Flex Sensor Working and Its Applications

We know that there are different types of sensors  available in the market where each sensor can be used based on the application. Likewise, a bend sensor or flex sensor is one kind of sensor used to measure the quantity of bending otherwise deflection. Generally, this sensor is fixed to the exterior, and the resistance of this sensor can be changed by twisting the exterior. These sensors are applicable in the Nintendo power glove, robot whisker sensors, door sensors, otherwise the main component in making alert stuffed animal toys.

What is a Flex Sensor?

A flex sensor is a kind of sensor which is used to measure the amount of defection otherwise bending. The designing of this sensor can be done by using materials like plastic and carbon. The carbon surface is arranged on a plastic strip as this strip is turned aside then the sensor’s resistance will be changed. Thus, it is also named a bend sensor. As its varying resistance can be directly proportional to the quantity of turn thus it can also be employed like a goniometer.


Types of Flex Sensor

These sensors are classified into two types based on its size namely 2.2-inch flex sensor & 4.5-inch flex sensor. The size, as well as the resistance of these sensors, is dissimilar except the working principle.

Therefore the suitable size can be preferred based on the necessity. Here this article discusses an overview of 2.2-inch flex-sensor. This type of sensor is used in various applications like computer interface, rehabilitation, servo motor control, security system, music interface, intensity control, and wherever the consumer needs to modify the resistance throughout bending.

Pin Configuration

The pin configuration of the flex sensor is shown below. It is a two-terminal device, and the terminals are like p1 & p2. This sensor doesn’t contain any polarized terminal such as diode otherwise capacitor, which means there is no positive & negative terminal. The required voltage of this sensor to activate the sensor ranges from 3.3V -5V DC which can be gained from any type of interfacing.



  • Pin P1: This pin is generally connected to the +ve terminal of the power source.
  • Pin P2: This pin is generally connected to GND pin of the power source.

Where to Use?

The flex-sensor can be used in the following two cases.


This sensor is used wherever you need to test the exterior of a device otherwise thing is planed or not. A flex-sensor could be used to check a door or window is opened or not. This sensor can be arranged at the edge of the door and once the door opens then this sensor also gets flexed. When the sensor bends than its parameters automatically change which can be designed to give an alert.

This sensor is used wherever you need to measure the Bent, Flex, otherwise, change of an angle for any device otherwise any instrument. The internal resistance of this sensor alters approximately linear with the angle of its flex. Thus by connecting the sensor to the device, we can have the flex angle within resistances of electrical parameter.

Working Principle

This sensor works on the bending strip principle which means whenever the strip is twisted then its resistance will be changed. This can be measured with the help of any controller.

This sensor works similar to a variable resistance because when it twists then the resistance will be changed. The resistance change can depend on the linearity of the surface because the resistance will be dissimilar when it is level.

When the sensor is twisted 450 then the resistance would be dissimilar. Similarly, when this senor is twisted to 900 then the resistance would be dissimilar. These three are the flex sensor’s bending conditions.

According to these three cases, the resistance will be normal in the first case, the resistance will be double as contrasted with the first case, and the resistance will be four-time when compared with the first case. So the resistance will be increased when the angle is increased.

Specifications & Features

The specifications and features of this sensor include the following.

  • Operating voltage of this sensor ranges from 0V to 5V
  • It can function on low-voltages.
  • Power rating is 1 Watt for peak & 0.5Watt for continuous.
  • Operating temperature ranges from -45ºC to +80ºC
  • Flat resistance is 25K Ω
  • The tolerance of resistance will be ±30%
  • The range of bend resistance will range from45K -125K Ohms


The applications of the flex-sensor include the following.

  • Medical Instruments
  • Peripherals of Computer
  • Robotics
  • Physical Therapy
  • Virtual Motion (Gaming)
  • Musical Instruments

Thus, this is all about flex sensor. From the above information, we can finally conclude that when this sensor is bent then the terminal resistance of this sensor will be changed. Here is a question for you, what are the benefits of using this sensor?