Construction Of An Automatic Power Failure With Digital Indicator For Change-Over Switch And Generator Starter

Project and Seminar Material For Electrical Electronics Engineering EEE

Project and Seminar Material For Electrical Electronics Engineering EEE


The need for auto-switching now, is more than even before. A device that could handle this auto-switching forms the basis for this project. This circuit is capable of turning ON a generator set whenever there is power failure.

This device “Automatic power failure with digital indicator for change-over switch and generator starter” is capable of changing from PHCN to GENERATOR and GENERATOR to PHCN when the power supply is restored.

This circuit solves the problem of manual switching or change-over process by using relays, voltage regulators, bridge rectifiers, capacitors e.t.c. in sending signals to a generating set.

Table Of Content

Preliminary Page(s)

  • Title Page
  • Approval Page
  • Dedication
  • Acknowledgement
  • Abstract
  • Table of Content

Chapter One

  • 1.0 Introduction

Chapter Two

  • 2.0 Literature Review

Chapter Three

  • 3.0 Description of Components
  • 3.1 Resistor
  • 3.2 Capacitor
  • 3.3 Voltage Regulator
  • 3.4 Bridge Rectifier
  • 3.5 Integrated Circuit (IC)
  • 3.6 Transformer
  • 3.7 Relay
  • 3.8 Zener Diode
  • 3.8 Diode

Chapter Four

  • 4.1 Block Diagram
  • 4.2 Circuit Diagram
  • 4.3 Assembling of the System
  • 4.4 Testing and Results
  • 4.4 Principle of Operation

Chapter Five

  • 5.1 Summary
  • 5.2 Recommendation
  • 5.3 Conclusion
  • References

Chapter One

1.0 Introduction

This automatic power failure with digital indicator for change-over switch and generator starter is a device with dual function. That is to say, it has two different functions in one, such that it first serves as a power failure indicator and at the same time serves as a change-over switch with a capability of starting a generator.

This device consists of a relay which is a device (electrical) that is interposed between the main circuit and the circuit breaker in such a manner that any abnormality in the circuit, acts on the relay, which in turn, if the abnormality is of dangerous character, causes the breaker to open and so to isolate the faulty element.

In this case, when supply from the Power Holding Company of Nigeria (PHCN) is interrupted, the relay triggers a signal to the generator which would immediately respond by starting automatically. Meanwhile, relays are capable of handling three (3) essential functions. They are:-

  1. Relays have a sensing element, also called the measuring element, which responds to the change in actuating quantity.
  2. It also has a comparing element. This element serves to compare the action of the actuating quantity on the relay with a pre-selected relay setting.
  3. Thirdly, the relay has a control element on a pick up of the relay, which accomplishes a sudden change in the control quantity such as closing of the operative circuit.

The two parts that make up this device ‘automatic power failure (digital indicator) with change-over switch and generator starter are as described below:-

I. Power Failure Indicator:

This is a device that gives an alert either by sounding an alarm, beeps, or by any other way whenever there is power outage in a system. The essence of this power failure indicator, which is digitally indicated, is to give a fast signal whenever there is power failure especially in a system where Uninterrupted Power Supply (UPS) is used.
This device also signals whenever there is a switching process either PHCN to GENERATOR or GENERATOR to PHCN.

Ii. Automatic Change-Over Switch With Generator Starter

The function of this automatic change-over switch with generator starter, is to switch automatically from PHCN supply to GENERATOR “Automatic change-over” and automatically switches ON GENERATOR set whenever there is power outage “Generator starter”. This device equally switches OFF the generator set and changes over to PHCN whenever power is restored.

Meanwhile, the kind of generator used in this case makes use of an electrical energy “Battery” to drive the prime-mover that will in turn switch ON the generator set.

Furthermore, the change-over switch can be constructed in two different ways which are:-

  1. Auto-manual change-over switch
  2. Automatic change-over switch with generator starter.

1. Auto-Manual Change-Over Switch

Here, an operator will be needed to be switching ON and OFF the generator set whenever there is power outage by PHCN and when power is restored. Moreover, the switching “change-over” from supply to generator and vice versa is done automatically. The types of generator used in this case uses mechanical energy to drive the prime-mover that in turn switches on the generator.

2. Automatic Change-Over Switch With Generator Starter

In this, here would not be need for a generator operator here, because everything is done automatically. The kind of generator used here makes use of electrical energy “battery” to turn the prime-mover.
The combination of all these in a modified way forms a system called “automatic power failure (digital indicator) with change-over switch and generator starter.

Chapter Five

Summary, Conclusion And Recommendation


From the circuit and its construction, we could see the importance of auto-switching and change-over. The circuit senses when there is power failure and immediately seeks for an alternative so as to avoid total black-out or shutdown.

The different components used in the construction help in signaling the generator set when to start and turn off after the restoration of power from the supply. An observer knows, through the power failure indicator when PHCN is in use and when the alternative power supply is also in use. Meanwhile, it aids manual switching and uses less time in the change-over process.


The following recommendations could be employed.

  1. The circuit is recommended for banks in handling interrupted power supply which has an effect on their systems.
  2. Hospitals can also enjoy this circuit so as to handle power seizure which could cause harm to patients.
  3. I recommend this circuit to hotels where power interruption affects their esteemed customers.
  4. Residential buildings are not left out, in that, it protects electronic gadgets at the supply of unrecompensed and unperceived voltage supply.
  5. Industries and stock exchange can also find the circuit interesting in its bid to increasing productivity which could be hampered by manual switching and change-over.


Based on the working principle and the components involved, we could make the following conclusions:-

  1. That the circuit is capable of indicating when there is power failure.
  2. That the circuit, through relays, is capable of auto-switching that is changing from PHCN to GEN and vice versa.
  3. That the circuit can start or turn ON any synchronized generating set.
  4. That the circuit is also capable of protecting any electrical or electronic gadget that is affected by low voltage supply.

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