density based traffic control system with mannual override

1
CHAPTER-1
1.1 SUFFERINGS
FIGURE 1.1: SUFFERED FROM TRAFFIC CONGESTION VS NOT SUFFERED
FROM TRAFFIC CONGESTION
1.2 TROUBLE VS SATISFACTION
97%
3%
0
20
40
60
80
100
120
suffered traffic congestion not suffered
Series 1

2
FIGURE 2.2: TROUBLE VS SATISFACTION WITH THE CURRENT SYSTEM
1.3 PUBLIC’S OPINION
94%
6%
problem with the current system
satisfied with the current system
0
20
40
60
80
wasting time
wasting fuel
79%
21%
publics opinion

3
CHAPTER 2
2.1OBJECTIVE OF THE PROJECT
This project aims at reducing traffic congestion and unwanted time delay during the traffic
light switch overs especially when the traffic is very low. It is designed to implement in places near
the junctions where the traffic signals are placed, in order to reduce the congestion in traffic. It
keeps a track of number of vehicles on each side of junction and accordingly adjusts the time for
each traffic light signals. The higher the number of vehicles on the road the longer will be the time
delay allotted for that corresponding traffic light signal.
2.2 OVERVIEW
The overview of this project is to implement density based traffic light control system using
IR technology and 89C51 microcontroller. 89C51 has very efficient architecture which can be
used for low end security systems and IR is widely adapted technology for communication.
2.3 PURPOSE
Purpose of the current work is to study and analyse the counting and control system by using
89C51 controller.
2.4 SCOPE
Current work focuses on effective use of IR sensor and 89C51 controllers for digital
security systems.

4
2.5 PROBLEM FORMULATION
The problem with the traffic system is that for every minute the vehicles at the junction
will be heavy and the traffic lights shall be changed to each side for some fixed time. Even though
there are no vehicles at particular side, the traffic signals will glow for fixed time. Due to this
vehicles at other side have to wait for the process to complete. So to reduce the wastage of time,
we can implement the system that controls the traffic based on the heavy flow of vehicles at any
particular side. With this system, we will identify the density of each side at the junction and
give path to the particular side which has heavy flow of vehicles and keep remaining at stop
position. So, for this to know the density at each side of the junction, we shall use IR technology
2.6 DESCRIPTION OF PROJECT
2.6.1 Existing System
Nowadays traffic lights are set on in the different directions with fixed time delay, following a
particular cycle while switching from one signal to other. This creates unwanted congestion during
peak hours. This is a time consuming system.
2.6.2 Proposed System
The density based traffic light control is an automated way of controlling signals in accordance
to the density of traffic in the roads. IR sensors are placed in the intersecting road at fixed distances
from the signal placed in the junction. The time delay in the traffic signal is set based on the density
of vehicles on the roads.
The IR sensors are used to sense the number of vehicles on the road. According to the IR count,
microcontroller takes appropriate decisions as to which road is to be given the highest priority and
the longest time delay for the corresponding traffic light and also providing an emergency way for
the ambulance.

5
2.7 PROCESS DESCRIPTION
As per the process diagram, initially the signals are started by giving the power supply. The
first step is to make sure that all the signals are all in ON condition. During this all the traffic
signals will blink in yellow light. This indicates that they are all in the working condition.
The next step is to check for the density of traffic on roads. The density is calculated by
means of IR circuit. Depending on the number of vehicles that cut the light travelling from the
receiver to transmitter of the IR circuit the count of the vehicles is registered in the microcontroller.
This is followed by the next step in which the microcontroller decides as to which road should
be given the highest priority. This is based on the density of traffic on each road and also it depends
on the speed at which an IR circuit registers the count.
The next step is to assign time delays for each road. The time delays have already been set
for certain specific counts in the microcontroller. As soon as the microcontroller receives the counts
from the IR circuit it will immediately detect the density of each road and accordingly allot the time
delays for which each signal will show the green light. The higher the traffic density, the longer will
be the time delay allotted.
In the final step, the microcontroller makes sure that the lowest density road is opened and
that the delay of the green light for that particular signal also comes to an end. Once all the roads are
opened in a sequence, then the microcontroller again goes back to the second step where it checks
for the density of traffic in each road. The whole process is repeated in cycle. The main point that is
to be noted regarding this process is that, whenever a particular road has no traffic, correspondingly,
the yellow light in the traffic signal will glow.

7
2.8 PARAMETERS CONSIDERED
Signal priority
1)normal loop
2)density loop
3)ambulance loop
Priority of roads
 Until there is no ambulance or no density the normal loop will continue with
an time delay of 5 sec when the density or ambulance occurs then the
particular road will be given green until the road becomes free
Priority of ambulance
In this case while the density is in working then if an ambulance occurs then the density
signals should break and the road on which ambulance is present will be given green by the external
switches given

8
2.9 BLOCK DIAGRAM
FIGURE 1.2: BLOCK DIAGRAM

9
CHAPTER-3
3.1 EMBEDDED SYSTEMS
An embedded system is a special-purpose computer system designed to perform one or a few
dedicated functions, often with real-time computing constraints. It is usually embedded as part of a
complete device including hardware and mechanical parts. In contrast, a general-purpose computer,
such as a personal computer, can do many different tasks depending on programming. Embedded
systems control many of the common devices in use today.
Since the embedded system is dedicated to specific tasks, design engineers can optimize it,
reducing the size and cost of the product, or increasing the reliability and performance. Some
embedded systems are mass-produced, benefiting from economics of scale. Physically, embedded
systems range from portable devices such as digital watches and mp4 players, to large stationary
installations like traffic lights, factory controllers, or the systems controlling nuclear power
stations. Complexity varies from low, with a single microcontroller chip, to very high with multiple
units, peripherals and networks mounted inside a large chassis or enclosure.
In general, "embedded system" is not an exactly defined term, as many systems have some
element of programmability. For example, handheld computers share some elements with
embedded systems such as the operating systems and microprocessors which power them but are
not truly embedded systems, because they allow different applications to be loaded and peripherals
to be connected.

