41finger Print Based ATM and Locker System

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1. Abbr Abbrev evia iati tion onss


2. Abstract


3. Introduction



Biometric i.

What is Biometrics? 5


Why go for Biometrics 6


Why finger Print Biometric 8


FP Patterns 9


Block Diagram 11


Block Diagram Explanation





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Schematic Explanation 16


Hardware Components 19 a.

Microcontroller 19


FP scanner 42


MAX-232 46




Power Supply 59


LCD 74


Buzzer 77


Keypad 79


Locker system 83 i.

DC motors 83

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H-Bridge 87


Circuit description



Software Concepts







Embedded C 106





Future Scope








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www.1000projects.com www.fullinterview.com www.chetanasprojects.com SYMBOL ACC B PSW SP DPTR  DPL DPH P0 P1 P2 P3 IP IE TMOD TCON T2CON T2MOD TH0 TL0 TH1 TL1 TH2

NAME Accumulator B register Program status word Stack pointer Data pointer 2 bytes Low byte High byte Port0 Port1 Port2 Port3 Interrupt priority control Interrupt enable control Timer/counter mode control Timer/counter control Timer/counter 2 control Timer/counter mode2 control Timer/counterr 0high byte Timer/counte Timer/counterr 0 low byte Timer/counte Timer/counterr 1 high byte Timer/counte Timer/counterr 1 low byte Timer/counte Timer/counterr 2 high byte Timer/counte


Timer/counter 2 low byte Timer/counter Serial control Serial data buffer Power control


Regulated Power Supply


Finger Print

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An embedded system is a special-purpose system in which the computer  is  is completely encapsulated by or dedicated to the device or system it controls. Unlike a general-purpose computer, such as a personal a  personal computer , an embedded system  performs one or a few pre-defined tasks, usually with very specific requirements. Since the system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass produced, benefiting from economies of scale. scale.

Biometrics: What is Biometrics?

The study of automated identification, by use of physical or behavioral traits.

Physical vs. Behavioral:


 – Fingerprint  – Iris  – Ear   – Face  – Retina  – Hands •


 – Signature  – Walking gait www.1000projects.com www.fullinterview.com www.chetanasprojects.com



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 – Typing patterns •


 – Voice

Why go for Biometrics?

 Authentication – the process of verifying that a user requesting a

network resource is who he, she, or it claims to be, and vice versa.  Conventional authentication methods 

something that you have – key, magnetic card or smartcard

something that you know – PIN or password

 Biometric authentication uses personal features 

something that you are


Biometrics has no risk of 

Forgetting it

Loosing it

Getting it stolen

Getting it copied

Being used by anyone else.

Essential Properties of a Biometric


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 – Everyone should have the characteristic •


 – No two persons have the same characteristic •


 – Characteristic should be unchangeable •


 – Characteristic must be measurable

Biometric System Process Flow

Pattern Recognition

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Descri Descripti ption on an and d cla classi ssific ficati ation on of meas measure uremen ments ts ta taken ken from from  physical or mental processes

Exam Examin inat atio ion n of pa patt tter ern n cha chara ract cter eris isti tics cs

Form Formul ulat atio ion n of th thee re reco cogn gnit itio ion n sy syst stem em

Impo Import rtan antt p part art of any any bi biom omet etri ricc syst system em

Why Fingerprint biometry? 

High Universality 

A majority of the population (>96%) have legible fingerprints

More than the number of people who possess passports,

license and IDs  High Distinctiveness 

Even identical twins have different fingerprints (most  biometrics fail)

Individuality of fingerprints established through empirical evidence

High Permanence 

Fingerprints are formed in the fetal stage and remain structurally unchanged through out life.

High Performance 

One of the most accurate forms of biometrics available

Best trade off between convenience and security

High Acceptability 

Fingerprint acquisition is non intrusive. Requires no training.

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Surety over the Cards and Keypads

Against to Cards Duplication, misplacement and improper disclosure of password

No excuses for RF/Magnetic Cards forget ness

No need to further invest on the Cards Cost

No need to further manage the Cards Writing Devices

Fingerprint Patterns

Loops  – Ridge lines enter from one side and curve around to exit from the same side  – 60-65% of population

Whorls  – Rounded or circular ridge pattern  – 30-35% of population

Arches  – Ridge lines enter from one side of print and exit out the other   – 5% of population

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LCD Display Power supply Micro controller


Key pad

Finger Print Module

M A X 2 3 2

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A variable regulated power supply, also called a variable bench power supply, is

one where where you can contin continuou uously sly adjust adjust the output output vo voltag ltagee to your your requir requireme ements nts.. Varying the output of the power supply is the recommended way to test a project after  ha havi ving ng do doub uble le ch check ecked ed pa part rtss plac placem emen entt ag agai ains nstt circu circuit it dr draw awin ings gs an and d th thee pa part rtss  placement guide. This type of regulation is ideal for having a simple variable bench  power supply. Actually this is quite important because one of the first projects a hobbyist should undertake is the construction of a variable regulated power supply. While a dedicated supply is quite handy e.g. 5V or 12V, it's much handier to have a variab var iable le supply supply on hand, hand, especia especially lly for testing testing.. Most Most digita digitall logic logic circuit circuitss and  processors need a 5 volt power supply. To use these parts we need to build a regulated 5 volt source. Usually you start with an unregulated power supply ranging from 9 volts to 24 volts DC (A 12 volt power supply is included with the Beginner Kit and the Microcontroller Beginner Kit.). Kit.). To make a 5 volt power supply, we use a LM7805 voltage regulator IC.

The LM7805 is simple to use. You simply connect the positive lead of your unregulated DC power supply (anything from 9VDC to 24VDC) to the Input pin, connect the negative lead to the Common pin and then when you turn on the power, you get a 5 volt supply from the Output pin.

Finger Print Scanner:

 is an electronic device used device used to capture a digital image of image of A fingerprint sensor  is the fingerprint pattern. The captured image is called a live scan. This live scan is

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com digitally processed to features)) processed to create a biometric template (a collection of extracted features which is stored and used for matching. It supports wide range of fingerprint sensor interoperability giving you a freedom to select suitable sensor that most fits to your application. Furthermore, the fingerprint data for enrollment and verification are compatible among different sensors, even if they are based on different technologies. This feature of unification  presents application manufacturers and system integrators with much more flexibility than ever before.

MAX- 232

To allow allow compat compatibi ibility lity among among data data commun communicat ication ion equipm equipment ent made made by variou variouss manu ma nufa fact ctur ures, es, an in inte terf rfaci acing ng st stan anda dard rd calle called d RS23 RS232 2 was was set by th thee Elec Electr tron onic ic Industries Association (EIA).This RS-232 standard is used in PCs and numerous types of equipment .However, since the standard was set long before the advent of the TTL logic family, its input and output voltage levels are not TTL compatible. In RS-232 ,a 1 is represented by -3 to -25V,while a 0 bit is +3 to +25V,making -3 to +3 un undefined. defined. For this reason, to connect any RS-232 to a microcontroller system we must use voltage converters such as MAX232 to convert the TTL logic levels to the RS-232 voltage levels and vice versa.

So here we are using this MAX-232 to have compatibility between the Finger Print Scanner and microcontroller. Microcontroller:

A Micro controller consists of a powerful CPU tightly coupled with memory RAM, ROM or EPROM), various I / O features such as Serial ports, Parallel Ports, Timer/Counters, Interrupt Controller, Data Acquisition interfaces-Analog to Digital Converter Conv erter (ADC), Digital to Analo Analog g Converter Converter (ADC), everything integrated integrated onto a single Silicon Chip.

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com It does not mean that any micro controller should have all the above said features on chip, Depending on the need and area of application for which it is de desi sign gned ed,, The The ON-C ON-CHI HIP P fe featu atures res pr pres esen entt in it may may or may may no nott in incl clud udee al alll th thee individual section said above. Any micr Any microc ocom ompu pute terr syst system em requ requir ires es memo memory ry to stor storee a se sequ quen ence ce of  instructions making up a program, parallel port or serial port for communicating with an external system, system, timer / counter for control purposes purposes like generating generating time delays, Baud Bau d rate for the serial port, port, apart apart from from the controlli controlling ng unit unit called called the Central Central Processing Unit


In this project we are using two types of keypads, one is the matrix keypad and the other is the normal key for selecting the mode of operation. Here we are doing all the transactions regarding bank like deposit, withdraw, etc. for this transactions and for entering the password we are using the 4X4 Matrix keypad. Using the normal keypad we are going to select the mode which we are going to  perform.


  This is the widely used output device to indicate the status. Here the transaction details are clearly displayed on the LCD.


This is the output device which we are using to indicate the unauthorized person.


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www.1000projects.com www.fullinterview.com www.chetanasprojects.com  Here we are demonstrating a DC motor as the Locker for the authorized persons in the Locker system mode.


This is the additional memory which we are using for the storage of the data for a  particular person.


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Schematic Explanation:

This schematic explanation includes the detailed pin connections of every device with the microcontroller. Let us see the pin connections of each and every device with the microcontroller in detail.

Power Supply:

The main aim of this power supply is to convert the 230V AC into 5V DC in order to give supply for the TTL or CMOS devices. In this process we are using a step down transformer, a bridge rectifier, a smoothing circuit and the RPS. Transformer:

At the primary of the transformer we are giving the 230V AC supply. The secondary is connected to the opposite terminals of the Bridge rectifier as the input. From other set of opposite terminals we are taking the output to the rectifier. The bridge rectifier converts the AC coming from the secondary of the transformer into pulsating DC. The output of this rectifier is further given to the smoother circuit which is capacitor in our project. The smoothing circuit eliminates the ripples from the pulsating DC and gives the pure DC to the RPS to get a constant DC voltage. The RPS regulates the voltage as per our requirement.

LCD module:

This module is used to display the status of voter and the competitor. This module consists of 8 data lines D0 – D7, which are connected to the 8 pins of  port0 (P0). www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com Additionally this module is having 3 control lines namely RS, RW and EN, which are connected to the port2 higher pins P2.7, P2.6 and P2.5 respectively. And the supply connections are given from the Power supply output 7805 to the VCC and VSS pins of the LCD.

Finger Print Scanner:

The finger print scanner which we are using in this project supports the RS-232 standard voltage levels where as our microcontroller supports TTL logic levels. To interface this finger print scanner with the microcontroller we require a level converter which is MAX-232 here.


The connections from finger print scanner are: The transmission line is connected to RS-232 input section and the receiver line is connected to the RS-232 output section on the MAX-232 IC to convert these voltage levels into TTL standards. And the concerned TTL logic levels are connected to the microcontroller TXD and the RXD lines. Scan key:

To enable the microcontroller to read the finger print present at the scanner we are using a scan key. After placing the finger on the scanner press this scan key to follow the further process. Mode Keys:

The mode keys concerned to different modes are connected as: Locker key is connected to P3.4 Passport verification key is connected to P3.5 and The ATM mode key is connected to P3.6. KEYPAD:

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com The connections regarding this Keypad are given to Port1 entirely because it is a 4 X 4 matrix keypad.

Locker system:

The locker system which is a motor here is connected to P2.2 and P2.3 through HBridge, which is used to rotate the motor in bi-direction.


The data pin and the clock pin of this PROM SDA and SCL are connected to P2.0 and P2.1 respectively. Buzzer:

Here the buzzer is connected to P3.3 to indicate the wrong transaction or the wrong  passport.

