Project Report on Microcontroller Based Traffic Light Controller.

Project Report on Microcontroller Based Traffic Light Controller

CONTENTS

1. ABSTRACT

2. INTRODUCTION

3. BLOCK DIAGRAM AND EXPLANATION

4. CIRCUIT DIAGRAM

5. HARDWARE DESCRIPTION

� MICROCONTROLLER UNIT

� LIGHT EMITTING DIODE (LED)

� DISPLAY

6. SOFTWARE

7. DATA SHEETS

8. COMPONENTS REQUIRED

9. FUTURE SCOPE

10. BIBLIOGRAPHY

Acknowledgement

I take this opportunity to express my deep gratitude and sincerest thank to my

project mentor, Mr. SANJOY BANERJEE for giving most valuable suggestion, helpful

guidance and encouragement in the execution of this project work.

I will like to give a special mention to my colleagues. Last but not the least I am

grateful to all the faculty members of Ardent Computech Pvt. Ltd. or their support.

ABSTRACT

Vehicular traffic at intersecting streets is typically controlled by traffic control lights.

The function of traffic lights requires sophisticated control and coordination to

ensure that traffic moves as smoothly and safely as possible.

In recent days electro-mechanical controllers are replaced by electronic circuits. The

accuracy & fault tolerant drive towards electronic circuits.

This project is developed to meet the requirements of solid state traffic light

controller by adopting microcontroller as the main controlling element, and led’s as the

indication of light. A micro controller is interfaced to led’s provide for centralized control

of the traffic signals. Microcontroller is programmed in such a way to adjust their timing

and phasing to meet changing traffic conditions. The circuit besides being reliable and

compact is also cost effective.

INTRODUCTION

Traffic congestion is a severe problem in many modern cities around the world.

Traffic congestion has been causing many critical problems and challenges in the major

and most populated cities. To travel to different places within the city is becoming more

difficult for the travelers in traffic. Due to these congestion problems, people lose time,

miss opportunities, and get frustrated. Traffic congestion directly impacts the

companies. Due to traffic congestions there is a loss in productivity from workers, trade

opportunities are lost, delivery gets delayed, and thereby the costs goes on increasing.

To solve these congestion problems, we have to build new facilities &

infrastructure but at the same time make it smart. The only disadvantage of making new

roads on facilities is that it makes the surroundings more congested. So for that reason

we need to change the system rather than making new infrastructure twice. Therefore

many countries are working to manage their existing transportation systems to improve

mobility, safety and traffic flows in order to reduce the demand of vehicle use.

The project uses simple Electronic components such as LED as TRAFFIC LIGHT

indicator and a MICROCONTROLLER for auto change of signal after a pre-specified

time interval.

Microcontroller AT89c51 is the brain of the project which initiates the traffic signal

at a junction. The led’s are automatically on and off by making the corresponding port

pin of the micro controller high. A seven segment display also connected to display the

timing of each signal. At a particular instant only one green light holds and other lights

hold at red. During transition from green to red, the present group yellow led and

succeeding group yellow led glows and then succeeding group led changes to green.

This process continues as a cycle.

BLOCK DIAGRAM

8051 MICRO

CONTROLLER

(AT89C51)

POWER SUPPLY

(+5v)

LED

HARDWARE DESCRIPTION

MICRO-CONTROLLER UNIT:

Micro-controller unit is constructed with ATMEL 89C51 Micro-controller chip. The

ATMEL AT89C51 is a low power, higher performance CMOS 8-bit microcomputer with

4K bytes of flash programmable and erasable read only memory (PEROM). Its high-

density non-volatile memory compatible with standard MCS-51 instruction set makes it

a powerful controller that provides highly flexible and cost effective solution to control

applications.

Fig-Block Diagram

Pin Description:-Pins 1-8:   Port 1:  Each of these pins can be configured as an input or an output.

Pin 9: RS A logic one on this pin disables the microcontroller and clears the contents of

most registers. In other words, the positive voltage on this pin resets the microcontroller.

By applying logic zero to this pin, the program starts execution from the beginning.

Pins10-17: Port 3 Similar to port 1, each of these pins can serve as general input or

output. Besides, all of them have alternative functions:

Pin10: RXD Serial asynchronous communication input or Serial synchronous

communication output.

Pin 11 :   TXD Serial asynchronous communication output or Serial synchronous

communication clock output.

Pin 12 :   INT0 Interrupt 0 input.

Pin 13: INT1 Interrupt 1 input.

