Indoor Devices Research Articles

Smart Light Electricity Automation and Monitoring System Based on the Internet of Things (IOT) on Campus Environment Prototype

Efficient management of electrical energy is very important in the campus environment to support energy savings. This research aims to design and implement an Internet of Things (IoT)-based Smart Light system that automates light control and monitors electricity consumption in real-time. The system uses an ESP32 microcontroller integrated with PIR sensor and LDR sensor modules for automatic control, as well as ACS712 current and ZMPT101B voltage sensors to monitor electrical power. The collected data is processed in the microcontroller to calculate the electric power and cost, then displayed through a PHP and MySQL-based web dashboard that can be accessed in real-time. Tests were conducted on the campus prototype, showing an average error of 2.78% for current and 0.086% for voltage on indoor devices, and 2.86% for current and 0.343% for voltage on outdoor devices. The system is proven to be able to control lights automatically based on user presence and lighting conditions. Test results show that the system provides accurate monitoring of electricity consumption while improving operational efficiency. For example, the indoor device has higher accuracy in monitoring consumption data than the outdoor device, even though both devices show optimal performance. This system is expected to support electrical energy savings, improve energy use efficiency, and become an innovative solution in IoT-based energy management on campus.

Evaluation of an Indoor Location System Using Edge Computing and Machine Learning Algorithms

Evaluation of an Indoor Location System Using Edge Computing and Machine Learning Algorithms

Optical design of multilayer antireflection coatings for indoor solar cell applications.

Multilayer antireflection coatings (ARCs) for solar cells are conventionally designed to enhance the photocurrent level obtained at normal incidence. This is mainly because outdoor solar panels are usually placed such that they can receive strong midday sunlight at a nearly vertical angle. However, in the case of indoor photovoltaic devices, the direction of light changes considerably with changes in the relative position and angle between the device and light sources; therefore, it is often difficult to predict the incident angle. In this study, we explore a method to design ARCs suitable for indoor photovoltaics by essentially taking into account the indoor lighting environment, which is different from the outdoor conditions. We propose an optimization-based design strategy that aims to enhance the average level of the photocurrent generated when a solar cell receives irradiance randomly from all directions. We apply the proposed method to design an ARC for organic photovoltaics, which are expected to be promising indoor devices, and numerically compare the resultant performance with that obtained using a conventional design method. The results demonstrate that our design strategy is effective for achieving excellent omnidirectional antireflection performance and allows the realization of practical and efficient ARCs for indoor devices.

Regulating the Donor–Acceptor Interfaces to Reduce Trap Density for Efficient Indoor Organic Solar Cells

Organic solar cells (OSCs) are promising candidates for powering the Internet of Things and off‐grid devices due to the rapid improvement in power conversion efficiency under indoor light. However, the reported indoor devices are often taken straightforwardly from the champion solar cells under AM1.5 G irradiance without further optimization or more target design, which may underestimate their performance due to trap‐assisted charge recombination caused by discrepancies in incident light spectrum and intensity. Herein, It is identified that regulation of donor–acceptor interfaces is critical for reducing trap density in the active layer and thus improving the performance of indoor OSCs. By investigating bulk heterojunction and bilayer devices composed of PM6 and ITIC or ITIC‐2 F, reduced trap density is demonstrated by mitigation of the structural disorder of the active layer, leading to improved open‐circuit voltage. Additionally, the trap depth has a negligible effect on the device's performance with indoor light illumination. The results establish the correlations between donor–acceptor interfaces and charge recombination losses in bulk heterojunction and bilayer OSCs under indoor light, providing novel optimization guidelines for high‐performing indoor OSCs.