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1. Micr Microc ocon ontr trol olle ler  r  2. Fi Fing nger er pri print nt sca scann nner  er  3. MAX-232 4. EEPROM 5. Power su supply 6. LCD module 7. Buzzer   8. Matr Matrix ix Keyp Keypad ad 9. Lock ocker sy syst stem em



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www.1000projects.com www.fullinterview.com www.chetanasprojects.com A Micro controller consists of a powerful CPU tightly coupled with memory RAM, ROM or EPROM), various I / O features such as Serial ports, Parallel Ports, Timer/Counters, Interrupt Controller, Data Acquisition interfaces-Analog to Digital Converter Conv erter (ADC), Digital to Analo Analog g Converter Converter (ADC), everything integrated integrated onto a single Silicon Chip. It does not mean that any micro controller should have all the above said features on chip, Depending on the need and area of application for which it is de desi sign gned ed,, The The ON-C ON-CHI HIP P fe featu atures res pr pres esen entt in it may may or may may no nott in incl clud udee al alll th thee individual section said above. Any An y micr microc ocom ompu pute terr syst system em requ requir ires es memo memory ry to stor storee a se sequ quen ence ce of  instructions making up a program, parallel port or serial port for communicating with an external system, system, timer / counter for control purposes purposes like generating generating time delays, Baud Bau d rate for the serial port, port, apart apart from from the controlli controlling ng unit unit called called the Central Central Processing Unit


In 1981,Intel corporation introduced an 8 bit microcontroller called the 8051.This microcontro micro controller ller had 128 bytes of RAM,4K bytes bytes of on-chip on-chip ROM, two timers, one serial port, and 4 ports(each 8-bits wide)all on single chip. At that time it was also referred to as a “system on a chip”.  

The 8051 is an 8-bit processor, meaning that the CPU can

work on only 8-bits of data at a time. Data larger than 8-bits has to be broken into 8 bit pieces to be processed by the CPU. The 8051 can have a maximum of 64K bytes of ROM; many manufacturers have put only 4Kbytes on chip.


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www.1000projects.com www.fullinterview.com www.chetanasprojects.com The major Features of 8-bit Micro controller ATMEL 89C51: 

8 Bit CPU optimized for control applications

Extensive Boolean processing (Single - bit Logic) Capabilities.

On - Chip Flash Program Memory

On - Chip Data RAM

Bi-directional and Individually Addressable I/O Lines

Multiple 16-Bit Timer/Counters

Full Duplex UART

Multiple Source / Vector / Priority Interrupt Structure

On - Chip Oscillator and Clock circuitry.

On - Chip EEPROM

Figure.1 Block Diagram








 4 I/O



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PO P2 P1 P3




Fig.1: Oscillator Connection.

The P89C51 provides the following standard features: 4K bytes of Flash, 128  bytes of RAM, 32 I/O lines, two 16-bit timer/counters, five vector two-level interrupt architecture, a full duplex serial port, and on-chip oscillator and clock circuitry. In ad addi diti tion on,, th thee P89C P89C51 51 is de desi sign gned ed with with st stat atic ic lo logi gicc fo forr op oper erat atio ion n do down wn to ze zero ro frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.

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Memory Organization DATA MEMORY







EA = 0

EA = 1


External 00





Fig.3 Memory Structure of the 8051.

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Memory Organization Program Memory Figure 4 shows a map of the lower part of the program memory. After  reset, rese t, the CPU begins begins execut execution ion from from locati location on 0000H. 0000H. As shown shown in fig.4, fig.4, each interrupt is assigned a fixed location in program memory. The interrupt causes the CPU to jump to that location, where it executes the service routine. External Interrupt 0, for example, is assigned to location 0003H. If External Interrupt 0 is used, its service routine must begin at location 0003H. If the interrupt is not used, its service location is available as general purpose.

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001BH 8 bytes 0013H 000BH


0003H 0000H

Fig. 4 Program Memory.

Program memory addresses are always 16 bits wide, even though the actual amount o  program memory used may be less than 64Kbytes. External program execution sacrifices two of the 8-bit ports, P0 and P2, to the function of addressing the program memory.

Data Memory

The right half of Figure 3 shows the internal and external data memory spaces available on Philips Flash microcontrollers. Fig.6 shows a hardware configuration for  accessing up to 2K bytes of external RAM. In this case, the CPU executes from internal flash. Port0 serves as a multiplexed address/data bus to the RAM, and 3 lines of Port 2 are used to page the RAM. The CPU generates RD and WR signals as needed during external RAM accesses. You can assign up to 64K bytes of external www.1000projects.com 28 www.fullinterview.com www.chetanasprojects.com


www.1000projects.com www.fullinterview.com www.chetanasprojects.com data memory. External data memory addresses can be either 1 or 2bytes wide. One byte addresses are often used in conjunction with one or more other I/O lines to page the RAM, as shown in Fig.6. Two-byte addresses can also be used, in which case the high address byte is emitted at Port2.

FFH Upper 128 80H 7FH Lower 128 00





Ports Status and control Special  bits register Timers function Registers 5 Internal Data Memory. Fig.5 Fig. Memory. Stack pointer  Accumulator  (etc)

Internal data memory addresses are always 1 byte wide, which implies an address space of only 256bytes. However, the addressing modes for internal RAM can infact accommodate 384 bytes. Direct addresses higher than 7FH access one memory space and indirect addresses higher than 7FH access a different memory space. Thus, Figure.7 shows the Upper 128 and SFR space occupying the same block of addresses, 80H through FFH, although they are physically separate entities. Figure.8 shows how the lower 128 bytes of RAM are mapped. The lowest 32 bytes are grouped into 4  banks of 8 registers. Program instructions call out these registers as R0 through R7. Two bits in the Program Status Word (PSW) select which register bank is in use. This architecture allows more efficient use of code space, since register instructions are shorter than instructions that use direct addressing.

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Fig.6 the lower 128 bytes of Internal RAM

The next 16 bytes above the register banks form a block of bit-addressable memory space. spa ce. The microc microcon ontrol troller ler instru instructi ction on set includ includes es a wide wide select selection ion of single single-bi -bitt instructions, and these instructions can directly address the 128 bits in this area. These  bit addresses are 00H through 7FH. All of the bytes in the Lower 128 can be accessed acce ssed  by either direct or indirect addressing.

REGISTERS: In the CPU, registers are used to store information temporarily. That information could be a byte of data to be processed, or an address pointing to the data to be fetched. The vast majority majority of 8051 8051 registers are 8–bit 8–bit registers. In the 8051 8051 there is only one data type: 8bits. The 8bits of a register are should in the diagram from the MSB(most significant significant bit) D7 to the LSB(least significant bit)D0. With an 8-bit data type, any data larger than 8bits must be broken into 8-bit chunks before it is  processed. Since there are a large number of registers in the 8051, we will concentrate on some of the widely used general-purpose registers and cover special registers in future chapters. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



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D7 D6 D5 D4 D3 D2 D1 D0 The most widely used registers of the 8051 are A (accumulator), B, R0, R1, R2, R3, R4, R5, R5, R6, R7, DPTR (data pointer), pointer), and PC (program counter). All of the above registers are 8-bits, except DPTR DPTR and the program program counter. The accumulator, register A, is used for all arithmetic and logic instructions.

SFRs (Special Function Registers) Among the registers R0-R7 R0-R7 are part of the 128 bytes of RAM memory . what about registers registers A,B, PSW, PSW, and DPTR? Do they also have addresses? addresses? The answer answer is yes. In the 8051, registers registers A, B, PSW PSW and DPTR are part of the group group of registers registers commonly commo nly referred to as SFR (special (special function function registers). There are many special special function funct ion registers registers and they are widely used. The SFR can be accessed by the names (which is much easier) easier) or by their addresses. addresses. For example, example, register A has address address E0h, and register B has been ignited the address F0H, as shown in table.


Name Accumulator B register Program status word Stack pointer Data pointer 2 bytes

Address 0E0H 0F0H 0D0H 81H


L Hoigwh bbyyttee Port0 Port1 Port2 Port3 Interrupt priority control Interrupt enable control Timer/counter mode control Timer/counter control Timer/counter 2 control Timer/counter m mo ode2 co control Timer/counter 0high byte Timer/counter 0 low byte

8 82 3H H 80H 90H 0A0H 0B0H 0B8H 0A8H 89H 88H 0C8H 0C9H 8CH 8AH

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com TH1 TL1 TH2 TL2 RCAP RC AP2H 2H RCAP2L SCON SBUF PCON

Timer/counter 1 high byte Timer/counter 1 low byte Timer/counter 2 high byte Timer/counter 2 low byte T/C T/C 2 ca capt ptur uree regi regist ster er high high byte byte T/C 2 ca capture re regist steer llo ow by byte Serial control Serial data buffer Power control

8DH 8BH 0CDH 0CCH 0CBH 0CBH 0CAH 98H 99H 87H


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Pin Diagram of AT89C51 Pin Description Description VCC

Pin 40 provides supply voltage to the chip. The voltage source is +5v. GND Pin 20 is the ground.

Ports 0, 1, 2 and 3

As shown in pin diagram, the four ports P0, P1, P2, and P3 each use of 8 pins, making the 8-bit ports. All the ports upon Reset are configured as input, since P0-P3 have FFH on them. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com Port 0

Port 0 occupies a total of 8 pins (pins 32-33). 32-33). It can be used for input or output. Port0 is also designated as AD0-AD7, allowin allowing g it to be used for both address and data. When connecting an 8051/31 8051/31 to an external memory, port 0 pro provides vides both address and data. The 8051 multiplexes address and data throug through h port 0 to save pins. ALE=0, it provides data D0-D7, but but when ALE=1, it has address A0-A7 A0-A7.. Therefore, ALE is used for de-multiplexing address and data with the help of a 74LS373 latch. In the 8051-based systems where there is no external memory connection, the pins of P0 must be connected externally to a 10k –ohm –ohm pull-up resistor. This is due to the fact that P0 is an Open drain, Unlike P1, P2, P2, P3. Open drain is a term used for MOS chips in the same way that open collector is used used for TTL chips. In many systems using the 8751, 89C51, or DS89C4x0 chips, we normally connect P0 to pull-up resistors. With external pull-up resistors connected connected to P0, it can be used as a simple I/O port, just like P1 and P2. In contrast to Port 0, ports p1, p2, p2, and p3 do not not need any pull-up resistors since they already have pull-up resistors internally. Upon reset,  ports p1, p2, ad p3 are configured configured as input ports. Port 1

Port 1 occupies occupies a total of 8-pins (pins1-8). (pins1-8). It can be used as input or output. output. In contrast to port 0, this port does not need any pull-up resistors since it already has  pull-up resistors internally. Upon reset, port1 is configured as an input input port. Port 2

Port 2 occupies a total 8 pins (pins 21-28). It can be used as input or output. However, in 8031-based systems, port2 is also designated as A8-A15, indicating its dual function. Since an 8051/31 8051/31 is capable of accessing 64K 64K bytes of external memory, it needs a path for the 16 bits of the address. address. While P0 provides the lower 8  bits via A0-A7, it is the job of p2 is used for for the upper 8 bits of the 16-bit address, and it cannot be used for I/O. Just like P1, port 2 does not need any pull-up resistors since it already has pull-up resistors internally. Upon reset, port2 is configured as an input input  port.

Port 3

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com Port 3 occupie occupiess a total of 8 pins pins (pins (pins 10-17). 10-17). It can be used used as input input or output. output. P3 does not need any pull-up pull-up resistors, resistors, just as P1 and P2 did not. Although Although Port 3 is configured as an input port upon reset, this is not the way it is most commonly used. Port 3 has the additional function of providing some extremely important signals such as interrupt interrupts. s. The The below below table provide providess these these alt altern ernate ate function functionss of P3.

This This is

information applies to both 8051 and 8031 chips.

Alternate Functions of PORT3

Port 3 also receives some control signals for Flash programming and verification.


Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. ALE/PROG

Prior to each reading from external memory, the microcontroller will set the lower address byte (A0-A7) on P0 and immediately after that activates the output ALE. Upon receiving signal from the ALE pin, the external register (74HCT373 or  74HCT375 circuit is usually embedded) memorizes the state of P0 and uses it as an address for memory chip. In the second part of the microcontroller’s machine cycle, a signal on this pin stops being emitted and P0 is used now for data transmission (Data Bus). In this way, by means of only one additional (and cheap) integrated circuit, data www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com multiplexing from the port is performed. This port at the same time used for data and address transmission.


