This started out as a quick'n'dirty hack for my printer but I've found it really useful so far. It's a printed base with a battery, buzzer, switch and some PTFE tubing. Your filament will run in the short PTFE tube and along the way holding the switch open, disconnecting the buzzer circuit. As soon as your filament runs out/passes through completely, the circuit will close and the buzzer will start singing the song of it's people. This instantly lets you know it's time to hook up a new spool! I know you could do a more advanced version and hook it up to your controller but this is a simple add-on that works on any printer without any hacking, just put it between your spool and extruder and you're good to go! Check me out at: Youtube: http://www.youtube.com/c/MrCrankyfaceProjects Instagram: https://www.instagram.com/mr.crankyface/ 3d hubs: https://www.3dhubs.com/malm%C3%B6/hubs/mrcrankyface Patreon: http://patreon.com/Mrcrankyface