TRANFORMER OVERLOAD ALERT (THROUGH VOICE ANNOUNCEMENT)
TABLE OF CONTENTS
PAGE NO
ABSTRACT CHAPTER-1 INTRODUCTION
1. Motivation 2. Problem Statement 3. Related Work 4. Scope Of Work 5. Thesis Outline
I
1-9
CHAPTER -2 IMPORTANT APPROACHES TO THE PROJECT
1
10-29
1.Microcontroller 2.Introduction to Microcontroller 3.Microcontroller core features 4.Advantages of using a Microcontroller over 5. Microprocessor Applications
6.PIC 16f877A Controller 7.Introduction to PIC 16f877A Controller 8. Features of PIC 16f877A Controller 9.Pin Diagram of PIC 16f877A Controller 10. Block Diagram of PIC 16f877A Controller 11.Power Supply Unit 12..Step down transformer Rectifier Unit Input filter Regulator Unit Output filter 13. LCD display 14. Relay Driver Features of Drivers Pin Connection Relays Electromechanical Relays Operation of Electromechanical Relays 15.Load Types 16.Resistive Loads 17.Inductive Loads
2
High or Low in Rush Ac or Dc 18.DC Motor
CHAPTER -3 DESCRIBING ABOUT PROJECT IMPLEMENTATION
3.1 Block Diagram of Lab Automation System 3.2 Description of Block Diagram 3.3 Circuit Diagram of Lab Automation System 3.4 Power Supply Circuit Diagram 3.5 Circuit Description 3.5.1 Power Supply 3.5.2 Controller Circuit
30-41
CHAPTER-4
Implementation
42-43
CHAPTER-5
Hardware requirement
44
3
CHAPTER -6
CONCLUSION
45
Applications Conclusion Future scope of the project
CHAPTER -7 BIBLIOGRAPHY APPENDIX –A 46 47
4
CHAPTER 1 INTRODUCTION
5
2.1 INTRODUCTION The project report describes the design Development and Fabrication of One demo unit of the project work “TRANSFORMER OVERLOAD ALERT” by using embedded systems. Now a day, with the advancement technology, particularly in the field of Microcontrollers, all the activities in our daily living have become a part of Information technology and we find microcontrollers in each and every application. Thus, trend is directing towards Microcontrollers based project works. However, in this project work to program the ON/OFF timings different machines the microcontroller interacts with RTC IC. Then the decisions are taken with the help of microcontroller and associated software. The microcontroller block is playing a major role in this project work. The micro controller chip used in this project work is PIC 16F877A and this is like heart of the project work. The PIC 16F877A microcontroller is a 40-pin IC. The entire project was developed in embedded systems. A system is something that maintains its existence and functions as a whole through the interaction of its parts. E.g. Body, Mankind, Access Control, etc A system is a part of the world that a person or group of persons during some time interval and for some purpose choose to regard as a whole, consisting of interrelated components, each component characterized by properties that are selected as being relevant to the purpose. ? Embedded System is a combination of hardware and software used to achieve a single specific task.
6
?
Embedded systems are computer systems that monitor, respond to, or control an external environment.
? ? ?
Environment connected to systems through sensors, actuators and other I/O interfaces. Embedded system must meet timing & other constraints imposed on it by environment. An embedded system is a microcontroller-based, software driven, reliable, real-time control system, autonomous, or human or network interactive, operating on diverse physical variables and in diverse environments and sold into a competitive and cost conscious market. An embedded system is not a computer system that is used primarily for processing, not a
software system on PC or UNIX, not a traditional business or scientific application. High-end embedded & lower end embedded systems. High-end embedded system - Generally 32, 64 Bit Controllers used with OS. Examples Personal Digital Assistant and Mobile phones etc. Lower end embedded systems - Generally 8, 16 Bit Controllers used with a minimal operating systems and hardware layout designed for the specific purpose. Examples Small controllers and devices in our everyday life like Washing Machine, Microwave Ovens, where they are embedded in. Microcontrollers are embedded inside some other device so that they can control the features or actions of the project. Another name for a microcontroller therefore is “Embedded Controller”. Microcontrollers are dedicated to one task and run one specific program. The program is stored in ROM (read only memory) and generally does not change. Microcontrollers are often low-price devices. Coming to our project whenever the students standing in front of the door for entering in to the lab is sensed by the IR sensor; this signal sends to controller through signal conditioning circuit. The controller takes it as an interrupt signal and gives control signal to the drive unit to
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open the door. Same like this in side lab if any human being sensed by the controller through IR transceiver it will further turn ON the fans, AC, lights using driver unit.
2.2.2 INTRODUCTION TO RELAYS A relay is usually an electromechanical device that is actuated by an electrical current. The current flowing in one circuit causes the opening or closing of another circuit. Relays are like remote control switches and are used in many applications because of their relative simplicity, long life, and proven high reliability. Relays are used in a wide variety of applications throughout industry, such as in telephone exchanges, digital computers and automation systems. Highly sophisticated relays are utilized to protect electric power systems against trouble and power blackouts as well as to regulate and control the generation and distribution of power. In the home, relays are used in refrigerators, washing machines and dishwashers, and heating and airconditioning controls. Although relays are generally associated with electrical circuitry, there are many other types, such as pneumatic and hydraulic. Input may be electrical and output directly mechanical, or vice versa.
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CHAPTER-3 IMPORTANT APPROACHES TO THE PROJECT
9
3.1
MICROCONTROLLER
3.1.1 INTRODUCTION TO MICROCONTROLLER A computer-on-a-chip is a variation of a microprocessor which combines the processor core (CPU), some memory, and I/O (input/output) lines, all on one chip. The computer-on-a-chip is called the microcomputer whose proper meaning is a computer using a (number of) microprocessor(s) as its CPUs, while the concept of the microcomputer is known to be a microcontroller. A microcontroller can be viewed as a set of digital logic circuits integrated on a single silicon chip. This chip is used for only specific applications. Most microcontrollers do not require a substantial amount of time to learn how to efficiently program them, although many of them, which have quirks, which you will have to understand before you, attempt to develop your first application. Along with microcontrollers getting faster, smaller and more power efficient they are also getting more and more features. Often, the first version of microcontroller will just have memory and digital I/O, but as the device family matures, more and more pat numbers with varying features will be available. In this project we used PIC 16f877A microcontroller. For most applications, we will be able to find a device within the family that meets our specifications with a minimum of external devices, or an external but which will make attaching external devices easier, both in terms of wiring and programming.
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For many microcontrollers, programmers can built very cheaply, or even built in to the final application circuit eliminating the need for a separate circuit. Also simplifying this requirement is the availability of micro-controllers wit SRAM and EEPROM for control store, which will allow program development without having to remove the micro controller for the application circuit. 3.1.2 MICRO CONTROLLER CORE FEATURES ? ? ? ? ? High-performance RISC CPU. Only 35 single word instructions to learn. All single cycle instructions except for program branches which are two cycle. Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle. Up to 8K x 14 words of FLASH Program Memory, Up to 368 x 8 bytes of Data Memory (RAM) Up to 256 x 8 bytes of EEPROM data memory. ? ? ? ? ? ? ? ? ? ? ? ? Pin out compatible to the PIC16C73B/74B/76/77 Interrupt capability (up to 14 sources) Eight level deep hardware stack Direct, indirect and relative addressing modes. Power-on Reset (POR). Power-up Timer (PWRT) and Oscillator Start-up Timer (OST). Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation. Programmable code-protection. Power saving SLEEP mode. Selectable oscillator options. Low-power, high-speed CMOS FLASH/EEPROM technology. Fully static design.
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? ? ? ? ? ? ? ?
InSingle 5V In-Circuit Serial Programming capability. In-Circuit Debugging via two pins. Processor read/write access to program memory. Wide operating voltage range: 2.0V to 5.5V. High Sink/Source Current: 25 mA. Commercial and Industrial temperature ranges. Low-power consumption. In this project we used PIC 16f877A microcontroller. PIC means Peripheral Interface
Controller. The PIC family having different series, the series are 12- Series, 14- Series, 16Series, 18- Series, and 24- Series. We used 16 Series PIC microcontrollers. 3.1.3 ADVANTAGES OF USING A MICROCONTROLLER OVER MICROPROCESSOR A designer will use a Microcontroller to ? ? ? ? ? ? Gather input from various sensors Process this input into a set of actions Use the output mechanisms on the Microcontroller to do something useful RAM and ROM are inbuilt in the MC. Cheap compared to MP. Multi machine control is possible simultaneously.
Examples The 8051 (ATMEL), PIC (Microchip), Motorola (Motorola), ARM Processor
3.1.4 APPLICATIONS:
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? ? ? ?
Cell phones. Computers. Robots. Interfacing to two pc’s.
