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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.

ACKNOWLEDGEMENT

Our Quest for practical knowledge led us in to the esteemed Organization

Automatic Electric Co. (Lonavla), which is a hall of fame. If words are considered as

symbols of approved and tokens of acknowledges, then let Words play the heralding role

of expressing our gratitude. We profusely thank our director Sri. Mr. Pramod Kale and

our university Coordinator Dr. D. Shaligram for their encouragement and support

through out the project.

We extend our heartiest thanks to our respected Project coordinator,

Mrs. Preeti Salunkhe, who is always a constant source of inspiration for us and for her

motivations in making this project completion.

We are very thankful to our beloved guide Ms. Jyutika Nalawade, for her

valuable and patient guidance throughout our endeavor. We remember With Regards and

respect the assistance and encouragement given by her. We are very much indebted to

our beloved parents who have given this opportunity to join in this course and are great

source of encouragement for us. Above all, the GRACE OF GOD of all creations led us

to complete our project successfully.

Department of Electronics science, University of Pune (Sep’06-Feb’07) of 63


EXECUTIVE SUMMERY

In our day to day life we use a lot many devices to satisfy our needs or to make

our life comfortable and luxurious. Every device needs a power supply, to work on. And

for the optimum functioning of the device it is necessary that the supply should be

reliable. That is, it should provide a constant voltage.

But this is not possible always. There are many reasons due to which there is a

fluctuation in the supply voltage. This change in the supply voltage may cause the

device to damage or make it work in an undesired way, which no one would desire.

Hence the best alternative is to regulate the supply voltage. This is what we have

tried to achieve here. Our project is supply voltage regulation, using controller and SCR.

In our project we provide the load with a constant voltage of 240 V ac., in spite of

any variation in the input voltage. The voltage regulation is achieved by controlling the

firing angle of the SCR so precisely that the load receives a constant supply. The

voltage across the load is stepped down and provided to ADC. ADC will produce a

digital signal corresponding to the input analog signal. This digital signal from ADC is

then processed by the controller and generates a firing pulse for SCR, hence controlling

the load current.



INDEX

1. INTRODUCTION .………………………………………………. 4

2. AIM & OBJECTIVES ....………………………………………... 7

3. PROJECT PLANNING .…………………………………………. 9

4. BLOCK DIAGRAM ...………..………………………………… 12

5. BLOCK DIAGRAM DESCRIPTION .……….………………… 14

6. COMPONENT SEPECIFICATIONS .…………………………. 18

7. CIRCUIT DIAGRAM .…………………………………………. 47

8. FUNCTIONALITY .……………………………………………. 49

9. SOFTWARE FLOW CHART .…………………………………. 51

10. RESULTS & CONCLUSION .…………………………………. 58

11. BIBLIOGRAPHY .……………………………………………... 60



CHAPTER 1

Introduction



INTRODUCTION

In our day to day life we use a lot many devices to satisfy our needs or to make

our life comfortable and luxurious. Every device needs a power supply, to work on. And

for the optimum functioning of the device it is necessary that the supply should be

reliable. That is, it should provide a constant voltage.

But this is not possible always. There are many reasons due to which there is a

fluctuation in the supply voltage. This change in the supply voltage may cause the

device to damage or make it work in an undesired way, which no one will desire.

Hence the best alternative is to regulate the supply voltage. This is what we have

tried to achieve here. Our project is supply voltage regulation, using controller and SCR.

Silicon Controlled Rectifiers also called Thyristors controller, employing novel

technology, which is designed to provide a price effective solution for applications that

require power, current or voltage regulation with some power factor correction and a

smother process control. Traditional phase-angle control causes lots of harmonic

current distortion on the main power supply. This in turn creates voltage distortion which

affects power quality. There is no simple accessory available for reducing this problem.

However, when simple voltage or current regulation is required often phase-

angle control is the most cost effective solution.



