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Alcohol Measurement with the MQ-3 Sensor

A project that measures alcohol vapour in the air with an MQ-3 gas sensor and writes the analog value and the threshold state to the Serial Monitor every half second. The analog value (0-1023) rises as the alcohol concentration goes up; the Limit value shows whether the threshold set with the trimmer on the board has been crossed. No extra library needed. The sensor's heater gets warm while it runs; on first use, leave the sensor powered for a while (ideally 24 hours), and let it warm up for a few minutes before measuring. The code uses 115200 baud, so pick 115200 in the Serial Monitor too.

What you need

• 1 × Arduino Uno R3
• 1 × MQ-3 Alcohol Gas Sensor
• 4 × Jumper Wire - Male/Female

Wiring steps

1. 1

   Power the sensor

   

   Plug a red jumper wire into the 5V pin on the Arduino's POWER header. Connect its other end to the top pin, pin 1 (VCC), in the MQ-3 module's pin row. The sensor's heater runs on 5V.

2. 2

   Ground (GND) connection

   

   Plug a black jumper wire into the GND pin on the Arduino's POWER header. Connect its other end to the module's pin 2 (GND).

3. 3

   Connect the digital output (DOUT)

   

   Plug a green jumper wire into the Arduino's digital pin 8. Connect its other end to the module's pin 3 (DOUT). When the alcohol level crosses the threshold set with the trimmer on the board, this pin goes LOW and the Serial Monitor shows Limit: 0 (DOUTpin = 8).

4. 4

   Connect the analog output (AOUT)

   

   Plug a blue jumper wire into pin A0 on the Arduino's ANALOG IN header. Connect its other end to the module's bottom pin, pin 4 (AOUT). The code reads the alcohol concentration on this pin as a value from 0 to 1023 (AOUTpin = A0).

Arduino sketch

const int AOUTpin = A0; // 0 yerine A0 kullanıldı
const int DOUTpin = 8; 
int limit; 
int value; 

void setup() {
  Serial.begin(115200); 
  pinMode(DOUTpin, INPUT);
} 

void loop() {
  value = analogRead(AOUTpin);
  limit = digitalRead(DOUTpin);
  
  Serial.print("Alcohol value: ");
  Serial.print(value);
  Serial.print("  |  Limit: ");
  Serial.println(limit); // println ile satır burada bitirildi
  
  delay(500);
}

What the Serial Monitor shows

Alcohol value: 250  |  Limit: 1
Alcohol value: 253  |  Limit: 1
Alcohol value: 248  |  Limit: 0