Design And Construction Of A Microcontroller Based Digital Countdown Timer

Timers are frequently used in the industries to run process/operation with predefined time interval. The most popular type of timer is the programmable timer that has various facilities to configure the timer by users. However, it is expensive to build such timer using ICs and discrete components. Moreover, when programmable timer is used for laboratory instruments, it is expected to be flexible to handle. Microcontroller has the potential to solve these constraints. In this development work, we have developed a microcontroller based programmable timer with digital display system that can be configured to connect the AC main line to the instruments for a specific time interval. This device can function in two modes: manual mode and programmable mode. In the programmable mode, the device connects AC main line to the power outlet for a set interval. The device has been designed and tested in the laboratory.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• PROBLEM STATEMENT
• OBJECTIVE OF THE PROJECT
• SCOPE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• APPLICATION OF THE PROJECT
• LIMITATION OF THE PROJECT
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• REVIEW OF TIMING DEVICES
• DESCRIPTION OF TIME MANAGEMENT
• THE IMPORTANCE OF TIME MANAGEMENT IN LECTURE

CHAPTER THREE

3.0       METHODOLOGY

• SYSTEM BLOCK DIAGRAM
• SYSTEM BLOCK DESCRIPTION
• SYSTEM CIRCUIT DIAGRAM
• SYSTEM DESCRIPTION AND OPERATION
• SYSTEM SWITCHING CIRCUIT
• SYSTEM FLOW CHAT
• DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

TEST AND RESULT ANALYSIS

• INSTALLATION OF THE COMPLET DESIGN
• CONSTRUCTION PROCEDURE AND TESTING
• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION
• PROBLEM ENCOUNTERED
• DISCUSSION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

• INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

Timers that schedule an event according to a predefined time value in the future are an integral part of many real-time embedded systems, similar to setting an alarm clock. They find applications in the control of sequential functions of industrial machinery at varying time intervals, in the laboratory to power instruments for a specific time and perform processes for a specific duration. Usually, two kind of timer are frequently used in various applications such as mechanical and electronic timers. Electronics timers are manufactured today to meet the complex function of industries. The Electronic timer consists of a crystal controlled stable oscillator, sequencing logic circuits, driving circuits and a digital display system with a facility depends on the application for connecting the output to individual machinery/system to control the operation at pre-determined time interval.

The timers which can be configured to set time interval is called programmable timer. The programmable timer is usually designed with different functions that would be flexible to customize by the users. To build such timer, many ICs and components are required. Therefore, manufacturing cost prohibit deploying programmable timer in many applications. Moreover, when programmable timer is used in laboratory, it should be sophisticated. In this development work, we have developed a microcontroller based programmable timer with digital display system. It works in two modes: manual mode and programmable mode. In manual mode, it can function like switch board. In the programmable mode, user can set the time how long AC main line could be connected to the power outlet. Then, it is disconnected automatically. The time is set for hours, minutes and seconds i.e. the time format is HH:MM: SS. Therefore, the maximum time would be 99h: 59m: 59s. The remaining time is shown on the display system designed with six seven-segment LEDs.

1.2                                                  PROBLEM STATEMENT

Due to inaccuracy in time schedule keeping in most of our publics such when an assignment or presentation is given to someone with a time limit schedule. This device is helpful to someone in such situation. It helps the user to be very accurate and conscious of the assigned time.

1.3                                                   AIM OF THE PROJECT

The main aim of this work is to design a down counter that counts from a specified time to 00:00.

1.4                                         SIGNIFICANCE OF THE PROJECT

Microcontroller based countdown timer with digital display system that can be configured to connect the AC main line to the instruments for a specific time interval. Sometimes when there is a need to switch on or off electrical appliances or gadgets after a predetermined time. This device is used to switch on/off any electrical appliance (load) through a relay switch after the specified time set in minutes or seconds.

1.5                                                 SCOPE OF THE PROJECT

A countdown timer is a down counter that counts from a specified time to 00:00. It is used in many devices such as washing machine, televisions, microwave ovens, etc. This countdown timer has three states: the running state where it counts down, the pause state where it displays the paused time and the reset state to set the countdown. The countdown is displayed on a set of four seven segment displays using the microcontroller PIC-16F72A buzzer sounds when the countdown gets over.

The timer can be easily set with four switches (S3 through S6) to select minutes/seconds, hundredths, tenths and units. Two more switches are used to start (S2) and stop (S1) the timer.

1.6                                          APPLICATION OF THE PROJECT

It is used in many devices to control their working time such as in washing machine, televisions, microwave ovens, etc. And also in some public places such as presentation hall, wresting ground etc.

1.7                                         METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. programming of microcontroller
2. Design and calculation for the changeover was carried out.
3. Studying of various component used in circuit.

• Construct a digital changeover circuit.
• Finally, the whole device was cased and final test was carried out.

1.8                                        PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to this study. In this chapter, the background, significance, objective, application, and scope of the project of this work was discussed.

Chapter two is on literature review of the study. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.