A trio of parts that will allow you to suspend your spool on a 80x12.7x12.7mm load cell for processing remaining filament in an Arduino MCU with an OLED display and interface buttons.
This was designed to fit into the stock Ender 3 bracket in place of the hollow filament holder, and for the load cell to be attached to both bracket and spool with the appropriate M4/M5 hardware for the load cell.
I printed the bracket at 100% infill, as it will be supporting the entire weight of the system, but that may be overkill. You're welcome to experiment. The rest I printed at a lower, but still pretty high, infill. I tend to overbuild things, as you can probably tell from this design.
The spool holder is designed to take 4 10mmOD x 5mmID bearings for the spool to roll upon, and should press fit into place with little trouble. If they are too loose and threaten to fall off, a little dab of adhesive on the inner race should secure them in place.
I have recently completely redesigned the interface panel. The inside is now constructed with a proper perfboard installation, and the Nano, buzzer, HX711, and micro tac switches are soldered to the board, along with the requisite I2C pullup and button pulldown resistors.
10kg Load Cell and HX711 Amplifier
0.96" I2C OLED
This is a functional, but potentially not complete, version of the Filament Minder software. Instructions for use are on the Github readme.