Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-OB8/A |
| Manufacturer | Allen‑Bradley (Rockwell Automation) |
| Product Type | ControlLogix DC Sourcing Output Module |
| Number of Outputs | 8 (2 groups of 4) |
| Output Type | Sourcing (24 VDC nominal) |
| Operating Voltage Range | 10 to 30 VDC |
| Rated Current per Point | 2.0 A @ 60 °C (140 °F) |
| Maximum Module Current | 8.0 A @ 60 °C |
| On‑State Voltage Drop | ≤ 1.2 VDC @ 2 A |
| Off‑State Leakage Current | ≤ 1 mA per point |
| Switching Response (ON) | ≤ 1 ms typical |
| Switching Response (OFF) | ≤ 2 ms typical |
| Backplane Current (5.1 VDC) | 165–250 mA |
| Power Dissipation (Max) | 2.5–4.7 W |
| Isolation (Field to Logic) | 50 V continuous |
| Operating Temperature | 0 °C to 60 °C (32 °F to 140 °F) |
| Terminal Block | 1756‑TBNH / 1756‑TBSH (20‑pin) |
Main Features and Advantages
High‑current drive capability: Unlike standard 0.5 A output modules, the 1756‑OB8/A delivers 2 A per point, allowing it to directly drive heavy inductive loads like large contactor coils and solenoid valves without requiring external power relays. This reduces panel space, wiring complexity, and potential failure points. The module supports high inrush currents (e.g., 4 A for 10 ms), ensuring reliable pickup of inductive devices.Robust electrical design and diagnostics: The outputs are arranged in two isolated groups, providing fault containment and preventing a single fault from taking down the entire module. Each channel features independent status indication via a green LED for quick visual troubleshooting. The module’s solid‑state outputs offer fast switching speeds (≤1 ms ON, ≤2 ms OFF) for precise timing control in high‑speed sequencing applications.Integration and reliability: As part of the ControlLogix family, the 1756‑OB8/A is configured and diagnosed using Rockwell’s Studio 5000 environment, providing integrated module status and fault reporting. Its industrial‑grade construction ensures reliable operation in noisy electrical environments with high immunity to EMI/RFI.
Application Field
The 1756‑OB8/A is widely deployed in heavy industrial sectors requiring direct control of high‑power actuators. In automotive manufacturing and material handling, it drives conveyor belt motor starters, palletizer solenoids, and robotic tooling end‑effectors. For water/wastewater treatment, the module controls large‐diameter valve actuators and pump contactors, leveraging its ability to handle long cable runs and inductive spikes. In mining and bulk material processing, the 1756‑OB8/A operates hydraulic manifold solenoids and heavy‐duty brake releases where high current and reliability are critical. It is also specified in machine safety systems (when used within a safety‐rated system architecture) to control safety contactors and safety‐related motor drives.
Related Products
- 1756‑OB16I: A 16‑point isolated DC output module offering higher point density but lower current per point (0.5 A), suitable for general-purpose loads.
- 1756‑OW16I: A 16‑point relay output module for mixed AC/DC voltage applications where isolation per point is required.
- 1756‑IB16I: The complementary 16‑point DC input module, commonly used in the same chassis for complete I/O control.
- 1756‑L7x Series: ControlLogix controllers (e.g., L71, L72, L75) that serve as the central processor for the 1756‑OB8/A.
- 1756‑PA75 / PB75: Power supplies used to energize the chassis housing the module.
- 1756‑TBNH: The standard 20‑pin removable terminal block used for field wiring connections.
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