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DESIGN AND CONSTRUCTION OF A STABLE  MULTIVIRATOR

DESIGN AND CONSTRUCTION OF A STABLE  MULTIVIRATOR
ABSTRACT

The aim of this work is to design and fabricate an astable multivibrator. An Astable Multivibrator is an oscillator circuit that continuously produces rectangular wave without the aid of external triggering. Astable Multivibrator is also known as Free Running Multivibrator. The astable multivibrator is not stable and it repeatedly switches from one state to the other. Astable Multivibrator using 555 Timer is very simple, easy to design, very stable and low cost. It can be used for timing from microseconds to hours.

 

 

 

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRACT
TABLE OF CONTENT

CHAPTER ONE

    1. INTRODUCTION
    2. AIM OF THE PROJECT
    3. OBJECTIVE OF THE PROJECT
    4. SIGNIFICANCE OF THE PROJECT
    5. APPLICATION OF THE PROJECT
    6.  ADVANTAGES OF THE PROJECT
    7. STATEMENT OF THE PROBLEMS

CHAPTER TWO

2.0     LITERATURE REVIEW

2.1     OVERVIEW OF THE STUDY

2.2     HISTORICAL BACKGROUND OF THE STUDY

2.3      OPERATIONAL REVIEW OF ASTABLE

2.4     DESCRIPTION OF 555 TIMERS IC

2.5     HISTORICAL BACKGROUND OF 555 TIMER IC

CHAPTER THREE
3.0     CONSTRUCTION METHODOLOGY
3.1      BASICS OF THE SYSTEM
3.2      SYSTEM DIAGRAM
3.3      CIRCUIT DESCRIPTION

3.4     CIRCUIT WITH INTERNAL BLOCK DIAGRAM

3.5      THEORY OF RESISTOR
3.5      THEORY OF CAPACITOR
CHAPTER FOUR
RESULT ANALYSIS
4.0      CONSTRUCTION PROCEDURE
4.1      CASING AND PACKAGING
4.2      ASSEMBLING OF SECTIONS
4.3      TESTING OF SYSTEM OPERATION
4.4      PACKAGING
4.5      MOUNTING PROCEDURE
4.6      RESULT
4.7      COST ANALYSIS

CHAPTER FIVE 
5.1      CONCLUSION
5.2      REFERENCES

 

CHAPTER ONE
1.1                                                        INTRODUCTION
A multivibrator is an electronic circuit used to implement a variety of simple two-state devices such as relaxation oscillators, timers and flip-flops. It consists of two amplifying devices (transistors, vacuum tubes or other devices) cross-coupled by resistors or capacitors. The first multivibrator circuit, the astable multivibrator oscillator, was invented by Henri Abraham and Eugene Bloch during World War I. They called their circuit a “multivibrator” because its output waveform was rich in harmonics.
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.
Multivibrators are classified into three types based on the circuit operation, namely Astable multivibrators, Bistable multivibrators and Monostable multivibrators. The astable multivibrator is not stable and it repeatedly switches from one state to the other. In monostable multivibrator, one state is stable and remaining state is unstable. A trigger pulse is the root to the circuit to enter the unstable state. When the circuit enters into the unstable state, then it will return to the normal state after a fixed time. A bistable mutivibrator circuit is stable that can be changed from one stable to other stable by an external trigger pulse. This multivibrator circuit is also called as flip-flop which can be used to store one bit of data.
However, for the course of this work we are dealing with an astable type of multivibrator. This type of multivibrator includes two amplifying stages that are connected with a two capacitive-resistive coupling networks in a positive feedback.
The designing of astable multivibrator using a 555 timer IC is done by using  ransistors and operational amplifiers. The 555 timer IC affords exact time delay from ms to hours. The oscillation frequency can be measured manually by small modification. 555 timer IC is a relatively cheap, stable and user-friendly integrated circuit and that is apt for circuit designers with for both astable and monostable applications. The first 555 integrated circuit was designed in the year 1971 by the corporation of Signetics as the SE555 or NE555. Astable multivibrator using 555 IC is a simple oscillator circuit that generates continuous pulses. The frequency of the circuit can be controlled by shifting the values of resistors R1, R2 ad capacitor C1.

1.2                                              OBJETIVE OF THE PROJECT
There are three different types of multivibrator, but the main aim of this work is to design an astable multivibrator using a 555 timer IC.

1.3                                             OBJECTIVE OF THE PROJECT
After completing this work, student involved would able to learn:

  1. What is a 555 timer IC.
  2. What is an a stable Multivibrator.
  3. How 555 timer IC works as an astable multivibrator.
  4. How it produces square wave.
  5. What is the role of capacitor in an astable multivibrator circuit.

 

1.4                                         SIGNIFICANCE OF THE PROJECT
The oscillation frequency can be measured manually by small modification. 555 timer IC is a relatively cheap, stable and user-friendly integrated circuit.

1.5                                         APPLICATIONS OF THE PROJECT
The applications of Astable multivibrators involve in radio gears to transmit and receive radio signals and also in time, morse code generators and some systems which require a square wave like analog integrated circuits and TV broadcasts.

1.6                                          ADVANTAGES OF THE PROJECT
These multivibrators are changes between one stable state to another continuously. This permits multivibrators to power themselves & achieve work at a constant rate without impact from any external forces or actions. Also, these multivibrators are low cost to produce, and simple to design.

1.7                                            PROBLEMS OF THE PROJECT
These multivibrators do not transfer the whole o/p signal to the i/p. This is due to resistance in the circuit, nonexistence of a totally closed loop at the o/p terminals, and the leaning of one transistor/capacitor to absorb energy at a somewhat different rate than the other. Although the amplifier restores the lost energy when it amplifies the signal, the signal will finally be too small to be of any use.

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