Arduino Mega + Ramps 1.6 + 5 Volt on Z Min Sense

[gvdtec]

Hello. I have tried to search for my answer, but I cannot find a direct answer to my problem. Here is my problem in a nut shell:

I built my 3D printer with an inductive/proximity sensor on the Z axis. I am powering the sensor with 5 volts from an ATX power supply. Between the sense and the ground pin of the sensor I placed a 10K resistor because it already has a 10K resistor built in the sensor so that would divide the 5 volts into 2 = 2.5 volts. (5 volts seems to work for this sensor even though it is rated between 6 and 36 volts).

Now here is what happened; one of the legs on second 10K resistor broke off and allowed 5 volts through to the Ramps 1.6 + Mega 2560. I replaced the 10K resistor and the 3D printer is still working, but the Z axis now moves down when homing, but stops before the sensor has been triggered, leaving it too far from the bed to print properly. Disconnecting the Z min sensor from the Ramps 1.6 allows the Z axis to move continuously, so now I am unsure if the sensor is giving a signal even when it reads 0 volts when tested/triggered as it normally reads 2.5 volts. Or maybe the sense pin on the Ramps is reading something other than 0 volts from the sensor.

Now I have two opinions; #1: The sensor is still working fine, but the Ramps or Mega has been affected by the 5 volts. #2: My 500 watt ATX power supply could be sending something through the sensor's sense wire that is triggering the sense pin.

I have been unable to fix my problem as I don't have a spare Ramps or Mega to test it, so I am hoping there is something else that I could do.

One more question; Can 5 volts damage the Ramps or Mega on the sense pin? If so, is there something I can replace to make it work again instead of replacing the Ramps or Mega?

Thank you all for your help and reading this through.

[JCA34F]

Post a link to the sensor's datasheet.

[gvdtec]

May I please provide you with the name of the sensor as I am not getting a datasheet that represents the correct values of this Chinese version of the item. It is as follow: SN04-N, 4mm DC 6-36V 3 Wires NPN NO Inductive Proximity Sensor Detection Switch (SN04N). When the sensor is powered it gives 2.5 volt and when its sensor is triggered it goes down to 0 volt. Marlin has been configured according to this behavior and the printer has been working like this for many months until now.

PS: I have also observed an irregularity that might shed some light onto what may be the cause, however it is a bit sporadic; if I turn off the heat-bed everything works fine or in other words it homes like normal.