Search Results (27)

An antenna-level bias-line-free, optically controlled pattern-reconfigurable planar antenna for wideband sub-6 GHz applications is presented. The proposed antenna consists of four tapered-slot radiating units arranged in a compact planar configuration and excited through a reconfigurable feeding network incorporating four light-dependent resistors (LDRs). By selectively illuminating LDRs using aligned LEDs, the corresponding feed arms are activated without DC-bias lines embedded in the antenna itself, enabling pattern switching while avoiding a complicated biasing network. The antenna supports ten radiation states, including four principal directions (0°, 90°, 180°, and 270°), four diagonal directions (45°, 135°, 225°, and 315°), and two dual-beam excitations (0°/180° or 90°/270°). Measured results show impedance matching over 3.3–6.7 GHz for all states (at −10 dB |S₁₁| reference), with a realized gain of 5.8–6.3 dBi and a total radiation efficiency of 86–90% across the operating band. The proposed approach offers a compact, wideband, and practically implementable platform for bias-free pattern reconfiguration suitable for coverage and interference adaptation in sub-6 GHz wireless systems. Full article

Particle Image Velocimetry (PIV) has recently evolved from a costly, specialized technique into an accessible method thanks to affordable hardware and open-source software. This work introduces a time calibration validation method tailored for low-cost or Do-It-Yourself (DIY) PIV systems. By utilizing inexpensive components such as light-dependent resistors (LDRs), basic resistors, and data acquisition devices or microcontrollers, the study enables accurate timing analysis of light pulses from synchronized lasers or LEDs. Experimental data obtained in real time using a National Instruments USB-6003 DAQ device confirm the system’s ability to detect light pulses with high temporal resolution. Through voltage signal interpretation, the synchronization accuracy of light sources is validated across different sampling rates. Moreover, the study demonstrates how the internal frequency settings of PIVlab, an open-source PIV software package, can be customized to enhance acquisition flexibility. Timing deviations of up to 20% were identified across selected default frequency settings. The proposed method ensures that low-cost systems maintain sufficient accuracy for phase-sensitive flow measurements, such as oscillatory flow or wave action, contributing to the broader adoption of PIV in resource-limited environments. It presents a low-cost method for validating timing accuracy in PIV systems, employs widely available components and is adaptable to multiple platforms, and enables precise synchronization checks critical for flow visualization. Full article

Low-cost and portable analytical devices are increasingly relevant for decentralized measurements, in situ monitoring, and educational applications. This study presents the design, construction, and validation of a low-cost, portable colorimeter for the indirect determination of ethanol in aqueous solutions via dichromate oxidation. Built with accessible components, including an Arduino microcontroller, an RGB LED, and a light-dependent resistor (LDR) photodetector, the device provides a simple open-hardware platform for visible-range colorimetric measurements without the need for optical filters. Ethanol concentration is determined through oxidation in an acidic medium, generating an optical response proportional to the analyte concentration. Data processing is performed using open-source Python scripts combined with Gaussian fitting for signal extraction and calibration. The main novelty of the system lies in integrating simplified optical components, open-hardware architecture, and computational signal processing to obtain reliable analytical responses in a portable, accessible format. The device’s performance was compared with a commercial UV–Vis spectrophotometer, showing linear behavior over 0.5–1.5% (v/v) ethanol (R² = 0.99) and relative errors below 11% for beverage samples. These results demonstrate that the proposed system is a reliable and cost-effective alternative for rapid ethanol analysis in relatively simple alcoholic matrices. Full article

Single-chip integration technology for multifunctional sensors has become an important development direction due to its low power consumption and versatile functionality. However, the fabrication compatibility between different sensing components remains a key challenge for high-performance integrated sensors, often leading to complex processes and increased costs. This work presents a microfabrication-compatible photo-magnetic integrated sensor chip based on micro–nano processing methods. The integrated sensor chip includes giant magnetoresistance (GMR) and a light-dependent resistor (LDR). The fabrication process was based on standard MEMS fabrication with compatibility and cost-effectiveness. The experimental results demonstrated that the chip can simultaneously realize both optical and magnetic detection with magnetic field sensitivity of 3.74 mV/Oe and photodetection sensitivity of 0.79 $\mathsf{\mu }$A/($\mathsf{\mu }$W/cm²) at a 5 V bias. The integrated sensor features high-sensitivity magnetic performance and weak-light detection capability, with promising application in robotics and advanced manufacturing fields. Full article

