ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 12, June 2013 179 Abstract —This paper presents the fuzzy logic control based solar tracking system using Arduino Uno. Stepper motor helps in tracking the axis of the sun and keeps the panel in direction of the sun all day long and a Buck DC-DC Converter has been used for Maximum Power Point Tracking. The proposed fuzzy logic controller has been implemented and tested using MATLAB. The above sun tracking power generation system has been tested in real time using Arduino Uno. The designed system increases the energy generation efficiency of the solar cells. Index Terms—Arduino Uno, Buck DC-DC converter, Fuzzy control, Stepper motor. I. INTRODUCTION With the increase in demand of electric energy nowadays and depleting resources, renewable energy sources have started playing an important role in electric power generation. From the various renewable sources, solar energy has proved to be good choice for electric power generation, since it can be directly converted into electrical energy by photovoltaic modules. Despite of solar energy being a good source of energy, there is a need to improve the methods to harness this energy [1]. This can be achieved by axial tracking and maximum power point tracking. For efficient implementation of these methods, the controllers are mainly based on the conventional methods like Perturbation & Observation, hill climbing etc. and the relatively new and intelligent approaches like Fuzzy control, Neural networks etc [2]. The advantage of the fuzzy logic control is that it does not strictly need any mathematical model of the plant. It is based on plant operator experience, and it is very easy to implement. Hence, many complex systems can be controlled without knowing the exact mathematical model of the plant. In addition, fuzzy logic simplifies dealing with the nonlinearities in systems [2]-[3]. Sun tracking is a technique to constantly track the sun’s direction throughout the day so as to increase the efficiency of the system. It can be implemented using a motor, sensors and gear box for the position control [4]-[5]. Position control can be done in two directions i.e. horizontal and vertical using two different DC motors [6]. Controlling the position of the panel in the direction of the sun can be even achieved by stepper motor too [7]-[8]. Maximum Power Point Tracking (MPPT) is basically a technique to track the constantly changing maximum power point of a solar panel. It consists of two main parts, a microcontroller to track the MPP and a power converter to convert the generated voltage from the source to a desired level for the load. Fuzzy control algorithm has been implemented to control the on/off time of the MOSFET switch of the Buck DC-DC converter [9]. If there is an ac load at the output then an inverter with the DC-DC converter can be used to match the load side [10]. So far fuzzy logic control based solar trackers with different configurations have been implemented on FPGA and PIC microcontroller and but the control logic in this research has been implemented on a simple microcontroller board Arduino Uno [9]-[11]. This controller consists of Atmega 328 microcontroller which is a simple platform to implement the control logic. II. PHOTOVOLTAIC (PV) SYSTEM MODELLING To understand the electronic behavior of a solar cell, it is useful to create a model which is electrically equivalent, and is based on discrete electrical components whose behavior is well known. From the solid-state physics point of view, the cell is basically a large area p-n diode with the junction positioned close to the top surface. An ideal solar cell may be modeled by a current source in parallel with a diode; in practice no solar cell is ideal, so a shunt resistance and a series resistance component are added to the model [9]-[12]. From Fig. 1 ܫ= ܫ  − ܫ ܦ – ܫ  ܪ (1) Where, I is the output current, I L is the photo generated current, I D is the diode current and I SH is the shunt current in Amperes. ܫ ܦ = ܫ  exp  ݍ ܬ  − 1 (2) Where, I 0 is the reverse saturation current (A), n is the diode ideality factor (1 for an ideal diode), q is the elementary charge [1.60217646 X 10 -19 C], k is the Boltzmann’s constant [1.3806503 X 10 -23 J/K], T is the absolute temperature. The characteristic equation of a solar cell which relates the output current and voltage is as follows: ܫ= ܫ  − ܫ  ݌ ݍ+ܫ    − 1− +ܫ     ܪ  (3) Fig. 1: Equivalent circuit of solar cell [12] Fuzzy control based solar tracker using Arduino Uno Dipti Bawa, C.Y. Patil Department of Instrumentation and Control, College of Engineering, Pune