Some IoT definers think of edge devices as things like routers and switches.
Others think it’s the closest device to the bottom with an IP address.
Still others think it’s the gateway device connecting the whatever to the Internet.
Those devices may be on the edge of an IT concept of the world, but they’re far from the edge of the industrial world.
For me, the edge device is the device at the end of the wire; like a pushbutton, pilot light, limit switch, proximity switch, color sensor, pressure transducer, temperature transducer, …well, you get the idea. How do you get those devices onto the IIoT?
PROFINET is the backbone used to connect these devices and PROFINET devices do have IP addresses.
Here’s how these real edge devices connect:
PROFINET devices. There are devices with an inherent PROFINET port; like drives, vision systems, and RFID readers. Connect to its PROFINET port and it is connected to the IIoT.
Limit switches and other non-electronic devices. An electromechanical limit switch performs a simple task without electronics. Connect it to an I/O block with a PROFINET port and even it is connected to the IIoT.
Intelligent devices with no Ethernet inside. Believe it or not, there are electronic devices that do not have an Ethernet port. Take the lowly prox switch. It has a microcontroller but no space or cost room to include an Ethernet port. IO-Link is the perfect solution here – it uses the existing I/O wiring and the capacity of its microcontroller to send and receive digital communication for configuration and diagnostics. And, of course, you can use an IO-Link master with a PROFINET port to connect this device to the IIoT.
IO-Link is a prime example, but not the only one: PROFIBUS PA, HART, and FF for process devices can connect to the IIoT through PROFINET; as can legacy buses from the pre-Industrial Ethernet era like DeviceNet. And for all of these and more, that connectivity to PROFINET is done via proxy which is defined in the open PROFINET specification.
–Cark Henning