in guiding the design of new interface circuits for PEH.