The QT511 is a new enhanced version of the Quantum Research QWheel chip.
The QT511 is a new enhanced version of the Quantum Research QWheel chip. The new TSSOP chip is targeted primarily at portable applications, featuring low power consumption, enhanced operation under difficult sensing conditions and adds the facility to place a button in the centre of the scroll wheel without triggering false ‘wheel’ detects. QWheel touch wheel technology is like a ‘capacitive potentiometer’, where the wiper is a finger.

The electrode consists of a simple resistive ring element placed behind the plastic panel; three capacitive QT sensing channels are connected to this ring, and the signals processed to 7bit of absolute position.

The result is output on an SPI serial interface.

The device can be set to sense through panels up to 3mm thick, and even through gloves.

The entire circuit with the electrode ring 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 is more reliable.

The QT511 is ideal for control panels in personal electronics, appliances, shaft encoders, automotive controls, or almost any consumer product where you need a knob or rotary control (brightness, volume, temperature, power, menu selection etc).

The QT511 uses a very simple circuit with no external active components or moving parts.

Unique features of the QT511 include: full self-calibration with drift compensation to compensate for slow changes due to aging or environmental conditions; ‘proximity wake up’ function detects hand movement up to 50mm away; powered by mere microamps from 2.5-5V; uses spread-spectrum signal acquisition for high immunity to external noise sources and ultralow RF emissions.

When placed behind glass or plastic, the circuit creates a smooth, sealed, nearly indestructible rotary touch control that can replace virtually any mechanical encoder or potentiometer.

It does not require a hole or knob and therefore has no service or maintenance problems.

Applications include menu selection, volume, lighting, position, temperature and speed controls.

Market sectors include consumer electronics and appliances, audio, HVAC controls, communications, toys and games, industrial controls, aerospace, military and automotive controls.

The QT511 is available from stock from Saelig at $2.38 (5000-unit).

Also available is a $95 evaluation board E510 which uses included QSlide PC software to demonstrate touch position.