Final Project File Meenal

7/31/2019 Final Project File Meenal

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DIGITAL CODE LOCK SYSTEM MEENAL

CHAPTER.1

INTRODUCTION

Security is a prime concern in our day-today life. Everyone wants to be as

much secure as possible. An access control for doors forms a vital link in a

security chain. The microcontroller based digital lock for Doors is an access

control system that allows only authorized persons to access a restricted

area. The system is fully controlled by the 8 bit microcontroller AT8051

which has a 2Kbytes of ROM for the program memory. The password is

stored in the EPROM so that we can change it at any time. The system has a

Keypad by which the password can be entered through it. When the entered

password equals with the password stored in the memory then the relay gets

on and so that the door is opened. If we entered a wrong password for more

than three times then the Alarm is switched on.

INSTRUMENTATION ENGG.[Type text] Page 1


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BLOCK DIAGRAM

Fig.1



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BLOCK DESCRIPTION

1. KEYPAD: The input is taken from a 4x3 Keypad .Keypad has 12 keys

(4x3) starting from 1,2,3,4,5,6,7,8,9,*,0,# (please see the schematic for layout).

Numeric keys are used for entering numbers. '*' is used as the Cancel key and

'#' is used as the Enter key.

2. MICROCONTROLLER: The controller is the heart of the circuit.

It is used to do all the programming of the circuit.

3. RELAY:It is used as a switch. It functions according to the controller

output.

4. LCD: - The output is displayed over the LCD Screen.



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CIRCUIT DIAGRAM

Fig.2



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CIRCUIT DESCRIPTION

1. KEYPAD MATRIX:

Keypad has 12 keys (4x3) starting from 1,2,3,4,5,6,7,8,9,*,0,# (please see the schematic for

layout). Numeric keys are used for entering numbers. '*' is used as the Cancel key and '#' is

used as the Enter key.

2. MICROCONTROLLER:-

The controller is used to do all the programming. It has the following features:-

It provides many functions (CPU, RAM, ROM, I/O, interrupt logic, timer, etc.) in a

singlepackage

8-bit ALU, Accumulator and 8-bit Registers; hence it is an 8-bit microcontroller

8-bit data bus - It can access 8 bits of data in one operation

16-bit address bus - It can access 216 memory locations - 64 KB (65536 locations)

each of RAM and ROM

On-chip RAM - 128bytes (data memory)

On-chip ROM - 4 Kbytes (program memory)

Fourbyte bi-directional input/outputport

http://en.wikipedia.org/wiki/Central_processing_unithttp://en.wikipedia.org/wiki/Random_access_memoryhttp://en.wikipedia.org/wiki/Read-only_memoryhttp://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Interrupthttp://en.wikipedia.org/wiki/Timerhttp://en.wikipedia.org/wiki/Integrated_circuit_packaginghttp://en.wikipedia.org/wiki/8-bithttp://en.wikipedia.org/wiki/Microcontrollerhttp://en.wikipedia.org/wiki/Data_bushttp://en.wikipedia.org/wiki/Address_bushttp://en.wikipedia.org/wiki/Kilobytehttp://en.wikipedia.org/wiki/Byteshttp://en.wikipedia.org/wiki/Bytehttp://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Central_processing_unithttp://en.wikipedia.org/wiki/Random_access_memoryhttp://en.wikipedia.org/wiki/Read-only_memoryhttp://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Interrupthttp://en.wikipedia.org/wiki/Timerhttp://en.wikipedia.org/wiki/Integrated_circuit_packaginghttp://en.wikipedia.org/wiki/8-bithttp://en.wikipedia.org/wiki/Microcontrollerhttp://en.wikipedia.org/wiki/Data_bushttp://en.wikipedia.org/wiki/Address_bushttp://en.wikipedia.org/wiki/Kilobytehttp://en.wikipedia.org/wiki/Byteshttp://en.wikipedia.org/wiki/Bytehttp://en.wikipedia.org/wiki/Input/output


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UART (serial port)

Two 16-bit Counter/timers

Two-level interrupt priority

Power saving mode

A particularly useful feature of the 8051 core is the inclusion of a Boolean processing

engine which allows bit-level Boolean logic operations to be carried out directly and

efficiently on internal registers and RAM. This feature helped cement the 8051's popularity

in industrial control applications. Another valued feature is that it has four separate register

sets, which can be used to greatly reduce interrupt latency compared to the more common

method of storing interrupt context on a stack.

The 8051 UARTs make it simple to use the chip as a serial communications interface.

External pins can be configured to connect to internal shift registers in a variety of ways,

and the internal timers can also be used, allowing serial communications in a number of

http://en.wikipedia.org/wiki/Serial_porthttp://en.wikipedia.org/wiki/Timerhttp://en.wikipedia.org/wiki/Interrupthttp://en.wikipedia.org/wiki/Power_managementhttp://en.wikipedia.org/wiki/Boolean_datatypehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Boolean_logichttp://en.wikipedia.org/wiki/Processor_registershttp://en.wikipedia.org/wiki/Interrupt_latencyhttp://en.wikipedia.org/wiki/Context_switchhttp://en.wikipedia.org/wiki/UARThttp://en.wikipedia.org/wiki/Serial_porthttp://en.wikipedia.org/wiki/Timerhttp://en.wikipedia.org/wiki/Interrupthttp://en.wikipedia.org/wiki/Power_managementhttp://en.wikipedia.org/wiki/Boolean_datatypehttp://en.wikipedia.org/wiki/Bithttp://en.wikipedia.org/wiki/Boolean_logichttp://en.wikipedia.org/wiki/Processor_registershttp://en.wikipedia.org/wiki/Interrupt_latencyhttp://en.wikipedia.org/wiki/Context_switchhttp://en.wikipedia.org/wiki/UART


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modes, both synchronous and asynchronous. Some modes allow communications with no

external components. A mode compatible with an RS-485 multi-point communications

environment is achievable, but the 8051's real strength is fitting in with existing ad-hoc

protocols (e.g., when controlling serial-controlled devices).

