fire sensing robot
DESCRIPTION
this is the documentation of fire sensingTRANSCRIPT
FIRE SENSING ROBOT
INDEX
CONTENTS
1. Abbreviations
2. Introduction
3. Block Diagram
4. Block Diagram Description
5. Schematic
6. Schematic Description
7. Hardware Components
Microcontroller
H-BRIDGE
Smoke sensor
POWER SUPPLY
Buzzer
8. Circuit Description
9. software
10.Conclusion (or) Synopsis
11. Future Aspects
12. Bibliography
ABBREVIATIONS
SYMBOL NAME
ACC Accumulator
B B register
PSW Program status word
SP Stack pointer
DPTR Data pointer 2 bytes
DPL Low byte
DPH High byte
P0 Port0
P1 Port1
P2 Port2
P3 Port3
IP Interrupt priority control
IE Interrupt enable control
TMOD Timer/counter mode control
TCON Timer/counter control
T2CON Timer/counter 2 control
T2MOD Timer/counter mode2 control
TH0 Timer/counter 0high byte
TL0 Timer/counter 0 low byte
TH1 Timer/counter 1 high byte
TL1 Timer/counter 1 low byte
TH2 Timer/counter 2 high byte
TL2 Timer/counter 2 low byte
SCON Serial control
SBUF Serial data buffer
PCON Power control
INTRODUCTION
A robot is officially defined by as an automatically controlled, reprogrammable,
multipurpose manipulator programmable in three or more axes. The field of robotics
may be more practically defined as the study, design and use of robot systems for
manufacturing (a top-level definition relying on the prior definition of robot).
Typical applications of robots include welding, painting, ironing, assembly, pick and
place, packaging and palletizing, product inspection, and testing, all accomplished with
high endurance, speed, and precision.
Robot types, features
The most commonly used robot configurations are articulated robots, SCARA robots and
gantry robots (aka Cartesian Coordinate robots, or x-y-z robots). In the context of general
robotics, most types of robots would fall into the category of robot arms (inherent in the
use of the word manipulator in the above-mentioned ISO standard). Robots exhibit
varying degrees of autonomy:
Some robots are programmed to faithfully carry out specific actions over and over
again (repetitive actions) without variation and with a high degree of accuracy.
These actions are determined by programmed routines that specify the direction,
acceleration, velocity, deceleration, and distance of a series of coordinated
motions.
Other robots are much more flexible as to the orientation of the object on which
they are operating or even the task that has to be performed on the object itself,
which the robot may even need to identify. For example, for more precise
guidance, robots often contain machine vision sub-systems acting as their "eyes",
linked to powerful computers or controllers. Artificial intelligence, or what passes
for it, is becoming an increasingly important factor in the modern industrial robot.
History
George Devol applied for the first robotics patents in 1954 (granted in 1961). The first
company to produce a robot was Unimation, founded by George Devol and Joseph F.
Engel berger in 1956, and was based on Devol's original patents. Unimation robots were
also called programmable transfer machines since their main use at first was to transfer
objects from one point to another, less than a dozen feet or so apart. They used hydraulic
actuators and were programmed in joint coordinates, i.e. the angles of the various joints
were stored during a teaching phase and replayed in operation. They were accurate to
within 1/10,000 of an inch. Unimation later licensed their technology to Kawasaki Heavy
Industries and Guest-Nettlefolds, manufacturing Unimates in Japan and England
respectively. For some time Unimation's only competitor was Cincinnati Milacron Inc. of
Ohio. This changed radically in the late 1970s when several big Japanese conglomerates
began producing similar industrial robots.
In 1969 Victor Scheinman at Stanford University invented the Stanford arm, an all-
electric, 6-axis articulated robot designed to permit an arm solution. This allowed it to
accurately follow arbitrary paths in space and widened the potential use of the robot to
more sophisticated applications such as assembly and arc welding. Scheinman then
designed a second arm for the MIT AI Lab, called the "MIT arm." Scheinman, after
receiving a fellowship from Unimation to develop his designs, sold those designs to
Unimation who further developed them with support from General Motors and later
marketed it as the Programmable Universal Machine for Assembly (PUMA).
In 1973 KUKA Robotics built its first robot, known as FAMULUS, this is the first
articulated robot to have six electromechanically driven axes.
Interest in robotics swelled in the late 1970s and many companies entered the field,
including large firms like General Electric, and General Motors (which formed joint
venture FANUC Robotics with FANUC LTD of Japan). US start-ups included Automatix
and Adept Technology, Inc. At the height of the robot boom in 1984, Unimation was
acquired by Westinghouse Electric Corporation for 107 million US dollars.
Westinghouse sold Unimation to Stäubli Faverges SCA of France in 1988. Stäubli was
still making articulated robots for general industrial and clean room applications as of
2004 and even bought the robotic division of Bosch in late 2004.
Eventually the myopic vision of American industry was superseded by the financial
resources and strong domestic market enjoyed by the Japanese manufacturers. Only a few
non-Japanese companies managed to survive in this market, including Adept Technology,
Stäubli-Unimation, the Swedish-Swiss company ABB (ASEA Brown-Boveri), the
Austrian manufacturer igm Robotersysteme AG and the German company KUKA
Robotics.
