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INTRODUCTION
1.1 OBJECTIVE OF THE WORKTo provide people with a comfortable and convenient living environment,
smart home has become an important research issue. Automatic and intelligent
technologies are applied to the home environment to improve the quality of life.
This reminding mechanism for the user in a smart home environment. We
focus on objects that the user would bring along when he/she goes out. The RFID
technology is used to sense the objects the user brings along at the front door. In the
object database, an object is recorded not only by its name along with a unique RFID
number, but also its class. When the user leaves home, the reminder system checks
the objects in his/her bags and pockets, and compares the objects with a list of objects
generated by the system according to the date of the week and the events on the
calendar. The system then sends a reminder object list to the user by using speaker.
The background setting of this system is in a general home environment. An
RFID reader is installed near the front door and RFID tags are attached to the objects
the user would take out. Whenever the user goes out, the objects he/she brings along
with are detected by the reader and saved in the database.
We are using GSM for alerting the user by sending message or calling them.
We are using like fire sensor, gas sensor, smoke sensor, IR transmitter and receiver,
LDR which contributes in making a complete smart home.
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1.2 BLOCK DIAGRAM
Fig 1.1 Block Diagram
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INTRODUCTION TO EMBEDDED SYSTEMS
An embedded system is a special-purpose system in which the computer
is completely encapsulated by or dedicated to the device or system it controls.
Unlike a general-purpose computer, such as 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.
Personal digital assistants (PDAs) or handheld computers are generally
considered embedded devices because of the nature of their hardware design,
even though they are more expandable in software terms. This line of definition
continues to blur as devices expand.
Physically, embedded systems range from portable devices such as digital
watches and MP3 players, to large stationary installations like traffic lights,
factory controllers, or the systems controlling nuclear power plants. In terms of
complexity embedded systems can range from very simple with a single
microcontroller chip, to very complex with multiple units, peripherals and
networks mounted inside a large chassis or enclosure.
2.1 EXAMPLES OF EMBEDDED SYSTEMS1 .Automatic teller machines (ATMs)
2. Cellular telephones and telephone switches
3. Engine controllers and antilock brake controllers for automobiles
4. Handheld calculators, Handheld computers
5. Medical equipment
6. Personal digital assistant, Videogame consoles
7. Computer peripherals such as routers and printers
8. Industrial controllers for remote machine operation.
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RF-ID
3.1 INTRODUCTION TO RF-IDRadio Frequency Identification (RFID) is a general term that is used to
describe a system that transmits the identity (in the form of a unique serial number) of
an object wirelessly, using radio waves. RFID is evolving as a major technology
enabler for tracking goods and assets around the world. A great deal of attention is
being paid to RFID by the IT industry, media and analysts. According to studies by
Benchmark Research, in 2004 three quarters of manufacturing companies are now
aware of RFID, of which a third are already using, piloting or investigating RFID
applications for their organizations.
Fig 3.1 Radio Frequency Identification (RFID) Circuit
Anticipating the potential benefits of RFID, many of the world’s major
retailers are trialing RFID tagging for pallets and cases shipped into and out of their
distribution centres. The consequence of this RFID activity in the retail sector is likely
to impact on around 200,000 manufacturers and suppliers globally, and will fuel the
market for hardware and software to support RFID.
RFID has many applications outside of the retail supply chain including many
familiar ones such as vehicle security, commuter tags and security badges for access
control into buildings.
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3.2 THE DEVELOPMENT OF RFIDOver the years methods for capturing and storing information have evolved
from paper and card systems, through keyboard data entry, bar code data capture and
are now augmented by technological improvements such as touch screens on the shop
floor. All of these initiatives have been aimed at improving accuracy, completeness
and timeliness of information. However these all rely on access to a host computer
system to make use of data collected.
So, how does RFID differ from other methods of identification and data
capture? A typical RFID system is made up of three components: tags, readers and the
host computer system.
3.2.1 TAGS
An RFID tag is a tiny radio device that is also referred to as a transponder,
smart tag, smart label or radio barcode. The tag comprises a simple silicon microchip
(typically less than half a millimeter in size) attached to a small flat aerial and
mounted on a substrate. The whole device can then be encapsulated in different
materials (such as plastic) dependent upon its intended usage. The finished tag can be
attached to an object, typically an item, box or pallet and read remotely to ascertain its
identity, position or state.
3.2.2 READERS
The reader, sometimes called an interrogator or scanner, sends and receives
RF data to and from the tag via antennae.
A reader may have multiple antennae that are responsible for sending and
receiving radio waves. The readers can be fixed or mobile, can read information
stored on the tags and write information to them. This can be achieved without direct
line of sight and in environments where traditional data collection could not operate.
A major advantage is that information can be written to the tag multiple times so
storing a history that travels with the article.
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3.2.3 HOST COMPUTER
The data acquired by the readers is then passed to a host computer, which may
run specialist RFID software or middleware to filter the data
and route it to the correct application, to be processed into useful information.
RFID is not a new technology, in fact it was first used by the US military
during WWII, but wider deployment chain was slow due to the high costs of
equipment and its limited reliability in volume environments. RFID equipment has
steadily fallen in price as volumes increase and microchip unit production costs fall.
With the ability to store several kilobytes of data in addition to the ‘number plate’
identifier it could be viewed as a form of ‘mass distributed database’ that has the
potential to become ubiquitous - billions of tags in daily use throughout the world on
all objects that are produced, stored, moved, sold and maintained.
3.3 AUTOMATIC IDENTIFICATIONRFID technologies are grouped under the more generic Automatic
Identification (Auto-ID) technologies. Examples of other Auto-ID technologies
include Smartcards and Barcodes. RFID is often positioned as next generation bar-
coding because of its obvious advantages over barcodes. However, in many
environments it is likely to co-exist with the barcode for a long time. The barcode
labels that triggered a revolution in identification systems back in the 1970’s are now
cheap and commonly used, but have several limitations:
Low storage capacity
1. They only represent a family of items and not an individual or unique item
durability (as mostly printed paper)
2. Low read range
3. They can only be read when line of sight is established
4. They can only be read one at a time
5. They cannot be written to or reprogrammed
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3.4WHAT IS RFID AND HOW WILL IT HELP YOU?Radio Frequency Identification (RFID) is a silicon chip-based transponder that
communicates via radio waves. RFID has been commercially available for many
years, but the latest RFID developments now offer the compatibility with an express
logistics and transport system to enable the following potential improvements to
service:
1. Increased security of your package and items within your shipment.
2. Visibility of items within your shipment without opening the package
3. Later cut-offs due to automated and simultaneous identification
4. “Near” real time track and trace, which is dynamic, automated and proactiv
through links to GPS (global positioning system) and communications systems
5. Condition monitoring (eg, temperature, vibration, humidity) through links to micro
sensors
6. Counterfeit protection through validation of genuine goods throughout the logistics
process - Intellectual Property Rights (IPR).
3.5 WHY RFID TECHNOLOGY?Identification processes that rely on AIDC technologies are significantly
more reliable and less expensive than that are not automated.
RFID represents a technological advancement in AIDC because it offers
advantages that are not available in other AIDC systems such as bar codes. RFID
offers these advantages because it relies on radio frequencies to transmit information
rather than light, which is required for optical AIDC technologies.
RFID products often support other features that bar codes and other AIDC
technologies do not have, Without optical line of sight, because radio waves can
penetrate many materials, At greater speeds, because many tags can be read quickly,
whereas optical technology often requires time to manually reposition objects to
make their bar codes visible, and Over greater distances, because many radio
technologies can transmit and receive signals more effectively than optical
technology under most operating conditions. such as rewritable memory, security
features, and environmental sensors that enable the RFID technology to record a
history of events. The types of events that can be recorded include temperature
changes, sudden shocks, or high humidity. Today, people typically perceive the
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label identifying a particular object of interest as static, but RFID technology can
make this label dynamic or even “smart” by enabling the label to acquire data about
the object even when people are not present to handle it.
RFID is short for Radio Frequency Identification. Generally a RFID system
consists of 2 parts. A Reader, and one or more Transponders, also known as
Tags. RFID systems evolved from barcode labels as a means to automatically identify
and track products and people. You will be generally familiar with RFID systems as
seen in:
3.5.1ACCESS CONTROL FID Readers placed at entrances that require a person to pass their proximity
card (RF tag) to be “read' before the access can be made.
3.5.2CONTACT LESS PAYMENT SYSTEMS
RFID tags used to carry payment information. RFIDs are particular suited to
electronic Toll collection systems. Tags attached to vehicles, or carried by
people transmit payment information to a fixed reader attached to a Toll station.
Payments are then routinely deducted from a users account, or information is changed
directly on the RFID tag.
3.5.3PRODUCT TRACKING AND INVENTORY CONTROL
RFID systems are commonly used to track and record the movement of
ordinary items such as library books, clothes, factory pallets, electrical goods and
numerous items.
