This is an easy-to-build timer to use while washing your hands which doesn't involve trying to sing a song in your head. Just wave your hand in front of it and wait for the LEDs to go off.
Here are the modules I used to build it, but honestly, you could replace any of them with whatever you have in your parts box. The display could be a 7-segment display, or even a handful of LEDs instead. The proximity sensor could be replaced with an ultrasonic rangefinder, or a light-break setup but it's best to avoid a physical switch that people would have to press before washing!
Display module:
Proximity sensor:
Arduino:
- Use any Arduino or Arduino-compatible board. I used an Arduino Micro because it was small and I had one handy but anything will work.
A bit of perfboard is also useful to hold everything together. I 3D-printed a case for it but it could also be placed in a translucent food container (with a cutout for the proximity sensor).
Hook up the signal wires as follows (again, not critical, the pins are configurable in software):
- D2 - display SCLK
- D3 - display CS
- D4 - display DATA
- D5 - sensor OUT
The project uses the PlatformIO environment (https://platformio.org). If you install that, you
should be able to open this folder, and then Build and Upload. If you prefer a different IDE,
then simply copying the code in src/main.cpp should be enough (don't forget to install the
MD libraries).
Libraries:
The STL file for the enclosure I used is in the enclosure folder. There's no special mounting needed -
just lay it flat on a table with the display / sensor installed and fix them with some hot glue.
License: CC Attribution-NonCommercial https://creativecommons.org/licenses/by-nc/4.0/