Thyristors and triacs are switched on by using a gate. They automatically switch

off again when the conducted current reaches zero.

Therefore, these devices can be used in power regulators and by switching at a

predetermined position on the AC sine wave (the phase-angle) the effective voltage can

be reduced or increased. This can be used to regulate voltage or power to a load.

In our project we provide the load with a constant voltage of 240 V ac., in spite of

any variation in the input voltage. The voltage regulation is achieved by controlling the

firing angle of the SCR so precisely that the load receives a constant supply. The

voltage across the load is stepped down and provided to ADC. ADC will produce a

digital signal corresponding to the input analog signal. This digital signal from ADC is

then processed by the controller and generates a firing pulse for SCR, hence controlling

the load current.



CHAPTER 2

Aim & Objective



AIM & OBJECTIVE

AIM:-

To develop a system for controlling fluctuation in the three phase Voltage supply

using SCR and Controller.

OBJECTIVE:-

To upgrade the existing three phase analog regulatory system, to a three phase,

microcontroller based SCR drive system. So that if any fluctuation comes in three phase

voltage supply, controller will Sense that fluctuation and accordingly give triggering

pulses to the SCR to get controlled regulated output at the load.



CHAPTER 3

Project planning



PROJECT PLANNING

Exactly what was planned in the project?

To design hardware for voltage regulation by using SCR bridge To sense fluctuation in the single phase voltage supply.

To sense zero crossing of the input sine wave.

To get correct firing angle of SCR for getting correct control voltage.

To calculate the correct delay time for giving trigger pulse to SCR.

To trigger SCR depending upon calculated data and get the regulated

output.

To implement the same for three phase voltage supply.

What is achieved?

We designed hardware for voltage regulation by using SCR bridge We sensed fluctuation in the single phase voltage supply.

We sensed zero crossing of the input sine wave.

We got correct firing angle of SCR for getting correct control voltage.



We calculated the correct delay time for giving trigger pulse to SCR.

TIME SCHEDULING

S.NO SCHEDULE DAYS

1 Understanding project details 2

2 Finalizing project modules 3

3 Data collection 7

4 Selection of Microcontroller and its peripherals 4

5 Component search 11

6 Circuit Design 5

7 Hardware assembly 7

8 Hardware testing and debugging 7

9 Software coding (for calculating correct delay for different

angle)

2

10 Preparing look up table for different ADC values 1

11 Software coding(for voltage fluctuation) 3

12 Testing code on hardware 8



13 Project report & presentation 3

CHAPTER 4

Block Diagram



BLOCK DIAGRAM


POWER SUPPLY

SCR BRIDGE CKT

230V AC

MICRO--CONTROLLER

O/P ZEROCROSSINGDETECTOR

CLOCK & RESET CKT

POTENTIAL DIVIDER

24V AC


CHAPTER 5


ADC


Block Diagram Description

BLOCK DIAGRAM DESCRIPTION



POWER SUPPLY

This is the first block of our system. We have used a step-down centre tap

transformer, with the voltage rating of 240V ac as primary voltage and 24-0-24V ac as

the secondary voltage. The current rating of the transformer is 500mA.

The stepped-down ac signal is supplied to the rectifier & regulator. It consists of a

simple rectifier diode bridge network along with some filtering circuit, for smoothing out

the input signal. This filtered and rectified signal is then regulated using a positive

voltage regulator, to the desired value (say 5 V dc & 15 V dc) and also negative voltage

regulator to the desired value (say -15 V dc).For these purpose; we are using three

regulator chips.

LM7805 (+5V DC)

MC7815C (+15V DC)

L7915 (-15V DC)

The basic input requirement of the two regulators 7815 & 7915 is 23v dc. i.e. it

needs at lest this voltage to provide a constant +/-15V. This is why we have selected

the center-tap transformer of 24V dc. But the input voltage requirement of 7805 is just

about 13v dc; hence we have reduced the voltage of the transformer to 13V through a

resistor in series.