3.6 HOW DO RFIDS WORKShown below is a typical RFID system. In every RFID system the transponder
Tags contain information. This information can be as little as a single binary bit , or
be a large array of bits representing such things as an identity code, personal medical
information, or literally any type of information that can be stored in digital binary
format
Shown is a RFID transceiver that communicates with a passive Tag. Passive tags
have no power source of their own and instead derive power from the incident
electromagnetic field. Commonly the heart of each tag is a microchip. When the Tag
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enters the generated RF field it is able to draw enough power from the field to access
its internal memory and transmit its stored information. When the transponder Tag
draws power in this way the resultant interaction of the RF fields causes the voltage at
the transceiver antenna to drop in value. This effect is utilized by the Tag to
communicate its information to the reader. The Tag is able to control the amount of
power drawn from the field and by doing so it can modulate the voltage sensed at the
Transceiver according to the bit pattern it wishes to transmit.
Fig3.2 RFID System
3.6 HISTORY OF RFIDRadio frequency identification has been around for decades. It’s generally said
that the roots of radio frequency identification technology can be traced back to
World War II. The Germans, Japanese, Americans and British were all using radar—
which had been discovered in 1935 by Scottish physicist Sir Robert Alexander
Watson-Watt—to warn of approaching planes while they were still miles away. The
problem was there was no way to identify which planes belonged to the enemy and
which were a country’s own pilots returning from a mission. The Germans discovered
that if pilots rolled their planes as they returned to base, it would change the radio
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signal reflected back. This crude method alerted the radar crew on the ground that
these were German planes and not Allied aircraft (this is, essentially, the first passive
RFID system).
INTRODUCTION TO GSM
A GSM modem is a specialized type of modem which accepts a SIM card, and
operates over a subscription to a mobile operator, just like a mobile phone. From the
mobile operator perspective, a GSM modem looks just like a mobile phone. When a
GSM modem is connected to a computer, this allows the computer to use the GSM
modem to communicate over the mobile network. While these GSM modems are
most frequently used to provide mobile internet connectivity, many of them can also
be used for sending and receiving SMS and MMS messages. A GSM modem can be a
dedicated modem device with a serial, USB or Bluetooth connection, or it can be a
mobile phone that provides GSM modem capabilities.
A GSM modem exposes an interface that allows applications such as Now
SMS to send and receive messages over the modem interface. The mobile operator
charges for this message sending and receiving as if it was performed directly on a
mobile phone. To perform these tasks, a GSM modem must support an “extended AT
command set” for sending/receiving SMS messages.
Fig 4.1 GSM Modem
GSM modems can be a quick and efficient way to get started with SMS,
because a special subscription to an SMS service provider is not required. In most
parts of the world, GSM modems are a cost effective solution for receiving SMS
messages, because the sender is paying for the message delivery.
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4.1 ARCHITECTURE OF GSM SYSTEM A GSM network is composed of several functional entities, whose functions
and interfaces are specified. Figure 1 shows the layout of a generic GSM network.
The GSM network can be divided into three broad parts. The Mobile Station is carried
by the subscriber. The Base Station Subsystem controls the radio link with the Mobile
Station. The Network Subsystem, the main part of which is the Mobile services
Switching Center (MSC), performs the switching of calls between the mobile users,
and between mobile and fixed network users. The MSC also handles the mobility
management operations. The Mobile Station and the Base Station Subsystem
communicate across the air so known as the air interface or radio link.
Architecture of GSM system consist of three parts .They Are
(i)Base Station Subsystem (BSS)
(ii)Network Switching Subsystem (NSS)
(Iii)Operation Support Subsystem (OSS)
Fig: 4.2 Architecture of GSM
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4.1.1MOBILE STATION
The mobile station (MS) consists of the mobile equipment (the terminal) and a
smart card called the Subscriber Identity Module (SIM). The SIM provides personal
mobility, so that the user can have access to subscribed services irrespective of a
specific terminal. By inserting the SIM card into another GSM terminal, the user is
able to receive calls at that terminal, make calls from that terminal, and receive other
subscribed services. The mobile equipment is uniquely identified by the International
Mobile Equipment Identity (IMEI). The SIM card contains the International Mobile
Subscriber Identity (IMSI) used to identify the subscriber to the system, a secret key
for authentication, and other information. The IMEI and the IMSI are independent,
thereby allowing personal mobility. The SIM card may be protected against
unauthorized use by a password or personal identity number.
4.1.2 BASE STATION SUBSYSTEM
The Base Station Subsystem is composed of two parts, the Base Transceiver
Station (BTS) and the Base Station Controller (BSC). These communicate across the
standardized Abis interface, allowing (as in the rest of the system) operation between
components made by different suppliers. The Base Transceiver Station houses the
radio transceivers that define a cell and handles the radio-link protocols with the
Mobile Station. In a large urban area, there will potentially be a large number of BTSs
deployed, thus the requirements for a BTS are ruggedness, reliability, portability, and
minimum cost. The Base Station Controller manages the radio resources for one or
more BTSs. It handles radio-channel setup, frequency hopping, and handovers, as
described below. The BSC is the connection between the mobile station and the
Mobile service Switching Center (MSC).
4.1.3 NETWORK SWITCHING SUBSYSTEM
The central component of the Network Subsystem is the Mobile services
Switching Center (MSC). It acts like a normal switching node of the PSTN or ISDN,
and additionally provides all the functionality needed to handle a mobile subscriber,
such as registration, authentication, location updating, handovers, and call routing to a
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roaming subscriber. These services are provided in conjunction with several
functional entities, which together form the Network Subsystem.
The MSC provides the connection to the fixed networks (such as the PSTN or
ISDN). Signalling between functional entities in the Network Subsystem uses
Signalling System Number 7 (SS7), used for trunk signalling in ISDN and widely
used in current public networks. There are three different data bases in the NSS. They
are
1. Home Location Register (HLR): The Home Location Register (HLR) and
Visitor Location Register (VLR), together with the MSC, provide the call-routing and
roaming capabilities of GSM. The HLR contains all the administrative information of
each subscriber registered in the corresponding GSM network, along with the current
location of the mobile. The location of the mobile is typically in the form of the
signaling address of the VLR associated with the mobile as a distributed database
station. The actual routing procedure will be described later. There is logically one
HLR per GSM network, although it may be implemented
2. Visitor Location Register VLR): The Visitor Location Register (VLR)
contains selected administrative information from the HLR, necessary for call control
and provision of the subscribed services, for each mobile currently located in the
geographical area controlled by the VLR. Although each functional entity can be
implemented as an independent unit, all manufacturers of switching equipment to date
implement the VLR together with the MSC, so that the geographical area controlled
by the MSC corresponds to that controlled by the VLR, thus simplifying the
signalling required.
3. Authentication Center (AUC): The other two registers are used for
authentication and security purposes. The Equipment Identity Register (EIR) is a
database that contains a list of all valid mobile equipment on the network, where each
mobile station is identified by its International Mobile Equipment Identity (IMEI). An
IMEI is marked as invalid if it has been reported stolen or is not type approved. The
Authentication Center (AUC) is a protected database that stores a copy of the secret
key stored in each subscriber's SIM card, which is used for authentication and
encryption over the radio channel.4.2 GSM NETWORK OPERATORS
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T-Mobile and Cingular operate GSM networks in the United States on the
1,900 MHz band. GSM networks in other countries operate at 900, 1,800, or 1,900
MHz
4.3 GSM CARRIER FREQUENCIES GSM networks operate in a number of different carrier frequency ranges
(separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G),
with most 2G GSM networks operating in the 900 MHz or 1800 MHz bands. Where
these bands were already allocated, the 850 MHz and 1900 MHz bands were used
instead (for example in Canada and the United States). In rare cases the 400 and
450 MHz frequency bands are assigned in some countries because they were
previously used for first-generation systems. Most 3G networks in Europe operate
in the 2100 MHz frequency band. Regardless of the frequency selected by an
operator, it is divided into timeslots for individual phones to use. This allows eight
full-rate or sixteen half-rate speech channels per radio frequency. These eight radio
timeslots (or eight burst periods) are grouped into a TDMA frame. Half rate channels
use alternate frames in the same timeslot. The channel data rate for all 8 channels is
270.833 Kbit/s, and the frame duration is 4.615 ms. The transmission power in the
handset is limited to a maximum of 2 watts in GSM850/900 and 1 watt in
GSM1800/1900.
4.4 GSM AT COMMANDS AT Commands are used to perform different operations is GSM module
Short message commands
4 .4.1PREFERRED MESSAGE FORMAT +CMGF DESCRIPTION
The message formats supported are text mode and PDU mode. In PDU mode, a
complete SMS Message including all header information is given as a binary string
(in hexadecimal format).Therefore, only the following set of characters is allowed:
{‘0’,’1’,’2’,’3’,’4’,’5’,’6’,’7’,’8’,’9’, ‘A’,‘B’,’C’,’D’,’E’,’F’}. Each pair or characters
are converted to a byte (e.g.: ‘41’ is converted to the ASCII character ‘A’, whose
ASCII code is 0x41 or 65). In Text mode, all commands and responses are in ASCII
characters.
The format selected is stored in EEPROM by the +CSAS command.Syntax:
Command syntax: AT+CMGF
Command Possible responses
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AT+CMGF?
Note :possible message format
+CMGF=1
Ok
Note :Text mode
Table 4.1 Command syntax: AT+CMG
4.4.2 SEND MESSAGE + CMGS
To send a message in text mode CMGS command usedDescription:
The <address> field is the address of the terminal to which the message is
sent. To send the message, simply type, <ctrl-Z> character (ASCII 26). The text can
contain all existing characters except <ctrl-Z> and <ESC> (ASCII 27). This command
can be aborted using the <ESC> character when entering text. In PDU mode, only
hexadecimal characters are used (‘0’…’9’,’A’…’F’).
