Design And Construction Of A 1.3V To 15V Variable Power Adapter With A Seven Segment Display

CHAPTER ONE: INTRODUCTION

1.1 BACKGROUND

In today’s world almost all the appliances used are made up of electronics such as handsets, smart phones, digital cameras, iPods, laptops, e.t.c. With the advancement in science and technology these electronics are built based on minimal optimisation so as to minimise the amount of power consumption.

With the rapid growth of highly developed technology of instant communication, computerization, industrial automation and space exploration, the feats would not have been possible without the advent of electrical /electronic engineering. In electrical and telecommunication engineering field, systems and equipments like amplifiers, satellites, microwave link systems to name but a few depend for their correct operations upon the availability of stable well regulated D.C power supplies. In experimental laboratories, the use of well regulated D.C power supplies becomes inevitable because the result of these experiments depends largely on the quality power supply used.(Amadi, 2010).

The construction of this project will be useful presently and in the future. The main requirement of a well regulated D.C power supply unit are: good regulations, low ripple, low output impedance and strict output short-circuit protection.

Many devices have different range of voltage input and can be owned by a single person, each of these electronic devices will have an adapter which can make a room look clumsy and much heat will be dissipated when using many adapters.

Instead of having an adapter for each device, a single adapter is manufactured to power up each device at different voltage range but it is limited in such a way that it gives only discrete values(e.g. 9V, 12V, 16V, and so on).

1.2       PROBLEM STATEMENT

Nowadays, electrical power supply is the one of important element in human being needs. Most of human activities is very depending onthe demand of electrical power supply. In other words, without electrical power supply, almost the whole of activities is become postponed or worse cancelled. Some devices that have input voltages of 1.5V, 3.5V, 7.5V, e.t.c, cannot be powered by such adapter which is aforementioned. There is a need for a variable power adapter which will have continuous range of variable output voltage (say 1.3V to 15V) with a seven segment display that shows the selected output voltage.

1.3 AIM AND OBJECTIVES

AIM

To design a 1.3V to 15V variable power adapter with a seven segment display.

OBJECTIVES

The specific objectives are to;

• Design a power supply.
• Design a regulator unit.
• Design a display unit.
• Develop software that controls the microcontroller (hex file).
• Construction of the whole circuit.

1.4 SCOPE

This adapter accepts voltage from A.C outlet and gives out a range of variable output voltage of 1.3V to 15V at a current of 1A. The working circuit is divided into mainly three sections namely A.C section, regulator section and microcontroller section.

A.C section consists of a fuse, a transformer, a full wave rectifier and voltage smoothing circuit.

The regulator section is a voltage regulator IC (LM317), a potentiometer, post filters and some associated circuitry.

The microcontroller section consists of a PIC16F876microcontroller, seven segment display sub-unit and the software which is embedded on the microcontroller.

1.5 SIGNIFICANCE

This variable adapter plays a very important role in the field of electronics. Scientist and engineers need this kind of adapter to power up most of their devices in the laboratory since most devices in electronics laboratory need direct current (D.C) voltage input and many devices range from different values. This adapter gives a room for the selection of the required voltage value by varying the output with a potentiometer, for it can supply a D.C voltage ranging from 1.3V to 15V. In our houses, schools, offices, we also need such an adapter to charge phones, iPods, digital cameras, smart phones, e.t.c.

CHAPTER FIVE: SUMMARY, CONCLUSION

AND RECOMMENDATION

5.1 SUMMARY

The variable regulated D.C power supply utilizes a 240V A.C supply which is stepped down by a 15V centre tapped transformer. The transformer is connected to a fuse of 3A to protect the transformer and the circuit. The circuit is incorporated with four diodes which forms the bridge rectifier circuit. The capacitors do the smoothening of the voltage which is rectified by the bridge rectifier. After the smoothening, the LM317 voltage regulator takes in the input from its Vin pin, the Vadj pin is connected to a potentiometer in series with a resistor and grounded and the regulated voltage output is on the Vout pin with two protective diodes. The output voltage is fed to a microcontroller which manipulates and displays the output voltage on a seven segment display by the help of a program.

5.2 CONCLUSION

The aim of a project is to make the students adopt the theories into practical realization for the benefits of mankind. The circuit was constructed and tested; the output voltage was varied from 0V to 15V. It is a huge success.

5.3 RECOMMENDATION

This project has limitations among which are time factor, technical specifications and finance. These areas should be looked into for improvement on subsequent works on the same topic through the following:

• Project construction and writing should be taught for at least two semesters of part IV and part V.
• Government, through project related corporate bodies should help fund or finance students’ projects to improve the quality and possibly standardize the project for the market.
• The university can construct more of this project for use in the laboratory / workshop instead of buying from the market thereby depleting the resources of the institution.
• The project as a course should be weighted the same as such course as electronics, telecommunication, programming etc so that the students will take it more serious than it is obtained currently. There is still more room for improvement on the variable regulated D.C power supply.