Silver–Bismuth Halide Double Salts for Lead‐Free Photovoltaics: Insights from Symmetry‐Based Modeling

Ag/Bi halide double salts, also called rudorffites, constitute a promising path to achieve low‐cost, high‐efficiency lead‐free optoelectronic devices, in particular solar cells. These materials present tunable gaps within the visible range, high short‐circuit currents, and interesting efficiencies in outdoor and indoor devices. Herein, a combination of symmetry analysis and first‐principles calculations is used to explore the structural, electronic, and optical properties of prototypical rudorffites solar cell absorbers AgBiI4 and Ag3BiI6. The challenges to model those ternary materials are first established. It is shown that Ag/Bi double salts cannot be modeled as random alloys. Second, a Wyckoff position splitting method is developed leading to the generation of model structures, which are unique for each compound, and agrees with experimental structural data. These structures are used to establish the optoelectronic properties of AgBiI4 and Ag3BiI6. Finally, the ideal photovoltaic performance of the materials is predicted through the spectral limited maximum efficiency approach. It is shown that AgBiI4 presents a slightly higher potential for solar cell applications, and the realized devices are mostly limited by the low open‐circuit voltage. The structural models developed here can help unveiling complex properties of the materials and explore substitutional engineering within halide double salts.

Hand-Held Haptic Navigation Devices for Actual Walking.

In this survey, we give an overview of hand-held haptic navigation devices specifically designed for and tested with pedestrians. We distinguish devices for indoor use and for outdoor use as the implementation is usually quite different. Outdoor devices make use of Global Positioning Systems (GPS) tracking built-in in smartphones; indoor devices use a variety of sensors, and tracking and localization systems and these are usually restricted to a small part of a building. Overall, the high success rates reported in the studies show that vibrotactile stimulation via a hand-held user interface is suitable for navigation instructions, as in all experiments (almost) all participants reached their goal. An issue for several of the indoor devices is that walking speeds were (much) lower than normal walking speeds and path efficiency was relatively low. However, these issues might be overcome with some training as in most studies there was hardly any practice time. Several of the outdoor devices seem quite close to taking the last step before commercial use. In the Discussion, we evaluate the suitability of the devices for persons with visual and/or hearing impairments. Especially devices that provide very specific instructions, such as, 'go straight' or 'go right,' seem valuable for this population.

Wi-Fi technology and human health impact: a brief review of current knowledge.

An enormous increase in the application of wireless communication in recent decades has intensified research into consequent increase in human exposure to electromagnetic (EM) radiofrequency (RF) radiation fields and potential health effects, especially in school children and teenagers, and this paper gives a snap overview of current findings and recommendations of international expert bodies, with the emphasis on exposure from Wi-Fi technology indoor devices. Our analysis includes over 100 in vitro, animal, epidemiological, and exposure assessment studies (of which 37 in vivo and 30 covering Wi-Fi technologies). Only a small portion of published research papers refers to the “real” health impact of Wi-Fi technologies on children, because they are simply not available. Results from animal studies are rarely fully transferable to humans. As highly controlled laboratory exposure experiments do not reflect real physical interaction between RF radiation fields with biological tissue, dosimetry methods, protocols, and instrumentation need constant improvement. Several studies repeatedly confirmed thermal effect of RF field interaction with human tissue, but non-thermal effects remain dubious and unconfirmed.

High performance indoor light harvesters with a wide-gap donor polymer PBDB-T

Organic solar cells have received widespread attention with the development of indoor light harvesters. Due to the narrow emission spectra and weak light intensity of indoor emissions, the short-circuit current of indoor devices is largely restricted, and there would be an additional voltage loss around 0.15 V from the light intensity difference. However, most state-of-the-art cells cannot be adopted as indoor photovoltaics directly, because their small optical bandgaps lead to open-circuit voltage ( V OC ) values in the range of ~0.6 V in dim-lighting, which is difficult to drive most of internet of things. Herein, we revaluate the photovoltaic performance under indoor illuminances by combining a wide-gap polymer PBDB-T with various electron-accepting materials. The PBDB-T: BTA3 cell achieves an excellent efficiency higher than 25% under a 1000 lux 2700K LED illumination. The V OC value of such a device can still maintain close to 1 V under indoor cases. We then compare the underlying mechanism of the PBDB-T-based bulk heterojunctions (BHJs) with multiple techniques, and the results indicate the unchanged advantage of high V OC helps the BTA3-based cell shows the best indoor device performance when the light source is switched from AM1.5G to low illumination. This work revaluates the selection of state-of-the-art indoor light harvesters, and demonstrate an excellent optimal efficiency of the PBDB-T:BTA3 indoor cell up to 25.6%, with a desirable V OC of 0.99 V. In this work, we revaluate the relationship between high Voc and high performance of OPV devices for indoor light applications by combining a wide-gap polymer donor PBDB-T with a series of electron-accepting materials. We also demonstrate an excellent optimal efficiency of the PBDB-T: BTA3 indoor cell up to 25.6%, with a desirable Voc of 0.99 V.

