Project Report: Design of Over/Under Voltage Protection Circuit

This report details the design and implementation of an over and under voltage protection circuit, focusing on protecting home appliances from voltage surges and fluctuations. The project involved designing a time-delay circuit using components like relays, transistors, and the NE555N timer to provide reliable and low-cost protection. The report covers the project background, objectives, the student's role as a team leader, engineering knowledge applied, and the challenges faced, such as the relay driver issue and its solution. The project aimed to create a standalone circuit that could be integrated between the power supply and the load, protecting devices like TVs and refrigerators. The report includes circuit diagrams, discusses the implementation of the transformer, and describes the testing and evaluation of the prototype. The project successfully demonstrated the effectiveness of the voltage protection system, offering a practical solution for safeguarding electrical devices from voltage-related damage and ensuring their longevity.

Competency
Demonstration Report
(CDR)
Career Episode 3

CE 3.1: Project Introduction
Name of the Project : Design and construction of over voltage and under
voltage protective device
Geographical Location : [Please Fill]
Project Duration : [Please Fill]
Organization : [Please Fill]
Position in the Project : Team Leader
CE 3.2. Project Background
CE 3.2.1: Characteristics of the Project
The development of the auto cut off circuit has allowed in the implementation of various
equipments including transistors. The integration of the auto cut off circuit has allowed to protect
the loads of various heavy electrical devices including TV and refrigerators. Further, I have
learned that the integration of the auto cutoff circuit has provided protection from both the under
and over line voltages. Furthermore, these circuits can be utilized for as the vital circuit between
the load and supply as the manual or automatic stabilizer. Therefore, I undertook the project for
the design and development of over and under voltage protection circuit with reliable and low
cost time delay characteristics that helps in protecting the electrical devices from surges. I have
evaluated, build and designed the circuit that could be used in the home devices including home
devices including refrigerator.
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CE 3.2.2: Objectives developed for project
In this project, I have developed my significant aim to design a on-time delay circuit for
providing protection against the switching surge and over and under voltage. Further, I have
fabricated the circuit design in with the various electrical equipments including Tv and
refrigerator than can be used as home appliances. In addition to that I have also focused on
implementing the circuit as standalone between the load and supply. Apart from that, for the
successful development of the system, I have developed the detailed objectives for the proect
completion within deadline:
 To determine the working principal for over voltage and under voltage protective
device;
 To identify the major components required for the implementation of the voltage
protective devices;
 To evaluate and understand the working principals and operation of the various
electrical components;
 To design the circuit for protecting the devices against voltage surges;
 To implement the hardware design and components required for the design of the
protection devices;
CE 3.2.3: My area of work
I have worked as a team leader for the proper implementation and design of the voltage
protector. I have selected and determined the appropriate components required for the
implementation of the voltage protector system. In order to develop the working principle and
connectivity among the different elements, I have selected relay, transistors, zener diode,
potentiometer, NE555N timer, capacitors, diode and one transformer.
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CE 3.2.4: Project Group
Figure 1: Team Member Associated with the Project
CE 3.2.5: My responsibilities throughout the project
I have worked in this project as a team members for the proper completion and
demonstration of the implementation work require for the design and development of the voltage
protection devices. In addition to that, I have allocated the work modules to the different team
members based on their work capabilities and technical understanding.
CE 3.3: Distinctive Activity
CE 3.3.1: Comprehending the Theory of the project
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I have used the time delay concept for developing the under and over voltage circuit
protection. I have employed the basic principle for transformer operation in this system. The
theory that the magnetic field can be produced by electrical current and the production of the
magnetic field induces significant amount of voltage. Magnetic flux can be developed by
changing the current flow direction in the primary coil. While on the other hand, voltage can be
produced by changing the magnetic flux in the secondary coil.
CE 3.3.2: Engineering Knowledge and Skills applied in the project
Figure 2: Circuit Design
I have implemented the circuit design while selecting the appropriate hardware required
for the design of the voltage protection devices. I have used the rectifier for alternating the AC
current into required DC in a particular direction. Through this I have achieved rectification of
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the voltage through the circuit. I have used full-wave rectification for converting the polarities
while obtaining high voltage yield of the current. For this I have selected the application of
