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CHAPTER-1
INTRODUCTION
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INTRODUCTION
1.1 Objective
All the time men/women are not available in such cases we use FIRE
FIGHTING ROBO with supervisory control to stop the fire accidents.The objective of
this project is to operate the robot to detect and to stop the fire.
1.2 Introduction to embedded systems
An embedded system is a special-purpose computersystem designed toperform one or a few dedicated functions, often with real-time computing constraints. It
is usually embedded as part of a complete device including hardware and mechanical
parts. In contrast, a general-purpose computer, such as a personal computer, can do
many different tasks depending on programming. Embedded systems control many of
the common devices in use today.
Since the embedded system is dedicated to specific tasks, designengineers can optimize it, reducing the size and cost of the product, or increasing 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 MP4 players, to large stationary installations like traffic lights,
factory 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 enclosure.
In general, "embedded system" is not an exactly defined term, as many
systems have some element of programmability. For example, handheld computers
share some elements with embedded systems, such as the operating systems and
microprocessors which power them. But are not truly embedded systems, because
they allow different applications to be loaded and peripherals to be connected.
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http://wiki/Computerhttp://wiki/Real-time_computinghttp://wiki/Personal_computerhttp://wiki/Economies_of_scalehttp://wiki/MP4_playerhttp://wiki/MP4_playerhttp://wiki/Traffic_lighthttp://wiki/Nuclear_power_planthttp://wiki/Microcontrollerhttp://wiki/Handheld_computerhttp://wiki/Real-time_computinghttp://wiki/Personal_computerhttp://wiki/Economies_of_scalehttp://wiki/MP4_playerhttp://wiki/Traffic_lighthttp://wiki/Nuclear_power_planthttp://wiki/Microcontrollerhttp://wiki/Handheld_computerhttp://wiki/Computer -
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1.3 History of embedded systems
In the earliest years of computers in the 1930-40s, computers were
sometimes dedicated to a single task, but were far too large and expensive for most
kinds of tasks performed by embedded computers of today. Over time however, the
concept of programmable controllers evolved from traditional electromechanical
sequencers, via solid state devices, to the use of computer technology.
One of the first recognizably modern embedded systems was the Apollo
Guidance Computer, developed by Charles Stark Draper at the MIT Instrumentation
Laboratory. At the project's inception, the Apollo guidance computer was considered
the riskiest item in the Apollo project as it employed the then newly developed
monolithic integrated circuits to reduce the size and weight. An early mass-produced
embedded system was the Automatics D-17 guidance computer for the Minuteman
missile, released in 1961. It was built from transistorlogic and had a hard disk for main
memory. When the Minuteman II went into production in 1966, the D-17 was
replaced with a new computer that was the first high-volume use of integrated
circuits. This program alone reduced prices on quad nand gate ICs from $1000/each to
$3/each, permitting their use in commercial products.
Since these early applications in the 1960s, embedded systems have
come down in price and there has been a dramatic rise in processing power and
functionality. The first microprocessor for example, the Intel 4004, was designed for
calculators and other small systems but still required many external memory and
support chips. In 1978 National Engineering Manufacturers Association released a
"standard" for programmable microcontrollers, including almost any computer-basedcontrollers, such as single board computers, numerical, and event-based controllers.
As the cost of microprocessors and microcontrollers fell it became
feasible to replace expensive knob-based analog components such as potentiometers
and variable capacitors with up/down buttons or knobs read out by a microprocessor
even in some consumer products. By the mid-1980s, most of the common previously
external system components had been integrated into the same chip as the processorand this modern form of the microcontroller allowed an even more widespread use,
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http://wiki/Programmable_controllershttp://wiki/Electromechanicalhttp://wiki/Apollo_Guidance_Computerhttp://wiki/Apollo_Guidance_Computerhttp://wiki/Charles_Stark_Draperhttp://wiki/Minuteman_(missile)http://wiki/Minuteman_(missile)http://wiki/Transistorhttp://wiki/Digital_circuithttp://wiki/Hard_diskhttp://wiki/Sheffer_strokehttp://wiki/Microprocessorhttp://wiki/Intel_4004http://wiki/Calculatorhttp://wiki/Analog_electronicshttp://wiki/Potentiometerhttp://wiki/Variable_capacitorhttp://wiki/Microcontrollerhttp://wiki/Programmable_controllershttp://wiki/Electromechanicalhttp://wiki/Apollo_Guidance_Computerhttp://wiki/Apollo_Guidance_Computerhttp://wiki/Charles_Stark_Draperhttp://wiki/Minuteman_(missile)http://wiki/Minuteman_(missile)http://wiki/Transistorhttp://wiki/Digital_circuithttp://wiki/Hard_diskhttp://wiki/Sheffer_strokehttp://wiki/Microprocessorhttp://wiki/Intel_4004http://wiki/Calculatorhttp://wiki/Analog_electronicshttp://wiki/Potentiometerhttp://wiki/Variable_capacitorhttp://wiki/Microcontroller -
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which by the end of the decade were the norm rather than the exception for almost all
electronics devices.
