Allen Bradley 1745-E156 I/O Expansion Unit

The Allen-Bradley 1745-E156, also cataloged as the 1745-E156 I/O Expansion Unit, operates as a dedicated hardware component for discrete signal extension within SLC 150 architecture systems.

Hardware Specifications

Backplane Bus Interconnect & I/O Density Scaling

• Determinism & Bus Execution: The 1745-E156 expansion unit connects to the primary SLC 150 controller via a ribbon cable bus, extending system I/O point capacity while executing logic scans synchronously with the main CPU.
• Firmware Flash Compatibility & Addressing: Hardware registers map directly into the base controller memory tables, allowing firmware execution without additional network protocol configuration overhead.
• Galvanic Isolation & Noise Suppression: Integrated channel optocouplers isolate backplane logic circuits from transient field noise and line surges across field terminals.

Frequently Asked Questions

Q: Can the 1745-E156 expansion unit be connected or removed while the main processor is powered?

A: No. Hot-swapping is prohibited. Master AC or DC power to the controller base unit must be disconnected before connecting or disconnecting the expansion bus ribbon cable.

Q: How is synchronization maintained between the primary SLC 150 unit and the 1745-E156 module?

A: Bus clock and frame timing pass directly through the dedicated ribbon interconnect cable, maintaining deterministic I/O updates during each processor scan cycle.

Field Installation Guidelines

• Physical Mounting & Spacing: Mount the chassis securely to the control enclosure panel using standard mounting hardware. Maintain a minimum vertical clearance of 50 mm (2 inches) above and below the housing for unhindered air convection.
• Interconnect Cable Setup: Ensure the multi-conductor ribbon bus cable is locked into the expansion headers on both the main processor and the 1745-E156 chassis prior to applying circuit power.
• Grounding & Cable Separation: Attach a low-impedance copper ground wire from the frame ground terminal directly to the central cabinet earth bus. Separate low-voltage DC lines from high-voltage AC lines by at least 200 mm to avoid inductive noise coupling.