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Description
Technical Specifications
Product Model | 1746-OBP16 (1746-OBP16A / 1746-OBP16 Series A)Manufacturer | Allen-Bradley / Rockwell AutomationProduct Type | SLC 500 16-Channel Digital DC Sourcing (PNP) Output Module with Electronic ProtectionNumber of Outputs | 16 (Two Groups of 8: Group 0 = Outputs 0–7, Group 1 = Outputs 8–15)Output Type | Sourcing (PNP), Positive Switching — Load connected between Output Terminal and 0 V DC (DC Common)Nominal Output Voltage | 24 V DC (Operating Range: 20.4 – 26.4 V DC per IEC 61131-2)Max Output Current per Point | 0.5 A (500 mA) @ 60 °C deratedMax Output Current per Group | 4.0 A (Group 0: Out 0–7; Group 1: Out 8–15)Min Load Current | 1.0 mA (typical)Off-state Leakage | ≤ 0.5 mAOn-state Voltage Drop | ≤ 1.2 V DC @ rated currentTurn-On / Turn-Off Time | ≤ 1.0 ms / ≤ 1.0 ms (typical)Backplane Current Draw | 190 mA max @ 5 V DC; 0 mA @ 24 V DC (field power is external)Protection Features | Electronic short-circuit protection per group, thermal overload shutdown w/ auto-recovery, reverse polarity protection on field powerIndicators | 1 × Module Status (Green/Red FLT), 16 × Per-Point Output Status LEDs (Green = Output Energized)Required Terminal Base | 1746-TB2, 1746-TB3, 1746-TB2S, 1746-TB3S, 1746-TB2H (high-density), or equivalent 1746-series screw / spring clamp baseSlot Width | 1 Slot (35 mm / 1.38 in — standard SLC 500 module width)Operating Temperature | 0 °C to +60 °C (32 °F to 140 °F)Dimensions (H×W×D) | 141 × 35 × 117 mm (5.55 × 1.38 × 4.61 in)Certifications | cULus Listed, CE, C-Tick, Class I Division 2 (Groups A,B,C,D) when installed in appropriate enclosureCompatible Processors | All SLC 500 Modular Processors: 1747-L511/L512/L513/L521/L522/L523/L531/L532/L533/L541/L542/L543/L551/L552/L553/L554 etc.
Main Features and Advantages
Enhanced electronic protection vs. legacy modules: The defining advantage of the 1746-OBP16 over the base-model 1746-OB16 is its built-in electronic short-circuit and overload protection on each output group. If an output is shorted to DC common or the group load exceeds 4.0 A, the module electronically shuts down the affected group, illuminates the fault indication, and reports the condition to the SLC processor—preventing damage to the module’s output transistors. Once the fault is cleared and power cycled or the group reset via backplane command, normal operation resumes automatically, eliminating blown fuses and reducing spare-parts inventory.Per-point LED diagnostics for faster troubleshooting: Sixteen individual green LEDs correspond one-to-one with output points 0–15. A lit LED confirms the module is actively driving the output, allowing maintenance technicians to distinguish between a PLC logic issue (LED off when it should be on = logic/fault problem upstream) and a field-side problem (LED on but device doesn’t actuate = broken wire, bad solenoid, missing field power). This simple visual cue cuts average troubleshooting time dramatically on the plant floor.Separate group power terminals for flexible wiring: The 1746-OBP16 divides its 16 outputs into two independently powered groups, each with its own VDC (+) and DC Common (–) screw terminals on the terminal base. This lets users isolate critical outputs (e.g., safety-related or always-on devices) on one group and general-purpose outputs on the other, or supply each group from a separately fused 24 V DC source for better fault containment. It also simplifies compliance with NFPA 79 or IEC 60204segregated control circuit requirements.Direct compatibility and hot-swap capability: The 1746-OBP16 is a true form-fit-function replacement for the 1746-OB16 in any existing SLC 500 rack. When used with a removable terminal base (1746-TB2/TB3 series), the module can be withdrawn and replaced without disconnecting field wires—only the module itself is unplugged. In systems programmed to handle I/O faults gracefully (Major/Minor fault handling configured in the SLC processor), the replacement module is recognized on the next I/O scan and normal operation resumes with no download required.High noise immunity and industrial-grade design: Outputs are optically isolated from the SLC 500 backplane (500 V AC isolation, I/O to system), providing strong immunity to electrical noise generated by inductive loads such as contactors and solenoid valves. Although external flyback diodes or snubber circuits are still recommended on highly inductive AC-coil interposing relays, the module’s robust design handles typical 24 V DC panel-mount relay coils and solid-state indicator loads reliably in electrically noisy environments.
Application Field
The 1746-OBP16 is the workhorse 24 V DC digital output module for SLC 500-based control systems across a broad spectrum of industries. In discrete manufacturing—automotive component stamping, assembly lines, packaging machinery—it directly switches 24 V DC pneumatic solenoid valves on pick-and-place heads, activates stack lights (and/or audible alarms via interposing relays), and energizes part-presence indicators on test fixtures. Its 0.5 A per-point rating is sufficient for most pilot devices and small interposing relays; larger loads such as motor starters are typically switched through 24 V DC coil interposing relays driven by the 1746-OBP16.In material handling systems (conveyor sortation, palletizers, AS/RS), the module controls divert-arm solenoids, photo-eye emitter power, zone-stop brakes, and status beacons. The two-group independent power structure is particularly useful here: one group may be powered from a UPS-backed 24 V DC supply to keep status and safety-alert outputs active during brief main-power interruptions, while the other group is on the standard machine supply and drops out with the rest of the process—an arrangement easily implemented with the 1746-OBP16.Process skids and water/wastewater applications also make frequent use of this module to operate 24 V DC final control elements, local alarm horns, or valve-positioner enable circuits where the control logic resides in a SLC 500 processor communicating with a DCS or SCADA host via DH-485, DF1, or (via an Ethernet bridge) EtherNet/IP. OEM machine builders value the module’s compact single-slot footprint, UL/cULus listing, and the fact that it requires no additional configuration beyond slot assignment in RSLogix 500—making it straightforward to document and support across multiple machine variants. For legacy systems originally equipped with 1746-OB16 modules, upgrading to the protected 1746-OBP16 is a common preventive measure to reduce nuisance fuse-related downtime and gain per-point diagnostics without altering the existing I/O addressing or field wiring.