The integration of microcontrollers has further increased the
applications for which embedded systems are used into areas where traditionally a
computer would not have been considered. A general purpose and comparatively low-
cost microcontroller may often be programmed to fulfill the same role as a large
number of separate components. Although in this context an embedded system is
usually more complex than a traditional solution, most of the complexity is contained
within the microcontroller itself. Very few additional components may be needed and
most of the design effort is in the software. The intangible nature of software makes it
much easier to prototype and test new revisions compared with the design and
construction of a new circuit not using an embedded processor
1.4 Classification of Embedded systems
Embedded systems are divided into,
1.Autonomous
2.Real-time
3.Networked and
4.Mobile categories.
Autonomous systems function in standalone mode. Many embedded
systems used for process control in manufacturing units and automobiles fall under
this category. In process control systems the inputs originate from transducers that
convert a physical quantity, such as temperature, into an electric signal. The systemoutput controls the device. In standalone systems, the deadlines or response times are
not critical. An air-conditioner can be set to turn on when the temperature reaches a
certain level. Measuring instruments and CD players are examples of autonomous
systems.
Real time systems are required to carry out specific tasks in a specified
amount of time. These systems are extensively used to carry out time critical tasks inprocess control. For instance, a boiler plant must open the valves if the pressure
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exceeds a particular threshold. If the job is not carried out in the stipulated time, a
catastrophe may result.
Networks embedded systems monitor plant parameters, such as
temperature, pressure, and humidity, and send the data over the network to a
centralized system for online monitoring. A network-enabled web camera monitoring
the plant floor transmits its video output to remote controlling organization.
Mobile gadgets need to store databases locally in their memory. These
gadgets imbibe powerful computing and communication capabilities to perform real
time as well as non-real time tasks and handle multimedia applications. The gadgets
embed powerful processor and OS, and a lot of money with minimal power
consumption.
1.5 Applications of embedded systems
Embedded systems have virtually entered every sphere of our lives,
right from the time we work out on trade mills in the gym, to the cars we drive today.
Embedded systems cover a broad range of products that generalization is difficult.
Some broad categories are
Aero Space and Defense electronics -Flight safety, flight management, fire
control.
Automotive - auto safety, braking and steering systems, car information
systems.
Broadcast and Entertainment - audio control systems, camera systems, DVD
players.
Consumer/Internet Applications - Handheld computers, internet hand held
devices, point-of-sale systems like ATM.
Medical Electronics - cardiovascular devices, real time imaging system
(patient monitoring systems).
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Mobile data infrastructures - wireless LANS, pagers, wireless phones, satellite
terminals (VSATs).
