Gas Leakage Alarm

1. INTRODUTION

             Gas leak detection methods became a concern after the effects of harmful gases on human health were discovered. Many technologies and devices have been developed to detect, monitor, and alert the leakage of a wide array of gases. Now here we are introducing a gas leakage alarm where a gas sensor forms the heart of the circuit.

Different types of gas detectors are;

1. Electrochemical Detectors.
2. Infrared Point Detectors.
3. Semiconductor Detectors.
4. Ultrasonic Detectors.
5. Holographic Detectors.

             Here we are using MQ-6 Semiconductor Sensor in detecting gas leakage. Sensitive material of MQ-6 gas sensor is SnO_2, which with lower conductivity in clean air. When the target combustible gas exist, the sensors conductivity is higher along with the gas concentration rising.

             This project is designed to detect the LPG from 100parts per million (PPM) to 10,000 PPM. Whenever LPG is detected, the sensor produces the output voltage, which is depended on the amount of gas leakage. This voltage drives the transistor into saturation region. A buzzer is connected to produce audible alert signal.

            This project uses regulated 5V, 750mA power supply for charging the battery. 7805 three terminal voltage regulator is used for voltage regulation.

2. BLOCK DIAGRAM

Transistor driver          circuit

Sensitivity     Control Circuit

LPG Sensor

  

 

  

			Buzzer

 

                                Power supply to all sections

2.1 BLOCK DESCRIPTION

             Block diagram consist of mainly five blocks

1. LPG sensor.

2. Sensitivity control circuit.

3. Transistor driver circuit.

4. Buzzer.

5. Power supply.

2.1. LPG SENSOR

          The sensor module utilizes an MQ-6 as the sensitive component and has a protection resistor and an adjustable resistor on board. The MQ-6 gas sensor is highly sensitive to LPG, iso-butane, propane & less   sensitive to alcohol, cooking fume and cigarette smoke.  The resistance of the sensitive component changes as the concentration of the target gas changes.

2.2. SENSITIVITY CONTROL CIRCUIT

            An integrated circuit voltage comparator is equivalent to an Operational Amplifier, Such as the LM358, with two NPN transistors added to the output of each amplifier. This arrangement produces an open collector output for each of the two comparators in an LM358 chip.

      

   

             The output is switched ON or OFF depending on the relative voltages at the PLUS and MINUS inputs of the comparator. The inputs are quite sensitive and a difference of only a few milli volts between the two will cause the output to turn on or off.

2.3. TRANSISTOR DRIVER CIRCUIT

           The output voltage from comparator circuit drives the transistor into saturation region. A buzzer connected to the transistor produce audible alert signal when the transistor is on.

           BC548 transistor is used in the circuit.

                             

2.4. BUZZER

           A buzzer is an audio signaling device. Basic Electromechanical Buzzer with single sound output and DC operating Voltage. It is easy to use and ideal for warning indication. The buzzer sounds when you close the circuit and stops when you open the circuit.                                 

2.5. POWER SUPPLY

         A power supply is a device that supplies electrical energy to one or more electric loads. Here power is supplied to all the section.

3. CIRCUIT DIAGRAM AND WORKING

3.1 CIRCUIT DIAGRAM

 

 

3.2 WORKING

            The circuit consists of a sensor which senses gas. The sensor is connected to the IC LM358 as a comparator. The comparator output is fed to an LED. For generating the sound signals the comparator output is fed to the second comparator. Here the second comparator is fed with a reference voltage which is fed from a7805 voltage regulator. The output is fed to the buzzer.

            Connect the sensor to the circuit. Initially when the sensor MQ-6 detects the gas it generates a voltage which is send to pin number 3 of LM358 .Here the first op-amp in LM358 is used .Reference voltage of 5v is applied to pin number 2 of LM358 . The input of the first op-amp is compared and output is taken from pin number 1.This will glow the led connected to pin number 1. In order to generate a sound signal, additional circuitry is attached to the present circuit .For this pin number 5 is shorted with pin number 1. Again a reference voltage of 5v from a 7805 voltage regulator, fed with 9v, is fed to pin number 6 of LM358 .During this time the second op-amp of LM358 functions. Hence inputs at pin number 6 and 5 are compared. When the output at pin number 5 goes above the reference input there is a 0 to 1 transition in the output pin number 7 .This will glow the led connected to pin number 7. Correspondingly it switches on the transistor Q1. When Q1 reaches saturation it activates the buzzer and it generates the desired sound.

