1734-OB8S 8-Channel 24V DC Safety Output Module 1A per Channel

The 1734-OB8S is an eight-channel digital safety output module designed for distributed machine-safety control. It provides eight 24V DC solid-state current-sourcing outputs for switching compatible safety contactors, interposing devices and other approved safety-related loads.

Unlike a standard eight-channel digital output module, the 1734-OB8S is intended for safety functions requiring output monitoring, fault detection and controlled transition to a safe state. When incorporated into a correctly designed and validated safety-control system, it can support applications up to SIL CL 3, Performance Level e and Category 4.

The module operates from a 19.2–28.8V DC field supply. Output capacity depends on the surrounding temperature. At 40°C, each output can supply up to 1A with a total module limit of 8A. At 55°C, the limits decrease to 0.5A per output and 2A for the complete module.

This temperature-dependent current rating is an important selection difference. The connected load current, output grouping, cabinet temperature and duty cycle must be checked before installation.

Key Differentiating Features

• Eight 24V DC safety output channels
• Solid-state current-sourcing output design
• Up to 1A per output at 40°C
• Up to 8A total module current at 40°C
• Temperature-dependent output-current derating
• Designed for distributed safety-control applications
• Supports redundant single-channel or dual-channel output structures
• Output monitoring and fault-detection capability
• Status indication for power, lock and eight output channels
• 50V continuous field-to-system isolation
• Compact DIN-rail installation
• Open-style construction for cabinet mounting

Temperature-Dependent Output Capacity

The maximum output current must be selected according to the actual surrounding air temperature.

At 40°C:

• Maximum current per output: 1A
• Maximum total module current: 8A

At 55°C:

• Maximum current per output: 0.5A
• Maximum total module current: 2A

The total current of all active channels must remain within the applicable module limit. Cabinet ventilation, neighboring heat sources and module orientation can affect the surrounding temperature.

Do not describe every channel as continuously supporting 1A without also stating the total module limit and temperature condition.

Safety Application Role

The 1734-OB8S can be used to control safety-related output devices such as contactors, valves and interface relays when these devices are compatible with the module output characteristics.

Safety performance is determined by the complete system rather than the output module alone. The controller configuration, network, wiring architecture, external devices, diagnostic coverage, fault exclusions and validation procedure all affect the achieved safety level.

Single-channel and dual-channel output arrangements may be used according to the required safety function. The selected structure must be documented and validated by qualified safety personnel.

Difference From Similar Models

1734-OB8S Versus 1734-OB8

The 1734-OB8S is a safety output module. The similarly named 1734-OB8 is a standard digital output module and should not be substituted in a validated safety function.

1734-OB8S Versus 1734-IB8S

The 1734-OB8S provides safety outputs. The 1734-IB8S is a safety input module for receiving signals from emergency-stop buttons, safety switches and other input devices.

1734-OB8S Versus 1734-OB8SK

The additional K suffix identifies a conformal-coated version. Verify the complete catalog number on the product label before ordering a replacement.

Typical Applications

• Emergency-stop output control
• Safety contactor switching
• Guard-door interlock systems
• Safety valve control
• Conveyor safety circuits
• Packaging machine protection
• Robotic cell isolation
• Assembly-line safety systems
• Material handling equipment
• Machine retrofit and replacement projects

Installation and Selection Notes

The module is open-style equipment and must be installed inside a suitable industrial enclosure. For installations requiring environmental protection, use an enclosure with an appropriate ingress-protection rating.

A 35 mm DIN rail is used for mounting the terminal bases. Each safety module requires two compatible terminal bases.

Compatible terminal-base options include:

• Two 1734-TB or 1734-TBS terminal bases
• Two 1734-TOP, 1734-TOPS, 1734-TOP3 or 1734-TOP3S terminal bases

Do not use 1734-TB3 or 1734-TB3S terminal bases with this module.

Use a compliant SELV or PELV field-power source. For applicable installations, the power source must also remain within the specified 150VA limit.

Before replacement, verify the complete catalog number, product series, firmware requirements, terminal-base configuration, controller project and safety signature. Replacing the hardware without confirming the safety configuration may prevent the system from operating correctly.

Frequently Asked Questions

1. How many output channels does 1734-OB8S provide?

It provides eight solid-state 24V DC safety output channels.

2. Is this an input or output module?

It is a digital safety output module. It should not be described as a discrete input module.

3. What is the field-power range?

The specified field-power range is 19.2–28.8V DC.

4. Can every output supply 1A?

Each output can supply up to 1A at 40°C, subject to an 8A total module limit. At 55°C, the limits decrease to 0.5A per output and 2A per module.

5. What safety level can it support?

When used in an appropriately designed and validated safety system, it can support applications up to SIL CL 3, PLe and Category 4.

6. Is it interchangeable with 1734-OB8?

No. The 1734-OB8 is a standard digital output module and is not equivalent to the safety-rated 1734-OB8S.

7. Does the module include its terminal bases?

The terminal bases are separate installation components unless specifically included in the supplied package. Two compatible bases are required.

8. Can 1734-TB3 or 1734-TB3S bases be used?

No. These terminal-base versions should not be used with the 1734-OB8S.

9. Does the module have an enclosure rating?

The module itself is open-style equipment and must be mounted inside a suitable control enclosure.

10. Can it be replaced without changing the safety program?

Only after confirming the product series, firmware, terminal bases, controller configuration and existing safety signature.