CHAPTER-2
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BLOCK DIAGRAM
BLOCK DIAGRAM
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Micro
controller
89C51
RF
Receiver
Relay(blower)
Light
sensor
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Fig:2.1block diagram of fire fighting robot
CIRCUIT DIGRAM
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DC
Motor(right
wheel)
IR Sensor
DC Motor
(left wheel)
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+
-
U 2
L M 3 8 6
3
2
5
6
14 8
7
5 V
5 v
1 2 V
Q 3
B C 5 4 8
U 5
L 2 9 3
2
7
1 0
1 5
1
9
3
6
1 1
1 4
1 6
8
1 A
2 A
3 A
4 A
1 / 2 E N
3 / 4 E N
1 Y
2 Y
3 Y
4 Y
V C C 1
V C C 2
1 0 K
1 u c
7 8 0 5
Q 1
B C 5 4 7
1 0 k
1 0 K
1 0 K
1 2 V
B A T T E R Y
1 0 0 k
1 2 v
5 V
2 2 k
1 . 2 k
1 0 k
Y 1
C 4
C A P
1 0 K
C 4
C A P
5 V
U 1
8 0 5 1
2 9
3 0
4 0
3 1
1 9
1 8
9
3 9
3 83 7
3 6
3 5
3 4
3 3
3 2
1
2
3
4
5
6
7
8
2 1
2 22 3
2 4
2 5
2 6
2 7
2 8
1 0
1 1
1 2
1 3
1 4
1 5
1 6
1 7
P S E N
A L E
V C C
E A
X 1
X 2
R S T
P 0 . 0 / A D 0
P 0 . 1 / A D 1
P 0 . 2 / A D 2P 0 . 3 / A D 3
P 0 . 4 / A D 4
P 0 . 5 / A D 5
P 0 . 6 / A D 6
P 0 . 7 / A D 7
P 1 . 0
P 1 . 1
P 1 . 2
P 1 . 3
P 1 . 4
P 1 . 5
P 1 . 6
P 1 . 7
P 2 . 0 / A 8
P 2 . 1 / A 9
P 2 . 2 / A 1 0P 2 . 3 / A 1 1
P 2 . 4 / A 1 2
P 2 . 5 / A 1 3
P 2 . 6 / A 1 4
P 2 . 7 / A 1 5
P 3 . 0 / R X D
P 3 . 1 / T X D
P 3 . 2 / I N T 0
P 3 . 3 / I N T 1
P 3 . 4 / T 0
P 3 . 5 / T 1
P 3 . 6 / W R
P 3 . 7 / R D
5 V
C 3
c 1
1
2
5 V
+
-
U 2
L M 3 8 6
3
2
5
6
14 8
7
1
2
Q 2
B C 5 4 8 1 2 v
5 V
5 V
2 2 0 K
5 V
I N 4 0 0 7
R L 1
R E L A Y S P S T
4
3
1
2
+
-
U 2
L M 3 8 6
3
2
5
6
14 8
7
Fig 2.2 circuit diagram
Circuit Operation
When we switch on the robot, it will initialize in auto mode and starts moving.
For robot movement, two dc motors are used. To move forward, both the wheels
rotated with same speed. To turn left or right, corresponding wheel is stopped. L293driver is used to drive the DC motors. Two outputs of this driver can form into one H-
bridge and it can drive the motor in both the directions. The LDR is used to sense the
fire. It varies the resistance according to the light. It is connected in potential divider
using another 10K fixed resistor. Whenever light falls on it, it drops the voltage. This
voltage is compared using comparator against a threshold voltage set by preset. If the
voltage across LDR is less then threshold, the output is LOW else the output is high.
This signal is interfaced to controller. The controller operates the water jet relay
according to the input. The water jet is having another DC motor coupled to water
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tank. When the motor rotates, the pressure build up in the tank and water pumps out
of it through a nozzle.
For manual mode of operation, a remote is designed with another micro
controller interfaced with LCD, keys and RF receiver. The robot is interfaced with RF
receiver. ASK modules with 433MHz carrier is used for RF communication. When
we power up the remote, it scans the keys. If press up & down key together, it
toggles between manual and auto mode. In manual mode, if press each key, the robot
performs each operation like, moving forward, moving reverse, left , right and
releasing water. In this mode it doesnt take LDR feedback.
2.1 Microcontroller
Fig:2.3 pin diagram of micro controller
Microcontrollers are destined to play an increasingly important role in
revolutionizing various industries and influencing our day to day life more strongly
than one can imagine. Since its emergence in the early 1980's the microcontroller has
been recognized as a general purpose building block for intelligent digital systems.
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It is finding using diverse area, starting from simple children's toys to
highly complex spacecraft. Because of its versatility and many advantages, the
application domain has spread in all conceivable directions, making it ubiquitous.
As a consequence, it has generate a great deal of interest andenthusiasm among students, teachers and practicing engineers, creating an acute
education need for imparting the knowledge of microcontroller based system design
and development. It identifies the vital features responsible for their tremendous
impact, the acute educational need created by them and provides a glimpse of the
major application area.
A microcontroller is a complete microprocessor system built on a
single IC. Microcontrollers were developed to meet a need for microprocessors to be
put into low cost products. Building a complete microprocessor system on a single
chip substantially reduces the cost of building simple products, which use the
microprocessor's power to implement their function, because the microprocessor is a
natural way to implement many products.