Tracking Devices for Pets: Health Risk Assessment for Exposure to Radiofrequency Electromagnetic Fields.

Simple SummaryTo increase the probability of reunions occurring between owners and lost pets, tracking devices are applied to pets. The pet’s position is determined by satellites (e.g., GPS) and transmitted by radio frequencies (RFs) to a mobile phone. In this study, the health risks from exposure to radio frequencies emitted by radios, TVs, mobile networks, indoor devices (e.g., WLAN, Bluetooth), mobile phones, and in the use of such tracking devices were investigated. The radiation exposure was found to be well below international limit values, which means that adverse health effects are unlikely to occur. The risk of high exposure of pets is mainly caused by indoor RF-emitting devices, such as WLAN devices. This exposure can be limited through a reduction in the exposure time and an increase in the distance between the animal and the RF-emitting device. Even though the exposure of pets to total radiofrequency electromagnetic field (RF-EMF) levels was found to be below the limit values—and, therefore, not a health risk—recommendations are given for the use of tracking devices and to limit the exposure to indoor devices.Every year, approximately 3% of cats and dogs are lost. In addition to passive methods for identifying pets, radiofrequency tracking devices (TDs) are available. These TDs can track a pet’s geographic position, which is transmitted by radio frequencies. The health risk to the animals from continuous exposure to radiofrequency electromagnetic fields (RF-EMFs) was reviewed. Fourteen out of twenty-one commercially available TDs use 2G, 3G, or 4G mobile networks, and the others work with public frequencies, WLAN, Bluetooth, etc. The exposure of pets to RF-EMFs was assessed, including ambient exposure (radios, TVs, and base stations of mobile networks), exposure from indoor devices (DECT, WLAN, Bluetooth, etc.), and the exposure from TDs. The exposure levels of the three areas were found to be distinctly below the International Commission on Non-Ionising Radiation Protection (ICNIRP) reference levels, which assure far-reaching protection from adverse health effects. The highest uncertainty regarding the exposure of pets was related to that caused by indoor RF-emitting devices using WLAN and DECT. This exposure can be limited considerably through a reduction in the exposure time and an increase in the distance between the animal and the RF-emitting device. Even though the total RF-EMF exposure level experienced by pets was found to be below the reference limits, recommendations were derived to reduce potential risks from exposure to TDs and indoor devices.

Different Morphology Dependence for Efficient Indoor Organic Photovoltaics: The Role of the Leakage Current and Recombination Losses.

Efficient indoor organic photovoltaics (OPVs) have attracted strong attention for their application in indoor electronic devices. However, the route to optimal photoactive film morphology toward high-performance indoor devices has remained obscure. The leakage current dominated by morphology exerts distinguishing influence on the performance under different illuminations. We have demonstrated that morphology reoptimization plays an important role in indoor OPVs, and their optimal structural features are different from what we laid out for outdoor devices. For indoor OPVs, in order to facilitate low leakage current, it is essential to enhance the crystallinity, phase separation, and domain purity, as well as keeping small surface roughness of the active layer. Furthermore, considering the reduced bimolecular recombination at low light intensity, we have shown that PM6:M36-based indoor devices can work effectively with a large ratio of the donor and acceptor. Our work correlating structure-performance relation and the route to optimal morphology outlines the control over device leakage current and recombination losses boosting the progress of efficient indoor OPVs.

