Flex Sensors with Arduino: A Guide for Makers

 If you're a maker or an electronics enthusiast looking to add sensor technology to your Arduino projects, flex sensors can be a fascinating and versatile option. In this blog post, we'll explore the basics of flex sensors and how you can interface them with an Arduino to create interactive projects that respond to changes in flex.

What are Flex Sensors?

Flex sensors, also known as bend sensors or flex/bend sensors, are devices that can detect changes in their shape or bending. They are typically made of a flexible material that changes its resistance when bent, and this change in resistance can be measured and interpreted to determine the extent of bending.

Flex sensors come in various shapes and sizes, but the most common type is the linear flex sensor, which is long and narrow, resembling a strip or ribbon. Linear flex sensors are often used in applications where the bending direction needs to be precisely controlled, such as in robotics, gaming, virtual reality, or wearable devices.

Flex Sensors with Arduino 

Arduino, an open-source electronics platform, provides an ideal platform for interfacing with flex sensors. With its easy-to-use hardware and software ecosystem, Arduino allows you to quickly and easily connect and program flex sensors to create interactive projects.

Here's a step-by-step guide on how to interface a linear flex sensor with an Arduino:

Step 1: Gather Materials

You will need the following materials for this project:

• Arduino board (such as Arduino Uno or Arduino Nano)
• Linear flex sensor
• 100KOhm resistor
  
• Breadboard
• Jumper wires
• Multimeter (optional, for measuring resistance)

Step 2: Connect Flex Sensor to Arduino

Following shows the circuit diagram of connecting flex sensor with Arduino.

• Place the flex sensor on the breadboard, and connect one end of the flex sensor to the 5V pin on the Arduino board using a jumper wire.
• Connect the other end of the flex sensor to the A0 analog pin on the Arduino board using a jumper wire.
• Connect one leg of a 100k ohm resistor to the A0 pin, and connect the other leg to the ground (GND) pin on the Arduino board.
• Use additional jumper wires to connect the VCC and GND pins on the Arduino board to the respective rails on the breadboard for power and ground.

 Step 3: Upload Code to Arduino

• Open the Arduino IDE (Integrated Development Environment) on your computer.

• Write or copy and paste the following code into the Arduino IDE:

 Let's break down the code step by step:

• int flexPin = A0;: This line declares a variable named flexPin and assigns it the value A0. A0 refers to the analog input pin on the Arduino board to which the flex sensor is connected. This pin will be used to read the analog values from the flex sensor.

• int flexVal = 0;: This line declares a variable named flexVal and initializes it with the value 0. This variable will be used to store the analog value read from the flex sensor.

• void setup(): This is the setup function in Arduino, which runs once when the Arduino is powered on or reset.

• Serial.begin(9600);: This line initializes the serial communication between the Arduino board and the computer at a baud rate of 9600. This allows you to send and receive data between the Arduino and the computer through the serial monitor for debugging and monitoring purposes.

• pinMode(flexPin, INPUT);: This line sets the flexPin as an input pin, indicating that the flex sensor is connected to this pin and will be used to read analog values.

• void loop(): This is the loop function in Arduino, which runs repeatedly after the setup function.

• flexVal = analogRead(flexPin);: This line reads the analog value from the flexPin using the analogRead() function and stores it in the flexVal variable. The analogRead() function converts the analog voltage from the flex sensor into a digital value ranging from 0 to 1023.

• flexVal = map(flexVal, 200, 1023, 0, 1023);: This line maps the analog value of flexVal from the range of 200 to 1023 to a new range of 0 to 1023. This is done using the map() function, which scales the values from one range to another.

• Serial.print("Flex: ");: This line prints the text "Flex: " to the serial monitor.

• Serial.println(flexVal);: This line prints the value of flexVal to the serial monitor followed by a newline. This allows you to monitor the flex sensor readings in the serial monitor.

• delay(1000);: This line introduces a delay of 1000 milliseconds (1 second) before the next iteration of the loop. This helps to control the rate at which the analog values are read and printed to the serial monitor.

• Upload the code to your Arduino board using a USB cable.

• Open the Serial Monitor in the Arduino IDE to view the flex sensor values.

Step 4: Test and Calibrate Flex Sensor

• Flex the sensor strip and observe the changes in the values displayed on the Serial Monitor. The values should change as you bend the sensor.

• Take note of the minimum and maximum values displayed when the sensor is at its fully extended and fully bent positions, respectively.

• Based on these minimum and maximum values, you can calibrate the flex sensor to suit your project's requirements. For example, you can use the Arduino map() function to scale the sensor values to a specific range, or use the sensor values to trigger actions or events in your project based on certain thresholds.

Step 5: Build Your Project

Now that you have successfully interfaced the flex sensor with Arduino and calibrated it, you are ready to build your project! With the flex sensor providing real-time data on the bending of the sensor, you can use it to control various aspects of your project.