Picture of Breathalyzer Microphone
The breathalyzer microphone is a system for the inconscpicuous collection of blood-alcohol content level data sets. In other words, you can measure a person's sobriety with a device, that for all intents and purposes, looks no different than a standard microphone. This tool adds new dimensions of truthiness to any standard interview. It can also easily be adapted for karaoke.

Don't be intimated by the number of steps. It's one of the least complicated projects I've ever made.

This project was initially developed with the love and support of the Eyebeam OpenLab.

Step 1: Go get stuff

Picture of Go get stuff
You will need:
- A MQ-3 Alcohol Sensor (available via Futurlec. Allow a few weeks for shipping from Thailand. Be warned! Ordering anything else from Futurlec may place your order on backorder and leave you waiting a long, long, time without being notified).
- An XLR microphone (you can pick up cheap dynamic XLR microphones intended for karaoke all over the internet)
- An Arduino Decimilla
- Logomatic Data Logger (via Sparkfun)
- An SD Card (can get a cheap 256MB card at Radioshack)
- An SD Card reader
- XLR to 1/4" stereo plug
- A professional-looking audio device (working or not)
- resistors (100K, 10K, 1K)
- a schottky diode
- Acrylic or cardboard
- glue
- solid hookup wire
- 9V battery plug
- 9V battery
- isopropyl rubbing alcohol
- a 12 pack and some friends

(other stuff for interfacing Arduino and data logger?)

Soldering iron
Wire cutters
Mini screwdriver set
Needle nose pliers
Power drill or other rotary tool
Scissors, saw and/or laser cutter (see step 15)
Where do the wires on the stereo plug go?
Where is the file for the mounting bracket? I can't find it :)
randofo (author)  margmorg8131 year ago
Ack. Long gone most likely. For a while Sparkfun.com was selling breakout boards for these sensors. I think they may still. It is approximately the same size as the file I had made and is pretty cheap.
Giedow2 years ago
Now explain to me how a mic analyses your breath for alcohol
randofo (author)  Giedow2 years ago
The alcohol sensor does this.
Giedow randofo2 years ago
that is a valid point
this is hilarious randy. every sunday is karaoke night at the bar across the street from my apartment, I'd love to use this as some kind of kill switch on the audio system, get those crazies off the mic faster...
evix5 years ago
It'd be great to interface this with a karaoke, or rock band mic!
oweng4000 evix4 years ago
And then set up the mic at your local bar's karaoke night.
Warlrosity6 years ago
Can you do it with a cheapie breth tinig
FeedTheGrid6 years ago
DarkAngel096 years ago
Is there anywhere else you can get the alcohol sensor besides in Thailand I do not have that amount of time and i want to try and build this microphone
randofo (author)  DarkAngel096 years ago
Not that I know of, but you can get the datasheet off the website and probably pull a part number off of there. Then you can just do a google search for it. I won't say its impossible, but it may be hard to track down. If you pay an extra $16 in shipping (or so) you can get it much sooner.
Cool. do you think you could explain how it works i'm thinking of building the sensor myself...even though i may epicly fail at it.
Did you have to "preheat" the alcohol gas sensor? I just received mine and it started off in the 1000 range. I've had it plugged in for about an hour or two now and it's down to the 800 range. The datasheet mentions a 24 hour preheat time. I think the normal range is supposed to be from 160 to 1024.
Redgerr7 years ago
wow, i like the idea a lot... ill have to be careful next time i take an interview :O make sure this isnt in there >:O i hope they dont catch me :P
Redgerr Redgerr7 years ago
uhh, jk btw i dont drink :)
youprobably do and dont know it
baneat7 years ago
If someone's drunk enough to try singing into it, you'll know lol. No breathalyser needed.
chalky7 years ago
just think how easily this could be 'hooked up' and Incorporated into a vehicle so the ignition would not start if the drivers pi$$ed! GENIOUS!!!
It's called an "ignition interlock device". In Arizona you have to get one installed in your car if you get pulled over and blow positive for alcohol, even if your BAC was under the legal limit.
Nesagwa chalky7 years ago
They have those already.
i know somebody with one she says its a real pain and likes to break but she still likes it beter the losing her licence lol
antennas7 years ago
Just so long as you realize that this won't be terribly accurate. It takes deep lung air to get an accurate reading of blood alcohol content, not the air that would go over the mic while talking. BUT it does sound like a fun toy at parties, but nothing more.
randofo (author)  antennas7 years ago
Indeed. Right now accuracy is my largest problem. However, I'd like to get it to a point where I have calibrated and tested it enough to be able to claim an approximate BAC level range.
rickfmdj7 years ago
Cool and LMAO!
how covert... *adds this to spy gizmos group* i give it a 4.5!
hunrichs7 years ago
oh this is great!. further modification that might be fun would be to make a version where the recorder actually ONLY works above a certain BAC threshold. less useful, perhaps, but guaranteed to result in consistent silliness.
gmoon7 years ago
Might-ie cool. Can the Arduino fetch data from the logger, or is the logger itself write-only? (you can read the card, of course, externally.)
Wow! You finally did it! I've been waiting for this for a long time! 5*s and faved.
RyanPotter7 years ago
Dude, right off the bat you earned 5 stars for using the word 'truthiness' and second, this is a brilliant idea! I see big karaoke applications for this device.
bumpus7 years ago
Excellent Randy!
This would be quite the project to take to school....


Hooray for Colbert!
pyro2227 years ago
hehe, you said truthiness... Nice! Very cool tut!
zachninme7 years ago
Awesome job Randy! What's the output from the sensor, analog? I like the laser-cut circuit templates. Did you have any problems with them, such as burning the plastic w/ your soldering iron?
randofo (author)  zachninme7 years ago
How did you find this? I didn't publish it yet :) The sensor is a really basic and relatively stable analog sensor. The soldering worked alright. The acrylic doesn't melt too easily and the connections were made quickly and slightly over the surface of the plastic, so it wasn't too large of a problem.
I'd love to say that I have 1337 skillz, but the truth is that I went to your memeber page, and it was there.
duck-lemon7 years ago
awesome! a new trick for undercover cops maybe....