10
3.2 CHARACTERISTICS
1. Embedded systems are designed to do some specific task, rather than be a general-purpose
computer for multiple tasks. Some also have real-time performance constraints that must be met,
for reasons such as safety and usability; others may have low or no performance requirements,
allowing the system hardware to be simplified to reduce costs.
2. Embedded systems are not always standalone devices. Many embedded systems consist of
small, computerized parts within a larger device that serves a more general purpose. For example,
the features an embedded system for tuning the strings, but the overall purpose of the Robot Guitar
is, of course, to play music. Similarly, an embedded system in automobiles provides a specific
function as a subsystem of the car itself.
3. The program instructions written for embedded systems are referred to as firmware, and are
stored in read-only memory or flash memory chips. They run with limited computer hardware
resources: little memory, small or non-existent keyboard and/or screen.
FIGURE 3.1 A TYPICAL EMBEDDED SYSTEM BLOCK DIAGRAM

11
3.3 MICROCONTROLLER
Microcontroller is a general purpose device, which integrates a number of the components
of a microprocessor system on to a single chip. It has inbuilt CPU, memory and peripherals to
make it as a mini computer. A microcontroller combines on to the same microchip:
 The CPU core
 Memory (both ROM and RAM)
 Some parallel digital i/o
Microcontrollers will combine other devices such as:
 A timer module to allow the microcontroller to perform tasks certain time periods.
 A serial I/O port to allow data to flow between the controller and other devices such as a
PIC or another microcontroller.
 An ADC to allow the microcontroller to accept analog input data processing.
Microcontrollers are:
 Smaller in size
 Consume less power
 Inexpensive
Microcontroller is a standalone unit, which can perform functions on its own without any
requirement for additional hardware like I/O ports and external memory.
The heart of the microcontroller is the CPU core. In the past, this has traditionally been
based on an 8-bit microprocessor unit. For example, Motorola uses a basic 6800 microprocessor
core in their 6805/6808 microcontroller devices.
In the recent years microcontrollers have been developed around specifically designed CPU
cores, for example the microchip PIC range of microcontrollers.
The micro controller, nowadays, is an indispensable device for electrical/electronic
engineers and also for technicians in the area, because of its versatility and its enormous
application. .Born of parallel developments in computer architecture and integrated circuit
fabrication, the microprocessor or computer on chip first becomes a commercial reality in 1971.

12
With the introduction of the 4 bit 4004 by a small, unknown company by the name of Intel
Corporation. Other, well established, semiconductor firms soon followed Intel's pioneering
technology so that by the late 1970's we could choose from a half dozen or so micro processor
type. The 1970s also saw the growth of the number of personal computer users from a Handful of
hobbyists and hackers to millions of business, industrial, governmental, defense, and educational
and private users now enjoying the advantages of inexpensive computing.
A bye product of microprocessor development was the micro controller. The same
fabrication techniques and programming concepts that make possible general-purpose
microprocessor also yielded the micro controller.
Among the applications of a micro controller we can mention industrial automation,
mobile telephones, radios, microwave ovens and VCRs. Besides, the present trend in digital
electronics is toward restricting to micro controllers and chips that concentrate a great quantity of
logical circuits, like PLDs (Programmable Logic Devices) and GALs (Gate Array Logic). In
dedicated systems, the micro controller is the best solution, because it is cheap and easy to
manage.
3.4 COMMUNICATION
Communication refers to the sending, receiving and processing of information by
electric means. As such, it started with wire telegraphy in the early 80's, developing with
telephony and radio some decades later. Radio communication became the most widely used
and refined through the invention of and use of transistor, integrated circuit, and other semi-
conductor devices. Most recently, the use of satellites and fiber optics has made
communication even more wide spread, with an increasing emphasis on computer and other
data communications.
A modern communications system is first concerned with the sorting, processing and
storing of information before its transmission. The actual transmission then follows, with
further processing and the filtering of noise. Finally we have reception, which may include
processing steps such as decoding, storage and interpretation. In this context, forms of
communications include radio, telephony and telegraphy, broadcast, point to point and mobile
communications (commercial and military), computer communications, radar, radio telemetry
and radio aids to navigation. It is also important to consider the human factors influencing a
particular system,

