Few day ago, I got an email from one of reader of bestengineeringprojects.com asking about how does the traffic police know the concentration of alcohol present in our breadth. For that purpose, I had designed a project called DIY Breathalyzer using various easily available electronics components. Before starting about description of project I would like to describe what breathalyzer is.
The breathalyzer or breathalyzer is an electronic device which is used to estimate the concentration of alcohol available in breath sample. This device is usually carried by traffic police, medical person etc. in order to check the blood alcohol content for either legal or medical purpose.
Circuit Description of DIY Breathalyzer using Arduino and MQ-3 Sensor Module
The circuit of DIY breathalyzer is shown in figure 1. It is designed using arduino uno board, MQ-3 sensor (alcohol sensor), few LEDs (indication of concentration of alcohol) and few other electronic components for working flawlessly. The working is quite straightforward, any one with little knowledge in arduino can understand easily.
MQ-3 is an alcohol sensor shown in figure 2, is used to estimate the concentration of alcohol present in breadth. The sensor is designed to detect alcohol thus it is very sensitivity and fast response to alcohol. This sensor can also detect benzine but its sensitivity to benzene is very small. MQ-3 has 6 pins where two are of heater and 4 pins for signal. The heater provides necessary work condition.
The AD0 pin of MQ-3 sensor module is connected to one of the analog pin (A0) from which we are going to read the information of alcohol. For sensitivity of sensor is adjusted using variable resistor attached to the board of MQ-3 sensor module.
The 10 LEDs is connected to the digital output of arduino (pin D0 through D9) through current limiting resistor which is connected in series as shown in circuit diagram (figure 1).
Software code: The software of DIY Breathalyzer using Arduino and MQ-3 Sensor Module is written in arduino programming language and compiled using arduino IDE. You can directly download the code and use it without any modification.
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//DIY Breathalyzer using Arduino and MQ-3 Sensor Module const int analogPin = 0; // pin that read the output of MQ-3 sensor const int totalLed = 10; // total number of leds use to see concentration int ledPins[] = {11,10,9,8,7,6,5,4,3,2};// pin assigned for LEDs void setup() { for (int currentLed = 0; currentLed < totalLed; currentLed++) { pinMode(ledPins[currentLed], OUTPUT);//make ledPins for output }} void loop() { int sensorReading = analogRead(analogPin);//read the value of sensor at analog pin A0 int ledLevel = map(sensorReading, 500, 1023, 0, totalLed); for (int currentLed = 0; currentLed < totalLed; currentLed++) { if (currentLed < ledLevel) { digitalWrite(ledPins[currentLed], HIGH); } else { digitalWrite(ledPins[currentLed], LOW); } } } |
Figure 3: Author Prototype for DIY Breathalyzer using Arduino and MQ-3 Sensor Module
PARTS LIST OF DIY BREATHALYZER USING ARDUINO AND MQ-3 SENSOR MODULE
| Resistors (all ¼-watt, ± 5% Carbon) |
| R1 – R10 = 270 Ω |
| Semiconductors |
| Arduino Uno Board
MQ-3 Sensor Module |
| Miscellaneous |
| LED1 – LED5 = 5mm Green color LED
LED6 – LED8 = 5mm Yellow color LED LED9, Led10 = 5mm Red color LED Connector as per required |