Syntax: In SMS text mode, the syntax of the +CMGS AT command is: (Optional
parameters are enclosed in square brackets.)
+CMGS= address[, address _type]<CR> sms_ message _body<Ctrl+z>Before we
discuss each of the parameters, let's see an example that gives you some idea of how
an actual command line should look like:
AT+CMGS="+85291234567",145<CR>This is an example for illustrating the syntax
of the +CMGS AT command in SMS text mode.<Ctrl+z>
The address Parameter
The first parameter of the +CMGS AT command, address, specifies the
destination address to send the SMS message to. Usually it is a mobile number
formatted using the typical ISDN / telephony numbering plan (ITU E.164/E.163). For
example, "+85291234567", "91234567", etc. Note that the value passed to the address
parameter should be a string, i.e. it should be enclosed in double quotes.
The address type parameter to The second parameter of the +CMGS AT command,
address type, specifies the type of the address assigned to the address parameter. Two values
are commonly used. They are 129 and 145.As address type is an optional parameter, it can be
omitted. If you do so, the GSM/GPRS modem or mobile phone will use the default value of
the address type parameter, which is.
1. 129 if the value of address does not start with a "+" character. For example,
"85291234567".
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2. 145 if the value of address starts with a "+" character. For example,
"+85291234567".
The <CR> Character <CR>, which represents the carriage return character,
follows the address_type parameter. When the GSM/GPRS modem or mobile phone
receives the carriage return character, it will send back a prompt formed by these four
characters: the carriage return character, the linefeed character, the ">" character and
the space character.
The sms_message_body Parameter
The third parameter of the +CMGS AT command, sms_message_body, specifies the
body of the SMS message to be sent. Entering the <Esc> character will cancel the
+CMGS AT command.
The <Ctrl+z> Character
When you finish entering the SMS message body, you have to enter the <Ctrl+z>
character to mark the end of the SMS message body. The GSM/GPRS modem or
mobile phone will then attempt to send the SMS message the SMS center
4.4.3 READ MESSAGE +CMGR
The AT command +CMGR (command name in text: Read Message) is used
to read a message from a message storage area. The location of the message to be read
from the message storage area is specified by an index number. The message to be
retrieved by the AT command +CMGR does not necessarily have to be an SMS
message. It can be of other message types such as status reports and cell broadcast
messages, but we will only focus on SMS messages here.
Format of the Information Response of the +CMGR AT Command in SMS Text
Mode:
If the GSM/GPRS modem or mobile phone successfully reads the SMS
message from message storage, it will return an information response to the
computer / PC. In SMS text mode, the format of the information response of the
+CMGR AT command is different for different message types. In the sections that
follow, we assume the message to be read is an SMS message but not of other
message types like status reports and cell broadcast messages.
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ATMEL MICROCONTROLLER5.1 GENERAL DESCRIPTION
The AT89S52 is a low-power, high-performance CMOS 8-bit microcomputer
with 8K bytes of Flash programmable and erasable read only memory (PEROM). The
device is manufactured using Atmel’s high density nonvolatile memory technology
and is compatible with the industry standard 80S51 and 80S52 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 Flash on a monolithic chip, the Atmel AT89C52 is a powerful
microcomputer which provides a highly flexible and cost effective solution to many
embedded control applications.
5.2 FEATURES OF MICROCONTROLLERThe AT89S52 provides the following standard features: 8Kbytes of Flash, 256
bytes of RAM, 32 I/O lines, three 16-bittimer/counters, a six-vector two-level
interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry.
In addition, the AT89S52 is designed with static logic for operation down to zero
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.
5.3 PIN CONFIGURATION
Fig 5.1 Pin Diagram
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5.4 PIN DESCRIPTIONVCC: Supply voltage.
GND: Ground.
Port 0: Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin
can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as
high-impedance inputs. Port 0 can also be configured to be the multiplexed low-
order,address/data bus during accesses to external program and data memory. In this
mode, P0 has internal pullups. Port 0 also receives the code bytes during Flash
programming and outputs the code bytes during program verification. External
pullups are required during program verification.
Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pullups.The Port 1 output
buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are
pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins
that are externally being pulled low will source current (IIL) because of the internal
pullups. In addition, P1.0 and P1.1 can be configured to be the timer/counter 2
external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX),
respectively, as shown in the following table.
Port Pin Alternate Functions: P1.0 T2 (external count input to Timer/Counter 2),
clock-out P1.1 T2EX (Timer/Counter 2 capture/reload trigger and direction control)
Port 1 also receives the low-order address bytes during Flash programming and
program verification.
Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pullups. The Port 2
output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins,
they are pulled high by the internal pullups and can be used as inputs. As inputs, Port
2 pins that are externally being pulled low will source current (IIL) because of the
internal pullups. Port 2 emits the high-order address byte during fetches from external
program memory and during accesses to external data memories that use 16-bit
addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pullups
when emitting 1s. During accesses to external data memory that uses 8-bit addresses
(MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2
also receives the high-order address bits and some control signals during Flash
programming and verification.
Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pullups. The Port 3
output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins,
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they are pulled high by the internal pullups and can be used as inputs. As inputs, Port
3 pins that are externally being pulled low will source current (IIL) because of the
pullups. Port 3 also serves the functions of various special features of the AT89S2, as
shown in the following table.
Port Pin Alternate Functions:
P3.0 RXD (serial input port) P3.1 TXD (serial output port) P3.2 INT0 (external
interrupt 0)
P3.3 INT1 (external interrupt 1) P3.4 T0 (timer 0 external input) P3.5 T1 (timer 1
external input)
P3.6 WR (external data memory write strobe) P3.7 RD (external data memory read
strobe)
Port 3 also receives some control signals for Flash programming and programming
verification.
RST: Reset input. A high on this pin for two machine cycles while the oscillator is
running resets the device.
ALE/PROG: Address Latch Enable is an output pulse for latching the low byte of the
address during accesses to external memory. This pin is also the program pulse input
(PROG) during Flash programming. In normal operation, ALE is emitted at a constant
rate of 1/6 the oscillator frequency and may be used for external timing or clocking
purposes. Note, however, that one ALE pulse is skipped during each access to
external data memory. If desired, ALE operation can be disabled by setting bit 0 of
SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC
instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has
no effect if the microcontroller is in external execution mode.
PSEN: Program Store Enable is the read strobe to external program memory. When
the AT89S52 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 Access Enable. EA must be strapped to GND in order to enable
the device to fetch code from external program memory locations starting at 0000H
up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally
latched on reset. EA should be strapped to VCC for internal program executions. This
pin also receives the 12-volt programming enable voltage (VPP) during Flash
programming when 12-volt programming is selected.
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XTAL1: Input to the inverting oscillator amplifier and input to the internal clock
operating circuit.
XTAL2: Output from the inverting oscillator amplifier.
5.5 89S52 BLOCK DIAGRAM
Fig 5.2Block diagram of AT89S52 microcontroller
5.6 INTERNAL MEMORY
Data Memory: The AT89S52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a parallel address space to the Special Function Registers (SFR). That means the upper 128 bytes have the same addresses as the SFR space but are physically separate from SFR space. When an instruction accesses an internal location above address 7FH, the address mode used in the instruction specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space.
The AT89S52 is a low power, high performance CMOS 8-bit microcontroller
with 8Kbytes of Flash programmable and erasable read only memory (PEROM
pinout. The on-chip Flash allows the program memory to be quickly reprogrammed
using a nonvolatile memory programmer such as the PG302 (with the ADT87
adapter). By combining an industry standard 8-bit CPU with Flash on a monolithic
chip, the 8952 is a powerful microcomputer which provides a highly flexible and cost
effective solution to many embedded control applications.
20
LIQUID CRYSTAL DISPLAY
6.1 INTRODUCTIONLiquid crystal display a type of display used in digital watches and many
portable computers. LCD displays utilize two sheets of polarizing material with a
liquid crystal solution between them. An electric current passed through the liquid
causes the crystals to align so that light cannot pass through them. Each crystal,
therefore, is like a shutter, either allowing light to pass through or blocking the light.
LCDs have become very popular over recent years for information display in
many smart ’appliances. They are usually controlled by microcontrollers. They make
complicated equipment easier to operate. LCDs come in many shapes and sizes but
the most common is the 20 character x 4 line display with no backlight. It requires
only 11 connections – eight bits for data (which can be reduced to four if necessary)
and three control lines (we have only used two here). It runs off a 5V DC supply and
only needs about 1mA of current. The display contrast can be varied by changing the
voltage into pin 3 of the display, usually with a trim pot.
Fig 6.1 Liquid Crystal Display
LCD adds a lot to our application in terms of providing a useful interface for
the user, debugging an application or just giving it a "Professional" look. The most
common type of LCD controller is the Hitachi 44780, which provides a relatively
simple interface between a processor and an LCD.
21
6.1DESCRIPTION FOR INTERFACING OF LCDTo get the display working requires eight bits of data, a register select line
(RS) and a strobe line (E). A third input, R/W, is used to read or write data to/from the
LCD. The eight bits of data are supplied from the controller port data lines and two
controller port control lines are used for RS (‘auto’) and E (‘strobe’). Basically the
LCD has two registers, a data register and a command register. Data is written into the
command register when RS is low and into the data register when RS is high. Data is
latched into the LCD register on the falling edge of Enable’.