13
Since they can always affect its design, planning and use. Wireless communication has
become an important feature for commercial products and a popular research topic within the last
ten years. There are now more mobile phone subscriptions than wired-line subscriptions. Lately,
one area of commercial interest has been low-cost, low-power, and short-distance wireless
communication used for personal wireless networks." Technology advancements are providing
smaller and more cost effective devices for integrating computational processing, wireless
communication, and a host of other functionalities. These embedded communications devices will
be integrated into applications ranging from homeland security to industry automation and
monitoring. They will also enable custom tailored engineering solutions, creating a
revolutionary way of disseminating and processing information. With new technologies and
devices come new business activities, and the need for employees in these technological areas.
Engineers who have knowledge of embedded systems and wireless communications will be in
high demand. Unfortunately, there are few adorable environments available for development and
classroom use, so students often do not learn about these technologies during hands-on lab
exercises. The communication mediums were twisted pair, optical fiber, infrared, and generally
wireless radio.
3.5 IR REMOTE THEORY
IR sensor is the combination of IR LED with Photo Diode. After this combination we
are connecting the Darlington Pair Transistor. End of the IR sensor we have to connect a
NOT gate for the inverting purpose means low input have corresponding low output. At last
this entire connector is connected to any one external interrupt to generating the interruption
of the main program.
Infra-Red actually is normal light with a particular colour. We humans can't see this
colour because its wave length of 950nm is below the visible spectrum. That's one of the reasons
why IR is chosen for remote control purposes, we want to use it but we're not interested in seeing
it. Another reason is because IR LEDs are quite easy to make, and therefore can be very cheap.IR
LED wave length range 1.6m to 7.4m. Materials used for IR LED are InSB, Ge,Si, GaAs, CdSe .
This IR is not in visible range for observation purpose.

14
CHAPTER-4
4.1 89C51 MICROCONTROLLER
4.1.1 Features
 Compatible with MCS 51™ Products
 4K Bytes of In System Reprogrammable Flash Memory
 Endurance: 1,000 Write/Erase Cycles
 Fully Static Operation: 0 Hz to 24 MHz
 Three level Program Memory Lock
 128 x 8·bit Internal RAM
 32 Programmable I/O Lines
 Two 16·bit Timer/Counters
 Six Interrupt Sources
 Programmable Serial Channel
 Low power Idle and Power down Modes
4.1.2 Description
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K
bytes of Flash programmable and erasable read only memory (PEROM). The device is
manufactured using Atmel's high-density non-volatile memory technology and is compatible
with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the
program memory to be reprogrammed in-system or by a conventional non-volatile memory
programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel
AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective
solution to many embedded control applications.

15
4.1.3 Architecture
FIGURE4.1 ARCHITECTURE OF 89C51 MICROCONTROLLER

16
4.1.4 Pin configurations
FIGURE 4.2: PIN CONFIGURATION

17
4.1.5 Pin descriptions
VCC
Pin 40 provides +5v input supply voltage
PORT 0
Port 0 is an 8-bit open drain 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
Port 1 is an 8-bit bidirectional 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. In addition, 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).Port 1 also receives the low-order address bytes during Flash
programming and verification
PORT 2
Port 2 is an 8-bit bidirectional I/O port with internal pull ups. The Port 2 output buffers
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.

18
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
Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers
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 also serves the functions of various special features of the AT89S52, as shown in the
following table.
TABLE 4.1: PORT 3 FUNCTIONS
Port Pin Alternate Functions
P3.0 RXD (serial input port)
P3.1 TXD (serial output port)
P3.2 INT0 (external interrupt 0)
P3.3 INT1 (external interrupt 1)
P3.4 T0 (timer 0 external input)
P3.5 T1 (timer 1 external input)
P3.6 WR (external data memory write
strobe)P3.7 RD (external data memory read strobe)
Port 3 also receives some control signals for Flash programming and verification.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is running
resets the device. This pin drives High for 96 oscillator periods after the Watchdog times out.
The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the
default state of bit DISRTO, the RESET HIGH out feature is enabled

19
ALE/PROG
Address Latch Enable (ALE) 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.
.
PSEN
Program Store Enable (PSEN) is the read strobe to external program memory. When the
AT89S52 is executing code from external program memory, PSEN is activated twice each
machine cycle, except that two PSEN activations are skipped during each access to external data
memory.
EA/VPP
External access enables. EA must be strapped to GND in order to enable the device to
fetch code from external program memory locations starting at OOOOH 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.
XTALl
Input to the inverting oscillator amplifier
XTAL2
Output from the inverting oscillator amplifier
4.1.6 Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which
can be configured for use as an on-chip oscillator, as shown in Figure 4.3. Either a quartz crystal or
ceramic resonator may be used. To drive the device from an external clock source, XTAL2
should be left unconnected while XTAL1 is driven as shown in Figure 4.4.

20
There are no requirements on the duty cycle of the external clock signal, since the input to the
internal clocking circuitry is through a divide by two flip-flops, but minimum and maximum voltage
high and low time specifications must be observed.
4.1.7 Power memory lock bits
On the chip are three lock bits which can be left unprogrammed (U) or can be programmed
(P) to obtain the additional features listed in the table below.
When lock bit is programmed, the logic level at the EA pin is sampled and latched during
reset. If the device is powered up without a reset, the latch initializes to a random value, and holds
the value until reset is activated. It is necessary that the latched value of EA be in agreement wi
the current logic level at that pin in order for the device to function properly.
FIGURE 4. 3: OSCILLATOR CONNECTIONS
C2
C1
XTAL1
XTAL1
GND
FIGURE 4. 4: EXTERNAL CLOCK DRIVE
CONFIGURATION
NC

21
TABLE 4.2: PROGRAM LOCK BITS AND ITS PROTECTION
Program Lock Bits
Protection Type
LB
1
LB
2
LB
3
1 U u u No program lock features
2 P u u MOV instructions executed from external program memory
are disabled from fetching code bytes from internal memory,
EA is sampled and latched on reset, and further programming
of the Flash is disabled3 P p u Same as mode 2, also verify is disabled
4 P p p Same as mode 3, also external execution is disabled