Pin 14: T0 Counter 0 clock input.

Pin 15: T1 Counter 1 clock input.

Pin 16: WR Write to external (additional) RAM.

Pin 17: RD Read from external RAM.

Pin 18, 19:   X2, X1  : Internal oscillator input and output. A quartz crystal which specifies

operating frequency is usually connected to these pins. Instead of it, miniature ceramics

resonators can also be used for frequency stability. Later versions of microcontrollers

operate at a frequency of 0 Hz up to over 50 Hz.

Pin 20: GND Ground.

Pin 21-28: Port 2 If there is no intention to use external memory then these port pins

are configured as general inputs/outputs. In case external memory is used, the higher

address byte, i.e. addresses A8-A15 will appear on this port. Even though memory with

capacity of 64Kb is not used, which means that not all eight port bits are used for its

addressing, the rest of them are not available as inputs/outputs.

Pin 29: PSEN If external ROM is used for storing program then a logic zero (0) appears

on it every time the microcontroller reads a byte from memory.

Pin 30: ALE Prior to reading from external memory, the microcontroller puts the lower

address byte (A0-A7) on P0 and activates the ALE output. After receiving signal from

the ALE pin, the external register (usually 74HCT373 or 74HCT375 add-on chip)

memorizes the state of P0 and uses it as a memory chip address. Immediately after

that, the ALU pin is returned its previous logic state and P0 is now used as a Data Bus.

As seen, port data multiplexing is performed by means of only one additional (and

cheap) integrated circuit. In other words, this port is used for both data and address

transmission.

Pin 31: EA By applying logic zero to this pin, P2 and P3 are used for data and address

transmission with no regard to whether there is internal memory or not. It means that

even there is a program written to the microcontroller, it will not be executed. Instead,

the program written to external ROM will be executed. By applying logic one to the EA

pin, the microcontroller will use both memories, first internal then external (if exists).

Pin 32-39:   Port 0:  Similar to P2, if external memory is not used, these pins can be used

as general inputs/outputs. Otherwise, P0 is configured as address output (A0-A7) when

the ALE pin is driven high (1) or as data output (Data Bus) when the ALE pin is driven

low (0).

Pin 40: VCC +5V power supply.

Micro-controller works according to the program written in it. The program is

written in such a way, so that this controller energizes or de-energizes the relays

according to the information received by the pushbuttons and the sensing probe.

The 8051 series of microcontrollers are highly integrated single Chip

microcomputers with an 8-bit CPU, memory, interrupt controller, timers, Serial I/O and

digital I/O on a single piece of silicon. The 8051 is an 8-bit Machine. Its memory is

organized in bytes and practically all its instruction deal with byte quantities. It uses an

Accumulator as the primary register for instruction Results. Other operands can be

accessed using one of the four different addressing modes available: register implicit,

direct, indirect or immediate. Operands reside in one of the five memory spaces of the

8051.

The five memory spaces of the 8051 are: Program Memory, External DataMemory, Internal Data Memory, Special Function Registers and Bit Memory.

Fig: 8051 Memory Representation

The Program Memory space contains all the instructions, immediate data and

constant tables and strings. It is principally addressed by the 16-bit Program Counter

(PC), but it can also be accessed by a few instructions using the 16-bit Data Pointer

(DPTR). The maximum size of the Program Memory space is 64K bytes. Several 8051

family members integrate on-chip some amount of either masked programmed ROM or

EPROM as part of this memory.

The Internal Data Memory of 8051’s on-chip memory consists of 256 memory

bytes organized as follows:

First 128 bytes: 00h to 1Fh Register Banks

20h to 2Fh Bit Addressable RAM

30 to 7Fh General Purpose RAM

Next 128 bytes: 80h to FFh Special Function Registers

The first 128 bytes of internal memory is organized as shown in figure and is

Referred to as Internal RAM, or IRAM.

Fig: Organisation of Internal RAM (IRAM) memory

Register Banks 00h to 1Fh:

The 8051 uses 8 general-purpose registers R0 through R7 (R0, R1, R2, R3, R4,

R5,R6, and R7).

Bit Addressable RAM: 20h to 2Fh:The 8051 supports a special feature which allows access to bit variables. This is

Where individual memory bits in Internal RAM can be set or cleared. In all there are

128 bits numbered 00h to 7Fh. Being bit variables any one variable can have a value 0

or 1. A bit variable can be set with a command such as SETB and cleared with a

Command such as CLR.

