Introduction: Extremely Loud Low Filament Alarm - Version 2.0

About: Welcome to my Instructables channel where I'll share my wacky and unique creations that hopefully others find useful, or better yet, inspire an evolution of even better ideas!

So thanks to user Daboke, we've collaboratively been able to improve this project and make it even better, cheaper, and easier to build. This is version 2.0!

Link to Version 1.0


  • Simple two part 3D printed housing
  • No soldering, or wiring, or any kind of electronics skills are needed
  • Dump switch is no longer needed
  • Only a single purchase part (the $7 window alarm) is required
  • No cutting or modifying of any part is required
  • Attaches directly to 3D printer frame
  • No longer just for bottom up feed setups
  • Can be used with normal filament feed direction
  • Designed for Ender 5, but should work for all printers with similar mounted extruders

PROJECT SUMMARY: This alarm attaches to an FDM 3D printer's filament line. If the filament runs out during a print, the alarm will go off alerting the user to pause the print and add more filament before the print is ruined and has to be restarted.


  1. Window Alarm
  2. T-Nuts and Screws (M4 Size)


  1. 3D Printer
  2. Allen wrench for M4 Screws

Step 1: 3D Print Alarm Housing

This was designed in Fusion 360, sliced in Cura, and printed on Ender 5.

I tried a few different orientations, and the one shown in the image above worked best (though it needs significant support cleanup afterwards) with supports everywhere on the part that holds the magnet and only where touching the build plate on the part that holds the alarm.

100% Infill. (Less infill will work, but you want the added weight to help ensure the sensor part falls away properly.)

NOTE1: I also included the native Fusion 360 file if anyone wants to modify if for their particular setup. If you do modify and make a new version please let me know by posting a make.

NOTE2: You can print in other orientations to lessen the required supports, however you want the pivot arms on the magnet part to be printed as shown above so they will bend and not break when spreading apart to engage the pivot holes on the alarm part.

Step 2: Mount to Printer Frame

Its a little tricky to get the T-Nuts to grab correctly, but once mounted you can "Set It And Forget It." Just make sure to feed the filament through it each time you change or replace a filament roll.

The hole in the front side of the housing is for tool access for the lower screw. Use the large square opening (its for the speaker of the alarm) for tool access for the top screw.

NOTE1: Ensure all the cables are out of the way so they do not prevent the sensor from swinging away and triggering the alarm when the filament runs out.

NOTE2: I lowered mine a bit after taking the picture. Once the alarm trips, you want to have as much time as possible to catch the end of the filament to make switching to a new roll easier.

Step 3: Finished

Now you can print without the worry of running out of filament mid-print. As user ChiefInstructor pointed out in the comments on Version 1.0, you do have to be present to hear the alarm, but hey most of us are stuck at home anyway right?

NOTE1: The one and only negative of Version 2.0 compared to Version 1.0 is now the alarm is turned on continuously. The batteries should last a long time as this is its normal intended operation. However, I recommend checking the battery from time to time (every 3 months is probably suitable). To do so, turn the alarm off, remove it from the housing, remove the battery cover, and press the battery check button. A green LED below the speaker will indicate good battery life.

NOTE2: The Mardi Gras Colors were not intentional. I simply ran out of green mid print and had just enough purple left over to finish it.

Thanks for taking the time to read through my Instructable. Please send me any questions or comments you might have. I try to answer them all. Stay safe and healthy! Happy Printing!

Again, a big thanks to Daboke for pointing out this design improvement.