This means the idea of using a microprocessor for low cost products
comes up often. But the typical 8-bit microprocessor based system, such as one using
a Z80 and 8085 is expensive. Both 8085 and Z80 system need some additional
circuits to make a microprocessor system. Each part carries costs of money. Even
though a product design may requires only very simple system, the parts needed to
make this system as a low cost product.
To solve this problem microprocessor system is implemented with a
single chip microcontroller. This could be called microcomputer, as all the major parts
are in the IC. Most frequently they are called microcontroller because they are used
they are used to perform control functions.
The microcontroller contains full implementation of a standard
MICROPROCESSOR, ROM, RAM, I/0, CLOCK, TIMERS, and also SERIAL
PORTS. Microcontroller also called "system on a chip" or "single chip
microprocessor system" or chip computer. Micro suggests that the device is small,
and controller tells you that the device' might be used to control objects, processes, or
events. Another term to describe a microcontroller is embedded controller, because
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the microcontroller and its support circuits are often built into, or embedded in, the
devices they control.
Today microcontrollers are very commonly used in wide variety of
intelligent products. For example most personal computers keyboards andimplemented with a microcontroller.
It replaces Scanning, Debounce, Matrix Decoding, and Serial
transmission circuits. Many low cost products, such as Toys, Electric Drills,
Microwave Ovens, VCR and a host of other consumer and industrial products are
based on "computer on a chip".
A microcontroller is a Computer-On-A-Chip, or, if you prefer, a
single- microcontrollers.
2.2 Block and pin diagram of micro controller
Fig: 2.4block and pin diagram of microcontroller
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2.3 Pin description
VCC
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 may 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 pull-ups. Port 0 also receives the code bytes during Flash
programming, and outputs the code bytes during program verification. External pull-
ups are required during program verification.
Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. 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 pull-ups 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 pull-ups. Port 1 also receives the low-order address bytes during Flash
programming and verification.
Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. 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 pull-ups 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 pull-ups. Port 2 emits the high-order address byte during fetches from
external program memory and during accesses to external data memory that use 16-bit
addresses (MOVX @ DPTR). In this application it uses strong internal pull-ups when
emitting 1s. During accesses to external data memory that use 8-bit addresses
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(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 pull-ups. The Port
3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins
they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port
3 pins that are externally being pulled low will source current (IIL) because of the
pull-ups. Port 3 also serves the functions of various special features of the AT89C51
as listed below:Port 3 also receives some control signals for Flash programming and
verification
Table:2.1 tabular form for port3
RST
Reset input. A high on this pin for two machine cycles while the
oscillator is running resets the device.
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ALE/PROG
Address Latch Enable 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 AT89C51 is executing code from external program memory, PSEN is
activated twice each machine cycle, except that two PSEN activations are skipped
during each access to external data memory.
EA/VPP
External 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, for parts that require 12-volt VPP.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock
operating circuit.
XTAL2
Output from the inverting oscillator amplifier. It should be noted that
when idle is terminated by a hard ware reset, the device normally resumes program
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execution, from where it left off, up to two machine cycles before the internal reset
algorithm takes control.
On-chip hardware inhibits access to internal RAM in this event, but
access to the port pins is not inhibited. To eliminate the possibility of an unexpected
write to a port pin when Idle is terminated by reset, the instruction following the one
that invokes Idle should not be one that writes to a port pin or to external memory.
2.4 Architecture of 89C51
Fig: 2.5 architecture of 89c51
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2.5Advantages of micro controller
If a system is developed with a microprocessor, the designer has to go
for external memory such as RAM, ROM or EPROM and peripherals and hence the
size of the PCB will be large enough to hold all the required peripherals. But, the
micro controller has got all these peripheral facilities on a single chip so development
of a similar system with a micro controller reduces PCB size and cost of the design.
One of the major differences between a micro controller and a
microprocessor is that a controller often deals with bits , not bytes as in the real world
application, for example switch contacts can only be open or close, indicators should
be lit or dark and motors can be either turned on or off and so forth.
