versatile power supply.doc

7/29/2019 Versatile power supply.doc

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VERSATILE POWER SUPPLY

Chapter 1

INTRODUCTION

A power supply is a device that supplies electrical energy to one or more electricloads. 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:

Electrical energy transmission systems. Common examples of this include power

supplies that convert AC line voltage to DC voltage.

Energy storage devices such asbatteries and fuel cells.

Electromechanical systems such as generators and alternators.

A power supply may be implemented as a discrete, stand-alone device or as an

integral device that is hardwired to its load. In the latter case, for example, low voltage DC

power supplies are commonly integrated with their loads in devices such as computers and

household electronics.

Constraints that commonly affect power supplies include:

The amount ofvoltage and current they can supply.

How long they can supply energy without needing some kind of refueling or

recharging (applies to power supplies that employ portable energy sources).

How stable their output voltage or current is under varying load conditions.

Whether they provide continuous or pulsed energy.

Chapter 2

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BILL OF MATERIALS

2.1 ELECTRONIC COMPONENTS:

Sr. No. Component Name Specifications

1. Resistors 3.3K, 220, 2.2K, 220, 1.8K, 120, 1.2K,

180, 820, 560, 18, 100, 330, 33

2. Capacitors 0.1f, 1000f 50V

3. LED Red colour

4. Diodes IN4007

5. Transistors BC558 (PNP)

6 FUSE 1A

7. IC LM317 Regulator

8. Transformer 230V AC Primary To18V AC, 1A

9. Rotary Switch Single pole double throw

10. Connecting wires

11. PCB 15cm10cm

2.2 MECHANICAL COMPONENTS:

Sr. No. Components

2. Spanner

3. Cutter

4. Nose plier

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5. Screw driver

6. Nuts, bolds

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Chapter 3

CIRCUIT DIAGRAM AND WORKING

Fig.3.1 Circuit Diagram of Versatile Power Supply

Using this circuit, we can obtain the following voltages (approx.) at a current limited

to one ampere: 3.3V, 5V, 6V, 9V, 12V and 15V.

The AC mains is stepped down by transformer X1 to deliver the secondary output of

18V AC at a maximum current of 1A dependent upon the load. The transformer output is

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rectified by the bridge rectifier comprising diodes D1 through D4, filtered by capacitor C1

and fed to regulator IC LM317,

LM317 is a 3-terminal positive regulator capable of providing 1.2V to 37 volts at

1.5A current to the load. Resistor R13 and selected combinations of resistors R1 through R12are used to produce approximately 3.3V, 5V, 6V, 9V, 12V and 15V at the output.

The desired resistors are selected by switching into conduction one of the six pnp

transistors T1 through T6 by grounding the corresponding transistor base using switches S1-

S5. For example, to get regulated 3.3V, simply switch to 3.3V ON. Consequently, transistor

T1 is forward biased to switch resistors R1 and R2 (in series) across ADJ pin of LM317 and

ground to produce 3.3V. Other voltages can be produced in the same way by using rotary

switch S1. Capacitor C2 bypasses any ripple in the output.

Diode D5 is used as the protection diode. Use a heat-sink for dissipation of heat from IC

LM317. The fuse-rated lamp provides protection against short circuit. This 1A rated power

supply can be used for testing of various circuit ideas as well as construction projects

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Chapter 4

HARDWARE DESCRIPTION

4.1 LM317 (3-TERMINAL ADJUSTABLE REGULATOR)

4.1.1 General Description

Fig.4.1 Front view of LM317

The LM317 series of adjustable 3-terminal positive voltage regulators is capable of

supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to

use and require only two external resistors to set the output voltage. Further, both line andload regulations are better than standard fixed regulators. Also, the LM117 is packaged in

standard transistor packages which are easily mounted and handled. In addition to higher

performance than fixed regulators, the LM117 series offers full overload protection available

only in ICs. Included on the chip are current limit, thermal overload protection and safe area

protection. All overload protection circuitry remains fully functional even if the adjustment

terminal is disconnected.

Normally, no capacitors are needed unless the device is

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Situated more than 6 inches from the input filter capacitors in which case an input bypass is

needed. An optional output capacitor can be added to improve transient response.

The adjustment terminal can be bypassed to achieve very high ripple rejection ratios

which are difficult to achieve with standard 3-terminal regulators. Besides replacing fixedregulators, the LM317 is useful in a wide variety of other applications. Since the regulator is

floating and sees only the input-to-output differential voltage, supplies of several hundred

volts can be regulated as long as the maximum input to output differential is not exceeded i.e.

avoid short-circuiting the output.

