[Engineering Feature]
USB Flexes Its Industrial Strength
Lean facilities in the industrial realm looking to make even quicker changes more simply may want to consider the improved USB standard.
As PCs proliferate, their technologies become more affordable for a growing range of industrial applications. Programmable automation controllers, for example, are basically ruggedized PCs. Meanwhile, Ethernet has transformed from an office/home network to an industrial network that’s rapidly becoming the norm in factories.
USB is also extending its industrial presence. Dataacquisition systems use it for easy connections and expansion. Robots employ USB for training and setup. More sensors are now being connected with the ubiquitous interface as well.
This industrial expansion comes atop phenomenal growth. In little more than a decade, USB has become as mainstream as any consumer electronics standard. Over 2.5 billion USB devices shipped last year, and there are more than 6 million installed USB products, according to Jeff Ravencraft, chairman of the USB Implementers Forum.
Industrial designers are adopting USB for the same reasons it’s popular in consumer markets. The standard’s plug-and-play capabilities are as foolproof as any computer interface, and its bandwidth is sufficient for a huge range of applications.
“When you look at all the buses, it’s one of the easiest to implement. And USB 2.0 has more bandwidth than many of the Ethernet networks installed today,” says Brett Burger, National Instruments’ data acquisition product manager.
USB’s 480 Mbits/s is about half the speed of Gigabit Ethernet, which is gaining acceptance even though it’s still a smaller portion of the installed base in industrial, says Burger. However, versatility is far more important than speed in many industrial applications. USB gives industrial designers the freedom to add components or systems, locating them remotely from the controller.
“You can put the data-acquisition hardware up to five meters from the host,” says Mark Bohm, a system architect for SMSC. “If you need an LCD panel with an HMI (human machine interface), you can put it wherever it’s best for the operator.”
DIVERSE APPLICATIONS USB’s reach continues to grow. New applications and new products are spiraling upward together, helping extend the architecture’s role in the industrial world.
In data acquisition, USB provides an easy way to add and swap out modules as needs change. NI now has nearly 50 modules, giving engineers a number of measurement options as they build test racks (Fig. 1). These modules span NI’s CompactDAQ, Compact Field Point, CompactRIO, and Compact Flash lines, with some other chassis also providing USB connectivity.
Other instrumentation companies are also broadening their lines. More of them are taking advantage of the display and control functions in a controller to make the USB modules as compact and efficient as possible.
“Our latest DMMs (digital multimeters) and switching modules have no buttons or displays, so they have a very small form factor,” says Tee Sheffer, CEO of Signametrics Corp. “Their power consumption and heat generation are also much lower.”
Signametrics’ DMM consumes only 2 W, well below the 30 W needed for competing devices that include displays and control buttons (Fig. 2). At that level, the device can be powered over the USB wiring, eliminating the need for a power cable.
Sensors are another technology that’s constantly changing as factories evolve. Versatile connectivity helps technicians install sensors quickly when lines change or when managers want another type of measurement.
“USB is being used for a lot of general-purpose I/O like proximity sensors,” says Dan Harmon, product manager at Texas Instruments. “It works very well for products with relatively low bandwidth that are fairly close to the controller.”
In other fields, USB’s presence affords end users more freedom. In robots, the connection helps operators meet the continuing changes that come with lean manufacturing and flexible manufacturing (Fig. 3).
“Our latest robot controllers support USB interface both on the door of the controller and on the teach pendant,” says Claude Dinsmoor, general manager of product development at FANUC Robotics America Inc. “Both offer the convenience of being able to load and save robot application data and programs to any common memory device/ stick.”
The popular link provides additional benefits. “USB on the robot provides easy-to-use local backup of application files in cases where the robot is not connected to a factory network via Ethernet,” says Dinsmoor.
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