Connecting a flex sensor to Arduino unlocks intuitive motion sensing for wearables, props, and custom controllers. This guide walks through wiring, calibration, and code patterns so you can start reading bend angles reliably.
Below is a quick reference that maps hardware options, signal behavior, and software settings you will use in most projects.
| Sensor Type | Typical Range | Interface | Recommended Resistor |
|---|---|---|---|
| Single‑point bend sensor | 90° to 180° | Voltage divider | 10 kΩ |
| Strip style flex sensor | 0–90° bend | Voltage divider | 47 kΩ |
| Multipoint bend array | Partial bend segments | Voltage divider or op‑amp | 10 kΩ to 100 kΩ |
| Capacitive bend sensor | Smooth curvature | Capacitive sensing | No resistor needed |
Selecting the Right Flex Sensor and Arduino Board
Choosing the right hardware combination affects range, sensitivity, and power usage.
Sensor options and specs
Small single‑point sensors suit finger joints, while long strip sensors work well for back or spine projects. Check the resistance curve at your expected bend angle, because not all sensors cover 0–90° linearly.
Compatible Arduino boards
Uno, Nano, and Leonardo are common for basic voltage divider readouts. For faster sampling or multiple sensors, consider the Due or ESP32, which offer more analog pins and processing power.
Wiring the Flex Sensor with a Voltage Divider
Proper wiring keeps noise low and ensures the analog read stays within the 0–Vcc range.
Voltage divider basics
Wire one sensor terminal to 5V, the other to an analog input, and place a fixed pull‑down resistor between that analog input and ground. This creates a variable voltage that the Arduino maps to bend degree.
Pinout example
Connect sensor terminal A to 5V, sensor terminal B to analog pin A0, and insert a 10 kΩ resistor between A0 and GND. Use short, twisted leads for the sensor to reduce interference.
Calibrating Readings and Mapping to Angle
Raw analog values change with temperature, supply voltage, and sensor age, so calibration is essential.
Collect baseline data
Record analog readings at known angles, such as fully flat, 45°, and 90° bends, using a consistent mounting setup.
Mapping in code
Use map() to convert your sensor range to degrees, then apply a light smooth or filter to reduce jitter during motion.
Key Takeaways and Next Steps
- Match sensor range to your project bend angle and test the actual resistance curve.
- Use a stable voltage divider with an appropriate fixed resistor for your sensor type.
- Calibrate at multiple known angles and implement filtering to handle noise.
- Secure all connections and keep wiring short to minimize interference and drift.
- Choose an Arduino board with enough analog pins and sampling speed for your number of sensors.
FAQ
Reader questions
Why does my flex sensor reading drift over time?
Drift can come from temperature changes, loose wiring, or worn conductive paths; stabilize by warming the sensor to operating temperature, securing connections, and applying a moving average filter in code.
Can I power the sensor directly from 3.3V on the Arduino?
Yes, if your sensor supports 3.3V operation; using 3.3V reduces current and noise, but you must update your calibration values and code reference to 3.3V instead of 5V.
How many flex sensors can I read with one Arduino Uno?
An Uno has 16 analog pins, so you can connect multiple sensors on separate pins; consider I2C multiplexers or a dedicated ADC if you need more channels or cleaner simultaneous sampling.
Is it better to use a voltage divider or an op‑amp circuit?
A voltage divider is simple and cheap, while an op‑amp buffer or instrumentation amp improves accuracy and loading protection for high‑impedance sensors and long cable runs.