Also, it makes an especially simple adjustable switching regulator, a programmable

output regulator, or by connecting a fixed resistor between the adjustment pin and output, the

LM317 can be used as a precision current regulator. Supplies with electronic shutdown can be

achieved by clamping the adjustment terminal to ground which programs the output to 1.2V

where most loads draw little current.

4.1.2 Features

Guaranteed 1% output voltage tolerance (LM317A)

Guaranteed max. 0.01%/V line regulation (LM317A)

Guaranteed max. 0.3% load regulation (LM117)

Guaranteed 1.5A output current

Adjustable output down to 1.2V

Current limit constant with temperature

P+ Product Enhancement tested

80 dB ripple rejection

Output is short-circuit protected

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Fig.4.2 Schematic diagram of IC LM317

4.1.3 Absolute Maximum Ratings

Power Dissipation Internally Limited

Input-Output Voltage Differential : +40V, 0.3VStorage Temperature : 65C to +150C

Lead Temperature:

4.1.4 Operating Temperature Range

LM317A : 40C TJ +125C

LM317 : 0C TJ +125C

4.1.5 Typical Applications

4.1.5.1 3.3V18V Adjustable Regulator

Full output current not available at high input-output voltages Needed if device is

more than 6 inches from filter capacitors. Optionalimproves transient response. Output

capacitors in the range of 1F to 1000F of aluminum or tantalum electrolytic are commonly

used to provide improved output impedance and rejection of transients.

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Fig.4.3 Adjustable voltage regulator using IC LM317

4.2 PNP GENERAL PURPOSE TRANSISTOR BC558

Fig.4.4 Transistor terminals

4.2.1 FEATURES

Low current (max. 100 mA)

Low voltage (max. 65 V).

4.1.2 APPLICATIONS

General purpose switching and amplification.

4.1.3 DESCRIPTION

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PNP transistor in a TO-92 ; SOT54 plastic package.

NPN complements :BC546, BC547 and BC548.

4.3 RECTIFIERS (DIODES) 1N4007G

4.3.1 FEATURES

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Glass passivity

High maximum operating temperature

Low leakage current

Excellent stabilityAvailable in ammo-pack.

4.3.2 DESCRIPTION

Rugged glass package, using a high temperature alloyed construction. This package is

hermetically sealed and fatigue free as coefficients of expansion of all used parts are atched.

4.3.3 ELECTRICAL CHARACTERISTICS

4.4 FUSES

A fuse is a piece of wire, often in a casing that improves its electrical characteristics.

If too much current flows, the wire becomes hot and melts. This effectively disconnects the

power supply from its load, and the equipment stops working until the problem that caused

the overload is identified and the fuse is replaced.

There are various types of fuses used in power supplies.

fast blow fuses cut the power as quick as they can

slow blow fuses tolerate more short term overload

wire link fuses are just an open piece of wire, and have poorer overload characteristics

than glass and ceramic fuses

Some power supplies use a very thin wire link soldered in place as a fuse.

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4.5 TRANSFORMER

A transformer is a static device that transfers electrical energy from one circuit to

another through inductively coupled conductorsthe transformer's coils. A varying current in

the first orprimary winding creates a varying magnetic flux in the transformer's core and thus

a varying magnetic field through thesecondary winding. This varying magnetic field induces

a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is

called mutual induction.

If a load is connected to the secondary, an electric current will flow in the secondary

winding and electrical energy will be transferred from the primary circuit through the

transformer to the load. In an ideal transformer, the induced voltage in the secondary

winding (Vs) is in proportion to the primary voltage (Vp), and is given by the ratio of

the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as

follows:

By appropriate selection of the ratio of turns, a transformer thus allows an alternating

current (AC) voltage to be "stepped up" by makingNs greater thanNp, or "stepped

down" by makingNs less thanNp.

In the vast majority of transformers, the windings are coils wound around a

ferromagnetic core, air-core transformers being a notable exception.

Transformers range in size from a thumbnail-sized coupling transformer hidden inside

a stage microphone to huge units weighing hundreds of tons used to interconnect

portions ofpower grids. All operate with the same basic principles, although the range

of designs is wide. While new technologies have eliminated the need for transformers

in some electronic circuits, transformers are still found in nearly all electronic devices

designed forhousehold ("mains") voltage. Transformers are essential for high-voltage

electric power transmission, which makes long-distance transmission economically

practical.

4.6 PRINTED CIRCUIT BOARD

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FR-4 is theNEMA grade designation for glass reinforced epoxy laminate sheets,

tubes, rods and printed circuit boards (PCB). FR-4 is made of woven fiberglass cloth with an

epoxy resin binder that is flame resistant (self-extinguishing). Note that FR-4 is a

specification - not a product in itself.

