Construction Of Automatic Change Over Switch For Power Failure With Generator Starter

Project and Seminar Material For Electrical Electronics Engineering EEE

Project and Seminar Material For Electrical Electronics Engineering EEE


Most industrial and commercial processes are dependent on electrical power. Power failure or outage in general does not promote development in public and private sectors. The investors do not feel secure to come into a country with constant or frequent power failure. This limits the development of industries.

In addition there are processes that cannot be interrupted because of their importance, for instance surgery operation in hospitals, transfer of money between banks and lots more.

This project presents the construction of an automatic changeover switch for power failure with generator starter that switches power supply from public supply to generator once there is public power supply outage and this is performed automatically.

This is achieved by the use of integrated circuits that have timing abilities and relay to effect switching.

Table Of Contents

Preliminary Page(s)

  • Title Page
  • Approval Page
  • Dedication
  • Acknowledgement
  • Abstract
  • Table Of Contents

Chapter One

1.0 Introduction

Chapter Two

2.0 Literature Review

Chapter Three

3.0 Research And Methodology

  • 3.1 Methodology
  • 3.2 Principle Of Operation
  • 3.3 Components Used And Their Functions

Chapter Four

4.0 Assembly Language Program

  • 4.1 How To Prepare The Veroboard
  • 4.2 Soldering
  • 4.3 Testing The Circuit

Chapter Five

  • 5.0 Conclusion
  • 5.1 Recommendation
  • 5.2 Bills Of Quantity
  • Reference

Chapter One


Power instability in developing countries creates a need for automation of electrical power generation or alternative source of power to back up the utility supply. This automation is required as the rate of power outage becomes predominantly high. Most industrial and commercial processes are dependent on power supply and if the processes of changeover are manual, serious time is not only wasted but also creates device or machine damage from human error during the changeover connections, and this could result in massive losses.

This project involves automatic changeover between main power supply and an auxiliary power supply, such as a generator. The project implements an automatic switching or starting of the power generator whenever the main power fails.

The basic operation of this project is to switch ON an auxiliary power supply (like a generator). This operation connects the power supply from the generator to the load after a predetermined time interval. This is intended to normalize the current from the generator. Switching is possible through the use of the relays which switch the battery voltage to ignition coil of the generator while the main power relay switches the load to either public supply or generator.

The system was designed to automatically change power supply back to the main supply moments after the A.C mains are restored and to switch OFF the generator. The device removes the stress of manually switching ON the generator when power failure occurs.

Whenever public supply is available, the relay 3 whose duty is to respond will immediately be energized and its two terminals C3 and B3 are connected together. Whenever the public supply is off from the transformer, the other two terminates C3 and A3 of the relay are connected together and the power circuit is then powered through the 12v battery.

The first important action to the circuit is the automatic resetting of both latches through Schmitt trigger and gate whenever there is public power supply. The gate allows Q and Q- of the latches to be at logical zero and one respectively. This is required for normal starting state. For the motor control latch Q is connected to transistor one through the base. The NPN device controls the relay. For Q at logical 1, transistor one is saturated and relay 1 is energized. Terminals C1 and B1 of the relay are connected together.

The operation allows electric current to flow through the motor / starter. It is noted that one of the motor terminals is already connected to 6v terminals i.e. positive side. The switching of the relay allows the other terminal to be grounded thereby completing the circuit of the electric motor.

The micro controller starts timing immediately, relay 3 supplies electric current to the logic control unit.
Relay 2 supplies power supply to the output load from two sources G and M. M represents public power supply and C1 represents supply from the generator.

Therefore the initial condition is the supply of power to the load through the normal A.C mains the control oscillator through its pin 3 sets the changeover latch for the Q output to change from logical zero to 1 for transistor two to be saturated in reversing the output condition of relay 2.


The operational process is outlined below:

  1. The power circuit of the generator is not active where there is A.C mains supply.
  2. Its response to A.C mains supply power failure is by switching on the starting mechanism of the generator.
  3. There is a delay in the loading of the generator so as to attain stability for a while. After the said delay, the generator is loaded.
  4. Power supply from the generator is interchanged immediately the A.C mains is restored. After this the generator is switched OFF.

Chapter Five

5.0 Conclusion

The various tests carried out and result obtained demonstrates that automatic change over switch for power failure with generator starter achieved its construction aims. The system worked accordingly to specification and quite satisfactory. The automatic change over switch is affordable and reliable. It is easy to operate, and it provides a high level of power supply when there is power failure. Finally it reduces stress associated with manual change over.

5.1 Recommendation

It can be seen that automatic change over switch can saves life and also reduce stress encountered when a manual change over is used. We there recommend it to both domestic and commercial users.

5.2 Bill Of Quantity

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