Progra Pro gram m Store Store Enable Enable is the read read strobe strobe to extern external al program program memory. memory. When When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. EA/VPP

External Exter nal Access. EA must be strapped to GND in order to enable the device to fetch code from external program memory memory locations starting at 0000 0000H H up to FFFFH. FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally internally latched on reset. EA should shoul d be strapped to VCC for internal internal program executio executions. ns. This pin also receives receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP. XTAL1 and XTAL2

The 8051 has an on-chip oscillator but requires an external clock to run it. Most often a quartz crystal oscillator is connected to inputs XTAL1 (pin19) and XTAL2 (pin18). The quartz crystal oscillator connected to X XTAL1 TAL1 and XT XTAL2 AL2 also needs two capacitors capacitors of 30pf value. value. One side of each capacitor capacitor is connected to the ground as shown in fig1. It must be noted that there are various speeds of of the 8051 family. Speed refers to the maximum maximum oscillator frequency frequency connected connected to XTAL. For exam example, ple, a 12-MHz chip must be connected to a crystal with 12 MHz frequency of no more than 20 MHz. When the 8051 is connected to a crystal oscillator and is powered up, we can observe the frequency on the XTAL2 pin using the oscilloscope. If you decide to use a frequency source other than a crystal oscillator, such as a TTL oscillator, it will be connected to XTAL1; XTAL2 is left unconnected. As shown in fig2.

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Fi Fig( g(1) 1) XTAL XTAL co conn nnec ecti tion on to 8051 8051

fi fig2 g2.. XT XTAL AL co conn nnec ecti tion on to an Exte Extern rnal al cl cloc ock  k 


Tab 6.2.2 Status of External Pins


On-chip timing/counting facility has proved the capabilities of the microcontroller for implementing the real time application. These includes pulse counting, frequency measurement, pulse width measurement, baud rate generation, etc,. Having sufficient number of timer/counters may be a need in a certain design application. The 8051 has two timers/counters. They can be used either as timers to generate a time delay or as counters to count events happening outside the www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com microcontroller. Let discuss how these timers are used to generate time delays and we will also discuss how they are been used as event counters.



Both Timer 0 and Timer 1 are 16 bits wide. Since the 8051 has an 8-bit

architecture, each 16-bit timer is accessed as two separate registers of low byte and high byte.


  The 16-bit register of Timer 0 is accessed as low byte and high byte. the low  byte register is called TL0(Timer 0 low byte)and the high byte byte register is referred to as TH0(Timer 0 high byte).These register can be accessed like any other register, such as A,B,R0,R1,R2,etc.for A,B,R0,R1,R2,etc.for example, the instruction ”MOV TL0, #4F”moves #4F”moves the value 4FH into TL0,the low byte of Timer 0.These registers can also be read like any other register.

D15 D14










D4 D3 D2

D0 TH0




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Timer 1 is also 16-bit register is split into two bytes, referred to as TL1

(Timer 1 low byte) and TH1 (Timer 1 high byte).these registers are accessible n the same way as the register of Timer 0.

TMOD (timer mode) REGISTER 


Both timers 0 and 1 use the same register, called TMOD, to set the various

timer operation modes. TMOD is an 8-bit register in which the lower 4 bits are set aside for Timer 0 and the upper 4 bits for Timer 1.in each case; the lower 2 bits are used to set the timer mode and the upper 2 bits to specify the operation.

TCON Register:

TCON controls the timer/counter operations. The lower four bits of TCON cater to interrupt functions, but the upper four bits are for timer operations. The details of the TCON register are shown below.






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Serial Communication:


Computers Computers can transfer transfer data in two ways: parallel parallel and serial. In

 parallel data transfers, often 8 or more lines (wire conductors) are used to transfer data to a device that is only only a few feet away. Examples Examples of parallel parallel transfers transfers are printers and hard disks; each uses cables with many wire strips. Although in such cases a lot of data can be transferred in a short amount amount of time by using many wires in parallel, parallel, the distance distance cannot be great. To transfer transfer to a device device located many meters meters away, the serial method method is used. In serial communicat communication, ion, the data is sent one bit at a time, in contrast to parallel communication, in which the data is sent a byte or more at a time. Serial communica communication tion of the 8051 is the topic of this chapter. chapter. The 8051 has seria seriall communication capability built into it, there by making possible fast data transfer  using only a few wires. Serial data communication uses two methods, asynchronous and synchronous. The synchronous synchronous method transfers a block of data at a time, while the asynchronou asynchronouss method transfers a single byte at a time. The 8051 transfers and receives data serially at many different baud rates. The  baud rate in the 8051 is programmable. This is done with the help of Timer1. The 8051 divides divides the crystal frequency frequency by 12 to get the machine machine cycle frequency. frequency. In the case case of XTAL XTAL=1 =11. 1.05 0592 92MH MHZ, Z, the the mach machin inee cy cycl clee freq freque uenc ncy y is 92 921. 1.6 6 KHz KHz (11.0592MH (11.0 592MHz/12= z/12=921. 921.6KHz) 6KHz)..

The 8051’s 8051’s serial communication communication UART circuitry circuitry

divides the machine cycle frequency of 921.6 kHz divided by 32 once more before it is used by Timer 1 to set the Baud rate. SBUF register

SBUF is an 8-bit register used solely for serial communication in the 8051.. For a byte of data to be transferred via the TXD lin 8051 line, e, it must be placed in the SBUF register. register. Similarly, Similarly, SBUF SBUF holds the byte byte of data when it is received by the the 8051’s RXD line. line. SBUF can be accessed like any other register in the 8051. SCON (serial control) register

The SCON register is an 8-bit register used to program the start bit, stop bit, and data bits of data framing, among other things. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com The following describes various bits of the SCON register.



Internal timer stages are as fallows

  XClk Divided  b 12

Divided  by 32

Divided  by X

Baud Rate


Divided by X box can be replaced with T1 timer so that by changing the value of timer we can obtain the required baud rate.

Let XClk


11.0592 MHz

Baud Rate


(XClk / 12 / 16 / 2 / X)

For attaining 9600 baud Rate, X can be calculated as  


11.0592 x 106 / 12 / 16 / 2 / 9600




So set the 2’s Complement of 3 in Timer 1 so that we can achieve 9600 baud rates.

Note: Assuming 8-bit Auto reload mode and 8-bit variable baud rate modes. Doubling the baud rate in the 8051:

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com There are two ways to increase the baud rate to data transfer in the 8051. 1. Use a high higherer- frequen frequency cy crystal crystal.. 2. Chan Change ge a bit bit in the the PCON register, shown below.


-- -- GF1



Option1 is not feasible in many situations since the system crystal is fixed. More Importantly, it is not feasible because the new crystal may not be compatible with the IBM PC serial COM port’s baud rate. Therefore, Therefore, we will explore option2. option2. there is a software s oftware way to double the baud rate of the 8051 while the crystal frequency is fixed. fixed. This is done done with with the register register called called PCON PCON (power (power control). control). The PCON PCON register is an 8-bit register. Of the 8 bits, some are unused, and some are used for the  power control capability of the 8051. The bit that is used for the serial communication is D7, the SMOD (serial (serial mode) bit. bit. When the 8051 8051 is powered up, up, D7 (SMOD) of  this PCON register is zero. We can set it to high high by software and thereby double the  baud rate.

INTERRUPTS: A single microcontroller can serve several devices. There are two ways to do that: INTERRUPTS or POLLING.


In polling the microcontroller continuously monitors the status of a given device; when the status condition is met, it performs the service .After that, it moves on to monitor the next device until each one is serviced. Although polling can monitor the status of several devices and serve each of them as certain condition are met. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



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In the interrupts method, whenever any device needs its service, the device notifies the microcontroller by sending it an interrupts signal. Upon receiving an interrupt signal,, the microcontrolle signal microcontrollerr interrupts interrupts whatever it is doing doing and serves the device. device. The  program associated with the interrupts is called the interrupt service routine (ISR).or  interrupt handler.

Six Interrupts in the 8051:

In reality, only five interrupts are available to the user in the 8051, but many manufacturers’ data sheets state that there are six interrupts since they include reset .the six interrupts in the 8051 are allocated as above. 1. Reset. When When the the reset pin is is activated, activated, the 8051 8051 jumps jumps to address address location location 0000.this is the power-up reset. 2. Two interrup interrupts ts are set aside aside for the timers: timers: one one for Timer Timer 0 and one one for Timer Timer 1.Memory location 000BH and 001BH in the interrupt vector table belong to Timer 0 and Timer 1, respectively. 3. Two interru interrupts pts are set set aside for hardware hardware extern external al harder harder interrupts. interrupts. Pin number 12(P3.2) and 13(P3.3) in port 3 are for the external hardware interrupts INT0 and INT1,respectively.These external interrupts are also referred to as EX1 and EX2.Memory location 0003H 0003H and 0013H in the interrupt vector table are assigned to INT0 and INT1, respectively. 4. Serial commun communicatio ication n has a single single interrupt interrupt that that belongs belongs to both both receive receive and transmit. The interrupt vector table location 0023H belongs to this interrupt.

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com Interrupt Enable Register

















Interrupt priority upon rest:

When the 8051 is powered up, the priorities are assigned according to the below table. in the below table we see, for example, that if external hardware interrupts 0 and 1 are activated at the same time, external interrupt 0 (INT0) is responded to first. Only after  INT0 has been serviced is INT1 serviced, since INT1 has the lower priority. In reality, the priority scheme in the table is nothing but an internal polling sequence in which the 8051 polls the interrupts in the sequence listed in the below table and responds accordingly.

8051/52 Interrupt Priority upon Reset

Highest to Lowest Priority External Interrupt 0


Timer Interrupt 0


External Interrupt 1


Timer Interrupt 1


Serial Communication


Timer 2(8052 only)

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Setting interrupts priority with the IP register

We can alter the sequence of above Table by assigning a higher priority to any one of the interrupts. This is done by programming a register called IP (interrupt  priority).below diagram shows the bits of IP register. Upon power-up power-up reset, the IP register contain all 0s, making the priority sequence based on the above table. To give a higher priority to any of the interrupt, we make the corresponding bit in the IP register high.


D7 --

D0 --


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A fingerprint sensor  is  is an electronic device used device used to capture a digital image of image of the fingerprint pattern. The captured image is called a live scan. This live scan is processed to  to create a biometric template (a collection of extracted features features)) digitally processed which is stored and used for matching.

General Descriptions

FIM30 is an evolutionary standalone fingerprint recognition module consisted of optic sensor and processing board. As CPU and highly upgraded algorithm are embedded www.1000projects.com 46 www.fullinterview.com www.chetanasprojects.com


www.1000projects.com www.fullinterview.com www.chetanasprojects.com into a module, it provides high recognition ratio even to small size, wet, dry, calloused fingerprint. High speed 1: N identification and 1: N verification. FIM 30 has functions of fingerprint enrollment, identification, partial and entire deletion and reset in a single board, it does not require connection with a separate PC, thereby offering convenient development environment. Off-line functionality stores logs on the equipment memory (up to 100 fingerprints) and it’s identified using search engine from the internal algorithm. Evolutionary standalone fingerprint recognition module FIM30 is ideal for on-line applications, because allows ASCII commands to manage the device from the host. On-line functionality, fingerprints to verify (1:1) or identify (1: N) can be stored on non volatile memory, or be sent by RS-232 port. Features  

On-line and off-line fingerprint identification incorporated

Identification rate 1:1 and 1:N; FAR: 1/100.000 y FRR: 1/1.000

Algorithm and high hardness optical sensor

It provides high recognition ratio even to small size, wet, dry, calloused fingerprint.

Fast acquisition of difficult finger types under virtually any condition.

Memory capacity for 100 fingerprints

Memory events: up to 2,000 authentications

Access host can be protected by fingerprint or password

It offers convenient development environment.

Two communication ports: RS-232 or host ( on-line applications )

ASCII protocol

Supply voltage: 5V

Small size and robust durability, it has longer life span.

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com This FIM 3030 is going to have the Optical Sensor to Enroll and Identify the Finger Print. Optical sensor

Optical fingerprint imaging involves capturing a digital image of the print using visible light light.. This type of sensor is, in essence, a specialized digital camera camera.. The top layer of the sensor, where the finger is placed, is known as the touch surface. Beneath this layer is a light-emitting phosphor layer which illuminates the surface of the finger. The light reflected from the finger passes through the phosphor layer to an state pixels  pixels (a charge-coupled device) device) which captures a visual image of array of solid state the fingerprint. A scratched or dirty touch surface can cause a bad image of the fingerprint. A disadvantage of this type of sensor is the fact that the imaging capabilities are affected by the quality of skin on the finger. For instance, a dirty or marked finger is difficult to image properly. Also, it is possible for an individual to erode the outer layer of skin on the fingertips to the point where the fingerprint is no longer visible. It can also be easily fooled by an image of a fingerprint if not coupled with a "live finger" detector. However, unlike capacitive sensors, this sensor technology is not susceptible to electrostatic discharge damage.

Target Application

 Door-lock system  Safe Box  Simple Access Controller   Vehicle Control  ATM ,And more

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Block Diagram

RS-232C communication data consist of 8-bit data, no parity, 1-bit start-bit and 1-bit stop-bit. Interfacing:

Here this FIM 3030 supports the serial communication protocol which is RS-232. we are interfacing serially by converting the TTL logic into RS-232 standards and vice versa.

For this hardware interfacing we are using MAX-232 as a level converter for reading and writing data.


Introduction: www.1000projects.com www.fullinterview.com www.chetanasprojects.com



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Serial RS-232 (V.24) communication works with voltages (-15V ... -3V

for high [sic]) and +3V ... +15V for low [sic]) which are not compatible with normal computer logic voltages. On the other hand, classic TTL computer logic operates  between 0V ... +5V (roughly 0V ... +0.8V for low, +2V ... +5V for high). Modern low-power logic operates in the range of 0V ... +3.3V or even lower. So, the maximum RS-232 signal levels are far too high for computer logic electronics, and the negative RS-232 voltage for high . Therefore, to receive serial data from an RS-232 interface the voltage has to be reduced, and the low and high voltage level inverted. In the other direction (sending data from some logic over RS-232) the low logic voltage has to be "bumped up", and a negative voltage has to be generated, too.

 Logic Voltages All this can be done with conventional analog electronics, e.g. a particular power  supply and a couple of transistors or the once popular 1488 (transmitter) and 1489 (receiver) ICs. However, since more than a decade it has become standard in amateur  electronics to do the necessary signal level conversion with an integrated circuit (IC) from the MAX232 family (typically a MAX232A or some clone). In fact, it is hard to find some The MAX232 & MAX232A

The MAX 232 translates RS232 voltages to TTL voltages. RS232 represent a binary 1 or HI anywhere between –3V to –12V, a zero logic or LOW, between 3V and 12V. TTL in the other hand responds to 0 to 2.1V as logic zero and 2.8V to 5V as a HI. The MAX 232 provides voltage translation so the TTL PIC 16F84 can understand the messages sent to it from the   computer. A serial cable is also provided to connect the MAX2 MA X232 32 to th thee PC an and d ju jump mper er ca cabl bles es to co conn nnect ect th thee MAX2 MAX232 32 to th thee micr micro o controller. The MAX232 from Maxim was the first IC which in one package contains the necessary drivers (two) and receivers (also two), to adapt the RS-232 signal voltage levels to TTL logic. It became popular, because it just needs one voltage (+5V) and www.1000projects.com 50 www.fullinterview.com www.chetanasprojects.com


www.1000projects.com www.fullinterview.com www.chetanasprojects.com generates the necessary RS-232 voltage levels (approx. -10V and +10V) internally. This greatly simplified simplified the design of circuitry. circuitry. Circuitry designers designers no longer longer need to design and build a power supply with three voltages (e.g. -12V, +5V, and +12V), but could just provide one +5V power supply, e.g. with the help of a simple 78x05 voltage converter. MAX232 (A) DIP Package

  DIP Package of MAX 232A A Typical Application

The MAX232 (A) has two receivers (converts from RS-232 to TTL voltage levels) and two drivers (converts from TTL logic to RS-232 voltage levels). This means only two of the RS-232 signals can be converted in each direction. There are not enough drivers/receivers in the MAX232 to also connect the DTR, DSR DS R, an and d DCD DCD si sig gnals nals.. Usu sual ally ly thes thesee si sign gnal alss ca can n be omitt mitted ed when when e. e.g. g. communicating with a PC's serial interface. If the DTE really requires these signals either a second MAX232 is needed, or some other IC from the MAX232 family can  be used (if it can be found in consumer electronic shops at all). An alternative for  DTR/DSR is also given below. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com Maxim's data sheet explains the MAX232 family in great detail, including the pin configuration and how to connect such an IC to external circuitry. This information can be used as-is in own design to get a working RS-232 interface. Maxim's data just misses one critical piece of information: How exactly to connect the RS-232 signals to the IC. So here is one possible example:

MAX232 to RS232 DB9 Connection as a DCE MAX232 Pin Nbr. MAX232 Pin Name Signal Voltage DB9 Pin 7



RS-232 7




RS-232 8
























RS-232 2




RS-232 3






 Connections between MAX 232 & RS 232 In addition one can directly wire DTR (DB9 pin 4) to DSR (DB9 pin 6) without going through any circuitry. This gives automatic (brain dead) DSR acknowledgement of an incoming DTR signal. Sometimes pin 6 of the MAX232 is hard wired to DCD (DB9 pin 1). This is not recommended. Pin 6 is the raw output of the voltage pump and inverter for the -10V voltage. Drawing currents from the pin leads to a rapid breakdown of the voltage, and as a consequence to a breakdown of the output voltage of the two RS-232 drivers. It is  better to use software which doesn't care about a bout DCD, but does hardware-handshaking via CTS/RTS only. The circuitry is completed by connecting five capacitors to the IC as it follows. The MAX232 needs 1.0µF capacitors, the MAX232A needs 0.1µF www.1000projects.com 52 www.fullinterview.com www.chetanasprojects.com


www.1000projects.com www.fullinterview.com www.chetanasprojects.com capacitors. MAX232 clones show similar differences. It is recommended to consult the the co corre rresp spon ondi ding ng da data ta sh sheet eet.. At least least 16 16V V capaci capacito torr ty type pess shou should ld be us used ed.. If  electrolytic or tantalic capacitors are used, the polarity has to be observed. The first  pin as listed in the following table is always where the plus pole of the capacitor  should be connected to.  Exter External nal Capacitors Capacitors

The 5V power supply supply is connected connected

to+5V: Pin 16 GND: Pin 15

MAX232(A) external Capacitors Capacitor + Pin - Pin Remark   C1 1 3 C2 4 5 C3 2 16 This looks non-intuitive, but because pin 6 is C4




on -10V, GND gets the + connector, and not the -


Drawbacks of MAX232:  The MAX-232 chip receives data from the receiver, and converts it to the

standard RS-232 data format that can be read in by a serial port on a personal computer or workstation.


For the RS-232 interface, a standard MAX232 chip is used for level conversion. Both use the on chip USART and thus the same firmware.

 CONN CONNECTIO ECTIONS NS IN MAX 232: 23 2: If you wanted to do a general RS-232 connection, you could take a bunch of long wires and solder them directly to the electronic circuits of the equipment you are using, but this tends to make a big mess and often those solder connections tend to  break and other problems can develop. To deal with these issues, and to make it easier 

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com to setup or take down equipment, some standard connectors have been developed that is commonly found on most equipment using the RS-232 standards


• Low power CMOS  — Active current less than 2 mA  — Standby current less than 8 mA • Hardware writes protection  — Write control pin • Internally organized as 256 x 8 • Two-wire serial interface  — Bidirectional data transfer protocol • 8-Byte page-write mode  — Minimized total write time per byte • Automatic word address incrementing  — Sequential register read • Self-timed write cycle  — Maximum write cycle time of 10 ms • 400 KHz Compatibility Endurance: 1, 000,000 cycles per byte • 8-pin PDIP, TSSOP, MSOP or SOIC packages • Filtered inputs for noise suppression


The IS24C02 is a low cost 2,048-bit serial EEPROM. It is fabricated using  ISSI ’s ’s advanced CMOS EEPROM technology and operates from a single supply. The IS24C02 is internally organized as a 256 x 8 memory bank. The IS24C02 features a serial interface and software protocol allowing operation on a simple 2-wire bus. Up to eight IS24C02s may be connected to the 2-wire bus by programming the A0, A1, and A2 inputs. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



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Address Inputs


Serial Data I/O


Serial Clock Input


Write Control Input





A0, A1, and A2 - The address inputs are used to set the least significant three bits of

the slave address. These inputs may be tied HIGH or LOW, or they may be actively driven. These inputs allow up to eight IS24C02 devices to be connected together on the bus. When left floating, A0, A1 and A2 are pulled to ground. The default values are zeros. Serial Data (SDA) - The SDA pin is a bidirectional pin used to transfer data into and

out of the device. Data may change only when SCL is LOW. It is an open-drain output, and may be wire ORed with any number of open-drain or open-collector outputs.

Serial Clock (SCL) - The SCL input is used to clock all data into and out of the

device. In the WRITE mode, data must remain stable when SCL is HIGH. In the READ mode, data is clocked out on the falling edge of SCL. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com Write Control (WC) - The Write Control input is used to disable any attempt to write

to the memory. When HIGH, the memory is protected; when LOW, the write function is normal. The part can be read independent of the state of WC pin. When not connected, this pin will be pulled LOW. ENDURANCE AND DATA RETENTION

The IS24C02 is designed for applications requiring high endurance write cycles and unlimited read cycles. It provides 10 years of secure data retention, with or without  power applied, after the execution of 1,000,000 1,000,000 write cycles. APPLICATIONS

The IS24C02 is ideal for high volume applications requiring low power and low density storage. This device uses a low-cost, space-saving 8-pin plastic package. Candidate applications include robotics, alarm devices, electronic locks, meters and instrumentation. GENERAL DESCRIPTION

The IS24C02 features a SERIAL communication, and supports bidirectional data transmission protocol allowing operation on a simple two-wire bus between the different devices connected somewhere on the system bus. The two-wire bus is defined as a serial data line (SDA), and a serial clock line (SCL).

The protocol defines any device that sends data onto the SDA bus as a transmitter, and the receiving device as a receiver. The device controlling the data transmission is named MASTER device, and the controlled device is named SLAVE device. In all cases, the IS24C02 will be a slave device, since it never initiates any data transfers. Up to eight IS24C02 can be connected to the bus. Device's physical  address inputs A0-A2

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com must be connected to either VCC or GND. When left floating, A0, A1 and A2 are  pulled to ground. The default values are zeros.

Following a START condition, the MASTER (transmitter) device must initiate the “Device Addressing Byte” including device type identifier, device address, and a read or write operation to select a slave device (receiver) connected to the system bus. The receiver will then respond with an Acknowledge by pulling the SDA line LOW. The Acknowledge is used to indicate successful data transfers. The transmitting device will release the data bus (SDA goes HIGH) after transmitting eight bits (one data bit is transferred at the falling edge of each clock cycle). During the ninth clock cycle, the receiver will pull the SDA line LOW to acknowledge the transmitter that it received the eight bits of data.


Both SDA and SCL lines remain HIGH when the SDA bus is not busy. A HIGH-toLOW transition of SDA line, while SCL is HIGH, is defined as the START condition. A LOW to- High transition of SDA line, while SCL is HIGH, is defined as the STOP condition.

