Overview
The Allen-Bradley 1785-L30B is a mid-range processor module for the PLC-5 automation platform, delivering reliable performance in legacy industrial control systems. With 32K words of user memory, this processor supports 1024 (any mix) or 1024 in + 1024 out (complementary) I/O devices. It supports installation of up to 29 racks, with 28 racks as Remote I/O racks. The module includes an integrated battery that maintains user and program data stored within the controller’s user memory when power is removed.
Key Features
- 32Kwords of user memory for program and data storage
- Two DH+/Remote I/O (Adapter or Scanner) and one serial port configurable for RS-232 and RS-422A/RS-423 standards
- Supports Remote I/O architecture with up to 28 Remote I/O racks using integrated DH+ and Remote I/O channels
- Flexible I/O support for up to 1024 mixed discrete and analog devices, or complementary 1024 input and 1024 output configurations
- Battery-backed RAM preserves program state during power loss
- Chassis-based installation in 1771 I/O frames
Technical Specifications
Key operating parameters and electrical characteristics:
- User Memory: 32K words
- Maximum Analog I/O: 1024
- Backplane Current: 2.3 Amperes at 5 Volts
- Communication Ports: 2x DH+/Remote I/O, 1x RS-232/RS-422A/RS-423 serial
- Operating Temperature: 0°C to +60°C
- Power Supply: 5V DC from backplane
- Mounting: Chassis-based in 1771 5-slot or larger frame
- Programming Software: RSLogix 5
Typical Applications
The 1785-L30B is widely deployed in:
- Legacy process control and data acquisition systems
- Motion control and sequencing applications with discrete and analog I/O
- Distributed Remote I/O networks using DH+ (Data Highway Plus)
- Manufacturing and assembly line automation
- Chemical, food processing, and utilities automation
Compatibility & Replacements
Compatible With
- Allen-Bradley 1771 Series I/O modules and chassis (5-slot or larger)
- PLC-5 automation platform
- DH+ (Data Highway Plus) network devices
- Remote I/O scanner configurations
- RS-232/RS-422A/RS-423 serial devices and DF1 protocol adapters
Replaces / Drop-In Replacement For
The 1785-L30B is compatible with other PLC-5/30 variants including Series A, C, D, and E modules. The 1768-L20B has specifications approximately half the capacity of the 1785-L30B. Verify processor series compatibility with your system integrator before ordering, as firmware revisions may affect performance.
Works With
- RSLogix 5 programming software (classic and current versions)
- DH+ communication protocol
- Remote I/O (RIO) protocol over DH+ and serial channels
- DF1 (Data Interchange Protocol) via optional serial adapter
- Ethernet interface modules (1771-A2B or similar) for network expansion
