This document describes the implementation of a solar illumination system with three-stage charging and dimming control. The system uses solar energy to charge a battery. A buck-boost converter regulates the voltage to continuously charge the battery. Another buck-boost converter supplies constant voltage from the battery to power LEDs for lighting and maintain consistent brightness even as the battery drains. A microcontroller monitors voltages and controls relays to switch between charging and lighting modes depending on available solar power.

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Implementation of Solar Illumination System with Three-Stage
Charging and Dimming Control Function
CONTENTS
1. INTRODUCTION
2. DESCRIPTION
3. BLOCK DIAGRAM
4. COMPONENTS LIST
5. SOFTWARES USED
6. ADVANTAGES
7. DISADVANTAGES
8. APPLICATIONS
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1. INTRODUCTION
Green energy includes solar energy, wind energy, tidal energy, hydro etc, which is widely used
and developed in recent years. Especially, Taiwan, which possesses subtropical climate, is very
suitable for the development of solar energy system. The application of solar energy is
more universal in daily now. In general, the solar power generation and solar illumination
system are more popular for people. With regard to solar illumination system, which can be
built while combined the charger and converter structure. It can charge the battery during the
day, while lighting the LED module at night. In recent year, many charge methods have been
widely used and discussed. For example constant current charging, constant voltage charging
and reflex charging, etc. Reflex charging needs large input power, constant current charging is
easily overcharge and constant voltage charging is unable to determine the charge current
during initial charge stage. So there are still some disadvantages and insufficient while use
unique charge method. In other sides, common linear dimming methods include constant
voltage dimming scheme and constant current dimming scheme.
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2. DESCRIPTION
In this project solar energy is used to charge the battery. Sometimes solar panel will not provide
enough voltage to charge battery due to insufficient sun light. So here a Buck Boost circuit is
used to boost the voltage to required level. A bulb or LED will be connected to battery as a
load, the battery supply is given to LED through another Buck Boost so that if battery voltage
reduces the intensity of light remains still due to constant voltage supplied by boost circuit.
3. BLOCK DIAGRAM
SOLAR
PANEL
VOLTAGE
DIVIDER
BUCK
BOOST
VOLTAGE
DIVIDER
CONTROLLER
BATTERY
RELAY
BUCK
BOOST
LED
Fig.1 Block diagram
In figure it shows solar panel is used to convert solar energy into voltage. Voltage generated at
panel output will depend on the intensity of solar light. As the solar light is unpredictable so the
output at solar panel will vary. With this variation it is not possible to charge the battery so the
output of panel is fed to Buck Boost block where this block will supply constant required
voltage to battery. A load (LED) is driven by the battery through Buck Boost circuit. So that if
battery voltage reduces but the supply to the LED remains same.
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If the panel voltage reduces in such a way that indicating that it is too dark than the LED
will turn ON where it is turned ON by activating relay by controller. As we need to measure
voltage which is normally higher than 5V this will be not tolerated by controller when ADC
input are fed so voltage dividers are used where this block will divide the voltage by 10 and
which will be sufficient to measure voltage.
4. COMPONENTS LIST
PIC18F458
Buck Boost
Baterry-12V
Voltage divider
Power Supply
Solar Panel
ALCD
5. SOFTWARES USED
MPLAB
PICkit-Microchip
ORCAD
6. ADVANTAGES
Solar energy is used which is freely available
Due voltage regulation by buck boost constant supply voltage is obtained
Low cost
7. DISADVANTAGES
Current ratings will be lower
8. APPLICATIONS
Used in vehicles
Used in street lights
Used in traffic lights
E-mail: info@wavedigitech.com; http://www.wavedigitech.com Phone: 91-9632839173