Survey of Millimeter-Wave Propagation Measurements and Models in Indoor Environments

The millimeter-wave (mmWave) is expected to deliver a huge bandwidth to address the future demands for higher data rate transmissions. However, one of the major challenges in the mmWave band is the increase in signal loss as the operating frequency increases. This has attracted several research interests both from academia and the industry for indoor and outdoor mmWave operations. This paper focuses on the works that have been carried out in the study of the mmWave channel measurement in indoor environments. A survey of the measurement techniques, prominent path loss models, analysis of path loss and delay spread for mmWave in different indoor environments is presented. This covers the mmWave frequencies from 28 GHz to 100 GHz that have been considered in the last two decades. In addition, the possible future trends for the mmWave indoor propagation studies and measurements have been discussed. These include the critical indoor environment, the roles of artificial intelligence, channel characterization for indoor devices, reconfigurable intelligent surfaces, and mmWave for 6G systems. This survey can help engineers and researchers to plan, design, and optimize reliable 5G wireless indoor networks. It will also motivate the researchers and engineering communities towards finding a better outcome in the future trends of the mmWave indoor wireless network for 6G systems and beyond.

Research and Development of Smart Home Security System Based on Wechat Control

With the improvement of living standards, people’s requirements for safety and comfort gradually improve, which requires us to constantly improve home security. With the rapid development of the Internet of things (hereinafter referred to as IOT), we have set up a smart home security system (hereinafter referred to as SHSS), which can be controlled by wechat. Through the IOT technology, the SHSS can contact various subsystems according to the needs of users, including lighting control, security protection, fire prevention and anti-theft, which will bring more humanized operation experience. Through wireless communication technology, we can monitor all kinds of indoor environment in real time, which will prevent illegal intrusion and other behaviors. At the same time, with the popularity of Android, IOS and other mobile platforms, SHSS has been developed into a variety of applications, such as wechat, which can realize remote control of indoor devices. Firstly, this paper analyzes the overall architecture and control module of SHSS. Then, this paper analyzes various subsystems, which can complete the system development in more detail.

Organic indoor light harvesters achieving recorded output power over 500% enhancement under thermal radiated illuminances

Organic photovoltaic (OPV) cells have found their potential applications in the harvest of indoor light photons. However, the output power of such indoor devices is usually far from the demand of the internet of things. Therefore, it is essential to boost the output power of indoor organic photovoltaics to a much higher level. As wildly deployed among industrial and civil luminous environments, thermal radiation-based indoor light sources are alternative candidates to supply the essential power of the off-grid electronics with a broad consecutive emission spectrum. In this work, we evaluated the photovoltaic performance of organic solar cells under indoor incandescent and halogen illuminations. Impressively, under such thermal radiations, an improvement over 500% of the output power density can be achieved in comparison with that under light-emitting diodes and fluorescent lamps, reaching a record high value of 279.1 μW cm−2 by the PM6:Y6-based device. The remarkable power output is originated from the extra near-infrared spectrum of indoor thermal lights, which restricts the effective area under 10 cm2 in achieving 1 mW output power. This work clarifies the feasibility of collecting photons radiated from indoor thermal light sources through OPV cells, and enlightens the further applications of indoor OPV cells under multiple illumination environments.

Eyes on the Goal! Exploring Interactive Artistic Real-Time Energy Interfaces for Target-Specific Actions in the Built Environment

Current research is focused on sensing and modeling occupant behavior to predict it and automate building controls. Another line of research recommends influencing the behavior of occupants through feedback mechanisms and engagement. Yet, most of the work has focused on pushing occupants to reduce energy consumption over a long time and does not explore the potential to guide users to take specific actions promptly. The study examines a new interface mechanism that aims to solicit immediate and predefined actions from occupants. Building on seminal research in the field, the study uses art visualization to reinterpret social feedback. We test this approach in an immersive interaction space where participants react to artistic visuals to attain predefined settings for three indoor devices. In the 197 interactions recorded, participants’ overall actions conformed with the predefined goals. The participants were able to reach all or some of the targets in more than 80%, within an average of less than 30 seconds. We also see that complementing the visuals with textual hints improved the interaction in terms of engagement and accuracy. We conclude that ambient, abstract, and artistic real-time goal-driven feedback is effective in influencing immediate actions. We recommend that guiding occupants didactically has a strong potential for advancing building controls.