The input of the regulator is provided with a filter capacitor of 10uF, 50v. and the

output with 0.01uf, forming a pie filter for better signal to noise ratio.

ZERO CROSSING DETECTOR

This circuit is containing of OP-AMP UA 741.This is mainly used to detect the

zero crossing of the input sine wave so that we can get Synchronization.



The output of ZCD is given to the PORT pin 2.5 of the Microcontroller. Here ZCD

is used so that we can give trigger angle to the SCR at Correct time.

The op-amp in the ZCD is just a sine to square wave generator. It converts in the

input 24V ac signal to the square wave of 5 V and of the same frequency as that of the

sine wave. Op-amp UA 741 is provided with a dual supply, obtained from the positive

and negative regulators (+15V & -15V dc).

The output pin of the ZCD is provided with a rectifying diode which restricts the

negative signal from reaching the controller pin to avoid any damage to it.

SCR BRIDGE NETWORK

This block consists of a pair of SCR & diodes. Input to the SCR Bridge circuit is

fluctuated Single phase voltage supply, which is given to anode of both the SCRs and

cathode of both the diodes. Cathode of both the SCRs and Anode of both the diodes

are provided to the load. We have assumed a resistive load of 10K ohm. From this load

resistor one voltage signal will go to the Potential divider for feedback purpose. This will

act as the input signal to the ADC.

The gate of the SCR is connected to the PORT2.0 and PORT2.1. A specific

triggering pulse is provided to the gate of the SCR of sufficient time delay so as to keep

the load voltage constant.

POTENTIAL DIVIDER

To get controlled output we need to give feedback signal from the SCR bridge

circuit to ADC. But here feed back signal is nearer of 240V. So, we required to step it

down to the +5V.

Because of this, here we have used potential divider network. From this potential

divider network we will get voltage signal around +5V. To obtain the voltage of 5V ac

from 240V ac we have used the network ratio of 59:1. The upper 59K resistor is fix while

the lower 1K is a pot of 10k. Then after this voltage signal is given to ADC0808.



ANALOG TO DIGITAL CONVERTER (ADC 0808) Here we get input from potential divider network which is around +5V. Then this

analog value is converted to digital data and is given to Microcontroller. ADC 0808 has

four channels but we need only one, hence we have selected channel 0 for input. The 8

bit digital output of ADC is provided to the port 1 of controller.

MICROCONTROLLER 89C51RD2

This block is the only decision making block, which decides whether any

fluctuation in the supply line has occurred or not. It continuously compares the signal

with the reference described in the software. If there is no change then SCR will be fired

by it at phase angle 0 deg. But if it finds some fluctuation, then it will generate the pulse

at a measured time delay to provide the firing angle of the SCR (through gate) such that

the fluctuations will be nullified, and the supply to the load remains unaffected, in-spite

the fluctuations.



CHAPTER 6

Components Specification



COMPONENT SPECIFICATION

POWER SUPPLY

SPECIFICATION OF IC LM7805:-

_ 3-Terminal Regulators

_ Output Current up to 1.5 A

_ Internal Thermal-Overload Protection

_ High Power-Dissipation Capability

_ Internal Short-Circuit Current Limiting

_ Output Transistor Safe-Area Compensation

Description informationThis series of fixed-voltage integrated-circuit voltage regulators is designed for a

wide range of applications. These applications include on-card regulation for elimination

of noise and distribution problems associated with single-point regulation. Each of these

regulators can deliver up to 1.5 A of output current. The internal current-limiting and

thermal-shutdown features of these regulators essentially make them immune to

overload. In addition to use as fixed-voltage regulators, these devices can be used with

external components to obtain adjustable output voltages and currents.

