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Description
The 1734-OB8S is an Allen-Bradley (Rockwell Automation) POINT Guard I/O safety module providing eight current-sourcing 24 V DC safety outputs for distributed machine safety systems. It is a solid-state module in the Bulletin 1734 POINT I/O family, designed to work with GuardLogix, Compact GuardLogix and SmartGuard controllers over CIP Safety.What distinguishes 1734-OB8S from a conventional output card is supervision. Each output can be configured as safety dual-channel, safety single-channel with pulse testing, or standard non-safety, and the module continuously monitors the output circuit — including the wiring and the downstream device — for the faults that would otherwise hide until a stop is demanded. Rockwell lists it as active lifecycle, which makes it a forward-looking choice rather than a legacy spare.
Application Scenarios
A robotic cell has a safety system built around a GuardLogix controller, with light curtains, gate switches and e-stop circuits distributed across the cell. The safety outputs drive contactor coils that remove drive power and vent pneumatic valves. On paper the system is compliant; in practice, the maintenance team lives with a nagging worry: a standard output that has silently failed “on” — a welded contactor, a short to 24 V in the field cable — will not be discovered until someone needs the machine to stop, and by then it is too late.That is the specific problem 1734-OB8S solves. Its output pulse testing works in the off direction: the module briefly pulls the output low in each cycle, and if a short to 24 V exists in the wiring, the pulse cannot pull the load low and the module flags an output short-to-24 V fault and trips the point to its safe state. This is the only practical way to detect a latched-on failure in a DC output circuit — the failure mode that conventional outputs cannot see at all.The second pain point is distributed safety architecture. Running safety-rated cable from a central cabinet to every remote zone is expensive, and every metre of cable is a fault source. 1734-OB8S places safety-rated outputs in a POINT I/O node next to the machine section, so safety contactors and valve solenoids are driven locally while the safety logic stays in the controller. Maintenance gains because faults are reported per channel with clear diagnostic bits, instead of requiring a technician to trace an entire safety loop by hand.
Parameter
| Main Parameters | Value/Description |
|---|---|
| Product Model | 1734-OB8S (POINT Guard I/O safety module; letter O, not zero) |
| Manufacturer | Allen-Bradley / Rockwell Automation; lifecycle status Active |
| Product Category | 8-channel safety sourcing digital output module (24 V DC current sourcing) |
| Output Configuration | 8 sourcing outputs, configurable per point as safety dual-channel, safety single-channel with pulse test, standard (non-safety) or unused |
| Output Voltage Range | 19.2 to 28.8 V DC (24 V DC nominal) — tolerates real-world supply variation without dropping out |
| Output Current | 1 A per point and 8 A per module at 40 °C; derated to 0.5 A per point and 2 A per module at 55 °C |
| Safety Rating | Minimum SIL 2 at module level; SIL 3 / PLe per EN ISO 13849-1 when used with a GuardLogix controller — system rating depends on architecture |
| Diagnostics | Electronic short-circuit protection and detection of short-to-24 V, short-to-0 V and cross-circuit faults; pulse-test output monitoring with readback |
| Response Time | Less than 6.2 ms — fast enough that module delay is a minor term in total safety stop-time calculation |
| Electrical Details | Voltage drop below 0.6 V (approx. 0.165 V typical), leakage current ≤ 0.1 mA, max field capacitance 950 nF per output; POINTBus current max 190 mA at 5 V DC; power dissipation approx. 3.02 W typical, 4.5 W max |
| Isolation | 50 V continuous basic insulation between field side and system side, type tested at 707 V DC for 60 s; no isolation between individual channels — relevant when planning channel grouping |
| Environmental and Mechanical | −20 to +55 °C operating, −40 to +85 °C storage, 5–95 % RH non-condensing; 5 g vibration at 10–500 Hz, 30 g operating shock; open-style enclosure for in-cabinet mounting; approx. 77 × 25 × 55 mm, approx. 62 g; DIN rail via POINT I/O terminal base with RIUP hot-swap and ADR support |
