Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor

Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor (Last Updated On: December 1, 2018)


In this project we have designed Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor for measuring the level of alcohol in human breathe. Simply we have interfaced MQ-135 Gas Sensor module with Arduino and 16*2 LCD module for display. The alcohol/Gas sensor we used is the MQ-135 sensor. This is a sensor that is not only sensitive to alcohol, particularly ethanol, which is the type of alcohol which is found in wine, beer, and liquor. Instead of MQ-135, you can use MQ2, MQ3, MQ5 module as well. Basically they all have similar functions.

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. The range ranges from 0.01 to 0.10. Most countries have a limit of about 0.05. For example, Greece, Greenalnd, and Iceland all have limits of 0.05. Canada has a higher limit set at 0.08. For our circuit, it can function as an alcometer so that we get an estimate of a person’s blood alcohol level.

Components Required

For designing Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor we need the following components:

1. Arduino UNO Board
2. 16*2 LCD
3. MQ-135 Sensor Module  (You can use MQ2/MQ3/MQ5 as well) - (Buy Online from Amazon)
4. LED
4. Breadboard
5. Connecting Jumper Wires

Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor

Now after managing this components do this following connections for designing Digital Tachometer using IR Sensor with Arduino for measuring RPM

LCD Pins 1, 3 ,5 ,16 ——— GND
LCD Pins 2, 16 ————— VCC (+5V)
LCD Pin 4 ——————– Arduino pin D7
LCD Pin 6 ——————– Arduino pin D6
LCD Pin 11 ——————- Arduino pin D5
LCD Pin 12 ——————- Arduino pin D4
LCD Pin 13 ——————- Arduino pin D3
LCD Pin 14 ——————- Arduino pin D2
MQ-135 Module Pin -GND —— GND
MQ-135 Module Pin +VCC —— VCC
MQ-135 Module Pin A0 — Arduino Pin A0
LED Pin +ve end ————- Arduino PinD10
LED Pin -ve end ————-GND

A connection diagram is given below as well. Simply assemble the circuit as this.

Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor

MQ-135 Gas/Alcohol Sensor Module


Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor
MQ-135 Module sensor has lower conductivity in clean air. When the target combustible gas exist, the sensors conductivity is more higher along with the gas concentration rising. Convert change of conductivity to correspond output signal of gas concentration. MQ135 gas sensor has high sensitivity to Ammonia, Sulphide and Benzene steam, also sensitive to smoke and other harmful gases. It is with low cost and suitable for different applications such as harmful gases/smoke detection.


1. Wide detecting scope
2. Fast response and High sensitivity
3. Stable and long life Simple drive circuit
4. Used in air quality control equipment for buildings/offices, is suitable for detecting of NH3, NOx, alcohol, Benzene, smoke, CO2, etc.
5. Size: 35mm x 22mm x 23mm (length x width x height)
6. Working voltage: DC 5 V
7. Signal output instruction.
8. Dual signal output (analog output, and high/low digital output)
9. ~ 4.2V analog output voltage, the higher the concentration the higher the voltage.

Working Mechanism

The MQ-135 alcohol sensor consists of a tin dioxide (SnO2), a perspective layer inside aluminium oxide micro tubes (measuring electrodes) and a heating element inside a tubular casing. The end face of the sensor is enclosed by a stainless steel net and the back side holds the connection terminals. Ethyl alcohol present in the breath is oxidized into acetic acid passing through the heat element. With the ethyl alcohol cascade on the tin dioxide sensing layer, the resistance decreases. By using the external load resistance the resistance variation is converted into a suitable voltage variation.

Arduino Source Code

So here is a source code for designing Alcohol Level Meter using Arduino & MQ-135 Alcohol/Gas Sensor. Simply copy the code and upload it to your Arduino Board using Arduino IDE.

#include <LiquidCrystal.h>
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

int ledPin = 10;
int sensorPin = A0;
int value;

void setup()
void loop() 
int Value = analogRead(sensorPin);
value = analogRead(A0);
lcd.print("Alcohol Lev.:");
if (value-50 > 400) 

     lcd.setCursor(0, 2);
    Serial.print ("Alert");   
  else {
      lcd.setCursor(0, 2);


Video Preview & Explanation

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