Once a UART, and a timer if necessary, have been configured, the programmer needs only

to write a simple interrupt routine to refill the send shift register whenever the last bit is

shifted out by the UART and/or empty the full receive shift register (copy the data

somewhere else). The main program then performs serial reads and writes simply by

reading and writing 8-bit data to stacks.

8051 based microcontrollers typically include one or two UARTs, two or three timers, 128

or 256 bytes of internal data RAM (16 bytes of which are bit-addressable), up to 128 bytes

of I/O, 512 bytes to 64 kB of internal program memory, and sometimes a quantity of

extended data RAM (ERAM) located in the external data space. The original 8051 core ran

at 12 clock cycles per machine cycle, with most instructions executing in one or two

machine cycles. With a 12 MHz clock frequency, the 8051 could thus execute 1 million

one-cycle instructions per second or 500,000 two-cycle instructions per second. Enhanced

8051 cores are now commonly used which run at six, four, two, or even one clock per

machine cycle, and have clock frequencies of up to 100 MHz, and are thus capable of an

even greater number of instructions per second. All SILabs, some Dallas and a few Atmel

devices have single cycle cores.

Common features included in modern 8051 based microcontrollers include built-in reset

timers with brown-out detection, on-chip oscillators, self-programmable Flash ROM

program memory, boot loader code in ROM, EEPROM non-volatile data storage, IC, SPI,

and USB host interfaces, CAN orLINbus, PWM generators, analog comparators, A/D and

D/A converters, RTCs, extra counters and timers, in-circuit debugging facilities, more

interrupt sources, and extra power saving modes.

http://en.wikipedia.org/wiki/EIA-485http://en.wikipedia.org/wiki/UARThttp://en.wikipedia.org/wiki/RAMhttp://en.wikipedia.org/wiki/Input/Outputhttp://en.wikipedia.org/wiki/Clock_frequencyhttp://en.wikipedia.org/wiki/Flash_ROMhttp://en.wikipedia.org/wiki/I%C2%B2Chttp://en.wikipedia.org/wiki/Serial_Peripheral_Interfacehttp://en.wikipedia.org/wiki/USBhttp://en.wikipedia.org/wiki/Controller%E2%80%93area_networkhttp://en.wikipedia.org/wiki/LINhttp://en.wikipedia.org/wiki/Pulse-width_modulationhttp://en.wikipedia.org/wiki/Analog_to_digital_converterhttp://en.wikipedia.org/wiki/Digital_to_analog_converterhttp://en.wikipedia.org/wiki/Real-time_clockhttp://en.wikipedia.org/wiki/EIA-485http://en.wikipedia.org/wiki/UARThttp://en.wikipedia.org/wiki/RAMhttp://en.wikipedia.org/wiki/Input/Outputhttp://en.wikipedia.org/wiki/Clock_frequencyhttp://en.wikipedia.org/wiki/Flash_ROMhttp://en.wikipedia.org/wiki/I%C2%B2Chttp://en.wikipedia.org/wiki/Serial_Peripheral_Interfacehttp://en.wikipedia.org/wiki/USBhttp://en.wikipedia.org/wiki/Controller%E2%80%93area_networkhttp://en.wikipedia.org/wiki/LINhttp://en.wikipedia.org/wiki/Pulse-width_modulationhttp://en.wikipedia.org/wiki/Analog_to_digital_converterhttp://en.wikipedia.org/wiki/Digital_to_analog_converterhttp://en.wikipedia.org/wiki/Real-time_clock


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3. RELAY:

A relay is an electrically operated switch. Many relays use an electromagnet to operate a

switching mechanism, but other operating principles are also used. Relays find applications

where it is necessary to control a circuit by a low-power signal, or where several circuits

must be controlled by one signal. The first relays were used in long distance telegraph

circuits, repeating the signal coming in from one circuit and re-transmitting it to another.

Relays found extensive use in telephone exchanges and early computers to perform logical

operations. A type of relay that can handle the high power required to directly drive an

electric motor is called a contactor. Solid-state relays control power circuits with no

moving parts, instead using a semiconductor device triggered by light to perform

switching. Relays with calibrated operating characteristics and sometimes multiple

operating coils are used to protect electrical circuits from overload or faults; in modern

electric power systems these functions are performed by digital instruments still called

"protection relays".

http://en.wikipedia.org/wiki/Electrichttp://en.wikipedia.org/wiki/Switchhttp://en.wikipedia.org/wiki/Contactorhttp://en.wikipedia.org/wiki/Electrichttp://en.wikipedia.org/wiki/Switchhttp://en.wikipedia.org/wiki/Contactor


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A relay is an electrically operated switch.

Current flowing through the coil of the relay

creates a magnetic field which attracts a lever and

changes the switch contacts. The coil current can

be on or off so relays have two switch positions

and most have double throw (changeover)

switch contacts as shown in the diagram.

Relays allow one circuit to switch a second

circuit which can be completely separate from the

first. For example a low voltage battery circuit

can use a relay to switch a 230V AC mains

circuit. There is no electrical connection inside

the relay between the two circuits, the link is

magnetic and mechanical.

The coil of a relay passes a relatively large

current, typically 30mA for a 12V relay, but itcan be as much as 100mA for relays designed to

operate from lower voltages. Most ICs (chips)

cannot provide this current and a transistor is

usually used to amplify the small IC current to the larger value required for the relay coil.

The maximum output current for the popular 555 timer IC is 200mA so these devices can

supply relay coils directly without amplification.

