OMRON EE-SX674A Slotted Mini-Photoelectric Sensor

OMRON EE-SX674A belongs to the EE-SX67 compact-mount series. It is a 4-pin connector-type sensor with NPN output and a 5 mm slot width.

Model Code Explanation

EE-SX674: Compact-mount version (for flush-mounting against equipment side walls), NPN output, connector type

A: Indicator LED lights when light is blocked. Terminal L selects between Dark-ON / Light-ON modes.

Corresponding PNP variant: EE-SX674R

Cable-output version: EE-SX674-WR (1 m cable)

Key Electrical Specifications

4-Pin Definition (Receptacle EE-1001)

1. ①：VCC(⊕) Power supply positive DC5-24V
2. ②：L Mode-select terminal
3. ③：OUT Signal output (NPN)
4. ④：GND(⊖) Power ground

Mode selection:

Terminal L open: Dark-ON (D-ON) (factory default for -A)

Terminal L shorted to VCC: Light-ON (L-ON)

⚠️Never connect terminal L to GND; this will damage the sensor.

Wiring Guidelines

1. NPN output, for PLC sink-input; connect the load between output and VCC.
2. Mating connector: EE-1001. Use EE-1001-1 for factory-pre-wired L-to-VCC to enable Light-ON without external wiring.
3. Direct soldering to pins: Soldering iron ≤350 ℃, soldering time ≤3 s, keep ≥1.5 mm clearance from pin base to avoid housing thermal damage.

Typical Applications

Home-position detection, limit sensing, counting, code-wheel speed measurement, printer paper detection, position sensing for automation equipment, small-mechanism arrival detection.

Direct Replacement Models

1. EE-SX474A: Identical footprint and pin-out, nearly identical performance, drop-in generation-upgrade replacement.
2. EE-SX674: Standard version (LED lights on light reception); hardware-pin compatible, different indicator logic.

Usage Notes

1. IP50 rating: Not suitable for water spray or heavy oil contamination. Dust covering the optical slot requires regular cleaning.
2. Sensed target thickness ≥0.8 mm, opaque materials (metal or plastic flags).
3. Mount so that the shutter flag fully interrupts the optical path; partial blocking causes unstable / chattering outputs.

Operating Principle of Slotted Photoelectric Sensors (Photointerrupters)

Models such as EE-SX674A are also known as U-shaped optical couplers / photointerrupters, a subclass of through-beam photoelectric sensors. Emitter and receiver are integrated on opposite sides inside one U-shaped housing.

Core Structure

1. Emitter side: Infrared LED continuously emits infrared light.
2. Receiver side: Opposite phototransistor receives infrared light.
3. Central U-slot: Space for shutter flag / target object to pass through.

Two Operating States

1. No object in slot (Light-on condition)

Infrared light from the LED strikes the phototransistor directly; the phototransistor turns on and sets the corresponding output level.

2. paque object inserted into slot (Light-blocked condition)

The shutter flag blocks the infrared beam. Light is cut off, the phototransistor receives no light and turns off; the output level reverses.

Sensing is achieved by detecting whether an object blocks the infrared light beam to judge presence / position.

Two Output Modes (D-ON / L-ON, selected via terminal L on EE-SX674A)

1. D-ON (Dark-ON, output active when light is blocked)

Shutter flag inserted and blocks light → output turns ON; flag removed → output turns OFF.

Commonly used for home-position and arrival-limit detection.

2. L-ON (Light-ON, output active when light passes through)

No obstruction in slot, light reaches receiver → output turns ON; shutter inserted to block light → output turns OFF.

NPN Output Logic (EE-SX674A)

NPN open-collector: When output is active, output pin pulls low to GND; when inactive, output is high-impedance.

Compatible with PLC sink inputs.

Key Characteristics

1. Emitter and receiver pre-aligned in one housing; only insert shutter flag into U-slot for installation, no optical alignment required.
2. Detects opaque objects only. Transparent thin sheets transmit light and cannot be detected.
3. Fast response, suitable for high-speed counting, code-wheel speed measurement, limit and home-position sensing.
4. Limitations: Fixed slot width; target flag must physically enter the slot. Dust and oil contamination over optics cause false triggering.

Simple Analogy

Imagine a flashlight on one side and an eye on the other, separated by a U-shaped gap. When an object slips into the gap and blocks the flashlight beam, the “eye” sees no light and the sensor registers an object present.

Application Scenarios for Slotted Photoelectric Sensors (U-Shaped Photointerrupters)

Taking OMRON EE-SX674A miniature slotted sensors as an example: compact size, fast response, good noise immunity. Detects opaque shutter flags for position, presence and rotational-speed counting.

1. Automation Equipment: Home-Position & Limit Detection (Most Common)

Robot axes, linear slide modules: home-position reset signals. A moving shutter flag enters the U-slot to trigger the arrival signal.

Small cylinders and electric slides: forward / rear limit detection to judge travel end-points.

Advantage: Wear-free compared with mechanical contact limit switches, long service life.

2. Rotational-Speed & Pulse Counting (with code-wheel)

Mount a notched code-wheel onto a motor shaft passing through the sensor slot. As the wheel rotates, gaps transmit light and solid segments block light, generating continuous pulse outputs.

Use-cases: speed monitoring, rotation counting, simple encoder-like pulse acquisition.

Suitable for low-to-medium-speed rotation; higher response frequency supports higher rotational speeds.

3. Printers & Office Equipment

Paper-path detection: paper-present detection, jam detection, paper-exit sensing.

Print-head position detection, cartridge position recognition.

Miniature slotted sensors are widely deployed inside office machines.

4. Small Conveyors & Production Lines

Work-piece-arrival detection using metal / plastic shutter flags to confirm parts reaching a station.

⚠️Cannot detect transparent films directly; an opaque shutter flag is mandatory.

5. Access-Control Gates & Small Actuator Mechanisms

Mini-turnstiles, flip-cover mechanisms, small door open / closed-state detection.

6. Household Appliances

Position sensing inside washing machines, coffee machines, robot vacuum cleaners; flip-cover and turntable position recognition.

7. 3D Printers & Engraving Machines

X/Y/Z-axis mechanical home-position and limit sensing for homing cycles.

8. Medical Devices

Small-equipment piston / slider arrival detection and counting.

Selection & Application Considerations

1. Slot width selection: EE-SX674A has a 5 mm slot. Target shutter flag thickness ≥0.8 mm; thin flags risk light leakage and false triggering.
2. Output type

NPN: for PLC sink-input (EE-SX674A)

PNP: for PLC source-input (EE-SX674R)

3. D-ON / L-ON modes

D-ON (Dark-ON): Output activates when shutter inserted; preferred for home-position / limit applications.

L-ON (Light-ON): Output activates with no shutter present.

4. Limitations

Most models IP50: Not waterproof; vulnerable to oil and dust. Dust accumulation over optics causes mis-operation.

Cannot detect transparent materials directly; detection relies on opaque mechanical shutter flags.

Difference vs. Separated-type Through-beam Photoelectric Sensors

Slotted sensors integrate emitter and receiver, requiring no optical alignment, but targets must physically enter the U-slot and are constrained by slot dimensions. Separated-type through-beam sensors support long detection distances, but require separate mounting and precise optical alignment between discrete emitter and receiver units.