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The technology that is presently used in shopping malls are billing of the products using bar
coding technique. A bar code is a set of parallel printed lines with different thickness which is
used to store coded information about a particular product. Bar codes are usually read with the
help of hand held or stationary laser scanners over which a bar code is run. A barcode is an
optical machine-readable representation of data relating to the object to which it is attached.
Originally barcodes represented data by varying the widths and spacing’s of parallel lines, and
may be referred to as linear or one-dimensional (1D). Later they evolved into rectangles, dots,
hexagons and other geometric patterns in two dimensions (2D). Although 2D systems use a
variety of symbols, they are generally referred to as barcodes as well. Barcodes originally were
scanned by special optical scanners called barcode readers; later, scanners and interpretive
software became available on devices including desktop printers and smartphones.
Bar code readers eliminate the need for manual entry of data. It is proven to be very
efficient in inventory, point of sale and tracking. A bar code reader uses a laser beam to read the
code. The laser beam moves over the barcode and is reflected by the lighter bars and absorbed by
the darker bars. The reader converts the pattern of reflected and non-reflected laser light into a
digital code which is unique to that product. The last number on the barcode is a check digit. If
this does not match the check digit calculated from the other numbers in the barcode then an
error beep is produced.
The data contained in a bar code is nothing more than product reference information,
which the computer uses to look up records associated with the product. Product records such as
on-hand balances, warehouse locations and production status can be readily obtained by
scanning a bar code.
Dept. of ECE
Prime College of Engineering
Bar code systems consist of two main components: the hardware (scanners and decoders)
to read the bar code labels, and the software to process the information and interface with your
existing business management software.
The main disadvantage of bar code technology is that if a barcode becomes scratched or
crumpled the reader may not be able to read it. The further disadvantages of bar code system are
listed below:
 Barcode readers require a direct line of sight to the printed barcode
 Reading barcodes is much more time-consuming; due to the fact that a direct line of sight
is required, if the items are not properly oriented to the reader it may take seconds to read
an individual tag. Barcode readers usually take a half-second or more to successfully
complete a read.
 Line of sight requirements also limit the ruggedness of barcodes as well as the reusability
of barcodes.
 Barcodes have no read/write capability; that is, you cannot add to the information written
on a printed barcode.
RFID is a “generic term for technologies that use radio waves to automatically identify
individual items. There are several methods of identifying objects using RFID, but the most
common is to store a serial number that identifies a product, and perhaps other information, on a
microchip that is attached to an antenna”. An essential aspect of any functional RFID system are
‘interrogators’ or ‘readers’ which are used to read or write to RFID tags.
Dept. of ECE
Prime College of Engineering
The advantages of RFID over bar codes are:
Read Rate: RFID has high throughput because nearly 100 tags can be scanned at a time.
But in barcodes, tags are read manually one after one.
Line of Sight: It is not required in RFID and items can be aligned in any direction, as
long as it is in the read range. But in barcode line of sight is required and items should be
oriented in a very particular manner.
Read or Write Capability: RFID has the ability to read, write, modify, and update.
Whereas, barcodes can only read.
Durability: RFID has the ability to scan in the harsh environment, as it is much better
protected and can also be attached internally. It easily gets damaged or removed and
cannot be scanned if it is dirty or greasy.
Security: In RFID information can be encrypted, password protected, so information
stored is much more secure and very difficult to replicate. Whereas barcodes can be
easily counterfeited.
Event Triggering: RFID has the ability to trigger particular events such as door openings,
alarms, etc. whereas barcodes cannot be used to trigger events.
Our project’s aim is to make utilize the advantages of RFID over barcodes so as to improve
the existing shopping mall system of billing. Each product of the shop consists of a RFID reader
and an RFID tag is attached to the trolley. By using RFID technology we can reduce large
queues near the cash counters in a shopping mall. Each customer will select a trolley with a
particular identification number and the bill of the products in the trolley will be automatically
summed up in the centralized billing system. The customer can readily pay the cash without the
need for waiting for each item to be scanned and billed using a bar code reader. The customer is
also provided with information such as weight, price etc. regarding the product. Thus the process
of shopping can be speed up. This project is based on embedded system, which is the
combination of software and hardware.
Dept. of ECE
Prime College of Engineering
Embedded system spans all aspects of modern life and there are many examples of their
use. An embedded system is a computer system designed for specific control functions within a
larger system, often with real-time computing constraints. It is embedded as part of a complete
device often including hardware and mechanical parts. By contrast, a general-purpose computer,
such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user
needs. Embedded systems control many devices in common use today.