Now a day's every system is automated in order to face new challenges. In the
present days Automated systems have less manual operations, flexibility, reliability
and accurate. Due to this demand every field prefers automated control systems.
Especially in the field of electronics automated systems are giving good performance.
In the present scenario of war situations, unmanned systems plays very important role
to minimize human losses. So this robot is very useful to do operations like detecting
fire.
Here is an automated unmanned system being designed around a
microcontroller which serves for detecting hazardous parameters such as smoke.
According to this project, a robot is designed which is made to move all the
time. Apart from this, the system also detects the presence of smoke with the help of a
smoke sensor. All the devices such as smoke sensor, motor by which robot is made to
move, buzzer are being interfaced to microcontroller which forms the control unit of
the project.
In the standby mode the robot is moved here and there. Whenever any
smoke is detected by the smoke sensor, the same is sensed and is intimated to the user
by the microcontroller using buzzer.
This project finds its place in places where one wants to make the unmanned
system to sense some hazardous condition.
BLOCK DIAGRAM:
MICRO CONTROLLER UNIT
FIRE SENSOR
BUZZER
BatteryMotorsDrivers
Block Diagram Explanation:
This Project mainly consists of Power Supply section, Microcontroller section, Motor
Driver section and a smoke sensor.
Power Supply Section: This section is meant for supplying Power to all the sections
mentioned above. It basically consists of a 9V DC battery followed by a positive voltage
regulator is used to regulate the required dc voltage for the Microcontroller circuit
operation. There is another power supply which is a 6V DC (four 1.5V batteries) is
required for the operation of the motor driver circuitry.
Microcontroller Section: This section forms the control unit of the whole project. This
section basically consists of a Microcontroller with its associated circuitry like Crystal
with capacitors, Reset circuitry, Pull up resistors (if needed) and so on. The
Microcontroller forms the heart of the project because it controls the devices being
interfaced and communicates with the devices according to the program being written.
Motor Driver Section: This section basically consists of the required circuitry to drive
the motors. This is nothing but an H-Bridge circuitry to drive the motors which controls
direction of the robot.
Smoke Sensor: smoke sensoris used in this project. Whenever the sensor finds smoke
at particular region in the robot’s path. Then the sensor gives the signal to
Microcontroller. The smoke sensor acts as a input source in this project.
Buzzer: The buzzer is an output source for the project. The buzzer is used as an
indication purpose for the occurrence of the high temperatures.
Schematic Explanation:
Firstly, the required operating voltage for Microcontroller 89s51 is 5V. Hence the
5V D.C. power supply is needed by the same. So in this project we are using +9V DC
battery for providing the required voltage for the circuit operation.
The 9V DC battery is connected to the LM7805 regulator so that it allows us to
have a Regulated Voltage which is +5V. This regulated voltage is filtered for ripples
using an electrolytic capacitor 100μF. Now the output from this section is fed to 40th pin
of 89s51 microcontroller to supply operating voltage. In this project, there is another
power supply which is 6V (four- 1.5V battery) supply. This is required for the operation
of the motor driver circuitry to drive the motors.
The microcontroller 89c51 with Pull up resistors at Port0 and crystal oscillator of
11.0592 MHz crystal in conjunction with couple of capacitors of is placed at 18th & 19th
pins of 89c51 to make it work (execute) properly.
The motor driver is nothing but a H-bridge circuitry for controlling motors. That
is for the controlling of the robot direction. The motor driver circuitry includes the two
H-Bridges. Each H-bridge will take care of controlling motor. Each H-bridge having
two inputs. That is, four inputs of two H-bridges are connected to the port pins P1.0,
P1.0, P1.2, P1.3 of the Microcontroller. According the logic values applied at the input
of the H-bridge circuitry the direction of the robot will be controlled. That will be done
through the software. Buzzer is connected to the port P2.0.smoke is connected to the port
P3.2.
HARDWARE USED:
MICROCONTROLLER
SMOKE SENSOR
MOTOR DRIVER
MOTOR
BUZZER
BATTERY
MICRO CONTROLLER (AT89S51)
Introduction:
A Micro controller consists of a powerful CPU tightly coupled with memory,
various I/O interfaces such as serial port, parallel port timer or counter, interrupt
controller, data acquisition interfaces-Analog to Digital converter, Digital to Analog
converter, integrated on to a single silicon chip.
If a system is developed with a microprocessor, the designer has to go for external
memory such as RAM, ROM, EPROM and peripherals. But controller is provided all
these facilities on a single chip. Development of a Micro controller reduces PCB size and
cost of design.
One of the major differences between a Microprocessor and a Micro controller is
that a controller often deals with bits not bytes as in the real world application.
Intel has introduced a family of Micro controllers called the MCS-51.
Figure: micro controller
Features:
• Compatible with MCS-51® Products
• 4K Bytes of In-System Programmable (ISP) Flash Memory
– Endurance: 1000 Write/Erase Cycles
• 4.0V to 5.5V Operating Range
• Fully Static Operation: 0 Hz to 33 MHz
• Three-level Program Memory Lock
• 128 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Full Duplex UART Serial Channel
• Low-power Idle and Power-down Modes
Description
The AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller with 4K
bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s
high-density nonvolatile memory technology and is compatible with the industry- standard
80C51 instruction set and pinout. The on-chip Flash allows the program memory to be
reprogrammed in-system or by a conventional nonvolatile memory programmer. By
combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip,
the Atmel AT89S51 is a powerful microcontroller which provides a highly-flexible and
cost-effective solution to many embedded control applications.
