report 7 th sem slc

8/8/2019 report 7 th sem slc

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ABSTRACT

One of the simplest ways to convert DC to AC is by using a multivibrator whichhas the ability to vary its output frequency when the potentiometer connectedexternally to it is varied. Though the output of a multivibrator is a square wave, itcan be made use for lighting applications by using filtering capacitors. Hence onesuch multivibrator is CD4047,which we found suitable for our project.

CD4047 is a CMOS low power monostable/astable multivibrator . The voltagerating of which is 20V.CD4047 consists of a gatable astable multivibrator.Astable operation is enabled by a high level on the ASTABLE input or a low levelon the ASTABLE input or both.the period of square wave can be adjusted byusing suitable capacitance and resistance(as shown in the design).

Since the output from the multivibrator is of low power, amplifying action has tobe performed in order to drive loads. For this purpose we use IRF 540 mosfetshave been used. These mosfets can drive loads upto 22A. The output from themultivibrator is fed to the gate of the mosfet . these mosfets along with theoutput transformer operate in class B push pull mode with centre tapping.

The inverter part of the emergency power supply is thus complete with threemajor parts mentioned above. Emergency power supply unit should be reusable,

hence to make reusable we should have provisions to charge the battery once itdrains. Thus we make use of a converter circuit which converts AC to DC.

The converter circuit incorporated in this emergency power system is a simplebridge rectifier with 4 Diodes connected as shown in the circuit diagram.Thediodes used here are 1N4007.The diode bridge is fed by a input transformerwhich converts 220V to 12V.The diode bridge is connected to the 12V 7.5-Ahrechargeable battery.

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CIRCUIT DIAGRAM

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LITERATURE SURVEY

Emergency power supply is an electrical apparatus that provides emergencypower to a load when the input power source, typically the utility mains, fails.

The above shown block diagram gives the working of an Emergency powersystem. When the mains is on the power from the mains is used to drive theload. When the mains fail the power stored in the battery is converted to AC ofrequired frequency to drive the load.An emergency power supply can be madean UPS by using proper control circuitry. Logic control circuits can be used ,so

that whenever the supply from the mains fail automatically the inverter is turnedON.

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CD4047 Low Power Monostable/Astable Multivibrator

General Description

The CD4047B is capable of operating in either the monostable or astable mode.It requires an external capacitor (between pins 1 and 3) and an external resistor(between pins 2 and 3) to determine the output pulse width in the monostablemode, and the output frequency in the astable mode.Astable operation is enabled by a high level on the astable input or low level onthe astable input. The output frequency (at 50% duty cycle) at Q and Q outputsis determined by the timing components. A frequency twice that of Q is availableat the Oscillator Output; a 50% duty cycle is not guaranteed.

Features Wide supply voltage range: 3.0V to 15V.

High noise immunity: 0.45 VDD (typ.)

Low power TTL compatibility: Fan out of 2 driving 74L or 1 driving 74LS.

Special features Low power consumption: special CMOS oscillator configuration.

Monostable (one-shot) or astable (free-running) operation.

True and complemented buffered outputs.

Only one external R and C required.

Astable multivibrator features Free-running or gatable operating modes.

50% duty cycle.

Oscillator output available.

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Good astable frequency stability.

Function table for astable operation

Terminals connected toVDD

Terminals connected toVSS

Output terminals

4,5,6,14 7,8,9,12 10,11,13

Block Diagram of CD4047

Recommended Operating Conditions

DC Supply Voltage (VDD) 0.5V to +18V DCInput Voltage (VIN) 0.5V to VDD +0.5V DCStorage Temperature Range (TS) 65C to +150C

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Power Dissipation (PD)Dual-In-Line 700 mWSmall Outline 500 mWLead Temperature (TL)(Soldering, 10 seconds) 260CDC Supply Voltage (VDD) 3V to 15V DCInput Voltage (VIN) 0 to VDD V DCOperating Temperature Range (TA) 40C to +85C

IRF540 N-CHANNEL 100V - 0.055 - 22A TO-220 LOW GATECHARGE STripFET II POWER MOSFET

Features

Typical Rds(on) = 0.055w

Exceptional dv/dt capability.

100% avalanche tested.

Low gate charge.

Application oriented characterization.

