this project we will use LPG sniffer and Fire detection project
controlled with gsm mobile. In this project we will make ROBOT to
find out LPG gas. When it will found GAS it will give buzzer and
will stop to indicate GAS found .Here in this project we show that
how we detect a gas or any type of gases and if we detect a gases
then alarm is on and the same time lcd display shows the gas
detection display. If the gas is detected then relay is off and
break the supply of gas applied to the vehicle or we can control any
type of electrical connection on or off by this relay operated
part of this project is gas sensor.
we use TGS gas sensor. This sensor is a 6 pin sensor . Top and
bottom of the sensor is covered with 100 mesh stainless stell wire
cloth. The heart of the sensor is the cylindrical form in the middle
of the unit. The cylinder is a ceramic material with the SnO2
material deposited on its surface. The heater coil is located inside
the ceramic cylinder. The heater has a resistance of 38 ohms.
Output of the gas sensor is connected the ic 555 as a monostable
trigger ic. As the sensor is detect a gas then ic 555 activate
automatically and then output of the ic 555 is connected to the
the microcontroller circuit we use ic 89s51 controller. Use of this
is is to control the one or many relay logic and at the same time
show the message on the lcd display. If no gas is detected then
display shows a everything is ok . If the gas is detected then show
a warning message on the screen and at the same time relay off the
the gas sensor interface we use gas sensor as a input logic. We
attach one ic 555 as with this sensor . Here ic 555 work as a
monostable timer. Sensor output is connected to the ic 555 pin no
2 via npn transistor. Pin no 2 is a negative trigger ic. When sensor
activate then positive output is available and this positive
output is converted into negative with the help of the NPN
transistor. Output of the NPN transistor is now connected to the
pin no 2 of the ic 555. Pinno 4 and 8 of the ic 555 is connected to
the positive supply. Pin no 1 is connected to the ground pin. Pin no
7 is the output pin. Pin no 6 and 7 is the time constant pin. Pin no
6 and 7 provide a time constant option. When ic 555 works then
output is available on the pin no 3 . Now this output is switching
by the further NPN transistor.One led is also connected to the
transistor circuit. Output of the npn transistor is available on the
collector point. This output from the collector of NPN is now
connected to the microcontroller pin no 1 which is port p1.0. Pin no
40 of the controller is connected to the positive supply. We supply
a 5 volt regulated power supply on this pin. For regulated power
supply we use one step down transformer . Step down transformer
step down the voltage from 220 volt ac to 9 volt ac. This ac is
converted into dc with the help of the rectifier circuit. Here we
use two diode as a full wave rectifier. Output of the rectifier is
now converted into 5 volt regulated supply with the help of 7805
regulator. IC 7805 regulator provide a 5 volt constant supply to
pin no 40 of the ic. Pin no 20 is connected to the ground pin. LCD
is connected to the port 0. Here we use 2 by 16 lcd for display. 2
by 16 means 2 line and 16 character.
output is available from the controller from port P2. One output is
buzzer and second output is relay output. Buzzer is on when
circuit sense a gas and relay switch off the supply chain.
control a relay we use two transistor circuit. Output from the
controller is drive the pnp transistor through 1 k ohm resistor.
Collector of the pnp transistor is connected to the npn transistor
through 1 k ohm resistor. Collector of the NPN transistor is
connected to the relay coil directly. . Here relay is for the
switching purpose only . As the transistor is on relay is on and
relay break the contact of supply chain.
In this project we use smart logic and control system of embedded
system by using microcontroller. In this project we use ic 89c51 as
a main processor.. microcontroller sense the signal and drive the
motor of the robotic vehicle. .
circuit is ic 8870. IC 8870 is a bcd to dtmf decoder. So our
first part of the circuit is our dtmf decoder. This part is very
much necessary, without using this part is not possible to interact
with the mobile phone or dtmf based any phone. Whenever we press
any switch from the transmitter phone then transmitter transmit some
signal as per the switch press. So on every press switch there is a
Output of the dtmf decoder is bcd.ur next circuit is how to convert
bcd signal into decimal signal. In this project we use ic 74154 as a
bcd to decimal decoder circuit. IC 74154 converts the bcd
signal into decimal signal . Output of the 74154 is active low.
