INTRODUCTION

Electricity flows in two ways: either in an alternating current (AC) or in direct current (DC).

Electricity or "current" is nothing but the movement of electrons through a conductor, like a

wire. The difference between AC and DC lies in the direction in which the electrons flow. In DC,

the electrons flow steadily in a single direction, or "forward." In AC, electrons keep switching

directions, sometimes going "forward" and then going "backward."

Alternating current is the best way to transmit electricity over large distances.

Comparison chart

Alternating Current Direct Current

Amount of energy

that can be carried

Safe to transfer over longer city

distances and can provide more power.

Voltage of DC cannot travel

very far until it begins to lose

energy.

Cause of the

direction of flow of

electrons

Rotating magnet along the wire. Steady magnetism along the

wire.

Frequency

The frequency of alternating current is

50Hz or 60Hz depending upon the

country.

The frequency of direct current

is zero.

Direction It reverses its direction while flowing in

a circuit.

It flows in one direction in the

circuit.

Current It is the current of magnitude varying

with time

It is the current of constant

magnitude.

Flow of Electrons Electrons keep switching directions -

forward and backward.

Electrons move steadily in one

direction or 'forward'.

Obtained from A.C Generator and mains. Cell or Battery.

Passive Parameters Impedance. Resistance only

Power Factor Lies between 0 & 1. it is always 1.

Types Sinusoidal, Trapezoidal, Triangular,

Square.

Pure and pulsating.

Power supply

A power supply is a device that supplies electrical energy to one or more electric loads. The term

is most commonly applied to devices that convert one form of electrical energy to another,

though it may also refer to devices that convert another form of energy (e.g., mechanical,

chemical, solar) to electrical energy. A regulated power supply is one that controls the output

voltage or current to a specific value; the controlled value is held nearly constant despite

variations in either load current or the voltage supplied by the power supply's energy source.

Every power supply must obtain the energy it supplies to its load, as well as any energy it

consumes while performing that task, from an energy source. Depending on its design, a power

supply may obtain energy from:

1. Electrical energy transmission systems. Common examples of this include power

supplies that convert AC line voltage to DC voltage.

2. Energy storage devices such as batteries and fuel cells.

5V DC REGULATED POWER SUPPLY

A DC power supply which maintains the output voltage constant irrespective of A.C mains

fluctuations or load variations is known as regulated D.C power supply. A regulated power

supply consists of an ordinary power supply and voltage regulating device.

For the electronics enthusiast, having a 5 volt DC power supply around in your workspace can be

very useful. Many op amps, micro controllers, and other digital ICs {integrated circuits} run off

5 volts (although most now take a range of 3-15 volts). Let’s build an inexpensive power supply

using some discrete components and a fixed voltage regulator IC.

COMPONENTS OF POWER SUPPLY

Transformer

A transformer is commonly used to step the input AC voltage level down or up. Most electronic

circuits operate from voltages lower than the AC line voltage so the transformer normally steps

the voltage down by its turn’s ratio to a desired lower level.

Bridge rectifier

The rectifier converts the AC sine wave into a pulsating DC wave. There are several forms of

rectifiers used but all are made up of diodes. Rectifier types and operation will be covered later

CAPACITOR

The rectifier produces a DC output but it is pulsating rather than a constant steady value over

time like that from a battery. A capacitor is used to remove the pulsations and create a constant

output.

REGULATOR

The regulator is a circuit that helps maintains a fixed or constant output voltage. Changes in the load or the AC line voltage will cause the output voltage to vary. Most electronic circuits cannot withstand the variations since they are designed to work properly with a fixed voltage. The regulator fixes the output voltage to the desired level then maintains that value despite any

output or input variations.

Resistor and LED

A resistor is used to prevent LED when the output is given to LED. It controls the output voltage

coming from the regulator for preventing the LED. A LED is used to check the existence of the

current that we want .We use animated LED in a DC power supply

.

Breadboard

A breadboard also known as protoboard is a type of solder less electronic circuit building. You

can build an electronic circuit on a breadboard without soldering.

Working

An AC powered regulated power supply usually uses a transformer to convert the voltage from

the wall outlet (mains) to a different, nowadays usually lower, voltage. If it is used to

produce DC, a rectifier is used to convert alternating voltage to a pulsating direct voltage,

followed by a capacitor, comprising one or more capacitors, resistors, to filter out (smooth) most

of the pulsation. The +5 volt power supply is based on the commercial 7805 voltage regulator IC.

This IC contains all the circuitry needed to accept any input voltage from 8 to 18 volts and

produce a steady +5 volt output, accurate to within 5% (0.25 volt). It also contains current-

limiting circuitry and thermal overload protection, so that the IC won't be damaged in case of

excessive load current; it will reduce its output voltage instead.

The 1000µf capacitor serves as a "reservoir" which maintains a reasonable input voltage to the

7805 throughout the entire cycle of the ac line voltage. A small remaining unwanted alternating

voltage component at mains or twice mains power frequency (depending upon whether half- or

full-wave rectification is used). Ripples unavoidably superimposed on the direct output voltage.

Construction

We used 220V AC voltage as transformer input. The step down transformer converts this 220V

in a lower voltage. This lower voltage goes into the rectifier where it is converted into DC. Then

we use capacitor of 100ouF as a filter for filtration of DC current.

Then we use a regulator 7805 to get exact 5 volts DC. Then we use 1k resistor and an animated

led to check the flow of regulated current. Then we use output wires to measure voltage from DC

Voltmeter.