LPG Gas Sensor Module – rhydoLABZ-wiki

RhydoLabz’s LPG Gas Sensor Module is designed to detect the presence of a dangerous LPG leak in your Home, car or in a service station, storage tank environment by interfacing with Microcontroller without ADC Channels and programming. In this version of LPG Gas sensor module two pots are included, one for trigger level setting and the other for setting sensitivity of the sensor. It allows to determine when a preset LPG gas level has been reached or exceeded. The module uses MQ-6 sensor to sense LPG leak. The MQ-6 can detect gas concentrations anywhere from 200 to 10000 ppm.

Interfacing with the sensor module is done through a 4-pin breadboard compatible SIP header and requires One I/O pin from the host microcontroller. The onboard microcontroller provide initial heating interval after power-up and then starts to measure LPG sensor output.If it found the LPG concentration above preset value , it will inform the Host controller by pulling the Output Pin to High and Starts to blink a onboard status LED. The sensor module is mainly intended to provide a means of comparing LPG sources and being able to set an alarm limit when the source becomes excessive.

The best location to fix Gas Sensor Module is near the Gas Cylinder or near the pipeline in case of piped gas connection. In case of LPG, when Gas leakage occurs , the gas will settle down near the floor because LPG is heavier than the air. So for best results it would be advisable to fit Gas Sensor Module nearly 1m above the floor.

Features:

Uses the MQ-6 LPG Gas Sensor
Easy SIP interface
Compatible with most microcontrollers
Analog Sensor voltage is available at ANG pin.
Onboard Status and Power LED
Onboard Pot for threshold setting
Onboard Pot for Sensitivity setting
On board microcontroller

Specifications:

PIN diagram:

Pin details of LPG Gas Sensor Module -V2 is as given below.

NOTE: 1. A high on OUT pin indicates LPG presence. This pin can be connected to the Digital I/O pin of the microcontroller.

2. ANG pin outputs a voltage (0-5V) corresponding to the level of LPG detected. This pin can be connected to the ADC pin of the microcontroller.

Layout:

Component details:

There are two potentiometers used in Gas Sensor Module . they are as follows:
- POT P1: The on-board POT P1 is used to set tolerance voltage for detecting the LPG presence. When LPG is detected, the OUT pin will be high. This will occurs when the output voltage is greater than the tolerance level set, using the POT P1.
- POT P2: The on-board POT P2 is used to set the sensitivity of the Gas sensor. We recommend you to calibrate the detector for 1000ppm of LPG concentration in air and use value of POT P2 about 20KΩ.
There are two leds in Gas Sensor Module . They are:
- D1: PWR Led. This Green Led indicates the Power input.
- D2: STS Led.The red status Led (STS) indicates the various status of LPG Sensor module eg. Power on, initialization & LPG detection. When the sensor is powered up, the STS led will blink twice to indicate the module is functional. There after STS Led will blinks every second till the module is getting ready ( Heating Zone) . After the sensor is initialized, the module will enter in to the ARM mode and ready to detect the gas concentration , during this period the STS led will blink in step of 3 seconds. When LPG is detected, the STS led will blink fast till the level goes below the set threshold.

Procedure For Calibration:

Place the gas sensor module in a clean environment.
Before powering up the module , first you need to set the sensitivity. According to the manufacture specification it is recommended to set the sensitivity to approximately 20k(by varying potentiometer P2) . In order to view the value ,place the multimeter probe to the ANG pin and the other end to the GND .
Once the sensitivity adjustment has been done, power up the module with 5v. At the first stage you can observe the STS(STATUS) led blinking twice i.e, in order to indicate the module is functioning. Below shows the STS led waveform.

