Product Overview
The Allen-Bradley 1756-L72K is a ControlLogix Logix5572 processor module engineered for demanding industrial automation environments. As part of the ControlLogix family, this processor delivers 4 MB of user memory and 0.98 MB of I/O memory, enabling complex control strategies without sacrificing performance. The conformal coating on the 1756-L72K protects the board from moisture, dust, and chemical contaminants, making it a dependable choice for harsh manufacturing floors.
With support for up to 128,000 digital I/O and 4,000 analog I/O, the 1756-L72K scales easily from mid-sized machines to large process lines. Its integrated USB 2.0 port (full speed, 12 Mbps) simplifies local programming and diagnostics, while the processor communicates seamlessly over EtherNet/IP, ControlNet, DeviceNet, Data Highway Plus, Remote I/O, and SynchLink networks.
Technical Specifications
Below are the key parameters for the Allen-Bradley 1756-L72K, ensuring you have the exact data needed for system design and integration.
| Specification |
Value |
| Manufacturer |
Rockwell Automation |
| Brand |
Allen-Bradley |
| Part Number |
1756-L72K |
| Series |
ControlLogix |
| Module Type |
Processor Module |
| I/O Memory |
0.98 MB |
| User Memory |
4 MB |
| Maximum I/O |
128,000 |
| Maximum Analog I/O |
4,000 |
| Maximum Digital I/O |
128,000 |
| Current Draw (1.2 V DC) |
5 milliamperes |
| Current Draw (5.1 V DC) |
800 milliamps |
| Power Dissipation |
2.5 Watts |
| Thermal Dissipation |
8.5 BTU per hour |
| Isolation Voltage |
30 Volts Continuous |
| Enclosure |
None (Open-Style) |
Performance & Memory Architecture
The 1756-L72K balances program capacity with data handling efficiency. Its 4 MB user memory accommodates extensive ladder logic, structured text, and function block routines, while the 0.98 MB I/O memory provides fast access to field devices. The processor manages up to 128,000 digital I/O points, which suits applications ranging from discrete manufacturing to batch processing.
The 5 milliampere draw on the 1.2 V DC rail and 800 milliamps on the 5.1 V DC rail keep power consumption modest, reducing heat load inside the control cabinet. With only 2.5 W power dissipation and 8.5 BTU per hour thermal output, the 1756-L72K contributes minimal thermal stress, easing cooling requirements and improving overall system reliability.
Real-World Applications
In automotive assembly lines, the 1756-L72K coordinates robotic cells and conveyor systems, leveraging its large digital I/O capacity to synchronize thousands of sensors and actuators. Its fast logic execution ensures precise timing, minimizing cycle delays.
For food and beverage processing, the conformal coating protects the processor from washdown chemicals and high humidity. The 1756-L72K manages batch recipes and temperature profiles with its 4,000 analog I/O channels, maintaining product quality while reducing downtime caused by environmental damage.
In oil and gas facilities, the processor integrates with third-party process and device networks via EtherNet/IP or ControlNet, enabling reliable data exchange with remote terminal units and safety systems. The 30 V continuous isolation voltage offers a buffer against transient surges, enhancing system robustness.
Installation & Setup Guidance
Mount the 1756-L72K in a ControlLogix chassis, ensuring proper seating in the slot and secure locking. Connect the 1.2 V DC and 5.1 V DC power supplies to the backplane; verify the current draws match the values above to avoid overloading the power supply. For programming, use the USB 2.0 port for direct connection to a PC running Rockwell Automation software. Always follow standard electrostatic discharge precautions during handling—the open-style enclosure leaves the board exposed.
Maintenance & Reliability
Because the 1756-L72K has no enclosure, periodic inspection for dust accumulation and physical damage is recommended. The conformal coating reduces corrosion risk, but ensure the cabinet environment remains within specified operating limits. Check the power supply voltages regularly—dips on the 5.1 V rail can cause erratic behavior. With proper care, the processor delivers long service life, minimizing unplanned downtime and lowering total ownership costs.
Compatibility & Integration
The 1756-L72K integrates with the full ControlLogix platform, including I/O modules, communication modules, and other processors. It supports EtherNet/IP, ControlNet, DeviceNet, Data Highway Plus, Remote I/O, and SynchLink networks. This broad protocol support allows the 1756-L72K to connect with legacy and modern devices, making it a versatile upgrade path for existing systems.
Selection Guide & Purchasing Advice
Before purchasing the 1756-L72K, verify your chassis slot type and power budget. Confirm that your application requires the 4 MB user memory and 128,000 digital I/O capacity; if not, consider a lower-tier processor to save cost. For new installations, check that your software version supports the Logix5572 firmware. PLC Source PRO offers genuine Allen-Bradley 1756-L72K modules with reliable availability—contact us for bulk pricing or expedited delivery options.