3.2 PIC MICROCONTROLLER 16F877A 3.2.1 INTRODUCTION TO PIC MICROCONTROLLER 16F877A The PIC 16f877A microcontroller is a 40-pin IC. The first pin of the controller is MCLR pin and the 5V dc supply is given to this pin through 10K? resistor. This supply is also given to 11th pin directly. The 12th pin of the controller is grounded. A tank circuit consists of a 4 MHZ crystal oscillator and two 22pf capacitors is connected to 13th and 14th pins of the PIC. 3.2.2 ? ? ? ? ? ? ? ? ? FEATURES OF PIC MICROCONTROLLER 16F877A Operating frequency: DC-20Mhz. Flash program memory (14 bit words):8K Data memory (in bytes): 368 EEPROM Data memory (in bytes):256 Interrupts: 15 I/o ports: A, B, C, D, E Timers: 3 Analog comparators: 2 Instructions: 35
3.2.3 PIN DIAGRAM OF PIC 16 F874A/877A
13
FIG 3.1 PIN DIAGRAM OF PIC 16 F874A/877A
3.2.4 FUNCTIONAL BLOCK DIAGRAM OF PIC 16F877A
14
FIG 3.2 PIN DIAGRAM OF PIC 16F874A/877A
15
3.3
POWER SUPPLY UNIT
CIRCUIT DIAGRAM
FIG 3.3 POWER SUPPLY UNIT POWER SUPPLY UNIT COSISTS OF FOLLOWING UNITS
1) Step down transformer 2) Rectifier unit 3) Input filter 4) Regulator unit v) Output filter 3.3.1 STEP DOWN TRANSFORMER The Step down Transformer is used to step down the main supply voltage from 230V AC to lower value. This 230 AC voltage cannot be used directly, thus it is stepped down. The Transformer consists of primary and secondary coils. To reduce or step down the voltage, the transformer is designed to contain less number of turns in its secondary core. The output from the
16
secondary coil is also AC waveform. Thus the conversion from AC to DC is essential. This conversion is achieved by using the Rectifier Circuit/Unit. Step down transformers can step down incoming voltage, which enables you to have the correct voltage input for your electrical needs. For example, if our equipment has been specified for input voltage of 12 volts, and the main power supply is 230 volts, we will need a step down transformer, which decreases the incoming electrical voltage to be compatible with your 12 volt equipment. 3.3.2 RECTIFIER UNIT The Rectifier circuit is used to convert the AC voltage into its corresponding DC voltage. There are Half-Wave, Full-Wave and bridge Rectifiers available for this specific function. The most important and simple device used in Rectifier circuit is the diode. The simple function of the diode is to conduct when forward biased and not to conduct in reverse bias.
Bridge rectifier: A bridge rectifier makes use of four diodes in a bridge arrangement to achieve full-wave rectification. This is a widely used configuration, both with individual diodes wired as shown and with single component bridges where the diode bridge is wired internally.
A diode bridge or bridge rectifier is an arrangement of four diodes in a bridge configuration that provides the same polarity of output voltage for either polarity of input voltage.
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When used in its most common application, for conversion of alternating current (AC) input into direct current (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a center-tapped transformer design. The Forward Bias is achieved by connecting the diode’s positive with positive of the battery and negative with battery’s negative. The efficient circuit used is the Full wave Bridge rectifier circuit. The output voltage of the rectifier is in rippled form, the ripples from the obtained DC voltage are removed using other circuits available. The circuit used for removing the ripples is called Filter circuit. 3.3.3 INPUT FILTER Capacitors are used as filter. The ripples from the DC voltage are removed and pure DC voltage is obtained. And also these capacitors are used to reduce the harmonics of the input voltage. The primary action performed by capacitor is charging and discharging. It charges in positive half cycle of the AC voltage and it will discharge in negative half cycle. So it allows only AC voltage and does not allow the DC voltage. The 1000µf capacitor serves as a "reservoir" which maintains a reasonable input voltage to the 7805 throughout the entire cycle of the ac line voltage. The four rectifier diodes keep recharging the reservoir capacitor on alternate half-cycles of the line voltage, and the capacitor is quite capable of sustaining any reasonable load in between charging pulses. This filter is fixed before the regulator. Thus the output is free from ripples. Input side the low pass filter has been used.
Low pass filter:
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One simple electrical circuit that will serve as a low-pass filter consists of a resistor in series with a load, and a capacitor in parallel with the load. The capacitor exhibits reactance, and blocks low-frequency signals, causing them to go through the load instead. At higher frequencies the reactance drops, and the capacitor effectively functions as a short circuit. The combination of resistance and capacitance gives you the time constant of the filter ? = RC (represented by the Greek letter tau). The break frequency, also called the turnover frequency or cutoff frequency (in hertz), is determined by the time constant: or equivalently (in radians per second):
One way to understand this circuit is to focus on the time the capacitor takes to charge. It takes time to charge or discharge the capacitor through that resistor: ?
At low frequencies, there is plenty of time for the capacitor to charge up to
practically the same voltage as the input voltage. ?
At high frequencies, the capacitor only has time to charge up a small amount
before the input switches direction. The output goes up and down only a small fraction of the amount the input goes up and down. At double the frequency, there's only time for it to charge up half the amount.
3.3.4 REGULATOR UNIT
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FIG 3.4 7805 REGULATOR Regulator regulates the output voltage to be always constant. The output voltage is maintained irrespective of the fluctuations in the input AC voltage. As and then the AC voltage changes, the DC voltage also changes. Thus to avoid this Regulators are used. Also when the internal resistance of the power supply is greater than 30 ohms, the output gets affected. Thus this can be successfully reduced here. Meanwhile it also contains current-limiting circuitry and thermal overload protection, so that the IC won't be damaged in case of excessive load current; it will reduce its output voltage instead. The regulators are mainly classified for low voltage and for high voltage. Further they can also be classified as: 1) Positive regulator ? ? ? Input pin Ground pin Output pin
It regulates the positive voltage. 2) Negative regulator ? ? ? Ground pin Input pin Output pin
It regulates the negative voltage.
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7805 VOLTAGE REGULATOR: The 7805 provides circuit designers with an easy way to regulate DC voltages to 5v. Encapsulated in a single chip/package (IC), the 7805 is a positive voltage DC regulator that has only 3 terminals. They are: Input voltage, Ground, Output Voltage.
7812 12V INTEGRATED CIRCUIT 3-TERMINAL POSITIVE VOLTAGE REGULATOR:
?
The 7812 fixed voltage regulator is a monolithic integrated circuit in a TO220 type package designed for use in a wide variety of applications including local, onboard regulation. This regulator employs internal current limiting, thermal shutdown, and safe area compensation.
?
With adequate heat-sinking it can deliver output currents in excess of 1.0 ampere. Although designed primarily as a fixed voltage regulator, this device can be used with external components to obtain adjustable voltages and currents.
3.3.5 OUTPUT FILTER The Filter circuit is often fixed after the Regulator circuit. Capacitor is most often used as filter. The principle of the capacitor is to charge and discharge. It charges during the positive half cycle of the AC voltage and discharges during the negative half cycle. The 10µf and .01µf capacitors serve to help keep the power supply output voltage constant when load conditions change. The electrolytic capacitor smooth’s out any long-term or low frequency variations. However, at high frequencies this capacitor is not very efficient. Therefore, the .01µf is included to bypass high-frequency changes, such as digital IC switching effects, to ground.
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LCD Display: Liquid crystal display (LCD) has material which combines the properties of both liquid and crystals. They have a temperature range within which the molecules are almost as mobile as they would be in a liquid, but are grouped together in an order form similar to a crystal. LCD DISPLAY:
More microcontroller devices are using 'smart LCD' displays to output visual information. The following discussion covers the connection of a Hitachi LCD display to a PIC microcontroller. LCD displays designed around Hitachi's LCD HD44780 module, are inexpensive, easy to use, and it is even possible to produce a readout using the 8 x 80 pixels of the display. Hitachi LCD displays have a standard ASCII set of characters plus Japanese, Greek and mathematical symbols. For an 8-bit data bus, the display requires a +5V supply plus 11 I/O lines. For a 4-bit data bus it only requires the supply lines plus seven extra lines. When the LCD display is not enabled, data lines are tri-state which means they are in a state of high impedance (as though they are disconnected) and this means they do not interfere with the operation of the microcontroller when the display is not being addressed.
The LCD also requires 3 "control" lines from the microcontroller.
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Enable (E)
This line allows access to the display through R/W and RS lines. When this line is low, the LCD is disabled and ignores signals from R/W and RS. When (E) line is high, the LCD checks the state of the two control lines and responds accordingly.
Read/Write (R/W)
This line determines the direction of data between the LCD and microcontroller. When it is low, data is written to the LCD. When it is high, data is read from the LCD.
Register select (RS) With the help of this line, the LCD interprets the type of data on data lines. When it is low, an instruction is being written to the LCD. When it is high, a character is being written to the LCD.
Logic status on control lines: E 0 Access to LCD disabled 1 Access to LCD enabled
R/W 0 Writing data to LCD 1 Reading data from LCD
RS 0 Instruction 1 Character
Writing data to the LCD is done in several steps: Set R/W bit to low Set RS bit to logic 0 or 1 (instruction or character) Set data to data lines (if it is writing) Set E line to high
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Set E line to low Read data from data lines (if it is reading). Reading data from the LCD is done in the same way, but control line R/W has to be high. When we send a high to the LCD, it will reset and wait for instructions. Typical instructions sent to LCD display after a reset are: turning on a display, turning on a cursor and writing characters from left to right. When the LCD is initialized, it is ready to continue receiving data or instructions. If it receives a character, it will write it on the display and move the cursor one space to the right. The Cursor marks the next location where a character will be written. When we want to write a string of characters, first we need to set up the starting address, and then send one character at a time. Characters that can be shown on the display are stored in data display (DD) RAM. The size of DDRAM is 80 bytes. The LCD display also possesses 64 bytes of Character-Generator (CG) RAM. This memory is used for characters defined by the user. Data in CG RAM is represented as an 8-bit character bitmap. Each character takes up 8 bytes of CG RAM, so the total number of characters, which the user can define, is eight. In order to read in the character bit-map to the LCD display, we must first set the CG RAM address to starting point (usually 0), and then write data to the display. The definition of a 'special' character is given in the picture.
