RFID Project

8/9/2019 RFID Project

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EMBEDDED PREPAID ENERGY METER WITH OVER

VOLTAGE AND OVERLOAD PROTECTION SYSTEM

1.1 INTRODUCTION:

In recent years, Indian power sector is facing serious problems in terms of lean revenue

collection in lieu of energy supplied and increasing energy requirements. All the steps

taken so far, regarding the improvement of the power scenario, are concerning the human

factor of the system but the metering and meter-reading system has to improve if revenue

collection is to be increased.

Electronic energy meters are replacing traditional electromechanical meters in

many residential, commercial and industrial applications because of the versatility and

low-cost afforded by electronic meter designs. In addition to that an electronic design can

protect against meter tampering and theft of service. An electronic energy meter can also

enable automatic meter reading (AMR), where energy metering data is transmitted to the

utility over an RF, power line or even infrared communications link. Improved accuracy

and lower power consumption are other benefits of electronic metering. With a

mechanical meter, the error in the basic energy usage measurement is on the order of 1%.

But with an electronic implementation, it is possible to reduce that error to less than

0.1%. Moreover, running the mechanical meter with its continuously spinning dial may

require hundreds of milliamps where as that power consumption can be reduced to a

couple milliamps in an electronic energy meter, producing big power savings for the

utility. Electronic meter designs also change the economics of manufacturing energy

meters. A single hardware design may be customized for different customers and markets

through changes in software. In addition, calibrating the finished meter is much easier

with an electronic meter design. Another consideration is the demand for mechanical-

meter replacements that are as inexpensive as possible. In parts of the developing world

where many new customers are being connected to the grid, the low cost of the electronic

meter is its main attraction.Electrical energy is measured by means of energy meter (watt-hour meter).

Energy meter is an integrating instrument and takes in to account both of the quantities

i.e. Power and time the product of which gives energy. Traditional energy monitoring

system is done through electromechanical energy meter installed in the premises of

customer. This present system is not to expected satisfaction to the energy supplying

Dept.Electronics & comm. Engg Siddaganga polytechnic, Tumkur-3

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Applications VEMS is an intelligent solution to the revenue crisis and energy thefts

prevalent in Indian power sector. Technical advances in metering technology and the use

of information technology will result in enhanced efficiency, revenues, and better

management and customer services. It will also facilitate load forecasting and control,

identify potential areas of theft, losses and take measures to rectify it.

S.A. Al-Qatari and A.R. Nu-Ali [4] discuss about Microcontroller based

automated billing system they present digital energy modules equipped with credit card

reading capability and charge automatically. Also, all service metering modules are

facilitated with an automatic service connection and disconnection based on the available

credit. The software structure commands the whole process via the microcontroller

input/output ports.

I.Hakki Cavdar [5] identifies illegal electricity usage and present a paper on A

Solution to Remote Detection of Illegal Electricity Usage via Power Line

Communications where AMR system via PLC is set in a power delivery

system, a detection system for illegal electricity usage may be easily

added in the existing PLC network. In the detection system, the second

digitally energy meter chip is used and the value of energy is stored.

The recorded energy is compared with the value at the main kilowatt-

hour meter. In the case of the difference between two recorded energydata, an error signal is generated and transmitted via PLC network.

STATEMENT OF THE PROBLEM

1. Tradition energy monitoring system is done by electromechanical energy meter

where the consumer manipulate the meter to cause it under register or even run

backwards and in some cases tampering techniques will be employed like

breaking the housing , jamming the mechanism and bypassing the energy meter

to effectively use electric energy.

2. In this busy world consumer has to wait in a long queue to pay the electricity bill.

3. There is no protection to our house hold electrical equipment as well as our life

due to over load and over voltage condition respectively.

4. Automated meter reading is not available in present mechanical energy meter

which could convey theft message to power supplying authority.


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2.1 Block Diagram:

EMBED PBrush

Fig.2.1 Block diagram of embedded prepaid energy meter


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2.2 OPERATION:

The brief description and block diagram of the project is explained as below. The total

block diagram is divided in to various blocks as indicated below.

1. Microcontroller

2. Power supply unit

3. Keypad

4. Digital Display

5. RS 232 serial interface

6. Over voltage, under voltage and over load protection7. Theft detection and Isolation

Microcontroller

In this project work the micro controller part plays a major role, which is used to

read and store the data received from the Keypad. According to the received information,

the micro controller displays the consumable energy and at the same time energizes the

relay. In this project Micro-controller unit is constructed with PIC 16F877 Micro-

controller chip. The PIC 16F877 is a low power, higher performance CMOS 8-bit

microcomputer with 8K bytes of flash programmable and erasable read only memory

(EEPROM).All this provides highly flexible and cost effective solution to control

applications.


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Micro-controller works according to the program written in it. The program is

written in such a way, so that the controller output is used to drive the display as well as

relay and alarm.

