The auto-leveling sensor will be replacing your 3D printers z-end stop on your control board. You won't need the old z-stop because your sensor will be probing the bed for it's z-position.



Make sure your sensor has a detecting distance of at least 4mm. In reality, this might be lower depending on the sensing material. Your sensor should be mounted close to the nozzle and able to reach near the corners of your print bed when mounted. There's a quick video by Tom's guide that includes set-up and modifying your sensor if you have the LJ12A3-4-Z/BX (blue tip) or find out yours requires voltage modification.



The sensor mentioned in this indestructible has an LED that turns on when triggered. It might be dim or not light at all if the sensor isn't getting enough voltage.



For the mount, 123D design is perfect designing simple objects like this and of course, thingiverse.com.



Wiring the LJ12A3-4-Z/BY Inductive Proximity Sensor:

1) Locate and disconnect the z-probe from your control board.



2) Connect the output voltage wire (labeled V-out [brown] in this case) to the S signal input on the same row of 3 pins your old z-end stop was connected. On RAMPS boards this pin is nearest to the outside of the board of the rows of endstop pins.



3) Connect the other 2 wires labeled + and - to a corresponding positive and negative power source on your board. This can be directly to your 12 power supply, where 12v connects to your board or, you can use the auxiliary 12v pins on the RAMPS board. (See RAMPS diagram).



4) The sensors mentioned here are "normally open" switches meaning, that signal is only sent to the board when triggered. You may need to check this line in your firmware. False = Normally Open (see picture) or CTRL+F search "Z_MIN_ENDSTOP_INVERTING" in the Arduino Sketch. (more about firmware in the next step)



5) Test the sensor on some metal, aluminum, copper, etc. The LED should light. For a final test, have the printer power disconnect / e-stop handy just in case and raise the z-axis manually to a safe height and home the z-axis (or all axis) and try to manually trigger the inductive sensor while it's above the print bed. If it worked like your old end stop, you're ready to mount the sensor and configure your firmware.



Design a sensor mount and choose level points

These sensors only have a sensing distance of ~4mm. Ideally, the sensor mount should be adjustable from a location that is lower than the tip of the nozzle to a few millimeters above. The z-axis offset can be adjusted in your gcode later. The ideal position for a 4mm sensor could be about 3mm higher than the nozzle. Set the sensor much lower than the nozzle at first to avoid bed-crashing.



Mount the sensor and move your hot end carriage around to 4 points and put 4 pieces of foil (or copper) tape under locations nearest the 4 corners of your print bed that your sensor can reach. It might help to put large pieces down temporarily until you fine-tune exactly where they will go. You should have at least 1-2cm² of tape for these sensors when complete.



*Plastic stuck on the nozzle can sometimes prevent probing and cause bed crashing.*

Clean or Pre-heat your extruder before homing or auto-leveling to avoid this.



Next step: Firmware Setup -->