## 3 Simulation Results
Based on the Ohm law, the input current will be:  
\[\text{I}_{\text{in}}=\frac{\text{U}_{\text{ent}}}{\text{R}_{1}+\text{R}_{2}}= \frac{\text{U}_{\text{out}}}{\text{R}_{1}} \tag{13}\]  
Out of this formula, the ratio between R1 and R2 has to be determined, so that Uent and Uout have concrete values. \[\text{R}_{2}=\text{R}_{1}*\frac{\text{U}_{\text{ent}}-\text{U}_{\text{out}}}{ \text{U}_{\text{out}}} \tag{14}\]  
In this case, we used a voltage divider instead of a voltage sensor of 25 V. The Arduino can only measure the voltage rates within the interval 0-5 V, thus Uin = 25 V and Uout = 5 V (maximum). The ratio between resistors can be calculated from the above formula, and the result will be:  
\[\text{R}_{2}=4*\text{R}_{1}\text{ and U}_{\text{ent}}=\text{U}_{\text{out}}* \frac{\text{R}_{1}+\text{R}_{2}}{\text{R}_{1}} \tag{15}\]  
Instead of two suitable resistors (not available), one resistor of 100 kOhm was used as R1, and two resistors, series connected, one of 100 kOhm and one of 300 kOhm, whose sum, equal to 400 kOhm, corresponded to R2. The voltage on the panel was equal to 5 multiplied by the voltage read on the Arduino, Uent = \(5*\text{U}_{\text{out}}\). Figure 16 shows the diagram of the voltage divider connected to the Arduino. Figure 14: Current encoder/sensor ACS 712. Figure 15: Voltage encoder/sensor. To the Arduino, the resistor R\({}_{1}\) was parallel connected through the pins GND and the analog pin A1. The characteristics of the development board Arduino Uno are presented in Refs. [25; 26]. A program was issued in the programming environment Arduino IDE to control the buck DC-DC converter through the P&O algorithm. Monitoring of the voltage at the output of the buck DC-DC converter as well as the power delivered to the receptor circuit was conducted. Figure 17 presents an image of the use of the buck-type DC-DC converter for supplying a resistive load from a DC source of adjustable voltage controlled through the current intensity instead of the photovoltaic system controlled through the development board Arduino Uno. The program for the development board Arduino Uno was saved in the flash memory of the microcontroller Atmega 328. The related results are presented in Table 3. The power increase in the photovoltaic system was carried out by increasing the voltage of the DC source through adjustable voltage controlled through the current intensity. The value of the filling factor PWM (duty-cycles) was read via the computer screen by accessing the option \"serial monitor\". The components of the experimental stand were as follows: 1--DC source of adjustable voltage controlled through the current intensity, 2--DC-DC buck converter, 3--Arduino Uno development board, 4--current sensor, 5--breadboard, 6--load resistance, 7--ammeter, 8--digital multimeter. The direct voltage source was of the DC-Power Supply HY 3005D type, voltage (0-30) Vdc, current (0-5) A. The load resistance was a variable power resistance in the range (0-30) \(\Omega\) at a current I = 5 A. The ammeter measured a maximum current of 5 A. The multimeter was used to measure the voltage in the range (0-200) Vdc. The values for the voltage U\({}_{\text{source}}\) and current intensity I\({}_{\text{source}}\) were read off the display of the voltage source and the values for the U\({}_{\text{load}}\) and current intensity for I\({}_{\text{load}}\) were read off the multimeter and ammeter. It was noticed that with an increase in the power supplied by the photovoltaic system, there will be an increase in the filling factor of the PWM signal  
Figure 16: Diagram of the voltage divider connected to the Arduino.