Block diagram:
Figure: Block diagram
Pin diagram:
Figure: pin diagram of micro controller
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 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 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
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
receives some control signals for Flash programming and verification. Port 3 also serves the
functions of various special features of the AT89S51, as shown in the following table.
RST:
Reset input. A high on this pin for two machine cycles while the oscillator is
running resets the device. This pin drives High for 98 oscillator periods after the Watchdog
times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this
feature. In the default state of bit DISRTO, the RESET HIGH out feature is enabled.
ALE/PROG:
Address Latch Enable (ALE) 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 (PSEN) is the read strobe to external program memory. When
the AT89S51 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.
XTAL1:
Input to the inverting oscillator amplifier and input to the internal clock operating
circuit.
XTAL2:
Output from the inverting oscillator amplifier.
Oscillator Characteristics:
XTAL1 and XTAL2 are the input and output, respectively, of an inverting
amplifier which can be configured for use as an on-chip oscillator, as shown in Figs
6.2.3. Either a quartz crystal or ceramic resonator may be used. To drive the device from
an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as
shown in Figure 6.2.4.There are no requirements on the duty cycle of the external clock
signal, since the input to the internal clocking circuitry is through a divide-by-two flip-
flop, but minimum and maximum voltage high and low time specifications must be
observed.
Fig 6.2.3 Oscillator Connections Fig 6.2.4 External Clock Drive Configuration
H-Bridge:
Fig: shows the H-Bridge operation. The H-Bridge consists of a four PNP
transistors such as Q1, Q2, Q3 and Q4. These transistors are arranged in a way that a DC
motor M can rotate. A and B are represented as two inputs for operating a motor through
the transistors. For the circuit operation, we are providing +12V DC as a VCC. The
operation will be explained as follows:
The inputs A and B can be applied as a either logic ‘0’ or logic ‘1’ ie., may be
either 5V DC voltage or Ground. If the input A =logic ‘0’ and B=logic’1’ then
transistors Q1 and Q4 will be ‘ON’ state and Q2 and Q3 will be ‘OFF’ state. The current
flows from Q1 to Q4 so that the motor M can rotate in clockwise direction.
If the input A =logic ‘1’ and B=logic’0’ then transistors Q1 and Q4 will be ‘OFF’
state and Q2 and Q3 will be ‘ON’ state. The current flows from Q1 to Q4 so that the
motor M can rotate in Anti-clockwise direction.
If the input A =logic ‘1’ and B=logic’1’ then transistors Q1 and Q4 will be ‘OFF’
state and Q2 and Q3 will be ‘OFF’ state. No current flows from in the circuit. The circuit
will be in hold condition. The motor will not rotate any direction. So, there is no wastage
of power will occur. Otherwise, if both inputs are low that is all transistors are come
under working and more current will flows in the circuit. But the motor will be at hold
condition. More power is wasted.
DC Motor
DC motors are configured in many types and sizes, including brush less, servo, and gear
motor types. A motor consists of a rotor and a permanent magnetic field stator. The magnetic
field is maintained using either permanent magnets or electromagnetic windings. DC motors are
most commonly used in variable speed and torque.
Motion and controls cover a wide range of components that in some way are used to
generate and/or control motion. Areas within this category include bearings and bushings,
clutches and brakes, controls and drives, drive components, encoders and resolves, Integrated
motion control, limit switches, linear actuators, linear and rotary motion components, linear
position sensing, motors (both AC and DC motors), orientation position sensing, pneumatics and
pneumatic components, positioning stages, slides and guides, power transmission (mechanical),
seals, slip rings, solenoids, springs.
Motors are the devices that provide the actual speed and torque in a drive system. This
family includes AC motor types (single and multiphase motors, universal, servo motors,
induction, synchronous, and gear motor) and DC motors (brush less, servo motor, and gear
motor) as well as linear, stepper and air motors, and motor contactors and starters.
In any electric motor, operation is based on simple electromagnetism. A current-carrying
conductor generates a magnetic field; when this is then placed in an external magnetic field, it
will experience a force proportional to the current in the conductor, and to the strength of the
external magnetic field. As you are well aware of from playing with magnets as a kid, opposite
(North and South) polarities attract, while like polarities (North and North, South and South)
repel. The internal configuration of a DC motor is designed to harness the magnetic interaction
between a current-carrying conductor and an external magnetic field to generate rotational
motion.
Buzzer
A buzzer or beeper is a signalling device, usually electronic, typically used in
automobiles, household appliances such as a microwave oven, or game shows. It most
commonly consists of a number of switches or sensors connected to a control unit that
determines if and which button was pushed or a preset time has lapsed, and usually
illuminates a light on the appropriate button or control panel, and sounds a warning in the
form of a continuous or intermittent buzzing or beeping sound.
Initially this device was based on an electromechanical system which was
identical to an electric bell without the metal gong (which makes the ringing noise).
