prasanna reportwork

8/2/2019 PRASANNA REPORTWORK

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1. INTRODUCTION


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1. INTRODUCTION

1.1PROJECT INTRODUCTION

In this project we are going to implement the traffic controller by using basic electronic

switches such as transistors ,diodes and basic elements resistors and capacitors .To control the

traffic we a have to Operate four LEDS (L1,L2,L3,L4)placed at junction. For that we are using

three multivibrators (M1, M2&M3) and two inverters. The basic circuit in traffic signal

controller is bistable circuit which has 2-stage regenerative feedback amplifier pairs .A bistable

circuit is one which can exist indefinitely in either of two stable states and which can be induced

to make an abrupt transition from one state to another by means of external excitation

1.2AREA OF PROJECT

A multivibrator is an electronic circuit used to implement a variety of simple two-state systemssuch as oscillators, timers and flip-flops. It is characterized by two amplifying devices

(transistors, electron tubes or other devices) cross-coupled by resistors or capacitors. The name

"multivibrator" was initially applied to the free-running oscillator version of the circuit because

its output waveform was rich in harmonics. There are three types of multivibrator circuits

depending on the circuit operation:

ASTABLE: In which the circuit is not stable in either state it continually switches fromone state to the other. It does not require an input such as a clock pulse.

MONOSTABLE: In which one of the states is stable, but the other state is unstable(transient). A trigger causes the circuit to enter the unstable state. After entering the unstable

state, the circuit will return to the stable state after a set time. Such a circuit is useful for creating

a timing period of fixed duration in response to some external event. This circuit is also known

as a one shot.

BISTABLE: In which the circuit is stable in either state. The circuit can be flipped from onestate to the other by an external event or trigger.


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Multivibrators find applications in a variety of systems where square waves or timed intervals

are required. For example, before the advent of low-cost integrated circuits, chains of

multivibrators found use as frequency dividers. A free-running multivibrator with a frequency of

one-half to one-tenth of the reference frequency would accurately lock to the reference

frequency. This technique was used in early electronic organs, to keep notes of different octaves

accurately in tune. Other applications included early television systems, where the various line

and frame frequencies were kept synchronized by pulses included in the video signal.

1.3 STATE OF REVIEW OF ART

Traffic is formally organized in many jurisdictions, with marked lanes, junctions, intersections,

interchanges, traffic signals or signs. Traffic is often classified by type: heavy motor vehicle (likecar, truck), other vehicle (e.g. moped, bicycle).Different classes may share speed limits and

easement or may be segregated. Some jurisdictions may have very detailed and complex rules of

the road.

The project Transistor Based Traffic Controller is based on the transistors which will provide

the controlling of the traffic depending on the density. According to the triggering of the

transistors i.e. the timing of the Green, Red, Orange lights will be glows for the particular time

depending upon the density. That will monitor the all control functionalities. According to the

signalling of triggering circuit, the traffic density will be monitored by lights.

1.4 PROBLEM DEFINITION

One of the main problems in our cities is traffic. This project proposed solution to traffic control.

The main design accept of this project is to control the traffic automatically and adding human

inelegancy to that automatic controller. Four-way intersection is the most common

configuration for roads that cross each other, and the most basic type. If signals do not control a

4-way intersection, signs or other features are typically used to control movements and make

clear priorities.

1.5 GOALS

This project is similar to normal automatic traffic light controller is it gives Green signals to

different directions with some constant time delay .In the normal traffic light controller there is

no possibility to change the time period of signals according to the traffic density if we want to


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change there is need to change the entire project If we consider this projecteventhough the

traffic from all directions may not be same and density will change as per time if we insert a

controller to this project. In this project we are going to use bistable circuits to analyze traffic

density. The bistable circuits and triggering circuits gives the appropriate result according to the

traffic. In the bistable circuit it is in one stable state until it applies a triggering signal. After

applying a triggering signal then it shifts in to another stable state. So the time period of

triggering signal determines period of light it glows. So giving appropriate triggering signals to

the bistable circuits controls traffic.

1.6 TOOLS REQUIRED

In this project we have chosen the bistable multivibrator as the basic part of the circuit. Thebistable multivibrator is used in three stages (M1, M2, and M3). The output of the stage M1 is

given to the stages M2and M3 through the inverter circuits. The triggering signals T1, T2 are

connected to the multivibrators. The LEDs are connected to the stages M2 and M3.A bistable

multivibrator is a circuit which can exists in either of indefinitely in either of two stable stats and

which can be induced to make an abrupt transition from one stable state to the other stable state

by means of external excitation.

Selection of components in the fixed-bias bistable multivibrator:

In this bistable multivibrator, it contains two regenerative feedback amplifier pairs. In the fixed-

bias binary the full supply voltage Vcc will appear across the transistor that is OFF. Since this

supply voltage Vcc is reasonably smaller than the collector breakdown voltage BVCE, Vcc is

restricted to a maximum of a few tens of volts. Under saturation conditions the collector current

Ic is maximum. Hence Rc must be chosen so that this value of Ic (~Vcc/Rc) does not exceed the

maximum permissible limit. The values of R1, R2 and VBB must be selected such that in one

stable state the base current is large enough to drive the transistor into saturation whereas in the

second stable state the emitter junction must be below cut-off. The signal at the output swing

VW is the change in collector voltage resulting from a transistor going from one state to other,

i.e. VW=Vc1Vc2. If the loading caused by R1 can be neglected, then the collector voltage of

the OFF transistor is Vcc. Since the collector saturation is few tenths of volt, then the swing VW

~Vcc, independently of Rc. The component values, the supply voltages and the values of ICBO,

hFE, VBE (sat), and VCE (sat) are sufficient for the analysis of transistor binary circuits.

Selection of components in the triggering circuit:


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In the triggering circuit we use astable multivibrator by using IC555 timer. The 555 is a

monolithic timer device which can be used to produce accurate and highly stable delays or

oscillations. It can be used to produce ranging from few microseconds to several hours. The NE

555can operates with a supply voltage in the range of 4.5v to 18v and is capable of sinking and

sourcing currents of 200mA.it CMOS version can operate over a supply range of 2v to 18v.it has

very high temperature stability, as it is designed to operate in the temperature range of -55to

125C.Two external resistances of 1K, 200kand a capacitor of 100F are used to form astable

multivibrator.

1.7CONTENTS OF PROJECT

In the first chapter we describe the introduction, area of research, review of state of art, problemdefinition, goals, tools required of the project. In the second chapter we describe the background

of the project In the third chapter we describe the proposed algorithm of traffic signal controller

which it contains the block diagram, circuit diagram, circuit operation, triggering circuit and its

waveforms.Inthe fourth chapter we describe the testing by applying input signals. In the fifth

chapter we describe the applications of the project.


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2. BACKGROUND


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2. BACKGROUND

2.1 MONOSTABLE MULTIVIBRATOR:

A monostable multivibrator has got only one stable state (the other state being quasi stable). The

stable state of a multivibrator is the state which the device can stay permanently. Only a proper

external triggering signal is applied, it will change its state. Quasi stable state means temporarily

stable state. The device cannot stay permanently in this state. After a predetermined time, the

device will automatically cone out of the quasi stable state. In monostable circuits, one coupling

element is a capacitor (ac coupling) and the other coupling element is a resistor (dc coupling). A

monostable multivibrator requires a triggering signal to change from the stable state to the quasi

stable state but no triggering signal is required for the reverse transition i.e. bring it from thequasi stable state to the stable state.

2.2ASTABLE MULTIVIBRATOR:

The astable multivibrator has got no stable state (both the stable states being quasi stable). In

astable multvibrators both coupling elements are capacitors (i.e. both are ac couplings). The

astable multivibrator does not require any triggering signal at all. It keeps changing from one

quasi stable state to another quasi stable state on its own the moment it is connected to the

supply.