Embedded systems contain processing cores that are typically either microcontrollers or
digital signal processors (DSP). The key characteristic, however, is being dedicated to handle a
particular task. Since the embedded system is dedicated to specific tasks, design engineers can
optimize it to reduce the size and cost of the product and increase the reliability and
performance. Some embedded systems are mass-produced, benefiting from economies of scale.
Physically, embedded systems range from portable devices such as digital watches and
MP3 players, to large stationary installations like traffic lights, controllers, or the systems
controlling nuclear power plants. Complexity varies from low, with a single microcontroller
chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or
Embedded systems are designed
to do some specific task, rather than be a general
purpose computer for multiple tasks. Some also
have real-time performance constraints that
must be met, for reasons such as safety and usability; others may have low or no performance
requirements, allowing the system hardware to be simplified to reduce costs.Embedded systems
are not always standalone devices. Many embedded systems consist of small, computerized parts
within a larger device that serves a more general purpose.
The program instructions written for embedded systems are referred to as firmware, and
stored in read-only memory or Flash memory chips. They run with
limited computer
hardware resources: little memory, small or non-existent keyboard or screen.
The main goal of our project is to saves time in this busy world for shopping. The
implementation of our project will attract the customer also. It is easy to maintain and also is
very reliable and compatible.
Dept. of ECE
Prime College of Engineering
Shopping mall is a place where most people from all walks of life will get their daily
necessities ranging from food product, apparels; gardening tools electrical appliances, and others.
The numbers of small and large shopping malls keep on increasing over the years throughout the
globe due to the demand of the public. Thus, the level of advancement of shopping mall system
and infrastructure also varies.
Compared to some foreign countries’ shopping mall system, there are still plenty of
spaces for improvement in terms of providing quality shopping experience to the consumers.
Consumers often face problems and inconvenience when shopping. These problems include
worrying that the amount of money brought is not enough for paying all the items wanted,
insufficient information of the items that are for sale and also wasting unnecessary time at the
cashier. Nowadays, if a consumer would like to buy something at a shopping mall, consumers
need to take the particular items from the display shelf and then queue up and wait for their turn
to make payment. Problem will surely arise when the size of a shopping mall is relatively huge.
Besides, consumers also need to queue for a long time at the cashier to wait for turn to make
payment. The time taken for consumers to wait for the customers in front of the queue to scan
every single item and then followed by making payment will definitely take plenty of time
particularly during the season of big sales or if the shopping mall still uses the conventional way
to key in the price of every item by hand to the cash register.
The problems stated above might eventually be solved by the implementation of RFID
technology in shopping mall. This can be done by simply attach an RFID reader to all the items
in shopping mall and attach a RFID tag with a LCD display on the shopping trolley. With the
implementation of this system, consumers can know the price of every item that are scanned in,
total price of all the items, and also brief details of the item such as the weight.
Dept. of ECE
Prime College of Engineering
Consumers will be able to get information of all the items at shopping mall, total up the
prices of items as they shop, and save unnecessary time at the cashier. This system is being
developed with the purpose to further enhance the existing shopping mall systems which are
mostly using barcodes. At which an RFID tag with a display unit will be attached to the shopping
trolley and an interface will also be embedded in this device in order to allow consumers to shop
with ease.
Dept. of ECE
Prime College of Engineering
3.1. Overview
The block diagram of the Smart Shop shown in figure (1) gives an overall idea about the
working of the project. It consists of a Microprocessor, Centralized Billing system, LCDs, trolley
with RFID Card, stock box with RFID card reader and Power Supply Unit. The Microcontroller,
being the main part, controls the overall operation of the system. The power required for the
working of the system is provided by the Power Supply Unit that supplies a power of 5V. The
LCD near the tray displays the total weight of the item in the tray, picked weight and the price
per Kg. The same data is displayed on the LCD on the trolley when the item is purchased. The
data to be displayed on the LCD on the trolley is send from the weighing tray through RF
transmission. The IR Sensor on the weighing tray is used to check the presence of the trolley
near the weighing tray. When the trolley is moved away from the weighing tray the bill of the
item is send to the Centralizes Billing System trough RF transmission
Dept. of ECE
Prime College of Engineering
Figure 3.1. : Block diagram representation of smart shop
Dept. of ECE
Prime College of Engineering
Figure 3.2. : Microcontroller- AT89C52
The microcontroller AT89C52 is the main part of the system. All the processing and
controlling actions are done on the microcontroller. The microcontroller serves as an
intermediate between weighing machine and centralized billing system.
3.2.2. SOFTWARE Embedded systems
An embedded system is a special purpose computer system, which is completely
encapsulated by the device it controls. It is called “embedded” because the micro controller is
inside some other system. An embedded system has specific requirements and performs predefined tasks unlike a general purpose personal computer. An embedded system is a combination
of computer hardware and software and perhaps additional mechanical or other parts, designed to
perform a dedicated function.