22
CHAPTER-5
5.1 INFRARED LED
IR sensor is the combination of IR LED with PHOTO DIODE. After this combination
we are connecting the DARLINGTON PAIR TRANSISTOR. End of the IR sensor we have to
connect a NOT gate for the inverting purpose means low input have corresponding low output
Infra-Red actually is normal light with a particular colour. We humans can't see this colour
because its wave length of 950nm is below the visible spectrum. That's one of the reasons why
IR is chosen for remote control purposes, we want to use it but we're not interested in seeing it.
Another reason is because IR LEDs are quite easy to make, and therefore can be very cheap.
Although we humans can't see the Infra-Red light emitted from a remote control doesn't
mean we can't make it visible. A video camera or digital photo camera can "see" the Infra-Red
light as you can see in this picture. If you own a web cam, point your remote to it, press any
button and you‘ll see the LED flicker. They do dozens of different jobs and are found in all kind
of devices. Among other things they form the numbers on digital clocks, transmit information
from remote controls, light up watches and tell you when your appliances are turned on.
Collected together, they can from images on a jumbo television screen or illuminate a traffic
light.
FIGURE: 5.1 IR LED USED IN REMOTE CONTROL

23
5.1.1 Darlington pair
An emitter follower offers high impedance of 500Kohms. For applications requiring still
higher input impedance, we may use what is called Darlington in place of conventional transistor.
This Darlington pair basically consists of two transistors cascaded in cc configuration. In the
figure shown below the input impedance of the second transistor constitutes the load impedance
of the first.
We thus conclude that in comparison with a conventional single transistor emitter follower
has in higher current gain, higher input impedance and almost the same voltage gain lower out
put impedances.
FIGURE: 5.2 Darlington Pair
5.2 MODULATION
Modulation is the answer to make our signal stand out above the noise. With
modulation we make the IR light source blink in a particular frequency. The IR receiver will
be tuned to that frequency, so it can ignore everything else. You can think of this blinking as
attracting the receiver's attention. We humans also notice the blinking of yellow lights at
construction sites instantly, even in bright daylight.

24
In the picture above you can see a modulated signal driving the IR LED of the transmitter on
the left side. The detected signal is coming out of the receiver at the other side.
FIGURE 5.3: modulated signal driving LED
In serial communication we usually speak of 'marks' and 'spaces'. The 'space' is the
default signal, which is the off state in the transmitter case. No light is emitted during the
'space' state. During the 'mark' state of the signal the IR light is pulsed on and off at a
particular frequency. Frequencies between 30 kHz and 60 kHz are commonly used in
consumer electronics. At the receiver side a 'space' is represented by a high level of the
receiver's output. A 'mark' is then automatically represented by a low level.
Please note that the 'marks' and 'spaces' are not the I-s and 0-s we want to transmit. The
real relationship between the 'marks' and 'spaces' and the I-s and 0-s depends on the protocol
that's being used. More information about that can be found on the pages that describe the
protocols.
5.3 TRANSMITTER
In the picture below we can see a modulated signal driving the IR LED of the transmitter
on the left side. The detected signal is coming out of the receiver at the other side.
FIGURE 5.4: IR TRANSMITTER

25
The transmitter usually is a battery powered handset. It should consume as little power as
possible, and the IR signal should also be as strong as possible to achieve an acceptable control
distance. Preferably it should be shock proof as well.
Many chips are designed to be used as IR transmitters. The older chips were dedicated to
only one of the many protocols that were invented. Nowadays very low power microcontrollers
are used in IR transmitters for the simple reason that they are more flexible in their use. When no
button is pressed they are in a very low power sleep mode, in which hardly any current is
consumed. The processor when wakes up to transmit the appropriate IR command only a key is
pressed.
FIGURE 5.5: TRANSISTOR CIRCUIT USED TO DRIVE IR LED
Quartz crystals are seldom used in such handsets. They are very fragile and tend to break
easily when the handset is dropped. Ceramic resonators are much more suitable here, because
they can withstand larger physical shocks. The fact that they are a little less accurate is not
important.
The current through the LED (or LEDs) can vary from 100mA to well over IA! In order
to get an acceptable control distance the LED currents have to be as high as possible. A trade-off
should be made between LED parameters, battery lifetime and maximum control distance. LED
currents can be that high because the pulses driving the LEDs are very short. Average power
dissipation of the LED should not exceed the maximum value though. You should also see to it
that the maximum peek current for the LED is not exceeded. All these parameters can be found
in the LED's data sheet.