transformer, two diodes, AC source and bridge configuration with four diodes. With the detailed
electronics equipments I was successful in developing the appropriate design for the circuitry.
Furthermore, I this project I have utilized transformer as one of the major devices used in the
system. I have employed my knowledge about the induction law for the development of step-
down transformer. Furthermore, I have employed faraday’s law of induction for identifying the
total voltage induces through the secondary coil used in the transformer. For determining the
voltage, I have used the following formula:
Vs = Ns x (d ϕ / d t)
In the above formula, I have used Vs for determining the instantaneous voltage, d ϕ as the
change in the magnetic flux and dt as the change in the time. On the other hand, I have used Ns
for determining the total number of turns. Through this I was successful in determine the
magnetic flux on both the coils of the transformers.
CE 3.3.3: Accomplishment and Task Performed
After the developing the appropriate plan for circuit design and implementation of the
voltage protection system, I have implemented ideal transformer as an significant element of the
circuitry. In addition to that, I have carried out detailed evaluation and analysis for determining
appropriate process is being followed during the process.
CE 3.3.4: Identified Issues and Their Solutions
Issue: I have used relay in this project for their particular switching mechanism. In this
project, I have utilized the relays for controlling the low power signal over the circuit. During the
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integration of the relay with the designed circuit, I have identified and defined the functionalities
for change over, normally closed and normally opened phase of the relay. I have found the
connectivity of the relay was successful. But, I have experienced significant issue in the project
progress, when I have connected the relay with the voltage source. I have observed that the
voltage output was not able to drive the relay in the circuit.
Solution: Therefore, for mitigating the solution I have focused on evaluating various
journals and books and determined the integrate relay driver for mitigating the solution.
Therefore, I have connected the relay with the NPN transistor. I have further applied the output
voltage obtained from the capacitor to the NPN transistor base with the application of resistors.
Further I have used diode in parallel to the relay coil in the circuit. Through this I was able to
eliminate the emf and obtain the current flowing through the relay coil. Therefore, the
application of the relay driver has enables proper working of the relay unit.
CE 3.3.5: Plan for producing creative and innovative work
In order to provide innovation and creativeness in this project, I have manually specified
the characteristics and the implementation for the timer 555. In this project I have specified 15 V
of supply voltage and 6 mA of supply current. In addition to that, the selection of timer 555 has
allowed me to determine and set the time from few milliseconds to several hours. In addition to
that, after the development of the complete prototype model for the system, I have conducted the
manual testing using the home appliances refrigerator. I was therefore, able to gain efficiency
and stability of the proposed system.
CE 3.3.6: Collaborative work
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I have followed and encouraged team work during the design and implementation of the
system. I have demonstrated the work activities and technical information required. I have
further used the time table, and resource matrix for allocating the work and resources. In addition
to that, I was involved with weekly meetings with the project team for evaluating the technical
issues and understanding the work being proceeds till date.
CE 3.4: Project Review
CE 3.4.1: Project Overview
Figure 3: Hardware Implementation
Overview: Throughout the project I was able to successfully develop the cutoff circuit
while minimizing the cost required for implementation. The fabrication of the circuit with the
application of diodes, transistors and other components has allowed be to successfully minimize
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the impact of power fluctuation. I have ensured that the developed system can be successfully
implemented in various home appliances including VCR, TV and refrigerator. Furthermore, the
system implementation was a success and the developed system was overcoming the sudden
resumption, failures and surges of voltage.
Output: The application of the on-time delay circuit does not only allow the protection of
the electrical devices but also enables the devices from physical hard due to the voltages surges.
In addition to that, I have observed that the application of ontime delay circuit helps in the
changeover of the voltage during the fluctuation of the voltage point. In this project, I have
determined that when the main supply provided to the devices goes over the limited voltage, the
load or the relay is immediately being turned off. I have further set the time delay of minimum to
5 seconds to maximum of 2 minutes duration.
CE 3.4.2: My contribution to work
Throughout the entire duration of the project I have followed the plan for implementing
the system and looked over duties and tasks being conducted by the propjet team. In addition to
that, I have showed my capability and skills for managing the project work as well as the team
members. Furthermore, with the application of my technical knowledge I was successful in
designing and implementing the voltage surges protection system for home appliances.
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