Solar Tracking System
Renewable energy is rapidly gaining importance as an energy resource as fossil fuel prices fluctuate. One of the most popular renewable energy sources is solar energy. Solar tracking enables more energy to begenerated because the solar panel is able to maintain a perpendicular profile to the sun’s rays.
There are three ways to increase the efficiency of a photovoltaic (PV) system.
1) The first is to increase the efficiency of the solar cell.
2) The second is to maximize the energy conversion from the solar panel.
A solar panel under an open circuit is able to supply a maximum voltage with no current, while under a short circuit is able to supply a maximum current with no voltage. In either case, the amount of power supplied by the solar panel is zero. The key is to develop a method whereby maximum power can be obtained from the voltage and current multiplied together.
The third method to increase the efficiency of a PV system is to employ a solar panel tracking system. As the sun moves across the sky during the day, it is advantageous to have the solar panels track the location of the sun, such that the panels are always perpendicular to the solar energy radiated by the sun. This will tend to maximize the amount of power radiated by the sun.
In years to come the need for energy will increase manifold while the reserve of conventional energy will deplete in rapid pace. To meet the growing demand of energy harnessing of non-conventional / renewable energy is the necessity. Among all the available non-conventional sources, solar energy isthe most abandunt and uniformly distributed. Though the technology of trapping the solar energy is in existence the process can be in proved to increase efficiency and make it cost-effective.
Renewable energy is rapidly gaining importance as an energy resource as fossil fuel prices fluctuate. One of the most popular renewable energy sources is solar energy. Many researches were conducted to develop some methods to increase the efficiency of Photo Voltaic systems (solar panels). One such method is to employ a solar panel tracking system .This project deals with a microcontroller based solar panel tracking system. Solar tracking enables more energy to be generated because the solar panel is always able to maintain a perpendicular profile to the sun’s rays.
Development of solar panel tracking systems has been ongoing for several years now. As the sun moves across the sky during the day, it is advantageous to have the solar panels track the location of the sun, such that the panels are always perpendicular to the solar energy radiated by the sun. This will tend to maximize the amount of power absorbed by PV systems. It has been estimated that the use of a tracking system, over a fixed system, can increase the power output by 30% - 60%. The increase is significant enough to make tracking a viable preposition despite of the enhancement in system cost. It is possible to align the tracking heliostat normal to sun using electronic control by a micro controller.
1.4 System Design
1)Must track the sun during daylight hours
During the time that the sun is up, the system must follow the sun’s position in the sky.
This must be done with an active control.
A base must be designed to allow installation without fasteners onto a flat section of roof
This system will be designed to be fully functional outdoors and resist any wind and weather complications.
3)Remote instrumentation to monitor status
A method will be implemented to allow the system to be monitored remotely.
The major components of this system are as follows. Each component required the student tomake decisions that would ultimately affect the final design, based on both technical as well asfinancial constraints.
4)The solar panel that will convert the radiation of the sun into electricity
The solar panel in direct sunlight is capable of sourcing 23V under open circuit
conditions, and approximately 0.75A under short circuit conditions. The solar panelused in this project was already available and therefore did not cost any moneytowards the project.
5)A base to support the solar panel
The base must be able to mount with no fasteners on a flat roof. It must also be large enough and heavy enough to provide a solid mounting point that will prevent the system from being damaged by strong winds.
6)A weather-resistant housing to protect the electronics
The final control box had two parts (bottom and top). The interface between the twoincluded a gasketed design for water-resistance.
7) A motor to move the solar panel as the sun traverses through the sky
The intent of the project was to automatically rotate the solar panel to orient the panelperpendicular to the sun’s rays.
8) Electronics to sense the sun’s position, and determine whether the solar panel needs to move
The approach employed to orient the panel with the sun was to find the point thatmaximized the amount of power being converted by the panel. Current was measuredthrough a fixed resistance to determine the power consumed.
