This document describes a solar-powered LED street light system with programmable intensity control. It uses LEDs which can be intensity controlled through pulse width modulation, allowing the lights to be dimmed at night to save energy when traffic is low. A microcontroller provides different light intensities at different late night times. Solar power charges a battery, with overload and deep discharge protection. The system components include a solar panel, microcontroller, LEDs, PWM, MOSFET, photovoltaic cells, resistors and capacitors.

1. LED BASED STREET LIGHT WITH
PROGRAMMABLE INTENSITY CONTROL USING
SOLAR POWER FROM PHOTOVOLTAIC CELLS
Submitted by
M.S.ARAVINDAN

2. High Intensity Discharge lamps (HID) used for urban street light
are based on principle of gas discharge, thus the intensity is not
controllable by any voltage reduction method as the discharge path
is broken.
White Light Emitting Diode (LED) can replace the HID lamps
where intensity control is possible by pulse width modulation. The
intensity control helps in saving energy during late nights while
traffic density on the streets is low.
A programmable microcontroller is engaged to provide different
intensities at the different times of late night for energy saving for
solar based system, using a charge controller for battery charging,
overload and deep discharge protection
ABSTRACT

3. HARDWARE REQUIREMENTS
POWER SUPPLY BLOCK
MICROCONTROLLER (AT89S52/AT89C51)
SOLAR PANNEL
LED
PWM
MOSFET
PHOTOVOLTAIC CELLS/SOLAR CELLS
LM324
1N4007/1N4148
 RESISTOR
 CAPACITOR

4. 230 V AC
50 Hz
5V
DC
12V step down
transformer
Filter(470µf)
5v RegulatorBridge rectifier

5.  It is a smaller computer
 Has on-chip RAM, ROM, I/O ports...
RAM ROM
I/O
Port
Timer
Serial
COM
Port
Microcontroller
CPU
A single chip

6. CPU
On-chip
RAM
On-chip
ROM for
program
code
4 I/O Ports
Timer 0
Serial
Port
OSC
Interrup
t
Control
External interrupts
Timer 1
Timer/Counter
Bus
Control
TxD RxDP0 P1 P2 P3
Address/Data
Counter
Inputs

7.  Compatible with MCS®-51 Products
 8K Bytes of In-System Programmable (ISP) Flash Memory
 Endurance: 10,000 Write/Erase Cycles
 4.0V to 5.5V Operating Range
 Fully Static Operation: 0 Hz to 33 MHz
 256 x 8-bit Internal RAM
 32 Programmable I/O Lines
 Three 16-bit Timer/Counters
 Eight Interrupt Sources
 Full Duplex UART Serial Channel
 Interrupt Recovery from Power-down Mode
 Watchdog Timer
 Dual Data Pointer

8.  The term duty cycle describes the proportion of on time to the regular
interval or period of time; a low duty cycle corresponds to low power,
because the power is off for most of the time.
 Duty cycle is expressed in percent, 100% being fully on.
 The main advantage of PWM is that power loss in the switching devices
is very low. When a switch is off there is practically no current, and when
it is on, there is almost no voltage drop across the switch.
 PWM works also well with digital controls, which, because of their on/off
nature, can easily set the needed duty cycle.
 The longer the switch is on compared to the off periods, the higher the
power supplied to the load is.

10. MOSFET(IRF 510)
The metal–oxide–semiconductor field-effect
transistor (MOSFET, MOS-FET, or MOS
FET) is a device used for amplifying or
switching electronic signals
The basic principle of the device a voltage on
the oxide-insulated gate electrode can induce a
conducting channel between the two other
contacts called source and drain
It is by far the most common transistor in
both digital and analog circuits, though the
bipolar junction transistor was at one time
much more common.

11. BC547 (NPN –Transistor)
The BC547 transistor is an NPN Epitaxial
Silicon Transistor.
It is used in general-purpose switching and
amplification BC847/BC547 series 45 V, 100
mA NPN general-purpose transistors.
The ratio of two currents (Ic/Ib) is called the DC Current Gain of
the device and is given the symbol of hfe or nowadays Beta, (β).

12. The current gain from the emitter to the collector
terminal, Ic/Ie, is called Alpha, (α), and is a function of the
transistor itself

13. 1N4148
The 1N4148 is a standard small signal silicon
diode used in signal processing.
 The 1N4148 is generally available in a DO-35
glass package and is very useful at high frequencies
with a reverse recovery time of no more than 4ns.
This permits rectification and detection of
radio frequency signals very effectively, as long as
their amplitude is above the forward conduction
threshold of silicon (around 0.7V) or the diode is
biased.

14. PHOTOVOLTAIC CELLS
Photovoltaic (PV) cells are made of special materials called
semiconductors such as silicon, which is currently the most commonly
used.
Basically, when light strikes the cell, a certain portion of it is
absorbed within the semiconductor material.
 PV cells also all have one or more electric fields that act to force
electrons freed by light absorption to flow in a certain direction.
This flow of electrons is a current, and by placing metal contacts on
the top and bottom of the PV cell, we can draw that current off to use
externally.

15. SOLAR PANEL
Expose the cell to light, and the energy
from each photon (light particle) hitting
the silicon, will liberate an electron and a
corresponding hole.
If this happens within range of the
electric field’s influence, the electrons will
be sent to the N side and the holes to the P
one, resulting in yet further disruption of
electrical neutrality
This flow of electrons is a current; the
electrical field in the cell causes a voltage
and the product of these two is power

16. WORKING OF PROJECT
Solar panel being a current source is used to change battery B1 via D10. While
the battery is fully charged the voltage at cathode point of D10 goes up. This
results in the set point voltage at pin 3 of U1:A to go up above the reference
voltage because the potential divider formed out of R12, 5K variable
resistor,R13 goes up.
This results in pin no 1 of U1:A to go high to switch ‘ON’ the transistor Q1
that places drive voltage to the Mosfet IRF640 .such that the current from solar
panel is bypassed via D11 and the Mosfet drain and source
Simultaneously pin 7 of U1:B also goes high to drive a led D1 indicating
battery is being fully charged
Whenever the solar charge is low the circuit utilizes the power from battery, if
the battery goes into deep discharge ,then it utilizes power from solar power then
the Led’s flashes light

17. THANKYOU