Electrical resistivity surveying is a fundamental geophysical technique for subsurface characterization, based on the measurement of apparent resistivity using the four-point method. The reliable acquisition of these data requires high-resolution and stable instrumentation, capable of detecting small variations in electrical signals.This article presents the development of a low-cost, high-resolution data acquisition system based on a 24-bit analog-to-digital converter (ADC), which enables the recording of injected currents and resulting voltages in the subsurface. The system incorporates automatic polarity reversal, allowing the discrimination of spontaneous potential and improving the quality of the measurements.The system was validated through laboratory tests of linearity, repeatability, temporal stability, and dynamic range, using precision resistors and comparing the results with a commercial resistivity meter. The results demonstrate stable and reproducible performance, with the capability to measure low-magnitude signals, making the system suitable for electrical resistivity surveying applications.
Soil degradation, freshwater scarcity, and urbanization are increasing the demand for resource-efficient food production systems. Controlled environment agriculture (CEA), particularly aeroponics, enables efficient crop production with reduced water and nutrient use; however, most existing systems rely on grid electricity and involve high implementation costs.This work presents TOTEM, an open-source, solar-powered vertical aeroponic system implemented for energy-autonomous soilless agriculture. Developed for universal replication, the design allows for modification or scaling using widely available materials. The system integrates a modular stacked architecture comprising growth, reservoir, pumping, filtration, control, and power units. A microcontroller-based embedded controller manages irrigation cycles and monitors chamber temperature and nutrient solution level, whereas a photovoltaic module enables fully off-grid operation.The system was built to support up to 24 plants within a compact footprint (0.078 m3) and validated using basil (Ocimum basilicum) under two successive harvest cycles. Results demonstrated stable irrigation performance, uniform nutrient distribution, and reliable operation on solar power. Biomass production confirmed the system capability to sustain plant growth under continuous operation.TOTEM provides a scalable, low-cost platform for vertical farming with applications in urban food production, research, and education, particularly in resource-limited or off-grid environments.
Wheel-passage monitoring is relevant to non-safety-critical railway applications such as temporary traffic observation, maintenance support measurements, and open-hardware field experimentation. This study presents an open-source, low-power wheel detector developed as a monitoring-oriented railway sensing node for operation under real field conditions. The proposed hardware combines a mechanically preloaded pedal, a reed-switch-based triggering arrangement, and an ultra-low-power electronic subsystem built around a prototype control platform. In deep-sleep mode, the prototype consumes approximately 10 µA. The mechanical behavior of the detector was analysed using MATLAB/Simscape, focusing on wheel-pedal contact, preload selection, transient displacement response, and contact-pressure evolution with wheel speed. Preload optimization based on an overshoot criterion showed that 24 mm is the minimum preload required to eliminate secondary penetration. At 90 km/h, the model predicted full damping within 17.076 ms, remaining below the 30 ms digital filtering window and thereby supporting stable single-event generation. A damping sensitivity analysis showed that this timing margin is preserved under reasonable variation of the assumed structural damping. Within the adopted reduced-order 2D plane-strain model with isotropic hardening, the cyclic elastoplastic assessment predicted a shakedown-like response, with residual vertical indentation approaching 0.70 mm, well below the 5 mm triggering allowance of the reed-switch mechanism. A field-installed prototype was evaluated over the 0-90 km/h speed range. A total of 500 monitored wheel-passage events were assessed, with no missed detections and no visible wheel-flange deformation after testing. The results support the feasibility of a low-cost, ultra-low-power, open-source wheel-passage detector for non-safety-critical railway monitoring.
