1785‑L40C Allen‑Bradley PLC‑5 ControlNet Processor

1785‑L40C Allen‑Bradley PLC‑5/40C ControlNet Processor

Product Introduction

The 1785‑L40C is a ControlNet processor module from Allen‑Bradley, belonging to the well‑established PLC‑5 product series. This controller is specifically designed for applications that require high‑speed, deterministic communication over ControlNet networks. It offers 48K words of battery‑backed SRAM, ensuring program retention during power interruptions. Moreover, the 1785‑L40C supports optional EEPROM backup through memory cards such as the 1785‑ME16, ‑ME32, ‑ME64, or ‑M100. The module mounts directly into a 1771 I/O chassis, making integration seamless for existing PLC‑5 installations.

ControlNet Capability & Communication

What sets the 1785‑L40C apart is its built‑in ControlNet capability. The module features a base‑configured RJ45 connector for ControlNet network access, with a transmission rate of 5 Mbit/s. You can select network update times from 2 to 100 ms, offering fine‑tuned control over communication latency. Additionally, the 1785‑L40C supports the 1785‑CHBM ControlNet Hot Backup Cartridge, which enables automatic system failover for critical processes. This makes the 1785‑L40C an excellent choice for redundant control architectures.

Beyond ControlNet, the processor includes several other ports. There is an 8‑pin mini‑DIN connector for programming, a 3‑pin default DH+ port, and a 25‑pin D‑shell serial port. This serial channel supports selectable baud rates from 57.6 kbit/s to 230.4 kbit/s, with scan times ranging from 10 ms per rack (at 57.6 kbit/s) down to 3 ms per rack (at 230.4 kbit/s). Furthermore, the control coprocessor expansion port provides additional scalability for future system upgrades.

Technical Specifications

The 1785‑L40C delivers robust I/O handling capabilities. It supports a maximum total I/O of 2048 points in any mix, or alternatively, 2048 inputs plus 2048 outputs in a complementary configuration. The processor also manages up to 2048 analog I/O channels. In terms of system architecture, the 1785‑L40C supports up to 61 I/O chassis total, with a maximum of 32 universal remote chassis per I/O link. The program scan time is 0.5 ms per K‑word (measured in bit logic), with a typical scan time of 2 ms per K‑word.

The controller draws 3.3A of backplane current at 5V DC and dissipates a maximum of 59 BTU/hour when operational. It works with a wide range of I/O modules, including 1771, 1794, 1746, and 1791 series, covering 8‑point, 16‑point, and 32‑point configurations as well as intelligent I/O modules. For non‑volatile program storage, the optional EEPROM cards provide reliable backup without requiring continuous battery power.

Mechanical & Environmental Parameters

The 1785‑L40C is built for industrial environments. Its operating temperature ranges from 0 to 60 °C (32 to 140 °F), with a non‑condensing relative humidity of 5–95%. For storage, the module endures temperatures from –40 to 85 °C (–40 to 185 °F). In terms of mechanical resilience, the 1785‑L40C withstands a 30G operational shock and vibrates at 1G across 10–500 Hz. It has an open‑style enclosure and weighs approximately 1.42 kg (3 lbs). The module carries UL, CE, CSA, and C‑TICK certifications, ensuring compliance with global safety and electromagnetic compatibility standards.

Installation Guidelines

Installing the 1785‑L40C is a straightforward process. First, select a suitable 1771 I/O chassis and ensure the backplane is powered off. Align the processor with the slot guides and push it firmly into place until the locking tabs engage. Next, connect the ControlNet network cable to the RJ45 port for high‑speed communication. For programming, use the 8‑pin mini‑DIN connector or the 25‑pin serial port. If you are setting up a hot backup system, install the 1785‑CHBM cartridge alongside the 1785‑L40C. After all connections are made, apply power and check the status LEDs for normal operation. Always consult the product manual for detailed wiring diagrams and configuration procedures.

Packaging List

Your shipment of the 1785‑L40C includes the following items:

• One 1785‑L40C PLC‑5/40C ControlNet processor module

• One battery (installed)

• One quick start guide

• Anti‑static packaging bag

Note: ControlNet cables, programming software, and mounting hardware are sold separately. No certificates or warranty documents are included in this package.

Shipping & Delivery

All orders are shipped via FedEx, UPS, or DHL to ensure reliable and timely delivery worldwide. Tracking information is provided within 24 hours of dispatch. For urgent requirements, expedited shipping options can be arranged upon request.

Frequently Asked Questions (FAQ)

1. What is the main difference between the 1785‑L40C and the standard 1785‑L40B?
The 1785‑L40C includes a built‑in ControlNet port for high‑speed deterministic networking, while the 1785‑L40B offers four DH+/Remote I/O ports instead. Both share the same 48K memory and 2048 I/O capacity.

2. Can I use the 1785‑L40C in a redundant hot backup system?
Yes. The 1785‑L40C supports the 1785‑CHBM ControlNet Hot Backup Cartridge, which enables automatic failover to a secondary processor for mission‑critical applications.

3. What I/O modules are compatible with the 1785‑L40C?
This controller works with 1771, 1794, 1746, and 1791 series I/O modules, including 8‑point, 16‑point, and 32‑point digital modules as well as intelligent analog modules.

4. How do I program the 1785‑L40C?
You can connect via the 8‑pin mini‑DIN programming port, the 25‑pin serial port (RS‑232), or through the ControlNet network using RSLogix 5 software.

5. What are the power requirements for the 1785‑L40C?
The module draws 3.3A from the backplane at 5V DC. Ensure your chassis power supply meets this current demand. Compatible power supplies include the 1771‑P4S, ‑P6S, ‑P4S1, and ‑P6S1 series.