The document outlines a project on designing an over/under voltage protection circuit aimed at safeguarding electrical appliances from power surges. It describes the circuit's functionality, methodology, components, and applications in various fields, emphasizing its simplicity and cost-effectiveness. The project highlights the significance of electrical safety and encourages further research for improved efficiency.

1. Faculty of Engineering Science and Technology
BACHELORS OF ENGINEERING (ELECTRICAL)
Fall -2019
Project Presentation for
Over/Under Voltage Protection Circuit
GROUP MEMBERS:
MUHAMMAD FAZIL MEMON
SHAHBAZ AHMED
RAZAULLAH

2. CONTENTS
Abstract
Introduction
Design
Cost
Methodology
Results
Applications
Conclusions
References

3. ABSTRACT
The Over and Under Voltage protection circuit can protect electrical appliance
from in the condition of power surges.
The project theme was to design an economical and efficient power protection
circuit that could be capable of safely isolating the power of machine incase of
power surges in mains.
This circuit is prototype circuit can be widely used for industrial and household
machines and appliances, by making small changes in component’s specification

4. INTRODUCTION
Today World’s strategic economical structure is majorly based on
electrical technology. Modern Science has a vast area of research in the
field of electrical based technologies
In The field of research and development, the safety of electrical
appliance has always been a primary goal
Similarly the project team with the guidance of their respected teachers
has developed an idea of protecting electrical appliance from most
commonly occurring problem of surging of mains
The Team has prepared a prototype circuit having dual protection
against surge
The circuit is responsible to cut off the main incoming supply incase the
voltage level has reached to its predefined high or low set limits.
The circuit stands fully functional in low voltage ranges, hence can be
used for experimental / analytical purpose for the coming batches of
Indus university.

5. Sr.NO Component Quantity Specification Cost (PKR)
1 Transformer 1 220-12Vac 500ma 180
2 Diode 4 1N4004 20
3 Capacitor 1 100uf 25V 10
4 Resistor 3 10K 10
5 Variable Resistor 2 10K 80
6 Zener Diode 2 1N4728A 30
7 Bipolar Junction
Transistor
2 NPN BC 547 40
8 Push Switch 1 SPST 30
9 SPDT Relay 1 12vDC 400Ohms 50
10 Others Box Fabrication, transport etc. 500
CIRCUIT DESIGN

6. CIRCUIT DESIGN

7. METHODOLOGY
As shown in the circuit diagram, a couple of transistor
stages are integrated together along with an output
relay, which is able to perform the function of super safe
voltage guard equipment. As explained above the
transistors sense the presence of the dangerous voltage
levels respectively and activate the relay to protect the
connected appliance from drastic situations. The cut
OFF supply will be immediately restored back once the
voltage returns to a safe level or reset switch has been
pressed.

8. The circuits described below are pretty simple in
design and may be easily built over a small piece
of a general purpose PCB or veroboard.
 On receiving the supply voltage the circuit will
operate by energizing T2 and the relay.
 The relay contacts will get latched so that the
entire circuit now receives the supply voltage
through its N/O contacts and the push button
may be simply released.
METHODOLOGY

9.  As long as the supply voltage is within the normal
range, the circuit remains latched and the output
appliance is safely powered.
 Now, if the voltage increases to an undesirable extent,
T1 will conduct, bringing the base voltage of T2 to
ground and thus deactivating T2 and the relay.
METHODOLOGY

10. Once the relay contacts are dislodged, the supply
to the appliance as well as the whole system is
broken. The circuit will remain unlatched until two
conditions are met viz.
i. The push button is pressed and
ii. The voltage is restored to its normal position.
The same will happen during the unsafe low
voltages.
METHODOLOGY

11. RESULT
The result of this project is brought up of a very
useful voltage protection circuit , which is easy
to design and implement on industrial or
household levels.
The circuit design is very simple using common
electrical components available components,
like transistor, resistors etc. which are easy
access from local markets.

12. APPLICATION
The over/under voltage protection is very important for
electrical appliance in every aspect of industrial, commercial
or household field.
Some examples of the circuits with similar concept of
operations are being used as of following
1. In K Electric Grid control system, to protect power feeders
over voltages
2. In Natural Gas Processing Plants To Protect Heavy Motors
used for pumping amine solution
3. In Central HVAC System, to protect compressors from low
voltages

13. CONCLUSION
The Over/Under voltage protection circuit
stands very useful in electrical technological
equipments. And this safety can be achieved by
using basic electrical/electronic components.
Continuous research and development on this
subject can increase circuit’s efficiency and
durability for the betterment of human being

14. REFRENCES
 www.electronchub.org
 www.brighthubengineering.com
 www.electronicproject.org
 www.homemade-circuits.com
 www.youtube.com/electronicsnmore