Overview
The Allen-Bradley 1794-ASB2 is a Flex I/O communication adapter designed to connect distributed I/O modules to legacy Allen-Bradley controller platforms. This 24VDC-powered adapter serves as a Remote I/O (RIO) interface, converting 24VDC to 5VDC for backplane module power. The 1794-ASB2 is a two-slot variant of the 1794-ASB series, optimized for space-constrained installations requiring up to two Flex I/O modules.
Key Features
- 24VDC Input / 5VDC Backplane Output: Built-in power supply converts 24VDC to 5VDC for the backplane to power Flex I/O modules
- Two-Slot Module Capacity: The 1794-ASB2 supports only two Flex I/O modules
- Multiple Communication Rates: Supports 57.6Kbps, 115.2Kbps, and 230.4kbps communication rates
- RIO Protocol Support: Utilizes legacy RIO protocol with Belden 9463 or equivalent cables for connecting to RIO scanner
- DIN Rail Mounting: Standard DIN rail mount for panel-mounted installations
- Block Transfer Instructions: Sends and receives data via Block Transfer Read (BTR) and Block Transfer Write (BTW) instructions; packets of data may be sent simultaneously or sequentially
Technical Specifications
- Power Supply: Intended supply voltage range 11VDC–31.2VDC, including 5% ac ripple; nominal supply 24VDC
- Power Consumption: Maximum consumption 450mA from 24V DC power input
- Power Dissipation: Maximum power dissipation 4.6 Watts at 31.2V DC; thermal dissipation 15.7 BTU/hour at 31.2V DC
- Communication Rate: 57.6Kbps, 115.2Kbps, and 230.4kbps
- Module Capacity: Two Flex I/O modules
- Backplane Output: 5VDC, 640mA
- Operating Temperature: 0 to 55°C (32 to 131°F)
- Storage Temperature: -40 to 85°C (-40 to 185°F)
- Dimensions: Approximately 4 x 2 x 4 inches
- Weight: 6 ounces
- Certifications: UL Listed Industrial Control Equipment for US and Canada (File E65584); UL Listed for Class I, Division 2 Group A, B, C, D Hazardous Locations (File E194810)
Typical Applications
- Distributed I/O interfacing for PLC-2, PLC-3, and PLC-5 systems
- SLC500 remote I/O expansion
- Legacy Logix platform integration via RIO protocol
- Remote terminal and sensor networks in manufacturing facilities
- Hazardous location installations (Class I, Division 2)
- Space-constrained control panels requiring compact two-module I/O distribution
Compatibility & Replacements
Compatible With
- Allen-Bradley Legacy controllers: PLC2, PLC3, PLC5
- SLC500 automation platforms
- Modern Logix controller platforms as well as 3rd party devices and encompass partner modules
- Remote I/O (RIO) capable scanners using Belden 9463 or equivalent cable
Replaces / Drop-In Replacement For
- 1794-ASB Series A, B, C (note: ASB2 is limited to 2 slots vs. original ASB at 8 slots)
- Other legacy Flex I/O two-slot adapters in PLC-5 and SLC500 systems
- Verify your legacy controller documentation for exact compatibility before ordering
Works With
- Block Transfer Read (BTR) and Block Transfer Write (BTW) instructions in ladder logic
- RIO protocol (legacy, not PROFINET or EtherNet/IP)
- Classic RSLogix platform for PLC-5 and SLC500 programming
- Studio 5000 via legacy I/O module libraries for Logix migration
