SN04 Inductive Proximity Sensor DC 4mm NPN/PNP NO/NC Detection Switch

SN04 Inductive Proximity Sensor — 4mm Sensing Range, NPN/PNP, NO/NC, DC 10–30V

The SN04 is a compact M12 cylindrical inductive proximity sensor designed for non-contact detection of metallic objects in industrial automation, CNC machines, robotics, and Arduino/PLC control systems. With a 4mm sensing range, IP67 waterproof rating, and a robust zinc alloy housing, it delivers reliable metal detection in demanding environments without physical contact — eliminating mechanical wear and extending service life indefinitely.

Specifications

• Sensing Type: Inductive (eddy current principle)
• Target Material: Ferrous and non-ferrous metals (steel, aluminum, copper, brass)
• Sensing Range: 4mm (standard target: 12×12mm mild steel)
• Supply Voltage: DC 10–30V
• Output Type: NPN or PNP (select variant)
• Output Mode: NO (Normally Open) or NC (Normally Closed) (select variant)
• Output Current: ≤200mA
• Voltage Drop (ON state): ≤2.5V
• Switching Frequency: ≤500Hz
• Operating Temperature: −25°C to +70°C
• Protection Rating: IP67 (dust-tight, immersion up to 1m)
• Housing: M12 × 1mm thread, zinc alloy body
• Cable: 3-wire, 2m PVC cable (Brown=VCC, Blue=GND, Black=Output)
• LED Indicator: Red LED, lights when target detected

NPN vs. PNP Output — Which to Choose?

• NPN (sinking): Output pulls LOW when activated. Connect output to PLC input or Arduino digital pin (with pull-up resistor). Most common in Asian industrial equipment.
• PNP (sourcing): Output pulls HIGH when activated. Connect directly to PLC sourcing inputs. Common in European industrial equipment.

NO vs. NC Output — Which to Choose?

• NO (Normally Open): Output circuit open when no target present; closes when metal detected. Use for presence detection.
• NC (Normally Closed): Output circuit closed when no target; opens when metal detected. Use for absence detection or fail-safe circuits.

Wiring (3-Wire)

• Brown wire: VCC (DC 10–30V positive)
• Blue wire: GND (DC negative)
• Black wire: Signal output (NPN: connect to load then to VCC; PNP: connect to load then to GND)

Arduino Wiring (NPN NO)

• Brown → 5V (or 12V external supply)
• Blue → GND
• Black → Arduino digital pin (with 10kΩ pull-up to 5V)
• Read with digitalRead() — LOW when metal detected

Typical Applications

• CNC machine tool position sensing (end stops, home switches)
• Conveyor belt metal object counting and detection
• Robotic arm joint position feedback
• 3D printer Z-axis homing (metal bed detection)
• PLC input for metal part presence verification
• Gear tooth and shaft rotation speed sensing
• Arduino and Raspberry Pi automation projects

Package Contents

• 1 × SN04 inductive proximity sensor with 2m cable
• 1 × M12 mounting nut

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