26
A simple transistor circuit can be used to drive the LED. A transistor with a suitable hfe
and switching speed should be selected for this purpose. The resistor values can simply be
calculated using Ohm’s law. Remember that the nominal voltage drop over an IR LED is
approximately 1.1V. The normal driver, described above, has one disadvantage. As the battery
voltage drops, the current through the LED will decrease as well. This will result in a shorter
control distance that can be covered.
An emitter follower circuit can avoid this. The 2 diodes in series will limit the pulses on
the base of the transistor to 1.2V. The base-emitter voltage of the transistor subtracts O.6V
from that, resulting in constant amplitude of O.6V at the emitter. This constant amplitude across
a constant resistor results in current pulses of a constant magnitude. Calculating the current
through the LED is simply applying ohm' law.
5.4 PHOTODIODES
Unfortunately for us there are many more sources of Infrared light. The sun is the brightest
source of all, but there are many others, like: light bulbs, candles, central heating system, and
even our body radiate Infrared light. In fact everything that radiates heat, also radiates Infrared
light. Therefore we have to take some precautions to guarantee that our IR message gets across to
the receiver without errors.
UV enhanced photodiodes are optimized for the UV and blue spectral regions,
Photodiodes are a two- electrode, radiation-sensitive junction formed in a semiconductor
material in which the reverse current varies with illumination. Photodiodes are used for the
detection of optical power and for the conversion of optical power to electrical power.
Photodiodes can be PN, PIN, or avalanche.
PN photodiodes feature a two-electrode, radiation-sensitive PN junction formed in a
semiconductor material in which the reverse current varies with illumination. PIN
photodiodes are diodes with a large intrinsic region sandwiched between P-doped and
N-doped semiconducting regions. Photons absorbed in this region create electron-hole pairs that
are then separated by an electric field, thus generating an electric current in a load circuit.

27
In most applications, the seven segments are of nearly uniform shape and size (usually
elongated hexagons, though trapezoids and rectangles can also be used), though in the case
of adding machines, the vertical segments are longer and more oddly shaped at the ends in an effort
to further enhance readability.
The numerals 0, 1, 6, 7 and 9 may be represented by two or more different glyphs on seven-
segment displays.
The seven segments are arranged as a rectangle of two vertical segments on each side with
one horizontal segment on the top, middle, and bottom. Additionally, the seventh segment bisects
the rectangle horizontally. There are also fourteen-segment displays and sixteen-segment
displays (for full alphanumeric); however, these have mostly been replaced by dot-matrix displays.
The segments of a 7-segment display are referred to by the letters A to G, where the
optional DP decimal point (an "eighth segment") is used for the display of non-integer numbers.
Using a restricted range of letters that look like (upside-down) digits, seven-segment
displays are commonly used by school children to form words and phrases using a technique
known as "calculator spelling".

28
CHAPTER 6
6.1 INTRODUCTION
The present chapter introduces the operation of power supply circuits built using filters,
rectifiers and then voltage regulators. Starting with an ac voltage, then filtering to a dc voltage is
obtained by rectifying the ac voltage, then filtering to a dc level and finally, regulating to obtain a
desired fixed dc voltage. The regulation is usually obtained from an IC voltage regulator unit,
which takes a dc voltage and provides a somewhat lower dc voltage, which remains the same even
if the input dc varies, or the output load connected to the dc voltage changes.
FIGURE 6.1: COMPONENTS OF LINEAR POWER SUPPLY

29
6.2 TRANSFORMER:
A transformer is an electrical device which is used to convert electrical power from
one Electrical circuit to another without change in frequency.
Transformers convert AC electricity from one voltage to another with little loss of power.
Transformers work only with AC and this is one of the reasons why mains electricity is AC.
Step-up transformers increase in output voltage, step-down transformers decrease in output
voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains
voltage to a safer low voltage. The input coil is called the primary and the output coil is called
the secondary. There is no electrical connection between the two coils; instead they are linked by
an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the
middle of the circuit symbol represent the core. Transformers waste very little power so the
power out is (almost) equal to the power in. Note that as voltage is stepped down current is
stepped up.
FIGURE 6.2: AN ELECTRICAL TRANSFORMER
The ratio of the number of turns on each coil, called the turn's ratio, determines the ratio
of the voltages. A step-down transformer has a large number of turns on its primary (input) coil
which is connected to the high voltage mains supply, and a small number of turns on its
secondary (output) coil to give a low output voltage.

30
Turns ratio = Vp/VS = Np/NS
Power Out= Power In
VS * IS=VP * IP
Vp = primary (input) voltage
Np = number of turns on primary coil
Ip = primary (input) current
6.3 RECTIFIER
A circuit which is used to convert ac to dc is known as RECTIFIER. The process of
conversion ac to dc is called "rectification"
6.3.1 Types of rectifiers
 Half wave Rectifier
 Full wave Rectifier
1. Centre tap full wave rectifier
2. Bridge type full bridge rectifier.
Full-wave Rectifier:
From the above comparison we came to know that full wave bridge rectifier as more
advantages than the other two rectifiers. So, in our project we are using full wave bridge rectifier
circuit.

31
TABLE 6.1: COMPARISONOF RECTIFIER CIRCUITS
Parameter
Type of Rectifier
Half wave Full wave Bridge
Number of diodes 1 2 4
PIV of diodes Vm 2Vm
Vm
D.C output voltage
Vm/z 2Vm/ 2Vm/
Vdc at no-load
0.318Vm 0.636Vm 0.636Vm
Ripple factor
1.21 0.482 0.482
Ripple frequency
F
2f 2f
Rectification efficiency
0.406 0.812 0.812
Transformer Utilization
Factor{TUF) 0.287
0.693 0.812
RMS voltage Vrms
Vm/2 Vm/V2 Vm/V2

32
Bridge Rectifier:
A bridge rectifier makes use of four diodes in a bridge arrangement to achieve full-
wave rectification. This is a widely used configuration, both with individual diodes wired as
shown and with single component bridges where the diode bridge is wired internally.
A bridge rectifier makes use of four diodes in a bridge arrangement as shown in fig (6.3)
to achieve full-wave rectification. This is a widely used configuration, both with individual
diodes wired as shown and with single component bridges where the diode bridge is wired
internally.
FIGURE 6.3: BRIDGE RECTIFIER
6.3.2 Operation
During positive half cycle of secondary, the diodes D2 and D3 are in forward biased
while D1 and D4 are in reverse biased as shown in the fig(b). The current flow direction is
shown in the fig (6.4) with dotted arrows.

