Cheap (very) Filament-Out Alarm

thingiverse

This is a quick and affordable way to create an alarm that alerts you when your filament runs out. It consists of a low-cost, battery-powered window alarm paired with an ultra compact micro switch. These alarms are widely available in stores, often sold for $5 for two units. I've even found them at my local Dollar Store for just $1 each. The switches can be purchased on eBay for a few cents apiece. To assemble everything, I used 2 half-inch long 2-56 screws. The micro switch is connected across the reed switch in the alarm. When the filament runs out, the switch closes and the alarm sounds extremely loudly! One advantage of this design is that you can still turn off the alarm using the switch on its side. The provided OpenSCAD file allows for easy customization to fit any micro switch you may already have. You could also modify it to accommodate 3mm filament. The included file works specifically with 1.75 filament.