Power supply circuit 

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... et al., 2009). Three previously developed tracking mod- els of the solar trackers are: passive tracker, microprocessor tracker and electro optical tracker. Passive systems with no motor and other electronic controllers to follow the sun, this kind of tracker contain a fluid such as Freon that is in the certain pipes .When the panel is not facing the sun sunlight, the Freon side of the frame will absorb more energy and become warmer than the other side, the temperature difference causes the hot steam, therefore, Freon volume increase pushes a piston and the panel will start to turn to the other side. This tracking system might be simple but has a moderate accuracy compared to the other methods. Solar trackers that are controlled by a digital controller, on the other hand, are working based on mathematical formulations of the sun path in the sky, utilized to predict sun location at each point of time. Based on these calculations, best spatial angle of the panel can be chosen. Electrical motors and converters are used for these types of systems by which large solar panels are controlled and can be used to follow the sun sensors electro optical receivers. This type of tracker is very accurate and has high precision, but needs precise installation, and can lead to some dif- ficulties to reach the desired result in terms of water and air favorable (Gay, Yerkes, & Wilson, 1982). The single axes tracking systems pivot on their axis facing east in the morning and west in the afternoon (Brunotte, Goetzberger, & Blieske, 1996). The tilt angle of the system is equal with the latitude angle of the loco because the revolution axis has to be always parallel with the polar axis. The dual axis solar trackers combine two motions so they are able to follow precisely the sun trajectory along the whole year. Consequently the dual axis solar trackers are more efficient than the single axis ones but also more expensive because they are using an extra-actuating system for the second axis (Comsit & Visa, 2007). In this work a two axes sun tracker has been designed and implemented which receives information through the photovoltaic cell and adjusts the correct direction using a digitally programmable derived system that is based on the maximum solar energy received by the converter panel. A prototype of the proposed solar system tracker was implemented and tested under practical conditions. Test results for the solar panel were compared and analyzed against traditional methods as presented in the next sections. There are three algorithms for tracking the Sun: The First algorithm function is the most basic mode for tracking. This algorithm uses defined function to move PV panels in a circle motion and locates the PV panels in a small angular region. This function also stores information and transports the panels to the point which gives the highest voltage in the circle. Then it runs this function again which is slow and not efficient. This tracking mode is named track A. Second algorithm function is designed for multiple tracking modes. It uses four points from vertices of a square in a defined func- tion in first algorithm to find both altitude and latitude. Second algorithm obtains V1 and V2 values from the square which is made by the discussed function, then uses another function to locates the PV panels to the best positions, where: V1 and V2 are two light voltage vectors. This tracking mode is named track B. Third algorithm is designed for the most precise tracking mode. This function uses Second algorithm once in each hour to find 5 points of data - altitude and horizontal arc - then uses interpolation for finding hour from day, day from year and longitude and latitude and predicts the next movement. The method that the third algorithm uses to find equations is like interpolation technique. This tracking mode is named track C. The final structure of the system block diagram is shown in Figure 1 (Shama, Roshani, Ahmadi, & Roshani, 2011). Hardware structure includes several sub- blocks such as: Input switches, power supply circuit, PV cells, controller, Drivers, step mo- tors, mechanical units, display units. The func- tions of these sub-blocks are explained in the subsections. There are five main switches in the designed circuit. These switches are used to apply external commands to controller unit by users. Each of these switches is used for a specified applica- tion. One of them is used for resetting; another one for calibration and the rest are for tracking modes selection which are track A, track B and track C, respectively. For more accuracy and speed, switches are implemented as shown in the Figure 2. A transformer is used to convert AC source volt- age to proper voltage. A diode bridge rectifies the transformer output. A voltage regulator and a capacitor unify this voltage to 5v dc. However by using larger PV cell and better material structure, there is no need for DC supply. The power supply circuit is shown in Figure 3. A solar cell is an electronic device that produces electricity when light falls on it. The light is absorbed and the cell produces dc voltage and current. The device has a positive and a negative contact between which the voltage is generated and through which the current can flow. You connect these contacts to whatever it is you want to power. Solar cells have no moving parts. Effectively they take light energy and convert it into electrical energy in an electrical circuit, exploiting a physical process known as the photovoltaic effect. The discovery of the photovoltaic effect is credited to the French physicist, Edmond Becquerel, in 1839. He found that by concentrating the sun’s light on one side of a battery the output current of the battery could be increased. This revolutionary discovery triggered the idea that one could produce energy from light by an artificial pro- cess. In 1883 an American inventor produced a solar cell from a material called selenium, but it was very inefficient. Selenium became used in light-exposure meters for cameras, but not for power production. It was not until the 1950s that practical solar cells were developed. In 1948 the transistor was invented, at Bell Labo- ratories in the United States, and it was found that the same high quality silicon wafers used for making transistors could be used to make solar cells. This work was published in 1954. From 1958 onwards the cells were employed in the space race. Solar cells are still the only sensible source of electrical power for space satellites, because they are in effect batteries that never run out (Garlovsky & Pickin, 1999). Silicon material is selected for the device with length of 8.4cm and width of 6.4cm which is shown in Figure 4. A digital microcontroller applied for controller unit in implemented device. Due to convert the analog signals from the solar panels to digital values for farther processing, an IC is needed such that support analog to digital conversion (Lakeou, Ososanya, Latigo, Mahmoud, Ka- ranga, & Oshumare, 2006). Also, if we send information through the serial port to the computer or use computer to control the device instead of the keys, the controller must have the capability of send- ing and receiving serial information (Shawn, 2005). Consequently, we used the IC (integrated circuit) Atmega32. Drivers are used to connect step motors and microcontrollers. Drivers transfer commands from the microcontroller to step motors. Each command preformed as a specified degree toward clockwise or anti clockwise rotation. According to modify rotation angle, gears with specified scales are selected. For power we can write ...