Relays are usually SPDT or DPDT but they can have many more sets of switch contacts,

for example relays with 4 sets of changeover contacts are readily available. For further

information about switch contacts and the terms used to describe them please see the page

on switches.


Circuit symbol for a relay

Relays

Relay showing coil and switch contacts
http://www.kpsec.freeuk.com/trancirc.htm#ichttp://www.kpsec.freeuk.com/trancirc.htm#ichttp://www.kpsec.freeuk.com/components/switch.htmhttp://www.kpsec.freeuk.com/components/switch.htmhttp://www.kpsec.freeuk.com/trancirc.htm#ichttp://www.kpsec.freeuk.com/components/switch.htm


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Most relays are designed for PCB mounting but you can solder wires directly to the pins

providing you take care to avoid melting the plastic case of the relay.

The supplier's catalogue should show you the relay's connections. The coil will be obvious

and it may be connected either way round. Relay coils produce brief high voltage 'spikes'

when they are switched off and this can destroy transistors and ICs in the circuit. To

prevent damage you must connect aprotection diode across the relay coil.

The animated picture shows a working relay with its coil and switch contacts. You can see

a lever on the left being attracted by magnetism when the coil is switched on. This lever

moves the switch contacts. There is one set of contacts (SPDT) in the foreground and

another behind them, making the relay DPDT.

The relay's switch connections are usually labeled COM, NC and NO:

COM = Common, always connect to this; it is the moving part of the switch.

NC = Normally Closed, COM is connected to this when the relay coil is off.

NO = Normally Open, COM is connected to this when the relay coil is on.

Connect to COM and NO if you want the switched circuit to be on when the relay

coil is on.

Connect to COM and NC if you want the switched circuit to be on when the relay

coil is off.

CHAPTER 2

LIQUID CRYSTAL DISPLAY

http://www.kpsec.freeuk.com/components/relay.htm#protect%23protecthttp://www.kpsec.freeuk.com/components/relay.htm#protect%23protect


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LCD:

Liquid Crystal Displays (LCD)

These components are specialized for being used with the microcontrollers, which means

that they cannot be activated by standard IC circuits. They are used for writing different

messages on a miniature LCD.

Amodel described here is for its low price and great possibilities most frequently used in

practice. It is based on the HD44780 microcontroller (Hitachi) and can display messages in

two lines with 16 characters each . It displays all letters of alphabet, greek letters,

punctuation marks, mathematical symbols etc. In addition, it is possible to display symbols

that user makes up on its own. Automatic shifting message on display (shift left and right),

appearance of the pointer, backlight etc. are considered as useful characteristics.

Pins Functions

There are pins along one side of the small printed board used for connection to the

microcontroller. There are total of 14 pins marked with numbers (16 in case the

background light is built in). Their function is described in the table bellow:

Function Pin Name Logic Description



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Number State

Ground 1 Vss - 0V

Power supply 2 Vdd - +5V

Contrast 3 Vee - 0 Vdd

Control of

operating

4 RS0

1

D0 D7 are interpreted ascommands

D0 D7 are interpreted as data

5 R/W0

1

Write data (from controller to

LCD)

Read data (from LCD to

controller)

6 E

0

1

From 1 to

0

Access to LCD disabled

Normal operating

Data/commands are transferred to

LCD

Data / commands

7 D0 0/1 Bit 0 LSB

8 D1 0/1 Bit 1

9 D2 0/1 Bit 2

10 D3 0/1 Bit 3

11 D4 0/1 Bit 4

12 D5 0/1 Bit 5

13 D6 0/1 Bit 6

14 D7 0/1 Bit 7 MSB

Tab.1

LCD screen



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LCD screen consists of two lines with 16 characters each. Each character consists of 5x8 or

5x11 dot matrix. This book covers 5x8 character display because it is commonly used.

Contrast on display depends on the power supply voltage and whether messages are

displayed in one or two lines. For that reason, variable voltage 0-Vdd is applied on pin

marked as Vee. Trimmer potentiometer is usually used for that purpose. Some versions of

displays have built in backlight (blue or green diodes). When used during operating, a

resistor for current limitation should be used (like with any LE diode).



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LCD Memory

There are three memory blocks inside the display:

DDRAM Display Data RAM CGRAM Character Generator RAM

CGROM Character Generator ROM

DDRAM Memory

DDRAM memory is used for storing characters that should be displayed. The size of this

memory is sufficient for storing 80 characters. One part of these locations is directly

connected to the characters on display.

All functions quite simply: it is sufficient to configure display so that addresses are

automatically incremented (shift right). Afterwards it sets starting value for the message

that should be displayed (for example 00 hex).

After that, all characters sent through lines D0-D7 will be displayed as a message we are

used to- from left to right. In this case, displaying starts from the first character in the first

line on display since the address is 00 hex. If more than 16 characters are sent, they all will

be also memorized but not visible. In order to display them, a shift command should be

used. Virtually, everything looks as if LCD display is a window which moves left-right

over memory locations with characters. In reality, that is how the affect of message

moving on the screen is obtained (from left to right or vice versa).

If cursor is on, it will appear at location which is currently addressed. In other words,

characters will appear at cursors position while the cursor is automatically moved to the



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next addressed location.

Since this is a sort of RAM memory, data can be written to and read from it. Disadvantage

is that the contents will be lost forever upon the power is off.

CGROM Memory

A map with all characters that can be displayed are written by default. Each character has

corresponding location.



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Addresses of CGROM memory locations match standard ASCII values of characters. It

means that if in a program being currently executed by the microcontroller is written send

letter P to port, the binary value 0101 0000 will appear on the port. This value is ASCII

equivalent to the letter P. When this binary number is sent to LCD, a symbol stored on

0101 0000 location in CGROM will be displayed. In other words, the letter P will be

displayed . This applies to all alphabet letters (upper- and lowercase), but not to numbers!

