Electronic Design

Compact Capacitive Keyboard Weathers Humidity And Dust

Operating in a hostile environment—or even in a busy office—can stress a conventional keyboard's reliability. Also, trimming both cost and size can complicate a keyboard's design. That's what Cirque Corp. of Salt Lake City, Utah, faced in engineering its Pocket Keyboard, which uses capacitive technology to address these concerns. Sold by Fellowes Inc. of Itasca, Ill., it's designed for Palm and Palm-compatible PDAs.

The Pocket Keyboard's capacitive Glidepoint technology can detect the center position of a finger on the pad, determining the desired key even if the finger is touching other adjacent keys at the same time (see the figure). Also, the Pocket Keyboard uses a raised grid on its top layer to provide tactile feedback. This helps, as there is no pressure feedback like that in conventional mechanical keyboards.

This keyboard has no moving parts, so there is nothing to wear out. It has an MTBF of 1 FIT (107 hours). The ABS plastic cover is water-resistant, and the keyboard itself can operate in 100% humidity. Its operating temperature ranges from −30°C to 65°C. And, it can handle a 20 G drop.

OEM versions of the keyboard are available. The current implementation uses a serial-port interface that sends ASCII codes. Since this is the same basic technology used in most laptop cursor pads, the keyboards can be configured for positional tracking as well.

The Glidepoint technology is flexible, too. It can literally be bent around objects, so flat surfaces are no longer a requirement for use. Combined with its durability and ability to work where other capacitive and mechanical devices cannot makes the Pocket Keyboard ideal for embedded systems.

More information is available at www.cirque.com and www.fellowes.com. Or, contact Cirque at (801) 467-1100 or Fellowes at (800) 495-4545.

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