Here we will use MQ-3 sensor. This sensor sensitive to alcohol, particularly ethanol, which is the type of alcohol which is found in wine, beer, and liquor.
This type of sensor circuit can be used as a breathalyzer to check a person’s blood alcohol level. Just as we exhale carbon dioxide when we breathe out, we also will breathe out some alcohol if we have alcohol in our blood. Any alcometer device can measure this alcohol content.
The more ethanol in your blood, the more there is in the air on exhalation. This alcohol content gives a good indication for if a person is drunk and how drunk they are.
The amount of alcohol exhaled into the air is proportional to the amount of alcohol which will be found in a person’s blood. Alcometers use a built-in formula to estimate blood alcohol content from exhaled air alcohol content.
For different countries, the level of alcohol in the blood that defines a person as over the limit for driving varies.In this circuit, it can function as an alcometer so that we get an estimate of a person’s blood alcohol level.
Disclaimer:Mouthwash, such as Listerine, contains alcohol. If you gargle mouthwash for a few seconds and then breathe into the sensor, the readings should jump and register. This is all that’s needed to test.You don’t have to drink alcohol in order to test this sensor.
- MQ-3 alcohol sensor
If you buy the complete board, there are 4 leads which need to be connect.
MQ-3 Alcohol Sensor Circuit Schematic:
void setup( )
void loop( )
value= analogRead(AOUTpin);//reads the analaog value from the alcohol sensor’s AOUT pin
limit= digitalRead(DOUTpin);//reads the digital value from the alcohol sensor’s DOUT pin
Serial.print(“Alcohol value: “);
Serial.println(value);//prints the alcohol value
Serial.print(limit);//prints the limit reached as either LOW or HIGH (above or underneath)
if (limit == HIGH)
digitalWrite(ledPin, HIGH);//if limit has been reached, LED turns on as status indicator
digitalWrite(ledPin, LOW);//if threshold not reached, LED remains off