QTouch

The QTouch® devices are charging a sense electrode of unknown capacitance to a known potential. The electrode is typically a copper area on a printed circuit board. The resulting charge is transferred into a measurement circuit. By measuring the charge after one or more charge-and-transfer cycles, the capacitance of the sense plate can be determined. Placing a finger on the touch surface introduces external capacitance that affects the flow of charge at that point. This registers as a touch. QTouch® microcontrollers can also be set up to detect the proximity of a finger, rather than absolute touch.

QTouch1.jpg

Signal processing in the decision logic makes QTouch® robust and reliable. False triggering due to electrostatic spikes or momentary unintentional touch or proximity is eliminated.

QTouch® sensors can drive single or multiple keys. Where multiple keys are used, each key can be set for an individual sensitivity level. Keys of different sizes and shapes can be used to meet both functional and aesthetic requirements.

Deploy in Touch or Proximity Mode
QTouch® technology can be deployed in two ways, normal or 'touch' mode and high-sensitivity or 'proximity' mode. The highly sensitive charge transfer proximity sensing is used to detect an end-user's approaching finger, and have the user interface interrupt the electronic equipment or electrical appliance to initiate a system function.

For excellent electromagnetic compatibility, QTouch® sensors use spread-spectrum modulation and sparse, randomized charging pulses with long delays between bursts. Individual pulses can be as short as 5% or less of the intra-burst pulse spacing. The benefits of this approach include lower cross-sensor interference, reduced RF emissions and susceptibility, and low power consumption.

Address False Touches and Environmental Conditions
Where several touch keys are close together, an approaching finger causes a change in capacitance around more than one key. Quantum's patented adjacent key suppression – AKS™ - uses an iterative technique to repeatedly measure the capacitance change on each key, compare the results and determine which key the user intended to touch. AKS™ then suppresses or ignores signals from all other keys, providing that the signal from the selected key remains above the threshold value. This prevents false touch detections on adjacent keys. AKS™ is selectable by the system designer.

QTouch® devices feature automatic drift compensation to account for slow changes due to ageing or changing environmental conditions. They have a dynamic range of several decades and do not require coils, oscillators, RF components, special cable or a lot of discrete parts. QTouch technology presents a simple, robust, elegant and affordable engineering solution.