Homing sensors issue with parallel port BOB

After googling a lot searching for schematics of similar BOBs, PNP NC sensors ecc i came up with this that I THINK should be an approximation of what is going on:

What i understood is that this kind of BOB is just made to have inputs like E-STOPS, mechanic switches ecc, because it simply wants the inputs to be driven by connecting / disconnecting them to /from gnd.

I assumed the position of the led into the sensors: that should explain why the leds only dim: the current from vcc, once the switch gets opened (when the sensor has something near) , can flow to gnd passing through the leds.
Also this would mean that actually those sensors only work thanks to the path to ground that is created through those LEDS...
Does this make sense?
How can i fix this? It looks that i simply have a BOB that is not meant to be used with this kind of sensor..

Muz94 wrote: How can i fix this? It looks that i simply have a BOB that is not meant to be used with this kind of sensor..

Were the sensors expensive? NPN would simplify things.

No, not really.
6 sensors for 2-3 euros each.
I will consider buying some NPN then.
Should i stick with NC? I bought them because i felt they were safer, but in this configuration even if i detach one of them, it doesn't trigger a limit error in linuxcnc.
With NPN however it should be different if i'm correct, the path to ground would be normally closed, and detaching one sensor would definitely change the logic value read by the control.


edit: i'm not fully sure that i really understood how everything works however, if the circuit is the one i drew i still don't understand how the bob is picking the correct logic level of the sensor... the path to ground should always be closed, but i guess that i don't really have enough knowledge of how all the pull-up / pull-down thing works

I think that I would suggest choosing NC or NO based on each particular target.

I think I would wire them all to a common point, with them all open in their normal position (either detecting a target or detecting a hole). Then I think that any one of them can switch the input pin to GND.