1785-LT2 Ser A (PU)

Allen Bradley Bulletin 1785 | LT2 PLC-5 Series PLC

Allen Bradley Bulletin 1785 | PLC-5/25 Enhanced Processor, 21k words memory, 1024 I/O capacity, Series A

The Allen-Bradley 1785-LT2 is a high-performance, enhanced programmable logic controller designed for the PLC-5 platform. Often designated as the PLC-5/25, it is engineered for mid-to-large scale industrial automation tasks that require high processing speed and expanded I/O management. It serves as the primary controller within the 1771 Universal I/O system, providing a deterministic and reliable brain for complex manufacturing and process control applications.

This Series A processor features 21,000 words of battery-backed user memory and supports a significant I/O capacity of up to 1,024 independent points. It installs into the leftmost slot of any 1771 Universal I/O chassis and can manage both the local I/O modules residing in the same rack and distributed I/O located in remote chassis via its integrated scanner capabilities. Its advanced instruction set allows for sophisticated mathematical calculations and complex data handling.

Communication flexibility is a key feature of the 1785-LT2. The front panel includes three dedicated communication channels that can be independently configured for Data Highway Plus (DH+) or Remote I/O (RIO). This allows the PLC-5/25 to participate in peer-to-peer messaging between controllers while simultaneously scanning remote I/O racks. The unit is equipped with a comprehensive set of diagnostic LEDs to provide immediate visual feedback on processor health, battery status, and network activity.

Built for continuous duty in heavy industrial environments, the module operates reliably across a temperature range of 0–60°C (32–140°F) and 5–95% non-condensing humidity. It draws 3.3A of current at 5VDC directly from the chassis backplane. The processor is designed with industrial-grade noise immunity and vibration resistance, ensuring stable operation in electrically noisy environments. It is UL listed, CSA certified, and CE compliant, meeting the essential standards for safety in global industrial machinery.

Key Specifications:

  - User Memory: 21,000 Words
  - Total I/O Capacity: 1,024 Points
  - Communication Channels: 3 (DH+ and RIO)
  - Backplane Current: 3.3A @ 5VDC
  - Platform: 1771 Universal I/O (PLC-5)
  - Series: A