Step 5: Build The Circuit

The Circuit is pretty straight forward.To connect the sensor, you have to connect one of the H pin to +5V Supply (use a external power supply) and the other one to Ground.Pin B (any of them) you connect to Ground.And pin A to arduino analog pin0 via 100k ohm potentiometer.To make the LEDs work, I have connected them in sequence using the Digital Pins 2 till 11 (ten LEDs total). Remember to use a resistor between 220Ω and 470Ω for each LED.I soldered the LEDs on a small protoboard and connected one wire to each LED which connected the LEDs to the arduino.To Power the arduino we are going to use a 9v battery and I also soldered a switch so that the breathalyzer can be switched on or off.I used a common switch for the 5v power supply and the arduino power supply.See the Last Image For The Circuit Diagram.