Juliette van der Pas
Published © CC BY-NC

A DIY Smart Insole to Check Your Pressure Distribution

The smart insole collects foot pressure data in real-time. Through Thinger.io the information is fed into a system that visualizes the data.

IntermediateFull instructions provided10 hours8,130
A DIY Smart Insole to Check Your Pressure Distribution

Things used in this project

Hardware components

Arduino MKR1000
Arduino MKR1000
×1
Force Sensitive Resistor
I've used Interlink model 402
×3
Wire Cable - By the Foot
OpenBuilds Wire Cable - By the Foot
×1
Resistor 10k ohm
Resistor 10k ohm
×3
Power Bank
×1
SparkFun Triple Axis Accelerometer Breakout - ADXL345
SparkFun Triple Axis Accelerometer Breakout - ADXL345
×1

Software apps and online services

Thinger.io Platform
Thinger.io Platform
Arduino IDE
Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)
Soldering iron (generic)
Don't forget to buy solder, heat shrink and other applicable accessoires if you don't have these

Story

Read more

Schematics

Hardware

Three FSR's (with voltage dividers) and an accelerometer.
Wiring xrvswdjvln

Code

Smart-Insole-Tutorial

Arduino
Full code of this tutorial
#define _DEBUG_  //Make sure this comes before any other includes or your board might crash

/*Please find the tutorial here: https://www.hackster.io/projects/a5ceae*/
#include <WiFi101.h> //Thinger
#include <ThingerWifi101.h> //Thinger
#include <Wire.h> //Accelerometer
#include <Adafruit_Sensor.h> //Accelerometer
#include <Adafruit_ADXL345_U.h> //Accelerometer

#define USERNAME "yourUsername"
#define DEVICE_ID "yourDevice"
#define DEVICE_CREDENTIAL "yourCredential"
#define SSID "yourSSID"
#define SSID_PASSWORD "yourSSIDPassword"

Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345); //Accelerometer

int x = 0; //Reset to 0 
int y = 0;
int z = 0;  

//*FSR sensors*/
#define noFSRs 3 // Number of FSRs connected
#define FSR1 A1  //Analogue ports
#define FSR2 A2 
#define FSR3 A3 

float fsrVoltageArray[3];       // The analog reading converted and                                      //scaled to voltage as a floating point                                  //number
float fsrForceArray[3];         // The force in Newton
float fsrWeightInGramsArray[3]; // Weight converted to grams

int   pinArray[3]       = {FSR1, FSR2, FSR3};    // The pin ID for the                                                    //three devices
float forceMaxArray[3]  = {100.0, 100.0, 100.0}; // Maximum forces                                                        //supported

float million = 1000000.0; // Unit for "1/micro
float conversionToKgrams = 1.0/9.80665;

long K       = 1000;
long R       = 10*K;    // R in K Ohm
long Vcc     = 5000;    // 5V=5000mV, 3.3V = 3300 mV
float voltageMax = 0.98 * Vcc; // Maximum voltage set to 95% of Vcc. Set                               //the force to the maximum beyond this                                 //value.

ThingerWifi101 thing(USERNAME, DEVICE_ID, DEVICE_CREDENTIAL); 
//Call to set up WiFi function

void setup(void) {
  Serial.begin(115200);
  thing.add_wifi(SSID, SSID_PASSWORD); 
  
  if(!accel.begin()) {   //Initialise the sensor 
    Serial.println("No ADXL345 detected.");
  } else {
    accel.setRange(ADXL345_RANGE_16_G); //Range for this sensor 
  
    thing["accelerometer"] >> [](pson& out){
        sensors_event_t event; 
        accel.getEvent(&event);
        out["x"] = event.acceleration.x;
        out["y"] = event.acceleration.y;
        out["z"] = event.acceleration.z;
    };
  }

   /*FSR sensors*/  
  thing["pressure"] >> [](pson & out) {
    out["FSR1"] = analogRead(FSR1);
    //    Serial.print("FSR1:");
    //    Serial.println(analogRead(FSR1));
    out["FSR2"] = analogRead(FSR2);
    //    Serial.print("FSR2:");
    //    Serial.println(analogRead(FSR2));
    
    out["FSR3"] = analogRead(FSR3);
    //    Serial.print("FSR3:");
    //    Serial.println(analogRead(FSR3));      
  };

  thing["voltage"] >> [](pson & out) {

    for (int FSR = 0; FSR < noFSRs; FSR++) {   

      fsrVoltageArray[FSR] = 0.0; //Reset values upon entry
      fsrForceArray[FSR]   = 0.0;
      
      int fsrPin   = pinArray[FSR];     
      int fsrReading = analogRead(fsrPin); 
       
      fsrVoltageArray[FSR] = (float) map(fsrReading, 0, 1023, 0, 5000);
    } //End of loop over FSR's

    out["FSR1voltage"] = fsrVoltageArray[0];
    out["FSR2voltage"] = fsrVoltageArray[1];
    out["FSR3voltage"] = fsrVoltageArray[2];
  };

  thing["newton"] >> [](pson & out) {
    for (int FSR = 0; FSR < noFSRs; FSR++) {  
    
         // The value of the force F as a function of the voltage V is           ///computed as: F(V) = (Fmax/Vmax) * V

         float force_value = (forceMaxArray[FSR]/voltageMax) * fsrVoltageArray[FSR];

         // Three situations are distinguished:
         //
         // 1. If V is too close to the maximum (as defined by voltageMax          // ), the force can
         //    go to infinity. This is avoided by setting it the maximum          //value as soon as it is higher than our threshold voltageMax.
         //
         // 2. If the computed force F is too small, we set it to zero to          // avoid noise effects.
         //
         // 3. In all other cases, we take the logarithmic value to 
         //reduce the sloop and better distinguish small changes.

         if ( fsrVoltageArray[FSR] < voltageMax ) {

           // V is not too high in this branch

           if ( force_value <= 1.00 ) {
              fsrForceArray[FSR] = 0.0; // Force is too small, set it to                                        // zero
           } else {
             fsrForceArray[FSR] = log10(force_value); // Value is okay,                                                       //take the log of                                                       //this
           }

        } else {

           // Cap the force if the voltage is too close to Vcc (for Vcc            //it would be infinity)

           fsrForceArray[FSR] = log10(forceMaxArray[FSR]);

           Serial.print("Cut off activated for FSR = "); Serial.println(FSR);
        }
    
   } // End of loop over FSRs
      out["FSR1newton"] = fsrForceArray[0];
      out["FSR2newton"] = fsrForceArray[1];
      out["FSR3newton"] = fsrForceArray[2];
  }; //End of thing 

    thing["weight"] >> [](pson & out) {

    //Straightforward computation to convert the force in Newton to the weight in grams

    for (int FSR = 0; FSR < noFSRs; FSR++) {  
      fsrWeightInGramsArray[FSR] = fsrForceArray[FSR] * conversionToKgrams * 1000.0;
    }
      out["FSR1weight"] = fsrWeightInGramsArray[0];
      out["FSR2weight"] = fsrWeightInGramsArray[1];
      out["FSR3weight"] = fsrWeightInGramsArray[2];
  }; //End of thing
} //End of setup

void loop(void) {
  thing.handle();
}

Credits

Juliette van der Pas

Juliette van der Pas

2 projects • 4 followers

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