These are the following features of embedded systems
 It is a combination of software and hardware.
 It is a system that has a computing device embedded into it.
 They are designed around a micro controller which integrates memory and peripherals.
Dept. of ECE
Prime College of Engineering
Characteristics and benefits of Embedded Systems
Sophisticated functionality.
Real time operation.
Low manufacturing cost.
Low power consumption.
Eliminates necessity of complex circuitry.
Smarter products.
Smaller size.
User friendly.
State of the art technology. Keil µ vision compiler
µVision is an IDE (Integrated Development Environment) that helps you write, compile, and
debug embedded program. It encapsulates the following components:
A project manager
Tool configuration
A powerful debugger
µVision adds many new features to the Editor like Text Templates, Quick Function
Navigation, Syntax Coloring with brace highlighting, Configuration Wizard for dialog based
startup and debugger setup.
Building and applications in µ vision:
To build (compile, assemble, and link) an application in µVision, you must:
1. Select Project - Open Project (for EG: \C166\EXAMPLES\HELLO\HELLO.UV2).
2. Select Project - Rebuild all target files or Build target.
Dept. of ECE
Prime College of Engineering
µVision2 compiles, assembles, and links the files in your project.
Creating your own application in µVision2:
To create a new project in µVision, you must:
1. Select Project - New Project.
2. Select a directory and enter the name of the project file.
3. Select Project - Select Device and select an AT89C52 device from the Device Database.
4. Create source files to add to the project.
5. Select Project - Targets, Groups, and Files. Add/Files, select Source Group1, and add the
source files to the project.
6. Select Project - Options and set the tool options. Note when you select the target device
from the Device Database™ all special options are set automatically. You typically only
need to configure the memory map of your target hardware. Default memory model
settings are optimal for most applications.
7. Select Project - Rebuild all target files or Build target.
To debug an application created using µVision2, you must:
1. Select Debug - Start/Stop Debug Session.
2. Use the Step toolbar buttons to single-step through your program. You may enter G, main
in the Output Window to execute to the main C function.
3. Open the Serial Window using the Serial #1 button on the toolbar.
4. Debug your program using standard options like Step, Go, Break, and so on.e
Device data base:
A unique feature of the Keil µVision2 IDE is the Device Database which contains
information about more than 400 supported microcontrollers. When you create a new µVision2
project and select the target chip from the database, µVision2 sets all assembler, compiler, linker,
and debugger options for you. The only option you must configure is the memory map. As new
devices become available, they are added to the database along with data sheets and header files.
Dept. of ECE
Prime College of Engineering
SMART SHOP Hyper terminal
HyperTerminal (also known as Hyper Term) is a communications and terminal emulation
program that comes with the Windows operating system, beginning with Windows 98.
HyperTerminal can be used to set up a dial-up connection to another computer through the
internal modem using Telnet or to access a bulletin board service (BBS) in another computer. It
can also be used to set up a connection for data transfer between two computers (such as your
desktop computer and a portable computer) using the serial ports and for serial-port control of
external devices or systems such as scientific instruments, robots, or radio communications
stations. HyperTerminal can also be used as a troubleshooting tool when setting up and using a
modem. You can send commands through HyperTerminal to make sure that your modem is
connected properly.
Developed by Hilgraeve from a more comprehensive communications program called Hyper
ACCESS, HyperTerminal has features similar to the Linux program, minicom. In Windows XP,
HyperTerminal can be located from the Start menu
Dept. of ECE
Prime College of Engineering
3.2.3. TROLLEY
Figure 3.3. : Trolley with RFID
A trolley is a small vehicle with wheels that can carry things. People can push trolleys.
There are different kinds of trolleys. There are shopping trolleys which are used in supermarkets
and other large stores with self-service. In American English these are called shopping carriages
or shopping carts. Customers can put things they want to buy in the trolley and then pay for
everything at the checkout. Usually they are then allowed to wheel the trolley with the things
they have bought out to their car.
In the trolley a LCD and a RFID tag is attached. RFID tag present in the trolley is read by
the RFID card reader, which identifies the trolley number in order to identify the corresponding
customer. The LCD displays the weight of the currently picked item, its corresponding price and
the total price of the commodities placed in the trolley. The total price of the commodities in the
trolley will be send to the centralized billing system.
Dept. of ECE
Prime College of Engineering
In weighing tray we use a weighing machine based on a load cell. A weighing machine is
a measuring instrument for determining the weight or mass of an object. It measures weight or
more specifically, either the tension or compression force of constraint provided by the scale.