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Before we access DD RAM after defining a special character, the program must set the DD RAM address. Writing and reading data from any LCD memory is done from the last address which was set up using set-address instruction. Once the address of DD RAM is set, a new written character will be displayed at the appropriate place on the screen. Until now we discussed the operation of writing and reading to an LCD as if it were an ordinary memory. But this is not so. The LCD controller needs 40 to 120 microseconds (uS) for writing and reading. Other operations can take up to 5 mS. during that time, the microcontroller cannot access the LCD, and so a program needs to know when the LCD is busy. We can solve this in two ways. One way is to check the BUSY bit found on data line D7. This is not the best method because LCD's can get stuck, and program will then stay forever in a loop checking the BUSY bit. The other way is to introduce a delay in the program. The delay has to be long enough for the LCD to finish the operation in process. Instructions for writing to and reading from an LCD memory are shown in the previous table.
At the beginning we mentioned that we needed 11 I/O lines to communicate with an LCD. However, we can communicate with an LCD through a 8-bit data bus. The wiring for connection via a 8-bit data bus is shown in the diagram below. In this example we use an LCD display with 2x16 characters, labeled LM16X212 by Japanese maker SHARP.
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INTERFACING PIC MICROCONTROLLER TO LCD:
10k
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
4MHz 22pf 22pf
1N4007 1 1N4007 230v + 1N4007 1N4007 step down transformer 1 1000uf LM7805
3
VIN
GND
VOUT
2
5v
PIC I6f877A
103
P O T +5v
7812
3 2
L C D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
+12v OUTPUT
+5v
o o
display Font: 5 x 8 dots Built-in Controller:HD44780 or Comp
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o o o
Input Data:4 Bits or 8-Bits Interface Power Supply: +4V Single Power Duty Cycle: 1/16 Duty
RELAY DRIVER The ULN2001A, ULN2002A, ULN2003 and ULN2004Aare high Voltage, high current Darlington arrays each containing seven open collector Darlington pairs with common emitters. Each channel rated at 500mAand can withstand peak currents of 600mA.Suppressiondiodesare included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout. These versatile devices are useful for driving a wide range of loads including solenoids, relays DC motors; LED displays filament lamps, thermal print heads and high power buffers. The ULN2001A/2002A/2003A and 2004A are supplied in 16pin plastic DIP packages with a copper lead frame to reduce thermal resistance. They are available also in small outline package (SO-16) as ULN2001D/2002D/2003D/2004D. 3.4.1 FEATURES OF DRIVER ? ? ? ? SEVENDARLINGTONS PER PACKAGE. OUTPUT CURRENT 500mA PER DRIVER (600mA PEAK) OUTPUT VOLTAGE 50V. INTEGRATED SUPPRESSION DIODES FOR
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? ? ? ? ? ?
INDUCTIVE LOADS. OUTPUTS CAN BE PARALLELED FOR HIGHERCURRENT. TTL/CMOS/PMOS/DTLCOMPATIBLE INPUTS. INPUTS PINNED OPPOSITE OUTPUTS TO SIMPLIFYLAYOUT
3.4.2 PIN CONNECTION
FIG 3.5 PIN CONNECTIONS OF A RELAY
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CHAPTER-4
DESCRIBING ABOUT PROJECT IMPLEMENTATION
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4.1
BLOCK
DIAGRAME
OF
TRANSFORMER
MONITORING
AND
SELF
PROTECTION SYSTEM
CURRENT TRANSFORMER
TEMPERATURE SENSOR
PIC MICROCONTROLLER
TRANSFORMER UNIT
SIGNAL CONDITIONING UNIT
LCD DISPLAY
POTENTIAL TRANSFORMER
DRIVER UNIT WITH RELAYS
KEYPAD UNIT
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4.2 DESCRIPTION OF THE BLOCK DIAGRAM The entire project is powered with the power supply unit, the project it needs two different dc power supply one is +12v it is maintained through LM7812 positive 12v regulator and one more dc +5v supply is maintained through LM7805 positive 5v regulator. Potential Transformer is designed for monitoring single-phase and three-phase power line voltages in power metering applications. 0-6v ac, 500ma.The primary terminals can be connected either in line-to-line or in line-to-neutral configuration. Current transformers provide insulation against the high voltage of the power circuit, and also supply the relays with quantities proportional to those of the power circuit, but sufficiently reduced in magnitude so that the relays can be made relatively small and inexpensive. Based on power transformer and current transformer the loads are working. Total four relay driver circuit is connected to controller. The driver is controlling four loads. Each load is connected to relay. For example the loads are ac load, fan, light, door motor, etc. Total four loads are controlling by using keypad.
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4.3 CIRCUIT DIAGRAM
1N4007 1N4007 1N4007 1N4007 1000uf +
103
5.1v
1N4007 1N4007 1N4007 1N4007 1000uf +
RESISTOR 10 ohms
LM324
100uf
105
1 2 3 4 5 +12V 6 7
14 13 12 11 10 9 8
+5v +5v +5v +5v
STEPDOWN
TRANSFORMER
K4
K3
K2
K1
10k
RESISTOR
4MHz
22pf
22pf
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
PIC16F877A
BUZZER
+5v
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 9 +12v
ULN 2003
LOAD
NC NO
PH
N
1N4007
U3 1
1N4007 1N4007 1N4007 1000uf +
VIN
GND
VOUT
2
LM7805
STEPDOWN
TRANSFORMER 1
U4 VIN
GND
3
VOUT
2
1 0 3 +12v OUTPUT POT +5v 1 2 3 4 5 6 7
L C D
LM 7812
3
8
9 10
11 12 13 14 15 16
+5v
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FIG 4.3 CIRCUIT DIAGRAM OF TRANSFORMER MONITORING AND SELF PROTECTION SYSTEM
4.4 POWER SUPPLY DIAGRAM
FIG 4.3 POWER SUPPLY DIAGRAM
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4.5 CIRCUIT DESCRIPTION 4.5.1 POWER SUPPLY Power supply unit consists of Step down transformer, Rectifier, Input filter, Regulator unit, Output filter. The Step down Transformer is used to step down the main supply voltage from 230V AC to lower value. This 230 AC voltage cannot be used directly, thus it is stepped down. The Transformer consists of primary and secondary coils. To reduce or step down the voltage, the transformer is designed to contain less number of turns in its secondary core. The output from the secondary coil is also AC waveform. Thus the conversion from AC to DC is essential. This conversion is achieved by using the Rectifier Circuit/Unit. The Rectifier circuit is used to convert the AC voltage into its corresponding DC voltage. There are Half-Wave, Full-Wave and bridge Rectifiers available for this specific function. The most important and simple device used in Rectifier circuit is the diode. The simple function of the diode is to conduct when forward biased and not to conduct in reverse bias. The Forward Bias is achieved by connecting the diode’s positive with positive of the battery and negative with battery’s negative. The efficient circuit used is the Full wave Bridge rectifier circuit. The output voltage of the rectifier is in rippled form, the ripples from the obtained DC voltage are removed using other circuits available. The circuit used for removing the ripples is called Filter circuit. Capacitors are used as filter. The ripples from the DC voltage are removed and pure DC voltage is obtained. And also these capacitors are used to reduce the harmonics of the input voltage. The primary action performed by capacitor is charging and discharging. It charges in
34
catiopositive half cycle of the AC voltage and it will discharge in negative half cycle. Here we used 1000µF capacitor. So it allows only AC voltage and does not allow the DC voltage. This filter is fixed before the regulator. Thus the output is free from ripples. Regulator regulates the output voltage to be always constant. The output voltage is maintained irrespective of the fluctuations in the input AC voltage. As and then the AC voltage changes, the DC voltage also changes. Thus to avoid this Regulators are used. Also when the internal resistance of the power supply is greater than 30 ohms, the output gets affected. Thus this can be successfully reduced here. The regulators are mainly classified for low voltage and for high voltage. Here we used 7805 positive regulator. It reduces the 6V dc voltage to 5V dc Voltage. The Filter circuit is often fixed after the Regulator circuit. Capacitor is most often used as filter. The principle of the capacitor is to charge and discharge. It charges during the positive half cycle of the AC voltage and discharges during the negative half cycle. So it allows only AC voltage and does not allow the DC voltage. This filter is fixed after the Regulator circuit to filter any of the possibly found ripples in the output received finally. Here we used 0.1µF capacitor. The output at this stage is 5V and is given to the Microcontroller In the power supply circuit two regulators are used. 7805 regulator is used to produce positive 5V dc and 7812 regulator produces positive 12V dc voltage. Relays and ULN 2003 drivers operates at 12V dc and microcontroller and sensors are operated at 5V dc voltage. The output of the 7805 regulator is connected to PIC 16f877A microcontroller, sensors and the output of the 7812 regulator is connected to driver ICs and relays. 4.5.2 CONTROLLER CIRCUIT The RTC PCF8583 is interfaced with PIC16F877A through synchronous serial port communication (i.e., I2C- Inter Integrated Communication), it takes two wire for communin one
