BLOCK DIAGRAM



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.

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.

[pic]

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

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CHAPTER 5

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 information

This 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 |Output voltage |Output current |Quiescent |Line regulation |Load regulation |Ripple rejection |

|input voltages |(V) | |Current |(mV) |(mV) |(dB) |

| | | |(mA) | | | |

|78XXC |5 |1A |8 |25 |50 |80 |

|(35) |12 | | |60 |120 |72 |

| |15 | | |75 |150 |70 |

|78LXXAC |5 |100Ma |3 to 5 |10 |5 |62 |

|(35) |12 | |3 to5 |20 |10 |54 |

| |15 | |3.1 to 5 |25 |12 |51 |

|78LXXC |5 |100mA |3 to 6 |10 |5 |60 |

|(35) |12 | |3 to 6.5 |20 |10 |52 |

| |15 | |3.1 to 6.5 |25 |12 |49 |

|78MXX (35) |5 |0.5A |4 to 10 |50 |100 |78 |

| |12 | |4 to 10 |120 |240 |71 |

| |15 | |4 to 10 |150 |300 |69 |

[pic][pic]

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.

[pic]

[pic]

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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

[pic] [pic]

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.

[pic]

[pic]

SPECIFICATION OF 1N4007 DIODE

• Low forward voltage drop.

• High surge current capability.

[pic]

[pic]

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• 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

[pic]

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

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• 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

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➢ PIN DIAGRAM:-

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➢ PIN DESCRIPTION

[pic]

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➢ 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.

➢ RESET

A 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 Mode

The 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 Mode

In 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 Mode

To 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

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[pic] [pic]

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Voltage Current Characteristic of SCR

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• 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

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➢ CONNETION DIAGRAM:-

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CHAPTER 7

Circuit Diagram

CIRCIUT DIAGRAM

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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:

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Read output of ADC:

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Pulse width Calculation:

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Delay calculation for firing pulse:

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Delay for firing:

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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

-----------------------

24V AC

POTENTIAL

DIVIDER

O/P

MICRO-

-CONTROLLER

CLOCK &

RESET

CKT

ZERO

CROSSING

DETECTOR

POWER

SUPPLY

SCR

BRIDGE

CKT

230V AC

ADC

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

Start

Activate

SOC

Monitor

EOC

Activate output enable

Activate

ALE

End

Start

Reset timer flag

Stop

timer

Start

timer

Load timer register

Set timer in mode zero

Is

TF=1

End

Yes

No

Start

Get value for timer register from look-up table

End

Start

End

Set timer in mode zero

Load timer with ADC Val.

Start

timer

Stop

timer

Reset timer flag

Is

TF=1

No

Yes

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