The use of IO Link devices is growing and understanding the differences in how they operate, and interface with standard communication protocols is important.
Ethernet and DeviceNet have dominated the plant floor for years and for those looking to utilize better data as smart manufacturing evolves IO Link could be a great solution.
Let’s recap some of the design characteristics of Ethernet and DeviceNet to ensure a solid foundation of understanding is in place.
At the basic definition Industrial Ethernet is considered using ethernet in an industrial setting. Typically, this is implemented with industry specific protocols like Profinet, Ethernet/IP, Modbus, Profibus, DeviceNet, CANopen, etc…
The devices (Sensors, Actuators, Pilot Lights, etc…) that use IO-Link are not equipped to be wired directly via ethernet. They require a module to utilize data the device is projecting and convert it to a useable format that ethernet recognizes. Traditional discrete IO utilizes IO Cards for the PLC, Point IO, on machine IO Blocks, etc… Through this method only discrete data is accessed from the sensor. With IO-Link you’re able to use an IO-Link Master with Ethernet/IP and easily get advanced data from the sensors back to the controller.
DeviceNet is the closest technology to IO-Link as it directly deals with sensors. DeviceNet is a fieldbus application-level protocol which was originally developed by Rockwell Automation. The primary function of DeviceNet was combining the power and signal cable into 1 wire. This reduced the installation time and space requirements while saving costs. To fully utilize DeviceNet, you are required to adopt DeviceNet specific cables, devices, sensors, etc…
DeviceNet follows the open systems interconnection (OSI) seven-layer model which includes:
Examining the physical layer, DeviceNet is a Trunk Line / Drop Line system. There are a variety of taps or connectors to add devices and branches to the trunk line as needed. There are different types of cables (flat and round (thick/Thin)) for the trunk and drop lines. The cable you choose is determined by the application and the distances of both the trunkline and droplines.
DeviceNet operates at 125, 250, or 500 Kilobits per second. The longer the cable length required, the slower the data rate will be. DeviceNet also requires terminating resistors on each end. As you can see there are a lot of factors that go into a DeviceNet system, and it has significant limitations.
Now that we have a better understanding of Ethernet and DeviceNet we will unpack how IO Link can be used to completely change the game.
IO-Link is embedded on a variety of devices ranging from sensors, actuators, stack lights, and pilot devices. It is an open-source protocol like DeviceNet and is being adopted by most industrial sensor/actuator manufacturers. It is a communication protocol but, is not a fieldbus like DeviceNet.
IO-Link requires the devices themselves to be IO-Link capable. Most manufacturers are offer this as a standard or an optional part number for the same device. You may already have IO-Link capable devices in your facility, or you could easily exchange existing devices for an IO-Link option.
The system requires an IO-Link Master which will have a Fieldbus connection to communicate IO-Link data back to the controller. There are a variety of options from On-Machine style blocks, In-Panel distributed IO, as well as PLC cards. The IO-Link Master is a defined IO Card fr the controller.
The power of IO Link comes in its flexibility. It adds bi-directional communications to devices you would utilize for a specific application. The cable is a standard 3+ wire sensor cable and that makes converting much easier as existing wiring can be utilized.
There you have it – IO Link has its place in the industrial environment and knowing the differences between it and other protocols will help you make the best decision for your applications.
For assistance selecting and implementing IO Link devices connect with our team of experts for hands on support.