Description
The LJ12A3-4-Z/BX is an M12 inductive proximity sensor that detects metal without touching it. Its NPN normally-open output pulls the black wire to 0 V when steel comes within about 4 mm of the blue face, which suits CNC and 3D printer end stops, part counters and PLC inputs that expect a sinking signal. For a sourcing (PNP) input, choose the LJ12A3-4-Z/BY PNP version.
Specifications
Datasheets
What’s in the box
About 1 m of 3-core cable with bare ends, plus two M12 hex nuts and two star lock washers.
Great for
Wiring & getting started
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Power it from 6 to 36 V DC
Brown to +V and blue to 0 V. A 12 V or 24 V supply is the usual choice.
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Connect the load to +V
Wire a relay coil, lamp or PLC input between the black wire and +V. When steel comes within about 4 mm, the black wire is pulled to 0 V and the load switches on.
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Reading it with Arduino, ESP32 or a printer board
Do not wire the black lead straight to a 3.3 V or 5 V pin while the sensor runs from 12 or 24 V. Fit a signal diode in series (cathode to the black wire, the band end), enable the pin’s pull-up, and join the board’s GND to the blue wire. The pin reads LOW when metal is detected. An optocoupler input works too.
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Mount it
Pass the barrel through a 12.5 mm hole and clamp it with a nut and star washer on each side. Leave the blue cap clear of the bracket, then set the gap to your target within 0 to 3.6 mm.
Note: Sensing range is quoted for mild steel. Aluminium, brass and stainless steel are detected at a shorter distance, and plastic, wood and glass are not detected at all.
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