Arduino Robotic Hand

Are you looking to create an easy and fun project using Arduino that you can impress your friends with? Well this robotic hand project is the right one for you.

This project uses a blend of all STEM subjects. Making this project will be a massive learning experience, or a rewarding project to create on the side.

Materials: Styrofoam, fishing line, sand paper, rubber bands, paper clips, hot glue, pliers, sewing needle, precision knife, marker.

Electronics: 5 servos, Arduino Nano, laptop/computer, 9V battery, breadboard.

The first and more important step, making sure your supplies are organized. One easy way you could mess up the project right at the start is by losing your fishing line or misplacing your knife. In order to start on the right track and make this project effortless is by having all your supplies organized and at the ready!

Try and keep your Electronics and your materials for the hand in different bags so you can very quickly grab a servo or some rubber bands without need to scrounge through your bag to find one particular thing.

MATERIALS NEEDED FOR THIS STEP: Ruler

Get your ruler and start measuring the dimension of your first finger. I started with my index finger and used centimeters, however, you can start with any finger and use any unit of measurement that you find most comfortable.

The finger is a 3D object, so be sure to measure all three dimensions. The length, width, and height of the finger. Take notes of the size of your finger so that you do not forget. Repeat this process for the four other fingers and write down the dimensions.

Even though your finger will not be a perfect rectangular prism (at least, it shouldn't be), we will still interpret the measurements as if it were a perfect rectangular prism, as we will need to for our next step

MATERIALS NEEDED FOR THIS STEP: Styrofoam, precision knife, ruler, marker

Using the measurements you recorded earlier, cut out rectangular prisms from the styrofoam for each of your fingers.

After cutting out your rectangular prisms, you will now need to cut off triangular prisms off each corner of your rectangular prism. We did 2 mm off each corner, but the amount you need to take off will vary as everyone's finger size will be different. Use your intuition and try your best to make it finger shaped. If you really aren't sure how much you need to cut, go for 1.5-2mm. We used 2mm as my fingers are bigger than the average finger.

After you are done with the cutting, it is now time to start the sanding portion of this step. Use your sand paper or sanding block and round off all of the edges. Keep sanding until you get a uniform cylinder. Try and sand off as little as possible as you will want to try and keep you fingers that same size. If you sand too much, the finger will no longer be it's original size and may be misshapen. After you have the cylinder, round off the top and create a hemisphere. This is to mimic the actual shape of the finger. Repeat this process for each rectangular prism you have.

MATERIALS NEEDED FOR THIS STEP: Styrofoam, precision knife, ruler, marker

You can't put your fingers anywhere unless you have the rest of you arm! You will need to measure out your palm and approximately half of your forearm. This is where you will later put your fishing line.

This step will be extreme similar to the last step, except you are using a different part of your arm.

MAKE SURE THE PALM AND HALF-FOREARM ARE ONE SINGULAR PIECE. If you cut them separately, you will need to use extra glue to stick them together. It will be less structurally sound and may fall apart later down the road.

MATERIALS NEEDED FOR THIS STEP: Styrofoam cylinders, precision knife, ruler, marker

Now that you have your cylinders with the hemisphere top, it is now time to cut the three sections of your finger; just like how your actual fingers are. You will only need to cut your thumb in half (the styrofoam, not your actual thumb) as there are only two sections in your thumb. You will want your sections to be as equal in size as you can get it, but it doesn't need to be perfect!

When you are done cutting each of the sections, you will need to cut 45 degree angles to created truncated cylinders for each of the sections so that they can bend when put together. Note that you will only need one cut for the top and bottom section and you will need two cuts for the middle section. The only exception for this is the thumb, as it has only two segments. Again, you will need to repeat this process for each finger.

The formula for a truncated cylinder is πr²(h1+h2+)/2

MATERIALS NEEDED FOR THIS STEP: Sewing needle, fishing line, paper clips, pliers, forearm + palm, styrofoam fingers, hot glue.

Using the needle and fishing line, put the fishing line through the hole in the needle and start by pushing the needle through the top of the palm. Then, after it is through the palm, going in the direction of the top of the palm, you take your finger segments and thread the fishing line through each segment using the needle. After that is finished, cut off the fishing line and make sure there is plenty of excess fishing line; enough to go down the length of your forearm and some extra. You will want to have a lot of excess. You can easily cut off unneeded fishing line, but you can't easily add more. Repeat this process for each finger.

Take your paperclips and pliers and start cutting your paper clips into pieces. You will want them in a U-shape so that you can stick them into the styrofoam and hold your fishing line in place Try and aim for 4-5 paper clip pieces for each finger's fishing line. After this, use your hot glue and add a little bit on the tip of each finger where the fishing line comes through. This makes so that when you pull the fishing line down, the finger will move along with it, rather than just pulling the fishing line by itself.

MATERIALS NEEDED FOR THIS STEP: Rubber bands, knife, hot glue, completed hand from step 6.

Take a rubber band and cut it into pieces. As you can see from the picture above, you can cut pieces than can connect each singular knuckle, or one that runs across the entire finger. We had to use both sizes for our two fingers, as our rubber bands wouldn't bring the finger back up after pulling the fishing line down. The amount of rubber bands you need will depend on the strength on your rubber bands and size of your fingers.

After this step, you will be fully done building the main hand!

MATERIALS NEEDED FOR THIS STEP: laptop/computer, Arduino

You will need to have some sort of basic code so that the fingers will actually move. We have created a basic code (Robotic_Hand_Code.ino) with tons of pre-programmed hand movements, such as a pinch, peace sign, fist, and counting from 1 to 5. You will need some basic programming knowledge of Arduino in order to work through the code and change what the hand will do in a loop. The photo above will tell you how to use each section of the code.

If you think you are experienced enough, go ahead and make your own code! It's extremely simple and won't require you to become a master programmer or anything.

Upload this code into your Arduino.

MATERIALS NEEDED FOR THIS STEP: 5 servos, laptop/computer, Arduino, hot glue, knife, breadboard.

Your servo arms should have holes in them so that you can put your fishing line through. You can tie it around so that it stays on, or you can do what I did to make it way easier. You put the fishing line through and then place a dab of hot glue when the hole and the fishing line meet. Once the glue hardens, the fishing line will be fully connected to the servo, and when the servo moves, so will the fishing line and finger!

You may need an extra piece of styrofoam or other material so that the servos won't move around. We dug out a rectangle with the size of the servo and add hot glue on the bottom. We put the servos in and let the glue harden. Then you can glue the styrofoam or other material with the servos on it under the forearm. Without this, the servos will slip and move around everywhere instead of pulling the finger.

Take your servos and attach the wires to the pin numbers that you have put in your code.

Now your hand is finished! Enjoy! You can go and show it all off to friends, no matter if they like it or not. You can make it do all sorts of things. It just can't do anything a hand can't do. Like singing or flying. Thanks for reading!

[NOTE] We had to only use two fingers as we didn't have access to a battery. Of course, you can do all five if you have a sufficient power source!

This Instructable was based on the low-cost robotic hand by MertArduino: Arduino - Make a Robotic Hand (Low Cost) : 6 Steps (with Pictures) - Instructables

My Instructable aims to expand more on the hand creation process and getting rid of the flex sensor portion.