Cheap (very) Filament-Out Alarm

thingiverse

This is a cheap way to throw together an alarm to let you know when your filament runs out. It consists of an inexpensive, battery-powered window alarm and an ultra mini micro switch. The alarms are widely available, often for about 2 for $5. I've even found them for $1 at the local Dollar Store. The switches are available on ebay for a few cents each. I used 2 half inch long 2-56 screws to hold everything together. The micro switch is simply wired across the reed switch in the alarm. When the filament runs out the switch closes and the alarm sounds LOUDLY! One advantage of this design is that you can still shut off the alarm with the switch on the side of the alarm. The openscad file is included, so you can easily customize the design for any micro switch you might already have. You could also modify it for 3mm filament. The provided file works with 1.75 filament.