LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor

LJ18A3-8-Z-BX (8mm) Inductive Proximity Sensor Detailed Explanation

What is it?

The LJ18A3-8-Z-BX Inductive Proximity Sensor is a non-contact sensor used to detect metal objects without physically touching them.

It is widely used in automation, CNC machines, and robotics as a replacement for mechanical switches.

How It Works

This sensor works based on electromagnetic induction:

• The sensor generates a high-frequency electromagnetic field

• When a metal object comes near:

  • Eddy currents are induced in the metal

  • This changes the sensor's internal signal

   

• The sensor detects this change and switches its output

No physical contact needed no wbody> Wire Color Function Brown / Red VCC (+6V to 36V DC) Blue / Green GND Black / Yellow Output (Signal)

Output Type (Important)

• Type: NPN (Normally Open - NO)

• Behavior:

  • No metal Output HIGH (or floating)

  • Metal detected Output LOW (connected to ground)

   

This is critical when interfacing with Arduino or PLC

Key Specifications

• Detection distance: 8 mm

• Operating voltage: 6V 36V DC

• Output current: up to 200300 mA

• Type: Inductive (metal only)

• Thread size: M18 (18mm diameter)

• Protection: IP67

  Response frequency: ~500 Hz

Important Notes

1. Detects Only Metal

• Works with:

  • Iron

  • Steel

  • Aluminum (reduced range)

• Does NOT detect:

  • Plastic

  • Wood

  • Glass

2. Sensing Distance

• Rated: 8 mm

• Real-world:

  • Iron full range

  • Aluminum less distance

3. Output Voltage Warning

• Output voltage = supply voltage

• If powered with 12V/24V output is also 12V/24V

You must use a voltage divider for microcontrollers like Arduino (5V/3.3V safe)

Working Example

Metal Object ApproachesElectromagnetic Field Disturbed67br>Controller Receives Signal

Applications

• Robotics (object detection)

• 3D printers (auto bed leveling / endstop)

• Industrial automation

• CNC machines

• Position sensing (metal parts)

Commonly used as a limit switch replacement

Advantages

• No physical contact

• Long life (no wear)

• Works in dusty/oily environments

• Fast switching

Limitations

• Only detects metal

• Requires DC power (636V)

• Needs level shifting for microcontrollers

• Detection distance varies with material

Practical Example (Arduino Use)

• Power sensor with 12V

  < near:

  • Arduino reads LOW

  • Trigger event (stop motor, count object, etc.)

Pro Tip

If you see variants like:

• BX NPN NO (this one)

• BY PNP NO

Choose based on your circuit type (NPN = s