Absolute maximum ratings over virtual junction temperature range (unless otherwise noted)Input voltage, VI: A7824C 40 V)

All others 35 V

Operating virtual junction temperature, TJ 150C

Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260C

Storage temperature range, Tst -65C to 150C



The LM7805 series of three terminal regulators are available with several fixed

output voltages. The voltages available allow regulators to be used in logic systems,

instrumentations, Hi-Fi and other solid state electronics equipment without any external

feedback components.

These ICs are designed as fixed voltage regulator and with adequate heat

sinking can deliver output currents in excess of 1A.The input capacitor Ci=0.33µF is

used, if regulator is located far from the power supply filter capacitor. It filters out the

effect of stray inductance of wire, ceramic or tantalum capacitor may be used. To

improve the transient response of regulator capacitor of 0.1µF is connected at output. It

utilizes common ground fir input and output and has dropout voltage (Vin – Vo) of 2 V.

Device type with input voltages

Output voltage(V)

Output current

QuiescentCurrent(mA)

Line regulation(mV)

Load regulation(mV)

Ripple rejection(dB)

78XXC(35)

51215

1A 8 256075

50120150

807270

78LXXAC(35)

51215

100Ma 3 to 53 to53.1 to 5

102025

51012

625451

78LXXC(35)

51215

100mA 3 to 63 to 6.53.1 to 6.5

102025

51012

605249

78MXX (35)

51215

0.5A 4 to 104 to 104 to 10

50120150

100240300

787169



SPECIFICATION OF MC7815 (+15V REGULATOR)

These voltage regulators are monolithic integrated circuits designed as fixed–

voltage regulators for a wide variety of applications including local, on–card regulation.

These regulators employ internal current limiting, thermal shutdown, and safe–area

compensation. With adequate heat sinking they can deliver output currents in excess of

1.0 A. Although designed primarily as a fixed voltage regulator, these devices can be

used with external components to obtain adjustable voltages and currents.

• Output Current in Excess of 1.0 A

• No External Components Required

• Internal Thermal Overload Protection

• Internal Short Circuit Current Limiting

• Output Transistor Safe–Area Compensation

• Output Voltage Offered in 2% and 4% Tolerance

• Available in Surface Mount D2PAK and Standard 3–Lead Transistor Packages

• Previous Commercial Temperature Range has been extended to a Junction

Temperature Range of –40°C to +125°C.



SPECIFICATION OF L7915 (-15V REGULATOR)

OUTPUT CURRENT UP TO 1.5A

OUTPUT VOLTAGES OF -5; -6; -8; -12; -15; -18; -20; -24V

THERMAL OVERLOAD PROTECTION

SHORT CIRCUIT PROTECTION

OUTPUT TRANSITION SOA PROTECTION



The L7900 series of three-terminal negative regulators is available in TO-220,

TO-220FP, TO-3 and D2PAK packages and several fixed output voltages, making it

useful in a wide range of applications. These regulators can provide local on-card

regulation, eliminating the distribution problems associated with single point regulation;

furthermore, having the same voltage option as the L7800 positive standard series, they

are particularly suited for split power supplies. If adequate heat sinking is provided, they

can deliver over 1.5A output current. Although designed primarily as fixed voltage

regulators, these devices can be used with external components to obtain adjustable

voltages and currents.



SPECIFICATION OF 1N4007 DIODE

• Low forward voltage drop.

• High surge current capability.



ZERO CROSSING DETECTOR

SPECIFICATION OF UA741(OP-AMP)

LARGE INPUT VOLTAGE RANGE

NO LATCH-UP

HIGH GAIN

SHORT-CIRCUIT PROTECTION

NO FREQUENCY COMPENSATION

SAME PIN CONFIGURATION AS THE UA709

The UA741 is a high performance monolithic operational amplifier constructed on

a single silicon chip. It is intended for a wide range of analog applications.

-Summing amplifier

- Voltage follower

- Integrator

- Active filter

- Function generator



The high gain and wide range of operating voltages provide superior

performances in integrator, summing amplifier and general feedback applications. The

internal compensation network (6dB/octave) insures stability in closed loop circuits.

