I thought about it and will probably design my own sensor instead. Using a load cell to detect resisting but moving filament before underextrusion happens in addition to movement using a Raspberry Pi that can also email me and offer a camera.

So the switch is not a part of the filament monitor at all and the photo os 90° turned? Then the red arrows show how the filament monitor is mounted. Okay, I get it.

As I said, to see the switch, you have to open the bottom of the printer ... is the "bottom limit" of the "heated bed". If you use large spools ... probably you have to find a different solution ... sorry.

Yes, I have. It has the same 3 photos on page 10 of 14. Page 12 of 14 shows an obviously different mounting position that is inpossible with 2.2Kg Colorfabb spools. Also no details on where that single switch in your second photo actually is.

@Marcus: have you looked at linked thread ? There is the pictures ... To mount the support you have to dismount the bottom of the printer. Each time you start a new print you have to push the "reset" button on the "filament monitor". First filament movement, after "reset", start the monitoring.

Where exactly is that mounted? Could you make a photo showing more of the surrounding? Is it below the extruder or between extruder and bowden tube? Where in the UM2 is that switch? Is it the reset-switch of the filament-monitor? PS: How does it detect that a new print is starting? Obviously it's not supposed to trigger while the printer is heating up.

I love it, man! Great work!