Micro-controllers are "embedded" inside some other device so that they can

control the features or actions of the product. Another name for a micro-controller is

"embedded controller". Micro-controllers are dedicated to one task and run one specific

program. The program is stored in ROM (read-only memory) and generally does not

change.

Micro-controllers are often low-power devices. A battery-operated Micro

controller might consume 50 milli watts. A micro-controller also takes input from the

device it is controlling and controls the device by sending signals to different componentsin the device.

Power supply unit

This power supply section will provide different DC voltages required for

different section of circuit. This unit converts the available 230volts AC to

required DC voltage level with help of transformer and filtering circuit. Since

Microcontroller operates with +5volts, and that of relay unit with 12 volts we

have developed that required voltage level. Filtering is done through electrolytic

capacitor and R.F interference can be avoided using 0.1f capacitor. To avoid

change in output due to changes in the input we are using regulated I.C.

RFID Module : This is radio frequency identity module which can identify the

amount specified in the smart card and transfers the coded information to

Microcontroller.It is a wireless system with a small range .

Digital Display:

Digital display is constructed using 7-segment common cathode unit. This is a

dynamic display or time multiplexed display that means each display unit will

display one after the other for 20msec but out eye cannot recognize it, so it looks

like ON for all period. Sinking unit (ULN 2003) is used with 7 segment common

cathode unit.

Over voltage, under voltage and over load protection:


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When the voltage variation is beyond the working range the equipments

connected may get damaged. To solve this problem we have provided this a

solution in this unit by cutting of the supply. Where predetermined voltage levels

are set by software or hardware.

Every device will have specific handling capacity which is in the range of few

milliamps to few amps. When the current flow through these devices exceeds the

maximum current capacity the device will damage immediately. This condition

may damage other circuitry & supporting units. Hence we are using this unit

which is going to measure current flow & switches off the load during overload

conditions.

It consists of current transformer which develops secondary voltage which

is proportional to load current which is then rectified, filtered & scaled before

connecting to analog input of microcontroller. Microcontroller will select this

analog input & converts it into digital value by using internal ADC. This digital

value is compared with the standard reference value to take decision about normal

or overload condition. If load current is abnormal the relay will turn off the load

& provides overload protection.


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3.1 Power supply unit:


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Fig.3.1 Power Supply Unit

The Power Supply Section is used to provide different DC voltages to different

sections of circuit. In our project we have design power supply to give +5v regulated

voltage at the output and also +12v and 12v regulated voltage at the output.


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We are converting the 230v AC into required DC voltage. We have a step down

transformer at the input. The Switch controls the ON and OFF condition of the power

supply. The fuse of 1 Ampere safeguards the power supply for over current flow theoutput voltage at the secondary of the transformer is 9v as shown in the circuit. This

AC voltage is given to rectifier circuit constructed by using bridge rectifier.

Electrolytic capacitor of 1000 mf is used as filter to give pure DC. The advantages offull wave rectifier are low ripple factor (0.48) high ratio of rectification (0.812) and

peak inverse voltage (PIV=Vm) the output of rectifier is given to capacitor filter

polarity. This smoothens the rectified voltage and gives pure DC.

The output of the filter is a pure DC but unregulated. The output voltage changes withvariations in Input voltage and load current. To obtain the regulated output voltage we

are using 3 pin IC voltage regulators. We have used 7805 fixed positive voltage

regulator to give +5v and other ICs are 7812 and 7912 voltage regulators to give+12v and 12v respectively. These regulators are provided with built in heat sink and

have internal circuitry to provide short circuit protection. The regulator output is

connected to output terminal as shown to indicate the presence of voltage at output

terminals we have connected a LED.

Power supply unit voltage is present. We have connected a 0.1 f capacitor acrossthe output terminals to suppress the effect of RF interference

3.2 LIQUID CRYSTAL DISPLAY (LCD):


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The LCD panel used in this block interfaced with micro-controller through the

output port. This is a 16 character x 3Line LCD module, capable of display

numbers, characters, and graphics. The display contains two internal byte-wide

registers, one for commands (RS=0) and the second for characters to be

displayed (RS=1). It also contains a user. Programmed RAM area (the

character RAM) that can be programmed to generate any desired character that

can be formed using a dot matrix. To distinguish between these two data areas,

the hex command byte 80 will be used to signify that the display RAM address

00h is chosen.

LCDs can add a lot to your application in terms of providing a useful interface for theuser, debugging an application or just giving it a "professional" look. The most common

type of LCD controller is the Hitachi 44780 which provides a relatively simple interfacebetween a processor and an LCD. Using this interface is often not attempted by

inexperienced designers and programmers because it is difficult to find good

documentation on the interface, initializing the interface can be a problem and thedisplays themselves are expensive.

Connection to a standard PC parallel port is mostly simple. Those displays can handle

eight bit input directly. They also need two extra lines to control which kind of data has

just arrived and when the data is meant to be stable. Those signals are called RS(Register

Select, i.e. instruction or data register) and EN(enable).

