Solar Mobile Charger is a useful kit to charge your mobile by solar energy. Photovoltaics (PV) are solar cells that produce electricity directly from sunlight. They are usually made of silicon –the same material that makes up the common beach sand. Solar cells operate according to what is called the photovoltaic effect (“photo” – light, “voltaic”- electricity). In the photovoltaic effect, bullets of sunlight photons striking the surface of semiconductor material such as silicon, liberate electrons from material atoms. Certain chemicals added to the materials composition (doping) help establish a path for the free electrons. This creates an electrical current. Through the photovoltaic effect, a typical 4 “silicon solar cell produces one watt of direct current electricity. To make it useful for powering normally used household or commercial appliances like TV, fridge or any other electrical machine /gadget, we may convert this low voltage DC electricity to 220v AC with the help of inverter which has already been popularized by the grace of electricity shortage throughout the country. The process of extracting and refining silicon with high purity from as cheap material as sand is very costly. This makes Photovoltaic solar panels costly. However free availability of solar power is an attractive proposition to use it and derive benefit of economy over longer periods.   
About the circuit :
Here four PV cells of 1.5 volts, 150 mA each are used to power the circuit. Since the PV panels provide Dc current only, we don’t require any inverter to charge batteries from this power.
Diode D1 is included to stop any charge flowing from the electronic circuit to PV panel. LED D3 is included to indicate that solar power is available. IC1 is LM317 wired in a constant voltage regulator mode.R2, R3, VR1 forms the feedback network for regulator and its output voltage can be set with VR1. D2 is again included to inhibit reverse flow of current from battery to the electronic circuit. Output voltage is adjustable from 3.5 v to 4.8 v depending upon availability of solar energy. The PV output voltage depends upon solar intensity and PV panel may give voltage in the range from 4 volts to 9 volts depending upon intensity of radiation. The mobiles batteries require power from 3.6 volts to 4.8 volts which can be available as and when solar intensity is adequate for the proper voltage to be applied to batteries. Therefore this charger may not charge the mobile continuously on cloudy day and may take more time to charge. However in summers it will charge continuously and charging will be faster. The panel may be kept facing south across east west so that it would receive solar radiation all through the day. To charge modern mobiles loaded with all facilities i.e. camera, Bluetooth, hard disc etc, we may have to use higher current capacity solar cells to increase the current capacity of the charger.

Solar Mobile Charger is a useful kit to charge your mobile by solar energy. Photovoltaics (PV) are solar cells that produce electricity directly from sunlight. They are usually made of silicon –the same material that makes up the common beach sand. Solar cells operate according to what is called the photovoltaic effect (“photo” – light, “voltaic”- electricity). In the photovoltaic effect, bullets of sunlight photons striking the surface of semiconductor material such as silicon, liberate electrons from material atoms. Certain chemicals added to the materials composition (doping) help establish a path for the free electrons. This creates an electrical current. Through the photovoltaic effect, a typical 4 “silicon solar cell produces one watt of direct current electricity. To make it useful for powering normally used household or commercial appliances like TV, fridge or any other electrical machine /gadget, we may convert this low voltage DC electricity to 220v AC with the help of inverter which has already been popularized by the grace of electricity shortage throughout the country. The process of extracting and refining silicon with high purity from as cheap material as sand is very costly. This makes Photovoltaic solar panels costly. However free availability of solar power is an attractive proposition to use it and derive benefit of economy over longer periods.   
About the circuit :
Here four PV cells of 1.5 volts, 150 mA each are used to power the circuit. Since the PV panels provide Dc current only, we don’t require any inverter to charge batteries from this power.
Diode D1 is included to stop any charge flowing from the electronic circuit to PV panel. LED D3 is included to indicate that solar power is available. IC1 is LM317 wired in a constant voltage regulator mode.R2, R3, VR1 forms the feedback network for regulator and its output voltage can be set with VR1. D2 is again included to inhibit reverse flow of current from battery to the electronic circuit. Output voltage is adjustable from 3.5 v to 4.8 v depending upon availability of solar energy. The PV output voltage depends upon solar intensity and PV panel may give voltage in the range from 4 volts to 9 volts depending upon intensity of radiation. The mobiles batteries require power from 3.6 volts to 4.8 volts which can be available as and when solar intensity is adequate for the proper voltage to be applied to batteries. Therefore this charger may not charge the mobile continuously on cloudy day and may take more time to charge. However in summers it will charge continuously and charging will be faster. The panel may be kept facing south across east west so that it would receive solar radiation all through the day. To charge modern mobiles loaded with all facilities i.e. camera, Bluetooth, hard disc etc, we may have to use higher current capacity solar cells to increase the current capacity of the charger.