End of an (electrical) era

[timo_gross]

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Just about every HP printer has one of these slotted optical sensors. Basically a pair of LEDs. Some of the print heads have a more complex one.

That stuff is really not expensive e.g. a TCST2103. Salvaging them from old printers can be frustrating, LEDs burn ( ) with wrong current, pinout is sometimes not clear. Extracting them from an old device is extra work.
I doubt that making the light barrier mechanically work is less hassle than fitting a hall sensor The automotive people seem to have settled on the Hall sensors.