PIN CONNECTIONS



MICROCONTROLLER

SPECIFICATION OF MICROCONTROLLER 89C51RD2

The 89C51RB2/RC2/RD2 device contains a non-volatile 16kB/32kB/64kB Flash

Program memory that is both parallel programmable and serial In-System and In-

Application Programmable. In-System Programming (ISP) allows the user to

download new code while the microcontroller sits in the application. In-

Application Programming (IAP) means that the microcontroller fetches new

program code and reprograms itself while in the system. This allows for remote

programming over a modem link. A default serial loader (boot loader) program in

ROM allows serial In-System programming of the Flash memory via the UART

without the need for a loader in the Flash code. For In-Application Programming,

the user program erases and reprograms the Flash memory by use of standard

routines contained in ROM. This device executes one machine cycle in 6 clock

cycles, hence providing twice the speed of a conventional 80C51. An

OTPconfiguration bit lets the user select conventional 12 clock timing if desired.

This device is a Single-Chip 8-Bit Microcontroller manufactured in advanced

CMOS process and is a derivative of the 80C51 microcontroller family. The

instruction set is 100% compatible with the 80C51 instruction set. The device

also has four 8-bit I/O ports, three 16-bit timer/event counters, a multi-source,

four-priority-level, nested interrupt structure, an enhanced UART and on-chip

oscillator and timing circuits. The added features of the P89C51RB2/RC2/RD2

make it a powerful microcontroller for applications that require pulse width

modulation, high-speed I/O and up/down counting capabilities such as motor

control.



FEATURES

80C51 Central Processing Unit.

On-chip Flash Program Memory with In-System Programming (ISP) and In-

Application Programming (IAP) capability.

Boot ROM contains low level Flash programming routines for downloading

via the UART.

Can be programmed by the end-user application (IAP)

6 clocks per machine cycle operation (standard)

12 clocks per machine cycle operation (optional)

Speed up to 20 MHz with 6 clock cycles per machine cycle(40 MHz equivalent

performance); up to 33 MHz with 12 clocks per machine cycle

Fully static operation

RAM expandable externally to 64 kB

4 level priority interrupt

8 interrupt sources

Four 8-bit I/O ports

Full-duplex enhanced UART

- Framing error detection

- Automatic address recognition

Power control modes

- Clock can be stopped and resumed

- Idle mode

- Power down mode

Programmable clock out

Second DPTR register

Asynchronous port reset

Low EMI (inhibit ALE)

Programmable Counter Array (PCA)

PWM

Capture/compare

BLOCK DIAGRAM



PIN DIAGRAM:-



PIN DESCRIPTION



OSCILLATOR CHARACTERISTICS

XTAL1 and XTAL2 are the input and output, respectively, of an inverting

amplifier. The pins can be configured for use as an on-chip oscillator. To drive the

device from an external clock source, XTAL1 should be driven while XTAL2 is left

unconnected. Minimum and maximum high and low times specified in the data sheet

must be observed.

This device is configured at the factory to operate using 6 clock periods per

machine cycle, referred to in this datasheet as “6 clock mode”. (This yields performance

equivalent to twice that of standard 80C51 family devices). It may be optionally

configured on commercially-available EPROM programming equipment to operate at 12

clocks per machine cycle, referred to in this datasheet as “12 clock mode”. Once 12

clock mode has been configured, it cannot be changed back to 6 clock mode.

RESETA reset is accomplished by holding the RST pin high for at least two machine

cycles (12 oscillator periods in 6 clock mode, or 24 oscillator periods in 12 clock mode),

while the oscillator is running.

To ensure a good power-on reset, the RST pin must be high long enough to

allow the oscillator time to start up (normally a few milliseconds) plus two machine

cycles.



