Introduction: The Electronic Nose (TfCd Project)

Your own build electronic Nose, this electronic nose warns you against a dirty fart environment or even worse, gas leaks!

Suffering with anosmia or born with a weak sense of smell? This represents a serious threat to the health of people and has a big influence on their social lives. Following this easy to build instructable these people will be a step closer to a safer en more comfortable life! The LED will blink when there is a gas leak or people in your environment fart.

Step 1: Components

  • Battery: 9 Volt
  • Arduino (in this example Duemilanovo)
  • Resistor 330 Ohm
  • Red LED Gassensor MQ5 (LPG, Natural gas or town gas)
  • Breadboard
  • Wires
  • Tools for soldering
  • Wearable (in this example: glasses)
  • Lighter (to test with)
  • Tape

Step 2: The Circuit

The first step is to make the circuit working. Therefore we use a breadboard so you can easily test your components and switch wires. On the Gassensor are four marks, connect the GND with the ground of the breadboard, the VCC with the 5V and the SIG with the Analog Pin 0. (NC=No Connection). To connect the red LED you need also a resistor. Connect the Led with the ground and Digital pin 13. Connect your Arduino to your computer to test the circuit and load the code.

Step 3: Program the Arduino

When the Gassensor detects gas the LED has to blink. Using an Arduino code you can make this principle work. If you want to read out the measurements of the gassensor you have to look into ‘Seriele monitor’ in Arduino. By changing the limit value, the LED will react different. In our situation the gas sensor measured in normal conditions around 250-350. When we apply a little gas the value jumped up. So we choose the limit to put on 400.

See here the code:

const int AOUTpin=0;//the AOUT pin of the MQ5 sensor goes into analog pin A0 of the arduino

const int DOUTpin=8;//the DOUT pin of the methane sensor goes into digital pin D8 of the arduino

const int ledPin=13;//the anode of the LED connects to digital pin D13 of the arduino

const int limit = 400;;// You can change this value to make the device more sensitive

int value;

void setup() {

Serial.begin(115200);//sets the baud rate

pinMode(DOUTpin, INPUT);//sets the pin as an input to the arduino

pinMode(ledPin, OUTPUT);//sets the pin as an output of the arduino


void loop()


value= analogRead(AOUTpin);//reads the analaog value from the methane sensor's AOUT pin

//limit= digitalRead(DOUTpin);//reads the digital value from the methane sensor's DOUT pin

Serial.print("Methane value: ");

Serial.println(value);//prints the methane value

Serial.print("Limit: ");

Serial.print(limit);//prints the limit reached as either LOW or HIGH (above or underneath)


if (value >= limit){

digitalWrite(ledPin, HIGH);//if limit has been reached, LED turns on as status indicator



digitalWrite(ledPin, LOW);//if threshold not reached, LED remains off



Step 4: Testing

First test the whole circuit on the breadboard and when it is working you can solder the circuit. A video of the test can be found above.

Step 5: Make It Wearable

When the test circuit is working properly, you can cut the wires to the appropriate length and solder the circuit. In our situation the person who needs this device wears glasses, so we apply the sensor and the LED to the glasses. You can wear the Arduino and battery around your neck or put in you backpack.

Step 6: Elaborate This Technology

Working principle
Electronic noses have undergone much development and are now used to fulfil industrial needs but for private use there is almost payable nothing on the market. There are a lot of people suffering with anosmia or just have a weak sense of smell. For these people a simple instructable like this could already be very helpful and save them from dangerous situations are uncomfortable social situations. This device now only reacts on LPG, Natural gas or town gas but when it also reacts on rotten food or bad breathe it can be used in a wider range.

Add other sensors
Another sensor, for example, can detect gasses emitted by spoiled food. The sensor consists of chemically modified carbon nanotubes, the same principle as a lot of other gas sensors.

Internet of things
At this moment the device is a wearable but of course the output signal can also be read on your smartphone. So only the sensors have to be close to your nose. Just add a wifi transmitter and the signals that the sensors detect can be send to your smartphone. There will not a led be blinking but your phone will give the alarm.