So in both these multivibrators they continually switch from one state to other state without any

control. So we use the bistable circuit which has two stable states whose time period of the states

can be changed by external triggering .The bistable multivibrator is shown below

2.3 BISTABLE CIRCUIT:

A bistable multivibrator has got two stable states. A bistable multivibrator requires a triggering

signal to change from one stable state to other. It requires another triggering signal for the

reverse transition. In bistable circuits both the coupling elements are resistors (i.e. both are dc

couplings).

OPERATION

The fig1 shows the circuit diagram of a fixed-bias bistable multivibrator using transistors. The

output of each amplifier is directly coupled to the input of the other amplifier. In one of the


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stable states, transistor Q1 is ON (i.e. in saturation) and Q2 is OFF (i.e. in cut-off), and in the

other stable state Q1 is OFF and Q2 is ON. Even though the circuit is symmetrical, it is not

possible for the circuit to remain in a stable state with both the transistors conducting (i.e. both

operating in active the region) simultaneously and carrying equal currents. The reason is that if

we assume that both transistors are biased equally and are carrying equal currents I1 and I2 and

supposes there is a minute fluctuation in the current I1; let us say it increases by a small amount

then the voltage at the collector of Q1 decreases. This will result in a decrease in voltage at the

base ofQ2. So Q2 conducts less and I2 decreases and hence the potential at the collector of Q2

increases. This results in an increase in the base potential of Q1. So, Q1 conducts still more and

I1 is further increased and the potential at the collector of Q1 is further reduced, and so on. So,

the current I1 keeps on increasing and the current I2 keeps on decreasing till Q1 goes into

saturation and Q2 goes into cut-off. This action takes place because of the regenerative feedback

incorporated into the circuit and will occur only if the loop gain is greater than one.

Fig2.1.Bistable circuit


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2.4 PIN DIAGRAM

Fig2.2.pin diagram of IC555 Timer

FUNCTIONS OF PINS:

PIN 1(Ground):

All the voltages are measured with respect to this terminal.

PIN 2(Triggering):

The IC555 uses two comparators. The voltage divider consists of three equal resistances. Due to

voltage divider, the voltage of non-inverting terminal of comparator 2 is fixed at Vcc/3. The

inverting input off comparator 2 which is compared with Vcc/3 is nothing but trigger input

brought out as pin number 2. When the trigger input is slightly less than Vcc/3, the comparator 2

output goes high. This output is given to reset input of R-S Flip Flop. So high output of

comparator 2 resets the Flip Flop.

PIN 3 (Output):

The complementary signal output () of the Flip Flop goes to pin3 which is the output. The load

can be connected in two ways. One between pin 3 and ground while other between pin3 and pin

8.

PIN 4 (Reset):

This is an interrupt to the timing device. When pin 4 is grounded, it stops the working of device

and makes it OFF. Thus pin 4 provides ON/OFF feature to the IC 555.

PIN 5 (Control Voltage Input):


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This pin is nothing but the inverting input terminal of comparator 1.The voltage divider holds the

voltage of this input at 2Vcc/3. This is reference level for comparator 1 with which threshold is

compared. If reference level required is other than 2Vcc/3 for comparator 1 then external input is

to be given to pin 5. If external input applied to pin 5 is alternating then the reference level for

comparator 1

Keeps on changing above and below 2Vcc/3. Due to this, the variable pulse width output is

possible. This is called pulse width modulation, which is possible due to pin 5.

PIN 6 (Threshold):

This is the non-inverting input terminal of comparator 1.the external voltage is applied to this pin

6. When this voltage is more than 2Vcc/3, the comparator 1 output goes high. This is given to the

set input of R-S Flip Flop. Thus high output of comparator 1sets the Flip Flop. This makes Q of

Flip Flop high and low. Thus the output of IC 555 at pin 3 goes low.

PIN 7 (Discharge):

This pin is connected to the collector of the discharge transistor Qd. When the output is high then

Q is low and transistor Qd is OFF. It acts as an open circuit to the external capacitor C to be

connected across it, so capacitor C can charge. When output is low, Q is high which drives the

base if Qd high, driving transistor Qd in saturation. It acts as short circuit, shorting the external

capacitor c to connect across it.