At power-on, the voltage on VCC and RST must come up at the same time for a

proper start-up. Ports 1, 2, and 3 will asynchronously be driven to their reset condition

when a voltage above VIH1 (min.) is applied to RESET. The value on the EA pin is

latched when RST is reasserted and has a further effect.

LOW POWER MODES

Stop Clock ModeThe static design enables the clock speed to be reduced down to 0 MHz

(stopped). When the oscillator is stopped, the RAM and Special Function Registers

retain their values. This mode allows step-by-step utilization and permits reduced

system power consumption by lowering the clock frequency down to any value. For

lowest power consumption the Power Down mode is suggested.

Idle ModeIn the idle mode (see Table 2), the CPU puts itself to sleep while all of the on-

chip peripherals stay active. The instruction to invoke the idle mode is the last

instruction executed in the normal operating mode before the idle mode is activated.

The CPU contents, the on-chip RAM, and all of the special function registers remain

intact during this mode. The idle mode can be terminated either by any enabled

interrupt (at which time the process is picked up at the interrupt service routine and

continued), or by a hardware reset which starts the processor in the same manner as a

power-on reset.

Power-Down ModeTo save even more power, a Power Down mode (see Table 2) can be invoked by

software. In this mode, the oscillator is stopped and the instruction that invoked Power

Down is the last instruction executed. The on-chip RAM and Special Function Registers

retain their values down to 2.0 V and care must be taken to return VCC to the minimum

specified operating voltages before the Power down Mode is terminated.

Either a hardware reset or external interrupt can be used to exit from Power

Down. Reset redefines all the SFRs but does not change the on-chip RAM. An external

interrupt allows both the SFRs and the on-chip RAM to retain their values.



To properly terminate Power Down, the reset or external interrupt should not be

executed before VCC is restored to its normal operating level and must be held active

long enough for the oscillator to restart and stabilize (normally less than 10 ms). With an

external interrupt, INT0 and INT1 must be enabled and configured as level-sensitive.

Holding the pin low restarts the oscillator but bringing the pin back high completes the

exit. Once the interrupt is serviced, the next instruction to be executed after RETI will be

the one following the instruction that put the device into Power Down.

SCR

SPECIFICATION OF MCR100

Introduction

PNPN devices designed for high volume, line-powered consumer applications such as

relay and lamp drivers, small motor controls, gate drivers for larger thyristors, and

sensing and detection circuits. Supplied in an inexpensive plastic TO-226AA package

which is readily adaptable for use in automatic insertion equipment.

Features

• Sensitive Gate Allows Triggering by Microcontrollers and Other Logic Circuits

• Blocking Voltage to 600 V

• ON State Current Rating of 0.8 Amperes RMS at 80°C

• High Surge Current Capability − 10 A

• Minimum and Maximum Values of IGT, VGT and IH Specified for Ease of

Design

• Immunity to dV/dt − 20 V/sec Minimum at 110°C

• Glass-Passivated Surface for Reliability and Uniformity



SYMBOL



Voltage Current Characteristic of SCR



ANALOG TO DIGITAL CONVERTER

SPECIFICATION OF ADC 0808

General Description

The ADC0808 data acquisition component is a monolithic CMOS device with an 8-

bit analog-to-digital converter, 8-channel multiplexer and microprocessor compatible

control logic.

The 8-bit A/D converter uses successive approximation as the conversion technique.

The converter features a high impedance chopper stabilized comparator, a 256R

voltage divider with analog switch tree and a successive approximation register. The 8-

channel multiplexer can directly access any of 8-single-ended analog signals. The

device eliminates the need for external zero and full scale adjustments. Easy interfacing

to microprocessors is provided by the latched and decoded multiplexer address inputs

and latched TTL TRI-STATEÉ outputs. The design of the ADC0808 has been optimized

by incorporating the most desirable aspects of several A/D conversion techniques. The

ADC0808 offers high speed, high accuracy, minimal temperature dependence, excellent

long-term accuracy and repeatability, and consumes minimal power. These features

make this device ideally suited to applications from process and machine control to

consumer and automotive applications.

