OVERVIEW

Official designation: Allen-Bradley 1778-OAC (Bulletin 1778 Series B, AC Output Module)

Role/Application: This module is an AC output component for PLC systems, converting controller signals to 120 VAC output power for driving industrial loads.

KEY SPECS SUMMARY

Power: 120 VAC

Interfaces / Ports: ISA connector

Indicators: 16 status indicators

Operating Temp: 0 to 60 degrees C

Platform / Compatibility: PLC controllers

Limit: 6A total; 2A per channel

Lifecycle: Refer to the latest manufacturer manual.

FREQUENTLY ASKED QUESTIONS

Technical Specifications:

Q: What is the maximum leakage current of a single output in the off state?

A: The maximum leakage current is 2 mA at 138 V AC, with a nominal leakage of 1 mA.

Wiring & Installation:

Q: What is the minimum required load current for the output triac switching device?

A: The triac switching device requires a minimum load current of 15 mA to ensure the circuit stays on.

Troubleshooting & Compatibility:

Q: What is the maximum current draw of the module from the I/O chassis backplane supply?

A: The module requires a maximum current of 350 mA from the plus 5 V DC output of the power supply.

Replacement & Upgrades:

Q: Is this 1778-OAC module still supported or recommended for new installations?

A: The 1778-OAC is considered End-Of-Life by the OEM, but repair services are often available.