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is SCL- Serial Clock and another one is SDA- Serial Data. The RTC PCF 8583 it connected to +5V dc supply which is from 7805 regulator through 330? resistors. Meanwhile the backup battery is connected to maintain the clock. The PIC 16f877A microcontroller is a 40-pin IC. The first pin of the controller is MCLR pin and the 5V dc supply is given to this pin through 10K? resistor. This supply is also given to 11th pin directly. The 12th pin of the controller is grounded. A tank circuit consists of a 4 MHZ crystal oscillator and two 22pf capacitors are connected to 13th and 14th pins of the PIC. The circuit consist one driver IC ULN 2003 is acts as voltage driver. It is a 16- pin IC. This is of NPN transistor type. And this IC is a combination of 7 transistors. At a time we can connect seven loads to each IC. In this project we used 2 relays and they connected to driver. These relays act as switches. The 8th pin of driver ICs is grounded and the 9th pin is connected to 12V dc voltage which is from 7812 regulator. First to two pins of driver IC are connected to RB0, RB1 pins of the controller respectively. Similarly 15th, 16th pins are connected to Relays R1 and R2, respectively. The relays used in this project are of Single pole Single throw type. The Relay Driver Circuit is the main circuit that enables the actual control over the applications. As per the project designed, the Relay Driver circuit signals the appliances to be used if the user is valid or authenticated. Here we are using transistor as the relay driver circuit. Relay is connected with the transistor, which generally contains five pins totally. The first two pins are connected with the transistor and contain the magnetic coil wound between them. The rest of the pins are common point, Normally Open (NO) point and Normally Close (NC) point. Initially common point is in contact with Normally Close point. The magnetic coil also contains an arrangement very similar to that of a hook. When supply is given at the supply point, the magnetic coil of the relay gets energized or activated. Due to this a magnetic field is created
36
that lifts the hook upwards. Thus the arrangement that was initially closed gets opened now. The status of the relay point gets changed (i.e. common point gets connected with normally open point). The status of the relay is depends upon the conduction of the transistor. The transistor configuration used here is that of common emitter mode. The conduction of the transistor depends on the base voltage of the transistor. The supply to the transistor is given from the regulator of the power supply board. Normally transistor acts as a switch. The switch then gets activated by the Microcontroller. The output of the relay driver circuit is given to any of the port pins. The Microcontroller is programmed to respond corresponding to the relay signal obtained. Thus the transistor acts as a switch to control the relay and indirectly controls the appliances. The keys were connected in RB7, RB6, RB5, and RB4 pins of the microcontroller. The LCD display unit it contains 16 pins the 1th & 2th - two pins supply pins 15th & 16th pin backlight pins, 3rd pin brightness adjustment pin, 4th pin RS-reset pin, 5th pin RW pin (read/write pin) 6th pin EN-enable pin these things are interfaced with microcontroller RC1, RC2, RC3 respectively and 7th to 14th pin are connected in PROTD of the microcontroller. Potential Transformer: Potential Transformer is designed for monitoring single-phase and three-phase power line voltages in power metering applications. 0-6v ac, 500ma.The primary terminals can be connected either in line-to-line or in line-to-neutral configuration. A Potential Transformer is a special type of transformer that allows meters to take readings from electrical service connections with higher voltage (potential) than the meter is normally capable of handling without at potential transformer Current transformer: 3A/1A, ac)
37
Current transformers provide insulation against the high voltage of the power circuit, and also supply the relays with quantities proportional to those of the power circuit, but sufficiently reduced in magnitude so that the relays can be made relatively small and inexpensive. The current transformers have several requirements as follows: mechanical construction, type of insulation (dry or liquid), ratio in terms of primary and secondary currents or voltages, continuous thermal rating, short-time thermal and mechanical ratings, insulation class, impulse level, service conditions, accuracy, and connections. Current transformers measure power flow and provide electrical inputs to power transformers and instruments. Current transformers produce either an alternating current or alternating voltage that is proportional to the measured current. There are two basic types of current transformers: wound and toroidal. Wound current transformers consist of an integral primary winding that is inserted in series with the conductor that carries the measured current. Toroidal or donut-shaped current transformers do not contain a primary winding. Instead, the wire that carries the current is threaded through a window in the toroidal transformer Current transformer and Potential transformers are connected to bridge rectifiers. These are used to measure the current and voltage of the load. The LCD displays the current and voltage of the load and the angle of the motor. And also the circuit consists of one operational amplifier (LM324). One potentiometer is connected to the op-Amp. The operational amplifier is connected to the AN0 –AN5 pins of the PIC micro controller. CT Performance and Requirements
Limitations when applied to relaying. The CT takes magnetizing current from the primary circuit and since this current does not flow into the relay branch, there is an error between the primary and relay currents. This is a major source of ratio error. Winding resistance is part of the CT burden and needs to be taken into account whean establishing the CT knee point
38
voltage (Vk) requirement for a particular application. This should be known The simplified CT equivalent circuit given in Figure 1 is first examined to establish a device's and the smaller it is the better. The knee point of the CT gives an indication of the burden the CT can accommodate. Recall that we are trying to get accurate signals up to current values in excess of 20 times rated and this is especially likely with bus bar CT's where fault levels are high. The knee point is the point on the magnetization curve where a large increase in magnetizing current produces a minimal increase in the output voltage needed to drive current through the secondary burden. This value is given directly in the CT specification: 10L200 where the 200 figure means the CT can produce 200 volts on the output with the current being within the stated accuracy. It must be remembered that the ratio of a CT greatly influences the maximum kneepoint that can be obtained by a CT. The kneepoint is basically the maximum secondary output voltage the CT can develop. The physical size of the CT and how much core iron is used determines the volt per turn on the secondary winding. This typically varies from 1.5 to 2.5V per turn, so given the number of turns which is the CT ratio; one can estimate the maximum obtainable kneepoint. Don't try and expect a 400V kneepoint out of a 400/5 ratio CT!
If the CT becomes saturated because of high flux in the core, it will not produce any secondary output current. In fact, the secondary will appear as load to the other parallel connected CT¹s. This is illustrated by the short across the magnetizing branch in Figure 2 and the load is simply the CT winding resistance. SIGNAL CONDITIONING CIRCUIT: AMPLIFIER (LM 324): FEATURES: - Low Supply-Current Drain Independent of Supply Voltage . . . 0.8 mA - Common-Mode Input Voltage Range Includes Ground, Allowing Direct Sensing Near Ground
39
- Low Input Bias and Offset Parameters - Input Offset Voltage . . . 3 mV. . . 2 mV Typ - Input Offset Current . . . 2 nA Type Input Bias Current . . . 20 nA. . . 15 nA Typ Differential Input Voltage Range Equal to Maximum-Rated Supply Voltage . . . 32 V(26 V for LM2902) -Open-Loop Differential Voltage Amplification . . . 100 V/mV -Internal Frequency Compensation
These devices consist of four independent high-gain frequency-compensated operational amplifiers that are designed specifically to operate from a single supply over a wide range of voltages. Operation from split supplies also is possible if the difference between the two supplies is 3 V to 32 V, and VCC is at least1.5 V more positive than the input common-mode voltage. The low supply-current drain is independent of the magnitude of the supply voltage. Applications include transducer amplifiers, dc amplification blocks, and all the conventional operational-amplifier circuits that now can be more easily implemented in single-supply-voltage systems.
40
CHAPTER-5
HARDWARE REQUIREMENTS
41
5.8 COMPONENTS USED
1. Step Down Transformer 2. Diodes 3. Capacitors
230/12V) – 1 No. 1N4007) – 4 No :1000µF – 1 No, 22pF- 2 Nos :7812 – 1 No, 7805 – 1 No :LED`s – 2Nos :ULN 2003 – 1No :16f877A – 1 No :Single Pole Single Throw Type 2Nos :4MHz – 1Nos :330 ? – 1Nos,10 K?- 5 No :1 K? – 2Nos
4. Regulators 5. Light Emitting Diodes 6. Driver ICs 7. PIC microcontroller 8. Relays 9. Crystal Oscillator 10. Resistors
11. Sensors
otential Transformer1No,Current Transformer 1No,Temperature sensor 1No
42
CHAPTER-6
CONCLUSION
43
APPLICATIONS 1. Home appliance 2. Factory AC controlling 3. Factory Light controlling 4. In college labs 5. In research institutes
CONCLUSION The System operated successfully. The transformer was monitored and controlled by using pic controller.
SCOPE OF FUTURE STUDY This project can be enhanced to set the timing through PC using RF wireless communication. Because now a day most of the people doing work with PC and by suing the same PC with combination of RF communication we can do different schedule for each and every appliances and machines in day wise, week wise, month wise and year wise by utilizing the same RTC PCF 8583.
