Configured for switching 32 discrete AC load circuits in PLC-5 chassis networks, the Allen-Bradley 1771-OAN/A (1771-OAN Digital Output Module) provides direct physical/electrical execution of triac-based 80-265 VAC output states.

Catalog Identity and Spare Cross-Reference

Hardware Specifications

Backplane Bus Behavior and Firmware Flash Compatibility

The 1771-OAN exchanges I/O state over the PLC-5 1771 backplane using the parallel remote I/O scan protocol. Backplane bus communication velocity licences are not user-configurable on 1771 hardware; scan rate is fixed by the adapter module and processor type. Firmware flash compatibility is irrelevant because the module contains no field-upgradable firmware—revision A hardware is keyed electronically through the chassis jumper and processor I/O configuration file. Replacement with 1771-OAN/A requires matching the processor's electronic keying setting to avoid a major fault on power-up. Triac outputs are zero-cross switched; optical isolation separates AC load power from 5 VDC backplane logic at 1500 VAC dielectric rating.

Ordering Information

• 1 x 1771-OAN module (base unit, revision subject to stock)
• 1 x 1771 removable terminal wiring arm (ships separate on new-old-stock units)

Site Wiring and Mounting Notes

• Seat module in any free 1771-A1B or higher chassis slot with keying strip aligned
• Terminate field AC supply to the removable terminal block, 14-22 AWG copper
• Bond chassis ground bar to panel ground before applying 80-265 VAC field power
• Do not mix 120 VAC and 240 VAC group supplies unless each group is independently fed
• Allow forced-air clearance above chassis: module dissipates heat through side rails

Frequently Asked Questions

Is the 1771-OAN hot-swappable under live backplane power?

No. PLC-5 1771 I/O does not support live insertion. Remove 5 VDC backplane power and AC field power before extracting the module. Triac snubber networks retain charge after AC removal; wait 30 seconds before handling terminal block.

What is the per-point current limit versus group limit?

Each of the 32 points is rated 1.0 A max. Points are grouped 8 per group, each group limited to 2.0 A. Total module current must not exceed 8.0 A across all four groups simultaneously.

Does revision A support 277 VAC field supply?

No. Upper bound is 265 VAC RMS. Applying 277 VAC exceeds triac blocking voltage margin and voids dielectric isolation ratings between load side and backplane logic.

How is zero-cross switching timed relative to 50 Hz and 60 Hz?

Triac fires at the next AC zero crossing after the backplane logic commands ON. Turn-on delay is bounded by half-cycle: 10 ms at 50 Hz, 8.33 ms at 60 Hz. Turn-off occurs at the following zero cross after OFF command.

Can 1771-OAN share a chassis with 1771-OBD DC output modules?

Yes. Mixed AC and DC output modules occupy separate slots and draw independent field power. Backplane 5 VDC logic current is the only shared resource; total chassis backplane current must stay under the power supply rating.

What wire gauge fits the terminal block?

Terminal block accepts 14 AWG to 22 AWG stranded or solid copper, 60 deg C rating minimum. Torque terminal screws to 0.8 N·m. Loose terminations cause thermal rise and intermittent triac firing.

Is electronic keying mandatory when replacing with 1771-OAN/A?

Processor I/O configuration has keying set to exact, compatible, or disabled. With exact keying, 1771-OAN/A replaces 1771-OAN without fault. With disabled keying, any 1771 32-point AC output occupies the logical address but electrical spec must still match load.

What happens to outputs on loss of backplane 5 VDC?

Triac gates lose drive and all 32 outputs transition to OFF state regardless of AC field power presence. Outputs do not latch last state. Restoring backplane power returns control to processor scan table.