Output of the 74154 is connected to the 89c2051 microcontroller. Ic
89c2051 microcontroller basically drive the motor for forward and
Output of the microcontroller is connected to the optocoupler
circuit. Here in this project we use ic pc 817 as a optocoupler to
interface the microcontroller to small slow speed dc gear motor.
One gear motor drive the vehicle and second gear motor change the
front wheel of vehicle..
WELCOME TO THE WORLD OF THE MICROCONTROLLERS.
Look around. Notice the smart “intelligent” systems? Be it the T.V,
washing machines, video games, telephones, automobiles, aero planes,
power systems, or any application having a LED or a LCD as a user
interface, the control is likely to be in the hands of a micro
Measure and control, that’s where the micro controller is at its
Micro controllers are here to stay. Going by the current trend, it
is obvious that micro controllers will be playing bigger and bigger
roles in the different activities of our lives.
So where does this scenario leave us? Think about it……
The world of Micro controllers
What is the primary difference between a microprocessor and a
micro controller? Unlike the microprocessor, the micro controller
can be considered to be a true “Computer on a chip”.
In addition to the various features like the ALU, PC, SP and
registers found on a microprocessor, the micro controller also
incorporates features like the ROM, RAM, Ports, timers, clock
circuits, counters, reset functions etc.
While the microprocessor is more a general-purpose device, used for
read, write and calculations on data, the micro controller, in
addition to the above functions also controls the environment.
We have used a whole lot of technical terms already! Don’t get
worried about the meanings at this point. We shall understand these
terms as we proceed further
now just be aware of the fact, that all these terms literally mean
what they say.
Bits and Bytes
Before starting on the 8051, here is a quick run through on the
bits and bytes. The basic unit of data for a computer is a bit. Four
bits make a nibble. Eight bits or two nibbles make a byte. Sixteen
bits or four nibbles or two bytes make a word.
1024 bytes make a kilobyte or 1KB, and 1024 KB make a Mega Byte or
Thus when we talk of an 8-bit register, we mean the register is
capable of holding data of 8 bits only.
The 8051 developed and launched in the early 80`s, is one of the
most popular micro controller in use today. It has a reasonably
large amount of built in ROM and RAM. In addition it has the ability
to access external memory.
The generic term `8x51` is used to define the device. The value of x
defining the kind of ROM, i.e. x=0, indicates none, x=3, indicates
mask ROM, x=7, indicates EPROM and x=9 indicates EEPROM or Flash.
A note on ROM
The early 8051, namely the 8031 was designed without any ROM.
This device could run only with external memory connected to it.
Subsequent developments lead to the development of the PROM or the
programmable ROM. This type had the disadvantage of being highly
The next in line, was the EPROM or Erasable Programmable ROM. These
devices used ultraviolet light erasable memory cells. Thus a program
could be loaded, tested and erased using ultra violet rays. A new
program could then be loaded again.
An improved EPROM was the EEPROM or the electrically erasable PROM.
This does not require ultra violet rays, and memory can be cleared
using circuits within the chip itself.
Finally there is the FLASH, which is an improvement over the EEPROM.
While the terms EEPROM and flash are sometimes used interchangeably,
TRANSFORMER 220 TO 9 VOLT AC
DIODE IN 4007(2)
MFD (1), 33 MFD (1), 27 PF (2).
NPN TRANSISTOR BC
PNP TRANSISTOR BC
RESISTOR 100 K (2),
1 K (4), 470 OHM (1), 10 K (3)
PULL UP RESISITOR
ARRAY. 10 K (1)
4.7 K (1)
RELAY 12 VOLT
PC817- 4 NOS
IC 555 TIMER
104 PG ACPACIOTR
10K REISTOR- 10 NOS
4.7 K- 2 NOS
DC GEARED MOTORS-
LPG GAS SENSOR- - 1
Motor circuit to drive
CIRCUIT AND THEORY ARRANGEMENT
CHECKING AVAILABILITY OF COMPONENTS
COMPONENT INSERTION AND SOLDERING