Data Validity Protocol

One data bit is transferred during each clock cycle. The data on the SDA line must remain stable during the HIGH period of the clock cycle, because changes on SDA line during the SCL HIGH period will be interpreted as START or STOP control signals. www.1000projects.com www.fullinterview.com www.chetanasprojects.com



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Device Addressing Byte Definitions

The most significant four bits of Device Addressing Byte (Bit 7 to Bit 4) are defined as the device type identifier. For IS24C02, this is fixed as 1010. The next three significant address bits (Bit 3 to Bit 1) address a particular device. Up to eight IS24C02 devices can be connected on the bus. These eight addresses are defined by the state of the A0, A1, and A2 inputs. The last  bit Bit 0 defines the write or read operation to be performed. When When set to “1”, a READ operation is selected; when set to “0” a WRITE operation is selected .


For a WRITE operation, the IS24C02 requires another 8-bit data word address following the Device Addressing Byte and Acknowledgement. This data word address provides access to any one of the 256 data words of device's memory array.

Upon receipt of the data word address, the IS24C02 responds with an Acknowledge on SDA, and waits for the next 8-bit data word, then again responding with an www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com Acknowledge. The master device terminates the Byte Write Operation by generating a STOP condition; afterward the IS24C02 begins the internal WRITE cycle to the nonvolatile memory array. Refer to Write Cycle Timing. All inputs are disabled during this write cycle and the device will not respond to any requests from the master.

Page Write

The IS24C02 is capable of 8-byte page- WRITE operation. A page-WRITE is initiated in the same manner as a byte write, but instead of terminating the internal write cycle after the first data word is transferred, the master device can transmit up to 7 more words. After the receipt of each data word, the IS24C02 responds immediately with an Acknowledge on SDA line, and the four lower order data word address bits are internally incremented by one while the four higher order bits of the data word address remain constant. If the master device should transmit more than 8 words,  prior to issuing the STOP condition, condition, the address counter will “roll over,” and the  previously written data will be overwritten. All inputs are disabled until completion completion of  the internal WRITE cycle.

Acknowledge Polling Once the internal write cycle has started and the IS24C02 inputs are disabled,

acknowledge polling can be initiated. This involves sending a start condition followed  by the Device Addressing Byte. The read/write bit is representation of the operation desired. Only if the internal write cycle has been completed will the IS24C02 respond with acknowledge on the SDA bus allowing the read or write sequence to continue.


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www.1000projects.com www.fullinterview.com www.chetanasprojects.com READ operations are initiated in the same manner as WRITE operations, except that the read/write bit of the device addressing byte is set to “1”. There are three READ operation options: current address read, random address read and sequential read. Current Address Read

The IS24C02 contains an internal address counter which maintains the address of the last data word accessed, incremented by one. For example, if the previous operation either a read or write operation addressed to the address location n, the internal address counter would increment to address location n+1. When the IS24C02 receives the Device Addressing Byte with a READ operation (read/write bit set to “1”), it will respond an Acknowledge and transmit the 8-bit data word stored at address location n+1. If the Current Address READ operation only accesses a single byte of data, the master device terminates the Current Address READ operation by pulling Acknowledge HIGH (lack of Acknowledge) indicating the last data word to be read, followed by a STOP condition.

Random Access Read

Random Address READ operation allows the master device to access any memory location in a random fashion. This operation involves a two-step process. First, the master device generates a START condition and initiates Device Addressing Byte with a dummy WRITE operation (read/write bit sets to “0”), followed by the address of the data word the master device is to READ. This procedure stores the desired address of data word to the internal address counter of the IS24C02.

After the data word address Acknowledge is received by the master device, the master  device now initiates a CURRENT ADDRESS READ by sending Device Addressing Byte with a READ operation (read/write bit sets to “1”). The IS24C02 responds with www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com an Acknowledge and transmits the eight data bits stored at the address location where the master device is to READ. At this point, the master device terminates the operation by pulling Acknowledge HIGH (lack of Acknowledge) indicating the last data word to be read, followed by a STOP condition.

Sequential Read

Sequential Reads can be initiated as either a Current Address Read or Random Address Read. The first data word is transmitted as with the other byte read modes, the master device now responds with an ACKnowledge indicating that it requires additional data from the IS24C02. The IS24C02 continues to output data for each ACKnowledge received. the master device terminates the sequential READ operation  by pulling ACKnowledge ACKnowledge HIGH (lack of ACKnowledge) indicatin indicating g the last data word to be read, followed by a STOP condition.

The data output is sequential; with the data from address n followed by the date from address n+1 ... etc. The address-counter increments by one automatically, allowing the entire memory contents to be serially read during sequential read operation. When the memory address boundary (address 255) is reached, the address counter “rolls over” to address 0, and the IS24C02 continues to output data for each Acknowledge received.

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A variable regulated power supply, also called a variable bench power supply,

is one where you can continuously adjust the output voltage to your requirements. Varying the output of the power supply is the recommended way to test a project after  having double checked parts placement against circuit drawings and the parts  placement guide. This type of regulation is ideal for having a simple variable bench power supply. Actually this is quite important because one of the first projects a hobbyist should undertake is the construction of a variable regulated power supply. While a dedicated supply is quite handy e.g. 5V or 12V, it's much handier to have a variable supply on hand, especially for testing. Most digital logic circuits and processors need a 5-volt power supply. To use these parts we need to build a regulated 5-volt source. Usually you start with an unregulated power supply ranging from 9 volts to 24 volts DC .To make a 5 volt  power supply, we use a LM7805 voltage regulator IC (Integrated Circuit). The IC is shown below.

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CIRCUIT FEATURES: Brief description of operation: Gives out well regulated +5V output, output current

capability of 100 mA Circuit protection: Built-in overheating protection shuts down output when regulator 

IC gets too hot Circuit complexity: Very simple and easy to build Circuit performance: performance: Very stable +5V output voltage, reliable operation Availability of components: Easy to get, uses only very common basic components

Based d on da data tash sheet eet ex exam ampl plee ci circ rcui uit, t, I ha have ve us used ed th this is ci circ rcui uitt Design Desig n testing: testing:  Base succesfully as part of many electronics projects Applications: Part of electronics devices, small laboratory power supply Power supply voltage: Unreglated DC 8-18V power supply s upply Power supply current: Needed output current + 5 mA

Few w doll dollar arss fo forr th thee elec electr tron onic icss co comp mpon onen ents ts + th thee in inpu putt Component Compo nent costs: costs:  Fe transformer cost.


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  This 5V dc acts as Vcc to the mi microcon crocontroller troller.. The excess voltage voltage is dissipated dissipated as heat via an Aluminum heat sink attached to the voltage regulator.


  power supply—A device for the conversion of available power of one one set of characteristics to meet specified requirements. Typical application of power supplies includes converting raw input power to a controlled or stabilized voltage and/or current for the operation of electronic equipment.


Power supplies belong to the field of power electronics, the use of

electronics for the control and conversion of electrical power. A power supply is sometimes called a power converter and the process is called power conversion. It is also sometimes called a power conditioner and the process is called power conditioning.


There are many types of power supplies. Most are designed to convert

high voltage AC mains electricity to a suitable low voltage supply for electronics www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com circuits and other devices. A power supply can be broken down into a series of  blocks, each of which performs a particular function. The power power supplies used in our  project, Digital Control of Three-Phase Induction Motor are +5V and+12V. and+12V.


These power supplies can be designed by a simple circuit

arrangement consisting of bridge rectifier (here we used diodes connected in bridge arrangement called the Diode Bridge), Capacitive or inductive filter, regulator (7812 for +12V and 7805 for +5V), resistor and Light Emitting Diode (LED) and transformer. The purpose of each component in the power supply design circuit shown in the schematic (drawn using Express SCH) is described below: TRANSFORMER:

Transformer is basically a one that transforms. A device used to transfer electric energy from one circuit to another, especially a pair of multiply wound, inductively coupled wire coils that affect such a transfer with a change in voltage, current, phase, or other electric characteristic. In other words Transformers convert AC electricity from one voltage to another with little loss of power.

Transformers work only with AC and this is one of the reasons why mains electricity is AC. If the output voltage of a transformer is greater than the input voltage, it is called a step-up transformer. If the output voltage of a transformer is less than the input voltage it is called a step-down transformer. Most power supplies use a stepdown transformer to reduce the dangerously high mains voltage (230V in UK) to a safer low voltage.

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The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the two coils; instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the middle of the circuit symbol shown below represent the core Transformers waste very little power so the power out is (almost) equal to the power in. Note that as voltage is stepped down current is stepped up.

The ratio of the number of turns on each coil, called the turns ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its  primary (input) coil, which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage.

Turns Ratio = Vp Vp / Vs = Np / Ns

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com Power Out = Power In i.e., Vs * Is =Vp * Ip

Where, Vp =Primary (input) voltage  

Np =Number of turns on primary coil


Ip =Primary (input) current Vs =Secondary (output) voltage  Ns =Number of turns on secondary coil  Is

=Secondary (output) current

Uses of transformers

Electric power transmission over long distances. The simplicity, reliability, and economy econo my of conversion conversion of voltages voltages by stationary stationary transformers transformers were the principal principal factor in the selection of alternating current power transmission.

High-voltage direct-current HVDC power transmission systems. Large, specially constructed power transformers are used for electric arc furnaces used in steel making.

Rotating transformers are designed so that one winding turns while the other  remain rem ainss station stationary ary.. These These can pass pass power power or radio radio signal signalss from from a statio stationar nary y mounting to a rotating mechanism, or radar antenna.

Sliding transformers can pass power or signals from a stationary mounting to a movi mo ving ng pa part rt such such as a mach machin inee tool tool he head ad.. Se Seee line linear ar va vari riab able le di diff ffere erent ntia iall transformer.

Some rotary transformers transformers are precisely precisely constructed in order to measure distances or angles. Usually they have a single primary and two or more secondaries, and elect ele ctro roni nicc circu circuit itss measu measure re th thee diffe differe rent nt ampl amplit itud udes es of th thee cu curr rren ents ts in th thee secondaries. See synchro and resolver.

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Small transformers are often used to isolate and link different parts of radio receivers and audio amplifiers, converting high current low voltage circuits to low current high voltage, or vice versa. See electronics and impedance matching. See also isolation transformer and repeating coil.

Balanced-to-unbalanced conversion. A special type of transformer called a balun is used used in radio radio and audio circuits circuits to conver convertt betwee between n balanc balanced ed circuit circuitss and unbalanced transmission lines such as antenna down leads. A balanced line is one in which the two conductors (signal and return) have the same impedance to ground: twisted pair and "balanced twin" are examples. Unbalanced lines include coaxial cable sand strip-line traces on printed circuit boards. A similar use is for  connecting the "single ended" input stages of an amplifier to the high-powered "push-pull" output stage.

Center Cen ter tap trans tra nsfor former merss:

 In electronics, a center tap is a wire that is connected to a point half way along one of  the windings of a transformer, inductor or a resistor. Center taps are sometimes used on inductors for the coupling of signals, although most tapings are not at the center  but usually near one end. In the case of resistors, tapping is usually done done only with  potentiometers, and center tapping is just a special case of normal operation of these devices. RECTIFIERS:

Rectification is a process of conversion of AC to DC. Here, the AC of transformer output is given to the rectifier input, which converts it to DC output. Basically, bridge rectifiers or diodes arranged in bridge called Diode arrangement are used for power supply design.

A bridge rectifier makes use of four diodes in a bridge arrangement to achieve fullwave rectification. This is a widely used configuration, both with individual diodes

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Current Flow in the Bridge Rectifier


For both positive and negative swings of the transformer, there is a forward path through the diode bridge. Both conduction paths cause current to flow in the same direction through the load resistor, accomplishing full-wave rectification.  

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  While one set of diodes is forward biased, the other set is reversing biased and effectively eliminated from the circuit.