Often these units were anchored to a wall or ceiling and used the ceiling or wall as a
sounding board. Another implementation with some AC-connected devices was to
implement a circuit to make the AC current into a noise loud enough to drive a
loudspeaker and hook this circuit up to a cheap 8-ohm speaker. Nowadays, it is more
popular to use a ceramic-based piezoelectric sounder like a Sonalert which makes a high-
pitched tone. Usually these were hooked up to "driver" circuits, which varied the pitch of
the sound or pulsed the sound, on and off.
Electronic symbol for a buzzer.
Metal disk with piezoelectric disk attached, as found in a buzzer
In game shows it is also known as a "lockout system," because when one person
signals ("buzzes in"), all others are locked out from signalling.Several game shows have
large buzzer buttons which are identified as "plungers".
The word "buzzer" comes from the rasping noise that buzzers made when they
were electromechanical devices, operated from stepped-down AC line voltage at 50 or 60
cycles. Other sounds commonly used to indicate that a button has been pressed are a ring
or a beep.
FIRE SENSOR:
The semiconductor (or IC for integrated circuit) temperature sensor is an electronic device fabricated in a similar way to other modern electronic semiconductor components such as microprocessors. Typically hundreds or thousands of devices are formed on thin silicon wafers. Before the wafer is scribed and cut into individual chips, they are usually laser trimmed.
Semiconductor temperature sensors are available from a number of manufacturers. There are no generic types as with thermocouple and RTDs, although a number of devices are made by more than one manufacturer. The AD590 and the LM35 have traditionally been the most popular devices, but over the last few years better alternatives have become available.
These sensors share a number of characteristics - linear outputs, relatively small size, limited temperature range (-40 to +120°C typical), low cost, good accuracy if calibrated but also poor interchangeability. Often the semiconductor temperature sensors are not well designed thermally, with the semiconductor chip not always in good thermal contact with an outside surface. Some devices are inclined to oscillate unless precautions are taken. Provided the limitations of the semiconductor temperature sensors are understood, they can be used effectively in many applications.
The most popular semiconductor temperature sensors are based on the fundamental temperature and current characteristics of the transistor. If two identical transistors are operated at different but constant collector current densities, then the difference in their base-emitter voltages is proportional to the absolute temperature of the transistors. This voltage difference is then converted to a single ended voltage or a current. An offset may be applied to convert the signal from absolute temperature to Celsius or Fahrenheit.
In general, the semiconductor temperature sensor is best suited for embedded applications - that is, for use within equipment. This is because they tend to be electrically and mechanically more delicate than most other temperature sensor types. However they do have legitimate application in many areas, hence their inclusion.
Types of semiconductor sensors
A summary of available semiconductor temperatures sensors is presented below, followed by more detail on some of the more popular devices. The sensors can be grouped into five broad categories: voltage output, current output, resistance output, digital output and simple diode types.
1. Voltage Output Temperature Sensors
The following sensors provide a voltage outputs signal with relatively low output impedance. All require an excitation power source and all are essentially linear.
Sensor Manuf. Output Tolerance
(range) Package Comments
AD22100 Analog Devices
22.5mV/°C at 5V
250mV offset
±2°C & ±4°C(-50 to +150°C)
TO-92SO-8
Output ratiometric with supply voltage - good with ratiometric ADC's
AD22103 Analog Devices
28mV/°C (at 3.3V),
250mV offset
±2.5°C(0°C to +100°C)
TO-92SO-8
Output ratiometric with supply voltage
LM135LM235LM335
National Semi, Linear
Tech
10mV/°K or10mV/°C
±2.7°C to ±9°C(-55°C to 150°C-40°C to 100°C)
TO-92TO-46
Zener like operation with scale trim pin, 400µA
LM34 National Semi 10mV/°F ±3°F & ±4°F
(-20°C to 120°C)
TO-46TO-92SO-8
Needs a negative supply for temperatures < -5°C
LM35 National Semi 10mV/°C ±1°C & ±1.5°C
(-20°C to 120°C)
TO-46TO-92SO-8
Needs a negative supply for temperatures < 10°C
LM45 National Semi 10mV/°C
500mV offset ±1°C & ±1.5°C
(-20°C to 120°C)
TO-46TO-9SO-8
LM35 with 500mV output offset
LM50 National Semi 10mV/°C
500mV offset ±3°C & ±4°C
(-40°C to 125°C)
TO-46TO-92SO-8
Low cost part, 500mV off set, easy to use
LM60 National Semi 6.24 mV
offset ±3°C & ±4°C
(-40°C to 125°C) SOT-23
Supply voltage down to 2.7V
S-8110S-8120
Seiko Instruments
-8.5 mV/°C(note neg. TC)
±2.5°C & ±5°C(-40°C to 100°C)
SOT-23SC-82AB
Very low 10µA operating current
TC102TC103TC1132TC1133
Telcom Semi 10 mV/°C ±8°C
(-20°C to 125°C) SOT-23TO-92
.