6.2 PIN DESCRIPTION OF LCD
Table 6.1 Pin description of LCD
From this description, the interface is a parallel bus, allowing simple and fast
reading/writing of data to and from the LCD. This waveform will write an ASCII
Byte out to the LCD's screen. The ASCII code to be displayed is eight bits long and is
sent to the LCD either four or eight bits at a time. If four bit mode is used, two
"nibbles" of data (Sent high four bits and then low four bits with an "E" Clock pulse
with each nibble) are sent to make up a full eight bit transfer. The "E" Clock is used to
initiate the data transfer within the LCD.
Sending parallel data, as either four or eight bits are the two primary modes of
operation. While there are secondary considerations and modes, deciding how to send
the data to the LCD is most critical decision to be made for an LCD interface
application.
Eight-bit mode is best used when speed is required in an application and at
least ten I/O pins are available. Four bit mode requires a minimum of six bits. To wire
a microcontroller to an LCD in four bit mode, just the top four bits (DB4-7) are
written to. The "R/S" bit is used to select whether data or an instruction is being
22
transferred between the microcontroller and the LCD. If the Bit is set, then the byte at
the current LCD "Cursor" Position can be reader written. When the Bit is reset, either
an instruction is being sent to the LCD or the execution status of the last instruction is
read back (whether or not it has completed).
6.3 INSTRUCTION SET TO PROGRAM LCD
Table 6.2 Instruction set of LCD
The bit descriptions for the different commands are: - Not used/Ignored. This bit can
be either "1" or "0"
Set Cursor Move Direction:
ID - Increment the Cursor After Each Byte Written to Display if Set
S - Shift Display when Byte Written to Display
Enable Display/Cursor
D - Turn Display On (1)/Off (0)
C - Turn Cursor On (1)/Off (0)
B - Cursor Blink On (1)/Off (0)
Move Cursor/Shift Display
SC - Display Shift On (1)/Off (0)s
RL - Direction of Shift Right (1)/Left (0)
Set Interface Length
DL - Set Data Interface Length 8(1)/4(0)
23
N - Number of Display Lines 1(0)/2(1)
F - Character Font 5x10(1)/5x7(0)
Poll the "Busy Flag"
BF - This bit is set while the LCD is processing
Move Cursor to CGRAM/Display
A – Address
Read/Write ASCII to the Display:
D – Data
Reading Data back is used in this application, which requires data to be moved
back and forth on the LCD. The "Busy Flag" is polled to determine whether the last
instruction that has been sent has completed processing. Before we send commands or
data to the LCD module, the Module must be initialized. For eight bit mode, this is
done using the following series of operations:Wait more than 15 msec after power is
applied.
1. Write 0x030 to LCD and wait 5 msecs for the instruction to complete
2. Write 0x030 to LCD and wait 160 usecs for instruction to complete
3. Write 0x030 AGAIN to LCD and wait 160 usecs or Poll the Busy Flag
4. Set the Operating Characteristics of the LCD
5. Write "Set Interface Length"
6. Write 0x010 to turn off the Display
7. Write 0x001 to Clear the Display
8. Write "Set Cursor Move Direction" Setting Cursor Behavior Bits
9. Write "Enable Display/Cursor" & enable Display and Optional Cursor
6.4 IR REMOTE CONTROL THEORYThe cheapest way to remotely control a device within a visible range is via
Infra-Red light. Almost all audio and video equipment can be controlled this way
nowadays. Due to this wide spread use the required components are quite cheap, thus
making it ideal for us hobbyists to use IR control for our own projects. This part of
my knowledge base will explain the theory of operation of IR remote control, and
some of the protocols that are in use in consumer electronics.
24
6.5 INFRA_RED LIGHTInfra-Red actually is normal light with a particular colour. We humans can't
see this colour because its wave length of 950nm is below the visible spectrum. That's
one of the reasons why IR is chosen for remote control purposes, we want to use it but
we're not interested in seeing it. Another reason is because IR LEDs are quite easy to
make, and therefore can be very cheap. Although we humans can't see the Infra-Red
light emitted from a remote control doesn't mean we can't make it visible. A video
camera or digital photo camera can "see" the Infra-Red light as you can see in this
picture. If you own a web cam you're in luck, point your remote to it, press any button
and you'll see the LED flicker.
Unfortunately for us there are many more sources of Infra-Red light. The sun
is the brightest source of all, but there are many others, like: light bulbs, candles,
central heating system, and even our body radiates Infra-Red light. In fact everything
that radiates heat, also radiates Infra-Red light. Therefore we have to take some
precautions to guarantee that our IR message gets across to the receiver without
errors.
6.5.1MODULATION
Modulation is the answer to make our signal stand out above the noise. With
modulation we make the IR light source blink in a particular frequency. The IR
receiver will be tuned to that frequency, so it can ignore everything else. You can
think of this blinking as attracting the receiver's attention. We humans also notice the
blinking of yellow lights at construction sites instantly, even in bright daylight.
Fig 6.2 Modulated Signal Driving The IR LED Of The Transmitter On The
Left Side
In the picture above you can see a modulated signal driving the IR LED of the
transmitter on the left side. The detected signal is coming out of the receiver at the
other side. In serial communication we usually speak of 'marks' and 'spaces'. The
25
'space' is the default signal, which is the off state in the transmitter case. No light is
emitted during the 'space' state. During the 'mark' state of the signal the IR light is
pulsed on and off at a particular frequency. Frequencies between 30kHz and 60kHz
are commonly used in consume electronics. At the receiver side a 'space' is
represented by a high level of the receiver's output. A 'mark' is then automatically
represented by a low level. Please note that the 'marks' and 'spaces' are not the 1-s and
0-s we want to transmit. The real relationship between the 'marks' and 'spaces' and the
1-s and 0-s depends on the protocol that's being used. More information about that can
be found on the pages that describe the
protocols.
6.5.2 THE TRANSMITTER
Fig 6.3 IR Transmitter Circuit
The transmitter usually is a battery powered handset. It should consume as
little power as possible, and the IR signal should also be as strong as possible to
achieve an acceptable control distance. Preferably it should be shock proof as well.
Many chips are designed to be used as IR transmitters. The older chips were dedicated
to only one of the many protocols that were invented. Nowadays very low power
microcontrollers are used in IR transmitters for the simple reason that they are more
flexible in their use. When no button is pressed they are in a very low power sleep
mode, in which hardly any current is consumed. The processor wakes up to transmit
the appropriate IR command only when a key is pressed.
Quartz crystals are seldom used in such handsets. They are very fragile and
tend to break easily when the handset is dropped. Ceramic resonators are much more
suitable here, because they can withstand larger physical shocks. The fact that they
are a little less accurate is not important.
26
The current through the LED (or LEDs) can vary from 100mA to well over
1A! In order to get an acceptable control distance the LED currents have to be as high
as possible. A trade-off should be made between LED parameters, battery lifetime and
maximum control distance. LED currents can be that high because the pulses driving
the LEDs are very short. Average power dissipation of the LED should not exceed the
maximum value though. You should also see to it that the maximum peek current for
the LED is not exceeded. All these parameters can be found in the LED's data sheet.
A simple transistor circuit can be used to drive the LED. A transistor with a
suitable HFE and switching speed should be selected for this purpose. The resistor
values can simply be calculated using Ohm's law. Remember that the nominal voltage
drop over an IR LED is approximately 1.1V. The normal driver, described above, has
one disadvantage. As the battery voltage drops, the current through the LED will
decrease as well. This will result in a shorter control distance that can be covered. An
emitter follower circuit can avoid this. The 2 diodes in series will limit the pulses on
the base of the transistor to 1.2V. The base-emitter voltage of the transistor subtracts
0.6V from that, resulting in a constant amplitude of 0.6V at the emitter. This constant
amplitude across a constant resistor results in current pulses of a constant magnitude.
Calculating the current through the LED
6.5.3 THE RECEIVER
Fig 6.4 IR Receiver
Many different receiver circuits exist on the market. The most important
selection criteria are the modulation frequency used and the availability in you region.
27
Fig 6.5 Block Diagram of IR Receiver
In the picture above you can see a typical block diagram of such an IR
receiver. Don't be alarmed if you don't understand this part of the description, for
everything is built into one single electronic component. The received IR signal is
picked up by the IR detection diode on the left side of the diagram. This signal is
amplified and limited by the first 2 stages. The limiter acts as an AGC circuit to get a
constant pulse level, regardless of the distance to the handset.
As you can see only the AC signal is sent to the Band Pass Filter. The Band
Pass Filter is tuned to the modulation frequency of the handset unit. Common
frequencies range from 30kHz to 60kHz in consumer electronics.
The next stages are a detector, integrator and comparator. The purpose of these three
blocks is to detect the presence of the modulation frequency. If this modulation
frequency is present the output of the comparator will be pulled low.
This concludes the theory of operation for IR remote control systems intended
for use in consumer electronics. I realize that other ways exist to implement IR
control, but I will limit myself to the description above. One of the issues not covered
here is security. Security is of no importance if I want to control my VCR or TV set.