An 8051 microcontroller would be the brains of the operation, sensing which positionof the panel yielded maximum power, and sending signals to the antenna motor tomove the solar panel accordingly.
This project is designed with solar panels, LDR, ADC, Microcontroller, Stepper Motor and its driving circuit.
In this project three LDRs are fixed on the solar panel at three distinct points. LDR (Light Dependant Resistor) varies the resistance depending upon the light fall. The varied resistance is converted into an analog voltage signal.
The analog voltage signal is then fed to an ADC. ADC is nothing but analog to digital converter which receives the two LDR voltage signals and converts them to corresponding digital signal. Then the converted digital signal is given as the input of the microcontroller. Microcontroller receives the two digital signals from the ADC and compares them. The LDR signals are not equal except for normal incidence of sunlight. When there is a difference between LDR voltage levels the microcontroller programme drives the stepper motor towards normal incidence of sunlight.
1.6 BLOCK DIAGRAM:
Fig 2.1 : General Block diagram of the Tracking system.
Fig 2.1 shows the general block diagram of the tracking system.
In this system the sun's light is tracked in order to generate power very effectively. For that purpose 3 LDR’s are used forsensing the light from the sun. Here 3 LDR’s are used so that the sun's path can be divided into 3 columns of 180° (East-West). The LDR outputs have been compared and the sun’s angle is traced. Hence the solar panel is moved towards the sun’s angle with the help of microcontroller by using stepper motor. In this operation the signal from the light sensor is given to the signal conversion circuit and then it is filtered before passing into the microcontroller.
Once the solar panel is completely moved to the west it will automatically turn into east direction for the next day using position sensors. In this operation the signal from the position sensor is given to the zener circuit in order to protect the Atmel IC from the over voltage before passing into the microcontroller. In this paper, the solar panel generates voltage up to the maximum value of 9.3 V.
Here both the position sensor and solar panel is kept in the mechanical model. In order to rotate the solar panel the stepper motor has been used. Here 12 V stepper motor is used. The stepper motor driving circuit is used to drive the stepper motor. The power supplyhas been given to both the stepper motor and Atmel IC are 12V and 5V, respectively by using step down transformer.
INTRODUCTION TO MICROCONTROLLER ARCHITECTURE
A microcontroller (or MCU) is a computer-on-a-chip used to controlelectronic devices. It is a type of microprocessor emphasizingself-sufficiency and cost-effectiveness, in contrast to a general-purposemicroprocessor (the kind used in a PC). A typical microcontroller containsall the memory and interfaces needed for a simple application,whereas a general purpose microprocessor requires additional chips toprovide these functions. A highly integrated chip that contains all the components comprisinga controller. Typically this includes a CPU, RAM, some form ofROM, I/O ports, and timers. Unlike a general-purpose computer, whichalso includes all of these components, a microcontroller is designed fora very specific task – to control a particular system. As a result, theparts can be simplified and reduced, which cuts down on productioncosts.
A microprocessoron a singleintegrated circuitintended to operateas an embeddedsystem. As well as a CPU, a microcontrollertypically includes small amounts of RAMand PROMand timersand I/O ports. A single chip that contains the processor the CPU, non-volatile memory for the program ROM or flash, volatile memory for input andoutput (RAM), a clock and an I/O control unit. A microprocessor on a single integrated circuit intended to operateas an embedded system. As well as a CPU, a microcontroller typicallyincludes small amounts of RAM and PROM and timers and I/O ports.
The definitions given by various sources describe microcontroller asan integrated circuit (IC) with processor as well as peripherals on chip.But the crux of the matter is the widespread uses of microcontrollersin electronic systems. They are hidden inside a surprising number ofproducts such as microwave oven, TV, VCR, digital camera, cell phone,Camcorders, cars, printers, keyboards, to name a few.