TMP35 Analog Devices
10 mV/°C ±3°C ±4°C
(10°C to 125°C)
TO-92SO-8
SOT-23
Similar to LM35 plus shutdown for power saving (not in TO-92)
TMP36 Analog Devices
10 mV/°C500 mV offset
±3°C ±4°C(-40°C to 125°C)
TO-92SO-8
SOT-23
Similar to LM50 plus shutdown (not in TO-92)
TMP37 Analog Devices
20 mV/°C ±3°C ±4°C
(5°C to 100°C)
TO-92SO-8
SOT-23 High sensitivity
LM94021LM94022
National Semi programmable±2.5°C
(-50°C to 150°C) SC80
Low power, easy to use
FM20 Fairchild -11.77 mV/°C±5°C
-55°C to 130°C SOT23 Low power
FM50 Fairchild 10 mV/°C ±3°C
-40°C to 125°C SOT23 Similar to LM50
The LM34 and LM35 parts are prone to oscillation if sensor cable capacitively loads their output. The symptom is an offset in the sensors output - something which is not always obvious. It is wise to always include the manufacturer's recommended resistor - capacitor network close to the sensor.
2. Current Output Temperature Sensors
The current output sensors acts as a high-impedance, constant current regulator typically passing 1 micro-amp per degree Kelvin and require a supply voltage of between 4 and 30 V.
Sensor Manuf. Output Tolerance
(range) Package Comments
AD590 Analog Devices
1µA/°K ±5.5°C & ±10°C
(-55°C to +150°C)
TO-52 An old favorite, but need to watch cable leakage currents
AD592 Analog Devices
1µA/°K ±1°C & ±3.5°C
(-25°C to +105°C)
TO-92 A more precise AD590
TMP17 Analog Devices
1µA/°K ±4°C
(-40°C to +105°C)
SO-8 Thermally faster AD590
LM134 National Programmable ±3°C & ±20°C TO-46 Not well specified, but
LM234LM334
Semi 0.1µA/°K to
4µA/°K (-25°C to +100°C)
TO-92 with calibration can be effective.
3. Digital Output Temperature Sensors
The digital temperature sensor is the first sensor to integrate a sensor and an analog to digital converter (ADC) on to a single silicon chip. In general, these sensors do not lend themselves for use with standard measuring devices because of their non standard digital interfaces. Many are designed specifically for the thermal management of microprocessor chips. A selection of representative devices is presented below:
Sensor Manuf. Output Tolerance
(range) Package Comments
LM95071 National Semi 14 bit SPI ±2°C
(-45°C to 150°C) SOT-5
High resolution(0.03°C)2.4-5.5V operation
LM56 National Semi 2 comparators with setable thresholds
±3°C & ±4°C(-40°C to 125°C)
SOP-8MSOP-8
Thermostat with two outputs with hysteresis
LM75 National Semi I2C Serial,
9 bit or 0.5°C resolution
±3°C(-55°C to +125°C)
SOP-8MSOP-8
Addressable, multi drop connection. Better suited to embedded systems
TMP03TMP04
Analog Devices
Pulse width modulation(mark-space
ratio)
±4°C(-25°C to 100°C)
TO-92SO-8
TSSOP-8
Nominal 35 Hz output with 1:1 mark-space ratio at 25°C
DS1620DS1621
National Semi 2 or 3 wire
serial, 0.5°C resolution
±0.5°C(0°C to 70°C)
±5°C(-55°C to 125°C)
SOP-8DIP-8
Also has digitally programmed thermostat output. ±0.03°C resolution possible
DS1624 Dallas 2 wire serial0.3°C
resolution
±5°C(-55°C to 125°C)
SOP-8DIP-8
Addressable, multi drop connection.
Also has 256 bits of EEPROM
DS1820 Dallas 1 wire serial
0.5°C resolution
±0.5°C(0°C to 70°C)
±5°C(-55°C to 125°C)
ModifiedTO-92
SSOP-16
Good un-calibrated tolerance over 0-70°C range.
DS1821 Dallas 1 wire serial
1°C resolution
±1°C(0°C to 70°C)
±2°C(-55°C to 125°C)
Modified TO-92TO-220
SO-8
Has a thermostat mode.
DS2435 Dallas 1 wire serial0.5°C or 1°C
resolution
±4°C(0°C to 127.5°C-40°C to 85°C)
TO-92modified
Also builds a time / temperature histogram
TCN75 Telcom Semi I2C Serial,
9 bit or 0.5°C resolution
±3°C(-55°C to +125°C)
DIP-8SOP-8
TSSOP-8
Second source for LM75
FM75 Fairchild
SMBus12 bit / 0.07°C
resolution
±4°C-40°C to 125°C
MSOP8
Variable resolution, threshold output
The Analog Devices parts are interesting. They employ a sigma-delta ADC that produces continuous pulse stream output with a mark-space ratio, which is proportional to the temperature. This makes for easy interfacing to a microprocessor and also for isolating by optical or other means. The same signal could also be passed through a low pass filter to generate an analog voltage.
The Dallas DS2435 goes beyond that of a sensor plus ADC by providing simple data reduction using an eight bin time / temperature histogram with definable bin boundaries. It appears to have been specifically designed for battery management, but other application could include food transport monitoring, machine use monitoring. This sensor demonstrated the way of the future in sensor technology where sensor, ADC, memory and microcontroller are integrated to form an application specific task very cost effectively.
4. Resistance Output Silicon Temperature Sensors
The temperature - versus - bulk resistance characteristics of semiconductor materials allow the manufacture of simple temperature sensors using standard silicon semiconductor fabrication equipment. This construction can be more stable than other semiconductor sensor, due to the greater tolerance to ion migration. However other characteristics (see below) require that care be taken in using these sensors.
