Difficulties in designing a filament movement sensor

  • I would like to get a better understanding why filament motion sensors are as difficult to design as they apparently are.
    In the olden days of computer mice, every mouse had both x and y motion sensors that were simply a slotted wheel actuated by the ball or whatever that were running on the surface the mouse ran on. The slotted wheels were extremely crude, low resolution devices yet did their job well.
    Why are all kinds of exotic ways used rather than a slotted wheel on an axle with a rubber wheel on the same axle in contact with the filament? The filament would be lightly pressed against the rubber wheel with an idler wheel.
    Resolution would be determined by the number of slots in the wheel as well as the diameter of the rubber wheel. If wear of the rubber is thought to be an issue then make it a hobbed steel wheel.
    Seems to be a lot simpler than having to verify the alignment of a magnet in each sensor like what is currently being done.

    I am assuming that the simple way was explored and dismissed for some reason and I am curious why.

  • I would guess that the difficulty is to transfer reliably the linear motion to the wheel rather than measuring the movement of the wheel.

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