4. LIST OF COMPONENTS

COMPONENTS	SPECIFICATI0N	QUANTITY
RESISTOR	330Ω	1
	960Ω	1
	1K	3
	10K	1
LED	-	2
COMPARATOR	IC LM358	1
GAS SENSOR	MQ-6	1
VOLTAGE REGULATOR	IC 7805	1
TRANSISTOR	BC458	1
BUZZER	-	1

4.1. COMPONENTS DESCRIPTION

4.1.2. RESISTOR

            A resistor is two-terminal passive electronic component which implements electrical resistance as a circuit element. When a voltage V is applied across the terminals of a resistor, a current I will flow through the resistor in direct proportion to that voltage. This constant of proportionality is called conductance, G. The reciprocal of the conductance is known as the resistance R, since, with a given voltage V, a larger value of R further "resists" the flow of current I as given by Ohm's law.

4.1.2. COMPARATOR

            An IC-LM358 is used as a comparator. The LM358 consists of two independent, high gain, internally frequency-compensated operational amplifiers internally frequency-compensated operational amplifiers designed specifically to operate from a single power supply over a wide range of voltages. Operation from dual power supplies is also possible, and the low power supply current drain is independent of the magnitude of the power supply voltage.

4.1.3. GAS SENSOR

            Sensitive material of MQ-6 gas sensor is SnO2, which with lower conductivity in clean air. When the target combustible gas exist, the sensor’s conductivity is higher along with the gas concentration rising. MQ-6 gas sensor has high sensitity to Propane, Butane and LPG, also response to Natural gas. The sensor could be used to detect different combustible gas, especially Methane; it is with low cost and suitable for different application.

4.1.6. VOLTAGE REGULATOR

            The IC7805 is a self-contained fixed linear voltage regulator integrated circuits. The IC7805 is commonly used in electronic circuits requiring a regulated power supply due to their ease-of-use and low cost. These devices support an input voltage anywhere from a couple of volts over the intended output voltage, up to a maximum of 35 or 40 volts, and typically provide 1 or 1.5 amps of current (though smaller or larger packages may have a lower or higher current rating).

4.1.4. LIGHT EMITTING DIODE

            A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. When a light-emitting diode is forward biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor.

4.1.7. BUZZER

            A buzzer or beeper is an audio signaling device, which may be mechanical, electromechanical, or piezoelectric. Typical uses of buzzers and beepers include alarms, timers and confirmation of user input.

4.1.5. TRANSISTOR

            A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal.

                                       

5.    PCB DESIGNT

              The printed circuit board manufacturing process is a difficult and complex series of operations to make a printed circuit board. Triangle Circuits' years of experience in manufacturing circuit boards has made us a preferred supplier of printed circuit boards for industry leading OEM's and Electronic Contract Manufacturers since 1979.

              We believe that by sharing our knowledge of the manufacturing process you will not only better understand the steps we take to manufacture a printed circuit board but also see the importance of each step in the process. We believe you will see why Triangle Circuits offers the best in quality, customer service and on time delivery for you.

5.1The Printed Circuit Board Manufacturing Process:

              The process starts once your files and specifications have been sent to Triangle Circuits. Our engineers review each order to ensure design for manufacturability and proper selection of materials and technologies before manufacturing begins.

5.2Patterning | Etching

              The majority of printed circuit boards are manufactured by applying a layer of copper over the entire surface of the circuit board substrate either on one side or both sides. This creates what is referred to as a blank printed circuit board, meaning the copper is everywhere on the surface. From here the unwanted areas are removed, this is called a subtractive method, the most common subtractive method is known as photoengraving.

5.3Photoengraving

              The photoengraving process uses a mask or photo mask combined with chemical etching to subtract the copper areas from the circuit board substrate The  photo mask is created with a photo plotter which takes the design from a CAD PCB software program. Lower resolution photo masks are sometimes created with the use of a laser printer using a transparency.

