Counting meters of filament with rotary encoder and encode disc

[jonbr]

I need some ideas and opinions about the component I am developing, through the rotation of the spool in filament maker, will let us know how many meters of filament we have made.

Iam using a simple optical rotary encoder and a encoder disc, counting digital signal, when sensor is close or note.

But I ran into a problem, how to calculate?

I know for example that a complete rotation of the spool rolls approximately 17.5cm.

However, this is easy to calculate with an empty spool.

However, it is clear that the filament will be wound continuously, as the filament will be one on top of the other, this length will increase, it will no longer be 17.5cm, and this number will be variable according to more filaments being wound one on top of the other. other.

What do you think about this?

[jhaine]

Have a separate roller for the filament to wrap say half the circumference which drives the rotary encoder. From the roller diameter and number of turns you can calculate the length that has passed.

[ruilviana]

Place the encoder to count the meters of filament on one of the two rolls and its measurement will not depend on the diameter of the spool.