Allen-Bradley 1756-ON8 ControlLogix AC Digital Output Module

The Allen-Bradley 1756-ON8 is a ControlLogix chassis-based AC digital output module designed for switching low-voltage AC industrial loads. Operating across a range of 10-30 V AC, it provides 8 triac outputs arranged in two individually isolated groups of 4 points. The module is well-suited for controlling low-voltage AC solenoids, indicators, and small contactor coils within standard ControlLogix automation architectures.

Functional Operation and Output Configuration

The module uses solid-state triac switching outputs designed for low-voltage AC circuits operating between 47 Hz and 63 Hz. Output points are configured into two separate groups (4 channels per group), enabling distinct field-side AC supply connections or phase isolation between groups.

Each channel supports up to 2 A continuous load current at maximum operating temperature (60 deg C). System integrators must manage total chassis thermal dissipation, as the entire module current capacity is rated at 5 A at 30 deg C and derated to 4 A at 60 deg C.

System Integration and Wiring Accessories

The 1756-ON8 mounts directly into any slot of a standard ControlLogix 1756 chassis. It communicates across the backplane using producer/consumer technology, broadcasting output state information and diagnostic data without polling overhead.

Field connections require a dedicated 20-pin Removable Terminal Block (RTB) or a pre-wired 1492 Interface Module (IFM) cable assembly. RTBs are available in both cage-clamp (1756-TBNH) and spring-clamp (1756-TBSH) terminal styles and must be ordered separately.

Specifications

Frequently Asked Questions

Q: Can the 1756-ON8 module be used to switch 120 V AC loads? A: No, the 1756-ON8 is designed specifically for low-voltage AC applications with an operating range of 10-30 V AC. For 120 V AC switching applications, a standard 120 V AC output module such as the 1756-OA8 or 1756-OA16 should be selected instead.

Q: Are the removable terminal blocks (RTBs) supplied with the module? A: No, removable terminal blocks such as the 1756-TBNH (cage clamp) or 1756-TBSH (spring clamp) are not included with the module and must be purchased separately.