2.6 Applications of Microcontrollers
Microcontrollers are designed for use in sophisticated real time
applications such as
1. Industrial Control
2. Instrumentation and
3. Intelligent computer peripherals
They are used in industrial applications to control
Motor
Robotics
Discrete and continuous process control In missile guidance and control
Telecommunication
Automobiles
For Scanning a keyboard
Driving an LCD
For Frequency measurements
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Period Measurements
2.7 Relay
Fig:2.6 relay
A relay is an electrically operated switch. Current flowing through the
coil of the relay creates a magnetic field which attracts a lever and changes the switch
contacts. The coil current can be on or off so relays have two switch positions and
they are double throw (changeover) switches. Relays allow one circuit to switch a
second circuit which can be completely separate from the first. For example a low
voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no
electrical connection inside the relay between the two circuits; the link is magnetic
and mechanical.
The coil of a relay passes a relatively large current, typically 30mA for
a 12V relay, but it can be as much as 100mA for relays designed to operate from
lower voltages. Most ICs (chips) cannot provide this current and a transistor is usually
used to amplify the small IC current to the larger value required for the relay coil. The
maximum output current for the popular 555 timer IC is 200mA so these devices can
supply relay coils directly without amplification.
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Fig: 2.7 outer view of realy
Relays are usually SPDT or DPDT but they can have many more sets
of switch contacts, for example relays with 4 sets of changeover contacts are readily
available. Most relays are designed for PCB mounting but you can solder wires
directly to the pins providing you take care to avoid melting the plastic case of the
relay. The animated picture shows a working relay with its coil and switch contacts.
You can see a lever on the left being attracted by magnetism when the coil is switched
on. This lever moves the switch contacts. There is one set of contacts (SPDT) in the
foreground and another behind them, making the relay DPDT.
The relay's switch connections are usually labeled COM, NC and NO.
COM = Common, always connect to this, it is the moving part of the switch.
NC = Normally Closed, COM is connected to this when the relay coil is off. NO = Normally Open, COM is connected to this when the relay coil is on.
2.7.1 Circuit description
This circuit is designed to control the load. The load may be
motor or any other load. The load is turned ON and OFF through relay. The relay ON
and OFF is controlled by the pair of switching transistors (BC 547). The relay is
connected in the Q2 transistor collector terminal. A Relay is nothing but
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electromagnetic switching device which consists of three pins. They are Common,
Normally close (NC) and Normally open (NO).
The relay common pin is connected to supply voltage. The
normally open (NO) pin connected to load. When high pulse signal is given to base of
the Q1 transistors, the transistor is conducting and shorts the collector and emitter
terminal and zero signals is given to base of the Q2 transistor. So the relay is turned
OFF state.
When low pulse is given to base of transistor Q1 transistor,
the transistor is turned OFF. Now 12v is given to base of Q2 transistor so the
transistor is conducting and relay is turned ON. Hence the common terminal and NO
terminal of relay are shorted. Now load gets the supply voltage through relay.
2.8 Light Sensor
Fig: 2.8 light sensor
2.8.1 Description
The internal components of a photoelectric control for a typical American
streetlight. The photo resistor is facing rightwards, and controls whether current flows
through the heater which opens the main power contacts. At night, the heater cools,
closing the power contacts, energizing the street light. It is basically light dependent
resistor. The heater/bimetal mechanism provides a built-in time-delay.
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A photo resistor or light dependent resistor or cadmium sulfide (CdS) cell is a
resistorwhose resistance decreases with increasing incident light intensity. It can also
be referenced as a photoconductor.
A photo resistor is made of a high resistance semiconductor. If light falling on
the device is of high enough frequency,photons absorbed by the semiconductor give
bound electrons enough energy to jump into the conduction band. The resulting free
electron (and its hole partner) conduct electricity, thereby loweringresistance.
A photoelectric device can be either intrinsic or extrinsic. An intrinsic
semiconductor has its own charge carriers and is not an efficient semiconductor, e.g.
silicon. In intrinsic devices the only available electrons are in the valence band, andhence the photon must have enough energy to excite the electron across the entire
band gap. Extrinsic devices have impurities, also called do pants, added whose ground
state energy is closer to the conduction band; since the electrons do not have as far to
jump, lower energy photons (i.e., longer wavelengths and lower frequencies) are
sufficient to trigger the device. If a sample of silicon has some of its atoms replaced
by phosphorus atoms (impurities), there will be extra electrons available for
conduction. This is an example of an extrinsic semiconductor.
