Keyence GC-S84 Safety I/O Unit

The Keyence GC-S84 is a safety input/output unit for the GC series programmable safety controllers. This module provides 8 safety inputs (Type 3, compatible with contact or PNP OSSD output devices) and 4 PNP safety outputs (500 mA per channel). It is certified for safety integrity levels up to SIL3 (IEC 61508) and Performance Level e (ISO 13849‑1). The GC‑S84 is designed to interface with emergency stop pushbuttons, safety light curtains, interlocking gates, and two‑hand control systems.

Technical Specifications

Safety inputs: 8 channels, Type 3, compatible with contact output devices or PNP OSSD output devices. Input ON level: ≥ 11 V / 2 mA; OFF level: ≤ 5 V / 1.5 mA. Short‑circuit current approx. 3 mA. Safety outputs: 4 channels, PNP transistor outputs, max load current 500 mA per channel, residual voltage ≤ 2.0 V. Auxiliary outputs: None. Test outputs: 2 channels, PNP, 100 mA max. Power supply: 24 V DC (19.2‑28.8 V), current consumption max. 60 mA. Protection circuits: overcurrent, reverse connection, surge protection. Dimensions: 22.2 mm (W) × 95 mm (D) × 90 mm (H). Weight approx. 130 g. Operating temperature: ‑10°C to +55°C. Storage temperature: ‑25°C to +70°C. Protection rating: IP20.

Key Features

• 8 safety inputs (Type 3, 24 V DC, sink/source selectable)

• 4 PNP safety outputs, 500 mA each

• SIL3 (IEC 61508), PL e / Cat. 4 (ISO 13849‑1)

• Test outputs (2 channels) for monitoring external contactors

• Configurable input delays and logic via GC Configurator software

• Short‑circuit and cross‑circuit detection

• Modular expansion: multiple GC‑S84 units can be connected

• DIN rail mounting (35 mm)

• LED indicators for power, input status, output status, and fault

Safety Functions

The GC‑S84 is used to monitor safety devices and initiate a safe stop when a hazard is detected. It can be configured for single‑channel or dual‑channel operation with or without cross‑circuit detection. The unit supports manual or automatic reset, with optional monitored reset requiring a feedback loop from external contactors. The test outputs provide pulsed signals to safety devices (e.g., light curtains) for OSSD compatibility or to check the wiring integrity of contactors. The unit also includes a short‑circuit and cross‑circuit detection feature that prevents unsafe states if wiring faults occur.

Configuration and Software

The GC‑S84 is configured using Keyence GC Configurator software (Windows‑based). The software provides a graphical interface for assigning input devices, setting logic functions (AND, OR, timing functions), and defining output behavior. Pre‑configured function blocks are available for emergency stop, safety gate, two‑hand control, and light curtain monitoring. The software also includes simulation mode for offline validation. The configuration is downloaded to the unit via USB or Ethernet (through a GC‑controller). The GC‑S84 can operate as a stand‑alone safety relay or as part of a larger GC‑series safety network.

Wiring and Installation

The GC‑S84 mounts on a 35 mm DIN rail. Power supply (24 V DC) is connected to the +24V and 0V terminals. Safety inputs (I1‑I8) are wired to the input device contacts or OSSD outputs. Test outputs (T1, T2) can be connected to test inputs of light curtains or used to drive external contactor feedback loops. Safety outputs (O1‑O4) connect to the contactor coils or other actuating elements. Use shielded cables for long wiring runs (max 100 m for inputs, 30 m for outputs). The unit is rated IP20 and must be installed in a control cabinet. All safety wiring must comply with local standards and the machine directive.

Applications

Typical applications include emergency stop monitoring on industrial machinery, safety gate interlocking, light curtain interfacing, two‑hand control on presses, and safety mat evaluation. The unit is commonly used in packaging machinery, robotics cells, automotive assembly lines, and printing presses.

Standards and Certifications

The GC‑S84 is certified by TÜV to IEC 61508 (SIL3), IEC 62061 (SIL CL3), and ISO 13849‑1 (Cat. 4, PL e). It also meets UL1998 for safety‑related software and is CE and RoHS compliant. The unit has been tested for industrial EMC per IEC 61131‑2 and FCC Part15B Class A.

Conclusion

The Keyence GC-S84 safety I/O unit provides flexible, high‑integrity safety monitoring in a compact DIN rail package. Its 8 inputs, 4 outputs, SIL3 certification, and easy configuration make it a versatile component for machine safety systems.