Proximity sensor that detects nearby metal, including aluminum foil; a great solution for heated bed calibration.The LJ18A3 is a PNP Normally Open (NO) type of proximity sensor.    Most modern 3D printer firmware have some sort of auto bed leveling procedure available, but you will need to enable it. You can use this sensor as the z_min_end stop for example, replacing your current end stop. Most firmware will also use the min end stop as a probe, but some allow a separate probe to be defined.    This sensor operates at 6-36V, so as the signal voltage is the same as the input voltage, also the signal will be 6-36V. You will need to down-convert the voltage to acceptable level for your electronics. Please see the linked schematic on how to connect this sensor to the end stop pins of your electronics board.  

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