Raise3D released a filament runout sensor for the N series. After a while they shared a new design of the housing for less stress on the filament.
I changed the design a bit. The bottom connecting parts for the print head were removed because this should be placed in the filament bay and not on the print head in my opinion. The bottom where the filament enters is now flat.
Make sure to attach the sensor very well to the printer/filament bay wall. Mine came loose once because Raise3D used double sided tape, the print head then pushed the teflon tube back and the teflon connector locked the tube. The gantry and motors made horrible noises when it tried to home. So I used epoxy glue to hopefully fix this, a picture of my current setup is above. I was surprised to see the Raise3D logo and indicator lights under the double sided tape!