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CHAPTER-7
BIBLIOGRAPHY
BIBLIOGRAPHY
45
BOOKS ? ? ? ? ? ? Customizing and programming ur pic microcontroller- Myke Predcko Complete guide to pic microcontroller -e-book C programming for embedded systems- Kirk Zurell Teach yourself electronics and electricity- Stan Giblisco Embedded Microcomputer system- onathan w.Valvano(2000) Embedded PIC microcontroller- John Peatman
WEB SITIES: ? ? ? Microchips.com http://www.mikroelektronika.co.yu/english/product/books/PICbook/0_Uvod.htm how stuff works.com
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doc_752610439.docx
TABLE OF CONTENTS
PAGE NO
ABSTRACT CHAPTER-1 INTRODUCTION
1. Motivation 2. Problem Statement 3. Related Work 4. Scope Of Work 5. Thesis Outline
I
1-9
CHAPTER -2 IMPORTANT APPROACHES TO THE PROJECT
1
10-29
1.Microcontroller 2.Introduction to Microcontroller 3.Microcontroller core features 4.Advantages of using a Microcontroller over 5. Microprocessor Applications
6.PIC 16f877A Controller 7.Introduction to PIC 16f877A Controller 8. Features of PIC 16f877A Controller 9.Pin Diagram of PIC 16f877A Controller 10. Block Diagram of PIC 16f877A Controller 11.Power Supply Unit 12..Step down transformer Rectifier Unit Input filter Regulator Unit Output filter 13. LCD display 14. Relay Driver Features of Drivers Pin Connection Relays Electromechanical Relays Operation of Electromechanical Relays 15.Load Types 16.Resistive Loads 17.Inductive Loads
2
High or Low in Rush Ac or Dc 18.DC Motor
CHAPTER -3 DESCRIBING ABOUT PROJECT IMPLEMENTATION
3.1 Block Diagram of Lab Automation System 3.2 Description of Block Diagram 3.3 Circuit Diagram of Lab Automation System 3.4 Power Supply Circuit Diagram 3.5 Circuit Description 3.5.1 Power Supply 3.5.2 Controller Circuit
30-41
CHAPTER-4
Implementation
42-43
CHAPTER-5
Hardware requirement
44
3
CHAPTER -6
CONCLUSION
45
Applications Conclusion Future scope of the project
CHAPTER -7 BIBLIOGRAPHY APPENDIX –A 46 47
4
CHAPTER 1 INTRODUCTION
5
2.1 INTRODUCTION The project report describes the design Development and Fabrication of One demo unit of the project work “TRANSFORMER OVERLOAD ALERT” by using embedded systems. Now a day, with the advancement technology, particularly in the field of Microcontrollers, all the activities in our daily living have become a part of Information technology and we find microcontrollers in each and every application. Thus, trend is directing towards Microcontrollers based project works. However, in this project work to program the ON/OFF timings different machines the microcontroller interacts with RTC IC. Then the decisions are taken with the help of microcontroller and associated software. The microcontroller block is playing a major role in this project work. The micro controller chip used in this project work is PIC 16F877A and this is like heart of the project work. The PIC 16F877A microcontroller is a 40-pin IC. The entire project was developed in embedded systems. A system is something that maintains its existence and functions as a whole through the interaction of its parts. E.g. Body, Mankind, Access Control, etc A system is a part of the world that a person or group of persons during some time interval and for some purpose choose to regard as a whole, consisting of interrelated components, each component characterized by properties that are selected as being relevant to the purpose. ? Embedded System is a combination of hardware and software used to achieve a single specific task.
6
?
Embedded systems are computer systems that monitor, respond to, or control an external environment.
? ? ?
Environment connected to systems through sensors, actuators and other I/O interfaces. Embedded system must meet timing & other constraints imposed on it by environment. An embedded system is a microcontroller-based, software driven, reliable, real-time control system, autonomous, or human or network interactive, operating on diverse physical variables and in diverse environments and sold into a competitive and cost conscious market. An embedded system is not a computer system that is used primarily for processing, not a
software system on PC or UNIX, not a traditional business or scientific application. High-end embedded & lower end embedded systems. High-end embedded system - Generally 32, 64 Bit Controllers used with OS. Examples Personal Digital Assistant and Mobile phones etc. Lower end embedded systems - Generally 8, 16 Bit Controllers used with a minimal operating systems and hardware layout designed for the specific purpose. Examples Small controllers and devices in our everyday life like Washing Machine, Microwave Ovens, where they are embedded in. Microcontrollers are embedded inside some other device so that they can control the features or actions of the project. Another name for a microcontroller therefore is “Embedded Controller”. Microcontrollers are dedicated to one task and run one specific program. The program is stored in ROM (read only memory) and generally does not change. Microcontrollers are often low-price devices. Coming to our project whenever the students standing in front of the door for entering in to the lab is sensed by the IR sensor; this signal sends to controller through signal conditioning circuit. The controller takes it as an interrupt signal and gives control signal to the drive unit to
7
open the door. Same like this in side lab if any human being sensed by the controller through IR transceiver it will further turn ON the fans, AC, lights using driver unit.
2.2.2 INTRODUCTION TO RELAYS A relay is usually an electromechanical device that is actuated by an electrical current. The current flowing in one circuit causes the opening or closing of another circuit. Relays are like remote control switches and are used in many applications because of their relative simplicity, long life, and proven high reliability. Relays are used in a wide variety of applications throughout industry, such as in telephone exchanges, digital computers and automation systems. Highly sophisticated relays are utilized to protect electric power systems against trouble and power blackouts as well as to regulate and control the generation and distribution of power. In the home, relays are used in refrigerators, washing machines and dishwashers, and heating and airconditioning controls. Although relays are generally associated with electrical circuitry, there are many other types, such as pneumatic and hydraulic. Input may be electrical and output directly mechanical, or vice versa.
8
CHAPTER-3 IMPORTANT APPROACHES TO THE PROJECT
9
3.1
MICROCONTROLLER
3.1.1 INTRODUCTION TO MICROCONTROLLER A computer-on-a-chip is a variation of a microprocessor which combines the processor core (CPU), some memory, and I/O (input/output) lines, all on one chip. The computer-on-a-chip is called the microcomputer whose proper meaning is a computer using a (number of) microprocessor(s) as its CPUs, while the concept of the microcomputer is known to be a microcontroller. A microcontroller can be viewed as a set of digital logic circuits integrated on a single silicon chip. This chip is used for only specific applications. Most microcontrollers do not require a substantial amount of time to learn how to efficiently program them, although many of them, which have quirks, which you will have to understand before you, attempt to develop your first application. Along with microcontrollers getting faster, smaller and more power efficient they are also getting more and more features. Often, the first version of microcontroller will just have memory and digital I/O, but as the device family matures, more and more pat numbers with varying features will be available. In this project we used PIC 16f877A microcontroller. For most applications, we will be able to find a device within the family that meets our specifications with a minimum of external devices, or an external but which will make attaching external devices easier, both in terms of wiring and programming.
10
For many microcontrollers, programmers can built very cheaply, or even built in to the final application circuit eliminating the need for a separate circuit. Also simplifying this requirement is the availability of micro-controllers wit SRAM and EEPROM for control store, which will allow program development without having to remove the micro controller for the application circuit. 3.1.2 MICRO CONTROLLER CORE FEATURES ? ? ? ? ? High-performance RISC CPU. Only 35 single word instructions to learn. All single cycle instructions except for program branches which are two cycle. Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle. Up to 8K x 14 words of FLASH Program Memory, Up to 368 x 8 bytes of Data Memory (RAM) Up to 256 x 8 bytes of EEPROM data memory. ? ? ? ? ? ? ? ? ? ? ? ? Pin out compatible to the PIC16C73B/74B/76/77 Interrupt capability (up to 14 sources) Eight level deep hardware stack Direct, indirect and relative addressing modes. Power-on Reset (POR). Power-up Timer (PWRT) and Oscillator Start-up Timer (OST). Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation. Programmable code-protection. Power saving SLEEP mode. Selectable oscillator options. Low-power, high-speed CMOS FLASH/EEPROM technology. Fully static design.
11
? ? ? ? ? ? ? ?
InSingle 5V In-Circuit Serial Programming capability. In-Circuit Debugging via two pins. Processor read/write access to program memory. Wide operating voltage range: 2.0V to 5.5V. High Sink/Source Current: 25 mA. Commercial and Industrial temperature ranges. Low-power consumption. In this project we used PIC 16f877A microcontroller. PIC means Peripheral Interface
Controller. The PIC family having different series, the series are 12- Series, 14- Series, 16Series, 18- Series, and 24- Series. We used 16 Series PIC microcontrollers. 3.1.3 ADVANTAGES OF USING A MICROCONTROLLER OVER MICROPROCESSOR A designer will use a Microcontroller to ? ? ? ? ? ? Gather input from various sensors Process this input into a set of actions Use the output mechanisms on the Microcontroller to do something useful RAM and ROM are inbuilt in the MC. Cheap compared to MP. Multi machine control is possible simultaneously.
Examples The 8051 (ATMEL), PIC (Microchip), Motorola (Motorola), ARM Processor
3.1.4 APPLICATIONS:
12
? ? ? ?
Cell phones. Computers. Robots. Interfacing to two pc’s.