33
FIGURE 6.4: POSITIVE HALF CYCLE
During negative half cycle of secondary voltage, the diodes D1 and D4 are in forward
biased while D2 and D3 are in reverse biased as shown in the fig(c). The current flow direction
is shown in the fig (c) with dotted arrows.
FIGURE 6.5: NEGATIVE HALF CYCLE

34
6.4 FILTER
A Filter is a device which removes the ac component of rectifier output but allows the
dc component to reach the load.
6.4.1 Capacitor Filter
We have seen that the ripple content in the rectified output of half wave rectifier is 121%
or that of full-wave or bridge rectifier or bridge rectifier is 48% such high percentages of ripples
is not acceptable for most of the applications. Ripples can be removed by one of the following
methods of filtering.
(a) A capacitor, in parallel to the load, provides an easier by -pass for the ripples voltage
though it due to low impedance. At ripple frequency and leave the D.C. to appear at the load.
(b) An inductor, in series with the load, prevents the passage of the ripple current (due
to high impedance at ripple frequency) while allowing the dc (due to low resistance to dc).
(c) Various combinations of capacitor and inductor, such as L-section filter section filter,
multiple section filter etc. which make use of both the properties mentioned in (a) and (b) above.
Two cases of capacitor filter, one applied on half wave rectifier and another with full wave
rectifier.
Filtering is performed by a large value electrolytic capacitor connected across the DC
supply to act as a reservoir, supplying current to the output when the varying DC voltage
from the rectifier is falling. The capacitor charges quickly near the peak of the varying DC, and
then discharges as it supplies current to the output. Filtering significantly increases the average
DC voltage to almost the peak value (1.4 x RMS value).

35
To calculate the value of capacitor(C),
C = NOP3OfOrORl
Where,
f =supply frequency,
r = ripple factor,
Rl = load resistance
Note: In our circuit we are using 1000QF hence large value of capacitor is placed to reduce
ripples and to improve the DC component.

36
6.5 REGULATOR
Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or
variable output voltages. The maximum current they can pass also rates them. Negative voltage
regulators are available, mainly for use in dual supplies. Most regulators include some
automatic protection from excessive current (‘overload protection’) and overheating (‘thermal
protection’). Many of the fixed voltage regulators ICs have 3 leads and look like power
transistors, such as the 7805 +5V 1A regulator shown on the right. The LM7805 is simple to
use. You simply connect the positive lead of your unregulated DC power supply (anything
from 9VDC to 24VDC) to the Input pin, connect the negative lead to the Common pin
and then when you turn on the power, you get a 5 volt supply from the output pin.
FIGURE 6.6: A THREE TERMINAL VOLTAGE REGULATOR
78XX
The Bay Linear LM78XX is integrated linear positive regulator with three terminals. The
LM78XX offer several fixed output voltages making them useful in wide range of applications.
When used as a zener diode/resistor combination replacement, the LM78XX usually results in an
effective output impedance improvement of two orders of magnitude, lower quiescent current.
The LM78XX is available in the TO-252, TO-220 & TO-263packages,
6.5.1 Features:
 Output Current of 1.54
 Output voltage Tolerance of 5%
 Internal thermal overload protection
 Internal Short-Circuit Limited
 Output Voltage 0V,6V,8V,9V,10V,12V,15V,18V,24V

37
CHAPTER-7
7.1 HARDWARE DESIGN
Designing of this system is possible when you select the specific controller to suite.
For this we selected 89C51 controller. With the help of 89C51 controller traffic control
system can be implemented successfully with the help IR technology. To the controller we
connected IR transmitter and receiver circuit. Instead of IR transmitter and receiver we can
go with photo diode and photo transmitters also. Here we are using four IR pairs for each
side.
Whenever vehicles reach the junction on each side, then IR detects the vehicle by
sending signal to controller and the controller will counts the count of vehicles. And
calculate the maximum count from them and give the path to side which has maximum count
by glowing green LED and other LED and other three sides red LED shall be glow.
BLOCKDIAGRAM

38
7.1.1 SCHEMATIC DIAGRAM
FIGURE 7.2:SCHEMATIC DIAGRAM

39
7.1.2 Schematic description
The main aim of this power supply is to convert the 230V AC into 5V DC in order to give
supply for the TTL. This schematic explanation includes the detailed pin connections of every
device with the microcontroller.
This schematic explanation includes the detailed pin connections of every device
with the microcontroller. Let us see the pin connections of each and every device with the
microcontroller in detail.
Power Supply
In this process we are using a step down transformer, a bridge rectifier, a smoothing
circuit and the RPS. At the primary of the transformer we are giving the 230V AC supply. The
secondary is connected to the opposite terminals of the Bridge rectifier as the input. From other
set of opposite terminals we are taking the output to the rectifier.
The bridge rectifier converts the AC coming from the secondary of the
Transformer into pulsating DC. The output of this rectifier is further given to the smoother
circuit which is capacitor in our project. The smoothing circuit eliminates the ripples from the
pulsating DC and gives the pure DC to the RPS to get a constant output DC voltage. The RPS
regulates the voltage as per our requirement.
Microcontroller
The microcontroller AT89S51 with Pull up resistors at Port0 and crystal oscillator of
11.0592MHz crystal in conjunction with couple of capacitors of is placed at 18th & 19th pins
of 89S51 to make it work (execute) properly.
IR Module:
The IR transmitter and receiver are input and output devices. This is connected to the port
P2 of the Microcontroller.
LEDs:
Here the LEDs are connected to one of microcontroller port by using resistor.

