Allen-Bradley 1785-L46B PLC-5/46 Standard Processor with Protected Memory

Product Overview

When your production line demands reliable control without overspending on unnecessary features, the Allen-Bradley 1785-L46B delivers a balanced solution. This PLC-5/46 standard processor combines protected memory with flexible I/O handling, helping you avoid costly downtime and unplanned upgrades. With 48K words of user memory and support for up to 2048 I/O points, it provides the processing power needed for medium-scale applications while keeping capital expenditure in check.

Technical Specifications Breakdown

The 1785-L46B offers 48 Kilowords of maximum user memory, which directly translates to the ability to store complex control programs without requiring additional memory modules. This reduces the need for frequent expansions, lowering total cost of ownership. Its maximum total I/O of 2048 (any mix) or 2048 input plus 2048 output in complementary mode gives you flexibility to match diverse field devices without oversizing the controller. The program scan time of 0.5 ms per K word (bit logic) and 2 ms per K word (typical) ensures fast logic execution, minimizing cycle times and improving throughput. I/O scan time per rack is 10 ms at 57.6 kbits/s, 7 ms at 115.2 kbits/s, and 3 ms at 230.4 mbits/s, allowing you to optimize network speed for cost-efficient data transfer.

Industry Applications

In manufacturing environments such as assembly lines, material handling, and packaging, the 1785-L46B provides reliable control for up to 61 I/O chassis, with 60 as remote racks. Its four Data Highway Plus (DH+) and Remote I/O (RIO) ports enable seamless integration with existing Allen-Bradley networks, reducing installation complexity and associated labor costs. The protected memory feature safeguards critical program data, preventing unauthorized modifications that could lead to production errors or safety incidents. By choosing this controller, you avoid the higher upfront cost of more advanced processors while still meeting performance requirements.

Installation & Setup Guidance

Install the 1785-L46B in the left-most slot of a 1771 chassis (models A1B, A2B, A3B, A3B1, A4B). Ensure the backplane current draw of 3.0 A at 5V DC is within your power supply capacity. The controller supports hardware addressing in 2-slot, 1-slot, or 1/2-slot modes, allowing you to match I/O module density to your application needs. Use the 1770-XYC battery for memory backup. For remote I/O, configure the ports as adapter or scanner mode as required. Proper installation reduces commissioning time and avoids costly rework.

Maintenance & Reliability

Routine inspection of the battery and memory modules helps prevent data loss. The 1785-L46B operates in a temperature range of 0-60 °C (32-140 °F) and 5-95% relative humidity (non-condensing), making it suitable for typical industrial environments. Its 30G shock and 1G vibration (10-500Hz) ratings ensure reliability in harsh conditions, reducing unexpected failures and maintenance costs. The protected memory feature also minimizes the risk of corruption, extending the controller's service life.

Compatibility & Integration

The 1785-L46B works with Bulletin 1771, 1794, 1746, and 1791 I/O modules, including 8-, 16-, and 32-point and intelligent modules. It supports EEPROM program backup via 1785-ME16, -ME32, -ME64, and -M100 memory modules. The serial port (RS-232-C/422-A/423-A) uses DF1 protocol. This broad compatibility allows you to reuse existing I/O investments, lowering the cost of system upgrades.

Selection Guide & Purchasing Advice

Before ordering, verify that your application requires the 48K word memory and 2048 I/O capacity of the 1785-L46B. For larger systems, consider higher-memory models. Ensure you have the correct 1771 chassis and power supply. For complete technical specifications, please contact BluePLC Industrial. Our team can help you confirm compatibility and availability, ensuring you get the right controller for your budget and performance needs.