Product Overview
The Allen-Bradley 1785-L40C is a ControlNet processor module designed for the PLC-5 family of control systems. It provides a robust platform for controlling field devices through the 1771 I/O chassis, offering 48K words of battery-backed SRAM and a maximum I/O capacity of 2048 points (any mix) or 2048 inputs plus 2048 outputs in a complementary setup. This module is engineered for reliability and performance in demanding industrial environments.
Technical Specifications
Key specifications for the 1785-L40C include:
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Module Type: ControlNet Processor Module
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Processor: PLC-5/40
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Max User Memory Words: 48 Kilowords
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Battery-Backed Static RAM: Yes
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EEPROM Program Backup (using 1785-ME16, -ME32, -ME64, -M100): Yes
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Protected Memory: No
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Max Total I/O: 2048 (any mix) or 2048 in + 2048 out (complementary)
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Max Analog I/O: 2048
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I/O Scan Time Per Rack: 10 ms at 57.6 kbits/s, 7 ms at 115.2 kbits/s, 3 ms at 230.4 mbits/s
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Max I/O Chassis Total: 61
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Max I/O Chassis Extended Local: 0
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Max I/O Chassis Universal Remote: 32 per I/O link
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RS-232-C/422-A/423-A Ports: 1
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Control Coprocessor Expansion Port: Yes
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UPC: 10612598139337
Key Features & Benefits
The 1785-L40C delivers several operational advantages:
- ControlNet network capability for high-speed, deterministic control
- Large memory capacity for complex programs and data logging
- Flexible I/O configuration supports a wide range of field devices
- Battery-backed SRAM preserves program and data during power loss
- Supports hot backup via 1785-CHBM cartridge for system redundancy
Industry Applications
This processor is well-suited for applications requiring reliable, real-time control. Typical uses include:
- Manufacturing assembly lines where precise sequencing and timing are critical
- Process control systems managing analog and discrete I/O across remote racks
- Material handling systems that demand coordinated motion and interlocks
In each scenario, the 1785-L40C provides the processing power and communication flexibility needed to maintain high throughput and minimize downtime.
Installation & Setup Guidance
When installing the 1785-L40C, ensure the module is seated firmly in the 1771 I/O chassis. Connect the ControlNet network cable to the RJ45 port and verify network termination. For programming, use the 8-pin mini-DIN connector with the appropriate programming cable. Configure the processor's memory and I/O mapping using the PLC-5 programming software before commissioning.
Maintenance & Reliability
Regular inspection of the battery status is essential to maintain program retention. Check the battery voltage annually and replace it proactively to avoid memory loss. Keep the module free from dust and moisture, and ensure ambient temperature stays within 0-60°C (32-140°F) to prevent overheating. The module's robust design withstands 30G shock and 1G vibration, ensuring long service life in harsh environments.
Compatibility & Integration
The 1785-L40C integrates seamlessly with 1771, 1794, 1746, and 1791 I/O modules, including 8-, 16-, and 32-point digital and intelligent modules. It supports ControlNet communication with a transmission rate of 5 Mbps and user-selectable network update times from 2-100 ms. The built-in RS-232/422/423 serial port enables connectivity to programming terminals and other serial devices.
Selection Guide & Purchasing Advice
Before purchasing, verify that the 1785-L40C meets your system's memory and I/O requirements. Confirm compatibility with your existing chassis and power supply. If you need hot backup capability, ensure the 1785-CHBM cartridge is available. For genuine, tested automation parts, PLC Source PRO offers reliable sourcing and fast delivery to keep your operations running.