So we have to connect ten data lines (8 bits + RS + EN) and one common ground (GND)

line, which makes eleven lines to the parallel port. Data read back is not supported by the

driver and so we do not need extra lines for this.

The follwing table shows the needed connections:

25 pin par.port function LCD pin Function

1 STROBE 6 EN


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2 Data 0 8 D0

3 Data 1 9 D1

4 Data 2 10 D2

5 Data 3 11 D3

6 Data 4 12 D4

7 Data 5 13 D5

8 Data 6 14 D6

9 Data 7 15 D7

14 Feed 4 RS

18-25 GND 1 GND

And since we only want to write data another connection is required. Make a permanent

connection from GND to pin 5 of the LCD module.

That's it! You may also want to connect the displays power supply pins (1 = GND, 3 =

+5V) to your gameport or your favourite +5V source.

This discription is only valid for my version of LCD display module! I will not be

responsible for any damage you might do to your display, your computer or anything ifyour display is wired in another way. Please consult your databook, datasheet or the

LCD-module-FAQ for more information.

But anyway the above information should be correct for most display modules.

Block Diagram:

Fig.3.2 Block diagram of LCD Display

3.3 Key Pad Unit:


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Microcon

troller

ParallelPort


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Fig.3.3.1 Key Pad Unit

Embedded systems which require user interaction must interface with devices that accept

user input (such as a keypad, bar code reader, or smart card acceptor), as well as devicesthat display information to the user (such as LED or LCD displays).

Figure above shows 44 Key pad interface to PIC 16F877 Microcontroller. In this 4 lines

of Port D is used as scan lines i.e., RD0-RD3 and remaining 4 lines are used as return

lines i.e., RD4-RD7. If no key is pressed in active scan row the return lines will be zero.

The scanning is repeated for all the rows sequentially. When scanning of all lines is

complete its start scanning the first row and repeats the operation until key depression is

found.

When any key is pressed the corresponding return line will have a high state and other

lines are zero. This is checked by scanning routine and identifies the pre determined key

position.

Block Diagram:


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Fig.3.3.2 Block diagram

Fig.3.3.3

3.4 Darlington Amplifier: -


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Micro

controller

ParallelPort


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It is the name given to a pair of similar transistors so connected that emitter of one

is directly joined to the base of the other. These two transistors are mounted in a single

package that as only three leads normally as shown below-

1. Base. 2. Emitter. 3. Collector.

Fig.3.4 Darlington Amplifier

It forms a double collector stage in multistage amplifiers. It is so because a

Darlington connection can be considered equivalent to two cascaded emitter followers. In

our project we have TIP 127 IC as Darlington amplifier. It has two pins [base, collector &

emitter] and provide with built in heat sink. We have added an external heat sink with

pins to dissipate more heat easily. The Darlington transistor is used to drive the coils of

stepper motor.

The buffer supplies base current to transistor Q1 (which is equal to collector current)

becomes vase current of Q2 and is amplified by the current gain of Q2. The result of all

this is that the device acts likes a single transistor with a current gain ( of Q1 x of

Q2) and base to emitter voltage of about 1.4v. The internal resistors help in turning off

the transistors. We have used TIP 127 in our project that has a minimum of 1000 at

1Amp. If we assume 600mA as load current, then the constant base current must be


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supplied by the buffer is only 0.6mA, which it can easily do. If the drive current required

for the Darlington is too high for the output. You can add a resistor from the transistor

base to +5v to supply added current.

. The Darlington pair is most often used in an emitter follower configuration

because of the excellent buffering it provides between a high impedance source and

low load impedance load.

ADVANTAGES OF THE DARLINGTON AMPLIFIER:

It can be formed from two adjacent transistors in an IC.

It has enormous impedance transformation capability.

It can transform a low impedance load in to a high impedance load. Hence, it is

used in a high gain OP-AMP that depends on very high input impedance.

3.5 Buzzer:


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The buzzer subsystem produces a 2 KHz audible tone when powered. The

buzzer will sound when the signal coming into the driver is high. It must be

connected to a transistor, Darlington ortransducerdriver subsystem.

The buzzer is connected between the supply rail (+ V) and the input

signal. This acts as load on the driver. When the input signal coming into the

buzzer subsystem is low, a potentialdifference across the buzzer causes current

to flow. It is this flow of current that causes the buzzer to sound.


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3.6 Relays:

A relay is an electrical switch that opens and closes under control of another

electrical circuit. In the original form, the switch is operated by an electromagnet to open

or close one or many sets of contacts.. a relay is able to control an output circuit of higher

power than the input circuit, it can be considered, in a broad sense, to be a form of

electrical amplifier.

These contacts can be either Normally Open (NO), Normally Closed (NC), or change-

over contacts.

Normally-open contacts connect the circuit when the relay is activated; the circuit

is disconnected when the relay is inactive. It is also called Form A Contact Or "Make"

Contact. Form A contact is ideal for applications that require to switch a high-current

power source from a remote device.