Parkinson's disease (PD) is a growing neurodegenerative disorder, with increasing global prevalence and challenges in both diagnosis and education. To assist in researching the domain of medical equipment and education training, this paper presents the design and implementation of a wearable device for continuous tremor-like motion monitoring in a laboratory prototype setting using low-cost materials and easy-to-build hardware. The tremor-like motion acquisition (TMA) is designed to be lightweight and non-intrusive, providing real-time acceleration-based motion measurement on the upper limb by measuring acceleration for both engineering research and educational demonstration. Notably, the TMA is constructed using fused deposition modeling techniques, offering a cost-efficient and rapid prototyping solution. Powered by a rechargeable battery, the TMA is designed for portability, with modular components that ensure flexibility and ease of maintenance. In addition, experimental tests are performed with a slider-crank mechanism to evaluate the data acquisition and motion-tracking capability under controlled mechanical excitation. As a result, the TMA meets design criteria, consisting of being lightweight, approximately 115 g, and low-cost, with a total hardware cost of $106.17, with a fast manufacturing time of 10 h. Furthermore, the monitoring tremor algorithm operates with results following the motion of the slider-crank mechanism and feeds the real-time data to software designed for smartphones, and no human-subject or clinical validation is conducted in this study.
The present study shows the instrumentation and control of a laboratory-scale post-combustion CO2 capture process (CO2-CP), including the implementation of a low-cost data acquisition system for monitoring and controlling the key process variables. This system simulates the capture of flue gases generated in thermoelectric power plants, as well as the operation of packed columns commonly employed in large-scale industrial applications. To ensure effective control, the developed platform continuously acquires and processes the operating variables throughout the experimental tests. Temperature and flow rate are acquired in real time using an open-source graphical user interface. Once the monitoring system was validated, experimental tests were conducted to evaluate the response of the CO2 absorption process under operating conditions. The experiments were performed using a 10% monoethanolamine (MEA) solution, where the absorption process exhibited an exothermic reaction, producing an approximately 2 °C temperature increase at the outlet of the absorption column and reaching saturation after approximately 300 s. In addition to monitoring the process's thermal behavior, maintaining mass balance throughout the system is essential to ensure stable operation and compliance with the continuity principle, whereby the inlet flow rate equals the outlet flow rate, thereby contributing to process stability and measurement reliability.
This paper presents the design and implementation of a compact and versatile device for generating and amplifying sinusoidal waveforms to drive inductive loads. The system is built around the AD9833 programmable waveform generator and the OPA548 high-current operational amplifier, forming a flexible platform capable of producing high-power sine wave excitation signals. The device can operate in two modes: internal signal generation using the AD9833 direct digital synthesis (DDS) module, or external signal input from a laboratory function generator, providing increased adaptability for various applications. To enable real-time monitoring and protection, an ACS724LLCTR-2P5AB-S Hall-effect current sensor is integrated into the output stage for accurate measurement of load current. The proposed design offers a cost-effective solution for applications requiring controlled excitation of inductive elements such as coils, transformers, or electromagnetic actuators. Experimental testing confirms the ability of the system to deliver stable amplified sine waves with reliable current sensing, making it suitable for laboratory experimentation, educational purposes, and small-scale industrial testing environments.
Many chemical measurement protocols require temperature control and stirring of the sample. Experimental procedures such as titration are usually performed in a laboratory using various devices, such as a bulky cryostat. In this paper, we describe a compact system that combines stirring and temperature control functions in a single unit. It can be assembled using 3D-printed parts and standard electronic components. The hardware is controlled using open-source software. Our system is designed for 100 ml samples with a controlled temperature range of ±7°C around the ambient temperature. The Arduino board can be controlled either via a terminal or through a master system. Its low manufacturing cost will make it easy to replicate and will allow for a wide range of analytical measurements using probes, including protocols with numerous replicates.
This paper presents the design and development of the Air Quality Detection and Safety-Targeted Instrument (ADESTI), a portable smart instrument for monitoring air quality in surgical operating rooms. The system is motivated by the need to detect deviations in oxygen concentration. Such deviations can indicate gas supply leakage or ventilation failure, which are safety concerns during surgical and anesthesia procedures. ADESTI integrates three gas sensors, namely an electrochemical oxygen sensor, a Non-Dispersive Infrared (NDIR) carbon dioxide sensor, and an electrochemical carbon monoxide sensor. It also includes an environmental sensor for temperature, humidity, barometric pressure, and light intensity. All sensors interface with an Arduino Mega 2560 R3 embedded system through the I2C and UART protocols for real-time data acquisition. The measured values are shown on an integrated Thin-Film Transistor (TFT) display. The enclosure is fabricated from Polylactic Acid Plus (PLA + ) by 3D printing to produce a compact and durable casing. The firmware, developed in the Arduino IDE, handles sensor initialization and real-time data acquisition and display. Characterization against reference instruments showed accuracies of 99.71% for O2, 98.84% for CO2, and 93.79% for CO, with precision above 99% for all three gas sensors. A key feature of ADESTI is that it combines the functions of four separate commercial instruments into a single low-cost and open-source device. It was field-validated across various surgical procedures at General Academic Hospital, Surabaya, Indonesia, at a total hardware cost of 355.10 USD. All design files, firmware, and the bill of materials are openly available at https://doi.org/10.17632/b6mgd6fgth.1.
