“We all have a special friend who needs supervision on a night out. Mine is called Geoffrey, and on his stag weekend it seemed prudent to have an outward display of how much of a liability he was likely to be.
This instructable outlines the construction of a medallion which contains a breathalyzer with a progress bar around the edge and an e-ink display in the middle. It is based on arduino code and uses an ESP32 board which is compatible with the arduino IDE.
You will need
Access to a 3D printer
Access to a laser cutter
Metalized laser cut material
Small lipo battery
Alcohol sensor - MQ3 or MQ4 breakout board [About £1 on eBay]
E-ink display [waveshare 2.13” SPI module ~ £15 from banggood]
ESP32 dev board with lipo charger [I used a lolin32 but adafruit now make the huzzah range which is very nice]
Neopixel compatible ring [32 pixels is the right size if you want to use the attached CAD]
Slide power switch [I used RS 829-0611]