Normally-closed contacts disconnect the circuit when the relay is activated; the

circuit is connected when the relay is inactive. It is also called Form B Contact Or

"Break" Contact. Form B contact is ideal for applications that require the circuit to

remain closed until the relay is activated.

Change-over contacts control two circuits: one normally-open contact and one

normally-closed contact with a common terminal. It is also called Form C Contact.


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OPERATION:

Fig.3.6.1

Relay unit

When a current flows through the coil, the resulting magnetic field attracts an

armature that is mechanically linked to a moving contact. The movement either makes or

breaks a connection with a fixed contact. When the current to the coil is switched off, the

armature is returned by a force that is half as strong as the magnetic force to its relaxed

position. Usually this is a spring, but gravity is also used commonly in industrial motor

starters. The magnetic flux in the armature induces a current in opposition to the current

provided to the coil called 'back emf'. There is a rush of current to operate the coil and

move the contacts, but once the armature is closed, the current required to hold the

armature closed is a small fraction of that, typically a tenth. Relays are manufactured to

operate quickly. In a low voltage application, this is to reduce noise. In a high voltage or

high current application, this is to reduce arcing.

If the coil is energized with DC current, regardless of the current through the

contacts, a diode is generally installed across the coil. When the coil is energized, a

magnetic field is established. When the coil is de-energized, the collapsing magnetic field


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will generate a spike of current that could damage the rest of the circuit. If the coil is

energized with AC current, a small copper ring is crimped to the end of the solenoid.

Alternating current is at zero volts 120 times a second. At zero volts, there's no magnetic

force holding the contacts closed. The small copper ring provides a small out of phase

current called a shadow pole. The sum of the AC current and the shadow pole keeps the

armature engaged at all times.

Relays are used:

To control a high-voltage circuit with a low-voltage signal, as in some types of

modems,

To control a high-current circuit with a low-current signal, as in the starter

solenoid of an automobile,

To detect and isolate faults on transmission and distribution lines by opening and

closing circuit breakers (protection relays),

To isolate the controlling circuit from the controlled circuit when the two are at

different potentials, for example when controlling a mains-powered device from a

low-voltage switch


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Relay circuit:

Relay circuit is used to activate the relay through microcontroller. In this circuit we

have to use a Darlington transistor (Tip122) for switch on the relay. The relay is an

electromagnetic device which energies when the supply is given. In this circuit, relay is

working in the positive logic. That means when the microcontroller gives high to the relay

circuit the Darlington transistor is switched on and also the relay is ON. When themicrocontroller gives low to the relay circuit the Darlington transistor is switched off and

also the relay is OFF. The two diodes are used for protecting t

he microcontroller from the load due to back EMF and EMI problems.

Fig.3.6.2 Circuit Diagram


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3.7 MICRO SWITCH:

A micro switch is a generic term used to refer to an electric switch that is able tobe actuated by very little physical force. They are very common due to their low cost and

extreme durability, typically greater than 1 million cycles and up to 10 million cycles for

heavy duty models. This durability is a natural consequence of the design. Internally a

stiff metal strip must be bent to activate the switch. This produces a very distinctive

clicking sound and a very crisp feel. When pressure is removed the metal strip springs

back to its original state. Common applications of micro switches include computer

mouse buttons and arcade game's joysticks and buttons. Micro switches are commonly

used in tamper switches on gate valves on fire sprinkler systems and other water pipe

systems, where it is necessary to know if a valve has been opened or shut. They have also

been used as anti-handling devices in booby trapped improvised explosive devices

manufactured by paramilitary groups.

The defining feature of micro switches is that a relatively small movement at the

actuator button produces a relative large movement at the electrical contacts, which

occurs at high speed (regardless of the speed of actuation). Most successful designs also

exhibit hysteresis, meaning that a small reversal of the actuator is insufficient to reverse

the contacts; there must be a significant movement in the opposite direction. Both of

these characteristics help to achieve a clean and reliable interruption to the switched

circuit.

The first micro switch was invented by Peter McGall in 1932 in Freeport, Illinois.

McGall was an employee of the Burgess Battery Company at the time. In 1937 he started

the company MICRO SWITCH, which still exists as of 2005. It is now owned by

Honeywell Sensing and Control.


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4.1 PIN CONFIGURATON OF PIC 16F874/7

4.0. Architecture of the PIC16F877 microcontroller

4.1. Overview of the File Registers

4.2. Overview of the 8-channel 10-bit ADC

4.3. Overview of the Hardware USART

4.3.1 Baud-Rate Generator, BRG


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Figure 4.1: PIC16F877 microcontroller [W9]


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The PIC16F877 is a high-performance FLASH microcontroller that providesengineers with the highest design flexibility possible. In addition to 8192x14words of FLASH program memory, 256 data memory bytes, and 368 bytes of

user RAM, PIC16F877 also features an integrated 8-channel 10-bit Analogue-to-Digital converter. Peripherals include two 8-bit timers, one 16-bit timer, aWatchdog timer, Brown-Out-Reset (BOR), In-Circuit-Serial Programming, RS-485 type UART for multi-drop data acquisition applications, and I2C or SPIcommunications capability for peripheral expansion. Precision timing interfacesare accommodated through two CCP modules and two PWM modules. [W3]

Overview of the File Registers

The data memory is partitioned into multiple banks which contain the generalpurpose registers and the special function registers. Bits RP1 and RP0 are the

bank select bits, these bits are found in the STATUS register (b6 & b5).