40
7.2 SOFTWARE COMPONENTS
Software used is:
 Keil software for C programming
 Proteus for schematic design
KEIL µVision3
µVision3 is an IDE (Integrated Development Environment) that helps you write, compile,
and debug embedded programs. It encapsulates the following components:
 Project Manager
 Facility
 Tool configuration
 Editor
 A powerful debugger
This software is used for execution of microcontroller programs.Keil development tools
for the MC architecture support every level of software developer from the professional
applications engineer to the student just learning about embedded software development.
The industry-standard Keil C compilers, macro assemblers, debuggers, real, time Kernels,
Single-board computers and emulators support all derivatives and help you to get more projects
completed on schedule. The Keil software development tools are designed to solve the complex
problems facing embedded software developers.
 When starting a new project, simply select the microcontroller you the device
database and the µvision IDE sets all compiler, assembler, linker, and memory
options for you.
 Numerous example programs are included to help you get started with the most
popular embedded avr devices.
 The Keil µVision debugger accurately simulates on-chip peripherals (PC, CAN, and
UART, SPl, interrupts, I/O ports, A/D converter, D /A converter and PWM modules) of
your avr device. Simulation helps you understand h/w configurations and avoids time

41
wasted on setup problems. Additionally, with simulation, you can write and test
applications before target h/w is available.
 When you are ready to begin testing your s/w application with target h/w, use the
MONS1, MON390, MONADl, or flash MONS1 target monitors, the lSDS1 in-System
 Debugger or the ULlNK USB- RTAG adapter to download and test program code on
your target system.
PROTEUS
Proteus is software for microprocessor simulation, schematic capture, and printed circuit
board (PCB) design. It is developed by Labcenter Electronics.
EMBEDDED C:
The programming Language used here in this project is an Embedded C Language. This
Embedded C Language is different from the generic C language in few things like
a) Data types
b) Access over the architecture addresses.
The Embedded C Programming Language forms the user friendly language with access
over Port addresses, SFR Register addresses etc.

42
Signed char:
 Used to represent the – or + values
 As a result, we have only 7 bits for the magnitude of the signed number, giving us
values from -128 to +127. Embedded C data types:
TABLE 7.1: DATA TYPES IN EMBEDDED C
Data Types Size in Bits Data Range/Usage
unsigned char 8-bit 0-255
signed char 8-bit -128 to +127
unsigned int 16-bit 0 to 65535
signed int 16-bit -32,768 to +32,767
Sbit 1-bit SFR bit addressable only
Bit 1-bit RAM bit addressable only
Sfr 8-bit RAM addresses 80-FFH only

43
IMPLEMENTATION
The applications as discussed in the design are implemented and the source code related
to the current work is included the forthcoming chapter.
SOFTWARE
µVision3
µvision3 is an IDE (Integrated Development Environment) that helps you write,
compile, and debug embedded programs. It encapsulates the following components:
 Project Manager
 Facility
 Tool configuration
 Editor
 A powerful debugger
To help you get started, several example programs (located in the C51Examples,
C251Examples,C166Examples, and ARM...Examples) are provided.
! HELLO is a simple program that prints the string "Hello World" using the Serial Interface.
µVision2
Building an Application in µVision2
To build (compile, assemble, and link) an application in µvisionz, you must:
1. Select Project - (for example, 166EXAMPLESHELLOHELLO.UV2). z. Select Project -
Rebuild all target files or Build target.
µvisionz compiles, assembles, and links the files in your project.

44
Creating Your Own Application in µVision2
To create a new project in µVision2 you must:
1. Select Project - New Project.
2. Select a directory and enter the name of the project file.
3. Select Project - Select Device and select an 8051, 251, or C16x/ST10 device from the
Device Database™.
4. Create source files to add to the project.
5. Select Project - Targets, Groups, Files, Add/Files, select Source Group1, and add the
source files to the project.
6. Select Project - Options and set the tool options. Note when you select the target device
from the Device Database™ all special options are set automatically. You typically only
need to configure the memory map of your target hardware. Default memory model
settings are optimal for most applications.
7. Select Project - Rebuild all target files or Build target.
Debugging an Application in µVision2
To debug an application created using uvision2, you must:
1. Select Debug - Start/Stop Debug Session.
2. Use the Step toolbar buttons to single-step through your program. You may enter G, main
in the Output Window to execute to the main C function.
3. Open the Serial Window using the Serial #1 button on the
toolbar. Debug your program using standard options like Step,
Go, Break, and so on.
Starting µVision2 and creating a Project
µVision2 is a standard Windows application and started by clicking on the program icon.
To create a new project file select from the uvision2 menu
Project - New Project. This opens a standard Windows dialog that asks you for the new
project file name.

