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koehler 1.75mm or 3mm filament alarm

I made this so as the spool winds down to the end I could have a chance to get to my printer to reload without wasting filament on an unfinished part. It happens more than you think. All parts can be sourced from radio shack for less than 10 dollars (or your preferred source).

1 – 1.75mm or 3mm filament alarm body printed in your favorite color

1 – SPDT Switch with roller lever pn 275-017

1 – Piezo buzzer pn 273-017

1 – electrical connector (molex 4 pin or 2 pin 0.10” connector or 9v battery plug as you prefer)

2 – #4 1/2” screws (home depot)

22 ga. Wire in your preferred colors. 4 to 10 ft depending on your power source

Solder (or crimp) wires to the N.C and C connectors of the spdt switch. The middle tab or N.O. will not be used

Solder the piezo buzzer close to the opposite end of the wiring for the switch.

Attach your preferred electrical connector to the buzzer and 2nd wire from the switch. I use a 12v DC outlet from my ATX power supply but a 9v battery will work just as well. Polarity does matter here so take a moment to test. (the buzzer will work with reversed polarity but not loud and clear)

Print 1 koehler 1.75mm filament alarm body and attach the sdpt switch using 2 screws thru the plate and into the switch mount holes. Adjust to open switch.

Feed filament through the alarm then plug in to your preferred power source. When not using it, Insert a short piece of filament as a placeholder. The other way is loud and annoying. You’ll know what I mean when it goes off.

Attach to 8mm rod above the extruder. The higher the better for time to get to your printer. The long slot allows the alarm body to swivel to avoid binding. I also cover the threaded rod with a straw split lengthwise to minimize friction. Great for direct attachment to Prusa Mendel style printers or an 8mm rod attached to a spool holder.
Rest at ease knowing it will tell you “ Hey buddy, I’m out of filament” throughout the house. Tell a friend.

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