General Purpose RAM: 30h to 7Fh:These 80 bytes of Internal RAM memory are available for general-purpose data

storage. Access to this area of memory is fast compared to access to the main memory

and special instructions with single byte operands are used. However, these 80 bytes

are used by the system stack and in practice little space is left for general storage. The

general purpose RAM can be accessed using direct or indirect addressing modes.

SFR Registers:The SFR registers are located within

the Internal Memory in the address range 80h

to FFh. Not all locations within this range are

defined. Each SFR has a very specific

function. Each SFR has an address (within

the range 80h to FFh) and a name which

reflects the purpose of the SFR. Although 128

byes of the SFR address space is defined

only 21 SFR registers are defined in the

standard 8051. Undefined SFR addresses

should not be accessed as this might lead to

some unpredictable results. Note some of the

SFR registers are bit addressable. SFRs are

accessed just like normal Internal RAM

locations.

PSW Program Status Word:

PSW, the Program Status Word is at address D0h and is a bit-addressable register.

The status bits are listed in table.

Table: Program status word (PSW) flags

Carry flag. CThis is a conventional carry, or borrows, flag used in arithmetic operations. The carry

flag is also used as the ‘Boolean accumulator’ for Boolean instruction operating at the

bit level. This flag is sometimes referenced as the CY flag.

Auxiliary carry flag. ACThis is a conventional auxiliary carry (half carry) for use in BCD arithmetic.

Flag 0. F0This is a general-purpose flag for user programming.

Register bank select 0 and register bank selects 1. RS0 and RS1These bits define the active register bank (bank 0 is the default register bank).

Overflow flag. OVThis is a conventional overflow bit for signed arithmetic to determine if the result of a

signed arithmetic operation is out of range.

Even Parity flag. PThe parity flag is the accumulator parity flag, set to a value, 1 or 0, such that the

number of ‘1’ bits in the accumulator plus the parity bit add up to an even number.

The register implicit, indirect and direct addressing modes can be used in

different parts of the Internal Data Memory space.

The Special Function Register space contains all the on-chip peripheral I/O

registers as well as particular registers that need program access. These registers

include the Stack Pointer, the PSW and the Accumulator. The maximum number of

Special Function Registers (SFR’s) is 128, though the actual number on a particular

8051 family member depends on the number and type of peripheral functions integrated

on-chip.

The External Data Memory space contains all the variables, buffers and data

structures that can't fit on-chip. It is principally addressed by the 16-bit Data Pointer

(DPTR), although the first two general purpose register (R0, R1) of the currently

selected register bank can access a 256-byte bank of External Data memory. The

maximum size of the External Data Memory space is 64Kbytes. External data memory

can only be accessed using the indirect addressing mode with the DPTR, R0 or R1.

REGULATOR

They maintain a constant voltage level independent of load condition or

variation in the amplitude of the Ac supply .An example of

regulator is LM78xx series It is the three terminal device

with input (1) , ground(2), output(3) as its terminals. The

voltage required for micro controller is 5V. Hence LM7805

voltage regulator is used. These devices require no

adjustments and have an output preset by manufactures to

industry standard voltages of 5, 6, 8, 12, 15, 18, 24V.

Zener regulator is incorporated for maintaining 12v regulated output used for sensing

probes and Electromagnetic relay.

Light Emitting Diode (LED):

A light-emitting diode (LED) is a semiconductor light source. The color of the

light is determined by the energy gap of the semiconductor.

PRINCIPLE:When a light-emitting diode is forward biased electrons are able to recombine

with electron holes within the device, releasing energy in the form of photons. This

effect is called electroluminescence. Electroluminescence (EL) is an optical and

electrical phenomenon in which a material emits light in response to the passage of an

electric current or to a strong electric field. The wavelength of the light emitted, and

thus its color depends on the band gap energy of the materials forming the p-n

junction. The materials used for the LED have a direct band gap with energies

corresponding to near-infrared, visible or near-ultraviolet light.

CONSTRUCTION : LEDs are usually built on an n-type substrate, with an electrode attached to the p-type

layer deposited on its surface. P-type substrates, while less common, occur as well.

Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate. Most

materials used for LED production have very high refractive indices. Light extraction in

LEDs is an important aspect of LED production.

