INDUCTIVE PROxIMITY SENSOR LJ12A3-4-Z/BX

🔹 LJ12A3-4-Z/BX Inductive Proximity Sensor – NPN, Normally Open (NO), M12 Threaded

The LJ12A3-4-Z/BX is a rugged M12 inductive proximity sensor designed for non-contact detection of metal objects. It outputs an NPN Normally Open (NO) signal, making it ideal for industrial automation, CNC limit switches, conveyor systems, Arduino projects, and 3D printer auto-leveling applications.

✅ Specifications:

• Sensor Type: Inductive Proximity Sensor

• Model: LJ12A3-4-Z/BX

• Housing Diameter: M12 (12mm) – Threaded cylindrical body

• Detection Distance: 4mm (max, for ferrous metals)

• Output Type: NPN, Normally Open (NO)

• Operating Voltage: DC 6V – 36V (typical: 10-30V DC)

• Output Current: 300mA max

• Current Consumption: ≤13mA (no-load)

• Switching Frequency: 500Hz (DC)

• Response Time: ≤2ms

• Hysteresis: ≤10% of detection distance

• Housing Material: Nickel-plated brass (corrosion-resistant)

• Protection Rating: IP67 (dust-tight and waterproof)

• Connection: 3-wire cable (approx. 1.2m – 2m length)

• Wire Colors: Brown (VCC), Black (OUT), Blue (GND)

• Indicator: Built-in LED (lights when metal is detected)

• Operating Temperature: -25°C to +70°C

📦 Features:
✔️ Non-contact metal detection – no moving parts
✔️ NPN NO output – active low (sinks to GND when activated)
✔️ IP67 rated – suitable for harsh environments
✔️ LED indicator for easy status monitoring
✔️ Potting sealed for vibration and moisture resistance
✔️ Easy mounting with M12 threaded body
✔️ Compatible with Arduino, PLCs, and microcontrollers (with proper wiring)

📦 Applications:
✔️ Industrial automation and assembly lines
✔️ CNC machine limit switches (home/end stops)
✔️ Conveyor belt object counting
✔️ 3D printer auto-leveling (BLTouch alternative)
✔️ Robotic arm position sensing
✔️ Door position monitoring (industrial)
✔️ Speed measurement (gear tooth detection)
✔️ DIY electronics and maker projects

🔧 Wiring Diagram:

Wire ColorConnectionFunctionBrownVCC (6-36V DC)Power inputBlueGNDGroundBlackOUT (NPN NO)Output (sinks to GND when active)

🔧 Connection to Arduino (5V Logic):
Since the sensor operates at 6-36V, it cannot be powered directly by Arduino’s 5V pin. Use an external 12V power supply and connect as follows:

Sensor WireConnectionBrown (+)External 12V DC (positive)Blue (-)External 12V DC (ground) + Arduino GNDBlack (OUT)Arduino digital pin (with external 10k pull-up resistor to 5V)

When metal is detected, the Black wire pulls LOW (0V).

⚠️ Important Notes:

• Detection distance varies depending on the metal type. Ferrous metals (iron, steel) give max range (4mm). Non-ferrous metals (aluminum, copper) reduce detection distance.

• Power supply requirement: Sensor requires 6-36V DC. Do not connect directly to 5V Arduino logic.

• NPN vs. PNP: This is an NPN (sinking) output. For PNP (sourcing), look for the LJ12A3-4-Z/BY variant.

• Normally Open (NO): Output is LOW (or open) when no metal is present. When metal is detected, output switches to LOW (active).

• Mounting: Use two M12 nuts (included typically) to secure the sensor. Avoid mounting near other metal objects that may interfere.