But when it comes to opening doors or cars it literally becomes a 'key' feature! Maybe
I will cover this issue later, but not for now.
You can find the protocols of some manufacturers in the link section at the top of this
page. This concludes the theory of operation for IR remote control systems intended
for use in consumer electronics. I realize that other ways exist to implement IR
control, but I will limit myself to the description above. One of the issues not covered
here is security. Security is of no importance if I want to control my VCR or TV set.
But when it comes to opening doors or cars it literally becomes a 'key' feature! Maybe
I will cover this issue later, but not for now.
28
I also realize that my small list of manufacturers is far from being complete. It is
hardly possible to list every manufacturer here. You can send me an e-mail if you
have details about other protocols that you feel should be added to my pages.
This page only described the basic theory of operation of IR remote control. It did not
describe the protocols that are involved in communication between transmitter and
receiver. Many protocols are designed by different manufacturers. You can find the
protocols of some manufacturers in the link section at the top of this page.
This pair of High power directional IR LED and Filtered photodiode can be used in
various kinds of sensing circuits. The narrow beam width IR LED emits focused IR
light and the filtered photodiode filters out ambient light without the need of any
external circuit. When used with proper circuit it can give upto 200 mm of reflective
sensing and can also be used in high speed applications like encoders. atures
IR LED (TSFF5210 - Vishay Semiconductor.
1 High reliability
2 High radiant power
3 High radiant intensity
4 Angle of half intensity: = ± 10°
5 Low forward voltage
6 Suitable for high pulse current operation
7 High modulation bandwidth: fc = 24 MHz 8 Good spectral matching with Si photo detectors
IR Photodiode (BPV10NF - Vishay Semiconductor)
9 High radiant sensitivity
10 Daylight blocking filter matched with 870 nm to 890 nm emitters
11 High bandwidth: > 100 MHz at VR = 12 V
12 Fast response times
13 Angle of half sensitivity: ± 20°
29
LIGHT DEPENDENT RESISTORS (LDR)
LDRs or Light Dependent Resistors are very useful especially in light/dark
sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as
1000 000 ohms, but when they are illuminated with light resistance drops
dramatically.
Fig 7.1 Basic Model of LDR
The animation above shows that when the torch is turned on, the
resistance of the LDR falls, allowing current to pass through it.
7.1 THIS IS AN EXAMPLE OF A LIGHT SENSOR CIRCUIT When the light level is low the resistance of the LDR is high. This
prevents current from flowing to the base of the transistors. Consequently The
LED does not light.
30
Fig 7.2 Example of Light sensor circuit
However, when light shines onto the LDR its resistance falls and
current flows into the base of the first transistor and then the second transistor.
the LED lights. The preset resistor can be turned up or down to increase or
decrease resistance, in this way it can make the circuit more or less sensitive.
31
A/D CONVERTER (MCP 3201)
8.1 INTRODUCTION TO A/D CONVERTERS The usual method of bringing analog inputs into a microprocessor is to use an
analog-to-digital converter (ADC). Here are some tips for selecting such a part and
calibrating it to fit our needs. In analog-to-digital converter (ADC) accepts an analog
input-a voltage or a current-and converts it to a digital value that can be read by a
Microprocessor. This hypothetical part has two inputs: a reference and the signal to be
measured. It has one output, an 8-bit digital word that represents the input value. The
reference voltage is the maximum value that the ADC can convert. Our example 8-bit
ADC can convert values from 0V to the reference voltage. This voltage range is
divided into 256 values, or steps.
The size of the step is given by: Vref/256
8.2 DESCRIPTIONThe Microchip Technology Inc.MCP3201 is a successive approximation 12-
bit Analog-to-Digital (A/D) Converter with on-board sample and hold circuitry. The
device provides a single pseudo-differential input. Differential Nonlinearity (DNL) is
specified at ±1 LSB, and Integral Nonlinearity (INL) is offered in ±1 LSB
(MCP3201-B) and ±2 LSB (MPC3201-C) versions. Communication with the device
is done using a simple serial interface compatible with the SPI protocol. The device is
capable of sample rates of up to 100ksps at a clock rate of 1.6MHz. The MCP3201
operates over a broad voltage range (2.7V - 5.5V).
8.3FEATURES1.12-bit resolution
2. ±1 LSB max DNL
3. On-chip sample and hold
4. SPI ® serial interface (modes 0,0 and 1,1)
5. Single supply operation: 2.7V - 5.5V
6. 100ksps max. Sampling rate at VDD= 5V
7. 50ksps max. Sampling rate at VDD= 2.7V
32
8. Low power CMOS technology
9. Industrial temp range: -40°C to +85°C
10. Pin PDIP, SOIC and TSSOP packages
8.4 APPLICATION1. Sensor Interface
2. Process Control
3. Data Acquisition
4. Battery Operated System
8.5 PIN DIAGRAM
Fig 8.1Pin Diagram of MCP3201
33
Table 8.1 Pin Function Table Of MCP 3201
8.6 PIN DESCRIPTIONSIN+Positive analog input. This input can vary from IN- to VREF + IN-.
IN-Negative analog input. This input can vary ±100Mv from VSS.
8.6.1 CS/SHDN (CHIP SELECT/SHUTDOWN)
The CS/SHDN pin is used to initiate communication with the device when
pulled low and will end a conversion and put the device in low power standby when
pulled high. The CS/SHDN pin must be pulled high between conversions.
8.6.2 CLK (SERIAL CLOCK)
The SPI clock pin is used to initiate a conversion and to clock out each bit of the
conversion as it takes place.
34
8.6.3 DOUT (SERIAL DATA OUTPUT)
The SPI serial data output pin is used to shift out the results of the A/D
conversion. Data will always change on the falling edge of each clock as the
conversion takes place.
Fig 8.2 Functional Block Diagram
8.7 COMBUSTIBLE GAS SENSOR – ANALOG OUT
Fig 8.3 Gas Sensor
35
Used in gas leakage detecting equipments for detecting of
LPG, iso-butane, propane, LNG combustible gases. The
sensor does not get trigger with the noise of alcohol,
cooking fumes and cigarette smoke.
Applications
1. Gas leak detection system
2. Fire/Safety detection system
3. Gas leak alarm / Gas detector Features
4. Simple analog output
5. High sensitivity to LPG, iso-butane, propane
6. Small sensitivity to alcohol, smoke
7. Fast response
8. Wide detection range
9. Stable performance and long life Specification Parameter Value Unit
10. Target Gas iso-butane, Propane, LPG
11. Detection Range 100 to 10000 PPM PPM (part per millions) Output Voltage
Range 0 to 5 VDC
12. Working Voltage 5 VDC
13. Current Consumption ≤180 mA
14. Warmup Time 10 Minutes
15. Calibrated Gas 1000ppm iso-butane
16. Response Time ≤10s Seconds
17. Resume Time ≤30s Seconds
18. Standard Working Condition Temperature:-10 to 65 deg C. Humidity:
≤95%RH
19. Storage Condition Temperature: -20-70 deg C Hum: ≤ 70%RH
PIN OUTS
# Pin Details
1. GND Power Supply Ground.
2. A.OUT Analog Voltage Out
3 +5V Supply voltage DC +5V regulated
Warm up Time
36
The sensor needs 10 minutes of warm up time after first power is applied.
After 10 minutes you can take its readings. During warm up time the output analog
voltage would go up from 4.5V to 0.5V in variation down gradually. During this
warm up time the sensor reading should be ignored. Using the Sensor .The sensor
needs 5V to operate, Give regulated +5V DC supply, The sensor will take around
180mA supply. The sensor will heat a little bit since it has internal heater that heats
the sensing element.
Testing the sensor Measure the output voltage through multi-meter between
A.OUT and Ground pins or Use microcontroller to measure the voltage output. Take
the sensor near combustible gas place like cooking gas stove with flame off or near
bottle of after shave liquid or cigarette light with flame off. You will notice sudden
jump in analog voltage output since the gas concentration will increase Sensitivity
Typical Sensitivity Characteristics of sensor for several gases in their
Temp 20 deg C
Humidity 65%
Oxygen concentration 21%
RL = 10K Ohm
Ro = Sensor resistance at 1000 ppm of LPG
in clean air
Rs = Sensor resistance at various concentrations of gases
Deriving Gas concentration from Output Voltage
Here is a the equation which convert analog output to PPM gas concentration
PPM = Analog Voltage in mV x 2
Example: Gas sensor voltage is giving output as
2500mV(2.5V) So the gas contentration in PPM = 2500x2 = 5000 PPM
Here is the table for your reference
PPM: 200 300 500 1000 2000 3000 5000 9000 10000
Voltage( mV) 100 150 250 500 1000 1500 2500 4500 500
37
SERIAL COMMUNICATION
9.1 INTRODUCTION TO SERIAL COMMUNICATIONIn telecommunication and computer science, the concept of serial
communication is the process of sending data one bit at a time, sequentially, over a
communication channel or computer bus. This is in contrast to parallel
communication, where several bits are sent as a whole, on a link with several parallel
channels. Serial communication is used for all long-haul communication and most
computer networks, where the cost of cable and synchronization difficulties make
parallel communication impractical. Serial computer buses are becoming more
common even at shorter distances, as improved signal integrity and transmission
speeds in newer serial technologies have begun to outweigh the parallel bus's
advantage of simplicity (no need for serializer and deserializer, or SerDes) and to
outstrip its disadvantages (clock skew, interconnect density).
