Allen Bradley 1785-L20B /E 1785L20B PLC- Processor 16K SRAM

The Allen-Bradley 1785-L20B is a PLC-5/20 programmable logic controller (PLC) processor designed for medium to large-scale industrial automation applications. With 16K words of user memory, Data Highway Plus (DH+), RS-232-C/422-A/423-A communication ports, and support for up to 512 I/O points, this processor provides fast execution times, extensive networking options, and high system reliability. The PLC-5 series is widely used in manufacturing, process control, and distributed industrial automation systems.

Technical Specifications

  • Manufacturer: Allen-Bradley (Rockwell Automation)
  • Model: 1785-L20B
  • Series: PLC-5/20
  • User Memory: 16K Words (Battery-backed SRAM)
  • EEPROM Program Backup Compatibility: 1785-ME16, -ME32, -ME64, -M100
  • Total I/O Capacity: 512 points (any mix of inputs/outputs)
  • Maximum Analog I/O: 512 points
  • I/O Scan Time per Rack:
    • 10 ms @ 57.6 kbps
    • 7 ms @ 115.2 kbps
    • 3 ms @ 230.4 kbps
  • Communication Ports:
    • 1 Data Highway Plus (DH+)
    • 1 DH+/Remote I/O (Adapter or Scanner Mode)
    • 1 RS-232-C/422-A/423-A Configurable Serial Port
  • Maximum I/O Chassis Supported: 13
  • Backplane Current Load: 3.3 A @ 5V DC
  • Mounting Type: 1771 I/O Chassis (left-most slot)
  • Programming Software: RSLogix 5
  • Operating Temperature: 0°C to 60°C (32°F to 140°F)

Key Features

  • High-speed processing for efficient execution of control logic
  • Supports multiple communication protocols for seamless integration into industrial networks
  • Expandable memory via EEPROM backup modules for program storage and recovery
  • Modular design for easy integration into 1771 I/O chassis
  • Remote I/O capability for distributed automation architectures
  • Reliable performance in industrial automation systems

Compatible Allen-Bradley Components

  • Allen-Bradley 1771 I/O Modules (Digital, Analog, Specialty I/O)
  • Allen-Bradley DH+ and Remote I/O Networks
  • FactoryTalk View HMI Software for real-time system monitoring
  • RSLogix 5 Programming Software
  • Allen-Bradley Power Supplies (1771 Series)

Industry Applications

  • Manufacturing and assembly automation
  • Process control in oil, gas, and chemical industries
  • Power generation and distribution control systems
  • Material handling and conveyor automation
  • Water and wastewater treatment plants

Installation & Operational Notes

  • Installs in the left-most slot of a 1771 I/O chassis
  • Ensure proper power supply compatibility for reliable operation
  • Use RSLogix 5 software for configuration, programming, and troubleshooting
  • Supports scheduled and unscheduled communication for flexible control architectures
  • Routine firmware updates and maintenance recommended for optimal system performance

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