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Figure 4.1a. PIC16F877 register file map

Each bank extends up to 7Fh (128 bytes). The lower locations of each bank are

reserved for the special function registers (shown in yellow). Above the specialfunction registers are general purpose registers (shown in blue), implemented asstatic RAM. All implemented banks contain special function registers. Some highuse special function registers from one bank may be mirrored in another bankfor code reduction and quicker access. Also notice that there are 16 generalpurpose global registers (shown in green), these registers can be accessed fromany bank.

Overview of the 8-Channel 10-bit ADC

At first it appears that the PIC16F877 has 8 built-in ADCs, but this is not the

case. Figure 4.2a shows a simplified block diagram of the analogue-to-digitalconverter module, clearly there is only one 10-bit ADC which can be connectedto only one of eight input pins at any one time.


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Figure 4.2a. Simplified block diagram of the PIC16F877 ADC module


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The input analogue channels AN4..0 are shared with port A, and channelsAN7..5 are shard with port E. If less than eight analogue channels are requiredthen some of the pins can be assigned as digital I/O port lines using PCFG3..0

bits (see datasheet). For example, if PCFG3..0 = 0010 then AN4..0 areconfigured as analogue inputs, while AN7..5 are digital (port E free), with VDDused as the reference.

On reset all pins are set to accept analogue signals. Pins that are reconfiguredas digital I/O should never be connected to an analogue signal. Such voltagemay bias the digital input buffer into its linear range and the resulting largecurrent could cause irreversible damage.[B3]

The 10-bit ADC uses a technique know as successive approximation, thefollowing mechanical analogy will help explain how it works. Suppose there is an

unknown weight, a balance scale and a set of precision known weights 1, 2, 4and 8 grams. A systemic technique can be used to calculate the unknownweight.

Place the 8g weight on the pan and remove if it is too heavy. Next place the 4gweight on the pan and remove if it is too heavy. Next place the 2g weight on thepan and remove if it is too heavy. Next place the 1g weight on the pan andremove if it is too heavy. The sum of the weights still on the pan yields thenearest lower value of the unknown weight. This is illustrated in figures 4.2b to4.2g.

Figure 4.2b. Unknown weight placed on the scales Figure 4.2c. 8g weight placed on the pan, not too heavy


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Figure4.2d. 4g weight placed on thepan, Figure 4.2e. 2gweightplaced on the pan, not too heavytoo heavy (remove)

Figure 4.2f. 1g weight placed on the pan, Figure 4.2g. Unknown weight is about 10g (1010)too heavy (remove)

The electronic equivalent to this successive approximation technique uses anetwork of precision capacitors configured to allow consecutive halving of a fixedvoltage VREF to be switched in to an analogue comparator, which acts as thebalance scale.

Generally the network of capacitors are valued in powers of two to subdivide the

analogue reference voltage (e.g. 1,2,4,8,16, etc). This sampling acquisitionprocess takes a finite time due to the charging time constant and is specified inthe datasheet as 19.72S.


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Overview of the Hardware USART

The Universal Synchronous Asynchronous Receiver Transmitter (USART)

module is one of the two serial I/O modules. The USART can be configured forasynchronous operation (UART) for communication with a PC or synchronousoperation for communicating with peripheral devices such as DAC or DACintegrated circuit.

Note bit SPEN (RCSTA:7) and bits TRISC:7..6 have to be set in order toconfigure pin PC6/TX/CK and RC7/RX/DT for USART operation. CSS (Ccompiler) will automatically configure these bits, but it is important to be awarethat if using fast_io(C) mode to manually configure port C, bits 7 & 6 must also bemanually set if using the hardware UART.

Baud-Rate Generator, BRG

This is basically a programmable 8-bit counter followed by a switchable

frequency flip flop chain which can be set up to give the appropriate samplingand shifting rates for the desired baud rate, based on the PICs crystal frequencyXTAL (e.g. for 20MHz, XTAL = 20) giving: -

{4.3.1.1}

{4.3.1.2}

{4.3.1.3}

It may be advantageous to use the high baud rate (BRGH = 1) even for slowerbaud clocks as this may reduce baud rate error in some cases.


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ADVANTAGES OF MICRO CONTROLLER:

Micro controller based system require less hard ware pcb size and cost is

less. Access time of on chip memory is less so speed of operation is more.

Less flexible.

Hard ware requirement is less.

More number of pins are multifunctional.

More number of bit handling instruction.

Less number of instruction refers to memory.

It consists of I/O ports, Memory,Timmer,Counter along with microprocessor circuit.