LPG gas sensor module enters into 3 zones
- Heating zone
- Armed zone
- Trigger or sensing zone

1.Heating Zone
Module enters to heating zone after the power up. It takes around 2.30 minutes for the device to gets heated up. Adjust the potentiometer P1 to around 1V threshold (in order to note down the threshold voltage, check across the 6th pin of IC using multimeter ).Once the module enters the heating zone ,STS led blinks once in a second and wave form is shown below:2.Armed zone
Module once after the heating zone, enters into the armed zone. This is the stage before the gas sensing zone. If the led blinks once in 4 second, it means there is no presence of gas and also indicates that calibration has been done successfully . After this stage Module enters to the Trigger or sensing Zone and STS led waveform is shown below.

3.Trigger or sensing Zone
Here the module enters to the gas sensing zone. If the module detects the GAS ,ie when the GAS concentration increases STS led will start blinking rapidly and will take around 250 msec ON time and same as OFF time. Fast blinking of LED indicates the presence of gas. When the gas concentration decreases, led will start blinking once in 4 seconds indicates absence of gas and STS led waveform is shown below.

Analog value > threshold value – STS led blinks faster
Analog value < threshold value – STS led blinks slower

How To Test:

1. Interfacing the LPG Sensor with PIC 16F877A microcontroller (RA3 as Analog pin of ADC)

Interfacing LPG sensor with PIC16F877A microcontroller, connection diagram shown below. Here ANG pin of sensor module is connected to analog pin3 (RA3) of microcontroller. This pin output a voltage (0-5V) corresponding to the level of LPG detected. It can be connected to the ADC pin of the microcontroller.

Interfacing the LPG Sensor with PIC 16F877A microcontroller (RA3 as Analog pin of ADC)), sample program shown below.

/********************************************************************************
* Microcontroller -- PIC 16 F877 - 40-pin - 8-bit *
* Clock Frequency is 20 MHz -- Period in 200 Nano Seconds *
* USART - BaudRate 9600 *
* This program is  used to read gas sensor value
*********************************************************************************/
#include<pic.h>
#include"delay.c"
int LPG_Value=0;
void ADC_init() ;
void send(char);
int adc_conv(int);
void SerialPortInit() ;
void SendData(char);
void display(int value );
 void MSdelay(unsigned int);
static void Send2USART(const char *CPtr1);

void main()
{
TRISC=0X80;
TRISA=0XFF;
SerialPortInit() ;
ADC_init();
while(1)
{
Send2USART("LPG Value:");          // send LPG value
LPG_Value=adc_conv(1);             // select channel 1 for LPG reading
display(LPG_Value );              // convert LPG value for display
SendData('\n');                   // new line
SendData('\r');                   // carriage return 
}
}
/*****************************************************************************
* Function    : Send2USART
* Description : Group of data send serially  
******************************************************************************/
static void Send2USART(const char *Cptr1)
{
while(*Cptr1 != '\0')
{
SendData(*Cptr1);
Cptr1++;
}
}
/*****************************************************************************
* Function    : display
* Description : Display adc value function
******************************************************************************/
void display(int value )
{
char k=1;
char array[4];
for(k=1;k<=4;k++)
{
array[k]=value%10;
value=value/10;
}
for(k=4;k>=1;k--)
{
SendData(array[k]+'0');
}
}
/*****************************************************************************
* Function    : SerialPortInit
* Description : Usart Initialization function - Baud Rate 9600
******************************************************************************/
void SerialPortInit()
{
GIE=1;
SYNC=0;
TXEN=1;
BRGH=1;
SPEN=1;
CREN=1;
PEIE=1;
RCIE=1;
SPBRG=129;
}
/*****************************************************************************
* Function    : ADC_init
* Description : Adc Initialization function 
******************************************************************************/
void ADC_init() 
{
ADFM=1;
PCFG3=0;
PCFG2=0;
PCFG1=0;
PCFG0=0;
}
/*****************************************************************************
* Function    : adc_conv
* Description : Adc Conversion function 
******************************************************************************/
int adc_conv(int channel)
{
int ab;
ADCON0=0x81|channel<<3;	                                      //channel selection
DelayMs(1);
ADGO=1;					//start AD conversion
while(ADGO!=0);			                  //waiting for competion of AD conversion
ab=ADRESH;				//assign 2bit value ADRSH register to variable ab
ab=ADRESH<<8;				//8 times shift  variable ab value 
ab=ab|ADRESL;				//combine ADRESL & ab value
return(ab);
}
/*****************************************************************************
* Function    : SendData
* Description : Send  a data serially
******************************************************************************/
void SendData(char sdata)
{
TXREG=sdata;
while(TRMT!=1);
}
/*****************************************************************************
* Function    : MSdelay
* Description : Generate 1ms delay
******************************************************************************/
 void MSdelay(unsigned int val)
  {
	unsigned int del,del1;
	for(del=1;del<=val;del++)
		{
		for(del1=0;del1<=331;del1++);
		}	
   }

