Project Background

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.

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;

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.

Project Group 

Figure 1: Team Member Associated with 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.

Comprehending the Theory of the project

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.

Characteristics of the Project

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 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 ? / d t)

In the above formula, I have used Vs for determining the instantaneous voltage, d ? 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.

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. 

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 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.

Objectives Developed for Project

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.

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.

Collaborative Work 

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.

Project Review

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 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.

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.