Force Sensitive Resistor

Overview

FSRs are sensors that allow you to detect physical pressure, squeezing and weight. They are simple to use and low cost. This is a photo of an FSR, specifically the Interlink 402 model. The 1/2" diameter round part is the sensitive bit.

The FSR is made of 2 layers seperated by a spacer. The more one presses, the more of those Active Element dots touch the semiconductor and that makes the resistance go down.