I got a pair of these http://www.electrozone.dk/sensors/flex-force/force-sensitive-resistor-12-5mm.html force sensitive resistors.
I got it working with a pull up (tried pull down too) resistor, and it connected to an analog pin. I can read the it just fine, the problem is just that when I don't touch it, it reads 0 like it should. But as soon as I just touch it a little, it jumps up to 4-500, and adding a little pressure more it goes up to 800. After that I need to press a lot harder to make it go up, and with around 1 kg pressure on it, it is at ~950, 1.5 kg ~960.
Anything I can do to make it more linear?
Here is the link to the device's datasheet: http://www.sparkfun.com/datasheets/Sensors/Pressure/fsrguide.pdf
From the curve graph (figure 2) is seems not linear at the low force end. The datasheet goes on to tell of various ways to correct or improve on linearity/accuracy.
It seems to both rely on area and force. I tested with both just pressing with a finger, and with a dvd between to make sure it was spread more out, and both gave very close to the same result.
I haven't really planned anything yet, I only got them because I ordered another arduino and saw they were cheap on the website. So just playing around with them for now.