Allen-Bradley 1746-OB16 SLC 500 Digital DC Output Module

The Allen-Bradley 1746-OB16, also cataloged as the 1746-OB16 SLC 500 digital output module, serves as the primary SLC 500 DC sourcing output module utilized to execute 16-point discrete load switching across SLC 500 backplane-controlled rack systems. Configured for 24 VDC signal-level switching in SLC 500 architectures, the Allen-Bradley 1746-OB16 provides direct electrical drive of field loads through transistor-based output stages managed via 5 VDC backplane logic.

Suffix Breakdown & Model Matrix

No formal suffix structure is defined in the provided documentation. The part number 1746-OB16 is treated as a fixed configuration within the SLC 500 output module family.

Hardware Specifications

SLC 500 Backplane Communication and I/O Switching Behavior

The 1746-OB16 interfaces with the SLC 500 backplane through 5 VDC logic-level signaling, where 0.28 A backplane current supports internal opto-isolation and transistor gate drive circuits. Output execution is determined by scan cycle update timing, with discrete ON/OFF transitions controlled by internal switching latency characteristics.

Each of the 16 channels is organized in a single output group, enabling consolidated return reference architecture. DC sourcing topology allows external field loads to be energized directly from the module output transistor stages, with switching governed by PLC logic state updates rather than mechanical relay action.

Thermal behavior is defined by per-point and total module dissipation limits, requiring thermal derating under elevated ambient conditions to maintain semiconductor junction stability.

Frequently Asked Questions (FAQ)

Q: Can the 1746-OB16 be hot-swapped while the SLC 500 rack is powered?
A: Hot-swapping is not specified. Standard practice requires system power removal before module insertion or removal to avoid backplane disturbance.

Q: Does backplane current change with output load activity?
A: No. The module consumes a fixed 0.28 A @ 5 VDC from the backplane independent of output switching state.

Q: What limits the maximum output switching speed?
A: Switching is constrained by internal transistor response and PLC scan cycle timing, with typical delays in the sub-millisecond range depending on load conditions.

Field Installation Guidelines

Install the module into an SLC 500 rack slot with correct backplane alignment to ensure full connector seating. Use the removable terminal block for field wiring termination, ensuring consistent torque application to prevent intermittent contact under DC switching load.

Maintain separation between DC output wiring and high-voltage conductors to reduce capacitive coupling across output channels. Grouped wiring should respect common reference design to prevent unintended return path interactions.

Verify load polarity and voltage range compatibility (10 to 50 V DC) before energization. Inductive loads require external suppression elements to limit voltage spikes during transistor turn-off events.