Solar lighting system
ABSTRACT:
Automatic Street Light Control System is a simple yet powerful concept, which uses transistor as
a switch. By using this system manual work share 100% removed. It automatically switches ON
lights when the sunlight goes below the visible region of our eyes. This is done by a sensor
called Light Dependant Resistor (LDR) which senses the light actually like our eyes. It
automatically switches OFF lights whenever the sunlight comes, visible to our eyes.
By using this system energy consumption is also reduced because nowadays the manually
operated street lights are not switched off even the sunlight comes and also switched on earlier
before sunset. In this project, no need of manual operation like ON time and OFF time setting.
LDR and transistor are the main components of the project. The resistance of light dependant
resistor (LDR) varies according to the light falling on it. This LDR is connected as biasing
resistor of the transistor. According to the light falls on the LDR, the transistor is operated in
saturation and cut off region. This transistor switches the relay to switch on / off the light.
This project uses regulated 12V, 750mA power supply. 7812 three terminal voltage regulator is
used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac output of
secondary of 230/18V step down transformer.
BLOCKDIAGRAM:
Street Light- 1
Solar Panel
Street Light -2
Battery with
reverse
chargeable
protection
Power Supply
Section
LDR Day
And Night
Sensor
Street Light- 3
For Details Contact: A.VINAY-9030333433, 0877-2261612
Power Supply:
Step Down
T/F
Bridge
Rectifier
Filter
Voltage
Regulator
This circuit uses regulated 12V, 750mA power supply. 7812 three terminal voltage regulator is
used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac output of
secondaryof230/18Vstep down transformer
Transformer:
Usually, DC voltages are required to operate various electronic equipment and these voltages are
5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input available at the
mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a
transformer. Thus, a step down transformer is employed to decrease the voltage to a required
level.
Rectifier:
For Details Contact: A.VINAY-9030333433, 0877-2261612
The output from the transformer is fed to the rectifier. It converts A.C. into
pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a bridge
rectifier is used because of its merits like good stability and full wave rectification.
The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using both half cycles
of the input ac voltage. The Bridge rectifier circuit is shown in the figure. The circuit has four
diodes connected to form a bridge. The ac input voltage is applied to the diagonally opposite
ends of the bridge. The load resistance is connected between the other two ends of the bridge.
For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct, whereas diodes D2
and D4 remain in the OFF state. The conducting diodes will be in series with the load resistance
RL and hence the load current flows through RL.
For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct whereas, D1 and
D3 remain OFF. The conducting diodes D2 and D4 will be in series with the load resistance
RL and hence the current flows through RL in the same direction as in the previous half cycle.
Thus a bi-directional wave is converted into a unidirectional wave.
Filter:
Capacitive filter is used in this project. It removes the ripples from the output of
rectifier and smoothens the D.C. Output received from this filter is constant until the mains
voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage
received at this point changes. Therefore a regulator is applied at the output stage.
Voltage regulator:
For Details Contact: A.VINAY-9030333433, 0877-2261612
As the name itself implies, it regulates the input applied to it. A voltage regulator is an electrical
regulator designed to automatically maintain a constant voltage level. In this project, power
supply of 5V and 12V are required.
In
order to obtain these voltage levels,
7805 and 7812 voltage regulators are
to
be used. The first number 78
represents positive supply and the
numbers 05, 12 represent the
required output voltage levels. The
L78xx series of three-terminal
positive regulators is available in TO-220, TO-220FP, TO-3, D2PAK and DPAK packages and
several fixed output voltages, making it useful in a wide range of applications. These regulators
can provide local on-card regulation, eliminating the distribution problems associated with single
point regulation. Each type employs internal current limiting, thermal shut-down and safe area
protection, making it essentially indestructible. If adequate heat sinking is provided, they can
deliver over 1 A output current.
Al though designed primarily as fixed voltage regulators, these devices can be
used with external components to obtain adjustable voltage and currents.
LDR(light dependent resistor or photoresistor):
A light dependent resistor
The symbol for a photoresistor
The internal components of a photoelectric control for a typical American streetlight.
The photoresistor is facing rightwards, and controls whether current flows through the heater
which opens the main power contacts. At night, the heater cools, closing the power contacts,
energizing the street light. The heater/bimetal mechanism provides a built-in light level transient
filter.
