1785‑L40B Allen‑Bradley PLC‑5 Processor Module

1785‑L40B Allen‑Bradley PLC‑5/40 Controller

Product Introduction 1785‑L40B

The 1785‑L40B from Allen‑Bradley is a standard processor module within the trusted PLC‑5 product family. This controller handles demanding automation tasks, from production lines to material handling systems. Its 48K‑word user memory provides ample space for complex logic programs, while the battery‑backed static RAM ensures data retention during power interruptions. For additional security, you can install an optional EEPROM backup (models 1785‑ME16, ‑ME32, ‑ME64, or ‑M100). This processor mounts easily into any PLC‑5 chassis, such as the 1771‑A1B, 1771‑A2B, 1771‑A3B, 1771‑A3B1, or 1771‑A4B.

Technical Specifications 1785‑L40B

The 1785‑L40B excels in both capacity and connectivity. First, it supports a maximum total I/O of 2048 points in any mix, or alternatively, 2048 inputs plus 2048 outputs in a complementary configuration. This flexibility allows you to tailor the system to your exact field device requirements. Specifically, the controller handles up to 61 I/O chassis in total, with a maximum of 32 remote chassis per I/O link. Moreover, the I/O scan time per rack is remarkably fast: 10 ms at 57.6 kbit/s, 7 ms at 115.2 kbit/s, and just 3 ms at 230.4 kbit/s. Therefore, this processor is well‑suited for time‑sensitive processes.

Communication is another strong point. The 1785‑L40B includes four built‑in DH+/Remote I/O ports, which can function as either an adapter or a scanner. Additionally, each port can operate on a separate network, enabling you to implement up to four independent DH+ or RIO networks simultaneously. For serial connectivity, there is one configurable serial port that supports RS‑232, RS‑423, and RS‑422A standards. This channel is ideal for point‑to‑point connections with programming terminals, HMIs, or other serial devices over shorter distances.

Furthermore, the controller draws a backplane current load of 3.3A and dissipates 17.3W of power. It requires a compatible power supply from the 1771‑P4S, ‑P6S, ‑P4S1, or ‑P6S1 series. The module also includes a control coprocessor expansion port for future scalability. Notably, the processor does not include protected memory, but its battery‑backed SRAM and optional EEPROM provide reliable non‑volatile storage for your programs.

Mechanical & Environmental Parameters

Environmental resilience is a key feature of the 1785‑L40B. For operating conditions, it withstands temperatures from 0 to 60 °C (32 to 140 °F), as tested per IEC 60068‑2‑1 (cold), IEC 60068‑2‑2 (dry heat), and IEC 60068‑2‑14 (thermal shock). When not in operation, the controller endures even harsher extremes, ranging from –40 to 85 °C (–40 to 185 °F) under similar IEC standards. This wide temperature tolerance makes the 1785‑L40B suitable for factory floors, outdoor enclosures, and other challenging industrial settings.

Installation Guidelines

Installing the 1785‑L40B is straightforward. Begin by selecting a suitable PLC‑5 chassis, such as the 1771‑A1B, 1771‑A2B, 1771‑A3B, 1771‑A3B1, or 1771‑A4B. Ensure the chassis backplane is powered off before insertion. Align the processor with the slot guides and firmly push it into place until the locking tabs engage securely. Next, connect the required power supply (e.g., 1771‑P4S) to the chassis. For communication, attach your DH+ or RIO cables to the appropriate ports, and use the serial port for programming or HMI links. Finally, apply power and verify the LED indicators show normal operation. Always refer to the user manual for detailed wiring diagrams and configuration steps.

Packaging List

Your shipment of the 1785‑L40B includes the following items:

• One 1785‑L40B PLC‑5/40 processor module

• One battery 1770‑XYC (installed)

• One user manual (quick start guide)

• Anti‑static packaging bag

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

Shipping & Delivery

We ship all orders via FedEx, UPS, or DHL to ensure fast and reliable delivery worldwide. Tracking numbers are provided within 24 hours of dispatch. For urgent projects, expedited shipping options are available upon request.

Frequently Asked Questions (FAQ)

1. What is the maximum I/O capacity of the 1785‑L40B?
The 1785‑L40B supports up to 2048 total I/O points in any combination, or 2048 inputs plus 2048 outputs in a complementary mode. This makes it ideal for medium‑to‑large control systems.

2. Can I use this controller with a remote I/O chassis?
Yes. The 1785‑L40B supports up to 32 remote chassis per I/O link, and you can have up to 61 chassis in total across the system. Each of its four ports can serve as a scanner for remote I/O networks.

3. What programming software is compatible with the 1785‑L40B?
This processor works with RSLogix 5 programming software. You can connect via the serial port using RS‑232 or through the DH+ network for online programming and monitoring.

4. How do I back up my program on the 1785‑L40B?
You have two options: the built‑in battery‑backed SRAM retains data during power loss, or you can install an optional EEPROM memory card such as the 1785‑ME16, ‑ME32, ‑ME64, or ‑M100 for non‑volatile storage.

5. What power supply do I need for the 1785‑L40B?
The controller draws 3.3A from the backplane. Compatible power supplies include the 1771‑P4S, ‑P6S, ‑P4S1, and ‑P6S1 series. Ensure your chassis power supply meets these current requirements.