Allen Bradley 1785-LT3 PLC-5/12 Processor Module

Product Overview

The Allen Bradley 1785-LT3, also known as the PLC-5/12 processor, functions as the central intelligence unit for 1771 Universal I/O systems. It manages complex control logic, executes high-speed data processing, and coordinates communication across multiple industrial networks. We provide this unit as 100% Brand New, original factory stock, ensuring the highest level of performance for legacy system maintenance and critical infrastructure upgrades.

Technical Specifications

The 1785-LT3 delivers high-density I/O management within a ruggedized single-slot module.

Engineering Advantages

• Optimized I/O Throughput: The 1785-LT3 offers variable baud rates for Remote I/O scanning. By utilizing the 230.4 kbits/s setting, engineers reduce rack scan times to just 3 ms, significantly improving the responsiveness of time-critical PID loops and high-speed motion triggers.

• Versatile Network Bridging: Integrated DH+ and Remote I/O channels allow the processor to operate as both a network master and a peer-to-peer node. This eliminates the need for external bridging hardware when connecting the processor to HMIs or other PLC-5 controllers.

• Rugged Memory Protection: The 6 Kiloword SRAM utilizes battery-backed protection to prevent data loss during power outages. This ensures that recipe parameters, counter values, and system states remains intact without requiring constant EEPROM burns.

• Expanded Serial Compatibility: The multi-protocol serial port (RS-232/422/423) facilitates direct connection to legacy SCADA systems, barcode readers, and serial printers. This onboard flexibility removes the cost and complexity of dedicated ASCII modules.

FAQs

• Can the 1785-LT3 handle analog-heavy applications?

  Yes. While the total I/O limit is 512, the processor supports up to 3072 max analog I/O points through block transfer programming. This makes it highly effective for water treatment and chemical processing plants requiring extensive sensor monitoring.

• What is the primary difference between the 1785-LT3 and other PLC-5 processors?

  The 1785-LT3 (PLC-5/12) targets small-to-medium applications. It offers 6KW of memory, whereas higher-tier models like the 1785-L40 provide larger memory capacities. However, it retains the full instruction set and communication flexibility of the more expensive units.

• Does this processor require a specific chassis?

  The 1785-LT3 installs into the left-most slot (Slot 0) of any 1771 Universal I/O Chassis. Ensure your power supply (e.g., 1771-P4 or P7) can provide the 2.5A current required specifically by this processor.

• How do I configure the communication baud rates?

  You set the DH+ and Remote I/O baud rates via physical DIP switches located on the side of the module. Ensure you configure these switches while the power is off to prevent communication errors during startup.