3.2 PIC MICROCONTROLLER 16F877A 3.2.1 INTRODUCTION TO PIC MICROCONTROLLER 16F877A The PIC 16f877A microcontroller is a 40-pin IC. The first pin of the controller is MCLR pin and the 5V dc supply is given to this pin through 10K? resistor. This supply is also given to 11th pin directly. The 12th pin of the controller is grounded. A tank circuit consists of a 4 MHZ crystal oscillator and two 22pf capacitors is connected to 13th and 14th pins of the PIC. 3.2.2 ? ? ? ? ? ? ? ? ? FEATURES OF PIC MICROCONTROLLER 16F877A Operating frequency: DC-20Mhz. Flash program memory (14 bit words):8K Data memory (in bytes): 368 EEPROM Data memory (in bytes):256 Interrupts: 15 I/o ports: A, B, C, D, E Timers: 3 Analog comparators: 2 Instructions: 35
3.2.3 PIN DIAGRAM OF PIC 16 F874A/877A
13
FIG 3.1 PIN DIAGRAM OF PIC 16 F874A/877A
3.2.4 FUNCTIONAL BLOCK DIAGRAM OF PIC 16F877A
14
FIG 3.2 PIN DIAGRAM OF PIC 16F874A/877A
15
3.3
POWER SUPPLY UNIT
CIRCUIT DIAGRAM
FIG 3.3 POWER SUPPLY UNIT POWER SUPPLY UNIT COSISTS OF FOLLOWING UNITS
1) Step down transformer 2) Rectifier unit 3) Input filter 4) Regulator unit v) Output filter 3.3.1 STEP DOWN TRANSFORMER The Step down Transformer is used to step down the main supply voltage from 230V AC to lower value. This 230 AC voltage cannot be used directly, thus it is stepped down. The Transformer consists of primary and secondary coils. To reduce or step down the voltage, the transformer is designed to contain less number of turns in its secondary core. The output from the
16
secondary coil is also AC waveform. Thus the conversion from AC to DC is essential. This conversion is achieved by using the Rectifier Circuit/Unit. Step down transformers can step down incoming voltage, which enables you to have the correct voltage input for your electrical needs. For example, if our equipment has been specified for input voltage of 12 volts, and the main power supply is 230 volts, we will need a step down transformer, which decreases the incoming electrical voltage to be compatible with your 12 volt equipment. 3.3.2 RECTIFIER UNIT The Rectifier circuit is used to convert the AC voltage into its corresponding DC voltage. There are Half-Wave, Full-Wave and bridge Rectifiers available for this specific function. The most important and simple device used in Rectifier circuit is the diode. The simple function of the diode is to conduct when forward biased and not to conduct in reverse bias.
Bridge rectifier: A bridge rectifier makes use of four diodes in a bridge arrangement to achieve full-wave rectification. This is a widely used configuration, both with individual diodes wired as shown and with single component bridges where the diode bridge is wired internally.
A diode bridge or bridge rectifier is an arrangement of four diodes in a bridge configuration that provides the same polarity of output voltage for either polarity of input voltage.
17
When used in its most common application, for conversion of alternating current (AC) input into direct current (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a center-tapped transformer design. The Forward Bias is achieved by connecting the diode’s positive with positive of the battery and negative with battery’s negative. The efficient circuit used is the Full wave Bridge rectifier circuit. The output voltage of the rectifier is in rippled form, the ripples from the obtained DC voltage are removed using other circuits available. The circuit used for removing the ripples is called Filter circuit. 3.3.3 INPUT FILTER Capacitors are used as filter. The ripples from the DC voltage are removed and pure DC voltage is obtained. And also these capacitors are used to reduce the harmonics of the input voltage. The primary action performed by capacitor is charging and discharging. It charges in positive half cycle of the AC voltage and it will discharge in negative half cycle. So it allows only AC voltage and does not allow the DC voltage. The 1000µf capacitor serves as a "reservoir" which maintains a reasonable input voltage to the 7805 throughout the entire cycle of the ac line voltage. The four rectifier diodes keep recharging the reservoir capacitor on alternate half-cycles of the line voltage, and the capacitor is quite capable of sustaining any reasonable load in between charging pulses. This filter is fixed before the regulator. Thus the output is free from ripples. Input side the low pass filter has been used.
Low pass filter:
18
One simple electrical circuit that will serve as a low-pass filter consists of a resistor in series with a load, and a capacitor in parallel with the load. The capacitor exhibits reactance, and blocks low-frequency signals, causing them to go through the load instead. At higher frequencies the reactance drops, and the capacitor effectively functions as a short circuit. The combination of resistance and capacitance gives you the time constant of the filter ? = RC (represented by the Greek letter tau). The break frequency, also called the turnover frequency or cutoff frequency (in hertz), is determined by the time constant: or equivalently (in radians per second):
One way to understand this circuit is to focus on the time the capacitor takes to charge. It takes time to charge or discharge the capacitor through that resistor: ?
At low frequencies, there is plenty of time for the capacitor to charge up to
practically the same voltage as the input voltage. ?
At high frequencies, the capacitor only has time to charge up a small amount
before the input switches direction. The output goes up and down only a small fraction of the amount the input goes up and down. At double the frequency, there's only time for it to charge up half the amount.
3.3.4 REGULATOR UNIT
19
FIG 3.4 7805 REGULATOR Regulator regulates the output voltage to be always constant. The output voltage is maintained irrespective of the fluctuations in the input AC voltage. As and then the AC voltage changes, the DC voltage also changes. Thus to avoid this Regulators are used. Also when the internal resistance of the power supply is greater than 30 ohms, the output gets affected. Thus this can be successfully reduced here. Meanwhile it also contains current-limiting circuitry and thermal overload protection, so that the IC won't be damaged in case of excessive load current; it will reduce its output voltage instead. The regulators are mainly classified for low voltage and for high voltage. Further they can also be classified as: 1) Positive regulator ? ? ? Input pin Ground pin Output pin
It regulates the positive voltage. 2) Negative regulator ? ? ? Ground pin Input pin Output pin
It regulates the negative voltage.
20
7805 VOLTAGE REGULATOR: The 7805 provides circuit designers with an easy way to regulate DC voltages to 5v. Encapsulated in a single chip/package (IC), the 7805 is a positive voltage DC regulator that has only 3 terminals. They are: Input voltage, Ground, Output Voltage.
7812 12V INTEGRATED CIRCUIT 3-TERMINAL POSITIVE VOLTAGE REGULATOR:
?
The 7812 fixed voltage regulator is a monolithic integrated circuit in a TO220 type package designed for use in a wide variety of applications including local, onboard regulation. This regulator employs internal current limiting, thermal shutdown, and safe area compensation.
?
With adequate heat-sinking it can deliver output currents in excess of 1.0 ampere. Although designed primarily as a fixed voltage regulator, this device can be used with external components to obtain adjustable voltages and currents.
3.3.5 OUTPUT FILTER The Filter circuit is often fixed after the Regulator circuit. Capacitor is most often used as filter. The principle of the capacitor is to charge and discharge. It charges during the positive half cycle of the AC voltage and discharges during the negative half cycle. The 10µf and .01µf capacitors serve to help keep the power supply output voltage constant when load conditions change. The electrolytic capacitor smooth’s out any long-term or low frequency variations. However, at high frequencies this capacitor is not very efficient. Therefore, the .01µf is included to bypass high-frequency changes, such as digital IC switching effects, to ground.
21
LCD Display: Liquid crystal display (LCD) has material which combines the properties of both liquid and crystals. They have a temperature range within which the molecules are almost as mobile as they would be in a liquid, but are grouped together in an order form similar to a crystal. LCD DISPLAY:
More microcontroller devices are using 'smart LCD' displays to output visual information. The following discussion covers the connection of a Hitachi LCD display to a PIC microcontroller. LCD displays designed around Hitachi's LCD HD44780 module, are inexpensive, easy to use, and it is even possible to produce a readout using the 8 x 80 pixels of the display. Hitachi LCD displays have a standard ASCII set of characters plus Japanese, Greek and mathematical symbols. For an 8-bit data bus, the display requires a +5V supply plus 11 I/O lines. For a 4-bit data bus it only requires the supply lines plus seven extra lines. When the LCD display is not enabled, data lines are tri-state which means they are in a state of high impedance (as though they are disconnected) and this means they do not interfere with the operation of the microcontroller when the display is not being addressed.
The LCD also requires 3 "control" lines from the microcontroller.
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Enable (E)
This line allows access to the display through R/W and RS lines. When this line is low, the LCD is disabled and ignores signals from R/W and RS. When (E) line is high, the LCD checks the state of the two control lines and responds accordingly.
Read/Write (R/W)
This line determines the direction of data between the LCD and microcontroller. When it is low, data is written to the LCD. When it is high, data is read from the LCD.
Register select (RS) With the help of this line, the LCD interprets the type of data on data lines. When it is low, an instruction is being written to the LCD. When it is high, a character is being written to the LCD.
Logic status on control lines: E 0 Access to LCD disabled 1 Access to LCD enabled
R/W 0 Writing data to LCD 1 Reading data from LCD
RS 0 Instruction 1 Character
Writing data to the LCD is done in several steps: Set R/W bit to low Set RS bit to logic 0 or 1 (instruction or character) Set data to data lines (if it is writing) Set E line to high
23
Set E line to low Read data from data lines (if it is reading). Reading data from the LCD is done in the same way, but control line R/W has to be high. When we send a high to the LCD, it will reset and wait for instructions. Typical instructions sent to LCD display after a reset are: turning on a display, turning on a cursor and writing characters from left to right. When the LCD is initialized, it is ready to continue receiving data or instructions. If it receives a character, it will write it on the display and move the cursor one space to the right. The Cursor marks the next location where a character will be written. When we want to write a string of characters, first we need to set up the starting address, and then send one character at a time. Characters that can be shown on the display are stored in data display (DD) RAM. The size of DDRAM is 80 bytes. The LCD display also possesses 64 bytes of Character-Generator (CG) RAM. This memory is used for characters defined by the user. Data in CG RAM is represented as an 8-bit character bitmap. Each character takes up 8 bytes of CG RAM, so the total number of characters, which the user can define, is eight. In order to read in the character bit-map to the LCD display, we must first set the CG RAM address to starting point (usually 0), and then write data to the display. The definition of a 'special' character is given in the picture.
