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Touch controllers support industrial apps

Posted: 28 Jan 2015 ?? ?Print Version ?Bookmark and Share

Keywords:Atmel? touch sensing? controller? sensor? industrial?

Atmel has unleashed its next-generation touch controllers that bring together two projective capacitance touch sensing technologies to boost performance in sub-optimal conditions. Aimed at consumer and automotive applications, the maxTouch U family also holds promise for bringing multi-touch and sliding operation to control panels in industrial settings, the company stated.

With the latest devices from Atmel, onscreen dirt and moisture, operation with gloved hands, and electromagnetic noise have been addressed with a combination of advanced analogue and digital signal processing.

The maXTouch mXT874U is the first sampling product in this family of touch controllers. According to the product datasheet, the controller is able to support stable 25mm-30mm finger hover tracking, 1mm passive stylus sensing, and 3.0mm glove touch. The device is also able to handle moisture on the screen while still providing reliable multi-touch detection.

The key to the maxTouch U family's capability, according to Atmel's senior director of touch marketing Binay Bajaj, is combining self- and mutual-capacitance touch capability in a single controller. "We quickly switch between the two modes," Bajaj noted, "which allows us to remove background noise."

Combining self-and mutual-capacitance brings numerous advantages, according to a presentation by Intel's senior touch technologist Geoff Walker. Self-capacitance, according to Walker, is insensitive to on-screen moisture and has the ability to project the capacitance-sensing field far enough to detect an object hovering over the touch sensor. Touching with a gloved finger, in effect, produces the equivalent of hovering at a fixed distance (thickness of the glove) and so can be sensed using self-capacitance.

But self-capacitance yields "ghosts" when more than one point is touched at the same time, and is relatively sensitive to the electromagnetic noise of LCDs. Mutual capacitance has the ability to unambiguously detect multiple touches along with offering higher noise immunity and greater touch accuracy. But it is sensitive to on-screen moisture and not as capable of handling gloves. The combination, however, allows each approach to resolve the problems of the other approach.

While the first maxTouch U products primarily target consumer and automotive applications, the industrial market should still take note. Many industrial touchscreen systems use older resistive, acoustic and IR technologies to address issues of surface contamination, gloved users and similar problems. But these technologies have limitations regarding features such as multi-touch and swiping motions that users are becoming used to in their consumer devices. "As people use capacitive touch more and more in their phones and tablets," Bajaj said, "they are wanting the same experience in their industrial controllers." Projected capacitive touch using combined self- and mutual capacitance approaches may well be the answer.

- Rich Quinnell
??EE Times

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