Hi everyone

I try to show you how you can connect npn sensor and setup repetier configuration for auto bed leveling.

This is my first project ,of course ı may have some mistake and some missing information however I regularly check the comment to help those who want to use auto bed leveling on their 3d printer :)

Step 1: Step1: About Sensor and 3d Printer

in generally we use in 3d printer NO and gnd at trigger about 5v.
There is a two type sensor ,pnp and npn.

npn sensor

when it connected to 12v ;
not trigger, give 8 -9 v which is ok for 3d printer
trigger, give zero volt , so everything is ok for 3d printer

pnp sensor

when it connected to 12v, it gives 12v at trigger. so it will damage 3d printer.

if your pnp sensor is working when cennected 5v , it is ok , but not working you should reduce the output voltage to 5v or less and you change the firmware for pnp sensor.

I have experience in capacitive npn sensor and ı will mention about this type of sensor.
I buyed this https://tr.aliexpress.com/item/High-Quality-LJC18A3-H-Z-BX-Approach-Sensor-Cylindrical-Capacitive-Proximity-Switch-NPN-6-36V/32627840658.html?isOrigTitle=true

Step 2: Step2: Connecting Sensor to Ramps1.4

In general brown +
blue -
black output.
also you can check from sensor datasheet.

connect brown and blue to 12v + -
and black to the z min ends stop ,''s'' pin

Step 3: Step3: Mount the Sensor

mount the sensor the most suitable location and note for the offset to the nozzle

Step 4: Step4: Repetier Configuration Setup for Auto Bed Leveling

Step 5: Step5: Z Prob Height and Offset

After complete step , check your sensor is working or not ,doing home z and trigger sensor so the z is stop.
ıf it is working , calculate the offset values.

z probe offset
these value for where is the sensor accordingly nozzle

extr.1 offset
these valuse for where is the nozzle acoordingly home position.

NOT: try - or + for your sensor position.

Step 6: Step6: Final

Change start gcode g28 to

G28 X0 Y0
G32 S1
and save the changes.

start the printing and see the nozzle head and stop the printing :

if it is high to the table, try some positive value for z prob height
if it rub the table try some negative value for z prob height
and after saving z prob height , sent g code M500 and start to print.