If one carefully looks at the map with characters in this memory, it can be seen that

addresses of all digits are shifted by 48 in comparison to the values of these digits

(address of the digit 0 is 48, of digit 1 is 49, of digit 2 is 50 etc.). For that reason and in

order to display digits correctly, each of them needs to be added a decimal number 48 prior

to being sent to LCD.

CGRAM memory

Beside being able to display all standard characters, the LCD can display symbols that user

defines on its own. It enables displaying cyrilic fonts as well as many other symbols which

fit to the frame of 5x8 dots size. RAM memory (CGRAM) in size of 64 bytes enables the

above.

The size of registers of this memory is a standard one (8 bits), but only 5 lower bits are in

use. Logic one (1) in every register represents a dimmed dot, while 8 locations considered

jointly represent one character. It is best illustrated on the figure below:



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Symbols are usually defined at the beginning of a program by simple writing zeros and

units to registers of CGRAM memory so that they form desirable shapes. In order to

display them it is sufficient to specify their address. Pay attention to the first columns in

CGROM map of characters- these are not addresses of RAM memory but symbols which

are discussed here. In this example, display 0 means - display , display 1 means -

display etc.

LCD Basic Commands

All data transferred to LCD through outputs D0-D7 will be interpreted as commands or as

data, which depends on logic state on pin RS:

RS = 1 - Bits D0 - D7 are addresses of characters that should be displayed. Built in

processor addresses built in map of characters and displays corresponding symbols.

Displaying position is determined by DDRAM address. This address is either previously

defined or the address of previously transferred character is automatically incremented.

RS = 0 - Bits D0 - D7 are commands which determine display mode. List of commands

which LCD recognizes are given in the table below:



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Command RS RW D7 D6 D5 D4 D3 D2 D1 D0Execution

Time

Clear display 0 0 0 0 0 0 0 0 0 1 1.64MsCursor home 0 0 0 0 0 0 0 0 1 x 1.64mS

Entry mode set 0 0 0 0 0 0 0 1 I/D S 40uS

Display on/off control 0 0 0 0 0 0 1 D U B 40uS

Cursor/Display Shift 0 0 0 0 0 1 D/C R/L x x 40uS

Function set 0 0 0 0 1 DL N F x x 40uS

Set CGRAM address 0 0 0 1 CGRAM address 40uS

Set DDRAM address 0 0 1 DDRAM address 40uS

Read BUSY flag (BF) 0 1 BF DDRAM address -

Write to CGRAM or DDRAM 1 0 D7 D6 D5 D4 D3 D2 D1 D0 40uSRead from CGRAM or

DDRAM1 1 D7 D6 D5 D4 D3 D2 D1 D0 40uS

I/D 1 = Increment (by 1) R/L 1 = Shift right

0 = Decrement (by 1) 0 = Shift left

S 1 = Display shift on DL 1 = 8-bit interface

0 = Display shift off 0 = 4-bit interface

D 1 = Display on N 1 = Display in two lines

0 = Display off 0 = Display in one line

U 1 = Cursor on F 1 = Character format 5x10 dots

0 = Cursor off 0 = Character format 5x7 dots

B 1 = Cursor blink on D/C 1 = Display shift

0 = Cursor blink off 0 = Cursor shift

Tab.2

Comparing to the microcontroller, LCD is an extremly slow component. Because of that It

was necessary to provide a signal which will indicate that display is ready to receive a new

data or a command following the previous one has been executed. That signal is called

busy flag and can be read from line D7. When the bit BF is cleared (BF=0), display is

ready to receive.



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LCD Connection

Depending on how many lines are used for connection to the microcontroller, there are 8-

bit and 4-bit LCD modes. The appropriate mode is determined at the beginning of the

process in a phase called initialization. In the first case, the data are transferred through

outputs D0-D7 as it has been already explained. In case of 4-bit LED mode, for the sake of

saving valuable I/O pins of the microcontroller, there are only 4 higher bits (D4-D7) used

for communication, while other may be left unconnected. Consequently, each data is sent

to LCD in two steps: four higher bits are sent first (that normally would be sent through

lines D4-D7), four lower bits are sent afterwards. With the help of initialization, LCD will

correctly connect and interprete each data received. Besides, with regards to the fact that

data are rarely read from LCD (data mainly are transferred from microcontroller to LCD)one more I/O pin may be saved by simple connecting R/W pin to the Ground. Such saving

has its price. Even though message displaying will be normally performed, it will not be

possible to read from busy flag since it is not possible to read from display.



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Luckily, solution is simple. It is sufficient to give LCD enough time to perform its task

upon sending every character or command. Since execution of the slowest command is

approximately 1.64mS, it will be quite enough to wait for approximately 2mS.

LCD Initialization

Once the power supply is turned on, LCD is automatically cleared. This process lasts for

approximately 15mS. After that, display is ready to operate. The mode of operating is set

by default. This means that:

1. Display is cleared

2. Mode

o DL = 1 Communication through 8-bit interface

o N = 0 Messages are displayed in one line



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o F = 0 Character font 5 x 8 dots

3. Display/Cursor on/off

o D = 0 Display off

o U = 0 Cursor off

o B = 0 Cursor blink off

4. Character entry

o ID = 1 Addresses on display are automatically incremented by 1

o S = 0 Display shift off

Automatic reset is mainly performed without any problems. Mainly but not always! If for

any reason power supply voltage does not reach full value in the course of 10mS, display

will start perform completely unpredictably. If voltage supply unit can not meet this

condition or if it is needed to provide completely safe operating, the process of

initialization by which a new reset enabling display to operate normally must be applied.

Algorithm according to the initialization is being performed depends on whether

connection to the microcontroller is through 4- or 8-bit interface. All left over to be done

after that is to give basic commands and of course- to display messages...

