Allen-Bradley 1768-L45 CompactLogix Controller with 3MB Memory

The Allen-Bradley 1768-L45 is a high-performance CompactLogix controller from Rockwell Automation, purpose-built for medium-sized control applications that demand both capability and cost-effectiveness. Above all, this controller delivers the full Logix platform experience, as it integrates a substantial 3MB of onboard memory for complex ladder logic, structured text, and function block programming. Consequently, it provides ample storage for large-scale programs, data logging, and system configurations. Furthermore, the 1768-L45 supports up to thirty (30) 1769 Compact I/O modules distributed across three (3) expansion banks, plus four (4) additional 1768 modules for enhanced functionality. As a result, this controller offers exceptional scalability and flexibility for a wide range of industrial automation tasks, including motion control, networking, and process monitoring.

Technical Specifications

The Allen-Bradley 1768-L45 combines robust processing power with versatile communication capabilities. To begin with, its core technical parameters are detailed below for a comprehensive understanding:

• Integrated Memory: 3MB (user program, data, and tag storage)

• Communication Port: One (1) fully isolated RS232 serial port

• Serial Protocol Support: DF1 Full/Half Duplex and DH485

• Maximum Serial Speed: 38.4 Kbps

• Supported I/O Modules: Up to 30 x 1769 Compact I/O modules + 4 x 1768 expansion modules

• Maximum I/O Banks: 3 local expansion banks

• Backplane Current Draw:

  • 2.0 A @ 24V DC (for controller and 1769 modules)

  • 5.6 A @ 5V DC (for 1768 modules)

  • 7.6 A @ 5.2V DC (total with both 1768 and 1769 modules)

• Power Consumption: 48.0 W maximum

• Power Dissipation: 8.3 W

• Isolation Voltage: 30V continuous (tested at 500V AC for 60 seconds)

• Recommended Programming Cable: 1747-CP3 or 1756-CP3 (right-angle to straight, 3m length)

• Optional Non-Volatile Memory: CompactFlash 1784-CF128 (sold separately)

• Enclosure Rating: Open style; Temperature Code T4 (135°C)

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

• Relative Humidity: 5% to 95% (non-condensing)

• Vibration (Operating): 10 to 500 Hz, 5G, 0.030 in. peak-to-peak

• Operational Shock: 30G; Non-operational Shock: 50G

• Dimensions (H x W x D): 131.6 x 67.4 x 121.8 mm (5.18 x 2.65 x 4.80 inches)

• Weight: Approximately 0.34 kg (11.9 oz)

• EMC Standard: CISPR 11 Group 1, Class A (industrial environment)

• Certifications: cUL-us listed (US and Canada standards)

Advanced Capabilities & System Integration

Beyond its core processing power, the Allen-Bradley 1768-L45 offers sophisticated integration features that streamline system design. For instance, it supports up to two (2) 1768 communication modules, enabling seamless connectivity to Ethernet networks via the 1768-ENBT (EtherNet/IP bridge) or 1768-EWEB (web server module) for remote monitoring and data exchange. Moreover, the embedded RS232 port provides a reliable serial link for programming, HMI communication, or legacy device integration using DF1 or DH485 protocols. In addition, the optional CompactFlash memory module (1784-CF128) allows for non-volatile program storage, facilitating easy firmware updates and program backups without a connected PC. Therefore, the 1768-L45 not only executes control logic efficiently but also serves as a versatile communication hub for mixed-network environments.

Installation & Mounting Guide

Installing the Allen-Bradley 1768-L45 is straightforward for any technician familiar with CompactLogix systems. Nevertheless, to ensure optimal performance and reliability, please follow these guidelines:

1. Chassis/Panel Mounting: First, mount the controller on a DIN rail or directly onto a panel using M4 or #8 screws. For safety, ensure the mounting surface is grounded and the system power is turned off before installation.

2. I/O Expansion Planning: Second, arrange the 1769 Compact I/O modules to the right of the controller in up to three banks. Additionally, place 1768 expansion modules to the left of the controller for communication or specialty functions. The 1768-L45 automatically detects the module configuration upon power-up.

3. Power Supply Connection: Third, verify that the power supply provides sufficient backplane current—specifically, 2.0A at 24V for the controller and 1769 modules, plus additional current for 1768 modules. Use a compatible CompactLogix power supply (e.g., 1769-PA2 or 1769-PB2).

4. Serial Communication Setup: Fourth, connect the programming cable (1747-CP3 or 1756-CP3) to the RS232 port. Furthermore, configure the serial settings (baud rate, parity, and protocol) via RSLogix 5000 software to match your host PC or HMI device.

5. Environmental Considerations: Finally, maintain the ambient temperature between 0°C and 60°C and ensure proper airflow around the controller. Keep humidity below 95% (non-condensing) and avoid exposure to excessive shock or vibration beyond the specified 5G limit.

What’s in the Box

• 1 x Allen-Bradley 1768-L45 CompactLogix Controller (3MB memory)

• 1 x Product configuration label (pre-attached)

• 1 x Installation Instructions sheet (publication 1768-IN001)

*(Please note: Programming cables 1747-CP3 / 1756-CP3 and optional CompactFlash 1784-CF128 are sold separately.)*

Frequently Asked Questions (FAQs)

Q1: How many I/O modules can the Allen-Bradley 1768-L45 support?
A: The 1768-L45 supports up to thirty (30) 1769 Compact I/O modules distributed across three (3) expansion banks, plus up to four (4) additional 1768 communication or specialty modules.

Q2: What programming cable is compatible with the 1768-L45?
A: The 1768-L45 uses either the 1747-CP3 or 1756-CP3 cable—both are right-angle connectors on the controller side and straight serial on the PC side, with a 3-meter length.

Q3: Can the 1768-L45 connect to an Ethernet network?
A: Yes, absolutely. While the 1768-L45 does not have built-in Ethernet, it supports the 1768-ENBT EtherNet/IP bridge module or the 1768-EWEB web server module as expansion options.

Q4: What is the total backplane current requirement for the 1768-L45 with 1768 and 1769 modules?
A: Specifically, the total backplane current draw is 7.6A at 5.2V DC when using both 1768 modules (5.6A at 5V) and 1769 modules (2.0A at 24V). Therefore, ensure your power supply meets this combined requirement.

Q5: Does the 1768-L45 have non-volatile memory for program storage?
A: The 1768-L45 has 3MB of integrated memory; however, for non-volatile backup, you can add the optional 1784-CF128 CompactFlash card, which stores programs and firmware independently of the controller battery.