How to Use Square FSR: Examples, Pinouts, and Specs

A Square FSR (Force-Sensitive Resistor) is an electronic component that changes its resistance in response to an applied force or pressure. This property makes it an invaluable sensor in a variety of applications, including touch-sensitive devices, robotics, interactive installations, and custom input devices. The FSR is simple to use and can be easily interfaced with microcontrollers such as the Arduino UNO.

• Resistance Range: Typically from a few hundred kilohms to a few ohms when pressure is applied.
• Force Sensitivity Range: Usually from a few grams to several kilograms.
• Response Time: Typically less than 1 ms.
• Operating Temperature: Usually between -30°C to 70°C.
• Active Area: The area where force can be applied, usually square in shape.

Note: The FSR is not polarized, meaning the pins are interchangeable.

To use the Square FSR in a circuit, you can create a voltage divider by connecting it in series with a pull-down resistor to the analog input of a microcontroller. Here's a simple schematic:

Vcc (5V) --- FSR --- Analog Pin --- Resistor (10kΩ) --- GND

• Calibration: Since FSRs can vary slightly, it's important to calibrate your sensor for the specific range of forces you expect in your application.
• Protection: Avoid applying excessive force that exceeds the sensor's maximum rating, as this can permanently damage the FSR.
• Stable Mounting: Ensure the FSR is mounted on a stable surface to get consistent readings.
• Avoid Sharp Objects: Sharp objects can puncture or otherwise damage the sensing area.

// Define the FSR pin and the pull-down resistor value
const int fsrPin = A0; // FSR connected to analog pin A0
const int fsrResistance = 10000; // 10kΩ pull-down resistor

void setup() {
  Serial.begin(9600); // Start serial communication at 9600 baud
}

void loop() {
  int fsrReading = analogRead(fsrPin); // Read the FSR value
  // Convert the reading to voltage
  float voltage = fsrReading * (5.0 / 1023.0);
  // Calculate the resistance of the FSR
  float fsrR = 5.0 / voltage - 1.0;
  fsrR = fsrResistance * fsrR;
  // Print the resistance value
  Serial.println("FSR Resistance: " + String(fsrR) + " ohms");
  delay(500); // Wait half a second before reading again
}

Note: The above code assumes a 5V supply from the Arduino UNO. Adjust the voltage in the code if using a different supply voltage.

• Inconsistent Readings: Ensure that the FSR is mounted on a stable surface and that connections are secure.
• No Change in Resistance: Verify that the FSR is properly connected in the circuit and that there are no breaks in the circuit path.
• Damaged FSR: If the FSR has been subjected to excessive force or sharp objects, it may be damaged and need replacement.

Q: Can I use the FSR with a 3.3V system? A: Yes, but you will need to adjust the voltage reference in your code accordingly.

Q: How do I calibrate the FSR for my application? A: Apply known weights or forces to the FSR and record the resistance or voltage changes. Use these values to create a calibration curve or table for your application.

Q: What is the lifespan of an FSR? A: The lifespan depends on the application and how frequently the FSR is used. In general, FSRs can withstand thousands to millions of actuations.

Q: Can I connect multiple FSRs to a single microcontroller? A: Yes, you can connect multiple FSRs to different analog pins on a microcontroller. Remember to use separate pull-down resistors for each FSR.

For further assistance or technical support, please contact the supplier or manufacturer of your Square FSR.