Features

Easy interface to all microprocessors

Operates ratio metrically or with 5 V dc or analog span adjusted voltage

reference.

No zero or full-scale adjust required



8-channel multiplexer with address logic

0V to 5V input range with single 5V power supply

Outputs meet TTL voltage level specifications

Standard hermetic or molded 28-pin DIP package

28-pin molded chip carrier package

Key Specifications

Resolution 8 Bits

Total Unadjusted Error g(/2 LSB and g1 LSB

Single Supply 5 VDC

Low Power 15 mW

Conversion Time 100 ms.

Absolute Maximum Ratings (Notes 1 & 2)If Military/Aerospace specified devices are required, please contact the National

Semiconductor Sales Office/Distributors for availability and specifications.

Supply Voltage (VCC) (Note 3) 6.5V

Voltage at Any Pin b0.3V to (VCC+0.3V) Except Control Inputs

Voltage at Control Inputs -0.3V to +15V

(START, OE, CLOCK, ALE, ADD A, ADD B, ADD C)

Storage Temperature Range -65C to +150C

Package Dissipation at TAe25C 875 mW

Lead Temp. (Soldering, 10 seconds)

Dual-In-Line Package (plastic) 260C

Dual-In-Line Package (ceramic) 300C

Molded Chip Carrier Package

Vapor Phase (60 seconds) 215C

Infrared (15 seconds) 220C

ESD Susceptibility (Note 8) 400V



BLOCK DIAGRAM



CONNETION DIAGRAM:-



CHAPTER 7

Circuit Diagram



CIRCIUT DIAGRAM

R 7

1 k

D 8

DIO

DE

C 2

10uf

T1

TR

AN

SF

OR

ME

R C

T

1 5

6

4 8

D 7

DIO

DE

2

-

+ U 8

UA

741C

3

26

7 14 5

Q 1S C R

U 2 L M 7 8 0 5

1 3V I N V O U T

D 1 D I O D E

U 9

AD

C08

08

7

1 0

1 1

1 21 6

2 2

2 32 42 5

2 62 72 8

12345

96

1 71 41 581 81 92 02 1

E O C

C L K

V C C

+V R E F-V R E F

A L E

A D D CA D D BA D D A

I N 0I N 1I N 2I N 3I N 4I N 5I N 6I N 7

O ES TA R T

D B 0D B 1D B 2D B 3D B 4D B 5D B 6D B 7

VCC

V C C

Y 1

20 M

HZ

C 3

0.1u

f

R 21 k

1

D 4 D I O D E

+5V

R 21 k

C 71 0 u f

U 6

M C 7 8 1 5 C1 3

V I N V O U T

R 6R 3

1 0 k

R 18 . 2 k

V C C

R 4

R4

+ R

5 +

R6

= 59

K

+15v

R 5

C 6 3 0 p f

-15v

C 53 0 p f

D 6D I O D E

24v DC

U 7L 7 9 1 5

2 3V I N V O U T

D 2D I O D E

D 3D I O D E C 4

0.1u

f

240v ac

Q 2S C R

P 2 . 5C 51 0 u f

U 3

89C

51

9

1 81 9

2 93 0

3 1

12345678

2 12 22 32 42 52 62 72 8

1 01 11 21 31 41 51 61 7

3 93 83 73 63 53 43 33 2

R S T

XTA L 2XTA L 1

P S E NA L E / P R O G

E A / V P P

P 1 . 0P 1 . 1P 1 . 2P 1 . 3P 1 . 4P 1 . 5P 1 . 6P 1 . 7

P 2 . 0 / A 8P 2 . 1 / A 9

P 2 . 2 / A 1 0P 2 . 3 / A 1 1P 2 . 4 / A 1 2P 2 . 5 / A 1 3P 2 . 6 / A 1 4P 2 . 7 / A 1 5

P 3 . 0 / R XDP 3 . 1 / TXD

P 3 . 2 / I N T0P 3 . 3 / I N T1

P 3 . 4 / T0P 3 . 5 / T1

P 3 . 6 / W RP 3 . 7 / R D

P 0 . 0 / A D 0P 0 . 1 / A D 1P 0 . 2 / A D 2P 0 . 3 / A D 3P 0 . 4 / A D 4P 0 . 5 / A D 5P 0 . 6 / A D 6P 0 . 7 / A D 7



CHAPTER 8

Functionality



FUNCTIONALITY

Here, in our project we are controlling the single phase supply voltage 240V ac

by triggering the SCR from Microcontroller.

Main purpose of our project is to get constant 240 V dc at load. To fulfill this task

we have to control the firing angle of SCR trigger pulse. And for control purpose

we have used Philips 89C52RD2 Microcontroller.

Main parts of our circuits are SCR bridge circuit, Power supply, Zero crossing

detector, Potential divider.