Figure 3.4. : Load cell
A load cell is a transducer which converts force into a measurable electrical output. Although
there are many varieties of load cells, strain gage based load cells are the most commonly used
type. Bending beam load cells require particular care when mounting to ensure good load
introduction and to prevent damage from side or non axial forces. Fully weld-sealed stainless
steel low capacity beams down to 5kg are now available offering excellent solutions to low
capacity weighing in harsh environments. Ideal for low capacity vessels or hoppers for process
weighing applications, also suitable for low profile platforms and roll-on platform scales
The bending beam load cell often takes the form of a dual cantilever design, which gives it the
important properties of moment insensitivity. This property is sometimes known as "off-centre
loading" capability or "single-point" capability, and makes the load cell very useful for weighing
platforms that are supported in the centre by one load cell only.
Dept. of ECE
Prime College of Engineering
A RFID card reader and infra red sensor is attached on to the weighing tray. RFID card
reader detects the trolley while the infra red sensors monitors the presence of trolley.
When a trolley is detected by the RFID card reader, then the weighing machine output is
stored as the total weight in the weighing tray. The customer picks the required quantity then the
picked weight is obtained by reducing the total weight from current weight in the weighing tray.
Figure 3.5. : Centralized Billing System
The centralized billing system provides effective customer service in supermarkets by
raising the efficiency shopping mall through quick billing of products. It is a computer which
computes the entire bill of the items in each trolley. It is placed at the checkout of the shop
At the check-out, the smart shopping trolley system transmits the list of items and total
cost to the cashier using wireless technology. This promotes quick shopping and immediate pay
without any queuing process. It reduces labor efforts and increases efficiency by minimizing
Dept. of ECE
Prime College of Engineering
Figure 3.6. : 20X4 Characters LCD
Hitachi HD44780 LCD controller is one of the most common dot matrix liquid crystal
display (LCD) display controllers available. The LCD is used to display data to the user. The
LCD has a 20x4 character display and can be programmed to display almost any kind of data to
the user. We use two 20x4 character LCDs, one on the stock box and the other on the trolley.
The LCD displays the net weight of the quantity, price per quantity, the weight of the
quantity took and the corresponding price of that quantity. The message to be displayed is send
to the LCD through data-bus. A set of control lines is needed for proper displaying of the
characters in the LCD.
Dept. of ECE
Prime College of Engineering
Figure 3.7. : IR Sensors
An IR LED, also known as IR transmitter, is a special purpose LED that transmits infrared
rays in the range of 760 nm wavelength. Such LEDs are usually made of gallium arsenide or
aluminium gallium arsenide. They, along with IR receivers, are commonly used as sensors.
The appearance is same as a common LED. Since the human eye cannot see the infrared
radiations, it is not possible for a person to identify whether the IR LED is working or not, unlike
a common LED. To overcome this problem, the camera on a cell phone can be used. The camera
can show us the IR rays being emanated from the IR LED in a circuit.
Here the IR sensor is placed on the stock box in order to sense or monitor the presence of
trolley in front of the stock box. When trolley’s presence is monitored an interrupt is generated
by the IR sensor which is send to the microcontroller.
3.2.8. RS-232
Dept. of ECE
Prime College of Engineering
Figure 3.8. : RS-232 Pin Details
In telecommunications, RS-232 is the traditional name for a series of standards for serial
binary single-ended data and control signals connecting between a DTE (Data Terminal
Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer
serial ports. The standard defines the electrical characteristics and timing of signals, the meaning
of signals. And it is also a standard protocol used in asynchronous serial communication. It is the
primary protocol used over modem lines.
The Microcontroller is setup to transfer data to the computer through the serial port
when a switch is flipped. The data is sent at a rate of 9600 baud using the RS232protocol. Many
modern personal computers have no RS-232 ports and must use an external converter to connect
to older peripherals.
Dept. of ECE
Prime College of Engineering
The figure below shows the power supply unit.
Figure 3.9. : Block Diagram of Power Supply Unit Transformer
Figure 3.10. : Transformer
A transformer is a static (or stationary) piece of which electric power in one circuit is
transformed into electric power of the same frequency in another circuit. It can raise or lower the
voltage in a circuit but with a corresponding decrease or increase in current. It works with the
principle of mutual induction. In our project we are using a step down transformer for providing
a necessary supply for the electronic circuits. Rectifier
Dept. of ECE
Prime College of Engineering
The DC level obtained from a sinusoidal input can be improved 100% using a process
called full wave rectification. It uses 4 diodes in a bridge configuration. From the basic bridge
configuration we see that two diodes are conducting (D2 & D3) while the other two diodes are in
OFF state during the period t=0 to T/2. Accordingly for the negative of input the conducting
diodes are D1 and D4. Thus the polarity across the load is the same. Filter
The filter circuit used here is the capacitor filter circuit where a capacitor is connected at
the rectifier output, and a DC is obtained across it. The filtered waveform is essentially a DC
voltage with negligible ripples, which is ultimately fed to the load. Regulator
Figure 3.11. : Regulator
The output voltage from the capacitor is more filtered and finally regulated. The voltage
regulator LM7805 is a device, which maintains the output voltage constant irrespective of the
change in supply variations, load variations and temperature changes.
