Seeed Grove User manual
2
Document Revision History
Revision
Date
Author
Description
1.0
Sep 22, 2015
Loovee
Create file
3
Contents
Document Revision History ········································································· 2
1. Introduction ······················································································· 2
2. Features···························································································· 3
3. Usage ······························································································ 4
3.1 Hardware Installation ·············································································· 4
3.2 Download Code and Upload ······································································ 4
3.3 Notification ·························································································· 7
3.4 Cautions ······························································································ 7
4. Resources ······················································································· 8
1
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
Grove - Alcohol Sensor is a complete alcohol sensor module for Arduino or Seeeduino. It is built
with MQ303A semiconductor alcohol sensor. It has good sensitivity and fast response to alcohol.
It is suitable for making Breathalyzer. This Grove implements all the necessary circuitry for
MQ303A like power conditioning and heater power supply. This sensor outputs a voltage inversely
proportional to the alcohol concentration in air.
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2. Features
Input Voltage: 5V
Working Current: 120mA
Detectable Concentration: 20-1000ppm
Grove Compatible connector
Highly sensitive to alcohol.
Fast response and resumes quickly after alcohol exposure.
Long life.
Compact form factor.
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3. Usage
3.1 Hardware Installation
Grove products have an eco system 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
Alcohol Sensor
5V
VCC
GND
GND
Analog A1
SCL
Analog A0
DAT
You can gain the present voltage through the DAT pin of sensor. Sensitivity can be regulated by
rotating the potentiometer. Please note the best preheat time of the sensor is above 48 hours. For
the detailed information about the Alcohol sensor please refer to the datasheet.
3.2 Download Code and Upload
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.
#define heaterSelPin 15
void setup() {
Serial.begin(9600);
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pinMode(heaterSelPin,OUTPUT); // set the heaterSelPin as digital output.
digitalWrite(heaterSelPin,LOW); // Start to heat the sensor
}
void loop() {
float sensor_volt;
float RS_air; // Get the value of RS via in a clear air
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 = sensor_volt/(5.0-sensor_volt); // omit *R16
Serial.print("sensor_volt = ");
Serial.print(sensor_volt);
Serial.println("V");
Serial.print("RS_air = ");
Serial.println(RS_air);
delay(1000);
}
Then, open the monitor of Arduino IDE, you can see some data are printed, write down the value
of RS_air and you need to use it in the following program. During this step, you may pay a while
time to test the value of RS_air.
#define heaterSelPin 15
void setup() {
Serial.begin(9600);
pinMode(heaterSelPin,OUTPUT); // set the heaterSelPin as digital output.
digitalWrite(heaterSelPin,LOW); // Start to heat the sensor
}
void loop() {
float sensor_volt;
float RS_gas; // Get value of RS in a GAS
float ratio; // Get ratio RS_GAS/RS_air
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int sensorValue = analogRead(A0);
sensor_volt=(float)sensorValue/1024*5.0;
RS_gas = sensor_volt/5.0-sensor_volt; // omit *R16
/*-Replace the name "R0" with the value of R0 in the demo of First Test -*/
ratio = RS_gas/RS_air; // 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 20ppm and the
maximum is 10000ppm, in an other word, we can get a concentration of gas between 0.002% and
1%. However, we can't provide a formula because the relation between ratio and concentration is
nonlinear.
3.3 Notification
The value varies between 500 - 905. Hence any value above 650 indicates alcohol vapor in the
vicinity.
Once exposed to alcohol vapor, it takes some time for the sensor value to decrease completely.
Yet, any new exposure will show instant increase in sensor value.
3.4 Cautions
Alcohol sensor is very sensitive semiconductor device. Handle with care.
Do not expose to organic silicon steam, alkali or corrosive gases.
Do not use freeze or spill water.
Maintain proper working voltage.
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