Product Overview
The Allen-Bradley 1794-ASB is a Flex I/O Remote I/O (RIO) communication adapter designed for distributed I/O architectures. This DIN rail mounted module provides a single RIO port that connects Flex I/O racks to RIO-capable controllers, including legacy Allen-Bradley PLC-2, PLC-3, PLC-5, and SLC 500 platforms, as well as modern Logix controllers and third-party devices.
The 1794-ASB supports communication rates of 57.6 Kbps, 115.2 Kbps, and 230.4 Kbps, and can host up to eight Flex I/O modules. It uses Block Transfer Read (BTR) and Block Transfer Write (BTW) instructions to exchange data with the controller, enabling flexible data packet handling.
Key Features & Benefits
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Legacy RIO Protocol: One (1) RIO port for connecting to existing RIO networks using Belden 9463 or equivalent cable.
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Multiple Data Rates: Supports 57.6, 115.2, and 230.4 Kbps to match system speed requirements.
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Expandable Capacity: Accommodates up to eight (8) Flex I/O modules for scalable distributed I/O.
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DIN Rail Mounting: Standard DIN rail installation simplifies panel integration.
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Diagnostic LEDs: Power, Adapter Active, Adapter Fault, and Local Fault indicators for quick status checks.
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Wide Temperature Range: Operates from 0 to 55 °C (32 to 131 °F) and stores from -40 to 85 °C (-40 to 185 °F).
Technical Specifications
| Parameter |
Value |
| Manufacturer |
Allen-Bradley |
| Product Type |
Remote IO Adapter |
| Part Number |
1794-ASB |
| Communication Port |
One (1) RIO port |
| Supported Protocol |
RIO |
| Data Transfer Speed |
57.6 Kbps, 115.2 Kbps, 230.4 Kbps |
| Module Capacity |
8 Modules |
| Mounting |
DIN Rail |
| Operating Temperature |
0 to 55 °C (32 to 131 °F) |
| Storage Temperature |
-40 to 85 °C (-40 to 185 °F) |
| Vibration |
5 g @ 10-500 Hz per IEC 68-2-6 |
| Operating Shock |
30 g peak acceleration, 11(+1) ms pulse width |
| Power Consumption |
330 mA @ 24V DC |
| External Power Supply |
450 mA at 24 Volts DC |
| Power Dissipation |
4.6 W @ 31.2V DC |
| Thermal Dissipation |
15.7 BTU/hr @ 24V DC |
| Enclosure |
IP20, Open Type |
| Indicators |
Power; Adapter Active; Adapter Fault; Local Fault |
| RIO Cable |
Belden 9463 or Equivalent |
| Weight |
0.38 lbs (0.17 kg) |
Industry Applications
The 1794-ASB is ideal for retrofitting or expanding legacy RIO-based systems in industries such as automotive, material handling, and process control. For example, a plant upgrading its PLC-5 system can use the 1794-ASB to integrate Flex I/O modules, extending the life of existing RIO cabling while adding new I/O points. Its daisy-chain topology allows efficient wiring in long conveyor lines.
Because the 1794-ASB supports both legacy and modern controllers, it offers a cost-effective bridge for gradual system migration without replacing all field wiring.
Installation & Setup
Mount the 1794-ASB on a standard DIN rail inside an appropriate enclosure (IP20, open type). Connect the RIO cable (Belden 9463 or equivalent) to the RIO port. Ensure a 24V DC power supply is available (nominal 24V DC, with input range 19.2-31.2V DC). Configure the communication rate (57.6, 115.2, or 230.4 Kbps) to match the scanner. Use BTR/BTW instructions in your control program to exchange data. Verify the module's diagnostic LEDs for proper operation.
Maintenance & Reliability
Regularly inspect the 1794-ASB for dust accumulation and ensure the enclosure remains clean and within the specified temperature range. Check cable connections for tightness and integrity. The module's vibration rating (5 g) and shock rating (30 g) ensure reliable operation in industrial environments. Periodic checks of the power supply voltage help prevent premature failures.
Compatibility & Integration
The 1794-ASB is compatible with Allen-Bradley legacy controllers (PLC-2, PLC-3, PLC-5), SLC 500 platforms, and modern Logix controllers. It also works with third-party devices that support RIO protocol. The adapter supports daisy-chain topology and can host up to eight Flex I/O modules. For systems using FLEX Integral analog modules, use a 1794-ASB Series D or later.
Selection Guide & Purchasing Advice
Before purchasing, verify your controller's RIO scanner compatibility and the required communication rate. Confirm the number of I/O modules you plan to connect (max 8). Ensure your enclosure meets IP20 requirements. For reliable sourcing, PLC Source PRO offers the Allen-Bradley 1794-ASB with detailed specifications and prompt support.