Dept. of ECE
Prime College of Engineering
The circuit diagram of the Smart Shop is shown in figure 3.1. As explained in the block
diagram, the main part of the system is the Microcontroller which control the overall operation
and all the other components like LCDs, weighing machine, Centralized Billing System, etc are
interfaced to the microprocessor . When the RFID card reader detects an RFID card a beep sound
is produced by the buzzer. Now the data from the weighing machine is send to the
Microcontroller, from where it is send to the LCD on the trolley. LCD near the weighing
machine displays the details regarding the item it the tray. IR Sensor senses the presence of the
trolley near the weighing tray. The bill of the item purchased is send to the Centralized Billing
System via RF transmission. Power Supply Unit that provide a supply of 5V that is needed for
the entire working of the system .It consists of a Step-down Transformer, a rectifier unit, a filter
unit, and a regulating unit.
Dept. of ECE
Prime College of Engineering
4.2.1 Power supply unit:
5V/9V/12V fixed power supply (Positive) at 1 Ampere current rating. Here step down
transformer with input of 230AC 50Hz and output of 5/12-0-5/12 volts (rms). 5/12=Required DC
output voltage.
The current rating has to be more than 1 Amp.
D1, D2, D3 andD4=Diodes 1N4007.
C1=1000 Micro Farad aluminum electrolytic capacitor.
For loads less than 100mA we can substitute with 220 Micro farad aluminum electrolytic
Voltage rating=2.5 times of output voltage.
C2=10Micro Farad aluminum electrolytic capacitor.
IC1 = 7805 for +5V DC output = 7812 for +12VDCouput
5V/9V/12V fixed power supply (Negative) at 1 Ampere current rating.
IC1 = 7805 for -5V DC output= 7812 for -12VDCouput
4.2.2. Microcontroller:
The speed of the microcontroller 89C52 is 0.9ns,
Use crystal oscillator of clock frequency 11MHz.
For resetting the microcontroller use 10K resistor.
For biasing use capacitor of 1nf as standard value.
Dept. of ECE
Prime College of Engineering
Figure 4.1. :Circuit diagram
Dept. of ECE
Prime College of Engineering
The following details explains the circuit diagram
The AT89C52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K
bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s
high-density nonvolatile memory technology and is compatible with the industry standard 80C51
instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed
in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit
CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89C52 is a
powerful microcontroller which provides a highly-flexible and cost-effective solution to many
embedded control applications
Flash memory can be erased in seconds compared to 20 minutes needed for 8751. For
this reason 89C52 is used in place of 8751 to eliminate the waiting time needed to erase the chip
and thereby speed up the development time. The development system requires a ROM burner
that supports flash memory. The entire contents of ROM should be erased in order to program it
again; the PROM burner itself does this. The 89C52 Flash reliably stores memory contents even
after 10,000 erase and program cycles. AT89C52 is a popular chip of this category from Atmel
The micro-controller generic part number actually includes a whole family of
microcontrollers that have numbers ranging from 8031 to 8751 and are available in N-channel
Metal Oxide Silicon (NMOS) and CMOS construction. 89C52 is an 8-bit micro-controller
having 40 pins arranged as DIP packages.
The features unique to micro-controllers include:
 Compatible with MCS-51® Products
 8K Bytes of In-System Programmable (ISP) Flash Memory
o Endurance: 1000 Write/Erase Cycles
 4.0V to 5.5V Operating Range
 Fully Static Operation: 0 Hz to 33 MHz
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Prime College of Engineering
 Three-level Program Memory Lock
 256 x 8-bit Internal RAM
 32 Programmable I/O Lines
 Three 16-bit Timer/Counters
 Eight Interrupt Sources
 Full Duplex UART Serial Channel
 Low-power Idle and Power-down Modes
 Interrupt Recovery from Power-down Mode
 Watchdog Timer
 Dual Data Pointer
 Power-off Flag
4.4.2. RFID
Radio frequency identification (commonly abbreviated to RFID) is so-named because it
relates to the identification of objects using EM radiation at radio frequencies. large range of
frequencies within the EM spectrum are referred to as Radio Frequencies (RF), which results in a
number of different forms of RFID. Once again, RFID systems may be categorized based on the
band of the EM spectrum that they operate in. RFID systems in the same band will generally
display similar characteristics; those in other bands may well operate very differently and
therefore be more or less suitable for a given application.