 Diode Bridge:

A diode bridge is an arrangement of four diodes connected in a bridge circuit as shown below, that provides the same polarity of output voltage for any polarity of the input voltage. When used in its most common application, for conversion of alternating current (AC) input into direct current (DC) output, it is known as a bridge rectifier. The diagram describes a diode-bridge design known as a full-wave rectifier or Graetz circuit. This design can be used to rectify single phase AC when  No transformer center tap is available.


The essential feature of this arrangement is that for both polarities of the voltage at the  bridge input, the polarity of the output is constant. When the input connected at the left corner of the diamond is positive with respect to the one connected at the right www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com hand corner, current flows to the right along the upper colored path to the output, and returns to the input supply via the lower one.  

When the right hand corner is positive relative to the left hand corner, current flows along the upper colored path and returns to the supply via the lower colored path.

AC, half-wave and full wave rectified signals In each case, the upper right output remains positive with respect to the lower right one. Since this is true whether the input is AC or DC, this circuit not only produces DC power when supplied with AC power: it also can provide what is sometimes www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com called cal led "reverse "reverse polarit polarity y protec protectio tion". n". That That is, it permit permitss normal normal functio functionin ning g when when  batteries are installed backwards or DC input-power supply wiring "has its wires crossed" (and protects the circuitry it powers against damage that might occur without this circuit in place). Prior Pri or to availa availabil bility ity of integr integrated ated electro electronic nics, s, such a bridge bridge rectifi rectifier er was always always constru con structed cted from from discre discrete te compon component ents. s. Since Since about about 1950, 1950, a single single four-te four-termi rminal nal component containing the four diodes connected in the bridge configuration became a standar stan dard d commer commercial cial compon component ent and is no now w availa available ble with with variou variouss voltag voltagee and current ratings. Capacitor:

A capacitor is a device that stores energy in the electric field created between a pair of  co cond nduc ucto tors rs on whic which h eq equa uall bu butt op oppo posi site te elec electri tricc ch charg arges es ha have ve be been en pl plac aced ed.. A capacitor is occasionally referred to using the older term condenser.  

A capacitor capacitor consists consists of two electrodes electrodes or plates, plates, each of of which which stores stores an opposite opposite

ch char arge ge.. These These tw two o plat plates es are co cond nduc ucti tive ve an and d ar aree separ separate ated d by an in insu sulat lator or or  dielectric. The charge is stored at the surface of the plates, at the boundary with the dielectric. dielect ric. Because each plate stores an equal but opposite charge, the total charge in the capacitor is always zero. The capacitor's capacitance (C) is a measure of the amount of charge (Q) stored on each plate for a given potential difference or voltage (V) which appears between the  plates:

In SI units, a capacitor has a capacitance of one farad when one coulomb of charge causes a potential difference of one volt across the plates. Since the farad is a very large unit, values of capacitors are usually expressed in microfarads (µF), nanofarads (nF) or Pico farads (pF). www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com The capacitan capacitance ce is propor proportio tional nal to the surface surface area of the conducti conducting ng plate plate and inversely proportional to the distance between the plates. It is also proportional to the  permittivity of the dielectric (that is, non-conducting) substance that separates the  plates.The capacitance of a parallel-plate capacitor is given by:

Where ε is the permittivity of the dielectric, A is the area of the plates and d is the spacing between them. Capacitors are commonly used in power supplies where they smooth the output of a full or half wave rectifier. They can also be used in charge pump circuits as the energy storage element in the generation of higher voltages than the input voltage. Capacitors are connected in parallel with the power circuits of most electronic devices and larger systems (such as factories) to shunt away and conceal current fluctuations from the primary power source to provide a "clean" power supply for signal or control circuits. circui ts. Audio equipment, equipment, for example, uses several capacitors capacitors in this way, to shunt shunt away power line hum before it gets into the signal circuitry. The capacitors act as a local reserve for the DC power source, and bypass Ac currents from the power supply. Capacitors are used in power factor correction. Such capacitors often come as three capacitors connected as a three phase load. Usually, the values of these capacitors are given not in farads but rather as a reactive power in volt-amperes reactive (VAr). The  purpose is to match the inductive loading of machinery which contains motors, to make the load appear to be mostly resistive. Capacitors are also used in parallel to interrupt units of a high-voltage circuit breaker  in order to distribute the voltage between these units. In this case they are called grading gradi ng capacitors. In schema schematic tic diagrams, diagrams, a capacitor capacitor used primarily primarily for DC charge storage is often drawn vertically in circuit diagrams with the lower, more negative,  plate drawn as an arc. The straight plate indicates the positive terminal of the device; if it is polarized Non-polarized electrolytic capacitors used for signal filtering are www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com typically drawn with two curved plates. Other non-polarized capacitors are drawn with two straight plates. Non-polarized Non-polarize d fixed capacitor

A non-polarized ("non polar") capacitor is a type of capacitor that has no implicit  polarity -- it can be connected either way in a circuit. Ceramic, mica and some electrolytic capacitors are non-polarized. You'll also sometimes hear people call them "bipolar" capacitors.


Polarized fixed capacitor

A polarized ("polar") capacitor is a type of capacitor that has implicit polarity -- it can only be connected one way in a circuit. The positive lead is shown on the schematic (and often on the capacitor) with a little "+" symbol. The negative lead is generally not shown on the schematic, but may be marked on the capacitor with a bar or "-" symbol. Polarized capacitors are generally electrolytes.

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Thee simpl Th simplee capaci capacito torr fil filte terr is th thee most most ba basi sicc ty type pe of po powe werr supp supply ly filte filter. r. The The applic app licatio ation n of the simple simple capacitor capacitor filter filter is very very limited limited.. It is someti sometimes mes used used on extrem ext remely ely high-v high-volt oltage age,, low-cu low-curren rrentt power power suppli supplies es for cathod cathodee ray and similar  similar  electron tubes, which require very little load current from the supply. The capacitor  filter filter is also also used used where where the power-sup power-supply ply ripple ripple frequen frequency cy is not critical; critical; this this frequency can be relatively high. REGULATORS:

 A regulator converts varying input voltage and produces produces a constant "regulated" output voltage.


The linear regulator is the basic building block of nearly every

 power supply used in electronics. The IC linear regulator is so easy to use that it is virt virtua uall lly y fool foolpr proo oof, f, an and d so inex inexpe pens nsiv ivee th that at it is usua usuall lly y on onee of th thee ch chea eape pest st components in an electronic assembly. A linear regulator operates by using a voltagecontrolled current source to force a fixed voltage to appear at the regulator output terminal. termin al. Series every electronic electronic circuit is designed designed to operate operate off of some supply voltage, volta ge, which is usually assumed assumed to be constant. constant. A voltage regulator regulator provides provides this www.1000projects.com www.fullinterview.com www.chetanasprojects.com



www.1000projects.com www.fullinterview.com www.chetanasprojects.com constant DC output voltage and contains circuitry that continuously holds the output voltage at the design value regardless of changes in load current or input voltage (this assumes that the load current and input voltage are within the specified operating range for the part).  

Voltage regulators are available in a variety of outputs, typically 5

volts, 9 volts and 12 volts. The last two digits in the name indicate the output voltage. The "LM78X "LM78XX" X" series series of voltag voltagee regula regulator torss are design designed ed for positi positive ve input. input. For  applications requiring negative input the "LM79XX" is used.




+ 5 volts

LM7809 LM7812

+ 9 volts + 12 volts


- 5 volts


- 9 volts


- 12 volts

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LIQUID CRYSTAL DISPLAY A liquid crystal display (LCD) is a thin, flat display device made up of any

number of color or monochrome pixels arrayed in front of a light source or reflector. Each  pixel consists of a column column of liquid crystal molecules molecules suspended between between two transparent electrodes, and two polarizing filters, the axes of polarity of which are perpendicular to each other. Without the liquid crystals between them, light passing through one would be  blocked by the other. other. The liquid crystal crystal twists the polarization of light light entering one filter to allow it to pass through the other. Many microcontroller devices use 'smart LCD' displays to output visual information. LCD displays designed around Hitachi's LCD HD44780 module, are inexpensive, easy to use, and it is even possible to produce a readout using the 8x80  pixels of the display. display. They have a standard standard ASCII set of characters characters and mathematical mathematical symbols. For an 8-bit data bus, the display requires a +5V supply plus 11 I/O lines. For a 4 bit data bus it only requires requires the supply lines plus seven extra lines. lines. When the LCD display display is not enabled, data lines are tri-state and they do not interfere with the operation of the microcontroller. Data can be placed at any location on the LCD. For 16×2 LCD, the address locations are:

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Address locations for a 2x16 line LCD


The LCD also requires 3 control lines from the microcontroller: 1) Enable (E)

This line allows access to the display through R/W and RS lines. When this line is low, the LCD is disabled and ignores signals from R/W and RS. When (E) line is high, the LCD checks the state of the two control lines and responds accordingly. 2) Read/Write (R/W)

This line determines the direction of data between the LCD and microcontroller. When it is low, data is written to the LCD. When it is high, data is read from the LCD. 3) Register select (RS) With the help of this line, the LCD interprets the type of data on data lines. When it is low, an instruction is being written to the LCD. When it is high, a character is being written to the LCD.

Logic status on control lines:


- 0 Access to LCD disabled - 1 Access to LCD enabled

• R/W - 0 Writing data data to LCD - 1 Reading data from LCD • RS

- 0 Instructions


1 Character 

Writing and reading the data from the LCD:

Writing data to the LCD is done in several steps: 1) Set R/W bit to low 2) Set RS bit to logic 0 or 1 (instruction or character) 3) Set data to data lines (if it is writing) 4) Set E line to high

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com 5) Set E line to low Read data from data lines (if it is reading): 1) Set R/W bit to high 2) Set RS bit to logic 0 or 1 (instruction or character) 3) Set data to data lines (if it is writing) 4) Set E line to high 5) Set E line to low


Most LCDs with 1 controller has 14 Pins and LCDs with 2 controller has 16 Pins (Two pins are extra in both for back-light LED connections).

Pin diagram of 2x16 line LCD

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Pin description of the LCD


A buzzer or beeper is a signaling device, usually electronic, typically used in automobiles,, household appliances such as a microwave oven, automobiles oven, or game shows. shows. It most commonly consists of a number of switches or switches or sensors connected sensors connected to a control unit that determines if and which button was pushed or a preset time has lapsed, and usually illuminates a light on the appropriate button or control panel, and sounds a warning in the form of a continuous or intermittent buzzing or beeping sound. sound. Initially this device www.1000projects.com www.fullinterview.com




www.1000projects.com www.fullinterview.com www.chetanasprojects.com was based on an electromechanical system which was identical to an electric bell  bell  without the metal gong (which makes the ringing noise). Often these units were anchored to a wall or ceiling and used the ceiling or wall as a sounding board. Another implementation with some AC-connected devices was to implement a circuit to make the AC current into a noise loud enough to drive a loudspeaker and hook this circuit up to a cheap 8-ohm speaker. Nowadays, it is more popular to use a ceramic based piezoelectric  based  piezoelectric sounder  sounder like a Sonalert which makes a high-pitched tone. Usually these were hooked up to "driver" circuits, which varied the pitch of the sound or  pulsed the sound on and off.

Electronic symbol for symbol for buzzer.

Metal disk with piezoelectric disk attached, as found in a buzzer  In game shows it is also known as a "lockout system," because when one person signals ("buzzes in"), all others are locked out from signalling.Several game shows have large buzzer buttons which are identified as "plungers". The word "buzzer" comes from the rasping noise that buzzers made when they were electromechanical devices, operated from stepped-down AC line voltage at 50 or 60 www.1000projects.com www.fullinterview.com




www.1000projects.com www.fullinterview.com www.chetanasprojects.com cycles. Other sounds commonly used to indicate that a button has been pressed are a ring or a beep.


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www.1000projects.com www.fullinterview.com www.chetanasprojects.com Keyboards and LCDs are the most widely used input/output devices of the 8051, and a basic understanding of them is essential. In this section, we first discuss keyboard fundamentals, along with key press and key detection mechanisms, Then we show how a keyboard is interfaced to an 8051.