Sensor Manuf. Output Tolerance
(range) Package Comments
KTY81KTY82KTY83KTY84KTY85
Phillips
1K or 2K at 25°C,
+0.8%/°CSee below
±1°C to ±12°C(-55°C to +150°Csome to 300°C)
SOD-70,SOT-23SOD-68SOD-80
Bulk resistance of silicon. Keep excitation current >0.1mA and < 1mA
KYY10KTY11KTY13
Siemens
1K or 2K at 25°C,
+0.8%/°CSee below
±1°C & ±3.5°C(-50°C to +150°C)
TO-92modified
Bulk resistance of silicon.
The silicon temperature sensor's resistance is given by the equation:
R = Rr ( 1 + a.( T - Tr ) + b.( T - Tr )2- c.(T - Ti)d )
where Rr is the resistance at temperature Tr and a, b, c and d are constants. Ti is an inflection point temperature such that c = 0 for T < Ti.
The resistance of some of these semiconductor sensors is dependent on the excitation current (due to current density effects in the semiconductor) and the polarity of the applied voltage. As with other non-passive temperature sensors, self-heating can induce errors.
There are a number of specialist cryogenic temperature sensors that use resistive semiconductor sensor elements made from silicon and germanium.
5. Diode Temperature Sensors
The ordinary semiconductor diode may be used as a temperature sensor. Cheap and nasty! The diode is the lowest cost temperature sensor and can produce more than satisfactory results if you are prepared to undertake a two point calibration and provide a stable excitation current. Almost any silicon diode is ok. The forward biased voltage across a diode has a temperature coefficient of about 2.3mV/°C and is reasonably linear. The measuring circuit is simple as shown to the right.
The bias current should be held as constant as possible - using constant current source, or a resistor from a stable voltage source.
Without calibration the initial error is likely to be too large - in the order of ±30°C - the largest of all the contact type temperature sensors. This initial error is greatly reduced if sensor grade parts are used.
One advantage of the diode as a temperature sensor is that it can be electrically robust - tolerant to voltage spikes induced by lightning strike. This is particularly true if power diodes (e.g. the common 1N4004) are used and a second back to back diode is used to limit power dissipation during high peak currents.
The transistor sensor is used in diode mode by connecting the base and collector together. If this is not done, the sensor is wired between base and emitter and the excitation current reduced by a factor of about 100. The result is a very low power, sensitive and linear sensor. The simplicity and performance of the sensor is under valued.
To improve the performance of the diode as a temperature sensor, two diode voltages (V1 and V2) can be measured at different currents (I1 and I2), typically selected to be about 1:10 ratio. The absolute temperature can be calculated from the equation:
T = (V1 - V2) / (8.7248x10-5 ln( I1 / I2))
The result is in Kelvins (K). This is the method employed by most integrated circuit temperatures sensors and explains why some output a signal proportional to absolute temperature.
Accuracy of semiconductor sensors
As can be seen from the above information, the "out of the box" or interchangeability accuracy of most semiconductor temperature sensors is not particularly good. In addition the raw sensing element is generally packaged in a standard case for electronic devices, which is less than ideal for precision temperature measurement. However, despite these shortcomings, the sensors are sensitive, reasonably linear and very usable.
If individual sensors are calibrated, significantly better measurement accuracy is possible. Typically, a two point calibration will yield a five-fold better accuracy and a three point calibration will yield a ten-fold improvement over the full temperature range. If the temperature range is limited, even better accuracies are possible. Due to the sensitivity of some sensors, they can be very good in measuring small temperature changes (as opposed to absolute measurement).
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. 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:
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 no
electrical connection between the two coils; instead they are linked by an alternating
magnetic field created in the soft-iron core of the transformer. The two lines in the middle
of the circuit symbol 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 turn’s ratio,
determines the ratio of the voltages. A step-down transformer has a large number of turns
on its primary (input) coil which is connected to the high voltage mains supply, and a
small number of turns on its secondary (output) coil to give a low output voltage.
An 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
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 diodes
1
2
4
PIV of diodes
Vm
2Vm
Vm
D.C output voltage
Vm/
2Vm/
2Vm/
Vdc,at
no-load
0.318Vm
0.636Vm 0.636Vm
Ripple factor
1.21
0.482
0.482
Ripple
frequency
f
2f
2f
Rectification
efficiency
0.406
0.812
0.812
Transformer
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 shown in
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)
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)
Filter:
A Filter is a device which removes the a.c component of rectifier output
but allows the d.c component to reach the load
Capacitor Filter:
We have seen that the ripple content in the rectified output of half wave rectifier is
121% or that of full-wave or bridge rectifier or bridge rectifier is 48% such high
percentages of ripples is not acceptable for most of the applications. Ripples can be
removed by one of the following methods of filtering.
(a) A capacitor, in parallel to the load, provides an easier by –pass for the ripples voltage
though it due to low impedance. At ripple frequency and leave the d.c.to appears the load.
(b) An inductor, in series with the load, prevents the passage of the ripple current (due to
high impedance at ripple frequency) while allowing the d.c (due to low resistance to d.c)
(c) Various combinations of capacitor and inductor, such as L-section filter section
filter, multiple section filter etc. which make use of both the properties mentioned in (a)
and (b) above. Two cases of capacitor filter, one applied on half wave rectifier and
another with full wave rectifier.