This paper presents a high-gain wide-band planar antenna with a Reconfigurable Intelligent Surface (RIS) for modern wireless communication applications. The antenna consists of two main parts, a basic antenna part with cross-line slots and two light-dependent resistor switches, and a second part based on the RIS layer for beam steering. The RIS is constructed from 5 × 5-unit cells with two sides, forming a square geometry. The antenna substrate is a dielectric layer of FR4 epoxy glass with a thickness of 1.6 mm. The RIS inclusions are designed and tested numerically to achieve the desired electromagnetic properties at the frequency band of interest. The fabricated prototype shows a wide band covering frequencies from 0.9 GHz to 3.5 GHz with S11 below −10 dB, achieving an antenna gain varying from 10.5 dBi up to 16.8 dBi. Experimental measurements show effective aperture usage in all configurations, and beam steering from +22° to −22° is accomplished without degrading side-lobe levels. The proposed antenna performance is tested against real-world measurements to evaluate channel performance in terms of bit error rate (BER) and channel capacity (CC). The proposed LDR-controlled design achieves compact beam steering with minimal insertion loss, unlike conventional RIS-assisted antennas that rely on PIN or varactor switches. Full article

A bias-free antenna tuning technique that eliminates conventional DC biasing networks is presented. The tuning mechanism is based on a Light-Dependent Resistor (LDR) embedded within the antenna structure. Optical illumination is used to modulate the LDR’s resistance, thereby altering the antenna’s effective electrical length and enabling tuning of its resonant frequency and operating bands. By removing the need for bias lines, RF chokes, blocking capacitors, and control circuitry, the proposed approach minimizes parasitic effects, losses, biasing energy, and routing complexity. This makes it particularly suitable for compact and energy-constrained platforms, such as Internet of Things (IoT) devices. As proof of concept, an LDR is integrated into a ring monopole antenna, achieving tri-band operation in both high and low resistance states. In the high-resistance (OFF) state, the fabricated prototype operates across 2.1–3.1 GHz, 3.5–4 GHz, and 5–7 GHz. In the low-resistance (ON) state, the LDR bridges the two arcs of the monopole, extending the current path and shifting the lowest band to 1.36–2.35 GHz, with only minor changes to the mid and upper bands. The antenna maintains linear polarization across all bands and switching states, with measured gains reaching up to 5.3 dBi. Owing to its compact, bias-free, and low-cost architecture, the proposed design is well-suited for integration into portable wireless devices, low-power IoT nodes, and rapidly deployable communications systems where electrical biasing is impractical. Full article

Fixed solar panels face significant energy loss as they cannot consistently capture optimal sunlight. Because of that, the overall efficiency of the PV panel will be reduced, and the installation requires larger land space to generate appropriate power; this stems from the use of a dual-axis solar tracking system, which can significantly increase overall energy production. The system is based on the combination of two approaches to precisely track the sunlight: first, using multiple LDRs (light-dependent resistors) as photo sensors to track the position of the sun by balancing the resistivity using a proportional integral deprival (PID) controller, and the second approach using the time-based control for cloudy days when sunlight is diffused, getting the time GPS coordinates and time to calculate the accurate position of the sun by determining the azimuth and altitude angle. This dual system significantly improves energy production by 33.23% compared to fixed systems and eliminates errors during shaded conditions while reducing unnecessary energy use from continuous GPS activation. The prototype uses two linear actuators for both angles and a 100-watt solar panel mounted on the dual-axis platform. Full article

Ecuador is grappling with a severe energy crisis, marked by frequent power outages. A recent study explored solar energy efficiency in the coastal city of Manta using an IoT real-time monitoring system to compare static photovoltaic (PV) systems with two single-axis solar tracking systems: one based on astronomical programming and the other using light-dependent resistor (LDR) sensors. Results showed that both tracking systems outperformed the static PV system, with net gains of 31.8% and 37.0%, respectively. The astronomical-programming-based system had a slight edge, operating its stepper motor intermittently for two minutes per hour, while the LDR system required continuous motor energization. The single-axis tracker using astronomical programming demonstrated notable advantages in energy efficiency and complexity, making it suitable for equatorial regions like Manta. The study also suggested potential further gains by adjusting solar positioning at shorter intervals, such as every 15 or 30 min. These findings enhance our understanding of solar tracking performance in equatorial environments, offering valuable insights for optimizing solar energy systems in regions with high solar radiation. By emphasizing customized solar tracking mechanisms, this research presents promising solutions to Ecuador’s energy crisis and advances sustainable energy practices. Full article

