Wireless anything brings to the table a multitude of benefits along with security and connectivity issues, which all need to be addressed. One of the most desirable features of wireless is mobility. Imagine being on the plant floor and you get a push message on your wireless HMI tablet from a programmable logic controller (PLC) whose process just went into alarm and needs immediate attention.
Push technology only works when the pushed information is present in your hands. The device in your hands can be a tablet, phone or proprietary device, but it almost has to be wireless in order to reap the benefits of mobility.
Typically, the wireless technology would be WiFi—the 802.11 wireless networking standards—at various frequencies. The handheld device would typically connect to the plantwide wireless router/switch network. Access points would be employed to extend the network to every corner of the floor to allow for messaging to get to where it needs to go 24/7.
Another option for wireless benefits is the ability to monitor and change the parameters of the process or machine being controlled. You would not want to change anything without being in front of the machine since data changes may need to be done only when the machine is in a rest state.
Should the machine be moving, an unwanted data change could provide for some exciting times.
So back to the application that I ran into. The application had 99 temperature controllers on a molding machine cell. The molds were dynamic, meaning that they moved on a carousel. The user needed the ability to change setpoints of the controller without stopping production. Normally, you would stop the carousel, connect to the controller network and change the setpoints as needed and then restart production.
This, as I understand it, was not acceptable to the operation. The controllers were not equipped to deal with wireless communications, so they employed a wireless bridge to go between the carousel and the plant floor. A wireless HMI was used to access the carousel’s network backbone to allow access to the temperature controllers, allowing for data change on the fly.
The application used a fixed HMI in a control cabinet at the site, but it could have easily been a mobile wireless tablet where the user could have changed data points from anywhere they could access the bridge.
This brings to light the need to understand wireless technology in general and who would implement this solution. Would the controls peeps set up the bridge with all the security issues being addressed, or would the IT group be tasked with the setup?
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One of the considerations may be creating a subnetwork to the main plant network, which would require a router instead of a bridge. Regardless, the security of the system would need to addressed.
Transmitting the service set identifier (SSID) of the bridge/router is a security no-no. Having credentials to log into the network is also a major requirement.
I was the main automation guy for a retail distribution center, which had mobile cranes for the automated storage and retrieval system (AS/RS). It used to run on busbars, and we changed it out for a wireless infrastructure. When it was fully completed, I discovered that the setup for the bridges wasn’t uniform and a few of the bridges transmitted the SSID out to the world.
The device on the front end of the bridge was a PLC controlling the crane. The back end connected to the plant’s wired network. I had a laptop with a wireless card, and, much to my dismay, I could directly connect to the wireless network and get online with the PLC.
An outside hacker could have connected and run havoc with the cranes and have access to the main network, which brings its own issues.
While the problem was indicated to the people who needed to know, the results could have been catastrophic. Security is a must, so, if in doubt, ask.
Wireless networks bring with ease of implementation, mobility, push technology and access to data everywhere 24/7. The caveats are interference in the air from industrial machinery and rotating devices. High-voltage systems can provide electrical issues for electronic components at any time.
Physical obstacles such as metal structures can impede signal strengths, which may cause issues in connectivity. Access point placement is paramount to create that wireless mesh for constant connectivity.
Once a wireless network is set up properly, it will serve the user well, from remote troubleshooting and data management to actual on-the-fly program changes without disturbing production.
It saves money and time. Implement wisely.