PIN 8 (Supply +Vcc):

The IC 555 timer can work with any supply voltage between 4.5V to 16V.

2.5 POWER SUPPLY:

The power supplies are designed to convert high voltage AC mains electricity to a suitable low

voltage supply for electronic circuits and other devices. A RPS (Regulated Power Supply) is the

Power Supply with Rectification,

Filtering and Regulation being done on the AC mains to get a Regulated power supply for

Microcontroller and for the other devices being interfaced to it.

A power supply can by broken down into a series of blocks, each of which performs a particular

function. A d.c power supply which maintains the output voltage constant irrespective of a.c

mains fluctuations or load variations is known as Regulated D.C PowerSupplyFor example

a5V regulated power supply system as shown below


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Fig2.3. Components of typical liner power supply

2.5.1 TRASFORMER:

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.

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. 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 Step-up transformers increase in output

voltage, step-down the 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. 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.


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Fig2.4. An electrical transformer

Turns ratio = Vp/ VS = Np/NS

Power Out= Power In

VS X IS=VP X IP

Vp = primary (input) voltage

Np = number of turns on primary coil

Ip = primary (input) current

2.5.2 RECTIFIER:

A circuit which is used to convert a.c to dc is known as RECTIFIER. The process of conversion

a.c to d.c is called rectification

TYPES OF RECTIFIERS:

Half wave Rectifier

Full wave rectifier

1. Centre tap full wave rectifier.

2. Bridge type full bridge rectifier.

FULLWAVE 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.

BRIDGE RECTIFIER:


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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 Fig2.5 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.

Fig2.5. A typical bridge rectifier circuit

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 Fig2.5.a. The current flow directions shown in the

Fig2.2.5.a With dotted arrows.

Fig2.5.a Current Flow in the Bridge Rectifier (for positive swing)


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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.2.5.b. The current flow direction is

shown in the Fig.2.5.b with dotted arrows.

Fig2.5.b Current Flow in the Bridge rectifier (for negative swing)

2.5.3 FILTER:

A Filter is a device which removes the a.c component of rectifier output but allows the d.c

component to reach the load.

CAPACITIVE 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 bypass 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 d.c (due to low resistance to d.c)

(c) Various combinations of capacitor and inductor, such as L-section filter, multiple section

filters 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 sectionanother with full wave rectifier.


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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 RMS value).

To calculate the value of capacitor(C),

C = *3*f*r*Rl

Where,

f = supply frequency,

r = ripple factor,

Rl = load resistance

Note: In our circuit we are using 1000F hence large value of capacitor is placed to reduce

ripples and to improve the DC component.

2.5.4REGULATOR:

Fig2.5. 12VRegulator

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.


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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.

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,

FEATURES:

Output Current of 1.5A

Output Voltage Tolerance of 5%

Internal thermal overload protection

Internal Short-Circuit Limited

Output Voltage 5.0V, 6V, 8V, 9V, 10V, 12V, 15V, 18V, 24V.


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3. PROPOSED ALGORTHIM OF TRANSISTOR BASED

TRAFFIC CONTROLLER


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3. PROPOSED ALGORTHIM OF TRANSISTOR BASED TRAFFIC CONTROLLER

3.1 BLOCK DIAGRAM

The is the block diagram of the project .It as 3 multivibrators (M1, M2&M3) and two triggering

circuits (T1, T2). The first multivibrator drives the other two multivibrators.here M1, M2, M3

are 3 bistable multivibrators.and has two stable states.

Fig3.1. Block diagram

In one stable state M1 activates the multivibrator M2 it again has two stable states in one stable

state L1 blinks .and in another stable state L2 blink. So in other stable state of M1, multivibrator

M3 gets activated. So it has two stable states in one stable state L3 blinks .and in another stable

state L4 blink. This process repeats for the continuous control of traffic light.


