Inaccurate Breathalyzer is still quite nice

Sure, [Hunter Scott’s] Breathalyzer can only differentiate between hammer and sober, but look how nice it came out. He’s using an MQ-3 alcohol sensor which, from previous projects, we know is very difficult to accurately calibrate. But if you want to monkey around with embedded systems you’ve got to have a goal. [Hunter] chose a gorgeous aluminum project enclosure, adding a big LCD display to the to the lit. The switch on the bottom selects between on, off, and charging modes. He’s using a USB charger from Adafruit to top off the lithium battery inside. Everything runs on 3.3V with the exception of the sensor which gets its 5V supply from a boost converter. An Arduino is the brains that pulls everything together.

See [Hunter’s] video description of the project embedded after the break.

14 thoughts on “Inaccurate Breathalyzer is still quite nice

  1. @osgeld & Koolguy007 – I think they are including typos just to encourage more comments these days. Of course BP is playing along…oh wait, so am I! Maybe I “need to use a it” after that glass of wine.

    Back On Topic – I would suggest that a *smaller* screen would help reduce the overall size. But if you’re really “hammer” you might not be able to read it.

  2. Sexy case, recessed screws cool. Dorky toggle switch sticking out where Murphy can turn it on and kill the battery, fail. The unit cannot be handled or put in anything without power switch coming on at random. Millions of flashlights are made the same way. You will find them dead when you pull them out to use what you thought was a good light.

    Hint, the voltage selector on older computer power supplies makes a great Murphy proof power switch!
    Mount behind a half inch (1cm) hole glued in place for sexy smooth lines, and no surprises.
    911 operators would like it if all pocket phones had the same feature. Murphy really likes to poke away at exposed controls.

  3. I would simply try to touch my nose. If you poke your eye out well you failed. Nice case. Too bad it is such a pain to calibrate.

  4. @ nootropic; I read your link. as far as calibrating the sensor, there are commercial gas cylinders available with different concentrations of alcohol vapor. They’re expensive, but if you are good at social engineering, any lab that does breathalyzers will have some to calibrate their machinery, and you wouldn’t need much. Another way would be to make a solution of alcohol and water, with the concentration adjusted so that the partial pressure of alcohol above the solution was a known value.

  5. You should use Henry’s Law for that. All the coefficients can be easily found online or you can consult Perry’s Chemical Engineering Handbook.

  6. So he basically slapped together a bunch of already made circuit boards and he calls this POS a project?
    Hackaday, how low can you go?

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