Introduction
The Allen-Bradley MicroLogix 850 and MicroLogix 1400 are integral members of the MicroLogix family, each with a long history of reliable service in industrial automation. Despite sharing a common lineage, these controllers cater to somewhat different needs and project requirements. The MicroLogix 850 is often favored for simpler control tasks with legacy compatibility, while the MicroLogix 1400 brings more advanced features suitable for moderately complex systems. This blog aims to clarify their key differences across hardware, communication, software, and application scenarios to help you choose the right controller for your specific industrial projects.
Hardware and I/O Configuration
At a glance, the Allen Bradley MicroLogix 1400 PLC offers more embedded I/O points right out of the box, with 32 fixed I/O points that include 20 digital inputs and 12 digital outputs, some of which can be relay or transistor type. It also supports limited analog inputs for finer process control.
The MicroLogix 850 has fewer embedded digital I/Os and fewer expansion options compared to the 1400, with physical design focused on compactness but less modular flexibility. The 1400’s ability to expand up to 256 I/O points makes it a compelling choice for systems requiring more extensive control over numerous devices.
Communication and Networking
Communication is another key distinction. The MicroLogix 1400 comes with a built-in Ethernet port supporting modern industrial protocols such as EtherNet/IP and Modbus TCP—essential for integration into today’s intelligent networks and SCADA systems. It also retains serial protocol support like DF1 and Modbus RTU, but notably does not include a USB port.
On the other hand, the MicroLogix 850 supports serial communication primarily with protocols like DF1 and DH-485. Ethernet support varies by model but generally leans towards older or basic Ethernet functionality. Compared to the 1400, the 850 lacks the enhanced network capabilities required for complex or connected factory environments.
Programming Software and Languages
Both controllers are programmed using the familiar RSLogix 500 software, which predominantly supports ladder logic programming. However, the MicroLogix 1400 permits faster scan times and supports more advanced instructions, including more sophisticated PID control than the 850. This allows the 1400 to manage more complex control tasks with improved efficiency.
Memory and Performance
The 1400 outperforms the 850 in available program memory—with the 1400 supporting roughly 20,000 program steps compared to around 7,000 on the 850—and offers increased data memory capacity. This means larger and more complex programs can run on the 1400 with fewer limitations. Scan speed differences further enhance the 1400’s suitability for real-time applications requiring faster processing cycles.
Application Suitability
If you're working on a small to medium automation project requiring basic input/output control and more traditional networking, the MicroLogix 850 is a cost-effective and reliable choice. It fits well in legacy plant settings where simplicity and proven performance are valued.
For medium complexity applications involving more extensive I/O needs, faster processing, and modern industrial networking—like packaging lines, assembly operations, utility monitoring, and process control—the MicroLogix 1400 comes into its own with greater versatility and future-proofing.
Additional Features & Considerations
Beyond I/O and communications, the MicroLogix 1400 includes several modern conveniences absent on the 850. It features a small, built-in LCD that allows operators and maintenance staff to view critical operational data and diagnostics without external equipment. A real-time clock enables event logging and scheduled operations, enhancing traceability and control.
The MicroLogix 850, while stable and reliable, lacks these advanced features, making it less ideal for projects requiring these newer capabilities.
Summary of Pros and Cons
Conclusion
When deciding between the MicroLogix 850 and MicroLogix 1400, consider the scale, complexity, and future growth of your automation project. The MicroLogix 850 delivers proven reliability for relatively simple control tasks with traditional networking needs. If the application demands higher I/O counts, faster processing, enhanced communication, and advanced operational features, the MicroLogix 1400 is the more capable and forward-looking solution. Thoughtful selection between these will optimize both your immediate project success and long-term operational flexibility.
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Asteam Techno Solutions Pvt. Ltd. is AVEVA (Formerly Wonderware) Registered System Integrator providing sale/service/support and execute the HMI/SCADA, Historian/MES Solutions to End-user & OEM/System Integrator community for their diverse needs. Leading single-source supplier & solution provider for industrial automation hardware and software solutions needed.
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