Seeed Grove User manual

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Grove - Gas Sensor(MQ9)
Version：1.0
Release date：9/20/2015
Wiki: http://www.seeedstudio.com/wiki/Grove_-_Gas_Sensor(MQ9)
Bazaar: http://www.seeedstudio.com/depot/Grove-Gas-SensorMQ9-p-1419.html

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Document Revision History
Revision
Date
Author
Description
1.0
Sep 21, 2015
Victor.He
Create file

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Contents
Document Revision History··································································································· 2
1. Introduction ···················································································································2
2. Features··························································································································3
3. Application Ideas············································································································4
4. Mechanic Dimensions···································································································· 5
5. Usage······························································································································6
5.1 Suggest Reading for Starter······························································································· 6
5.2 Hardware Installation········································································································ 6
5.3 How to use ························································································································ 7
6. Support·························································································································10
7. Version Tracker·············································································································11
8. Resources ·····················································································································12
9. Licensing·······················································································································13

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Disclaimer
For physical injuries and possessions loss caused by those reasons which are not related to product quality,
such as operating without following manual guide, natural disasters or force majeure, we take no
responsibility for that.
Under the supervision of Seeed Technology Inc., this manual has been compiled and published which
covered the latest product description and specification. The content of this manual is subject to change
without notice.
Copyright
The design of this product (including software) and its accessories is under tutelage of laws. Any action to
violate relevant right of our product will be penalized through law. Please consciously observe relevant local
laws in the use of this product.

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1. Introduction
The Grove - Gas Sensor (MQ9) module is useful for gas leakage detecting (in home and industry).
It can detect LPG, CO, and CH4. Based on its fast response time. Measurements can be taken as
soon as possible. Also the sensitivity can be adjusted by the potentiometer.

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2. Features
Wide detecting scope
Stable and long life
Fast response and High sensitivity

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3. Application Ideas
Gas leakage detecting
Toys

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4. Mechanic Dimensions
Electronic Characteristics
Items
Parameter name
Min
Type
Max
Unit
System Characteristics
VCC
Working Voltage
4.9
5
5.1
V
PH
Heating
consumption
0.5
-
340
mW
RL
Load resistance
can adjust
RH
Heater resistance
-
33Ω±5%
-
Ω
Rs
Sensing Resistance
2
-
20000
Ω
CO/CH4/LPG Scope
Detecting
concentration
200
-
1000/10000/10000
ppm

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5. Usage
5.1 Suggest Reading for Starter
Download Arduino and install Arduino driver
Getting Started with Seeeduino
How to choose a Gas Sensor
What's LEL
5.2 Hardware Installation
Grove products have an ecosystem and all have a same connector which can plug onto the Base
Shield. Connect this module to the A0 port of Base Shield, however, you can also connect Gas
sensor to Arduino without Base Shield by jumper wires.
Arduino UNO
Gas Sensor
5V
VCC
GND
GND
NC
NC
Analog A0
SIG
You can gain the present voltage through the SIG pin of sensor. The higher the concentration of
the gas, the bigger the output voltage of the SIG pin. Sensitivity can be regulated by rotating the
potentiometer. Please note the best preheat time of the sensor is above 24 hours. For the detailed
information about the MQ-9 sensor please refer to the datasheet.

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5.3 How to use
There're two steps you need to do before getting the concentration of gas.
First, connect the module with Grove Shield using A0 like the picture above. And put the sensor in
a clear air and use the program below.
void setup() {
Serial.begin(9600);
}
void loop() {
float sensor_volt;
float RS_air;// Get the value of RS via in a clear air
float R0;// Get the value of R0 via in LPG
float sensorValue;
/*--- Get a average data by testing 100 times ---*/
for(int x =0;x <100 ;x++)
{
sensorValue =sensorValue +analogRead(A0);
}
sensorValue =sensorValue/100.0;
/*-----------------------------------------------*/
sensor_volt =sensorValue/1024*5.0;
RS_air =(5.0-sensor_volt)/sensor_volt;// omit *RL
R0 =RS_air/9.9;// The ratio of RS/R0 is 9.9 in LPG gas
Serial.print("sensor_volt = ");
Serial.print(sensor_volt);
Serial.println("V");
Serial.print("R0 = ");
Serial.println(R0);
delay(1000);
}
Then, open the monitor of Arduino IDE, you can see some data are printed, write down the value
of R0 and you need to use it in the following program. During this step, you may pay a while time
to test the value of R0.
Second, put the sensor in one gas where the environment you want to test in. However, don't forget

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to replace the R0 below with value of R0 tested above
void setup() {
Serial.begin(9600);
}
void loop() {
float sensor_volt;
float RS_gas;// Get value of RS in a GAS
float ratio;// Get ratio RS_GAS/RS_air
int sensorValue =analogRead(A0);
sensor_volt=(float)sensorValue/1024*5.0;
RS_gas =(5.0-sensor_volt)/sensor_volt;// omit *RL
/*-Replace the name "R0" with the value of R0 in the demo of First
Test -*/
ratio =RS_gas/R0;// ratio = RS/R0
/*-------------------------------------------------------------------
----*/
Serial.print("sensor_volt = ");
Serial.println(sensor_volt);
Serial.print("RS_ratio = ");
Serial.println(RS_gas);
Serial.print("Rs/R0 = ");
Serial.println(ratio);
Serial.print("\n\n");
delay(1000);
}
Now, we can get the concentration of gas from the below figure

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According to the figure, we can see that the minimum concentration we can test is 200ppm and
the maximum is 10000ppm, in a other word, we can get a concentration of gas between 0.02%
and 1%. However, we can't provide a formula because the relation between ratio and concentration
is nonlinear.

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6. Support
Ask questions on Seeed forum.

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7. Version Tracker
Revision
Descriptions
Release
v0.9b
Initial public release
16,Aug,2011
v1.4
Replace some components
27,Aug,2014

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8. Resources
File:Gas Sensor Eagle files.zip
File:Gas Sensor Schematic.pdf
File:MQ-9.pdf

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9. Licensing
This documentation is licensed under the Creative Commons Attribution-ShareAlike License
3.0 Source code and libraries are licensed under GPL/LGPL, see source code files for details.