45
We suggest that you use a separate folder for each project. You can simply use the icon
Create New Folder in this dialog to get a new empty folder. Then select this folder and enter
the file name for the new project, i.e. Project1.
µVision2 creates a new project file with the name PROJECT1.Uv2 which contains a
default target and file group name. You can see these names in the Project
Window - Files.
Now use from the menu Project - Select Device for Target and select a CPU for your
project. The Select Device dialog box shows the uvisionz device database. Just select the
microcontroller you use. We are using for our examples the Philips 80C51RD+ CPU. This
selection sets necessary tool options for the 80C51RD+ device and simplifies in this way the tool
Configuration
Building Projects and Creating a HEX Files
Typical, the tool settings under Options - Target are all you need to start a new
application. You may translate all source files and line the application with a click on the Build
Target toolbar icon. When you build an application with syntax errors, uvisionz will display
errors and warning messages in the Output Window - Build page. A double click on a message
line opens the source file on the correct location in a µvisionz editor window. Once you have
successfully generated your application you can start debugging.
After you have tested your application, it is required to create an Intel HEX file to
download the software into an EPROM programmer or simulator. uvisionz creates HEX files
with each build process when Create HEX files under Options for Target - Output is
enabled. You may start your PROM programming utility after the make process when you
specify the program under the option Run User Program #1.
CPU Simulation
µvisionz simulates up to 16 Mbytes of memory from which areas can be mapped
for read, write, or code execution access. The uvisionz simulator traps and reports illegal
memory accesses being done.

46
In addition to memory mapping, the simulator also provides support for the integrated
peripherals of the various 8051 derivatives. The on-chip peripherals of the CPU you have
selected are configured from the Device
Database selection
You have made when you create your project target. Refer to page 58 for more
Information about selecting a device. You may select and display the on-chip peripheral
components using the Debug menu. You can also change the aspects of each peripheral using
the controls in the dialog boxes.
Start Debugging
You start the debug mode of uvisionz with the Debug - Start/Stop Debug Session
command. Depending on the Options for Target - Debug Configuration, uvisionz will load the
application program and run the start up code uvisionz saves the editor screen layout and
restores the screen layout of the last debug session. If the program execution stops, uvisionz
opens an editor window with the source text or shows CPU instructions in the disassembly
window. The next executable statement is marked with a yellow arrow. During debugging,
most editor features are still available.
For example, you can use the find command or correct program errors. Program source text
of your application is shown in the same windows. The µvisionz debug mode differs from the
edit mode in the following aspects:
 The "Debug Menu and Debug Commands" described on page z8 are Available. The
additional debug windows are discussed in the following.
 The project structure or tool parameters cannot be modified. All build Commands
are disabled.

47
Disassembly Window
The Disassembly window shows your target program as mixed source and assembly
program or just assembly code. A trace history of previously executed instructions may be
displayed with Debug - view Trace Records. To enable the trace history, set Debug -
Enable/Disable Trace Recording.
If you select the Disassembly Window as the active window all program step commands
work on CPU instruction level rather than program source lines. You can select a text line and set
or modify code breakpoints using toolbar buttons or the context menu commands.
You may use the dialog Debug - Inline Assembly. to modify the CPU instructions. That
allows you to correct mistakes or to make temporary changes to the target program you are
debugging

48
SYSTEM TESTING
Density based traffic control system is a system which identifies the density at each
side of the junction when vehicles reach near that junction. After connecting the circuit and
writing the code, then test it by sensing the IR sensor dated term used to describe an opto-
electronic means of sensing something, most commonly a photo detector of some type. The
system can be tested with the use of KEIL compiler. This is used to write programs for 89C51
controller. After writing programs using 89C51 programmer we can dump code into the
controller. Now develop the system by using IR transmitter and receiver, we can use photo
diode and photo transistors.
After initializing all the devices connected to the controller, while testing keep the
transmitter & receiver aligned in a straight position facing each other about a distance more
than 2 meter but not less than that.
If the transmitter and receiver are not in a aligned position data communication is
not possible. Connect the output of IR receiver to the controller port pin. If there is no intruder
the output pin will show low value. If there is any introduce it will show high value.

49
CONCLUSION
The density based traffic control system thus reduces the congestion and unwanted
delay in traffic by using IR sensors by the identifying the density on each side of a
junction. It also provides a path to ambulance in emergency situations, giving a way to new
era of traffic signal control.

50
BIBLIOGRAPHY
[Ben-Akiva et al., 2003] Ben-Akiva, M., Cuneo, D., Hasan, M., Jha, M., and Yang, Q.
(2003).Evaluation of freeway control using a microscopic simulation la b o r a t o r y.
Transportation research Part C: emerging technologies, 11-1:29-50.
[Broucke and Varaiya, 1996] Broucke, M. and Varaiya, P. (1996). A theory of
traffic flow in automated highway systems. Transportation research Part C: emerging
technologies, V4:181-210.
[Choi et al., 2002] Choi, W., Yoon, H., Kim, K., Chung, I., and Lee, S. (2002). A traffic
light controlling FLC considering the traffic congestion. In Pal, N. and Sugeno, M.,
editors, Advances in Soft Computing - AFSS 2002, International Conference on Fuzzy
Systems, pages 69-75.
[Findler and Stapp, 1992] Findler, N. and Stapp, J. (1992). A distributed approach to
Optimized control of street traffic signals. Journal of Transportation Engineering, 118-
1:99-110.
[Horowitz and Varaiya, 2000] Horowitz, R. and Varaiya, P. (2000).
Control design of an automated highway system. In Proc. IEEE, v ol. 88.
[Jin and Zhang, 2003] Jin, W. L. and Zhang, H. M. (2003). The formation and
structure of vehicle clusters in the payne-whitham traffic flow model. Transportation
Research Part B: Methodological, 37-3:207-223.

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