Description

This MOSFET series realized with STMicroelectronics unique STripFET processhas specifically been designed to minimize input capacitance and gatecharge. It is therefore suitable as primary switch in advanced high efficiency,high-frequency isolated DC-DC converters for Telecom and Computerapplications. It is also intended for any applications with low gate driverequirements.

Internal schematic diagram

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Absolute maximum ratings

VDS Drain-source Voltage (VGS = 0) 100 V

VDGR Drain-gate Voltage (RGS = 20 k ) 100 V

VGS Gate- source Voltage 20 V

ID Drain Current (continuous) at TC = 25C 22 A

ID Drain Current (continuous) at TC = 100C 15 A

dv/dt Peak Diode Recovery voltage slope 9 V/ns

Transformer

There are two transformers used in the circuit. One is a step up and the other isa step down transformer .step down transformer is used to step down thevoltage from 220V to 12V. Step down transformer is connected to the rectifiercircuit which charges the battery.

The step up transformer with centre tapping is used in the class B push pull

circuit. The step up transformer is a 12-0-12V to 220V transformer which is usedto drive the load by providing 220V rms at its secondary terminals.

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Details

Step down transformer input side 0-12V 2 Amps

Step up transformer output side 12-0-12V 5Amps

Battery

The battery used in the emergency power supply is a 12V 7.5 Ah sealed leadacid battery. Application of the emergency power supply demands arechargeable battery, hence rechargeable lead acid battery is used. The cycledurability of the battery used is 800-1000 cycles. The charging voltage of thebattery is 13.8V.

Diode

Diodes are the devices used in the converter circuit and the rectifying action isperformed by the diodes. Bridge rectifier circuit is used to convert AC to DC. Thediode used here is 1N4007.

RMS Reverse Voltage 700 Volts

Average Rectified Forward Current 2A

Operating and Storage JunctionTemperature Range

65 to +175 C

Other devices used

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Resistors680(1),820(1),330(1),390K(1),220(2).

Capacitors 220F 25V electrolytic capacitor(1),0.01F(1),0.1F

600V(1),2.2F 400V(1).

LEDs green(1),red(1).

DESIGN

CD 4047 is a lowpower multivibrator (Astable & Monostable) IC

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Frequency of O/P wave=50Hz.tA10=tA11=1/50Hz=4.40RC.

0.02sec=4.40Rc

Let us choose capacitor of 0.01F.

t=0.02 sec0.02=4.40R*0.01*10-6

R=0.02/(4.40R*0.01*10-6 )= 454.54k.

R=Rfixed+Rpotentiometer

Rfix=390kRpotentiometer(100k)=64.54k

O/P pulses at terminals t10 & t11 have the voltage of 6V when 0N.

IC operating current and voltage

From the datasheets,IC operating voltage varies from 3V-18V.

Here V=12V (permissible)

From the datasheets,DC input current to any one terminal=10mA.

Hence, a resistor should be chosen such that maximum current through eachterminal should not be more than 10mA.

Since there are four terminalsI < V/R

R > V/IR > 12/40mA=12/(40*10-3)=300 [I=40mA because there are 4 terminals

connected to the resistor]

We choose R=330 (next standard value)

MOSFET

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IRF 540 VDSS IA

100V 22A

VGS (Gate to Source Voltage)=20VVDS=12VVGS=6V

Vth=6V.

Choose the gate resistance =220ohm.

The value of resistance should be within 200-300 in order to damp theoscillations caused when sudden voltage is applied to the gate of the mosfet.Oscillations are caused due to the input capacitance of the mosfet which is of theorder of 500pF-3000pF and small inductance of the connecting wires.

Photos of working model

Charging mode : battery is being charged by the rectifiercircuit.

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Discharging mode: the power from the battery is used tocharge a cell phone.

APPLICATIONS

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Lighting application.

The designed emergency power supply can be used to light a 40Wincandescent bulb.

CFL lamps.

Fluorescent lamps of less than 60W.

Cell phone charging.Since the power rating of cell phone charger is within 10W, the designedemergency power supply can charge a cell phone.

Laptop charging.

Any other device of less than 60W can be used with the designedemergency power supply, except for motor loads. Motor loads cannot be

used because there are harmonic contents in the output waveform.

BIBLIOGRAPHY

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www.google.com

www.wikipedia.org

www.datasheetcatalog.com

www.electronicstutorials.com

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report 7 th sem slc

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