Interfacing the Keyboard to the 8051

At the lowest level, keyboards are organized in a matrix of rows and columns. The CPU accesses both rows and column through ports; therefore, with two 8-bit ports, an 8*8 matrix of keys can be connected to a microprocessor. When a key pressed, a row and column make a connect; otherwise, there is no connection between row and co colu lumn mn.. In IBM IBM PC key eyb board oards, s, a si sin ngle mic icro ro co con ntro troller ller (c (con onsi sist stin ing g of  microprocessor, RAM and EPROM, and several ports all on a single chip) takes care of software and hardware interfacing of keyboard. In such systems it is the function of   programs stored in the EPROM of micro controller to scan the keys continuously, identify which one has been activated, and present it to the motherboard. In this section we look at the mechanism by which the 8051 scans and identifies the key.

Scanning and identifying the key

  Figure13.5 shows a 4*4 matrix connected to two ports. The rows are connected to an output port and the columns are connected to an input port. If no key has been  pressed, reading the input port will yield 1s for all columns since they are all connected to high (Vcc) If all the rows are grounded and a key is pressed, one of the columns will have 0 since the key pressed provides the path to ground. It is the function of the micro controller to scan the keyboard continuously to detect and identify the key pressed. How it is done is explained next.

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Grounding rows and reading columns

  To detect a pressed key, the micro controller grounds all rows by providing 0 to the output latch, and then it reads the columns. If the data read from the columns is D3D0=1111, no key has been pressed and the process continues until a key press is detected. However, if one of the column bits has a zero, this means that a key press has occurred. For example, if D3-D0=1101, this means that a key in the D1 column has been pressed. After a key press is detected, the micro controller will go through the process of identifying the key. Starting with the top row, the micro controller  grounds it by providing a low to row D0 only; then it reads the columns. If the data read is all1s, no key in that row is activated and the process is moved to the next row. It grounds the next row, reads the columns, and checks for any zero. This process continues conti nues until the row is identified. identified. After identificatio identification n of the row in which the key has been pressed, the next task is to find out which column the pressed key belongs to. www.1000projects.com www.fullinterview.com




www.1000projects.com www.fullinterview.com www.chetanasprojects.com This should be easy since the microcontroller knows at any time which row and column are being accessed.

Assembly language program for detection and identification of key activation is given  below. In this program, it is assumed that P1 and P2 are initialized as output and input, respectively. Program13.1 goes through the following four major stages:

1. To make sure that the preceding key has been released, 0s are output to all rows at once, and the columns are read and checked repeatedly until all the columns are high. When all columns are found to be high, the program waits for a short amount of time  before it goes to the next stage of waiting for a key to be pressed. pressed.   2) To see if any key is pressed, the columns are scanned over and over over in an infinite loop until one of them has a 0 on it. Remember that the output latches connected to rows still have their initial zeros (provided in stage 1), making them grounded. After  the key press detection, it waits 20ms for the bounce and then scans the columns again. This serves two functions: (a) it ensures that the first key press detection was not an erroneous one due to spike noise, and(b) the 20ms delay prevents the same key  press from being interpreted as a multiple key press. If after the 20-ms delay the key is still pressed, it goes to the next stage to detect which row it belongs to; otherwise, it goes back into the loop to detect a real key press

3) To detect detect which which row the key press press belong belongss to, it grounds grounds one row at a time, reading the columns each time. If it finds that all columns are high, this means that the key press cannot belong to that row; therefore, it grounds the next row and continues until it finds the row the key press belongs to. Upon finding the row that the key press  belongs to, it sets up the starting address for the look-up table holding the scan sc an codes (or the ASCII value) for that row and goes to the next stage to identify the key. 4) To identify the key press, it rotates the column column bits, one one bit at a time, into the carry flag and checks to see if it is low. Upon finding the zero, it pulls out the ASCII code for that key from the look-up table; Otherwise, it increments the pointer to point to the next element of the look-up table. www.1000projects.com www.fullinterview.com




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Whil Wh ilee th thee ke key y pr press ess de dete tect ctio ion n is stand standar ard d fo forr al alll ke keyb yboa oard rds, s, th thee pr proc ocess ess fo for  r  determining which key is pressed varies. The look-up table method shown in program can be modified to work with any matrix up to 8*8.

There are IC chips such as National Semiconductors MM74C923 that incorporate keyboard scanning and decoding all in one chip. Such chips use combinations of  counters and logic gates (No micro controller).


The keypad is the most widely used input device for microcontroller. Here we are having two different sets of keypads one for entering the password and the other for electing a person.

Any way here we are using a momentary NO switch which is open by default. When ever we are pressing a key the concerned circuit will be closed and the resultant value will be read by microcontroller and depends on our program the controller will takes the further actions.

Schematic of momentary NO switch

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DC Motor  DC motors are motors are configured in many types and sizes, including brush less, less, serv servo, o, and ge gear ar moto motorr ty type pes. s. A motor   consists of a rotor and a permanent magnet mag netic ic field field stator. stator. The magnet magnetic ic field field is maintai maintained ned using using either either perman permanent ent magn ma gnet etss or elect electro romag magne neti ticc wind windin ings gs.. DC motors  motors  ar aree most most co comm mmon only ly us used ed in variable  




Motion and controls cover a wide range of components that in some

way are used to generate and/or control motion. Areas within this category include  bearings and bushings, clutches and brakes, controls and drives, drive components, encoders and resolves, Integrated motion control, limit switches, linear actuators, linear and rotary motion components, linear position sensing, motors (both motors (both AC and DC motors), motors), orientation orientation position sensing, sensing, pneumatics pneumatics and pneumatic pneumatic components, components,  positioning stages, slides and guides, power transmission (mechanical), seals, slip rings,solenoids,springs.

Motors are Motors  are the devices that provide the actual speed and torque in a drive system. system. This family family includes includes AC motor  types   types (single and multiphase multiphase motors, motors, univer uni versal, sal, servo motors, motors, induct induction ion,, synchr synchron onous ous,, and gear motor) motor) and DC motors (brush less, servo motor , and gear motor) as well as linear, stepper and air motors, motors, and motor  contactors  contactors and starters.  

In any electric motor, operation is based on simple electromagnetism.

A current-carryi current-carrying ng conductor conductor generates generates a magnetic magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in current in the conductor, and to the strength of the external magnetic field. As you are well aware of  from playing with magnets as a kid, opposite (North and South) polarities attract, whil wh ilee like like po polar larit itie iess (Nor (North th an and d Nort North, h, Sout South h an and d Sout South) h) repel repel.. The The in inte tern rnal al configurati confi guration on of a DC motor DC motor is designed to harness the magnetic interaction between www.1000projects.com www.fullinterview.com




www.1000projects.com www.fullinterview.com www.chetanasprojects.com a current-carrying current-carrying conductor and an external magnetic field to generate rotational motion.   Let's Let 's start by lookin looking g at a simple simple 2-pole 2-pole DC  DC  electric motor (here red represents a magnet or winding with a "North" polarization, while green represents a magnet or winding with a "South" polarization).

Ever Ev ery y DC  DC  motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator, commu tator, field magnet(s), and brushes. In most common DC motors (and all that Beamers will see), the external magnetic field is produced by high-strength permanent magnets1. The stator is the stationary part of the motor -- this includes the motor  casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotates with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator. The above diagram shows a common motor layout -- with the rotor  inside the stator (field) magnets.


The geometry of the brushes, commutator contacts, and rotor windings are

such that when power is applied, the polarities of the energized winding and the stator  magnet(s) are misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets. As the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the next winding. Given our example two-pole motor, the rotation reverses the direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic field, and driving it to continue rotating.

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In real life, though though , DC motors DC motors will always have more than two poles

(three (th ree is a very very common common number). number). In partic particula ular, r, this this avoids avoids "dead spots" in the commutator. You can imagine how with our example two-pole motor, if the rotor is exactly exactl y at the middle of its rotation rotation (perfectly aligned aligned with the field magnets), magnets), it will get "stuck" there. Meanwhile, with a two-pole motor, there is a moment where the commutator shorts out the power supply (i.e., both brushes touch both commutator  contacts simultaneously). This would be bad for the power supply, waste energy, and damage motor components as well. Yet another disadvantage of such a simple motor  is that it would exhibit a high amount of torque” ripple" (the amount of torque it could  produce is cyclic with the position of the rotor).


So since most small DC motors are of a three-pole design, let's tinker with the workings of one via an interactive animation (JavaScript required):


You'll notice a few things from this -- namely, one pole is fully energized

at a time (but two others are "partially" energized). As each brush transitions from one commutator contact to the next, one coil's field will rapidly collapse, as the next coil's field will rapidly charge up (this occurs within a few microsecond). We'll see more

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There's probably no better way to see how an average dc motor is put together,

than by just opening opening one up. Unfortunately Unfortunately this is tedious tedious work, as well as requiring requiring the destruction destruction of a perfectly perfectly good motor. motor. This is a basic 3-pole 3-pole dc motor, motor, with 2  brushes and three commutator contacts.

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DC motors are typically controlled by using a transistor 

configuration called an "H-bridge "H-bridge". ". This consists of a minimum of four mechanical or  solid-state switches, such as two NPN and two PNP transistors. One NPN and one PNP transistor are activated at a time. Both NPN and PNP transistors can be activated to cause a short across the motor terminals, which can be useful for slowing down the motor from the back EMF it EMF it creates.

 Basic Theory

H-bridge. Sometimes called a "full bridge" the H-bridge is so named because it has four switching elements at the "corners" of the H and the motor forms the cross bar. The key fact to note is that there are, in theory, four switching elements within the  bridge. These four elements are often called, high side left, high side s ide right, low side right, and low side left (when traversing in clockwise order). The switches are turned on in pairs, either high left and lower right, or lower left and high right, but never both switches on the same "side" of the bridge. If both switches on one side of a bridge are turned on it creates a short circuit between the battery plus and battery minus terminals. If the bridge is sufficiently sufficiently powerful powerful it will absorb that load and your batteries will simply drain quickly. Usually however the switches in question melt. To power the motor, you turn on two switches that are diagonally opposed. In the  picture to the right, imagine that the high side left and low side right switches are turned on. The current flows and the motor begins begins to turn in a "positive" "positive" direction. direction. Turn on the high side right and low side left switches, then Current flows the other direction through the motor and the motor turns in the opposite direction. www.1000projects.com www.fullinterview.com




www.1000projects.com www.fullinterview.com www.chetanasprojects.com Actually it is just that simple, the tricky part comes in when you decide what to use for switches. Anything that can carry a current will work, from four SPST switches, one DPDT switch, relays, transistors, to enhancement mode power MOSFETs. One more topic in the basic theory section, quadrants. If each switch can be controlled independently then you can do some interesting things with the bridge, some folks call such a bridge a "four quadrant device" (4QD get it?). If you built it out of a single DPDT relay, you can really only control forward or reverse. You can build a small truth table that tells you for each of the switch's states, what the bridge will do. As each switch has one of two states, and there are four switches, there are 16 possible states. However, since any state that turns both switches on one side on is "bad" (smoke issues forth: P), there are in fact only four useful states (the four quadrants) where the transistors are turned on.

High Side Left High Side Right Low Side Left Low Side Right Right On Off Off On Off On On Off On On Off Off Off Off On On

Quadrant Quadrant Descript Description ion Forward Running Backward Running Braking Braking

The last two rows describe a maneuver where you "short circuit" the motor which causes the motors generator effect to work against itself. The turning motor generates a voltage which tries to force the motor to turn the opposite direction. This causes the motor to rapidly stop spinning and is called "braking" on a lot of H-bridge designs. Of course there is also the state where all the transistors are turned off. In this case the motor coasts freely if it was spinning and does nothing if it was doing nothing.

