Circular Soft Potentiometer (Ribbon Sensor)

Manufactured by Spectra Symbol, these are nice little ribbon controllers (also known as 'soft potentiometers') with an adhesive backing. This shape is a circular soft potentiometer with a donut-shaped sensing region whose outer diameter is 55.96mm/2.2in and inner diameter is 35.63mm/1.4in.

There is a nominal 10K resistance across the two outer leads. The middle pin resistance with respect to either of the outer pins changes depending on where on the strip one presses. When no pressure is applied, the middle pin floats, so be sure to use some sort of weak pullup, such as 100K ohm.

To use Connect one side pin to ground via a 10K resistor in series. Connect the other side pin to your Vcc power line (3V, 5V etc) via a different 10K resistor in series. Then read the analog voltage on the center pin. It will range from 1/3 Vcc to 2/3 Vcc . Do not connect to Ground and Power directly!