LJ12A3-4-Z/BX Inductive Proximity NPN Sensor – NPN, Normally Open, 4mm – Support Documentation
Description
The LJ12A3-4-Z/BX is a rugged inductive proximity sensor in a cylindrical M12 housing. It detects metallic objects up to 4 mm away, using a normally-open NPN output configuration. The sensor includes an LED status indicator and is ideal for automation, CNC machines, 3D printers (particularly for bed-levelling), and industrial control applications.
Pin-Out & Wiring
This is a 3-wire sensor with the following connections:
| Wire Colour | Connection | Description |
|---|---|---|
| Brown | 6 – 36 V DC | Positive (V+ ) |
| Blue | 0 V (Ground) | Negative (GND) |
| Black | Signal Output (NPN, NO) | Switches low when metal is detected |
Specifications
| Parameter | Specification |
|---|---|
| Detection Distance | 4 mm (nominal) |
| Operating Voltage | DC 6 – 36 V |
| Output Type | NPN, Normally Open |
| Output Current | Up to 300 mA |
| Response Frequency | Approximately 100 Hz to 500 Hz |
| Operating Temperature | –25 °C to +65 °C |
| Housing | M12 nickel-plated brass, IP67 rated |
| Cable Length | Approximately 1 m |
Installation & Use
- Securely mount the sensor using the included nut in a stable position.
- Wire brown to the positive supply (6–36 V), blue to ground, and black as the signal endpoint connected to your controller or load.
- Connect the signal line via a pull-up resistor or compatible logic input—NPN outputs sink to ground when activated.
- Avoid running the motor or other high-emission equipment nearby to reduce interference.
Troubleshooting
- No output or LED not lighting: Confirm wiring and supply voltage are correct.
- Sensor constantly triggered or LED always on: Ensure no metal is within 4 mm of the sensing face; check wiring polarity.
- Intermittent detection: Keep target materials within the rated distance; avoid vibration or contamination on sensing surface.
- Output not compatible with microcontroller logic levels: Use a voltage divider or level shifter for 5 V logic interfacing.
FAQs
- Can it detect non-ferrous metals?
- Yes—but detection distance may be reduced compared to ferrous metals.
- What does the LED indicate?
- The built-in red LED illuminates when a metallic object is detected within range.
- Can I power it from a microcontroller’s 5 V supply?
- Although rated for 6 V minimum, some users have successfully run it at 5 V with careful wiring and pull-up arrangement—testing is advised.