Description
ABSTRACT
This work is on a mono stable multi vibrator. This is a type of multi vibrator in which one of the states is stable, but the other state is unstable (transient). A trigger pulse 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.
TABLE OF CONTENTS
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
TABLE OF CONTENT
CHAPTER ONE
- INTRODUCTION
- AIM OF THE PROJECT
- OBJECTIVE OF THE PROJECT
- SIGNIFICANCE OF THE PROJECT
- APPLICATION OF THE PROJECT
- SCOPE OF THE PROJECT
- DEFINITION OF TERMS
- METHODOLOGY
- PROJECT ORGANISATION
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 OVERVIEW OF MULTI VIBRATOR
2.2 TYPES OF MULTI VIBRATOR
2.3 DIFFERENT TYPE OF MONO-STABLE CONFIGURATION
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
3.5 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
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
A multi vibrator 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 multi vibrator circuit, the a stable multi vibrator oscillator, was invented by Henri Abraham and Eugene Bloch during World War I.[4][5] They called their circuit a “multi vibrator” because its output waveform was rich in harmonics.[6]
There are three types of multi vibrator circuits are: A stable multi vibrator, Mono stable multi vibrator and Bistable multi vibrator. In this work we are focusing on a mono-stable A mono-stable multi vibrator, also called a one shot, is an electronic circuit that generates an output pulse. When triggered, a pulse of pre-defined duration is produced. The circuit then returns to its stable state and produces no more output until triggered again.
Mono-stables may be considered as a biased form of multivibrator where it is stable in one state until triggered, then unstable and will return spontaneously.
If repeated application of the input pulse maintains the circuit in the unstable state, it is called a retriggerable mono-stable. If further trigger pulses do not affect the period, the circuit is a non-retriggerable mono-stable.
1.2 AIM / OBJECTIVE OF THE PROJECT
The main aim of the work is to design a multi vibrator that has only one stable output state. After carrying out this work, the student involved will be able to:
- Design and build Mono stable Multi vibrator circuit using 555 Timer chip
- Produce a time delay within a circuit as the frequency of the output signal is always the same as that for the trigger pulse input
- Measure timing information (Pulse width / T_on) of the mono-stable output when triggered
1.3 SCOPE OF THE PROJECT
The scope of this work covers building a mono-stable multi-vibrator circuit which is a circuit that has one stable state and one quasi stable state (astable state) using 555 timer. When an external trigger applied to the circuit, the multi-vibrator will jump to quasi stable state from stable state.
After the period of time it will automatically set back to the stable state, for returning to the stable state multi-vibrator does not require any external trigger. The time period to returning to stable state circuit is always depends on the passive elements in the circuit (resistor and capacitor values.
A mechanical analogy of a mono-stable device would be a momentary contact pushbutton switch, which spring-returns to its normal (stable) position when pressure is removed from its button actuator. Likewise, a standard wall (toggle) switch, such as the type used to turn lights on and off in a house, is a bistable device. It can latch in one of two modes: on or off.
All mono-stable multi vibrators are timed devices. That is, their unstable output state will hold only for a certain minimum amount of time before returning to its stable state. With semiconductor mono-stable circuits, this timing function is typically accomplished through the use of resistors and capacitors, making use of the exponential charging rates of RC circuits.
1.4 SIGNIFICANACE OF THE PROJECT
The mono-stable multi vibrators are used as timers, delay circuits, gated circuits etc
1.5 LIMITATION OF THE PROJECT
Mono-stable multi vibrator works with trigger. Mono-stable multi vibrator switches on to an unstable state when trigger is applied.
1.6 APPLICATIONS OF THE PROJECT
Mono-stable Multi vibrator can be used to simply trigger a circuit for a particular input. ie, in circuits involving Microcontrollers sensing particular parameters (touch, humidity etc.). Thus making the circuit respond to the inputs.
1.7 DEFINITION OF TERMS
The following list are terms associated with a timing pulse or waveform.
- Active HIGH – if the state change occurs from a “LOW” to a “HIGH” at the clock’s pulse rising edge or during the clock width.
- Active LOW – if the state change occurs from a “HIGH” to a “LOW” at the clock’s pulses falling edge.
- Duty Cycle – this is the ratio of the clock width to the clock period.
- Clock Width – this is the time during which the value of the clock signal is equal to a logic “1”, or HIGH.
- Clock Period – this is the time between successive transitions in the same direction, ie, between two rising or two falling edges.
- Clock Frequency – the clock frequency is the reciprocal of the clock period, frequency = 1/clock period. ( ƒ = 1/T ).
1.8 METHODOLOGY
To achieve the aim and objectives of this work, the following are the steps involved:
- Study of the previous work on the project so as to improve it efficiency.
- Draw a block diagram.
- Test for continuity of components and devices,
- Design and calculation for the device was carried out.
- Studying of various component used in circuit.
- Construction of the circuit.
- Finally, the whole device was cased and final test was carried out.
1.9 PROJECT ORGANISATION
The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.
CHAPTER FIVE
5.1 CONCLUSION
The study has been carried out successfully and the objectives of the study was completely achieved. At the end of the project a mono-stable multi vibrator was built using 555 timer IC. Mono-stable means that once the circuit is switched on it will time once and then stop. In order to start it again it must be switched on manually a second time.
A 555 timer circuit was used because the 555 timer IC (integrated circuit) is very stable, relatively cheap and reliable.