Reproducible electrochemical characterization in bench-scale flow cells remains limited by variability in cell architecture, assembly practices, and operating conditions across users and laboratories. Although numerous cell designs have been reported, comprehensive guidance detailing component selection, fabrication, assembly, and testing protocols is largely absent. Here, we present a compact flow cell engineered to improve experimental rigor while maintaining architectural flexibility and cost-effectiveness. The platform incorporates interchangeable components, enabling adaptation to diverse electrochemical applications including redox flow batteries, electrolyzers, and fuel cells, with additional modifications and ancillary balance of plant where necessary. The small-scale of the device lowers volume and area requirements for electrolytes and cell components, respectively, facilitating high-throughput, yet systematic studies of emerging chemistries and materials. As a representative use case, we characterize cell performance using two diagnostic configurations and a model redox electrolyte, common in flow battery literature. We also present a framework distinguishing marginal and total repeatability to quantify variability across independent cell builds and operators. Using cell polarization and galvanostatic cycling protocols, we demonstrate consistent performance across configurations and users. By coupling transparent design documentation with a quantitative repeatability framework, this work seeks to establish a reproducible foundation for bench-scale flow cell experimentation and to support cross-laboratory comparability in electrochemical research
Brain slice electrophysiology is a widely used approach for investigating synaptic physiology, network activity, and pharmacological responses. However, the high cost of commercial recording chambers and perfusion systems restricts accessibility in resource-limited laboratories. Here, we describe the design, fabrication, and electrophysiological validation of a fully integrated, open-source field recording platform for acute brain slice electrophysiology. The system comprises three independently assembled modules: a submerged recording chamber, a tissue-positioning stage, and a suction assembly, all fabricated via FDM (Fused Deposition Modeling) 3D printer using PLA (Polylactic Acid) filaments at a total material cost of approximately 1.23 USD. The platform was validated using acute hippocampal slices from adult male C57BL/6N mice. Field excitatory postsynaptic potential recordings from the CA3-CA1 Schaffer collateral pathway demonstrated high-fidelity signals and reproducible stimulus-response relationships, alongside stable 15-minute baselines. Thermal characterization confirmed uniform perfusate distribution and rapid temperature equilibration within the chamber bath. All design files and assembly instructions are openly available, with the hardware design files released under the CERN-OHL-S-2.0 license and the documentation under a CC BY 4.0 license, enabling straightforward replication by the broader neuroscience community.
We present a low-cost, reproducible head-mounted wearable system for first-person video capture and real-time medication-workflow monitoring. The device combines a Raspberry Pi Zero W, Pi Camera Module v3, PiSugar 2 Pro battery board, active buzzer, tactile push button, and a modular 3-D-printed PLA enclosure with elastic head straps. Weighing approximately 145 g and costing about USD 100 for the core wearable components (USD 168.78 for the complete development and configuration bill of materials), the system is designed for offline operation, local storage, and low-power embedded processing. The enclosure was modeled in DesignSpark Mechanical and fabricated as modular panels with integrated mounting, ventilation, and access features. The software stack runs on Raspberry Pi OS Lite with Python/OpenCV scripts for autonomous capture, local event flagging, and audible feedback. Pilot deployment confirmed stable operation, up to 7 h of battery-powered use, and practical wearability in clinical settings. This work provides a reproducible open-hardware platform for wearable monitoring in low-resource operating room environments.