2.2 Microcontroller Applications
The microcontroller applications are mainly categorized into thefollowing types:
Computers and peripherals
Imaging and video
Automobile industry is the main driving force in propelling the growth of microcontrollers.The 8- and 16-bit microcontrollers are used for low-end applicationsand lower-cost vehicles while the 32-bit microcontrollers are used forhigh-end application and high-end vehicles.
Embedding microcontrollers in the product offers some uniqueadvantages. For an example, in the latest technology washing machines a transmission is no longer required because a lower-cost AC inductionor reluctance motor controlled by sophisticated microcontroller-basedelectronics can provide all the normal machine cycles. Additionally,the electronically controlled induction or reluctance motor provides amore effective and gentler agitation (wash) cycle that allows the drumcontaining the clothes to be rotated first in one direction, then stopped,and rotated in the opposite direction without requiring any additionalmechanical device. This forward/reverse agitation cycle provides a moreeffective means of cleaning your clothes without damaging the fibersused to make them.
2.3 AT89S8252 CONTROLLER
- 8K Bytes of In-System Reprogrammable Downloadable Flash Memory
- SPI Serial Interface for Program Downloading
- Endurance: 1,000 Write/Erase Cycles
- 2K Bytes EEPROM – Endurance: 100,000 Write/Erase Cycles
- 4V to 6V Operating Range
- Fully Static Operation: 0 Hz to 24 MHz
- Three-level Program Memory Lock
- 256 x 8-bit Internal RAM
- 32 Programmable I/O Lines
- Three 16-bit Timer/Counters
- Nine Interrupt Sources
- Programmable UART Serial Channel
- SPI Serial Interface
- Low-power Idle and Power-down Modes
- Interrupt Recovery from Power-down
- Programmable Watchdog Timer
- Dual Data Pointer
- Power-off Flag
The AT89S8252 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of downloadable Flash programmable and erasable read-only memory and 2K bytes of EEPROM. The device is manufactured using Atmel’s high-density non-volatile memory technology and is compatible with the industry-standard 80C51 instruction set and pinot. The on-chip downloadable Flash allows the program memory to be reprogrammed In-System through an SPI serial interface or by a conventional non-volatile memory programmer. By combining a versatile 8-bit CPU with downloadable Flash on a monolithic chip, the Atmel AT89S8252 is a powerful microcontroller, which provides a highly-flexible and cost-effective solution to many embedded control applications.
The AT89S8252 provides the following standard features:
8K bytes of downloadable Flash,
2K bytes of EEPROM,
256 bytes of RAM,
32 I/O lines,
programmable watchdog timer,
two data pointers,
three 16-bit timer/counters,
six-vector two-level interrupt architecture,
a full duplex serial port,
On-chiposcillator and clock circuitry.
In addition, the AT89S8252 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next external interrupt or hardware reset. The downloadable Flash can be changed a single byte at a time and is accessible through the SPI serial interface. Holding RESET active forces the SPI bus into a serial programming interface and allows the program memory to be written to or read from unless lock bits have been activated.
2.3.4 BLOCK DIAGRAM
Fig 2.1: Pin out of AT89S8252
Port 0 is an 8-bit open drain bi-bidirectional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. Port 0 can also be configured to be the multiplexed low-order address/data bus during accesses to external program and data memory. In this mode, P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pull-ups are required during program verification.
Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups.
Some Port 1 pins provide additional functions. P1.0 and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively. Furthermore, P1.4, P1.5, P1.6, and P1.7 can be configured as the SPI slave port select, data input/output and shift clock input/output pins as shown in the following table. Port 1 also receives the low-order address bytes during Flash programming and verification.
Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups.
Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register.
Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.
Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups. Port 3 receives some control signals for Flash programming and verification. Port 3 also serves the functions of various special features of the AT89S8252, as shown in the following table.
Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.
Address Latch Enable is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming.
In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory.
If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.
Program Store Enable is the read strobe to external program memory. When the AT89S8252 is executing code from external program memory, PSEN is acti-vated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.
External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming when 12-volt pro-gramming is selected.