Product Overview

The Allen-Bradley 1785-LT functions as the central intelligence for PLC-5/15 Classic control systems. This processor executes complex ladder logic, manages floating-point math, and coordinates high-speed I/O communication across the 1771 Universal I/O platform. Despite its legacy status, the 1785-LT remains a critical component for maintaining existing infrastructure in automotive, food and beverage, and material handling sectors. We provide this unit as 100% Brand New and Original, ensuring your facility secures a reliable, high-performance replacement for aging or failed CPUs.

Technical Specifications

The 1785-LT balances memory capacity with robust communication protocols to handle localized and distributed control tasks.

Engineering Advantages

• Multi-Protocol Communication: The 1785-LT integrates both Data Highway Plus (DH+) and Remote I/O (RIO) on a single standalone scanner. This architecture allows the processor to act as a local controller while simultaneously broadcasting data to an HMI or supervisory PLC across the plant floor.

• Expansion Ready: While the base unit features 6K words of SRAM, engineers can expand this to 14K words using 1785-MR or 1785-MS modules. For permanent program security, the 1785-MJ EEPROM module prevents data loss even during long-term power outages.

• Advanced Addressing Modes: This CPU supports 2-slot, 1-slot, and 1/2-slot I/O addressing. This flexibility enables high-density 32-point I/O module integration without requiring a total overhaul of the chassis layout.

• Rugged Reliability: Built for 24/7 industrial cycles, the processor handles scan times of approximately 8ms for typical programs. Its convection-cooled design requires no internal fans, reducing mechanical failure points in dusty or oily environments.

FAQs

Q: Can the 1785-LT replace a 1785-LTB or 1785-LT Series B?

A: Yes. The 1785-LT is functionally interchangeable with the LTB variant. Ensure you verify the firmware version and hardware keying (located between pins 40-42 and 54-56) before inserting the new processor into your existing 1771 chassis.

Q: What is the primary indicator of a low battery on this processor?

A: The "BATT" LED on the front panel illuminates red when the 1770-XY lithium battery voltage drops below a safe threshold. You should replace the battery while the processor remains powered on to prevent the SRAM memory from clearing.

Q: Does this processor support Ethernet communication?

A: No. The 1785-LT lacks a native Ethernet port. To connect this processor to an Ethernet/IP network, you must utilize a sidecar module or a communication bridge like the 1761-NET-ENI or a ProSoft gateway.