Commercial environmental control systems for live cell imaging chambers frequently cost $10,000-20,000. This paper presents an open-source, PID-controlled heating module built entirely from off-the-shelf components for approximately $500. The system employs four adhesively mounted polyimide heater pads driven at 12 VDC through a closed-loop chain: a K-type thermocouple feeds a Delta DTB4848LV controller, whose analog output is converted to PWM and applied to the heaters via an opto-isolated MOSFET switch. The required heating power was determined through analytical thermal sizing and verified by finite-element simulation (ANSYS Mechanical), confirming that the cell culture region reaches 37 ° C at steady state. Bench testing validated these predictions: the system reached 37 ° C within approximately 41 min from a 22 ° C cold start and maintained 37.1 ± 0.4 ° C over 3 h of continuous operation. The modular, low-voltage design requires no permanent modification to the host instrument and scales to different chamber geometries by adjusting the number of heater pads. Although validated here on a CytoStretcher, a substrate-stretching platform with a compact culture area, the analytical sizing methodology, finite-element thermal model with integrated PID control, and generalization guide provided in the repository enable adaptation to other stage-top microscope cell culture chambers by users with basic heat transfer knowledge. Larger or more complex chambers may require additional insulation or multi-point temperature sensing to ensure spatial uniformity. All design files, simulation models, and the bill of materials are released under an open-source hardware license.
Various commercial systems have been developed for printing high-performance polymers such as polyetherimide (PEI) and polyetheretherketone (PEEK) for use in medical, aerospace, automotive, and electrical components.High-performance polymers offer improved chemical resistance, thermal resistance, and mechanical properties compared to commonly used FFF materials such as PLA, PETG, and ABS. However, high-performance polymers are difficult to print due to the high printing temperatures required, such as nozzle temperatures up to 450°C, chamber temperature of 150°C, and bed temperatures up to 170°C. Most commercial systems capable of fabricating these materials are cost-prohibitive and lack modularity for user customization or modifications. An open-source, high-temperature FFF 3D printer was designed and constructed for high-performance polymers to be easily constructed, highly modular, and user-friendly. The printer was built using readily available components and controlled with a Duet3D motherboard running RepRap firmware to be highly customizable. The frame was built with aluminum T-slot channels to allow for integration with sensors, such as additional thermocouples or cameras for robust process monitoring. The printer can accommodate a 500°C nozzle, 200°C bed, and 120°C chamber. The system was validated through successful fabrication of ULTEM 1010, ULTEM 9085, and PEEK components. Performance was evaluated using three ULTEM 1010 calibration cubes printed under optimized process parameters. Dimensional measurements were used to assess accuracy, precision, and repeatability of the printer.
The use of time-lapse electrical resistivity tomography (ERT) in environmental studies has increased considerably in recent years. This method serves to produce 2D or 3D images of the subsurface’s electrical properties, making it possible to monitor the evolution of hydrologic or biogeochemical processes over time. However, the high cost and limited flexibility of commercial equipment has restricted its accessibility. OhmPi addresses these issues by offering a cost-effective, open hardware resistivity meter designed for laboratory and mid-scale field monitoring experiments. Since its launch in 2020, OhmPi has evolved significantly in response to user requirements. The latest version, OhmPi v2024, features a redesigned architecture with a new multiplexer and an upgraded measurement board. This improves performance and accuracy while maintaining affordability, with a price tag of under €1500 for 16 electrodes. The software has been completely redesigned to offer advanced features such as remote control via a graphical interface, and an integrated web server with MQTT protocol for network integration, ensuring flexibility and ease of use. Backward compatibility has been maintained to ensure a seamless transition for existing users. Extensive testing with ground analogue circuits and small-scale field experiments has confirmed OhmPi ‘s improved sensitivity, stability and robustness. These upgrades further establish OhmPi ‘s position as a reliable and adaptable tool for environmental ERT applications, providing an affordable alternative to commercial systems without compromising on quality.
