safe lpg

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SAFE LPG FOR HOMEProject guide: Ms.Manjusree s.Group members:Sreelekshmi M.S.

Sreeja M.S. Reshma Manoharan

Sini P .V.

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Contents

• Aim• Block diagram• Circuit diagram• Flow diagram• Components description• Pic microcontroller• Input section (Gas sensor)• Output section(Gsm modem,Buzzer)• Advantages• Applications• Conclusion• References

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Introduction

• The number of deaths due to the explosion of gas cylinders has been increasing in recent years.

• Around 1500 people per annum lost their lives in LPG leakage accidents .

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Causes of accidents

• Careless handling of LPG cylinder leaving gas regulator ON while

not in use .• Old and damaged link pipe

between the stove and cylinder.• Bringing fire or igniting

fire near LPG cylinder.

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Why our project ?

• There is a need for a system to detect and also prevent leakage of LPG.

• Here we present a pic microcontroller based system to meet this requirement.

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Block diagram

GAS SENSOR (MQ6)

PIC MICRO

CONTROLLER (16F877A)

GSM MODULE

ALARM

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Circuit diagram

GAS SENSOR

GSM MODEM

BUZZER

PIC MICROCONTROLLER

POWER SUPPLY

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Circuit working• The circuit consists of two major modules namely, leakage detection

module and PIC microcontroller.

• It uses Microchip’s PIC 16F877A, which is an 8 bit microcontroller.

• The leakage detection module consists of the MQ-6 gas sensor to detect the amount of combustible gas present in the surrounding . The output of sensor module is connected to ADC of the PIC microcontroller. The microcontroller digitises the voltage and checks if the concentration is within safe levels.

• If the concentration of the combustible gases is beyond safe levels (the safety level is programmable(3V)) the microcontroller immediately activates an alarm and the and sends alert SMS about leakage to the stored numbers via GSM.

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Flow diagram

START ALARM AND SEND MESSAGE to stored number

Power ON

WITH IN SAFETY LEVEL

START

CLOSE

MCU sends “AT’ to GSM module

Is GSM modem replies

OK?

NO

YES

YES

NO

GET SENSOR INPUT

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Components description-gas sensor

1.Gas sensor (MQ6 gas sensor) Features:• High Sensitivity to LPG, iso-butane

and propane. • Detection Range: 100 - 10,000 ppm. • Fast Response Time: <10s

• Long life and low cost . • Simple drive circuit. Applications

• Gas leak detection system.• Fire/Safety detection system.• Gas leak alarm.• Gas detector.

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Basic circuit of gas sensorBasic circuit:The sensor requires two voltages, 1.heater voltage （ VH ）

2.circuit voltage （ VC ）• VH is used to supply certified

working temperature to the sensor.

• VC is used to detect voltage(VRL) on load resistance(RL).

• Heater is used to heat upsensing element .

In order to make the sensor with better performance, suitable RL value is needed.

VC

VH

RL

VRL

heater

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Continued........Technical data

Sensor type Semiconductor

Standard Encapsulation Bakelite (Black Bakelite)

Heater voltage(VH) 5.0V±0.2V ACorDC

Loop voltage(Vc) 5.0V±0.2V ACorDC

Load resistance(RL) Adjustable

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Continued............Structure and Configuration:• The sensor composed by Micro AL2O3 ceramic tube. Tin Dioxide (SnO2) sensitive layer. Measuring electrode (Au) Heater (nickel-cromium alloy)• They are fixed into a crust made by plastic and stainless steel

net.• The heater provides necessary work conditions for work of

sensitive components.• The enveloped MQ-6 have 6 pin ,4 of them are used to fetch

signals, and other 2 are used for providing heating current.

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Working principle-gas sensor

Sensing material-tin dioxide (SnO2)

1. Adsorption of oxygen on the crystal surface.

2.Reaction between surface oxygen and gases takes place.

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Continued....

• Reaction causes a dynamic change of electric potential on SnO2 crystal .

• This results in the decrease of sensor resistance under the presence of reducing gases such as CO,methane(conductivity increases).

In the presence of reducing gases ,sensor resistance decreases with increase of gas concentration

Sensor resistance in air

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Pic microcontroller 2. PIC16F877A• CMOS FLASH based 8-bit microcontroller• High-Performance RISC CPU• Operating speed: 20 MHz clock input,

200 ns instruction cycle.• 256 bytes of EEPROM data memory.• self programming.• 2 Comparators.• 8channels of 10-bit Analog-to-Digital (A/D) converter.• 2 capture/compare/PWM functions.• A synchronous serial port that can be configured as either 3-

wire SPI or 2-wire I2C bus, aUSART, and a Parallel Slave Port.

