What is a breathalyzer you may ask? It is a device for estimating blood alcohol content (BAC) from a breath sample.In simple terms it is a device to test weather a person is drunk or not. As the title suggests it runs on the arduino.Our breathalyzer uses the MQ-3 alcohol sensor from sparkfun.It is a simple and fun to do project.
This instructable explains how to create your own breathalyzer , making a shield for the arduino , putting the breathalyzer in a box, and making some changes to your breathalyzer.
This Breathalyzer is not meant to be used as a means of breathalyzing. The MQ-3 is not accurate enough to register exact BAC and is sensitive to temperature and humidity.Never drink and drive and if you do call me =D .
Step 1: Parts & Tools
~ Arduino Uno - Sparkfun.com
~ MQ-3 Alcohol Sensor - Sparkfun.com
~ 100k Ohm Potentiometer - Sparkfun.com
~ 330 Ohm Resistor - Sparkfun.com
~ 5 x Green LED's - Sparkfun.com
~ 3 x Yellow LED's - Sparkfun.conm
~ 2 x Red LED's - Sparkfun.com
~ 7805 Voltage Regulator - Local Electronics Store
~ 1000 uf Capacitor - Local Electronics Store
~ 2 x 9v Batteries - Local Electronics Store
~ Soldering Iron - Sparkfun.com
~ Solder Wire - Sparkfun.com
~ Jumper Wires -Sparkfun.com
~ Protoboard - Sparkfun.com
~ Project Box - Local Electronics Store
~ Inhaler Tube - I Found It In My House
Step 2: The Chemistry
When the user exhales into a breath analyzer, any ethanol present in their breath is oxidized to acetic acid at the anode:
CH3CH2OH(g) + H2O(l) → CH3CO2H(l) + 4H+(aq) + 4e-
At the cathode, atmospheric oxygen is reduced:
O2(g) + 4H+(aq) + 4e- → 2H2O(l)
The overall reaction is the oxidation of ethanol to acetic acid and water.
CH3CH2OH(l) + O2(g) → CH3COOH(l) + H2O(l)
The electrical current produced by this reaction is measured by a microprocessor, and displayed as an approximation of overall blood alcohol content (BAC) by the Alcosensor.