9.2 SERIAL BUSESIntegrated circuits are more expensive when they have more pins. To reduce
the number of pins in a package, many ICs use a serial bus to transfer data when
speed is not important. Some examples of such low-cost serial buses include SPI, I²C,
UNI/O, and 1-Wire.
9.3 ASYNCHRONOUS SERIAL COMMUNICATIONAsynchronous serial communication describes an asynchronous, serial
transmission protocol in which a start signal is sent prior to each byte, character or
code word and a stop signal is sent after each code word. The start signal serves to
prepare the receiving mechanism for the reception and registration of a symbol and
the stop signal serves to bring the receiving mechanism to rest in preparation for the
reception of the next symbol. A common kind of start-stop transmission is ASCII over
RS-232, for example for use in teletypewriter operation.
38
In the diagram, two bytes are sent, each consisting of a start bit, followed by seven
data bits (bits 0-6), a parity bit (bit 7), and one stop bit, for a 10-bit character frame.
The number of data and formatting bits, the order of data bits, and the transmission
speed must be pre-agreed by the communicating parties.
The "stop bit" is actually a "stop period"; the stop period of the transmitter may be
arbitrarily long. It cannot be shorter than a specified amount, usually 1 to 2 bit times.
The receiver requires a shorter stop period than the transmitter. At the end of each
character, the receiver stops briefly to wait for the next start bit. It is this difference
which keeps the transmitter and receiver synchronized.
9.4 MAX 232 PIN DIAGRAM
Fig 9.1 MAX 232 Pin Diagram
9.5 SPECIFICATIONS1. .Meets or Exceeds TIA/EIA-232-F and ITU Recommendation V.28
2. Operates from a Single 5-V Power Supply With 1.0-_F Charge-Pump
Capacitors
3. Operates up To 120 kbit/s
4. Two Drivers and Two Receivers
5. 30-V Input Levels
6. Low Supply Current 8 mA Typical
7. 2000-V Human-Body Model (A114-A)
39
9.6 DESCRIPTIONThe MAX232 is a dual driver/receiver that includes a capacitive voltage
generator to supply TIA/EIA-232-F Voltage levels from a single 5-V supply. Each
receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These receivers
have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept 30-V
inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels. The
driver, receiver, and voltage-generator functions are available as cells.
9.7 LOGIC DIAGRAM
Fig 9.2 Logic Diagram
9.8 DB-9 CONNECTORThe RS-232c standard is based on a low/false voltage between +3 to +15V,
and an high/true voltage between -3 to -15V (+/-12V is commonly used). Figure 27.4
shows some of the common connection schemes. In all methods the txd and rxd lines
are crossed so that the sending txd outputs are into the listening rxd inputs when
communicating between computers. When communicating with a communication
device (modem), these lines are not crossed. In the modem connection the dsr and dtr
lines are used to control the flow of data. In the computer the cts and rts lines are
connected. These lines are all used for handshaking, to control the flow of data from
sender to receiver. The null-modem configuration simplifies the handshaking between
computers. The three wire configuration is a crude way to connect to devices, and
data can be lost.
40
Fig 9.3 DB-9 Connector
9.9 COMMON RS232 CONNECTION SCHEMESCommon connectors for serial communications are shown in Figure 27.5.
These connectors are either male (with pins) or female (with holes), and often use the
assigned pins shown. In any connection the RXD and TXD pins must be used to
transmit and receive data. The COM must be connected to give a common voltage
reference. All of the remaining pins are used for handshaking.
41
9.10 RS232 PIN ASSIGNMENTS
Fig 9.4 RS232 Pin Assignments
The handshaking lines are to be used to detect the status of the sender and
receiver, and to regulate the flow of data. It would be unusual for most of these pins to
be connected in any one application. The most common pins are provided on the DB-
9 connector, and are also described below.
TXD/RXD - (transmit data, receive data) - data lines
DCD - (data carrier detect) - this indicates when a remote device is present
RI - (ring indicator) - this is used by modems to indicate when a connection is about
to be made.
CTS/RTS - (clear to send, ready to send)
DSR/DTR - (data set ready, data terminal ready) these handshaking lines indicate
when the remote machine is ready to receive data.
COM - a common ground to provide a common reference voltage for the TXD and
RXD.
When a computer is ready to receive data it will set the CTS bit, the remote machine
will notice this on the RTS pin.
42
REGULATED POWER SUPPLY
10.1 DESCRIPTIONA 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 (A 12 volt power
supply is included with the Beginner Kit and the Microcontroller Beginner Kit.). To
make a 5 volt power supply, we use a LM7805 voltage regulator IC (Integrated
Circuit). The IC is shown below.
Fig 10.1 LM7805 voltage regulator IC
43
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.
10.2 CIRCUIT FEATURES1. Brief description of operation: Gives out well regulated +5V output, output
current capability of 100 mA
2. Circuit protection: Built-in overheating protection shuts down output when
regulator IC gets too hot
3. Circuit complexity: Very simple and easy to build
4. Circuit performance: Very stable +5V output voltage, reliable operation
5. Availability of components: Easy to get, uses only very common basic
components
6. Design testing: Based on datasheet example circuit, I have used this circuit
succesfully as part of many electronics projects
7. Applications: Part of electronics devices, small laboratory power supply
8. Power supply voltage: Unreglated DC 8-18V power supply
9. Power supply current: Needed output current + 5 mA
10. Component costs: Few dollars for the electronics components + the input
transformer cost
10.3 BLOCK DIAGRAM
Fig10.2 Block Diagram of Typical Linear Power Supply
44
10.4 CIRCUIT DIAGRAM
Fig 10.3 Circuit diagram of Regulated Power Supply
45
KEIL U V2 SOFTWARE
11.1 KEIL SOFTWARE PROGRAMING PROCEDUREHow to write Embedded C Program in Keil Software.
11.2 PROCEDURE STEPS
Step-1: Install Keil MicroVision-2 in your PC, Then after Click on that “Keil UVision-2”
icon. After opening the window go to toolbar and select Project Tab then close
previous project.
46
Step-2:Next select New Project from Project Tab.
Step-3:
Then it will open “Create New Project” window. Select the path where you
want to save project and edit project name.
47
Step-4:Next it opens “Select Device for Target” window, It shows list of companies
and here you can select the device manufacturer company.
Step-5:
For an example, for your project purpose you can select the chip as 89c51/52
from Atmel Group. Next Click OK Button, it appears empty window here you can
observe left side a small window i.e, “Project Window”. Next create a new file.
48
Step-6:
From the Main tool bar Menu select “File” Tab and go to New, then it will open a
window, there you can edit the program.
Step-7:
Here you can edit the program as which language will you prefer either Assembly or
C.
49
Step-8:
After editing the program save the file with extension as “.c” or “.asm”, if you write a
program in Assembly Language save as “.asm” or if you write a program in C Language save
as “.c” in the selected path. Take an example and save the file as “test.c”.
Step-9:
Then after saving the file, compile the program. For compilation go to project
window select “source group” and right click on that and go to “Add files to Group”.
50
Step-9:
Here it will ask which file has to Add. For an example here you can add “test.c” as
you saved before.
Step-9:
After adding the file, again go to Project Window and right click on your “c file” then
select “Build target” for compilation. If there is any “Errors or Warnings” in your program
you can check in “Output Window” that is shown bottom of the Keil window.
51
Step-10:
Here in this step you can observe the output window for “errors and warnings”.
Step-11:
If you make any mistake in your program you can check in this slide for which error
and where the error is by clicking on that error.
52
Step-12:
After compilation then next go to Debug Session. In Tool Bar menu go to “Debug”
tab and select “Start/Stop Debug Session”.
Step-13:
Here a simple program for “Leds Blinking”. LEDS are connected to PORT-1. you
can observe the output in that port.
53
Step-14:
To see the Ports and other Peripheral Features go to main toolbar menu and select
peripherals.
Step-15:
In this slide see the selected port i.e, PORT-1.
54
Step-16:
Start to trace the program in sequence manner i.e, step by step execution and observe
the output in port window.
Step-17:
After completion of Debug Session Create an Hex file for Burning the Processor.
Here to create an Hex file go to project window and right click on Target next select “Option
for Target”.
55
Step-18:
It appears one window; here in “target tab” modify the crystal frequency as you
connected to your microcontroller.
Step-19:
Next go to “Output’ tab. In that Output tab click on “Create HEX File” and then click OK.
56
Step-20:
Finally Once again compile your program. The Created Hex File will appear in your
path folder.
57
ISP FLASH MICROCONTROLLER PROGRAMMER
12.1 FEATURES
Complete In-System Programming Solution for AVR Microcontrollers
Covers All AVR Microcontrollers with In-System Programming Support
Reprogram Both Data Flash and Parameter EEPROM Memories
Complete Schematics for Low-cost In-System Programmer
Simple Three-wire SPI Programming Interface
12.2 INTRODUCTION
In-System Programming allows programming and reprogramming of any
AVR microcontroller Positioned inside the end system. Using a simple three-wire SPI
interface, the In-System Programmer communicates serially with the AVR
microcontroller, reprogramming all non-volatile memories on the chip.
