FSR406 | Square Force Sensor | Large-Area Pressure Pad

FSR406 Large-Area Square Force Sensor for Pressure Pad Prototyping

The FSR406 is a large square force-sensitive resistor for broad pressure pads and contact surfaces. Its larger active area is useful when force may not be perfectly centered, such as under a robot foot, seat pad, fixture plate, or interactive panel.

Like other FSR sensors, it is read as a resistance change through a voltage divider. It can connect to Arduino, ESP32, Raspberry Pi Pico, and other ADC-based controllers; the Interlink FSR406 product information is a useful reference for mechanical design limits.

Choose the FSR406 when the sensor must cover more area than a small round FSR402. It is best for detecting relative pressure states and changes rather than precision mass measurement.

Technical Specifications

Board Layout & Label Guide

• Square sensing area: Apply load across the rectangular active area.
• Flexible tail: Keep the tail free from compression and sharp bending.
• Two-wire output: Wire the sensor as a variable resistor in a divider circuit.
• ADC signal: Read the divider midpoint with a microcontroller analog input.
• Top actuator: Use a flat or compliant layer to spread force over the active area.
• Bottom support: A rigid base improves repeatability for mat or foot-pad projects.
• Calibration marks: Record unloaded and loaded ADC values after final mounting.

Application Scenarios

1. Robot Gripper Contact Detection

Use FSR406 as a thin contact pad on a robot gripper finger. The sketch reads a voltage divider and reports whether the gripper is touching an object.

const int FORCE_PIN = A0;const int CONTACT_THRESHOLD = 260;void setup() { Serial.begin(115200);}void loop() { int raw = analogRead(FORCE_PIN); bool contact = raw > CONTACT_THRESHOLD; Serial.print(“force_raw=”); Serial.print(raw); Serial.print(” contact=”); Serial.println(contact ? “yes” : “no”); delay(100);}

2. Calibrated Pressure Pad

After measuring the raw ADC values for no load and a known load, this example maps the reading to a simple 0-100 pressure percentage.

const int FORCE_PIN = A0;const int RAW_EMPTY = 40;const int RAW_FULL = 820;void setup() { Serial.begin(115200);}void loop() { int raw = analogRead(FORCE_PIN); int percent = map(raw, RAW_EMPTY, RAW_FULL, 0, 100); percent = constrain(percent, 0, 100); Serial.print(“pressure_percent=”); Serial.println(percent); delay(200);}

3. Force Event Logger

For test fixtures, log only events above a threshold so the serial output stays readable during repeated pressing or loading.

const int FORCE_PIN = A0;const int EVENT_THRESHOLD = 500;unsigned long lastEvent = 0;void setup() { Serial.begin(115200);}void loop() { int raw = analogRead(FORCE_PIN); if (raw > EVENT_THRESHOLD && millis() – lastEvent > 500) { Serial.print(“force event, raw=”); Serial.println(raw); lastEvent = millis(); } delay(20);}

Packing List

• 1 x FSR406 Film Press Sensor

FAQ

Q: Can this sensor be used as a precision scale?
A: It is best for relative force, contact, and calibrated trend measurement. Use a load cell for certified weighing.

Q: Does the output increase linearly with force?
A: No. Film force sensors are nonlinear, so project-specific calibration is important.

Q: Can I use it with Arduino or ESP32?
A: Yes. Read it through a voltage divider using an analog input on an Arduino-compatible board or an OpenELAB Sensor Shield V5 setup.

Q: What resistor value should I start with?
A: 10 kOhm is a common first test value; increase it for lighter forces and decrease it for heavier force ranges.

Q: Can I cut or fold the sensor?
A: Do not cut the active area or conductive traces. Avoid sharp folds on the tail.

Q: Why do readings drift over time?
A: Mounting pressure, sensor hysteresis, temperature, and mechanical creep can all affect readings.

Q: How should I mount it?
A: Use a flat backing plate and a consistent actuator so force is applied to the sensing area, not the tail.

Q: Is it waterproof?
A: No. Protect the film and connector from moisture, abrasion, and conductive debris.