Device Connection Technology: An IOpener

By Joe Feeley, Editor in Chief

We might want to pay a little attention to a device connection technology that's largely unknown to North American machine builders.

IO-Link is a vendor-neutral sensor/actuator connection system supported by a consortium (www.io-link.com) of about 50 well-known automation suppliers. More familiar to Europe, it's been around for about five years—having spawned from the Profibus organization, which manages it—and is seeking support in the IEC standards organizations.

IO-Link touts simplified installation, automated parameter setting and expanded diagnostics, providing a universal communication scheme between a fieldbus network and intelligent I/O at the lower wiring levels. Profibus International's Carl Henning describes it as HART for discrete.

It requires no special or additional wiring, using a standard three-wire interface and unshielded cables. IO-Link-enabled sensors and binary sensors can connect to the same IO-Link module.

John Burns, Siemens Industry product manager for IEC communications products, pointed out how IO-Link provides configuration and diagnostic value at a recent Chicago event touting Siemens' new Innovations line of Sirius modular components for switching, starting, protecting and monitoring motors.

IO-Link is not another AS-i bus. It's point-to-point wiring, directly integrated in the sensor, and needs no special cables or sensor addressing.

There's not much deployment evidence being offered, but an example from IO-Link is a tire production application with automatic parameter setting using IO-Link. If a color sensor reports a defect during production, it can be replaced easily. The new color sensor gets its parameters from the PLC or a data server while the machine is still running.

Without such diagnostics, the machine produces and then stops suddenly because of a totally contaminated color sensor. Or changing tire color, for example, would mean stopping the machine, since the color sensor can't be reprogrammed during run time.

IO-Link might be a reminder that it's not inevitable that Ethernet's ubiquity will spread even to the lowest device level communications. It can be attractive to those who like point-to-point, but need more flexible configuration and device diagnostics.

This technology might be inviting, but the support will have to broaden. IO-Link masters are limited to Profibus/Profinet, although I hear that CC-Link and EtherNet/IP will have masters "soon." It also doesn't anticipate adding the ability to transmit safety-relevant data such as e-stop commands.

The big hurdle is user acceptance, so automation suppliers that genuinely push IO-Link eventually will have to demonstrate a full range of supported devices.

 Attractive to those who like point-to-point, but need more flexible configuration and device diagnostics.