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Continued.......... Parameter Name Value

Operating frequency DC-20MHZ

Program Memory (KB) 14-bit words,8K

interrupts 15

RAM Bytes 368

Data EEPROM (bytes) 256

Instruction set 35 instructions

Timers 2 x 8-bit, 1 x 16-bit

ADC 8 ch, 10-bit

Comparators 2

Temperature Range (C) -40 to 85

Operating Voltage Range (V) 2 to 5.5

Pin Count 40

i/o ports Ports A,B,C,D,E

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Output sections 3.MAX232 • The MAX232 is an integrated circuit, first created by Maxim Integrated Products.• It is a dual driver/receiver

and typically converts the RX, TX, CTS and RTS signals.

• The drivers provide RS-232 voltage level outputs from a single + 5 V supply via on-chip charge pumps and external capacitors.

• The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to standard 5 V TTL levels.

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Working of MAX232 When a MAX232 IC receives a

TTL level to convert, it changes a TTL Logic 0 to between +3 and +15 V, and changes TTL Logic 1 to between -3 to -15 V and vice versa for converting from RS232 to TTL

RS232 Line Type & Logic Level

RS232 Voltage

TTL Voltage to/from MAX23

Data Transmission (Rx/Tx) Logic 0

+3 V to +15 V 0 V

Data Transmission (Rx/Tx) Logic 1

-3 V to -15 V 5 V

Control Signals (RTS/CTS/DTR/DSR) Logic 0

-3 V to -15 V 5 V

Control Signals (RTS/CTS/DTR/DSR) Logic 1

+3 V to +15 V 0 V

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Continued...

• 4. Gsm modem • A GSM modem is a specialized type of modem which accepts

a SIM card, and operates over a subscription to a mobile operator, just like a mobile phone.

• The Modem is coming with 5V TTL interface, which allows us to connect directly to 5V microcontroller.

• It is suitable for SMS as well as DATA transfer.

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Continued

5.BUZZER• A buzzer or beeper is an audio signalling device,which may be

mechanical,electromechanical or piezoelectric.

• It is provided to immediately alert the people at home.

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Power supply

• 7805 converts 230V ac into 5V DC.• 5V is used as VCC for all ICs.

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Advantages

• Helps in decreasing chances of accidents.• User friendly operations.• Cheap and cost effective.• Easy to handle and implement.

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Disadvantages

• No protection circuitry is provided

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Applications

• Gas leakage detector (Domestic)• Combustible gas detector (Industrial)• Gas detector (Portable)• Homes• Factories• LPG storage• Gas cars• Hotels

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Future scope

• The system can be further enhanced by using a Real- Time clock to display the date and time .

• Temperature sensor can be used to detect sudden rise in temperature due to other sources that may be hazardous.

• The temperature sensor can also be used to display the

temperature and alert when too high or low temperatures are

reached.

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Conclusion

The device can not only be used for home security systems but also can be used in industries and other places to detect gas leaks and alert people, apart from taking required safety measures. For simpler and cost effective systems an RF transmitter and receiver system can also be used but the

coverage area will be limited .

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References

• http://www.wvshare.com/datasheet/Microchip_PDF/PIC16F877A.PDF

• Hanwei Electronics Co. Ltd, MQ 6 sensor Datasheet .• Sunithaa.J, Sushmitha.D “Embedded Control System for LPG Leak

Detection and Prevention”, international Conference on Computing and Control Engineering (ICCCE 2012), 12 & 13 April, 2012 .

• Microchip Inc., PIC 16F877A datasheet T. Iseki, H. Tai, and K. Kimura, "A portable remote methane sensor using a tunable diode laser," Meas. Sci. Technol.,Vol. 11, pp. 594–602, 2000.

• http://www.wvshare.com/datasheet/MAXIM_PDF/MAX220-MAX249.pdf

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Time lineFeb 8-Feb 13 Searched details of gas sensor,collected

datasheets of MQ6 gas sensor.

Feb 14-Feb 15 Discussed gas sensor details in our group,Studied about gas sensor MQ6.

Feb 16-feb 28

Collected papers of PIC microcontroller and studied.

March 8-march 14 Did PCB design,Discussed program of our project in our group.

March 15-march 22 Prepared slides for presentation.

Future works program completion,Design and implementation of circuit.

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Thank you