Flex Sensor (Bend Sensor) for Arduino, 2.2″ / 4.5″

A flex sensor (also called a bend sensor) is a thin plastic strip coated with a special conductive ink. When the sensor is flat, the ink has a set resistance. When you bend it, the conductive particles move further apart and the resistance rises. The more you bend it, the higher the resistance.

Connect it in a simple voltage divider with one resistor and your Arduino can read the bend angle on any analog pin. Fix one sensor along each finger of a glove and you can track hand movement. That makes it perfect for gesture-controlled robotic hands, wireless data gloves, sign language translation and VR/gaming controllers.

Flex sensors are a favourite for final-year engineering projects, science fairs and STEM robotics because they’re simple to use and the results are impressive.

Key Features

• Resistance increases with bending. Measure the bend angle accurately.
• Thin, light and flexible. Easy to fit on gloves, joints and wearables.
• Simple to use. One analog pin and one resistor.
• No power supply needed. It’s a passive sensor.
• Durable. Handles repeated bending cycles.
• Two sizes available: 2.2″ and 4.5″.
• Works with Arduino, ESP32, Raspberry Pi (with an ADC) and other microcontrollers.

Technical Specifications

Wiring with Arduino Uno (Voltage Divider)

Recommended resistor:

• 2.2″ sensor: 47kΩ
• 4.5″ sensor: 22kΩ

The flex sensor has no polarity, so either leg can go to 5V.

Example Arduino Code: Read Bend Angle

const int flexPin = A0;

// Calibrate these by reading the sensor flat and fully bent
const int flatValue = 520;
const int bentValue = 300;

void setup() {
  Serial.begin(9600);
}

void loop() {
  int reading = analogRead(flexPin);
  int angle = map(reading, flatValue, bentValue, 0, 90);
  angle = constrain(angle, 0, 90);

  Serial.print("Reading: ");
  Serial.print(reading);
  Serial.print("  |  Bend angle: ");
  Serial.print(angle);
  Serial.println(" degrees");
  delay(200);
}

Hold the sensor flat and note the reading, then bend it fully and note that reading. Put both values in the code to calibrate it.

Project Idea: Gesture-Controlled Robotic Hand

Fix one flex sensor on each finger of a glove. Read each one with an Arduino and map the values to servo motors on a 3D-printed robotic hand. The robot hand will copy your finger movements in real time. Add an HC-05 Bluetooth or nRF24L01 module to make it wireless.

Tips for Best Results and Long Life

• Bend in one direction only, with the printed side facing outward. Bending it the other way gives poor readings and can damage it.
• Protect the base. The joint where the pins meet the strip is the weakest point. Reinforce it with heat-shrink tubing, tape or hot glue.
• Don’t fold or crease it sharply. Smooth curves give the best readings and longest life.
• Don’t solder directly to the pins near the strip. Use female jumpers or a connector.
• Calibrate each sensor. Every flex sensor reads slightly differently.

Applications

• Data gloves and hand-tracking wearables
• Gesture-controlled robotic hands and arms
• Sign language translator gloves
• VR and gaming controllers
• Joint and posture monitoring (elbows, knees, back)
• Physiotherapy and rehabilitation devices
• Musical instruments and interactive art
• STEM and final-year engineering projects

Works Great With

• Arduino Uno R3 / Nano
• SG90 / MG996R Servo Motors
• HC-05 Bluetooth Module
• Resistor Kit
• 3D Printing Service (for robotic hand parts)

Package Includes

• 1 × Flex Sensor (2.2″ or 4.5″, depending on the option selected)