View Full Version : 3 pin npn LJ12A3-4-Z/AX proximity switch help

14-08-2017, 06:12 PM
I've just purchased 6 of these for my limit switches and having a hard time getting them to work. I'm no master of Mach 3 but believe it's set correct in the pins to work with the current wiring into the breakout board.

As I'm just trying to get them to work I've got one wired in to the Z axis limit switch, and the power to the 24V outlet from the BOB but likely to use the stepper drivers PSU once working.

So wiring I've got is pin 15 Z-axis and then pin 15 set to the X++ limit. Detects nothing nor does the LED on the switch light up.


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john swift
14-08-2017, 07:49 PM
a link to the manual for your breakout board and / or a photo showing the lable for the 6 way terminal block ( next to the relay ) will help

its not easy to see your connections to the brown proximity switch positive supply

how have you connected the 24V power supplies negative terminal to the breakout negative power in ??


14-08-2017, 07:56 PM

The brown cable is connected to the 24v outlet offered from the BoB. Now i've tested the sensors and they should light when they have at least 12v passing through them but they are not when connected to the breakout board so It could just be a simple output setting that is not toggled in the mach 3 settings that I am not aware of.

The negative is connected to the ground on the board below the input for the limits.


14-08-2017, 07:59 PM
Actually I just noticed, my input for the 24v is incorrect as It's a PSU in not an out as I have connected but I tried it earlier connected to the stepper driver PSU and had the same issue.

john swift
14-08-2017, 08:50 PM
is this how you connected the power suppy and proximity switch to the breakout board ?


if the breakout boards power supply negative in terminal is
connected to the limit switch common ground by the PCB's copper tracks it should work

but you may have to move the power supplies negative connection to the BOB's negative in to avoid noise problems
triggering the inputs