SOFTWARE NG BIT P2.4 NY BIT P2.3 NR BIT P2.5 SG BIT P0.4 SY BIT P0.5 SR BIT P0.3 WG BIT P2.1 WY BIT P2.2 WR BIT P2.0 EG BIT P0.1 EY BIT P0.0 ER BIT P0.2

ORG 0000H MOV P0,#0FFH MOV P2,#0FFHNORTH: CLR NG CLR SR CLR WR CLR ER ACALL DELAY CLR NY ACALL DELAY1 SETB NY ACALL DELAY1 CLR NY ACALL DELAY1 SETB NY ACALL DELAY1 CLR NY ACALL DELAY1 SETB NY ACALL DELAY1 SETB NG SETB SR SETB WR SETB EREAST: CLR EG CLR SR CLR WR CLR NR ACALL DELAY CLR EY ACALL DELAY1 SETB EY ACALL DELAY1 CLR EY ACALL DELAY1

SETB EY ACALL DELAY1 CLR EY ACALL DELAY1 SETB EY ACALL DELAY1 SETB EG SETB SR SETB WR SETB NRSOUTH: CLR SG CLR ER CLR WR CLR NR ACALL DELAY CLR SY ACALL DELAY1 SETB SY ACALL DELAY1 CLR SY ACALL DELAY1 SETB SY ACALL DELAY1 CLR SY ACALL DELAY1 SETB SY ACALL DELAY1 SETB SG SETB ER SETB WR SETB NRWEST: CLR WG CLR SR CLR ER CLR NR ACALL DELAY CLR WY ACALL DELAY1 SETB WY ACALL DELAY1 CLR WY ACALL DELAY1 SETB WY ACALL DELAY1 CLR WY ACALL DELAY1 SETB WY ACALL DELAY1 SETB WG SETB SR SETB ER SETB NR

AJMP NORTH

DELAY: MOV R0,#0FFHHERE2: MOV R1,#0FFHHERE1: MOV R2,#20HHERE: DJNZ R2,HERE DJNZ R1,HERE1 DJNZ R0,HERE2 RET

DELAY1: MOV R0,#0FFHHERE5: MOV R1,#0FFHHERE4: MOV R2,#02HHERE3: DJNZ R2,HERE3 DJNZ R1,HERE4 DJNZ R0,HERE5 RET

FUTURE SCOPE

This project can be enhanced in such away as to control automatically the

signals depending on the traffic density on the roads using sensors like IR

detector/receiver module extended with automatic turn off when no vehicles are

running on any side of the road which helps in power consumption saving.

This proximity detector using an infrared detector shown in fig.1 can be

used in various equipment like automatic door openers and burglar alarms. The

circuit primarily consists of an infrared transmitter and an infrared receiver. The

transmitter section consists of a 555 timer IC functioning in astable mode. It is

wired as shown in the fig. 2. The output from astable is fed to an infrared LED via

resistor R4, which limits its operating current. This circuit provides a frequency

output of 38 kHz at 50 per cent duty cycle, which is required for the infrared

detector/receiver module.

The receiver section comprises an infrared receiver module, a 555

monostable multivibrator, and an LED indicator. Upon reception of infrared

signals, 555 timer (mono) turns on and remains on as long as infrared signals are

received. When the signals are interrupted, the mono goes off after a few

seconds (period=1.1 R7xC6) depending upon the value of R7-C6 combination.

Thus if R7=470 kilo-ohms and

C6=4.7μF, the mono period will be around 2.5 seconds.

Both the transmitter and the receiver parts can be mounted on a single

breadboard or PCB. The infrared receiver must be placed behind the infrared

LED to avoid false indication due to infrared leakage. An object moving nearby

actually reflects the infrared rays emitted by the infrared LED. The infrared

receiver has sensitivity angle (lobe) of 0-60 degrees, hence when the reflected IR

ray is sensed, the mono in the receiver part is triggered. The output from the

mono may be used in any desired fashion. For example, it can be used to turn on

a light when a person comes nearby by energizing a relay. The light would

automatically turn off after some time as the person moves away and the mono

pulse period is over. The sensitivity of the detector depends on current-limiting

resistor R4 in series with the infrared LED. Range is approximately 40 cm. For

20-ohm value of R4 the object at 25 cm can be sensed, while for 30-ohm value of

R4 the sensing range reduces by 22.5 cm.

IR RECEIVER CIRCUIT

TRAFFIC LIGHT CONTROL MODULE USING SENSORS

BIBLIOGRAPHY

1) Microprocessor & microcontroller

-Soumitra Kumar Mandal

2) 8051 Microcontroller

-V Udayshankar & M S mallikarjunaswamy

3) www.wikipedia.org

4) www.microcontroller.com