Allen‑Bradley 871L-D20EP40-N4 Photoelectric Sensor

Overview

Model Code Explanation

• 871L: Cylindrical barrel photoelectric sensor series
• D: Diffuse reflective sensing mode
• 20: Sensing distance 2000 mm (2 m) maximum
• EP: Infrared LED emitter, standard plastic housing
• 40: M12 4-pin connector type
• N4: NPN sinking output, complementary NO+NC dual contact signal

Core Technical Specifications

Sensing Performance

• Sensing principle: Diffuse reflection (no separate reflector required)
• Max detection range: 2000 mm (adjustable via potentiometer)
• Light source: 880 nm infrared LED, invisible light to avoid operator glare
• Detection object: Opaque solid parts, cartons, plastic containers, metal workpieces
• Background suppression: Built-in short-range background suppression to ignore distant clutter

Electrical Parameters

• Supply voltage: 10–30 V DC
• Output type: NPN sinking, dual NO + NC switchable signal
• Rated load current: 100 mA per output
• Response speed: ≤1 ms fast switching for high-speed conveyor counting
• Reverse polarity, short-circuit and surge overvoltage protection integrated

Mechanical & Environmental

• Housing: 18 mm diameter cylindrical metal barrel
• Connection: M12 4-pin straight plug connector
• Protection rating: IP67 dustproof and waterproof
• Operating temperature: -20℃ ~ +60℃
• Mounting: Standard 18mm round bracket mounting
• Adjustment: Side potentiometer for sensing distance fine-tuning
• Visible indicator: Red LED status light (on when target detected)

Key Functions

1. Long-distance diffuse object detection
    
   Detect boxes, packages and workpieces up to 2 meters away without reflective plate, simplifying field installation layout.
2. Dual NPN NO/NC configurable output
    
   Switch between normally open or normally closed logic via internal wiring, flexible to match PLC digital input circuits.
3. Anti-interference infrared optical design
    
   Immune to ambient workshop lighting, avoids false triggering from fluorescent lamp or natural light interference.
4. Compact barrel industrial mounting
    
   Standard 18mm cylinder fits universal sensor brackets, easy to install on conveyor frames, machine tool fixtures.
5. Complete circuit self-protection
    
   Onboard reverse connection, short-circuit and ESD protection prevents sensor burnout during wiring errors.
6. Real-time detection status feedback
    
   Front LED indicator quickly confirms sensor working state for on-site maintenance troubleshooting.

Compatible Supporting Equipment

1. PLC Control Systems

• SLC 500 (1747-L532 CPU + 1746 DC digital input modules)
• MicroLogix 1200 (1762-L40BWA + 1762-RPLRTB40 terminal block)
• ControlLogix with Kinetix 6000 servo system (2094-BC02-M02-M)

2. Safety Components
    
   440R-N23126 safety relay, 440E-A13501 rope pull switch
3. Operator & Signal Parts
    
   800H-QR10A pushbutton, 800T-XD2P contact block
4. Network & Power Distribution
    
   1783-MMX14T2S managed Ethernet switch, 140M-I8P-C50S motor protection circuit breaker
5. Connection Accessories
    
   M12 4-core sensor cable, drag chain continuous-flex signal cables

Typical Industrial Applications

• Packaging line carton presence detection and counting
• Logistics conveyor parcel tracking and position sensing
• Metal processing machine workpiece feeding detection
• Water treatment equipment material level auxiliary monitoring
• Automated assembly station part missing inspection