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5.1 Circuit Diagram:


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5.2 Circuit operation:

Analog signals obtained form C.T and P.T are connected to RA0 and RA1. These

voltages are proportional to AC mains voltage and the load current. This voltage is scaled

in such a way that the analog value will not exceed +5volts since this is the maximum

voltage microcontroller can handle. We have connected a zener diode of 5.1volts across

the preset so that even if the analog voltage increases the zener diode will not conduct

beyond 5.1v and thus protect the Microcontroller chip from damage. These analog

voltages are connected to mux. The channel select lines will select only one analog input

at a time and transfers analog voltage to input of 10 bit successive approximation ADC.

The channel number is selected in ADCONO register. Start of conversion is sent on GO

bit of ADCONO to start conversion process. When the conversion is complete this line

GO/DONE becomes zero and transfers the digital value in ADRES register CONVO this

value is saved in to data memory for processing.

The same operation is done for second analog input also by selecting channel lines. The

digital values are stored in to data memory CONV1 for further processing. The value

present in CONVO register is compared with pre determined min-max value to check for

under voltage and over voltage condition. If the digital value is below the minimum orbeyond the Max it indicates under voltage and over voltage indicator. The value of

CONV1 is checked for reference value which indicates Max load current if the value of

CONV1 exceeds this Max limit it indicates the overload condition.

The values of CONV0 and CONV1 indicate the voltage and current.

These values are processed by the software to calculate the energy consumed by the user

at that instant of time as the values of CONV0 and CONV1 changes the amount of

energy consumed will also change and indicate the same in display unit.

The key pad interfaced to microcontroller consisting of 16 keys, this is used for

recharging process.. In this 4 lines of Port D is used as scan lines i.e., RD0-RD3 and

remaining 4 lines are used as return lines i.e., RD4-RD7.This keyboard is designed so as

to form a matrix of rows and columns. When a key is pressed the contact gets closed and

generates a high signal to the controller. Finally, it is the function of the microcontroller


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to scan the keyboard continuously to detect and identify the key pressed.When a key is

pressed in the keypad the software will scan the key code & store the corresponding

value into register file of RAM. This value indicates the character to be printed.

Depending on the inputted character microcontroller will issue binary combination to

stepper motors for printing the character is specified by the keypad entry. 4X4 keypad is

used to enter the pass word & other details of the alphanumeric character . It consists of

16 push to on switches.

We are using 16f877 microcontroller in our project. We are using port A as input

port, Rc4-Rc7 as input ports. Port B, Rc0-Rc3 and port D lines are used as output ports.

The driving capability of each port is 25mA.we can use each pin of each port as either

input port or output port. It also has watchdog timer, power up timer, power on

reset,oscillator,start up timer,ICD(in circuit debugger),LVP(low voltage

programming),three timers, the CCP(compare,capture&PWM

modules),EEPROM,8kX14 program memory,368 byte data memory, parallel slave port

etc.

We are using power supply unit constructed by using 12-0-12, 1A transformer.

The secondary voltage is applied to rectifier to convert AC to DC and then applied to

capacitor filter to get pure DC. This unregulated 12 volts DC voltage is connected to

relay circuit.The unregulated voltage is given to 7805 regulator IC to get +5v respectively

from the power supply unit. These voltages are applied to microcontroller,

buffer,relay,display driver & other circuitry as shown in circuit diagram

The software of our project will perform the entire operation one after

the other. This software is designed by using a window based software

microprocessor lab (MPLAB) and stored in to program memory of

microcontroller using programmer. This software can be modified easily to

suit the demands of the system.


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CURRENT TRANSFORMER (C.T):

Input turns =9 Turns, Gauge =18 S.W.G

Secondary =228 Turns, Gauge =32 S.W.G, Shell type

Maximum Input Current=10 A.

Current Transformer is connected in series to the lines. It is used to transform the high

current of a power line to a lower value of suitable voltage. The Primary winding has less

number of turns, which is constructed by using thick conductor to handle more current

and secondary winding is made of thin conductor with more number of turns.


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Initialize the Scratch CardNumber

Initialize Counters and Data

Check For Over Voltage

Start

Initialize GPRS & SFRS

Display

ADC Routine

IsVoltage

>240vDisplay High

Voltage

Voltage OK

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40

Turn on Buzzer &Turn off Load

Delay

Delay

Enter Scratch Card Number

Check Whether CardNumber Is Valid Or Not

Is CardNumber Valid

Display Not A ValidNumber

Display a ValidNumber

Display Amount OfPower Which Can Be

Utilized

Turn On Load

Measure thePower Consumed

DisplayEnergy Consumed


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No

Yes

No


41

Display over Load

Is LoadCurrent

MaximumValue

Delay

Compare the LoadCurrent

Turn on Buzzer

Turn Off Load

Load Current OK

Is MoreThan TenUnits


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Display Ten UnitsRemaining and