Figure 4.2. : RFID Tag
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Prime College of Engineering
An RFID system comprises two components an RFID reader and an RFID tag. Despite its
name, the RFID reader is really the transmitter in an RFID system. The electronics in the reader
uses an external power source to generate the signal that drives the readers antenna and which in
turn creates the appropriate radio wave. This radio wave may be received by an RFID tag, which
in turn reflects some of the energy it receives in a particular way (based on the identity of the
tag). Whilst this reflection is going on, the RFID reader is also acting as a radio receiver, so that
it can detect and decode the reflected signal in order to identify the tag.
There are a number of different types of RFID system, but one basic categorization is
based on the power source used by the tag
1. Passive tag RFID systems require no power source at the tag there is no battery. Instead, the
tag uses the energy of the radio wave to power its operation, much like a crystal radio. This
results in the lowest tag cost, but at the expense of performance.
2. Semi-passive tag RFID systems rely on a battery built into the tag in order to achieve better
performance (typically in terms of operating range). The battery powers the internal circuitry of
the tag during communication, but is not used to generate radio waves.
Figure 4.3. : RFID reader
3. Active tag systems use batteries for their entire operation, and can therefore generate radio
waves proactively, even in the absence of an RFID reader.
Dept. of ECE
Prime College of Engineering
Passive tag RFID systems are the most common type, and are often referred to simply
as RFID system. Passive tags are the simplest, smallest and cheapest version of an RFID tag as
they do not contain a built-in power source and consequently cannot initiate communication with
a reader. As the available power from the reader field diminishes rapidly with distance, passive
tags have practical read ranges that vary from about 10 mm up to about 5 meters.
Figure 4.4. MO SAWR ASK transmitter
The RF Transmitter is extremely small, and excellent for applications enquiring shortrange RF remote controls. Here we use MO SAWR ASK transmitter module. The main
advantage is its excellent performance and is simple to use. The control commands are also send
from this section through antenna to the RF remote receiver. The accuracy of sending and
receiving frequencies are achieved by the use of crystal oscillators. 433.92/315MHz Remote
Keyless-Entry Transmitter, SAW RESONATOR is used. The MO-SAWR is an ASK transmitter
module .The MO-SAWR is designed specifically for remote-control, wireless mouse and car
alarm system operating at 433.92.
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Prime College of Engineering
Figure 4.5. : OS-RX02-ASK receiver
The OS-RX02-ASK is an ASK Hybrid receiver module. It is an effective low cost
solution for using at the frequency of 315/433.92 MHZ. The super-regenerative design exhibits
exceptional sensitivity at a very low cost. This unit receives the signals from the RF remote
transmitter and it is fed in to the microcontroller. The OS-RX02-ASK is an ASK Hybrid receiver
module. Typical sensitivity of the receiver is-105dBm and the supply current is 3.5Ma. The main
features are
Low power consumption
Easy for application
Operation temperature range: -10℃~+60℃
Operation voltage: 5 Volts
Dept. of ECE
Prime College of Engineering
Motors are used to control the movement and working of lid of weighing tray.
Figure 4.6. : Gear motor
Gear motors are complete motive force systems consisting of an electric motor and a
reduction gear train integrated into one easy-to-mount and -configure package. This greatly
reduces the complexity and cost of designing and constructing power tools, machines and
appliances calling for high torque at relatively low shaft speed or RPM. Gear motors allow the
use of economical low-horsepower motors to provide great motive force at low speed such as in
lifts, winches, medical tables, jacks and robotics. They can be large enough to lift a building or
small enough to drive a tiny clock.
Gear motor is used to open the lid of the weighing tray at the instant when trolley is
detected and to close the lid when trolley moves away from the weighing tray.
The current from the microcontroller is not sufficient to drive the motors, hence we make use of
Driver IC.
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Prime College of Engineering
4.4.6. DRIVER IC
The current from the microcontroller is not sufficient to drive the motors. To boost the
current driver ICs are used.
Figure 4.7. : L293D
The driver IC used here is L293D. The Device is a monolithic integrated high voltage,
high current four channel driver designed to accept standard DTL or TTL logic levels and drive
inductive loads (such as relays solenoids, DC and stepping motors) and switching power
transistors. The important features of L293D are:
 600 mA output current capability per channel
 1.2A peak output current (non repetitive) per channel
 Enable facility
 Over temperature protection
 Logical "0" input voltage up to 1.5 V (high noise immunity)
 Internal clamp diodes
To simplify use as two bridges each pair of channels is equipped with an enable input. A
separate supply input is provided for the logic, allowing operation at a lower voltage and internal
clamp diodes are included. This device is suitable for use in switching applications at frequencies
up to 5 kHz. The L293D is assembled in a 16 lead plastic package which has 4 center pins
connected together and used for heat sinking.