2.9 Introduction to DC motor
2.9.1 History:
One of the first electromagnetic rotary motors was invented by Michael
Faraday in 1821 and consisted of a free-hanging wire dipping into a pool of mercury.
A permanent magnet was placed in the middle of the pool. When a current was passed
through the wire, the wire rotated around the magnet, showing that the current gave
rise to a circular magnetic field around the wire. This motor is often demonstrated in
school physics classes, but brine is sometimes used in place of the toxic mercury. This
is the simplest form of a class of electric motors called homopolar motors. A later
refinement is the Barlow's Wheel.
The modern DC motor was invented by accident in 1873, when Znobe
Gramme connected a spinning dynamo to a second similar unit, driving it as a motor.
2.9.2 What is dc motor?
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Dc motor is an electric motor converts electrical energy into mechanical
motion. The reverse task that of converting mechanical motion into electrical energy,
is accomplished by a generator or dynamo. In many cases the two devices are
identical except for their application and minor construction details.
DC motors are used when there is positioning requirement and also changes in
load and torque. DC motors can be conveniently interfaced to Bipolar DAC, or MPUs
can generate PWM to control them.
The classic DC motor has a rotating ligature in the form of an electromagnet.
A rotary switch called a commutate reverses the direction of the electric current twice
every cycle, to flow through the armature so that the poles of the electromagnet pushand pull against the permanent magnets on the outside of the motor. As the poles of
the armature electromagnet pass the poles of the permanent magnets, the commutate
reverses the polarity of the armature electromagnet. During that instant of switching
polarity, inertia keeps the classical motor going in the proper direction. (See the
diagrams below.)
A simple DC electric motor. When the coil is powered, a magnetic field is generated
around the armature. The left side of the armature is pushed away from the left
magnet and drawn toward the right, causing rotation.
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The armature continues to rotate.
When the armature becomes horizontally aligned, the commutate reverses the
direction of current through the coil, reversing the magnetic field. The process then
repeats.
2.10 REGULATED POWER SUPPLY
The power supplies are designed to convert high voltage AC mains
electricity to a suitable low voltage supply for electronics circuits and other devices. ARPS (Regulated Power Supply) is the Power Supply with Rectification, Filtering
and Regulation being done on the AC mains to get a Regulated power supply for
Microcontroller and for the other devices being interfaced to it. A power supply can
by broken down into a series of blocks, each of which performs a particular function.
A d.c power supply which maintains the output voltage constant irrespective of a.c
mains fluctuations or load variations is known as Regulated D.C Power Supply
For example a 5V regulated power supply system as shown below:
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2.10.1 Transformer:
A transformer is an electrical device which is used to convert electrical
power from one Electrical circuit to another without change in frequency.
Transformers convert AC electricity from one voltage to another with little
loss of power. Transformers work only with AC and this is one of the reasons why
mains electricity is AC. Step-up transformers increase in output voltage, step-down
transformers decrease in output voltage. Most power supplies use a step-down
transformer to reduce the dangerously high mains voltage to a safer low voltage. The
input coil is called the primary and the output coil is called the secondary. There is noelectrical connection between the two coils; instead they are linked by an alternating
magnetic field created in the soft-iron core of the transformer. The two lines in the
middle of the circuit symbol represent the core. Transformers waste very little power
so the power out is (almost) equal to the power in. Note that as voltage is stepped
down current is stepped up. The ratio of the number of turns on each coil, called the
turns ratio, determines the ratio of the voltages. A step-down transformer has a large
number of turns on its primary (input) coil which is connected to the high voltage
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mains supply, and a small number of turns on its secondary (output) coil to give a low
output voltage.
Fig:2.9 Electrical Transformer
Turns ratio = Vp/ VS = Np/NS
Power Out= Power In
VS X IS=VP X IP
Vp = primary (input) voltage
Np = number of turns on primary coil
Ip = primary (input) current
2.10.2 RECTIFIER:
A circuit which is used to convert a.c to dc is known as RECTIFIER. The
process of conversion a.c to d.c is called rectification
TYPES OF RECTIFIERS:
Half wave Rectifier
Full wave rectifier
1. Centre tap full wave rectifier.2. Bridge type full bridge rectifier.
Comparison of rectifier circuits:
Parameter
Type of Rectifier
Half wave Full wave Bridge
Number of diodes1 2 4
PIV of diodesVm 2Vm Vm
D.C output voltageVm/ 2Vm/ 2Vm/
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Vdc,at no-load0.318Vm 0.636Vm 0.636Vm
Ripple factor1.21 0.482 0.482
Ripple frequency F 2f 2f Rectification efficiency
0.406 0.812 0.812Transformer Utilization
Factor(TUF) 0.287 0.693 0.812
RMS voltage Vrms Vm/2 Vm/2 Vm/2
Full-wave Rectifier:
From the above comparison we came to know that full wave bridge rectifier
as more advantages than the other two rectifiers. So, in our project we are using full
wave bridge rectifier circuit.
