Elegant overkill: a printer filament monitor

This will email you if your 3D printer runs out of filament. It will work with any printer that uses filament on spools - though you will need to use a spool holder that uses ball bearings like those referenced in the instructions.
In contrast to the minimalist filament monitor I created specifically for the Replicator 2, this will work on a broad range of printers (with the above provisos) - and is significantly more complex. It uses an Arduino Uno with an Ethernet board, simple custom electronics and of course a chunk of software. Its elegance stems from the indirect "non-contact" filament movement tracking, accomplished by monitoring the changes in magnetic field vectors generated by the movement of the ball bearings that support the filament spools.
The greatest value of the downloadable materials is in providing a practical, debugged overall electronics design and software; this will save you a great deal of time even if you have to adapt the housings to suit different knobs, buttons, connectors etc.
All the source files, for 3D printer housing, electronics and software - are provided. You will need a modicum of expertise to replicate this; the software needs your email addresses and some other internet details and depending on your printer and how you build the electronic display board, you may need to adapt some of the 3D printed designs.
NOTE: check you have the latest software by date; it will be a separate download file. The ZIP bundle is likely to have an older version
[16.01.2015] - Circuit and EAGLE files updated to provide for correct 3.3V level shifting for OLED and a PCB layout