Making a switch

  • 20-Apr-2010 03:46 EDT

Hall-effect switches are letting suppliers such as Elobau do more in a grip.

The explosion of functions provided by electronic controls continues to force the developers of manual controls to adopt new technologies. One goal is to shrink the switches so that more of them can be housed in a joystick grip or other controller. Another is to make each switch more versatile, allowing operators to alter variable parameters precisely.

For example, Elobau Sensor Technology recently unveiled the 361G grip line, which has up to nine different functions. Three Hall-effect thumbwheel controllers and six push buttons are highlighted by backlights. Reed switch contacts with backlit illumination, as well as analog linear Hall-effect push buttons with 0.5- to 4.5-V output, are also available.

The growing use of Hall-effect switches underscores an industry-wide shift away from well-established electromechanical switches. “We’re migrating away from simple resistive potentiometers, moving to Hall-effect pots with PWM or CAN output,” said Jim Hoadley, Sales Vice President at Arens Controls.

The shift to noncontact technologies also helps reduce the volume of wiring, making it possible to jam more functions into less space.

“Switches are going from high-current technologies to Hall-effect sensors that let you run fewer wires and carry less current,” said David Ross, Marketing Vice President at Otto Engineering. “Output is in the milliamp range, so you don’t have to worry about the voltage spikes you see with older switches.”

That helps reduce the generation of electromagnetic interference, which is becoming more of an issue as more electronics are used on vehicles. An equally important factor for many Hall-effect switches is that they help operators adjust the speed of actuators by altering the amount of force they use.

“In addition to simple on-off capabilities, Hall-effect switches have a linear output. When you press the button, you get an output that’s proportional to the amount of pressure,” Ross said.

While it’s possible to shrink switches to very small sizes, ergonomic engineers have to devise techniques that help operators enhance their efficiency. Squeezing too many compact controls into too small an area doesn’t meet that goal.

“The electronics are getting smaller and smaller, so overall depth can be reduced. But we’re still limited by the size of the operator’s hand,” Hoadley said. “The ability to minimize the size of electronics far exceeds the operator’s ability to push small buttons.”

The vexing issue of operator overload is being addressed in part by using software control. The shift to digital switches makes it possible to alter more performance parameters without forcing operators to push more buttons and levers. Some OEMs are using this capability to let operators adjust performance levels for their personal preferences.

“There are an increased number of items where the operator can select rates using software,” said Dan Drescher, Crawler Product Marketing Manager at John Deere. “This extends to operator-selectable rates on the joysticks in electrohydraulics. In the K-series wheel loaders, different operators can have different presets.”

Though technical issues dominate the changes in switch technology, aesthetics also come into play. The look and feel of the cab includes appearance differentiation that’s carried over to switches. Operators are in constant interaction with switches, so visual appeal helps boost their perception of quality while also adding fun-to-use characteristics.

“We’re looking at switches that are more attractive. We’re using stainless steel surfaces and doing a lot with multicolor LEDs so that when you depress a switch it changes color, for example,” said Otto's Ross.

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