Introduction
Industrial automation relies on many small but essential components working together to control machines, processes, and systems efficiently. At the heart of this automation are I/O modules, which act as the bridge between a PLC and real-world devices such as motors, lamps, valves, and heaters. While PLCs handle logic and decision-making, I/O modules are responsible for turning those decisions into physical actions.
One such important module is the Allen-Bradley 2085-OA8, which belongs to the Micro800 family of automation products from Allen-Bradley. This output module plays a key role in switching AC-powered devices safely and reliably.
The purpose of this blog is to clearly explain what the 2085-OA8 is, how it works inside a control system, and where it is commonly used in real industrial applications.
What Is the Allen-Bradley 2085-OA8?
The Allen-Bradley 2085-OA8 is an 8-point digital AC output module designed for use with Micro800 PLC systems. In simple terms, it allows a PLC to control up to eight AC devices by switching them ON or OFF based on the logic program.
This module uses Triac-based outputs, which are solid-state electronic switches specifically suited for AC voltage. Unlike mechanical relays, Triacs have no moving parts, making them faster and more durable for frequent switching.
The 2085-OA8 is fully compatible with Micro850 PLCs and connects seamlessly to the Micro800 expansion system. Once installed, the PLC sends commands to the module, and the Triacs respond by allowing AC voltage to flow to the connected device, turning it on when required.
Key Technical Specifications
| Parameter | Specification |
| Model Number | 2085-OA8 |
| Module Type | Digital AC Output Module |
| Number of Outputs | 8 Channels |
| Output Technology | Solid-State (Triac) |
| Rated Output Voltage | 120–240V AC |
| Output Current Capacity | Moderate load current per channel (supports inrush current during startup) |
| Surge Current Capability | Suitable for short-duration inrush currents |
| Electrical Isolation | Yes, between field wiring and PLC electronics |
| Mounting Method | DIN-rail or Panel Mount |
| Form Factor | Compact design for space-efficient control panels |
| Operating Environment | Industrial-grade construction |
| Compliance & Certifications | UL, CE, and other standard industrial certifications |
How the 2085-OA8 Works in a Control System
In a typical control system, the PLC program decides when an output should turn ON or OFF. These commands are sent digitally to the 2085-OA8 module.
Inside the module, Triac outputs act as electronic switches. When activated, a Triac allows AC current to pass through to the connected device. When deactivated, it blocks the current, turning the device off.
Correct wiring and proper load selection are essential. Resistive loads, such as heaters or lamps, are straightforward and ideal for this module. Inductive loads, like solenoids or valves, can also be used but may require additional protection to manage electrical noise and inrush currents.
Where Is the Allen-Bradley 2085-OA8 Used?
The 2085-OA8 is commonly used in industries where AC-powered devices are standard. Many industrial environments prefer AC outputs because they integrate easily with existing infrastructure and field equipment.
AC output modules are especially popular in facilities where devices operate at higher voltages and where solid-state switching improves reliability and reduces maintenance needs.
Common Applications
This module is widely used in:
- Packaging and material handling machines to control actuators and indicators
- HVAC systems and building automation for switching fans, dampers, and heaters
- Industrial lighting and signal lamps on production floors
- Solenoids, valves, and small heaters in process automation
- OEM machine panels built around Micro850 PLCs
These applications benefit from reliable AC switching and compact system expansion.
Why Choose the 2085-OA8 for Automation Projects?
Compared to relay-based outputs, the 2085-OA8 offers silent operation, faster response times, and longer service life due to its solid-state design. Unlike DC output modules, it directly controls AC loads without additional interface devices.
The module allows easy expansion of Micro850 systems without the need for extra power supplies. Its balance of performance, reliability, and cost makes it a cost-effective solution for small to mid-size automation projects where AC control is required.
Important Installation and Usage Considerations
Each output has defined current limits, and exceeding them can damage the module. Proper load sizing is critical.
Because Triac outputs allow a small leakage current even when OFF, very sensitive devices may appear partially energized. This is normal and can be managed with proper load selection.
The 2085-OA8 is not suitable for high-current or heavy motor loads. In such cases, interposing relays or contactors should be used.
Always follow standard safety practices, including correct grounding, proper fusing, and adherence to wiring guidelines.
Comparison With Similar Micro800 Output Modules
Compared to relay output modules, the 2085-OA8 offers faster switching and longer life but lacks mechanical isolation.
Compared to DC output modules, it is specifically designed for AC voltage and cannot control DC loads.
Choosing the right output module depends on voltage type, load current, switching frequency, and application requirements.
Conclusion
The Allen-Bradley 2085-OA8 is a reliable 8-channel AC output expansion module designed for Micro850 PLC systems. It provides safe, efficient control of AC devices across many industries.
Its popularity comes from its solid-state design, compact size, and seamless integration into Micro800 systems. For engineers, OEMs, and system integrators, the 2085-OA8 offers a dependable solution for expanding AC output capacity without complexity.
FAQs
1. What type of output does the Allen-Bradley 2085-OA8 use?
It uses solid-state Triac-based AC outputs designed for 120–240V AC loads.
2. Can the 2085-OA8 be used with MicroLogix or CompactLogix PLCs?
No, it is designed specifically for Micro850 PLCs in the Micro800 family.
3. What loads are best suited for the 2085-OA8 module?
Resistive loads like lamps and heaters, and light inductive loads such as solenoids.
4. Is the 2085-OA8 suitable for inductive loads like solenoids?
Yes, but proper protection and correct sizing are recommended.
5. What is the difference between the 2085-OA8 and relay output modules?
The 2085-OA8 uses solid-state Triacs, while relay modules use mechanical contacts.
Reach Us
Asteam Techno Solutions Pvt. Ltd. is AVEVA (Formerly Wonderware) Registered System Integrator providing sale/service/support and executing the HMI/SCADA, Historian/MES Solutions to End-user & OEM/System Integrator community for their diverse needs.
