I decided to make a fingertip sensor for my robotic hand. this small sensor has 6 resistive touch sensors and one temp sensor. can easily be connected to any robotic hand. the temp sensor is selected as a NTC thermistor, because it is very small and sensitive to 2 decimal digits and 6 DIY resistive touch sensors made of double sided sticky tape, self adhesive copper sheet and Velostat. I am still working on it but as far as I can see it can detect the force of grab and type of grabbed material as rigid and soft. further study is needed with collected data...

I used a small Arduino Nano to process the data. the resistors are 100K but I am planning to test the system with 1Megaohm ones for more sensitivity. The simple sketch is as follows:

/* Fingertip Sensor 

 one thermistor and 6 resistive touch points on a fingertip

 reading temperature and touch data fron the sensor

 Dincer Hepguler, 2017

*/

int ThermistorPin = A0;

int TouchPin1 = A1;

int TouchPin2 = A2;

int TouchPin3 = A3;

int TouchPin4 = A4;

int TouchPin5 = A5;

int TouchPin6 = A6;

 

int Vo;

int V1;

int V2;

int V3;

int V4;

int V5;

int V6;

float R1 = 10000;

float logR2, R2, T;

float c1 = 1.009249522e-03, c2 = 2.378405444e-04, c3 = 2.019202697e-07;

 

void setup() {

Serial.begin(57600);

pinMode(TouchPin1,INPUT);

pinMode(TouchPin2,INPUT);

pinMode(TouchPin3,INPUT);

pinMode(TouchPin4,INPUT);

pinMode(TouchPin5,INPUT);

pinMode(TouchPin6,INPUT);

}

 

void loop() {

 

  Vo = analogRead(ThermistorPin);

  V1 = analogRead(TouchPin1);

  V2 = analogRead(TouchPin2);

  V3 = analogRead(TouchPin3);

  V4 = analogRead(TouchPin4);

  V5 = analogRead(TouchPin5); 

  V6 = analogRead(TouchPin6); 

  R2 = R1 * (1023.0 / (float)Vo - 1.0);

  logR2 = log(R2);

  T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));

  T = T - 273.15;

  //T = (T * 9.0)/ 5.0 + 32.0; 

 

  Serial.print("Temp: "); 

  Serial.print(T);

  Serial.print(" C"); 

  Serial.print(" ");

  Serial.print(V1);

  Serial.print(" ");

  Serial.print(V2);

  Serial.print(" ");

  Serial.print(V3);

  Serial.print(" ");

  Serial.print(V4);

  Serial.print(" ");

  Serial.print(V5);

  Serial.print(" ");

  Serial.print(V6);

  Serial.println();

  delay(100);

}