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3.2CIRCUIT DIAGRAM

Fig3.2.Circuit diagram


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3.3 CIRCUIT OPERATION:

The basic circuit in our project is bistable multivibrator. It has two stages regenerative feedback

amplifier pair .the regenerative feedback is produced by connecting the output of one transistor

to the input of another transistor. After applying power supply to the bistable multivibrator it is

one of the stable states .let us consider in one stable state the transistor Q1 is on and Q2 is off

and here we use inverter as an interface to the multivibrator s M1&M2.so as we assumed that

Q1 is on then Q3 becomes on then vcc is grounded .so the multivibrator gets M2 gets

deactivated .so as we considered that Q2 is off so the transistor Q4 will becomes off and then

vcc is applied to the multivibrator M3.so as vcc is applied it is in one of the stable states.in one

stable state Q7 is on and Q8 is off so the LED L3 will blink and then applying triggering signal

to this multivibrator there will be transition to another stable state so in another stable state L4

will blink. After applying triggering to M1 there will be state transition now Q1 becomes off and

Q2 becomes on the same process will takes place as in the case of multivibrator M3.so LEDS

L1&L2 will blink .The same process is repeated then traffic will be controlled.

3.4FUNCTION TABLE

The Function Table specifies which lights will glow when the transistors on let us consider in

one stable state the transistor Q1 is on and Q2 is off and here we use inverter as an interface to

the multivibrator s M1&M2.so as we assumed that Q1 is on then Q3 becomes on then vcc is

grounded .so the multivibrator gets M2 gets deactivated .so as we considered that Q2 is off so

the transistor Q4 will becomes off and then vcc is applied to the multivibrator M3.so as vcc is

applied it is in one of the stable states.in one stable state Q7 is on and Q8 is off so the LED L3

will blink


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3.5 TRIGGERING:

3.5.1. DESCRIPTION

The triggering signal which is usually employed to induce a transition from one state to the other

is either a pulse of short duration or a step voltage. This pulse or step may be introduced in such

a manner as will produce either symmetrical or unsymmetrical triggering. The stable states of the

bistable multivibrator can be changed by applying the triggering externally. Triggering is of two

types.

1. Applying the positive triggering to the OFF transistor.

2. Applying negative triggering to the ON transistor.

Here we are applying the negative triggering to the on transistor. Suppose that a positive pulse is

applied to the input of the off stage. The pulse is a combination of a positive step and a delayed

negative step. The result to be anticipated is therefore a combination of the response to a positive

step applied to the OFF device followed by a negative step applied to the ON stage. If the

amplitude of a positive step is large enough to flip the binary at its leading edge, then because of


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the greater triggering sensitivity to a negative step, the binary will flip back again at its trailing

edge.

Next consider a negative pulse applied to the ON stage. Since the binary responds to a smaller

negative step than positive step, we may adjust the pulse amplitude experimentally to prevent the

flip-flop from making a reverse transition on the trailing edge of the pulse.

3.5.2. TRIGGERING CIRCUIT USING ASTABLE MULTIVIBRATOR

In the astable multivibrator, the threshold input is connected to the trigger input. The external

resistances R1, R2 and capacitor C is used in the circuit. The circuit has no stable state. The

circuit changes its state alternately. Hence the operation is also called free running non sinusoidal

oscillator

Fig3.4.Triggering circuit using Astable Multivibrator

.

OPERATION:

When the Flip Flop is set, Q is high which drives the transistor Q in saturation and the capacitor

gets discharged. Now the capacitor voltage is nothing but the trigger voltage. So while

discharging, when it becomes less than Vcc/3, comparator 2 output goes high. This resets the

Flip Flop hence Q goes low and goes high. The low Q makes the transistor OFF. Thus

capacitor starts charging through the resistances R1, R2 and Vcc. As total resistances in the

charging path is (R1+R2), the charging time constant is (R1+R2) C.

Now the capacitor voltage is also a threshold voltage, while charging, capacitor voltage increases

i.e. the threshold voltage increases. When it exceeds 2Vcc/3, then the comparator 1 output goes

high which sets the Flip Flop. The Flip Flop output Q becomes high and output at pin 3 i.e.