Request ToRecharge

Is 00Units

42

DisplayValidity Over

Turn On Buzzer &Turn Off Load

Delay


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DELAY SUBROUTINE:


43

NO

Star

t

Is

Z=1

Clear watchdog timer initialize

temp register with 02

Initialize Step register with 10

Initialize FMS with Count

Is Z=1

Decrement temp by one and check for zero

Decrement step by one and check for zero

Is

Z=1

Return

YES

YES

NO

Decrement FMS by 1 check for zero result

Call monitor program to generate specific delay

NO

YES


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A D C ROUTINE

6.2 PROGRAMS


44

YES

Star

t

Configure Port A pins as analog Input pins

Select A/D input channel and turn on ADC

Select A/D Conversion clock

Issue start of conversion on GO bit and ADCONO

Wait for Conversion

Check for end of conversion by polling GO/DONE for zero

Isconversion

complete

Return

Read A/D result register for converted data memory

Save the contents into data memory

NO


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;project :pic based theft control system;Timebase:Crystal;Frequency:4 Mhz;device used : 16F877

;oscillator :xt;Watchdog :On

;------------------------------------------------

title" pic based theft control system"list p=16F877

;-----------------------------------------------timing EQU 01htmr0 equ 01h

pcl equ 02hstatus equ 03hfsr equ 04hporta equ 05hportb equ 06hportc equ 07hportd equ 08hporte equ 09hADCON1 equ 9fhADCON0 equ 1fh;---------------------------------------------------------

ram registersregreg1reg2tempdeldigitcountflags

msecondthridelytenhighermsblsblower


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convconv1high3high4high2

high1stepstep1stdeltdelnstep1estep1

;------------------------------------------------

org 00hgoto begin

begin;---------------------------------------------------------

clrf portaclrf portbclrf portcclrf portdclrf porte

goto start

seglut addwf pcl,1retlw 0b7hretlw 014hretlw 073hretlw 076hretlw 0d4hretlw 0e6hretlw 0e7hretlw 034h

retlw 0f7hretlw 0f6hretlw 00h

start

bsf status,5 ;select bank 1movlw 03fh ;port A < 0:4 > output


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movwf porta ;configure port Amovlw 00h ;port B < 0: 7 > outputmovwf portb ;configure port Bmovlw 00hmovwf portc

movlw 00hmovwf portdmovlw 00hmovwf portebcf status,5

;-------------------------------------------movlw 0fhmovwf high4movlw 0ahmovwf high3

movlw 015hmovwf high2movlw 0ahmovwf high1movlw 01hmovwf msbmovlw 0ahmovwf lsbcall displaycall onesec ;delaymovlw 016h

movwf high4movlw 00hmovwf high3movlw 05hmovwf high2movlw 0dhmovwf high1movlw 01hmovwf msbmovlw 0ahmovwf lsb

call displaycall onesec

;1--------------------------------------------------------------see1; call onesec

movlw 01movwf time1nop


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nopnopmovlw 01movwf time2nop

nopmovlw 01movwf time3nopnopmovlw 01movwf time4nop

devtop1 movlw 0ehmovwf high4

movlw 0fhmovwf high3movlw 019hmovwf high2movlw 0ahmovwf high1movlw 01hmovwf msbmovlw 0ahmovwf lsbcall display

call onesec ;delaymovlw 00hmovwf high4movlw 019hmovwf high3movlw 0fhmovwf high2movlw 015hmovwf high1movlw 0ahmovwf msb

movlw 0ahmovwf lsbcall displaycall onesecnopnopbtfsc portc,2goto devtop1


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topp1 nopnopbtfss porta,3call incr1nop

nopbtfss porta,0call decr1nopnopbtfss porta,1goto nextdev2nopnopgoto topp1

incr1 incf time1movlw 0ahcall seglutmovwf high4movwf high3movwf high2movwf high1movwf msbmovf time1,0call convert ;displayreturn

decr1decf time1

movlw 0ahcall seglutmovwf high4movwf high3movwf high2movwf high1movwf msbmovf time1,0

call convert ;displayreturn

;2------------------

nextdev2 movlw 016hmovwf high4movlw 0bhmovwf high3


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movlw 05hmovwf high2movlw 05hmovwf high1movlw 0ah

movwf msbmovlw 0ahmovwf lsbcall displaycall onesec

devtop2 movlw 0ehmovwf high4movlw 0fhmovwf high3

movlw 019hmovwf high2movlw 0ahmovwf high1movlw 02hmovwf msbmovlw 0ahmovwf lsbcall displaycall onesec ;delaymovlw 0ch

movwf high4movlw 014hmovwf high3movlw 00hmovwf high2movlw 015hmovwf high1movlw 0ahmovwf msbmovlw 0ahmovwf lsb

call displaycall onesecnopnopbtfsc porta,2goto devtop2

topp2 btfss porta,3call incr2


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btfss porta,0call decr2btfss porta,1goto nextdev3goto topp2

incr2 incf time2movlw 0ahcall seglutmovwf high4movwf high3movwf high2movwf high1movwf msbmovf time2,0call convert ;displayreturn

decr2 decf time2movlw 0ahcall seglutmovwf high4movwf high3movwf high2movwf high1movwf msbmovf time2,0call convert ;displayreturn

