Keypanel sensor IC detects human touch
8 May 2002
Switches, Relays & Keypads
The QT60161 digital charge-transfer ('QT') Qmatrix IC from Quantum Research is designed to detect human touch on up to 16 keys when used in conjunction with a scanned, passive X-Y matrix. According to the manufacturer, it can project the keys through almost any dielectric eg glass, plastic, stone, ceramic and even wood, up to a thickness of 5 cm or more. The touch areas are defined as simple 2-part interdigitated electrodes or conductive material, like copper or screened silver or carbon deposited on the rear of a control panel.
The key sizes can vary by a factor of 20:1 in surface area, while the sensitivity of each key can be set individually via simple functions over the SPI or UART port, for example, via Quantum's QmBtn program or from a host microcontroller. Key set-ups are stored in an onboard EEPROM and do not need to be reloaded with each power-up.
The device is designed specifically for appliances, electronic kiosks, security panels, portable instruments, machine tools or similar products that are subject to environmental influences or even vandalism. It is possible to manufacture 100%-sealed watertight control panels that are immune to humidity, temperature, dirt accumulation or the physical deterioration of the panel surface from abrasion, chemicals or abuse. To this end the device contains Quantum-pioneered adaptive auto self-calibration, drift compensation, and digital filtering algorithms that make the sensing function robust and survivable.
The IC can scan matrix touch keys over LCD panels or other displays when used with clear ITO electrodes arranged in a matrix. It does not require 'chip on glass' or other exotic fabrication techniques. Materials such as common PCB materials or flex circuits can be used for the matrix.
External circuitry consists of a resonator and a few capacitors and resistors, all of which can fit into a footprint of less than 6 cm2. Control and data transfer is via either a SPI or UART port; a parallel scan port provides backwards compatibility with scanned electromechanical keys.
For further information contact Analog Data Products SA, 011 531 1400.
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