Robotic Prosthetic Hand With Claw or 3d Printed Hand


Introduction: Robotic Prosthetic Hand With Claw or 3d Printed Hand

About: lost my arm at 18, now I'm hacking stuff for disabled people (or animals)

Making a muscle controlled robotic hand. Using an Arduino, a Myoware biometric EMG sensor, and a robotic claw, or 3D printed hand.

Step 1: Parts

1)Pro Trinket

2)USB Isolator

3)Myoware Muscle Sensor

4)Robotic claw

5)Power cable

Step 2: Wiring

MyoWare "+" to Pro Trinket 5V

MyoWare "-" to Pro Trinket GND

MyoWare "SIG" to Pro Trinket A0

Orange Servo Wire to Pro Trinket #3

Red Servo Wire to 5V

Brown Servo Wire to Ground

Step 3: Code


Servo myservo;

// constants

const int iServoPin = 3; // servo pin number

const int iSensorPin = A3; // muscle sensor pin number

const int iMaxServoVal = 1140; // HS-7940's fully extracted claw servo position PWM value (in microseconds)

const int iMinServoVal = 1800; // HS-7940's fully retracted claw servo position PWM value (in microseconds)

const int iMinThreshVal = 200; // muscle sensor threshold value to begin controlled extension

const int iServoStep = 10; // controls claw extension speed - increase to speed up

const unsigned long lLockOut = 2000L; // duration to hold max threshval to toggle the lock state (in milliseconds)//

// global variables

unsigned long lStartTime = 0L; // variable to store the time the timer was started

bool bStartLockTimer = false; // if true, the timer has been started; false otherwise

bool bActiveLock = false; // if true, the claws have been locked in fully extended state; unlocked otherwise.

void setup()


myservo.attach(iServoPin); // attaches the pin to the servo object

delay(10000); // 10 second delay to give you time to plug in the battery, stow it, and get clear


void loop()


// read muscle sensor value

int iSensorVal = analogRead(iSensorPin);

int iServoVal = iMinServoVal; // intialize to min value

// determine what state to put the claws in based on the sensor value

// three possible states

if(iSensorVal < iMinThreshVal)


// state 1 - below threshold - fully retract claws

iServoVal = iMinServoVal;




// state 2 - above max threshold - fully extend claws

iServoVal = iMaxServoVal;


// if sensor is in state 2, start timer to trigger lLockOut

if(iServoVal == iMaxServoVal)


// if the timer hasn't been started, then start it.

if(!bStartLockTimer) { lStartTime = millis(); bStartLockTimer = true;





// reset timer variables

lStartTime = 0L; bStartLockTimer = false;


// check to see if the timer was started and it runs for the amount of time required to trigger lock/unlock

if(bStartLockTimer && millis()-lStartTime >= lLockOut)


// toggle lock state

bActiveLock = !bActiveLock;

// reset timer variables

lStartTime = 0L;

bStartLockTimer = false;

// set servo value to max when locking




iServoVal = iMaxServoVal;


else // reset servo value to min when unlocking



iServoVal = iMinServoVal;


// pause for a second to allow the user to adjust to the new setting



// move the servo to the desired postion





// delay to not overload the ADC



Step 4: Mount to Arm

this will depend on the type of prosthetic you have. I had to use a bolt and dremel.

Step 5:



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