It is necessary to ensure safety in terms of health and accidents through the real-time monitoring of the construction site environment and workers. This problem has become of great importance due to the economic and social implications. Therefore, a sensor-based approach has been found to be beneficial in Building Information Modeling (BIM). Wireless Sensor Network (WSN) technologies are well-suited for the deployment of monitoring systems. A suitable technical solution for node communication in a WSN is Long Range (LoRa) modulation technology. In this study, an autonomous LoRa-based system for the monitoring of a construction site in Lungro, Calabria, Italy, is presented. The spatial monitoring of working personnel is achieved by employing a tracker device with an Inertial Measurement Unit (IMU) and a Global Positioning System (GPS) device. Accesses of personnel and gear to the site are registered using Radio Frequency Identification (RFID) tags equipped with protective gear. Fixed-position solar-powered sensor nodes are also employed for structural monitoring, i.e., movement sensors are used to monitor the variation of scaffolding, building structures, and under-work housing inclinations. Long Range Wide Area Network (LoRaWAN) gateways interface with the nodes and the internet for data exchange, enabling an Internet of Things (IoT) paradigm for the monitoring solution. A comprehensive overview of the workers and structural nodes, along with the RFID access management system and LoRaWAN gateway features, is provided in this article. A description of the web interface is also reported.

This paper presents the design and implementation of two front-ends for RF (Radio Frequency) energy harvesting, comparing them with the commercial one—P2110 by Powercast Co. (Pittsburgh, PA, USA) Both devices are implemented on a discrete element board with microstrip lines combined with lumped elements and are optimized for two different input power levels (−10 dBm and 10 dBm, respectively), at the GSM900 frequencies. The load has been fixed at 5kΩ, after a load-pull analysis on systems. The rectifiers stages implement two different Schottky diodes in two different topologies: a single diode and a 2-stage Dickson’s charge pump. The second one is compared with the P2110 by generating RF fields at 915 MHz with the Powercast Powerspot. The main aim of this work is to design simple and efficient low-cost devices, which can be used as a power supply for low-power autonomous sensors, with better performances than the current solutions of state-of-the-art equipment, providing an acceptable voltage level on the load. Measurements have been conducted for input power range −20 dBm up to 10 dBm; the best power conversion efficiency (PCE) is obtained with the second design, which reaches a value of 70% at 915 MHz. In particular, the proposed device exhibited better performance compared to the P2110 commercial device, allowing a maximum distance of operation of up to 22 meters from the dedicated RF power source, making it suitable even for IoT (Internet of Things) applications.

In this paper, a new implementation of an electronically tunable resistor-less floating inductance simulator using a second-generation voltage conveyor (VCII) is presented. The proposed circuit is resistor-free (benefiting from the intrinsic resistors at the Y terminals of the employed VCIIs) and composed of three VCIIs and a single grounded capacitor. Using a control current (I_con), the value of impedance at the Y terminal of the VCII is varied, whereby the value of the simulated inductance is tuned. The proposed circuit is designed at a transistor level using 0.18 µm TSMC CMOS parameters and ±0.9 V supply voltage. PSpice simulations are carried out to confirm the effectiveness of the proposed circuit. For a range of Icon from 0 µA to 50 µA, the value of the simulated L can be varied from −576 µH to −324 µH and from +316 µH to +576 µH for negative and positive simulators, respectively, in the frequency range of 100 kHz–3 MHz. Favorably, the value of the series resistance remains below 76 Ω. Simulation results show an error value below 4.8% and power consumption variation is from 1.64 mW to 1.92 mW. Moreover, application of the proposed circuit as a standard band-pass RLC filter is also included.

In this paper, a new second generation voltage conveyor (VCII) topology with adaptive bias is presented. For the first time, adaptive bias has been exploited in a CMOS VCII circuit, with the goal of reducing power consumption without sacrificing transient performance, in order to design an active building block suitable for very low power sensor interface applications. Dynamic bias is achieved by means of a circuit capable of both detecting the difference between the input voltage at voltage input terminal and the voltage at output terminal, producing an additional bias current proportional to this difference. It is important to note that the same circuit can also sense an increase of the input current at the current-input node, as the current variation produces a voltage change at voltage input terminal. The new topology has been designed in $0.35\ \mu\mathrm{m}$ AMS technology with $\mathrm{a}\pm 0.9\ \mathrm{V}$ supply voltage, and Spice simulations were performed to evaluate performance in terms of slew-rate and power consumption. The same VCII topology, but without dynamic biasing, was also considered for comparison purposes: simulation results showed that the proposed topology is able to guarantee a reduction of more than 2 orders of magnitude in power consumption, with only 3 times worsening of the slew-rate.