In-System Programming eliminates the physical removal of chips from the
system.This will save time, and money, both during development in the lab, and when
updating
The software or parameters in the field. This application note shows how to
design the system to support In-System Programming. It also shows how a low-cost
In-System Programmer can be made, that will allow the target AVR microcontroller
to be programmed from any PC equipped with a regular 9-pin serial port.
Alternatively, the entire In-System Programmer can be built into the system allowing
It To Reprogram Itself.
58
Fig 12.1 ISP_ programmer interface
12.3 THE PROGRAMMING INTERFACEFor In-System Programming, the programmer is connected to the target using
as few wires as possible. To program any AVR microcontroller in any target system, a
simple Six-wire interface is used to connect the programmer to the target PCB.
Below shows the connections needed.
The Serial Peripheral Interface (SPI) consists of three wires: Serial Clock
(SCK), Master In – Slave Out (MISO) and Master Out – Slave In (MOSI). When
programming the AVR, the In-System Programmer always operate as the Master, and
the target system Always operate as the Slave.
The In-System Programmer (Master) provides the clock for the
communication on the SCK Line. Each pulse on the SCK Line transfers one bit from
the Programmer (Master) To the Target (Slave) on the Master out – Slave in (MOSI)
line. Simultaneously, Each pulse on the SCK Line transfers one bit from the target
(Slave) to the Programmer (Master) on the Master in – Slave out (MISO) line.
59
EMBEDDED C
Embedded C (As a beginner when you start working with controller you might
be in a bit confused about the difference between C and Embedded C? Where shall I
write a code for my controller? This article will bring out the differences between C &
embedded C
When you start working with embedded C then you may feel that the
embedded C is quite similar to the conventional C. Then why it is been named
asembedded C?
· The C language is used for desktop application while embedded C is used for
microcontroller application.
· The C language uses the desktop OS memory, while embedded C uses the
controllers inbuilt or any externally attached memory. In the case of controller we
have very limited resources (controllers RAM, ROM, IO ports, etc.) so one must be
very careful about declaring and using the variable. At any instant of time you need to
be care full that you are not using the space more than the available one in the
controller or else the program will get crash, or you may not get the exact result.
· The embedded C needs a different platform then C. Almost every family of
controllers need a different platform to write their codes.
· A convention C code generates an OS compatible .exe file while embedded C
code generates a .hex file which has the machine codes to be dumped in the memory
of the controller.
· In C we use header files like stdio.h, which yield the output to be visible on OS
itself. In embedded C everything is same but the output files are directly loaded on the
controllers to test them.
· The C language is use to make a program for host interaction while embedded
C is use to implement the host on the controller which interact with the other
peripherals.
60
SOURCE CODE
#include<reg52.h>
#include<intrins.h>
#include<string.h>
//////////////////////////////////////////////////////////////////
#define LCD P0
void init_lcd(void);
void cmd_lcd(unsigned char);
void data_lcd(unsigned char);
void display_lcd(unsigned char *);
void delay_ms(int);
void integer_lcd(int);
void float_lcd(float);
/////////////////////////////////////////////////////////////////
void adc_convert (void);
unsigned char byte_read(void);
unsigned char byte0,byte1;
unsigned int num;
float val;
////////////////////////////////////////////////////////////////////
void serial_send(unsigned char);
void SEND_STR(unsigned char *);
////////////////////////////////////////////////////////////////
int i=0;int J=0;int L=0;
bit receive=0;
char k;
bit t_flag=0;
bit flag = 0;
unsigned char buff[10];
sbit DCLK = P1^0;
sbit SDAT= P1^1;
61
sbit CS =P1^2;
////////////////////////////////////////////////////////
sbit IR1=P1^5;///////////////////CHECKING
sbit IR2=P1^4;//////////////////LDR
sbit IR3=P1^3;/////////////////FIRE
sbit LED=P2^1;/////////////////LED
sbit SP1=P3^2;///////////////////CELL
sbit SP2=P3^3;//////////////////PURSE
sbit SP3=P3^4;/////////////////FIRE
sbit SP4=P3^5;/////////////////LIGHT
sbit SP5=P3^6;///////////////////SMOKE
sbit SP6=P3^7;///////////////////SMOKE
////////////////////////////////////////////////////////////
void serial_int(void)interrupt 4
{
flag=0;
if(RI)
{
receive=1;
RI = 0;
if(k<10)buff[k++]=SBUF;
}
else
{
t_flag=1;
TI=0;
}
}
////////////////////////////////////////////////////////////////////
void main(void)
{
SP1=SP2=SP3=SP4=SP6=SP5=1;
62
LED=0;
SCON = 0x50;
TMOD = 0x20;
TH1 = -3;
TR1 = 1;
IE=0x91;
i = 0;
init_lcd();cmd_lcd(0x80);
display_lcd("RF-ID & GSM BASED ");
cmd_lcd(0xC0);
display_lcd("SMART HOME REMINDER SYSTEM");
delay_ms(1000);
cmd_lcd(0x01);
while(1)
{
cmd_lcd(0xc0);
adc_convert();
delay_ms(100);
flag=1;
if(receive==1)
{
cmd_lcd(0x01);
for(i=0;i<10;i++);
cmd_lcd(0x01);
k=0;buff[i]='\0';
cmd_lcd(0xc9);
display_lcd(buff);
if(!strcmp(buff,"3000FFC668"))
{
J=J+1;
strcpy(buff,"CELL");
cmd_lcd(0xC9);
display_lcd("CELL");
delay_ms(10);
63
}
if(!strcmp(buff,"3000FFCE9C"))
{
L=L+1;
strcpy(buff,"PURSE");
cmd_lcd(0xC9);
display_lcd("PURSE");
delay_ms(10);
}
}
////////////////////////////////////////////////////////////
if(IR1==1)
{
cmd_lcd(0x80);
display_lcd("REMINDER SYSTEM ");
delay_ms(10);
if(J==1)
{
cmd_lcd(0x80);
display_lcd("CELL ");
delay_ms(100);
SP1=0;SP6=1;
}
if(L==1)
{
cmd_lcd(0x80);
display_lcd("PURSE ");
delay_ms(100);
SP2=0;SP6=1;
}
if(J==1 & L==1)
{
cmd_lcd(0x80);
display_lcd("CELL PURSE ");
64
delay_ms(100);
SP6=0;SP1=0;SP2=0;
}
}
if(IR2==0)
{
cmd_lcd(0x80);
display_lcd("NOLIGHT AVALABLE ");
delay_ms(100);
LED=1;SP4=1;
}
if(IR2==1)
{
cmd_lcd(0x80);
display_lcd("LIGHT AVALABLE ");
delay_ms(100);LED=0;
SP4=0;
SEND_STR("AT+CMGS=");
serial_send('"');
SEND_STR("7702272106");
serial_send('"');
SEND_STR("\r\n");
SEND_STR("LIGHT AVALABLE ");
SEND_STR("\r\n");
serial_send(0x1A);delay_ms(500);
////////////////////////////////////////////////
SEND_STR("AT+CMGS=");
serial_send('"');
SEND_STR("8886313963");
serial_send('"');
SEND_STR("\r\n");
SEND_STR("LIGHT AVALABLE ");
SEND_STR("\r\n");
65
serial_send(0x1A);delay_ms(500);
}
if(IR3==0)
{
cmd_lcd(0x80);
display_lcd("FIRE OCCURED ");
delay_ms(100);
SP3=0;
SEND_STR("AT+CMGS=");
serial_send('"');
SEND_STR("7702272106");
serial_send('"');
SEND_STR("\r\n");
SEND_STR("FIRE OCCURED ");
SEND_STR("\r\n");
serial_send(0x1A);delay_ms(500);
/////////////////////////////////////////////////////
SEND_STR("AT+CMGS=");
serial_send('"');
SEND_STR("8886313963");
serial_send('"');
SEND_STR("\r\n");
SEND_STR("FIRE OCCURED ");
SEND_STR("\r\n");
serial_send(0x1A);delay_ms(500);
}
if(IR3==1)
{
cmd_lcd(0x80);
display_lcd("N0 FIRE OCCURED ");
delay_ms(100);
SP3=1;
}
i = 0;receive=0;
66
delay_ms(100);
}
}
////////////////////////////////////////////////////////////////////
void adc_convert (void)
{
DCLK=1;
CS=1; //low to high to start conversion
CS=0;
byte1=byte_read(); //msb result from adc
byte0=byte_read(); //lsb result from adc
CS=1;
num=(byte1&0x1f); //
num=((num<<8)|byte0)>>1;
val=(num*5.00)/4096;
float_lcd(val);
display_lcd("V");
if(val > 4.00)
{
cmd_lcd(0x80);
display_lcd("GAS OCCURED ");
delay_ms(100);
SP5=0;
SEND_STR("AT+CMGS=");
serial_send('"');
SEND_STR("7702272106");
