## 3 Measurement, Control, and Communication Architecture
### Custom-Designed Hardware Components
#### 3.1.1 Voltage and Current Measurement Board  
To accurately monitor the electrical power generated by the SWT after AC-DC conversion, a custom-designed PCB was developed for real-time acquisition of voltage and current. The board integrates high-precision transducers and isolated power supplies and is responsible for interfacing the analog signals to the data acquisition system controlled by the Arduino(r) MEGA. In contrast to commercial general-purpose modules, the board was designed to match the specific operating ranges of small wind turbines, while maintaining a compact layout and using cost-effective, easily sourced components. This approach facilitates replicability in academic and experimental contexts, making it suitable for low-cost research platforms.  
Figure 3 shows the complete design of the custom PCB, including the layout (a), the physical implementation with labeled components and signal terminals (b), and the electrical schematic used for sensor and power supply integration (c). The board receives DC  
current and voltage from the rectifier, processes them via galvanically isolated transducers, and outputs scaled analog signals labeled A1 and A2 for acquisition by the microcontroller.  
The PCB includes a voltage transducer (LEM(r) LV 25-P, LEM International SA, Geneva, Switzerland) [38] and a non-invasive current transducer (LEM(r) LA 55-P, LEM International SA, Geneva, Switzerland) [39], both manufactured by LEM(r) International SA. These sensors are powered by isolated DC-DC converters to ensure galvanic isolation and signal integrity, minimizing noise coupling into the analog measurement chain. The outputs of the sensors are scaled analog voltages, fed directly to the analog input pins of the microcontroller for digitization.  
As shown in the schematic (Figure 3c), the LV 25-P voltage transducer is connected through a high-impedance input resistor to limit primary current and define the voltage scaling range. The board includes two isolated DC-DC converters (PS1 and PS2) that provide \(\pm\)15 V and +5 V supplies to power the transducers independently from the main controller, preserving electrical isolation and avoiding ground loops. All grounds (GND1-GND4) are internally referenced to ensure consistent signal behavior across the measurement chain.  
A detailed list of the components used in the design of the measurement board is provided in Table 2.  
Figure 3: Printed circuit board designed to measure the voltage and current generated by the wind turbine: (**a**) layout design; (**b**) assembled board; (**c**) schematic diagram.  
A1 and A2 signals are acquired by the Arduino(r) analog-to-digital converter (ADC) and used in the control algorithm running on the microcontroller. Power terminals on the PCB provide the necessary \(\pm\)15 V and +5 V for the correct operation of the transducers and associated circuitry as well as to power the boost converter. The sensors' outputs require calibration to maintain accurate measurements. This is done by applying known reference voltages and currents, adjusting the sensor outputs to match expected values. Small resistors are used in the calibration circuit to compensate for any initial offsets in the sensor readings, improving the precision of the voltage and current measurements.