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/********************************************************************************

* Microcontroller -- PIC 16 F877 - 40-pin - 8-bit *

* Clock Frequency is 20 MHz -- Period in 200 Nano Seconds *

* USART - BaudRate 9600 *

* This program is used to read gas sensor value

*********************************************************************************/

#include<pic.h>

#include"delay.c"

int LPG_Value=0;

void ADC_init() ;

void send(char);

int adc_conv(int);

void SerialPortInit() ;

void SendData(char);

void display(int value );

void MSdelay(unsigned int);

static void Send2USART(const char *CPtr1);

void main()

{

TRISC=0X80;

TRISA=0XFF;

SerialPortInit() ;

ADC_init();

while(1)

{

Send2USART("LPG Value:"); // send LPG value

LPG_Value=adc_conv(1); // select channel 1 for LPG reading

display(LPG_Value ); // convert LPG value for display

SendData('\n'); // new line

SendData('\r'); // carriage return

}

/*****************************************************************************

* Function : Send2USART

* Description : Group of data send serially

******************************************************************************/

static void Send2USART(const char *Cptr1)

{

while(*Cptr1 != '\0')

{

SendData(*Cptr1);

Cptr1++;

}

/*****************************************************************************

* Function : display

* Description : Display adc value function

******************************************************************************/

void display(int value )

{

char k=1;

char array[4];

for(k=1;k<=4;k++)

{

array[k]=value%10;

value=value/10;

}

for(k=4;k>=1;k--)

{

SendData(array[k]+'0');

}

/*****************************************************************************

* Function : SerialPortInit

* Description : Usart Initialization function - Baud Rate 9600

******************************************************************************/

void SerialPortInit()

{

GIE=1;

SYNC=0;

TXEN=1;

BRGH=1;

SPEN=1;

CREN=1;

PEIE=1;

RCIE=1;

SPBRG=129;

}

/*****************************************************************************

* Function : ADC_init

* Description : Adc Initialization function

******************************************************************************/

void ADC_init()

{

ADFM=1;

PCFG3=0;

PCFG2=0;

PCFG1=0;

PCFG0=0;

}

/*****************************************************************************

* Function : adc_conv

* Description : Adc Conversion function

******************************************************************************/

int adc_conv(int channel)

{

int ab;

ADCON0=0x81|channel<<3; //channel selection

DelayMs(1);

ADGO=1; //start AD conversion

while(ADGO!=0); //waiting for competion of AD conversion

ab=ADRESH; //assign 2bit value ADRSH register to variable ab

ab=ADRESH<<8; //8 times shift variable ab value

ab=ab|ADRESL; //combine ADRESL & ab value

return(ab);

}

/*****************************************************************************

* Function : SendData

* Description : Send a data serially

******************************************************************************/

void SendData(char sdata)

{

TXREG=sdata;

while(TRMT!=1);

}

/*****************************************************************************

* Function : MSdelay

* Description : Generate 1ms delay

******************************************************************************/

void MSdelay(unsigned int val)

{

unsigned int del,del1;

for(del=1;del<=val;del++)

{

for(del1=0;del1<=331;del1++);

}

Upload the example code in PIC and connect LPG sensor module with PIC 16F877A . Then open serial monitor, LPG sensor will give values as shown below. When LPG sensor module detects gas, the value will change.

