Design and Programming of a Micro-controller-Based Solar Tracking System

This paper is regarding design and program an Micro-controller Arduino Uno board by 1 using Arduino software to work as a photo-sensor(Active) single axial solar tracker system(SASTS). 2 A solar panel, two photo-resistors (LDR) in two sides (north/south) of the photo-voltaic(PV) and 3 a servo motor are connected to the Uno board, which is running a code that prepared by Arduino 4 software IDE in advanced then it works as a tracking system. Here, the LDRs send the signal of 5 presence or absence of the light to the board and based on that sent signal the Uno reflects a new 6 signal to the servo motor to rotate and finds the light source. Lastly, the photo-sensor single axis 7 tracker is made while Continuously, the system tries to face the panel to the sun and whilst changing 8 the irradiance intensity it starts searching to find the angle of highest irradiance. Based on results 9 that are extracted from the data, the tracker system significantly boosts the output efficiency of the 10 solar panel. By using the Micro-controller Uno board, LDRs, servo motor and special designed 11 mechanical base, the tracking system is constructed, based on acquired data the influence of the STS 12 on the increasing the solar panel efficiency is more obvious. Significantly, the tracker system rises the 13 efficiency of the PV . 14

• Tracking based on date and time (Active) 36 • Fixed or manually change tracker 37 Mainly, the Active STS can be divided into Single axial and dual axial tracker. When the single axial 38 STS only tracks solar in azimuth path but can't track solar in altitude path [3]. Strongly, the cost of the 39 tracker's structure (Mechanical base, installation) depends on the amount and type of material that 40 want to be used. Also, the geometry of the structure is important in order to be expensive [4]. Here, 41 the paper seeks to investigate the effect of the STS on the output efficiency of the solar panel.Based on 42 the measured data the efficiency has raised by 20%. Solar radiation is the main key to achieve output efficiency from the PV. The irradiance has two-part, the first is the direct beam, that reached to the PV surface and the second is reflected irradiance which is reflected from the PV surface, in addition to that; it does not provide energy to PV in order to produce electricity [5]. The direct irradiance received on the PV surface is given by the equation whereI D is direct irradiance, θ is irradiance angle, and I DN is normal direct irradiance. Sun position can be determined by two angles: Altitude angle and Azimuth angle. this angle is given by While the second angle is given by torque which can be handle by the servo motor (MG-996R). the main point is that the Uno board 55 can supply the servo motor for rotation with specifying speed and angle. The rigidness and low air 56 resistance are the good points of the mechanical structure of the SASTS. LDR is abbreviation from Light Dependent Resistance, it made from semiconductor materials and its resistance depend on the intensity of the light, by increasing the light the resistance will decrease and wise versa [5]. Here, the LDR working as photo-sensor and two LDR's are used and when the light intensity be different on them, their resistances can not be equal, like Figure4 and the circuit would be unbalanced, then, they will send a signal to Uno board and based on the written code in the micro-controller a signal send to the servo motor to rotate until the LDR's circuit to be balanced again [14]. From Equations 4 and 5, if R 1 = R 2 and V LDR1 = V LDR2 = V g and then R LDR1 = R LDR2 while 68 balance mode, as mentioned before, the resistance value of each LDR depends on the intensity of 69 the light, therefore, this will produce unbalance system if the intensity of the light change too. This 70 phenomenon helps to make a photo-sensor system that continuously searches for maximum intensity 71 to have a balance between both east-LDR and west-LDR.  The switching interface circuit used for some purposes, the input voltage from the solar panel is around 12V and this amount of voltage is high for microcomputer to read, as it has been mentioned before those pins can support maximum 5V in both digital and analog. Accordingly, the voltage divider board is designed by R 5 to R 10 and the regulated voltage would be directed toward Uno board through the outgoing signal from the digital pins. The aim of using of R 1 , R 2 , R 3 , R 4 are just for protection of MOSFET's. The MOSFET's work based on the digital pins of the Uno board, while the micro-controller would respond based on the signal from the written code on the board. Additional purpose of designed circuit is to have several different voltages. Each of the MOSFETs can be turned ON by the digital pins of the micro-controller and each time Uno receive one voltage data, once,the first switching mode has been finished then the new as a switching modes will emerge such as double transistors, triple and quadruple based on the aforementioned modes the Uno board can receive about 14 different voltage measurements. Based on Kirchhoff's Voltage Law (KVL), the input voltage (V-pv) and the voltage on R 5 and R 10 is Both resistors (R 5 and R 10 ) are connected in series, thus, based on Kirchhoff's Current Low (KCL) the amount of current which passes through each resistors are same so, equation 6 can be rearrange as shown in equation 7: The output voltage which is a part of the total resistance and can be determined as equation 8.
The output voltage of solar panel is 11.25V and R 5 =147KΩ and R 10 =100KΩ, while, the output voltage of the Uno board can be determined by substituting the values in to equation 8 as depicted in equation 9.
The acquired output voltage (4.45V)is a satisfactory value for the input to the micro-controller. That 83 process of determination of output voltage of switching interface board will be repeated for all other 84 resistors.   only voltage data will be measured, but, based on the code the uploaded to the Uno bard, the current 120 and power for each data will be derived by the known resistors which have been used in the circuit.

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As discussed before, the Uno board is the heart of the system. Based on the written code by 132 Arduino IDE it takes responsibility for any coming situation. The data have been achieved from 133 the experiments and shown in both Tables 2, 3 and Figures 9a 9b ,10a

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In this section the effective of the SASTS can find and understand on the improving the efficiency of the PV. So, the boost of efficiency is determined by the ratio of the achieved MPP point by using SASTS to the MPP point is obtained from a fixed solar panel. The MPP2 is obtained from using STS and MPP1 from the fixed case, the efficiency can be determining as below: where η is efficiency MPP2= 675 mW with STS achieved from the graphs, for a fixed case as shown  Figure 10b were shown that the high amount of the solar radiation has been converted to the electrical 151 energy, because, the MPP point is higher than the previous case. Definitely, it can be said that the main 152 reason for that is the minimization of the deflection angle of radiation by the solar tracker system. The

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MPP is about 21 times greater than the MPP of the fixed case, thus the solar tracker (photo-sensor 154 tracker) is so effective on boosting the output energy for the PV system.

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Significantly, using SASTS caused to achieve more power from the solar panel and provide to (usually north part of the earth and far locations from equator line).

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STS caused to speed up the charging of the battery, the battery charging almost depends on the 170 power and efficiency of the PV. So, when the efficiency of the PV increased the charging of the battery 171 will be faster. Thus, the battery will not going to die sooner than its lifetime.

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There are some drawbacks of the SASTS as discussed below:

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The SASTS may not be able to track all sun motion paths thus, some of the radiation time will be 174 wasted and it will not be used and the output efficiency will be less than the peak value.

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It needs energy to work, for a large project, a large amount of energy needs to handle the process 176 For its utilization, the wide and flat ground is needed. That Means, a suitable place is required to put angle of the incident ray is more and the influence of the using solar tracker system can be more 186 understandable.

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Use higher power solar panel since, MPP points are more sensible during finding.

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Do the same procedure with two axial solar tracker system, it maybe the effective of the tracker will 189 be highly observe.

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Using MATLAB Simulink for doing this kind of procedures. The following abbreviations are used in this manuscript: