Hardware

Measuring the water table level is a critical factor in irrigated agriculture in arid regions, as it can significantly influence the exchange of water and nutrients with crops. This work presents the design, implementation, and field validation of an open-source, solar-powered IoT device for autonomous groundwater level monitoring, combining long-range low-power LoRa communication, a non-contact pressure-based level sensor using the trapped-air capillary method, and an efficient power management stage that seamlessly switches between solar and battery power. Unlike existing commercial leveloggers, which are costly and lack integrated wireless telemetry and solar-based autonomy, the proposed platform is presented as a fully open-source, low-cost alternative purpose-built for unattended deployment in areas without grid power or cellular coverage. The system was validated through a multi-day field trial and dedicated communication tests, demonstrating a stable power conversion efficiency of 84–90%, a five-day autonomous operation without any deep-discharge event, high linearity ($R^2$ = 0.9998) of the level module over a 0–2 m range with a resolution of approximately 1.94 mm per ADC count, and a reliable LoRa link of up to 8.51 km in an urban/suburban environment despite non-line-of-sight conditions. With an estimated hardware cost of approximately $100 USD per unit, the device represents a low-cost, low-maintenance tool capable of generating knowledge about water resources to optimize irrigation and crop management in the face of climate change.

This work proposes and experimentally validates a structured development flow from rapid prototyping to printed circuit board (PCB) implementation for embedded systems operating in constrained environments. The approach is applied to a battery pack monitoring system for sounding rockets, and it is responsible for acquiring voltage, current, and temperature data and transmitting telemetry via an RS-422 interface at 38.4 kbps. The methodology starts with the integration of commercially available modules and evolves to a custom PCB while preserving the validated functional architecture. Experimental validation was conducted through bench and tri-axial vibration tests, demonstrating consistent system performance in sensing, processing, and telemetry, with no observed signal degradation or discontinuities. The results confirm that the proposed approach preserves system functionality and reduces development uncertainty, while providing a clear framework for design stages, validation procedures, and component selection. Furthermore, the findings support the use of low-cost commercial off-the-shelf (COTS) components in non-critical applications when appropriate validation strategies are applied, while emphasizing the need for additional qualification for critical use cases. The development flow is explicitly designed to support TRL progression, such that the evidence accumulated at each stage provides the traceability required for future qualification under critical classification.

This paper describes the design and implementation of PolyUAnalog, a modular and open-source polyphonic analog synthesizer. The architecture utilizes the AS3397 analog voice chip, with each voice managed by a dedicated RP2040 microcontroller. System coordination, including MIDI processing and voice allocation, is handled by a central conductor board communicating over an $I^{2}C$ bus. Technical implementation details and associated measurements are provided regarding real-time DCO pitch stabilization via a PID feedback loop and the generation of high-resolution control voltages using filtered Pulse Width Modulation (PWM). The complete hardware schematics and C++ software stack are documented to facilitate replication, modification, and further development within the electronic musical instrument community.