Allen-Bradley PLC-5 1785-L20E Programmable Logic Controller

Overview

The Allen-Bradley 1785-L20E is a PLC-5/20E Processor Module designed for reliable control and communication within industrial automation environments. As part of the Allen-Bradley PLC-5 family, it provides Ethernet connectivity, advanced memory management, and flexible I/O configuration options, making it suitable for mid-scale automation systems requiring dependable networked control.

Built to withstand harsh operating conditions, the 1785-L20E integrates robust communication ports, high-speed processing, and wide environmental tolerance for demanding manufacturing and process control applications.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Product Line: PLC-5 Series

• Part Number: 1785-L20E

• Processor Type: PLC-5/20E

• Product Type: Programmable Logic Controller Module

• Memory Capacity: 16 Kwords of user memory

• Non-Volatile Backup: Supported with EEPROM modules (1785-ME16, 1785-ME32, 1785-ME64, 1785-M100)

• Battery Type: 1770-XYC, for memory retention

• Protected Memory: Not available

• Total I/O Capacity: 512 I/O points (any mix) or 512 inputs + 512 outputs in complementary mode

• Analog I/O Capacity: Up to 512 points

• I/O Chassis Support: Up to 13 total; 12 remote I/O chassis supported

• Local I/O Racks: Maximum of 4 (addresses 0–3)

• I/O Scan Time per Rack: 10 ms @ 57.6 kbps, 7 ms @ 115.2 kbps, 3 ms @ 230.4 kbps

• Embedded Communication Ports:

• 1 x DH+ (fixed)

• 1 x DH+/Remote I/O (adapter or scanner)

• 1 x Serial port (configurable for RS-232, RS-423, or RS-422A)

• 1 x Ethernet interface

• Backplane Current Load: 2.3 A

• Power Dissipation: 12 W typical

• Recommended Power Supplies: 1771-P4S, 1771-P6S, 1771-P4S1, 1771-P6S1

• Control Co-Processor Port: Supported

• Operating Temperature: 0°C to +60°C (32°F to 140°F)

• Storage Temperature: -40°C to +85°C (-40°F to 185°F)

• Humidity: 5% to 95%, non-condensing

• Weight: 3.13 lbs (1.42 kg)

Key Features

• Ethernet-Enabled Control: Integrates Ethernet communication for seamless network connectivity.

• Flexible I/O Management: Supports up to 512 digital and analog I/O channels for scalable automation.

• Durable Architecture: Complies with IEC 60068 environmental testing standards for temperature and shock resistance.

• Comprehensive Communication: Includes DH+, Remote I/O, and multi-protocol serial interfaces.

• Reliable Memory Retention: Battery-backed static RAM and optional EEPROM storage ensure data preservation.

• Compatible Power Options: Works with multiple 1771-series power supplies for design flexibility.

Applications

• Process control systems in manufacturing plants

• Industrial machinery automation

• Material handling systems

• Distributed control networks using ControlNet or Ethernet/IP

• Retrofit and maintenance of legacy Allen-Bradley PLC-5 installations

FAQ

Q: What is the memory capacity of the 1785-L20E processor?
A: It features 16 Kwords of user memory, expandable with external EEPROM modules.

Q: Can this processor communicate over Ethernet?
A: Yes, it has a built-in Ethernet interface in addition to DH+, Remote I/O, and serial communication ports.

Q: Which power supplies are compatible with this module?
A: It supports 1771-P4S, 1771-P6S, 1771-P4S1, and 1771-P6S1 units.

Q: Does it support ControlNet?
A: No, this model supports Ethernet and DH+ networks, not ControlNet.