serial_send('"');
SEND_STR("\r\n");
SEND_STR("GAS OCCURED ");
SEND_STR("\r\n");
serial_send(0x1A);delay_ms(500);
///////////////////////////////////////////
SEND_STR("AT+CMGS=");
serial_send('"');
67
SEND_STR("8886313963");
serial_send('"');
SEND_STR("\r\n");
SEND_STR("GAS OCCURED ");
SEND_STR("\r\n");
serial_send(0x1A);delay_ms(500);
}
if(val<4.00)
{
cmd_lcd(0x80);
display_lcd("N0 GAS OCCURED ");
delay_ms(100);
SP5=1;
}
}
////////////////////////////////////////////////////////////////////
unsigned char byte_read (void)
{
unsigned char i,c=0,mask=0x80;
for (i=0;i<8;i++)
{
DCLK=0;
if (SDAT==1)
c|=mask;
DCLK=1;
mask>>=1;
}
return c;
}
////////////////////////////////////////////////////////////////////////
void init_lcd(void)
{
68
cmd_lcd(0x28);
cmd_lcd(0x28);
cmd_lcd(0x28);
cmd_lcd(0x0C);
cmd_lcd(0x06);
cmd_lcd(0x01);
}
void cmd_lcd(unsigned char var)
{
LCD = ((var & 0xF0) | 0x08);
LCD = 0;
LCD = ((var << 4) | 0x08);
LCD = 0;
delay_ms(2);
}
void data_lcd(unsigned char var)
{
LCD = ((var & 0xF0) | 0x0a);
LCD = 0;
LCD = ((var << 4) | 0x0a);
LCD = 0;
delay_ms(2);
}
void display_lcd(char *str)
{
while(*str)
data_lcd(*str++);
}
void delay_ms(int cnt)
{
int i;
while(cnt--)
for(i=0;i<500;i++);
}
69
void SEND_STR(unsigned char *s)
{
while(*s)
serial_send(*s++);
}
void serial_send(unsigned char buf)
{
t_flag= 0;
SBUF = buf;
while(t_flag == 0);
}
void integer_lcd(int n)
{
unsigned char c[6];
unsigned int i=0;
if(n<0)
{
data_lcd('-');
n=-n;
}
if(n==0)
data_lcd('0');
while(n>0)
{
c[i++]=(n%10)+48;
n/=10;
}
while(i-->=1)
data_lcd(c[i]);
}
70
void float_lcd(float f)
{
int n;
float temp;
n=f;
integer_lcd(n);
data_lcd('.');
temp=f-n;
if(temp>=0.00&&temp<=0.09)
data_lcd('0');
f=temp*100;
n=f;
integer_lcd(n);
}
71
SCHEMATIC DIAGRAM
LE D TX
123456789
1011121314
G N DV C CV E ER SR WE ND 0D 1D 2D 3D 4D 5D 6D 7
H
c lk
F R O M IS P
GND
s m o k e s e n s o r o / p
10uf/63v
10uf/63v
- +
B R I D G E R E C TI F I E R1
4
3
2
123
LE D
F R O M IS PD 4
10K PULLUP
1 2 3 4 5 6 7 8 9
Vcc
R1
R2
R3
R4
R5
R6
R7
R8
H
V C CV C C
p1 . 1
P 1^5
V C C
V C C
D 5
G N D
B
10uf/63v
GND
V C C
R E G U LA TO R78 0 51 3
2
V I N V O U T
GN
D
8 . 2 K
22 0 oh m s
P 0 . 4
L D R
5K
LE D TX
4 . 7 K
P 0 .3
f ire s e ns o r
P 1^3
11 . 0 59 2 M H z
C R Y S TA L
V C C
P 3. 1 (TXD )
V C C
M A X232
1
34
5
2
6
12
9
11
10
13
8
14
7
1516
C 1 +
C 1 -C 2 +
C 2 -
V +
V -
R 1 O U T
R 2 O U T
T1 I N
T2 I N
R 1 I N
R 2 I N
T1 O U T
T2 O U T
GN
DV
CC
P1^4
V C C
S W 1
GND
V C C
A T8 9 S 52
231817
20 2119
9101112
1413
1615
383736353433323130292827262524
22
12345678
3940
P 2 . 2 (A 10 )XTA L 2P 3 . 7 (R D )
G N D P 2. 0 (A 87 )XTA L 1
R S TP 3 . 0 (R XD )P 3 . 1 (TXD )P 3 . 2 (I N T0 )
P 3 . 4 (T0 )P 3 . 3 (I N T1 )
P 3 . 6 (W R )P 3 . 5 (T1 )
P 0 . 1 (A D 1 )P 0 . 2 (A D 2 )P 0 . 3 (A D 3 )P 0 . 4 (A D 4 )P 0 . 5 (A D 5 )
P O . 6 (A D 6 )P 0 . 7 (A D 7 )
E E / V D DA LE / P R O G
P S E NP 2. 7 (A 15 )P 2 . 6 (A 14 )P 2 . 5 (A 13 )P 2 . 4 (A 12 )P 2 . 3 (A 11 )
P 2 .1 (A 9 )
P 1 . 0 (T2 )P 1 . 1 (T2E X)P 1 . 2P 1 . 3P 1 . 4P 1 . 5P 1 . 6P 1 . 7
P 0 . 0 (A D 0 )V C C
10K PULLUP
123456789
VccR
1R
2R
3R
4R
5R
6R
7R
8
33 p f
p1 . 0
c s / s hd n
GND
5K
GND GND
10K PULLUP
123456789
Vcc
R1
R2
R3
R4
R5
R6
R7
R8
R S
XTA L -1
XTA L -1
1000
uf
GND
R S T
XTA L -2
V C C
10 4 p f
P 0 . 6
I R R E C I V E R c h e c k in g
E N
D 7
GND
220
10uf
MCP 3201
2
3
5
6
7
1 8
4
I N +
I N -
C S / S H D N
D O U T
C L K
V R E F V C C
V S S
F R O M IS P
D 6
J 2
t o t ra n s f o rm er
12
10 K
V C C
GND
GSM MODEM
P 0. 5
V C C
GND GND
33 p f
IN +
do u t
XTA L -2
4
5
6
1
2
3
GND
A
G N D
P 0. 7
10uf/63v
V C C
R S T
33 p f
V C C
p1 . 2
220
GND
P 0.1
72
RESULT
73
ADVANTAGES AND DISADVANTAGES
ADVANTAGES1. Power consumption is less as we are using only 5 volt power supply.
2. Because of its versatility we can use in home automation, industry automation etc.
3. It is easy to use.
4. By the use of this project we can save energy.
5. It is cost effective due to advancement of VLSI.
6. It is easily available in the market.
7. With the use of the remainder system in the project we can save our time. .
8. It makes life easier and comfortable
9. Buzzer is replaced by voice IC.
DISADVANTAGES1 .If power is cut then the system will not work
2. GSM fails to alert the user when network coveraging area is poor
3. LDR is highly sensitive so light becomes off even in full moon night.
4. We need RFID tag for every goods
5. Gas sensor detects even small amount of smoke like cigarette smoke and alert the
user which is undesirable.
6. When large numbers of products with RFID tags are stored together in the same
scanning field, the reader can energize multiple tags at once..
74
APPLICATIONS
1. It can be applied for home, industries and shopping mall.
2. It can be applied in coil mines.
3. It can be used for security purpose.
4. We can use the project for gas leakage detection in coil mines, home and industries.
5. LDR can be used in street light, coil mines, tunnels and industries.
6. Fire sensor can be used for fire detection in home, industries, forest fire.
8. User can instantly determine the general location of tagged assets anywhere
within the facility with the help of active RFID technology.
9. The project can be used as remainder system for those people who forget their
utilities.
10. It makes life easier and comfortable.
11. Smoke sensor can be used in petrol pumps where smoke is strictly prohibited.
12. In shopping malls we can use for detecting stolen goods and instead of giving
buzzer it gives voice which makes easier to detects.
.
75
FUTURE SCOPE
In future we can go for full fledged environment which cover more distance
and sense the tag automatically means no need to show the tag. Now we are using this
project as a reminding and monitoring purpose but in future we can control the device
using advance technologies. Microcontroller AT89S52 can be replaced by higher
microcontroller where both transmission and reception can be simultaneously.
Here we are using SI300 module which is capable of only sending, receiving and
calling purpose but in future we can use GSM900 module for sending the pictorial
view of the particular place to respective user which is used for security purpose
.We can introduce Relay switch for operating the device from distant place.
In future we can use RF-ID in hospital for tracking their special patients. It will be
mainly very useful in mental care hospitals where doctors can track each and every
activity of the patient.
76
CONCLUSION
This project presents an approach based on RF-ID and GSM based remainder
system for smart home. Through the use of this project we can make life easier and
comfortable. In this project we have used Gas sensor for detection of gas leakage, fire
and smoke which overcome the problem of occurrence of fire. We are also using RF-
ID card for reminding purpose which helps people to save their valuable time.
Here we are using LDR for saving power and GSM module for sending
messages to alert the user. In our project we have implemented voice IC instead of
buzzer for reminding purpose.
At the end we can conclude that this project is going to play a remarkable role
in forthcoming days in making life easier and sophisticated.
77
BIBLIOGRAPHY
REFERRENCE BOOK1. “The AVR Microcontroller and Embedded Systems” By Muhammad Ali Mazidi
and Janice Gillispie Mazidi. Pearson Education.
2. ATMEL AVR Data sheets
3. Hand book for Digital IC’s from Analogic Devices
4. Jonathan Westhues's Proximity Website
5. microID 125 kHz RFID System Design Guide
6. FCC Rules
WEBSITES1. www.atmel.com
2. www.howstuffworks.com
3. www.google.com
4. www.wikipedia.com
5. www.maxim-ic.com
78