24
Before we access DD RAM after defining a special character, the program must set the DD RAM address. Writing and reading data from any LCD memory is done from the last address which was set up using set-address instruction. Once the address of DD RAM is set, a new written character will be displayed at the appropriate place on the screen. Until now we discussed the operation of writing and reading to an LCD as if it were an ordinary memory. But this is not so. The LCD controller needs 40 to 120 microseconds (uS) for writing and reading. Other operations can take up to 5 mS. during that time, the microcontroller cannot access the LCD, and so a program needs to know when the LCD is busy. We can solve this in two ways. One way is to check the BUSY bit found on data line D7. This is not the best method because LCD's can get stuck, and program will then stay forever in a loop checking the BUSY bit. The other way is to introduce a delay in the program. The delay has to be long enough for the LCD to finish the operation in process. Instructions for writing to and reading from an LCD memory are shown in the previous table.
At the beginning we mentioned that we needed 11 I/O lines to communicate with an LCD. However, we can communicate with an LCD through a 8-bit data bus. The wiring for connection via a 8-bit data bus is shown in the diagram below. In this example we use an LCD display with 2x16 characters, labeled LM16X212 by Japanese maker SHARP.
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INTERFACING PIC MICROCONTROLLER TO LCD:
10k
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
4MHz 22pf 22pf
1N4007 1 1N4007 230v + 1N4007 1N4007 step down transformer 1 1000uf LM7805
3
VIN
GND
VOUT
2
5v
PIC I6f877A
103
P O T +5v
7812
3 2
L C D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
+12v OUTPUT
+5v
o o
display Font: 5 x 8 dots Built-in Controller:HD44780 or Comp
26
o o o
Input Data:4 Bits or 8-Bits Interface Power Supply: +4V Single Power Duty Cycle: 1/16 Duty
RELAY DRIVER The ULN2001A, ULN2002A, ULN2003 and ULN2004Aare high Voltage, high current Darlington arrays each containing seven open collector Darlington pairs with common emitters. Each channel rated at 500mAand can withstand peak currents of 600mA.Suppressiondiodesare included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout. These versatile devices are useful for driving a wide range of loads including solenoids, relays DC motors; LED displays filament lamps, thermal print heads and high power buffers. The ULN2001A/2002A/2003A and 2004A are supplied in 16pin plastic DIP packages with a copper lead frame to reduce thermal resistance. They are available also in small outline package (SO-16) as ULN2001D/2002D/2003D/2004D. 3.4.1 FEATURES OF DRIVER ? ? ? ? SEVENDARLINGTONS PER PACKAGE. OUTPUT CURRENT 500mA PER DRIVER (600mA PEAK) OUTPUT VOLTAGE 50V. INTEGRATED SUPPRESSION DIODES FOR
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? ? ? ? ? ?
INDUCTIVE LOADS. OUTPUTS CAN BE PARALLELED FOR HIGHERCURRENT. TTL/CMOS/PMOS/DTLCOMPATIBLE INPUTS. INPUTS PINNED OPPOSITE OUTPUTS TO SIMPLIFYLAYOUT
3.4.2 PIN CONNECTION
FIG 3.5 PIN CONNECTIONS OF A RELAY
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CHAPTER-4
DESCRIBING ABOUT PROJECT IMPLEMENTATION
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4.1
BLOCK
DIAGRAME
OF
TRANSFORMER
MONITORING
AND
SELF
PROTECTION SYSTEM
CURRENT TRANSFORMER
TEMPERATURE SENSOR
PIC MICROCONTROLLER
TRANSFORMER UNIT
SIGNAL CONDITIONING UNIT
LCD DISPLAY
POTENTIAL TRANSFORMER
DRIVER UNIT WITH RELAYS
KEYPAD UNIT
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4.2 DESCRIPTION OF THE BLOCK DIAGRAM The entire project is powered with the power supply unit, the project it needs two different dc power supply one is +12v it is maintained through LM7812 positive 12v regulator and one more dc +5v supply is maintained through LM7805 positive 5v regulator. Potential Transformer is designed for monitoring single-phase and three-phase power line voltages in power metering applications. 0-6v ac, 500ma.The primary terminals can be connected either in line-to-line or in line-to-neutral configuration. Current transformers provide insulation against the high voltage of the power circuit, and also supply the relays with quantities proportional to those of the power circuit, but sufficiently reduced in magnitude so that the relays can be made relatively small and inexpensive. Based on power transformer and current transformer the loads are working. Total four relay driver circuit is connected to controller. The driver is controlling four loads. Each load is connected to relay. For example the loads are ac load, fan, light, door motor, etc. Total four loads are controlling by using keypad.
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4.3 CIRCUIT DIAGRAM
1N4007 1N4007 1N4007 1N4007 1000uf +
103
5.1v
1N4007 1N4007 1N4007 1N4007 1000uf +
RESISTOR 10 ohms
LM324
100uf
105
1 2 3 4 5 +12V 6 7
14 13 12 11 10 9 8
+5v +5v +5v +5v
STEPDOWN
TRANSFORMER
K4
K3
K2
K1
10k
RESISTOR
4MHz
22pf
22pf
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
PIC16F877A
BUZZER
+5v
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 9 +12v
ULN 2003
LOAD
NC NO
PH
N
1N4007
U3 1
1N4007 1N4007 1N4007 1000uf +
VIN
GND
VOUT
2
LM7805
STEPDOWN
TRANSFORMER 1
U4 VIN
GND
3
VOUT
2
1 0 3 +12v OUTPUT POT +5v 1 2 3 4 5 6 7
L C D
LM 7812
3
8
9 10
11 12 13 14 15 16
+5v
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FIG 4.3 CIRCUIT DIAGRAM OF TRANSFORMER MONITORING AND SELF PROTECTION SYSTEM
4.4 POWER SUPPLY DIAGRAM
FIG 4.3 POWER SUPPLY DIAGRAM
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4.5 CIRCUIT DESCRIPTION 4.5.1 POWER SUPPLY Power supply unit consists of Step down transformer, Rectifier, Input filter, Regulator unit, Output filter. The Step down Transformer is used to step down the main supply voltage from 230V AC to lower value. This 230 AC voltage cannot be used directly, thus it is stepped down. The Transformer consists of primary and secondary coils. To reduce or step down the voltage, the transformer is designed to contain less number of turns in its secondary core. The output from the secondary coil is also AC waveform. Thus the conversion from AC to DC is essential. This conversion is achieved by using the Rectifier Circuit/Unit. The Rectifier circuit is used to convert the AC voltage into its corresponding DC voltage. There are Half-Wave, Full-Wave and bridge Rectifiers available for this specific function. The most important and simple device used in Rectifier circuit is the diode. The simple function of the diode is to conduct when forward biased and not to conduct in reverse bias. The Forward Bias is achieved by connecting the diode’s positive with positive of the battery and negative with battery’s negative. The efficient circuit used is the Full wave Bridge rectifier circuit. The output voltage of the rectifier is in rippled form, the ripples from the obtained DC voltage are removed using other circuits available. The circuit used for removing the ripples is called Filter circuit. Capacitors are used as filter. The ripples from the DC voltage are removed and pure DC voltage is obtained. And also these capacitors are used to reduce the harmonics of the input voltage. The primary action performed by capacitor is charging and discharging. It charges in
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catiopositive half cycle of the AC voltage and it will discharge in negative half cycle. Here we used 1000µF capacitor. So it allows only AC voltage and does not allow the DC voltage. This filter is fixed before the regulator. Thus the output is free from ripples. Regulator regulates the output voltage to be always constant. The output voltage is maintained irrespective of the fluctuations in the input AC voltage. As and then the AC voltage changes, the DC voltage also changes. Thus to avoid this Regulators are used. Also when the internal resistance of the power supply is greater than 30 ohms, the output gets affected. Thus this can be successfully reduced here. The regulators are mainly classified for low voltage and for high voltage. Here we used 7805 positive regulator. It reduces the 6V dc voltage to 5V dc Voltage. The Filter circuit is often fixed after the Regulator circuit. Capacitor is most often used as filter. The principle of the capacitor is to charge and discharge. It charges during the positive half cycle of the AC voltage and discharges during the negative half cycle. So it allows only AC voltage and does not allow the DC voltage. This filter is fixed after the Regulator circuit to filter any of the possibly found ripples in the output received finally. Here we used 0.1µF capacitor. The output at this stage is 5V and is given to the Microcontroller In the power supply circuit two regulators are used. 7805 regulator is used to produce positive 5V dc and 7812 regulator produces positive 12V dc voltage. Relays and ULN 2003 drivers operates at 12V dc and microcontroller and sensors are operated at 5V dc voltage. The output of the 7805 regulator is connected to PIC 16f877A microcontroller, sensors and the output of the 7812 regulator is connected to driver ICs and relays. 4.5.2 CONTROLLER CIRCUIT The RTC PCF8583 is interfaced with PIC16F877A through synchronous serial port communication (i.e., I2C- Inter Integrated Communication), it takes two wire for communin one