For Details Contact: A.VINAY-9030333433, 0877-2261612
A photoresistor or light dependent resistor (LDR) is a resistor whose resistance decreases with
increasing incident light intensity; in other words, it exhibits photoconductivity. It can also be
referred to as a photoconductor or CdS device, from "cadmium sulfide," which is the material
from which the device is made and that actually exhibits the variation in resistance with light
level. Note that CdS is not a semiconductor in the usual sense of the word (not doped silicon).
A photoresistor is made of a high resistance semiconductor. If light falling on the device is of
high enough frequency, photons absorbed by the semiconductor give bound electrons enough
energy to jump into the conduction band. The resulting free electron (and its hole partner)
conduct electricity, thereby lowering resistance.
A photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own
charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only
available electrons are in the valence band, and hence the photon must have enough energy to
excite the electron across the entire bandgap. Extrinsic devices have impurities, also called
dopants, added whose ground state energy is closer to the conduction band; since the electrons
do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower
frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms
replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction.
This is an example of an extrinsic semiconductor. Photoresistors are basically photocells.[2]
Solar Panel:
Solar power us a renewable source of energy, which has become increasingly popular
in modern times. It has obvious advantages over non-renewable energy sources, such as coal, oil
and nuclear energy. It is non-polluting, reliable and can produce energy anywhere that there is
sun shining, so its resources are not going to run out anytime soon. It even has advantages over
other renewable energy sources, including wind and water power. Solar power is generated using
solar panels, which do not require any major mechanical parts, such as wind turbines. These
mechanical parts can break down and cause maintenance issues and can also be quite noisy. Both
of these issues are virtually non-existent with solar panels. Also, the solar cells that connected
together make up the solar panels, can last up to several decades without replacement.
However, there is a drawback to solar power- energy can only be produce when the sun is
shining. To overcome this usually solar panels are coupled with back up rechargeable batteries,
which can store excess power generated during the day and use it to provide energy to systems
when there is no sun shining. In this way solar power can be used to power houses and other
large scale systems. In these systems DC-AC conversion is needed. This is because the solar
panel produces an output that is DC (Direct Current) and the power supply in homes usually runs
off AC (Alternating Current), so conversion is required.
For Details Contact: A.VINAY-9030333433, 0877-2261612
Solar panel image:
Working:
In systems that utilize solar panels as the source of energy it is recommended to employ some sor
t of storage device. A storage device can prove very useful as it can store any unused energy gen
erated by the solar panel throughout the day and, in turn, this store Energy can be used to power
a system when no sunlight is available to the solar panel, thus making the system more practical.
The most realistic choice for this storage device is a backup battery. So when there is no sunlight
we use power supply section
Led:
A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator
lamps in many devices and are increasingly used for general lighting. Appearing as practical
electronic components in 1962, early LEDs emitted low-intensity red light, but modern versions
are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.
When a light-emitting diode is switched on, electrons are able to recombine with holes within the
device, releasing energy in the form of photons. This effect is called electroluminescence, and
the color of the light (corresponding to the energy of the photon) is determined by the
energy band gap of the semiconductor. An LED is often small in area (less than 1 mm2), and
integrated optical components may be used to shape its radiation pattern. LEDs have many
advantages over incandescent light sources including lower energy consumption, longer lifetime,
improved physical robustness, smaller size, and faster switching. However, LEDs powerful
enough for room lighting are relatively expensive, and require more precise current and heat
management than compact fluorescent lamp sources of comparable output
Light-emitting diodes are used in applications as diverse as aviation lighting, automotive
lighting, advertising, general lighting, and traffic signals. LEDs have allowed new text, video
displays, and sensors to be developed, while their high switching rates are also useful in
advanced communications technology. Infrared LEDs are also used in the remote control units of
many commercial products including televisions, DVD players and other domestic appliances.
For Details Contact: A.VINAY-9030333433, 0877-2261612
Led image:
Advantages:
1. Highly sensitive
2. Works according to the light intensity
3. Fit and Forget system
4. Low cost and reliable circuit
5. Complete elimination of manpower
6. Can handle heavy loads up to 7A
7. System can be switched into manual mode whenever required
Applications:
1. Balcony / stair case / parking Lightings
2. Street lights
3. Garden Lights
For Details Contact: A.VINAY-9030333433, 0877-2261612