## 3 Methodology
### Experimental Test Procedures  
The experimental setup procedures were implemented on a Minipa protoboard to reduce circuit dimensions and minimize losses due to the Joule effect. The assembled circuits are shown in Figure 5. A 1 M\(\Omega\), 0.2 W potentiometer was used in the resistive circuit of Figure 5a, and a 16 V capacitor with 100 uF and a DB107 bridge rectifier were used in the full-wave rectifier circuit of Figure 5b.  
An external amplifier and a 100 mV sinusoidal signal generator were connected to adjust the frequency and amplitude of the input signal to the shaker. The signal generator was linked to the amplifier for compatibility with the shaker. A spectrum analyzer monitors the input signal to the shaker, while the oscilloscope monitors the output signal from the  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **PZT-5H** & **P5-13B** \\ \hline Substrate material & Copper & FeNi (Iron and Nickel) \\ Length of the beam & 59 mm & 55 mm \\ Width of the beam & 31 mm & 20 mm \\ Thickness of the beam & 0.4 mm & 0.52 mm \\ [PERSON]’s modulus of the bar, E & 11.2 \(\times\) 1010 N/s\({}^{2}\) & 11.0 \(\times\) 1010 N/s\({}^{2}\) \\ Density of beam material, \(p\) & 8700 \(\times\) 103 kg/m\({}^{2}\) & 8110 \(\times\) 103 kg/m\({}^{2}\) \\ Mass & 16 g & 12 g \\ Damping, c & 0.58 N.s/m & 0.48 N.s/m \\ Stiffness, K & 215.33 N/m & 464.82 N/m \\ Piezo capacitance, C\({}_{0}\) & 7.4 \(\times\) 10\(-\)7 F & 1.66 \(\times\) 10\(-\)7 F \\ Force factor, \(\alpha\) & 1.52 \(\times\) 10\(-\)3 N/Volts & 6.5 \(\times\) 10\(-\)3 N/Volts \\ Natural frequency, fn & 18.3 Hz & 31.1 Hz \\ Coupling factor, k31 & 0.49 & 0.45 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters of piezoelectric transducers.  
Figure 4: Diagram of the experimental setup.  
piezoelectric transducer. Voltmeters and ammeters measure the voltages and currents of the transducer.  
The cantilevered configuration was employed with a mass at the end of the piezo to adjust the resonance frequency and maximize energy generation.  
The selection of resistors and capacitors in the circuits (Figure 5) was primarily driven by practical considerations to ensure stable operation and ease of tuning. In the resistive circuit (Figure 5a), a 1 M\(\Omega\), 0.2 W potentiometer was chosen for its wide resistance range, which facilitated practical adjustments during testing. This allowed fine-tuning the load without needing to swap components, thus streamlining the experiment. For the rectifier circuit (Figure 5b), the 100 \(\mu\)F, 16 V capacitor was selected based on its effectiveness in smoothing the output signal and reducing ripple under the operational conditions of the experiment. The 100 \(\mu\)F value was determined through preliminary tests that showed it provided an optimal balance between charge time and voltage stabilization, while the 16 V rating ensured reliable performance without component failure during voltage fluctuations. These choices were made to maintain efficiency and stability throughout the testing process.  
Signals were acquired by a system with LVDT, an oscilloscope, a spectrum analyzer, and a digital multimeter, with data acquisition and visualization performed on the computer.  
The natural frequencies of the systems were characterized using an oscilloscope and spectrum analyzer with an impact hammer and accelerometer. The piezo capacitances were measured using a function generator and an oscilloscope. The generation response in the resonance regions was evaluated by varying the potentiometer values. For the DC-DC buck circuit, the power response was analyzed as a function of the excitation frequency adjusted by the generator.