The flex sensor defined as a bend detecting sensor, one of the prominent sensors that have got numerous applications in robotics, medical, and haptic technology. These are variable resistance in which the resistance of sensors changes in accordance with the bend, which can be measured using any microcontroller. In short, this is a flexible sensor that changes its output when it is bent or when force is applied to it. Hence also works as a Force sensor. The Flex sensor provides an active sensing area of 5cm with a flex resistance of 25K Ω and length of 2.2inch. A connector of 0.1″ spaced used and breadboard-friendly makes the installation easier.
This sensor provides two output wires. As the sensor flexed or bend, the resistance between these two wires increases. It should be considered that the base of the sensor is sensitive to bending and may get damaged. Hence care should be taken that you bend only the sensing area. For best results, securely mount the base and bottom portion and only allow the actual flex sensor to flex.
During nominal resistance, the surface of the Flex sensor is completely linear. When it bents 45º angle the Flex Sensor resistance increases to twice as before. And when bents 90º the resistance varies as high as four times than the nominal resistance. As a result, the resistance across the terminals rises linearly with a bent angle. So in short the flex sensor converts flex angle to resistance parameter. For better convenience, we convert this resistance parameter to a voltage parameter using a voltage divider circuit. This voltage parameter is fed into ADC for digital output.