This Tutorial is about the FlexiForce sensor. In this tutorial I will show you the easiest and simplest way how to calibrate the flexiforce sensor, During the calibration we will be measuring some known weights with this sensor, I personally don’t recommend using flexiforce sensor for weight measurement, for weight measurement load cell is the best choice, I have very detailed tutorials on weight measurement using load cell and hx711 “Click Her” if in case you want to watch this tutorial. In this tutorial, I will be using weights only for demonstration purposes. This tutorial covers the extreme basics, how to use the flexiforce sensor with Arduino, while in the upcoming tutorials we will be using this sensor in security-based projects, we will also be using this sensor in a plastic injection molding machine for pressure monitoring, we will also be using this in robots.
For the step by step explanation, you can watch a video Tutorial “Click Here”
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A flexiforce sensor is also known as the force Sensoring Resistor. The Flexiforce sensor or force sensing resistor is made up of such type of material whose resistance changes when a force or pressure or mechanical stress is applied. A flexiforce sensor is also known as force sensitive resistor “FSR”.
As you can see clearly in the picture, the flexiforce sensor has three legs or pins. The middle one is not used.
The circular area of the sensor is the effective area of the sensor, where the force or pressure will be applied. To apply the force or pressure exactly at this area I cut a piece of hard rubber in a circular shape and fix it using hot glue. Now our sensor is ready.
FlexiForce sensor is connected in series with a 10k resistor, you can try some other resistors like 1 megaohm or 3.3k if you want to measure high force or high pressure. The Flexiforce sensor and the 10k resistor makes a voltage divider, this way for different forces or pressure values we will get different voltages.
From this voltage variation which is due to the force or weight, we can calculate the weight in pounds or kgs. So make sure you have some known weights, I have 1kg and 3kg weights which I will use for the calibration. A 47uf capacitor is connected in parallel with the 10k resistor, you can use a small value capacitor, the purpose of this capacitor is to stop the voltage fluctuation and get stable values. We will read these voltages using the Arduino’s analog pin A0. Once again if you want to measure high pressure or weight then use a small value resistor.
For the Flexiforce sensor interfacing watch video Tutorial “Click Here”
Arduino FlexiForce sensor programming
for the step by step program explanation watch Video Tutorial “Click Here”
float cf = 19.5; // caliberation factor
int ffs1 = A0; // FlexiForce sensor is connected analog pin A0 of arduino or mega.
int ffsdata = 0;
ffsdata = analogRead(ffs1);
vout = (ffsdata * 5.0) / 1023.0;
vout = vout * cf ;
Serial.print("Flexi Force sensor: ");
Watch Video Tutorial: