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Making the world a better place one prosthetic hand at a time

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Building a prothestic hand with a 3D printer that can be controlled by a muscle sensor and a servo motor

What we wanted to create was a prosthetic hand that anyone could customize and that would give you the ability to control your grasp on things. To do so, we came up with the idea of associating a muscle sensor with a servo motor and strings. The muscle sensor would interact with the motor so that everytime you contracted a muscle it would make the motor turn so that it tightened the strings.

document - 22.75 kB - 05/17/2018 at 08:27

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  • Project Session 5

    Elena06/12/2018 at 16:39 0 comments

    Almost every problem we had we almost solved. We finished printing the parts of the hand and had some issues with some of the fingers so we had to put screws on to join the hand and the finger because we were out of time to print it again. We finally found a code that woked with the sensor, unfortunately our muscle sensor stopped working so we replaced it with a potentiometre just to show what the hand was supposed to do. We had to tweak some things and we finally finished our project. The hand is not perfect but we are happy with the result as the time we had to complete this project was very limited.

  • Project Session 4

    Isidora05/17/2018 at 10:07 0 comments

    Today, we're trying to print some parts of our prosthetic hand. We had some problems with the 3D Printer, and resolved them by downloading an other version of Cura (the software used to print).
    ADVICE : take time because the printing can take up to 16 hours...

    Also, we continued to test out the muscle sensor and the servo motor.

    Tips : - Download an earlier version of the cura software if it doesn't work with your printer.

    - Print the flexible parts if possible on a common "plate" and the hard part on another that way the printer doesn't mess up.

  • Project Session 3

    Isidora05/03/2018 at 09:59 0 comments

       Today we received the items necessary for our project. We started doing the programs that would enable the muscle sensor and the servo motor to work together. What we want to achieve is the motor being able to tighten the strings on the flexi-hand using the data from the muscle sensor.
       We did research on the material needed for the hand and we found that the best is FilaFlex.

  • Project session 2

    Elena04/12/2018 at 09:32 0 comments

    After establishing our project on the first session, we had to make a list of things to buy for the project to work. We discovered that we had to make a lot of changes for our project to be realistic and makeable. We also had to stay under 2OO euros of purchase. And we added the idea of having a muscle sensor control the tightness of the strings making the hand grasp something.

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  • 1
    Print

    Download and use these files to print the different parts : https://www.thingiverse.com/thing:380665/#instructions

    You will need to print 7 parts of the hand : - Bat Connection

    - Finger Hinge Plate

    - Flexy Hinge Plate

    - Gauntlet (Long or Short however you choose)

    - Finger Plate

    - Hand Body

    - Thermoform Palm

    For the flexible and non-flexible parts we printed almost everything except the Flexy Hinge Plate in non-flexible material. But you can print it in whichever plastic you feel is best for each part.

  • 2
    Code for the sensor and servo motor
    #include 
    
    //Threshold for servo motor control with muscle sensor. 
    //You can set a threshold according to the maximum and minimum values of the muscle sensor.
    #define THRESHOLD 130
    
    //Pin number where the sensor is connected. (Analog 0)
    #define EMG_PIN 0
    
    //Pin number where the servo motor is connected. (Digital PWM 3)
    #define SERVO_PIN 3
    
    //Define Servo motor
    Servo SERVO_1;
    
    /*-------------------------------- void setup ------------------------------------------------*/
    
    void setup(){
      
      
      //Set servo motor to digital pin 3
      SERVO_1.attach(SERVO_PIN);
    }
    
    /*--------------------------------  void loop  ------------------------------------------------*/
    
    void loop(){
    
      //The "Value" variable reads the value from the analog pin to which the sensor is connected.
      int value = analogRead(EMG_PIN);
    
      //If the sensor value is GREATER than the THRESHOLD, the servo motor will turn to 170 degrees.
      if(value > THRESHOLD){
        SERVO_1.write(170);
      }
    
      //If the sensor is LESS than the THRESHOLD, the servo motor will turn to 10 degrees.
      else{
        SERVO_1.write(10);
      }
    
      //You can use serial monitor to set THRESHOLD properly, comparing the values shown when you open and close your hand.
      Serial.println(value);
    }
    
    
    

    Don't forget to first visualize  the signal received from the muscle sensor with the analog sensor code which you can find in arduino example codes to establish the threshold.


    We, first, wanted to do our project with a muscle sensor but is quite difficult. However, here, you can see what it would have looked like.
  • 3
    Assemble

    For the third step, assemble everything, the arduino card and the flexy-hand and try to make everything work. Here are pictures of all the cable placement between the arduino card, the servo motor and the potentiometre ( the muscle sensor broke). we can also find the circuits on the internet.

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