FR-4 glass epoxy is a popular and versatile high pressure thermoset plastic laminate

grade with good strength to weight ratios. With near zero water absorption, FR-4 is most

commonly used as an electrical insulator possessing considerable mechanical strength. The

material is known to retain its high mechanical values and electrical insulating qualities in

both dry and humid conditions. These attributes, along with good fabrication characteristics,

lend utility to this grade for a wide variety of electrical and mechanical applications.

FR-4 epoxy resin systems typically employbromine, a halogen, to facilitate flame

resistant properties in FR-4 glass epoxy laminates. Some applications where destruction of

the fiberglass sheet, tube, rod orPCB is a desirable trait will still use G-10 non flame

resistant

Chapter 5

PCB LAYOUT

PCB Manufacturing Process

Different steps involved in the fabrication of a PCB are follows

1. Components layout designing

2. PCB layout designing

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3. Transferring the PCB layout design onto the PCB laminate

4. Developing for etching the PCB.

5. Other operations like drilling, cutting, tinning etc

5.1 Components Layout designing

Components layout designing is the placement of different components with their

inter connections as per the circuit diagram on the PCB. This exercise usually begins with an

estimate of the size of the PCB (length & breadth) needed to accommodate various circuit

components. Having placed all the components, the inter connections can be made by

drawing lines (known as tracks)

5.2 PCB Layout designing

PCB Layout designing is the mirror image of components layout. The component

layout is drawn looking from the components side whereas the PCB layout is drawn looking

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from the copper side. It is obtained by taking a carbon copy of the components lay out by

placing a reversed carbon underneath the paper.

Softwares used for PCB layout designing:

For circuit simulation: NI MULTISIMFor circuit designing: NI ULTIBOARD

Fig5.1 PCB layout (with components) using NI-ULTIBOARD

5.3 Transferring PCB layout on to PCB laminate

First the PCB laminate is chosen. The copper side of the laminate is thoroughly

cleaned with petrol to make it completely free from contaminants. The PCB layout is drawn

on the copper side. Care should be taken to mark the position of holes. The same is redrawn

giving proper width to different tracks and leaving proper space using permanent marker.

5.4 Etching

In this process, all excess copper is removed leaving behind only the drawn pattern.To do etching the aqueous solution of ferric chloride with the quantity depending upon the

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size of the PCB to be etched is then poured in the tray. The etching process may take about

half an hour. The laminate is now thoroughly washed in water after etching is completed. The

mark is then removed with alcohol.

Fig.5.2 Transferred layout on actual PCB from photo paper

5.5 Drilling-Tinning

After etching the process employed is drilling of holes. The diameter of holes varies

from component to component. It is 1mm per IC pins, 1.25mm for resistors and capacitors

1.5mm for diodes and even larger mounting presets. Using a soldering iron can do the

oxidation of copper portions can be prevented by tinning that.

5.6 Soldering

Soldering is the process of joining metals by lower melting metal to wet or alloy with

adjoined surfaces.5.6.1 Solder

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Solder is the joining material that melts below 427 degree Celsius. Soldered joints in

electronic circuits will establish string connection between components leads .The popularly

used solders are alloys of tin & lead that melts below the melting point of tin.

5.6.2FluxesIn order to make the surfaces accept solder readily, the component terminals are made

free from oxides and other obstructing films. The leads are cleaned chemically or by abrasion

using blades or knives. Small amounts of lead coating are done on the clean portion of leads

using soldering iron.

This process is called tinning. Zinc chloride or ammonium chloride separately or in

combination are used fluxes. These are in available in petroleum jelly as paste flux. The

residues which remain after soldering are washed out with more water accompanied by

brushing.

5.6.3Soldering Iron

It is the tools used to melt the solder apply at the joints in the circuits. It operates in

230volts mains supply. The iron bit at the tip of it gets heated up within few minutes. 50W

and 25W soldering irons are commonly used soldering purpose.

5.7 Soldering Procedure

Fig.5.3 Through hole wave soldering process

1. The layout of the connection of the components in the circuit is taken. The chord of the

soldering iron is plugged to the main supply to get it heated up.

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2 The component leads are straightened and cleaned using blade or knife. Then a little flux is

applied on the leads. A little solder is taken on soldering iron and is applied on molten solder

on the leads. Care is taken to avoid the components getting heated up.

3. The components are mounted on the PCB by bending the leads of components using nosepliers.

4. Flux is applied on the joints to solder it. To avoid dry soldering and heating up of the

components, it is done in minimum time.

5. The residues are removed using water and brush.

Fig.5.4 soldering techniques

Chapter 6

COST OF PROJECT

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Sr. No. Component Name Cost (in Rs.)