Refer to the Figure below for the procedure on 8-bit initialization:



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In case of 4-bit initialization, the procedure is as follows:



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CHAPTER 4

POWER SUPPLY

POWER SUPPLY

Fig.3

Power supply is used to drive the circuit. Inappropriate voltage will damage the entire

circuitry therefore it constitutes a very important part of the circuit.

Every electronic circuit requires power for its operation. Every function simple or complex

is controlled by the power supply. Even a little variation in voltage can damage all the

circuitry. So power supply is of prime importance in all the circuits. The power supply

which we get is a.c. operating at 220Volts.But as our electronic circuits work only on d.c.

therefore; we cannot employ direct usage of supply which we get. In order to overcome



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this, we require various process namely transformation, rectification, smoothing or filtering

and regulation. These entire process using bridge rectifiers are illustrated below:

Fig.4

Power supply is used to drive the circuit. Inappropriate voltage will damage the entirecircuitry therefore it constitutes a very important part of the circuit.

Every electronic circuit requires power for its operation. Every function simple or complex

is controlled by the power supply. Even a little variation in voltage can damage all the

circuitry. So power supply is of prime importance in all the circuits. The power supply

which we get is a.c. operating at 220Volts.But as our electronic circuits work only on d.c.

therefore; we cannot employ direct usage of supply which we get : . In order to overcome

this, we require various process namely transformation, rectification, smoothing or filtering

and regulation. All these process using bridge rectifier are illustrated below

Fig.5

Now lets study the detail of all the processes step by step.

TRANSFORMATION:-

As already discussed the supply which we get is 220V A.C. supply. In order to decrease the

magnitude of the voltage we make use of step down transformer. This transformer has



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more windings in the primary coil than in the secondary coil. So the voltage output at the

secondary is an A.C. supply with magnitude less than 220V as shown below:

Fig.6

RECTIFICATION:-

As all the electronic circuits work on DC therefore this low voltage A.C. cannot be directly

fed to our circuit. Thus a process of rectification is required. In this process, A.C. voltage is

converted into D.C. voltage using two semiconductor rectifying diodes as shown below:

Fig.7

Now as the two diodes D1 and D2 are connected in the opposite manner. Therefore one of

the diode gets forward biased during the positive half of the a.c input and other getsforward biased during the negative half of the a.c. input. Thus during the positive half cycle

rectification takes place through diode D1(diode D2 being reverse biased, cannot rectify)

and during the negative half cycle, the rectification takes place through the diode D2(diode

D1 being reverse biased, cannot rectify). But as at least one of the diode always remain in



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the conducting mode therefore both the halves of the a.c. input gets rectified and hence the

name full wave rectifier.

CHAPTER .4

SMOOTHING/FILTRATION



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The output of the rectification process is a varying D.C. As the D.C. waveform cannot be

varying so it means that rectification is not 100% efficient due to which there is still some

component of the input A.C. present in the D.C. voltage which is responsible for the

variation. So in order to remove this A.C. component we require filtration or smoothing of

the signal. This can be done using an electrolytic capacitor of 2200uf. As the capacitor

offers infinite impedance to the D.C. signal and Zero impedance to the A.C. signal

therefore, it allows the A.C. component to pass through and blocks the D.C. component.

This means it will filter out the D.C. component from the input signal. Thus the output of

the process will be a pure D.C. supply as shown below:

Fig.8

Now there is still some variation indicating that output D.C. voltage is not having constant

magnitude. This is due to the capacitor used for filtration. Its time of charging and

discharging are not equal due to which the filtration is not up to the mark. For making the

output voltage assume a constant value we need a voltage regulator.

Fig.9



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REGULATION

Voltage regulator is used for this purpose mainly from the series of 78- - of the transistor.

For getting the constant output of 5 volts we make use of 7805 voltage regulator. This

process takes place as shown below:

This completes all the processes. Now we have a constant D.C. supply with us which can

be fed to any electronic circuit without any problem

Fig.10

LIST OF COMPONENTS:-



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Tab.3

CHAPTER.5


S.No. Code Name Value Price

1. R1-R4R5

R6,R7

Resistors 10k 330 ohms

1k

25paisa

each

2. VR1 Potentiometer 10k 5

3. C1,C2

C3

C4

Capacitors 33Pf

10F

100nF

1

3

1

4. IC1

LCD1,LED2

LCD

Microcontroller

LED

LCD

AT8051

5mm

16*2

55

1

10

5. Q1

J1

J3

Crystal

Connector

connector

12MHz

3 Pin

4 pin

10

10


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Software tools

Orcad for circuit designing .We first make schematic in it. This in turn creates lay out of

PCB.

Keil for compiling. Microcontroller understands hex files. But as hex files are very

complicated therefore we make use of the software keil. Programming in keil makes use of

C or Assembly language which are easily programmable. Keil on its own converts these

files to hex files.

Proload After the formation of hex file we need to insert this hex file into the micro

controller so that it executes the program written in the keil. For this purpose we make use

of proload.

FLUX

In high-temperature metal joining processes (welding, brazing and soldering), the primary

purpose offlux is to prevent oxidation of the base and filler materials. Tin-lead solder, for

example, attaches very well to copper, but poorly to the various oxides of copper, which

form quickly at soldering temperatures. Flux is a substance which is nearly inert at room

temperature, but which becomes strongly reducing at elevated temperatures, preventing the

formation of metal oxides. Secondarily, flux acts as a wetting agent in the soldering

process, reducing thesurface tension of the molten solder and causing it to better wet out

the parts to be joined.