The input to the SCR bridge circuit is 240V ac. From this circuit we get output

which will initially be fluctuating so for controlling purpose we will take a feedback

signal from output.

Now, we have to give this feedback signal to Analog to Digital converter but here

the feedback signal is of around 240V dc. When ADC 0808 can operates up to

+5 V dc. It will be damaged if we apply 240V dc to it. So for that we must have to

use some kind of step down circuitry. Here we have used Potential divider

circuitry. By the use of Potential divider we will step it down to around +5V dc

signal. Now it is safe to apply that signal to ADC 0808.

Here input to the ADC 0808 is analog signal which will be converting to the digital

signal. And that digital signal will be fed to the Microcontroller.

Microcontroller is the main decision making block of our project which is used to

control the firing angle of SCR. Digital signal which we get from the ADC 0808 is

then compared to the values which are stored in look table. And according to that

look table controller will take required value of firing angle. As per firing angle

controller will calculate the delay and according that delay Controller will give

triggering pulses to the gate of the SCR. So that we get controlled output.

But controller must have to give the triggering pulses at correct time means it

must have be synchronization with input signal. For that purpose we have used



zero crossing detector. So that when input analog signal will cross zero voltage

level, then only controller will give trigger pulse to the SCR.

CHAPTER 9

Software Flow-chart



Flow charts: Main Program:




START

Set port P1 as input port

Read output of ADC

Delay calc. for firing pulse

Delay for firing pulse

Set port pin P2.0

Pulse width delay

Reset port pin P2.0

Is ZCD=

1

A

R

No

Yes



A

Set port pin P2.1

Delay for firing pulse

Delay calc. for firing pulse

Read output from ADC

Is ZCD=

1

Reset port pin P2.1

Pulse width delay

R

Yes

No


Read output of ADC:


Start

Activate SOC

Monitor EOC

Activate output enable

ActivateALE

End


Pulse width Calculation:


Start

Reset timer flag

Stop timer

Start timer

Load timer register

Set timer in mode zero

Is TF=1

End

Yes

No


Delay calculation for firing pulse:


Start

Get value for timer register from look-up

table

End


Delay for firing:


Start

End

Set timer in mode zero

Load timer with ADC Val.

Start timer

Stop timer

Reset timer flag

Is TF=1

No

Yes


CHAPTER 10

Result & Discussion



RESULT AND DISCUSSION

Here by we have designed a device that is capable of detecting the fluctuations

in the input mains supply.

We designed hardware for voltage regulation by using SCR Bridge, which

senses fluctuations in the single phase voltage supply across the load and nullifies it.

Hence our device is capable of regulating the single phase mains supply to a

constant dc supply across the load, irrespective of any changes in the supply, hence

providing protection to the load device from getting damaged due to sudden variations

in the mains.



CHAPTER 11

Bibliography


block diagram - 123seminarsonly.com€¦ · web viewour project is supply voltage regulation, using...

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