Filament Weight Scale

First: An unabashed plea for donations. Even small amount can help make it possible for me to continue working on these and other subjects. Thanks in advance.

This device pairs a load cell (strain guage) with a spool holder. It is connected to an esp32 processor with a display that shows the remaining weight of the filament that is left on the spool.
Spools are numbered and the esp32 remembers the weight if the spool is changed with another one. Using the knob and display the correct spool is selected when changed.
When a new spool is loaded the user sets the weight of the new spool, usually 1kg. The software then calculates the weight of the spool so it can calculate how much filament is left at any time. Because the load cell is cantilevered it is also necessary to enter the width of the spool when a new one is installed. The number of the spool should be written on the spool in case it is changed for a different one before it is empty.
The display shows the current spool numbe