Fluxes currently available include water-soluble fluxes (no VOC's required for removal)

and 'no-clean' fluxes which are mild enough to not require removal at all. Performance of

the flux needs to be carefully evaluated; a very mild 'no-clean' flux might be perfectly

http://en.wikipedia.org/wiki/Flux_(metallurgy)http://en.wikipedia.org/wiki/Reducinghttp://en.wikipedia.org/wiki/Wetting_agenthttp://en.wikipedia.org/wiki/Surface_tensionhttp://en.wikipedia.org/wiki/Surface_tensionhttp://en.wikipedia.org/wiki/Volatile_organic_compoundhttp://en.wikipedia.org/wiki/Volatile_organic_compoundhttp://en.wikipedia.org/wiki/Flux_(metallurgy)http://en.wikipedia.org/wiki/Reducinghttp://en.wikipedia.org/wiki/Wetting_agenthttp://en.wikipedia.org/wiki/Surface_tensionhttp://en.wikipedia.org/wiki/Volatile_organic_compound


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acceptable for production equipment, but not give adequate performance for a poorly-

controlled hand-soldering operation.

Traditionalrosin fluxes are available in non-activated (R), mildly activated (RMA)

and activated (RA) formulations. RA and RMA fluxes contain rosin combined

with an activating agent, typically an acid, which increases the wettability of

metals to which it is

applied by removing existing oxides. The residue resulting from the use of RA flux is

corrosive and must be cleaned off the piece being soldered. RMA flux is formulated to

result in a residue which is not significantly corrosive, with cleaning being preferred but

optional.

http://en.wikipedia.org/wiki/Rosinhttp://en.wikipedia.org/wiki/Rosinhttp://en.wikipedia.org/wiki/Corrosivehttp://en.wikipedia.org/wiki/Rosinhttp://en.wikipedia.org/wiki/Corrosive


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CHAPTER .6

Soldering Tools

The only tools that are essential to solder are a soldering iron and some solder. There are,

however, lots of soldering accessories available (see soldering accessories for more

information).

Different soldering jobs will need different tools, and different temperatures too. For circuit

board work you will need a finer tip, a lower temperature and finer grade solder. You may

also want to use a magnifying glass. Audio connectors such as XLR's will require a larger

tip, higher temperature and thicker solder. Clamps and holders are also handy when

soldering audio cables.

Soldering Irons

There are several things to consider when choosing a soldering

iron.

Wattage

adjustable or fixed temperature

power source (electric or gas)

portable or bench use

I do not recommend soldering guns, as these have no temperature control and can get too

hot. This can result in damage to circuit boards, melt cable insulation, and even damage

connectors.

Wattage

It is important to realise that higher wattage does not necessarily mean hotter soldering

iron. Higher wattage irons just have more power available to cope with bigger joints. A low

wattage iron may not keep its temperature on a big joint, as it can loose heat faster than it

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can reheat itself. Therefore, smaller joints such as circuit boards require a lesser wattage

iron - around 15-30 watts will be fine. Audio connectors need something bigger - I

recommend 40 watts at least.

Temperature

There are a lot of cheap, low watt irons with no temperature

control available. Most of these are fine for basic soldering, but

if you are going to be doing a lot you may want to consider a

variable temperature soldering iron. Some of these simply have a boost button on the

handle, which is useful with larger joints, others have a thermostatic control so you can

vary the heat of the tip.

If you have a temperature controlled iron you should start at about 315-345C (600-650F).

You may want to increase this however - I prefer about 700-750F. Use a temperature that

will allow you to complete a joint in 1 to 3 seconds.

Power

Most soldering irons are mains powered - either 110/230v AC,

or benchtop soldering stations which transform down to low

voltage DC. Also available are battery and gas powered. These

are great for the toolbox, but you'll want a plug in one for your

bench. Gas soldering irons loose their heat in windy outside conditions more easily that a

good high wattage mains powered iron.

Portability

Most cheaper soldering irons will need to plug into the mains. This is fine a lot of the time,

but if there is no mains socket around, you will need another solution. Gas and battery

soldering irons are the answer here. They are totally portable and can be taken and used

almost anywhere. They may not be as efficient at heating as a good high wattage iron, but

they can get you out of a lot of hassle at times.



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If you have a bench setup, you should consider using a soldering

station. These usually have a soldering iron and desoldering iron

with heatproof stands, variable heat, and a place for a cleaning

pad. A good solder station will be reliable, accurate with its

temperature, and with a range of tips handy it can perform any

soldering task you attempt with it.

Solder

The most commonly used type of solder is rosin core. The rosin

is flux, which cleans as you solder. The other type of solder is

acid core and unless you are experienced at soldering, you

should stick to rosin core solder. Acid core solder can be tricky,

and better avoided for the beginner.

Rosin core solder comes in three main types - 50/50, 60/40 and 63/37. These numbers

represent the amount of tin and lead are present in the solder,as shown below.

Solder

Type% Tin % Lead

Melting Temp

(F)

50/50 50 50 425

60/40 60 40 371

63/37 63 37 361

Any general purpose rosin core solder will be fine.

Soldering Accessories

Soldering Iron Tips

Try to use the right size tip whenever you can. Smaller wires

and circuit boards require small fine tips, and mic cable onto an



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XLR would need a larger tip. You can get pointed tips, or flat tipped ones (sometimes

called 'spade tips'). If you have a solder station with a desolderer, you will also want a

range of desoldering tips and cleaners.

Soldering Iron Stands

These are handy to use if you are doing several or more joints. It

is a heat resistant cradle for your iron to sit in, so you don't have

to lie it down on the bench while it is hot. It really is essential if

you are planning to do a lot of bench soldering as it is only a

matter of time before you burn something (probably your elbow resting on the hot tip) if

you don't use one.

Clamps

I strongly recommend clamps of some sort. Trying to hold your

soldering iron, the solder, and the wire is tricky enough, but

when you have to hold the connector as well it is almost

impossible. The are however, adjustable clamps that can be

manipulated to hold both the connector and the wire in place so you still have two free

hands to apply the heat and the solder. These are cheap items, and I know mine have paid

for themselves many times over.

