I have a LJ18A3-8-Z/BX NPN NO proximity sensor (orange tip) that I am wiring to a GT 2560 board. Right now I have the blue lead to fan 3 connector gnd, brn lead to fan 3 pos (12 vdc), and plan to hook the blk lead to z min sig connector. When I test the probe, I show .078 vdc when open (no led) and 4.7 vdc when closed (led on).
Now for what has me confused. First, I thought that NPNs needed resistors and PNP were the ones that automatically reduced voltage to a 5 vdc signal. I see several posts on here that say the orange tipped sensor is PNP but it definitely states that it is NPN. Second, my board has 2 pins for the Z min end stop. When I check with my meter, the lower pin shows 4.7 vdc and the upper pin shows 2.8 vdc. My schematic shows that the upper pin should be Bat+ and the lower should be Signal. Why would the signal pin have positive voltage with nothing connected? Am I right in assuming that the pin with lower voltage is signal even though it doesn't match the schematic? I checked all the other end stop connections and they all show the same voltages with nothing connected. When I back probe the connector the voltages remain the same. When I manually close the z axis end stop both pins show 4.7 vdc as expected. Just a thought, when I mod the firmware, would that reverse the pins so that the correct pin is signal? Lastly, does the way I plan on wiring the sensor sound like it should work? I tested the sensor and it responds as it should. Thanks for any help on this. I have a couple of days to wait for my longer extruder fan screws to arrive so I can mount the sensor. I would like to try and get the firmware and hardware up and running in the meantime. Is there firmware out there for the Geeetech prusa I3 Pro b or what would be the easiest way to configure the machine for auto level. I've seen references to programs that assist in setting up firmware but no links to the program.Thanks Again.