- Arduino nano
- 0.91" OLED with I2C interface
- MQ-3 alcohol sensor
- power source - 9V battery
To start programming I firstly built a prototype using breadboard. (I skipped the switch which cut the power off, because during programming I am powering whole device via USB)
According to datasheet first important thing is preheat the sensor, so I set the preheat time to 2minutes (after 2 minutes sensor reading has stopped decreasing). For the preheat time I proggramed a fancy animated loading screen.
After this I used simple analog read to read the value from sensor every 500ms. I am using millis() function to measure time between program loops - thanks to this I won't stop whole program using delay() function (multithreading 😎).
To print every text horizontally centered I created the print_in_centre() function.
Everything printed on the screen is managed by print_reading() function.
It's really hard to calibrate properly this sensor - so it could show per mille value. By now I just calibrated it as good as I am able to in my home conditions. I designed housing in such a way that I will be able to calibrate it in the future if needed.
I designed housing for the breathalyzer using Autodesk Inventor in the most precise way so no glue is needed to assemble my device.
In the next step I 3D prineted the enclosure using my Ender 3 V2 printer.
Finally I was able to assemble whole project