In this study, a modular, multi-step, photometric microflow injection analysis (micro-FIA) system for the automatic determination of Cu(II) in a bioreactor was developed. The system incorporates diverse 3D-printed modules, including a platform formed by a mixer module to mix Cu(II) with hydroxylamine, which reduces Cu(II) to Cu(I) linked to a diluter module via a Tesla valve, a chelation mixer module, a disperser module, and a detector module provided by an LED light source at λ = 455 nm and a light dependence resistor (LDR) as a light intensity detector. The system measures the color intensity resulting from the chelation between Cu(I) and neocuproine. The micro-FIA system demonstrated good capability for automatic and continuous Cu(II) determination, in a wide range of Cu concentrations, from 34 to 2000 mg L⁻¹. The device exhibits a good repeatability (coefficient of variation below 2% across the measured concentration range), good reproducibility, and has an accuracy of around 100% between 600 and 1900 mg L⁻¹. Real samples were analyzed using both the micro-FIA system and an atomic absorption spectroscopy method, revealing no statistically significant differences. Additionally, a Tesla valve located before the detector substituted a 3-way solenoid valve, eliminating the need for moving parts. Full article

This research presents an analysis of the five-position angle in both single-axis (one-axis tracking) and dual-axis (two-axis tracking) solar tracking systems. The study compares these tracking systems, where four solar panels move simultaneously, with a fixed solar panel system. The findings revealed that the five-position angle Sun-tracking technique resulted in lower energy consumption by the tracking mechanism than in the case of an all-time solar tracking system. The key component of the implemented system is a light-dependent resistor (LDR) sensor for controlling the motion of the motor for five positions on the vertical axis and horizontal axis, processed by a microcontroller to ensure the necessary solar tracking always moves in a perpendicular direction. According to the results, the voltage, current, and power increased with both one-axis and two-axis tracking compared to those of the fixed solar panel system under the same conditions. However, when evaluating the total energy with numerical integration methods, one-axis and two-axis provided 183.12 Wh and 199.79 Wh, respectively. Consequently, the energy production of the one-axis tracking system and the one-axis tracking system was found to be 16.71% and 24.97%, respectively, when compared to the fixed-axis system. Thus, the five-position angles of the sun-tracking technique resulted in lower energy consumption than is the case of an all-time solar tracking system. Full article

A novel design of a reconfigurable MIMO antenna array of a 3D geometry-based solar cell integration that is operating at sub-6 GHz for self-power applications in a 5G modern wireless communication network. The proposed antenna array provides three main frequency bands around 3.6 GHz, 3.9 GHz, and 4.9 GHz, with excellent matching impedance of S₁₁ ≤ −10 dB. The proposed MIMO array is constructed from four antenna elements arranged on a cubical structure to provide a low mutual coupling, below −20 dB, over all frequency bands of interest. Each antenna element is excited with a coplanar waveguide (CPW). The proposed radiation patterns are controlled with two optical switches of Light Dependent Resistors (LDRs). The proposed antenna array is fabricated and tested experimentally in terms of S-parameters, gain and radiation patterns. The maximum gain is found to be 3.6 dBi, 6.9 dBi, and 3.5 dBi at 3.6 GHz, 3.9 GHz, and 4.9 GHz, respectively. It is realized that the proposed array realizes a significant beam forming by splitting the antenna beam and changing the main lobe direction at 3.9 GHz after changing LDR switching statuses. Such an antenna array is found to be very applicable for femtocell wireless communication networks in the 5G systems. Full article