Classroom Attendance Systems Based on Bluetooth Low Energy Indoor Positioning Technology for Smart Campus

Student attendance during classroom hours is important, because it impacts the academic performance of students. Consequently, several universities impose a minimum attendance percentage criterion for students to be allowed to attend examinations; therefore, recording student attendance is a vital task. Conventional methods for recording student attendance in the classroom, such as roll-call and sign-in, are an inefficient use of instruction time and only increase teachers’ workloads. In this study, we propose a Bluetooth Low Energy-based student positioning framework for automatically recording student attendance in classrooms. The proposed architecture consists of two components, an indoor positioning framework within the classroom and student attendance registration. Experimental studies using our method show that the Received Signal Strength Indicator fingerprinting technique that is used in indoor scenarios can achieve satisfactory positioning accuracy, even in a classroom environment with typically high signal interference. We intentionally focused on designing a basic system with simple indoor devices based on ubiquitous Bluetooth technology and integrating an attendance system with computational techniques in order to minimize operational costs and complications. The proposed system is tested and demonstrated to be usable in a real classroom environment at Rangsit University, Thailand.

Towards a reactive system for managing big trajectory data

Spatio-temporal events often describe the movements of an object in terms of space, time, and potential other attributes. Significant knowledge can be inferred by analysing them, either individually or atomically in form of trajectories. The trajectories can abstract additional properties and lead to deeper value. Moreover, external contextual information can be attributed to them to change their structure and lead to different perspectives. Because of this potentially valuable knowledge, nowadays indoor and outdoor tracking devices are used everywhere; generating countless events instantaneously. However, the extraction of knowledge from such heterogeneous, massive data is not a trivial task. In other terms, there is a need for a sophisticated system that is efficient in terms of distributed computing, failure handling, responsiveness, and abstraction. To answer this need, our study incorporates a fully fledged, reactive system for big trajectory data management. The system is unique of its kind because it is actor-based and features responsiveness, resiliency, and elasticity. Furthermore, our system is implemented using Scala; hence, we have the expressive power of both the Object-Oriented (OO) and Functional Programming (FP) paradigms. Allowing us to reach a higher level of abstraction to be able to process any trajectory type. The scope of this paper is to detail our system and discuss elasticity, routing strategies, load balancing, and our proper fault-tolerance mechanism. To fulfill this study, we consider the Geolife project’s GPS trajectory dataset.

Experimental Demonstration of MmWave Vehicle-to-Vehicle Communications Using IEEE 802.11ad.

Millimeter wave (mmWave) vehicle-to-vehicle (V2V) communications has received significant attention as one of the key applications in 5G technology, which is called as Giga-V2V (GiV2V). The ultra-wide band of the GiV2V allows vehicles to transfer gigabit data within a few seconds, which can achieve platooning of autonomous vehicles. The platooning process requires the rich data of a 4K dash-camera and LiDAR sensors for accurate vehicle control. To achieve this, 3GPP, a global organization of standards that provides specifications for the 5G mobile technology, is developing a new standard for GiV2V technology by extending the existing specification for device-to-device (D2D) communication. Meanwhile, in the last decade, the mmWave spectrum has been used in the wireless local area network (WLAN) for indoor devices, such as home appliances, based on the IEEE 802.11ad (also known as Wireless Gigabit Alliance (WiGig)) technology, which supports gigabit wireless connectivity of approximately 10 m distance in the 60-GHz frequency spectrum. The WiGig technology has been commercialized and used for various applications ranging from Internet access points to set-top boxes for televisions. In this study, we investigated the applicability of the WiGig technology to the GiV2V communications through experiments on a real vehicular testbed. To achieve this, we built a testbed using commercial off-the-shelf WiGig devices and performed experiments to measure inter-vehicle connectivity on a campus and on city roads with different permitted vehicle speeds. The experimental results demonstrate that disconnections occurred frequently due to the short radio range and the connectivity varied with the vehicle speed. However, the instantaneous throughput was sufficient to exchange large data between moving vehicles in different road environments.