Filtering is performed by a large value electrolytic capacitor connected across the
DC supply to act as a reservoir, supplying current to the output when the varying DC
voltage from the rectifier is falling. The capacitor charges quickly near the peak of the
varying DC, and then discharges as it supplies current to the output. Filtering
significantly increases the average DC voltage to almost the peak value (1.4 × RMS
value).
To calculate the value of capacitor(C),
C = ¼*√3*f*r*Rl
Where,
f = supply frequency,
r = ripple factor,
Rl = load resistance
Note: In our circuit we are using 1000µF. Hence large value of capacitor is placed
to reduce ripples and to improve the DC component.
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. Most regulators include some
automatic protection from excessive current ('overload protection') and overheating
('thermal protection'). Many of the fixed voltage regulator 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 6.1.6 A Three Terminal Voltage Regulator
78XX:
The Bay Linear LM78XX is integrated linear positive regulator with three
terminals. The LM78XX offer several fixed output voltages making them useful in wide
range of applications. When used as a zener diode/resistor combination replacement, the
LM78XX usually results in an effective output impedance improvement of two orders of
magnitude, lower quiescent current. The LM78XX is available in the TO-252, TO-220 &
TO-263packages,
Features:
• Output Current of 1.5A
• Output Voltage Tolerance of 5%
• Internal thermal overload protection
• Internal Short-Circuit Limited
• No External Component
• Output Voltage 5.0V, 6V, 8V, 9V, 10V,12V, 15V, 18V, 24V
• Offer in plastic TO-252, TO-220 & TO-263
• Direct Replacement for LM78XX
Circuit Description
The robot direction is controlled through the motor driver circuitry. There
are two motors are present which controls the direction the robot. The motor driver
circuitry is designed with two H-bridges as shown in the Motor driver section. Basically
the H-bridge is constructed with the help of four PNP transistors. These transistors are
connected in such a manner to run the motor in both clockwise and anticlockwise
directions based on the input logics applied at the inputs of the H-bridge. So that
depending on the logics applied for the inputs of the two H-bridges the direction of the
robot will be controlled.
According to this project, a robot is designed which is made to move
all the time. Apart from this, the system also detects the presence of smoke with the
help of a smoke sensor. All the devices such as smoke sensor, motor by which robot is
made to move, buzzer are being interfaced to microcontroller which forms the control
unit of the project.
In the standby mode the robot is moved here and there. Whenever any
smoke is detected by the smoke sensor, the same is sensed and is intimated to the user
by the microcontroller using buzzer.
SOFTWARE Components
ABOUT SOFTWARE
Software used is:
*Keil software for C programming
*Express PCB for lay out design
*Express SCH for schematic design
KEIL µVision3
What's New in µVision3?
µVision3 adds many new features to the Editor like Text Templates, Quick Function
Navigation, and Syntax Coloring with brace high lighting Configuration Wizard for
dialog based startup and debugger setup. µVision3 is fully compatible to µVision2 and
can be used in parallel with µVision2.
What is µVision3?
µVision3 is an IDE (Integrated Development Environment) that helps you write, compile,
and debug embedded programs. It encapsulates the following components:
A project manager.
A make facility.
Tool configuration.
Editor.
A powerful debugger.
Express PCB
Express PCB is a Circuit Design Software and PCB manufacturing
service. One can learn almost everything you need to know about Express PCB from the
help topics included with the programs given.
Details:
Express PCB, Version 5.6.0
Express SCH
The Express SCH schematic design program is very easy to use. This software
enables the user to draw the Schematics with drag and drop options.
A Quick Start Guide is provided by which the user can learn how to use it.
Details:
Express SCH, Version 5.6.0
EMBEDDED C:
The programming Language used here in this project is an Embedded C
Language. This Embedded C Language is different from the generic C language in few
things like
a) Data types
b) Access over the architecture addresses.
The Embedded C Programming Language forms the user friendly language with access
over Port addresses, SFR Register addresses etc.
Embedded C Data types:
Data Types Size in Bits Data Range/Usage
unsigned char 8-bit 0-255
signed char 8-bit -128 to +127
unsigned int 16-bit 0 to 65535
signed int 16-bit -32,768 to +32,767
sbit 1-bit SFR bit addressable only
bit 1-bit RAM bit addressable only
sfr 8-bit RAM addresses 80-FFH
only
Unsigned char:
The unsigned char is an 8-bit data type that takes a value in the range of 0-
255(00-FFH). It is used in many situations, such as setting a counter value, where there is
no need for signed data we should use the unsigned char instead of the signed char.
Remember that C compilers use the signed char as the default if we do not put the key
word
Signed char:
The signed char is an 8-bit data type that uses the most significant bit (D7 of
D7-D0) to represent the – or + values. As a result, we have only 7 bits for the magnitude
of the signed number, giving us values from -128 to +127. In situations where + and – are
needed to represent a given quantity such as temperature, the use of the signed char data
type is a must.
Unsigned int:
The unsigned int is a 16-bit data type that takes a value in the range of 0 to
65535 (0000-FFFFH).It is also used to set counter values of more than 256. We must use
the int data type unless we have to. Since registers and memory are in 8-bit chunks, the
misuse of int variables will result in a larger hex file. To overcome this we can use the
unsigned char in place of unsigned int.