Soft robotic grippers are attractive for cooperative object transport in multi-robot systems because they tolerate positioning errors and reduce the risk of damage to fragile items. However, many Fin-Ray effect grippers lack integrated force feedback, require empirical tuning of geometry, and are not documented as open hardware, which limits their adoption in research and teaching platforms. This work presents the design, fabrication, instrumentation, and validation of an open-source Fin-Ray soft gripper tailored for caging-based manipulation with mobile robots. The gripper combines 3D-printed TPU fingers optimized via finite element analysis, a thin-film piezo-resistive force sensor, and an STM32-based proportional controller that regulates gripping force in real time. The complete hardware stack, including mechanical models, firmware, and a Python graphical interface for monitoring and control, is released as open design files. The sensor was characterized in the range from approximately 0.1 N to 5 N. A third-order polynomial calibration yields an average accuracy of 70.8 % over this interval, with reduced accuracy at very low forces, and an average coefficient of variation of 1.10 %, which indicates highly repeatable measurements. Static closed-loop tests against a rigid object show convergence to a 0.981 N force setpoint with small steady-state error. Dynamic interaction tests confirm that the controller compensates for external perturbations by adjusting the gripper aperture. Energy measurements reveal an average current consumption near 250 mA during regulation, with peaks around 1 A when rejecting disturbances. These results indicate that the proposed gripper is suitable as a low-cost, reproducible end-effector for cooperative manipulation experiments in multi-robot systems.
Physical Unclonable Functions (PUFs) are widely recognized for deriving strong cryptographic keys from inherent manufacturing variations in hardware. A popular class of PUFs is extracted from memory modules already integrated into computing systems, offering a cost-efficient method for generating strong cryptographic keys. Various techniques exist for extracting PUF responses from such memory modules, including repeated row activation and exploitation of charge leakage effects, known as row hammering, variations in supply voltage, intentional violations of memory timing specifications, as well as the use of random startup values and data retention characteristics. To perform such experiments, especially on novel non-volatile memory modules, a dedicated measurement ecosystem is required, which is presented in this work. The proposed setup uses a custom PCB to connect different types of memories to reconfigurable hardware. An optimized hardware design was developed and deployed on an FPGA, enabling the execution of PUF experiments on various memory modules. The system allows for dynamic adjustment of timing specifications and voltage levels, even during experiment execution. Finally, a program is provided that schedules the experiments, retrieves the results, and enables persistent storage and evaluation methods.
Accurate and real-time monitoring of optical density (OD) is one of the key requirements for control of microbial fermentations. It provides insight into current cell concentration and growth dynamics of microbial cell cultures by measuring optical density at 600 nm (OD600). In combination with additional chemical (e.g. pH, dissolved oxygen), and physical (e.g. temperature) parameters, adjustments of culture conditions can be made during cultivation. Optical density is determined through either in-line, on-line or off-line measurements, although on a laboratory scale manual sampling (off-line) is typically performed due to the high acquisition costs of on-line devices. UV/Vis spectrometers or photometers are generally used for this purpose, but these are not suitable in resource-limited settings or for small-scale laboratories or field applications due to their acquisition costs and the limited possibility of self-performed repairs and modifications. Using widely available electronic components and 3D printing, we designed a self-calibrating photometer capable of precise OD600 measurements for bioprocess monitoring. This device is intended to offer an affordable and robust solution for both laboratory-scale experiments and field applications, where portability and ease of use are paramount.
Small sounding rockets provide an accessible, cost-effective platform for education and experimental research, especially at universities. In such projects, the onboard computer (OBC) is essential to mission reliability. It is responsible for sensor data acquisition, real-time flight-state detection, data logging, and actuation during recovery events. This work presents the design and implementation of a dedicated OBC for small experimental rockets, together with systematic validation using an integrated hardware-in-the-loop (HIL) simulation framework. The proposed OBC integrates an ARM-based STM32F407 microcontroller, a multi-sensor measurement suite including inertial and barometric sensors, non-volatile data storage, dual pyrotechnic channels, a robust power-management subsystem, and a fully deterministic software architecture tailored for real-time flight-event detection. Complementing the flight hardware, the HIL environment reproduces the electrical, timing, and communication behavior of onboard sensors with high fidelity. Synthetic measurements derived from flight-dynamics simulations are injected through a dedicated interface, enabling end-to-end validation of data acquisition, state-transition logic, and onboard memory logging without requiring physical launches. Experimental HIL results demonstrate reliable detection of high-energy, low-energy, and apogee flight phases under realistic conditions, validating both the hardware design and algorithmic performance. The datasets and design files released with this work provide a reproducible foundation for educational and research activities in similar avionics projects.