Magnifying glass

If you are doing work on PCBs (printed circuit boards) you may

need to get a magnifying glass. This will help you see the tracks

on the PCB, and unless you have exceptional sight, small chip

resistors are pretty difficult to solder on well without a

magnifying glass. Once again, they are not expensive, and some clamps come with one that

can mount on the clamp stand.



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Solder Wick

Solder wick is a mesh the you lie on a joint and heat. When it

heats up it also melts the solder which is drawn out of the joint.

It is usually used for cleaning up solder from tracks on a circuit

board, but you will need a solder sucker to clean out the holes in

the circuit board. Place the wick on the solder you want to remove then put your soldering

iron on top of the wick. The wick will heat up, then the solder will melt and flow away

from the joint and into wick.

Solder Suckers

If you don't have a solder station with desolderer, and you work

on PCB's, you are going to need one of these before too long.

They are spring loaded and suck the melted solder out of the joint. They are a bit tricky to

use, as you have to melt the solder with your iron, then quickly position the solder sucker

over the melted solder and release the spring to suck up the solder. I find solder wick to be

easier to use and more effective.

Fume Extractors

Solder fumes are poisonous. A fume extractor will suck the

fumes (smoke) into itself and filter it. An absolute must for your

health if you are setting up a soldering bench.

Preparation

Step 1: Preparation

If you are preparing the cable for a connector, I strongly

suggest you put any connector parts on now (the screw

on part of an XLR, or casing of a 1/4" jack for



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example). Get into the habit of sliding these on before you start on the cable, or else you

can bet it won't be long before you finish soldering your connector only to discover you

forgot to put the connector casing on, and have to start all over again.

Once you have all the connector parts on that you need, you will need to strip your cable.

This means removing the insulation from the end of the wire and exposing the copper core.

You can either use a wire stripper, side cutters, or a knife to do this.

The obvious tool to choose to strip a wire would be......a

wire stripper. There are many types of wire stripper, and

most of them work the same. You simply put the wire

in, and squeeze it and pull the end bit off. It will cut to a preset depth, and if you have

chosen the right depth it will cut the insulation off perfectly. It is possible to choose the

wrong depth and cut too deeply, or too shallow, but they are very easy to use.

On the other hand, some people (myself included) prefer to use a knife or side cutters. I use

side cutters for small cable and a Stanley knife for bigger cables...and although I have a

couple of wire strippers, I haven't used them for years. This may seem odd, but I've got my

side cutters and knife with me anyway, and they do the job fine.

If you are using side cutters (as shown

here), position them about 10mm (1/2

inch) from the end, and gently squeeze

the cutters into the insulation to pierce

it, but not far enough to cut the copper

strands of the core. Open the cutters slightly so you can turn the wire and pierce the rest of

the insulation. You may have to do this a few times to cut through all of the insulation, but

it is better to cut too shallow and have to turn and cut again rather than cut the core and

have to start again. Now you should be able to slide the insulation off with your cutters, or

pull it off with your fingers. This may sound a tedious method, but in no time at all you

will be able to do it in two cuts and a flick of the cutters.



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I won't explain how I use a knife to do larger cable, as I'd hate someone to slice a finger or

thumb open following my instructions. Using a sharp blade like that certainly does have it's

risks, so stick with wire cutters or side cutters if you are at all unsure.

If your connector has been used before, make sure you remove any

remnants of wire and solder from the contacts. Do this by putting

the tip of your soldering iron into the hole and flicking the solder

out when it has melted. Common Sense Alert! Please be careful

when you flick melted solder...flick it away from you.

Tinning

Step 2: Tinning

Whatever it is you are soldering, you should 'tin' both

contacts before you attempt to solder them. This coats

or fills the wires or connector contacts with solder so

you can easily melt them together.

To tin a wire, apply the tip of your iron to the wire for a

second or two, then apply the solder to the wire. The solder should flow freely onto the

wire and coat it (if it's stranded wire the solder should flow into it, and fill the wire). You

may need to snip the end off afterwards, particularly if you have put a little too much solder

on and it has formed a little ball at the end of the wire.

Be careful not to overheat the wire, as the insulation will

start to melt. On cheaper cable the insulation can 'shrink

back' if heated too much, and expose more copper core

that you intended. You can cut the wire back after you

have tinned it, but it's best simply not to over heat it.



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The larger the copper core, the longer it will take to heat up enough to draw the solder in,

so use a higher temperature soldering iron for larger cables if you can.

To tin a contact on an audio XLR connector, hold the

iron on the outside of the the contact for a second or

two, then apply the solder into the cavity of the contact.

Once again, the solder should flow freely and fill the

contact. Connectors such as jacks have contacts that are

just holes in a flat part of the connector. To tin these you

put your iron on it, and apply the solder to where the iron is touching. The solder should

flow and cover the hole.

Once you have tinned both parts, you are ready to solder them together.

Soldering

Step 3: Soldering

This step can often be the easiest when soldering audio

cables.



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You simply need to place your soldering iron onto the contact to melt the solder.

When the solder in the contact melts, slide the wire into the contact.

Remove the iron and hold the wire still while the solder solidifies again.

You will see the solder 'set' as it goes hard.

This should all take around 1-3 seconds.

A good solder joint will be smooth and shiny.

If the joint is dull and crinkly, the wire probably

moved during soldering.

If you have taken too long it will have have

solder spikes.

If it does not go so well, you may find the insulation has melted, or there is too much

stripped wire showing. If this is the case, you should desolder the joint and start again.

Cleaning Your Soldering Iron

You should clean your tip after each use. There are many cleaning solutions and the

cheapest (and some say best) is a damp sponge. Just rub the soldering iron tip on it after

each solder.