Dept. of ECE
Prime College of Engineering
4.4.7. BUZZER
Figure 4.8. : Buzzer
A buzzer or beeper is an audio signaling device, which may be mechanical,
electromechanical, or piezoelectric. Typical uses of buzzers and beepers include alarm devices,
timers and confirmation of user input such as a mouse click or keystroke.
The buzzer produces a beep sound when the RFID card reader detects the RFID tag on the
Dept. of ECE
Prime College of Engineering
This project requires a simple single polarity DC power supply. Existing power supplies
may be too big either in power output or physical size. Just a simple power supply is required.
For most non-critical applications the best and simple choice for a voltage regulator is the
3-terminal type. The three terminals are input, ground and output.
This power supply circuit provides a single DC power supply. With the appropriate
choice of transformer and 3-terminal voltage regulator pairs we can easily build a small power
supply delivering up to one amp at +/-5V, +/-9V, +/-12V, +/-15V or +/-18V. The power supply
circuit has to provide the centre tapped transformer and the three terminal pair of regulators you
want: 7805 & 7905, 7809 & 7909, 7812 &7912, 7815 &7915 or 7818 & 7918. We have to note
that the + and – regulators do not have to be matched, we can for example, use a +5V and +12V
pair. Voltage regulators are 7812 and 7805 fitted with this circuit to give +12
Power supply unit consists of the following units:
1. Step down transformer
2. Rectifier unit
3. Input filter
4. Regulator unit Step down transformer:
It is used to step down the main supply voltage by using step down transformer. It
consists of primary and secondary coils. The o/p from the secondary coil is also AC wave form.
So we have to convert the easy wave form into dc voltage by using rectifier unit.
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Prime College of Engineering
SMART SHOP Rectifier unit:
We have to convert AC voltage to DC using rectifier. Bridge rectifier is used. This o/p
voltage often rectifier is in rippled form, so we have to remove ripples from DC voltage. Input filter:
Capacitor acts as filter. The principle of the capacitor is charging and discharging. It
charges in the positive half cycle of the AC voltage and it will discharge in the negative half
cycle. So this allows only AC voltage and does not allow the DC voltage. This filter is fixed
before the regulator. Regulator unit:
Regulator regulates o/p voltage constant. It is classified into:
1. Input pin
2. Ground pin
3. Output pin
Dept. of ECE
Prime College of Engineering
As explained before the major components in Smart Shop are
RFID tag in the trolley and RFID card reader in the stock box.
IR sensor.
LCD Display near the stock box and in the trolley.
RF Transmitter and Receiver.
Centralized Billing System.
Working of the Smart Shop is as explained below:
When the customer brings the trolley near a stock box containing any item to be purchased, RFID
card reader in the stock box detects the RFID card (RFID Tag) in the trolley. Once the tag has been
detected the lid of the stock box is opened with the help of a gear motor. An IR Sensor is used to detect
the presence of the trolley near the stock box. LCD near the stock box displays the information regarding
the item such as total weight of the item in the stock box, price per kilogram.
When the customer picks the required amount of the item from the stock box and the picked
weight of the item is displayed in the LCD near the stock box. The corresponding details are also
displayed in the LCD in the trolley. Now when the customer moves away from the stock box these details
are send to the Centralized Billing System through RF transmitter. The movement of trolley away from
the stock box is sensed by the IR sensor. The bill is send to the billing system only after the trolley is
moved away from the stock box.
Dept. of ECE
Prime College of Engineering
A Printed Circuit Board (PCB) is used to mechanically support and electrically connect
electronic components using conductive paths or tracks or signal traces etched from copper
sheets laminated onto a non conductive substrate. It is also referred to as Printed Wiring Board or
Etched Wiring Board. A Printed Circuit Board (PCB) populated with electronic components is a
Printed Circuit Assembly (PCA), also known as Printed Circuit Board Assembly (PCBA).
Alternative to PCBs include wire wrap and point to point construction. PCBs are often less
expensive and more reliable than these alternatives, though they require more layout effort and
higher initial cost. PCBs are much cheaper and faster for high volume production since
production and soldering of PCB can be done by automated equipments.
Printed circuits are fabricated by first drawing and etching pattern. This pattern is then
photographed and reproduced on clear plastic sheet. The plastic sheet is placed over a copper
coated glass epoxy or phenolic board and the assemble undergoes a photochemical process. And
the resulting copper coated board consists of the printed tracks which interconnects the
components as per the schematic diagram.
