Proximity Inductive NPN NO Switch Sensor LJ12A34Z-BX

Features:

• Detects metallic objects without touching them using electromagnetic induction
• Detection distance: 4mm
• High precision detection of large metal fields
• Red LED indicator lights up when a metallic object is detected
• NPN Normally Open (NO) type output
• Operating voltage: 6–36V DC or 5V DC
• Output current: 300mA (DC), 400mA (AC)
• Standard detected object: Mild steel (12×12×1mm)
• Response frequency: 500Hz
• M12 threaded body for easy mounting
• IP65 rated for dust and water resistance
• Operating temperature: -25 to 70 °C (-13 to 158 °F)
• Reverse connection protection included

Principle of Work:

This sensor operates using electromagnetic induction. It generates a high-frequency magnetic field via an internal coil. When a metallic object enters this field, eddy currents are induced in the object, disturbing the original magnetic field. The sensor detects this disturbance and outputs a digital signal (connected to ground) to indicate detection. Only metallic objects are detectable.

Pinout of the Module:

• VCC: Power supply 6-36V DC (Brown wire)
• GND: Ground (Blue wire)
• OUT: Digital output (Black wire)

Applications:

• 3D Printers: Bed leveling and object detection (e.g., aluminum heated bed)
• CNC Machines: Tool and workpiece position sensing
• Robotics: Metal object detection in industrial paths
• Conveyor Systems: Sorting and detection of metal parts, cans, bottles
• Security Systems: Detection of weapons or metallic items

Circuit Diagram:

• Sensor to Arduino:
  • VCC → VCC
  • GND → GND
  • OUT → A2
• Resistor: 10KΩ pull-up resistor on output line

Library:

No library required to use with Arduino

Example Arduino Code:

const int Pin = 2;

void setup() {
  pinMode(Pin, INPUT);
  Serial.begin(9600);
}

void loop() {
  int sensorValue = digitalRead(Pin);
  if (sensorValue == HIGH) {
    Serial.println("no Object");
  } else {
    Serial.println("Object Detected");
  }
  delay(500);
}

Code Explanation:

• Pin: Connected to the sensor’s OUT pin (Digital Pin 2)
• setup(): Initializes the pin and serial communication
• loop(): Continuously checks sensor state and prints message

Technical Specifications:

• Detection distance: 4mm
• Setting distance: 0–3.2 mm
• Supply voltage: 6–36V DC or 5V DC; AC versions: 90–250V, 36V, 380V
• Output current: 300mA max (DC), 400mA (AC)
• Standard detected object: Mild steel (12×12×1mm)
• Sensing object: Magnetic metals preferred
• Response frequency: 500Hz
• Output indication: Red LED
• Short-circuit protection: Not included
• Reverse connection protection: Yes
• Insulation resistance: ≥50MΩ
• Dielectric strength: 1000VAC, 1 min
• Mounting: M12 bracket
• IP Rating: IP65
• Operating Temperature: -25 to 70°C

Comparisons:

• LJ12A3-4-Z/BX (Inductive Sensor):
  • Works by electromagnetic field interaction
  • Detects only metallic objects (preferably magnetic)
  • Short detection range: 4mm
  • Commonly used in 3D printers and CNC machines
• Photoelectric/Infrared Sensors:
  • Work using light reflection
  • Detect metallic and non-metallic objects
  • Longer detection range (up to several meters)
  • Used in doors, vending machines, security systems

Resources:

• Link 1