Signed int:
Signed int is a 16-bit data type that uses the most significant bit (D15 of D15-
D0) to represent the – or + value. As a result we have only 15 bits for the magnitude of
the number or values from -32,768 to +32,767.
Sbit (single bit):
The sbit data type is widely used and designed specifically to access single bit
addressable registers. It allows access to the single bits of the SFR registers.
Accessing SFR addresses 80-FFH
Another way to access the SFR RAM space 80-FFH is to use the sfr data type.
This is shown in the below example .Both the bit and byte addresses for the P0-P3 ports
are given in the table. Notice in the given example that there is no #include<reg51.h>
statement which allows us to access any byte of the SFR RAM space 80-FFH.
Single Bit Addresses of Ports
P0 Addr P1 Addr P2 Addr P3 Addr Ports Bit
P0.0 80H P1.0 90H P2.0 A0H P3.0 B0H D0
P0.1 81H P1.1 91H P2.1 A1H P3.1 B1H D1
P0.2 82H P1.2 92H P2.2 A2H P3.2 B2H D2
P0.3 83H P1.3 93H P2.3 A3H P3.3 B3H D3
P0.4 84H P1.4 94H P2.4 A4H P3.4 B4H D4
P0.5 85H P1.5 95H P2.5 A5H P3.5 B5H D5
P0.6 86H P1.6 96H P2.6 A6H P3.6 B6H D6
P0.7 87H P1.7 97H P2.7 A7H P3.7 B7H D7
DATA CONVERTION PROGRAMS IN EMBEDDED C
Many micro-controllers have a real time clock (RTC) where the time and date
are kept even when the power is off. These time and date are often in packed BCD by
RTC. To display them they must be converted to ASCII. So, in this topic we are showing
application of logic and instructions in the conversion of BCD and ASCII.
ASCII numbers
On ASCII key boards, when the key “0” is activated, “0110000” (30h)
is provided to the system. Similarly 31h (0110001) is provided for the key “1”, and so on
as shown in the table
Packed BCD to ASCII conversion
The RTC provides the time of day (hour, minutes, seconds) and the date (year,
month, day) continuously, regardless of whether the power is ON or OFF. In the
conversion procedure the packed BCD is first converted to unpacked BCD. Then it is
tagged with 0110000 (30h).
ASCII code for Digits 0-9
Key ASCII (hex) Binary BCD (unpacked)
0 30 011 0000 0000 0000
1 31 011 0001 0000 0001
2 32 011 0010 0000 0010
3 33 011 0011 0000 0011
4 34 011 0100 0000 0100
5 35 011 0101 0000 0101
6 36 011 0110 0000 0110
7 37 011 0111 0000 0111
8 38 011 1000 0000 1000
9 39 011 1001 0000 1001
ASCII to packed BCD conversion
To convert ASCII to packed BCD it is first converted to unpacked and then
combined to make packed BCD. For example 4 and 7 on the keyboard give 34h and 37h
respectively the goal is to produce 47h or “0100 0111” which is packed BCD.
Key ASCII unpacked BCD packed BCD
4 34 00000100
7 37 00000111
01000111 or 47h
Checksum byte in ROM
To ensure the integrity of ROM contents, every system must perform the
checksum calculation. The process of checksum will detect any corruption of the contents
of ROM. One of the cause of the ROM corruption is current surge either when the system
is turned on or during operation. To ensure data integrity in ROM the checksum process
uses, what is a checksum byte. The is an extra byte that is tagged to the end of the series
of the of data.
To calculate the checksum byte of a series of bytes of data, the following steps can be
used
1) Add the bytes together and drop the carries.
2) Take the 2’s complement of the total sum. This is the checksum byte , which
becomes the last byte of the series
Binary (hex) to decimal and ASCII conversion in embedded C
In C-language we use a function call “printf” which is standard IO library
function doing the conversions of data from binary to decimal, or vice versa. But here we
are using our own functions for conversions because it occupies much of memory.
One of the most commonly used is binary to decimal conversion. In devices
such as ADC chips the data is provided to the controller in binary. In order to display
binary data we need to convert it to decimal and then to ASCII. Since the hexadecimal
format is a convenient way of representing binary data we refer to binary data as hex. The
binary data 00-FFH converted to decimal will give us 000 to 255.
One way to do this is to divide it by 10 and keep the remainder, for example
11111101 or FDH is 253 in decimal. The following is one version of the algorithm for
conversion of hex (binary) to decimal.
Quotient Remainder
FD/0A 19 3(low digit) LSD
19/0A 2 5(middle digit)
2(high digit) (MSD)
CONCLUSION
The project “SMOKE SENSING AND ALERTING SYSTEM WITH
ANDROID” has been successfully designed and tested. Integrating features of all the
hardware components used have developed it. Presence of every module has been reasoned
out and placed carefully thus contributing to the best working of the unit. Secondly, using
highly advanced IC’s and with the help of growing technology the project has been
successfully implemented.
BIBLIOGRAPHY
NAME OF THE SITES:
1. WWW.MITEL.DATABOOK.COM
2. WWW.ATMEL.DATABOOK.COM
3. WWW.FRANKLIN.COM
4. WWW.KEIL.COM
REFERENCES
1. 8051-MICROCONTROLLER AND EMBEDDED SYSTEM.
Mohd. Mazidi.