Design And Construction Of A Simple Time Delay Circuit

ABSTRACT

Time Delay is defined as the controlled period between the functioning of two events. A Time Delay relay is a combination of an electromechanical output relay and a control circuit. The control circuit is comprised of solid state components and timing circuits that control operation of the relay and timing range. Time delay relays have a broad choice of timing ranges from less than one second to many days. There are many choices of timing adjustments from calibrated external knobs, DIP switches, thumbwheel switches, or recessed potentiometer. The output contacts on the electromechanical output relay are direct wired to the output terminals. The contact load ratings are specified for each specific type of time delay relay.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

1.1   INTRODUCTION

1.2   OBJECTIVE OF THE PROJECT

1.3   PURPOSE OF THE PROJECT

1.4   SIGNIFICANCE OF THE PROJECT

1.5   APPLICATION OF THE PROJECT

1.6   SCOPE OF THE PROJECT

1.7   PROJECT WORK ORGANIZATION

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF THE STUDY
• TYPES OF TIME DELAY RELAYS (TDRS)

2.3     REVIEW OF TIMING DEVICES

2.4     DESCRIPTION OF TIME MANAGEMENT

CHAPTER THREE

3.0     METHODOLOGY

3.1      SYSTEM BLOCK DIAGRAM

3.2       SYSTEM BLOCK DESCRIPTION

3.3     REQUIRED COMPONENTS

3.4      CIRCUIT DIAGRAM

3.5     WORKING OF TIME DELAY CIRCUIT

3.6     DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

4.1      RESULT ANALYSIS

4.2      CONSTRUCTION PROCEDURE AND TESTING ANALYSIS

4.3      CASING AND PACKAGING

4.4      ASSEMBLING OF SECTIONS

4.5       CONSRUCTION OF THE CASING

4.6       ECONOMIC OF THE PROJECT

4.7      PROJECT EVALUATION

4.8      RELIABILTY

4.9      PROJECT EVALUATION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.1                                                        INTRODUCTION

The power supply of these modern electronic devices is vulnerable to spikes in the mains line so it gives a time delay of one minute before applying power to the device. This prevents deleterious effects due to inrush current and spurious spikes at power on.

Inrush current at power on or power resumes after a power failure can cause unexpected damage in power supply of electronic devices. The spurious spike in the power supply when power resumes is due to heavy magnetic flux in the distribution transformer in the mains network. If a short delay is provided, such damages can be avoided. The time delay relay circuit described here is intended for this purpose. It gives power to the device only after one to two minutes of delay after the power is switched on.

In this project is on a Simple Time Delay Circuit Using 555 Timer IC. This circuit consists of 2 switches one for start the delay time and other for reset. It also has a potentiometer to adjust the time delay, where you can increase of decrease the time delay by just rotating the potentiometer.

In this work a 9 V battery and 5V optional relay was used for switching the AC load. A 5v voltage regulator is used for giving 5v regular supply to the circuit.

A Relay is an electromechanical device that acts as a switch between two terminals. The switching operation is achieved by energizing or de energizing the coil in the relay.

These relays provide a “Time Delay” between the energizing or de-energizing of the coil and movement of the armature. Such relays are called Time Delay Relays.

A Time Delay Relay consists of a normal electromechanical relay along with a control circuit to control the relay operation and timing.

1.2                                             OBJECTIVE OF THE PROJECT

A delay used to separate the occurrence of two events, especially in a mechanical or electronic device. The main aim of this work is to construct a device that switches on a load after a period of the set time.

1.3                                             OBJECTIVE OF THE PROJECT

At the end of this work the student involved should be able to:

(a) Describe how a RC network can produce a time delay.

(b) Describe how the voltage across a charging or discharging capacitor in a RC circuit varies with time, including the interpretation of decay graphs for RC networks.

(c) Describe how the time delay may be changed by varying R and/or C.

(d) Describe the action of a 555 monostable timer and then use the equation T= 1.1 RC, where T is the pulse duration.

1.4                                              PURPOSE OF THE PROJECT

The time delay relay circuit described here is intended for this purpose. It gives power to the device only after one to two minutes of delay after the power is switched on.

1.5                                         SIGNIFICANCE OF THE PROJECT

When electrical and electronic devices are switched on, they load the supply network momentarily with high current pulses, called inrush current. This peak currents (Iinr_p) can be extremely high, from few times nominal device current (Inom) to few 10 times nominal current, depends on device topology and its built-in inrush protection. Circuit breakers and switches have to be designed for these peak currents to prevent unpredictable trips or contact welding. Besides this, such high current pulses produce voltage dips in the supply voltage, which in turn can cause malfunctions in other consumer circuits powered from the same supply. Often, this inrush current is not given sufficient consideration or is overlooked, which can lead to unexpected circumstances later on.

Overvoltage protection: Time Delay Switching device can be equipped with addition of overvoltage protection which reduces risk of supplied device defect or malfunction due to lighting strikes or other overvoltage source.

1.6                                          APPLICATION OF THE PROJECT

Providing time-delayed switching to start a motor, control a load, or affect a process, time delay circuits are typically used in industrial applications and consumers equipment such as in voltage stabilizer

1.7                                                 SCOPE OF THE PROJECT

A 555 timer ic and relay is the major components used in this work. A Relay is an electromechanical device that acts as a switch between two terminals. The switching operation is achieved by energizing or de energizing the coil in the relay.

This relay provides a “Time Delay” between the energizing or de-energizing of the coil and movement of the armature. A Time Delay Relay consists of a normal electromagnetically relay along with a control circuit to control the relay operation and timing.

Upon application of input voltage, the time delay relay is ready to accept a trigger. When the trigger is applied, the time delay (t) begins. At the end of the time delay (t), the output is energized and remains in that condition as long as either the trigger is applied or the input voltage remains. If the trigger is removed during the time delay (t), the output remains de-energized & the time delay (t) is reset.

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 project. In this chapter, the background, significance, objective limitation and problem of this project were discussed.

Chapter two is on literature review of this project. 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.