Hi,

I have a BF20L mill converted to CNC and I'm using a CNC4PC C10S breakout board to control everything.
At the moment I'm trying to connect 3 NPN sensors (normally closed) to the dedicated input pins (10-13 or 15) of the board.
However, I cannot figure out how to connect them properly, so that when a sensor cable breaks, the limit switch in Mach3 gets triggered (on active low).

The sensors are powered by a 24V DC power supply.
According to the manual, you should set the jumper for the pins to pull down. Which I did.
The rest of the connections are exactly as shown in attached picture (see the red arrow), which comes from the manual.

When the sensor senses nothing, it reads 0V at the input pin.
When the sensor senses an object, it reads a little over 5V at the input pin.
At this point I could set Mach3 to active high and be done with it.
However, in the event of a cable breaking, I'm not sure that Mach3 will register it.

Can anyone explain how the current flows thru these diagrams?
Btw, I've also tried replacing the 25 Kohm resister by connecting the 5V from the breakout board directly to the sensor (see the blue arrow).
This gives me 5V at the input pin when then sensor senses nothing, but also when the sensor senses an object.

Any help is much appreciated!
Justin