Skip to product information
1 of 1

Blue PCB Electronics

5B3 Flex Sensor 4.5" inch

5B3 Flex Sensor 4.5" inch

Regular price Dhs. 120.00
Regular price Sale price Dhs. 120.00
Sale Sold out
View full details
4.5 Inch Flex Sensor 

A simple flex sensor 4.5 inch in length made by SPARKFUN. As the sensor is flexed, the resistance across the sensor increases. The resistance of the flex sensor changes when the metal pads are on the outside of the bend (text on inside of bend). Connector is 0.1" spaced and bread board friendly. Check datasheet for full specifications.
1. Angle Displacement Measurement
2. Bends and Flexes physically with motion device
3. Possible Uses
4. Robotics
5. Gaming (Virtual Motion)
6. Medical Devices
7. Computer Peripherals
8. Musical Instruments
9. Physical Therapy
10. Simple Construction
11. Low Profile

Here is the schemetics:

Package included:
  • 1 x 4.5 Inch Flex Sensor

Example Circuit

The simplest way to incorporate this sensor into your project is by using it in a voltage divider. This circuit requires one resistor. Many values from 10KΩ to 100KΩ will work. If you have a resistor kit, you may want to introduce some trial-and-error to hone in on that perfect static resistance.

A value between the minimum and maximum resistance values is usually a good choice. We'll use a 47kΩ resistor in this example. Here's the hookup:


Example circuit fritzing diagram


And a schematic:


Example circuit schematic


The 47kΩ resistor on the ground side, and the flex sensor on the 5V side, means as the flex sensor's resistance increases (meaning the sensor is bending) the voltage on A0 will decrease.

Example Program

Here is a simple Arduino example based on the circuit above. Copy and paste this into your Arduino IDE, then upload!

const int FLEX_PIN = A0; // Pin connected to voltage divider output

// Measure the voltage at 5V and the actual resistance of your
// 47k resistor, and enter them below:
const float VCC = 4.98; // Measured voltage of Ardunio 5V line
const float R_DIV = 47500.0; // Measured resistance of 3.3k resistor

// Upload the code, then try to adjust these values to more
// accurately calculate bend degree.
const float STRAIGHT_RESISTANCE = 37300.0; // resistance when straight
const float BEND_RESISTANCE = 90000.0; // resistance at 90 deg

void setup() 
  pinMode(FLEX_PIN, INPUT);

void loop() 
  // Read the ADC, and calculate voltage and resistance from it
  int flexADC = analogRead(FLEX_PIN);
  float flexV = flexADC * VCC / 1023.0;
  float flexR = R_DIV * (VCC / flexV - 1.0);
  Serial.println("Resistance: " + String(flexR) + " ohms");

  // Use the calculated resistance to estimate the sensor's
  // bend angle:
                   0, 90.0);
  Serial.println("Bend: " + String(angle) + " degrees");


After uploading, open your serial monitor, and set the baud rate to 9600 bps.

If you bend the flex sensor, you should see resistance and estimated angle calculations change:


flex sensor readings to serial monitor


If the value's don't seem correct, make sure the constants VCC and, more importantly, R_DIV are accurate. If you used something other than a 47kΩ resistor, enter that value in for R_DIV.

Through trial-and-error, try to hone in on more accurate values for STRAIGHT_RESISTANCE and BEND_RESISTANCE -- your flex sensor's resistance when it's straight and bent at 90°.