Radio frequency identification (RFID) represents an emerging platform for passive RF-powered wireless sensing. Differential Multi-port RFID systems are widely used to enable multiple independent measurands to be gathered, or to overcome channel variations. This paper presents a dual-port/dual-integrated circuit (IC) RFID sensing tag based on a shared aperture dual-polarized microstrip antenna. The tag can be loaded with different sensors where the received signal strength indicator (RSSI) of one IC is modulated using a sensor, and the other acts as a measurand-insensitive reference, for differential sensing. The 868 MHz tag maintains a minimum unloaded read range of 14 m insensitive to deployment on metals or lossy objects, which represents the longest reported range of a multi-port RFID sensing tag. The tag is loaded with a light-dependent resistor (LDR) to demonstrate its functionality as a battery-less wireless RFID light sensor. Following detailed RF characterization of the LDR, it is shown that the impedance, and consequently the RSSI, of the sensing tag are modulated by changing the light intensity, whereas the reference port maintains a mostly unchanged response for a correlated channel. The proposed tag shows the potential for channel variations-tolerant differential RFID sensing platforms based on polarization-diversity antennas. Full article

The performance of perovskite solar cells (PSCs) has been improved throughout the years. These photovoltaic (PV) cells can be used to power Internet of Things (IoT) devices for indoor applications. A perovskite PV energy harvesting system with a stand-by battery that continuously powers an IoT device is developed in this work. The battery is required to complement the PSCs when the latter have difficulties in power delivery during low or no irradiance. The performance of the energy harvesting circuit as well as the battery charge and discharge scenarios are investigated. Voltage matching between the PSC and the battery is achieved by a boost converter. The PSC energy harvesting system uses fractional open-circuit voltage (FOCV) based maximum power point tracking (MPPT), which utilizes a Sample and Hold (S&H) circuit. The FOCV technique is based on a comparison of the perovskite PV open circuit voltages and the maximum power points. For each irradiance level, the maximum power point is unique, and this work uses a light-dependent resistor (LDR) to adjust the scaling constant in MPPT. Case studies include various scenarios under 1000 lux fluorescent light and 1 sun irradiance as well as a consideration of different battery states. Full article

Crop geometry plays a vital role in ensuring proper plant growth and yield. Check row planting allows adequate space for weeding in both direction and allowing sunlight down to the bottom of the crop. Therefore, a light detection and ranging (LiDAR) navigated electronic seed metering system for check row planting of maize seeds was developed. The system is comprised of a LiDAR-based distance measurement unit, electronic seed metering mechanism and a wireless communication system. The electronic seed metering mechanism was evaluated in the laboratory for five different cell sizes (8.80, 9.73, 10.82, 11.90 and 12.83 mm) and linear cell speed (89.15, 99.46, 111.44, 123.41 and 133.72 mm·s⁻¹). The research shows the optimised values for the cell size and linear speed of cell were found to be 11.90 mm and 99.46 mm·s⁻¹ respectively. A light dependent resistor (LDR) and light emitting diode (LED)-based seed flow sensing system was developed to measure the lag time of seed flow from seed metering box to bottom of seed tube. The average lag time of seed fall was observed as 251.2$\pm$5.39 ms at an optimised linear speed of cell of 99.46 mm·s⁻¹ and forward speed of 2 km·h⁻¹. This lag time was minimized by advancing the seed drop on the basis of forward speed of tractor, lag time and targeted position. A check row quality index ($I_{CRQ}$) was developed to evaluate check row planter. While evaluating the developed system at different forward speeds (i.e., 2, 3 and 5 km·h⁻¹), higher standard deviation (14.14%) of check row quality index was observed at forward speed of 5 km·h⁻¹. Full article

In this paper, a prototype of a semi-automatic lab-on-PCB for agarose gel preparation and electrophoresis is developed. The dimensions of the device are 38 × 34 mm${}^2$ and it includes a conductivity sensor for detecting the TAE buffer (Tris-acetate-EDTA buffer), a microheater for increasing the solubility of the agarose, a negative temperature coefficient (NTC) thermistor for controlling the temperature, a light dependent resistor (LDR) sensor for measuring the transparency of the mixture, and two electrodes for performing the electrophoresis. The agarose preparation functions are governed by a microcontroller. The device requires a PMMA structure to define the wells of the agarose gel, and to release the electrodes from the agarose. The maximum voltage and current that the system requires are 40 V to perform the electrophoresis, and 1 A for activating the microheater. The chosen temperature for mixing is 80 ${}^{\circ }$C, with a mixing time of 10 min. In addition, the curing time is about 30 min. This device is intended to be integrated as a part of a larger lab-on-PCB system for DNA amplification and detection. However, it can be used to migrate DNA amplified in conventional thermocyclers. Moreover, the device can be modified for preparing larger agarose gels and performing electrophoresis. Full article