1. Resistors 3/-

2. Capacitors 16/-

3. LED 1/-

4. Diodes 3/-

5. Transistors 12/-

6. Fuse 2/-

7. IC LM317 10/-

8. Transformer 85/-

9. Switches 40/-

10. Connecting wires 10/-

11. PCB 35/-

TOTAL COST 227/-

Chapter 7

POWER SUPPLY APPLICATIONS

7.1. Computer power supply

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A modern computer power supply is a switch with on and off supply designed to

convert 110-240 V AC power from the mains supply, to several output both positive (and

historically negative) DC voltages in the range + 12V,-12V,+5V,+5VBs and +3.3V. The first

generation of computers power supplies were linear devices, but as cost became a drivingfactor, and weight became important, switched mode supplies are almost universal.

The diverse collection of output voltages also have widely varying current draw

requirements, which are difficult to all be supplied from the same switched-mode source.

Consequently most modern computer power supplies actually consist of several different

switched mode supplies, each producing just one voltage component and each able to vary its

output based on component power requirements, and all are linked together to shut down as a

group in the event of a fault condition.

7.2. Welding power supply

Arc welding uses electricity to melt the surfaces of the metals in order to join them

together through coalescence. The electricity is provided by a welding power supply, and can

either be AC orDC. Arc welding typically requires high currents typically between 100 and

350 amps. Some types of welding can use as few as 10 amps, while some applications ofspot

welding employ currents as high as 60,000 amps for an extremely short time. Older welding

power supplies consisted oftransformers orengines driving generators. More recent supplies

use semiconductors and microprocessors reducing their size and weight.

7.3. AC adapter

A linear orswitched-mode power supply (or in some cases just a transformer) that is

built into the top of a plug is known as a "plug pack", "plug-in adapter", "adapter block",

"domestic mains adapter" or just "power adapter". Slang terms include "wall wart" and

"power brick". They are even more diverse than their names; often with either the same kind

of DC plug offering different voltage orpolarity, or a different plug offering the same

voltage. "Universal" adapters attempt to replace missing or damaged ones, using multiple

plugs and selectors for different voltages and polarities. Replacement power supplies must

match the voltage of, and supply at least as much current as, the original power supply.

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The least expensive AC units consist solely of a small transformer, while DC adapters

include a few additional diodes. Whether or not a load is connected to the power adapter, the

transformer has a magnetic field continuously present and normally cannot be completely

turned off unless unplugged.

Because they consume standby power, they are sometimes known as "electricity

vampires" and may be plugged into a power strip to allow turning them off. Expensive

switched-mode power supplies can cut off leaky electrolyte-capacitors, use powerless

MOSFETs, and reduce their working frequency to get a gulp of energy once in a while to

power, for example, a clock, which would otherwise need a battery.

Chapter 8

CONCLUSION

Versatile power supply is a device which provides output in the form of various D.C

voltages ranging from 4V to 16V. This device is very helpful for testing various electronic

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circuits. It can be used for charging batteries, mobiles etc. This homemade device very handy,

cheap and is of great use.

This kit can be advanced in terms of getting perfect D.C. output, voltages even

greater, more current rating and compact size.

Chapter 9

REFERENCES

1. http://www.alldatasheet.com/datasheet-pdf/pdf/8619/NSC/LM317.html

2. http://en.wikipedia.org/wiki/Power_supply

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3. http://www.datasheetcatalog.org/datasheet/philips/BC558.pdf

4. http://www.datasheetcatalog.org/datasheet/philips/1N4005.pdf

5. http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS009063.PDF

6. http://www.datasheetcatalog.org/datasheet/vishay/cfa0207.pdf

7. http://www.ohmite.com/catalog/pdf/appnotes_res_select.pdf

8. http://www.pcb123.com/tutorials/PDF%20Documents/PCBDesignTutorialRevA.pdf

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http://www.datasheetcatalog.org/datasheet/philips/BC558.pdfhttp://www.datasheetcatalog.org/datasheet/philips/1N4005.pdfhttp://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS009063.PDFhttp://www.datasheetcatalog.org/datasheet/vishay/cfa0207.pdfhttp://www.ohmite.com/catalog/pdf/appnotes_res_select.pdfhttp://www.pcb123.com/tutorials/PDF%20Documents/PCBDesignTutorialRevA.pdfhttp://www.datasheetcatalog.org/datasheet/philips/BC558.pdfhttp://www.datasheetcatalog.org/datasheet/philips/1N4005.pdfhttp://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS009063.PDFhttp://www.datasheetcatalog.org/datasheet/vishay/cfa0207.pdfhttp://www.ohmite.com/catalog/pdf/appnotes_res_select.pdfhttp://www.pcb123.com/tutorials/PDF%20Documents/PCBDesignTutorialRevA.pdf