LJ12A3-4-Z/BX NPN proximity sensor with its coiled cable, brown, black and blue leads, two M12 nuts and two star lock washers

LJ12A3-4-Z/BX Inductive Proximity Sensor - NPN NO, 4 mm

$5.79 NZD
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LJ12A3-4-Z/BX NPN proximity sensor with its coiled cable, brown, black and blue leads, two M12 nuts and two star lock washers
  • LJ12A3-4-Z/BX NPN proximity sensor with its coiled cable, brown, black and blue leads, two M12 nuts and two star lock washers
  • Close view of the LJ12A3-4-Z/BX with both nuts and star washers fitted on the M12 thread, showing the label and red indicator lamp
  • LJ12A3-4-Z/BX sensor marked with its 56.7 mm body length and M12 thread
LJ12A3-4-Z/BX Inductive Proximity Sensor - NPN NO, 4 mm
SKU: SEN-LJ12A3-4-NPN-NO

LJ12A3-4-Z/BX Inductive Proximity Sensor - NPN NO, 4 mm

$5.79 NZD
Order before 7:30am for same-day dispatch Dispatch 7 days a week, excluding public holidays

NZ Post: 1-2 days urban · 2-4 days rural

No GST added (we're not GST registered). Shipping from $5.99 urban / $9.99 rural, or free pick-up in Te Awamutu.

Buy more, pay less Prices shown are per unit. Add enough of this item and the lower rate applies on its own at checkout. There is no code to enter and you do not need to buy a pack. Choosing a tier here just sets the quantity for you. Larger quantities go out in the same bag, so packing, handling and postage cost us less per unit. We pass that saving straight on to you, so you can buy more for less.

Easy 30-day returns · 12-month warranty

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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

ModelLJ12A3-4-Z/BX
OutputNPN, normally open, 3-wire
Supply6 to 36 V DC (12 to 24 V nominal)
Sensing distance4 mm ±10% with a steel target
Set distance0 to 3.6 mm
Output current300 mA maximum
Response frequency500 Hz
BodyM12 thread, 56.7 mm long, non-flush
Housing / faceNickel-plated brass / ABS
RatingIP67 sensor body
Temperature-30 to +65 °C
WiresBrown +V, blue 0 V, black output

Datasheets

Full technical datasheet PDF

What's in the box

1×
LJ12A3-4-Z/BX sensor with attached cable

About 1 m of 3-core cable with bare ends, plus two M12 hex nuts and two star lock washers.

Great for

Z-axis or homing end stop on a CNC router or 3D printer
Counting steel bolts or gear teeth going past
Detecting a gate, arm or carriage at the end of travel
Feeding a sinking (NPN) PLC input

Wiring & getting started

  1. 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.

  2. 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.

  3. 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.

  4. 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.

Frequently Asked Questions

Answers to the questions buyers ask most.

Is this sensor NPN or PNP?
NPN, normally open. When metal is detected the black wire is pulled to 0 V, so it suits sinking inputs and loads wired between black and +V. For a sourcing input, use the LJ12A3-4-Z/BY PNP version.
Can I connect it to an Arduino, ESP32 or 3D printer board?
Yes, through a diode or an optocoupler. Power the sensor from 6 to 36 V DC, fit a signal diode in series with the black wire (cathode to the sensor), enable the pin's pull-up and join the grounds. The pin reads LOW when metal is detected. 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.
Will it work from 5 V?
No, plan on 6 V or more. The sensor is rated 6 to 36 V DC, and 12 or 24 V is the usual supply. A 5 V supply is below its rating and the range is not guaranteed.
What does it detect, and how far?
Metal only. Mild steel switches it at up to 4 mm, and 0 to 3.6 mm is the reliable working gap. Aluminium, brass and stainless steel switch at a shorter distance, and plastic, wood and glass are not detected.
How do I mount it?
Pass the M12 barrel through a 12.5 mm hole and clamp it with one nut and star washer on each side of the bracket. This is a non-flush sensor, so leave the blue cap standing clear of the metal bracket.
What is included?
One sensor with about 1 m of attached 3-core cable (brown, blue, black, bare ends), two M12 hex nuts and two star lock washers.

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Why Buy from NZN

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I'm Lukas, an engineering student and maker based in Te Awamutu. NZN grew out of a CNC build that dragged on for months because every missing cable, bolt or electronic part meant another overseas order. I started the shop so Kiwi makers can spend more time building and less time waiting for the next parcel.

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