This force-sensing resistor (FSR) from Interlink Electronics is a passive component that acts as a variable resistor, with resistance decreasing in response to increasing applied force, which makes it easy to add a touch interface to your project or create a robot with much more sophisticated tactile senses than are possible with simple lever switches. The polymer thick film (PTF) device is optimized for use in human touch control of electronic devices and can sense an applied force anywhere in the active area ranging from a few dozen grams to a few kilograms (0.2 N to 20 N).

In our tests, the resistance exceeded 1 MΩ with no applied pressure and dropped to a clearly detectable and very stable 50 kΩ with a 20 g weight placed on it. Pushing on the pad as hard as possible dropped the resistance to around 200 Ω. This resistance range is well suited to work directly with the internal pull-ups of many microcontrollers such as AVRs and PICs. The FSR was responsive enough and sensitive enough to distinctly pick up light, rapid finger taps, and it was even able to pick up the vibrations of a small vibration motor placed on it on the motor’s side.

Example applications

• Pressure-sensitive touch user interface
• Tactile sensor for robotic appendages
• Drum pad for an electronic instrument
• Alarm system sensor:
  • alert when an object is removed
  • alert when intruder steps on it