Hm, very interesting. So it is a discrete array of printed thick-film
resistors and a 9-tap conductive switch with 'rolling' contacts.
This is not how most modern FSRs work; those use a sandwich of two
contact layers and a resistive layer. The more pressure applied, the
better (lower) the resistance gets. Yamaha's design is very interesting,
though if those rubber buttons start to dry-rot new ones might be tough to
obtain. New ones could be made (the circuit board part is almost easy) by
an injection-molding neoprene plastics place.
What values of resistance are measured for each tap?
Scott
/∗∗/
On Wed, 6 Oct 2004, David Rogoff wrote:
> Well, I looked inside the sensors (see "sensor guts.jpg" in the Files
> page), and it makes more sense. Each sensor has a divider chain of
> resistors with 9 taps that come out under the (conductive) rubber
> pad. You can see the rubber pad on the left is on its side, showing
> the angle on the underside. As you press the key harder, the pad
> makes contact with more of the taps, pulling off higher voltages.
> This explains the jumps I measured.
>
> Scott, do you know if most FSRs work like this?