A Robotic Controllable Hand




Posted in CraftArt

Introduction: A Robotic Controllable Hand

This hand is a prototype to a robotic hand. I made two different versions of this hand.

The first version is with the Servo motors, it can be used to reach further objects since the hand is bigger than a normal hand. This project, made with recycled wood, has five fingers, that each have two phalanges. A Servo motor attached to a string, guided by a straw, controls the movement of one finger. The Servo motors are controlled by a code on Arduino.

The second version is with the glove. The hand is supposed to help a person with a disabled hand. Let's say that someone has difficulties with the movement of their hand because of arthritis, broken bones or even the malfunctions of their hand ligaments, they can use this homemade hand to help them close their hand. As you can see on the picture, you slide your hand in the glove and and close your fingers. This could be a fun way to do some exercices to help your hand recover. The movement of the wooden fingers are due to the plastic string attached to the fingers of the blood.

I also made a 3D model previously and I built my fingers based on that model.

Step 1: Tools and Materials


-Mechanical saw


-Hot glue gun




-Bench vice


-Plank of wood

-Piece of wood

-Plastic string

-5 Servo motors



-Rods (in this case they were pieces of LEGO)







Step 2: Preparation of Your Servo Motor

1-I removed the black box (the plug for the pins) by pulling a piece of plastic.

2- Using pliers, I removed the pins from the black box and I inserted one in each end of the wires.

Step 3: Servo Motor Programming

1-I downloaded the Arduino software.

2- I programmed five Servo motor's so that they would start at 0 degree, then go to 180 degrees and finally come back to their initial position. There is a delay of 1 second between each positions. I programmed it in a loop.

This is a link to the program is used

Step 4: Cutting of the Wood for One Finger

1-Using the mechanical saw, I cut pieces of wood like in the picture.(in cm)

*2 pieces (0.5 x 6 x 1.75)

*1 piece (1.25 x 6 x 1.75)

*1 piece (2 x 2.5 x 1.75)

*1 piece (2 x 2 x 1.75)

*2 pieces (0.5 x 4.5 x 1.75)

*1 small piece with a whole in the middle

It doesn't have to be exact

2-I drilled holes on the ends of the pieces.

Step 5: Assembling a Finger

1-I glued the piece (2 x 2.5 x 1.75) between the two pieces (0.5 x 6 x 1.75) using hot glue.

2-I placed the piece (1.25 x 6 x 1.75) between the ends of the pieces (0.5 x 6 x 1.75) so that the lego rod can go through the three holes drilled.

3-I hot glued the ends of the lego rods to the sides of the wood, so that when the rod moves, the extremity phalanx moves with it.

4-I put a lego rod in the middle of the hole from the middle phalanx and i hot glued the wood to the rod.

5-I placed the pieces (0.5 x 4.5 x 1.75) on each sides of the LEGO rod and hot glued the piece (2 x 2 x 1.75) at the bottom.

6-I hot glued parts of straws on both of the phalanx.

7-I attached the end of the plastic string to the small piece of wood with the hole in the middle, then I passed the other end through the straws.

8-On the other side of the finger, I hot glued an elastic like on the picture.

Step 6: Making of All the Fingers

Repeat step 4 and 5, four other times.

Step 7: The Fingers and the Palm

1- I cut the palm of my hand with the mechanical saw.

2-I hot glued the fingers on the edge of the palm.

3- I taped the palm with black tape (for aesthetics)

Step 8: Wire 5 Servo Motors

1-I connected the brown wires from all the Servos to the (+) row.

2-I connected the red wires from all the Servos to the (-) row.

3-I connected the yellow wire from each Servo to one Pin (3, 5, 6, 9, 10)

4-I wired the GND output to the (+) row.

5- I wired the 5V output to the (-) row.

Step 9: Installing the Servo Motors on the Hand

1-I attached the plastic string of one finger to the horn of a Servo motor in a way that the string is tense and I taped the Servo to the palm of the hand.

2-Repeat this for all the fingers.

*I only have 4 Servo motors on the hand because the fifth one broke and I did not have time to order another one.

Step 10: Last Step!

Plug the circuit to your computer and download the code onto the arduino.

Step 11: Conclusion

During the making of this project, I encountered many issues.

First, I built a hand which had four fingers with three phalanx, plus a thumb. The issue was that the rotation of the Servo motor was not covering the whole folding and unfolding of the finger, so the finger only bend to about half of its magnitude. I tried to lengthen the horn, using a toothpick, a straw and a piece of lego. I also attempted to modify the Servo motor in order to make it turn 360 degrees but, I could not figure a way to controle it, so that it would only do one 360 degree. The Servo motor was make multiples 360 degrees. None of these alternatives worked. To solve this problem, I had to remove the last phalanx of the four finger.

Second, when I first tried to fold one finger using a Servo motor, I realised that the finger remained folded and did not go back to its initial position. To resolve this problem, I first attempted to hot glue small pieces of elastic between two phalanx, then I tried to put a small elastic around two nails, finally I found that the best option was to hot glue an elastic along the whole finger. The elastic passes through a straw in order to guide the elastic.

Third, I had trouble making a code to sychronize 5 Servo motors turn simultaneously since it was my first time using arduino. I researched how to program it and created this code I am using.

Fourth, at first I had 5 Servo motor, but one of them was not working well so I opened it uo and realised that one of the gears was missing a tooth which was stopping the full rotation of the motor.

In the future, I would like to polish this project by making it look more like a robotic hand. I would achieve this goal by remaking the hand using a 3D printer. I would also add to the code a sequence to make the fingers move individually.

I would also like to add a new aspect to the hand which is to pick up small objects using coffee grounds and a balloon. I would cover the tips of the fingers with a ballon filled with coffee grounds and used a doubled function vacum to control the hand.

Step 12:

This is a video with another code



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    Yes! I just finished updating my instructable :)