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becomes low. High Q drives transistor Q in saturation and capacitor starts discharging through

resistances Rb and transistor Qd. Thus the discharging time constant is R2C. When capacitor

voltage becomes less than Vcc/3, comparator 2 output goes high, resetting the Flip Flop. This

cycle repeats. Thus when capacitor C is charging, output is high while when it is discharging the

output is low. The output is a rectangular wave. The capacitor voltage is exponentially rising and

falling.

3.5.3. TRIGGERING WAVEFORMS

The first pulse of T1 is applied to multivibratorM1, so the LED L1glows.the first pulse of T2 is

applied to multivibratorM2with a time delay to T1then LED2 glow. Then it glows for certain

period of time. After that the second pulse of T1 arrives and triggers the multivibratorM3then

LED3glows.then it also glows for certain period of time .after that the second pulse of T2 also

arrives which triggers the multivibrator 3then LED4 glow

Fig 3.5.waveforms


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4. TESTING


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4. TESTING

The fig8 shows the arrangement of traffic controller. It contains 8 LEDS out of which are 4green

and 4 red lights and which were placed four directions to control the traffic. If green light glowson one direction then red glows in the remaining directions.

Fig.4.1.Arrangement of Traffic Controller

After applying first triggering pulse to T1 then it activates the multivibrator M1 and then green

light glows in one direction. Since in the remaining directions the red light glows because the

inverters are connected to the output of multivibrators s shown in Fig 4.1


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Fig4.2.Blinking of light when multivibrator 2 is one stable state

let us consider in one stable state the transistor Q1 is on and Q2 is off and here we use inverter as

an interface to the multivibrator s M1&M2.so as we assumed that Q1 is on then Q3 becomes on

then vcc is grounded .so the multivibrator gets M2 gets deactivated .so as we considered that

Q2 is off so the transistor Q4 will becomes off and then vcc is applied to the multivibrator

M3.so as vcc is applied it is in one of the stable states.in one stable state Q7 is on and Q8 is off

so the LED L3 will blink


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5. RESULTS


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5. RESULTS

After applying power supply to the bistable multivibrator it is one of the stable states .let us

consider in one stable state the transistor Q1 is on and Q2 is off and here we use inverter as aninterface to the multivibrator s M1&M2.so as we assumed that Q1 is on then Q3 becomes on

then vcc is grounded .so the multivibrator gets M2 gets deactivated .so as we considered that

Q2 is off so the transistor Q4 will becomes off and then vcc is applied to the multivibrator

M3.so as vcc is applied it is in one of the stable states.in one stable state Q7 is on and Q8 is off

so the LED L3 will blink and then applying

triggering signal to this multivibrator there will be transition to another stable state so in anotherstable state L4 will blink. After applying triggering to M1 there will be state transition now Q1

becomes off and Q2 becomes on the same process will takes place as in the case of multivibrator

M3.so LEDS L1&L2 will blink .The same process is repeated then traffic will be controlled.


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6. APPLICATIONS

This is used in the traffic controller systems. As we have used multivibrators in this project they

are used in digital circuit design this circuit is the vital heart of all digital electronics, computers,

pulse-code telephony and soon. A multivibrator a.k.a. flip-flop, is a device which can settle in

one of two stable states.. They are the basis of counting and time-code and so on.

7. REFERENCES

[1] Jacob Millman and Herbert Taub, 1965, Pulse, Digital, and switching Waveforms: Devices

and circuits for their generation and processing, McGraw-Hill Book Company, NY, LCCCN 64-

66293.

[2]. Joseph Petit and Malcolm McWhorter, 1970, Electronic Switching, Timing, and Pulse

Circuits: 2nd Edition, McGraw-Hill Book Company, NY, LCCCN: 78-114292.

[3]. Jacob Millman and Christos Halkias, 1967, Electronic Devices and Circuits, McGraw- Hill

Book Company, NY, ISBN 07-042380-6.

[4] Linvill, J.G.: Nonsaturating Pulse Circuits Using Two Junction Transistors


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