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is SCL- Serial Clock and another one is SDA- Serial Data. The RTC PCF 8583 it connected to +5V dc supply which is from 7805 regulator through 330? resistors. Meanwhile the backup battery is connected to maintain the clock. The PIC 16f877A microcontroller is a 40-pin IC. The first pin of the controller is MCLR pin and the 5V dc supply is given to this pin through 10K? resistor. This supply is also given to 11th pin directly. The 12th pin of the controller is grounded. A tank circuit consists of a 4 MHZ crystal oscillator and two 22pf capacitors are connected to 13th and 14th pins of the PIC. The circuit consist one driver IC ULN 2003 is acts as voltage driver. It is a 16- pin IC. This is of NPN transistor type. And this IC is a combination of 7 transistors. At a time we can connect seven loads to each IC. In this project we used 2 relays and they connected to driver. These relays act as switches. The 8th pin of driver ICs is grounded and the 9th pin is connected to 12V dc voltage which is from 7812 regulator. First to two pins of driver IC are connected to RB0, RB1 pins of the controller respectively. Similarly 15th, 16th pins are connected to Relays R1 and R2, respectively. The relays used in this project are of Single pole Single throw type. The Relay Driver Circuit is the main circuit that enables the actual control over the applications. As per the project designed, the Relay Driver circuit signals the appliances to be used if the user is valid or authenticated. Here we are using transistor as the relay driver circuit. Relay is connected with the transistor, which generally contains five pins totally. The first two pins are connected with the transistor and contain the magnetic coil wound between them. The rest of the pins are common point, Normally Open (NO) point and Normally Close (NC) point. Initially common point is in contact with Normally Close point. The magnetic coil also contains an arrangement very similar to that of a hook. When supply is given at the supply point, the magnetic coil of the relay gets energized or activated. Due to this a magnetic field is created
36
that lifts the hook upwards. Thus the arrangement that was initially closed gets opened now. The status of the relay point gets changed (i.e. common point gets connected with normally open point). The status of the relay is depends upon the conduction of the transistor. The transistor configuration used here is that of common emitter mode. The conduction of the transistor depends on the base voltage of the transistor. The supply to the transistor is given from the regulator of the power supply board. Normally transistor acts as a switch. The switch then gets activated by the Microcontroller. The output of the relay driver circuit is given to any of the port pins. The Microcontroller is programmed to respond corresponding to the relay signal obtained. Thus the transistor acts as a switch to control the relay and indirectly controls the appliances. The keys were connected in RB7, RB6, RB5, and RB4 pins of the microcontroller. The LCD display unit it contains 16 pins the 1th & 2th - two pins supply pins 15th & 16th pin backlight pins, 3rd pin brightness adjustment pin, 4th pin RS-reset pin, 5th pin RW pin (read/write pin) 6th pin EN-enable pin these things are interfaced with microcontroller RC1, RC2, RC3 respectively and 7th to 14th pin are connected in PROTD of the microcontroller. Potential Transformer: Potential Transformer is designed for monitoring single-phase and three-phase power line voltages in power metering applications. 0-6v ac, 500ma.The primary terminals can be connected either in line-to-line or in line-to-neutral configuration. A Potential Transformer is a special type of transformer that allows meters to take readings from electrical service connections with higher voltage (potential) than the meter is normally capable of handling without at potential transformer Current transformer: 3A/1A, ac)
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Current transformers provide insulation against the high voltage of the power circuit, and also supply the relays with quantities proportional to those of the power circuit, but sufficiently reduced in magnitude so that the relays can be made relatively small and inexpensive. The current transformers have several requirements as follows: mechanical construction, type of insulation (dry or liquid), ratio in terms of primary and secondary currents or voltages, continuous thermal rating, short-time thermal and mechanical ratings, insulation class, impulse level, service conditions, accuracy, and connections. Current transformers measure power flow and provide electrical inputs to power transformers and instruments. Current transformers produce either an alternating current or alternating voltage that is proportional to the measured current. There are two basic types of current transformers: wound and toroidal. Wound current transformers consist of an integral primary winding that is inserted in series with the conductor that carries the measured current. Toroidal or donut-shaped current transformers do not contain a primary winding. Instead, the wire that carries the current is threaded through a window in the toroidal transformer Current transformer and Potential transformers are connected to bridge rectifiers. These are used to measure the current and voltage of the load. The LCD displays the current and voltage of the load and the angle of the motor. And also the circuit consists of one operational amplifier (LM324). One potentiometer is connected to the op-Amp. The operational amplifier is connected to the AN0 –AN5 pins of the PIC micro controller. CT Performance and Requirements
Limitations when applied to relaying. The CT takes magnetizing current from the primary circuit and since this current does not flow into the relay branch, there is an error between the primary and relay currents. This is a major source of ratio error. Winding resistance is part of the CT burden and needs to be taken into account whean establishing the CT knee point
38
voltage (Vk) requirement for a particular application. This should be known The simplified CT equivalent circuit given in Figure 1 is first examined to establish a device's and the smaller it is the better. The knee point of the CT gives an indication of the burden the CT can accommodate. Recall that we are trying to get accurate signals up to current values in excess of 20 times rated and this is especially likely with bus bar CT's where fault levels are high. The knee point is the point on the magnetization curve where a large increase in magnetizing current produces a minimal increase in the output voltage needed to drive current through the secondary burden. This value is given directly in the CT specification: 10L200 where the 200 figure means the CT can produce 200 volts on the output with the current being within the stated accuracy. It must be remembered that the ratio of a CT greatly influences the maximum kneepoint that can be obtained by a CT. The kneepoint is basically the maximum secondary output voltage the CT can develop. The physical size of the CT and how much core iron is used determines the volt per turn on the secondary winding. This typically varies from 1.5 to 2.5V per turn, so given the number of turns which is the CT ratio; one can estimate the maximum obtainable kneepoint. Don't try and expect a 400V kneepoint out of a 400/5 ratio CT!
If the CT becomes saturated because of high flux in the core, it will not produce any secondary output current. In fact, the secondary will appear as load to the other parallel connected CT¹s. This is illustrated by the short across the magnetizing branch in Figure 2 and the load is simply the CT winding resistance. SIGNAL CONDITIONING CIRCUIT: AMPLIFIER (LM 324): FEATURES: - Low Supply-Current Drain Independent of Supply Voltage . . . 0.8 mA - Common-Mode Input Voltage Range Includes Ground, Allowing Direct Sensing Near Ground
39
- Low Input Bias and Offset Parameters - Input Offset Voltage . . . 3 mV. . . 2 mV Typ - Input Offset Current . . . 2 nA Type Input Bias Current . . . 20 nA. . . 15 nA Typ Differential Input Voltage Range Equal to Maximum-Rated Supply Voltage . . . 32 V(26 V for LM2902) -Open-Loop Differential Voltage Amplification . . . 100 V/mV -Internal Frequency Compensation
These devices consist of four independent high-gain frequency-compensated operational amplifiers that are designed specifically to operate from a single supply over a wide range of voltages. Operation from split supplies also is possible if the difference between the two supplies is 3 V to 32 V, and VCC is at least1.5 V more positive than the input common-mode voltage. The low supply-current drain is independent of the magnitude of the supply voltage. Applications include transducer amplifiers, dc amplification blocks, and all the conventional operational-amplifier circuits that now can be more easily implemented in single-supply-voltage systems.
40
CHAPTER-5
HARDWARE REQUIREMENTS
41
5.8 COMPONENTS USED
1. Step Down Transformer 2. Diodes 3. Capacitors
230/12V) – 1 No. 1N4007) – 4 No :1000µF – 1 No, 22pF- 2 Nos :7812 – 1 No, 7805 – 1 No :LED`s – 2Nos :ULN 2003 – 1No :16f877A – 1 No :Single Pole Single Throw Type 2Nos :4MHz – 1Nos :330 ? – 1Nos,10 K?- 5 No :1 K? – 2Nos4. Regulators 5. Light Emitting Diodes 6. Driver ICs 7. PIC microcontroller 8. Relays 9. Crystal Oscillator 10. Resistors
11. Sensors
otential Transformer1No,Current Transformer 1No,Temperature sensor 1No42
CHAPTER-6
CONCLUSION
43
APPLICATIONS 1. Home appliance 2. Factory AC controlling 3. Factory Light controlling 4. In college labs 5. In research institutes
CONCLUSION The System operated successfully. The transformer was monitored and controlled by using pic controller.
SCOPE OF FUTURE STUDY This project can be enhanced to set the timing through PC using RF wireless communication. Because now a day most of the people doing work with PC and by suing the same PC with combination of RF communication we can do different schedule for each and every appliances and machines in day wise, week wise, month wise and year wise by utilizing the same RTC PCF 8583.
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CHAPTER-7
BIBLIOGRAPHY
BIBLIOGRAPHY
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BOOKS ? ? ? ? ? ? Customizing and programming ur pic microcontroller- Myke Predcko Complete guide to pic microcontroller -e-book C programming for embedded systems- Kirk Zurell Teach yourself electronics and electricity- Stan Giblisco Embedded Microcomputer system- onathan w.Valvano(2000) Embedded PIC microcontroller- John Peatman
WEB SITIES: ? ? ? Microchips.com http://www.mikroelektronika.co.yu/english/product/books/PICbook/0_Uvod.htm how stuff works.com
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