# FSR Tutorial!

What is a Force Sensitive Resistor?

FSRs are sensors that allow you to detect physical pressure, squeezing and weight. They are simple to use and low cost.

FSR's are basically a resistor that changes its resistive value (in ohms) depending on how much its pressed. These sensors are fairly low cost, and easy to use but they're rarely accurate. They also vary some from sensor to sensor perhaps 10%. So basically when you use FSR's you should only expect to get ranges of response. While FSRs can detect weight, they're a bad choice for detecting exactly how many pounds of weight are on them.

However, for most touch-sensitive applications like "has this been squeezed or pushed and about how much" they're a good deal for the money!

Some basic stats

These stats are specifically for the Interlink 402, but nearly all FSRs will be similar. Checking the datasheet will always illuminate any differences

• Size: 1/2" (12.5mm) diameter active area by 0.02" thick (Interlink does have some that are as large as 1.5"x1.5")
• Price: \$7.00 from the Adafruit shop
• Resistance range: # Infinite/open circuit (no pressure), 100K ohms (light pressure) to 200 ohms (max. pressure)
• Force range: Force range: 0 to 20 lb. (0 to 100 Newtons) applied evenly over the 0.125 sq in surface area
• Power supply: Any! Uses less than 1mA of current (depends on any pullup/down resistors used and supply voltage)
• Datasheet (note there are some mathematical inconsistencies in here)

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sumit0001 year ago
why you are dividing fsrconductance by 80 and in else part by 30.

(if (fsrConductance <= 1000) {
fsrForce = fsrConductance / 80;
Serial.print("Force in Newtons: ");
Serial.println(fsrForce);
} else {
fsrForce = fsrConductance - 1000;
fsrForce /= 30;
Serial.print("Force in Newtons: ");
Serial.println(fsrForce);

kindly Explain this part of the code..
cdragos george1 year ago
very good tutorial about how to interface a force sensor. also, I add this tutorial in my article about force sensors
burnerjack013 years ago
Curious if once calibrated at zero, 1/3,2/3 and full scale, do these devices hold as far as remaining consistent?
With low linearity, what was the application these were designed for?
ermitanio5 years ago
A very interesting Instructable. Thanks
rimar20005 years ago
Very interesting!