;3---------------------------------------nextdev3 movlw 016h

movwf high4movlw 0bhmovwf high3movlw 05hmovwf high2movlw 05hmovwf high1movlw 0ah

movwf msbmovlw 0ahmovwf lsbcall displaycall onesec

devtop3 movlw 0eh


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movwf high4movlw 0fhmovwf high3movlw 019hmovwf high2

movlw 0ahmovwf high1movlw 03hmovwf msbmovlw 0ahmovwf lsbcall displaycall onesec ;delaymovlw 0dhmovwf high4movlw 014h

movwf high3movlw 0fhmovwf high2movlw 0bhmovwf high1movlw 015hmovwf msbmovlw 0ahmovwf lsbcall displaycall onesec

btfsc porta,2goto devtop3

topp3 nopbtfss porta,3call incr3btfss porta,0call decr3btfss porta,1goto nextdev4goto topp3

incr3 nopnopincf time3

nopnopmovlw 0ahcall seglutmovwf high4


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movwf high3movwf high2movwf high1movwf msbmovf time3,0

call convert ;displayreturn

decr3 decf time3movlw 0ahcall seglutmovwf high4movwf high3movwf high2movwf high1movwf msb

movf time3,0call convert ;displayreturn

;4------------------------------------nextdev4 movlw 016h

movwf high4movlw 0bhmovwf high3movlw 05hmovwf high2movlw 05h

movwf high1movlw 0ahmovwf msbmovlw 0ahmovwf lsbcall displaycall onesec

devtop4 movlw 0ehmovwf high4movlw 0fh

movwf high3movlw 019hmovwf high2movlw 0ahmovwf high1movlw 04hmovwf msbmovlw 0ah


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movwf lsbcall displaycall onesec ;delaymovlw 0ehmovwf high4

movlw 017movwf high3movlw 01hmovwf high2movlw 014hmovwf high1movlw 0ahmovwf msbmovlw 0ahmovwf lsbcall display

call onesecnopnopbtfsc porta,2goto devtop4

topp4 nopnopbtfss porta,3call incr4nopnop

btfss porta,0call decr4nopnopbtfss porta,1goto nextdev5nopnopgoto topp4

incr4 nop

nopincf time4nopnopmovlw 0ahcall seglutmovwf high4movwf high3


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movwf high2movwf high1movwf msbmovf time4,0call convert ;display

nopnopreturn

decr4 nop

nopdecf time4nopmovlw 0ahcall seglutmovwf high4

movwf high3movwf high2movwf high1movwf msbnopnopmovf time4,0call convert ;displaynopnopreturn


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7.1 ADVANTAGES

It is easy to operate, oneremaining

while some units. Inform to recharge before the disconnection.

It is rugged and reliable.

Protects an authorized usage of power.

Reduces the burden of vigilance system.

DIS-ADVANTAGES

It has limited memory size and hence less numbers can be saved

It is desired for single phase system.

APPLICATIONS

It can be used in houses, shops,banks hospitals and institutions. It can be used in commercial applications like small scale and medium

scale and large scale industries.


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7.2 CONCLUSION:

The project MICRO CONTROLLER based prepaid energy meter withover voltage protection is working satisfactorily for different test conditions. Theperformance of the project can be improved by using hall ticket current relays forheavy loads and protecting the system from over load short circuit by providingelectric circuit breaker conditions. The same unit can be used to design 3 phaseenergy meter by making small modifications in the circuit.It can be designed toprevent power theft and unauthorized usage.


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7.3 BIBILIOGRAPHY

Books:

1. Industrial and power electronics; devices, circuits, systems and application by

Harish .C. Rai, umesh publication, 10th edition.

2. OP-AMPs and Linear integrated circuits, Ramakant .A.Gayakwad, pearson

education, 4th edition.

3. Design with PIC microcontrllers, John.B.Peatman

4. The 8051 Microcontrroller and embedded system by Muhammad Ali Mazidi and

Janice Gillespie Mazidi,Low price edition

5. Electrical Machine design by A.K.Sawhney.

6. Microprocessor and TTL hand Book, B.P.B publication.

7. Power Electronics by Rashid.

Web sites:

1. www.google.com2. www.fairchildsemicondutor.com

3. www.microchip.com

4. www.electronicprojects.com

5. www.ieeexplore.org


58
http://www.google.com/http://www.fairchildsemicondutor.com/http://www.microchip.com/http://www.electronicprojects.com/http://www.ieeexplore.org/http://www.google.com/http://www.fairchildsemicondutor.com/http://www.microchip.com/http://www.electronicprojects.com/http://www.ieeexplore.org/


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7.4 APPENDIX


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VOLTAGE AND OVERLOAD PROTECTION SYSTEM72

RFID Project

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