Where is the IP Address on an Allen Bradley PLC?

When dealing with Allen Bradley Programmable Logic Controllers (PLCs), it's important to understand the differences between various addressing schemes used in automation networks. Unlike other network devices, Allen Bradley PLCs do not have discrete IP addresses in the traditional sense. Instead, they use system addresses that are unique to each device within the network. This article will guide you through locating and understanding these addresses, especially for the popular MicroLogix 1100 model.

Locating the IP Address on the MicroLogix 1100

For Allen Bradley PLCs like the MicroLogix 1100, finding the IP address can be straightforward if you know where to look. Most Allen Bradley PLCs utilize graphical user interfaces (GUIs) to manage settings, including networking configurations. To find the IP address:

Connect to the MicroLogix 1100's operator interface (OI). Navigate to the Network Setup or Settings menu. Locate and select the Network Configuration option. Within this menu, you should see the IP address and other network settings.

Understanding System Addresses and Device Numbers

Allen Bradley PLC networks require more detailed addressing than simple IP addresses. Instead, each device in the network is assigned a system address that consists of several parts:

System Address: A unique number assigned to each PLC, typically in the format of hex values such as 01A2-0983-0000 or 83B3-0DC4-0000. Device Number: A unique number assigned to each module on the PLC, usually ranging from 001 to 255 for most models.

These addresses are essential for communicating and controlling devices within the network. The system address, in particular, is crucial for network identification. Each PLC and module within the network must have a unique system address to avoid conflicts and ensure reliable communication.

Setting Up Networks with Multiple Devices

When configuring Allen Bradley networks, it's important to adhere to best practices to maintain system resiliency. Here are some guidelines:

Network Resiliency: Following the recommendation, install no more than 8 devices on a single network to ensure optimal performance and redundancy. Addressing Scheme: Plan your addressing scheme carefully, ensuring that each device has a unique system address and device number. This will prevent communication issues and ensure that the network operates smoothly. Effect of Network Size: The length of the system address can vary from 2 hex digits up to 8 hex digits, depending on the number of devices in the network. A larger network may require more complex addressing to maintain order and clarity.

Conclusion

While Allen Bradley PLCs do not use traditional IP addresses, understanding the system addresses and device numbers is crucial for network management. By locating the IP address on your MicroLogix 1100 or other Allen Bradley devices, and setting up the network correctly, you can ensure reliable and efficient operation. Proper addressing and network configuration are key to maintaining a robust and error-free automation system.