I have been programming Programmable Logic Controllers (PLCs) for the last 5 years. I’ve finally decided to take some time and share the knowledge I’ve acquired over the multiple roles I had within manufacturing sites.
Arren Bradley has been my platform of choice due to the fact that I’ve received critical training focused on these controllers early on in my career.
As an Electrical Engineer, I had never taken a class on PLCs before I started working. Furthermore, I had no idea what they were. It seems that the industrial manufacturing industry is extremely secretive about the technology and has a hard time training younger individuals on their technology. However, there is a massive gap between what is industry needs in terms of individuals who know these systems and graduates coming out of universities and trade schools.
Many opportunities exist in the manufacturing sector which requires some knowledge of PLCs, HMIs, and other control related technologies.
In this first tutorial, I will be covering the process of connecting to a brand new MicroLogix 1100 PLC. This process may seem obvious, but presents quite a few challenges which I had to face many times.
Ethernet Configuration on MicroLogix 1100 PLC
Before we jump into the hardware, it’s important to verify the current settings on the processor.
Most PLCs are equipped with an LCD screen which will provide the user with information. In terms of connecting to the device, we’re looking for an IP address.
For a MicroLogix 1100 PLC, you will find this information in Advanced Settings > ENET Cfg.
Once you reach this settings page, you will be presented with information about the Physical Address (MAC), the IP as well as the Subnet Mask for the controller. For a brand new controller, the user will be presented with a screen which displays the MAC address only. It’s important to take a note of it as it will be used in BOOTP later in this tutorial.
Configuring the Port Settings of our Computer
It’s very important to get the computer settings right before you can talk to your PLC.
In case of a brand new PLC, it’s important to give our Network Card the opportunity to set the IP address based on what the PLC will supply. To do so, open the Control Panel, navigate to the Network Settings and set the IPv4 address to “Obtain an IP Address Automatically”. By selecting this option, you will be able to see the PLC through the BOOTP utility.
Once the setting takes effect, launch BOOTP from your programs and allow the computer to scan for connected devices.
Within a minute or two, you should see the PLC (by MAC address) listed within the window. Select the PLC, click “add relation” and enter an IP address of your choice. Verify that the IP was taken by the PLC by visiting the exact same screen as described above. At this point, you should see the MAC as well as the IP address in the settings screen of the PLC.
Establishing Connection through RSLinx
RSLinx is the networking communication tool for Allen Bradley hardware. It allows one to establish a connection to a PLC or any other device over Rockwell networks. Within the tool, one will find “drivers” which can be used to scan the network for miscellaneous devices.
In our case, the first step will be to connect the PLC to the computer (this step should have already been completed previously) and set the IP address of the PC to be on the same network. In my tutorial, I’ve set the IP address to be 192.168.1.40 for the PLC and 192.168.1.200 for the PC.
By adding an EtherNet/IP driver to the RSLinx software, I’m able to scan for the appropriate device and verify that a link has been established to my PLC. If there is no link, the PLC icon will be a red cross indicating that the signal is not reaching the device.
Working with RSLogix 500
RSLogix 500 is an environment which allows one to establish a connection and program PLC devices. Although newer tools (such as RSLogix & Studio 5000) have been developed by Rockwell, RSLogix 500 is still widely used within the industry. For the most part, this tool offers the same capabilities as the newer versions. However, it’s much less intuitive and creates challenges for those who aren’t accustomed to working with it.
If you’re working with a brand new controller, it will have no program loaded on it. Therefore, go into “New”, select the type of controller you’re working with (in my case it’s a MicroLogix 1100) and create a blank program.
To connect to the PLC, go into “Comms” > “System Comms”, locate the PLC of your choice and hit Download (WARNING: downloading to a PLC will mean that you’re erasing absolutely everything that’s currently on it.). If there is already a program on the PLC, you should be using the Upload button which will transfer the program from the LPC onto your computer.
You’re now Online with the controller!
Conclusion on Establishing a Connection with a MicroLogix 1100 PLC
Once you’ve gone through the process a few times, it becomes much easier working with different kinds of controllers, RSLinx, BOOTP & RSlogix 500.