Rotary sensors use charge transfer sensing chip to cut cost by over 60% - Embedded.com

Rotary sensors use charge transfer sensing chip to cut cost by over 60%

SOUTHAMPTON, England — Quantum Research Group has developed the QT510 QWheel integrated circuit, which it believes will cut the cost of rotary touch sensing by 60% in consumer electronic products.

In high volume, existing rotary capacitive sensors cost around US$5 but implementing a touch wheel based on the QWheel's QT sensing could cut the cost to under US$2. In many cases the technology is less expensive than mechanical equivalents, and is also more reliable.

QWheel touch wheel technology can be thought of as a 'capacitive potentiometer', where the wiper is a finger. The electrode consists of a resistive ring element placed behind the plastic panel. Three capacitive QT sensing channels are connected to this ring and the signals processed to 7-bits of absolute position. Output is via a standard SPI serial interface. No external active components are needed and the 14-pin SOIC device operates from a single 2.5V to 5V supply.

The device can be set to sense through panels up to 3mm thick, and even through gloves. 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 avoiding service or maintenance problems.

The QT510 uses spread-spectrum modulation for high immunity to external noise sources and low RF emissions. It includes drift compensation to account for slow changes due to aging or changing environmental conditions. The part will also operate in a low power mode while a proximity mode allows the device to detect hand movement up to 50mm away from the panel surface; this can be made to activate a display or product from standby, before the user even touches the product.

Applications for the QWheel technology could include menu selection, volume, lighting, position, temperature, and speed controls.

The E510 evaluation board includes an interface converter to connect it to a PC, plus display software. The E510 PCB comes fully assembled and tested ready for adhering to the supplied plastic demo panel or to the inside of the user's end product.

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