5.4Lamination

              Many printed circuit boards are made up of multiple layers; these are referred to as multi-layer printed circuit boards. They consist of several thin etched boards or trace layers and are bonded together through the process of lamination.

5.5Drilling

              Each layer of the printed circuit board requires the ability of one layer to connect to another; this is achieved through drilling small holes called "VIAS". These drilled holes require precision placement and are most commonly done with the use of an automated drilling machine. These machines are driven by computer programs and files called numerically controlled drill or (NCD) files also referred to as excellent files. These files determine the position and size of each file in the design.

              Some files require very small vias to be drilled which results in heavy wear and tear of the drill bit itself. Drilling through different substrates may require the drill bit to be made of tungsten carbide and are costlier than other materials but required to provide a proper hole.

              Controlled depth drilling can be used to drill just one layer of the circuit board rather than drilling through all the layers. This can be accomplished by drilling the individual sheets or layers of the PCB prior to lamination.

 

Blind Vias   :  Is when the holes connect a layer to the outside surface

Buried Vias : Is when the holes only connect interior layers and not to the outside surface.

            The walls of each hole (for multi-layer boards) are copper plated to form plated- through holes that connect the conductive layers of the printed circuit board.

5.6 Solder Plating \ Solder Resist

            Pads and lands which will require components to be mounted on are plated to allow solder ability of the components. Bare copper is not readily solder able and requires the surface to be plated with a material that facilitates soldering. In the past a lead based tin was  used to plate the surfaces, but with RoHS compliance enacted newer materials are being used such as nickel and gold to both offer solder ability and comply with RoHS standards

PCB LAYOUT

                               

SOLDERING

The principles of good soldering practice include the following:

1)      Selection of the proper joint design and clearance.

2)      Selection of the right solder and flux.

3)       Adequately cleaning the joint components.

4)       Fluxing and assembling components with proper replacement or addition of solder.

5)      Heating the joint to the right soldering temperature for optimum time. The soldering operation is performed by bringing molten solder in contact with the preheated surfaces and heating the joint area to a good wetting temperature. This is roughly 55 to 80°C above the melting point of the solder alloy itself. Under these conditions, good wetting can occur.

6)       The solder is then left to cool and freeze as quickly as possible in order to avoid disturbing the joint during solidification and causing internal micro cracks to form. The soldered joint is then cleaned to remove any undesirable flux residues on the surfaces and to ensure the integrity of the soldered joint.

 

6.    ADVANTAGES AND DISADVANTAGES

6.1 ADVANTAGES

Ø  Good sensitivity to Combustible gas in wide range  

Ø  High sensitivity to Propane, Butane and LPG                                      

Ø  Long life and low cost

Ø  Simple drive circuit

Ø In our daily life security is an important aspect that we face. The advances in the field of electronics have made many security systems.

6.2. DISADVANTAGES

Ø Less sensitive to alcohol, cooking fume and cigarette smoke

7. APPLICATION

                                                                         

             Gas leak detection methods became a concern after the effects of harmful gases on human health were discovered. The Gas leakage alarm can be used for a wide range of applications, and can be used in industrial plants, refineries, wastewater treatment facilities, vehicles, and around the home.

Ø  It has wide application in various security system

Ø  It is used in Domestic gas leakage detector

Ø  Industrial Combustible gas detector

Ø  Portable gas detector

8.  CONCLUSION

          Our project High sensitive LPG sensor with gas leakage alert buzzer finds many applications in domestic and industrial purposes as a security alarm.

            A high sensitive LPG sensor with gas leakage alert buzzer was designed and constructed. The output has been verified to standard quality and is successfully done.

            We take this opportunity to once again thank everyone who contributed directly or indirectly to this project. 

9. FUTURE SCOPE

            As we already discussed Gas leakage alarm is a security device that has wide application in modern field.

           

Ø  As security system in household purpose.

Ø  Applicable in Industries.

Ø  A good security system in LPG outlets.

Ø  Applicable in Automobiles.

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