DIY Portable Breathalyzer


Introduction: DIY Portable Breathalyzer


This is an instruction, how I built a DIY portable breathalyzer. I designed an enclosure for this project.

Features of the device:

- measures the actual ethanol concentration level

- shows the level of actual gas concentration in 8 channel LED display

How to use video:


Arduino and Fritzing source code:

How to use

· turn on the device with the switch

· wait as long as only 2 LEDs are on (the heating in the sensor should warm up)

· the measured value is shown continuously

· blow into the sensor for at least 3 seconds

· wait and read the value

Step 1: BOM List

The components from Aliexpress. BOM


Material Name amount unit price USD total price USD link

Single Slot 18650 Battery Holder 1 pc 0,28 $/pc 0,28 $/total row

MQ-3 Alcohol Gas Sensor 1 pc 1,18 $/pc 1,18 $/total row

LED-s DIY module 1 pc 0,62 $/pc 0,62 $/total row

Arduino MiniPro Microcontroller Module 1 pc 1,68 $/pc 1,68 $/total row

3 Position Mini Slide Switch 1 pc 0,05 $/pc 0,05 $/total row

Rechargeable battery 18650 Li-ion 2600mAh 1 pc 2,47 $/pc 2,47 $/total row

Micro USB 5V 1A 18650 TP4056 Lithium Battery Charger Module 1 pc 1,30 $/pc 1,30 $/total row

DIY Prototype PCB 1 pc 0,14 $/pc 0,14 $/total row

DC-DC Mini Step Up Power Module 1-5V To 5V 1 pc 0,05 $/pc 0,05 $/total row

Cable 1 pc 0,02 $/pc 0,02 $/total row

Total material cost of the project: 7,79 $/total project


The following tools are needed:

Soldering station 1 pc 67,8 $/pc 67,80 $/total row

Diagonal Cutters 1 pc 7,78 $/pc 7,78 $/total row

Third Hand 1 pc 14,7 $/pc 14,70 $/total row

Wire Strippers 1 pc 9,11 $/pc 9,11 $/total row

Solder 1 pc 3,69 $/pc 3,69 $/total row

Forceps 1 pc 1,89 $/pc 1,89 $/total row

Screwdriver 1 pc 4,39 $/pc 4,39 $/total row

Arduino mini pro programmer 1 pc 7 $/pc 7,00 $/total row

Total tools cost of the project: 116,36 $/total project

Step 2: ​Assembly

Take all component and connect them according to the schematic. Use a DIY Prototype PCB and solder everything, use wires to connect PIN-s. The LEDs module should be soldered to the back of the Arduino board to save space.

To check it is working, use any alcohol and put the opening of the glass next to the sensor, it should turn on all LEDs.

Step 3: Software / Housing


Connect the Arduino board to a PC. Use Arduino IDE to compile an upload the program to the Arduino. The code is full of comments.

Arduino and Fritzing source code:


Create a housing to protect electronics to be damaged by touching. The housing can be a 3D printed or small plastic boxes.


Or you can crochet a housing, use this instruction:



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    2 Discussions

    Unfortunately, I didn't have any etalon gas, so I simply placed some cotton wool immersed in alcohol (70% from a pharmacy) before the sensor. The maximum readout was 600 digits. Dividing this by 8 gives the range for 1 LED (75 digits).