Another option is to use tip cleaner. This comes in a little pot

that you push the tip into. This works well if your tip hasn't been

cleaned for a while. It does create a lot of smoke, so it is better

not to let the tip get so dirty that you need to use tip cleaner.



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Some solder stations come with a little pad at the base of the

holder. If you have one of these, you should get into the habit of

wiping the tip on the pad each time you apply solder with it.

If you need to clean solder off a circuit board, solder wick is

what you need. You place the wick on the joint or track you

want to clean up, and apply your soldering iron on top. The

solder melts and is drawn into the wick. If there is a lot of solder

the wick will fill up, so gently pull the wick through the joint and your iron, and the solder

will flow into it as it passes.

Tips and Tricks

1. Melted solder flows towards heat.

2. Most beginning solderers tend to use too much solder and heat the joint for too

long.

3. Don't move the joint until the solder has cooled.

4. Keep your iron tip clean.

5. Use the proper type of iron and tip size.

Troubleshooting

If either of the parts you are soldering is dirty or greasy, the solder won't take (or 'stick') to

it. Desolder the joint and clean the parts before trying again.

Another reason the solder won't take is that it may not be the right sort of metal. For

example you cannot solder aluminium with lead/tin solder.

If the joint has been moved during soldering, it may look grainy or dull. It may also look

like this if the joint was not heated properly while soldering.



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If the joint was overheated the solder will have formed a spike and there will be burnt flux

residue.

CHAPTER.7

Potentiometer

Variable resistors used as potentiometers have all three

terminals connected.

This arrangement is normally used to vary voltage, for example to set the switching point

of a circuit with a sensor, or control the volume (loudness) in an amplifier circuit. If the

terminals at the ends of the track are connected across the power supply then the wiper

terminal will provide a voltage which can be varied from zero up to the maximum of the

supply.


Potentiometer Symbol


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Presets

These are miniature versions of the standard variableresistor. They are designed to be mounted directly onto the

circuit board and adjusted only when the circuit is built. For

example to set the frequency of an alarm tone or the

sensitivity of a light-sensitive circuit. A small screwdriver or similar tool is required to

adjust presets.

Presets are much cheaper than standard variable resistors so they are sometimes used in

projects where a standard variable resistor would normally be used.

Multiturn presets are used where very precise adjustments must be made. The screw must

be turned many times (10+) to move the slider from one end of the track to the other,

giving very fine control.

Preset

(open style)

Presets

(closed style)Multiturn preset

Regulator

7805 is an integrated three-terminal positive fixed linear voltage regulator. It supports an

input voltage of 7 volts to 35 volts and output voltage of 5 volts. It typically has a current

rating of 1 amp although both higher and lower current models are available. Its output

voltage is fixed at 5.0V. The 7805 also have a built-incurrent limiteras a safety feature.


Preset Symbol
http://var/www/apps/conversion/wiki/Linear_regulatorhttp://var/www/apps/conversion/wiki/Linear_regulatorhttp://var/www/apps/conversion/wiki/Voltagehttp://var/www/apps/conversion/wiki/Voltshttp://var/www/apps/conversion/wiki/Ampacityhttp://var/www/apps/conversion/wiki/Ampacityhttp://var/www/apps/conversion/wiki/Amperehttp://var/www/apps/conversion/w/index.php?title=Current_limiter&action=edithttp://var/www/apps/conversion/w/index.php?title=Current_limiter&action=edithttp://var/www/apps/conversion/wiki/Linear_regulatorhttp://var/www/apps/conversion/wiki/Voltagehttp://var/www/apps/conversion/wiki/Voltshttp://var/www/apps/conversion/wiki/Ampacityhttp://var/www/apps/conversion/wiki/Ampacityhttp://var/www/apps/conversion/wiki/Amperehttp://var/www/apps/conversion/w/index.php?title=Current_limiter&action=edit


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The 7805 will automatically reduce output current if it gets too hot. It belongs to a family

of three-terminal positive fixed regulators with similar specifications and differing fixed

voltages from 8 to 15 volts.

The last two digits represent the voltage; for instance, the 7812 is a 12-volt regulator. The78xx series of regulators is designed to work in complement with the 79xx series of

negative voltage regulators in systems that provide both positive and negative regulated

voltages, since the 78xx series can't regulate negative voltages in such a system.

The 7805 is one of the most common and well known of the 78xx series regulators, as its

small component count and medium-power regulated 5V make it useful for powering TTL.

Working:-

There are two sensors which are connected to sense the vehicle at the entry-point of the

parking. These sensors inform the microcontroller about the number of vehicles entering

into the parking area. This enables the microcontroller to keep the record of the number of

vehicles and appropriately release the control signal to indicate to the driver of the vehicle

whether there is any more space in the parking area or not. If the space is there, then the

microcontroller releases the control signal to open up the gates using stepper motor.

There are various slot sensors which will keep the record of the status of slots whether

available or not. If the slot is available, then they display the no. of the corresponding slot

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so that the driver of the vehicle becomes aware of the available slot, thus avoiding the

traffic jams within and outside the parking slot.

However, if the slot is not available they will indicate it and will not give signal to the

stepper motor to open up the gates at the entry.

CONCLUSIONS

The project DIGITAL CODE LOCK SYSTEM has been successfully designed and

tested. It has been developed by integrating features of all the hardware components used.

Presence of every module has been reasoned out and placed carefully thus contributing to

the best working of the unit. Secondly, using highly advanced ICs and with the help of

growing technology the project has been successfully implemented.



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References

www.datasheetarchive.com

www.google.com

www.wikipedia.com

www.answers.com

http://www.datasheetarchive.com/http://www.google.com/http://www.wikipedia.com/http://www.answers.com/http://www.datasheetarchive.com/http://www.google.com/http://www.wikipedia.com/http://www.answers.com/


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