Bridge Rectifier: A bridge rectifier makes use of four diodes in a bridge arrangement
to achieve full-wave rectification. This is a widely used configuration, both with
individual diodes wired as shown and with single component bridges where the
diode bridge is wired internally.
A bridge rectifier makes use of four diodes in a bridge arrangement as shownin fig (a) to achieve full-wave rectification. This is a widely used configuration, both
with individual diodes wired as shown and with single component bridges where the
diode bridge is wired internally.
Fig (A)
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Operation:
During positive half cycle of secondary, the diodes D2 and D3 are in
forward biased while D1 and D4 are in reverse biased as shown in the fig(b). The
current flow direction is shown in the fig (b) with dotted arrows.
FIG (B)
During negative half cycle of secondary voltage, the diodes D1 and D4 are
in forward biased while D2 and D3 are in reverse biased as shown in the fig(c). The
current flow direction is shown in the fig (c) with dotted arrows.
Fig(C)
2.10.3 VOLTAGE REGULATOR:
Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or
variable output voltages. The maximum current they can pass also rates them.
Negative voltage regulators are available, mainly for use in dual supplies. Mostregulators include some automatic protection from excessive current ('overload
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protection') and overheating ('thermal protection'). Many of the fixed voltage
regulators ICs have 3 leads and look like power transistors, such as the 7805 +5V 1A
regulator shown on the right. 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.
Fig 2.10 A Three Terminal Voltage Regulator
7805 Regulator:
The Bay Linear LM7805 is integrated linear positive regulator with three
terminals. The LM7805 offer several fixed output voltages making them useful in
wide range of applications. When used as a zener diode/resistor combination
replacement, the LM7805 usually results in an effective output impedanceimprovement of two orders of magnitude, lower quiescent current. The LM7805 is
available in the TO-252, TO-220 & TO-263packages,
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CHAPTER 3
RESULTS AND DISCUSSION
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RESULTS AND DISCUSSION
By using this procedure we designed a program and run successfully,
and it was implemented in the target.In this project we are successfully designed a robot to implement in the
application ofFIRE FIGHTING ROBOT.
3.1 Discussion
Here we just design a model to implement this application and the
major limitation is the sensitivity of the sensors what we are implemented. Here we
can able to detect up to few centimetres only. If we can increase the sensitivity of
sensors then we can use our system in real time applications like military, navy,
industries etc....
3.2 Advantages
1. Reduce the manpower to find out the fire
2. Economical3. Easy to implement
3.3 Applications
1. Manufacturing industries
2. Fireworks industries
3. Textiles
4. Military applications
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CHAPTER 4
CONCLUSION
4.Conclusion
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The proposed system based on Atmel microcontroller is found to be
more compact, user friendly and less complex, which can readily be used in order to
perform. Several tedious and repetitive tasks. Though it is designed keeping in mind
about the need for industry, it can extended for other purposes such as commercial &
research applications. Due to the probability of high technology (Atmel
microcontroller) used this FIRE FIGHTING ROBOT is fully software controlled
with less hardware circuit.
CHAPTER 5
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REFERENCES
References
1. Printed circuit boards-design & technology by Walter c boss
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2. Electrical estimating and costing-surjit singh (dhanpat rai & co).
3.Atmel corporation microcontroller Databook Oct 1995.4. 8051 microcontroller architecture and programming Kenath Ayala.
5.Michael Barr, Programming embedded systems in C &C++, TMH 19906.The 8051 Microcontroller and Embedded systems Muhammad Ali. Mazidi
and Janice Gillespie Mazidi.
Websites
www.atmel.com
www.microchip.com www.8052.com
www.beyondlogic.org
www.ctv.es/pckits/home.html
www.aimglobal.org
www.wikimapia.com
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