Southampton,UK Quantum Research Group has released enhanced versions of its QSlide and QWheel chips, known as the QT411 and QT511 respectively. The devices, which are available in TSSOP packages, are targeted primarily at portable and home appliance applications and feature lower power consumption, enhanced operation under difficult sensing conditions and the facility to place a mechanical button in the centre of the scroll wheel (QT511) without the wheel reporting an unintended touch. Both chips feature a user-selectable sleep time to reduce power consumption to as low as 20 µA in idle mode. Improved performance under rapid temperature cycling makes the devices useful in kitchen appliances such as microwave ovens and washing machines. The electrodes required for operation consist of either a simple resistive linear strip (QT411) or ring (QT511) behind a plastic or glass panel. Three connections are made to the sensing element and signals are processed to provide 128 points of absolute resolution. Output is via an SPI serial interface.
The QT411 and QT511 sense through panels up to 3 mm thick and can even work through gloves. The entire circuit with the electrode ring or strip can be fabricated on a single-sided PCB for very low cost. In many cases the technology is less expensive than mechanical equivalents, and in all cases it is more reliable. Circuits are simple, with no external active components or moving parts. Both chips feature self-calibration over life with automatic drift compensation, operate from a 2.5 – 5 V supply, and use spread-spectrum signal acquisition for high noise immunity and low RF emissions. The devices enable the creation of smooth, sealed and extremely rugged touch controls that can replace virtually any mechanical encoder or potentiometer. Panels no longer need holes or knobs, so there are no service or maintenance problems. Applications include menu selection, volume, lighting, position, temperature and speed controls. The QT411 and QT511 are available now. The QT411 costs $1.07 and the QT511 $1.28 each, in 100,000+ quantities. Evaluation boards are available for both parts.
Quantum Research Group Ltd , Southampton,UK. www.qprox.com.