How to Use Basic Force Sensing Resistor (FSR): Examples, Pinouts, and Specs

A Force Sensing Resistor (FSR) is a type of variable resistor that changes its resistance based on the amount of force or pressure applied to its surface. When no force is applied, the FSR exhibits a very high resistance, but as pressure increases, its resistance decreases. This makes it an ideal component for detecting and measuring force or pressure in a variety of applications.

• Touch-sensitive devices: Used in touchpads, musical instruments, and interactive displays.
• Pressure detection: Common in medical devices, such as pressure-sensitive mats or gloves.
• Robotics: Enables robots to sense and respond to physical interactions.
• Gaming peripherals: Used in pressure-sensitive buttons or controls.
• Wearable technology: Integrated into smart clothing for activity tracking.

Below are the key technical details for a typical Basic Force Sensing Resistor (FSR):

The FSR typically has two pins, which are used to connect it to a circuit. Below is a description of the pins:

1. Basic Circuit Setup:

   • Connect one pin of the FSR to a voltage source (e.g., 5V).
   • Connect the other pin to ground through a pull-down resistor (typically 10 kΩ).
   • The voltage at the junction between the FSR and the resistor can be read as an analog signal, which varies with the applied force.

2. Reading the Signal:

   • The voltage across the pull-down resistor increases as the resistance of the FSR decreases (with more force applied).
   • This voltage can be read using an analog-to-digital converter (ADC) on a microcontroller, such as an Arduino.

• Calibration: FSRs are not highly precise, so calibration is necessary for accurate force measurements.
• Force Range: Avoid applying forces beyond the specified range to prevent damage.
• Mechanical Stress: Ensure the FSR is mounted securely but not under constant stress when idle.
• Temperature Effects: Be aware that temperature changes can slightly affect the FSR's resistance.

Below is an example of how to connect and read data from an FSR using an Arduino UNO:

// Define the analog pin connected to the FSR
const int fsrPin = A0; // FSR connected to analog pin A0
int fsrValue = 0;      // Variable to store the analog reading

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

void loop() {
  fsrValue = analogRead(fsrPin); // Read the analog value from the FSR
  Serial.print("FSR Value: ");
  Serial.println(fsrValue); // Print the FSR value to the Serial Monitor

  // Add a small delay to make the output more readable
  delay(100);
}

• Connect one pin of the FSR to 5V.
• Connect the other pin to both:
  • Analog pin A0 on the Arduino.
  • A 10 kΩ resistor, which is connected to ground.

1. No Response from the FSR:

   • Cause: Loose connections or incorrect wiring.
   • Solution: Double-check all connections and ensure the FSR is properly connected to the circuit.

2. Inconsistent Readings:

   • Cause: Poor contact with the FSR or environmental factors (e.g., temperature).
   • Solution: Ensure the FSR is securely mounted and calibrate the sensor for your specific application.

3. FSR Output Stuck at Maximum or Minimum:

   • Cause: The pull-down resistor value may be incorrect.
   • Solution: Use a resistor value between 4.7 kΩ and 10 kΩ for most applications.

Q: Can the FSR measure exact force values?
A: FSRs are not designed for precise force measurements. They are best used for detecting relative changes in force or pressure.

Q: How do I extend the lifespan of an FSR?
A: Avoid applying excessive force, and ensure the FSR is not exposed to extreme temperatures or humidity.

Q: Can I use an FSR with a 3.3V system?
A: Yes, FSRs are compatible with 3.3V systems, but ensure the pull-down resistor value is appropriate for the lower voltage.

Q: What is the response time of an FSR?
A: The response time is typically less than 1 millisecond, making it suitable for real-time applications.