Force Sensor Resistor is great way for measuring pressure and force. You can buy it from NYU computer store or from Sparkfun. It is also included in ITP physical computing kit.

Application

The sensor allows one to detect and measure the change in the applied force and also the rate at which the force is changing. It could detect contact or touch. Identify force thresholds and trigger actions. Its force sensitivity is optimized for use in human touch control of electronic devices.The FSR sensors have wide usage in the commercial and industry arena. The FSR can be applied to various fields such as industry, medical science, robotics, automotive, recreational and body pressure equipment.

  • Industrial Application : Nip Roller, Robotic Grip Forces, Packaging Seals - See detail
  • Medical Application : Insulin Pump, Surgical Instruments, Neck/Back/Knee-Brace Fit - See detail
  • Dental Occlusal Analysis System - See detail
  • Recreation / Entertainment Application : Training devices, Toys & Electronic Games - See detail
  • Automotive Application : Automotive Crash Tests, Brake Pad, Airbag Force - See detail
  • Building Tap-Tile for dance or installation applications
  • Building virtual percussion instrument controllers
  • Example applications
  • And more...

Electrical Characteristics

Datasheet Download

ParameterValue
Size RangeMax : 20" x 24" / Min : 0.2" x 0.2"
Device Thickness0.008h x 0.050h
Force Sensitivity Range< 100g to > 10kg
Pressure Sensitivity Range< 1.5psi to > 150psi
Part-to-Part Force Repeatability+-15% to +-25% of established nominal resistance
Single Part Force Repeatable+-2% to +-5% of established nominal resistance
Force ResolutionBetter than 0.5% full scale
Break Force20g to 100g
Stand-Off Resistance> 1M
Switch CharacteristicEssentially zero travel
Device Rise Time1-2 msec
Lifetime> 10 million actuation
Temperature Range-30 degree Celsius to +70 degree Celsius
Maximum Current1mA/cm2 of applied force
Maximum Voltage5V
Sensitivity to NoisePassive device

How it works

Force Sensor Resistor displays a decrease in resistance with an increase in the force applied to the active surface.
FSR is composed of 3 portions ( Interlink Electronics Model No. 402 ).

  • Vent : The vent assures pressure equilibrium.
  • Spacer : The width of gap and fingers of the conductive grid.
  • Active Area : The area responds to force with decrease in resistance.
  • Tail : The area where the busing system terminates.

At first, this sensor acts like a switch. It quickly goes from not being touched to feeling the force inflicted on it. From there on it continues to document the touch and its particular force. It does reach a saturation point, where pressing harder is no longer detectable. Its a passive device since it starts out in a constant state that needs to be disrupted by the touch. It tracks the force applied to it instantly, I could not perceive a delay in the information sent. Its not affected by noise or vibration.

Microcontroller Connections & Pin Descriptions

There are two pins for a FSRs electrical access at the end of tail. Connect one pin to power (5V) and the other pin to Microcontroller.

This sensor has two solder tabs but its best to not attempt to actually solder them. Other solutions like female to male headers that are soldered to wire on the male side and have space to insert the tabs on the female side or wire wrapping work much better. One side connects to ground with a 10 k resistor and also goes to an analog input on Arduino and the other one goes to power. Connect FSR to Arduino

(Diagram made with Fritzing - download)

Code for Arduino

int fsrPin = 0; //Analog pin input for FSR on ARduino
int fsrValue = 0; //FSR values
void setup () {
  Serial.begin (9600); //Set serial boudrate to 9600
}
void loop (){
  fsrValue = analogRead(fsrPin);//reads FSR
  Serial.println (fsrValue);//prints FSR values on serial monitor
  delay (100);//delay for 100 milliseconds
}

Values that you will be receiving from FSR will change between 0-1023.

DIY FSR's

It is really easy to make your own FSR sensor. Here is a good instructables that we prepared.

This report prepared by Chang Soo Lee (11/27/05), Anaid Gomez Ortigoza, Shagun Singh and Mustafa Bagdatli(11/22/2010).