2. Gas leakage alarm

LPG gas is heavier than air, when it leaks from a cylinder the gas will settle down near the floor. This can cause fire or suffocation if not dealt with.The circuit that detects the leakage of LPG gas and alerts the user through buzzer indication is as shown below.

A high on OUT pin of gas sensor module indicates LPG presence. A preset in the module is used to set the threshold value of tolerance.The gas sensor module output goes high when the gas level reaches or exceeds certain point. This will turn on the transistor and activates the buzzer.

Resources:

LPG Gas Sensor – MQ-6 Datasheet

How to Buy:

Click here to buy RhydoLABZ’s LPG Gas Sensor Module -V2

Support:

Please share your ideas with us, visit our forum for discussion

Frequently Asked Questions(FAQ):

Q.Is a warm-up time needed before using the gas sensor?

Ans:Yes. The sensor needs some time in order to reach its chemical equilibrium.

Q.In what range of concentration can gas sensor MQ-6 measure the gas?

Ans:The MQ-6 can detect gas concentrations anywhere from 200 to 10000ppm.

Q.What is “gas sensitivity”?

Ans:It is (Rs in clean air)/(Rs in gas), where Rs means Sensor Resistance. Since Rs generally decreases in gas, the gas sensitivity is below 1.

Q.What is “gas response”?

Ans:It is the time for the sensor to respond after the gas reaches the sensor.

Q.What are the applications of LPG Gas Sensor – MQ-6?

Ans:They are used in gas leakage detecting equipments in family and industry, are suitable for detecting of LPG, iso-butane, propane, LNG, avoid the noise of alcohol and cooking fumes and cigarette smoke.

Luke says:

August 30, 2014 at 2:18 pm

would like to ask for the file of #include”delay.c” could you post up or teach me how to do it? I am using MQ-2 sensor.

Harikrishnan says:

November 27, 2015 at 10:29 am

That header includes predefined delay functions.
You can even create one for yourself with the help of a simulator or with good knowledge of program flow.

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nisar says:

May 18, 2016 at 5:20 pm

Can we replace MQ6 by MQ2 in this circuit? and what will be the need to do that?

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1. Hari Krishnan says:
  
  May 23, 2016 at 11:34 am
  
  Though we haven’t tried the MQ2 on these boards, the MQ2 should work fine on this.
  After all, the basic circuit connections for MQ series of sensors are almost same.
  The loop voltage and the heater voltage for both of these sensors are same (5V), so there is no harm with the voltage ratings.
  
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Munavir says:

July 30, 2015 at 9:33 am

Sir, how we can show the gas leakage during our demonstration

Harikrishnan says:

September 29, 2015 at 7:37 am

Try using a cigarette lighter.

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Rajesh says:

February 16, 2016 at 4:11 pm

sir can you provide circuit diagram of this sensor module.

Hari Krishnan says:

April 22, 2016 at 5:00 pm

We will check if the circuit belongs to our open-source category.
If yes, we will definitely let you know.

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ABINAYA says:

February 20, 2016 at 3:46 am

SIR,PLEASE GIVE ME CODE FOR MQ6 USING PIC16F887 HENCE MY CODE HAS SOME ERRORS.

Reenu Singh says:

March 24, 2016 at 8:05 am

I want to display different values of gases ,like LPG,iso-butane,propane etc. separately
how can i do that ??
can any one help?

Phong says:

May 11, 2016 at 11:47 am

Sir, how we can show the relationship between the value A0 (sensor module) and the gas concentration

alex says:

August 18, 2016 at 2:57 am

can u please help me how to create delay header , please

Hari Krishnan says:

August 19, 2016 at 11:21 am

Sorry for the mishap. The code will be updated shortly & you can use function MSdelay(1); instead of DelayMs(1);. This eliminates the need of any header file.

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