Ultra-thick semi-crystalline photoactive donor polymer for efficient indoor organic photovoltaics

An in-depth study on the photovoltaic characteristics under indoor lights, i.e., light-emitting diode (LED), fluorescent lamps, and halogen lamps, was performed with varying the photoactive layer thickness (120–870 nm), by comparing those under 1-sun condition. The semi-crystalline mid-gap photoactive polymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole)] (PPDT2FBT) and a fullerene derivative, [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) were used as a photoactive layer. In the contrary to the measurements under 1-sun condition, the indoor devices show a clearly different behavior, showing the thickness tolerant short-circuit current density (JSC) and fill factor (FF) values with 280–870 nm thick photoactive layers. The retained JSC and FF values of thick indoor devices were discussed in terms of the parasitic resistance effects based on the single-diode equivalent circuit model. The much lower series/shunt resistance (Rs/RP) ratio was measured with thick photoactive layer (≥280 nm), resulting in negligible decreases in the JSC and FF values even with a 870-nm-thick active layer under the LED condition. Under 1000 lx LED light, the PPDT2FBT:PC70BM device showed an optimum power conversion efficiency (PCE) of 16% (max power density, 44.8 μW/cm2) with an open-circuit voltage of 587 mV, a JSC of 117 μA/cm2, and a FF of 65.2. The device with a 870-nm-thick active layer still exhibited an excellent performance with a PCE of 12.5%. These results clearly suggest that the critical parasitic resistance effects on the performance vary depending on the light illumination condition, and the large RP associated with the viable thick photoactive layer and the well-matched absorption (of photoactive layer) with the irradiance spectrum (of indoor light) are essential to realize efficient indoor photovoltaic cells with high JSC and FF.

Green Survivable Collaborative Edge Computing in Smart Cities

As an integrated environment deployed with wired and wireless infrastructures, the smart city heavily relies on the wireless-optical broadband access network. The information flows captured by indoor devices are sent to optical network units through front-end wireless mesh sensor networks (WMNs) and, finally, reach the optical line terminal for industrial/commercial decision making via the passive optical network backhaul. To reduce the backhaul bandwidth saturated by this conventional approach, edge devices are deployed at the front-end WMN to preprocess information flows. Based on collaborative edge computing, home users or factory workers customize their computing services as virtual networks embedded onto the common WMN. In this paper, we propose the green survivable virtual network embedding for the collaborative edge computing in smart cities. We mathematically formulate the problem and derive the corresponding bound. Extensive simulations with real traces demonstrate the algorithm effectiveness.

Case study of an advanced integrated comfort control algorithm with cooling, ventilation, and humidification systems based on occupancy status

In this study, we propose a new control algorithm based on occupancy status for indoor environmental devices to maintain thermal comfort while saving energy of residential buildings. The algorithm consists of two parts: an environmental data driven model for the occupancy status detection and an integrated comfort algorithm for operating the indoor devices. To detect the occupancy status, a multinomial logistic regression model is developed based on the data obtained from passive infrared (PIR) sensors, a door sensor, CO2 concentrations, and lighting electricity consumption. The occupancy status is categorized into three classes: away, active, and inactive (sleep).The new control algorithm integrates and operates air-conditioning, ventilation, and humidification systems by considering the outdoor environment, and ensuring indoor thermal comfort and energy savings at each occupancy status. The control algorithm is evaluated at different outdoor conditions with a testbed that consists of a variable refrigerant flow (VRF) air conditioning system, humidifier, and ventilation system.The performance of the proposed control algorithm is experimentally compared with that of a conventional individual control method in terms of the thermal comfort and energy consumption. The results show that the advanced integrated comfort control system improves the thermal comfort and decreases the energy consumption. Specifically, Case 1 (active, hot, and mild humidity) exhibits a 6.3% energy reduction and 64% improvement in the thermal comfort. Case 2 (active, hot, and low humidity) shows a 21% energy reduction and 72% improvement in the thermal comfort. Case 3 (inactive, comfort indoors) displays a 7% energy increase and 31% improvement in the thermal comfort. These results confirm that the proposed advanced integrated comfort control algorithm could be useful for designing better space environmental control to ensure thermal comfort and energy conservation.