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1. Usin Using g Rela Relay ys: A simple implementation of an H Bridge using four SPST relays is shown. Terminal A is High Side Left, Terminal B is High Side Right, Terminal C is Low Side Left and Terminal D is Low Side Right. The logic followed is according to the table above.

Warning:  Never Never turn on A and C or B and D at the same time. This will lead to a short circuit of the battery and will lead to failure of the relays due to the large current.

2. Usin Using g Tra Trans nsis isto tors rs::

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com We can can bett better er cont contro roll our our moto motorr by us usin ing g tran transi sist stor orss or Fiel Field d Ef Effe fect ct Transistors (FETs). Most of what we have discussed about the relays H-Bridge is true of these circuits. See the diagram showing how they are connected. You should add diodes across the transistors to catch the back voltage that is generated by the motor's coil when the power is switched on and off. This fly  back voltage can be many times higher than the supply supply voltage! For information on building an H-Bridge using Transistors, Transistors , have a look here. here. Warning: If you don't use diodes, you could burn out your transistors. Also the same warning as in the diode case. Don't turn on A and C or B and D at the same time.

Transistors, being a semiconductor device, will have some resistance, which causes them to get hot when conducting much current. This is called not being able to sink or source very much power, i.e.: Not able to provide much current from ground or from plus voltage. Mosfets are much more efficient, they can provide much more current and not get as hot. They usually have the fly back diodes built in so you don't need the diodes anymore. This helps guard against fly back voltage frying your ICs. To use Mosfets in an H-Bridge, you need P-Channel Mosfets on top because they can "source" power, and N-Channel Mosfets on the bottom because then can "sink" power. www.1000projects.com www.fullinterview.com




www.1000projects.com www.fullinterview.com www.chetanasprojects.com It is important that the four quadrants of the H-Bridge circuits be turned on and off properly. When there is a path between the positive and ground side of  the H-Bridge, other than through the motor, a condition exists called "shoot through". This is basically a direct short of the power supply and can cause semiconductors to become ballistic, in circuits with large currents flowing. There are H-bridge chips available that are much easier, and safer, to use than designing your own H-Bridge circuit.


This section describes the flow of the project from time to time and the internal operation of the circuit.

Up on the power on, the microcontroller initializes the finger print module, LCD, keypad, and the Locker system to their initial states as stated in the program which is loaded into the microcontroller.

Before starting the actual operation here we have to specify the mode which hich we ar aree us usin ing g lik like ATM ATM or Lock Locker er or fo forr PAS PASSPOR PORT verification.

After pressing any one of the keys specified the controller initializes to that particular mode.

In any one of the modes, the FP module is waiting for a finger print to  be scanned and a nd when we place the finger and press the scan key a low logic will be read by that pin and controller starts comparison among the finger prints available in the data base with the present finger print.

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ATM mode: If the match found then the controller enables the matrix

keypad which further enables the process of transactions

During Durin g each key press the concerned concerned port pin of the controller controller reads a logic low signal to indicate a particular operation as specified.

If any one of he option key like DEPOSIT, WITHDRAW, MINI,  pressed the concerned data will automatically stored in the external memory through the SDA line through which controller is going to access the information of the users.

controlle llerr enable enabless the Locker Lock er mode: mode:  If the match found then the contro matrix keypad which further enables the locker system operation.

PASSPORT verification: verification: If the match found then the controller gets

the information of the particular person and will be displayed on the LCD.

If the match not found in the data base then the keypad and the locker  are remain in the disabled state and it will be indicated.

All these process while transactions or any fault will be displayed on the LCD to which microcontroller sends the data through the data lines (D0 – D7).

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SOFTWARE CONCEPTS: The software used for this project is:



Embedded C

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KEIL IDE: Keil uVision is what the software we are using for the programming. In this software editor we are writing the program in any of the languages like ASM or Embedded C.

µVision3 Overview The µVision3 IDE is a Windows-based software development platform that combines a robust editor, project manager, and makes facility. µVision3 integrates all tools including the C compiler, macro assembler, linker/locator, and HEX file generator. µVision3 helps expedite the development process of your embedded applications by  providing the following: 

Full-featured source code editor,

Device database for configuring the development tool setting,

Project manager for creating and maintaining your projects,

Integrated make facility for assembling, compiling, and linking your embedded applications,

Dialogs for all development tool settings,

True integrated source-level Debugger with high-speed CPU and peripheral simulator,

Advanced GDI interface for software debugging in the target hardware and for  connection to Keil ULINK,

Flash programming utility for downloading the application program into Flash ROM,

Links to development tools manuals, device datasheets & user’s guides.

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www.1000projects.com www.fullinterview.com www.chetanasprojects.com The µVision3 IDE offers numerous features and advantages that help you quickly and successfully develop embedded applications. They are easy to use and are guaranteed to help you achieve your design goals.


The µVision3 Simulator is the only debugger that completely simulates all on-chip peripherals


The µVision3 Device Database automatically configures the development tools for the target microcontroller.


Identical Target Debugger and Simulator User Interface.


µVision3 incorporates project manager, editor, and debugger in a single environment.


Write and test application code before production hardware is available.

Investigate different hardware configurations to optimize the hardware design. Sophisticated systems can be accurately simulated by adding your own  peripheral drivers.

Mistakes in tool settings are practically eliminated and tool configuration time is minimized.

The same tool can be used for debugging and programming. No extra configuration time required.

Accelerates application development. While editing, you may configure debugger features. While debugging, you may make source code modifications.

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Steps to Create a PROJECT:

µVision3 includes a project manager which makes it easy to design applications for an ARM based microcontroller. You need to perform the following steps to create a new project:

Select the Toolset (only required for ARM Projects).  Projects).  

Create Project File and Select CPU.  CPU.  

Project Workspace - Books.  Books. 

Create New Source Files.  Files.  

Add Source Files to the Project.  Project. 

Create File Groups.  Groups. 

Set Tool Options for Target Hardware.  Hardware. 

Configure the CPU Startup Code.  Code.  

Build Project and Generate Application Program Code.  Code. 

Create a HEX File for PROM Programming. Programming.

The detailed description to create a project will be discussed with snap shots below for better understanding the tool.



Click on the Keil uVision Icon on Desktop



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The following fig will appear 


Click on the Project menu from the title bar 


Then Click on New Project



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Save the Project by typing suitable project name with no extension in u r own folder sited in either C:\ or D:\


Then Click on Save button above.


Select the component for u r project. i.e. Atmel……


Click on the + Symbol beside of Atmel



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Select AT89C51 as shown below


Then Click on “OK”


The Following fig will appear 



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Then Click either YES or NO………mostly “NO”


 Now your project is ready to USE


 Now double click on the Target1, Target1, you would get another optio option n “Source group 1” as shown in next page.


Click on the file option from menu bar and select “new”



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The next screen will be as shown in next page, and just maximize it by double clicking on its blue boarder.


 Now start writing program in either in “C” or “ASM”


For a program written in Assembly, then save it with extension “. asm” and for “C” based program save it with extension “ .C”



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 Now right click on Source group 1 and click on “Add files to Group Source”



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 Now you will get another window, window, on which by default “C” files will appear.


 Now select as per your file extension given while saving the file


Click only one time on option “ADD”


 Now Press function key F7 to compile. compile. Any error will appear if so happen.



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If the file contains no error, then press Control+F5 simultaneously.


The new window is as follows


Then Click “OK”



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 Now Click on the Peripherals from menu bar, and and check your required port as shown in fig below


Drag the port a side and click in the program file.


 Now keep Pressing function key “F11” “F11” slowly and observe.


You are running your program successfully



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EXPRESS SCH: Express PCB is the software tool which consists two functionalities one regarding the Circuit designing and the other for PCB designing. Here we are using Express SCH for designing the circuit regarding the project.

Take a few minutes to acquaint yourself with the Express SCH program's display. You will notice that there are two toolbars, one along the top and another along the left side. At the bottom of of the display is a status bar.

Drawing a Schematic

Express SCH is a very easy to use Windows application for drawing schematics. While not required, we suggest that you draw a schematic for your circuit before designing the PC board. By linking the schematic to the PCB, y you ou will save time designing and be less likely to make mistakes. You will also discover that the user interface for Express SCH and Express PCB is so similar that after spending the few minutes to learn one, the other will already be familiar.



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Embedded C:

What is an embedded system?

An embedded system is an application that contains at least one programmable computer and which is used by individuals who are, in the main, unaware that the system is computer-based.

Which programming language should you use?

Having decided to use an 8051 processor as the basis of your embedded system, the next key decision that needs to be made is the choice of programming language. In order to identify a suitable language for embedded systems, we might begin by making the following observations: 

Computers (such as microcontroller, microprocessor or DSP chips) only accept instructions in ‘machine code’ (‘object codes’). Machine code is, by definition, in the language of the computer, rather than that of the  programmer. Interpretation of the code by the programmer programmer is difficult and error prone.

All software, whether in assembly, C, C++, Java or Ada must ultimately be translated into machine code in order to be executed by the computer.

Embedded processors – like the 8051 – have limited processor power and very limited memory available: the language used must be efficient.

The language chosen should be in common use.

Summary of C language Features:

It is ‘mid-level’, with ‘high-level’ features (such as support for functions and modules), and ‘low-level’ features (such as good access to hardware via pointers). 

It is very efficient.



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It is popular and well understood.

Even desktop developers who have used only Java or C++ can soon understand C syntax.

Good, well-proven compilers are available for every embedded processor (8 bit to 32-bit or more).

Basic C program structure:

//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - //Basic blank C program that does nothing // Includes //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - #include <reg51.h reg51.h> >

// SFR declarations

Void main (void) {  While (1); {  Body of the loop

// Infinite loop

 }  }


// match the braces


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After selecting the mode of operation, the optical sensor takes the finger print and compares with the previously stored database. If the present finger prints matches with any one of the previously stored data then the controller sends a signal to enable the keypad. For each key press a low logic value will be present at the concerned pin of the microcontroller and by reading this value the controller will do the further actions as specified in the program. The concerned transaction by the user is loaded in the external memory in this case what we are using is EEPROM of 2K bytes at a  particular location in the memory. All these functions which are performed by the user are simultaneously displayed on the LCD. In case any of the finger print is not matched with the data the Locker system is not opened and the Keypad is not enabled at all by giving the indication in the form of buzzer.



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1. The performan performance ce of the system system can be be further further improved improved in terms terms of operatin operating g speed, memory capacity by using the advanced controllers. 2. The storage storage memory memory of the the particular particular user can be increased increased by interfa interfacing cing the controller to the PC for all these transactions. 3. The device device can be made made to perform perform better better by provid providing ing the power power supply supply with with the help of Battery to reduce the requirement of main AC supply. 4. A speaking speaking voice voice alarm used used to indicate indicate the the unauthorized unauthorized person person accessing accessing the the ATM and the Locker system and to indicate the wrong Passport. 5. The system system can be made made to commun communicate icate with with modems modems or mobile mobile phone phoness to alert the user on every transaction in the ATM mode and to alert the authorities in the Passport verification mode.



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A step by step approach in designing the microcontroller based system for securing the transactions of the user and providing the security for the locker system and even more for the PASSPORT verification using a finger print scanner has been followed. The result obtained in providing the security is quite reliable in all the three modes.

The system has successfully overcome some of the aspects existing with the present technologies, by the use of finger print Biometric as the authentication Technology.



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The 8051 Micro controller and Embedded Systems   -Muhammad Ali Mazidi


Janice Gillispie Mazidi

The 8051 Micro controller Architecture, Programming & Applications


-Kenneth J.Ayala

Fundamentals Of Micro processors and Micro computers


Micro processor Architecture, Programming & Applications


-Ramesh S. Gaonkar 

Electronic Components



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-D.V. Prasad

WEB Resources: www.atmel.com www.8051projects.com www.microsoftsearch.com www.geocities.com

www.alldatasheet.com www.bioenable.com



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