Dept. of ECE
Prime College of Engineering
The first step of assembling is to procure a printed circuit board. The fabrication of the
program counter plays a crucial role in the electronic field. The success of a circuit also depends
on the PCB. As far as cost is concerned the 25% of total cost is gone for PCB design and
We are using a micro controller based system that handles high frequencies. In the high
frequency circuit the data may be easily violated in the PCB due to physical parameters. This is
the track capacitance and inductance can cause the cross talk in the buses. Also unwanted noise
can be induced into supply rails and from there it can affect the total response.
Design of PCB is concerned as the last step of electronic circuit design as well as first
step in the production of PCBs. The design of PCB consists of designing of the layout followed
by the generation of the art work. EXPRESS PCB is a powerful tool for designing electronic
circuit diagrams.
5.2.1. Processing the film
The layout is printed in a butter paper using a laser printer. The layout is transferred to
copper clad sheet using the screen print procedure. First a negative screen of the layout is
prepared with the help of a professional screen printer. The copper clad sheet is kept under the
screen. The screen printing ink is poured on the screen and brushed through the top of the screen.
The printed board is kept under shade for few hours till the ink become dry.
Etching medium is prepared with the un-hydrous ferric chloride and water. The printed
board is kept in this medium till the exposed copper dissolves in the solution completely. After
that the board is taken out and rinsed in flowing water under a tap. The ink is removed with the
help of NC thinner. The board is coated with soldering in order to prevent oxidation.
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Prime College of Engineering
Another screen, which contains component side layout, is prepared and the same is
printed on the component side of the board. A paper epoxy laminate is used in the board.
5.2.2. Standard requirements
The minimum conductor width of finished PCB shall not be less than 0.05mm for signal
and 0.4mm for power line. The standard ratio is taken as 1:1, 5:2 for signal power and ground
5.2.3. Cleaning
Surface of copper clad may contain oxides greases, oils or solid. They should be removed by
the following procedure.
Wipe with cotton wool soaked with tricolor ethylene.
Dip in 10% HCl solution at room temperature.
Scrap with powder.
Rinse with chlorine free water.
5.2.4. Artwork transfer
Art work transfer can be done in many ways and the procedure used in work is named
fabrication process, usually used methods are:
Silk screen printing
Photographic method
Direct method
First methods are used for industrial and professional applications. In direct method artwork
is transferred to clad sheet in 1:1 ratio using paint or permanent ink. This method is used where a
single PCB is needed.
Dept. of ECE
Prime College of Engineering
5.2.5. Etching
Etching is the process of removing unwanted copper from the processed board using
etching solution. For this the PCB is dipped into the etching solution. Usually ferric chloride
solution is used. It is stirred for the speedy action. After etching the board is cleaned using
Isopropylene alcohol.
5.2.6. Drilling
The holes for mounting components are drilled using a high speed of drilling machine.
The size of the layout designing depending holes to drill will be specified during the upon the
component lead diameter. For drilling we use the mm drill bit.
5.2.7. Varnish coating
If the board is unprotected copper oxides are formed over the conductor and it affects
arability and neatness of the board. For this insulation coating such as varnish can be used.
Dept. of ECE
Prime College of Engineering
Figure 5.1. : PCB Layout
Dept. of ECE
Prime College of Engineering
 The circuit board fabrication cost is lower with mass quantity production.
 Electronic circuit characteristics will be maintained without introducing parasitic
capacitance with a proper circuit board design.
 Component wiring and assembly can be mechanized in a circuit board manufacturing
 PCBs offer uniformity of electrical characteristics from assembly to assembly.
 The location of electronics paths is fixed and so it simplifies component identification
and maintenance of equipments.
 Inspection time is reduced because printed circuit board eliminates the probability of
 Chances of miswiring or short circuited wiring are minimized.
 They have colour code for different connections and hence easy to identify.
 More neater look and even a layman can work on them
 In case of fault connections, it can be easily checked.
Dept. of ECE
Prime College of Engineering
The room should be well ventilated an exhaust fan should be installed in the room where
a continuous work of PCB production goes on.
Unnecessary contact with the solvents should be avoided.
No operation should be carried out near open flames or in the presence of excessive heat.
Containers for resist, developer, dye, thinner and rinse should be of glass, stainless steel
or enamelware.
Plastic should not be used while handling the above chemicals.
The containers and tank should be kept covered when not in use.
Water should not come in contact with these chemicals before use.
The room should be lightened with a low wattage yellow coloured lamp for the
preparation of the board before exposure and for developing after exposure.
Dept. of ECE
Prime College of Engineering